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Biomedical subjects

S Hurwitz

Publications and source records attributed to S Hurwitz.

At least 217 records · Page 12Linked to original sources
PubMed1979

The amino acid and energy requirements of broiler breeder hens.

Three trials, involving 1000 broiler breeder hens each, were conducted under rather uniform conditions in order to test the applicability of two models for calculating the amino acid requirements of broiler breeders, and to evaluate their energy requirements. The birds fed diets based on Model A (which assumes that all of the egg white and shell membrane proteins are synthesized during albumen formation and secretion at the expense of tissue proteins) produced at a rate greater than the planned target, whereas Model B (which assumes that only ovoglycoproteins and shell membranes are thus produced) supported a production close to the anticipated performance. This indicates the validity of Model B, developed for egg layers, to predict the requirements of the most limiting amino also for broiler breeder hens. The resulting practical diets contained considerably lower protein levels than customary. According to Model B, minimal amino acid requirements for broiler breeder hens producing a daily egg mass of 52.7 g. having a body weight of 3.5 kg and gaining weight at a rate of 4 g/day, calculated to be as follows (g/hen/day): methionine, .57; sulfur amino acids, .83; lysine, .76; arginine, 1.11; threonine, .72; valine, .92; isoleucine, .85; leucine, 1.25; tryptophane, .19; histidine,

Amino Acids↗
PubMed1979

Acne vulgaris. Current concepts of pathogenesis and treatment.

Although the basic cause of acne vulgaris remains unknown, considerable data that concern its pathogenesis and that have been accumulated in recent years allow a rational and therapeutically successful approach to the management of this disorder. To date, there is no single treatment for acne. Therapy must be individualized, with appropriate variations and modifications as the degree or severity of this disorder fluctuates. Today, this goal can be achieved by proper selection of available medications, coupled with the cooperation of the patient, and the knowledge, continued interest, and enthusiasm of the physician and his staff.

Acne Vulgaris↗
PubMed1978

Combination chemotherapy including bleomycin in the treatment of advanced Hodgkin's disease.

Fifty-six patients with advanced Hodgkin's disease were treated with a combination of nitrogen mustard, a vinca alkaloid (vincristine or vinblastine), procarbazine, prednisone and bleomycin, given in repeated cycles. Complete remission was achieved in 33 out of 53 evaluable patients (62,5%). The complete remission rate in patients who had received prior radiation therapy alone (65%) was similar to that in previously untreated patients (73%). Patients who had previously received combination chemotherapy, either alone or together with radiation therapy, responded less well to this regimen of therapy, with a complete remission rate of less than 40%. The complete remission rate was not influenced by the histological subtype of the Hodgkin's disease. Twenty-three of the 33 responders (70%) remain in continuous complete remission. The median for this group has not been reached but will be in excess of 24 months. Major bleomycin toxicity was not encountered in this study. Lung function was monitored throughout but no consistent changes were encountered. The degree of haematological toxicity caused by treatment was no greater than would have been expected without bloemycin. Although the results obtained with the 5-drug combination were satisfactory, the follow-up to date does not suggest that the addition of bleomycin to the convention 4-drug regimen has significantly affected the outcome.

Adolescent↗
PubMed1978

Involvement of cholecalciferol metabolism in birds in the adaptation of calcium absorption to the needs during reproduction.

1. The metabolism of calcium and cholecalciferol in quail (Coturnix coturnix japonica) and chicken (Gallus domesticus) during maturation was correlated to gonadal activity and plasma oestrogen levels. 2. Birds with undeveloped ovaries (immature), developed ovaries but not laying (mature), and after laying 3-8 eggs (laying), were used in the first series. 3. Birds in which egg production had been arrested by Nicarbazin, were used in the second series. 4. Plasma 17 beta-oestradiol and calcium were elevated in the mature bird, with no further change in the laying bird. Kidney 25-hydroxycholecalciferol-1-hydroxylase and intestinal calcium-binding protein increased slightly in the mature bird, whereas they were grossly elevated in the laying bird. 5. Calcium and phosphorus absorption were markedly elevated in the laying bird. 6. No changes were noted in plasma 25-hydroxycholecalciferol, at any stage of maturation. 7. During the arrest of egg production by Nicarbazin, 17 beta-oestradiol level, calcium concentration of plasma, and medullary bone were maintained. Kidney 25-hydroxy-cholecalciferol-1-hydroxylase, intestinal calcium-binding protein and absorption of calcium were strikingly reduced. 8. The results suggest that changes in calcium absorption and cholecalciferol metabolism during maturation in birds are not directly affected by gonadal hormones; they appear to represent an adaptation to the increased calcium needs due to medullary bone formation and, more importantly, to the large losses of calcium imposed by shell formation.

Adaptation, Physiological↗
PubMed1978

Differential response of calcium transport systems in laying hens to exogenous and endogenous changes in vitamin D status.

Changes in intestinal calcium absorption, calcium deposition into egg shell, and intestinal, renal and uterine calcium-binding protein (CaBP) in laying hens were related to changes in 25 hydroxycholecalciferol-1-hydroxylase activity (1-hydroxylase), or to the supplementation of 1alpha-hydroxycholecalciferol (1alpha-OH-CC). The onset of egg production resulted in an increased kidney 1-hydroxylase activity and intestinal and uterine CaBP. Renal concentrations of CaBP remained unchanged. Intestinal calcium and phosphorus absorption, during the period of egg shell formation, and duodenal calcium-binding protein (CaBP), were higher in 1alpha-OH-CC-fed than in cholecalciferol-fed hens. Renal or uterine CaBP and calcium deposition into the egg shell did not fluctuate with the vitamin D source or concentration. 1alpha-OH-CC injection into non-laying Nicarbazinfed hens resulted in an increase in intestinal but not renal or uterine CaBP concentrations. It is suggested that (a) CaBP in various organs responded independently to the same stimuli; and (b) calcium deposition into egg shell and uterine CaBP level are not related to kidney 1-hydroxylase activity or concentration of 1,25 dihydroxycholecalciferol.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1978

Phosphate absorption and excretion in the young turkey, as influenced by calcium intake.

Phosphorus absorption in the young turkey, measured with the aid of yttrium-91 as a reference substance, was linear with phosphorus intake. This observation suggested the lack of adaptation of the phosphorus transport mechanism to changes in the phosphorus needs. Phosphorus retention and bone ash initially increased with increased intake to plateau at a dietary phosphorus concentration of about 0.8%. The excess phosphorus absorbed from diets higher in phosphate, was eliminated in the urine. Plasma inorganic phosphate was linear with absorbed phosphate. The apparent phosphorus absorption from the basal vegetable diet was 45% of the intake and that of the inorganic supplement, sodium phosphate and calcium monophosphate, was about 100%, at low calcium intakes. Increasing the calcium intake above 440 mg/day progressively depressed the absorption of phosphate. This inhibitory action of calcium on phosphate absorption was resolved into a linear coefficient.

Animals↗
PubMed1978

Retrograde movement of digesta in the duodenum of the chick: extent, frequency, and nutritional implications.

Movement of digesta from the duodenum to the gizzard of chicks was assessed by injection of 99mTc-diethyl-triamino-pentaacetic acid via an indwelling cannula in the hepatic bile duct. The change in location of isotope with time was followed with a Gamma Camera. About 40% of the injected isotope refluxed to the gizzard within 2 minutes of injection. Clearance of the isotope from the gizzard had a T1/2 of some 20 minutes. Some possible implications of retrograde movement of digesta were examined. Cholesterol, bile salts and pancreatic enzymes were found in the gizzard at 10% to 20% of duodenal concentrations. The proteolysis and lipolysis in the gizzard and duodenum were determined in chicks fed a duet containing 91Y as a non-absorbed reference substance. Thirty percent of the feed triglycerides were found hydrolysed in the gizzard as compared to 50% to 60% in the duodenum. Proteins were 30% to 50% trichloroacetic acid soluble in the gizzard reaching almost 70% in the duodenum. A small net secretion of both fatty acids and protein was observed in the gizzard, probably due to reflux of endogenous secretions from the duodenum. The nutritional significance of these results is discussed.

Animal Nutritional Physiological Phenomena↗
PubMed1978

Calcium-binding protein and kidney 25-hydroxycholecalciferol-1-hydroxylase activity in turkey poults.

A vitamin D-dependent calcium-binding protein (CaBP) has been found in the intestinal mucosa of turkeys (Meleagris gallopavo). This protein is similar, if not identical, to the corresponding one found in the intestine of the chicken (Gallus domesticus). The concentration of intestinal CaBP in the intestine of cholecalciferol-fed turkey poults was twice that found in the intestine of the domestic chicken of parallel age. Dietary calcium or phosphorus restriction resulted in a significant increase in intestinal CaBP. This increase was less pronounced than that obtained in chickens. The relationship between duodenal CaBP and dietary calcium appears to be linear. Cholecalciferol (vitamin D) deficiency or dietary calcium, but not phosphorus, restriction resulted in an increase of kidney 25 hydroxycholecalciferol-1-hydroxylase activity in vitro. The values of activity obtained in turkeys were higher than those obtained under the same experimental conditions in chicks. Bone ash was reduced by dietary calcium, phosphorus or cholecalciferol restriction. Plasma inorganic phosphorus was lower in either cholecalciferol- or phosphorus-restricted turkeys. Plasma calcium was significantly higher in the phosphorus-restricted turkeys than in the calcium-restricted or control turkeys.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1978

New formal approaches to the determination of energy and amino acid requirements of chicks.

Body weight and the intake of metabolizable energy of chicks as function of age, were resolved into a linear equation from which the energy requirements for maintenance and growth were extracted. The metabolizable energy requirement for maintenance was calculated to be 1.91 and 1.62 Cal./g. 2/3, and that for weight gain was 2.05 and 2.19 Cal./g. for male White Rock and female 2--8-week old Leghorn chicks, respectively. The amino acid requirements of growing broiler chicks were calculated from the maintenance requirements, body weight gain and body weight, the proportions of feather protein in total body protein, and the amino acid composition of carcass and feathers. The requirements thus calculated, correlated well with various values in the literature. Diets formulated on the basis of the present model, were lower in protein and amino acid contents than those formulated on the basis of NRC allowances. These differences were pronounced in diets designed for 6--8 week old chicks. The weight gains obtained were similar for both types of diets. Feed conversion were slightly poorer and abdominal fat higher in chicks fed the model diets. It is concluded that the present model can serve, at least as an initial approach, to calculate the protein and amino acid requirements.

Amino Acids↗
PubMed1977

Amino acid absorption along the intestinal tract of chicks fed heated and raw soybean meal.

Net absorption of individual amino acids along the intestinal tract was determined in chicks fed heated soybean meal (HS) and raw soybean meal (RS) using 91Y as a reference substance. In the duodenum of chicks fed either diet, the absorption of the amino acids varied. In chicks fed the RS diet, the differences were greater than in chicks fed the HS diet, and most of the values were negative. Methionine was the most rapidly absorbed amino acid. No cystine was found in the upper parts of the intestinal tract of chicks fed either diet. A linear relationship was obtained between the amino acid absorption values in the duodenum of chicks fed either diet. The differences recorded seem to be due to nitrogen secretion, which is enhanced in RS-fed chicks. The differences between individual amino acid absorption decreased gradually in the other segments and attained in the lower ileum an average cumulative value of 90% and 70% in chicks fed on HS and RS respectively. The 20% difference was probably a result of the inhibited digestion in the intestine (duodenum excluded) of chicks fed RS. The results indicate that the absorption process can proceed even when the digestion is inhibited.

Amino Acids↗
PubMed1977

Beta-adrenergic stimulation of cyclic AMP content and parathyroid hormone release from isolated bovine parathyroid cells.

The effects of beta-adrenergic agonists and antagonists on cyclic AMP (cAMP) accumulation and parathyroid hormone (PTH) release from isolated bovine parathyroid cells have been determined. Beta-adrenergic agonists markedly stimulate cAMP production and PTH release with an order of potency (-) isoproterenol greater than (-)epinephrine greater than greater than (-) norepinephrine, suggesting a beta2-type adrenergically mediated process. Both effects are blocked by the beta-blocker propranolol with the strict stereospecificity expected for a beta-adrenergic response. Low calcium concentrations also stimulate cAMP accumulation, but the cyclic nucleotide response under these conditions is only 3% of that obtained with isoproterenol, raising the possibility that factors other than cAMP may control low calcium-mediated PTH release. The release of PTH by low calcium is also not blocked by propranolol, confirming the independence of the response to low ambient calcium from the beta-adrenergic receptor. These studies substantiate further the utility of the isolated parathyroid cell preparation for studying secretagogue-mediated alterations in cyclic nucleotides and hormone secretion. Isolated cells also also make feasible the direct identification of beta-adrenergic receptors in parathyroid cell membranes and whole cells.

Adrenergic beta-Agonists↗
PubMed1977

Direct identification of beta-adrenergic receptors on isolated bovine parathyroid cells.

The radioiodinated beta-blocker iodohydroxybenzylpindolol ([125I]HYP) has been used to identify directly and characterize beta-adrenergic receptors in isolated bovine parathyroid cells. [125I]HYP was bound rapidly and reversibly to isolated bovine parathyroid cell membranes. Scatchard analysis revealed a single class of binding sites with high affinity (4 X 10(10M-1) and low capacity (0.7 pmol/mg). Saturation analysis of [125I]HYP binding to intact bovine parathyroid cells suggested a site with similar affinity on whole cells and with a binding capacity of 5000-10,000 sites/cell. True dissociation constants (Kd's) for beta-adrenergic agonists and antagonists were in good agreement with activation constants (KA'S) and inhibition constants (KI'S) for effects on adenylate cyclase in membrane preparations. These constants also were in reasonable agreement with KA'S and KI'S previously shown for effects of agonists and antagonists on cAMP accumulation and PTH release in whole cells. This study shows by direct analysis that beta-adrenergic receptors exist on isolated bovine parathyroid cells, and that there is close coupling between receptor binding, effects on cAMP and hormonal release. This represents still another system in which [125I]HYP has been successfully used to study beta adrenergic receptors in membrane as well as intact cell preparations.

Adenylyl Cyclases↗
PubMed1977

Use of 1alpha-hydroxycholecalciferol in the prevention of bovine parturient paresis.

A synthetic biologically active derivative of vitamin D (350 microgram of 1alpha-hydroxycholecalciferol [1alpha(OH)CC]) was injected into 2 nonlactating 7-year-old Israeli-Friesian cows. Plasma calcium values increased after 24 hours, peaked at 48 hours, and returned to base-line values 120 hours after injection. An injection of 350 microgram of 1alpha(OH)CC was given to 23 parturient-paresis-prone Israeli-Friesian cows from 7 days to 6 hours prepartum; 13 cows were injected once, 6 were injected twice, and 4 were injected 3 times, all at 48-hour intervals. Parturient-paresis-prone cows (n = 23) of the same breed were used as controls. Within 0 to 36 hours postpartum, plasma calcium concentrations were found to be higher in cows injected with 1alpha(OH)CC than in the control cows. The increase was highly significant (P less than 0.01) in cows injected at least twice. None of the cows injected with 1alpha(OH)CC, within 72 to 24 hours prior to calving developed parturient paresis; but 9 of 23 control cows developed parturient paresis. Prior to calving, none of the injected cows developed hypercalcemia and there was no local or systemic clinically detectable signs of toxiosis. When given at the right time prepartum, 1alpha(OH)CC is considered to be an improvement over previous methods of preventing bovine parturient paresis.

Animals↗