Cholinesterases from the marine mussels Mytilus galloprovincialis Lmk. and M. edulis L. and from the freshwater bivalve Corbicula fluminea Müller

In order to improve the molecular basis for the use of bivalve cholinesterases as a reliable biomarker for aquatic pollution, the polymorphism and characterization of these enzymes in Mytilus edulis, Mytilus galloprovincialis and Corbicula fluminea were investigated. All results are consistent with the presence of only one pharmacological form of cholinesterase in each species. The molecular masses were 180 kDa for the two marine mussels and 240 kDa for C. fluminea. The cholinesterases are anchored to the membrane by a glycosyl inositol phosphate like the G^a form (type I) described in vertebrates. Surprisingly, these cholinesterases were poorly inhibited by organophosphorous compounds compared to enzymes from other sources. This suggests that these bivalves could be used as a biomarker for acute rather than chronic contaminations by anticholinesterase insecticides.     

Taxonomic and nomenclatural notes on Syrrhopodon gaudichaudii Mont. (Calymperaceae) and S. hawaiicus Müll.Hal.

Syrrhopodon gaudichaudii Mont. is lectotypified and its key features are discussed. A neotype is designated for Syrrhopodon hawaiicus Müll.Hal. and the taxon is placed in synonymy with S. gaudichaudii. A key to the species of Syrrhopodon occurring in the Hawaiian Islands is provided.     

Müllerian inhibiting substance in reproduction and cancer.

During embryogenesis normal male phenotypic development requires the action of Müllerian Inhibiting Substance (MIS) which is secreted by Sertoli cells of the fetal testis. As testes differentiate in genetic (XY) males, they produce MIS which causes regression of the Müllerian ducts, the anlagen of the female reproductive tract. Soon thereafter, testicular androgens stimulate the Wolffian ducts. In females, on the other hand, MIS is not produced by grandulosa cells until after birth, before which, estrogens induce Müllerian duct development, while the Wolffian ducts passively atrophy in the absence of androgenic stimulation. High serum MIS levels in males are maintained until puberty, whereupon they fall to baseline levels. In females MIS is undetectable in serum until the peripubertal period when values approach the baseline levels of males. This distinct pattern of sexual and ontogenic expression presupposes and requires tight regulation. MIS may play a role in gonadal function and development. Our laboratory has shown that an important role for ovarian MIS is to inhibit oocyte meiosis, perhaps providing maximal oocyte maturation prior to selection for ovulation and subsequent fertilization. Furthermore, Vigier et al. (Development 100:43-55) have recently obtained evidence that MIS may influence testicular differentiation, coincident with inhibition of aromatase activity. Current structure-function studies demonstrate that MIS, like other growth regulators in its protein family, requires proteolytic cleavage to exhibit full biological activity. MIS can be inhibited by epidermal growth factor. This antagonism, which is common to all MIS functions so far investigated, is associated with inhibition of EGF receptor autophosphorylation. We have provided evidence that bovine MIS can inhibit female reproductive tract tumors arising in adults.(ABSTRACT TRUNCATED AT 250 WORDS)     

遗传工程学家A.M.Chakrabarty

Ananda M.Chakrabsrty是一位著名的遗传工程学家和美国生物化学家协会、微生物协会、工业微生物协会以及美国科学促进会的成员。他于1938年4月4日诞生在印度的Sainthia,1965年在加尔各答大学获得生物化学博士学位。后来,他到了美国的伊利     

K.M.贝柯夫院士

卓越的苏联生理学家K.M贝柯夫不幸于1959年5月13日在列宁格勒病逝。享年七十三岁。貝柯夫1912年畢业于喀山大学医学系,畢业后在該校著名生理学家領导下担任工作。1921年开始在巴甫洛夫实驗室工作。1932年任全苏实驗医学研究所应用生理学研究室主任。1933—1950年任該所一般生理学研究室主任。同时又領导海軍医学院生理教研組的工作、1945年被选为苏联医学科学院院士。1946年被选为苏联科学院院士。1948年任医学科学院中樞神經系統研究所所長。1950年以后一直     

Nitrogenase. VIII. M?ssbauer and EPR spectroscopy. The MoFe protein component from Azotobacter vinelandii OP.

We have studied the molybdenum-iron protein (MoFe protein, also known as component I) from Azobacter vinelandi using M?ssbauer spectroscopy and electron paramagnetic resonance on samples enriched with 57Fe. These spectra can be interpreted in terms of two EPR active centers, each of which is reducible by one electron. A total of four different chemical environments of Fe can be discerned. One of them is a cluster of Fe atoms with a net electronic spin of 3/2, one of them is high-spin ferrous iron and the remaining two are iron in a reduced state (probably in clusters). The results are as follows: Chemical analysis yields 11.5 Fe atoms and 12.5 labile sulfur atoms per molybdenum atom; the molecule contains two Mo atoms per 300 000 daltons. The EPR spectrum of the MoFe protein exhibits g values at 4.32, 3.65 and 2.01, associated with the ground state doublet of a S = 3/2 spin system. The spin Hamiltonian H = D(S2/z minus 5/4 + lambda(S2/x minus S2/y)) + gbeta/o S-H fits the experimental data for go = 2.00 and lambda = 0.055. Quantitative analysis of the temperature dependence of the EPR spectrum yields D/k = 7.5 degrees K and 0.91 spins/molybdenum atom, which suggests that the MoFe protein has two EPR active centers. Quantitative evaluation of M?ssbauer spectra shows that approximately 8 iron atoms give rise to one quadrupole doublet; at lower temperatures magnetic spectra, associated with the groud electronic doublet, are observed; at least two magnetically inequivalent sites can be distinguished. Taken together the data suggest that each EPR center contains 4 iron atoms. The EPR and M?ssbauer data can only be reconciled if these iron atoms reside in a spin-coupled (S = 3/2) cluster. Under nitrogen fixing conditions the magnetic M?ssbauer spectra disappeared concurrently with the EPR signal and quadrupole doublets are obserced at all temperatures. The data suggest that each EPR active center is reduced by one electron. The M?ssbauer investigation reveals three other spectral components characteristic of iron nuclei in an environment of integer or zero electronic spin, i.e. they reside in complexes which are "EPR-silent". One of the components (3-4 iron atoms) has M?ssbauer parameters characteristic of the high-spin ferrous iron as in reduced ruberdoxin. However, measurements in strong fields indicate a diamagnetic environment. Another component, representing 9-11 iron atoms, seems to be diamagnetic also. It is suggested that these atoms are incorporated in spin-coupled clusters.