The genetic defect in multiple endocrine neoplasia type 2A maps next to the centromere of chromosome 10

Multiple endocrine neoplasia type 2A (MEN2A) is a rare cancer syndrome that is inherited in an apparently autosomal dominant fashion. Previous linkage studies had assigned the MEN2A locus to chromosome 10 in the pericentromeric region. We recently have described several new easily scorable RFLPs for the chromosome 10-specific alpha satellite DNA (the D10Z1) locus that is known, on the basis of previous in situ hybridization experiments, to lie at the centromere. We report here tight linkage between MEN2A and D10Z1, as demonstrated by a maximum lod score of 12.02 at the recombination frequency of zero (1-lod-unit support interval 0-4 cM), indicating that the genetic defect in MEN2A lies in the immediate vicinity of the centromere. By means of a set of ordered polymorphic DNA markers from the pericentromeric region, multipoint as well as pairwise linkage analyses place the MEN2A locus at the middle of a small region (approximately 11 cM) bracketing the centromere with FNRB (at 10p11.2) and RBP3 (at 10q11.2) on either side, providing further support for the centromeric location of the MEN2A locus. Marked sex difference in recombination frequencies exists in this pericentromeric region: significantly (P less than .01) more female than male crossovers were observed across all of the adjacent intervals D10S24-FNRB, FNRB-D10Z1, and D10Z1-RBP3. However, a sex difference was not seen in the 7-cM interval from RBP3 to D10S5, suggesting that large variation in the sex difference in recombination can occur over small chromosomal regions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Preferential Osmolyte Accumulation: a Mechanism of Osmotic Stress Adaptation in Diazotrophic Bacteria

A common cellular mechanism of osmotic-stress adaptation is the intracellular accumulation of organic solutes (osmolytes). We investigated the mechanism of osmotic adaptation in the diazotrophic bacteria Azotobacter chroococcum, Azospirillum brasilense, and Klebsiella pneumoniae, which are adversely affected by high osmotic strength (i.e., soil salinity and/or drought). We used natural-abundance ¹³C nuclear magnetic resonance spectroscopy to identify all the osmolytes accumulating in these strains during osmotic stress generated by 0.5 M NaCl. Evidence is presented for the accumulation of trehalose and glutamate in Azotobacter chroococcum ZSM4, proline and glutamate in Azospirillum brasilense SHS6, and trehalose and proline in K. pneumoniae. Glycine betaine was accumulated in all strains grown in culture media containing yeast extract as the sole nitrogen source. Alternative nitrogen sources (e.g., NH₄Cl or casamino acids) in the culture medium did not result in measurable glycine betaine accumulation. We suggest that the mechanism of osmotic adaptation in these organisms entails the accumulation of osmolytes in hyperosmotically stressed cells resulting from either enhanced uptake from the medium (of glycine betaine, proline, and glutamate) or increased net biosynthesis (of trehalose, proline, and glutamate) or both. The preferred osmolyte in Azotobacter chroococcum ZSM4 shifted from glutamate to trehalose as a consequence of a prolonged osmotic stress. Also, the dominant osmolyte in Azospirillum brasilense SHS6 shifted from glutamate to proline accumulation as the osmotic strength of the medium increased.     

Burrowing behaviour in the crayfish, Cambarus diogenes diogenes girard

The crayfish, Cambarus diogenes diogenesGirard (1852), spends most of its life cycle in individually constructed underground burrows. The architectural behavioral patterns and sequences with which adult C. d. diogenes excavate an underground chamber were evaluated. Two motor patterns (Pushing and Carrying) and three burrow stages (shallow depression, angular pit, and burrow with two openings) were identified. During the development of burrowing behaviour in juveniles, a third motor pattern (Fanning) occurred. While the three motor patterns are functional soon after hatching, crayfish may learn to orient the Carrying motor pattern for the most efficient excavation of a stage-3 burrow with two openings. The ground-water level determined the final structure of a burrow.     

Development of a Defined Medium for Growth of Cercospora rosicola Passerini

A simple synthetic liquid medium containing a single amino acid, glucose, salts, trace metals, and thiamine was developed for cultivation of Cercospora rosicola Passerini. Thiamine was shown to be important to growth. Culture of C. rosicola Passerini in a chemically defined medium makes possible studies of (+)-abscisic acid biosynthesis and regulation.     

XY female mice express H-Y antigen

Karyotypically XY individuals of the C57BL/6J-Y^POS mouse stock develop as females or hermaphrodites, but never as normal males. The aberrant sexual development results from the interaction of the C57BL/6J genetic background with the M. poschiavinus-derived Y chromosome. XY females from this stock were assayed for H-Y antigen. By the criteria of skin-grafting, the cell-mediated lympholysis test, and the popliteal lymph node assay, these XY females are antigenically indistinguishable from normal C57BL/6 males. Implications for the hypothesis that H-Y antigen induces formation of the mammalian testis are discussed.     

Transposition of the gene cluster CYC1-OSM1-RAD7 in yeast

A mutant of the yeast Saccharomyces cerevisiae contains an increased amount of iso-1-cytochrome c because two copies of a segment, denoted COR, were transposed to a new position on chromosome VII, while the original COR region was retained at the normal position on chromosome X; this COR segment encompasses the CYC1, OSM1 and RAD7 loci which determine, respectively, iso-1-cytochrome c, osmotic sensitivity and ultraviolet light sensitivity. The analysis of genomic DNA with cloned probes indicates that the length of the COR segment is approximately 12,000 base-pairs. We suggest that certain normal strains of yeast, which possibly may contain reiterated sequences, can produce extended transpositions similar to prokaryotes.     

Uridine Metabolism in the Goldfish Retina During Optic Nerve Regeneration: Whole Retina Studies

Accumulation of radioactivity from [3H]uridine in incubations of whole goldfish retinas is increased in the ipsilateral retina during a period of regeneration that follows unilateral optic nerve crush. Brief incubations to investigate the nature of enhanced labeling of the acid-soluble fraction showed a peak uptake 4 days following crush, with a gradual decrease to control levels by 21 days following crush. That nucleoside uptake may not mediate the effect is supported by the observation that the rate of uptake of 5'-deoxyadenosine, a nonmetabolizable nucleoside analog, is the same in post-crush (PC) and normal (N) retinal incubations. Following brief incubations of PC and N retinas with [3H]uridine, there is enhanced labeling in PC retinas relative to N retinas of recovered UMP, UDP, UTP, and uridine nucleotide sugars, whereas recovery of labeled uridine itself is slightly decreased. The results suggest that the increased accumulation of radioactivity in PC retinas following incubation with uridine reflects an increase in the activities of retinal uridine kinase and uridine nucleotide kinases.     

Age-related motor and catecholomine alterations in mice on levodopa supplemented diet

Old mice reared on regular diet show reduced motor activity, decreased basal adenylate cyclase, and increased MAO activities compared to adults. Brain DDC and COMT activities, DA, NE levels and DA-stimulated adenylate cyclase remained unchanged. By contrast, mice fed levodopa for life did not develop decreased motor activity with aging, lived about 50% longer, had slightly elevated whole brain DA and NE levels and failed to develop the expected rise in MAO activity with aging. Levodopa did not alter the number of dopaminergic and muscarinic cholinergic receptors or the adenylate cyclase activity in the striatum during aging. On levodopa, hepatic and renal DA, dopa, and HVA increased but the latter two returned to basal levels by mid life. In liver, DDC was unchanged but MAO tended to be higher in levodopa-fed mice. Thus, motor impairment is an age-related phenomenon in mice associated with selective alterations in brain dopaminergic systems, which may be prevented by dietary levodopa. Extracerebral tissues, through possibly adaptive metabolic mechanisms, play a significant role in regulating brain catecholamines during chronic administration of large doses of levodopa.