Diet‐Induced Changes in Stearoyl‐CoA Desaturase 1 Expression in Obesity‐Prone and ‐Resistant Mice

Objective: To investigate stearoyl‐coenzyme A desaturase (SCD) 1 expression in obesity‐prone C57BL/6 mice and in obesity‐resistant FVB mice to explore the relationship of SCD1 expression and susceptibility to diet‐induced obesity. Research Methods and Procedures: Nine‐week‐old C57BL/6 and FVB mice were fed either a high‐ or low‐fat diet for 8 weeks. Body weight and body composition were measured before and at weeks 4 and 8 of the study. Energy expenditure was measured at weeks 1 and 5 of the study. Hepatic SCD1 mRNA was measured at 72 hours and at the end of study. Plasma leptin and insulin concentrations were measured at the end of study. Results: When C57BL/6 mice were switched to a calorie‐dense high‐fat diet, animals gained significantly more body weight than those maintained on a low‐calorie density diet primarily due to increased fat mass accretion. Fat mass continued to accrue throughout 8 weeks of study. Increased calorie intake did not account for all weight gain. On the high‐fat diet, C57BL/6 mice decreased their energy expenditure when compared with mice fed a low‐fat diet. In response to 8 weeks of a high‐fat diet, SCD1 gene expression in liver increased >2‐fold. In contrast, feeding a high‐fat diet did not change body weight, energy expenditure, or SCD1 expression in FVB mice. Discussion: Our study showed that a high‐fat hypercaloric diet increased body adiposity first by producing hyperphagia and then by decreasing energy expenditure of mice susceptible to diet‐induced obesity. Consumption of a high‐fat diet in species predisposed to obesity selectively increased SCD1 gene expression in liver.     

Ectopic localization of putative AII amacrine cells in the outer plexiform layer of the developing FVB/N mouse retina

The FVB/N mouse is a model of retinitis pigmentosa which shows a rapid loss of photoreceptors during early postnatal (P) life. We investigated the cellular localization of glycine transporter 1 (GlyT-1) in the developing FVB/N mouse retina. In control retinas, the developmental pattern of GlyT-1-immunoreactive amacrine cells was well in accordance with a previous report. However, in the FVB/N mouse retina, some GlyT-1-labeled amacrine cells sent their processes into the outer plexiform layer (OPL) from P14 onward. From P21 onward, GlyT-1-labeled cells were visible in the OPL. These cells were further characterized by double-label immunofluorescence experiments with an antiserum against disabled 1 (Dab-1), and showed Dab-1 immunoreactivity, indicating that these cells are putative AII amacrine cells. These results clearly demonstrate that AII amacrine cells have the potential capacity to respond to photoreceptor degeneration by migrating or sprouting their processes into the OPL in the developing FVB/N mouse retina.This study was supported by a Korea Research Foundation Grant (2001, PF0005) from the Ministry of Education     

Acute locomotor responses to cocaine in adolescents vs. adults from four divergent inbred mouse strains

Growing evidence suggests that adolescent mice display differential sensitivity to the acute locomotor activating effects of cocaine as compared to adults, but the direction of the difference varies across studies and the reasons are not clear. Few studies have directly examined genetic contributions to age differences in locomotor stimulation from cocaine. The goal of this study was to determine the extent to which reduced stimulation in C57BL/6J adolescents as compared to adults generalizes to other strains. Therefore, we examined male and female mice from four genetically divergent inbred stains (BALB/cByJ, C57BL/6J, DBA/2J and FVB/NJ) at two ages, postnatal day 30 and postnatal day 65. Mice received either saline or cocaine (15 or 30 mg/kg), and then immediately were placed back into their home cages. Locomotor activity was recorded continuously in the home cage by video tracking. Adolescents displayed reduced stimulation as compared to adults for C57BL/6J, BALB/cByJ and female FVB/NJ mice. No age differences were observed for DBA/2J or male FVB/NJ. No main effects of sex were observed. Strain differences in pharmacokinetics, neural development or physiology could contribute to the observed differences between ages across strains. Future comparative studies could discover biological differences between strains that explain age differences in cocaine sensitivity.     

Delayed Sry and Sox9 expression in developing mouse gonads underlies B6-Y(DOM) sex reversal

The phenomenon of B6-Y(DOM) sex reversal arises when certain variants of the Mus domesticus Y chromosome are crossed onto the genetic background of the C57BL/6J (B6) inbred mouse strain, which normally carries a Mus musculus-derived Y chromosome. While the sex reversal has been assumed to involve strain-specific variations in structure or expression of Sry, the actual cause has not been identified. Here we used in situ hybridization to study expression of Sry, and the critical downstream gene Sox9, in strains containing different chromosome combinations to investigate the cause of B6-Y(DOM) sex reversal. Our findings establish that a delay of expression of Sry(DOM) relative to Sry(B6) underlies B6-Y(DOM) sex reversal and provide the first molecular confirmation that Sry must act during a critical time window to appropriately activate Sox9 and effect male testis determination before the onset of the ovarian-determining pathway.     

Fmr1基因敲除对小鼠生理发育和繁殖性能的影响

目的对清洁级FVB.KO和FVB的生理发育指标和繁殖性能进行分析比较,探讨Fmr1基因敲除对小鼠生理发育和繁殖性能的影响。方法挑选10周龄清洁级FVB.KO和FVB各20只（雌雄各半）,采取1∶1同居,全部同胞兄妹近交繁殖,测定新生仔鼠生理发育指标和品系繁殖性能。结果 FVB.KO在耳廓分离、体毛长出、门齿萌发、眼睑开裂等生理发育指标上和FVB比较接近,在平均每窝产仔数和离乳率等方面偏低,在雌雄比例上有显著差异。结论 Fmr1基因敲除对小鼠生理发育和繁殖性能影响较小,对后代雌雄比例可能有一定的影响。     

Heligmosomoides polygyrus: decreased apoptosis in fast responder FVB mice during infection

Primary infection with Heligmosomoides polygyrus in some strains of mice is chronic although fast responder mouse strains eliminate the parasite in a short period of time. The reason for the differences is unknown. In this study apoptosis, proliferation, IL-2 and IL-6 production of mesenteric lymph node (MLN) and spleen cells in vitro from fast (FVB) and slow (C57Bl/6) responder mice were compared during H. polygyrus infection. FVB cells showed decreased apoptosis, more proliferation and more cytokine production than cells from C57Bl/6 mice during infection. At the beginning of infection in C57Bl/6 mice the apoptosis of CD4(+) but not CD8(+) cells significantly increased in MLN and spleen cell cultures. Apoptosis, when the first immune signal is given by infective larvae, might play an important role in the modulation of the response in slow responder mice.