Dietary zinc deficiency has no effect on auditory brainstem responses in the rat

Zinc has been shown to effect--in vitro--a number of processes associated with neurotransmission. We have tested whether the rate of impulse conduction--in vivo--as measured from the latencies of auditory brainstem responses (ABR), is influenced by dietary zinc deficiency in the rat. Dietary zinc deficiency for up to 26 wk had no effect on the wave I-IV interval compared to zinc-adequate fed animals. The results are discussed in relation to the observed constancy of brain overall and extracellular fluid zinc concentrations under conditions of dietary zinc deficiency.     

Plasmid cloning vectors replicating in Escherichia coli,amino acid-producing coryneform bacteria and Methylobacillus sp.

Summary Four hybrid plasmids were constructed from the cryptic plasmid pAM330 (from Brevibacterium lactofermentum; 4.5 kb) and the broadhost-range plasmid pGV1106 (9.0 kb; Km^r Sm^r) isolated from Escherichia coli. All of them were mobilized from E. coli into the Gram-negative methylotrophic bacterium Methylobacillus sp. and two of these constructs (pCEM300 and pCEM400) were transferred by transformation into B. flavum and Corynebacterium glutamicum. Their kanamycin-resistance determinant coming from Gram-negative hosts was expressed in these Gram-positive bacteria. Both pCEM300 and pCEM400 are very stably maintained in B. flavum and represent suitable vectors for gene cloning in coryneform producers of amino acids.     

Frequent derepression of G6PD and HPRT on the marsupial inactive X chromosome associated with cell proliferation in vitro

X chromosome dosage compensation in Marsupials is like that in eutherian mammals except that the paternal X chromosome is always inactive, and silence of this chromosome is not well maintained. We previously showed that the unstable inactivation of the paternal G6PD allele is associated with the lack of DNA methylation in the 5' CpG cluster. Even though this CpG island is unmethylated, the paternal allele (marked by an enzyme variant) is at least partially and often severely repressed in most tissues of the opossum, so that factors other than methylation must inactivate the locus. Here we report that when cell cultures are established from these tissues, the silent G6PD locus is depressed. Although often complete, the extent of derepression differs among tissues and within different cell types in the same tissue, and is not accompanied by obvious changes in the pattern of chromosome replication. Studies of the HPRT locus in these cells show that the paternal HPRT allele also derepresses in cultured cells. These observations suggest that without DNA methylation to maintain the silence of the locus, tissue or cell-specific factors act to repress the silent locus, but are unable to maintain inactivity through cell division, or are lost as cells proliferate in culture.     

Isolation and structure of corazonin, a cardioactive peptide from the American cockroach

Corazonin, a new cardioaccelerating peptide, has been isolated from the corpora cardiaca of the American cockroach, Periplaneta americana, and its structure determined to be Glp-Thr-Phe-Gln-Tyr-Ser-Arg-Gly-Trp-Thr-Asn-amide. The peptide stimulated heart beat at concentrations as low as 0.2 nM, which makes it the most potent insect cardioactive neuropeptide.     

The achondroplasia gene is not linked to the locus for neurofibromatosis 1 on chromosome 17

Summary We have investigated genetic linkage of von Recklinghausen neurofibromatosis (NF1) and achondroplasia (ACH) using chromosome-17 markers that are known to be linked to NF1. Physical proximity of the two loci was suggested by the report of a patient with mental retardation and the de novo occurrence of both NF1 and ACH. Since the chance of de novo occurrence of these two disorders in one individual is 1 in 600 million, this suggested a chromosomal deletion as a single unifying molecular event and also that the ACH and NF1 loci might be physically close. To test this, we performed linkage analysis on a three-generation family with ACH. We used seven DNA probes that are tightly linked to the NF1 locus, including DNA sequences that are known to flank the NF1 locus on the centromeric and telomeric side. We detected two recombinants between the ACH trait and markers flanking the NF1 locus. In one recombinant, the flanking markers themselves were nonrecombinant. Multi-point linkage analysis excluded the ACH locus from a region surrounding the NF1 locus that spans more than 15cM (lod score < -2). Therefore, analysis of this ACH pedigree suggests that the ACH locus is not linked to the NF1 locus on chromosome 17.     

The phylogenic position of Peptococcus niger based on 16S rRNA sequence studies

A 1330 base-pair fragment of a 16S rRNA gene has been amplified, cloned and sequenced. Comparison to other 16S rRNA sequences of eubacteria showed that P. niger represents a deep branch within the subdivision "Gram-positive with Gram-negative cell walls". It is not related to peptostreptococci, representatives of this genus studied so far are more closely related to clostridia.     

5,6,7,8-Tetrahydromethanopterin-dependent enzymes involved in methanogenesis

Abstract In the process of methanogenesis, 5,6,7,8-tetrahydromethanopterin (H₄MPT) is the carrier of the C₁ unit at the formyl through methyl state of reduction. By the transfer of a formyl group from formylmethanofuran, 5-formyl- and 10-formyl-H₄MPT are formed in hydrogenotrophic and methylotrophic organisms, respectively. Cyclohydrolysis of the 5- and 10-formyl derivatives then yields 5,10-methenyl-H₄MPT, which is reduced in two subsequent coenzyme F₄₂₀-dependent reactions to 5-methyl-H₄MPT. Following the transfer of the methyl group to coenzyme M, the substrate of the terminal step in methanogenesis, methylcoenzyme M, is produced. In this paper properties of the enzymes catalyzing the individual H₄MPT-dependent reactions are discussed.     

Effects of training at simulated altitude on performance and muscle metabolic capacity in competitive road cyclists

Differences between the effects of training at sea level and at simulated altitude on performance and muscle structural and biochemical properties were investigated in 8 competitive cyclists who trained for 3-4 weeks, 4-5 sessions/week, each session consisting of cycling for 60-90 min continuously and 45-60 min intermittently. Four subjects, the altitude group (AG), trained in a hypobaric chamber (574 torr = 2300 m above sea level), and the other four at sea level (SLG). Before and after training work capacity was tested both at simulated altitude (574 torr) and at sea level, by an incremental cycle ergometer test until exhaustion. Work capacity was expressed as total amount of work performed. Venous blood samples were taken during the tests. Leg muscle biopsies were taken at rest before and after the training period. AG exhibited an increase of 33% in both sea level and altitude performance, while SLG increased 22% at sea level and 14% at altitude. Blood lactate concentration at a given submaximal load at altitude was significantly more reduced by training in AG than SLG. Muscle phosphofructokinase (PFK) activity decreased with training in AG but increased in SLG. All AG subjects showed increases in capillary density. In conclusion, work capacity at altitude was increased more by training at altitude than at sea level. Work capacity at sea level was at least as much improved by altitude as by sea level training. The improved work capacity by training at altitude was paralleled by decreased exercise blood lactate concentration, increased capillarization and decreased glycolytic capacity in leg muscle.