Alterations in the lipids of bone caused by hypervitaminosis A and D

1. The total lipid, phospholipid, total and free fatty acid, free and esterified cholesterol contents of the long bones of normal, hypervitaminotic A, D and A plus D rats were determined. 2. Toxic amounts of vitamin A decreased the total fatty content, whereas toxic amounts of vitamin D increased triglycerides, esterified cholesterol and in particular the phospholipids of bone. 3. An interaction occurred between toxic amounts of vitamins A and D, which prevented, to a large extent, the alterations in bone lipids that occur in hypervitaminosis D. 4. The studies suggest an involvement of vitamin D in lipid metabolism and tend to support the idea that lipids are involved in ossification.     

Vanadate-stimulated oxidation of NAD(P)H

Vanadate stimulates the oxidation of NAD(P)H by biological membranes because such membranes contain NAD(P)H oxidases which are capable of reducing dioxygen to O₂⁻ and because vanadate catalyzes the oxidation of NAD(P)H by O₂⁻, by a free radical chain mechanism. Dihydropyridines, such as reduced nicotinamide mononucleotide (NMNH), which are not substrates for membrane-associated NAD(P)H oxidases, are not oxidized by membranes plus vanadate unless NAD(P)H is present to serve as a source of O₂⁻. When [NMNH] greatly exceeds [NAD(P)H], in such reaction mixtures, one can observe the oxidation of many molecules of NMNH per NAD(P)H consumed. This reflects the chain length of the free radical chain mechanism. We have discussed the mechanism and significance of this process and have tried to clarify the pertinent but confusing literature.     

Characterization and sequence of a Thermomonospora fusca xylanase.

TfxA is a thermostable xylanase produced by the thermophilic soil bacterium Thermomonospora fusca. The enzyme was purified to homogeneity from the culture supernatant of Streptomyces lividans transformed by plasmid pGG92, which carries the gene for TfxA, xynA. The molecular mass of TfxA by sodium dodecyl sulfate-polyacrylamide gel electrophoresis is 32 kDa. TfxA is extremely stable, retaining 96% of its activity after 18 h at 75 degrees C. It has a broad pH optimum around pH 7 and retains 80% of its maximum activity between pH 5 and 9. The native enzyme binds strongly to both cellulose and insoluble xylan even though it has no activity on cellulose. Treatment of TfxA with a T. fusca protease produced a 24-kDa catalytically active fragment that had the same N-terminal sequence as TfxA. The fragment does not bind to cellulose and binds weakly to xylan. The Vmax values for TfxA and the fragment are 600 and 540 mumol/min/mg, respectively, while the Kms are 1.1 and 2.3 mg of xylan per ml, respectively. The DNA sequence of the xynA gene was determined, and it contains an open reading frame that codes for a 42-amino-acid (42-aa) actinomycete signal peptide followed by the 32-kDa mature protein. There is a 21-aa Gly-Pro-rich region that separates the catalytic domain from an 86-aa C-terminal binding domain. The amino acid sequence of the catalytic domain of TfxA has from 40 to 72% identity with the sequence of 12 other xylanases from seven different organisms and belongs to family G.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of a recombinant antibody produced in the course of a high yield fed-batch process

Many mammalian cell fed-batch processes rely on maintaining the cells in a viable and productive state for extended periods of time in order to reach high final concentrations of secreted protein. In the work described herein, a nonamplified NSO cell line was transfected with a vector expressing a recombinant human anti-HIV gp 120 monoclonal antibody (Mab) and a selectable marker, glutamine synthetase. A fed-batch process was developed which improved product yields tenfold over the yields reached in batch culture. In this case, the clone was cultured for a period of 22 days and produced 0.85 g Mab/L. To gauge the effect of extended culture lifetime on product quality, biochemical characteristics of MAb isolated from different time points in the fed-batch culture were determined. The apparent molecular weight of the MAb was constant throughout the course of the culture. Isoelectric focusing revealed four major charged species, with a fifth more acidic species appearing later in the culture. The antigen binding kinetics were constant for MAb isolated throughout the culture period. Glycosylation analysis, on the other hand, revealed that MAb produced later in the culture contained greater percentages of truncated N-acetylglucosamine and highmannose N-glycans. Possible contributions to this underglycosylated material from either cell lysis or synthesis from noviable cells were found to be negligible. Instead, the viable cells appeared to be secreting more truncated and high mannose MAb glycoforms as the culture progressed. (c) 1994 John Wiley & Sons, Inc.     

Barriers to prenatal care for low-income women.

Inadequate prenatal care is associated with poor birth outcomes. Recognizing barriers to care is necessary to improve results. Postpartum in-hospital interviews were conducted with women admitted through emergency departments with no physician of record (n = 69) in 8 Sacramento hospitals during April and May 1991. A focus group of local obstetrician-gynecologists was used to determine physicians'' attitudes about caring for low-income women. We undertook the study in response to an increased number of "no doc" births. The inability to find a physician willing to accept them was reported by the women as the single largest barrier to obtaining care, cited by 64% of women overall and 96% of those who tried but were unable to obtain care. Transportation difficulties were a problem regardless of women''s success in obtaining care and were ranked as the top barrier by women who never tried to obtain care. Physicians cited administrative difficulties and reimbursement levels of Medi-Cal plus extra care requirements and resource dependency of low-income patients as barriers to caring for this population. The value ascribed to prenatal care by women and physicians'' perceptions of women''s attitudes about care contrasted sharply. The link between poor women and physicians providing obstetric services can be fragile. The difficulty finding physicians willing to take them indicates that these women need special support services to ensure adequate care during pregnancy.     

The effect of intrinsic curvature on supercoiling: Predictions of elasticity theory

Elasticity theory of naturally curved rods is employed to study the effects of intrinsic curvature on the properties of the equilibrium conformations of supercoiled DNA. The results stand in sharp contrast to those obtained when the molecule is viewed as being straight in its relaxed form. Starting from very fundamental principles of the theory, we show that the torsion of an open segment with a curved duplex axis can vary when the temperature, and along with it, the intrinsic twist is changed. Conversely, an imposed helicity, such as might be associated with binding to a histone, can change the intrinsic twist. It is also shown that another consequence of the presence of naturally curved sequences is that the twist density will, in general, vary with position along the chain in all equilibrium states. Then portions of the molecule will be more or less susceptible to interaction with other agents sensitive to such a variation. Finally, some closed equilibrium global structures uniquely associated with intrinsic curvature are discussed. © 1993 John Wiley & Sons, Inc.