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Biomedical subjects

B Schwartz

Publications and source records attributed to B Schwartz.

At least 37 records · Page 2Linked to original sources
PubMed2001

Lipid II: total synthesis of the bacterial cell wall precursor and utilization as a substrate for glycosyltransfer and transpeptidation by penicillin binding protein (PBP) 1b of Escherichia coli.

An essential feature in the life cycle of both gram positive and gram negative bacteria is the production of new cell wall. Also known as murein, the cell wall is a two-dimensional polymer, consisting of a linear, repeating N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) motif, cross-linked via peptides appended to MurNAc. The final steps in the maturation of murein are catalyzed by a single, bifunctional enzyme, known as a high MW, class A penicillin binding protein (PBP). PBPs catalyze polymerization of the sugar units (glycosyltransfer), as well as peptide cross-linking (transpeptidation) utilizing Lipid II as substrate. Detailed enzymology on this enzyme has been limited, due to difficulties in obtaining sufficient amounts of Lipid II, as well as the availability of a convenient and informative assay. We report the total chemical synthesis of Lipid II, as well as the development of an appropriate assay system and the observation of both catalytic transformations.

Bacterial Proteins↗
PubMed2001

Nuclear polarization of hydrogen molecules from recombination of polarized atoms.

The nuclear polarization of H(2) molecules formed by recombination of polarized H atoms on a Cu surface was measured as a function of external magnetic field and of temperature of the surface. The proton polarization of the molecules was determined by scattering of a longitudinally polarized 203-MeV proton beam in the Indiana University Cyclotron Facility storage ring. The nuclear polarization of the molecules, relative to the polarization of the atoms before recombination, increased from near zero in a weak magnetic field to 0.42 +/- 0.02 in a 0.66 T field. A simple model of the relaxation accounts quantitatively for the observations.

Journal Article↗
PubMed2001

The role of copper in topa quinone biogenesis and catalysis, as probed by azide inhibition of a copper amine oxidase from yeast.

All known copper amine oxidases (CAOs) contain 2,4,5-trihydroxyphenylalanine quinone (TPQ) as a redox cofactor. TPQ is derived posttranslationally from a specific tyrosine residue within the protein itself, and is utilized by the enzyme to oxidize amines to aldehydes. Several oxidative mechanisms for both turnover and the biogenesis of the cofactor have been proposed in recent years, which differ mainly in the nature of the interaction of oxygen with the enzyme. In this study, azide is used to probe the role of copper in catalysis and biogenesis, especially with respect to potential interactions between the metal and oxygen. During turnover, it is found that azide is a noncompetitive inhibitor with respect to O(2), most consistent mechanistically with oxygen binding off the metal prior to reaction. During biogenesis, it is found that azide likely prohibits ligation of the precursor tyrosine to the copper, thus preventing the formation of this key intermediate. This result is consistent with previous proposals, where the copper-tyrosine unit is the species that undergoes reaction with O(2). In addition, it is found that oxygen consumption is kinetically uncoupled from TPQ formation; this leads to an expanded kinetic model for biogenesis, with important implications for previous results.

Amine Oxidase (Copper-Containing)↗
PubMed2001

Apoptosis (programmed cell death) in colonic cells: from normal to transformed stage.

We determined apoptosis in whole rat colonic tissue and in isolated colonocytes from the various rat crypt regions in preneoplastic stages up to frank neoplasia following administration of the procarcinogen, dimethylhydrazine (DMH). Apoptotic cells were determined by the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL)-method, by evaluating sections stained with hematoxylin and eosin, and caspase-1 immunostaining. Apoptotic cells in whole colonic tissue from untreated rats were confined to the upper crypt while, in DMH-treated rats apoptotic and caspase-1 positive cells were located in the crypt proliferative regions. Numerous apoptotic and caspase-1-positive cells were found in sections from early tumors while in the delayed tumors, apoptotic-positive cells were absent and number of caspase-1-positive cells was negligible. A marked reduction in the apoptotic index along the crypt was observed in isolated transformed colonic cells, this was not the case for caspase-1-positive cells. We conclude that: (i) in colorectal tumors at progressive stage apoptosis is altered, (ii) the mechanistic alteration in apoptosis may be located between caspase-1-protease activity and the fragmentation process of DNA.

1,2-Dimethylhydrazine↗
PubMed2001

Could plasmid-mediated gene transfer into the myocardium be augmented by left ventricular guided laser myocardial injury?

Early studies have indicated no correlation between the amount of mechanical injury and the level of myocardial gene expression following direct plasmid vector injection. Recently, however, evidence suggests that combined laser myocardial injury and plasmid-based gene delivery exert synergistic effects on gene expression and activity. The purpose of the study was to determine whether laser-induced myocardial injury followed by transendocardial gene transfer increases gene expression compared to gene transfer alone. We assessed the ability of a plasmid vector to express its transgene after injection into porcine ischemic myocardium with and without preceding laser myocardial injury. Thirteen animals had transendocardial injections of the luciferase reporter gene in a plamid vector using a catheter-based injection system. Injections (0.5 mg per animal, 50 microg per injection site) were divided into 10 sites in the ischemic territory. Eight animals underwent transendocardial laser injury of the ischemic region (2 Joule per pulse x 10 sites) prior to gene delivery. In five animals, gene injection sites were dispersed between laser channels, and in three animals laser and gene delivery were applied in close proximity (< 5 mm) or at the same location. Luciferase activity was measured at 3 and 7 days. Luciferase expression in ischemic zones was markedly elevated at day 3 and 7, and similar whether animals were pretreated using laser injury followed by gene transfer compared to gene transfer alone. Neither same-spot injection nor dispersed gene delivery were associated with augmented gene expression compared to gene transfer alone. Using the above-described catheter-based approach to combine localized laser injury and injection of naked DNA into ischemic myocardium, laser injury did not augment gene expression above levels present with gene transfer alone.

Animals↗
PubMed2001

Adsorption of cationized bovine serum albumin onto epithelial crypt fractions of the rat colon.

The purpose of the study was to characterize mucosal attachment of a cationized model protein, bovine serum albumin (BSA), onto the various fractions of colonic crypts epithelium in the rat. BSA was labeled with fluorescein isothiocyanate (FITC) and its surface net electric charge was modified from negative to positive. Attachment of the cationized protein (CF-BSA) onto rat colonic epithelium was performed by incubation of colonic everted sacs in medium containing cationized or non-cationized FITC-labeled BSA. Using a nonenzymatic isolation procedure, colonocytes were harvested from five horizontal fractions of the colonic crypts. BSA adhesion to the isolated colonocytes was quantified spectrofluorometrically. In addition, the effect of increasing concentrations of Mg(2+) on the adsorption of the cationized BSA onto the surface of colonic epithelium was evaluated by measuring its ability to displace the adhered BSA from its binding sites. BSA cationization facilitated protein adherence to the colon epithelium in a crypt depth-dependent manner. The largest extent of adherence was observed in the outer layer (first fraction) of the colon. Binding persisted to approximately half the depth of the crypts. The relation between CF-BSA concentration in the incubation medium and the amount of CF-BSA adsorbed onto the colonic epithelium was exponential in nature. The addition of electrolyte (Mg(2+)) caused a detachment of the CF-BSA. The adsorption process was characterized by Langmuir's adsorption isotherm. It is concluded that cationized BSA could be useful as a targetable drug platform in cases where the target site is the gastrointestinal epithelium.

Adsorption↗
PubMed2001

Electrospray ionization mass spectrometry analysis of lysophospholipids in human ascitic fluids: comparison of the lysophospholipid contents in malignant vs nonmalignant ascitic fluids.

Lysophospholipids (lyso-PLs), including various glycerol-based and sphingosine-based lysophospholipids, play important roles in many biochemical, physiological, and pathological processes. The classical methods to analyze these lipids involve gas chromatography and/or high-performance liquid chromatography, which are time-consuming, cumbersome, and sometimes inaccurate due to the incomplete separation of closely related lipid species. We now describe the quantitative analysis of lyso-PLs in ascites samples from patients with ovarian cancer using electrospray ionization spectrometry. Three new classes of lyso-PL molecules are detected: alkyl-LPA, alkenyl-LPA, and methylated lysophosphatidylethanolamine. Importantly, the following lysophospholipid species are significantly increased in ascites from patients with ovarian cancer, compared to patients with nonmalignant diseases (e.g., liver failure): LPA (including acyl-, alkyl-, and alkenyl-LPA species), lysophosphatidylinositol, and sphingosylphosphorylcholine. Lysophosphorylcholine contents are also significantly different among ascitic fluids from the two groups of patients. However, the total phosphate content in ascites samples from patients with ovarian cancer is not significantly different compared to that from patients with nonmalignant disease.

Ascites↗
PubMed2001

Mechanisms of biosynthesis of protein-derived redox cofactors.

Prior to 1990, redox cofactors were widely believed to be small molecule, dissociable compounds. In the past 10 years, however, four novel redox cofactors have been discovered, each of which is derived from posttranslational modification of specific amino acids within their cognate enzymes. These include topa quinone, found in copper amine oxidases, lysine tyrosyl quinone, found in lysyl oxidase, tryptophan tryptophylquinone, found in methylamine dehydrogenase, and the cysteine-cross-linked tyrosine found in galactose oxidase. The processes by which these cofactors are formed, called biogenesis, is currently a major focus of mechanistic work in this field. In this review, the latest progress toward elucidating the various biogenesis mechanisms is discussed, along with possible linkages between the chemistries involved in catalysis and biogenesis.

Amino Acid Oxidoreductases↗
PubMed2001

Vaccination policies and programs: the federal government's role in making the system work.

Government agencies play a key role, from preclinical development to postlicensure monitoring, in making vaccinations one of the leading public health interventions. Important steps in this process include development and testing of vaccine antigens, evaluation of clinical and manufacturing data leading to licensure, formulation of recommendations, vaccine purchase, defining strategies to improve coverage, compensation of those injured by vaccine adverse reactions, and monitoring vaccine impact and safety. Using examples of newly recommended vaccines, this article describes the infrastructure that underlies a safe and effective program and highlights some of the opportunities and threats likely to impact the system in coming years.

Adverse Drug Reaction Reporting Systems↗
PubMed2001

Measurement of iris color using computerized image analysis.

PURPOSE: To develop a standardized method for measuring from iris photographs, light and dark segments of areas and densities of iris color. METHODS: Computerized image analysis was used to measure the iris photographs. The reproducibility of this method was studied in 30 normal eyes with three different colored irides, green-brown, blue-grey brown and yellow-brown. Three photographs were taken of each iris with a slit lamp camera at three different exposures at baseline. The photographs were repeated with exposure providing for the best reproducibility at 6.5 +/- 1.7 months as a first follow-up after baseline and 3.6 +/- 0.8 months following the first follow-up visit. At least one measurement was made for each photograph. RESULTS: The mean percent coefficient of variation (standard deviation of triplicate measurements/mean x 100) ranged from 1.0 to 4.1% for area and density measurements. Furthermore, the range of mean percent differences between baseline and follow-up visits ranged from 1.2 to 6.3%. CONCLUSION: We have developed a standardized method which appears suitable for measuring changes over time in iris color.

Aged↗
PubMed2001

Enhanced ocular hypotensive response to timolol in rabbits with prior dexamethasone treatment.

The purpose of this study was to determine glucocorticoid modulation of ocular pressure to timolol applied topically to rabbit eyes that were pretreated with dexamethasone. Rabbits were pretreated with five applications of topical 0.007% of dexamethasone (0.01% dexamethasone phosphate) or saline drops, administered at ten min intervals. The eyes were then treated with timolol maleate drops at concentrations of free base of 0.00007%, 0.0007%, 0.007% and 0.07%. An additional group of rabbits received dexamethasone pre-treatment only. Intraocular pressure was measured for the next four hr. Enhanced lowering of intraocular pressure was observed with dexamethasone pretreatment. Rabbits receiving the smaller dose of timolol had the least decrease in pressure. The most significant decreases in pressures occurred at 45 min after the administration of timolol with an average difference of 4.8 mm Hg between the timolol- and dexamethasone/timolol-treated eyes for the three largest concentrations of timolol. This synergism between glucocorticoids and beta-adrenergic blockers in lowering IOP may be potentially useful in the therapy of ocular hypertension and glaucoma.

Administration, Topical↗
PubMed2001

Emergency department overcrowding following systematic hospital restructuring: trends at twenty hospitals over ten years.

OBJECTIVE: Hospital restructuring often results in fewer inpatient beds, increased ambulatory services, and closures of hospitals or emergency departments (EDs). The authors sought to determine the impact of systematic hospital restructuring on ED overcrowding. METHODS: Time series analyses of average monthly overcrowding for EDs in Toronto, Ontario, Canada, from 1991 and 2000 (n = 20 hospitals, 120 months) were conducted. Autoregression models evaluated the rate of increase of overcrowding before and during systematic restructuring. A secondary analysis included total ED visits, patient age, and sex distribution as covariates. Seasonality was assessed by means of spectral analysis. RESULTS: Severe and moderate overcrowding averaged 3% and 14% of the time each month, respectively, over the whole period. Before restructuring (n = 74 months), severe and moderate overcrowding averaged 0.5% and 9% per month, respectively; during restructuring (n = 46 months), the monthly averages were 6% and 23%, respectively. Neither severe nor moderate overcrowding was increasing before restructuring. During restructuring, however, both increased significantly (severe 0.2% per month [p < 0.0001]; moderate 0.5% per month [p < 0.0001]). Similar results were found after controlling for ED utilization. Female gender independently predicted increased overcrowding; older age predicted reduced moderate overcrowding; number of total visits was not a predictor. Spectral analysis revealed significant seasonality in overcrowding. CONCLUSIONS: Hospital restructuring was associated with increased ED overcrowding, even after controlling for utilization and patient demographics. Restructuring should proceed slowly to allow time for monitoring of its effects and modification of the process, because the impact of incremental reductions in hospital resources may be magnified as maximum operating capacity is approached.

Adult↗
PubMed2001

Evaluation of a medium (STGG) for transport and optimal recovery of Streptococcus pneumoniae from nasopharyngeal secretions collected during field studies.

Field studies of Streptococcus pneumoniae (pneumococci) nasopharyngeal (NP) colonization are hampered by the need to directly plate specimens in order to ensure isolate viability. A medium containing skim milk, tryptone, glucose, and glycerin (STGG) has been used to transport and store NP material, but its ability to preserve pneumococci has not been evaluated. Our objective was to qualitatively and semiquantitatively evaluate the ability of STGG to preserve pneumococci in NP secretions. Entwined duplicate calcium alginate NP swab samples were obtained from children. One swab was plated directly onto a gentamicin blood agar plate; the other was placed in STGG. Growth from the directly plated specimen was compared with growth from an STGG aliquot immediately cultured or stored at -70 degrees C for 9 weeks, -20 degrees C for 9 weeks, or 4 degrees C for 5 days. Of 186 specimens, 96 (52%) were positive for pneumococci from the direct plating; 94 (98%) of these were positive from the fresh STGG specimen. Pneumococci were recovered from all 38 positive specimens frozen at -70 degrees C, all 18 positive specimens frozen at -20 degrees C, and 18 of 20 positive specimens stored at 4 degrees C. Recovery of pneumococci after storage of NP material in STGG medium at -70 degrees C is at least as good as that from direct plating. Storage at -20 degrees C is also acceptable. Storage at 4 degrees C for 5 days is not ideal.

Child, Preschool↗
PubMed2001

The effect of a community intervention trial on parental knowledge and awareness of antibiotic resistance and appropriate antibiotic use in children.

BACKGROUND: Overuse of antibiotics for children's upper respiratory infections is widespread and contributes to the emergence of antibiotic-resistant bacteria. OBJECTIVE: To assess changes in knowledge and awareness regarding antibiotic resistance and appropriate antibiotic use after community-wide educational interventions to reduce inappropriate antibiotic use. DESIGN: Baseline survey conducted during June through July 1997 and postintervention survey of baseline participants during June through August 1998. SETTING: Communities in northern Wisconsin. PARTICIPANTS: Parents of 729 randomly selected children <4 years of age were called until 215 in each of the intervention and control areas were reached. Of the 430 baseline participants, 365 (85%) participated in the postintervention survey. INTERVENTION: Parent-oriented activities included distribution of materials and presentations. Physician-oriented activities included formal presentations and small group meetings. OUTCOME MEASURE: Change in awareness about antibiotic resistance and knowledge about antibiotic indications. RESULTS: A higher proportion of parents in the intervention area (53%) were exposed to 2 or more local educational messages, compared with the control area (23%). From the baseline to the postintervention survey, the percentage of parents with a high degree of antibiotic resistance awareness increased more in the intervention area (58% to 73%) than in the control area (60% to 65%). In the intervention area, there was also a larger increase in knowledge regarding appropriate indications for antibiotic use, compared with the control area. The proportion of parents who expected an antibiotic for their child and did not receive one declined in the intervention area (14% to 9%), while it increased in the control area (7% to 10%). In addition, the percentage of parents in the intervention area who brought their child to another physician because they did not receive an antibiotic decreased (5% to 2%), while it increased in the control area (2% to 4%). CONCLUSION: Parental knowledge and awareness about antibiotic indications and antibiotic resistance can be changed with educational interventions directed at parents and clinicians.

Adult↗
PubMed2001

Invasive group A streptococcal infection and nonsteroidal antiinflammatory drug use among children with primary varicella.

OBJECTIONS: To test the hypothesis that nonsteroidal antiinflammatory drug use increases the risk of necrotizing soft tissue infections and, secondarily, all invasive group A streptococcal (GAS) infections in children with primary varicella infection. METHODS: We conducted a prospective, multicenter case-control study among children <19 years old. Cases were children hospitalized with primary varicella complicated by invasive GAS infection or necrotizing soft tissue infection identified by a network of 45 pediatric infectious disease specialists located throughout the United States. Controls were children with uncomplicated primary varicella residing in the same communities as the cases. Data on medical history, clinical features of the varicella infection, signs and symptoms of infectious complications, and medication use were collected by structured telephone interviews. Univariate and multivariate matched odds ratios were calculated using conditional logistic regression. RESULTS: Between June 1996 and September 1998, 52 cases of invasive GAS infection, including 21 with necrotizing soft tissue infection, and 172 controls with uncomplicated primary varicella were enrolled. Risk of invasive GAS infection was increased among children who were nonwhite (multivariate odds ratio [OR] 3.8, 95% confidence interval [CI]: 1.4-11), living in low-income households (OR 5.1, 95% CI: 1.7-15), exposed to varicella at home (OR 6.4, 95% CI: 2.6-16), or had a persistent high fever (OR 9.6, 95% CI: 2.8-33). Antipyretic regimen was associated with several measures of varicella illness severity among the controls. The risk of necrotizing soft tissue infection was not associated with the use of ibuprofen before the development of signs or symptoms of this complication (OR 1.3, 95% CI: 0.33-5.3). Risk of any invasive GAS infection was increased among children who had received ibuprofen (OR 3.9, 95% CI: 1.3-12), but not acetaminophen (OR 1.2, 95% CI: 0.50-3.0). However, there was no evidence of increasing risk with increasing duration of ibuprofen use. Subgroup analyses revealed that the risk of invasive GAS infection was increased only among children who had received both acetaminophen and ibuprofen. CONCLUSIONS: These data do not support the hypothesis that nonsteroidal antiinflammatory drugs, or ibuprofen in particular, increase the risk of necrotizing GAS infections. A statistically significant association was observed between nonnecrotizing invasive GAS infection and ibuprofen use; however, because of potential confounding, the meaning of this unexpected result is unclear. Nonetheless, these data suggest that parents use ibuprofen or ibuprofen together with acetaminophen to treat high fever and severe illness, which seems to identify children at high risk for invasive GAS infection.

Acetaminophen↗
PubMed2001

A community intervention trial to promote judicious antibiotic use and reduce penicillin-resistant Streptococcus pneumoniae carriage in children.

OBJECTIVE: Inappropriate use of antibiotics is common in primary care, and effective interventions are needed to promote judicious antibiotic use and reduce antibiotic resistance. The objective of this study was to assess the impact of parent and clinician education on pediatric antibiotic prescribing and carriage of penicillin-nonsusceptible Streptococcus pneumoniae in child care facilities. METHODS: A nonrandomized, controlled, community intervention trial was conducted in northern Wisconsin Clinicians. Clinic staff received educational materials and small-group presentations; materials were distributed to parents through clinics, child care facilities, and community organizations. Prescribing data were analyzed for 151 clinicians who provided primary pediatric care; nasopharyngeal carriage of penicillin-nonsusceptible S pneumoniae was assessed for 664 children in the baseline period (January-June 1997) and for 472 children in the postintervention period (January-June 1998). RESULTS: The median number of solid antibiotic prescriptions per clinician declined 19% in the intervention region and 8% in the control region. The median number of liquid antibiotic prescriptions per clinician declined 11% in the intervention region, compared with an increase of 12% in the control region. Retail antibiotic sales declined in the intervention region but not in the control region. Among participating children in child care facilities, there were no significant differences in antibiotic use or penicillin-nonsusceptible S pneumoniae colonization between the intervention and control regions. CONCLUSIONS: A multifaceted educational program for clinicians and parents led to community-wide reductions in antibiotic prescribing, but in child care facilities, there was no apparent impact on judicious antibiotic use or colonization with drug-resistant S pneumoniae. Longer follow-up time or greater reductions in antibiotic use may be required to identify changes in the pneumococcal susceptibility.

Anti-Bacterial Agents↗