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M Baum

Publications and source records attributed to M Baum.

At least 145 records · Page 8Linked to original sources
PubMed1998

Renal Na/H exchanger NHE-3 and Na-PO4 cotransporter NaPi-2 protein expression in glucocorticoid excess and deficient states.

Administration of pharmacologic doses of glucocorticoid in vivo increases renal proximal tubule apical membrane Na/H exchange and decreases Na/PO4 cotransport activity (1). Current data suggest that the NHE-3 and NaPi-2 proteins mediate significant fractions of proximal tubule apical membrane Na/H exchange and Na/PO4 cotransport, respectively. This study examines whether glucocorticoid excess or deficiency affects NHE-3 and NaPi-2 protein abundance and the intrarenal distribution of these transporters. Protein abundance of NHE-3 and NaPi-2 in control rats was compared to rats rendered glucocorticoid-deficient by bilateral adrenalectomy, and to rats receiving pharmacologic doses of dexamethasone using immunoblots and immunohistochemistry. Adrenalectomy had modest effects on NHE-3 protein abundance, but dexamethasone administration to either adrenalectomized or sham-operated rats significantly increased NHE-3 protein abundance in both the proximal tubule and thick ascending limb, but not the thin descending limb. Adrenalectomy increased NaPi-2 protein abundance in the proximal tubule, whereas dexamethasone administration dramatically suppressed NaPi-2 protein on the apical membrane in both adrenalectomized and sham-operated animals. No significant reciprocal increase in subapical NaPi-2 staining was seen in the dexamethasone-treated rats. The present study shows that glucocorticoids regulate proximal tubule apical membrane Na/H exchange and NaPi cotransport by changes in protein abundance of NHE-3 and NaPi-2, respectively.

Adaptor Protein Complex 3↗
PubMed1998

Somatic growth in infant heart transplant recipients.

UNLABELLED: Infant heart transplantation is now entering its second decade of clinical experience. To understand better issues relating to somatic growth, this retrospective study will describe growth patterns in a group of infant heart transplant recipients. Early growth: growth velocity from birth to transplantation in 77 infants transplanted before 6 months of age was compared with growth velocity from transplant to 3 months. Growth from 3 to 6 months and from 6 to 12 months after transplantation is described. Growth velocities (mean +/- SD) for weight (g/d) and length (cm/yr) for these 4 time periods respectively were: 7+/-14 and 27+/-22, 32+/-9 and 35+/-14, 17+/-7 and 24+/-10, 12+/-6 and 17+/-8. Growth velocities for both weight (p<0.01) and length (p = 0.04) were significantly improved in the first 3 months after transplantation. Late growth: Growth beyond 5 yr post-transplantation was described in a group of 51 infants transplanted in the first year of life and who survived at least 5 yr (median 6.8 yr, range 5.0 to 10.9). Most recent growth parameters (z-score; mean +/- SD) were: weight -0.55+/-1.2, height -0.48+/-0.97 and weight for height -0.16+/-0.96. Factors (with significant p-values) evaluated for their possible influence on late height (<5th percentile vs. > or =5th percentile) were: age at transplant, hospital days from transplant to discharge, hospital days 1st year after transplantation (p = 0.019), hospital days after 1st year, rejection episodes 1st year, rejection episodes 1-5 yr (p = 0.02) mid-parental height (p = 0.008) and isotopic glomerular filtration rate (p = 0.055). CONCLUSION: Growth while awaiting infant heart transplantation is poor, but adequate catch-up growth does occur. Beyond 5 yr most (88%) infant heart transplant recipients have weight and height in the normal range. Early illness, late rejection and genetic growth potential may play the largest role in later height attainment.

Body Height↗
PubMed1997

Psion of the times.

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Breast Neoplasms↗
PubMed1997

Apical extracellular calcium/polyvalent cation-sensing receptor regulates vasopressin-elicited water permeability in rat kidney inner medullary collecting duct.

During antidiuresis, increases in vasopressin (AVP)-elicited osmotic water permeability in the terminal inner medullary collecting duct (tIMCD) raise luminal calcium concentrations to levels (> or = 5 mM) above those associated with the formation of calcium-containing precipitates in the urine. Calcium/polycation receptor proteins (CaRs) enable cells in the parathyroid gland and kidney thick ascending limb of Henle to sense and respond to alterations in serum calcium. We now report the presence of an apical CaR in rat kidney tIMCD that specifically reduces AVP-elicited osmotic water permeability when luminal calcium rises. Purified tIMCD apical membrane endosomes contain both the AVP-elicited water channel, aquaporin 2, and a CaR. In addition, aquaporin 2-containing endosomes also possess stimulatory (G(alpha q)/G(alpha 11) and inhibitory (G(alpha i1, 2, and 3)) GTP binding proteins reported previously to interact with CaRs as well as two specific isoforms (delta and zeta) of protein kinase C. Immunocytochemistry using anti-CaR antiserum reveals the presence of CaR protein in both rat and human collecting ducts. Together, these data provide support for a unique tIMCD apical membrane signaling mechanism linking calcium and water metabolism. Abnormalities in this mechanism could potentially play a role in the pathogenesis of renal stone formation.

Animals↗
PubMed1997

A centromere DNA-binding protein from fission yeast affects chromosome segregation and has homology to human CENP-B.

Genetic and biochemical strategies have been used to identify Schizosaccharomyces pombe proteins with roles in centromere function. One protein, identified by both approaches, shows significant homology to the human centromere DNA-binding protein, CENP-B, and is identical to Abp1p (autonomously replicating sequence-binding protein 1) (Murakami, Y., J.A. Huberman, and J. Hurwitz. 1996. Proc. Natl. Acad. Sci. USA. 93:502-507). Abp1p binds in vitro specifically to at least three sites in centromeric central core DNA of S. pombe chromosome II (cc2). Overexpression of abp1 affects mitotic chromosome stability in S. pombe. Although inactivation of the abp1 gene is not lethal, the abp1 null strain displays marked mitotic chromosome instability and a pronounced meiotic defect. The identification of a CENP-B-related centromere DNA-binding protein in S. pombe strongly supports the hypothesis that fission yeast centromeres are structurally and functionally related to the centromeres of higher eukaryotes.

Amino Acid Sequence↗
PubMed1997

Kinesin-driven microtubule motility in the presence of alkaline-earth metal ions: indication for a calcium ion-dependent motility.

We studied the effect of alkaline-earth metal ions on the kinesin-driven gliding of microtubules, using a narrow glass chamber enabling the exchange of buffer components without interrupting microscopic observation. Under standard conditions (0.5 mM Mg2+), microtubules were found to glide at a mean velocity of about 0.6 micron/s. Motility was widely ceased after removing Mg2+. Subsequent addition of Ca2+ restored motility (maximal mean gliding velocity measured: 0.26 micron/s at 2.5 mM Ca2+). Also in the presence of Sr2+ or Ba2+ a slow gliding could be observed (0.025 micron/s and 0.014 micron/s, respectively, at 0.5 mM). After removal of Ca2+, Sr2+, or Ba2+ and re-addition of Mg2+, the gliding velocities reached approximately the values determined under standard conditions. Motility was not changed when 0.5 mM Ca2+, Sr2+, or Ba2+ were applied together with Mg2+. Microtubule gliding stopped after substitution of 0.5 mM BeCl2 for Mg2+. When both BeCl2 and Mg2+ were present, the mean gliding velocity was reduced to 0.29 micron/s. In addition, many microtubules were released from the kinesin coated glass surface, indicating that the beryllium salt disorders the binding between kinesin and microtubules. Our results confirm that Mg2+ is the most suitable cofactor for kinesin driven microtubule motility. However, they also demonstrate that brain kinesin can generate motility when Ca2+ was substituted for Mg2+.

Animals↗
PubMed1997

[Sports and the immune system].

Acute exercise is followed by a mobilization of white blood cells, mainly induced by increased levels of catecholamines and cortisol. NK-cells react the most intensive, they can increase fivefold after intensive exercise. Additionally a weak acute-phase reaction occurs. Most of these changes normalize during twenty-four hours. Parameters of the humoral immune system may be different from the pre-exercise levels up to seventy-two hours. Repeated physical exercise, which is typical for sports, is followed only by small changes of immunologic parameters under conditions of rest. Epidemiological studies give clues that the rate of upper respiratory tract infections in athletes can be described by a j-shaped curve. Moderately active subjects have the lowest rate of infection. For this influence of exercise on health mainly functional changes seem to be important. Especially after excentric exercise immunological cells can be seen in the muscle tissue, which remove destructed tissue. Not very much is known about the role of the immune system in the regeneration of tendons and other bradytrophic tissues.

Cytokines↗
PubMed1997

Moderate and exhaustive endurance exercise influences the interferon-gamma levels in whole-blood culture supernatants.

The aim of this study was to investigate whether moderate or exhaustive endurance exercise influences cytokine levels in whole-blood culture supernatants after stimulation. Therefore, eight healthy subjects were first exposed to moderate exercise on a cycle ergometer for 30 min at 70% of their 4-mmol/l lactic acid (anaerobic) threshold, and 1 week later to exhaustion (for 90 min) at their anaerobic threshold. Blood samples were taken before, 30 min after and 24 h after each exercise bout. The following lymphocyte subpopulations were determined: CD14-positive(+)/CD45+, CD4+, CD8+, and CD16+. Cytokine levels in the supernatants were measured by enzyme-linked immunosorbent assay (ELISA). Production of interleukin (IL)-1beta, IL-6 and tumour necrosis factor (TNF)-alpha were induced with lipopolysaccharides (LPS), and that of IL-2 and interferon (IFN)-gamma with staphylococcal enterotoxin B (SEB) and phytohaemagglutinin (PHA). Cortisol levels were also determined by ELISA. The lymphocyte subset distribution was observed to be unchanged after moderate exercise. Thirty minutes after exhaustive exercise, the CD16+ count was found to be significantly lower, whereas 24 h later the CD4+ count was significantly higher than pre-exercise counts. Moderate exercise influenced the IFN-gamma production (PHA-stimulated), which increased significantly from 974 (391) pg/ml before exercise to 1450 (498) pg/ml 24 h later. Thirty minutes after exhaustive exercise the IFN-gamma level in the supernatants (SEB-stimulated) was significantly decreased (from 14470 (11840) pg/ml before exercise to 6000 (4950) pg/ml after exercise). The IL-1beta and TNF-alpha production per monocyte was also significantly reduced.

Adolescent↗