Improved potency assay for recombinant bovine somatotropin by high-performance size-exclusion chromatography.

A high-performance size-exclusion chromatographic method was developed for the determination of potency of recombinant bovine somatotropin (rbST) monomer and the estimation of dimer and soluble aggregates in bulk drug substances. These proteins can be completely extracted from bulk drug substances with sodium borate-ethylenediamine-tetraacetic acid disodium salt (EDTA) at pH 9.5 and separated on TSK G3000SW column with a mobile phase of pH 7.3 sodium borate-EDTA. The results demonstrated that this method was a non-denaturing assay for the determination of potency of rbST monomer and the data obtained in this study correlated well with data of the hypophysectomized rat body weight gain bioassay. The rbST monomer and dimer in the separation were verified by liquid chromatography-electrospray mass spectrometry. This method was optimized and validated.

Analysis of tilmicosin in swine liver extracts by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry.

Tilmicosin is a semisynthetic macrolide antibiotic used in the treatment of respiratory disease in cattle and swine. The technique of liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) was employed in an on-line capacity for the analysis of tilmicosin in extracts from spiked swine liver. Increasing the potential in the cone/skimmer region of the ion source resulted in an increased abundance of unique structurally indicating fragment ions of tilmicosin. Three ions, [M+H]+ and two diagnostic fragment ions were chosen for confirmation of the presence of tilmicosin in swine liver tissue extracts using the mass spectrometer in selected-ion monitoring mode. The ion abundance ratios arising from any given combination of ions in data acquired from extracts of swine liver tissue spiked with tilmicosin at 5 and 10 ppm were within +/- 10% of the corresponding mean standard abundance ratio, and duplicate sample analyses exhibited < 10% relative standard deviation. These results suggest the potential for the application of LC/APCI-MS as a confirmatory technique for tilmicosin in swine liver.

Low urinary chiro-inositol excretion in non-insulin-dependent diabetes mellitus.

BACKGROUND AND METHODS: Inositol is a major component of the intracellular mediators of insulin action. To investigate the possible role of altered inositol metabolism in non-insulin-dependent diabetes mellitus (NIDDM), we used gas chromatography and mass spectrometry to measure the myo-inositol and chiro-inositol content of urine specimens from normal subjects and patients with NIDDM: The study subjects were whites, blacks, and Pima Indians. The type of inositol and its concentration in insulin-mediator preparations from muscle-biopsy specimens from normal subjects and diabetic patients were also determined. RESULTS: The urinary excretion of chiro-inositol was much lower in the patients with NIDDM (mean [+/- SE], 1.8 +/- 0.8 mumol per day) than in the normal subjects (mean, 84.9 +/- 26.9 mumol per day; P less than 0.01). In contrast, the mean urinary myo-inositol excretion was higher in the diabetic patients than in the normal subjects (444 +/- 135 vs. 176 +/- 46 mumol per day; P less than 0.05). There was no correlation between chiro-inositol excretion and the age, sex, or weight of the diabetic patients, nor was there any correlation between urinary chiro-inositol and myo-inositol excretion in either group. The results were similar in a primate model of NIDDM, and chiro-inositol excretion was decreased to a lesser extent in animals with prediabetic insulin resistance. chiro-Inositol was undetectable in insulin-mediator preparations from muscle-biopsy samples obtained from patients with NIDDM: Similar preparations from normal subjects contained substantial amounts of chiro-inositol. Furthermore, the chiro-inositol content of such preparations increased after the administration of insulin during euglycemic-hyperinsulinemic-clamp studies in normal subjects but not in patients with NIDDM: CONCLUSIONS: NIDDM is associated with decreased chiro-inositol excretion and decreased chiro-inositol content in muscle. These abnormalities seem to reflect the presence of insulin resistance in NIDDM:

[3H]myoinositol incorporation into phospholipids in liver microsomes from humans with and without type II diabetes. The lack of synthesis of glycosylphosphatidylinositol, precursor of the insulin mediator inositol phosphate glycan.

A class of inositol phosphate-containing oligosaccharides (IPG) derived from a membrane glycan-phosphatidylinositol precursor (GPI) has been identified as a possible mediator of insulin action. Saltiel's laboratory has recently communicated an in vitro assay for the synthesis of GPI in rat liver microsomes. Herein we have established this method in rat and human liver microsomes, it being our end point to evaluate if the pool of GPI was normal in diabetes and if failure of insulin to generate IPG from GPI could be involved in the mechanism of insulin resistance in Type II diabetes. However, subsequent to the detailed study of [3H]myoinositol incorporation into phospholipids in liver microsomes from our study subjects, we demonstrated by gas chromatography/mass spectrometry analysis that the material reported to be GPI is a mixture of lysophospholipids that does not contain hexosamine, ethanolamine, or amino acids.

A simple procedure for the preparation and purification of the oligosaccharide components of the glycosylphosphatidylinositol anchor of membrane proteins.

The oligosaccharide components of the glycosylphosphatidylinositol anchors of Trypanosoma brucei variant surface glycoproteins have been prepared and purified by treatment with hydrolytic enzymes and solvent extraction procedures followed by HPLC purification using a specific oligosaccharide binding matrix (Glyco-Pak N, by Waters). Three oligosaccharide peaks (peaks I, II and III) were resolved by a single isocratic HPLC step (70% acetonitrile in water). The material from these peaks was hydrolyzed in acid and analyzed by GC/MS. GC/MS analysis of the material obtained from each peak demonstrated the presence of inositol, glucosamine, and mannose in a 1:1:3 ratio. A variable number of galactose residues were detected in each peak. The galactose:inositol ratios of the purified components were 1:1, 2:1, and 3:1 for peaks I, II and III, respectively, suggesting that the separation obtained depends primarily on the number of sugar residues present in each fraction.