Application of an automated enzymatic technique for the determination of non-esterified fatty acids in bovine blood.

An enzymatic method for the measurement of non-esterified fatty acid (NEFA) concentrations in blood was applied to samples from dairy cows. The method was carried out on a discrete analyser and showed considerable savings over other methods, particularly in time. The precision of the method was very high and the accuracy was good within normal concentration ranges when compared with an extraction reference method. Using this enzymatic method, it is possible to measure NEFA concentrations in bovine serum or plasma on a routine basis. The results will be of particular value in assessing the metabolic and nutritional status of cows in the post parturient period.

Size and lipolytic capacity of bovine adipocytes from subcutaneous and internal adipose tissue.

Adipose tissue samples were taken from five dairy cows in early lactation. Various external and internal sites were chosen, and after isolation of the adipocytes, their size and lipolytic capacity were measured. It was found that cells from all the sites showed high lipolytic activity, although there was a four-fold difference between cells from perirenal fat and those from omental fat, which showed the highest activity. It was not possible to detect any relationship between diameter and lipolytic capacity of the adipocytes.

Comparison of biochemical and histological methods of estimating fat content of liver of dairy cows.

The degree of fatty infiltration of the liver was estimated in two herds of dairy cows using biochemical and stereological methods. Estimation of hepatic triglyceride content biochemically or of fractional volume of fat in hepatocytes stereologically are both reliable methods of assessing fatty infiltration of the liver in the dairy cow. Estimation of hepatic total lipid content is not considered an acceptable alternative because the high basal level of non-triglyceride lipid masks the increase in hepatic triglyceride content which is characteristic of fatty liver.

Comparison of glucose and acetate as substrates for lipid synthesis in bovine adipocytes.

The metabolic capacity of bovine adipocytes was studied using isolated cells from subcutaneous adipose tissue of four dairy cows before and after calving. The lipogenic capacity was assessed by measuring the incorporation of 14C-glucose and 14C-acetate into lipid. In the cells taken from the cows before calving, 14C-acetate was incorporated into lipid at a much higher rate than 14C-glucose but, after calving, incorporation of both substrates was very low. The results show that 14C-acetate uptake into lipid is a more sensitive indicator of the lipogenic capacity of adipocytes of dairy cows.

The metabolic activity of bovine adipocytes before and after parturition.

Adipocytes were isolated from biopsies of the subcutaneous adipose tissue of dairy cows before and after parturition. The diameter of the cells was measured and their lipogenic and lipolytic capacities were assessed by measurement of 14C-glucose incorporation and glycerol release. The concentration of non-esterified fatty acids (NEFA) in plasma at the time of biopsy was also measured. In the post calving samples, lipogenic activity of the adipocytes was reduced to a third of the precalving level, and oxidation of glucose to carbon dioxide almost ceased. Lipolytic activity increased five-fold after calving, and this was associated with an increase in plasma NEFA concentrations.

The neutralization of transmissible gastroenteritis virus by normal heterotypic serum.

Exposure of transmissible gastroenteritis virus of pigs to unheated normal heterotypic serum resulted in a drop in infectivity, an effect which was lost after heating the serum to 56 degrees C for 30 min or by treatments inactivating complement. Analysis of virus proteins, RNA and lipids, and centrifugation studies showed little difference between inactivated and control virus, but electron microscopy of negatively stained particles after treatment with serum revealed holes in the virus envelope, characteristic of those caused by complement in the presence of antibody.

Lipids of transmissible gastroenteritis virus and their relation to those of two different host cells.

The lipids of two cell types (primary pig kidney and secondary adult pig thyroid) and those of transmissible gastroenteritis virus (TGEV) grown in these cells were studied using 14C-palmitic acid. Differences were demonstrated between the incorporation of isotopically labelled lipid precursors in the two cell types and it was found that the phospholipid and glycolipid profiles of purified TGEV closely resembled those of the host cell in which it was grown.

Isolation of subviral components from transmissible gastroenteritis virus.

Exposure of purified transmissible gastroenteritis virus, a porcine coronavirus, to non-ionic detergents resulted in the removal of the surface projections and greater than 98% of the virus lipid. Virus RNA was associated with a subviral particle which had a sedimentation coefficient of 650S, compared with 495S for the intact virion, and which banded in Cs2SO4 gradients at 1-295 g/ml. Negatively stained preparations of subviral particles were shown by electron microscopy to contain spherical particles of 60 to 70 nm diam., similar in appearance to those derived from oncornaviruses. Polyacrylamide gel electrophoresis of the polypeptides from isolated subviral particles showed that these structures contained three of the four major virus structural proteins, the arginine-rich polypeptide VP2 and the two membrane glycopolypeptides VP2 and 4. The detergent-liberated surface projections, composed of a single species of sulphated glycopolypeptide, VPI, were isolated by rate-zonal centrifugation through sucrose gradients followed by precipitation with ammonium sulphate in the presence of bovine serum albumin.

Characterization of Mycoplasmatales virus-laidlawii 3.

Purified preparations of Mycoplasmatales virus-laidlawii 3 were negatively stained and studied by electron microscopy. They were seen to consist of uniform sized particles having a polyhedral head, 57 nm by 61 nm, and a short tail, 25 nm long, joined to the head at one vertex by a collar. The particles were shown to have buoyant densities of 1-477 g/ml in CsC1, 1-32 g/ml and 1-26 g/ml in potassium tartrate and a sedimentation coefficient, S20,W, OF 290 +/- 13. They are composed of 35-2% double-stranded DNA and five structural polypeptides with approximate mol. wt. of 172000, 81000 73000, 68000 and 43000. The classification of the virus from its morphology and chemical properties is discussed.