Production of age-related DNA strand breakage in brain cells of senescence-accelerated prone (SAMP1) mouse.

Amounts of DNA strand breaks were estimated by the proportion of cells without tails (PCWT) and the average lengths of tail momentum (ALTM) in comet images of tissue cells of senescence-accelerated prone (SAMP1) mouse and senescence-accelerated resistant (SAMR1) mouse. The PCWT and ALTM of brain cells from SAMR1 were unchanged from 4 to 15 months of age. In the case of SAMP1 brain cells, the PCWT decreased and the ALTM increased in an age-related manner from 8 to 15 months of age. In the cases of liver and kidney, the PCWT and the ALTM of both SAMP1 and SAMR1 cells showed constant values from 4 to 15 months of ages.

Unstable heart rate and temperature regulation predict mortality in AKR/J mice.

Elderly populations face greater risks of mortality when exposed to changes in environmental stress. The purpose of the following study was to develop an age-dependent susceptibility model that achieved the following three goals: 1) to operationally define homeostasis by assessing the stability and periodicity in physical activity, heart rate (HR), and deep body temperature (T(db)), 2) to specify alterations in activity, HR, and T(db) regulation that signal imminent death, and 3) to test the hypothesis that the decay in homeostasis associated with imminent death incorporates the coincident disintegration of multiple physiological systems. To achieve these goals, the circadian regulation of activity, HR, and T(db) was assessed using radiotelemeters implanted in AKR/J (n = 17) inbred mice at approximately 190 days of age. During a 12:12-h light-dark cycle, weekly measurements were obtained at 30-min intervals for 48-h periods until each animal's natural death. The average (+/-SE) life span of surgically treated animals did not differ from untreated controls (319 +/- 12 vs. 319 +/- 14 days). Cardiac and thermal stability were characterized by a circadian periodicity, which oscillated around stable daily averages of 640 +/- 14 beats/min in HR and 36.6 +/- 0.1 degrees C in T(db). Stable HR and T(db) responses were compared with extreme conditions 3 days before death, during which a disintegration of circadian periodicity was coincident with a fall in the daily average HR and T(db) of approximately 29 and approximately 13% lower (i.e., 456 +/- 22 beats/min and 31.7 +/- 0.6 degrees C), respectively. The results further suggested that multiple predictors of cardiac and thermal instability in AK mice, including significant bradycardia, hypothermia, and a loss of circadian periodicity, forecast life span 5-6 wk before expiration.

Interstrain variation in murine aerobic capacity.

PURPOSE: The contribution of genetic factors to aerobic capacity is unknown. The purpose of this study was to measure maximal aerobic performance among inbred strains of mice to provide basic heritability estimates. METHODS: Eight female mice, 8 to 10 wk old, in 10 inbred strains (A/J, AKR/J, Balb/cJ, C(3)H/HeJ, C57Bl/6J, C57L/J, C(3)Heb/FeJ, CBA/J, DBA/2J, and SWR/J) were run on a treadmill until exhaustion. The protocol started at 22 m.min(-1) and increased in speed approximately 6 m.min(-1) every 4 min. After 4 min at 42.4 m.min(-1), the grade was increased 2% every 4 min thereafter until the mouse could not run off of the shock grid (150 V; 1.5 mA). RESULTS: There were significant differences between inbred strains in maximal duration of exercise accomplished (P < 0.0001). The order of strain-specific exercise duration was Balb/cJ > SWR/J > CBA/J > C57L/J > C3H/HeJ > C3Heb/FeJ > C57Bl/6J > AKR/J > DBA/2J > A/J. Two measures of heritability in the broad sense, intraclass correlation (0.73), and the coefficient of genetic determination (0.58) were both significant. CONCLUSION: These data indicate that there is a strong genetic contribution to aerobic capacity in mice.

Biliary cholesterol hypersecretion in gallstone-susceptible mice is associated with hepatic up-regulation of the high-density lipoprotein receptor SRBI.

Enhanced hepatocellular trafficking of cholesterol to the bile canaliculus and cholesterol hypersecretion appears critical for gallstone formation. Therefore, we studied in more detail the hepatic cholesterol transport pathways in a mouse model of cholesterol gallstone disease. Biliary lipid secretion rates, plasma lipoprotein levels, hepatic expression of lipoprotein receptors, lipid regulatory enzymes, and putative cholesterol transporting proteins were analyzed in gallstone-susceptible C57L/J and gallstone-resistant AKR/J mice, which were fed a lithogenic diet. Biliary cholesterol hypersecretion in C57L mice was associated with decreased plasma high-density lipoprotein (HDL) cholesterol levels and significant hepatic induction of the HDL receptor (SRBI) and cholesteryl ester hydrolase. In response to the lithogenic diet, fatty-acid binding protein of liver (FABPL) was markedly induced in both mouse strains. Caveolin 1 was elevated only in plasma membranes of gallstone-susceptible C57L mice, which also failed to down-regulate cholesterol synthesis. These data suggest a role of the reverse cholesterol transport pathway for genetically determined gallstone susceptibility in the mouse.

A comparative study of 2-deoxyglucose patterns of glomerular activation in the olfactory bulbs of C57 BL/6J and AKR/J mice.

We have studied the patterns of glomerular activation evoked in the olfactory bulbs of C57BL/6J and AKR/J mice by olfactory stimulations with amyl acetate or isovaleric acid. Patterns of glomerular activation were obtained with the 2-deoxyglucose method and subsequently compared using a computer-assisted image analysis. The mice of both inbred strains stimulated with amyl acetate or isovaleric acid were characterized by areas of high 2-deoxyglucose uptake in their glomerular layer. Statistical comparisons of the patterns demonstrated that they were odor-specific. Although C57BL/6J mice have been found to be specifically anosmic to isovaleric acid, our findings indicate that their olfactory system is topographically activated by olfactory stimulations with this odorant. However, patterns of glomerular activity evoked by isovaleric acid stimulations are not similar in the two studied strains.

[Effects of exposure of spontaneously leukemic mice (AKR mice) to an electric field]. / Effects de l'exposition à un champ électrique de souris spontanément leucémiques (souris AKR).

Spontaneously leukemic AKR mice were exposed from 6 weeks age to a 50 kV/m electric field 12 hrs./day. In this study, carrying on 50 exposed and 50 sham-exposed mice, like in the two preceding experiments, the exposed group mortality is lightly retarded, and reaches 100% only 10 weeks after the sham-exposed group. These differences are not however statistically significative.

Further studies on migration and colonization of leukemic lymphoblasts in AKR and HSS inbred mice.

AKR and HSS lymphoid leukemias were transplanted into identical mouse strains and changes in pyruvate kinase activity were measured in thymus, mesenteric lymph node and spleen during the posttransplantation period. The heterogeneity of the cellular density and the size distribution were determined in the HSS spleen cells in order to get more information about the settlement and proliferation of the transplanted leukemic lymphoblasts. The data obtained suggest that this model system may be useful for a follow up the fate of leukemic blast cells in the host animal.

Effects of chronic daily exposure to tobacco smoke on the high leukemic AKR strain of mice.

Daily exposure of the high leukemic AKR strain of mice to low levels of fresh tobacco smoke (TS) produces significantly different mortality profiles associated with both the sex of the animals and the age at which TS exposure commences. Females tend to be susceptible and die sooner than males, where a significant proportion of animals survives longer than age-matched controls. This prolongation of life appears to be due to a failure of the leukemic state to be mobilized in the TS-exposed males. Exposure of both the females and the males to the TS does not induce significant detectable immunological reactivity against the leukemic cells for several parameters tested, possibly due to a significant enhancement of suppressor activity in the serum of the chronically exposed animals over and above that which also occurs in age-matched control animals.

Thymic stroma in AKR mice: its function and virus production.

This study reports experiments with thymic stromal remnants in AKR mice, a strain with a high natural incidence of thymic lymphoma. A method has been developed in which thymic stromal cells which survive a 4-week culture period, 1 week at 24 degrees C and 3 weeks at 37 degrees C are suitable for grafting. Most thymic lymphocytes die under these conditions. Stromal remnants were studied by culturing and grafting under the kidney capsule of 2-month-old syngeneic mice. Their in vitro morphology and virus production, their ability to reconstitute a new thymus from host progenitors and their eventual lymphoma development was evaluated. The stromal remnants were from: 1- and 3-month-old normal mice; 6-10-month-old normal mice; 21-28-day-old animals treated with the lymphomagenic virus, SL3-3, at 3 days of age. Our data show that thymic stromal function as measured by lymphoid reconstitution of thymic stromal grafts of AKR mice is not impaired with age or by the presence of oncogenic virus. Oncogenic viruses are found in the thymic stroma of old mice and in thymic stroma of young virus-treated mice. Oncogenic viruses are not found in thymic stroma of young normal mice. Lymphoma can develop in the grafted stromal remnants expressing lymphomagenic virus.

Effect of coordinated therapeutic assays using C. parvum, interferon and arginine butyrate on spontaneous disease and survival of AKR mice.

AKR mice, known to develop spontaneous leukemia in almost 100% of cases, were studied throughout their life-span. Different treatments combining a potent immune stimulator, Corynebacterium parvum (CP), with interferon (IFN) and arginine butyrate were initiated at the 15th week of life. In a preliminary series of experiments, CP (200 micrograms), IFN (20,000 units) and butyrate 50 mM) were employed in a well-defined chronological order. In controls, the mean survival time (MST) was 35.17 +/- 1.67 weeks and the final survival rates was 0/50 mice for all experiments. Only CP associated with arginine butyrate significantly augmented the MST (42.5 +/- 3.66 weeks) and final survival rate (9/35 mice). In an adjusted set of experiments, reducing the IFN concentration to 10,000 and 5,000 units and that of butyrate to 6 mM greatly improved the results. The MST was substantially increased with the combinations of CP + IFN + butyrate (41.4 +/- 1.86 weeks), CP + IFN (42.73 +/- 3.29 weeks) and butyrate + IFN (41 +/- 2.34 weeks), as well as the final survival rates (8/15, 10/15 and 6/15 mice respectively). An important finding was that when CP and IFN were used separately, they were ineffective.

Age-related auditory loss and genetics: an electrocochleographic comparison of six inbred strains of mice.

A genetic baseline was established for age-related auditory loss in the laboratory mouse (Mus musculus). Auditory nerve isoelectric thresholds were obtained in young, middle aged, and elderly mice at frequencies from 2 to 64 kHz. Six inbred strains of diverse genetic origin and widely varying life spans (298 to 774 days) were examined. Each strain displayed an age-related loss similar to that most often seen in the aging human (i.e., high-frequency losses occurred earliest, followed by losses of middle, and then of lower frequencies). The ranking of these strains in terms of the best to the poorest cochlear function in old age is as follows: SJL/J, AU/SsJ, AKR/J, A/J, C57BR/cdJ, and LP/J. Males and females were equally affected by the aging process.

The status of concanavalin A receptors on the lymphocytes of leukemic AKR mice: inhibition of redistribution by high concentrations of the lectin.

Cell-electrophoretic and fluorescence microscopic investigations were carried out on the interaction of concanavalin A with the splenic lymphocytes of normal and spontaneously leukemic AKR mice. The normal splenic lymphocytes (NSL) showed a biphasic profile of electrophoretic mobility (EPM) as a function of the concentration of Con A, under capping conditions. The mean EPM of NSL increased at low concentrations of the lectin and was reduced below that of untreated cells at higher (greater than or equal to 15 micrograms/ml) concentrations of the lectin. The leukemic cells (LSL) also showed enhancement in EPM at low concentrations of Con A. At high concentrations of the same, however, the mean EPM of LSL was the same as that of untreated cells. In the case of NSL the reduction in EPM at high concentration of Con A is known to be brought about by post-redistributional binding of excess lectin to new receptor sites which emerge after capping of the first type of receptors. Similar investigations of the electrokinetic characteristics of Con A-receptor interaction on leukemic cells revealed that only a single type of receptor was present on LSL. These receptors were inducible to redistribution at low concentrations of Con A. High concentrations of the lectin, however, inhibited the redistribution of the receptors to Con A on LSL. This was confirmed when LSL treated with high concentrations of Con A were relieved from this inhibition by moderate concentrations of alpha-methyl glucoside, which dissociates cell bound Con A. Very low or very high concentrations of alpha-MG were ineffective. The receptors to Con A on LSL were thus behaviorally distinguishable from those on NSL. These data clearly demonstrate that the malignant transformation in AKR mice is also associated with alterations in the properties of receptors to a multivalent ligand Con A.

A model to study drug effects on lymphoma and normal cell populations using the AKR/J mouse.

The existence of an AKR subline, AKR(Rb6.15)1A1d, with a chromosome marker provided a means to differentiate between proliferating lymphoma and normal cell populations within a single animal. An AKR(Rb6.15)1A1d lymphoma cell line has been maintained for 6 yr by serial passage in AKR/J recipients. The mice die in 7 +/- 2.0 days with evidence of extensive infiltration of the tissues by lymphoma cells. Cytogenetic analysis showed that approx. 1% of the metaphase cells in the bone marrow of mice at day 1 of the lymphoma passage were of the AKR(Rb6.15)1A1d donor-type. This increased to 54% by day 4 and 96% by day 6. The number of donor-type metaphase cells per humerus increased from 3.4 +/- 0.29 (X 10(3] at day 1 to 2.0 +/- 0.49 (X 10(5] at day 4 with a concomitant decrease in the number of non-lymphoma host-type metaphase cells. The population doubling time of donor-type metaphase cells per humerus was 12 +/- 1.4 h. At day 4, there was a significant decrease in the percentage of donor-type metaphase cells in mice that had been treated with BCNU (19.0 +/- 5.85%) or spirogermanium (38.6 +/- 5.85%) 24 h earlier. For BCNU treated animals, this also represented a decrease to 4.4 +/- 1.1 (X 10(4] donor-type metaphase cells per humerus.

A new murine model of accelerated senescence.

Five senescence-prone series of mice (P-1, P-2, P-3, P-4 and P-5) and three senescence-resistant series (R-1, R-2 and R-3) were obtained by continuous sister-brother breeding from five original litters of AKR mice with severe deterioration, and the three original litters of AKR mice with normal aging, respectively. A grading score system was adopted to evaluate the degree of senescence of these mice and a steady and irreversible increase in this grading score was seen with advancing age in both the R and P series. The high grading score in the P series was due to an earlier onset of loss of passivity and reactivity, loss of skin glossiness and increased coarseness, hair loss, periophthalmic lesions, increased lordokyphosis of the spine and a more marked increase in their severity with advancing age as compared to the R series. Among the P series, P-2 showed a 100% incidence of systemic amyloidosis after 6 months of age and P-3 a 70% incidence of cataract over 16 months of age. The life span in the P series was shortened by about 26% of that of the R series. In view of the evidence obtained from the survivors, the growth rate and Gompertz function, the aging pattern in the P series was considered to be an acceleration of senescence. The P series has been named "SAM" ("Senescence Accelerated Mouse").

Hoarding behavior of AKR, C57BL/6 mice and their F1 in their home living space: an automatic recording technique.

Earlier genetic analysis of food hoarding behavior in mice used test situations in which animals were allowed to hoard food only during short time periods. This paper describes a technique to measure food hoarding over long time periods. Small discs of standard food are equipped with a steel clip and each passage of a mouse bringing such a food disc from the food search enclosure to the nest is detected by an electromagnetic sounding lead connected to a pen recorder. Preliminary results show that female mice begin to hoard earlier than males; one of the two reciprocal F1 has a shorter latency to hoard than the other one. Results also show differences between two parental inbred strains and their reciprocal F1 for the light-dark distribution of hoarding.

Induction of interferon in AKR mice by murine leukaemia viruses.

A high percentage of AKR mice develop spontaneous leukaemia which has shown to be associated with the early expression of ecotropic murine leukaemia virus (MuLV) and the subsequent expression of xenotropic as well as polytropic MuLVs. Generally, mice infected with any one of several groups of viruses, including MuLVs, have been shown to produce interferon (IF). However, we report here that AKR mice produce no IF, despite that fact that infectious, endogenous MuLV is expressed in these mice from birth.

Effect of bleeding on irradiation-induced erythropoiesis in the spleen of AKR mice.

The effect of erythropoietin, increased by bleeding, on the erythropoiesis induced by irradiation in the spleen of AKR mice, has been studied. The following parameters were measured to quantify the erythropoietic activity: the number and size of hematopoietic nodules (colonies) and proerythroblasts in the spleen, the spleen, blood and red-cell 59Fe uptake and the hematocrit and reticulocytes in the blood. Under erythropoietic stimulus an increase in the number and size of colonies was observed and these colonies were observed sooner because of their more rapid growth. The proerythroblasts in the spleen appeared earlier, and there were increases in the spleen, blood and red-cell 59Fe uptake and in the hematocrit and reticulocytes in the blood.

Prevention of spontaneous leukemia in AKR mice by type-specific immunosuppression of endogenous ecotropic virogenes.

AKR/J mice, 80-90% of which ordinarily die of spontaneous lymphocytic leukemias by 12 months of age, were significantly protected from developing leukemia in the initial experiment by a single course of treatment with AKR serotype-specific antibodies mad in goats and processed as immune gamma globulin (IgG). In experiment 1, IgG was given on the day of birth and on four additional days, and finished on day 14. This schedule resulted in suppression of over 4 logarithms of normal virogene expressions up to 25 days of age and led to partial viral suppression for over 200 days of age. At 365 days of age, 20 of 24 (83.3%) control animals were dead of leukemia whereas six of 30 (20%) treated animals had died of leukemia. In a second experiment, only four inoculations of IgG were given from birth to 20 days, after which they were given three inoculations of radiation-killed vaccine specific for AKR-Gross leukemia virus and one injection of murine sarcoma virus-Gross leukemia virus 10 days later. This combined immunization procedure provided significant virus suppression up to 288 days of age. At 300 days of age, 30 of the 50 (60%) controls had died of leukemia while only 1 of 24 (4.2%) of the immunized mice developed fatal leukemia; the significance of protection for each of the experiments was P LESS THAN 0.001. We conclude that these data establish in classical fashion with type-specific immunosuppression the determining role of type-C endogenous virogenes in leukemogenesis and, at the same time, also established the feasibility of nearly total prevention of leukemia in AKR mice.