Diurnal changes in blood metabolites and their relation to plasma growth hormone and time of feeding in mithun heifers (Bos frontalis)

The aim of the present study was to investigate what, if any, diurnal changes occur in blood metabolites in relation to plasma growth hormone (GH) and feeding time among mithun (Bos frontalis), a semi-wild ruminant. Blood samples were collected at hourly intervals during a 24 h span from 6 mithun heifers (averaging 2.5 yr of age and averaging 230 kg in weight) that were fed twice a day at 11:00 and 16:00 h. Samples were assayed for plasma GH and blood metabolites, non-esterified fatty acids (NEFA), glucose, and alpha-amino nitrogen. The total sampling period was divided into a 1) postprandial (after meal) period (period I: 11:00 to 21:00 h) and 2) interprandial period (period II: 22:00 to 10:00 h) and also into night (20:00 to 05:00 h) and day (06:00 to 10:00 h) periods for statistical analysis. Plasma glucose and alpha-amino nitrogen levels increased (p<0.01), and plasma NEFA and GH decreased (p<0.01) after each meal. No diurnal rhythmicity was detected in plasma glucose or alpha-amino nitrogen levels. Interestingly, plasma NEFA and GH levels were higher (p<0.01) during the interprandial (period II) and night periods, indicating an energy deficit that occurred progressively during the interprandial period of nocturnal feed deprivation. In twice-daily-fed mithuns we conclude that: 1) plasma metabolites and GH exhibited a definite pattern of change with time of feeding; 2) concentrations of plasma NEFA were higher nocturnally due to an energy deficit and that GH levels were higher during the interprandial period after the second meal; 3) the interprandial period after the second feeding may be considered to constitute a short-term food deprivation; 4) the longer interprandial period of 19 h in this study between the second and subsequent morning meal may be changed into equally divided feedings to minimize the short-term energy deficit; and 5) blood sampling for blood metabolites in mithuns should be conducted at a fixed time of day with special emphasis on time of feeding.     

Medullary lateral tegmental field: control of respiratory rate and vagal lung inflation afferent influences on sympathetic nerve discharge

We used spectral analysis and event-triggered averaging to determine the effects of chemical inactivation of the medullary lateral tegmental field (LTF) on 1) the relationship of intratracheal pressure (ITP, an index of vagal lung inflation afferent activity) to sympathetic nerve discharge (SND) and phrenic nerve activity (PNA) and 2) central respiratory rate in paralyzed, artificially ventilated dial-urethane-anesthetized cats. ITP-SND coherence value at the frequency of artificial ventilation was significantly (P<0.05; n=18) reduced from 0.73+/-0.04 (mean+/-SE) to 0.24+/-0.04 after bilateral microinjection of muscimol into the LTF. Central respiratory rate was unexpectedly increased in 12 of these experiments (0.28+/-0.03 vs. 0.95+/-0.25 Hz). The ITP-PNA coherence value was variably affected by chemical inactivation of the LTF. It was unchanged when central respiratory rate was also not altered, decreased when respiratory rate was increased above the rate of artificial ventilation, and increased when respiratory rate was raised from a value below the rate of artificial ventilation to the same frequency as the ventilator. Chemical inactivation of the LTF increased central respiratory rate in four of six vagotomized cats but did not significantly affect the PNA-SND coherence value. These data demonstrate that the LTF 1) plays a critical role in mediating the effects of vagal lung inflation afferents on SND but not PNA, 2) helps maintain central respiratory rate in the physiological range, but 3) is not involved in the coupling of central respiratory and sympathetic circuits.     

Effects of coenzyme Q(10) administration on its tissue concentrations,mitochondrial oxidant generation,and oxidative stress in the rat

Coenzyme Q (CoQ(10)) is a component of the mitochondrial electron transport chain and also a constituent of various cellular membranes. It acts as an important in vivo antioxidant, but is also a primary source of O(2)(-*)/H(2)O(2) generation in cells. CoQ has been widely advocated to be a beneficial dietary adjuvant. However, it remains controversial whether oral administration of CoQ can significantly enhance its tissue levels and/or can modulate the level of oxidative stress in vivo. The objective of this study was to determine the effect of dietary CoQ supplementation on its content in various tissues and their mitochondria, and the resultant effect on the in vivo level of oxidative stress. Rats were administered CoQ(10) (150 mg/kg/d) in their diets for 4 and 13 weeks; thereafter, the amounts of CoQ(10) and CoQ(9) were determined by HPLC in the plasma, homogenates of the liver, kidney, heart, skeletal muscle, brain, and mitochondria of these tissues. Administration of CoQ(10) increased plasma and mitochondria levels of CoQ(10) as well as its predominant homologue CoQ(9). Generally, the magnitude of the increases was greater after 13 weeks than 4 weeks. The level of antioxidative defense enzymes in liver and skeletal muscle homogenates and the rate of hydrogen peroxide generation in heart, brain, and skeletal muscle mitochondria were not affected by CoQ supplementation. However, a reductive shift in plasma aminothiol status and a decrease in skeletal muscle mitochondrial protein carbonyls were apparent after 13 weeks of supplementation. Thus, CoQ supplementation resulted in an elevation of CoQ homologues in tissues and their mitochondria, a selective decrease in protein oxidative damage, and an increase in antioxidative potential in the rat.     

cAMP activates BKCa channels in pulmonary arterial smooth muscle via cGMP-dependent protein kinase

The signal transduction mechanisms defining the role of cyclic nucleotides in the regulation of pulmonary vascular tone is currently an area of great interest. Normally, signaling mechanisms that elevate cAMP and guanosine-3',5'-cyclic monophosphate (cGMP) maintain the pulmonary vasculature in a relaxed state. Modulation of the large-conductance, calcium- and voltage-activated potassium (BK(Ca)) channel is important in the regulation of pulmonary arterial pressure, and inhibition (closing) of the BK(Ca) channel has been implicated in the development of pulmonary hypertension. Accordingly, studies were done to determine the effect of cAMP-elevating agents on BK(Ca) channel activity using patch-clamp studies in pulmonary arterial smooth muscle cells (PASMC) of the fawn-hooded rat (FHR), a recognized animal model of pulmonary hypertension. Forskolin (10 micro M), a stimulator of adenylate cyclase and an activator of cAMP-dependent protein kinase (PKA), and 8-4-chlorophenylthio (CPT)-cAMP (100 micro M), a membrane-permeable derivative of cAMP, opened BK(Ca) channels in single FHR PASMC. Treatment of FHR PASMC with 300 nM KT5823, a selective inhibitor of cGMP-dependent protein kinase (PKG) activity inhibited the effect of both forskolin and CPT-cAMP. In contrast, blocking PKA activation with 300 nM KT5720 had no effect on forskolin or CPT-cAMP-stimulated BK(Ca) channel activity. These results indicate that cAMP-dependent vasodilators activate BK(Ca) channels in PASMC of FHR via PKG-dependent and PKA-independent signaling pathways, which suggests cross-activation between cyclic nucleotide-dependent protein kinases in pulmonary arterial smooth muscle and therefore, a unique signaling pathway for cAMP-induced pulmonary vasodilation.     

Molecular basis of vitamin E action: tocotrienol modulates 12-lipoxygenase,a key mediator of glutamate-induced neurodegeneration

Vitamin E is a generic term for tocopherols and tocotrienols. This work is based on our striking evidence that, in neuronal cells, nanomolar concentrations of alpha-tocotrienol, but not alpha-tocopherol, block glutamate-induced death by suppressing early activation of c-Src kinase (Sen, C. K., Khanna, S., Roy, S., and Packer, L. (2000) J. Biol. Chem. 275, 13049-13055). This study on HT4 and immature primary cortical neurons suggests a central role of 12-lipoxygenase (12-LOX) in executing glutamate-induced neurodegeneration. BL15, an inhibitor of 12-LOX, prevented glutamate-induced neurotoxicity. Moreover, neurons isolated from 12-LOX-deficient mice were observed to be resistant to glutamate-induced death. In the presence of nanomolar alpha-tocotrienol, neurons were resistant to glutamate-, homocysteine-, and l-buthionine sulfoximine-induced toxicity. Long-term time-lapse imaging studies revealed that neurons and their axo-dendritic network are fairly motile under standard culture conditions. Such motility was arrested in response to glutamate challenge. Tocotrienol-treated primary neurons maintained healthy growth and motility even in the presence of excess glutamate. The study of 12-LOX activity and metabolism revealed that this key mediator of glutamate-induced neurodegeneration is subject to control by the nutrient alpha-tocotrienol. In silico docking studies indicated that alpha-tocotrienol may hinder the access of arachidonic acid to the catalytic site of 12-LOX by binding to the opening of a solvent cavity close to the active site. These findings lend further support to alpha-tocotrienol as a potent neuroprotective form of vitamin E.     

Geraniol-derived 1,2,4-trioxanes with potent in-vivo antimalarial activity

Geraniol, an abundantly available naturally occurring allylic alcohol, has been used as a starting material to prepare a series of 6-[alpha-(3'-aryl-3'-hydroxypropyl)vinyl]-1,2,4-trioxanes. Some of these novel trioxanes have shown very promising antimalarial activity against multi-drug resistant Plasmodium yoelii in mice by both intramuscular (im) and oral routes.     

Single-stranded adenine-rich DNA and RNA retain structural characteristics of their respective double-stranded conformations and show directional differences in stacking pattern

The structural preorganization of isosequential ssDNA and ssRNA hexamers d/r(GAAAAC)(1) [J. Am. Chem. Soc. 2003, 125, 9948] have been investigated by NMR and molecular dynamics simulations. Analysis of the nuclear Overhauser effect spectrometry (NOESY) footprints in the aqueous solution has shown that there is a substantial population of ordered right-handed helical structure in both hexameric single-stranded DNA and RNA, which are reminiscent of their respective right-handed helical duplex form, despite the fact these single-stranded molecules are devoid of any intermolecular hydrogen bonds. The NMR-constrained molecular dynamics (1.5 ns) derived geometries of the adenine-adenine overlaps at each dinucleotide step of the hexameric ssDNA (1a) and ssRNA (1b) show that the relatively electron-rich imidazole stacks above the electron-deficient pyrimidine in 5' to 3' direction in ssDNA (1a) while, in contradistinction, the pyrimidine stacks above the imidazole in the 5' to 3' direction in ssRNA (1b). This also means that the pi-frame of the 5'-pyrimidine can interact with the relatively positively charged imino and amino protons in the 3' direction in ssRNA and in the 5' direction in ssDNA, thereby stabilizing the twist and slide observed in the stacked oligonucleotides. The differently preferred stacking geometries in ssDNA and ssRNA have direct physicochemical implications for self-assembly and pK(a) modulation by the nearest-neighbor interactions, as well as for the dangling-end stabilization effects and imino-proton reactivity.