Search PubMed⌕ Search

Biomedical subjects

R H Behrens

Publications and source records attributed to R H Behrens.

At least 73 records · Page 4Linked to original sources
PubMed1990

Automated enzymatic assays for the determination of intestinal permeability probes in urine. 1. Lactulose and lactose.

Lactulose is becoming the disaccharide of choice in the dual sugar assessment of passive permeability of the small intestinal mucosa. However its more widespread use is hampered by current analytical methods which are tedious and time consuming. An automated spectrophotometric technique for the assay of this sugar in urine is presented in which lactulose is linked by a series of enzyme reactions to the equimolar production of NADPH. In addition to lactulose, the procedure also gives accurate values for lactose, glucose and fructose in the urine sample. The assay has been shown to be highly specific for lactulose and lactose and was not affected by high concentrations of other sugars or other urinary constituents. Within assay and between assay precision were similar with the coefficient of variation for both sugars in the range 0.4-1.6%. The technique represents a significant improvement in time, simplicity and precision on existing methods of analysis.

Disaccharides↗
PubMed1987

Factors affecting the integrity of the intestinal mucosa of Gambian children.

The interrelationship between diarrhea, malnutrition, and small bowel integrity was investigated prospectively in 68 Gambian infants aged 0-18 mo. Profiles of growth and morbidity were recorded for 8 mo. Each month intestinal permeability was measured by the differential uptake of orally administered lactulose (L) and mannitol (M). In well infants the mean L:M ratio was 0.42 (range 0.11-1.42). This ratio was increased slightly for underweight (60-80% wt for age) infants (mean 0.52) but considerably for those with marasmus (less than 60% wt for age) (mean 1.3, p less than 0.001), for those with acute or chronic diarrhea (mean 1.0 and 2.85, respectively; p less than 0.001), or with measles (mean 1.4, p less than 0.001). Sequential studies of ward patients with malnutrition and diarrhea showed a rapid fall in L:M ratios with resolution of diarrhea. These studies suggest that damage to the small intestine may play an important part in the development of infant malnutrition in The Gambia.

Carbohydrate Metabolism↗
PubMed1987

Radionuclide tests for the assessment of intestinal permeability.

14C labelled-D-mannitol and aquo (ethylene-diaminetriacetoacetic acid) 51chromium (III) (51Cr EDTA) have been evaluated as markers of intestinal permeability in twenty-four healthy control subjects, sixteen patients with recently diagnosed coeliac disease and twenty subjects with coeliac disease in remission on a gluten-free diet. The percentage excretion of 14C mannitol in urine collected for 6 h was significantly less in patients with coeliac disease (mean 6.7%) than controls (mean 13.5%). Conversely the excretion of 51Cr EDTA was significantly greater in patients with coeliac disease (mean 1.23%) compared with controls (mean 0.28%). The mean ratio of the percentage excretion of 51Cr to the percentage excretion of 14C was 0.29 in patients with untreated coeliac disease compared with 0.023 for healthy control subjects (P less than 0.001). Patients with untreated coeliac disease were clearly separated from control subjects by use of the 51Cr EDTA: 14C mannitol ratio but not by the excretion of independent markers.

Adult↗
PubMed1986

Protein losing enteropathy associated with Nippostrongylus brasiliensis infestation and its impact on albumin homoeostasis in rats fed two levels of dietary protein.

Alterations in plasma albumin concentration and gastrointestinal permeability have been investigated in rats infected with the nematode Nippostrongylus brasiliensis and fed adequate or low protein diets. Infection caused only minor changes in growth and food consumption of well nourished rats but resulted in significant reductions in those fed the low protein diet. Animals in both dietary groups were able to mount an immune response beyond day 10 post-infection (p.i.) which caused expulsion of the parasites, but this was less effective in rats fed the low protein food. Uninfected rats fed the low protein diet had significantly lower plasma albumin concentrations than their well nourished counterparts. Animals of both dietary groups showed a progressive reduction in plasma albumin concentration as the infection developed but values returned towards normal as the parasites were expelled. The reduction in plasma albumin concentration was closely associated with increases in gastrointestinal leakage of plasma protein but losses were far greater in the protein deficiency animals. Beyond day 10 p.i. protein loss decreased in both dietary groups and by day 21 p.i. had returned to normal in well nourished animals but not those fed the low protein diet. Intestinal permeability measured by the lactulose:mannitol ratio technique gave similar results to the protein loss data. Permeability increased as the infection progressed then fell as the worms were expelled but remained above control values in infected protein deficient animals. Overall, animals fed the low protein diet were more severely affected by the parasite than were their well fed counterparts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Traveller's diarrhoea; a controlled study of its effect on chloroquine and proguanil absorption.

The potential for traveller's diarrhoea to impair proguanil and chloroquine absorption and cause chemoprophylaxis failure was investigated in a study involving recently returned travellers who were either asymptomatic or presented with diarrhoea. A routine dose of chemoprophylaxis was administered to 12 travellers with diarrhoea and 12 asymptomatic subjects. The subjects undertook a lactulose-mannitol intestinal permeability test and were bled hourly after prophylaxis ingestion. Plasma analysis of chloroquine and proguanil from serial samples revealed a significantly lower proguanil Cmax (146 ng/mL vs. 196 ng/mL, P = 0.05), and longer tmax (3.1 h vs. 2.6 h, P = 0.05) in the diarrhoea cohorts. The absorption coefficient was lower for proguanil (0.57 vs. 0.76) but the difference did not quite reach levels of significance. Chloroquine kinetics were similar in both groups. The diarrhoea cohort had a three-fold higher lactulose absorption, influencing the mean lactulose mannitol:ratio, 0.114 +/- 0.17 compared to the control ratio of 0.02 +/- 0.01 (P = 0.04). Symptomatic subjects had impaired mucosal function which reduced the absorption of proguanil but not chloroquine, a phenomenon which may reduce prophylactic efficacy.

Adult↗
PubMedDate not supplied

Multidrug assay method for antimalarials.

A general separation strategy, involving solid-phase extraction followed by reversed-phase ion-pairing HPLC with an organic counter ion for a set of 11 widely used antimalarial drugs and metabolites has been developed. The basis underlying the separation has been explored and work, including quantitative data, has been carried out on illustrative separations which form the basis of novel quantitative assays of groups of antimalarials which are relevant to current prophylaxis and treatment of malaria.

Antimalarials↗
PubMedDate not supplied

Schistosomiasis prophylaxis in vivo using N,N-diethyl-m-toluamide (DEET).

Topical N,N-Diethyl-m-toluamide (DEET) was studied as a schistosomiasis prophylactic in vivo for the use of individuals with limited exposure. Fifteen subjects, on a 3-week expedition to Lake Malawi in September 2001, applied 50% DEET to their skin after exposure to lake water. No subjects developed evidence of a new infection at 3-month follow-up.

Administration, Cutaneous↗
PubMedDate not supplied

Knowledge of malaria, risk perception, and compliance with prophylaxis and personal and environmental preventive measures in travelers exiting Zimbabwe from Harare and Victoria Falls International airport.

BACKGROUND: Travel associated malaria is a major health risk for visitors to malaria endemic destinations. To examine the knowledge of malaria prevention, risk perception, current prophylactic behavior, and compliance with chemoprophylaxis and personal and environmental protection measures we conducted a study in a cohort of travelers exiting Zimbabwe from two international airports during a peak malaria transmission period. METHODS: Data were collected by pretested self-administered questionnaires from 595 adults in the departure lounges of Harare and Victoria Falls International airports. Excluded were children and travelers from the African continent. A multilingual research assistant supervised data collection. RESULTS: The majority of travelers obtained health advice prior to travel. Patterns of protective behavior and compliance with prophylaxis were inconsistent with a high perception of malaria threat and good knowledge. About 23% of travelers failed to use chemoprophylaxis during their visit. In the group of travelers who used chemoprophylaxis, 18% were noncompliant. Fifteen drug combinations were in use. Full compliance with medication plus use of personal preventive measures always was estimated as 13%. Forgetfulness was the main cause of noncompliance, followed by deliberate omission due to side effects. Of 57 travelers who reported side effects from current medication, over half used mefloquine. CONCLUSIONS: There is a need to examine how people process personal risk and communications about risk. We must recognize the competition between precautionary measures against malaria and other life demands that are imposed by travel, especially in young long stay travelers and persons visiting primarily for business purposes. Mediating a protective response will also depend on judgments about the effectiveness of the action, strengthening travelers intentions toward adherence, and increasing efficacy perception by individuals and their peers. Conflicts in prophylactic recommendations need to be resolved. As ecotourism develops in Zimbabwe and other malaria regions, stakeholders in this rapidly growing industry must be made aware of the important role they can play in protecting clients from malaria.

Adult↗