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Biomedical subjects

V Allen

Publications and source records attributed to V Allen.

At least 19 recordsLinked to original sources
PubMed1998

Replacements of single basic amino acids in the pleckstrin homology domain of phospholipase C-delta1 alter the ligand binding, phospholipase activity, and interaction with the plasma membrane.

The pleckstrin homology (PH) domain of phosphatidylinositol-specific phospholipase C-delta1 (PLC-delta1) binds to both D-myo-inositol 1,4, 5-trisphosphate (Ins(1,4,5)P3) and phosphatidylinositol 4, 5-bisphosphate (PtdIns(4,5)P2) with high affinities. We have previously identified a region rich in basic amino acids within the PH domain critical for ligand binding (Yagisawa, H., Hirata, M., Kanematsu, T., Watanabe, Y., Ozaki, S., Sakuma, K., Tanaka, H., Yabuta, N., Kamata, H., Hirata, H., and Nojima, H. (1994) J. Biol. Chem. 269, 20179-20188; Hirata, M., Kanematsu, T., Sakuma, K., Koga, T., Watanabe, Y., Ozaki, S., and Yagisawa, H. (1994) Biochem. Biophys. Res. Commun. 205, 1563-1571). To investigate the role of these basic residues, we have performed site-directed mutagenesis replacing each of the basic amino acid in the N-terminal 60 residues of PLC-delta1 (Lys24, Lys30, Lys32, Arg37, Arg38, Arg40, Lys43, Lys49, Arg56, Lys57, and Arg60) with a neutral or an acidic amino acid. The effects of these mutations on the PH domain ligand binding properties and their consequence for substrate hydrolysis and membrane interactions of PLC-delta1 were analyzed using several assay systems. Analysis of [3H]-Ins(1,4,5)P3 binding, measurement of the binding affinities, and measurements of phospholipase activity using PtdIns(4,5)P2-containing phospholipid vesicles, demonstrated that residues Lys30, Lys32, Arg37, Arg38, Arg40, and Lys57 were required for these PLC-delta1 functions; in comparison, other mutations resulted in a moderate reduction. A subset of selected mutations was further analyzed for the enzyme activity toward substrate present in cellular membranes of permeabilized cells and for interaction with the plasma membrane after microinjection. These experiments demonstrated that mutations affecting ligand binding and PtdIns(4,5)P2 hydrolysis in phospholipid vesicles also resulted in reduction in the hydrolysis of cellular polyphosphoinositides and loss of membrane attachment. All residues (with the exception of the K43E substitution) found to be critical for the analyzed PLC-delta1 functions are present at the surface of the PH domain shown to contain the Ins(1,4,5)P3 binding pocket.

Amino Acid Sequence↗
PubMed1997

Regulation of inositol lipid-specific phospholipase cdelta by changes in Ca2+ ion concentrations.

Studies of inositol lipid-specific phospholipase C (PLC) have elucidated the main regulatory pathways for PLCbeta and PLCgamma but the regulation of PLCdelta isoenzymes still remains obscure. Here we demonstrate that an increase in Ca2+ ion concentration within the physiological range (0.1-10 microM) is sufficient to stimulate PLCdelta1, but not PLCgamma1 and PLCbeta1, to hydrolyse cellular inositol lipids present in permeabilized cells. The activity of PLCdelta1 is further enhanced in the presence of phosphatidylinositol transfer protein (PI-TP). Both full activation by Ca2+ ions and stimulation in the presence of PI-TP require an intact PH domain involved in the membrane attachment of PLCdelta1. The physiological implication of this study is that PLCdelta1 could correspond to a previously uncharacterized PLC responsible for Ca2+ ion-stimulated inositol lipid hydrolysis observed in many cellular systems.

Animals↗
PubMed1997

Measurement of angioplasty lumen volume and wall compliance: a laboratory study.

We have developed a device and technique for measuring the pressure-volume characteristics of an arterial segment from a standard angioplasty balloon, enabling us in this laboratory study to investigate the ability of the technique to measure changes in lumen volume and wall compliance. Percutaneous transluminal coronary angioplasty (PTCA) is a valuable clinical procedure for alleviating arterial stenosis, but the long-term success of the technique is less than ideal. The ability to monitor the effect of the balloon on the artery during inflations could lead to improvements in the technique. In this study, 10 different lumen diameters (1.6 to 3.4 mm) were produced in a Perspex block, and six different wall compliances produced with silicone tubes of constant inner diameter (2.0 mm) but different outer diameters (3.5 to 6.0 mm) A standard PTCA balloon was inflated under automatic control at a constant rate of 0.05 ml s-1 to 800 kPa (8 bar). Pressure and volume data were recorded to computer continuously throughout the procedure. Differences in lumen volume of +/-0.01 ml and wall compliance of +/-5% could be differentiated with greater than 95% confidence. We conclude that our technique allows small changes in lumen volume and wall compliance to be differentiated using a standard angioplasty catheter and balloon.

Angioplasty, Balloon, Coronary↗
PubMed1995

Angioplasty pressure-volume measurement.

An instrument has been developed for controlled inflation and deflation of an angioplasty balloon. The mean difference between inflation to 800 kPa in air and a simulated coronary artery is 71.2 kPa. The repeatability of four inflation/deflation cycles is 6.4 kPa with the balloon in air and 9.0 kPa in the simulated artery.

Angioplasty, Balloon, Coronary↗
PubMed1994

A 12-year experience with enterovesical fistulas.

OBJECTIVES: To review our experience with enterovesical fistulas in order to determine the most accurate diagnostic studies and most effective method of treatment. METHODS: A retrospective record review of 76 patients who were diagnosed and treated for enterovesical fistulas over a 12-year period was performed. Data collection focused on presenting symptoms, urinary disease process, diagnostic studies, and methods of management. RESULTS: Diverticular disease was the primary etiologic factor in the majority of patients (59%), with colonic malignancy, granulomatous bowel disease, and radiation therapy accounting for the majority of the remainder. Cystoscopy (60%) and cystography (44%) were the most sensitive diagnostic studies. There was no statistical difference in the complication rate between groups treated with single or multistage repair. CONCLUSIONS: One-stage repair of enterovesical fistulas can be safely performed when the cause is diverticular or granulomatous bowel disease. Staged repairs may be more judicious in patients with large intervening pelvic abscesses or those in whom advanced malignancy or radiation changes are present.

Adult↗
PubMed1994

Simplified body-surface electrocardiographic maps with depolarization magnitude and direction.

A new technique is presented for extracting the magnitude and direction of ventricular depolarization at the body surface from surface electrocardiographic (ECG) map data. Bipolar electrocardiograms were obtained from 36 sites on the chest surface in five normal subjects. The direction and magnitude of depolarization as seen from the chest surface were calculated for 18 body-surface areas centred between electrode positions V1 and V6. Each area was bounded by three electrodes with an electrode spacing of 5 cm. A major depolarization component could be calculated for all triangular areas, with 48% of areas having a smaller second component. The area with the greatest magnitude in each subject had a depolarization vector pointing downwards and to the left, with an average angle to the horizontal of 55 degrees. This was consistent with an average angle of 51 degrees obtained from the subjects' 12-lead electrocardiograms. There was more variability in vector angle between adjacent areas on the right-hand side. At the V5/V6 areas, close to the cardiac apex, the vector component had an upwards orientation in all subjects, opposing the overall downward component of ventricular depolarization. The technique was able to determine local depolarization directions which were in agreement with the normal cardiac vector derived from standard electrocardiography. Reversal of the vector direction close to the cardiac apex and the collision of depolarization components from different directions could be detected. This simple form of body-surface mapping can reduce the essential features of depolarization to a single map, and provide information not directly available from a 12-lead electrocardiogram.

Adult↗
PubMed1994

Immunohistological expression of p53 in primary pT1 transitional cell bladder cancer in relation to tumour progression.

OBJECTIVE: To determine whether p53 expression is a marker of tumour progression in superficially invasive (pT1) transitional cell carcinoma of the bladder. PATIENTS AND METHODS: The immunohistochemical status of the p53 protein in 28 pT1 primary bladder cancers was determined on frozen tissue and archival paraffin block sections using three primary antibodies (CM-1, PAB1801 and D07). The findings were compared with the patients' progress. All the patients, except for those who died during the course of the study, were followed up by check cystoscopy for a minimum of 2 years. RESULTS: Immediately adjacent frozen sections stained identically in 10 of 16 cases for CM-1 and PAB1801. For paraffin sections, identical staining patterns were seen for PAB1801 and D07 in 21 of 26 sections. However, inter- and intra-tumour staining for p53 was very variable, even with the same antibody. The heterogeneity of p53 positive cell distribution in the tumours indicates potential for significant sampling errors if random sections are chosen as representative of p53 status. CONCLUSION: The p53 status of the primary tumours did not relate to patient outcome. The results obtained do not support the use of immunohistological p53 expression as a discriminating prognostic indicator in pT1 transitional cell carcinoma of the bladder.

Biomarkers, Tumor↗
PubMed1993

Repeatability of subject/bed interface pressure measurements.

The repeatability of a technique for measuring interface pressures has been assessed. Pressure was measured using a Talley SA500 Pressure Evaluator under six anatomical sites (occiput, scapula, elbow, sacrum, buttock, and heel) of six healthy subjects lying supine on a Clinifloat mattress (trademark, SSI). For each site of each subject, four repeat readings were taken per day on four separate days. Mean pressures varied significantly between subjects (p < 0.02), though differences in mean pressures between sites were greater. Pressure was not significantly related to subject mass. The overall repeatability of the technique was +/- 0.77 kPa (+/- 5.8 mm Hg) which was much smaller than the range of pressures found under different sites (2.72 kPa or 20.4 mm Hg at the sacrum to 9.00 kPa or 67.5 mm Hg at the heel). Repeatability varied from site to site, from +/- 0.47 kPa (+/- 3.5 mm Hg) at the buttocks to +/- 1.20 kPa (+/- 9.0 mm Hg) at the heel. Measurements were found to vary significantly more between days than between repeats on the same day (p < 0.02).

Adult↗
PubMed1993

Accuracy of interface pressure measurement systems.

Interface pressure measurement is needed to assess beds designed to prevent pressure sores, so it is therefore important to establish the accuracy of interface pressure measuring systems. In this study, the Talley SA500 pressure evaluator (with 28 mm and 100 mm sensor pads), the DIPE (with 100 mm sensor pad), and a water-filled bladder system (with 0.1 ml and 0.3 ml water) were assessed. Measurement errors were evaluated using a loading system with pressures up to 7.4 kPa (55 mm Hg) in steps of 0.9 kPa (6.9 mm Hg). All systems tested over-measured interface pressure, the error being approximately linearly proportional to the loading pressure. The repeatability for a given system was approximately constant. The mean error (+/- SD) (%) and repeatability (kPa) for the systems were: 28 mm Talley 12 +/- 1%, +/- 0.07 kPa; 100 mm Talley 15 +/- 1%, +/- 0.07 kPa; DIPE 27 +/- 3%, +/- 0.12 kPa; 0.1 ml water bladder 17 +/- 1%, +/- 0.13 kPa; 0.3 ml water bladder 26 +/- 3%, +/- 0.07 kPa. Different interfaces affected accuracy markedly, and repeatability was affected when an inhomogeneous interface was used. The study shows that the errors associated with interface pressure measurement systems can be substantial, and can vary from one system to another.

Beds↗
PubMed1993

Air-fluidized beds and their ability to distribute interface pressures generated between the subject and the bed surface.

Pressures were measured under five anatomical sites prone to pressures sores for ten subjects, supine and sitting on two different air-fluidized beds. The beds were the Clinitron (trademark, SSI) and the Fluidair Plus (trademark, KCI Mediscus). Mean supine pressures were less than 4 kPa under four sites. The average supine buttock pressure was 2.65 kPa. This increased to 3.71 kPa upon sitting up, though pressures did not rise above the accepted capillary closing pressure, on either bed. Low interface pressures at these sites were due to good moulding between subject and bed. Heel pressures averaging 7.08 kPa, were a factor of 2.67 times greater than buttock pressure, and were higher than expected considering the depth the heels sunk to in both beds. This exceeded the accepted capillary closing pressure and was attributed to covering sheets preventing true floatation at the heels.

Adult↗
PubMed1992

The influence of temperature and organic matter on the bactericidal activity of short-chain organic acids on salmonellas.

Acetic and lactic acids and BioAdd, a commercial preparation of formic and propionic acid, were tested at a concentration of 0.1% (w/w) at 20, 30, 40 and 50 degrees C and in the presence of organic material for bactericidal activity against Salmonella serotype Kedougou. BioAdd was the most active of the solutions at all temperatures, followed by lactic acid and acetic acid. The presence of horse blood at all four temperatures, and milk and serum at 50 degrees C, did not greatly affect the antibacterial activity of the acids although yeast extract (50 degrees C) provided some protection for the salmonella. Acid activity was related to low pH values although the bactericidal activity of acetic acid with blood and milk was greater than the unadulterated acid even though the pH was 0.4 units higher.

Acetates↗
PubMed1991

Naturally acquired Pasteurella multocida subsp. multocida infection in a closed colony of rabbits: characteristics of isolates.

Twelve litters, comprising 41 rabbits aged 35 to 60 days old, in a closed university colony, were monitored for acquisition of nasal Pasteurella multocida subsp. multocida infection. Isolates from 11 infected rabbits were characterized by colonial morphology, capsular type, biotype and antibiotic resistance. Selected isolates were further characterized by somatic antigen typing. Two major strains of P. multocida subsp. multocida were detected in the colony. One strain had mucoid colonies, fermented few carbohydrates and was serotype A:5, whereas, the other strain had smooth iridescent colonies, non-typeable capsular antigen, type 3 somatic antigen and fermented more than twice as many carbohydrates.

Animals↗
PubMed1991

Naturally acquired Pasteurella multocida infection in rabbits: clinicopathological aspects.

A cohort of 41 New Zealand White rabbits, 35 to 60 days old, from twelve litters were followed for twelve weeks for development of pasteurellosis. Eleven of 19 rabbits in five litters acquired Pasteurella multocida infection. The incubation period was difficult to determine as P. multocida infection was detected both before and after the onset of rhinitis. The response of rabbits to infection varied from subclinical infection to death from systemic pasteurellosis. Atrophy of the maxilloturbinates of the nares was detected in rabbits with chronic rhinitis associated with P. multocida infection.

Animals↗
PubMed1984

Analysis of CAD gene amplification using a combined approach of molecular genetics and cytogenetics.

CAD is a multifunctional protein which catalyzes the first three steps of de novo uridine biosynthesis. Rodent cells resistant to PALA, a specific inhibitor of the ATCase activity of CAD, overproduce the CAD protein and CAD mRNA as a direct result of the amplification of the CAD gene. In order to study the mechanism of CAD gene amplification, a functional Syrian hamster CAD gene was inserted into a cosmid vector using molecular cloning techniques. The cloned genes were assayed for biological function by fusing CAD-deficient Chinese hamster ovary (CHO) cell mutants with protoplasts of E. coli containing the CAD cosmids. Two clones with functional CAD genes were isolated and shown to contain inserts 40 and 45 kb long. The cloned genes could also be introduced into wild type CHO cells by selecting for cells which became resistant to high PALA concentrations in a single step. Transformations of mutant and wild type CHO cells contained multiple active copies of the donated Syrian hamster CAD genes in addition to their endogenous CHO CAD genes. The cloned genes in all transformants analyzed are integrated into host cell chromosomes at single locations defined by in situ hybridization. Independently isolated transformants contain the donated genes in different chromosomes. Co-transformation of CHO cells with two different genes by protoplast fusion is also shown to be possible.

Animals↗
PubMed1984

Further observations on the excretion of salmonella in the faeces of calves fed milk substitute.

Swabs of rectal faeces were obtained daily for 28 days from 90 calves reared in five batches during the summer of 1983. The calves were purchased unweaned in markets and fed a milk-substitute diet. Salmonella typhimurium phage type DT204c was isolated from calves in four batches and Salmonella newport from one. When the data from the 90 calves were considered together the incidence of salmonellas, excretion rose to peak between 5 and 7 days after purchase before declining to low levels during the fourth week. Salmonella was isolated from 55 (61%) calves; 30 were positive on up to four occasions while 21 and 4 animals respectively were positive between 5 and 11 and 15 and 20 times. In the majority of animals infection was probably subclinical since treatment with antibacterial drugs and excretion of S. typhimurium coincided in four calves only.

Animal Feed↗