Search PubMed⌕ Search

Biomedical subjects

S Reid

Publications and source records attributed to S Reid.

At least 127 records · Page 7Linked to original sources
PubMed1993

A reappraisal of the role of caffeine in ECT.

Caffeine lengthens ECT seizures, perhaps by lowering the convulsive threshold. The authors assessed the impact of caffeine on the convulsive threshold and seizure duration. The convulsive threshold and seizure durations of 12 inpatients receiving right unilateral ECT were determined with and without caffeine pretreatment. Caffeine did not change the convulsive threshold, but it did lengthen seizure duration. Caffeine's lengthening of seizure duration without affecting the convulsive threshold is an uncertain benefit in right unilateral ECT.

Brain↗
PubMed1992

Avoiding rapid growth at high cell densities: a potentially important optimisation criterion for hybridoma cultures.

Inhibition caused by rapid changes in the environment has earlier been observed in hybridoma cultures following deliberate step-changes in the culture environment. This paper presents evidence of similar effects occurring during the normal span of continuous cultures fed enriched medium at low dilution rates (0.002-0.005 1/h). The effect of this observation on optimisation is discussed. In continuous culture at a dilution rate of 0.013 1/h, a viable cell density of 4 x 10(9) cells/l was achieved by gradually increasing the nutrient concentration in the feed medium. The MAb titre was 200 mg/l representing a 6-fold increase compared to batch culture and a 2-fold increase compared to continuous culture using standard medium.

Antibodies, Monoclonal↗
PubMed1992

Modelling the growth and protein production by insect cells following infection by a recombinant baculovirus in suspension culture.

A mathematical model has been developed to describe the growth and infection of insect cells by recombinant baculoviruses. The model parameters were determined from a series of independent experiments involving batch suspension culture. The profiles generated by the model for cell growth, virus production and protein production agree with those observed in experiments. Presently, the model simulates only systems where cells are not growth-limited. The model is useful in aiding the design and optimization of large-scale systems for production of biological insecticides as well as recombinant proteins and in delineating those areas which are limiting the process and require further, more fundamental, investigation.

Animals↗
PubMed1992

Overexpression of the trk tyrosine kinase rapidly accelerates nerve growth factor-induced differentiation.

To investigate the role of the gp140trk receptor tyrosine kinase in nerve growth factor (NGF)-induced differentiation, we have overexpressed gp140trk in the NGF-responsive PC12 cell line. Here we demonstrate that overexpression of gp140trk results in marked changes in NGF-induced differentiation. Whereas PC12 cells elaborated neurites after 2 days of continuous exposure to NGF, PC12 cells overexpressing gp140trk by 20-fold(trk-PC12) began this process within hours. Compared with wild-type PC12 cells, trk-PC12 exhibited an increase in both high and low affinity NGF-binding sites. Furthermore, trk-PC12 cells displayed an enhanced level of NGF-dependent gp140trk autophosphorylation, and this activity was sustained for many hours following ligand binding. The tyrosine phosphorylation or activity of several cellular proteins, such as PLC-gamma 1, PI-3 kinase, and Erk1 and the expression of the mRNA for the late response gene transin were also sustained as a consequence of gp140trk overexpression. The data indicate that overexpression of gp140trk in PC12 cells markedly accelerates NGF-induced differentiation pathways, possibly through the elevation of gp140trk tyrosine kinase activity.

Animals↗
PubMed1991

Characterization of functional calcitonin gene-related peptide receptors on rat lymphocytes.

Calcitonin gene-related peptide (CGRP), a vasoactive neuropeptide present in peripheral neurons, is released at local sites of inflammation. In these studies specific high affinity adenylyl cyclase linked CGRP receptors were characterized on rat lymphocytes. The distribution, affinity, and specificity of CGRP receptors was analyzed by radioligand binding. 125I-[His10]CGRP binding to rat lymphocytes was rapid, reaching equilibrium by 20 to 30 min at 22 degrees C, and dependent on cell concentration. The dissociation constants, Kd, for the CGRP receptor on purified T and B lymphocytes are 0.807 +/- 0.168 nM and 0.387 +/- 0.072 nM and the densities are 774 +/- 387 and 747 +/- 244 binding sites/cell, respectively. Competition binding studies determined that rat CGRP inhibits 125I-[His10]CGRP binding to lymphocytes with the highest affinity (Ki = 0.192 +/- 0.073) followed by human CGRP and the CGRP receptor antagonist CGRP8-37. 125I-[His10]CGRP binding to rat lymphocytes was not inhibited by the neuropeptides substance P, calcitonin, or neuropeptide Y. Lymphocyte CGRP receptor proteins were identified by affinity labeling by using disuccinimidyl suberate to covalently cross-link 125I-[His10]CGRP to its receptor. Specifically labeled CGRP binding proteins visualized by SDS-PAGE analysis had molecular masses of 74.5 and 220 kDa. A third high molecular mass protein band which did not penetrate the gel was also observed. In functional studies, CGRP stimulated a rapid, sustained increase in cAMP with an ED50 of approximately 8 pM. In experiments comparing optimal concentrations of isoproterenol, a beta 2-adrenergic agonist, and CGRP, intracellular cAMP elevation after isoproterenol treatment returned to basal levels by 30 min, whereas cAMP was still elevated at 60 min after CGRP treatment. The response to CGRP was specific in that it could be completely blocked by CGRP8-37. The presence of high affinity functional CGRP receptors on T and B lymphocytes provides evidence for a modulatory role for CGRP in regulating lymphocyte function.

Adenylyl Cyclases↗
PubMed1991

Weaning of three hybridoma cell lines to serum free low protein medium.

A general weaning procedure is described which allowed a range of hybridomas to be weaned readily off serum without loss of antibody production. Initial work was carried out with one cell line only (SPO1 cells) and one serum substitute containing a final protein concentration of 40 mg l-1. The SPO1 cells were first adapted to a range of readily available basal media and then weaned off serum by a range of protocols. From this work an optimal weaning protocol and basal medium for weaning were determined. These were then used to wean the SPO1 cells and two other cell lines off serum with a second, protein free, serum substitute with varying concentrations of defined proteins added. All three cell lines investigated were readily weaned off serum by this protocol at protein concentrations as low as 1 mg l-1. No loss of antibody production was observed with any of the cell lines. The weaning procedure outlined in both simple and rapid and has been successfully adopted in our laboratory by relatively inexperienced cell culture technicians.

Animals↗
PubMed1991

Role of amniotic fluid cytogenetic analysis in the evaluation of recent fetal death.

Chromosome abnormalities may be present in approximately 10% of cases of fetal death. Because of cell maceration and autolysis, the likelihood of successful karyotype analysis of fetal tissue varies inversely with the time between fetal death and delivery. In an attempt to reduce the influence of these postmortem changes, we obtained amniotic fluid cells for cytogenetic studies from 12 fetuses as soon as possible after the diagnosis of fetal death was confirmed. We also obtained fetal tissue for cell culture in ten of the cases immediately following evacuation of the uterus. Cell culture was successful in 11 of 12 amniotic fluid specimens and in only one of ten fetal tissue specimens (p less than 0.001). Since the results of cytogenetic studies are of such importance in counseling patients regarding recurrence risk for fetal death, we recommend that amniotic fluid cells be obtained for karyotype analysis at the time of diagnosis of fetal death rather than awaiting delivery of a potentially macerated and autolyzed fetus.

Amniotic Fluid↗
PubMed1991

Isokinetic trunk-strength deficits in people with and without low-back pain: a comparative study with consideration of effort.

The purposes of this study were to determine (a) the degree and distribution of isokinetic trunk strength deficits in people with chronic low-back pain (CLBP) and (b) to what degree subject effort during testing affects those deficits. We measured the isokinetic trunk strengths of three subject groups on the Cybex Trunk Extension/Flexion machine. Groups 1 and 2 consisted of 155 men and women with CLBP who were divided into maximal (n = 115) and submaximal (n = 40) groups according to their torque/position curve variability. Group 3 was made up of 32 back-healthy men and women who served as controls. The results demonstrated that men had higher flexion and extension torques than women did for all groups. The control group had higher flexion and extension torques than the maximal-effort CLBP group did. The extensors had a proportionally greater deficit than the flexors did in this LBP group. Comparing the two groups with CLBP, the maximal-effort group had higher flexion and extension torques than the submaximal effort group did, and the extensors showed a greater deficit. Degree of effort during testing does affect the results. Therapists should consider extensor strengthening and reeducation exercises when designing exercise programs to restore normal function in people with chronic CLBP.

Adult↗
PubMed1990

Liquid chromatography/mass spectrometry of plasma glucose and secreted glucuronate for metabolic studies in humans.

Negative ion thermospray liquid chromatographic/mass spectrometric methods have been developed for the determination of isotopic enrichments for glucose and acetaminophen-uridine diphosphate glucuronate from (1-2H1)glucose, (1-2H1)galactose and (2-13C)acetate in humans. The error of estimate ranged from below 1% to 5%. The advantages of the method include fast analysis (up to 35 per hour), eased sample preparation, good precision, sensitivity comparable with gas chromatography/mass spectrometry and better than with isotope ratio mass spectrometry.

Blood Glucose↗
PubMed1990

Hybridoma growth limitations: the roles of energy metabolism and ammonia production.

Energy metabolism and the production of ammonia in hybridoma cell culture and its inhibitory effects on cell growth are reviewed. The interactive roles of glucose and glutamine metabolism affect the rate of production of ammonia, and these interactions are described. It is shown that growth inhibition usually occurs between 2-4 mM ammonia although some cell lines have been shown to adapt to much higher concentrations, particularly in continuous culture. In batch cultures cell growth appears to be particularly susceptible to increased ammonia concentrations during the early stages of growth; ammonia increased the rate of cell death in the late stage of batch growth. The specific productivity of monoclonal antibodies is much less sensitive to the released ammonia than is growth; lower volumetric productivities relate to the lower viable cell concentrations which are achieved at the high ammonia levels. Techniques to prevent ammonia accumulation or remove ammonia selectively have been relatively unsuccessful to date.

Ammonia↗
PubMed1990

The effect of heart rate on Doppler flow velocity systolic-diastolic ratios in umbilical and uteroplacental arterial waveforms.

In an analysis of the influence of heart rate on Doppler flow velocity waveform-systolic/diastolic ratios from 1555 umbilical artery waveform studies and from 1497 uteroplacental waveform studies, a negative correlation was observed between the ratio and the corresponding heart rate. This relationship was not influenced by gestational age and was similar in pregnancies with normal outcomes when compared with all pregnancies. The magnitude of this inverse relationship is such that the effect of heart rate on systolic/diastolic ratios must be considered when Doppler flow velocity waveform analyses are used as experimental tools to assess placental vascular resistance but it does not appear to be an important factor in general clinical practice when measurements are made during fetal inactivity and when heart rates are within normal ranges.

Blood Pressure↗
PubMed1990

A comparison of two methods of eliciting the ankle jerk.

Two methods of eliciting the ankle jerk have been compared. One, the traditional method, involved tapping the Achilles tendon (the tendon tap); the other (the plantar tap) involved tapping the sole of the foot. The study was done on 110 inpatients in the medical wards of a teaching hospital. The results showed an 89% agreement between the two methods. The extent of agreement was unrelated to the level of experience of the examiner. Forty three per cent of patients favoured the plantar tap method; 14% the tendon tap. The plantar tap method of eliciting the ankle jerk is an acceptable alternative to the traditional method.

Adult↗
PubMed1990

Prevention of experimental cancer and immunostimulation by vitamin E (immunosurveillance).

Eighty young adult male Syrian hamsters were divided into four equal groups. Group 1 animals had the right buccal pouches painted with a 0.1% solution of 7,12 dimethylbenz(a)anthracene (DMBA) three times per wk for 28 wk. Group 2 animals were similarly painted with DMBA for 28 wk but were also given 140 micrograms vitamin E in 0.4 ml mineral oil three times weekly on days alternate to DMBA painting. Group 3 animals were used as DMBA-vehicle controls. Group 4 animals were vitamin E controls. Animals were killed after 28 wk, the pouches photographed and tumors counted, measured. The pouches were fixed in formalin, sectioned in paraffin and studied histologically and histochemically for tumor necrosis factors alpha and beta. All animals in Group 1 and 3 had gross tumors of the right buccal pouch. None of the animals in Group 2 had grossly visible tumors. Microscopic studies revealed that, while no gross tumors were seen in the Group 2 animals, there was histologic evidence of dysplasia and early carcinoma-in-situ undergoing degeneration. Immunohistochemical staining revealed a dense infiltrate of mononuclear cells adjacent to tumor sites with a large number of cytotoxic T lymphocytes and macrophages. Vitamin E appears to prevent tumor formation by stimulating a potent immune response to selectively destroy tumor cells as they begin to develop into recognizable microscopic foci of carcinoma.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

Studies on hybridoma and insect cells in suspension culture.

Our laboratory has over a period of four years conducted extensive research into the metabolism and batch, fed-batch, continuous, perfusion and serum-free culture of hybridomas with a view to increasing the productivity of these animal cell lines. A brief overview of this work and future plans will be presented here. In addition an overview of our more limited work on the Baculovirus expression system using insect cell culture, begun during 1989, will also be given.

Animals↗