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Biomedical subjects

S Hurwitz

Publications and source records attributed to S Hurwitz.

At least 91 records · Page 5Linked to original sources
PubMed1991

Response of broiler chickens and turkey poults to food restriction of varied severity during early life.

1. Cobb male (7-d-old) and female (6-d-old) chicks and BUT male and female turkeys (7-d-old), were subjected to food restriction of varying severity for 7, 5, 10 and 7d, respectively. 2. The energy allowance was calculated to support from 0% to 75% of the growth rate typical of species, strain and sex. 3. In male and female broilers kept up to 56 and 50 d, respectively, a high rate of weight gain after the restriction period (refeeding period) overcame the growth retardation attributable to restriction, except in the birds which had been subjected to the most severe regimen. In the mildest regiments, body weights reached slightly higher values than those of the ad libitum-fed controls. Overall food conversion efficiency was significantly improved in males and abdominal fat content was reduced in both sexes, regardless of the severity of restriction. 4. Body weights of male and female turkeys, aged 147 and 112 d respectively, of the groups subjected to the milder (75% growth) restriction, significantly exceeded those of the controls. Food conversion efficiency and meat yield were improved by early-age food restriction but carcase fat was not affected. 5. The results for both species of either sex suggest that a mild food restriction applied at an age of about 1 week and allowing for 60 to 75% of normal growth, may offer an economic advantage over a continuous ad libitum feeding regimen.

Animal Feed↗
PubMed1991

Increased skin tearing in broilers and reduced collagen synthesis in skin in vivo and in vitro in response to the coccidiostat halofuginone.

In vivo and in vitro experiments were conducted in an effort to elucidate the mechanism of suppression by halofuginone of skin strength in broilers. In the in vivo study, halofuginone was included at concentrations of 0, 1.5, 3, and 6 mg/kg of diet, corresponding to 0, 50, 100, and 200%, respectively, of the amount recommended for use as a coccidiostat. Each dietary treatment was given to 260 female broiler day-old chickens. Skin tearing was evaluated at the processing plant. Skin collagen and Kjeldahl-nitrogen were determined chemically. At the age of 7 wk, BW and feed efficiency were affected only in birds consuming the diet containing the highest concentration of the drug. Skin tearing increased but skin collagen concentration decreased in a dose-dependent manner. Fibroblasts were obtained by collagenase digestion from chicken skin and cultured. The cultured cells were incubated with various concentrations of halofuginone, monensin, and nicarbazin, and [3H]proline incorporation was evaluated in collagenase-digestible (representing mostly collagen) and nondigestible proteins exported by the cells into the medium. Halofuginone, at a concentration as low as 10(-11) M, inhibited incorporation of [3H]proline into collagenase-digestible proteins, but did not affect incorporation of [3H]proline into collagenase-nondigestible proteins. Even at concentrations as high as 10(-9) M, neither monensin nor nicarbazin affected collagenase-digestible proteins. The in vitro results suggest that halofuginone specifically inhibits collagen synthesis by skin fibroblasts. Results of both in vivo and in vitro trials suggest that the increase of skin tearing during processing, induced by halofuginone, is caused by direct suppression of skin collagen synthesis.

Animals↗
PubMed1991

The role of the growth plate in longitudinal bone growth.

The epiphyseal growth plate is the main site of longitudinal growth of the long bones. At this site, cartilage is formed by the proliferation and hypertrophy of cells and synthesis of the typical extracellular matrix. The formed cartilage is then calcified, degraded, and replaced by osseous tissue. Proliferation and differentiation of cartilage cells (i.e., chondrocytes) as studied mostly in culture, is regulated by various endocrine, paracrine, and autocrine agents such as growth hormone, insulin-like growth factor-I (IGF-I), transforming growth factor (TGE-beta), and vitamin D metabolites (1,25-dihydroxycholecalciferol and 24,25-dihydroxycholecalciferol). Avian chondrocyte proliferation is enhanced by agents which use adenosine 3':5'-cyclic monophosphate as a second messenger, such as parathyroid hormone or prostaglandin-E2, and is depressed by guanosine 3':5'-cyclic monophosphate agonists, such as atrial natriuretic peptide. Several of the regulating agents also affect synthesis of the main extracellular components (i.e., collagen and proteoglycans) and their transfer to the extracellular space. Cartilage calcification involves matrix vesicles secreted by the chondrocytes at a specific stage. Calcification probably involves some initial nucleation agent and participation of phosphatases. During sexual maturation, the growth plate closes by an unknown mechanism and longitudinal bone growth ceases. Disorders in the metabolism of the controlling agents or the cellular responses in growth plate may lead to several deformities classified as dysplasias. In poultry, this class of disorders is represented by chondrodystrophy and dyschondroplasia.

Animals↗
PubMed1991

Skin tearing in broilers in relation to skin collagen: effect of sex, strain, and diet.

The relationship between skin tearing and collagen in broilers was investigated in two trials in which strain and sex, and strain and diet served as factorial-arranged variables, respectively. In the first trial, males and females of three strains were examined. Both skin tearing and skin collagen were significantly influenced by strain and sex without any significant strain by sex interaction. Skin collagen, expressed as a fraction of fresh skin protein (N x 6.25) was lower and skin tearing was higher in females than in males, particularly in the most susceptible strain. In the second trial, the effects of supplementary protein or methionine and of a low-density diet were tested in females of two strains that differed in their susceptibility to skin tearing. High dietary protein reduced skin tearing and increased skin collagen. The significant diet by strain interaction resulted from the more pronounced response of the susceptible strain. Neither supplementary methionine nor feeding of low-dietary-density diet significantly affected skin tearing or skin collagen.

Animals↗
PubMed1991

Characterization of growth and development of male British United turkeys.

Body weight and the size of various organs (tibia, pectoral muscle, leg muscle, liver, spleen, and testes) were monitored in growing male turkeys (British United Turkeys) in an effort to characterize their growth pattern. The results were fitted with either a single- or a double-component Gompertz equation, describing single and diphasic growth patterns, respectively, using an iterative nonlinear estimation algorithm. The diphasic model with an early and a late growth component provided a better description of the body weight function than the single-phase model. The start of sexual maturation, evidenced by testicular development, marked the transition age between the early and the late phases of growth. A single-component Gompertz equation was sufficient to describe growth of various individual organs. Growth of bone and liver appeared to follow the early growth component, whereas the path of muscle development appeared to be closer to the later growth component. The results suggest that the diphasic growth behavior of male turkeys is caused by a differential growth rate of various organs, rather than by a periodicity in the overall growth rate.

Animals↗
PubMed1991

Methylphenidate in depressed medically ill patients.

BACKGROUND: The purpose of the authors' study was to evaluate the efficacy of methylphenidate in the medically ill depressed patients and to examine the factors that appear to affect therapeutic response and side effects. METHOD: Hospital charts were reviewed for 29 patients who received trials of methylphenidate for treatment of depressive disorders while admitted to a medical/surgical unit. RESULTS: Of the 29 patients, 16 (55%) had moderate or marked improvement, all within 2 days of commencing treatment with the maximal dose. Of the 25 nondelirious patients, 16 (64%) had moderate or marked improvement, and the presence of delirium was significantly associated with decreased response. Therapeutic response was significantly correlated with maximum methylphenidate dose. Side effects were noted in 8 (28%) patients; most side effects were mild (tachycardia or agitation), and all reversed after the medication was discontinued. CONCLUSIONS: Methylphenidate provides a safe and effective alternative to tricyclic antidepressants in medically ill populations but appears to be less effective in the presence of delirium.

Adjustment Disorders↗
PubMed1990

Cyclic AMP-dependent inhibition of collagen synthesis in avian epiphyseal cartilage cells: effect of chicken and human parathyroid hormone and parathyroid hormone-related peptide.

Avian cartilage cells derived from epiphyseal growth-plate and avian skin fibroblasts were cultured in vitro. Production of cAMP by cartilage cells was stimulated by the synthetic fragments (1-34) of chicken (cPTH), human (hPTH) parathyroid hormone and by parathyroid hormone-related peptide (PTHrP). The enhancement of cAMP production by any of the peptides could be blocked by the parathyroid hormone analogue (3-34)PTH, suggesting interaction with PTH specific receptors. When incubated with [3H]proline, both cell types released radiolabelled collagenase-digestible and non-digestible proteins into the medium. cPTH, hPTH, PTHrP, forskolin, prostaglandin E2 (PGE2) and 8-bromo cAMP inhibited collagen production in cartilage cells with only minor effects on non-collagenase digestible proteins. No effect of cAMP on collagen production by fibroblasts was observed. The present results provide additional evidence that avian growth-plate cartilage cells are targets for PTH, and are first to demonstrate the response of a non-mammalian system to mammalian PTHrP. The data suggest that collagen production by epiphyseal growth-plate cartilage cells is inhibited by PTH and that this inhibition is mediated by cAMP.

Animals↗
PubMed1990

Melanoma in children.

Four cases of malignant melanoma in children younger than 17 years of age are presented. Several preexisting conditions increase the risk of development of melanoma during childhood. These include giant congenital melanocytic nevi, the familial dysplastic nevus syndrome, and xeroderma pigmentosum. The role of small congenital lesions and sporadic dysplastic nevi in the development of melanoma in children is less clear. The signs and symptoms associated with melanoma in children are similar to those in adults, as are the histopathologic features, biologic behavior, and treatment of this tumor. The inadequacy of available therapy for metastatic melanoma underscores the necessity for the early diagnosis and prompt surgical treatment of melanomas in children.

Adolescent↗
PubMed1990

Acne Vulgaris: Its Pathogenesis and Management.

The prognosis for the thousands of young people who seek treatment for acne is growing considerably brighter. Elimination of old misconceptions, together with many promising and proven new medications, has done much to improve the management of acne. The author emphasizes that therapy must be individualized, with appropriate variations and modifications as the severity of the disorder fluctuates.

Journal Article↗
PubMed1989

Inhibition of aldosterone secretion by atrial natriuretic peptide in chicken adrenocortical cells.

Dispersed chicken adrenocortical cells were preincubated with atrial natriuretic peptide (rANP), sodium nitroprusside (SNP) or 8-bromo cyclic GMP, followed by incubations with ACTH, chicken PTH, cholera toxin or various steroid intermediates of aldosterone production. Cyclic AMP production and aldosterone secretion were evaluated, in order to determine the sites of ANP inhibition in the sequence of events leading to aldosterone secretion. Dose-dependent inhibitory effects on ACTH-stimulated aldosterone secretion by rANP and SNP were observed. Both agents appeared to stimulate cGMP production by the particulate fraction of the avian adrenocortical cells. Aldosterone production, stimulated by cyclic AMP agonists such as ACTH, chicken PTH and cholera toxin, was significantly inhibited by ANP. On the other hand, ANP did not interfere with production or degradation of cAMP. Each of the aldosterone intermediates--pregnenolone, progesterone, 11-deoxycorticosterone and corticosterone--promoted aldosterone production when included in the incubation media. Atrial natriuretic peptide and SNP inhibited aldosterone secretion when enhanced by the intermediates, by about 40-60%, but the ACTH-stimulated secretion was inhibited by over 90%. The results suggest two sites of inhibition by ANP in the pathway of aldosterone synthesis and secretion: synthesis of cholesterol or pregnenolone, and conversion of corticosterone to aldosterone. The inhibition by 8-bromo cGMP of aldosterone secretion and the similar sites of inhibition for ANP and SNP suggest that cyclic GMP mediates the inhibition in both cases.

Adrenal Cortex↗
PubMed1989

Modulation of responsiveness of the adenylate cyclase system in avian chondroprogenitor cells by pertussis toxin, PTH, and PGE2.

Chondroprogenitor cells, derived from avian tibia epiphyseal growth plate, were cultured in vitro. Incubation of these cells with pertussis toxin augmented their cAMP response to parathyroid hormone (PTH), attenuated the response to forskolin, but did not modify the response to PGE2. Pertussis toxin modulation of the cAMP response was accompanied by ADP ribosylation of two proteins with molecular weights of 39 and 40 kD. Using specific antibodies, the 39 kD protein was identified as the inhibitory guanine nucleotide binding protein (Gi) of the adenylate cyclase system. The other ADP-ribosylated protein has not been identified. Preincubation of the chondroprogenitor cells with PTH or PGE2 resulted in time-dependent heterologous desensitization of the cAMP response to a second challenge of either hormone. The cells did not recover from the densitization for at least 18 h after removal of the hormones. PTH and PGE2 treatment did not affect the cAMP response to forskolin and cholera toxin. The PTH-dependent cAMP production was also not altered by forskolin treatment. PTH homologous desensitization was not affected by pertussis toxin treatment, but the heterologous desensitization due to PGE2 was significantly attenuated. These results suggest that exposure of chondroprogenitor cells to PTH and PGE2 results in heterologous desensitization of the cAMP response. The desensitization is not due to changes in the adenylate cyclase activity. The pertussis toxin-sensitive G proteins are involved in the PTH heterologous rather than homologous desensitization of the cAMP response.

Adenosine Diphosphate Ribose↗
PubMed1989

Effects of collateral blood vessel ligation and electrical conditioning on blood flow in dog latissimus dorsi muscle.

Utilization of skeletal muscle as a myocardial substitute requires it to undergo two major modifications: mobilization to the site of action and adaptation to continuous activity. We have examined the effects of collateral blood vessel ligation, which would accompany mobilization, on blood flow in control and electrically conditioned canine latissimus dorsi (LD) muscle. Blood flows were measured at rest and during a vigorous isometric fatigue test. In 22 control muscles, electrical stimulation during the fatigue test resulted in a sevenfold increase in muscle blood flow (0.26 +/- 0.18 ml/g/min at rest, 1.69 +/- 0.84 ml/g/min during stimulation). No difference was detected in flow to distal and proximal portions of the muscle. In three muscles where collateral vessels were ligated immediately before measurement of blood flow, flow in the proximal portion of the muscle was not significantly different from control, but in the distal portion, stimulation failed to elicit an increase in flow (0.12 +/- 0.13 ml/g/min at rest, 0.16 +/- 0.07 ml/g/min during stimulation). In animals allowed a 3-week recovery period following collateral vessel ligation, stimulation-induced increases in blood flow were detected but remained lower than control. Muscles which had been conditioned by continuous electrical stimulation for 6-7 weeks at 2 or 10 Hz generated less peak isometric tension than controls (peak tension = 4.5 +/- 1.7 kg control, 2.4 +/- 0.7 kg following 2 Hz conditioning, 1.6 +/- 0.4 kg following 10 Hz conditioning). However, these muscles demonstrated an increased resistance to fatigue.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1989

Risk factors for nosocomial candidemia: a case-control study in adults without leukemia.

PURPOSE: The purpose of this study was to define risk factors for nosocomial candidemia in adult patients without leukemia at a tertiary care medical center. PATIENTS AND METHODS: All patients with nosocomial candidemia between August 1, 1981, and October 31, 1984, were included if they met strict selection criteria and did not have acute or chronic leukemia. For each case, one control was selected from among patients admitted during the same month/year and matched for hospital service and duration of hospitalization up to the first blood culture that grew Candida species. Logistic regression was used to obtain estimates of risk after simultaneously controlling for other variables. RESULTS: Candida albicans caused 24 of the 48 fungemias studied. The risk factors identified included the presence of a central line (odds ratio, 26.4; 95% confidence interval, 1.5 to 451.1); bladder catheter (13.0 1.3 to 131.4); two or more antibiotics (25.1, 2.1 to 318); azotemia (22.1, 2.2 to 223.2); transfer from another hospital (21.3, 1.7 to 274.5); diarrhea (10.2, 1.03 to 101.4); and candiduria (27.0, 1.7 to 423.5). A prior surgical procedure was associated with lowered risk (0.1, 0.01 to 0.9), suggesting perhaps that medical service patients are at higher risk than those on surgical services. Because total parenteral nutrition was always administered by means of a central line, it could not be shown to increase the risk over that conferred by a central line alone. CONCLUSIONS: This study has defined seven major risk factors for nosocomial candidemia. These findings should facilitate development of rational approaches to preventing infection and may assist clinicians in identifying those patients in whom this life-threatening complication is likely to occur.

Adolescent↗
PubMed1989

Renal and adrenal adenosine 3',5'-monophosphate production and corticosteroid secretion in response to synthetic chicken parathyroid hormone-(1-34).

The activity of synthetic chicken (c) PTH-(1-34) amide was tested in dispersed chicken and rat kidney and adrenocortical cells. In the adrenal cells the effect of intact cPTH was also evaluated. In chicken kidney cells, the time- and dose-response patterns of cAMP production were similar for cPTH-(1-34) amide and human (h) PTH-(1-34), whereas rat kidney cells were considerably more sensitive to hPTH-(1-34) than to cPTH-(1-34) amide. The agonist effects of both hPTH-(1-34) and cPTH-(1-34) amide in kidney cells were inhibited by the bovine PTH-(3-34) analog. In chicken adrenocortical cells, cPTH-(1-34) amide stimulated cAMP production and steroid secretion. This action of the peptide was inhibited by bovine PTH-(3-34) and hPTH-(1-34), which by themselves showed no agonist effects. The maximal response of steroid secretion to cPTH-(1-34) amide was significantly lower than that to ACTH, but intact cPTH (supplied as a semipurified parathyroid extract) stimulated steriodogenesis to the same extent as ACTH. In rat adrenocortical cells, intact cPTH stimulated both cAMP formation and steriodogenesis, but cPTH-(1-34) amine showed no agonist effect. The action of the intact hormone in the rat adrenal could be inhibited by cPTH-(1-34) amide. The present results demonstrate the interaction of cPTH-(1-34) with kidney and adrenocortical cells of either chicken or rat. The cAMP and steroidogenic responses of the adrenocortical cells to PTH appear to be dependent (completely in the rat and partially in the chicken) on some sequence beyond the 1-34 region.

Adrenal Cortex Hormones↗