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At least 757 records · Page 42Linked to original sources
PubMed1982

Synthesis and biological activity of vitamin D2 3 beta-glucosiduronate and vitamin D2 3 beta-sulfate: role of vitamin D2 conjugates in calcium homeostasis.

To ascertain the physiologic function of vitamin D2 conjugates in calcium homeostasis, we synthesized vitamin D2 3 beta-glucosiduronate and vitamin D2 3 beta-sulfate in pure form and tested their biological activity in vitamin D deficient rats fed a low calcium diet. Vitamin D2 3 beta-glucosiduronate was active in promoting calcium transport in the intestine at a dose of 100 pmol per rat. It increased calcium mobilization from bone and soft tissue at a dose of 1000 pmol per rat. This conjugate was less active than equimolar doses of vitamin D2. These results demonstrate that vitamin D2 3 beta-glucosiduronate can be utilized by the rat as a source of vitamin D. In contrast, vitamin D2 3 beta-sulfate was biologically inert. It failed to increase calcium transport in the duodenum of vitamin D deficient rats except at the highest doses tested (greater than 100,000 pmol/rat). It was similarly ineffective in increasing calcium mobilization from bone and soft tissue. Our results lead us to conclude that vitamin D2 3 beta-glucosiduronate is probably utilized by the rat after hydrolysis to the free sterol; on the contrary, the sulfate is not biologically active except at the highest doses tested.

Animals↗
PubMed1989

Long-acting estrogenic responses of estradiol fatty acid esters.

Estradiol esters at C-17 and C-3 with palmitic, stearic and oleic acids were chemically synthesized and then evaluated for their long-acting estrogenic responses in ovariectomized rats. The duration of the biological effects was measured after a single subcutaneous dose of 0.1 mumol of each ester and compared with those observed with 17 beta-estradiol, estradiol 3-benzoate and estradiol 17-enanthate. Vaginal citology, uterophyc action, serum gonadotropins inhibition and 17 beta-estradiol levels were measured 0, 5, 10, 20, 30 and 60 days after injection. The results disclosed that most of the estradiol derivatives evaluated exhibited a long-acting estrogenic action. However, the monoesters at C-17 showed longer effects that monoesters at C-3, while the estradiol diesters exhibited the shortest effects. In addition as shown by its low serum levels, all estradiol esters with unsaturated fatty acids show a decreased E2 absorption. The overall results indicated that esterification of E2 with long chain fatty acids provided long-acting properties to it, being higher with C-17 esters. Whether some of these compounds could be employed in substitutive endocrine therapy remains to be established.

Animals↗
PubMed1983

Effect of hypothermia during hypoxic hypotension on cerebral metabolism.

The beneficial vs deleterious effects of hypothermia superimposed on hypoxia and hypotension have been argued and are clinically important. In this study, cerebral cytochrome a,a3 redox state and the quantity of intracerebral oxygenated hemoglobin (HbO2) were measured continuously and noninvasively in rats subjected to hemorrhagic hypotension (MAP = 30 mm Hg) and hypoxia (F1O2 = 7.5%) utilizing near infrared spectrophotometry. Prior to the experiment the rats were briefly respired on 100% oxygen to establish 100% oxidation of cytochrome a,a3 and hemoglobin, and at the conclusion of the experiment they were respired on 100% nitrogen to establish 100% reduction. Data are reported as percent oxidation within this range at baseline and after 15 and 30 min of hypoxic hypotension. Arterial blood gases were measured. Body temperature as monitored by a rectal probe was altered by placing anesthetized-paralyzed rats inside a circulating water jacket. Three groups of rats were studied: 38, 33, and 22 degrees C. Group III rats had a significantly (P less than 0.01) greater quantity of intracranial HbO2 than group I or II. Since MAP was held constant at 30 mm Hg, we assume this is largely due to the higher (P less than 0.01) arterial PO2 in group III (101.5) compared to group I and II (48.5, 51.3). Both groups II and III had a significantly (P less than 0.01) greater oxidation of cytochrome a,a3 indicating greater oxygen availability for a given metabolic rate. This was associated with improved survival inasmuch as all rats in groups II and III lived, and only one group I rat survived. It can be concluded that, as used in this study, hypothermia is beneficial and deserves further investigation.

Animals↗
PubMed1991

Rapid reduction of intestinal cytochrome a,a3 during lethal endotoxemia.

In vivo near-infrared spectrophotometry was used to determine whether lethal endotoxemia impairs small intestinal oxidative phosphorylation as reflected by the redox state of mitochondrial cytochrome a,a3 (AA3). Adult male Sprague-Dawley rats were anesthetized with 2.1% isoflurane in 30% O2:70% N2O, and the small intestine was partially exteriorized for spectrophotometric monitoring (OMNI-3). By 5 min after an iv bolus of Escherichia coli endotoxin (40 mg/kg, LD90, n = 7) a significant shift toward reduction in intestinal AA3 had occurred in association with hypotension and a marked fall in both superior mesenteric artery blood flow (SMAF) and cardiac output. In a separate group (n = 7) SMAF was kept at the baseline level by periodic infusions of donor rat plasma begun 1 min after endotoxin injection, and the reduction in AA3 was again found despite the fluid loading intervention which successfully maintained not only organ blood flow, but also cardiac output and mean arterial pressure in their normal ranges. Further experiments (n = 34) measuring SM vascular bed oxygen consumption indicated that intestinal VO2 remained unchanged during early endotoxemia. These findings suggest a rapid impairment of oxidative phosphorylation by endotoxin which seems to occur through direct (and/or indirect) toxic cellular effects rather than through impaired tissue perfusion.

Animals↗
PubMed1995

Cytotoxic ent-kaurene diterpenoids from Isodon gesneroides.

From Isodon gesneroides, three new cytotoxic diterpenoids, gesneroidins A, B and C, together with one known diterpenoid, dawoensin A, were isolated, and the structure determination and unambiguous assignment of their stereochemistry and NMR spectral data were made by a combination of one-and two-dimensional NMR techniques, computer modelling calculations and X-ray analysis.

Anti-Infective Agents↗
PubMed1996

Coumarins and antiplatelet aggregation constituents from Formosan Peucedanum japonicum.

Four new khellactone esters, (-)-trans-3'-acetyl-4'-senecioylkhellactone, (+-)-cis-3'-acetyl-4'-tigloylkhellactone, (+-)-cis-4-tigloylkhellactone, (+)-trans-4'-tigloylkhellactone, together with 14 known coumarins, isoimperatorin, psoralen, bergapten, xanthotoxol, cnidilin, (-)-selinidin, (-)-deltoin, (+)-pteryxin, (+)-peucedanocoumarin III, xanthotoxin, imperatorin, (+)-marmesin, (+)-oxypeucedanin hydrate, (+)-peucedanol and three chromones, eugenin, (-)-hamaudol, (+)-visamminol, have been isolated from the root of Formosan Peucedanum japonicum. The structures of the new compounds were elucidated by spectral data. The identities of (+)-trans-3'-tigloyl-4'-acetylkhellactone, formerly reported as a new compound, and (+)-cis-3'-angeloyl-4'-acetyl-khellactone, with the known (+)-peucedanocoumarin III and (+)-pteryxin, respectively, are discussed. Among the isolates, seven compounds, eugenin, (-)-selinidin, (+)-pteryxin, imperatorin, bergapten, cnidilin and (+)-visamminol, show strong antiplatelet aggregation activity in vitro.

Coumarins↗