RESUMO

A general assumption in visual neuroscience is that basic receptive field properties such as orientation and direction selectivity are constructed within intrinsic neuronal circuits and feedforward projections. In addition, it is assumed that general neuronal excitability and responsiveness in early visual areas is to a great extent independent of feedback input originating in areas higher in the stream. Here, we review the contribution of feedback projections from MT, V4 and pulvinar to the receptive field properties of V2 neurons in the anesthetized and paralyzed monkey. Importantly, our results contradict both of these assumptions. We separately inactivated each of these three brain regions using GABA pressure injections, while simultaneously recording V2 single unit activity before and hours after inactivation. Recordings and GABA injections were carried out in topographically corresponding regions of the visual field. We outline the changes in V2 activity, responsiveness and receptive field properties for early, mid and late post-injection phases. Immediately after injection, V2 activity is globally suppressed. Subsequently, there is an increase in stimulus-driven relative to spontaneous neuronal activity, which improves the signal-to-noise coding for the oriented moving bars. Notably, V2 tuning properties change substantially relative to its pre-injection selectivity profile. The resulting increase or decrease in selectivity could not be readily predicted based on the selectivity profile of the inactivated site. Finally, V2 activity rebounds before returning to it pre-injection profile Our results show that feedback projections profoundly impact neuronal circuits in early visual areas, and may have been heretofore largely underestimated in their physiological role.

Assuntos

RESUMO

The aim of this study was to conduct cytoarchitectonic studies and choline acetyltransferase (ChAT) immunohistochemical analysis to delimit the cholinergic groups in the encephalon of the rock cavy (Kerodon rupestris), a crepuscular Caviidae rodent native to the Brazilian Northeast. Three young adult animals were anesthetized and transcardially perfused. The encephala were cut in the coronal plane using a cryostat. We obtained 6 series of 30-µm-thick sections. The sections from one series were subjected to Nissl staining. Those from another series were subjected to immunohistochemistry for the enzyme ChAT, which is used in acetylcholine synthesis, to visualize the different cholinergic neural centers of the rock cavy. The slides were analyzed using a light microscope and the results were documented by description and digital photomicrographs. ChAT-immunoreactive neurons were identified in the telencephalon (nucleus accumbens, caudate-putamen, globus pallidus, entopeduncular nucleus and ventral globus pallidus, olfactory tubercle and islands of Calleja, diagonal band of Broca nucleus, nucleus basalis, and medial septal nucleus), diencephalon (ventrolateral preoptic, hypothalamic ventrolateral, and medial habenular nuclei), and brainstem (parabigeminal, laterodorsal tegmental, and pedunculopontine tegmental nuclei). These findings are discussed through both a functional and phylogenetic perspective.

Assuntos

RESUMO

The present work had the objective of detecting the occurrence of Equine Piroplasmosis in horses housed in the 3rd Guards Cavalry Regiment (GCR) - Brazilian Army (BA) ˗ Porto Alegre, RS-Brazil, as well as to demonstrate the proactivity of PCR (Polymerase Chain Reaction) technique, aiming at the judicious use of the resources involved in the training and employment of Equines in the Brazilian Army. Fifty horses of the 3rd GCR - Porto Alegre ˗ RS, which are employed for Sport, Military Ceremonial, Law and Order Guarantee Operations (LOGO), were evaluated by means of the 18s r RNA screening with PCR technique, thirty eight horses with Babesia Caballi and Theileria Equi were detected, which corresponds to an incidence of 76% of the horses effective analyzed at the time. In this way, it can be verified that the Military activity have its "performance and effectiveness" factors threatened in case the health of the principal of his means employed, that is the horse, is compromised. The PCR technique then offers a reliable and feasible tool for the detection of Equine Piroplasmosis in BA horses.(AU)

O presente trabalho teve como objetivo detectar a ocorrência de Piroplasmose equina em cavalos alojados no 3º Regimento de Cavalaria de Guarda (RCG) - Exército Brasileiro (EB) - Porto Alegre, RS, Brasil, bem como demonstrar a forma proativa do método da PCR (reação em cadeia de polimerase), objetivando o uso criterioso dos recursos envolvidos no treinamento e emprego de equinos no Exército Brasileiro. Foram avaliados 50 cavalos da 3ª GCR-Porto Alegre, RS, empregados nas modalidades de: esporte, cerimonial militar e operações de garantia da lei e da ordem (GLO), por meio da triagem da região do genoma 18S rRNA mediante a aplicação do método da PCR. Foram positivas as amostras de 38 equinos para Babesia caballi e Theileria Equi, o que corresponde a uma incidência de 76% dos cavalos efetivos analisados na época. Dessa forma, verifica-se que as atividades militares tem seus fatores de "desempenho e efetividade" ameaçados no caso da saúde do principal de seus meios empregados, o Cavalo, estar comprometida. A técnica de PCR, então, oferece uma ferramenta confiável e viável para a detecção de Piroplasmose em equinos do EB.(AU)

Assuntos

RESUMO

The present work had the objective of detecting the occurrence of Equine Piroplasmosis in horses housed in the 3rd Guards Cavalry Regiment (GCR) - Brazilian Army (BA) ˗ Porto Alegre, RS-Brazil, as well as to demonstrate the proactivity of PCR (Polymerase Chain Reaction) technique, aiming at the judicious use of the resources involved in the training and employment of Equines in the Brazilian Army. Fifty horses of the 3rd GCR - Porto Alegre ˗ RS, which are employed for Sport, Military Ceremonial, Law and Order Guarantee Operations (LOGO), were evaluated by means of the 18s r RNA screening with PCR technique, thirty eight horses with Babesia Caballi and Theileria Equi were detected, which corresponds to an incidence of 76% of the horses effective analyzed at the time. In this way, it can be verified that the Military activity have its "performance and effectiveness" factors threatened in case the health of the principal of his means employed, that is the horse, is compromised. The PCR technique then offers a reliable and feasible tool for the detection of Equine Piroplasmosis in BA horses.(AU)

O presente trabalho teve como objetivo detectar a ocorrência de Piroplasmose equina em cavalos alojados no 3º Regimento de Cavalaria de Guarda (RCG) - Exército Brasileiro (EB) - Porto Alegre, RS, Brasil, bem como demonstrar a forma proativa do método da PCR (reação em cadeia de polimerase), objetivando o uso criterioso dos recursos envolvidos no treinamento e emprego de equinos no Exército Brasileiro. Foram avaliados 50 cavalos da 3ª GCR-Porto Alegre, RS, empregados nas modalidades de: esporte, cerimonial militar e operações de garantia da lei e da ordem (GLO), por meio da triagem da região do genoma 18S rRNA mediante a aplicação do método da PCR. Foram positivas as amostras de 38 equinos para Babesia caballi e Theileria Equi, o que corresponde a uma incidência de 76% dos cavalos efetivos analisados na época. Dessa forma, verifica-se que as atividades militares tem seus fatores de "desempenho e efetividade" ameaçados no caso da saúde do principal de seus meios empregados, o Cavalo, estar comprometida. A técnica de PCR, então, oferece uma ferramenta confiável e viável para a detecção de Piroplasmose em equinos do EB.(AU)

Assuntos

RESUMO

The objective of the present study was to evaluate the effect of treatment with prosta-glandin F2α (PGF2α) at the beginning of the protocol for ovulation synchronization on follicular dy-namics in Bos indicus (Gyr; n=11), Bos taurus (Holstein Black and White, HBW; n=10), and crossbred animals (Gyr x HBW; n=12). On a random day of the estrous cycles (day 0, D0), the animals received 2.0 mg estradiol benzoate (EB) intramuscularly plus an intravaginal progesterone (P4) device, which was maintained for 8 days (day 8, D8). Half the heifers of each group received a dose of 25 mg PGF2αintramuscularly at the time of insertion of the intravaginal P4 device. When the intravaginal device was removed (D8), all animals received another dose of 25 mg PGF2α intramuscularly, followed by intramuscular injection of 1.0 mg EB 24 h later (day 9, D9). Ultrasonographic evaluations were per-formed at intervals of 24 hours from D0 to D8 and at intervals of 12 hours from removal of the P4 device to 96 hours thereafter. Samples were collected on days 0, 3, 6, 8, 10 and 22 for the measurement of P4. The mean maximum diameter of the dominant follicle (DF) was smaller (P=0.01) in Gyr heifers (10.0 ± 0.8 mm) than in Gyr x HBW (13.0 ± 0.6 mm) or HBW (12.5 ± 0.8 mm). Furthermore, treatment with PGF2α on D0 increased (P=0.02) the maximum diameter of DF (12.9 ± 0.5 vs. 10.9 ± 0.7 mm)...

O objetivo do presente estudo foi avaliar o efeito do tratamento com prostaglandina F2α (PGF2α)no início do protocolo de sincronização da ovulação, sobre a dinâmica folicular de novilhas Bos indicus (Gir; n=11), Bos taurus (Holandesa Preto e Branco - HPB; n=10) e cruzadas (Gir x HPB; n=12). Em dia aleatório do ciclo estral (dia 0 - D0), os animais receberam 2,0 mg de benzoato de es-tradiol (BE) via intramuscular, mais um dispositivo intravaginal de progesterona (P4) que foi man-tido por oito dias (dia 8 – D8). Metade das novilhas de cada grupo recebeu uma dose de 25 mg de PGF2α via intramuscular no momento da inserção do dispositivo intravaginal de P4. Na retirada do dispositivo intravaginal (D8), todos os animais receberam outra dose de 25 mg de PGF2α via intra-muscular e 24 h após (dia 9 - D9) receberam 1,0 mg de BE via intramuscular. Foram realizadas ava-liações ultrassonográficas com intervalos de 24 horas do D0 até o D8 e com intervalos de 12 horas da retirada do dispositivo de P4 até 96 horas. Para a dosagem de P4, foram colhidas amostras nos dias 0; 3; 6; 8; 10 e 22. A média do diâmetro máximo do folículo dominante (FD) foi menor (P=0,01) nas novilhas Gir (10,0 ± 0,8 mm) do que nas cruzadas Gir x HPB (13,0 ± 0,6 mm) ou HPB (12,5 ± 0,8 mm). Além disso, o tratamento com PGF2α no D0 aumentou (P=0,02) o diâmetro máximo do FD (12,9 ± 0,5 mm vs. 10,9 ± 0,7 mm) nos três grupamentos genéticos avaliados. A taxa de crescimento do FD foi menor (P=0,008) nas novilhas Gir (0,8 ± 0,1 mm/dia), do que nas novilhas cruzadas (1,3 ± 0,1 mm/dia) ou HPB (1,2 ± 0,1 mm/dia)...

Assuntos

RESUMO

The objective of the present study was to evaluate the effect of treatment with prosta-glandin F2α (PGF2α) at the beginning of the protocol for ovulation synchronization on follicular dy-namics in Bos indicus (Gyr; n=11), Bos taurus (Holstein Black and White, HBW; n=10), and crossbred animals (Gyr x HBW; n=12). On a random day of the estrous cycles (day 0, D0), the animals received 2.0 mg estradiol benzoate (EB) intramuscularly plus an intravaginal progesterone (P4) device, which was maintained for 8 days (day 8, D8). Half the heifers of each group received a dose of 25 mg PGF2αintramuscularly at the time of insertion of the intravaginal P4 device. When the intravaginal device was removed (D8), all animals received another dose of 25 mg PGF2α intramuscularly, followed by intramuscular injection of 1.0 mg EB 24 h later (day 9, D9). Ultrasonographic evaluations were per-formed at intervals of 24 hours from D0 to D8 and at intervals of 12 hours from removal of the P4 device to 96 hours thereafter. Samples were collected on days 0, 3, 6, 8, 10 and 22 for the measurement of P4. The mean maximum diameter of the dominant follicle (DF) was smaller (P=0.01) in Gyr heifers (10.0 ± 0.8 mm) than in Gyr x HBW (13.0 ± 0.6 mm) or HBW (12.5 ± 0.8 mm). Furthermore, treatment with PGF2α on D0 increased (P=0.02) the maximum diameter of DF (12.9 ± 0.5 vs. 10.9 ± 0.7 mm)...(AU)

O objetivo do presente estudo foi avaliar o efeito do tratamento com prostaglandina F2α (PGF2α)no início do protocolo de sincronização da ovulação, sobre a dinâmica folicular de novilhas Bos indicus (Gir; n=11), Bos taurus (Holandesa Preto e Branco - HPB; n=10) e cruzadas (Gir x HPB; n=12). Em dia aleatório do ciclo estral (dia 0 - D0), os animais receberam 2,0 mg de benzoato de es-tradiol (BE) via intramuscular, mais um dispositivo intravaginal de progesterona (P4) que foi man-tido por oito dias (dia 8 D8). Metade das novilhas de cada grupo recebeu uma dose de 25 mg de PGF2α via intramuscular no momento da inserção do dispositivo intravaginal de P4. Na retirada do dispositivo intravaginal (D8), todos os animais receberam outra dose de 25 mg de PGF2α via intra-muscular e 24 h após (dia 9 - D9) receberam 1,0 mg de BE via intramuscular. Foram realizadas ava-liações ultrassonográficas com intervalos de 24 horas do D0 até o D8 e com intervalos de 12 horas da retirada do dispositivo de P4 até 96 horas. Para a dosagem de P4, foram colhidas amostras nos dias 0; 3; 6; 8; 10 e 22. A média do diâmetro máximo do folículo dominante (FD) foi menor (P=0,01) nas novilhas Gir (10,0 ± 0,8 mm) do que nas cruzadas Gir x HPB (13,0 ± 0,6 mm) ou HPB (12,5 ± 0,8 mm). Além disso, o tratamento com PGF2α no D0 aumentou (P=0,02) o diâmetro máximo do FD (12,9 ± 0,5 mm vs. 10,9 ± 0,7 mm) nos três grupamentos genéticos avaliados. A taxa de crescimento do FD foi menor (P=0,008) nas novilhas Gir (0,8 ± 0,1 mm/dia), do que nas novilhas cruzadas (1,3 ± 0,1 mm/dia) ou HPB (1,2 ± 0,1 mm/dia)...(AU)

Assuntos

RESUMO

The selection of offspring from the desired sex can be one of the determining factors to increase the genetic progress and farmer ́s profitability in either beef or dairy cattle. In fact, the use of sex-sorted sperm has been applied worldwide combined with artificial insemination (AI) upon estrus detection in heifers. Additionally, several researches have been performed aiming to investigate the use of sex-sorted sperm during timed AI (TAI) programs and for insemination of superstimulated donors for in vivo embryo programs. Pregnancy per AI (P/AI) of cyclic heifers inseminated in estrus with sex-sorted sperm has been reported to be approximately 75 to 80% of the P/AI of heifers inseminated with non-sorted sperm. Insemination of superstimulated cows with sex-sorted sperm has been reported to reduce the production of viable embryos. Recently, however, it has been demonstrated that P/AI and embryo production per flushing resulting from AI with sex-sorted sperm may be improved when the time of AI is postponed in relation to the time of AI with non-sorted sperm. The P/AI of non stimulated females and fertilization rates and number of embryos recovered from superstimulated females were increased when AI occurred between 16 and 24 h after the onset of estrus (i.e. 6 to 14 h before ovulation). Nonetheless, despite the improvements achieved in the last decade, there is still a significant individual variability in fertility among bulls that have their sperm se x-sorted. It is critical that the pre-determination of the sire fertility is a paramount when sex-sorted sperm is utilized in commercial AI and ET programs. Thus, the aim of this review is to discuss the main concepts related to the use of sex-sorted sperm in TAI and ET programs, addressing some strategies to increase the efficiency of the technique.

Assuntos

RESUMO

The selection of offspring from the desired sex can be one of the determining factors to increase the genetic progress and farmer ́s profitability in either beef or dairy cattle. In fact, the use of sex-sorted sperm has been applied worldwide combined with artificial insemination (AI) upon estrus detection in heifers. Additionally, several researches have been performed aiming to investigate the use of sex-sorted sperm during timed AI (TAI) programs and for insemination of superstimulated donors for in vivo embryo programs. Pregnancy per AI (P/AI) of cyclic heifers inseminated in estrus with sex-sorted sperm has been reported to be approximately 75 to 80% of the P/AI of heifers inseminated with non-sorted sperm. Insemination of superstimulated cows with sex-sorted sperm has been reported to reduce the production of viable embryos. Recently, however, it has been demonstrated that P/AI and embryo production per flushing resulting from AI with sex-sorted sperm may be improved when the time of AI is postponed in relation to the time of AI with non-sorted sperm. The P/AI of non stimulated females and fertilization rates and number of embryos recovered from superstimulated females were increased when AI occurred between 16 and 24 h after the onset of estrus (i.e. 6 to 14 h before ovulation). Nonetheless, despite the improvements achieved in the last decade, there is still a significant individual variability in fertility among bulls that have their sperm se x-sorted. It is critical that the pre-determination of the sire fertility is a paramount when sex-sorted sperm is utilized in commercial AI and ET programs. Thus, the aim of this review is to discuss the main concepts related to the use of sex-sorted sperm in TAI and ET programs, addressing some strategies to increase the efficiency of the technique. (AU)

Assuntos

RESUMO

The present study evaluated the effect of the type of norgestomet ear implant (new vs. used) on the ovarian follicular response (experiment 1) and pregnancy per artificial insemination (AI) (P/AI; experiment 2) of beef heifers subjected to an estradiol plus progestin timed artificial insemination (TAI) program. In experiment 1, 57 cyclic beef heifers were randomly assigned to one of two groups according to the type (new or previously used for 9 days) of norgestomet ear (NORG) implant. At the time of NORG implant insertion, the heifers were treated with 2 mg of intramuscular estradiol benzoate. Eight days later, the NORG implants were removed, and the heifers received an intramuscular administration of 150 µg of d-cloprostenol, 300 IU of equine chorionic gonadotropin, and 0.5 mg of estradiol cypionate. The heifers had their ovaries scanned every 12 hours from the time of NORG implant removal to 96 hours after verifying the occurrence and timing of ovulation. No difference (P = 0.89) was observed in the ovulation rates between the two treatments (new = 80.0%; 24/30 vs. used = 81.5%; 22/27). However, the heifers treated with a used NORG implant had (P = 0.04) higher proportion (36.4%; 8/22) of early ovulation (between 36 and 48 hours after NORG implant removal) compared with the heifers treated with a new NORG implant (8.3%; 2/24). In experiment 2, at the beginning of the synchronization protocol, 416 beef heifers were randomly assigned into two groups, as described in the experiment 1. Two days after the NORG implant removal, the heifers were reassigned to be inseminated at 48 or 54 hours after NORG implant removal. There was an interaction (P = 0.03) between the type of NORG implant and the timing of TAI on P/AI. The timing of insemination only had an effect (P = 0.02) on the P/AI when the heifers were treated with a used NORG implant [(TAI 54 hours = 41.9% (44/105) vs. TAI 48 hours = 58.6% (58/99)]. In conclusion, beef heifers synchronized with a used NORG implant plus estradiol exhibited a higher proportion of earlier ovulations, and TAI in these heifers should be performed 48 hours after removal of used NORG implants.

Assuntos

RESUMO

Two experiments were conducted to evaluate the effects of equine chorionic gonadotropin (eCG) treatment on ovarian follicular response, luteal function, and pregnancy in buffaloes subjected to a timed artificial insemination (TAI) protocol during the nonbreeding season. In experiment 1, 59 buffalo cows were randomly assigned to two groups (with and without eCG). On the first day of the synchronization protocol (Day 0), cows received an intravaginal progesterone (P4) device plus 2.0 mg estradiol benzoate im. On Day 9, the P4 device was removed, all cows were given 0.150 mg PGF(2α) im, and half were given 400 IU eCG im. On Day 11, all cows were given 10 µg of buserelin acetate im (GnRH). Transrectal ultrasonography of the ovaries was performed on Days 0 and 9 to determine the presence and diameter of the largest follicle; between Days 11 and 14 (12 hours apart), to evaluate the dominant follicle diameter and the interval from device removal to ovulation; and on Days 16, 20, and 24 to measure CL diameter. Blood samples were collected on Days 16, 20, and 24 to measure serum P4. In experiment 2, 256 buffaloes were assigned to the same treatments described in experiment 1, and TAI was performed 16 hours after GnRH treatment. Pregnancy diagnosis was performed by ultrasonography 30 days after TAI. Treatment with eCG increased the maximum diameter of dominant follicles (P = 0.09), ovulation rate (P = 0.05), CL diameter (P = 0.03), and P4 concentrations (P = 0.01) 4 days after TAI, and pregnancy per AI (52.7%, 68/129 vs. 39.4%, 50/127; P = 0.03). Therefore, eCG improved ovarian follicular response, luteal function during the subsequent diestrus, and fertility for buffalo subjected to a TAI synchronization protocol during the nonbreeding season.

Assuntos

RESUMO

Two experiments were designed to evaluate the effect of different insemination times (12 and 24h or 18 and 30h) and different types of semen (sex-sorted or non-sorted sperm) on embryo production in Nelore (Bos indicus) and Holstein (Bos taurus) superstimulated donors. In the first experiment, hormonal superstimulation of ovarian follicular development in Nelore donors (n=71) was performed in randomly allocated animals to one of the three treatment groups, and they were inseminated at 12 and 24h after an ovulatory stimulus with pLH treatment was applied, either with sex-sorted (4.2×10(6) sperm/insemination; S12/24; n=17) or non-sorted sperm (20×10(6) sperm/insemination; NS12/24; n=18), or they were inseminated at 18 and 30h using sex-sorted sperm (4.2×10(6) sperm/insemination; S18/30; n=19). A greater number of transferable embryos were found when sex-sorted sperm was used to inseminate the animals at 18 and 30h (4.5±3.0) compared to insemination at 12 and 24h (2.4±1.8; P<0.001). However, a greater embryo production (6.8±2.6) was obtained with non-sorted sperm. In the second experiment, the same insemination times and semen types were used in lactating high-production Holstein cows (n=12). A crossover design was employed in this trial. A lesser embryo production (P=0.007) was found in Holstein donors that were inseminated using sex-sorted sperm at 12 and 24h (4.6±3.0) compared to non-sorted sperm (8.7±2.8). However, intermediate results were obtained when the inseminations with sex-sorted sperm were performed at 18 and 30h (6.4±3.1). These results supported the current hypothesis that it is possible to improve embryo production using sex-sorted sperm in B. indicus and B. taurus superstimulated donors when the inseminations are performed near the same time as time-synchronized ovulations. However, the embryo production for timed artificial insemination (TAI) with sex-sorted sperm was still less than the production with non-sorted sperm.

Assuntos

RESUMO

1. In the present study, we investigated the influence of the pulvinar nucleus upon response properties of single cells in the second visual area (V2) of Cebus monkeys. The method used consisted of the inactivation of a portion of the lateral pulvinar by GABA injections while studying the response properties of cells in V2 at the same visuotopic location as that of the inactivation. 2. After GABA injection in the pulvinar, most cells in V2 (67%) showed changes in spontaneous and/or stimulus-driven activities. Contrary to the effect found with inactivation of the striate cortex, which promotes a reduction in the response of V2 neurons, we found that the main effect of pulvinar inactivation was an increment in stimulus-driven responses of V2 cells (39% of units studied). A reduction of responses was observed in 27% of units. 3. A change in orientation and/or direction selectivity was found in 91% of cells after inactivation of the pulvinar. Most commonly, the orientation selectivity of a neuron was decreased during pulvinar inactivation. 4. The inactivation results indicate that the pulvinar projections have a modulatory effect on the activity of V2 cells.

Assuntos

RESUMO

We examined the distribution of the enzyme dihydronicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) in the superior colliculus (SC) of the New World monkey Cebus apella, and the co-localization of this enzyme with the calcium-binding proteins (CaBPs) calbindin-D28K, parvalbumin and calretinin. Despite the intensely labeled neuropil, rare NADPH-d-positive cells were observed in the stratum griseum superficiale (SGS). Most of the labeled cells in the SC were found in the intermediate layers, with a great number also in the deeper layers. This pattern is very similar to that described in the opossum (Didelphis marsupialis) and in the cat, and different from the pattern found in the rat, which shows labeled cells mainly in the SGS. Cells doubly stained for NADPH-d and CaBPs were observed throughout the SC, although in a small number. Of the NADPH-d-positive cells, 20.3% were doubly labeled for NADPH-d and parvalbumin, 10.2% revealed co-localization with calretinin, and 5.6% with calbindin. The low number of double-stained cells for NADPH-d and the CaBPs indicates that these molecules must participate in different functional circuits within the SC.

Assuntos

RESUMO

We studied the distribution of the calcium-binding proteins calbindin, parvalbumin and calretinin, in the superior colliculus and in the lateral geniculate nucleus of Cebus apella, a diurnal New World monkey. In the superior colliculus, these calcium-binding proteins show different distribution patterns throughout the layers. After reaction for calretinin one observes a heavy staining of the neuropil with few labeled cells in superficial layers, a greater number of large and medium-sized cells in the stratum griseum intermediale, and small neurons in deep layers. The reaction for calbindin revealed a strong staining of neuropil with a large number of small and well stained cells, mainly in the upper half of the stratum griseum superficiale. Intermediate layers were more weakly stained and depicted few neurons. There were few immunopositive cells and little neuropil staining in deep layers. The reaction for parvalbumin showed small and medium-sized neurons in the superficial layers, a predominance of large stellate cells in the stratum griseum intermediale, and medium-sized cells in the deep layers. In the lateral geniculate nucleus of Cebus, parvalbumin is found in the cells of both the P and M pathways, whereas calbindin is mainly found in the interlaminar and S layers, which are part of the third visual pathway. Calretinin was only found in cells located in layer S. This pattern is similar to that observed in Macaca, showing that these calcium-binding proteins reveal different components of the parallel visual pathways both in New and Old World monkeys.

Assuntos

RESUMO

Based on cytoarchitectonic criteria, the primate pulvinar nucleus has been subdivided into medial (PM), lateral (PL), and inferior (PI) regions. However, these subdivisions show no correlation with those established by electrophysiological, immunocytochemical, or neuroanatomical tracer studies. In this work, we studied the connections of the pulvinar nucleus of Cebus monkey with visual areas V1, V2, V4, MT, and PO by means of retrograde fluorescent tracers injected into these areas. Based on the projection zones to cortical visual areas, the visual portion of the pulvinar of Cebus monkey was subdivided into three subregions: P1, P2, and P3, similar to those described in the macaque (Ungerleider et al., 1984). In Cebus, P1 includes the centrolateral portion of traditionally defined PI and adjacent portion of PL. P2 is located in the dorsal portion of PL and P3 includes the medial portion of PI and extends dorsally into adjacent PL and PM. In addition, we studied the histology of the pulvinar using multiple criteria, such as cytoarchitecture and myeloarchitecture; histochemistry for cytochrome oxidase, NADPH-diaphorase, and acetylcholinesterase; and immunocytochemistry for two calcium-binding proteins, calbindin and parvalbumin, and for a neurofilament recognized by the SMI-32 antibody. Some of these stains, mainly calbindin, showed additional subdivisions of the Cebus pulvinar, beyond the traditional PI, PL, and PM. Based on this immunohistochemical staining, the border of PI is moved dorsally above the brachium of the superior colliculus and PI can be subdivided in five regions (PI(P), PI(M), PI(C), PI(L), and PI(LS)). Regions P1, P2, and P3 defined based on efferent connections with cortical visual areas are not architectonically/neurochemically homogeneous. Rather they appear to consist of further chemoarchitectonic subdivisions. These distinct histochemical regions might be related to different functional modules of visual processing within one connectional area.

Assuntos

RESUMO

Cortical projections to the middle temporal (MT) visual area were studied by injecting the retrogradely transported fluorescent tracer Fast Blue into MT in adult New World monkeys (Cebus apella). Injection sites were selected based on electrophysiological recordings, and covered eccentricities from 2-70 deg, in both the upper and lower visual fields. The position and laminar distribution of labeled cell bodies were correlated with myeloarchitectonic boundaries and displayed in flat reconstructions of the neocortex. Topographically organized projections were found to arise mainly from the primary, second, third, and fourth visual areas (V1, V2, V3, and V4). Coarsely topographic patterns were observed in transitional V4 (V4t), in the parieto-occipital and parieto-occipital medial areas (PO and POm), and in the temporal ventral posterior area (TVP). In addition, widespread or nontopographic label was found in visual areas of the superior temporal sulcus (medial superior temporal, MST, and fundus of superior temporal, FST), annectent gyrus (dorsointermediate area, DI; and dorsomedial area, DM), intraparietal sulcus (lateral intraparietal, LIP; posterior intraparietal, PIP; and ventral intraparietal, VIP), and in the frontal eye field (FEF). Label in PO, POm, and PIP was found only after injections in the representation of the peripheral visual field (> 10 deg), and label in V4 and FST was more extensive after injections in the central representation. The projections from V1 and V2 originated predominantly from neurons in supragranular layers, whereas those from V3, V4t, DM, DI, POm, and FEF consisted of intermixed patches with either supragranular or infragranular predominance. All of the other projections were predominantly infragranular. Invasion of area MST by the injection site led to the labeling of further pathways, including substantial projections from the dorsal prelunate area (DP) and from an ensemble of areas located along the medial wall of the hemisphere. In addition, weaker projections were observed from the parieto-occipital dorsal area (POd), area 7a, area prostriata, the posterior bank of the arcuate sulcus, and areas in the anterior part of the lateral sulcus. Despite the different nomenclatures and areal boundaries recognized by different models of simian cortical organization, the pattern of projections to area MT is remarkably similar among primates. Our results provide evidence for the existence of many homologous areas in the extrastriate visual cortex of New and Old World monkeys.

Assuntos

RESUMO

The representation of the two eyes in striate cortex (V1) of Cebus monkeys was studied by electrophysiological single-unit recordings in normal animals and by morphometric analysis of the pattern of ocular dominance (OD) stripes, as revealed by cytochrome oxidase histochemistry in V1 flat-mounts of enucleated animals. Single-unit recordings revealed that the large majority of V1 neurons respond to the stimulation of either eye but are more strongly activated by one of them. As in other species of monkey, neurons with preference for the stimulation of the same eye are grouped in columns 300-400 microns wide, spanning all cortical layers. Monocular neurons are clustered in layer IVc, specially in its deeper half (IVc-beta), and constitute less than 10% of the population of other layers. Neurons with equal responses to each eye are more commonly found in layer V than elsewhere in V1. In the supragranular layers and in granular layer IVc-alpha neurons strongly dominated by one of the eyes tend to be broadly tuned for orientation, while binocularly balanced neurons tend to be sharply tuned for this parameter. No such correlation was detected in the infragranular layers, and most neurons in layer IVc-beta responded regardless of stimulus orientation. Ocular dominance stripes are present throughout most of V1 as long, parallel or bifurcating bands alternately dominated by the ipsi- or the contralateral eye. They are absent from the cortical representations of the blind spot and the monocular crescent. The domains of each eye occupy nearly equal portions of the surface of binocular V1, except for the representation of the periphery, where the contralateral eye has a larger domain, and a narrow strip along the border of V1 with V2, where either eye may predominate. The orderliness of the pattern of stripes and the relationship between stripe arrangement and the representation of the visual meridians vary with eccentricity and polar angle but follow the same rules in different animals. These results demonstrate that the laminar, columnar and topographic distribution of neurons with different degrees of OD in V1 is qualitatively similar in New- and Old World monkeys of similar sizes and suggest that common ancestry, rather than parallel evolution, may account for the OD phenotypes of contemporaneous simians.

Assuntos

RESUMO

We have studied the tangential distribution of cytochrome oxidase (cytox)-rich patches in striate cortex of normal and monocularly enucleated Cebus apella monkeys. Patch spatial density and patch cross-sectional area were analysed in cytox-reacted tangential sections of flat-mounted preparations of V1. In the upper cortical layers of V1, and specially in the middle of layer III, the Cebus has well-delimited cytox-rich patches. Rows of patches are less conspicuous in Cebus than in Old World monkeys. The spatial density of patches is nearly constant throughout the binocular field representation in V1, with a mean value of 4 patches per mm2. In the monocular portions of V1, however, patch spatial density diminishes. In most cases, mean patch cross-sectional area decreases slightly towards the representation of the periphery in V1. However, patches in the representation of the monocular crescent tend to be larger than those in the adjacent binocular representation. The small variation of cytox patch topography with eccentricity contrasts with the large variation of cortical point-image size in V1. In monocularly enucleated monkeys, patches are larger and darker above and below the ocular dominance stripes of the remaining eye than in the alternate stripes. After long-term enucleation, the patches corresponding to the remaining eye columns appeared larger than in normal controls. In contrast, there is no difference in size between the patches located in the deprived and undeprived monocular crescent representations, although both patch and interpatch regions are darker staining in the latter. These results suggest the existence of competitive interactions which modify the cortical intrinsic organization even in adult monkeys.

Assuntos