PubMed Health⌕ Search

Biomedical subjects

M R Hall

Publications and source records attributed to M R Hall.

At least 19 recordsLinked to original sources
PubMed2006

Histochemical and immunohistochemical evidence of a bacterium associated with lesions of epizootic bovine abortion.

Epizootic bovine abortion (EBA), a tick-transmitted disease of pregnant cattle grazing foothill pastures, is a major cause of reproductive failure in California and adjacent states. Affected fetuses develop a chronic disease, resulting in late-term abortion or premature calving. Despite investigations spanning 50 years, to the authors' knowledge, the etiologic agent of EBA has not yet been isolated from affected fetuses or the tick vector. The diagnosis of EBA is based on gross and microscopic lesions. Recently, documentation that the etiologic agent is susceptible to antibiotics and identification of a unique 16S deltaproteobacterial rDNA gene sequence in 90% of thymus tissues from aborted fetuses have supported the role of a bacterial infection as the cause of EBA. To determine whether bacteria could be detected in the tissues, histochemical staining and immunohistochemical procedures were used on formalin-fixed, paraffin-embedded tissues. Use of a modified Steiner silver stain revealed small numbers of intracytoplasmic bacterial rods in 37 of 42 thymic samples from EBA-affected fetuses. Improved detection was achieved by use of immunohistochemical staining with serum from EBA-affected fetuses that resulted in detection of numerous bacterial rods in the cytoplasm of histiocytic cells in the thymus from all 42 EBA-affected fetuses. Immunohistochemical examination of additional tissues from 21 field and experimental EBA cases revealed positively stained intracytoplasmic bacterial rods in many organs with inflammatory lesions. Use of the modified Steiner stain and immunohistochemical staining of tissues from negative-control fetuses failed to reveal organisms. To the authors' knowledge, this is the first report to document morphologic evidence of a bacterium associated with the lesions of EBA.

Abortion, Veterinary↗
PubMed2001

Occurrence of verotoxin-producing Escherichia coli in dairy heifers grazing an irrigated pasture.

Verotoxin-producing Escherichia coli (VTEC) produce one or two toxins known as VT1 and VT2. These toxins have been associated with several human illnesses. Dairy cattle harboring VTEC represent a potential health hazard because they enter the food chain as ground beef. The objective of this study was to assess the occurrence of VTEC in dairy heifers. A total of 91 fecal samples were rectally collected during four periods (spring, summer, fall, and winter of 1999) from 23 heifers. A random sample (n=530) of potential VTEC isolates were tested for verotoxicity and were screened by the polymerase chain reaction (PCR) for presence or absence of VT1 and/or VT2 genes. Thirteen isolates from two heifers (from the winter collection) were verotoxic and were confirmed as E. coli. VTEC were only detected during winter with an occurrence rate of 9.5%. Using PCR, five isolates had the VT1 gene while the remaining eight had the VT2 gene. The sequence and expression of VT1 and VT2 genes were confirmed. No E. coli O157:H7 was detected, but serotyping revealed that the five VT1-positive isolates were O26:NM (a non-motile strain of O26). The remaining eight isolates were untypeable. Identification of VTEC-positive cattle before slaughter is a critical step in any on-farm strategy to minimize the risk of beef contamination with such pathogens.

Animals↗
PubMed2001

Shiga toxin-producing Escherichia coli in beef heifers grazing an irrigated pasture.

Shiga toxin-producing Escherichia coli (STEC) produce toxins that have been associated with several human illnesses. E. coli O157:H7 is the most well-studied STEC and was first associated with consumption of improperly cooked ground beef in 1982. E. coli O157:H7 is not the only foodborne STEC because other STEC serotypes are also associated with human illnesses. The objective of this study was to assess prevalence of STEC in 23 yearling beef (Angus) heifers grazing an irrigated grass pasture in spring (April), summer (July), fall (October), and winter (December) of 1999. A total of 86 fecal samples were rectally collected and were subjected to microbiological testing for the presence of STEC. Nine E. coli isolates from five heifers (one in spring and fall and three in winter) were toxic to Vero cells. Of these isolates, four were E. coli O157:H7, two belonged to the serogroup O6, one O39:NM, one O113:H-, and the final isolate was untypable. The STEC prevalence rate in our herd ranged from 4% (spring) to 15% (winter). Based on detecting both O157:H7 and non-O157:H7 STEC in our heifers, it is clear that screening fecal samples should not be limited to E. coli O157:H7. Identification of STEC-positive cattle prior to slaughter should help in reducing the risk of beef contamination with such foodborne pathogens if pre- and/or postharvest control measures are applied to such animals.

Animals↗
PubMed2000

Reversed-phase high-performance liquid chromatography of catecholamines and indoleamines using a simple gradient solvent system and native fluorescence detection.

A reversed-phase HPLC method using a C18 column and a two-mobile-phase gradient elution system containing only volatile components has been developed for separation of norepinephrine, octopamine, epinephrine, dopamine, dihydroxyphenylalanine, tyramine, tyrosine, serotonin, 5-hydroxytryptophan, N-acetyl-serotonin and tryptophan. Mobile phase A contains 0.05% aqueous trifluoroacetic acid and methanol (97.5:2.5, v/v) and mobile phase B contains 0.05% aqueous trifluoracetic acid and methanol (40:60, v/v). This method has the advantage that the mobile phase can be removed completely, without salt residues, from the eluted fractions thus simplifying further analytical procedures on isolated fractions. The elution profile of standards is related to structural characteristics allowing prediction of retention times of known compounds and insight into possible structural characteristics of unknown components in a mixture. Detection is via native fluorescence using excitation at 220 nm and emission at 320 nm and under the conditions described has a sensitivity range from 2.5 to 25 pmol, although the sensitivity range can be extended depending on the emission wavelength used.

Amines↗
PubMed2000

Tumor development and cytokine production by human colon tissues and carcinoma cell lines.

BACKGROUND AND OBJECTIVES: Solid tumors evade the host immunologic responses they initiate by unknown mechanisms. The authors investigated patterns of cytokine content in human colon carcinomas, colon cancer cell lines in vitro, and nude mouse xenografts from those lines in order to clarify those mechanisms. METHODS: Epithelial tumor cell lines were developed from specimens of human colon adenocarcinoma. Aliquots of these cells were then xenografted into female heterozygous BALB/c nu/+ immunologically deficient mice and serially passaged. Original tumors, cell lines, and resultant xenografts were then analyzed for histology/cytology and for levels of TGF-beta and TNF-alpha by enzyme linked immunoassay. RESULTS: Cytokine levels were elevated beyond baseline mucosal levels in original tumors and xenograft mouse tumors but not detectable in extracts from epithelial cultures. CONCLUSIONS: While the precise source of cytokine production remains unclear, these data suggest tumor/host interactions not found in pure epithelial cancer cells in culture.

Adenocarcinoma↗
PubMed1999

An atraumatic method to establish human colon carcinoma in long-term culture.

Techniques for creation of colon carcinoma epithelial cells lines in long-term culture have been available for years, but these techniques have involved mechanical or enzymatic methods to separate epithelial cells from surrounding tissues. While this practice has been intermittently successful, the effect of these traumatic methods on long-term cellular behavior is unknown. Samples of colon carcinoma from patient volunteers were subjected to serial nonenzymatic disruptions of carcinoma cells from surrounding fibrous tissues. Cells were collected, allowed to proliferate, and then tested for their epithelial characteristics (mucin, vimentin, cytokeratin, colon-specific antigen, carcinoembryonic antigen) by immunohistochemistry and flow cytometry. Growth characteristics were determined by phase-contrast microscopy, multiple passage, and freeze/thaw effects. Tumorigenicity was proven in nude mice. Of 11 initial attempts, three resulted in stable long-term culture lines of cells which are demonstrated to behave similarly to the original tumors from which they were derived. This technique adds another reliable in vitro tool for the study of colon carcinoma.

Adenocarcinoma↗
PubMed1999

Studies on primary cell cultures derived from ovarian tissue of Penaeus monodon.

As part of a bioassay approach to investigate ovarian development and function, primary cell cultures were derived from Penaeus monodon ovaries at various stages of maturation. These cultures were established in modified Grace's or modified 2x L-15 media. Various supplements including growth factors, vitamins and minerals were trailed. Four morphologically different types of cells (epithelioid, fibroblastic, rounded, and epithelioid with large nuclei) were maintained for up to 17 months. Epithelioid cells grew best in modified Grace's medium but were generally short-lived (less than two months). Fibroblast-like cells formed confluent monolayers in modified 2x L-15 medium, were passaged three times and survived for 17 months. In other cultures, millions of rounded cells migrated from tissue. They survived for prolonged periods (up to ten months), either loosely attached to the flask or suspended in the medium. A change in dominant cell type from fibroblastic to epithelioid was observed in some cultures after three or nine months incubation. These epithelioid cells which had very large nuclei, grew to confluence but could not be sub-cultured. It is noteworthy that the rounded cells and the epithelioid cells with the large nuclei both produced vitellogenin in protein-free media.

Animals↗
PubMed1999

Characterization of antigenic proteins from Tritrichomonas foetus recognized by antibodies in rabbit serum, bovine serum and bovine cervicovaginal mucus.

Tritrichomonas foetus is an obligate parasite of the bovine urogenital tract and is recognized as 1 of the more common infectious agents causing decreased reproductive efficiency in beef cattle. Infections result in reproductive failure and produce considerable economic loss. Vaccination of heifers with vaccines containing T. foetus induces elevated serological responses to many T. foetus antigens, decreases the rate and/or length of infection with T. foetus, and decreases fetal loss caused by infection. Because T. foetus infections are usually limited to lumen and mucosal surfaces of the reproductive tract, it has been assumed that protection from infection and abortion is partially mediated by immunoglobulins in the uterus and vagina. The objective of this study was to identify and characterize specific antigens of T. foetus that show promise for use in a recombinant vaccine that will generate a protective mucosal immune response in cattle. Surface proteins were identified by using polyclonal rabbit anti-trichomonal sera eluted from paraformaldehyde-fixed cells. Analyses of these proteins, utilizing mucosal antibodies from vaccinated and convalescent cows, have identified proteins involved in generating a local immune response. Western immunoblot analysis indicates that these proteins are well conserved and are excellent candidates for incorporation into a recombinant vaccine.

Animals↗
PubMed1997

Assemblin homolog of herpes simplex virus type 1 retains proteolytic activity when expressed as a recombinant two-chain enzyme.

The herpes simplex virus type 1 (HSV) maturational proteinase is synthesized as a precursor that undergoes two autoproteolytic cleavages; one at its (M)aturational site, which eliminates its carboxyl "tail," and a second at its (R)elease site, which separates the amino proteolytic half of the precursor from its nonproteolytic carboxyl half. In cytomegalovirus (CMV) the proteolytic half of the precursor, called assemblin, undergoes a third cleavage at an (I)nternal site that converts it from a single-chain to a two-chain enzyme that retains activity. The HSV assemblin homolog has no I site and therefore does not form a counterpart two-chain enzyme. In the work reported here we have cloned and expressed HSV sequences that encode mimics of the An and Ac subunits of two-chain CMV assemblin. We show that when these HSV sequences are coexpressed in eukaryotic cells, the resulting subunits associate spontaneously to form an active two-chain enzyme. We also show that the two-chain HSV enzyme, like the natural one-chain form, retains its marked preference for HSV over CMV substrates, and that intertypic recombinant two-chain assemblin (e.g., HSV An/CMV Ac) does not form because the cross-species subunits do not interact. We conclude from these results that (i) there are not intrinsic structural differences in the HSV assemblin homolog that preclude its functioning as a CMV-like two-chain enzyme, (ii) the substrate selectivity shown by the single-chain HSV enzyme was not noticeably relaxed in the HSV two-chain mimic, and (iii) the interactive domains, through which the An and Ac portions of the single-chain enzymes associate, differ between HSV and CMV.

Amino Acid Sequence↗
PubMed1997

Independently cloned halves of cytomegalovirus assemblin, An and Ac, can restore proteolytic activity to assemblin mutants by intermolecular complementation.

Herpesviruses encode an essential serine proteinase called assemblin that is responsible for cleaving the precursor assembly protein during the process of capsid formation. In cytomegalovirus (CMV), assemblin undergoes autoproteolysis at an internal (I) site located near the middle of the molecule. I-site cleavage converts the enzyme to an active two-chain form consisting of the subunits An and Ac. We have recently shown that the recombinant An and Ac subunits can spontaneously associate within eukaryotic cells to yield active two-chain proteinase. This finding indicates that the subunits are able to independently assume their correct functional conformations and led us to test whether they are capable of intermolecular complementation. This was done by coexpressing inactive mutant (point, deletion, and insertion) forms of assemblin together with the wild-type subunit (either An or Ac) corresponding to the domain of assemblin that was mutated. Results of these experiments showed that both An and Ac are able to rescue the enzymatic activity of assemblin mutants. I-site cleavage of the mutated assemblin occurred during complementation but was not absolutely required, as shown by effective complementation of inactive assemblins with noncleavable I sites. We have also shown that intermolecular complementation can rescue the activity of an inactive mutant full-length proteinase precursor and can occur between different species of CMV (e.g., human CMV subunit can rescue activity of mutant simian CMV assemblin). These results indicate that assemblin is able to form active multimeric structures that may be of functional importance.

Cytomegalovirus↗
PubMed1997

Assemblin, an essential herpesvirus proteinase.

The herpesvirus maturational proteinase, called assemblin, is essential for the production of infectious virus and represents a new molecular target for the development of antivirals. A brief summary of the synthesis, structure, and function of this fascinating enzyme is presented here.

Animals↗
PubMed1996

Cytomegalovirus assemblin: the amino and carboxyl domains of the proteinase form active enzyme when separately cloned and coexpressed in eukaryotic cells.

The cytomegalovirus (CMV) serine proteinase assemblin is synthesized as a precursor that undergoes three principal autoproteolytic cleavages. Two of these are common to the assemblin homologs of all herpes group viruses: one at the maturational site near the carboxyl end of the precursor and another at the release site near the midpoint of the precursor. Release-site cleavage frees the proteolytic amino domain, assemblin, from the nonproteolytic carboxyl domain of the precursor. In CMV, a third autoproteolytic cleavage at an internal site divides assemblin into an amino subunit (An) and a carboxyl subunit (Ac) of approximately the same size that remain associated as an active "two-chain" enzyme. We have cloned the sequences encoding An and Ac as separate genes and expressed them by transfecting human cells with recombinant plasmids and by infecting insect cells with recombinant baculoviruses. When An and Ac from either simian CMV or human CMV were coexpressed in human or insect cells, active two-chain assemblin was formed. This finding demonstrates that An and Ac do not require synthesis as single-chain assemblin to fold and associate correctly in these eukaryotic systems, and it suggests that they may be structurally, if not functionally, distinct domains. An interaction between the independently expressed An and Ac subunits was demonstrated by coimmunoprecipitation experiments, and efforts to disrupt the complex indicate that the subunit interaction is hydrophobic. Cell-based cleavage assays of the two-chain assemblin formed from independently expressed An and Ac also indicate that (i) its specificity for both CMV and herpes simplex virus native substrates is similar to that of single-chain assemblin, (ii) R-site cleavage is not essential for the activity of two-chain recombinant assemblin, and (iii) the human CMV and simian CMV An and Ac recombinant subunits are functionally interchangeable.

Amino Acids↗
PubMed1995

Migratory fat deposition in European quail: a role for prolactin?

The present study addresses the role of prolactin as a regulator of migratory fattening in European quail (Coturnix coturnix). Plasma prolactin levels in captive birds undergoing migratory fattening in an outdoor aviary and in the laboratory were measured by radioimmunoassay with an antibody raised against recombinant-derived chicken prolactin. No strong association between prolactin and migratory fattening was apparent, and prolactin levels were more closely related to daylength, with the highest concentrations being reached on long days. Plasma prolactin profiles were similar in intact and castrated male quail. Prolactin was secreted in a daily rhythm, with the highest concentrations occurring early in the photophase. However, when birds were food-restricted for 50 days during a migratory phase, there was no difference in fat deposition between birds food-deprived for the first half of the daily photophase compared with those deprived for the second half. Fattening was reduced in the food-restricted birds relative to ad libitum-fed controls, but there was no difference in plasma prolactin levels between the groups. Injections of ovine prolactin (4 mg/kg) significantly increased food intake and body mass of birds maintained on long days, but there were no differences in fattening between birds injected in the morning compared with those injected in the afternoon. Collectively, these results do not support a major role for prolactin in the regulation of migratory fat deposition in European quail.

Adaptation, Physiological↗
PubMed1995

Congenital leukemia: comprehensive nursing care for a rare disease: a case study.

Congenital leukemia is a rare hematological disorder. The initial manifestation of the disease may be the presence of blue or gray skin nodules. The presence of these nodules along with hyperleukocytosis, anemia, hepatosplenomegaly, and central nervous system leukemic involvement are characteristic of the disease. Treatment involves the administration of chemotherapy by protocol. Response to the chemotherapy is generally poor. Infants with Down syndrome may have a transient manifestation of leukemia known as a leukemic disorder; this will resolve without chemotherapy. Other neonatal disorders can also mimic congenital leukemia; the infant must be evaluated for these, in addition to the definitive diagnosis made via bone marrow aspiration and examination. There are many nursing care interventions for the infant with suspected congenital leukemia. The family of an infant with a suspected or diagnosed leukemia requires concrete information and psychosocial support because the prognosis for these infants is grave. We describe the level of care and subsequent outcome for a premature infant who was diagnosed with congenital leukemia and treated with chemotherapy in a Level III nursery.

Humans↗
PubMed1995

Specific antibodies in serum and vaginal mucus of heifers inoculated with a vaccine containing Tritrichomonas foetus.

Thirty-five heifers were allotted to 3 groups. Group 1 (control) consisted of 10 heifers that were not vaccinated and were challenge exposed by breeding to infected bulls. Group 2 (natural challenge exposure) consisted of 10 heifers that were vaccinated and challenge exposed by breeding to infected bulls. Group 3 (experimental challenge exposure) consisted of 15 heifers that were vaccinated and challenge exposed by breeding to infected bulls and by intravaginal inoculation with 10(7) Tritrichomonas foetus. Total immunoglobulin concentrations and specific trichomonal antibodies were determined in serum and vaginal secretions of heifers, using radial immunodiffusion and ELISA procedures. Control heifers remained infected for a mean of 10.6 weeks (range, 0 to 18 weeks), and heifers of the natural and experimental challenge-exposure groups remained infected for 3.2 and 5.0 weeks, respectively (range, 0 to 12 weeks). Total serum and cervicovaginal mucus concentrations of IgM, IgA, IgG1, and IgG2 did not change significantly after vaccination or challenge exposure. However, ELISA titers of total trichomonal antibodies increased up to 1:10,000 (range, 1:400 to 1:10,000) in serum after vaccination, and increased approximately tenfold above background in cervicovaginal mucus. In serum, the predominant trichomonal antibody isotype was IgG1, although trichomonal IgA and IgM antibodies also increased. The predominant trichomonal antibody detected in cervicovaginal mucus was IgA. Antibody titers in serum and cervicovaginal mucus of vaccinated heifers were not increased by infection. However, in control heifers, the total local trichomonal antibody response increased three- to fivefold after infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Surface binding and clearance of calcitonin by avian osteoclasts.

Osteoclasts, isolated from chick tibias and maintained in culture for 4-6 days, were treated with biotinylated calcitonin followed by fluorescent avidin. In 2 min the entire cell surface fluoresced, by 7.5 min fluorescence was centrally clustered and by 10 min fluorescence had diminished to background levels. Specific binding was blocked by excess unlabeled calcitonin and not influenced by unrelated peptide. The results show that avian osteoclasts bind calcitonin specifically and that the bound calcitonin is rapidly cleared from the cell surface, which indicates involvement of receptor-mediated endocytosis.

Animals↗
PubMed1994

Double modulation of 5-fluorouracil with interferon alpha 2a and high-dose leucovorin: a phase I and II study.

Twenty-nine patients with adenocarcinomas of gastrointestinal or unknown primary, and three with advanced neuroendocrine tumours, were entered into a study of bolus plus infusional 5-fluorouracil (FUra) modulated with high-dose leucovorin (LV) and recombinant interferon alpha 2a (IFN-alpha). Successive cohorts of > or = 4 patients received IFN-alpha at 1.5, 3, 4.5, 6 and 9 MU on alternate days throughout the treatment period. The FUra/LV regimen consisted of: LV 200 mg m-2 i.v. infusion over 2 h, FUra 400 mg m-2 i.v. bolus then FUra 400 mg m-2 i.v. infusion over 22 h, all repeated on day 2, on a 14-day cycle. FUra was given at 75% dose for the first course, increasing (in the absence of WHO grade > or = 2 toxicity) to 87.5% for the second and 100% for subsequent courses up to a maximum of 12. The maximum tolerated dose (MTD) of IFN-alpha was 6 MU on alternate days, with 7/8 patients at 9 MU requiring dose reductions. At 6 MU IFN-alpha, the MTD of FUra was not exceeded at 100% (i.e. 400 mg m-2 bolus and infusion, days 1 and 2), and FUra-related toxicities (mucosal, haematological, dermatological) were extremely mild. Twenty-nine patients were assessable for tumour response, among whom WHO criteria partial responses were seen in 7/14 with colorectal, 1/4 with gastric, 0/1 with pancreatic, 1/3 with neuroendocrine and 3/6 with unknown primaries. Median response duration was 51 weeks. Minor responses and stable disease were seen in a further six patients. Median survival of patients with advanced adenocarcinomas was 9 months, with 33% surviving beyond 18 months. This schedule offers a safe way of co-administering FUra, LV and IFN-alpha. The addition of IFN-alpha, while causing significant independent toxicity, does not significantly increase the dose-limiting mucosal toxicities of FUra/LV. Further investigation is required to determine the contribution of IFN-alpha to the anti-tumour activity of the combination.

Adenocarcinoma↗