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Biomedical subjects

A Bar

Publications and source records attributed to A Bar.

At least 73 records · Page 4Linked to original sources
PubMed1983

Learning disability assessed through audiologic and physiologic measures: a case study.

This report describes a child with central auditory dysfunction. Audiologic tests (Willeford Battery and Staggered Spondaic Word Test) indicate a brain-stem dysfunction but normal cortical functioning. Electrophysiologic tests corroborated these results. Brain-stem auditory-evoked responses (BAERs) indicated an absent contralateral peak III bilaterally when stimulating each ear separately. This is the first reported case where brain-stem dysfunction on audiologic tests were associated with specific electrophysiologic changes in the BAER.

Audiometry↗
PubMed1983

Adaptive microcomputer control of an artificial knee in level walking.

An experimental microcomputer controlled prosthesis is discussed, where knee damping is governed by kinematic signals, picked up from both legs. The control algorithm is based on division of the walking cycle into ten stages; each stage characterized by an appropriate damping level which governs the restraining moment at the knee, as functionally required. Stage identification is carried out by the kinematic inputs. The experimental prosthesis was tested on one amputee, the first author of this paper. The control system was found to be more advantageous than a conventional valve system in significantly reducing hip muscular effort on the prosthetic side. Gait symmetry is also improved.

Computers↗
PubMed1983

Simulation of calcium homeostasis: modeling and parameter estimation.

The system that regulates plasma calcium in the bird has been formalized into a model based on a series of differential equations and solved by computer simulation. Bone, kidney, and intestine have been considered as the control subsystems, with parathyroid hormone and 1,25-dihydroxycholecalciferol as the regulating hormones. The parameters used in the simulation model have been computed either from published results or by specifically designed experiments described here. For the estimation of parameters, an iterative procedure has been developed that was designed to minimize the sum of square errors between observed and system-simulated values. Parameters of 1,25-dihydroxycholecalciferol metabolism were experimentally obtained from the kinetic behavior of the 3H-labeled hormone in rachitic birds after a single dose. Model parameters have been adjusted using the results of in vivo calcium loading and validated by an EDTA infusion experiment. The simulation model has been used to study the hierarchy of the activities of the three control subsystems and of the regulating hormones, at different calcium intakes. Positive or negative errors in plasma calcium resulted in an asymmetry in the activities of the controlling systems, bone and kidney, whereas the intestine is characterized by its relatively long response time.

Animals↗
PubMed1983

Effects of alignment variables on thigh axial torque during swing phase in AK amputee gait.

It is suggested that a major source of discomfort for above-knee amputees during the swing phase of walking, is the thigh axial torque (TAT) transferred at the stump--socket interface. The relation between TAT and variations in its six relevant alignment adjustments, has been investigated. A computerized routine has been established which indicates optimum choice of alignment setting, based on minimal TAT peaks. Feasibility for attenuating swing phase TAT has been demonstrated in three simulated patterns of amputee gait. As a conclusion, it is suggested that a useful clinical tool could be based on the presented alignment optimization procedure and may be expanded to include other factors associated with swing and stance phase comfort and performance.

Amputation, Surgical↗
PubMed1983

The amino acid requirements of growing turkeys. 1. Model construction and parameter estimation.

A model has been formulated to calculate the protein and amino acid requirements for growing turkeys. A requirement was taken as the sum of the needs for maintenance, for gain in carcass weight without feathers, and for the feathers. Parameters used in the model were obtained from a study of carcass composition along the growth period and from two balance trials with adult turkeys. The maintenance requirement was considered to be the sum of the needs for replacing skin and intestinal protein losses and for the obligatory creatinine excretion in the urine. Nitrogen retention was determined at 2.3 g/day in protein-fed adult (17 kg) male turkeys as an estimate for the replacement needs for skin protein loss. Creatinine excretion in these birds was 123 mg/day. When fed an N-free diet, 16.5 kg adult turkeys excreted a total of 3.5 g/day amino acids as a result of intestinal losses. The protein requirement for maintenance was estimated at 32 mg/day/g2/3 of body weight by summing up the different needs and dividing by .85, the coefficient of protein absorption. Protein and amino acid analyses of nude carcass and feathers and the growth curve were used to calculate the requirements for growth. These were then related to energy intake predicted by equations, which included previously determined coefficients for maintenance and growth (Hurwitz et al., 1980a), and the results of carcass lipid analysis. The calculated amino acid requirements were similar to those of the National Research Council (1977).

Amino Acids↗
PubMed1982

Cholecalciferol requirements of young turkeys under normal conditions and during recovery from rickets.

Day-old turkeys fed vitamin D-deficient diets became rachitic within 17-24 days. The symptoms included reductions in body weight, plasma calcium and inorganic phosphorus, plasma and intestinal calcium-binding protein (CaBP), plasma 25-hydroxycholecalciferol [25(OH)D3], bone ash, and kidney 25(OH)D3-24-hydroxylase and a rise in kidney 25(OH)D3-1-hydroxylase activity. Supplementation of the diet with 12.5 micrograms cholecalciferol per kilogram was sufficient to promote maximal body weight and normal plasma calcium, Plasma calcium, plasma phosphorus and bone ash. Feeding diets containing 250 or 1250 micrograms cholecalciferol per kilogram resulted in a reduced body weight. An increased in the concentration of plasma 25(OH)D3 with increasing dietary cholecalciferol concentration was observed. Feeding vitamin D-deficient rachitic birds for 4 days a diet containing 50 micrograms cholecalciferol per kilogram restored plasma calcium and phosphorus and bone ash. Body weight remained lower than that of the control for an additional 6-day period. Additional cholecalciferol, 25(OH)D3 or 1 alpha-hydroxycholecalciferol in the diet, intramuscular injection of the vitamin D derivatives, or a high-calcium, high-phosphorus diet did not accelerate the recovery from the rachitic state.

Animals↗
PubMed1981

Relationships between cholecalciferol metabolism and growth in chicks as modified by age, breed and diet.

Fast-growing heavy (White Rock) chicks, fed a vitamin D-deficient diet, exhibited a higher activity of kidney 25-hydroxycholecalciferol-1-hydroxylase (1-hydroxylase) than slow-growing light (White Leghorn x Rhode Island Red) chicks fed the same diet. 1-Hydroxylase and duodenal calcium-binding protein (CaBP) declined with age. Feeding of low energy diets with or without vitamin D resulted in a slower rate of growth and reduced 1-hydroxylase activity and CaBP concentration. Severe dietary restriction of either calcium or phosphorus resulted in a lower growth rate as well as a duodenal CaBP as compared to a moderate mineral restriction. The severe dietary calcium restriction also resulted in a lower 1-hydroxylase activity than that resulting from a moderate restriction. The results clearly indicate that high 1-hydroxylase activity and a high intestinal CaBP are associated with a high growth rate.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1980

Observations of the use of 1 alpha hydroxycholecalciferol in the prevention of bovine parturient paresis.

Varying doses of 1 alpha-hydroxycholecalciferol (1 alpha-HCC) (50, 150, 250 and 350 micrograms) in propylene glycol were injected intramuscularly into 30 dry adult Israeli Friesian cows. Fourteen of these animals received a second dose; four were given 250 or 350 micrograms 48 hours after the first dose and 10 were given 350 micrograms 72 hours after the first dose. Plasma calcium rose after 24 hours at all dose levels except 50 micrograms. A dose-dependent peak in plasma calcium was reached after three to four days, followed by a return to baseline five days (150 micrograms) and eight days (250 and 350 micrograms) post injection respectively. Repeating the injection 48 or 72 hours later increased the time span by three and four days respectively. The effect of plasma inorganic phosphate was double that on plasma calcium. Plasma magnesium declined slightly three days post injection. High calcium feeding in conjunction with one or two injections of 350 micrograms 1 alpha-HCC did not modify the response of plasma calcium. An injection of 350 micrograms of 1 alpha-HCC was given once to 40 parturient paresis-prone cows of the same breed and twice at 72-hour intervals to 37 such cows. Six of the animals received 5 mg of flumethasone together with the second injection and 13 received it 48 hours later. This was to induce parturition, which occurred within 24 to 48 hours. None of the cows injected earlier than 24 hours prepartum developed parturient paresis in comparison with 22 out of 60 control animals which did. The results suggest that 1 alpha-HCC is useful in the prevention of bovine parturient paresis.

Animals↗
PubMed1980

Glucose absorption and starch digestion in the intestine of the chicken.

Starch digestion and glucose absorption were determined in vivo along the chick's (Gallus domesticus) intestine, using 91Y and 51Cr-EDTA as unabsorbed reference substances. About 65% of the ingested starch was digested up to the end of the duodenum, 85% up to the end of the jejunum and about 97% at the terminal ileum. A fraction of about 97% of the glucose, ingested or released from ingested starch, was absorbed. The duodenum was the major site of glucose absorption which continued at a decreased rate down the small intestine. Glucose absorption increased linearily with luminal concentration with no indication of saturation. The apparent permeability for glucose was similar for the jejunum and ileum.

Animals↗
PubMed1980

Absorption and excretion of cholecalciferol and of 25-hydroxycholecalciferol and metabolites in birds.

The absorption and excretion in vivo of cholecalciferol or 25-hydroxycholecalciferol (25-HCC) were determined in chicks (Gallus domesticus) and turkeys (Meleagris gallopavo). The overall net cholecalciferol or 25-HCC absorption in chicks and cholecalciferol in turkey poults was 66.5 +/- 3.3, 74.9 +/- 3.7 and 83.6 +/- 7.1% of the intake, respectively. The absorption of cholecalciferol or 25-HCC in chicks and turkeys occurred at the upper part of the intestine. 25-HCC, esters and non-polar metabolites of cholecalciferol or 25-HCC, and their polar metabolites, were secreted in the duodenum of chicks and turkeys but were partially reabsorbed at the upper part of the jejunum.

Animals↗
PubMed1979

The interaction between dietary calcium and gonadal hormones in their effect on plasma calcium, bone, 25-hydroxycholecalciferol-1-hydroxylase, and duodenal calcium-binding protein, measured by a radioimmunoassay in chicks.

Male chicks, fed low, normal, or high calcium- and cholecalciferol-containing diets for 14 days, were given three combined injections of 17 beta-estradiol and testosterone (7 and 2.4 mg/kg/dose, respectively) or the vehicle alone, at 3-day intervals. The hormonal treatment resulted in increased plasma calcium and medullary bone calcium concentrations, independently of the dietary calcium intake. Kidney 25-hydroxycholecalciferol-1-hydroxylase and duodenal calcium-binding protein were increased in response to gonadal hormones. The magnitude of this response markedly diminished with increased calcium intake and almost completely disappeared in chicks fed the high calcium diet. The results suggest that the increases in plasma calcium and medullary bone formation due to gonadal hormones are independent of calcium intake while the effect of hormones on duodenal calcium-binding protein and the 25-hydroxycholecalciferol-1-hydroxylase activity appears to be mediated through the change in calcium needs due to medullary bone formation.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗