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Biomedical subjects

C House

Publications and source records attributed to C House.

At least 37 records · Page 2Linked to original sources
PubMed1995

African horse sickness and African carnivores.

African horse sickness (AHS) is a disease that affects equids, and is principally transmitted by Culicoides spp. that are biological vectors of AHS viruses (AHSV). The repeated spread of AHSV from sub-Saharan Africa to the Middle East, northern Africa and the Iberian peninsula indicate that a better understanding of AHS epizootiology is needed. African horse sickness has long been known to infect and cause mortality among domestic dogs that ingest virus contaminated meat, but it is uncertain what role carnivores play in transmission of the virus. We present evidence of widespread natural AHS infection among a diversity of African carnivore species. We hypothesize that such infection resulted from ingestion of meat and organs from AHS-infected prey species. The effect of AHS on the carnivores is unknown, as is their role in the maintenance cycle of the disease.

Africa↗
PubMed1994

Mammalian AMP-activated protein kinase shares structural and functional homology with the catalytic domain of yeast Snf1 protein kinase.

The AMP-activated protein kinase is responsible for the regulation of fatty acid synthesis by phosphorylation of acetyl-CoA carboxylase. It may also regulate cholesterol synthesis via phosphorylation and inactivation of hormone-sensitive lipase and hydroxymethylglutaryl-CoA reductase. We have purified the AMP-activated protein kinase 14,000-fold from porcine liver. The 63-kDa catalytic subunit co-purifies with two proteins of 40 and 38 kDa that may function as subunits. Partial amino acid sequence of the 63-kDa subunit revealed a striking homology with the catalytic domain of the yeast protein kinase transcriptional regulator Snf1 and its plant homologs. The Snf1 (72 kDa) and Snf4 (36 kDa) complex was also purified and found to phosphorylate the AMP-activated protein kinase peptide substrate, HMRSAMSGLHLVKRR-amide, but was not activated by AMP. Both Snf1/4 and the AMP-activated protein kinase phosphorylate and inactivate yeast acetyl-CoA carboxylase in vitro. These results indicate that during evolution the catalytic domain sequences of the Snf1 protein kinase subfamily have been exploited in the control of mammalian lipid metabolism and raise the possibilities that the AMP-activated protein kinase may have other substrates involved in regulating gene expression pathways, as well as Snf1 homologs participating in the control of lipid metabolism in many eukaryotic organisms.

AMP-Activated Protein Kinases↗
PubMed1994

Further studies on the efficacy of an inactivated African horse sickness serotype 4 vaccine.

The immunity induced by two inoculations of a commercial inactivated African horse sickness (AHS) serotype 4 (AHSV-4) vaccine was studied. No adverse reaction was observed in five horses following vaccination. Following challenge-inoculation, no clinical signs attributable to AHS, no viraemia indicating infection, and no anamnestic response was observed in the vaccinated ponies. Two control ponies developed clinical signs typical of AHS, high levels of viraemia, and died 7 and 8 days postchallenge-inoculation. The quality of immunity induced by the two-dose regimen was compared with a one-dose regimen from a previous study; in the one-dose study following challenge-inoculation, six of nine ponies were protected from clinical signs of AHS, seven of the nine vaccinated ponies developed an anamnestic response, and one pony had a viraemia about 10(3) 50% mouse lethal dose of AHSV-4 per ml of blood for 3 days following challenge-inoculation. The utility of an efficacious inactivated AHS vaccine in the control and eradication of AHS from a non-endemic area is discussed. The lack of viraemia following vaccination with an inactivated vaccine and the prevention of vector infection by animals exposed to field virus are important in the eradication of AHS.

African Horse Sickness↗
PubMed1994

Substrate and pseudosubstrate interactions with protein kinases: determinants of specificity.

Protein crystallography has revealed that protein kinases have extended protein-substrate-binding grooves associated with their active sites. Some protein kinases are autoinhibited by a mechanism in which part of their structure, termed a pseudosubstrate, occupies the active site. Substrates and pseudosubstrates occupy overlapping regions within the extended substrate-binding groove, making multiple specific electrostatic and non-polar contacts. With masterly economy, Nature has exploited the active site in many protein kinases to both recognize substrates with great specificity and autoregulate by remaining inactive until the appropriate activation signal is received.

Amino Acid Sequence↗
PubMed1994

Evidence of natural bluetongue virus infection among African carnivores.

Bluetongue is an International Office of Epizootics List A disease described as the century's most economically devastating affliction of sheep. Bluetongue (BLU) viruses were thought to infect only ruminants, shrews, and some rodents, but recently, inadvertent administration of BLU virus-contaminated vaccine resulted in mortality and abortion among domestic dogs. We present evidence of natural BLU virus infection among African carnivores that dramatically widens the spectrum of susceptible hosts. We hypothesize that such infection occurred after ingestion of meat and organs from BLU virus-infected prey species. The effect of BLU virus on endangered carnivores such as the cheetah and African wild dog requires urgent investigation. Also, the role of carnivores in the epizootiology of this disease needs elucidation.

Africa↗
PubMed1993

The detection of foot-and-mouth disease virus in oesophageal-pharyngeal samples by a polymerase chain reaction technique.

A polymerase chain reaction (PCR) technique was used to detect the presence of foot-and-mouth disease virus (FMDV) in oesophageal-pharyngeal(OP) samples from experimentally infected steers. Ten-fold dilutions of OP samples were also diluted, inoculated onto lamb kidney cell cultures, and incubated overnight. The cultures that did not show overt cytopathogenic effects (CPE) of FMDV infection were frozen and thawed; both the fluid and the cell pellet were tested by the PCR technique. The PCR detected FMDV in the fluids of 57% of the cell cultures inoculated with 2-20 tissue culture infective doses-50% (TCID50) and of 33% of cell cultures inoculated with the 0.4-2 TCID50. The PCR detected FMDV in cell pellets of all cell cultures inoculated with 20 TCID50, of 71% of cell cultures inoculated with 2-20 TCID50 and of 50% of cell cultures inoculated with 0.2-2 TCID50. A diagnostic scheme using PCR and cell culture that would provide rapid and sensitive detection of FMDV in OP samples is proposed.

Animals↗
PubMed1992

A pathogenesis study of foot-and-mouth disease in cattle, using in situ hybridization.

Eight calves were exposed in an aerosol chamber to nebulized foot-and-mouth disease virus. Two control animals were exposed in a similar manner to cell culture media only. Animals were euthanized at intervals and various tissues examined by in situ hybridization using a biotinylated RNA probe corresponding to a portion of the viral gene coding for the polymerase enzyme. By this technique large amounts of viral nucleic acid were found in coronary band, interdigital cleft and tongue as early as six hours postexposure, indicating a very rapid delivery from the portal of entry to the predilection sites for lesion development. This occurred well before the onset of viremia which by virus isolation was not detectable until 30 hours postexposure. The in situ hybridization signal in these tissues decreased in intensity and extent with time to focally positive areas, occasionally surrounding a vesicle. Other epidermal sites not normally thought of as sites for foot-and-mouth lesion development, such as carpus and eyelid, also had some viral nucleic acid detectable at various time intervals. In the lung by in situ hybridization, alveolar septa had viral nucleic acid early in infection (6-18 h postexposure) while later (36-96 h postexposure), the in situ hybridization signal was prominent in alveolar macrophages.

Animals↗
PubMed1991

Viral haemorrhagic disease of rabbits in Mexico: epidemiology and viral characterization.

A fatal disease of rabbits was first reported in the People's Republic of China in 1984. Since 1986, the disease has been reported in most countries of Europe and in the Republic of Korea. In 1989 a similar disease, presumably linked to the importation of rabbit meat from the People's Republic of China, spread rapidly through ten states in Mexico; it was eradicated during the same year by "stamping-out" measures. In Mexico, as was the case in other outbreaks, morbidity and mortality reached 80-90% with few clinical signs. In pathogenesis studies, the primary sites of replication were in the small intestinal crypt and villous epithelium, hepatocytes and splenic lymphocytes. Many organs, including the lung and kidney, contained acutely infarcted tissue and haemorrhages resulting from a terminal disseminated intravascular coagulopathy. The disease and the characteristics of the virus isolated in Mexico are similar to isolates from Europe and the Republic of Korea. The comparative morphologic, from Europe and the Republic of Korea. The comparative morphologic, immunologic, and in situ nucleic acid hybridization evidence for a parvovirus aetiology are summarized.

Animals↗
PubMed1990

Mutagenesis of the pseudosubstrate site of protein kinase C leads to activation.

Protein kinase C is maintained in an inactive state by the action of an inhibitory region within the effector binding domain of the kinase. It has been suggested that a short stretch of amino acids (pseudosubstrate site) mediates this inhibition by binding to the active site and preventing substrate interaction [House, C. and Kemp, B. E. (1987) Science 238, 1726-1728]. A mutated version of protein kinase C-alpha containing a glutamic acid for alanine substitution in this region has been analysed for biochemical properties and biological function. Consistent with the importance of this pseudosubstrate site in regulating kinase activity, this altered protein has a significantly increased effector-independent kinase activity relative to wild-type protein kinase C-alpha and shows increased sensitivity to activation by proteolysis. The increased activity of this protein in the intact cell was confirmed by its ability to stimulate expression from a phorbol-ester-inducible reporter construct in a transient transfection system. Expression of a mutant kinase with the pseudosubstrate sequence deleted causes greater induction in this transient expression system, consistent with this kinase being independent of effectors and thus constitutively active.

Animals↗
PubMed1990

Protein kinase C pseudosubstrate prototope: structure-function relationships.

A structure-function study of the protein kinase C (PK-C) pseudosubstrate sequence (R19FARK-GALRQKNV31) has been undertaken. The role of specific residues was investigated using an alanine substitution scan. Arg-22 was the most important determinant in the inhibitor sequence, since substitution of this residue by alanine gave a 600-fold increase in the IC50 value to 81 +/- 9 microM. Substitutions of other basic residue also increased the IC50, 5-, 11- and 24-fold for the Ala-19, Ala-23 and Ala-27 substitutions, respectively. The importance of basic residues in determining the potency of the pseudosubstrate peptide reflects the requirements for these residues in peptide substrate phosphorylation. The residues Gly-24, Leu-26 and Gln-28 were also important for pseudosubstrate inhibitor potency. The large difference in the IC50 value for the [A22]PK-C(19-31) peptide makes it a valuable control in studies employing the pseudosubstrate peptide to explore functional roles of PK-C.

Amino Acid Sequence↗
PubMed1990

Inactivation of viral agents in bovine serum by gamma irradiation.

Cell culture origin or suckling mouse brain origin viruses of Akabane disease, Aino, bovine ephemeral fever, swine vesicular disease, hog cholera, bluetongue, and minute virus of mice were each suspended in bovine serum. Aliquots (1 mL) were exposed to various doses of gamma radiation from a 60Co source while at -68 degrees C. Aliquots (100-mL) of serum from a steer experimentally infected with foot-and-mouth disease virus were similarly irradiated. The samples were assayed for infectivity in cell culture systems before and after irradiation, and the data points were analyzed by linear regression. The irradiation doses (in megarads) necessary to inactivate one log10 of viral infectivity (D10) was calculated for each virus. D10 is otherwise known as the slope of the regression line. The r2 value, a measure of association with 1.0 = perfect fit, was also calculated for each regression line. The values (D10, r2) for each virus were as follows: Akabane, 0.25, 0.998; Aino, 0.35, 0.997; bovine ephemeral fever, 0.29, 0.961; swine vesicular disease, 0.50, 0.969; foot-and-mouth disease, 0.53, 0.978; hog cholera, 0.55, 0.974; bluetongue, 0.83, 0.958; and minute virus of mice, 1.07, 0.935.

Animals↗
PubMed1990

Laboratory diagnosis of African horse sickness: comparison of serological techniques and evaluation of storage methods of samples for virus isolation.

Five serological methods of diagnosing African horse sickness were evaluated, using a battery of serum samples from experimental horses vaccinated and challenged with each serotype of African horse sickness virus (AHSV1 through AHSV9): agar gel immunodiffusion (AGID), indirect fluorescent antibody (IFA), complement fixation (CF), virus neutralization (VN), and enzyme-linked immunosorbent assay (ELISA). The 5 tests were also compared using a panel of field samples, convalescent equine sera with antibodies to domestic equine viral diseases, and sera from horses awaiting export. The ELISA described in this paper was group specific. It did not require calibration with a standard positive serum but did yield elevated values with negative sera that were repeatedly frozen and thawed or heat inactivated. The IFA test was sensitive but could not be used on some field sera as the control cells exhibited fluorescence, possibly due to the animal being recently vaccinated with cell culture material. Sixty-two experimental sera were compared by VN, CF, AGID, and ELISA. Forty sera, 10 positive and 30 negative, were correctly classified by the 5 serologic assays. The 22 remaining sera gave mixed reactions. The AGID had no false positive results but had false negative results for up to 20% of the samples, depending upon the comparison. The VN, CF, and ELISA were similar in their variability. The length of time that virus could be recovered from a viremic blood sample was compared in an evaluation of storage methods for virus isolation samples. Washed erythrocytes were held at 4 C, washed erythrocytes plus stabilizer were held at -70 C, and blood that was drawn into a preservative (oxalate/phenol/glycerol) was held at 4 C.(ABSTRACT TRUNCATED AT 250 WORDS)

African Horse Sickness↗
PubMed1989

A synthetic peptide analog of the putative substrate-binding motif activates protein kinase C.

A 29-residue synthetic peptide, Leu530-Leu-Tyr-Glu-Met-Leu-Ala-Gly-Gln-Ala-Pro-Phe-Glu-Gly-Glu-Asp -Glu-Asp- Glu-Leu-Phe-Gln-Ser-Ile-Met-Glu-His-Asn-Val-NH2(558), corresponding to part of the catalytic domain of protein kinase C, is a potent activator of the enzyme, with a Ka of approx. 10 microM. Activation was 59 +/- 4% of that observed with phosphatidylserine, predominantly due to an increased Vmax, partially calcium-dependent, observed with all three isoenzymes (alpha, beta, gamma), and resulted in autophosphorylation. It is proposed that the region between Gly528 and Arg583 is part of the protein substrate binding region of protein kinase C and synthetic peptide analogs of this region activate the enzyme by blocking the action of the enzyme's basic pseudosubstrate autoregulatory region.

Animals↗
PubMed1989

Evaluation of techniques to demonstrate foot-and-mouth disease virus in bovine tongue epithelium: comparison of the sensitivity of cattle, mice, primary cell cultures, cryopreserved cell cultures and established cell lines.

Tongue epithelia infected with each of the 7 serotypes of foot-and-mouth disease virus (FMDV) were used to evaluate in vivo and in vitro systems for the detection of FMDV. Cattle inoculated by the intradermal route in the tongue (IDL) and suckling mice inoculated intraperitoneally were compared for susceptibility to FMDV with freshly prepared bovine thyroid cell cultures; cultures from cryopreserved bovine thyroid, bone marrow, mammary gland, myocardium, tongue, ovary and kidney cells; cultures from cryopreserved embryonic ovine kidney, newborn ovine kidney, ovine testicle, bone marrow, and chloroid plexus cells; and the continuous porcine kidney cell lines MVPK-1 and S6. The mean titers determined for each serotype in each system were statistically compared. The FMDV titers obtained in freshly prepared bovine thyroid cell cultures and by cattle IDL inoculation were the highest and were statistically indistinguishable. The titers obtained by suckling mouse inoculation were significantly lower than the titers obtained in thyroid cultures for serotypes A, C, Asia 1, and SAT 3. The cattle IDL assay was significantly more sensitive than the mouse assay for serotype A. The cell cultures from the cryopreserved newborn ovine kidney and embryonic ovine kidney were significantly less susceptible to serotype Asia 1 when compared with the fresh bovine thyroid cultures, but not significantly different when compared with the cattle assay for all serotypes. Cryopreservation of bovine thyroid cells directly after trypsinization resulted in the loss of susceptibility to FMDV serotype SAT 2. The other cryopreserved cell culture systems exhibited no or minimal susceptibility to all 7 serotypes, or exhibited considerable inconsistency. The established cell lines MVPK-1 and S6 were not susceptible to serotype A, and were less sensitive to serotype C than other culture systems. Quality control of cell cultures used to evaluate field specimens for FMDV was critical. The cell cultures of cryopreserved ovine kidney cells provided the most practical diagnostic system.

Animals↗