RESUMEN
Between January 2005 and December 2006, the larval habitats and seasonal abundances of 21 species of Culicoides (Diptera: Ceratopogonidae) found in association with livestock on a farm in northern Sardinia were studied. Culicoides were collected using two light traps (one placed in a sheep shed and the other near water ponds) and reared from mud collected in and along the margins of a small and a large water pond. The mammalophilic Culicoides imicola Kieffer and Culicoides newsteadi Austen were the most prevalent (>95%) of 20 species in the sheep shed, whereas the ornithophilic Culicoides univittatus Vimmer, Culicoides sahariensis Kieffer, Culicoides festivipennis Kieffer, Culicoides circumscriptus Kieffer and Culicoides cataneii Clastrier were most abundant in the traps set at the ponds (73%) and in 16 species of Culicoides reared from laboratory-maintained mud samples retrieved from three microhabitats (a non-vegetated pond shoreline, 20 cm above a pond shoreline, the shoreline of a secondary, permanently inundated, grass-covered pool). The species reared most abundantly from along the pond shoreline were C. festivipennis, C. circumscriptus and C. sahariensis, whereas those most prevalent at the grassed pool were C. cataneii and C. festivipennis. C. imicola was found to breed preferentially in mud 20 cm above the pond shoreline, whereas C. newsteadi was restricted almost entirely to the grassed pool, which had a high organic matter content. Using the light trap and adult emergence data, the seasonal abundance patterns of the eight species of Culicoides were determined. In general, there was good correspondence between light trap catches and emergence trends. Well-defined emergence peaks indicate four or five generations for C. festivipennis and C. circumscriptus and three generations for C. cataneii, C. newsteadi and Culicoides jumineri Callot & Kremer. The emergence trends for C. imicola and C. sahariensis were unimodal, but, because they stretched over several months, indicated that a number of overlapping generations had occurred. Adults of C. imicola were reared and captured only sporadically in the first half of the year, gradually building to a peak in autumn. Conversely, C. newsteadi was reared throughout the year and displayed three clearly defined peaks (in winter, spring and autumn); captures of C. newsteadi in the light traps peaked in May-June and again to a lesser extent in autumn. In Sardinia the late seasonal peak in the abundance of C. imicola occurs in synchrony with outbreaks of bluetongue (BT) in sheep, which is consistent with earlier findings elsewhere in the Mediterranean basin and in Africa that it is the principal vector of bluetongue virus (BTV). Although the status of C. newsteadi as a vector of BTV is not known, its low-level presence in winter and heightened abundances in spring may provide a pathway along which the virus can overwinter.
Asunto(s)
Ceratopogonidae/fisiología , Ecosistema , Insectos Vectores/fisiología , Estaciones del Año , Ovinos/parasitología , Animales , Biodiversidad , Cruzamiento , Italia , Larva , Densidad de Población , Agua/parasitologíaRESUMEN
Spermatogenesis is the process of proliferating and differentiating germ cells that require highly coordinated cellular interactions. Intercellular junctions are important in maintaining communication between testicular cells. In particular, gap junctions play an important role in this event. Connexin43 (Cx43) is the most abundant protein forming a gap junction in a vertebrate testis. It is expressed in several cells types of Rana esculenta testes. The use of reverse transcriptase-PCR analysis demonstrates that expression levels of Cx43 are regulated by estradiol and testosterone in both in vivo and in vitro experiments.
Asunto(s)
Conexina 43/metabolismo , Regulación de la Expresión Génica/genética , Hormonas Esteroides Gonadales/metabolismo , Rana esculenta/metabolismo , Testículo/metabolismo , Animales , Conexina 43/genética , MasculinoRESUMEN
The olive fly, Bactrocera oleae, is the key pest on olives in the Mediterranean area. The pest can destroy, in some cases, up to 70% of the olive production. Its control relies mainly on chemical treatments, sometimes applied by aircraft over vast areas, with their subsequent ecological and toxicological side effects. Bacillus thuringiensis is a spore-forming soil bacterium which produces a protein crystal toxic to some insects, including the orders of Lepidoptera, Diptera, and Coleoptera and other invertebrates. The aim of this study was to search for isolates toxic to B. oleae. Several hundred B. thuringiensis isolates were obtained from olive groves and olive presses in different areas of Greece, Sardinia (Italy), and Spain and from cooperating scientists throughout the world. Some isolates were found toxic only to adults or larvae and some to both stages of the olive fly. In addition, the most toxic isolates were assayed on Opius concolor Szepl. (Hym. Braconidae), the most important parasitoid of the olive fruit fly. Only 3 isolates out of 14 gave significant mortality against this parasitoid. Several of the most toxic crystalliferous isolates may contain novel toxins since they gave no PCR products when probed with primers specified for 39 known toxin genes.
Asunto(s)
Bacillus thuringiensis , Dípteros/microbiología , Larva/microbiología , Animales , Bacillus thuringiensis/aislamiento & purificación , Proteínas Bacterianas/genética , Cartilla de ADN , Reacción en Cadena de la Polimerasa , TemperaturaRESUMEN
In the present study, the antidepressant efficacy of a controlled-release (CR) formulation of trazodone was evaluated in 18 depressed patients treated with 150 mg (no. = 10) or 75 mg (no. = 8) nocte doses of the drug for 7 weeks, according to an open design. Drug plasma levels were evaluated on days 7, 14, 28 and 35 of treatment. Moreover, at the end of treatment, the plasma concentration-time curve of the CR trazodone was assessed. CR trazodone was effective in improving depressive and anxious symptomatology as well as in ameliorating the quality of sleep in 13 patients with a low incidence of side effects. Nonresponder subjects had morning plasma levels of trazodone below the value of 650 ng/ml. The pharmacokinetic profile of CR trazodone, observed after 35 days of treatment, may account for both the low occurrence of untoward side effects and the therapeutic efficacy of the single dose at nighttime.
Asunto(s)
Trastorno Depresivo/tratamiento farmacológico , Trazodona/sangre , Trazodona/uso terapéutico , Adulto , Anciano , Relación Dosis-Respuesta a Droga , Femenino , Humanos , Masculino , Persona de Mediana Edad , Trazodona/administración & dosificación , Resultado del TratamientoRESUMEN
The pharmacokinetic and pharmacodynamic characteristics of a controlled-release (CR) formulation of trazodone were evaluated in healthy subjects who received acutely 150 mg and 75 mg of the CR trazodone and equal amounts of the conventional formulation on separate occasions. Plasma trazodone concentrations were measured by HPLC. The pharmacokinetic profile of CR trazodone was characterized by a slower increase in drug plasma levels and a lower and retarded peak plasma concentration without any modification in the total amount of trazodone absorbed over 24 hrs. The side effects were less severe and less frequent than with the conventional formulation.
Asunto(s)
Trazodona/farmacología , Trazodona/farmacocinética , Adulto , Preparaciones de Acción Retardada , Relación Dosis-Respuesta a Droga , Femenino , Humanos , Masculino , Valores de ReferenciaRESUMEN
The correlation between prolactin (PRLR) and oestrogen (ER) or progesterone receptors (PgR) in breast cancer and a possible prognostic significance of PRLR at 10 year follow-up have been investigated in the Naples (GUN) adjuvant trial. A total of 308 pre- and post-menopausal patients with early breast cancer, who entered the trial from 1 February 1978 to 31 December 1983, received randomly Tamoxifen (TM), 30 mg per die for 2 years, or no therapy. PRLR status was known in 229 (74.3%) patients. Values of specific binding less than 1% were considered negative. PRLR was positive in 75/229 (32.8%). ER was assayed in 210/229 (91.7%) patients and PgR in 188/229 (82.1%). No significant correlation, by the Spearman test, was found between PRLR and ER or PgR, while ER status was highly interrelated with PgR status. By the Cox model no evidence of an independent prognostic role of PRLR on disease-free survival (DFS) was observed, nor an interaction between PRLR and adjuvant treatment with TM was found.
Asunto(s)
Neoplasias de la Mama/química , Receptores de Estrógenos/análisis , Receptores de Progesterona/análisis , Receptores de Prolactina/análisis , Adulto , Neoplasias de la Mama/mortalidad , Femenino , Estudios de Seguimiento , Humanos , Persona de Mediana Edad , Pronóstico , Tasa de SupervivenciaRESUMEN
Ten year disease-free survival (DFS) results of the Naples randomized trial of adjuvant tamoxifen (TM), 30 mg per day for 2 years versus no therapy according to receptor levels, are reported. From Feb. 1, 1978, through Dec. 31, 1983, 308 pre- and postmenopausal patients with early breast cancer entered the trial. Estrogen receptor (ER) data were available on 239 (77.6%) patients, progesterone receptor (PgR) data on 194 (63.0%), and both receptor data on 181 (58.8%). ER and PgR were assayed by dextran-coated charcoal technique in a single laboratory. The effect of adjuvant TM was significantly related to ER and PgR concentration of the primary tumor. The greatest TM benefit on DFS was evident in patients with the highest levels of receptors. The interaction between the treatment effect and receptor concentration was found whether ER and PgR were considered separately or together.
Asunto(s)
Neoplasias de la Mama/tratamiento farmacológico , Receptores de Estrógenos/análisis , Receptores de Progesterona/análisis , Tamoxifeno/uso terapéutico , Adulto , Anciano , Neoplasias de la Mama/metabolismo , Terapia Combinada , Femenino , Estudios de Seguimiento , Humanos , Menopausia , Persona de Mediana Edad , Estadificación de NeoplasiasRESUMEN
Steady-state plasma levels of trazodone were determined by HPLC in 11 elderly depressed patients who underwent a 5-week pharmacological treatment with 150 mg/day trazodone in three oral administrations. Clinical antidepressant response, assessed with three different clinical improvement criteria, was significantly correlated with steady-state plasma trazodone concentrations. Moreover, the steady-state plasma trazodone concentration of 650 ng/ml was identified as the threshold value for a good antidepressant response. No correlation was found between the occurrence of side effects and plasma levels of trazodone.
Asunto(s)
Trastorno Depresivo/tratamiento farmacológico , Trazodona/administración & dosificación , Administración Oral , Anciano , Trastorno Depresivo/sangre , Trastorno Depresivo/psicología , Relación Dosis-Respuesta a Droga , Femenino , Humanos , Masculino , Persona de Mediana Edad , Escalas de Valoración Psiquiátrica , Trazodona/farmacocinéticaRESUMEN
Treatment with tamoxifen (TM), alone or in combination with cyclophosphamide, methotrexate, and fluorouracil (CMF), was used as an adjuvant to surgery in 433 patients with stage I, II, or III(T3a) breast cancer. Oestrogen receptors (ER) and progesterone (PgR) receptors were assayed in most cases. 308 premenopausal node-negative and postmenopausal node-negative or node-positive patients were randomised to receive TM, 30 mg daily for 2 years, or no further therapy. 125 premenopausal node-positive patients were randomised to receive either CMF for nine courses plus TM or CMF alone. After a median follow-up of 63 months TM significantly reduced the incidence of relapses and deaths compared with no therapy. A significant interaction between treatment effect and ER/PgR status was seen. Disease-free and overall survival were similar after treatment with CMF+ TM or CMF.
Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Neoplasias de la Mama/tratamiento farmacológico , Tamoxifeno/uso terapéutico , Adulto , Anciano , Neoplasias de la Mama/análisis , Neoplasias de la Mama/mortalidad , Neoplasias de la Mama/cirugía , Ensayos Clínicos como Asunto , Terapia Combinada , Ciclofosfamida/administración & dosificación , Ciclofosfamida/efectos adversos , Evaluación de Medicamentos , Femenino , Fluorouracilo/administración & dosificación , Fluorouracilo/efectos adversos , Estudios de Seguimiento , Humanos , Italia , Metástasis Linfática , Menopausia/sangre , Metotrexato/administración & dosificación , Metotrexato/efectos adversos , Persona de Mediana Edad , Recurrencia Local de Neoplasia/prevención & control , Cooperación del Paciente , Pronóstico , Distribución Aleatoria , Receptores de Estrógenos/análisis , Receptores de Progesterona/análisis , Tamoxifeno/administración & dosificación , Tamoxifeno/efectos adversosRESUMEN
The binding of 125I-labeled ovine prolactin (oPRL) to membrane preparations of several tissues from the male green frog, Rana esculenta, collected during the year is reported. PRL binding to kidney fractions was generally high (range 5-45%). A maximum was observed in the month of October, whereas the lowest value was found during the summer season. The binding to skin fractions was equally high (range 5-25%) and the annual profile parallels that of renal fractions. In the liver, a lower specific binding (range 3-4%) occurred consistently during the year, whereas no detectable binding was found in the muscle. The 125I-oPRL binding was inhibited by oPRL and oGH but not by oFSH or oLH. Scatchard analysis gave dissociation constants of 0.4-1 x 10(-10) M and binding capacity of about 20 fmol/mg of membrane proteins was observed in both the skin and kidney fractions. No receptor sites were detectable in 30-day hypophysectomized animals. The administration of oPRL or a crude homogenate of the frog hypophysis induced the appearance of specific PRL binding. Testosterone is able to restore prolactin binding in hypophysectomized animals, as PRL treatment does.
Asunto(s)
Rana esculenta/fisiología , Receptores de Prolactina/análisis , Animales , Hipofisectomía , Riñón/fisiología , Masculino , Microsomas/metabolismo , Microsomas Hepáticos/metabolismo , Prolactina/farmacocinética , Prolactina/farmacología , Rana esculenta/metabolismo , Receptores Androgénicos/análisis , Receptores de Prolactina/biosíntesis , Estaciones del Año , Fenómenos Fisiológicos de la Piel , Testosterona/farmacocinética , Testosterona/farmacologíaRESUMEN
The female of the Mexican leaf frog, Pachymedusa dacnicolor, displays a marked annual ovarian cycle. This consists of a long period of vitellogenic stasis, starting in early fall, soon after the breeding season, and ending in early spring. Oogonial proliferation continues throughout the year and new previtellogenic follicles are formed continuously. During the period of vitellogenesis, from spring to early summer, early, advanced, and postvitellogenic follicles are all found together, a situation that continues through the breeding season. This is correlated with the fact that a breeding female can lay three or more clutches per season. Breeding can begin as early as June and end as late as early September, with peak spawning activity taking place during July and August. An examination of the ovarian hormone secretion pattern in P. dacnicolor during the year revealed that plasma levels of testosterone and estradiol correlated with ovarian growth and attained highest levels in amplectant and ovulating females. Both hormones showed quite similar plasma levels and patterns of change during the annual reproductive cycle. Lowest plasma levels of testosterone and estradiol were found during fall and winter, in females possessing exclusively previtellogenic ovarian follicles. Plasma progesterone levels were maintained at a very low level throughout the year, except for the ovulatory surge, when amplectant and ovulating females may show a three- to sixfold increase. Plasma androstenedione showed a low peak during this phase of the reproductive cycle. Plasma levels of 5 alpha-dihydrotestosterone were 13 to 30 times lower than plasma testosterone levels. The potential roles of these gonadal steroids in controlling ovarian activity and reproduction are discussed briefly.
Asunto(s)
Anuros/fisiología , Ovario/fisiología , Reproducción , Animales , Femenino , Oocitos/citología , Oocitos/fisiología , Ovario/citología , Ovulación , Periodicidad , Estaciones del AñoRESUMEN
The Mexican leaf frog, Pachymedusa dacnicolor, an inhabitant of the semiarid, subtropical Mexican lowlands, displays a well-defined seasonal testicular cycle. Testis weight seems to be a reliable index of the reproductive status of the animal and plasma levels of androgens (testosterone, T; 5 alpha-dihydrotestosterone, DHT; androstenedione, A) correlate not only with testicular growth, but with callosity development, reproductive behavior, and breeding. During the fall and winter, testis weight reaches its minimum as do plasma concentrations of T, DHT, A, and estradiol-17 beta (E). Plasma levels of progesterone (P) are maintained at a very low level throughout the year. During the fall and winter, spermatogenesis is almost entirely absent and the callosities are white and smooth. No signs of reproductive behavior (calling and amplexus) are evident. Late spring marks the initiation of spermatogenesis, testis weight increase, darkening of callosities, and increase in plasma levels of androgens. The magnitude of callosity development and the onset of calling and amplectant behavior are correlated with a great rise in plasma androgen levels. Although plasma T concentrations were higher than plasma levels of DHT and A, this androgen failed to stimulate the development of callosities and calling behavior in successfully castrated males.
Asunto(s)
Anuros/fisiología , Reproducción , Andrógenos/sangre , Animales , Masculino , Orquiectomía , Tamaño de los Órganos , Estaciones del Año , Conducta Sexual Animal , Espermatogénesis , Testículo/anatomía & histología , Testículo/fisiologíaRESUMEN
Androgen, progesterone and estrogen receptors were analyzed in 12 primary colonic cancers and 16 primary rectal cancers. Androgen and progesterone receptors were positive in some colonic cancers and rectal carcinomas; however, none of the specimens analyzed showed estradiol receptor.
Asunto(s)
Neoplasias del Colon/análisis , Receptores Androgénicos/análisis , Receptores de Progesterona/análisis , Neoplasias del Recto/análisis , Adulto , Anciano , Pólipos del Colon/análisis , Femenino , Humanos , Masculino , Persona de Mediana Edad , Pronóstico , Ensayo de Unión Radioligante , Receptores de Estradiol/análisisRESUMEN
The effect of adjuvant CMF (cyclophosphamide, methotrexate, and 5-fluorouracil) and tamoxifen (TM) on hypothalamic-pituitary-ovarian function was studied in 120 women with stage I-II operable breast cancer. Sixty patients were premenopausal, of whom 25 were treated with CMF for 9 cycles, 25 with CMF for 9 cycles + TM for 2 years, started concurrently, and 10 with TM alone for 2 years. Sixty patients were postmenopausal and they were all treated with TM alone for 2 years. In all groups treatment was started within 4 weeks of mastectomy. Plasma levels of estrone (E1), estradiol-17 beta (E2), follicle-stimulating hormone, luteinizing hormone (LH), prolactin (Prl), testosterone (T) and thyroid-stimulating hormone (TSH) were determined in all patients before surgery and again at 3-month intervals from initiation of the adjuvant therapy. In ten patients of each treatment group FSH-LH and Prl-TSH release was determined following stimulation with releasing hormones. CMF and CMF+TM therapy resulted in amenorrhea in 42/50 premenopausal patients with decrease of E1+E2 (p less than 0.001) and elevation of FSH (p less than 0.001) and LH (p less than 0.01) plasma concentration to postmenopausal levels. In premenopausal women treated with TM a marked increase of E1+E2 (p less than 0.001) was observed with unaltered FSH-LH plasma concentration. A significant fall of Prl also occurred in these patients. In postmenopausal women and premenopausal patients with CMF-induced amenorrhea TM produced a marked fall of FSH-LH and a decrease of Prl plasma level. Plasma TSH and T were not affected in any patient by any of the treatment regimens. The results of the stimulatory tests are in agreement with the hormonal changes observed under basal conditions and indicate that, whereas CMF suppresses the ovary and does not alter hypothalamic-pituitary function, TM induces profound changes of the hypothalamic-pituitary-ovarian axis.
Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Neoplasias de la Mama/terapia , Sistema Hipotálamo-Hipofisario , Ovario/fisiopatología , Tamoxifeno/efectos adversos , Adulto , Amenorrea/inducido químicamente , Neoplasias de la Mama/fisiopatología , Ciclofosfamida/efectos adversos , Femenino , Fluorouracilo/efectos adversos , Humanos , Mastectomía , Menopausia , Metotrexato/efectos adversos , Persona de Mediana Edad , Pruebas de Función Ovárica , Pruebas de Función Hipofisaria , Factores de TiempoRESUMEN
The effect of adjuvant CMF (cyclophosphamide, methotrexate and 5-fluorouracil) and tamoxifen (TM) on endocrine function was studied in 120 women with stage I-II operable breast cancer. Sixty patients were premenopausal, of whom 25 were treated with CMF for 9 months, 25 received CMF for 9 months + TM for 2 years, started concurrently, and 10 TM alone for 2 years. In all groups treatment was started within 4 weeks from mastectomy. Sixty patients were postmenopausal and they were all treated with TM alone for 2 years. Plasma levels of estrone + estradiol -17 beta (E1 + E2), follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (Prl), and testosterone (T) were determined in all patients before surgery and again at 3-month intervals from initiation of the adjuvant therapy. In ten patients of each treatment group FSH-LH and Prl-TSH release was determined following stimulation with releasing hormones. CMF and CMF + TM therapy resulted in amenorrhea in the majority of premenopausal patients with decrease of E1 + E2 and elevation of FSH-LH plasma concentration to levels of the post-menopausal. In premenopausal women treated with TM a marked increase of E1 + E2 was observed with unaltered FSH-LH plasma concentration. A significant fall of Prl was also present in these patients. In postmenopausal women and premenopausal patients with CMF-induced amenorrhea TM produced a marked fall of FSH-LH and a decrease of Prl plasma level. In no patients was plasma T affected by any of the treatment regimens.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica , Neoplasias de la Mama/terapia , Adulto , Neoplasias de la Mama/sangre , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/cirugía , Terapia Combinada , Ciclofosfamida/administración & dosificación , Femenino , Fluorouracilo/administración & dosificación , Hormonas/sangre , Humanos , Menopausia , Metotrexato/administración & dosificación , Persona de Mediana Edad , Tamoxifeno/administración & dosificaciónRESUMEN
Plasma and testicular testosterone concentrations in the frog, Rana esculenta, were studied by radioimmunoassay and showed similar seasonal fluctuations. The increase in testicular androgen during November preceded that occurring in the plasma by 2 months. Pituitary products and gonadotrophin releasing hormone, and the responsiveness of the testis to these substances play an important role in determining the hormone profile.
Asunto(s)
Rana esculenta/metabolismo , Estaciones del Año , Testosterona/metabolismo , Animales , Buserelina/farmacología , Hipofisectomía , Técnicas In Vitro , Hormona Luteinizante/farmacología , Masculino , Adenohipófisis/fisiología , Testículo/efectos de los fármacos , Testículo/metabolismo , Testosterona/biosíntesis , Testosterona/sangre , Extractos de Tejidos/farmacologíaRESUMEN
Seasonal plasma progesterone, androstenedione, estrone, and 17 beta-estradiol concentrations in the female Rana esculenta were determined by radioimmunoassay during the 1979 and 1981 seasons. Plasma levels of these steroids were highest just before the first ovulatory wave in spring and lowest after the breeding season. In the 1979 season (during the 1981 season hormones were not assayed in January, November, and December) progesterone, androstenedione, and estradiol levels showed another peak in November-December. During the breeding months, i.e., late March to late June, progesterone, androstenedione, and estradiol levels showed intermittent ups and downs corresponding roughly to the ovulatory waves. In addition, during the breeding season progesterone and androstenedione levels had a higher average in frogs with "ripe" ovaries than in those with "spent" ovaries. Relationships between seasonal steroid levels and ovarian activity are briefly discussed.
Asunto(s)
Androstenodiona/sangre , Estradiol/sangre , Progesterona/sangre , Rana esculenta/sangre , Estaciones del Año , Anfibios/fisiología , Animales , Estrona/sangre , Femenino , Ovario/fisiología , Ovulación , Radioinmunoensayo , ReproducciónRESUMEN
The interactions between thyroid hormones and receptors for steroid hormones and prolactin in dorsal skin and caudal fin of Triturus cristatus carnifex were studied during the annual cycle. Thyroidectomy induces an increase of prolactin binding in the dorsal skin and caudal fin in the animals captured in March. In these thyrodectomized animals the androgen receptors became undetectable. Results indicate that in Triturus cristatus carnifex the thyroid induces an increase of androgen receptors and a decrease, that is removed by thyroidectomy, of prolactin receptors.
Asunto(s)
Receptores Androgénicos/análisis , Receptores de Superficie Celular/análisis , Receptores de Esteroides/análisis , Glándula Tiroides/fisiología , Triturus/metabolismo , Animales , Masculino , Prolactina/metabolismo , Receptores Androgénicos/metabolismo , Receptores de Superficie Celular/metabolismo , Receptores de Prolactina , Receptores de Esteroides/metabolismo , Estaciones del Año , Piel/metabolismo , Hormonas Tiroideas/fisiología , TiroidectomíaRESUMEN
Plasma progesterone levels were determined three days after weaning in 151 sows Landrace x Large White. Furthermore, the influence of bromocriptine (Parlodel, Sandoz) was studied on the resumption of ovarian activity in 19 sows during the hot season. An increased progesterone base-line level was shown during the June-July-August period as compared with May and September-October. No correlation was found between progesterone levels and the percentage of sows which returned to estrus 10 days after weaning except when progesterone levels reached and exceeded 0.9 ng/ml; in this case, no sow resumed ovarian activity in normal time. Bromocriptine treatment had no influence on the resumption of ovarian activity, suggesting that prolactin is not involved in the lack of estrus after weaning. An influence of environmental factors is also suggested.