Biomedical subjects

S Hurwitz

Publications and source records attributed to S Hurwitz.

At least 127 records · Page 7Linked to original sources

PubMed1987

Absorption of protein, fatty acids and minerals in young turkeys under heat and cold stress.

1. Absorption of protein, fatty acids, calcium, phosphate and potassium by young turkeys maintained at thermoneutral (24 degrees C), hot (35 degrees C) and cold (8 degrees C) conditions was examined. 2. Non-acclimatised, heat-stressed birds absorbed less potassium and phosphate, whereas absorption of nitrogen, fatty acids and calcium was not altered, as compared with birds at 24 degrees C. Non-acclimatised, cold-stressed birds absorbed less calcium than control birds and more nitrogen than non-acclimatised, heat-stressed birds. 3. Heat acclimatization might reduce the adverse effect of heat stress on potassium and phosphate absorption.

Animals↗

PubMed1987

Serodiagnosis of invasive aspergillosis in patients with hematologic malignancy: validation of the Aspergillus fumigatus antigen radioimmunoassay.

Six hundred sixteen sera from 79 hematology patients admitted on 152 occasions were analyzed for validation of the Aspergillus fumigatus antigen radioimmunoassay (RIA). Invasive aspergillosis developed on 24 admissions of 22 patients. Maximal antigenic activity was significantly higher in patients with invasive aspergillosis than in controls (P less than .0005). At the level of antigenic activity selected as the cutoff value, the sensitivity of the RIA was 74%, the specificity 90%, the positive predictive value 82%, and the negative predictive value 85%. Antigen was detected before invasive aspergillosis was suspected during 30% of admissions and before pathological or even preliminary microbiological evidence for disease in 46%. In 17 (77%) of the 22 episodes of pulmonary aspergillosis, the RIA would have been the first positive diagnostic test for aspergillosis or would have confirmed a diagnosis established by other means. Overall, the test would have been of clinical usefulness in diagnosis, management, and prognosis in 80% of 16 fatal cases.

Agranulocytosis↗

PubMed1987

Vitamin D metabolism and calbindin (calcium-binding protein) in aged laying hens.

Calbindin (calcium-binding protein) concentration, vitamin D metabolism and shell quality were investigated in young (7- to 9-mo-old) and aged (19- to 21-mo-old) laying hens consuming normal or low levels of calcium (Ca). Although egg weight and percent of cracked eggs were higher and egg production and shell density (mg/cm2) were lower (significantly, P less than 0.01) in aged hens, shell weight, plasma Ca and duodenal and egg shell gland calbindin were similar to those of young hens. Dietary Ca restriction reduced shell weight, shell density and structural bone and plasma Ca in both the young and aged birds. The production of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] and its concentration in the plasma were higher in hens fed low dietary levels of Ca than in hens fed normal Ca levels only in the younger hens. However, a slightly higher production of 1,25(OH)2D3 and concentration of duodenal calbindin were also observed in severely Ca-restricted (1.4% Ca for 19 d) aged hens than in the younger hens. The results suggest that the aged hen loses its ability to adapt to changes in Ca intake or needs through mechanisms involving modulation of vitamin D metabolism.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗

PubMed1987

Calcium dynamics: a model system approach.

A computerized model used to simulate calcium metabolism in growing chicks combines growth equations with differential equations that account for the amount and action of various components of the plasma calcium regulating subsystems--intestine, kidney and bone. These in turn are modulated by the calcium-regulating hormones: parathyroid hormone and 1,25-dihydroxycholecalciferol. Simulation with this model indicated oscillations in the plasma calcium concentration in growing chicks under normal dietary conditions. The oscillations diminish in amplitude and finally disappear when dietary calcium concentrations are either reduced or elevated. These oscillations, triggered by the perturbation imposed by growth, are the result of the dual action of parathyroid hormone on bone on the one hand and on intestinal calcium absorption via the 1,25-dihydroxycholecalciferol synthesizing system on the other and the difference in the response time between the two subsystems. Simulation also predicts that at high or low intakes of calcium, the capacity of the control systems is exceeded and oscillation in plasma. calcium diminish and finally disappear. Bone calcium, simulated for different calcium concentrations, mimics documented experimental results.

Animals↗

PubMed1987

Model of plasma calcium regulation: system oscillations induced by growth.

The process of growth was included in a model for simulation of calcium homeostasis in the chick, using data of carcass composition and a model of growth and energy intake. Computer simulations, made for chickens between 0 and 10 wk of age, predicted oscillations in plasma calcium and its major regulatory systems. Analysis of the oscillations indicated a periodicity of approximately 55 h. The oscillations were proportionally dependent on the rate of growth, disappearing almost completely when growth rate was made equal to zero. Subject to the validity of the model, it is suggested that the oscillations in plasma calcium and some of the components of the regulatory systems are induced by a continuous perturbation (growth) resulting in a dual response to the main regulatory hormone, parathyroid hormone, one rapid with a response time of minutes (bone), and one delayed, with a response time of hours (calcium absorption via the metabolism of 1,25-dihydroxychole-calciferol). It is also suggested that some of the normal variance and some of the rhythmicity observed previously in various components of the calcium regulatory system may be the results of spontaneous oscillations.

Animals↗

PubMed1987

Concentration of adrenocortical hormones in relation to cation homeostasis in birds.

The effects of dietary Na+, K+, and Cl- and of acute stress on plasma levels of Na+, K+, aldosterone, and corticosterone were evaluated in vivo in birds. The dietary effects were studied in growing White Rock chicks, whereas the larger turkey was preferred for the acute stress study. Although plasma corticosterone remained unaffected, plasma aldosterone concentration decreased with increasing levels of dietary Na+ reaching a minimum at a dietary level of 72 meq/kg. Plasma Na+ remained unchanged when dietary Na+ levels increased up to 72 meq/kg but then rose with increasing Na+ intake. Plasma K+ was slightly depressed by high levels of dietary Na+ and increased by dietary K+. Neither plasma Na+ nor circulating adrenal hormones were affected by dietary K+ or dietary Cl-. Acute stress stimulated both aldosterone and corticosterone without any effect on the levels of the plasma minerals. The results suggest that of the two main corticoids, only aldosterone responds to dietary Na+ in chicks. This is in contrast to the indiscriminate stimulation of both hormones by stress, indicating different pathways of stimulation. The results also suggest that aldosterone is involved in the regulation of plasma Na+ only at low intakes of Na+ and that dietary K+ and Cl- are not involved in the aldosterone-Na+ feedback relationship.

Acute Disease↗

PubMed1987

Response of adrenal cells to parathyroid hormone stimulation.

Dispersed adrenal cells of avian and bovine origin were incubated with human (h) 1-34 parathyroid hormone (PTH(1-34)), bovine (b) PTH(1-84), bPTH(3-34), avian (a) PTH, and with ACTH. Kidney tubular cells, the established target cells for PTH, were used for comparison. Cyclic AMP (cAMP) accumulation and steroid hormone (aldosterone and corticosterone) secretion were measured in response to the hormones. In the bovine adrenocortical cells PTH of both bovine and avian origin stimulated cAMP production, but the aPTH action was more pronounced. The maximal cAMP response of avian adrenocortical cells to aPTH was 15-fold greater than that of ACTH, but a 20-times higher concentration of aPTH was required to reach half-maximal response. Avian PTH stimulated steroid hormone secretion in the chick adrenocortical cells, but the induced secretion was similar to that induced by ACTH, despite the difference in cAMP accumulation. Human PTH(1-34) and bPTH(1-84), which stimulated cAMP production in kidney cells, and the conventional antagonist bPTH(3-34) inhibited aPTH stimulation of cAMP accumulation in avian adrenocortical cells, but did not interfere with ACTH action. Furthermore, cAMP stimulation by aPTH and ACTH in avian adrenal cells was additive. The results establish the adrenal as a target organ for PTH, and suggest that the PTH acts through specific receptors, distinct from those for ACTH.

Adrenal Glands↗

PubMed1987

Field rickets in turkeys: relationship to vitamin D.

Thirty-two outbreaks of leg disorders in turkeys were investigated during 1981-1985. Among them, 22 were characterized by a low percentage of bone ash and were considered as field rickets. Most of the field rickets cases exhibited reduced plasma calcium and inorganic phosphorus. Plasma 25-hydroxyvitamin D3 and intestinal calcium-binding protein were lower in the rachitic than in normal turkeys. These symptoms are typical of rickets resulting from vitamin D deficiency. The vitamin D3 equivalence of a diet that had been fed during field rickets outbreaks was assayed biologically and found to be 111 micrograms/kg diet, about eight times the minimal requirement. In two other cases no symptoms of rickets were observed in turkeys fed diets that had been previously consumed during field rickets outbreaks. The results indicate that in some cases of field rickets there was no involvement of dietary factors and confirm a previous suggestion that field rickets may result from defects in metabolism of vitamin D3, or in its expression.

Animals↗

PubMed1987

Differential responses to dietary carbohydrates and fat of turkeys kept at various environmental temperatures.

Interactions between environmental temperature and dietary energy sources were evaluated in 6 to 9-wk and 9 to 12-wk-old turkeys using weight gain, feed efficiency, and carcass fat as response criteria. The dietary variables (soybean oil or glucose) were added in five or six increments at the expense of each other or of the fiber supplements, keeping the minima for protein and amino acid/energy constant. The resulting diets were fed to birds kept at 10 and 27 C. Duplicate experiments were conducted for each mode of dietary variable addition. Parallel increases in body weight gain and feed efficiency were obtained at the two temperatures when fat replaced carbohydrates or fiber, thereby raising dietary energy density. Some responses of weight gain and feed efficiency at the two temperatures were obtained also with a graded isocaloric addition of fat but the response was significant only at 27 C and not at 10 C. A greater response of gain and feed efficiency to energy supplied by dietary glucose was obtained at 10 C as compared with 27 C. Dietary fat supplementation resulted in increased deposition of carcass fat when given together with energy or isocalorically regardless of environmental temperature. Carcass fat was increased by glucose-energy at the low temperature only.

Adipose Tissue↗

PubMed1987

Efficacy of intensive plasmapheresis in thrombotic thrombocytopenic purpura.

Forty-one patients with thrombotic thrombocytopenic purpura were treated at the Hospital of the University of Pennsylvania, Philadelphia, between 1975 and 1985. Initially, early splenectomy was performed. However, since 1981, more intensive plasma exchange therapy (increase in frequency and size of exchange) has been used as the primary modality of treatment for this disorder. A reduction of the mortality rate over time has been observed. For the period 1975 to 1980, the mortality rate was 41% (seven of 17). In contrast, for the period 1981 to 1985, the mortality rate decreased to 17% (four of 24). These observations support the concept that the initial management of thrombotic thrombocytopenic purpura with intensive daily plasma exchange is associated with improved survival. The role of platelet inhibitors and corticosteroids needs yet to be defined.

Adrenal Cortex Hormones↗

PubMed1986

Factors associated with psychological distress in cancer patients.

We studied the mental health of 1,278 patients with cancer and 645 family members of patients with cancer to delineate clinical and demographic characteristics associated with poor psychological status. For both patients and their matched relatives, there was a direct relationship between poorer mental health scores and younger age. Highly significant age differences emerged as well for subscale scores of anxiety, depression, and general positive affect in patients, and for depression, emotional ties, and loss of control in relatives. Treatment status, performance status, and sex also contributed significantly to mental health scores. Patients at greatest risk for psychological problems are young, female, receiving palliative or active treatment as opposed to follow-up care, and symptomatic or not fully ambulatory. Clinicians should be alert to the potential for psychological problems among patients in these categories.

Adaptation, Psychological↗

PubMed1986

Relation of human T lymphotropic virus type III antibodies to T lymphocyte subset abnormalities in hemophiliac patients.

The relationship of T lymphocyte subset abnormalities and the presence of antibodies to the human T lymphotropic virus type III (HTLV-III) was evaluated in 66 adult patients with hemophilia. Positive test results for antibodies to HTLV-III were observed in 62 percent of patients with hemophilia A and 9 percent of patients with hemophilia B. Patients with HTLV-III antibodies had lower percentages and numbers of T helper (T4) cells and increased percentages of T suppressor (T8) cells compared with percents in patients without antibodies to HTLV-III. The mean T4/T8 ratio for antibody-negative patients was 1.45 compared with 0.65 for antibody-positive patients (p less than 0.0005). These abnormalities were more apparent among hemophiliac patients who received factor VIII concentrates. The strong association of lymphocyte subset abnormalities and seroreactivity to this virus suggests that infection by HTLV-III has occurred in this population rather than a passive exposure to viral antigens contained in factor concentrates.

Adolescent↗

PubMed1986

Parameter estimation for ligand binding systems kinetics applied to 1,25-dihydroxycholecalciferol.

A mathematical analysis of the kinetics of the hormone-receptor interaction was applied to the 1,25-dihydroxycholecalciferol-intestinal receptor system. The exact analytical solution and the numerical integration of the kinetic equation were installed in a Statistical Analysis System (SAS) computer program to estimate the rate constants of the reaction. Estimates of the parameters obtained by these two methods are similar, demonstrating that the numerical integration can be combined with the nonlinear regression procedure for least-squares parameter fitting using a simple SAS program. This enables estimation of kinetics rate constants when the kinetic equation cannot be solved analytically. The ratio of the rate constants (ka/kd) found by the nonlinear procedure is close to the independently determined equilibrium (Scatchard) constant in the nonlinear analysis.

Animals↗

PubMed1986

Carcass minerals in chickens (Gallus domesticus) during growth.

Moisture, sodium, potassium, calcium, phosphate and magnesium were determined in the carcass of male chickens (Gallus domesticus) between the ages of 1 and 70 days. Moisture decreased rapidly during the first 3 days of life, followed by a more moderate decline. Sodium and potassium concentrations decreased with age, but not in a parallel fashion. Some of the changes with age could be explained on the basis of an extra- and intracellular fluid shifts. Calcium and phosphate concentration increased with age, reflecting skeletal calcification. Carcass magnesium concentration increased during the first 3 days of life and did not change significantly thereafter.

Aging↗

PubMed1986

Regulation of kidney calcium-binding protein in the bird (Gallus domesticus).

The possible involvement of plasma calcium and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] in the regulation of the concentration of kidney calcium-binding protein (CaBP) was investigated. Chicks were fed diets varying in Ca2+ and P, with or without vitamin D. CaBP and 1,25(OH)2D3 were determined by competitive binding assays. A significant correlation between plasma and kidney 1,25(OH)2D3 was found, the linear regression equation of best-fit was plasma 1,25(OH)2D3 = 0.14 + 1.56 kidney 1,25(OH)2D3. In the vitamin D-fed chicks, kidney CaBP varied independently of the circulating or organ level of 1,25(OH)2D3 (P greater than 0.05), but was lower in the vitamin D-deficient than in the vitamin D-fed birds. A significant correlation was observed between kidney CaBP and plasma calcium (Cap). The regression equations were CaBP = Cap/(85.57-4.00 Cap) (R = 0.845) and CaBP = 0.0558 + 0.0404 Cap (R = 0.749), for vitamin D-treated and vitamin D-deficient chicks, respectively. The results suggest that the concentration of kidney CaBP is modulated by plasma calcium, but one or more of the vitamin D metabolites may be required for its synthesis.

Animals↗

PubMed1986

Relationship between endogenous cyclic AMP production and steroid hormone secretion in chick adrenal cells.

Dispersed chick adrenal cells were incubated with either ACTH, cholera toxin or forskolin. All three agents stimulated cyclic AMP accumulation and secretion of corticosterone and aldosterone by the dispersed cells. The dose-response to ACTH was similar for cyclic AMP and corticosterone but aldosterone secretion appeared to be more sensitive to ACTH stimulation. Concentrations higher than 10(-8) M of ACTH caused suppression of corticosterone output but not of cyclic AMP accumulation or aldosterone secretion. A significant cyclic AMP accumulation occurred within 30 min of exposure to ACTH whereas significant increases in steroid secretion were observed only after 30 min. An early increase (within 30 min) in cyclic AMP accumulation with both cholera toxin and forskolin was not accompanied by any significant stimulation of steroid secretion, which occurred only after 120 min. The results with the avian adrenal cells are consistent with the thesis that steroid production in the adrenocortical cells is stimulated by cyclic AMP-dependent pathways, whereas steroid release may be modulated by others.

Adrenal Glands↗

PubMed1986

Comparison of allogeneic bone marrow transplantation and chemotherapy in adult acute nonlymphocytic leukemia. An Eastern Cooperative Oncology Group Study.

To compare the value of ABMT (allogeneic bone marrow transplantation) in first or second remission vs. conventional chemotherapy in adults with acute nonlymphocytic leukemia, we examined retrospectively the outcome of a recently completed chemotherapy trial. We evaluated the survival of patients, with and without histocompatible siblings, who were less than or equal to 45 years old and who had achieved initial complete remission. Of 20 patients who were referred by their physicians for ABMT in first remission, seven relapsed (median duration of remission, 4 months) prior to ABMT, three refused, and 10 underwent ABMT. Nine patients received ABMT in second remission. In comparison to the results of chemotherapy in patients who lacked histocompatible siblings (median duration of survival, 18.5 months), the survival of patients transplanted in first remission was worse (median, 8 months), whereas the survival of patients transplanted in second remission was substantially better (median greater than 22 months). Although ABMT in second remission clearly offers the potential for long-term survival not available by means of conventional chemotherapy, the value of ABMT in first remission remains uncertain.

Acute Disease↗

PubMed1986

Reduced affinity of intestinal receptors for 1,25-dihydroxycholecalciferol in phosphorus-deficient chicks.

The binding of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) to its intestinal receptor was studied in chicks fed a phosphorus (P)-deficient diet. The equilibrium association constant (Ka) was determined by Scatchard analysis. Association (Kass) and dissociation (Kdis) rate constants were determined in experiments on hormone uptake and release respectively. The Ka, determined at 4, 12 and 19 degrees C, decreased progressively during P deficiency, due to the decrease in Kass, but Kdis was not affected. During prolonged P deficiency the concentration of binding sites (Nmax) also decreased. Duodenal calcium-binding protein (CaBP) increased during 10 days of P deficiency and then decreased. The long-term decrease in receptor affinity and Nmax may account for the observed reduction in receptor occupancy and the decrease in the high level of intestinal CaBP stimulated during early P deficiency. The resulting decrease in Ca absorption may minimize the hypercalcaemia induced by the deficiency.

Animals↗