HAR1 mediates systemic regulation of symbiotic organ development

Symbiotic root nodules are beneficial to leguminous host plants; however, excessive nodulation damages the host because it interferes with the distribution of nutrients in the plant. To keep a steady balance, the nodulation programme is regulated systemically in leguminous hosts. Leguminous mutants that have lost this ability display a hypernodulating phenotype. Through the use of reciprocal and self-grafting studies using Lotus japonicus hypernodulating mutants, har1 (also known as sym78), we show that the shoot genotype is responsible for the negative regulation of nodule development. A map-based cloning strategy revealed that HAR1 encodes a protein with a relative molecular mass of 108,000, which contains 21 leucine-rich repeats, a single transmembrane domain and serine/threonine kinase domains. The har1 mutant phenotype was rescued by transfection of the HAR1 gene. In a comparison of Arabidopsis receptor-like kinases, HAR1 showed the highest level of similarity with CLAVATA1 (CLV1). CLV1 negatively regulates formation of the shoot and floral meristems through cell-cell communication involving the CLV3 peptide. Identification of hypernodulation genes thus indicates that genes in leguminous plants bearing a close resemblance to CLV1 regulate nodule development systemically, by means of organ-organ communication.     

氦浴温度对超流氦噪声沸腾压力振动的影响

噪声沸腾是超流氦传热中的一个特殊现象，对这种现象的充分认识有助于超流氦在诸如超导磁体的冷却等方面的实际应用．氦浴温度是影响噪声沸腾的一个重要因素．本文运用脉冲电流加热一个大小为２．５ｃｍ×２．５ｃｍ的小试样，同时用一个压力传感器测量了在不同氦浴温度下噪声沸腾时的压力振动，并对不同氦浴温度下噪声沸腾的压力振动曲线进行了详细的分析．实验结果显示在过冷态超流氦的沸腾中，一个极薄的气膜在小试样上振动，几乎没有什么噪声；而在饱和态超流氦的沸腾中，一个小试样大小相当的气泡在其表面上反复振动，并伴随着巨大的噪声和强烈的机械振动．氦浴温度对噪声沸腾的影响主要体现在对噪声沸腾的特征频率和沸腾状态发生改变时的临界静压液柱等方面．     

SEM surface morphology of the contractile cells in the rat seminiferous tubules.

The SEM observation of the basal surface of the contractile cells in the boundary tissue of the seminiferous tubule of the rat revealed that the contractile cells are extremely flat, vary in shape from rectangular to hexagonal, and are arranged close to each other, in the fashion of a tiled floor, around the seminiferous epithelium.     

Cloning of adiponectin receptors that mediate antidiabetic metabolic effects

Adiponectin (also known as 30-kDa adipocyte complement-related protein; Acrp30) is a hormone secreted by adipocytes that acts as an antidiabetic and anti-atherogenic adipokine. Levels of adiponectin in the blood are decreased under conditions of obesity, insulin resistance and type 2 diabetes. Administration of adiponectin causes glucose-lowering effects and ameliorates insulin resistance in mice. Conversely, adiponectin-deficient mice exhibit insulin resistance and diabetes. This insulin-sensitizing effect of adiponectin seems to be mediated by an increase in fatty-acid oxidation through activation of AMP kinase and PPAR-alpha. Here we report the cloning of complementary DNAs encoding adiponectin receptors 1 and 2 (AdipoR1 and AdipoR2) by expression cloning. AdipoR1 is abundantly expressed in skeletal muscle, whereas AdipoR2 is predominantly expressed in the liver. These two adiponectin receptors are predicted to contain seven transmembrane domains, but to be structurally and functionally distinct from G-protein-coupled receptors. Expression of AdipoR1/R2 or suppression of AdipoR1/R2 expression by small-interfering RNA supports our conclusion that they serve as receptors for globular and full-length adiponectin, and that they mediate increased AMP kinase and PPAR-alpha ligand activities, as well as fatty-acid oxidation and glucose uptake by adiponectin.     

Formation of beta-amyloid protein deposits in brains of transgenic mice

Deposits of beta-amyloid are one of the main pathological characteristics of Alzheimer's disease. The beta-amyloid peptide constituent (relative molecular mass 4,200) of the deposits is derived from the beta-amyloid precursor protein (beta-APP) which is expressed in several different isoforms. The two most prevalent beta-APP isoforms are distinguished by either the presence (beta-APP751) or absence (beta-APP695) of a Kunitz serine protease inhibitor domain. Changes in the abundance of different beta-APP messenger RNAs in brains of Alzheimer's disease victims have been widely reported. Although these results have been controversial, most evidence favours an increase in the mRNAs encoding protease inhibitor-containing isoforms of beta-APP and it is proposed that this change contributes to beta-amyloid formation. We have now produced an imbalance in the normal neuronal ratio of beta-APP isoforms by preparing transgenic mice expressing additional beta-APP751 under the control of a neural-specific promoter. The cortical and hippocampal brain regions of the transgenic mice display extracellular beta-amyloid immunoreactive deposits varying in size (less than 5-50 microns) and abundance. These results suggest that one mechanism of beta-amyloid formation may involve a disruption of the normal ratio of neuronal beta-APP isoform expression and support a direct relationship between increased expression of Kunitz inhibitor-bearing beta-APP isoforms and beta-amyloid deposition.     

Plastid proteins crucial for symbiotic fungal and bacterial entry into plant roots

The roots of most higher plants form arbuscular mycorrhiza, an ancient, phosphate-acquiring symbiosis with fungi, whereas only four related plant orders are able to engage in the evolutionary younger nitrogen-fixing root-nodule symbiosis with bacteria. Plant symbioses with bacteria and fungi require a set of common signal transduction components that redirect root cell development. Here we present two highly homologous genes from Lotus japonicus, CASTOR and POLLUX, that are indispensable for microbial admission into plant cells and act upstream of intracellular calcium spiking, one of the earliest plant responses to symbiotic stimulation. Surprisingly, both twin proteins are localized in the plastids of root cells, indicating a previously unrecognized role of this ancient endosymbiont in controlling intracellular symbioses that evolved more recently.     

SEM surface morphology of the contractile cells in the rat seminiferous tubules

Summary The SEM observation of the basal surface of the contractile cells in the boundary tissue of the seminiferous tubule of the rat has revealed that the contractile cells are extremely flat, vary in shape from rectangular to hexagonal, and are arranged close to each other, in the fashion of a tiled floor, around the seminiferous epithelium.     

Improved treadmill to avoid foot and tail injuries of small animals

Summary A treadmill was improved so as to eliminate foot and tail injuries in small test-animals. The improvement was inexpensive and easily fabricated by the researchers.     

ACTH response induced by interleukin-1 is mediated by CRF secretion stimulated by hypothalamic PGE

Summary We investigated whether hypothalamic prostaglandin E₂ (PGE₂) and corticotropin releasing factor (CRF) are responsible for the development of the adrenocorticotropic hormone (ACTH) response induced by interleukin-1 (IL-1). The present results show that ACTH responses induced by intravenous injection of IL-1 were suppressed by systemic pretreatment with indomethacin and that intrahypothalamic injection of PGE₂ stimulates the secretion of ACTH. Furthermore, systemic pretreatment with anti-CRF antibody significantly suppressed the ACTH response induced by intrahypothalamic injection of PGE₂. These data suggest that the ACTH response induced by IL-1 is mediated by CRF secretion stimulated by hypothalamic PGE₂.