The effect of administration of estradiol and testosterone on body growth of young male rats.

The influence of estradiol and testosterone on body growth of young male Wistar rats was investigated. In the first experiment, estradiol was given to intact ad libitum fed male rats at 32, 37 and 42 days of age. Moreover, two untreated groups of animals were used: one was fed restrictedly according to the food intake of animals receiving estradiol and another was fed ad libitum. The animals were sacrificed at 47 days of age. Both untreated groups of animals achieved significantly higher body weight and length of tibia than estradiol treated animals. Also the growth of the tail of untreated animals was more intensive than that of estradiol treated animals. In the second experiment, estradiol was given to intact ad libitum fed male rats at 30, 35 and 45 days of age. Moreover, testosterone was given to a half of these animals at 45, 50 and 55 days of age. The animals were sacrificed at 60 days of age. Administration of testosterone significantly increased the growth of the tail and tibia in comparison to the animals which did not receive testosterone after estradiol administration. The results of the present study show that the inhibitory effect of estradiol on body growth of young male rats is not only the result of decreased food intake and that testosterone can improve the skeletal growth of male rats altered by previously given estradiol.     

Application of morphometric methods to the cytologic study of intradermal nevi.

Twenty-one intradermal nevi were studied by morphometric methods in an attempt to morphologically characterize the two types of nevus cell--epithelioids, type A, and fusiforms, type C--and to quantify the differences between them. Morphometric parameters of the intradermal nevi were compared with similar parameters of melanocytes and melanoma cells so that the maturation rates of the nevi cells could be established and to see if the parameters might indicate the degree of malignancy. Superficial nevus cells were differentiated from deep cells by their larger size and larger nuclear area. Nuclear area appeared to have potential for differentiating benign from malignant tumors. Decrease in cellular area appeared to indicate maturation rather than atrophy. Melanoma cells were differentiated by their larger size. Cell nuclear perimeter appeared to have confirmatory value, while cell perimeter was inconclusive.     

Effect of tubocurarine on the central generator of embryonic spontaneous motility.

The continuous administration of d-tubocurarine (6.5 +/- 0.4 mg/kg e.w./24 h) to chick embryos from the 4th to the 12th day of incubation had a positive effect on defects produced in the development of spontaneous motility either by decentralization of the spinal cord or by chemical phenobarbital depression, or by a combination of both experimental factors. In normal embryos, d-tubocurarine had no effect on the development of spontaneous motility.     

Identification and characterization of a luteinizing hormone/chorionic gonadotropin (LH/CG) receptor precursor in a human kidney cell line stably transfected with the rat luteal LH/CG receptor complementary DNA.

It is well established that the LH/CG receptor expressed in gonadal cells is an 85- to 92-kilodalton (kDa) glycoprotein. Additionally, however, a number of reports have noted the existence of other putative receptor species, but few attempts have been made to characterize these variant receptor species. A cell line [293L(wt1)] had previously been isolated which expresses large numbers of high affinity cell surface LH/CG receptors. Visualization of the LH/CG receptor species expressed in these cells and in rat luteal cells using ligand blots revealed 85- and 90-kDa LH/CG receptors, respectively, while immunoblots revealed another 68-kDa glycoprotein receptor in both cell types. The presence of both the 85- and 68-kDa receptor species was confirmed using immunoprecipitation and affinity purification of metabolically labeled 293L(wt1) cells. Enzymatic deglycosylations established that the 85-kDa receptor is a sialoprotein, while the 68-kDa species contains exposed high mannose residues. Protease digestion before LH/CG receptor immunoprecipitations localized the 85-kDa receptor on the plasma membrane, while the 68-kDa receptor was shown to be located intracellularly. Pulse-chase experiments were then used to positively establish that the 68-kDa receptor protein is actually a precursor of the 85-kDa LH/CG receptor species.     

Metabolism of oxygen radicals in peroxisomes and cellular implications.

Peroxisomes are subcellular respiratory organelles which contain catalase and H2O2-producing flavin oxidases as basic enzymatic constituents. These organelles have an essentially oxidative type of metabolism and have the potential to carry out different important metabolic pathways. In recent years the presence of different types of superoxide dismutase (SOD) have been demonstrated in peroxisomes from several plant species, and more recently the occurrence of SOD has been extended to peroxisomes from human and transformed yeast cells. A copper,zinc-containing SOD from plant peroxisomes has been purified and partially characterized. The production of hydroxyl and superoxide radicals has been studied in peroxisomes. There are two sites of O2- production in peroxisomes: (1) in the matrix, the generating system being xanthine oxidase; and (2) in peroxisomal membranes, dependent on reduced nicotinamide adenine dinucleotide (NADH), and the electron transport components of the peroxisomal membrane are possibly responsible. The generation of oxygen radicals in peroxisomes could have important effects on cellular metabolism. Diverse cellular implications of oxyradical metabolism in peroxisomes are discussed in relation to phenomena such as cell injury, peroxisomal genetic diseases, peroxisome proliferation and oxidative stress, metal and salt stress, catabolism of nucleic acids, senescence, and plant pathogenic processes.     

Benzodiazepines in the brain

Great progress has been made in the last 5 yr in demonstrating the presence of benzodiazepines (BDZs) in mammalian tissues, in beginning studies on the origin of these natural compounds, and in elucidating their possible biological roles. Many unanswered questions remain regarding the sources and biosynthetic pathways responsible for the presence of BDZs in brain and their different physiological and/or biochemical actions. This essay will focus on recent findings supporting that: (1) BDZs are of natural origin; (2) mammalian brain contains BDZs in concentrations ranging between 5.10⁻¹⁰–10⁻⁸ M; (3) dietary source of BDZs might be a plausible explanation for their occurrence in animal tissues, including man; (4) the formation of BDZ-like molecules in brain is a possibility, experimentally supported; (5) BDZ-like molecules including diazepam andN-desmethyldiazepam are elevated in hepatic encephalopathy; and (6) natural BDZs in the brain are involved in the modulation of memory processes. Future studies using the full range of biochemical, physiological, behavioral, and molecular biological techniques available to the neuroscientist will hopefully continue to yield exciting and new information concerning the biological roles that BDZs might play in the normal and pathological functioning of the brain.     

Proteins and glycosaminoglycans in the intercellular matrix of the human cumulus-oophorus and their effect on conversion of proacrosin to acrosin.

Human cumuli-oophori were cultured in vitro in the presence of radioactive protein and polysaccharide precursors. The time course of the cumulus cell secretion was traced by histoautoradiography. Matrix solubilization, and sodium dodecyl sulphate polyacrylamide gel electrophoresis and high-performance liquid chromatography showed that proteoglycan (Mr greater than 1,700,000) was the main cumulus cell product that was prevailingly deposited in the cumulus intercellular matrix and partly released into the culture medium. It was capable of accelerating the conversion of proacrosin to acrosin and this activity was abolished by enzymatic removal of chondroitin sulphate, the predominant glycosaminoglycan of this proteoglycan fraction. None of the other fractions, including a proteoglycan of Mr 80,000-90,000, containing heparan sulphate, accelerated the conversion of proacrosin to acrosin under the conditions used. The results suggest that chondroitin sulphate is the active component of the high-Mr proacrosin activator of the human cumulus-oophorus.     

Characteristics of the microsporidian Enterocytozoon bieneusi: a consequence of its development within short-living enterocytes.

Ultrastructural studies were done on developmental stages of Enterocytozoon bieneusi obtained from HIV seropositive patients suffering from diarrhea. The presence of elaborate multilamellar structures suggest that they give rise to various membrane systems needed for rapid production of disseminating stages.     

The effect of cyclophosphamide and gamma irradiation on adenosine deaminase and purine nucleoside phosphorylase in mice

Changes in ADA and PNP activities in the spleens and thymuses of mice were studied after a single administration of cyclophosphamide (CY, 200 mg/kg) and after whole-body gamma irradiation (5.5 Gy), applied alone or three days after CY application. In the first days after the treatment the enzyme activities were significantly depressed (p less than 0.01) with the exception of ADA in the spleen, where a high elevation (220-380%) in relation to controls was observed. During the regeneration period a pronounced rise of PNP activity in the spleen occurred mainly after a combined application of CY and irradiation (270%). In the thymus the regeneration was manifested by a mild increase of both ADA and PNP activities towards control values. The findings suggest that the expressive changes of ADA and PNP activities, participating in the purine salvage pathway, may, after a cytotoxic treatment, influence the nucleotide pool and DNA synthesis in lymphoid organs.     

On the opportunity cost of the photosynthate invested in stem elongation reactions mediated by phytochrome

Summary Seedlings of shade-intolerant species react to alterations of the light climate caused by their neighbors with morphological changes that may influence the pattern of resource acquisition and utilization at the whole-canopy level. One such change, the increased stem elongation rate that is triggered by low red (R, 660 nm) to far-red (FR, 730 nm) ratios (R:FR) in dense canopies, might reduce the amount of assimilates available for leaf area expansion or root growth, and in that way affect resource capture by the canopy. We have tested this hypothesis by comparing the growth of both isolated individuals and canopies of the weed Amaranthus quitensis under conditions differing only in the spectral distribution of the incident light. When canopies received the full spectrum of sunlight, the stems were a large proportion (40–57%) of total biomass. Filtering the FR waveband (and hence raising the R:FR ratio to eliminate the neighbors' proximity-signal) resulted in shorter canopies with lighter stems. However, the growth of leaves and roots was not promoted by this treatment, indicating that the opportunity cost of the assimilates invested in the stems was nil or very small. Filtering the FR had no effect on biomass accumulation when plants were grown as isolated individuals. The higher growth of the canopics under full spectrum could be due to a higher light interception or to a higher efficiency of light conversion into biomass. The first possibility is weakened by the observation that filtering the FR had no effect on the dynamics of soil covering by the crops. The second is indirectly strengthened by results of an experiment with isolated plants showing that stem elongation, stem growth, and total plant biomass can be increased by reducing the flux of R light received by the stems without affecting the light climate of the leaves. Further work is needed to distinguish between these two possibilities; whatever the cause, our results show that the elongation responses to decreased R:FR may lead to a net increase in canopy productivity, and do not necessarily have a negative impact on the growth of resource-harvesting organs.