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At least 1,603 records · Page 89Linked to original sources
PubMed1987

Steric course of the rhodium-catalyzed decarbonylation of chiral 4-methyl-[1-3H,2-2H1]pentanal.

(R)- and (S)-4-methyl-[1-3H,2-2H1]pentanal were prepared from L- and D-leucine via leucic acid and (S)- and (R)-4-methyl-[2-2H1]pentanoic acid. Decarbonylation of these samples with tris-(triphenylphosphine)rhodium chloride followed by Kuhn-Roth oxidation of the resulting 2-methylbutane gave chiral acetic acid of 35% e.e. S and 31% e.e. R configuration, respectively. The decarbonylation reaction thus proceeds with net retention of configuration, possibly accompanied by some racemization.

Caproates↗
PubMed2006

Glial cells dilate and constrict blood vessels: a mechanism of neurovascular coupling.

Neuronal activity evokes localized changes in blood flow. Although this response, termed neurovascular coupling, is widely used to monitor human brain function and diagnose pathology, the cellular mechanisms that mediate the response remain unclear. We investigated the contribution of glial cells to neurovascular coupling in the acutely isolated mammalian retina. We found that light stimulation and glial cell stimulation can both evoke dilation or constriction of arterioles. Light-evoked and glial-evoked vasodilations were blocked by inhibitors of cytochrome P450 epoxygenase, the synthetic enzyme for epoxyeicosatrienoic acids. Vasoconstrictions, in contrast, were blocked by an inhibitor of omega-hydroxylase, which synthesizes 20-hydroxyeicosatetraenoic acid. Nitric oxide influenced whether vasodilations or vasoconstrictions were produced in response to light and glial stimulation. Light-evoked vasoactivity was blocked when neuron-to-glia signaling was interrupted by a purinergic antagonist. These results indicate that glial cells contribute to neurovascular coupling and suggest that regulation of blood flow may involve both vasodilating and vasoconstricting components.

8,11,14-Eicosatrienoic Acid↗
PubMed1979

In vitro C-20, 22 desmolase regulation of pregnenolone supply in first trimester human placenta.

Homogenates of first trimester human placentae were incubated with [26-14C]chloresterol. Using reverse-isotope dilution analysis [14C]isocaproic acid was isolated and characterized. A progressive increase in [14C]isocaproic acid formation with increasing gestation suggestive of a regulatory mechanism at the C-20, 22 desmolase site in the supply of placental pregnenolone was noted.

Caproates↗
PubMed1983

Evidence for cleavage of [26-14C]cholesterol side-chain by human foetal membranes in vitro.

With a view to establish the hitherto undescribed role of cholesterol in foetal-membranous steroidogenesis, homogenates of term chorion pars reflexa and amnion pars reflexa and pars placentaris collected from 6 women after spontaneous labour at term (38 to 41 weeks gestation) were incubated with [26-14C]cholesterol. Using reverse-isotope dilution analysis, [14C]isocaproic acid was isolated and characterized. This conversion constitutes strong evidence that C-20, 22-desmolase activity, normally present in the adrenal, gonadal and placental tissues, is present in the homogenates of both membranes. The efficiency of the enzymic conversion suggests that the chorion possesses a more active desmolase system compared to that of the amnion.

Adult↗
PubMed1979

Substrate specificity of the lactate dehydrogenase isoenzyme C4 from human spermatozoa and a possible selective assay.

The activity of lactate dehydrogenase (EC 1.1.1.27) in normal human sperm lysates and in human heart and liver homogenates was determined by using a variety of 2-oxoacids as substrates. Sperm preparations were active with pyruvate, 2-oxobutanoate, 2-oxopentanoate and 2-oxohexanoate, while heart and liver extracts utilized only pyruvate and 2-oxobutanoate. Selective staining after gel electrophoresis indicated that the fraction corresponding to lactate dehydrogenase C4, the sperm-specific isoenzyme, was responsible for the utilization of substrates with a linear chain of 3 to 6 carbon atoms. The use of 5 mM 2-oxohexanoate allowed the selective determination of isoenzyme C4 in preparations containing different lactate dehydrogenase molecular forms.

Caproates↗
PubMed2001

Attraction of Anopheles (Diptera: culicidae) to volatile chemicals in Western Kenya.

Anopheles gambiae s.l. and Anopheles funestus Giles are the primary vectors of malaria in East Africa. Identification of host-location olfactory cues may increase trap sensitivity for vector control and surveillance programs. Solid-state army miniature light traps were operated near sleeping humans in huts at night without lights and augmented with the potential attractants: L-lactic acid, Limburger cheese volatiles, hexanoic acid, and carbon dioxide. Mosquito response varied between species and gender. Female An. funestus exhibited a greater response to traps baited with L-lactic acid in combination with carbon dioxide than carbon dioxide alone in two different experiments.

Animals↗
PubMed1985

Calmodulin concentration in the uterus during pregnancy and influence of sex steroids.

Calmodulin concentration in pregnant rat uteri increased gradually and reached a level about three times that in non-pregnant rat at term. In human beings, uterine calmodulin content at term was about three times that in non-pregnant uteri, but there was no significant difference between the levels in uteri at term with and without labor pain. Estrogen increased the rat uterine calmodulin concentration, but progesterone did not change it.

17 alpha-Hydroxyprogesterone Caproate↗
PubMed1987

Maintenance of neonatal rat B cells in glucose-depleted medium: a perifusion study.

Two groups of monolayer cultures of pancreatic cells from the neonatal rat were maintained in glucose-depleted TCM 199 medium, supplemented with 5.5 mmol galactose/l, with or without 0.1 mmol 2-deoxyglucose/l. Another group was kept in medium with 5.5 mmol galactose/l alone, following exposure for 2 days to a medium with 5.5 mmol galactose/l and 10 mumol iodoacetic acid/l to kill fibroblasts selectively. Each of these monolayers was cultured in a perifusion system for a total of 7 days so that phasic insulin secretion could be compared. On day 0, B cells responded in a monophasic fashion to acute challenge with 16.7 mmol glucose/l whereas, in the presence of 10 mumol forskolin/l and 1 mmol 3-isobutyl-1-methyl-xanthine/l, the same dose of glucose stimulated a biphasic response of approximately the same magnitude. At a concentration of 10 mmol/l, leucine and 2-ketoisocaproate both produced only minimal increase in the second phase of secretion above the basal level. No response to secretagogues was seen under culture conditions without 2-deoxyglucose. In contrast, addition of 2-deoxyglucose to the galactose-supplemented medium stimulated B cells to secrete insulin in a biphasic fashion in response to a single dose of glucose, and the stimulatory effects of leucine and 2-ketoisocaproate were also remarkably increased. Moreover, when exposed to a linear concentration gradient of glucose, leucine or 2-ketoisocaproate, these B cells responded to secretagogues in a dose-dependent fashion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Demonstration of in vivo metabolic effects of 3,5-di-iodothyronine.

The objective of the present study was to test in vivo the metabolic effects of 3,5-di-iodothyronine (3,5-T2) in unanesthetized and unrestrained male Sprague-Dawley rats. Amino acid and lipid metabolisms were investigated by breath tests using as tracers the 13C-carboxyl-labeled molecules of leucine, alpha-ketoisocaproic acid (KIC) and octanoic acid, in four different groups of rats: hypothyroid animals (receiving propylthiouracil (PTU) and iopanoic acid), hypothyroid animals treated with either a daily i.p. injection of 3,5-T2 (25 micrograms/100 g body weight), or tri-iodothyronine (T3) (1 microgram/100 g body weight), and control euthyroid animals receiving equivalent volumes of the vehicle solutions. Energy expenditure was measured by continuous monitoring of O2 consumption and CO2 production in these different groups. Daily energy expenditure was decreased by 30% in PTU-treated rats. The chronic treatments with 3,5-T2 and T3 restored daily energy expenditure to the control level. 13CO2 recovered in breath following the i.v. injection of octanoic acid-[1-13C] was decreased in hypothyroid animals compared with control animals (P < 0.05) and restored to control values by T3 and 3,5-T2 treatments. The 13CO2 recovered in breath after i.v. injection of leucine-[1-13C] was increased in PTU-treated compared with control animals (P < 0.05). Chronic treatment with either 3,5-T2 or T3 restored 13CO2 to control values. Excretion of 13CO2 recovered in breath following the i.v. injection of KIC-[1-13C] was increased in PTU-treated compared with control animals. Chronic treatments with either 3,5-T2 or T3 did not restore KIC decarboxylation. These results suggest that 3,5-T2 exerts metabolic effects on energy expenditure, on both lipid beta-oxidation and leucine metabolism in hypothyroid rats. We conclude that 3,5-T2 is a metabolically active iodothyronine.

Amino Acids↗
PubMed2006

Prostaglandin facilitates afferent nerve activity via EP1 receptors during urinary bladder inflammation in rats.

We examined the effects of loxoprofen, a cyclooxygenase inhibitor, and ONO-8711, an EP1-receptor antagonist, on afferent nerve activity during acetic acid (AA, 0.1% v/v)-induced inflammation of the rat urinary bladder. Distension stimulation was performed (vesical pressure of 30 cm H2O) for 2 min. The neuronal discharge was recorded from L6 dorsal root filaments. The discharge was observed just after the beginning of distension and increased gradually thereafter. When the vesical pressure returned to control value, the discharge diminished abruptly. AA infusion increased the total number of spikes to 198 +/- 38.8% of control values. AA infusion also produced asynchronous discharge in 39% of the animals. Loxoprofen administration (1 mg/kg, i.v.) reduced the number of spikes to 40.3 +/- 14.8% of control values. ONO-8711 administration (1 and 3 mg/kg, i.v.) reduced the number of spikes to 81.6 +/- 1.6% and 32.2 +/- 7.4% of control values, respectively. These data indicate that loxoprofen or EP1-receptor antagonist inhibit the inflammation-related neuronal activity. EP1 receptors in the peripheral afferent nerve terminal and/or urothelium may facilitate the primary afferent nerve activity, which elicits the inflammation-induced micturition reflex.

Acetic Acid↗