C57BL/6J Research Articles

Mapping anti-müllerian hormone ( amh) and related sequences in the mouse: Identification of a new region of homology between MMU10 and HSA19p

A panel of 78 backcross progeny, BALB cJ × ( BALB cJ × CAST Ei )F 1 was used to map the gene encoding anti-Müllerian hormone ( Amh), also called Müllerian inhibiting substance, to mouse Chromosome 10 (MMU10). This analysis identified a new region of linkage homology between human Chromosome 19p (HSA 19p) and MMU10 and localized an apparent recombinational hot spot in ( C57BL 6J × Mus spretus) F 1 females [compared with ( BALB cJ × CAST Ei )F 1 males] to the interval between phenylalanine hydroxylase ( Pah) and mast cell growth factor ( Mgf). In addition, eight unlinked polymorphic sequences, provisionally designated Amh-related sequences ( Amh-rs1 through Amh-rs8), were identified by Southern blot analysis using Amh probes. Amh-rs1, -rs2, -rs4, and -rs7 were mapped to MMU1, 13, 12, and 15, respectively, by recombinant inbred (RI) strain and intraspecific backcross analyses. The NXSM RI strain distribution patterns for the four unmapped loci are also presented.

Mapping genes encoding drug-metabolizing enzymes in recombinant inbred mice

Probes for cytochrome P450IVA (P450IVA), α- and π-class glutathione S-transferases (GST), and phenol-metabolizing UDP-glucuronyltransferase (UDPGT-K39) detected restriction fragment length variants (RFLVs) between C57BL 6J and DBA 2J mice. These variants were used to map the P450IVA genes ( Cyp4a) to chromosome 4, close to Mtv-13 and Pmv-19, midway between brown ( b) and Gpd-1; GSTα genes were mapped to chromosome 9, with a cross-hybridizing sequence mapping to another chromosome; the GSTπ genes were mapped to the distal end of chromosome 1 near Pmv-21; one UDPGT-K39 variant to chromosome 1, between Acrg and Emv-17, and another showed linkage to Odc-10 on an unidentified chromosome. No RFLVs were detected with probes for P450IID, P450 reductase, androsterone-metabolizing UDPGT, GSTμ, or microsomal GST.

Molecular genetic linkage maps of mouse chromosomes 4 and 6

We have generated a moderate resolution genetic map of mouse chromosomes 4 and 6 utilizing a ( C57BL 6J × Mus spretus) F1 × Mus spretus backcross with RFLPs for 31 probes. The map for chromosome 4 covers 77 cM and details a large region of homology to human chromosome 1p. The map establishes the breakpoints in the mouse 4-human 1p region of homology to a 2-cM interval between Ifa and Jun in mouse and to the interval between JUN and ACADM in human. The map for mouse chromosome 6 spans a 65-cM region and contains a large region of homology to human 7q. These maps also provide chromosomal assignment and order for a number of previously unmapped probes. The maps should allow the rapid regional assignment of new markers to mouse chromosomes 4 and 6. In addition, knowledge of the gene order in mouse may prove useful in determining the gene order of the homologous regions in human.

Social success and voluntary ethanol consumption in mice of C57BL/6J and CBA/Lac strains

Voluntary ethanol (20% solution) consumption in mice of C57BL/6J (C57) and CBA/Lac (CBA) strains with consecutive experience of victories (winners) or defeats (losers) in daily intermale agonistic confrontations were studied. Winners and losers of the CBA strain maintained the ethanol consumption on the same level. Losers of the C57 strain increased the ethanol consumption most dramatically during the second week of testing, while winners of this strain did not change the ethanol intake. The aspiration to the social contact estimated by behavioral activity as a reaction to the other male significantly increased in “drinking” losers of the C57 strain. The influence of heredity and emotional state of animals formed by their social success on voluntary ethanol consumption are discussed.

Comparison of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin‐mediated hepatotoxicity in C57BL/6J and DBA/2J mice

The toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was examined by clinical chemistry and liver histopathology in Ah-responsive C57BL/6J (C57) and Ah-nonresponsive DBA/2J (DBA) mice. Hepatotoxicity was assessed at 1, 3, and 7 d following a single ip injection of TCDD at doses that maximally induce hepatic aryl hydrocarbon hydroxylase (AHH) activity (3 micrograms/kg for C57 and 30 micrograms/kg for DBA mice) and at doses approaching the LD50 (150 micrograms/kg for C57 and 600 micrograms/kg for DBA mice). Histological examination of liver sections was found to be a more sensitive detection method for TCDD-induced hepatic changes than clinical chemistry analyses. Dramatic differences in the development and type of liver injury were observed between TCDD-treated C57 and DBA mice. C57 mice given 3 micrograms TCDD/kg developed mild to moderate hepatic lipid accumulation in the absence of both inflammation and necrosis. Severe fatty change and mild inflammation and necrosis occurred in C57 mice that received 150 micrograms TCDD/kg. In contrast, DBA mice exposed to 30 micrograms TCDD/kg developed hepatocellular necrosis and inflammation without any fatty change. Only slight hepatic lipid accumulation occurred with some necrosis and inflammation in DBA mice given 600 micrograms TCDD/kg. The Ah locus may play a role in determining the sensitivity of C57 mice to the steatotic effects of TCDD.

Unique alterations of neuropeptide content in median eminence, amygdala, and dorsal vagal complex of 3- and 6-week-old diabetes mutant mice

The nature of the genetic defects which define the obese ( ob) and diabetes ( db) loci in mice remain unknown, but both produce similar syndromes when maintained in the same strain of mice. There is some evidence suggesting a lesion in the central nervous system (CNS) in db db mice, while ob ob mice appear to have a primary lesion outside the CNS. In a search for further evidence of a unique central lesion in db db mice, we have examined neuropeptide content in selected, microdissected brain areas in both of these mutants and lean controls. In order to rule out possible interactions of the db mutation with the genetic background, diabetes mice of both C57BL KsJ and C57BL 6J strains were studied. When concentrations of nine neuropeptide immunoreactivities were examined in up to seven microdissected areas of the brain, C57BL 6J ob ob mice showed only one reproducible alteration, a lower content of β-endorphin-like immunoreactivity (LI) in the preoptic area at both 3 and 6 weeks of age as compared with lean littermates. In contrast, db db mice of both C57BL 6J and C57BL KsJ strains exhibited alterations in a total of four peptides in three brain areas: lower concentration of somatostatin-LI in median eminence, higher Met-enkephalin-LI in dorsal vagal complex of the medulla oblongata, higher substance P-LI and lower vasoactive intestinal polypeptide (VIP)-LI in amygdala. The concentrations of the peptides studied in medial basal hypothalamus, lateral hypothalamus, substantia nigra, and preoptic area were not reproducibly altered in db db mice. These data provide preliminary evidence for unique brain abnormalities in db db mice in specific areas that are involved in processing of neural signals that can affect the islets of Langerhans, gonadotropin secretory patterns, and many other visceral functions. The observations suggest that selected neurons or fibers in the amygdala, dorsal vagal complex (DVC), and/or median eminence may be directly affected by the genetic defect in db db mice, ultimately resulting in obesity, insulin resistance, and hyperinsulinemia, as well as associated endocrine abnormalities. The very different findings in brain areas of ob ob mice are consistent with the hypothesis that a somewhat different mechanism, or possibly a defect in a different component of the same neuroendocrine pathway, is primarily involved in producing the similar syndrome in ob ob mice of the same strain.

Mapping of Col3a1 and Col6a3 to proximal murine chromosome 1 identifies conserved linkage of structural protein genes between murine chromosome 1 and human chromosome 2q

We have investigated the degree of synteny between the long arm (q) of human chromosome 2 and the proximal portion of mouse chromosome 1. To define the limits of synteny, we have determined whether mouse homologs of seven human genes mapping to chromosome 2q cosegregated with anchor loci on mouse chromosome 1. The loci investigated were NEB Neb , ELN Eln , COL3A1 Col3a1 , CRYG len-2 , FN1 Fn-1 , VIL Vil , and COL6A3 Col6a3 . Ren-1,2 and Acrg were included as two proximal mouse chromosome 1 anchor loci. The segregation of restriction fragment length polymorphisms at these loci was analyzed in the progeny of Mus spretus × C57BL 6J hybrids backcrossed to the C57BL 6J inbred strain. We found that five of the structural protein loci and the two anchor loci form a linkage group on proximal murine chromosome 1. The proposed gene order of this group of linked markers is centromere -Col3a1 - Len-2-Fn-1-Vil-Acrg-Col6a3-Ren1,2-Neb and Eln are linked neither to each other nor to any other marker on proximal mouse chromosome 1. Therefore, the mouse loci Col3a1 and Col6a3 are identified as flanking markers of the linkage group of structural protein loci. The estimated genetic map distances are Col3a1-13.3 cM- Len-2-3.4 cM- Fn-1-3.8 cM- Vil-9.6 cM- Acrg-2.1 cM- Col6a3-18.3 cM- Ren1,2. The available map information for human chromosome 2q markers and mouse chromosome 1 markers presented here tentatively identifies Col3a1 and Col6a3 as the border markers that define the limits of the syntenic chromosome segment. The order of mouse genes on chromosome 1 and their human homologs on chromosome 2q also appears to be conserved, suggesting that mapping of murine genes on the conserved segment may be useful to predict gene order in man.

Innate and adaptive immune responses in a social conflict paradigm

Social conflict stress was examined for its effects on in vitro and in vivo immunity in mice. Adaptive immunity, as measured by the generation of primary IgM antibody responses to the T-dependent antigen keyhole limpet hemocyanin, was suppressed following chronic (>1 day), but not acute (<1 day), stress periods while the IgM response to the T-independent antigen polyvinylpyrrolidone was not affected. In vitro proliferative responses of splenocytes to the T cell mitogen concanavalin A and the B cell mitogen lipopolysaccharide were unaffected. Acute (<1 day) stress dramatically increased innate immunity as measured by a luminol-dependent chemiluminescence assay of phagocytic cell function. DBA 2J mice averaged a 269% increase in phagocytosis as compared to a 412% increase in C57BL 6J . This differential effect of stress on immune responsiveness indicates that alterations in innate immunity in addition to adaptive immunity should also be considered when evaluating neuroendocrine and immune interactions in response to stress.

The murine situs inversus viscerum ( iv) gene responsible for visceral asymmetry is linked tightly to the Igh-C cluster on chromosome 12

The iv gene controls left-right determination during murine organogenesis. To map this gene, we analyzed backcross progeny produced by mating ( C57BL 6J × MEV Ty )F 1 -iv/+ heterozygotes to C57BL 6J -iv homozygotes. Hybridization of a murine ecotropic virus probe and several homeotic box gene probes coupled with analysis of dominant visible markers enabled us to exclude the iv locus from much of the mouse genome. Spurred by a recent report that mapped the iv gene to mouse chromosome 12 which was not excluded by our previous work, we used the polymerase chain reaction on our larger cohort to determine that the iv gene is indeed linked tightly to the Igh-C locus on this chromosome: we observed 0 156 recombinants between the iv and Igh-C loci. Combining data from the two studies demonstrates that the murine iv gene is close ( 1 201 recombinants) to the Igh-C cluster on chromosome 12.

Differential toxicity of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) in [formula omitted] mice congenic at the Ah locus

The acute toxicity of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) was examined in male C57BL 6J mice differing only at the Ah locus. Wild type mice ( Ah b b ; “ b b ” ) were treated once with 0, 50, 100, 200, 300, and 400 μg TCDD/kg po while congenic mice ( Ah d d ; “ d d ” ) received a single dose of 0, 400, 800, 1600, 2400, and 3200 μg TCDD/kg. Mice were checked daily, weighed twice a week, and those that survived, killed 35 days post-treatment. The LD50 values were 159 and 3351 μg/kg for b b and d d mice, respectively. Mean time to death was 22 days and was independent of dose and genotype. Decrease in body weight gain was noted in both strains 5 days after treatment and occurred at doses ≥ 100 μg/kg in b b mice and 1600 μg/kg in d d mice. Dose-related increases in liver weight (both absolute and relative to body weight) and decreases in thymus, spleen, testes, and epididymal fat pad weights were observed at 8–24-fold higher doses in d d than in b b mice. A dose-related increase in segmented neutrophils was observed in both strains. Serum chemistry values indicated that 8–24× greater doses of TCDD were needed to elevate sorbitol dehydrogenase, alanine aminotransferase, and 5′-nucleotidase and to decrease total and esterified cholesterol in d d than in b b mice. Few effects were seen on total bile acids, serum triglycerides, glucose, or nonesterified cholesterol. In the liver, hepatocellular cytomegaly, fatty change, and bile duct hyperplasia occurred in both strains in a dose-related manner, as did thymic and splenic atrophy. Necrosis of germinal epithelium in the testes and edema in the stomach submucosa occurred at acutely toxic doses. These lesions also occurred at doses 8–24× greater in d d than in b b mice. Thus, the spectrum of toxicity is independent of the allele at the Ah locus, but the relative dose needed to bring about various acute responses is approximately 8–24× greater in congenic mice homozygous for the “d” allele than for the wild type animals carrying two copies of the “b” gene.

Effects of an α2-adrenoceptor antagonist on glucose tolerance in the genetically obese mouse ( [formula omitted][formula omitted

This study examines the effects of a relatively selective α 2-adrenoceptor antagonist, 8-( l-piperazinyl)imado-[1,2-α] pyrazine (compound A), and the preferential α 2-agonist clonidine on blood glucose, glucose tolerance, and plasma insulin levels in the C57BL 6J ob ob mouse and its lean littermate. While clonidine raised blood glucose levels and impaired glucose tolerance, oral administration of compound A resulted in decreased blood glucose levels, as well as improved glucose tolerance in ob ob mice. Insulin levels in ob ob mice treated with clonidine were significantly reduced, while compound A raised insulin levels threefold and blocked the effects of clonidine when co-administered to the same animals. Clonidine-induced hyperglycemia in lean littermates was not accompanied by a decrease in insulin levels, while a small but significant increase in insulin levels was observed by compound A administration. Glycogen synthesis in diaphragm of ob ob mice was enhanced after oral administration of compound A and was accompanied by an increase in plasma insulin levels. Concomitant treatment with a potent somatostatin analog to inhibit insulin release blocked the effects of the α 2-adrenoceptor antagonist, compound A. These observations suggest that the α 2-antagonist studied, increased plasma insulin levels with an accompanying reduction in blood glucose and an improvement in glucose tolerance in a genetic model of insulin resistance. Differential sensitivity to α 2-agonist in these genetically obese mice, ob ob , was demonstrated by decreased insulin levels due to clonidine administration.

Pharmacokinetics of [ 125I]-2-lodo-3,7,8-trichlorodibenzo- p-dioxin in mice: Analysis with a physiological modeling approach

2,3,7,8-Tetrachlorodibenzo- p-dioxin (TCDD) is a potent inducer of hepatic microsomal enzymes. The influence of an inducing dose of TCDD on tissue distribution and other pharmacokinetic behavior of a TCDD analog in the mice was examined by employing a high specific activity radioligand, [ 125I]-2-iodo-3,7,8-trichlorodibenzo- p-dioxin (ITCDD). Female C57BL 6J mice were pretreated with 0.1 μmol/kg of TCDD or the vehicle only, followed by 0.1 nmol ITCDD/kg 3 days later. The control animals had the highest concentration of ITCDD-derived radioactivity in the fat, but the TCDD-pretreated animals had the highest concentration in their livers. Whole-body elimination of ITCDD approximated first-order behavior, and induction by pretreatment with the inducing dose of TCDD almost doubled the rate of excretion (control mice, t 1 2 = 14.2 days ; pretreated mice, t 1 2 = 8.0 days ). All disposition results in naive and pretreated mice were satisfactorily described by a consistent physiologically based pharmacokinetic model (Leung el al., 1988a) in which induction increased the amount of microsomal ITCDD-binding protein from 1.75 to 20 nmol/liver and increased the rate constant for metabolism of free ITCDD from 1 to 3/hr/kg liver. The binding affinity of the microsomal ITCDD-binding protein was the same (20 n m) in both induced and noninduced mice. Model simulations indicated a time delay in the elimination of nonparent ITCDD metabolites from the body and a more rapid absorption of the parent ligand in the pretreated mice. Consistent with previous physiological modeling with TCDD in different mouse strains, the primary factor influencing the liver/fat concentration ratio appears to be the affinity and capacity of the microsomal TCDD-binding proteins, which are altered by induction. These dose-dependent pharmacokinetic differences with ITCDD are important considerations for TCDD risk assessment in which data from high dose rodent experiments are extrapolated to predict behavior at much lower environmental concentrations in exposed humans.

2,3,7,8-Tetrachlorodibenzo- p-dioxin pretreatment of female mice altered tissue distribution but not hepatic metabolism of a subsequent dose

Lipid partitioning of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) inadequately explains its tissue distribution since higher concentrations occur in liver than fat except at high doses. This study provides in vivo evidence that an inducible, saturable system plays a predominant role in disposition of [ 14C]TCDD in female mice at doses between 5 and 20 μg/kg. Female C57BL 6J mice were gavaged with 0, 5, or 15 μg TCDD/kg, received a subsequent gavage of 5 or 20 μg [ 14C]TCDD after 6 days, and were killed 1 day later. In mice pretreated with 5 and 15 μg TCDD/kg and subsequently dosed with 20 μg [ 14C]TCDD/kg, liver weight and [ 14C]TCDD concentration increased. Total liver [ 14C]TCDD burden increased about 50% in both pretreatment groups. Concentrations of [ 14C]TCDD in kidney, fat, heart, lung, gastrointestinal tract, but not plasma or splenic lymphocytes, decreased in a reciprocal manner. Alterations in absorption, concentrations of polar metabolites of [ 14C]TCDD in liver, and hepatic lipid content failed to explain these results. About 97% of hepatic 14C was hexane extractable. HPLC of this extract indicated [ 14C]TCDD was the only significant nonpolar form of radiolabel in liver. In mice pretreated with 5 μg TCDD/kg and subsequently dosed with 5 μg [ 14C]TCDD/kg, a more marked pretreatment disposition response was observed. These results are consistent with a predominant role for an inducible, high affinity, low capacity system in whole animal pharmacokinetics of TCDD.

The gene for the ubiquitous octamer-binding protein Oct-1 is on human chromosome 1, region cen-q32, and near Ly-22 and Ltw-4 on mouse chromosome 1

Oct-1 is a sequence-specific transcription and DNA replication factor that recognizes the octameric sequence ATGCAAAT. This protein shares an extended region of sequence similarity, called the POU domain, with the lymphoid-specific transcription factor Oct-2, the pituitary-specific transcription factor Pit-1, and the Caenorhabditis elegans cell lineage gene product unc-86. Two subdomains, POU-related homeobox and POU-specific box, lie within the POU domain. Unlike other POU or homeodomain proteins. Oct-1 is ubiquitously expressed. A ubiquitous 95- to 100-kDa protein that has the same DNA-binding properties and is variously referred to as OTF-1, NFIII, or OBP100 is probably identical to Oct-1. The human gene was mapped by Southern blot analyses of human × rodent hybrid cell lines to chromosome 1, region cen-q32. In Chinese hamster × mouse hybrid cell lines the mouse locus was also mapped to chromosome 1. With the BXD (from progenitor strains C57BL 6J and DBA 2J ) set of recombinant inbred strains of mice, the murine gene was localized on the linkage map of mouse chromosome 1. There were no recombinants among 26 strains with Ly-22 and 1 recombinant among 24 strains with Ltw-4. The gene symbol is OTF1 for humans and Oct-1 for mouse.

Genetic heterogeneity of lipoproteins in inbred strains of mice: Analysis by gel-permeation chromatography

To assess genetic variation of murine lipoprotein profiles, plasma lipoproteins of 11 inbred strains, AKR J , BALB cByJ , C3H HeJ , C57BL 6J , C57BL 6ByJ , C57L J , DBA 1LacJ , 129 J , NZB B1NJ , PL J , and SWR J , were analyzed by gel-permeation chromatography (fast peptide liquid chromatography) and nondenaturing gradient gel electrophoresis. Vena caval blood was drawn after 18 to 20 hours of fasting. Plasma triglyceride and cholesterol concentrations ranged from 12.9 mg/dL ( C57BL 6ByJ ) to 66.9 mg/dL ( C3H HeJ ) and from 54.8 mg/dL ( AKR J ) to 128.5 mg/dL ( NZB B1NJ ), respectively. Mouse strain-related heterogeneities of very low-, low-, and high-density lipoprotein (VLDL, LDL, and HDL, respectively) concentrations were documented; VLDL-triglyceride concentrations ranged from 7.5 mg/dL to 38.8 mg/dL, LDL cholesterol from 12.0 mg/dL to 39.6 mg/dL, and HDL cholesterol from 41.3 mg/dL to 92.4 mg/dL. Hyper-VLDL-triglyceridemia was present in C3H HeJ and SWR J strains and hyper-LDL-cholesterolemia in NZB B1NJ , C3H HeJ , and DBA/1 LacJ. VLDL cholesterol/VLDL triglyceride ratios also ranged widely among strains (0.13 to 0.43), with C57BL 6J , C57BL 6ByJ , and C57L J , the strains particularly susceptible to diet-induced atherosclerosis, having the highest VLDL-lipid ratio. LDL and HDL size heterogeneities were also observed. LDL and HDL diameters ranged between 24.1 nm and 29.4 nm, and between 9.24 nm and 10.32 nm, respectively. Although LDL sizes showed no segregation, HDL sizes fell into two groups. C57L J and C57BL 6J possessed low HDL-cholesterol concentrations and small-sized HDL. HDL sizes were positively correlated with HDL-cholesterol concentrations ( r = .90, P < .001) and LDL-cholesterol concentrations ( r = .85, P < .001), but LDL sizes did not correlate with lipoprotein concentrations. The correlation between HDL sizes and HDL cholesterol concentrations was still significant ( r = .88, P < .003), even if C57L J and C57BL 6ByJ , which are similar to C57BL 6J , were omitted from the analysis. Further studies on the contributions of genetic and dietary factors to the strain-related lipoprotein heterogeneities in inbred strains of mice should prove to be useful for understanding the control of lipoprotein metabolism.

A molecular genetic linkage map of mouse chromosome 4 including the localization of several proto-oncogenes

We have constructed a 64-cM molecular genetic linkage map of mouse chromosome 4 using interspecific backcross animals derived from mating C57BL 6J and Mus spretus mice. Several proto-oncogenes and common sites of viral integration have been assigned regional locations on chromosome 4 including Mos, Lyn, Jun, Lmyc, Lek, Fgr, and Dsi-1. Additional loci mapped in this study to chromosome 4 were Tsha, Mup-1, Rrm2-ps1, Ifa, and Anf. A comparison of our mapping data with inbred strain mapping data did not show any evidence for inversions or deletions on chromosome 4. New regions of synteny were defined between mouse chromosome 4 and human chromosomes 1 and 8; a region of homology was found between mouse chromosome 4 and human chromosome 6. This linkage map will provide a framework for identifying homologous genes in mice and humans that may be involved in various disease processes.

Characterization of a highly unstable mouse minisatellite locus: Evidence for somatic mutation during early development

A highly unstable mouse minisatellite locus, Ms6-hm, has been identified in mouse DNA fingerprints produced by cross-hybridization with human minisatellite probe 33.6. A 7-kb allele of Ms6-hm was cloned from a C57BL 6J mouse and collapsed to a 400-bp plasmid insert on propagation in Escherichia coli due to loss of the majority of minisatellite repeat units. Sequence analysis revealed that Ms6-hm has evolved by amplification within a member of the MT (mouse transcript) family of interspersed repetitive elements. Linkage analysis localized Ms6-hm near the brown coat color gene ( b) on chromosome 4. Multiallelism and heterozygosity at this locus within inbred strains result from a high germline mutation rate to newlength alleles (2.5% per gamete). Mice mosaic for cells carrying a nonparental allele in somatic tissue, and in some cases also in the germline, provide evidence for additional, somatic, mutation events at Ms6-hm. In two mosaic mice the fraction of cells containing the nonparental allele has been shown to be indistinguishable in different adult tissues. These somatic mutation events at Ms6-hm must therefore occur very early in development, preceding the allocation of somatic lineages, and the same pool of primitive ectoderm cells must contribute equally to all somatic tissues. Under low-stringency hybridization conditions the collapsed subclone of Ms6-hm cross-hybridizes to other unstable loci in the mouse genome to generate a novel and highly individual specific mouse DNA fingerprint.

Localization of the mouse gene for secreted phosphoprotein 1 ( Spp-1) (2ar, osteopontin, bone sialoprotein 1, 44-kDa bone phosphoprotein, tumor-secreted phosphoprotein) to chromosome 5, closely linked to Ric (Rickettsia resistance)

We have used a cDNA probe for mouse secreted phosphoprotein 1 (Spp-1, also known as 2ar, osteopontin, bone sialoprotein 1, 44-kDa bone phosphotein, tumor-secreted protein) to find a restriction fragment length polymorphism in the gene from C57BL 6J and DBA 2J mice. The strain distribution pattern in 25 BXD recombinant inbred lines is identical with that previously determined for the dominant, autosomal gene, Ric r ( Rickettsia resistance). This places Spp-1 on mouse chromosome 5 with a 95% confidence limit of being within 4.32 cM of Ric. Evidence supporting the possibility of allelism between Spp-1 and Ric is briefly discussed.

2,2′,4,4′,5,5′-Hexachlorobiphenyl as a 2,3,7,8-tetrachlorodibenzo- p-dioxin antagonist in [formula omitted] mice

At doses as high as 750 to 1000 μmol/kg, 2,2′,4,4′,5,5′-hexachlorobiphenyl (HCBP) did not cause fetal cleft palate, suppress the splenic plaque-forming cell response to sheep red blood cells, or induce hepatic microsomal ethoxyresorufin O-deethylase (EROD) in C57BL 6J mice. Despite the lack of activity of HCBP in eliciting any of these aryl hydrocarbon (Ah) receptor-mediated responses, competitive binding studies indicated that HCBP competitively displaced 2,3,7,8-[ 3 H] tetrachlorodibenzo-p- dioxin (TCDD) from the murine hepatic cytosolic receptor. Cotreatment of C57BL 6J mice with TCDD (3.7 nmol/kg) and HCBP or 4,4′-diiodo-2,2′,5,5′-tetrachlorobiphenyl (I 2-TCBP) (400 or 1000 μmol/kg) showed that both compounds partially antagonized TCDD-mediated cleft palate and immunotoxicity (i.e., suppression of the splenic plaque-forming cell response to sheep red blood cells), and HCBP antagonized TCDD-mediated hepatic microsomal EROD induction. Thus, HCBP and I 2-TCBP, like the commercial polychlorinated biphenyl mixture Aroclor 1254, were partial antagonists of TCDD action in C57BL 6J mice; however, it was also apparent from the results that Aroclor 1254 was the more effective antagonist at lower doses. Using [ 3 H] TCDD , it was also shown that some of the effects of HCBP on TCDD-mediated cleft palate may be due to the decreased levels of TCDD found in the fetal palates after cotreatment with TCDD and HCBP. 4,4′-[ 125 I 2] diiodo-2,2′,5,5′- tetrachlorobiphenyl ([ 125I 2] TCBP ) of high specific activity (3350 Ci/mmol) was synthesized and used to investigate the direct binding of this compound to the murine hepatic Ah receptor or other cytosolic proteins. No direct specific binding was observed between 125 I 2- TCBP and any cytosolic proteins using a sucrose density gradient assay procedure. These results contrasted with previous studies with Aroclor 1254 that suggested that this mixture acted as a competitive Ah receptor antagonist.

Role of endogenous enkephalins in locomotion and nociception studied with peptidase inhibitors in two inbred strains of mice (C57BL/6J AND DBA/2J)

Acetorphan, a parenterally active enkephalinase inhibitor, induced dose-dependently a naloxone-reversible analgesia on the hot-plate jump test in DBA/2J (DBA2) mice but was devoid of effects in C57BL/6J (C57) mice. By contrast, acetorphan increased locomotion in both strains; however, the DBA2 strain was much more sensitive than C57 mice to the locomotor stimulant effect. The increased locomotion was antagonized by naloxone in both strains. These data suggest that endogenous enkephalins modulate nociception and locomotion in the two inbred strains differently.