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Biomedical subjects

J F Miller

Publications and source records attributed to J F Miller.

At least 163 records · Page 9Linked to original sources
PubMed1990

Antagonism of stimulation-produced antinociception from ventrolateral pontine sites by intrathecal administration of alpha-adrenergic antagonists and naloxone.

Focal electrical stimulation of the ventrolateral pontine tegmentum in conscious rats induced antinociception in approximately one-half of the animals screened, as indicated by a marked suppression of the thermally evoked tail-flick flexion reflex. The effectiveness of ventrolateral pontine stimulation in elevating tail-flick latency was significantly reduced by intrathecal microinjection of 30 micrograms of the non-selective alpha-adrenergic antagonist phentolamine, and was largely abolished by a 60-micrograms dose of this drug. The blockade of ventrolateral pontine stimulation-produced antinociception by phentolamine was maximal by 15 min postinjection, and was still evident 60 min after drug microinjection. Ventrolateral pontine stimulation-produced antinociception was also attenuated by intrathecal administration of the alpha 2-selective antagonist yohimbine (37 micrograms) and the opioid antagonist naloxone (30 micrograms), but not the alpha 1 antagonist WB-4101 (37 micrograms), the beta-adrenergic antagonist propranolol (111.6 micrograms) nor the serotonergic antagonist methysergide (30 micrograms). However, the antagonism of pontine stimulation-produced antinociception by naloxone was unlike that of phentolamine and yohimbine, in that it developed slowly and was only evident at 60 min postinjection. Hence naloxone's site of action may be distant from the injection site. These data indicate that the thermal antinociception produced by stimulation of the ventrolateral pons is mediated through spinal alpha 2-receptors and opioid receptors of uncertain location. The close proximity of many of the effective electrode placements to the rostral A5 and ventral subcoerulear A7 noradrenergic cell groups suggests that noradrenergic spinopetal projections arising from these groups are involved in mediating the antinociception induced by stimulating these sites.

Adrenergic alpha-Antagonists↗
PubMed1990

Selection of the T-cell repertoire in transgenic mice expressing a transplantation antigen in distinct thymus subsets.

Transgenic mice that expressed a transplantation antigen, H-2Kb, in an unusual tissue distribution have been developed. Gene-regulatory elements from the immunoglobulin heavy-chain locus (Emu enhancer and heavy chain promoter) were linked to the class I Kb gene and the construct microinjected into fertilized mouse eggs of a different haplotype. It was expected that such gene-regulatory elements would direct expression of the foreign class I molecules only to B and T lymphocytes. However, expression was also detected in a subset of thymus medullary epithelium. The Kb molecules expressed on this thymic subset were unable to positively select T cells for passage to the periphery. The mice were, however, tolerant of the cell types expressing the foreign Kb molecules and were also tolerant of Kb presented as skin grafts. These results suggest that not all components of thymic epithelium are involved in positive selection of T cells and that transplantation antigens expressed on non-dendritic cells can induce tolerance.

Animals↗
PubMed1990

Prevention of diabetes in non-obese diabetic I-Ak transgenic mice.

The non-obese diabetic (NOD) mouse develops insulin-dependent diabetes mellitus (IDDM) with mononuclear cell infiltration of the islets of Langerhans and selective destruction of the insulin-producing beta-cells, as in humans. Most infiltrating cells are T lymphocytes, and most of these carry the CD4 antigen. Adoptive transfer of T cells from diabetic NOD mice into irradiated NOD or athymic nude NOD mice induces diabetes. Susceptibility to IDDM in NOD mice is polygenic, with one gene linked to the major histocompatibility complex class II locus, which in NOD mice expresses a unique I-A molecule but no I-E. Speculation exists as to the role of the I-A molecule in the diabetes susceptibility of NOD mice, especially regarding the significance of specific unique residues. To examine the role of the NOD I-A molecule in IDDM pathogenesis, we made NOD/Lt mice transgenic for I-Ak by microinjecting I-Ak alpha- and beta-genes into fertilized NOD/Lt eggs. Insulitis was markedly reduced and diabetes prevented in NOD/Lt mice expressing I-Ak.

Animals↗
PubMed1990

Mechanism of action of cyclosporine A in vivo. II. T cell priming in vivo to alloantigen can be mediated by an IL-2-independent cyclosporine A-resistant pathway.

Cyclosporine A (CsA) inhibits T lymphocyte activation in vitro by blocking at a pretranslational level the production of IL-2 and other cytokines. It is widely assumed that the effectiveness of CsA as an immunosuppressive drug is secondary to a similar mechanism of action in vivo. We have previously demonstrated that certain parameters of T cell activation in the draining popliteal lymph node in response to the injection of alloantigen in the footpad were either completely resistant or enhanced by the administration of CsA. In the present study, we have shown that the mechanism of action of CsA in vivo is identical to that seen in vitro as CsA completely suppressed the induction of IL-2 mRNA as detected in a nuclease protection assay in lymph node cells from alloantigen-primed animals. Nevertheless, T cells from CsA-treated animals appeared to have undergone both priming and differentiation. Thus, upon culture in vitro in the presence of CsA, cells from CsA-treated animals manifested a vigorous proliferative response that could not be inhibited by the addition of a large panel of anti-cytokine mAb. Furthermore, cells from CsA-treated animals demonstrated an enhanced secondary response to the priming alloantigen, which suggests that they had undergone clonal expansion in vivo. Although CTL activity was markedly suppressed in cells from CsA-treated animals, after a 36-h culture in the absence of CsA, CTL activity equivalent to that detected in cells from nontreated animals was present. Collectively, these data support the existence of an alternative IL-2-independent, CsA-resistant pathway of T cell activation/differentiation that may play a prominent role in the generation of certain T effector functions in vivo.

Animals↗
PubMed1990

Tolerance and diabetes in transgenic mice over-expressing class I histocompatibility molecules in pancreatic beta cells.

The Class I gene, H-2Kb, was linked to the rat insulin promoter and the construct inoculated into fertilized mouse eggs to produce lines of transgenic mice. Mice which expressed the Class I molecule in the beta cells of the pancreas developed diabetes and progressive loss of their pancreatic beta cells. This occurred whether the transgene product was syngeneic or allogeneic with respect to its host. No lymphocytic infiltration was ever seen in transgene expressing mice, even in those deliberately immunized with H-2Kb-bearing cells. When the transgene product was allogeneic, spleen cells from the transgenic mice stimulated in vitro with irradiated B10.A(5R) cells (KbDd), could kill H-2d targets in vitro, but not targets bearing H-2Kb. Responsiveness of spleen cells to H-2Kb targets returned with advancing age, as the severity of diabetes increased. The results indicate that diabetes in this model occurs independently of the immune system, and point to an extra-thymic mechanism of tolerance induction dependent on the continuous presence of antigen.

Animals↗
PubMed1990

Autogenous regulation of the Bordetella pertussis bvgABC operon.

The bvgABC operon of the bacterial pathogen Bordetella pertussis encodes a sensory transduction system that regulates the expression of several virulence genes in response to environmental stimuli. In this study we have examined the transcriptional regulation of the bvgABC operon. Transcriptional bvg::lacZYA fusions in Escherichia coli show that the bvgABC operon is autogenously activated. Autoactivation is inhibited by the same environmental stimuli that result in the lack of expression of bvg-activated genes in B. pertussis. These observations were confirmed in B. pertussis using a chromosomal chloramphenicol acetyltransferase transcriptional fusion in bvgC. Transcriptional initiation sites upstream of bvgA were mapped by primer extension analysis in E. coli and B. pertussis. Two differentially regulated bvg promoters were identified. The bvgP1 promoter is a positively autoregulated promoter located 90 base pairs upstream of bvgA. The bvgP2 promoter is located 141 base pairs upstream of bvgA and does not appear to require any positive regulatory factors for activity. These results suggest a model describing the regulatory events that take place upstream of the bvgABC operon.

Base Sequence↗
PubMed1990

Transgenic models of T-cell self tolerance and autoimmunity.

Self-tolerance is generally induced by intrathymic clonal deletion of T cells with reactivity directed to antigens synthesized within the thymus (Kappler et al. 1987, Kisielow et al. 1988). It may also be induced in peripheral T cells when these encounter antigens unique to extra-thymic tissues. Two transgenic models have been particularly useful in the study of peripheral self tolerance: in one model, a known antigen is expressed in a particular extra-thymic site; in the other, the T-cell repertoire is predominantly reactive to this antigen. We, and others, have shown that expression of class I or II MHC molecules in defined extra-thymic sites leads to a state of T-cell tolerance. To account for this, we have proposed two hypotheses which have different implications for autoimmune disease. According to one, tolerance is imposed by deletion or functional silencing of specific high-affinity cytolytic T cells; alternatively, the target cell for tolerance induction may be a regulatory IL-2-producing T-cell, rather than the effector cell itself. To distinguish between these hypotheses it is essential to examine the fate of T cells which have the potential to react to the transgene product. Since the frequency of such T cells is low and there is no dominant clonotype for H-2Kb, which is the class I molecule we used, it was necessary to create double transgenic mice by mating class I transgenic mice with transgenic mice whose T-cell pool was compared of cells reactive to H-2Kb and could be detected by an antibody directed to the TCR. Initial studies showed that such T cells did persist despite the presence of antigen to which they may be reactive. If these double transgenic mice can be shown to be tolerant, they will offer a rich source of tolerant T cells for detailed investigation of their phenotype and fate, and they will be most useful in enabling us to probe the mechanisms responsible for the induction of peripheral self tolerance. Transgenic mouse technology has also been used successfully to unravel the genetic influences which may lead to or prevent autoimmunity. In particular, we have prevented autoimmune diabetes in the nonobese diabetic mouse by introducing a non-NOD MHC class II gene and further work is implicating the failure of intrathymic positive selection of a protective cell as one step in the pathogenesis of diabetes in NOD mice.

Animals↗
PubMed1990

Alterations in plasma volume and protein during cycle exercise throughout pregnancy.

The purpose of this investigation was to determine the effects of cycle exercise on maternal plasma volume (PV) and protein dynamics during pregnancy. Sixteen healthy gravidas (age = 23 +/- 4.6 yr) cycled for 5 min (75 W) at 4 wk intervals throughout term. Venous blood samples were drawn immediately prior to and during the last minute of exercise. Relative (percent) PV changes during exercise were calculated from hematocrit ratios and hemoglobin concentrations. Plasma was analyzed for total protein ([TP]) and albumin ([ALB]) concentrations and colloid osmotic pressure (COP). Resting blood volumes were also estimated (carbon monoxide rebreathing) so that absolute PV (ml) and TP and ALB contents (g) could be determined. COP increases (P less than 0.001) during exercise were similar at all gestational ages. Plasma volume, TP, and ALB decreased during exercise with significantly (P less than 0.001) greater losses occurring from 29-32 wk gestation. This may indicate an increase in capillary permeability to large molecules when vascular volume was highest.

Adult↗
PubMed1990

Cardiac output responses of primigravid women during exercise determined by the direct Fick technique.

We compared metabolic and cardiovascular responses to aerobic exercise with the direct Fick technique in women during and after pregnancy. Seven subjects were studied at 37 weeks' gestation and again 12 weeks postpartum. All were tested at rest and during four sequential exercise bouts consisting of 5 minutes at each of two cycle (50 and 75 W) and two treadmill (67 m x min-1 at 2.5 and 12% grade) protocols. Oxygen consumption (VO2) and heart rate were measured during the fifth minute of exercise. Arterial and mixed venous oxygen contents, obtained from catheters placed in the radial and pulmonary arteries, respectively, were used to calculate arterial-venous oxygen difference. Cardiac output and stroke volume were calculated from the Fick equation. Responses of VO2, cardiac output, and stroke volume were greater when exercise was performed at 37 weeks' gestation as compared with postpartum. In contrast, heart rate response (during cycling) and arterial-venous oxygen difference (during treadmill walking) were less when exercise was performed during pregnancy. Our results indicate that there is no compromise in maternal cardiac output during either cycle or treadmill exercise performed late in pregnancy as compared with postpartum conditions.

Adult↗
PubMed1989

Tolerance of class I histocompatibility antigens expressed extrathymically.

Although convincing evidence has been obtained for the imposition of self-tolerance by the intrathymic deletion of self-reactive T cells, the development of tolerance to antigens which are expressed only in the periphery is not so well understood. We have approached this question by creating transgenic mice which carry a class I major histocompatibility complex (MHC) gene (H-2Kb) linked to the rat insulin promoter. Mice expressing the transgene develop diabetes, but do not appear to mount an immune response against the transgene-expressing pancreatic beta-cells, even when the transgene is allogeneic with respect to the endogenous host H-2 antigens. We have now explored the mechanism of this tolerance further. We find that spleen cells from pre-diabetic transgenic (RIP-Kb) mice do not kill targets bearing H-2Kb, whereas thymus cells from the same mice do. The unresponsiveness of these spleen cells can be reversed in vitro by providing recombinant interleukin-2 (rIL-2). In older, diabetic mice, responsiveness develops as the pancreatic beta-cells are lost. Our results point to an extrathymic mechanism of tolerance induction, dependent on the continuous presence of antigen and the lack of IL-2 in the local environment of potentially reactive T cells.

Animals↗
PubMed1989

Coordinate regulation and sensory transduction in the control of bacterial virulence.

Genes and operons that encode bacterial virulence factors are often subject to coordinate regulation. These regulatory systems are capable of responding to various environmental signals that may be encountered during the infectious cycle. For some pathogens, proteins that mediate sensory transduction and virulence control are similar to components of other bacterial information processing systems. Understanding the molecular mechanisms governing global regulation of pathogenicity is essential for understanding bacterial infectious diseases.

Bacteria↗
PubMed1989

In vivo studies of DnaA binding to the origin of replication of Escherichia coli.

We have shown that DnaA, a protein required for initiation of DNA replication in Escherichia coli, binds to three of four DnaA binding sequences in the replicative origin oriC (boxes R1, R2 and R4). Protein-oriC DNA interactions in minichromosomes carried by wild-type and dnaA mutant strains were demonstrated by in vivo footprinting using dimethylsulfate treatment of intact cells. The same characteristic enhancement/protection pattern was seen in wild-type minichromosomes or mutants defective in oriC function but carrying the four DnaA boxes. Minichromosomes in dnaA (Ts) mutants showed no protein binding at non-permissive temperatures and reduced binding even at permissive temperatures. In vivo footprints of the wild-type strain were identical to those obtained in vitro using purified DnaA proteins and oriC DNA. Transcription into oriC affected the binding of DnaA protein to the DnaA boxes. These findings suggest that the protein causing the in vivo footprints at oriC is DnaA.

Bacterial Proteins↗
PubMed1989

Immunological tolerance: new approaches using transgenic mice.

Transgenic technology allows the introduction into the germline of an animal of a known gene coding for a normally foreign antigen, and by means of a specific promoter, the direction of its expression to specific tissues. The antigen is therefore synthesized by the animal as an authentic self molecule, at a particular stage in development, and in a particular site. In this review, J.F.A.P. Miller and colleagues discuss this radically new approach to the investigation of the mechanism of acquired immunological tolerance to self components.

Animals↗
PubMed1989

Hope-inspiring strategies of the critically ill.

Sixty persons who had been critically ill were studied to determine what mechanisms they used to maintain or increase their hope while confronting a life-threatening event. Patients were interviewed 2 to 4 days after discharge from a critical care unit. Responses to the interviews were categorized into nine hope-inspiring themes. The findings provide direction for developing strategies to inspire hope in the critically ill.

Attitude to Health↗
PubMed1989

Analysis of language-speech samples with salt and pepper.

Microcomputer-aided analysis of spontaneous language-speech samples offers researchers an efficient means of analyzing large amounts of data. It may be necessary, however, to format samples for more than one software program in order to obtain comprehensive morpho-syntactic and phonetic/phonologic analyses. This paper suggests a procedure for the combined use of SALT (Systematic Analysis of Language Transcripts, Miller & Chapman, 1985) and PEPPER (Programs to Examine Phonetic and Phonologic Evaluation Records, Shriberg, 1986) that is designed to minimize the duplication of effort involved in following two different formatting procedures. Results of a study undertaken to explore methodological issues in the combined use of SALT and PEPPER generally support the validity, reliability, and efficiency of the procedure. Results also raise some issues concerning the use of narrow phonetic transcription as opposed to standard orthographic transcription of continuous language-speech samples.

Data Collection↗