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Biomedical subjects

J Thomas

Publications and source records attributed to J Thomas.

At least 595 records · Page 33Linked to original sources
PubMed1987

[Effects of chemical and radiographic factors on the treatment of renal lithiasis using extracorporeal external shock-wave lithotripsy].

The systematic collection and filtration of urine for three days after extracorporeal shock wave lithotripsy (ECSWL) has enabled the chemical analysis of the stones treated in 90% of cases. We have been able to demonstrate a correlation between the chemical nature and the mode of fragmentation of the stones. Calcium oxalate monohydrate, brushite and cystine stones form fairly large, well separated, angular fragments with sharp edges. Calcium oxalate dihydrate, calcium phosphate and magnesium ammonium-phosphate (struvite) stones are reduced to an amorphous dust. These findings have direct therapeutic implications, as it is absolutely essential to make sure that no large stone fragments are left in the urinary tract after lithotripsy. These elements led us to try to evaluate the chemical nature and the hardness of the stones on the basis of the radiological findings, in order to adopt the best possible therapeutic strategy. Calcium oxalate dihydrate stones have a striated, spiky and non-homogeneous appearance on plain X-rays. They are frequently responsible for filling defects on intravenous pyelography. They are friable stones which are easily fragmented. In contrast, calcium oxalate monohydrate stones present a regular homogeneous opacity on plain X-rays with no filling defect on intravenous pyelography. These stones are hard and are broken up, with difficulty, into large fragments on the initial fluoroscopic images at the start of treatment. Many stones have a mixed composition (calcium oxalate monohydrate, calcium oxalate dihydrate and calcium phosphates): the plain X-ray does not provide sufficient information and the presence of a filling defect on intravenous pyelography may or may not be suggestive of a friable stone.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium Oxalate↗
PubMed1987

[Cystine calculi. In vitro solubility and chemical structure].

A series of cystine stones extracted from the same subject by pyelotomy was used to study the in vitro solubility of these stones in various solutions. Isotonic bicarbonated saline presented a definite dissolving action, but the stone dissolved relatively slowly alpha-mercapto-propionyl-glycine was much more active, even when mixed urine. N-acetylcystine had the same degree of effectiveness as alpha-mercapto-propionyl-glycine. One stone in this series, which was partially covered by a coating of calcium phosphate, dissolved much more slowly than the other stones. In subjects with cystine stones, longstanding large stones are frequently mixtures of phosphates and cystine and, in 21 cases, chemical analyses and infra-red spectrography demonstrated the presence of calcium phosphate on the surface or in the inferior of these stones, associated with ammoniaco-magnesium phosphate in three cases. The presence of phosphates makes oral medical treatment ineffective, but mixed stones are more friable than pure cystine stones and are therefore easier to treat by extracorporeal lithotripsy.

Chemical Phenomena↗
PubMed1987

National survey of hospital policies on pharmaceutical sales representatives' activities.

Hospital pharmacy directors were surveyed nationwide to determine hospital policies on activities of pharmaceutical sales representatives (PSRs). The data were collected by means of a mail survey sent to pharmacy directors in a random sample of 854 hospitals. The survey asked them to indicate whether they had written or unwritten PSR policies and who was responsible for developing and enforcing them and describe the actual policies with regard to access controls, detailing controls, and exhibit controls. The response rate was 52.2%. Of the responding hospitals, 66.6% had written policies. However, many of those with written policies had developed them only recently. The pharmacy director was responsible for developing and enforcing policies on PSR activities in most of the hospitals, although pharmacy and therapeutics committees or purchasing directors developed and enforced such policies in some hospitals. Many hospitals rely on only an oral briefing during the PSR's first visit to communicate policy. The hospitals with written policies tend to be more likely than those without written policies to place specific limits on PSR access to hospitals and on detailing activities. A wide variability exists among the hospitals in the degree of formalization of PSR policies and in the nature of controls on PSRs.

Data Collection↗
PubMed1987

[Proliferation kinetics of MCF-7 cell cultures. II. Synchronization and cell recruitment induced by hormones].

The culture of MCF-7 cells in well known experimental conditions and the analysis of the cellular uptake of 3HTdR under the influence of estrogens (17-beta-E2) and antiestrogens (OH-TAM) at precise concentration levels (10(-6)/10(-9) M) have made possible the study of the growing kinetic process of the cellular cultured population and the determination of the action of such hormonal preparations on the same process. The main findings are as follows: the growing rate of the cultured cells appears to slow down in presence of OH-TAM; the reason for this slowing growth seems to be the "blockade" of the cultured cells in the last part of G1 phase, a phenomenon that has proved to be dose-dependent; by the stimulating effect of the 17-beta-E2, the MCF-7 cells, synchronized in G1, progress simultaneously in their vital cycle during, at least, three divisory cycles; and this "recruitment" effect seems to be characteristic of the estrogen since the synchronization process fades or disappears when the 17-beta-E2 is absent from the culture medium.

Cell Division↗
PubMed1987

[Treatment of hypertrophic cardiomyopathy with nifedipine and propranolol in combination].

Fifteen patients (14 males and 1 female) with hypertrophic cardiomyopathy, ranging from 22 to 67 years of age (mean: 45.5 years) were treated with oral nifedipine and propranolol for 6 to 24 (mean: 18) months. Twelve of the patients had been pretreated with a mean oral dose of 560 mg verapamil for 60 to 93 (mean 78.5) months, showing slight subjective and objective improvement. Treatment with nifedipine and propranolol was terminated in five cases, due to deterioration or side effects after 6 and 12 months, respectively. During combined therapy, two patients reported improvement, whereas in five cases there was no change and eight patients reported deterioration. There was no change in the Sokolow index. The radiologically determined heart volume increased in 10 out of 15 patients and in the total group from 887 +/- 214 to 938 +/- 248 ml/1.73 m2. Echocardiographic measurements showed a significant increase in left atrial diameter from 40.0 +/- 9 to 44.0 +/- 11 mm, whereas ventricular wall thickness remained unchanged. Thus, high-dose verapamil therapy seems superior to nifedipine-propranolol therapy in patients with hypertrophic cardiomyopathy.

Adult↗
PubMed1986

Membrane electrogenesis and sodium transport in filamentous nitrogen-fixing cyanobacteria.

Transport of Na+ and its relationship with membrane potential (delta psi m) was examined in Anabaena L-31 (a fresh water cyanobacterium) and Anabaena torulosa (a brackish water cyanobacterium) which require Na+ for diazotrophic growth. The data on the effect of N,N'-dicyclohexylcarbodiimide indicated that delta psi m was generated by electrogenic proton extrusion predominantly mediated by ATPase(s). In addition, operation of a plasmalemmabound, non-ATP-requiring, H+-pumping terminal oxidase was suggested by the sensitivity of delta psi m to anaerobiosis, cyanide and azide, all of which inhibit aerobic respiration. The response of delta psi m to external pH and external Na+ or K+ concentrations indicated that a diffusion potential of Na+ or K+ may not contribute significantly to delta psi m. Kinetic studies showed that Na+ influx was unlikely to be a result of Na+/NA+ exchange but was a carrier-mediated secondary active transport insensitive to low concentrations (less than 10 mM) of external K+. There was a close correspondence between changes in delta psi m and Na+ influx; all the treatments which caused depolarisation (such as low temperature, dark, cyanide, azide, anaerobiosis, ATPase inhibitors) lowered Na+ influx whereas treatments which caused hyperpolarisation (such as 2,4-dinitrophenol, nigericin) enhanced Na+ influx. Remarkably low intracellular Na+ concentrations were maintained by these cyanobacteria by means of active efflux of the cation. The basic mechanism of Na+ transport in the fresh water and the brackish water cyanobacterium was similar but the latter demonstrated less influx, more efficient efflux, more affinity of carriers for Na+ and less accumulation of Na+, all attributes favouring salt tolerance.

Biological Transport↗
PubMed1986

Postconfluency MDCK monolayers as an in vitro model of solid tumor chemosensitivity.

Shortly after reaching confluency, canine MDCK cells enter a prolonged state of basal growth with doubling times of 200-300 hours. These values are similar to those commonly exhibited by in vivo solid tumors at clinically relevant sizes. By comparison with rapidly growing sparse density cultures, the postconfluent monolayers displayed a pronounced resistance to deazauridine, deoxyspergualin, and 5-fluorouridine. Drug concentrations required for unit levels of effect increased from several fold to several orders of magnitude as cells entered high density basal growth. This high density chemoresistance was observed for both growth inhibition and cytotoxicity, but was much more pronounced with the former. Dose-response curves were biphasic, suggesting that growth inhibition and cytotoxicity may be mediated by different mechanisms of drug action. The pronounced chemoresistance of postconfluent MDCK monolayers is similar to that encountered with many clinical solid neoplasms. It suggests that postconfluency monolayers, like multicellular spheroids and cellular multilayers, may provide better in vitro models of solid tumor chemosensitivity than subconfluent monolayer and suspension cultures.

Animals↗
PubMed1986

Character of (D-Phe-7) ACTH4-10-induced excessive grooming.

Rats receiving (D-Phe-7) ACTH4-10 exhibited excessive grooming during the first half of the hour-long observation period. This resulted in total grooming scores of about one-half of those produced by the longer ACTH fragments, ACTH1-24 or ACTH1-16 NH2. The excessive grooming induced by (D-Phe-7) ACTH4-10 was due to an enhancement of duration of grooming bouts and not to an increase in the frequency of occurrence. Furthermore, the neuropeptide-induced excessive grooming was eliminated by prior treatment with naloxone.

Adrenocorticotropic Hormone↗
PubMed1986

Obesity and hypertension in a longitudinal study of black physicians: the Meharry Cohort Study.

Obesity has been considered a risk factor among the precursors of essential hypertension for many years. Most related studies were general population surveys or predominantly white, male cohorts. This paper reports results of a longitudinal study of former black medical students, now practicing physicians for an average of 22.5 years. A remarkably high 43.8% were found to have developed hypertension. Fifty nine per cent of those who became obese during the study were hypertensive compared with 40% of the non-obese, 36% of those initially obese only, and 45% of those obese on both examinations. The risk ratio was 1.7 for the most obese (greater than or equal to 130% relative body weight) compared with 1.0 for the leanest group Dynamic weight change together with baseline diastolic blood pressure, were more prominent precursors than the other variables studied. Weight control would appear to be a potentially important nonpharmacologic hypertension risk reduction measure.

Adult↗
PubMed1986

Urinary schistosomiasis in Maiduguri, north east Nigeria.

From January to December 1983, 12,207 specimens of urine were examined for ova of Schistosoma haematobium and 753 (6.17%) were positive. From this group, 44 adult patients were investigated for urinary tract abnormalities. Haematuria was the commonest presenting symptom (81.8%) followed by lower abdominal pain (77.3%) and dysuria (68.2%). Urinalysis revealed proteinuria in 55.5%, leucocyturia in 90.9% and microhaematuria in 88.6% of patients. Twenty-four hour protein excretion ranged from 230 mg to 2.2 g (mean 960 mg). Serum creatinine was raised in one patient (2.2 mg dl-1), Urological abnormalities included calcification of the bladder in 36.4%, ureteric strictures and dilatations in 65.9%, hydronephrosis in 9.1%, squamous cell carcinoma of the bladder in 4.5%, vesicle calculus in 2.3%, and multiple granulomatas in the bladder in 2.3% of the patients. The results of the study suggest that a sizeable population of this area is at risk of developing urological complications and consequently chronic renal insufficiency.

Adolescent↗