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Biomedical subjects

H D Lehmann

Publications and source records attributed to H D Lehmann.

At least 19 recordsLinked to original sources
PubMed1993

Inhibition by the combined Ca2+ and 5-HT2 receptor antagonist nexopamil (LU 49938) of intracoronary thrombus formation in a canine model of arterial stenosis and intimal damage.

We investigated the effects of nexopamil, a combined Ca2+/5-HT2 antagonist on thrombus formation in vivo and on platelet aggregation in vitro. In anesthetized mongrel dogs, cyclic flow reductions (CFRs) in the left anterior descending coronary artery (LAD) were induced by implanting a constrictor after the endothelium was injured mechanically. The CFRs were due to intracoronary thrombus formation. After CFRs were recorded for 1 h, the test compounds were injected intravenously (i.v.) for 2 min. Measurements were made for another hour. Nexopamil (0.05 mg/kg) completely abolished CFRs during the first 30 min after application without significantly altering hemodynamics. The same effect was noted with 0.02 mg/kg ketanserin (5-HT2/alpha 1 antagonist). The Ca2+ antagonist gallopamil reduced CFRs only in the highest hemodynamically tolerable dose by 40%. Serotonin-induced platelet aggregation in dog platelet-rich plasma (PRP) in vitro was most potently inhibited by ketanserin (IC50 0.55 x 10(-8) M), followed by nexopamil (IC50) 0.81 x 10(-7) M) and gallopamil (IC50 1.76 x 10(-6) M). Because serotonin is an important pathophysiologic mediator in unstable angina, 5-HT2 receptor antagonism should be of considerable benefit by preventing platelet activation and aggregation. The combination with calcium-antagonistic activity leads to an increase in coronary blood flow (CBF) and a decrease in cardiac oxygen demand. Therefore, the effects noted with nexopamil should be of importance in treating patients with coronary artery disease.

Animals↗
PubMed1992

Investigation of dialysis membranes with atomic force microscopy.

AFM was used to investigate dialysis membranes made of regenerated cellulose by the cuoxam process. The membranes were either Cuprophan or experimental samples, modified with different amounts of diethylaminoethylcellulose (DEAE). Atomic force microscopes with optical-lever detection systems were used to image the dry membranes in air as received from the manufacturer as well as wet membranes in a swollen state under water. Differences could be observed between modified and unmodified as well as between dry and wet membranes.

Cellulose↗
PubMed1992

The puzzle of Alzheimer's disease (AD).

A compromised defensive system of brain cells against aluminium, together with local defects in glucose metabolism, causes AD. Lack of citrate is a driving force and free cis-aconitate or glutamate are potential carriers, which enable the exotoxin to cross lipid membranes. Only a few aluminium ions replace magnesium in key positions. They block the reversibility of phosphorylation reactions, which are important for short term memory: sensitization of the insulin receptor and protein phosphorylations. Due to disturbed phosphorylation of the cytoskeleton, protein synthesis runs out of balance. Efforts to restore the disturbed reactions result in AD specific deposits. Aluminium ions are the common cause for the induction of AD pathogenesis in patients with genetic defects, with mechanical brain lesions or with minor infarcts, as well as with changes in the relation between numbers of neurons and neuron nursing glia cells due to age.

Aluminum↗
PubMed1992

[Evaluation of anti-arrhythmia agents in the animal model].

In view of the results of CAST, researchers working in the field of experimental arrhythmia have been increasingly focusing on the quest for new anti-arrhythmic modes of action and ways of detecting pro-arrhythmic properties of antiarrhythmic drugs at an early stage. Here, the experimental methods available play a particularly important role. While trying to assess anti-arrhythmic effects without investigating electro-physiological parameters in isolated tissue would be inconceivable, the degree to which the results of in vitro studies can be transferred to the intact organism is limited because of the complex nature of the arrhythmias. Of the various existing in vivo models, the most commonly employed are those in which arrhythmia is induced after experimental surgical interventions causing ischemia and infarction, followed by reperfusion. This shows that researchers are striving to "create" pathophysiologically-defined conditions and, as far as possible, a pathophysiological situation which is similar to that in the patient. Guidelines were laid down for this model complex in the Lambeth Conventions (1988) in order to improve uniformity of the methods and better comparability of the results generated by different investigators. Of the existing arrhythmia models, the ventricular re-entry arrhythmia model after myocardial infarction triggered by programmed stimulation, which was devised by Spear/Moore (1983), has proven to be particularly useful in the assessment of antiarrhythmics and is used by many researchers. Class II and III antiarrhythmics can be identified reliably by this method, whereas class I antiarrhythmics are mostly inconspicuous.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

[Pharmacological characterization of the new highly potent beta-adrenergic receptor blocker soquinolol].

The present pharmacological test results characterize soquinolol (5-[3-tertiary butylamino-2-hydroxypropoxy]-2-formyl-1,2,3,4- tetrahydroisoquinoline mucate, We 704, Sertum) as a highly potent non-subtype-selective beta-adrenergic receptor blocker, which is devoid of any intrinsic sympathomimetic activity. Its localanaesthetic activity (membrane stabilizing effect) is very weak. It also shows good enteral efficacy and long duration of action. In binding studies with heart (Ki beta 1 = 3.25 nmol/l) and lung membranes (Ki beta 2 = 0.85 nmol/l) its binding profile was found to be similar to that of propranolol. Soquinolol inhibits the isoprenaline-induced tachycardia (EC50% = 48 micrograms/l) in the guinea-pig Langendorff heart in vitro to the same degree as propranolol. However, in the conscious dog soquinolol's beta 1-adrenergic blocking activity (ED 50%) on intravenous injection (5.5 micrograms/kg) and oral administration (5.8 micrograms/kg) is about twice as great as that of pindolol and 19 times (i.v.) or 138 times (p.o.) greater than that of propranolol. These results suggest 95% enteral efficacy for soquinolol (pindolol 88%, propranolol 13%). The differences in soquinolol's and propranolol's efficacy detected in vitro and in vivo are partially attributable to differences in their kinetic properties namely the lower protein binding and the higher distribution volume of soquinolol. In the conscious dog, soquinolol inhibits beta 1-(ED 50% = 4.0 micrograms/kg) and beta 2-receptors (ED 50% = 2.7 micrograms/kg) at dose levels which do not differ significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1988

[Involvement of the urogenital system in non-Hodgkin lymphoma (primary and secondary involvement)].

According to the literature the non-Hodgkin-lymphoma is involving the kidney and its capsule, the hilus of the kidney and the retroperitoneal space in some instances. Today one assumes that the disease is originating unifocally therefore one can achieve a healing or complete remission by radical surgery when one or both kidneys or a testicle are involved. Prior to this generalised disease must be ruled out. Two cases are reported where one or both kidneys were involved showing long survival time or cure. The prognosis, however, is very poor when the urogenital system is included in systemic forms of non-Hodgkin-lymphoma.

Aged↗
PubMed1986

[Paravesical angiofollicular hyperplasia of the lymph nodes (so-called Castleman tumor). A contribution to differential diagnosis of benign retroperitoneal space-occupying lesions].

Clinical and pathological presentation of a benign so-called "Castleman Tumour", is very rare in the urological literature. It caused impression of the bladder and displacement of the right ureter in a 47-year-old male patient with a six-year case history. Detailed description of the two types of tumours is presented differing both histologically and clinically. This adds to the differential diagnosis in cases of space occupying lesions in the retroperitoneal cavity.

Castleman Disease↗
PubMed1985

Comparison between continuous and intermittent administration of Estracyt in the treatment of carcinoma of the prostate.

Ninety-five patients with prostatic carcinoma, stages A-D and of all histological grades were randomized between a continuous and an intermittent treatment regimen of Estracyt (estramustine phosphate). 77 patients were evaluated (46 with continuous and 31 with intermittent therapy). Remissions were seen in 13 (28%) and (13%), respectively. Stable disease was recorded in 30 (65%) and 24 (77%), respectively. Progression experienced 3 (6%) and 3 (10%) respectively. 19% were unable to continue therapy due to intolerable gastrointestinal side effects (7 patients receiving continuous and 8 patients receiving intermittent therapy).

Aged↗
PubMed1985

Pharmacodynamic interaction of gallopamil and propranolol in the conscious dog.

The interaction of gallopamil (Procorum) and propranolol was studied in conscious trained dogs by injecting gallopamil intravenously (consecutive injection of 0.0464, 0.1 and 0.215 mg/kg at 30-min intervals) with and without propranolol pre-medication (0.464 mg/kg i.v., 10 min before the first injection of gallopamil). An intraindividual comparison of the cardiovascular effects was made. The interaction was mostly minor and occurred only with the highest dose of gallopamil. It was noticeable most in the influence on myocardial contractility which was more pronounced than the influence on electrophysiological parameters. A shift in threshold doses was not observed. Much more pronounced effects of the gallopamil-propranolol interaction become apparent when the animals were at the same time subjected to vagal blockade (methylatropine). In this situation, combined administration of gallopamil and propranolol led to a greater reduction of contractility, increase of AV block and occurrence of asystole. As regards the latter, a shift in the threshold dose occurred. The differences in the intensity of the interaction between gallopamil and propranolol in animals with or without vagal blockade are therefore a consequence of the presence or absence of reflex regulation. The findings explain, and relativize, the clear-cut interaction in the anaesthetized dog demonstrated by other authors, i.e. experimental conditions matching an autonomic blockade.

Animals↗
PubMed1984

[Kidney tumors in the elderly patient over 75].

35 patients (17 females, 18 males), ranging from 75 to 92 years of age, underwent nephrectomy because they suffered from renal tumours, which in 12 cases had preoperatively a total blockage of the renal artery after angiography. A total of 27 retroperitoneal and 8 transperitoneal operations were performed. Indications as well as post-operative complications and long-term effects are dealt with. Except suppurative pyelonephritis of the residual kidney neither temporary nor permanent renal insufficiency could be observed. Even in patients of advanced age, nephrectomy will yield satisfactory longterm results and prevent the formation of metastases.

Adenoma↗
PubMed1984

[Effect of plant glycosides on resistance and capacitance vessels].

In the anaesthetized cat, SCOA ( Miroton ), a product which contains extracts from Scilla , Convallaria , Oleander and Adonis , displays not only its well-known positive inotropic effect but has also constrictor effects on veins when applied in intravenous doses of 21.5-100 GPU /kg ( GPU = guinea-pig units, i.e. cardiotoxic equivalents related to 1 g body weight of guinea-pigs). The latter effect differs in that it is somewhat more prolonged. With intraduodenal administration the doses required to achieve equal peak effects as with intravenous injection are about 4 times larger and this suggests a relatively good enteral availability in the cat. SCOA constricts not only veins but also arteries. However, this latter effect is comparatively small and occurs only after intraarterial infusion of high doses (9.1 and 91 GPU /min, respectively).--The cardiac glycosides contained in the drug product primarily account for its vasoactive qualities. The venous constrictor effect correlates with the guinea-pig units. In qualitative respects, the pure glycosides cymarin , convallatoxin , proscillaridin , and scillaren exert equal effects. There is, however, evidence that the correlation between the effect on veins and on the heart differs for the glycosides tested. Based on equal guinea-pig units, the adonis extract, for instance, acts on capacitance vessels about twice as much as scilla , oleander and convallaria extracts. Cymarin , too, has a stronger effect on veins than would be expected from its cardiotoxic effect. The action on arteries and veins are based on different mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

[Optimizing conservative urinary calculus expulsion].

A multicentric randomised and prospective study on conservative treatment of ureteric calculi had been performed. The frequency and transit time of spontaneously passing of the stones, side effects and cost of treatment have been compared under classic spasmoanalgetic therapy and a phytotherapeutic medicament (Urol). In the group with spasmoanalgetic therapy 85.5% of the stones passed spontaneously, in the group with Urol medication 89.3% of the stones. There was no significant difference concerning the transit time of stones between the two groups, but side effects and costs were less in the Urol-group.

Adolescent↗
PubMed1983

6-Aryl-4,5-dihydro-3(2H)-pyridazinones. A new class of compounds with platelet aggregation inhibiting and hypotensive activities.

This paper reports on the synthesis and pharmacological activity of 6-aryl-4,5-dihydro-3(2H)-pyridazinone derivatives. The compounds exhibit an aggregation inhibiting action on human platelets in vitro and on rat platelets under ex vivo conditions, as well as a hypotensive action on rats. The strongest pharmacological effects were found with dihydropyridazinones, which have a 6-[p-[(chloroalkanoyl)amino]phenyl] substituent, together with a methyl group in the 5-position. The antiaggregation activity of compounds of this type is in vitro up to 16000 times and ex vivo up to 370 times greater than that of acetylsalicylic acid; the hypotensive action is up to 40 times as great as that of the comparative substance dihydralazine.

Animals↗
PubMed1983

Regeneration of hemofiltrate by anodic oxidation of urea.

Urea can be oxidized electrochemically in a chloride solution to carbon dioxide, water, and nitrogen. The microkinetics of this hypochlorite-mediated urea oxidation are elucidated. Based on this kinetic information, the optimal conditions and construction principles for an electrochemical reactor are deduced. The construction of a cheap, disposable oxidation cell and necessary auxiliary equipment are described. In vitro data are reported for urea removal. A 36-L volume was used to simulate a 60-kg patient; 18 L was recirculated through a 0.12-m2 oxidation cell. Within 3 h, 35 g urea could be removed from the system. The technical and economic possibilities as well as safety requirements for hemofiltrate regeneration to a reinfusable substitution solution by anodic urea oxidation are discussed critically. Although the process does not appear to be economically practical for discontinuous hemofiltration, it might be desirable for continuous (24 h/day) treatment.

Blood↗