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Biomedical subjects

W H Peters

Publications and source records attributed to W H Peters.

At least 145 records · Page 8Linked to original sources
PubMed1981

Studies on (Na+ + K+)-activated ATPase. XLIX. Content and role of cholesterol and other neutral lipids in highly purified rabbit kidney enzyme preparation.

(1) The neutral lipids and the free and bound fatty acids of a highly purified (Na+ + K+)-ATPase preparation from rabbit kidney outer medulla have been analysed. (2) On a dry weight basis, the total lipid content is nearly the same as the total protein content, and consists for 66% of phospholipids and for 34% of neutral lipids and free fatty acids. In the latter category cholesterol is the main component (71%). (3) On a molar basis the enzyme preparation contains 382 mol phospholipids, 67 mol free fatty acids, 9, 16 and 12 mol mono-, di- and triacylglycerols, 249 and 19 mol free and esterified cholesterol per mol enzyme. (4) The fatty acid composition of each lipid and of the free fatty acid fraction, present in the enzyme preparation, is reported. (5) All cholesterol and part of the phospholipids can be removed by hexane extraction, leaving 66% of the (Na+ + K+)-ATPase activity. Oxidation of all cholesterol to cholest-4-en-3-one by cholesterol oxidase leaves 85% of the (Na+ + K+)-ATPase activity. These results indicate that cholesterol is not essential for (Na+ + K+)-ATPase activity.

Animals↗
PubMed1981

(Na/ + K+)ATPase has one functioning phosphorylation site per alpha subunit.

(Na+ + K+)ATPase contains two different subunits, a catalytic subunit (alpha) and a subunit with uncertain function (beta). The enzyme binds ATP, ouabain and vanadate, and can be phosphorylated by ATP as well as by inorganic phosphate. From the previously reported maximal binding and phosphorylation capacities of 3.5--4.3 nmol P per mg protein (based on Lowry protein determination) and the earlier molecular weight value of approximately 250,000, a molar binding and phosphorylation capacity of 0.87--1.07 mol per mol enzyme was derived. As it is generally agreed that the enzyme molecule contains two alpha subunits or even a multiple of two, it has been suggested that the enzyme operates by means of a so-called "half-of-the-sites mechanism" whereby only of the two alpha subunits can be phosphorylated at any one time. We now present evidence that every alpha subunit can be phosphorylated simultaneously, which rules out the operation of such a mechanism.

Adenosine Triphosphate↗
PubMed1978

[The extragradient of agar-gel electrophoresis in hyperlipoproteinemia].

In the present paper we report on the occurrence of an extra band suggesting a possible M-component in a case of hyperlipoproteinaemia with excessive elevation of lipid values. The enhanced apolipoproteins result in a distinct extra band in the alpha2-beta1-interzone of protein electrophoresis. The extra band disappeared after treatment of the hyperlipoproteinaemia.

Blood Protein Electrophoresis↗
PubMed1978

Inhibition of translation of lens mRNAs in a messenger dependent reticulocyte lysate by cap analogues.

The nuclease treated reticulocyte lysate forms a highly efficient and completely mRNA-dependent cell-free system. In this system the functioning of the cap on eukaryotic mRNAs was explored by blocking cap recognition with cap analogues. Translation of capped mRNAs was severely inhibited, while translation of uncapped mRNAs was unaffected. It is concluded that this cell-free system can be used for screening cap dependence in the translation of specific mRNAs, like calf lens mRNAs. At 1.2 mM m7G5'p, 0.16 mM m7G5'pp or 0.16 m7G5'ppp5'G, translation of all lens mRNAs was totally inhibited. At lower concentrations the sensitivity to cap analogues was different for the various species of lens crystallin messenger. gamma-Crystallin mRNA showed relatively the lowest response. The translation of added polyribosomes was also inhibited by the cap analogue. It is concluded that translation of all crystallin messengers is cap-dependent.

Cell-Free System↗
PubMed1978

The effect of the messenger RNA concentration on the competitive inhibition of translation by cap-analogues.

Inhibition of translation of several mRNA species in a micrococcal nuclease treated reticulocyte lysate by cap analogues was compared with the competition between two mRNAs. Inhibition characteristics were very similar, only complete mRNA molecules inhibited at concentrations 150 times lower than m7 G5'ppp5'G. The inhibition of mRNA translation by cap analogues could be neutralized by the addition of extra mRNA in a manner predicted from the competitive nature of the inhibition by cap analogues.

Binding, Competitive↗
PubMed1978

Plasma concentrations of insulin and free fatty acids in dietary-induced obesity of Wistar-rats before and after glucose stimulation.

Colony-bred Wistar-rats develop obesity after long term feeding with a high-fat diet (50% fat, w/w). According to previous investigations a disturbed glucose tolerance after i.v. glucose load could be described for obese rats. Therefore, we measured peripheral IRI-concentrations before and after glucose stimulation in controls and fat-fed rats. In obese animals we observed a basal hyperinsulinemia in the dynamic phase of development of obesity. In controls and fatty rats, no differences in the peripheral insulin response to an i.v. glucose stimulation could be demonstrated, nor did we find indications of an impaired early insulin response in fatty rats. In accordance with the glucose tolerance study, obese rats in the dynamic phase showed lower FFA-levels (fasting state) and a slower decrease of FFA-concentrations after the glucose-induced insulin enhancement. Changing the feeding schedule at 20 weeks of age, e.g. feeding control diets to fatty rats for 4 weeks, reduced basal IRI-concentrations in these animals to control values. Assuming the secondary nature of the basal hyperinsulinemia in obese rats, our present results demonstrate that the observed impairment of glucose tolerance may be related to the peripheral insulin resistance of skeletal muscle and/or hypertrophied adipose tissue.

Animals↗
PubMed1977

[Kidney changes in experimental obesity].

In a survey renal changes in human obesity as well as in experimental obesity of laboratory animals are discussed. Own results are described about a comparison of biochemical and morphological studies on an experimental model of dietary-induced obesity after long-time feeding of a high-fat diet. Obese rats show normal concentrations of plasma proteins after feeding of a high-fat diet of some weeks. Urea-nitrogen levels are not modified as compared to control animals. Despite the mean levels of creatinine concentration in the dynamic and static phase of obesity are not different, some obese rats show increased creatinine values in the dynamic phase. Our histological studies reveal no pathological abnormalities of renal structures and blood vessels.

Animals↗
PubMed1977

Basal hyperinsulinemia in Wistar-rats rendered obese by a high-fat diet.

Basal plasma insulin levels were measured in Wistar-rats rendered obese by feeding a high-fat diet (50% fat, w/w). During the period of rapid weight-gaining ("dynamic phase" of the development of obesity) fat-fed rats show elevated basal insulin levels in the peripheral blood plasma. No further enhancement occurred in the so-called "static phase" of obesity. Changing the feeding schedule at 20 weeks of age, e.g. feeding control diets (3% fat, w/v) for 4 weeks to fatty rats, results in a depression of insulin levels to control values together with a reduction of the body weight. The findings are discussed in relation to the dietary induced alterations of carbohydrate and lipid metabolism of obese rats.

Animals↗
PubMed1977

[Results of oral methionine loads in normal subjects and patients with liver diseases using an analyzer short program].

Control subjects and patients with liver diseases (cirrhosis, fatty liver) were given an oral methionine load with 100 mg L-Met/kg body weight. Amino acid chromatography was made by a short-program particularly suitable for the diagnosis of hereditary disorders of methionine metabolism. Met-tolerance in blood plasma as well as cystathionine, homocystine and the mixed disulfide homocysteine-cysteine in plasma and urine were investigated. Methylmalonic acid excretion in the urine was determined by gas chromatography. Patients with liver diseases showed some pathological changes of methionine tolerance after the load. However, cystathionine and homocysteine could not be demonstrated. No methylmalonic acid excretion occurred in normal subjects and patients with liver diseases after the methionine load.

Adolescent↗
PubMed1976

[Biochemical parameters of blood plasma, and body and organ weights of Wistar rats with dietarily-induced experimental obesity].

The authors investigated in rats with dietarily-induced obesity certain biochemical parameters of the blood plasma as well as body and organ weights during the dynamic and the static phase of obesity development. They determined total cholesterol, total protein, albumin, creatinine, urea nitrogen and transaminases. After 4-5 weeks, the animals on a high-diet (50% of fat) had body weights which were, on an average, by 90% higher than those of the control animals. This difference persisted during the static phase. In the animals on a high-fat diet, body length was greater. The high-fat diet (which contains a great proportion of sunflower oil) leads to a decrease of the plasma cholesterol level in obese rats. The plasma-protein bodies, creatinine and urea nitrogen values as well as those for transaminases permit, as parameters for function and damage, to draw conclusions as to kidney and liver damages in the animals on high-fat diet. There were no differences in plasma protein between the control and experimental animals. On the contrary, obese rats showed in some cases high creatinine concentrations during the dynamic phase. Differences in urea nitrogen were not observed between the two groups of animals. Increases in alanine aminotransferase were found in the animals on high-fat diet as a manifestation of fatty degeneration of the liver. A synopsis of weight curves, biochemical parameters and histological findings permits the conclusion that, besides of dietarily-induced metabolic alterations, no additional organic lesions occurred during the present animal experiment on dietarily-induced obesity.

Alanine Transaminase↗
PubMed1975

[Prenatal brain damage in maternal, untreated phenylketonuria].

Several reports in literature exist about mentally retarded non-phenylketonuric offspring from untreated phenylketonuric mothers with normal intelligence. One additional case is added who was detected after screening of about 1600 pregnant women. Biochemical investigations of the mother identified her as "classical phenylketonuria". Column chromatographic analysis of amino acids in amniotic fluid revealed a very high pheylalanine level and the diminution of the other, especially essential amino acids. The estimated amino acids in fetal brain also revealed a very high phenylalanine level. Routine screening for phenylketonuria by means of the Guthrie's test is recommended for all pregnant women at the first visit of the counseling.

Amino Acids↗
PubMed1975

[Histidine tolerance in low skin histidase activity].

An oral histidine loading test (100 mg L-His/kg body weight) was performed in 8 deaf patients with low histidase activity in the str. corneum of the skin. Beside an elevated plasma phenylalanine level resulting in a Phe/Tyr-quotient of 1,09 +/- 0,15 the basal level of histidine was slightly enhanced in patients with deafness, but without statistical significance. After histidine loading no differences of the histidine tolerance curves could be observed suggesting the heterozygosity state for histidinaemia. Thin-layer chromatographic investigation of imidazole compounds revealed some abnormal findings after loading. The results are discussed with regard to the clinical and biochemical heterogeneity of histidinaemia.

Adolescent↗