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Biomedical subjects

H Weber

Publications and source records attributed to H Weber.

At least 181 records · Page 10Linked to original sources
PubMed1994

[Therapeutic indications, principles and guidelines of differential drug therapy of cardiac arrhythmias].

Several arrhythmias have different causes and different needs for therapy. Indications for antiarrhythmic therapy is related either due to an increased mortality risk, predominantly if ventricular arrhythmias are present, or due to a decreased quality of life, especially in supraventricular arrhythmias (SVA). In the past decades diagnostic and therapeutic methods were improved, many new antiarrhythmic drugs entered the clinical use and new devices came up. In general the number of therapeutic strategies increased up to the confusing present stage. Drug therapy of SVA is furthermore based on the use of calciumantagonists, beta-blockers and digitalis, with a smaller amount other class III and class I antiarrhythmic agents. Nevertheless new curative methods were developed like the various ablation-techniques, which gives the patient a tremendous chance to live without any attack and without any drug. In ventricular arrhythmias the hopes of a mortality reduction due to drug therapy could not be fulfilled, especially in the use of class I antiarrhythmic agents. They seemed to be proarrhythmogenic, which increases with the impairment of left ventricular function. Only class III antiarrhythmic drugs could reduce the increased mortality risk in specific populations. Consequently drug therapy in ventricular arrhythmias will be done cautiously under the aspects of proarrythmogenicity and the lack of convincing results, that the suppression-hypothesis works. Alternative therapeutic methods came up and should not withheld in high risk patients.

Anti-Arrhythmia Agents↗
PubMed1993

The natural course of acute sciatica with nerve root symptoms in a double-blind placebo-controlled trial evaluating the effect of piroxicam.

To study the natural history of acute sciatica, 208 patients with obvious symptoms and signs of a lumbar radiculopathy (L5 and S1) were examined within 14 days of onset. A concomitant double-blind investigation of the effect of the nonsteroidal anti-inflammatory drug piroxicam was performed. The results measured by visual analog scale and Roland's functional tests showed a satisfactory improvement throughout the 4 weeks of observation. The piroxicam-treated group had same results as the control group. Based on questionnaires at months 3 and 12 approximately 30% of the patients still complained about back trouble and 19.5% were out of work after 1 year. Four patients underwent surgery during this period.

Adult↗
PubMed1993

Different mechanisms of recognition of bacteriophage Q beta plus and minus strand RNAs by Q beta replicase.

Our earlier work on the recognition of Q beta plus strand RNA by replicase had shown by RNase degradation and by electron microscopic techniques that specific binding interactions occurred at two internal sites, the S-site and the M-site, but not at the 3'-end, i.e. the site of initiation of synthesis. Using essentially similar methods, we have found now for binding complexes of replicase with the minus strand a completely different pattern, namely considerable terminal binding, whereas binding to internal sites was without detectable specificity. In the case of plus strand complexes, simultaneous binding at the two internal sites and at a terminal site could be demonstrated by electron microscopy after initiation of RNA synthesis in the presence of host factor, GTP and ATP. A variant plus strand RNA containing a 490 nucleotide duplication near the 5'-end resulted in similar double-looped complexes, however with an elongated free arm, showing that the protein-bound terminal site was the 3'-end of the RNA. Interestingly, the same two-looped structures were also found for complexes consisting of plus strand RNA and host factor without replicase. This suggests that the role of the host factor on the plus strand template is to bring the 3'-end into the proximity of the S-site/M-site domain, where replicase can initiate on it. In contrast, the 3'-end of the minus strand appears to be directly available to the enzyme.

Coliphages↗
PubMed1993

Angiotensin II stimulation of rapid protein tyrosine phosphorylation and protein kinase activation in rat aortic smooth muscle cells.

In cultured rat aortic smooth muscle cells, angiotensin II (AII) treatment led to increased tyrosine phosphorylation of cellular proteins with apparent molecular masses of 42, 44, 75, and 120 kDa, respectively, as assessed by antiphosphotyrosine immunoblotting. Increased protein tyrosine phosphorylation was observed within 1 min of AII addition and was maximal by 30 min. The overall pattern of AII-stimulated protein tyrosine phosphorylation was distinct from that observed following treatment of rat aortic smooth muscle cells with platelet-derived growth factor-BB. Specific antibodies were used to identify the AII-stimulated 42- and 44-kDa tyrosine-phosphorylated proteins as the "mitogen-activated protein kinases," p42mapk and p44mapk, respectively. Raf-1, a 70-74-kDa serine/threonine protein kinase, was not tyrosine-phosphorylated in response to AII but was found to be hyperphosphorylated as evidenced by retarded protein mobility in SDS gel analysis. Taken together, these data indicate that AII binding to vascular smooth muscle cells leads to rapid activation of a complex cascade of protein kinases, including protein kinase C, Raf-1, MAP kinases, and an undefined intracellular protein tyrosine kinase(s) that may be coordinately involved in signal transduction leading to cell proliferation.

Angiotensin II↗
PubMed1993

A sucrose-synthase gene of Vicia faba L.: expression pattern in developing seeds in relation to starch synthesis and metabolic regulation.

Copy-DNA clones encoding a single class of sucrose-synthase (SUCS; EC 2.4.1.13) subunit have been isolated and sequenced from a Vicia faba L. seed cotyledonary library. Southern analyses indicated the existence of only one gene. Transcript levels determined by Northern blot hybridisation steadily increased until the middle of development [25-35 days after flowering (DAF)] and declined thereafter. Sucrose levels approximately paralleled levels of SUCS mRNA. The activity of SUCS increased with decreasing fructose and glucose concentrations and peaked about 10 d later than mRNA levels. In-vitro culture experiments demonstrated that increasing the sucrose concentration leads to increased levels of SUCS mRNA. The SUCS mRNA was also synthesised in seed-coat tissue, but in lower amounts than in cotyledons and with a different developmental profile. The early peak level of SUCS mRNA (20 DAF) in seed coats coincided with the peak in the amount of sucrose and with a peak of transiently synthesised starch.

Amino Acid Sequence↗
PubMed1993

Context dependent amplitude modulations of express and regular saccades in man and monkey.

Saccadic reaction times and amplitudes were determined in four human subjects and two rhesus monkeys when they made saccades to visual targets appearing in different spatial or temporal contexts. Two stimuli were presented at different positions, either simultaneously (global condition) or in random order (range condition). Both the gap and the overlap paradigm were used. The characteristics of different groups of saccades defined by the separate peaks in the distribution of the saccadic reaction times as express and regular saccades, were analysed and compared. It is shown that, in man and monkey, the amplitudes of express saccades undergo the same or even stronger context-dependent changes as do those of regular saccades. Furthermore, the presence or absence of the fixation point also influences the saccadic amplitudes, at least for the express saccades. We conclude that the neural mechanisms that determine the amplitudes of the express saccades are more strictly under the control of the physical and physiological conditions of the stimulus situation, whereas regular saccades have greater--although not complete--dependence on the psychological context and, in particular, the subject's effort.

Adult↗
PubMed1993

The time of secondary saccades to primary targets.

When a first saccade is made in response to a single, suddenly appearing stimulus it often misses the target. The retinal error may be very large, in particular in those cases where the subject anticipates the target location and initiates a saccade to a wrong position. We have analyzed the time of the occurrence of the secondary saccades by which the subject corrects these errors. Using the gap task with random target locations we found that large errors after anticipatory saccades--especially those after direction errors--can be corrected very fast. The latencies of these corrective saccades (being measured from target onset, not from the end of the primary saccade) form bimodal distributions with a first peak at 100 ms. It is therefore concluded that large errors can be corrected by express secondary saccades.

Attention↗
PubMed1993

Separate populations of visually guided saccades in humans: reaction times and amplitudes.

The saccadic eye movements of 20 naive adults, 7 naive teenagers, 12 naive children, and 4 trained adult subjects were measured using two single target saccade tasks; the gap and the overlap task. In the gap task, the fixation point was switched off before the target occurred; in the overlap task it remained on until the end of each trial. The target position was randomly selected 4 degrees to the left or 4 degrees to the right of the fixation point. The subjects were instructed to look at the target when it appeared, not to react as fast as possible. They were not given any feedback about their performance. The results suggest that, in the gap task, most of the naive subjects exhibit at least two (the teenagers certainly three) clearly separated peaks in the distribution of the saccadic reaction times. The first peak occurs between 100 and 135 ms (express saccades), the second one between 140 and 180 ms (fast regular), and a third peak may follow at about 200 ms (slow regular). Other subjects did not show clear signs of two modes in the range of 100 to 180 ms, and still others did not produce any reaction times below 135 ms. In the overlap task as well three or even more peaks were obtained at about the same positions along the reaction time scale of many, but not all subjects. Group data as well as those of individual subjects were fitted by the superposition of three gaussian functions. Segregating the reaction time data into saccades that over- or undershoot the target indicated that express saccades almost never overshoot. The results are discussed in relation to the different neural processes preceding the initiation of visually-guided saccades.

Adolescent↗
PubMed1993

Enhanced procoagulant activity of mononuclear leukocytes in patients with atopic dermatitis and psoriasis.

Fibrin deposition is an important histopathological feature of inflammatory skin lesions and is mediated in part, by procoagulants generated by mononuclear leucocytes (MNL). We examined whether MNL from patients with atopic dermatitis or psoriasis generate enhanced procoagulant activity (PCA). MNL isolated from the peripheral blood of 15 healthy control individuals, 15 patients with atopic dermatitis and 15 patients with psoriasis were incubated for 24 h in the presence or absence of bacterial lipopolysaccharide (LPS). MNL or the cell culture supernatants were then added to recalcified human plasma to determine the clotting time. We found that in both atopic dermatitis and psoriasis MNL cultured in the presence or absence of LPS expressed greatly enhanced PCA (p < 0.01 to < 0.002). Supernatants from MNL cultures from patients with psoriasis, but not those from patients with atopic dermatitis, also generated augmented PCA (p < 0.002). In psoriasis, PCA normalized after successful topical treatment with anthralin. We conclude that enhanced PCA is a characteristic feature of MNL in both atopic dermatitis and psoriasis. In psoriasis the enhanced PCA is directly related to disease activity.

Adolescent↗
PubMed1993

Spark erosion procedure: a method for extensive combined fixed and removable prosthodontic care.

Restoration that uses a combination of fixed and removable partial dentures, which involves precision attachments and telescopic procedures, represents one of the highest levels of functional and esthetic therapy. In the past, these restorations were mostly made with high gold-content alloys. The dental spark erosion procedure offers a sophisticated method for using base metal alloys for these complex restorations. This procedure combines the functional and esthetic advantages of precision restorations with the advantageous properties of base metal alloys such as low thermal conductivity, high strength, and lower cost.

Copper↗
PubMed1993

Two amino acid substitutions in the tomato mosaic virus 30-kilodalton movement protein confer the ability to overcome the Tm-2(2) resistance gene in the tomato.

The Tm-2(2) resistance gene is used in most commercial tomato cultivars for protection against infection with tobacco mosaic virus and its close relative tomato mosaic virus (ToMV). To study the mechanism of this resistance gene, cDNA clones encompassing the complete genome of a ToMV strain (ToMV-2(2)) that was able to break the Tm-2(2) resistance were generated. Chimeric full-length viral cDNA clones were constructed under the control of the cauliflower mosaic virus 35S RNA promoter, combining parts of the wild-type virus and ToMV-2(2). Using these clones in cDNA infection experiments, we showed that the 30-kDa movement protein of ToMV-2(2) is responsible for overcoming the Tm-2(2) resistance gene in the tomato. DNA sequence analysis revealed four amino acid exchanges between the 30-kDa proteins from wild-type ToMV and ToMV-2(2), Lys-130 to Glu, Gly-184 to Glu, Ser-238 to Arg, and Lys-244 to Glu. To clarify the involvement of the altered amino acid residues in the resistance-breaking properties of the ToMV-2(2) movement protein, different combinations of these amino acid exchanges were introduced in the genome of wild-type ToMV. Only one mutant strain which contained two amino acid substitutions, Arg-238 and Glu-244, was able to multiply in Tm-2(2) tomato plants. Both amino acid exchanges are found within the carboxy-terminal region of the movement protein, which displays a high variability among different tobamoviruses and has been shown to be dispensable for virus transport in tobacco plants. These observations suggest that the resistance conferred by the Tm-2(2) gene against ToMV depends on specific recognition events in this host-pathogen interaction rather than interfering with fundamental functions of the 30-kDa protein.

Base Sequence↗
PubMed1993

Developmental regulation and tissue distribution of the liver transcription factor LFB1 (HNF1) in Xenopus laevis.

The transcription factor LFB1 (HNF1) was initially identified as a regulator of liver-specific gene expression in mammals. It interacts with the promoter element HP1, which is functionally conserved between mammals and amphibians, suggesting that a homologous factor, XLFB1, also exists in Xenopus laevis. To study the role of LFB1 in early development, we isolated two groups of cDNAs coding for this factor from a Xenopus liver cDNA library by using a rat LFB1 cDNA probe. A comparison of the primary structures of the Xenopus and mammalian proteins shows that the myosin-like dimerization helix, the POU-A-related domain, the homeo-domain-related region, and the serine/threonine-rich activation domain are conserved between X. laevis and mammals, suggesting that all these features typical for LFB1 are essential for function. Using monoclonal antibodies, we demonstrate that XLFB1 is present not only in the liver but also in the stomach, intestine, colon, and kidney. In an analysis of the expression of XLFB1 in the developing Xenopus embryo, XLFB1 transcripts appear at the gastrula stage. The XLFB1 protein can be identified in regions of the embryo in which the liver diverticulum, stomach, gut, and pronephros are localized. The early appearance of XLFB1 expression during embryogenesis suggests that the tissue-specific transcription factor XLFB1 is involved in the determination and/or differentiation of specific cell types during organogenesis.

Amino Acid Sequence↗