Effect of growth substrate on thermal death of thermophilic bacteria.

The heat sensitivity of gram-negative, hydrocarbon-utilizing thermophilic bacteria was altered by a change in growth substrate. Thermophilic strains CC-6, BI-1, and LEH-1, grown with acetate or n-heptadecane as the carbon source, had a higher survival rate when incubated 5 degrees C above their maximum growth temperature than cells of the same organism after growth on glucose or glycerol. There was a correlation between the growth substrated, heat resistance, and the ratios of cellular n-hexadecanoic acid/branched hexadecanoic acid and n-heptadecanoic acid/branched heptadecanoic acid. The bacterial cells that were more heat resistant had ratios of straight-chain/branched-chain fatty acids above 1.0, whereas the heat-sensitive cells had ratios below 0.6.     

SEM analysis of amphibian mesodermal migration

Summary At the end of gastrulation, the lateral mesoderm of amphibian embryos migrates ventrally between the ectoderm and the endoderm. The present study is an examination of the morphology of the leading cells of the mesodermal sheet and of the substratum over which they move (the inner surface of the ectoderm). The cells of the leading edge of the mesoderm are generally round, with very short and narrow flattened projections in the forward direction. These projections do not have a ruffled morphology, regardless of whether fixation is carried out before or after the ectoderm and mesoderm are dissected away from the endoderm. The inner surface of the ectoderm is covered with fine (450–500A) filamentous extracellular material and the ectoderm cells sometimes extend cytoplasmic processes (approx. 0.1 wide) onto the leading surface of the mesoderm or onto adjacent ectoderm cells. These studies indicate that the morphology of cell migration in amphibians is closer to that seen inFundulus than to that characteristic of chick or mammalian cells.This paper is dedicated to the memory of Mac V. Edds, Jr., who warmly encouraged the developmental biologists of the Pioneer Valley     

The snRNP E protein multigene family contains five pseudogenes with common mutations.

Sequence data from three previously-uncharacterized members of the snRNP E protein multigene family suggest that each is a non-transcribed processed pseudogene, even though one clone has the potential to code for a full-length protein with greater than 90% similarity to previously-characterized E protein cDNAs. Each of the newly-analyzed family members is without introns, contains a tract of polyadenylic acid residues, and is flanked by short direct repeats. In addition, the three sequences all contain point mutations that distinguish them from the E protein coding sequence. Seven point mutations are common to the three sequences described here and to two previously-described E protein pseudogenes. Although all of these mutations are transitions, only 5 of 7 could have been generated by deamination of methylated cytosines in inactive genes. Thus, the common mutations in the pseudogenes suggest an origin other than the expressed gene that we have described. Allelic variants for two of the pseudogenes were detected and repetitive elements are located near four of the five E protein pseudogenes that have been characterized.     

Macrophage dependence of peripheral sensory nerve regeneration: possible involvement of nerve growth factor.

The levels of NGF and NGF receptor mRNA, the degree of macrophage recruitment, and the ability of sensory and motor axons to regenerate were measured in C57BL/Ola mice, in which Wallerian degeneration following a nerve lesion is very slow. Results were compared with those from C57BL/6J and BALB/c mice, in which degeneration is normal. We found that in C57BL/Ola mice, apart from the actual lesion site, recruitment of macrophages was much lower, levels of mRNA for both NGF and its receptor were raised only slightly above normal, and sensory axon regeneration was much impaired. Motor axons regenerated quite well. These results provide in vivo evidence that macrophage recruitment is an important component of NGF synthesis and of sensory (but not motor) axon maintenance and regrowth.     

Rats chronically injected with urine from Huntington's chorea patients do not striatal damage

Rats were injected subcutaneously for 147 consecutive days with large volumes of urine from control subjects and from patients with Huntington's chorea (HC) in an effort to test for presence of a possible neurotoxic substance in HC. No evidence of illness was observed in animals treated with HC urine, and their behavior did not differ from animals treated with control urine. After rats were sacrificed, striatum was examined for the biochemical and neuropathological changes seen in human striatum in HC. No deficiency of γ-aminobutyric acid content, nor reduction in activities of glutamic acid decarboxylase and choline acetyltransferase, was found in striatum of rats chronically treated with HC urine. Also, no significant differences were found between striatum of control and experimental rats by light or electron microscopy. These results neither support for exclude the possibility of a neurotoxic mechanism for the neuronal loss characteristic of HC.     

The effect of histone hyperacetylation on the nuclease sensitivity and the solubility of chromatin

We have examined the effects of histone hyperacetylation upon nuclease digestion of nuclei and subsequent fractionation of chromosomal material in the presence of MgCl2. DNase I shows a maximum sensitivity towards hyperacetylated nuclei at somewhat elevated ionic strengths (150-200 mM NaCl), whereas micrococcal nuclease exhibits no specificity for acetylated nuclei over a broad range of ionic strengths. Fractionation in the presence of MgCl2 of hyperacetylated nuclei digested with micrococcal nuclease results in a substantial increase in the amount of soluble chromatin relative to that obtained with control nuclei. This increased yield of Mg2+-soluble chromatin results from the recruitment into this fraction of oligonucleosomes containing extremely hyperacetylated histones. These results suggest that contiguous nucleosomes containing highly acetylated histones may be altered in their ability to interact with themselves and with other nucleosomes.     

Cytochalasin B blocks sperm incorporation but allows activation of the sea urchin egg

Cytochalasin B (CB) (2 × 10⁻⁶ M) prevents the incorporation of sperm into the eggs of Lytechinus pictus and Strongylocentrotus purpuratus as judged by light and transmission electron microscopy (TEM). At lower concentrations of CB (2 × 10⁻⁷ M), sperm are successfully incorporated into the egg, but their migration in the area of the egg cortex is impaired. The site of action of CB on the sperm may be on the initial rotation of the sperm nucleus in the cortex; the subsequent migration is not affected by CB. Although sperm incorporation is prevented at the higher CB concentrations, the eggs become activated—as judged by cortical reaction, increased protein synthesis and increased respiration. These findings raise the concept that egg activation by sperm could result from some pre-fusion event and hence that sperm-egg fusion would not be a prerequisite for the triggering of development. An alternative hypothesis is that fusion occurs between the acrosome process membrane and egg membrane, but since CB has destroyed the integrity of the cortex actin, the fusion bridge is so weak that it cannot be maintained without some contractile or cytoskeletal support by the cortex. The sperm may activate the CB-treated egg in the same manner as pricking with a microelectrode sometimes does.     

Regulation of the immune response to tumor antigen. VIII. The effects of host specific anti-I-J antibodies on the immune response to tumors of different origin

The efficiency of in vivo therapy using alloantisera produced to interact specifically with I-J subregion encoded determinants has been investigated in two etiologically distinct syngeneic tumor systems, both of which have been shown to evoke suppressor T-cell host responses. Administration of 2 μl/day of anti-I-J^k alloantisera caused a significant reduction in the growth of the P815 methylcholanthrene (MCA)-induced mastocytoma or the 1316 ultraviolet (uv) radiation-induced fibrosarcoma in the syngeneic host. Inhibition of tumor growth with anti-I-J antibody treatment occurred in normal as well as in subcarcinogenically uv-treated hosts given the uv-induced 1316 fibrosarcoma, even though the normal host is capable of spontaneously rejecting the tumor graft in the absence of external manipulation. Evidence is also provided that the effects of anti-I-J antibody treatment are not due to direct interactions with the tumor cells, or to contaminating antiviral antibody activity within the antiserum. We have previously demonstrated the reduction of tumor growth in two antigenically distinct MCA-induced tumor systems (S1509a, SAI) using similar treatments. The data presented herein thus reinforce the possibility that such means of therapy may be beneficial to the treatment of a wide variety to tumor types where suppression represents a detrimental component of the host response, and may also provide some insight into the mechanisms underlying the effects of uv radiation on the immune response to tumor antigen.