Procedure for exteriorizing the carotid artery in the bovine

Structural morphing in a symmetry-mismatched viral vertex

Large biological structures are assembled from smaller, often symmetric, sub-structures. However, asymmetry among sub-structures is fundamentally important for biological function. An extreme form of asymmetry, a 12-fold-symmetric dodecameric portal complex inserted into a 5-fold-symmetric capsid vertex, is found in numerous icosahedral viruses, including tailed bacteriophages, herpesviruses, and archaeal viruses. This vertex is critical for driving capsid assembly, DNA packaging, tail attachment, and genome ejection. Here, we report the near-atomic in situ structure of the symmetry-mismatched portal vertex from bacteriophage T4. Remarkably, the local structure of portal morphs to compensate for symmetry-mismatch, forming similar interactions in different capsid environments while maintaining strict symmetry in the rest of the structure. This creates a unique and unusually dynamic symmetry-mismatched vertex that is central to building an infectious virion.

In icosahedral viruses, a symmetry-mismatched portal vertex is assembled by inserting a 12-fold-symmetric portal complex into a 5-fold-symmetric capsid environment. Here, the authors report a near-atomic-resolution in situ cryo-electron microscopy structure of this symmetrically mismatched viral vertex from bacteriophage T4.

Transposition of the common carotid artery in standing cattle

OBJECTIVE

To describe a method for permanent transposition of the common carotid artery (CCA) in standing cattle.

STUDY DESIGN

Experimental study.

ANIMALS

Eight healthy, adult, lactating Holstein-Friesian cows.

METHODS

Cows were restrained with the head and neck extended by using halters, head catch, and squeeze chute. Surgery was performed under local anesthesia and intravenous sedation. The right CCA was approached through a skin incision dorsal and parallel to the jugular vein. The skin incision was extended through the brachiocephalicus and longus capitus muscles. When the vessel was present, ligation of accessory vessels of the CCA and internal jugular vein was performed to facilitate exposure. The artery was sharply dissected from the carotid sheath and elevated by using Penrose drains. The muscles were closed in two layers, leaving the artery in a subcutaneous position. The incision was protected with a tie-over bandage for 1 week. Sampling from the CCA was initiated approximately 6 weeks after surgery.

RESULTS

The CCA was successfully transposed and used for repeated arterial blood sampling in all eight cows. No cows had intraoperative complications or evidence of surgical site infection. One cow had a postoperative suture reaction at the site of a suture used for maintaining the tie-over bandage. All arteries remained patent for use in subsequent studies.

CONCLUSION

Permanent translocation of the CCA was successful in all cows in this study and consistently allowed serial arterial blood sampling.

CLINICAL SIGNIFICANCE

Common carotid artery translocation is possible without general anesthesia in adult cattle and is useful in studies requiring serial sampling of arterial blood.

Effects of environmental heat and intake of tall fescue seed infested with Acremonium coenophialum on the acid-base status of young bulls

Effects of high environmental temperature and dietary intake of tall fescue (Festuca arundinacea) seed containing the endophyte Acremonium coenophialum on bovine acid-base status were studied using 3 groups of bull calves (2 Simmental, 1 Angus). Experimental animals were housed in controlled-climate chambers and subjected to gradual increases in environmental temperature, first while being fed an endophyte-free diet and then while being fed a diet containing 17% endophyte-infested fescue seed. Marked acid-base disturbances were not observed in any animals. In general, Pco2, HCO3-, base excess, and arterial blood pH values were reduced in response to heat stress, both with endophyte-free and endophyte-containing diets. In most individuals anion gap increased. These results reflected metabolic compensation for mild chronic alveolar hyperventilation and retention of organic acids. These findings suggest that, under conditions similar to those found during the summer in central Missouri, normal cattle should not be at great risk of developing respiratory alkalosis or other severe acid-base disturbances as a result of heat stress and/or intake of tall fescue endophyte.

Forage intake, ruminal dry matter disappearance, and ruminal blood volatile fatty acids for steers in 18 and 32 degrees C temperatures

Six steers with rumen cannulas and exteriorized carotid arteries were fed chopped alfalfa, orchardgrass, or tall fescue hay in ambient temperatures (18 and 32 degrees C) using a factorial arrangement of forage and temperature with repeated measurements. Arterial blood, venous blood, and rumen fluid were sampled for VFA at 0, 2, 4, and 7 h after forage was offered. Rate of digestion of plant cell wall was determined by in vitro methods. Rate of ingesta and particulate passage was determined by 144Ce marker. Volatile fatty acid concentrations in blood plasma and rumen fluid were not related to forage voluntary intake. Voluntary forage intake was related to calculated ruminal disappearance of cell wall (r2 of .94). Elevated ambient temperature, 32 degrees C, depressed voluntary forage intake but did not increase ruminal or blood VFA concentrations.

Techniques for measuring blood flow in splanchnic tissues of cattle

A useful approach of the study of nutrient absorption and metabolism is in vivo measurement of blood flow across portal-drained viscera and liver, and flux of bloodborne metabolites, successful application of the approach requires correct placement of chronic catheters in appropriate blood vessels. Additionally, catheters must stay patent long enough to allow the animal to recover from surgery and to complete an experimental protocol. This paper describes surgical techniques to install chronic catheters in mesenteric veins, the hepatic portal vein, and an hepatic vein of cattle. Techniques for access to arterial blood are described also. Materials, equipment, and supplies required for surgery, blood sampling, and blood flow determination are described. Commercial sources of supplies are suggested. Blood flow is measured by downstream dilution of para-aminohippurate, which is infused into a mesenteric vein. Examples of blood flow data for three types of cattle are provided.

Partition of portal-drained visceral net flux in beef steers. 1. Blood flow and net flux of oxygen, glucose and nitrogenous compounds across stomach and post-stomach tissues

1. Blood from chronic indwelling catheters in the caudal aorta and anterior mesenteric, gastrosplenic and hepatic portal veins was used to measure blood flow and net flux of oxygen, glucose and nitrogenous compounds across hepatic portal-drained viscera (PDV), post-stomach (anterior mesenteric-drained viscera (MDV] and stomach tissues of two beef steers (390 kg mean live weight). 2. Steers were fed in sequence on (1) chopped lucerne (Medicago sativa) hay (twelve meals/d), (2) chopped lucerne hay (two meals/d) and (3) a pelleted concentrate diet containing 780 g ground maize/kg (two meals/d). The lucerne hay and concentrate contained 26.5 and 16.8 g nitrogen/kg respectively. 3. Five measurements of net flux (blood flow multiplied by venous-arterial concentration differences (VA] were obtained hourly on 2 d for each dietary regimen, beginning 0.5 h before feeding at 08.00 hours. Blood flow was measured by downstream dilution of p-aminohippurate (PAH). 4. Blood flow across MDV averaged 42% of PDV blood flow (665 litres/h). 5. Net use of O2 across MDV accounted for 51% of net PDV use of O2 (920 mmol/h). This disproportionate use of O2 in relation to blood flow was due to greater VA for O2 across MDV than across stomach tissues. Dietary regimen had no effect on the proportions of PDV blood flow and net O2 consumption attributable to MDV or stomach tissues. 6. When lucerne was given, net glucose use across MDV represented 69% of PDV use (35 mmol/h). When concentrate was given, MDV glucose use switched to net absorption (29 mmol/h), reducing net PDV glucose use to 1 mmol/h. 7. When concentrate was given, net MDV absorption of alpha-amino-N (AAN) increased from 98 to 190 mmol/h, yet net PDV absorption (101 mmol/h) was not affected. Net stomach AAN flux increased from -7 to -69 mmol/h when concentrate was given, negating the increase in net MDV absorption. 8. Net absorption of ammonia-N across MDV represented 28 and 52% of net PDV absorption when lucerne and concentrate were given respectively. Net NH3-N absorption across PDV was lower when lucerne was given than when concentrate was given (295 v. 154 mmol/h), reflecting lower dietary N intake (153 v. 83 g/d). Net MDV absorption of NH3-N was not affected by diet. Net removal of blood urea-N (BUN) across PDV (101 mmol/h) was not affected by diet. Across MDV, BUN removal was lower when concentrate was given than when lucerne was given (32 v. 77 mmol/h).(ABSTRACT TRUNCATED AT 400 WORDS)

Net portal-drained visceral and hepatic metabolism of glucose, L-lactate, and nitrogenous compounds in lactating holstein cows

Net portal-drained visceral and hepatic flux of glucose, L-lactate, alpha-amino N, NH3N, urea N, glutamate, and glutamine were measured in four Holstein cows. Cows were fed a 60:40 corn silage: concentrate diet ad libitum and milked at 12-h intervals. Six to 16 d postpartum chronic catheters were established in hepatic portal, hepatic, and mesenteric veins and a carotid artery was elevated. Twelve Measurements of net flux, the mathematical product of blood flow (measured by p-aminohippurate dilution) and venous-arterial concentration difference, were obtained for each cow at hourly intervals during 1 d of wk 4 and 8 postpartum. Dry matter, N, and energy digestion trials began 1 to 2 d after blood sampling. Dry matter intake and milk yield averaged 15.6 and 32.2 kg/d. Portal-drained visceral blood flow averaged 80% of hepatic blood flow (2041 L/h). Net flux of NH3N, urea N, and alpha-amino N across portal-drained viscera represented 68, 54, and 51% of N apparently digested. There was net use of glucose by portal-drained viscera. Hepatic glucose production (3.1 kg/d) exceeded calculated mammary glucose requirements. Net hepatic removal of L-lactate, alpha-amino N, and NH3N represented 115, 43, and 101%, respectively, of their net absorption by portal-drained viscera. Net hepatic L-lactate and alpha-amino N removal could account maximally for 17.4 and 16.5% of glucose produced.