A family of type I keratin genes and the homeobox-2 gene complex are closely linked to the rex locus on mouse chromosome 11

Type I and type II keratins are major constituents of intermediate filaments that play a fundamental role in the cytoskeletal network. By using both somatic cell hybrids and conventional and interspecific linkage crosses, several genes encoding type I keratins, including the epidermal keratin K10, were shown to be closely linked to the homeobox-2 complex and the rex locus on mouse chromosome 11. The absence of crossovers between type I keratin-encoding genes and rex (N = 239), a locus affecting hair development, raises the possibility that mutations at rex and neighboring loci affecting skin and hair development involve type I keratin genes.     

The mouse genome: an overview.

A genetic map with one molecularly marked locus per cM will be available for the mouse in the near future. A map of this density should provide molecular reference points that connect genetic and physical maps, identify sites to initiate positional cloning studies for the molecular characterization of mutant loci, and define homologous regions of mouse and human genomes.     

Computer processing of intracardiac electrograms for conduction studies.

Computer techniques developed to process intracardiac signals recorded in dogs are presented. The signals under measurement are the auricular and ventricular monophasic action potentials and the His bundle electrogram. Computerized measurement of significant timing parameters on simultaneous recordings of these signals can assess quite precisely changes in the normal conduction scheme of the heart provoked by different experimental protocols. Increased accuracy is mainly due to the objective way of defining wave onsets and the processing power of the system used. Signal recording, signal acquisition, automatic waveform measurements, interactive process and production of end result graphs by computer are all described.     

The potential bioavailability of organic C,N, and P through enzyme hydrolysis in soils of the Mojave Desert

Increases in the growth rate of plants and microbes in the Mojave Desert in response to predicted increases in precipitation and CO₂ due to global climate change may induce nutrient limitations. This study was designed to measure the pool of potentially bioavailable nutrients in soils of the Mojave Desert. Soils were collected from shrub and interspace microsites and then subjected to amendment with buffered solutions of an excess of various enzymes. The products of each enzyme reaction were then measured and the maximum quantity of hydrolyzable substrates was calculated. In interspace and shrub microsite soils, respectively, 14.5 and 9.7% of the organic C in the form cellulose, 60.0–97.8% and 61.2–100.0% of the organic N in the form protein, and 44.0 and 57.5% of the organic P was hydrolyzable. There were significant differences between microsites for hydrolyzable substrate using all enzyme amendments, except protease. We propose that accumulations of hydrolyzable organic C, N, and P in the Mojave Desert could be a result of the persistently dry soil conditions often found in desert ecosystems and the immobilization of enzymes, which may result in low diffusivity of soil substrates and enzymes and, accordingly, little degradation of organic C, N, and P. Alternatively, rapid nutrient cycling and immobilization by soil microorganisms could account for accumulations of organic C, N, and P. Further refinement of the methods used in this study could lead to a valuable tool for the assessment of potential bioavailability of nutrients in a variety of soils.     

Determination of pyridine nucleotide contents of cell monolayers by bioluminescence

In this paper, we describe methods to assay specifically the NAD+, the NADP+, the NADH and the NADPH contents of cell monolayers. After an acid or an alkaline extraction, respectively for the oxidized or the reduced pyridine nucleotides, each type of nucleotide can be separately quantified with the use first, of specific reducing enzymes (lactate or glucose-6-phosphate dehydrogenases), followed by a bioluminescence enzymatic reaction [NADP(H)-FMN oxidoreductase and luciferase]. The assays hence developed are sensitive, reliable and specific. An application of the method with pulmonary alveolar macrophage monolayers is also described.