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Biomedical subjects

J M Thompson

Publications and source records attributed to J M Thompson.

At least 55 records · Page 3Linked to original sources
PubMed1999

Hyponatremia in ultradistance triathletes.

PURPOSE: Hyponatremia ([plasma sodium] <135 mmol x L(-1)) is a potentially serious complication of ultraendurance sports. However, the etiology of this condition is still uncertain. This observational cohort study aimed to determine prospectively the incidence and etiology of hyponatremia in an ultradistance triathlon. METHODS: The subjects consisted of 605 of the 660 athletes entered in the New Zealand Ironman triathlon (3.8-km swim, 180-km cycle, and 42.2-km run). Subjects were weighed before and after the race. A blood sample was drawn for measurement of plasma sodium concentration after the race. RESULTS: Complete data on pre- and postrace weights and plasma sodium concentrations were available in 330 race finishers. Postrace plasma sodium concentrations were inversely related to changes in body weight (P = 0.0001). Women (N = 38) had significantly lower plasma sodium concentrations (133.7 vs 137.4 mmol x L(-1); P = 0.0001) than men (N = 292) and lost significantly less relative weight (-2.7 vs -4.3%; P = 0.0002). Fifty-eight of 330 race finishers (18%) were hyponatremic; of these only 18 (31%) sought medical care for the symptoms of hyponatremia (symptomatic). Eleven of the 58 hyponatremic athletes had severe hyponatremia ([plasma sodium] < 130 mmol x L(-1)); seven of these 11 severely hyponatremic athletes were symptomatic. The relative body weight change of the 11 severely hyponatremic athletes ranged from 2.4% to +5%; eight (73%) of these athletes either maintained or gained weight during the race. In contrast, relative body weight changes in the 47 athletes with mild hyponatremia ([plasma sodium] 130-134 mmol x L(1)) were more variable, ranging from -9.25% to +2.2%. CONCLUSIONS: Hyponatremia is a common biochemical finding in ultradistance triathletes but is usually asymptomatic. Although mild hyponatremia was associated with variable body weight changes, fluid overload was the cause of most (73%) cases of severe, symptomatic hyponatremia.

Adult↗
PubMed1999

Molecular characterization of the hemin uptake locus (hmu) from Yersinia pestis and analysis of hmu mutants for hemin and hemoprotein utilization.

Sequence analysis of the hemin uptake locus (hmu) of Yersinia pestis revealed five genes, hmuRSTUV, required for use of hemin and hemoproteins as iron sources. The translated gene products have homologies with proteins of the hemin transport genes of several gram-negative bacteria. Promoters were identified upstream of hmuP'R (p1) and upstream of hmuS (p2); p1, which contains a Fur box, is regulated by iron and Fur, while p2 exhibits weak, but constitutive, activity. HmuR, which has homology with TonB-dependent outer membrane (OM) receptors, is localized to the OM of Y. pestis and is required for utilizing hemin and all hemoproteins under iron-depleted conditions. The proposed ABC transporter, HmuTUV, is necessary for use of hemin, hemin-albumin, and myoglobin, but not hemoglobin, hemoglobin-haptoglobin, or heme-hemopexin, as iron sources. In the absence of HmuTUV, HmuS, a cytoplasmic protein, is involved in use of hemoglobin and heme-hemopexin. In mice, the 50% lethal doses of Y. pestis DeltahmuP'RSTUV mutants injected subcutaneously or retro-orbitally did not differ from that of the Hmu(+) parent strain. Thus, the hmu system is not essential for infection in mice via these routes. Growth studies showed that a DeltahmuP'RSTUV mutant could grow in iron-depleted medium containing high concentrations of hemoglobin, suggesting that an Hmu-independent, lower-affinity hemoglobin uptake system may exist.

Amino Acid Sequence↗
PubMed1999

Understanding variation in resident needs and services in homes for adults.

Long term care in the U.S. has been influenced greatly by the emergence and growth of alternatives to traditional nursing homes. Adult homes provide personal care and assistance to an increasing number of elderly and represent a growth sector of long term care services. However, adult homes have not been discussed widely in the healthcare literature. This paper summarizes findings from a study of adult homes and profiles their operating characteristics, services, and resident needs. Findings indicate differences between licensed and unlicensed homes for adults in terms of the needs of their residents, use of external resources and referral to other sources of care. Implications for coordination of care for the elderly are addressed.

Activities of Daily Living↗
PubMed1999

Sex differences in self-silencing.

The construct of self-silencing was proposed to account for women's greater vulnerability to developing depression. This study of 1,117 students (795 women and 322 men) explored possible explanations for the empirical finding that men self-silence to the same or greater extent than women. Analysis showed that men reported more self-silencing than women. A factor analysis confirmed the subscale structure of the Silencing the Self Scale for women and men, with relatively few departures from the originally proposed subscales. Depression and self-silencing scores were correlated positively for both men and women. The results of two multiple regressions, performed separately for men and women, showed that depressive symptomatology accounted for a significant percentage of the variance in self-silencing but that social desirability did not account for a significant increment in the variance accounted for in silencing the self. The scores on the Care as Self-sacrifice and the Divided Self subscales were intercorrelated for women, but not for men, indicating that there may be a sex difference in perception of self-silencing behavior.

Adolescent↗
PubMed1999

RpoS function in Salmonella Typhimurium LT2 monitored in a skim milk model food.

In Salmonella Typhimurium, the stationary phase sigma factor RpoS regulates the expression of genes associated with adaptation, survival, and virulence. Expression of rpoS is known to be under environmental control and yet, to date, there have been no studies that assess the expression of this global regulator in real food systems. Skim milk represents a useful model food; using an spvRA::luxCDABE reporter construct, we have determined RpoS availability from an inoculum of Salmonella Typhimurium LT2. We report that RpoS activity increases exponentially at the end of the logarithmic phase of growth, consistent with data from nutrient media.

Animals↗
PubMed1998

Ursodiol prophylaxis against hepatic complications of allogeneic bone marrow transplantation. A randomized, double-blind, placebo-controlled trial.

BACKGROUND: Hepatic complications are a major cause of illness and death after bone marrow transplantation. OBJECTIVE: To confirm the results of a pilot study that indicated that ursodiol prophylaxis could reduce the incidence of veno-occlusive disease of the liver. DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: Tertiary care teaching hospital. PATIENTS: 67 consecutive patients undergoing transplantation with allogeneic bone marrow (donated by a relative) in whom busulfan plus cyclophosphamide was used as the preparative regimen and cyclosporine plus methotrexate was used to prevent graft-versus-host disease. INTERVENTION: Before the preparative regimen was started, patients were randomly assigned to receive ursodiol, 300 mg twice daily (or 300 mg in the morning and 600 mg in the evening if body weight was > 90 kg), or placebo. MEASUREMENTS: Patients were prospectively evaluated for the clinical diagnosis of veno-occlusive disease, the occurrence of acute graft-versus-host disease, and survival. RESULTS: The incidence of veno-occlusive disease was 40% (13 of 32 patients) in placebo recipients and 15% (5 of 34 patients) in ursodiol recipients (P = 0.03). Assignment to placebo was the only pretransplantation characteristic that predicted the development of veno-occlusive disease. The most significant predictor of 100-day mortality was the diagnosis of veno-occlusive disease. The difference in actuarial risk for hematologic relapse in patients with chronic myelogenous leukemia and nonhepatic toxicities between the two groups was not statistically significant (13% in the ursodiol group and 20% in the placebo group; P > 0.2). CONCLUSION: Ursodiol prophylaxis seemed to decrease the incidence of hepatic complications after allogeneic bone marrow transplantation in patients who received a preparative regimen with busulfan plus cyclophosphamide.

Adult↗
PubMed1998

Panic disorder: coronary spasm as a basis for cardiac risk?

Patients with panic disorder often complain of angina-like chest pain during panic attacks, but this is not usually considered life-threatening. We describe three patients with panic disorder and documented cardiac ischaemia during episodes of chest pain. In two, it progressed to myocardial infarction. As none had atherosclerosis evident at coronary angiography, the mechanism was presumed to be coronary artery spasm. These cases illustrate that pain typical of angina during panic attacks may have an organic cause.

Adult↗
PubMed1998

Risk factors for preterm birth: a New Zealand study.

AIM: To identify risk factors for preterm birth. METHODS: A cross sectional study. The study population was 1800 infants selected randomly from all babies born over a three-year period. Of these, 85 (4.8%) were classified preterm (less than 37 completed weeks gestation). Data were collected from obstetric records and parental interviews. RESULTS: Risk factors associated with an increased risk of preterm birth after controlling for potential confounders included smoking during pregnancy (adjusted relative risk (RR) = 2.7, 95% confidence interval (CI) = 1.3, 5.4), and multiple birth (adjusted RR = 48.8, 95% CI = 18.1, 131.4). Urinary tract infection was significant at the 7% level (adjusted RR = 2.3, 95% CI = 1.0, 5.6). Alcohol intake in third trimester was associated with a reduced risk of preterm birth (adjusted RR = 0.4, 95% CI = 0.2, 0.7). CONCLUSION: Maternal smoking and multiple births were the most important modifiable risk factors in this study for preterm birth and may contribute to 17% and 11% of preterm births respectively.

Cross-Sectional Studies↗
PubMed1998

Sympathetic activity in patients with panic disorder at rest, under laboratory mental stress, and during panic attacks.

BACKGROUND: The sympathetic nervous system has long been believed to be involved in the pathogenesis of panic disorder, but studies to date, most using peripheral venous catecholamine measurements, have yielded conflicting and equivocal results. We tested sympathetic nervous function in patients with panic disorder by using more sensitive methods. METHODS: Sympathetic nervous and adrenal medullary function was measured by using direct nerve recording (clinical microneurography) and whole-body and cardiac catecholamine kinetics in 13 patients with panic disorder as defined by the DSM-IV, and 14 healthy control subjects. Measurements were made at rest, during laboratory stress (forced mental arithmetic), and, for 4 patients, during panic attacks occurring spontaneously in the laboratory setting. RESULTS: Muscle sympathetic activity, arterial plasma concentration of norepinephrine, and the total and cardiac norepinephrine spillover rates to plasma were similar in patients and control subjects at rest, as was whole-body epinephrine secretion. Epinephrine spillover from the heart was elevated in patients with panic disorder (P=.01). Responses to laboratory mental stress were almost identical in patient and control groups. During panic attacks, there were marked increases in epinephrine secretion and large increases in the sympathetic activity in muscle in 2 patients but smaller changes in the total norepinephrine spillover to plasma. CONCLUSIONS: Whole-body and regional sympathetic nervous activity are not elevated at rest in patients with panic disorder. Epinephrine is released from the heart at rest in patients with panic disorder, possibly due to loading of cardiac neuronal stores by uptake from plasma during surges of epinephrine secretion in panic attacks. Contrary to popular belief, the sympathetic nervous system is not globally activated during panic attacks.

Adrenal Medulla↗
PubMed1998

Sheepskin bedding and the sudden infant death syndrome. New Zealand Cot Death Study Group.

We carried out a nationwide case-control study, comparing 393 case patients with sudden infant death syndrome (SIDS) with 1592 control subjects, in order to examine sheepskin bedding as a risk factor. Sheepskin use was similar for case patients and control subjects (both, 42%; adjusted odds ratio [OR] = 1.28; 95% CI = 0.92, 1.79). Sheepskin use among the control subjects was associated with socioeconomic advantage. The relative risk for SIDS with sheepskin use was significantly increased in the infants placed prone to sleep (adjusted OR = 1.70; 95% CI = 1.08, 2.67), but not for infants placed in the supine or lateral position (adjusted OR = 0.82; 95% CI = 0.45, 1.48). An interaction between sheepskin use and bed sharing was also found. Sheepskin use was associated with a decreased risk of SIDS among infants sharing beds (adjusted OR = 0.61; 95% CI = 0.38, 0.99), but an increased risk among infants not bed sharing (adjusted OR = 2.25; 95% CI = 1.32, 3.86). We conclude that if an infant needs to be placed prone to sleep for medical reasons, a sheepskin should not be used as underbedding. However, for infants placed supine to sleep, sheepskins are not associated with an increased risk of SIDS.

Animals↗
PubMed1998

Human muscle sympathetic activity and cardiac catecholamine spillover: no support for augmented sympathetic noradrenaline release by adrenaline co-transmission.

1. Evidence from animal studies indicates that circulating adrenaline may be taken up into sympathetic nerves, facilitating the release of noradrenaline. To test whether adrenaline acts as a co-transmitter in humans we studied eight healthy men (aged 19-23 years) during isometric handgrip before and after an adrenaline infusion (1-3 micrograms/min for > 30 min). Sympathetic activity was assessed using radiotracer kinetic techniques to measure total and cardiac spillovers of noradrenaline and adrenaline, and microneurography to measure muscle sympathetic activity. 2. During the adrenaline infusion systolic blood pressure and heart rate increased significantly and diastolic blood pressure decreased. Total noradrenaline spillover, and arterial and coronary sinus plasma noradrenaline concentrations, increased significantly. Muscle sympathetic nerve traffic increased both during and after the end of the infusion. 3. Thirty minutes after the end of the adrenaline infusion there was adrenaline release from the heart (1.5 +/- 0.4 ng/min, mean +/- S.E.M.) indicating that significant adrenaline loading of cardiac sympathetic nerves had occurred. At this time muscle sympathetic nerve traffic and total body and cardiac noradrenaline spillovers were similar (P > 0.05) to pre-adrenaline infusion values (nerve traffic 24 +/- 4 versus 21 +/- 3 bursts/min; total noradrenaline spillover 698 +/- 98 versus 618 +/- 119 ng/min; cardiac noradrenaline spillover 16.2 +/- 2.8 versus 13.9 +/- 3.9 ng/min). 4. Isometric handgrip contraction evoked similar responses pre- and post-adrenaline infusion in total and cardiac noradrenaline spillovers and in muscle sympathetic activity. 5. The results do not support the theory that adrenaline is a co-transmitter facilitating noradrenaline release from human sympathetic nerves.

Adult↗
PubMed1998

Internal jugular venous spillover of noradrenaline and metabolites and their association with sympathetic nervous activity.

It is recognized that the brain plays a pivotal role in the maintenance of blood pressure and the control of myocardial function. By combining direct sampling of internal jugular venous blood with a noradrenaline isotope dilution method, for examining neuronal transmitter release, and microneurographic nerve recording, we were able to quantify the release of central nervous system noradrenaline and its metabolites and investigate their association with efferent sympathetic nervous outflow in healthy subjects and patients with pure autonomic failure. To further investigate the relationship between brain noradrenaline, sympathetic nervous activity and blood pressure regulation we examined brain catecholamine turnover, based on the internal jugular venous overflow of noradrenaline and its principal central nervous system metabolites, in response to a variety of pharmacological challenges. A substantial increase was seen in brain noradrenaline turnover following trimethaphan, presumably resulting from a compensatory response in sympathoexcitatory forebrain noradrenergic neurones in the face of interruption of sympathetic neural traffic and reduction in arterial blood pressure. In contrast, reduction in central nervous system noradrenaline turnover accompanied the blood pressure fall produced by intravenous clonidine administration, thus representing the blood pressure lowering action of the drug. Following vasodilatation elicited by intravenous adrenaline infusion, brain noradrenaline turnover increased in parallel with elevation in muscle sympathetic nervous activity. While it is difficult to assess the source of the noradrenaline and metabolites determined in our studies, available evidence implicates noradrenergic cell groups of the posterolateral hypothalamus, amygdala, the A5 region and the locus coeruleus as being involved in the regulation of sympathetic outflow and autonomic cardiovascular control.

Adolescent↗
PubMed1998

Sleeping position, breastfeeding, bedsharing and passive smoking in 3-month-old Swedish infants.

Parents of 1028 infants who attended community-based infant health clinics were interviewed concerning infant sleeping position, feeding habits, bedsharing and passive smoking at 3 months of postnatal age. In addition, they were asked to state which source of information had mainly influenced them in the choice of the sleeping position. Fifteen per cent of the infants were regularly laid to sleep in the prone position, compared with 72% (1991) before official guidelines concerning infant sleeping position were issued. The overall prevalence of exclusive breastfeeding was 70.4%. Prevalence of maternal smoking was 17.9% and 22.8% of the infants were regularly bedsharing with the parents. Those mothers who did not comply with official recommendations regarding infant sleeping position were also less likely to follow other recommendations concerning infant care practices. Prone sleeping infants were more likely to be formula fed and exposed to passive smoking, and hence associated with additional risk factors for sudden infant death syndrome.

Breast Feeding↗
PubMed1998

0.125% ropivacaine is similar to 0.125% bupivacaine for labor analgesia using patient-controlled epidural infusion.

UNLABELLED: We compared the effects of 0.125% ropivacaine with 0.125% bupivacaine in laboring patients using patient-controlled epidural analgesia (PCEA). Fifty-one ASA physical status I or II term parturients with functioning epidural catheters were randomized to receive ropivacaine or bupivacaine using a prospective, double-blind design. Basal infusions (6 mL/h) were supplemented with patient-controlled boluses (5 mL) every 10 min as required. For inadequate analgesia, patients were administered 10-mL boluses of study solution until comfortable. There were no differences in verbal pain scores, amount of local anesthetics used, sensory levels, motor blockade, labor duration, mode of delivery, side effects, or patient satisfaction between the two local anesthetics. We conclude that 0.125% ropivacaine and bupivacaine are clinically indistinguishable and are both highly effective for labor analgesia using PCEA. IMPLICATIONS: This study compared labor analgesia from 0.125% ropivacaine and 0.125% bupivacaine using patient-controlled epidural analgesia. We found no significant differences in local anesthetic use, analgesic characteristics, or side effects between 0.125% ropivacaine and 0.125% bupivacaine. We conclude that these two drugs are clinically indistinguishable at this concentration.

Adult↗
PubMed1998

Rat alpha3/beta4 subtype of neuronal nicotinic acetylcholine receptor stably expressed in a transfected cell line: pharmacology of ligand binding and function.

We stably transfected human kidney embryonic 293 cells with the rat neuronal nicotinic acetylcholine receptor (nAChR) alpha3 and beta4 subunit genes. This new cell line, KXalpha3 beta4R2, expresses a high level of the alpha3/beta4 receptor subtype, which binds (+/-)- [3H]epibatidine with a Kd value of 304+/-16 pM and a Bmax value of 8942 +/- 115 fmol/mg protein. Comparison of nicotinic drugs in competing for alpha3/beta4 receptor binding sites in this cell line and the binding sites in rat forebrain (predominantly alpha4/beta2 receptors) revealed marked differences in their Ki values, but similar rank orders of potency for agonists were observed, with the exception of anatoxin-A. The affinity of the competitive antagonist dihydro-beta-erythroidine is >7000 times higher at alpha4/beta2 receptors in rat forebrain than at the alpha3/beta4 receptors in these cells. The alpha3/beta4 nAChRs expressed in this cell line are functional, and in response to nicotinic agonists, 86Rb+ efflux was increased to levels 8-10 times the basal levels. Acetylcholine, (-)-nicotine, cytisine, carbachol, and (+/-)-epibatidine all stimulated 86Rb+ efflux, which was blocked by mecamylamine. The EC50 values for acetylcholine and (-)-nicotine to stimulate 86Rb+ effluxes were 114 +/- 24 and 28 +/- 4 microM, respectively. The rank order of potency of nicotinic antagonists in blocking the function of this alpha3/beta4 receptor was mecamylamine > d-tubocurarine > dihydro-beta-erythroidine > hexamethonium. Mecamylamine, d-tubocurarine, and hexamethonium blocked the function by a noncompetitive mechanism, whereas dihydro-beta-erythroidine blocked the function competitively. The KXalpha3 beta4R2 cell line should prove to be a very useful model for studying this subtype of nAChRs.

Animals↗
PubMed1998

Chitinolytic activity in Chromobacterium violaceum: substrate analysis and regulation by quorum sensing.

Quorum sensing control mediated by N-acyl homoserine lactone (AHL) signaling molecules has been established as a key feature of the regulation of exoenzyme production in many gram-negative bacteria. In Chromobacterium violaceum ATCC 31532 a number of phenotypic characteristics, including production of the purple pigment violacein, hydrogen cyanide, antibiotics, and exoproteases are known to be regulated by the endogenous AHL N-hexanoyl-L-homoserine lactone (HHL). In this study we show that C. violaceum produces a set of chitinolytic enzymes whose production is regulated by HHL. The chitinolytic activity was induced in strains grown in the presence of chitin as the sole carbon source and quantitated in the secreted proteins by using p-nitrophenol analogs of disaccharide, trisaccharide, and tetrasaccharide oligomers of N-acetylglucosamine. By using 4-methylumbelliferyl analogs of the same oligomers of N-acetylglucosamine as substrates for proteins separated and renatured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, at least six enzymes were detected: a chitobiase with high specificity to a dimeric substrate of 87 kDa, two N-acetylglucosaminidases with apparent molecular masses of 162 and 133 kDa, two endochitinases of 108 and 67 kDa, and a chitobiosidase of 56 kDa. In addition, two unidentified bands of >205 kDa were found where a tetrameric chitin derivative was used as a substrate. A pleiotropic mini-Tn5 mutant of C. violaceum (CV026) that is defective in HHL production and other quorum-sensing-regulated factors was also found to be completely deficient in chitinolytic activity. Growth of this mutant on minimal medium with chitin supplemented with culture supernatant from the C. violaceum wild-type strain or 10 microM synthetic HHL restored chitinase production to the level shown by the parental strain. These results constitute the most complete evidence so far for regulation of chitinolytic activity by AHL signaling in a gram-negative bacterium.

Acetylglucosaminidase↗
PubMed1998

Acute changes in trabecular bone connectivity and osteoclast activity in the ovariectomized rat in vivo.

Estrogen deficiency results in a loss of trabecular bone mass and structure that leads to an increased incidence of osteoporotic fractures. The purpose of this study was to determine the time course for trabecular structure deterioration and changes in bone turnover just after ovariectomy in the rat. Six-month-old female virgin Sprague-Dawley rats had their right proximal tibia scanned by X-ray tomographic microscopy (XTM) at baseline (day 0). Animals were then randomized into two groups, and in each group 9 were sham-operated and 11 were ovariectomized and had repeat XTM scans on days 5, 13, 29, and 42 postovariectomy in group 1 and on days 8, 13, 33, and 50 postovariectomy in group 2. Urine was collected for deoxypyridinoline (DPD) cross-link measurements 24 h before each XTM scan and analyzed by ELISA. Trabecular bone structural variables and bone turnover endpoints were calculated from XTM data and standard histomorphometry. Trabecular connectivity decreased 27% by days 5 and 8 postovariectomy (p < 0.01) and continued to decrease up to day 50 postovariectomy (p < 0.01). The trabecular bone volume decreased 25% by 8 days postovariectomy (p < 0.01), and it continued to decrease through day 50. DPD cross-link excretion had increased 37% on day 13 (p < 0.01) and by over 100% of baseline by day 50 postovariectomy. Trabecular bone connectivity and volume deteriorate rapidly while DPD cross-link excretion increased more slowly in acute estrogen deficiency. These data suggest that if an agent is to preserve fully trabecular bone structure, it must be instituted very early in the estrogen-deficient state. They also suggest that a lag time exists before DPD excretion properly mirrors newly induced conditions of high bone turnover in this rat model.

Amino Acids↗