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Biomedical subjects

J C Smith

Publications and source records attributed to J C Smith.

At least 361 records · Page 20Linked to original sources
PubMed1991

Reduced survival of neonates due to vitamin A deficiency during pregnancy in the guinea pig.

Neonatal vitamin A stores are limited even in well-nourished full-term infants and are yet smaller in the premature infant. The object of this experiment was to determine whether vitamin A deficiency could be induced in pregnant guinea pigs and, if so, whether it would affect vitamin A status of the neonate. Adult (600 g) guinea pigs were fed a casein-agar diet that was vitamin A deficient (AD). Controls (vitamin A adequate) were orally dosed weekly with 2 mg of retinyl palmitate. Weight gains of dams and birth weights of neonates did not differ. No external signs of deficiency were observed. Six of eight AD and seven of eight vitamin A-adequate dams carried pregnancy to term (greater than or equal to Day 64). One AD dam died during delivery. Liver retinol concentrations were below the detection limit (less than 3 micrograms/g) for all AD neonates and dams and in postpartum serum of AD dams. Of neonates born greater than or equal to Day 64, 15 of 18 AD were dead or moribund compared with 4 of 22 vitamin A adequate. The unexpectedly severe effect on the neonate indicates that the guinea pig will be a sensitive model for investigating the affect of poor maternal vitamin A status on neonatal vitamin A-dependent functions. However, a less severe maternal deprivation should be used for such studies.

Animals↗
PubMed1991

Circadian rhythm in anaerobic power and capacity.

Anaerobic power and capacity were measured in nine college-age men at four different times of day: 03.00 h, 09.00 h, 15.00 h, and 21.00 h. Modified Wingate tests were performed against a common resistance of 5.5 kg (0.074 +/- 0.004 kg per kg body mass). Peak power was defined as the highest power output during a 5-s period in the test, and anaerobic capacity was defined as the total external work during the 30-s test. Peak power tended to differ across testing times (F = 2.50, p = .10), with the mean at 21.00 h about 8% higher (p less than .05) than at 03.00 h. Anaerobic capacity differed across the times of day (F = 9.58, p less than .01), with the means at 15.00 h and 21.00 h about 5% higher (p less than .05) than at 03.00 h and 09.00 h. These results suggest that there are circadian rhythms in anaerobic power and capacity.

Adult↗
PubMed1991

Maternal mortality surveillance, United States, 1979-1986.

To understand further the epidemiology and causes of maternal death, the Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, CDC, reviewed all identified maternal deaths in the United States, including Puerto Rico, for the period from 1979 through 1986. The maternal mortality ratio for the period was 9.1 deaths/100,000 live births. The ratios increased with age and were higher among women of black and other minority races than among white women for all age groups, particularly for women ages greater than or equal to 40 years. Unmarried women had a higher risk of death than married women. Women who had received any prenatal care had a lower risk of dying than women who had received no care (RR = 0.19, 95% confidence limits (CL) 0.15, 0.23). Women who received no prenatal care had a gestational age-adjusted risk of maternal death 5.7 times that of women receiving care defined as "adequate." The risk of maternal death increased with decreasing levels of education for all age groups, particularly among women ages greater than or equal to 35 years. The causes of death varied for different outcomes of pregnancy; pulmonary embolism was the leading cause of death following the delivery of a live birth. Future studies aimed at developing strategies to reduce the risk of maternal deaths in the United States should use enhanced surveillance and collect more information about each death, which would allow for better understanding of factors associated with maternal mortality.

Adult↗
PubMed1991

Abortion surveillance, United States, 1988.

Since 1980, the number of legal abortions reported to CDC has remained fairly stable, varying each year by less than 3%. In 1988, 1,371,285 abortions were reported--a 1.3% increase from 1987. The abortion ratio for 1988 was 352 legally induced abortions/1,000 live births, and the abortion rate was 24/1,000 women ages 15-44 years. The abortion ratio was higher for black women and women of other minority races and for women less than 15 years of age. However, the abortion ratio for women less than 15 years was lower in 1988 than in any previous year since 1972. Women undergoing legally induced abortions tended 1) to be young, white, and unmarried, 2) to live in a metropolitan area, 3) to have had no previous live births, and 4) to be having the procedure for the first time. Approximately half of all abortions were performed before the eighth week of gestation, and greater than 85% were performed during the first trimester of pregnancy (less than 13 weeks of gestation). Black women and women of other minority races tended to obtain abortions later in pregnancy than did white women; however, age was a more dominant influence than race. Younger women tended to obtain abortions later than older women. Educational level strongly influenced when an abortion was performed; better educated women had an abortion earlier in gestation.

Abortion, Legal↗
PubMed1991

Rehabilitation of neurologic disability related to human immunodeficiency virus.

Acquired immunodeficiency syndrome (AIDS) is globally fatal; before death, it often causes a multitude of medical complications leading to significant physical impairment and functional loss. Specifically, the neuropathology associated with AIDS can be diverse, and it ranges from inconsequential cerebrovascular insults to rapidly progressive neuronosis. Moreover, physical impairments may present any time during the course of the disease and even before knowledge of seropositivity. We present three patients infected with human immunodeficiency virus (HIV), each with a different form of neuropathology, who were treated by rehabilitative services and who gained reasonable functional benefits within moderate time periods. The growing number of HIV-infected persons with physical debilitation mandates a rational, knowledgeable approach to rehabilitation intervention. This article highlights the importance of a thorough understanding of the neurologic complications of AIDS in setting realistic goals and in improving the quality of life for these individuals.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Graded changes in dose of a Xenopus activin A homologue elicit stepwise transitions in embryonic cell fate.

The protein XTC-MIF, a Xenopus homologue of activin A and a potent mesoderm-inducing factor, can induce responding animal pole explants to form several different cell types in a dose-dependent manner, higher doses eliciting more dorso-anterior tissues. This graded response, characteristic of classically postulated morphogens, may underlie pattern formation, but the response of intact animal caps to XTC-MIF provides only a crude indication of trends. Here we report the effects of XTC-MIF on dispersed blastomeres rather than intact animal caps. Under these conditions, responding cells distinguish sharply between doses of pure XTC-MIF differing by less than 1.5-fold. Two different response thresholds have been found, defining three cell states. This suggests that XTC-MIF has an instructive effect. Notochord and muscle are both induced in the same narrow dose-range. Mixing treated with untreated cells does not seem to shift the dose thresholds, showing that at least some cells can stably record the received dose of inducing factor.

Actins↗
PubMed1990

Identification of a potent Xenopus mesoderm-inducing factor as a homologue of activin A.

The first inductive interaction in amphibian development is mesoderm induction, when a signal from the vegetal hemisphere of the blastula induces mesoderm from overlying equatorial cells. Recently, several 'mesoderm-inducing factors' (MIFs) have been discovered. These cause isolated Xenopus animal caps to form mesodermal cell types such as muscle, instead of their normal fate of epidermis. The MIFs fall into two classes. One comprises members of the fibroblast growth factor (FGF) family, and the other members of the transforming growth factor type beta (TGF-beta) family. Of the latter group, the most potent is XTC-MIF, a protein produced by Xenopus XTC cells. Here we show that XTC-MIF is the homologue of mammalian activin A. Activins modulate the release of follicle-stimulating hormone from cultured anterior pituitary cells and cause the differentiation of two erythroleukaemia cell lines. Our results indicate that these molecules may also act in early development during formation of the mesoderm.

Activins↗
PubMed1990

A novel, rapid method for the isolation of terminal sequences from yeast artificial chromosome (YAC) clones.

The recent development of yeast artificial chromosome (YAC) vectors has provided a system for cloning fragments that are over ten times larger than those that can be cloned in more established systems. We have developed a method for the rapid isolation of terminal sequences from YAC clones. The YAC clone is digested with a range of restriction enzymes, a common linker is ligated to the DNA fragments and terminal sequences are amplified using a vector specific primer and a linker specific primer. Sequence data derived from these terminal specific products can be used to design primers for a further round of screening to isolate overlapping clones. The method also provides a convenient method of generating Sequence Tagged Sites for the mapping of complex genomes.

Base Sequence↗
PubMed1990

NMR, calorimetric, spin-label, and optical studies on a trifluoromethyl-substituted styryl molecular probe in dimyristoylphosphatidylcholine vesicles and multilamellar suspensions: a model for location of optical probes.

NMR, calorimetric, and optical spectroscopic studies have been performed on a trifluoromethyl-substituted styryl molecular probe bound to vesicles and multilamellar suspensions formed from dimyristoylphosphatidylcholine (DMPC). In the fluorine NMR spectrum at 35 degrees C there are two partially resolved resonances, but these collapse to an apparently single resonance at temperatures above 60 degrees C. However, a line-shape analysis is not consistent with exchange between two sites on an NMR time scale, and the two resonances are assumed to be due to probe sites in the inner and outer leaflets of the vesicles. Two fluorescence lifetimes, each associated with one of these sites, characterize the decay curves for the molecular probe bound to DMPC vesicles. The shift reagent Eu(FOD)3 and several nitroxide spin labels covalently bound to lipophilic structures strongly attenuate the lower frequency component of the fluorine NMR spectrum and also shift the other resonance to higher frequencies. The effect of two spin labels on the probe fluorine T2 relaxation time has been used to estimate the distance between the spin label unpaired electron and the trifluoromethyl group. The location of the spin label site in the membrane was determined from the effect of the unpaired electron on the lipid 13C linewidths. A model for the location of the probe in the bilayer was developed from the above information and refined using molecular mechanics calculations on a probe-DMPC lipid complex. The long axis of the probe parallels the bilayer normal; the styryl-group portion of the optical chromophore is located slightly below the glycerol backbone, and the remainder of the chromophore extends well into the hydrophobic region of the bilayer. Therefore, the optical properties of the probe should not be significantly influenced by alterations of the membrane surface charge density. Parameters derived from DSC studies in the gel-to-lipid crystal phase transition of DMPC are extremely sensitive to the probe. Even at 0.0001 mol fraction of probe, the transition is substantially broadened, and the delta H for the transition has increased, just as one predicts for the formation of a tight complex described above.

Calorimetry↗
PubMed1990

A 3.5 genome equivalent multi access YAC library: construction, characterisation, screening and storage.

The construction of a yeast artificial chromosome (YAC) primary gridded library of 35,000 clones from human lymphoblastoid (48,XXXX) cell line DNA is described. The average YAC size is approximately 350kb representing a greater than 3.5 times coverage of the genome. The library is stored at -70 degrees C as gridded clones on nylon filters impregnated with 20% glycerol and as glycerol suspensions of individual clones in microtitre plates providing a prolonged multi-user potential. To date we have used 14 single copy probes to screen this library by colony hybridisation as well as PCR and have isolated between 1 and 5 YAC clones for every probe.

Cell Line↗