Comparison of baseline sister-chromatid exchanges (SCE), cyclophosphamide-, ethylnitrosourea (ENU)-induced SCE, ENU-induced cell-cycle delay and chromosome aberrations between Peru and laboratory mice

The baseline sister-chromatid exchange (SCE) frequency and sensitivity to the effects of the mutagens cyclophosphamide (CPP) and ethylnitrosourea (ENU) in bone-marrow cells of descendants of wild mice trapped from Rimac valley in Peru (Peru mice) were studied and compared to the same effects in laboratory mice. Baseline SCE of the Peru mice were significantly higher than those of the C57BL/6J and DBA/2 mice. The average SCE/cell of 4 Peru mice was 5.4 (range 3.8-7.6), while the average of SCE/cell of either 4 C57BL or 5 DBA mice was 3.2 (range 3.0-3.4). The variation of SCE/cell among Peru mice studied was statistically significant whereas among C57BL or DBA mice it was not. SCE frequencies of primary cultures derived from the ear tissue of 10 Peru (mean SCE/cell = 8.5) were also significantly higher than those of 6 C57BL mice (mean SCE/cell = 7.4). CPP treatment resulted in a dose-dependent increase of SCE frequencies in bone-marrow cells of all the mice. However, some of Peru mice treated with CPP had significantly higher SCE than the other Peru mice and than all of the C57BL and DBA mice treated with equivalent dose. ENU induced increased SCE frequencies in Peru and C57BL mice. Again some of Peru mice either had significantly higher SCE, greater extent induced cell-cycle delay or chromosome aberrations (CA) than other Peru mice and than of all the C57BL mice treated with equivalent dose.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cyclophosphamide-Induced IN VIVO Sister Chromatid Exchanges (Sce) in MUS MUSCULUS. III. Quantitative Genetic Analysis

In vivo cyclophosphamide (CP)-induced sister chromatid exchanges (SCEs) were evaluated in females from five genetic strains of mice (C57BL/6J, C3H/S, 129/ReJ, BALB/c and DBA/2) and their F₁ hybrids. Baseline (noninduced) SCE values differ significantly among strains, 129/ReJ having the lowest and DBA/2 having the highest mean SCE per cell values. In general, the baseline SCE of a given F₁ is within the range of its corresponding parental strains or near the lower parental value. Furthermore, there is a genotype-dependent increase in mean SCEs per cell with CP dose. Strain differences in SCE induction are noted particularly at the two higher CP doses (4.50 and 45.0 mg/kg). In general, F₁ hybrids involving a strain with high induced SCEs and a strain with low induced SCEs exhibit mean SCE values that are closer to the value of the lower strain. F₁ s involving two strains with high SCEs or two strains with low SCEs yield SCEs not different from parental strains. The method of diallel cross analysis showed the order of dominance of these strains in SCE induction to be 129/ReJ BALB/c C3H/S DBA/2 C57BL/6J. These results support the involvement of predominantly nonadditive genetic factors as major gene(s) in SCE induction. In addition, involvement of random and independent events in SCE induction is suggested by the distribution of SCEs which follows a Poisson distribution.     

Plasma levels of proteins of the alternative complement pathway in inbred mice that differ in resistance to Trypanosoma congolense infections.

Inbred BALB/c, A/J, and C57B1/6J mice were infected with Trypanosoma congolense (Trans Mara strain), clone TC13, and monitored for parasitemia, survival times, and plasma levels of complement components C3, C5, factor B, and factor H. Parasitemia was highest in BALB/c, intermediate in A/J, and lowest in C57Bl/6J mice. The mean survival times were 11.5 +/- 0.9, 23.8 +/- 2.3, and 119 +/- 26 days for BALB/c, A/J, and C57Bl/6J mice, respectively. Preinfection levels of factor H were significantly correlated with survival times (r = 0.7722, P less than 0.001). Marked differences were observed between the plasma levels of C3, factor B, and factor H in the 3 mouse strains following infection. Complement C5 levels showed the fewest changes. In the initial postinfection period, BALB/c mice had highest increases in the levels of the 4 complement proteins but also had the greatest declines toward the end of the infection. Factor H levels showed a biphasic increase in BALB/c and C57Bl/6J, but not in A/J mice, with peaks at days 3 and 9. Complement C3 levels declined in all mice toward the terminal stage of the disease. In the late stages of infection, factor B levels markedly decreased in BALB/c but significantly increased in C57Bl/6J mice. Factor B levels measured at the terminal stages in BALB/c, A/J, and C57Bl/6J were correlated positively with their respective survival times (r = 0.714, P less than 0.01). The results suggest that genetic differences in the alternative complement pathway might affect the resistance to T. congolense infections.     

Sister-chromatid exchanges in lymphocytes from infants with Down's syndrome

Sister-chromatid exchange (SCE) frequencies were studied in blood lymphocytes from 12 patients (3 females and 9 males) with Down's syndrome (DS). The mean frequency of SCE per metaphase for the patients (both sexes) was 9.2 +/- 0.8 which was significantly higher (P less than 0.01) than the mean SCE value (5.1 +/- 0.2) scored for 16 healthy infants (8 females and 8 males). A significant increase in the mean frequency of SCE in 12 parents of infants with DS (8.7 +/- 0.9 SCE/cell) was noticeable when compared with 20 parents of normal infants (6.3 +/- 0.1 SCE/cell). Increases in cellular division with reduction in their replication were also observed in patients with DS. Treatment with mitomycin C (0.05 micrograms/ml), hycanthone (0.1 micrograms/ml) and gamma-radiation (0.1 Gy) revealed a significant (P less than 0.01) increase in frequencies of SCE in DS lymphocytes and in those of their parents as compared to controls. These data may reveal a familial hypersensitivity reaction to these agents. The results indicate a genomic instability and deranged DNA-repair mechanisms which are accentuated by exposure to mutagenic agents, the underlying causal factor for which might be genetic.     

Analyses of sister-chromatid exchange and cell-cycle kinetics in mouse T- and B-lymphocytes from peripheral blood cultures

A reliable mouse peripheral blood lymphocyte culture assay has been developed for sister-chromatid exchange analysis. Crucial aspects for optimal mitogenesis include: (1) the addition of 5 X 10(5) leucocytes/ml culture; (2) the use of animals with leucocyte counts from 5 to 7 X 10(6)/ml; and (3) the addition of 6% mouse plasma for the first 24 h of a total 54-h incubation. When 7 micrograms phytohemagglutinin/ml were used to stimulate T-lymphocytes, the mitotic index was 3.4 +/- 0.3%, 28 +/- 2.3% of the metaphases were in first-division, and the SCE frequency/metaphase was 7.3 +/- 0.2 (n = 14 mice). When B-lymphocytes were stimulated with 60 micrograms lipopolysaccharide/ml, the mitotic index was 4.5 +/- 0.3%, 64 +/- 3.3% of the metaphases were in first-division, and the SCE frequency/metaphase was 4.6 +/- 0.1 (n = 7 mice). This culture method consistently yields sufficient numbers of metaphases from both B- and T-lymphocytes for SCE and chromosome-breakage studies.     

Induction of sister-chromatid exchanges by DNA-damaging agents and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) in synchronous Chinese hamster ovary (CHO) cells

Synchronous CHO cells were obtained by mitotic selection; synchrony was maintained up to the 5th cell cycle. The mitotic cells were seeded into T-25 flasks or P-60 plastic petri dishes, and cultured for 1 h at 37 degrees C, then the cells were treated by X-ray, UV light, and mitomycin C. The cells were then cultured for 2 cell cycles with TPA and BrdUrd and sister-chromatid exchanges (SCE) analyzed by the FPG method. Following X-irradiation, the frequency of induced SCE increased linearly with dose reaching a maximum of 19.8 times the control frequency after 200 rad. With higher doses, the SCE frequency declined. In the presence of TPA, SCE frequencies were 1.8 times control levels for all X-ray doses studied (0-800 rad), the frequency seen in non-irradiated cultures treated with TPA. The induced SCE frequency also increased linearly following treatment with UVL and mitomycin C, reaching levels higher than 1.8 times controls with doses exceeding 2.5 J/m2 UVL or mitomycin C (30 min). In the presence of TPA, the SCE frequencies increased to 1.8 times controls following low UVL and mitomycin C doses, but were not influenced by TPA in the higher dose range (above 2.5 J/m2 or 10(-10) M mitomycin C. Most of the SCE were induced by X-rays during the first S phase after treatment. Following higher UVL doses (5 J/m2), however, the SCE frequency remained elevated (1.5 times controls) for 4 cell cycles after exposure.     

Reduced frequencies of Mitomycin-C induced sister chromatid exchanges in AKR Mice

Summary The frequencies of base-line and Mitomycin-C (MMC) induced sister chromatid exchanges (SCE) were surveyed in four inbred strains of mice. In contrast to the C57B1/6J, CBA/J, and A/J strains where frequencies of SCE increased linearly with increasing dose of MMC, levels of SCE were significantly lower in AKR/J mice at high MMC concentrations. At a dose of 5 mg/kg MMC, chromosomal aberrations were more frequent in bone marrow cells of AKR/J mice than in C57B1/6J mice. These observations suggest an altered response to DNA damage in the AKR mouse strain.     

Endothelin-mediated vasoconstriction in early atherosclerosis is markedly increased in ApoE-/- mouse but prevented by atorvastatin

We have discovered that endothelin-1 (ET-1) vasoconstriction is significantly enhanced in aortas of young (8-16-week-old) apolipoprotein E-deficient (ApoE-/-) mice devoid of atherosclerotic lesions (maximum response expressed as a percentage of the mean response to 100 mM KCl (E(MAX)) = 55.7% +/- 19.5% KCl, n = 5) compared to age-matched C57BL/6/J control animals (E(MAX) = 12.6% +/- 2.5% KCl, n = 8), indicating that alterations in the endothelin system may contribute to disease progression, at least in this animal model. There was no difference in the potency of ET-1 to contract aorta from the two groups (C57BL/6/J pD2 = 8.74 +/- 0.30; ApoE-/- pD2 = 8.50 +/- 0.15, P > 0.05). This increased response was specific to ET-1, as it was not observed with phenylephrine or U46619, nor was it due to a non-receptor mediated increase in contractile sensitivity, as there was no change in response to KCl between the two groups. [125I]ET-1 bound with subnanomolar affinity (K(D)) to aorta (K(D) = 0.018 +/- 0.002 nM, n = 4) and, with an order of magnitude lower affinity, to heart (K(D) = 0.47 +/- 0.05, n = 5) of C57BL/6/J mice with binding densities (B(MAX)) of 9.3 +/- 2.4 fmol mg(-1)protein and 100 +/- 14 fmol mg(-1) protein, respectively. Alterations in vascular reactivity to ET-1 could not be explained by increased endothelin receptor density or affinity, as these were not altered in aorta (K(D) = 0.011 +/- 0.003 nM; B(MAX) = 10.1 +/- 3.9 fmol mg(-1), n = 4) and heart (K(D) = 0.43 +/- 0.04 nM; B(MAX) = 115 +/- 26 fmol mg(-1), n == 6) of ApoE-/- animals. The ratio of ET(A) to ET(B) receptors in heart of control and ApoE-/- mice was similar, comprising 89% and 85% ET(A) receptors, respectively. In isolated aorta from ApoE-/- mice on the Western diet, which more closely resembled more advanced stages of the disease in man, the augmented ET-1 vasoconstrictor response was maintained (E(MAX) = 25.2% +/- 6.8% KCl, n = 9); however, it was completely prevented in animals that had received 10 weeks of oral atorvastatin (30 mg kg(-1) day(-1)) (E(MAX) = 4.0% +/- 1.5% KCl, n = 5), a concentration that was chosen because it did not affect plasma cholesterol and triglyceride levels. Therefore, this protective prevention of enhanced ET-1 vasoconstriction in ApoE-/- mice by atorvastatin was independent of its lipid-lowering properties.     

Effect of hyperthermia on the frequency of sister-chromatid exchanges in patients with cancer of cervix uteri

The frequencies of sister-chromatid exchanges (SCE) were studied in patients with cancer of the cervix uteri and normal controls at 37 degrees C and 40 degrees C. At 37 degrees C the mean frequency of SCE was found to be 8.26 +/- 1.91 in untreated patients with cervical cancer and 7.91 +/- 1.68 in cancer patients treated with radiotherapy; these values were significantly higher than the control value of 5.34 +/- 1.28 exchanges. Increase of the growth temperature to 40 degrees C elevated the SCE frequency to 11.95 +/- 2.12 in patients without radiotherapy treatment, 13.37 +/- 2.17 in patients with radiotherapy treatment and 7.82 +/- 1.84 in normal controls. These data indicate that there is a differential induction of SCEs by hyperthermia in the lymphocytes of control women and patients with cancer of the cervix uteri.     

NO-donating aspirin inhibits intestinal carcinogenesis in Min (APC(Min/+)) mice

The chemopreventive effect of nitric oxide-releasing aspirin (NO-ASA) against gastrointestinal tumorigenesis was evaluated in Min (APC(Min/+)) mice. NO-ASA consists of a traditional ASA that bears covalently attached to it an NO-releasing moiety. Four groups (N=10) of six-week-old female C57BL/6J APC(Min/+) and the corresponding C57BL/6J(+/+) wild type mice were treated either with vehicle or NO-ASA 100 mg/kg/day intrarectally for 21 days. There were no signs of overt toxicity including gastrointestinal toxicity from NO-ASA. Vehicle treated Min mice had 24.7 +/- 3.8 tumors (mean +/- SEM) and NO-ASA treated Min mice had 10.1 +/- 1.4 tumors (59% reduction; P<0.001). Wild type mice showed no tumors. NO-ASA did not affect cell proliferation in small intestinal mucosa, determined by immunohistochemical staining for PCNA. Our findings establish the strong inhibitory effect of NO-ASA in intestinal carcinogenesis in the Min mouse and suggest that this agent merits further evaluation as a chemopreventive agent against colon cancer.     

Sister chromatid exchange in chromosomes of sheep (Ovis aries)

Blood lymphocyte cultures from 32 Comisana and Laticauda sheep breeds (15 males and 17 females) raised in Southern Italy were studied using sister chromatid exchange (SCE) test. Of the 932 cells studied, the SCE-mean value was 7.20 +/- 2.5 per cell for both breeds. Indeed, the SCE mean values were 7.12 +/- 2.45 and 7.28 +/- 2.55 in Comisana and Laticauda breeds, respectively, and the differences were not significant. No statistical differences were noticed between male and female cells (7.25 +/- 2.39 and 7.16 +/- 2.60, respectively). The SCE frequency distribution did not follow a Poisson distribution. The number of SCE were significantly higher than expected in chromosomes 1, 2 and 3 (p < 0.001) and significantly lower than expected in the X and remaining chromosomes (p < 0.001) on the basis of relative chromosome lengths.     

Effect of mouse age and genotype on the frequency of sister chromatid exchange in bone marrow cells

No differences were found in both the baseline and mitomycin C induced levels of sister chromatid exchanges (SCE) between 101/H and C57BL/6J mice differing in chromosome mutability. An increase with the age of the spontaneous and mutagen induced SCE rates was similar in the strains compared, though instability of chromosomes was much higher in old 101/H than in C57BL/6J mice. Thus, no correlation was observed between chromosomal aberration and SCE levels in these strains. As 101/H mice were recently found to be DNA repair-deficient, possible connection of SCE and repair is discussed.     

Performance of ten inbred mouse strains following assisted reproductive technologies (ARTs)

Superovulation, in vitro fertilization, embryo cryopreservation, and embryo transfer are assisted reproductive technologies (ARTs) widely used in laboratory mice. Inbred strains of mice have inherent genetic differences that cause them to respond differently to these technologies. Knowing how common inbred strains will perform when used for ARTs will ensure the most efficient use of mice, time, and resources. In this study, we characterized the ability of 10 inbred strains: 129S1/SvImJ, A/J, BALB/cJ, BALB/cByJ, C3H/HeJ, C57BL/6J, DBA/2J, FVB/NJ, NOD/LtJ, and SJL/J to superovulate, fertilize in vitro, and produce live pups subsequent to embryo transfer. Three-week-old female mice were superovulated using eCG (5.0 IU) and hCG (5.0 IU). The resulting oocytes were fertilized in vitro in human tubal fluid medium with spermatozoa of the same strain. The following day, two-cell embryos were either transferred into pseudopregnant recipient females or cryopreserved. The cryopreserved embryos were later thawed and transferred into pseudopregnant recipient females. Differences in response to superovulation, fertilization, and number of live born produced after embryo transfer were observed between strains, substantiating the influence of genetic variability on ARTs. The response to the superovulation treatment varied among strains and ranged from 5+/-1(A/J) to 40+/-3 (129S1/SvImJ) normal oocytes per female. The average proportion of oocytes that fertilized ranged among strains from 24% (129S1/SvImJ) to 93% (DBA/2J and A/J). The average proportion of two-cell embryos that were transferred into recipient females and subsequently developed into live pups varied from 5% (A/J) to 53% (C57BL/6J) for fresh embryos and from 18% (BALB/cByJ) to 45% (129S1/SvImJ) for thawed embryos.     

Strain-dependent beta-adrenergic receptor function influences myocardial responses to isoproterenol stimulation in mice

Recently, we showed that compared with the A/J inbred mouse strain, C57BL/6J (B6) mice have an athlete's cardiac phenotype. We postulated that strain differences would result in greater left ventricular (LV) hypertrophy in response to isoproterenol in B6 than A/J mice and tested the hypothesis that a differential response could be explained partly by differences in beta-adrenergic receptor (beta-AR) density and/or coupling. A/J and B6 mice were randomized to receive daily isoproterenol (100 mg/kg sc) or isovolumic vehicle for 5 days. Animals were studied using echocardiography, tail-cuff blood pressure, histopathology, beta-AR density and percent high-affinity binding, and basal and stimulated adenylyl cyclase activities. One hundred twenty-eight mice (66 A/J and 62 B6) were studied. Isoproterenol-treated A/J mice demonstrated greater percent increases in echocardiographic LV mass/body weight (97 +/- 11 vs. 20 +/- 10%, P = 0.001) and in gravimetric heart mass/body weight versus same-strain controls than B6 mice. Histopathology scores (a composite of myocyte hypertrophy, nuclear changes, fibrosis, and calcification) were greater in isoproterenol-treated A/J vs. B6 mice (2.8 +/- 0.2 vs.1.9 +/- 0.3, P < 0.05), as was quantitation of myocyte damage (22.3 +/- 11.5 vs. 4.3 +/- 3.5%). Interstrain differences in basal beta-AR density, high-affinity binding, and adenylyl cyclase activity were not significant. However, whereas isoproterenol-treated A/J mice showed nonsignificant increases in all beta-AR activity measures, isoproterenol-treated B6 mice had lower beta-AR density (57 +/- 6 vs. 83 +/- 8 fmol/mg, P < 0.05), percent high-affinity binding (15 +/- 2 vs. 26 +/- 3%, P < 0.005), and GTP + isoproterenol-stimulated adenylyl cyclase activity (10 +/- 1.1 vs. 5.8 +/- 1.5 pmol cAMP.mg(-1).min(-1)) compared with controls. High-dose, short-term isoproterenol produces greater macro- and microscopic cardiac hypertrophy and injury in A/J than B6 mice. A/J mice, unlike B6 mice, do not experience beta-AR downregulation or uncoupling in response to isoproterenol. Abnormalities in beta-adrenergic regulation may contribute to strain-related differences in the vulnerability to isoproterenol-induced cardiac changes.     

Genetic factors at the enterocyte level account for variations in intestinal cholesterol absorption efficiency among inbred strains of mice.

Interindividual and interstrain variations in cholesterol absorption efficiency occur in humans and animals. We investigated physiological biliary and small intestinal factors that might determine variations in cholesterol absorption efficiency among inbred mouse strains. We found that there were significant differences in cholesterol absorption efficiency measured by plasma, fecal, and lymphatic methods: <25% in AKR/J, C3H/J, and A/J strains; 25-30% in SJL/J, DBA/2J, BALB/cJ, SWR/J, and SM/J strains; and 31-40% in C57L/J, C57BL/6J, FVB/J, and 129/SvJ strains. In (AKRxC57L)F1 mice, the cholesterol absorption efficiency (31 +/- 6%) mimicked that of the C57L parent (37 +/- 5%) and was significantly higher than in AKR mice (24 +/- 4%). Although biliary bile salt compositions and small intestinal transit times were similar, C57L mice displayed significantly greater bile salt secretion rates and pool sizes than AKR mice. In examining lymphatic cholesterol transport in the setting of a chronic biliary fistula, C57L mice displayed significantly higher cholesterol absorption rates compared with AKR mice. Because biliary and intestinal transit factors were accounted for, we conclude that genetic variations at the enterocyte level determine differences in murine cholesterol absorption efficiency, with high cholesterol absorption likely to be a dominant trait. This study provides baseline information for identifying candidate genes that regulate intestinal cholesterol absorption at the cellular level.     

The effects of genetic variation in N-acetyltransferases on 4-aminobiphenyl genotoxicity in mouse liver

Inbred, congenic and transgenic strains of mice were characterized for acetylation of p-aminobenzoic (PABA) and the carcinogen 4-aminobiphenyl (4ABP). C57Bl/6 mice have the NAT2*8 allele, A/J mice have NAT2*9 and congenic B6.A mice have NAT2*9 on the C57Bl/6 background. The first transgenic strain with human NAT1, the functional equivalent of murine NAT2, was also tested. The murine NAT2*9 allele correlated with a slow phenotype measured with the murine NAT2 selective substrate PABA. The two strains having this allele also had a lower capacity to acetylate 4ABP. A line with five copies of the human NAT1 transgene was bred for at least five generations with either C57Bl/6 or A/J mice. There was no significant change in PABA NAT activity on the C57Bl/6 background but a 2.5-fold increase was seen in hNAT1:A/J compared with A/J. The effect of variation in NATs on 4ABP genotoxicity was assessed in these strains. Twenty-four hours after exposure to a single oral dose of 120 mg 4ABP/kg, hepatic 4ABP-DNA adducts were detected by immunofluoresence in all strains. Nuclear fluorescence intensities (mean+/-S.D.) were 41.1+/-3.6 for C57Bl/6, 37.9+/-1.11 for A/J and 36.3+/-2.44 for B6.A. There was no correlation between murine NAT2 alleles and 4ABP-DNA adduct levels. Similar results were seen with the transgenic strains. The data indicate that the range of variation present in these strains of mice was insufficient to alter susceptibility to 4ABP genotoxicity. The impact of these relatively modest differences in the acetylation of the activation of 4ABP may be masked by other competing biotransformation reactions since 4ABP is a substrate for both NAT1 and NAT2. Mouse models with variation in both isoforms are needed to adequately assess the role of variation in NATs in susceptibility to 4ABP genotoxicity.     

Characterization of hyperinsulinemic recombinant inbred (RI) strains (SMXA-5 and SMXA-9) derived from normoinsulinemic SM/J and A/J mice.

We discovered two mouse strains (SMXA-5 and SMXA-9) with hyperinsulinemia among the substrains and progenitor strains (SM/J and A/J) of the SMXA recombinant inbred (RI) strains, and characterized the two strains at 20 weeks of age. SMXA-5 (mean +/- S.E.M: 9.6 +/- 1.7 ng/ml) and SMXA-9 (7.7 +/- 1.3 ng/ml) males had higher serum immunoreactive insulin levels than SM/J (1.4 +/- 0.3 ng/ml) and A/J (1.1 +/- 0.1 ng/ml) males in the nonfasting condition. The hypoglycemic response to insulin at 30 min after injection was significantly less in SMXA-5 males than in SM/J mice. Glucose tolerance test revealed that the incidence of impaired glucose tolerant males was 58% (11/19) in SMXA-5 and 42% (10/24) in SMXA-9 strains, but none in SM/J and A/J strains. SMXA-5 (209 +/- 29 mg/dl) and SMXA-9 (235 +/- 31 mg/dl) had higher serum triglyceride levels than SM/J (126 +/- 14 mg/dl) and A/J (89 +/- 5 mg/dl) males in the nonfasting condition. Histologic examination revealed enlarged islets in the pancreas of hyperinsulinemic SMXA-5 male mice. Moreover, SMXA-5 and SMXA-9 mice exhibited mild obesity. SMXA-5 and SMXA-9 males were therefore characterized by hyperinsulinemia, impaired glucose tolerance, hypertriglyceridemia and mild obesity which resembled some of the phenotypes of human Syndrome X, although both progenitor strains were normal so far as we examined. Since the RI strains are a powerful tool to facilitate polygenic-trait analysis, SMXA-5 and SMXA-9 mice will be useful materials to investigate the genetic basis of complex diseases, and are possible new metabolic models in relation to hyperinsulinemia.     

Reducing exposure to laboratory animal allergens

Laboratory animal allergy is a serious health problem. We examined several possible allergen-reducing strategies that might be effective in the working mouse room. Ambient allergen concentrations were measured when mice were maintained under several conditions: conventional housing versus ventilated cage racks operated under negative or positive pressure. We found that housing mice in ventilated cages operated under negative pressure and using ventilated changing tables reduced ambient mouse allergen (Mus m 1) concentrations tenfold, compared with values when mice were housed in conventional caging and using a conventional (non-ventilated) changing table. Housing mice in positively pressurized cages versus conventional cages did not reduce ambient allergen values. Cleaning mouse rooms at an accelerated frequency also did not reduce ambient Mus m 1 concentration. We also quantified ambient allergen values in several areas of The Jackson Laboratory. A facility-wide survey of Mus m 1 concentrations indicated that allergen concentrations were undetectable in control areas, but ranged from a mean (+/- SEM) 0.11 +/- 0.02 ng/m3 to 5.40 +/- 0.30 ng/m3 in mouse rooms with different cage types. The percentage of animal caretakers reporting allergy symptoms correlated significantly with ambient allergen concentrations: 12.9% reported symptoms in the rooms with the lowest allergen concentration (0.14 +/- 0.02 ng/m3), but 45.9% reported symptoms in rooms with the highest concentration (2.3 +/- 0.4 ng/m3). These data indicate that existing technology can significantly reduce exposure to laboratory animal allergens and improve the health of animal caretakers.     

Sister chromatid exchange (SCE) for the first time in Casertana pig breed

Lymphocyte cell cultures from 30 Casertana pigs (13 males and 17 females), reared in southern Italy, underwent the sister chromatid exchange (SCE) test. The Casertana pig is an endangered native breed from the region of Campania, raised chiefly half-wild. In the 1500 cells we studied, the mean SCE was 6.32+/-2.92 and SCE frequency did not follow a Poisson distribution. A higher mean value of SCE cell(-1) was found in the older group (SCE cell(-1)=6.68+/-2.95) compared with the younger (SCE cell(-1)=5.94+/-2.84), the difference being statistically significant (P<0.01). To our knowledge, this is the first investigation in a representative sample of Italian pig breed using the SCE test. Furthermore, this is the first report where the differences found in the mean SCE values were related to age in domestic species.     

Hyperhomocysteinemia increases arterial permeability and stiffness in mice

We have reported that hyperhomocysteinemia (HHcy) evoked by folate depletion increases arterial permeability and stiffness in rats and that low folate without HHcy increases arterial permeability in mice. In this study, we hypothesized that HHcy independently increases arterial permeability and stiffness in mice. C57BL/6J mice that received rodent chow and water [control (Con), n=12] or water supplemented with 0.5% L-methionine (HHcy, n=12) for 18+/-3 wk had plasma homocysteine concentrations of 8+/-1 and 41+/-1 microM, respectively (P<0.05), and similar liver folate (approximately 12+/-2 microg folate/g liver). Carotid arterial permeability, assessed as dextran accumulation using quantitative fluorescence microscopy, was greater in HHcy (3.95+/-0.4 ng.min-1.cm-2) versus Con (2.87+/-0.41 ng.min-1.cm-2) mice (P<0.05). Stress versus strain curves generated using an elastigraph indicated that 1) maximal stress (N/mm2), 2) physiological stiffness (low-strain Young's modulus, mN/mm), and 3) maximal stiffness (high-strain Young's modulus, N/mm) were higher (P<0.05) in aortas from HHcy versus Con mice. Thus, chronic HHcy increases arterial permeability and stiffness. Carotid arterial permeability also was assessed in age-matched C57BL/6J mice before and after incubation with 1) xanthine (0.4 mg/ml)/xanthine oxidase (0.2 mg/ml; X/XO) to generate superoxide anion (O2-) or 50 microM DL-homocysteine in the presence of 2) vehicle, 3) 300 microM diethylamine-NONOate (DEANO; a nitric oxide donor), or 4) 10(-3) M 4,5-dihydroxy-1,3-benzene disulfonic acid (tiron; a nonenzymatic intracellular O2- scavenger). Compared with preincubation values, X/XO and dl-homocysteine increased (P<0.05) permeability by 66+/-11% and 123+/-8%, respectively. DL-Homocysteine-induced increases in dextran accumulation were blunted (P<0.05) by simultaneous incubation with DEANO or tiron. Thus, acute HHcy increases arterial permeability by generating O2- to an extent whereby nitric oxide bioavailability is reduced.