Search

The sexual phenotype of an adult mammal depends on whether the fetal gonad has differentiated as a testis or as an ovary. Because individuals of XY or XXY sex chromosome constitution develop as males, while XX and XO individuals develop as females, the presence of a Y chromosome seems normally to be required for testis differentiation and its absence to be necessary for differentiation of an ovary. The nature of the hypothetical Y-dependent substance responsible for masculinization of the indifferent gonad has been a matter for debate. A male-specific transplantation antigen, H-Y, has been known for many years and more recently a serologically detected antigen, also male-specific, has been reported. Those who believe that the two are antigenically distinct refer to the latter as SDM (serologically detected male) antigen, but many refer to both as H-Y antigen. The hypothesis that H-Y is itself the Y-dependent testis inducer, although supported by little or no direct evidence, is economical and hence attractive. H-Y antigen is frequently stated to be the substance responsible for primary sex determination (for example, see ref. 11). We report here that H-Y is absent from certain mice that develop testes and are of indisputably male phenotype, hence this transplantation antigen is unlikely to be responsible for testis determination.

Genetically mast cell-deficient W/Wv mice are useful for the analysis of mast cell biology, especially as recipients of bone marrow cells and skin pieces. Inasmuch as suspension and clonal cultures of mast cells have been developed, we combined these in vivo and in vitro systems. Suspension-cultured mast cells had morphological and biochemical characteristics similar to those of mucosal mast cells (MMC). However, i.p. injection of such cultured mast cells gave rise to development of cells with characteristics similar to those of connective tissue mast cells (CTMC). When peritoneal cells of normal +/+ mice were cultured in methylcellulose, pure mast cell colonies appeared. Cells from individual mast cell colonies were divided and injected into the skin and stomach wall of W/Wv mice; CTMC developed in the skin and MMC in the stomach mucosa. This indicates the presence of a common precursor for CTMC and MMC. Morphology of such bipotent mast cell precursors was studied by using micromanipulation. About 4% of morphologically identifiable peritoneal mast cells may function as the bipotent precursors. Although W/Wv mice showed a defect in resistance against ixodid ticks, injection of suspension-cultured mast cells normalized the defect. The four examples mentioned above indicate that combinations of in vivo and in vitro systems increase the usefulness of W/Wv mice.

Male mice homozygous for the little gene mutation (lit) were originally reported to have a marked incidence of infertility. We have previously reported that these diminutive mice have normal spermatogenesis and testicular steroidogenesis. In the present study, one research goal was to determine if the reported infertility was due to a defect in male sexual behavior. Quantitative analyses of male sexual behavior of little mice and their normal siblings were completed. Natural breeding trials were also performed to reexamine the fertility of little male mice. The experimental results suggested that little mice require significantly longer times for the first mount, first intromission, and ejaculation. More importantly, the investigation provided evidence that the little mice were not infertile but that they were subfertile. The diminutive size of the little mice may be the primary etiological factor for the observed subfertility.

Motor nerves of mice affected with hereditary 'motor endplate disease' were examined by means of electrophysiological and morphological techniques. Conduction velocity was slower, the refractory period was prolonged and the temperature sensitivity higher in mutants as compared to controls of the same age. Most of the axons examined in the electron microscope showed signs of paranodal demyelination. The relationship between the morphological and the electrophysiological findings is discussed. We conclude that alterations in the motor axons can account for the failures in neuromuscular transmission described previously in the med mutation.

The mutant mouse pearl, characterized by its hypopigmentation, has a specific functional defect in a sensory system--the retina. The intact pearl mouse has reduced sensitivity in the dark-adapted condition. Normal sensitivity is restored by isolation and superfusion of the retina with bicarbonate-buffered Ringer solution, suggesting that the retinal expression of the pearl mutation depends on a diffusible substance. The pearl phenotype is described as a possible model for human congenital stationary night blindness.

A profound decrease in activities of the two lysosomal serine proteinases, elastase, and cathepsin G, was found in neutrophils of four independent beige mutants. Elastase and cathepsin G activities were assayed with the specific synthetic substrates MeO-Suc-Ala-Ala-Pro-Val-MCA and Suc-Ala-Ala-Pro-Phe-pNA, respectively. The defect is intrinsic to cells of beige mice, since transplantation of bone marrow from normal to mutant mice restored normal proteinase activity, and normal mice transplanted with beige marrow produced neutrophils with a deficiency of proteinase activity. The loss of elastase and cathepsin G activity was confirmed by separation of [3H]diisopropylfluorophosphate-labeled proteins on denaturing gels, which also revealed that other serine proteinases are at normal levels in beige neutrophil extracts. The deficiency of lysosomal proteinase activity appears specific, in that four other common neutrophil lysosomal enzymes, plus the spectrum of major neutrophil proteins are not affected by the beige mutation. The deficiency of proteinase activity is likely not the primary genetic alteration of the beige mutation, since more than one proteinase is affected, and heterozygous F1 mice have normal rather than intermediate levels of both proteinases. The lowered proteinase activity may contribute to the high susceptibility of beige mice and Chediak-Higashi patients to infection.

Mice of the RF strain are unusually susceptible to the development of leukemia, both spontaneously and after whole body irradiation. Cell culture and transplantation techniques were used to study the proliferative capacity of hematopoietic tissues of these mice. The growth characteristics of granulopoietic cells of young, non-irradiated RF mice were compared with those from a leukemia-resistant strain, C57BL/6J (B6). Marrow from RF mice showed a substantial reduction in the number of colony-forming units in culture (CFUC). The numbers of marrow cells capable of forming colonies in the spleen of lethally irradiated syngeneic mice (CFUS) were also reduced. The spleens from non-irradiated RF mice were almost twice the size of those from B6 mice. Despite these differences the numbers of circulating peripheral leukocytes and percent of polymorphonuclear leukocytes were similar in the two strains. Bone marrow from RF mice may be analogous to that of certain human "preleukemic" states in which alterations in marrow cells are demonstrable in culture.

Humans with Chediak-Higashi Syndrome (CHS) and several animal species with similar defects have been reported to have increased susceptibility to infection, including abscess formation, associated with granulocyte abnormalities. These defects were investigated by comparing mice of the SB/Le strain, homozygous for the beige mutation, with their heterozygous littermates and with normal BALB/c mice with respect to the ability to form intraabdominal abscesses. Mice were autopsied 7 days after the intraperitoneal inoculation of a mixture of Bacteroides fragilis, Escherichia coli and an abscess-potentiating agent, bran. Although homozygous beige mice formed more numerous abscesses than controls, the total abscess sizes and bacterial contents were not significantly different. Histopathologically, the abscesses resembled those in normal mice. Phagocytic killing assays using granulocytes from beige mice of the SB/Le and C57BL/6J strains showed no significant differences between homozygous beige mice and controls. Within the context of these experiments in which neutrophil function in vivo and in vitro was examined with respect to anaerobic and facultative Gram-negative bacteria, it is concluded that beige mice can respond adequately to an infectious bacterial challenge. The increased susceptibility to an infection seen in various species with CHS-like disease may relate to virulence factors of the infecting organisms and defects in host defences documented by others but not manifest in these experiments.

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.

Using the criteria of virus susceptibility as defined by the 50 percent lethal dose response and the percent cumulative mortality response it was shown that the diabetic mutation db, located on chromosome 4, exerted a particular influence on the host response to CB4 challenge. Neither the yellow obese mutation Ay on chromosome 2 nor the misty coat color mutation located one centimorgan from the db mutation had the same effect on CB4 response. The obese diabetic mutation ob located on chromosome 6 appeared to enhance susceptibility to CB4. However, the high susceptibility of the inbred C57BL/6J line on which the ob mutation is found was apparently a significant contributing factor to the ob mutant high virus susceptibility. The response to CB4 was also a useful criteria to discern differences in the genetic background of closely related inbred lines. Based on the CB4 LD50 values the C57BL/6J inbred line was the most susceptible while the C57BL/Ks inbred line was the most resistant. However, using the percent cumulative mortality response as an index of host resistance, the C57BL/KsJ was the most susceptible and the C57BL/Ks the least. These findings further support the thesis that genetic predisposition to diabetes mellitus, as characterized by the mutation db on chromosome 4 is associated with a particular susceptibility and host response to coxsackie-virus B4. It also illustrates that under specific conditions, comparison of the response to virus challenge can be used as an indicator of genetic differences between closely related inbred lines.

We studied the reparative process after inhalation exposure to 20 ppm of nitrogen dioxide (NO2) in the lungs of hemizygous blotchy male (Blo/g) and heterozygous blotchy female (Bio/+) mice. Age-matched siblings (C3Hf) without the blotchy gene at X-chromosome locus (+/y) and +/+) served as control animals. After exposure to NO2 for 28 days, there was a marked progression in the extent of emphysema in Blo/y mice associated with a significant decrease of internal surface area (p < 0.05) and an increase in the mean linear intercept (p < 0.005). In contrast, +/y, Blo/+, and +/+ mice showed mild airspace enlargement without decrease in internal surface area after similar exposures. Blo/y mice killed 1 month after cessation of NO2 exposure showed a persistent, mild chronic bronchiolitis that was more frequent and of greater severity than that present in control +/y mice. Alveolar macrophages in the Blo/y mice were larger than those in +/y, +/+, and Blo/+ mice both before and after exposure to NO2. Crystalloid inclusions were observed in the enlarged alveolar macrophages of the Blo/g mice only after exposure to NO2, but were not seen in control animals. These observations indicate that the pattern of lung injury and repair after subacute exposure to 20 ppm of NO2 in the Blo/y mouse differs from that present in age-matched siblings in that inherited abnormalities in alveolar macrophage function may exist in addition to the previously described alterations in connective tissue proteins. Both of these alterations may influence the development of emphysema in the blotchy male mouse.

Cell suspensions from cerebellar primordia of 12-day mouse embryos were grafted into the cerebellum of 4-month-old Purkinje cell degeneration (pcd) mutant mice and examined 2-3 months later. In contrast to those of nontreated mutants, all of the grafted cerebella exhibited Purkinje cells that had migrated into the molecular layer, where they were clustered over its superficial two-thirds. These Purkinje cells develop flattened dendritic trees perpendicular to bundles of parallel fibers. Ultrastructural examination of their synaptic inputs and outputs disclosed that (i) as in normal cerebella, climbing fibers and axons from basket and stellate cells synapse on thick dendrites, whereas parallel fibers almost exclusively contact the distal spiny branchlets, and (ii) a substantial number of Purkinje cell axons reach their appropriate targets in the deep cerebellar nuclei, where they establish synaptic connections on large and small neurons. These results indicate that embryonic Purkinje cells grafted into the cerebellum of adult mice with heredodegenerative ataxia integrate themselves very specifically into the cerebellar circuitry of the recipient mouse, where they can replace the missing Purkinje cells. They also provide a morphological basis favoring the notion of functional restorative capabilities of neural grafts in systems in which neurons are connected in an almost point-to-point manner.

Homozygotes of the mouse mutant limb-deformity (ld) reveal a reduced fertility and a high mortality of newborns. Unilateral and bilateral aplasia of kidneys is very common. In unilateral aplasia the right side is affected most, with no sex preference. All extremities show aplasias and synostoses, with 22 malformation types in the forelimbs and 8 types in the hindlimbs. Primary and secondary fusions of limb elements are found.

The activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase), as a marker for myelinogenesis, was measured in different parts of the nervous system of dilute-lethal mutant mice (d1/d1). The activity in terms of micromoles of 2'-AMP formed per milligram of protein of homogenate per minute was found to be exceedingly reduced in the cerebrum, brain stem, and medulla oblongata, slightly reduced in the cerebellum and cervical spinal cord, but not reduced in the thoracic spinal cord and the optic and sciatic nerves. These results clearly indicate that dilute-lethal mutant mice show poor myelination in the cerebrum, brain stem, and medulla oblongata.

The hypothesis that male diabetes mutant mice (C57Bl/KsJ-db/db) are suffering from impairment of testicular steroidogenic function and pituitary LH release was tested. A smaller postpubertal increase of testicular weight and a reduction of plasma testosterone and androstenedione levels by 65% at 17 weeks of age were most obvious from the comparison to homozygous lean controls. The ability of constant amounts of Leydig cells, either in crude interstitial cell or in purified Leydig cell suspensions, to respond to maximal doses of hCG or cyclic AMP-was reduced by at least 40% in adult diabetes mice. This defect could be attributed to a 40% decrease of steroid-17 alpha-monooxygenase activity as compared to lean mice. No differences occurred, however, if Leydig cells were submaximally stimulated. GnRH-stimulated pituitary LH release was not significantly changed. The impairment of testicular steroidogenic function in diabetes mutant mice may represent a further aspect of infertility of these animals and of diabetes mellitus.

To elucidate the biochemical basis of hereditary muscle diseases in an experimental mammal, we performed polypeptide analyses on skeletal muscles of neuromuscular mutants of the mouse. In one of these, "arrested development of righting response" (adr), the concentration of the soluble Ca2+-binding protein parvalbumin was drastically reduced in comparison to wild type. This reduction was not an unspecific consequence of muscle disease, as it was not observed in two other neuromuscular mouse mutants, "wobbler" (wr) and "motor endplate disease" (med or medjo). Isometric twitches of adr muscle had only slightly prolonged contraction and half-relaxation times, yet long-lasting after-contractions were observed upon repeated (20-100 Hz) direct stimulation. Thus, parvalbumin may be mainly involved in the relaxation after tetanic contraction of fast-twitch fibers.

Sl/Sld mutant mice are profoundly deficient in tissue mast cells as a result of a defect in the microenvironment promoting the development of these cells. To facilitate the analysis of the Sl mutation, we attempted to establish an in vitro system in which the in vivo defect of Sl/Sld mice could be reproduced. 3T3 cell lines were established from 17-day-old embryos of Sl/Sld and congenic +/+ genotypes and were cocultured with mast cells obtained in vitro from the bone marrow of +/+ mice. All eight 3T3 cell lines derived from +/+ of T-cell-derived growth factors. By contrast, none of eight 3T3 cell lines from Sl/Sld embryos supported mast cells under similar conditions. The defect in Sl/Sld 3T3 cells was further characterized as a failure to induce the G1-to-S transition in synchronized mast cells upon contact, suggesting that the Sl gene product is indispensable for this activity. When 3T3 cells of +/+ genotype, grown on pieces of cellulose acetate membrane, were transplanted into the peritoneal cavity of Sl/Sld mice, mast cells appeared locally in the transplanted 3T3 cell layers. These results suggested an essential role of fibroblasts in vivo as the tissue microenvironment promoting the development of mast cells and that they are defective in Sl/Sld mice. The present coculture system duplicated mast-cell deficiency of Sl/Sld mice in vitro and should prove useful for analysis of the Sl gene product.

Compared with normal littermates, the op/op mice had very few macrophages in the peritoneal cavity and severely reduced numbers of monocytes in the peripheral blood. Moreover, osteopetrotic animals demonstrated an altered distribution of hemopoietic tissue with a 10-fold decrease in the number of marrow cells. Liver hemopoiesis persisted in 4-wk-old mice as evidenced by the presence of hemopoietic stem cells (HSC). Moreover, the concentration of HSC was decreased in marrow and increased in the spleen of op/op mice. In spite of the paucity of cells of monocyte-macrophage lineage in vivo, progenitor cells from hemopoietic tissues of op/op mice formed increased numbers of monocyte-macrophage colonies in vitro in the presence of exogenous colony-stimulating activity (CSA). The source of this critical CSA was a medium conditioned by stromal fibroblastoid colonies formed in vitro by normal marrow cells. Therefore, these data suggest that op/op mice possess normal monocyte-macrophage-osteoclast progenitor cells but these cells are unable to fully differentiate in the op/op mouse microenvironment. In support of this, in cultures of stromal fibroblastoid colonies from op/op marrow or spleen, the concomitant growth of macrophages, normally very dense, was drastically reduced. Moreover, transplantation of op/op spleen cells into lethally irradiated littermate recipients resulted in their hemopoietic reconstitution without signs of macrophage defect. Thus, the op/op splenic cells do not transfer the disease and are capable of normal differentiation in normal in vivo environment. These observations support the hypothesis that the defect in op/op mice is a result of the failure of hemopoietic stromal fibroblastoid cells to release sufficient amounts of CSA necessary for normal differentiation of cells of the monocyte-macrophage lineage.

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.

Extracts of liver from hemizygous affected mice with the X-linked spfash mutation have 5 to 10 percent of normal ornithine transcarbamylase (OTC) activity, yet the homogeneous enzyme isolated from these extracts is identical to that in controls. The OTC messenger RNA from mutant livers programs the synthesis of two distinct OTC precursor polypeptides--one normal in size, the other distinctly elongated. Both precursors are imported and proteolytically processed by mitochondria, but only the normal one is assembled into active trimer. This novel phenotype may result from a mutation in the structural gene for OTC leading, primarily, to aberrant splicing of OTC messenger RNA and, secondarily, to formation of a structurally altered precursor whose posttranslational pathway is ultimately futile because its mature mitochondrial form is not capable of assembly and functional expression.

In the mouse, the homozygous presence of the rd gene results in the genetically programmed death of the photoreceptor cells of the retina. Using congenic strains of mice and a novel, sensitive, immunological approach for visualizing unique retinal proteins, we identified four bands of protein whose concentrations are regulated by the homozygous presence of the gene for retinal degeneration. Since these proteins (with apparent molecular weights of 23, 33, 55, and 69 kD) are present in normal adult mouse retinas and absent from rodless retinas, and from other mouse non-retinal tissues including brain, heart, kidney and liver, the data support the identification of these proteins as being retina specific. These proteins are not peculiar to the normal mouse retina; but rather, all four (23, 33, 55 and 69 kD) are common to rat retina; three (23, 33, and 55 kD) are common to bovine retina; and presently at least two, 23 and 69 kD, are clearly detectable in normal, adult human retina. The temporal appearance and disappearance of the four retinal specific protein bands coincide with the morphological maturation and degeneration of the photoreceptor cell population. Collectively, the present data suggest that one or more may be photoreceptor specific. These observations present the first step in the identification and characterization of specific soluble proteins correlated with the biochemical phenotype of the rd gene and the death of photoreceptor cells of the retina.

The X-ray induction of micronuclei and structural chromosomal aberrations was studied in bone-marrow cells of normal and dwarf (dw) mice in combination with thyroxine and/or prolactin treatment or otherwise. Hormone treatment clearly increased micronuclei induction but not chromosome breakage, suggesting that indirect effects were involved. Since no clear differences in the timing of the final stage of erythropoiesis could be found, it is likely that the indirect effects are mediated via the formation-differentiation kinetics of erythroblasts. The induction of reciprocal translocations by X-rays in stem cell spermatogonia of dwarf mice was lower than in normals and treatment with prolactin, growth hormone and/or thyroxin, did not influence the chromosomal radiosensitivity of spermatogonial stem cells.

Pregnant A/WySn mice, 20 to 30% of whose offspring have spontaneous cleft lip, were treated with thyroxine. Following treatment, cleft lip and normal embryos died, but cleft lip embryos died at a higher rate. The increased liability of cleft lip embryos to thyroxine-induced death was considered as a possible experimental route to identify the basic genetic defect that causes cleft lip. A time-response study indicated that cleft lip embryos responded more than normals following treatment on any of days 7 to 12 of gestation, that there is no sharply defined critical period, and that normal and cleft lip embryos do not differ in time of maximum sensitivity. A dose-response study showed linear responses of normal and cleft lip embryos on a probit-log dose scale, with a common slope and LD50's of 1.9 and 1.3 mg respectively. These dose-response properties indicate that normal and cleft lip embryos are probably killed by the same mechanism, but differ in dosage tolerance. That is, they differ quantitatively, not qualitatively. Thyroxine did not significantly change the cleft lip frequency, and the difference between normal and cleft lip embryos that leads to cleft lip itself is therefore not in the same pathway as that which leads to thyroxine-induced death. A hypothetical example of the defect basic to both pathways is presented.

Treatment of Snell dwarf mice with high concentrations of human growth hormone from pituitaries as well as of bacterial origin, significantly increased the frequencies of chromosomal aberrations in bone-marrow cells, as measured by the micronucleus test. In vitro treatment of Chinese hamster ovary (CHO) cells with the two types of hormone likewise induced structural chromosomal aberrations.

The hyt/hyt mouse (BALB/cBY-hyt, C.hytRF) provides a useful model for exploring the effect of inherited severe primary hypothyroidism. Studies were undertaken to try to define the basis of the primary hypothyroidism in mice homozygous for the autosomal recessive gene, hyt. These mice had congenital hypothyroidism of fetal onset after 15 days post conception. Through their lifetime, the hyt/hyt mice had reduced serum thyroxine (T4), triiodothyronine (T3), reduced thyroid gland intralumenal colloid on electron microscopy and a 100-fold elevation of TSH-like activity compared to hyt/+ littermates. Thyroglobulin made in hyt/hyt animals was similar in size to normal thyroglobulin which was inconsistent with a major structural thyroglobulin gene defect. The thyroglobulin was iodinated. Marked, erratic dilation of rough endoplasmic reticulum (RER) was noted in hyt/hyt mouse follicular cells. Despite these ultrastructural findings, pulse chase and immunoprecipitation studies with isolated hyt/hyt and normal thyroid glands indicated that normal thyroglobulin processing occurred in the RER and Golgi of the hyt/hyt mice. The hyt/hyt thyroid glands were hypoplastic compared to hyt/+ littermates. Histologically, the hyt/hyt thyroid glands demonstrated an increase in smaller follicular cells, and greater variability in follicular size compared to hyt/+ littermates. Histological and ultrastructural abnormalities in the gland were similar to those seen in certain cases of human congenital hypothyroidism with TSH receptor insensitivity of the thyroid gland. These findings along with the significant TSH elevation, the reduction in colloid and in serum T3 and T4, the efficacy of the hypothalamo-pituitary-thyroid feedback system, and previous observations of reduced iodine uptake and intrathyroidal T4, suggested that primary hypothyroidism in the hyt/hyt mouse might be due to a defect in TSH responsivity of the thyroid gland.

Neonatal unirradiated mice of W-mutant genotypes, with a hematopoietic stem cell defect and anemia, were injected i.v. with normal fetal liver hematopoietic cells. Efficient, long-term engraftment occurred as a result of the competitive advantage to the donor stem cells. The frequency of engraftment and rate of repopulation characteristically diminish in the series W/Wv, Wf/Wf, and Wv/+, in which the severity of the endogenous defect is progressively less. H-2 compatibility is required in the inbred strain combinations examined; other histocompatibility loci play a minor role in some strain combinations. Engraftment is due to self-renewing hematopoietic stem cells ancestral to myeloid and lymphoid lineages. The more mildly defective mutants display much greater variability in the kinetics of repopulation--a result consistent with seeding by single, or very few, stem cells that form developing clones. Engraftment efficiency is reduced by prolonged culture of fetal liver cells during experimental infection by recombinant retroviruses; nevertheless, after 24 h in vitro to achieve retroviral marking, stem cells retain their ability to repopulate and develop in W/Wv neonates.

Beige (C57BL/6J-bgj/bgj) mice are the murine counterpart of the Chédiak-Higashi syndrome, exhibiting abnormal lysosomes in phagocytes. These mice, however, responded normally to Corynebacterium parvum killed bacterial vaccine with splenomegaly and an increase in peritoneal macrophages. The C. parvum-elicited macrophages showed normal immunoglobulin G Fc- and C3b-mediated rosettes and phagocytosis. The antitumor action of the macrophages was assessed against the Lewis lung carcinoma, a tumor that is sensitive to inhibition by activated macrophages both in vitro and in vivo. The elicited macrophages from beige mice showed delays in vitro in cytostatic and cytotoxic activity against the tumor cells, as compared with C57BL/6J-+/+ control mice. The early delays in activity disappeared after 12 to 24 hr, when antitumor activity was similar to that exhibited by C. parvum-elicited macrophages of the C57BL/6J-+/+ mice. These delays in antitumor activity of beige mouse macrophages may be analogous to the delays observed in the bactericidal activity of beige mouse granulocytes. The ultimate antitumor activity, however, was comparable in beige and +/+ C. parvum-elicited macrophage. Moreover, the resistance of mice in vivo to the Lewis lung tumor was not markedly impaired. The growth of the primary tumors and the mean times to death of the tumor-bearing animals of both strains were similar.

Black and albino littermate mice of the same inbred strain were compared to see if precocious development of the visual system, as indicated by the first detected eye-opening within a litter, is due to alleles at the albino locus. In 32 litters of C57BL/6J-c2J mice the frequency of first detected eye-opening in albinos was not significant; there were no sex or maternal effects. In 16 litters of B10.D2/nSn-c4J mice the frequency of first detected eye-openings in male, but not female, blacks was significant; there were no maternal effects. The results surely do not rule out the possibility of abnormalities in the timing of the developmental sequence of the visual system in albinos; The entire sequence must be examined with appropriate genetic controls.

Mast cells are critical for the expression of certain IgE-mediated responses, but the precise contributions of mast cells to biological processes not involving IgE are obscure. We have employed genetically mast cell-deficient WBB6F1-W/Wv and WCB6F1-S1/S1d mice to investigate the roles of mast cells in several different biological responses. This work strongly suggests that mast cells are not required for the elicitation of contact sensitivity (CS) responses, suppressor T cell-dependent tolerance to CS, reserpine-induced inhibition of CS responses, or bleomycin-induced pulmonary fibrosis. By contrast, mast cells appear to contribute to the acute gastric injury induced by ethanol and the acute inflammation of the skin induced by croton oil.

The open-eye birth defect of mice caused by the lgMl mutation was prevented by prenatal administration of thyroxine (T4) to the pregnant mother. Treatment on days 10 to 11 of gestation was most effective in preventing open-eyes. A contrasting worsening of the defect was seen after treatment on day 14 of gestation. A dose-response relationship for prevention appeared to be present up to a dose of 0.1 mg/mouse, after which 39% of fetuses had both eyes closed compared to 2% in controls. Higher doses appeared to give little or no further increase in beneficial effect. Scanning electron microscopy was used to compare thyroxine-treated and untreated lgMl/lgMl and normal CBA/J day 16 or 17 fetal eyes. Mutant eye closure after thyroxine differed from untreated mutant in the growth of both upper and lower eyelids across the eye and in increased numbers of rounded periderm cells on the advancing lid edges. The underlying epithelial tissue layer appeared to fuse closed. The induced eye closure in the mutant was not normal, however. The periderm cell layer had disorderly fusion at the outer canthus, premature flattening, and failure to fuse in the inner canthus.

The lethal 't alleles' of the T complex on mouse chromosome 17 (refs 1, 2) have been assigned to six complementation groups (the definitive classes being t0, t9, t12, tw1, tw5 and tw73), each causing embryonic death at a particular stage. Intercomplementation heterozygotes (txty) show 'partial' complementation, so that only some txty offspring survive. These survivors appear morphologically normal; indeed the females, being fertile, seem entirely normal. The txty males, however, are sterile. Among the reasons given for this sterility in some txty males are low motility of the txty spermatozoa, and an inability to effect fertilization either in vitro or in vivo even when already present at the site of fertilization. Spermatozoa from sterile txty males were reported to be apparently present in 'normal' numbers in the uterus, although actual ejaculate numbers have not been quoted for these, or indeed for normal fertile males. In the human, typical ejaculate counts of less than 20 x 10(6) spermatozoa, where the normal ejaculate contains 100-250 x 10(6), are judged to indicate clinical sterility. The comparison of numbers of spermatozoa10 ejaculated into the female tract by sterile t6tw5, t6tw32 and tw5tw32 (all 'strong' mutations2) and control mice clearly shows an even greater oligozoospermia (about 100 times less than controls) occurring in the txty males.

Mice homozygous for the beige gene (bg/bg) are a homologue of the Chédiak-Higashi syndrome of man and are known to be selectively defective in natural killer (NK) cells. We have compared the susceptibility of bg/bg and bg/+ C57BL/6J mice to infection with murine cytomegalovirus (MCMV). Beige mice are more susceptible to lethal infection and develop 33- to 43-fold higher virus titers in the liver, spleen, and kidney than do bg/+ mice after a sublethal infection, although virus replication is the same in vitro in cultured fibroblasts or epithelial cells from these mice. Inoculation with a sublethal dose of virus stimulates a NK cell response, although this is lower in bg/bg mice despite higher titers of interferon type 1 than in bg/+. A dose of MCMV that is lethal only to bg/bg augments cytotoxicity within 12 hr in bg/+ mice, whereas cytotoxicity in bg/bg remains very low. In bone marrow chimeras, recipients of bg/bg marrow were more susceptible to MCMV and had lower NK cell responses after virus inoculation than did recipients of marrow from bg/+ donors. The greater susceptibility of beige mice to the virus suggests that NK cells may contribute to resistance early in McMV infection.

Adrenalectomy (ADX) prevents the excessive weight gain in the genetically obese ob/ob and db/db mice. To test the possibility that this results from increased energy expenditure due to increased thermogenesis in brown adipose tissue (BAT), we measured GDP binding to mitochondria from interscapular brown adipose tissue (BAT) in db/db and ob/ob mice and their lean controls after adrenalectomy, with and without corticosterone replacement. Both the vehicle treated and corticosterone treated db/db and ob/ob mice had lower body weights than the sham-operated mice GDP binding to mitochondria from IBAT was significantly lower in both the db/db and ob/ob mice than in their lean controls. Adrenalectomy significantly increased GDP binding in all mice compared to the respective sham-operated mice, but, the percentage increase was always greater in the db/db and ob/ob mice. Corticosterone treatment of adrenalectomized db/db, ob/ob or lean mice lowered GDP binding to sham levels. Our data confirm previous findings that adrenalectomy results in increased GDP binding to mitochondria from IBAT. Injections of corticosterone into adrenalectomized mice results in a decrease in GDP binding to values which are similar to values in sham-operated mice. Thus adrenalectomy may inhibit the development of obesity by increasing the thermic activity in IBAT.

Observations that the long-sleep (LS) and short-sleep (SS( mouse lines differ in their depressant response to barbiturates, and that the difference between lines becomes greater as lipid solubility increases, prompted this investigation of the effects of alcohols that differ in lipid solubility. Results indicate that LS and SS mice differ significantly in their sleep time responses to propanol, butanol, and 3-methyl butanol, as well as ethanol: their hypothermic responses showed a similar pattern, but only the response to ethanol differed significantly between lines. For both sleep time and hypothermia, the difference between lines decreased with increasing lipid solubility. In all cases, the LS mice were more sensitive than the SS to the depressant effects of the alcohol. Similar ratios of SS:LS waking brain ethanol and butanol levels indicated that CNS sensitivity to long-chain alcohols is similar to that for ethanol. A pharmacokinetic study revealed higher ethanol levels for LS than for SS mice at all time points in blood, fat, and brain body compartments. Blood ethanol elimination curves showed that the SS mice eliminate ethanol at a faster rate than do the LS.