Search PubMed⌕ Search

Biomedical subjects

J Davis

Publications and source records attributed to J Davis.

At least 235 records · Page 13Linked to original sources
PubMed1994

Why do ambiguous figures reverse?

For much of this century the dominant theory of reversal of ambiguous figures has been neural satiation. We suggest a very different kind of theory based on the consequences of the typical instructions given to subjects in experiments on reversal. In analyzing these instructions in preliminary experiments we conclude that what matters is the subject's knowledge that the figure is reversible and specific knowledge of how its alternative construals appear. This leads to an intention to reverse the figure. In one experiment we demonstrate that recent experience with the ambiguous figure and its two modes of appearance does not lead to its reversal if the subject does not know the figure is reversible. In another experiment we demonstrate that when the subject does know the ambiguous figure is reversible, it nonetheless will not tend to reverse if the intention to do so is contravened by a different intention. We suggest that the intention to reverse cannot succeed unless the subject "knows" how to carry it out and, further, that the intention may become involuntary and automatic.

Female↗
PubMed1994

Moderate hypoglycemia impairs the function of the inferior colliculus in the awake rat.

To assess the effect of acute hypoglycemia on the brain stem auditory pathway, we implanted electrodes into the inferior colliculus (IC) and subsequently recorded auditory-evoked potentials from the IC (ICEP) and brain stem (BAEP) in normal awake rats during euglycemic and hypoglycemic hyperinsulinemia (2 hours). Latencies of the ICEP and peak V of the BAEP were significantly prolonged by hypoglycemia (approximately 2.7 mmol/L). The change in the BAEP was principally between peak III and peak V. suggesting an effect in or near the IC. ICEP and BAEP latencies did not change during euglycemic hyperinsulinemia. We conclude that the function of the IC is very sensitive to episodes of moderate hypoglycemia. These data provide direct evidence that the scope of adverse central nervous system effects resulting from hypoglycemia extends beyond cognitive centers to include the brain stem.

Acute Disease↗
PubMed1994

A study on the effects of low haemoglobin on postnatal women.

OBJECTIVE: to assess the effect of low haemoglobin (Hb) on the mental and physical health of postnatal women. DESIGN: survey conducted between May 1991 and February 1992. SETTING: maternity unit in district general hospital in the UK. PARTICIPANTS: 1010 postnatal women who had delivered a live baby, did not stay in hospital for seven or more days postnatally, whose baby was not admitted to the neonatal unit and who did not have a current psychiatric disorder. MEASUREMENTS: Hb levels at 'booking', 34 weeks gestation, three days and six weeks post delivery; the Edinburgh Postnatal Depression Scale (EPDS) and a self-completion questionnaire at ten days, four weeks and six weeks post delivery. FINDINGS: women with a low Hb are more likely to be under 25 years of age, primiparous, be anaemic at 34 weeks gestation, not to have had a normal delivery, have had a blood loss greater than 250 ml and to have had heavy lochia postnatally. Low Hb levels were not associated with high EPDS scores. Low Hb levels were related to reports of low energy, breathlessness, faintness/dizziness, painful perineal sutures and tingling in fingers and toes at ten days post delivery. Whilst tiredness persisted to six weeks post delivery the other symptoms disappeared. IMPLICATIONS FOR PRACTICE: in order to reduce the incidence of postnatal anaemia a review of policies for testing is recommended so that the incidence of physical problems in the first six weeks can be reduced. There is a need for further research into the causes and potential alleviation of tiredness.

Adolescent↗
PubMed1994

Polyribosome targeting to microtubules: enrichment of specific mRNAs in a reconstituted microtubule preparation from sea urchin embryos.

A subset of mRNAs, polyribosomes, and poly(A)-binding proteins copurify with microtubules from sea urchin embryos. Several lines of evidence indicate that the interaction of microtubules with ribosomes is specific: a distinct stalk-like structure appears to mediate their association; ribosomes bind to microtubules with a constant stoichiometry through several purification cycles; and the presence of ribosomes in these preparations depends on the presence of intact microtubules. Five specific mRNAs are enriched with the microtubule-bound ribosomes, indicating that translation of specific proteins may occur on the microtubule scaffolding in vivo.

Animals↗
PubMed1994

Effect of isradipine in black patients with very severe hypertension. 24-hour ambulatory blood pressure monitoring and echocardiographic evaluation.

Fifty consecutive black patients with very severe hypertension (sitting diastolic blood pressure > or = 120 mm Hg and systolic > or = 210 mm Hg by the conventional cuff method) were treated in an open-label study (without a placebo or active drug control group) for 3 months with a long-acting preparation of isradipine (Dynacirc SRO), during which time serial changes in 24-h ambulatory blood pressure monitoring (ABPM), left ventricular (LV) mass index, and LV systolic function were evaluated. Mean 24-h ABPM was reduced from 184 +/- 13/119 +/- 6 to 148 +/- 18/96 +/- 11 mm Hg at 3 months (P < .0001). The reduction in BP was sustained for 24 h after dosing. Simultaneous BP measurements using a conventional cuff method and Dinamap were significantly different from the ABPM pre- and posttherapy, suggesting a marked "white coat" pressor effect. LV mass index regressed from 143 +/- 36 to 122 +/- 32 g/m2 at 3 months (P < .02). Heart rate and mean body weight were unchanged. Left ventricular performance was not adversely affected. Cardiac index and fractional shortening changed insignificantly, from 2.6 +/- 0.6 to 2.7 +/- 0.5 L/min/m2, and from 28 +/- 6 to 31 +/- 7%, respectively. Adverse effects were few and tended to disappear during the treatment period. All of the clinical laboratory parameters tested remained unchanged. We conclude that in this group of patients long-acting isradipine 1) showed a marked and sustained antihypertensive action demonstrated by 24-h ABPM; and 2) was well tolerated and associated with LV mass regression without adverse effect on systolic cardiac function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Nifedipine versus captopril in the management of moderate hypertension in black patients.

The efficacy of nifedipine (20 to 40 mg twice daily) and captopril (25 to 50 mg twice daily) was assessed during a 12-week single-blind randomized trial in 41 moderately hypertensive black patients (mean 24-h diastolic blood pressure [BP] > or = 90 mm Hg and < 115 mm Hg). Nifedipine and captopril were administered as monotherapy in increasing dosage while a diuretic was added after 8 weeks in patients who failed to reach the target BP (24-h mean diastolic BP < 90 mm Hg) on monotherapy. After 8 weeks of monotherapy, the mean 24-h ambulatory BP was reduced from 156 +/- 12/101 +/- 5 to 128 +/- 11/84 +/- 7 mm Hg (P < .0001) in the nifedipine group while it remained essentially unchanged (156 +/- 15/101 +/- 7 to 158 +/- 17/102 +/- 9) in the captopril group. Left ventricular (LV) mass index was also reduced significantly (P < .05) in the nifedipine group, while cardiac index and fractional shortening changed marginally. The addition of diuretic in the captopril group (16/21 patients) resulted in a significant fall in BP to 123 +/- 11/81 +/- 7. Only 2/20 patients in the nifedipine group required the addition of diuretic. The overall incidence of side effects was similar with both treatments but the addition of diuretic in the captopril group was followed by adverse changes in serum sodium (P < .01), urea (P < .05), and creatinine (P < .01) levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Iliac crest reconstruction after tricortical graft harvesting.

Twenty-eight patients underwent anterior iliac crest reconstruction after the harvesting of autogenous tricortical graft. The anterior iliac crest was reconstructed using the resected rib from the thoracoabdominal approach. The authors evaluated graft site pain and residual deformity, radiographic evidence of rib incorporation, and the incidence of lateral femoral cutaneous nerve injury. There were no reports of graft site pain greater than "acceptable" levels, requiring nonnarcotic analgesics on an intermittent basis and not interfering with activities of daily living. Four lateral femoral cutaneous nerve neuropraxias were recorded, none of clinical significance. The authors advocate the use of autogenous tricortical anterior iliac crest bone graft when performing reconstructive spinal surgery, followed by reconstruction of the iliac crest with the resected rib from the surgical approach.

Adolescent↗
PubMed1994

Evaluating the long-term performance of a foam-core hospital replacement mattress.

Many hospitals have begun replacing their standard mattresses with pressure-reducing foam mattresses to eliminate the costly overlays that have been used for comfort and to protect patients at risk for development of pressure ulcers. Although researchers have tested the performance of new mattresses and have shown that many may be of use with patients at high risk, no information is available on the pressure-reducing capabilities of used mattresses. This study was designed to evaluate changes with use in the support characteristics of foam-core hospital replacement mattresses. In the first part of the study, interface pressure measurements were made at regular intervals over an extended period of use. Sixty mattresses were randomly selected from 750 mattresses currently in use at St. Luke's Episcopal Hospital, Texas Medical Center, Houston. The mattresses were labeled and marked at three selected points, and interface pressures under a standard load were measured at approximately 3-month intervals for 12 months. In the second part of the study, the stiffness of the foam, a measure of the foam's ability to support a weight, was measured at selected points on the mattresses. Patient reports of discomfort in the sacral area and of "sinking" into the middle of the mattress prompted this phase of the study. The stiffness profiles of 25 new mattresses were compared with those of 25 randomly selected mattresses that had been in regular use for at least 24 months. Data analyzed from part one showed trends that indicated that the interface pressures increased at each site during the course of the study; however, an analysis of variance indicated that the changes were not statistically significant during the time frame of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Beds↗
PubMed1994

Ethanol increases hepatocyte water volume.

Mouse hepatocytes respond to osmotic stress with adaptive changes in transmembrane potential, Vm, such that hypotonic stress hyperpolarizes cells and hypertonic stress depolarizes them. These changes in Vm provide electromotive force for redistribution of ions such as Cl-, and this comprises part of the mechanism of hepatocyte volume regulation. We conducted the present study to determine whether ethanol administered in vitro to mouse liver slices increases hepatocyte water volume, and whether this swelling triggers adaptive changes in the Vm. Cells in mouse liver slices were loaded with tetramethylammonium ion (TMA). Changes in hepatocyte water volume were computed from measurements with ion sensitive microelectrodes of changes in intracellular activity of TMA (a1TMA) that resulted from water fluxes. Ethanol (70 mM) increased hepatocyte water volume immediately, and this peaked at 17% by 7 to 8 min, by which time a plateau was reached. Liver slices also were obtained from mice treated 12 hr prior with 4-methylpyrazole (4 mM). The effect of ethanol on their hepatocyte water volume was identical to that from untreated mice, except that the onset and peak were delayed 2 min. Hepatocyte Vm showed no differences between control or ethanol-treated cells during the course of volume changes. In contrast, hyposmotic stress, created by dropping external osmolality 50 mosm, increased Vm from -30 mV to -46 mV. Ethanol did not inhibit this osmotic stress-induced hyperpolarization, except partially at high concentrations of 257 mM or greater. We infer that ethanol-induced swelling of hepatocytes differs from that resulting from hyposmotic stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Safety, immunogenicity, and efficacy of a malaria sporozoite vaccine administered with monophosphoryl lipid A, cell wall skeleton of mycobacteria, and squalane as adjuvant.

A Plasmodium falciparum circumsporozoite protein (PfCSP) recombinant fusion protein, R32NS1(81), formulated with monophosphoryl lipid A, cell wall skeleton of mycobacteria, and squalane (Detox) was administered to 12 volunteers. One volunteer had malaise and self-limited painful induration at the injection site after the second dose and declined further immunization. The other 11 volunteers tolerated the three doses of 1,230 micrograms of vaccine, but most complained of sore arms; in five cases the pain or malaise was severe enough to interfere with work or sleep. Two weeks after the third dose of vaccine, four of the 11 immunized volunteers had > or = 14 micrograms/ml of antibodies to the repeat region of the PfCSP in their serum. Two of these four volunteers did not develop P. falciparum parasitemia when challenged by the bite of five mosquitoes carrying P. falciparum sporozoites. The seven volunteers with lower levels of antibodies and 11 of 11 controls developed parasitemia. These data are consistent with other studies, and indicate that vaccine-induced antibodies against the repeat region of PfCSP can prevent effective sporozoite infection of hepatocytes in humans. The challenge is to improve the immunogenicity of PfCSP-based vaccines, and to develop methods for including PfCSP peptides as components of multitarget malaria vaccines.

Adjuvants, Immunologic↗
PubMed1994

Why another leaflet?

Mary Rutledge and Joanne Davis explain why they produced a leaflet to promote healthy eating to children at school. Liz Bixby describes a leaflet on bronchiolitis, which won the HVA award at this year's annual professional conference.

Bronchiolitis↗
PubMed1994

Coping and communication among parents and children with human immunodeficiency virus and cancer.

Coping strategies and communication of three groups of 20 preschool children and their parents were compared. One group was composed of children infected with the human immunodeficiency virus (HIV) who displayed clinical symptoms of the disease; the second group was composed of children diagnosed with cancer; and the third group was composed of healthy children. Results indicated that the parents of children with life-threatening illnesses reported greater degrees of wishful thinking than did control subjects. Furthermore, parents of children with HIV reported more wishful thinking than did parents of children with cancer. Finally, significantly more children with cancer were aware of their diagnosis than were children with HIV. The findings in this study suggest coping and communication difficulties for parents and children with HIV.

Adaptation, Psychological↗