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Biomedical subjects

M Ritchie

Publications and source records attributed to M Ritchie.

At least 19 recordsLinked to original sources
PubMed2001

Deletion of the alpha(1,3)galactosyl transferase (GGTA1) gene and the prion protein (PrP) gene in sheep.

Nuclear transfer offers a cell-based route for producing precise genetic modifications in a range of animal species. Using sheep, we report reproducible targeted gene deletion at two independent loci in fetal fibro-blasts. Vital regions were deleted from the alpha(1,3)galactosyl transferase (GGTA1) gene, which may account for the hyperacute rejection of xenografted organs, and from the prion protein (PrP) gene, which is directly associated with spongiform encephalopathies in humans and animals. Reconstructed embryos were prepared using cultures of targeted or nontargeted donor cells. Eight pregnancies were maintained to term and four PrP-/+ lambs were born. Although three of these perished soon after birth, one survived for 12 days. These data show that lambs carrying targeted gene deletions can be generated by nuclear transfer.

Animals↗
PubMed2000

Emotion recognition in schizophrenia: further investigation of generalized versus specific deficit models.

In this study, the authors examined the nature of emotion perception in schizophrenia. Two samples of people with schizophrenia, one receiving acute care for a recent exacerbation of symptoms and the other receiving extended care, were compared with a nonclinical control group on emotion perception and general perception measures. The nonclinical control group obtained the highest scores on all of the study measures, and the acutely ill group obtained the lowest scores. Furthermore, the acutely ill sample had a specific deficit in emotion perception that remained present after controlling for performance on the general perception tasks. Conversely, the deficits in emotion discrimination in the extended-care sample reflected generalized poor performance. Differences in performance on the emotion identification task between the 2 clinical groups were reduced when controlling for active symptoms.

Adult↗
PubMed1999

In vivo development of Theileria annulata: major changes in efferent lymph following infection with sporozoites or allogeneic schizont-infected mononuclear cells.

The object of these experiments was to study the pathogenesis and kinetics of Theileria annulata infection in the efferent lymph of the draining lymph nodes of calves. Efferent lymphatics of calves were cannulated prior to infection with T. annulata sporozoite or an allogeneic schizont cell line. Potentially lethal sporozoite challenge induced cell shut-down from days 4-6 and then a massive increase in output of blasting cells (both infected and non-infected) in the efferent lymph. The rate of lymph flow and total cell output increased to 5 to 10-fold from day 6 onwards. Sporozoites were never isolated from the efferent lymph. However, large numbers of parasite-infected cells were seen in efferent lymph from the sixth day of infection. The animals inoculated with an allogeneic T. annulata-infected cell line exhibited only a small increase in flow rate and cell output. Parasite-infected cells of recipient origin were seen in efferent lymph from day 11 onwards. However, cells of donor origin were never isolated either from efferent lymph or peripheral blood. Thus the parasite transferred from the inoculated donor cell line to the cells of the recipient before schizonts appeared in efferent lymph.

Animals↗
PubMed1998

Human cells unable to express decoron produced disorganized extracellular matrix lacking "shape modules" (interfibrillar proteoglycan bridges).

The shapes of extracellular matrices are determined by positioning collagen fibrils in the right places, oriented and maintained viv-à-vis each other. The fibrils are linked orthogonally by dermatan/chondroitin sulfates or keratan sulfate (in small proteoglycans) attached every approximately 65 nm via their protein moieties to collagen fibrils at specific binding sites. These regular repeating structures are the "shape modules." The characteristic arrays of orthogonal interfibrillar bridges were missing and the extracellular matrix was totally disorganized in matrices produced by fibroblasts taken postmortem from skin of an electively aborted fetus which did not express decoron in culture, thus supporting the shape module hypothesis. Biglycon, dermatan sulfate, heparan sulfate, collagen, and hyaluronan were produced by these cells but did not contribute to a normal extracellular matrix. A similar electron histochemical and biochemical survey of extracellular matrices produced by seven normal and eight osteogenesis imperfecta cell lines from donors of different ages and both sexes showed no comparable disruptions of their matrices. This investigation appears to be the first to demonstrate systematically proteoglycan:collagen interactions in matrices produced by cultured human cells.

Adult↗
PubMed1998

Effect of muscle injection site and drug temperature on pre-anaesthetic sedation in pigs.

The responses of 83 Meishan gilts given azaperone (1.0 mg/kg) and ketamine (5 mg/kg) intramuscularly at one of four sites: the cervical muscles (20); the triceps muscle (m triceps brachii) (20); the middle gluteal muscle (m gluteus medius) (22); and the fascia lata muscle (m fascia lata) (21) were recorded. There were more reactions to the injection into the fascia lata muscle than to injections into the middle gluteal muscle and the triceps muscle (P = 0.024) and fewest after injections into the cervical muscles (P = 0.013). The injection site did not influence the time from injection to recumbency but there was least variability with the fascia lata muscle. The degree of sedation achieved, and the response to venous cannulation were similar in all four groups. There were no long-term complications (lameness or abscess formation) associated with the injections at any of the sites. In a second study with 68 pigs the same drug mixture was injected into the triceps muscle at either 6 to 8 degrees C (23), 19 to 22 degrees C (23) or 38.5 to 40.5 degrees C (22). There was no significant difference (P = 0.078) between the numbers of responses to the injections at each temperature. Mean time to recumbency was shortest with the injections at the highest temperature although the differences were not statistically significant (P = 0.498). The degree of sedation achieved, the response to venous cannulation and the incidence of complications were similar in all three groups.

Absorption↗
PubMed1997

Human factor IX transgenic sheep produced by transfer of nuclei from transfected fetal fibroblasts.

Ovine primary fetal fibroblasts were cotransfected with a neomycin resistance marker gene (neo) and a human coagulation factor IX genomic construct designed for expression of the encoded protein in sheep milk. Two cloned transfectants and a population of neomycin (G418)-resistant cells were used as donors for nuclear transfer to enucleated oocytes. Six transgenic lambs were liveborn: Three produced from cloned cells contained factor IX and neo transgenes, whereas three produced from the uncloned population contained the marker gene only. Somatic cells can therefore be subjected to genetic manipulation in vitro and produce viable animals by nuclear transfer. Production of transgenic sheep by nuclear transfer requires fewer than half the animals needed for pronuclear microinjection.

Animals↗
PubMed1996

Generality of connotative meaning across methods and subjects.

A test was made of the generality of the connotative meaning scores of evaluation, activity, and potency in a dictionary of the 1000 most frequent words in English that has been used as the basis of a computer system to measure the expression of emotional tone. This was done by correlating those scores with the values for evaluation and activity given for words also found in two independently created dictionaries, one based upon adults' ratings and one upon ratings by children. In replicated findings reported by the authors of the dictionary for adults' responses support for the generality of evaluation scores was more strong than that for activity scores. For the ratings by children the generality of both evaluation and activity dimensions received strong support.

Adult↗
PubMed1995

Client self medication on a psychogeriatric unit.

1. Changing trends in health care reflect increasing involvement with clients and families in the development of treatment plans, such as self medication planning. 2. Acting as an advocate for the client, the nurse, in consultation with the client and the multidisciplinary team, developed a consumer-centered program, which allowed the client to master a complicated medication regime prior to discharge. 3. Discharge planning, follow-up, and evaluation of medication compliance, ensured continuity of care, successful outcomes, and reduced use of in-hospital health care dollars.

Aged↗
PubMed1993

Echocardiographic characterization of the improvement in right ventricular function in patients with severe pulmonary hypertension after single-lung transplantation.

OBJECTIVES: This study was designed to characterize immediate, early and long-term changes in right ventricular structure and function, as defined by two-dimensional and Doppler echocardiography, after single-lung transplantation in patients with severe pulmonary hypertension. BACKGROUND: Single-lung transplantation has recently been shown to dramatically improve hemodynamics in patients with primary pulmonary hypertension who had unsuccessful medical therapy. METHODS: Fourteen patients with severe pulmonary hypertension who underwent single-lung transplantation were studied with transthoracic and transesophageal two-dimensional and Doppler echocardiography. Right ventricular dimensions were measured in the apical four-chamber view. Right ventricular ejection and acceleration times and peak velocity of tricuspid regurgitation were measured by Doppler study. Results of right heart catheterization were available early (< 3 months) after transplantation in 10 of 13 patients and late after transplantation (6 months to 2 years) in 11 patients. RESULTS: In the early posttransplantation studies, right ventricular dimensions decreased and fractional area change and ejection fraction increased in all patients, but right ventricular wall thickness did not change significantly. Tricuspid regurgitation lessened markedly in all patients. Long-term decreases in right ventricular dimension and improvement in systolic function were sustained. Right ventricular wall thickness significantly decreased compared with the early postoperative value (0.76 +/- 0.1 cm compared with 0.63 +/- 0.14 cm, p < 0.02). CONCLUSIONS: Two-dimensional echocardiography demonstrates sustained improvement in right ventricular function after single-lung transplantation for severe pulmonary hypertension despite severe preoperative dysfunction.

Cardiac Catheterization↗
PubMed1993

Reproductive performance in relation to uterine and embryonic traits during early gestation in Meishan, large white and crossbred sows.

Previous studies have shown that females of the Chinese Meishan breed and of their F1 cross with European Large White pigs are very prolific, producing about four more piglets per litter than control Large White females. The main cause of this prolificacy is enhanced prenatal survival for a given ovulation rate in Meishan and F1 females and this is controlled by genes of the mother, not those of the conceptus. The objectives of this study were to determine whether genotypic differences in embryo survival were apparent in the period immediately after attachment and to compare embryonic and uterine development at this time. Sows in their third parity (20 Large White, 14 Meishan, 25 Large White x Meishan F1 and 25 Meishan x Large White F1) were killed 20-22 days after mating and their reproductive tracts recovered for further study. There were significant differences between the purebred sows, and crossbred sows were approximately intermediate for the number of corpora lutea (20.7 +/- 0.9, 27.8 +/- 1.1, 22.4 +/- 0.8 and 23.3 +/- 0.8 for the four genotypes, respectively), the number of embryos (15.2 +/- 0.9, 23.4 +/- 1.1, 17.2 +/- 0.8 and 18.8 +/- 0.8, respectively) and the proportionate embryo survival (0.74 +/- 0.04, 0.84 +/- 0.04, 0.78 +/- 0.03 and 0.82 +/- 0.03, respectively). There was a negative association within genotype between embryo survival and the number of corpora lutea. Adjusting for the genotypic difference in the number of corpora lutea increased the genotypic differences in embryo survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
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↗