Biomedical subjects

J E Bell

Publications and source records attributed to J E Bell.

At least 145 records · Page 8Linked to original sources

PubMed1979

Uncultured cells in amniotic fluid from normal and abnormal foetuses.

Direct smears of uncultured amniotic fluid cells were analysed in 41 pregnancies between 17 and 22 weeks of gestation. These included 27 normal pregnancies where a healthy child was born at term, six anencephalic and five spina bifida pregnancies, and three other abnormal pregnancies. In normal amniotic fluid, epithelioid cells predominated but small numbers of histiocyte-like cells, typical macrophages and elongated cells were also present. The proportion of macrophages and elongated cells was significantly increased in all anencephalic cases. Two of the spina bifida cases also showed abnormal cellular proportions. Haemosiderin and lipid material was demonstrated in some of the cellular proportions. Haemosiderin and lipid material was demonstrated in some of the macrophages. Tissue smears and histological preparations suggest that these cells may originate from both the amnion and the fibrovascular membrane covering the neural lesion. This direct method of observation of amniotic fluid cells, not involving culture techniques, could provide a rapid means of prenatal diagnosis of anencephaly, and may help in the diagnosis of spina bifida.

Amniotic Fluid↗

PubMed1979

Central nervous system defects in early human abortuses.

Thirteen embryos with various central nervous system (cns) defects were examined macroscopically and by serial sectioning, and were compared with seven control embryos. All had been aborted spontaneously. Examples of anencephaly, anencephaly with spina bifida, spina bifida alone, encephalocele, iniencephaly and cyclops were found. Histological assessment was directed mainly to the cns, the skeletal axis, the neural-crest derivatives and remaining viscera. The cns was affected by postmortem change in some cases. Brain tissue was absent in most anencephalic embryos and spinal-cord tissue was absent at the level of the external lesion in all except one of the spina-bifida embryos. Defects such as diastematomyelia were found occasionally. Widespread abnormalities were found in the cartilaginous vertebral colun. The meninges were unusually vascular, but other neural crest derivatives appeared to be normal. The possible causes of absent brain or spinal cord are discussed and the findings are compared with the pathology of cns defects in childhood.

Abortion, Spontaneous↗

PubMed1979

Adventitious contamination of intravenous admixtures during sterility testing.

The extent to which contamination of intravenous fluids measured by inhospital sterility-testing may be due to adventitious contamination (i.e., contamination introduced during the sterility-testing procedure) was studied. All one-liter admixtures prepared during a three-day period in a busy centralized i.v. admixture service were studied. Samples of i.v. admixtures were cultured before and after administration by direct ioculation or by culturing the membrane through which the admixture was filtered. Samples of similarly cultured large-volume parenterals served as controls. Contamination rates for control and admixture samples were not significantly different (p = 0.23). Of 10 control and test (admixture) solutions showing contamination before administration, only one test solution again showed contamination after administration but this was with a different microbe. The results suggest that adventitious contamination during sampling/culturing procedures is a component of, and possibly a dominant factor in, the contamination rates detected by inhospital sterility tests. Combined with infection surveillance, sterility tests may be of value when infections are possibly related to admixture contamination.

Bacteria↗

PubMed1978

Central nervous system abnormalities--contrasting patterns in early and late pregnancy.

A total of 509 specimens of spontaneous abortion were studied. Of 364 complete specimens, 15 (4.1%) had central nervous system (CNS) abnormalities. The defects which were seen were anencephaly, spina bifida, iniencephaly, encephalocele and anencephaly combined with complete rachischisis. A high proportion (five out of 15) had the more unusual defects of iniencephaly and encephalocele. All except one had ceased development at less than 12 weeks of gestation. Sex chromatin studies showed that males outnumbered females amount CNS defective fetuses. When the month of conception was calculated for these abnormal pregnancies, summer and winter peaks were detected. Only one of the 15 patients had a family history of neural tube defect (NTD). Histological examination of all small fetuses aborted spontaneously revealed two additional facts. First, in fetuses with a localised external CNS defect, the internal abnormality was more extensive. Second, the CNS was also abnormal in some fetuses with no visible external defect. The proportion of abnormality is much higher than at birth and is also higher than in other surveys of spontaneous abortion. We suggest that screening for serum alphafetoprotein should be undertaken and amniocentesis considered in pregnancies subsequent to an abortion of this type.

Abortion, Spontaneous↗

PubMed1977

The family in physical therapy.

Family Focus is a training program implemented by the Division of Physical Therapy at Stanford University in cooperation with the Mental Research Institute of Palo Alto, California. Through this program, inpatients at the Stanford University Hospital and their families have the opportunity to live in a modular home on the hospital grounds prior to discharge and receive training in the activities they will need to carry out at home. Psychologists consult with the physical therapists on ways to help the family cope with stressful situations. The advantages of including the entire family in health care planning and treatment are described and suggestions are made for applying the principles in any physical therapy setting.

Adaptation, Psychological↗

PubMed1976

The kinetic mechansim of bovine milk galactosyltransferase. The role of alpha-lactalbumin.

Initial rate parameters obtained with bovine galactosyltransferase at saturating Mn2+ concentrations, and a variety of acceptors including N-acetylglucosamine, glucose, ovalbumin, and di-N-acetylglucosamine are inconsistent with an ordered addition of UDP-galactose and acceptor substrates to the enzyme-Mn2+ complex. Inhibition patterns with N-acetylglucosamine or UDP-glucose as inhibitors of the galactosylation of ovalbumin indicated that either UDP-galactose or N-acetylglucosamine can bind to an enzyme-Mn2+ complex by a random equilibrium mechanism. Initial rate studies also indicate that alpha-lactalbumin may bind to either an enzyme-Mn2+-acceptor complex or an enzyme-Mn2+-UDP-galactose complex, suggesting that lactose synthesis also proceeds by a random equilibrium addition of substrates and alpha-lactalbumin. From the initial rate data assuming the random equilibrium mechanism, the dissociation constants for UDP-galactose, acceptor substrates, and alpha-lactalbumin from the appropriate complexes have been calculated. These values are in good agreement with those obtained independently by nonkinetic methods, providing additional support for the proposed random equilibrium mechanism. From similar studies with a cross-linked complex of alpha-lactalbumin and transferase, dissociation constants for UDP-galactose and acceptor substrates from the enzyme-Mn2+-alpha-lactalbumin complex were calculated. Comparison of each of the dissociation constants in the substrate addition phase shows that the binding of acceptor substrates and alpha-lactalbumin to enzyme-Mn2+ complexes is highly synergistic; the affinity of alpha-lactalbumin for the enzyme-Mn2+ acceptor complex is about 2 orders of magnitude greater than for the enzyme-Mn2+ complex. Similarly, the affinity of the acceptor for the enzyme-Mn2+-alpha-lactalbumin complex is about 2 orders of magnitude greater than the enzyme-Mn2+ complex. Synergism is also observed between alpha-lactalbumin and UDP-galactose binding but the synergism is much less than that observed with acceptor substrates and alpha-lactalbumin. Thus, the large decrease in the Michaelis constant for glucose in the presence of alpha-lactalbumin, which is observed for lactose synthesis by the galactosyltranferase, is primarily the result of the high degree of synergism in the binding of alpha-lactalbumin and glucose to enzyme-Mn2+ complexes. This synergism also accounts for the activation of N-acetyllactosamine synthesis by alpha-lactalbumin at low concentrations (less than 2 mM) of N-acetylglucosamine. An abortive enzyme-Mn2+-UDP-acceptor complex in the product release phase of the reaction appears to account for the inhibition of either lactose, or N-acetyllactosamine synthesis at a high concentration of either N-acetylglucosamine or glucose. This abortive complex is further stabilized by alpha-lactalbumin, thus the resulting substrate inhibition is observed at much lower acceptor concentrations in the presence of alpha-lactalbumin.

Acetylglucosamine↗

PubMed1976

Comparative evaluation of drug interaction publications--1976.

The usefulness of several reference books in the retriveal and application of drug interaction information was evaluated. Each publication was evaluated as to whether it included information that would be necessary to determine if a suspected interaction was actually occurring. Twenty drug combinations which may interact were studied. In addition, the general format and features of each publication were reviewed. The American Pharmaceutical Association's Evaluations of Drug Interactions and Hansten's Drug Interactions were reviewed favorably on all points. Stockley's Drug Interactions and their Mechanisms was considered nearly as complete and certainly as authoritative. Cohen's Drug Interactions: A Handbook for Clinical Use, Gant's Drug Interaction Index: A Survey of Drug Interactions and Hartshorn's Handbook of Drug Interactions, were deemed useful as an added check if an interaction suspected clinically was not included in any of the former group.

Drug Information Services↗

PubMed1975

Conformational changes of glyceraldehyde-3-phosphate dehydrogenase induced by the binding of NAD. A unified model for positive and negative cooperativity.

The fluorescence of the natural coenzyme, NADH, is used to monitor the environment of the nicotinamide moiety at the active centre of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12). Changes of the fluorescence quantum yield and polarization of a small amount of NADH, totally bound by an excess of enzyme, show that at half-saturation of the oligomer with NAD a conformational change is induced which affects the active centre regions of the remaining subunits. This conformational transition is not effected by adenosine diphosphoribose, suggesting that the binding of the nicotinamide moiety of NAD to two subunits is essential for the change of tertiary structure of the remaining subunits that causes the observed changes of the fluorescence properties of the ADH "tracer probe". It is suggested that this conformational transition of the oligomer is responsible for the major decrease of affinity for NAD which occurs at half-saturation, and possibly for the activation by NAD+ of the reductive dephosphorylation reaction catalysed by the enzyme. It is also suggested, by analogy with haemoglobin, that the molecular basis of the negative cooperativity may be the creation of additional intersubunit bonds during the binding of the first two NAD molecules to the tetramer, and a change from a "relaxed" quaternary structure to a "tense" structure at half-saturation.

Adenosine Diphosphate Sugars↗

PubMed1975

Modification of bovine alpha-lactalbumin with N-bromosuccinimide and 2-hydroxy-5-nitrobenzylbromide.

Reaction of alpha-lactalbumin at pH 7 in aqueous solution with either 2-hydroxy-5-nitrobenzylbromide or N-bromosuccinimide yields derivatives in which only 2 of the 4 tryptophan residues are modified. All 4 residues of tryptophan are modified under the similar conditions in 8 M urea. Structural analysis of the modified derivatives revealed that tryptophans 26 and 118 are the sole reactive residues and that tryptophan 118 reacts more rapidly than tryptophan 26. The fluorescence of alpha-lactalbumin modified to varying extents with N-bromosuccinimide indicates that tryptophan 118 is exposed to solvent whereas tryptophan 26 is in a more hydrophobic environment. The chemical reactivities and fluorescence properties of tryptophans 26 and 118 are consistent with the proposed conformations of alpha-lactalbumin based on its similarity with egg white lysozyme. The kinetic properties of both derivatives of alpha-lactalbumin containing up to 2 modified residues indicate that each derivative has decreased affinity for the galactosyltransferase but that at saturating concentrations, Km and Vmax for lactose synthesis are unchanged from those of native alpha-lactalbumin.

2-Hydroxy-5-nitrobenzyl Bromide↗

PubMed1975

Studies of coenzyme binding to rabbit muscle glyceraldehyde-3-phoshate dehydrogenase.

The binding of NAD+, NADH and adenosine diphosphoribose (Ado-PP-Rib) to a stable, highly active and nucleotide-free preparation of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase (D-glyceraldehyde-3-phosphate: NAD+ oxidoreductase (phosphorylating), EC 1.2.1.12) has been studied. All three nucleotides quench the protein fluorescence to the same extent when they bind to the enzyme, and this property has been used to measure the dissociation constants for the two high-affinity binding sites for the nucleotides. The results indicate negative interactions between, or non-identify of, these two binding sites, to which NAD+ and NADH bind with similar affinity. The binding of NAD+ to the enzyme has been studied by spectrophotometric titrations at 360 nm. It appears that the binding of NAD+ to each of the four subunits of the enzyme contributes equally to the intensity of this 'Racker' band. The dissociation constants associated with the binding of the third and fourth molecules of NAD+ estimated from such titrations confirm some previous estimates. The binding of NADH to the enzyme causes a decrease of intensity of the absorbance of the coenzyme at 340 nm, and the dissociation constants for binding of the third and fourth molecules of NADH have been estimated from spectrophotometric titrations. They are the same as those for NAD+. Judging by the apparent dissociation constants, negative interactions on binding the third molecule of NAD+ or NADH are more marked than those associated with the binding of the second and fourth molecules, suggesting that a major conformational change occurs at half-saturation of the tetramer with coenzyme.

Adenosine Diphosphate Sugars↗

PubMed1974