PL Mice Research Articles

Risedronate prevents early radiation-induced osteoporosis in mice at multiple skeletal locations

Introduction Irradiation of normal, non-malignant bone during cancer therapy can lead to atrophy and increased risk of fracture at several skeletal sites, particularly the hip. This bone loss has been largely attributed to damaged osteoblasts. Little attention has been given to increased bone resorption as a contributor to radiation-induced osteoporosis. Our aims were to identify if radiation increases bone resorption resulting in acute bone loss and if bone loss could be prevented by administering risedronate. Methods Twenty-week-old female C57BL/6 mice were either: not irradiated and treated with placebo (NR + PL); whole-body irradiated with 2 Gy x-rays and treated with placebo (IR + PL); or irradiated and treated with risedronate (IR + RIS; 30 μg/kg every other day). Calcein injections were administered 7 and 2 days before sacrifice. Bones were collected 1, 2, and 3 weeks after exposure. MicroCT analysis was performed at 3 sites: proximal tibial metaphysis, distal femoral metaphysis, and the body of the 5th lumbar vertebra (L5). Osteoclasts were identified from TRAP-stained histological sections. Dynamic histomorphometry of cortical and trabecular bone was performed. Circulating TRAP5b and osteocalcin concentrations were quantified. Results In animals receiving IR + PL, significant ( P < 0.05) reduction in trabecular volume fraction relative to non-irradiated controls was observed at all three skeletal sites and time points. Likewise, radiation-induced loss of connectivity and trabecular number relative to NR + PL were observed at all skeletal sites throughout the study. Bone loss primarily occurred during the first week post-exposure. Trabecular and endocortical bone formation was not reduced until week 2. Loss of bone volume was absent in animals receiving IR + RIS. Histology indicated greater osteoclast numbers at week 1 within IR + PL mice. Serum TRAP5b concentration was increased in IR + PL mice only at week 1 compared to NR + PL ( P = 0.05). Risedronate treatment prevented the radiation-induced increase in osteoclast number, surface, and TRAP5b. Conclusions This study demonstrated a rapid loss of trabecular bone at several skeletal sites after whole-body irradiation. Changes were accompanied by an increase in osteoclast number and serum markers of bone loss. Risedronate entirely prevented bone loss, providing further evidence that an increase in bone resorption likely caused this radiation-induced bone loss.

Direct effects of recombinant human endostatin on tumor cell IL-8 production are associated with increased endothelial cell apoptosis in an orthotopic model of human pancreatic cancer

Purpose: Recombinant human endostatin (rhES) is an antiangiogenic agent derived from collagen XVIII which inhibits tumor growth in subcutaneous models of various human malignancies. However, its effectiveness in an orthotopic xenograft model of an abdominal neoplasm has not been demonstrated. Design: An orthotopic model of pancreatic cancer was established in 6-week-old male athymic mice from either of 2 human cell lines (L3.6pl or BxPC3). Established tumors were treated with 40 mg/kg rhES or vehicle controls for up to 3 weeks. Tumors were analyzed by immunohistochemistry for TUNEL / CD31, IL-8, VEGF, and bFGF. We also measured direct effects of rhES on tumor cell angiogenic factor production by ELISA in vitro. Results: Overall tumor burden was not reduced with rhES treatment in mice inoculated with either cell line. Peritoneal carcinomatosis in the L3.6pl mice was greater in those treated with rhES than in those treated with normal saline or citrate buffer (p < 0.05). Treatment with rhES lowered IL-8 levels 32-47% in vivo (p < 0.001) and 40-65% in vitro (p < 0.05) in the fast-growing L3.6pl tumors but not in the slow-growing BxPC3 tumors (p < 0.05). rhES also increased the levels of endothelial cell apoptosis 16- to 24-fold in vivo in the L3.6pl mice, but not in the BxPC3 mice (p < 0.05). Conclusions: rhES down-regulated IL-8 levels and induced endothelial cell apoptosis the more aggressive cell line in a xenograft model of pancreatic cancer. Nonetheless, these effects were not sufficient to produce significant inhibition of tumor growth.

Kidney changes in multiparous, nulliparous and ovariectomized mice fed either a nutrient-sufficient or -deficient diet containing cadmium

As a simulation of the etiological factors known for Itai-Itai disease, a syndrome characterized by renal dysfunction and osteomalacia in its Japanese victims, female mice were subjected to the individual and combined stresses of dietary Cd, nutrient-deficient diet, multiparity and ovariectomy. Renal function as affected by the etiological factors was periodically evaluated by determination of protein, amino acid, glucose and Cd concentrations in urine; periodic changes in skeletal Ca status were assessed relative to current renal function. Renal metabolism of Cd, Zn and Cu was also examined. At age 68 days, female mice were given nutrient-sufficient (+) or -deficient (−), purified diets containing either 0.25 (environmental), 5, or 50 ppm Cd as CdCl 2; the nutritional composition of (−) diet simulated that of food consumed by Japanese victims of Itai-Itai disease. At age 70 days, half of the females began a breeding regimen of six consecutive, 42-day rounds of pregnancy/lactation (PL mice); the remainder were maintained as virgin, non-pregnant controls (NP mice). Limited numbers of PL and NP mice were sacrificed at the end of each reproductive round. PL(+) mice taken in a given round had successively borne litters in that round and all preceding ones. PL(−) females taken at the end of round (R)-l, -2 and -3 had successively borne litters through those rounds; those taken at the end of R-5 or R-6 had nonsuccessively borne litters in four of five or three of six rounds, respectively. At the conclusion of the 252-day reproductive period, remaining females entered the 392-day, post-reproductive phase of the experiment. At age 546 days (mid-R-12), PL females having successfully borne at least three litters were ovariectomized (OV) to mimic human menopause; at the same time, NP females were either ovariectomized or sham-operated (SO). After surgery, all females were maintained to age 714 days (mid-R-16), then sacrificed. Spot urine samples were taken from individual mice at the end of most reproductive rounds (R-2 → 6), prior to surgery (rnid-R-10), and prior to final sacrifice (late-R-15); samples were also collected via metabolism cages at the end of R-10. Food consumption, monitored on a weekly basis over the first nine rounds, was generally not significantly affected by dietary Cd level or nutrient deficiencies in females of the same reproductive status; consumption was increased about 2.5-fold in PL versus NP groups during the reproductive period and about 1.4-fold during the post-reproductive period. At each of the three dietary Cd levels and after all reproductive rounds, mean renal Cd concentrations were 1.2- to 5.6-fold higher in PL than NP mice. After six reproductive rounds, renal Cd concentrations in PL(+) and (−) groups exposed to 50 ppm Cd had reached 155 and 179μg Cd/g kidney, respectively. Although these levels fell within a concentration range (145–200 μg Cd/g) where cadmium-induced renal dysfunction could be anticipated, no significant, Cd-dependent changes in mean urinary amino acid or protein concentrations were found. Moreover, among the same population, a 12% incidence of elevated urinary Cd (≥ 250 ng/ml) was noted, however none of the affected individuals exhibited depressed total calcium content (TCa) or calcium:dry weight ratios (Ca:DW) for femur. Such results suggested that the Cd-induced, skeletal demineralization observed in mice during the reproductive period (Bhattacharyya et al., Toxicology 1988a; 50: 193–204; Whelton et al., Toxicology 1994; 91: 235–251) likely occurred in the general absence of cadmium-induced renal dysfunction. By the end of the post-reproductive period, the incidence of elevated urinary Cd increased to 26% among ovariectomized females; of these, 89% with urinary Cd ≥ 345 ng/ml exhibited decreases in TCa and/or Ca:DW values for femur or lumbar vertebrae that exceeded one S.D. of their group mean. Such results suggested that skeletal demineralization observed at this time (Whelton et al., Toxicology 1997a; 119: 103–121) likely occurred, for at least a portion of the population, in the presence of an ovariectomy-enhanced, cadmium-induced nephrotoxicity. During the reproductive period, small increases in Zn and Cu concentrations (ca. 1.8- and 1.5-fold, respectively) were observed for kidneys of (−) diet mice with very large increases in renal Cd concentrations (ca. 7700-fold) analogous to results previously found for (+) diet mice (Bhattacharyya et al., Toxicology 1988b; 50: 205–215). A threshold Cd concentration below which the concentration of Zn was relatively constant and independent of Cd concentration was identified (13.6 μg Cd/g kidney); no similar threshold could be observed for Cu. At the end of six rounds, less Zn was found in the kidneys of PL(−) mice exposed to Cd at the 50 than 5 ppm level, however more Cu was found in the kidneys of both NP and PL(−) mice.

Hepatic levels of cadmium, zinc and copper in multiparous, nulliparous and ovariectomized mice fed either a nutrient-sufficient or -deficient diet containing cadmium

As a simulation of etiological factors known for Itai-Itai disease, female mice were subjected to the individual and combined stresses of dietary cadmium, nutrient-deficient diet, multiparity and ovariectomy. From age 68 days, female mice were maintained on either nutrient-sufficient (+) or -deficient (−), purified diets containing either 0.25 (environmental), 5, or 50 ppm Cd as CdCl 2; the nutritional composition of (−) diet simulated that of food consumed by Japanese women who contracted Itai-Itai disease. At age 70 days, half of the mice began a breeding regimen of six consecutive, 42-day rounds of pregnancy/lactation (PL mice); the remainder were maintained as virgin, non-pregnant controls (NP mice). Limited numbers of PL and NP mice were sacrificed at the end of each reproductive round. PL(+) mice taken in a given round had successively borne litters in that round and all preceding ones. PL(−) females taken at the end of round (R)-l, −2 and −3 had successively borne litters through those rounds; those taken at the end of R-5 or −6 had nonsuccessively borne litters in four of five or three of six rounds, respectively. At the end of the 252-day reproductive period, remaining females entered the 392-day, post-reproductive phase of the experiment. At age 546 days (mid-R-12), PL females having successfully borne at least three litters were ovariectomized (OV) to mimic human menopause, while NP females were either ovariectomized or sham-operated (SO). After surgery, all females were maintained to age 714 days (mid-R-16), then sacrificed. Food consumption, monitored on a weekly basis over the first nine rounds, was in general not significantly affected by dietary Cd level or nutrient deficiencies for females of the same reproductive status; consumption was increased about 2.5-fold in PL versus NP groups during the reproductive period and about 1.4-fold during the post-reproductive period. Over the reproductive period, small increases in liver concentrations of Zn and Cu were observed (ca. 3.1- and 2.5-fold, respectively) with far larger increases for Cd (ca. 22200-fold). Threshold hepatic Cd concentrations below which the concentrations of Zn and Cu were relatively constant and independent of Cd concentration were identified; they were 2.7 μg Cd/g liver for Zn and 3.3 μg Cd/g liver for Cu for females consuming (+) diet, and 4.9 μg Cd/g liver for Zn and 4.5 μg Cd/g liver for Cu for females consuming (−) diet. Regardless of Cd exposure level, round-by-round hepatic concentrations of Cd were generally 2- to 6-fold higher in PL than NP mice, while Zn or Cu levels were generally only 1.1- to 2.5-fold higher. For each reproductive round, hepatic concentrations of Cd in NP females were consistently about 10-fold greater in mice exposed to 50 than 5 ppm dietary Cd; corresponding Zn levels were essentially equivalent. For PL females, Cd levels were about 7-fold greater in 50 than 5 ppm Cd-exposed groups, however Zn concentrations were about 45% decreased. The pattern of Cd, Zn and Cu sequestration established during the reproductive period clearly differed from that of the post-reproductive period. Between R-6 and -16, hepatic concentrations of Cd, Zn and Cu appreciably decreased (14–69%) in 5 ppm Cd-exposed NPOV and PLOV females regardless of diet-type consumed. At the 50 ppm Cd level, Cd and Zn concencentrations dramatically rose with increases in Cd (37–129%) exceeding those of Zn (12–21%).

Skeletal changes in multiparous, nulliparous and ovariectomized mice fed either a nutrient-sufficient or -deficient diet containing cadmium

As a simulation of the etiological factors known for Itai-Itai disease, a syndrome characterized by osteomalacia and renal dysfunction in its Japanese victims, female mice were subjected to the individual and combined stresses of dietary cadmium, nutrient-deficient diet, multiparity and ovariectomy; the calcium-depleting effect of each factor was evaluated by determining Ca levels in femur and lumbar vertebrae. At age 68 days, female mice were given nutrient-sufficient (+) or -deficient (−), purified diets containing either 0.25 (environmental), 5, or 50 ppm Cd as Cdcl 2; the nutritional composition of (−) diet simulated that of food consumed by Japanese victims of Itai-Itai disease. At age 70 days, half of the females began a breeding regimen of six consecutive, 42-day rounds of pregnancy/lactation (PL mice); the remainder were maintained as virgin, non-pregnant controls (NP mice). Limited numbers of PL and NP mice were sacrificed at the end of each reproductive round. PL(+) mice taken at the end of round (R)-6 had successively borne litters in all six rounds, while PL(−) counterparts had nonsuccessively borne only three. At the conclusion of the 252-day reproductive period, remaining females entered the 392-day, post-reproductive phase of the experiment. At age 546 days (mid-R-12), PL females having successfully borne at least three litters were ovariectomized (OV) to mimic human menopause; at the same time, NP females were either ovariectomized or sham-operated (SO). After surgery, all females were maintained to age 714 days (mid-R-16), then sacrificed. During the post-reproductive period, food consumption by females of the same reproductive status was unaffected by elevated levels of Cd or nutrient-deficiencies in diet. However by R-16, Cd at 50 vs. 0.25 ppm had reduced body mass by 11% in both NP and PLOV females, femur and lumbar vertebral calcium content (TCa) by 20 and 25% in the respective groups, and femur and vertebral calcium/dry weight ratios (Ca/DW) by 12 and 11%. Alternative R-16 comparisons indicated that (−) diet also diminished skeletal Ca, but that the additional factors of (prior) multiparity and ovariectomy generated only small and non-significant effects. Comparison of skeletal status between the ends of the reproductive and post-reproductive periods indicated that (1) individual NP groups, regardless of Cd exposure, generally sustained small decreases in TCa and CaDW over time (consistent with aging), but PL groups without exception secured significant gains (consistent with cessation of multiparous activity), (2) skeletal integrity of PL groups was significantly more compromised by the combination of Itai etiological factors at the end of R-6 than R-16, and (3) among those factors, the most demineralizing over lifetime were chronic exposure to Cd followed by ingestion of (−) diet. Despite these findings, skeletal degeneration characteristic of the Itai-Itai syndrome was ultimately not duplicated in this mouse model suggesting that the full-blown disease required primary and profound skeletal demineralization secondarily supported and enhanced by renal dysfunction.

Transcutaneous photodynamic therapy alters the development of an adoptively transferred form of murine experimental autoimmune encephalomyelitis.

Transcutaneous photodynamic therapy (PDT), utilizing benzoporphyrin derivative monoacid ring A (BPD, verteporfin) and whole-body light exposure, was assessed for its capacity to modify the course of adoptively transferred experimental autoimmune encephalomyelitis (EAE) in PL mice. Using a novel cell culture technique to facilitate the induction of this neurodegenerative condition, disease signs commenced 3-4 weeks after the transfer of myelin basic protein (MBP)-reactive lymph node or spleen cells to naive syngeneic recipients. Mice administered MBP-sensitized lymph node cells preincubated with BPD followed by whole-body 690 nm light irradiation (15 J/cm2) did not display symptoms of EAE. Although almost all animals given MBP-sensitized spleen cells developed EAE, mice given BPD (1 mg/kg) and the light treatment 24, 48 or 120 h after spleen cell transfer exhibited significantly less severe disease symptoms than control animals. Mice given the photodynamic treatment 24 h after spleen cell transfer also exhibited a significantly later disease onset than the control animals. Treatment of mice with PDT 24 h prior to spleen cell transfer did not influence subsequent disease severity but modestly delayed its onset. In the absence of directed light, BPD did not influence the development of EAE. Spinal cord tissues were evaluated for the presence of T cell receptor (TCR) V alpha 4 mRNA transcripts that specifically encode for the TCR alpha-chain of MBP-reactive T cells of PL mice. Using the polymerase chain reaction, V alpha 4 TCR mRNA transcripts were present in spinal cord samples prepared from almost all control mice but in only about one-half of spinal cord samples prepared from mice treated with PDT 24 h after spleen cell transfer. These observations indicated that PDT had limited the expansion of MBP-specific V alpha 4+ T cells within the central nervous system. Transcutaneous PDT represents a new technique with which to approach the treatment of autoimmune disease.

A myelin oligodendrocyte glycoprotein peptide induces typical chronic experimental autoimmune encephalomyelitis in H-2b mice: fine specificity and T cell receptor V beta expression of encephalitogenic T cells.

A predominant response to myelin oligodendrocyte glycoprotein (MOG) was recently observed in patients with multiple sclerosis (MS). To study the possible pathogenic role of T cell response to MOG in MS, we have investigated the encephalitogenic potential of MOG. Synthetic MOG peptides, pMOG 1-21, 35-55, 67-87, 104-117 and 202-218, representing predicted T cell epitopes, were injected into C57BL/6J and C3H.SW (H-2b) mice. The mice developed significant specific T cell responses to pMOG 1-21, pMOG 35-55 and pMOG 104-117. However, pMOG 35-55 was the only MOG peptide which could induce neurological impairment. The highly reproducible disease was chronic, with ascending paralysis and neuropathology comparable with those observed in experimental autoimmune encephalomyelitis (EAE) induced by myelin basic protein or proteolipid protein, except that in H-2b mice the disease was consistently non-remitting. These features differ markedly from those which we recently observed in PL (H-2u) mice with pMOG 35-55-induced disease. In PL mice, pMOG 35-55-induces atypical chronic relapsing EAE, the expression and progression of which are unpredictable. Hence, in different mouse strains, the same MOG peptide can induce typical EAE characterized by ascending paralysis, or atypical EAE with unpredictable clinical signs. pMOG 35-55-specific T cells from H-2b mice recognized an epitope within amino acids 40-55 of the MOG molecule, and pMOG 40-55-reactive T cell lines were encephalitogenic upon transfer into syngeneic recipients. The encephalitogenic pMOG 35-55-reactive C57BL/6J T cell lines expressed V beta 1, V beta 6, V beta 8, V beta 14 and V beta 15 gene segments, and the pMOG 35-55-reactive C3H.SW T cell lines expressed V beta 1, V beta 2, V beta 6, V beta 8, V beta 10, V beta 14, and V beta 15 gene segments. However, in both mouse strains, the utilization of the V beta 8 gene product was predominant (40-43%). The highly reproducible encephalitogenic activity of pMOG 35-55 strongly suggests a pathogenic role for T cell reactivity to MOG in MS and supports the possibility that MOG may also be a primary target antigen in the disease.

Determination of the agretopic residues of a peptide co-restricted to different class II isotypes, I-Au and I-Eu, and its application for preparation of a synthetic peptide vaccine against influenza virus A/Aichi/2/68.

We have defined that residues 46 and 54 on a synthetic peptide composed of residues 43-58 of pigeon cytochrome c (p43-58) work as agretopes (sites bound to an MHC molecule) in I-Ab mice. Substitution of amino acid residues on these positions altered the peptide to bind with the other MHC molecules. Furthermore, by substituting the agretopic residues with a variety of amino acids, we could determine the class II binding motif for each MHC molecule. In the present study, immunogenicity of a peptide, 46R50V54A, carrying valine (V) at epitopic (site bound to TCR) position 50, arginine (R) and alanine (A) at agretopic positions 46 and 54 of the p43-58, respectively has been analyzed in B10.PL (H-2u) mice. We found that this peptide bound to two different class II isotypes, I-Au and I-Eu. Arginine at position 46 or alanine at position 54 of the 46R50V54A was shown to be critical for binding to I-Au or I-Eu, respectively. Further, on the basis of this class II binding motif we could prepare potent peptide vaccines against influenza A/Aichi/2/68 virus in B10.PL mice.

Skeletal changes in multiparous and nulliparous mice fed a nutrient-deficient diet containing cadmium

Female mice were given nutrient-deficient, purified diets containing either 0.25 (environmental), 5, or 50 ppm Cd; the nutrient quality of each was patterned after deficiencies known to be present in food consumed by Japanese women who contracted Itai-Itai disease. One-half of the mice were bred for six consecutive, 42-day rounds of pregnancy/lactation (PL mice); remaining females were non-pregnant, virgin controls (NP mice). PL and NP mice were sacrificed at the end of rounds 1, 2, 3, 5, or 6. PL mice taken during the first three rounds were successively pregnant; those taken in later rounds experienced gestation/lactation either four (round 5) or three (round 6) non-successive times. No consistent round-by-round decreases in diet consumption or body weight occurred among NP mice during the 252 days of cadmium exposure, however a significant decrease in femur calcium content (11–17%) was observed in virgin groups exposed to 50 vs. 0.25 ppm Cd. Similar femur decalcification (14–20%) was observed in PL mice, however calcium loss at 50 ppm Cd paralleled decreases in food consumption (24%) and body weight (9–17%). Significant but smaller decreases in the calcium/dry weight (Ca/DW) ratio were found for NP and PL groups consuming 50 ppm dietary Cd. Over the 6-round experiment, exposure to cadmium was found to effect smaller decreases in both femur Ca content and Ca/DW ratio than either consumption of nutrient-deficient diet or multiparous experience. Demineralization results for PL mice provide evidence that the combination of chronic ingestion of cadmium in a nutrient-deficient diet and multiparous activity likely played a role in the ethiology of Itai-Itai disease; results for NP mice additionally suggest that decalcification may have been initiated in human females at a time prior to the multiparous and menopausal stages of life.

Adoptively transferred experimental autoimmune encephalomyelitis in SJL/J, PL/J, and (SJL/J x PL/J)F1 mice. Influence of I-A haplotype on encephalitogenic epitope of myelin basic protein.

Abstract Guinea pig basic protein (GPBP)-immune lymph node cells (LNC) from SJL, PL, and SJL x PL (F1) mice proliferated to whole GPBP and GPBP fragments 1-37, 43-88, and 89-169. All three strains of mice developed experimental allergic encephalomyelitis (EAE) by active immunization with whole GPBP or by passive transfer of LNC cultured with whole GPBP. SJL (H-2s) and PL (H-2u) mice developed EAE by active immunization with fragments 89-169 or 1-37, respectively, or by passive transfer of LNC cultured with the same Ag. F1 mice developed EAE by active immunization only with fragment 1-37 or by passive transfer of LNC cultured with either of the above fragments. Removal of macrophages (MO) from immune-F1 LNC resulted in the loss of a proliferative response and the ability to transfer EAE. Reconstitution of MO-depleted immune F1 T cells with either F1-, SJL-, or PL-MO restored the proliferative responses to whole GPBP and the three fragments. Cultures of immune F1 T cells reconstituted with any of the three MO populations and incubated with whole GPBP passively transferred EAE into naive F1 mice. Immune F1 T cells cultured with F1 MO in the presence of either fragment 1-37 or 89-169 transferred EAE. F1 T cells cultured with SJL MO were able to transfer EAE only if the Ag was fragment 89-169, whereas F1 T cells cultured with PL MO were able to transfer disease only if incubated in the presence of fragment 1-37. F1 mice are passively susceptible to EAE induced by adoptive transfer of cells reactive to either the N-terminal or C-terminal fragment and that the encephalitogenic determinant of GPBP is related to the genome of MO present in vitro.

Kidney changes in multiparous mice fed a nutrient-sufficient diet containing cadmium

Female mice were given nutrient-sufficient, purified diets containing cadmium at either 0.25, 5, or 50 ppm, as described in the accompanying publication [1]. One-half of the females were bred for 6 consecutive 42-day rounds of pregnancy/lactation (PL mice); remaining females were non-pregnant controls (NP mice). PL mice and NP controls were sacrified after 1, 2, 4, or 6 consecutive rounds of pregnancy/lactation. At all levels of dietary cadmium and after all reproductive rounds, kidney cadmium concentrations were 2–5-fold higher in PL than NP mice. After 6 rounds of reproduction, the mean concentration of cadmium in the kidneys of PL mice exposed to dietary cadmium at 50 ppm was 115 μg Cd/g kidney, close to the critical concentration for cadmium-induced renal damage (200 μg/g). No consistent increases in the concentrations of amino acids, protein, or cadmium in urine were observed in the NP or PL mice in our study, indicating that cadmium-induced renal dysfunction had not yet appeared. Very small increases in kidney concentrations of zinc and copper were observed with large increases in kidney cadmium concentrations. Threshold cadmium concentrations below which the concentrations of zinc and copper were relatively constant and independent of cadmium concentration were identified; they were 7.2 μg Cd/g kidney for zinc and 13 μg Cd/g kidney for copper. In this study, cadmium-induced decreases in bone-mineral content occurred in the PL mice exposed to cadmium at 5 and 50 ppm (see accompanying publication). Data presented here indicate that the latter bone changes occurred in the absence of cadmium-induced renal dysfunction of the type that results in increased aminoaciduria/proteinuria. They suggest that the bone disease of Itai-Ital patients may also have started prior to the onset of this type of renal dysfunction.

Skeletal changes in multiparous mice fed a nutrient-sufficient diet containing cadmium

Female mice were given nutrient-sufficient, purified diets containing either 0.25, 5, or 50 ppm Cd. One-half of the females were bred for 6 consecutive 42-day rounds of pregnancy/lactation (PL mice); remaining females were non-pregnant controls (NP mice). PL mice and NP controls were sacrificed after 1, 2, 4, or 6 consecutive rounds of pregnancy/lactation. No consistent, cadmium-dependent decreases in body weight, femur calcium content, or calcium/dry weight (Ca/DW) ratio occured among the NP mice during the 252 days of cadmium exposure. In contrast, significant, cadmium-dependent decreases in body weight (3–11%), femur calcium content (15–27%), and Ca/DW ratio (5–7%) occurred in the multiparous mice exposed to 50 vs 0.25 ppm Cd. In addition, among the PL mice, the effect of cadmium was dose-dependent, with femur calcium contents decreasing significantly as the cadmium exposure level increased from 0.25 to 5 then 50 ppm Cd P < 0.05. Results demonstrate that dietary cadmium exposure had a greater effect on the skeletons of dams exposed to cadmium during the stresses of pregnancy and lactation than in non-pregnant controls. The results provide evidence that the combination of cadmium exposure and multiparity may have played a role in the etiology of Itai-Itai disease in Japan.

Histocompatibility-linked genetic control of susceptibility to age-dependent polioencephalomyelitis in mice

Susceptibility to induction of immune polioencephalomyelitis (IPE) was found to be controlled by a gene that is closely linked to the H-2 complex. Whereas mice of the AKR (H-2k) strain were susceptible to IPE induction, H-2-congenic mice, AKR.H-2b (H-2b from C57BL/6) and AKR.M (H-2m), were resistant. However, susceptibility to IPE may be under additional control by a gene(s) outside of the H-2 region, since both C57BL/6 (H-2b) mice and congenic B6.H-2k mice (H-2k from AKR) were resistant to IPE induction. F1 hybrid mice derived from AKR (susceptible) and DBA/2 (resistant) mice were susceptible to IPE induction, indicating that susceptibility is dominant in at least one gene, but susceptibility developed at a later age in the hybrid mice than in AKR mice. B6.PL-Ly-2a Ly-3a/Cy, C57BR, C57L, PL, and RF strain mice were resistant to ipe induction. Thus, of the 12 inbred strains tested so far, only two (C58 and AKR) are susceptible to IPE.

Antibody to Murine Leukemia Virus: Genetic Control Linked to the H-2 Locus in PL Mice

Abstract Mice of a wide variety of inbred strains naturally produce antibody against endogenous ecotropic leukemia viruses (MuLV) (1, 2). This immune response appears to be strain specific, however, since mice of high leukemic strains and mice of some low leukemic strains do not produce appreciable amounts of antibody against MuLV. The failure of mice of high leukemic strains to produce antibody against MuLV is not the result of immunologic tolerance induced by persistent viral replication, since F1 hybrids of mice of high and low leukemia strains produce high titers of antiviral antibody (3, 4). Recently, we have described that the immune nonresponsiveness of AKR mice is genetically controlled by an immune response (Ir) gene in the IXth linkage group (3). We describe here a similar observation with mice of the high leukemic PL strain, thus suggesting that a genetically controlled immune nonresponsiveness to MuLV may be a general characteristic of mice of high leukemic strains.