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Biomedical subjects

R Schmidt

Publications and source records attributed to R Schmidt.

At least 487 records · Page 27Linked to original sources

Cyclization studies with tetra- and pentapeptide sequences corresponding to beta-casomorphins.

The tetrapeptide Boc-D-Orn-Phe-D-Pro-Gly-OH and the pentapeptide sequence Boc-Tyr(tBu)-D-Orn-Phe-D-Pro-Gly-OH were used to study the influence of different coupling reagents on the yield and purity of these model peptides. The simple structure prevented racemization and cyclodimerization and facilitated the ring formation. The most favorable effects on yield and purity were obtained in both reactions using diphenyl-phosphoryl azide (DPPA) and norborn-5-ene-2,3-dicarboximidodiphenylphosphate (NDPP), while the cyclizations with the powerful activating reagents benzotriazol-1-yl-oxy-tris(dimethylamino)-phosphonium hexafluorophosphate (BOP) and 2-(1-H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU) with the exception of the cyclopentapeptide reaction with HBTU/4-dimethylaminopyridine gave unsatisfactory results.

Amino Acid Sequence↗

Does cerebrovascular insufficiency contribute to Alzheimer's disease?

The differential diagnosis of vascular dementia (VD) and Alzheimer's disease (AD) based on clinical assessment and neuropsychologic testing is still associated with a relatively high degree of inaccuracy compared to neuropathology standards. This is especially true in the identification of mixed forms between AD and VD. The present study investigates the potential of neuroimaging methods in providing additional information in dealing with this problem. Magnetic resonance imaging (MRI) of the brain identified a relatively high percentage (39%) of patients with AD (with ischemia scores of 4 and less) with basal ganglia hyperintensities and also demonstrated basal ganglia lacunae and infarcts in some of these patients. These findings indicate that in these cases a vascular component, consistent with the mixed form of dementia, may contribute to the etiology of the disease. These findings also underscore the clinical usefulness of MRI in the further differentiation of the dementias.

Aged↗

Guinea pig cochlear blood flow under definite sound exposure-hydrogen clearance measurement.

Blood flow measurements were carried out on 18 coloured guinea pigs (8 animals served as control group) before and during definite sound exposure (12 kHz, 110 dB SPL). The exposure time amounted to 60 min. The anaesthesia was carried out according to the following schedule: a mixture consisting of 70 mg alpha-chloralose/kg b.w. and 400 mg urethane/kg b.w. was injected intraperitoneally. The relaxation was performed by means of i.p. application of 3 mg Tricuran/kg b.w./h. The hydrogen clearance measurements (HCM) were carried out under artificial respiration with control of arterial pH, endexpiratory CO2 content, as well as blood pressure and body temperature. After a duration of noise exposure of 30-45 min the cochlear blood flow reached an average level of 80% of the initial point. This level remained mainly unchanged until the end of noise exposure (60 min). Our HMC's confirm Laser Doppler flowmetry findings.

Acoustic Stimulation↗

Brain magnetic resonance imaging and neuropsychologic evaluation of patients with idiopathic dilated cardiomyopathy.

We compared brain magnetic resonance imaging and neuropsychologic performance in 20 neurologically asymptomatic patients suffering from idiopathic dilated cardiomyopathy (mean age 41 [range 18-49] years) and 20 age-matched controls (mean age 38 [range 28-49] years). Patients exhibited a significantly higher rate of cerebral infarcts (20% versus 0%, p less than 0.05) and cortical (50% versus 5%, p less than 0.01) and ventricular (55% versus 15%, p less than 0.02) atrophy than controls. Accordingly, semiquantitative volumetric measurements yielded a significantly increased ventricular-to-intracranial cavity ratio in the patients (6.2 +/- 2.9% versus 4.1 +/- 1.3%, p less than 0.01). This ratio and the cortical atrophy ratings correlated positively with disease duration (r = 0.63 and 0.54, p less than 0.05). Cognitive test performance was significantly worse in patients than in controls and was most impaired in those patients with morphologic cerebral abnormalities.

Adult↗

Sterile and endotoxin free dialysis fluid for hemodialysis.

As the quality of water in dialysis fluid varies considerably, and, in view of the fact that endotoxin or active derivates can cause acute and chronic side effects in patients under hemodialysis treatment, the dialysis fluid must be sterile and endotoxin-free. The predialyzer fluid in 20 hemodialysis patients was investigated. The bacterial loading was between 5/ml and 12,000/ml, the endotoxin concentration was high and extremely variable. Therefore we introduced the ultrafiltration of the dialysis fluid by a polyamide hollow fiber membrane before entering the dialyzer. All samples were free of bacteria, and the concentration of endotoxin was lower than the detectable limit. With this procedure we can obtain sterile dialysis fluid, which is endotoxin free. Our preliminary results showed that Interleukin-1 in the patients was significantly (p less than 0.005) lower under ultrafiltration of the dialysis fluid than without ultrafiltration.

Colony Count, Microbial↗

Flunarizine in migraine prophylaxis: the clinical experience.

Apart from the treatment of migraine attacks, prophylaxis may be required when certain criteria of frequency, duration, or severity are met. In a series of placebo-controlled, double-blind studies, the effectiveness of the cerebral calcium antagonist flunarizine (Sibelium) in migraine prophylaxis was shown. In further investigations, the effectiveness of flunarizine was similar to that of propranolol, metoprolol, pizotifene, and methysergide. The side effects described for treatment with flunarizine were somnolence, weight gain, and, in rare cases, depressive mood and extrapyramidal motor disorders. Considering the benefit/risk relation, flunarizine and the beta-adrenergic agents propranolol and metoprolol are now regarded as the drugs of choice. The mechanism of action of flunarizine in migraine prophylaxis is largely unexplained, but the antihypoxic effect of flunarizine is discussed in this context. The search for predicting factors for a successful treatment with flunarizine and the investigation of an injectable solution for the treatment of acute migraine attacks must be left to future research.

Flunarizine↗

Flunarizine in the treatment of vestibular vertigo: experimental and clinical data.

Because maintenance antivertiginous treatment with commonly used drugs is only moderately effective, there is still need for new therapeutic concepts in the therapy of vestibular vertigo. The cerebral calcium antagonist flunarizine (Sibelium) revealed positive vestibular effects in experimental animal studies and in healthy volunteers. Clinical trials versus placebo and reference drugs proved flunarizine to be effective in the treatment of vestibular disorders. Somnolence, weight gain, and, in rare cases, extrapyramidal symptoms and depression were discussed as side effects. Further studies on flunarizine's mechanism of action are needed to elucidate whether its clinical effects are indeed due to calcium-entry blockade.

Animals↗

Biological isoeffect distributions: consideration of the influence of dose per fraction and overall treatment time. A possible tool in future treatment planning.

The biological isoeffect distributions are calculated on the basis of the physical isodose distributions. They consider parameters of biological relevance such as the dose per fraction and the overall treatment time. A clinical example is presented to illustrate the method. The technique presented in this paper only requires minimal modifications in the conventional computer programs for treatment planning and can be updated very easily. The calculation of biological isoeffect distributions is a simple technique to facilitate the transfer of new radiobiological and clinical findings on alpha/beta ratios, tolerance doses and repopulation kinetics, into treatment planning. However, before they can be introduced into clinical practice, more reliable radiobiological data on normal tissues and tumours are required.

Carcinoma, Bronchogenic↗

[Primary and secondary aorto-intestinal fistula in infrarenal aortic replacement].

During the past 20 years 17 patients with abdominal-aortic-intestinal fistulas have been operated in our department. Hospital-letality accounted till 1986 with 75%. Since then we preferred direct reconstruction by implantation of a vascular graft, covered by omentum in primary fistulas. Hospital letality could be reduced by this management to 0% in primary fistulas by a total survival rate of 67%.

Aorta, Abdominal↗

[A new biological vascular prosthesis].

In an experimental study on sheeps a new biologic vascular graft was implanted, 30 x in carotidal, 30 x in aortal position. Only one early occlusion of the graft, due to technical reasons, could be observed. Without aneurysmatic degeneration all graft were in function at the time of harvesting the samples. Morphologically a "revitalisation" of the grafts could be proved.

Animals↗

Changes in rheology and red blood cell function under recombinant human erythropoietin therapy.

The rh-EPO is a potent drug to treat renal anaemia. RBC aggregation is not influenced by the rh-EPO therapy. Membrane elasticity and RBC deformability improve remarkably after rh-EPO which might benefit microcirculation. Rh-EPO therapy can not prolong RBC life span. Obviously uremic milieu alone determines RBC life time. Rh-EPO treatment corrects renal anemia by increasing the number of RBC and the RBC volume.

Adult↗

[Esophageal diverticula. Clinical aspects and therapy].

18 patients (10 male, 8 female) with an average age of 57 years were operated for diverticula of the esophagus. We found 11 pharyngoesophageal diverticula, 5 parabronchial and 2 epiphrenic diverticula. Major symptoms were dysphagia and regurgitation in pharyngoesophageal diverticula. Dysphagia, substernal pain and hiccough in parabronchial and epiphrenic diverticula. The treatment was resection of diverticula which was combined with myotomy in case of pharyngoesophageal diverticula. 2 patients had severe secondary wound healing. Other postoperative dysfunctions of the esophagus or symptomatic recurrences were not seen.

Aged↗

131I treatment of thyroid papillary carcinoma in a patient with renal failure.

Procedures for 131I ablation in renal failure are not known. In one patient receiving dialysis, detailed dosimetry and health safety aspects were obtained. The results showed insignificant contamination of equipment, but a surprisingly significant reduction in biologic half-life of 131I due to efficient dialysis extraction. The data indicate that 131I ablation can be done safely and easily during dialysis but that much higher 131I doses must be used to achieve equivalent results to those obtained in patients with normal renal function.

Adult↗

Thyrotoxic crisis in Graves' disease: indication for immediate surgery.

Thyrotoxic crisis (thyroid storm) is a rare complication of hyperthyroidism. It can be observed not only in thyroid autonomy with latent hyperfunction after exposure to iodine, but also in Graves' disease with overt hyperfunction. Adequate management of thyrotoxic crisis is still controversial. We report about four patients (four women, mean age 75 years) with Graves' disease who developed thyrotoxic crisis during therapy with antithyroid drugs so that surgical intervention became necessary. The patients had been admitted to the hospital for nonspecific symptoms such as headache, cachexy, and psychosis. Thyroid hormone levels had reached twice the normal range prior to surgery. All patients showed severe neurological deficits leading to coma. In three cases euthyroidism was achieved within two days after surgery. The neurological symptoms disappeared after an average of four days. The postoperative course did not show severe complications and all patients recovered completely. Especially in the elderly a monosymptomatic or nonspecific course of thyroid storm with neurological symptoms may represent a severe and life-threatening situation. In these cases surgery can become necessary even if euthyroidism has not been achieved preoperatively.

Aged↗

[The role of TSH psychological and somatic changes in thyroid dysfunctions].

The characteristic psychic and somatic features found in patients with overt hyper- or hypothyroidism are usually attributed to elevated or diminished levels, respectively, of thyroid hormones. This concept does not sufficiently explain our previous investigations in which the same symptoms, albeit attenuated, were also seen in patients suffering from so-called latent disturbances of thyroid function. This state of disorder, however, exhibits normal concentrations of peripheral thyroid hormones. Only the response of thyroid-stimulating hormone (TSH) to thyrotropin-releasing hormone (TRH) stimulation is in accordance with the behaviour of the overt thyroid dysfunction and enables its differentiation from the euthyroid state. In this context, we investigated the question as to whether pathologic signs in thyroid disorders are correlated to alterations of peripheral thyroid hormones or to changes in the hypothalamus pituitary axis. Therefore, we investigated two groups of ten patients each who suffered from latent hyper- or hypothyroidism, respectively, and ten euthyroid controls. All were matched from sex and age. Endocrine function was estimated by TRH testing, TT3, TT4 and thyroxine binding globulin (TBG). Psychologic testing was performed by questionnaires concerning subjective somatic symptoms, emotional disturbances, psychomotoric performance, cognitive impairment and personality. Patients with latent hyperthyroidism were more subject to somatic symptoms and affective complaints than were those who had latent hypothyroidism. As compared with controls, there were significant differences in exhaustion and pain in the limbs and heart. In terms of affective complaints, patients were more depressive, anxious, touchy and irritable; their personalities showed a higher degree of emotional lability, excitement and irritability.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

[Ergometric results of r-erythropoietin treatment of hemodialysis patients].

To investigate the effect of partial correction of anemia in patients maintained by chronic intermittent hemodialysis on exercise capacity, patients underwent a bicycle acido-ergometry before and after treatment with recombinant human erythropoietin. The results demonstrate a (subjective) improvement of exercise capacity without any evidence for that in the pH values.

Acid-Base Equilibrium↗