C3H mice have larger spleens, lower platelet counts, and shorter platelet lifespans than C57BL mice: an animal model for the study of hypersplenism.

Several studies have shown that C3H mice have a modal megakaryocyte ploidy class of 32N as opposed to the 16N found in all other mouse strains tested. In addition to higher megakaryocyte DNA content, C3H mice are characterized by greater 35S-sulfate incorporation into platelets but somewhat lower platelet counts than C57BL mice. The aim of this study was to determine the etiology of mild thrombocytopenia in C3H mice. Several studies have indicated that an increase in platelet 35S incorporation parallels increased megakaryocyte ploidy. Thus the higher 35S incorporation by C3H mouse platelets is likely related to their higher megakaryocyte ploidy, but these differences do not explain the lower platelet counts observed in C3H mice. To elucidate the paradox of relatively low platelet counts in C3H mice despite elevated platelet 35S incorporation, we performed a hematological evaluation (including assessment of platelet counts and lifespans) and measured (relative) spleen size in C3H and C57BL mice. Our data confirm earlier reports of significantly lower platelet counts in C3H mice (p < 0.0005) compared with C57BL mice. We also found that C3H mice have larger spleens (p < 0.0005) than C57BL mice. Other groups of C3H and C57BL mice were splenectomized to determine the role of the spleen in decreasing platelet counts in C3H mice compared with C57BL mice. C3H mice had an average platelet lifespan of 4.8 days, which was significantly shorter (p < 0.01) than the 5.7-day platelet lifespan observed in normal C57BL mice. Platelet lifespans for splenectomized C3H mice were significantly (p < 0.005) longer than those found in intact C3H control mice, but splenectomy of C57BL mice had no effect on their platelet lifespans (p < 0.40). The lengthened platelet lifespans of splenectomized C3H mice indicate that the spleens of C3H mice were sequestering or destroying platelets at a faster rate than the spleens of C57BL mice. These data lead to the hypothesis that the relatively large spleens of C3H mice produce mild thrombocytopenia with increased platelet production (shorter platelet lifespan) compared with spleens of C57BL mice.

Quantitative measurements on the haemopoietic systems of three strains of mice.

Quantitative measurements on the haemopoiedic systems of SAS/4, 3H and RFM mice have been used to calculate the distribution and population sizes of haemopoietic cells in the bone marrow, spleen and peripheral blood. Considerable strain differences have been found in the sizes of haemopioetic stem cell populations and in the distribution of these cells within the haemopioetic system, although the incidence of CFU-S was shown to be uniform throughout skeletal sites of haemopioesis. The seeding efficiency of colony forming cells in the spleen, measured by the 'f" factor 24 hours after irradiation and transplantation, also differs between strains and between the bone marrow and spleen of the strains investigated.

Prolactin and growth hormone levels in different inbred strains of mice: patterns in association with estrous cycle, time of day, and perphenazine stimulation.

These experiments were designed to compare prolactin (PRL) and growth hormone (GH) secretion in strains of mice with varying incidences of mammary tumors. In addition to the basal levels, PRL concentrations were compared after stimulation with perphenazine. Although pituitary concentrations of PRL and pituitary serum concentrations of GH appeared to be generally higher in strains with high incidence of mammary tumors, basal PRL levels in single decapitate serum samples seemed to have little correlation with the incidence of mammary tumors in different strains. However, PRL concentrations in sera after perphenazine injection followed a pattern characteristic of the mammary tumor incidence rate of the strain: C3H/St and CBA/St--the two high-incidence strains--had lower levels of PRL; C57BL/St and BALB/cST--the two low-incidence strains--had higher levels; and DBA/2St--the medium-incidence strain--had an intermediate level. PRL contents of the pituitary glands were depleted virtually equally in all strains except the BALB/cSt. These results suggested that the rate of metabolism of PRL in strains with high incidence of mammary tumors may be faster than in those with low incidences. Perphenazine had no influence on GH secretion in most mice. The strain-specific differences in PRL and GH concentrations were usually present even during cyclical and diurnal fluctuations. Serum PRL and GH levels were generally higher during the follicular phase and lower during the luteal phase of the estrous cycle in both C3H/St and C57BL/St strains. There were signs of episodic secretion of PRL together with evidences of circadian periodicity in the secretion of PRL and GH in mice of both strains. The levels of GH were usually high during the morning hours of those of PRL high during the evening hours. The data show a high degree of specificity in the secretion of PRL and GH im mice of different inbred strains, and it is possible that these strain-specific differences may be an important factor in the development of mammary tumors.

Two different mechanisms of immune-complex trapping in the mouse spleen during immune responses.

The capacity of immune-complex (IC) trapping was examined using purified horse radish peroxidase (HRP)-anti-HRP (PAP) on frozen sections of mouse spleen in vitro. We investigated the trapping mechanisms by applying the IC with or without fresh mouse serum added on the spleen sections of naive as well as immunized mice. When the PAP was applied alone, it mainly located on the macrophages in red pulp. In the splenic white pulp of immunized mice, PAP was trapped on follicular dendritic cells (FDC) in a small area of the germinal center whereas it scarcely bound to the splenic white pulp of non-immunized mice. An antibody against mouse Fc receptor (2.4G2) blocked the trapping but antibodies against mouse complement receptor (8C12, Mac-1 and 7G6) did not. When the PAP was applied mixed with fresh mouse serum, it bound on FDC in the primary follicles in the spleen of non-immunized mice. The density and area of IC trapping increased in the spleen of immunized mice. IC trapping in the presence of fresh mouse serum was blocked by the antibodies 8C12 and 7G6 but not by 2.4G2 or Mac-1.

Deoxyribonuclease II (DNase II) activity in mouse tissues and body fluids.

The distribution of deoxyribonuclease II (DNase II) in tissues and body fluids was examined in 12-week-old C3H/He mice. Activity was observed in most tissues and body fluids except erythrocytes and serum, but their levels were quite different among tissues. Activity was high in the spleen, salivary gland, and preputial gland, moderate in the liver, kidney, thymus, lung, heart, pancreas, seminal vesicle, coagulating gland and prostate and low in the brain, testis and muscles. Sex difference, males having a significantly higher DNase II activity level than females, was observed in salivary gland, kidney and urine.

Haemoglobin variants in mice.

Haemoglobin variants were studied in wild and laboratory house mice (Mus musculus), including standard and new inbred strains, using starch-gel electrophoretic technique. Single (Hbbs) or diffuse (Hbbd) types of haemoglobin were found in all of them. The embryonic haemoglobin pattern was different from although similar to that of the adult in all the strains. The haemoglobins revealed monomorphism in the inbred strains, while polymorphism was observed in non-inbred laboratory and wild mice.

Comparative hemostatic parameters in BALB/c, C57BL/6 and C3H/He mice.

This study describes micro-methods to determine biological parameters in plasma of three strains of mice. Platelet count was significantly different among strains. C57BL/6 mice showed the highest values (988 x 10(3)/microL) and BALB/c the lowest (782 x 10(3)/microL). Fibrinogen levels were 2.55 (C57BL/6), 2.37 (BALB/c) and 2.28 g/L (C3H/He). Some inter-strain differences were observed in factor XIII (94, 118 and 114%) and plasminogen levels (142, 80 and 135%) in C57BL/6, BALB/c and C3H/He, respectively. Additionally, we observed individual mice factor XIII and plasminogen levels between 80 to 200% and 65 to 180%, respectively, in relation to pooled human plasma; and between 70 to 185% and 70 to 155%, respectively, against pooled mice plasma. To our knowledge, this is first report in the literature in diverse mice strains regarding hemostasis, mainly on factor XIII, plasminogen levels, and a very simple test that allows measurement of endogenous fibrinolytic activity present in the plasma. The different results are discussed in relationship with existing literature regarding if the animals in some studies were maintained under strict pathogen-free conditions, the collection of blood was from the heart or eye and if the analysis method was tested by counting manually or automatically. This work could contribute useful knowledge to the field of investigations regarding hemostatic disorders using mouse models, especially for laboratories that are not well equipped.

Age-Related Reference Intervals of the Main Biochemical and Hematological Parameters in C57BL/6J, 129SV/EV and C3H/HeJ Mouse Strains.

BACKGROUND: Although the mouse is the animal model most widely used to study the pathogenesis and treatment of human diseases, reference values for biochemical parameters are scanty or lacking for the most frequently used strains. We therefore evaluated these parameters in the C57BL/6J, 129SV/EV and C3H/HeJ mice. METHODOLOGY/PRINCIPAL FINDINGS: We measured by dry chemistry 26 analytes relative to electrolyte balance, lipoprotein metabolism, and muscle/heart, liver, kidney and pancreas functions, and by automated blood counter 5 hematological parameters in 30 animals (15 male and 15 female) of each mouse strain at three age ranges: 1-2 months, 3-8 months and 9-12 months. Whole blood was collected from the retro-orbital sinus. We used quality control procedures to investigate analytical imprecision and inaccuracy. Reference values were calculated by non parametric methods (median and 2.5(th) and 97.5(th) percentiles). The Mann-Whitney and Kruskal-Wallis tests were used for between-group comparisons. Median levels of GLU, LDH, Chol and BUN were higher, and LPS, AST, ALP and CHE were lower in males than in females (p range: 0.05-0.001). Inter-strain differences were observed for: (1) GLU, t-Bil, K+, Ca++, PO(4)- (p<0.05) and for TAG, Chol, AST, Fe++ (p<0.001) in 4-8 month-old animals; (2) for CK, Crea, Mg++, Na++, K+, Cl- (p<0.05) and BUN (p<0.001) in 2- and in 10-12 month-old mice; and (3) for WBC, RBC, HGB, HCT and PLT (p<0.05) during the 1 year life span. CONCLUSION/SIGNIFICANCE: Our results indicate that metabolic variations in C57BL/6J, 129SV/EV and C3H/HeJ mice after therapeutic intervention should be evaluated against gender- and age-dependent reference intervals.

Genotype-specific environmental impact on the variance of blood values in inbred and F1 hybrid mice.

Mice are important models for biomedical research because of the possibility of standardizing genetic background and environmental conditions, which both affect phenotypic variability. Inbred mouse strains as well as F1 hybrid mice are routinely used as genetically defined animal models; however, only a few studies investigated the variance of phenotypic parameters in inbred versus F1 hybrid mice and the potential interference of the genetic background with different housing conditions. Thus, we analyzed the ranges of clinical chemical and hematologic parameters in C3H and C57BL/6 inbred mice and their reciprocal F1 hybrids (B6C3F1, C3B6F1) in two different mouse facilities. Two thirds of the blood parameters examined in the same strain differed between the facilities for both the inbred strains and the F1 hybrid lines. The relation of the values between inbred and F1 hybrid mice was also affected by the facility. The variance of blood parameters in F1 hybrid mice compared with their parental inbred strains was inconsistent in one facility but generally smaller in the other facility. A subsequent study of F1 hybrid animals derived from the parental strains C3H and BALB/c, which was done in the latter housing unit, detected no general difference in the variance of blood parameters between F1 hybrid and inbred mice. Our study clearly demonstrates the possibility of major interactions between genotype and environment regarding the variance of clinical chemical and hematologic parameters.

Protective serum effects in tumor immunity.

Administration of serum presumed to contain tumor-specific antibodies supported the rejection in immunized mice of syngeneic fibrosarcoma implants which receded after an initial period of s.c. growth. Passive transfer of immune serum to unsensitized mice, sublethally radiated and injected with normal lymph node cells, protected the recipients against i.v. but not against s.c. implantation of syngeneic mammary carcinoma cells. Injection of immune serum assisted the recovery of mice in a state of tumor-induced specific immune depression induced by a large. s.c. mammary carcinoma implant and maintained after surgical cure by injections of serum presumed to contain soluble tumor antigen.

Age dependent change in size distribution of blood cells in fetal and young mice.

The mean corpuscular volume (MCV) and the size distribution of circulating blood cells were determined in the fetal mice of C3H/He strain by using a new electric cell size analyser, Coulter Channelyzer C-256. On the 12th day of gestation, the volume of circulating blood cells was distributed between approximately 240-820 fl (mode at 470 fl), and the MCV was 534.9 +/- 30.1 fl, i. e., ten to eleven times that of adult one. On the 14th day, two types of cell population were observed; one with smaller cell volume and another with larger one corresponded to that of the blood cells on day 12. Therefore, two peaks were observed to be at 140 and 501 fl in the size distribution curve. The cell population with large volume observed on day 12-14 had been almost disappeared by the 16th day of gestation, and the small blood cells became dominant. The MCV of blood cells was then decreased with the development of fetus, from 188.2 +/- 19.3 fl on day 16, to 135.1 +/- 7.3 fl on day 18, and 117.5 +/- 7.2 fl on day 20. The size of blood cells continued to decrease gradually after birth, and became adult range by 8 weeks after birth. The MCV values of the blood cells were 120.9 +/- 8.6 fl, 87.5 +/- 6.2 fl, and 48.7 +/- 0.8 fl for the newborns of 1 day and 7 days old, and the adult mice, respectively. White blood cells were not separated from the blood samples in this study. However, the size distribution and MCV presented above were appeared to be related essentially to the red blood cells, since the number of white blood cells are negligible small compared with that of the red cells.

Histopathologic observations in weanling B6C3F1 mice and F344/N rats and their adult parental strains.

Weanling Fischer 344/N (F344) rats and the first filial hybrid of C57BL/6 x C3H (B6C3F1) mice and retired breeders from the parental stocks of these strains were monitored over a 5-yr-period by examining the histopathology of selected organs and comparing those results to viral and mycoplasmal serology and the intestinal tract bacterial flora of each animal on an individual basis. Serology gave no evidence of viral infection, but Mycoplasma arthriditis antibodies were detected. Reactivity of serum of adult C57BL/6 female mice with control cells or media (tissue culture, TC) was seen in a significant number of mice. TC reactivity correlated positively with lymphoid perivascular infiltrates, predominantly of the lungs, suggesting an allergic response in development of the lesions. Other lesions of note consisted of Harderian gland inflammation of rats, focal necrotizing lesions of the liver of both species, and thickening of the pleura and adjacent pulmonary interstitium of weanling rats. Embolization of bacteria from the gastrointestinal tract to the liver was considered a possible cause of the liver necrosis in both species. Although lesions of the lung and Harderian gland of the rats are similar to those caused by known viral agents, the cause of the latter could not be determined as these animals were negative for viral antibodies and the former was considered to be related to incomplete pulmonary development in the young rat. Features differentiating the lesions observed in animals of this survey from those caused by viral infection are discussed.

Sex- and strain-related differences in megakaryocytopoiesis and platelet production in C3H and BALB/c mice.

In an effort to explain the different platelet production capabilities of male and female mice, megakaryocyte and platelet indices were measured on castrated male and oophorectomized female C3H and BALB/c mice, along with suitable intact controls. In agreement with our previous work, intact male BALB/c mice had higher platelet counts and percent incorporation of sulfur 35 into platelet values than did intact female BALB/c mice. Also, both intact BALB/c and C3H male mice had higher platelet counts than their castrated counterparts. Fewer femoral megakaryocytes were found in intact BALB/c and C3H male mice than in their female counterparts (p less than 0.05), but only BALB/c male mice had larger megakaryocytes than BALB/c female mice (p less than 0.0005). Castration caused increased numbers and decreased sizes of megakaryocytes (p less than 0.05) in both strains of mice, but oophorectomy did not change the characteristics of megakaryocytes in these mice. In all treatment groups, C3H mice had megakaryocytes with higher average deoxyribonucleic acid content than did BALB/c mice (p less than 0.0005), that is, BALB/c mice had greater percentages of 8N and 16N megakaryocytes than did C3H mice, but C3H mice had higher proportions of 32N and 64N megakaryocytes than did BALB/c mice (p less than 0.05 to p less than 0.0005). Although a difference in megakaryocyte ploidy was not detected between intact male and intact female C3H mice, BALB/c female mice had elevated percentages of low ploidy classes (8N) when compared with BALB/c male mice (p less than 0.005). Intact male C3H mice had higher percentages of 16N megakaryocytes (p less than 0.05) than did their neutered counterparts.(ABSTRACT TRUNCATED AT 250 WORDS)