Localization of the ca-mediated apparent ion selectivity in the cross sectional volume of soybean roots

A major portion of the calcium in a soybean root appears to be in less than 10% of the root volume. Specifically, Ca is considered to be almost entirely localized in the epidermal cell layer. This relationship was established from consideration of rates and extent of ion absorption and ion interactions during the absorption process.

Presence of calcium at the root-solution interface was associated with a change in the apparent selectivity of K over Mg by soybean roots. Accumulation of calcium by soybean roots was negligible.

     

Predicting variability in catch-per-effort in Atlantic cod, Gadus morhua, trap and gillnet fisheries

The relationships between catch rates and fish abundance, hydrographic conditions and fishing effort, for Atlantic cod caught by trapnets (fixed gear) and gillnets (non-fixed gear) in the northern Gulf of St Lawrence have been quantified. Daily changes in trap catch rates were accounted for by changes in salinity, currents and mean local cod densities in 1985 ( R ²= 0.78), and predicted 1986 trap catch rate changes (by 1985 model) were correlated significantly with those observed ( r = 0.60, P < 0.05). In contrast, the daily changes in 1985 gillnet catch rates were determined by currents, maximum (not mean) local cod densities, and fishing effort (negative) ( R ²= 0.68), while predicted 1986 gillnet catch rates (by 1985 model) were significantly correlated with those observed ( r = 0.35, P < 0.05). Seasonal catchability coefficients of the traps were similar in 1985 and 1986, but for gillnets this index was an order of magnitude higher in 1986 than in 1985.     

MR弥散加权成像对鉴别诊断良恶性椎体压缩性骨折的临床价值研究

目的：探讨MR弥散加权成像（DWI）鉴别诊断良恶性椎体压缩性骨折的临床价值。方法：对57例经临床或病理证实的椎体良恶性压缩性骨折患者行矢状位T1M、T2WI、T2WI／FS及DWI扫描,研究其在常规序列和DWI序列上的表现,将常规MR序列和DWI序列检出率进行比较,测量正常椎体及病变椎体的表观弥散系数（ADC）值,并进行统计学分析。结果：（1）MR常规序列和DWI序列（b=500s／mm2）表现：良性椎体压缩性骨折呈长T1长或等T2改变,T2WI／FS呈高信号,DWI可以呈高信号、等信号及低信号;恶性椎体压缩性骨折呈长T1长T2信号,大部分病灶T2WUFS及DWI呈高信号,少数变现为低信号;（2）MR常规序列和DWI序列（b=500s／mm2）病灶检出率的比较：T1WI、T2WI／FS及DWI序列病灶检出率均高于T2WI序列,其间的差别有显著性意义（P〈0．01）,T1WI、T2WI／FS及DWI序列病灶检出率之间无显著性差异（P〉0．01）;（3）ADC值比较：在DWI（b=500s／mm2）上,良性组ADC值为（2．03±0．83）×10^3mm^2/s,恶性组ADC值为（1．37±0．75）×10^-3mm^2/s,正常组ADC值为（0．36±0．21）×10^-3mm^2／s,成像条件相同时,良性组高于恶性组,两组间有明显的统计学意义（P〈0．05）。结论：DWI可较好的反映椎体的弥散特征,ADC值作为量化指标可对良恶性椎体压缩性骨折进行可靠鉴别。     

Haemosporidian Parasites of Antelopes and Other Vertebrates from Gabon,Central Africa

Re-examination, using molecular tools, of the diversity of haemosporidian parasites (among which the agents of human malaria are the best known) has generally led to rearrangements of traditional classifications. In this study, we explored the diversity of haemosporidian parasites infecting vertebrate species (particularly mammals, birds and reptiles) living in the forests of Gabon (Central Africa), by analyzing a collection of 492 bushmeat samples. We found that samples from five mammalian species (four duiker and one pangolin species), one bird and one turtle species were infected by haemosporidian parasites. In duikers (from which most of the infected specimens were obtained), we demonstrated the existence of at least two distinct parasite lineages related to Polychromophilus species (i.e., bat haemosporidian parasites) and to sauropsid Plasmodium (from birds and lizards). Molecular screening of sylvatic mosquitoes captured during a longitudinal survey revealed the presence of these haemosporidian parasite lineages also in several Anopheles species, suggesting a potential role in their transmission. Our results show that, differently from what was previously thought, several independent clades of haemosporidian parasites (family Plasmodiidae) infect mammals and are transmitted by anopheline mosquitoes.     

The genetic effects of competition in seaweed flies

In spite of abundant evidence that intra- and inter-specific competition occurs in natural communities, there is surprisingly little to suggest it is a major force promoting genetic change. This report assesses the genetic effects of competition in two species of seaweed fly, Coelopa frigida and C. pilipes. In laboratory cultures of C. frigida the relative survival of heterozygotes at the Adh locus, which was being used as a marker for the large αβ chromosomal inversion, was greater than that of homozygotes. In monocultures of C. frigida this competitive superiority was dependent on larval density. At low densities facilitation was seen, whereas at high larval densities there was competition. In mixed cultures of the two species, interspecific competition contributed to the differential mortality of C. frigida , and observations of natural populations suggested that competition may have similar effects to those described in laboratory culture. A possible mechanism involving the supply of nutritive microorganisms is proposed to underly both intra- and inter-specific competition. In seaweed flies, competition and the consequent differential mortality appear to be forces maintaining rather than reducing genetic variation.     

Life history variations in populations of American shad, Alosa sapidissima (Wilson), spawning in tributaries of the St John River, New Brunswick

Shad were sampled at four locations in the St John River area, New Brunswick; St John Harbour, Kennebecasis River, Washademoak Lake and Mactaquac Dam. The effect of the St John Harbour fishery on upstream spawning populations was minimal. Mactaquac Dam began operation in 1967 and since that time the populations of shad arriving at that facility have been in a state of flux. When shad populations from Kennebecasis River and Washademoak L. were compared, the Washademoak Lake population exhibited higher relative fecundity, lower mean age at maturity and possessed a lower proportion of repeat spawners. The combinations of reproductive characteristics occurring in the populations of the St John River were the same as those occurring over the Atlantic coast range of shad. The possible environmental factors influencing the variations in reproductive characteristics are discussed.     

Germline mutations in BMPR1A/ALK3 cause a subset of cases of juvenile polyposis syndrome and of Cowden and Bannayan-Riley-Ruvalcaba syndromes

Juvenile polyposis syndrome (JPS) is an inherited hamartomatous-polyposis syndrome with a risk for colon cancer. JPS is a clinical diagnosis by exclusion, and, before susceptibility genes were identified, JPS could easily be confused with other inherited hamartoma syndromes, such as Bannayan-Riley-Ruvalcaba syndrome (BRRS) and Cowden syndrome (CS). Germline mutations of MADH4 (SMAD4) have been described in a variable number of probands with JPS. A series of familial and isolated European probands without MADH4 mutations were analyzed for germline mutations in BMPR1A, a member of the transforming growth-factor beta-receptor superfamily, upstream from the SMAD pathway. Overall, 10 (38%) probands were found to have germline BMPR1A mutations, 8 of which resulted in truncated receptors and 2 of which resulted in missense alterations (C124R and C376Y). Almost all available component tumors from mutation-positive cases showed loss of heterozygosity (LOH) in the BMPR1A region, whereas those from mutation-negative cases did not. One proband with CS/CS-like phenotype was also found to have a germline BMPR1A missense mutation (A338D). Thus, germline BMPR1A mutations cause a significant proportion of cases of JPS and might define a small subset of cases of CS/BRRS with specific colonic phenotype.     

黑皮质素受体-4调节通路的研究进展

黑皮质素系统来自阿片-促黑素细胞皮质素原,在中枢摄食行为和能量平衡代谢中起到重要作用,此系统生理功能的发挥主要通过与下丘脑神经元细胞上特定膜受体（黑皮质素受体）结合完成。黑皮质素受体（MCR）有五种亚型（MC1R-MC5R）,其中参与体重调节的受体主要是黑皮质素受体3（MC3R）和黑皮质素受体4（MC4R）。MC4R属于G蛋白耦联受体,具有七次跨膜结构。作为一种膜受体,MC4R发挥体重调节作用,一方面受外界激动剂或拮抗剂的调节;另一方面,此受体活化后会影响到细胞内的信号调节通路。研究MC4R的功能首先要了解受体的结构,本文对G蛋白耦联受体的结构进行了较详细的叙述,MC4R经信号调节通路,激活腺苷酸环化酶,增加cAMP的浓度,最终通过影响细胞内基因的转录和翻译,来调节体重和能量的消耗。     

血液磁极化疗法对糖尿病兔胰岛功能的影响

目的观察血液磁极化疗法(简称血磁治疗)对糖尿病(DM)的治疗效果和对胰岛功能的影响。方法制备了四氧嘧啶DM兔模型20只,随机分为两组,即DM模型血磁治疗组及DM模型未治疗组,同时设立正常对照组10只,分别测定治疗前后空腹血糖(FPG)、糖化血红蛋白(HbA1c)、胰岛素(INS)及C-肽(C-P),并于观察期结束后处死动物取胰腺组织常规石蜡包埋切片,行HE及Mallory三色法特殊染色观察3组胰岛形态学变化。结果血磁治疗显著降低DM兔的FPG(P<0.001)。DM治疗组INS及C-P水平较治疗前明显升高(P<0.01),与未治疗组相比差异显著(P<0.05)。胰岛病理改变可见治疗组β细胞数量明显多于DM未治疗组,提示血磁疗法具有促进胰岛修复,改善胰岛功能的作用。结论血磁疗法能够促进DM时受损胰岛组织的修复,改善胰岛β细胞分泌功能,降血糖作用明显。