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Biomedical subjects

D G Brownstein

Publications and source records attributed to D G Brownstein.

At least 19 recordsLinked to original sources
PubMed2006

Mice with skin-specific DNA repair gene (Ercc1) inactivation are hypersensitive to ultraviolet irradiation-induced skin cancer and show more rapid actinic progression.

Ercc1 has an essential role in the nucleotide excision repair (NER) pathway that protects against ultraviolet (UV)-induced DNA damage and is also involved in additional repair pathways. The premature death of simple Ercc1 mouse knockouts meant that we were unable to study the role of Ercc1 in the skin. To do this, we have used the Cre-lox system to generate a skin-specific Ercc1 knockout. With a Cre transgene under control of the bovine keratin 5 promoter we achieved 100% recombination of the Ercc1 gene in the epidermis. Hairless mice with Ercc1-deficient skin were hypersensitive to the short-term effects of UV irradiation, showing a very low minimal erythemal dose and a dramatic hyperproliferative response. Ultraviolet-irradiated mice with Ercc1-deficient skin developed epidermal skin tumours much more rapidly than controls. These tumours appeared to arise earlier in actinic progression and grew more rapidly than tumours on control mice. These responses are more pronounced than have been reported for other NER-deficient mice, demonstrating that Ercc1 has a key role in protecting against UV-induced skin cancer.

Animals↗
PubMed2001

Murine gammaherpesvirus-68 infection causes multi-organ fibrosis and alters leukocyte trafficking in interferon-gamma receptor knockout mice.

Murine gammaherpesvirus-68 (MHV-68) infection in interferon-gamma receptor knockout mice (IFN-gammaR(-)/(-)) results in splenic fibrosis and excessive loss of splenocytes. In our present study we found that MHV-68 infection in IFN-gammaR(-)/(-) mice also resulted in fibrosis and atrophy of the mediastinal lymph nodes, interstitial pulmonary fibrosis and fibrotic changes in the liver. Atrophy and cellular depletion of the spleen in IFN-gammaR(-)/(-) was not the result of increased cell death. The loss of splenocytes in IFN-gammaR(-)/(-) mice, which was most evident on day 23 after infection, correlated with an increase in the number of leukocytes in peripheral blood. At the peak of leukocytosis, on day 23 after infection, peripheral blood cells from infected IFN-gammaR(-)/(-) mice were unable to traffic through the fibrosed spleens of IFN-gammaR(-)/(-) mice but were able to enter the spleens of wild-type mice. This indicates that leukocytosis was in part the result of emigration of cells from the spleen and their subsequent exclusion of re-entry at the height of fibrosis. Significant cytokine and chemokine changes were observed in spleens of IFN-gammaR(-)/(-) mice. IFN-gamma, tumor necrosis factor-alpha (TNF-alpha ), TNF-beta, interleukin-1beta (IL-1beta), transforming growth factor-beta1 (TGF-beta1), lymphotactin, and MIP-1beta were elevated on day 14 after infection whereas chemokines IP-10 and MIG were significantly reduced. These changes suggest a role for dysregulated cytokines and chemokines in severe organ-specific fibrosis with implications for immune-mediated fibrotic disorders.

Animals↗
PubMed2001

Analysis of a novel strain of murine gammaherpesvirus reveals a genomic locus important for acute pathogenesis.

Infection of mice by murine gammaherpesvirus 68 (MHV-68) is an excellent small-animal model of gammaherpesvirus pathogenesis in a natural host. We have carried out comparative studies of another herpesvirus, murine herpesvirus 76 (MHV-76), which was isolated at the same time as MHV-68 but from a different murid host, the yellow-necked mouse (Apodemus flavicollis). Molecular analyses revealed that the MHV-76 genome is essentially identical to that of MHV-68, except for deletion of 9,538 bp at the left end of the unique region. MHV-76 is therefore a deletion mutant that lacks four genes unique to MHV-68 (M1, M2, M3, and M4) as well as the eight viral tRNA-like genes. Replication of MHV-76 in cell culture was identical to that of MHV-68. However, following infection of mice, MHV-76 was cleared more rapidly from the lungs. In line with this, there was an increased inflammatory response in lungs with MHV-76. Splenomegaly was also significantly reduced following MHV-76 infection, and much less latent MHV-76 was detected in the spleen. Nevertheless, MHV-76 maintained long-term latency in the lungs and spleen. We utilized a cosmid containing the left end of the MHV-68 genome to reinsert the deleted sequence into MHV-76 by recombination in infected cells, and we isolated a rescuant virus designated MHV-76(cA8+)4 which was ostensibly genetically identical to MHV-68. The growth properties of the rescuant in infected mice were identical to those of MHV-68. These results demonstrate that genetic elements at the left end of the unique region of the MHV-68 genome play vital roles in host evasion and are critical to the development of splenic pathology.

Animals↗
PubMed2001

Role of tachykinins in the host response to murine gammaherpesvirus infection.

Tachykinins function not only as neurotransmitters but also as immunological mediators. We used infection of tachykinin-deficient (PPT-A(-/-)) mice and wild-type controls with murine gammaherpesvirus to assess the role of tachykinins in the host response to a virus infection. Although infection was ultimately controlled in PPT-A(-/-) mice, there were higher titers of infectious virus in the lungs, accompanied by a more rapid influx of inflammatory cells. Clearance of latently infected cells from the spleen was also delayed. This is the first report of the direct influence of tachykinins in the host response to a virus infection.

Animals↗
PubMed2000

Dual infection with Pneumocystis carinii and Pasteurella pneumotropica in B cell-deficient mice: diagnosis and therapy.

BACKGROUND AND PURPOSE: The clinical presentation, diagnosis, histopathologic findings, and elimination of dual respiratory tract infection with Pasteurella pneumotropica and Pneumocystis carinii were studied in 100 adult barrier-reared C.B17 and MRL- lpr mice homozygous for a targeted mutation of the JH region of the immunoglobulin heavy chain. METHODS: Necropsy, aerobic bacteriologic culture of hematogenous and pulmonary tissues, histochemical staining of pulmonary tissues, polymerase chain reaction analysis of pulmonary tissues and feces, and viral serologic testing were performed on 19 clinically affected mice and 8 clinically normal mice, then later on antibiotic-treated and caesarian re-derived mice. Therapeutic strategies included sequential administration of trimethoprim/ sulfamethoxazole and enrofloxacin or enrofloxacin administration and caesarian rederivation. RESULTS: Clinically affected mice had diffuse, nonsuppurative, interstitial pneumonia with superimposed pyogranulomatous lobar pneumonia that was detected microscopically. Affected lung tissue yielded pure culture of P. pneumotropica. Aged-matched, clinically normal mice of both genotypes had interstitial histiocytic pneumonia without lobar pneumonia, and P. pneumotropica was not isolated. Histochemical staining of lung tissues from normal and clinically affected mice revealed scattered cysts consistent with P. carinii, principally in the interstitium. Treatment with sulfamethoxazole/trimethoprim and enrofloxacin eliminated bacteriologic detection of P. pneumotropica, decreased mortality from 50% to 6%, and improved breeding performance. CONCLUSION: A successful antibiotic therapy and rederivation approach, incorporating enrofloxacin, cesarian section, and isolator rearing, was developed for B cell-deficient mice with opportunistic infections.

Animals↗
PubMed2000

Metastatic large intestinal adenocarcinoma in two rhesus macaques (Macaca mulatta).

Spontaneous colonic adenocarcinomas were diagnosed in two rhesus macaques (Macaca mulatta). Although both tumors caused partial obstruction of the colon, they were histologically different. One resembled the commonly described "napkin-ring" adenocarcinoma similar to those found in the descending and sigmoid colon of humans. The other neoplasm, a "tubular" lesion, invaded the full thickness of the colonic wall at the ileocecal-colonic junction. Both tumors were associated with metastasis, which is uncommon in the rhesus monkey.

Adenocarcinoma↗
PubMed1999

Mice deficient of Lats1 develop soft-tissue sarcomas, ovarian tumours and pituitary dysfunction.

The lats gene has been identified as a tumour suppressor in Drosophila melanogaster using mosaic screens. Mosaic flies carrying somatic cells that are mutant for lats develop large tumours in many organs. The human LATS1 homologue rescues embryonic lethality and inhibits tumour growth in lats mutant flies, demonstrating the functional conservation of this gene. Biochemical and genetic analyses have revealed that LATS1 functions as a negative regulator of CDC2 (ref. 3). These data suggest that mammalian LATS1 may have a role in tumorigenesis. To elucidate the function of mammalian LATS1, we have generated Lats1-/- mice. Lats1-/- animals exhibit a lack of mammary gland development, infertility and growth retardation. Accompanying these defects are hyperplastic changes in the pituitary and decreased serum hormone levels. The reproductive hormone defects of Lats1-/- mice are reminiscent of isolated LH-hypogonadotropic hypogonadism and corpus luteum insufficiency in humans. Furthermore, Lats1-/- mice develop soft-tissue sarcomas and ovarian stromal cell tumours and are highly sensitive to carcinogenic treatments. Our data demonstrate a role for Lats1 in mammalian tumorigenesis and specific endocrine dysfunction.

Animals↗
PubMed1997

Differential pathogenesis of lethal mousepox in congenic DBA/2 mice implicates natural killer cell receptor NKR-P1 in necrotizing hepatitis and the fifth component of complement in recruitment of circulating leukocytes to spleen.

Innate resistance of C57BL/6 (B6) mice to lethal mousepox is controlled by multiple genes. Previously, four resistance genes were localized to specific subchromosomal regions and transferred onto a susceptible DBA/2 (D2) background by serial backcrossing and intercrossing to produce congenic strains. Intraperitoneally inoculated ectromelia virus was uniformly lethal and achieved similar titers in B6 and D2 mice but elicited differential responses in liver, spleen, and circulating blood leukocytes. The distribution of these response phenotypes in congenic strains linked control of phenotypes with specific subchromosomal regions. D2.R1 mice, which carried a differential segment of chromosome 6, exhibited a B6 liver response and intermediate spleen and circulating leukocyte responses. D2.R2 and D2.R4 mice, which carried differential segments of chromosomes 2 and 1, respectively, exhibited a D2 liver response, a B6 spleen response, and an intermediate circulating leukocyte response. The localization of control of liver response phenotypes to chromosome 6 implicates cells that express natural killer (NK) cell receptor NKR-P1 alloantigens. The localization of control of spleen and circulating leukocyte responses to chromosomes 1, 2, and 6 implicates NK cells, the fifth component of complement, and a gene near the selectin gene complex in recruitment of circulating leukocytes to spleen.

Animals↗
PubMed1995

Chromosome mapping of Rmp-4, a gonad-dependent gene encoding host resistance to mousepox.

DBA/2 (D2) mice are susceptible and C57BL/6 (B6) mice are resistant to lethal mousepox. A congenic resistant strain, D2.B6-Rmp-4r (D2.R4), was developed by serially backcrossing male mice that survived ectromelia virus infection with D2 mice, beginning with (B6 x D2)F1 mice. Male D2.R4 mice were at least 300-fold more resistant to lethal mousepox than male D2 mice. Female D2.R4 mice were 100-fold more resistant than male D2.R4 mice and 500-fold more resistant than female D2 mice. Neonatal gonadectomy prevented development of resistance in D2.R4 mice of both sexes. Differences in resistance between strains and between sexes correlated with restriction of virus replication in spleen and liver, but gender differences were less evident in liver than in spleen. High-resolution interval mapping of the 19 autosomes of D2.R4 mice using dispersed informative microsatellites as marker loci revealed a segment of distal chromosome 1 to be of B6 origin. Haplotypes for a marker locus, D1Mit57, from the differential segment were determined in (D2.R4 x D2)F1 x D2 backcross mice, which were then infected with ectromelia virus. Significantly more heterozygotes than homozygotes survived ectromelia virus infection in both sexes. Whereas nearly all surviving males were heterozygotes, 44% of surviving females were homozygotes. These results indicate that resistance in D2.R4 mice is determined by a gonad-dependent gene on distal chromosome 1, provisionally named Rmp-4, and by an ovary-dependent factor that is not genetically linked to Rmp-4.

Animals↗
PubMed1995

Papilloma formation in human foreskin xenografts after inoculation of human papillomavirus type 16 DNA.

A mouse model of high-risk human papillomavirus infection was developed in which human papillomavirus (HPV) type 16 DNA was inoculated into human foreskin grafted to the skin of severe combined immunodeficient (scid) mice. Grafted skin contained human epidermis and dermis and, like normal human skin, expressed involucrin in differentiating keratinocytes. HPV type 16 DNA, attached to gold particles, was delivered directly into human epidermal cells and induced exophytic papilloma with histologic features of papillomavirus infection, including koilocytosis and expression of papillomavirus capsid antigen. This model should be useful for determining in vivo the functions of viral genes and for developing strategies to prevent and treat HPV-associated disease. It may also be of value in developing animal models of other human skin diseases.

Animals↗
PubMed1995

Innate resistance to lethal mousepox is genetically linked to the NK gene complex on chromosome 6 and correlates with early restriction of virus replication by cells with an NK phenotype.

Most inbred strains of mice, including DBA/2 (D2), are highly susceptible to the lethal effects of ectromelia virus, but C57BL/6 (B6) mice are innately resistant. Resistance is controlled by multiple, unlinked, autosomal dominant genes. Of 101 male (B6 x D2)F1 x D2 backcrossed (N2) mice, 18 died after ectromelia virus challenge and all were homozygous for the D2 allele at the proline-rich protein (Prp) locus on distal chromosome 6 (P < 0.001). This association was suggested by the patterns of susceptibility to lethal mousepox in recombinant inbred strains derived from B6 and D2 mice (D. G. Brownstein, P. N. Bhatt, L. Gras, and R. O. Jacoby, J. Virol. 65:1946-1951, 1991). The association between the Prp locus and susceptibility to lethal mousepox also held for N2 male mice that were castrated as neonates, which increased the percentage that were susceptible to 40. Spleen virus titers were significantly augmented in B6 (NK1.1+) mice depleted of asialo GM1+ or NK1.1+ cells, whereas spleen virus titers were unaffected in D2 (NK1.1-) mice depleted of asialo GM1+ cells. These results suggest that a gene or genes within the natural killer gene complex, adjacent to the Prp locus, determine strain variations in resistance to lethal ectromelia virus infection.

Animals↗
PubMed1993

Ectromelia virus replication in major target organs of innately resistant and susceptible mice after intravenous infection.

The kinetics of ectromelia virus replication in the spleen and liver and of alpha/beta interferon production in the spleen were determined during the first 3 days after intravenous infection with the virulent Moscow strain in resistant C57 BL/6 and susceptible DBA/2 mice. Virus replication in the spleen as measured by assays for virus DNA and infectious centers was suppressed in C57BL/6 mice relative to DBA/2 mice within the first 1 or 2 days of infection. Infectious centers increased in DBA/2 mice but not in C57 BL/6 mice. Differences in virus replication between strains were less discrete when spleens were assayed for infectious virus than when they were assayed for infectious centers because infectious centers of most C57 BL/6 mice had more infectious virus than infectious centers of DBA/2 mice. Virus replication in the liver, the major target organ, as measured by virus DNA and infectious virus assays, was suppressed in C57 BL/6 mice relative to DBA/2 mice 3 days after infection but not before that interval. The results indicate that genetic control of ectromelia virus replication begins within the first 1 or 2 days of infection in the spleen but is delayed in the liver and that genetic control is directed at the prevention of virus spread more than at virus replication.

Animals↗
PubMed1993

Lack of detectable enhanced pulmonary histopathology in cotton rats immunized with purified F glycoprotein of respiratory syncytial virus (RSV) when challenged at 3-6 months after immunization.

The cotton rat model has been used to evaluate the potential for immunogens to induce respiratory syncytial virus (RSV)-enhanced pulmonary histopathology. A recent study evaluated purified F protein in this model when animals were challenged intranasally with RSV 3 or 6 months after immunization. The authors concluded that the purified F protein was associated with the same level of histopathological changes as observed with the positive control, a formalin-inactivated RSV immunogen. Three pathologists have independently evaluated the lung sections from the animals of this study and the results are reported in this article. In contrast to the previously published data, we have found that F protein was associated with a substantially milder and qualitatively different response to that observed with the formalin-inactivated RSV vaccine. We concluded that the minimal histological changes observed and lack of clinical disease make it very difficult to assess the issue of enhanced pulmonary RSV disease with the cotton rat model.

Analysis of Variance↗