Sequence analysis of Gardner-Arnstein feline leukaemia virus envelope gene reveals common structural properties of mammalian retroviral envelope genes

We have sequenced the envelope (env) gene and most of the adjacent 3' long terminal repeat (LTR) of Gardner-Arnstein feline leukaemia virus subtype B. The LTR of this virus contains, at corresponding positions, all signal sequence elements known from other retroviral LTRs. The deduced amino acid sequence of the longest open reading frame was compared with env polypeptide sequences of several murine leukaemia viruses. This allowed us to predict the positions of both p12/15env and gp70 polypeptides as well as a hydrophobic leader polypeptide. The env polypeptides of the different viruses show long stretches of homology and similar hydrophilicity profiles in the p12env region and in the carboxy-terminal half of gp70 (constant region). The most extensive variations are confined to certain parts of the amino-terminal half of gp70 (differential region). In this region, however, feline leukaemia virus and murine mink cell focus forming viruses are still closely related. A correspondingly spaced pattern of identical, short amino acid sequences appears in three different parts of the env polyprotein, suggesting its evolution from a primordial env-related precursor by tandem duplications.

Characterization of messenger RNA specific for carcinoembryonic antigen

Total poly(A)-containing RNA extracted from a rectal carcinoma was translated in a rabbit reticulocyte lysate. By addition of either a monoclonal or a polyclonal antibody, both monospecific for carcinoembryonic antigen, one protein with an apparent molecular weight of 85,000 was specifically precipitated, as shown by electrophoresis of the immunoprecipitate on sodium dodecylsulfate polyacrylamide gels. This protein behaves similarly to CEA isolated from liver metastases of a colon tumor in its property of being resistant to cleavage by cyanogen bromide. These findings suggest that this protein represents the CEA precursor protein. When we consider the high carbohydrate content of 60% of CEA, the observed molecular weight of the CEA precursor protein is in agreement with the reported molecular weight of 180,000 for CEA. By sedimentation of poly(A)-containing tumor RNA through a sucrose gradient, and by in vitro translation of each fraction of the gradient, the sedimentation coefficient of CEA-specific mRNA was found to be about 22 S.

Nucleotide sequence of the envelope gene of Friend murine leukemia virus

The envelope gene of the helper-independent, highly leukemogenic virus Friend murine leukemia virus was sequenced by using a molecular clone of a Friend murine leukemia provirus. The deduced amino acid sequences of the envelope proteins gp70 and p15env were homologous to the sequences of Moloney murine leukemia virus (86%) and Akv (76%). However, a stretch of about 40 amino acid residues near the middle of gp70 was dissimilar in Friend and Moloney murine leukemia viruses and Akv. In this type-specific region the gp70s of all three viruses contained more than 30% proline residues, giving this sequence a very rigid conformation. We suggest that this rigid and highly variable region of gp70 participates in infection by recognition of cell surface receptors and, in addition, might contribute to the different oncogenic spectra of murine leukemia viruses.

Changes of extracellular Na+, K+, Ca2+ and H+ of the ischemic myocardium in pigs

In open-chest pigs during severe myocardial ischemia [K+]e, [Ca2+]e and [H+]e increase, [Na+]e increases transiently reaching control values after 30 min. Extracellular osmolality of the ischemic area increases due to an H2O-shift from the ECS to the ICS. The increase of [Na+]e and [Ca2+]e must b explained by the shrinkage of the ECS due to the H2O-shift. The increase of [Ca2+]e is additionally caused by the decrease of pHe. The increase of [K+]e is mainly caused by the release of K+ from the ICS. The changes of [K+]e and [K+]i cause a decrease of the membrane potential to a range in which slow response potentials and re-entry excitations can occur. The increase of [K+]e therefore seems to be a major factor to cause early post-ischemic arrhythmias.

Effect of actinomycin D on nucleic acid hybridization: the cause of erroneous DNA elongation during DNA synthesis of RNA tumor viruses in vitro

Actinomycin D, known for its suppression of cellular RNA synthesis and for the reduction of the rate of synthesis of double-stranded DNA by the RNA tumor virus RNA-dependent DNA polymerase, was found to interact with single-stranded DNA in such a way as to inhibit DNA . DNA and DNA . RNA hybridizations. This finding is discussed in the light of the observation that DNA elongation during DNA synthesis of RNA tumor viruses is blocked in vitro in the presence of actinomycin D. It thus supports the model that hybridization is a necessary step during RNA tumor virus DNA synthesis.

The time-distance diagram: a new method to analyze ureteral peristalsis by cineradiography

We assessed ureteral peristalsis in dogs by cineradiography and analyzed the films in a single frame follow-up by measuring the position of bolus front and rear end in relation to the bladder and the kidney. The data were plotted as function of time in a time-distance diagram. The bolus rear end which is the active contractile rings, as proven by electromyography, travels with constant velocity. The bolus front shows remarkable changes in propagation velocity which can be explained by differences in wall forces that resist the opening of the ureteral lumen. Thus, the time-distance diagram describes precisely the constantly changing dynamics of ureteral peristalsis along the entire ureter.

Effect of viral RNase H on the avian sarcoma viral genome during early transcription in vitro

We investigated the influence of viral RNase H on the transcription of the avian sarcoma virus RNA in a virion-associated reaction. The ability of RNase H to degrade the RNA moiety of the initially formed RNA-DNA hybrid at the 5' end of the viral genome was found to be greatly dependent on the exact concentration of nonionic detergent used to activate the reaction. At a detergent concentration optimal for extensive and faithful in vitro transcription of avian sarcoma virus RNA by the virion-associated RNA-dependent DNA polymerase, most of the 5' terminus of the RNA was digested in 30 min at 41 degrees C. At higher than optimal detergent concentrations, however, little of that RNA was digested. We conclude that removal of the 5'-terminal redundancy in the RNA after its transcription into DNA is a prerequisite for base pairing of the DNA to the 3'-terminal redundant sequence. Lack of removal of this sequence leads to incorrect elongation and substantial reduction of DNA synthesis. When tested with a synthetic RNA-DNA hybrid, virion-associated RNase H did not reveal a detergent dependence.

Elongation of DNA complementary to the 5' end of the avian sarcoma virus genome by the virion-associated RNA-dependent DNA polymerase

RNA-dependent DNA synthesis in a virion-associated reaction has been described as being dependent upon the detergent concentration used for disruption of the virion. In this study, the Triton X-100 concentration was found to affect the elongation of the initially synthesized DNA complementary to the last approximately 100 nucleotides at the 5' end of the RNA (cDNA100). Whereas elongation of cDNA100 increased with time of incubation at the optimal detergent concentration, this process was retarded at higher detergent concentrations. At the optimal detergent concentration, elongated DNA was of low chemical complexity, indicating that extension of cDNA100 occurred at a unique site on the RNA. Higher than optimal detergent concentrations resulted in nonspecific elongation and in DNA of high chemical complexity. This was shown by oligopyrimidine tract analysis. Furthermore, actinomycin D was observed to inhibit the elongation of cDNA100 at the optimal detergent concentration. The nature of the elongation process was elucidated by analysis of DNA synthesized in a virion-associated reaction in the presence of bacteriophage Qbeta RNA. At the optimal detergent concentration DNA complementary only to avian sarcoma virus RNA was synthesized, whereas at higher concentrations DNA was copied from both avian sarcoma virus and Qbeta RNA. We conclude that the elongation mechanism of cDNA100 is affected by the detergent concentration and elongation is unspecific at higher than optimal detergent concentrations. The mechanism by which the nonionic detergent stimulates DNA synthesis has not yet been resolve. We assume that other factors in addition to DNA polymerase are involved in elongation of cDNA100.

Nucleotide sequence at the 5' terminus of the avian sarcoma virus genome

Transcription of DNA from the RNA genome of avian sarcoma virus by RNA-directed DNA polymerase in vitro initiates on a primer (tRNATrp) located near the 5'-terminus of the viral genome. One of the major products of transcription is a single-stranded DNA chain complementary to a sequence of 101 nucleotides immediately distal to the site of initiation of DNA synthesis. We have determined the complete nucleotide sequence of this transcribed chain for the Prague strain of avian sarcoma virus, a partial sequence of the transcribed chain for the Bratislava 77 strain of avian sarcoma virus, and the sequence of a DNA transcript that is shorter than the transcribed single-stranded chain. Our data define the location of tRNATrp on the genome of avian sarcoma virus and provide the sequence of 119 nucleotides at the 5'-terminus of the genome. Portions of this sequence may be involved in the binding of RNA-directed DNA polymerase, the initiation of translation from viral messenger RNA, the extension of RNA-directed DNA synthesis from the 5'- to the 3'-terminus of viral RNA, and the integration of viral DNA into the host genome.

Nucleotide sequence that binds primer for DNA synthesis to the avian sarcoma virus genome

Initiation of transcription from the genome of avian sarcoma virus by RNA-directed DNA polymerase in vitro requires tRNAtrp as a primer. The tRNA is bound to the viral genome by a sequence of 16 contiguous nucleotides (U-C-A-C-G-U-C-G-G-G-G-U-C-A-C-Cp), beginning with the penultimate base at the 3' terminus of the primer and extending through the acceptor stem into loop IV of the tRNA. Consequently, the native conformation of the tRNA must be disrupted by the binding of primer to the viral genome. The binding sequence does not include two adjacent residues of pseudouridine in loop IV, which distinguish the primer from many other tRNAs, and the 3' terminal adenosine of primer may also be excluded from base pairing with the viral genome.

Critical assessment of the xenon washout technic for measurement of placental blood flow

The xenon washout technic has been assessed as a method for measuring placental blood flow in humans. In the first group of 20 patients, the ¹³³Xe injection was made blindly into the placenta; in the second group of 20 patients, a new technic was employed to ensure injection into the vascular (intervillous) space. The results have been calculated as clearance half-times, in seconds. Both groups gave widely differing results. After comparing the clearance half-times for ¹³³Xe with those for ^99mTc-albumin, it was concluded that with intervillous ¹³³Xe injections, a true xenon washout effect does not occur. Thus, calculations for blood flow in ml/g tissue/unit time are not considered valid. Further, the method cannot be recommended as a test for the action of drugs on placental blood flow. Firstly, under the influence of spontaneous placental pressure variations, single measurements are of limited value. Secondly, as blood examinations have shown the needle puncture itself may damage fetal vessels, permitting possibly dangerous fetomaternal transfusion.