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Biomedical subjects

B Walter

Publications and source records attributed to B Walter.

At least 19 recordsLinked to original sources
PubMed1992

Fundamentals of dry reagent chemistries: the role of enzymes.

It is evident that the specificity and catalytic efficiency of enzymes has revolutionized clinical diagnostics. Developing dry reagent systems provides convenience to the user as well as devices that are more versatile and suitable for a variety of analyses. Most dry reagent chemistries are usually less than 7 cm2 x 300 microns thick and are packaged as discrete test devices, which reduces spoilage of unused reagents. Sample volumes needed for analysis are usually in the range of 3-30 microL; the 10-microL volume is most commonly used. The use of such small volumes makes these devices suitable for neonatal and geriatric patients where large sample volumes are not often available. Hence, 150 microL of serum (approximately 300 microL of blood) is sufficient for at least 15 different analyses on a sample. Dry reagent chemistries are easy to store, readily available for use, and disposable. Only application of a sample is needed to start an analysis.

Enzymes↗
PubMed1992

[Pathomechanical aspects of intra-articular calcaneus fractures. Typing, grading and surgical therapy].

The forces to produce fractures of the os calcis are combined compression and shear under a cranio-caudal impulse of 10-40 kN and a short time of stroke about 10-40 ms. The main patterns in biomechanics of calcaneal fractures are the time of stroke and the geometrical position of the foot in the moment of impact. Furthermore individual structural changes of the calcaneal cancellous bone, age, diseases as Diabetes mellitus and vascular obliterations are to be respected. Operative treatment of these fractures needs an understanding of the pathomechanism of the intracalcaneal shear-tension-forces. With plantarflexion of the foot combined with vertical forces within 40 ms to the anterior talocalcanear facette impact-fractures of the anterior part can be expected. These forces develop a posterior directed shear tension parallel to the axis of the os calcis, dividing the bone horizontally in two parts (Typ A, 44-56%), well-known as tongue-type fracture. Compression of the posterior talo-calcaneal joint leads to an impact of this structure producing the joint depression type within about 30 ms in dorsoflexion of the foot (Type B, 42%) together with sagittal shear fractures. High-energy forces are supposed to produce the so-called primary fractures of the sustentacular process in about 10 ms in a supinated position of the foot (Type C, 2-10%); these fractures represent in cases of dislocation an indication for open reduction and internal fixation. In our own experience with 45 cases in 35 patients using the lateral or/and medial approach no infection happened. Palmer's lateral approach was preferred.

Biomechanical Phenomena↗
PubMed1991

Transient and locally restricted expression of the ros1 protooncogene during mouse development.

The ros1 gene was detected originally by virtue of its transforming potential; the cDNA of the human protooncogene was isolated from a tumor cell line expressing the gene ectopically. It encodes a receptor-type tyrosine specific protein kinase which is closely related to sevenless in Drosophila. Here we report the novel and remarkable in vivo expression pattern of c-ros1, which was determined in the mouse. By a combination of RNase protection and in situ hybridization, we find transient c-ros1 expression during development in the kidney, intestine and lung, coinciding with major morphogenetic and differentiation events in these organs. This temporally restricted nature of expression is unusual for tyrosine kinase receptors and suggests a role for ros1 during development. Furthermore, in kidney development c-ros1 transcripts are confined to subgroups of ureter cells known to be involved directly in inductive interactions between ureter epithelium and metanephric mesenchyme. Thus, this study implicates for the first time a tyrosine kinase receptor in mesenchymal epithelial interactions and suggests a molecular basis for these important inductive events in development.

Animals↗
PubMed1991

[Prosthetic rehabilitation of a case of total amelogenesis imperfecta].

A young adolescent girl suffering from Amelogenesis imperfecta was examined. The treatment plan: teeth kept vital, preparation of provisional resin crowns and their replacement by definitive single crowns. Thus re-establishing aesthetics and function, and furthermore the possibility of giving this young patient the pleasure of finally being able to smile, no longer hiding her teeth.

Adolescent↗
PubMed1990

How Trp repressor binds to its operator.

We propose that the generally accepted model of a single Trp repressor dimer binding to a center of symmetry in the natural trp operator (Otwinowski et al., 1988) is wrong. We show here that the Trp repressor binds to a sequence whose center is located four base pairs either to the right or to the left of the central axis of symmetry that was previously identified. We show that: (i) the oligonucleotide used by Otwinowski et al. is not retarded by the Trp repressor in a mobility shift assay under conditions wherein a shorter oligonucleotide carrying our consensus sequence is retarded, (ii) that methylation protection experiments on the full natural operator sequence and the short oligonucleotide protect similar patterns and (iii) that by varying every base in the shorter oligonucleotide, we can demonstrate an optimal sequence for Trp repressor binding.

Bacterial Proteins↗
PubMed1990

Functional analysis of a complex oncogene arrangement in biotype III Agrobacterium tumefaciens strains.

The ubiquitous grapevine-associated octopine/cucumopine Ti plasmids of biotype III Agrobacterium tumefaciens strains carry two T regions, TA and TB, with a complex oncogene arrangement. Within the octopine/cucumopine group, two main strain types were identified: 'large TA' strains with a TA region resembling the TL region of the biotype I octopine strain Ach5 and 'small TA' strains with a similar T region organization as the 'large TA' strains but with a large internal TA deletion. Structural and functional studies of the representative 'large TA' strain Tm4 revealed six oncogenes. Each oncogene was inserted in a disarmed vector and tested for biological activity using the corresponding oncogenes of Ach5 as standards. Five Tm4 oncogenes, TA-iaaM, T-ipt, T-6b, TB-iaaH and TB-iaaM, were shown to be active, the IS-interrupted TA-iaaH gene was inactive. To study the role of each gene in the pTiTm4 context, several single and multiple pTiTm4 mutations were constructed. It was shown that whereas TA-iaaM and TB-iaaH are essential for tumour formation on grapevine, T-ipt, T-6b and TB-iaaM are not. The avirulence of the TA-iaaM- mutant was shown to be due to an inhibitory effect of the T-ipt gene, since a TA-iaaM-/T-ipt- double mutant was fully virulent. We conclude that the TA-iaaM gene of 'large TA' strains is specifically required to counteract the tumour growth inhibiting activity of the T-ipt gene. Both TA-iaaM and T-ipt are absent from the 'small TA' strains. A model on the roles and interactions of the different oncogenes in 'large TA' and 'small TA' strains is presented.

Chromosome Deletion↗
PubMed1990

RNA2 of grapevine fanleaf virus: sequence analysis and coat protein cistron location.

The nucleotide sequence of the genomic RNA2 (3774 nucleotides) of grapevine fanleaf virus strain F13 was determined from overlapping cDNA clones and its genetic organization was deduced. Two rapid and efficient methods were used for cDNA cloning of the 5' region of RNA2. The complete sequence contained only one long open reading frame of 3555 nucleotides (1184 codons, 131K product). The analysis of the N-terminal sequence of purified coat protein (CP) and identification of its C-terminal residue have allowed the CP cistron to be precisely positioned within the polyprotein. The CP produced by proteolytic cleavage at the Arg/Gly site between residues 680 and 681 contains 504 amino acids (Mr 56019) and has hydrophobic properties. The Arg/Gly cleavage site deduced by N-terminal amino acid sequence analysis is the first for a nepovirus coat protein and for plant viruses expressing their genomic RNAs by polyprotein synthesis. Comparison of GFLV RNA2 with M RNA of cowpea mosaic comovirus and with RNA2 of two closely related nepoviruses, tomato black ring virus and Hungarian grapevine chrome mosaic virus, showed strong similarities among the 3' non-coding regions but less similarity among the 5' end non-coding sequences than reported among other nepovirus RNAs.

Amino Acid Sequence↗
PubMed1989

The nucleotide sequence of satellite RNA in grapevine fanleaf virus, strain F13.

The nucleotide sequence of cDNA copies of grapevine fanleaf virus (strain F13) satellite RNA has been determined. The primary structure obtained was 1114 nucleotides in length, excluding the poly(A) tail, and contained only one long open reading frame encoding a 341 residue, highly hydrophilic polypeptide of Mr37275. The coding sequence was bordered by a leader of 14 nucleotides and a 3'-terminal non-coding region of 74 nucleotides. No homology has been found with small satellite RNAs associated with other nepoviruses. Two limited homologies of eight nucleotides have been detected between the satellite RNA in grapevine fanleaf virus and those in tomato black ring virus, and a consensus sequence U.G/UGAAAAU/AU/AU/A at the 5' end of nepovirus RNAs is reported. A less extended consensus exists in this region in comovirus and picornavirus RNA.

Amino Acid Sequence↗
PubMed1989

Plasma clearance of bile acids in the rat: hepatic uptake under physiological conditions without countertransport.

Studies in rats by others indicated that sulfobromophthalein (BSP), bilirubin and indocyanine green are taken up by the liver and can be transported back to plasma against the prevailing concentration gradient (= countertransport). The present in vivo study was designed to determine whether the bile acids cholic acid and taurocholic acid under physiological conditions undergo appreciable countertransport as has been suggested by experiments in isolated hepatocytes. Experiments with BSP (controls) showed that injections of unlabeled BSP into rats five minutes after the administration of radiolabeled BSP was followed by a release of radioactivity into plasma (BSP-countertransport). In contrast bile acid countertransport could not be demonstrated, no matter whether it was tested 1, 5 or 8 minutes after the administration of radiolabeled cholic- or taurocholic acid.

Animals↗
PubMed1988

Construction of dry reagent chemistries: use of reagent immobilization and compartmentalization techniques.

The development of dry reagent systems has provided convenience to the user as well as devices that are more versatile and suitable for a variety of analyses. Most dry reagent chemistries are usually less than 7 cm2 by 300 micron thick packaged as discrete test devices. This reduces spoilage of unused reagents. Sample volumes needed for analysis are usually in the range of 3-30 microliter, with 10 microliter most commonly used. The use of such small volumes makes these devices suitable for neonatal and geriatric patients where large sample volumes are not often available. Hence, 150 microliter of serum (approximately 300 microliter blood) is sufficient for at least 15 different analyses on a sample. Dry reagent chemistries are easy to store, readily available for use, and disposable. Only application of a sample is needed to start an analysis.

Blood Chemical Analysis↗
PubMed1988

Normal ABR's in dyslexic children.

Auditory Brain stem Responses (ABR) were recorded in 24 severely constitutional dyslexic--and 21 normal children. The response latencies of the two groups were almost identical. We conclude that dysfunction of the brain stem auditory pathways should not be expected in dyslexic children.

Adolescent↗
PubMed1988

Auditory brain stem responses in dyslexic and normal children. A prospective clinical investigation.

Auditory Brain stem Responses (ABR) were performed prospectively in 24 severely constitutionally dyslexic children. None of the subjects showed any signs of organic or psychologic abnormality. The results were matched with a corresponding group of normal children. The response latencies of the two groups were almost identical (no statistically significant difference). We conclude that dysfunction of the brain stem auditory pathways should not be expected in constitutionally dyslexic children.

Adolescent↗