Biomedical subjects

R G Miller

Publications and source records attributed to R G Miller.

At least 199 records · Page 11Linked to original sources

PubMed1990

The metabolic basis of recovery after fatiguing exercise of human muscle.

We investigated the metabolic basis of human muscular fatigue and recovery utilizing 31P magnetic resonance spectroscopy and measurements of maximum voluntary contraction (MVC). We produced fatigue by sustained MVC for 4 minutes in 2 different muscles (adductor pollicis, tibialis anterior) and obtained similar results in both muscles. During fatiguing exercise, there was a nonlinear relationship between MVC and both phosphocreatine and total inorganic phosphate. By contrast, there was a roughly linear relationship between the decline in MVC and the accumulation of both H+ and H2PO4-. However, during recovery after exercise, MVC rapidly returned to control levels while H+ recovered with a much slower time course. On the other hand, H2PO4- rapidly returned to control values with a time course similar to MVC. In addition, the relationship of H2PO4- to MVC was similar during both fatigue and recovery. Thus, during fatigue as well as during recovery, changes in MVC correlate best with H2PO4-, suggesting that this metabolite is an important factor in human muscle fatigue.

Adenosine Triphosphate↗

PubMed1990

Ganciclovir in the treatment of progressive AIDS-related polyradiculopathy.

We present 7 HIV-infected patients with a unique, subacute, progressive polyradiculopathy. All had AIDS, sacral sensory loss, acute urinary retention, and progression to flaccid paraparesis in days to weeks. Cytomegalovirus was cultured from spinal fluid of 4 patients, and postmortem examination of the 1st 5 patients disclosed an inflammatory polyradiculopathy with cytomegalic inclusions. The inclusion-bearing cells were immunocytochemically positive for cytomegalovirus. Two patients who received early anti-cytomegalovirus treatment with ganciclovir improved. Thus, early recognition and treatment with ganciclovir may be effective in this otherwise fatal condition.

Acquired Immunodeficiency Syndrome↗

PubMed1990

Excessive muscular fatigue in patients with spastic paraparesis.

We used intermittent tetanic contractions and 31P magnetic resonance spectroscopy to investigate human tibialis anterior muscle metabolism and fatigability in a group of patients with spastic paraparesis and in normal controls. During intermittent tetanic stimulation, the decline in tension was significantly greater in patients than in controls, and the half-relaxation time of the tetanus was more prolonged. Moreover, the decline in phosphocreatine and intracellular pH was significantly greater in patients than in controls. These observations suggest that biochemical changes in the muscles of patients with upper motor neuron lesions may contribute to their excessive fatigability.

Action Potentials↗

PubMed1990

The isolation of salmonellae from poultry environmental samples by several enrichment procedures using plating media with and without novobiocin.

A two-part study was conducted to examine the efficacy of several enrichment-broth techniques and of plating media for detecting salmonellae from poultry environmental samples. The data are reported on pooled samples collected from five poultry houses. The samples were cultured for salmonellae, using up to four different enrichment procedures and employing plating media with and without novobiocin. The primary enrichment-broth procedures were: 1) buffered peptone water preenrichment to Hajna's tetrathionate (TT) broth; and 2) direct inoculation in TT broth. The delayed secondary-enrichment procedure involved prolonged incubation at room temperature and transfer of the primary broths. The plating media consisted of: 1) xylose lysine desoxycholate agar (XLD); 2) xylose lysine desoxycholate agar containing 15 or 20 micrograms per mL of novobiocin (XLDN); 3) brilliant green sulfapyridine agar (BGSP); and 4) brillant green agar containing 20 micrograms per mL of novobiocin (BGN). Of the 94 Salmonella-positive recoveries from the enrichment broths in which complete comparisons could be made, an average of 75% were recovered from the primary enrichment broths and an average of 86% were recovered from the delayed secondary-enrichment broths. Of the 254 Salmonella-positive isolations in which complete comparisons could be made, an average of 65% were isolated on the plating media without novobiocin and an average of 97% were isolated on the plating media containing novobiocin. Overall, the delayed secondary enrichment and enteric plates supplemented with novobiocin significantly improved Salmonella detection from the farm environmental samples.

Animals↗

PubMed1990

Myotonic dystrophy: quantification of muscle weakness and myotonia and the effect of amitriptyline and exercise.

The purpose of this study was to quantify the degree of muscle weakness and myotonia in 12 patients with myotonic dystrophy (MD), and to quantitatively determine the effects of a four- to six-month therapeutic trial of amitriptyline. Patients had exercised with weights for one or more years. Some had shown initial improvement in muscle strength, but had reached a plateau; others had not improved when the study began. Muscle weakness was quantified by comparing the five-second maximum voluntary contraction (MVC) in newtons (N) per kg (body weight) of 12 patients and 20 healthy subjects. Knee extensor, elbow flexor, and first dorsal interosseous (FDI) muscles were compared. Myotonia was quantified by measuring relaxation times (RTs) at the end of the five-second MVC produced by FDI, as the time taken for the MVC to decrease by 50% and 75% (referred to as 1/2 and 3/4RT). The results were as follows: (1) the mean muscle strength of each of the three muscles of the patients was significantly (p less than .001) reduced compared with healthy subjects; and (2) 1/2 and 3/4RT means of the patients (vs healthy subjects) were significantly prolonged (p less than .01). Eight of the patients participated in a therapeutic trial of amitriptyline. Therapeutic effects were quantified by measuring muscle strength, 1/2 and 3/4RT, and percent change in evoked muscle action potential (MAP) from the FDI muscle after a ten-second MVC, to determine change in excitability. Mean muscle strength of FDI improved from .27 to .33N/kg, (p less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMed1990

Cell surface recognition determinants involved in triggering the lymphokine activated killer cell phenomenon: enhanced killing of modified "anti-self" targets by varying LAK culture conditions.

Lymphokine activated killer (LAK) cells were first described by Rosenberg, et al in the early 1980s. In attempting to grow lymphoid cells infiltrating solid tumors, they discovered that such cells, when incubated with the cytokine Interleukin-2 (IL-2), gained the ability to lyse a wide range of auto and allogeneic tumors while sparing normal non-malignant cells. A number of preliminary clinical trials have shown that when LAK cells and IL-2 are infused into patients with end-stage metastatic cancer, impressive tumor regression, and in some cases tumor eradication, can occur, albeit in the face of significant toxicity. Little is understood about how a potential target cell "signals" its malignant character to a LAK cell. Our approach to this problem has been to investigate the role of the absence or modification of certain self antigens which seem to provide LAK cells with a lysis trigger. By manipulating the culture conditions in which the killer cells are grown, we provide evidence that different subsets of LAK cells may lyse different types of tumor targets. These differences may be important in fine-tuning LAK treatment that is more active at the tumor site in vivo and less toxic to patients.

Animals↗

PubMed1989

Gap junction particle density of horizontal cells in goldfish retinas lesioned with 6-OHDA.

The I1 dopaminergic interplexiform cells of the fish retina are believed to modulate horizontal cell coupling by increasing gap junction resistance. Dopamine also modulates the morphology of horizontal cell gap junctions and mimics the effects of light adaptation. To determine whether the light-dependent changes in gap junction morphology are due to endogenous dopamine release, horizontal cell gap junctions were studied in goldfish retinas lacking dopaminergic neurons. Dopaminergic interplexiform cells were destroyed by intraocular injections of 6-hydroxydopamine in both eyes. After lesioning, fish were treated in one of four ways: (1) light-adapted, (2) dark-adapted (1 hour), (3) light-adapted and given an intraocular injection of dopamine, or (4) dark-adapted (1 hour) and injected with dopamine. The effectiveness of lesioning was evaluated by autoradiographic detection of [3H]-dopamine uptake in the retina of one eye. Retinas in which lesioning of the contralateral eye was deemed effective were processed for freeze-fracture electron microscopy and the particle density of horizontal cell gap junctions determined. Lesioned retinas, whether light- or dark-adapted, had elevated horizontal cell soma gap junction particle densities compared to lesioned retinas treated with dopamine. These results demonstrate that high soma gap junction particle densities can be correlated with the absence of dopamine and low densities associated with the presence of dopamine. The differences in gap junction particle density between lesioned and lesioned + dopamine-treatment were similar to differences between nonlesioned dark-adapted (1 hour) and light-adapted retinas, respectively. Therefore, the particle density of light- and dark-adapted soma gap junctions suggests a greater release of dopamine in light-adapted fish than in 1 hour dark-adapted fish.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1989

In vivo administration of histoincompatible lymphocytes leads to rapid functional deletion of cytotoxic T lymphocyte precursors.

It is well established that a single intravenous injection of F1 lymphocytes can rapidly and specifically reduce the ability of a parental recipient to generate CTL against donor alloantigens in a subsequent MLR. By fluorescently labeling the injected cells, we have been able to identify, and if desired, remove them in cell suspensions prepared from recipient spleen and lymph node. The injected cells, whether F1 or syngeneic, appeared to form part of the normal recirculating pool. Removal of injected F1 cells from responder lymph node or spleen cell suspensions had no effect on the response reduction observed in the 5-d in vitro MLR (typically 80% reduction for responder cells taken 2 d after injection of F1 cells). When the frequency of CTL precursors (CTLp) was measured by limiting dilution, it was reduced to the same degree as the MLR response, implying that response reduction is due to a reduction in the number of activatable CTL in the responder cell suspension. An equal mixture of responder cells from treated (i.e., F1 injected) and control mice gave a measured CTLp frequency equivalent to the average of the separate frequencies, implying the absence of suppressor cells active in vitro. Labeled F1 cells recovered from a first recipient could be used to induce response reduction in a second recipient. The results are discussed in terms of APCs that functionally delete rather than stimulate CTLp that recognize them (i.e., a "veto mechanism"). These experiments appear to rule out a role for in vivo-induced suppressor cells up to 8 d after injection of semiallogeneic cells but do not address the question of whether they are induced at later times.

Animals↗

PubMed1989

T cell function and expression are dramatically altered in T cell receptor V gamma 1.1J gamma 4C gamma 4 transgenic mice.

We have characterized transgenic mice carrying a functional T cell receptor (TCR) C gamma 4 (V gamma 1.1J gamma 4C gamma 4) gene. Results indicate that active transcription of the C gamma 4 transgene can influence expression of the endogenous C gamma 4, C gamma 1 (V gamma 3-, V gamma 4-, V gamma 2-, or V gamma 5J gamma 1C gamma 1) and C gamma 2 (V gamma 1.2J gamma 2C gamma 2) genes, while the ultimate expression of other TCR delta, alpha, and beta chain genes, as well as the adult T cell response, are relatively unaltered. Cells expressing transgenic C gamma 4 and endogenous delta TCR transcripts can migrate to the skin as dendritic epithelial cells (DEC) even though C gamma 4 cells are rarely, if at all, found in the skin. Transgenic and control mice were compared at 2 weeks, 6-7 weeks, and older. At 2 weeks, the thymus of transgenic mice, particularly the medulla, was much larger than control. Moreover, peripheral lymphoid tissues of younger mice were markedly (as much as 100-fold) more immunoreactive (both Con A response and alloreactivity). These differences, although persistent, became smaller in older mice. The data suggest that transgene expression has a major effect on T cell development and reactivity.

Animals↗

PubMed1989

Central core disease: ultrastructure of the sarcoplasmic reticulum and T-tubules.

The modified Golgi staining method was used to study the sarcoplasmic reticulum (SR) and t- tubules of skeletal muscle in central core disease. Significant pathological changes were documented in both of these organelles in seven patients. Pathological changes were seen in both core and non-core regions, with the abnormalities being greatest in the cores. In noncore regions, distortions in the normal anatomy were minor. In cores, there was much more significant distortion of the normal anatomy and also an increase in the amount of SR and number of t-tubules.

Adult↗

PubMed1989

Investigations of muscle bioenergetics with 31P NMR.

Many factors have been proposed to contribute to the development of muscle fatigue, but as yet a definitive assessment of their relative contributions has not been possible. To determine whether changes in bioenergetic factors are determinants of muscle force during the development of fatigue, simultaneous measurements were made during fatiguing exercise of the decline in muscle force and changes in phosphorus (31P) nuclear magnetic resonance (NMR) spectra. The results showed that the decline in force strongly correlated with a rise in inorganic phosphate (Pi) concentration; in contrast, fatigue correlated less strongly with intracellular pH. Similar results were found in different muscles and with different exercise protocols. They suggest that the rise in [Pi] is a mechanism that produces progressive inhibition of the force-generating reaction, while energy availability is not limiting. Down-regulation of force and energy utilization are consistent with fatigue being not simply a disruptive process, but an adaptive response that establishes an equilibrium between energy supply and demand.

Adenosine Triphosphate↗

PubMed1989

Functional heterogeneity in allospecific cytotoxic T lymphocyte clones. III. Direct correlation between development of syngeneic cytotoxicity and loss of veto activity; implications for the mechanism of veto action.

Two veto active allospecific cytotoxic T-cell clones (CTL), 4A2 and 4B3, were studied for the development of autoreactivity. The 4A2 CTL became autoreactive within 6 days when cultured without appropriate allospecific stimulator cells, whereas the 4B3 CTL retained its alloreactivity without becoming autoreactive when cultured under these conditions. Simultaneously with the development of autoreactivity, the 4A2 CTL lost its veto activity. Limiting dilution cultures of normal allospecific 4A2 CTL cells and autoreactive 4A2 CTL cells and mixtures of both showed that the former CTL cells were capable of inhibiting clonal growth of the autoreactive CTL cells in a dose-dependent manner. We suggest that this growth inhibition reflects veto activity, i.e. cells capable of growing are inhibited by autorecognition of veto active allospecific 4A2 CTL cells. Taken together, the present results indicate that the existence of intraclonal down-regulation of potentially autoreactive cells is a normal feature of allospecific cytotoxic T-cell clones.

Animals↗

PubMed1989

Nonmetabolic fatigue in exercising human muscle.

Human muscle fatigue, assessed by declining maximum voluntary contraction (MVC), may be caused by impairment of excitation-contraction coupling as well as by metabolic alterations within the muscle. To distinguish between these 2 possibilities, we assessed changes in excitation-contraction coupling by measuring twitch tension (TT) and twitch potentiation (P-TT) of the human adductor pollicis and tibialis anterior, while we analyzed metabolic changes using 31P magnetic resonance spectroscopy. Low-intensity exercise produced a much greater fall of TT and P-TT than MVC, high energy phosphates, or intracellular pH (pHi). In addition, the recovery of TT and P-TT was much slower than recovery of MVC, high energy phosphates, or pHi. These results suggest that the greater fall of TT and the delayed recovery following low-intensity exercise are caused by impaired excitation-contraction coupling.

Action Potentials↗

PubMed1989

Increased muscular fatigue in patients with neurogenic muscle weakness: quantification and pathophysiology.

The strength of maximum voluntary contraction (MVC) and muscular fatigue measured from ankle dorsiflexors and knee extensors of 15 patients with neurogenic muscle weakness was compared with those of 20 healthy subjects. Muscle weakness, defined as the failure to generate the expected force, was determined by two methods: (1) manual muscle testing and (2) measurement of MVC using a force transducer. Muscle strength was then quantified as the MVC in Newtons (N)/kg body weight. The percent decrease in both MVC (the Fatigue Index [FI]), and rectified-integrated electromyogram (RIEMG) at the end of 60sec of sustained MVC were computed. There were three main findings. (1) Muscle strength was significantly (p less than 0.001) reduced in both muscles of the patient group: in ankle dorsiflexors, means = 1.62 +/- 0.7N/kg vs 4.8 +/- 0.5N/kg; in knee extensors, means = 3.2 +/- 1.8N/kg vs 7.8 +/- 1.5N/kg. (2) Fatigue was significantly greater (p less than 0.01) in the patient group: for ankle dorsiflexors, means = 50 +/- 15% vs 34 +/- 13%; and for knee extensors, means = 62 +/- 17% vs 46 +/- 15%. There was a negative correlation between muscle strength and FI of only the knee extensors of the patients (r = -0.88, p less than 0.001). (3) The mean decline in RIEMG of the two muscles combined was also significantly greater (p less than 0.001) in the patient group (means = 48 +/- 16% vs 2 +/- 11%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1989

Brother/sister pairs affected with early-onset, progressive muscular dystrophy: molecular studies reveal etiologic heterogeneity.

An autosomal recessive (AR) form of muscular dystrophy that clinically resembles Duchenne/Becker types exists, but its frequency is unknown. We have studied three unrelated affected brother/sister pairs and their families for deletions and polymorphisms with the entire dystrophin cDNA and other DNA probes from the Xp21 region to test for involvement of the DMD locus. In family 1 a large intragenic deletion was found in the affected male. The affected sister was heterozygous for this deletion, but the mother was not, implying germinal mosaicism. In family 2, no deletion was detected in the affected male. RFLP analysis revealed that the affected male and an unaffected sister shared a complete Xp21 haplotype while the affected sister had inherited a recombinant Xp21 region resulting from a crossover between pERT 87-15 and J-Bir. Only the 5' region of the dystrophin gene was shared with the affected boy. X-inactivation studies using a polymorphism in the 5'-flanking region of the HPRT gene, in conjunction with methylation-sensitive enzymes, revealed random X inactivation in the affected girl's leukocytes. In a muscle biopsy from the affected male, the dystrophin protein was present in normal amount and size. Family 3 was informative for four RFLPs detected with dystrophin cDNA probes which span the entire gene. The affected male was found to share the complete dystrophin RFLP haplotype with his unaffected brother, while his affected sister had inherited the other maternal haplotype. It is concluded that the clinical presentation of early-onset, progressive muscular dystrophy in a male and in his karyotypically normal sister can be caused by mutations at different loci. While in family 1 a deletion in the dystrophin gene is responsible, this gene does not appear to be involved in families 2 and 3.

Child↗

PubMed1989

The T-cell receptor repertoire is strikingly similar in older nude mice compared to normal adult mice.

Due to the absence of a normal thymus, nude mice are characterized by low numbers of mature T cells. It has been shown in older nude mice that appreciable numbers of Thy-1+, CD8+ and, to a much lesser extent, CD4+ T cells can be found. A second T-cell receptor (TCR), gamma delta-TCR, has been shown to be expressed by a large number of T cells in young and old nude mice. Recent data suggest that certain gamma and delta chain variable (V), diversity (D), joining (J) and constant (C) region genes are associated with both temporal and spatial organization of the gamma delta-T-cell repertoire in normal mice. In this study we observed the predominant use of V gamma 2J gamma 1C gamma 1 and V delta 5J delta 1C delta in the spleen of older nude mice. In the skin, a near exclusive expression of V gamma 3J gamma 1C gamma 1 and V delta 1J delta 2C delta gene segments was observed. In addition, a dendritic epidermal cell (DEC) clone was isolated from the skin of a nude mouse and expressed a gamma delta receptor consisting of V gamma 3J gamma 1C gamma 1 and V delta 1J delta 2C delta. Preliminary results show that this clone kills only YAC (and NK target) and not other tumor targets. The killing can be redirected by anti-CD3 monoclonal antibody which suggests that the receptor is potentially functional. These results demonstrate that without normal thymus development nude mice not only produce gamma delta-T cells with a lytic potential, but also manage to express gamma delta-TCR's that are similar in spatial arrangement to normal mice. This suggests a possible difference in the requirements for gamma delta-TCR ontogeny.

Aging↗

PubMed1988

The autoimmune mouse MRL/Mp-lpr/lpr contains cells with spontaneous cytotoxic activity against target cells bearing self-determinants.

Spontaneously cytotoxic cells possessing specificity and having a complex pattern of reactivity directed at least partly against self-determinants develop by the age of 10 weeks in the autoimmune mouse strain MRL/Mp-lpr/lpr (MRL-lpr) and by the age of 6 months in C57BL/6-lprl/lpr. Similar effector cells do not develop in either MRL/Mp-+/+(MRL-+/+) or normal C57BL/6 mice up to 6 months old. Freshly prepared suspensions of both lymph node and bone marrow cells from individual MRL-lpr mice could kill Con A- or LPS-induced blast cells and fresh thymocytes from MRL-+/+ and other mouse strains with strong preference for strains carrying (self)-H-2k determinants in a 4-hr51Cr release assay. These results imply that self-reactive cells are generated as part of the lpr gene defect.

Animals↗

PubMed1988

A sensitive dot blot procedure for detecting mRNA in lymphoid cells grown in liquid culture.

A sensitive dot blot procedure for detecting RNA transcripts with radiolabelled cDNA probes in small numbers of cells in suspension culture is described. For a frequent mRNA species such as that for immunoglobulin in an IgM secretor hybridoma, as few as 30 cells can be detected using a C mu probe; for a less frequent mRNA species such as transcripts coding for alpha, beta or gamma genes of the T cell receptor in T cell tumors or CTL clones, as few as 3 X 10(3) to 10(4) cells can be detected using C alpha, C beta or C gamma probes. High sensitivity is achieved by confining the cells to a very small area on the filter on which they are probed, and by treating the filter with formaldehyde.

Animals↗