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Biomedical subjects

I Davis

Publications and source records attributed to I Davis.

At least 55 records · Page 3Linked to original sources
PubMed1994

Topographical analysis of cortical evoked activity during a variable demand spatial processing task.

This experiment studied changes in brain activity as subjects performed a variable demand spatial rotation task. The task involved the sequential presentation of a template histogram and a spatially rotated comparison histogram. Task difficulty was manipulated by varying the number of bars and the degree of rotation. Topographical analysis of the brain event-related activity data indicated the presence of negative components that were maximal at the vertex within 80 ms and bilaterally in the temporal lobes within 140 ms of stimulus onset and that appeared to be insensitive to changes in task difficulty. Demand-sensitive potentials were recorded, however. Positive components corresponding to P200 and P300 activity were recorded symmetrically around site PZ. The P200 component declined in amplitude, but showed no changes in latency as task demand increased. P300 activity declined in both amplitude and latency as the task became more difficult. Finally, a positive component was recorded over right central cortex approximately 490 ms after stimulus onset. This component declined in amplitude but increased in latency as task difficulty increased.

Adult↗
PubMed1994

Evoked potential, cardiac, blink, and respiration measures of pilot workload in air-to-ground missions.

Brain evoked potentials were successfully recorded from F-4 pilots during air-to-ground training missions. They were recorded during two flight segments. During one the pilot was flying, and during the other, the weapon systems officer was flying the aircraft. The P2 component of the brain-evoked potential evidenced reduced amplitude during the pilot-flying segment, while the N1 component was reduced during both flight tasks compared to ground-based tasks. These data indicate that the P2 amplitude is sensitive to the level of pilot workload. These results were further substantiated using simultaneously recorded physiological data and subjective workload measures. For example, cardiac inter-beat intervals decreased during flight segments relative to those recorded when performing a tracking task, and further reduced for the pilot-flying vs. the weapon systems officer-flying segment. Eye blink measures were sensitive to the visual demands of the various tasks. These data show that evoked potentials can be recorded during flight, and that, together with cardiac and eye blink data, they provide a composite picture of operator state.

Aerospace Medicine↗
PubMed1992

Elevation of fasting serum lipids in patients treated with low-dose cyclosporine for severe plaque-type psoriasis. An assessment of clinical significance when viewed as a risk factor for cardiovascular disease.

BACKGROUND: Hyperlipidemia has received little attention as a side effect of cyclosporine therapy for severe psoriasis. OBJECTIVE: We report changes in fasting serum lipids in patients treated with low-dose oral cyclosporine for psoriasis and discuss their significance. METHODS: Twenty-two patients with severe, recalcitrant, plaque-type psoriasis were treated with cyclosporine, 5 mg/kg/day, for 12 to 16 weeks. Fasting serum lipid levels (triglycerides, cholesterol, and high-density lipoproteins) were measured at 2-week intervals. RESULTS: The mean serum triglyceride level increased from 117.8 +/- 11.7 mg/dl before initiation of therapy to 183.9 +/- 31.4 mg/dl after 2 weeks of treatment, without further significant change during the remainder of the study (p less than 0.007). A significant elevation of serum cholesterol from 207.1 +/- 8.1 mg/dl initially to 247.4 +/- 10.2 mg/dl after 2 weeks of treatment occurred (p less than 0.001) and persisted with continued cyclosporine therapy. No consistent alteration in high-density lipoprotein was noted (p less than 0.42). CONCLUSION: Serum lipids should be closely monitored in psoriasis patients receiving intermediate or long-term therapy with cyclosporine, especially in the presence of elevated baseline values.

Adult↗
PubMed1992

Clinical uses of growth factors.

The haemopoietic growth factors are a diverse group of hormones with effects on different haemopoietic cell lineages and at various points in their developmental differentiation. The biology of many of these factors is now well understood. They have entered clinical trials and have demonstrated benefits in particular clinical situations. The thrust of current phase II and III clinical investigations now is to use these factors, alone or in combinations, to modify various disease states and to ameliorate many of the side-effects of other therapeutic agents, particularly cytotoxic anticancer agents. Many other disease states also lend themselves to therapy with these growth factors. Other haemopoietic growth factors have not been as extensively studied in humans but hold great promise. In this chapter, the current status of the haemopoietic growth factors presently under clinical trial has been reviewed. In addition, several factors which have been recently described but which have not yet entered clinical trials have been discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Topical alpha-interferon ointment with dimethyl sulfoxide in the treatment of recurrent genital herpes simplex.

The recent in vivo appearance of acyclovir-resistant strains of herpes simplex virus stresses the need for new therapeutic agents to combat this common virus. Topical interferon preparations may help fill this void. In the present study dimethyl sulfoxide was combined with alpha-interferon in an ointment base to increase percutaneous penetration. In this double-blind, placebo-controlled trial, patients with recurrent genital herpes simplex using the topical alpha-interferon preparation had a more rapid cessation of viral shedding when compared to the placebo group (66% culture negative on day 1 vs. 25% of placebo patients; p less than 0.02). In the 90-day post-treatment period, interferon-treated patients had fewer recurrences than their placebo-treated counterparts (1.18 vs. 2.25). This reduction while not statistically significant was encouraging (p less than 0.10).

Administration, Topical↗
PubMed1991

Apical localization of pair-rule transcripts requires 3' sequences and limits protein diffusion in the Drosophila blastoderm embryo.

The peripheral cytoplasm (periplasm) of the Drosophila blastoderm embryo is subdivided into apical and basal compartments by a layer of nuclei. We have demonstrated three classes of periplasmic transcript localization: apical, basal, and unlocalized (apical and basal), each of which depends on 3' sequences. We define 3' apical localization signals within the even-skipped, fushi tarazu, and hairy pair-rule segmentation genes and the alpha 1-tubulin and bicoid genes. 3' human alpha-globin sequences direct transcripts basally. Transcript destination depends on transcript structure, not on transcript stability or chromosomal location. Apical transcripts direct apical compartmentalization of cytoplasmic protein. We propose that apical localization of pair-rule transcripts restricts lateral protein diffusion, thereby allowing pair-rule proteins to define sharp boundaries and precise spatial domains.

Animals↗
PubMed1991

Human interleukin-4: an immunomodulator with potential therapeutic applications.

Human interleukin-4 (IL-4) is a 20kDa cytokine produced by activated T cells and has an extensive range of stimulatory and inhibitory effects on the wide range of cells which express its receptor. It specifically promotes the immunoglobulin class switch to IgE and IgG4 and potently co-stimulates with CD40 monoclonal antibodies the long term proliferation of human B cells. It has variable effects on T cells, but predominantly has inhibitory actions on monocytes suggesting a potential therapeutic role as an anti-inflammatory agent. There is evidence for indirect anti-cancer activity of IL-4 both in animal models and in in vitro studies on human tumour infiltrating lymphocytes. In addition, IL-4 directly inhibits the in vitro proliferation of the majority of B cell neoplasms. Phase I studies of IL-4 in patients with cancer have commenced and promising observations have been made in patients with haematological malignancies receiving low, well-tolerated doses.

Adjuvants, Immunologic↗
PubMed1991

Prospective analysis of cardiopulmonary responses to laparoscopic cholecystectomy.

This prospective study evaluates the extent and temporal course of the cardiorespiratory effects of CO2 during laparoscopic cholecystectomy in otherwise healthy patients. Sixteen patients (M:F = 3:13, average age = 40.2 +/- 14.1 years) were monitored with capnography, transesophageal cardiac output, continuous blood pressure, heart rate, and pulse oximetry. Arterial blood gases were obtained immediately before insufflation of the abdomen with CO2 and before desufflation. Average operative time was 137 +/- 13 minutes. Patients were paralyzed and mechanically ventilated. Minute ventilation was increased if EtCO2 exceeded 45 mmHg or rose by more than 12 mmHg from baseline. End tidal (EtCO2) and arterial CO2 (PaCO2) increased from 31.4 +/- 0.7 mmHg to 42.1 +/- 1.6 mmHg and 33.3 +/- 0.7 mmHg to 43.7 +/- 1.2 mmHg, respectively, during the course of the procedure. Arterial pH decreased from 7.43 +/- 0.01 to 7.34 +/- 0.01, while bicarbonate concentration remained unchanged. Thirteen of the 16 patients required increased minute ventilation due to hypercarbia detected by capnography. Blood pressure increased from 78 +/- 2 mmHg (mean) at the start to 98 +/- 2 mmHg. This increase was coincidental with the maximal PaCO2. Good agreement was observed between paired EtCO2 and PaCO2 measurements. Laparoscopic cholecystectomy with carbon dioxide insufflation causes significant respiratory acidosis and associated cardiovascular changes in otherwise healthy patients. Careful monitoring and cautious application of this technique in patients with pre-existing cardiopulmonary disorders will be required to prevent acute decompensation.

Acidosis, Respiratory↗
PubMed1988

Group education for obese patients with type 2 diabetes: greater success at less cost.

It has been suggested that much effort expended in teaching diabetic diets is ineffective and wasteful. We have tested a different system by randomly allocating 75 newly diagnosed obese Type 2 diabetic patients to usual 'unstructured' clinic care or to group education by diabetes specialist nurses and a dietitian. Patients allocated to group education attended five 90-min group sessions during the first 6 months. Six months after diagnosis they had lost more weight (median (95% Cl), 7 (5.5-9) vs 2(1-5)kg, p less than 0.002) and were better controlled (HbA1:7.5 (7.0-8.1) vs 9.5 (8.7-10.4)%, p less than 0.001) than those randomized to the usual clinic system. At 1 year (after no further visits) the difference in weight loss was less (5.5 (4-6.5) vs 3 (2-4) kg, p less than 0.05) and diabetic control was similar (HbA1:9.0(8.2-9.8) vs 9.9(8.9-10.9)%. At 1 year only 14(39%) of the education group and 9(23%) of those attending the clinic had a fasting blood glucose less than 7.0 mmol l-1.

Blood Glucose↗
PubMed1988

Hemispheric asymmetries in phonological processing assessed with probe evoked magnetic fields.

Auditory Evoked Magnetic Fields (EFs) to tonal stimuli were recorded at homotopic maxima over the left and right auditory areas in nine subjects. Recordings were made during two conditions, both involving simultaneous presentation of the probe tone stimuli and a set of tape-recorded verbal material. During the control condition subjects were instructed to attend to the tones and ignore the verbal material. In the phonological processing condition they were instructed to ignore the tones and attempt to identify a phonological target item which was embedded in the verbal material. EFs obtained during both conditions were characterized by an early N1m and a later P2m component corresponding to the N1 and P2 components of auditory evoked potentials (EPs). During the phonological condition, the amplitude of the N1m was significantly reduced in both hemispheres symmetrically whereas the amplitude of the P2m was attenuated to a significantly greater degree in the left hemisphere. These data are in agreement with previous EP evidence of greater interference of linguistic processing with processing of irrelevant probe stimuli in the left hemisphere, indicative of greater left hemisphere involvement in language tasks.

Acoustic Stimulation↗
PubMed1987

Intrathecal morphine in aortic aneurysm surgery.

The purpose of this study was to compare the peri-operative conditions produced by intrathecal morphine with those that result from conventional analgesia in aortic aneurysm surgery. Low-dose intrathecal morphine provides a level of analgesia during operation indistinguishable from that of moderate doses of parenteral opiate, but is no more effective in attenuating autonomic responses to the procedure. Analgesia is prolonged into the postoperative period, does not cause clinically evident respiratory depression and can be enhanced by small doses of intravenous opiate. The principal advantage of intrathecal morphine is the avoidance of irregular and inadequate pain relief in the early, and most painful, part of the postoperative period. Low-dose intrathecal morphine appears safe, effective and feasible in aortic aneurysm surgery and provides an alternative to traditional management with parenteral opiates.

Adult↗