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Enzyme histochemical and immunohistochemical characterization of oval and parenchymal cells proliferating in livers of rats fed a choline-deficient/DL-ethionine-supplemented diet.

Male outbred Sprague-Dawley rats were fed a choline-deficient diet containing 0.10% DL-ethionine for up to 30 weeks. Liver slices from rats killed 4, 6, 10, 14, 22 and 30 weeks after starting the treatment were histochemically analyzed for the following parameters: basophilia, expression of cytokeratin 19 (which in the liver is bile duct epithelial cell-specific), glycogen content and activities of glycogen synthetase (SYN), glycogen phosphorylase (PHO), glucose-6-phosphatase (G6PASE), glucose-6-phosphate dehydrogenase (G6PDH), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), glycerin-3-phosphate dehydrogenase (G3PDH), 'malic enzyme' (MDH), alkaline phosphatase (ALKPASE) and gamma-glutamyltranspeptidase (GGT). The diet induced necrosis of single parenchymal cells and a massive proliferation of oval cells within 4-6 weeks; thereafter cholangiofibroses, cystic cholangiomas and some cholangiofibromas, but no cholangiocarcinomas, were observed. Oval cells, cholangiofibroses, cystic cholangiomas and cholangiofibromas expressed cytokeratin 19, whereas parenchymal cells, foci of altered hepatocytes and hepatocellular adenomas did not; this observation does not support a precursor-product relationship between oval and parenchymal cells. SYN, PHO, G6PASE, G6PDH, GAPDH, G3PDH, MDH, ALKPASE and GGT activities were detected in oval cells; cholangiofibrotic lesions, cystic cholangiomas and cholangiofibromas stained strongly for GAPDH, G3PDH and MDH. In livers from rats fed the diet for 10 weeks, single hepatocytes storing high amounts of glycogen appeared in the parenchyma. There was no indication of a transition from the oval cell population to hepatocytes storing glycogen in excess. Foci of glycogen-storing cells were scattered all over the lobes after 14 and 22 weeks; they had increased G6PASE, G6PDH, ALKPASE and GGT activities. Mixed cell foci and hepatocellular adenomas developed within 22-30 weeks and exhibited a remarkable decrease of G6PASE activity, a strong increase of G6PDH, GAPDH, G3PDH and MDH activities as well as extremely high ALKPASE and GGT activities. The data support the concept that during hepatocarcinogenesis, a number of sequential changes in the activities of various enzymes involved in carbohydrate metabolism occur and that a correlation between morphology and enzyme pattern in the focal lesions does in fact exist. Furthermore, our results suggest that two different cell lineages are involved in the development of cholangiocellular tumors from oval cells and hepatocellular tumors from hepatocytes.

Alkaline Phosphatase↗

Isozyme frequency patterns in Drosophila pavani associated with geographical and seasonal variables.

Fourteen population samples of Drosophila pavani were obtained from a number of localities in Chile. The populations sampled were dispersed over 7 degrees of latitude and 1800 meters of elevation, and were drawn at three different times. Sixteen electrophoretic loci were assayed for each population; eight of the loci were analyzed statistically for geographic variation; the other eight were essentially monomorphic. For all eight variable loci, variation in allelic frequencies among populations was highly significant. In all cases, a significant portion of the variation among populations was associated with variation in gross environmental variables (latitude, elevation, month of collection). The implications of the evidence were discussed, and the authors concluded that there was suggestive evidence for selection.

Acid Phosphatase↗

Patterns of gene variation in central and marginal populations of Drosophila robusta.

The central and marginal populations of D. robusta differ greatly in the level of inversion polymorphism; the marginal populations are monomorphic or nearly so and the central populations are highly polymorphic. This paper presents the frequencies of alleles at forty gene loci in various populations of D. robusta, studied by electrophoresis of proteins and enzymes. Population samples were obtained from eight widely separated populations of D. robusta which included the central, the extreme marginal and the intervening populations between the center and the margins. We find that the proportion of polymorphic loci and average heterozygosity per individual is slightly higher in the marginal populations than the central populations. In D. robusta on an average, 39% of the loci are polymorphic and the average proportion of loci heterozygous per individual is 11%. A breakdown of loci in three categories, viz, hydrolytic enzymes and some other enzymes, larval proteins and glycolytic and Kreb's cycle enzymes, shows that in all populations the level of polymorphism is highest in the hydrolytic enzymes, intermediate in larval proteins and least in the glycolytic and Kreb's cycle enzymes. On the average, the proportion of loci heterozygous per individual for three groups of loci is: hydrolytic enzymes and others (.164), larval proteins (.115) and glycolytic and Kreb's cycle enzymes (.037). We also observe that in all populations the level of polymorphism on the X chromosome is far less than the expected 38%; in salivary gland cells the euchromatic length of the X chromosome is 38% of the entire genome. Lower levels of polymorphism for the X chromosome loci are explained due to low probability of balanced polymorphisms for the X-linked loci since the conditions for establishment of balanced polymorphism for X-linked loci are more restrictive than for the autosomal loci.-The polymorphic loci can be grouped according to pattern of allele frequencies in different populations as follows: (1) The allele frequencies are similar in all populations at the XDH, Pep-1 and Hex-1 loci. (2) The alleles at the Est-1, Est-2, Amy loci and the AP-4(1.0) and the LAP-1(.90) alleles show north south clinal change in frequency. (3) There is north south and east west differentiation at the Pt-5, Pt-8 and Pt-9 loci and the allele AP-4(.81). (4) Polymorphism at loci such as Fum, B.Ox, Hex-8, Pep-2 and Pep-3 are restricted to only one or two of the populations. (5) Allele frequencies at the MDH and ODH loci fluctuate between populations. (6) Allele frequencies at many polymorphic loci such as Est-1, Est-2, LAP-1, AP-4, Pt-5, Pt-8, Pt-9, Pt-16, MDH, Fum change clinally within a gene arrangement. The pattern of gene variation in D. robusta is very complex and cannot be easily explained due to migration of neutral alleles between once-isolated populations or to semi-isolation of neutral alleles. The observations of the pattern of allele variation in different populations, high levels of polymorphism in the marginal populations which have small population size and low levels of polymorphism of the X chromosome loci all support the argument in favor of balancing selection as the main mechanism for the maintenance of these polymorphisms. Environmental factors must play a role in the maintenance of a great deal of these polymorphisms, since we observe clinal allele frequency changes even within a given inversion type.

Acid Phosphatase↗

Inherited biochemical variation in Drosophila melanogaster: noise or signal? I. Single-locus analysis.

A study was conducted using small effective population size as an experimental design to test selective neutrality of seven isozyme polymorphisms. Loci varied as to the degree to which the decay of heterozygosity over 21 generations was retarded. Selection for heterozygotes, overdominance, is implicated for at least four of seven loci. Of these ADH gave the largest heterozygote excess in the presence of inbreeding. An interaction between the small population size treatment and excess heterozygosity suggests that (1) the loci studied may be selectively neutral and linked to other loci which are under the influence of selection or (2) the selection coefficients for the loci studied are not independent of the background genotype. In either case four of the seven enzymes studied are signaling the operation of selection. The problem of distinguishing the effect of a single marker from that of a chromosome segment is emphasized. The identification of the genetic unit of selection is crucial to any interpretation of the meaning of enzyme polymorphisms.

Alcohol Oxidoreductases↗

Dosage compensation of genes on the left and right arms of the X chromosome of Drosophila pseudoobscura and Drosophila willistoni.

We have investigated the occurrence of dosage compensation in D. willistoni and D. pseudoobscura, two species whose X chromosome is metacentric with one arm homologous to the X and the other homologous to the left arm of chromosome 3 of D. melanogaster. Crude extracts were assayed for isocitrate dehydrogenase (XR), glucose-6-phosphate dehydrogenase (XL?), 6-phosphogluconate dehydrogenase (XL?), and alpha-glycerophosphate dehydrogenase (chromosome 2) in D. willistoni, and for esterase-5 (XR), glucose-6-phosphate dehydrogenase (XL?), 6-phosphogluconate dehydrogenase (XL?) and amylase (chromosome 3) in D. pseudoobscura. Our results indicate that a mechanism for dosage compensation is operative in both arms of the X chromosome of these two species.

Alleles↗

Effect of dietary DL-ethionine and/or DL-methionine on egg laying and activities of some cytoplasmic NAD linked-dehydrogenases and NADPH-producing enzymes in liver of Japanese quail, Coturnix coturnix japonica.

The effect of dietary DL-ethionine and/or DL-methionine on egg laying, and activities of some NAD linked-dehydrogenases and NADPH-producing enzymes in liver of Japanese quail, Coturnix coturnix japonica was investigated. A 0.30% DL-ethionine plus 0.30% DL-methionine supplemented diet reversed partially the egg laying inhibited by the diet with 0.30% DL-ethionine alone. No inhibitory effect on egg laying was observed for the diet supplemented with 0.30% DL-methionine alone. In marked contrast to the decreased activity of L-glycerol 3-phosphate dehydrogenase and malate dehydrogenase, significantly increased activity of lactate dehydrogenase was obtained for quail fed the DL-ethionine, and the DL-ethionine plus the DL-methionine supplemented diet, respectively. No marked changes in activities of these three dehydrogenases were obtained for quail fed the diet supplemented with DL-methionine alone. Although decreased activity was observed for all of the four NADPH-producing enzymes in quail fed the diet supplemented with DL-ethionine alone, the DL-ethionine plus DL-methionine, the smallest decrease was obtained for NADP-isocitrate dehydrogenase. The diet supplemented with DL-methionine alone induced markedly the respective activity of malic enzyme and glucose 6-phosphate dehydrogenase. These results indicate a relatively important function of NADP-isocitrate dehydrogenase for NADPH-production even under DL-ethionine toxicity and suggest complicated relationships between egg production and activities of enzymes associated with carbohydrate and lipid metabolism in quail liver.

Alcohol Oxidoreductases↗

Effect of feeding frequency on growth and body composition of gastrostomized rat pups.

Two groups of rat pups were gastrostomized at 24 hours of age and formula-fed each hour or once every 6 hours a daily intake equal to 33% of their body weight. They were killed at age 5 to 7 days when body weight had reached twice that at time of gastrostomy; organ weights, body composition and hepatic activity of glucose-6-phosphate-dehydrogenase (G-6-PD) and alpha-glycerophosphate dehydrogenase (alpha-GPD) were determined. The stomach, small intestine, liver and spleen of pups fed 4 times each day were significantly larger than those of pups fed hourly. Food efficiency (gain/kcal) of pups fed each hour was significantly greater than that of pups fed every 6 hours; however, because pups fed each hour gained more water and less fat, an estimate of the percentage of energy intake utilized for growth was significantly less for these animals than for those fed every 6 hours. Concentration of calcium was greater and concentration of sodium was less in the carcasses of pups fed each hour than in the carcasses of pups fed 4 times daily. Total liver activities of G-6-PD and alpha-GPD were significantly less in pups fed each hour but the activity of these enzymes expressed per milligram of liver protein did not differ significantly between the two feeding groups.

Animals↗

Synergistic effect of Adh alleles in Drosophila melanogaster.

In laboratory cultures of Drosophila melanogaster derived from an African population, the quantities of six out of seven enzymes (G6PD, IDH, GPDH, ME, MDH, PGM and ADH) were higher in Adh-FF homozygotes than they were in Adh-SS. In crosses between Adh-FF and Adh-SS flies, the differences segregated as co-dominant alleles of a single Mendelian gene closely linked, or identical, to the Adh locus. The generality of these associations was suggested by the study of a French population with a very different history and genetic background. The possibility that the associations were caused by artefacts of the immunodiffusion techniques, or to a linked inversion (In(2L)t), was excluded. Possible ways by which the Adh locus may affect the quantities of other enzymes are discussed.

Alcohol Dehydrogenase↗