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31.
E. Rosón R. Gallego T. García-Caballero E. P. Heimer A. M. Felix F. Domínguez 《Histochemistry and cell biology》1990,94(6):597-599
Summary Using immunohistochemical methods, we have investigated the cellular distribution of prothymosin alpha (ProT) in adult rat testis. A policlonal antibody raised against thymosin alpha 1 conjugated to keyhole limpet hemocyanin was used. ProT immunoreactivity was observed in the cytoplasm and nucleus of spermatogonia and primary spermatocytes in initial phases of the first meiotic division, preleptotene, leptotene and zygotene. However, in pachytene phase they already showed a weak or negative staining. On the other hand, secondary spermatocytes, spermatids, spermatozoa and Sertoli cells were not stained. Based on this fact we suggest that ProT is present in the proliferative cycle in the final steps of G1 phase, throughout the S and G2 phases and in initial steps of the prophase. 相似文献
32.
Summary The influence of starvation on renal carbohydrate metabolism was studied in the proximal and distal fragments of the nephron. Starvation induced a double and opposite adaptation mechanism in both fractions of the renal tubule. In renal proximal tubules, the gluconeogenic flux was stimulated progressively during a period of 48 hours of starvation (2.15 fold), due, in part, to a significant increase in the fructose 1,6-bisphosphatase and phosphoenolpyruvate carboxykinase activities although with different characteristics. Fructose 1,6-bisphosphatase activity from this tubular fragment increased only at subsaturating subtrate concentration (68%) which involved a significant decrease in the Km (35%) for fructose 1,6-bisphosphate while there was no change in Vmax. This behaviour clearly indicates that it is related to modifications in the activity of the preexistent enzyme in the cell. Proximal phosphoenolpyruvate carboxykinase activity increased proportionally at both substrate concentrations (86 and 89% respectively) which brought about changes in Vmax without changes in Kin, all of which are in accordance with variations in the cellular levels of the enzyme. In the renal distal tubules, the glycolytic capacity drastically decreased throughout the starvation time. At 48 hours 65% of inhibition was shown. We have found a short term regulation of phosphofructokinase activity by starvation which involves an increase in Km (2.2 fold) without changes in Vmax, as a result of these kinetic changes, an inactivation of phosphofructokinase was detected at subsaturating concentration of fructose 6-phosphate. On the contrary, this nutritional state did not modify the kinetic behaviour of renal pyruvate kinase. Finally, neither proximal glycolytic nor distal gluconeogenic capacities and related enzymes activities were changed during starvation. 相似文献
33.
Histopathology of experimental Aspergillus fumigatus keratitis 总被引:2,自引:0,他引:2
Histopathological studies in rabbit's eyes, 7 and 14 days after intracorneal inoculation with 1×105
Aspergillus fumigatus conidia have been performed.Similar lesions were found in both periods with fungal hyphae in the anterior third of corneal stroma, round cell infiltration from the sclero-corneal edge and in the anterior chamber and, neovascularization.No lesions were found in the Descemet's membrane.Gomori silver-methenamine stain with hematoxiline-eosine counter-stain was found to be the most reliable stain to detect fungal presence in corneal stroma, and Masson's trichromic stain in the study of pathological changes in ocular elements. 相似文献
34.
M A García-Pérez 《Spatial Vision》1988,3(2):129-142
A multichannel model incorporating visual inhomogeneity is presented in this paper. The parameters that describe inhomogeneity have been experimentally obtained both at threshold and in several suprathreshold conditions. At threshold, probability summation is taken into account in order to determine the spatial extent of visual channels from experimental data showing an asymptotic increase in sensitivity with increasing grating area. At suprathreshold contrast, the region where luminance variations at several scales are visible has also been found. The results support a spatially limited multichannel model of early visual processing and set out a basis for studying perceptual phenomena from the viewpoint of linear space-variant visual processing. 相似文献
35.
The role and source of gibberellins (GAs) involved in the development of parthenocarpic fruits of Pisum sativum L. has been investigated. Gibberellins applied to the leaf adjacent to an emasculated ovary induced parthenocarpic fruit development on intact plants. The application of gibberellic acid (GA3) had to be done within 1 d of anthesis to be fully effective and the response was concentration-dependent. Gibberellin A1 and GA3 worked equally well and GA20 was less efficient. [3H]Gibberellin A1 applied to the leaf accumulated in the ovary and the accumulation was related to the growth response. These experiments show that GA applied to the leaf in high enough concentration is translocated to the ovary. Emasculated ovaries on decapitated pea plants develop without application of growth hormones. When [3H] GA1 was applied to the leaf adjacent to the ovary a substantial amount of radioactivity accumulated in the growing shoot of intact plants. In decapitated plants, however, this radioactivity was mainly found in the ovary. There it caused growth proportional to the accumulation of CA1. Application of LAB 150978, an inhibitor of GA biosynthesis, to decapitated plants inhibited parthenocarpic fruit development and this inhibition was counteracted by the application of GA3 (either to the fruit, or the leaf adjacent to the ovary, or through the lower cut end of the stem). All evidence taken together supports the view that parthenocarpic pea fruit development on topped plants depends on the import of gibberellins or their precursors, probably from the vegetative aerial parts of the plant.Abbreviations FW
flesh weight
- GAn
gibberellin An
- HPLC
high-performance liquid chromatography 相似文献
36.
Summary Phenotypic analyses of genetic combinations involving the gene extramacrochaetae (emc) reveal its participation in the differentiation of both sensory elements and wing veins. The study of near-amorphic alleles of emc in mitotitc recombination clones indicates that it also affects cell proliferation. These clones show abnormal sizes, shapes and spatial distribution. They differentiate extra sensory elements as well as extra veins. A gain of function mutation in the gene causes opposite phenotypes in both differentiation systems. The effects of the mutant on proliferation and patterning are consistent with the emc gene being involved in the transfer of information between neighbouring cells, which leads to the spatial expression of the achaetescute gene complex and genes involved in vein formation. 相似文献
37.
C López-García A Molowny F J Martínez-Guijarro J M Blasco-Ibá?ez J A Luis de la Iglesia A Bernabeu J M García-Verdugo 《Histology and histopathology》1992,7(4):725-746
The cerebral cortex of Squamate reptiles (lizards and snakes) may be regarded as an archicortex or "reptilian hippocampus". In lizards, one cortical area, the medial cortex, may be considered as a true "fascia dentata" on grounds of its anatomy, connectivity and cyto- chemo-architectonics of its main zinc-rich axonal projection. Moreover, its late ontogenesis and postnatal development support this view. In normal conditions, it shows delayed postnatal neurogenesis and growth during the lizard's life span. Remnant neuroblasts in the medial cortical ependyma of adult lizards seasonally proliferate. The late-produced immature neurocytes migrate to the medial cortex cell layer where they differentiate and give off zinc-containing axons directed to the rest of cortical areas. This results in a continuous growth of the medial cortex and its zinc-rich axonal projection. Perhaps the most important characteristic of the lizard medial cortex is that it can regenerate after having been almost completely destroyed. Recent experiments in our laboratory have shown that chemical lesion of its neurons (up to 95%) results in a cascade of events; first, those related with massive neuronal death and axonal-dendritic retraction and, secondly, those related with a triggered neuroblast proliferation and subsequent neo-histogenesis, and the regeneration of an almost new medial cortex that shows itself undistinguishable from a normal undamaged one. This is the only report to our knowledge that an amniote central nervous centre may regenerate by new neuron production and neo-histogenesis. Perhaps the medial cortex of lizards may be used as a model for neuronal regeneration and/or transplant experiments in mammals or even in primates. 相似文献
38.
Evidence for a role of protein kinase C zeta subspecies in maturation of Xenopus laevis oocytes. 总被引:4,自引:1,他引:3 下载免费PDF全文
I Dominguez M T Diaz-Meco M M Municio E Berra A García de Herreros M E Cornet L Sanz J Moscat 《Molecular and cellular biology》1992,12(9):3776-3783
A number of studies have demonstrated the activation of phospholipase C-mediated hydrolysis of phosphatidylcholine (PC-PLC) both by growth factors and by the product of the ras oncogene, p21ras. Evidence has been presented indicating that the stimulation of this phospholipid degradative pathway is sufficient to activate mitogenesis in fibroblasts as well as that it is sufficient and necessary for induction of maturation in Xenopus laevis oocytes. However, the mechanism whereby PC-PLC transduces mitogenic signals triggered by growth factors or oncogenes remains to be elucidated. In this study, data are presented that show the involvement of protein kinase C zeta subspecies in the channelling of the mitogenic signal activated by insulin-p21ras-PC-PLC in Xenopus oocytes as well as the lack of a critical role of protein kinase C isotypes alpha, beta, gamma, delta, and epsilon in these pathways. 相似文献
39.
We studied the behavior of the Poeciliid fishGambusia affinis after the introduction of 3 substances into their tank: a homogenization ofGambusia affinis, a homogenization of the Anabantid fishBetta splendens, and a blank made of distilled water. The response of the fish was measured as a change in their spatial distribution in
the tank after the introduction of the substance. Two sizes of fish were used, and theGambusia homogenization produced clear alarm reactions in both, the fish fleeing to the bottom of the tank. This is one of a few examples
available of recognition of alarm substances in non-ostariophysian fish. In addition, we found that the small fishes that
had recently been exposed to the alarm substance stayed in an ‘alert state’, in which they had an increased sensitivity to
mechanical and visual fright stimuli. 相似文献
40.
Nacyra Assad-García Neftali Ochoa-Alejo Enrique García-Hernández Luis Herrera-Estrella June Simpson 《Plant cell reports》1992,11(11):558-562
A protocol for the Agrobacterium-mediated transformation of tomatillo was developed. Up to 40 transgenic plants could be obtained in experiments using 60 cotyledon expiants. The transformed nature of the regenerated plants was confirmed by NPT II and Southern blot hybridization analysis. Using the b-glucuronidase system the tissue specific and developmental patterns of expression of the Cauliflower Mosaic Virus 35S promoter were determined in transgenic tomatillo plants. It was found that this promoter is developmentally regulated during fruit and seed formation. 相似文献