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Biomedical subjects

R Douglas

Publications and source records attributed to R Douglas.

At least 19 recordsLinked to original sources
PubMed2006

Topical anaesthesia before nasendoscopy: a randomized controlled trial of co-phenylcaine compared with lignocaine.

OBJECTIVE: To evaluate the relative effectiveness of co-phenylcaine (lignocaine 5% with phenylephrine) and lignocaine 5% sprays when administered prior to rigid nasendoscopy. DESIGN: Randomized, double blind controlled study. SETTING: Teaching hospital otolaryngology unit. PARTICIPANTS: Thirty patients requiring routine outpatient rigid nasendoscopy were administered five puffs of either co-phenylcaine or lignocaine 5% spray which had been randomly assigned to either the first or the second visit. Ten minutes later nasendoscopy was performed. Immediately after nasendoscopy the ease of performance of the procedure and the quality of the view achieved was rated on a visual analogue scale by the endoscopist and the patients recorded the level of pain experienced on a visual analogue scale. Two weeks later, the patients returned for a repeat nasendoscopy, receiving the alternate spray. MAIN OUTCOMES MEASURES: Ease of performance and quality of view of achieved by endoscopists and pain experienced by patients, both measured with visual analogue scales. RESULTS: The ease of passage of the endoscope and quality of the view obtained was found to be greater after the administration of co-phenylcaine [visual analogue scores 84 (95% CI: 80-89) than after lignocaine and 77 (95% CI: 73-81) (P < 0.01)]. The two sprays produced similar levels of topical anaesthesia. CONCLUSIONS: Nasendoscopy can be performed with minimal discomfort after the administration of either co-phenylcaine or lignocaine 5% sprays. The vasoconstricting action of co-phenylcaine increases the ease of passage of the endoscope and quality of the view obtained by the endoscopist.

Administration, Topical↗
PubMed2002

Induction of apoptosis by a nonnucleoside human immunodeficiency virus type 1 reverse transcriptase inhibitor.

Inhibition of human immunodeficiency virus type 1 reverse transcriptase (RT) by both nucleoside and nonnucleoside RT inhibitors profoundly inhibits virus replication. Nucleoside RT inhibitors are known to be toxic, but there is little information regarding the toxicities of nonnucleoside RT inhibitors (NNRTI). We demonstrate that efavirenz (an NNRTI) induces caspase- and mitochondrion-dependent apoptosis of Jurkat T cells and human peripheral blood mononuclear cells. The clinical relevance of these observations is not yet clear.

Alkynes↗
PubMed2000

Increased dissolved oxygen in Pacific intermediate waters due to lower rates of carbon oxidation in sediments.

Concentrations of dissolved oxygen in the ocean seem to correlate well with climate instabilities over the past 100,000 years. For example, the concentration of dissolved oxygen in Pacific intermediate waters was considerably higher during Pleistocene glacial periods than it is today. This has been inferred from the presence of bioturbated sediments, implying that oxygen levels were sufficient for burrowing organisms to live. Today, basins in the northeastern Pacific Ocean are floored by laminated sediments implying lower oxygen levels, which may be explained by reduced ventilation. Here we report a recent return to bioturbated sediments in the northeastern Pacific Ocean since the late 1970s. From the carbon isotope composition of benthic foraminifers living in the sediment, we infer a twofold decrease in the carbon oxidation rate occurring within sediments, equivalent to an increase in dissolved oxygen concentration of 15-20 micromoles per litre. These changes, at the edges of the Santa Barbara, Santa Monica and Alfonso basins, are coincident with a change in North Pacific climate which has reduced upwelling by 20-30% and increased sea surface temperatures by 1.5-3 degrees C. This suggests that climate effects on surface productivity, reducing the supply organic matter to sediments, may have had a greater effect on benthic oxygen levels than changes in ocean circulation patterns.

Animals↗
PubMed2000

Disruption of the IFN-gamma cytokine network in chronic lymphocytic leukemia contributes to resistance of leukemic B cells to apoptosis.

Recent evidence indicates that the slowly expanding population of CD5+ B cells that characterizes chronic lymphocytic leukemia (CLL) results primarily from defects in responses to cytokines that regulate apoptosis (e.g. I1-4, TGF-beta, IFN-alpha, IFN-gamma). We have now demonstrated not only that the enhanced anti-apoptotic effect of IFN-gamma on these neoplastic B cells is apparently mediated through increased levels of IFN-gamma receptors but also that there are increased numbers of IFN-gamma-expressing CD4 and CD8 T cells in these patients. This is the strongest evidence to date that multiple alterations in the IFN-gamma cytokine network contribute to the pathogenesis of CLL.

Adult↗
PubMed2000

The role of HIV-related chemokine receptors and chemokines in human erythropoiesis in vitro.

In order to better define the role of HIV-related chemokines in human erythropoiesis we studied: A) the expression of chemokine receptors, both on human CD34(+) cells which include erythroid progenitors and on more mature erythroid cells; B) the functionality of these receptors by calcium flux, chemotaxis assay and phosphorylation of mitogen-activated protein kinases (MAPK) p42/44 (ERK1/ERK2) and AKT, and finally C) the influence of chemokines on BFU-E formation. We found that HIV-related chemokine receptor CXCR4, but not CCR5, is detectable on human CD34(+) BFU-E cells. CXCR4 surface expression decreased during erythroid maturation, although CXCR4 mRNA was still present in cells isolated from differentiated erythroid colonies. SDF-1, a CXCR4 ligand, induced calcium flux and phosphorylation of MAPK (p42/44) and AKT in CD34(+)KIT(+) bone marrow mononuclear cells which contain BFU-E, as well as chemotactic activity of both human CD34(+) BFU-E progenitors and erythroid cells isolated from day 2-6 BFU-E colonies. Responsiveness to SDF-1 decreased when the cells differentiated to the point of surface expression of the erythroid-specific marker Glycophorin-A. In contrast, the CCR5 ligands (macrophage inflammatory protein-1alpha [MIP-1alpha], MIP-1beta, and RANTES) did not activate calcium flux, MAPK and AKT phosphorylation or chemotaxis of CD34(+)KIT(+) cells or cells isolated from the BFU-E colonies. Interestingly, none of the chemokines tested in this study had any effect on BFU-E colony formation. In conclusion, only CXCR4 is functional, and its specific ligand SDF-1 may therefore play an important role in the homing and/or retention of early erythroid precursors in the bone marrow environment.

Antigens, CD34↗
PubMed1999

Adaptive neural coding dependent on the time-varying statistics of the somatic input current.

It is generally assumed that nerve cells optimize their performance to reflect the statistics of their input. Electronic circuit analogs of neurons require similar methods of self-optimization for stable and autonomous operation. We here describe and demonstrate a biologically plausible adaptive algorithm that enables a neuron to adapt the current threshold and the slope (or gain) of its current-frequency relationship to match the man (or dc offset) and variance (or dynamic range or contrast) of the time-varying somatic input current. The adaptation algorithm estimates the somatic current signal from the spike train by way of the intracellular somatic calcium concentration, thereby continuously adjusting the neurons' firing dynamics. This principle is shown to work in an analog VLSI-designed silicon neuron.

Adaptation, Physiological↗
PubMed1999

Multilineage potential of adult human mesenchymal stem cells.

Human mesenchymal stem cells are thought to be multipotent cells, which are present in adult marrow, that can replicate as undifferentiated cells and that have the potential to differentiate to lineages of mesenchymal tissues, including bone, cartilage, fat, tendon, muscle, and marrow stroma. Cells that have the characteristics of human mesenchymal stem cells were isolated from marrow aspirates of volunteer donors. These cells displayed a stable phenotype and remained as a monolayer in vitro. These adult stem cells could be induced to differentiate exclusively into the adipocytic, chondrocytic, or osteocytic lineages. Individual stem cells were identified that, when expanded to colonies, retained their multilineage potential.

Adipocytes↗
PubMed1999

Complex response to periodic inhibition in simple and detailed neuronal models.

Constant current injection with superimposed periodic inhibition gives rise to phase locking as well as chaotic activity in rat neocortical neurons. Here we compare the behavior of a leaky integrate-and-fire neural model with that of a biophysically realistic model of the rat neuron to determine which membrane properties influence the response to such stimuli. We find that only the biophysical model with voltage-sensitive conductances can produce chaotic behavior.

Animals↗
PubMed1998

Clinical usage of intravenous immunoglobulins in Auckland.

AIMS: To review the indications for prescription of intravenous immunoglobulin (IVIg), in Auckland and the associated adverse effects. METHODS: All patients who received IVIg infusions in four major hospitals in Auckland in 1996 were identified from blood bank records. Clinical details were recorded from case notes. RESULTS: One hundred and thirty-five cases were identified and 131 records were available for review. Hypogammaglobulinaemia (n = 38) and thrombocytopenia (n = 38) were the two most common indications for 44% of Primary hypogammaglobulinaemia accounted for IVIg. the IVIg prescribed. IVIg was only used in one patient with hypogammaglobulinaemia secondary to chronic lymphocytic leukaemia and in one case of graft-versus-host disease. Adverse reactions were noted in 13 cases (10%). Headache (n = 4) and fever (n = 4) were the most commonly recorded side-effects. One patient developed acute renal failure after IVIg infusion. Written consent was documented in 7 patients (5%). CONCLUSIONS: The indications for IVIg prescription were generally consistent with the recommendations of the Australasian Society of Blood Transfusion. Use of IVIg in haematological conditions other than immune thrombocytopaenic purpura was infrequent. Most of the IVIg infusions were administered uneventfully but some minor side effects were recorded and one significant clinical event may have been causally related to IVIg infusion.

Agammaglobulinemia↗
PubMed1998

Effect of methimazole, with or without L-thyroxine, on remission rates in Graves' disease.

Medical treatment of Graves' disease involves antithyroid drugs with or without the addition of exogenous T4. There have been conflicting reports as to whether the addition of T4 improves remission rates or delays relapse. To evaluate this issue in a North American population, 199 patients were treated with methimazole until they were euthyroid. They were then randomized to either methimazole alone in a dose sufficient to normalize TSH (group 1), or to 30 mg methimazole daily plus sufficient T4 to maintain TSH in the upper normal range (group 2), or to 30 mg methimazole daily plus sufficient T4 to suppress TSH below 0.6 mIU/L (group 3). After 18 months, methimazole was stopped, and T4 was continued in groups 2 and 3. Because not all patients in groups 2 and 3 achieved their target TSH concentration, they were reassigned to group A (TSH > or = 1.0) or group B (TSH < 1.0), based on the mean TSH achieved during methimazole treatment. One hundred forty-nine patients have been followed for at least 6 months after stopping methimazole (mean 27 months). Fifty-eight percent of patients have relapsed. There were no significant differences in relapse rates after stopping methimazole. Among those patients who did relapse, however, there was a significant difference in the months to relapse after stopping methimazole between groups B and 1 (group 1: 3.3 +/- 0.7, group A: 5.6 +/- 0.8, group B: 7.4 +/- 1.7; P = 0.01 for the comparison between groups B and 1). We conclude that the addition of T4 to methimazole does not improve long-term remission rates in Graves' disease.

Adult↗
PubMed1998

Triage services: a profile of high utilization.

With challenges continuing to be presented to health care delivery, inappropriate out-patient service utilization is of utmost concern to all health care service providers. This study is an examination of the utilization patterns of 189 veterans in an urban Veterans Administration Medical Center (VAMC). Factors found to be related to high utilization of ambulatory care triage clinic services for veterans who had presented for at least two unscheduled visits in the past six months include: patient perception of health status; number of prescription medications; and social needs. Implications for social work practice, program development and research are discussed.

Analysis of Variance↗