Growth of Acinetobacter sp. strain HO1-N on n-hexadecanol: physiological and ultrastructural characteristics.

The growth of Acinetobacter sp. strain HO1-N on hexadecanol results in the formation of intracytoplasmic membranes and intracellular rectangular inclusions containing one of the end products of hexadecanol metabolism, hexadecyl palmitate. The intracellular inclusions were purified and characterized as "wax ester inclusions" consisting of 85.6% hexadecyl palmitate, 4.8% hexadecanol, and 9.6% phospholipid, with a phospholipid-to-protein ratio of 0.42 mumol of lipid phosphate per mg of inclusion protein. The cellular lipids consisted of 69.8% hexadecyl palmitate, 22.8% phospholipid, 1.9% triglyceride, 4.7% mono- and diglyceride, 0.1% free fatty acid, and 0.8% hexadecanol, as compared with 98% hexadecyl palmitate and 1.9% triglyceride, which comprised the extracellular lipids. Cell-associated hexadecanol represented 0.05% of the exogenously supplied hexadecanol, with hexadecyl palmitate accounting for 14.7% of the total cellular dry weight. Acinetobacter sp. strain HO1-N possesses a mechanism for the intracellular packaging of hexadecyl palmitate in wax ester inclusions, which differ in structure and chemical composition from "hydrocarbon inclusions" isolated from hexadecane-grown cells.     

Assignment of the porcine major histocompatibility complex to chromosome 7 by in situ hybridization

The major histocompatibility complex (SLA) of the domestic pig (Sus scrofa) was regionally mapped to 7p12----q12 by in situ hybridization with an SLA class I-specific recombinant DNA probe. This localization contradicts linkage data suggesting a possible assignment of the SLA locus to porcine chromosome 15.     

Large-conductance Ca2+-activated K+ channels in freshly dissociated smooth muscle cells

Freshly dissociated cells from the stomach muscularis of the toad Bufo marinus have been employed to carry out a systematic set of electrophysiological studies on the membrane properties of smooth muscle. The existence of Ca2+-activated K+ channels became apparent during the first studies under current clamp. In subsequent studies under voltage clamp, a Ca2+-activated. TEA-sensitive outward current was evident, and it was more than an order of magnitude larger than any other current observed in the cells. The channel responsible, at least in part, for this large outward current has been identified on the basis of single-channel records, and some of its main characteristics have been studied. It is similar in many respects to the large-conductance, Ca2+-activated K+ channel seen in other preparations. This channel has now been found in a considerable diversity of smooth muscle types.     

Interactions of the neurotoxic amine 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine with monoamine oxidases.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a thermal breakdown product of a meperidine-like narcotic used by drug abusers as a heroin substitute, produces Parkinsonian symptoms in humans and primates. The nigrostriatal toxicity is not due to MPTP itself but to one or more oxidation products resulting from the action of monoamine oxidase (MAO) on this tertiary allylamine. Both MAO A and B catalyse the oxidation of MPTP to the 1-methyl-4-phenyl-2,3-dihydropyridinium species (MPDP+), which undergoes further oxidation to the fully aromatic 1-methyl-4-phenylpyridinium species (MPP+). These bio-oxidations are blocked by selective inhibitors of MAO A and B. Additionally, MPTP, MPDP+ and MPP+ are competitive inhibitors of MAO A and B. The A form of the enzyme is particularly sensitive to this type of reversible inhibition. Both MAO A and B also are irreversibly inactivated by MPTP and MPDP+, but not by MPP+. This inactivation obeys the characteristics of a mechanism-based or 'suicide' process. The inactivation, which is accompanied by the incorporation of radioactivity from methyl-labelled MPTP, is likely to result from covalent modification of the enzyme.     

Isolation of low-copy-number sequences that neighbor satellite DNA in mammals

To investigate the role of satellite DNA in eukaryotic genomes, we isolated from an African green monkey (Cercopithecus aethiops) genomic library cloned segments containing the previously described deca-satellite linked to low-copy-number genomic sequences. Three such clones were obtained. The low-copy-number sequences in the three clones do not cross-hybridize suggesting that they derive from different genomic loci. The structure of one of the clones, λAMkA, is described in detail. Subcloned segments containing the low-copy-number sequences from λAMkA anneal to monkey, human and mouse genomic DNA. The subcloned probes were used to select clones containing homologous sequences from a second, independent monkey library as well as from human and mouse genomic libraries. Several of the newly isolated monkey clones hybridized to probes containing the species-specific deca- and -satellites, confirming the genomic association of the low-copy-number sequence in λAMkA with satellite DNA. Moreover, several of the human and mouse clones hybridized to species-specific human and mouse satellite DNAs, respectively. These experiments indicate that the low-copy-number sequence in λMkA and its association with satellite DNA is conserved in primates and rodents.     

Litter decomposing and ectomycorrhizalBasidiomycetes in an igapó forest

An igapó forest near the confluence of Rio Tarumã Mirim (Tarumãzinho) and Rio Negro has been studied. It is a typical ectotroph forest with a raw humus layer and suppressed litter decomposing activity by Higher (i.e., carpophore-producing) Fungi. The number of the latter is about one-fifth of that observed in the (anectotrophic) terra firme forest. All ectotrophically mycorrhizal fungi observed belonged in three families:Amanitaceae, Boletaceae, Russulaceae. Leguminosae are dominant, and of theseAldina latifolia andSwartzia cf.polyphylla were demonstrably ectomycorrhizal. The scarcity of mineral nutrients in the soils of igapó, campinarana and campina is overcome by direct cycling through ectomycorrhizae. This is in contrast to other black- and white-water inundated forest communities in Amazonia.Litter Decomposition and Ectomycorrhiza in Amazonian Forests3. Previous contributions seeSinger & Araujo (1979) andSinger & al. (1983).     

In vivo metabolic intermediates of phospholipid biosynthesis in Rhodopseudomonas sphaeroides

The in vivo metabolic pathways of phospholipid biosynthesis in Rhodopseudomonas sphaeroides have been investigated. Rapid pulse-chase-labeling studies indicated that phosphatidylethanolamine and phosphatidylglycerol were synthesized as in other eubacteria. The labeling pattern observed for N-acylphosphatidylserine (NAPS) was inconsistent with the synthesis of this phospholipid occurring by direct acylation of phosphatidylserine (PS). Rather, NAPS appeared to be kinetically derived from an earlier intermediate such as phosphatidic acid or more likely CDP-diglyceride. Tris-induced NAPS accumulation specifically reduced the synthesis of PS. Treatment of cells with a bacteriostatic concentration of hydroxylamine (10 mM) greatly reduced total cellular phospholipid synthesis, resulted in accumulation of PS, and stimulated the phosphatidylglycerol branch of phospholipid metabolism relative to the PS branch of the pathway. When the cells were treated with a lower hydroxylamine dosage (50 microM), total phospholipid synthesis lagged as PS accumulated, however, phospholipid synthesis resumed coincident with a reversal of PS accumulation. Hydroxylamine alone was not sufficient to promote NAPS accumulation but this compound allowed continued NAPS accumulation when cells were grown in medium containing Tris. The significance of these observations is discussed in terms of NAPS biosynthesis being representative of a previously undescribed branch of the phospholipid biosynthetic sequence.     

Immunoelectron microscopic studies of desmin (skeletin) localization and intermediate filament organization in chicken cardiac muscle

We studied the localization of desmin (skeletin), the major protein subunit of muscle-type intermediate filaments, in adult chicken cardiac muscle by high resolution immunoelectron microscopic labeling of ultrathin frozen sections of the intact fixed tissues. We carried out single labeling for desmin and double labeling for both desmin and either vinculin or alpha-actinin. In areas removed from the intercalated disk membranes, we observed desmin labeling between adjacent Z-bands in every interfibrillar space. Where these spaces were wide and contained mitochondria, convoluted strands of desmin labeling bridged between the periphery of neighboring Z-bands and the mitochondria. The intermediate filaments appeared to be organized in a more three-dimensional manner within the interfibrillar spaces of cardiac as compared to skeletal muscle. Near the intercalated disks, desmin labeling was intense within the interfibrillar spaces, but was completely segregated from the microfilament attachment sites (fascia adherens) where vinculin and alpha-actinin were localized. Desmin therefore appears to play no role in the attachment of microfilaments to the intercalated disk membrane. We discuss the role of intermediate filaments in the organization of cardiac and skeletal striated muscle in the light of these and other results.     

Interruption of an alpha-satellite array by a short member of the KpnI family of interspersed, highly repeated monkey DNA sequences.

We describe here the interruption of a cloned African green monkey alpha-satellite array by an 829-base-pair-long nonsatellite DNA segment. Hybridization experiments indicate that the sequences within the interruption are homologous to segments frequently found in the 6-kilobase-pair-long members of the KpnI family of long, interspersed repeats. These data confirm and extend earlier results suggesting that sequences common to the KpnI family can occur independently of one another and in segments of variable lengths. The 829-base-pair-long segment, which is termed KpnI-RET, contains a terminal stretch of adenosine residues preceded by two typical but overlapping polyadenylation sites. KpnI-RET is flanked by direct repeats of a 14-base-pair-long segment of alpha-satellite that occurs only once in the satellite consensus sequence. These structural features suggest that KpnI-RET was inserted into the satellite array as a movable element.