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Biomedical subjects

S Thomas

Publications and source records attributed to S Thomas.

At least 631 records · Page 35Linked to original sources
PubMed1988

Spatial relationship of chromosomes 9 and 22 at metaphase in patients with chronic myelogenous leukemia (CML).

One hundred patients with Ph1-chromosome-positive chronic myelogenous leukemia (CML) with t(9;22) are included in the present investigation. The position of the Ph1 chromosome in relation to the normal as well as the abnormal chromosomes 9 was localized at metaphase in 1,000 bone-marrow cells. Our study suggests that the rearranged chromosomes, i.e., Ph1 and t(9;22), are closer together than their normal homologues. This impression is based on extensive statistical analysis. The intimate relationship may be due to the fact that they carry reciprocal genetic material responsible for a power of attraction between them. Alternatively, it is tempting to hypothesize that there may be a DNA sequence homology in the bands of chromosomes 9q and 22q involved in the reciprocal translocation perpetuating this relationship in subsequently generating cells during mitotic cell divisions. Furthermore, c-abl and bcr genes might play some role in maintaining the spatial relationship.

Chromosomes, Human, Pair 22↗
PubMed1988

Electric shock-mediated transfection of cells. Characterization and optimization of electrical parameters.

The effect of various parameters on the electric shock-mediated permeabilization and transfection of CHO cells has been investigated. Up to 70% of the cells can be maintained transiently permeable to erythrosin B for periods of at least 1 h at 20 degrees C. Electrical conditions optimal for transient permeabilization were also optimal for efficient DNA transfection by pSV2neo. However, the DNA must be present during exposure to the electric field for efficient transformation. The same requirement existed for voltage-induced DNA toxicity. The results suggest that DNA moves into the cells by electrophoresis, not by simple diffusion. Based on these observations a simple, rapid procedure for optimizing the conditions for electric shock-mediated DNA transfer into cells has been developed.

Animals↗
PubMed1988

The pulsed dye laser versus the Q-switched Nd:YAG laser in laser-induced shock-wave lithotripsy.

To date, there are two fairly well-established alternatives for laser-induced shock-wave lithotripsy in clinical practice. The Q-switched Nd:YAG laser is distinguished by the high-stone selectivity of its coupler systems. The necessity of a coupler system and its fairly small conversion rate of light energy into mechanical energy present serious drawbacks. Furthermore, the minimal outer diameter of the transmission system is 1.8 mm. The pulsed-dye laser can be used with a highly flexible and uncomplicated 200-micron fiber. However, the laser system itself is more complicated than the Q-switched Nd:YAG laser and requires a great deal of maintenance. Biological evaluation of damage caused by direct irradiation shows that both laser systems produce minor damage of different degrees. YAG laser lithotripsy with the optomechanical coupler was assessed in 31 patients with ureteral calculi. The instability and limited effectiveness of the fiber application system necessitated auxiliary lithotripsy methods in 14 cases. Dye-laser lithotripsy is currently being tested in clinical application. Further development, such as systems for blind application or electronic feedback mechanisms to limit adverse tissue effects, have yet to be optimized. Nevertheless, laser-induced shock-wave lithotripsy has the potential to become a standard procedure in the endourologic management of stone disease.

Animals↗
PubMed1988

Functional and histological restitution in the urinary tract after Nd:YAG laser coagulation.

Current development in endourologic equipment has made possible the endoscopic application of the Nd:YAG laser in the treatment of urothelial tumors of the whole urinary tract. The clinical results are rather promising. We controlled with various methods the healing processes of 14 rabbit ureters after Nd:YAG laser treatment as to morphological repair and physiological function. The ureters were irradiated transrenally with an energy of 60 J coagulating all wall layers. Healing of the laser lesions nearly to normal in all animals was observed 4 to 6 weeks after treatment. The prevailing histological and physiological changes in the ureter are extremely slight and do not disturb the normal ureteral function. The results show the complete healing process of the ureter after laser coagulation and make the application of Nd:YAG laser in the upper urinary tract much more predictable.

Animals↗
PubMed1988

[Laser-induced shockwave lithotripsy--in vitro trial and animal experiment studies].

Laser induced shock wave lithotripsy is a new procedure to destroy gallstones. Stones of up to 500 mg are destroyed within 5 min. Severe reactions of the soft tissue cannot be observed in animal studies. No perforations, stenoses or thermic lesions after wound healing were observed. The development of an optomechanical transducer replacing the optical lens system at the end of the transmission guide allows its handling in flexible endoscopes. Clinical use is therefore possible from the technical aspect.

Animals↗
PubMed1988

Adaptive respiratory responses of trout to acute hypoxia. I. Effects of water ionic composition on blood acid-base status response and gill morphology.

The effects of various levels of hypoxia (PWO2 ranging from 10 to 60 Torr) on arterial blood gases (PaO2 and PaCO2) and acid-base status were investigated in trout at 15 degrees C. The hypoxic responses of two stocks of trout living in natural waters having very different levels of NaCl (1.0 mmol.L-1 and 0.1 mmol.L-1) and carbonate alkalinity (0.4 mmol.L-1 and 2.4 mmol.L-1) were compared. The use of an extracorporeal circulation method made it possible to continuously monitor the pH changes. The different patterns of the acid-base status observed in response to hypoxia depend on the evolution of PaO2. Two critical PaO2 thresholds were defined. Crossing the upper (about 15 Torr) induces metabolic acidosis which is normally followed by pH recovery, while crossing the lower (about 10 Torr) promotes loss of capacity to compensate acidosis. The NaCl concentration of the water drastically modifies the fish sensitivity to hypoxia: fish living in water with a low NaCl concentration have less resistance to hypoxic exposure. This may be explained by the fact that in fish living in low NaCl concentrations, the secondary gill lamellae are surrounded by chloride cells, which considerably reduce the surface area available for gas exchange. Consequently a modest fall in PWO2 induces a drastic reduction of the arterial oxygen tension which crosses the lower critical PaO2 threshold.

Acid-Base Equilibrium↗
PubMed1988

Adaptive respiratory responses of trout to acute hypoxia. II. Blood oxygen carrying properties during hypoxia.

The effects of deep and acute hypoxia (PwO2 = 25 Torr) on oxygen transport characteristics (Hill number (n) and P50) were investigated in trout at 15 degrees C. When a fish is submitted to such an acute and deep hypoxia, a metabolic acidosis develops as soon as the arterial oxygen tension drops to about 15 Torr. We first showed that the hemoglobin of blood sampled at the end of the acidification period has an increased oxygen affinity. This improved affinity could be explained by the internal alkalisation of erythrocytes due to the extrusion of protons via a beta-adrenergic stimulation of Na+/H+ exchanges occurring at the onset of hypoxia and responsible for extracellular acidosis. Secondly we observed a significant increase (about 20%) of the number of blood cells per volume of blood during the acidosis. This cell number stays constant afterwards. The dual effects of a higher hemoglobin oxygen affinity and a greater amount of available hemoglobin improving blood oxygen loading at the fish gills appear to be a fast adaptive response to acute hypoxia. Surprisingly, we found that the elevated affinity occurring during acidosis remained constant as long as the fish were maintained in hypoxia, in spite of possible large variations of extracellular pH (pHe). This result is difficult to reconcile with the idea that the increase in affinity is imposed by intracellular pH (pHi), since in red blood cells pHi depends on pHe, thus any modification of pHe would in this case modify oxygen affinity.

Animals↗
PubMed1988

Adaptive respiratory responses of trout to acute hypoxia. III. Ion movements and pH changes in the red blood cell.

In the preceding paper acute hypoxia was shown to elicit within minutes an increase in the blood O2 affinity. From the present data it appears that this rapid change in blood P50 value can be ascribed to an important alkalization of the red blood cell despite a simultaneous decrease in extracellular pH (pHe). The intracellular alkalization is only partially due to beta-adrenergic stimulation of Na/H exchange, deoxygenation of hemoglobin and the rapid decrease of PaCO2 due to hyperventilation being involved in this process via the chloride shift. This high value of intraerythrocytic pH (pHi) is then maintained practically constant throughout the time the fish is kept in hypoxia despite wide changes of external pH. The blocking of pHi accounted for the constant O2 content observed during hypoxia. The uncoupling of pHi from pHe, which occurs at the onset of hypoxia, is still unexplained: for instance, it is not due to inhibition of the anion exchanger responsible for the passive distribution of H+ across the red cell membrane. A general scheme of all the mechanisms involved in the emergency adaptive response to acute hypoxia is presented.

Animals↗
PubMed1988

An anatomic guide for arthroscopic visualization of the wrist capsular ligaments.

Wrist arthroscopy allows examination of the palmar capsular wrist ligaments without extensive exposure. Arthroscopic examination of the wrist requires an accurate knowledge of the ligamentous anatomy as seen from inside the joint. In this study 13 fresh cadaver wrists were examined from the inside out to provide a visual guide for ligament identification during arthroscopy. The major palmar capsular ligaments seen from the inside of the wrist at the radiocarpal joint include the radioscaphoid, radioscaphocapitate, radiolunate, radioscapholunate, ulnolunate, ulnotriquetral ligaments, and the ulnar capsule. At the midcarpal joint, the scaphocapitate, radioscaphocapitate, triquetrocapitate, and triquetrohamate ligaments are identified palmarly. Dorsally, constant capsular structures at the radiocarpal joint are the radiolunate and radioulnotriquetral ligaments along with a prominent synovial fold.

Aged↗
PubMed1988

Bone mineral metabolism in experimental diabetes mellitus: osteocalcin as a measure of bone remodeling.

The etiology of diabetic osteopenia has not been established. The value of serum osteocalcin (BGP) as a marker of the bone abnormalities and the possible role of the polyol pathway in diabetic osteopenia were investigated. Three groups of rats were studied over 7 weeks: group D (n = 12), rats with streptozotocin (55 mg/kg)-induced diabetes given saline by gavage; group DS (n = 12), rats with streptozotocin-induced diabetes given the aldose reductase inhibitor sorbinil (25 mg/kg) daily by gavage; and group C (n = 6), saline-injected controls. Circulating levels of ionized calcium, BGP, amino-terminal PTH, and glucose were measured on days 0, 7, 14, 28, and 49. Tibial bone specimens were examined for the presence of aldose reductase by immunocytochemistry and by histomorphometry after tetracycline labeling. Diabetic rats with or without sorbinil treatment failed to gain weight [group D, 234 +/- 26 g; group DS, 217.0 +/- 40 g; group C, 310 +/- 33 g (mean +/- SD)]. Serum BGP levels decreased significantly in the diabetic rats within 7 days and remained lower throughout the study. BGP values on day 7 were: group D, 47.7 +/- 4.9 ng/ml; group DS, 65.9 +/- 5.5 ng/ml; and group C, 90.4 +/- 4 ng/ml (mean +/- SEM). Serum PTH levels were similar in all groups, except for day 49, when an increase in the D group was observed. Bone histomorphometry showed decreased bone remodeling in the D group, which confirmed the serum BGP findings. Aldose reductase was detectable in the small blood vessels and in bone itself. Sorbinil failed to influence the biochemical or bone histomorphometric abnormalities associated with diabetes. Serum BGP may be a valuable marker for the decreased bone remodeling in insulinopenic diabetes.

Aldehyde Reductase↗
PubMed1988

Cyclosporin-A in vivo produces severe osteopenia in the rat: effect of dose and duration of administration.

Cyclosporin-A (CsA) inhibits the in vitro bone-resorbing effects of cytokines. We investigated the in vivo effects of CsA on rat bone mineral metabolism. Three groups of male Sprague-Dawley rats were administered vehicle or low dose (7.5 mg/kg) or high dose (15 mg/kg) CsA for 14 and 28 days. Ionized calcium, PTH, serum bone Gla protein, blood urea nitrogen, creatinine, magnesium, and 1,25-dihydroxyvitamin D were determined serially. No significant changes in calciotropic hormones or renal function were noted. Significant bone resorption and trabecular bone loss occurred in the high dose group by day 14 and in both groups by day 28. Bone Gla protein was significantly increased within 2 weeks in both dosage groups (P less than 0.005), reflecting increased bone remodeling. CsA in vivo resulted in an unexpected and significant increase in bone remodeling, with striking bone loss. These effects are dependent on the duration and dose of CsA and appear to be mediated at a local level.

Animals↗
PubMed1988

Attitudes to computers in a teaching hospital.

The importance of a positive attitude to computers was recognised as a crucial element in the success of any project to introduce computerisation to the ward areas of a major teaching hospital. Nurses, ward clerks and doctors were expected to enter and/or access information on ward terminals. A study was designed to identify their concerns and attitudes towards the introduction of ward terminals prior to the beginning of a pilot project. Intervention to address these concerns and education to train staff took place during the trial. A post-trial questionnaire to assess the success of the pilot project and changes in attitudes was completed and analysed. The pilot project was deemed successful and full implementation in all ward areas is planned.

Attitude of Health Personnel↗