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M Ritchie

Publications and source records attributed to M Ritchie.

10 recordsLinked to original sources
PubMed1992

Comparison of a direct fecal Shiga-like toxin assay and sorbitol-MacConkey agar culture for laboratory diagnosis of enterohemorrhagic Escherichia coli infection.

A direct fecal Shiga-like toxin assay (DSLTA) was used to prospectively screen 9,449 unselected stool samples, received at the British Columbia Provincial Health Laboratories and the Metropolitan Laboratories of Vancouver, for Shiga-like toxin I and Shiga-like toxin II. The results were compared with results of routine stool culture on sorbitol-MacConkey agar (SMAC) for Escherichia coli O157:H7. Of 80 specimens positive by either method, 59 (74%) and 74 (93%) were positive by SMAC and DSLTA, respectively; 53 (66%) were positive by both methods, 21 (26%) were positive by DSLTA only, and 6 (7%) were positive by SMAC only. On further screening, Shiga-like toxin-producing E. coli were detected in 8 (38%) of the 21 stools positive by DSLTA only, including serotypes O157:H7 (1 stool), O26:K60 (5 stools), O128:K67 (1 stool), and O103:H2 (1 stool). For the remaining 13 stools in which no SLTEC was found but DSLTA was positive, clinical information revealed that 11 of 12 patients had diarrheal illnesses, and 4 of these 11 had bloody diarrhea or hemolytic-uremic syndrome. Stools positive only by SMAC were collected earlier in the illness than stools positive by DSLTA, suggesting that free fecal toxin levels may be too low to detect at this time. Overall we found that DSLTA detected 19% more positive specimens than SMAC and that Shiga-like toxin-producing E. coli serotypes other than E. coli O157:H7 are causing disease in the province of British Columbia, Canada.

Bacterial Toxins↗
PubMed1992

Mechanism controlling ovulation rate in ewes in relation to seasonal anoestrus.

Three experiments were carried out during seasonal anoestrus in Finnish Landrace and Scottish Blackface ewes, to establish whether the differences between the breeds in ovulation rate are functional during the non-breeding season and are therefore independent of the mechanism controlling ovulation. In Expt 1, follicles greater than or equal to 2 mm in diameter were dissected from the ovaries of both breeds and incubated individually for 2 h to assess their ability to secrete oestradiol and testosterone. In both breeds, follicles producing greater than or equal to 500 pg oestrogen/ml/h (oestrogen-active) were readily identifiable from a population producing less (oestrogen-inactive). The number of oestrogen-active follicles in each breed was similar to the number of ovulations near the end of the breeding season. Oestrogen-active follicles also had more luteinizing hormone (LH) receptors and larger diameters than oestrogen-inactive follicles. There were, however, no significant differences between the two follicle types in follicular fluid or in-vitro testosterone concentrations. In Expt 2, seasonally anoestrous Scottish Blackface ewes were unilaterally ovariectomized; the second ovary was removed 7 days later. Follicles from both ovaries were processed as described for Expt 1; oestrogen-active follicles were categorized according to their ability to produce greater than 500 pg/ml/h. There were twice as many oestrogen-active follicles in the second ovary as in the first ovary; the number of oestrogen-active follicles in the second ovary was also similar to the total number of oestrogen-active follicles in both ovaries of the Scottish Blackface ewes in Expt 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Anestrus↗
PubMed1991

Evidence endogenous interferon production contributed to the lack of ocular virulence of an HSV intertypic recombinant.

An intertypic recombinant isolated from rabbit kidney cells following co-transfection of HSV-1(17) and HSV-2(186) DNA failed to induce overt ocular pathology when inoculated onto the murine sacrificed cornea at concentrations as high as 10(7) PFU per eye. In contrast, both parents induced corneal disease at a 1000-fold lower dose. The reason(s) for the failure of the intertypic recombinant, designated RO25X, to induce corneal pathology was investigated. It was found that the recombinant was 100-fold more sensitive to the inhibitory effects of interferon (IFN) alpha/beta than the parent strains in corneal button growth studies in vitro. R025X readily grew in cultured mouse corneal fibroblasts at a low multiplicity of infection. However, the peak titer was approximately 8-fold lower than that of strain 17. Addition of rabbit anti-IFN alpha/beta to the culture medium resulted in a 4 to 5-fold increase in infectious titer compared to its growth in the absence of antiserum. Most significantly, when mice were pre-treated in vivo with anti-IFN alpha/beta 24 hours prior to virus corneal infection, 67% of the recipients developed moderate to severe stromal keratitis, whereas none of the controls developed corneal pathology. Blepharitis was also significantly increased in incidence and severity in the antiserum treated hosts. We conclude that the inability of R025X to induce ocular disease was due, at least in part, to the inhibitory effects of interferon produced in response to infection.

Animals↗
PubMed1990

Direct responses in males and correlated responses for reproduction in females to selection for testicular size adjusted for body weight in young male lambs.

Selection based upon testicular diameter adjusted for body weight at 6, 10 and 14 weeks of age was used to produce two lines of sheep, with either high or low testicular size. Ten generations of selection were carried out and the estimate of the realized heritability of the selection criterion was 0.53 +/- 0.01. There were significant positive correlated responses to selection for testicular diameter at 6, 10 and 14 weeks of age, but the correlated responses in body weight at these ages were negative. In mature females, there were significant negative correlated responses to selection in premating body weight in the 1st, 2nd and 3rd breeding season and in the day of the first oestrus in the 2nd breeding season. Litter size per ewe mated had a small positive correlated response to selection in the second breeding season. This latter response appeared to be due to a positive correlated response in fertility, ewes from the High-line having a significantly higher probability of conceiving to a single mating than those from the Low-line. There was no significant correlated response in ovulation rate or litter size per ewe lambing and the genetic correlation between these traits and the selection criterion is likely to be close to zero. This may be due to the adjustment for body weight used, but it is possible that, in any event, body weight in young rams may be a better predictor of female ovulation rate than testicular diameter. These results do not rule out the possibility that testicular size in rams older than those selected would provide a good predictor of genetic merit for female ovulation rate.

Animals↗
PubMed1986

Benign persistent pneumoperitoneum in scleroderma.

We present a 68-year-old patient who, over a two-year period, was observed to have persistent benign pneumoperitoneum. The free air was present in the abdominal cavity without gastrointestinal perforation or pneumatosis cystoides intestinalis. The persistent pneumoperitoneum was a benign process and was not associated with peritonitis or other ill effects. The source of the free air was not clear. Conceivably, microperforations occurring in colonic diverticula or in distended intestinal wall induced the persistent benign pneumoperitoneum.

Aged↗
PubMed1985

Unscheduled DNA synthesis in mononuclear leukocytes from patients with colorectal polyps.

The mononuclear leukocytes from peripheral blood samples of individuals with (n = 30) and without (n = 48) colonic polyps were examined for their abilities to carry out unscheduled DNA synthesis (UDS) induced by N-acetoxy-N-2-fluorenylacetamide (N-AcO-2-FAA). Individuals with polyps had significantly reduced UDS values compared to the nonpolyp group (P less than 0.01). Furthermore, in a more comprehensive study, patients with hyperplastic polyps had N-AcO-2-FAA-induced UDS values not significantly different from control individuals who were asymptomatic and free from colonic disease as judged by complete colonoscopy. However, patients who had had adenomatous polyps in their large bowel had significantly reduced levels of N-AcO-2-FAA-induced UDS in their mononuclear leukocytes (P less than 0.005). When N-AcO-2-FAA binding to DNA determinations were made in parallel and DNA repair proficiency indices were calculated (i.e., N-AcO-2-FAA-induced UDS/N-AcO-2-FAA binding to DNA), the patients with adenomatous polyps were still shown to be deficient in carrying out DNA repair synthesis. Since adenomatous polyps of the large bowel are considered the premalignant lesion for colorectal cancer, we postulate that reduced UDS may be a genetically sensitive marker that is useful in studying the mechanisms of genetic predisposition to colorectal cancer.

Acetoxyacetylaminofluorene↗
PubMedDate not supplied

Recombinant leukocyte interferon treatment of chronic hepatitis B.

We have investigated the efficacy of a relatively prolonged course of recombinant leukocyte interferon treatment in 14 chronic HBsAg-, HBeAg-, hepatitis B virus DNA- and DNA polymerase-positive carriers. alpha-Interferon was administered for 9 weeks. Six of 14 treated carriers have a sustained loss of HBeAg, hepatitis B virus DNA and DNA polymerase. Four subsequently lost HBsAg (28.5%). Elevated pretreatment SGPT concentrations, histologic chronic active hepatitis, an exacerbation of chronic hepatitis with an increase in SGPT concentrations in the last weeks of treatment and possibly recent onset of the carrier state was associated with complete inhibition of viral replication. None of 11 matched, untreated HBsAg-, HBeAg-, hepatitis B virus DNA- and DNA polymerase-positive carriers monitored during the same period lost HBsAg. The effect of recombinant leukocyte interferon may require an appropriate host-immune response. The efficacy of recombinant leukocyte interferon therapy is restricted, but it may be of benefit in a proportion of carriers, if these carriers can be precisely identified.

Adult↗