Biomedical subjects

K C Hayes

Publications and source records attributed to K C Hayes.

At least 109 records · Page 6Linked to original sources

PubMed1991

Post-polio fatigue: a 31P magnetic resonance spectroscopy investigation.

Changes in high energy phosphates (HEP) and intramuscular pH during exercise were measured in 17 patients with post-polio fatigue and in 28 healthy controls using 31P magnetic resonance spectroscopy (MRS). Subjects performed a dynamic hand grip exercise at low and high intensity. Mean changes in the HEP and pH showed no significant differences between the groups, although the post-polio group's response was highly variable. Six patients showed evidence of a lower lactate accumulation during the high intensity exercise when compared with controls. These data suggest that the whole body fatigue experienced by polio survivors is not related to any systemic metabolic abnormality.

Adult↗

PubMed1991

Reinforcement of motor evoked potentials in patients with spinal cord injury.

Transcranial magnetic stimulation of the motor cortex has been used to investigate the putative existence of spared motor pathways in spinal cord injured patients with clinically complete paralysis. Particular consideration was given to methods of neurological reinforcement likely to minimize the risk of false negative interpretation of absent motor evoked potentials (MEPs). The principal methods of reinforcement included target and remote muscle contractions and conditioning of MEPs with a brief (20 msec) train of cutaneous stimulation (500 Hz: duration 0.1 msec) delivered 20-150 msec prior to cortical stimulation. Twelve control subjects and 26 patients with severe traumatic spinal cord injury underwent cortical stimulation delivered from a Cadwell MES-10 (70-100% intensity) through a 9-cm focal-point coil. Electromyographic responses were recorded from surface electrodes in bipolar configuration and amplified (3 dB down at 10 Hz-1 kHz) prior to storage. MEPs were recorded, following reinforcement, in muscles with clinically complete paralysis in 4/26 patients. In each case, MEPs were of low amplitude (less than 0.5 mV), polyphasic, and with variable and prolonged latencies. MEPs were evoked in severely paretic (clinically incomplete paralysis) muscles in 6/8 patients only when neurological reinforcement was employed. Conditioning of MEPs in tibialis anterior with preceding cutaneous stimulation to the plantar surface (subthreshold for evoking a flexion reflex) yielded a well-defined modulation of MEP amplitude in control subjects. An early (Conditioning-Test (C-T) intervals 20-45 msec) period of inhibition of MEPs (mean = 60% of control) was followed by a period (C-T intervals 50-90 msec) of facilitation (mean = 345%) and a subsequent (C-T intervals 90-150 msec) period of inhibition (mean = 0%). In spinal cord injured patients the same conditioning paradigm failed to reveal MEPs, but did result in the appearance of suprathreshold flexion reflexes in 2 patients at 20-55 msec C-T intervals. This summation of convergent but subliminal cortical and cutaneous inputs to the target motoneuron pool provided additional evidence of preserved cortical influence on segmental structures that was not detectable by other means. These results extend previous reports of electrophysiological evidence of spared motor pathways in spinal cord injured patients with complete paralysis, and affirm the need for neurological reinforcement as a routine procedure in cortical stimulation studies of spinal cord injuries.

Adult↗

PubMed1990

Anticipatory postural control in children.

Postural responses, triggered by sensory feedback, are present very early in a child's development. The purpose of the present study was to investigate the ability of children to anticipate postural disturbances caused by self-initiated movements and their ability to coordinate anticipatory postural adjustments with movement execution. Children (N = 32) aged 4 to 14 years were asked to stand quietly on a stable force plate and to raise their right arm forward (or backward) to the horizontal position after a visual stimulus. Changes in the center of pressure beneath the feet were recorded before and during the arm raise. The anticipatory (feedforward) postural patterns seen before the arm movement, and noted in a previous study of adults, were present in the youngest of the children (4 years, 2 months). Longer reaction times and inconsistent postural responses (in the anteroposterior direction) suggest that children are less capable than adults of coordinating the anticipated postural adjustment with the forthcoming limb movement, however. In the lateral plane, anticipatory postural responses were initiated more consistently.

Journal Article↗

PubMed1990

Taurine concentrations in plasma and whole blood in humans: estimation of error from intra- and interindividual variation and sampling technique.

The "normal" physiological taurine status in human plasma and whole blood was evaluated for day-to-day variation. Because plasma taurine concentrations can vary by greater than or equal to 100% because of sampling and analytical techniques, various blood-collecting and -handling procedures were compared to ascertain the most reliable method for measuring plasma taurine. Blood collection into EDTA-wetted plastic syringes at room temperature proved most reliable. Plasma and whole-blood taurine concentrations were determined in the same 13 women and 11 men three times within a 10-d period. The normal plasma taurine concentration was 44 +/- 9 mumol/L (mean +/- SD; n = 40) in fasting subjects and 42 +/- 7 mumol/L (n = 30) in semi-fasted individuals, with an intraindividual variation of 9 +/- 5%. Whole-blood taurine concentrations ranged from 164 to 318 mumol/L and had an intraindividual variation of 11 +/- 5%. Inter-individual variation averaged 12 +/- 7% for plasma and 7 +/- 6% for whole blood taurine. Because plasma and whole-blood taurine concentrations were not correlated, assessment of both would provide the most accurate estimate of taurine status. Short of that, whole-blood taurine would appear to be the best single measure.

Blood Specimen Collection↗

PubMed1990

Dietary predictors of symptom-associated gallstones in middle-aged women.

In 1980, 88,837 women aged 34-59 y completed a semiquantitative food frequency questionnaire and were followed for 4 y. Four hundred thirty-three women reported a cholecystectomy for recent cholecystitis, and 179 reported unremoved, newly symptomatic gallstones diagnosed by ultrasound or x ray. Among the 59,306 women with Quetelet's index of relative weight less than 25 kg/m2, inverse associations were observed between intakes of vegetable fat and vegetable protein and the risk of reportedly symptomatic gallastones, after adjusting for age, Quetelet's index in 1980, weight change between 1976 and 1980, energy intake, and alcohol intake. The relative risk in the highest quintile of vegetable fat intake, as compared with the lowest quintile, was 0.6 [95% confidence interval (CI), 0.4-0.9], and the corresponding relative risk for vegetable protein intake was 0.7 (95% CI, 0.6-0.9). No significant associations were found with energy-adjusted intakes of cholesterol, animal fat, animal protein, carbohydrate, or sucrose.

Adult↗

PubMed1990

Dietary palmitic acid (16:0) enhances high density lipoprotein cholesterol and low density lipoprotein receptor mRNA abundance in hamsters.

In order to examine the qualitative effect of different fats and specific fatty acids on plasma lipids and lipoprotein metabolism, six low fat, cholesterol-free diets were fed to young male hamsters (10/group) for a 4-week period. Fat blends were formulated with coconut oil, palm oil, soybean oil, high oleic acid safflower oil, butter, corn oil, and canola oil. Diets contained 13% energy as fat and dietary polyunsaturate/saturate ratios ranged from 0.12 to 1.04, one of which incorporated the American Heart Association-recommended concentrations of saturates, monoenes, and polyenes and another reflected the current American Fat Blend. In three diets the polyunsaturate/monounsaturate/saturate ratio was held constant while only the 12:0, 14:0, and 16:0 were varied. Plasma lipoproteins and apoproteins were assessed in conjunction with the abundance of specific hepatic and intestinal mRNA for the low density lipoproteins (LDL) receptor and various apolipoproteins associated with cholesterol metabolism. The plasma cholesterol response was lowest with the American Heart Association blend and equally elevated by the more saturated, low polyene diets (polyunsaturate/saturate, 0.12-0.38). Replacing 12:0 plus 14:0 from coconut oil with 16:0 as palm oil induced a significant increase in high density lipoprotein (HDL) cholesterol with a trend toward decreased LDL. These shifts in lipoprotein cholesterol were corroborated by measures of the LDL/HDL ratio, the plasma apolipoprotein B/apolipoprotein A1 ratio, and differences in the synthesis of apolipoproteins and the LDL receptor based on estimates of the mRNA for these proteins in the liver and gut, using specific cDNA probes for apolipoprotein A1, apolipoprotein B, apolipoprotein E, and the LDL receptor. Although it has been suggested that dietary polyenes lower total plasma cholesterol, including HDL, and that saturated fat increases both these pools of cholesterol, the current data represents the first evidence that a specific saturated fatty acid, i.e., palmitic acid, may enhance HDL production.

Animals↗

PubMed1989

Weight, diet, and the risk of symptomatic gallstones in middle-aged women.

To assess the risk factors for symptomatic gallstones, 88,837 women in the Nurses' Health Study cohort (age range, 34 to 59 years) were followed for four years after completing a detailed questionnaire about food and alcohol intake in 1980. A total of 433 cholecystectomies and 179 cases of newly symptomatic, unremoved gallstones, diagnosed by ultrasonographic examination or x-ray films, were reported during the four-year follow-up. The age-adjusted relative risk for very obese women, who had a Quetelet index of relative weight (weight in kilograms divided by the square of the height in meters) of more than 32 kg per square meter, was 6.0 (95 percent confidence interval, 4.0 to 9.0), as compared with women whose relative weight was less than 20 kg per square meter. For slightly overweight women (relative weight, 24 to 24.9 kg per square meter), the relative risk was 1.7 (95 percent confidence interval, 1.1 to 2.7). Overall, we observed a roughly linear relation between relative weight and the risk of gallstones. Among the 59,306 women whose relative weight was less than 25 kg per square meter, a high energy intake (greater than 8200 J per day), as compared with a low energy intake (less than 4730 J per day), was associated with an increased incidence of symptomatic gallstones (relative risk, 2.1; 95 percent confidence interval, 1.4 to 3.3), and an alcohol intake of at least 5 g per day was associated with a decreased incidence as compared with abstention (relative risk, 0.6; 95 percent confidence interval, 0.4 to 0.8). Parity did not appear to be an important risk factor after an adjustment was made for relative weight. These data support a strong association between obesity and symptomatic gallstones and suggest that even moderate overweight may increase the risk.

Adult↗

PubMed1989

Plantarflexor muscle function in young and elderly women.

Contractile properties of the ankle plantarflexor muscles were compared between groups of young (means = 26 y) and elderly (means = 82 y) women. The H-reflex muscle contraction in the elderly group was characterized by a significant slowing of torque generation, as compared to the young women (means for average rate of torque development were young = 0.16 Nm ms-1 +/- 0.02 (SE), elderly = 0.09 Nm ms-1 +/- 0.02, P less than 0.05). However, the proportion of the total motor unit pool activated by the reflex was similar for the young and elderly groups at 63% and 70%, respectively. Maximal voluntary isometric torques were significantly lower (71%) in the elderly (young means = 135.3 Nm +/- 9.3, elderly means = 39.2 Nm +/- 2.9, P less than 0.01). These results are consistent with, and extend, previous reports showing decreased strength and speed of contraction in elderly muscle. Given that the average body weight was similar for the young and elderly groups, it was concluded that the aged plantarflexor muscles exhibited considerable impairment in ability to generate stabilizing torques about the ankle joint.

Adult↗

PubMed1989

Taurine deficiency syndrome in cats.

Taurine deficiency occurs in a large number of cats fed unfortified commercial diets. Deficiency arises because cats are unable to absorb all the taurine in processed diets and/or are unable to synthesize the deficit between absorption and requirement, which makes taurine an essential amino acid for cats. Taurine-depleted cats develop retinal degeneration, cardiomyopathy, altered white-cell function, and abnormal growth and development. Taurine deficiency is best estimated from the plasma-taurine concentration, with values less than 30 mumol/l considered deficient.

Animals↗

PubMed1989

Taurine modulates platelet aggregation in cats and humans.

To explore the relationship between whole-body taurine status and function, the taurine concentration in plasma and platelets was measured and evaluated in terms of ex vivo collagen-induced platelet aggregation in taurine-depleted cats and taurine-supplemented humans. Taurine status exerted a significant effect on platelet aggregability. Platelets from taurine-depleted cats were twice as sensitive to aggregation as platelets from cats receiving taurine. On the other hand, platelets from humans with normal taurine status increased resistance to aggregation by 30-70% when supplemented with taurine at 400 or 1600 mg/d, respectively. Decreased platelet aggregability was associated with increased platelet taurine and glutathione concentrations and decreased thromboxane release on aggregation. These data indicate that taurine in vivo stabilizes platelets against aggregation such that during taurine depletion platelets become overly sensitive whereas during supplementation their tendency to aggregate is depressed.

Adult↗

PubMed1989

Lactose protects against estrogen-induced pigment gallstones in hamsters fed nutritionally adequate purified diets.

To evaluate the impact of dietary factors on gallstone induction in hamsters, male Syrian hamsters were fed for 2-8 wk purified diets that varied in type and amount of simple sugar (glucose vs. lactose, 17.5-72%), fat (2-5%), fiber (0-15%) and estrogen (0 or 300 micrograms/kg diet). Plasma and liver cholesterol and plasma triglycerides were measured, daily weight gain was determined, cecal weights were obtained, and gallbladder bile was scored by light microscopy and analyzed chemically for its lithogenicity and gallstone incidence. Lactose reduced plasma lipids, especially triglycerides, and hepatic cholesterol accumulation, and maintained a lower biliary cholesterol concentration. When fed at 30% or more, lactose reduced weight gain, increased cecal volume 2- to 4-fold and prevented gallstone formation. Diarrhea and death from 'wet tail' was associated with gallstones and was frequent in hamsters fed glucose without fiber, but its incidence was essentially eliminated by rice flour plus fiber or lactose. Under these experimental conditions of time and diet, estrogen supplementation was required for the formation of gallstones. These appeared to be pigment stones containing a minimal amount of cholesterol. In summary, pigment gallstones were induced in less than 8 wk in hamsters fed estrogen-supplemented purified diets. Lactose feeding improved lipid metabolism and reduced gallstone formation, apparently through its impact on large bowel metabolism.

Animals↗

PubMed1989

Intramuscular recording in neurodiagnostic studies.

Intramuscular (IM) recordings are often used in nerve conduction studies involving deep or proximal muscles and in other electrodiagnostic tests. Little is known of how various needle electrode configurations and placements influence the characteristics of the evoked responses and their clinical interpretation. The present set of investigations sought to characterize the amplitude, waveform, consistency, latency and muscle discrimination capabilities of IM recordings from a variety of muscles using monopolar, concentric and bipolar electrodes. Results indicate that 1) all forms of IM electrodes studied show marked changes in response waveform with changes in position of the electrode tip, but the monopolar electrode configuration shows the least amount of change; 2) the concentric electrode does not differentiate well between deep and superficial muscle responses; 3) the latency of the evoked response does not change with the depth of penetration within a muscle; 4) the latency of response recorded from IM electrodes may be longer, the same or shorter than that recorded from surface electrodes; and 5) monopolar electrodes should be used when onset latency or waveform is the critical parameter to be recorded from deep or atrophied muscles.

Adult↗

PubMed1989

Methodological considerations contributing to variability of the quadriceps H-reflex.

The clinical usefulness of the quadriceps H-reflex is limited because of the difficulty of elicitation and its inherent variability in amplitude. In the present study we attempted to identify the influence of methodological variables (head position and remote muscle contractions) on the amplitude of the H-reflex evoked in vastus medialis, vastus lateralis and rectus femoris from the right leg of 13 healthy adult subjects. Square wave stimuli (1-ms duration) were delivered percutaneously to the femoral nerve. The 50% maximal amplitude H-reflexes were evoked while the subject reclined with head facing to the right, left, up and down or while the subject performed Jendrassik's maneuver. The results show a significant increase in the reflex amplitude when the subject's head was turned to the right; there was either a mild increase or no change in amplitude of the response when the subjects faced to the left, up and down. The evoked potential tended to decrease when the subjects closed their eyes; however, the tendency to increase with neck position was not changed. Remote muscle contractions enhanced the amplitude of the response. These results present further evidence of the characteristics of the quadriceps H-reflex and identify postural influences as one controllable source of variability in the L3-L4 root electrodiagnostic test.

Adult↗

PubMed1989

Dietary n-3 fatty acids and arthritis.

We have evidence that dietary fish oil (FO) decreases severity of collagen-induced arthritis (CIA), changes the fatty acid composition of macrophage (M phi) membrane phospholipids, decreases M phi synthesis of prostaglandins (PGs), changes chemotactic ability of M phi s, and affects metabolism of acute phase proteins. Gender also has pronounced effects on susceptibility to CIA and M phi prostaglandin profiles. The mechanisms by which dietary n-3 fatty acids may act to alleviate symptoms of CIA, as well as interactions of dietary n-3 and n-6 fatty acids and gender are discussed. We suggest that the ability of FO diets to influence favourably the course of chronic inflammatory diseases is mediated via alterations in n-6 fatty acid metabolism and that intrinsic differences in n-6 fatty acid metabolism may account not only for our reported gender differences in incidence and severity of CIA, but also the well-documented sexual dimorphism in immune/inflammatory responses in general.

Acute-Phase Proteins↗

PubMed1989

Effect of exercise on postural sway in the elderly.

Fifty female subjects, aged 72-92 (mean 82) years, were enrolled in a 12-week (36 classes) exercise program aimed at increasing postural stability. Subjects were residents of sheltered apartments, rest homes or nursing homes, well enough and mobile enough to participate in the classes. The subjects were randomized into an exercise or a control group. Their postural sway, standing at rest on a force platform, was measured with eyes open and eyes closed. The groups were well matched in all respects. The results showed no improvement in the postural sway as a result of the exercise program. We hypothesize that increasing postural sway in the elderly represents a deterioration in, for the most part, the nervous system and may at this extreme of life indicate an irreversible loss of function. For this reason no improvement in postural sway may be possible.

Accidental Falls↗

PubMed1989

Retinal pigment epithelium possesses both LDL and scavenger receptor activity.

The lipid metabolism of photoreceptors depends in part on the retinal pigment epithelium (RPE). One aspect of cholesterol homeostasis in cultured bovine RPE was evaluated by measuring low-density lipoprotein (LDL) and scavenger receptor activity with [125I]-LDL and [125I]Ac-LDL, respectively. Incubation of RPE cells in the presence of increasing concentrations of LDL or Ac-LDL resulted in down-regulation of the LDL receptor but not the scavenger receptor, patterns consistent with the presence of both receptors on these cells. This receptor profile distinguishes the RPE cell from fibroblasts and indicates its similarity to macrophages and arterial endothelial cells.

Animals↗

PubMed1988

Increased urinary methylmalonic acid excretion in breast-fed infants of vegetarian mothers and identification of an acceptable dietary source of vitamin B-12.

Increased urinary methylmalonic acid (UMMA) concentrations might indicate vitamin B-12 deficiency. Our study tested the hypothesis that elevated UMMA in breast-fed infants is associated with decreased maternal serum B-12 concentrations. UMMA concentrations were measured in 17 vegetarian mothers and their infants and in six infants of nonvegetarian mothers. Serum vitamin B-12 concentrations were determined in all mothers. Range of UMMA for vegetarian infants (3-924 mcg/mg [2.6-790.9 mumol/mmol] creatinine) was much broader than that for omnivorous infants (2-25 mcg/mg [1.7-21.4 mumol/mmol] creatinine). Maternal UMMA and serum vitamin B-12 were negatively correlated (r = -0.700, p = 0.003). Infant UMMA concentrations correlated positively with maternal UMMA concentrations (r = 0.686, p = 0.003) and inversely with maternal serum vitamin B-12 concentrations (r = -0.681, p less than 0.001). In three infants with high UMMA concentrations, vitamin B-12 treatment (oral B-12, vitamin B-12 injection, or a modification of maternal diet within the vegetarian philosophy) led to an abrupt decrease of UMMA.

Adult↗

PubMed1988

A fish oil diet reduces the severity of collagen induced arthritis after onset of the disease.

We have previously reported that compared to a corn oil diet a fish oil diet (5% by weight) fed to B10R.III mice before the induction of collagen induced arthritis markedly reduced disease severity. In this study we determine whether a fish oil diet could reduce the severity of collagen induced arthritis if begun after the arthritis was clinically apparent. Mice were initially fed either a fish oil or corn oil diet and immunized with bovine type II collagen 4 weeks later. At the onset of collagen-induced arthritis, half of the corn oil fed mice were switched to fish oil and arthritis assessed on a weekly basis. Four weeks after the diet change until killing 5 weeks later, the mice switched to fish oil developed much less severe arthritis than the corn oil fed controls. Thus the severity index of corn oil fed mice ranged between 9.4 and 7.1; the severity index of fish oil fed mice was between 6.8 and 4.3 while the mice switched to fish oil ranged between 7.2 and 5.6. Analysis of peritoneal macrophages 13 weeks after immunization showed that macrophages from fish oil fed mice incorporated eicosapentaenoic acid into phospholipids and produced less arachidonate products than corn oil fed mice. There was no difference between macrophages obtained from mice switched from corn oil to fish oil and those maintained on fish oil with respect to fatty acid composition of membrane phospholipids or prostaglandin profile. These results suggest that arthritis severity may be modulated after the onset of CIA by altering the PG profile of macrophages present at inflammatory sites.

Animals↗