Electrophysiologic studies have demonstrated that adrenal medulla chromaffin cells express voltage-dependent P/Q-, N-, L-, and R-type Ca²⁺ channels and that these channels regulate release of norepinephrine and epinephrine. However, N-type Ca²⁺ channel α_1B-deficient mice with a CBA/JN background show normal plasma norepinephrine and epinephrine levels, presumably owing to compensation by other gene(s). To examine the expression patterns of the P/Q-type α_1A, L-type α_1C/α_1D, and R-type α_1E, β₁, β₂, β₃, and β₄ subunits, as well as of tyrosine hydroxylase (Th), dopamine β hydroxylase (Dbh), and phenylethanolamine-N-methyltransferase (Pnmt) in the adrenal gland of α_1B-deficient mice, we used real-time quantitative reverse transcription–polymerase chain reaction and Western blot analyses. The expression levels of α_1A, β₄, Th, and Th phosphorylated at serine 40 were higher in homozygous mice than in wild-type and heterozygous mice, but the expression levels of α_1C, α_1D, α_1E, β₁, β₂, β₃, Dbh, and Pnmt did not differ among wild-type, heterozygous, and homozygous mice. These results suggest that the compensatory mechanisms to maintain normal levels of epinephrine and norepinephrine in the adrenal gland of N-type Ca²⁺ channel α_1B-deficient mice include increased expression of α_1A and β₄ subunits and increased catecholamine biosynthetic activity.

We have established an inbred line of mice deficient in insulin receptor substrate 2 (IRS2) that have a C57BL/6J Jcl genetic background (B6J-IRS2^–/– mice) as an animal model for typical type 2 diabetes mellitus (DM). We investigated the effect of age and sex on glucose tolerance and insulin resistance and on the activities of enzymes related to lipid metabolism in the liver and skeletal muscle of B6J-IRS2^–/– mice. Glucose tolerance tests (GTT), insulin tolerance tests (ITT), and sampling for chemical analysis were performed at ages of 6, 14, and 24 wk. GTT showed that both genders of B6J-IRS2^–/– mice had impaired glucose tolerance at the ages of 6 and 14 wk, whereas 24-wk-old female B6J-IRS2^–/– mice showed almost glucose tolerance comparable to that of wild-type mice, although 24-wk-old male B6J-IRS2^–/– mice still showed impaired glucose tolerance. ITT revealed that both male and female B6J-IRS2^–/– mice remained insulin-resistant at all time points. Hepatic lipogenetic enzyme activities were higher in B6J-IRS2^–/– mice than in wild-type mice at 6, 14 and 24 wk of age. In addition, plasma glucose, triglyceride, free fatty acid, total cholesterol, and insulin concentrations in B6J-IRS2^−/− mice were significantly higher than those in wild-type mice at most time points; plasma triglycerides in 14-wk-old B6J-IRS2^–/– mice were lower than those of wild-type mice. These findings suggest that young B6J-IRS2^–/– mice are useful as type 2 DM models.

The extent to which mitogenic growth factors influence embryo development is not well characterized. We sought to determine the effect of epidermal growth factor (EGF) and transforming growth factor α (TGFα) on naturally fertilized (in vivo-derived) and in vitro-fertilized mouse embryos, compared with that on cloned (intracytoplasmic nuclear injection-derived) mouse embryos, in which EGF and TGFα expression is markedly reduced. Immunoneutralization of EGF, TGFα, and EGF receptor by using specific antibodies significantly reduced the blastocyst development rate (in vivo-derived: 66%, 63%, and 63%, respectively; in vitro-fertilized: 57%, 55%, and 56%, respectively), increased the number of apoptotic nuclei (in vivo-derived: 9%, 10%, and 9%, respectively; in vitro-fertilized: 13%, 13%, and 13%, respectively), decreased the total number of cells (in vivo-derived: 87%, 85%, and 86%, respectively; in vitro-fertilized: 86%, 85%, and 86%, respectively), and increased the inner cell mass:trophectoderm ratios (in vivo-derived: 1:2.70 ± 0.05, 1:2.73 ± 0.04, 1:2.71 ± 0.06, respectively; in vitro-fertilized: 1:2.94 ± 0.02, 1:2.96 ± 0.02, 1:2.95 ± 0.02, respectively). In most cases, combined treatment with neutralizing antibodies to both EGF and TGF accentuated changes in these parameters. Further, the effect of combined immunoneutralization on these parameters in fertilized embryos was no different from those in cloned embryos. Therefore, normal expression of mitogenic growth factors is crucial for successful development of mouse embryos before implantation. Inhibiting the action of mitogenic growth factors causes fertilized embryos to exhibit developmental characteristics similar to those of cloned embryos, which may partially explain the poor developmental potential of cloned mammalian embryos.

Recent studies have shown that 'return to home cage' can serve as a reward for maze learning in adult male mice. The present study examined whether the same reward is an effective motivator of learning in young and old mice and included females in the study design. We tested 25- and 65-d-old HS mice and 85- and 800-d-old B6D2F₂ mice in a Lashley III maze. Return to home cage motivated maze acquisition in all groups. Compared with 65-d-old HS mice, 25-d-olds acquired the maze more slowly, took longer to achieve the test criterion, and showed increased latency to reach the goal box. There was no difference between 85- and 800-d-old B6D2F₂ mice in rate of acquisition. This reward procedure may reduce the potentially confounding effects of deprivation or aversive stimuli on maze performance and may be suitable as a motivational procedure for a wide range of subject groups.

Outbred NIH/S male mice were housed from weaning in groups of 4 without enrichment (control) or with nesting material (nest), nesting material and a box (nest-and-box), or nesting material and a tube (nest-and-tube) as environmental modification. The aim of the study was to investigate effects of widely recommended nesting material and additional shelters on male mice. The aggressiveness of the mice in their home cages clearly increased in the nest group, as assessed by the number of wounds. In the nest group, fighting was a stressful situation for the mice, leading to changes in weight gain and in the weights of the thymus, adrenals, spleen, and epididymal adipose tissue. Moreover, the agonistic behavior of these mice toward an intruder was increased both in individual tests (an intruder with the individual mouse) and group tests (an intruder with a group of mice). The provision of a box or tube as a shelter, in addition to nesting material, prevented intracage fighting and did not lead to alterations in the weight gain or organ weights of the mice. However, the agonistic behavior of mice with shelters was slightly increased in behavioral tests. Anxiety in the elevated plus-maze was not affected by any of the housing systems. In conclusion, the agonistic behavior of NIH/S mice, an aggressive strain, seemed to be easily enhanced by these environmental modifications. The suitability of any enrichment should be carefully evaluated, especially when highly aggressive mice are used.

Immunocompromised murine xenotransplantation models have become an important tool to study stem cell biology. One of the most common recipient strains used is the NOD/SCID mouse, which offers sufficient longevity to quantify moderate levels of engraftment. During pilot experiments, we noted incisor abnormalities 5 to 6 wk after nonmyeloablative doses of irradiation. Here we report a detailed examination of this phenomenon and propose possible explanations and management strategies. A total of 15 NOD/SCID mice received 3 Gy total body irradiation (TBI) and were monitored over 9 wk. A control group of 15 mice were treated in exactly the same way as the study mice except that they did not receive irradiation. A total of 9 TBI mice developed incisor abnormalities between days 40 and 50 after irradiation, resulting in rapid weight loss. No mice in the control group developed incisor abnormalities, however 3 were euthanized prematurely due to the development of thymic lymphoma. Upon development of incisor abnormalities and weight loss, 2 mice in the TBI group had their teeth trimmed and received soft food. Both mice made a rapid recovery and survived for the remainder of the study. The development of incisor abnormalities occurred in 2 substrains, and alterations in antibiotic use and supplementation of the vitamin content of feeds did not prevent the abnormalities. Investigators working with this model should be aware of this complication and modify protocols appropriately.

We sought to use ultrasonography to quantify renal size and echogenicity in a mouse model of polycystic kidney disease. We imaged 36 wild-type (WT) and juvenile cystic kidney (jck) mice by using a standard ultrasound unit and 10–5 MHz linear transducer. Mice were imaged at 3 (6 WT, 7 jck), 6 (7 WT, 5 jck), and 9 (6 WT, 5 jck) wk of age. Kidney length, width, and height were recorded for volume calculation. Sagittal images of both kidneys were recorded for assessment of intensity. Quantitative values were obtained from areas of similar depth and gain settings. Kidney and liver intensities were determined for calculation of their ratio. Representative histologic kidney sections were stained with hematoxylin and eosin and digitized for calculation of cyst number, mean cyst area, and percentage cystic area. We found that renal volume was greater in jck than WT mice at 3 (P < 0.0001), 6 (P < 0.0001), and 9 (P < 0.0001) wk of age. In addition, kidney intensity and kidney:liver ratio were higher in jck than WT mice at 3 (P < 0.002 for both parameters), 6 (P < 0.04), and 9 wk (P < 0.008). Kidneys with smaller mean cyst size and less percentage cystic space had higher intensity values. We therefore conclude that ultrasound measures of renal volume and intensity can noninvasively identify jck-affected mice as early as 3 wk of age. Cortical intensity is greater in jck versus WT mice and appears affected by percentage cyst area and mean cyst size.