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Biomedical subjects

L Day

Publications and source records attributed to L Day.

At least 37 records · Page 2Linked to original sources
PubMed2000

Osmotic threshold and sensitivity for vasopressin release and fos expression by hypertonic NaCl in ovine fetus.

In adults, hyperosmolality stimulates central osmoreceptors, resulting in arginine vasopressin (AVP) secretion. Near-term fetal sheep have also developed mechanisms to respond to intravascular hypertonicity with stimulation of in utero AVP release. However, prior studies demonstrating fetal AVP secretion have utilized plasma tonicity changes greater than those required for adult osmotically induced AVP stimulation. We sought to examine near-term fetal plasma osmolality threshold and sensitivity for stimulation of AVP secretion and to correlate plasma hormone levels with central neuronal responsiveness. Chronically instrumented ovine fetuses (130 +/- 2 days) and maternal ewes simultaneously received either isotonic or hypertonic intravascular NaCl infusions. Maternal and fetal plasma AVP and angiotensin II (ANG II) levels were examined at progressively increasing levels of plasma hypertonicity. Intravenous hypertonic NaCl gradually elevated plasma osmolality and sodium levels. Both maternal and fetal plasma AVP increased during hypertonicity, whereas ANG II levels were not changed. Maternal AVP levels significantly increased with a 3% increase in plasma osmolality, whereas fetal plasma AVP significantly increased only at higher plasma osmolality levels (over 6%). Thus the slope of the regression of AVP vs. osmolality was greater for ewes than for fetuses (0.232 vs. 0.064), despite similar maternal and fetal plasma osmolality thresholds for AVP secretion (302 vs. 304 mosmol/kg). Hyperosmolality induced Fos immunoreactivity (FOS-ir) in the circumventricular organs of the fetal brain. FOS-ir was also demonstrated in the fetal supraoptic and paraventricular nuclei (SON and PVN), and double labeling demonstrated that AVP-containing neurons in the SON and PVN expressed Fos in response to intravenous NaCl. These results demonstrate that, in the ovine fetus at 130 days of gestation, neuroendocrine responses to cellular dehydration are functional, although they evidence a relatively reduced sensitivity for AVP secretion compared with the adult.

Age Factors↗
PubMed2000

Romantic acts and depression.

The aim of the present study was to provide an examination of the relationship between the importance individuals attach to romantic acts and depressive symptoms. Among 140 male and 160 female English undergraduate students, the importance individuals attach to romantic acts is significantly negatively correlated with higher scores on the Beck Depression Inventory and the Depression symptoms subscale of the General Health Questionnaire among the men only.

Adolescent↗
PubMed1999

Relationship between belief in good luck and general health.

62 undergraduate university students were administered the 12-item Belief in Good Luck Scale of Darke and Freedman and the General Health Questionnaire of Goldberg and Williams. Scores on belief in good luck showed a significant correlation of -.29 with anxiety and -.35 with depression but correlations were not significant for somatic symptoms (.15) and social dysfunction (.15).

Adolescent↗
PubMed1998

Dynamic calibration of mechanically, air- and electromagnetically braked cycle ergometers.

In this study we measured the accuracy of the following types of cycle ergometer against the criterion of a dynamic calibration rig (DCR): 35 friction-braked (Monark), 5 research-grade air-braked (Repco) and 5 electromagnetically braked (2 Siemens, 1 Elema-Schonander, 1 Ergoline, 1 Warren E. Collins). Monark ergometer power outputs over the range 58.9-353.2 W significantly (P < 0.001) underestimated those registered by the DCR with mean accuracies of 91.7-97.8%. The least accurate individual reading for each of the six up-scale (0-353.2 W) power outputs ranged from 81.6 to 91.6%; corresponding down-scale (353.2-0 W) accuracies were 85.1-92.5%. A hysteresis effect was furthermore evident for this ergometer in that up-scale measurements were significantly (P < 0.05) greater than down-scale ones. In addition, when the oldest [mean (SD): 11.3 (2.3) years old] and newest [1.4 (0.8) years old] eight ergometers were compared, the latter were significantly (P < 0.05) more accurate over the range 117.7-294.3 W. Apart from the two lowest power outputs of 47 W (62.2-96.0% accuracy) and 127 W (88.0-97.7% accuracy), the individual up-scale and down-scale accuracies of the Repco ergometers ranged from 98.0 to 104.2% for power outputs of 272.7-1137.8 W and the means were not significantly different from those of the DCR. There was also no evidence of hysteresis. Except for the initial power output of 50 W (40 rev/min: 83.8-99.2% accuracy; 60 rev/min: 93.2-122.6% accuracy), the individual accuracies of the electromagnetically braked ergometers ranged from 89.3 to 101.4% over the up-scale range of 100-400 W, and none of the means were significantly different from those of the DCR. The variability of individual errors for the preceding data emphasises that all cycle ergometers should be validated against the criterion of a DCR if accurate power outputs are required.

Atmosphere↗
PubMed1998

Physiology of somatosensory perception: cerebral lateralization and extinction.

OBJECTIVE: To demonstrate the effects of cerebral lateralization and temporal dynamics on somatosensory perception. BACKGROUND: We postulated that perceptual thresholds for simple somatosensory stimuli would be less in the left than the right hand, and that a left/right asymmetry in extinction would exist in healthy right-handed subjects (but not in left-handed subjects). During the course of these experiments we also examined the controversy concerning the temporal dynamics of somatosensory perception. METHODS: A total of 126 healthy subjects (age range, 6 to 73 years) participated in the study. Effects of handedness, age, vigilance, gaze, and temporal interval on somatosensory perception were examined in a series of experiments. Brief electric pulses were applied to the index finger of one or both hands. RESULTS: Perceptual thresholds are lower in the left than the right hand of healthy right-handed subjects in a large cohort across a wide age range. Left-handed subjects have no overall asymmetry. Even after compensation for baseline threshold differences, single stimuli in right-handed subjects are perceived more readily in the left than the right hand, and left-hand targets are more difficult to mask. Leftward eye/head gaze lowers thresholds in both hands of right-handed subjects (compared with right or straight gaze). Extinction was consistently maximal when the mask followed the target by 50 to 100 msec. CONCLUSIONS: The findings demonstrate clearly that left/right perceptual thresholds for simple somatosensory stimuli are asymmetric in healthy right-handed subjects. Both central and peripheral asymmetries exist. The central asymmetry and gaze effects are consistent with right cerebral dominance for externally directed attention. Access of somatosensory stimuli to conscious awareness is delayed and particularly vulnerable to disruption at 50 to 100 msec after onset of the stimulus.

Adolescent↗
PubMed1998

Helping children talk.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Ovine fetal laryngeal chemoreflex thresholds and respiratory effects.

In newborn infants, laryngeal contact with solutions of low chloride concentration or pH evokes swallowing, laryngeal adduction, and respiratory inhibition (laryngeal chemoreflex). To determine whether the laryngeal chemoreflex is present during fetal life and its effect on fetal respiratory activity, eight time-bred ewes (128 +/- 2 days) were prepared with fetal electrocortical diaphragm and esophageal electrodes and a nasopharyngeal catheter. After a 60-minute control period, increasing volumes (0.1 to 1.0 ml/kg) of 0.15 mol/L NaCl or distilled water (0.05 to 1.0 ml/kg) and decreasing concentrations of NaCl (0.15 to 0.02 mol/L) at a fixed volume (0.3 ml/kg) were sequentially administered through the nasopharyngeal catheter (38 degrees C). The minimum water volume that stimulated swallowing was significantly less than the minimum 0.15 mol/L NaCl volume (0.10 +/- 0.02 vs. 0.70 +/- 0.05 ml/kg). The maximum NaCl concentration that stimulated swallowing was 0.04 +/- 0.01 mol/L During the control period, respiratory activity averaged 14.6 +/- 0.7 breaths/minute and did not change during absent swallow responses or isotonic saline-induced swallows. However, respiratory activity significantly decreased during water (4.7 +/- 0.6 breaths/minute) and hypotonic saline-induced swallow responses (3.7 +/- 0.7 breaths/minute). Fetal electrocortical activity did not change during absent or stimulated swallows. We conclude that laryngeal water or hypotonic saline solution may stimulate fetal swallowing and suppress fetal respiratory activity, similar to the newborn laryngeal chemoreflex. We speculate that an exaggeration of the laryngeal chemoreflex apnea response in the newborn may predispose to sudden infant death syndrome.

Animals↗
PubMed1996

A controlled trial of idebenone in Huntington's disease.

One hundred patients with clinically diagnosed Huntington's disease (HD) were randomized to either idebenone, an antioxidant and enhancer of oxidative metabolism, or placebo, in a 1-year, double-blind, parallel-group study aimed at slowing the rate of progression of the disease. Ninety-one patients completed the study. There were no significant differences between groups on the primary outcome measures of the Huntington's Disease Activities of Daily Living Scale (ADL-an index of functional status) and the Quantified Neurologic Examination (QNE). Sample size calculations based on progression of the ADL and QNE in this study group revealed that a larger study group is necessary to detect any differences less than an almost complete halting of the disease. This argues for multicenter efforts for future therapeutic trials in HD.

Activities of Daily Living↗
PubMed1995

Principle-based ethics and nurses' attitudes towards artificial feeding.

Nurses often institute artificial feeding for patients who would otherwise starve. Recently, the courts in the United States have favoured withholding or withdrawing feedings from patients who currently refuse or previously gave some indication they would refuse artificial nutrition and hydration. This paper investigates under what circumstances nurses feel justified in withholding artificial nutrition and hydration. Structured interviews were conducted with 40 cancer care nurses from two sites, and 40 dementia care nurses from two sites. The interviews were based on two vignettes, one involving an alert patient with terminal cancer, the other a patient suffering end-stage Alzheimer's dementia, and were analysed for themes coinciding with principles of deontological ethics. Investigators found that autonomy, beneficence and non-maleficence most often guided nurses' decisions to withhold or implement artificial feeding.

Arizona↗
PubMed1995

Practical limits to the uniform determination of death act.

Death is a transition laden with meaning. Rather than overrule a common lifeworld understanding of death with scientific criteria, a process of involvement and interpretation might help health-care practitioners understand what death means for the family and the patient and possibly allow all to come to some shared agreement on appropriate treatment. The UDDA was offered as a way to standardize the practice of diagnosing death based on brain-related criteria. While these criteria may be essential to recognizing death in certain circumstances, they should not be used as the final word on withdrawal of life-support in the absence of or in place of an understanding with the patient's family.

Brain Death↗
PubMed1994

The dynamic calibration of cycle ergometers.

The components of our rig, which is used for the dynamic calibration of cycle ergometers, were purchased for $4,080 (USA); interfacing the instrument with a computer and printer increased the cost by an additional $2,550 (USA). The rig is essentially a torque balance and was therefore validated against the primary measurements of: angular velocity (rev.min-1), distance (m) and mass (kg). Summing the inaccuracies associated with these 3 measurements yields a worst case error of only 0.3%. The coefficients of variation for a dynamic calibration rig and mechanically braked Monark cycle ergometer assembly ranged from 0.6 to 3.2% for 6 trials at each of the following power outputs: 117.7, 176.6, 235.4, 294.3 and 353.2 W. The instrument therefore has a high degree of precision.

Calibration↗
PubMed1994

Analysis of hydrolytic products from choline-labeled host cell phospholipids during growth of Rickettsia prowazekii.

A phospholipase activity has been associated with the interaction of Rickettsia prowazekii with the surface of erythrocytes and competent host cells as well as during the growth of the rickettsiae within their host cells. Both fatty acid and lysophosphatides have been found in the interaction of rickettsiae with the surface of eucaryotic cells; this finding provided strong evidence for the activity of a phospholipase A. However, fatty acids, but not lysophosphatides, were found during the growth of rickettsiae within cells in which the phospholipids had been radiolabeled with oleic acid; this observation left the type of phospholipase activity in doubt. In this study, the water-soluble components of phospholipid hydrolysis by phospholipase A plus lysophospholipase and phospholipase C were determined following the growth of rickettsiae in host cells in which the phospholipids had been radiolabeled with choline. In infected cells relative to mock-infected cells, there was a loss of phosphatidylcholine with a corresponding increase not in lysophosphatidylcholine but in the water-soluble components. There was a large increase in glycerylphosphorylcholine (185%) and a smaller increase in phosphorylcholine (16%). These results indicate that both phospholipase A activity (plus a lysophospholipase activity) and phospholipase C were increased during infection by R. prowazekii and that the former was the predominant activity.

Animals↗
PubMed1994

Ovine fetal swallowing and renal responses to oligohydramnios.

Amniotic fluid (AF) volume regulation is dependent on a balance between fluid production and fluid resorption. We examined the effects of reduced AF volume on AF production by fetal urine and resorption by fetal swallowing and the response of these parameters to AF volume replacement. Eight time-dated pregnant ewes (125 +/- 1 days gestation) were studied before (day 1) and after (day 3) AF and fetal urine drainage. Drainage resulted in a significant decrease in AF volume (415 +/- 89 to 157 +/- 36 ml). Fetal urine osmolality increased (139 +/- 10 to 286 +/- 33 mosmol/kgH2O), while urine flow did not change significantly (0.31 +/- 0.04 to 0.23 +/- 0.06 ml/min), resulting in nonsignificant increases in osmolar, sodium, and chloride excretions. Fetal electromyographic swallowing activity decreased 30% (1.0 +/- 0.1 to 0.7 +/- 0.1 swallows/min; P < 0.05), while net esophageal flow decreased 74% (0.31 +/- 0.12 to 0.07 +/- 0.04 ml/min; P < 0.05). On day 4, 0.15 M NaCl (500 ml; 37 degrees C) was administered into the AF over 30 min. During the 2 h after reinfusion, urine flow (0.29 +/- 0.07 to 0.40 +/- 0.09 ml/min) and osmolar sodium and chloride excretion significantly increased, though fetal swallowing activity and esophageal flow did not change. Thus the ovine fetus responded to reduced AF volume by maintaining AF production and decreasing AF resorption. In response to AF replacement, urine flow increased while fetal swallowing activity did not change, consistent with an intramembranous pathway for fetal AF resorption.

Amniotic Fluid↗
PubMed1993

Effect of gamma interferon on phospholipid hydrolysis and fatty acid incorporation in L929 cells infected with Rickettsia prowazekii.

Treatment of Rickettsia prowazekii-infected L929 cells with gamma interferon (IFN-gamma) immediately after infection altered the lipid metabolism of the host cells as determined by measurement of phospholipid hydrolysis and oleic acid incorporation into phospholipids and neutral lipids. At 48 h postinfection, there was increased phospholipid hydrolysis in infected cultures relative to mock-infected cultures and a further increase in radiolabeled phospholipid hydrolysis in IFN-gamma-treated infected cultures. Oleic acid, the radiolabeled product of hydrolysis, was found in both the free fatty acid and neutral lipid fractions. None of the mock-infected cultures demonstrated increased hydrolysis of their radiolabeled phospholipids in response to treatment with IFN-gamma. Most of the radiolabeled oleic acid incorporated into cultures in the interval between 24 and 48 h after infection and IFN-gamma treatment was present in the phospholipid fraction. However, the neutral lipid fraction from the infected cultures that had been IFN-gamma treated was labeled to a greater extent than that from the untreated cultures. Thin-layer chromatographic analysis of the neutral lipid fractions from both the hydrolysis and incorporation experiments demonstrated that most of the radiolabel was in triglycerides. The infected cultures at 30 h were intact as assessed by the exclusion of trypan blue, but at 48 h postinfection in the IFN-gamma-treated infected cultures more than half of the cells were unable to exclude trypan blue. In no case did the mock-infected cells show substantial damage as a result of IFN-gamma treatment.

Animals↗
PubMed1993

Maternal/fetal dehydration: prolonged effects and responses to oral rehydration.

Dehydration induces marked alterations in maternal-fetal fluid homeostasis and accompanying fetal endocrine responses. We sought to determine if the increase in fetal plasma arginine vasopressin (AVP) levels during maternal dehydration is mediated by fetal plasma hypovolemia in addition to hyperosmolality and to examine maternal and fetal plasma atrial natriuretic factor (ANF) responses to maternal dehydration and oral rehydration. Seven pregnant ewes (127 +/- 1 day) were water deprived for 72-96 h, and five of these were orally rehydrated. Dehydration induced significant increases in maternal plasma osmolality (pOSM) (300 +/- 2 to 325 +/- 8 mosmol/kg) and AVP (3.0 +/- 0.4 to 18.9 +/- 4.0 pg/ml), and decreases in plasma ANF levels (28.1 +/- 3.1 to 19.7 +/- 3.1 pg/ml). Fetal pOSM (293 +/- 3 to 314 +/- 4 mosmol/kg), AVP (2.5 +/- 0.6 to 8.1 +/- 4.8 pg/ml), and urinary fractional sodium excretion increased significantly, whereas plasma ANF and fetal blood volume did not change. After maternal water access maternal plasma AVP decreased rapidly in comparison to the gradual decrease in maternal pOSM. Fetal plasma AVP levels did not change significantly and fetal pOSM decreased more slowly than maternal pOSM. Fetal plasma ANF increased in association with increased urine flow and glomerular filtration rate after maternal rehydration. These data indicate marked differences in fetal and maternal plasma ANF and AVP responses with dehydration-induced increases in fetal plasma AVP being secondary to plasma hyperosmolality, rather than hypovolemia. Rapid suppression of maternal plasma AVP may contribute to the slower equilibration of fetal pOSM during oral, as compared with intravenous, maternal rehydration.

Animals↗