不同时间尺度环境因子对黑河下游胡杨(Populus euphratica)径向生长的影响

本研究以黑河下游额济纳旗成熟的河岸胡杨林为对象,分析不同年龄胡杨(Populus euphratica)的年轮宽度序列与不同时间尺度环境因子的关系。结果表明:①在年尺度上,气温是影响胡杨径向生长的主要因子,但不同年龄胡杨对气温的响应有所不同。②在季节尺度上,休眠季气温越高越有利于壮龄胡杨的径向生长,而生长季气温越高越不利于老龄胡杨的径向生长。③在月尺度上,前一年3月和当年9月的平均气温越高,对壮龄胡杨的径向生长越有利,而当年10月平均气温越高,对老龄胡杨的径向生长越不利;前一年7月径流量的增加对老龄胡杨的径向生长有利,而当年2月径流量的增加对壮龄胡杨径向生长有利。综上所述,在季节和年等相对较长的时间尺度上,气温是影响胡杨径向生长量的主要因素,随着时间尺度的缩小,胡杨对环境因子的响应更为细化,并且表现出一定的滞后效应。径流量作为重要的环境因子在月尺度上才突显出来,前一年7月和当年2月的径流补给对胡杨径向生长有极大的促进作用。因此,在黑河统一调度管理过程中,可通过适度调增2月和7月洪水的下泄量来满足胡杨径向生长对水分的需求。     

IMPACT OF TISSUE INHOMOGENEITY ON DOSE DISTRIBUTION IN THE CANINE CARPAL AND TARSAL REGIONS FOR COBALT AND 6 MV PHOTONS

We quantified the effect of tissue inhomogeneity on dose distribution in a canine distal extremity resulting from treatment with cobalt photons and photons from a 6 MV accelerator. Monitor units for a typical distal extremity treatment were calculated by two methods, using equally weighted, parallel-opposed fields. The first method was a computed tomography (CT)-based, computerized treatment plan, calculated without inhomogeneity correction. The second method was a manual point dose calculation to the isocenter. A computerized planning system was then used to assess the dose distribution achieved by these two methods when tissue inhomogeneity was taken into account. For cobalt photons, the median percentage of the planning target volume (PTV) that received <95% of the prescribed dose was 4.5% for the CT-based treatment plan, and 26.2% for the manually calculated plan. For 6 MV photons, the median percentage of the PTV that received <95% of the prescribed dose was <1% for both planning methods. The PTV dose achieved without using inhomogeneity correction for cobalt photons results in potentially significant under dosing of portions of the PTV.     

Identification of food-derived collagen peptides in human blood after oral ingestion of gelatin hydrolysates

In the present study, we identified several food-derived collagen peptides in human blood after oral ingestion of some gelatin hydrolysates. Healthy human volunteers ingested the gelatin hydrolysates (9.4-23 g) from porcine skin, chicken feet, and cartilage after 12 h of fasting. Negligible amounts of the peptide form of hydroxyproline (Hyp) were observed in human blood before the ingestion. After the oral ingestion, the peptide form of Hyp significantly increased and reached a maximum level (20-60 nmol/mL of plasma) after 1-2 h and then decreased to half of the maximum level at 4 h after the ingestion. Major constituents of food-derived collagen peptides in human serum and plasma were identified as Pro-Hyp. In addition, small but significant amounts of Ala-Hyp, Ala-Hyp-Gly, Pro-Hyp-Gly, Leu-Hyp, Ile-Hyp, and Phe-Hyp were contained.     

The muscle protein Dok-7 is essential for neuromuscular synaptogenesis

The formation of the neuromuscular synapse requires muscle-specific receptor kinase (MuSK) to orchestrate postsynaptic differentiation, including the clustering of receptors for the neurotransmitter acetylcholine. Upon innervation, neural agrin activates MuSK to establish the postsynaptic apparatus, although agrin-independent formation of neuromuscular synapses can also occur experimentally in the absence of neurotransmission. Dok-7, a MuSK-interacting cytoplasmic protein, is essential for MuSK activation in cultured myotubes; in particular, the Dok-7 phosphotyrosine-binding domain and its target in MuSK are indispensable. Mice lacking Dok-7 formed neither acetylcholine receptor clusters nor neuromuscular synapses. Thus, Dok-7 is essential for neuromuscular synaptogenesis through its interaction with MuSK.     

Identification of the core motif of the BRCA2 C-terminal RAD51-binding domain by comparing canine and human BRCA2

Mammary tumors are the most common tumors in women and non-spayed female dogs. One of the reasons for mammary tumors is mutations of the tumor suppressor gene, BRCA2. BRCA2 participates in homologous recombination repair by interacting with the RAD51 recombinase. BRCA2 has two RAD51-binding domains, consisting of BRC repeats and the C-terminal RAD51-binding domain, respectively. Although several studies have addressed the function of the C-terminal RAD51-binding domain of human BRCA2, the amino acid sequences required for the RAD51-interaction activity remain unclear. In this study, the C-terminal RAD51-binding domains of canine and human BRCA2 were compared; the canine domain displayed a weaker interaction with RAD51. This difference was attributed to the C-terminal portion of the domain via a comparison between canine and human domains. Furthermore, peptides shorter than those previously reported displayed RAD51-interacting activity, and a core motif of this domain consisting of 25 amino acids was identified. Since a mutation (S3323N) was reported in the core motif of this domain, the effect of this mutation was evaluated. The mutant exhibited similar RAD51-binding activity as that of the wild-type protein, suggesting that the mutation was functionally neutral. These data suggested that the C-terminal portion of the BRCA2 C-terminal RAD51-binding domain influenced its RAD51-interaction activity, and a minimum core motif of 25 amino acids was identified in this domain. These data may help clarify BRCA2 function, as well as the tumorigenic effects of BRCA2 mutation.     

Comparison of N-terminal pro-atrial natriuretic peptide and three cardiac biomarkers for discriminatory ability of clinical stage in dogs with myxomatous mitral valve disease

Plasma N-terminal pro-atrial natriuretic peptide (NT-proANP) concentration increases with progression of myxomatous mitral valve disease (MMVD) in dogs. This multicentre, prospective study compared plasma NT-proANP, N-terminal pro-brain natriuretic peptide (NT-proBNP), ANP, and cardiac troponin I (cTnI) concentrations in dogs with MMVD for their characteristics and discriminatory ability to detect cardiac dilatation and congestive heart failure (CHF). Thirty-six healthy dogs and 69 dogs with MMVD were included. Clinical variables were obtained via physical examination, thoracic radiography, and echocardiography. The discriminatory ability of each cardiac biomarker (CB) to determine the presence or absence of cardiac dilatation (event 1) and CHF (event 2) was evaluated using the receiver operating characteristic curves. Plasma NT-proANP, NT-proBNP, and ANP concentrations showed a significant association with the left atrium/aorta ratio (P<0.01). The area under the curve of plasma NT-proANP and NT-proBNP concentrations were 0.72 and 0.75, respectively in event1 and 0.72 and 0.76, respectively in event2. Plasma NT-proANP and NT-proBNP concentrations showed sensitivity 80.0 and 80.0%; specificity 67.6 and 64.7% in event1 (cutoff value; 8,497.81 pg/ml and 1,453.00 pmol/l, respectively) and sensitivity 85.7 and 81.0%; specificity 60.4 and 64.6% in event2 (cutoff value; 8,684.33 pg/ml and 1,772.00 pmol/l, respectively). In dogs with MMVD, plasma NT-proANP, NT-proBNP, and ANP concentrations increase with left atrial enlargement. Particularly, plasma NT-proANP and NT-proBNP concentrations appeared to be equally useful in the discriminatory ability to detect cardiac dilatation and CHF.     

Identification of c-kit mutations-independent neoplastic cell proliferation of canine mast cells

Gain-of-function mutations in the proto-oncogene c-kit have been considered the molecular mechanism of neoplastic proliferation of mast cells. However, the importance of c-kit gene mutations is not well evaluated in canine mast cell tumors (MCTs). In the present study, we established and characterized a mast cell line, HRMC, derived from a dog with MCT. We also examined c-kit mutations in HRMC cells and assessed an inhibitory effect of a tyrosine kinase inhibitor, STI571, on HRMC cells. HRMC cells had cytoplasmic metachromatic granules, chymase and tryptase, and expressed both KIT and FcepsilonRI on the cell surface. HRMC cells contained histamine and released beta-hexosaminidase through FcepsilonRI cross-linking and calcium ionophore stimulation. Nucleotide sequence analysis demonstrated no mutations in an open reading frame of c-kit cDNA and genomic DNA of the juxtamembrane domain of c-kit in HRMC cells. STI571 did not show any inhibitory effects on the proliferation of HRMC cells. These findings clearly demonstrated the existence of c-kit mutations-independent neoplastic canine mast cell proliferation. The growth factor-independent mast cell line established in this study might be valuable to explore novel mechanisms of c-kit mutations-independent neoplastic proliferation of mast cells in dogs.     

Expression of nerve growth factor in itchy skins of atopic NC/NgaTnd mice

Although the possible involvement of neurotrophic factors in itchy skins of atopic dermatitis has been predicted, the exact mechanism by which itch is induced remains unclear. Since nerve growth factor (NGF) has crucial effects on development and functions of sensory nerves, we determined production of NGF and extension of nerve fibers in skins of NC/NgaTnd mice with or without atopic dermatitis. NC/NgaTnd mice spontaneously develop atopic dermatitis-like skin lesions when they are raised in air-unregulated conventional circumstances. We quantified scratching behavior of NC/NgaTnd mice during the development of dermatitis using a novel analytical system and compared to clinical skin severity scores. A significant correlation between the severity of dermatitis and the increase in the number of scratches was identified, indicating that scratching behavior may associate with clinical skin conditions. NGF contents in the skin lesions of conventional NC/NgaTnd mice were significantly higher than those in SPF mice. Positive reactions for NGF were observed in keratinocytes and fibroblasts in affected skins of conventional NC/NgaTnd mice. Immunohistochemical analysis showed the extension of protein gene product 9.5-positive nerve fibers from the dermis toward the epidermis at the skin lesions. These results suggest that sensory nerves induced by NGF may contribute to development of itch, and that NGF produced at the affected site may provide abnormal skin sensitivity in atopic dermatitis.