Attenuated defense response and low basal blood pressure in orexin knockout mice

The perifornical area of the hypothalamus has been known as the center for the defense response, or "fight or flight" response, which is characterized by a concomitant rise in arterial blood pressure (AP), heart rate (HR), and respiratory frequency (Rf). We examined whether orexin, a recently identified hypothalamic neuropeptide, contributes to the defense response and basal cardiovascular regulation using orexin knockout mice. Microinjection of a GABA-A receptor antagonist, bicuculline methiodide (0.1-1 mM in 20 nl), to the perifornical area in urethane-anesthetized wild-type mice elicited dose-dependent increases in AP, HR, and Rf. Although similar changes were observed in orexin knockout mice, intensities were smaller and duration was shorter than those in wild-type mice. Moreover, in an awake and freely moving condition, telemeter-indwelling orexin knockout mice showed diminished cardiovascular and behavioral responses to emotional stress in the resident-intruder test. We also found that basal AP in orexin knockout mice was significantly lower in both anesthetized (117 +/- 8 mmHg in wild type and 92 +/- 3 in knockout) and conscious (125 +/- 6 mmHg in wild type and 109 +/- 2 in knockout) conditions. alpha-Adrenergic blockade with prazosin or ganglion blockade with hexamethonium canceled the difference in basal AP. HR and cardiac contractile parameters by echocardiography did not differ between the two strains of mice. These results indicate lower sympathetic vasoconstrictor tone in knockout mice. The present study suggests that orexin-containing neurons in the perifornical area play a role as one of the efferent pathways of defense response and also operate as a regulator of AP at basal condition by activating sympathetic outflow.     

Syntheses and biological evaluation of novel quinuclidine derivatives as squalene synthase inhibitors

Squalene synthase (E.C. 2.5.1.21) catalyses the reductive dimerization of two molecules of farnesyl diphosphate to form squalene and is involved in the first committed step in cholesterol biosynthesis. Inhibition of this enzyme is therefore an attractive target for hypocholesterolemic strategies. A series of quinuclidine derivatives incorporating a tricyclic system was synthesized and evaluated for their ability to inhibit squalene synthase in vitro. A 9H-fluorene moiety was found to be optimal as the tricyclic system for potent inhibitory activity. Improved activity can be achieved with a conformationally constrained three-atom linkage connecting the tricyclic system with the quinuclidine nucleus. Among these compounds, (Z)-3-[2-(9H-fluoren-2-yloxy)ethylidene]-quinuclidine hydrochloride 31 was found to be a potent inhibitor of squalene synthase derived from hamster liver and human hepatoma cells with IC(50) values of 76 and 48 nM, respectively. Oral dosing of compound 31 demonstrated effective reduction of plasma non-HDL cholesterol levels in hamsters.     

Genetic ablation of orexin neurons in mice results in narcolepsy, hypophagia, and obesity

Orexins (hypocretins) are a pair of neuropeptides implicated in energy homeostasis and arousal. Recent reports suggest that loss of orexin-containing neurons occurs in human patients with narcolepsy. We generated transgenic mice in which orexin-containing neurons are ablated by orexinergic-specific expression of a truncated Machado-Joseph disease gene product (ataxin-3) with an expanded polyglutamine stretch. These mice showed a phenotype strikingly similar to human narcolepsy, including behavioral arrests, premature entry into rapid eye movement (REM) sleep, poorly consolidated sleep patterns, and a late-onset obesity, despite eating less than nontransgenic littermates. These results provide evidence that orexin-containing neurons play important roles in regulating vigilance states and energy homeostasis. Orexin/ataxin-3 mice provide a valuable model for studying the pathophysiology and treatment of narcolepsy.     

Impaired proliferative response of V alpha 24 NKT cells from cancer patients against alpha-galactosylceramide

Human invariant V alpha 24(+) NKT cells are a relatively new subpopulation of lymphocytes. It has been reported that V alpha 24 NKT cells are significantly involved in some human diseases. We have evaluated the number and function of V alpha 24 NKT cells in both healthy volunteers and cancer patients. In this study we found that V alpha 24 NKT cells in unfractionated PBMCs obtained from cancer patients did not respond efficiently to alpha-galactosylceramide (alpha-GalCer) in vitro. Thus, their proportion after stimulation with alpha-GalCer was smaller than that found in healthy volunteers. However, the cancer patients' V alpha 24 NKT cells retained cytotoxic activity against malignant target cells, and they could efficiently proliferate to alpha-GalCer when fractionated by sorting. Furthermore, we found that addition of G-CSF to the culture could restore the low proliferative response of V alpha 24 NKT cells from cancer patients. These results suggest that some functions of NKT cells in cancer patients are impaired, and this observation carries significant implications for immunotherapy-based cancer treatments.     

Importance of permafrost as a source of water for plants in east Siberian taiga

Stable oxygen isotope ratios of plant water (sap water) were observed at Spasskaya Pad experimental forest near Yakutsk, Russia in 1997–1999. The ¹⁸O of sap water in larch trees (Larix gmelinii) decreased soon after leaf unfolding every year, indicating that snowmelt water was used in the beginning of summer. During mid to late summer, a clear difference in the water source used by plants was observed between wet summers and severe drought summers. The ¹⁸O values of water in larch trees were high (–17.8 to –16.1) in August 1999 (wet summer), but low (–20.4 to –19.7) in August 1998 (drought summer). These results indicated that plants used rainwater during a wet summer, but meltwater from permafrost was used by plants during a drought summer. One important role of permafrost is to provide a direct source of water for plants in a severe drought summer; another role is to keep surplus water in the soil until the next summer. If this permafrost system is disturbed by future global warming, unique monotypic stands of deciduous larch trees in east Siberia might be seriously damaged in a severe drought summer.     

Single nucleotide polymorphisms of thrifty genes for energy metabolism: evolutionary origins and prospects for intervention to prevent obesity-related diseases

The "thrifty" genotype and phenotype that save energy are detrimental to the health of people living in affluent societies. Individual differences in energy metabolism are caused primarily by single nucleotide polymorphisms (SNPs), some of which promote the development of obesity/type 2 diabetes mellitus. In this review, four major questions are addressed: (1) Why did regional differences in energy metabolism develop during evolution? (2) How do genes respond to starvation and affluence? (3) Which SNPs correspond to the hypothetical "thrifty genes"? (4) How can we cope with disease susceptibility caused by the "thrifty" SNPs? We examined mtDNA and genes for energy metabolism in people who live in several parts of Asia and the Pacific islands. We included 14 genes, and the SNP frequencies of PPAR gamma 2, LEPR, and UCP3-p and some other genes differ significantly between Mongoloids and Caucasoids. These differences in SNPs may have been caused by natural selection depending on the types of agriculture practiced in different regions. Interventions to counteract the adverse effects of "thrifty" SNPs have been partially effective.