Biomedical subjects

C A Miller

Publications and source records attributed to C A Miller.

At least 55 records · Page 3Linked to original sources

PubMed1999

A mechanical energy analysis of gait initiation.

The analysis of gait initiation (the transient state between standing and walking) is an important diagnostic tool to study pathologic gait and to evaluate prosthetic devices. While past studies have quantified mechanical energy of the body during steady-state gait, to date no one has computed the mechanical energy of the body during gait initiation. In this study, gait initiation in seven normal male subjects was studied using a mechanical energy analysis to compute total body energy. The data showed three separate states: quiet standing, gait initiation, and steady-state gait. During gait initiation, the trends in the energy data for the individual segments were similar to those seen during steady-state gait (and in Winter DA, Quanbury AO, Reimer GD. Analysis of instantaneous energy of normal gait. J Biochem 1976;9:253-257), but diminished in amplitude. However, these amplitudes increased to those seen in steady-state during the gait initiation event (GIE), with the greatest increase occurring in the second step due to the push-off of the foundation leg. The baseline level of mechanical energy was due to the potential energy of the individual segments, while the cyclic nature of the data was indicative of the kinetic energy of the particular leg in swing phase during that step. The data presented showed differences in energy trends during gait initiation from those of steady state, thereby demonstrating the importance of this event in the study of locomotion.

Adult↗

PubMed1999

Activation of silent replication origins at autonomously replicating sequence elements near the HML locus in budding yeast.

In the budding yeast, Saccharomyces cerevisiae, replicators can function outside the chromosome as autonomously replicating sequence (ARS) elements; however, within chromosome III, certain ARSs near the transcriptionally silent HML locus show no replication origin activity. Two of these ARSs comprise the transcriptional silencers E (ARS301) and I (ARS302). Another, ARS303, resides between HML and the CHA1 gene, and its function is not known. Here we further localized and characterized ARS303 and in the process discovered a new ARS, ARS320. Both ARS303 and ARS320 are competent as chromosomal replication origins since origin activity was seen when they were inserted at a different position in chromosome III. However, at their native locations, where the two ARSs are in a cluster with ARS302, the I silencer, no replication origin activity was detected regardless of yeast mating type, special growth conditions that induce the transcriptionally repressed CHA1 gene, trans-acting mutations that abrogate transcriptional silencing at HML (sir3, orc5), or cis-acting mutations that delete the E and I silencers containing ARS elements. These results suggest that, for the HML ARS cluster (ARS303, ARS320, and ARS302), inactivity of origins is independent of local transcriptional silencing, even though origins and silencers share key cis- and trans-acting components. Surprisingly, deletion of active replication origins located 25 kb (ORI305) and 59 kb (ORI306) away led to detection of replication origin function at the HML ARS cluster, as well as at ARS301, the E silencer. Thus, replication origin silencing at HML ARSs is mediated by active replication origins residing at long distances from HML in the chromosome. The distal active origins are known to fire early in S phase, and we propose that their inactivation delays replication fork arrival at HML, providing additional time for HML ARSs to fire as origins.

Base Sequence↗

PubMed1998

Overlapping 3'-end formation signals and ARS elements: tightly linked but functionally separable.

3'-End formation signals are closely associated with autonomous replicating sequences (ARSs) in Saccharomyces cerevisiae in that ARSs frequently contain signals that direct 3'-end formation (Chen et al., 1996). Mutationally-inactivated ARSs that co-reside with 3'-end formation sequences do not disrupt 3'-end formation, thus demonstrating that replication function does not affect termination function. To test the corollary possibility that 3'-end formation is important for replication function, we made point mutations in ARS305 that increase readthrough of the 3'-end formation signals and determined plasmid replication efficiency. Replication efficiency, as assessed by plasmid stability assays, was not altered by mutations affecting 3'-end formation when transcription through the ARS was either absent or highly-induced. Under conditions of high-level transcription through the ARS, the rate of plasmid loss in both wild-type and mutated terminators increased over five-fold from rates observed during transcriptionally repressed conditions. This result indicates that the native 3'-end formation signal is incapable of protecting the replication function when high levels of transcription are directed into the ARS. Thus, the compact nature of the S. cerevisiae genome, rather than a functional inter-dependence, may account for close association of transcription terminators and ARSs.

Base Sequence↗

PubMed1998

Assessment of aryl hydrocarbon receptor complex interactions using pBEVY plasmids: expressionvectors with bi-directional promoters for use in Saccharomyces cerevisiae.

The pBEVY (bi-directional expression vectors for yeast) plasmids were designed with constitutive and galactose-induced bi-directional promoters to direct the expression of multiple proteins in Saccharomyces cerevisiae . Using human estrogen receptor as a test gene, relatively balanced expression levels from each side of a bi-directional promoter were observed. Expression of a functional heterodimeric transcription factor composed of human aryl hydrocarbon receptor (Ahr) and aryl hydrocarbon receptor nuclear translocator (Arnt) proteins was accomplished using a single pBEVY plasmid. Previous studies suggest that inhibitory cross-talk between the estrogen receptor and the Ahr/Arnt complex may occur and that Hsp90-Ahr complex formation is important for Ahr-mediated signal transduction. Evidence for functional interaction among these proteins was investigated using pBEVY plasmids in a yeast system. No inhibitory cross-talk was observed in signaling assays performed with yeast that co-expressed Ahr, Arnt and estrogen receptor. In contrast, Ahr/Arnt-mediated signal transduction was reduced by 80% in a temperature-sensitive Hsp90 strain grown under non-permissive conditions. We conclude that pBEVY plasmids facilitate the examination of multiple protein interactions in yeast model systems.

Dimerization↗

PubMed1998

A splicing variant of a death domain protein that is regulated by a mitogen-activated kinase is a substrate for c-Jun N-terminal kinase in the human central nervous system.

The mitogen-activated kinase activating death domain protein (MADD) that is differentially expressed in neoplastic vs. normal cells (DENN) was identified as a substrate for c-Jun N-terminal kinase 3, the first demonstration of such an activity for this stress-activated kinase that is predominantly expressed in the brain. A splice isoform was identified that is a variant of MADD. A protein identical to MADD has been reported to be expressed differentially in neoplastic vs. normal cells and is termed "DENN." We demonstrated differential effects on DENN/MADD in a stressed vs. basal environment. Using in situ hybridization, we localized both the substrate and the kinase to large pyramidal neurons in the human hippocampus. It was interesting that, in four of four patients with neuropathologically confirmed acute hypoxic changes, we detected a unique translocation of DENN/MADD to the nucleolus. These changes were apparent only in neurons sensitive to hypoxia. Moreover, in those cells, translocation of the substrate was accompanied by nuclear translocation of JNK3. These findings place DENN/MADD and JNK in important hypoxia insult-induced intracellular signaling pathways. Our conclusions are important for future studies for understanding these stress-activated mechanisms.

Alternative Splicing↗

PubMed1998

Chondroitin sulfate proteoglycan specific to retinal horizontal neurons.

ABSTRACT Proteoglycans (PGs) are a diverse group of highly glycosylated macromolecules that are implicated in the development and maintenance of neuronal circuitry. With its highly ordered, layered structure, the retina ideally serves to define the synthesis, processing, and distribution of these molecules within a specific cellular subpopulation. In retinal sections, monoclonal antibody (MAb) 6A2 immunostained a horizontal cell-specific antigen. Antigen 6A2 was expressed within abundant processes in the outer plexiform layer and in rare neurites that extend across the inner nuclear layer to the inner plexiform layer. Ultrastructurally, the antigen was localized to cisternae within horizontal cell somata, along tubulovesicular structures in dendrites, and in the perisynaptic space encircling presynaptic terminals of the cone photoreceptor triad. These findings suggest that this PG is synthesized within the horizontal cells, transported to the terminals, and released into the extracellular spaces just proximal to the synapse. Based on the focal stain in the adjacent photoreceptor cell, it is possible that antigen is pinocytosed by this cell and is concentrated at the ribbon synapse. In Western immunoblots of retinal homogenates, MAb 6A2 recognized a heterogeneous chondroitin sulfate (CS) PG (CSPG) of approximately 400-500 kDa. After sequential enzymatic removal of CS glycosaminoglycans, a major broad band of 300-500 kDa was identified by MAb 1B5, which detects CSPGs that bear uronic acid linked to unsulfated N-acetylgalactosamine as the initial disaccharide in the CS chain. Localization of this PG around presynaptic terminals of the horizontal neuron and at the ribbon synapse suggests that it may play a modulatory and sustaining role at the synapse.

Animals↗

PubMed1998

Peptides bind to eosinophils in the rat stomach.

BACKGROUND: An immunological role for eosinophils has been well established. However, roles for eosinophils in the physiological functions of the organs they populate are little explored. METHODS: Fixed, frozen, then vibratomed sections of rat stomach were exposed to biotinylated 1-17 gastrin (bG17), biotinylated gastrin-releasing peptide (bGRP), biotinylated neuromedin C (bNC), biotinylated vasoactive intestinal peptide (bVIP), and biotinylated substance P (bSP). Binding sites were identified using an avidin-biotin-glucose oxidase complex and tetranitroblue tetrazolium staining. RESULTS: bG17, bGRP, and bNC all bound to cells in the lamina propria and to a lesser extent in the submucosa. Neither bVIP nor bSP bound to cells in these sections. Stained cells were identified as eosinophils in the light microscope on the basis of their distribution and staining properties using the Luna stain for eosinophils and in the transmission electron microscope (TEM) on the basis of a light/TEM matching process. Plastic sections viewed in the light microscope showed that stain was localized to a granular component in the cytoplasm of the eosinophils. No other cell type, specifically neither mast cells nor plasma cells, stained. G17 competed for the bG17 binding site better than did NC. A competition study in which polyglutamic acid failed to compete with bG17 for the binding site, and the observation that bG17, bGRP, and bNC did not bind to other positively charged sites (e.g., collagen, red blood corpuscles), demonstrated that binding was not due to nonspecific electrostatic interactions alone. Binding of bG17 to a CCK(B)/gastrin-type receptor was ruled out when specific receptor antagonists failed to block binding. CONCLUSIONS: The particulate nature of the binding site suggests a secretory substance. If so, eosinophils might use that substance to destroy, neutralize, or control the activity of peptide hormones bound to it in the extracellular space.

Animals↗

PubMed1998

Frontotemporal dementia: neuropil spheroids and presynaptic terminal degeneration.

We compared the neuropathological changes of 6 patients with clinically diagnosed lobar dementia. In the 4 patients with histopathology consistent with frontotemporal dementia (FTD), moderate neuronal loss contrasted with marked cortical and subcortical gliosis. We found silver-positive, carbohydrate-rich, spheroidal enlargements of presynaptic terminals within the neuropil of specific central nervous system regions. The spheroids were immunopositive for the cytoskeletal proteins tau, the high molecular weight neurofilament subunit (NF-H), and beta-tubulin. No abnormal tau phosphorylation and only rare ubiquitin immunoreactivity were detected in these structures. Carbohydrate modifications, including advanced glycation end products within the spheroid matrix, were confirmed by lectin binding, and by anti-pentosidine immunoreactivity, an indicator of oxidative stress. Ultrastructurally, the spheroids consisted of unmyelinated, membrane-enclosed structures filled with randomly arrayed pairs of filaments, approximately 8 to 10 nm in diameter, that were sparsely labeled with antibodies to unmodified tau (T14) and NF-H. Despite clinical overlap, the central nervous systems of our FTD patients are distinguishable from those of other patients with other lobar dementias, including Pick's disease and corticobasal degeneration, by the absence of abnormally phosphorylated neuronal or glial tau inclusions. The neuropil spheroids are dystrophic changes of certain selectively vulnerable presynaptic terminals, suggesting a retrograde degenerative process in FTD.

Adult↗

PubMed1998

Electrically evoked compound action potentials of guinea pig and cat: responses to monopolar, monophasic stimulation.

We recorded electrically evoked compound action potentials (EAPs) from guinea pigs and cats using monophasic current pulses delivered by a monopolar intracochlear electrode. By using simple stimuli, we sought results that could shed light on basic excitation properties of the auditory nerve. In these acute experiments, the recording electrode was placed directly on the auditory nerve. Responses to anodic and cathodic stimulus pulses were recorded separately to evaluate stimulus polarity effects. Several polarity-dependent properties were observed. Both EAP morphology and latency were polarity-dependent, with greater latencies for cathodic stimulation. Threshold stimulus level was also polarity-dependent, but in different directions in the two species: cats had lower cathodic thresholds while guinea pigs had lower anodic thresholds. We also observed that the slopes of the EAP amplitude-level functions depended upon stimulus polarity. In most cases where EAP saturation amplitude could be measured, that amplitude was similar for anodic and cathodic stimuli, suggesting that either stimulus polarity can recruit all fibers, or at least a comparable numbers of fibers. The common findings (e.g., EAP morphology and polarity-dependent latency) observed in these two species suggest results that can be extrapolated to responses obtained in humans, while the species-specific findings (e.g., dependence of threshold on polarity) may point to underlying anatomical differences that caution against overgeneralization across species. Some of our observations also bear upon hypotheses of how electrical stimuli may excite different sites on auditory nerve fibers.

Action Potentials↗

PubMed1998

It takes two to tango: understanding and acquiring symmetrical verbs.

Children's ability to understand symmetrical verbs was investigated, along with adults' use of linguistic and visual cues to learn novel symmetrical verbs. Symmetrical verbs encode a relationship r between two entities such that X r Y entails Y r X. In Experiment 1, sixteen children (mean age 4;8) acted out two types of sentences with symmetrical and asymmetrical verbs. Eight adult judges viewed videotapes of the children's performance and tried to guess what sentence type was being enacted. Judges' performance was predicted (p < .05) by the verb type, symmetrical or asymmetrical. In Experiment 2, seventy-two adult subjects received visual and linguistic cues to the meanings of novel verbs. Both cue types affected subjects' judgments about whether the new verbs were symmetrical or asymmetrical (p < .05).

Adult↗

PubMed1998

Deficits in finite verb morphology: some assumptions in recent accounts of specific language impairment.

The grammatical morphology deficits common in children with specific language impairment (SLI) are characterized in some models as linguistic deficits. Such models must assume some mechanism for correct productions of finite verb forms. Three such assumptions were tested by analyzing speech samples from 18 children with SLI (aged 3 years 6 months to 6 years 9 months). Assumption 1, that nonfinite forms are used consistently until replaced by memorized finite forms, was tested by examining the distribution of verb types in present third-person singular and noun types in present third-person singular contractible copula contexts. Significantly more word types than expected were inflected inconsistently. Both Assumption 2, that finite and nonfinite verb forms are memorized but used indiscriminately, and Assumption 3, that affixation rules are applied indiscriminately, predict random use of finite forms. This prediction was not supported.

Child↗

PubMed1998

Cutaneous adverse effects associated with terbinafine therapy: 10 case reports and a review of the literature.

Terbinafine is an allylamine antifungal agent widely used to treat dermatophyte onychomycosis and dermatomycoses. We report 10 severe cutaneous adverse reactions associated with terbinafine therapy which required discontinuation of the antifungal agent: erythema multiforme (five patients), erythroderma (one), severe urticaria (one), pityriasis rosea (one) and worsening of pre-existing psoriasis (two patients). The spectrum of cutaneous adverse effects associated with terbinafine therapy is reviewed. Patients should be counselled about discontinuing terbinafine at the onset of a cutaneous eruption and about seeking medical advice about further management.

Adult↗

PubMed1998

Destabilized inheritance of pSC101 and other Escherichia coli plasmids by DpiA, a novel two-component system regulator.

We identified a gene (dpiA, Destabilizer of Plasmid Inheritance) which, when overexpressed in Escherichia coli, destabilizes the inheritance of pSC101 and other iteron-containing plasmids as disparate as mini-F and RK6 but not the inheritance of P1, RSF1010 and ColD. These effects of DpiA, which functions like an effector protein for a previously undescribed two-component signal transduction system, were reduced by mutations known to promote pSC101 replication and partitioning. dpiB, a gene encoding the putative histidine kinase of this two-component system, is located immediately 5' to dpiA and adjacent to a DpiA-induced target promoter that transcribes genes having homology to citrate lyase operon genes, citC, citD and citE, of Klebsiella pneumoniae. Disruption of dpiB reversed or reduced the effect of DpiA overproduction on pSC101 inheritance. A second DpiA target, the promoter for a gene (appY) implicated in E. coli's response to anaerobiosis, is repressed by DpiA. A mutation in dpiA at a site commonly conserved and phosphorylated in two-component system effector proteins abolished the effects of DpiA overproduction on pSC101 inheritance and negative regulation of appY expression. Our findings suggest a possible mechanism by which environment and/or cellular stimuli may influence plasmid inheritance.

Amino Acid Sequence↗

PubMed1998

Evaluation of tire-derived fuel for use in nitrogen oxide reduction by reburning.

Tire-derived fuel (TDF) was tested in a small-scale (44 kW or 150,000 Btu/hr) combustor to determine its feasibility as a fuel for use in reburning for control of nitrogen oxide (NO). TDF was gravity-fed into upward flowing combustion gases from a primary natural gas flame doped with ammonia to simulate a high NO combustion process. Emissions of NO, oxygen, carbon dioxide, carbon monoxide, and particulate matter were measured. The tests varied the nominal primary NO level from 600 to 1,200 ppm and the primary stoichiometry from 1.1 to 1.2, and used both natural gas and TDF as reburn fuels. The reburn injection rate was varied to achieve 8-20% of the total heat input from the reburn fuel. NO emissions reductions ranged between 20 and 63% when using TDF, depending upon the rate of TDF injection, primary NO, and primary stoichiometry. NO emission reductions when using natural gas as the reburn fuel were consistently higher than those when using TDF. While additional work remains to optimize the process and evaluate costs, TDF has been shown to have the potential to be a technically viable reburning fuel.

Air Pollution↗

PubMed1998

CD34 augmentation improves allogeneic T cell-depleted bone marrow engraftment.

T cell depletion (TCD) performed by elutriation has decreased the incidence of acute and chronic graft-versus-host disease (GvHD) following bone marrow transplantation (BMT). However, as with all forms of TCD, patients may experience graft failure (10%), delayed engraftment, and mixed chimerism. Because 66%-75% of the CD34+ cells coseparate with the small lymphocytes, which are removed by elutriation, we designed a phase I trial in HLA-identical siblings to determine if the readdition of these previously lost small CD34+ cells would improve elutriation's engraftment kinetics. CD34+ cells were isolated from the small cell fraction of 10 consecutive donor grafts and infused into the recipients along with the TCD graft. The positively selected product had a mean T cell content of 1.2 x 10(5)/kg and was 80% CD34+, doubling the CD34+ content of the graft. All patients engrafted promptly with a median time to 500 neutrophils/mm3, untransfused 50,000 platelets/mm3, and discharge from the hospital of 19 (range 10-25), 24 (14-52), and 24 (18-29) days, respectively. Acute GvHD occurred in 2 patients, and no patient had chronic GvHD. Augmenting stem cell dose may be an efficient and safe alternative for overcoming TCD-associated delayed engraftment and graft failure, rather than increasing immunosuppression.

Adult↗

PubMed1998

Assessing the performance of local public health systems: a survey of state health agency efforts.

Throughout the past decade, growing attention has focused on ways to monitor the performance of local public health organizations and ensure the adequacy of their services. We surveyed representatives of the nation's state health agencies during 1997 to examine their processes for local public health performance assessment. Eighty-eight percent of agencies reported some involvement in assessment activities. Of these agencies, 50 percent reported having an assessment process that was currently operative. States reported using a diversity of assessment methods. Results suggest that states are developing performance assessment processes that are tailored to local resources, needs, and priorities.

Community Health Services↗

PubMed1998

Core function-related local public health practice effectiveness.

This article assesses the extent to which the U.S. population in 1995 was being effectively served by public health's three core functions (assessment, policy development, and assurance). A random sample of local health departments (LHDs) stratified by population size and type of jurisdiction was asked to provide their opinion of, as well as indicate performance on 20 core function-related measures of local public health practice. The article concludes that, in 1995, the nation fell far short of its year 2000 national objective, which called for 90 percent of the population to be served by an LHD effectively carrying out public health's core functions. Considerable capacity building and performance improvement is needed within the public health system.

Humans↗

PubMed1998

Differential effects of non-REM and REM sleep on sensory gating in rats.

Sensory gating in rats can be measured with a double click paradigm. The diminished response towards the second click is a physiological manifestation of reduced sensory input. This physiological process seems to be disturbed in human psychoses. It is thought that gating, as measured with this paradigm, is a preattentive, involuntary phenomenon which is not modulated by attention. If this is indeed the case, than it is hypothesized that gating should not be modulated by non-REM sleep. In the present experiment pairs of clicks (500 ms interval) were presented during wakefulness, non-REM as well as REM sleep and cortical auditory evoked potentials (AEP's) were recorded in chronically implanted rats. Rather similar AEP's were found after the first and second stimulus. However, the amplitudes of the various components of the second AEP were smaller than those of the first AEP, suggesting a gated response. This was the case during all three levels of vigilance. The amplitudes of both AEP's showed the more often reported changes in amplitude during sleep and REM sleep. Clear differences were seen in gating: compared to wakefulness a decrease in gating was found during REM sleep while gating was unchanged during non-REM sleep. The latter outcome seems to confirm that gating in rats is indeed a preattentive process. Finally, results were discussed in terms of neuronal properties of thalamic relay cells and it is suggested that firing properties of thalamic relay cells are not involved in this type of sensory gating.

Acoustic Stimulation↗