Scanning electron microscopic studies of megakaryocytes and platelet formation in the dog and rat

Megakaryocyte morphology and platelet formation in canine and murine bone marrows were studied by scanning electron microscopy. In situ-fixed bone marrow preparations and cell suspensions of bone marrow provided complementary information for the 2 species (dogs and rats). Cylindrical processes (proplatelets) of variable length and thickness, originating from the megakaryocyte surface, were in the larger marrow sinusoids and the central vein. Regional constrictions along the length of proplatelets, particularly near their apical region, and the presence of fragments of such processes supported the concept of platelet formation through segmentation of proplatelets. Megakaryocytes presented varied morphology. Surface features resembling platelets were observed on megakaryocytes, indicating that platelets may have been released through surface budding. In conclusion, megakaryocytes formed long proplatelet processes that actively migrated to venous sinusoids to release platelets by fragmentation. Scanning electron microscopy analysis revealed a complex and variable megakaryocyte surface topography. The platelet-like structures on megakaryocyte surfaces may represent platelet release by a budding mechanism. The similarity between murine platelet release and canine platelet release demonstrates that data from rodent models may be applicable to nonrodents.     

Congenital meningocele-encephalocele in an experimental swine herd

Fourteen instances of meningocele-encephalocele in an experimental herd were recorded over a 5-year period. Thirteen of these affected animals were subjected to extensive pedigree analyses. Familial associations were strong, and clearly the meningocele-encephalocele in this herd was under genetic influence. However, additional studies are needed to clarify the mode of inheritance and, perhaps, to identify other factors that might be involved.     

Identification and fine mapping of quantitative trait loci for backfat on bovine chromosomes 2, 5, 6, 19, 21, and 23 in a commercial line of Bos taurus

Backfat thickness is one of the major quantitative traits that affects carcass quality in beef cattle. In this study, we identified and fine-mapped QTL for backfat EBV on bovine chromosomes 2, 5, 6, 19, 21, and 23 using an identical-by-descent haplotype-sharing analysis in a commercial line of Bos taurus. Eleven haplotypes were found to have significant associations with backfat EBV at the comparison-wise P-value threshold, and one at the chromosome-wise P-value threshold on bovine chromosomes 5, 6, 19, 21, and 23. On average, the 12 significant haplotypes had an effect of 0.62 SD on backfat EBV, ranging from 0.38 SD to 1.33 SD. The 12 significant haplotypes spanned nine chromosomal regions, one on chromosome 5 (65.4 to 70.0 cM), three on 6 (8.2 to 11.8 cM, 63.6 to 68.1 cM, and 81.5 to 83.0 cM), three on 19 (4.8 to 15.9 cM, 39.4 to 46.5 cM, and 65.7 to 99.5 cM), one on 21 (46.1 to 53.1 cM), and one on 23 (45.1 to 50.9 cM). Among the nine chromosomal regions, six were new QTL regions and three showed remarkable agreement with QTL regions that were previously reported. Eight of the nine QTL regions were localized to less than or close to 10 cM in genetic distance. The results provide a useful reference for further positional candidate gene research and marker-assisted selection for backfat.     

Therapeutic effect of hyaluronic acid on experimental osteoarthrosis of ovine temporomandibular joint.

A symptomatic relief by hyaluronic acid (HA, MW: 3.5 x 10(6)), which is synthesized by Streptococcus spp, was investigated in experimental ovine osteoarthrosis. Bilateral osteoarthrosis (OA) of the temporo-mandibular joints (TMJs) was induced by perforating discs and by scrapping subchondral condylar surface. HA was intra-articularly injected into the left joints of 6 sheep on 7, 10, 14, 17 and 21 days after the operation and physiological saline as the control was injected into the contralateral (right) joints on the same day. Three sheep were killed at I month post-operation (MPO) and the remaining three sheep were killed at 3 MPO. Various responses such as proliferation of fibrous tissue, denudation, erosion, osteophyte formation, subcortical cyst formation and ankylosis were observed radiographically and histopathologically. The treatment of HA ameliorated the degenerative changes and lowered the osteoarthrotic score in the left joints at I MPO (9.96 vs 5.81) and 3 MPO (10.86 vs 5.29) compared to the right joints. These results indicate that a repeated intra-articular injection of HA inhibits the progression of OA in ovine TMJs by inducing the development of articular cartilage and by reducing the proliferation of fibrotic tissue.     

Immunohistochemical demonstration of Leu-7 (HNK-1), Neurone-specific Enolase (NSE) and Protein-Gene Peptide (PGP) 9.5 in the developing camel (Camelus dromedarius) heart

The development of the heart-conducting system has been controversially discussed. The common opinion that these specialized myocytes originate from mesodermal precursors has been challenged when nerve-specific antigens (Leu-7, NF, GIN2) were demonstrated in embryonic hearts of various species, suggesting a neural crest contribution to the embryonic conducting tissue. Anti-Leu-7 (HNK-1) antibodies were reported to reliably mark the conducting system in developing rat, chicken and human hearts. The present investigation was carried out on the hearts of 15 camel fetuses at 35, 45, 60, 75 and 100 cm crown-rump length (three specimens for each stage), in addition to three adult hearts. We investigated the antigenicity of cardiac structures for Leu-7, NSE (Neurone specific Enolase) and PGP (Protein Gene Peptide) 9.5. In all specimens investigated, both NSE and PGP 9.5 were expressed by cardiac nerves and conducting system components. The sinuatrial and atrioventricular nodes, the atrioventricular bundle as well as subendocardial and intramyocardial Purkinje fibers were stained. In contrast, the developing conducting system did not react with anti-Leu-7 antibody, although Leu-7 antigenicity was strongly expressed by the developing cardiac nerves. In adult camel hearts, the same pattern of immunoreactivity for the markers studied was still retained. Our results show that the expression of marker proteins for the developing conducting system is species-specific. Therefore, these markers are of little significance in discussions on the possible neurogenic nature of the heart conducting tissue.     

Gastric granulomatous cryptococcosis mimicking gastric carcinoma in a dog.

An ulcerated lesion resembling a tumour in the lesser curvature of the stomach of a 3-year-old male Dobermann pinscher was found to be caused by Cryptococcus neoformans. The dog had been vomiting for two months and had slight leucocytosis and anaemia. Biopsies of the ulcerated lesion revealed granulomatous inflammation and many cryptococci, which were particularly prominent in PAS and mucicarmine stained sections. No other lesions were found at necropsy.     

Small intestinal starch digestion in steers: effect of various levels of abomasal glucose, corn starch and corn dextrin infusion on small intestinal disappearance and net glucose absorption

Eight Holstein steers (four at 300 kg, four at 406 kg) fitted with an elevated carotid artery, hepatic portal and mesenteric venous catheters, and abomasal and ileal cannulas were used in several 4 x 4 Latin square experiments to evaluate small intestinal starch digestion. They were fed alfalfa hay at 1.5% of BW and abomasally infused with water or glucose, corn starch or corn dextrin (one carbohydrate per Latin square) at 20, 40 or 60 g/h, with subsequent determination of small intestinal disappearance and net portal glucose absorption. Increasing the amount of all three carbohydrates infused abomasally increased the amount of carbohydrate disappearing in the small intestine. Increased infusion of glucose caused a continual increase (linear, P less than .01) in net glucose absorption, whereas net glucose absorption for starch and dextrin was maximal at the 20 g/h infusion (quadratic, P less than .05). With the 60 g/h infusion, 94% of the glucose but only 38% of starch and 29% of small intestinal dextrin disappearance could be accounted for as net glucose absorption, leaving a large portion of starch and dextrin disappearance unaccounted for. Of the infused starch and dextrin passing the ileum, 5.8 and 7.3%, respectively, was unpolymerized glucose, indicating that, at least in the distal small intestine, complete starch hydrolysis exceeded the capacity for glucose disappearance. It is concluded that only about 35% of the raw corn starch disappearing in the steer's small intestine resulted in net portal glucose absorption.     

Effect of dietary modification of muscle long-chain n-3 fatty acid on plasma insulin and lipid metabolites, carcass traits, and fat deposition in lambs

In a previous study we showed that feeding fish meal significantly increased muscle long chain n-3 fatty acids (FA) and hot carcass weight. In this study we compared the effect of fish meal and fish oil on increasing muscle long-chain FA. We also investigated whether the increase in carcass weight was due to the effect of dietary enrichment of muscle long-chain n-3 FA on muscle membrane phospholipids and(or) to rumen by-pass protein provided by fish meal. Forty crossbred ([Merino x Border Leicester] x Poll Dorset) wether lambs between 26 and 33 kg BW were randomly assigned to one of five treatments: 1) basal diet of oaten:lucerne chaff (Basal); 2) Basal + fish meal (9% DM) = FM; 3) Basal + fish oil (1.5% DM) with protected sunflower meal (9% DM ) = FOSMP; 4) Basal + fish oil (1.5% DM) = FO; or 5) Basal + protected sunflower meal (10.5% DM) = SMP. Daily intake of ME (9.60 - 10.5 MJ ME/d) and CP (150 to 168 g/d) in all treatments was kept similar by varying the ratio of oaten:lucerne chaff and by feeding the animals at 90% ad libitum intake. Blood samples were collected at the start of the experiment and on the day (d 42) prior to slaughter. Lambs were then slaughtered at a commercial abattoir. At 24 h postmortem carcass traits were measured and longissimus thoracis muscle taken for analysis of FA of phospholipid and triglyceride fractions. Lambs fed FO and FOSMP showed a marked increase in muscle longchain n-3 FA (P < 0.001) and a reduction in magnitude of the rise in insulin concentration (P < 0.001) after feeding compared with lambs fed Basal and SMP diets. Lambs in FM had a moderate increase (P < 0.001) in muscle long-chain n-3 FA content. Compared with Basal diet, both plasma total cholesterol (P < 0.02) and high-density lipoprotein cholesterol (P < 0.001) levels were greater in SMP and less in FO and FOSMP treatments. The i.m. fat content was reduced (P < 0.05) in FM and FO treatments, but carcass weight was increased only with fish meal (P < 0.03). Adding SMP to FO produced muscle with an intermediate level of i.m. fat, whereas muscle long-chain n-3 FA, i.m. fat, and insulin concentration were unchanged with SMP treatment. These results indicate that an increase in carcass weight in FM may be due to the supply of ruminally undegraded protein. They also suggest that fish oil along with fish meal can increase long-chain n-3 FA content in phospholipid of muscle membrane. This may be associated with reduced i.m. fat content and altered insulin action and lipoprotein metabolism.     

Predicting behavioral changes associated with age-related cognitive impairment in dogs

OBJECTIVE: To monitor the progression of age-related behavioral changes in dogs during a period of 6 to 18 months and to determine whether signs of dysfunction in any of 4 behavioral categories can be used to predict further impairment. DESIGN: Age-stratified cohort study. ANIMALS: 63 spayed female and 47 castrated male dogs 11 to 14 years of age. PROCEDURE: Data were collected from randomly selected dog owners who were interviewed by telephone twice at a 12- to 18-month interval; data were included if the dog had lived > or = 6 months between interviews. The interview focused on signs of impairment in the following behavioral categories: orientation in the home and yard, social interactions with human family members, house training, and the sleep-wake cycle. Dogs were determined to have impairment in 0 behavioral categories (on the basis of < or = 1 sign for each category), impairment in 1 category (> or = 2 signs of dysfunction in that category), or impairment in > or = 2 categories. RESULTS: Between interviews, 22% (16/73) of dogs that did not have impairment in a category at the time of the first interview developed impairment in that category by the time of the second interview. Forty-eight percent (13/27) of dogs that had impairment in 1 category at the time of the first interview developed impairment in > or = 2 categories by the time of the second interview and were significantly more likely to develop impairment in > or = 2 categories, compared with dogs that initially had impairment in 0 categories. Dogs with 1 sign of dysfunction in orientation were significantly more likely to develop impairment in that category, compared with dogs that had 0 signs of dysfunction in orientation. CONCLUSIONS AND CLINICAL RELEVANCE: Age-related behavioral changes in dogs are progressive. Clinicians should consider trying to predict which dogs are most likely to become progressively impaired during the subsequent 6 to 18 months.