RESUMEN
Energy-filtering transmission electron microscopy (EFTEM) allows the determination of elemental distributions out of a sequence of energy filtered images. Combined with electron tomography, EFTEM is a powerful tool to obtain three-dimensional chemical maps from sub-cellular structures. However, there is no existing software in the public-domain for the computation and analysis of 3D-chemical maps. Here, we present a Java-based program to compute 3D-elemental distribution. This program is available as a set of plug-ins for the public-domain Java image processing program Image J inspired by NIH Image. Its implemented algorithms have been successfully applied to the three-dimensional localization of iron granules in semi thin (200 nm) epon sections from the vent worm Riftia pachyptalia.
Asunto(s)
Bacterias/citología , Cuerpos de Inclusión/química , Energía Filtrada en la Transmisión por Microscopía Electrónica , Poliquetos/microbiología , Programas Informáticos , Tomografía , Algoritmos , Animales , Secciones por Congelación , Procesamiento de Imagen Asistido por Computador , Imagenología Tridimensional , Hierro/análisisRESUMEN
Acquisition of a great number of energy-filtered images in a TEM (EFTEM) around the characteristic signal with a low energy-selecting slit allows display of the electron energy loss (EEL)-spectrum of regions of interest (ROIs) of a sample. These EEL-spectra can be submitted to the different treatments already in use for electron energy loss spectroscopy (EELS). In particular, it is possible to fit the experimental background with different mathematical models, using images acquired below and above a characteristic ionization edge. After this fitting, elemental maps can be computed by subtraction of the extrapolated/interpolated background from the characteristic images. In this work, we compared two mathematical models for background fitting-the Egerton power law and the log-polynomial law. We studied the low-energy region (40-150 eV) and a higher-energy region (350-600 eV) with the aid of software for interactive processing of EFTEM image series that we developed. The analyzed elements were the constitutive elements: iron, phosphorus, nitrogen, and oxygen in several biological materials. Two analytical TEMs, one equipped with a post-column and the other with an in-column spectrometer, were used. Our experimental results confirm that the power law is very sensitive to the value of the energy loss of the pre-edge images when the background is computed by extrapolation. The log-polynomial model is less sensitive than the power law model to the value of the energy loss of the pre-edge images in the low energy region. For the oxygen K edge at 535 eV, it gives the best fit when it is combined with the interpolation method. The use of programs that facilitate the handling of EFTEM image series, and the controlled calculation of the background under the characteristic images, represent a step forward in the generation of elemental maps.
Asunto(s)
Microscopía Electrónica/métodos , Animales , Bacterias/ultraestructura , Nucléolo Celular/ultraestructura , Diagnóstico por Imagen/métodos , Ferritinas/ultraestructura , Hígado/ultraestructura , Masculino , Poliquetos/microbiología , Sensibilidad y Especificidad , Porcinos , Testículo/ultraestructuraRESUMEN
The beta-chitin microfibrils from the deep-sea hydrothermal vent worm Riftia pachyptila were studied in both mature and fresh tubes experimentally obtained. The methods used were electron diffraction and electron diffraction contrast images, in conjunction with an electron-energy filter, operated in the zero-loss mode. In both studied samples, microfibrils are organized in successive layers, inside which they are parallel. However, the fresh tube is less densely packed and diffraction data show that these microfibrils may be in a partially hydrated state. These results indicate that a later step occurs in the compaction of the tube material once it has been extruded. Comparison of filtered and unfiltered diffraction patterns shows that zero-loss filtering significantly improves both working conditions and quality of diffraction recordings.
Asunto(s)
Quitina/ultraestructura , Matriz Extracelular/química , Matriz Extracelular/ultraestructura , Citoesqueleto de Actina/ultraestructura , Animales , Diseño de Equipo , Procesamiento de Imagen Asistido por Computador , Microscopía Electrónica/instrumentación , Microscopía Electrónica/métodos , Modelos Estructurales , Poliquetos/fisiología , Poliquetos/ultraestructura , Agua de MarRESUMEN
Fibrillar collagens represent the most abundant extracellular matrix components surrounding fibroblasts. Although there is a large heterogeneity in the collagen composition and in the physiological functions of different tissues, interactions between cells and native collagens monomers are mediated by only two integrins, the alpha1beta1 and alpha2beta1 integrins. In tissue, fibroblasts are exposed to collagen polymers, supramolecular assemblies which might play a role on the availability of the cell-binding sites at the surface of the fibrils. We have addressed this issue by investigating the patterns of adhesion structures in normal human skin fibroblasts exposed to collagen monomers or polymers. Our results showed that cell morphology, cell adhesion pattern, actin organization, and distribution of integrin subunits, talin, vinculin, and phosphotyrosine-containing proteins are dependent on the supramolecular organization of the collagens. In particular, compared to monomers, collagen polymers induced a looser organization of the actin network and a linear clustering of integrins, talin, vinculin, and phosphotyrosine-containing proteins. These results emphasize the role of the physical state of collagen on cellular interactions and underline the role of the extracellular matrix in the phenotypic modulation of fibroblasts. Furthermore, our studies suggest the existence of a local heterogeneity in the biological activity of collagen fibrils.
Asunto(s)
Colágeno/farmacología , Citoesqueleto/efectos de los fármacos , Fibroblastos/efectos de los fármacos , Piel/citología , Actinas/análisis , Células Cultivadas/efectos de los fármacos , Células Cultivadas/fisiología , Células Cultivadas/ultraestructura , Citoesqueleto/química , Fibroblastos/fisiología , Fibroblastos/ultraestructura , Técnica del Anticuerpo Fluorescente Indirecta , Humanos , Integrinas/análisis , Microscopía Electrónica , Microscopía Electrónica de Rastreo , Periodicidad , Fosfotirosina/análisis , Talina/análisis , Vinculina/análisisRESUMEN
1. Phenylephrine-induced contractions of rabbit isolated trigone and urethra were antagonized in a competitive manner by alfuzosin (pA2 7.44 and 7.30, respectively) and prazosin. 2. The characteristics of [3H]-prazosin binding to human prostatic adenoma tissue were evaluated. [3H]-prazosin was potently displaced by alpha 1-adrenoceptor specific agents including alfuzosin, its (+)- and (-)-enantiomers and prazosin (IC50 0.035, 0.023, 0.019 and 0.004 microM, respectively), but only weakly by alpha 2-adrenoceptor selective agents, for example, yohimbine (IC50 = 6.0 microM). 3. In the pithed rat, alfuzosin (0.03-0.3 mg kg-1, i.v.) markedly inhibited pressor responses produced by the alpha 1-selective agonist, cirazoline but inhibited only slightly responses to the alpha 2-selective agonist, UK 14,304. Alfuzosin (1 mg kg-1, i.v.) had minimal effects against responses mediated by stimulation of prejunctional alpha 2-receptors (UK 14,304-induced inhibition of sympathetic tachycardia). 4. In the anaesthetized cat, alfuzosin (0.001-1 mg kg-1, i.v.) and prazosin (0.001-0.3 mg kg-1, i.v.) produced dose-related inhibition of the increases in urethral pressure caused by stimulation of sympathetic hypogastric nerves. Prazosin was approximately 5 fold more potent than alfuzosin. When phenylephrine was employed to induce urethral and vascular alpha 1-mediated tone simultaneously, prazosin inhibited both stimuli with similar potency whereas alfusozin was 3-5 fold more potent against elevated urethral pressure. This functional uroselectivity of alfuzosin was more evident by the intraduodenal route, since doses of 0.03 and 0.1 mg kg-1 alfuzosin inhibited urethral pressure with minimal effects on arterial blood pressure. 5. Alfuzosin is a potent selective alpha1-adrenoceptor antagonist in tissues of the lower urinary tract including the human prostate. This provides a pharmacological basis for its use in the treatment of benign prostatic hypertrophy.
Asunto(s)
Antagonistas Adrenérgicos alfa/farmacología , Quinazolinas/farmacología , Sistema Urinario/efectos de los fármacos , Adenofibroma/metabolismo , Antagonistas Adrenérgicos alfa/farmacocinética , Animales , Unión Competitiva/efectos de los fármacos , Gatos , Estado de Descerebración/fisiopatología , Estimulación Eléctrica , Femenino , Corazón/efectos de los fármacos , Humanos , Técnicas In Vitro , Masculino , Fenilefrina/antagonistas & inhibidores , Fenilefrina/farmacología , Prazosina/farmacocinética , Prazosina/farmacología , Neoplasias de la Próstata/metabolismo , Quinazolinas/farmacocinética , Conejos , Ratas , Sistema Nervioso Simpático/fisiología , Células Tumorales Cultivadas , Uretra/efectos de los fármacos , Vasoconstricción/efectos de los fármacosRESUMEN
This paper undertakes a parallel analysis of the gelation mechanisms, structure and rheological properties of gelatin and collagen gels. Although the molecular compositions of collagen and gelatin are almost identical, gelation proceeds from distinct mechanisms and leads to different types of molecular assemblies. First are presented the properties of the solutions, based on their structural and rheological characterization; then the mechanisms of gelation in the networks, observed by Transmission Electron Microscopy, of three types of gels: gelatin gels, Type I collagen gels and gels made of cuticle collagen extracted from annelid worms. The rheological investigation of the sol-gel transition of gelatin is described within the context of the theories of percolation and scaling laws. Different experimental approaches to the kinetics of gelation are presented, combining dynamic light scattering and rheology in respect to gelatin gels.
Asunto(s)
Colágeno/ultraestructura , Gelatina/ultraestructura , Animales , Anélidos/ultraestructura , Biopolímeros , Geles , Luz , Microscopía Electrónica , Reología , Dispersión de RadiaciónRESUMEN
In this review, we present structural and ultrastructural localizations of fibronectin (FN) in the larval and adult skin of the frog (Rana esculenta) either in in vivo or in in vitro conditions. The ventral skin of the tadpole contains membrane-associated FN-plaques disposed around the epidermal and dermal cells during their climactic rearrangement. Moreover, lines of fibrillar FN are detected inside the breaks opened in the derived collagen. The ventral skin of the adult frog reveals FN distributed in the three superimposed tissues forming the skin, i.e. the epidermis, the dermis and the subcutaneous tissue. In vivo, the epidermis is devoid of FN except for the mitochondria-rich cells (MRCs) which contain FN cytoplasmic granules. The dermis reveals two distinct collagenous networks showing FN localizations. A vertically-oriented network formed by thick tracts contains axis of fibrillar FN connecting the upper dermis devoid of FN to the FN-rich subcutaneous tissue. In contiguity with an horizontally-oriented network comprises thin tracts formed by clear spaces separating the superimposed collagen bundles of the dermal stratum compactum. These tracts contain aligned FN-granules. Inside the thick and thin tracts, the dermal and pigment cells present membrane-associated In vitro (in organ culture conditions) MRCs of the epidermis maintain their FN localization and, in addition, the stratum germinativum cells show cytoplasmic FN granules. Epidermal cells, in the vicinity of the cut edges of the cultivated skin fragment, modify their shape and acquire membrane-associated FN-plaques located between desmosomes. The FN localizations in these two collagenous networks of the dermis remain unchanged. In the same way, the FN-rich subcutaneous tissue is unmodified. In summary, the FN distribution in the larval skin is related to the cell rearrangement during the metamorphic climax, and, in the adult skin to the cell migration during the wound healing process and the pigment cell patterning. The cell migration is demonstrated, in organ culture conditions, by antiFN serum used as an experimental tool. FN is an important substrate used in the dermal breaks of the larval skin, and in the dermal tracts of the adult skin, both allowing the dermal and pigment cell migration.
Asunto(s)
Fibronectinas/metabolismo , Piel/química , Animales , Comunicación Celular , Movimiento Celular , Epidermis/química , Epidermis/fisiología , Fibronectinas/química , Fibronectinas/ultraestructura , Melanocitos/fisiología , Metamorfosis Biológica , Rana esculenta/crecimiento & desarrollo , Piel/crecimiento & desarrollo , Piel/ultraestructuraRESUMEN
The pigment pattern of the ventral skin of the frog Rana esculenta is compared in skin fragments grown for 24 hr with or without antiserum directed to fibronectin (anti-FN). Melanocyte-stimulating hormone (MSH) was added to the medium during the last hour in culture in order to enhance visibility of melanophores in the ventral region of the frog skin. Comparison of these two treatments provides information regarding the precise localization of melanophores in the dermal tracts and their involvement in the pigment pattern of the ventral frog skin. In this regard, the whitish pigment pattern of skin fragments is compared to the tiny black spots found on anti-FN treated skin fragments and the abundant blotchy spots found on skin cultured alone. The distribution of melanophores in the dermal tracts observed in vertical semithin sections is found to be related to the three different levels of the dermal tracts. This report demonstrates the importance of fibronectin as a substrate for the melanophore migration, the importance of the tract level for the melanophore localization both involved in the pigment pattern of the ventral skin.
Asunto(s)
Fibronectinas/análisis , Melanóforos/química , Rana esculenta/anatomía & histología , Piel/citología , Animales , Anticuerpos/inmunología , Femenino , Fibronectinas/inmunología , Masculino , Hormonas Estimuladoras de los Melanocitos , Pigmentación , Piel/ultraestructuraRESUMEN
In anuran amphibians, the specific color pattern of the skin is expressed after metamorphosis, and its formation involves pigment cell migrations. Pigment cells are differently distributed in the tadpole, larval, and froglet skin. To learn more about their fate during metamorphic climax and in the young froglet, we focused our attention on the different localizations of larval melanophores and iridophores in the ventral skin of Rana esculenta before and during skin homing. Localizations of melanophores and iridophores can be elucidated at the developmental stages suggested by Taylor and Kollros (TK stages). At TK stage II (during early premetamorphosis), large melanophores beneath the larval skin are detected. At TK stage X, dispersed melanophores lie under bundles of muscular striated fibrils near the larval skin; they are also observed at the vascular level. At TK stage XVII (prometamorphosis), melanophores are extended on the inner side of the basement lamellar collagen. At the end of prometamorphosis, iridophores are located with melanophores in the separating space between attached basement collagen and derived basement collagen. At TK stage XX (earlier climax), melanophores and iridophores are detected inside the upper extremities of fractures opened in the derived basement collagen. At TK stage XXIV (later climax), both types of larval pigment cells are observed in the inner extremities of breaks derived from the fractures. During climax, these pigment cells occupy the well-formed breaks. At TK stage XXV in young froglet, the pigment cells remain alone in the breaks formed in the derived basement collagen. Briefly, breaks in the basement lamellar collagen are opened by invading cell processes of mesenchymal cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Metamorfosis Biológica , Pigmentación/fisiología , Rana esculenta/crecimiento & desarrollo , Piel/crecimiento & desarrollo , Animales , Membrana Basal/metabolismo , Membrana Basal/ultraestructura , Movimiento Celular , Colágeno/metabolismo , Piel/citología , Fenómenos Fisiológicos de la PielRESUMEN
In this report, we studied the formation of breaks in the frog dermis during its remodelling at climactic metamorphosis. This remodelling consisted of detachment of the basement lamella collagen from the epidermis. The detached part, called derived collagen, was progressively fractured by breaks. We focused our attention on dermal cell localization during break formation. Firstly, at early climax, dermal cells were localized inside fractures opened in the derived collagen. Secondly, at the later climax, the fractures became breaks, making room for the dermal cells themselves. Thirdly, in derived collagen of the froglet, the well-opened breaks contained elongated dermal cells. At climax, DAB immunoperoxidase staining of fibronectin revealed a granular pattern at the surface of epidermal and dermal cells. Unexpected staining revealed that the dermal breaks contained fibronectin in the form of vertical lines. The foregoing results suggest that the dermal breaks are migratory pathways for dermal cells in derived collagen remodelled at climax.
Asunto(s)
Metamorfosis Biológica/fisiología , Rana esculenta/crecimiento & desarrollo , Piel/citología , Animales , Movimiento Celular/fisiología , Colágeno/análisis , Fibronectinas/análisis , Inmunohistoquímica , Piel/químicaRESUMEN
The geometrical characteristics of fibrillar organizations are studied by electron microscopy in structures obtained in vitro in cell-free assembled collagen gels, and in vivo in dermal tracts of anuran skin. We analyze several characteristics of the fibrils including the diameter, the outline, the curvature and the extrafibrillar space. We analyze also the variation of fibrillar orientation (twist) in longitudinal and transverse thin sections of these structures. The results are compared in the Discussion to determine to what extent these fibrillar patterns are similar to liquid crystalline organizations and to what extent they result from a self-assembly or a cell-assembly process.
Asunto(s)
Colágeno/ultraestructura , Piel/ultraestructura , Animales , Bovinos , Recuento de Células , Colágeno/aislamiento & purificación , Femenino , Procesamiento de Imagen Asistido por Computador , Técnicas In Vitro , Masculino , Rana esculenta , Piel/químicaRESUMEN
The pigmentation pattern of ventral skin of the frog Rana esculenta consists mainly of melanophores and iridophores, rather than the three pigment cells (xanthophores, iridophores, and melanophores) which form typical dermal chromatophore units in dorsal skin. The present study deals with the precise localization and identification of the types of pigment cells in relation to their position in the dermal tracts of uncultured or cultured frog skins. Iridophores were observed by dark-field microscopy; both melanophores and iridophores were observed by transmission electron microscopy. In uncultured skins, three levels were distinguished in the dermal tracts connecting the subcutaneous tissue to the upper dermis. Melanophores and iridophores were localized in the upper openings of the tracts directed towards the superficial dermis (level 1). The tracts themselves formed level 2 and contained melanophores and a few iridophores. The inner openings of the tracts made up level 3 in which mainly iridophores were present. These latter openings faced the subcutaneous tissue In cultured skins, such pigment-cell distribution remained unchanged, except at level 2 of the tracts, where pigment cells were statistically more numerous; among these, mosaic pigment cells were sometimes observed.
Asunto(s)
Cromatóforos/ultraestructura , Melanóforos/ultraestructura , Rana esculenta/anatomía & histología , Piel/citología , Animales , Células Cultivadas , Femenino , MasculinoRESUMEN
The functional and structural changes induced by apical wheat germ agglutinin (WGA) 100 micrograms/ml exposure on frog urinary bladder have been investigated and the possible correlations between these effects discussed. Bladders, apically exposed to WGA for 30 min to 3 hr exhibit a marked reduction of their response to antidiuretic hormone (ADH) challenge and of their hydrosmotic reactivity. Structural changes triggered by WGA treatment are: 1. apical invaginations of the plasma membrane, interpreted as endocytotic in nature, taking into account the results of carbohydrate cytochemical detection and horseradish peroxidase (HRP) exposure: 2. cytoskeleton disorganization and microvilli collapse. These phenomena do not interfere with cortical granule traffic and are independent of ADH challenge: they occur in ADH-stimulated bladders as well as in bladders at rest. These findings could be interpreted as follows: binding of the divalent lectin WGA to its coat specific receptors would induce changes in the apical membrane structure which in turn could provoke disorganization and disruption of apical cytoskeletal elements associated with plasma membrane. Reduction of bladder response to ADH challenge could result from a reduced recycling of aggrephores, as they are associated with cytoskeletal elements in the subapical cytoplasm. Collapse of microvilli and endocytotic events also could result from apical cytoskeleton disruption, as microvilli are sustained by bundles of actin filaments interconnected with apical cytoskeletal filaments and as plasma membrane is associated with apical cytoskeleton. However, these two last events evidently occur in ADH-challenged or non-challenged bladders.
Asunto(s)
Agua Corporal/metabolismo , Vejiga Urinaria/efectos de los fármacos , Vasopresinas/antagonistas & inhibidores , Aglutininas del Germen de Trigo/farmacología , 8-Bromo Monofosfato de Adenosina Cíclica/farmacología , Animales , Transporte Biológico/efectos de los fármacos , Gránulos Citoplasmáticos/fisiología , Citoesqueleto/efectos de los fármacos , Endocitosis/efectos de los fármacos , Histocitoquímica , Técnicas In Vitro , Microvellosidades/efectos de los fármacos , Permeabilidad , Rana esculenta , Vejiga Urinaria/fisiología , Vejiga Urinaria/ultraestructuraRESUMEN
During wound-healing in cultured frog skin fragments, fibronectin (FN) was detected in the dermal-epidermal junction. Intracellular fibronectin was stained using permeabilization and DAB immunoperoxidase. With electron microscopy intracytoplasmic FN granules were localized in the epidermal processes of the stratum germinativum cells protruding towards the dermis and in their marginal regions (membrane-associated plaques). Faint staining was visible at the level of the lamina densa and inside some parts of the lamina lucida. In comparison, contrasted ultrathin sections revealed classical disorganization of the dermal-epidermal junction. In the presence of anti-fibronectin serum during the whole time of culture, fibronectin-antifibronectin binding was visualized in the form of sparse cytoplasmic granules in the epidermal processes of the stratum germinativum cells. Contrasted ultrathin sections emphasized the continuity between the tonofilaments, the anchoring filaments and the anchoring fibrils. Briefly, anti-fibronectin serum inhibits the disorganization of the dermal-epidermal junction in cultured wounded skin.
Asunto(s)
Epidermis/lesiones , Fibronectinas/fisiología , Piel/lesiones , Cicatrización de Heridas/fisiología , Animales , Anticuerpos , Gránulos Citoplasmáticos/ultraestructura , Epidermis/ultraestructura , Fibronectinas/ultraestructura , Técnicas para Inmunoenzimas , Técnicas In Vitro , Filamentos Intermedios/ultraestructura , Microscopía Electrónica , Rana esculenta , Piel/ultraestructuraRESUMEN
We have developed a technique for recovering apical membranous sheets from amphibian urinary bladders by gelatin stripping. The tissue is mounted on a lucite support and the apical surface is first stuck onto a gelatin-coated glass slide at 30 degrees C. This sandwich is then chilled on ice and the bladder is pulled away from the slide. Preliminary results indicate that this simple technique could be used to remove membranous apical sheets of various sizes, almost devoid of cytoplasmic contamination and without significant damage to the underlying cell structures. The method could also be adapted to prepare perforated cells and to study the cohesive forces between the different layers of the tissue.
Asunto(s)
Membrana Celular/ultraestructura , Vejiga Urinaria/ultraestructura , Animales , Fraccionamiento Celular/instrumentación , Fraccionamiento Celular/métodos , Epitelio/ultraestructura , Gelatina , Vidrio , Técnicas In Vitro , Microscopía Electrónica , Rana esculentaRESUMEN
Small trypsinized explants from ventral skin of frogs (Rana esculenta) were maintained in culture for 4 days during which a newly formed epithelium differentiated along the cut edges of the dermis. During the first 6 h adjacent cells produced numerous interdigitating lamellipodia. After 2 days, epithelial polarity was restored by the formation of zonulae occludentes and the epithelial cells were joined by a few small newly formed desmosomes and by numerous interdigitations. Bipartite junctional complexes consisting of a zonula occludens, followed by a series of typical desmosomes, and characteristic of adult frog epidermis were formed only after 4 days. When cultured in the presence of an inhibitor of protein synthesis (cycloheximide) the trypsinized epidermis no longer formed desmosomes. Therefore pools of one or more crucial desmosomal proteins must be very low or non-existent. However, cycloheximide did not prevent the formation of cell contact specializations, consisting of a highly developed system of complex lamellar interdigitations, between adjacent cells.
Asunto(s)
Desmosomas/ultraestructura , Uniones Intercelulares/ultraestructura , Piel/ultraestructura , Animales , Células Cultivadas , Cicloheximida/farmacología , Femenino , Masculino , Microscopía Electrónica , Rana esculenta , Piel/efectos de los fármacosRESUMEN
In pentobarbital-anesthetized rats prepared for hemodynamic measurements with Doppler flow probes, intravenous (i.v.) infusions of fenoldopam (2.5 - 160.0 micrograms/kg/min during 15 min) decreased mean carotid artery blood pressure, total peripheral, hindquarter, renal, and mesenteric vascular resistances and increased renal blood flow strongly. The hypotensive effects attained a maximum within the first 3 min of infusion but waned by greater than 30% at the end of fenoldopam administration. This tolerance was observed for calculated total peripheral and hindquarter vascular resistances and to a lesser extent for mesenteric resistance. However, it was absent on the renal vascular bed. Pretreatment with either enalapril, pepstatine, or bilateral nephrectomy significantly increased the hypotensive response to fenoldopam and attenuated the development of tolerance. In conscious spontaneously hypertensive rats (SHR), enalapril potentiated strongly the small blood pressure-lowering activity of fenoldopam. The fall in blood pressure produced by fenoldopam was specifically blocked by SCH 23390, an antagonist of DA-1 dopamine receptors. In normotensive vasopressin-supported pithed rats given phenoxybenzamine plus propranolol, fenoldopam, like SCH 23390, blocked the vasodepressor effects of i.v. bolus injection of dopamine and fenoldopam. In pithed rats, fenoldopam evoked a pressor response that was significantly reduced by enalapril, SCH 23390, or bilateral nephrectomy. In conclusion, fenoldopam exerts DA-1 agonist and antagonist effects. The latter property, together with the activation of the renin-angiotensin system, appears to be responsible for the development of tolerance to the fenoldopam evoked-hypotension. The lack of a tolerance at the level of the renal vascular bed is possibly due to the existence of a large population of DA-1 receptors in this region.
Asunto(s)
Antihipertensivos/farmacología , Benzazepinas/farmacología , Vasodilatadores/farmacología , Albuterol/administración & dosificación , Albuterol/farmacología , Animales , Antihipertensivos/administración & dosificación , Benzazepinas/administración & dosificación , Dopamina/farmacología , Esquema de Medicación , Tolerancia a Medicamentos , Fenoldopam , Hemodinámica/efectos de los fármacos , Masculino , Ratas , Ratas Endogámicas SHR , Vasodilatadores/administración & dosificaciónRESUMEN
Fibronectin (FN) localizations in the epidermal cells of the frog Rana esculenta were detected in isolated ventral skin fragments 4 day-cultured with or without an NaCl transepithelial gradient and aldosterone. Without the gradient, few mitochondria-rich cells (MRCs) were FN-detected. Stratum germinativum and spinosum cells also contained fibronectin. With the gradient, numerous MRCs were detected. Below them, in the stratum germinativum, clear spaces were recognized. Aldosterone with or without the gradient modified the above effects: in both cases, many MRC contained fibronectin. It was interesting to note that, for each type of culture, stratum germinativum cells were dramatically FN-detected.
Asunto(s)
Aldosterona/farmacología , Epidermis/análisis , Fibronectinas/análisis , Cloruro de Sodio/farmacología , Animales , Biomarcadores/análisis , Células Cultivadas , Células Epidérmicas , Epidermis/efectos de los fármacos , Epidermis/ultraestructura , Femenino , Masculino , Mitocondrias/análisis , Rana esculentaRESUMEN
In pithed rats, blood pressure dose-response curves to i.v. cirazoline, methoxamine and phenylephrine (full alpha-1 adrenoceptor agonists) exhibited higher maxima than those to B-HT 920, M-7, UK-14,304 (full alpha-2 adrenoceptor agonists) and indanidine (Sgd 101/75: partial alpha-1 adrenoceptor agonist). For an 80 mm Hg increase in blood pressure, full alpha-1 adrenoceptor agonists enhanced total peripheral, renal and mesenteric vascular resistances significantly more than alpha-2 adrenoceptor stimulants or indanidine. In contrast, all compounds produced a similar degree of hindquarter vasoconstriction, suggesting that both types of alpha adrenoceptors have the same functional importance in this skeletal muscle vascular bed. Application of a multivariate discriminant analysis to the drug-induced changes in the total peripheral and mesenteric vascular resistances associated with a pressor effect of 80 mm Hg allowed their assignment to two distinct groups corresponding to the full alpha-1 and the full alpha-2 adrenoceptor agonists plus indanidine. All investigated compounds in low doses increased cardiac output, which returned to base-line values after high doses of alpha-1 but plateaued after high doses of alpha-2 adrenoceptor agonists or indanidine. alpha-1 adrenoceptor agonists decreased whereas alpha-2 stimulants and indanidine successively increased and then decreased renal blood flow. Finally, all investigated compounds increased hindquarter blood flow at low doses but decreased it at high doses. The ratios of the doses of cirazoline required to produce a 100% rise in systemic and local vascular resistances in the presence or in the absence of prazosin were of similar magnitude. This was also true for M-7 when studied in the presence or in the absence of yohimbine. These findings suggest pharmacological identity within alpha-1 as well as within alpha-2 adrenoceptor populations in all investigated vascular beds. Finally, the calcium entry blocker diltiazem did not affect the increases in systemic and regional resistances evoked by cirazoline but depressed profoundly the effects of M-7 and indanidine. In conclusion, full alpha-1 and alpha-2 adrenoceptor agonists can be discriminated easily on the basis of their systemic and regional hemodynamics in the pithed rat. That the hemodynamic effects of the partial alpha-1 adrenoceptor agonist indanidine are similar to those of alpha-2 adrenoceptor agonists and susceptible to calcium channel blockade suggests that the alpha-1 adrenoceptors stimulated by this drug have the same coupling modality as alpha-2 adrenoceptors and share with the latter the same functional expression when stimulated.
Asunto(s)
Agonistas alfa-Adrenérgicos/farmacología , Hemodinámica/efectos de los fármacos , Animales , Presión Sanguínea/efectos de los fármacos , Gasto Cardíaco/efectos de los fármacos , Estado de Descerebración , Masculino , Especificidad de Órganos , Ratas , Flujo Sanguíneo Regional/efectos de los fármacos , Relación Estructura-Actividad , Resistencia Vascular/efectos de los fármacosRESUMEN
Purified type I collagen gel used as culture substrate was composed of unstriated fibrils. Before culture, gel fragments were coated with culture medium with or without fetal calf serum (FCS+ coated or FCS- coated gels). Each gel fragment was apposed to a fragment of frog skin at the medium/air interface in Trowell culture chamber. After 7 days at 20 degrees C, the coated gels were covered with newly formed epidermis containing fibronectin localized around the keratinocytes, whose morphology was considerably modified. Fibroblast-shaped keratinocytes were localized in the anterior zone of the newly formed epidermis on FCS+ gels. The long axis of the cells was parallel to the gel surface, where numerous unstriated fibrils were located. Polyhedral keratinocytes were located in the posterior zone on FCS+ gels or the anterior and posterior zones on FCS- gels with the long axis perpendicular to the gel surface. Numerous cross-striated fibrils were found under the cultured keratinocytes in the vicinity of the basal filipodia. This model is useful for the study of collagen gel reorganization by keratinocytes.