Biomedical subjects
Publications and source records attributed to R Green.
The structure of a conserved hairpin loop involved in peptidyl-tRNA recognition by 50S ribosomal subunits has been solved by NMR. The loop is closed by a novel G-C base pair and presents guanine residues for RNA recognition.
We have previously demonstrated that CD34+ cells, selected from peripheral blood progenitor cells (PBPC), can be expanded in ex vivo culture and can be infused in tandem with unmanipulated PBPC with little or no toxicity. In this study, four patients (two non-Hodgkin's lymphoma (NHL), two multiple myeloma (MM)) received myeloablative conditioning prior to stem cell rescue using ex vivo expanded cells alone. The two patients with NHL received cyclophosphamide and total body irradiation (CY/TBI) and the two patients with MM, busulphan and melphalan (Bu/M). One case received an inadequate CFU-GM dose, despite expansion, and in one case the expanded cells were contaminated. No definitive conclusions may therefore be drawn concerning engraftment in these two cases. However, the other two cases received high doses of committed progenitors. Following infusion of the expanded material, all four patients failed to show sustained neutrophil engraftment and none showed evidence of platelet engraftment. Back-up, unmanipulated PBPC were therefore infused on days 14, 34, 32 and 28 and subsequently all four cases achieved satisfactory engraftment of both neutrophils and platelets. In conclusion, we feel that, CD34+ cells, expanded ex vivo using the conditions described in this report, may not provide durable engraftment following fully myeloablative conditioning.
Hematopoietic stem and progenitor cells express the CD34 antigen. Techniques have been developed that enable purified populations of CD34+ cells to be selected from hematopoietic tissues. These selected CD34+ cells have several potential applications, including CD34 selection to obtain a tumor purging effect in autologous transplantation studies and using CD34+ cells as the starting cells for ex vivo expansion studies and as a vehicle for gene transduction protocols. We have investigated the feasibility of using cryopreserved peripheral blood progenitor cells (PBPC) for CD34 selection. Cells could be recovered from cryopreservation with good yields and high viability. After CD34 selection, the final product was, on average, 84% pure, with a recovery of 54%. These cells retained extensive proliferative potential, as demonstrated by ex vivo expansion culture. We believe that cryopreserved PBPC could be thawed, and CD34+ cells could be selected and used for transplantation following high-dose chemotherapy.
We studied the prevalence and relationship of stress and working conditions with adverse reproductive outcomes in a cohort of female US law-school alumnae. A total of 584 female lawyers (74% response), aged 25 to 63, responded to a mailed questionnaire. Job hours per week was a strong predictor of job stress. In a logistic regression analysis, women working > 45 hours/week were five times as likely to report high stress as those working < 35 hours/week. Marriage and length of time on the job showed a small inverse association with stress. Women who worked more than 45 hours/week during their first trimester of pregnancy were more likely to report high stress at work during pregnancy. After being adjusted for confounding factors, weekly job hours during the first trimester of pregnancy showed a strong independent association with spontaneous abortion risk (odds ratio [OR], 3.0; 95% confidence interval [CI], 1.4 to 6.6). Seven or more alcohol drinks/week was also independently associated with spontaneous abortion risk (OR, 4.8; 95% CI, 1.5 to 18.1). Self-reported stress during pregnancy was positively but not statistically significantly associated with spontaneous abortion (OR, 1.4; 95% CI 0.8 to 2.3).
Sibling sex ratio (the ratio of brothers to sisters) was calculated for 444 boys with gender identity disorder (or with behaviors consistent with this diagnosis). The probands were ascertained from several researchers with expertise with this disorder and from the English language case report literature between 1938 and 1995. Among the probands with at least one sibling (N = 333), the results showed that boys with gender identity disorder had a significant excess of brothers to sisters, 131.1:100, when compared with the expected secondary sex ratio of 106:100. The excess of brothers replicated a previous study by Blanchard, Zucker, Bradley, and Hume (1995), in which the sibling sex ratio was 140.6:100. Further analyses showed that the probands were born later relative to their brothers than they were relative to their sisters. These findings are amenable to several psychosocial and biological explanations, which require further investigation.
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The ribosome is a large multifunctional complex composed of both RNA and proteins. Biophysical methods are yielding low-resolution structures of the overall architecture of ribosomes, and high-resolution structures of individual proteins and segments of rRNA. Accumulating evidence suggests that the ribosomal RNAs play central roles in the critical ribosomal functions of tRNA selection and binding, translocation, and peptidyl transferase. Biochemical and genetic approaches have identified specific functional interactions involving conserved nucleotides in 16S and 23S rRNA. The results obtained by these quite different approaches have begun to converge and promise to yield an unprecedented view of the mechanism of translation in the coming years.
Exposure and sensitization to dog allergen is a significant cause of asthma. In this study we investigated the distribution, aerodynamic characteristics, and particle-size distribution of the major dog allergen Can f 1. Dust samples were collected in 50 homes with a dog and 50 homes without dogs. Airborne Can f 1 concentration was measured in 28 homes with dogs and 36 homes without a dog. Particle-size distribution was determined by using 10 separate Andersen sampler measurements in a dog-handling facility, and in 10 homes with dogs, and by repeated measurements in a home with one dog. High levels of Can f 1 (> 10 microg/g) were found in dust in all but one home with a dog and in eight of 50 homes without dogs. Airborne Can f 1 levels varied greatly between the homes with dogs (range: 0.3 to 99 ng/m3). Low levels of airborne Can f 1 (range: 0.4 to 1.1 ng/m3) were detected in 11 of 36 homes without a dog. Can f 1 was predominantly associated with large particles collected on the first stage of the Andersen sampler (> 9 microm), which averaged 42 to 49% of the total allergen recovered in the dog-handling facility and in homes with dogs. Small particles (< 5 microm diameter) also carried Can f 1, and these particles comprised approximately 20% of the total airborne allergen load. There was an excellent concordance between the results obtained in different sampling areas, and between the total Can f 1 recovered on the Andersen sampler and on the parallel filter. In conclusion, airborne Can f 1 was detectable in undisturbed conditions in all homes with dogs and in almost one third of the homes without dogs. In houses with dogs, a significant proportion (approximately 20%) of airborne Can f 1 was associated with small particles (< 5 microm diameter). Owing to their aerodynamic characteristics, these particles would be expected to remain airborne for a long period and, when inhaled, could penetrate into the lower airways and initiate asthma attacks.
Synthetic RNA stem loops corresponding to positions 28-42 in the anticodon region of tRNA(Phe) bind efficiently in an mRNA-dependent manner to ribosomes, whereas those made from DNA do not. In order to identify the positions where ribose is required, the anticodon stem-loop region of tRNA(Phe) (Escherichia coli) was synthesized chemically using a mixture of 2'-hydroxyl- and 2'-deoxynucleotide phosphoramidites. Oligonucleotides whose ribose composition allowed binding were retained selectively on nitrocellulose filters via binding to 30S ribosomal subunits. The binding-competent oligonucleotides were submitted to partial alkaline hydrolysis to identify the positions that were enriched for ribose. Quantification revealed a strong preference for a 2'-hydroxyl group at position U33. This was shown directly by the 50-fold lower binding affinity of a stem loop containing a single deoxyribose at position U33. Similarly, defective binding of the corresponding U33-2'-O-methyl-substituted stem-loop RNA suggests that absence of the 2'-hydroxyl group, rather than an altered sugar pucker, is responsible. Stem-loop oligoribonucleotides from different tRNAs with U33-deoxy substitutions showed similar, although quantitatively different effects, suggesting that intramolecular rather than tRNA-ribosome interactions are affected. Because the 2'-hydroxyl group of U33 was shown to be a major determinant of the U-turn of the anticodon loop in the crystal structure of tRNA(Phe) in yeast, our finding might indicate that the U-turn conformation in the anticodon loop is required and/or maintained when the tRNA is bound to the ribosomal P site.
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OBJECTIVE: To describe the cost of medicines used in the treatment of allergic rhinitis in South Africa. DESIGN: MIMS was used as the reference for the list of drugs, drug formulation and size, and recommended dosage. These figures were then checked against the package insert of each agent. The cost of each agent was originally derived from the same source, but for standardisation purposes the blue book price was used. Measure of effectiveness was derived from the International Consensus Report on the Diagnosis and Management of Rhinitis. Costs per treatment periods of 10 days (course) and 30 days (month) were calculated. The 'cost' differs from the 'price' in that it takes efficacy into account. MAIN OUTCOME MEASURES: Cost of drugs used in the treatment of allergic rhinitis. RESULTS: The least costly treatments for allergic rhinitis are the intranasal corticosteroids. Sodium cromoglycate was the most costly, being nearly 20 times more expensive than the nasal steroids. Anticholinergic sprays and topical decongestants were also more costly than nasal steroids, as were the antihistamines. The older-generation antihistamine, ketotifen, was not only more costly than the four oral newer-generation agents in this class but has the added disadvantage of greater sedative side-effects. All oral antihistamines were outclassed by the topical antihistamine, levocabastine. CONCLUSIONS: This study in no way aims to recommend treatment for allergic rhinitis. However, it highlights the need to consider efficacy of a drug before unit price in the selection of treatment regimens. It is therefore a comment on practical issues in drug selection in the treatment of allergic rhinitis.
OBJECTIVES: To describe the clinical features of Caucasian childhood asthmatics in Johannesburg in order to compare these with a similar population of black asthmatic children resident in Soweto. DESIGN: In a prospective study, a history was obtained by means of an investigator-administered questionnaire. MAIN OUTCOME MEASURES: Presenting asthma symptoms, precipitants of symptoms, concomitant diagnoses, individual and family background of allergy and 'delay to diagnosis' of asthma (age at symptom onset subtracted from age at diagnosis) from history and allergen sensitivity as assessed by skin-prick tests (SPTs). RESULTS: Of the 468 (297 boys) asthmatics studied, 456 (97.4%) presented with cough, 362 (77.3%) with wheeze, 286 (61.1%) with a tight chest and 277 (59.2%) with breathlessness. Cough as sole symptom occurred in 102 (21.8%) while only 8 (1.7%) wheezed and did not cough. Commonest symptom triggers were upper respiratory tract infections and activity/exercise. An individual atopic background was common-allergic rhinitis in 413 (88.2%)-as was a family history of atopy, present in 390 (83.3%). Prolonged symptomatic periods occurred in most patients before asthma was diagnosed (among children diagnosed after the age of 4 years, 50% had been symptomatic for more than 3 years). 'Delay to diagnosis' was not influenced by presenting symptoms or by previous hospitalisation for asthma. Other respiratory diagnoses of bronchitis and pneumonia were common, possibly because of misdiagnosis. Commonest allergens on SPT were corn pollen, Bermuda and 5-grass mix, and standardised mites. Aside from wheat, food allergy was uncommon. CONCLUSIONS: Cough was the commonest presenting symptom despite its still being regarded as a less classic symptom of asthma that may account for misdiagnosis and a high frequency of other respiratory diagnoses. Associated allergy, especially allergic rhinitis, occurred frequently. Many aspects of presentation in whites were similar to those in Soweto children, although the latter had a more frequent concomitant diagnosis of tuberculosis, and recognised dust and cold weather as more frequent triggers. Differences might be influenced by the care-giving situation.
A post menopausal female with severe vomiting and weight loss in association with elevated thyroid hormone levels is presented. Signs and symptoms of thyrotoxicosis were not evident at presentation. Possible pathophysiological mechanisms and treatment are discussed. Antithyroid therapy with carbimazole and propranolol induced rapid resolution of her symptoms and marked improvement in well-being. Radioactive iodine ablation of her thyroid gland was performed later and she has remained asymptomatic.
BACKGROUND: A high level of total plasma homocysteine is a risk factor for atherosclerosis, which is an important cause of death in renal failure. We evaluated the role of this as a risk factor for vascular complications of end-stage renal disease. METHODS AND RESULTS: Total fasting plasma homocysteine and other risk factors were documented in 176 dialysis patients (97 men, 79 women; mean age, 56.3 +/- 14.8 years). Folate, vitamin B12, and pyridoxal phosphate concentrations were also determined. The prevalence of high total homocysteine values was determined by comparison with a normal reference population, and the risk of associated vascular complications was estimated by multiple logistic regression. Total homocysteine concentration was higher in patients than in the normal population (26.6 +/- 1.5 versus 10.1 +/- 1.7 mumol/L; P < .01). Abnormally high concentrations (> 95th percentile for control subjects, 16.3 mumol/L) were seen in 149 patients (85%) with end-stage renal disease (P < .001). Patients with a homocysteine concentration in the upper two quintiles (> 27.8 mumol/L) had an independent odds ratio of 2.9 (CI, 1.4 to 5.8; P = .007) of vascular complications. B vitamin levels were lower in patients with vascular complications than in those without. Vitamin B6 deficiency was more frequent in patients than in the normal reference population (18% versus 2%; P < .01). CONCLUSIONS: A high total plasma homocysteine concentration is an independent risk factor for atherosclerotic complications of end-stage renal disease. Such patients may benefit from higher doses of B vitamins than those currently recommended.
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1. Interlobular ducts were isolated from the rat pancreas and maintained in short-term tissue culture. Fluid secretion from these isolated ducts was measured using micropuncture techniques, intracellular calcium concentration ([Ca2+]i) by fura-2 microspectrofluorimetry, and cyclic AMP by radioimmunoassay. 2. Applying secretin and ACh simultaneously to ducts caused either a stimulation or an inhibition of fluid secretion depending on the doses employed. 3. The inhibitory effect of secretin and ACh could be relieved by atropine, and by the protein kinase C (PKC) inhibitors staurosporine and 1-(5-isoquinolinylsulphonyl)-2-methyl-piperazine (H-7). 4. Activation of PKC by 12-O-tetradecanoylphorbol-13-acetate (TPA) and phorbol 12, 13-dibutyrate (PDBu) inhibited secretin-evoked fluid secretion. 5. ACh and TPA also inhibited fluid secretion stimulated by the adenylate cyclase activator, forskolin. 6. Neither secretin nor the PKC activators and inhibitors had any effect on either the increase in [Ca2+]i evoked by ACh or the increase in intracellular cyclic AMP evoked by secretin and forskolin. 7. We conclude that the inhibitory effect of combined doses of secretin and ACh on ductal fluid secretion is probably mediated by PKC at a point in the secretory mechanism distal to the generation of intracellular messengers.
Pan T, helper, and cytotoxic lymphocytes were isolated from the human peripheral blood mononuclear cell fraction by antibody staining, ferritin labeling, and deposition on glass slides. Two distinct forms of ferritin were used: one was native horse spleen ferritin, and the other was magnetoferritin. Magnetoferritin was obtained by reconstituting the horse spleen ferritin iron core with superparamagnetic magnetite instead of the usual paramagnetic ferrihydrite crystal. The cell deposition on microscopic glass slides in the magnetic field was obtained by an instrument that was adapted from an industrial magnetic deposition analyzer, the ferrograph. The identity of cells in the magnetic deposits was confirmed by comparing the cell fractions in the feed and in the eluate with the use of flow cytometry. The immunostaining protocol amplified the number of ferritin molecules per cell surface antigen 20-70 times. Magnetoferritin, but not native ferritin, imparted a sufficient magnetic moment to cells to deplete the labeled cell population between 67 and 88% of its initial concentration in a magnetic field of 1.67 Tesla (T), a field gradient of 2.57 T/mm, and a flow rate of 0.01 ml/min. This study showed that the magnetic moment of magnetoferritin was sufficient for immunomagnetic isolation of lymphocytes from mononuclear cell preparations in the modified ferrograph.