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B Schwartz

Publications and source records attributed to B Schwartz.

At least 109 records · Page 6Linked to original sources
PubMed1998

Long-term, high level in vivo gene expression after electric pulse-mediated gene transfer into skeletal muscle.

Gene delivery to skeletal muscle is a promising strategy for the treatment of muscle disorders and for the local or systemic secretion of therapeutic proteins. However, current DNA delivery technologies have to be improved. We report very efficient luciferase gene transfer into muscle fibres obtained through the delivery of square-wave electric pulses of moderate field strength (100-200 V/cm) and of long duration (20 ms) to muscle previously injected with plasmid DNA. This intramuscular 'electrotransfer' method increases reporter gene expression by more than 100 times. It is noteworthy that this expression remains high and stable for at least 9 months. Moreover, intramuscular electrotransfer strongly decreases the interindividual variability usually observed after plasmid DNA injection into muscle fibres. Therefore, DNA electrotransfer in muscle possesses broad potential applications in gene therapy and for physiological, pharmacological and developmental studies.

Animals↗
PubMed1998

Neurocircuitry of conditioned inhibition of analgesia: effects of amygdala, dorsal raphe, ventral medullary, and spinal cord lesions on antianalgesia in the rat.

Pain inhibition (analgesia) is produced by learned danger signals and inhibited by learned safety signals (antianalgesia). Conditioned analgesia is mediated by brain-to-spinal pathways releasing spinal endogenous opiates. Spinal morphine mimics learned danger signals in producing analgesia, which is inhibited by antianalgesia. The circuitry mediating antianalgesia is unknown. These experiments demonstrate that raphe dorsalis, raphe magnus, and spinal dorsolateral funiculus lesions abolish antianalgesia. Other lesions had no effect on antianalgesia. More important, lesions that blocked development of conditioned analgesia did not block development of antianalgesia. Thus, neural circuitries mediating analgesia and antianalgesia were found to be distinct, and conditioned inhibition of analgesia was found to act by inhibiting the most distal part of the conditioned analgesia circuit, namely, the spinal cord.

Amygdala↗
PubMed1998

Invasive group A streptococcal disease in metropolitan Atlanta: a population-based assessment.

Active, population-based surveillance for invasive group A streptococcal (GAS) disease was conducted in laboratories in metropolitan Atlanta from 1 January 1994 through 30 June 1995. Clinical and laboratory records were reviewed and isolates characterized. One hundred and eighty-three cases of invasive GAS disease were identified (annual incidence, 5.2 cases/100,000). The incidence was highest among blacks (9.7/100,000 per year; relative risk (RR), 1.92; confidence interval (CI), 1.69-2.19; P < .0001) and the elderly, particularly nursing home residents (RR, 13.66; CI, 7.07-26.40; P < .0001). The mean age of patients was 41.3 years (range, 0-95 years). Skin and soft-tissue infections were most common. Mortality was 14.4%; risk of death was significantly higher for patients with streptococcal toxic shock syndrome (STSS) (RR, 9.73; CI, 3.34-29; P = .0008) and individuals infected with M-type 1 (RR, 7.40; CI, 1.5-16; P = .0084). Fourteen percent of invasive GAS infections were STSS and 3% were necrotizing fasciitis. Invasive GAS disease was associated with varicella infection in children (RR, 12.19; CI, 5.58-26.62; P < .0001). M (or emm) types included M1 (16%), M12 (12%), and M3 (11%). Continued study of GAS disease is essential to further define risk factors and risk of secondary cases and to develop effective prevention strategies.

Adolescent↗
PubMed1998

The rationale for population-based surveillance for Haemophilus influenzae type b meningitis.

Although Haemophilus influenzae type b (Hib) conjugate vaccines have been spectacularly successful, nearly eradicating Hib disease in countries where used routinely, they are relatively expensive. In many countries the incidence of Haemophilus influenzae type b (Hib) disease is uncertain, and it is unclear whether the local burden of Hib disease warrants the costs of adding Hib vaccine to the routine immunization program. Population-based surveillance to assess the local burden of Hib disease can help decision makers with this process. Although pneumonia is more common than meningitis, surveillance for Hib meningitis and invasive disease is likely to be more feasible and efficient than surveillance for Hib pneumonia. Standardization of laboratory methods for the isolation and identification of H. influenzae from CSF specimens is essential to successful surveillance. Should a country decide to introduce Hib conjugate vaccine as a routine immunization, population-based surveillance data collected before and after the introduction of vaccine can be used to monitor its impact. Finally population-based surveillance for bacterial meningitis also can provide information on the incidence of pneumococcal and meningococcal infections and on serogroup or serotype distributions that will be important when evaluating the new vaccines for those pathogens that are being developed.

Child, Preschool↗
PubMed1998

A streptococcal score card revisited.

OBJECTIVE: To evaluate the utility of a simple scoring system as a predictor of obtaining a positive throat culture for group A streptococci (GAS). DESIGN: Prospective descriptive study. Scores were assigned prior to the availability of the results of throat cultures. SETTING: Emergency department and walk-in clinic of the Children's Hospital of Pittsburgh. PATIENTS: Patients were 365 children between the ages of two and 16 years with acute onset of sore throat and a history of or documentation of fever within the preceding 24 hours. INTERVENTIONS: A streptococcal score was assigned on the basis of a 6-point schema in which the features were 1) age; 2) season; 3) temperature of at least 38.3 degrees C; 4) adenopathy; 5) pharyngeal erythema, edema, or exudate; and 6) no symptoms of a viral upper respiratory infection (conjunctivitis, rhinorrhea, or cough). A throat culture was performed for the isolation of GAS. MAIN OUTCOME MEASURE: Positive predictive value of the streptococcal score in identifying children with a positive throat culture for GAS. RESULTS: A score of 5 or 6 predicted a positive culture for GAS in 59 and 75% of children, respectively. In patients with evidence of acute pharyngitis, the combination of age between five and 15 years, fever and absence of upper respiratory symptoms predicted a positive culture for GAS in 72% of patients. CONCLUSIONS: The score can be used to predict the likelihood that a throat culture will be positive for GAS.

Acute Disease↗
PubMed1998

Opsonic antibodies to the surface M protein of group A streptococci in pooled normal immunoglobulins (IVIG): potential impact on the clinical efficacy of IVIG therapy for severe invasive group A streptococcal infections.

The surface M protein of group A streptococci (GAS) is one of the major virulence factors for this pathogen. Antibodies to the M protein can facilitate opsonophagocytosis by phagocytic cells present in human blood. We investigated whether pooled normal immunoglobulin G (IVIG) contains antibodies that can opsonize and enhance the phagocytosis of type M1 strains of GAS and whether the levels of these antibodies vary for different IVIG preparations. We focused on the presence of anti-M1 antibodies because the M1T1 serotype accounts for the majority of recent invasive GAS clinical isolates in our surveillance studies. The level of anti-M1 antibodies in three commercial IVIG preparations was determined by enzyme-linked immunosorbent assay (ELISA), and the opsonic activity of these antibodies was determined by neutrophil-mediated opsonophagocytosis of a representative M1T1 isolate. High levels of opsonic anti-M1 antibodies were found in all IVIG preparations tested, and there was a good correlation between ELISA titers and opsonophagocytic activity. However, there was no significant difference in the levels of opsonic anti-M1 antibodies among the various IVIG preparations or lots tested. Adsorption of IVIG with M1T1 bacteria removed the anti-M1 opsonic activity, while the level of anti-M3 opsonophagocytosis was unchanged. Plasma was obtained from seven patients with streptococcal toxic shock syndrome who received IVIG therapy, and the level of anti-M1 antibodies was assessed before and after IVIG administration. A significant increase in the level of type M1-specific antibodies was found in the plasma of all patients who received IVIG therapy (P < 0.006). The results reveal another potential mechanism by which IVIG can ameliorate severe invasive group A streptococcal infections.

Animals↗
PubMed1998

Current attitudes regarding use of antimicrobial agents: results from physician's and parents' focus group discussions.

Antibiotics are widely prescribed for children with nonspecific upper respiratory tract infections, contributing to the recent emergence of resistant pneumococci. To understand the reasons for the overprescription of antibiotics, we conducted focus groups with parents and with pediatricians and family physicians to assess their attitudes regarding the use of antibiotics. Physicians asserted that their own antibiotic prescribing could be safely reduced. Parental expectation to receive antibiotics was a major factor influencing their overuse of antibiotics. Parents indicated that they would be satisfied with the medical visit even if antibiotics were not prescribed, provided the physician explained the reasons for the decision. This study highlights differences in physician and parent perceptions about antibiotic overuse and suggests that educational efforts to narrow this communication gap will be important for improving antibiotic use.

Adult↗
PubMed1998

Rapid hematopoietic recovery after multicycle high-dose chemotherapy: enhancement of filgrastim-induced progenitor-cell mobilization by recombinant human stem-cell factor.

PURPOSE: To assess the mobilization potential and safety of recombinant human stem-cell factor (SCF) when coadministered with filgrastim to untreated women with poor-prognosis breast cancer. PATIENTS AND METHODS: Eligible women had breast cancer with 10 or more positive axillary nodes, or estrogen receptor-negative tumor with 4 positive nodes, or stage III disease. Patients were randomized to receive SCF plus filgrastim or filgrastim alone. Filgrastim 12 microg/kg daily was administered for 6 days by continuous subcutaneous infusion. SCF was administered by daily subcutaneous injection at 5, 10, or 15 microg/kg concurrent with filgrastim for 7 days, or 10 microg/kg daily starting 3 days before filgrastim for a total of 10 days (SCF pretreatment). Apheresis was performed on days 5, 6, and 7 of filgrastim administration. Patients then had three cycles of epirubicin 200 mg/m2 and cyclophosphamide 4 g/m2 every 28 days, each supported by one third of the apheresis product. RESULTS: Sixty-two women were treated. Greater yields occurred in patients who received SCF 10 microg/kg daily plus filgastim than those who received filgrastim alone (P=.013 for CD34+ cells; P=.07 for granulocyte-macrophage colony-forming cells [GM-CFCs]). The difference was more marked with SCF-pretreatment than concurrent SCF. Fewer aphereses were required to reach the predetermined target of peripheral-blood progenitor/stem cells (PBPCs) in women who received SCF. SCF was generally well tolerated. Hematologic recovery was rapid after each of the three cycles of chemotherapy. There was no difference in recovery between the different treatment groups. CONCLUSION: Mobilization of PBPCs by filgrastim is significantly enhanced by coadministration of SCF, and commencing SCF before filgrastim can optimize this effect. SCF has the potential to reduce the number of aphereses required to collect a target number of PBPCs.

Adult↗
PubMed1998

Sodium butyrate induces retinoblastoma protein dephosphorylation, p16 expression and growth arrest of colon cancer cells.

Sodium butyrate causes alteration of colon cancer cell morphology and biology towards that of a more differentiated phenotype. The retinoblastoma gene encodes a nuclear phosphoprotein (pRb) present in a wide range of human cancer cell lines including colon cancer cell lines. pRB is synthesized throughout the cell cycle and phosphorylated in a phase specific manner: the predominant proteins in G0/G1 are the unphosphorylated species (110 kD) whereas phosphorylated pRb (112-114 kD) are in S and G2. 110 kD pRb binds transcription factors and prevents transcription of responsive genes such as the gene for thymidine kinase, which are expressed in late G1. The precise mechanisms controlling cell arrest are unknown, but recent data suggest that cyclin-dependent kinase inhibitors such as p16 may play a role. The aim of the present study was to assess the effect of sodium butyrate on cell cycle staging, thymidine kinase activity, phosphorylation of the pRb protein and expression of p16. We show that sodium butyrate treatment induces differentiation of LS174T colon cancer cells, inhibits thymidine kinase activity concomitantly with induction of pRb dephosphorylation, p16 transcription and cell cycle arrest at G0/G1. Initial dephosphorylation was observed 24 h after treatment of LS174T cells with sodium butyrate, whereas complete shift to the dephosphorylated form was observed 3 days after treatment. Induction of pRb dephosphorylation by sodium butyrate preceded inhibition of growth and the specific cell cycle arrest. RNase protection assay with a p16 specific riboprobe showed undetectable levels in proliferating cells to several fold increase in differentiated colonocytes. In conclusion, the results provide evidence for a specific cellular mechanism of butyrate induced growth arrest and differentiation of a colon cancer cell line.

Alkaline Phosphatase↗
PubMed1997

Ability of single-site mutants of citrate synthase to catalyze proton transfer from the methyl group of dethiaacetyl-coenzyme A, a non-thioester substrate analog.

The catalytic strategies of enzymes (such as citrate synthase) whose reactions require the abstraction of the alpha-proton of a carbon acid remain elusive. Citrate synthase readily catalyzes solvent proton exchange of the methyl protons of dethiaacetyl-coenzyme A, a sulfur-less, ketone analog of acetyl-coenzyme A, in its ternary complex with oxaloacetate. Because no further reaction occurs with this analog, it provides a uniquely simple probe of the roles of active site interactions on carbon acid proton transfer catalysis. In view of the high reactivity of the analog for proton transfer to the active site base, its failure to further condense with oxaloacetate to form a sulfur-less analog of citryl-coenzyme A was unexpected, although we offer several possible explanations. We have measured the rate constants for exchange, k(exch), at saturating concentrations of the analog for six citrate synthase mutants with single changes in active site residues. Comparisons between the values of k(exch) are straightforward in two limits. If the rate of exchange of the transferred proton with solvent protons is rapid, then k(exch) equals the forward rate constant for proton transfer, and k(exch) values for different mutants compare directly the rate constants for proton transfer. If the exchange of the transferred proton with protons in the bulk solution is the slow step and the equilibrium constant for proton transfer is unfavorable (as is likely), then k(exch) equals the product of the equilibrium constant for proton transfer and the rate constant for exchange of the transferred proton with bulk solvent. If that exchange rate with bulk solution remains constant for a series of mutant enzymes, then k(exch) values compare the equilibrium constants for proton transfer. The importance of the acetyl-CoA site residues, H274 and D375, is confirmed with D375 again implicated as the active site base. The results with the series of oxaloacetate site mutants, H320X, strongly suggest that activation of the first substrate, oxaloacetate, through carbonyl bond polarization, not just oxaloacetate binding in the active site, is required for the enzyme to efficiently catalyze proton transfer from the methyl group of the second substrate.

Acetyl Coenzyme A↗
PubMed1997

Effects of the carcinogen dimethylhydrazine (DMH) on the function of rat colonic crypts.

Rats injected with dimethylhydrazine for 5 weeks (DMH, 40 mg/kg body weight) invariably develop colonic cancer after a latency of some 10-14 weeks. Preliminary studies have suggested that Na+ absorption by surface colonic crypt cells is attenuated in the preneoplastic period (8-12 weeks after the first injection of DMH). The present study of glucocorticoid-treated (dexamethasone 6 mg/kg body weight, s.c. 3 days or triamcinolone 30 mg/kg body weight, s.c. 3 days) rats was undertaken to examine the ion transport properties of rat distal colon during this period in more detail. Ussing chamber studies of the distal colon and whole-cell patch-clamp measurements in surface cells, mid-crypt cells and crypt-base cells obtained from isolated crypts were performed. In Ussing chamber studies the equivalent short-circuit current inhibitable by amiloride (10 micromol/l) DMH-treated rats was about 40% of control. In addition, the hyperpolarizing effect of amiloride (10 micromol/l) on membrane voltage (Vm) was strongly attenuated in surface and mid-crypt cells of DMH-treated rats. Carbachol (CCH, 100 micromol/l), which predictably hyperpolarized surface, mid-crypt cells and crypt-base cells of control rats, had no significant effect on Vm in DMH-treated rats, but increased membrane conductance (Gm) significantly. This indicates that CCH probably activates both Cl- and K+ channels in all three colonic crypt compartments in the DMH-treated rats. Forskolin (5 micromol/l), which has the most pronounced effect in crypt-base cells in control rats, depolarized Vm and enhanced Gm in all three compartments in DMH-treated rats. These data indicate that DMH profoundly alters Na+ and Cl- transport in colonic crypts prior to the appearance of colonic adenocarcinoma and that these effects can be summarized as follows: (1) the Na+ conductance of surface cells is attenuated; (2) cells along the length of the crypt-lumen axis tend to lose their normal response to CCH and instead show simultaneous and comparable increases in K+and Cl- conductances; (3) the effect of forskolin is enhanced along the entire crypt axis. As a result colonic crypt transport is shifted to predominant Cl- secretion, findings which are characteristic of colonic carcinoma cell lines such as HT29 and T84 cells.

Animals↗
PubMed1997

Characterization of sodium and chloride conductances in preneoplastic and neoplastic murine colonocytes.

Glucocorticoids, such as dexamethasone, induce amiloride-sensitive Na+ conductances in rat distal colon epithelium. The activity of these conductances diminishes from the surface to the base of the crypt whereas cAMP-stimulated Cl- secretion decreases from the crypt base to the surface. These gradients are likely to be perturbed during carcinogenesis. We therefore determined the magnitude of Na+ and Cl- conductances in colonocytes isolated from normal and carcinogen-treated rats. Colon carcinogenesis was induced by injection of dimethylhydrazine (DMH) (18 mg/kg) for 5 weeks. Before sacrifice animals were treated for 3 days with dexamethasone. Colonocyte populations from the surface to the crypt base (C1-C5) were harvested from the distal colon by a Ca2+-chelating procedure. The activity of Na+ conductances was determined by uptake of 22Na+ by surface and crypt colonocyte populations and by membrane vesicles in the presence and absence of 10 microM amiloride. In control rats Na+ conductance was highest in surface colonocytes and absent in the crypt base. As early as 2 weeks after initiation of DMH treatment amiloride-inhibited Na+ uptake was virtually absent in the upper crypt. Transcriptional assessment of the alpha-, beta- and gamma-subunits that constitute the epithelial Na+ channel revealed that DMH treatment reduces the expression of beta-subunit mRNA. We then examined 36Cl- efflux from isolated colonocytes of normal and carcinogen-treated rats in response to forskolin (0.01 mM). Forskolin induced a marked rise in cAMP in lower crypt cells concomitant with a significant stimulation of 36Cl- efflux. Intracellular cAMP increased in upper crypt cells in response to forskolin without an increase in 36Cl- efflux. By contrast, upper crypt colonocytes from DMH-treated rats showed forskolin-stimulated efflux beginning 4 weeks after initiation of treatment. We conclude that induction of Na+ conductances by glucocorticoids is inhibited during the early stages of chemical carcinogenesis due to lack of induction of the beta-subunit of the channel. By contrast, Cl- transport is stimulated both in surface and lower crypt cell compartments during different stages of chemical carcinogenesis.

Amiloride↗