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Biomedical subjects

C A Lewis

Publications and source records attributed to C A Lewis.

At least 91 records · Page 5Linked to original sources
PubMed1990

Glutamate stimulates release of Ca2+ from internal stores in astroglia.

We report here that, in the absence of external Ca2+, glutamate produces a transient increase in intracellular Ca2+ [( Ca2+]i) in cultured spinal cord astrocytes, by mobilizing internal Ca2+ stores. [Ca2+]i was measured with Fura-2 using the ratiometric method. Astrocytes were identified by immunostaining for glial fibrillary acidic protein. Glutamate and quisqualate consistently caused a transient increase in [Ca2+]i, with both the response amplitude and latency being graded functions of agonist concentration. Some cells produced multiple transients. N-Methyl-D-aspartate, kainate and aspartate were ineffective. We conclude that the quisqualate subtype of glutamate receptors mediates release of Ca2+ from internal stores in mammalian astrocytes.

Animals↗
PubMed1990

Developmental changes in the regulation of glycine-activated Cl- channels of cultured rat medullary neurons.

Glycine-activated currents in 1- to 11-day-old rat medullary neurons were studied using patch clamp techniques. Glycine produced neither repeatable whole-cell current responses nor single-channel activity in the cell-attached mode until cells were in culture for a week or more. However, Cl- channels were present at the early stages because glycine-activated channels were seen in excised, inside-out patches. Furthermore, for cells less than a week in culture, 10 patches which did not exhibit glycine-activated Cl- channels in the cell-attached mode did upon excision. Consequently, the activation properties of these Cl- channels undergo a developmental change in that some cellular factor(s) presumably prevents the Cl- channels from opening in the intact cell during the initial stages in culture.

Animals↗
PubMed1989

Characteristics of glycine-activated conductances in cultured medullary neurons from embryonic rat.

Characteristics of glycine-activated currents in 10- to 20-day-old neurons were studied using the gigaseal whole-cell technique. Glycine activated a Cl- conductance that was blocked by strychnine acting as a mixed inhibitor, effecting both Imax and Kd. Glycine receptors with at least two different sensitivities to strychnine were found, based on the apparent inhibition constants (Ki). These two Ki values were associated with different Hill coefficients for the glycine responses. Cs+ activated the same receptor and also activated a relatively nonselective cation conductance.

Animals↗
PubMed1989

Radionuclide imaging of ureteric peristalsis.

Dynamic renal scintigraphy is a successful and minimally invasive technique for evaluating renal function. An extension to the basic technique involving fast-frame acquisition and a modified analysis is described which enables ureteric function to be examined. Ureteric peristalsis was assessed in 32 patients using this technique. The results from 5 representative studies are described in detail. Normally functioning ureters exhibit peristaltic contractions at a frequency of up to 3/min. Hyperperistalsis that exceeds 4 contractions/min is associated with obstruction. Peristaltic behaviour in 9 patients examined before and after ESWL was not altered.

Adult↗
PubMed1988

Chronic malnutrition, dental caries, and tooth exfoliation in Peruvian children aged 3-9 years.

A cross-sectional evaluation of dental caries in primary teeth and nutritional status was conducted involving 285 Peruvian children from low socioeconomic conditions aged 3-9 y. Forty-nine percent of the children were found to be chronically malnourished (stunted) whereas acute malnutrition (wasting) was infrequent (2%). Stunted children showed a delayed exfoliation of primary teeth. The caries prevalence curve as a function of age (ie, a plot of decayed, extracted, and filled teeth vs age) was found to be shifted to the right by approximately 15 mo in stunted children as compared with well-nourished children. Children aged 7-9 y with stunted growth showed a significantly higher percentage of carious teeth than did well-nourished children of the same age (40 and 29%, respectively; p less than 0.005). Nutritional deficits that lead to chronic malnutrition not only may affect tooth exfoliation but also appear to render the primary teeth more susceptible to caries attack later in life.

Child↗
PubMed1988

Estimated radiation doses to different organs among patients treated for ankylosing spondylitis with a single course of X rays.

A follow-up study of over 14,000 patients treated with a single course of X rays for ankylosing spondylitis demonstrated a substantial excess risk of developing cancer. Previously the excess risk of leukaemia has been related to the estimated mean radiation dose to the active bone marrow but detailed estimates were not made of the radiation doses to other organs. In the present work, data extracted from the original treatment records of a random sample of one in 15 patients have been used to make dose estimates, using Monte Carlo methods, for 30 specific organs or regions of the body and 12 bone marrow sites. Estimates of the mean and median organ doses, standard deviations and ranges have been tabulated. Detailed distributions are presented for six organs (lung, bronchi, stomach, oesophagus, active bone marrow and total body). Comparison with the earlier bone marrow estimates and more recent theoretical estimates shows good agreement.

Adult↗
PubMed1987

Fatty acids, cholesterol, and their roles in ischemia.

Dietary fatty acids and cholesterol have been associated with the development of atherosclerosis. This paper suggest metabolic pathways involved in this process. Specific fatty acids (DGLA, GLA) with high specificity for cholesterol transport enzymes give a high efficiency for transport of cholesterol to the liver. Arachidonic acid (AA) is proposed to block the endogenous conversion of dietary linoleic acid to GLA and DGLA, which results in impared cholesterol transport to the liver and increased serum levels. Increased levels of cholesterol and its oxygenation products promote the release of AA from membrane phospholipids and its conversion to thromboxane, resulting in a positive feedback reaction of thrombus formation and ischemia.

Cholesterol↗
PubMed1986

Pulmonary epithelial permeability: vascular background effects on whole lung and regional half-time values.

Pulmonary epithelial permeability was first measured by Jones et al. We have adapted their technique for use with a gamma camera. Both regional half-time values and background correction factors vary from apex to base in the lung. Examination of two methods of background correction show: that inter-segmental half-time comparison is possible without applying individual correction factors to regions. the use of a region of interest with similar vascular supply to that of the lung eliminates the need for a background correction technique that relies upon an intravenous injection of radioisotope. The inter-renal area provides such a vascular area.

Adult↗
PubMed1985

Clearance of 99m-technetium-labelled DTPA in asbestos-exposed subjects without clinical or radiological evidence of interstitial lung disease.

The half-time clearance of an inhaled aerosol of 99m-technetium-labelled diethylene triamine pentacetate from lung to blood (T1/2LB) was measured using a gamma camera in 20 non-smoking subjects (mean age 54, range 40-69 years) with previous occupational asbestos exposure, but no clinical or radiological evidence of asbestosis, and 20 non-smoking normal subjects (mean age 54, range 40-62). Mean T1/2LB was 44.7 minutes (range 12-102) in exposed subjects, significantly less than 57.2 minutes (range 30.5-109) in normal subjects (P less than 0.05). There was no correlation between age and T1/2LB in either group. In exposed subjects T1/2LB showed a weak rank correlation with the membrane component of DLco (Dm) (r = 0.40, P less than 0.05) but no significant correlation with FVC, TLC, DLco, Kco, resting Pao2 or change in Pao2 on exercise. In six exposed subjects T1/2LB was shorter than in any of the normal subjects. These six did not differ from the other 14 exposed subjects in any physiological variables. T1/2LB is abnormal in some asbestos-exposed subjects without clinical, radiological or physiological evidence of asbestosis. Follow-up will show whether it is an early indicator of development of interstitial lung disease.

Adult↗