Quantitative studies on the nuclei of muscle of congenitally dystrophic mice

Stereological analyses of the pattern of distribution of heterochromatin and euchromatin in nuclei of muscle fibres are reported. Patterns of distribution found in myonuclei from extensor digitorum longus muscle of C57BL/6Jdy2J/dy2J dystrophic mice were compared with those found in myonuclei from the same muscle of clinically unaffected littermates and of normal control mice. Using a well-known spatial pattern analysis technique, clear differences between these types of nuclei were found. Such differences are clearly of value in helping our understanding of the pathological processes occurring in dystrophic muscle, and may be relevant to future identification and diagnosis of abnormal muscle.     

The polyamide method of solid phase peptide and oligonucleotide synthesis

A versatile system of solid-phase peptide synthesis based on polar polyamide resins, a range of reversible peptide-resin linkage agents, and Nα-t-butoxycarbonyl or fluorenylmethoxycarbonyl-amino acids has been developed. Principles used in the design of the method are discussed and illustrated by synthesis of a number of natural peptides. Application of these principles to oligodeoxyribonucleotide synthesis has provided for the first time a practical solid phase method in the nucleotide field.     

Effects of hypoxia on muscle protein synthesis and anabolic signaling at rest and in response to acute resistance exercise

Chronic reductions in tissue O(2) tension (hypoxia) are associated with muscle atrophy and blunted hypertrophic responses to resistance exercise (RE) training. However, the effect of hypoxia on muscle protein synthesis (MPS) at rest and after RE is unknown. In a crossover study, seven healthy men (21.4 ± 0.7 yr) performed unilateral leg RE (6 × 8 repetitions at 70% 1-repetition maximum) under normoxic (20.9% inspired O(2)) and normobaric hypoxic (12% inspired O(2) for 3.5 h) postabsorptive conditions. Immediately after RE the rested leg was biopsied, and a primed continuous infusion of [1,2-(13)C(2)]leucine was maintained for 2.5 h before final biopsies from both legs to measure tracer incorporation and signaling responses (i.e., ribosomal S6 kinase 1). After 3.5 h of hypoxia, MPS was not different from normoxia in the rested leg (normoxia 0.033 ± 0.016 vs. hypoxia 0.043 ± 0.016%/h). MPS increased significantly from baseline 2.5 h after RE in normoxia (0.033 ± 0.016 vs. 0.104 ± 0.038%/h) but not hypoxia (0.043 ± 0.016 vs. 0.060 ± 0.063%/h). A significant linear relationship existed between MPS 2.5 h after RE in hypoxia and mean arterial blood O(2) saturation during hypoxia (r(2) = 0.49, P = 0.04). Phosphorylation of p70S6K(Thr389) remained unchanged in hypoxia at rest but increased after RE in both normoxia and hypoxia (2.6 ± 1.2-fold and 3.4 ± 1.1-fold, respectively). Concentrations of the hypoxia-responsive mTOR inhibitor regulated in development and DNA damage-1 were unaltered by hypoxia or RE. We conclude that normobaric hypoxia does not reduce MPS over 3.5 h at rest but blunts the increased MPS response to acute RE to a degree dependent on extant SpO(2).     

The evolution of the reproductive system of Urodasys (Gastrotricha: Macrodasyida)

Macrodasyidan gastrotrichs are hermaphrodites with complex reproductive organs that function in sperm transfer and receipt, but homology among the organs of members of different clades remains undetermined, as does a broader understanding of evolutionary trends in the reproductive biology of macrodasyidans. In this study, we investigate the evolution of reproduction in Urodasys, a clade of 15 macrodasyidan species that shows variability in reproductive mode (hermaphroditic and parthenogenetic) and sexual anatomy. We use partial 18S rDNA sequence data from 30 specimens representing five described species, sequence data from one undescribed species in GenBank, and sequence data from a potentially new species found at Capron Shoal, Florida, to gain insight into the phylogeny of the clade and clarify evolutionary trends in reproductive modality. Based on a total of 33 specimens of seven potential species, we found that members of Urodasys can be separated into three clades reflective of different reproductive modalities: Clade I, species with paired male and female gonads but without accessory sexual organs; Clade II, species with a single left testis, paired ova, and accessory organs including a sclerotic stylet; and Clade III, parthenogenetic species without testes or accessory organs. In addition, we find that the potentially new species from Florida can form spermatophores, a condition shared with another species in Clade I. Herein, we describe this novel spermatophore‐bearing species and discuss the significance of spermatophore formation in the genus.     

Products of lipopolysaccharide-activated macrophages (tumor necrosis factor-alpha, transforming growth factor-beta) but not lipopolysaccharide modify DNA synthesis by rat trophoblast cells exhibiting the 80-kDa lipopolysaccharide-binding protein

Pregnancy losses from gram negative bacterial infections could be caused by direct effects of LPS on placental cells, or indirectly via LPS activation of macrophages in the uteroplacental unit. To evaluate those alternatives, LPS, LPS-activated peritoneal cells, conditioned medium from LPS-activated peritoneal cells, and some purified and recombinant molecules known to be secreted by activated macrophages were tested for their abilities to modify DNA synthesis by rat trophoblast cells. Three trophoblast cell lines derived from midgestation placentas of outbred and inbred rats were used for the experiments. Although the 80-kDa LPS-binding protein was demonstrated on trophoblast cells, LPS alone had no effect on the ability of trophoblast cells to synthesize DNA. In cocultures, trophoblast cell DNA synthesis was slightly enhanced by low concentrations of both unstimulated and LPS-activated peritoneal cells. At higher concentrations, LPS-activated cells caused significant inhibition of DNA synthesis by trophoblast cells. Conditioned media from LPS-activated peritoneal cells were highly inhibitory to trophoblast cell DNA synthesis. When specific molecules likely to be components of those media were tested, IL-1 was found to have a modest but reproducible stimulatory effect and PGE2 did not change trophoblast cell incorporation of [3H]TdR. In contrast, trophoblast cell DNA synthesis was markedly inhibited in a dose-dependent manner by both TNF-alpha and TGF-beta 1. No differences in the sensitivity of trophoblast cells from outbred and inbred rats were observed. Given the limitations of the experimental model system, the results suggest that in cases of infection by gram-negative bacteria LPS may have an adverse effect on pregnancy by stimulating resident macrophages to generate and release molecules that are inhibitory to trophoblast cell DNA synthesis.     

Isolation of a bacterium resembling Pirellula species from primary tissue culture of the giant tiger prawn (Penaeus monodon).

During attempts to establish tissue cultures from hepatopancreas, heart, and hemolymph of the giant tiger prawn (Penaeus monodon), using a medium including penicillin, streptomycin, and amphotericin B, bacterial contamination in the form of a sheet of growth attached to the tissue culture vessel was a persistent problem. Contaminant bacteria were teardrop-shaped cells arranged in rosettes, and electron microscopy revealed buds, crateriform structures, and the absence of a peptidoglycan layer in the cell wall, features characteristic of bacteria in the Planctomyces-Pirellula group, a phylogenetically distinct group of eubacteria. Two strains of contaminant bacteria were isolated in pure culture. Both exhibited morphology and antibiotic resistance consistent with their membership in the Planctomyces-Pirellula group (order Planctomycetales) of eubacteria. Tissue culture media for marine invertebrates may select for such bacteria if high concentrations of cell wall synthesis-inhibiting antibiotics are included.