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Biomedical subjects

R Allen

Publications and source records attributed to R Allen.

At least 235 records · Page 13Linked to original sources
PubMed1984

The pathogenesis of Dieulafoy's gastric erosion.

The solitary gastric erosion of Dieulafoy is rarely recognized but is not an uncommon cause of massive upper gastrointestinal hemorrhage. The English literature has only recently described this lesson in vivo. Its etiology and pathogenesis has remained poorly defined since first described in 1896. We have recently studied a series of nine cases (the largest English literature series), five of which were recognized and diagnosed at operation. Multiple tissue staining techniques were used to study the biopsy specimens for "clues" as to the pathogenesis of this lesion to be a vascular dysplasia that is associated with chronic gastritis and that thrombosis and necrosis of the abnormally tortuous submucosal artery occurs before perforation and exigent bleeding. The total lack of inflammatory reaction at the base of the lesion precludes a diagnosis of "ulceratio simplex" as originally described.

Adult↗
PubMed1983

Time series methods in the monitoring of intracranial pressure. Part 2: Comparative study and initial assessment.

The primary objective of monitoring intracranial pressure (ICP) is to detect a reduction in brain compliance at an early stage in order to be able to initiate corrective therapy and thus ensure that an adequate cerebral perfusion is maintained. This paper describes studies aimed at assessing the value of several time series analysis techniques as a basis for a scheme of monitoring ICP. The theoretical foundations for this work were laid in part 1. The paper begins with the outline of a suite of computer programs that were written to implement the techniques selected. Early results from studies with the programs are presented and the discussion is directed towards explaining practical aspects and limitations of the methods that were experienced. It is concluded that the most promising avenue for future development is the use of a dynamic linear model with a recursive parameter estimator within an adaptive framework. The direction of this future work is presented.

Computers↗
PubMed1983

Time series methods in the monitoring of intracranial pressure. Part 1: Problems, suggestions for a monitoring scheme and review of appropriate techniques.

Intracranial hypertension is a dangerous condition and poses a constant threat to patients suffering, for example, a severe head injury. Anticipation of this condition can, however, be difficult. This paper introduces problems that are created in patient management by the pathophysiology of intracranial hypertension and describes methods that have been devised to anticipate the condition, indicating their limitations. A scheme incorporating trend detection and prediction is then suggested for monitoring intracranial pressure (ICP). Several techniques from the fields of time series analysis and control engineering were selected as candidates for the basis of the scheme. These are described and their strengths and weaknesses discussed in the context of the ICP monitoring scheme. The application of time series methods to patient monitoring is reviewed in parallel with these descriptions to indicate the momentum of developments in this area of work. This theoretical background has enabled the direction of further work to be established. In particular it is suggested that adaptive methods are necessary to provide a satisfactory response to significant changes in the measured variable, to avoid repeated alarms and to allow useful short-term predictions of the variable to be made.

Humans↗
PubMed1983

Functional changes of intermediate filaments in fibroblastic cells revealed by a monoclonal antibody.

We describe reversible changes of intermediate filaments of fibroblastic cells associated with changes in the functional state of the cells. The changes are revealed by comparing the immunofluorescence patterns given by a monoclonal antibody and a polyclonal serum, both recognizing vimentin. The state of the filaments depends on culture density; this effect cannot be attributed to the nutritional state of the cells, their growth rate, or substances released into the medium. It seems to depend mainly on the aggregation of filaments during strong cell movements. The possible significance of these findings for the functional role of intermediate filaments is discussed.

Animals↗
PubMed1983

Differential pulse polarographic determination of iodine in foods and nutritional products.

A differential pulse polarographic procedure is described for the analysis of iodine in foods and nutritional products. Samples with iodine concentrations ranging from 5000 to 0.2 ppm have been successfully analyzed using this procedure. Precision averaged between 2 and 10% relative to the iodine level measured. Recoveries of added iodine ranged from 89 to 108% with external standards, and 97-100% by an analyte additions technique. Samples analyzed include dried almonds, whey protein concentrate, nonfat dried milk, sea kelp, vitamin-mineral nutritional supplements, diet meal replacement products, dried green beans, dried mushrooms, and wheat germ.

Food Analysis↗
PubMed1982

Immunoglobulin E and the eczema-asthma syndrome in early childhood.

250 infants from atopic families were investigated to determine the relation between serum IgE concentrations and the development of atopic symptoms. In 44 (17.6%) atopy developed before the age of two years, 60 (24%) had doubtful symptoms, and 146 (58.4%) were clinically clear. Those who were definitely affected had higher serum IgE than those who were unaffected but 50% of them had serum IgE within the normal range. 9% of the clinically unaffected infants had raised serum IgE. Breast-feeding was in no way protective against either the development of atopy or an increase in IgE to abnormal levels.

Asthma↗
PubMed1982

Intestinal absorption of amino acid derivatives: importance of the free alpha-amino group.

The intestinal absorption of L-lysine-p-nitroanilide, L-alanine-p-nitroanilide, and glycine-p-nitroanilide was studied in the presence of competitive inhibitors in a perfused rat intestine. It ws observed that L-lysine-p-nitroanilide absorption was inhibited by L-lysine methyl ester and L-arginine-beta-naphthylamide but not by N alpha-acetyl-L-lysine methyl esters. L-Alanine-p-nitroanilide absorption was inhibited by L-alinine methyl ester but not by beta-alanine methyl ester. It was further observed that N alpha-benzoyl-L-arginine-p-nitroanilide and N alpha-succinyl-L-phenylalanine-p-nitroanilide were poorly absorbed. It was concluded that the peptidase in the brush border region that serves as the hydrolysis site requires a free alpha-amino group (an aminopeptidase), and that passive absorption of these compounds occurs only to a small extent.

Amino Acids↗
PubMed1982

Disseminated cryptococcosis after transurethral resection of the prostate.

A 63-year-old man presenting with acute retention and dysuria underwent transurethral resection of the prostate for suspected benign prostatic hypertrophy. Ten days postoperatively he developed disseminated cryptococcosis. Re-examination of the prostatic chips revealed cryptococcal prostatitis. Treatment consisted of amphotericin, flucytosine and transfer factor along with wedge resection of a pulmonary toruloma. He remains well 12 months after cessation of treatment. This appears to be the first case report in Australia of cryptococcal prostatitis with dissemination after transurethral resection of the prostate.

Amphotericin B↗
PubMed1982

RBC and plasma levels of haloperidol and clinical response in schizophrenia.

The authors conducted a fixed-dose study of haloperidol blood levels and clinical response in schizophrenic in patients and found that those with steady-state RBC haloperidol levels in the range of 2.4--5.4 ng/ml showed greater improvement than those with lower or higher levels. They found a similar , although nonsignificant, curvilinear relationship between plasma haloperidol levels and clinical response. These findings suggest that the relationship between haloperidol blood levels and clinical response fits a therapeutic window for the treatment of schizophrenia.

Adolescent↗
PubMed1982

Effects of neuroleptics on platelet monoamine oxidase activity.

Platelet MAO activity in schizophrenics was significantly decreased, by about 15%, after 3 weeks of treatment with haloperidol. Treatment with thioridazine or butaperazine also tended to decrease platelet MAO activity. The neuroleptic-induced decrease began to appear within a few days of treatment and did not show tolerance over 1-2 months of treatment with haloperidol. Platelet MAO activity of schizophrenic patients measured during drug-free base-line was not significantly different from that of normal controls, but MAO activity of schizophrenics was significantly lower than normals after 3 weeks of treatment with neuroleptics. The extent of decrease in platelet MAO activity correlated negatively with base-line prolactin and its increase after 24 hr. With PEA as substrate, the decrease in activity correlated positively with steady state plasma haloperidol.

Adult↗
PubMed1981

Evidence for two types of rat liver microsomes with differing permeability to glucose and other small molecules.

Radioisotope flux measurements using Millipore filtration revealed two populations of rat liver microsomes designated type A and B. Type A and B vesicle are similar in that both are essentially impermeable to sucrose yet permeable to Cl-. About 70% of the microsome (type A) are permeable to D-glucose, L-glucose, 2-deoxy-D-glucose, D-mannose, D-mannitol, uridine, glycine, L-leucine, choline+, Tris+, Rb+, K+, and Na+. Other solutes such as D-gluconate-, D-glucosamine+, N-acetyl-D-glucosamine, L-glutamate-, L-lysine+, sulfate2-, oxalate2-, and phosphate anions transverse type A vesicles with an intermediate rate. All of the above solutes except Cl- pass with a comparatively slow rate the remaining 30% type B vesicles. Both type A and B microsomes are relatively impermeable to glucose 6-phosphate and related monophosphates. Membrane potential measurements using liver microsomes and control membrane vesicles derived from rabbit skeletal muscle sarcoplasmic reticulum indicated that type A liver microsomes, despite being permeable to K+ and Na+, either lack or contain only a small number of highly conducting K+ and Na+ structures, such as the K,Na channel of sarcoplasmic reticulum. Treatment with the anion transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid lowered the permeability of type A vesicles to several uncharged and negatively charged solutes including D-glucose and gluconate-. These results suggest that a large fraction of liver microsomes is rendered permeable to various biologically relevant solutes and ions, perhaps through the presence of one or more channels with a maximal diameter of approximately 7-8 A which select(s) against solutes on the basis of their size and charge.

Animals↗
PubMed1981

Permeability of reconstituted sarcoplasmic reticulum vesicles. Reconstitution of the K+, Na+ channel.

Permeability properties of reconstituted rabbit skeletal muscle sarcoplasmic reticulum vesicles were characterized by measuring efflux rates of [3H]inulin, [3H]choline+, 86Rb+, and 22Na+, as well as membrane potential changes using the voltage-sensitive probe, 3,3'-dipentyl-2,2'-oxacarbocyanine. Native vesicles were dissociated with deoxycholate and were reconstituted by dialysis. Energized Ca2+ accumulation was partially restored. About 1/2 of the reconstituted vesicles were found to be 'leaky', i.e., permeable to choline+ of Tris+ but not to inulin. The remaining reconstituted vesicles were 'sealed', i.e., impermeable to choline+, Tris+ and inulin. Sealed reconstituted vesicles could be further subdivided according to their K+, Na+ permeability. About 1/2, previously designated Type I, were readily permeable to K+ and Na+, indicating the presence of the K+, Na+ channel of sarcoplasmic reticulum. The remaining sealed vesicles (Type II) formed a permeability barrier to K+ and Na+, suggesting that they lacked the K+, Na+ channel. These studies show that the K+, Na+ channel of sarcoplasmic reticulum can be solubilized with detergent and reconstituted with retention of activity. Furthermore, our results suggest that part or all of the decreased Ca2+-loading efficiency of reconstituted vesicles may be due to the presence of a significant fraction of leaky vesicles.

Animals↗