Search PubMed⌕ Search

Biomedical subjects

K C Hayes

Publications and source records attributed to K C Hayes.

At least 181 records · Page 10Linked to original sources
PubMed1978

Taurine: an essential nutrient for the cat.

Cats fed a purified diet containing purified casein as the source of protein develop retinal degeneration due to the lack of taurine in the diet. To test whether cats can synthesize this sulfur amino acid from sulfate or cystine, radioisotopes of these substances were injected into taurine-depleted and control cats. Sulfate did not serve as a precursor for taurine synthesis, whereas cystine underwent only a moderate conversion to taurine. This is in keeping with the low level of cysteinesulfinic acid (CSA) decarboxylase activity in cat liver. There was no difference between the activity of CSA decarboxylase in tissues from control cats and that in tissues from taurine-depleted cats. The pattern of tissue accumulation of [35S]taurine and from [35S]cystine also indicated that tissues from taurine-depleted cats do not synthesize [35S]taurine more rapidly than tissues from control cats. The data did not indicate a difference in taurine uptake by tissues of control and deficient cats, but progressive accumulation in deficient cats suggested that the turnover rate of taurine is decreased by the deficiency. Since supplementation of the purified diet with cysteine has been found previously to be inadequate to prevent progressive taurine depletion of the retina and its subsequent degeneration and since conversion of sulfur compounds to taurine in vivo is inadequate, taurine can be considered an essential nutrient for the cat.

Animals↗
PubMed1978

Taurine deficiency in the kitten: exchange and turnover of [35S] taurine in brain, retina, and other tissues.

Kittens fed a purified diet containing partially-purified casein as the source of protein become taurine-deficient and develop retinal degeneration. The present studies report the exchange and turnover of taurine in different areas of brain, retina and other tissues and fluids of control and taurine-deficient kittens. The various tissues and fluids have different rates of exchange and different half-lives of taurine; taurine deficiency causes a range of changes in these parameters. Generally, tissues and fluids from taurine-deficient kittens accumulated more [35S] taurine and had a longer half-life of taurine than tissues and fluids from control kittens. Nine areas of brain were studied and, of these areas, olfactory bulb had the greatest concentration of taurine. Olfactory bulb resisted taurine depletion to a greater extent than other areas; and, in contrast to other areas of brain, in taurine-deficient kittens, it accumulated [35S] taurine for most of the experiment. Retina resisted taurine depletion and, in taurine-deficient kittens but not in control kittens, it accumulated [35S] taurine throughout the experiment. The amount of taurine conjugated to bile acids was unchanged by the taurine depletion, but the kinetic behavior was altered and was similar to that of retina. The results provide support for the suggestion that, in the kitten at least, taurine is most important for the functions of bile and retina and that taurine depletion affects retina before bile. Taurine may have special importance in olfactory bulb but not necessarily in other regions of brain.

Adrenal Glands↗
PubMed1977

Hypercholesterolemia and triglyceride secretion rates in monkeys fed different dietary fats.

The influence of hypercholesterolemia on the triglyceride secretion rate was studied in both squirrel and cebus monkeys fed coconut oil, corn oil, or safflower oil. The triglyceride secretion rate (TGSR) was determined in vivo following the administration of Triton WR1339, which blocks the clearance of very low density lipoprotein (VLDL). Thus, the increase observed in circulating triglyceride after Triton administration presumably reflecte hepatic triglyceride (VLDL) secretion in the fasted state. The VLDL-TGSR was lowest in hypercholesterolemic monkeys and highest in those fed unsaturated fat diets and having a low serum cholesterol. In all instances, TGSR was inversely correlated with the plasma cholesterol concentration. While a definitive explanation for these observations must await further investigation, the possibility that circulating low density lipoprotein (LDL) acts to feed back on VLDL secretion is discussed. The decreased TGSR associated with the diet-induced cholesterolemia also implies clearance of VLDL is impaired under these conditions.

Animals↗
PubMed1977

Dynamic properties of human motor units in the Hoffmann--reflex and M response.

The dynamic properties of motor units involved in unrestrained H-reflexes and M responses have been studied in seven normal adult males. A linear relationship was observed between the peak to peak EMG of the M response and its twitch tension. Linear relationships were also noted between the EMG and peak displacement, velocity, and acceleration of the evoked muscle twitch for both the H-reflex and the M response. Contraction times for motor units recruited in the H-reflex were longer than those for the M response at low levels of motor unit recruitment. For both responses, however, the contraction times (time to peak force) were markedly shorter than those reported for isometric conditions. Differences were also noted between the H-reflex and M response in the absolute values of the tension to EMG ratio. These differences, together with the longer contraction times for the H-reflex, are quite consistent with the view that different motor unit subpopulations are recruited in the early stages of the two responses. The results and their interpretation, in terms of differential motor unit recruitment, generally confirm the conclusions of studies in which isometric twitch contractions have been investigated.

Adult↗
PubMed1976

Densitometric quantitation of neutral lipids on ammonium sulfate impregnated thin-layer chromatograms.

A procedure is described which extends the densitometric quantitation of phospholipids on ammonium sulfate impregnated thin-layer chromatograms by Gluck et al. to include total lipid, free and esterified cholesterol, free fatty acid and triglyceride. Lipids separated on thin-layer plates containing silica gel G impregnated with ammonium sulfate were charred upon heating and absorbance was measured densitometrically. Thus, the necessity of spraying or submersing in a charring agent was eliminated, uniform charring became possible, and quantitation over a wider range of sample sizes than most densitometric procedures was obtained. One linear relationship existed for concentrations of standards over the range of 0.0-3.0 mug and another line from 4.0-50.0 mug. Both accuracy and precision of the method were highly reliable.

Ammonium Sulfate↗
PubMed1976

Dietary influence on bile acid conjugation in the cat.

Cats fed a semipurified diet containing casein as the source of protein develop taurine deficiency. In order to establish whether this had an adverse effect on bile, kittens and adult cats were fed the casein diet or that diet with a supplement of taurine, cystine, or methionine, and gall bladder bile was characterized for its taurine-glycine conjugation and the cholesterol: phospholipid: bile acid ratio. The data indicate that cats conjugate their bile acids almost exclusively with taurine, and though plasma and retinal pools of taurine are largely depleted by feeding the casein diet, the conjugation of bile acids is only moderately affected. A major conversion to glycine conjugation did not occur, but free cholic acid did increase with decreased taurine conjugation. Dietary supplements of methionine or cystine, precursors of taurine, failed to satisfy the taurine requirement for bile acids in kittens whereas methionine appeared to satisfy this requirement in adult cats. The cholesterol: phospholipid: bile acid profile was not appreciably altered by these dietary circumstances. It would appear that kittens may require dietary taurine and that taurine pools in cats may be biologically independent of one another.

Age Factors↗
PubMed1976

Effect of dietary fat on hepatic metabolism of 14C-oleic acid and very low density lipoprotein triglyceride in the gerbil.

In order to compare in vitro and in vivo aspects of lipid metabolism and lipoprotein secretion associated with the hyperlipemia of saturated fat feeding, gerbils were fed a diet containing 15% coconut oil or safflower oil for 6 weeks. In vitro incorporation of fatty acid was determined by measuring 14C-oleic acid incorporation into hepatic lipis in liver fasting gerbils following Triton WR1339 injection. The plasma lipoprotein profile was assessed by agarose electrophoresis. Coconut oil produced a hypertriglyceridemia and hypercholesterolemia associated with the appearance of very low density migrating lipoprotein, not seen with the safflower oil. Coconut oil also increased the hepatic triglyceride content, enhanced 14C-oleic acid incorporation into total lipid, and favored fatty acid incorporation into triglyceride; safflower oil facilitated esterification of oleic acid into phospholipid. Triton blockade of gerbils fed safflower oil resulted in twice the triglyceride secretion rate of those fed coconut oil. Our interpretation of the data is that dietary polyunsaturated fat favors incorporation of fatty acids into phospholipid, enhances both triglyceride secretion and the plasma transport and clearance of triglyceride and cholesterol and that the hyperlipemia of coconut oil feeding reflects a reduced metabolic clearnace of circulating lipid associated with that dietary fat.

Animals↗
PubMed1976

Hematological development of the infant squirrel monkey (Saimiri sciureus).

Hematologic developmental norms from infant squirrel monkeys indicate a relative maturation of the hematopoietic system by 16 weeks. The elevated hemoglobin, hematocrit, red blood cell count, MCV and MCH at birth are followed by a decreasing hemoglobin (decreasing red blood cell count and MCV) until 4 weeks of age. A reticulocytosis then occurs until the hemoglobin level approximates adult concentrations by 16 weeks of age with gradual changes in this as well as hematocrit, red blood cell count, MCV and MCH thereafter. Total leukocytes and segmented neutrophils are elevated at birth and decrease rapidly in the first 2 weeks, reaching stabile values by 16 weeks. An opposite trend is seen with the lymphocyte population. Plasma protein and albumin concentrations show a nadir at 2 weeks of age with the albumin levels stabilizing by 10 weeks and the total protein concentration continuing to increase throughout the 1st year.

Age Factors↗
PubMed1976

Retinal degeneration in cats fed casein. I. Taurine deficiency.

All cats fed a taurine-free casein diet for at least 23 weeks have shown granularity with a hyper-reflective white zone in the area centralis, nondetectable electroretinograms (ERG's), and structural changes indicating photoreceptor cell degeneration. The present study has demonstrated that cats fed this casein diet have a selective decrease in plasma and retinal taurine concentrations by five weeks; taurine levels were about 4 per cent of normal in plasma, and 60 per cent of normal in retina. After 10 weeks, taurine levels were 2 to 4 per cent of normal in plasma and reached a minimum of 20 to 30 per cent of normal in the retina. These biochemical changes occurred in association with a delay in the cone ERG implicit time at five weeks and reduced cone and rod ERG amplitudes at 10 weeks. During this period, retinal DNA content (as a measure of cell viability) and fundus appearance were normal. By 23 weeks, ERG's were nondetectable, retinal DNA content was reduced, and the fundus showed typical changes in the area centralis. These studies help to establish a biological role for taurine in maintaining photoreceptor cell function and viability in the cat.

Animals↗
PubMed1976

Retinal degeneration in cats fed casein. II. Supplementation with methionine, cysteine, or taurine.

All cats fed a taurine-free casein diet for 23 weeks have shown a nondetectable electroretinogram (ERG) in association with a plasma and retinal taurine deficiency. In the present study, the casein diet was supplemented with either taurine or taurine precursors (methionine or cysteine) for 23 weeks to see if retinal function would be preserved. Cats fed the casein diet supplemented with methionine or cysteine showed ERG's reduced in amplitude and delayed in implicit time and had plasma and retinal taurine levels that were well below normal by 23 weeks. Only those cats given taurine in the diet (i.e., those fed chow or casein supplemented with taurine) retained normal ERG function and normal plasma and retinal taurine concentrations. These findings establish a role for taurine in maintaining normal retinal function in the cat.

Animals↗
PubMed1975

Retinal degeneration associated with taurine deficiency in the cat.

A degeneration of the retinal photoreceptor cells develops in cats when casein is the source of dietary protein. Amino acid profiles indicate that the degeneration is associated with a selective decrease in plasma and retinal taurine concentrations. A sulfur amino acid deficit in the casein diet combined with specific amino acid requirements of the cat appear related to this unique expression of taurine deficiency.

Amino Acids↗
PubMed1975

Effects of fatiguing isometric exercise upon achilles tendon reflex and plantar flexion reaction time components in man.

Effects of three different fatiguing local muscular exercises upon plantar flexion reaction time and achilles tendon reflex time have been studied in 24 normal males. The Exercise Conditions, each involving a series of 30 maximal voluntary isometric contractions (MVC) of the plantar flexors, differed by allowing either 5, 10 or 20 sec rest interval between each MVC. Decrements in strength ranged from 15% to 34% MVC. Trend analysis of the fatigue patterns revealed that a cubic orthogonal polynomial equation was sufficient to describe the profile of MVC decrement for all conditions. Following the fatiguing exercise, simple visual reaction time (plantar flexion), and its two components, premotor and motor time, failed to demonstrate any change from Pre Exercise Conditions. Achilles Tendon Reflex Times, however, demonstrated a marked augmentation, as manifest in reduced total reflex times, contraction times and half relaxation times. These results may suggest the differential fatigue of motor units employed in the three motor tasks, viz. MVC, voluntary reaction and achilles tendon reflex. A plausible explanation for the augmentation of the reflex contraction resides in the known potentiating effect of elevated intramuscular temperature. Alternatively, one might postulate a neurally mediated increase in gain of the stretch servomechanism. The possibility of both mechanisms being operative is not excluded.

Achilles Tendon↗