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Biomedical subjects

H D Ritchie

Publications and source records attributed to H D Ritchie.

At least 19 recordsLinked to original sources
PubMed2000

Grazing methods and stocking rates for direct-seeded alfalfa pastures: I. Plant productivity and animal performance.

A 4-yr study was conducted to determine the effects of two grazing methods (GM) at two stocking rates (SR) on alfalfa pasture plant productivity and animal performance and to ascertain the effect of grazing systems on subsequent performance of steers fed a high-concentrate diet. Eight pasture plots (.76 ha) were seeded in 1988 with alfalfa (Medicago sativa L. var. WL225) and divided into two blocks of four pastures each. Grazing methods consisted of a traditional four-paddock or an intensive 13-paddock system. Pastures were managed to allow a 36-d rest period with an average grazing season of 110 d. The low and high SR were 5.9 vs 11.7, 5.3 vs 10.5, 5.3 vs 7.9, and 5.3 vs 7.9 steers/ha for years 1989 to 1992, respectively. Following the grazing season, steers were placed in a feedlot and fed a high-concentrate diet (81% high-moisture corn, 14% corn silage, 5% protein-mineral supplement) for an average of 211 d. There was no effect of GM on herbage mass, pasture phase ADG, or live weight gain/hectare. Increasing the number of paddocks was beneficial when herbage mass was limited and stocking rate was above 7.9 steers/ha. Increasing SR above 7.9 steers/ha decreased herbage mass and pasture-phase ADG. As forage allowance increased, pasture-phase ADG increased quadratically (R2 = .82, P < .001), reached a plateau, and then decreased. Previous grazing system did not influence the performance of steers in the feedlot or their carcass characteristics. Optimum SR is dependent on herbage mass produced.

Animal Husbandry↗
PubMed1998

Staphylococcus aureus genetic loci impacting growth and survival in multiple infection environments.

The Gram-positive bacterium Staphylococcus aureus infects diverse tissues and causes a wide spectrum of diseases, suggesting that it possesses a repertoire of distinct molecular mechanisms promoting bacterial survival in disparate in vivo environments. Signature-tag transposon mutagenesis screening of a 1520-member library identified numerous S. aureus genetic loci affecting growth and survival in four complementary animal infection models including mouse abscess, bacteraemia and wound and rabbit endocarditis. Of a total of 237 in vivo attenuated mutants identified by the murine models, less than 10% showed attenuation in all three models, emphasizing the advantage of screening in diverse disease environments. The largest gene class identified by these analyses encoded peptide and amino acid transporters, some of which were important for S. aureus survival in all animal infection models tested. The identification of staphylococcal loci affecting growth, persistence and virulence in multiple tissue environments provides insight into the complexities of human infection and on the molecular mechanisms that could be targeted by new antibacterial therapies.

ATP-Binding Cassette Transporters↗
PubMed1998

Identification and characterization of the PutP proline permease that contributes to in vivo survival of Staphylococcus aureus in animal models.

Staphylococcus aureus is an important pathogen of humans and other animals, causing bacteremia, abscesses, endocarditis, and other infectious syndromes. A signature-tagged mutagenesis (STM) system was adapted for use in studying the genes required for in vivo survival of S. aureus. An STM library was ultimately created in S. aureus RN6390, with Tn917 being used to create the transposon mutations. Pools of S. aureus RN6390 mutants were screened in mouse abscess, bacteremia, and wound infection models for growth attenuation after in vivo passage. One of the mutants that was identified displayed marked attenuation following large-pool screening in all three animal models, which was confirmed in bacteremia and endocarditis models of infection with a smaller pool of mutants. Sequence analysis of the entire open reading frame showed a 99% identity to the high-affinity proline permease (putP) gene characterized in another strain of S. aureus. In wound and murine abscess infection models, the putP mutant was approximately 10-fold more attenuated than was wild-type strain RN6390. Another S. aureus strain transduced with the putP mutation also displayed an attenuated phenotype after passage in the wound model. A [3H]proline uptake assay showed that less proline was specifically transported into the putP mutant than into strain RN6390. The reduced viability of the bacteria possessing the mutation in the S. aureus high-affinity proline permease suggests that proline scavenging by the bacteria is important for in vivo growth and proliferation and that analogs of proline may serve as potential antistaphylococcal therapeutic agents.

Amino Acid Transport Systems, Neutral↗
PubMed1994

Weight gain and reproductive performance of spring-born beef heifer calves intraruminally administered oxfendazole.

The effect of oxfendazole (Synanthic) on weight gain and reproductive performance of spring-born heifer calves was evaluated at five locations (IL, IN, MI, MO, ND). Three hundred thirty-eight mixed-breed beef heifers (293.4 kg) blocked by weight and age were randomly allotted to one of two treatments. Treatment 1 heifers were dewormed via intraruminal injection of oxfendazole. Treatment 2 heifers served as a control. Heifers were comingled during the winter phase in semi-confinement during the period from late January to late May (winter phase). Heifers were sorted by treatment at the beginning of the grazing season (approximately May 24, 1991) and remained separate until the end of the study (approximately July 31, 1991; summer phase). Dewormed heifers received oxfendazole (4.5 mg/kg BW) in late January and again 28 and 56 d after the beginning of the grazing season. Fecal samples were taken every 21 d from January through September and assayed for gastrointestinal parasite eggs. Fecal egg counts were similar across treatments at the beginning of the trial (P = .34). Deworming decreased fecal egg counts throughout the trial. Twenty-eight days after initial deworming a significant treatment effect on fecal egg counts was observed (P < .01). Winter ADG was significantly higher (P < .01) for dewormed heifers than for controls (.60 vs .52 kg, respectively). Summer ADG was not different between treatments. Dewormed heifers were 7.4 kg heavier than controls (P < .05) at the end of the trial. Age of puberty was not affected by treatment (P = .64). First-service conception and final pregnancy rates were not different between treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Effects of using sires selected for yearling weight and crossbreeding with beef and dairy breeds: birth and weaning traits.

Data consisting of 948 calf records collected from 1978 to 1982 were analyzed to determine the effects of breeding methods used to improve commercial herds genetically on birth and weaning traits. Four distinct groups were used in the project: Group 1 (G1), an unselected, random mating Hereford control line; Group 2 (G2), a Hereford group using sires selected for yearling growth; Group 3 (G3), a rotational cross with Angus, Hereford, Charolais and Simmental breeds; and Group 4 (G4), a rotational cross with Angus, Hereford, Simmental and Holstein-Friesian breeds. Traits analyzed were birth weight (BW), calving difficulty (CD), percent assisted births (%AB), percent born alive (%BL), preweaning average daily gain (PWDG), relative growth rate (RGR), weaning weight (WWT) and percent weaned (%WND). The use of high yearling weight sires in G2 increased calf size (P less than .01) at birth and weaning by 8.9 and 28.1 kg, respectively, along with increased CD (P less than .01). Use of rotational crossbreeding systems increased calf size and growth from birth to weaning (P less than .01), but decreased CD and %AB (P less than .01) by .17 units and 13.5%, respectively. Including Holstein-Friesian in G4 resulted in further increases in preweaning growth (P less than .01) and calving ease was improved without affecting BWT compared with G3.

Animals↗
PubMed1983

Experience with the 'Triple Test' in pancreatic disease.

The results of the secretin-pancreozymin test, duodenal aspirate cytology and hypotonic duodenography (the Triple Test), performed during a single duodenal intubation in patients with pancreatic or ampullary carcinoma, chronic pancreatitis and non-pancreatic disease were analysed retrospectively. Thirty-five of 36 carcinoma patients and all 11 chronic pancreatitis patients had an abnormal result. One hundred and sixteen of 170 non-pancreatic disease patients had a normal result. It would appear that the Triple Test (TT) may be a useful screening test for pancreatic disease.

Cholecystokinin↗
PubMed1982

Patterns of small intestinal motility in duodenal ulcer patients before and after vagotomy.

Prolonged (18-24 hours) recordings of the pattern of small intestinal motor activity have been made, using radiotelemetry, in seven patients before surgery for chronic duodenal ulcer, seven after truncal vagotomy, and four with persistent post-vagotomy diarrhoea. There was no difference in the pattern of fasting cyclical activity between the three groups but the duration of feeding activity after a standard meal was reduced in asymptomatic truncal vagotomy patients compared with duodenal ulcer controls (p less than 0 . 05). In patients with post-vagotomy diarrhoea, the duration of the feeding pattern was further reduced compared with the asymptomatic post-vagotomy patients (p less than 0 . 001). It is suggested that altered emptying of food from the stomach in these patients together with duodenal receptor insensitivity is the probable explanation of these changes.

Adult↗
PubMed1977

The gastrointestinal myoelectric response to 13-Nle-motilin infusion during interdigestive and digestive states in the conscious dog.

Gastrointestinal myoelectric activity was studied in three conscious fasted dogs with electrodes surgically implanted in the stomach and small intestine, during separate and combined intravenous infusions of 13-norleucine motilin (13-nle-motilin) and pentagastrin (PG). Basal recordings confirmed the presence of regular interdigestive myoelectric complexes (MC's). 13-nle-motilin infusion below 50 ng/kg-h was without effect: higher doses up to 400 ng/kg-h resulted in the interpolation of one or more MC's in the spontaneous sequence. The rate of aboral transit of 13-nle-molitin-induced MC's did not differ significantly from that of spontaneous MC's. When MC's were abolished by feeding or PG infusion, simultaneous 13-nle-motilin administration was without effect on spike activity, but slightly attenuated the accelerating effect of gastrin on the gastric pacemaker frequency. The myoelectric events triggered by 13-nle-motilin suggest that in the conscious dog the polypeptide may not act directly on the smooth muscle cell, as it does in vitro, but through an extra-enteric neural control mechanism which is uncoupled by gastrin.

Aminocaproates↗
PubMed1976

Metabolism of histamine in secreting and isolated canine stomach.

Total 14C activity in juice secreted by gastric pouches of six dogs and seven isolated canine stomachs was determined in response to intravenous and intra-arterial infusions of histamine and [14C]histamine. The proportions of 14C attributable to histamine, Nalpha-methylhistamine (NalphaMeH), Nalpha,Nalpha-dimethylhistamine (NalphaNalphaMe2H), N-telle-methylhistamine (NtauMeH), imidazole acetic acid (ImAA), N-methylimidazole acetic acid (NtauMeImAA), acetylhistamine (AcH), and histaminol (HOH) were defined using thin-layer chromatography. Similar estimates were made at the end of infusions on blood, gastric mucosa, and gastric muscle. Methylation was the major, or sole, route of metabolism of histamine in the gastric mucosa, and the major product was inactive NtauMeH. Small quantities of the active NalphaMe derivatives, particularly NalphaNalphaMe2H, were identified in both the juice and mucosa. Little or no ImAA, NtauMeImAA, AcH, and HOH were present in juice from isolated stomachs while they did occur in the juice from intact dogs, demonstrating they are extragastric metabolites of histamine. A major mucosal function of methylation of histamine is inactivation, although NalphaMe derivatives formed may play a role in the secretagogue action of histamine.

Acetates↗
PubMed1976

Motilin-induced electrical activity in the canine gastrointestinal tract.

Myoelectric activity induced by a synthetic analogue of the duodenal polypeptide motilin, was studied in isolated vascular-perfused canine duodenum and stomach, and in conscious dogs with serosal electrodes implanted in the stomach and the small intestine. In the isolated preparation, the duodenum was found to be four times as sensitive as the antrum to the polypeptide, showing a dose-dependent increase in spike activity within two minutes after administration of the polypeptide. By contrast, in the conscious fasted animal, the only response to motilin, above a threshold dose, was the interpolation of a premature migrating myoelectric complex in the spontaneous interdigestive sequence, appearing fifteen to twenty minutes after the start of infusion. Since the essential difference between the ex vivo and the intact intestine was the preservation of efferent and afferent nervous connections in the latter, it seems that in the conscious animal, the response to exogenous motilin is modulated by the innervation of the intestine, or, alternatively, motilin interacts with the centre controlling the pattern of motor activity in the small intestine rather than directly with smooth muscle. The latter hypothesis is supported by the observation that motilin had no effect on the motor activity of the small intestine during the infusion of pentagastrin which abolishes spontaneous migrating myoelectric complexes.

Action Potentials↗
PubMed1976

Effects of 13-nle-motilin on the electrical and mechanical activity of the isolated perfused canine stomach and duodenum.

Synthetic 13-norleucine-motilin (13-nle-motilin), structural and biological analogue of the naturally-occurring duodenal polypeptide, motilin, is known to stimulate antral and duodenal motor activity in vitro, but delays gastric emptying in man. In this study the direct actions of the synthetic polypeptide on myoelectrical activity and intraluminal pressure have been studied in the isolated vascular-perfused canine stomach and duodenum. 13-nle-motilin increased intraluminal pressure in the pylorus and duodenum, and dose-response analysis showed the duodenum to be twice as sensitive as the pylorus to the polypeptide. Pressure changes in the antrum were small and not dose-related, but, whereas the basic electrical rhythm in the duodenum was not altered, slow wave frequency, rhythm, and propagation in the antrum were disturbed. Electronic analysis of the duodenal spike increase which accompanied pressure rises demonstrated correlations between increases in spikes, intraluminal pressure, and dose. These results show that the direct effect of the polypeptide on adjacent organs may explain the combination of increased motor activity with delayed gastric emptying as a consequence of disturbance in the co-ordination between antrum, pylorus, and duodenum.

Animals↗
PubMed1975

How should the common bile duct be explored?

An attempt has been made to find which of 3 operations currently in use for exploring the bile ducts gave the best clinical results. For this purpose 3 series of consecutive patients treated at The London Hospital over a 12-year period have been studied retrospectively. The operations used were as follows: (1) conventional supraduodenal choledochotomy; (2) transduodenal biliary sphincterotomy; and (3) a combined approach. The mortality in the supraduodenal series was 4 (4%) of 101 patients and in the transduodenal series 2 (2.4%) of 82 patients. Both routes were used in 26 patients, of whom 2 (7.7%) died. Early complications were commoner after choledochotomy than after biliary sphincterotomy, but when both procedures were combined the incidence was higher still. Late complications were also more frequent after both the supraduodenal and the combined approach, residual or recurrent stones and cholangitis being 6 times more common than after sphincterotomy alone. Postexploratory cholangiography, however, was not used routinly in the supraduodenal series and might conceivably have reduced this factor further, but not below 3. Stenosis occurred in one patient after choledochotomy and in one patient after the combined operation but not after sphincterotomy alone. In this study, therefore, transduodenal biliary sphincterotomy gave the lowest mortality and morbidity. With the combined procedure, however, the mortality and morbidity were much higher than after either method alone.

Adult↗
PubMed1975

Sphincter patency and hepatic BSP uptake after biliary sphincterotomy.

An attempt has been made to assess the patency and function of the choledochoduodenal junction after biliary sphincterotomy by estimating the first arrival time of injected bromsulphalein (BSP) in duodenal aspirate and the effect of morphine on this. Studies on 49 patients 1--12 years after this operation showed the arrival time to be normal in 47, but in 2 cases there was delay, which suggests that stenosis may develop in time in abot 4 per cent of cases. This had not been detected clinically, radiologically, or by liver function testing. Although it did not effect the BSP arrival time in T-tube bile, morphine was found to prolong the duodenal arrival time in control patients and also after sphincterotomy of the type used, indicating that the protective mechanism of the sphincter region may not have been destroyed by this operation. Abnormal BSP retention in plasma has been reported up to 5 years afte supraduodenal exploration of the bile ducts in 30 per cent of cases. Similarly, in the present study after biliary sphincterotomy plasma BSP levels were above normal in 14 of 49 patients, suggesting that this abnormality reflects the original pathological condition rather than the type of operation used to deal with it.

Cholecystectomy↗