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Biomedical subjects

V McDonald

Publications and source records attributed to V McDonald.

At least 55 records · Page 3Linked to original sources
PubMed1994

Efficacy of selected disinfectants against mycobacteria and cryptosporidia.

We have tested the in-vitro efficacy of various disinfectants against clinical isolates of Mycobacterium tuberculosis, Mycobacterium avium-intracellulare, and against the protozoon Cryptosporidium parvum. The disinfectants were tested both with and without an organic load. 'Sactimed sinald' (a quaternary ammonium compound), 'Steris 20' (a peracetic acid compound) and 'Pentapon DC1' (a beta-ene compound) were all equally as effective as 'Cidex' (glutaraldehyde) against all the mycobacteria tested, as well as C. parvum. 'Virkon' (a per-oxygen compound) and 'Phoraid' (an iodine compound) were less effective than glutaraldehyde. 'Pentapon DHY' (a beta-ene compound) was ineffective against any of the organisms tested. We have also assessed a method of determining disinfectant efficacy using [35S]-methionine labelling of proteins, which appears promising, although it requires further evaluation.

Animals↗
PubMed1994

Detection and species identification of Cryptosporidium oocysts using a system based on PCR and endonuclease restriction.

The polymerase chain reaction (PCR) was used to produce a 556 bp nucleotide stretch, employing primers based on the published sequence of the 18S rRNA genes in Cryptosporidium parvum and C. muris. This sequence was found to contain 3 Mae I endonuclease restriction sites, 1 of which was present only in C. parvum. Mae I restriction of PCR products from 2 C. parvum isolates (one of human origin and the other of bovine origin), 1 C. muris isolate, and 1 C. baileyi isolate, showed a specific and reproducible profile for C. parvum that was different from the one obtained for both C. muris and C. baileyi. From these data, new Mae I restriction maps were proposed for the three species. The system was then used to screen 6 C. parvum isolates (from human and bovine hosts), and the C. parvum-specific profile was obtained for all isolates examined. It should be possible to adapt this protocol to detect small numbers of C. parvum oocysts in environmental samples (e.g. in water supplies).

Animals↗
PubMed1994

Mechanisms of innate and acquired resistance to Cryptosporidium parvum infection in SCID mice.

SCID mice, which lack T and B cells, were used as hosts to investigate the nature of both T cell-independent and T-cell-dependent immune responses to infection with Cryptosporidium parvum. We found previously that SCID mice developed chronic infections in which the level of oocyst excretion was low up to about eight weeks post-infection but then increased significantly to cause morbidity and death after 13 weeks. In the present study, weekly administration of an anti-IFN-gamma monoclonal antibody (MoAb) resulted in a shortened prepatent time, significant increase in oocyst excretion and early onset of disease and death. These results suggested an immunologically mediated resistance to C. parvum in the SCID host which required the production of IFN-gamma. Attempts to demonstrate a role for TNF in nonspecific immunity were unsuccessful as injection of mice at weekly intervals with an anti-TNF MoAb failed to alter the course of infection. In contrast to the chronic infection observed in the mice above, SCID mice reconstituted with spleen cells from naive BALB/c mice were able to recover. Depletion of CD4+ cells from the donor population abrogated this protective effect. Mice receiving spleen cells depleted of CD8+ cells were able to recover but the patent infection was prolonged compared with those obtained in mice receiving unfractionated cells. These results demonstrate that CD4+ cells are necessary for the development of immunity to C. parvum infection in reconstituted SCID mice, but, in addition, that CD8+ cells also make a significant contribution to this immunity.

Animals↗
PubMed1994

Cryptosporidium muris in adult mice: adoptive transfer of immunity and protective roles of CD4 versus CD8 cells.

The aim of this study was to investigate the role of the CD4 and CD8 T cells in immunity to cryptosporidia by using Cryptosporidium muris and a mouse model of infection. Two approaches were used, each involving the use of rat anti-T-cell surface marker monoclonal antibodies (MAbs). In the first, the adoptive transfer of immunity was studied by using the CB.17 SCID mouse (which lacks T and B cells) as the host; in the second, the effect on susceptibility of BALB/c mice to infection was examined following depletion of T cells or subsets of T cells. In adoptive immunity experiments, the conditions which differentiated between resistance associated with reconstitution of SCID mice with naive BALB/c lymphocytes and the transfer of immunity with primed lymphocytes from infected animals were determined. Primed spleen or mesenteric lymph node cells conferred better protection to recipients than naive cells when obtained from donors which had developed resistance to infection. Adoptive immunity was abrogated when Thy.1 cells or CD4 cells were depleted from primed cells, while depletion of CD8 cells could reduce the level of protection. In the study of C. muris in BALB/c mice, treatment with either anti-Thy.1 plus anti-Lyt.1 or anti-CD4 MAbs increased susceptibility to a primary infection as determined by the size and duration of oocyst production, but an anti-CD8 MAb produced an increase only in oocyst shedding. Thus, both CD4 and, to a lesser extent, CD8 cells appeared to be involved in resistance to primary and secondary C. muris infection.

Animals↗
PubMed1993

Isoenzyme variation within the genus Cryptosporidium.

Soluble extracts of the oocysts of Cryptosporidium parvum had demonstrable, but low, activities of malate dehydrogenase (MDH, EC. 1.1.1.37), carboxylesterase (ES, EC 3.1.1.1) and lactate dehydrogenase (LDH, EC. 1.1.1.27) following thin-layer starch-gel electrophoresis. Much higher activities of glucose phosphate isomerase (GPI, EC. 5.3.1.9) and phosphoglucomutase (PGM, EC. 2.7.5.1) were found, and zymograms of these two enzymes were used to characterise isolates of C. parvum from human, bovine, ovine and cervine sources, C. muris from the brown rat and C. baileyi from young turkeys. PGM and GPI zymograms clearly distinguished between C. parvum, C. muris and C. baileyi. The five isolates of C. parvum showed the same electrophoretic mobility for GPI, whereas the PGM mobility of the single human isolate of C. parvum examined was clearly different from that of the other isolates. This is the first report of the use of isoenzymes to distinguish between species and isolates of Cryptosporidium.

Animals↗
PubMed1992

PCR cloning and nucleotide sequence determination of the 18S rRNA genes and internal transcribed spacer 1 of the protozoan parasites Cryptosporidium parvum and Cryptosporidium muris.

The genes encoding 18S rRNA and internal transcribed spacer 1 (1TS1) of Cryptosporidium parvum and Cryptosporidium muris were amplified from oocysts by PCR utilizing primers complementary to conserved regions of the 5' end of 18S and 5.8S rRNA. PCR products were cloned and the complete nucleotide sequences of two clones of each Cryptosporidium species were determined. The 18S rRNA genes of C. parvum and C. muris showed more than 99% sequence identity.

Animals↗
PubMed1992

Comparative study of the antigenic composition of oocyst isolates of Cryptosporidium parvum from different hosts.

An investigation was made of the antigenic composition of oocyst isolates of Cryptosporidium parvum by immunoblotting using rabbit polyclonal or murine monoclonal antibodies (MoAbs) developed against this parasite. Using the polyclonal antibodies in blots, a common antigenic profile was obtained from a number of human oocyst isolates from AIDS patients and immunocompetent children in the UK and Portugal. Antigenic differences were observed, however, between a human isolate from Turkey and these other human isolates. The antigenic profiles of oocyst isolates from deer and cattle were similar, but the profiles of the animal and human isolates differed to some extent. Two MoAbs which, in immunofluorescence microscopy, reacted with the surface of the C. parvum sporozoite were also used in blots. A major antigen(s) from 9 of 11 human oocyst isolates recognized by these MoAbs had a molecular weight of 47 kD, but the sizes of the corresponding antigens of the remaining 2 human isolates, one from Turkey (same as above) and one from the UK, were 45.5 and 51 kD, respectively. The equivalent antigen(s) from 4 bovine and 4 ovine isolates was 48 kD. One of the MoAbs failed to react in blots with 2 of the isolates, 1 human and 1 bovine.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Analysis of oocyst wall and sporozoite antigens from three Cryptosporidium species.

A comparison was made of the antigenic composition of oocyst walls and sporozoites from Cryptosporidium baileyi from turkeys, C. muris from rodents, and C. parvum from ruminants, employing immunoblotting and immunofluorescence. In immunoblotting, oocyst antigens were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting (immunoblotting) and detected with rabbit polyclonal anti-C. muris or -C. parvum antibodies or murine monoclonal antibodies developed against C. parvum. Immunofluorescence was used to investigate the reactivity of these monoclonal antibodies with air-dried excystation mixtures of sporozoites and oocysts of the different species. The results from both types of experiment indicated that the three Cryptosporidium species could be differentiated immunologically. In comparison, few antigenic differences were found between a number of isolates of C. parvum in immunoblotting. There was also evidence to suggest that C. parvum and C. baileyi were more closely related antigenically to one another than to C. muris.

Animals↗
PubMed1992

Immune responses to Cryptosporidium muris and Cryptosporidium parvum in adult immunocompetent or immunocompromised (nude and SCID) mice.

Adult murine models of Cryptosporidium infection involving Cryptosporidium muris and C. parvum were used to study immunity to cryptosporidiosis in the mammalian host. Immunocompetent BALB/c or C57BL/6 mice developed a highly patent infection with the RN 66 strain of C. muris but overcame the infection and were immune to reinfection. In contrast, severe combined immunodeficiency (SCID) mice or nude mice had a chronic infection lasting at least 109 days. The development of the C. muris infection appeared to be confined to the gastric epithelium in immunocompetent and immunocompromised mice. SCID mice injected intraperitoneally with histocompatible spleen or mesenteric lymph node cells from uninfected BALB/c mice were able to recover from the C. muris infection. The protective effect of donor spleen cells was not reduced by depletion of the B cell population but was significantly reduced by depletion of Thy.1 cells. Treatment of C57BL/6 or BALB/c mice during infection with a gamma interferon-neutralizing monoclonal antibody, but not a tumor necrosis factor-neutralizing monoclonal antibody, resulted in a significant increase in oocyst production. In the C. parvum model, a severe and eventually fatal chronic infection with a cervine isolate was established in SCID mice, with parasitization occurring in the ileum, cecum, and colon. SCID mice injected with unprimed BALB/c spleen cells prior to inoculation of C. parvum oocysts were resistant to infection. These results suggested that the two animal models should be valuable in the study of immunity to cryptosporidial infection.

Animals↗
PubMed1991

Ultrarapid urokinase in hemodialysis access occlusion.

Over a 3-month period, 14 consecutive hemodialysis access occlusions were treated with 1-1.25 million IU of urokinase (UK) delivered at a rate of 20,000 IU/min. After systemic heparin administration, lytic infusion via the crossed-catheter technique was performed with use of pediatric microdrip pumps, with determination of success within 1 hour. Patency was established radiographically in 11 of 14 occlusions, for a 79% immediate success rate. At 285-day mean follow-up, 9% (one of 11) remained patent without further radiologic or surgical intervention; graft survival was 64% (seven of 11). No significant complications occurred with use of ultrarapid UK. The 1-hour outpatient procedure safely allowed for rapid triage between surgical and radiologic intervention, minimal catheter manipulation or physician dependency, shorter duration compression of any bleeding venipuncture sites during UK administration, and greater patient comfort because of shortened procedure times.

Arteriovenous Shunt, Surgical↗
PubMed1991

Biliary strictures in hepatic transplantation.

Between August 1985 and December 1990, 198 liver transplantations were performed. Among 18 patients, 20 biliary strictures were identified, which were categorized as anastomotic (n = 6), nonanastomotic central hilar (n = 8), and nonanastomotic peripheral (n = 6). Pretransplant disease, hepatic artery patency, presence of acute or chronic rejection, and donor cold ischemia times were tabulated for each case. Among the six patients with peripheral strictures, three had sclerosing cholangitis prior to transplantation. Three patients with nonanastomotic strictures experienced chronic rejection. The mean cold ischemia time for patients with nonanastomotic strictures was 9.75 hours versus 8.1 hours for nonstrictured transplants (P = .025). Balloon dilation was performed in 13 patients; follow-up longer than 6 months was available for nine patients. Dilation was successful in four cases. Among the five failures, only one patient has needed surgery. An association was noted between nonanastomotic biliary strictures and prolonged donor cold ischemia time, between peripheral nonanastomotic strictures and pretransplant sclerosing cholangitis, and between nonanastomotic strictures and chronic rejection. Percutaneous balloon dilation was found useful in the treatment of the strictured transplant.

Biliary Tract Diseases↗
PubMed1991

Characteristics and specificity of hybridoma antibodies against oocyst antigens of Cryptosporidium parvum from man.

Hybridoma antibodies (HAbs) against oocyst antigens of a human isolate of Cryptosporidium parvum were developed by fusion of SP2/0 mouse myeloma cells and spleen cells from BALB/c mice immunized with oocyst homogenates. In an indirect immunofluorescence antibody test (IFAT), using as antigen a mixture of air-dried sporozoites and oocysts, HAbs labelled either the oocyst wall or areas of the sporozoite, including the whole organism, the entire surface, a polar region or the interior. Most of the HAbs were specific for the sporozoite surface, and few of them recognized the oocyst wall. In Western blot analysis of oocyst antigens, sporozoite surface-reactive monoclonal antibodies (MoAbs) recognized one or more of seven polypeptide bands with molecular weights in the range 47- greater than 200 kD, and all reacted with the 47 kD band. Each of four heterologous parasite isolates had a unique recognition pattern with a panel of MoAbs in IFAT, suggesting antigenic differences may exist between strains of C. parvum. The ability to differentiate between parasite isolates by immunological methods might be of value in epidemiological studies of cryptosporidiosis.

Animals↗
PubMed1990

In vitro cultivation of Cryptosporidium parvum and screening for anticryptosporidial drugs.

Sporozoites of Cryptosporidium parvum which were excysted in vitro from oocysts isolated from calves or patients with acquired immune deficiency syndrome underwent development in monolayers of the mouse fibroblast cell line L929. Asexual multiplication occurred, with the maximum numbers of parasites usually being observed between 24 and 48 h after infection. Gametocytes were also found, but their numbers were relatively small compared with those of the asexual stages. A study was made of the effect on parasite development of 20 antimicrobial agents, most of which were anticoccidial or antimalarial agents. The majority of the drugs had a limited inhibitory effect on parasite development, but usually only at high concentrations. The two most active drugs were monensin and halofuginone, which reduced parasite multiplication by more than 90% at high concentrations. In the case of monensin, however, inhibition of parasite development at higher concentrations was due, at least in part, to a toxic effect of the drug on the host cells.

Acquired Immunodeficiency Syndrome↗