Changes in movement and ataxic gait with development in genetically ataxic mice: a comparison with the level of cerebellar cyclic nucleotide

Spontaneous movement and ataxic gait in ataxic mice showing various pathological changes in the cerebellum were investigated according to developmental stage by the open-field method of comparison with normal mice. As the cerebellum contains relatively high levels of cyclic nucleotide, its concentrations was measured by radioimmunoassay to elucidate the correlation between spontaneous movement and ataxic gait and the neurological changes. The movements of Rolling Mouse Nagoya (RMN), Weaver and Reeler mice without Purkinje Cell Degeneration (PCD) were found to decrease at 4 and 12 weeks of age. The degree of ataxic gait worsen in RMN, was unchanged in Reeler and improved in Weaver and PCD mice. The cerebellar c-GMP concentration of ataxic mice was decreased, while no significant changes in c-AMP concentration were found in comparison with normal mice. With development, the level of cerebellar c-GMP in Weaver mice increased, but this was not apparent in RMN, Reeler or PCD mice. The results of this investigation indicated that there may be some relation between the degree of ataxic gait and the level of cerebellar c-GMP in Weaver mice.     

Reduction of nerve growth factor level in the brain of genetically ataxic mice (weaver, reeler)

By a highly sensitive enzyme immunoassay we measured the level of nerve growth factor (NGF) in the cerebellum and cerebrum of the neurologically mutant mice, weaver, reeler and Purkinje cell degeneration (PCD). A significant decrease in NGF level was observed in both cerebellum and cerebrum of weaver and reeler mutants of either sex. However, there was no such difference between normals and mutants in the case of the PCD mice. These results show that weaver and reeler mice have abnormalities of NGF synthesis and/or degradation not only in the cerebellum but also in the cerebrum.     

Phenotypic characterization of a genetically diverse panel of mice for behavioral despair and anxiety

Background

Animal models of human behavioral endophenotypes, such as the Tail Suspension Test (TST) and the Open Field assay (OF), have proven to be essential tools in revealing the genetics and mechanisms of psychiatric diseases. As in the human disorders they model, the measurements generated in these behavioral assays are significantly impacted by the genetic background of the animals tested. In order to better understand the strain-dependent phenotypic variability endemic to this type of work, and better inform future studies that rely on the data generated by these models, we phenotyped 33 inbred mouse strains for immobility in the TST, a mouse model of behavioral despair, and for activity in the OF, a model of general anxiety and locomotor activity.

Results

We identified significant strain-dependent differences in TST immobility, and in thigmotaxis and distance traveled in the OF. These results were replicable over multiple testing sessions and exhibited high heritability. We exploited the heritability of these behavioral traits by using in silico haplotype-based association mapping to identify candidate genes for regulating TST behavior. Two significant loci (-logp >7.0, gFWER adjusted p value <0.05) of approximately 300 kb each on MMU9 and MMU10 were identified. The MMU10 locus is syntenic to a major human depressive disorder QTL on human chromosome 12 and contains several genes that are expressed in brain regions associated with behavioral despair.

Conclusions

We report the results of phenotyping a large panel of inbred mouse strains for depression and anxiety-associated behaviors. These results show significant, heritable strain-specific differences in behavior, and should prove to be a valuable resource for the behavioral and genetics communities. Additionally, we used haplotype mapping to identify several loci that may contain genes that regulate behavioral despair.     

Elevated immunoreactive-somatostatin levels in the brain of ataxic mutant mice

Immunoreactive-somatostatin (IR-SRIF) levels were investigated in the brain of 4 types of ataxic mice (Rolling Mouse Nagoya, Weaver, PCD, Staggerer) with different cerebellar pathologies. IR-SRIF concentrations (ng/mg) were found to be significantly elevated in both cerebellum and cerebrum of all ataxic mutant mice, IR-SRIF (ng/organ) was found to be increased in the cerebellum and cerebrum in Rolling Mouse Nagoya and PCD compared with control mice. The gel-filtration profile (Sephadex G-50) in the cerebellar extracts of Rolling Mouse Nagoya proved to be identical to that of control mice. Three peaks of IR-SRIF were found to be uniformly elevated in Rolling Mouse Nagoya, with the highest peak coinciding with authentic somatostatin-14. The present results suggest that elevated levels of IR-SRIF in the brain may play a role in the mechanism underlying the manifestation of ataxia in ataxic mutant mice, especially in Rolling Mouse Nagoya and PCD.     

Studies on parasitemia courses and mortality in mice infected with genetically distant Trypanosoma cruzi clonets.

The biological characterization of bloodstream forms of eleven Trypanosoma cruzi cloned stocks, corresponding to two genetically similar clonets (19 and 20) and one distant clonet (39), according to multilocus enzyme electrophoresis analysis, showed dissimilar parasitemia in an experimental isogenic mouse model. While clonet 39 stocks gave low parasitemias, clonets 19 or 20 stocks gave high parasitemias, independently of the inocula (10(2) and 10(4) bloodstream forms) used. High parasitemia did not always associate with greater mortality. Statistical studies on mortality using a low inocula showed significantly higher mortality with clonet 39 stocks when compared to clonets 19 or 20 stocks. Finally, in order to confirm the identity of each stock studied, typing by molecular karyotype was performed before inoculating mice.     

Studies on induction of polydactyly in rats with cytosine arabinoside.

The development of the retino-tectal projection in Rana pipiens has been studied by the intraocular injection of small amounts of [³H]proline at late embryonic and at several larval stages. After survival periods varying from 1–24 hr the distribution of the radioactively labeled proteins in the axons of the retinal ganglion cells was studied autoradiographically. It is evident from the appearance of labeled proteins in the optic nerve and chiasm at late embryonic and early larval stages that there is a rapid phase of axonal transport at these stages and that some fraction of the materials transported in this phase are distributed to the tips of the growing axons.The first retinal fibers reach the contralateral optic tectum at embryonic Stage 22; at this stage they are confined to the rostrolateral portion of the tectum where the first tectal neurons are generated. At successively later stages the fibers appear to grow across the surface of the tectum in a general rostrolateral to caudomedial direction, reaching the dorsal part of the mid-tectum at larval Stage II and the lateral part of its caudal third by Stage V. However, it is not until relatively late larval stages (XVIII) that the fibers reach the caudomedial region of the tectum, and it is only at the time of metamorphosis (Stage XXV) that the retinal projection appears to cover the entire tectum.     

Interval timing in genetically modified mice: a simple paradigm

We describe a behavioral screen for the quantitative study of interval timing and interval memory in mice. Mice learn to switch from a short-latency feeding station to a long-latency station when the short latency has passed without a feeding. The psychometric function is the cumulative distribution of switch latencies. Its median measures timing accuracy and its interquartile interval measures timing precision. Next, using this behavioral paradigm, we have examined mice with a gene knockout of the receptor for gastrin-releasing peptide that show enhanced (i.e. prolonged) freezing in fear conditioning. We have tested the hypothesis that the mutants freeze longer because they are more uncertain than wild types about when to expect the electric shock. The knockouts however show normal accuracy and precision in timing, so we have rejected this alternative hypothesis. Last, we conduct the pharmacological validation of our behavioral screen using d -amphetamine and methamphetamine. We suggest including the analysis of interval timing and temporal memory in tests of genetically modified mice for learning and memory and argue that our paradigm allows this to be done simply and efficiently.     

Planarians in pharmacology: parthenolide is a specific behavioral antagonist of cocaine in the planarian Girardia tigrina

Planarians are traditional animal models in developmental and regeneration biology. Recently, these organisms are arising as vertebrate-relevant animal models in neuropharmacology. Using an adaptation of published behavioral protocols, we have described the alleviation of cocaine-induced planarian seizure-like movements (pSLM) by a naturally-occurring sesquiterpene lactone, parthenolide. Interestingly, parthenolide does not prevent the expression of pSLM induced by amphetamines; in vertebrates, amphetamines interact with the same protein target as cocaine. Parthenolide is also unable to prevent pSLM elicited by the cholinergic com-pounds nicotine and cytisine or by the glutamatergic agents L- or D- glutamic acid or NMDA. Thus, we conclude that parthenolide is a specific anti-cocaine agent in this experimental organism.     

Studies of the effect of retinoic acid on anterior neural tube closure in mice genetically liable to exencephaly

Previously we have shown that all SELH/Bc mouse embryos close their anterior neural tubes by an abnormal mechanism and that 10-20% of SELH/Bc embryos are exencephalic. The purposes of these studies were (1) to observe the effects of retinoic acid on the frequency of exencephaly in SELH/Bc embryos; (2) to compare the SELH/Bc response with those of normal strains and of other neural tube mutants; and (3) to compare, between SELH/Bc and a normal strain (SWV/Bc), the effects of retinoic acid on morphology of the closing anterior neural tube. SELH/Bc was more liable to retinoic acid-induced exencephaly than were normal strains. After maternal treatment with 5 mg/kg retinoic acid on day 8.5 of gestation, 53% of SELH/Bc embryos had exencephaly, compared with 22% in ICR/Bc and 14% in SWV/Bc. When these results were transformed according to the assumptions of the developmental threshold model, the effects of genotype and retinoic acid appeared to be additive. Similar treatment on day 9 or 10 of gestation had little or no effect on the frequency of exencephaly in SELH/Bc mice. These results are similar to the reported responses of the curly-tail and Splotch mutants, where frequencies of spina bifida but not exencephaly were decreased. This pattern suggests that studies of effects of periconceptional vitamin treatment on risk of human neural tube defects should consider anencephaly and spina bifida separately. The study comparing the morphology of anterior neural tube closure in SELH/Bc and normal SWV/Bc embryos showed that retinoic acid delays the elevation of the mesencephalic neural folds. This results in a "stalling" of many embryos in the first steps of neural tube closure, with their neural folds remaining convex and splayed wide apart. The delay in fold elevation was superimposed on the different closure patterns of the two strains. The overall conclusion is that there is no nonadditive interaction in the parameters studied between retinoic acid treatment and the SELH/Bc genotype.     

Changes of ataxia, spontaneous movement and the cerebellar noradrenaline system with aging in ataxic mice

Changes of cerebellar weight, spontaneous movement and ataxia with aging were investigated in Weaver and cytosine arabinoside-injected mice (Ara-C). In addition, changes of cerebellar NA and MHPG concentrations in both mice were measured by high performance liquid chromatography. Cerebellar weight increased with aging in both mice. Spontaneous movements in Weaver mice were not significantly changed, but Ara-C mice showed a decreasing tendency with aging. Ataxic gait improved with aging in Weaver mice, but not in Ara-C mice. With aging, cerebellar NA and MHPG concentrations were decreased in controls, but not in Ara-C mice. In Weaver mice, cerebellar MHPG concentration was decreased. These results suggest that NA turnover in ataxic mice is different from that in controls, but is not correlated closely with ataxia.     

Characterization of a genetically identifiable component of complement in mice

The hemolytic properties of the sera of complement positive and complement negative strains of mice were studied. The results suggested that the complement negative sera lacked an activity of complement analagous to C'1 which when present is called hc¹. Certain physical and chemical properties of hc¹ were examined. It was destroyed when serum was heated to 56°C, but was resistant to heating when slightly purified. Hc¹ was still precipitable by specific antiserum after treatment with 8 molar urea, but was no longer hemolytically active. Neither the hemolytic nor precipitating activity of hc¹ was altered by treatment with either 0.1 molar ethylenediamine-tetraacetic acid or 0.1 molar 2-mercaptoethanol. Initial attempts made to purify hc¹ are described.     

A comparison of the antinociceptive and behavioral effects of D-Arg substituted dipeptides and tetrapeptides in mice

Intracerebroventricular administration of D-Arg substituted dipeptides, H-Tyr-D-Arg-OMe and H-Tyr(Et)-D-Arg-OMe, and D-Arg2 substituted N-terminal tetrapeptides of dermorphin, H-Tyr-D-Arg-Phe-Gly-OEt and H-Tyr(Et)-D-Arg-Phe-Gly-OEt resulted in dose-related and naloxone-reversible antinociceptive effects. Among them, tetrapeptides not only exhibited much more potent and prolonged activities than dipeptides but also were significantly antagonized even by a low dose of naloxone. Spontaneous motor activity was lowered by dipeptides throughout the observation period, which was scarcely antagonized by naloxone. Tetrapeptides elicited locomotor hyperactivity following an initial locomotor suppression. Only the locomotor hyperactivity was significantly antagonized by naloxone. These results suggest that tetrapeptides induce the effects via opioid receptors, whereas the effects of dipeptides are involved in various systems non-specifically.     

Phenotypic variation in a genetically identical population of mice.

The parental alleles of an imprinted gene acquire their distinctive methylation patterns at different times in development. For the imprinted RSVIgmyc transgene, methylation of the maternal allele is established in the oocyte and invariably transmitted to the embryo. In contrast, the methylation of the paternal allele originates during embryogenesis. Here, we show that the paternal methylation pattern among mice with identical genetic backgrounds is subject to extensive variation. In addition to this nongenetic variation, the process underlying RSVIgmyc methylation in the embryo is also subject to considerable genetic regulation. The paternal transgene allele is highly methylated in an inbred C57BL/6J strain, whereas it is relatively undermethylated in an inbred FVB/N strain. Individual methylation patterns of paternal alleles, and therefore all of the variation (nongenetic and genetic) in methylation patterns within an RSVIgmyc transgenic line, are established in early embryogenesis. For each mouse, the paternal RSVIgmyc allele is unmethylated at the day-3.5 blastocyst stage, and the final, adult methylation pattern is found no later than day 8.5 of embryogenesis. Because of the strong relationship between RSVIgmyc methylation and expression, the variation in methylation is also manifest as variation in transgene expression. These results identify embryonic de novo methylation as an important source of both genetic and nongenetic contributions to phenotypic variation and, as such, further our understanding of the developmental origin of imprinted genes.     

Estrogen receptors in the kidney: Lessons from genetically altered mice

Background: Sex differences in human and animal models of kidney disease suggest that estrogen receptor (ER)-mediated events may modulate these processes. Genetically altered mice lacking one or both ERs provide a powerful tool to study these phenomena.Objective: This article examines sex differences in the kidney, particularly the role of ERs.Methods: To identify pertinent studies in genetically altered mice, a literature search was conducted on the MEDLINE database from January 1966 to July 2007, using the search terms estrogen receptor, kidney, and mice. Our group examined the effect of the ER-α knockout genotype on the kidney in streptozotocin-induced diabetes mellitus and compensatory kidney growth after uninephrectomy.Results: Female mice lacking ERa had reduced renal growth, including glomerular enlargement after 2 weeks of streptozotocin-induced diabetes mellitus and compensatory kidney growth 48 hours after uninephrectomy.Conclusion: ER-mediated events influence kidney growth and disease in female mice.     

Semi-natural and enclosed groups of Macaca mulatta: a behavioral comparison

Differences in aggression and grooming frequencies between enclosed and semi-natural groups of Macaca mulatta were studied quantitatively. Group composition, group densities and time of day were held constant. Results indicated that semi-natural monkey groups were significantly more aggressive, while enclosed groups exhibited significantly higher grooming frequencies. These results raise the question: Do alterations in behavioral frequencies lead to changes in social behavior patterns and group social organization?     

Studies on the mechanism of hypertriglyceridemia in the genetically obese Zucker rat

The possibility that impaired removal of lipoprotein triglyceride from the circulation may be a participating factor in the hypertriglyceridemia of the obese Zucker rat was examined. We found no significant differences in the heparin-released lipoprotein lipase (LPL) activities of the adipose tissue, skeletal muscle, and heart (expressed per gram of tissue) from the lean and obese Zucker rats. Furthermore, the kinetic properties of adipose tissue and heart LPL from the lean and obese rats were similar, indicating that the catalytic efficiency of the enzyme was unaltered in the obese animals. The postheparin plasma LPL activities of lean and obese rats were also similar. However, the postheparin plasma hepatic triglyceride lipase (H-TGL) activity in the obese rats was elevated. The higher activity of H-TGL could not alleviate the hypertriglyceridemia in these animals. Since hypertriglyceridemia in the obese rats could also be due to the hepatic production of triglyceride-rich lipoproteins which are resistant to lipolysis, we therefore isolated very low density lipoproteins (VLDL) from lean and obese rat liver perfusates and examined their degradation by highly purified human milk LPL. Although certain differences were observed in hepatic VLDL triglyceride fatty acid composition, the kinetic patterns of LPL-catalyzed triglyceride disappearance from lean and obese rat liver perfusate VLDL were similar. The isolated liver perfusate VLDL contained sufficient apolipoprotein C-II for maximum lipolysis. These results indicate that impaired lipolysis is not a contributing factor in the genesis of hypertriglyceridemia in the genetically obese Zucker rat. The hyperlipemic state may be attributed to hypersecretion of hepatic VLDL and consequent saturation of the lipolytic removal of triglyceride-rich lipoproteins from the circulation.