Altered levels of histone H1(0) and DNA topoisomerase activity in the liver of the tumour-bearing rat

Walker 256 carcinoma cells were injected subcutaneously into the dorsal region of rats. After 9 days of tumour growth increases were observed in liver mass and DNA content and in the incorporation of [3H]-thymidine into liver DNA. These changes were accompanied by a fall in the H1(0) fraction of liver histones and rises in both DNA topoisomerase I and II activities.     

Interchangeability of growth factors in early G(0)-G(1) period of cell cycle

The retrovesical hydatid cyst is a very rare site. The authors have observed six cases over a 12-year period. The diagnosis is often delayed. The clinical features are dominated by pain and compression of adjacent organs. Clinical examination sometimes reveals a hypogastric mass. The topographic diagnosis is based on ultrasonography and IVU. Treatment is surgical: retroperitoneal cystopericystectomy. The course is often favourable.     

Glucosamine metabolism in regenerating rat liver

1. Glycoprotein synthesis was investigated with [1-14C]glucosamine in vivo. [14C]Glucosamine was administered intravenously 24h after hepatectomy to rats. 2. Incorporation into the acid-soluble fraction was maximum at 15 min after injection both in sham-operated and hepatectomized rats. 3. Enhancement of incorporation into UDP-N-acetylhexosamine in regenerating liver was observed. However, its specific activity was lower, because of a greater enhancement of synthesis de novo of the amino sugar. 4. In the liver acid-insoluble fraction, maximum incorporation of [14C]glucosamine was at 30 min in sham-operated rats and 2 h in hepatectomized rats respectively. 5. In sham-operated rats, incorporation into the plasma acid-insoluble fraction followed that of the liver acid-insoluble fraction, but hepatectomy resulted in a rapid enchancement of incorporation into plasma. 6. It is concluded that synthesis of liver glycoproteins is stimulated after partial hepatectomy and that glycoproteins synthesized are released rapidly into the plasma.     

Yield of chromosome aberrations induced by x-irradiation in regenerating rat liver cells at different periods of the generation cycle

The yield of cells with chromosome aberrations was studied using 630 rad X-irradiated liver cells of intact and hepatectomied rats, hepatectomy being performed 2-24 hours before irradiation. The radiosensitivity was variable throughout the cell cycle. The kinetic curve of radiosensitivity changes shows two ranges of radioresistance: in the early period G1 and in the middle period S, as well as the range of a relatively high sensitivity in the middle of period G1. The increase in radiosensitivity is also characteristic of the G0-G1 transition (4 hours after the stimulation).     

Manipulation of metallothionein expression in the regenerating rat liver using antisense oligonucleotides

In order to gain some insight into the fate of fumarate synthesised in the cytosol in the purine nucleotide cycle and in amino acid catabolism, the capability of both rat kidney mitochondria and acidotic rat kidney mitochondria to take up either externally synthesised, via adenylsuccinate lyase, or added fumarate in exchange with intramitochondrial malate or aspartate was tested by means of both spectrophotometric and isotopic techniques. The appearance of either malate or aspartate caused by the presence of fumarate was revealed outside normal and acidotic mitochondria by using specific substrate detecting systems. Consistently, externally added fumarate was found to cause efflux of either [14C]-malate or [14C]-aspartate from loaded mitochondria. The occurrence in rat kidney mitochondria of two separate translocators, i.e., fumarate/malate and fumarate/aspartate carriers, is shown in the light of saturation kinetics and the different inhibitor sensitivity. The fumarate/aspartate antiporters found in normal and acidotic mitochondria appear to differ from each other.     

Semi-quantitative ultrastructural analysis of the localization and neuropeptide content of gonadotropin releasing hormone nerve terminals in the median eminence throughout the estrous cycle of the rat

The ultrastructural appearance of gonadotropin releasing hormone-immunoreactive elements was studied in the external zone of the median eminence of adult female Wistar rats. On the one hand, the purpose of the study was to determine the distribution of gonadotropin releasing hormone terminals towards the parenchymatous basal lamina at the level of hypothalamo-hypophyseal portal vessels, throughout the estrous cycle. On the other hand, we have semi-quantified the gonadotropin releasing hormone content in nerve terminals or preterminals during this physiological condition. A morphometric study was coupled to a colloidal 15 mn gold postembedding immunocytochemistry procedure. Animals were killed at 09.00 on diestrus II, 0.900, 10.00, 13.00, 17.00 and 18.00 on proestrus and 09.00 on estrus (n = 4-8 rats/group). A preliminary light microscopic study was carried out to identify an antero-posterior part of median eminence strongly immunostained by anti-gonadotropin releasing hormone antibodies but which was, in addition, easily spotted. This last condition was necessary to make a good comparison between each animal. Contacts between gonadotropin releasing hormone nerve terminals and the basal lamina were observed only the day of proestrus. Such contacts, however, were rare and in the great majority of cases, gonadotropin releasing hormone terminals are separated from basal lamina by tanycytic end feet. The morphometric analysis showed no significant variation in average distance between gonadotropin releasing hormone terminals and capillaries throughout the estrous cycle. Consequently, it did not appear that a large neuroglial plasticity exists during the estrous cycle. However, the observation of contacts only on proestrus together with some ultrastructural images evoke the possibility of a slight plasticity. The semi-quantitative results show that the content of gonadotropin releasing hormone in the nerve endings presented two peaks on proestrus: one at 09.00 (23 +/- 5 particles/micrograms2, P < 0.03) before the onset of luteinizing hormone surge, and the second at 18.00 (16 +/- 2 particles/micrograms2, P < 0.01) concomitantly with the luteinizing hormone surge, when compared to baseline values on proestrus 10.00 (8 +/- particles/micrograms2).     

Synthesis of secretory protein in regenerating liver of rat after partial hepatectomy

Albumin immunoreactivity in the liver was examined on days 2, 5 and 10 after two-thirds partial hepatectomy by light and ultrastructural immunoperoxidase methods and the ultrastructural area of the rough endoplasmic reticulum (ER) in hepatocytes was measured. Albumin immunoreactivity was seen in the rough ER and Golgi apparatus of all hepatocytes in the hepatectomized liver and ultrastructural analysis showed a significantly greater area of rough ER on day 5 than on days 2 or 10. Albumin mRNA was studied by the in situ hybridization technique using radioisotopes and their numbers were determined visually. Albumin mRNA was present as grains in all hepatocytes and the grains varied in number during regeneration of the liver, being more abundant on day 5 than on days 2 or 10. The activity of [3H]-leucine incorporated into albumin synthesis, an indicator of translational activity, was higher on days 5 and 10 than on day 2 and was highest on day 5. In conclusion, albumin synthesis varied during liver regeneration after partial hepatectomy, being reduced at the peak of cell proliferation on day 2 and being most active on day 5.     

Germ cell genotype controls cell cycle during spermatogenesis in the rat

Spermatogenesis is one of the most productive self-renewing systems in the body: on the order of 10(7) spermatozoa are produced daily per gram of testis tissue. In each mammalian species, the time required for completion of the process is unique and unalterable. Because the process is supported by somatic Sertoli cells, it has generally been thought that cell-cell interaction between germ and Sertoli cells controls the duration of cell cycles and cellular organization. We have used the newly developed technique of spermatogonial transplantation to examine which cell type(s) determines the rate at which germ cells proceed through spermatogenesis. Rat germ cells were transplanted into a mouse testis, and the mouse was killed 12.9-13 days after administration of a single dose of [3H]thymidine. The most advanced rat cell type labeled was the pachytene spermatocyte at stages VI-VIII of the spermatogenic cycle. In animals given only rat cells, some endogenous spermatogenesis of the mouse recovered. The most advanced labeled mouse cell types in recipients killed 12.9-13 days after administration of a single dose of [3H]thymidine were meiotic cells or young spermatids, which is consistent with a spermatogenic cycle length comparable to the 8.6 days reported for the mouse. The same results were obtained if a mixture of rat and mouse cells were transplanted. There existed two separate timing regimens for germ cell development in the recipient mouse testis; one of rat and one of mouse duration. Rat germ cells that were supported by mouse Sertoli cells always differentiated with cell cycle timing characteristic of the rat and generated the spermatogenic structural pattern of the rat, demonstrating that the cell differentiation process of spermatogenesis is regulated by germ cells alone.     

Hepatic kinetics of SCP-1 (N-[alpha-(1,2-benzisothiazol-3(2H)-ona-1, 1-dioxide-2-yl)-acetyl]-p-aminophenol) compared with acetaminophen in isolated rat liver

Since substantial bias can result from assigning some type of mean exposure to a group, risk assessments based on epidemiological data should avoid the grouping of data whenever possible. However, ungrouped data are frequently unavailable, and the question arises as to whether an arithmetic or geometric mean is the most appropriate summary measure of exposure. It is argued in this paper that one should use the type of mean for which the total risk that would result if every member of the population was exposed to the mean level is as close as possible to the actual total population risk. Using this criterion an arithmetic mean is always preferred over a geometric mean whenever the dose response is convex. In each of several data sets examined in this paper for which the dose response was not convex, an arithmetic mean was still preferred based on this criterion.     

Inhibition of DNA methylation by S-adenosylethionine with the production of methyl-deficient DNA in regenerating rat liver

Ethionine, a liver carcinogen, was administered p.o. (300 mg/kg) to rats 17 hr after partial hepatectomy. At 6 hr after administration of the ethionine, hepatic S-adenosylethionine levels were 30- to 40-fold greater than the hepatic level of S-adenosylmethionine. A 10-fold ratio of S-adenosylethionine to S-adenosylmethionine still persited at 24 hr after ethionine administration. When given at 17 hr after partial hepatectomy, ethionine produced a 30% inhibition of DNA synthesis, measured by the incorporation of [methyl-3H]thymidine at 23 to 24 hr after partial hepatectomy (6 to 7 hr after ethionine administration). DNA synthesized during this interval was methyl deficient as judged by the reduced incorporation of radioactivity from L-[methyl-3H]methionine into 5-methylcytosine residues of DNA. In an assay for DNA methylation in vitro using whole nuclei, the methyl-deficient DNA was methylated by S-adenosylmethionine 8 times more than was control DNA; the DNA methylation was competitively inhibited by S-adenosylethionine. These data suggest that S-adenosylethionine, formed in vivo from ethionine, competitively inhibits the methylation of DNA in vivo by S-adenosylmethionine, resulting in the production of methyl-deficient DNA.     

Stability and folding of the cell cycle regulatory protein, p13(suc1)

Recreationally abused substances include both legal and illegal agents, broadly classified as opioids, psychostimulants, sedatives, cannabis (marijuana), hallucinogens, inhalants, dissociative anesthetics (phencyclidine), anticholinergics, ethanol, and tobacco. These substances are associated with an array of neurological emergencies resulting from overdose, withdrawal, and other medical and neurological complications.