Biomedical subjects
Publications and source records attributed to G J Miller.
A patient with typical chronic lymphocytic leukemia (CLL) who developed central nervous system involvement is presented. The CLL was of B-cell origin and the neurological involvement consisted of perivascular infiltration in the spinal cord.
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A bioassay, based on tumorigenicity, has been developed to determine the mechanism whereby the blastocyst of the mouse controls malignant expression of embryonal carcinoma. The assay is based upon the incidence of tumors obtained when known numbers of cells of the 402AX strain of embryonal carcinoma are injected into strain 129 mice, compared to the incidence obtained when the same number of embryonal carcinoma cells are incorporated into Swiss-Webster blastocysts that are then injected in strain 129 animals. The results indicate that the blastocyst can regulate one embryonal carcinoma cell consistently; it may have a slight effect on three, but it cannot regulate four or five of them. The position of the embryonal carcinoma cell in the blastocyst is important. Regulation occurs if the embryonal carcinoma cell is placed in the blastocoele cavity, but enhancement of tumorigenicity is obtained if it is placed between the zona pellucida and the trophectoderm. By contrast, the blastocyst is unable to regulate a single B-16 melanoma cell placed in the blastocoele cavity, indicating a degree of specificity for the regulatory process.
Fasting serum high-density lipoprotein (HDL) cholesterol, other lipid concentrations and related characteristics have been measured in 87% of 261 residents aged over 5 years on the small isolated island of Salt Cay, Turks and Caicos Isles. Only one subject, a hypertensive woman, had a major electrocardiographic Q wave abnormality, and none of the islanders had clinical coronary heart disease. These findings, together with local clinical experience indicated a low incidence of coronary heart disease in this community. Adult mean concentrations of HDL cholesterol (1.6 mmol/l) and serum total triglyceride (0.81 mmol/l) were relatively high and low respectively compared with those of men and women in North American communities. Unlike findings in North America, there was no significant sex difference in HDL cholesterol concentration apparent in adulthood and this was not explained by sex differences in alcohol consumption (positively correlated with HDL cholesterol in both sexes) or adiposity (negatively correlated with HDL cholesterol in men only). Residents who were recovering from an epidemic of mild upper respiratory infection had on average a 9% reduction in HDL cholesterol concentration compared with the remainder of the community. The lipoprotein lipid pattern in these people is consistent with a low cardiovascular risk status, and might account for the apparent absence of coronary heart disease on the island.
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Prediction equations have been evolved for the assessment of vital capacity, total lung capacity, and the single breath carbon monoxide transfer factor in haemoglobin SS and haemoglobin SC disease. These relationships take account of the growth disorder and anaemia in the sickle-cell states. The results suggest that, in the clinically stable state, any effects of alveolar capillary sickling and haemoconcentration and any altered reactivity of haemoglobins S and C with the test gas are of no significance for clinical respiratory physiology. Sex differences in lung function appear independent of haemoglobin type.
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The freeze-fracturing technique has been used to investigate membrane architecture in the mesophyll and bundle sheath chloroplasts of Zea mays. The structural organization of mesophyll chloroplasts is virtually identical to that of other species of higher plants which have been investigated with this technique. Characteristic distributions of particles of various sizes are seen on each fracture face after membrane splitting during the fracturing process, and these distributions indicate the differentiation of the membrane system into sacked (grana) and unstacked (stroma) regions, typical of grana-containing chloroplasts. Bundle sheath chloroplasts contain very few grana, and the thylakoids of these plastids are therefore largely unstacked. Analysis of artificially unstacked mesophyll chloroplasts indicates that this difference is not merely related to the presence or absence of adhesion between adjacent thylakoids, but reflects a substantial difference in membrane substructure between mesophyll and bundle sheath photosynthetic membranes. Bundle sheath thylakoids contain virtually the same number of small (P fracture face) particles as mesophyll thylakoids, but contain only 40% as many of the larger (E fracture face) tetrameric particles. These differences, together with biochemical data indicating the comparative deficiency of bundle sheath chloroplasts in Photosystem II activity, suggest that the E face particles are related to the presence or absence of Photosystem II activity.
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1. The relation between plasma high-density lipoprotein (HDL) cholesterol concentration and multiple coronary-risk factor status has been assessed in fifty-two middle-aged clinically healthy men from urban and rural Jamaica. 2. Rural hill-farmers had a superior exercise performance (assessed by the responses to submaximal test exercise), less body fat, and lower fasting levels for plasma total cholesterol, low-density liproprotein (LDL) cholesterol, total triglyceride and blood glucose than urban businessmen. Mean plasma HDL cholesterol was considerably higher in farmers then businessmen. 3. Multilinear regression analysis showed HDL cholesterol concentration to be independently and inversely correlated with plasma triglyceride, LDL cholesterol and diastolic blood pressure and that these relationships applied across the urban and rural sub-groups. There was also some evidence that HDL cholesterol concentration increased with stature. When these factors were taken into account, age, ethnic group, adiposity, weight, exercise performance, smoking history and blood glucose made no further significant contribution to the prediction of HDL cholesterol concentration. 4. Thus plasma HDL cholesterol concentration was highest in those subjects with the lowest coronary-risk as predicted by their multiple risk-factor status, an observation which supported other evidence that coronary-risk is inversely related to plasma HDL concentration. 5. The results raise the possibility that coronary-risk can be more simply estimated from the plasma HDL cholesterol concentration than from a consideration of other major lipid risk factors and blood pressure.
We have investigated the structure of the photosynthetic membrane in a mutant of barley known to lack a chlorophyll-binding protein. This protein is thought to channel excitation energy to photosystem II, and is known as the "light-harvesting chlorophyll-protein complex." Extensive stacking of thylakoids into grana occurs in both mutant and wild-type chloroplasts. Examination of membrane internal structure by freeze-fracturing indicates that only slight differences exist between the fracture faces of mutant and wild-type membranes. These differences are slight reductions in the size of particles visible on the EFs fracture face, and in the number of particles seen on the PFs fracture face. No differences can be detected between mutant and wild-type on the etched out surface of the membrane. In contrast, tetrameric particles visible on the etched inner surface of wild-type thylakoids are extremely difficult to recognize on similar surfaces of the mutant. These particles can be recognized on inner surfaces of the mutant membranes when they are organized into regular lattices, but these lattices show a much closer particle-to-particle spacing than similar lattices in wild-type membranes. Although several interpretations of these data are possible, these observations are consistent with the proposal that the light-harvesting chlorophyll-protein complex of photosystem II is bound to the tetramer (which is visible on the EFs face as a single particle) near the inner surface of the membrane. The large tetramer, which other studies have shown to span the thylakoid membrane, may represent an assembly of protein, lipid, and pigment comprising all the elements of the photosystem II reaction. A scheme is presented which illustrates one possibility for the light reaction across the photosynthetic membrane.
The localization of the chlorophyll-protein complexes inside the thylakoid membrane of Acetabularia mediterranea was determined by fractionating the chloroplast membrane with EDTA and Triton X-100, by using pronase treatment, and by labeling the surface-exposed proteins with 125I. The effects of the various treatments were established by electrophoresis of the solubilized membrane fractions and electron microscopy. After EDTA and pronase treatment, the membrane structure was still intact. Only the two chlorophyll-protein complexes of 67,000 and 152,000 daltons and an additional polypeptides were found in the membrane before the EDTA and pronase treatment. The 125,000 dalton complex seems to be buried inside the lipid layer. The 23,000 dalton subunit of the 67,000 dalton complex is largely exposed to the surface of the EDTA-insoluble membrane and only the chlorophyll-binding subunit of 21,500 daltons is buried inside the lipid layer.
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The body cholesterol pool increases with decreasing plasma-high-density-lipoprotein (H.D.L.) but is unrelated to the plasma concentrations of total cholesterol and other lipoproteins. This finding supports existing evidence that H.D.L. facilitates the uptake of cholesterol from peripheral tissues and its transport to the liver for catabolism and excretion. Plasma-H.D.L., is reduced in several conditions associated with an increased risk of future ischaemic heart-disease (I.H.D.), namely hypercholesterolaemia, hypertriglyceridaimia, male sex, obesity, and diabetes mellitus, while subjects with existing clinical I.H.D. have lower levels of H.D.L. than healthy subjects within the same community. It is proposed that a reduction of plasma-H.D.L. concentration may accelerate the development of atherosclerosis, and hence I.H.D., by impairing the clearance of cholesterol from the arterial wall.
A series of squirrel monkeys received segmental femoral replacements in a study of the strength of the interface developed between the implant and bone. Implants were either made completely of bioglass-ceramic, or 316L stainless steel with a flame-sprayed coating of bioglass. Fracture torque, energy at fracture, and shear stress at failure were compared to values obtained from a control group of pairs of tibias. Femurs containing bulk bioglass-ceramic implants showed about a 25% difference in strength compared to the opposite bone, while femurs containing flame-sprayed implants exhibited extremely low structural strength. While the strength of the metal-glass bond was very low (less than 500 kgf/cm2), the bone-bioglass bond was found to be at least as strong as the bioglass-ceramic, and at least 3/4 as strong as the host bone.
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