Prolonged survival of female AKR mice fed diets supplemented with methionine and choline

Female mice of the AKR/J (AK) strain were fed a control diet (Purina Rodent Laboratory Chow) or a lipotrope-supplemented diet (Purina Rodent Chow plus 2% D,L-methionine and 1% choline chloride) beginning at 1 day after weaning. Food consumption and weight gain were found to be the same in both groups of animals. Mice of this inbred strain spontaneously develop thymic lymphoma, with close to 100% mortality expected by 12-13 months of age. Two separate experiments were carried out with 50 mice per group in one, and 40 mice per group in the other. The slopes of the survival curves for the animals in the control group and supplemented group of mice diverged after the animals reached 6.5 months of age. In both experiments, 20% of the mice receiving supplemented diet were still alive at 1 year, while 3% in one experiment and 8% in the other experiment survived in the control groups. Each experiment was terminated when the animals reached 13 months of age. At that time the survival rate of the controls was 2 and 4%, and survival in the groups of mice receiving supplemented diet was 14 and 18%. Necropsy revealed that the animals in both groups had advanced malignant lymphoma. Our results demonstrate that intake of a chow diet that is supplemented with moderate quantities of methionine and choline results in enhanced survival of spontaneously leukemic AK mice, in comparison with animals of this strain fed the same diet without supplements of choline and methionine.

Experimentally induced plague infection in the northern grasshopper mouse (Onychomys leucogaster) acquired by consumption of infected prey

In this study, 20 laboratory reared Onychomys leucogaster from a parental population that is naturally exposed to plague were each fed a white mouse that had been inoculated with Yersinia pestis. Three of the 20 O. leucogaster died, four survived with antibody titers against Y. pestis and 13 survived with no titer against Y. pestis. In contrast, when 20 O. leucogaster from a plague naive parental population were fed infected prey, seven died and 13 survived with no antibody titer against Y. pestis. Our results suggest another means by which O. leucogaster from populations that are naturally exposed to plague may acquire the disease.

Effects of hantaviral infection on survival, growth and fertility in wild rat (Rattus norvegicus) populations of Baltimore, Maryland

Survival, growth rates, body size and fertility of wild caught Norway rats (Rattus norvegicus), infected and uninfected with a Hantavirus (antigenically related to Seoul virus), were compared. No differences were found in the survival of seronegative versus seropositive rats, as measured by mark-recapture experiments. Growth rates, as measured by weight gain but not by increased body length, were slower in seropositive, sexually mature (greater than 200 g) rats, although no differences in the ultimate body size of infected versus uninfected rats were found. No differences in external measures of sexual maturity, or in embryo counts or testes sizes, were found for infected versus uninfected rats. We conclude that hantaviral infections have little or no impact on demographic processes in Norway rat populations.

Experimental encephalomyocarditis virus infection in Mongolian gerbils (Meriones unguiculatus)

Two strains of Mongolian gerbils (Meriones unguiculatus), Tumble Brook (TUM) and Japan Medical Science (JMS), were intraperitoneally inoculated with the D variant of encephalomyocarditis virus (EMC-D) and killed 3 days later. Mortality was significantly higher in females than in males. Evidence of viral replication was detected in the heart of both strains and in the pancreas of the TUM strain. Histopathological alterations were found in the heart and pancreas. Heart lesions involved foci of necrosis with inflammatory cell infiltration and calcification in both strains. Pancreatic lesions were restricted to the exocrine glands; islets of Langerhans were rarely and secondarily involved in the extensive destruction of exocrine glands. Severe acinar cell necrosis with marked inflammatory edema was conspicuous in TUM, whereas only slight acinar cell involvement was detected in JMS gerbils. Immunoperoxidase staining showed viral antigens in intracytoplasmic vacuoles in damaged acinar cells.

A plague epizootic in the white-tailed prairie dogs (Cynomys leucurus) of Meeteetse, Wyoming

Surveillance for sylvatic plague (Yersinia pestis) was conducted near Meeteetse, Wyoming (USA) from 24 May to 14 June 1985. Ten species of fleas were collected from white-tailed prairie dogs (Cynomys leucurus), and from their burrows and associated rodents. Five of these flea species and two adult prairie dogs were positive for plague. The progression of this plague epizootic appeared to be slower and the intensity was less than in previous epizootics in other prairie dog colonies. The plague epizootic occurred within the only known colony of black-footed ferrets (Mustela nigripes) and was a potential threat to the food source of this endangered species.

Spontaneous tumors in aging (C57BL/6N x C3H/HeN)F1 (B6C3F1) mice

Spontaneous tumors in untreated (C57BL/6N x C3H/HeN)F1 (B6C3F1) mice used as controls in carcinogenicity tests were recorded. In both sexes, the development of spontaneous tumors was age-related. In 244 male mice, the most common tumors were hyperplastic nodules of the liver, hepatocellular carcinomas, malignant lymphomas/leukemias, lung adenomas, and adenocarcinomas. In 246 female mice, the most common tumors were malignant lymphomas/leukemias, pituitary adenomas, neoplastic nodules of the liver, hepatocellular carcinomas, and lung adenomas. Hepatocellular carcinomas metastasized in 20.3% of the animals with these tumors. Few other tumors except malignant lymphomas and leukemias metastasized. Various tumors of other organs and/or tissues were found at low incidences.

High mortality with severe dystrophic cardiac calcinosis in C3H/OUJ mice fed high fat purified diets

Severe degenerative myocardial disease occurred in female C3H/OUJ mice fed purified diets for 36 weeks; the diet contained 5% or 20% fat as non-hydrogenated soybean oil. Deaths of lactating females of this group (17/35 high fat diet and 7/35 low fat diet animals) were due to sudden cardiovascular collapse. Cardiomegaly with marked atrial and ventricular myocardial mineralization was seen at necropsy. Histologically, the random, myopathic foci were characterized by severe myocardial degeneration, mineralization, and fibrosis. Mural thrombosis, pulmonary arteriosclerosis, and mild myocardial inflammatory cell infiltrates were also present. Pathological changes were similar to those of dystrophic cardiac calcinosis, an incidental necropsy finding in certain mouse strains.

Susceptibility of inbred Syrian golden hamsters (Mesocricetus auratus) to lethal disease by lymphocytic choriomeningitis virus

An acutely lethal LCMV disease model has been established in the Syrian golden hamster (Mesocricetus auratus) in which lethality and disease are dependent upon both the inbred hamster strain and the LCMV strain. Young adult inbred, male and female, hamsters were tested for lethal-disease susceptibility by lymphocytic choriomeningitis virus (LCMV) strains, WE or Armstrong (ARM). With WE inocula, PD4 and MHA inbred hamsters were highly susceptible to a wasting disease. LVG and LHC inbred hamsters were intermediate in susceptibility; some of these animals died of wasting illness, and others exhibited minimal disease and survived. CB and LSH hamsters were highly resistant to any disease by WE. Mean survival times of susceptible hamsters given lethal WE inocula approximated 2.5 weeks and were not dependent on virus dose. By 1.5 weeks after WE inoculation wasting disease signs were notable and consisted of lethargy, progressive body weight loss, and diarrhea. The LCMV strain, ARM, was avirulent for all hamster strains, causing neither death nor disease. Hamsters surviving WE or ARM inoculation appeared healthy, produced LCMV antibody, and acquired resistance to further lethal WE challenge. Despite hamster-lethality differences. WE and ARM appeared comparably immunogenic for all hamster strains, based on host antibody titers. A number of other differences between the LCMV strains were, however, noted which could be relevant to virus virulence and lethality for hamster hosts. These included guinea pig lethality, temperature sensitivity, and plaque morphology.

Differential effects of riboflavin and RRR-alpha-tocopheryl acetate on the survival of newborn RCS rats with inheritable retinal degeneration

The dystrophic RCS rat is one of the most important animal models available for investigating retinal degeneration. In addition to the characteristic progressive loss of neural retina the strain is hampered by a high rate of mortality during the first week of life. Death rate during this period is greatly influenced by diet. A 69% reduction in mortality was achieved by supplementing a purified diet with double the amount of AIN-76 vitamin mix. The objective of this study was to identify vitamin(s) in the AIN-76 mix responsible for the enhanced survival. The experiment determined the effect on survival of independently doubling the concentration of each vitamin present in the AIN-76 vitamin mix. This was done by single addition of individual vitamins to a complete purified diet. Survival was determined in litters whose mothers and grandmothers had been provided the supplemented diets as their sole source of food. Supplementation with riboflavin increased mortality by 19%, whereas RRR-alpha-tocopheryl acetate supplementation reduced the mortality by 73%. The effect of RRR-alpha-tocopheryl acetate was equivalent to that achieved by supplementation with complete vitamin mix. First-week survival of pups (born alive) rose from 72.3% +/- 11.0 to 92.5% +/- 3.8 when the level of vitamin E was increased from 50 to 100 IU/kg diet.

Acceleration of age-associated immune decline and mortality by early repeated administration of bestatin to C57BL/6 mice

The effect of chronic treatment with an immunostimulating agent, bestatin, on age-associated immune decline was assessed in C57BL/6 mice. Animals were given weekly doses of bestatin (100 micrograms/mouse, i.p.) from 7 months of age until death, and immune responses (natural killer cell activity, T cell cytotoxicity in vitro and in vivo, delayed-type hypersensitivity reaction, lymphoproliferative responses to mitogens, production of interleukin-2, macrophage functions) were tested at 11, 15, and 20 months. Most of the functions were reduced in 15-17-month-old mice, but evidence of reduced macrophage activities appeared only in limiting conditions (low lipopolysaccharide stimulation for interleukin-1 production and low concentration of macrophages in the cytostatic test). Bestatin administration produced a transient increase in natural killer (NK) cell activity and in vivo T cell cytotoxicity, followed (15-20 months of age) by a depression of NK and T cell-mediated responses. Only macrophage functions were stimulated in 20-month-old bestatin-treated mice. This unresponsiveness coincides with an accelerated mortality of bestatin-treated mice and a significant increase in the number of spontaneous tumor-bearing animals. The stimulation of T cells by bestatin seems to be mediated by a primary activation of macrophages to release immune mediators. Several reasons for the bestatin-induced immunodepression can be postulated including a high dose of bestatin, leading to toxicity or unresponsiveness; induction of suppressor cells; and overproliferation of T cells due to the mitogenic activity of bestatin, which may act as a promoting factor for tumor development.

Paresis of peristalsis and ileus lead to death in lactating mice

Based on the examination of 45 dead and 5 moribund female mice during a 2-year period, we are able to describe a new disease entity: ileus of the small intestine in lactating mice caused by a paresis of peristalsis. Diarrhoea was not observed and inflammation and infectious agents were not found. Females were affected during the 2nd week of their first lactation. The condition may have a mortality rate as high as 40%. It is assumed that exhaustion (calcium, glucose, etc.) is the cause of this condition. Consequently, the development of a dietary supplement or of a special diet for lactating mice may prove beneficial in preventing this disease. Endogenic (Clostridia) or exogenic toxic components may also play a role.

[Occurrence of sick animals in conventional guinea pigs obtained from commercial breeders during 1964 to 1982]

A quarantine was performed on conventional Hartley guinea pigs free from Streptococcus zooepidemicus, Bordetella bronchiseptica and Salmonella spp., but infected with Eimeria caviae, which were purchased from twenty-five commercial breeders by the National Institute of Health. Physical examinations revealed an incidence of 0.88 per cent or 1,461 sick animals in 166, 050 guinea pigs quarantined during the period 1964 to 1982. The result obtained showed the following significant differences between the periods 1964 to 1971 and 1972 to 1982: Annual incidence of sick animals in the period 1972 to 1982 increased twice as many as 0.56 to 0.81 per cent during the 1964 to 1971, and monthly incidence showed bimodal occurrence at April and October in the former period but continual occurrence from November to April in the latter period. Major clinical signs in the former period were death and diarrhea, which occurred usually within a week after arrival of the guinea pigs at our institute and caused significant decrease of body weight, but those in the latter period were retarded growth and weakness which became detectable during 1-3 weeks after arrival of the animals. Discussions were made on possible reasons concerning the differences in incidence of sick animals during the two periods.

[Studies on coccidiosis in guinea pigs. 1. Clinico-pathological observation]

Clinico-pathological and parasitological studies have been performed on spontaneous and experimental coccidiosis in guinea pigs. Among 11,244 Hartley guinea pigs purchased from suppliers during 1968, 410 (3.6%) of the animals had diarrhea due to coccidiosis. The incidence rate was high in the spring and fall with a mortality rate of 14.4 per cent. A particularly high number of fatal cases were found in the spring. In experimentally induced coccidiosis, clinical signs observed were diarrhea, dehydration, weight loss and death. The diarrhea developed in all animals on the eleventh day after infection and continued for one to five days. Food and water intakes were markedly reduced after the appearance of diarrhea, followed by anorexia and dehydration. Correlating with the appearance of diarrhea was a striking drop in body weight of the guinea pigs. Death usually occurred on the third to fifth day after the onset of diarrhea. The mortality rate was 30 per cent. The major macroscopic findings were characterized by a markedly thickened wall from the ascending to the descending colon and gelatinous edema of the mesenterium of the spiral of the ascending colon. Histologically, there was marked hyperplasia of the mucosal epithelium in the colon and numerous coccidia at different stages of development within the mucus membrane. In the advanced stages of the disease, there was degeneration and desquamation of the epithelia, marked edematous change and infiltration of neutrophil leukocytes and lymphocytes into the lamina propria and submucosa, many oocysts in the lumen of the intestine and in the intestinal glands.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of amino acids, B vitamins and butylated hydroxyanisole as protective agents against pyrrolizidine alkaloid toxicity in rats

Supplementation of the diets of rats with branched chain amino acids (BCAA: leucine, isoleucine, valine) did not alter their susceptibility to chronic poisoning by tansy ragwort (Senecio jacobaea), which contains hepatotoxic pyrrolizidine alkaloids (PA). Phenobarbital in the diet, which alters liver microsomal enzyme activity, also did not alter susceptibility to PA poisoning. A combination of butylated hydroxyanisole (BHA), cysteine and BCAA did increase (P less than .05) survival time of rats fed tansy ragwort. Dietary BHA and cysteine increased the survival time of rats injected with the PA monocrotaline, with evidence that addition of vitamin B12 and folic acid improved the effectiveness of this treatment. In a chronic feeding trial with tansy ragwort, a combination of BHA and cysteine increased (P less than .05) the survival times of rats, showing protective activity against PA poisoning. A mixture of B-complex vitamins, or vitamin B12-folic acid, was not effective in improving the response.

A breeding study to control chronic progressive nephrosis in rats

Breeder male Sprague-Dawley rats were categorized as potential low and high protein excretors at 4 months of age. The average selection values of these two groups were 0.59 and 1.75 mg/ml, respectively. Paris of females were mated to these males in two breeding cycles in the fashion of a diallele cross. The heritability index based on protein excretion values of 263 male offspring at 6 months of age from both cycles of high and low excretor males was 0.526 with approximate variance of 0.0668. Significantly different (p less than 0.01) survival distributions were shown. The mean and median survival times of the high excretor offspring were 611.1 and 652 days, respectively, compared to 651.4 and 680.5 days, respectively, in low excretor offspring. The proportion of offspring with marked chronic progressive nephrosis was significantly greater (p less than 0.01) in the high excretor group, both prior to and after 700 days of age, than that of offspring in the low excretor group. The selection of low excretor males for breeding stock appears to offer a practical basis for minimizing the total expression of chronic progressive nephrosis in this strain of rat.

Survival of hamsters fed graded levels of two protein sources

Two protein sources (supplemented casein and lactalbumin), which were well-utilized by Syrian hamsters in previous 3-week experiments, were fed in long-term studies. Casein supplemented with methionine and cysteine was fed for 20 weeks at levels of 4, 20, and 40 g/100 g diet. The lowest level did not support normal growth and resulted in the highest mortality rate during the first 10 weeks of feeding. The higher levels caused increased mortality in females, in association with decreasing body weights between 16 and 20 weeks. Kidney weights and incidences of lower nephron nephrosis at 20 weeks were elevated in both sexes fed the 40 g/100 g levels of supplemented casein by comparison with the 10 g/100 g level. In a separate experiment, lactalbumin was fed for life at 10, 20, and 40 g/100 g diet levels, and its effects compared to those with a commercial diet. The lactalbumin diet supported somewhat slower growth rates, but improved survival when compared to commercial diet-fed groups. Survival was longest in both sexes fed the 20 g lactalbumin/100 g diet levels for life.

Pathological effects of pine needle ingestion in pregnant mice

Consumption of Ponderosa pine (Pinus ponderosa) needles causes reproductive dysfunction in mice during early and late gestation. Consumption during early gestation results in considerable embryotoxicity which is not a result of starvation. Temporary loss of coordination and lethargy are observed in the females. Consumption of the pine needle diet results in a weight loss which persists throughout gestation. Feeding the pine needle diet from the tenth day of gestation results in spleen atrophy observable by day twelve and adrenal hypertrophy by day thirteen. The adrenal hypertrophy is characterized by an increase in the medullary component of the gland from the normal 12% medulla present on day ten to approximately 35% medulla present in the glands of those females surviving past day fourteen. Few fetal deaths are observed prior to day fifteen but the incidence of fetal death reaches 80% by day sixteen of gestation. If the dead fetuses are not aborted, maternal death follows fetal death by approximately two days; however, if the dead fetuses are aborted the females survive.

[Pathological studies on spontaneous tumors in mice (author's transl)]

The incidence and histopathology of the spontaneous tumors in over 2-year-old ddY strain mice, an outbred widely used in Japan, are described. The incidences of the total spontaneous tumors were 47.5% in males and 66.7% in females in actual numbers. These, however, could be corrected to 64.4% and 80.0%, respectively, when the accidental death are omitted from the results. The incidences of the pulmonary tumors were very high; 39.2% in males and 26.7% in females of the total spontaneous tumors, respectively. Other tumors which showed high incidences were, lymphoid tumors; 17.5% in males and 19.2% in females and mammary tumors; 26.7% exclusively in females. However, no strain-specific tumors were observed which are common in inbred strains such as leukemia in AKR or mammary tumors in C3H strains, partly suggesting broad genetic variation of the strains. Histopathological examination revealed prevailing types of the tumors to be papillary adenoma of pulmonary tumors, simple adenoma of mammary tumors and poorly differentiated lymphosarcoma of lymphatic tissues.