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Biomedical subjects

K Becker

Publications and source records attributed to K Becker.

At least 37 records · Page 2Linked to original sources
PubMed2005

Electron-impact ionization of silicon tetrachloride (SiCl4).

We measured absolute partial cross sections for the formation of various singly charged and doubly charged positive ions produced by electron impact on silicon tetrachloride (SiCl4) using two different experimental techniques, a time-of-flight mass spectrometer (TOF-MS) and a fast-neutral-beam apparatus. The energy range covered was from the threshold to 900 eV in the TOF-MS and to 200 eV in the fast-neutral-beam apparatus. The results obtained by the two different experimental techniques were found to agree very well (better than their combined margins of error). The SiCl3(+) fragment ion has the largest partial ionization cross section with a maximum value of slightly above 6x10(-20) m2 at about 100 eV. The cross sections for the formation of SiCl4(+), SiCl+, and Cl+ have maximum values around 4x10(-20) m2. Some of the cross-section curves exhibit an unusual energy dependence with a pronounced low-energy maximum at an energy around 30 eV followed by a broad second maximum at around 100 eV. This is similar to what has been observed by us earlier for another Cl-containing molecule, TiCl4 [R. Basner, M. Schmidt, V. Tamovsky, H. Deutsch, and K. Becker, Thin Solid Films 374 291 (2000)]. The maximum cross-section values for the formation of the doubly charged ions, with the exception of SiCl3(++), are 0.05x10(-20) m2 or less. The experimentally determined total single ionization cross section of SiCl4 is compared with the results of semiempirical calculations.

Journal Article↗
PubMed2005

Suitability of a malachite green procedure to detect minimal amounts of phosphate dissolved in acidic solutions.

The study describes the suitability of a colorimetric method (malachite green procedure) for detection of minimal amounts of phosphate (7.3-29.1 micromol/L) in different acidic solutions (hydrochloric acid, oxalic acid, maleic acid, perchloric acid, tartaric acid, citric acid, lactic acid and acetic acid) adjusted to pH 2.0. A mixture of the respective phosphate concentrations with distilled water served as control. The experiments were run with ten repeats in series. Assessment of intra- and interassay coefficient of variation and lower limit of quantification revealed that depending on the acid used, the applied method is a reliable and suitable tool to detect and quantify minimal phosphate contents in small samples of acidic solutions that have the potential to cause erosive dental lesions.

Acids↗
PubMed2005

Improving estimates of trophic shift in Nile tilapia, Oreochromis niloticus (L.), using measurements of lipogenic enzyme activities in the liver.

To test whether the measurement of selected enzyme activities could be used to estimate more precisely the trophic shift of C isotopes, Nile tilapia (Oreochromis niloticus) were fed semi-synthetic diets differing in their lipid contents (1.7%, 5.0%, 10.8% and 20.0%). The diets were formulated to contain the same amount of nitrogen and metabolizable energy and were made from casein, wheat starch, corn germ oil supplemented with vitamins, minerals and L-arginine. The influence of the different diets on the activity of two lipogenic enzymes, ATP-citrate lyase and malic enzyme, on delta13C values in the whole fish, the liver and their correlation was investigated. There was a strong positive correlation between delta13C values in the lipids of whole fish and those of their livers. The activities of lipogenic enzymes increased significantly with increasing trophic shift of C isotopes (Deltadelta13Cdiet-fish values) in the lipids. If the relationship between trophic shift and enzyme activity can be confirmed in situations where feed quantity and quality are not known, the determination of enzyme activities would enable better estimates of the trophic shift to be made thus significantly improving back-calculation of diets from stable isotope data.

ATP Citrate (pro-S)-Lyase↗
PubMed2005

Impact of modified acidic soft drinks on enamel erosion.

OBJECTIVE: To evaluate the enamel erosive potential of modified acidic soft drinks under controlled conditions in an artificial mouth. MATERIALS AND METHODS: From each of 144 bovine incisors one enamel sample was prepared. Labial surfaces of the samples were ground flat, polished and covered with adhesive tape, leaving an exposed area. The samples were distributed among four (A-D) groups for treatment with A: Coca-Cola, B: Sprite; C: Sprite light, D: orange juice. Either 1.0 mmol l(-1) calcium (Ca) or a combination (comb.) of 0.5 mmol l(-1) calcium plus 0.5 mmol l(-1) phosphate plus 0.031 mmol l(-1) fluoride was added to the beverages. Samples of each group were subdivided into three subgroups (-original; -Ca and -comb.) for treatment with original and modified drinks. De- and remineralization cycles were based on a standard protocol described earlier. Surface loss of the specimens was determined using profilometry after test procedure. RESULTS: In all subgroups, loss of enamel was observed. The enamel loss recorded for the samples rinsed with original Sprite and original orange juice was significantly higher compared with all other solutions (P = 0.001). Lowest enamel loss was recorded for the original Coca-Cola group (P = 0.001). With the exception of Coca-Cola, demineralization with the modified beverages led to significantly lower losses compared with the respective original solutions. CONCLUSION: Modification of the test soft drinks with low concentrations of calcium or a combination of calcium, phosphate and fluoride may exert a significant protective potential with respect to dental erosion.

Animals↗
PubMed2005

Postinfectious vasculopathy with evolution to moyamoya syndrome.

BACKGROUND: Parainfectious vascular events are a known complication of bacterial meningitis, typically occurring within two weeks of disease onset. Delayed vascular complications are rare. We present a case of progressive vasculopathy following bacterial meningitis. CASE DESCRIPTION: A 20 year old woman developed progressive vasculopathy after successful treatment of pneumococcal meningitis. Within eight months of her infection, angiography revealed the appearance of moyamoya syndrome. Despite aggressive immunomodulation and anticoagulation, she had multiple strokes. Autopsy confirmed severe narrowing of proximal cerebral vasculature with absence of inflammation or atherosclerosis. CONCLUSIONS: The inflammation and subsequent postinfectious autoimmune response associated with meningitis can lead to a progressive vasculopathy and may represent a pathophysiologic mechanism for the arterial occlusions seen in moyamoya syndrome.

Adult↗
PubMed2005

Modern strategies in the prevention of implant-associated infections.

The application of medical devices either for temporary or permanent use has become an indispensible part of almost all fields of medicine. However, foreign bodies are associated with a substantial risk of bacterial and fungal infections. Implant-associated infections significantly contribute to the still increasing problem of nosocomial infections. To reduce the incidence of such infections, specific guidelines providing evidence-based recommendations and comprising both technological and nontechnological strategies for prevention have been established. Strict adherence to hygienic rules during insertion or implantation of the device are aspects of particular importance. Besides such basic and indispensable aspects, the development of new materials which could withstand microbial adherence and colonization has become a major topic in recent years. Modification of surface by primarily physico-chemical methods may lead to a change in specific and unspecific interactions with microorganisms and, thus, to a reduction in microbial adherence. Medical devices made out of a material that would be ideally antiadhesive or at least colonization-resistant would be the most suitable candidates to avoid colonization and subsequent infection. However, it appears impossible to create a surface with an absolute 'zero'-adherence due to thermodynamical reasons and due to the fact that a modified material surface is in vivo rapidly covered by plasma and connective tissue proteins. Therefore, another concept for the prevention of implant-associated infections involves the impregnation of devices with various antimicrobial substances such as antibiotics, antiseptics, and/or metals. In fact, already commercially available materials for clinical use such as antimicrobial catheters have been introduced, in part with considerable impact on subsequent infections. However, future studies are warranted to translate the knowledge on the pathogenesis of device-associated infections into applicable prevention strategies.

Anti-Bacterial Agents↗
PubMed2005

Effects of antioxidants on glutathione levels and clinical recovery from the malnutrition syndrome kwashiorkor--a pilot study.

Kwashiorkor is a severe edematous form of malnutrition with high prevalence and lethality in many African countries, and repeatedly has been reported to be associated with oxidative stress. The therapy of kwashiorkor is still ineffective. In this pilot study, we tested the hypothesis that oral application of thiol-containing antioxidants increases glutathione status and is beneficial for the clinical recovery of kwashiorkor patients. The longitudinal clinical intervention study was carried out at St Joseph's Hospital, Jirapa, Ghana. Children with severe kwashiorkor were randomly assigned to either a standard treatment (ST) receiving a therapeutic protocol based on the recommendations of the WHO or to one of three study groups receiving in addition 2 x 600 mg reduced glutathione or 2 x 50 mg alpha-lipoic acid or 2 x 100 mg N-acetylcysteine per day. Patients were followed up clinically and biochemically for 20 days and compared with 37 healthy controls. Both glutathione and alpha-lipoic acid supplementation had positive effects on survival. Also, the blood glutathione concentrations correlated positively with survival rates. Furthermore, the initial skin lesions, glutathione and total protein concentrations were found to be strong predictors of survival. The data strongly suggest that a therapy restoring the antioxidative capacity by applying cysteine equivalents in the form of glutathione and/or alpha-lipoic acid is beneficial for biochemical and clinical recovery of kwashiorkor patients.

Acetylcysteine↗
PubMed2004

Peptides and hydrolysates from casein and soy protein modulate the release of vasoactive substances from human aortic endothelial cells.

Food proteins were shown to affect atherogenic risk factors, which is supposed to be related to specific peptide sequences encrypted within their primary sequence. The aim of this study was to evaluate the effects of peptides and hydrolysates from two food proteins, casein and soy protein, on endothelial cell functions (cell proliferation and release of vasoactive substances). Cell proliferation was not influenced by dipeptides and most of the tripeptides, whereas several total hydrolysates from casein and soy protein inhibited cell proliferation at higher concentrations (>0.25 mg/mL; P<0.05). The release of one or more of the vasoactive substances, thromboxan B2 (stable marker of thromboxan A2), 6-keto-prostaglandin F1alpha (stable marker of prostaglandin I2), endothelin-1, and nitric oxide, was significantly influenced by the incubation with various peptides compared with control cells (P<0.05). Various hydrolysate fractions from casein and soy protein influenced the release of 6-keto-prostaglandin F1alpha and nitric oxide (P<0.05) but did not influence the release of thromboxan B2 and endothelin-1. In conclusion, the present study demonstrates that peptides and hydrolysate fractions from casein and soy protein influence endothelial cell function as evidenced by the modulation of endothelial cell proliferation and alterations in the release of vasoactive substances.

Adult↗
PubMed2004

The dopamine D4 receptor gene exon III polymorphism is associated with novelty seeking in 15-year-old males from a high-risk community sample.

In recent years, studies focussing on a possible association between the dopamine D4 receptor (DRD4) gene exon III polymorphism and the personality trait of novelty seeking (NS) have yielded inconsistent results. The present study sought to examine the association of the DRD4-7r allele with NS in a sample of 303 15-year-old adolescents (144 males, 159 females) using data from a high-risk community sample. The Junior Temperament and Character Inventory--JTCI/12-18 was administered to assess dimensions of adolescent temperament. Males in the DRD4-7r allele group scored significantly higher on the NS (p=.002) and the harm avoidance (p=.045) scales than males without this allele. In females no association with temperament was observed. This association could not be explained by the presence of either an attention-deficit/hyperactivity disorder (ADHD) or a DRD4 by ADHD interaction.

Attention Deficit Disorder with Hyperactivity↗
PubMed2004

Laparoscopic cholecystectomy in acute cholecystitis: indication, technique, risk and outcome.

BACKGROUND: Laparoscopic cholecystectomy (LC) has become the treatment of choice for symptomatic cholelithiasis. However, the laparoscopic approach has remained controversial for patients with acute cholecystitis (AC) because of technical difficulties that, compared with open cholecystectomy (OC), might lead to higher complication rates, particularly common bile duct (CBD) injuries and infection. METHODS: We reviewed recent clinical findings on feasibility, safety and potential benefits of LC in patients with AC. An electronic search using the PubMed and MEDLINE databases was performed using the terms laparoscopic cholecystectomy, open cholecystectomy and acute cholecystitis. Pertinent references from articles and books not identified by the search engines were also retrieved. Relevant surgical textbooks were also reviewed. CONCLUSIONS: The early laparoscopic approach has been shown to be technically feasible and at least equally as safe as the open approach. However, extensive inflammation, adhesions and consequent increased oozing can make laparoscopic dissection of Calot's triangle and recognition of the biliary anatomy hazardous and difficult. Therefore, conversion to OC remains an important treatment option to secure patient safety in such difficult conditions. The question of whether intraoperative cholangiography (IOC) should be used routinely or only selectively has never been resolved. Proponents for each side have put forward compelling arguments.

Cholecystectomy, Laparoscopic↗
PubMed2004

The anomalous shape of the cross section for the formation of SF3+ fragment ions produced by electron impact on SF6 revisited.

The partial ionization cross section for the formation of SF(3) (+) fragment ions following electron impact on SF(6) is known to have a pronounced structure in the cross section curve slightly above 40 eV. We used the mass-analyzed ion kinetic energy (MIKE) scan technique to demonstrate the presence of a channel contributing to the SF(3) (+) partial ionization cross section that we attribute to the Coulomb explosion of doubly charged metastable SF(4) (2+) ions into two singly charged ions SF(3) (+) and F(+), with a threshold energy of about 45.5 eV. Thus the observed unusual shape of the SF(3) (+) partial ionization cross section is the result of two contributions, (i) the direct formation of SF(3) (+) fragment ions via dissociative ionization of SF(6) with a threshold energy of 22 eV and (ii) the Coulomb explosion of metastable SF(4) (2+) ions with a threshold energy of about 45.5 eV. A detailed analysis of the MIKE spectrum reveals an average kinetic energy release of about 5 eV in the Coulomb explosion of the SF(4) (2+) ions with evidence of a second channel corresponding to an average kinetic energy release of about 1.1 eV.

Journal Article↗
PubMed2004

[Environmental Survey for Children-- the environmental module of KiGGS. I. Design and research program].

The German Environmental Survey for Children (GerES IV) is the environment-oriented module of the National Health Interview and Examination Survey for Children and Adolescents (KiGGS) which is being performed nationwide in Germany. From 2003 to 2006, a random subsample of 1800 children aged 3-14 years is being studied with regard to their body burden and health impairments linked to housing conditions and the personal environment- and health-relevant behaviour. The basic study programme includes the analysis of blood, urine, tap water and house dust as well as the application of an extensive questionnaire. The data gained from this population sample, which is representative for Germany's children, are the basis for deriving reference values to characterise the background exposure of children aged 3-14 years. Trends over time can be detected and the success of environmental policies verified by comparing the data with those of the German Environmental Survey 1990/92 (GerES II), also conducted in close cooperation with the National Health Survey, which included children aged 6-14 years. By linking the data from the Environmental and the Health Surveys, health-relevant environmental exposures can be detected and different scientific hypotheses can be tested. The main subjects that are being dealt with using subcollectives of GerES IV are 'VOC and eye and nasopharynx irritation', 'indoor allergens and allergic diseases of the respiratory system', 'chromium, nickel, fragrances and contact allergens', and 'noise, hearing capacity and stress hormones'.

Adolescent↗
PubMed2004

[Typical benign epilepsy potentials in childhood (Rolandic spikes)--neurobiological and neuropsychological symptoms and their clinical significance in child and adolescent psychiatry].

INTRODUCTION: Rolandic epilepsy is the most frequent epileptic syndrome in childhood, electroencephalographically characterized by focal sharp waves, so called rolandic spikes (benign epileptiform discharges of childhood). These discharges occur in about 1.5 to 2.4% of children; only 10% of them suffer from epileptic seizures. METHODS: This paper reviews genetic, epidemiological, radiological, neurophysiologic, metabolic and neuropsychological findings in children with rolandic discharges. RESULTS: The epileptologic course is favorable, seizures and EEG features usually resolve completely at puberty. In contrast to former assumptions, symptoms range from infrequent seizures to neuropsychological deficits and behavior problems, even in children without overt seizures. The impact of rolandic spikes on the development of affected children and their behavior is unclear. Two models try to elucidate the relation between EEG discharges and neuropsychological disorders. The first regards neuropsychological disturbances as transient cognitive impairment due to epileptiform discharges; the second model strengthens the role of a hereditary impairment of brain maturation. CONCLUSIONS: The benefit of pharmacotherapy for treating neuropsychiatric symptoms in children with rolandic spikes but without overt seizures remains to be clarified.

Adolescent↗
PubMed2004

Are regulatory problems in infancy precursors of later hyperkinetic symptoms?

AIM: To examine whether regulatory problems in infancy predict later hyperkinetic symptoms in childhood and pre-adolescence. METHODS: In a prospective longitudinal study of 319 children at risk of later developmental problems and psychopathology, hyperkinetic behaviour problems were assessed at the ages of 2, 4.5, 8 and 11 y by means of a standardized parent interview. Infant regulatory problems at the age of 3 mo were determined from multiple sources of information. An observational procedure was used to assess the quality of mother-infant interaction. RESULTS: At the age of 3 mo, 17% of the infants (n = 55; 27 boys, 28 girls) suffered from multiple regulatory problems. Compared to a control group (n = 264), these children presented more hyperkinetic symptoms throughout childhood. Negativity in the mother-infant interaction and early family adversity each contributed to later hyperkinetic symptoms. When controlling for family adversity, the association between infant multiple regulatory problems and later hyperkinetic problems was rendered insignificant. CONCLUSIONS: These findings suggest that multiple regulatory problems may not be a key variable for later hyperkinetic problems. The impact of early family adversity factors clearly outweighed that of infant psychopathology on later behaviour disorder.

Attention Deficit Disorder with Hyperactivity↗
PubMed2004

Parasuicide online: Can suicide websites trigger suicidal behaviour in predisposed adolescents?

The present case report describes a 17-year-old female who explicitly visited suicide web forums, where she researched reliable suicide methods, contacted an anonymous user and purchased substances for the implementation of suicide. The risk of Internet use by vulnerable youth is discussed. Psychiatric exploration should include questions of manner and frequency of media use. The application of media guidelines for suicide prevention is demanded for websites, as are accessible self-help sites for suicidal persons targeted to youthful users.

Adolescent↗