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Biomedical subjects

W Weber

Publications and source records attributed to W Weber.

At least 91 records · Page 5Linked to original sources
PubMed2000

Family study of girls with attention deficit hyperactivity disorder.

OBJECTIVE: Because attention deficit hyperactivity disorder (ADHD) is relatively infrequent among girls, little is known about the causes of ADHD in girls. To help fill this gap in the literature, the authors assessed the familial transmission of ADHD in families ascertained through girls. METHOD: Interviewers who were blind to diagnosis administered structured psychiatric interviews to 140 girls with ADHD and their 417 first-degree relatives and to 122 girls without ADHD and their 369 first-degree relatives. RESULTS: The relatives of the ADHD girls had a significantly higher prevalence of ADHD, according to either the DSM-III-R or DSM-IV definition, than the relatives of the comparison girls. However, this did not differ from the prevalence the authors reported previously for families of boys with ADHD. Like the boys' families, the relatives of the girl probands also had significantly higher prevalences of antisocial, mood, anxiety, and substance use disorders, although the prevalence of familial antisocial disorders was lower than had been observed in the boys' families. There was no association between the DSM-IV subtypes of the probands and relatives. CONCLUSIONS: The familial transmission of ADHD and comorbid disorders generalizes to families of girls with ADHD. Neither proband gender nor subtype influences the familial transmission of ADHD.

Adolescent↗
PubMed2000

Torquability of microcatheter guidewires: the resulting torsional moment.

Guidewires for microcatheters used for the subselective catheterization of small vessels must meet high quality requirements in regard to handling, steerability, radiopacity and physical properties. The aim of this paper is to classify one of the factors that determine the physical and mechanical parameters of a number of existing microcatheter guidewires. A torsion-testing equipment for guidewires was devised. Nitinol wires were tested and compared with the austenitic stainless steel variants. 13 different commercial wires were tested. Tensile strength, shear modulus and wire diameter are the determining factors of the torsional rigidity of guidewires. By interpreting the measured torsional momentums various statements concerning the torsional rigidity of different wires can be made. The properties of guidewires are characteristic features of a system and friction and flexible strength examinations have to be carried out to design new variants of wires to meet the requirements of interventional physicians.

Algorithms↗
PubMed2000

Intracranial vertebrobasilar stenosis: angioplasty and follow-up.

BACKGROUND AND PURPOSE: When medication fails to improve symptoms of atherosclerotic stenosis of the intracranial vertebral and basilar arteries, percutaneous transluminal angioplasty (PTA) is considered. However, because investigators disagree on the usefulness of this procedure, we conducted a retrospective study to evaluate the indications, efficacy, and safety of PTA. METHODS: Twenty patients underwent PTA of the vertebral (n = 14) or basilar (n = 6) artery, 18 for neurologic signs and symptoms of arterial stenosis that recurred or progressed despite pharmacotherapy and two prophylactically. Neurologic examinations were performed before and after the procedure and arterial patency was evaluated at follow-up by digital subtraction angiography and/or MR angiography. Imaging follow-up was available for 14 (70%) of the 20 patients, neurologic follow-up for 15 (75%). RESULTS: The stenosis was successfully dilated in all patients, and on follow-up neuroradiologic examinations, vessel patency could be seen in 12 (86%) of 14 patients. Only one (7%) of 15 patients who returned for a follow-up neurologic examination had new symptoms (caused by occlusion of the vertebral artery 4 months after the procedure). One patient had a reversible neurologic deficit and one had hemiparesis after PTA. No patient died as a result of PTA. CONCLUSION: In our study, PTA of intracranial vertebrobasilar arteries was associated with a low mortality and morbidity rate and with a high degree of patency. This technique may therefore be regarded as an effective means of improving the patency of stenotic arteries. In selective cases, it might be considered for use prophylactically.

Aged↗
PubMed2000

Care for the Caregivers: a program for Canadian military chaplains after serving in NATO and United Nations peacekeeping missions in the 1990s.

The Mental Health Department of the Canadian Forces Support Unit (Ottawa) developed the Care for the Caregivers program to help participants deal with stressful events experienced directly or vicariously from the NATO and United Nations military missions of the 1990s. The program was developed after complaints of postdeployment stress were received from various military care providers. The objectives were to improve the skills of support personnel and to reduce the distress that some caregivers experienced. Thirty-one chaplains who had been exposed to stressful military operations participated in five workshops. These educational 4-day small-group workshops covered topics such as post-traumatic stress disorder, vicarious traumatization, coping techniques, spirituality, self-care, and family issues. An adult education model was chosen to encourage dialogue. Outcomes included reports of professional and personal benefits, requests for additional programs, local education initiatives, and referrals to mental health professionals. Having met its objectives, the program has become a normal concluding part of stressful deployments.

Adaptation, Psychological↗
PubMed2000

Phylogenetic relationships of human populations in sub-Saharan Africa.

This study utilizes the GM/KM immunoglobulin allotype system to elucidate the phylogenetic relationships of sub-Saharan Africans. The importance of understanding the relatedness of these peoples stems from the sub-Saharan region being the possible birthplace of humans. Haplotype distributions were determined for 19 populations and compared using chi-square analysis. Published data of other sub-Saharan Africans and representative populations worldwide were also added for comparison. Genetic distances between populations were calculated based on haplotype frequencies, and genetic relationships were observed through principal components analysis. Data from the GM/KM system showed a genetic homogeneity of the Bantu populations, with some exceptions, supporting the possibility of a common origin of these peoples. The Malagasy appeared as a divergent population, most likely due to Southeast Asian/Austronesian admixture, as indicated by the presence of the GM*AF B haplotype. The Cape Coloured also showed a divergence, with their genetic structures containing Caucasoid and Khoisan contributions. Finally, the Mbuti Pygmies appeared genetically isolated and had the highest frequency of the GM*A B haplotype out of all studied populations.

Africa South of the Sahara↗
PubMed1999

Further characteristics of the Ca(2+)-inactivated Cl(-) channel in Xenopus laevis oocytes.

Removal of extracellular Ca(2+) activates ion channels in the plasma membrane of defolliculated oocytes of the South Africa clawed toad Xenopus laevis. At present, there is controversy about the nature of the Ca(2+)-inactivated ion channels. Recently, we identified one of these channels as a Ca(2+)-inactivated Cl(-) channel (CaIC) using single channel analysis. In this work we confirm and extend previous observations on the CaIC by presenting a decisive extension of the regulation and inhibition profile. CaIC current is reversibly blocked by the divalent and trivalent cations Zn(2+) (half-maximal blocker concentration, K(1/2) = 8 muM), and Gd(3+) (K(1/2) = 20 muM). Furthermore, CaIC is inhibited by the specific Cl(-) channel blocker NPPB (K(1/2) approximately 3 muM). Interestingly, CaIC-mediated currents are further sensitive to the cation channel inhibitor amiloride (500 muM) but insensitive to its high affinity analogue benzamil (100 muM). An investigation of the pH-dependence of the CaIC revealed a reduction of currents in the acidic range. Using simultaneous measurements of membrane current (I(m)), conductance (G(m)) and capacitance (C(m)) we demonstrate that Ca(2+) removal leads to instant activation of CaIC already present in the plasma membrane. Since C(m) remains constant upon Ca(2+) depletion while I(m) and G(m) increase drastically, no exocytotic transport of CaIC from intracellular pools and functional insertion into the plasma membrane is involved in the large CaIC currents. A detailed overview of applicable blockers is given. These blockers are useful when oocytes are utilized as an expression system for foreign proteins whose investigations require Ca(2+)-free solutions and disturbances by CaIC currents are unwanted. We further compare and discuss our results with data of Ca(2+)-inactivated cation channels reported by other groups.

Amiloride↗
PubMed1999

Minimum field strength in precessional magnetization reversal

Ultrafast magnetic field pulses as short as 2 picoseconds are able to reverse the magnetization in thin, in-plane, magnetized cobalt films. The field pulses are applied in the plane of the film, and their direction encompasses all angles with the magnetization. At a right angle to the magnetization, maximum torque is exerted on the spins. In this geometry, a precessional magnetization reversal can be triggered by fields as small as 184 kiloamperes per meter. Applications in future ultrafast magnetic recording schemes can be foreseen.

Journal Article↗
PubMed1999

N-acetyltransferase 2 influences cancer prevalence in hMLH1/hMSH2 mutation carriers.

Hereditary nonpolyposis colorectal cancer (HNPCC), an inherited cancer predisposition syndrome, has been associated with germline mutations in DNA mismatch repair (MMR) genes. Because a deficiency in MMR does not predict a specific cancer phenotype, modifying genes may account in part for the variation in disease expression. We determined the N-acetyltransferase 2 (NAT2) genotype in 26 unaffected and 52 cancer-affected hMLH1/hMSH2 mutation carriers coming from 21 Swiss HNPCC families. Slow acetylators were found to be significantly (P < 0.03) more prevalent in the group of affected mutation carriers. Our results suggest a protective effect of the NAT2 rapid acetylator phenotype, an observation that could have implications for genetic counseling and management of MMR gene mutation carriers.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Influence of selection criteria on mutation detection in patients with hereditary nonpolyposis colorectal cancer.

BACKGROUND: Hereditary nonpolyposis colorectal cancer (HNPCC) is linked genetically to mutations in DNA mismatch repair (MMR) genes. Because a deficiency in MMR does not predict a specific phenotype, the original selection criteria may be too restrictive in identifying additional families. The current study was performed to determine whether a relaxation of the Amsterdam criteria (AC) could be applied to identify more families associated with DNA MMR. METHODS: Twenty-eight unrelated Swiss families (15 complying with the AC and 13 fulfilling extended criteria [EC] to include other tumors of the HNPCC spectrum as well) were screened for mutations in the MMR genes hMSH2 and hMLH1, using single-stranded conformation polymorphism and direct DNA sequencing. Microsatellite instability (MSI) was determined in 14 families. A comparison was made between the phenotypic characteristics of the mutation positive and mutation negative families. RESULTS: Ten AC families (67%) harbored germline mutations in hMLH1 (6 kindreds) or hMSH2 (4 kindreds). In none of the EC kindreds could an unambiguous disease-causing mutation be identified. Seven of eight AC families were found to display MSI whereas all colorectal carcinomas (CRC) in eight EC kindreds were MSI stable. CRC patients from mutation positive families had an earlier age at diagnosis (44 years vs. 49 years) and appeared to have a better survival (11.1 years vs. 7.7 years). CONCLUSIONS: Extending the AC to include extracolonic tumors of the HNPCC spectrum results in a very low mutation detection rate for hMSH2 and hMLH1. The EC families appear to represent an alternative genetic entity not necessarily related to DNA MMR gene mutations because they do not display MSI.

Adult↗
PubMed1999

Shedding light on the dark and weakly fluorescent states of green fluorescent proteins.

Recent experiments on various similar green fluorescent protein (GFP) mutants at the single-molecule level and in solution provide evidence of previously unknown short- and long-lived "dark" states and of related excited-state decay channels. Here, we present quantum chemical calculations on cis-trans photoisomerization paths of neutral, anionic, and zwitterionic GFP chromophores in their ground and first singlet excited states that explain the observed behaviors from a common perspective. The results suggest that favorable radiationless decay channels can exist for the different protonation states along these isomerizations, which apparently proceed via conical intersections. These channels are suggested to rationalize the observed dramatic reduction of fluorescence in solution. The observed single-molecule fast blinking is attributed to conversions between the fluorescent anionic and the dark zwitterionic forms whereas slow switching is attributed to conversions between the anionic and the neutral forms. The predicted nonadiabatic crossings are seen to rationalize the origins of a variety of experimental observations on a common basis and may have broad implications for photobiophysical mechanisms in GFP.

Amino Acid Sequence↗
PubMed1999

[Pseudoaneurysm of the extracranial internal carotid artery. Treatment by stent and coil implantation].

Pseudoaneurysms of the extracranial internal carotid artery (ICA) can be caused by external injury or may be due to spontaneous dissection. Pseudoaneurysms bear an increased risk of arterio-arterial embolism. Treatment of pseudoaneurysms is influenced by the location and the type of injury, associated injuries, collaterals to the ipsilateral hemisphere, neurological signs and symptoms, growth of the lesion and patient age. Potential treatment regimen include conservative and medical approaches with anticoagulation and antiplatelet therapy, extra-intracranial bypass, resection of the pseudoaneurysm with vessel reconstruction, ligation or endovascular balloon occlusion of the ICA. Pseudoaneurysms of the ICA adjacent to the skull base require a major surgical procedure. If there are contra-indications for vessel occlusion conservative or medical treatment used to be the only therapeutic alternatives. We report the treatment of two patients with extracranial ICA pseudoaneurysms after blunt injury with stent placement (in one case combined with coil embolization) as a further treatment option.

Adult↗
PubMed1999

Pseudo Chiari type I malformation secondary to cerebrospinal fluid leakage.

Cerebrospinal fluid (CSF) leakage may occur spontaneously, iatrogenically or from spinal trauma. Postural headache is the cardinal symptom; dizziness, diminished hearing, nausea and vomiting are additional symptoms. In neurological examinations cranial nerve palsies may be found. Due to low CSF pressure neuroimaging studies may reveal dural enhancement and vertical displacement of the brain. We describe a patient with the history of an uncomplicated lumbar discectomy at the level L4-5 and the typical clinical symptoms of intracranial hypotension. MRI of the craniocervical junction showed typical features of a Chiari type-I malformation. After neurosurgical ligation of a CSF leak at L4-5 caused by lumbar disc surgery, the patient was free of orthostatic headache. A repeated MRI showed a striking reduction of the previous downward displacement of the cerebellar tonsils and pons.

Adult↗
PubMed1999

Clinical correlates of ADHD in females: findings from a large group of girls ascertained from pediatric and psychiatric referral sources.

OBJECTIVE: The scientific literature about attention-deficit hyperactivity disorder (ADHD) is based almost exclusively on male subjects, and girls with ADHD may be underidentified and undertreated. The aim of this study was to examine clinical correlates of ADHD in females using comprehensive assessments in multiple domains of functioning. METHOD: Subjects were 140 girls with ADHD and 122 comparison girls without ADHD ascertained from pediatric and psychiatric referral sources of the same age and social class. Subjects were assessed with structured diagnostic interviews, psychometric tests assessing intellectual functioning and academic achievement, as well as standardized assessments of interpersonal, school, and family functioning by raters who were blind to clinical diagnosis. RESULTS: Compared with female controls, girls with ADHD were more likely to have conduct, mood, and anxiety disorders; lower IQ and achievement scores; and more impairment on measures of social, school, and family functioning. CONCLUSIONS: These results extend to girls previous findings in boys indicating that ADHD is characterized by prototypical core symptoms of the disorder, high levels of comorbid psychopathology, and dysfunction in multiple domains. These results not only support findings documenting phenotypic similarities between the genders but also stress the severity of the disorder in females.

Adolescent↗
PubMed1999

Intracellular processing of endocytosed triglyceride-rich lipoproteins comprises both recycling and degradation.

The current study was performed to investigate the intracellular fate of triglyceride-rich lipoproteins. Triglyceride-rich lipoproteins are responsible for the delivery of lipids to various tissues, however, their intracellular pathway has not yet been elucidated. Here radiolabeled triglyceride-rich lipoproteins, associated with lipoprotein lipase, were used for the quantitative evaluation of the intracellular metabolism. Pulse chase experiments showed that after 90 minutes approximately 60% of the labeled protein, mainly apoproteins E and C, was released intact into the medium, where it re-associates with lipoproteins. Apoprotein B, in contrast, was degraded, following the same pathway as the apoprotein B from low density lipoproteins. In kinetic experiments uptake and intracellular fate of triglyceride-rich lipoproteins was compared to that of transferrin and low density lipoproteins. These experiments revealed that apoproteins were retained inside the cell much longer than transferrin, and unlike low density lipoproteins were not degraded. Using immunofluorescence it was shown that apoprotein E and lipoprotein lipase follow a distinct route from the sorting compartment to the surface, which is clearly distinguishable from the perinuclear transferrin recycling compartment. In contrast, the fluorescence labeled lipids were delivered to lysosomal compartments. The data presented here show that surface proteins of triglyceride-rich lipoproteins, such as apoproteins E and C and lipoprotein lipase follow a recycling pathway, whereas lipids and high molecular mass core proteins are degraded.

Apoproteins↗