Preribosomal ribonucleoprotein particles are a major component of a nucleolar matrix fraction

Biochemical and morphological studies were performed on Novikoff hepatoma ascites cell nucleolar matrix fractions prepared by deoxyribonuclease I digestion and high-molarity salt extractions essentially according to a published method [Berezney, R., & Buchholz, L. A. (1981) Exp. Cell Res. 20, 4995-5002]. The nucleolar matrix fraction was enriched in polypeptides of molecular mass of 28, 37.5, 40, 70, 72, 110 (protein C23), and 160 kDa, compared to the nuclear fraction in which polypeptides of molecular mass of 31, 33.5, 43.5, 46, 50, 56, and 59 kDa were predominant. About one-fourth of the protein, half of the RNA, and less than 4% of the DNA originally present in the nucleoli remained in the matrix fraction. Addition of single agents such as ethylenediaminetetraacetic acid, ribonuclease A, or mercaptoethanol during preparation had no significant effect on the polypeptide composition of the nucleolar matrix fraction. However, the combination of mercaptoethanol and ribonuclease A caused most of the RNA and protein to be removed, including protein C23 and the 160-kDa polypeptide, with polypeptides in the range of Mr 30 000-50 000 remaining. Electron microscopy of nucleolar matrix fractions revealed the presence of particles similar in size to the granular elements of nucleoli. However, when ribonuclease A and mercaptoethanol were included in the procedure, only amorphous material remained. Many proteins of nucleolar preribosomal RNP particles were also associated with the nucleolar matrix fraction. RNA from the nucleolar matrix fraction was enriched in sequences from 18S and 28S ribosomal RNA. These results indicate that preribosomal RNP particles are major constituents of a nucleolar matrix fraction prepared by the deoxyribonuclease I-high-molarity salt method.     

Quantitation of the Myelin-Associated Glycoprotein in Human Nervous Tissue from Controls and Multiple Sclerosis Patients

Myelin-associated glycoprotein (MAG) was measured by radioimmunoassay in the human CNS and peripheral nervous system (PNS). The level of MAG, expressed as ng/microgram of total protein, was approximately 20-fold higher in whole homogenates of cerebral white matter (4.7 +/- 0.60) than of peripheral nerve (0.12-0.28). MAG concentrations were only slightly higher in the isolated myelin fractions from these tissues: CNS myelin, 5.6 ng/microgram; PNS myelin, 0.37 ng/microgram. The levels of MAG were measured in nine plaques, periplaque regions, and areas of macroscopically normal-appearing white matter (NAWM) from six separate multiple sclerosis brains and compared with the levels of other myelin proteins in the same samples. MAG and other myelin proteins were reduced to very low levels in plaques. The levels of MAG and basic protein (BP) and the activity of 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) in periplaque areas were significantly lower than those in control white matter, and MAG and BP levels were also significantly reduced in NAWM. In a periplaque region and NAWM from the most rapidly progressing case of multiple sclerosis examined, the MAG content was between 30 and 35% of the control level, whereas BP and PLP levels and CNP activity were between 50 and 85% of control values. The reduction of MAG content in periplaque regions from all nine multiple sclerosis plaques examined was significantly greater than the reductions of BP level and CNP activity. In NAWM samples, the mean reduction of MAG content was also greater than the reductions of BP level and CNP activity, but the difference was only statistically significant in comparison to CNP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterisation of the arrestment responses of Trichogramma evanescens

Summary Contact kairomones and oviposition in a host egg stimulated arrestment behaviour in Trichogramma evanescens, characterised by a reduction in walking speed and increased turning. Previous oviposition experience did not influence a parasitoid's response to contact kairomones, but successive encounters with kairomone patches resulted in parasitoids habituating to the contact chemical. Oviposition on a kairomone patch did not reverse this habituation effect. It was concluded that contact kairomones and host eggs will both contribute independently to the duration of a patch visit. The selection of patches by T. evanescens will depend on its response to kairomones. Results from this study indicate that the application of contact kairomones to field crops will not necessarily increase the probability of parasitoids finding hosts.     

Distribution of nitrate assimilation between the root and shoot of legumes and a comparison with wheat

Legumes of the Phaseoleae ( Glycine max L. Merr., Phaseolus coccineus L., P. vulgaris L., Vigna radiata L. Wilczek and V. unguiculata L. Walp.), when grown on 10 m M nitrate, had a low in vitro nitrate reductase (NR) activity in the root compared to the shoot (<15%). In legumes of the Vicieae ( Cicer aerietinum L., Pisum sativum L. and Vicia faba L.), Genisteae ( Lupinus albus L.) and Trifolieae ( Medicago sativa L. and M. truncatula Gaertn.), 30–60% of their total NR activity was in the root. The Phaseoleae had a higher nitrate content in the shoot. Decreasing the nitrate supply increased the relative proportion of NR activity in the root of garden pea ( Pisum sativum ) and wheat but did not alter the predominantly leaf-based assimilation of nitrate in Phaseolus vulgaris. When in vitro NR activity of the pea shoot was compared with the in vivo NR activity and the rate of accumulation of reduced N by this tissue, similar values were obtained. In vitro NR activity of the wheat shoot was 5 times its in vivo NR activity and 12 times its rate of accumulation of reduced N.     

tert–butylhydroperoxide—Induced toxicity in isolated hepatocytes: Contribution of thiol oxidation and lipid peroxidation

Incubation of isolated rat hepatocytes with tert-butylhydroperoxide resulted in marked cytotoxicity preceded by intracellular glutathione depletion and extensive lipid peroxidation. Addition of antioxidants delayed, but did not prevent, this toxicity. A significant decrease in protein-free sulfhydryl groups also, occurred in the presence of tert-butylhydroperoxide; direct oxidation of protein thiols and mixed disulfide formation with glutathione were responsible for this decrease. The involvement of protein thiol depletion in tert-butylhydroperoxide–induced cytotoxicity is suggested by our observation that administration of dithiothreitol, which caused re-reduction of the oxidized sulfhydryl groups and mixed disulfides, efficiently protected the cells from toxicity. Moreover, depletion of intracellular glutathione by pretreatment of the hepatocytes with diethyl maleate accelerated and enhanced the depletion of protein thiols induced by tert-butylhydroperoxide and potentiated cell toxicity even in the absence of lipid peroxidation.     

Dramatic founder effects in Amerindian mitochondrial DNAs

Southwestern American Indian (Amerindian) mitochondrial DNAs (mtDNAs) were analyzed with restriction endonucleases and found to contain Asian restriction fragment length polymorphisms (RFLPs) but at frequencies very different from those found in Asia. One rare Asian HincII RFLP was found in 40% of the Amerindians. Several mtDNAs were discovered which have not yet been observed on other continents and different tribes were found to have distinctive mtDNAs. Since the mtDNA is inherited exclusively through the maternal lineage, these results suggest that Amerindian tribes were founded by small numbers of female lineages and that new mutations have been fixed in these lineages since their separation from Asia.     

Reexamination of the efficacy of vaccination against mousepox

Experiments were conducted to evaluate the efficacy of three strains of vaccinia virus, IHD-T, Lister and Wyeth, to immunize the BALB/cByJ mouse against infection with ectromelia virus. Mice vaccinated with any of the strains were protected for at least 12 weeks against clinically apparent disease when challenged with cage-mates infected with a virulent stain (NIH-79) of ectromelia virus. However, 4 to 8 weeks after vaccination mice were capable of transmitting virus to non-vaccinated cage-mates. The results are discussed within the context of the current practices for preventing and controlling ectromelia epizootics.     

Conditioned media from cultured cystic fibrosis fibroblasts inhibits Na/K ATPase activity

Conditioned culture media taken from fibroblast cell lines derived from skin biopsies of control or of patients with Cystic Fibrosis (CF) were incubated with membranes of rat submandibular glands. The Na/K - ATPase activity of these membranes was inhibited when treated with CF-media, including both ouabain sensitive and insensitive activities. However, the membrane associated Mg-ATPase, Ca-ATPase, and both basal and hormone-stimulated adenylate cyclase activities were relatively unaffected. Thus, a factor or factors produced by CF-fibroblasts was shown to be active in a cell-free system derived from an exocrine gland.     

Clearance rates of sessile rotifers: in vitro determinations

We measured laboratory clearance rates of 10 rotifer and one unidentified bryozoan species from 3 different lakes using ³²P labeled algae (Chlamydomonas) or yeast (Rhodotorula). Clearance rates for all rotifers fed yeast ranged from < 2.0 to > 260 µl · animal^–1 · h^–1 depending on species. The in vitro clearance rates of two sessile rotifers (Ptygura crystallina and P. pilula) were not significantly different from previously measured in situ rates (Wallace and Starkweather 1983). Clearance rates for 5 rotifers fed algae ranged from < 5.0 to > 90.0 µl · animal^–1 · h^–1. Ptygura beauchampi, P. crystallina, P. pilula, Floscularia conifera, and F. melicerta ingested both cell types but their clearance rates varied substantially among species and between cell types. There was a substantial time-dependent loss of 32P from formalin-fixed animals (Sinantherina socialis) awaiting processing. This loss stabilized at approximately 20 hours and was estimated to be about 40% of the initial ingested label. Clearance rates for the bryozoan fed yeast or algae were highly variable, ranging from < 1.0 to > 3 000 µl · animal^–1 · h^–1.     

Gibberellins in immature seeds and dark-grown shoots of Pisum sativum

Gibberellins (GAs) A₁₇, A₁₉, A₂₀, A₂₉, A₄₄, 2OH-GA₄₄ (tentative) and GA₂₉-catabolite were identified in 21-day-old seeds of Pisum sativum cv. Alaska (tall). These GAs are qualitatively similar to those in the dwarf cultivar Progress No. 9 with the exception of GA₁₉ which does not accumulate in Progress seeds. There was no evidence for the presence of 3-hydroxylated GAs in 21 day-old Alaska seeds. Dark-grown shoots of the cultivar Alaska contein GA₁, GA₈, GA₂₀, GA₂₉, GA₈-catabolite and GA₂₉-catabolite. Dark-grown shoots of the cultivar Progress No.9 contain GA₈, GA₂₀, GA₂₉ and GA₂₉-catabolite, and the presence of GA₁ was strongly indicated. Quantitation using GAs labelled with stable isotope showed the level of GA₁ in dark-grown shoots of the two cultivars to be almost identical, whilst the levels of GA₂₀, GA₂₉ and GA₂₉-catabolite were significantly lower in Alaska than in Progress No. 9. The levels of these GAs in dark-grown shoots were 10²- to 10³-fold less than the levels in developing seeds. The 2-epimer of GA₂₉ is present in dark-grown-shoot extracts of both cultivars and is not thought to be an artefact.Abbreviations cv cultivar - GA_n gibberellin A_n - GC gas chromatography - GC-MS combined gas chromatographymass spectrometry - HPLC high-pressure liquid chromatography - KRI Kovats retention index - MeTMSi methyl ester trimethylsilyl ether