Genetic basis of murine antibacterial defense to streptococcal lung infection.

To evaluate the effect of genetic background on antibacterial defense to streptococcal infection, eight genetically diverse strains of mice (A/J, DBA/2J, CAST/Ei, FVB/NJ, BALB/cJ, C57BL/6J, 129/SvImJ, and C3H/HeJ) and tlr2-deficient mice (C57BL/6(tlr2-/-)) were infected with three doses of Streptococcus zooepidemicus (500, 5,000, or 50,000 colony-forming units) by alveolar challenge. There was a range of susceptibility between the strains at each dose and time point (6, 24, and 96 h). At the lowest dose, the 129/SvImJ and C3H/HeJ strains had significantly higher bacterial counts at all time points after infection, when compared to A/J, DBA/2J, CAST/Ei, FVB/NJ, which were resistant to infection at the low dose of innoculum.

Independence and reproducibility across microarray platforms.

Microarrays have been widely used for the analysis of gene expression, but the issue of reproducibility across platforms has yet to be fully resolved. To address this apparent problem, we compared gene expression between two microarray platforms: the short oligonucleotide Affymetrix Mouse Genome 430 2.0 GeneChip and a spotted cDNA array using a mouse model of angiotensin II-induced hypertension.

Light pulses do not induce c-fos or per1 in the SCN of hamsters that fail to reentrain to the photocycle.

Circadian activity rhythms of most Siberian hamsters (Phodopus sungorus sungorus) fail to reentrain to a 5-h phase shift of the light-dark (LD) cycle. Instead, their rhythms free-run at periods close to 25 h despite the continued presence of the LD cycle. This lack of behavioral reentrainment necessarily means that molecular oscillators in the master circadian pacemaker, the SCN, were unable to reentrain as well.

Cardiac transcriptional response to acute and chronic angiotensin II treatments.

Exposure of experimental animals to increased angiotensin II (ANG II) induces hypertension associated with cardiac hypertrophy, inflammation, and myocardial necrosis and fibrosis. Some of the most effective antihypertensive treatments are those that antagonize ANG II. We investigated cardiac gene expression in response to acute (24 h) and chronic (14 day) infusion of ANG II in mice; 24-h treatment induces hypertension, and 14-day treatment induces hypertension and extensive cardiac hypertrophy and necrosis.

Juvenile Siberian hamsters display torpor and modified locomotor activity and body temperature rhythms in response to reduced food availability.

Siberian hamsters as young as 16 and 28 d displayed torpor in response to treatment with 2,500 mg/kg 2-deoxy-D-glucose and reduced food availability, respectively. In addition, most food-restricted hamsters displayed increased locomotor activity and elevated body temperatures in the 3 h immediately preceding daily food delivery. This anticipatory activity disappeared within a few days of reimposition of ad lib.

Homeostatic regulation of sleep in arrhythmic Siberian hamsters.

Sleep is regulated by independent yet interacting circadian and homeostatic processes. The present study used a novel approach to study sleep homeostasis in the absence of circadian influences by exposing Siberian hamsters to a simple phase delay of the photocycle to make them arrhythmic. Because these hamsters lacked any circadian organization, their sleep homeostasis could be studied in the absence of circadian interactions.

Melatonin production accompanies arousal from daily torpor in Siberian hamsters.

Arousal from deep hibernation is accompanied by a transient rise of melatonin (Mel) in circulation; there are no comparable analyses of Mel concentrations in species that undergo much shallower, shorter duration episodes of daily torpor. Serum Mel concentrations were determined during arousal from both natural daily torpor and torpor induced by 2-deoxy-D-glucose (2-DG) treatment (2,500 mg/kg, intraperitoneal [IP]); blood samples were drawn from the retro-orbital sinus of anesthetized Siberian hamsters. For animals kept in darkness during torpor, Mel concentrations were highest during early arousal when thermogenesis is maximal, and they decreased as body temperature increased during arousal and returned to baseline once euthermia was reestablished.

Loss of circadian organization of sleep and wakefulness during hibernation.

We investigated circadian and homeostatic regulation of nonrapid eye movement (NREM) sleep in golden-mantled ground squirrels during euthermic intervals between torpor bouts. Slow-wave activity (SWA; 1-4 Hz) and sigma activity (10-15 Hz) represent the two dominant electroencephalographic (EEG) frequency components of NREM sleep. EEG sigma activity has a strong circadian component in addition to a sleep homeostatic component, whereas SWA mainly reflects sleep homeostasis [Dijk DJ and Czeisler CA.

Temperature dependence of gonadal regression in Syrian hamsters exposed to short day lengths.

We sought to determine whether ambient temperature (T(a)) affects gonadal function by altering the rate at which circadian rhythms entrain to short day lengths. Syrian hamsters were housed in cages where they received 14 h of light per day ("long days," 14L) at 22 degrees C. Hamsters were then transferred to cages to receive 10 h of light per day ("short days," 10L) and kept at 5, 22, or 28 degrees C or were maintained in 14L at 22 degrees C.