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Biomedical subjects

I M Zulak

Publications and source records attributed to I M Zulak.

7 recordsLinked to original sources
PubMed1986

Ammonia (NH3 and N2H3) direct chemical ionization mass spectrometry of underivatized prostaglandin-H2 and other selected stable prostaglandins.

A study of the positive and negative ion, ammonia (NH3 and N2H3) direct chemical ionization mass spectrometry of highly purified prostaglandin endoperoxide (PGH2) is presented. The positive ion spectra were characterized by an intense [M + NH4]+ adduct at m/z 370 and several fragment ions, most notably a [M + NH4-H2O]+ ion at m/z 352 and an ion at m/z 298, assigned as the [M + NH4-72]+ ion of 12-hydroxy-5,8,10-heptadecatrienoic acid formed form PGH2 in the spectrometer. The negative ion spectra of PGH2 were characterized by a base peak at m/z 352 [M]- and by an ion at m/z 334 corresponding to the loss of water from the parent ion. A combination of negative ion and deuterated ammonia reagent gas was used in making assignments and in demonstrating that the spectra observed were due to intact PGH2 and its stable PGE2 and PGD2 isomers formed in the spectrometer. In addition, use of the latter reagent gas was shown to clearly distinguish between several arachidonic acid metabolites, differing in their number of exchangeable protons. Furthermore, preliminary results with several stable prostaglandins indicate that the spectra are sensitive to different functional groups that are present. Consequently, it would appear that negative and positive ion, NH3 (N2H3) direct chemical ionization mass spectrometry would be useful in the analysis of labile arachidonic acid metabolites, without the need for prior derivatization.

Ammonia↗
PubMed1986

A fast, nondestructive purification scheme for prostaglandin H2 using a nonaqueous, bonded-phase high-performance liquid chromatography system.

Arachidonic acid metabolism produces several biologically important compounds including the leukotrienes and prostaglandins. Prostaglandin H2 (PGH2) is the first metabolite in the arachidonic acid cascade leading to all other prostaglandins. Pivotal to our understanding of PGH2's biology is the ability to separate it in pure form from the numerous other arachidonic acid metabolites produced in a biological milieu. The extensive literature on PGH2 biology and metabolism has relied almost exclusively on the traditional method of separation using gravity flow silicic acid columns. In our hands, such PGH2 preparations were found to contain varying amounts of 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT), PGE2, PGF2 alpha and other minor impurities as determined by further chromatographic and mass spectral analyses. Analytical separation of PGH2 and other arachidonic acid metabolites has been accomplished using reversed-phase HPLC. However, the labile nature of this molecule in aqueous systems makes such techniques unacceptable for preparative isolation of high purity PGH2 and has necessitated the development of a totally nonaqueous separation. To this end, we attempted several stationary phases and found that the cyano-bonded phase showed the best selectivity for resolving PGH2 from its major contaminants. Separations were performed on self-packed columns using a hexane-isopropanol gradient. Peaks were detected both by liquid scintillation counting and uv spectrophotometry (214 nm). Structure assignments were made by chromatographic comparison with authentic standards (PGF2 alpha, PGE2), biological activity (PGH2--platelet aggregation), and by ammonia direct chemical ionization mass spectrometry (HHT, hydroxy-5,8,10,14-eicosatetraenoic acid, PGH2, PGE2, PGF2 alpha). The latter technique, which by its very nature volatilizes all organic material in the sample, was particularly useful in determining not only that the PGH2 preparations were free from the aforementioned side products, but that they were also free from lipid, protein, and other potential residues frequently found in biological preparations.

Animals↗
PubMed1983

Citrate accumulation by a Golgi apparatus-rich fraction from lactating bovine mammary gland.

1. Golgi apparatus-rich fractions from lactating bovine mammary gland rapidly accumulated citrate from incubation medium. Characteristics of this process suggested that a citrate transport system may be present in Golgi apparatus membranes. 2. Endoplasmic reticulum fractions accumulated citrate at nearly the same rate as Golgi apparatus; secretory vesicle fractions displayed lower ability to accumulate citrate. Intact epithelial cells (acini) from lactating mammary gland did not accumulate citrate. 3. Citrate accumulation by Golgi apparatus was pH and temperature sensitive but was not altered by metabolic inhibitors. 4. These observations suggest a role for Golgi apparatus in packaging intracellular citrate for secretion into milk.

Animals↗
PubMed1978

Iron deficiency hyperlipidemia in 18-day-old rat pups: effects of milk lipids, lipoprotein lipase, and triglyceride synthesis.

Three levels of iron (5, 29, 307 ppm iron) were fed to rats from conception through the 18th day of lactation. Dams in the 5 ppm iron group and pups in the 5 and 29 ppm iron groups developed anemia characterized by lower hemoglobin and hematocrit values than control animals. Liver and spleen levels of iron in dams and pups in the 5 and 29 ppm iron groups were lower than in the 307 ppm iron groups. Milk iron was lower in the 5 ppm iron group than in the 29 and 307 ppm iron groups. Pups in the 5 ppm iron group had hyperlipidemia characterized by elevated serum triglycerides, cholesterol, and phospholipids. Milk lipids and post-heparin plasma lipoprotein lipase levels in pups did not differ among experimental groups. Triglyceride and CO2 production from [U-14C]glucose were significantly greater in the iron-deficient pups than in control pups. Hyperlipidemia in 18-day-old iron-deficient rat pups appears to be related to increased endogenous production of triglycerides.

Anemia, Hypochromic↗
PubMed1976

Adenosine triphosphate in milk.

Freshly secreted goat's milk contains a number of viable metabolic pathways including those for the synthesis of triglycerides and phospholipids. Toward understanding this matter, amounts of the fundamentally important energy substrate, adenosine triphosphate, in goat's milk were evaluated. Milk left in the goat udder overnight had less adenosine triphosphate (12.4 muM) than fresh secreted milk (37.6 muM). In similar experiments the skim milk derived from whole accumulating in the udder overnight was lower in adenosine triphosphate (14.2 muM) than skim milk from freshly secreted milk (26.0 muM). To determine changes in quantities of adenosine triphosphate after milking, milks were divided into two parts, one containing only milk and the other milk plus 2,4-dinitrophenol and sodium arsenate, inhibitors of oxidative and substrate level phosphorylation. Adenosine triphosphate in milk decreased during 4-h in vitro incubations, and the rate of decline was markedly greater in the presence of the inhibitors. Thus, freshly secreted goat's milk contains significant amounts of adenosine triphosphate, and more can be synthesized therein after removal from the udder. In limited samples human and bovine milks contained much lower concentrations of the compound than those in goat's milk.

Adenosine Diphosphate↗