Light‐dependent changes of tomato glutamine synthetase in response to Pseudomonas syringae infection or phosphinothricin treatment

Glutamine synthetase (GS, EC 6.3.1.2), a key enzyme in nitrogen assimilation, was investigated in tomato ( Lycopersicon esculentum Mill. cv. Hellfrucht Frühstamm) leaves infected with Pseudomonas syringae pv. tomato (Pst) or treated with the herbicide phosphinothricin (PPT), an irreversible inhibitor of GS. GS activity decreased markedly when Pst infection occurred in illuminated leaves, but only a slight decrease in relation to control leaves was observed under non‐photosynthetic conditions. In leaves treated with PPT, a rapid inhibition of GS activity was observed under all experimental conditions. When bacterial infection or herbicide treatment was carried out in the light, cytosolic GS (GS1) appeared as the predominant GS polypeptide; however, under non‐photosynthetic conditions GS2 remained the most abundant molecular GS species as occurs in non‐stressed plants. These results suggest a close correlation between the photosynthetic process and changes in the relative proportions of GS polypeptides during infection or herbicide treatment. Ammonium has been described as an inducer of GS genes, but as ammonium accumulated during all treatments, other light‐dependent factors could be involved in GS regulation of stressed leaves.     

Circular dichroism study of ribonuclease A mutants containing the minimal structural requirements for dimerization and swapping

Four residues Pro19, Leu28, Cys31 and Cys32 proved to be the minimal structural requirements in determining the dimeric structure and the N-terminal segment swapping of bovine seminal ribonuclease, BS-RNase. We analyzed the content of secondary and tertiary structures in RNase A, P-RNase A, PL-RNase A, MCAM-PLCC-RNase A and MCAM-BS-RNase, performing near and far-UV CD spectra. It results that the five proteins have very similar native conformations. Thermal denaturation at pH 5.0 of the proteins, studied by means of CD measurements, proved reversible and well represented by the two-state ND transition model. Thermodynamic data are discussed in the light of the structural information available for RNase A and BS-RNase.     

Analysis of airborne pollen in the town of Almería (South-East Spain), 1995–1996

The first results are presented of an aerobiological analysis of the atmosphere of the town of Almería, carried out between November 1995 and October 1996. A Lanzoni volumetric spore trap was used for sample collection. The composition and seasonal evolution of the pollen spectrum were determined over a 1-year period in relation to the vegetation and climatic conditions of the study area. Twenty-six pollen types were identified as accounting for >0.05% of the total pollen collected. The main sources of airborne pollen were Palmae (17.76%),Olea (16.10%), Chenopodiaceae/Amaranthaceae (13.99%), Urticaceae (10.18%) and Poaceae (8.64%). The annual pollen variation presented a period of maximum emission from March to June, with a subsequent, less intensive period from August to November. The minimum pollen values were obtained from December to February. The highest concentrations occurred in May, which was also the month which presented the highest pollen diversity, whereas the lowest values were observed in January.     

High levels of soluble IFN γ receptor α chain in the plasma of rheumatoid arthritis patients

Soluble receptors for hormones and cytokines have beendescribed. They can serve as natural blockers of theirrespective ligands. The natural soluble interferongamma receptor (sIFNR) has been isolated andcharacterized only in urine. Chromatography of human(hu) plasma from rheumatoid arthritis (RA) patientsand controls on immobilized hu IFN orantibodies against IFN R chainpermitted us to isolate the sIFNR. Thereceptor isolated from one control is a protein witha molecular weight between 60-67 kDa depending on thepresence of reducing agents. We detected asignificantly higher level of plasma sIFNR inpatients with rheumatoid arthritis than in apparentlyhealthy subjects.     

Albutensin A, an ileum-contracting peptide derived from serum albumin, acts through both receptors for complements C3a and C5a

Albutensin A is an ileum-contracting peptide derived from serum albumin. The sequences of bovine, human and porcine albutensin A are ALKAWSVAR, AFKAWAVAR, and AFKAWSLAR, respectively. These albutensin A homologs all exhibited biphasic ileal contractions in the longitudinal strips of guinea pig ileum. The order of potency in the contraction was porcine > bovine > human homologs. The ileal contraction profiles were similar to those of oryzatensin and casoxin C, agonist peptides for complement C3a receptors derived from rice albumin and bovine -casein, respectively. All three homologs of albutensin A have homology with the COOH-terminal sequences of complements C3a and C5a, which are essential for their activities; porcine albutensin A showed the highest homology. Indeed, porcine albutensin A was confirmed to act through both C3a and C5a receptors by a radioreceptor assay and cross-desensitization in the ileal contraction. In addition, bovine and human homologs also showed affinity for both receptors. This study suggests that a bioactive peptide acting through both C3a and C5a receptors is released by the proteolytic cleavage of serum proteins other than complement components.     

Visuomotor transformations: early cortical mechanisms of reaching

Recent studies of visually guided reaching in monkeys support the hypothesis that the visuomotor transformations underlying arm movements to spatial targets involve a parallel mechanism that simultaneously engages functionally related frontal and parietal areas linked by reciprocal cortico-cortical connections. The neurons in these areas possess similar combinations of response properties. The multimodal combinatorial properties of these neurons and the gradient architecture of the parieto-frontal network emerge as a potential substrate to link the different sensory and motor signals that arise during reaching behavior into common hybrid reference frames. This convergent combinatorial process is evident at early stages of visual information processing in the occipito-parietal cortex, suggesting the existence of re-entrant motor influences on cortical areas once believed to have only visual functions.     

人血清脂蛋白(a)中纤维蛋白溶酶原位点测定

用单克隆抗载脂蛋白(a)抗体为包被抗体,酶标抗纤维蛋白溶酶原(Pg)抗体为检测抗体建立了人血清脂蛋白(a)［Lp(a)］中Pg位点的酶联免疫吸附试验法.方法特异,测定范围为28～880 mg/L,变异系数批内为4%～6%,批间为7%～9%.检测了正常人、冠心病(CHD)和肾衰血透患者(CRF)血清Lp(a)、Lp(a)中Pg位点和Pg/Lp(a)比值.结果示正常人血清Lp(a)水平分别同Pg、Pg/Lp(a)呈正、负相关.CHD和CRF患者Lp(a)、Pg位点和Pg/Lp(a)比值明显高于正常人,认为Lp(a)中Pg位点测定对于动脉粥样硬化的病理生理研究具有特殊的价值.