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Biomedical subjects

S Arnold

Publications and source records attributed to S Arnold.

At least 37 records · Page 2Linked to original sources
PubMed2002

Abnormal brain activation on functional MRI in cognitively asymptomatic HIV patients.

BACKGROUND/OBJECTIVES: A previous fMRI study demonstrated increased brain activation during working memory tasks in patients with HIV with mild dementia. The current study aims to determine whether patients who are HIV-1 positive and have normal cognitive function also show increased brain activation on fMRI. METHODS: Blood oxygenation level-dependent (BOLD) fMRI was performed in 10 patients with HIV (CD <500) and 10 age-, sex-, education-, and handedness-matched seronegative subjects. Each subject performed a battery of neuropsychological tests and fMRI with three tasks (0-back, 1-back, and 2-back) that required different levels of attention for working memory. RESULTS: Compared with control subjects, patients with HIV showed greater magnitude of brain activation (BOLD signal intensity changes, p <or= 0.001) in the lateral prefrontal cortex, with normal performance during fMRI and on a battery of neuropsychological tests. The patients with HIV also showed increased activated brain volume in the lateral prefrontal cortex (p = 0.007) but not in other activated regions, including the posterior parietal cortex, supplementary motor area, thalamus, caudate, and occipital cortex. The increase in activated brain volume was independent of task difficulty. CONCLUSION: Increased brain activation in subjects who are positive for HIV precedes clinical signs or deficits on cognitive tests. Early injury to the neural substrate may necessitate increased usage of brain reserve to maintain normal cognitive function. BOLD fMRI appears to be more sensitive than clinical and neuropsychological evaluations for detecting early HIV-associated brain injury.

AIDS Dementia Complex↗
PubMed2002

Optimizing high strength acetic acid bioprocess by cognitive methods in an unsteady state cultivation.

Methods of adapting micro-organisms to an inhibiting factor in an active industrial bioprocess were examined with an acetic acid fermentation as model. With the aim of automatic control, a fuzzy-logic system was developed on the basis of the collected knowledge of skilled vinegar brewers. In a first step, this fuzzy system was to assess the actual adaptation degree of the bacteria on the basis of data from robust and reasonably priced sensors. From this information an appropriate setpoint value for the inhibiting factor 'final acid concentration' was derived for each batch cycle. As a result a further acid tolerance was found after several batch cycles. This adaptation effect should be used to increase the product concentration to more than 20 g per 100 ml acetic acid with a high productivity. The stepwise adapted culture was productive over the aimed acetic acid concentration, a 10% improvement of the product formation rate could be found compared with the status before conditioning. High product concentration and increased productivity finally result in shorter cycle times, less transport and storage volumes, an improved utilization of energy and material resources, and, last but not least, they are an essential steps towards the fulfillment of economical and ecological demands.

Acetic Acid↗
PubMed2002

Determination of hemisphere dominance for language: comparison of frontal and temporal fMRI activation with intracarotid amytal testing.

The reliability of frontal and temporal fMRI activations for the determination of hemisphere language dominance was evaluated in comparison with intracarotid amytal testing (IAT). Twenty-two patients were studied by IAT (bilateral in 13, unilateral in 9 patients) and fMRI using a paradigm requiring semantic decisions. Global and regional (frontal and temporoparietal) lateralisation indices (LI) were calculated from the number of activated (r>0.4) voxels in both hemispheres. Frontolateral activations associated with the language task were seen in all patients, temporoparietal activations in 20 of 22. Regional LI corresponded better with IAT results than global LI. Frontolateral LI were consistent with IAT in all patients with bilateral IAT (including three patients with right dominant and one patient with bilateral language representation) and were not conflicting in any of the patients with unilateral IAT. Temporoparietal LI were discordant with IAT in two patients with atypical language representation. In the determination of hemisphere dominance for language, regional analysis of fMRI activation is superior to global analysis. In cases with clear-cut fMRI lateralisation, i.e. consistent lateralised activation of frontal and temporoparietal language zones, IAT may be unnecessary. FMRI should be performed prior to IAT in all patients going to be operated in brain regions potentially involved in language.

Adolescent↗
PubMed2002

[Doppler ultrasound assisted hemorrhoid artery ligation. A new therapy in symptomatic hemorrhoids].

In 1995, Morinaga et al. (Japan) reported on a new technique in the treatment of hemorrhoids. We report the results of our first 105 patients thus treated. By a specially designed proctoscope coupled with a Doppler transducer, the hemorrhoidal arteries are looked for and ligated. All stages of hemorrhoid were treated. This method is painless, successful, and has a low rate of complications. It is for outpatients and is an alternative to all other methods in the treatment of hemorrhoids.

Adult↗
PubMed2001

Cytochrome C oxidase and the regulation of oxidative phosphorylation.

Life of higher organisms is essentially dependent on the efficient synthesis of ATP by oxidative phosphorylation in mitochondria. An important and as yet unsolved question of energy metabolism is how are the variable rates of ATP synthesis at maximal work load during exercise or mental work and at rest or during sleep regulated. This article reviews our present knowledge on the structure of bacterial and eukaryotic cytochrome c oxidases and correlates it with recent results on the regulatory functions of nuclear-coded subunits of the eukaryotic enzyme, which are absent from the bacterial enzyme. A new molecular hypothesis on the physiological regulation of oxidative phosphorylation is proposed, assuming a hormonally controlled dynamic equilibrium in vivo between two states of energy metabolism, a relaxed state with low ROS (reactive oxygen species) formation, and an excited state with elevated formation of ROS, which are known to accelerate aging and to cause degenerative diseases and cancer. The hypothesis is based on the allosteric ATP inhibition of cytochrome c oxidase at high intramitochondrial ATP/ADP ratios ("second mechanism of respiratory control"), which is switched on by cAMP-dependent phosphorylation and switched off by calcium-induced dephosphorylation of the enzyme.

Adenosine Triphosphate↗
PubMed2001

Kinetic modeling and simulation of in vitro transcription by phage T7 RNA polymerase.

This study provides a mathematical model of T7 RNA polymerase (T7 RNAP) kinetics under in vitro conditions targeted at application of this model to simulation of dynamic transcription performance. A functional dependence of transcript synthesis rate is derived based on: (a) essential reactant concentrations, including T7 RNAP and its promoter, substrate nucleotides, and the inhibitory byproduct inorganic pyrophosphate; (b) a distinction among vector characteristics such as recognition sequences regulating transcription initiation and termination, respectively; and (c) specific properties of the nucleotide sequence including both transcript length and nucleotide composition. Inactivation kinetics showed a half-life of T7 RNAP activity of 50 min under the conditions applied in vitro using the isolated enzyme. Model parameters and their precision are estimated using dynamic simulation and nonlinear regression analysis. The particular novelty of this model is its capability to incorporate linear genomic sequence information for simulation of nonlinear in vitro transcription kinetics.

Computer Simulation↗
PubMed2001

The role of a proline-induced broken-helix motif in alpha-helix 2 of Bacillus thuringiensis delta-endotoxins.

Bacillus thuringiensis delta-endotoxins (Cry proteins), are widely used for insect control and plant protection. They are water-soluble proteins that insert into membranes forming ion channels. In most Cry toxins alpha-helix 2 is broken by a highly conserved proline residue (Pro70 in Cry1Ab), generating a broken-helix motif. The flexibility of the motif was altered through site-directed mutagenesis. It was found that increasing the flexibility of the motif decreased the stability, the ion transport ability and the toxicity of the protein. By removing the broken-helix motif, the biological properties were restored to a wild type level.

Alanine↗
PubMed2001

Central pontine myelinolysis in a patient with anorexia nervosa.

UNLABELLED: Myelinolysis may occur as a severe complication of eating disorders, especially anorexia nervosa (AN). One of the most important reasons can be a rapid correction of hyponatremia caused by tubulopathy, water intoxication (WI), or abuse of diuretics in individuals with AN. METHOD AND RESULTS We report on a 24-year-old female patient with an 8-year history of AN. A rapid correction of severe hyponatremia and hypokalemia induced by WI led to central pontine myelinolysis, which was confirmed by magnetic resonance imaging (MRI) examination. Besides affective lability, incoherence, and an acute confusional state, surprisingly, no severe neurological symptoms emerged. CONCLUSION: Thus, physicians should be aware of the risk of pontine myelinolysis with new psychiatric symptoms emerging in the absence of obvious neurological deficits.

Adult↗
PubMed2001

Antisense inhibition of BRCA1 expression and molecular analysis of hereditary tumors indicate that functional inactivation of the p53 DNA damage response pathway is required for BRCA-associated tumorigenesis.

OBJECTIVE: The purpose of this investigation was to test the hypothesis that mutation of TP53 is a requirement for BRCA-associated cancer development. METHODS: A cell line experimentally deficient in BRCA1 protein was constructed using a regulatable antisense expression vector expressing 4000 bp from the BRCA1 cDNA. Changes in BRCA1, p53, and p21 protein levels were assayed by immunoblotting. Ovarian tumors with germline mutations in BRCA1 or BRCA2 were screened for mutations in TP53 by single-strand conformation polymorphism analysis. RESULTS: Antisense inhibition of BRCA1 protein caused p53 and p21 protein levels to rise, indicating that partial loss of BRCA1 function activates the p53 DNA damage response pathway. Somatic mutation of TP53 was observed in 7 of 14 BRCA-associated ovarian tumors. CONCLUSIONS: Our findings provide novel evidence that loss of BRCA1 function in human cells activates the p53 DNA damage response pathway and that loss of this pathway, by somatic mutation of TP53, is a likely requirement for BRCA-associated tumor development.

BRCA1 Protein↗
PubMed2001

Minimally invasive operation techniques for inguinal hernia: spectrum of indications in Austria.

At the beginning of the 1990s, the introduction of endoscopic surgery led to the surgical treatment of hernias being reconsidered. At present, there are three groups of surgical procedures: conventional procedures (Shouldice, Bassini), open, tension-free mesh procedures (Lichtenstein, Gilbert, Rutkow) and endoscopic procedures, predominantly transabdominal preperitoneal hernioplasty (TAPP) and total extraperitoneal hernioplasty (TEP). The debate about the optimum treatment for hernias provoked by the endoscopic procedures is understandable in view of the large number of hernia operations performed. Numerous studies, some randomised, have demonstrated both advantages and disadvantages for the individual surgical procedures. In addition to the recurrence and complication rates, the cost factor and socio-economic aspects of the operations are playing an increasingly important role in deciding which method should be used. In December 1995, Austrian surgeons concerned with the problems of hernia repair both before and since the introduction of laparoscopic hernia repair came together for a consensus conference. During the meeting, the relevant aspects were summarised and a range of indications were established for surgical interventions. The main recommendation was that conventional open surgery, which can be performed under local anaesthesia, is indicated in unilateral uncomplicated primary hernias. Endoscopic hernioplasty is indicated if the contralateral findings are inconclusive or the hernia is bilateral or recurrent. The Zürser Hernienforum (Zürs Hernia Forum) has now been founded. The function of this forum is to carry out a prospective randomised study of inguinal hernia surgery throughout Austria.

Austria↗
PubMed2001

Language regression in childhood.

Language regression is observed both in autistic regression and as part of acquired epileptic aphasia (Landau-Kleffner Syndrome). We prospectively identified 177 children with language regression at four major medical centers, and their clinical characteristics were recorded. Their mean age at regression was 22.8 months. The mean time-to-specialist referral was 38 months of age. Most children (88%) met criteria for autism or manifested autistic features. Males (P = 0.02) and children less than 3 years of age who regressed (P = 0.016) had a higher probability of developing autistic behaviors. Seizures were more common in children who regressed after they reached 3 years of age (P < 0.001), and children with seizures were less likely to have associated autistic regression (P < 0.001). Electroencephalogram abnormalities were reported in 37% of patients and were more common in children with seizures (P < 0.001). At last follow-up, language function was impaired in 88% of the children, although some improvement was noted in 57%. We conclude that the loss of previously acquired language at any age, even if that language only includes a few words or communicative gestures, is often associated with a more global regression in cognition and/or behavior and has serious implications for future function. Early identification and referral of these children is necessary to allow for diagnosis and intervention.

Brain↗
PubMed2001

Sebaceous adenitis in the Akita: clinical observations, histopathology and heredity.

Ninety-seven pure-bred Akitas were examined clinically and histologically for sebaceous adenitis. The diagnosis was established histologically in 23 Akitas by demonstrating an inflammatory reaction targeted against the sebaceous glands or a reduction in the number of glands. The clinical course of sebaceous adenitis in the Akita was similar to that seen in other breeds. The first skin lesions occurred mainly on the dorsal midline and ears. Compared with the Poodle, the age at first onset of the disease was more variable and the hair loss affected mainly the undercoat. The progression of sebaceous gland destruction varied between dogs and was not seen in all cases. Because bud-like sebaceous gland proliferation could be identified, it seems that regeneration of the sebaceous glands may occur. An autosomal recessive inheritance appears to be possible. Apart from a genetic background, immune-mediated factors possibly influence the onset and course of sebaceous adenitis.

Animals↗
PubMed2001

Quantitative analyses of the biomineralization of different hard tissues.

The primary crystallites of the different developing hard tissues have an apatite structure. However, they have crystal lattice distortions representing an intermediate state between amorphous and fully crystalline. We have applied energy-filtering transmission electron microscopy in the selected area electron diffraction mode to analyse different stages of crystal formation in dentine, bone, enamel and inorganic apatite mineral. We have obtained quantitative information on the degree of crystal lattice distortion using the paracrystal theory of Hosemann and Bagchi. We have found that the early formed crystallites of the hard tissues being analysed have a paracrystalline character comparable to biopolymers. However, with maturation, the lattice fluctuations of the crystallites of the hard tissues bone, enamel and dentine decrease to form a typical (para)crystalline character. Also the decrease of the organic proportion in the matrix corresponds to the decrease of the lattice fluctuation of the crystallites in the different hard tissues during maturation.

Animals↗
PubMed2001

A longitudinal analysis of cytotoxic T lymphocyte precursor frequencies to the hepatitis B virus in chronically infected patients.

Individuals with acute hepatitis B virus (HBV) infection characteristically mount a strong, multispecific cytotoxic T lymphocyte (CTL) response that is effective in eradicating virus. In contrast, this response in chronic carriers is usually weak or undetectable. Since it is generally acknowledged that HBV pathogenesis is immune-mediated, the occurrence of episodes of active liver disease in many carriers suggests that these individuals can mount active CTL responses to HBV. To see whether the detection of circulating CTLs is related to these flare episodes, we have determined the CTL precursor (CTLp) frequencies to HLA-A2-restricted viral peptides in seven patients over a 12-24-month period of their disease. Limiting dilution analyses (LDA) were performed longitudinally to five epitopes comprising the viral capsid (HBc), envelope (HBs) and polymerase (pol) proteins. Assays were performed against a mixture of peptides, or against each individual peptide, to measure overall CTL activity and the multispecificity of the responses, respectively. Since two of the patients were treated with recombinant human interleukin-12 (rHuIL-12) at the time, with one individual achieving complete disease remission a year later after being treated with interferon-alpha, we were also able to examine the effects of these cytokines on HBV cytotoxicity. Our results indicate that weak but detectable CTL responses do occur in chronic carriers which are generally associated with disease flares, although CTLps were also seen occasionally during minimal disease activity. The range of specificities varied between individuals and within each individual during the course of the disease. Finally, we also provide evidence that CTL reactivity is stimulated following treatment with certain cytokines, but is dependent on the time of administration.

Adult↗
PubMed2001

Unsuspected atypical hemispheric dominance for language as determined by fMRI.

PURPOSE: We sought to illustrate the value of functional magnetic resonance imaging (fMRI) in the presurgical assessment of hemispheric dominance for language by means of an illustrative case report. METHODS: fMRI with two language paradigms was performed in a right-handed patient without familial sinistrality suffering from a left frontal focal epilepsy. RESULTS: Both fMRI paradigms revealed unequivocally lateralized right hemispheric activation. Atypical language representation was confirmed by Wada test. The further presurgical workup could be restricted to subdural strip recordings instead of the initially intended grid implantation. After resective surgery, no language deficits were apparent. CONCLUSIONS: Hemispheric dominance for language should be assessed by fMRI in all patients before surgery in areas potentially relevant for language in either cerebral hemisphere. fMRI may influence the further diagnostic workup and should be performed before other invasive diagnostic procedures.

Adult↗
PubMed2001

Ictal ECD-SPECT differentiates between temporal and extratemporal epilepsy: confirmation by excellent postoperative seizure control.

We investigated whether ictal single photon emission computed tomography (SPECT) with 99Tcm-ethyl cysteinate dimer (ECD) could differentiate between temporal (TE) and extratemporal epilepsy (ETE) in 30 consecutive patients (n = 21 for TE, n = 9 for ETE), all of whom had excellent postoperative seizure control (class I according to Engel's classification). Ictal SPECT showed isolated temporal hyperperfusion in 90% (19 out of 21) of the TE patients and normal perfusion in two patients. All the ETE patients had ictal SPECT findings consistent with extratemporal seizure onset. The sensitivity of ictal ECD-SPECT for correct localization of the seizure onset zone was 80% in all patients, 86% in TE patients and 66% in ETE patients. Although ictal ECD-SPECT has a lower sensitivity in ETE than in TE, it can be used to clearly distinguish between TE and ETE. It provides non-invasive imaging information for use in further diagnostic and treatment strategies in patients with drug-resistant focal epilepsy.

Adolescent↗
PubMed2001

Primary ciliary dyskinesia with situs inversus totalis, hydrocephalus internus and cardiac malformations in a dog.

A nine-month-old golden retriever bitch was presented with exercise intolerance and recurrent nasal discharge. Based on clinical, radiographic and ultrasonographic examination, a diagnosis of rhinitis, situs inversus totalis and tricuspid valve insufficiency was established. The results of video- and electron microscopy studies of the respiratory epithelium were compatible with primary ciliary dyskinesia (PCD). However, no evidence of a primary ultrastructural defect of the cilia was found. The dog was euthanased because of the poor prognosis. At necropsy, a hydrocephalus internus and a subaortic stenosis were additionally diagnosed. PCD, in combination with situs inversus, has been previously reported in golden retrievers, but without a concomitant hydrocephalus internus. Furthermore, concomitant occurrence of internal cardiac malformation and PCD has not previously been reported in the dog.

Animals↗