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Biomedical subjects

M Winick

Publications and source records attributed to M Winick.

At least 55 records · Page 3Linked to original sources
PubMed1978

The effects of folic acid supplementation during pregnancy in the rat.

1. Twenty-four Sprague-Dawley female rats were randomly assigned to three groups (groups A, B, C). Group A was given a folic acid-free diet and groups B and C received 0.0018 g folic acid/kg diet. Rats in group C were also given a supplement of 1 mg folic acid/d by intraperitoneal injection. 2. After 14 d of feeding the rats were mated. The diets were continued throughout gestation. On day 21, of gestation the dams were killed and their livers and products of conception assayed for RNA, DNA, protein and tetrahydrofolate dehydrogenase (5,6,7,8-tetrahydrofolate dehydrogenase; EC 1.5.1.3) activity. 3. The foetuses, placentas and livers from supplemented rats (group C) were significantly larger than those from groups A and B and had a higher content of RNA, DNA and protein. Those tissues from group A dams were smaller than those from the other groups and had a correspondingly reduced nucleic acid and protein content. 4. The activity of tetrahydrofolate dehydrogenase, the first and rate-limiting enzyme in the metabolism of folate, was increased in the folate supplemented rats (group C) and reduced in the rats given a folic acid-free diet (group A). These changes in enzyme activity could explain the differences in nucleic acid biosynthesis and growth shown by the different groups.

Animals↗
PubMed1978

Effect of malnutrition and rehabilitation on the metabolism of polyamines in rat liver.

In adult male rats the activity of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMD) and the concentration of putrescine and spermidine increased markedly 3 to 4 weeks after feeding the animals a 6% casein diet. Incorporation of [14C]orotic acid into nuclear RNA also increased during this period of time. In contrast, spermine concentration remained unchanged. During the fifth week of protein restriction enzyme activities, putrescine and spermidine concentrations and orotic acid incorporation returned to control levels. After the restricted rats were put on a control diet there was a rapid increase above control levels in ODC activity and a proportionally smaller increase in SAMD activity. Putrescine and spermidine concentration also increase above control levels. Both enzyme activities and polyamine concentrations were within normal levels 96 hours after refeeding. Spermine values were unmodified by refeeding. After a transient rise 12 hours after refeeding, incorporation of labeled orotic acid into RNA decreased significantly for the rest of the experiment.

Adenosylmethionine Decarboxylase↗
PubMed1978

Studies on ribosomal RNA synthesis in vivo in rat liver during short-term protein malnutrition.

To better understand the increased incorporation of [14C] orotate into rRNA, as detailed study of liver rRNA synthesis was performed on young rats fed a 6% casein diet for 1 week. From 10 to 180 minutes after i.v. injection of [14C] orotate, nucleolar RNA specific activity of malnourished rats was 1.6 times higher than controls. Polyacrylamide gel electrophoresis revealed that 45S pre-rRNA from malnourished rats was synthesized more rapidly than controls. Specific activities of other nucleolar RNA species was increased but the time of appearance of labeled peaks did not change. The cellular cytoplasmic rRNA pool was reduced to 70% of controls, the time of appearance of labeled rRNA in the cytoplasm was the same, but cytoplasmic rRNA specific activity was 2.1 times greater than controls. Absorbance profiles and radioactivity patterns of nucleoplasmic RNA were similar in the two groups of rats. Nucleoplasmic radioactivity patterns were complex and heterodispersed, and the amount of radioactivity was greatest in RNA from malnourished rat liver. Our data indicate that short-term dietary protein restriction leads to cellular events which increase the synthesis of nuclear RNA. Nucleolar RNA is processed and transported to the cytoplasm in a manner similar to controls.

Animals↗
PubMed1977

Effects of malnutrition on some aspects of RNA metabolism in the maternal liver and fetal tissues at different stages of pregnancy in the rat.

A comparison was made between rats fed diets containing either 5% casein or 25% casein, both being supplemented with DL-methionine, from the first day of pregnancy. Livers of dams killed on days 7, 14, and 21 and whole fetuses on days 12, 14, and 21 were weighed, analyzed for protein, RNA and DNA content and assayed for ornithine decarboxylase (ODC) and S-adenosyl-L-methionine decarboxylase (SAMD). Free and total alkaline ribonuclease activity were also measured in the maternal livers. Malnutrition reduced the characteristic increase in content of DNA, RNA and protein in the maternal liver and fetus. In control rats total hepatic RNase activity increased and free RNase activity decreased during late pregnancy. In the deprived group, total activity decreased and free activity increased during late pregnancy. Liver and fetal ODC and SAMD activities were reduced by undernutrition. These studies show that malnutrition reduced both growth and the accretion of RNA in livers and fetuses of rat dams. These changes coincide with a reduced activity of polyamine synthesizing enzymes suggesting that there is a functional relationship between polyamines and RNA. High hepatic free RNase activity in malnourished dams may help to limit any build up in RNA content.

Adenosylmethionine Decarboxylase↗
PubMed1975

Activity of alkaline RNase in placentas of malnourished women.

Pregnancies were compared in 18 Ecuadorian women of low socioeconomic status and 11 of high socioeconomic status. Objective evidence of malnutrition was demonstrable in virtually all of the women from the low socioeconomic group and in none from the high socioeconomic group. Birth weight and placental weight were significantly lower in the malnourished group. Nucleic acid and protein content of placentas were slightly lower and activity of alkaline ribonuclease was markedly elevated. The data reinforce animal studies and demonstrate for the first time in human subjects that alkaline RNase activity is increased in placentas from malnourished women. We suggest that activity of this enzyme in placenta may prove to be a useful marker of maternal and fetal nutritional status.

Ecuador↗
PubMed1975

Vitam A deficiency and fetal growth and development in the rat.

Studies were conducted to examine in detail the effects of vitamin A deficiency on fetal growth and development in the rat. The gradations of deficiency were examined in two studies. The first included total vitamin A depletion followed by retinoic acid supplements, and the second included three different levels of restricted intake of retinyl acetate (42, 16, or 8 mug of retinol equivalents/day/kg of body weight) in vitamin A-depleted rats. In the first study, extensive fetal resorption and death were observed in retinoic acid-fed females after day 14 of gestation. These findings confirmed the morphological studies of Thompson and associates (Proc. Roy. Soc. London, Ser. B 159, 510-535, 1964) who found the earliest Detectable histological lesions to be in the placentas at days 15-16 of pregnancy. Analyses were carried out of the total weight, the DNA, RNA, and protein contents of fetuses and placentas of different gestational ages in retinyl ester-fed and retinoic acid-fed females. Biochemical changes indicative of a reduced rate of cell division were observed in both fetus and placenta by day 14 in the retinoic acid-fed rats. The few live fetuses in this group maintained a growth rate of only 60-70% of that of the fetuses of retinyl ester-fed dams after day 14. By contrast, the growth rate of the placentas (of live fetuses) after day 14 of gestation was not as consistently affected by retinol deficiency. Restriction of retinyl acetate intake (in the second study) significantly reduced both the total litter size and the number of live pups per litter. Most of the females in the retinyl acetate-restricted groups delivered pups that had normal body weight and appeared normal on visual inspection. Significant differences from normal controls were seen only in the neonates from dams given 8 mug of retinol equivalents (per kg of body weight per day), which had smaller livers and kidneys than the control neonates. In contrast, the weights of the brains of the neonates in all three retinyl acetate-restricted groups showed no differences from control values. Vitamin A assays on maternal and neonatal sera and livers indicated that the transport of vitamin A across the placenta was well regulated, and suggested that this transport is maintained with high priority in the presence of maternal deficiency. The effects of vitamin A deficiency on fetal growth and development might reflect primary effects on the placenta, with secondary effects on the fetus, or primary direct effects on the fetus itself. The mechanisms of the observed effects remain to be explained.

Animals↗
PubMed1975

Effects of early undernutrition and subsequent refeeding on alkaline ribonuclease activity of rat cerebrum and liver.

The effect of undernutrition and subsequent rehabilitation on free and total alkaline ribonuclease activity (RNase) of cerebrum and liver was studied in 14- and 21-day-old rats. Free RNase activity was higher in both organs at 14 and 21 days of age. However, at day 21 the difference was statistically significant only in liver. Total RNase activity was not changed by undernutrition in cerebrum and was reduced in liver. Nutritional rehabilitation returned both free and total RNase activities to control levels in liver but had no apparent effect on cerebrum. The elevation of free RNase seems to be secondary to a reduced concentration of inhibitor protein and not to de novo synthesis of RNase.

Age Factors↗
PubMed1975

The response of the right ventricle to experimentally induced pulmonary artery obstruction.

Banding of the main pulmonary artery was undertaken in 11 litter-mate puppies and 8 young adult beagle dogs to study the response of the right ventricle to pressure loading. Five puppies and 3 young adult dogs acted as controls, undergoing sham surgical procedures without pulmonary artery banding. In one banded puppy and one banded young adult dog, adequate banding was not achieved and each was subsequently considered with its respective control group. A trans-band gradient of 15 mm Hg or greater was deemed a successful banding procedure. Banded puppies showed an increase in the trans-band pressure gradient in the year following surgery whereas young adult dogs showed a fall in the gradient, despite satisfactory banding as shown by cardiac catheterization 14 days after surgery. Cardiac muscle analyses indicated that the right ventricle of puppies responded to pulmonary banding by an increase in total organ weight, total tissue protein, DNA and RNA without altering the protein/DNA and RNA/DNA ratios. By contrast, young adult dogs showed only slight and insignificant increases in the protein/DNA and RNA/DNA ratios. Thus the response of the right ventricle to pulmonary artery banding in puppies is hyperplastic in nature, while in young adult animals the response to a similar stress load is with mild muscular hypertrophy and dilatation. This differential cellular response to the same stimulus based on the age of the organism is another demonstration of the principle that growth responses in the young involve cellular proliferation while those in the adult consist primarily of cell enlargement. It is, therefore, perhaps erroneous to refer to cardiac enlargement in newborns and infants as cardiac hypertrophy.

Animals↗