Evidence for an Adenovirus Type 2-Coded Early Glycoprotein

We have identified an adenovirus type 2 (Ad2)-induced early glycopolypeptide with an apparent molecular weight of 20,000 to 21,000 (20/21K), as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The 20/21K polypeptide could be labeled in vivo with [(3)H]glucosamine. [(35)S]methionine- and [(3)H]-glucosamine-labeled 20/21K polypeptides bound to concanavalin A-Sepharose columns and were eluted with 0.2 M methyl-alpha-d-mannoside. The pulse-labeled polypeptide appeared as a sharp band with an apparent molecular weight of 21K, but after a chase it converted to multiple bands with an average molecular weight of 20K. This variability in electrophoretic mobility is consistent with glycosylation or deglycosylation of the 20/21K polypeptide. Analysis of the pulse and pulse-chase-labeled forms by using partial proteolysis indicated that the polypeptides were highly related chemically, but not identical. Most of the 20/21K polypeptide is localized in the cytoplasm fraction of infected cells lysed by Nonidet P-40. The 20/21K polypeptide and a 44K polypeptide, labeled with [(35)S]methionine or [(3)H]glucosamine in Ad2-infected human cells, were precipitated by a rat antiserum against an Ad2-transformed rat cell line (T2C4), but not by antisera against three other Ad2-transformed rat cell lines, or by serum from nonimmune rats. The partial proteolysis patterns of the 20/21K and the 44K polypeptides were indistinguishable, indicating that the two polypeptides are highly related, and suggesting that the 44K polypeptide might be a dimer of the 20/21K polypeptide. The 20/21K polypeptide was also induced in Ad2-early infected monkey and hamster cells. These results imply that the 20/21K polypeptide is synthesized in Ad2-infected human, monkey, and hamster cells, and in one but not all Ad2-transformed rat cells. Thus, the 20/21K polypeptide is probably viral coded rather than cell coded and viral induced.     

Effect of N,N-Dicyclohexylcarbodiimide on Acetylcholine Release from Torpedo Synaptosomes and Proteoliposomes Reconstituted with the Proteolipid Mediatophore

The mediatophore is a presynaptic membrane protein that has been shown to translocate acetylcholine (ACh) under calcium stimulation when reconstituted into artificial membranes. The mediatophore subunit, a 15-kDa proteolipid, presents a very high sequence homology with the N,N'-dicyclohexylcarbodiimide (DCCD)-binding proteolipid subunit of the vacuolar-type H(+)-ATPase. This prompted us to study the effect of DCCD, a potent blocker of proton translocation, on calcium-dependent ACh release. The present work shows that DCCD has no effect on ACh translocation either from Torpedo synaptosomes or from proteoliposomes reconstituted with purified mediatophore. However, using [14C]DCCD, we were able to demonstrate that the drug does bind to the 15-kDa proteolipid subunit of the mediatophore. These results suggest that although the 15-kDa proteolipid subunits of the mediatophore and the vacuolar H(+)-ATPase may be identical, different domains of these proteins are involved in proton translocation and calcium-dependent ACh release and that the two proteins have a different membrane organization.     

How predatory mites cope with the web of their tetranychid prey: a functional view on dorsal chaetotaxy in the Phytoseiidae

It has been proposed from behavioural observations that the ability of Phytoseiidae to penetrate the web is related to chaetotaxy. As phytoseiid species differ widely in chaetotaxy, as well as in their ability to cope with complex webs, this hypothesis was tested by studying relations between these two variables. In this paper we develop a simple method to quantify the degree to which the soma is protected from contact with the silk and apply it to phytoseiid species for which behavioural performance in the web is known from the literature. It is found that the better protected species experience less hinder from complex webs, such as produced byTetranychus spp. Moreover, they appear to be more successful in exterminating local populations ofTetranychus spp. Thus, setal patterns in the Phytoseiidae may well be a good indicator for selecting candidates for biological control ofTetranychus spp. Finally, we propose a parsimonious scenario for the evolution of dorsal chaetotaxy in the Phytoseiidae.     

Effect of imazaquin on absorption,translocation, and pattern of distribution of chlormequat chloride in winter wheat

The role of imazaquin in the absorption, translocation, and distribution of chlormequat chloride in CYCOCEL^* CL has been studied in winter wheat. Three treatments were applied to the 5th leaf of the main stem at growth stage 5 (Feekes Large scale): (1)¹⁴C-chlormequat chloride, (2) CYCOCEL^* CL containing¹⁴C-chlormequat chloride, and (3) CYCOCEL^* CL containing¹⁴C-imazaquin. Tracing of the radioactivity was followed in the treated leaf, main stem, tillers, and roots. Results showed that more than 85% of the radioactivity absorbed remained in the treated leaf. Ten days after the application of chlormequat chloride alone, 94.4% of the¹⁴C-chlormequat was found in the treated leaf, 2.9% in the main stem, 1.2% in the tillers, and 1.4% in the root system versus 88.2, 8.2, 2.1, and 1.4%, respectively, for the chlormequat chloride plus imazaquin treatment. It was concluded that imazaquin increases the mobility and the pattern of distribution of chlormequat chloride in the plant.     

Mutations within an intron and its flanking sites: Patterns of novel polypeptides generated by mutants in one segment of the cob-box region of yeast mitochondrial DNA

Summary We have undertaken a systematic examination of the polypeptides accumulating in thirteen (out of 23) mutants in the intron cluster box7 and its flanking clusters box2 and box9 of the cob-box (cytochrome b) region of the mitochondrial genome of Saccharomyces cerevisiae. We have subjected these polypeptides to fingerprint analysis, both sequential and in parallel, with two proteases in order to disclose sequence homologies and differences between the different novel polypeptides themselves, and between them and the wild type product of the gene, i.e. apocytochrome b. One of our aims has been to establish the existence of possible correlations between the nature of the novel polypeptides and the fine structure genetic map of that segment of the mitochondrial genome.Our results show that all box7 mutants accumulate the following set of polypeptides not seen in wild type cells: a) a characteristic set of large polypeptides consisting of three species: p56, p42 and p35 or p34.5; b) a polypeptide p23; c) a much shorter fragment (of which the apparent molecular weight varies from 12.5 to 13, according to the mutation) with the exception of two mutants; d) in addition, the majority accumulate in varying amounts a polypeptide p30 closely related to but not identical with apocytochrome b.Moreover only two box7 mutants accumulate a polypeptide in the range of mobilities corresponding to 25–27 Kd (referred to as class p26) while such a polypeptide is seen in all box9 and box2 mutants examined with one exception in box2.Only one mutant in box2 resembles box7 mutants with respect to criterion a), and no box2 or box9 mutants resemble box7 mutants with respect to criterion c); criteria b) and d) appear to apply equally well to mutants in all three clusters.Fingerprint analysis, carried out with polypeptides p56, p42, p35, p34.5, p30, p26, p23, discloses that a) The polypeptides belonging to the same class of mobility exhibit very similar if not identical sequences in various cases. b) These polypeptide classes, except p56, p42 and p26, share considerable sequence homologies with wild type apocytochrome b, perhaps encompassing 50% or more of the wild type sequences. b) Polypeptides belonging to the classes p42 and p26 exhibit less extensive but nevertheless significant homologies with the wild type sequence. c) Sequences in polypeptides belonging to class p56 are virtually indistinguishable from ones in cytochrome oxidase subunit I.The inferences from these findings are 1) one gene can produce a multiplicity of polypeptide products that share a common sequence at the promoter-proximal (N-terminal) portion, but diverge beyond these regions of homology. 2) Both the multiplicity of products in single mutants, and the protein structure found, argue against the divergent segments to be due to frameshift terminations, and instead suggest that the novel products are consequences of mRNA processing defects (excision and/or ligation) at and near intron regions. 3) Mutations at edges and the center of an intron can generate similar polypeptide patterns, i.e. produce analoguous mRNA processing defects. 4) Mutations in exons, at their boundary with introns, can produce polypeptide patterns indistinguishable from those at the neighbouring intron; they diverge and eventually become typically exonlike in mutants localized at increasing distances from the boundary. 5) Taken together these findings argue that pre-mRNA processing extends beyond the boundaries of the intron proper and that certain exonsequences participate in excision and ligation. 6) Accumulated pre-mRNAs, resulting from defects in splicing can be translated. 7) Product p56 is formally analogous to p23, as a faulty but highly conserved partial product of the wild type protein, the former of Cox I (oxi3 gene), the latter of the cob-box gene proper. Therefore both genes may utilize identical RNA processing elements which are affected by box7 mutations. 8) A small amount of product similar to p56 may accumulate even in some wild types but not in others. This observations suggests that in certain nuclear backgrounds RNA processing may be more error-prone than in others.Publication No. XXXX from the Department of Chemistry, Indiana UniversitySupported by Research Grant GM 12228 from the National Institute of General Medical Sciences, National Institutes of Health; recipient of Research Career Award K06 05060 from the same Institute.Supported by Délégation Générale à la Recherche Scientifique et Technique grant n⁰ 78-70341     

Differentiation of Ca2+ pumps linked to plasma membrane and endoplasmic reticulum in the microsomal fraction from intestinal smooth muscle

ATP promotes ⁴⁵Ca uptake by the microsomal fraction from the longitudinal smooth muscle of guinea-pig ileum and this uptake is stimulated by oxalate. As the microsomal fraction is made up of various subcellular entities, we examined the localization of the Ca²⁺-transport activity by density gradient centrifugation, taking advantage of the selective effect of digitonin (at low concentration) on the density of plasmalemmal elements. When the ⁴⁵Ca-uptake activity was measured in the absence of oxalate, its behavior in subfractionation experiments closely paralleled that of the plasmalemmal marker 5′-nucleotidase. In contrast, the additional Ca²⁺-transport activity elicited by oxalate behaved like NADH-cytochrome $\text{c}$ reductase, a putative endoplasmic reticulum marker. The endoplasmic reticulum vesicles constituted only a small part of the membranes in the microsomal fraction, which explains that their Ca²⁺-storage capacity was not detectable in the absence of Ca²⁺-trapping agent. Low digitonin concentrations selectively increased the Ca²⁺ permeability of the plasmalemmal vesicles. The two Ca²⁺-transport activities were further differentiated by their distinct sensitivities to K⁺, vanadate and calmodulin. In this respect, the oxalte-insensitive and oxalate-stimulated Ca²⁺-transport systems resembled, respectively, the sarcolemmal and sarcoplasmic reticulum Ca²⁺ pumps in cardiac and skeletal muscle, in accordance with the subcellular locations established by density gradient centrifugation.     

Pure red cell hypoplasia associated with long-arm deletion of chromosome 5

Summary A further instance of the new hematologic entity of pure red cell hypoplasia with deletion of the long arm of a chromosome 5(5q-) was seen in a 59-year-old white male. Examination of the bone marrow showed depressed erythroid cells with normal granulocytic and megakaryocytic precursors. Chromosomal analysis showed deletion of a chromosome 5 without any apparent translocation. This karyotype may be associated with acute leukemia.     

Separation of Linked Markers in Chinese Hamster Cell Hybrids: Mitotic Recombination Is Not Involved

A search for mitotic recombination was carried out using mutant subclones of cultured Chinese hamster ovary cells. Recombination events were sought between the linked loci specifying the enzymes hypoxanthine phosphoribosyl transferase and glucose-6-phosphate dehydrogenase. It was shown by fluctuation analysis that markers at these two loci co-segregate from doubly heterozygous pseudotetraploid hybrid cells more than 90% of the time. The minority class of segregants, which had lost one marker without losing the other, were genetically analyzed to distinguish between the possibilities of mitotic recombination and deletion of chromosomal material. Nine clones in which a linkage disruption had occured were studied, using further cell hybridization and segregation. In three cases, a recessive lethal loss of genetic information was indicated, suggesting the deletion mechanism. In six cases, it was demonstrated that no new linkage relationships had been established concomitant with linkage disruption. Thus, in all nine clones, the evidence indicated that mitotic recombination was not involved in the events that disrupted linkage between these two loci. If mitotic recombination takes place at all in this system, the rate must be less than about 10^-6 per cell per generation.