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Biomedical subjects

J Thomson

Publications and source records attributed to J Thomson.

At least 91 records · Page 5Linked to original sources
PubMed1994

Thermodynamic and structural consequences of changing a sulfur atom to a methylene group in the M13Nle mutation in ribonuclease-S.

Two fragments of pancreatic ribonuclease A, a truncated version of S-peptide (residues 1-15) and S-protein (residues 21-124), combine to give a catalytically active complex. We have substituted the wild-type residue at position 13, methionine (Met), with norleucine (Nle), where the only covalent change is the replacement of the sulfur atom with a methylene group. The thermodynamic parameters associated with the binding of this variant to S-protein, determined by titration calorimetry in the temperature range 10-40 degrees C, are reported and compared to values previously reported [Varadarajan, R., Connelly, P. R., Sturtevant, J. M., & Richards, F. M. (1992) Biochemistry 31, 1421-1426] for other position 13 analogs. The differences in the free energy and enthalpy of binding between the Met and Nle peptides are 0.6 and 7.9 kcal/mol at 25 degrees C, respectively. These differences are slightly larger than, but comparable to, the differences in the values for the Met/Ile and Met/Leu pairs. The structure of the mutant complex was determined to 1.85 A resolution and refined to an R-factor of 17.4%. The structures of mutant and wild-type complexes are practically identical although the Nle side chain has a significantly higher average B-factor than the corresponding Met side chain. In contrast, the B-factors of the atoms of the cage of residues surrounding position 13 are all somewhat lower in the Nle variant than the Met wild-type.(ABSTRACT TRUNCATED AT 250 WORDS)

Calorimetry↗
PubMed1994

Effects of ciprofibrate on LDL metabolism in man.

This study examined the effects of ciprofibrate therapy (100 mg/day) on plasma lipids, lipoproteins and low density lipoprotein (LDL) kinetic heterogeneity in moderately hypercholesterolaemic subjects. The drug lowered plasma triglyceride and cholesterol by 41% and 17%, respectively. Very low density lipoprotein (VLDL) cholesterol fell by 38%, LDL cholesterol fell by 22%, while the content of the lipid in high density lipoprotein (HDL) increased by 11%. LDL structural and metabolic heterogeneity were assessed before and during therapy in eight subjects. Density gradient centrifugation was used to fractionate LDL into three species. LDL-I, the least dense, was not affected by therapy whereas LDL-II and LDL-III were decreased by 28% (P < 0.01) and 31% (N.S.). Baseline turnover studies revealed that LDL catabolism was subnormal and this was the cause of the raised cholesterol in these subjects. Ciprofibrate therapy increased the apoLDL fractional catabolic rate (FCR) by 19%, principally by inducing a 38% enhancement (P < 0.03) in apoLDL removal by the receptor pathway. ApoLDL kinetics exhibited metabolic heterogeneity both before and during drug therapy. Analysis of plasma decay curves for the LDL tracer and urinary excretion data indicated that the lipoprotein comprised two metabolically distinct species, one with an FCR of about 0.50 pools/day (Pool A), the other with an FCR of about 0.18 pools/day (Pool B). Drug therapy decreased synthesis of and hence reduced the plasma mass of apoLDL in the slow metabolised pool B. This perturbation in synthesis was linked to the change in plasma triglyceride concentration. The resultant reduced proportion of pool B vs. pool A material accounted for the observed promotion of LDL receptor-mediated clearance. Ciprofibrate, therefore, produced beneficial changes in the plasma levels of VLDL, LDL and HDL and in the metabolism of LDL.

Adult↗
PubMed1994

Role of plasma triglyceride in the regulation of plasma low density lipoprotein (LDL) subfractions: relative contribution of small, dense LDL to coronary heart disease risk.

The concentration of plasma LDL subfractions is described in four groups of normocholesterolaemic (total plasma cholesterol < 6.5 mmol/l) male subjects consisting of men with and without coronary artery disease (CAD+/-), as determined by angiography, post-myocardial infarct survivors (PMI) and normal, healthy controls. The CAD(+) and PMI groups were distinguished from the CAD(-) and controls by raised concentrations of plasma triglyceride, very low density lipoprotein (VLDL) cholesterol, small, dense LDL (LDL-III density (d) 1.044-1.060 g/ml) and lower concentrations of high density lipoprotein (HDL) cholesterol and large, buoyant LDL (LDL-I d 1.025-1.034 g/ml). In all groups, a subfraction of intermediate density, LDL-II (d 1.034-1.044 g/ml), was the predominant LDL species but was not related to coronary heart disease risk. Plasma triglyceride showed a positive association with LDL-II (r = 0.51, P < 0.001) below a triglyceride level of 1.5 mmol/l. Above this threshold of 1.5 mmol/l, LDL-II and LDL-I showed significant negative associations with triglyceride (LDL-II r = -0.5, P < 0.001; LDL-I r = -0.45, P < 0.001). Small, dense LDL-III showed a weak positive association with triglyceride that became highly significant above the 1.5 mmol/l threshold (r = 0.54, P < 0.001). While age was positively related to LDL-II within the control subjects (r = 0.3, P < 0.05), there was no difference in the percentage abundance or concentration of LDL-III within control and CAD(-) subjects above and below the age of 40 years. Smoking was associated with a relative deficiency of the LDL-I subfraction (LDL-I to LDL-III ratio in smokers = 0.77, in ex-smokers = 0.95, in non-smokers = 1.89; P < 0.01), as was beta-blocker medication (% LDL-I, users vs. non-users, P < 0.05). Both of these effects could be explained by their primary influence on plasma triglyceride. Analysis of the frequency distributions for the three LDL subfractions revealed the concentration of small, dense LDL-III to be bimodal around a concentration of 100 mg (lipoprotein mass)/100 ml plasma. The calculation of odds ratios based on this figure indicated relative risk estimates of 4.5 (chi 2: P < 0.01) for the presence of coronary artery disease and 6.9 (chi 2: P < 0.001) for myocardial infarction.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

The in-vitro detection and quantitation of ovine bone marrow precursors of multipotential colony-forming cells.

The in-vitro detection and quantitation of ovine bone-marrow precursors of multipotential colony-forming cells (pre-multi CFC) is described. After 5 and 10 days in liquid culture containing medium conditioned by long term bone marrow stromal cell layers (SCM) along with lymph node-conditioned medium (LNCM) or recombinant ovine interleukin-3 (rov IL-3), increased numbers of multi CFC developed from bone marrow precursors as detected by subsequent soft agar clonogenic assay of mixed phenotype colonies. From a variety of cytokines and conditioned media (CM) tested that included recombinant ovine granulocyte-macrophage colony-stimulating factor (rov GM-CSF) and recombinant human macrophage colony-stimulating factor (rhu M-CSF), the combination of SCM plus LNCM or rov IL-3 supported the maximum numbers of multi-CFC in liquid culture. The development of multi CFC from precursors was demonstrated in bone marrow cells treated with a dose of mafosfamide that inactivated > 98% of clonogenic CFC. Quantitative limit dilution analysis of 10 bone marrow samples revealed an average of one pre-multi CFC per 34147 unfractionated cells (range 1:14230-81433). Pre-multi CFC were enriched 38-fold (average) in the 2.0% of bone marrow cells remaining after depletion of lymphocytes and myeloid/erythroid cells expressing the antigen recognized by monoclonal antibody 175. The quantitative assay also revealed preliminary evidence that the pre-multi CFC may consist of subpopulations differing in their sensitivity to mafosfamide.

Adjuvants, Immunologic↗
PubMed1993

Evaluation of product equivalence during process optimization for manufacture of a human IgM monoclonal antibody.

We have developed a battery of tests to characterize monoclonal antibodies and assess the effect of potential manufacturing process changes. Tryptic peptide mapping, molecular weight determination by HPLC and classical light scattering, isoelectric focussing, oligosaccharide mapping by HPAE-PAD chromatography, circular dichroism spectra and differential scanning calorimetry were applied as sensitive assays of antibody structure. Biological activity was assessed by measurement of specific antigen binding activity, binding spectrum and opsonic activity. Pharmacokinetics was assessed by clearance rate studies in rats. The sensitivity of this battery of assays was demonstrated by the ability to readily detect differences between a human monoclonal antibody (IgM-2) produced by in vitro cell culture versus ascites culture. These same tests support equivalence of a second monoclonal antibody (IgM-1) produced before and after in vitro cell culture process improvements which resulted in a twofold increase in product titer.

Animals↗
PubMed1993

Effect of culture conditions on IgM antibody structure, pharmacokinetics and activity.

Culture conditions affect the binding activity, charge heterogeneity, conformational stability, glycosylation, and pharmacokinetics of human monoclonal IgM HMAB-10058. The 10058 human/human/murine trioma was grown in serum-free airlift suspension culture, hollow fiber perfusion culture, or in nude mouse ascites. The ascites-produced antibody showed reduced conformational stability, greater charge and glycoform heterogeneity, and a lower average degree of sialylation than the in vitro culture-produced material. Mean residence time after IV injection in rats was approximately 80-fold greater for the ascites culture-produced material, but specific binding activity was less than 5% of that for the airlift-produced material. In vitro culture in serum-supplemented media (in a hollow fiber perfusion reactor or in shake-flasks) resulted in antibody with pharmacokinetics intermediate between the serum-free airlift and ascites-produced materials. Incubation of airlift-produced antibody in ascites fluid also resulted in material with intermediate pharmacokinetics. Conclusions regarding the effect of culture conditions on antibody product cannot be generalized, as in vitro-produced antibody derived from two related cell lines (HMAB-10233 and HMAB-10390) had long mean residence times similar to that of ascites-produced HMAB-10058.

Animals↗
PubMed1993

Laboratory investigation of PRRS virus infection in three swine herds.

Late in 1991, an enveloped RNA virus (now called porcine reproductive and respiratory syndrome [PRRS] virus) was identified as the etiologic agent for mystery swine disease. In 1992, laboratory procedures for the diagnosis of this disease evolved rapidly, and veterinary diagnosticians started applying these tests to field cases. This report is written from the perspective of veterinary laboratory diagnosticians and utilizes 3 case studies to define the advantages and disadvantages of the various available diagnostic laboratory PRRS test procedures in different clinical situations. The diagnostic procedures currently used in our laboratory for investigating PRRS are pathologic examination, serologic testing, fluorescent antibody (FA) testing, and virus isolation. Interstitial pneumonia, characterized by mononuclear cell infiltration of alveolar walls with normal airway epithelium, is a hallmark lesion for the disease, especially in neonatal pigs with respiratory distress. Interstitial pneumonia is not a specific lesion and must be coupled with other tests to verify PRRS virus infection. Demonstration of seroconversion is helpful, especially in sows that have experienced reproductive failure. The indirect FA test detects antibody sooner than the serum neutralization test and will likely become the serologic test of choice. The direct FA test on fresh tissue utilizes monoclonal antibody and is useful for investigating PRRS virus-associated pneumonia. Virus isolation utilizing swine alveolar macrophages has also been a useful diagnostic procedure. All of the above tests have been universally unrewarding when applied to aborted, mummified, or stillborn piglets.

Animals↗
PubMed1992

Treatment of postmenopausal osteoporosis with calcitriol or calcium.

BACKGROUND AND METHODS: Osteoporosis is a common problem whose management is controversial. To evaluate the efficacy and safety of calcitriol (1,25-dihydroxyvitamin D3) in the treatment of postmenopausal osteoporosis, we conducted a three-year prospective, multicenter, single-blind study in 622 women who had one or more vertebral compression fractures. The women were randomly assigned to receive treatment with calcitriol (0.25 micrograms twice a day) or supplemental calcium (1 g of elemental calcium daily) for three years. New vertebral fractures were detected by means of lateral roentgenography of the spine each year, and calcium absorption was measured in 392 of the women. RESULTS: The women who received calcitriol had a significant reduction in the rate of new vertebral fractures during the second and third years of treatment, as compared with the women who received calcium (second year, 9.3 vs. 25.0 fractures per 100 patient-years; third year, 9.9 vs. 31.5 fractures per 100 patient-years; P less than 0.001). This effect was evident only in women who had had five or fewer vertebral fractures at base line (second year, 5.2 vs. 25.3 fractures per 100 patient-years; third year, 4.2 vs. 31.0 fractures per 100 patient-years; P less than 0.0001). The groups also differed significantly in the number of peripheral fractures; 11 such fractures occurred in 11 women in the calcitriol group, whereas 24 occurred in 22 women in the calcium group (P less than 0.05). There was no significant difference between the groups in the incidence of side effects requiring withdrawal of treatment (8.6 percent in the calcitriol group vs. 6.5 percent in the calcium group). CONCLUSIONS: Continuous treatment of postmenopausal osteoporosis with calcitriol for three years is safe and significantly reduces the rate of new vertebral fractures in women with this disorder.

Aged↗
PubMed1992

The inhibition of the oxidation of low density lipoprotein by (+)-catechin, a naturally occurring flavonoid.

(+)-Catechin inhibited the copper-catalysed oxidation of human low density lipoprotein (LDL) in a dose-dependent manner with complete inhibition at 20 micrograms/mL. The flavonoid at a concentration of 50 micrograms/mL also inhibited oxidation of LDL induced by the mouse transformed macrophage J774, human monocyte-derived macrophages and vascular endothelial cells isolated from human umbilical cords. LDL modified by copper-catalysed or cell-induced oxidation was endocytosed and degraded by human macrophages at a much greater rate than native LDL. LDL reisolated from copper or cell incubations in the presence of (+)-catechin was endocytosed and degraded at rates similar to native LDL. (+)-Catechin appeared to inhibit the uptake and degradation by macrophages of cell-modified LDL. The actions of (+)-catechin on cell-induced oxidation of LDL are consistent with the ability of flavonoids of similar structure to inhibit lipoxygenases and with a role for lipoxygenases in cell-induced modification of LDL in vivo.

Animals↗
PubMed1992

Purification and adhesion receptor phenotype of ovine bone marrow-derived haemopoietic colony-forming cells.

Ovine haemopoietic progenitor cells that form colonies (CFC) in soft agar cultures were compared to more mature bone marrow cells for their level of expression of the adhesion receptor molecules ovine (ov) CD44, ov CD11a (LFA-1) and ov CD58 (LFA-3) as well as the 175-antigen using specific monoclonal antibodies. Ov CD44, ov CD11a and ov CD58 were expressed on all CFC of the myeloid (non-erythroid) series, whereas ov CD44 and ov CD11a expression was very low or absent from a small number of blast and erythroid series CFC. Within the mature non-erythroid population of myeloid cells, neutrophils retained a low level of expression of ov CD11a. Most CFC representing all lineages strongly expressed the ov CD44 antigen. In contrast, the majority of CFC lacked the 175-antigen, as did bone marrow lymphocytes, basophils and mast cells. This property of CFC was exploited in a negative selection technique using panning and immunomagnetic beads to select CFC from other bone marrow cells with a 116-125-fold enrichment, 12-14% purity and 29-40% yield. These results demonstrate that ovine CFC express some of the molecules necessary to allow adhesion to haemapoietic stromal cells and vascular endothelium in the tissues. Future studies will concentrate on the function of the adhesion receptor molecules in medullary and extra-medullary haemopoiesis and inflammatory cell development in sheep.

Animals↗
PubMed1992

Nutrient intake and weight/height of Saudi patients at King Faisal Specialist Hospital in Riyadh, Saudi Arabia.

Nutrition surveys in the past showed some mild and moderate degrees of malnutrition in young children below 10 years of age. Deficiency diseases like anaemia were also reported. This survey is part of a large study of 1005 patients and sitters to see the relationship of diet and disease. Seven hundred and fourteen patients were subsampled and became the subject of this report to find out if the nutritional status of the children surveyed 10 to 15 years ago had any major change. It also presented some new information about nutritional status of older groups up to 96 years of age. It was found that weight for height and height for age of children up 14 years (except the girls GT 10-LE 14 years) could now compare with the US NCHS standard. The adolescent girls' (up to age 18) weight for height were statistically lower than the standard. Later in life, with some influences from the other female members of the household, and because of their limited activity, the women's weights were even higher than the standard. The adolescent males' weights were within standard, but the adult males' from age 18 were statistically lower than NCHS. Height for age from age 14 years for all were statistically lower than standard and was attributed to poor nutritional states in the past. Energy intakes of the adult males and iron intakes of the infants below one year of age were significantly lower than standard. Low energy intakes of the adult males confirm low weight for height performance. The same problem with iron of milk-fed infants of 10 to 15 years ago was still encountered. This shows that some traditional practice of infant feeding still persists despite the improvement in the quality of life and standard of living of the Saudis due to the economic upheaval created by oil. This survey emphasizes the importance of follow-up reports to see the changes in the people's state of health after a period of transition from economic dependence to affluence.

Adolescent↗
PubMed1991

Reactivity of the workshop monoclonal antibodies with ovine bone marrow cells and bone marrow-derived monocyte/macrophage and mast cell lines.

The workshop monoclonal antibodies were tested by flow cytometry for reactivity against: (1) ovine bone marrow cells, (2) cultured bone marrow-derived monocyte/macrophage cell lines and (3) cultured bone marrow-derived mast cell lines. Both single and two-colour immunofluorescence tests were performed. The results of these analyses are presented and discussed.

Animals↗
PubMed1991

Intraoperative radiation therapy of pancreatic carcinoma: a report of RTOG-8505. Radiation Therapy Oncology Group.

The Radiation Therapy Oncology Group in 1985 began a study of IORT plus external beam radiation therapy for patients with locally unresected, non-metastatic pancreatic cancer. Patients were treated with a combination of 2000 cGy of IORT and postoperative external beam radiation therapy to 5040 cGy in combination with IV 5-FU (500 mg/m2/day on the first 3 days of the external beam treatment). As patients were registered on study prior to exploration, it was expected that a number of patients would be excluded from further analysis at the time of surgery. Eighty-six patients were entered on study through 6/1/88 and analyzed through 4/90. Fifty-one patients were fully analyzable. Median survival time of the 51 patients was 9 months with an 18-month actuarial survival rate of 9%. Local control could not be adequately evaluated in this multi-institutional study. Major postoperative complications were not excessive and occurred in 12% of patients. Two patients had major late morbidity leading to death, one from duodenal bleeding and the second from biliary obstruction. Although this study does demonstrate the feasibility of IORT in a multi-institutional setting, it does not demonstrate any advantage of IORT over conventional therapy for this disease.

Carcinoma, Intraductal, Noninfiltrating↗