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Biomedical subjects

J London

Publications and source records attributed to J London.

At least 91 records · Page 5Linked to original sources
PubMed1982

Use of 2-deoxy-D[1-11C]glucose for the determination of local cerebral glucose metabolism in humans: variation within and between subjects.

The deoxyglucose technique for the measurement of local cerebral glucose metabolism (LCMRgl) has been widely applied in animals utilizing 14C-deoxyglucose and in humans employing 18F-fluorodeoxyglucose. Repeat studies in humans over a relatively brief period of time have not been possible because of the 110-min half-life of fluorine-18. With the synthesis of 11C-deoxyglucose it has now become possible to utilize this short-lived (20 min) tracer for the measurement of LCMRgl and to determine its variability within subjects over a 2-h period. The kinetic rate constants for 11C-deoxyglucose were determined for gray and white matter and found to be very similar to those for 18F-fluorodeoxyglucose, suggesting that these two analogues of glucose have similar affinities for the facilitated transport system and are similar substrates for hexokinase in the brain. The coefficient of variation of repeated measurements of LCMRgl in a series of six normal subjects was 5.5% to 8.7% for various gray matter structures and 9.7% and 14.0% for white matter structures. The pattern of cerebral metabolic rates is relatively constant in a given individual when the conditions of the study are unchanged. The ability to make repeat measurements in the same subject reduces the variance due to between-subject differences, allowing smaller changes in LCMRgl to be detected with confidence.

Brain↗
PubMed1982

Xylitol-mediated transient inhibition of ribitol utilization by Lactobacillus casei.

The growth of Lactobacillus casei strain Cl-16 at the expense or ribitol was inhibited if the non-metabolizable substrate xylitol was included in the medium at concentrations of 6 mM or greater. At these concentrations, xylitol, did not competitively inhibit ribitol transport. The cessation of growth was caused by the intracellular accumulation of xylitol-5-phosphate, which occurred because growth on ribitol had gratuitously induced a functional xylitol-specific phosphotransferase system but not the enzymes necessary for the further metabolism of xylitol-5-phosphate. Eventually, the cells overcame the xylitol-mediated inhibition by repressing the synthesis of enzyme II of the xylitol phosphotransferase system so that xylitol-5-phosphate would no longer be accumulated within the cell.

Bacterial Proteins↗
PubMed1982

Origins of the mycoplasmas: sterol-nonrequiring mycoplasmas evolved from streptococci.

We report the establishment of a phylogenetic relationship between the sterol-nonrequiring mycoplasmas (Acholeplasma species) and streptococci. Three specific antisera prepared against purified Streptococcus faecalis fructose diphosphate aldolase and glyceraldehyde-3-phosphate dehydrogenase and Pediococcus cerevisiae glyceraldehyde-3-phosphate dehydrogenase were used for comparative enzyme immunological studies; the Ouchterlony double-diffusion technique and the quantitative microcomplement fixation procedure were employed. The reactions obtained provide evidence showing that all seven ACholeplasma species studied (A. laidlawii, A. granularum, A. modicum, A. oculi, A. axanthum. A. hippikon, and A. equifetale) are phylogenetically related to streptococci and that they evolved from streptococci. The data strongly suggest that the acholeplasmas comprise a distinct evolutionary group that has diverged from streptococci belonging to Lancefield group D or N. No reactions were observed between these enzyme antisera and cell extracts from six fermentative Mycoplasma species. These results support the view that mycoplasmas are derived from various bacteria.

Acholeplasma↗
PubMed1982

Effect of interferons on protein synthesis in human lymphocytes: enhanced synthesis of eight specific peptides in T cells and activation-dependent inhibition of overall protein synthesis.

Lymphoblastoid and fibroblast IFN inhibited PHA stimulation of overall protein synthesis in human lymphocytes by ca. 30%. Inhibition occurred within the first 6 hr of PHA treatment and was not progressive. DNA synthesis at 48 hr was inhibited to the same extent. Overall protein synthesis in resting lymphocytes was not detectably inhibited by IFN concentrations up to 1000 U/ml. Thus, inhibition of protein synthesis and subsequent reduction of cell proliferation by IFN require certain early events in mitogen activation. Resting lymphocytes were not unresponsive to IFN treatment, however. Two-dimensional electrophoretic analysis of newly synthesized proteins after IFN treatment showed enhanced synthesis of a specific set of eight peptides (I-peptides), which were shown to be synthesized in T lymphocytes. This enhancement was produced by both IFN-alpha and IFN-beta after 4 to 6 hr of exposure and was identical for all lymphocyte donors studied. After growth stimulation, IFN treatment produced no enhancements of additional peptides, although the original eight I-peptides were enhanced as usual. It is concluded that the biochemical activities of the I-peptides, which remain to be determined, cannot inhibit protein synthesis in resting lymphocytes, but may do so after mitogen activation, when the major physiologic restriction of lymphocyte protein synthesis is released. Alternatively, the I-peptides may be unrelated to regulation of protein synthesis but may be involved in viral protection or enhancement of NK activity.

Blood Proteins↗
PubMed1981

Detection and characterization of lymphocytes bearing receptors for peanut agglutinin by a specific rosetting technique.

Murine lymphocytes bearing receptors for peanut agglutinin (PNA) have been visualized using a specific rosetting technique. The lymphocytes were incubated with PNA and mixed with neuraminidase-treated sheep red blood cells. The percentage of the PNA rosetting lymphocytes found in the various organs studied was dependent upon the PNA concentration. In the spleen, the PNA rosetting lymphocytes were primarily T cells with low PNA concentration while both T and B lymphocytes were rosetted with high PNA concentration. In the fetal liver and thymus PNA rosetting lymphocytes were present in small amounts early in fetal life, increasing and reaching adult levels by late fetal life. The present study shows that the rosetting technique is more sensitive than previously described techniques for the detection of various lymphocyte subpopulation having receptors for PNA.

Animals↗
PubMed1981

Study of rat lymphocytes by use of peanut agglutinin.

Peanut agglutinin (PNA) was used to identify rat lymphocyte subpopulations. The binding of PNA on the surface of lymphocytes was assessed by fluorescence microscopy using fluoresceinated PNA. It was shown that most of the thymocytes and bone marrow cells have receptors for PNA; in spleen and lymph nodes the percentages of PNA-positive cells are around 40%. PNA was also used as a potentially mitogenic lectin. It was ascertained that lymphocytes incubated with PNA are stimulated only if they are pretreated with neuraminidase, and that only 'immunocompetent' thymocytes exhibit a very weak response. The fact that PNA slightly inhibits the [3H]uridine uptake of resting thymocytes might explain the weak mitogenicity of PNA.

Animals↗
PubMed1980

Attachment of oral Cytophaga species to hydroxyapatite-containing surfaces.

Model systems simulating the cementum portion of teeth were used to characterize the attachment process by which certain species of oral Cytophaga initiate the colonization of the tooth root surface in vitro. The adsorption of these bacteria to spheroidal hydroxyapatite beads and mechanically powdered root material followed Langmuir isotherm kinetics. From such data, the number of binding sites per 20 mg of substrate and the affinity constants were evaluated for two strains of Cytophaga sp. Resting cells of the two strains tested adhered relatively tenaciously to hydroxyapatite beads in numbers similar to those observed with cells of Streptococcus sanguis. Attachment of bacteria to the substrates was partially inhibited by (i) coating the substrates with human serum or saliva, (ii) pretreating cell suspensions with proteinase K or phospholipase C or D, or (iii) exposing the cells to temperatures greater than 60 degrees C for 15 min. Treating resting cell suspensions with pronase, neuraminidase, phospholipase A2, or 0.1 M ethylenediaminetetraacetic acid had no effect on the attachment process.

Absorption↗
PubMed1980

Peanut agglutinin. VI. Identification of murine T lymphocyte subsets during ontogenesis by use of peanut agglutinin and Ly-6.2 antiserum.

Fluoresceinated peanut agglutinin (PNA-FTC), Thy-1.2, and Ly-6.2 antisera were used to identify various murine T lymphocyte subpopulations during fetal and perinatal life. By means of double immunofluorescence labeling, we identified three T lymphocyte subsets: PNA+Ly-6.2+, PNA+Ly-6.2-, PNA-Ly-6.2+ having distinct distribution in the adult thymus and spleen. The study of the appearance of these three subsets in fetal liver, thymus, and spleen has shown that they did not occur similarly. The PNA+Ly-6.2+ subset was present in all three organs during fetal life and at a level rather similar to that of adult life; the PNA+Ly-6.2- subset was also present in the three fetal organs; conversely, the percentage of the PNA-Ly-6.2+ spleen cells was very low in fetal and neonatal life and increased significantly between 1 and 2 wk of age. Our results demonstrate that during fetal life, lymphocyte subsets are phenotypically differentiated as in adult life and that differentiation of T lymphocytes occurs preferentially through various lineages present during early ontogenesis. Moreover, quantitative modulation of some of these subsets is shown from fetal to adult life and may explain some of the immunologic immature features of young murine spleen.

Adrenal Cortex Hormones↗
PubMed1980

Peanut agglutinin. V. Thymocyte subpopulations in the mouse studied with peanut agglutinin and Ly-6.2 antiserum.

Thymocyte heterogeneity has been studied by the use of two cell surface markers--the Ly-6.2 alloantigen and peanut agglutinin (PNA) receptor. The previously described distribution of Ly-6 on corticoresistant and PNA binding to corticosensitive thymocytes has been confirmed. Double immunofluorescence labeling experiments in combination with techniques of physical enrichment for "mature" thymocytes have resulted in the identification of a novel subset of T cells carrying both the Ly-6 antigen and PNA receptors. Purification by fluorescence cell sorting of corticosteroid-treated thymocytes, labeled with monoclonal anti-Ly-2.2 antiserum, for phenotypically mature Ly-1+23-lymphocytes causes a concomitant enrichment in the proportion of Ly-6-positive cells, which lack the PNA receptor. The implications of these findings for the maturational pathways within the thymus are discussed.

Adrenal Cortex Hormones↗
PubMed1979

Peanut agglutinin. II. Characterization of the Thy-1, Tla and Ig phenotype of peanut agglutinin-positive cells in adult, embryonic and nude mice using double immunofluorescence.

The Thy-1, Tla and Ig phenotype of peanut agglutinin (PNA)-binding cells was characterized in various strains of mice. In the thymus, PNA was found to bind principally but not exclusively to the Thy-1+ Tla + Ig-- steroid-sensitive cortical thymocytes. Thy1 + Tla -- Ig -- steroid-resistant cells are not labeled with PNA. In other lymphoid organs, PNA bound to a minority of T or null cells but generally not to B cells. During ontogeny, PNA + and PNA -- T lineage cells appear simultaneously in the liver at day 10 of gestation, in the thymus at day 11 and in the spleen at day 18. No evidence was found for a maturation from PNA + to PNA -- cells. Prethymocytes present in nude mice were also divided into a PNA + and PNA -- population.

Animals↗
PubMed1979

Peanut agglutinin. IV. A tool for studying human mononuclear cell differentiation.

Peanut agglutinin (PNA) has previously been shown to be a 'marker' for early T subpopulations in mice. We have investigated whether it could also be used in the study of human mononuclear cells. 50--60% of human thymocytes have binding sites for PNA. When separated on a discontinuous Ficoll gradient, the PNA-positive thymocytes are found preferentially in the layers corresponding to the immunoincompetent cells. In the peripheral blood only 5% of the mononuclear cells are PNA-positive and we have shown that these cells are monocytes. In tonsils 13% of PNA+ cells are found and they are mostly lymphocytes. Thus, PNA is a marker for some T cell subsets present in the thymus and tonsils.

Adult↗
PubMed1979

Colonization of the cementum surface of teeth by oral Gram-negative bacteria.

By using in vitro assays, a group of related, filamentous gram-negative bacteria isolated from subgingival plaque deposits of patients with periodontal disease were found to colonize intact teeth. Tentatively identified as members of the genus Cytophaga, these isolates exhibited a preference for colonizing the cementum surface of the root. Examination of intact teeth after several weeks of colonization revealed that the root substructure had been extensively demineralized.

Culture Media↗
PubMed1979

Transfer of plasmid-mediated antibiotic resistance from streptococci to lactobacilli.

The transmissible plasmid pAMbeta1, which codes for erythromycin and lincomycin resistance, was conjugally transferred from a Lancefield group F Streptococcus to a strain of Streptococcus avium. Both organisms served as pAMbeta1 donors for three strains of Lactobacillus casei. Introduction of pAMbeta1 into one of the L. casei strains caused the organism to lose its native 6.7 X 10(6)-dalton plasmid. Loss of the native plasmid produced no alterations in the organism's growth characteristics or fermentation pattern.

Conjugation, Genetic↗
PubMed1979

Pentitol metabolism in Lactobacillus casei.

Strains of Lactobacillus casei capable of growing on either ribitol or xylitol carry out a heterolactic fermentation producing ethanol, acetate, and a mixture of D- and L-lactate. Following conversion of the pentitols to ribulose 5-phosphate or xylulose 5-phosphate via enzymatic steps unique to these organisms, the intermediate products are further metabolized by enzymes of the pentose pathway. The initial enzymes of the pathway, i.e., pentitol:phosphoenolypyruvate phosphotransferase and penititol phosphate dehydrogenase, do not appear to be stringently regulated by glucose or intermediate products of glycolysis.

Acetates↗
PubMed1978

Rapid method for identification and enumeration of oral Actinomyces.

Serotype-specific antisera prepared against whole cells of Actinomyces viscosus, A. naeslundii, and A. israeli were labeled with fluorescein dye and used to detect and quantitate antigenically related microorganisms in human dental plaque. By relating the DNA content of the dental plaque microflora to the number of Actinomyces present in the plaque samples, a reproducible method was developed for specifically enumerating five serotypic representatives of this genus found in human plaque.

Actinomyces↗
PubMed1978

Erythrocyte concentrations of the lithium ion: clinical correlates and mechanisms of action.

When lithium carbonate is administered to individuals, there is considerable intersubject variation in the extent of accumulation of Li+ by erythrocytes. The primary reason for this is differences in the activity of a Li+-Na+ counterflow system, which, under clinical conditions, removes Li+ from the cell. It appears that some bipolar patients accumulate more Li+ in their red cells than either unipolar depressives or normal controls. The precise clinical characteristics of the bipolar patients who accumulate relatively large amounts of erythrocyte Li+ need to be clarified in future research. Finally, the measurement of red cell concentrations of Li+, in addition to the usual plasma measurement, can be used as an indicator of patient compliance.

Biological Transport, Active↗