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Results for “Mice, Quaking”

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At least 19 recordsLinked to original sources

PubMed1995

Endocytic depletion of L-MAG from CNS myelin in quaking mice.

Quaking is an autosomal recessive hypo/dysmyelinating mutant mouse which has a 1-Mbp deletion on chromosome 17. The mutation exhibits pleiotrophy and does not include genes encoding characterized myelin proteins. The levels of the 67-kD isoform of the myelin-associated glycoprotein (S-MAG) relative to those of the 72-kD isoform (L-MAG) are increased in the quaking CNS, but not in other dysmyelinating mutants. Abnormal expression of MAG isoforms in quaking may result from altered transcription of the MAG gene or from abnormal sorting, transport, or targeting of L-MAG or S-MAG. To test these hypotheses, we have determined the distribution of L-MAG and S-MAG in cervical spinal cord of 7-, 14-, 21-, 28-, and 35-d-old quaking mice. In 7-d-old quaking and control spinal cord, L- and S-MAG was detectable in periaxonal regions of myelinated fibers and in the perinuclear cytoplasm of oligodendrocytes. Between 7 and 35 d, L-MAG was removed from the periaxonal membrane of quaking but not control mice. Compared to control mice, a significant increase in MAG labeling of endosomes occurred within oligodendrocyte cytoplasm of 35-d-old quaking mice. S-MAG remained in periaxonal membranes of both quaking and control mice. Analysis of the cytoplasmic domain of L-MAG identifies amino acid motifs at tyrosine 35 and tyrosine 65 which meet the criteria for "tyrosine internalization signals" that direct transmembrane glycoproteins into the endocytic pathway. These results establish that L-MAG is selectively removed from the periaxonal membrane of CNS-myelinated fibers by receptor-mediated endocytosis. The loss of L-MAG from quaking periaxonal membranes results from increased endocytosis of L-MAG and possibly a decrease in L-MAG production.

Amino Acid Sequence↗

PubMed1975

Lipid and fatty acid composition of testes of quaking mice.

Testes of quaking mice (sterile mutants) and of controls were analyzed for major lipid classes and fatty acid composition. Of the main lipid classes, only cholesterol esters differed significantly in concentration between the two groups (1.01 for quakers vs 0.69 mg/g wet wt of tissue for controls). The concentration of triglycerides was 4.5-5.0 that of total phosphatides 18-19 and that of free cholesterol 1.9-2.0 mg/g for mutants and controls. The concentrations of phosphatidyl ethanolmanine and of sphingomyelin were both lower in quaking than in normal mice, but only the change in the former was statistically significant. Phosphatidyl choline was the major phosphatide (43-45% of total phosphatides) followed by phosphatidyl ethanolamine (24-26%) and sphingomyelin, phosphatidyl serine, and phosphatidyl inositol (all ca. 7% of total phosphatides). Minor differences between the mutants and controls were observed in concentrations of fatty acids of major lipid classes. The mutants, sterile because of faulty spermatid differentiation, had normal quantities of 22:6 w3 and 22:5 w6. These data are consistent with the hypothesis that the 22-carbon polyenes are associated with the formation of spermatids, rather than with their final differentiation into spermatozoa.

Animals↗

PubMed1978

In vivo incorporation of 32P into myelin basic protein from normal and quaking mice.

Myelin basic protein in normal mice is phosphorylated. Since phosphorylation can decrease the net positive charge of the myelin basic protein, this could affect molecular interactions between this protein and other myelin components. In this study 32P incorporation into small and large components of the myelin basic protein was studied in immature and young adult mice and also in Quaking mutants which have a severe myelin deficit. We found a short half-life of 32P in myelin basic protein. The 32P specific activity of myelin basic protein was higher in immature and Quaking mice than in young adult animals. Of the 32P-labeled basic proteins of control and Quaking mice, the small component had a slightly higher specific activity than the large component. Although the small basic protein is quantitatively decreased in Quaking mice, the ratio of specific activity of small to large basic protein is similar in control and Quaking animals. Since Quaking and immature mice have many uncompacted myelin lamellae, these preliminary results suggest that phosphorylation and dephosphorylation could be involved in compaction mechanisms.

Aging↗

PubMed1987

Copper, manganese and zinc in the developing brain of control and quaking mice.

Copper, manganese and zinc were measured by flameless atomic absorption spectrophotometry in the developing brain of normal and quaking mice. The latter is a neurological mutant presenting early arrest of myelination. Copper concentration was increased by 200% between 10 and 20 days after birth and then leveled off in adult mice. Manganese concentration increased both in control mice and in quaking mice from 3 to 20 days by 200% and then decreased by 19% in control mice and 24% in quaking mice at adult age. Zinc increased by 93% in control and 173% in quaking mice between 10 and 20 days of age, and then progressively declined until 62 days. The mouse brain accumulates considerably all the 3 metals during early development. During the first 20 days, the augmentation is 6-fold for copper, 5-fold for manganese and 5.5-fold for zinc. In quaking, alterations are not very important.

Animals↗

PubMed1987

Myelin-associated glycoprotein in the central and peripheral nervous system of quaking mice.

The myelin-associated glycoprotein (MAG) was quantitated in the CNS and PNS of quaking mice and the levels compared to the levels of myelin basic protein (MBP) and 2':3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) activity. In the brainstems of 36-day-old quaking mice, MBP, MAG, and CNPase were reduced to 12, 16, and 29% of control levels, respectively. In the sciatic nerves of the 36-day-old quaking mice, MBP and CNPase were 38 and 75% of control levels, respectively, whereas the concentration of MAG was unchanged or slightly increased. Similar quantitative results were obtained for the sciatic nerves and spinal roots of 7-month-old quaking mice. Immunoblots showed that the principal MAG band from the brainstems, sciatic nerves, and spinal roots of the quaking mice had a higher than normal apparent Mr. In addition, there was a minor component reacting with anti-MAG antiserum in the brainstems of the quaking mice that had a slightly lower Mr than control MAG and was not detected in the normal mice. The results for the quaking mice are compared with those from similar studies on other mutants with dysmyelination of the CNS and PNS.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗

PubMedDate not supplied

Radial component of central myelin in normal and quaking mice.

Radial component of myelin sheaths was investigated in C57BL and quaking mice. In immature myelinated fibres of C57BL mice, more than one group of radial component were observed in the several regions of myelin sheaths while in mature fibres, one group of radial component was localized between the internal mesaxon and outer tongue process which were situated within 90 degrees of each other. In thinly myelinated fibres of adult quaking mice, numerous groups of radial component were found at random distance and directions but they were always closely related to the cytoplasmic islands of oligodendroglia. Even in quaking mice, small well myelinated fibres showed normal mature pattern of radial component. Possible functional significance of radial component was briefly discussed.

Aging↗

PubMedDate not supplied

Chronological study of oligodendroglial alterations and myelination in quaking mice.

Chronological morphological investigation was carried out in the spinal cord of quaking mice from day 3 to day 130. Numbers of myelinated fibres were far fewer in quaking mice at day 3 compared to controls. However, when the animals became older, myelination progressed and numbers of myelinated fibres increased although myelin sheaths remained far thinner than the size of axons. Many oligodendroglia during day 5 to 15 in quaking mice revealed prominent dilation and proliferation of smooth walled vesicles and cisterns but after 20 days, such changes were no longer observed. Tortuous bizarre oligodendroglial processes, aberrant myelination and myelin figures were very prominent around day 5--15, but such changes also gradually subsided. Density of glial cells during pre-myelination gliosis was similar in both quaking and control mice. However, glial cell population decreased far slower pace than controls when myelination progressed. Thus, glial cell density remained proportionally higher in quaking than controls although the density declined with age in both.

Aging↗

PubMed1988

Cerebellar allografts in brain of quaking mice.

Fragments of normal embryonic cerebellum were transplanted into adult Quaking mice to examine using peroxidase-antiperoxidase immunocytochemistry the development of genetically normal tissue in an abnormal host environment. The Quaking mouse animals used as hosts are characterized by defective myelin associated glycoprotein. Normal characteristic expression and distribution of neurofilaments was observed in the cerebellar grafts. Nonphosphorylated epitopes of neurofilaments were seen in Purkinje cell bodies and dendrites. The phosphorylated epitopes of neurofilaments were observed in basket cell axons. Phosphorylated epitopes were also present in numerous myelinated axons, which were probably fibers from deep cerebellar nuclei. These data support the notion that neurogenesis with alternative connections can occur in transplants. Staining patterns with myelin associated glycoprotein and myelin basic protein also suggest that normal myelination occurs in grafts transplanted to the brains of Quaking mice.

Animals↗

PubMed1986

Incorporation of radioactivity from U-14C-glucose into oligodendrocytes and myelin of quaking mice and their littermate controls.

Oligodendrocytes and myelin were purified from the cerebra of quaking mice and their littermate controls (11-60 days of age) after injecting the animals intraperitoneally with U-14C-glucose. A peak of incorporation of radioactivity in the lipid extract of oligodendrocytes of both quaking and normal mice at 16-18 days of age was found, suggesting that the onset of myelination in the cerebra starts approximately at the same time for quaking mice and their littermate controls. Nevertheless the level of incorporation per cell was lower in the oligodendrocytes of quaking mice (50% of the control). The pattern of incorporation into myelin during development was similar between the two strains, but the specific activity as measured in dpm/mg protein was higher in the myelin of young quaking animals (up to 16 days). Peaks of incorporation were found in cerebrosides and sulfatides of oligodendrocytes and myelin in normal controls at 18 days. In the quaking mice these peaks were absent in oligodendrocytes and much delayed in the myelin of the mutant. The results would suggest that the defect in the quaking mutant in respect to myelination is in oligodendrocyte metabolism and thus in an early stage of the assembly of the myelin membrane.

Animals↗

PubMed1983

[Hereditary demyelination in mutant quaking mice (breeding and light microscopy)].

Data on breeding of mutant Quaking mice (MQM) and the results of light microscopy and morphometric examination of the central and peripheral nervous systems in them and in control mice varying in ages from 12 days to 4 months are presented. MQM were shown to have a decreased total volume of the white matter due to underdevelopment of myelin because of disturbed function of myelin-forming cells (oligodendrocytes). At the same time oligodendrocytes retain their capacity for proliferation and are normally located interfascicularly in the white matter having the same density of occurrence and the same average volume of the nucleus as in controls, but morphologically they are similar to oligodendroblasts. Another morphological feature of MQM consists of intensive vacuolation of their gray and white matter. However, light microscopy could not determine whether the vacuoles 1 to 9 microns in diameter were located intra- or extracellularly. No pathological changes in neurocytes, astrocytes or capillaries were observed.

Animals↗

PubMed1980