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Biomedical subjects

B J Smith

Publications and source records attributed to B J Smith.

At least 307 records · Page 17Linked to original sources
PubMedDate not supplied

Prolonged in vivo residence times of antibody fragments associated with albumin.

Antibody fragments can be expressed at a high level in microbial systems, but they may have limited therapeutic value because they are rapidly eliminated from the body. We demonstrate here that site-specific conjugation or binding of bacterially derived Fab' to the long-lived protein serum albumin allows full retention of the antibody's binding characteristics while imparting the albumin's longevity in vivo. In rats the area under the curve for Fab' conjugated to rat serum albumin was 17-fold greater than for the control of Fab' conjugated to cysteine. Again, a bispecific F(ab')(2) with specificity for rat serum albumin showed an area under the curve about 8-fold greater than did a F(ab')(2) without specificity to albumin. Genetic fusions of scFv to albumin were similarly long-lived and could be expressed in yeast to provide the basis of a cost-effective production system.

Animals↗
PubMedDate not supplied

The oxidation of 4-aminobiphenyl by horseradish peroxidase.

The oxidation of the carcinogen 4-aminobiphenyl (4-ABP) catalyzed by the model peroxidase enzyme horseradish peroxidase (HRP) was investigated. 4-ABP served as a reducing cosubstrate for HRP during the enzyme-catalyzed reduction of the synthetic hydroperoxide, 5-phenyl-4-penten-1-yl hydroperoxide, to its corresponding alcohol. Spectral analysis during the incubation of HRP, 4-ABP, and H2O2 showed an increase in absorbance at 230 and 325 nm and decrease at 270 nm, suggesting metabolite formation. Oxygen consumption was not detected in incubations of HRP, 4-ABP, and H2O2. However, oxygen uptake was observed after the addition of glutathione, which indicated that a free radical metabolite of 4-ABP was formed by the peroxidase. The 4-ABP free radical reacted with glutathione forming a glutathionyl radical which, in turn, reacted with and consumed oxygen. HPLC analysis of organic extracts of incubations with HRP, [3H]-4-ABP, and H2O2 showed the formation of one major peak identified by mass spectroscopy as 4,4'-azobis(biphenyl). The addition of glutathione to the incubations decreased the formation of 4-ABP metabolites, suggesting a reduction of the 4-ABP free radical and/or the formation of glutathione conjugates. Subsequent HPLC analysis of incubations including [35S]glutathione indicated formation of several unidentified 4-ABP-glutathione conjugates as well as recovery of parent compound. These studies suggest that HRP metabolizes 4-ABP by a one-electron oxidation mechanism, resulting in formation of a free radical. This radical can either react with a second radical to form azobis(biphenyl), be reduced by glutathione back to parent, or react with glutathione to form glutathione conjugates.

Aminobiphenyl Compounds↗
PubMedDate not supplied

Mutagenic activation of benzidine requires prior bacterial acetylation and subsequent conversion by prostaglandin H synthase to 4-nitro-4'-(acetylamino)biphenyl.

We have used the Ames test in combination with prostaglandin H synthase (PHS) to study the bioactivation of benzidine as well as other aromatic amines. Previous investigations established that the formation of benzidine mutagens by PHS is dramatically enhanced in Salmonella typhimurium strains with high levels of acetyl CoA-dependent arylamine N-acetyltransferase/arylhydroxylamine O-acetyltransferase activity despite the fact that acetylation of aromatic amines decreases their susceptibility to oxidation by peroxidases. In this study, we used a new strain (YG1012) that has very high acetylation capability to investigate the metabolism and mutagenicity of benzidine and N-acetylbenzidine catalyzed by PHS (from ram seminal vesicle microsomes) and horseradish peroxidase (HRP). YG1012 bacteria rapidly acetylated benzidine to N-acetylbenzidine and N,N'-diacetylbenzidine. Preincubation of the bacteria with benzidine before addition of PHS increased the mutagenicity. Under conditions identical to those used to assess mutagenicity, PHS metabolized benzidine rapidly, but the substrate was not totally consumed, with about 40% of the original concentration remaining intact. These data suggest that conversion to N-acetylbenzidine may be the initial step in the bioactivation of benzidine in the PHS-mediated Ames assay. N-Acetylbenzidine is a cosubstrate for PHS peroxidase activity as measured by 5-phenyl-4-pentenyl hydroperoxide reduction, spectral changes, and formation of protein adducts. N-Acetylbenzidine was converted to mutagens by PHS but not HRP, with enhanced mutagenicity observed in bacteria with high acetylation activity. We used reverse- phase HPLC to characterize the metabolites of N-acetylbenzidine formed by PHS and HRP.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetamides↗
PubMedDate not supplied

Ovarian toxicity of 4-vinylcyclohexene and related olefins in B6C3F1 mice: role of diepoxides.

4-Vinylcyclohexene (VCH) is an ovarian toxicant in mice. Studies have established that bioactivation of VCH to epoxides is required for its ovotoxicity, with vinylcyclohexene diepoxide being the most potent epoxide of VCH in terms of follicular depletion. To determine the role of the diepoxide in the ovarian toxicity of VCH and related compounds, a structure-activity study was conducted. Following administration (ip) of VCH for 30 days, a significant depletion of ovarian follicles was observed. No alteration of small ovarian follicle counts occurred following treatment with structural analogues of VCH (vinylcyclohexane, ethylcyclohexene, and cyclohexene) that contain only a single unsaturated site. These VCH analogues were converted to monoepoxides both in vitro and in vivo. In addition, when the monoepoxide forms of the VCH analogues were administered to mice, they were not ovotoxic. These results indicate that vinylcyclohexene diepoxide may be the ultimate ovotoxic metabolite of VCH. A diepoxide was also shown to be critical for butadiene- and isoprene-induced follicular loss. Butadiene monoepoxide, butadiene diepoxide, and isoprene were ovotoxic. In contrast, the monoepoxide, epoxybutane, was not ovotoxic. The ovotoxicity of these compounds correlated with their chemical reactivity as assessed by alkylation of nicotinamide. Vinylcyclohexene diepoxide and butadiene diepoxide had a 3.5- to 10-fold higher chemical reactivity as compared to their monoepoxide precursors and structurally related monoepoxides. Thus, a relationship exists between chemical reactivity and ovotoxicity. Only those compounds which are metabolized to a diepoxide or are a diepoxide were ovotoxic. The formation of these diepoxide metabolites may in turn be linked to the ovarian toxicity and carcinogenicity of these olefins.

Alkenes↗
PubMedDate not supplied

Sequence of human tissue inhibitor of metalloproteinases and its identity to erythroid-potentiating activity.

Collagen fibres form the stable architecture of connective tissues and their breakdown is a key irreversible step in many pathological conditions. The destruction of collagen is usually initiated by proteinases, the best known of which is the metalloproteinase collagenase (EC 3.4.24). Collagenase and related metalloproteinases are regulated at the level of their synthesis and secretion, through the action of specific stimuli such as hormones and cytokines, and also at the level of their extracellular activity through the action of a specific inhibitor, TIMP (tissue inhibitor of metalloproteinases), which irreversibly forms inactive complexes with metalloproteinases. Although the mechanisms governing the production of TIMP are unknown, immunologically identical forms of this glycoprotein have been detected in a wide variety of human body fluids and cell and tissue culture media. We therefore suggested that under physiological conditions this ubiquitous inhibitor predominates over active metalloproteinases and that tissue destruction may arise when any perturbation of this controlling excess arises. However, further progress towards testing this theory has been hindered by a lack of knowledge about the structure of TIMP and insufficient material for studying it in model systems. Here we describe the structure of TIMP predicted from its complementary DNA, its synthesis in Escherichia coli and transfected animal cells, and the finding that it is identical to a protein recently reported to have erythroid-potentiating activity (EPA).

Amino Acid Sequence↗
PubMedDate not supplied

Federal early childhood special education policy: a model for the improvement of services for children with disabilities.

Services in early childhood special education for children with disabilities, birth through 5 years, and their families have expanded and improved substantially in the past 25 years. The federal government, through legislation, regulation, and a variety of incentives, has played an integral role in this progress. The authors review the evolution of federal education policy in early childhood and the accomplishments achieved, including the development of the Handicapped Children's Early Education Program, the Early Childhood Research Institutes, and Public Law 99-457, the Handicapped Infant and Toddler Program (Part H). This history can serve as a model for federal involvement in the improvement of services for other groups of individuals with special needs.

Child, Preschool↗
PubMedDate not supplied

The genetics of retinoblastoma and current diagnostic testing.

We review the genetics of retinoblastoma and the most recent molecular detection methods. Retinoblastoma, the most common intraocular tumor in children, occurs in either a heritable or non-heritable form. The heritable form, which is highly penetrant and predisposes individuals to a considerably greater second tumor risk, can be distinguished most definitively through the use of genetic testing. Genetic testing for individuals and families suspected of carrying the heritable mutations can help ensure that more comprehensive treatment plans and accurate genetic counseling for affected individuals and their families are provided.

DNA, Neoplasm↗
PubMedDate not supplied

Cost comparison of at-home treatment of deep venous thrombosis with low molecular weight heparin to inpatient treatment with unfractionated heparin.

AIMS: Low molecular weight heparins (LMWH) permit safe and effective treatment of uncomplicated deep venous thrombosis (DVT) at home. The aim of this study was to evaluate the cost minimization, cost shifting and patient satisfaction associated with at-home DVT treatment using the LMWH enoxaparin, compared to standard inpatient care in an Australian health-care setting. METHODS: Subjects presenting with a principal diagnosis of uncomplicated DVT to the Emergency Department at The Queen Elizabeth Hospital, Adelaide, were recruited over 1997-1999. Costs to the hospital, to Federal funding (Medicare) and to patients were tracked prospectively, and satisfaction was also measured. Subjects were matched to historical controls (1994-1997) for age, gender and level of comorbidity (same or lower) by two medical officers who were blinded to costs. Control costs were obtained using the clinical costing system Trendstar, and adjusted for consumer price index. RESULTS: Twenty-eight subjects participated in the at-home programme. Of these, 26 were discharged without any inpatient admission (including one who agreed to self-injection) and two were admitted briefly. Audit demonstrated that only 29% of eligible subjects were managed at home. Mean (SEM) total treatment cost was $756 (76) per patient for at-home, and $2,208 (146) for controls. Minimal cost shifts to patients and to Medicare occurred, and satisfaction was high. CONCLUSIONS: At-home treatment of uncomplicated DVT using enoxaparin in an Australian metropolitan setting provides effective cost minimization, with little cost-shifting. Our cost minimisation estimates are conservative as most at-home subjects received enoxaparin twice daily (now used once per day) and controls had at least as high comorbidity. However, uptake of the at-home programme was limited.

Anticoagulants↗
PubMedDate not supplied

Early sexual activity among adolescents in small towns and rural areas: race and gender patterns.

A 1987 survey of 758 eighth-grade students from three rural counties in Maryland revealed that 61 percent of males and 47 percent of females have engaged in sexual intercourse, and that 77 percent of black students and 40 percent of whites have ever had intercourse. A logistic regression analyzing the effects of race and gender shows that the odds that young black teenagers would have had intercourse are over five times those for whites, and that the odds for males are about twice those for females. The introduction of developmental, individual, academic and behavioral factors into the regression model has little effect on these odds ratios. Separate logistic analyses of four subgroups--white males, white females, black males and black females--reveal no consistent associations between sexual activity and the factors examined. For example, such types of problem behavior as cigarette smoking and use of alcohol or certain other drugs are associated with the likelihood of sexual activity, but the specific type of behavior involved differs by subgroup: Cigarette smoking is related to an increased likelihood of sexual activity just among white females, while alcohol consumption is associated with sexual experience among black females and white males only. Use of drugs other than marijuana or alcohol is linked to a 5-9 times greater risk of sexual activity among whites, but not to any significantly increased risk among blacks, whereas living in a town (rather than in the country) is significantly associated with the likelihood of sexual intercourse among both white and black males, but not among females of either race.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Measurement of plasma prostaglandin F2 alpha using capillary gas chromatography negative ion chemical ionization mass spectrometry.

A stable isotope dilution gas chromatography/mass spectrometry method for the measurement of prostaglandin F2 alpha (PGF2 alpha) in plasma has been developed. The linearity of the method was 0 to 250 pg per ml, day-to-day precision of five percent at a level of 80 pg per ml, and a limit of detection of one pg per ml. Evaluation of the absolute recovery of PGF2 alpha through the sample clean-up steps using tritium labelled PGF2 alpha gave recoveries of 68 +/- 5 percent. A preliminary reference range estimated a mean plasma PGF2 alpha level of 83 +/- 13 pg per ml (n = 7) with a range of 62 to 103 pg per ml in healthy adults. The major application of this method will be in research protocols studying changes of PGF2 alpha in toxemia of pregnancy.

Adult↗
PubMedDate not supplied

Prostaglandins and cancer.

This paper reviews the role of prostaglandins (PGs) in cancer. Specific topics of discussion include: (1) the potential use of PGs as tumor markers, (2) PG mediation of hypercalcemia of cancer, and (3) the use of PG synthesis inhibitors in cancer therapy.

Animals↗
PubMedDate not supplied

Frequency of calcium binding by monoclonal immunoglobulins in multiple myeloma.

Total and ionized calcium and other related parameters were measured in 34 patients with multiple myeloma. Hypercalcemia was not a major feature of the group of patients studied with only three patients exhibiting marked increases in total (Ca total) and ionized (Ca++) calcium concentrations. The Ca++/Ca total ratio was also maintained within relatively narrow limits. No major differences were found in the calcium fractions of patients with different types of multiple myeloma. Serum immunoreactive parathyroid hormone showed no consistent relationship with either the total or ionized calcium concentration. There were no correlations between increased total protein or reduced serum albumin concentrations and changes in total and ionized calcium fractions or Ca++/Ca total ratios. These results imply that in this group of myeloma patients, there was no significant binding of calcium by the monoclonal immunoglobulins.

Antibodies, Monoclonal↗