Enumeration of chlorine-stressed organisms with acridine orange 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride (AOINT)

Direct microscopic enumeration ofEnterobacter cloacae with the acridine orange 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride technique (AOINT) was compared with spread plate counts on nonselective media to establish the usefulness of the former technique in the enumeration of chlorine-stressed cells. Results indicate that the techniques are comparable when the organisms are not stressed. However, AOINT is more sensitive than are plate counts in the detection of chlorine-stressed cells.     

Occurrence of diphthamide in archaebacteria

We examined the nature of the diphtheria toxin fragment A recognition site in the protein synthesis translocating factor present in cell-free preparations from the archaebacteria Thermoplasma acidophilum and Halobacterium halobium. In agreement with earlier work (M. Kessel and F. Klink, Nature (London) 287:250-251, 1980), we found that extracts from these organisms contain a protein factor which is a substrate for the ADP-ribosylation reaction catalyzed by diphtheria toxin fragment A. However, the rate of the reaction was approximately 1,000 times slower than that typically observed with eucaryotic elongation factor 2. We also demonstrated the presence of diphthine (the deamidated form of diphthamide, i.e., 2-[3-carboxyamide-3-(trimethylammonio)propyl]histidine) in acid hydrolysates of H. halobium protein in amounts comparable to those found in hydrolysates of similar preparations from eucaryotic cells (Saccharomyces cerevisiae and HeLa). Diphthine could not be detected in hydrolysates of protein from the eubacterium Escherichia coli. Whereas both archaebacterial and eucaryotic elongation factors contain diphthamide, they differ importantly in other respects.     

Genetic Analysis of Murine Arylsulfatase C and Steroid Sulfatase

SWR/J mice possess two- to threefold higher 4-methylumbelliferyl sulfate (4MUS), dehydroepiandrosterone sulfate (DHEAS) and estrone sulfate (E1S) sulfatase activities in liver and kidney extracts than do A/J mice. These interstrain activity differences are maintained throughout the 6- to 45-day postnatal period. Characteristics of the hepatic activities of SWR/J mice suggest that all three activities reside in the same enzyme. Biochemical properties of the SWR/J and A/J enzyme were not significantly different. Expression of hepatic enzyme activity is subject to regulation by an autosomal locus possessing two alleles with additive effects. Postnuclear E1S- and DHEAS-sulfatase activities are primarily microsomal. Although postnuclear hepatic 4MUS-sulfatase activity is predominantly microsomal, renal activity is primarily nonmicrosomal. Only that portion of 4MUS-sulfatase occurring in cell membranes appears capable of hydrolyzing E1S and DHEAS. The hepatic- and renal-specific subcellular distributions of 4MUS-sulfatase activity may reflect tissue differences in enzyme processing. Renal 4MUS-sulfatase activity is also controlled by an autosomal gene with two alleles having additive effects. Positive correlation between hepatic and renal 4MUS-sulfatase activities indicates that both activities are most likely influenced by the same gene.     

The differentiation of glial cells and glia limitans in organ cultures of chick spinal cord

Summary Differentiation of glial cells and the glia limitans in organ cultures of chick spinal cord explanted at early neural tube stages, alone or with adjacent tissues, was studied by electron microscopy. Oligodendrocytes and astrocytes comparable to those seen in the chicken in vivo were observed, mainly in areas of good neuronal differentiation. A glia limitans with basal lamina, comparable to that in vivo, was found when spinal cord was bordered by normally adjacent tissues. When it was surrounded by vitelline membrane only, a characteristic limiting layer of glial processes, but no basal lamina, was seen. Contact with a filter membrane (Millipore) elicited excessive differentiation of glial filaments and modified cell fine structure; no glia limitans was formed. Supported by Grant 5 RO 1 NB 0637 from the United States Public Health Service.     

Time of origin of Mauthner's neuron in Xenopus laevis embryos

The time of the last DNA replication of the Mauthner's neuron precursor cell has been investigated using radioautography. Embryos of Xenopus laevis were labeled at different stages of early development by single microinjections of tritiated thymidine. Labeling times were designed to cover the entire period of development between gastrula and hatching stages. The embryos were fixed at later stages (41 to 44, according to Nieuwkoop and Faber, 1967), when the Mauthner neuron can be readily distinguished by its characteristically large size and large nucleolus.Mauthner neurons of embryos which received tritiated thymidine from stage 10 (beginning of gastrulation) to stage 12 (advanced gastrula, medium yolk plug) were always labeled. Those embryos which received the isotope at or after stage $\text{12}\text{1}\text{2}$ (advanced gastrula, small yolk plug) were never found labeled. These results imply that the last DNA replication of the cell destined to give rise to the Mauthner neuron occurs during the last gastrula stages. This last DNA replication immediately proceeds the time of the so-called “histogenetic determination” of the Mauthner neuron proposed to correspond to stage 13 (slit blastopore) by Stefanelli (1951).Therefore it appears that the developmental program of the Mauthner neuron involves a remarkably early cessation of DNA replication closely followed by histogenetic determination. This is the earliest known event of this type for a specific, well characterized neuron in the amphibian embryo.     

Combination Chemotherapy using L-Asparaginase,Daunorubicin, and Cytosine Arabinoside in Adults with Acute Myelogenous Leukaemia

Cytosine arabinoside and daunorubicin used in an intensive intermittent regimen have been shown to be an effective combination for the induction of complete remissions in 14 out of 23 adult patients with acute myelogenous leukaemia. This gives an overall complete remission rate of 60%. A further patient had a good partial remission. The addition of L-asparaginase to the regimen has not increased the incidence of remission and there were more side effects in the L-asparaginasetreated group. Of the 10 patients treated with L-asparaginase in addition to cytosine arabinoside and daunorubicin, five achieved a complete remission. Of the 13 patients treated with cytosine arabinoside and daunorubicin without L-asparaginase, nine achieved a complete remission and one a good partial remission.     

Primate evolution of a human chromosome 1 hypervariable repetitive element

Summary The clone designated hMF #1 represents a clustered DNA family, located on chromosome 1, consisting of tandem arrays displaying a monomeric length of 40 bp and a repetition frequency of approximately 7×10³ copies per haploid genome. The sequence hMF #1 reveals multiple restriction fragment length polymorphisms (RFLPs) when human genomic DNA is digested with a variety of 4–6-bp recognition sequence restriction enzymes (i.e., Taq I, Eco RI, Pst I, etc.). When hamster and mouse genomic DNA was digested and analyzed, no cross-species homology could be observed. Further investigation revealed considerable hybridization in the higher primates (chimpanzee, gorilla, and orangutan) as well as some monkey species.The evolutionary relationship of this repetitive DNA sequence, found in humans, to that of other primates was explored using two hybridization methods: DNA dot blot to establish copy number and Southern DNA analysis to examine the complexity of the RFLPs. Homology to the hMF #1 sequence was found throughout the suborder Anthropoidea in 14 ape and New and Old World monkey species. However the sequence was absent in one species of the suborder Prosimii. Several discrepancies between established evolutionary relationships and those predicted by hMF #1 exist, which suggests that repetitive elements of this type are not reliable indicators of phylogenetic branching patterns. The phenomenon of marked diversity between sequence homologies and copy numbers of dispersed repetitive DNA of closely related species has been observed inDrosophila mice,Galago, and higher primates. We report here a similar phenomenon for a clustered repeat that may have originated at an early stage of primate evolution.     

Enhancement of habitat heterogeneity and species richness on rocky shores inundated by sand

Summary Many rocky shores are subject to periodic inundation by sand, which is often thought to reduce species richness by eliminating organisms intolerant of sand scour or sand smothering. However, regular disturbance (e.g. inundation) should promote richness by preventing the development of low diversity climax communities. A study of faunal richness on 10 regularly inundated shores showed that inundation does promote richness, but by increasing habitat heterogeneity. Some species are excluded from parts of the shore by sand, but because of the patchiness of sand deposits they are rarely excluded from the entire shore. Other species are found only on rocks associated with sand, while typically sandy shore animals occur in the sand deposits themselves. Total richness (281 species) was greater than for local noninundated shores and sandy beaches combined.