Analysis of unintegrated avian RNA tumor virus double-stranded DNA intermediates

Previous studies by Guntaka et al. have shown that the unintegrated DNA intermediates of avian RNA tumor virus replication can be readily isolated from cultures of the quail tumor line QT-6 at 1 day after infection. The intermediates include double-stranded linear and covalently closed circular DNA species. Using the analysis procedure of Southern together with previously obtained information regarding the sites of action of certain restriction endonucleases on avian sarcoma virus DNA, we have further characterized the viral DNA intermediates. Evidence is presented that, relative to the RNA genome, most of the linear species possess a direct terminal sequence redundancy equivalent to 0.5 X 10(6) +/- 0.3 X 10(6) daltons of double-stranded DNA. Some of the circular forms also possess a sequence redundancy of 0.21 X 10(6) +/- 0.03 X 10(6) daltons.

Specific site of action for single-strand specific nuclease on the double-stranded circular DNA intermediates of an avian RNA tumor virus

Circular viral DNA intermediates obtained from the quail tumor line, QT6, at 1 day after infection, were opened at one specific location by the single-strand specific nuclease, S1, of Aspergillus oryzae. This site was no longer accessible to the S1 nuclease when circles were first opened at another location with a restriction endonuclease.

Correlation of albumin production rates and albumin mRNA levels in livers of normal, diabetic, and insulin-treated diabetic rats

We have studied the effects of alloxan-induced diabetes and subsequent insulin replacement on albumin and total hepatic protein synthesis. Diabetes resulted in a reduction to approximately 20% of normal in albumin synthesis relative to the rate of total protein synthesis in vivo and a reduction to 10% in the absolute rate of albumin secretion by perfused livers. In contrast, the synthesis of total secretory protein and retained hepatic protein was affected to a lesser extent by diabetes. Treatment of diabetic rats with insulin restored rates of albumin and total hepatic protein synthesis to normal levels. The molecular basis of these alterations in albumin synthesis was investigated by examining albumin mRNA levels in livers of normal, diabetic, and insulin-treated diabetic animals. The level of albumin mRNA, whether assayed by cell-free translation or by hybridization to a specific complementary DNA probe, was markedly decreased in livers of diabetic animals and was restored to normal by insulin treatment. These changes occurred in parallel with changes in the rates of albumin secretion observed in perfused liver, suggesting that albumin mRNA content is the primary factor responsible for altering rates of albumin synthesis under these conditions.

Molecular basis of reduced albumin synthesis in Morris hepatoma 7777

The level of albumin mRNA in the normal Buffalo rat liver and Morris hepatoma 7777 was compared by molecular hybridization with albumin complementary DNA (cDNA) and translational assays. Albumin mRNA was found to be 10% of the total rat liver poly(A)-containing RNA population but reduced approximately fourfold in the case of Morris hepatoma 7777. An equivalent decrease of albumin mRNA activity in the hepatoma was detected by translation in a mRNA-dependent cell-free protein-synthesizing system. A proportional increase in total hepatoma poly(A)-containing RNA was not observed, indicating that there was a true fourfold reduction of albumin synthesis in the hepatoma. DNA excess hybridization with albumin cDNA did not reveal any apparent change in albumin gene frequency in the hepatoma compared to normal liver. Complementary DNA copies of total liver and hepatoma poly(A)-containing RNA were synthesized and employed in homologous and heterologous hybridization reactions. Analyses of these reactions showed a high degree of homology between the poly(A)-containing RNA of the liver and hepatoma, with some difference in the relative sequence abundancy. However, qualitative differences were detected in hepatoma 7777 consistent with the concept of alterations in the control of gene expression upon neoplastic transformation.

Restriction enzyme sites on the avian RNA tumor virus genome

Full-size single-stranded DNA transcripts of the avian RNA tumor virus genome were isolated from the products of the endogenous reaction of detergent-disrupted avian sarcoma virus particles. These transcripts were converted with Escherichia coli DNA polymerase I and 32P-labeled nucleoside triphosphates into labeled double-stranded DNA. The latter DNA was used to map the sites of action of seven restriction enzymes (Pvu I, Hpa I, Kpn I, Xba I, EcoRI, HindIII, and Xho I) on the genome of three strains of avian sarcoma virus (Prague B, Prague C, and Bratislava 77).

In vitro transcription of mouse mammary tumor virus RNA into DNA

The in vitro transcription of the B-type mouse mammary tumor virus RNA into DNA is similar to that obtained with certain C-type viruses: synthesis can be initiated on an RNA primer molecule approximately the size of a tRNA, and a unique linkage (rA-dC) exists between this primer and the DNA product.

Synthesis and secretion of rat albumin in vivo, in perfused liver, and in isolated hepatocytes. Effects of hypophysectomy and growth hormone treatment

The effects of hypophysectomy on albumin and total protein synthesis in rat liver were investigated in vivo, in perfused liver, and in isolated hepatocytes. In all systems, hypophysectomy resulted in about a 50% decrease in the rate of total protein synthesis and a 30 to 50% decrease in the relative rate of albumin synthesis. Albumin synthesis accounted for 11 to 13% of total protein synthesis in all normal systems, but represented only 5 to 8% of the total in all systems derived from hypophysectomized rats. Growth hormone, administered subcutaneously to hypophysectomized rats for 5 days, restored the relative rate of albumin synthesis to normal in vivo; however, only partial restoration was demonstrated in the in vitro systems. Perfused livers and isolated hepatocytes exhibited linear rates of total protein and albumin secretion for 3 h. The rate of albumin secretion by normal perfused livers was 3 times that of perfused livers from hypophysectomized animals, being 0.54 and 0.17 mg/g of liver/h, respectively. Isolated hepatocytes synthesized total protein and albumin at nearly the same rate as perfused livers. The amount of albumin secreted by cells derived from normal and hypophysectomized rats was 0.38 and 0.10 mg/ml of packed cells/h, respectively. Ribosome half-transit times for albumin and total liver protein were 1.6 to 1.7 min in isolated liver cells derived from both normal and hypophysectomized rats. Analysis by polyacrylamide gel electrophoresis showed no difference in the qualitative distribution of the proteins secreted by perfused livers and isolated hepatocytes.

Translation of albumin messenger RNA in a cell-free protein-synthesizing system derived from wheat germ

Purified rat liver albumin mRNA directed the synthesis of albumin in a mRNA-dependent cell-free protein-synthesizing system derived from wheat germ extracts. The [3H]leucine-labeled in vitro translation product reacted with antibodies specific for albumin and co-migrated with authentic 14C-labeled serum albumin during gel electrophoresis in the presence or absence of sodium dodecyl sufate. Higher concentrations of potassium and magnesium ions were required for the translation of albumin mRNA than for total liver mRNAs. These requirements were consistent for the purified albumin as well as when it was a component in the liver mRNA mixture. At the higher potassium or magnesium concentrations, only intact albumin molecules were synthesized, whereas lower concentrations of these ions caused the production of antibody-reactive fragments. These fragments were apparently the result of premature termination of peptide synthesis and not due to endogenous proteolytic activity.

Use of specific radioactive probes to study transcription and replication of the influenza virus genome

Specific radioactive probes have been obtained for both influenza virion RNA (vRNA) and for its complement (complementary RNA or cRNA): 32P-labeled complementary DNA (cDNA) synthesized with the avian sarcoma virus reverse transcriptase, and [125I]vRNA, respectively. From the kinetics of annealing of these two probes to RNA from canine kidney cells infected with the WSN strain of influenza virus, we have determined the average number of cRNA and vRNA sequences in the nucleus and cytoplasm as a function of time after infection. Immediately after infection, a small amount of vRNA is detected, presumably from the inoculum virus. As expected, the amount of cRNA is insignificant. During the first 1.75 h of infection, the most significant increase observed is in cRNA sequences. Most of these cRNA sequences are found in the cytoplasm, but a significant amount (30%) is found in the nucleus. During this time, a small but significant increase in vRNA is also detected in the nucleus and cytoplasm. From 1.75 to 2.75 h, the absolute amounts of both cRNA and vRNA increase, predominantly in the cytoplasm, with cRNA remaining as the majority species. Subsequently, the amount of vRNA increases with respect to cRNA and becomes the majority species. At 3.75 h, 95% of both cRNA and vRNA are found in the cytoplasm. Addition of actinomycin D at 1.75 h completely suppresses the subsequent ninefold increase in cRNA and does not have a significant effect on the subsequent 14-fold increase in cytoplasmic vRNA. This assay is also able to detect the cRNA produced as a result of primary transcription, operationally defined as the cRNA produced in the presence of 100 mug of cycloheximide per ml added at zero time of infection. Increases in cRNA in the presence of cycloheximide are detectable in both the nucleus and the cytoplasm. Addition of actinomycin D as well as cycloheximide at zero time completely suppresses the appearance of cRNA in the cytoplasm, whereas a large fraction (50%) of the increase in nuclear cRNA still occurs.

Isolation of rat liver albumin messenger RNA

Rat liver albumin messenger RNA has been purified to apparent homogeneity by means of polysome immunoprecipitation and poly(U)-Sepharose affinity chromatography. Specific polysomes synthesizing albumin were separated from total liver polysomes through a double antibody technique which allowed isolation of a specific immunoprecipitate. The albumin-polysome immunoprecipitate was dissolved in detergent and the polysomal RNA was separated from protein by sucrose gradient centrifugation. Albumin mRNA was then separated from ribosomal RNA by affinity chromatography through the binding of poly(U)-Sepharose to the polyadenylate 3' terminus of the mRNA. Pure albumin mRNA migrated as an 18 S peak on 85% formamide-containing linear sucrose gradients and as a 22 S peak on 2.5% polyacrylamide gels in sodium dodecyl sulfate. It coded for the translation of authentic liver albumin when added to a heterologous protein-synthesizing cell-free system derived from either rabbit reticulocyte lysates or wheat germ extracts. Translation analysis in reticulocyte lysates indicated that albumin polysomes were purified approximately 9-fold from total liver polysomes, and that albumin mRNA was purified approximately 74-fold from albumin polysomal RNA. The total translation product in the mRNA-dependent wheat germ system, upon addition of the pure mRNA, was identified as authentic albumin by means of gel electrophoresis and tryptic peptide chromatography.

Ultrastructural evidence for loss of the trophoblastic layer in the chorioallantoic placenta of Australian bandicoots (Marsupialia: Peramelidae)

In most marsupials, placentation involves only the yolk sac; however, in the bandicoot family, Peramelidae, a functional chorioallantoic placentation develops in addition (Hill, 1895, 1897, 1900; Flynn, '22, '23). This duality is viewed as having evolutionary significance because most eutheria have both placentae. Furthermore, the bandicoot trophoblast was reported to vanish from the chorioallantoic site in late gestation (Hill, 1897; Flynn, '23); whereas, the eutherian trophoblast is identifiable throughout later pregnancy and may act as an immunological barrier between maternal and fetal genotypes (Kirby '68). Thus we have re-examined this singular chorioallantoic placenta of the bandicoot in plastic sections with light and electron microscopy. A distinctive feature of the bandicoot placentation is the transformation of the uterine simple columnar luminal epithelium into a highly vascular lining composed almost entirely of discrete syncytial masses (homokaryons). Endometrial blood vessels penetrate among the homokaryons to create a rich network of large diameter capillaries at extremely superficial locations near the maternal surface. In the chorioallantoic placenta (7 mm to 10-11 mm crown-rump embryos) the microvillous surface of the maternal homokaryons interdigitates with the microvillous border of the fetal trophoblast with desmosomal interaction. This trophoblast consists of a single layer of tall columnar undifferentiated cells rich in ribosomes-polysomes, poor in cytoplasmic membranes, and with large nuclei that have distinct clumps of heterochromatin and conspicuous nucleoli. It is thus remarkable that these undifferentiated cells disappear as a recognizable layer later in gestation (12 mm crown-rump embryos). Flynn's hypothesis that the trophoblastic cells disappear by fusing with maternal syncytia gains support from the existence of two populations of nuclei in the syncytial masses only at the chorioallantoic site. One population is comparable to that occurring in the homokaryons pf the yolk sac placenta, i.e., pale staining nuclei with little heterochromatin and small peripheral nucleoli. However, the other nuclei resemble those of the trophoblast cells. Since the trophoblastic cells before their disappearance as a layer possess properties associated with potential for further differentiation, the possibility of fusion between the maternal homokaryons and fetal trophoblastic cells to form heterokaryons composed of two genotypes merits fur

Efficeint transcription of RNA into DNA by avian sarcoma virus polymerase

The DNAase digestion end-product of calf thymus DNA contains oligonucleotides that will function as primers for the efficient transcription into DNA of many naturally-occurring RNA's by purified avian sarcoma virus RNA-directed DNA polymerase. The labeled DNA transcripts so obtained are valuable as probes for molecular hybridization studies. Typical applications of the method include the efficient transcription into DNA of 18 and 28 S rRNA as well as the RNA's of avian sarcoma virus, polio virus, influenza virus, satellite tobacco necrosis virus and tobacco mosaic virus. In addition, when these primers are added to avian sarcoma virus particles that have been partially-disrupted with non-ionic detergent there is 6-fold stimulation of the endogenous RNA-directed DNA synthesis.

Effect of hypophysectomy on the synthesis of rat liver albumin

Hypophysectomy of adult rats results in approximately a 50% decrease in the rate of albumin synthesis relative to total liver protein synthesis. This decrease is accompanied by a proportional decline in the number of albumin-synthesizing polysomes, as determined by the binding of 125I-Labeled anti-albumin antibody, and indirect immunoprecipitation of [3H]leucine-labeled albumin-synthesizing polysomes. Furthermore, this decrease is associated with an equivalent reduction in the amount of total membrane-bound polysomes, whereas total free polysomes show little quantitative change. The size of the specific albumin-synthesizing polysomes, as well as the size of the total polysomes, however, appear to be the same following hypophysectomy as in the normal untreated animal. These observations are consistent with the finding that the relative amount of albumin mRNA activity also decreases approximately 50%, as assayed in a heterologous cell-free protein-synthesizing system using exogenous liver RNA prepared from either isolated polysomes or total liver homogenates. The decrease in albumin production in the hypophysectomized rat, therefore, is apparently the result of a reduction in the amount of active albumin mRNA. The concomitant decrease in albumin-synthesizing polysomes appears to reflect a similar reduction in the amount of total membrane bound polysomes. Thus, a major physiological defect in hypophysectomy may be a preferential decline in membrane-bount polysomes accompanied by a reduction in mRNA levels, which is represented by the decrease in albumin synthesis.

Cellular mechanisms involved in cyclic stromal renewal of the uterus. I. The opossum, Didelphis virginiana

At the close of a uterine cycle, the remodelling of the endometrial stroma of the North American opossum involves removal of extracellular material by macrophages. This study provides cytochemical and ultrastructural evidence which indicates that the laden macrophages are eliminated from the endometrium through emigration across the glandular and luminal epithelia. During diestrus or the early postpartum period, the abundant uterine glands relinguish their secretory function to acquire a transient function in the transportation of emigrating stromal cells. During the first three postpartum days endometrial regression in the stroma is marked by sudden appearance of monocytes, macrophages, lymphocytes, and plasma cells. Ultrastructural and cytochemical evidence indicates that the macrophages engulf the extracellular macromolecular material which, in the opossum, consists primarily of ground substance. Macrophages filled with ingested extracellular material aggregated beneath the glandular and luminal epithelia, where they acquire an extracellular coat that resembles the material of the basal lamina elsewhere. A fibroblast-like cell closely invests the macrophage at the time the extracellular material appears. Simultaneously, the secretory glandular epithelium is being converted to a highly ciliated one. Macrophages, often accompanied by lymphocytes, acquire intraepithelial positions in the glands. From here these stromal cells gain entrance to the glandular lumens. At this time the luminal contents are rich in acid phosphatase activity which most likely reflects the high lysosomal content of the emigrating macrophages. Evidence suggests that these intraluminal macrophages and lymphocytes are swept, by the recently differentiated ciliary lining, toward the glandular orifices and into the uterine cavity. It is hypothesized that this cyclic appearance and transepithelial elimination of macrophages is a cellular mechanism for removing large amounts of extracellular material without disruption of the endometrium.

Site on the RNA of an avian sarcoma virus at which primer is bound

In vitro transcription of the avian tumor virus RNA by RNA-directed DNA polymerase is initiated on the unique cellular 4S RNA. Previous studies have shown that on the average there is one such RNA primer hydrogen bonded to each viral 35S RNA. The present study confirms that finding and demonstrates that, at least for the majority of 35S RNA molecules, the primer is bound at a site close to the 5'-terminus.

Transcription of DNA from the 70S RNA of Rous sarcoma virus. I. Identification of a specific 4S RNA which serves as primer

The enzymatic transcription of DNA from the 70S RNA of Rous sarcoma virus (RSV) is initiated on the 3' terminus of a molecule of 4S RNA which is hydrogen bonded to the viral genome. We labeled this primer with radioactive deoxynucleotides, and demonstrated that its release from 70S RNA by thermal denaturation was accompanied by a reduction in the template activity of the viral RNA. Two-dimensional electrophoresis in polyacrylamide gels separated the 4S RNAs associated with the 70S RNA of RSV into approximately eight fractions, each of which appeared to contain a discrete species of tRNA. The RNA in one of these fractions served as the principal primer for initiation of DNA synthesis by both detergent-disrupted virions of RSV and purified RNA-directed DNA polymerase with RSV 70S RNA as template.

Transcription of DNA from the 70S RNA of Rous sarcoma virus. II. Structure of a 4S RNA primer

The 70S RNA of Rous sarcoma virus contains 4S RNAs which serve as primers for the initiation of DNA synthesis in vitro by the RNA-directed DNA polymerase of the virus. We purified these primers in three different ways-by isolation of the covalent complex between primer and nascent DNA, by differential melting of the 70S RNA, and by two-dimensional electrophoresis in polyacrylamide gels. The 4S RNAs purified by these procedures were homogeneous and possessed very similar if not identical nucleotide compositions and sequences. The RNAs were approximately 75 nucleotides long, had pG at the 5' terminus and CpCpA(OH) at the 3' terminus, and contained a number of minor nucleotides characteristic of tRNA. In contrast to most tRNA's, the primer lacked rTp and contained Gp (Psip, Psip, Cp) Gp (possibly in place of the characteristic sequence GprTpPsipCpGp). At least 50% of the 4S primers available on 70S RNA were utilized in a standard polymerase reaction in vitro.

Reproductive characteristics of wild native Australian Rattus (Rodentia: Muridae)

Reproduction in field populations of the five species and 13 of 14 subspecies of native Australian Rattus is compared, using both materials personally collected and museum specimens. We have separated each subspecies into juvenile and adult categories, the dividing point reflecting the approximate size at which sexual maturity is reached. Occurrence of pregnancies and juveniles, treated monthly, permit estimates of time and length of seasonal breeding for each subspecies. Information on gonads and accessory sex glands is given for both breeding and non-breeding adults and for juveniles. All Australian subspecies of Rattus have a fundamentally similar mechanism of reproduction. Those attaining high densities have the highest ovulation rates, the largest litter sizes, and the greatest number of teats. Furthermore, in the two subspecies of high reproductive potential for which we have evidence, females can be precocious in attaining sexual maturity under field conditions.