毛乌素沙地南缘沙丘生物结皮对凝结水形成和蒸发的影响

在水分极度匮乏的荒漠生态系统,凝结水是除降雨之外最重要的水分来源之一,它对荒漠生态系统结构、功能和过程的维持产生重要的影响。为探明半干旱沙区生物结皮表面的凝结水形成和蒸发特征,采用自制的微型蒸渗计(直径7 cm、高5 cm的PVC管)实验观测了不同类型地表(裸沙、浅灰色藻类结皮、黑褐色藻类结皮和苔藓结皮)对凝结水形成和蒸发的影响。结果表明:(1)观测期间共有20次凝结水形成记录,除降雨天气外,几乎每天都能观测到水分凝结现象;(2)不同类型地表凝结水总量依次为(1.998±0.075),(2.326±0.083),(2.790±0.058)和(3.416±0.068) mm,生物结皮表面的凝结水总量显著大于裸沙(P < 0.05);随生物结皮的发育,不同类型生物结皮表面的凝结水总量呈增加的趋势,凝结水总量之间差异显著(P < 0.05);观测期间不同类型地表日平均凝结水量依次为(0.100±0.003),(0.116±0.004),(0.140±0.002)和(0.171± 0.003) mm,不同类型地表日平均凝结水量之间差异极显著(P < 0.01);(3)凝结水形成过程的观测结果显示,凝结水19:00开始形成,23:00-凌晨1:00形成不明显,1:00-7:00继续形成,除浅灰色藻类结皮外,太阳升出后在黑褐色藻类结皮和苔藓结皮表面继续形成少量的凝结水;凝结水7:30开始蒸发,10:30到11:00之间结束蒸发,凝结水在裸沙和浅灰色藻类结皮中的保持时间显著大于黑褐色藻类结皮和苔藓结皮中的保持时间(P < 0.05);(4)凝结水的形成受大气温度、地表温度、空气相对湿度和大气地表温度差等气象因素的影响,但其形成过程不与某一个气象因素呈简单的线性关系。     

A high ratio of chromogranin A to synaptin/synaptophysin is a common feature of brains in Alzheimer and Pick disease

Chromogranin A and synaptin/synaptophysin were characterized by immunological methods in human autopsy brain tissue from patients with Alzheimer's and Pick's disease. In immunoblots there was no qualitative difference between the antigens in control and diseased brain, but significant quantitative differences were found. In all Alzheimer cases there was a significantly lower level of synaptin/synaptophysin, whereas chromogranin A was higher in 4 out of 5 cases and in all cases relative to synaptin/synaptophysin. An analogous finding was obtained for Pick's disease. Immunohistologically a consistent staining of neuritic plaques for chromogranin A, but not for secretogranin II was found in Alzheimer cases. In Pick's disease the characteristic Pick bodies showed an analogous specific immunostaining.     

Interaction of saposins, acidic lipids, and glucosylceramidase

Activity of lysosomal glucosylceramidase is stimulated by two small glycoproteins, saposin A and C, which are, together with two other similar glycoproteins, derived from a single precursor protein. This enzyme is also stimulated by naturally occurring acidic lipids, such as phosphatidylserine and gangliosides. Using highly purified glucosylceramidase, saposins, and acidic lipids, the mechanism of enzyme stimulation was studied by investigating complex formation between the three components and by examining effects on activity caused by changing amounts of saposins and acidic lipids, individually or in combination. The results indicated that acidic lipids form a water-soluble complex with glucosylceramidase but not with saposins and that saposins and acidic lipids each bind to the enzyme at two different sites for the activation. Based on these observations, the previously proposed three-binding sites model of glucosylceramidase, activator, and substrate was modified to one composed of four binding sites: one for carbohydrate of the substrate, one for aglycon, one for acidic lipids, and one for saposins.     

Naringin levels in citrus tissues : I. Comparison of different antibodies and tracers for the radioimmunossay of naringin

The preparation of a tritiated radiotracer that was used in the radioimmunoassay of naringin (naringenin-7-O-α-rhamnosyl- (1-2)-β-d-glucopyranoside) and which was synthesized by reduction of the carbonyl group of the flavanone is reported. The resulting assay has a detection limit of 0.5 picomole per 0.1 milliliter, is specific for the 7-neohesperidoside substitution on flavanones, and can measure naringin in crude extracts of plant tissues. This radioimmunoassay is compared with three other naringin immunoassays which use antibodies raised against two different haptens and different tracers labeled with ¹²⁵I or ³H. The applicability of the methods to the quantification of naringin and other flavanone neohesperidosides in citrus tissue is discussed.     

Airway reactivity to methacholine in nonatopic asymptomatic adults

We studied 50 nonsmoking volunteers, ages 18-35 yr, with no past or present history or physical examination findings of asthma, rhinitis, allergic disease, or recent respiratory infections, to evaluate the usefulness of the methacholine bronchoprovocation challenge (MBPC) as a screening test for asthma. All were skin-test-negative to 29 aeroallergens and had base-line pulmonary function values greater than 80% predicted. Fourteen (28%) subjects had a drop in forced expiratory volume in 1 s (FEV1) of 20% or greater at a provocative dose (PD20FEV1) less than or equal to 225 breath units. Moreover, when these subjects were compared with 21 asymptomatic allergic asthmatics, there was significant overlap between the two groups in concentration of methacholine causing this decline in FEV1. A positive MBPC at methacholine concentrations less than or equal to 5 mg/ml was not diagnostic of asthma, and a negative MBPC at methacholine concentrations greater than or equal to 10 mg/ml did not rule out asthma. These data strongly suggest that MBPC should not be used as the sole factor for the diagnosis of clinically significant asthma. A positive MBPC is one indication of the presence of airway hyperresponsiveness and thus is only one of many factors that must be considered in the diagnosis of asthma.     

Monoclonal antibodies identify common and differentiation-specific antigens on the plasma membrane of guard cells of Vicia faba L.

Monoclonal antibodies were raised against the plasma membrane of Vicia faba L. guard cells by immunizing either with total membranes from purified guard-cell protoplasts or with sealed, predominantly right-side-out plasma-membrane vesicles prepared from abaxial epidermes of V. faba by aqueous two-phase partitioning. Hybridoma screening was performed by enzyme-linked immunosorbent assay using polystyrene-adsorbed plasma-membrane vesicles as solid phase and by indirect immunofluorescence analysis using unfixed, immobilized protoplasts in a microvolume Terasaki assay. A range of monoclonal antibodies was characterized and is reported here. One monoclonal antibody, G26-6-B2, is guard-cell-specific and does not react with mesophyll-cell protoplasts of the same species. It binds to a periodate-resistant but trypsin-labile epitope, probably a differentiation-specific plasma-membrane protein.Abbreviations ELISA enzyme-linked immunosorbent assay - FITC fluorescein isothiocyanate - GCP guard cell protoplast(s) - Ig immunoglobulin - MAB monoclonal antibody - MCP mesophyll-cell protoplast(s) - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis