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Biomedical subjects

D Graham

Publications and source records attributed to D Graham.

At least 37 records · Page 2Linked to original sources
PubMed1990

"Pacecare"--a computerized database for pacemaker follow-up.

A computerized database for pacemaker follow-up has been designed to run on IBM compatible hardware and to accept pulse generator and lead models of all manufacturers. Stored data includes patient, physician and implant details, indications for pacing, underlying rhythm, complications and management, program settings, and follow-up measurements. Typing is minimized by the use of "pop-up" lists and prepared pulse generator template displays. At each follow-up visit a patient's file is retrieved by surname or number, a visit record created, and measurements documented. As the template of the previous visit is used, recording of the clinic visit takes less than 1 minute. Changes in pacing rates (base or magnet), pulse widths, lead thresholds, lead impedance, and battery cell impedance can be displayed graphically for immediate recognition of end-of-life parameters or suspected malfunction. The program will print patient, implantation and clinic visit summary reports, clinic appointment lists, letters to patients, and annual reports. Two Melbourne hospitals have now entered over 3,600 patients into the database. Valuable information has been obtained regarding implantation details and trends with pulse generator and lead usage. Pacecare is a sophisticated, yet user friendly, computerized database for pacemaker follow-up. Recording of clinic visits is fast and changes in testing parameters can be recognized immediately.

Computer Systems↗
PubMed1990

Ploidy of smooth muscle tumours: retrospective image analysis study of formalin fixed, paraffin wax embedded tissue.

The feasibility of using an image analyser, the CAS 100, to assess the ploidy of smooth muscle tumours on formalin fixed paraffin wax embedded tissue was assessed. Various different methods of assessment were compared. A paraffin wax block of 15 leiomyomata and 13 leiomyosarcomata yielded serial sections of 3 microns, 5 microns, and 7 microns and a cytospin preparation (from a 50 micron section). Sections and cytospin preparations were stained with Feulgen and quantified using the CAS 100. The suitability of lymphocytes, previously suggested to be unsuitable as control cells in tissue sections due to the compact nature of their DNA, was assessed in sections and cytospin preparations and compared with endothelial cells, the standard alternative, on the same slide. Despite having a mean nuclear area of only 18.5 microns 2 in sections lymphocytes had a similar diploid peak--that is, 4.1 pg--to endothelial cells (mean nuclear area 39 microns 2). A comparison of 3 microns, 5 microns, and 7 microns sections showed 5 microns to be the optimal thickness. Cytospin preparations yielded histograms of superior quality than those from tissue sections. All 15 leiomyomata had a 5C exceeding rate of less than 0.3%. Ten of 11 histologically malignant tumours had a 5C exceeding rate of more than 5% (mean 14%) in sections and cytospins. Two leiomyosarcomata that had arisen in the lower gastrointestinal tract had a mitotic rate of less than or equal to 1/10 per high power fields and yielded histograms similar to those of the leiomyomata. It is concluded that formalin fixed, paraffin wax embedded tissue can be used for DNA quantification by image analysis; that tissue sections yield poorer results than cytospin preparations; that lymphocytes are reliable control cells in cytospin preparations; and that a population of cell greater than 5C is seen in 90% of leiomyosarcomata.

Cell Separation↗
PubMed1990

High density lipoprotein inhibits low density lipoprotein binding and uptake by bovine aortic endothelial cells.

The antiatherogenic effect of high density lipoprotein (HDL) has been attributed to either an inhibition of cholesterol uptake or to reversed cholesterol transport from peripheral cells. In order to determine whether HDL competitively blocks receptor-mediated low density lipoprotein (LDL) binding and uptake, bovine aortic endothelial cells (BAECs) were cultured in Dulbecco's modified Eagles Medium (DMEM) containing 10% LDL-free fetal bovine serum, and incubated with 125I-LDL in concentrations of either 10 or 25 micrograms protein/mL. Varying amounts of HDL (0-200 micrograms/mL) were added to the media. Following a twenty-four hour incubation period at 37 degrees C, 125I-LDL binding and uptake were measured. At the lower concentration of 125I-LDL, which represents high-affinity receptor binding, there was no significant difference in either binding or uptake within the range of HDL concentrations studied. At the higher concentration of LDL, however, there was a marked inhibition of 125I-LDL binding (p less than .006) and uptake (p less than, 001; ANOVA), which did not saturate at the highest HDL concentrations used. These data suggest that HDL does not influence high-affinity, receptor-mediated binding and uptake of LDL but that its effect is seen at a concentration of LDL representing nonspecific binding. The lack of saturation at increasing concentrations of HDL also indicates that HDL-receptor interaction is not essential for the effect.

Animals↗
PubMed1990

Mechanisms of oxygen free radical-induced calcium overload in endothelial cells.

Unregulated increases in intracellular calcium levels with subsequent cytoskeletal disruption have been implicated in tissue injury caused by oxygen free radicals (OFRs). The purpose of these experiments was to study the kinetics of free intracellular calcium in endothelial cells on exposure to exogenous OFRs and investigate the mechanisms of this altered homeostasis. Monolayers of endothelial cells were labeled with a calcium-sensitive probe and exposed to exogenous OFRs generated with hypoxanthine and xanthine oxidase. Intracellular calcium changes were monitored dynamically by continuous measurement of fluorescence with a spectrofluorometer. A sustained rise in intracellular Ca++ levels reaching a peak at 5 minutes was observed. This effect was blocked by superoxide dismutase and catalase. Removal of calcium from the medium or chelating the extracellular calcium with ethyleneglycoldiamine tetraacetate significantly blunted the response to OFRs (p less than 0.05). Preincubation of the cells with verapamil did not alter the observed increase in Ca++i. Addition of another divalent cation (Mn++) to the medium partially blocked the rise in calcium levels (p less than 0.05). Membrane potential measurements assessed fluorometrically, with the fluorescent probe bisoxonol, demonstrate a transient hyperpolarization of the plasma membrane on exposure to OFRs, temporally associated with the rise in [Ca++]i. In summary, OFRs cause an increase of intracellular calcium in endothelial cells. This response is dependent on extracellular calcium and independent of voltage-sensitive calcium channels. The increase can be partially inhibited by other divalent cations. These results suggest that the transformation of the plasma membrane components (lipid peroxidation and cross-linking of proteins) caused by OFRs may produce cation ionophores.

Animals↗
PubMed1989

Complete sequence of the lamprey fibrinogen alpha chain.

The complete amino acid sequence of the lamprey fibrinogen alpha chain has been determined by a combination of peptide sequencing and cDNA and genomic cloning. The chain, which has an apparent molecular weight by dodecyl sulfate-polyacrylamide gel electrophoresis of ca. 100,000, is composed of 961 amino acid residues and has a calculated molecular weight of 96,722. It is distinguished by a large number of 18-residue repeats in a region where mammalian fibrinogens have 13-residue repeats. The data are in accord with our previous finding that the lamprey alpha chain has a distinctive amino acid composition, almost half the residues being glycine, serine, or threonine. The chain differs from mammalian alpha chains in that there are no cysteines in the carboxy-terminal half, and thus no intrachain loop, nor are there any RGD sequences in the lamprey alpha chain. Taken together with previous data on the sequences of the beta and gamma chains, the findings bear significantly on our understanding of fibrin formation. The alpha chain also provides an interesting case of structural convergence during evolution.

Amino Acid Sequence↗
PubMed1989

A common binding site for tricyclic and nontricyclic 5-hydroxytryptamine uptake inhibitors at the substrate recognition site of the neuronal sodium-dependent 5-hydroxytryptamine transporter.

An investigation of the site of interaction of a variety of tricyclic and nontricyclic 5-HT uptake inhibitors with the neuronal sodium-dependent 5-HT transporter was undertaken. The dissociation of [3H]paroxetine binding induced by indalpine (10 microM), SL 81.0385 (10 microM), fluoxetine (10 microM), citalopram (10 microM), paroxetine (0.15 microM), imipramine (10 microM) and 5-HT (50 microM) produced monophasic dissociation curves and gave t1/2 values of dissociation similar to that induced by dilution alone. In inhibition studies of [3H]paroxetine binding with citalopram, imipramine and 5-HT, increases in the concentration of [3H]radioligand used led to parallel rightward shifts of the inhibition curves with no diminution of the maximum degree of inhibition (Imax). "Schild-type" analyses of the data obtained from the inhibition curves with these 3 compounds gave slopes close to unity. In chemical modification studies, treatment of membrane fractions with N-ethylmaleimide led to a pronounded reduction in specific [3H]paroxetine binding. Preincubation of these membranes with SL 81.0385, fluoxetine, imipramine, tryptamine and 5-HT provided significant protection against this NEM-induced inactivation. The above findings are interpreted to provide evidence for a common or at least overlapping binding site for the tricyclic and nontricyclic 5-HT uptake inhibitors with the substrate recognition site of the neuronal sodium-dependent 5-HT transporter.

Animals↗
PubMed1989

Effect of estradiol on low density lipoprotein uptake by bovine aortic endothelial cells.

The means by which estrogen retards atherosclerosis cannot be explained solely by changes in circulating lipoprotein levels. We studied the effects of 17 beta-estradiol on the binding, incorporation, and degradation of low density lipoprotein (LDL) by cultured bovine aortic endothelial cells (BAEC). Estrogen receptors in the cytoplasm and nucleus of BAEC could be demonstrated by immunofluorescent staining. Estradiol was found not to affect surface binding of LDL to BAEC. However, at physiologic concentrations (50 pg/ml), estradiol did enhance LDL uptake by the BAEC (P less than 0.005). This enhancement was present but somewhat reduced at higher concentrations of estrogen (P less than 0.05). Only approximately 10% of incorporated LDL was trichloroacetic acid soluble, indicating a low rate of LDL degradation. The relative rate of LDL breakdown within the BAEC was not altered by estrogen. These results, showing estrogen stimulation of LDL uptake by the BAEC, do not clarify the protective effect of this hormone. It is speculated that estrogen may augment the cellular clearance of LDL.

Animals↗
PubMed1989

Effects of argon laser radiation on aortic endothelial cells: early membrane changes and proliferative response.

Membrane fluidity, transmembrane signaling responses, and proliferative characteristics of endothelial cells were studied to characterize biochemical and molecular changes after treatment with argon laser energy. Bovine aortic endothelial cells grown in monolayers were irradiated at 50, 100, and 200 J with an argon laser (wavelength, 488 and 514 nm). Proliferation, assayed by [3H]thymidine incorporation, was measured daily for 6 days. An initial lag phase was observed for irradiated cells when compared to nonirradiated controls (P less than 0.03), with eventual recovery by the third day. Membrane fluidity, determined by fluorescence anisotropy, was measured 1 hr after irradiation. A decrease in static rotational motion of 1,6-diphenyl-1,3,5-hexatriene (DPH) was noted in irradiated versus nonirradiated cells indicating a decrease in membrane fluidity (P less than 0.02). Dynamic studies of intracellular calcium and pH flux utilizing fluorescent probes demonstrated a preserved response to mitogenic stimulation. An increase in intracellular Ca2+ with a concomitant alkalinization of the intracellular milieu was observed in irradiated and non-irradiated cells in response to stimulation with endothelial cell growth factor (ECGF). These responses resemble those characterized for other mitogens. Argon laser energy applied to aortic endothelial cells decreases membrane fluidity early after irradiation. These alterations probably cause the initial lag observed in their proliferative response; however, the capacity to respond to exogenous mitogenic stimulation is maintained.

Animals↗
PubMed1989

cDNA cloning reveals that the major group rhinovirus receptor on HeLa cells is intercellular adhesion molecule 1.

A 90-kDa surface glycoprotein was previously isolated and shown to be required for infection by the "major" group of human rhinovirus (HRV) serotypes. In the present work, the amino acid sequence of the receptor protein was obtained from CNBr and tryptic peptides. Using degenerate oligonucleotides predicted from the peptide sequences, we identified four cDNA clones that encode a 3-kilobase mRNA. The clones were ligated, subcloned in a simian virus 40 expression vector, and used to transfect receptor-negative Vero (monkey) cells. Results showed that transfected cells expressed receptor molecules capable of binding HRV and a monoclonal antibody which recognizes the major group HRV receptor. The cloned receptor cDNA encoded a protein with a sequence nearly identical to that of the intercellular adhesion molecule 1 (ICAM-1), indicating that the two surface proteins are one and the same. Both proteins have identical mass, carbohydrate composition, and tissue distribution. In addition, major group receptors on HeLa cells could be induced with various cytokines in a manner similar to the ICAM-1 ligand. A similar induction of the HRV "minor" group receptor was not observed.

Amino Acid Sequence↗
PubMed1989

Neuropathology of vigabatrin.

1. Neuropathological changes in experimental animals have been observed with vigabatrin treatment in mice, rats and dogs. 2. These changes have comprised intramyelinic oedema which is reversible on cessation of treatment. 3. In human studies so far, no intramyelinic oedema has been noted. It is not clear whether humans will show the neurotoxicity observed in animals; close monitoring of patients is indicated.

Aminocaproates↗
PubMed1989

The effect of estrogen on low-density lipoprotein binding kinetics in aortic endothelial cells.

The inhibition of atherosclerosis by estrogen has been shown clinically and experimentally, but the mechanism by which this occurs is unknown. Previous studies have shown that estrogen enhances the uptake of low-density lipoprotein (LDL) by bovine aortic endothelial cells (BAEC) while not altering membrane binding at saturating levels of LDL. In this study the effect of estrogen on LDL binding kinetics has been investigated. Computer-assisted Scatchard analysis of binding data suggests a single-site binding model. Estrogen-treated BAEC showed a lower binding affinity (Ka = 2.47 +/- 0.74 E7 M-1) than control cells (1.95 +/- 0.21 E7 M-1) (p = 0.0012). Estrogen-treated cells, however, had a greater binding capacity (Bmax = 1.26 +/- 0.07 E-10M) than control cells (Bmax = 8.49 +/- 0.44 E-11M) (p = 0.0004). The latter was due primarily to a difference in LDL binding at higher concentrations of LDL (greater than 40 micrograms/ml). These findings are consistent with an estrogen-stimulated increase in low-affinity binding of LDL to BAEC, which may not be directly receptor mediated and which appears to enhance the uptake of LDL at higher lipoprotein concentrations. Such alterations in LDL uptake by endothelial cells could influence the formation of atherosclerotic plaque.

Animals↗
PubMed1989

A simple modification of closed suction drainage systems.

A simple modification (patent pending) of existing systems of closed suction drainage is described herein. This system maintains patency in a closed sterile manner and facilitates sampling of drainage for laboratory analysis.

Drainage↗
PubMed1988

Clinicopathological study of neurological complications due to hypertensive disorders of pregnancy.

Forty-three women with neurological complications secondary to eclampsia or severe pre-eclampsia were studied by CT scanning and in six intracranial pressure (ICP) monitoring was carried out. In seven women who died, neuropathological findings were correlated with clinical features. Cerebral oedema was present in 27 of the patients studied and the severity of oedema correlated to the duration of intermittent seizures. In five of the six women who had ICP measured, this was found to be transiently high. Intracranial haemorrhage was demonstrated in four of the 43 women, all of whom died. Hypoxic-ischaemic cerebral damage and fibrinoid necrosis were the most important neuropathological lesions identified. The management of neurological complications of eclampsia may be placed upon a more rational basis by an understanding of the mechanisms responsible for these lesions.

Adolescent↗
PubMed1988

Experimental rhinovirus infection in human volunteers exposed to ozone.

We studied 24 young adult male volunteers experimentally inoculated with type 39 rhinovirus to determine whether the course of viral infection was modified by exposure to moderate levels of ozone (0.3 ppm for 6 h per day) over the 5 days after virus inoculation. No differences in rhinovirus titers in nasal secretions, recruitment of neutrophils into nasal secretions, levels of interferon in nasal lavage fluid, in vitro lymphocyte proliferative responses to rhinovirus antigen, or levels of convalescent serum neutralizing antibody to type 39 rhinovirus were demonstrated in relation to ozone exposure. The level and pattern of ozone exposure used in this experiment had no demonstrable adverse effects on the immune responses necessary to limit and terminate rhinovirus infection of the upper respiratory tract.

Adult↗
PubMed1988

Painful heel syndrome: radiographic and treatment assessment.

From July 1980 to January 1986, 170 patients who had unilateral heel pain were examined, x-ray filmed, and treated in a similar fashion. Radiographs of painful and nonpainful heels were measured. There was a statistically significant increased thickness of the heel fat pad and subfascial area compared with that of the control subject (the nonpainful side). A tightness of the Achilles tendon and a new sign, which the authors are designating as the "saddle" sign, were other prominent features. A treatment program of stretching exercises and walking seemed to be effective in relief of symptoms.

Heel↗