Application of radiotelemetry to the survey of acorn dispersal byApodemus mice

We examined the applicability of radiotelemetry to studies of acorn dispersal byApodemus mice and compared its efficiency with the of this spool-and-line method. Installation of a transmitter (2.2 g) onto acorns did not interfere with the transporting and feeding behavior of the mice. We were able to detect all transmitter-installed acorns and follow the daily changes in the sites in which they were hoarded, while we missed 59% of the spool-tied acorns due to mice breaking the threads. Mice carried transmitter-installed acorns farther than spool-tied ones. The radiotelemetry method is superior to the spool-and-line method and useful for the study of hoarding behavior in rodents.     

Human HE2 (μB) and μA motifs show the same function as whole IgH intronic enhancer in transgenic mice

In the murine IgH gene intronic enhancer (ENH_iH), two major functional domains were reported. One is the E4/octomer region and another includes the A and B motifs. In the human ENH_iH, it was reported that the HE2, which corresponds to the murine B, and E6 motifs play an important role in an enhancer activity and a tissue-specificity at cellular level. Here we examined thein vivo function of the E6, A and HE2 motifs within the human ENH_iH by using the transgenic mice technique. The A and HE2 motifs together revealed almost the same enhancer function as the whole human ENH_iH, but the E6 motif had lesser enhancer acitivty and tissue-specificity.     

cDNA approaches to isolation of the mouse mutant weaver gene

The mouse autosomal recessive mutant gene weaver (wv) results in abnormalities in cerebellum, substantia nigra and testis. Although a subtracted cDNA library prepared by removing P31 (wv/wv) sequences from a P1 (wv/+) library should contain mainly nonrepetitive neonatal sequences, unfortunately, repetitive sequences still appear during screening. Two clones, one repetitive, the other not, are used to illustrate the problems encountered in attempting to isolate the weaver gene from a subtracted cDNA library.Special issue dedicated to Dr. Sidney Ochs.     

The anticonvulsant effect of citalopram on El mice,and the levels of tryptophan and tyrosine and their metabolites in the brain

Serotonin (5-HT) plays an important role in the seizures of El mice since the seizure threshold of El mice correlates with the 5-HT concentration in the central nervous system. In this study, the anticonvulsant effect of a 5-HT reuptake blocker, citalopram, was evaluated behaviorally and biochemically. El mouse convulsions were inhibited by oral administration of citalopram for 2 weeks. Citalopram increased tryptophan and tyrosine amounts, and decreased the 5-HT, 5-hydroxy-indoleacetic acid, kynurenine, and dopamine amounts in the brain. These findings show that citalopram depresses monoaminergic metabolism. Given the known convulsant effect of kynurenine, it is suggested that its decrease by citalopram may involve attenuation of El mice seizures.     

Resynchronization of the Circadian Corticosterone Rhythm After a Light/Dark Shift in Juvenile and Adult Mice

Most of the extensive literature concerning the resynchronization of circadian rhythms after a Zeitgeber shift is devoted to the dependence of resynchronization on the mode of the shift and the strength of the Zeitgeber, as well as on the circadian function investigated. Ontogenetic influences have rarely been investigated. Therefore, we studied the resynchronization of several circadian rhythms in juvenile and adult female laboratory mice. We present here the results concerning the corticosterone rhythm. The daily rhythms were determined as transverse profiles (2-h intervals) before as well as 3, 7, and 14 days after an 8-h phase delay of the light/dark cycle produced by a single prolongation of dark time. The corticosterone concentration in serum was determined radioimmunologically. In the control animals the daily patterns were bimodal, with main maxima at the end of the light time and secondary ones just after lights on. Ontogenetic differences were small. In adult mice the amplitude was slightly increased due to an increase in the maximum values, and the time of highest hormone concentrations was slightly phase advanced. In juvenile mice, a distinct daily pattern with a phase position in relation to the light/dark cycle corresponding to that of control animals was present on the 3rd day after the Zeitgeber shift. The daily mean as well as the minimum and maximum values increased initially and reached the values of control animals during the second week. In adult animals, a pronounced daily rhythm with the normal phase position was present only at the 7th postshift day. The amplitude, daily mean, and maximum values were decreased, and the minimum values were increased. The initial values were not reached even after 2 weeks. The results show that resynchronization was faster in juvenile mice compared with adult mice. As a possible cause for the observed age-related differences, a not yet stabilized phase-coupling between various circadian rhythms is supposed.     

Systemic amyloidosis in transgenic mice carrying the human mutant transthyretin (Met 30) gene

To analyze the pathologic processes of amyloid deposition in type I familial amyloidotic polyneuropathy (FAP), mice were made transgenic by introducing the human mutant transthyretin (TTR) gene(MT-hMet 30). An inbred strain of mouse, C57 BL/6, was chosen. Transgenic mice were killed using ether anesthesia at 3-mo intervals up to 24 mo after birth. In these transgenic mice, amyloid deposition started in the gastrointestinal tract, cardiovascular system, and kidneys and extended to various other organs and tissues with advancing age. The pattern of amyloid deposition was similar to that observed in human autopsy cases of FAP, except for its absence in the choroid plexus and in the peripheral and autonomic nervous systems. We extracted the amyloid fibrils from kidneys of these mice with a human mutant TTR gene and analyzed them immunochemically and electronmicroscopically. Deposited amyloid was shown to be composed of human mutant TTR and mouse serum amyloid P component. Amyloid fibril from transgenic mice was morphologically and immunohistochemically similar to that of human FAP. The most striking pathologic feature of the transgenic mice was the absence of amyloid deposition in the peripheral and autonomic nervous tissues. Thus, other intrinsic factors may be involved in amyloid deposition in the nervous tissues of human FAP.     

The radiosensitivity of spermatogonial stem cells in C3H/101 F1 hybrid mice

The radiosensitivity of spermatogonial stem cells of C3H/HeH × 101/H F₁ hybrid mice was determined by counting undifferentiated spermatogonia at 10 days after X-irradiation. During the spermatogenic cycle, differences in radiosensitivity were found, which were correlated with the proliferative activity of the spermatogonial stem cells. In stage VIII_irr, during quiescence, the spermatogonial stem cells were most radiosensitive with a D₀ of 1.4 Gy. In stages XI_irr−V_irr, when the cells were proliferatively active, the D₀ was about 2.6 Gy. Based on the D₀ values for sensitive and resistant spermatogonia and on the D₀ for the total population, a ratio of 45:55% of sensitive to resistant spermatogonial stem cells was estimated for cell killing.

When the present data were compared with data on translocation induction obtained in mice of the same genotype, a close fit was obtained when the translocation yield (Y; in % abnormal cells) after a radiation dose D was described by Y = e^τD, with τ = 1 for the sensitive and τ = 0.1 for the resistant spermatogonial stem cells, with a maximal e^τD of 100.