Biomedical subjects
Publications and source records attributed to R R MacGregor.
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Human polymorphonuclear leukocytes were homogenised in isotonic sucrose and subjected to analytical subcellular fractionation by sucrose density gradient centrifugation. The gradient fractions were assayed for leucine aminopeptidase and for principal organelle marker enzymes. Leucine aminopeptidase, when assayed with both L-leucine-7-amido-4-methyl-coumarin and leucyl-2-naphthylamide as substrate, showed a unimodal distribution with an equilibrium density of 1.18 g X cm-3. This distribution was quite distinct from that exhibited by marker enzymes for all the recognized subcellular organelles: there was no leucine aminopeptidase associated with the plasma membrane. Fractionation experiments with neutrophils treated with isotonic sucrose containing a low concentration of digitonin, and studies with the non-permeant ectoenzyme inhibitor, diazotised sulphanilic acid, confirmed that leucine aminopeptidase had a purely intracellular localisation. Fractionation experiments with neutrophils homogenised in sucrose medium containing digitonin, showed leucine aminopeptidase associated with a membrane fraction. It is suggested that leucine aminopeptidase is located to the membrane of a previously unrecognised population of cytoplasmic granules of the human neutrophil.
Cell aggregates of bovine parathyroid tissue were prepared by limited collagenase digestion and placed in culture in Weymouth's MB752/1 (calcium = 3.3 mg/100 ml) containing 5% fetal bovine serum and supplemented with insulin alone, or insulin, hydrocortisone, transferrin and epidermal growth factor. Only insulin was required for the maintenance of PTH secretion over a 9-day period. The cell aggregates spread to form monolayer in 3-5 days. The majority of the cells in monolayer were polygonal with well-defined borders. Nuclei were round and the cytoplasm was free of vacuoles. Cell cultures responded to secretory stimulation by low calcium or by isoproterenol with increases in the secretion of PTH and SP-1. At low calcium, about 18% of both the cellular PTH and SP-1 was secreted per hour, and up to 50% of the cell content of these proteins was released per hour upon stimulation by isoproterenol and low calcium combined. The responses to calcium and isoproterenol decreased as a function of time in culture, and calcium responses often disappeared completely by 10 days of culture. When cells were cultured in medium containing a higher (5 mg%) than standard concentration of calcium between days 3-6 of culture, the degree of secretory inhibition attainable with high calcium was greater than that of cells cultured in the standard medium. When secreted hormonal peptides were separated by SDS-gel electrophoresis prior to RIA, it was found that the secretion of intact hormone was sensitive to calcium. For every molecule of PTH secreted into the medium, 1.5-2 mole-equivalents of carboxyl fragments were also released. Calcium control of fragment release was not as stringent as that of PTH release.
Tissue slices or dispersed cells of bovine parathyroid gland were incubated with [3H]leucine to label the intracellular proteins and then tested for their secretory response to isoproterenol and cycloheximide at different calcium concentrations. Secretion of the newly synthesized as well as the older PTH and SP-I was stimulated by isoproterenol at all calcium levels tested, even when it was maximally enhanced by low calcium. Cycloheximide interfered with neither the secretory process nor the secretory response to different stimuli, but decreased the amount of PTH and SP-I secreted. We conclude that the inhibitor decreased the secretion by reducing the supply of PTH and SP-I. Calculations derived from the data reveal that, under most secretory conditions, newly synthesized PTH contributed a major portion of the total hormone secretion in bovine parathyroid cells.
Cardiobacterium hominis is a fastidious bacterium of the normal mouth flora. It has rarely been recognised in the past as a human pathogen and has been difficult to recover from the bloodstream. Mistaken diagnoses and delays in therapy have been common. We report a 29-year-old man with C. hominis endocarditis who was initially treated for a presumed collagen-vascular disorder with anti-flammatory drugs. The organism was eventually recovered in brain-heart infusion medium after prolonged incubation, and cure was accomplished with parenteral penicillin. Special blood culturing methods should be used if endocarditis caused by a fastidious organism is clinically suspected.
Delivery of polymorphonuclear cells (PMN) to sites of bacterial invasion is a critical step in host defense. Renal transplant patients have a defect in PMN delivery caused by glucocorticoid immunosuppressive therapy that leads to increased susceptibility to infection. Because inhibited granulocyte adherence is often associated with poor delivery, the effects of propranolol and of ascorbic acid were measured for both of these functions. Propranolol caused a short-lived increase in adherence and no change in delivery in normal volunteers, so it was not studied in transplant patients. Ascorbic acid also failed to affect adherence in normal controls, but increased depressed adherence in transplant patients from a mean value of 27.7% to 48.0% when given daily for 3-4 weeks. PMN delivery increased to normal following 3-6 weeks of ascorbic acid, 4 g/day in a similar group of patients with low adherence prior to treatment. Pretreatment delivery was 3.06 X 10(5) and rose to 1.18 X 10(6) PMN after treatment (P less than 0.02), with no change noted in graft function. Thus, ascorbic acid treatment may improve PMN host defense in renal transplant patients.
Spiroperidol labeled with carbon-11, a short-lived positron-emitting radionuclide, was used to determine the time course of specific binding of this radioligand to the neuroleptic receptor in vivo in the rat. The three major bran pools--specifically bound, nonspecifically bound, and free (unbound)--were determined over a 60-mm time course by a rapid filtration technique, utilizing (-)- and (+)-butaclamol pretreatments to assess total and nonspecifically bound activities, respectively, in striatum and cerebellum. The ratio of specifically to nonspecifically bound pools in the striatum was 4.1 at 30 min and 5.1 at 60 min. Thus [11C]spiroperidol may be useful for labeling neuroleptic receptors in vivo for serial studies using positron emission transaxial tomography.
Fresh parathyroid gland homogenates and fractions thereof were analyzed for their content of PTH and carboxyl-terminal fragments of the hormone. The tissue proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and then extracted from gel fractions for RIA. Native PTH and PTH-(37-84) were used as standards to mark the migration positions of these peptides in the gels. The RIA for carboxyl-terminal hormone fragments used PTH-(37-84) as radioiodinated tracer and responded equally on a molar basis to either PTH or PTH-(37-84), making possible quantitative evaluation of both peptides in one assay after their separation. The results indicated that tissue homogenates contain 0.3-0.5 PTH-(37-84) moleq for each mole of PTH. Particulate fractions of the homogenates contained 0.15-0.3 moleq of fragment/mol PTH, while the high speed supernatant fraction of the homogenate contained about 2 moleq of fragment/mol PTH. When the experiments were performed using homogenization and fractionation buffers that contained numerous protease inhibitors, the ratios of carboxyl-terminal PTH fragment to intact hormone were not decreased, indicating that the hormone fragments were not produced during tissue processing. In addition, PTH added to tissue homogenates was not degraded during subsequent manipulations. The results demonstrate that fresh bovine parathyroid tissue contains substantial levels of carboxyl-terminal PTH peptide fragments, which can be measured by RIA after separation from PTH and other hormonal species. The data support the hypothesis that hormone fragments reside in regions of the cell different from those that contain PTH.
We have obtained a crude enzyme preparation from bovine parathyroid gland homogenates which when incubated with PTH, cleaves the hormone into two major fragments. Isolation and chemical analysis has led to the identification of these peptides, the 1-34 fragment and the 35-84 fragment. Digestion of PTH was totally inhibited by the inclusion of the cathepsin D inhibitor, pepstatin, in the enzyme digest. A comparison of the digest obtained using the crude enzyme fraction vs. digestion of PTH by purified bovine cathepsin D led to the findings that the same peptide products were formed in each case. The natural 1-34 hormone fragment derived from the procedure has been determined to be fully biologically active in a bone resorption system.
The clinical efficacy of clindamycin was compared with that of penicillin in a randomized study of the treatment of community-acquired putrid lung abscess. After starting therapy, patients treated with clindamycin had a shorter febrile period and fewer days of fetid sputum than patients treated with penicillin (mean 4.4 versus 7.6 days and 4.2 versus 8.0 days, respectively, p less than 0.05). Four of 20 patients treated with penicillin had clinically significant pulmonary or pleural extension of their infection within 10 days after starting therapy; this was not found in any of 19 patients treated with clindamycin (p less than 0.05). Penicillin treatment failed in two additional patients after 20 days of therapy. Within 1 month after treatment, 1 of 4 patients given penicillin for 3 weeks had relapse, but none of the 13 patients given clindamycin for 3 or 6 weeks, and none of the 5 patients given penicillin for 6 weeks had relapse. Overall, only 8 of 15 patients treated with penicillin who could be followed to the end of the study were cured, whereas all 13 patients treated with clindamycin who could be followed were cured (p less than 0.01). These results suggest that penicillin may not be optimal therapy for anaerobic lung abscess.
We describe the application of macroautoradiography, a relatively simple, quantifiable method for the evaluation of positron-emitting and gamma-emitting radiopharmaceuticals. We have investigated the response properties of two types of film to positron (F-18) and negatron (C-14) emitters. Variations in the response of film to increasing film-to-source distance are described, along with the effects of different intensifying screens and mounting tape. Digitization of whole-body autoradiograms (WBARG) in small animals was performed by using a videodensitometry system (videocamera interfaced to a computer). Quantitation was derived from analysis of a series of step-wedge standards that covered the range of radioactivities in the sample. By using a close-up lens on the videocamera, a 2- by 2-cm field is digitized as a 128 X 128 array, each pixel representing 156 X 156 micron. The effect of chlorpromazine (CPZ) on glucose metabolism in mice was studied by giving C-14 2DG followed by CPZ and F-18 FDG in the same animal. Muscle activity decreased and brown-fat activity increased. The high spatial resolution of this technique enables quantification in structures as small as the basal ganglia in mice. The use of dual-nuclide ARG permits each animal to be its own control, which greatly increases the utility of this method.
Polymorphonuclear leukocytes were isolated from the peripheral blood of rabbits by Ficoll-Hypaque centrifugation followed by dextran sedimentation. The granulocytes were homogenized in isotonic sucrose and subjected to analytical subcellular fractionation by sucrose density gradient centrifugation. Leucine aminopeptidase, when assayed with L-leucine-7-amido-4-methyl-coumarin as substrate, showed a similar distribution to N-acetyl-beta-glucosaminidase and thus is localized to the tertiary granules. There was no leucine aminopeptidase associated with the plasma membrane of these cells. Further experiments with purified plasma membranes and inhibitor studies using diazotized sulphanilic acid further confirmed that leucine aminopeptidase had a purely intracellular localization. Vitamin B-12 binding protein showed a similar localization to alkaline phosphatase indicating that, as in human polymorphonuclear leukocytes, vitamin B-12 binding protein is located to the specific granules.
(1) Increased metabolic trapping of labeled fluorouridine reflects the interaction of three parameters in rapidly proliferating tissues: increased rates of intracellular phosphorylation, increased rates of transport, and increased rates of synthesis of RNA. (2) We have taken advantage of these metabolic phenomena, demonstrating in this paper that the uptake of 18F-5-fluorouridine, a positron-emitting radiopharmaceutical, can provide a very practical means for measuring changes in proliferative states of tissues in vivo. (3) Two major changes in proliferative states have been examined: one involves changes in growth of normal mouse tissues induced by pharmacological agents; the other involves tumor growth and neoplastic infiltration in mice and rabbits. (4) We describe tracer experiments with 18F-5-fluorouridylate, prepared by enzymatic means, and with 18F-5-fluorouridine, prepared by both enzymatic means and direct radiochemical procedures. (5) Uptakes of 18F after a pulse of 18F-5-fluorouridine were increased in mouse spleen following phenylhydrazine treatment to induce increased splenic erythropoiesis. (6) Uptakes of 18F in various mouse tissues were decreased following pretreatment with actinomycin D. This finding is consistent with the known inhibitory action of actinomycin on RNA synthesis. (7) Intracerebral Zimmerman ependymoblastoma tumors showed extraordinarily high uptakes of fluorine-18 in mice injected intravenously with 18F-5-fluorouridylate or with 18F-5-fluorouridine in contrast to very low uptakes by normal brain tissue. (8) After intracerebral injection of mice with suspensions of L1210 leukemia cells, distant organs such as lung, liver, and spleen became involved. These tissues showed significant increases of radioactivity after pulse labeling with 18F-5-fluorouridylate consistent with histological evidence for infiltration of these tissues by neoplastic cells. (9) Intramuscular VX2 carcinoma tumors in rabbits showed localized uptakes of 18F significantly higher than surrounding normal muscle tissue. (10) The most important clinical implication of the present work is the promise that 18F-5-fluorouridine uptakes can be followed in humans by positron emission tomography. This would provide a direct means of measuring different rates of in vivo proliferation in neoplasms, hematologic tissues and other organs undergoing rapid growth changes.
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Three patients with liver metastases from colon carcinoma were studied with 2-deoxy-2-[F-18]fluoro-d-glucose (F-18-FDG) using positron emission tomography. The radioactivity in the metastatic tumor increased continuously following the injection of F-18-FDG, whereas it decreased in normal liver tissue. This resulted in the tumor to normal-liver ratio of 3.3-4.7 at 50 min after injection. The liver tumor was visualized as an increased accumulation of radioactivity in all patients, with the central area of the tumor showing less activity. These preliminary results suggest that F-18-FDG may be useful as a positive imaging agent for the detection and characterization of liver tumors.
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Endothelial injury is important in the pathogenesis of thrombosis, atherosclerosis, disseminated intravascular coagulation, and vasculitis. The ability of several common human viruses to infect cultures of endothelial cells obtained from human umbilical veins or bovine thoracic aorta was demonstrated. Indicators of infection included cytopathology, viral growth curves, and antigen detection by immunofluorescence. Herpes simplex virus type 1, adenovirus type 7, measles virus, and parainfluenza virus type 3 infected both human venous and bovine aorta endothelium. Mumps virus, poliovirus type 1, and echovirus type 9 grew only in human venous cells; coxsackievirus B4 infected only bovine arterial cultures; and cytomegalovirus, influenza A/Victoria/75 (H3N2) virus, and respiratory syncytial virus failed to grow in either cell culture. During replication some viruses caused acute lytic changes; some produced chronic, less destructive alterations; and other induced no apparent cytopathology. The results suggest that viral replication within endothelium may be important in the pathogenesis of viral disease of initiation of vessel-wall injury.
Transient granulocytopenia develops during the first few minutes of hemodialysis, and is associated with a marked increase in granulocyte adherence as the cells marginate in the pulmonary circulation. The increased adherence is mediated by factors present in the plasma, thought to be complement components activated by the dialysis coil. In the present study, an assay of plasma for adherence-augmenting activity shows that it is maximal at 15 min after starting dialysis, and undetectable at 40 min. The factor is not affected by heating to 56 degrees C for 30 min, or by incubation at 37 degrees C for 7 days, nor does dialysis for 24 h against physiologic saline diminish its activity. However, exposure to pH 6.0 reduces the activity to 58.4% of control, and pH 5.0 reduces it to 40.1%. Finally, pretreatment of patients with prednisone before hemodialysis does not prevent granulocytopenia or increased adherence. These findings are discussed in relation to the known properties of various biologically active fragments of complement.