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Biomedical subjects

S Kaufman

Publications and source records attributed to S Kaufman.

At least 55 records · Page 3Linked to original sources
PubMed1999

The prolonged hematologic effects of a single injection of PEG-rHuMGDF in normal and thrombocytopenic mice.

A single injection of > or =10 microg/kg PEG-rHuMGDF in mice causes a dose-dependent increase in circulating platelets beginning on day 3 and peaking on days 5-6. The mean platelet volume and platelet distribution width at doses > or =100 microg/kg initially increase in a dose-dependent fashion and later decrease. However, the mean platelet volume does not change when platelets are incubated with PEG-rHuMGDF in vitro. The number of marrow megakaryocytes increases in a dose-dependent fashion as early as day 1 and peaks on day 3. Marrow megakaryocyte colony-forming units (CFU-Meg) do not increase on days 1-3 at a dose of 100 microg/kg (a dose that increases platelet numbers two- to threefold and may be clinically relevant), but the relative frequency of high ploidy megakaryocytes and the proportion of large marrow megakaryocytes (29-50 microm in diameter) increases. After a dose of 1,000 microg/kg the percentage of megakaryocytes in mitosis peaks at 24-48 hours and the percentage of megakaryocytes incorporating BrdU is maximal at 48 hours, the relatively delayed peak of BrdU incorporation most likely representing endomitosis. The relative frequency of type II and III megakaryocytes peaks on days 3 and 4, respectively. Pharmacokinetic analysis of PEG-rHuMGDF shows peak serum concentrations at 2-4 hours and a terminal half-life of 11.4+/-2.5 hours. A single injection of PEG-rHuMGDF ameliorates carboplatin-induced megakaryocytopenia and thrombocytopenia in a dose-response dependent fashion. In conclusion, a single injection of PEG-rHuMGDF increases megakaryocyte and platelet production in normal and myelo-suppressed mice.

Acetylcholinesterase↗
PubMed1999

Characterization of expression of the gene for human pterin carbinolamine dehydratase/dimerization cofactor of HNF1.

Pterin carbinolamine dehydratase/dimerization cofactor of HNF1 (PCD/DCoH) is a dual-function protein. In the cytoplasm it acts as a dehydratase in the regeneration of tetrahydrobiopterin, the cofactor for aromatic amino acid hydroxylases. In the nucleus, it functions as a dimerization cofactor of HNF1 and increases the transcriptional activity of HNF1. To deepen our understanding of this protein, we characterized its expression in human tissues and cells. Human PCD/DCoH was present predominantly in liver and kidney, with significant amounts in testis and ovary, trace amounts in lung, and undetectable levels in whole brain, heart, and spleen. It was expressed in all of the cells that were examined. Importantly, it was also present in the nucleus of HeLa cells, which lack HNF1, and in the cytoplasm of fibroblasts that have little or no tetrahydrobiopterin. The expression of human PCD/DCoH in the liver and nonhepatic cells was compared at both the mRNA and protein levels. Although the mRNA level in liver was only fourfold higher than that in keratinocytes and fibroblasts, the hepatic PCD/DCoH protein level was 20-fold higher than that in normal human epidermal keratinocytes and dermal fibroblasts. Cloning of the 5' and 3' untranslated region (UTR) of human keratinocyte PCD/DCoH revealed that it has 53 bp more of GC-rich 5' untranslated sequence than the published liver PCD/DCoH. In vitro transcription and translation analysis showed that the longer 5' UTR resulted in about a 35% decrease in translation efficiency. These data show that human PCD/DCoH is not only present in cells where tetrahydrobiopterin is synthesized or HNF1 is present but is a widely distributed protein. Its differential expression in different tissues and cells is regulated not only at the transcriptional level but also at the translational level.

3' Untranslated Regions↗
PubMed1999

Intravenous midazolam for sedation of children undergoing procedures: an analysis of age- and procedure-related factors.

OBJECTIVE: This study was performed to determine the doses of midazolam used for sedation during procedures in children, and the frequency of adverse events. METHODS: We performed a retrospective analysis of data collected for a prospective study of flumazenil in children who had received midazolam for a procedure (n = 91, 1-17 years). RESULTS: Practitioners used a wide range of total midazolam doses (0.03-0.6 mg/kg); mean doses ranged from 0.09 +/- 0.06 mg/kg in adolescents to 0.26 +/- 0.13 mg/kg in toddlers (P < 0.001). Opioids were also used in 84% of patients. Twenty-six percent of children with normal lungs, most of whom had received relatively high opioid doses, developed decreased oxygen saturation (as low as 65%) after sedation. Other adverse events included airway obstruction (n = 3) and vomiting (n = 1). CONCLUSIONS: The frequent choice of midazolam, usually combined with an opioid, indicates its wide acceptance. Midazolam doses were inversely related to age. The presence of vomiting, airway obstruction, and decreased oxygen saturation underlines the importance of appropriate personnel, equipment, and monitors during sedation.

Adolescent↗
PubMed1998

Reactivity of the flavin semiquinone of nitric oxide synthase in the oxygenation of arginine to NG-hydroxyarginine, the first step of nitric oxide synthesis.

Nitric oxide synthase (NOS) is a heme protein that catalyzes the oxygenation of L-arginine in the presence of NADPH to form nitric oxide, L-citrulline and NADP+, and proceeds via two partial reactions: 1) L-Arginine --> NG-hydroxy-L-arginine 2) NG-Hydroxy-L-arginine --> L-citrulline + nitric oxide Calmodulin, FAD, FMN and tetrahydrobiopterin are required for both reactions. Reactions 1 and 2 require the input of 2 and 1 electron equivalents, respectively. Under normal multiple turnover conditions, these electrons are ultimately derived from NADPH. We previously reported that NOS contains an endogenous reductant that, in the absence of NADPH, can support the single-turnover oxygenation of L-arginine to NG-hydroxy-L-arginine and a relatively small amount of L-citrulline [Campos, K. L., Giovanelli, J., and Kaufman, S. (1995) J. Biol. Chem. 270, 1721-1728]. This reductant has now been identified as the stable flavin semiquinone free radical (FSQ). Its oxidation appears to be coupled to the formation of NG-hydroxy-L-arginine and L-citrulline. The rate of FSQ oxidation is two orders of magnitude slower than the flux of electrons from NADPH through NOS during normal turnover of the enzyme, indicating that FSQ is not the proximal electron donor for heme under these conditions.

Arginine↗
PubMed1998

The regulation of dopamine release from striatum slices by tetrahydrobiopterin and L-arginine-derived nitric oxide.

The regulation of dopamine release by 6(R)-tetrahydrobiopterin (BH4) and l-arginine-derived nitric oxide was examined by using a method of superfusion of rat striatum slices in vitro. l-Arginine, which can produce nitric oxide (NO) through the action of NO synthase, induces a concentration-dependent increase of [3H] dopamine release in the superfusate of striatum slices. Pretreatment with inhibitors of NO synthase or with inhibitors of BH4 synthesis diminishes the increase of [3H] dopamine release mediated by arginine. This increase is almost completely restored following repletion of intracellular BH4 levels by incubation of the slices with 7, 8-dihydrobiopterin. Adding exogenous BH4 directly to the superfusion fluid leads to a massive increase in [3H] dopamine release which can be inhibited 75% by superoxide dismutase and catalase, but is not inhibited by NG-nitro-arginine, a NO synthase inhibitor, or alpha-methyl-p-tyrosine, a tyrosine hydroxylase inhibitor. The increase of intracellular BH4 concentration by dihydrobiopterin administration causes a small increase of dopamine release which can be partially diminished by NG-nitro-arginine or alpha-methyl-p-tyrosine. It is suggested that the increase of dopamine release stimulated by an enhancement of intracellular BH4 is dependent on its cofactor activity with NO synthase and tyrosine hydroxylase. This study has also demonstrated that BH4 is a regulator of NO-mediated dopamine release in the striatum. Published by Elsevier Science B.V.

Animals↗
PubMed1998

Human white blood cells and hair follicles are good sources of mRNA for the pterin carbinolamine dehydratase/dimerization cofactor of HNF1 for mutation detection.

Pterin carbinolamine dehydratase/dimerization cofactor of HNF1 (PCD/DCoH) is a protein that has a dual function. It is a pterin 4alpha-carbinolamine dehydratase that is involved in the regeneration of the cofactor tetrahydrobiopterin during the phenylalanine hydroxylase- catalyzed hydroxylation of phenylalanine. In addition, it is the dimerization cofactor of HNF1 that is able to activate the transcriptional activity of HNF1. Deficiencies in the gene for this dual functional protein result in hyperphenylalaninemia. Here we report for the first time that the PCD/DCoH mRNA is present in human white blood cells and hair follicles. Taking advantage of this finding, a sensitive, rapid and convenient method for screening mutations occurring in the coding region of this gene has been described.

Cloning, Molecular↗
PubMed1998

Osteoprotegerin ligand is a cytokine that regulates osteoclast differentiation and activation.

The ligand for osteoprotegerin has been identified, and it is a TNF-related cytokine that replaces the requirement for stromal cells, vitamin D3, and glucocorticoids in the coculture model of in vitro osteoclastogenesis. OPG ligand (OPGL) binds to a unique hematopoeitic progenitor cell that is committed to the osteoclast lineage and stimulates the rapid induction of genes that typify osteoclast development. OPGL directly activates isolated mature osteoclasts in vitro, and short-term administration into normal adult mice results in osteoclast activation associated with systemic hypercalcemia. These data suggest that OPGL is an osteoclast differentiation and activation factor. The effects of OPGL are blocked in vitro and in vivo by OPG, suggesting that OPGL and OPG are key extracellular regulators of osteoclast development.

Amino Acid Sequence↗
PubMed1998

Identification of hepatic nuclear factor 1 binding sites in the 5' flanking region of the human phenylalanine hydroxylase gene: implication of a dual function of phenylalanine hydroxylase stimulator in the phenylalanine hydroxylation system.

Phenylalanine hydroxylase stimulator (PHS) is a component of the phenylalanine hydroxylation system that is involved in the regeneration of the cofactor tetrahydrobiopterin. It is also identical to the dimerization cofactor of hepatocyte nuclear factor 1 (HNF1) (DCoH) that is able to enhance the transcriptional activity of HNF1. Moreover, it has the structural potential for binding macromolecules such as proteins and nucleic acids, consistent with its involvement in gene expression. We investigated whether PHS/DCoH could enhance the expression of phenylalanine hydroxylase (PAH). Cotransfection assays showed that DCoH itself could not transactivate the 9-kb human PAH 5' flanking fragment. However, this 9-kb fragment was transactivated by HNF1 in a dose-dependent manner with a maximum of nearly 8-fold activation; DCoH potentiated this transactivation by another 1.6-fold. The HNF1 binding sites were located at -3.5 kb in a region that is 77.5% identical to the mouse liver-specific hormone-inducible PAH gene enhancer. This study suggests a possible dual function of PHS in vivo in the human phenylalanine hydroxylation system: it is involved in the regeneration of the cofactor tetrahydrobiopterin and can also enhance the expression of the human PAH gene.

Animals↗
PubMed1998

Adrenomedullin suppresses atrial natriuretic factor (ANF) secretion from isolated atrium.

Atrial natriuretic factor (ANF) secretion was studied using isolated perfused right atria prepared from rats. Adrenomedullin (ADM), a recently identified 52-amino acid peptide whose biological activity has a striking resemblance to that of ANF, was added to the perfusate at a concentration of 1 microg/ml. The concentration of ANF secreted into the perfusate was measured by radioimmunoassay, under basal conditions (atrial wall unstressed), and during atrial distention (intraluminal pressure raised to 4 and to 6 cm water). It was found that basal secretion of ANF was not altered by ADM. However, when intraluminal pressure was raised, there was a significantly smaller increase in ANF secretion in the ADM-infused atria than in the control atria. It is concluded that ADM significantly reduces stretch-induced secretion of ANF, while having only minimal effects on basal secretion. Such an inhibitory mechanism would ensure the necessary negative feedback mechanism to counter the previously-reported stimulatory actions of ANF on ADM secretion. Moreover, these results support the hypothesis that ADM could be responsible for the reduction in stretch-induced ANF release observed during pregnancy.

Adrenomedullin↗
PubMed1998

Correlation of rat hepatic phenylalanine hydroxylase, with tetrahydrobiopterin and GTP concentrations.

Hepatic phenylalanine hydroxylase is reported to be more abundant in experimentally-diabetic rats; whereas livers of animals fed a high protein diet, where gluconeogenesis also prevails, have normal amounts of this enzyme. In this study, in addition to seeking an explanation for this effect of experimental diabetes, we also examined the effects of providing alternative dietary gluconeogenic substrates. In rats fed a diet composed of 40% (w/w) glycerol, the specific activities of hepatic phenylalanine hydroxylase are decreased to about 60% of control values. There is no effect on the apparent state of phosphorylation of the enzyme. However, studies on the incorporation of radiolabelled leucine into liver phenylalanine hydroxylase suggested that there was a decreased rate of synthesis. Similarly, animals fed a diet containing 85% (w/w) fructose also have diminished phenylalanine hydroxylase activities. Under all of the above circumstances and also in streptozotocin-induced diabetic animals, alterations in the concentrations of the hydroxylase cofactor, tetrahydrobiopterin and of GTP closely correlate with the effects on the enzyme activities. They are elevated in livers of diabetic animals and significantly diminished in livers of rats fed diets rich in glycerol or fructose. These observations suggest that in adult rat both liver tetrahydrobiopterin concentrations and the expression of hepatic phenylalanine hydroxylase are regulated by GTP [210].

Animals↗
PubMed1998

Alternative splicing at the 3'-cDNA of human tryptophan hydroxylase.

Two alternatively spliced transcripts of human tryptophan hydroxylase (TPH) were identified that differed at the 3' end of the open reading frame. Comparison of the human TPH cDNA and genomic sequences revealed that an intron containing an in-frame stop codon could be alternatively spliced out of intron 11. This splicing would give rise to two human TPH isoforms with different C termini; the one that derives from the nonspliced intron contains a putative cyclic AMP-dependent protein kinase site, whereas the other one, which is 22 amino acids longer, does not. Analysis of various human tissues by RT-PCR revealed that the spliced TPH mRNA species was detected in all the postmortem tissues we tested, but the nonspliced species was expressed in only some tissues.

Alternative Splicing↗
PubMed1998

Abnormal expression of brush-border membrane transporters in the duodenal mucosa of two patients with microvillus inclusion disease.

BACKGROUND: Microvillus inclusion disease is a congenital disorder characterized by secretory diarrhea. Patients demonstrate villus atrophy, loss of microvilli, and internalized inclusions of microvilli within the cytoplasm of small intestinal enterocytes. The exact molecular defect in these patients is not known. Two infants are described in this report with microvillus inclusion disease. Case 1 was a 3-month-old boy who developed secretory diarrhea shortly after birth. Case 2 was a 9-month-old boy who had abrupt onset diarrhea at 2 weeks of age resulting in weight loss and dehydration. Light microscopy revealed total villus atrophy with minimal crypt hyperplasia, and electron microscopic examination revealed variably shortened microvilli and cytoplasmic microvillus inclusions in both patients. METHODS: Poly (A)+ RNA was purified from duodenal biopsies and RT-PCR reactions were performed. Normal human intestinal RNA was used as a positive control. Primers specific for human NHE-1, NHE-2, NHE-3 (2 sets), sodium-glucose transporter (SGLT1), and beta-actin were used. RESULTS: Results showed that NHE-1 and beta-actin cDNAs amplified to similar levels in both patient and control samples. However, the expression of NHE-2 and SGLT1 was much higher in the control sample than in the patient samples. Additionally, NHE-3 mRNA was not detected in the patient samples using two sets of NHE-3 specific primers. CONCLUSIONS: The patients with microvillus inclusion disease have defects in apical but not basolateral membrane transport systems, and these defects are related to the pathogenesis of the disease.

Diarrhea↗
PubMed1998

Effect of pregnancy and steroid hormones on plasma adrenomedullin levels in the rat.

Pregnancy is characterized by volume expansion and vasodilation. We investigated whether the hypotensive peptide adrenomedullin (ADM) might be a significant factor in the cardiovascular adaptation to pregnancy. Rats were prepared with indwelling cannulae. Plasma ADM levels were measured by RIA before mating, at 7, 14, and 21 days of pregnancy, and at 7 days postpartum. We also investigated the effects on plasma ADM levels of administering estrogen, progesterone, and the metabolite of progesterone 3 alpha-OH-5 alpha-pregnan-20-one (3 alpha-OH-DHP); this last steroid has been implicated in altering reflex control of blood pressure and volume during pregnancy. Plasma ADM levels increased progressively during pregnancy from 123 +/- 27 pg/mL in virgin animals to 404 +/- 50 pg/mL at 21 days of pregnancy. The levels returned to pre-pregnancy values postpartum. 3 alpha-OH-DHP caused a significant rise in plasma ADM levels, whereas neither estrogen nor progesterone had any effect. We suggest that ADM may be an important contributing factor to the vasodilation associated with normal pregnancy. Active metabolites of progesterone, rather than progesterone itself, may be at least partially responsible for stimulating the release of ADM.

Adrenomedullin↗
PubMed1998

Pregnancy-induced changes in central response to atrial distension mimicked by progesterone metabolite.

In virgin female rats, atrial distension (an index of blood volume expansion) causes an increase in c-fos expression in the paraventricular nucleus of the lateral hypothalamus. During pregnancy, this response is markedly attenuated. We tested the effects of 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha-OH-DHP) on activation of central pathways following stimulation of the atrial volume receptors. Not only does this progesterone metabolite increase during pregnancy, but it has already been implicated in pregnancy-induced changes in the baroreflex. Female rats were prepared with indwelling venous cannulas and intracardiac balloons that, when inflated, caused a discrete localized stimulation of the atrial volume receptors in the absence of changes in cardiac hemodynamics. Seven days later, the rats were infused with 3alpha-OH-DHP dissolved in cyclodextrin and the intracardiac balloons were inflated. One hour later, the rats were killed and fixed by perfusion and the brains were prepared for visualization of c-fos activity. Infusion with 3alpha-OH-DHP significantly reduced the central response to atrial distension, i.e., it mimicked pregnancy. These results are consistent with the suggestion that this metabolite of progesterone may be an important factor in cardiovascular adaptation to pregnancy.

Animals↗
PubMed1998

Thirty-eight-year evaluation of a surgical technique to protect the external branch of the superior laryngeal nerve during thyroidectomy.

The purpose of this study is to evaluate a surgical technique for the preservation of the function of the external branch of the superior laryngeal nerve (EBSLN) during total thyroid lobectomy and total thyroidectomy. Permanent injury to this nerve can be a disaster, especially in singers and professional speakers who depend on control of pitch, and a clear and forceful voice. Voice changes may be either obvious or subtle. For better voice analysis, a detailed questionnaire is necessary. Thus, the evaluation in this study is based on laryngoscopy of 934 nerves in 675 patients and detailed subjective voice evaluation of 66 patients during the last 2 years of the study. There are 2 surgical principles. First, the EBSLN is not routinely exposed; the distal 1.5 to 2.0 cm (critical area) of the superior thyroid vessels are carefully dissected, exposed, and ligated, preferably independently. Careful observation ensures that the EBSLN is not included in the ligature. Second, the ultimate evaluation of the surgical technique is the effect of voice changes on the patient's lifestyle. Laryngoscopy of 934 nerves found bowing, temporary in 4 patients and permanent in 1 patient (limited follow-up). Of the 66 patients with voice evaluations, 14 had changes: 9 had temporary changes, while 5 had permanent changes. In these 14 patients, voice changes had no effect on lifestyle in 13, and the effects were indeterminate in 1 (unavailable for follow-up). The estimated deleterious effect of voice changes on lifestyle is no greater than 1.5% of the 66 patient responders.

Anatomy, Artistic↗
PubMed1998

Dr(a) (Cromer-related blood group antigen)-incompatible renal transplantation.

BACKGROUND AND OBJECTIVES: Cromer system antigens, a series of blood group antigens of very high frequency, are not considered to be clinically significant in transfusion. In renal transplantation only the ABO blood group antigens are considered essential. The Drori blood group antigen is present in serum and has been found to reside on the renal tubular basement membrane and Bowman's capsule. The effect of anti-Dra on the renal parenchyma has not been evaluated. MATERIALS AND METHODS: A unique case of renal transplantation of an incompatible Dr(a+) kidney to a Dr(a-) patient with anti-Dra in her serum is presented. RESULTS: Graft function was immediately good. The titer of anti-Dra remained unchanged following transplantation. CONCLUSION: The successful outcome of a case of a Drori (Dra)-incompatible kidney transplantation confirmed the lack of clinical significance of the anti-Dra relating to transplantation.

Adult↗
PubMed1997

Studies on the enzymatic and transcriptional activity of the dimerization cofactor for hepatocyte nuclear factor 1.

The relationship between the enzymatic and the transcriptional activity of the bifunctional protein pterin-4a-carbinolamine dehydratase/dimerization cofactor for hepatocyte nuclear factor 1 (DCoH) has been elucidated by site-directed mutagenesis. DCoH dimers harbor a binding site for hepatocyte nuclear factor 1 (HNF1), two active centers that bind pterins, and a saddle-shaped surface that resembles nucleic acid binding domains. Two domains of the protein have been selectively targeted to determine if a change in one activity affects the other. No strong correlation has been found, supporting the idea that carbinolamine dehydratase activity is not required for HNF1 binding in vitro or transcriptional coactivation in vivo. Double mutations in the active center, however, influence the in vivo transcriptional activity but not HNF1 binding. This finding suggests that some active center residues also are used during transcription, possibly for binding of another (macro)molecule. Several mutations in the saddle led to a surprising increase in transcription, therefore linking this domain to transcriptional regulation as well. The transcriptional function of DCoH therefore is composed of two parts, HNF1 binding and another contributing effect that involves the active site and, indirectly, the saddle.

Animals↗