Search PubMed⌕ Search

Biomedical subjects

A Becker

Publications and source records attributed to A Becker.

At least 253 records · Page 14Linked to original sources
PubMed1997

Strain differences in pentylenetetrazol-kindling development and subsequent potentiation effects.

Rats from two different strains, i.e. Wistar rats and Lister hooded rats, were investigated for their ability to acquire the kindling syndrome. After having received 13 kindling stimulations (injection of pentylenetetrazol), the animals were tested for subsequent alterations in induction and maintenance of hippocampal long-term potentiation (LTP) and, moreover in glutamate binding. It was found that rats from both strains did not differ in the response to the initial injection of pentylenetetrazol (PTZ) and the amplitude of the population spike. This suggests that some aspects of basic central excitability are equivalent. Wistar rats acquired the kindling syndrome rapidly whereas seizure outcome was poor in Lister rats. As regards hippocampal LTP, the population spike was only dramatically increased in Wistar rats after kindling completion. Glutamate binding was not altered in animals from the Lister strain. The results suggest that changes in glutamate binding and the increase in the population spike are characteristic consequences of kindling.

Animals↗
PubMed1997

A multivalent PDZ-domain protein assembles signalling complexes in a G-protein-coupled cascade.

How are signalling molecules organized into different pathways within the same cell? In Drosophila, the inaD gene encodes a protein consisting of five PDZ domains which serves as a scaffold to assemble different components of the phototransduction cascade, including the principal light-activated ion channels, the effector phospholipase C-beta and protein kinase C. Null inaD mutants have a dramatically reorganized subcellular distribution of signalling molecules, and a total loss of transduction complexes. Also, mutants defective in a single PDZ domain produce signalling complexes that lack the target protein and display corresponding defects in their physiology. A picture emerges of a highly organized unit of signalling, a 'transduclisome', with PDZ domains functioning as key elements in the organization of transduction complexes in vivo.

Amino Acid Sequence↗
PubMed1997

The nucleotide sequence of Saccharomyces cerevisiae chromosome IV.

The complete DNA sequence of the yeast Saccharomyces cerevisiae chromosome IV has been determined. Apart from chromosome XII, which contains the 1-2 Mb rDNA cluster, chromosome IV is the longest S. cerevisiae chromosome. It was split into three parts, which were sequenced by a consortium from the European Community, the Sanger Centre, and groups from St Louis and Stanford in the United States. The sequence of 1,531,974 base pairs contains 796 predicted or known genes, 318 (39.9%) of which have been previously identified. Of the 478 new genes, 225 (28.3%) are homologous to previously identified genes and 253 (32%) have unknown functions or correspond to spurious open reading frames (ORFs). On average there is one gene approximately every two kilobases. Superimposed on alternating regional variations in G+C composition, there is a large central domain with a lower G+C content that contains all the yeast transposon (Ty) elements and most of the tRNA genes. Chromosome IV shares with chromosomes II, V, XII, XIII and XV some long clustered duplications which partly explain its origin.

Base Sequence↗
PubMed1997

The regulatory protein MucR binds to a short DNA region located upstream of the mucR coding region in Rhizobium meliloti.

The Rhizobium meliloti MucR protein is known to regulate the biosynthesis of the two exopolysaccharides, succinoglycan and galactoglucan. The mucR gene was successfully overexpressed in Escherichia coli BL21 cells by heat shock induction using a two-plasmid system. Cell extracts of the production strain contained about 20% of a polypeptide of 17 kDa apparent molecular mass, corresponding to the size expected for MucR. As shown by an electrophoretic mobility shift assay, these extracts were active in the specific retardation of a 219-bp DNA fragment including 134-bp of the non-coding region upstream of the mucR gene. Primer extension analysis showed that this DNA fragment was located within the transcribed region upstream of the mucR gene. Competition experiments revealed that a 44-bp sequence present within the 134-bp upstream of the mucR gene contained the MucR binding site. Although binding of MucR to this site exhibited a moderate dissociation constant of Kd approximately 1.4 x 10(-7) M, the reaction was highly specific since fragments containing binding sites for the homologous Ros protein from Agrobacterium tumefaciens were not able to compete for MucR binding.

Bacterial Proteins↗
PubMed1997

Molecular cloning and characterization of a novel putative carboxylesterase, present in human intestine and liver.

A full-length cDNA coding for a putative intestinal carboxylesterase (iCE) was isolated from a human small intestine cDNA library. The cDNA has an open reading frame of 559 amino acids with up to 65% homology to other carboxylesterases of different mammalian species. The deduced amino-acid sequence contains many structural features, that are highly conserved among all carboxylesterase isoenzymes, like the serine esterase active site, an ER-retention signal and one Asn-Xxx-Thr site for N-linked carbohydrate addition. Northern blot analysis revealed that the corresponding mRNA is 3.4-3.6 kb in size and is preferentially expressed in human intestine with a weak signal also in liver. Analysis of cells from the gastrointestinal tract unveiled site-specific, transcriptional regulation of iCE, with higher expression in small intestine and lower expression in colon and rectum. The high expression in small intestine is attributable to a higher expression in jejunum compared to duodenum and ileum.

Amino Acid Sequence↗
PubMed1997

Early and longtime modifications of temperature regulation after severe head injury. Prognostic implications.

In summary, despite almost normal body temperatures in thermoneutrality, thermoregulatory characteristics in posttrauma patients are evidently altered and modified. These changes make the patients more susceptible to variations of the ambient temperatures and reduce their ability to counteract heat loads. They are more in danger of suffering heat stroke under external thermal load and during work or sport activities. In certain cases this could mean an important reduction of the daily quality of life.

Adult↗
PubMed1997

Structural organization and characterization of the promoter region of a human carboxylesterase gene.

A gene encoding a human liver carboxylesterase has been isolated and characterized. Analysis of three overlapping genomic lambda clones revealed that the gene spans about 30 kb and is made of 14 exons being 39 to 379 bp in length. The encoded protein is 550 amino acids long and is highly homologous to carboxylesterases of various mammalian species. The transcription start site was determined by 5'-RACE PCR. An additional 900 bp of DNA from the 5' flanking region of the gene was cloned and sequenced in order to elucidate the structure of the promoter. In this sequence several possible binding sites for transcription factors have been identified, but no TATA-box was present. When different parts of the putative promoter region were ligated in front of the luciferase gene and the constructs were transfected into CHO cells, the reporter gene was effectively transcribed, as demonstrated by the expression of enzyme activity.

Amino Acid Sequence↗
PubMed1997

Efficacy of a vancomycin solution to prevent bacteremia associated with an indwelling central venous catheter in neutropenic and non-neutropenic cancer patients.

We evaluated the efficacy of a vancomycin solution in the prevention of bacteremia caused by vancomycin-sensitive organisms (VSO) in cancer patients with a tunneled central venous catheter (CVC). Eighty-three patients who had a single lumen CVC were randomized to use a heparin solution (25 U/ml) for daily catheter flush with (HepVan) or without (Hep) vancomycin, 25 mcg/ml. Febrile episodes were recorded, and central and peripheral blood cultures were drawn before beginning antibiotic therapy. Patients participated in follow-up to 16,677 catheter days (8,666 Hep and 8,011 HepVan), and 143 febrile episodes were recorded (82 Hep and 61 HepVan). Forty-four episodes of bacteremia occurred, 23 of them due to VSO (16 occurred in the Hep group and 7 in the HepVan group (P = 0.19). VSO bacteremia occurred in 14 neutropenic (absolute neutrophil count < 500 x 10(9)/l) episodes (7 Hep vs. 7 HepVan) and in 9 non-neutropenic episodes (9 Hep vs. O HepVan; P = 0.013). Vancomycin effectively prevented bacteremia by VSO in non-neutropenic patients, supporting the idea that intraluminal colonization of indwelling CVCs contributes to bacteremia only in these patients.

Adolescent↗
PubMed1997

Diazepam--its effects on the development of pentylenetetrazol kindling, related learning impairments, and neuronal cell loss.

Epileptics frequently experience cognitive disturbances. It was speculated that seizure activity causes neuronal cell loss which might, in part, contribute to these disturbances. To shed light on this problem, the kindling (pentylenetetrazol) model of epilepsy was used. Diazepam (DZP) was intraperitoneally injected (0.5 or 2.5 mg kg-1) in the course of kindling development. Six weeks after kindling completion the animals were tested for their performance in a shuttle-box and finally, the brains were processed for histological examination. It was found that DZP suppressed the expression of motor seizures. Kindled animals showed a significantly diminished shuttle-box performance. This impairment was not ameliorated by DZP. Moreover, the learning performance in control animals pretreated with DZP was low suggesting long-lasting alterations due to DZP application. In kindled animals the number of neurones in the hippocampal CA1 region was significantly reduced and this effect was counteracted by the substance. The presented data suggest that seizure suppression and a reduction in neuronal cell loss must not automatically result in improved learning performance.

Analysis of Variance↗
PubMed1997

Iodide or L-thyroxine to prevent recurrent goiter in an iodine-deficient area: prospective sonographic study.

In a randomized study, prevention of goiter recurrence with L-thyroxine was compared with pure iodide substitution after thyroid surgery for nodular goiter in an iodine-deficient area. Altogether 107 patients were followed up for 52 weeks after thyroid resection. The thyroid volume was determined sonographically. Free thyroxine, total thyroxine, thyrotropin, thyroglobulin, and antibodies to thyroglobulin and thyroid peroxidase were measured. The thyroid volume decreased slightly over the course of a year in the two therapy groups. There was no significant difference between the two groups. Recurrences were seen with both L-thyroxine medication and iodide substitution. The thyroglobulin levels fell significantly over the 52-week follow-up period in the iodide group. Antibody formation was not observed under iodine substitution. In an area of iodine deficiency, substitution with iodide is just as effective as medicating the patients with L-thyroxine for preventing recurrences.

Female↗
PubMed1997

Kindling of the dorsal and the ventral hippocampus: effects on learning performance in rats.

The hippocampus represents a heterogeneous structure which has been associated with different functions. It has been suggested that it plays an important role in both learning and memory and epileptogenesis. Thus, it is not surprising that seizure activity generated in the hippocampal formation interferes with memory storage. Little is known about the functional differentiation between the dorsal (DH) and ventral hippocampus (VH). To study this functional differentiation, we kindled Wistar rats either in the DH or in the VH by electrical stimulation. Afterwards, learning performance of these rats was tested in three different models, i.e., response to change (short-term memory), shuttle box (two-way active avoidance), and Y-chamber (brightness discrimination reaction). It was found that VH-kindled rats reached higher seizure scores than DH-kindled rats, but there was no difference in seizure duration. Kindling induced in the VH significantly impaired shuttle box learning, whereas DH-kindled rats showed a dramatically worsened acquisition in the brightness discrimination task. Different anatomical projections probably account, in part, for these differences.

Animals↗
PubMed1997

Effect of age on pentylenetetrazol-kindling and kindling-induced impairments of learning performance.

Epileptogenesis during ontogeny may not be linearly related to time. It is known that the behavioral manifestations of seizures are age-dependent, but more research is needed to clarify ontogenetic aspects of epilepsies and related alterations, including cognitive deficits. Kindling is an accepted animal model for the study of the convulsive component of epilepsy and its consequences on behavior. Recently, we demonstrated an impairment in acquisition of a conditioned reaction in young adult kindled rats, using pentylenetetrazol (PTZ) as the kindling stimulus. The present study was undertaken to investigate the dependence on age of alterations in the induction of PTZ kindling in rats. We started the kindling protocol in 4-, 6-, and 8-week- and 6-, 12-, 18-, and 24-month-old rats. The PTZ kindling showed an age-dependent decrease in expression of convulsions. The diminished kindling capacity was already seen in 6-month-old rats. In contrast, kindling-related impairment effects on cognitive functions increased with age. Thus, the correlation between learning impairment and occurrence of tonic-clonic seizures that we had demonstrated in 8-week-old rats was abolished in older rats. On the other hand, when the kindling procedure was started in 6-week-old rats, no impairment was found in fully kindled rats.

Aging↗
PubMed1997

Differences between two substrains of AB mice in the opioid system.

Animals from two substrains of AB mice, i.e., ABH/Md and ABG/Md, differ in the occurrence of aggressive behavior. After maturation, male ABH mice regularly exhibited abnormal aggressive behavior making group-housing impossible. In contrast, ABG animals never showed such behavioral patterns. To elucidate the role of opioid mechanisms, we tested the reaction of these animals to morphine in the hot plate test. Moreover, specific DAMGO binding was measured. It was shown that mice from control groups differed significantly in reaction to the thermal stimulus. ABH mice had significantly longer reaction times. With increasing doses of morphine this difference disappeared, suggesting different levels of basal activity in endogenous opioid systems. This is underlined by significantly lower DAMGO binding in aggressive ABH mice. The results suggest that differences in endogenous opioid systems may account for differences in aggressiveness.

Aggression↗
PubMed1997

Cleidocranial dysplasia: Part 2--Treatment protocol for the orthodontic and surgical modality.

The principles on which the present approach to the treatment of cleidocranial dysplasia are based were stated in part 1 of this article. Comparison was made with two other methods and the advantages of the present method were described in terms of (a) how this method is adapted to the clinical features of the condition, (b) when surgical intervention is appropriate, (c) how the dynamic appliance system may be adapted to the changing environment as more teeth erupt, and (d) the importance of rapidly bringing about the eruption of the anterior teeth. The practical aspects of the treatment are now described step-by-step with illustrations taken from the treatment of several different patients.

Adolescent↗
PubMed1997

Cleidocranial dysplasia: Part 1--General principles of the orthodontic and surgical treatment modality.

Over several decades, occasional reports of dental treatment provided by an individual practitioner to patients suffering with cleidocranial dysplasia have appeared in the literature. In the past, the main treatment was prosthetic replacement. Orthodontic treatment has only recently been considered as a serious treatment option, with success being described in several aspects of this treatment modality, in published individual case reports. Given the rarity of the condition, guidelines for the treatment of cleidocranial dysplasia are difficult to find in the literature, because few practitioners have treated enough cases to be in a position to make such recommendations. Two different approaches have been proposed in the past and are discussed here. The relative advantages of a third approach are expounded in detail.

Child↗