核能谱与两类转动惯量的精确表达式

用最小二乘拟合法,将稀土区的能谱实验数据,拟合不同的能谱公式,从而证明E=a〔(1+bI(I+1))~(1/2)-1〕是符合得较好的,本文还推导了与上述能谱相应的两类转动惯量,并以此与实验计算值进行比较,结果仍很满意.     

高梁叶中的多核纤维和分隔纤维

高粱(Sorghum vulgares Pers.)叶中的纤维在发育过程中出现多个细胞核现象,细胞核的数目1～7个,一般为1～3个。这种多核纤维的细胞核形状也不同,有圆球形、纺锤形和伸长的线形。纤维中出现的多核现象是由于纤维在早期发育过程中连续进行核分裂形成的,或者是发育的分隔纤维在形成横隔前出现短暂的多核时期。除这种多核纤维外,高粱叶中还青许多具有生活原生质体的分隔纤维。     

Endocrine and exocrine pancreatic function after camostate-induced growth of the organ

It is well known that oral administration of camostate induces hyperplasia and hypertrophy of the rat pancreas. It is not clear, however, whether pancreatic hormone and enzyme secretion are affected by camostate treatment.In rats, daily administration of 200 mg camostate/kg b. wt for 14 days significantly increased pancreatic weight and pancreatic content of DNA, protein, amylase, lipase, trypsin and chymotrypsin, as well as the amount of insulin, glucagon and somatostatin. In the intact animal, blood glucose levels and serum concentrations of insulin and glucagon in response to an oral glucose load were not impaired after camostate treatment. In the isolated perfused pancreas, however, insulin and glucagon secretions were reduced, whereas somatostatin release was not affected. The volume of pancreatic juice produced by the unstimulated isolated perfused organ, as well as protein and enzyme secretion, were increased after camostate treatment. Likewise, the isolated perfused pancreas from camostate-treated rats secreted a larger volume of pancreatic juice and more protein in response to cholecystokinin (CCK), while enzyme secretion was affected in a non-parallel manner: amylase release was markedly reduced, lipase release was unchanged, and release of trypsin and chymotrypsin was increased.     

Dual role of cAMP duringDictyostelium development

cAMP plays an essential role duringDictyostelium development both outside and inside the cell. Membrane-bound receptors and adenylyl cyclase are responsible for sensing and producing extracellular cAMP, whereas a phosphodiesterase is responsible for maintaining a low basal level. The molecular events underlying this type of hormone like signalling, which are now beginning to be deciphered, will be presented, in the light of cAMP analogue studies. The importance of intracellular cAMP for cell differentiation has been demonstrated by the central role of the cAMP dependent protein kinase. Mutants as well as strains obtained by reverse genetics will be reviewed which lead to our current understanding of the role of intracellular cAMP in the differentiation of both stalk and spore cells.     

Can purchasing power parity help forecast the dollar?

This paper examines the information on future exchange rate movements provided by the doctrine of purchasing power parity (PPP). Previous research has studied this issue by analyzing the time-series properties of period-by-period levels of, or changes in, exchange rates. In contrast, the present study focuses on the durations of periods in which exchange rates deviate from their PPP levels. If PPP provides information about future exchange rate movements, these durations should exhibit positive duration dependence. That is, the probability of returning to PPP levels should increase as the period of deviation increases. Parametric hazard functions estimated using data from eighteen countries provide no evidence of positive duration dependence. These results are robust to alternative definitions of PPP and to alternative functional specifications. While exchange rates take prolonged swings away from their PPP levels and then eventually return, these movements apparently constitute Monte Carlo cycles in which, at any point in time, the probability of moving back toward PPP is the same as the probability of moving farther away. Thus, PPP provides no useful information on future exchange rate changes, a result consistent with market efficiency.     

灰色理论在化学研究中用作建模与预测新的方法

研究了灰色理论作为一种有用的化学计量学多元建模与定量预测新方法的可行性，将其应用于某些不确定关系如电泳迁移率，色谱保留值和农药需求量等建模，定量预测结果良好。     

汽轮发电机端部似稳涡流场数学模型

导出了描述发是端部涡流场的边值问题，并讨论了此问题的确定性。导出了与此边值问题等价的条件变化问题，并给出了三维行波场下变分式的具体形式。对ＱＦＳ－３００－２型汽轮发电机的端部场作了实例计算，计算结果与测试结果是一致的，证实了本文所提出的数学模型的正确性。     

cDNA cloning of bovine substance-K receptor through oocyte expression system

The neuropeptide receptors which are present in very small quantities in the cell and are embedded tightly in the plasma membrane have not been well characterized. Mammals contain three distinct tachykinin neuropeptides, substance P, substance K and neuromedin K, and it has been suggested that there are multiple tachykinin receptors. By electrophysiological measurement, we have previously shown that Xenopus oocytes injected with brain and stomach mRNAs faithfully express mammalian substance-P and substance-K receptors, respectively. Here we report the isolation of the cDNA clone for bovine substance-K receptor (SKR) by extending this method to develop a new cloning strategy. We constructed a stomach cDNA library with a cloning vector that allowed in vitro synthesis of mRNAs and then identified a particular cDNA clone by testing for receptor expression following injection of the mRNAs synthesized in vitro into the oocyte system. Because oocytes injected with exogenous mRNAs can express numerous receptors and channels, our new strategy will be applicable in the general molecular cloning of these proteins. The result provides the first indication that the neuropeptide receptor has sequence similarity with rhodopsin-type receptors (the G-protein-coupled receptor family) and thus possesses multiple membrane-spanning domains.     

Suppression of in vitro haematopoiesis following human immunodeficiency virus infection

Viral infections are frequently associated with haematological disorders. Abnormalities including leukopenia, anaemia and thrombocytopenia are commonly observed in patients with the acquired immune deficiency syndrome (AIDS) or the AIDS-related complex (ARC). The underlying cause of these haematological abnormalities is poorly understood. We report here that bone marrow progenitors isolated from AIDS or ARC patients are responsive to recombinant human granulocyte-macrophage colony stimulating factor (rGM-CSF) and recombinant erythropoietin. Antibodies present in the serum of patients infected with the human immunodeficiency virus (HIV), however, could suppress the growth of these progenitors, but not the growth of progenitors from HIV seronegative controls. A component of this immune-mediated suppression appears to be antibodies directed towards the envelope glycoprotein (gp120) of HIV.     

Activation of a G protein promotes agonist responses to calcium channel ligands

The activation of a guanine nucleotide binding (G) protein is an essential step in coupling certain receptors to the inhibition of voltage-activated calcium channels. We have previously observed that analogues of GTP potentiate the effect of receptor agonists and inhibit calcium currents in cultured dorsal root ganglion (DRG) neurones. A residual sustained 'L-type' component of the calcium channel current is resistant to inhibition by internal guanosine 5'-O-3-thiotriphosphate (GTP-gamma-S). Because calcium channel antagonists such as D600, nifedipine and diltiazem inhibit L currents, we examined their effect on GTP-gamma-S-modified currents. These compounds all produced a rapid and very marked potentiation of calcium channel currents in the presence of internal GTP-gamma-S and this effect was prevented by pertussis toxin which ADP ribosylates the G proteins Gi/Go (for review see ref. 10). We suggest that this potentiation indicates that activated G protein can interact with the calcium channel, and that this enhances the action of calcium channel ligands at their agonist sites on the channel in its resting state. These results represent the first electrophysiological evidence that guanine nucleotides are able to influence cellular responses to calcium channel ligands.