Biomedical subjects
Publications and source records attributed to G Jones.
A model is described for the binding of non-steroidal inhibitors of aromatase to the enzyme with interaction of a ligand with the Fe3+-haem of the cytochrome. The model suggests that the inhibitors utilise a common binding site with ring A of the steroidal substrates.
Two human hepatoma cell lines, Hep G2 and Hep 3B, were screened for vitamin D3-25-hydroxylase enzyme activity by incubation with radioactive vitamin D3. A compound co-chromatographing with 25-OH-D3 was synthesized in both cell lines but its rate of synthesis was tenfold greater in Hep 3B than in Hep G2 cells. The identity of the compound was confirmed by comparing its chromatographic properties with authentic 25-OH-D3 on three different high pressure liquid chromatography systems. Its production was suppressed by adding fetal calf serum (10%), lipoprotein-deficient fetal calf serum, or pure vitamin D-binding globulin to the medium. The mechanism of action of these plasma proteins appears to involve retardation of uptake of the substrate. These two cell lines offer considerable potential as defined in vitro models for studying the effects of physiological factors on the 25-hydroxylation of vitamin D3.
Explore the source record for details and available documents.
Previous work has shown that 25-hydroxyvitamin D3 (25-OH-D3) and 1 alpha, 25-dihydroxyvitamin D3 (1,25-(OH)2D3) may be metabolized in the mammalian kidney through a side chain oxidation pathway resulting in C23-C24 cleavage, yielding 24,25,26,27-tetranor-23-OH-D3. In the present study, we have used UMR-106 clonal osteoblast cells to demonstrate that products of the side chain oxidation pathway are produced by an osteoblast-like cell. Cells cultured on microcarrier beads and incubated in the presence of pharmacological levels of substrate (1.4 microM, either 25-OH-D3 or 1,25-(OH)2D3) produced sufficient quantities of metabolite to allow identification through mass spectrometry. In addition, putative metabolites were identified through comigration with authentic standards on three high pressure liquid chromatography systems, chemical modification by NaBH4 and periodate, and UV spectral characterization. The pathway was undetectable unless the cells had been exposed to 1,25-(OH)2D3 prior to incubation with substrate. We have shown that 1,25-(OH)2D3 induces the 24-hydroxylase and perhaps also the other enzymes of this pathway in the bone cell. Although we used pharmacological concentrations of substrate to demonstrate the existence of the side chain oxidation pathway in bone cells, physiological levels of 25-OH-D3 or 1,25-(OH)2D3 were also metabolized through the pathway, at least as far as the penultimate product. We speculate that the side chain oxidation pathway may be ubiquitous among vitamin D target tissues.
The two major electrophoretic forms (pI 5.5, 5.3) of juvenile hormone esterase were independently isolated from hemolymph of larval Trichoplusia ni. A simple and rapid preparation procedure of poly(ethylene glycol) precipitation, Sephadex gel filtration and chromatofocusing is described. Analytical isoelectric focusing showed only one peak of juvenile hormone esterase activity in the respective purified samples, whereas there were four (two major) such peaks in the hemolymph. The amino acid composition of the two forms was similar. The comparison of peptides obtained after protein fragmentation by cyanogen bromide showed that juvenile hormone esterases A and B were very similar, although definitely not identical, in amino acid sequence. The immunological comparisons of juvenile hormone esterases suggested that the number of polyclonal antibody binding sites on both forms was the same. There were no detected differences between immunoreactive properties of juvenile hormone esterase from the hemolymph of different stages of larval maturation. The influence of the active site of the enzyme on its antigenic properties was studied by immunocompetition. The inactive, heat-denatured juvenile hormone esterase can only partially protect against inhibition of its activity by the antibodies, whereas an organophosphate inhibitor which covalently binds to the catalytic center of the enzyme did not change the immunoreactive properties in comparison to active juvenile hormone esterase from hemolymph. These data show that heat-denatured juvenile hormone esterase has lost at least one or more epitopes, but the catalytic site of the enzyme is distinct from the epitopes.
The Time relations between maternal rubella infection in pregnancy and the presence and type of defects in the children were determined from the records of 422 children with confirmed congenital rubella, registered in the National Congenital Rubella Surveillance Programme. In the 106 children born after laboratory-proven maternal infection, no defects were recorded following infection after the 17th week of pregnancy, but in the remaining 316 children defects followed infection reported to be as late as 33 weeks. The striking difference underlines the importance of serological investigation of pregnant women who present with a rash or a history of contact with rubella. With proven infection later than the 16th week the risk of fetal damage seems to be very small. Of 148 children followed up to school age, 40 (27%) attended normal schools.
A number of basic metamorphosis-associated proteins were identified from several noctuid species. All of these proteins have molecular weights in the range of 73,000 to 74,000. Two of the proteins in Trichoplusia ni and Heliothis virescens were found to be suppressible by a juvenile hormone analog.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The Ph1 chromosome is present in 95% of patients with chronic myelogenous leukaemia (CML). The Ph1 chromosome also occurs in 5-25% of children and adults with acute lymphoblastic leukaemia (ALL). This observation raises questions as to whether these diseases are similar or identical. In patients with CML the c-abl and bcr genes are translocated and abnormally expressed. We studied molecular events related to bcr and c-abl in five patients with ALL to determine its relationship to CML. Four had the Ph1 chromosome; the fifth a probable Ph1 chromosome. c-abl and bcr abnormalities identical to CML were detected in four suggesting a common molecular basis. One patient with the Ph1 chromosome and c-abl translocation lacked these molecular changes but had abnormal c-abl gene transcription apparently unrelated to bcr. These data suggest that Ph1 chromosome positive ALL is heterogeneous; in some patients the molecular abnormality is identical to CML; in others c-abl is likewise involved but via a different mechanism.
This paper describes the use of a home microcomputer to produce a highly versatile yet relatively inexpensive interactive video system. The program has been designed to introduce medical students to the examination of the mentally ill patient, but the technique is ideally suited to demonstrate examination and treatment techniques in all medical specialties.
The physical work capacity, body composition, and physiological characteristics of 12 law enforcement officers (9 males, 3 females) were measured. Subjects included a representative sample from the occupational categories of detective, staff, investigative and patrol officer. Mean maximal oxygen uptake of the men was 42.1 +/- 8.9 ml.kg-1min-1 with mean values of 41.5 +/- 8.7 ml.kg-1min-1 for the women. Measurement of body composition indicated an average of 24.4 +/- 7.1% body fat for the men and 30.9 +/- 1.2% for the women. Muscular power, strength, and endurance as measured by isolated limb flexion-extension movement and fitness test performance was considered average with no excessive bilateral differences. The results of this study were compared with other investigations of law enforcement officers of similar age groups. The officers displayed average or above health and physical fitness scores for their age classification and were able to complete all police task-oriented tests.
Side-chain oxidation of vitamin D is an important degradative pathway. In the present study we compared the enzymes involved in side-chain oxidation in normal and Hyp mouse kidney. Homogenates of normal mouse kidney catalyze the conversion of 25-hydroxyvitamin D3 to 24,25-dihydroxyvitamin D3, 24-oxo-25-hydroxyvitamin D3 and 24-oxo-23,25-dihydroxyvitamin D3. After subcellular fractionation, total side-chain oxidative activity, estimated by the sum of the three products synthesized per milligram protein under initial rate conditions, coincided with the mitochondrial enzyme marker succinate-cytochrome-c reductase. Treatment of normal mice with 1,25-dihydroxyvitamin D3 (1.5 ng/g) resulted in an eightfold increase in mitochondrial enzyme activity, with no change in apparent Km but a significant rise in Vmax. With 24,25-dihydroxyvitamin D3 as the substrate, normal renal mitochondria produced 24-oxo-25-hydroxyvitamin D3 and 24-oxo-23,25-dihydroxyvitamin D3, and the synthesis of these metabolites could be increased sixfold by pretreatment with 1,25-dihydroxyvitamin D3. In the Hyp mouse, the side-chain oxidation pathway showed similar subcellular distribution of enzyme activity. However, product formation from 25-hydroxyvitamin D3 and 24,25-dihydroxyvitamin D3 was twofold greater in mutant than in normal mitochondria. Furthermore, 1,25-dihydroxyvitamin D3 pretreatment of Hyp mice resulted in a 3.4-fold increase over basal metabolism of both 25-hydroxyvitamin D3 and 24,25-dihydroxyvitamin D3. These results demonstrate that (i) kidneys from normal and Hyp mice possess basal and 1,25-dihydroxyvitamin D3 inducible enzyme system(s) in the mitochondrial fraction, which catalyze the side-chain oxidation of 25-hydroxyvitamin D3 and 24,25-dihydroxyvitamin D3, and (ii) the Hyp mutation appears to perturb the renal metabolism of both substrates only in the basal state.
The present series of experiments used gas chromatography to identify vapor-phase photoproducts liberated during excimer laser irradiation of cardiovascular tissues in air and blood. In air, laser beams produced from ArF (193 nm) and XeF (351 nm) excimer laser gas mixtures were delivered to samples of myocardium and atherosclerotic coronary arterial segments through the wall of a quartz cell, using 8-40 mJ/pulse. In blood, 351 nm were delivered via an optical fiber, using 14 mJ/pulse. When the experiments were performed using an air-tissue interface, the dominant photoproducts identified in order of elution from the gas chromatographic column were methane, acetylene, ethylene, ethane, propyne, allene, propylene, propane, and butene. When a fiberoptic was used to accomplish 351-nm excimer laser tissue ablation in a blood field, a similar gas chromatographic spectral distribution was observed. These vapor-phase photoproducts are indistinguishable from those observed following continuous wave laser irradiation or flame torching of cardiovascular tissues. Thus, despite the fact that excimer laser ablation of cardiovascular tissues is characterized by the absence of signs of thermal injury, the results of these experiments suggest that the predominant mechanism of excimer ablation is, like continuous-wave laser irradiation, a thermal process.
The present study was undertaken to evaluate the response of Hyp mice to regulators known to inhibit renal 25-hydroxyvitamin D3-1-hydroxylase (1-hydroxylase) and stimulate renal 25-hydroxyvitamin D-24-hydroxylase (24-hydroxylase). Renal mitochondrial metabolism of 25-hydroxyvitamin D3 (25OHD3) was initially examined in vitamin D- and calcium-deprived normal and mutant mice (with no detectable 24-hydroxylase) treated with either calcium, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], or both calcium + 1,25-(OH)2D3. In normal mice, 1,25-(OH)2D3 treatment was more effective than calcium in turning off 1-hydroxylase and turning on 24-hydroxylase activity; serum calcium, however, was similarly increased by both treatments. Although calcium + 1,25-(OH)2D3 did not result in a further change in 25OHD3 metabolism in normal mice, a further elevation in serum calcium was apparent. In Hyp mice, treatment with calcium + 1,25-(OH)2D3 resulted in a greater decrease in 1-hydroxylase and a greater increase in 24-hydroxylase and in serum calcium than treatment with either agent alone. In spite of similar serum calcium levels in both genotypes, 24-hydroxylase was 20-fold, 3-fold, and 8-fold greater in Hyp mice relative to normals treated with calcium, 1,25-(OH)2D3, and calcium + 1,25-(OH)2D3, respectively. Kinetic studies revealed that the maximum velocity (Vmax) for induced 24-hydroxylase was 6-fold greater than normal in Hyp mice whereas the apparent Michaelis-Menten constant (Km) was not different in the two groups of calcium + 1,25-(OH)2D3-treated mice. The effect of 1,25-(OH)2D3 treatment on the above serum and renal parameters was also examined in vitamin D replete normal and Hyp mice. A sharp rise in serum phosphate was observed in 1,25-(OH)2D3-treated Hyp mice whereas normal littermates experienced marked hypercalcemia in response to treatment. Renal 24-hydroxylase was significantly stimulated by 1,25-(OH)2D3 treatment in both normal and Hyp mice and genotype differences were not apparent. The present study demonstrates that vitamin D- and calcium-deprived Hyp mice are more responsive to signals which induce 24-hydroxylase than normal littermates; Vmax for induced 24-hydroxylase is 6-fold greater in Hyp mice than in normal littermates whereas apparent Km is unchanged; the inhibitory control of 1-hydroxylase appears to be intact in the mutant strain; induced 24-hydroxylase is similar in vitamin D replete normal and Hyp mice; and vitamin D status can thus modify the response of both genotypes to treatment with 1,25-(OH)2D3.(ABSTRACT TRUNCATED AT 400 WORDS)
The inducibility of 1 alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3] binding by all-trans-retinoic acid (RA) was examined in tumor-derived clonal bone cell lines, in established clonal cell lines derived from normal embryonic bone, and in cultured bone cell populations freshly isolated from 18- and 21-day fetal and 5-day-old neonatal rat calvaria. Levels of 1,25-(OH)2D3 binding were determined using a single saturating dose (84 pM) of 3H-labeled 1,25-(OH)2D3. Bone-derived tumor cell lines (ROS 17/2.8, ROS 17/2, RCJ 3.2T.1, RCJ 3.2.4.1CAM, RCJ 3.2CE2.1) possessed high basal levels of binding and showed increases in 1,25-(OH)2D3 binding after culture for 24 hours in the presence of 10(-5) M RA. The non-tumor-derived established bone cell lines (RCB 2.2A, RCB 2.2B, RCB 2.2C, RCB 2.2D) showed low basal 1,25-(OH)2D3 binding levels and no change in response to RA, while first subcultures of bone cell populations derived from fetal and neonatal rat calvaria showed decreased 1,25-(OH)2D3 binding, following similar treatment with RA. In representative cell populations, the dose dependency of the RA effect was established. The observed differences in response to RA in the cell lines tested seem to be dependent on whether the cells originated from normal or tumor tissue.