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Biomedical subjects

C Lehmann

Publications and source records attributed to C Lehmann.

At least 73 records · Page 4Linked to original sources
PubMed1991

The surgical treatment of noma.

Noma is a gangrenous stomatitis affecting children from developing countries. It may leave dreadful mutilations around the mouth, with amputation of the lips, cheek, nose, lids, maxilla, palate, or mandibula. Reconstruction should take into account the size of the defect, the presence of trismus or constriction of the mandible, the age of the child, and the child's general condition. During the last 3 years, eight patients were treated at the Unit of Plastic and Reconstructive Surgery of the Hôpital Cantonal Universitaire. Except in one case, tracheostomy was avoided, thanks to intranasal intubation by fibroscopy. These children, aged 2 to 9 years, underwent 31 general anesthesias and complex reconstructive procedures, including latissimus dorsi musculocutaneous pedunculated and free flaps, cranial flaps with galea, cranial bone and skin grafts, and retroauricular temporal skin flaps. All patients were able to return to Africa with dramatic functional and cosmetic improvements. However, satisfactory mouth opening and mandibular function were not always obtained.

Child↗
PubMed1991

Comparative inhibition of hepatitis B virus DNA polymerase and cellular DNA polymerases by triphosphates of sugar-modified 5-methyldeoxycytidines and of other nucleoside analogs.

Of a series of 14 nucleoside 5'-triphosphates, those of 2',3'-dideoxy-3'-fluoro-5-methylcytidine, 3'-azido-2',3'-dideoxy-5-methylcytidine, 2',3'-dideoxy-3'-fluoroguanosine, 2',3'-didehydro-2',3'-dideoxy-5-methylcytidine, 2',3'-dideoxy-3'-fluoro-5-ethylcytidine, and 2',3'-dideoxy-3'-fluoroadenosine emerged as the most potent inhibitors of hepatitis B virus DNA polymerase (50% inhibitory dose, 0.03 to 0.35 microM). In contrast, cellular DNA polymerases proved to be resistant to (alpha) or partially affected by (beta) these analogs. These compounds are among the most effective and selective inhibitors of endogenous hepatitis B virus DNA polymerase recognized to date.

Deoxycytidine↗
PubMed1991

Ion transport in epithelial cells from the bovine trachea in culture: effects of dexamethasone and aldosterone.

The ion transport properties of epithelial cells from the bovine trachea grown in culture were investigated. The cellular uptake of 22Na+, 36Cl- and 86Rb+ was measured and the sensitivity of ion uptake to amiloride and bumetanide revealed the presence of the transport pathways that exist in the native tissue. The action of corticosteroids, dexamethasone and aldosterone (0.1 or 1.0 microM), was studied by measuring the short-circuit current and the uptake of Na+ and Cl- following a treatment of 18 h, 2 or 8 days. The results showed that, in each situation, dexamethasone enhanced markedly the amiloride-sensitive current and Na+ uptake. In contrast, aldosterone exerted no detectable effect on the ion transport and electrical properties.

Absorption↗
PubMed1991

Superoxide dismutase promotes ATP and GTP restoration of rat small intestine during postischaemic reperfusion.

The small intestine of rats was prepared according to a procedure which is taken for preservation and transplantation in clinical practice. The blood supply of the rat intestine was completely interrupted for 30 min in situ. During this period the lumen of the intestine was rinsed with Ringer-lactate solution. This ischaemic period was followed by 10 min of reperfusion. As a result a decrease in ATP, and GTP concentrations, and of the total adenine nucleotide content during the preservation period occurred. In animals pretreated with superoxide dismutase (i.v. application; superoxide dismutase preparation from human erythrocytes) an accelerated restoration of nucleotide concentrations during the reperfusion period was observed. From the beneficial effect of superoxide dismutase it can be concluded, that there is a considerable formation of active species of oxygen which disturb the energy generation by the mitochondrial respiratory chain during ischaemia/re-oxygenation.

Adenine Nucleotides↗
PubMed1990

[Changes in the motility of the small intestine after autologous and allogenic transplantation in the dog].

The early and the late motility of the donor organ was measured after 13 allogeneic and 4 autologous small bowel transplantations in mongrel dogs. The postoperative motility indices were increased in contrast to the preoperative values. The activity of allogeneic transplants were greater than these of autologous intestinal segments. The basal tonus of the intestinum obtains a higher level because inhibiting central nervous influences are omitted after the denervation of the mesenteric radix. The contraction frequency remained constant. Disturbances of the motility model with irregular contractions and decrease of the frequency become evident in case of ischemia and rejection of the transplant still before the clinical signs.

Animals↗
PubMed1990

[Biochemical serum parameter changes during and after autologous small intestine transplantation in animal experiments. I. Intra- and immediate postoperative period].

Biochemical parameters sodium, potassium, lactate, alkaline phosphatase, ASAT, and ALAT were examined at the beginning of the operation, before, and 0, 2, 4, 6 hours after implantation of a small bowel autograft in an autologous model of intestinal transplantation in dogs. By the way of these early biochemical studies we have got information about metabolic situation during organ transplantation, efficiency of preservation and vitality of the graft. Using the given method safe preservation of small bowel can be guaranteed. Postoperatively only little changes of laboratory parameters occur.

Alanine Transaminase↗
PubMed1989

Inhibition of HIV-replication by 3'-fluoro-modified nucleosides with low cytotoxicity.

From a series of newly synthesized 3'-fluoro-modified nucleosides the C-5-chloro-substituted derivative of 2',3'-dideoxy-3'-fluorouridine (FddUrd) and the 4-thio analogue of 2',3'-dideoxy-3'-fluorothymidine (FddUrd) emerged as the most efficient and selective anti-HIV agents. Their antiviral doses (ED50) proved to be 700-and 480-fold below their toxic doses (CD50) in MT-4 cells. The 50% inhibitory dose of cell proliferation of the 5-chloro-substituted FddUrd and its parent agent FddUrd was found to be in the millimolar range for various other human cell-lines and for mouse CFU-GM. The 5'-triphosphate of FddUrd as well as of its 5-Chloro derivative are demonstrated to be two of the most active and selective inhibitors of the HIV-reverse transcriptase (IC50 = 0.07 +/- 0.01 and 0.04 +/- 0.006 microM).

Animals↗
PubMed1989

Solid-phase synthesis of oligoribonucleotides using 9-fluorenylmethoxycarbonyl (Fmoc) for 5'-hydroxyl protection.

Efficient solid-phase synthesis of a series of oligoribonucleotides of up to 20 residues is described that utilises the 9-fluorenylmethoxycarbonyl group (Fmoc) for 5'-protection and 4-methoxytetrahydropyran-4-yl (Mthp) for 2'-protection of ribonucleotide monomers and a phosphoramidite coupling procedure. The Fmoc group is removed after each coupling step by treatment with 0.1M DBU in acetonitrile. Oligoribonucleotides are isolated in 2'-protected form in good yield and shown to be readily and efficiently deprotected by mild acidic treatment.

Base Sequence↗
PubMed1989

Diphenylamine-2-carboxylate stimulates sodium ion transport in frog skin epithelium.

1. Diphenylamine-2-carboxylate (DPC), added to the mucosal side of the frog skin, increased reversibly the short-circuit current (I0), even in SO2-(4) Ringer. Amiloride blocked this effect. 2. The maximal stimulation was 140% of the control value and the EC50 was 0.26 mM DPC. 3. The stimulatory effect of DPC was additive to that of oxytocin. 4. The dose-response curves for amiloride determined in the absence and in the presence of 1 mM DPC showed an IC50 of 1.0 microM and 0.8 microM amiloride, respectively. 5. Thus DPC, a blocker of Cl- channels in various Cl-transporting epithelia, exerts a stimulatory effect on the amiloride-sensitive Na+ transport in frog skin.

Amiloride↗
PubMed1989

Effects of alpha 1-adrenoceptor blocker prazosin on microcirculation in terminal rabbit ileum.

The influence of the specific alpha 1-blocker prazosin on the microcirculation of the terminal ileum was examined in 10 rabbits. For this purpose an isotope clearance test was carried out by administering 133-Xenon solution into the intestinal wall before and after the intra-arterial injection of prazosin (1.0 mg) via the superior mesenteric artery. These experiments were supplemented by haemodynamic and thermographic measurements in a further group of 5 rabbits. Due to the systemic circulatory effect of prazosin, i.e. the drug-induced hypotension, the bowel segment exhibited, contrary to expectations, significantly delayed values for isotope elimination indicating a reduced local tissue clearance and blood supply. Thermographic observations also confirmed the impairment of mesenteric blood flow after prazosin. Therapeutic applicability of alpha 1-adrenoceptor blockers to treat intestinal circulatory disturbances in diseases of vascular genesis thus remains dubious.

Adrenergic alpha-Antagonists↗
PubMed1989

Solid-phase synthesis of oligoribonucleotides.

An efficient method is described for solid-phase synthesis of oligoribonucleotides that involves use of the 9-fluorenylmethoxycarbonyl group (Fmoc) for 5'-protection, 4-methoxytetrahydropyran-4-yl (Mthp) for 2'-protection and a phosphoramidite coupling procedure.

Drug Stability↗
PubMed1989

Motility, haemodynamics and responsibility to vasoactive agents after revascularization of autotransplanted small intestine segments in the dog.

Functional and haemodynamic changes occurring after revascularization of an autotransplanted small intestine segment were studied in acute experiments performed in 10 dogs under pentobarbital anaesthesia. Intestinal motility and mesenteric blood flow of the segment were measured with intraluminal pressurized balloon and electromagnetic flowmeter, respectively. The time-course of observations was divided, according to the findings, into three main periods (phases 1 to 3). In the initial phase (1) the bowel exhibited very slight spontaneous motility which was found to increase moderately but significantly after denervation and isolation of the graft still left in situ before transplantation (phase 2). After declamping of anastomoses of the retransplanted graft (which was protected by cooling to 4 degrees C after being removed from the body) a short period (approximately 2 min) of reactive hyperaemic flow increase was observed in association of vigorous bowel movements lasting for a more prolonged (approximately 15 min) period of time (phase 3a and 3b). Reactivity of the retransplanted vasculature as compared to the denervated control revealed a marked relative shift in adrenergic balance, tested by dopamine, to the vasoconstrictor range, but it showed no change in responses to general haemodynamic or haemorheologic interventions, tested by veratrine and pentoxifylline, respectively. However, the basic levels of blood supply (controlled also by thermography) and systemic blood pressure remained unaltered after transplantation. Regarding the critical role of functional changes immediately after transplantation in determining the survival of bowel grafts, these observations may contribute to a more effective monitoring of surgical interventions.

Animals↗
PubMed1989

[The effect of the alpha1-receptor blocker prazosin on the microcirculation in the terminal ileum of rabbits].

The effect of the specific alpha1-blocker prazosin (Adversuten) on the microcirculation in the region of the terminal ileum was examined on 10 rabbits. Before and after injection of prazosin into the superior mesenteric artery an isotope-clearance of a 133Xe-solution, applied into the intestinal wall, was performed. Because of the systemic blood pressure decreasing effect of prazosin the circulation of the examined part of the intestine was reduced in spite of the intended vasodilation of the intestinal vessels. The therapeutic applicability of alpha-blockers for intestinal diseases of vascular genesis remains questionable.

Animals↗