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Biomedical subjects

R Behrens

Publications and source records attributed to R Behrens.

At least 19 recordsLinked to original sources
PubMed2002

Imported Falciparum malaria in Europe: sentinel surveillance data from the European network on surveillance of imported infectious diseases.

Malaria continues to have a high morbidity rate associated among European travelers. Thorough recording of epidemiological and clinical aspects of imported malaria has been helpful in the detection of new outbreaks and areas of developing drug resistance. Sentinel surveillance of data collected prospectively since 1999 has begun within TropNetEurop, a European network focusing on imported infectious diseases. TropNetEurop appears to cover approximately 10% of all patients with malaria seen in Europe. Reports of 1659 immigrants and European patients with Plasmodium falciparum malaria were analyzed for epidemiological information and data on clinical features. Regional data were quite diverse, reflecting local patterns of immigration and international travel. By far, the most infections were imported from West Africa. Europeans had more clinical complications; consequently, all deaths occurred in this group. Compared with European standards, the mortality rate was low (0.6% in Europeans). Data from TropNetEurop member sites can contribute to our understanding of the epidemiological and clinical findings regarding imported falciparum malaria.

Adolescent↗
PubMed2001

Presynaptic Ca2+-activated K+ channels in glutamatergic hippocampal terminals and their role in spike repolarization and regulation of transmitter release.

Large-conductance Ca(2+)-activated K(+) channels (BK, also called Maxi-K or Slo channels) are widespread in the vertebrate nervous system, but their functional roles in synaptic transmission in the mammalian brain are largely unknown. By combining electrophysiology and immunogold cytochemistry, we demonstrate the existence of functional BK channels in presynaptic terminals in the hippocampus and compare their functional roles in somata and terminals of CA3 pyramidal cells. Double-labeling immunogold analysis with BK channel and glutamate receptor antibodies indicated that BK channels are targeted to the presynaptic membrane facing the synaptic cleft in terminals of Schaffer collaterals in stratum radiatum. Whole-cell, intracellular, and field-potential recordings from CA1 pyramidal cells showed that the presynaptic BK channels are activated by calcium influx and can contribute to repolarization of the presynaptic action potential (AP) and negative feedback control of Ca(2+) influx and transmitter release. This was observed in the presence of 4-aminopyridine (4-AP, 40-100 microm), which broadened the presynaptic compound action potential. In contrast, the presynaptic BK channels did not contribute significantly to regulation of action potentials or transmitter release under basal experimental conditions, i.e., without 4-AP, even at high stimulation frequencies. This is unlike the situation in the parent cell bodies (CA3 pyramidal cells), where BK channels contribute strongly to action potential repolarization. These results indicate that the functional role of BK channels depends on their subcellular localization.

4-Aminopyridine↗
PubMed2001

Mev X rays and photoneutrons from femtosecond laser-produced plasmas.

We demonstrate a novel method to monitor the total angular distribution of the spectrum of hard x-ray emission from a plasma generated with femtosecond laser pulses with an intensity of 5 x 10(18) W/cm2 on a solid target. Measured and calculated angular distributions of x rays show a pronounced anisotropy for MeV photon energies. We complemented the spectral information by demonstrating a (gamma,n) nuclear reaction with a tabletop laser system.

Journal Article↗
PubMed2001

Balloon dilation is preferable to bougienage in children with esophageal atresia.

BACKGROUND AND STUDY AIMS: Esophageal strictures are a common problem after surgical repair in children with esophageal atresia. The traditional procedure in these patients is dilation using bougie dilators, usually controlled fluoroscopically or endoscopically. Nowadays, an alternative technique is balloon-catheter dilation. The aim of this study was to report our experience with pneumatic balloon dilation and to compare this method with previously performed bougienage with regard to efficacy. PATIENTS AND METHODS: Over 16 years, 34 patients who developed symptomatic strictures were encountered at our institution. In the first 9 years 12 patients underwent 178 bougienages (group C). In the last 7 years six patients who had undergone 202 previous bougienages (group B), and 16 patients who had undergone no bougienages (group A), underwent 52 dilations. The dilation was carried out under intravenous sedation using a combination of midazolam and etomidate. The balloon was placed in the stricture endoscopically and the procedure was performed under fluoroscopic and endoscopic control. RESULTS: In all patients the dilation was effective and involved minimal trauma. The strictures required 1 to 7 procedures (median 2) over a maximum of 18 months (median 3 months) for a good treatment result. The complications observed were two perforations, one of them with pneumothorax (both treated conservatively), and two compressions of the trachea (interruption of the procedure, but efficient dilation was eventually achieved). The method was more effective than bougienage (1 to 60 bougienages were required per patient, median 9). CONCLUSIONS: Compared with traditional bougienage, balloon dilation of esophageal strictures is less traumatic and more effective. Complications are rare and can be managed conservatively. In our opinion this procedure is the appropriate treatment for strictures, even in very small infants, after repair of esophageal atresia.

Catheterization↗
PubMed2000

Fission yeast retrotransposon Tf1 integration is targeted to 5' ends of open reading frames.

Target site selection of transposable elements is usually not random but involves some specificity for a DNA sequence or a DNA binding host factor. We have investigated the target site selection of the long terminal repeat-containing retrotransposon Tf1 from the fission yeast Schizosaccharomyces pombe. By monitoring induced transposition events we found that Tf1 integration sites were distributed throughout the genome. Mapping these insertions revealed that Tf1 did not integrate into open reading frames, but occurred preferentially in longer intergenic regions with integration biased towards a region 100-420 bp upstream of the translation start site. Northern blot analysis showed that transcription of genes adjacent to Tf1 insertions was not significantly changed.

Binding Sites↗
PubMed2000

hKCNMB3 and hKCNMB4, cloning and characterization of two members of the large-conductance calcium-activated potassium channel beta subunit family.

We cloned two beta subunits of large-conductance calcium-activated potassium (BK) channels, hKCNMB3 (BKbeta1) and hKCNMB4 (BKbeta4). Profiling mRNA expression showed that hKCNMB3 expression is enriched in testis and hKCNMB4 expression is very prominent in brain. We coexpressed BK channel alpha (BKalpha) and BKbeta4 subunits in vitro in CHO cells. We compared BKalpha/beta4 mediated currents with those of smooth muscle BKalpha/beta1 channels. BKbeta4 slowed activation kinetics more significantly, led to a steeper apparent calcium sensitivity, and shifted the voltage range of BK current activation to more negative potentials than BKbeta1. BKalpha/beta4 channels were not blocked by 100 nM charybdotoxin or iberiotoxin, and were activated by 17beta-estradiol.

Amino Acid Sequence↗
PubMed2000

Pharmacokinetics of orally administered omeprazole in children. International Pediatric Omeprazole Pharmacokinetic Group.

OBJECTIVES: The aim of this study was to examine the pharmacokinetics of orally administered omeprazole in children. METHODS: Plasma concentrations of omeprazole were measured at steady state over a 6-h period after administration of the drug. Patients were a subset of those in a multicenter study to determine the dose, safety, efficacy, and tolerability of omeprazole in the treatment of erosive reflux esophagitis in children. Children were 1-16 yr of age, with erosive esophagitis and pathological acid reflux on 24 h-intraesophageal pH study. The "healing dose" of omeprazole was that at which subsequent intraesophageal pH study normalized. Children remained on this dose for 3 months, and during this period the pharmacokinetics were measured. RESULTS: A total of 57 children were enrolled in the overall healing phase of the study. Pharmacokinetic study was optional for subjects and was performed in 25 of the 57 enrolled. The doses of omeprazole required were substantially higher doses per kilogram of body weight than in adults. Values of the pharmacokinetic parameters of omeprazole were generally within the ranges previously reported in adults. However, the plasma levels, area under the plasma concentration versus time curve (AUC), plasma half-life (t(1/2)), and maximal plasma concentration (Cmax), were lower in the younger age group, when the AUC and Cmax were normalized to a dose of 1 mg/kg. Furthermore, within the group as a whole, these values showed a gradation from lowest in the children 1-6 yr of age to higher in the older age groups. CONCLUSIONS: The pharmacokinetics of omeprazole in children showed a trend toward higher metabolic capacity with decreasing age, being highest at 1-6 yr of age. This may explain the need for higher doses of omeprazole on a per kilogram basis, not only in children overall compared with adults but, in many cases, particularly in younger children.

Administration, Oral↗
PubMed1999

Late manifestation of Indian childhood cirrhosis in a 3-year-old German girl.

UNLABELLED: We report on a 3.8-year-old German girl who presented with signs of subacute liver failure based on a 4-month history. Investigations done before admission excluded infectious, metabolic and immunological diseases. Laboratory findings were increased values of aminotransferases, hyperbilirubinaemia, hyperammonaemia and deteriorated plasmatic coagulation. Caeruloplasmin and serum copper concentrations were normal; however, urinary copper excretion was elevated (80 microg/l). Liver biopsy showed a micronodular liver cirrhosis and an extremely high liver copper concentration (1400 microg/g dry weight). Epidemiological investigations revealed an elevated copper concentration (8645 microg/l, normal: <2000) and a low pH value (6.3) of the drinking water supplied by copper pipes. The girl had been exposed to copper-contaminated drinking water since the age of 2 years. CONCLUSION: Laboratory, histopathological findings and a proven chronic copper intoxication lead to the diagnosis of Indian childhood cirrhosis in a German girl. Whereas this disease is mostly described in patients with increased copper intake in infancy, our patient developed toxic liver cirrhosis with relatively late copper exposure. Indian childhood cirrhosis should be considered in the differential diagnosis of early childhood liver cirrhosis.

Child, Preschool↗
PubMed1999

Dual versus triple therapy of Helicobacter pylori infection: results of a multicentre trial.

OBJECTIVE: To compare dual therapy (omeprazole and amoxicillin) with triple therapy (omeprazole, amoxicillin, and clarithromycin) in the treatment of Helicobacter pylori infection. The efficacy of 1 mg/kg/day omeprazole was randomly compared with 2 mg/kg/day. STUDY DESIGN: 252 patients (median age, 11.0 years; range, 3-18) presenting with chronic abdominal pain underwent endoscopy and a 13C-urea breath test. Gastric biopsy specimens were taken for histological examination and for the rapid urease test. Patients were treated for two weeks: group A (n = 63) received amoxicillin (50 mg/kg; maximum, 2 g/day), group B (n = 73) received amoxicillin and clarithromycin (20 mg/kg; maximum, 1 g/day). Both groups were randomly treated with either 1 or 2 mg/kg omeprazole (maximum, 80 mg/day). Diagnostic procedures were repeated four weeks after the end of treatment. RESULTS: 11 patients were excluded; 136 patients were H pylori positive (56%), 105 of whom were re-examined after treatment. Helicobacter pylori was eradicated in 52% of group A and 83% of group B. The dose of omeprazole had no influence on the eradication rate. Specificity and sensitivity of the rapid urease test were 94% and 93%, respectively. Specificity and sensitivity of the 13C-urea breath test were 93% and 95%, respectively. CONCLUSIONS: Dual therapy can no longer be recommended. Triple therapy is more effective than dual therapy in the eradication of H pylori infection. The lower dose of 1 mg/kg omeprazole was as effective as 2 mg/kg.

Adolescent↗
PubMed1999

Another case of achalasia-microcephaly syndrome.

The first German patient with achalasia-microcephaly syndrome is described. The mother was exposed to the anti-malarial drug Mefloquine during the first 8 weeks of pregnancy.

Abnormalities, Drug-Induced↗
PubMed1998

[Eosinophil cationic protein in a 39-year-old patient with Churg-Strauss syndrome].

HISTORY AND CLINICAL FINDINGS: A 39-year-old woman in good health suddenly developed painful paraesthesia and incomplete paresis of all four limbs. Furthermore, arterial hypertension and tachycardia were found. The patient reported a history of chronic allergic rhinitis for 10 years and asthma one year. INVESTIGATIONS: Laboratory data showed an increased leucocyte count with a substantial increase in eosinophils in peripheral blood as well as in bone marrow. Nonspecific inflammatory markers such as erythrocyte sedimentation rate, C-reactive protein, fibrinogen as well as eosinophil cationic protein (ECP) were also increased. Histological investigations of a skin-muscle biopsy of the quadriceps revealed necrotizing vasculitis with extravascular granulomata and histiocytic giant cells. DIAGNOSIS, TREATMENT AND COURSE: Based on the diagnosis of Churg-Strauss syndrome treatment with methylprednisolone (500 mg every second day) was started, but was found to be ineffective after 10 days. Symptoms responded well to a subsequent course of 150 mg cyclophosphamide combined with 50 mg prednisolone per day. Pareses and pain were significantly reduced and all qualitative nerve functions returned to normal within two weeks of treatment. Laboratory parameters, especially the ECP, were similarly normalized. CONCLUSION: Churg-Strauss syndrome should be considered in the differential diagnosis of unexplained polyneuropathy. Determination of ECP may not only help in the diagnosis but does also facilitate monitoring of treatment and of further course of the disease.

Adult↗
PubMed1998

Safety and efficacy of interferon retreatment in children with chronic hepatitis B.

UNLABELLED: More than 50% of children with chronic hepatitis B do not respond to treatment with alpha-interferon. Since these patients continue to display high viral replication and progressive liver disease, retreatment should be considered. To date it has not been well evaluated whether a second course of treatment could increase the response rate. In two alpha-interferon retreatment trials in adult patients the response rate, defined by seroconversion from HBeAg to anti-HBe, ranged between 11% and 44%. One beta-interferon retreatment study in children reported a seroconversion rate of 32%. Regrettably, none of the studies included a control group observing the 'spontaneous' seroconversion rate after a first interferon cycle. Thus, a nonrandomized alpha-interferon retreatment study in children including control patients was performed. Alpha-interferon for retreatment was administered 3 times a week for 16-24 weeks in 15 children (5-16 years) at least 6 months after ceasing the first cycle. Four children received 5 MU/m2 of a natural alpha-interferon and 11 children 9 MU/m2 recombinant alpha-interferon 2b. Follow up was 18-47 months after initial treatment. In parallel, a control group of 19 unretreated children with comparable clinical and demographic data was followed for 12-39 months. HBeAg seroconversion was observed in 5 (33%) of the retreated children and in 5 (26%) of the control patients during follow up. The difference is not significant. In the initially nonresponding children, those with high ALT levels before the first treatment showed late HBeAg seroconversion more frequently than those with low ALT levels (P=0.017) irrespective of retreatment. The ALT level before retreatment was not a predictor for response. CONCLUSIONS: A second cycle of alpha-interferon during the 3 years following the first treatment in nonresponding children with chronic hepatitis B can be safely performed but did not increase HBeAg/anti-HBe seroconversion compared with the spontaneous seroconversion rate of patients without retreatment.

Adolescent↗
PubMed1997

Percutaneous endoscopic gastrostomy in children and adolescents.

BACKGROUND: Long-term nasogastric tube feeding is often associated with irritation of the hypopharynx or dislocation of the tube. These pitfalls may be circumvented by percutaneous endoscopic gastrostomy. Although frequently used in adults, there is limited experience with the procedure in children. METHODS: A series of 139 patients (aged 3 weeks to 36.5 years, mean age, 4.4 years; weight 3.1-60 kg, mean weight, 15 kg) underwent placement of a percutaneous endoscopic gastrostomy because of central dysphagia (n = 103); general dystrophy caused by chronic renal failure, congenital heart disease, neoplasms, or cystic fibrosis (n = 26); requirement for special diets (n = 7); malnutrition related to respiratory insufficiency (n = 2); and gastric volvulus (n = 1). RESULTS: The percutaneous endoscopic gastrostomy was placed either in the stomach (n = 122) or in the duodenum (n = 15). In two patients a direct percutaneous endoscopic jejunostomy was performed, because duodenal placement proved impossible. Percutaneous endoscopic gastrostomies were placed using intravenous sedation (midazolam, etomidate, or diazepam). None of the patients required general or inhalation anesthesia. We observed 19 complications including: dislocation of the duodenal part into the stomach (n = 5); inflammation at the insertion site (n = 3); perforation of the stomach (n = 2), which healed under conservative treatment; disconnection of the retention disk (n = 4); occlusion of the tube (n = 4), and chronic vomiting (n = 1). Mean lifetime of a percutaneous endoscopic gastrostomy was more than 1 year. CONCLUSIONS: Percutaneous endoscopic gastrostomy provides a major improvement for children requiring long-term tube feeding. High efficacy and low rates of complication suggest that percutaneous endoscopic gastrostomy should be considered more often, even in infants.

Adolescent↗