PubMed Health⌕ Search

Biomedical subjects

B J Jackson

Publications and source records attributed to B J Jackson.

16 recordsLinked to original sources
PubMed1999

Structural changes in the recombinant, NADP(H)-binding component of proton translocating transhydrogenase revealed by NMR spectroscopy.

We have analysed 1H, 15N-HSQC spectra of the recombinant, NADP(H)-binding component of transhydrogenase in the context of the emerging three dimensional structure of the protein. Chemical shift perturbations of amino acid residues following replacement of NADP+ with NADPH were observed in both the adenosine and nicotinamide parts of the dinucleotide binding site and in a region which straddles the protein. These observations reflect the structural changes resulting from hydride transfer. The interactions between the recombinant, NADP(H)-binding component and its partner, NAD(H)-binding protein, are complicated. Helix B of the recombinant, NADP(H)-binding component may play an important role in the binding process.

Amino Acid Sequence↗
PubMed1993

Bacterial contaminants of collected and frozen human milk used in an intensive care nursery.

BACKGROUND: Use of human milk for preterm and high-risk neonates conveys many potential benefits but also poses practical difficulties. This prospective study examined the prevalence and degree of bacterial contamination of human milk used in the intensive care nursery. METHODS: One hundred eight milk samples collected from 40 mothers were tested for contamination. Samples from mothers whose milk showed a high degree of contamination were retested after counseling on collection methods. RESULTS: Only 12.5% of the samples showed no bacterial growth. Of the contaminated samples, 38% contained > 30,000 colony-forming units/ml. The most common contaminants were Staphylococcus epidermidis (82%) and Acinetobacter (9%), but other contaminants were also encountered. CONCLUSIONS: There were not statistically identifiable common characteristics of mothers whose milk showed abundant bacterial contamination. Only 30% of these mothers showed improvement in the degree of contamination after counseling regarding techniques of milk collection.

Acinetobacter↗
PubMed1993

Aerobes isolated in fecal microflora of infants in the intensive care nursery: relationship to human milk use and systemic sepsis.

BACKGROUND: Staphylococcus epidermidis is a leading cause of nosocomial sepsis in the intensive care nursery. The relationship between rates of gastrointestinal colonization and the incidence of systemic sepsis with S. epidermidis in hospitalized neonates is under investigation. METHODS: In this study, we enrolled 46 infants consecutively admitted to the intensive care nursery (mean +/- standard deviation, birth weight 1300 +/- 337 gm, gestational age 29.4 +/- 2.2 weeks). At the time of enrollment, infants had been fed enterally for at least 1 week (28 were fed formula and 18 received their own mothers' frozen milk). Stool samples were collected when infants were 2 to 3 weeks of age (16.3 +/- 7.4 days). RESULTS: Aerobic stool flora were present in 65% of all patients. Human milk use was associated with a significant increase in the presence of aerobic stool flora (78% vs 46%, p = 0.035), as well as more frequent isolation of S. epidermidis. The incidence of S. epidermidis sepsis was 33% in those infants whose stool specimens grew S. epidermidis and 3.5% in those whose stool specimens did not (p < 0.01). CONCLUSIONS: These findings suggest the gastrointestinal tract as a possible site of entry for S. epidermidis in the hospitalized preterm infant. In addition, frozen human milk may be a vehicle for gastrointestinal S. epidermidis colonization.

Adult↗
PubMed1993

Biosynthesis of asparagine-linked oligosaccharides in Saccharomyces cerevisiae: the alg2 mutation.

In the yeast Saccharomyces cerevisiae, the alg2 mutation causes temperature-sensitive growth and abnormal accumulation of the lipid-linked oligosaccharide Man2GlcNAc2-PP-Dol (Jackson et al., Arch. Biochem. Biophys., 272, 203-209, 1989; Huffaker and Robbins, Proc. Natl. Acad. Sci. USA, 80, 7466-7470, 1983). A gene having the function and genomic location of ALG2 was cloned from libraries based on the multicopy plasmid YEp24 and on the centromere plasmid YCp50. Alg2 mutants transformed with plasmids containing ALG2 regained the capacity to grow and to synthesize lipid-linked oligosaccharides normally at the previously non-permissive temperature. ALG2 was essential for viability in haploid and diploid yeast. The ALG2 gene was transcribed into a single mRNA of 1.7 kb in size. The stability of ALG2 mRNA, assessed after thermal inactivation of RNA polymerase II in an rpb1-1 mutant (Herrick et al., Mol. Cell. Biol., 10, 2269-2284, 1990) was very low, with a t1/2 of < 5 min. The ALG2 transcript accumulation was growth dependent, and it was at least an order of magnitude lower in stationary phase cells compared to exponentially growing cells. The putative translation product of ALG2 contained a potential dolichol recognition domain similar to that found in all three glycosyltransferases of the lipid-linked pathway that have been sequenced.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Prevalence and toxigenicity of Clostridium difficile isolates in fecal microflora of preterm infants in the intensive care nursery.

Fecal isolates of Clostridium difficile and its toxin B were followed prospectively in 50 preterm intensive care nursery (ICN) patients. The first stool specimen was obtained after 1 week of enteral feeding, at 15 +/- 1 days of life, and 2 more specimens were collected at 2-week intervals, 24 +/- 1 and 32 +/- 2 days of life. The stools were cultured for C. difficile, and tested for C. difficile toxin B. In the first specimen 15% of stools grew C. difficile. In the second specimen C. difficile isolation rates increased to 33% and plateaued. Toxin B was detected in 71, 93 and 100% of culture-positive stools in the first, second, and third specimens, respectively. C. difficile colonization was not associated with a higher incidence of necrotizing enterocolitis or diarrhea, and using precollected, frozen human milk did not protect from C. difficile colonization.

Bacterial Proteins↗
PubMed1992

Pharmacokinetic and metabolic aspects of the moclobemide-food interaction.

The effect of a protein-rich meal on the pharmacokinetics of moclobemide was studied after intravenous (75 mg) and oral (100 mg) administrations of this selective MAO-A inhibitor to eight healthy male volunteers. The meal chosen did not affect plasma concentration-time curves of the drug after oral administration apparently, because the influence of blood flow changes to the liver on hepatic first-pass metabolism (AUC increases) and on systemic clearance (AUC decreases) balance each other out.

Adolescent↗
PubMed1990

Multiple delivery methods for an interdisciplinary audience: assessing effectiveness.

Recent federal legislation has provided guidelines for intervention services for infants and toddlers with handicaps, birth to age three, and their families. Many disciplines, including nursing, will be involved in providing these services. Serving on an interdisciplinary team or acting as a consultant requires appropriate preparation. Many professionals are not comfortable with their roles in serving this new population, due in part to the limited emphasis on the handicapped infant and toddler in most basic preservice professional education programs. The project described here was useful in helping an interdisciplinary audience develop knowledge and skills needed for intervention services for infants and toddlers.

Child Health Services↗
PubMed1989

Synthesis of lipid-linked oligosaccharides in Saccharomyces cerevisiae: Man2GlcNAc2 and Man1GlcNAc2 are transferred from dolichol to protein in vivo.

Transfer of truncated oligosaccharides to protein in vivo and the structure of Man2GlcNAc2 synthesized by intact yeast (Saccharomyces cerevisiae) were investigated in the alg2 mutant. At the nonpermissive temperature the alg2 mutant accumulates lipid-linked oligosaccharides that migrate on Bio-Gel P4 in the range expected for Man2GlcNAc2 and Man1GlcNAc2 (T.C. Huffaker and P.W. Robbins (1983) Proc. Natl. Acad. Sci. USA 80, 7466-7470). We characterized the oligosaccharides, derived from protein and lipid, by comigration with standards on HPLC and by Smith degradation followed by HPLC. Man2GlcNAc2 and Man1GlcNAc2 are found on protein in alg2, since their release from a protein-containing precipitate of alg2 cells is N-glycanase (peptide-N4[N-acetyl-beta-glucosaminyl]asparagine amidase) dependent. Transfer also occurred in alg2/pAC3 cells, which carry ALG2 on a multicopy plasmid that confers partial correction of the oligosaccharide phenotype. The alg2/pAC3 cells are viable at 36 degrees C. Two isomers of Man2GlcNAc2, Man1----3ManGlcNAc2 and Man1----6ManGlcNAc2, were present on lipid and protein. The transfer of Man2GlcNAc2 and Man1GlcNAc2 to protein by intact cells supports topological models that postulate access by early intermediates to the lumen of the endoplasmic reticulum.

Borohydrides↗
PubMed1986

Regulation of the balanced synthesis of membrane phospholipids. Experimental test of models for regulation in Escherichia coli.

In Escherichia coli, highly effective regulation controls the balanced synthesis of membrane phospholipids, important for optimal growth. Regulation is such that normally about 70% of a common pool of cytosine liponucleotide precursor is utilized by phosphatidylserine synthase and eventually converted to phosphatidylethanolamine, while about 30% is utilized by the competing enzyme phosphatidylglycerophosphate synthase and converted to phosphatidylglycerol (25%) plus cardiolipin (5%). Although the ratio of phosphatidylglycerol to cardiolipin may vary with conditions of growth, the sum of these two lipids remains relatively constant at about 30% of the total. Alternative models, postulating coordinate regulation of the two competing enzymes, or independent feedback regulation are proposed. These models were tested in experiments in which phosphatidylglycerol was continuously removed from growing cells treated with arbutin (4-hydroxyphenyl-O-beta-D-glucoside), causing its conversion to arbutinphosphoglycerol (Bohin, J.-P., and Kennedy, E.P. (1984) J. Biol. Chem. 259, 8388-8393.) The synthesis of phosphatidylglycerol was increased by a factor of 7 in cells treated with arbutin, with only small changes in phospholipid composition and with no significant change in the level of phosphatidylglycerophosphate synthase. The synthesis of phosphatidylethanolamine was not significantly increased, decisively eliminating the model that requires coordinate regulation of phosphatidylserine synthase and phosphatidylglycerophosphate synthase, and supporting the model of independent feedback inhibition, sensitive to very small changes in composition of cellular phospholipids.

Arbutin↗
PubMed1985

The dilute phospholipid APTT: a sensitive assay for verification of lupus anticoagulants.

A simple sensitive method for verification of lupus anticoagulants utilizing dilution of phospholipid in the activated partial thromboplastin time (APTT) system is described. Patient plasma, mixed with an equal volume of normal plasma, is activated with micronized silica. To this mixture are added different dilutions of Thrombofax and then calcium chloride. Clotting times are plotted linearly against the logarithm of the phospholipid dilutions and slopes are calculated by regression analysis. In this assay the mean negative slope of 19 plasmas that contained anti-phospholipid activity was five times greater than those of normal plasma or those obtained from patients having single or multiple coagulation factor deficiencies such as those induced by warfarin. The assay can be modified to test heparinized plasmas. Thus, it is a sensitive means by which to verify the presence of lupus anticoagulants in patients who have congenital or acquired factor deficiencies or who are receiving anticoagulant therapy.

Autoantibodies↗
PubMed1984

Plasma enalapril levels and hormonal effects after short- and long-term administration in essential hypertension.

Enalapril lowers blood pressure both acutely and during long-term therapy in patients with essential hypertension. After a single 10 mg dose of enalapril a close relationship between plasma enalaprilic acid (MK-422) levels, angiotensin converting enzyme (ACE) inhibition and the acute hypotensive and hormonal effects was demonstrated. During long-term administration of enalapril, a similar relationship between the plasma enalaprilic acid level, ACE inhibition and the hypotensive effect was shown, although the dose-response curve for plasma enalaprilic acid to ACE inhibition was displaced to the right compared to the acute dose-response curve. Several weeks' administration of enalapril was needed to reach stable plateau levels of plasma enalaprilic acid and ACE inhibition. During long-term treatment with enalapril in essential hypertension, there was sustained inhibition of ACE and the associated hormonal changes.

Aldosterone↗
PubMed1984

Biosynthesis of membrane-derived oligosaccharides: characterization of mdoB mutants defective in phosphoglycerol transferase I activity.

Phosphoglycerol transferase I, an enzyme of the inner, cytoplasmic membrane of Escherichia coli, catalyzes the in vitro transfer of phosphoglycerol residues from phosphatidylglycerol to membrane-derived oligosaccharides or to the model substrate arbutin (p-hydroxyphenyl-beta-D-glucoside). The products are a phosphoglycerol diester derivative of membrane-derived oligosaccharides or arbutin, respectively, and sn-1,2-diglyceride (B. J. Jackson and E. P. Kennedy, J. Biol. Chem. 258:2394-2398, 1983). Because this enzyme has its active site on the outer aspect of the inner membrane, it also catalyzes the transfer of phosphoglycerol residues to arbutin added to the medium (J.-P. Bohin and E. P. Kennedy, J. Biol. Chem. 259:8388-8393, 1984). When strains bearing the dgk mutation, which are defective in the enzyme diglyceride kinase, are grown in medium containing arbutin, they accumulate large amounts of sn-1,2-diglyceride, a product of the phosphoglycerol transferase I reaction. Growth is inhibited under these conditions. A further mutation in such a dgk strain, leading to the loss of phosphoglycerol transferase I activity, should result in the phenotype of arbutin resistance. We have exploited this fact to obtain strains with such mutations, designated mdoB, that map near min 99. Such mutants lack detectable phosphoglycerol transferase I activity, cannot transfer phosphoglycerol residues to arbutin in vivo, and synthesize membrane-derived oligosaccharides devoid of phosphoglycerol residues. These findings offer strong genetic support for the function of phosphoglycerol transferase I in membrane-derived oligosaccharide biosynthesis.

Alleles↗
PubMed1983

The biosynthesis of membrane-derived oligosaccharides. A membrane-bound phosphoglycerol transferase.

Membrane-derived oligosaccharides, found in the Escherichia coli periplasmic space (Schulman, H., and Kennedy, E. P. (1979) J. Bacteriol. 137, 686-688), are composed of 8-10 units of glucose, the sole sugar, in beta 1 leads to 2 and beta 1 leads to 6 linkages (Schneider, J. E., Reinhold, V., Rumley, M. K., and Kennedy, E. P. (1979) J. Biol. Chem. 254, 10135-10138). Oligosaccharides in this family are variously substituted with succinyl ester residues, as well as with sn-1-phosphoglycerol and phosphoethanolamine, both derived from membrane phospholipids. These negatively charged oligosaccharides may function in cellular osmoregulation since their synthesis is under osmotic control (Kennedy, E. P. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 1092-1095). We now report initial characterization of an enzyme catalyzing transfer of phosphoglycerol residues from phosphatidylglycerol to membrane-derived oligosaccharides or to synthetic beta-glucoside acceptors. The products are sn-1,2-diglyceride and beta-glucoside-6-phosphoglycerol. Localized in the inner membrane, the transferase has a requirement for divalent cations, of which manganese is most effective, and a pH optimum of 8.9 in vitro.

Cations, Divalent↗
PubMedDate not supplied

Theophylline N-demethylations as probes for P4501A1 and P4501A2.

Polycyclic aromatic hydrocarbons present in cigarette smoke induce cytochromes P4501A1 and P4501A2. These isozymes are of toxicological importance because they convert several environmental pollutants to reactive intermediates that form covalent adducts with cellular DNA resulting in mutations and/or malignant transformations. The aim of our research was to investigate whether theophylline metabolites could be used as probes for P4501A1 and P4501A2. It is known that at least two human P450 isozymes are involved in theophylline metabolism. The N-demethylations of theophylline to 3-methylxanthine (3-MX) and 1-methylxanthine (1-MX) appear to be mediated by P4501A1 and/or P4501A2 and the 8-hydroxylation by different isozymes. Theophylline metabolism was measured in liver microsomes from control, benzo(a)pyrene (BP)-, and isosafrole (ISO)-induced rats. Theophylline was also incubated in microsomes prepared from cells expressing high levels of human P4501A1 and P4501A2. A plot of v vs. v/S was linear for 3-MX in the ISO-induced microsomes, but nonlinear for 1-MX, indicating that P4501A2 mainly forms 3-MX, whereas P4501A1 and 1A2 probably mediate 1-MX. A similar nonlinear relation was also obtained in the BP-induced microsomes. Incubation of theophylline in the microsomes from the cells indicated that only 1-MX could be measured in cells expressing P4501A1, and both 1-MX and 3-MX were formed in the P4501A2 cell microsomes. Therefore 1-MX seems to be mediated by P4501A1/P4501A2 and 3-MX specifically by P4501A2, and theophylline N-demethylations can be used as probes for P4501A1 and P4501A2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗