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Biomedical subjects

J F Miller

Publications and source records attributed to J F Miller.

At least 199 records · Page 11Linked to original sources
PubMed1988

Immunoglobulin gene expression is a normal differentiation event in embryonic thymocytes.

By in situ hybridization to frozen sections of mouse embryos, we have localized cells transcribing the Ig C mu gene during ontogeny. Transcripts were detected from before day 14 of gestation in individual pre-B cells in the liver and, surprisingly, in a large proportion of thymocytes between days 15 and 18. The level of mu RNA sequences in the thymus at day 17 was much higher than has been observed for adult thymocytes; from grain counts, the amount of mu RNA was similar to that observed for Ti gamma RNA. These findings suggest that Ig and Ti genes are under similar transcriptional controls during Ti gene recombination and that elevated mu RNA production is a normal event early in the intrathymic differentiation of T cells.

Animals↗
PubMed1988

Early receptive and productive language skills in preterm and full-term 8-month-old infants.

Early receptive and productive language skills were examined for preterm low birthweight infants and full-term normal birthweight infants from middle-class homes. Nineteen preterm infants and 19 full-term infants were observed in a laboratory setting at the gestationally corrected age of 8 months. To avoid the frequent confound between prematurity and low socioeconomic status, mothers of the two groups of infants were matched on educational levels. Regression analyses were used to assess the relative influence of infant cognitive skills, infant sociability, infant birth status, and the mothers' language input as possible predictors of infant receptive language and vocal behavior. Receptive language skills were associated with higher cognitive performance, greater sociability, and preterm birth. Productive language skills were associated with higher cognitive performance. On the basis of this research, the prognosis for language development in preterm infants raised in middle-class homes appears to be excellent.

Child Language↗
PubMed1988

Molecular characterization of T-cell antigen receptor expression by subsets of CD4- CD8- murine thymocytes.

Precursors of all T-lineage cells are found in a population of thymocytes that lack the CD4 and CD8 surface glycoproteins. These "double-negative" thymocytes are markedly heterogeneous in their expression of other surface markers and include cells at various stages of development. In this study, CD4- CD8- adult murine thymocytes were separated into subsets based on the expression of the "heat stable antigen" (HSA) and of Ly 1 (CD5). The sorted subsets were analyzed directly (without prior expansion in culture) for T-cell antigen receptor (TcR) gene rearrangement and mRNA expression and for TcR and CD3 cell-surface protein expression. Very little surface CD3 or TcR expression was detected on the major HSA+ Ly 1low subset. However, the HSA+ Ly 1high, HSA- Ly 1high, and HSA- Ly 1low subsets all contained cells with surface expression of CD3 and TcR. In contrast to previous studies, we found no subset that exclusively expressed either the alpha beta or gamma delta heterodimer, although the ratio of alpha beta+ to gamma delta+ varied widely. Two of these three subsets (HSA- Ly 1low and HSA- Ly 1high) showed very high usage of V beta 8 gene products in the alpha beta heterodimer, but nevertheless included approximately equal to 15% non-V beta 8 alpha beta forms. All CD4- CD8- subsets were found to have extensively rearranged their TcR gamma genes and to express gamma mRNA. Expression of a high ratio of mature [1.3 kilobases (kb)] to truncated (1.0 kb) beta message and presence of alpha message was largely restricted to subsets with TcR alpha beta surface expression.

Animals↗
PubMed1988

High-voltage electroporation of bacteria: genetic transformation of Campylobacter jejuni with plasmid DNA.

Electroporation permits the uptake of DNA by mammalian cells and plant protoplasts because it induces transient permeability of the cell membrane. We investigated the utility of high-voltage electroporation as a method for genetic transformation of intact bacterial cells by using the enteric pathogen Campylobacter jejuni as a model system. This report demonstrates that the application of high-voltage discharges to bacterial cells permits genetic transformation. Our method involves exposure of a Campylobacter cell suspension to a high-voltage exponential decay discharge (5-13 kV/cm) for a brief period of time (resistance-capacitance time constant = 2.4-26 msec) in the presence of plasmid DNA. Electrical transformation of C. jejuni results in frequencies as high as 1.2 x 10(6) transformants per microgram of DNA. We have investigated the effects of pulse amplitude and duration, cell growth conditions, divalent cations, and DNA concentration on the efficiency of transformation. Transformants of C. jejuni obtained by electroporation contained structurally intact plasmid molecules. In addition, evidence is presented that indicates that C. jejuni possesses DNA restriction and modification systems. The use of electroporation as a method for transforming other bacterial species and guidelines for its implementation are also discussed.

Bacteriological Techniques↗
PubMed1988

Pressure and Temperature Effects on Growth and Methane Production of the Extreme Thermophile Methanococcus jannaschii.

The marine archaebacterium Methanococcus jannaschii was studied at high temperatures and hyperbaric pressures of helium to investigate the effect of pressure on the behavior of a deep-sea thermophile. Methanogenesis and growth (as measured by protein production) at both 86 and 90 degrees C were accelerated by pressure up to 750 atm (1 atm = 101.29kPa), but growth was not observed above 90 degrees C at either 7.8 or 250 atm. However, growth and methanogenesis were uncoupled above 90 degrees C, and the high-temperature limit for methanogenesis was increased by pressure. Substantial methane formation was evident at 98 degrees C and 250 atm, whereas no methane formation was observed at 94 degrees C and 7.8 atm. In contrast, when argon was substituted for helium as the pressurizing gas at 250 atm, no methane was produced at 86 degrees C. Methanogenesis was also suppressed at 86 degrees C and 250 atm when the culture was pressurized with a 4:1 mix of H(2) and CO(2), although limited methanogenesis did occur when the culture was pressurized with H(2).

Journal Article↗
PubMed1988

Differing mechanisms of exercise flow augmentation at the mitral and aortic valves.

To determine the mechanisms by which blood flow increases across the mitral and aortic valves during exercise, 18 normal men were studied during graded supine and upright bicycle exercise at matched workloads. Mitral valve orifice and ascending aortic blood velocities were recorded by Doppler echocardiography during steady states at each stage of exercise. Parasternal two-dimensional echocardiographic imaging of the ascending aorta adjacent to the aortic valve orifice and the mitral valve orifice at the tips of the valve leaflets was used to calculate changes in cross-sectional area during exercise. Heart rate increased from rest to exercise from 67 to 150 beats/min (124%) during supine exercise and from 72 to 147 beats/min (104%) during upright exercise. Stroke volume increased 20% during supine and 46% during upright exercise; the increase in stroke volume was statistically significant when rest and exercise were compared and when the magnitude of change was compared vs position (p less than .05). The increase in stroke volume measured at the ascending aorta was accomplished by an increase in the velocity-time integral (+15% supine and +48% upright, p less than .05), with little change in aortic cross-sectional area (5% supine and 0% upright, p = NS). By contrast, the increase in flow rate measured at the mitral valve was predominantly due to an increase in mean diastolic cross-sectional area (+29% supine and 34% upright, p less than .05); the velocity-time integral did not increase significantly (-10% supine and 4% upright; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Mitral valve prolapse in patients with prior rheumatic fever.

It is known that rheumatic heart disease frequently results in isolated mitral regurgitation without concomitant mitral stenosis, especially in countries with a high prevalence of rheumatic fever. However, more recent surgical pathologic data also have demonstrated a high incidence of mitral valve prolapse in cases of rheumatic heart disease, which suggests that rheumatic fever may be a cause of mitral valve prolapse. To determine whether this association of mitral valve prolapse and rheumatic heart disease is present in a stable clinic population, we studied 30 patients who had an apical systolic murmur and a well-documented history of rheumatic fever with dynamic auscultation, two-dimensional echocardiography, and pulsed Doppler examinations. Twenty of the 30 patients (67%) had findings on physical examination consistent with isolated mitral regurgitation and 25 patients (84%) had mitral regurgitation by Doppler examination. Echocardiography demonstrated mitral valve prolapse in 24 patients (80%), whereas only one of the total study group had echocardiographic findings consistent with mitral stenosis. We conclude that (1) the presence of an isolated systolic murmur in patients with a history of rheumatic fever frequently represents pure mitral regurgitation secondary to mitral valve prolapse and (2) postinflammatory changes in valvular tissue resulting from rheumatic fever may be the etiology of mitral valve prolapse in these patients.

Adult↗
PubMed1987

Expression of T cell antigen receptor and immunoglobulin genes in lymphoid organs visualized by in situ hybridization.

In situ hybridization techniques were used to detect expression within lymphoid tissues of genes encoding T cell receptor (TCR) alpha, beta and gamma chains, as well as immunoglobulin kappa light chain. Transcripts of these genes were specifically detected in frozen sections of thymus, spleen and lymph node but not in non-lymphoid tissues. Differences in the level of beta chain gene transcription were observed within and between the thymus cortex and medulla, with approximately 60% and 34% of cells in these areas labelled, respectively. Expression of the TCR alpha chain genes was more homogeneous, while amongst the cells transcribing the gamma chain gene, there was a subpopulation of 0.2% of heavily labelled cortical thymocytes. Labelling of T cell dependent areas of spleen and lymph nodes was observed with each of the TCR probes, but neither alpha nor beta gene expression was seen in lymphoid tissues of athymic nude mice. The gamma chain gene was, however, expressed in both spleen and lymph nodes of these mice. These results indicate that TCR gene expression is not limited to a small subpopulation of T cell precursors. They are discussed in relation to T cell differentiation within the thymus.

Animals↗
PubMed1987

Isolation and characterization of a subunit form of the light-harvesting complex of Rhodospirillum rubrum.

A new method is described for the isolation of subunits of the light-harvesting complex from Rhodospirillum rubrum (wild type and the G-9 mutant) in yields that approach 100%. The procedure involved treating membrane vesicles with ethylenediaminetetraacetic acid-Triton X-100 to remove components other than the light-harvesting complex and reaction center. In the preparation from wild-type cells, a benzene extraction was then employed to remove carotenoid and ubiquinone. The next step involved a careful addition of the detergent n-octyl beta-D-glucopyranoside, which resulted in a quantitative shift of the long-wavelength absorbance maximum from 873 to 820 nm. This latter complex was then separated from reaction centers by gel filtration on Sephadex G-100. The pigment-protein complex, now absorbing at 820 nm, contained two polypeptides of about 6-kilodalton molecular mass (referred to as alpha and beta) in a 1:1 ratio and two molecules of bacteriochlorophyll (BChl) for each alpha beta pair. This complex is much smaller in size than the original complex absorbing at 873 nm but probably is an associated form such as alpha 2 beta 2 X 4BChl or alpha 3 beta 3 X 6BChl. The 820-nm form could be completely shifted back to a form once again having a longer wavelength lambda max near 873 nm by decreasing the octyl glucoside concentration. Thus, the complex absorbing at 820 nm appears to be a subunit form of the original 873-nm complex.

Amino Acids↗
PubMed1987

Interaction in vivo between hapten-specific suppressor T cells and an in vitro cultured helper T cell line.

The interaction in vivo between hapten-specific suppressor T cells (Ts) and a hapten-specific T helper (Th) cell line was examined. Antigen-specific Ts were induced in CBA mice by i.v. priming with 3 X 10(7) syngeneic spleen cells (SC) that were chemically coupled with the hapten azobenzenearsonate (ABA). Transfer of splenic T cells from these mice by i.v. injection suppressed the induction in syngeneic assay hosts of ABA-reactive helper and cytotoxic T cell (Tc) responses. Although the Th responses and their suppression were ABA specific, in that they were not induced or activated by trinitrophenyl (TNP)-coupled SC, both Tc responses and their suppression were occasionally nonspecific. Induction of Th was assayed by measuring the release from primed lymph node cells of IL 2 and IL 3 in response to haptenated SC in vitro. Both cytotoxic and Th responses could be made dependent on the provision of exogenous Th by reducing the antigen dose. This stratagem allowed the assay in vivo of a long-term cultured ABA-specific Th cell line (E9). Injection of 10(5) E9 cells/mouse (with antigen, in the rear footpad) helped the induction of both Tc and Th in response to a reduced dose of antigen. These responses, which were dependent on the E9 cell line, were also suppressed by i.v. transferred Ts. When normal doses of antigen were used, the injection of 10(5) E9 Th overcame suppression. These results show that Ts act by inhibiting the activation of Th, thereby suppressing Th-dependent responses generally. The fact that the E9 Th cell line could be suppressed also shows that long-term culture of T cells does not affect their capacity to be regulated in vivo.

Animals↗
PubMed1987

Endogenous immunoreactive glia maturation factor-like molecule in astrocytes and glioma cells.

Using the monoclonal antibody G2-09 raised against bovine glia maturation factor (GMF), we conducted a survey of GMF-like immunoreactivity in various cell types. Of all the normal and neoplastic cells tested, only extracts from astroblasts, gliomas, Schwann cells and schwannomas, but not their conditioned media, possessed endogenous GMF-like immunoreactivity. The presence of immunoreactive GMF correlated well with GMF bioactivity. Using the same monoclonal antibody, the GMF-like factor in astroblasts and C6 glioma cells was characterized by immunofluorescence, immunoadsorption and immunoblotting. Immunofluorescence confirmed the intracellular location of GMF. Immunoadsorption completely eliminated the GMF-like bioactivity from the cell extracts. Immunoblotting identified a protein band having a mol. wt. of 14,000 Da. Thus, the evidence strongly supports the argument that the GMF-like factor in astroblasts and C6 cells is identical with GMF from the bovine brain. In order to explain the fact that astroblasts and C6 cells are both the source and targets of GMF, we propose the hypothesis that GMF functions as an injury signal, being released from the injured glia and serving as a stimulant for gliosis in the neighboring intact glia.

Animals↗
PubMed1987

Distribution of immunoreactive glia maturation factor-like molecule in organs and tissues.

Using the monoclonal antibody G2-09 raised against bovine glia maturation factor (GMF), we screened various rat organs and tissues for GMF-like immunoreactivity. In the adult animal, with the exception of the heart, GMF was found exclusively in the nervous system, with the cerebellum exhibiting higher specific activity than other brain regions. The nature of the immunoactivity in the heart is presently unclear. None of the body fluids collected from humans, including serum and cerebrospinal fluid, possessed detectable GMF immunoactivity. A phylogenetic comparison revealed the presence of GMF in the brain of al vertebrates studied, from fish to primates. GMF was absent from bacteria and yeast. An ontogenetic study on rats showed the highest GMF level in the fetal brain, with a gradual but steady decrease after birth. However, a substantial amount of GMF persisted even in older animals. GMF was localized in astrocytes and Bergmann glia in the rat brain, using immunostaining at the light microscopic level.

Age Factors↗
PubMed1987

Induction of cytoskeletal alterations in C6 glioma by glia maturation factor.

C6 rat glioma cells respond to glia maturation factor (GMF) with characteristic morphological alterations. Observed under phase-contrast microscopy, the cells changed from a rounded morphology in random formation to a spindle-shaped appearance in parallel arrays. Observed under scanning electron microscopy, GMF led to a decrease in the number of microvilli and cell surface knobs. Transmission electron microscopy demonstrated the appearance of numerous microtubules aligned with the long axis of the cells after GMF stimulation. The change in cell shape and histotypic pattern was inhibited by vinblastin, further implicating the involvement of microtubules. Immunofluorescence using anti-alpha-tubulin revealed a well-defined cytoskeletal system in GMF-stimulated cells but not in the control cells. Finally, an increase in tubulin was confirmed with enzyme-linked immunosorbent assay (ELISA) on extracts from these cultures. The findings indicate that morphological alterations induced by GMF are associated with changes in the quantity and arrangement of microtubules.

Animals↗
PubMed1987

Coaggregation of the T-cell receptor with CD4 and other T-cell surface molecules enhances T-cell activation.

The CD4 molecule, expressed by T cells restricted by class II major histocompatibility complex (MHC) molecules, is believed to play a role in T-cell activation. We have previously suggested that CD4 interacts with the T-cell receptor for antigen (TCR) and with class II MHC and that this dual interaction stabilizes the bond between the TCR and antigen in association with MHC. To investigate the contribution of CD4-TCR interaction, we have used the murine monoclonal anti-TCR V beta 8 antibody F23.1 to activate cloned T cells. Weak activation by soluble biotinylated F23.1 was markedly enhanced by crosslinking with either avidin or with anti-immunoglobulin (anti-Ig). The monoclonal anti-L3T4 antibody GK1.5, which normally inhibits the activation induced by F23.1, did not inhibit when GK1.5 and F23.1 were coaggregated on T cells by anti-Ig, and in many experiments activation was enhanced. Coaggregation of anti-Thy-1.2, anti-H-2Kk, or anti-LFA-1 with F23.1 also enhanced T-cell activation, although, unlike GK1.5, these antibodies in soluble form had no effect on the response to F23.1. These results are consistent with a model for T-cell activation that proposes a primary interaction between L3T4 and the TCR to stabilize TCR complexes and so to enhance T-cell activation. A related but less specific accessory role for other T-cell surface molecules is also suggested. We propose that the cellular interaction that leads to physiological T-cell activation not only achieves TCR ligation but also promotes through their ligation or redistribution the interaction of other T-cell surface molecules, all of which contribute to the overall strength of the activation signal.

Animals↗
PubMed1987

Abelson virus transformation of an interleukin 2-dependent antigen-specific T-cell line.

Abelson murine leukemia virus (A-MuLV) carries the gene v-abl, one of a group of oncogenes with structural and functional (tyrosine kinase) homology to three growth factor receptors. Work in this and other laboratories has shown that A-MuLV infection can render myeloid and lymphoid cells independent of the growth factors interleukin 3 and granulocyte-macrophage colony-stimulating factor. We have now shown that v-abl can also relieve interleukin 2 (IL-2) dependence in T cells. We infected a cloned IL-2-dependent antigen-specific cell line. Transformed cells were generated which were factor independent and tumorigenic. The transformants each bore unique v-abl DNA inserts and expressed v-abl mRNA. No elevation of expression of either IL-2 or its receptor could be detected in these cells. Thus, A-MuLV can short-circuit the dependence of hematopoietic cells on IL-2, IL-3, and possibly granulocyte-macrophage colony-stimulating factor, none of whose receptors are known to be of the tyrosine kinase type.

Abelson murine leukemia virus↗