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Biomedical subjects

R Green

Publications and source records attributed to R Green.

At least 127 records · Page 7Linked to original sources
PubMed1998

Dietary intake of cobalamin in elderly people who have abnormal serum cobalamin, methylmalonic acid and homocysteine levels.

OBJECTIVE: To determine if poor dietary intake can explain the cobalamin-related abnormalities often seen in the elderly. DESIGN: Prospective laboratory survey with a follow-up dietary assessment. SETTING: Social centers for the elderly and an outpatient clinic. SUBJECTS: Ninety-five free-living subjects >60y old with abnormal or suspicious findings in cobalamin-related tests and 78 subjects >60y old with normal results. INTERVENTIONS: Serum cobalamin, methylmalonic acid and homocysteine determinations to assess cobalamin status and a one year food-frequency questionnaire to assess cobalamin intake. RESULTS: Only three of the 173 subjects (1.7%), one of whom had normal cobalamin status, ingested <2 microg cobalamin/d, the Recommended Daily Allowance. Sixty-nine subjects (39.9%) ingested <6 microg/d, but they did not have more abnormal serum cobalamin or metabolite values than those ingesting >6 microg. Ordering all subjects by quintiles according to cobalamin intake revealed no significant trends or differences in any of the serum values either. Moreover, arranging subjects by results of tests of cobalamin status showed that the subjects with abnormal cobalamin status did not differ in cobalamin intake from those with normal cobalamin status, although they did differ in use of supplements. Finally, cobalamin intake, with or without supplements, did not correlate with serum cobalamin or metabolite levels. The absence of any association between cobalamin status and intake contrasts sharply with the significant correlation between folate intake and folate status (P = 0.0001). CONCLUSIONS: The high frequency of mildly abnormal cobalamin status in the elderly cannot be attributed to poor intake of cobalamin. Nondietary explanations, such as malabsorption and other phenomena, must always be sought to explain mild cobalamin deficiency in the elderly.

Aged↗
PubMed1998

Domestic allergens in public places III: house dust mite, cat, dog and cockroach allergens in British hospitals.

BACKGROUND: Exposure and sensitization to indoor allergens is a major cause of asthma. OBJECTIVES: This study investigated the levels of house dust mite, cat, dog and cockroach allergens in the dust and air in hospitals and the effects of regular vacuum cleaning on allergen levels in hospital chairs. METHODS: Der p 1, Fel d 1, Can f 1 and Bla g 2 were measured in the dust collected by vacuuming upholstered chairs and a 1 m2 area of carpet and mattress in 14 hospitals. Air samples were collected using an air sampler (flow rate 60 L/min) on 10 separate days for 4 h in the outpatient department in one of the hospitals during busy clinics when patients were waiting for their appointments. In addition, dust samples were collected on four occasions, at 4-weekly intervals, from 36 fabric covered chairs in the outpatient area of a busy chest clinic by vacuuming each chair for 2 min. During the intervening weeks, 18 of the chairs (active group) were each cleaned by vacuuming for 1 min, three times per week. Der p 1, Fel d 1, Can f 1 and Bla g 2 were assayed using monoclonal antibody-based ELISA. RESULTS: In total, 83 carpets, 69 mattresses and 42 upholstered chairs were sampled. The levels of dust mite allergen Der p 1 and cockroach allergen Bla g 2 found in the hospital setting were low. High levels of Fel d 1 (GM 22.9 microg/g, range 4.5-58) and Can f 1 (GM 21.6 microg/g, range 4-63) were found in upholstered chairs. Airborne Can f 1 was detected on every occasion (range 0.12-0.56 ng/m3), whilst detectable airborne Fel d 1 was found on 7 out of the 10 sampling days (range 0.09-0.22 ng/m3). Der p 1 and Bla g 2 were below the detection limit in all airborne samples. Following repeated vacuuming the mean cat and dog allergen levels decreased significantly (P<0.001) and were almost fivefold lower in the vacuumed chairs compared with the control group. CONCLUSIONS: Low levels of mite allergen are unlikely to be of any clinical significance to mite-sensitive asthmatic patients. However, upholstered chairs in hospitals constitute a significant reservoir of cat and dog allergen. Inhalation of airborne allergen in patients attending their hospital appointment may exacerbate asthma in those highly allergic to cats or dogs. These results question the wisdom of introducing soft furnishings and carpets into hospitals. Three-times weekly vacuuming significantly reduces allergen levels in upholstered chairs.

Air Pollution, Indoor↗
PubMed1998

Gibberellins promote flowering of arabidopsis by activating the LEAFY promoter

The gibberellin class of plant hormones has been implicated in the control of flowering in several species. In Arabidopsis, severe reduction of endogenous gibberellins delays flowering in long days and prevents flowering in short days. We have investigated how the differential effects of gibberellins on flowering correlate with expression of LEAFY, a floral meristem identity gene. We have found that the failure of gibberellin-deficient ga1-3 mutants to flower in short days was paralleled by the absence of LEAFY promoter induction. A causal connection between these two events was confirmed by the ability of a constitutively expressed LEAFY transgene to restore flowering to ga1-3 mutants in short days. In contrast to short days, impairment of gibberellin biosynthesis caused merely a reduction of LEAFY expression when plants were grown in long days or with sucrose in the dark. As a first step toward identifying other small molecules that might regulate flowering, we have developed a rapid in vitro assay for LEAFY promoter activity.

Journal Article↗
PubMed1998

The effect of dry heat on mite, cat, and dog allergens.

BACKGROUND: Various techniques have been tried in an attempt to reduce allergen levels in homes. This study investigated the effect of dry heat on mite, cat, and dog allergens. METHODS: Samples (50 mg) of Dermatophagoides pteronyssinus and D. farinae cultures, and of house dust rich in the major cat and dog allergens Fel d 1 and Can f 1 were heated for 5, 10, 15, 30, and 60 min at 60 degrees, 80 degrees, 100 degrees, 120 degrees, and 140 degrees C. Control samples remained at room temperature. Extracts were assayed with the appropriate two-site mono- or mono/polyclonal sandwich ELISA. RESULTS: For Der p 1, the breakdown was proportional to temperature and heating time; after 30 min at 120 degrees C, allergen levels were reduced to < 1% of control. Der p 2 was more heat stable, requiring 140 degrees C for 30-60 min to achieve > 99% reduction. D. farinae groups 1 and 2 allergens showed results similar to those obtained with D. pteronyssinus. In contrast, Can f 1 and Fel d 1 were considerably more thermostable, with 50% and 70%, respectively, of allergen remaining after 60 min at 140 degrees C. CONCLUSIONS: The effect of dry heat on allergens increased with increasing time and temperature, cat and dog allergens demonstrating greater heat resistance than mite allergens. Dry heating methods may represent an alternative technique for removal of mite allergens; however, the greater stability of Fel d 1 and Can f 1 suggests that this procedure may not be appropriate for pet allergens.

Allergens↗
PubMed1998

A new protocol for the measurement of picomole quantities of magnesium in rat renal tubular fluid.

The analysis of picomolar quantities of magnesium by electrothermal atomic absorption spectrophotometry (EAAS) was studied using a Perkin-Elmer-Zeeman 3030 spectrophotometer. The absorbance signal was not heavily dependent on the atomization temperature, but was greatly reduced when ashing temperatures in excess of 1200 degrees C were applied. The magnesium signal was significantly depressed in the presence of excess chloride in the sample matrix. However, use of NH4NO3 as a matrix modifier was sufficient to overcome this artefact. The analytical sensitivity was 0.15 absorbance units pmol-1 and the detection limit was 0.04 pmol. Using nanolitre constriction pipettes to dispense standards, the mean coefficient of variation was 5%. Measurement of magnesium handling in the rat proximal convoluted tubule revealed a significant correlation between the tubular fluid-to-plasma ultrafiltrate (TF/UF) concentration ratio for magnesium and the tubular fluid-to-plasma (TF/P) concentration ratio for [3H]inulin (r2 = 0.56, n = 17). This indicated that magnesium is concentrated during its passage along the proximal tubule. In contrast, this was not the case for sodium (r2 = 0.11, n = 16). Mean (TF/UF)Mg (1.16 +/- 0.07, n = 17) for random punctures was significantly greater than that for sodium ((TF/UF)Na = 1.02 +/- 0.02, n = 16). Despite concentration of magnesium in the lumen, significant net reabsorption of magnesium was observed along the length of the tubule (fractional reabsorption, FRMg = 19.4 +/- 3.0%, n = 17). In conclusion, EAAS provides a highly sensitive, reproducible and technically simple method for measuring picomolar quantities of magnesium in renal tubular fluid.

Animals↗
PubMed1998

A mutant of Mycobacterium smegmatis defective in dipeptide transport.

A mutant of Mycobacterium smegmatis unable to use the dipeptide carnosine (beta-alanyl-L-histidine) as a sole carbon or nitrogen source was isolated. Carnosinase activity and the ability to grow on beta-Ala and/or L-His were similar in the mutant and the wild type. However, the mutant showed significant impairment in the uptake of carnosine. This study is the first description of a peptide utilization mutant of a mycobacterium.

Biological Transport↗
PubMed1998

Potassium permeability in the absence of fluid reabsorption in proximal tubule of the anesthetized rat.

A luminal microperfusion technique was used to examine the K+ permeability of surface proximal convoluted tubules (PCT) in the kidney of anesthetized rats. Transtubular potassium concentration ([K+]) gradients were varied by altering the concentration of KCl in luminal perfusates, to which 32 mmol/l of the impermeant solute raffinose was also added to prevent net fluid reabsorption. The arithmetic mean transtubular [K+] gradient was highly predictive of net potassium flux, yielding an apparent K+ permeability of 31.9 +/- 1.7 x 10(-5) cm/s in the absence of fluid reabsorption. When compared using identical calculation techniques, we found this was not significantly different from the permeability derived in a previous study when fluid reabsorption was present [J. D. Kibble, M. Wareing, R. W. Wilson, and R.Green. Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 27): F778-F783, 1995]. We conclude that fluid reabsorption does not affect the apparent permeability of the proximal tubule to potassium. The apparent permeability to 86Rb, measured following its addition to luminal perfusates, was not significantly different from the value obtained for K+, suggesting that rubidium is a useful marker for net potassium movements in the PCT of the rat.

Absorption↗
PubMed1998

Health professionals' responses to multiple sclerosis and motor neurone disease.

This study compares the responses of health professionals to multiple sclerosis (MS) and motor neurone disease (MND) in order to determine similarities and variations in responses to the two disorders and the issues critical to caring for patients with these conditions. Health professionals were more negative about MND compared with MS in terms of the amount they felt able to offer patients, their confidence in managing patients and their ability to convey hope. For a number of issues concerning the management of patients, the level of difficulty experienced by health professionals was similar for both MS and MND. These were resource issues, the health professionals' ability to remain positive in the face of progressive disability, interdisciplinary team problems and difficulties regarding patient care. The main concern of health professionals, for both conditions, was the effect of progressive disability on the patient. For MND, management issues which health professionals found comparatively more difficult than for MS were patients' short prognosis and impending death, communication problems and progressive disability. Issues which were comparatively more difficult for MS than MND were changes in patients' affect, cognition and personality, problems with planning care because of the disorder's unpredictable course, problems with diagnosis such as making and disclosing the diagnosis, and the tendency for patients to be difficult or demanding. Some notable differences in responses between health professionals in different health care settings were found. The findings have implications for changing health professionals' conceptualization of 'hope', developing ways of improving communication between health professionals in different health care settings so as to enable them to learn from each other's expertise and experiences and redressing gaps in service provision, especially for young people with MS.

Attitude of Health Personnel↗
PubMed1998

Recovered memories of childhood sexual abuse. Implications for clinical practice.

BACKGROUND: The growth in the USA of 'recovered memory therapy' for past sexual abuse has caused great public and professional concern. It became apparent that the polarisation of views and fierce controversy within the American psychiatric community was in danger of bringing psychotherapy into disrepute and it seemed important to examine objectively the scientific evidence before such polarisation developed in the UK. METHOD: A small working group reviewed their own experience, visited meetings and centres with expertise in this field, interviewed 'retractors' and accused parents, and then began a comprehensive review of the literature. RESULTS: There is a vast literature but little acceptable research. Opinions are expressed with great conviction but often unsupported by evidence. CONCLUSIONS: The issue of false or recovered memories should not be allowed to confuse the recognition and treatment of sexually abused children. We concluded that when memories are 'recovered' after long periods of amnesia, particularly when extraordinary means were used to secure the recovery of memory, there is a high probability that the memories are false, i.e. of incidents that had not occurred. Some guidelines which should enable practitioners to avoid the pitfalls of memory recovery are offered.

Art Therapy↗
PubMed1998

Sexual functioning in post-operative transsexuals: male-to-female and female-to-male.

Sex reassignment surgery has been performed on thousands of transsexual patients during the past 30 y. Yet, reports of sexual responsivity of post-operative patients are very rare. Reports of physiological measures of sexual arousal are non-existent. Seven reports are received and summarized. Methodological shortcomings and the questionable validity of self-reports render the interpretation of sexual responsivity, notably orgasm, difficult. Laboratory-based research is needed with patients who have undergone the broadening variety of surgical genital reconstruction for the male and female transsexual.

Adult↗
PubMed1998

Inherited thrombophilia and pregnancy: the obstetric perspective.

The identified main causes of inherited thrombophilia are deficiencies of antithrombin (AT), protein C, or protein S, resistance to activated protein C associated with Factor V Leiden mutation, mutant factor II, and inherited hyperhomocysteinemia. For women from symptomatic families, these defects may be associated with an increased risk of venous thrombosis during pregnancy and/or recurrent fetal loss. Inherited thrombophilia is common and appears to be a multigenic disorder. The thrombotic risk seems to be greatest for women who have AT deficiency or more than one thrombophilic defect. The abnormalities that are now recognized are only part of the genetic predisposition to thrombosis. When assessing thrombotic risk during pregnancy, acquired risk factors as well as genetic predisposition should be considered. Increasing age, obesity, immobility, and delivery by cesarean section are major acquired risk factors. Pregnancy should be planned as far as possible, and each patient should be managed individually. During pregnancy, heparin is the anticoagulant of choice, and treatment with warfarin should be avoided because of risks for the fetus. When patients receive long-term treatment with warfarin, pregnancy should be avoided or planned, and warfarin should be discontinued before conception or as soon as pregnancy is confirmed and before 6-weeks' gestation. For women who have AT deficiency, the incidence of thrombosis during pregnancy is between 20 and 40%. Adjusted-dose heparin throughout pregnancy is recommended, followed by warfarin for at least 3 months postpartum. For patients who have Factor V Leiden, mutant factor II, or a deficiency of protein C or protein S, treatment can be based on personal and family history. Thromboprophylaxis during late pregnancy and postpartum should be considered. Fetal loss may be increased for women with inherited thrombophilia. The risk appears to be greatest for women with AT deficiency and women with more than one thrombophilic defect. For women with recurrent fetal death and inherited thrombophilia, a number of case reports claim that prophylaxis with heparin during pregnancy has resulted in successful pregnancy.

Anticoagulants↗
PubMed1997

The role of active transport in potassium reabsorption in the proximal convoluted tubule of the anaesthetized rat.

1. We have previously assessed the contributions of diffusion and convection to net potassium reabsorption in the rat proximal convoluted tubule (PCT). The present study was conducted to evaluate the role of active transport in convective potassium reabsorption by measuring the transepithelial potassium reflection coefficient (sigmaK) in the presence and absence of cyanide in anaesthetized rats previously prepared for in vivo microperfusion. 2. Osmotic water permeability (Pf) was measured in double-perfused tubules (lumen and peritubular capillaries) by manipulating the applied transepithelial osmotic gradient between -30 and +40 mosmol (kg H2O)(-1) using raffinose added to or subtracted from luminal perfusates. Pf was unaffected by the presence of cyanide when the estimated dissipation of osmotic gradients along each tubule were taken into account. 3. The proportion of K+ (and Na+) convectively transported with water fluxes (i.e. sigmaK) was not affected by cyanide. In the absence of active transport and following correction for any diffusive component, sigmaK was 0.56 +/- 0.13, indicating substantial solvent drag which probably occurs via the paracellular pathway. 4. However, cyanide caused a reduction in net potassium flux over the entire range of fluid fluxes used in double-perfusion experiments. Subsequent single-perfusion experiments (tubule lumen only) using the specific K+-H+-ATPase inhibitor, SCH28080, failed to reveal any direct evidence for a primary active K+ transporting mechanism involved in K+ reabsorption in the PCT.

Absorption↗
PubMed1997

Mutations at nucleotides G2251 and U2585 of 23 S rRNA perturb the peptidyl transferase center of the ribosome.

Previous experiments have shown that the phylogenetically conserved G2252 of 23 S rRNA forms a Watson-Crick base-pair with C74 of peptidyl-tRNA. In the studies presented here, site-directed mutations were introduced at two other conserved positions in 23 S rRNA, G2251 and U2585, that were previously implicated in interaction of the CCA acceptor end of tRNA with the 50 S subunit P site. The mutant 23 S rRNAs were characterized by determining (1) the in vivo phenotypes, (2) the ability of mutant ribosomes to bind tRNA oligonucleotide fragments in vitro, using footprinting with allele-specific primer extension and (3) the ability of mutant ribosomes to catalyze peptide bond formation using a chimeric reconstitution approach. Mutations at either position confer a dominant lethal phenotype when the mutant 23 S rRNA is coexpressed with the endogenous wild-type 23 S rRNA. Mutations at 2585 disrupt binding of the wild-type (CCA) tRNA oligonucleotide fragment and cause a modest decrease in the peptidyl transferase activity of reconstituted ribosomes. By contrast, mutations at 2251 abolish both binding of the wild-type (CCA) tRNA fragment and peptidyl transferase activity using the wild-type tRNA fragment. In neither case was the loss of binding or peptidyl transferase activity suppressed by mutations in the tRNA oligonucleotide fragment. Chemical modification analysis revealed that mutations at 2251 perturb the reactivity of bases 2584 to 2586, providing further evidence that the 2250 loop of 23 S rRNA interacts, either directly or indirectly, with the 2585 region in the central loop of domain V of 23 S rRNA.

Base Composition↗
PubMed1997

An encapsulation system for the immunoisolation of pancreatic islets.

Over a thousand combinations of polyanions and polycations were tested to search for new polymer candidates that would be suitable for encapsulation of living cells. The combination of sodium alginate, cellulose sulfate, poly (methylene-co-guanidine) hydrochloride, calcium chloride, and sodium chloride was most promising. In parallel, a novel multiloop chamber reactor was developed to control the time of complex formation and to negate gravitational effects such as pancreatic islet sedimentation and droplet deformation during the encapsulation process. Encapsulated rat islets demonstrated glucose-stimulated insulin secretion in vitro, and reversed diabetes in mice. This new capsule formulation and encapsulation system allows independent adjustments of capsule size, wall thickness, mechanical strength, and permeability, which may offer distinct advantages for immunoisolating cells.

Animals↗