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At least 55 records · Page 3Linked to original sources
PubMed1983

A 2.4-kilobase-pair fragment of the Friend murine leukemia virus genome contains the sequences responsible for friend murine leukemia virus-induced erythroleukemia.

Friend murine leukemia virus (F-MuLV) is a replication-competent, ecotropic, NB-tropic retrovirus which produces a rapidly fatal erythroleukemia in susceptible strains of mice. We previously molecularly cloned the entire F-MuLV genome. Transfection of this cloned DNA into NIH 3T3 mouse fibroblasts produces a virus with the same leukemia-inducing characteristics as F-MuLV. To identify which portion of the F-MuLV genome is responsible for causing leukemia, we made recombinant viruses between subgenomic fragments of F-MuLV DNA and another retrovirus--Amphotroph clone 4070. Amphotroph clone 4070 is a replication-competent, amphotrophic, N-tropic virus which does not produce any detectable malignancy in mice. A 2.4-kilobase-pair fragment of F-MuLV DNA was isolated. This DNA fragment encompassed approximately 700 base pairs from the 3' end of the F-MuLV pol gene and 1.7 kilobase pairs of the env gene including all of gp70 and the N-terminal four-fifths of p15E. A molecularly cloned fragment of Amphotroph DNA was ligated to the 2.4-kilobase-pair F-MuLV DNA, and an 8.3-kilobase-pair hybrid F-MuLV-Amphotroph DNA was subcloned into a new plasmid (p5a25-H). Transfection of p5a25-H DNA into fibroblasts resulted in the production of a replication-competent, ecotropic, N-tropic retrovirus--5a25-H virus. Inoculation of this virus into newborn NIH Swiss mice caused leukemia within 4 to 6 months. The disease caused by 5a25-H was pathologically and histologically indistinguishable from the disease caused by F-MuLV. We conclude that the F-MuLV sequences needed to cause disease are contained in these 2.4 kilobase pairs of DNA.

Animals↗
PubMed1998

The entire nucleotide sequence of friend-related and paralysis-inducing PVC-441 murine leukemia virus (MuLV) and its comparison with those of PVC-211 MuLV and Friend MuLV.

PVC-441 murine leukemia virus (MuLV) is a member of the PVC group of Friend MuLV (F-MuLV)-derived neuropathogenic retroviruses. In order to determine the molecular basis for the difference in neuropathogenicity between PVC-441 and the previously characterized PVC-211 MuLVs, the entire nucleotide sequence of PVC-441 MuLV was determined and compared with those of PVC-211 and F-MuLV. The results suggest that PVC-441 and PVC-211 MuLVs were formed as a result of random mutations of F-MuLV and developed differently. The distinct pathogenicities of PVC-441 and PVC-211 MuLVs were maintained in the viruses regenerated from their molecular clones, and the sequences responsible for the pathological differences observed can be localized to the env gene. The amino acid sequence of PVC-441 deduced from its nucleotide sequence revealed a number of differences from PVC-211, the most striking of which was a difference at position 129 of the SU proteins in the two viruses. Host range studies with a brain capillary endothelial cell line (RTEC-6) and Chinese hamster ovary cells (CHO-K1) revealed that PVC-441, like PVC-211, could infect these cells but its efficiency of infection was lower than that of PVC-211. These results may account for the difference in neuropathogenicity between PVC-441 and PVC-211.

Animals↗
PubMed1989

Inactivation of Friend erythroleukemia virus and Friend virus-transformed cells by merocyanine 540-mediated photosensitization.

The Friend virus complex was used as a model to study the effects of merocyanine 540 (MC 540)-mediated photosensitization on enveloped viruses. Simultaneous exposure to the lipophilic dye MC 540 and white light inactivated cell-free virus, cell-associated virus, and virus-transformed cells. When used under experimental conditions that are known to preserve most mature blood cells, at least some coagulation factors, and a significant portion of the pluripotent hematopoietic stem cell compartment, MC 540-mediated photosensitization reduced virus titers by greater than or equal to 4 log and the concentration of in vitro clonogenic erythroleukemia cells by greater than or equal to 5 log. Animals that received a single intravenous injection of photosensitized virus were resistant to a subsequent challenge with live virus. High sensitivity to MC 540-mediated photosensitization appears to be a property that is shared by other enveloped viruses. Thus, photosensitization mediated by MC 540 may be of benefit in the sterilization of blood products (in particular, cellular products), the production of vaccines, and selected areas of antiviral therapy.

Animals↗
PubMed1979

Susceptibility of Friend virus antigen-modulated erythroleukemic cells to lysis by T lymphocytes from mice with dormant Friend virus infections.

Spleen cells from DBA/2 mice with dormant Friend leukemia virus (FLV) infections or from mice immunized with x-irradiated FLC-745 erythroleukemic cells are not cytolytic for FLC-745 cells when tested directly, but acquire cytolytic activity in vitro by cultivation with x-irradiated FLC-745 cells. Spleen cells cultured from normal mice do not acquire such cytolytic activity. Cytolytic activity resides in the T lymphocyte population. Alloantiserum, but not antisera against FLV-virion polypeptides, inhibited the lysis of FLC-745 cells by cytolytic T lymphocytes. To understand further the role of cellular and humoral immune anti-FLV responses in mice with dormant FLV-infections, in vitro experiments were conducted that mimicked the in vivo FLV-specific immune environment of these mice. We found that FLV-immune serum from mice with dormant FLV-infections modulated FLV-antigen expression on the surfaces of FLC-745 cells without affecting their susceptibility to lysis by cytolytic T lymphocytes. These results suggest that cytolytic T lymphocyte restrain the outgrowth of FLV-antigen-modulated erythroleukemic cells in mice with dormant FLV infections and that the targets for cell-mediated lysis may be H-2d-associated antigens.

Animals↗
PubMed1986

A radiosensitive T-lymphocyte associated with resistance of DBA/2 mice harboring Friend leukemia virus-dormant infections to transplantable Friend leukemia virus-erythroleukemia cells.

The immunobiology of Friend erythroleukemia virus (FLV) has been the focal point of much research into immunological control of leukemia. We have been studying a murine model in which a rapidly fatal FLV infection of DBA/2 mice is suppressed to a dormant state by treatment with statolon, a double stranded RNA extract of Mycoplasma stoloniferum. We report here that mice with FLV-dormant infections resist the accumulation of transplanted FLV-transformed erythroleukemia cells (FLC-745) and that FLC-745 cells persist in the spleen for a prolonged period. Winn assays revealed that the spleen of FLV-dormant mice contain radiosensitive T-lymphocytes with anti-FLC-745 cell activity. Whole body irradiation of FLV-dormant mice abrogated their resistance to transplanted FLC-745 cells and confirmed the radiosensitivity of the protective immune response.

Animals↗
PubMed2006

Opioid and cannabinoid receptors: friends with benefits or just close friends?

mu-Opioid (MOP) and cannabinoid CB1 receptors mediate overlapping pharmacological responses in clinically important areas such as drug abuse and pain management, and functional interactions between agonists at these receptors have long been recognized. In the present issue of this Journal, Rios and co-workers have provided the first strong evidence that the two receptors interact directly when coexpressed in the same cells. The authors report a close physical association between MOP and CB1 receptors and novel pharmacological interactions of MOP and CB1 agonists. They argue that MOP/CB1 heterodimer formation explains these interactions. If correct, the direct interaction of MOP and CB1 pharmacophores in a quaternary complex would provide real benefits by opening the potential for development of novel MOP/CB1 small molecules or new strategies for use of current ligands. However, a lot more evidence will be required before the heterodimer interpretation can be accepted. If it turns out that MOP and CB1 receptors do not readily form hetero-oligomers, the study by Rios and co-workers shows that they are still friends but there may be few benefits.

Animals↗
PubMed2006

A psychoeducational codependency support group for older adults who reside in the community: friends supporting friends.

Older adults with loved ones who are dependent on alcohol or drugs often experience the adverse effects of a codependent relationship. Many experience anxiety, low self-esteem, depression, and suicidal thoughts. A pilot psychoeducational codependency support group was developed to promote well-being and reduce the adverse effects of codependency among older persons. The study participants were a voluntary convenience sample of 22 older adults (ages 65 and older) residing in the community. A pretest and posttest were administered. Six 90-minute group sessions based on a curriculum developed by the authors were held during a 2-month period. Yalom's Therapeutic Factors were used to evaluate the group process. Results indicated that older adults benefit from a psychoeducational support group format and that codependency issues can be reduced.

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