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Biomedical subjects

T McBride

Publications and source records attributed to T McBride.

At least 19 recordsLinked to original sources
PubMed2000

Increased depolarization, prolonged recovery and reduced adaptation of the resting membrane potential in aged rat skeletal muscles following eccentric contractions.

Previously it was shown in young-adult muscles that eccentric contractions (EC) produce a significant (24 h) depolarization of the resting membrane potential (RMP), and that in-vitro (Gd(3+)) and in-vivo (streptomycin) blockade of stretch activated ion channels (SAC) result in a partial repolarization of the RMP. The portion of the depolarization not restored by SAC blockade is believed to be from sarcolemmal injury. A second exposure to EC results in less depolarization and a more rapid recovery of the RMP. Aged muscles were subjected to the same EC protocol to test the hypotheses that: (1) Aged muscles will experience a more significant and prolonged depolarization of the RMP following EC. (2) The depolarization in aged muscles will occur by a greater contribution from membrane damage, rather than the opening of SAC. (3) The aged muscles will demonstrate a reduced capacity to adapt to EC, and will experience a similar degree of depolarization following repeated exposures to EC. The results indicate a significantly greater and longer lasting depolarization in aged compared to young-adult muscles. Blocking SAC did not produce a repolarization of the RMP in aged muscles. Aged muscles had a significantly reduced adaptive response to EC compared to young-adult. It is speculated that the different response in aged muscles results from a reduced number of functional SAC.

Adaptation, Physiological↗
PubMed2000

Development of perfluorocarbon tracer technology for underground leak location.

A method has been developed for the atmospheric sampling and analysis of four perfluorocarbon tracer (PFT) compounds simultaneously at the parts per trillion (ppt) level. PFTs were pre-concentrated using adsorbent tube air sampling. Analysis was achieved by thermal desorption (TD) and gas chromatography (GC) with electron capture detection (ECD). Efficient separation of the PFTs from the other sample constituents was achieved by use of a capillary porous layer open tubular (PLOT) GC column without the need to cool the GC oven to sub-ambient temperatures using liquid coolants (M. de Bortoli and E. Pecchio, J. High Resolut. Chromatogr., 1985, 8, 422) or for a catalytic destruction step to remove interferents (T. W. D'Ottavio, R. W. Goodrich and R. N. Dietz, Environ. Sci. Technol., 1986, 20, 100). Results from test field trials with two volatile PFTs that were buried to simulate an underground leaking cable were successful. The PFTs were detected above ground level to pinpoint the leak position. The highest tracer concentrations were detected within 1 m of the simulated leak positions 2 days after tracer burial. The developed technology was applied to an oil leaking high voltage electricity cable. One PFT was added to the cable oil which enabled detection of the oil leak to within 3 m. The reported method has many advantages over currently used leak detection methods and could, in the future, be applied to the detection of underground leaks in a variety of cables and pipes.

Chromatography, Gas↗
PubMed2000

Adaptation of pregnant ewes to an exclusive onion diet.

A diet consisting entirely of cull onions fed to pregnant ewes produced Heinz body hemolytic anemia in all sheep after 21 d. After 28 d of daily consumption of 20 kg of onions/ewe, the anemia stabilized, and for the remaining 74 d the packed cell volume increased in the majority of sheep, although it did not return to normal. Compared to control ewes fed an alfalfa and grain diet, the onion-fed ewes had comparable body condition scores and fleece weights. There was no significant difference (alpha = 0.05) in pregnancy or lambing rate, number of lambs born/ewe exposed, or number of lambs born/ewe lambing. Greater numbers of sulfate-reducing bacteria (Desulfovibrio spp) and more ruminal hydrogen sulfide were present in onion-fed sheep compared to controls. Although an average 27% reduction in packed cell volume and Heinz body anemia developed in the onion-fed ewes, on the basis of this study it appears that pregnant ewes may be fed a pure onion diet with minimal detrimental effects. This adaptation to a pure onion diet is in part likely due to the apparent ability of the sheep's rumen to quickly develop a population of sulfate-reducing bacteria that decrease the toxicity of onion disulfides.

Adaptation, Physiological↗
PubMed1999

Total anorectal and partial vaginal reconstruction with dynamic graciloplasty and colonic vaginoplasty after extended abdominoperineal resection: report of a case.

PURPOSE: Quality of life is altered after abdominoperineal resection, because of permanent iliac colostomy. Psychological rehabilitation is even more difficult after extended abdominoperineal resection to the vagina, because of the loss of both continence and sexual functions. We report the first case of total anorectal and vaginal reconstruction using dynamic graciloplasty and colonic vaginoplasty after extended abdominoperineal resection. METHODS: A 46-year-old female underwent extended abdominoperineal resection with posterior colpectomy for a low rectal adenocarcinoma infiltrating the anal sphincter and vagina. Anorectal reconstruction was performed with coloperineal anastomosis and double dynamic graciloplasty. Vaginal reconstruction was performed using a 10-cm, isolated, rotated sigmoid loop. The procedure was performed in three stages, including abdominoperineal resection with reconstruction, implantation of the stimulator, and closure of the temporary ileostomy. RESULTS: Resting and electrostimulated pressures of the neosphincter were 40 and 110 cm H2O respectively. Continence was achieved for formed stools two months after closure of the stoma, with spontaneous defecations (30-90 minutes). The patient experienced regular sexual activity six months after closure of the stoma. CONCLUSION: This new original technique can be proposed in selected young females after extended abdominoperineal resection, to preserve continence, sexual activity, and body image.

Adenocarcinoma↗
PubMed1999

The changing landscape of health care financing and delivery: how are rural communities and providers responding?

Rural communities have not kept pace with the recent dramatic changes in health care financing and organization. However, the Medicare provisions in the Balanced Budget Act of 1997 will require rural providers to participate in the new systems. Case studies revealed the degree of readiness for change in six rural communities and charted their progress along a continuum, as reflected in three sets of activities: the development of networking; the creation of new strategies for managing patient care; and the adoption of new methods for contracting with health insurers. Some communities had constructed highly integrated systems, whereas others were just beginning to change their billing practices; a few were signing contracts for capitated care, in contrast to those that were resisting discounts in current fee structures. These six rural areas still have considerable ground to cover before their health care organization and financing reach the levels achieved by urban communities.

Aged↗
PubMed1999

A comparative volumetric analysis of the prefrontal cortex in human and baboon MRI.

The proportion of prefrontal cortex in humans was compared to the proportion of prefrontal cortex in baboons (Papio anubis). Prefrontal cortex, dorsal prefrontal, orbital prefrontal cortex and total brain volumes were determined from magnetic resonance images of 20 healthy adult human females and 5 adult female baboons. Results showed that the proportion of prefrontal cortex volume relative to total brain volume in humans was significantly larger in humans than in baboons. The percentage of prefrontal cortex relative to total brain volume was 12.51 for humans and 10.68 for baboons. Similarly, the proportion of both dorsal and orbital prefrontal cortex volumes is larger in human brains. Relative to total brain volume, the percentages of dorsal and orbital prefrontal cortex was 8.22% and 4.29% respectively in humans and 7.21% and 3.47% in baboons. A regression analysis showed that the human prefrontal cortex was larger than would be predicted for a baboon of equal total brain volume. These results suggest that increased prefrontal lobe volume could underlie some of the differences between human and hominoid primates. On the other hand, the small magnitude of the difference might underlie similarities between the species and should encourage a search for other structures that are disproportionately larger in humans.

Adult↗
PubMed1997

Expectations of nursing home use in the Health and Retirement Study: the role of gender, health, and family characteristics.

Economic models of life cycle behavior suggest that expectations about future events may affect savings, insurance, and retirement planning. This article uses data from the first wave of the Health and Retirement Survey (HRS) to examine how personal characteristics and health conditions influence expectations of nursing home use. Subjective expectations of nursing home use are quite close to known probabilities of lifetime use. There are marked differences in the determinants of expectations for women and men that also conform to actual behavior. There is strong evidence that women and men incorporate what is known about nursing home risk into their own expectations, even many years prior to the time when they are most likely to need long-term care.

Black or African American↗
PubMed1995

Prenatal auditory experience directs species-typical perceptual responsiveness in bobwhite quail chicks (Colinus virginianus).

The present study examined the role of the relationship between pre- and postnatal stimulus cues in directing perceptual preferences of bobwhite quail chicks. Bobwhite quail were exposed to either prenatal auditory or prenatal auditory-visual stimulation. Both prenatal auditory and auditory-visual stimulation resulted in accelerated responsiveness to combined postnatal auditory-visual cues. However, whether or not subjects displayed accelerated perceptual responsiveness depended on the relationship between the nature of the pre- and postnatal auditory stimuli used. These results demonstrate the salience of auditory cues in directing early postnatal perceptual behavior in precocial birds and help to explicate why prior research in this area has found that augmented prenatal sensory stimulation can result in either accelerated or decelerated patterns of perceptual functioning.

Aging↗
PubMed1994

Specific postnatal auditory stimulation interferes with species-typical visual responsiveness in bobwhite quail chicks.

The effects that a manipulation of sensory experience may have on perceptual development are likely to depend on a number of factors, including the amount and the type of stimulation provided. To examine the relative influence of these stimulation factors on early perceptual organization, this study exposed bobwhite quail hatchlings to augmented amounts of bobwhite chick distress calls, bobwhite chick contentment calls, domestic chicken distress calls, or no additional auditory stimulation during the first 72 hr following hatching. Results showed that bobwhite hatchlings exposed to bobwhite chick distress calls do not exhibit species-typical visual responsiveness to maternal cues. In contrast, bobwhite hatchlings exposed to bobwhite chick contentment calls, domestic chicken hatchling distress calls, or no augmented auditory stimulation exhibited species-typical auditory and visual responsiveness to maternal cues. These results demonstrate intermodal effects of postnatal sensory stimulation and suggest that specific types of postnatal auditory stimulation, rather than simply increased amount of stimulation, are necessary to interfere with species-typical intersensory functioning.

Animal Communication↗
PubMed1994

Risk of entering nursing homes for long versus short stays.

Research on the risk of nursing home use has generally not distinguished between risk for long versus short stays. This paper presents an analysis of data from the 1982-84 National Long-Term Care Surveys to identify characteristics of disabled persons that predicted one or the other type of stay. Measures that are recognized to be strong predictors of nursing home use in general, such as dependencies in activities of daily living and cognitive impairment, were not significantly associated with admission for short stays. Results from the multivariate analysis were also used to make projections of lifetime risk of long and short stays. Approximately one-third of lifetime nursing home risk applies to stays of 90 days or less.

Activities of Daily Living↗
PubMed1992

Lysosomes as key organelles in the pathogenesis of prion encephalopathies.

The causation, structural origin, and mechanism of formation of spongiform lesions in transmissible encephalopathies are unknown. We have used immunogold electron microscopy to locate ubiquitin conjugates, hsp 70, and beta-glucuronidase (markers of the lysosomal compartment) and prion protein (PrP) in both control and scrapie-infected mouse brain. In scrapie-infected brain, lysosomes and lysosome-related structures (multivesicular and tubulovesicular dense bodies) are present in abnormally high numbers in neuronal cell processes. These structures contain PrP, together with the lysosomal markers ubiquitin conjugates, hsp 70, and beta-glucuronidase, which could also be identified spilling from tubulovesicular dense bodies into areas of early rarefaction in neuronal processes; we suggest that these areas of rarefaction are the precursor lesions of spongiform change. We advance the hypothesis that spongiform change is brought about by cytoskeletal disruption in neuronal processes caused by liberation of hydrolytic enzymes from lysosomes overloaded with the abnormal isoform of PrP (PrPsc). We suggest that the lysosomal system is probably acting as the bioreactor for processing of normal PrP to the abnormal isoform. The continuous production of increasing quantities of abnormal PrPsc in lysosome-related bodies will eventually cause disruption of the lysosomal membrane with destruction of the neuronal cytoskeleton and the initiation of vacuolation. Later, death of the cell will be associated with release of the PrPsc isoform into the extracellular environment. Repeated rounds of phagocytosis, lysosomal biogenesis of PrPsc, lysosomal membrane rupture, hydrolytic enzyme release, and neuronal lysis will lead to an exponential increase in cell damage and cell death.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Mutation spectrum of copper-induced DNA damage.

The ability of metal ions to damage DNA and cause mutagenesis has been analyzed with reversion and forward mutation assays using single-stranded DNA templates. We previously reported that incubation of phi X174 am3 DNA with Fe2+ in vitro results in mutagenesis when the treated DNA is transfected into Escherichia coli spheroplasts (Loeb, L. A., James, E. A., Waltersdorph, A. M., and Klebanoff, S. J. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 3918-3922, 1988). We now extend these studies to other metal ions. Of the metal ions tested, copper ions were the most mutagenic; the frequency of mutants produced was equal to or greater than that produced by Fe2+. Mutagenesis by Cu+ was diminished by catalase, mannitol, and superoxide dismutase suggesting the involvement of H2O2, hydroxyl ions, and superoxide, respectively. However, the findings that Cu+ and Cu2+ are nearly equally mutagenic and that the mutagenic activities are not completely inhibited by oxygen free radical scavengers make it unlikely that the mechanism for mutagenesis is simply the production of hydroxyl free radicals. The spectra of mutations produced by either copper ion using the lacZ gene as a target are very similar and differ from those reported with other agents. The predominant mutagenic sequence changes are single-base substitutions, the most frequent being replacement of a template C by a T. This transition presumably results from mispairing of an altered C with deoxyadenosine. Copper-induced mutations are not randomly distributed. Instead, they are found predominantly in clusters suggesting direct interaction of copper ions with specific nucleotide sequences in DNA. Evidence is considered that the high frequency of C----T transitions may be a common manifestation of DNA damage by oxygen radicals.

Bacteriophage phi X 174↗
PubMed1991

Pulmonary function studies in a newborn with congenital laryngeal atresia.

Congenital laryngeal atresia is a rare cause of upper airway obstruction that leads to death unless a surgical airway is immediately established. We were able to resuscitate a baby boy with laryngeal atresia by the placement of an 18-gauge plastic intravenous cannula into the trachea, connected in turn to a 3-mL syringe without the plunger, and then to the connector to a 7.0-mm endotracheal tube. This arrangement allowed hand ventilation and sufficient gas exchange until a formal tracheotomy was established minutes later. The baby boy had deficient abdominal musculature (without cryptorchidism or obstructive uropathy), bilateral inguinal hernias, and idiopathic hypercalcemia (since spontaneously resolved), but no other major anomalies. His survival allowed measurements of pulmonary function in lungs distal to an obstructed upper airway, an arrangement that mimics experiments that examine the influence of lung fluid volume and pressure on developing lungs. The baby's lungs had a forced vital capacity (FVC) in the upper limits of normal (not grossly enlarged lungs seen in newborn animals undergoing ligation of the trachea in utero). Maximal expiratory flow at 25% of FVC from residual volume (MEF25) was decreased, indicating airway obstruction involving smaller airways. Although direct laryngoscopy failed to find a opening in the larynx, some communication probably existed during development to allow some drainage of lung fluid. This opening, in the form of a persistent pharyngoglottic duct, prevented gross distention of the developing lung, but provided an insufficient airway at birth.

Airway Resistance↗
PubMed1991

Predicting nursing-home admission and length of stay. A duration analysis.

Information on who enters nursing homes and how much nursing-home care people use continues to be important for the consideration of various long-term care policies. Research on how characteristics of noninstitutionalized disabled elderly persons are related to both risk of admission and length of stay is presented here. Hazard models were developed using data from the 1982-84 National Long-Term Care Survey. Personal characteristics of elderly persons and state policy variables had varying effects on nursing-home use in a 2-year period.

Activities of Daily Living↗
PubMed1990

A randomized controlled trial of glucocorticoid prophylaxis against experimental rhinovirus infection.

The effects of combined intranasal and systemic glucocorticoid steroids on the local inflammatory response, and symptoms due to experimental rhinovirus infection were studied in 45 adults randomized to prophylaxis with either placebo or steroids. Intranasal beclomethasone (168 micrograms twice a day) was begun 4 days before viral challenge and continued 5 days after challenge. Oral prednisone (30 mg twice daily) was given for 3 days beginning 1 day before challenge. During the first 48 h after viral inoculation, nasal obstruction, nasal mucus weights, and kinin concentrations in nasal lavages were lower in steroid recipients, but subsequent increases in these variables in the steroid group resulted in no significant cumulative differences between treatment groups. These data suggest that steroid prophylaxis may suppress nasal inflammation and cold symptoms during the first 2 days in experimental rhinovirus colds.

Administration, Intranasal↗
PubMed1988

Lingual thyroid in a young infant presenting as airway obstruction: report of a case.

A case of lingual thyroid causing airway obstruction in a 3-month-old infant is reported. Endoscopic examination for stridor disclosed an obstructing 4 X 3 cm base of tongue lesion. Nuclear isotope scanning confirmed this to be the only thyroid tissue present in this patient. A transoral excision using the CO2 laser was performed without complication. Only one other case of airway obstruction in the young infant secondary to lingual thyroid has been reported, that being the original case description in 1869. A review of the embryology and discussion of the suggested therapies is presented. The rationale for use of the CO2 laser for this lesion is discussed.

Airway Obstruction↗