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Biomedical subjects

J West

Publications and source records attributed to J West.

At least 19 recordsLinked to original sources
PubMed1992

Whiplash and its effect on the visual system.

Whiplash or indirect injuries to the neck as a consequence of motor vehicle collisions are a common occurrence in which the frequency of ocular complications is largely unknown. Ophthalmic and oculomotor function was investigated in a longitudinal study of 39 cases who had their initial ophthalmological assessment within one week of the whiplash injury. Ten of 39 cases had ocular symptoms and signs which developed shortly after the accident. The principal abnormality in 6 of these was decreased convergence and accommodation, superior oblique muscle paresis in 2, decreased stereoacuity in 1 and bilateral vitreous detachments in 1 patient. All but 2 had complete resolution of their symptoms within 9 months. Four other patients were asymptomatic but had ophthalmic signs which resolved within 3 months. Oculomotor abnormalities following whiplash injuries are generally mild, have a good prognosis, and would appear from this study to be commoner than hitherto expected.

Accidents, Traffic↗
PubMed1992

A prospective study examining the changes in factors that affect visual acuity following trabeculectomy.

Many patients report subjective changes in vision following trabeculectomy. In a prospective study of 16 eyes, we have tried to determine the causes of these visual changes. Ninety-four per cent of eyes showed a change in uncorrected Snellen acuity 1 week following surgery. This change was due to a myopic shift in refraction secondary to changes in the anterior chamber depth. A 1 mm change in anterior chamber depth results in approximately a 2 dioptre change in refractive sphere. Visual acuity starts to return to pre-operative levels by the third post-operative week, from which point no eyes showed a deterioration in corrected acuity of more than one line of Snellen. The vertical corneal radius of curvature is reduced in the early post-operative period and there is a with-the-rule change in corneal astigmatism. This resolves over longer follow-up and the possible causes of this are discussed. No changes were noted in corneal thickness and there was no evidence of macular oedema over the follow-up period. Patients should be warned of these possible visual changes pre-operatively as many will have normal acuity prior to surgery.

Aged↗
PubMed1992

Prevention of acute postoperative pressure rises in glaucoma patients undergoing cataract extraction with posterior chamber lens implant.

Acute elevations in intraocular pressure (IOP) commonly follow extracapsular cataract extraction and lens implant in glaucoma patients. Thirty six patients with glaucoma undergoing cataract extraction and posterior chamber lens implantation received one of three treatments. Group 1: 500 mg of Diamox Sustets (acetazolamide) 1 hour preoperatively (10 patients); Group 2: peroperative intracameral Miochol (acetylcholine) (11 patients); Group 3: the above treatments combined (15 patients). IOPs were measured at 3, 6, 9, and 24 hours postoperatively. The average of the maximum pressure rises above the preoperative level over the 24 hour period was greatest for the group receiving acetazolamide only at 8.9 mm Hg; for the acetylcholine group the average maximum rise was 6.3 mm Hg; while the combined treatment group showed a decrease of 0.7 mm Hg. IOP rises of > 6 mm Hg were seen in 7% of patients (one of 15) in the combined treatment group, 45% (five of 11) of the acetylcholine group, and 70% (seven of 10) of the acetazolamide group. IOP rises of > 10 mm Hg were seen in 7% of the combined treatment group, in 18% of the acetylcholine only group, and in 50% of the acetazolamide only group. A pressure rise > 20 mm Hg was seen in one patient receiving acetazolamide only and one patient receiving acetylcholine only. The difference between the acetylcholine group and the combined group for rises > 6 mm Hg was significant using the chi 2 test while the acetazolamide group showed a significant difference for rises > 6 and 10 mm Hg compared with the combined group. All acute pressure rises were recorded before or at 9 hours following operation except in the combined treatment patient where the rise occurred at 24 hours. To prevent the acute IOP rises seen following cataract surgery with lens implant in glaucoma patients we recommend combined ocular hypotensive therapy.

Acetazolamide↗
PubMed1992

Class I and IV antiarrhythmic drugs and cytosolic calcium regulate mRNA encoding the sodium channel alpha subunit in rat cardiac muscle.

Previous studies have shown that chronic in vivo treatment with the antiarrhythmic drug mexiletine produces an increase in sodium channel number. We examined whether chronic mexiletine treatment would similarly regulate the level of mRNA encoding the cardiac sodium channel. RNA isolated from cardiac tissue was probed with a 2.5-kilobase cRNA transcribed with T7 RNA polymerase from the clone Na 8.4, which encodes nucleotides 3361-5868 of the alpha subunit of the RIIA sodium channel subtype. Chronic mexiletine treatment produced a 3-fold increase in the level of mRNA encoding sodium channel alpha subunits. Previous studies of cultured skeletal muscle cells had suggested that chronic sodium channel blockade may mediate an increase in sodium channel mRNA by changes in cytosolic Ca2+ concentration. To address this issue, we assessed whether verapamil would also produce up-regulation of the level of mRNA encoding the sodium channel and whether the calcium ionophore A23187 would produce the opposite effect on mRNA level. Verapamil treatment increased sodium channel mRNA level up to 3-fold, whereas in vitro A23187 treatment decreased the mRNA level 5-fold. The combination of verapamil and mexiletine produced no further increase in the mRNA level, compared with that seen with the single agents, suggesting a convergent second messenger pathway for the actions of these two drugs. These data show that the level of mRNA encoding sodium channels is substantially increased during antiarrhythmic drug treatment and suggest that change in cytosolic Ca2+ concentration is the second messenger involved in the regulation of levels of mRNA encoding the alpha subunit of the cardiac sodium channel.

Animals↗
PubMed1992

Asepsis--transplant infection control in the OR.

1. A source of microorganisms, a mode of transmission, and a susceptible host are needed for infection to occur. Transplant recipients are susceptible because normal defense mechanisms are undermined by cytotoxic agents and steroids to prevent rejection of the allograft. 2. The specific type of organ transplant affects the site and type of infection. The stress of surgery and the duration of the operative procedure are important risk factors. The more the patient is subjected to invasive procedures, the greater the risk for infection. 3. The responsibility of maintaining sterility for the transplant patient falls on all personnel involved from procurement to implantation. The OR nurse and others involved in transplantation must be aware at all times of the potential introduction of contaminants to the transplant patient.

Asepsis↗
PubMed1991

Characterization of three Agrobacterium tumefaciens avirulent mutants with chromosomal mutations that affect induction of vir genes.

Three Agrobacterium tumefaciens mutants with chromosomal mutations that affect bacterial virulence were isolated by transposon mutagenesis. Two of the mutants were avirulent on all hosts tested. The third mutant, Ivr-211, was a host range mutant which was avirulent on Bryophyllum diagremontiana, Nicotiana tabacum, N. debneyi, N. glauca, and Daucus carota but was virulent on Zinnia elegans and Lycopersicon esculentum (tomato). That the mutant phenotype was due to the transposon insertion was determined by cloning the DNA containing the transposon insertion and using the cloned DNA to replace the wild-type DNA in the parent bacterial strain by marker exchange. The transposon insertions in the three mutants mapped at three widely separated locations on the bacterial chromosome. The effects of the mutations on various steps in tumor formation were examined. All three mutants showed no alteration in binding to carrot cells. However, none of the mutants showed any induction of vir genes by acetosyringone under conditions in which the parent strain showed vir gene induction. When the mutant bacteria were examined for changes in surface components, it was found that all three of the mutants showed a similar alteration in lipopolysaccharide (LPS). LPS from the mutants was larger in size and more heavily saccharide substituted than LPS from the parent strain. Two of the mutants showed no detectable alteration in outer membrane and periplasmic space proteins. The third mutant, Ivr-225, was missing a 79-kDa surface peptide. The reason(s) for the failure of vir gene induction in these mutants and its relationship, if any, to the observed alteration in LPS are unknown.

Bacterial Proteins↗
PubMed1990

Tubulin is phosphorylated at tyrosine by pp60c-src in nerve growth cone membranes.

We show here that tubulin is the major in vivo substrate of the tyrosine-specific protein kinase pp60c-src in nerve growth cone membranes. Phosphotyrosine antibodies were used to demonstrate phosphotyrosyl residues in a subpopulation of alpha- and beta-tubulin that was highly enriched in a subcellular fraction of growth cone membranes from fetal rat brain. The presence of phosphotyrosine-modified isoforms of alpha- and beta-tubulin in vivo was confirmed by 32p labeling of rat cortical neurons in culture. Tubulin in growth cone membranes was phosphorylated at tyrosine in endogenous membrane phosphorylation reactions (0.068 mol phosphotyrosine/mol alpha-tubulin and 0.045 mol phosphotyrosine/mol beta-tubulin), and phosphorylation was specifically inhibited by antibodies directed against pp60c-src, which is localized in the growth cone membranes. pp60c-src was capable of directly phosphorylating tubulin as shown in immune complex kinase assays with purified brain tubulin. Phosphopeptide mapping revealed a limited number of sites of tyrosine phosphorylation in alpha- and beta-tubulin, with similar phosphopeptides observed in vivo and in vitro. These results reveal a novel posttranslational modification of tubulin that could regulate microtubule dynamics at the growth cone.

Animals↗
PubMed1977

Circulatory response to systemic infusion of norepinephrine in the pregnant ewe.

Seven pregnant ewes from 100 to 137 days of gestation were infused with systemic doses of norepinephrine and uterine arterial flow dose-response curves were determined. A constant infusion of norepinephrine at a mean rate of 0.24 mug per minute per kilogram led to a 39.3 per cent decrease in total uterine arterial blood flow as measured with isotope-labeled microspheres while systemic pressure was unaltered. At this dose the reduction in endometrial blood flow (--64 per cent) was significantly greater than that in either the myometrium (--45 per cent) or placental cotyledons (--31 per cent) (p less than 0.005). Significant decreases in blood flow to small bowel, skeletal muscle, vagina, cervix. Fallopian tubes, kidneys, spleen, pancreas, and mammary gland were documented. There were no significant increases in blood flow. This study demonstrates that during the period or pregnancy studied, the overwhelming response to norepinephrine is vasoconstriction and that the vascular beds of all the tissues of pregnant uterus are sensitive to the alpha-adrenergic effects of norepinephrine.

Animals↗