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Biomedical subjects

R Barlow

Publications and source records attributed to R Barlow.

At least 19 recordsLinked to original sources
PubMed1998

The relation between immunoglobulin G antibodies to Chlamydia trachomatis and poor ovarian response to gonadotropin stimulation before in vitro fertilization.

OBJECTIVE: To determine whether a relation exists between previous exposure to Chlamydia trachomatis and impaired ovarian response to gonadotropin stimulation. DESIGN: Controlled clinical study. SETTING: Two university IVF centers. PATIENT(S): Two hundred forty-two patients receiving IVF treatment and 81 control patients. Ninety-four patients with a poor response to IVF, defined by cycle cancellation in response to a daily stimulation dose of 300 IU of FSH, and 148 patients with a good response were matched for age. Twenty-eight pregnant controls and 53 controls of proven fertility also were included. INTERVENTION(S): Serum samples were obtained from patients and controls. Serum levels of immunoglobulin (Ig) G antibodies to C. trachomatis were determined by ELISA. MAIN OUTCOME MEASURE(S): The prevalence of serum IgG antibodies to C. trachomatis in critically defined poor responders was compared with that of age-matched good responders. RESULT(S): A significantly higher proportion of poor responders had serum IgG antibodies to C. trachomatis compared with good responders (44.7% and 30.4%, respectively). Patients undergoing IVF had a significantly higher prevalence of IgG antibodies to C. trachomatis (36%) than did either pregnant or nonpregnant controls (12%). CONCLUSION(S): A significantly higher prevalence of serum IgG antibodies to C. trachomatis was observed in critically defined poor responders, suggesting a possible detrimental effect of C. trachomatis on subsequent ovarian function.

Adult↗
PubMed1997

Deciphering a neural code for vision.

Deciphering the information that eyes, ears, and other sensory organs transmit to the brain is important for understanding the neural basis of behavior. Recordings from single sensory nerve cells have yielded useful insights, but single neurons generally do not mediate behavior; networks of neurons do. Monitoring the activity of all cells in a neural network of a behaving animal, however, is not yet possible. Taking an alternative approach, we used a realistic cell-based model to compute the ensemble of neural activity generated by one sensory organ, the lateral eye of the horseshoe crab, Limulus polyphemus. We studied how the neural network of this eye encodes natural scenes by presenting to the model movies recorded with a video camera mounted above the eye of an animal that was exploring its underwater habitat. Model predictions were confirmed by simultaneously recording responses from single optic nerve fibers of the same animal. We report here that the eye transmits to the brain robust "neural images" of objects having the size, contrast, and motion of potential mates. The neural code for such objects is not found in ambiguous messages of individual optic nerve fibers but rather in patterns of coherent activity that extend over small ensembles of nerve fibers and are bound together by stimulus motion. Integrative properties of neurons in the first synaptic layer of the brain appear well suited to detecting the patterns of coherent activity. Neural coding by this relatively simple eye helps explain how horseshoe crabs find mates and may lead to a better understanding of how more complex sensory organs process information.

Animals↗
PubMed1997

Utilization of health services among rural women in Gujarat, India.

This study examined the effects of four sets of factors on use of curative health services among rural women living in Gujarat, India. The sets of factors analyzed were as follows: (1) the demographic characteristics of the women; (2) the characteristics of the household in which they lived; (3) the characteristics of the environment in which they lived; and (4) the price and convenience of care. The study focused on rural married women aged 17-45 who had at least one child. Nested multiple logistic regressions were computed on cross-sectional data to assess the simultaneous influences of the independent variables on (1) reports of episodes of illness (2) use of curative services among rural women who reported an illness and (3) use of a specific service. Four types of service were examined as outcomes of interest, namely, private doctors, Aga Khan Health Services centres, government health centres, and traditional healers. Other things being equal, women's education, income, family structure and kinship affiliation were significant predictors of use of service. Women seemed to be more sensitive to travel time to the health service and its associated costs (purdah restrictions, transportation and time costs) than to the direct costs of service. Factors such as women's occupation and sanitation facilities, while associated with use of service in the expected direction, were not significant predictors of use of service. Implications for health planning are offered, including initiatives to implement health promotion and disease prevention programs in addition to increasing access to the existing health services. Avenues for future studies are suggested, particularly in regard to decision-making processes affecting the health-seeking behavior of rural women. It is recommended that such policies and studies should consider the cultural environment in addition to the existing pluralistic health system.

Adolescent↗
PubMed1997

Lymphogranuloma venereum: biopsy, serology, and molecular biology.

A 21 year old woman presented with painful groin lymphadenopathy and malaise. Lymph node biopsy, to exclude atypical infection and malignancy, suggested the diagnosis of lymphogranuloma venereum. This diagnosis was confirmed by serology and polymerase chain reaction, with the patient subsequently admitting to a casual sexual contact within the United Kingdom. Alternative methods of investigation of this disease are discussed.

Adult↗
PubMed1996

Kinetic characteristics of the erythrocyte sodium-lithium countertransporter in subjects with coronary artery disease.

Sodium-lithium countertransport activity, external affinity for sodium (kNa) and maximal rate of turnover (Vmax), were characterized in 21 male subjects (aged 45 to 65 years) with angiographically proven coronary artery disease; these were compared with a matched group of healthy controls. No significant differences in countertransport activity were noted between the coronary artery disease patients and the healthy controls. By contrast, the median [range] kNa in the coronary artery disease group (8.5 [2.6 to 30.5] mmol/L Na) was significantly lower than that in the controls (59.9 [5.9 to 240.5] mmol/L Na; P < .0001). This reduction was accompanied by a significantly lower mean Vmax (controls 0.403 +/- 0.187 v coronary artery disease group 0.248 +/- 0.121 mmol Li/L RBC/h; P < .01). The findings suggest that disturbed behavior of the sodium-lithium countertransporter is not confined to hypertension but may represent a broader-based membrane dysfunction associated with vascular disease.

Aged↗
PubMed1995

Ethnic origin and hypertension-associated alterations in sodium-lithium countertransport kinetics.

In Caucasian subjects, elevated erythrocyte sodium-lithium countertransport (SLC) activity, displaying an increased affinity for external Na+ (decreased KNa), has a strong association with hypertension and has also been proposed as a potential marker for vascular disease. We have compared SLC activity and the kinetic components, KNa and maximal rate of turnover (Vmax), of the countertransporter in groups of Caucasian, Asian and Black hypertensive subjects matched for ethnicity, age and sex with healthy normotensive controls. SLC activity was the same in all ethnic groups irrespective of the presence of hypertension. Similarly, hypertension had no impact on Vmax values within each ethnic group (normotensive vs. hypertensives: Caucasian, 0.360 +/- 0.186 vs. 0.335 +/- 0.137; Asian, 0.324 +/- 0.078 vs. 0.273 +/- 0.105; black people, 0.192 +/- 0.123 vs. 0.178 +/- 0.082 mmol Li/l erythrocytes h). However, in black people compared with the other two ethnic groups, Vmax was lower for both controls and hypertensives (P < 0.05; ANOVA). Median KNa values in hypertensive subjects were consistently lower than their normotensive counterparts in all ethnic groups (P < 0.01; Kruskal-Wallis); Caucasians, (89.1 vs. 41.2 mmol Na; P = 0.01), Asians (121.1 vs. 33.1; P = 0.04) and black people (74.4 vs. 27.2 mmol Na; P = 0.02; Wilcoxon). The results show that Vmax is altered in black people independently of the presence of hypertension. This contrasts with KNa which, for each ethnic group studied, is reduced in the hypertensive compared with the normotensive state.

Adult↗
PubMed1994

Comparison of the binding of nicotinic agonists to receptors from human and rat cerebral cortex and from chick brain (alpha 4 beta 2) transfected into mouse fibroblasts with ion channel activity.

(-)-Nicotine, cytisine and carbachol evoked 86Rb efflux from mouse fibroblasts stably transfected with alpha 4 beta 2 chick brain nicotinic subunits. This response to (-)-nicotine was inhibited by mecamylamine and dihydro-beta-erythroidine and was mirrored by a rise in intracellular Ca2+ measured by microspectrofluorimetry. Lobeline and isoarecolone methiodide evoked no significant 86Rb from cells and unlike the above agonists displayed significantly different IC50 values for the displacement of [3H]nicotine from mammalian (rat and human cerebral cortex) and transfected fibroblast membranes.

Animals↗
PubMed1993

Platelet activating factor, lyso-platelet activating factor and arachidonic acid release in normal human skin and the influence of topical steroid treatment.

1. Previous, in vitro, studies have established the synthesis of platelet activating factor (PAF) by the 're-modelling' pathways in which the activation of a phospholipase A2 (PLA2) enzyme catalyses the hydrolysis of an ether-acyl-phosphocholine to give concomitant release of lyso-PAF, the immediate precursor of PAF, and arachidonic acid, the precursor of the icosanoids. The aim of this study was to investigate the relationship between PAF and eicosanoid release in human skin, and to study the effect of treatment of skin with a topical steroid, on the release of PAF, lyso-PAF and arachidonic acid. 2. A novel assay procedure was developed for the simultaneous assay of PAF and lyso-PAF in skin exudates from abrasions and suction blisters in normal human skin. In addition we assayed arachidonic acid and prostaglandin E2 (PGE2), a representative eicosanoid. 3. The mean amounts of mediator recovered in the first 30 min period following abrasion were PAF 0.43, lyso-PAF 11.9, PGE2 25.7 and arachidonic acid 760 pmol/sample. The molar ratio of PAF:lyso-PAF:arachidonic acid in skin exudates from abrasions was 1:30:1800 and in suction blister exudates was 1:90:3660. 4. Time course studies showed a decline in the recoveries of arachidonic acid and lyso-PAF, of about 50% in 2 h. In contrast, PAF was recovered in exudates at a constant rate over 2 h but PGE2 release decreased by more than 90% after the initial 30 min period. 5. Topical application under occlusion, of 0.05% clobetasol propionate, a potent corticosteroid, significantly reduced lyso-PAF by 30% in suction blister exudates but did not significantly alter the concentrations of PAF or arachidonic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗
PubMed1993

Increased interleukin 6, but reduced interleukin 1, in delayed pressure urticaria.

Interleukin 1 (IL-1) and interleukin 6 (IL-6) were measured by bioassays in suction-blister exudates from lesional skin, from skin immediately following a pressure challenge, and from control skin (not subjected to pressure) of patients with delayed pressure urticaria. IL-6 activity in lesional exudates was significantly higher than in exudates from the other two sites. IL-1 activity in lesional exudates was not significantly higher than in the control exudates, but significantly less IL-1 activity was found immediately after pressure challenge than from the control site.

Adult↗
PubMed1993

OSHA's final bloodborne pathogens standard: Part II.

The Bloodborne Pathogens Standard has specific requirements for employee hazard communication and training as well as management of regulated waste, contaminated laundry, and housekeeping procedures. OSHA recognizes the benefits of prophylactic use of hepatitis B vaccine and requires that it be made available, at no charge, to all employees who have occupational exposure to blood or other potentially infectious materials. The goal of the Bloodborne Pathogens Standard is to reduce the occupational risk of morbidity and mortality associated with diseases such as hepatitis B and human immunodeficiency virus (HIV).

Health Personnel↗
PubMed1992

Homozygous hereditary C3 deficiency due to a partial gene deletion.

The molecular mechanism of C3 deficiency in an Afrikaans patient with recurrent pyogenic infections was studied. Restriction enzyme analysis showed a gene deletion of 800 base pairs (bp) mapping to the alpha chain of C3. Amplification of genomic DNA, using the PCR, demonstrated that the deletion included exons 22 and 23 of the C3 gene. Truncated mRNA was shown in an Epstein-Barr virus-transformed B-cell line by PCR amplification of first-strand cDNA. A consequence of this deletion was that the RNA transcribed 3' to the deletion was out of frame, resulting in formation of a stop codon 19 bp downstream from the deletion. The molecular basis of the deletion was compatible with homologous recombination between two Alu sequences located in introns 21 and 23. An unrelated nonconsanguineous relative and two of a sample of 174 Afrikaans-speaking individuals were heterozygous carriers of the same gene deletion. The wide prevalence of this null allele in this population is probably due to the effects of a small founder population. The presence of this deletion in the C3 gene is not compatible with production of any functional C3, supporting the idea that study of such patients offers a valid model for understanding physiological activities of C3 in vivo in humans.

Base Sequence↗
PubMed1992

OSHA's final bloodborne pathogens standard. Part I.

The Bloodborne Pathogens Standard is the first standard promulgated by OSHA that addresses a biological hazard in the workplace. This Standard applies to all workers with occupational exposure to blood or other potentially infectious materials. To achieve compliance, the employer must determine and document exposure. Also, a written exposure control plan must be available that stipulates the use of appropriate methods of compliance such as engineering controls, work practice controls, and the use of personal protective equipment.

Humans↗
PubMed1992

Role of the occupational health nurse in the year 2000: perspective view.

From a historical perspective, occupational health nursing practice has changed in response to historic events and societal needs. The occupational health nurse today is expected to meet a variety of challenges and assume various roles within occupational health service settings. These roles require a sophisticated knowledge base and problem solving skills which are empirically based and multidisciplinary in their approach. The occupational health nurse can effect on local and public health issues through research and influence on public values and opinion. With the increasing demand for health care cost containment, occupational health nurses must meet the challenges of today and those of the future through program planning, research, and policy making.

Forecasting↗
PubMed1990

Enantiomers: how valid is Pfeiffer's rule?

In the 1950s Pfeiffer observed that the relative potencies of the enantiomers (mirror-image isomers) of several drugs appeared to be related to the dose of the racemate used clinically. The difference was greatest with the most active compounds and he suggested reasons for what has become known as 'Pfeiffer's rule'. In this short article Dick Barlow points out that there is a corollary to the rule - that the activity of the weaker enantiomer is determined by the activity of the more potent one - which is intuitively imporbable. With more examples and in a simpler situation, the picture is more complex and there are marked exceptions. The ideas behind Pfeiffer's rule overlook differences in molecular flexibility and there is a need for a revised model that takes entropy differences into account, particularly as recent developments in the elucidation of receptor structure are likely to revive interest in Pfeiffer's rule.

Pharmacology↗