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Biomedical subjects

R Wagner

Publications and source records attributed to R Wagner.

At least 307 records · Page 17Linked to original sources
PubMed1991

Time course of interictal EEG patterns induced by a penicillin injection into the olfactory cortex.

In awake rats, the time courses of behavioural and cortical interictal hyperactivity patterns were investigated following an injection of the GABA antagonist Na-penicillin (PCN) (125 IU/0.5 microliters) into the olfactory or motor cortex. The cortical EEG was recorded by means of 6 AgAgCl-electrodes, behaviour was videotaped simultaneously. Behavioural hyperactivity developed immediately after PCN injection. It lasted longer than 2.5 to 4 h in the olfactory but less than 30 min in the motor cortex group of rats. The interictal EEG pattern of the olfactory group was characterized by a slow establishing of three centers of high cortical activity. They were located in the ipsilateral central and the contralateral frontal and occipital cortex. In the motor cortex group, however, a cortical center of high activity developed immediately after the PCN injection near the injection site only, or additionally, over the homotopic area of the contralateral hemisphere. The results indicate different susceptibility properties in the underlying neuronal networks. Ongoing epileptiform activity obviously modifies this susceptibility in a site-specific manner. Moreover, the time-correlated occurrence of high activity in the frontal motor and occipital cortex evoked by a PCN injection into the olfactory cortex suggests a close coupling of these three areas. A coupling between the frontal motor, occipital and focal area could not be shown, if PCN was injected into the motor cortex.

Animals↗
PubMed1991

Enzyme sensor-FIA-system for on-line monitoring of glucose, lactate and glutamine in animal cell cultures.

Enzyme sensors for glucose, lactate and glutamine were connected via flow-injection analysis (FIA) devices to two different bioprocesses. They were used for on-line process control of perfused bioreactor systems containing mammalian cell lines producing a monoclonal antibody and recombinant interleukin-2. The biosensor system gives direct access to important process data which can be used as control parameters for long term cell cultivation systems.

Animals↗
PubMed1991

Analysis of sequence elements important for the synthesis and control of ribosomal RNA in E coli.

The regulation of the synthesis of ribosomal RNA is a key problem for the understanding of bacterial growth. Many different regulatory mechanisms involving cis and trans acting components participate in a concerted way to achieve the very efficient, flexible and coordinated production of this class of molecules. We have studied three different sequence regions within a ribosomal RNA transcription unit which are believed to control different stages of ribosomal RNA expression. In the first part of the study the function of AT-rich sequences upstream of the -35 hexamer of rRNA promoter P1 in the activation of rRNA transcription was analyzed. We confirm that a sequence dependent bend upstream of P1 is responsible for the high promoter activity. Experiments employing linker scanning mutations demonstrated that the distance as well as the angular orientation of the bent DNA is crucial for the degree of activation. In addition, the effect of the trans activating protein Fis on the transcription initiation of promoter P1 was investigated. We can show, using the abortive initiation assay, that the predominant effect of Fis is due to an increase in the affinity of RNA polymerase for the promoter (binding constant KB) while the isomerisation rate (kf) from a closed to an open RNA polymerase promoter complex is not altered significantly. We also describe the characterization of sequence determinants important for stringent regulation and growth rate control. Evidence is provided that the discriminator motif GCGC is a necessary but not sufficient element for both types of control. Furthermore we show that not simply a particular DNA primary structure but the higher order conformation of the complete promoter region is recognized and triggers the two regulatory mechanisms, both of which are apparently mediated by the effector molecule guanosine tetraphosphate (ppGpp). Finally, we have carried out a systematic mutational analysis of the rrnB leader region preceding the structural gene for 16S RNA. We could demonstrate that highly conserved sequence elements within the rrnB leader, which were believed to be involved in transcription antitermination have post-transcriptional functions. We present evidence that these sequence elements direct the biogenesis of active ribosomal particles.

Base Sequence↗
PubMed1991

Carboxylic acids and tetrazoles as isosteric replacements for sulfate in cholecystokinin analogues.

A series of analogues of the satiety-inducing peptide cholecystokinin (CCK-8) was prepared in which the sulfated tyrosine required for activation of peripheral receptors was replaced with a carboxy(alkyl)- or tetrazolyl(alkyl)-phenylalanine to investigate whether an organic acid could serve the role of the sulfate group at the receptor. The necessary intermediates were prepared by previously reported procedures or by alkylation of carboxy(alkyl)- or tetrazolyl(alkyl)phenylmethyl bromides with a glycine-derived anion followed by protecting-group manipulations, and these were incorporated into derivatives of acetyl-CCK-7 using solid-phase synthesis. Peptide analogues were evaluated in a CCK-binding assay for affinity for either peripheral (CCK-A) receptors using homogenated rat pancreatic membranes as the receptor source or for central (CCK-B) receptors using bovine striatum as the receptor source. They were further evaluated for effects on food intake in rats after intraperitoneal (ip) injection. A number of the compounds reported are active in the CCK-A receptor binding assay although less potent than acetyl-CCK-7 and decrease food intake with comparable potency to acetyl-CCK-7. In a meal feeding model designed to assess appetite suppressant activity, acetyl-CCK-7 has an ED50 of 7 nmol/kg ip, while the ED50s of Ac-Phe(4-CH2CO2H)-Met-Gly-Trp-Met-Asp-Phe-NH2 (28) and Ac-Phe[4-(tetrazol-5-yl)]-Met-Gly-Trp-Met-Asp-Phe-NH2 (34) were 9 and 11 nmol/kg ip, respectively. An analogue of 28 lacking the N-terminal acetamido group, 3-[4-(carboxymethyl)-phenyl]propanoyl-Met-Gly-Trp-Met-Asp-Phe-NH2 (50), was also active in the meal feeding assay with an ED50 of 3 nmol/kg ip. Its anorexic effect was blocked by simultaneous administration of the CCK-A receptor antagonist MK 329, indicating that the observed anorexic activity is mediated by CCK-A receptors. We conclude from this work that the requirement for a negative charge at the CCK-A receptor provided in the natural substrate by a sulfate group can be satisfied by organic acids.

Animals↗
PubMed1991

Progression to type I diabetes in autoimmune endocrine patients with islet cell antibodies.

In an 11-yr screening program carried out on serum samples sent to an autoimmune serology laboratory, 158 patients with clinical or subclinical autoimmune endocrine manifestations and islet cell antibodies (ICAs) in the absence of overt diabetes were identified and followed for the development of insulin-dependent (type I) diabetes. Twenty-two (13.9%) developed type I diabetes in a follow-up of up to 12 yr (mean +/- SE 4.8 +/- 3.2 yr). The probability of being free of type I diabetes was 69.8% at 10 yr after the first detection of ICAs. Progression to disease was influenced by 1) the amount of ICAs represented by high titers (63% of those with ICAs greater than or equal to 20 Juvenile Diabetes Foundation units being free of type I diabetes at 10 yr), ICA persistency (59% being free of type I diabetes; P less than 0.02 vs. nonpersistent ICA), and complement-fixing (CF)-ICAs (63% being free of type I diabetes; P less than 0.05 vs. non-CF-ICA); 2) the coexistence of insulin autoantibodies (IAAs) (25% being free of type I diabetes; P less than 0.005 vs. IAA-); and 3) a positive family history (1st-degree relative) for type I diabetes (32% being free of type I diabetes; P less than 0.005 vs. no family history). There was a trend for diabetes to develop earlier in males of a younger age. No relationships were found with the number, type, or clinical expression of the associated autoimmunities or with a family history of such disorders.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Surgical treatment results in colonic obstruction].

Between 1982 and 1988 94 patients with obstruction of the colon were operated (52 male, 42 female, median age 66 years). Carcinoma accounted for the majority of cases: in 51% of patients enteral, in 9% local tumor growth extraenteral, in 17% peritoneal carcinosis. Therapeutic procedures were chosen according to the necessities in benign courses and in extraenteral tumor growth. In obstructing colorectal carcinoma (48 patients) a policy of primary tumor resection was pursued. 48 patients (40%) developed postoperative complications, 3 patients (3.1%) had to be reoperated. The overall mortality rate in patients with acute obstructions of all courses was 9.6%, in patients with obstruction secondary to carcinoma 14.6%. 74% of patients with colorectal tumors had TNM tumor stage III and IV. The 5-years-survival rate amounted to 21% overall, but after primary tumor resection it was 47%.

Aged↗
PubMed1991

[Risks of combined surgical treatment of acquired heart valve defects and coronary heart disease].

In the past years the number of patients with combined treatment of the heart valves and coronary arteries rised as well as the patients age did. In 1980-1987 the rate of patients with aortic valve replacement and simultaneous aorto-coronary bypass was 10.9% in those who underwent aortic valve replacement and 2.9% in those who had aorto-coronary bypass operation. Since 1988 the ratios changed to 18.2% and 4.9%. For the calculation of the operative risk of the combined operative treatment (AVR + CABG, MVR + CABG) we compared these groups with those patients with isolated operations (MVR, AVR, CABG). We studied all patients during 1980 and July 1989. The hospital mortality of combined procedures was significantly increased. The mortality among female patients was higher as compared to the male group. The age of patients treated by the combined procedures was higher as compared to the isolated procedures. The mean age of the patients which died was severely increased as compared to the isolated procedures. However, in the combined procedures this increase was not as pronounced as in the isolated groups. Patients with combined procedures had a higher NYHA class. The risk factors of the combined procedures were comparable to isolated CABG.

Aortic Valve↗
PubMed1990

The signal for growth rate control and stringent sensitivity in E. coli is not restricted to a particular sequence motif within the promoter region.

Hybrid promoter constructs were used to determine the DNA sequence requirements for stringent and growth rate control within a promoter region. The promoters were obtained by fusing complementing sequence regions located upstream and downstream from the GCGC discriminator motif of the growth rate regulated rRNA P1 promoter and a non-regulated tac promoter variant. The activities and the regulatory response of the hybrid promoters were determined in vivo using a promoter test vector system with the chloramphenicol acetyltransferase (CAT) reporter gene. Measurements were made at different growth rates and after starvation for isoleucine to induce the stringent response. Neither the upstream nor the downstream sequence of P1 relative to the GCGC discriminator motif conferred comparable regulatory features when fused to the complementing sequences of the non-regulated mutant tac promoter. A minor response to amino acid deprivation or changes in the growth rate was noted for the hybrid promoter with the rrnB P1 upstream segment and the tac downstream element, pointing to a slightly different importance of the two sequence elements for regulation. The parallel effects for stringent as well as growth rate regulation of the hybrid promoters supports the view of a common mechanism for both types of control. However, none of the promoter sequence elements on its own was able to restore the complete regulatory behaviour of their 'parent' promoters.

Base Sequence↗
PubMed1990

The tL structure within the leader region of Escherichia coli ribosomal RNA operons has post-transcriptional functions.

We have investigated a series of mutations within a plasmid encoded E. coli ribosomal RNA leader region. The mutations are localized within a structure known as tL, which has been shown to mediate RNA polymerase pausing in vitro, and which is assumed to have a control function in rRNA transcription antitermination. The effects of the mutated plasmids were analyzed by in vivo and in vitro experiments. Some of the base change mutations led to severely reduced cell growth. As opposed to previous results obtained with mutants where the tL structure has been deleted in part or totally, the tL base change mutations did not result in polar transcription in vivo, rather they revealed a general reduction in the amount of the promoter proximal 16S versus the distal 23S RNA. The deficiency of the 16S RNA, which was most pronounced for some of the slowly growing transformants, can only be explained by a post-transcriptional degradation. In addition, many mutants showed a defective processing after the initial RNase III cut. In line with these results a quantitative analysis of the ratio of ribosomal subunits and 70S tight couple ribosomes showed a reduced capacity to form stable 70S particles for the slowly growing mutants. Together, these findings indicate an important function of the tL structure in post-transcriptional events like processing of rRNA precursors and correct assembly of 30S subunits.

Escherichia coli↗
PubMed1990

A quantitative assessment for transcriptional pausing of DNA-dependent RNA polymerases in vitro.

A simple definition for pause strength (tau i) has been given, quantitatively describing transcriptional pausing of RNA polymerases. It permits derivation of practical assessments, based on single-round transcription reactions, which measure the average time a polymerase stops in vitro at certain sites during transcription elongation. We demonstrate that pause strengths can be determined with high accuracy when transcription elongation is started simultaneously from radioactively labeled and purified ternary complexes and transcripts are separated on sequencing gels. Our concept is exemplified by measuring pause strengths on supercoiled templates in the leader region of the Escherichia coli rrnB operon in the presence and the absence of the transcription factor NusA.

Bacterial Proteins↗
PubMed1990

Watching G proteins at work.

It has been known for over a century that rod photoreceptors in the living retina contract and swell in response to light. Although it is still not known whether this structural light-response is of any functional significance, it has recently been possible to correlate the underlying molecular processes with the activation and deactivation of the photoreceptor G protein, transducin. The technique of light-scattering allows the monitoring of minute changes in cell dimensions, and using this non-invasive experimental approach it can be shown that certain properties of the coupling between transducin and rhodopsin are different in a structurally well-preserved system as compared with rod material used for conventional biochemical studies. Thus, not unlike a psychiatrist, who often learns more about a patient's 'interiors' by observing the body language than by direct interrogation, a biochemist, studying the 'body language' of a cell, may extract information about delicate 'cell interior processes' that would be perturbed by more direct experimental approaches.

Animals↗
PubMed1990

Production of recombinant human interleukin-2 with BHK cells in a hollow fibre and a stirred tank reactor with protein-free medium.

For the production of recombinant human interleukin-2 (IL-2) two different culture processes, a 1-2 liter homogeneous stirred bubble-free aerated system and a dense cell hollow fibre bioreactor were compared. Cultivations were carried out with serum- or protein-free medium formulations. In the stirred culture 0.75 mg IL-2 were produced with 1 l of perfused medium at a maximum cell number of 3 X 10(10). The product yield in the hollow fibre module was only 0.23 mg l-1 at a maximum cell number of 6 X 10(10). In contrast to results with hybridoma or EBV-transformed cell lines, in which hollow fibre bioreactors showed comparable efficiency to perfused stirred tank reactors, the tissue-like cell density is disadvantageous as adherent cells tend to stick together leaving insufficient intercellular space for removal of product.

Animals↗
PubMed1990

The cytotoxic effect of ajoene, a natural product from garlic, investigated with different cell lines.

The sulfur-containing compound ajoene (4,5,9-trithiadodeca-1,6,11-triene-9-oxide) which arises from alliin, a cysteine derivative stored in garlic bulbs, was produced synthetically by decomposition of allicin. Its cytotoxic effect was tested using human primary fibroblasts (FS4), a permanent, non-tumorgenic cell line derived from baby hamster kidney cells (BHK21) and a tumorgenic lymphoid cell line derived from a Burkitt lymphoma (BJA-B). The cytotoxic action was in the range 2-50 micrograms/ml depending on the cell density. ED50 values, estimated on the basis of fmol ajoene/cell, revealed slightly higher doses for the primary cell (FS4) than the permanent line (BHK), whereas the tumorgenic BJA-B cells were most sensitive.

Animals↗
PubMed1990

Single- vs multiple-dose pharmacokinetics of clozapine in psychiatric patients.

Clozapine plasma levels were monitored in 16 patients during a series of three consecutive treatments (single dose-multiple dose-single dose). Each patient received a single 75-mg dose (3 x 25 mg) with clozapine tablets, and serial plasma samples were collected over 48 hr after the dose. At 48 hr, a multiple-dose regimen was started, consisting of an initial dose escalation period followed by dosing at a constant regimen for at least 6 days. After the last dose, serial plasma samples were again obtained over 72 hr. Drug was then withheld for at least 7 days, a final single 75-mg dose was given, and plasma sampling was repeated. A subset of the patient population (N = 7) was used to test for a food effect during the single-dose treatments. The pharmacokinetic parameters between the initial and the final single dose periods were not significantly different. Similarly, there were no differences within patients when given the dose after fasting (fed 1 hr after dose) or with a meal. In contrast, the terminal elimination rate differed between the single-dose and the multiple-dose treatments (t1/2 m3 = 7.9 hr single dose and 14.2 hr multiple dose) (P less than 0.05) and the dose-normalized area under the plasma concentration/time curves increased 27% with multiple dosing. Since a previous study in patients (Choc et al., Pharm. Res. 4:402-405, 1987) showed dose proportionality of clozapine plasma concentrations during multiple-dose regimens, the present results cannot be described by Michaelis-Menten kinetics.

Adult↗
PubMed1990

Intimal protection of bypass-veins during intraoperative storage in blood or Euro-Collins-solution: the role of medium, temperature, and time.

The patency-rate of venous bypasses depends - beside other important factors - upon the integrity of the transplanted vessel, especially on the condition of the tunica intima. Under this aspect we examined by light microscopy a total of over 1100 slices of human as well as animal vein-segments which had been stored in arterial heparinized blood or Euro-Collins-Solution at 4 degrees C, 20 degrees C and 37 degrees C up to 90 minutes. The results show that veins should be used immediately after harvesting. If intraoperative storage is necessary blood at a temperature between 20 degrees C and 37 degrees C is the better medium for storage periods up to 90 minutes.

Animals↗
PubMed1990

Major histocompatibility complex haplotype studies in Ashkenazi Jewish patients with pemphigus vulgaris.

Of 26 Ashkenazi Jewish patients with pemphigus vulgaris, 24 (92.3%) carried the major histocompatibility complex (MHC) class II alleles HLA-DR4, DQw3, of which all were of the subtype DR4, DQw8. From studies of the patients and their families, haplotypes were defined. It was found that, of the patients who carried HLA-DR4, DQw8, 75% carried one or the other (and in one case, both) of two haplotypes [HLA-B38, SC21, DR4] or HLA-B35, SC31, DR4. The former is a known extended haplotype among normal Jews, with a frequency of 0.102, and the latter may also be an extended haplotype in this ethnic group, with a frequency of 0.017 among normal haplotypes from Jews. Of the remaining DR4-positive patients, all but one had a presumed D-region segment (defined as SC21, DR4, DQw8 or SC31, DR4, DQw8 with variable HLA-B) of these haplotypes. Only one patient had DR4, DQw8 without any other markers of the extended haplotypes. The number of homozygotes and heterozygotes for DR4, DQw8 was consistent with dominant but not recessive (P less than 0.01) inheritance of a class II or a class II-linked susceptibility gene for the disease. Since the disease is entirely attributable to the presence of an antibody to an intraepidermal intercellular cement substance, it is likely that the class II susceptibility gene (on [HLA-B38, SC21, DR4, DQw8], HLA-B35, SC31, DR4, DQw8, or their segments, in Jewish patients) controls the production of the antibody as a dominantly expressed immune response gene.

Alleles↗
PubMed1990

TSH secretion in Cushing's syndrome: relation to glucocorticoid excess, diabetes, goitre, and the 'sick euthyroid syndrome'.

Thyrotrophin (TSH) secretion was studied in 63 patients with Cushing's syndrome (53 patients with pituitary dependent Cushing's disease, eight with adrenocortical tumours, and two with the ectopic ACTH syndrome). Prior to treatment, TSH response to 200 micrograms of TRH intravenously was significantly decreased compared to controls; TSH response was 'flat' (increment less than 2 mU/l) in 34 patients (54%). Patients with a flat response to TRH had significantly higher morning and midnight cortisol levels than patients with a TSH response of 2 mU/l and more; this was not due to differences in serum thyroid hormone levels. Basal TSH, TSH increment after TRH, and stimulated TSH value, but not serum triiodothyronine, were correlated with cortisol measurements (0800 h serum cortisol, midnight cortisol, and urinary free corticoid excretion). After exclusion of 40 patients with additional disease (severe systemic disease, diabetes mellitus, or goitre), cortisol-TSH correlations were even more pronounced (r = -0.73 for midnight cortisol and stimulated TSH levels), while in the patients with additional complications, these correlations were slight or absent. Successful treatment in 20 patients was associated with a rise in thyroid hormone levels and the TSH response to TRH. These results indicate that (1) the corticoid excess but not serum T3 is the principal factor regulating TSH secretion in Cushing's syndrome, (2) a totally flat response to TRH is rare, and (3) TSH suppression and lower than normal serum thyroid hormone levels are reversible after treatment. Since factors like severe systemic disease, diabetes mellitus and goitre also affect TSH secretion, they tend to obscure the statistically significant correlations between cortisol excess and TSH secretion.

Adult↗