Search PubMed⌕ Search

Biomedical subjects

M Baum

Publications and source records attributed to M Baum.

At least 109 records · Page 6Linked to original sources
PubMed1999

Plasma lycopene concentrations in humans are determined by lycopene intake, plasma cholesterol concentrations and selected demographic factors.

Higher plasma lycopene concentrations have been associated with a reduced risk of several chronic diseases. Determinants of lycopene concentrations in humans have received limited attention. We had blood lycopene concentrations and lycopene consumption data available from 111 participants in a two-center cancer prevention trial involving beta-carotene and examined determinants of plasma lycopene levels cross-sectionally. The median plasma lycopene level was 0.59 micromol/L (range 0.07-1.79). Low plasma concentrations of lycopene were associated with the following variables in univariate analyses: study site (Florida lower than Connecticut, P = 0.001), being nonmarried (P = 0.02), having lower income (P = 0.003), being nonwhite race/ethnicity (P = 0.03), having lower dietary lycopene intake (r = 0.29, P = 0.002), having lower plasma cholesterol (r = 0. 43, P = 0.0001) and triglyceride levels (r = 0.26, P = 0.005), and consuming less vitamin C (r = 0.20, P = 0.03). Women had slightly higher plasma lycopene levels than men (0.65 vs. 0.58 micromol/L; P = 0.31), despite lower dietary intake of lycopene (1,040 vs. 1,320 microg/d; P = 0.50). Plasma lycopene levels did not differ in smokers and nonsmokers. In stepwise regression analyses, the determinants of plasma lycopene were plasma cholesterol, dietary lycopene, and marital status; these three variables explained 26% of the variance in plasma lycopene. Relatively few lifestyle and demographic factors were important determinants of plasma lycopene levels, with plasma cholesterol, marital status, and lycopene intake being of greatest importance.

Adult↗
PubMed1999

Evaluation of the MRL diagnostics dengue fever virus IgM capture ELISA and the PanBio Rapid Immunochromatographic Test for diagnosis of dengue fever in Jamaica.

We evaluated two new commercial dengue diagnostic tests, the MRL Diagnostics Dengue Fever Virus IgM Capture ELISA and the PanBio Rapid Immunochromatographic Test, on serum samples collected during a dengue epidemic in Jamaica. The MRL ELISA method correctly identified 98% (78 of 80) of the samples as dengue positive, while the PanBio test identified 100% (80 of 80). Both tests were 100% (20 samples of 20) specific.

Adolescent↗
PubMed1999

Thyroid hormone stimulates the renal Na/H exchanger NHE3 by transcriptional activation.

Thyroid hormone stimulates renal proximal tubule NaCl and NaHCO3 absorption in part by activating the apical membrane Na/H exchanger NHE3. We used a renal epithelial cell line, the opossum kidney (OK) cell, to define the mechanism by which 3,5,3'-triiodothyronine (T3) increases NHE3 activity. T3 stimulated NHE3 activity, an effect that was blocked by inhibition of cellular transcription or translation. The increase in activity was associated with increases in steady-state cell surface and total cellular NHE3 protein and NHE3 transcript abundance. T3 stimulated transcription of the NHE3 gene and had no effect on NHE3 transcript stability. The transcriptional activity of the 5'-flanking region of the rat NHE3 gene was stimulated by T3 when expressed in OK cells. When heterologously expressed rat NHE3 transcript levels were clamped constant with a constitutive promoter in OK cells, T3 has no effect on rat NHE3 protein abundance, suggesting the absence of regulation of NHE3 protein stability or translation. These studies demonstrate that T3 stimulates NHE3 activity by activating NHE3 gene transcription and increasing NHE3 transcript and protein abundance.

Animals↗
PubMed1999

Neonatal rabbit proximal tubule basolateral membrane Na+/H+ antiporter and Cl-/base exchange.

The present in vitro microperfusion study examined the maturation of Na+/H+ antiporter and Cl-/base exchanger on the basolateral membrane of rabbit superficial proximal straight tubules (PST). Intracellular pH (pHi) was measured with the pH-sensitive fluorescent dye 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein in neonatal and adult superficial PST. Na+/H+ antiporter activity was examined after basolateral Na+ addition in tubules initially perfused and bathed without Na+. Neonatal Na+/H+ antiporter activity was approximately 40% that of adult segment (9.7 +/- 1.5 vs. 23.7 +/- 3.2 pmol. mm-1. min-1; P < 0.001). The effect of bath Cl- removal on pHi was used to assess the rates of basolateral Cl-/base exchange. In both neonatal and adult PST, the Cl-/base exchange activity was significantly higher in the presence of 25 mM HCO-3 than in the absence of HCO-3 and was inhibited by cyanide and acetazolamide, consistent with Cl-/HCO-3 exchange. The proton flux rates in the presence of bicarbonate in neonatal and adult tubules were 14.1 +/- 3.6 and 19.5 +/- 3.5 pmol. mm-1min-1, respectively (P = NS), consistent with a mature rate of Cl-/HCO-3 exchanger activity in neonatal tubules. Basolateral Cl-/base exchange activity in the absence of CO2 and HCO-3, with luminal and bath cyanide and acetazolamide, was greater in adult than in neonatal PST and inhibited by bath DIDS consistent with a maturational increase in Cl-/OH- exchange. We have previously shown that the rates of the apical membrane Na+/H+ antiporter and Cl-/base exchanger were approximately fivefold lower in neonatal compared with adult rabbit superficial PST. These data demonstrate that neonatal PST basolateral membrane Na+/H+ antiporter and Cl-/base exchanger activities are relatively more mature than the Na+/H+ antiporter and Cl-/base exchangers on the apical membrane.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1999

Increased training load and the beta-adrenergic-receptor system on human lymphocytes.

The influence of increased training on the sympathoadrenergic system was investigated. Moderately trained male subjects (n = 15) increased their training within 10 wk by 60%; eight of the subjects increased their training volume, and seven increased their training intensity. Before and after the training, an exhaustive treadmill exercise was carried out. Acute treadmill exercise increased beta-adrenergic receptor number on mononuclear lymphocytes, isoproternol-stimulated cAMP production, and plasma catecholamine concentration. The increase of receptor number can at least partially be explained by a changed lymphocyte composition at rest and after exercise. After training, the exercise-induced increase of beta-adrenergic receptor number was significantly blunted, and the exercise-induced increase of the isoproternol-stimulated cAMP production per beta-receptor was enhanced. Subjects who experienced increased symptoms of physical discomfort and/or mood changes showed an enhanced cAMP production after training. These findings point to an altered regulation of the receptor and postreceptor mechanisms as an effect of a 10-wk period of hard training.

Adrenergic beta-Agonists↗
PubMed1999

Neonatal and adult rabbit renal brush border membrane vesicle solute reflection coefficients.

The interaction between solute and water in epithelial transport is represented by the solute reflection coefficient. Because the osmotic water transport process changes in the rabbit proximal tubule during maturation, there is a potential for the solute reflection coefficients to also undergo maturational changes. In the present study, we directly examined solute reflection coefficients in neonatal and adult brush border membrane vesicles (BBMV) using the stop-flow light-scattering technique. Reflection coefficients for NaCl, KCl, NaHCO3 and urea were found to be identical in the neonatal and adult BBMV and were not different from 1. Thus, although the water transport pathway undergoes changes in the proximal tubule during maturation, there is no evidence for changes in solute and water interaction. Because the reflection coefficients are not different from 1, there is no evidence for solvent drag in the proximal tubule apical membrane in either the neonatal or adult tubule.

Aging↗
PubMed1999

Maturational changes in rabbit renal brush border membrane vesicle urea permeability.

Urea transport in the proximal tubule is thought to occur by passive diffusion through the lipid bilayers of the cell membranes. The lipid composition of cell membranes changes during maturation and may directly affect urea permeability of proximal tubule membranes. The present study examined the maturation of urea transport in rabbit renal brush border membrane vesicles (BBMV). BBMV from adult and neonatal (9- to 11-d-old) New Zealand white rabbits were loaded with 500 mM urea and mixed with an iso-osmotic mannitol solution using a stop-flow instrument. Vesicle shrinkage, due to efflux of urea, was followed with light scattering and urea permeability was calculated from an exponential fit of the data. Urea permeability was significantly lower in the neonatal BBMV than the adult at 25 degrees C (0.34+/-0.04 x 10(-6) versus 0.56+/-0.03 x 10(-6) cm/sec;p < 0.001, n=7) and 37 degrees C (0.45+/-0.04 x 10(-6) versus 0.66+/-0.03 x 10(-6) cm/sec; p=0.001, n=7). There was no effect of 250 microM phloretin on urea permeability in either adult or neonatal BBMV at either temperature. The activation energy for urea diffusion was higher in the neonatal than the adult BBMV. Because the maturational increase in urea permeability could potentially be due to a sodium-dependent urea transporter in the adult BBMV, the sodium dependence of urea uptake in adult BBMV was examined. There was no difference in urea permeability in the presence or absence of 20 mM NaCl. Permeability of the lipid-soluble molecule, glycerol, was also found to be the same in the neonatal and adult BBMV. Urea transport in the apical membrane of neonatal and adult proximal tubules is not phloretin sensitive, a finding consistent with diffusion of urea via the lipid bilayer. The rate of urea diffusion is lower in neonatal membranes and may be an important factor in overall urea excretion. This may also play a role in developing and maintaining a high medullary urea concentration and thus the ability to concentrate the urine during renal maturation.

Animals↗
PubMed1999

Use of aromatase inhibitors in the adjuvant treatment of breast cancer.

The value of endocrine treatment of early breast cancer has been illustrated by the antioestrogen, tamoxifen, which has now been available for nearly 30 years. However, if the recognised side effects and pharmacological properties of tamoxifen are taken into consideration, it is possible that other endocrine treatments that are now available can provide equal or superior efficacy, along with improved tolerability. One such group of agents is the aromatase inhibitors specifically the new-generation triazole aromatase inhibitors, such as anastrozole and letrozole, which have both shown tolerability and efficacy advantages over standard treatments in postmenopausal women with advanced breast cancer. There are convincing reasons why the new generation of aromatase inhibitors have advantages over tamoxifen. For instance, from their agonist properties, the effects on the endometrium and tumour stimulation seen with tamoxifen would not be expected, nor would the visual disturbances that have been associated with the triphenylethylene compounds, including tamoxifen. A number of aromatase inhibitors, for instance, anastrozole, letrozole and exemestane, are currently being investigated for treatment of early breast cancer. The results of the trials of aromatase inhibitors and tamoxifen will, in the next few years, define whether or not the new-generation aromatase inhibitors have a role to play in the treatment of postmenopausal women with early breast cancer.

Antineoplastic Agents↗
PubMed1999

Drug use and syphilis. Co-factors for HIV transmission among commercial sex workers in Guyana.

A cross-sectional survey was conducted among 124 street- and brothel-based female commercial sex workers (CSWs) in Georgetown in January and February 1997 to determine the seroprevalence of human immunodeficiency virus (HIV) infection and describe the sexual practices and drug use patterns. Their median age was 30 years (range 17 to 52 years). 119 (88%) reported regular alcohol consumption while looking for clients, 27 (22%) said they smoked cocaine and 51 (42%) reported use of marijuana. Street-based CSWs were significantly more likely to report marijuana use (p = 0.033). 72% reported that they never used condoms with regular sex partners and 35% reported that they never used condoms with clients. Brothel-based women were significantly more likely to report consistent condom use with their clients (p = 0.05). 46% (54/118) tested HIV positive and 28% (33/118) had a positive serological test for syphilis. Factors that were significantly associated with HIV infection included a positive serological test for syphilis (OR = 7.56; 95% CI = 2.7-21.97; p < 0.01) and a history of having received treatment for syphilis (OR = 2.93; 95% CI = 1.12-7.8). Weak associations were also found between HIV infection and a history of cocaine use (OR = 2.57; 95% CI = 0.95-7.11; p = 0.039); having more than four clients per night (OR = 5.14; 95% CI = 1.65-16.74; p = 0.04); and a history of receiving treatment for salpingitis (OR = 2.31; 95% CI = .93-5.75; p = 0.0035). No statistically significant association was found between HIV infection and marijuana use nor any sociodemographic variables (age, place of work, and duration of sex work). There is an urgent need for a community based behavioural intervention programme targetting this high risk population.

Adolescent↗
PubMed1999

Setting up a breast cancer family history clinic.

Breast cancer causes around 21,000 deaths per year in the UK, the vast majority of these occurring in women aged over 50 years with no genetic predisposition to the disease. Screening and symptomatic services for these women, although by no means perfect or homogeneous, have gradually improved over the last 10 years and, perhaps as a result of this, together with increased use of adjuvant systemic therapy, mortality in this group has fallen. Despite this reassuring state of affairs, media interest in the disease and patients' perception of their risk of developing breast cancer have risen. Part of this is undoubtedly due to the new scientific developments in cancer genetics and, in particular, identification of the BRCA1 gene in 1994 and BRCA2 gene shortly afterwards. These genes are dominantly inherited with up to 80% penetrance; thus, women (and occasionally men) inherit these genes and have a high lifetime risk of developing breast cancer, usually at a younger age than average and possibly of a more aggressive phenotype. Unaffected family members can now be screened and, if they prove carriers, screening for early detection and prevention strategies such as bilateral prophylactic mastectomy can be offered. Because of the high risk of ovarian cancer in BRCA1 carriers, screening or prophylactic ovariectomy may also be considered.

Adult↗
PubMed1998

Association of terminal chromosome 1 deletion with sertoli cell-only syndrome.

We report on del(1)(q44), developmental delay, cryptorchidism, and seizure disorder in a 19-year-old man. Endocrinologic evaluation showed delayed puberty and elevated gonadotropins. Testicular biopsy was consistent with Sertoli cell-only syndrome. The case illustrates a previously an unreported manifestation in males with del(1)(q44), and suggests a link between the development of germinal epithelium and genes in the 1q44 area.

Adult↗
PubMed1998

Maturational changes in rabbit renal brush border membrane vesicle osmotic water permeability.

We have recently shown that the osmotic water permeability (Pf) of proximal tubules from neonatal rabbits is higher than that of adults (AJP 271:F871-F876, 1996). The developmental change in Pf could be due to differences in one or more of the components in the path for transepithelial water transport. The present study examined developmental changes in water transport characteristics of the proximal tubule apical membrane by determining Pf and aquaporin 1 (AQP1) expression in neonatal (10-14 days old) and adult rabbit renal brush border membrane vesicles (BBMV). AQP1 abundance in the adult BBMV was higher than the neonatal BBMV. At 25 degrees C the Pf of neonatal BBMV was found to be significantly lower than the adult BBMV at osmotic gradients from 50 to 250 mOsm/kg water. The activation energy for osmotic water movement was higher in the neonatal BBMV than the adult BBMV (9.19 +/- 0.37 vs. 5.09 +/- 0.57 kcal . deg-1 . mol-1, P < 0.005). Osmotic water movement in neonatal BBMV was inhibited 17.9 +/- 1.3% by 1 mm HgCl2 compared to 34.3 +/- 3.8% in the adult BBMV (P < 0.005). These data are consistent with a significantly greater fraction of water traversing the apical membrane lipid bilayer in proximal tubules of neonates than adults. The lower Pf of the neonatal BBMV indicates that the apical membrane is not responsible for the higher transepithelial Pf in the neonatal proximal tubule.

Animals↗