The development of the inner layer of backfat in fetal and young pigs

The development of the innermost layer of backfat was studied histologically and histochemically in fetuses from Yorkshire sows at 45, 60, 65, 75, 85, 90, 105, 110, and 112 d of gestation. Samples were also obtained from fetuses at 110 d of gestation from Ossabaw sows and from sows selected for high (obese) or low (lead) backfat thickness. Fetuses from some sows were decapitated at 45 d of gestation and samples were obtained from these fetuses at 110 d of gestation. The inner layer develops before 75 d of gestation and has stromal-vascular characteristics that clearly distinguish it from the middle layer of backfat. For instance, a well organized and dense collagen matrix immediately surrounds small fat cell clusters in the inner layer. Most fat cell cluster capillaries (in the inner layer) reacted strongly for ATPase histochemically and are histologically immature. The inner layer morphology and cell size was similar in Ossabaw, obese and lean fetuses. The number of PAS (Periodic Acid Schiff) positive cells were dependent on fetal strain. The number was highest in obese fetuses and lowest in Ossabaws. Comparison of decapitated fetuses and weight-matched controls indicated that the inner layer was most affected by decapitation. A decreased organization and amount of collagen was associated with larger fat cell clusters in decapitated fetuses, and most fat cell cluster capillaries reacted little for ATPase histochemically and were histologically mature. The range in inner-layer fat cell diameter was wider in decapitated fetuses (11 to 55 micron) than in control fetuses (11 to 30 micron). These results demonstrate that the characteristics of the inner layer are clearly different from the other layers and that the amount and organization of collagen was inversely associated with the size of fat cell clusters and fat cells and with the maturity of the adipocyte-associated capillaries.     

Effect of maternal diet on skeletal muscle composition and metabolism and on bone dimensions and composition of the fetal pig

The purpose of the present study was to determine the effect of addition of fat to sow diets on selected muscle and bone traits of the fetus. Crossbred dams were assigned to receive one of four dietary treatments at 80 d of gestation. Percentage added poultry fat in the diet was 0, 2.3, 12.7 or 29.6%. Isocaloric-isonitrogenous diets (7,000 kcal ME) were fed once daily. At 110 d of gestation, sows were anesthetized with fluothane and nitrous oxide. Fetuses were removed by Caesarean section. Fetal body weight, biceps femoris muscles and femur wet weights and blood (concentration of protein, free fatty acids and triacylglycerol), muscle (percentage dry matter, concentration of DNA, RNA, protein and lipid) and bone (percentage dry matter, lipid, ash and length) traits were not influenced by maternal dietary fat content. The rates of oxidation of palmitate and of lipid to CO2 and the rates of incorporation of palmitate into triacylglycerol and into phospholipid by fetal pig muscle also were not influenced by maternal dietary fat content. It was suggested that fetal skeletal muscle can mobilize glycogen and, to a limited extent, lipid stores.     

Evaluation of d,l-ethionine as a mechanism for pancreatic islet regeneration in dogs

Objective To determine whether induction of pancreatic necrosis and islet proliferation by d,l‐ethionine has potential for treating dogs with b ‐cell insufficiency. Design Eighteen mixed breed dogs of both sexes were given d,l‐ethionine at 100 mg/kg three times weekly for 2 weeks; 6 dogs were euthanased at 2, 14 and 28 d after the last dose. Methods Clinical signs during administration and recovery were assessed. Routine biochemical analyses were performed before each ethionine dose and then once weekly. Faecal samples were examined weekly for malassimilated nutrients and blood. Blood coagulation screening tests (OSPT and APTT) were determined on four dogs after ethionine administration. Intravenous glucose tolerance tests were conducted before the first and after the last ethionine dose and then fortnightly. All dogs were necropsied and pancreas, liver, kidney and jejunum were examined microscopically. Results During ethionine administration all animals displayed vomiting, inappetence, diarrhoea (often with blood), weight loss and depression. Three dogs were euthanased prematurely due to severe illness, but those allowed to recover were eating and brighter 7 d after cessation of ethio‐nine administration. Serum concentrations of TLI, amylase and lipase increased initially, then decreased, during administration but returned to normal during recovery. Concentrations of ALT, ALP, unconjugated and conjugated bilirubin increased during administration then decreased slowly. Histological examination revealed hepatic lipidosis and necrosis, but no renal or jejunal lesions. In most dogs, faecal examination demonstrated increased undigested starch and muscle, as well as increased digested and undigested fat, during ethio‐nine administration or early during the recovery period, suggesting transient malassimilation. APTT was unchanged but OSPT was prolonged in all dogs. There was no impairment of insulin secretion or glucose intolerance and C‐peptide concentrations were unaffected. Immediately after ethionine administration there was delayed insulin degradation and by day 43 there was evidence of increased insulin sensitivity. Conclusion d,l‐ethionine administration in dogs appeared not to interfere with insulin secretion, but caused clinical signs and laboratory changes indicative of pancreatic exocrine necrosis, severe hepatobiliary disease and transient malas‐similation. Pancreatic and hepatic dysfunction was severe but clinical recovery occurred after ethionine administration ceased. The severe side‐effects observed with d,l‐ethionine should preclude its potential use for treating diabetes mellitus in dogs.     

The use of tiletamine hydrochloride and zolazepam hydrochloride for sedation of the mountain brushtail possun Trichosurus caninus Ogilby (Phalangeridae: Marsupialia)

SUMMARY A combination of tiletamine hydrochloride and zolazepam hydrochloride in a 1:1 ratio by weight was used successfully to sedate mountain brushtail possums, Trichosurus caninus, in the field. A standard total dose of 50 to 60 mg provided adequate sedation for the completion of a range of handling procedures. We describe the induction time, dose rate and side-effects associated with the use of tiletamine and zolazepam in T caninus.     

Preferences of veterinarians for drugs to treat heart disease in dogs and cats

SUMMARY Responses (473) were collated from a questionnaire sent to 5054 veterinarians in Australia enquiring about drug preferences for treating cardiac disease in dogs and cats. When treating a small breed dog with endocardiosis and mild left congestive heart failure, 74% of 472 respondents used a diuretic, 67% a theophylline derivative, 27% a vasodilator and 20% a positive inotrope. Frusemide was the preferred diuretic and digoxin the preferred inotrope, but vasodilator use varied. Low sodium diets were “often recommended” by 71% of respondents. Propranolol was preferred to diltiazem for treating feline hypertrophic cardiomyopathy. Digoxin was clearly preferred for treating supraventricular dysrhythmias, while lignocaine and digoxin were preferred equally for ventricular dysrhythmias. Respondents appeared more willing than US veterinarians to use theophylline derivatives and prasozin, and less inclined to employ nitrates, hydralazine, inotropes other than digoxin, and low sodium diets.     

Comparison of induced corpora lutea from prepuberal gilts and spontaneous corpora lutea from mature gilts: hydroxysteroid dehydrogenase activity

The activity of hydroxysteroid dehydrogenases was histochemically quantified in corpora lutea (CL) from prepuberal gilts induced to ovulate and mature gilts. Prepuberal (P) gilts, 120 to 130 d of age were induced to ovulate with 1,500 IU pregnant mare serum gonadotropin (PMSG) followed 72 h later by 500 IU human chorionic gonadotropin (hCG). Three P gilts and three mature (M) gilts each were ovariectomized on d 10, 14, 18, 22 and 26 (d 0 = day of hCG for P gilts and onset of estrus for M gilts). Gilts ovariectomized on d 14, 18, 22 and 26 were hysterectomized on d 6 to ensure luteal maintenance. At the time of ovariectomy, CL were frozen in liquid nitrogen and then stored at -80 C until analysis. Cryostat sections (12 microns) were histochemically analyzed for delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta OHSD), 17 alpha-hydroxysteroid dehydrogenase (17 alpha OHSD) and 20 alpha-hydroxysteroid dehydrogenase (20 alpha OHSD). The intensity of staining (greater enzyme activity resulted in darker staining) was quantified using a Zeiss SF microscope integrated with a Zonax photometer, which measured the percentage of light transmitted through a given area (22,500 microns 2) of the tissue section. Data were subjected to analysis of variance using the general linear models procedure of Statistical Analysis System (SAS). The 3 beta OHSD activity did not change over days, but the mean activity (throughout all days) in the P gilts (32.6 +/- 1.8) tended (P less than .08) to be elevated above that of M gilts (27.9 +/- 1.7).(ABSTRACT TRUNCATED AT 250 WORDS)     

Mitotic activity in fetal and early postnatal porcine adipose tissue

Tritiated thymidine autoradiography and histochemistry were used to study the development of subcutaneous adipose tissue of lean and obese fetuses and postnatal pigs. A pattern of tritiated thymidine uptake by pre-adipocytes and adipocyte lipid accumulation was demonstrated during the growth of the fetal pig. In the youngest fetuses there was a period of intense stromal cell mitotic activity before any adipocyte lipid accumulation. During subsequent fetal development, clusters of tightly arranged stromal cells were formed. Lipid accumulation occurred only in these cell clusters. During this time of cell cluster formation and lipid accumulation, mitotic activity was minimal. In obese fetuses, stromal cell mitotic activity overlapped temporarily with the cell cluster formation and lipid accumulation period. In early postnatal pigs, fat cell clusters increased in size until they "physically filled" the adipose tissue. In pigs 3 d and older, there was extensive mitotic activity of cells within the fat cell clusters. The synthesis of this second bed of pre-adipocytes and the altered developmental pattern in the obese fetuses is suggested to be due to the influence of a high fat diet. The significance of these findings in terms of plausible links between pre-adipocyte mitosis and lipid accumulation is discussed.     

Extrinsic regulation of domestic animal-derived myogenic satellite cells II

The existence of myogenic satellite cells was reported some 47 years ago, and, since that time, satellite cell research has flourished. So much new information is generated (daily) on these cells that it can be difficult for individuals to keep abreast of important issues related to their activation and proliferation, the modulation of the activity of other cell types, the differentiation of the cells to facilitate normal skeletal muscle growth and development, or to the repair of damaged myofibers. The intent of this review is to summarize new information about the extrinsic regulation of myogenic satellite cells and to provide specific mechanisms involved in altering satellite cell physiology. Where possible, examples from agriculturally important animals are used for illustrative purposes.     

Alterations of serum insulin-like growth factor-I (IGF-I) and IGF-binding proteins (IGFBPs) in swine infected with the protozoan parasite Sarcocystis miescheriana.

The effects of a Sarcocystis miescheriana infection on insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding proteins (IGFBPs) were investigated to determine possible mechanisms of growth retardation in growing pigs. Sixteen pigs averaging 14 kg body weight were divided into 4 groups of 4 pigs each and infected either with 0.5, 1.0, or 3.0 × 10⁶ sporocysts of S. miescheriana. Four pigs were retained as non-infected controls; however, they became serologically positive during the course of the infection. Effects also were investigated in 2 groups of 3 pregnant sows. One group was infected with 0.5 × 10⁶ sporocysts and the other group was retained as uninfected controls. Body weights of infected growing pigs were depressed as compared to controls following the acute phase 15 d after infection (dai). Serum concentrations of IGF-I dropped significantly (p < 0.05) during the acute phase of infection in all infected groups of growing pigs. Conversely, the amounts of unsaturated serum IGFBPs were elevated significantly (p < 0.05) during the acute phase of infection. Specifically, serum concentrations of IGFBP-1, IGFBP-2, and IGFBP-4 were elevated at this time, as determined by ligand blot analysis. There was no association between growth factor alterations and tissue damage as measured by serum creatinine kinase and aspartate aminotransferase levels. The extent of effects in growing pigs was related to the amount of the original parasite inoculum.

During the acute phase of infection 2 of 3 pregnant sows aborted. The third sow went to term, but piglets were stillborn or died within 24 hr. Compared to uninfected controls, serum concentrations of IGF-I in infected pregnant sows were depressed during and after the acute phase of the infection. Levels of unsaturated serum IGFBPs in pregnant sows were not affected.

These data suggest that decreased IGF-I levels and/or elevated levels of specific forms of IGFBPs may be a mechanism by which growth is affected in feeder pigs infected with S. miescheriana.     

Dynamics of Oxidation of a Fe2+-Bearing Aluminosilicate (Basaltic) Melt

Rutherford backscattering spectroscopy (RBS) and microscopy demonstrate that the approximately 1400°C oxidation of levitated droplets of a natural Fe2+-bearing aluminosilicate (basalt) melt occurs by chemical diffusion of Fe2+ and Ca2+ to the free surface of the droplet; internal oxidation of the melt results from the required counterflux of electron holes. Diffusion of an oxygen species is not required. Oxidation causes the droplets to go subsolidus; magnetite (Fe3O4) forms at the oxidation-solidification front with a morphology suggestive of a Liesegang-band nucleation process.