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M Baum

Publications and source records attributed to M Baum.

At least 55 records · Page 3Linked to original sources
PubMed2001

Thrombocytopenia in HIV-infected drug users in the HAART era.

The present case-control study compared 26 HIV+ drug users having persistent thrombocytopenia (TCP<150 000/mm(3)) with 54 available age, gender and HIV CDC classification matched controls with normal platelet counts. Participants were followed longitudinally over a 2-year period (1998-2000), and hematological alterations evaluated in relationship to antiretroviral treatment, drug use and nutritional (selenium) status. Demographic information and medical history, including antiretroviral treatment were obtained. Blood was drawn for complete cell blood count, T lymphocytes and viral load. Sixty-nine percent of the individuals with persistent TCP and 49% of the controls were receiving antiretrovirals. At baseline, no significant differences in CD4 existed between the two groups. Over time, CD4 cell count declined in the cases (P = 0.05) and a significantly higher proportion of the cases (38%) developed AIDS (CD4<200 cell/mm(3)), as compared to the controls (18%, P = 0.004). A high risk for development of thrombocytopenia was observed with specific drug use (heroin 2.96 times, P = 0.0007), selenium levels below 145 microg/l (6 times, P = 0.008), and abnormal liver enzyme (SGOT) levels (2 times, P = 0.002). Together, these results indicate a number of factors that may be sensitive predictors of thrombocytopenia, which, despite antiretroviral treatment, appears to be related to more rapid disease progression in drug users.

Adult↗
PubMed2001

Ontogeny of rabbit proximal tubule urea permeability.

Urea transport in the proximal tubule is passive and is dependent on the epithelial permeability. The present study examined the maturation of urea permeability (P(urea)) in in vitro perfused proximal convoluted tubules (PCT) and basolateral membrane vesicles (BLMV) from rabbit renal cortex. Urea transport was lower in neonatal than adult PCT at both 37 and 25 degrees C. The PCT P(urea) was also lower in the neonates than the adults (37 degrees C: 45.4 +/- 10.8 vs. 88.5 +/- 15.2 x 10(-6) cm/s, P < 0.05; 25 degrees C: 28.5 +/- 6.9 vs. 55.3 +/- 10.4 x 10(-6) cm/s; P < 0.05). The activation energy for PCT P(urea) was not different between the neonatal and adult groups. BLMV P(urea) was determined by measuring vesicle shrinkage, due to efflux of urea, using a stop-flow instrument. Neonatal BLMV P(urea) was not different from adult BLMV P(urea) at 37 degrees C [1.14 +/- 0.05 x 10(-6) vs. 1.25 +/- 0.05 x 10(-6) cm/s; P = not significant (NS)] or 25 degrees C (0.94 +/- 0.06 vs. 1.05 +/- 0.10 x 10(-6) cm/s; P = NS). There was no effect of 250 microM phloretin, an inhibitor of the urea transporter, on P(urea) in either adult or neonatal BLMV. The activation energy for urea diffusion was also identical in the neonatal and adult BLMV. These findings in the BLMV are in contrast to the brush-border membrane vesicles (BBMV) where we have previously demonstrated that urea transport is lower in the neonate than the adult. Urea transport is lower in the neonatal proximal tubule than the adult. This is due to a lower rate of apical membrane urea transport, whereas basolateral urea transport is the same in neonates and adults. The lower P(urea) in neonatal proximal tubules may play a role in overall urea excretion and in developing and maintaining a high medullary urea concentration and thus in the ability to concentrate the urine during renal maturation.

Aging↗
PubMed2001

The renal nerve is required for regulation of proximal tubule transport by intraluminally produced ANG II.

The proximal tubule synthesizes and luminally secretes high levels of angiotensin II, which modulate proximal tubule transport independently of systemic angiotensin II. The purpose of this in vivo microperfusion study is to examine whether the renal nerves modulate the effect of intraluminal angiotensin II on proximal tubule transport. The decrement in volume reabsorption after addition of 10(-4) M luminal enalaprilat is a measure of the role of luminal angiotensin II on transport. Acute denervation decreased volume reabsorption (2.97 +/- 0.14 vs. 1.30 +/- 0.21 nl. mm(-1). min(-1), P < 0.001). Although luminal 10(-4) M enalaprilat decreased volume reabsorption in controls (2.97 +/- 0.14 vs. 1.61 +/- 0.26 nl. mm(-1). min(-1), P < 0.001), it did not after acute denervation (1.30 +/- 0.21 vs. 1.55 +/- 0.19 nl. mm(-1). min(-1)). After chronic denervation, volume reabsorption was unchanged from sham controls (2.26 +/- 0.28 vs. 2.70 +/- 0.19 nl. mm(-1). min(-1)). Addition of luminal 10(-4) M enalaprilat decreased volume reabsorption in sham control (2.70 +/- 0.19 vs. 1.60 +/- 0.10 nl. mm(-1). min(-1), P < 0.05) but not with chronic denervation (2.26 +/- 0.28 vs. 2.07 +/- 0.20 nl. mm(-1). min(-1)). Addition of 10(-8) M angiotensin II to the lumen does not affect transport due to the presence of luminal angiotensin II. However, addition of 10(-8) M angiotensin II to the tubular lumen increased the volume reabsorption after both acute (1.30 +/- 0.21 vs. 2.67 +/- 0.18 nl. mm(-1). min(-1), P < 0.05) and chronic denervation (2.26 +/- 0.28 vs. 3.57 +/- 0.44 nl. mm(-1). min(-1), P < 0.01). These data indicate that renal denervation abolished the luminal enalaprilat-sensitive component of proximal tubule transport, which is consistent with the renal nerves playing a role in the modulation of the intraluminal angiotensin II mediated component of proximal tubule transport.

Absorption↗
PubMed2001

Evidence-based art?

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Evidence-Based Medicine↗
PubMed2001

Perinatal renal ischemia resulting in hypertensive cardiomyopathy.

Three neonates presented with malignant hypertension during the first week of life; 2 of them had congestive heart failure. Although none had indwelling umbilical artery catheters, unilateral renovascular lesions were diagnosed by nuclear perfusion scans. Angiotensin-converting enzyme inhibitor therapy produced rapid recovery. Hypertension must be included in the differential diagnosis of infants presenting with congestive heart failure and acidosis. Ultrasonography is not sensitive enough to exclude renovascular lesions. We emphasize the importance of early diagnosis and treatment.

Acidosis↗
PubMed2001

Thiazide diuretics arrest the progression of nephrocalcinosis in children with X-linked hypophosphatemia.

OBJECTIVE: X-linked hypophosphatemia (XLH) is characterized clinically by rickets, hypophosphatemia, and hyperphosphaturia. Conventional treatment of XLH with oral phosphate and vitamin D is associated with increased urinary calcium excretion and nephrocalcinosis. Thiazide diuretics decrease urinary calcium excretion. The objective of this study was to determine the effect of thiazide diuretics on the clinical and radiologic course of nephrocalcinosis in children with XLH. METHODS: The effect of hydrochlorothiazide (HCTZ) on clinical and radiologic progression of nephrocalcinosis was evaluated in 11 children with XLH. All patients had been treated previously with vitamin D and oral phosphate and had radiologic evidence of nephrocalcinosis. The average age of the patients at the start of HCTZ was 6.6 +/- 1.0 years. The effect of oral HCTZ at 0.8 +/- 0.1 mg/kg body weight per day given for 3.3 +/- 0.6 years on the progression of nephrocalcinosis and urinary calcium excretion was evaluated. RESULTS: There was no change in serum phosphorous, calcium, potassium, and chloride after HCTZ therapy. HCTZ therapy increased serum bicarbonate and decreased urinary calcium excretion. The grade of nephrocalcinosis increased from 0.4 +/- 0.2 to 1.5 +/- 0.3 in the 2.3 +/- 0.3 years before initiation of HCTZ therapy, whereas the degree of nephrocalcinosis was stable after 3.3 +/- 0.6 years of HCTZ therapy (1.5 +/- 0.3 vs 3.0 +/- 0.3). CONCLUSION: HCTZ decreased urinary calcium excretion but did not result in the resolution of nephrocalcinosis. However, when compared with the control period, HCTZ prevented the progression of nephrocalcinosis in children with XLH.

Calcium↗
PubMed2001

Human herpesvirus 8 can be transmitted through blood in drug addicts.

Human Herpes virus type-8 (HHV-8) seroprevalence was studied in a population of HIV positive intravenous drug users (IVDUs) from Argentina. Analysis of this population also indirectly made it possible to study HHV-8 blood transmission, because these individuals frequently engage in needle sharing behavior and are capable of acquiring a broad array of blood borne pathogens, including Hepatitis B/C virus. The seroprevalence of HHV-8 in IVDUs was compared to a group of non-IVDUs and HIV negative individuals. Of the 223 individuals tested, 13.45% were HHV-8 positive, 16.99% in the IVDUs group, and 5.71% in the non-IVDUs. Among HIV positive IVDUs, 25/144 (17.36%) were also HHV-8 seropositive. The seropositivity rate of HHV-8 in HIV negative IVDUs was 11.1%. In contrast, HHV-8 seroprevalence in HIV negative heterosexual individuals without drug usage behavior was even lower (5.71%). The rate of HHV-8 infection in HIV positive IVDUs was three times as high compared to the non IVDU HIV negative individuals, suggesting that IVDU is a risk for HHV-8 infection. Furthermore, it was found that IVDUs showed a very high rate of Hepatitis B/C (52.77%), which also correlate with HHV-8 infection in this population (23.68%). All Hepatitis B/C positive individuals were also HIV positive. Our data confirm other studies showing that individuals who share needles are at risk for acquiring Hepatitis B/C and HIV infections. In addition, our results suggest that they are also at risk to acquiring HHV-8 infection by the same route.

Adult↗
PubMed2001

Ventriculo-peritoneal shunt and breast carcinoma.

Ventriculo-peritoneal (V-P) shunt is a frequently performed surgical procedure for treating hydrocephalus. The incidence of breast carcinoma in the UK is 20,000 cases per year. We present a case of a patient with breast carcinoma in association with V-P shunt.

Breast Neoplasms↗
PubMed2000

Developmental outcomes and cognitive functioning in infant and child heart transplant recipients.

Pediatric heart transplantation has become a mainstay in the treatment of end-stage heart disease in infants and children. There is, however, sparse information on post-transplant developmental and cognitive functioning. At Loma Linda University Children's Hospital 223 infants have undergone heart transplantation surgery with a survival rate of 73% (n=165). This article reports on four areas of investigation of this cohort of infants. Infant development: Two studies were done utilizing the Bayley Scales of Infant Development (mean 100, S.D.+/-15). The first study (n=48) showed mean values within the normal range [Mental Development Index (MDI) 87; Psychomotor Developmental Index (PDI) 90]. The second study (n=23) showed developmental scores within normal limits in 4-8 month olds with a tendency for decline in development at 12-24 months (MDI 83, PDI 77). Child development: Ninty-one infant recipients were greater than 5 years old. Forty-five children were excluded because of long distances from the hospital, second transplantation, abnormal karyotype, primary language non-English, or invalid testing. The Wechsler Preschool and Primary Scale of Intelligence-Revised testing of 5-6-year-olds (n=23) showed a Full Scale IQ of 74, Performance IQ of 76, and Verbal IQ of 77. The Wechsler Intelligence Scale for Children-III testing of 7-10-year-olds (n=23) showed a Full Scale IQ of 86, Performance IQ of 89, and Verbal IQ of 86. The Wechsler Individual Achievement Test (mean 100, S.D.+/-15) yielded a Total Composite of 91, Mathematics Composite of 86, Language Composite of 98, and a Reading Composite of 94. Visual spatial skills: Visual motor integration (mean 100, S.D.+/-15) was evaluated in 5-10-year-olds with a mean of 87; however, 52% of the children had scores below 1 S.D. Subtests from the Wechsler scales that assess visual motor and visual spatial skills indicated significant deficits. Behavior: Younger children (n=33) demonstrated behaviors indicative of social isolation. Older children (n=36) showed behavior that was within the normal limits, but depression was noted in a significant number of them. Conclusions: Infant heart transplant recipients demonstrate IQ and achievement levels within the normal range, but there is a significant amount of variability with more children than would be expected scoring in the lower ranges. Children with heart transplantation are at risk for visual spatial skill deficits. Young children are at risk for social isolation while symptoms of depression are noted in older children.

Journal Article↗
PubMed2000

Clinical outcome 10 years after infant heart transplantation.

The feasibility of heart transplantation for infants has now been established. Clinical outcome data is necessary to assist in targeting areas for improvement and for counseling families considering this option. This report describes clinical outcome in 29 infant heart transplant recipients who have survived at least 10 years. A query of the transplant database, referring physicians and parental questionnaire was performed. Patient survival for the overall infant population is 64% at 13 years. Parents of 19/29 (55%) children described them as developmentally normal. Three children have had a severe developmental outcome. Sixteen of 29 children are in mainstream school environments. Four have repeated one grade in school. Speech delay was present in 10/26 (38%). Somatic growth is normal in 88%. All children are NYHA class I. Renal function shows only modest insufficiency with most recent BUN (mean+/-S.D.)=25+/-7 mg/dl and serum creatinine=0.8+/-0.2 mg/dl. Only four children have creatinine levels >1 mg/dl. No child requires dialysis. No children have developed post-transplant lymphoproliferative disease beyond 10 years. Four children have experienced rejection beyond 10 years with one mortality due to rejection and transplant coronary artery disease. Conclusion: Heart transplantation during infancy is technically feasible and results in good survival. Many children have some degree of learning disability but most are mild and the children function well in society. Improvements in surgical techniques may improve developmental outcome. Other side-effects of immunosuppression are manageable and most survivors have a good functional outcome.

Journal Article↗
PubMed2000

Publishing surgery.

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Faculty, Medical↗
PubMed2000

Maturational changes in rabbit renal basolateral membrane vesicle osmotic water permeability.

We have recently demonstrated that while the osmotic water permeability (Pf) of neonatal proximal tubules is higher than that of adult tubules, the Pf of brushborder membrane vesicles from neonatal rabbits is lower than that of adults. The present study examined developmental changes in the water transport characteristics of proximal tubule basolateral membranes by determining aquaporin 1 (AQP1) protein abundance and the Pf in neonatal (10-14 days old) and adult rabbit renal basolateral membrane vesicles (BLMV). At 25 degrees C the Pf of neonatal BLMV was significantly lower than the adult BLMV at osmotic gradients ranging from 40 to 160 mOsm/kg water. The activation energies for osmotic water movement were identical in the neonatal and adult BLMV (8.65 +/- 0.47 vs. 8.86 +/- 1.35 kcal x deg(-1) x mol(-1). Reflection coefficients for sodium chloride and sodium bicarbonate were identical in both the neonatal and adult BLMV and were not different from one. Mercury chloride (0.5 mM) reduced osmotic water movement by 31.3 +/- 5.5% in the adult BLMV, but by only 4.0 +/- 4.0% in neonatal vesicles (P < 0.01). Adult BLMV AQP1 abundance was higher than that in the neonate. These data demonstrate that neonatal BLMV have a lower Pf and AQP1 protein abundance than adults and that a significantly greater fraction of water traverses the basolateral membrane lipid bilayer and not water channels in neonates compared to adults. The lower Pf of the neonatal BLMV indicates that the basolateral membrane is not responsible for the higher transepithelial Pf in the neonatal proximal tubule.

Aging↗
PubMed2000

Effect of temperature on kinesin-driven microtubule gliding and kinesin ATPase activity.

DeCuevas et al. [J. Cell Biol. 116 (1992) 957-965] demonstrated by circular dichroism spectroscopy for the kinesin stalk fragment that shifting temperature from 25 to 30 degrees C caused a conformational transition. To gain insight into functional consequences of such a transition, we studied the temperature dependence of a full-length kinesin by measuring both the velocity of microtubule gliding across kinesin-coated surfaces and microtubule-promoted kinesin ATPase activity in solution. The corresponding Arrhenius plots revealed distinct breaks at 27 degrees C, corroborating the temperature-dependent conformational transition for a motility-competent full-length kinesin. Microtubules were found to glide up to 45 degrees C; at higher temperatures, kinesin was irreversibly damaged.

Animals↗