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Biomedical subjects

M Wilson

Publications and source records attributed to M Wilson.

At least 577 records · Page 32Linked to original sources
PubMed1988

Magnetic resonance imaging with even-echo rephasing sequences in the assessment and management of giant intracranial aneurysms.

The role of magnetic resonance imaging in the assessment of giant intracranial aneurysms was compared with angiography and contrast-enhanced computed tomography (CT) in 18 patients. The use of T1- and T2-weighted spin-echo (SE) sequences demonstrated both the presence and the evolution of thrombus within these lesions. High-velocity flow within the parent vessels and still-patent lumen could be defined as an area of absent signal. The use of even-echo rephasing (EER) sequences provided a rapid technique for demonstrating and confirming the presence of luminal flow, which is shown as areas of high signal. The combination of SE and EER techniques proved superior to CT in the assessment of thrombus and flow patterns in these lesions, as well as enabling superior demonstration of the patency of the parent vessel following surgical ligation. Computed tomography remains the most accurate method of defining the presence and location of associated calcification.

Adult↗
PubMed1988

The in vitro effects of amine fluorides on plaque bacteria.

Forty strains of bacteria which may be isolated from subgingival plaque were tested for their in vitro susceptibility to several amine fluorides and a commercial formulation (Elmex gel) containing these compounds. The amine fluorides were active against a wide range of plaque bacteria with gram-positive strains tending to be more sensitive than gram-negatives. The minimum inhibitory concentrations ranged from 45 to 1440 micrograms/ml with approximately half of the strains being inhibited at a concentration of 130 micrograms/ml of amine fluoride. The Elmex gel had a bactericidal effect on all of the strains tested and exhibited a rapid killing action at high dilutions. These in vitro findings suggest that amine fluorides may be useful in the treatment or prophylaxis of plaque-related diseases.

Amines↗
PubMed1988

Effect of capsular material from Haemophilus actinomycetemcomitans on bone collagen synthesis in vitro.

Capsular material was extracted from Haemophilus actinomycetemcomitans, an organism associated with localised juvenile periodontitis, and examined for its effect on the in vitro synthesis of collagen and DNA in mouse calvaria. The material was found to cause a significant inhibition of both collagen and DNA synthesis at concentrations as low as 10 ng ml-1. The ability of capsular material to inhibit bone formation, together with its previously described bone resorbing activity, suggests that it may contribute to the rapid alveolar bone loss which is characteristic of localised juvenile periodontitis.

Animals↗
PubMed1988

The role of bacterial surface components in periodontal destruction.

This paper reports the activity associated with capsule-derived material and lipopolysaccharide extracted from Actinobacillus actinomycetemcomitans on connective tissue cells. The ability of lipopolysaccharide (LPS) to initiate inflammatory and destructive processes in the pathogenesis of periodontal disease was compared to that of capsular material (CM). The biological activities investigated were cytotoxicity to fibroblasts, stimulation of in-vitro bone resorption and Interleukin 1-like activities.

Actinobacillus↗
PubMed1988

Histologic lesions in broiler chicks given cyclopiazonic acid orally.

Cyclopiazonic acid dissolved in corn oil was administered by gavage to broiler chicks (n = 80) daily, from the day of hatching for 23 days. Chicks were assigned to 3 groups (1, 2, or 4 mg of cyclopiazonic acid/kg of body weight); a control group was given corn oil. Each group was composed of 10 male and 10 female chicks. Surviving chicks were euthanatized and necropsied on day 24. Histologic examination revealed that the most common lesions consisted of necrosis and hemorrhage or hyperplasia of the mucosa of the proventriculus and hepatocellular vacuolation. Skeletal muscle degeneration, characterized by myofiber swelling or fragmentation accompanied by an infiltrate of macrophages and heterophils, was detected in the group given 4 mg/kg. This degeneration was associated with an increase of plasma creatine kinase activity. Focal hepatocellular and splenic necrosis also developed in the groups given 4 mg/kg.

Administration, Oral↗
PubMed1987

Is changing hypothalamic activity important for control of ovulation?

The activity of the hypothalamic gonadotrophin releasing hormone pulse generator in women with regular ovulatory and anovulatory menstrual cycles was assessed to see whether changes therein are important determinants of normal and impaired ovarian function. Endogenous gonadotrophin releasing hormone secretion was inferred by measurement of the pituitary luteinising hormone response by characterisation of pulsatile luteinising hormone release over eight hours on three occasions during the course of follicular development and once during the luteal stage of the same cycles. In 13 ovulatory cycles (serum progesterone concentration greater than 25 nmol/l) confirmed by ovarian ultrasonography a pronounced variability in luteinising hormone pulse patterns among subjects was compatible with ovulation. In the luteal stage of ovulatory cycles the luteinising hormone interpeak interval (85 min, range 42-125) was significantly longer than that during the early follicular (64 min, 40-103), mid-follicular (62 min, 37-107), and late follicular (59 min, 39-80) stages of the same cycles. Thus in ovulatory cycles no increase in frequency of the gonadotrophin releasing hormone pulse generator was detected during follicular development, though this activity decreased in the luteal stage. In five late follicular stage studies in which part of the preovulatory luteinising hormone surge was captured no change in pulse frequency of luteinising hormone was detected compared with the mid-follicular stage of the same cycles or when compared with the late follicular stage of other cycles when no luteinising hormone surge was captured. Though mean luteinising hormone concentrations in luteinising hormone surge series (36 IU/l) were high, the amplitude of luteinising hormone pulses (165%) was only slightly greater than during non-surge late follicular stage studies (145%). Hence no change in hypothalamic gonadotrophin releasing hormone activity is required to generate the preovulatory discharge of luteinising hormone in man, which occurs as a result of the sensitising action of rising oestradiol concentrations on pituitary responsiveness to the same hypothalamic input signal. Luteinising hormone pulse frequency, peak amplitude, and mean serum luteinising hormone concentrations in seven anovulatory cycles (progesterone concentration less than 10 nmol/l) were not different from those at comparable stages of ovulatory cycles. These data suggest that the primary abnormality in this group of regularly menstruating anovulatory women lies in the ovary rather than in the hypothalamic control of the anterior pituitary.

Adult↗
PubMed1987

Prescription medications in infancy and early childhood.

The prescription medication exposures of a cohort of 222 children during their first five years of life were investigated. Excluding the three outliers, the cohort received 1852 medications (average per child, 8.46; mode, six; range, 0 to 37) during 1358 (23%) of the total 6017 visits made in five years. The greatest number of medications were administered or prescribed between 7 and 12 months of age. The majority (62%) of the medications over five years were oral preparations, and 87% were prescribed for two weeks or less. Antibacterials, bronchodilators, and antifungal-anti-yeasts accounted for 80% of the 1852 medication courses. One third of all medications were for ampicillin or amoxicillin. High medication recipients were likely to have chronic conditions, especially recurrent otitis media and/or asthma, and were likely to be high users of our health facility.

Age Factors↗
PubMed1987

Stimulus categorization by brain-damaged patients.

Patients with localized insult to the right hemisphere, or to either the anterior or the posterior portion of the left hemisphere, as well as neurologically intact controls, evaluated stimuli on a seven-point rating scale for their degree of category membership. The stimuli were taken from one of two continua, one composed of fruit and vegetable items, and the other of items differing in hue and shape. Different subsets of stimuli provided different contexts for the judgments of category membership. The two left-hemisphere groups showed anomalies in categorizing the fruit and vegetable items but not the perceptual items, while the reverse was true for the right-hemisphere patients. Moreover, both left-hemisphere groups demonstrated context effects in their judgments of the representativeness of the fruit and vegetable items, but differed in the way in which they responded to changing contexts. Left posterior patients demonstrated weak category boundaries and even reclassified items. In contrast, patients with left anterior damage showed highly categorical responses and less differentiation of items within a category. All groups showed striking context effects in judgments of perceptual items in terms of changes in representativeness ratings and the location of a category boundary. Alternative interpretations of the results are offered.

Brain Damage, Chronic↗
PubMed1987

Noise analysis predicts at least four states for channels closed by glutamate.

For ion channels that are opened by neurotransmitters, analysis of current noise has given valuable information on the kinetics of synaptic channel gating. In depolarizing bipolar cells of the vertebrate retina, we have recently characterized a synaptic current for which the neurotransmitter glutamate closes channels, and for which the channel open probability is low even in the absence of glutamate. We present here predictions for the current noise spectrum expected for various models of glutamate's action on the ion channels. Comparison of these theoretical predictions with experimental data allows us to rule out several simple kinetic schemes for the action of glutamate, and to conclude that the channels closed by glutamate must be able to exist in at least four different states.

Animals↗
PubMed1987

The role of lipopolysaccharides in endotoxin-induced thymocyte proliferation and chondrocyte collagenase synthesis.

Crude endotoxin preparations from Haemophilus actinomycetemcomitans and Bacteroides gingivalis showed activity in the two principal bio-assays for interleukin 1--the lymphocyte activating factor assay and stimulation of chondrocyte collagenase synthesis. Lipopolysaccharides purified from the crude endotoxins had reduced activity in the chondrocyte collagenase assay. The activity of the endotoxins may be due to synergic interaction between their lipopolysaccharides and other, as yet unidentified, bacterial components.

Animals↗
PubMed1987

Lipopolysaccharide (endotoxin) from individual periodontally involved teeth.

The amount of lipopolysaccharide (LPS) in the root surface-associated material from individual periodontally-involved teeth has been determined. LPS was found in the surface material from all of the teeth and the amount present ranged from 19-394 ng/tooth. No significant correlation was found between the amount of LPS extracted from a particular tooth and the mean pocket depth associated with the tooth. However, a weak correlation (rs = +0.461, 0.05 greater than p greater than 0.01) was found between the amount of LPS and the % loss of attachment.

Aged↗
PubMed1987

Neurotransmitter-induced currents in retinal bipolar cells of the axolotl, Ambystoma mexicanum.

1. Whole-cell patch clamping was used to study the membrane properties of isolated bipolar cells and the currents evoked in them by putative retinal neurotransmitters. 2. Isolated bipolar cells show an approximately ohmic response to voltage steps over most of the physiological response range, with an average input resistance of 1.3 G omega and resting potential of -35 mV. These values are underestimates because of the shunting effect of the seal between the patch electrode and the cell membrane. Depolarization beyond -30 mV produces rapid activation (10-100 ms) of an outward current (carried largely by potassium ions), which then inactivates slowly (0.5-2 s). 3. Of five candidates for the photoreceptor transmitter, four (aspartate, N-acetylhistidine, cadaverine, putrescine) had no effect on bipolar cells. The fifth substance, L-glutamate, opened ionic channels with a mean reversal potential of -12 mV in some cells (presumed hyperpolarizing bipolar cells), and closed channels with a mean reversal potential of -13 mV in other cells (presumed depolarizing bipolar cells). 4. The conductance increase induced by glutamate in presumed hyperpolarizing bipolar cells was associated with an increase in membrane current noise. Noise analysis suggested a single-channel conductance for the glutamate-gated channel of 5.4 pS. The power spectrum of the noise increase required the sum of two Lorentzian curves to fit it, suggesting that the channel can exist in three states. 5. The conductance decrease induced by glutamate in presumed depolarizing bipolar cells was associated with a decrease in membrane current noise that could be described as the sum of two Lorentzian spectra, and which suggested a single-channel conductance of 11 pS. The noise decrease implies that the channels closed by glutamate are not all open in the absence of the transmitter. 6. GABA (gamma-aminobutyric acid) and glycine, transmitters believed to mediate lateral inhibition in the retina, open chloride channels in isolated bipolar cells, and increase the membrane current noise. Noise analysis suggested that the channels gated by GABA and glycine have conductances of 4.4 and 7.5 pS respectively. The noise spectra required the sum of two Lorentzian curves to fit them. 7. By whole-cell patch clamping cells in retinal slices, the synaptic transmitter released by photoreceptors was shown to close channels with an extrapolated reversal potential around -3 mV in depolarizing bipolar cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1987

Evaluation of commercial serodiagnostic kits for toxoplasmosis.

To evaluate commercially available diagnostic kits for human immunoglobulin G to Toxoplasma gondii, we purchased three enzyme immunoassay (EIA) (Cordia-T, Toxo Bio-EnzaBead, and Toxoelisa), two indirect hemagglutination (IHA) (TPM-Test and ToxHAtest), one fluoroimmunoassay (Toxoplasma-G FIAX), and one latex agglutination (Eiken Toxotest-MT) kit from U.S. suppliers. A total of 100 serum specimens, including 27 that were negative (less than 1:16) and 73 that were positive for the various titers in the Toxoplasma indirect immunofluorescence (IIF) test, were tested once with each kit; serum samples with discrepant results were retested. Qualitatively, results obtained with the Toxo Bio-EnzaBead EIA, the TMP-Test IHA, and FIAX, and the Toxotest-MT latex agglutination kits agreed exactly with those of IIF. Although all IIF-positive serum samples were detected by the Cordia-T and the Toxoelisa EIAs, four samples determined to be negative by IIF were identified as positive with the Cordia-T kit, and six negative samples by IIF were determined to be positive with the Toxoelisa kit. Results of the ToxoHAtest IHA kit were extremely difficult to read. Quantitatively, the seven kits were difficult to compare because the expression of results was not standardized. Of the four kits that gave positive results in titers, Toxoplasma-G FIAX had the closest agreement with IIF, as determined by the Spearman rank correlation coefficient (0.9168), followed by the Eiken Toxotest-MT (0.8293), the Toxo Bio-EnzaBead (0.7553), and the TPM-Test (0.7206) kits.

Animals↗
PubMed1987

Production of monoclonal antibodies to Naegleria fowleri, agent of primary amebic meningoencephalitis.

Monoclonal antibodies (MAbs) to Naegleria fowleri, the etiologic agent of primary amebic meningoencephalitis (PAM), have been produced and used as probes to identify N. fowleri amebae in brain sections of patients who died of that disease. These MAbs were characterized for their specificity by the indirect immunofluorescence assay (IIF), dot immunobinding assay (DIBA), and enzyme-linked immunotransfer blot technique (EITB). The MAbs reacted intensely with all strains of N. fowleri tested originating from different geographic areas in the IIF and DIBA tests, but showed no reactivity with four other species of Naegleria, N. gruberi, N. jadini, N. lovaniensis, and N. australiensis, or a strain of Acanthamoeba castellanii. In the EITB assay the MAbs reacted with the antigens of N. fowleri and produced intensely staining bands at the 160-, 104-, 93-, and 66-kilodalton (kDa) regions and several minor bands at the 30- and 50-kDa regions. The MAbs also reacted with the antigens of N. lovaniensis and produced a darkly staining band at 160 kDa and a diffusely staining band at 116 kDa, indicating that these antigens were shared by the two species. The MAbs, however, showed no reactivity with N. jadini and N. gruberi in the EITB assay.

Amebiasis↗
PubMed1987

Structure of the receptive fields of bipolar cells in the salamander retina.

1. The receptive-field structure of bipolar cells in the salamander retina has been examined using isolated retinae from dark-adapted eyes. 2. Receptive-field mapping was carried out with a 25-microns diam spot of light whose wavelength and intensity was intended to stimulate rods rather than cones. 3. Both hyperpolarizing and depolarizing bipolar cells showed receptive fields having a single central point of maximum sensitivity from which sensitivity declined radially. Antagonistic surrounds could not be demonstrated using a small spot of light. 4. The diameter of receptive fields was found to vary between 374 and 662 micron, consistent with a single bipolar cell being effectively connected to 323-1,275 rods. 5. Lucifer yellow injections of bipolar cells revealed dendritic arbors whose greatest dimensions varied between 43 and 70 microns, consistent with a direct synaptic connection of between 10 and 24 rods to each bipolar cell. 6. We rule out signal spread within the rod network, extensive lateral ramification of rod process, nonlinearity of synaptic transmission, and light scatter, as possible explanations of large bipolar cell receptive fields. It seems likely, instead, that signals are extensively shared between bipolar cells.

Ambystoma↗