Raman spectroscopic analysis of biochemical changes in individual triglyceride-rich lipoproteins in the pre- and postprandial state.

Individual triglyceride-rich lipoprotein (TGRL) particles derived from human volunteers are nondestructively analyzed by laser tweezers Raman microspectroscopy, and information on their composition and distribution is obtained. The Raman signature of single optically trapped very low-density lipoproteins (VLDL), a subclass of TGRL, which play an important role in cardiovascular disease, exhibits distinct peaks associated with molecular vibrations of fatty acids, proteins, lipids, and structural rearrangements of lipids. Our analysis of pre- and postprandial VLDL exhibits the signature of biochemical changes in individual lipoprotein particles following the consumption of meals. Interaction of VLDL with endothelium leads to the breakdown of complex triacylglycerols and the formation of a highly ordered core of free saturated fatty acids in the particle. A particle distribution analysis reveals trends in the degree to which this process has occurred in particles at different times during the postprandial period. Differences in particle distributions based on the different ratios of polyunsaturated to saturated fats in the consumed meals are also easily discerned. Individual lipoprotein particles hydrolyzed in vitro through addition of lipoprotein lipase (LpL) exhibit strikingly similar changes in their Raman spectra. These results demonstrate the feasibility of monitoring the dynamics of lipid metabolism of individual TGRL particles as they interact with LpL in the endothelial cell wall using Raman spectroscopy.

Bovine leukemia virus alters growth properties and casein synthesis in mammary epithelial cells.

Bovine leukemia virus (BLV) is widespread in US dairy herds, yet only about 1% of infected cattle develop bovine leukosis and are culled from the herd. A major concern is whether BLV infection of dairy cows alters milk yield. Although several studies have examined the effect of BLV on milk production in vivo, the results were inconclusive. No in vitro studies have been done. The discovery of BLV in mammary epithelial cells (MEC) of infected cows raises the possibility that the virus could affect these cells directly. The purpose of this study was to use an in vitro system to determine if BLV could alter milk yield by altering cell number and/or milk production per cell. A short-term cell line established from the MEC of a BLV-negative cow, and a proven casein-producer mouse cell line, Comma D, were stably transfected with a plasmid containing the entire BLV genome. Untransfected parental lines served as negative controls. The BLV-containing bovine MEC line has a reduced population-doubling time, higher saturation density, and increased longevity. The Comma D line is an already-transformed cell line, and growth properties did not change after transfection with BLV. Under appropriate differentiation conditions, both the bovine and mouse MEC transfected with BLV displayed decreased casein production and mRNA synthesis compared with control cell lines without BLV. Our results suggest that effects of BLV infection on milk production may not be related solely to overall animal health but may also be mediated directly at a cellular level.

HCG binding to the testicular LH receptor is similar in fertile, subfertile, and infertile stallions.

Recent evidence in our laboratory suggests that the cause of idiopathic subfertility/infertility in breeding stallions may originate in the testes at the luteinizing hormone (LH) receptor or postreceptor level. The objective of this research was to determine if LH receptor binding activity is altered in subfertile and infertile stallions. Six fertile, three subfertile, and three infertile stallions, ages 11-23 years, were classified according to normal semen parameters and pregnancy rates and then castrated in the breeding season. Blood was collected prior to castration, and plasma was stored until analyzed for LH, follicle stimulating hormone (FSH), estrogen conjugates (EC), estradiol (E2), testosterone (T), and inhibin (I) by radioimmunoassay (RIA). Testicular cell membranes were prepared and snap-frozen until analyzed for LH binding activity by radioreceptorassay (RRA) using increasing amounts of I125 human chorionic gonadotropin (hCG). Luteinizing hormone receptor numbers and affinity constants were determined by Scatchard analysis. Plasma LH, FSH, EC, E2, and T levels did not differ between fertile and subfertile stallions, but LH and FSH were significantly higher (P < 0.05) and EC, E2, T, and I levels were significantly lower (P < 0.05) in infertile stallions as compared to fertile and subfertile stallions. Receptor number (Rt) and affinity constants Ka were similar (P > 0.05) between fertile (Rt = 9.44 x 10(-11) M, Ka = 0.300 x 10(10) M-1), subfertile (Rt = 13.02 x 10(-11) M, Ka = 0.194 x 10(10) M-1), and infertile (Rt = 7.65 x 10(-11) M, Ka = 0.380 x 10(10) M-1) stallions. In conclusion, these data suggest that an endocrine dysfunction in the testes of stallions with poor fertility may not be due to a LH receptor disorder but may be due to a postreceptor malfunction.