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Biomedical subjects

S Palmer

Publications and source records attributed to S Palmer.

At least 127 records · Page 7Linked to original sources
PubMed1994

Modified multipurpose catheter enhances clinical utility for cardiac catheterizations.

The Multipurpose technique for coronary arteriography employs a single catheter. The benefits are a reduction in the cost of the procedure and a shorter procedural time by experienced operators. To enhance the performance of these catheters, a modification was made in the materials and tip design, and these modifications were clinically evaluated in a small study. Compared to the control group of patients (n = 41), patients catheterized with the Multipurpose-SM (n = 43) were shown to have a shorter procedural time as measured by a reduced fluoroscopy time (7.08 min vs. 9.52 min, P = .007). This difference is statistically significant at a 95% confidence level and resulted in less radiation exposure to the operator and cath lab staff. The procedural time was significantly reduced by fewer catheter exchanges (19% study vs. 46% control; P = .006), which were needed to successfully complete the procedure. The new Multipurpose-SM catheter also demonstrated enhanced flexibility for cannulating coronary arteries with superior or anterior takeoffs. This study concludes that the utilization of a modified Multipurpose-SM catheter is safe and effective in cannulating both the left and right coronary arteries, bypass grafts, and performing left ventriculography. The primary benefits of using this modified catheter are reduced fluoroscopy time and the need for fewer catheter exchanges.

Aged↗
PubMed1994

Diurnal variation in leaf extension of Salix viminalis at two nitrogen supply rates.

To investigate how nitrogen supply might affect the biophysical factors controlling diurnal variation in leaf extension, pot-grown Salix viminalis L. were supplied with nitrogen at a low relative addition rate of 0.05 g N g(-1) N day(-1) (low N) or were given free access to all nutrients (high N). Leaf extension, turgor pressure, turgor after stress relaxation and the plastic extensibility of leaf tissue were determined for growing leaves every 4 h during two days of clear skies in August. Plants in the high-N treatment had a significantly higher relative growth rate, dry weight, shoot/root ratio, leaf nitrogen concentration, total leaf area, final area of single leaves and epidermal cell size than plants in the low-N treatment. The periodicity of leaf extension was similar in both treatments with high values during the afternoon and early evening, and negligible values during the night and in the early morning. The maximum rate of leaf extension was higher in high-N than in low-N plants. Leaf water potential and leaf osmotic potential decreased in the morning and increased in the afternoon with highest values during the night. Calculated values of turgor pressure showed no consistent diurnal trend and did not correlate with the rate of leaf extension. There was no consistent difference in turgor between treatments. Turgor after stress relaxation varied diurnally. The difference between turgors before and after stress relaxation also varied diurnally and was largely in phase with the diurnal pattern of leaf extension. These data are consistent with either a causal role for growth turgor (difference between turgors before and after stress relaxation) in the regulation of cell expansion, or a diurnal variation in turgors after relaxation, attributable to different capacities for cell wall loosening at different times of day. Plastic extensibility of leaf tissue showed no diurnal pattern but consistently higher values were found in high-N than in low-N plants. We conclude that the effects of nitrogen supply on leaf water relations did not limit leaf extension, but that nitrogen supply did affect processes associated with cell wall loosening and enlargement. Nitrogen supply did not affect final values of turgor after relaxation, but it presumably affected the rate at which relaxation proceeded.

Journal Article↗
PubMed1994

Genetic analysis in a female manifesting haemophilia B.

A 5 year old female child presented with a psoas haematoma as the first manifestation of haemophilia B. Molecular genetic studies were performed to investigate the inheritance of the disorder and the mechanisms by which females may express the haemophilia B phenotype are discussed.

Child, Preschool↗
PubMed1993

Outbreak of SRSV gastroenteritis at an international conference traced to food handled by a post-symptomatic caterer.

In an outbreak of small round structured virus (SRSV) gastroenteritis at an international AIDS conference 67 people were ill with diarrhoea or vomiting, one requiring admission to hospital. Epidemiological investigations demonstrated that the vehicle of infection was food prepared by a foodhandler who was recovering from a mild gastrointestinal illness. The food most strongly associated with illness, coronation chicken, was prepared by the food handler on the second day after symptoms ceased. The investigation confirms the view that foodhandlers may contaminate food with SRSVs after cessation of symptoms and should remain off work until at least 48 h after recovery.

Adolescent↗
PubMed1993

Increased CD11/CD18 expression on the peripheral blood leucocytes of patients with HIV disease: relationship to disease severity.

In HIV disease increased adhesion between leucocytes themselves and between leucocytes and endothelium may contribute to cell loss and viral spread. Using a novel method for the preparation of blood leucocytes for flow cytometry, we report increased expression of leucocyte adhesion molecules (LeuCAMs) (CD11/CD18) on peripheral blood leucocytes of patients with HIV disease compared with normal controls. Patients were divided into two groups on the basis of CD4 T lymphocyte numbers (those with > 0.5 x 10(9)/l and those with < 0.2 x 10(9)/l), and assessed for p24 antigen expression, viral load and serum tumour necrosis factor (TNF) levels as well as LeuCAM expression. Patients with < 0.2 x 10(9)/lCD4 cells had more p24 antigen and more HIV infectious virus and more serum TNF than those with > 0.5 x 10(9)/l. Whilst the percentages of only monocytes and polymorphs expressing CD11b were significantly increased in patients with the least CD4 cells, the density of LeuCAMs, expressed as mean fluorescence intensity (MFI), was significantly increased on all leucocytes, with the most significant increases being seen on patients with the fewest CD4 T cells. Our findings are consistent with leucocyte activation by a soluble factor, although we could find no correlation between levels of TNF and LeuCAM expression. The increased expression of adhesion molecules on peripheral blood leucocytes could play a role in the cellular extravasation and aggregation seen in HIV disease.

Adult↗
PubMed1993

The application of a rapid D-dimer test in suspected pulmonary embolus.

A prospective, consecutive series of plasma D-dimer (D-D) using a rapid, sensitive, and semiquantitative latex agglutination test from 169 patients clinically suspected of having acute pulmonary embolus (PE) was performed to determine its clinical utility in acute PE. All patients had ventilation/perfusion (V/Q) scans and 20 patients (12%) subsequently had pulmonary arteriography (PAG). The 20 patients who subsequently had PAG were used to establish the predictive value(s). In 10 patients with normal D-D results, none had PE according to PAG. In 10 patients with abnormal D-D results, seven showed PE by PAG and three did not show PE by PAG. The sensitivity, specificity, positive predictive values, and negative predictive values of the plasma D-D tests for acute PE based on PAG were 1.00, 0.77, 0.70, and 1.00, respectively. In nine patients with indeterminate V/Q scans who had PAG, four had PE and the D-D result was abnormal. Five of these patients did not have PE and the D-D result was abnormal in three and normal in two. Seventeen patients had high-probability V/Q scans, all of whom had abnormal D-D results. Only one had PAG that showed PE in this group. A normal D-D result using a rapid latex agglutination method can effectively exclude the diagnosis of acute PE. The negative predictive value of the rapid latex agglutination method is as good as the more cumbersome enzyme-linked immunosorbent assay methods. An abnormal result is nonspecific and is not useful in the diagnosis of acute PE. While some "false positives" did occur, there were no false-negative results. The best use of the D-D test is in the examination of the patient with indeterminate V/Q studies. We conclude that the D-D test can rapidly provide information in determining whether a patient needs further angiographic studies.

Blood Coagulation Tests↗
PubMed1993

Plasma D-dimer: a useful tool for evaluating suspected pulmonary embolus.

Although ventilation-perfusion lung scanning is widely used in evaluating patients with suspected pulmonary embolus, additional rapid screening tests are needed to supplement scintigraphy in patients in whom the scan is indeterminate or the scan results are discordant with clinical suspicion. D-dimer is a fibrin degradation product which should be elevated in the presence of intravascular coagulation. We prospectively studied patients referred for lung scanning by obtaining a plasma D-dimer latex agglutination assay at the time of the scan. Of 64 patients who had pulmonary angiography to confirm the diagnosis, 16 were positive for pulmonary embolus and only one had a normal D-dimer. The D-dimer was normal in 27 of 48 patients without embolus and elevated in 21. Although an elevated D-dimer level is a nonspecific finding, we conclude that a normal D-dimer is a good negative predictor for pulmonary embolus, with a negative predictive value of 0.97.

Enzyme-Linked Immunosorbent Assay↗
PubMed1992

Role of the adenylate cyclase, phosphoinositidase C and receptor tyrosyl kinase systems in the control of hepatocyte proliferation by hepatocyte growth factor.

Hepatocyte growth factor (HGF) is the most potent known mitogen for hepatocytes in primary culture. However, the mechanisms through which HGF induces hepatocyte proliferation have not been defined. Here we have investigated the role of the adenylate cyclase, phosphoinositidase C and tyrosine kinase signalling systems in the control of hepatocyte proliferation by HGF using freshly isolated or cultured adult rat hepatocytes. We show that human recombinant HGF caused a dose-dependent increase in hepatocyte DNA synthesis with a maximal effect at 10 ng/mL and an EC50 of 5.9 ng/mL. HGF had no effect on hepatocyte adenylate cyclase activity or intracellular cAMP levels. Elevation of hepatocyte cAMP levels resulted in inhibition of HGF-stimulated DNA synthesis. HGF stimulated inositol phospholipid hydrolysis with a maximal effect at 25 ng/mL and potentiated the effect of vasopressin (10(-8) and 10(-9)M). HGF (100 ng/mL) caused an increase in the phosphorylation on tyrosine of an unknown hepatocyte protein with a molecular mass of 36 kDa. Thus, we have shown that HGF, like epidermal growth factor (EGF), can activate the phosphoinositidase C and tyrosine kinase systems in rat hepatocytes. As with EGF, these intracellular signalling systems may underlie HGF-induced hepatocyte proliferation.

Adenylyl Cyclases↗
PubMed1992

Phosphorylation of the spliced variant forms of the recombinant stimulatory guanine-nucleotide-binding regulatory protein (Gs alpha) by protein kinase C.

Recombinant forms of Gs alpha-1 and Gs alpha-4 were shown to act as substrates for a purified preparation of brain protein kinase C. Both forms of Gs alpha were thermally denatured during the incubation such that phosphorylation was virtually complete (greater than 90%) after 30 min. The quantity of phosphate incorporated into approximately equivalent starting amounts of the two forms of Gs alpha (4.8 pmol of Gs alpha-1 and 5.5 pmol of Gs alpha-4) at maximal phosphorylation were 0.23 +/- 0.08 pmol for Gs alpha-1 and 0.56 +/- 0.12 pmol for Gs alpha-4. Since both forms of Gs alpha were thermally denatured to the same extent after 30 min, the increased phosphorylation state of Gs alpha-4 provides evidence that Gs alpha-4 contains an additional phosphorylation site. Bray and co-workers [Bray, Carter, Simmons, Guo, Puckett, Kamhollz, Spiegel & Nirenberg (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 8893-8897] proposed that an additional phosphorylation site may exist at the splice junction in Gs alpha-4. The guanine-nucleotide-free form of Gs alpha appears to be the preferred substrate for phosphorylation. This interpretation is based upon the following observations. (i) Guanosine 5'-[beta-thio]diphosphate at micromolar concentrations inhibits the susceptibility of Gs alpha to phosphorylation; (ii) beta gamma-subunits, which inhibit GDP release from Gs alpha-GDP at millimolar Mg2+ concentrations, also inhibit the susceptibility of Gs alpha to phosphorylation; and (iii) guanosine 5'[beta gamma-imido]triphosphate inhibits the susceptibility of Gs alpha to act as a substrate for phosphorylation. These studies suggest that there is potential for cross-talk between receptors which trigger PtdIns(4,5)P2 hydrolysis and subsequently protein kinase C activation, and receptors which stimulate adenylate cyclase via Gs.

Alkaloids↗
PubMed1992

A prospective randomized study of 4.1 French catheters utilizing the percutaneous right brachial approach for the diagnosis of coronary artery disease.

To determine the utility of 4.1 French (F) catheters in diagnosing coronary artery disease, 50 patients were randomized to 4.1F Multipurpose or Judkins catheters utilizing the percutaneous right brachial approach. The randomized 4.1F tip shape catheter completed the procedure in 40% of the patients, and overall the 4.1F catheters completed the catheterization in 72% of the cases. With excessive or prolonged manipulation, the catheters were noted to kink and soften and required replacement for a catheter of similar or larger size. In 28% of the cases, larger F sizes (5F and 6F) were used to complete the procedure. There was 1 (2%) procedural complication. The total procedural success (accounting for all F sizes) without clinical complication was 98%. There was no difference between the 4.1F Judkins or Multipurpose catheter shapes for coronary arteriography by either qualitative or quantitative angiographic analysis. Left ventricular opacification was improved with the 4.1F Pigtail vs. the 4.1 Multipurpose by qualitative angiographic analysis. When the 4.1F angiograms were compared by quantitative angiography in blinded, but not randomized fashion to angiograms performed with 6F Judkins catheters, there was improved opacification of the LAD and diastolic frame of the left ventriculogram with the larger catheter. This difference was not noted with qualitative angiography. This study indicates that 4.1F catheters can be utilized from the right brachial approach for the diagnosis of coronary artery disease, thus avoiding the need for supine bedrest associated with routine femoral artery catheterization while maintaining diagnostic accuracy.

Brachial Artery↗
PubMed1992

A prospective randomised trial of 4 Gy or 8 Gy single doses in the treatment of metastatic bone pain.

270 patients with painful bone metastases requiring palliative radiotherapy were randomised to receive single fractions of 4 Gy or 8 Gy in a randomised trial. Pain scores and analgesic usage were recorded before treatment and at 2, 4, 8 and 12 weeks. Pain was assessed by patients on a 4 point graded scale using pain charts administered by a central trials office. Response was defined as an improved rating compared to the pretreatment value. Compliance with the pain chart was 72% at 4 weeks. At 4 weeks, the actual response rates were 69% for 8 Gy and 44% for 4 Gy (p less than 0.001), but there was no difference in complete response (no pain) rates at 4 weeks or duration of response between the two arms. It is concluded that 8 Gy gives a higher probability of pain relief than 4 Gy, but that 4 Gy can be an effective alternative in situations of reduced tolerance.

Bone Neoplasms↗
PubMed1992

Grouping based on phenomenal similarity of achromatic color.

It is widely acknowledged that a precondition for the perception of the world of objects and events is an early process of organization, and it has generally been assumed that such organization is based on the Gestalt laws of grouping. However, the stage at which such grouping occurs, whether early or late, is an empirical question. It is demonstrated in two experiments that grouping by similarity of neutral color is based not on similarity of absolute luminance at the level of the proximal stimulus, but on phenomenal similarity of lightness resulting from the achievement of lightness constancy. An alternative explanation of such grouping based on the equivalence of luminance ratios between elements and background is ruled out by appropriate control conditions.

Adult↗
PubMed1992

Screening of pregnant women for evidence of current hepatitis B infection: selective or universal?

This paper reports the findings of a retrospective survey which assessed the accuracy of the selective screening programme for hepatitis B infection. The survey was undertaken in the antenatal clinics of West Lambeth Health Authority during 1988 and 1990. Forty per cent of hepatitis B positive patients were not screened, which highlights the problems associated with selective screening programmes. The implications for obstetricians and midwives are discussed, and recommendations are made.

Ethnicity↗
PubMed1991

Differences in the regulation of endothelin-1- and lysophosphatidic-acid-stimulated Ins(1,4,5)P3 formation in rat-1 fibroblasts.

Endothelin-1 (ET-1)- and lysophosphatidic acid (LPA)-stimulated PtdIns(4,5)P2 hydrolysis has been studied in Rat-1 fibroblasts. Although both agonists caused the dose-dependent accumulation of inositol phosphates, a number of differences were observed. LPA induced a transient increase in Ins(1,4,5)P3 mass which returned to basal levels within 90 s, whereas the response to ET-1 did not desensitize, with levels remaining at 3-4 times basal values for up to 15 min. Stimulated decreases in mass levels of PtdIns(4,5)P2 mirrored Ins(1,4,5)P3 formation for both agonists. Experiments with electropermeabilized cells demonstrated that the effects of both agonists are stimulated by a phospholipase C controlled by a guanine-nucleotide-binding regulatory protein; however, there are differences in the nature of these interactions. The inositol phosphate response to ET-1 is poorly potentiated by guanosine 5'-[gamma-thio]triphosphate (GTP[S]) and markedly inhibited by guanosine 5'-[beta-thio]diphosphate (GDP[S]), whereas that to LPA is potentiated by GTP[S] but is relatively insensitive to GDP[S]. In addition, LPA decreased the lag time for the onset of GTP[S]-stimulated [3H]InsP3 accumulation, whereas ET-1 was without effect. Phorbol 12-myristate 13-acetate treatment of the cells inhibited LPA-stimulated, but not ET-1-stimulated, inositol phosphate formation in both intact and permeabilized cells, suggesting that the site of protein kinase C-mediated phosphorylation may be blocked in ET-1-stimulated Rat-1 cells. The results indicate that the receptor-G-protein-phospholipase C interaction for the two agonists may not conform to the same model.

Animals↗
PubMed1991

Multiple sources of sn-1,2-diacylglycerol in platelet-derived-growth-factor-stimulated Swiss 3T3 fibroblasts. Evidence for activation of phosphoinositidase C and phosphatidylcholine-specific phospholipase D.

Platelet-derived growth factor (PDGF) stimulated sn-1,2-diacylglycerol (DAG) mass formation in Swiss 3T3 fibroblasts with a lag time of some 30 s. The response was biphasic, with the second phase being sustained over time. PDGF also stimulated the formation of Ins(1,4,5)P3 with a similar lag time to the DAG response, suggesting that DAG is derived from PtdIns(4,5)P2 hydrolysis at this time point. PDGF-stimulated phosphatidylcholine (PtdCho) hydrolysis in Swiss 3T3 fibroblasts, as measured by the formation of water-soluble choline metabolites and phosphatidylbutanol (PtdBut) accumulation, was by a phospholipase D (PLD)-catalysed pathway which was kinetically downstream of initial PtdIns(4,5)P2 hydrolysis. Accumulation of PtdBut increased up to 15 min, suggesting that PLD activity is not rapidly densitized in response to PDGF. The kinetics of PtdCho hydrolysis closely paralleled the second phase of DAG formation, strongly suggesting that during prolonged stimulation periods PtdCho is a major source of DAG in these cells. However, since PtdIns(4,5)P2 breakdown was also prolonged, PDGF-stimulated DAG may be derived from both phospholipids. Down-regulation of protein kinase C (PKC), by pre-treatment with phorbol 12-myristate 13-acetate, abolished both [3H]choline and [3H]PtdBut formation, suggesting that PLD-catalysed PtdCho hydrolysis may be dependent on PKC activation, supporting its dependence on prior PtdIns(4,5)P2 hydrolysis.

Cell Line↗