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Biomedical subjects

R E Smith

Publications and source records attributed to R E Smith.

At least 217 records · Page 12Linked to original sources
PubMed1990

Phosphatidylserine transport in Rhnull erythrocytes.

Phosphatidylserine transport in normal and Rhnull red blood cells was determined by measuring characteristic morphologic changes induced by synthetic phospholipids. Treating normal A+ cells with commercial anti-A antisera, anti-Rho(D) antisera, or with saturating concentrations of purified Rho(D) antibodies had no effect on phosphatidylserine transport. Normal B- cells treated with purified anti-B antibodies transported phosphatidylserine at rates equal to those of cells not treated with antibody. Rhnull cells, deficient in the protein bearing the Rho(D) antigen, incorporated dimyristoylphosphatidylcholine and dimyristoylphosphatidylserine at rates and to extents similar to normal cells. Furthermore, incorporated phosphatidylserine, but not phosphatidylcholine, was rapidly transported across the membrane bilayer. Energy depletion or treatment with sulfhydryl reagents inhibited phosphatidylserine transport equally in normal and Rhnull cells. These results indicate that, although Rhnull cells have numerous membrane defects, they are capable of adenosine triphosphate-dependent transport of exogenously added dimyristoylphosphatidylserine. Normal phosphatidylserine transport in the presence of anti-Rho(D) antibodies or in cells deficient in the Rho(D) polypeptide indicates that this protein is not the aminophospholipid transporter.

Adult↗
PubMed1990

Results of penetrating keratoplasty for the treatment of corneal perforations.

We retrospectively analyzed 46 consecutive cases of penetrating keratoplasty performed as part of the treatment of corneal perforations; the minimum follow-up time after keratoplasty was 7 months. Predisposing conditions leading to perforation were an infectious keratitis in 26 eyes (57%), trauma in 14 eyes (30%), and corneal melt associated with ocular surface disorder in 6 eyes (13%). The success of penetrating keratoplasty in the treatment of corneal perforation depended on the timing of surgery and the cause of the perforation. If the perforation was traumatic in origin, delaying surgery for at least 3 months significantly improved the chances for graft success. Eighty percent of the penetrating keratoplasties delayed 3 months following primary repair of corneal laceration remained clear, and 50% of these patients had a visual acuity of 20/60 or better. If penetrating keratoplasties were performed for an infectious corneal perforation, grafts had a better chance to remain clear if surgery could be delayed. All grafts performed for corneal perforation associated with melting and ocular surface abnormalities failed.

Adolescent↗
PubMed1990

A fatal case of low titer anti-PR cold agglutinin disease.

Cold agglutinin disease typically produces a low-grade hemolytic anemia. We describe herein the unusual occurrence of an anti-PR cold agglutinin with high thermal amplitude which caused significant and ultimately fatal hemolytic anemia at very low titers.

Aged↗
PubMed1990

Myelofibrosis: a review of clinical and pathologic features and treatment.

The purpose of this review is to discuss and clarify the current understanding of the pathogenesis, clinical manifestations, and treatment of MF. MF may be either a primary or secondary disorder. It is characterized by an increased deposition of bone marrow collagen, fibronectin, and laminin. Present evidence indicates that MF may be mediated by platelet or megakaryocyte growth factors, decreased prostaglandin mediated stem cell inhibition, immune complex deposition, and both fibroblast and endothelial cell proliferation. Recently acute MF has been recognized to be identical to acute megakaryocytic leukemia. Secondary MF usually responds to appropriate treatment of the underlying disease. Primary MF is usually treated by blood product support, but may be responsive to androgens, splenectomy, splenic irradiation, chemotherapy, or bone marrow ablation with marrow reconstitution.

Combined Modality Therapy↗
PubMed1990

Psychology of the young athlete. Stress-related maladies and remedial approaches.

This article has presented a theoretical framework for understanding the stress process. The conceptual model of stress specifies relations among situational, cognitive, physiologic, and behavioral factors. Each of these basic components of the model is assumed to be influenced by personality and motivational variables. At the situational level, stress involves the balance or imbalance between situational demands and the resources available to deal with them. However, these situational factors affect the person primarily through the intervening influence of cognitive processes. Among the most important of these processes are appraisal of (1) the situational demands, (2) available personal and social resources, (3) the possible consequences of failure to meet the demands, and (4) the perceived meaning of the consequences. A reciprocal relation exists between cognitive and physiologic processes; the nature of the appraisals influences the level of physiologic arousal that is likely to occur, and arousal in turn influences the ongoing appraisal process through physiologic feedback mechanisms. Finally, the behavioral component of the model includes the person's learned behavior tendencies, task-relevant skills, and social skills. Personality and motivational individual difference variables are important; they influence the kinds of situations to which people expose themselves, how they appraise themselves and the situations, how they react physiologically, and how they customarily respond at the behavioral level. With respect to the consequences of stress, mounting evidence suggests that a significant number of young athletes experience adverse psychological, behavioral, and health-related effects. In fact, because of anticipated stresses, some children decline to participate in the first place. Competitive stress detracts from enjoyment of sports, causes performance impairment, and contributes significantly to the drop-out rate in youth sports. Evidence also indicates that competitive stress can cause loss of sleep and put youngsters at greater risk for sustaining athletic injuries. However, although extremely high levels of stress are experienced by a minority of young athletes, the level of stress elicited by youth sports is generally no greater than that found in other achievement-oriented activities in which children participate. The conceptual model of stress not only provides a framework for identifying sources of stress, but also suggests foci for intervention strategies designed to reduce stress in youth sports. In this article, consideration has been given to prominent situational demands that contribute to competitive stress and to various approaches for counteracting the stress-inducing factors. Specifically, measures may be instituted that decrease situational demands associated with winning and losing, organization and administration of sport programs, coaching roles and relationships, and parent roles and responsibilities.(ABSTRACT TRUNCATED AT 400 WORDS)

Child↗
PubMed1990

Conjunctive moderator variables in vulnerability and resiliency research: life stress, social support and coping skills, and adolescent sport injuries.

In life event research relating to vulnerability and resilience factors, single moderator variables have typically been the focus of study. Little is known about the ways in which moderator variables may interact with one another to increase vulnerability or resilience. We propose a distinction between conjunctive moderation, in which multiple moderators must co-occur in a specific combination or pattern to maximize a relation between a predictor and an outcome variable, and disjunctive moderation, in which any one of a number of moderators maximizes the predictor-criterion relation. Our results indicate that social support and psychological coping skills are statistically independent psychosocial resources and that they operate in a conjunctive manner to influence the relation between life stress and subsequent athletic injury in adolescents. Only athletes low in both coping skills and social support exhibited a significant stress-injury relation, and in that vulnerable subgroup, negative major life events accounted for up to 30% of the injury variance. Methodological considerations in the assessment of conjunctive moderator effects are discussed.

Adaptation, Psychological↗
PubMed1990

Heat production by the human left ventricle: measurement by a thermodilution technique.

STUDY OBJECTIVE - The aim was to study the feasibility of measuring heat production by the human left ventricle with a view to using this variable as an index of left ventricular mechanical efficiency. DESIGN - The transcoronary temperature difference was derived from catheter mounted thermistors placed percutaneously in the aortic root and coronary sinus. Left ventricular blood flow was measured by continuous thermodilution in the coronary sinus, and heat removal by coronary venous blood was calculated from blood flow and the transcoronary temperature difference. Diffusional heat loss was measured using temperature/time curves recorded in aorta and coronary sinus after a bolus injection of cold saline into pulmonary artery. The heat loss from the system into the endothermic reactions of haemoglobin was calculated from left ventricular oxygen extraction using an assumed respiratory quotient. The energy released by left ventricular myocardial metabolism (EEO2, calculated from oxygen extraction), was compared to measured left ventricular heat production, and the mechanical efficiency of the left ventricle was calculated by the formula: Efficiency = (EEO2 - HLV)/EEO2. PATIENTS - Fifteen conscious patients with anginal chest pain were studied at the time of cardiac catherisation and coronary arteriography. MAIN RESULTS - The transcoronary temperature difference was in the range 0.10-0.32 (mean 0.21) degrees C. Total left ventricular heat production, equal to the sum of heat removed by the blood stream, diffusional loss and endothermic reactions (HLV) was in the range 1.5-4.6 (mean 2.7) watts. The values of EEO2 obtained were in the range 2.4-6.5 (mean 4.0) watts, and the calculated mechanical efficiency of the left ventricle was 0.24-0.55 (mean 0.34). CONCLUSIONS - The measurement of heat production by the human left ventricle is safe and practical. This technique promises to be of value in the clinical investigation of the relationship between myocardial function and energy utilisation.

Adult↗
PubMed1990

Rheumatoid arthritis and hypercoagulable state.

Rheumatoid arthritis is not considered to be associated with recurrent thrombosis. We report a patient, who while receiving anticoagulants had repeated life-threatening episodes of thrombosis. She later developed severe rheumatoid arthritis. After receiving successful antiarthritic therapy and withdrawal of anticoagulants, she had no further episodes of thrombosis.

Arthritis, Rheumatoid↗
PubMed1990

A simple, combined fluorogenic and chromogenic method for the assay of proteases in gingival crevicular fluid.

Substrate impregnated paper discs were prepared using peptidyl derivatives of 7-amino-4-trifluoromethylcoumarin (AFC). After incubation with test solutions, the green, UV-induced fluorescence of AFC liberated by enzyme activity was distinguishable from the blue-violet fluorescence of the substrates. The AFC could then be coupled with p-dimethylaminocinnamaldehyde to form a colored Schiff base. Semi-quantiative assessments of disc fluorescence and color were made by comparison with AFC/substrate standards. Assays with discs impregnated with MeOSuc-Ala-Ala-Pro-Val-AFC, Z-Gly-Gly-Arg-AFC and Ala-Pro-AFC for elastase-, trypsin-, and dipeptidyl peptidase (DPP) IV-like activities respectively were evaluated using purified DPP IV and 100 eluates of crevicular fluid collected on filter paper strips from 10 gingivitis and periodontitis patients. The results showed that, within their working ranges, scores of disc fluorescence and color were reasonably accurate and reliable by comparison with enzyme activities measured in parallel quantitative fluorimetric assays with the same substrates. Using disc color, which was more sensitive than fluorescence, it was generally possible to measure all three enzyme activities in crevicular fluid samples from 5 periodontitis patients with varying degrees of gingival inflammation and pocketing. Disc color assays require no special apparatus and could be used for enzyme estimations in the clinical setting.

Amino Acid Sequence↗
PubMed1990

Infrequent involvement of c-fos in avian leukosis virus-induced nephroblastoma.

To determine whether c-fos is involved in avian leukosis virus-induced nephroblastoma, 28 tumors from chickens were analyzed for novel fos fragments. DNA from 1 of 16 clonal outgrowths (in chicken 6561) contained novel fos-related EcoRI and KpnI fragments which hybridized to both v-fos and viral probes. Oncogenicity tests using filtered 6561 tumor cell homogenates did not reveal a tumor-inducing transduction of c-fos. We conclude that c-fos is only an occasional target for proviral insertions or new transductions in avian leukosis virus-induced nephroblastoma. The results also identify a polymorphism in c-fos in K28 chickens and demonstrate that unintegrated viral DNA is not a general characteristic of avian leukosis virus-induced nephroblastoma.

Animals↗
PubMed1990

Assessment of the influence of NaF or 1,25-(OH)2 vitamin D3 on the proliferative bone effect of an avian osteopetrosis virus, MAV-2(O).

1,25-(OH)2 vitamin D3 (D3) and sodium fluoride (NaF) were given to chicken embryos and newly hatched chickens infected with a slow onset strain of avian osteopetrosis-inducing virus [MAV-2(O)] to determine if either agent influenced MAV-2(O)-induced proliferation of bone. Embryos were administered MAV-2(O) and treated with: 1) up to 240 micrograms NaF or up to 100 ng D3 as embryos; 2) up to 1.8 g NaF/kg or up to 9.5 micrograms D3/kg after hatching: or 3) 240 micrograms NaF as embryos and up to 1.8 g NaF/kg after hatching. Administration of MAV-2(O) alone resulted in expansion of the cortical diameter of bone. Coadministration of NaF or D3 with MAV-2(O) did not influence the change in cortical diameter seen with MAV-2(O) alone at 18 days of incubation, and 3 and 6 weeks after hatching. Increased osteoid relative to bone (hyperosteoidosis), with NaF and MAV-2(O) compared to MAV-2(O) alone, and NaF compared to untreated controls reflected delayed mineralization of osteoid, a known fluoride effect. We conclude that the administration of NaF or D3 did not influence the incidence, severity or time of onset of the MAV-2(O)-induced proliferative changes of bone.

Animals↗
PubMed1990

Effects of inhibitors on proteinase activities in gels following isoelectric focussing.

Homogenates of rat submandibular glands were electrophoresed on isoelectric focussing gels and bands of proteinase activity demonstrated by means of overlay membranes impregnated with fluorogenic oligopeptide substrates. Inhibition characteristics of individual proteinase bands were tested within the gels and after excision and subsequent elution from the gels. Some bands of activity were resistant to inhibition by pre-incubation of the gel with certain inhibitors, but were subsequently found to be inhibited when tested with the same substrate after elution. These inconsistencies were influenced by the use of different substrates. The results indicate that, though some useful screening information may be obtained by applying inhibitors to the gels, this system does not permit a reliable assessment of inhibition characteristics which require subsequent elution and assay.

Amino Acid Sequence↗