Growth In Young Mice Research Articles

FGF Ligands and Receptors in Osteochondral Tissues of the Temporomandibular Joint in Young and Aging Mice.

Fibroblast growth factors (FGFs) are a family of 22 proteins and 4 FGF receptors (FGFRs) that are crucial elements for normal development. The contribution of different FGFs and FGFRs for the homeostasis or disease of the cartilage from the mandibular condyle is unknown. Therefore, our goal was to characterize age-related alterations in the protein expression of FGF ligands and FGFRs in the mandibular condyle of mice. Mandibular condyles of 1-, 6-, 12-, 18-, and 24-month-old C57BL/6J male mice (5 per group) were collected and histologically sectioned. Immunofluorescence for FGFs that have been reported to be relevant for chondrogenesis (FGF2, FGF8, FGF9, FGF18) as well as the activated/phosphorylated FGFRs (pFGFR1, pFGFR3) was carried out. FGF2 and FGF8 were strongly expressed in the cartilage and subchondral bone of 1-month-old mice, but the expression shifted mainly to the subchondral bone as mice aged. FGF18 and pFGFR3 expression was limited to the cartilage of 1-month-old mice only. Meanwhile, pFGFR1 and FGF9 were mostly limited to the cartilage with a significant increase in expression as mice aged. Our results indicate FGF2 and FGF8 are important growth factors for mandibular condylar cartilage growth in young mice but with limited role in the cartilage of older mice. In addition, the increased expression of pFGFR1 and FGF9 and the decreased expression of pFGFR3 and FGF18 as mice aged suggest the association of these factors with aging and osteoarthritis of the cartilage of the mandibular condyle.

Statins repress hedgehog signaling in medulloblastoma with no bone toxicities.

The Hedgehog (Hh) pathway plays an indispensable role in bone development and genetic activation of the pathway results in medulloblastoma (MB), the most common malignant brain tumor in children. Inhibitors of Hh pathway (such as vismodegib and sonedigib), which are used to treat MB, cause irreversible defects in bone growth in young children. Cholesterol is required for the activation of the Hh pathway, and statins, inhibitors of cholesterol biosynthesis, suppress MB growth by repressing Hh signaling in tumor cells. Here, we investigate the role of cholesterol biosynthesis in the proliferation and Hh signaling in chondrocytes, and examine the bone development in mice after statin treatment. Statins significantly inhibited MB growth in young mice, but caused no defects in bone development. Conditional deletion of NADP steroid dehydrogenase-like (NSDHL), an enzyme necessary for cholesterol biosynthesis, suppressed cholesterol synthesis in chondrocytes, and disrupted the growth plate in mouse femur and tibia, indicating the important function of intracellular cholesterol in bone development. Hh pathway activation and the proliferation of chondrocytes were inhibited by statin treatment in vitro; however, statins did not impair bone growth in vivo due to insufficient penetration into the bone. Our studies reveal a critical role of cholesterol in bone development, and support the utilization of statins for treatment of MB as well as other Hh pathway-associated malignancies.

Abstract 4400: Hematopoietic age at onset of breast cancer dictates disease aggressiveness and progression

Abstract Aging is strongly associated with increased risk of developing breast cancer. Young age at diagnosis is typically associated with more aggressive disease, while breast cancer is generally more indolent in older women. Among the different breast cancer subtypes, triple negative breast cancer (TNBC) accounts for ∼15% of invasive breast cancer cases and TNBC patients have a poor prognosis due to lack of targeted therapies and limited sensitivity to chemotherapy. Emerging studies indicate that older women with TNBC have a better outcome than younger women for reasons that are unclear. Nevertheless, older patients tend to suffer co-morbidities associated with chemotherapy and often forego treatment, resulting in disease recurrence and a poor outcome for these patients. Treatment of TNBC therefore presents age-specific challenges. Here, we investigated how age affects the composition and function of pro-tumorigenic bone marrow cells using TNBC models that enable us to interrogate the impact of bone marrow derived cells on both tumor cells and the tumor microenvironment. Consistent with clinical observations, we found that disease progression was significantly more aggressive in young mice relative to aged mice. We identified age- and tumor-dependent molecular and functional changes to bone marrow derived hematopoietic cells that impact TNBC progression. A specific population of Sca1+/cKit- bone marrow cells that expresses CSF1R and secretes the growth factor granulin to support stromal activation and robust tumor growth in young mice, fails to promote tumor outgrowth in aged mice, resulting in maintenance of disease indolence. Importantly, bone marrow cells from young mice are sufficient to activate a tumor-supportive microenvironment and rescue tumor progression in aged mice. The results presented here indicate that hematopoietic age is an important determinant of TNBC aggressiveness and provide rationale for investigating age-stratified therapies designed to prevent activation of tumor-promoting bone marrow cells. Citation Format: Jaclyn Sceneay, Timothy Marsh, Irene Wong, Yuanbo Qin, Andreas Sjödin, Björn Nilsson, Sheila A. Stewart, Sandra S. McAllister. Hematopoietic age at onset of breast cancer dictates disease aggressiveness and progression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4400.

Hematopoietic Age at Onset of Triple-Negative Breast Cancer Dictates Disease Aggressiveness and Progression.

Triple-negative breast cancer (TNBC) is considered an early onset subtype of breast cancer that carries with it a poorer prognosis in young rather than older women for reasons that remain poorly understood. Hematopoiesis in the bone marrow becomes altered with age and may therefore affect the composition of tumor-infiltrating hematopoietic cells and subsequent tumor progression. In this study, we investigated how age- and tumor-dependent changes to bone marrow-derived hematopoietic cells impact TNBC progression. Using multiple mouse models of TNBC tumorigenesis and metastasis, we found that a specific population of bone marrow cells (BMC) upregulated CSF-1R and secreted the growth factor granulin to support stromal activation and robust tumor growth in young mice. However, the same cell population in old mice expressed low levels of CSF1R and granulin and failed to promote tumor outgrowth, suggesting that age influences the tumorigenic capacity of BMCs in response to tumor-associated signals. Importantly, BMCs from young mice were sufficient to activate a tumor-supportive microenvironment and induce tumor progression in old mice. These results indicate that hematopoietic age is an important determinant of TNBC aggressiveness and provide rationale for investigating age-stratified therapies designed to prevent the protumorigenic effects of activated BMCs. Cancer Res; 76(10); 2932-43. ©2016 AACR.

Age and sex affect αCTLA-4 efficacy alone and combined with αB7-H1 or regulatory T cell depletion in a melanoma model.

Abstract Background Most cancer patients are aged but most preclinical studies are in young hosts. We tested age effects on immunotherapy to further our understanding and identify strategies. Methods Young (3 mos) and aged (~26 mos) BL6 mice were injected subcutaneously with syngeneic B16 melanoma cells. 7 days later, mice got 2 μg denileukin diftitox (DD), an FDA-approved IL-2/diphtheria toxin or 200 μg αCD25 (both to deplete Tregs) ± 50 μg αCTLA-4 or 100 μg αB7-H1. 5 days later mice got a 2nd treatment. Results αCTLA-4 depleted intra-tumor Tregs in young but not aged males, a major age effect. In young BL6 males or females αCTLA-4 + αB7-H1 rejected B16 tumors better than either single agent. In aged males, αCTLA4 + αB7-H1 treated B16, but surprisingly accelerated tumors in aged females. Individual agents were effective in young hosts but had negligible effects in the aged. αCTLA-4 + either DD or αCD25 to deplete Tregs significantly reduced tumor growth in young mice but DD was better than αCD25. Neither combo treated B16 in aged mice. This DD dose did not deplete Tregs in aged mice as well as young, but higher DD doses were equally effective. In support, in Foxp3DTR mice, in which we deplete ~100% Treg (versus 20–50% with DD or αCD25), aged mice potently rejected B16. Conclusions Cancer immunotherapy studies in young give an incomplete understanding of clinical effects and mechanisms in the aged most at risk for cancer. We identify major Treg effects and differential Treg depletion efficacy of αCTLA4 and DD contributing to treatment failures in the aged and means to mitigate effects. With appropriate treatments, even very old mice can mount effective anti-tumor immunity. Novel sex differences in aged are unlikely estrogen-related and require further study.

Metabolic Reprogramming by Hexosamine Biosynthetic and Golgi N-Glycan Branching Pathways.

De novo uridine-diphosphate-N-acetylglucosamine (UDP-GlcNAc) biosynthesis requires glucose, glutamine, acetyl-CoA and uridine, however GlcNAc salvaged from glycoconjugate turnover and dietary sources also makes a significant contribution to the intracellular pool. Herein we ask whether dietary GlcNAc regulates nutrient transport and intermediate metabolism in C57BL/6 mice by increasing UDP-GlcNAc and in turn Golgi N-glycan branching. GlcNAc added to the drinking water showed a dose-dependent increase in growth of young mice, while in mature adult mice fat and body-weight increased without affecting calorie-intake, activity, energy expenditure, or the microbiome. Oral GlcNAc increased hepatic UDP-GlcNAc and N-glycan branching on hepatic glycoproteins. Glucose homeostasis, hepatic glycogen, lipid metabolism and response to fasting were altered with GlcNAc treatment. In cultured cells GlcNAc enhanced uptake of glucose, glutamine and fatty-acids, and enhanced lipid synthesis, while inhibition of Golgi N-glycan branching blocked GlcNAc-dependent lipid accumulation. The N-acetylglucosaminyltransferase enzymes of the N-glycan branching pathway (Mgat1,2,4,5) display multistep ultrasensitivity to UDP-GlcNAc, as well as branching-dependent compensation. Indeed, oral GlcNAc rescued fat accumulation in lean Mgat5−/− mice and in cultured Mgat5−/− hepatocytes, consistent with N-glycan branching compensation. Our results suggest GlcNAc reprograms cellular metabolism by enhancing nutrient uptake and lipid storage through the UDP-GlcNAc supply to N-glycan branching pathway.

Bortezomib Is Cytotoxic to the Human Growth Plate and Permanently Impairs Bone Growth in Young Mice

Bortezomib, a novel proteasome inhibitor approved for the treatment of cancer in adults, has recently been introduced in pediatric clinical trials. Any tissue-specific side effects on bone development have to our knowledge not yet been explored. To address this, we experimentally studied the effects of bortezomib in vivo in young mice and in vitro in organ cultures of rat metatarsal bones and human growth plate cartilage, as well as in a rat chondrocytic cell line. We found that bortezomib while efficiently blocking the ubiquitin/proteasome system (UPS) caused significant growth impairment in mice, by increasing resting/stem-like chondrocyte apoptosis. Our data support a local action of bortezomib, directly targeting growth plate chondrocytes leading to decreased bone growth since no suppression of serum levels of insulin-like growth factor-I (IGF-I) was observed. A local effect of bortezomib was confirmed in cultured rat metatarsal bones where bortezomib efficiently caused growth retardation in a dose dependent and irreversible manner, an effect linked to increased chondrocyte apoptosis, mainly of resting/stem-like chondrocytes. The cytotoxicity of bortezomib was also evaluated in a unique model of cultured human growth plate cartilage, which was found to be highly sensitive to bortezomib. Mechanistic studies of apoptotic pathways indicated that bortezomib induced activation of p53 and Bax, as well as cleavage of caspases and poly-ADP-ribose polymerase (PARP) in exposed chondrocytes. Our observations, confirmed in vivo and in vitro, suggest that bone growth could potentially be suppressed in children treated with bortezomib. We therefore propose that longitudinal bone growth should be closely monitored in ongoing clinical pediatric trials of this promising anti-cancer drug.

Aging-associated B7-DC+ B cells enhance anti-tumor immunity (162.24)

Abstract Because most cancer patients are aged and because immunological functions are altered during aging, it is important to account for aging-associated immunological alterations in the design of new cancer immunotherapies. We thus compared immune populations in young and aged mice and found that B7-DC+ (PD-L2/CD273) B cells, a minor population in young mice, were significantly increased in aged mice. Induction of both Th1 and Th17 cells was significantly augmented by B7-DC+ B cells from aged mice and this effect was blocked with anti-B7-DC antibodies in vitro and in vivo. Moreover, retardation of tumor growth in aged mice was largely B7-DC-dependent. Tumor growth in young mice was significantly inhibited by immunization with B7-DC+ B cells from aged mice due to increased induction of tumor antigen-specific cytotoxic T lymphocytes (CTLs). These data indicate that B7-DC+ B cells could play an important role in aging-associated cancer immunopathology as well as other aging-associated-diseases, and further suggest that B7-DC+ B cells have potential for future cancer immunotherapy.

Abstract LB-107: Aptitude for running in mice is age and strain-dependent but not predictive of tumor response

Abstract Quality of life is a major consideration in attempting to design intervention strategies for delaying aging and age-related diseases. Preclinical studies depend on the use of reliable animal models, and the mouse has been used extensively in this regard. Quality of life can be evaluated in mice by measuring the functional status of various organ and physiological systems that are important in the health/physiological performance of an animal and that are shown to change with age in mice and/or humans. These physiological parameters would then be predicted to give a read-out of the animal's functional status relevant to human aging and quality of life. We conducted various assays of physiological function over the lifespan of male C57Bl/6 and BC6 F1 mice at 4, 12, 20, and 28 months of age. We report here on the correlation of running activity with tumor response. The inclination and capacity of mice to engage in voluntary spontaneous activity is a viable measure of their general physical aptitude. Response to the B16 melanoma tumor cell line is a measure of the host microenvironment to enhance or suppress tumor progression. We used in-cage running wheels connected to computers with monitoring software to assess the speed, distance and time the mice engaged in running behavior. Two months later, 1x105 B16 melanoma tumor cells were injected subcutaneously into the left inguinal space and repeated in the right axillary space. At 14 days post-injection, mice were terminated and tumors weighed and measured for size. Cohort numbers were 11-12 mice per age group and genotype. Four-month-old CB6 F1 mice ran further and had less tumor volume than age-matched B6 mice (16 Km vs. 11 Km and 360 mm vs. 800 mm, respectively). Total distance ran significantly decreased in each group to 0.9 Km and 2.2 Km, respectively, in mice at 28 months of age. All mice developed tumors. Tumor volume decreased in B6 mice from 4 months to 12 months to 450 mm and did not change with increasing age. Tumor volume in CB6 F1 mice remained constant at about 350 mm at all ages. In conclusion, CB6 F1 mice are more inclined to be physically active at a young age but less physically active at an old age compared to B6 mice, suggesting that running at a young age is not a predictor of physical aptitude for aging. Aging was not associated with increased tumor volume suggesting that non-genetic factors may be involved in the increased cancer incidence seen with increasing age. The aptitude for running may be associated with decreased tumor growth in young mice but not old mice. These preliminary data provide insight into the biological relevance of physiological assessment procedures in mice to help determine valid areas of focus in clinical trials of aging intervention. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-107. doi:1538-7445.AM2012-LB-107

Aging‐associated B7‐DC+ B cells enhance anti‐tumor immunity via Th1 and Th17 induction

Because most patients with cancer are aged and because immunological functions are altered during aging, it is important to account for aging-associated immunological alterations in the design of new cancer immunotherapies. We thus compared immune populations in young and aged mice and found that B7-DC(+) (PD-L2/CD273) B cells, a minor population in young mice, were significantly increased in aged mice. Induction of both Th1 and Th17 cells was significantly augmented by B7-DC(+) B cells from aged mice, and this effect was blocked with anti-B7-DC antibodies in vitro and in vivo. Moreover, retardation of tumor growth in aged mice was largely B7-DC dependent. Tumor growth in young mice was significantly inhibited by immunization with B7-DC(+) B cells from aged mice owing to increased induction of tumor antigen-specific cytotoxic T lymphocytes. These data indicate that B7-DC(+) B cells could play an important role in aging-associated cancer immunopathology as well as in other aging-associated diseases and further suggest that B7-DC(+) B cells have potential for future cancer immunotherapy.

Caloric restriction leads to high marrow adiposity and low bone mass in growing mice

The effects of caloric restriction (CR) on the skeleton are well studied in adult rodents and include lower cortical bone mass but higher trabecular bone volume. Much less is known about how CR affects bone mass in young, rapidly growing animals. This is an important problem because low caloric intake during skeletal acquisition in humans, as in anorexia nervosa, is associated with low bone mass, increased fracture risk, and osteoporosis in adulthood. To explore this question, we tested the effect of caloric restriction on bone mass and microarchitecture during rapid skeletal growth in young mice. At 3 weeks of age, we weaned male C57Bl/6J mice onto 30% caloric restriction (10% kcal/fat) or normal diet (10% kcal/fat). Outcomes at 6 (n = 4/group) and 12 weeks of age (n = 8/group) included body mass, femur length, serum leptin and insulin-like growth factor 1 (IGF-1) values, whole-body bone mineral density (WBBMD, g/cm(2)), cortical and trabecular bone architecture at the midshaft and distal femur, bone formation and cellularity, and marrow fat measurement. Compared with the normal diet, CR mice had 52% and 88% lower serum leptin and 33% and 39% lower serum IGF-1 at 6 and 12 weeks of age (p < .05 for all). CR mice were smaller, with lower bone mineral density, trabecular, and cortical bone properties. Bone-formation indices were lower, whereas bone-resorption indices were higher (p < .01 for all) in CR versus normal diet mice. Despite having lower percent of body fat, bone marrow adiposity was elevated dramatically in CR versus normal diet mice (p < .05). Thus we conclude that caloric restriction in young, growing mice is associated with impaired skeletal acquisition, low leptin and IGF-1 levels, and high marrow adiposity. These results support the hypothesis that caloric restriction during rapid skeletal growth is deleterious to cortical and trabecular bone mass and architecture, in contrast to potential skeletal benefits of CR in aging animals.

Effect of methotrexate and folinic acid on skeletal growth in mice

To investigate whether chronic administration of medium doses of methotrexate (MTX) causes suppression of skeletal growth in young mice and to determine whether folinic acid supplementation could reverse this effect. Four equal groups of Balb/c young male mice (6 animals in each group; mean body weight 11.9 +/- 0.25 g, in their rapid growth phase) were subjected to the following drug treatment for a period of 3 wk. Group 1 was given intraperitoneal MTX (3.5 mg kg(-1) body weight) every second day. Group 2 received folinic acid (7.0 mg kg(-1) body weight) intraperitoneally every second day. Group 3 was given both drugs (MTX every second day and folinic acid 8 h post-MTX injection). Group 4 was injected with physiological saline every other day to serve as a control group. Total body weight of the animals in each group was monitored every second day for the entire study period. The animals were sacrificed, the bilateral femurs and tibias of each animal were harvested and X-rays of the bones were taken. The length of each femur and tibia was measured using a micrometer. Measurements from the radiographs were also recorded using image analysis software. The MTX concentrations in the plasma and the folate levels in erythrocytes were determined. The heights of the distal femoral and the proximal tibial growth plate for each animal were measured on histological tissue sections. Mean lengths of both the tibia and femur of animals were compared in the four treatment groups. A significant decrease in the mean lengths (one-way ANOVA, p < 0.005) was observed in the group receiving MTX alone. Similarly, there was a significant decrease (p < 0.001) in the height of the femoral and tibial growth plate in this group when compared with the other groups. The main effect of MTX seemed to be on the hypertrophic proliferative zone of chondrocytes in the growth plate. Furthermore, animals in this MTX-treated group also showed increased levels of MTX in plasma and low levels of erythrocyte folate. These data show that chronic administration of MTX induces suppression of skeletal growth in mice, possibly through the inhibition of the pathway of de novo DNA synthesis. Folinic acid treatment following MTX administration appears to reverse this growth inhibition. Based on these observations, children suffering from juvenile rheumatoid arthritis, osteosarcoma or acute lymphoblastic leukaemia and receiving MTX over long periods of time could be at risk of short-term suppression of skeletal growth. If this is the case, it is possible that they could benefit from dietary supplementation with folinic acid.

Role of immune response as determinant of tumor progression in function of host age in the B16 melanoma

Aging constitutes the major cause for the development of most neoplastic diseases. However, tumors in aged people present with a lower degree of aggressiveness than in young patients. The reasons for this paradoxical behavior are not clear. We attempted to verify whether the immune system has a role in the relation between host age, immune response and tumor progression. We compared the growth rate of B16 melanoma and a highly malignant variant, the B16/Col/R, in young and aged mice that have or have not undergone splenectomy. The following results were obtained: (1) Splenectomy stimulated growth in the parental melanoma in both young and aged mice, indicating a protective role of the spleen against this tumor at all ages; (2) Spleen ablation provoked inhibition of the highly-metastatic variant growth in young mice, suggesting a stimulatory role of the spleen in this case; (3) By contrast, in aged mice inoculated with the B16/Col/R variant, splenectomy enhanced tumor growth, indicating a defensive role of the spleen. Age favors a positive host response against the aggressive clone of the melanoma. Differential host response in young versus aged mice can explain, in this tumor system, the difference in tumor progression rate as a function of age.

The effects on complement component 3 of dietary variation of protein, fat and vitamin E during growth of young mice

Some studies have shown that nutrition lowers overall immunity to disease. To further elucidate the role of nutrition on immunity, we have investigated the effect on serum Complement C3 by three nutrients, protein, lipid and vitamin E, in BALB/c mice for up to 24 weeks. The group with high dietary vitamin E had slightly higher C3 for the first four months but by the 22nd week was lower than control. The groups receiving high or low protein had, respectively, high or low C3. Injection of thymosin fraction 5 increased the C3, suppressed by the low protein diet. The group on the high lipid diet had high C3 until the 14th week whereupon it declined to control level by the 22nd week. The low lipid diet resulted in low C3 during the early weeks but increased to control level by the 22nd week. We conclude that diet is important to complement mediated immunity of young mice. Protein calorie malnutrition (PCM) lowers overall immunity to disease (1, 2). The increased incidence of serious gram negative infections including sepsis, of defective inflammatory responses, and of decreased opsonizing activity in serum of PCM patients parallels the symptoms of people with congenital (3) or nutritionally (1) associated deficiency of complement. Complement C 3, a crucial intersection point where the paths of nonspecific immunity and antibody mediated immunity join on the way to destroying foreign organisms, is susceptible to: general nutritional status (4), deficiencies of calcium and magnesium (5), or high levels of lead (6). To further elucidate the role of nutrition on immunity, we have investigated the effect of three nutrients, protein, lipid and vitamin E, on serum C 3 levels in mice for up to 24 weeks. Because overnutrition can also affect immunity (7), we have studied both high and low nutrient levels. A part of protein deficiency is the damage to the thymus and thymus gland hormone production. Therefore the thymic factors on complement production during protein malnutrition is measured.

Brain growth in young mice: Evidence on the theory of phrenoblysis

Brain growth was studied from day of birth through 23 days of age in three outbred and one inbred groups of mice. The results showed that the brain grows rapidly from Birth through 11 days and quite slowly thereafter. We found no evidence of the several spurts and plateaus in growth that are central to the theory of phrenoblysis (correlated brain and mind growth). Our results show the main features of mouse brain growth to parallel those of human brain growth except for timing of rapid and slow growth.

Inhibition of growth in young mice treated with pentazocine: Reversal by naltrexone

One week old mice were injected subcutaneously once daily with d,l-methadone (5 mg/kg), pentazocine, naltrexone, naloxone, nalorphine or nalbuphine, each at 10 mg/kg. The remaining half of each litter was used as control. Only methadone and pentazocine groups showed reduced weight gain after 3 weeks of treatment (P < 0.01). Injection of pentazocine in dosages of 5–20 mg/kg inhibited weight gain and protein synthesis in a dose-related manner. The incorporation of labeled leucine was followed in brain, liver and muscles. Methadone and pentazocine groups showed a significant decrease in protein synthesis in all tissues studied. The nalbuphine, nalorphine, naloxone, and naltrexone-treated groups incorporated leucine normally, correlating with normal weight gain. These data suggest that pentazocine, unlike the other mixed agonist-antagonists and antagonists, adversely affects the growth of very young animals when administered chronically. A specific opioid effect is suggested by the fact that naltrexone given concomitantly with the pentazocine prevents development of the biochemical lesion.

Inhibition of growth in young mice treated with d,l-methadone

Neonatal mice were treated with d,l-methadone, 1-α-acetylmethadol (LAAM) or the narcotic antagonists, naloxone, nalorphine or levallorphan. Litter mates were injected with normaal saline solution and handled in the same way. Treatment began on the second postpartum day and continued daily or on alternate days for up to 6 weeks. Injection of methadone in dosages of 2 mg/kg to 8 mg/kg inhibited weight gain in a log dose-related fashion. LAAM, 1 mg/kg or 2 mg/kg also retarded weight gain. Mice gained weight normally when naloxone, 10 mg/kg was injected with methadone, 2 mg/kg. Furthermore the daily injection of d-methadone, 4 mg/kg, did not inhibit weight gain nor did any of the narcotic antagonists. There findings indicate that growth inhibition induced by methadone is a stereospecific, opioid effect.

SUBTOTAL PANCREATECTOMY AND GROWTH OF YOUNG MICE.

Removal of the distal 75% of the pancreas may be done in adults without producing diabetes or deficiency of external pancreatic secretion. This procedure is often employed in the treatment of malignant and benign tumors. Resection of the body and tail of the pancreas may also be useful in treatment of an occasional patient who sustains severe trauma to the pancreas with complete transection, or with a crushing injury involving the distal portion of this organ. Little data are available, however, concerning the effect of extensive pancreatic resection upon the young, growing individual. Although such a procedure does not result in the development of diabetes, the quantitative requirements for exocrine secretion during the phase of rapid growth have not been established. This experiment was designed to evaluate the effect of distal subtotal pancreatectomy on the growth and metabolism of young mice. Material and Methods Ninety C-3-H mice, each 4 weeks

SECOND-DAY MINIMUM IN THE GROWTH CURVE OF MICE SUBJECTED TO MAGNETIC FIELDS.

IN a previous communication1 it was shown that strong static magnetic fields retard, the growth of young mice. The maximum weight difference, relative to identically housed controls, is reached after 10–12 days of residence in a homogeneous field of 4,200 œ strength. In the first such experiments, conducted in 1948 in the Institute for Experimental Physics of the University of Budapest, as well as in the twelve subsequent experiments conducted on several hundred mice in the laboratory of the Biomagnetic Research Foundation in Evanston, Illinois, a sharp drop in the weight of the mice was observed on the second day of residence in the field, followed by a steep increase up to the base line.