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Ultrastructural analysis of haemopoiesis in W/Wv anaemic mice.

This study is an ultrastructural analysis of haemopoiesis in W/Wv anaemic mice in whom the anaemia is caused by a defect in the haemopoietic stem cell. Cellularity of marrow is normal but there is an increase in the proportion of less mature cells suggesting a delay in maturation. In addition, heterochromatin constitutes a higher proportion than normal of the nucleus in most stages of maturation suggesting a defect in DNA activation. The findings suggest that in this strain not only the differentiation of the haemopoietic stem cell but also the maturation of the committed cell is defective.

Anemia, Macrocytic

Association of Salmonella typhimurium with, and its invasion of, the ileal mucosa in mice.

A wild-type strain of Salmonella typhimurium and three mutant rough colonial variants of the wild type were compared for their ability to become associated with and invade the ileal mucosa of germfree and specific-pathogen-free mice. The rough-mutant strains differed from the wild type in having incomplete lipopolysaccharides lacking one or more sugars in the polysaccharide moiety. The wild-type and mutant strains also differed one from the other in the types of appendages (flagella, pili) on their surfaces. Depending upon the dosage of bacteria given, all mutant strains as well as the wild type could associate with and invade the intestinal mucosa of infected gnotobiotic mice. If the infecting dosage was high enough, at least two of the mutant strains and the wild type invade the intestinal mucosa of the specific-pathogen-free animals. O antigen, flagella, or pili do not appear to be essential for the association of S. typhimurium with the mucosal surface of the mouse ileum. O antigen on the bacterial cell surface may be important, but not essential, for invasion of the ileal mucosa.

Animals

Cadmium metabolism in cdm/cdm mice.

The uptake and metabolism of cadmium by cadmium-susceptible (+/+) and cadmium-resistant (cdm/cdm) strains of mice have been compared. These strains did not differ with respect to the quantitative uptake of cadmium into liver, kidney, or testis. After intraperitoneal administration of a nontoxic dose, more than 80% of the cadmium in liver and testis of both strains is bound to low molecular weight proteins. The chromatographic behavior of these cadmium-binding proteins is not affected by cdm genotype.

Animals

Asymmetry in the serological response and mixed lymphocyte reactions between C57Bl/6 and the congenic mutant C57Bl/6.CH-2ba [H(Zl)].

Asymmetry in the relationship between the H-2K mutant strain C57Bl/6.CH-2ba (H-2ba) and the wild-type congenic C57Bl/6 has been demonstrated both in MLR and serologically by haemagglutination. MLR between these strains, when B6 was the responder, was as strong as that toward allogeneic stimulator cells: H-2ba was regularly less responsive toward B6. Responses in both directions were increased, in terms of augmented proliferative responses, by prior immunization. In this context the MLR resembles that towards minor H-locus antigens rather than those controlled by the H-2 locus. Immunization of (H-2ba X BALB/c)F1 hybridgs with B6 lymphoid cells induced the production of a haemagglutinating antibody not directed toward any known H-2 specificity. The B6 haemagglutinogen, termed He, was present on B6 lymphoid as well as red blood cells. Segregation studies of F2 and back-cross progeny of (H-2ba X BALB/c)F1 hybrids suggest that the response to He is controlled by two Ir genes, one of which is linked to H-2.

Animals

Defect in regulation of membrane transport of monosaccharides in dystrophic muscle.

The penetration of a nonmetabolized glucose analogue, 3--O-methyl-D-glucose, across the plasma membranes of tissues from dystrophic mice and cardiomyopathic (dystrophic) hamsters has been compared with that of normal controls. Under basal conditions the penetration of test sugar was similar in lens and diaphragm of normal and dystrophic 129/ReJ mice. Stimulation of sugar transport by 2,4-dinitrophenol did occur in normal but not in dystrophic diaphragm. A submaximal concentration of insulin had a more variable effect in dystrophic than in normal muscle while a supramaximal concentration of the hormone increased the uptake of the glucose analogue to an equal extent in the two tissues. In the BIO 14.6 strain of cardiomyopathic hamsters, uncoupling of oxidative phosphorylation did not increase sugar transport in extensor digitorum longus muscles, while the normal effect was observed in dystrophic soleus and in both these muscles of the random bred controls. The absence of an effect by a condition simulating anoxia suggests that in dystrophy, certain muscles are unable to accelerate the entry of glucose when this is required.

Animals

Regulation of lipopolysaccharide-induced granulopoiesis and macrophage formation by spleen cells. I. Relationship between colony-stimulating factor release and lymphocyte activation in vitro.

Addition of bacterial lipopolysaccharide (LPS), a B cell mitogen, to mouse spleen cultures strongly stimulated production of colony-stimulating factor (CSF), the humoral regulator of granulopoiesis, and macrophage formation in vitro. Secretion of CSF from LPS-stimulated spleen cells coincided with cellualr DNA synthesis and cell transformation and both activities could be attributed to the lipid A moiety of the molecule. Different experimental approaches were used to study the relationship of CSF release and lymphocyte activation in response to LPS: a) modification of LPS with polymyxin B, an antibiotic bactericidal for most Gram-negative bacteria, caused a marked reduction in mitogenic activity, although the ability to induce CSF was not significantly altered; b)spleen cells from CBA/N mice, a mutant strain with an x-linked genetic defect in immunologic and mitogenic responses to polyclonal activators including LPS, showed diminished mitogeinc responses; however, high levels of CSF were produced; c) mitotic and DNA inhibitors (colchicine and cytosine arabinoside) did not affect CSF release although they completely inhibited mitogenicity. Thus, the spleen cell population participating in the process of LPS-induced CSF generation is probably a nondividing, terminally differentiated one without need for DNA synthesis. In addition, it was also shown that active RNA and protein synthesis are needed in this process.

Animals

Defective transient endogenous spleen colony formation in S1/S1d mice.

WCB6F1 mice of the genotype S1/S1d did not form transient 5-day endogenous spleen colonies following midlethal irradiation, either spontaneously or in response to postirradiation bleeding. Their hematologically normal (+/+) littermates produced colonies equivalent in number and morphologic type to a normal strain (D2B6F1), as evaluated by both macroscopic and microscopic criteria. Bone marrow cells from S1/S1d mice, when transplanted into lethally irradiated +/+ mice, were able to generate equivalent numbers of transient endogenous spleen colonies (TE-CFUs), as compared to that obtained when syngeneic +/+ marrow cells were injected into lethally irradiated +/+ recipients. A defective growth of an early class of hematopoietic progenitor cells, resulting in the clinical course of the S1/S1d anemia is suggested and confirms previous reports on the microenvironmental nature of this abnormality.

Anemia

Rate of egg penetration in vitro accelerated by T/t locus in the mouse.

Spermatozoa from fertile mice heterozygous for tw32, a recessive lethal allele of the T/t locus, were compared to normal spermatozoa in a fertilization in vitro system. The rate of egg penetration following insemination in vitro was determined for epididymal spermatozoa from C57BL/6-tw32/+ mice and for epididymal spermatozoa from C57BL/6-+/+ mice. At one hour after insemination, the mean of penetration +/- standard deviation for spermatozoa from BL/6-tw32/+ mice was 20% +/- 2.1 (109 eggs observed, 5 experiments), while the mean for spermatozoa from BL/6-+/+ mice was 1% +/- 1.5 (107 eggs observed, 4 experiments). By five hours post-insemination, the levels of egg penetration were not significantly different. These results suggest that tw32 increases the initial rate of egg penetration. Preliminary observations of sperm motility and sperm-egg association at one hour post-insemination in vitro do not support the hypothesis that this earlier penetration is due to improved sperm progress to the egg. Rather, the earlier penetration may be a result of changes in the timing of capacitation, the acrosome reaction, or sperm-egg fusion. It is possible that the earlier penetration may play a role in the distortion of the transmission ratio of tw32.

Animals

Defective oxidative metabolism of myodystrophic skeletal muscle mitochondria.

A small-scale procedure for preparing tightly coupled intact skeletal muscle mitochondria from myodystrophic (myd/myd) mice is described. Mitochondrial preparations derived from heart, liver, and skeletal muscle of myd/myd and their littermate (+/?) controls are characterized with respect to their cytochrome content and their oxidative and phosphorylative capacities. Our data indicate that there is an impairment in the NADH CoQ region of the respiratory chain of myodystrophic skeletal muscle mitochondria. Both heart and liver mitochondria of myd/myd exhibited normal activities of respiratory chain-linked oxidative phosphorylation.

Adenosine Diphosphate

New muscle transplant method produces normal twitch tension in dystrophic muscle.

Grafting newborn muscle is an innovative method of muscle transplant. This method overcomes hypoxia in the deeper fibers and facilitates reinnervation and revascularization of the grafted muscle fibers, thus promoting the survival and development of the characteristics of the donor muscle. The result achieved is superior to that obtained from mature muscle grafts or from minced muscle transplants. When an intact soleus from a 1-day-old normal mouse was grafted into a recipient soleus of a 20-day-old dystrophic C57BL/6J-dy2J mouse, the actively developing normal graft helped to improve the structure and function of the dystrophic muscle. When compared to the intact dystrophic solei, the test dystrophic muscles five to six months after operation showed increases in cross-sectional area, in wet weight, in twitch and tetanic tension, and in the number of muscle fibers with high resting membrane potentials. This is the first procedure to have raised the muscle twitch tension in an adult dystrophic mouse to the normal level.

Action Potentials

Gap junctional vesicles in the neural tube of the splotch (Sp) mutant mouse.

The lumbosacral region of the neural tube was studied by means of transmission electron microscopy in retrospectively confirmed normal (+/+; Sp/+) and abnormal (Sp/Sp) embryos of the splotch mutant mouse early on the ninth day of gestation when the caudal neural groove is normally in the process of closing to form the neural tube. In abnormal embryos, a consistent feature is the presence of gap junctional vesicles, particularly in the region of the neural groove which subsequently fails to close, whereas these structures are rarely observed in similar areas of normal embryos. The possible significance of gap junctional vesicles is discussed in terms of cellular adhesion during early neurogenesis.

Animals

Development of Dickie's small eye, a mutation in the house mouse.

A new semidominant mutation in the laboratory mouse, Dickie's small eye (Dey), is described. It is localized on chromosome 2. Heterozygotes show reduced body size, small eyes with coloboma, small or lacking lens with cataract, abnormal folding of the retina and reduction of the pigment layer. The anterior chamber is usually missing. Homozygotes apparently die early in pregnancy.

Animals

45Ca2+ uptake by dispersed pancreatic islet cells: effect of D-glucose and the calcium probe, chlorotetracycline.

Uptake of 45Ca2+ was studied in dispersed pancreatic islet cells from non-inbred ob/ob-mice. Like whole islets the dispersed cells responded to 20 mM D-glucose with a markedly increased 45Ca2+-labeling of both the lanthanum-nondisplaceable and the lanthanum-displaceable calcium pools. The pronounced effect of D-glucose could not be reproduced with 3-O-methyl-D-glucose, L-glucose, D-mannose, L-leucine, or D-leucine; however, 45Ca2+ uptake was greater in the presence of L-leucine as compared with D-leucine. 45Ca2+ uptake by dispersed cells or whole islets was stimulated severalfold by 100 microM or more chlorotetracycline. At the concentration of only 10 microM, chlorotetracycline had no effect on whole islets and partially inhibited 45Ca2+ uptake by the dispersed cells. The ability of D-glucose to stimulate 45Ca2+ uptake by islets or dispersed cells remained in the presence of 10 microM chlorotetracycline. Islet cell suspensions apparently represent a valid model for studying how Ca2+ interacts with the cells. However, when using chlorotetracycline as fluorescent Ca2+ probe, attention must be paid to it potential ionophoric activity. At only 10 microM, the drug seems to monitor a peripheral pool of Ca2+, some of which may reside in normal transport channels.

Animals

Succinate dehydrogenase activity in the developing molar of the hairless mouse Mus musculus.

Succinate dehydrogenase activity in the odontogenic tissues of the hairless mouse (hr/hr) has been studied from the initiation of the dental lamina through apposition. Enzyme activities were designated as negative, slight, moderate and strong as a function of intensity of the reaction product. Enzyme levels in the odontogenic tissues increased with advancing tooth morphogenesis. Greatest activity was observed in the ameloblastic layer which peaked on the fourth to sixth postnatal days. This cell layer displayed higher enzyme activity than the ectomesenchymally-derived odontoblasts. Succinate dehydrogenase activity appeared to be related to the degree of differentiation and functional competence on the odontogenic tissues of the hairless mouse.

Animals