A genetic study of the human low-voltage electroencephalogram

Summary The studied phenotype, the low-voltage electroencephalogram (LVEEG), is characterized by the absence of an alpha rhythm from the resting EEG. In previous studies, evidence was found for a simple autosomal-dominant mode of inheritance of the LVEEG. Such a polymorphism in brain function can be used as a research model for the stepwise elucidation of the molecular mechanism involved in those aspects of neuronal activity that are reflected in the EEG. Linkage with the variable number of tandem repeats (VNTR) marker CMM6 (D20S19) and localization of an LVEEG (EEGV1) gene on 20q have previously been reported, and genetic heterogeneity has been demonstrated. This latter result has been corroborated by studing new marker (MS214). The phenotype of the LVEEG is described here in greater detail. Its main characteristic is the absence of rhythmic alpha activity, especially in occipital leads, whereas other wave forms such as beta or theta waves may be present. Analysis of 17 new families (some of them large), together with 60 previously described nuclear families, supports the genetic hypothesis of an autosomal-dominant mode of inheritance. Problems connected with the analysis of linkage heterogeneity, exclusion mapping, and the study of multipoint linkage are discussed. A possible explanation of the localization of LVEEG in the close vicinity of another gene influencing synchronization of the normal EEG, the gene for benign neonatal epilepsie, is given.     

Long-term survival of Legionella pneumophila serogroup 1 under low-nutrient conditions and associated morphological changes

Abstract Extended survival of Legionella pneumophila , using both a clinical and an environmental isolate, was studied in drinking water, creek water, and estuarine water microcosms. Legionella populations were monitored by acridine orange direct counts (AODC) and viable count on buffered charcoal yeast extract agar amended with alpha-ketoglutarate (BCYEα). Initial colony counts of the clinical isolate in drinking and creek water microcosms were 2 × 10⁸ cfu/ml and, after incubation for 1.5 years, the plate counts decreased to 3 × 10⁶ cfu/ml. The AODC counts, however, did not change significantly. The clinical isolate in estuarine water decreased in plate counts to 10² (cfu/ml) over the same period. After incubation for 1.5 years at 15°C in the microcosms, Legionella plate counts of creek and drinking water decreased by two logs. Direct microscopic examination of aliquots removed from all microcosms revealed the presence of small bacilli, large bacilli and rare filamentous cells. The environmental isolate demonstrated only one colony morphology upon culture on BCYEα. Interestingly, after four months incubation in the microcosm, upon plating the clinical isolate on BCYEα, two distinct colony types were evident. Examination by immunofluorescent staining employing a monoclonal antibody against L. pneumophila revealed both bacillus and filamentous forms. The total cellular proteins of both morphotypes were examined by sodium dodecyl sulfate polyacrylyamide gel electrophoresis (SDS-PAGE), demonstrating identical protein patterns. Those Legionella cells remaining culturable during 1.5 years of incubation grew rapidly when transferred to BCYEα. Incubation was continued and it was found that some strains of L. pneumophila serogroup 1 can remain viable for longer than 2.4 years under low-nutrient conditions.     

Localization of the gene for a third G protein β-subunit to mouse chromosome 6 near Raf-1

The large family of signal transducing proteins known as G proteins are heterotrimers that dissociate into an independent α-subunit and βγ-subunit complex after ligand binding or other stimulation. For Gα, at least 30 distinct sequences representing 10 different classes have been identified. On the other hand, cDNAs for only three Gβ-subunit genes have been isolated so far. All three of the Gβ genes have been chromosomally mapped in the human, but only two in the mouse. Using a human retinal cDNA for the third G protein β-subunit, we have mapped the corresponding gene, termed Gnb-3, to mouse Chromosome 6 with somatic cell hybrids and have positioned it distal to but near the marker Raf-1 by analysis of the progeny of three genetic crosses.     

Molecular cloning and characterization of the mouse UDP-N-acetylglucosamine:α-3- -mannoside β-1,2-N-acetylglucosaminyltransferase I gene

The biosynthesis of protein-bound complex N-glycans in mammals requires a series of covalent modifications governed by a large number of specific glycosyltransferases and glycosidases. The addition of oligosaccharide to an asparagine residue on a nascent polypeptide chain begins in the endoplasmic reticulum. Oligosaccharide processing continues in the Golgi apparatus to produce a diversity of glycan structures. UDP-N-acetylglucosamine:α-3- -mannoside β-1,2-N-acetylglucosaminyltransferase I (EC 2.4.1.101; GlcNAc-TI) is a key enzyme in the process because it is essential for the conversion of high-mannose N-glycans to complex and hybrid N-glycans. We have isolated the mouse gene encoding GlcNAc-TI (Mgat-1) from a genomic DNA library. The mouse sequence is highly conserved with respect to the human and rabbit homologs and exists as a single protein-encoding exon. Mgat-1 was mapped to mouse Chromosome 11, closely linked to the gene encoding interleukin-3 by the analysis of multilocus interspecies backcrosses. RNA analyses of Mgat-1 expression levels revealed significant variation among normal tissues and cells.     

Partition coefficients of plant cuticles for monoterpenes

Summary Cuticle/water partition coefficients (K_c/w) for d-limonene, -pinene and -pinene were determined by an extrapolation and a desorption method. The sorption experiments were carried out with isolated angiosperm and gymnosperm cuticles and with [¹⁴C]-labelled monoterpenes, which were obtained biosynthetically. Both methods were suitable for the determination of the K_c/w of volatile hydrophobic compounds. For the angiosperm cuticles the partition coefficients are of the order of 10⁴, which indicates a high accumulation of monoterpenes in the cuticle. The values of the conifer cuticles of Picea abies (L.) Karst. and Abies alba Mill., however, are lower due to their high lignin content. This is proved by the increase of the partition coefficients after removal of polar and phenolic components. The K_c/w can be estimated with good accuracy from the octanol/water partition coefficient, which was determined experimentally.     

The use of toluidine blue for in situ detection of micro-organisms in foods

The use of toluidine blue to stain cryosections of food samples to detect sites of microbial growth was examined. The method successfully detected colonies and single cells of both yeasts and bacteria at magnifications of x 400 or below in the majority of foods studied. The method demonstrates great potential for studying the micro-environments in which micro-organisms grow.     

Characterization of recombinant human renin: Kinetics,pH-stability, and peptidomimetic inhibitor binding

The kinetic behavior andpH-stability of recombinant human renin was analyzed using a new fluorogenic substrate based on the normal P₆-P₃ renin cleavage sequence in human angiotensinogen. The design of this fluorogenic substrate makes possible, for the first time, direct monitoring of the kinetics of proteolytic conversion of prorenin to renin. ThepH-stability profile for renin, measured with the substrate at 25°C, indicated a broad plateau of stability betweenpH 6.0 and 10.0. Analysis of thepH-activity profile of renin for the substrate indicated a minimumK _m (1.8 µM) atpH 7.4 and a maximumV _m betweenpH 7.4 and 8.0. The thermodynamics of the binding of a novel, soluble, peptidomimetic inhibitor to renin indicated it is possible to retain the tight-binding characteristics and enthalpy contributions to binding of larger peptide-derived inhibitors, while reducing inhibitor size and entropic contributions to binding. A novel derivative of the fluorogenic substrate, containing a 3-methyl histidine substitution at the P₂ site, was used to test the recent hypothesis that renin functions by virtue of substrate-directed catalysis.