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Biomedical subjects

S Lewis

Publications and source records attributed to S Lewis.

At least 397 records · Page 22Linked to original sources
PubMed1984

The involvement of central alpha adrenoceptors in the antihypertensive actions of methyldopa and clonidine in the rat.

The antihypertensive effects of methyldopa and clonidine result from agonist activity at alpha adrenoceptor sites within the brain. Methyldopa is converted enzymatically to alpha-methylnoradrenaline in noradrenergic neurones in rat brain and replaces the natural transmitter, noradrenaline. Radioligand receptor studies show that alpha-methylnoradrenaline differs from noradrenaline in being much more selective (70 times) for the alpha 2 subclass of adrenoceptors than noradrenaline and it is likely that the antihypertensive action of methyldopa results from selective activation of alpha 2 adrenoceptors by alpha-methylnoradrenaline in the nucleus tractus solitarius and the anterior hypothalamus. Radioligand studies also show that clonidine is a selective alpha 2 adrenoceptor agonist although it probably interacts with alpha 1 adrenoceptors at higher concentrations. With regard to a withdrawal syndrome after cessation of clonidine treatment, the cardiovascular and behavioural components can now be characterised in a rat model. The components include increases in basal blood pressure and heart rate, as well as increases in cardiovascular reactivity and also increases in rapid eye movement (REM) sleep, body shakes and tremor which is reminiscent of an opiate withdrawal syndrome. Increased central noradrenergic activity is involved in this syndrome and alpha 1 and alpha 2 adrenoceptors mediate opposing effects on the REM sleep rebound component.

Animals↗
PubMed1983

Essential fatty acids and maladjusted behaviour in children.

It has been suggested that hyperactivity may be produced by a deficiency in essential fatty acids (EFA) leading to a deficit in prostaglandin (PG) formation. The red blood cells EFAs levels were examined in 23 maladjusted children and in 20 normal children. Although no individual EFA showed statistically significant differences between the normal and maladjusted children, multivariate analysis showed that the levels of EFA series 2 PG precursors in maladjusted children were significantly lower than in controls as predicted (P = 0.0001).

Adolescent↗
PubMed1983

Changes in coronary heart disease risk factors associated with increased treadmill time in 753 men.

Associations between changes in treadmill time and changes in coronary heart disease risk factors were studied in 753 middle-aged men seen between 1978-1981 at the Cooper Clinic in Dallas, Texas. Men were free of known disease at baseline. Significant increases (p less than 0.01) in exercise habits and treadmill time were seen over the course of the study; average follow-up was 1.6 years. In bivariate analyses, increases in treadmill time and weight loss were associated with improvements (p less than 0.01) in risk factors. Multiple regression models were calculated for several risk factors with age, length of follow-up, change in weight, and change in treadmill time as independent variables. After controlling for confounding, increase in treadmill time was independently associated with decreases in the total cholesterol/high density lipoprotein-cholesterol ratio (p less than 0.01) and serum uric acid (p less than 0.05). High density lipoprotein-cholesterol rose with increase in treadmill time (p less than 0.05).

Adult↗
PubMed1983

Terminating chemotherapy: another stage in coping with childhood leukemia.

As physicians become increasingly capable of managing the physical aspects of cancer, the psychological responses of patients and their families take on growing importance. The present study sought to assess the psychological experience of parents whose leukemic children are finishing chemotherapy. Nineteen mothers and one father of children whose chemotherapy had been discontinued were interviewed. The results suggested that negative reactions including anxiety and fears relating to relapse may be a normal emotional response. This paper discussed aspects of the experience of caring for a leukemic child that contribute to this fear and anxiety and possible ways of easing parents' discomfort.

Adaptation, Psychological↗
PubMed1982

A species comparison of the histamine H2-receptor on mast cells and basophils.

The histamine H2-agonist dimaprit was employed in experiments to investigate the role of H2-receptors in mediator release systems from the rat, guinea-pig and man. Whereas inhibition of histamine release by dimaprit was observed in all 3 species, this effect appeared not always to be related to H2-receptor occupancy. Although the data in general support previous evidence for the presence of H2-receptors on human basophils and guinea-pig mast cells, the use of dimaprit as a pure H2-agonist in these studies is questioned. No evidence for H2-receptors on rat mast cells was obtained.

Animals↗
PubMed1982

Continuing kappa-gene rearrangement in a cell line transformed by Abelson murine leukemia virus.

A cell line transformed by Abelson murine leukemia virus, called PD, is capable of carrying out kappa-gene rearrangement while growing in culture. Subclones of PD have diverse kappa-gene structures, and some derivatives show evidence of continued joining activity after as many as three subclonings. Analysis of PD sublineages has shown that a rearranged chromosome can undergo secondary kappa-gene rearrangements, producing either a new rearrangement or a deletion of C kappa. Although the PD line actively rearranges its kappa genes, its rearranged heavy-chain genes show little variation, and there is no rearrangement of lambda genes. In PD subclones, DNA fragments representing the reciprocal product of kappa-gene rearrangement are often evident, and they may undergo either further rearrangement or deletion. The implications of multiple rearrangements on a single chromosome and of the maintenance of reciprocal fragments are considered in the context of a model that postulates that the V kappa and J kappa segments are not all organized in the DNA in the same transcriptional direction, leading to inversions rather than deletions during joining.

Abelson murine leukemia virus↗
PubMed1982

Serological and cytological evidence for increased Y-chromosome related material in Sxr,XY (sex-reversed carrier, male) mice.

In order to define the nature of the genetic lesion which gave rise to Sxr, the sex-limited autosomal dominant sex reversal condition in the mouse, cytological and serological studies were carried out comparing Sxr,XY (males carrying the sex-reversal gene) and normal XY male mice. Cytotoxic H-Y antisera were absorbed by splenocytes or sperm from both Sxr,XY and normal XY male mice. Our results indicate that for both types of tissue, Sxr,XY cells absorbed consistently greater amounts of cytotoxic activity than did normal XY cells. Whole-mount electron micrographs as well as light micrographs of silver-stained spermatocytes suggest that during meiotic prophase in Sxr,XY males, the paracentromeric region of the normal Y chromosome pairs with a supernumerary Y chromosomal fragment. This fragment can be identified as one of Y chromosomal origin by its thickened axial core. Taken together, our findings support the notion that the Sxr syndrome in the mouse can be due to a supernumerary Y chromosomal fragment containing male determining factors (including one or more H-Y structural or regulatory genes) rather than to a constitutive autosomal mutation.

Animals↗
PubMed1982

High-contrast film copying for thallium 201 cardiac image processing.

To evaluate the usefulness of high-contrast film copying as an economical means of enhancing contrast in thallium 201 cardiac images, stress and rest studies of 47 patients with and 19 patients without coronary artery disease were evaluated. A total of 66 sets of four different image formats were independently interpreted by five observers. The analysis of the receiver operating characteristic curves suggested that the high-contrast film copies were superior to their original analog images and comparable with computer-processed images in diagnostic yield. It appears that contrast enhancement by simple film copying can improve the accuracy of 201Tl image interpretation.

Coronary Disease↗
PubMed1982

A statistical analysis of the spectral moments used in EMG tests of endurance.

EMG and bandlimited noise (BLN) signals of comparable spectra were processed to compute the centroid and median frequencies and the high/low ratio for different record lengths, signal amplitudes, and noise bandwidths. The spectral moments of EMG and BLN showed similar statistical properties, independent of record length and amplitude. The signal-to-noise ratios of the moments increased with record length. Relatively short records were sufficient to obtain low coefficients of variations especially for the centroid, which was the most stable and sensitive to changes in the underlying spectra. The high/low ratio was the least stable moment. A change of 10 and 3.9% in the centroid over successive records of overall duration of 8 and 10 s, respectively, was just sufficient to detect a spectral shift at the P less than 0.05 level. The equivalent percents for the high/low ratio were 66 and 32.5, respectively. These thresholds of significance were related to time constants of equivalent exponential trends in the spectra used to study fatigue. This relationship makes the results of the present study applicable to a wide variety of EMG tests of endurance.

Electromyography↗
PubMed1982

Five-year experience of a community outreach program for the elderly.

The authors report on more than 2,000 impaired elderly people who were referred to a geriatric outreach program during its first 5 years of operation. These patients were referred by a wide variety of professionals and private citizens, who were usually concerned about the person's ability to care for himself or herself or about psychiatric symptoms. The most common diagnosis was dementing illness (21% of the patients), followed by depression (13%). Intervention usually involved making appropriate plans based on an accurate diagnosis, often including coordinating the services of other agencies. A follow-up of 100 patients showed that most of the patients who were still living had maintained their independence.

Aged↗
PubMed1981

Identification of 2-nitrofluorene in diesel exhaust particulates.

Diesel exhaust particulates contain mutagens which are direct-acting in the Ames test. A dichloromethane extract of these particulates was separated by liquid chromatography and analyzed by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). 2-Nitrofluorene, a known carcinogen and direct mutagen, was positively identified by comaxima of ion fragments and retention time on the gas chromatograph.

Air Pollutants↗
PubMed1981

Pre- and postoperative evaluation of renal function in patients with staghorn calculi utilizing quantitative renal scanning.

Differential quantitative renal scans using 99-technetium diethylene triaminepentaacetic acid (DTPA) or 131I Hippuran were obtained properatively on 12 patients with unilateral or bilateral staghorn calculi. Of the 14 renal units studied, 12 kidneys underwent anatrophic nephrolithotomy, pyelolithotomy, or a combination of both techniques; 2 patients underwent nephrectomy based on poor function of the affected side preoperatively. Postoperative follow-up scans were obtained on the 12 kidneys undergoing stone cleanout. Seven of 12 kidneys (58 per cent) studied pre- and postoperatively showed moderate to significant improvement in per cent contribution to total renal function. Seven of 10 kidneys (70 per cent) studied pre- and postoperatively showed improvement in glomerular filtration rate or effective renal plasma flow. The scans revelaed no dramatic difference in postoperative functional loss between pyelolithotomy and anatrophic nephrolithotomy. The computerizewd quantitative renal scan helps in selection of surgical technique and objective postoperative assessment of surgical results.

Adult↗