Genetic heterogeneity in tuberous sclerosis

Tuberous sclerosis (TSC) is an autosomal dominant disorder characterized by widespread hamartosis. Preliminary evidence of linkage between the TSC locus and markers on chromosome 9q34 was established, but subsequently disputed. More recently, a putative TSC locus on chromosome 11 has been suggested and genetic heterogeneity seems likely. Here we describe an approach combining multipoint linkage analysis and heterogeneity tests that has enabled us to obtain significant evidence for locus heterogeneity after studying a relatively small number of families. Our results support a model with two different loci independently causing the disease. One locus (TSC1) maps in the vicinity of the Abelson oncogene at 9q34 and a second locus (TSC2) maps in the region of the anonymous DNA marker Lam L7 and the dopamine D2 receptor gene at 11q23.     

Synthesis of functional bovine opsin in insect cells under control of the baculovirus polyhedrin promoter

In vitro expression of cDNA encoding bovine opsin is accomplished using the baculovirus expression vector system. Full-length opsin was synthesized which was recognized by poly- and monoclonal antisera raised against bovine rhodopsin. Upon infection with a recombinant virus, 1×10⁶ insect cells produced up to 3 g opsin. Incubation of the in vitro synthesized opsin with 11-cis retinal produced a hydroxylamine-stable, photosensitive pigment.Abbreviations dpi days post infection - pfu plaque forming units - AcNPV Autographa californica nuclear polyhedrosis virus     

Reversible conversion of coenzyme F420 to the 8-OH-AMP and 8-OH-GMP esters,F390-A and F390-G,on oxygen exposure and reestablishment of anaerobiosis in Methanobacterium thermoautotrophicum

Intracellular levels of F₃₉₀ (AMP and GMP adducts of the 5-deazaflavin cofactor F₄₂₀) in Methanobacterium thermoautotrophicum were analysed after gasing fermenter cultures with several consecutive cycles of substrate gas and gas mixtures containing 5% oxygen. No F₃₉₀ was detected in growing cells, hydrogen starved cells and CO₂ starved cells prior to O₂ contamination. Also, no F₃₉₀ was found in hydrogen depleted cells after O₂ treatment. Exposure of exponentially growing cells and CO₂ starved cells to oxygen lead to the formation of F₃₉₀ species; the increase in the detected amount of F₃₉₀ was coupled to a decrease of the F₄₂₀ level. As soon as anaerobiosis was reestablished F₃₉₀ cofactors were degraded and growth proceeded. Independent of the physiological condition of Methanobacterium thermoautotrophicum methanopterin was formed upon O₂ exposure. After normal growth conditions were restored the level of detected methanopterin decreased again.     

Filtering of behaviourally relevant temporal parameters of a grasshopper's song by an auditory interneuron

Summary In females of the acridid grasshopperChorthippus biguttulus, thoracic auditory interneurons were investigated with respect to their selectivity for temporal parameters of the conspecific song. Special attention was given to the detection of small gaps in the syllables of the song, since behavioural experiments have shown that the presence or absence of gaps is critical for the female's Innate Releasing Mechanism (cf. Fig. 1).The spiking response of one ascending interneuron, the AN4, shows filtering properties which closely resemble the behavioural reactions (cf. Figs. 1, 3 and 5b). The difference in the AN4's reaction to stimuli with gaps and uninterrupted stimuli is maintained over the behaviourally relevant intensity range (Fig. 4). This reaction is reliable enough that the stimulus type could be inferred by higher centres even from single stimulus presentations. Hence, this neuron is likely to participate in the task of gap detection and probably is a part of the neuronal filter network which determines the characteristics of the Innate Releasing Mechanism of this species. However, this interneuron is not species-specific: A homologue exists in other acridids as well and, inLocusta migratoria, has similar response characteristics (Fig. 6). The inferences of this observation for the evolution of an Innate Releasing Mechanism are discussed.Abbreviations CNS central nervous system - PST-histogram post-stimulus-time-histogram - SPL sound pressure level - IRM Innate Releasing Mechanism     

Transfection of the cloned human excision repair gene ERCC-1 to UV-sensitive CHO mutants only corrects the repair defect in complementation group-2 mutants

The human DNA-excision repair gene ERCC-1 is cloned by its ability to correct the excision-repair defect of the ultraviolet light- and mitomycin-C-sensitive CHO mutant cell line 43-3B. This mutant is assigned to complementation group 2 of the excision-repair-deficient CHO mutants. In order to establish whether the correction by ERCC-1 is confined to CHO mutants of one complementation group, the cloned repair gene, present on cosmid 43-34, was transfected to representative cell lines of the 6 complementation groups that have been identified to date. Following transfection, mycophenolic acid was used to select for transferants expressing the dominant marker gene Ecogpt, also present on cosmid 43-34. Cotransfer of the ERCC-1 gene was shown by Southern blot analysis of DNA from pooled (500-2000 independent colonies) transformants of each mutant. UV survival and UV-induced UDS showed that only mutants belonging to complementation group 2 and no mutants of other groups were corrected by the ERCC-1 gene. This demonstrates that ERCC-1 does not provide an aspecific bypass of excision-repair defects in CHO mutants and supports the assumption that the complementation analysis is based on mutations in different repair genes.     

A mechanical analysis of the closed Hancock heart valve prosthesis

In order to obtain mechanical specifications for the design of an artificial leaflet valve prosthesis, a geometrically non-linear numerical model is developed of a closed Hancock leaflet valve prosthesis. In this model, the fibre reinforcement of the leaflet and the viscoelastic properties of frame and leaflets are incorporated. The calculations are primarily restricted to 1/6 part of the valve and a time varying pressure load is applied. The calculations are verified experimentally by measuring the commissure displacements and leaflet centre displacement of a Hancock valve. The numerically obtained commissure displacements are found to be linearly dependent on the pressure load, and the slope of the curves is hardly dependent on loading type and loading velocity. Experimentally a difference is found between the three commissure displacements, which is also predicted numerically using a simplified asymmetric total valve model. Besides, experimentally a clear dependency of commissure displacements on frame size is found. For the leaflet centre displacement, a qualitative agreement exists between numerical prediction and experimental result, although the numerical predicted values are systematically higher. The numerically obtained stress distributions revealed that the maximum von Mises intensity in the membranes occurs in the vicinity of the commissure in the free leaflet area (0.2 N mm-2). Wrinkling of the membranes may occur in the coaptation area near the leaflet suspension. The maximum fibre stress is found near the aortic ring in the fibres which form the boundaries of the coaptation area (0.64 N mm-2). These locations seem to correlate with some common regions of tissue valve failure.     

Surface areas,lengths and volumes of Picea abies (L.) Karst. needles: determination,biological variability and effect of environmental factors

Summary A method for the rapid determination of the lengths and surface areas of very large samples of needles of Picea abies (L.) Karst. using a computer-aided image analysis system was developed. Two independent methods for measuring non-destructively the volumes of individual needles and of all needles attached to a twig were devised. The surface areas and lengths of about 38000 needles sampled from the three youngest needle age-classes (1986, 1985, 1984) of 48 trees approximately 130 years old at four sites in the Fichtelgebirge mountains (N. E. Bavaria, FRG) were measured. The frequency distributions of lengths and areas for each site and age-class are given. Variability of needle size was fairly large. Even though the sites differed in climate, soil, and air pollution levels no consistent effect of these factors on needle size could be detected. Needle lengths and surface areas did not correlate with either the total chlorophyll content of the needles or the degree of crown thinning. The needle surface area (in mm²) of fully developed P. abies needles can be estimated by the empirical equation surface area = 4.440 x needle length -24.8 (r = 0.937), and the needle volume (in mm³) by needle volume = 0.208 x projected needle area ^1.353 (r = 0.969).