Showing papers by "University of Luxembourg published in 1992"

No-bridge of Drosophila melanogaster: portrait of a structural brain mutant of the central complex.

Abstract: The mutant no-bridge (nobKS49) has its name from a structural defect in the protocerebral bridge of the central complex. This rod-shaped neuropil in nobKS49 has a large gap at the sagittal midplane, with some of the missing material accumulated more laterally. Mutant nob flies have a reduced maximal and average walking speed. Leg coordination is disturbed during turning but not while walking straight. Motivation for walking is low and steps are small due to slow forward swinging of the legs. Flies spontaneously may pass into an autistic (and possibly spastic) state in which they can move their legs and even perform cleaning movements but do not walk or fly. They spontaneously recover if left undisturbed. Gynandromorph experiments place the focus of the walking defects into the head. Mutant flies have a reduced tendency to escape when mechanically stimulated. In a brightly lit arena they do not avoid a black square above the horizon and they are negatively phototactic. In tethered flight optomotor responses are normal but the amplitude of spontaneous torque modulations as well as the number of torque spikes are reduced. If a single black bar is slowly rotated around the fly, the normal response pattern is observed. It vanishes, however, at moderately fast angular velocity at which the wild type still is fully responsible. The behavioral defects support the notion that the protocerebral bridge is part of a higher center for the regulation of behavior.

Clinical and laboratory features of type 1 diabetic children at the time of diagnosis.

Abstract: The French incidence study has registered all new cases of Type 1 diabetic children under 20 years of age, from a population of 2.32 million, in an exhaustive and prospective manner. Three hundred and forty cases were identified between 1 January 1988 and 31 December 1989, yielding a mean annual incidence rate 7.3 per 10(5). The lowest rate was observed in the youngest age group (0-4 yr: 4.1 per 10(5)) and the highest around pubertal development (10-14 yr: 11.5 per 10(5)). Details of the previous personal and family history, and the clinical and biological pictures of the disease at diagnosis were recorded. Almost 8 per cent of the children had a first-degree relative with Type 1 diabetes. Polyuria, weight loss, fatigue and abdominal pain were the most frequently reported symptoms, which were of median duration 4.4 months. Mean weight loss before diagnosis was 9.4 +/- 6.8 (+/- SD)% of body weight and was not significantly related to age. Ketonuria was detected in 83.8 per cent and acidosis (total CO2 less than or equal to 18 mmol l-1, if measured) in 48 per cent of the cases. Ketonuria and acidosis were significantly more frequent in the younger age group than in the rest of the group (p less than 0.001).

Degenerations of Generalized Krichever Novikov algebras on Tori

Abstract: Degenerations of Lie algebras of meromorphic vector fields on elliptic curves (i.e. complex tori) which are holomorphic outside a certain set of points (markings) are studied. By an algebraic geometric degeneration process certain subalgebras of Lie algebras of meromorphic vector fields on P^1 the Riemann sphere are obtained. In case of some natural choices of the markings these subalgebras are explicitly determined. It is shown that the number of markings can change. AMS subject classification (1991): 17B66, 17B90, 14F10, 14H52, 30F30, 81T40

The Relationship Between Cardiovascular Responses in the Laboratory and in the Field: The Importance of “Active Coping”

Abstract: The cardiovascular response to psychological stimuli is central to current research and theorising on the psychophysiological and neurogenic aspects of cardiovascular disease. It is implicated in the development of hypertension (Folkow 1982; Obrist 1981; Fredrikson and Matthews 1990), coronary atherosclerosis (Manuck et al. 1983), and as the physiological mechanism linking type A behaviour and coronary heart disease or even as a risk factor in its own right (Krantz and Manuck 1984). Outside the area of cardiovascular disease, cardiovascular reactivity is related to the development and maintenance of anxiety and panic disorders (Clark 1986; Ehlers et al. 1988).

A Graph Theoretic Criterion for Determining the Number of Clusters in a Data Set.

Abstract: This article is concerned with procedures for determining the number of clusters in a data set. Most of the procedures or stopping rules currently in use involve finding internally coherent and externally isolated clusters, but do not derive from the formal structure of the respective clustering model. Based on the graph theoretic concepts of minimal spanning tree, maximal spanning tree, and homomorphic function, a new criterion is advanced that yields a well-defined clustering solution. Its performance in determining the number of clusters in several empirical data sets is evaluated by comparing it to four prominent stopping rules. It is shown that the proposed criterion not only possesses mathematically attractive properties but also may contribute to solving the number-of-clusters problem.

Molecular biology of oncogenes and cardiovascular hypertrophy.

Abstract: The terms oncogene and proto-oncogene have caused much confusion because they appear to imply the presence of genes that are mostly expressed in tumours, which of course bear almost no relevance to cardiovascular disease. In fact, proto-oncogenes are normal genes found in the genome of every individual; mutated forms of these genes causing malignancy are called oncogenes. About 60 proto-oncogenes have been identified (reviewed in [1,2]) among the estimated 50000–100000 genes expressed in mammalian organisms [3]. Some, such as c-fos, c-jun, c-myc, c-srcand members of the ras family, are probably ubiquitous, whereas some are expressed only in specialized tissues, e.g. the recently discovered c-vavin haematopoetic tissue [4]. In addition, a still small family of six (perhaps more) tumour suppressor genes exists (the retinoblastoma gene, p53, the Wilms’ tumour gene, etc.), mutations of which have been found in many tumours, but their role in cardiovascular tissue is only now being defined (reviewed in [5]). Transgenic mice expressing the large T antigen, the transforming protein from SV 40 virus, develop atrial tumours [6,7] when the T antigen is directed to the atrium by use of the promoter of the atrial natriuretic peptide (ANP); this may be due to binding of large T antigen to the retinoblastoma protein (and other proteins), suggesting that it plays a role in the control of cardiac growth. Proto-oncogenes encode proteins anywhere along the signal transduction pathway from the extracellular ligand to regulatory factors that bind to DNA (reviewed in [2,8,9]). Figure 1 gives a summary. It is immediately obvious that defective regulation of the function of one or (more frequently) more of these strategic genes may cause aberrant growth. Therefore, the question of what role the proteins encoded by proto-oncogenes play in cardiovascular hypertrophy is equivalent to which signal transduction mechanisms operate when a hypertrophic stimulus occurs.

Sequence analysis of polymerase chain reaction amplified t(14;18) chromosomal breakpoints in formalin fixed, paraffin wax embedded follicular lymphoma.

Abstract: AIMS: To determine whether junctional sequences of rearranged chromosomes can be amplified by use of the polymerase chain reaction (PCR) and whether direct sequence analysis of the PCR products is possible, using DNA from formalin fixed, paraffin wax embedded biopsy specimens. METHODS: DNA was extracted from paraffin wax embedded, formalin fixed lymphoma specimens, and junctional sequences of rearranged chromosomes were amplified by the PCR. The products were used as templates for asymmetrical PCR. Subsequently, direct sequence analysis was performed using the chain termination method. RESULTS: Formalin fixed, paraffin wax embedded biopsy specimens and PCR amplification could be used to determine the nucleotide sequences of junctional regions of rearranged chromosomes t(14;18) from patients with follicular lymphoma. CONCLUSION: The identification of junctional sequences of the translocation in follicular lymphoma provides a molecular "fingerprint" of t(14;18) of the lymphoma of an individual patient and can be used for the detection of clone specific DNA in any biopsy tissue obtained from the patient. The strategy used for rapid sequence analysis of PCR amplified DNA sequences will be useful in many areas of molecular pathology.

Entwicklung eines Simulationsprogramms zum scale-up von Hydrierreaktoren

Abstract: Development of a simulation program for the scale-up of hydrogenation reactors. The scale-up of trickle-bed reactors to pilot and production scale has been difficult and necessitated considerable over-dimensioning. Therefore a simulation program based on a cell model has been developed in which the dimensions of a cell are directly related to the dimensions of the catalyst particles used. The kinetic equation is formulated with an effective rate coefficient as the only key parameter to be adjusted. With this coefficient the intrinsic rate coefficient, the mass transfer, and the incomplete catalyst particle wetting are considered. The model was applied to the hardening of fatty acids and the hydrogenation of fatty acid methyl esters in laboratory reactors. Comparison with experimental results of pilot and industrial scale is favourable. Thus the model can be used for the scale-up of trickle-bed reactors.

Transformation from a U(3) to a pseudo U(3) basis of the matrix representation of a deformed Nilsson Hamiltonian

Abstract: In recenl puhlications Ca.<;tailOs, Moshinsky and Quesne obtained explicitly the oper- ator U that transforms us from a U(3) to pseudo U(3) basis. They then applied it to a spherical Nilsson lIarniltonian lo show tha1 it lransforms iuto a similar olle in which the coefficient of the spin oebit ter m c.hanges and, in (act, bf'comes very small roc lhe parameters of the Nilsson lIamiltonian taken foc experimental results in lile spectra of heavy l111clei. In this papee we consider lhe deformed Nilsson Hamiltonian H. 'Ve show how we can obtain ils malrix elements in an oscillator basis wilh spin and we lhen obtain lhe corresponding reslIlts roc Ji = U JI Uf. Thus we have lhe ground work for event.ualIy obtaining the operator fOflo of ji.