Regulation of cytoplasmic mRNA prevalence in sea urchin embryos. Rates of appearance and turnover for specific sequences

Complementary DNA clones representing cytoplasmic poly(A) RNAs of sea urchin embryos were hybridized with metabolically labeled cytoplasmic RNA preparations and the rates of appearance and of decay for each transcript species were determined at the blastula-gastrula stage of development. The prevalence of the transcripts chosen for this study ranged, on average, from about one molecule per cell to a few hundred molecules per cell. The embryos were labeled continuously for 18 hours with [3H]guanosine, beginning at 24 hours post-fertilization. The amount of cytoplasmic [3H]poly(A) RNA that hybridized to each cloned sequence was determined and the specific activity of the [3H]GTP pool was measured in the same embryos. Rate constants for the entry of each transcript species into the cytoplasm, and for its decay were extracted from these data. The embryo transcript species identified by the cloned probes displayed a range of stabilities. Half-lives of only a few hours were measured both for a very rare sequence and for a moderately prevalent sequence. Other newly synthesized transcripts, including sequences that first appear during embryonic development, as well as sequences also represented in maternal RNA, are far more stable. We conclude that cytoplasmic RNA turnover rate is a major variable in the determination of the cytoplasmic level of expression of embryo genes. The entry rates of the transcripts into the cytoplasm also varied, from a few molecules per embryo per minute to several hundred, depending on the sequence. By comparing the mass of transcripts of a given sequence in the embryo to the mass of transcripts of that sequence accumulating as a result of new synthesis, the point at which embryo transcription accounts for the major fraction of the cytoplasmic molecules could be estimated. This calculation showed that for some sequences maternal transcripts persist well beyond gastrulation, while other embryo poly(A) RNA species are largely the product of transcription in the embryo nuclei from the blastula stage onwards. There is no single stage at which all maternal transcripts are suddenly replaced by newly synthesized embryo transcripts. Primary transcription rates were measured for two sequences by determining accumulation of label in these RNA species soon after addition of [3H]guanosine to the cultures. Comparing these rates to the cytoplasmic entry rates, we did not detect a significantly greater nuclear transcription of the sequence homologous to the cloned probe.

Metabolism of vitamin K and vitamin K 2,3-epoxide via interaction with a common disulfide

The effects of thiols and sulfhydryl blocking reagents on the reduction of vitamin K to vitamin K hydroquinone and vitamin K 2,3-epoxide to vitamin K and vitamin K hydroquinone catalyzed by rat hepatic microsomes were investigated to determine the mechanism(s) for these reactions. Both vitamin K and vitamin K 2,3-epoxide reductions were catalyzed more effectively with dithiols than with monothiols as the reductant. The sulfhydryl reagent N-ethylmaleimide (NEM) inhibited vitamin K and vitamin K 2,3-epoxide reduction much more effectively when microsomes were initially treated with dithiothreitol (prereduced). In prereduced microsomes iodoacetamide was approximately half as effective an inhibitor of vitamin K and vitamin K 2,3-epoxide reduction as NEM, but in microsomes not prereduced it was more effective. Iodoacetic acid was ineffective as an inhibitor. Vitamin K or vitamin K 2,3-epoxide added to prereduced microsomes blocked subsequent inhibition by NEM of vitamin K and vitamin K 2,3-epoxide metabolism, respectively. Vitamin K added to prereduced microsomes also blocked inhibition by NEM of vitamin K 2,3-epoxide metabolism, and vitamin K 2,3-epoxide addition blocked inhibition by NEM of vitamin K metabolism. Vitamin K did not diminish the rate of vitamin K 2,3-epoxide metabolism, however, nor did vitamin K 2,3-epoxide diminish the rate of vitamin K metabolism. These data establish that exogenous thiol compounds promote the reduction of at least one protein disulfide which participates in the metabolism of vitamin K and vitamin K 2,3-epoxide. Presumably, the resultant sulfhydryl groups are reoxidized to the disulfide form during the metabolism of either vitamin which protects them from reaction with NEM.

Differential expression of the actin gene family of Strongylocentrotus purpuratus

Molecular probes that individually recognize the 3' nontranslated regions of six actin genes were utilized in RNA gel blot hybridizations to detect RNAs complementary to each gene in embryonic and adult tissues of Strongylocentrotus purpuratus. In addition the probes were used in DNA excess filter hybridizations to estimate the relative contribution of the different actin genes. All six genes produce relatively stable mRNAs, and each displays a characteristic and distinct pattern of expression. On the basis of their expression in the egg, early embryos, or in adult coelomocytes, it is concluded that genes termed CyI, CyIIa, CyIIb, CyIIIa, and CyIIIb encode cytoskeletal actin proteins. Actin gene M gives rise to mRNAs that are found only in tissues containing muscle. Actin genes CyI, CyIIa, CyIIb, and M are expressed in both adult and embryonic tissues, giving rise to transcripts 2.1-2.2 kb in length. Expression of genes CyIIIa and CyIIIb is confined to the embryo. Gene CyIIIa provides the major embryonic actin mRNA, which is 1.8 kb in length. Three of the cytoskeletal actin genes are linked over a 30-kb distance in the S. purpuratus genome. We show that the actin genes included in this linkage group are not coordinately expressed.

Sea urchin actin gene subtypes. Gene number, linkage and evolution

The actin gene family of the sea urchin Strongylocentrotus purpuratus was analyzed by the genome blot method, using subcloned probes specific to the 3' terminal non-translated actin gene sequence, intervening sequence and coding region probes. We define an actin gene subtype as that gene or set of genes displaying homology with a given 3' terminal sequence probe, when hybridized at 55 degrees C, 0.75 M-Na+. By determining the often polymorphic restriction fragment band pattern displayed in genome blots by each probe, all, or almost all of the actin genes in this species could be classified. Our evidence shows that the S. purpuratus genome probably contains seven to eight actin genes, and these can be assigned to four subtypes. Studies of the expression of the genes (Shott et al., 1983) show that the actin genes of three of these subtypes code for cytoskeletal actins (Cy), while the fourth gives rise to a muscle-specific actin (M). We denote the array of S. purpuratus actin genes indicated by our data as follows. There is a single CyI actin gene, two or possibly three CyII genes (CyIIa, CyIIb, and possibly CyIIc), three CyIII actin genes (CyIIIa, CyIIIb, CyIIIc), and a single M actin gene. Comparative studies were carried out on the actin gene families of five other sea urchin species. At least the CyIIa and CyIIb genes are also linked in the Strongylocentrotus franciscanus genome, and this species also has a CyI gene, an M actin gene and at least two CyIII actin genes. It is not clear whether it also possesses a CyIIc actin gene, or a CyIIIc actin gene. The genome of a more closely related congener, Strongylocentrotus dröbachiensis, includes 3' terminal sequences suggesting the presence of a CyIIc gene. In S. franciscanus and S. dröbachiensis the first intron of the CyI gene has remained homologous with intron sequences of both the CyIIa and CyIIb genes, indicating a common origin of these three linked cytoskeletal actin genes. Of the four S. purpuratus 3' terminal subtype probe sequences only the CyI 3' terminal sequence has been conserved sufficiently during evolution to permit detection outside of the genus Strongylocentrotus. An unexpected observation was that a sequence found only in the 3' untranslated region of the CyII actin gene in the DNA of S. dröbachiensis and S. purpuratus is represented as a large family of interspersed repeat sequences in the genome of S. franciscanus.

Thiazides III. Evidence of dose proportionality of hydrochlorothiazide 25, 50 and 100 mg tablets

A pilot bioavailability study was carried out where two subjects each were administered a dose of 25, 50 or 100 mg of commercially available hydrochlorothiazide (HCT) tablets. Plasma and urine samples were collected and analyzed by HPLC. A maximum plasma concentration of 50-285 ng/ml was reached in 1-2 hours, and plasma levels declined very rapidly with a half life of about 2-4 hours during first 12 hours period. The AUC was calculated using the trapezodial rule. A linear correlation was seen between the dose administered and amount of drug excreted.

Effects of nucleoside analogues on the expression of herpes simplex type 1-induced proteins

Exposure of herpes simplex virus type 1 (HSV-1)-infected Vero cells to the nucleoside analogues 5-iodo-5'-amino-2',5'-dideoxyuridine (AIdUrd), 5-iodo-2'-deoxyuridine (IdUrd) or 5'-amino-2',5'-dideoxythymidine (5'-AdThd) resulted in altered expression of HSV-1-induced proteins. Infected cell proteins (ICPs) synthesized in the presence of the nucleoside analogues were compared by sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis to ICPs from non-drug-treated cells and it was found that there was no effect on HSV-1-induced alpha proteins but beta and gamma proteins were reduced as much as 60%. There were three exceptions: ICP 35 (Mr = 46,000) and ICP 39 (Mr = 36,000) were not reduced and ICP 36 (Mr = 42,000) was increased during drug treatment. Progeny virions were isolated from drug-treated infected Vero cells and were compared to progeny isolated from control cells with respect to their polypeptide make-up and for their ability to induce HSV-1 proteins in non-drug-treated Vero cells. The progeny virus from drug-treated cells exhibited altered protein patterns on SDS-polyacrylamide gels with respect to control HSV-1. The progeny virions from AIdUrd- or IdUrd- but not from 5'-AdThd-treated cells were defective in their abilities to induce proteins upon subsequent infection of non-drug-treated Vero cells. Two unusual phosphoproteins were detected; one with an apparent molecular weight of 30,000 was induced by progeny virus from AIdUrd-treated cells and another at approximately 69,000 was induced by progeny virus from 5'-AdThd-treated cells.

Design and performance of a field exposure system for evaluation of the ecological effects of SO2 on native grassland

We describe the design and performance of two replicate field exposure systems for evaluating the ecological effects of chronic SO2 exposure on 0.5 ha plots of native Montana grassland. The SO2 was supplied at a constant rate to each plot through a network of 2.5-cm inside diameter aluminum pipes set parallel to and approximately 0.7 m above the ground with 0.8-mm SO2 release holes at 3-m intervals. The resulting SO2 concentrations on the plots varied with micrometeorological conditions. Fumigations were essentially continuous from April through October for 5 yr on one set of four plots and for 4 yr on another set of four plots. Frequency distributions of SO2 concentrations were approximately log-normal and qualitatively similar to those from various area and point sources. The diurnal pattern of SO2 concentrations was strongly correlated with the reciprocal of windspeed. Nighttime concentrations averaged almost double daytime concentrations. The diurnal concentration pattern resembled an area source more closely than a point source, a direct result of using constant SO2 source strength. Plume strikes could be simulated by turning the system on only during pre-specified meteorological conditions. Similarly, seasonal variations in area source concentrations could be simulated by varying source strength on the plots. The data from 5 years use of the system indicate that the fine-scale behavior of SO2 concentrations would be realistic.

Incorporation of E-5-(2-halovinyl)-2'-deoxyuridines into deoxyribonucleic acids of herpes simplex virus type 1-infected cells

E-5-(2-Bromovinyl)-2'-deoxyuridine (BrvdUrd) and E-5-(2-iodovinyl)-2'-deoxyuridine (IvdUrd) are among the most potent and selective inhibitors of herpes simplex virus type 1 (HSV-1) replication. To elucidate the site of inhibition, we examined whether the halovinyl analogs are incorporated into DNA using two approaches. (i) In assays with purified DNA polymerases omitting dTTP from the reaction system, addition of either BrvdUTP or IvdUTP increased the polymerization reaction, indicating that these two analog triphosphates can be alternate substrates. (ii) When HSV-1-infected Vero cells were grown in the presence of either BrvdUrd or IvdUrd, there was an increase in the density of both the viral and cellular DNA. The viral DNA had 40% of its thymidine moiety substituted by IvdUrd when the concentration of [125I]IvdUrd was 24 microM (in the absence of added thymidine). At 30 microM BrvdUrd and 1 microM [2-14C]thymidine, the viral DNA had only 11% of its thymidine moiety substituted by BrvdUrd, presumably because of the presence of added thymidine. Following digestion of [125I]IvdUrd-substituted DNA with DNase 1, venom phosphodiesterase, and alkaline phosphatase, the radioactivity co-migrated with nonradioactive IvdUrd in thin layer chromatography. Under similar conditions, no detectable incorporation of either [125I]IvdUrd or BrvdUrd into mock-infected Vero cell DNA was observed. Thus, IvdUrd and BrvdUrd are incorporated into DNA of HSV-1 infected cells but not into DNA of uninfected cells.

Anterior interbody fusion in fractures and fracture-dislocations of the spine

Twenty-five cases of unstable fractures and fracture-dislocations of the spine are reviewed. They were treated at the Catholic Medical College and Centre in a 3-year period, 1975 to 1978. 1. Eleven of the 25 patients were treated by anterior interbody fusion performed at 6 to 8 weeks from injury or initial surgery. 2. Eleven patients had neurological deficits, 3 with incomplete lesions and 8 with complete lesions. Open reduction and decompression laminectomies were performed on patients having neurological deficits prior to anterior interbody fusion. Two patients with incomplete paraplegia showed marked neurological recovery whilst one with complete paraplegia regained some sensation. 3. Solid clinical fusion was obtained in all but one patient within four months of interbody fusion. 4. Amongst the 18 patients with kyphosis at the time of admission 10 had a final improvement of their kyphosis ranging from 3 to 10 degrees (average 6 degrees). Three had no change and 5 demonstrated a mild increase of kyphosis (average 4 degrees). 5. Pain was relieved in 21 patients out of 25. The advantages of this technique include effective stabilization, prevention of late deformity and relatively early mobilization without internal fixation.

Primary structure, gene organization and polypeptide expression of poliovirus RNA

The primary structure of the poliovirus genome has been determined. The RNA molecule is 7,433 nucleotides long, polyadenylated at the 3' terminus, and covalently linked to a small protein (VPg) at the 5' terminus. An open reading frame of 2,207 consecutive triplets spans over 89% of the nucleotide sequence and codes for the viral polyprotein NCVPOO. Twelve viral polypeptides have been mapped by amino acid sequence analysis and were found to be proteolytic cleavage products of the polyprotein, cleavages occurring predominantly at Gln-Gly pairs.

Effect of acetylcholine on the norepinephrine-induced positive chronotropy and increase in cyclic nucleotides of isolated rabbit sinoatrial node

Transmural stimulation of, or application of nicotine to, the isolated rabbit sinoatrial (SA) node resulted in initial negative and late positive chronotropy. Simultaneous application of acetylcholine and norepinephrine produced a similar biphasic chronotropic effect. These procedures produced an initial increase in cyclic guanosine 3':5'-monophosphate (cyclic GMP) and a delayed elevation in cyclic adenosine 3':5'-monophosphate (cyclic AMP). The initial and late effects on rate and nucleotide levels were inhibited by pretreatment with atropine and propranolol, respectively. Pretreatment with atropine shortened the time of maximum increase in cyclic AMP level and heart rate from 3 to 1 minute after the simultaneous application of acetylcholine and norepinephrine and enhanced the positive chronotropic effect. Physostigmine prolonged the duration of the increase in cyclic GMP and negative chronotropic effect after the simultaneous application. These results suggest that when acetylocholine and norepinephrine are present simultaneously in the SA node region, the former interacts predominantly with muscarinic receptors and stimulates the cyclic GMP system, which in effect delays the cyclic AMP elevation and reduces the positive chronotropic effect of norepinephrine. However, these effects of acetylcholine cannot be explained solely on the basis of changes in the cyclic GMP level, because sodium nitroprusside produced a marked elevation of the cyclic GMP levels without decreasing the heart rate and did not affect the norepinephrine-induced increase in pacemaker rate and cyclic AMP. Sodium nitroprusside may affect cyclic GMP pools other than those susceptible to acetylcholine. These cyclic GMP pools may not exert chronotropic effects.

Effect of cholera enterotoxin on pacemaker rate and cyclic adenosine 3':5'-monophosphate in isolated rabbit sinoatrial node

The positive chronotropic effect of cholera enterotoxin on isolated rabbit sinoatrial (S-A) node was investigated. This toxin produced a time and dose-related increase in pacemaker rate and cyclic adenosine 3':5'-monophosphate (cyclic AMP) levels and shifted to the left the dose-response curves of norepinephrine on the pacemaker rate and cyclic AMP content in the S-A node. Thus, the sensitivity of the S-A node to norepinephrine was increased by the toxin. These effects of the toxin were not blocked by propranolol. There was a linear relation between the increases in pacemaker rate and cyclic AMP content after application of both the toxin and norepinephrine. However, the slope of the regression line relating pacemaker rate to cyclic AMP level differed with these two agents. These results suggest that cholera enterotoxin increases pacemaker rate with activation of the adenylate cyclase system in the S-A node, but the mechanism differs from that of norepinephrine.

Selective toxicity of purine deoxynucleosides for human lymphocyte growth and function

A role for the enzymes adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) and purine-nucleoside phosphorylase (purine-nucleoside:orthophosphate ribosyl-transferase, EC 2.4.2.1) in the functional maturation of lymphoid cells has been revealed by the association of inherited deficiencies of these enzymes and profound immune deficiency. Previous studies have suggested that the selective toxicity for lymphocytes may be mediated by the accumulation of toxic deoxynucleoside metabolites, likely through the action of specific kinases enriched in lymphoid cells. In order to study possible mechanisms whereby lymphocyte function may be impaired in these disorders, we have studied the effect of nucleosides and their deoxy analogues on both T and B lymphocyte growth and function. In the presence of deoxyguanosine, there was marked inhibition of T lymphoblast growth, phytohem-agglutinin-induced cell proliferation, and T suppressor cell activity. T helper cell activity and the differentiation of B cells to an antibody-secreting stage were unaffected. Deoxyadenosine was much less inhibitory, but in the presence of an inhibitor of adenosine deaminase, its effects on lymphocyte growth and function were markedly potentiated. The addition of deoxycytidine prevented deoxyadenosine toxicity in all assays, whereas it only interfered with deoxyguanosine effects on T lymphoblast growth. These studies provide some initial understanding for the selective loss of specific lymphocyte functions in individuals with inborn errors of purine metabolism.

Protein aggregation in C-phycocyanin. Studies at very low concentrations with the photoelectric scanner of the ultracentrifuge

Solutions of C-phycocyanin of very low concentrations were examined by sedimentation-velocity studies in the Spinco model E ultracentrifuge equipped with a photoelectric scanning system and a monochromator. At sufficiently low concentrations complete disaggregation from the hexamer to the monomer was observed. The equilibrium constant of monomer to hexamer was estimated to be approx. 10(30). For studies of aggregation over the complete range of concentration, C-phycocyanins from Phormidium luridum and Lyngbya sp. were used. Sedimentation-velocity studies at high concentration with schlieren optics are reported for C-phycocyanins from Anabaena variabilis and Lyngbya sp. The pH-dependence of aggregation and the temperature-dependence of trimer-hexamer equilibrium for phycocyanins from these algae were found to be similar to those of other C-phycocyanins. The principal feature of the pH-dependence is the dominance of hexamers at the isoelectric point. Increasing temperature increased the amount of hexamer and decreased the amount of trimer.