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Biomedical subjects

S W Davis

Publications and source records attributed to S W Davis.

At least 55 records · Page 3Linked to original sources
PubMed1991

Protective immunity to toxoplasmosis in pigs vaccinated with a nonpersistent strain of Toxoplasma gondii.

The RH strain of Toxoplasma gondii is highly virulent; 1 infective organism is uniformly lethal for mice. Three pigs inoculated SC with 10(3) tachyzoites of the RH strain developed fever, but otherwise remained normal, and T gondii was not demonstrated in their tissues by bioassay into mice. To determine whether vaccination with the RH strain could induce protective immunity to oral challenge with T gondii oocysts, 12 pigs were divided into 3 groups (A, B, C) of 4 pigs each. Pigs in groups A and B were inoculated IM with 10(6) tachyzoites of the RH strain and 4 pigs in group C served as uninoculated controls. Except for fever, the pigs remained clinically normal after inoculation with the RH strain and T gondii was not found by bioassay in mice of tissues from 4 pigs euthanatized 64 days after inoculation. Pigs in groups B and C were challenge-inoculated orally with 10(4) (4 pigs) or 10(5) (4 pigs) T gondii oocysts 72 days after vaccination with the RH strain. The previously uninoculated pigs developed fever, anorexia, and diarrhea from 3 to 8 days after the oocyst challenge. One of the 2 pigs given 10(5) oocysts became moribund because of toxoplasmosis and was euthanatized 9 days after inoculation. Pigs vaccinated with the RH strain remained free of clinical signs after challenge with oocysts. Results of the bioassays indicated that fewer tissue cysts developed in the RH strain-vaccinated pigs than in the previously uninoculated control pigs.

Animals↗
PubMed1991

Computerized literature searching in a teaching family practice center.

Computerized literature searching was introduced into a family practice residency office site after a series of training sessions. BRS Colleague was the searching program used. Over 15 months, 147 searches were conducted, primarily by faculty. Because residents used the system infrequently, they preferred to find a faculty member to help with the search rather than complete the search by themselves. The mean number of searches per faculty user was 6.4 and the median number of documents found per search was 15. The users were moderately satisfied with the search process (2.4 on a scale of 1 as excellent to 5 as unusable). Search strategies tended to be unsophisticated, often using only one of several possible related search terms. Most searches took a limited amount of time (5 to 20 minutes). The program was sufficiently successful to warrant continuation. Computerized literature searching offers a method to meet the physicians' needs for ready access to information on patient-related questions.

Follow-Up Studies↗
PubMed1990

Taenia taeniaeformis: evasion of complement-mediated lysis by early larval stages following activation of the alternative pathway.

Activation of the alternative pathway of complement by T. taeniaeformis oncospheres and early stage metacestodes, although a factor in host defense against primary infection, does not directly lead to the killing of the parasite larvae observed prior to day 6 post-infection in innately resistant BALB/cByJ inbred mice. Immunogold labelling techniques clearly demonstrated tegument-associated C3 on in vitro-activated oncospheres incubated with non-immune mouse sera. However, C5, a protease necessary for the assembly of the membrane attack complex, was not detected. Early stage larvae cultured from in vitro-activated oncospheres escaped membrane damage and survived incubation in non-immune sera from both BALB/cByJ and taeniid-susceptible C3H/HeDub mice. Comparisons of cobra venom factor-treated and untreated C5-deficient B10.D2osn mice revealed no significant differences in parasite burden and local eosinophil infiltration at 6 days post-infection, suggesting that the terminal arm of the complement system is necessary for the previously reported role of complement in resistance to primary infection in BALB/cByJ and C3H/HeDub mice. An in vivo test of chemotaxis indicated that although both complement-intact mouse strains examined responded to intraperitoneal injections of inulin, there were lower numbers of eosinophils in C3H/HeDub mice than in BALB/cByJ mice, perhaps pointing to possible mouse strain differences in C5a generation/catabolism or eosinophil ability to respond to C5a. Lectin-binding studies showed an affinity of PNA for the exposed surface of taeniid oncospheres and 4-day post-infection metacestodes; however, binding of lectin to the carbohydrate moiety did not inhibit complement activation.

Animals↗
PubMed1990

Effect of depletion of L3T4+ cells on resistance to early primary infection of mice with Taenia taeniaeformis.

The role of L3T4+ T lymphocytes in early primary infection with the metacestode of T. taeniaeformis was investigated by selective removal of these cells in vivo by parenteral injections with the rat monoclonal antibody (MAb) GK1.5 directed against the L3T4 molecule. Comparisons between treated and non-treated BALB/cByJ mice, normally resistant to infection with T. taeniaeformis, demonstrated that the treated mice had a greater percentage of viable parasites in the livers. Eosinophils were prominent in the region immediately surrounding parasite larvae in control mice, whereas treated mice showed virtually no eosinophil infiltration. Additionally, fewer tissue macrophages were evident near parasite larvae in the treatment group when compared to controls. The more susceptible C3H/HeDub strain mice demonstrated similar responses following treatment with the MAb, including diminished parasite killing and limited inflammatory cell infiltration. When C3H/HeDub mice were injected with the cytotoxic agent vinblastine sulfate, which has been shown to diminish Lyt-2+ suppressor cell activity, these mice remained unable to mount a strong local cellular response to the larval parasite. It is suggested that L3T4+ T lymphocytes play a crucial role in the innate resistance to T. taeniaeformis infection during the first 6 days post-infection. Effects seen following vinblastine treatment may be a result of drug-induced alterations in leukocyte chemotaxis, toxicity to other effector T cell populations, or a specific depletion of a functional Lyt-2+ T cell population that is required in addition to L3T4+ T cells for the expression of resistance to primary infection with T. taeniaeformis.

Animals↗
PubMed1990

The complete DNA sequence of vaccinia virus.

The complete DNA sequence of the genome of vaccinia virus has been determined. The genome consisted of 191,636 bp with a base composition of 66.6% A + T. We have identified 198 "major" protein-coding regions and 65 overlapping "minor" regions, for a total of 263 potential genes. Genes encoded by the virus were located by examination of DNA sequence characteristics and compared with existing vaccinia virus mapping analyses, sequence data, and transcription data. These genes were found to be compactly organized along the genome with relatively few regions of noncoding sequences. Whereas several similarities to proteins of known function were discerned, the function of the majority of proteins encoded by these open reading frames is as yet undetermined.

Amino Acid Sequence↗
PubMed1990

A DNA ligase gene in the Copenhagen strain of vaccinia virus is nonessential for viral replication and recombination.

Biochemical and genetic analyses have been conducted to determine whether a vaccinia virus open reading frame (orf) with extensive homology to the Saccharomyces cerevisiae DNA ligase gene encodes a functional ligase activity. This orf in HindIII A, designated A50R, is capable of encoding a 552-amino-acid, 63.4-kDa polypeptide. Full-length A50R mRNA produced in vitro directed the synthesis of a polypeptide with an apparent molecular weight of 57 kDa. Significantly, translation reactions programmed with A50R mRNA were capable of ligating a 3-kb Notl restriction fragment into multimers. DNA ligase activity was not detectable when either truncated sense or full-length antisense mRNA was translated in vitro. In extracts prepared from cells infected with wt vaccinia virus, DNA ligase activity was detected as assayed by the formation of a 57 kDa ligase-AMP adduct which was expressed early in the viral replication cycle. In cells infected with a DNA ligase deletion mutant no equivalent AMP-labeled adduct was detected. Relative to wt virus, the DNA ligase deletion mutant exhibited no significant differences in homologous recombination. These results indicate that the vaccinia orf A50R encodes a functional DNA ligase expressed early in infection, but this DNA ligase is nonessential for either recombination or viral replication.

Amino Acid Sequence↗
PubMed1990

Vaccinia virus host range genes.

A gene encoding an 18-kDa polypeptide (ORF C7L) located in the vaccinia virus HindIII C fragment was shown to be functionally equivalent to previously described host range gene (ORF K1L) spanning the HindIII K/M fragment junction. Either C7L or K1L host range gene is necessary and sufficient by itself to allow replication of vaccinia virus on human cells. Deletion of both C7L and K1L genes from the wild-type vaccinia genome is required to derive a virus deficient for replication on human cells. Further, an ORF encoding a 77-kDa polypeptide derived from cowpox (CP77kDa) and previously shown to allow vaccinia to overcome the restriction for replication on Chinese hamster ovary cells could substitute for the vaccinia host range genes C7L and K1L in permitting replication of the virus on human cells. Additionally, the three unique host range genes C7L, K1L, and CP77kDa were functionally equivalent for vaccinia replication on pig kidney cells, but not on rabbit kidney cells.

Animals↗
PubMed1988

Testicular cancer. Adolescent knowledge and attitudes.

To study what adolescents know or feel about testicular cancer (TC), 1,364 males, mean age 14.9 years, were given an 85-item pretest questionnaire. Although 28% had heard of TC, none knew how to perform a testicular self-examination (TSE). Analysis of the attitude questions showed that adolescents are afraid of getting TC, are unsure about whether it can be self-diagnosed, and do not know whether recovery is more likely with early diagnosis. Black adolescents were less knowledgeable about and more afraid of getting TC than white adolescents; males of lower socioeconomic status (SES) and males with more contact with cancer were also more afraid of getting TC than higher SES and low-cancer contact groups. Although 75% reported having a complete physical examination by a physician within the previous 15 months, less than 2% reported being taught TSE. Having had a recent physical examination made no difference in the knowledge of or attitudes toward TC.

Adolescent↗
PubMed1988

Some reasons for compliance and noncompliance in a health maintenance organization breast cancer screening program.

Impressive reductions in breast cancer mortality have been demonstrated through regular screening programs using mammograms and clinical breast examinations. Nevertheless, only a small proportion of American women obtain annual mammograms. The US HEALTHCHECK breast cancer screening program offered free breast cancer screening to age-eligible members of a Health Maintenance Organization. Subscribers were mailed packets of materials and asked to return a Breast Risk Assessment Form to determine their eligibility to receive a free mammogram. This study was conducted to assess why women did or did not return a Breast Risk Assessment Form. Brief telephone interviews were conducted with a random sample of compliers and noncompliers (n = 502). Women who complied by returning the Risk Assessment Form said more frequently that they were unlikely to get breast cancer, were older, and more likely to have read the materials and to have rated them positively than women who did not return the Risk Assessment Form.

Adult↗
PubMed1984

Genetically engineered poxviruses: a novel approach to the construction of live vaccines.

Gene splicing techniques have been used to modify the smallpox vaccine virus thus providing a generic approach for the construction of live vaccines directed against a variety of heterologous infectious disease agents. The technique involves translocating a particular gene from an infectious agent into the genetic material of the smallpox vaccine virus. This unique foreign gene, selected because it contains the information essential for the synthesis of an antigen important in immunity to that particular infectious disease agent, is now expressed under the regulation of the engineered smallpox vaccine virus. On immunization with this live recombinant vaccine, the body is fooled into thinking that it was infected by the foreign infectious disease agent and mounts a defensive attack resulting in immunity to that particular infectious agent. Three examples of this approach are provided. Thus, smallpox vaccine viruses were engineered to express genes encoding the hepatitis B virus surface antigen (HBsAg), the herpes simplex virus glycoprotein D (HSV-gD) and the haemagglutinin (HA) from influenza virus. These foreign gene products when synthesized in vitro under vaccinia virus regulation were shown to be antigenic by a variety of serological tests. When these recombinant vaccinia viruses were inoculated into laboratory animals, the heterologous gene products elicited the production of specific antibodies thus demonstrating that they were immunogenic. Serum neutralizing antibodies were demonstrated to be present for both influenza and herpes simplex viruses. Additional studies in mice showed that a recombinant smallpox vaccine virus expressing a gene from herpes simplex virus effectively protected the mice when subsequently challenged with what would normally be lethal doses of infectious herpes simplex virus.

Animals↗
PubMed1984

The role of the pharmacist in a geriatric nursing home: a literature review.

This review delineates the pharmacist's controversial clinical role in nursing homes as it has developed within the legal, social, and economic climate of the Medicaid and Medicare conditions of participation. Special problems of the geriatric institutionalized patient include polypharmacy, adverse reactions, the overuse of prn drugs, and inadequate physician contact. These problems are compounded by an impoverished scientific data-base for appropriate drug use in the aged. Studies that clarify the impact consultant pharmacists have on the number of drugs prescribed, adverse reactions, and cost containment are compiled and evaluated. It is shown that pharmacists can reduce the number and cost of drugs. Physician acceptance of pharmacists' recommendations was found to be at least 60 percent in these reports. Well-controlled studies are lacking in the literature.

Aged↗
PubMed1983

Construction of live vaccines by using genetically engineered poxviruses: biological activity of recombinant vaccinia virus expressing influenza virus hemagglutinin.

Recombinant vaccinia viruses containing the cloned hemagglutinin (HA) gene from influenza virus were constructed. The biological activity of these poxvirus vectors was demonstrated both in vitro and in vivo. Expression of HA in cells infected with recombinant vaccinia was detected by using specific anti-HA antiserum and 125I-labeled protein A, showing that HA synthesized under the regulation of vaccinia virus was antigenic. Immunization of rabbits with these recombinant poxviruses resulted in the production of antibodies reactive with authentic influenza HA as detected by radioimmunoassay, by inhibition of HA erythrocyte agglutination, and by neutralization of influenza virus infectivity. The production of antibodies directed against influenza HA suggested that the HA gene expressed in vaccinia is immunogenic. These data indicate the potential of genetically engineered poxviruses for use as generic live vaccine vehicles that have both human and veterinary applications.

Animals↗