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T Peters

Publications and source records attributed to T Peters.

At least 145 records · Page 8Linked to original sources
PubMed1994

A table-mounted stereotactic system for digital angiography: a means of standardizing arteriovenous malformation measurement.

A detachable noninvasive table-mounted stereotactic device is described for use with digital radiography. The device is designed for standard two-view orthogonal projections but may be adjusted to allow for projections angled from the axial plane. When applied to the imaging of arteriovenous malformations (AVMs), it negates the influence of a variety of geometric and mechanical factors which would otherwise interfere with the determination of size. An accurate appreciation of AVM size, in turn, would allow a more reliable means of categorization of AVMs into distinctive groups for classification purposes and prognostication.

Algorithms↗
PubMed1994

Frameless stereotaxy for surgery of the epilepsies: preliminary experience. Technical note.

Frameless stereotactic techniques used in conjunction with three-dimensional images allow accurate planning and performance of a variety of neurosurgical procedures. The authors have used the frameless stereotactic Allegro Viewing Wand system to provide real-time correlation of the operating field and computerized images in 42 neurosurgical operations, including 31 epilepsy procedures. The system consists of an image-processing computer that creates three-dimensional and triplanar images; a mobile computer to display reformatted magnetic resonance images; and a hand-guided, articulated, position-sensing arm with a probe. At the start of the operation, the probe identifies the patient's facial and scalp features and correlates these with the computerized images. The position-sensing arm can then guide the operation and locate anatomical structures and lesions of interest. This system can be used to advantage in performing smaller craniotomies and intraoperatively locating anatomical structures and lesions to be removed. Postoperative magnetic resonance images demonstrate that this technique was accurate to within 3 mm in measuring the anteroposterior resection of fixed structures, such as hippocampus and corpus callosum. Disadvantages include longer preoperative preparation for data analysis and lack of both real-time computer analysis of tissue removal and angiographic data display. Preliminary experience suggests that the viewing wand system's advantages outweigh the disadvantages, and it is most helpful as an adjunctive navigational device in the microsurgical treatment of epilepsy.

Adolescent↗
PubMed1994

Measuring functional health status in primary care using the COOP-WONCA charts: acceptability, range of scores, construct validity, reliability and sensitivity to change.

BACKGROUND: The COOP-WONCA charts comprise six scales designed to measure functional health status in primary care. AIM: A study was undertaken to describe the acceptability, distribution of chart scores, construct validity, test-retest reliability and sensitivity to change when these charts were used in the United Kingdom. METHOD: For acceptability, distribution of scores and construct validity, data were obtained from 100 consecutive consulting patients aged 16 years and over and 100 non-consulting age-sex matched individuals from one general practice. In order to examine reliability and sensitivity to change, both groups were followed up two weeks later. RESULTS: Regarding acceptability, four patients refused to complete the charts during the initial recruitment of the consulters; 74 out of 100 non-consulters returned the first postal questionnaire. The follow-up questionnaire was returned by 68 out of 100 consulters and 57 out of 74 non-consulters. Overall distributions of scores demonstrated reasonable variation. Regarding construct validity, differences between the consulters and non-consulters were all in the anticipated direction and reached statistical significance for three of the six charts. For reliability, the proportion of non-consulters whose scores were unchanged ranged from 56% to 73%. For those whose scores changed, the differences were small and evenly balanced. For sensitivity to change, the proportion of consulters whose scores altered ranged from 45% to 59% with mean changes all indicating improvements in health. There were larger changes for patients consulting about acute problems than for those with chronic problems. CONCLUSION: It appears that the charts were acceptable, with reasonable distributions of scores and evidence of construct validity. Moderate levels of reliability and sensitivity to change were demonstrated. This study suggests that the COOP-WONCA charts are suitable for measuring functional health status in primary care in the UK.

Adolescent↗
PubMed1994

[The current pathogenetic aspects of diarrhea in ulcerative colitis].

The authors consider different mechanisms participating in progression of diarrhea in ulcerative colitis. The involvement of osmotic component was suggested in view of incomplete hydrolysis of carbohydrates by small intestinal glucoamylase under mono- and bisubstrate digestion, whereas diarrhea secretory component develops in participation of cyclic nucleotides. Motor mechanism is also present in diarrhea as evidenced by high concentrations of blood motilin and changes in intestinal evacuation and motility. Polycomponent dysbioses detected in ulcerative colitis patients may also be essential for pathogenesis of diarrhea. Determination of the leading component in each diarrhea case is thought helpful in valid choice of individual therapeutic policy.

Adolescent↗
PubMed1993

A Monte Carlo method for conformational analysis of saccharides.

A Metropolis Monte Carlo (MMC) algorithm was applied to explore conformational spaces spanned by the exocyclic dihedral angles of four disaccharides alpha-D-Man(1-->3)-alpha-D-Man(1-->O)Me (1), alpha-D-Man(1-->2)-alpha-D-Man(1-->O)Me (2), methyl beta-cellobioside (3), and methyl beta-maltoside (4). The simulation method uses the HSEA force field and randomly samples the conformational space with an automatic preference for low-energy states. In comparison to a systematic grid search, MMC offers a much more convenient and efficient protocol for the computation of ensemble average values of experimentally accessible NMR parameters such as NOE effects or 3J coupling constants. Energy barriers of a few kcal/mol were found to be surmounted easily when running the simulations with the temperature parameter set at room temperature, whereas passing significantly higher barriers required elevated temperature parameters. Ensemble average NOE values were calculated using the MMC technique and a conventional systematic grid search showing that the MMC method adequately samples the conformational spaces of 1-4. Theoretical NOEs derived for global or local minimum conformations are different from ensemble average values, and it is shown that averaged NOEs agree significantly better with experimental data. Ensemble average NOEs for 1 derived from MMC/HSEA, and previously reported MM2CARB and AMBER calculations all showed good agreement with experimental data, with MMC/HSEA giving the closest fit.

Algorithms↗
PubMed1993

Atrophy of mesial structures in patients with temporal lobe epilepsy: cause or consequence of repeated seizures?

We studied 70 epileptic patients by using magnetic resonance imaging volumetric measurements of amygdala (AM) and hippocampal formation (HF). Fifty patients presented with intractable temporal lobe epilepsy (TLE), 10 patients had focal extratemporal lobe epilepsy, and 10 had generalized epilepsy. In 91% of the 45 TLE patients without foreign tissue lesions, there was significant smallness of the AM and/or HF coinciding with the side of electroencephalographic seizure onset. No significant smallness or asymmetry was demonstrated in patients with focal extratemporal or generalized epilepsy. We performed a linear regression analysis, plotting the number of years of recurrent seizures and the estimated seizure frequency against the volumes of the AM and HF. There was no correlation between either of these two parameters and AM or HF volume (p > 0.9). There was also no correlation between the patient's age and volumetric measurements of AM or HF, nor did these measurements correlate with the occurrence of generalized seizures. On the other hand, patients with antecedent prolonged febrile convulsions in early childhood had significantly smaller AM and HF, compared with those without such a history (p < 0.001). The findings indicate that repeated seizures or longer duration of epilepsy do not cause increased atrophy of AM or HF that is measurable by volumetric magnetic resonance imaging.

Adolescent↗
PubMed1993

Frequency of hepatitis C in acute post-transfusion hepatitis after open-heart surgery: a prospective study in 1,476 patients.

Post-transfusion hepatitis was studied prospectively in 1,476 patients undergoing open-heart surgery between 1985 and 1988. Thirty-three (2.2%) patients suffered from post-transfusion hepatitis. Acute post-transfusion hepatitis was attributed to hepatitis B in one case and to hepatitis C in ten patients (0.7%). Four additional patients had preexisting serologic markers of hepatitis C. In 22 (1.5%) patients, hepatitis B or C was excluded as a cause of liver disease. Seroconversion for hepatitis C virus occurred from 3 weeks to more than 6 months after infection. Chronic hepatitis C developed in four patients. In addition, seroconversion to anti-HCV was observed in four patients with moderately elevated aminotransferases. In the control patients anti-HCV antibodies were found in 0.5%. The characteristics of acute hepatitis C after blood transfusion are shown and compared to 22 patients with acute hepatitis non-A, non-B, non-C. The etiology of these 22 cases is discussed.

Aged↗
PubMed1993

Conformational analysis of alpha-D-Fuc-(1-->4)-beta-D-GlcNAc-OMe. One-dimensional transient NOE experiments and Metropolis Monte Carlo simulations.

One-dimensional transient NOE build-up curves were measured for the synthetic disaccharide alpha-D-Fuc-(1-->4)-beta-D-GlcNAc 1 utilizing Gaussian shaped pulses. Simulated build-up curves from Metropolis Monte Carlo simulations were compared to the experimental data. Disaccharide 1 is structurally related to methyl beta-D-maltoside in that it also contains an alpha-(1-->4) linkage, and it has the same configuration of groups around the glycosidic linkage. Analysis of NOEs in methyl beta-D-maltoside is restricted to those observed upon selective excitation of H1' because of severe spectral overlap. The situation is different in 1 where 1H-NMR signals are well separated. Several interglycosidic NOEs were observed. The corresponding build-up curves allowed an accurate determination of the conformational preferences at the glycosidic linkage in 1. Comparison of experimental and theoretical NOE build-up curves showed clearly that rigid minimum-energy models cannot account for the experimental data. The best fit of experimental NOE build-up curves was obtained with theoretical curves from a 2 x 10(6) step Metropolis Monte Carlo simulation with the temperature parameter set at 1000 K. Finally, it was observed that only the interglycosidic NOE H5'/H6-pro-S significantly depends upon varying conformation distributions at the alpha-(1-->4)-glycosidic linkage, induced by choosing different temperature parameters for the Metropolis Monte Carlo simulations.

Carbohydrate Conformation↗
PubMed1993

Sequence analysis of hepatitis B virus DNA in immunologically negative infection.

It was previously demonstrated that the serum of some patients without immunological evidence of HBV infection contains the virus. Here we demonstrated by sequence analysis that the serum of such a patient contained a mixed HBV population. In comparison with HBV genomes of different genotypes twenty-two nucleotide variations were found in all clones sequenced in parallel. One nucleotide variation was identified within the enhancer I. Twelve of the twenty-two nucleotide variations caused altogether fifteen changes of amino acid sequence in known or predicted viral proteins. The proteins of the P open reading frame, which are most important for viral replication, were affected by nine amino acid substitutions. Three amino acid substitutions concerned the product of the X gene, a transcriptional transactivator of various viral and cellular promoters. Three mutations were only observed in some of the clones. One point mutation affected the direct repeats of the enhancer II. It occurred together with an 8 bp-deletion involving the C promoter region and the X gene. The third mutation was a single insertion, causing a fusion of the X and C gene. One or several of the identified mutations could be responsible for the diminished rate of replication and consequently for the low-titred, immunologically negative HBV infection.

Base Sequence↗
PubMed1993

Comparison of drug abuse fatalities and emergencies.

During a 9-month period, drug abuse emergencies were investigated prospectively and compared with drug-related fatalities of the same period. The emergency patients were of younger age, the proportion of women and the prevalence of infections with HIV, HBV and HCV was higher than in drug-related deaths. Additional alcohol consumption was similar in both groups but more frequent in drug-addict emergencies where the patients were 20-30 years of age. It is suggested that the emergency patients might characterise a special risk group of drug addicts and might be a target for interventional help to prevent fatalities.

Adolescent↗
PubMed1993

Drug abuse emergencies in Hamburg 1990/91.

During a 30-month investigation of the prevalence and structure of drug emergencies in Hamburg, data from all ambulances were analysed. From January 1991 to June 1992 there were 1565 drug-related emergency patients suffering a life-threatening event in Hamburg (1097 male, 350 female, 118 without information concerning the sex) to whom medical care was given by an emergency team. The number of cases grew strongly from 538 in 1990 to 720 in 1991. The place where the patients were found was very often in the region around the main railway station and near to the Reeperbahn, but we could also observe a scene south of the river Elbe.

Adult↗
PubMed1993

An improved model for studies on transdermal drug absorption in-vivo in rats.

In rats, transdermal drug absorption can be studied under physiological conditions by cannulating the peripheral skin vein, draining the are of the skin which is used for drug application, and collecting the blood. This method leads to decreased blood volume, which causes a reduction in skin blood flow and limits the maximal duration of the experiment. We improved the model by replacing the collected blood with blood from donor animals, so enabling the measurement of transdermal absorption over a period of 5 h under near constant conditions of blood pressure, haematocrit and skin blood flow. The model was applied to the transdermal absorption of [3H]prazosin and [3H]scopolamine and their permeability coefficients, fluxes and lag-times were determined. The model is suitable for measurements of transdermal drug absorption under in-vivo conditions, both for comparison of absorption profiles of different drugs and of the same drug in different formulations.

Administration, Cutaneous↗
PubMed1993

MRI volumetric measurement of amygdala and hippocampus in temporal lobe epilepsy.

We performed MRI volumetric measurements of the amygdala (AM), the hippocampal formation (HF), and the anterior temporal lobe in a group of 30 patients with intractable temporal lobe epilepsy (TLE) and in seven patients with extratemporal lobe foci. Measurements were analyzed with a semiautomated software program and the results compared with those of normal controls and correlated with the findings of all other investigations. In particular, we compared the results with the lateralization of epileptic abnormalities in the EEG. Volumetric studies of AM and HF showed lateralization of measurable atrophy consistent with that derived from extracranial and intracranial EEG examinations. The HF volumes were more sensitive and provided a lateralization in 87%. Combined measurements of AM and HF showed lateralization in 93%, always congruent with the results of EEG lateralization. This slight but important additional improvement in discrimination justifies using AM measurements in MRI volumetric studies of mesial temporal structures. Volumetric studies combined with other currently employed noninvasive techniques may diminish the need for invasive methods of investigation in patients with TLE.

Adult↗
PubMed1993

Interference of N-(1-[4-(4-fluorophenoxy)butyl]-piperidinyl)-N-methyl- 2-benzothiazolamine with Na+/H+ exchange and Na+/Ca2+ exchange in purified cardiac sarcolemmal membranes.

The effect of R 56865 (N-[1-[4-(4-fluorophenoxy)butyl]-piperidinyl]-N-methyl-2- benzothiazolamine, CAS 104606-13-5) on Na+/H+ exchange and Na+/Ca2+ exchange was studied in isolated cardiac sarcolemmal vesicles. R 56865 inhibited Na+/H+ exchange with an ED50 of 180 mumol/l at a concentration of 0.05 mmol/l Na+. The potency of R 56865 decreased with increasing concentrations of Na+. Na+/Ca2+ exchange was also inhibited. The ED50 amounted to 45 mumol/l. This ED50 was close to that of the reference compound dichlorobenzamil (ED50 = 27 mumol/l). The inhibitory potency of R 56865 on Na+/H+ and Na+/Ca2+ exchange is far too low to explain the already reported beneficial effects of this inhibitor of Na+ and Ca+ overload during ouabain intoxication and ischemia and reperfusion.

Amiloride↗
PubMed1992

Veratridine activates a silent sodium channel in rat isolated aorta.

To investigate the existence of silent Na+ channels, isolated rat aorta was treated with veratridine (0.1 mM) and the resulting Ca2+ uptake was determined. After 30-min incubation the total tissue uptake of Ca2+ and Ca2+ uptake increased from 2.325 +/- 0.017 to 2.614 +/- 0.080 nmol/mg wet weight (ww) and from 162.6 +/- 9.7 to 218.1 +/- 13.0 pmol/mg ww, respectively. The veratridine-induced Ca2+ uptake was blocked by tetrodotoxin (1 microM; to 17 +/- 5%) but not altered by amiloride (10 microM-1 mM). Activation of Na+/Ca2+ exchange by Na+ removal increased Ca2+ uptake from 74.2 +/- 4.5 to 97.3 +/- 5.3 pmol/mg ww, which was suppressed by amiloride (10 microM-1 mM). Nifedipine (10 nM) and verapamil (0.1 microM) at concentrations at which depolarization-induced Ca2+ uptake was diminished did not attenuate veratridine-induced Ca2+ uptake. Phenytoin at 0.1 mM reduced the Ca2+ uptake induced by veratridine or by depolarization. R 56865 (0.1 microM) and R 59494 (1 microM), novel anti-ischemic compounds inhibiting slowly inactivating Na+ channels, suppressed the veratridine-induced but not the depolarization-induced Ca2+ uptake. Guanidinium uptake was increased by veratridine (0.1 mM) from 371.2 +/- 7.2 to 574.8 +/- 45.9 pmol/mg ww. These results suggest that the rat aorta possesses a Na+ channel which is electrically silent under normal conditions but could be activated by veratridine.

Amiloride↗
PubMed1992

Synthesis and conformational and NMR studies of alpha-D-mannopyranosyl and alpha-D-mannopyranosyl-(1----2)-alpha-D-mannopyranosyl linked to L-serine and L-threonine.

alpha-D-Mannopyranosyl and alpha-D-mannopyranosyl-(1----2)-alpha-D- mannopyranosyl linked to L-serine and L-threonine have been synthesised as model substances for the linkage region in certain O-linked glycoproteins. Metropolis Monte Carlo simulations were performed with a modified version of the GESA program, to yield theoretical NOEs and interatomic distances as ensemble-average values, and these were compared with results from steady-state NOE experiments. The NOEs were determined as ensemble-average and as global minimum values. NMR chemical shift differences, obtained for signals of the glycopeptides relative to those of the respective monomers, were interpreted in terms of short inter-residue atomic distances as found within the global minima, and on the basis of averaged distances derived from Monte Carlo simulations.

Carbohydrate Conformation↗