Observation of two-neutrino double-beta decay in 136Xe with the EXO-200 detector

We report the observation of two-neutrino double-beta decay in (136)Xe with T(1/2) = 2.11 ± 0.04(stat) ± 0.21(syst) × 10(21) yr. This second-order process, predicted by the standard model, has been observed for several nuclei but not for (136)Xe. The observed decay rate provides new input to matrix element calculations and to the search for the more interesting neutrinoless double-beta decay, the most sensitive probe for the existence of Majorana particles and the measurement of the neutrino mass scale.

Congenital Hydrocephalus in Genetically Engineered Mice

There is evidence that genetic factors play a role in the complex multifactorial pathogenesis of hydrocephalus. Identification of the genes involved in the development of this neurologic disorder in animal models may elucidate factors responsible for the excessive accumulation of cerebrospinal fluid in hydrocephalic humans. The authors report here a brief summary of findings from 12 lines of genetically engineered mice that presented with autosomal recessive congenital hydrocephalus. This study illustrates the value of knockout mice in identifying genetic factors involved in the development of congenital hydrocephalus. Findings suggest that dysfunctional motile cilia represent the underlying pathogenetic mechanism in 8 of the 12 lines ( Ulk4, Nme5, Nme7, Kif27, Stk36, Dpcd, Ak7, and Ak8). The likely underlying cause in the remaining 4 lines ( RIKEN 4930444A02, Celsr2, Mboat7, and transgenic FZD3) was not determined, but it is possible that some of these could also have ciliary defects. For example, the cerebellar malformations observed in RIKEN 4930444A02 knockout mice show similarities to a number of developmental disorders, such as Joubert, Meckel-Gruber, and Bardet-Biedl syndromes, which involve mutations in cilia-related genes. Even though the direct relevance of mouse models to hydrocephalus in humans remains uncertain, the high prevalence of familial patterns of inheritance for congenital hydrocephalus in humans suggests that identification of genes responsible for development of hydrocephalus in mice may lead to the identification of homologous modifier genes and susceptibility alleles in humans. Also, characterization of mouse models can enhance understanding of important cell signaling and developmental pathways involved in the pathogenesis of hydrocephalus.

Cardiomyopathy in α-Kinase 3 (ALPK3)–Deficient Mice

Cardiomyopathy developed in mice deficient for α-kinase 3 (ALPK3), a nuclear kinase previously implicated in the differentiation of cardiomyocytes. Alpk3–/– mice were produced according to normal Mendelian ratios and appeared normal except for a nonprogressive cardiomyopathy that had features of both hypertrophic and dilated forms of cardiomyopathy. Cardiac hypertrophy in Alpk3–/– mice was characterized by increased thickness of both left and right ventricular (LV and RV) walls and by markedly increased heart weight and increased heart weight/body weight and heart weight/tibia length ratios. Magnetic resonance imaging studies confirmed the increased thickness in both septal and LV free walls at end-diastole, although there was no significant change in LV wall thickness at end-systole. Myocardial hypertrophy was the predominant feature in Alpk3–/– mice, but several changes more typically associated with dilated cardiomyopathy included a marked increase in end-diastolic and end-systolic LV volume, as well as reduced cardiac output, stroke volume, and ejection fractions, suggesting LV chamber dilation. Magnetic resonance imaging showed a 50% reduction in both septal and free wall LV contractility in Alpk3–/– mice. Interstitial fibrosis and inflammation were notably absent in Alpk3–/– mice; however, light and electron microscopy revealed altered cardiomyocyte architecture, characterized by reduced numbers of abnormal intercalated discs being associated with mild disarray of myofibrils. These lesions could account for the impaired contractility of the myofibrillar apparatus and contribute to the pathogenesis of cardiomyopathy in Alpk3–/– mice.

Pathology of congenital generalized lipodystrophy in Agpat2-/- mice

Congenital generalized lipodystrophy (CGL) comprises a heterogeneous group of rare diseases associated with partial or total loss of adipose tissue. Of these, autosomal recessive Berardinelli-Seip congenital lipodystrophy (BSCL) is characterized by the absence of metabolically active subcutaneous and visceral adipose tissues. Metabolic abnormalities associated with lipodystrophy include insulin resistance, hypertriglyceridemia, hepatic steatosis, and diabetes. One form of BSCL has been linked to genetic mutations affecting the lipid biosynthetic enzyme 1-acyl-sn-glycerol 3-phosphate O-acyltransferase 2 (AGPAT2), which is highly expressed in adipose tissue. Precisely how AGPAT2 deficiency causes lipodystrophy remains unresolved, but possible mechanisms include impaired lipogenesis (triglyceride synthesis and storage), blocked adipogenesis (differentiation of preadipocytes to adipocytes), or apoptosis/necrosis of adipocytes. Agpat2(-/-) mice share important pathophysiologic features of CGL previously reported in humans. However, the small white adipose tissue (WAT) depots consisting largely of amoeboid adipocytes with microvesiculated basophilic cytoplasm showed that adipogenesis with deficient lipogenesis was present in all usual locations. Although well-defined lobules of brown adipose tissue (BAT) were present, massive necrosis resulted in early ablation of BAT. Although necrotic or apoptotic adipocytes were not detected in WAT of 10-day-old Agpat2(-/-), the absence of adipocytes in aged mice indicates that these cells must undergo necrosis/apoptosis at some point. Another significant finding in aged lipodystrophic mice was massive pancreatic islet hypertrophy in the face of chronic hyperglycemia, which suggests that glucotoxicity is insufficient by itself to cause β-cell loss and that adipocyte-derived factors help regulate total β-cell mass.

Histopathological and neurological features of Atg4b knockout mice

This investigation found that genetic inactivation of mouse Atg4b, 1 of the 4 mammalian homologs of the autophagy-related gene Atg4, resulted in amorphous globular bodies in the neuropil of the deep cerebellar nuclei and adjacent vestibular nuclei but nowhere else in the brain or other tissues. The spheroid-like bodies in the deep cerebellar and vestibular nuclei showed heterogeneous composition, reactivity with anti-ubiquitin antibody, and staining characteristics of proteinaceous material. Atg4b-deficient (Atg4b (-/-)) mice also showed a mild but measurable impairment of motor performance on the Rotarod. Atg4b (-/-) mice produced by breeding heterozygous parents were produced at a slightly lower than expected ratio to heterozygous and wild-type siblings but showed no other clear abnormalities in a battery of screening tests. These findings appear to be different than those reported for inactivation of other Atg4 homologs, suggesting that these homologs have tissue-specific functions beyond redundancy.

An alternative splicing variant in Clcn7-/- mice prevents osteopetrosis but not neural and retinal degeneration

The ubiquitously expressed chloride channel 7 (CLCN7) is present within the ruffled border of osteoclasts. Mutations in the CLCN7 gene in humans (homologous to murine Clcn7) are responsible for several types of osteopetrosis in humans, and deficiencies in CLCN7 can present with retinal degeneration and a neuronal storage disease. A previously reported Clcn7(-/-) mouse showed diffuse osteopetrosis accompanied by severe retinal and neuronal degeneration. In contrast, the authors produced a novel Clcn7(-/-) mutant where mice did not develop osteopetrosis but still developed lethal neural and retinal degeneration. In these mice, there was a rapid progressive loss of the outer nuclear layer and photoreceptor layers of the retina. Laminar degeneration and necrosis of neurons in layers IV and V of the cerebral cortex and in the CA2/CA3 regions of the hippocampus were associated with intraneuronal accumulations of autofluorescent granules (periodic acid-Schiff positive). The extensive reactive gliosis was always associated with the accumulation of intraneuronal cytoplasmic material. The authors found, through quantitative real time polymerase chain reaction analyses, that an alternate Clcn7 transcript (previously identified only in bone marrow) showed minimal expression in the brain and eye but moderate expression in bone, which correlates with rescue of the osteopetrotic phenotype in the face of continued retinal and neuronal degeneration. Findings in this knockout mouse model prove that osteopetrotic compression of the brain is not responsible for neuronal and retinal degeneration in CLCN7-deficient mice; rather, they suggest that neurotoxicity is most likely due to lysosomal dysfunction as a result of the functional lack of this chloride channel in the central nervous system and eye.

Tubulin tyrosine ligase-like 1 deficiency results in chronic rhinosinusitis and abnormal development of spermatid flagella in mice

Tubulin tyrosine ligase-like 1 (TTLL1) protein is a member of the tubulin tyrosine ligase superfamily of proteins that are involved in the posttranslational polyglutamylation of tubulin in axonemal microtubules within cilia and flagella. To investigate the physiological role of TTLL1, the authors generated mice with a gene trap mutation in the Ttll1 gene that provide confirmation in a mammalian model that polyglutamylation plays an important role in some ciliary and flagellar functions. For the first time, mice homozygous for the Ttll1 mutation exhibited accumulations of exudates in the nasal passages and sinuses, rhinosinusitis, otitis media, and male infertility. In homozygous mutant male mice, abnormal sperm morphology and function were characterized by shortened or absent flagella and immotility. Although homozygous mutant males were infertile, the females were fertile. These findings are consistent with a diagnosis of primary ciliary dyskinesia (PCD) resulting from ciliary dysfunction. They indicate that Ttll1 is essential for normal motility of respiratory cilia and the biogenesis and function of sperm flagella but that the defect does not result in the hydrocephalus or laterality defects often seen in other forms of PCD. The absence of early-onset lethal hydrocephalus in Ttll1-mutant mice may enable studies to evaluate the long-term effects of PCD in the respiratory system of mice. Although no mutations in the orthologous gene have been linked with PCD in humans, investigating the role of TTLL1 and polyglutamylation of tubulin in cilia and flagella should advance an understanding of the biogenesis and function of these organelles in mammals and have potential diagnostic and therapeutic applications.

Spontaneous acute tumor lysis syndrome as a cause of early deaths in short-term carcinogenicity studies using p53 +/- mice

Acute tumor lysis syndrome (ATLS) is a potentially lethal condition precipitated by the massive release of intracellular components such as nucleic acids, potassium, and phosphorus, following a rapid and widespread lysis of tumor cells. Herein, the authors describe the high incidence and characteristic histopathologic lesions of acute ATLS in p53-deficient mice used in 2 short-term carcinogenicity studies. ATLS was a frequent cause of early death in p53 (+/-) mice in these studies and was consistently associated with the presence of disseminated lymphoma and leukemia. Although a heavy tumor burden and leukemia were present in all affected mice, the absence of ATLS in other mice with equally severe lymphoma and leukemia indicates that these tumor burdens are necessary but insufficient to cause ATLS in mice. The hallmark histopathologic findings of ATLS in mice are the disseminated microemboli composed of nuclear and cytoplasmic debris derived from lysed tumor cells. The mechanical obstruction of capillary beds by these microemboli appeared to be the proximate cause of the early deaths of mice in these studies. Microemboli may contribute to the pathogenesis of acute renal failure and other clinical signs associated with ATLS in other species. Recognition of ATLS in laboratory animals is critical in studies intended to evaluate the efficacy and/or toxicity of anticancer treatments, where early deaths due to ATLS might otherwise be attributed to test article toxicity. Further studies on the role of microemboli in the pathogenesis of ATLS may elucidate pathogenetic mechanisms and lead to improved approaches to clinical management and treatment of this potentially lethal condition.

Situs inversus in Dpcd/Poll-/-, Nme7-/- , and Pkd1l1-/- mice

Situs inversus (SI) is a congenital condition characterized by left-right transposition of thoracic and visceral organs and associated vasculature. The usual asymmetrical positioning of organs is established early in development in a transient structure called the embryonic node. The 2-cilia hypothesis proposes that 2 kinds of primary cilia in the embryonic node determine left-right asymmetry: motile cilia that generate a leftward fluid flow, and immotile mechanosensory cilia that respond to the flow. Here, we describe 3 mouse SI models that provide support for the 2-cilia hypothesis. In addition to having SI, Dpcd/Poll(-/-) mice (for: deleted in a mouse model of primary ciliary dyskinesia) and Nme7(-/-) mice (for: nonmetastatic cells 7) had lesions consistent with deficient ciliary motility: Hydrocephalus, sinusitis, and male infertility developed in Dpcd/Poll(-/-) mice, whereas hydrocephalus and excessive nasal exudates were seen in Nme7(-/-) mice. In contrast, the absence of respiratory tract lesions, hydrocephalus, and male infertility in Pkd1l1(-/-) mice (for: polycystic kidney disease 1 like 1) suggested that dysfunction of motile cilia was not involved in the development of SI in this line. Moreover, the gene Pkd1l1 has considerable sequence similarity with Pkd1 (for: polycystic kidney disease 1), which encodes a protein (polycystin-1) that is essential for the mechanosensory function of immotile primary cilia in the kidney. The markedly reduced viability of Pkd1l1(-/-) mice is somewhat surprising given the absence of any detected abnormalities (other than SI) in surviving Pkd1l1(-/-) mice subjected to a comprehensive battery of phenotype-screening exams. However, the heart and great vessels of Pkd1l1(-/-) mice were not examined, and it is possible that the decreased viability of Pkd1l1(-/-) mice is due to undiagnosed cardiovascular defects associated with heterotaxy.

[A new procedure for the estimation of physical fitness of patients during clinical rehabilitation using the 6-minutes walk test]

AIMS OF THE INVESTIGATION: The repetition of the 6-minutes walk test (6 MWT) in older patients is frequently performed in order to document the maximal walking distance, although it is not recommended in any guidelines on exercise tests and although there is common consent to save clinical resources in terms of time and staff. Therefore, we have examined whether and to what extent the repetition of the walk tests helps patients to get more familiar with this kind of exercise test. Thus the acquired physiological data should reliably describe the physical fitness of the patients at the beginning and at the end of their clinical rehabilitation.

METHODS

35 patients performed their walk tests before and after 3 - 4 weeks of clinical rehabilitation. Each test has been repeated after one hour of recovery. The patients were instructed to walk during 6 minutes as fast as possible. They were equipped with a mobile pulse oximeter for recording oxygen saturation and heart rate. The distance, S, and the heart rate, fc, were measured. Measurements were performed every 30 seconds and recorded. The efficiency, E (E = S/6/fc), was calculated as the ratio of distance per minute and the mean heart rate during the test.

RESULTS

In the first test the patients walked 416 +/- 63 m at a heart rate of 104.7 +/- 15.7 beats/min, in the first repeated test 454 +/- 71 m at a heart of 106.3 +/- 17.4 beats/min. In the second test, after clinical therapy, they walked 438 +/- 58 m at a heart rate of 106.3 +/- 17.4 beats/min, in the second repeated test 473 +/- 56 m at 108.6 +/- 13.2/min. The difference of the walking distances of the tests at the entrance were found to be 38.4 +/- 26.2 m (+ 9.3 +/- 6.2%), at the end of clinical rehabilitation 35 +/- 26 m (+ 8.4 +/- 6.4%). Both differences are found to be independent from the distance of the first test. They are not significantly different. The efficiency was not significantly different in the initial and final test (0.673 +/- 0.129 and 0.689 +/- 0.085 m/beat, respectively). The difference in efficiency, when repeating the tests at the beginning, was: 0.053 +/- 0.062 m/beat; at the end of the rehabilitation: 0.042 +/- 0.047 m/beat. They are found to be similar.

CONCLUSIONS

The distances the patients walked in the repeated tests at the entrance and at the end of their clinical rehabilitation were, besides the calculated efficiency, E, significantly increased. However, the increases in distance and efficiency are identical on both occasions, therefore the repetition delivers no further information. The test should be performed without repetitions in clinical routine investigations. The patient's performance in the second walk test with an unchanged distance at a lower heart rate reveals an improved physical fitness. This is solely described by an increase of efficiency, E. Therefore the introduction of E is a suitable measure of the quantified effect of exercise training, even if the patient is not cooperative during the tests. E is proved to be a suitable estimation for the assessment of physical fitness as a benefit of clinical rehabilitation.

Comparative pathology of murine mucolipidosis types II and IIIC

UDP-GlcNAc: lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase) is an alpha(2)beta(2)gamma(2) hexameric enzyme that catalyzes the first step in the synthesis of the mannose 6-phosphate targeting signal on lysosomal hydrolases. In humans, mutations in the gene encoding the alpha/beta subunit precursor give rise to mucolipidosis II (MLII), whereas mutations in the gene encoding the gamma subunit cause the less severe mucolipidosis IIIC (MLIIIC). In this study we describe the phenotypic, histologic, and serum lysosomal enzyme abnormalities in knockout mice lacking the gamma subunit and compare these findings to those of mice lacking the alpha/beta subunits and humans with MLII and MLIIIC. We found that both lines of mutant mice had elevated levels of serum lysosomal enzymes and cytoplasmic alterations in secretory cells of several exocrine glands; however, lesions in gamma-subunit deficient (Gnptg(-/-)) mice were milder and more restricted in distribution than in alpha/beta-subunit deficient (Gnptab(-/-)) mice. We found that onset, extent, and severity of lesions that developed in these two different knockouts correlated with measured lysosomal enzyme activity; with a more rapid, widespread, and severe storage disease phenotype developing in Gnptab(-/-) mice. In contrast to mice deficient in the alpha/beta subunits, the mice lacking the gamma subunits were of normal size, lacked cartilage defects, and did not develop retinal degeneration. The milder disease in the gamma-subunit deficient mice correlated with residual synthesis of the mannose 6-phosphate recognition marker. Of significance, neither strain of mutant mice developed cytoplasmic vacuolar inclusions in fibrocytes or mesenchymal cells (I-cells), the characteristic lesion associated with the prominent skeletal and connective tissue abnormalities in humans with MLII and MLIII. Instead, the predominant lesions in both lines of mice were found in the secretory epithelial cells of several exocrine glands, including the pancreas, and the parotid, submandibular salivary, nasal, lacrimal, bulbourethral, and gastric glands. The absence of retinal and chondrocyte lesions in Gnptg(-/-) mice might be attributed to residual beta-glucuronidase activity. We conclude that mice lacking either alpha/beta or gamma subunits displayed clinical and pathologic features that differed substantially from those reported in humans having mutations in orthologous genes.

Ectonucleoside triphosphate diphosphohydrolase type 5 (Entpd5)-deficient mice develop progressive hepatopathy, hepatocellular tumors, and spermatogenic arrest

Ectonucleoside triphosphate diphosphohydrolase type 5 (ENTPD5, also CD39L4) is a soluble enzyme that hydrolyzes purine nucleoside diphosphates. Genetic inactivation of ENTPD5 in mice (Entpd5(-/-)) resulted in 2 major histopathologic lesions: hepatopathy and aspermia. The hepatopathy was progressive and characterized by centrilobular hepatocyte hypertrophy, oval cell proliferation, bile staining of Kupffer cells, and hepatocyte degeneration with increasing incidence and severity of degenerative lesions, development of multiple foci of cellular alteration, and hepatocellular neoplasia with age. Greatly increased proliferation of hepatocytes in young adult as well as aged Entpd5(-/-) mice was demonstrated by Ki67 immunohistochemistry and 5'-bromo-3'-deoxyuridine incorporation. Of 15 Entpd5(-/-) mice between 44 and 69 weeks of age, all showed foci of cellular alteration in the liver, and at least 6 of 15 developed hepatocellular carcinoma (HCC), hepatocellular adenoma, or both. Significantly, none of these lesions were observed in 13 wild-type Entpd5(+/+) littermates. These findings, combined with the historically low incidence (about 5%) of HCC in mice up to 2 years of age with the same genetic background, strongly suggest that loss of Entpd5 promotes hepatocellular neoplasia in mice. In humans, ENTPD5 has been found to be identical to the PCPH proto-oncogene, and dysregulation of this gene has been demonstrated in some human cancers. This mouse model could contribute to the understanding of the influence of ENTPD5/PCPH on cellular proliferation and neoplasia.

Testis size, sperm characteristics and testosterone concentrations in four species of shrews (Mammalia, Soricidae)

The aim of this study was to establish and compare the sperm characteristics in four shrew species in the context of the sperm competition hypothesis. As expected, the large relative testis size in promiscuous species was associated with a high number of cauda epididymal spermatozoa and a high concentration of circulating testosterone. In addition, in Sorex and Neomys, species with high intensity of sperm competition, the spermatozoa stored in cauda epididymis were characterized by high percentage of progressive motility whereas in Crocidura and Suncus, the cauda epididymal spermatozoa were motile but with very low percentage of progressive motility. This capability is achieved only following the passage through the vas gland, a specialized region for sperm storage located along the vas deferens in these shrew species. The hypothesis that sperm competition is positively correlated with spermatozoa length could not be confirmed. In Crocidura and Suncus, the total sperm length is increased by the large sperm head due to a big acrosome. This trait, specific to the subfamily Crocidurinae, may results from a selective pressure independent of the context of sperm competition, related to a specific, but as yet unclear role, for the acrosome during the fertilization.