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Biomedical subjects

B K Evans

Publications and source records attributed to B K Evans.

At least 19 recordsLinked to original sources
PubMed1992

Evidence for direct vasoconstrictor activity of melatonin in "pressurized" segments of isolated caudal artery from juvenile rats.

Responses of isolated, 60 mmHg 'pressurized' segments of the distal caudal artery of adult and juvenile Wistar rats to melatonin and the selective alpha 2-adrenoceptor agonist 5-bromo-6-[2-imidazolin-2-ylamino]-quinoxaline bitartrate (UK-14304) were examined using the Halpern pressure myograph. Melatonin showed no direct vasoconstrictor activity in vessels from adult rats, whereas UK-14304 produced moderate vasoconstriction (pD2-7.43 +/- 0.09). In the presence of phenylephrine-induced tone, melatonin produced a variable but small constrictor response (less than 10 microns reduction in diameter) in some vessels; the response to 1 mumol/l UK-14304 was less than in the absence of tone. In vessels isolated from juvenile rats, melatonin caused concentration-dependent vasoconstriction with a maximum response about 70% of the maximum response elicited by UK-14304. Vessels from juvenile rats were more sensitive to melatonin (pD2-9.40 +/- 0.07) than they were to UK-14304 (pD2-8.12 +/- 0.14). In the presence of phenylephrine-induced tone, the vasoconstrictor responses to both melatonin and IK-14304 were markedly less; the sensitivity to melatonin was not different from that seen in the absence of tone. These findings indicate that 'pressurized' segments of the isolated distal caudal artery may provide a simple and convenient, functional model of melatonin receptors. The findings also appear to implicate melatonin in thermoregulatory processes in juvenile rats.

Aging↗
PubMed1992

A pharmacokinetic study of sulphasalazine and two new formulations of mesalazine.

We have examined the pharmacokinetics of enteric coated sulphasalazine compared with two new formulations of mesalazine. These consisted of microgranules of mesalazine coated with Eudragit S in a concentration of either 20 or 25% dry lacquer substance; these in turn were enclosed in capsules coated with Eudragit L. In-vitro dissolution studies of coated microgranules showed that drug release was pH dependent. Studies in 7 normal volunteers showed median peak concentrations of 5-amino-salicylic acid and N-acetyl-5-amino-salicylic acid occurred at about 6 hours with both microgranular preparations, compared with sulphasalazine at 15 h. The microgranule formulation coated with 20% Eudragit S gave serum levels and overall systemic absorption similar to values with sulphasalazine. This new formulation may be of value for delivering mesalazine and other therapeutic agents to the colon.

Adult↗
PubMed1991

Duchenne's muscular dystrophy: review and recent scientific findings.

In this brief review, we describe the clinical manifestations of Duchenne's muscular dystrophy (DMD) and other similar syndromes, outline the history of the dystrophin gene's identification and its relationship to these muscular dystrophies, and relate the importance of the gene's discovery to clinical neurology. We do not discuss treatment.

Animals↗
PubMed1990

Tripotassium dicitrato bismuthate enemas in the treatment of ulcerative proctitis.

Eleven patients with active proctitis or proctosigmoiditis completed one month's treatment with tripotassium dicitrato bismuthate enemas administered at night. Symptoms, sigmoidoscopic appearances, and the histological grade of acute inflammation were assessed at the commencement of therapy and after one month. An overall score of these features showed improvement in 9 of 11 patients, which encourages further investigation of bismuth in controlled trials for patients with inflammatory bowel disease.

Adult↗
PubMed1990

Paraneoplastic motor neuron disease and renal cell carcinoma: improvement after nephrectomy.

A 74-year-old man had a paraneoplastic motor neuron disease mimicking amyotrophic lateral sclerosis. He had an elevated erythrocyte sedimentation rate, other laboratory abnormalities, and a previously undiagnosed renal cell carcinoma. Four months after nephrectomy, his strength had improved and he had no fasciculations. Seven other patients with cancer and motor neuron disease improved or stabilized after tumor treatment. Even though it is rare, paraneoplastic motor neuron disease is important to diagnose because it may be treatable.

Aged↗
PubMed1989

Distribution of substance P in the enteric plexuses of the small intestine of the platypus, Ornithorhynchus anatinus.

A study was made of substance P-like-immunoreactive nerves within the small intestine of platypus, an Australian prototherian mammal. Both immunoreactive nerve cell bodies and fibers were present. No immunoreactive fibers were found in mesenteric nerves or on intramural blood vessels, suggesting that extrinsic sensory neurons containing substance P do not innervate platypus ileum. This was further supported by the result of in vitro experiments. Although applied substance P (10(-9) M-3 x 10(-8) M) caused contraction of the longitudinal muscle, neither mesenteric nerve stimulation nor application of capsaicin caused contractions.

Animals↗
PubMed1989

The effects of multivitamins and minerals on children with Down syndrome.

The effects of high-dosage multivitamin and mineral supplements on 15 children with Down syndrome aged between 7.5 and 63 months were studied in a placebo-controlled crossover trial. Active treatment was associated with decreased developmental progress, and various side-effects were reported by the parents. The only suggestions of benefit were parents' observations of improvement in general appearance and skin freshness. However, the parents were willing to continue using the treatment and to recommend it to other parents, despite the side-effects.

Child, Preschool↗
PubMed1989

Reversible neuromuscular syndrome in malnourished children.

Six young children are reported who were malnourished, with hypotonia, weakness and absent stretch reflexes, both proximally and distally, but with normal sensory examinations. Motor and sensory nerve conduction velocities also were normal. Five had mildly abnormal electromyograms, with scattered fibrillations, positive sharp waves and increased insertional activity, both proximally and distally. After adequate nutrition in hospital, all the children's reflexes returned and strength improved. Weight for height was an important indicator: it was decreased when the muscle stretch reflexes were absent and increased when they returned. The neurological and electrodiagnostic findings imply that this is a reversible lower motor-neuron or muscle disorder.

Child, Preschool↗
PubMed1989

HTLV-I-associated myelopathy and polymyositis in a US native.

A patient who had always lived in the United States had an HTLV-I infection and a chronic myelopathy clinically mimicking amyotrophic lateral sclerosis. Needle EMG and nerve conduction studies were consistent with anterior horn cell disease but muscle biopsy showed denervation and an inflammatory myopathy. Serum HTLV-I antibody tests were positive and HTLV-I DNA was present in peripheral leukocytes. This is the 1st reported US native with HTLV-I-associated myelopathy and polymyositis.

Aged↗
PubMed1986

Fluctuation of simian virus 40 (SV40) super T-antigen expression in tumors induced by SV40-transformed mouse mammary epithelial cells.

Higher-molecular-weight forms of the simian virus 40 (SV40) large tumor antigen (T-Ag), designated super T-Ag, are commonly found in SV40-transformed rodent cells. We examined the potential role of super T-Ag in neoplastic progression by using a series of clonal SV40-transformed mouse mammary epithelial cell lines. We confirmed an association between the presence of super T-Ag and cellular anchorage-independent growth in methylcellulose. However, tumorigenicity in nude mice did not correlate with the expression of super T-Ag. In the tumors that developed in nude mice, super T-Ag expression fluctuated almost randomly. Cell surface iodination showed that super T-Ag molecules were transported to the epithelial cell surface. The biological functions of super T-Ag remain obscure, but it is clear that it is not important for tumorigenicity by SV40-transformed mouse mammary epithelial cells. Super T-Ag may be most important as a marker of genomic rearrangements by the resident viral genes in transformed cells.

Animals↗
PubMed1985

Absorption of delayed-release prednisolone in ulcerative colitis and Crohn's disease.

The absorption and urinary excretion of [3H]prednisolone after oral ingestion was examined using hard gelatin capsules with and without a coating of Eudragit-S which delayed release of the contents. In 6 patients with ulcerative colitis absorption was delayed until the preparation reached the colon but the total absorption was unchanged. In 6 patients with Crohn's disease and ileal strictures the preparation broke proximal to the stricture and absorption was delayed until this occurred (within 4-12 h). In 5 patients with Crohn's disease and intestinal resections the capsules broke unreliably.

Adult↗
PubMed1979

Quantitative structure--activity relationships and carminative activity II: steric considerations.

The unexplained variation in the relationships between carminative activities and octanol--water distribution coefficients of various classes of compounds was explained. The steric substituent constant (Es) value, van der Waals volume, and molecular connectivity were introduced into a previously derived correlation. Each parameter brought about an improvement, and molecular connectivity was the most successful. Correlations containing molecular connectivity was the most successful. Correlations containing molecular connectivity terms explained the excess variation. The results were in agreement with a mechanism in which carminative activity depended on the availability of the oxygen atom in the functional group of the molecule and was reduced when the substituent attached to the oxygen hindered the interaction between the oxygen atom and the receptor.

Animals↗
PubMed1979

Reinnervation following guanethidine-induced sympathectomy of adult rats.

The reinnervation of various tissues by autonomic neurons has been studied in adult rats which had been sympathectomized by chronic guanethidine treatment (30 or 60 mg/kg/day for 8--15 weeks). In the heart, iris, ileum, mesentery, vas deferens and epididymis, fluorescence histochemistry reveals an almost complete disappearance of adrenergic fibres which is very longlasting. Even after 63 weeks few fluorescent fibres can be seen in these tissues and the density of innervation is not increased by incubation in alpha-methylnoradrenaline. The superior cervical ganglion represents an exception; large numbers of fluorescent fibres but few fluorescent ganglion cells were apparent during recovery. Axon counts carried out by electron microscopy on the vas deferens showed that after recovery for one year the number of axons was similar to that of controls; however, the pattern of innervation was abnormal, small granular vesicles were rarely seen and there was little uptake of 5-hydroxydopamine. On the basis of this evidence and of some pharmacological data it is suggested that there is a limited reinnervation by adrenergic axons accompanied by a great increase in the number of non-adrenergic, possibly cholinergic, axons.

Animals↗