Biomedical subjects
Publications and source records attributed to C A Mitchell.
A case of pulmonary actinomycosis presenting with a right calf abscess and complicated by effusive constrictive pericarditis is discussed. Clinical improvement occurred with antibiotic therapy and pericardiectomy. There was no evidence of recurrence after 18 months.
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This study evaluated the potential of high photosynthetic photon flux (PPF) from high-pressure sodium (HPS) lamps, alone or in combination with metal halide (MH) plus quartz iodide (QI) incandescent lamps, to support lettuce growth, with or without N supplementation. Varying exposures to radiation from combined HPS, MH, and QI lamps influenced dry weight gain and photosynthetic pigment content of hydroponically grown Black-Seeded Simpson' lettuce (Lactuca sativa L.) seedlings. Cumulative leaf dry weight declined with increasing exposure, up to 20 hours per day, to 660 micromoles m-2 s-1 of photosynthetically active radiation (PAR) from HPS lamps concomitant with constant 20 hours per day of 400 micromoles m-2 s-1 from MH + QI lamps. Leaves progressively yellowed with increasing exposure to radiation from the three-lamp combination, corresponding to lower specific chlorophyll content but not to specific carotenoid content. Lettuce grown under 20-hour photoperiods of 400, 473, or 668 micromoles m-2 s-1 from HPS radiation alone had the highest leaf dry weight at a PPF of 473 micromoles m-2 s-1. Chlorophyll, but not carotenoid specific content, decreased with each incremental increase in PPF from HPS lamps. Doubling the level of N in nutrient solution and supplying it as a combination of NH4+ and NO3- partially ameliorated adverse effects of high PPF on growth and pigment content relative to treatments using single-strength N as NO3-.
Lenburg and Mitchell tell us the time for student outcome assessment has arrived. They examine the philosophic assumptions underlying this system and share the experience gleaned by the New York Regents External Degree programs. Testing options ranging from observed care of real patients to patient simulations to interactive video exams are discussed.
We have identified the structure of phosphatidylinositol 3-phosphate (PtdIns(3)P), phosphatidylinositol 3,4-bisphosphate (PtdIns(3,4)P2) and phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3) in human platelets. These lipids accounted for less than 2% of the total 32P incorporated into inositol phospholipids in the platelets. All three lipids were labeled in unstimulated platelets, but incorporation of 32P changed rapidly by 15 s after thrombin stimulation, suggesting that they are important in platelet activation. Specific inositol polyphosphate phosphatases were used to both identify the lipid structures and to determine the route of synthesis of these lipids. During 32P labeling and after thrombin stimulation of human platelets, as much as 60% of the total radioactivity present in PtdIns(3,4)P2 was found in the D-4 phosphate and only 35% in the D-3 phosphate indicating that PtdIns(3)P is the precursor of PtdIns(3,4)P2. In addition, the D-5 and D-4 phosphates of PtdIns(3,4,5)P3 each contained 35-40% of the total radioactivity in the molecule compared with only 18-28% in the D-3 position, suggesting that PtdIns(3,4)P2 and not PtdIns(4,5)P2 is the major precursor of this lipid. These results define the predominant pathway for synthesis of these lipids in platelets as PtdIns----PtdIns(3)P----PtdIns(3,4)P2----PtdIns(3,4,5)P3.
Familial expansile osteolysis is a rare and possibly unique form of hereditary bone dysplasia with dental manifestations that has affected 42 members of a Northern Ireland family for five generations. Twenty-seven family members, aged 3 to 60 years, were examined clinically and radiographically, and it was found that cervical and/or apical root resorption is an early manifestation of the dysplasia. Of the 20 family members with skeletal manifestations of familial expansile osteolysis, 16 showed root resorption. Root resorption may therefore be a good prognosticator for later bone involvement.
The major ultrastructural events in murine skeletal muscle fibers were examined 3 to 24 hr after segmental injury induced by painting with aldehyde fixative. At 3 hr the viable stump of injured myofibers was separated from the necrotic segment by a zone of supercontracted myofibrils. No demarcating membrane was evident at this time, although occasionally collapsed segments of plasmalemma partially covered the viable stump. By 12 hr after injury myonuclei near the viable stump were centrally placed and numerous whorls of membrane material appeared in the vicinity of the Golgi apparatus. At this stage a convoluted, tortuous membrane exhibiting extensive interdigitations has sealed the structurally normal part of the injured fiber. The myoplasm immediately within this demarcating membrane possessed few myofilaments but numerous vesicles and tubules, several of which were continuous with the demarcating membrane; most degraded sarcoplasmic organelles remained external to the demarcating membrane and leukocytes were observed internalizing the debris. It appears that after segmental injury to skeletal muscle fibers, active production of new sarcoplasmic membranes occurs, which contributes to the formation of the part of the plasmalemma that demarcates the viable portion of the muscle fiber from the injured area.
Growth factors and transforming proteins that activate tyrosine phosphorylation have been shown to cause an increased labeling of 3-phosphate-containing phosphatidylinositols. Turnover correlates with the formation of a complex between phosphatidylinositol 3-kinase, the activated protein-tyrosine kinase, and other proteins thought to participate in transmembrane signaling. When human platelets are treated with thrombin, labeling of 3-phosphate-containing phosphatidylinositols is stimulated with a time course and concentration dependence consistent with a role for these lipids in platelet activation. We now report that when human platelets are stimulated with thrombin, a complex forms between phosphatidylinositol 3-kinase, a protein-serine/threonine kinase, and an uncharacterized platelet membrane protein. The complex is immunoprecipitated from detergent lysates of thrombinstimulated platelets by a rabbit antiserum prepared against a peptide from the cytoplasmic domain of the mouse platelet-derived growth factor (PDGF) receptor. The antigen is not the PDGF receptor, since complex formation is not stimulated by PDGF and thrombin-induced complexes are not precipitated by another rabbit antiserum against the same peptide or by monoclonal anti-human PDGF receptor antibodies. Formation of the complex is rapid (within 30 sec) and occurs at thrombin concentrations that stimulate platelet aggregation and secretion (50% of maximal complex formation at 0.03 unit of thrombin per ml). We propose that the complex initiates formation of 3-phosphate-containing phosphatidylinositols that may function in platelet activation.
Physical agitation applied as periodic seismic stress (shaking) reduced stem elongation, leaf expansion, and biomass accumulation by vegetative soybeans. Level of photon flux (PPF) influenced the type and extent of plant response to mechanical stress. Plant parts responded differently as PPF varied between 135 and 592 micromoles m-2 s-1. Stem length was significantly reduced by seismic stress at 135 micromoles m-2 s-1 but this effect was insignificant at higher PPFs. Reduced stem length resulted from an inhibition of internode elongation. Stem diameter was unaffected by stress at the PPFs tested. In contrast to effects on stem elongation, leaf area was insensitive to stress treatments at 135 micromoles m-2 s-1 but was progressively inhibited by stress as PPF increased. Statistically significant reductions in shoot f. wt and d. wt by seismic stress occurred only at 295 micromoles m-2 s-1. Root biomass accumulation was not affected by seismic stress at any PPF used in this study.
The purpose of this case report is to 1) briefly describe the traditional above-knee (AK) quadrilateral socket, 2) describe the contoured adducted trochanteric-controlled alignment method (CAT-CAM) socket, 3) describe the management of a patient with a temporary CAT-CAM prosthesis, and 4) explain how the CAT-CAM prosthesis approach has resolved a medically complex clinical problem. The 49-year-old patient in this case study received a left AK amputation in 1984 and was provided with a quadrilateral socket. She abandoned this prosthesis after 2 years because of her dissatisfaction with the device (ie, poor fit, awkwardness, excessive energy expenditure) and because of her compromised cardiac condition. The patient was fitted with a CAT-CAM prosthesis in 1988 and reported increased comfort, ease of donning and doffing, and increased gait efficiency with the CAT-CAM prosthesis as compared with the quadrilateral socket. The patient required 19 days of prosthetic training and was discharged independent in ambulation and transfers using two straight canes. We consider the CAT-CAM prosthesis an improvement over the quadrilateral socket for increasing ambulation independence in the individual with AK amputation and other medical complications.
The dental histopathology is described of patients suffering from Familial Expansile Osteolysis (FEO), a rare and unique autosomal dominant disease which has severe bony as well as dental consequences. The predominant dental features are resorption of the cervical and apical regions of the roots, premature depositions both of irregular secondary dentin, which causes narrowing of the pulp cavities, and of cellular cementum, which causes patchy narrowing of the periodontal ligament. The dental pulp shows age-like changes, including multiple pulp stones and the ligament vasculature appears to be abnormal. Evidence for involvement of enamel is equivocal. This combination of dental effects together with the bony lesions distinguishes the disease from idiopathic external resorption of either the single or multiple kind, despite similarities in the histopathology of the resorptive lesions; and from other non-hereditary and hereditary osteolytic diseases.
We report the case of a 50-year-old lady who presented with arterial thrombosis in the setting of thrombocytopenia. Investigations confirmed the diagnosis of idiopathic thrombocytopenic purpura. A spontaneous platelet aggregating factor (SPAF) was isolated from the immunoglobulin fraction of the patient's plasma. The isolated IgG irreversibly aggregated platelet-rich plasma and washed platelets, an effect abolished by pretreating the platelets with aspirin. The activity of the IgG was greatly enhanced by subaggregatory concentrations of thrombin and adrenalin and was localized to the F(ab')2 of the molecule. Plasmapheresis in combination with anti-platelet therapy resulted in an increase in the patient's platelet count, reduced platelet aggregating activity of plasma and significant clinical improvement. We suggest that the presence of this platelet aggregating IgG contributed to the development of thrombosis in our patient and postulate that a similar factor may explain the paradox of thrombosis observed in a select group of thrombocytopenic patients.
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We have identified, isolated, and characterized a second inositol polyphosphate-5-phosphatase enzyme from the soluble fraction of human platelets. The enzyme hydrolyzes inositol 1,4,5-trisphosphate (Ins (1,4,5)P3) to inositol 1,4-bisphosphate (Ins(1,4)P2) with an apparent Km of 24 microM and a Vmax of 25 mumol of Ins(1,4,5)P3 hydrolyzed/min/mg of protein. The enzyme hydrolyzes inositol (1,3,4,5)-tetrakisphosphate (Ins(1,3,4,5)P4) at a rate of 1.3 mumol of Ins(1,3,4,5)P4 hydrolyzed/min/mg of protein with an apparent Km of 7.5 microM. The enzyme also hydrolyzes inositol 1,2-cyclic 4,5-trisphosphate (cIns(1:2,4,5)P3) and Ins(4,5)P2. We purified this enzyme 2,200-fold from human platelets. The enzyme has a molecular mass of 75,000 as determined by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by gel filtration chromatography. The enzyme requires magnesium ions for activity and is not inhibited by calcium ions. The 75-kDa inositol polyphosphate-5-phosphatase enzyme differs from the previously identified platelet inositol polyphosphate-5-phosphatase as follows: molecular size (75 kDa versus 45 kDa), affinity for Ins(1,3,4,5)P4 (Km 7.5 microM versus 0.5 microM), Km for Ins(1,4,5)P3 (24 microM versus 7.5 microM), regulation by protein kinase C, wherein the 45-kDa enzyme is phosphorylated and activated while the 75-kDa enzyme is not. The 75-kDa enzyme is inhibited by lower concentrations of phosphate (IC50 2 mM versus 16 mM for the 45-kDa enzyme) and is less inhibited by Ins(1,4)P2 than is the 45-kDa enzyme. The levels of inositol phosphates that act in calcium signalling are likely to be regulated by the interplay of these two enzymes both found in the same cell.
Effects of different ratios incandescent (ln) to fluorescent (Fl) radiation were tested on growth of 'Waldmann's Green' leaf lettuce (Lactuca sativa L.) in a controlled environment. After 4 days of treatment, dry weight, leaf area, relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and photosynthetic rate (Pn) were greater for plants grown at 84 rather than 16% of total irradiance (82 W m-2) from ln lamps. Although leaf dry weight and area were 12-17% greater at 84% ln after the first 8 days of treatment, there were no differences in RGR or Pn between treatments during the last 4 days. If 84% ln was compared with 50% ln, all cumulative growth parameters, RGR, NAR and Pn were greater for 84% ln during the first 4 days of treatment. However, during the second 4 days, RGR was greater for the 50% ln treatment, resulting in no net difference in leaf dry weight or area between treatments. Shifting from 84 to 50% ln radiation between the first and second 4 days of treatment increased plant dry weight, leaf area, RGR and NAR relative to those under 84% ln for 8 days continuously.
A 40-50% reduction in soybean [Glycine max (L.) Merr. cv. Century 84] hypocotyl elongation occurred 24 h after application of mechanical stress. Exogenous Ca2+ at 10 mM inhibited growth by 28% if applied with the Ca2+ ionophore A23187 to the zone of maximum hypocotyl elongation. La3+ was even more inhibitory than Ca2+, especially above 5 mM. Treatment with ethyleneglycol-bis-(beta-aminoethylether)-N, N, N', N'-tetraacetic acid (EGTA) alone had no effect on growth of non-stressed seedlings at the concentrations used but negated stress-induced growth reduction by 36% at 4 mM when compared to non-treated, stressed controls. Treatment with EDTA was ineffective in negating stress-induced growth inhibition. Calmodulin antagonists calmidazolium, chlorpromazine, and 48/80 also negated stress-induced growth reduction by 23, 50, and 35%, respectively.
A 30-year-old female with mild asthma presented with high fever, hypotension, pleuritic chest pain, vomiting and diarrhea. Chest radiograph showed consolidation of the right upper lobe, and S. pyogenes was cultured from blood and sputum. Following initial rapid recovery the patient relapsed ten days after antibiotics were ceased, with rapid development of a large abscess cavity. Clinical improvement occurred following reinstitution of treatment including intravenous penicillin. Progressive radiological resolution eventuated during outpatient follow-up. This case demonstrates that S. pyogenes pneumonia may occur without an antecedent viral infection or major predisposing condition, cause rapid cavitation despite antiobiotic therapy and resolve satisfactorily with prolonged penicillin therapy.
A random sample of 600 registered professional nurses in New York State were asked to rate the relevance of The North American Nursing Diagnosis Association's list of defining characteristics for the six most frequently used nursing diagnostic categories on Likert-type scales. The diagnostic categories were Alteration in Comfort: Pain; Anxiety; Impaired Physical Mobility; Impaired Skin Integrity: Actual; Self-Care Deficit; and Knowledge Deficit. Based on 148 usable responses, the results indicated critical and supporting characteristics and total content validity scores for each of six diagnostic categories. The only defining characteristic that did not attain at least supporting status was "Regretful" for the diagnosis of anxiety.