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Biomedical subjects

M Sternberg

Publications and source records attributed to M Sternberg.

At least 19 recordsLinked to original sources
PubMed2006

Substitutional boron in nanodiamond, bucky-diamond, and nanocrystalline diamond grain boundaries.

Although boron has been known for many years to be a successful dopant in bulk diamond, efficient doping of nanocrystalline diamond with boron is still being developed. In general, the location, configuration, and bonding structure of boron in nanodiamond is still unknown, including the fundamental question of whether it is located within grains or grain boundaries of thin films and whether it is within the core or at the surface of nanoparticles. Presented here are density functional tight-binding simulations examining the configuration, potential energy surface, and electronic charge of substitutional boron in various types of nanocrystalline diamond. The results predict that boron is likely to be positioned at the surface of isolated particles and at the grain boundary of thin-film samples.

Journal Article↗
PubMed2006

Advanced glycation endproducts (AGEs): Pharmacological inhibition in diabetes.

AGE inhibitors may act by various mechanisms at different steps of advanced glycation endproduct (AGE) formation (depending on oxidative stress and/or carbonyl stress) and AGE-mediated damage: trapping of reactive dicarbonyl species; antioxidant activity by transition metal chelation; other antioxidant activity including free radical scavenging; AGE cross-link breaking; AGE receptor (RAGE) blocking; RAGE signaling blocking; glycemia reduction by anti-diabetic therapy; aldose reductase inhibition; shunting of trioses-P towards the pentose-P pathway by transketolase activation. Most of the inhibitors have several sites of action. Practically one can distinguish drugs specifically developed as AGE inhibitors or AGE breakers; RAGE and receptor signaling blockers; other therapeutic compounds which were found subsequently to possess also AGE inhibitor activity, including dietary antioxidants. Encouraging results obtained in studies of various AGE inhibitors, conducted in vitro and in diabetic animals, are summarized in this review. However most of the clinical trials have been more or less disappointing, in part because of side effects; the long-term therapeutic interest of the most recently developed AGE inhibitors or breakers remains to be demonstrated in diabetes.

Cross-Linking Reagents↗
PubMed2006

Quantum chemical study of mechanisms for oxidative dehydrogenation of propane on vanadium oxide.

We have carried out a hybrid density functional study of mechanisms for oxidative dehydrogenation of propane on the (010) surface of V2O5. The surface was modeled using both vanadium oxide clusters and a periodic slab. We have investigated a Mars-van Krevelen mechanism that involves stepwise adsorption of the propane at an oxygen site followed by desorption of a water molecule and propene, and subsequent adsorption of an oxygen molecule to complete the catalytic cycle. The potential energy surface is found to have large barriers, which are lowered somewhat when the possibility of a triplet state is considered. The barriers for propane adsorption and propene elimination are 45-60 kcal/mol. The highest energy on the potential energy surface at the B3LYP/6-31G* level of theory is about 80 kcal/mol above the energy of the reactants and corresponds to formation of an oxygen vacancy after water elimination. Subsequent addition of an oxygen molecule to fill the vacancy is predicted to be energetically downhill. The reactions of propane at a bridging oxygen site and at a vanadyl site have similar energetics. The key results of the cluster calculations are confirmed by periodic calculations. Factors that may lower the barriers on the potential energy surface, including the interaction of vanadium oxide clusters with a support material and a concerted reaction with O2, are discussed.

Journal Article↗
PubMed2006

Carbon ad-dimer defects in carbon nanotubes.

The adsorption of carbon dimers on carbon nanotubes leads to a rich spectrum of structures and electronic structure modifications. Barriers for the formation of carbon dimer induced defects are calculated and found to be considerably lower than those for the Stone-Wales defect. The electronic states introduced by the ad-dimers depend on defect structure and tube type and size. Multiple carbon ad-dimers provide a route to structural engineering of patterned tubes that may be of interest for nanoelectronics.

Journal Article↗
PubMed2005

Substitutional nitrogen in nanodiamond and bucky-diamond particles.

The inclusion of dopants (such as nitrogen) in diamond nanoparticles is expected to be important for use in future nanodevices, such as qubits for quantum computing. Although most commercial diamond nanoparticles contain a small fraction of nitrogen, it is still unclear whether it is located within the core or at the surface of the nanoparticle. Presented here are density functional tight binding simulations examining the configuration, potential energy surface, and electronic charge of substitutional nitrogen in nanodiamond and bucky-diamond particles. The results predict that nitrogen is likely to be positioned at the surface of both hydrogenated nanodiamond and (dehydrogenated) bucky-diamond, and that the coordination of the dopants within the particles is dependent upon the surface structure.

Journal Article↗
PubMed2001

Associations of depression, self-esteem, and substance use with sexual risk among adolescents.

BACKGROUND: Adolescents are the population at highest risk for acquiring sexually transmitted diseases (STDs). Previous research has suggested that mental health problems, including depression and low self-esteem, may play an important role in the development and maintenance of sexual risk behaviors. METHODS: National Longitudinal Study of Adolescent Health data from baseline interviews of 7th-12th graders reporting sexual intercourse in the preceding year were analyzed. Using logistic regression, associations of depressive symptoms, self-esteem, and substance use with condom nonuse at last sexual intercourse and with ever having had an STD were explored separately for each gender. RESULTS: Among boys (N = 3,192), depressive symptoms were associated with an increased risk of condom nonuse at last sexual intercourse. The association between depressive symptoms and STD appeared to be mediated by alcohol and marijuana use. For girls (N = 3,391), depressive symptoms were associated with a history of STD, but not with condom nonuse. Self-esteem was not significant in any model that included depressive symptoms. CONCLUSIONS: Adolescents with depressive symptoms are at risk for not using a condom and for having an STD. Further research is needed to elucidate the relationship among depression, substance use, and sexual risk to optimize STD prevention strategies for adolescents.

Adolescent↗
PubMed2000

Geographic variation of HIV infection in childbearing women with syphilis in the United States.

OBJECTIVES: Substantial biologic and epidemiologic data indicate the importance of syphilis as a potential cofactor for sexual transmission of HIV infection, but few detailed data exist on the geographic covariation of these two important sexually transmitted infections. DESIGN: HIV prevalence in childbearing women and primary and secondary (P&S) syphilis data from 29 states were examined to explore the importance of the epidemiology of syphilis as a factor in facilitating HIV transmission. METHOD: The spatial relationship between P&S syphilis and HIV infection in the health districts of 29 states was analyzed and adjusted for demographic and socioeconomic factors such as racial composition, income, housing, education levels, and access to medical services using the 1990 US census, and geographic location. RESULTS: In 29 states and the District of Colombia, 448 health districts, representing more than 75% of the US population, reported HIV prevalence rates for mothers' district of residence. The HIV seroprevalence ranged from 0 to 1258/10 000 in these health districts. The incidence of P&S syphilis from 1984-1994 in these districts ranged from 0 to 87/100 000. The P&S syphilis incidence was positively associated with the prevalence of HIV infection among childbearing women (P < 0.0001). CONCLUSIONS: Syphilis that persists in communities in the United States appears to represent a 'sentinel public health event' reflecting risk for sexual HIV transmission. These findings, along with other biologic and epidemiologic information, reinforce the importance of syphilis as an indicator for targeting HIV prevention efforts generally, as well as syphilis control as a specific HIV-prevention strategy.

Confounding Factors, Epidemiologic↗
PubMed1999

CAFASP-1: critical assessment of fully automated structure prediction methods.

The results of the first Critical Assessment of Fully Automated Structure Prediction (CAFASP-1) are presented. The objective was to evaluate the success rates of fully automatic web servers for fold recognition which are available to the community. This study was based on the targets used in the third meeting on the Critical Assessment of Techniques for Protein Structure Prediction (CASP-3). However, unlike CASP-3, the study was not a blind trial, as it was held after the structures of the targets were known. The aim was to assess the performance of methods without the user intervention that several groups used in their CASP-3 submissions. Although it is clear that "human plus machine" predictions are superior to automated ones, this CAFASP-1 experiment is extremely valuable for users of our methods; it provides an indication of the performance of the methods alone, and not of the "human plus machine" performance assessed in CASP. This information may aid users in choosing which programs they wish to use and in evaluating the reliability of the programs when applied to their specific prediction targets. In addition, evaluation of fully automated methods is particularly important to assess their applicability at genomic scales. For each target, groups submitted the top-ranking folds generated from their servers. In CAFASP-1 we concentrated on fold-recognition web servers only and evaluated only recognition of the correct fold, and not, as in CASP-3, alignment accuracy. Although some performance differences appeared within each of the four target categories used here, overall, no single server has proved markedly superior to the others. The results showed that current fully automated fold recognition servers can often identify remote similarities when pairwise sequence search methods fail. Nevertheless, in only a few cases outside the family-level targets has the score of the top-ranking fold been significant enough to allow for a confident fully automated prediction. Because the goals, rules, and procedures of CAFASP-1 were different from those used at CASP-3, the results reported here are not comparable with those reported in CASP-3. Nevertheless, it is clear that current automated fold recognition methods can not yet compete with "human-expert plus machine" predictions. Finally, CAFASP-1 has been useful in identifying the requirements for a future blind trial of automated served-based protein structure prediction.

Algorithms↗
PubMed1999

Trichomoniasis in pregnant human immunodeficiency virus-infected and human immunodeficiency virus-uninfected congolese women: prevalence, risk factors, and association with low birth weight.

OBJECTIVE: We sought to assess the prevalence of and risk factors for vaginal trichomoniasis in human immunodeficiency virus-infected and human immunodeficiency virus-uninfected pregnant Congolese women and its relationship to pregnancy outcomes. STUDY DESIGN: We performed a nested case-control study of 215 infected and 206 uninfected mothers who responded to questionnaires, underwent sexually transmitted disease testing (including culture for trichomoniasis shortly after delivery), and underwent assessment of infant outcomes. Maternal variables and birth outcomes were assessed according to presence or absence of trichomoniasis and human immunodeficiency virus. RESULTS: Trichomoniasis was present in 18.6% of human immunodeficiency virus-positive and 10.2% of human immunodeficiency virus-negative women, respectively (odds ratio, 2.0; 95% confidence interval, 1.1-3.6), and was significantly associated with low birth weight (odds ratio, 2.4; 95% confidence interval, 1.2-4.5). In multivariate analyses trichomoniasis remained associated with low birth weight, and adjustments were made for other risk factors associated with low birth weight. CONCLUSION: These findings suggest an association between trichomoniasis and low birth weight independent of human immunodeficiency virus infection and other risk factors. Further studies are needed to assess the impact of antenatal screening and treatment for trichomoniasis on pregnancy outcomes.

Adult↗
PubMed1999

Cyclic guanosylmonophosphate urinary excretion in parasympathicomimetic or parasympatholytic syndromes induced by reserpine or diphemanil-methylsulfate.

Parasympathetic hyperactivity is found in some infants presenting faint episodes and could be responsible of certain Sudden Infant Death Syndrome cases. Therefore it was interesting to look for a noninvasive biochemical indicator of parasympathetic activity. A parasympaticomimetic syndrome associated with muscarinic receptor stimulation, which has been followed during 48 h, was obtained in the awake rat by reserpine injection (6.25 mg/kg at T0 and T24h), and a model of prolonged parasympatholytic syndrome, by administration of diphemanil-methylsulfate (DPMS), a muscarinic receptor inhibitor, in drinking water (mean daily dosis: 150 mg/kg). Significant bradycardia and tachycardia were respectively observed. In the reserpine-treated rats we found significantly increased cyclic guanosylmonophosphate (cGMP) urinary excretion between T24h and T48h, when compared with vehicle-treated controls (+87% in one experiment, +135% in the other, when expressed in pmol/microg creatinine); norepinephrine urinary excretion between T24h and T48h was decreased (-44%); the increase in cGMP urinary excretion was not significantly modified by the NO-synthase inhibitor, L-nitroarginine-methyl-ester. In the DPMS-treated rats, we observed a significantly decreased cGMP (-20%) and increased norepinephrine urinary excretion (+61%). Thus cGMP excretion varied in opposite directions in the reserpine- and DPMS-treated rats. The link between these modifications in cGMP excretion and muscarinic receptor stimulation or blockade has still to be fully demonstrated. Urinary cGMP excretion could be tested as screening parameter in infants at risk of faint episodes associated with bradycardia.

Animals↗
PubMed1999

Incident syphilis among women with multiple admissions to jail in New York City.

Although early syphilis morbidity in New York City (NYC) has declined to a record low, syphilis seroreactivity among women jailed in NYC is approximately 25%. By use of a retrospective cohort-type analysis of longitudinal serologic and treatment data collected at the time of each incarceration, the incidence of syphilis infection among 3579 susceptible women jailed multiple times in NYC between 23 March 1993 and 10 April 1997 was estimated. Syphilis incidence densities were estimated by use of continuous, time-homogeneous Markov models. There was a total of 289 incident infections. The overall incidence density was 6.5 infections per 100 woman-years (95% confidence interval, 5.7-7.2), which exceeds the 1997 early syphilis rate among women in NYC by>1000-fold. The persisting high incidence of syphilis in this population underscores the importance of aggressive syphilis control in correctional settings, even in the face of declining local early syphilis rates.

Adult↗
PubMed1998

Employment after spinal cord injury: differences related to geographic region, gender, and race.

OBJECTIVE: To compare employment outcomes after spinal cord injury (SCI) as a function of several important participant characteristics. DESIGN: Field study survey of the employment history of two large samples of people with SCI. Outcomes were compared as a function of multiple participant characteristics. SETTING: A large rehabilitation hospital in the Southeast, with the collaboration of two Midwestern hospitals. PARTICIPANTS: One thousand thirty-two individuals with SCI, 597 from the Southeast and 435 from the Midwest. MAIN OUTCOME MEASURES: The Life Situation Questionnaire-revised (LSQ-R), a self-report measure, was used to identify biographic status and to document employment history. RESULTS: On the average, currently employed participants were Caucasian, were younger when injured, had paraplegia, and had completed more years of education. Geographic differences in employment rates disappeared when controlled for multiple factors, including years of education. However, even after controlling for years of education, Caucasian participants were 2.8 times more likely than minority participants to be working at the time of the study. CONCLUSIONS: Rehabilitation professionals need to find creative means to identify and neutralize barriers to employment among individuals from minority groups and to identify meaningful avocations for individuals who are injured when they are near retirement.

Adolescent↗
PubMed1998

Effect of long-term treatment with a purified micronized flavonoid fraction on pancreatic mononuclear cell infiltration in diabetic BB rats.

Bio Breeding (BB) rats develop a genetically determined insulin-dependent diabetes, because of the early destruction of pancreatic beta cells of Langerhans islets, massively infiltrated by inflammatory mononuclear cells. S 5682, registered as Daflon, 500 mg, is a purified micronized flavonoid fraction (90% diosmin, 10% hesperidin), which has been shown to possess antiinflammatory properties, including anti-free radical activity, effects on vascular permeability, venous tone, and perivenous inflammation. We studied the effect of S 5682 on the course of pancreatic insulitis in diabetic BB rats. All the diabetic BB rats were hyperglycemic, with an increase of plasma levels of fructosamine, alpha-1 acid glycoprotein, and fibrinogen, and a dramatic decrease of C-peptide level. These parameters were not modified by S 5682. Pancreas histologic studies showed that in S 5682-treated diabetic BB rats, lymphocytic infiltration of Langerhans islets was less important and frequent than in untreated diabetic BB rats. By quantitative analysis, a highly significant difference was observed for insulitis, as well as perivasculitis, between S 5682-treated and untreated diabetic BB rats. This inhibitory effect of S 5682 on pancreatic mononuclear cell infiltration may be useful for a complementary treatment to decrease the development of insulitis in human insulin-dependent diabetes mellitus.

Animals↗
PubMed1997

Mortality after spinal cord injury: an 11-year prospective study.

OBJECTIVE: To identify the relative risk of mortality after spinal cord injury (SCI) as a function of level of psychosocial, vocational, and medical adjustment. DESIGN: A prospective design was used: data on life adjustment was obtained at one time (1985), with subsequent survival status ascertained 11 years later (1996). Logistic regression was used to identify the relative risk of mortality given the level of adjustment on a number of predictor variables. SETTING: All participants were selected from outpatient files of a Midwestern university hospital. PARTICIPANTS: A total of 345 participants with SCI completed study materials in 1985 (a 78% response rate), 330 of whom could be definitively classified in 1996 as either survivor or deceased. Of these 330 participants, 84% were alive in 1996 (n = 278) and the other 16% were deceased (n = 52). MAIN OUTCOME MEASUREMENTS: The Life Situation Questionnaire (LSQ) was used to measure nine primary predictors related to life adjustment after SCI, including employment status and eight predictor scales: Medical Instability, Adjustment, General Satisfaction, Emotional Distress, Dependency, and Poor Health. The LSQ was also used to generate data on 34 individual items that were used in exploratory predictive analyses. RESULTS: All but one of the 8 primary adjustment predictors from 1985 significantly predicted 1996 mortality status. Dependency and low overall satisfaction were among the most significant predictors of mortality. CONCLUSIONS: Overall quality of life is important to the longevity of people with SCI, and comprehensive rehabilitation programs are needed to promote a level of life adjustment that maximizes longevity after SCI.

Activities of Daily Living↗
PubMed1996

Effect of an aldose reductase inhibitor on type IV collagen production by human endothelial cells cultured in high glucose.

Diabetic microangiopathy is characterized by a thickening of capillary basement membranes associated with type IV collagen accumulation. An increase in type IV collagen content of the aortic wall is also observed in macroangiopathy. In order to analyse the importance of the polyol pathway in the development of the collagen metabolism alterations seen in diabetic angiopathy and their prevention by aldose reductase inhibitors, we have studied the effects of sorbinil on the high glucose-induced stimulation of type IV collagen biosynthesis in human umbilical vein endothelial cells. Primary cultures were exposed to high glucose (16.7 mmol/l), with and without 0.11 mmol/l sorbinil, for 3 or 6 days after beginning of confluence. We measured the soluble type IV collagen secreted into the culture medium and the insoluble type IV collagen accumulated in the extracellular matrix and cells, by ELISA. We also studied [14C]proline incorporation into the newly synthesized collagenous and total proteins in the culture supernatant and in the extracellular matrix and cell fraction. High glucose decreased the number of cells and increased the amount of type IV collagen in the culture supernatant and in the extracellular matrix and cell fraction. It also increased proline incorporation into the newly synthesized collagenous and total proteins in the culture supernatant and in the extracellular matrix and cell fraction. Sorbinil corrected all these high glucose-induced alterations. The corrective effects of sorbinil on the proliferation and on type IV collagen metabolism of endothelial cells cultured in high glucose may be attributed to prevention of polyol pathway dysregulation.

Aldehyde Reductase↗