Mupirocin activity against methicillin-resistant Staphylococcus aureus.
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Fatty Acids↗
Biomedical subjects
L H Evans
Publications and source records attributed to L H Evans.
Characterization of polytropic MuLVs from three-week-old AKR/J mice.
An immunological focus assay using monoclonal antibodies on live adherent in vitro cell lines was employed to detect and isolate different types of murine leukemia viruses (MuLVs) from spleen and thymus cells of young (less than 1 month of age) AKR/J mice. In agreement with earlier studies, ecotropic viruses were detected from cells of both tissues in all mice tested, although only trace levels of ecotropic MuLV infectious centers were found with thymus cells from mice of this age. Polytropic MuLVs were not detected in mice less than 3 weeks of age; however, between the ages of 3 and 4 weeks, polytropic viruses were detectable in assays of spleen cells from 50% of the mice. No polytropic MuLVs were detected in assays of thymocytes from any mice of this age. Several polytropic MuLVs obtained from spleens of young mice were further characterized. All of the isolates were infectious for both mink and SC-1 (feral mouse) cells, and exhibited interference properties typical of polytropic MuLVs. However, none of the viruses induced obvious cytopathic effects (CPE) on mink cells. All of the viruses appeared antigenically similar with regard to their reactivities to a panel of 12 monoclonal antibodies directed at envelope antigens of polytropic MuLVs. RNase T1-resistant oligonucleotide analysis of a polytropic MuLV from a 26-day-old mouse indicated that its entire env gene was derived from nonecotropic sequences while the remainder of its genome was indistinguishable from the ecotropic parent. The isolate thus exhibited a genome structure typical of Class II polytropic MuLVs and is the first example of this type of MuLV isolated from AKR/J mice. Examination of polytropic MuLVs derived from the spleens and thymuses of 5- to 6-month-old mice indicated that only 2 of 10 isolates examined induced CPE on mink cells. Furthermore, most of the CPE-negative viruses isolated from spleen and thymus cells of these mice exhibited in vitro host ranges and antigenic reactivities similar to isolates from young mice, suggesting that this type of polytropic MuLV may originate in the spleen, subsequently spread to other tissues, and persist throughout the preleukemic period. The detection of polytropic viruses in a large proportion of very young mice is in contrast to previous studies which have not detected polytropic virus production in AKR mice less than 5 to 6 months of age.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Bilateral bicipital bursitis in a cow.
A 5-year-old Ayrshire cow with severe forelimb lameness of 6 weeks' duration was determined to have bilateral bicipital bursitis. Results of synovial fluid analyses were compatible with nonseptic bursitis. The cow's lameness resolved in 7 days after box stall confinement, parenteral treatment with nonsteroidal anti-inflammatory drugs, and a single intrabursal injection of a combination of methylprednisolone, sodium hyaluronate, and gentamicin sulfate. Lameness had not recurred during the 22 months since discharge.
Animals↗
Friend and Moloney murine leukemia viruses specifically recombine with different endogenous retroviral sequences to generate mink cell focus-forming viruses.
A group of mink cell focus-forming (MCF) viruses was derived by inoculation of NFS/N mice with Moloney murine leukemia virus (Mo-MuLV 1387) and was compared to a similarly derived group of MCF viruses from mice inoculated with Friend MuLV (Fr-MuLV 57). Antigenic analyses using monoclonal antibodies specific for MCF virus and xenotropic MuLV envelope proteins and genomic structural analyses by RNase T1-resistant oligonucleotide finger-printing indicated that the Moloney and Friend MCF viruses arose by recombination of the respective ecotropic MuLVs with different endogenous retrovirus sequences of NFS mice.
Animals↗
Infectious entry of murine retroviruses into mouse cells: evidence of a postadsorption step inhibited by acidic pH.
The entry into cells by many enveloped RNA viruses is accomplished by endocytosis and subsequent penetration of the endosomal membrane by an acidic pH-dependent fusion event. In the current study, we examined early events in the infectious entry of mouse retroviruses, using as a framework the observation that infection of a mouse tail skin cell line by the ecotropic virus Friend murine leukemia virus was inhibited at mildly acidic pH (pH 6). This inhibition operated on a postadsorption step, since binding of virus was unaffected at this pH. The rate of penetration of preadsorbed virus, which displayed first-order kinetics, was markedly affected by changes in the pH of the medium. The half-time for disappearance of infectious cell surface virus at 37 degrees C was approximately 10 min at pH 7.6. At pH 6.0, however, greater than 98% of the adsorbed infectivity remained at the cell surface after 45 min. This cell surface virus, though not infecting the cell at pH 6.0, retained its capacity to enter and infect the cell when the pH of the medium was raised. Acidic pH had little effect on the rate of fluid uptake by the cells, as measured by internalization of [3H]sucrose, indicating that global inhibition of endocytosis had not occurred. In contrast, cell fusion induced by Friend murine leukemia virus was optimal at pH 7.6 but markedly inhibited at a pH of less than 6.4. This inhibitory effect of acidic pH on membrane fusion is unique among the enveloped viruses which have been studied and would preclude entry of Friend murine leukemia virus from within acidified endocytic vesicles. Entry of other members of the ecotropic, mink cell focus-forming, and xenotropic host range groups displayed similar pH sensitivity. However, one xenotropic virus was relatively resistant to the effect of acidic pH, suggesting that differences might exist in the requirements for entry of different retroviruses.
Animals↗
Generation of mink cell focus-forming viruses by Friend murine leukemia virus: recombination with specific endogenous proviral sequences.
A family of recombinant mink cell focus-forming viruses (MCF) was derived by inoculation of NFS mice with a Friend murine leukemia virus, and their genomes were analyzed by RNase T1-resistant oligonucleotide fingerprinting. The viruses were obtained from the thymuses and spleens of preleukemic and leukemic animals and were evaluated for dualtropism and oncogenicity. All these isolates induced cytopathic foci on mink cells but could be classified into two groups based on their relative infectivities for SC-1 (mouse) or mink (ATCC CCL64) cells. One group of Friend MCFs (F-MCFs) (group I) exhibited approximately equal infectivities for SC-1 and mink cells, whereas a second group (group II) infected mink cells 1,000- to 10,000-fold more efficiently than SC-1 cells. Structural analyses of the F-MCFs revealed that group I and group II viruses correlated with recombination of Friend murine leukemia virus with two distinct, but closely related, endogenous NFS proviral sequences. No correlation was found between the type of F-MCF and the tissue of origin or the disease state of the animal. Furthermore, none of the F-MCF isolates were found to be oncogenic in NFS/N or AKR/J mice. F-MCFs of both groups underwent extensive substitution of ecotropic sequences, involving much of the gag and env genes of group I F-MCFs and most of the gag, pol, and env genes of group II F-MCFs. All F-MCF isolates retained the 3' terminal U3 region of Friend murine leukemia virus. Comparison of the RNAs of the F-MCFs with RNAs of MCFs derived from NFS.Akv-1 or NFS.Akv-2 mice indicated that the F-MCFs were derived from NFS proviral sequences which are distinct from the sequences contained in NFS.Akv MCF isolates. This result suggested that recombination with particular endogenous proviral sequences to generate MCFs may be highly specific for a given murine leukemia virus.
Base Sequence↗
An immunological focus assay for murine leukemia viruses on viable attached cell lines.
An assay is described for the detection and isolation of murine leukemia virus (MuLV)-infected cells in viable monolayers. The procedure utilizes antisera or monoclonal antibodies which specifically bind cell surface viral antigens of infected cells. Bound antibodies are subsequently detected by binding with 125I-labeled Staphylococcus aureus protein A followed by autoradiography of the tissue culture vessel. Focal areas of infection can be identified from the autoradiograph and infected cells can subsequently be isolated and subcultured as MuLV-producing cell lines. With appropriate antibodies the procedure should be useful for the direct isolation of minor components, including mutants, in complex virus mixtures.
Animals↗
Congenitally incompetent cervix in a mare.
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Animals↗
Complications of cleft palate repair in large animals.
Seven foals, 2 horses, and 2 calves were presented to the George D. Widener Hospital for Large Animals at New Bolton Center and the Large Animal Clinic at Auburn University for surgical repair of cleft palate. All animals had preexisting pneumonia. Initial repair of cleft palate in 6 foals, 2 horses, and 2 calves was performed via mandibular symphysiotomy. Primary repair of cleft soft palate in a foal was attempted through a pharyngotomy incision after fracture of the basal hyoid bone; however, exposure was inadequate and mandibular symphysiotomy had to be done. Dehiscence of a portion of the cleft palate occurred in all cases (10 of 11) that survived the immediate postoperative period. A 2nd repair was attempted in 3 foals; however, dehiscence of the palate recurred. Osteomyelitis of the mandibular symphysis developed in 6 animals; dehiscence of the lower lip occurred in 3 animals. Serious complications after surgery led to euthanasia or death of 5 animals. Of the 6 surviving animals, 4 did not grow normally. All survivors experienced chronic nasal discharge often contaminated with food material. Although mandibular symphysiotomy provided adequate exposure for surgical repair of cleft palate, serious complications have not been overcome.
Animals↗
Isolation of a transformation-defective deletion mutant of Moloney murine sarcoma virus.
A transformation-defective (td) deletion mutant of Moloney murine sarcoma virus (td Mo-MSV) and a transforming component termed Mo-MSV 3 were cloned from a stock of clone 3 Mo-MSV. To define the defect of the transforming function, the RNA of td Mo-MSV was compared with those of Mo-MSV 3 and of another transforming variant termed Mo-MSV 124 and with helper Moloney murine leukemia virus (Mo-MuLV). The RNA monomers of td Mo-MSV and Mo-MSV 3 comigrated on polyacrylamide gels and were estimated to be 4.8 kilobases (kb) in length. In agreement with previous analyses, the RNA of Mo-MSV 124 measured 5.5 kb and that of Mo-MuLV measured 8.5 kb. The interrelationships among the viral RNAs were studied by fingerprinting and mapping of RNase T(1)-resistant oligonucleotides (T(1)-oligonucleotides) and by identification of T(1)-oligonucleotides present in hybrids formed by a given viral RNA with cDNA's made from another virus. The nontransforming td Mo-MSV RNA lacked most of the Mo-MSV-specific sequence, i.e., the four 3'-proximal T(1)-oligonucleotides of the six T(1)-oligonucleotides that are shared by the Mo-MSV-specific sequences of Mo-MSV 3 and Mo-MSV 124. The remaining two Mo-MSV-specific oligonucleotides identified td Mo-MSV as a deletion mutant of MSV rather than a deletion mutant of Mo-MuLV. td Mo-MSV and Mo-MSV 124 exhibited similar deletions of gag, pol, and env sequences which were less extensive than those of Mo-MSV 3. Hence, td Mo-MSV is not simply a deletion mutant of Mo-MSV 3. In addition to their MSV-specific sequences, all three MSV variants, including td Mo-MSV, shared the terminal sequences probably encoding the proviral long terminal repeat, which differed from their counterpart in Mo-MuLV. This may indirectly contribute to the oncogenic potential of MSV. A comparison of td Mo-MSV sequences with either Mo-MSV 124 or Mo-MSV 3 indicated directly, in a fashion similar to the deletion analyses which defined the src gene of avian sarcoma viruses, that Mo-MuLV-unrelated sequences of Mo-MSV are necessary for transformation. A definition of transformation-specific sequences of Mo-MSV by deletion analysis confirmed and extended previous analyses which have identified Mo-MuLV-unrelated sequences in Mo-MSV RNA and other studies which have described transformation of mouse 3T3 fibroblasts upon transfection with DNAs containing the Mo-MSV-specific sequence.
Cell Transformation, Viral↗
Envelope gene sequences which encode the gp52 protein of spleen focus-forming virus are required for the induction of erythroid cell proliferation.
A series of insertion-deletion mutants was constructed in a molecularly cloned DNA copy of the Friend strain of spleen focus-forming virus (SFFV). The mutants were produced by inserting a synthetic oligonucleotide linker containing the recognition sequence of SalI endonuclease into several different locations of the SFFV DNA. Three classes of mutants were isolated: insertion-deletion mutants in the 5' half of the SFFV genome, in the long terminal repeat of the SFFV genome, and in the env gene of the SFFV genome. The env gene mutant has a deletion of sequences shared in common between the env gene of SFFV and the env genes of mink cell focus-inducing murine leukemia viruses. From analyses of the biological activity of the various mutants and a biologically active subgenomic SFFV DNA fragment described herein, we can deduce that the coding sequence encompassing the env gene of SFFV is required for the biological activity. This region, required for the pathogenic phenotype, cannot be larger than 1.5 kilobase pairs, a size only slightly more than that sufficient to encode the nonglycosylated precursor of the gp52 env gene product.
Base Sequence↗
Structural and functional studies of the Friend spleen focus-forming virus: structural relationship of SFFV to dualtropic viruses and molecular cloning of a biologically active subgenomic fragment of SFFV DNA.
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Animals↗
Biological activity of the spleen focus-forming virus is encoded by a molecularly cloned subgenomic fragment of spleen focus-forming virus DNA.
A biologically active subgenomic DNA fragment of a polycythemia-inducing strain of the replication-defective spleen focus-forming virus (SFFV) has been molecularly cloned. The SFFV DNA fragment includes 2.0 kilobase pairs (kbp) from the 3' end of SFFV, the long terminal repeat sequences of SFFV, and 0.4 kbp from the 5' end of SFFV. The fragment contains the previously described env-related gene of SFFV. All the properties associated with SFFV can be assigned to this SFFV DNA fragment by using a two-stage DNA transfection assay with infectious helper virus DNA. The virus recovered from the transfection assays can induce erythroblastosis, splenic foci, and polycythemia in infected mice. Fibroblast cultures transfected with the SFFV DNA fragment synthesize gp52, the known intracellular product of the env-related gene of SFFV. gp52 can also be detected in spleens from diseased mice infected with the virus recovered in the two-stage transfection. The results are consistent with the hypothesis that the env-related gene sequences of SFFV and their product gp52 are required for the initiation of SFFV-induced disease.
Animals↗
Cryoneurectomy in the horse.
Cryoneurectomy was performed experimentally on 10 digital plantar nerves of normal horses. All nerves were frozen to -30 C, using a double freeze-thaw cycle. Nerves were harvested at 10 days and at 4, 12, 16, and 24 weeks and were examined histologically for evidence of regeneration. The terminal portion of the transected nerves treated with cryosurgery did not have any signs of regeneration or neuroma formation at these periods. Cryoneurectomy was performed on 101 nerves of 32 horses with diseases requiring neurectomy. Twenty-seven of these nerves had been subjected to previous neurectomy, and painful neuromas had developed. After cryoneurectomy, painful neuroma formation was 15% in this group and was 4% in the nerves that had not had a neurectomy prior to cryoneurectomy. Neuritis lasting 10 days developed in 1 horse.
Animals↗
Replication of spleen focus-forming Friend virus in fibroblasts from C57BL mice that are genetically resistant to spleen focus formation.
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Animals↗
Spleen focus-forming Friend virus: identification of genomic RNA and its relationship to helper virus RNA.
The genome of the defective, murine spleen focus-forming Friend virus (SFFV) was identified as a 50S RNA complex consisting of 32S RNA monomers. Electrophoretic mobility and the molecular weights of unique RNase T1-resistant oligonucleotides (T1-oligonucleotides) indicated that the 32S RNA had a complexity of about 7.4 kilobases. Hybridization with DNA complementary to Friend murine leukemia virus (Fr-MLV) has distinguished two sets of nucleotide sequences in 32S SFFV RNA, 74% which were Fr-MLV related and 26% which were SFFV specific. By the same method, SFFV RNA was 48% related to Moloney MLV. We have resolved 23 large T1-oligonucleotides of SFFV RNA and 43 of Fr-MLV RNA. On the basis of the relationship between SFFV and Fr-MLV RNAs, the 23 SFFV oligonucleotides fell into four classes: (i) seven which had homologous equivalents in Fr-MLV RNA; (ii) six more which could be isolated from SFFV RNA-Fr-MLV cDNA hybrids treated with RNases A and T1; (iii) eight more which were isolated from hybrids treated with RNases A and T1; and (iv) two which did not have Fr-MLV-related counterparts. Surprisingly, the two class iv oligonucleotides had homologous counterparts in the RNA of six amphotropic MLV's including mink cell focus-forming and HIX-MLVs analyzed previously. The map locations of the 23 SFFV T1-oligonucleotides relative to the 3' polyadenylic acid coordinate of SFFV RNA were deduced from the size of the smallest polyadenylic acid-tagged RNA fragment from which a given oligonucleotide was isolated. The resulting oligonucleotide map could be divided roughly into three segments: two terminal segments which are mosaics of oligonucleotides of classes i, ii, and iii and an internal segment between 2 and 2.5 kilobases from the 3' end containing the two oligonucleotides shared with amphotropic MLVs. Since SFFV RNA consists predominantly of sequence elements related to ecotropic and amphotropic helper-independent MLVs, it would appear that the transforming gene of SFFV is not a major specific sequence unrelated to genes of helper viruses, as is the case with Rous sarcoma and probably withe other defective sarcoma and acute leukemia viruses.
Base Sequence↗
Synthesis and glycosylation of polyprotein precursors to the internal core proteins of Friend murine leukemia virus.
Synthesis and post-translational processing of murine leukemia virus proteins were analyzed in a murine cell line (Eveline) that produces large amounts of Friend lymphatic leukemia virus. Immunoprecipitation of l-[(35)S]methionine-labeled cell extracts demonstrated that several different virus-specific proteins antigenically related to the virion core (gag) proteins p12 and p30 become radioactive within 1 min of labeling and exhibit labeling kinetics characteristic of primary translation products. The most abundant of these were proteins with molecular weights of 75,000 and 65,000. There were, in addition, two large glycosylated polyproteins with apparent molecular weights of 220,000 and 230,000, which were precipitated by antisera to p30 or p12 but not by antiserum to the major envelope glycoproteins gp69/71. Several lines of evidence, including labeling with d-[(3)H]glucosamine and binding to insolubilized lectins, suggested that the 75,000-dalton internal core polyprotein is slowly processed to form a glycoprotein with an apparent molecular weight of 93,000. On the contrary, the 65,000-dalton protein appeared to be an immediate precursor to the virion core proteins. Its processing can involve intermediates containing p30 and p12 antigens with molecular weights of 50,000 and 40,000; however, the latter did not appear to be obligatory intermediates. The detection of the 40,000-dalton protein suggested that the genes for p30 and p12 are adjacent on the viral genome. These results indicated that there are several pathways of synthesis and post-translational processing of polyprotein precursors to the gag proteins and that several of these polyproteins are glycosylated. A comparison of gag precursor processing in rapidly growing, slowly growing, and stationary cells indicated that different pathways are favored under different conditions of cell growth. Our analysis of envelope glycoprotein synthesis has confirmed the existence of two rapidly labeled 90,000-dalton glycoproteins, which appear to be precursors to the envelope glycoproteins gp69/71.
Cell Cycle↗
Absorption and circular dichroism spectra of different forms of mushroom tyrosinase.
The circular dichroism spectrum of resting mushroom tyrosinase between 800 and 400 nm showed two bands at 755, and 653 nm. The CD spectrum of resting tyrosinase between 400 and 250 nm showed oxygen-sensitive changes at 350 nm upon treatment of tyrosinase with hydroxylamine or hydrogen peroxide. These were similar to changes observed on regeneration of aged hemocyanin by similar procedures. A structural relationship between the active sites of hydroxylamine- or hydrogen peroxide-treated tyrosinase and hemocyanin is suggested by these observations, confirming inferences based upon other studies (Jolly, Jr., R.L., Evans, L.H., Makino, N. and Mason, H.S. (1974) J. Biol. Chem. 249, 335-345 and Schoot Uiterkamp, A.J.M. and Mason, H.S. (1973) Proc. Natl. Acad, Sci. U.S. 70, 993-996).
Agaricales↗