Transcobalamin II--cobalamin binding sites are present on rabbit germ cells.

Specific binding sites for rabbit transcobalamin II have been found on isolated adult rabbit germ cells. Scatchard analysis revealed a single class of binding sites for [57Co]cyanocobalamin-transcobalamin II with an association constant (Ka) of 1.3 x 10(10) M-1 and 700 sites per cell. Binding was reversible, saturable and calcium dependent. Electron microscope radioautography following incubation with iodinated transcobalamin II at 4 degrees C led to a detectable labeling mainly restricted to the plasma membrane.     

Common denominators in the etiology and pathology of visceral lesions of cystic fibrosis and Keshan disease

The common denominator of a unique disseminated multi-focal milliary myocardial hyaline necrosis and fibrosis in Keshan disease (KSD) and cystic fibrosis (CF) and a commonality of the affected age groups of fetuses and preschool children led to the review of existing KSD autopsy material to search for pancreatic and hepatic lesions considered pathognomonic for CF. Pancreatic lesions considered pathognomonic for CF were found in 595, or 35% of 1700 documented cases of KSD. The pancreatic lesions were limited to tissues of fetuses and preschool children. Adults dying of KSD had diagnostic lesions limited to the cardiovascular system, liver, and skeletal muscle. Varying degrees of focal biliary cirrhosis were identified in 850, or 50% of the KSD autopsies, and 85, or 5% developed severe lobular cirrhosis. The common denominator in CF and KSD appears to be a primary or induced secondary selenium deficiency in age-susceptable humans, prenatally at or around 22 wk of fetal life, during early postnatal life, or during the rapid-growth preschool years. The basic difference between the natural history of CF and KSD is that the selenium deficiency is totally environmental in KSD and appears to be the result of a maternal malabsorptive syndrome or an abnormality of selenium transfer in CF.     

Selective inhibition of MAO-A in serotonergic synaptosomes by two amphetamine metabolites, p-hydroxyamphetamine and p-hydroxynorephedrine

The present study was carried out mainly to clarify whether the two amphetamine metabolites, p-hydroxyamphetamine (P-OHA) and p-hydroxynorephedrine (p-OHN) are taken up by mouse brain 5-hydroxytryptamine (5-HT) nerve terminals to inhibit type A monoamine oxidase (MAO-A) and then potentiate the abnormal behavior, head-twitch. Of the two metabolites, only intracerebroventricular p-OHA, at 80 μg/mouse, sufficient to cause a head-twitch response (HTR), appreciably inhibited MAO-A activity without affecting MAO-B activity in homogenates of the mouse striatum, hypothalamus and the rest of the forebrain; and p-OHN did not inhibit either type of MAO at the dose tested. Estimation of intra- and extrasynaptosomal MAO-A activity showed that both metabolites significantly inhibited only the intrasynaptosomal deamination of 5-HT by MAO-A with p-OHA being more potent. Taken together with our previous findings, these present results clearly indicate that p-OHA may accumulate in the 5-HT nerve terminals through the uptake system, and concomitantly inhibit MAO-A activity. These actions of p-OHA may increase intraneuronal 5-HT levels and then potentiate 5-HT release to cause interaction with the post-synaptic 5-HT receptors.     

背联体贻贝棘尾虫的形态,形态发生及其调节现象

背联体贻贝棘尾虫的每一虫腹面含有相当于正常棘尾虫的腹面纤毛系统,背联两虫任意一侧属于一虫的背面有4列背触毛,它们的排列分布相似于正常棘昆虫的第1—4列背触毛,另一虫背面打2列背触毛,它们相似于正常棘尾虫的第5、6列背触毛。结果表明,背联体棘尾虫是其中两虫各以背面第4列和第5列背触毛之间的皮层区相联接形成的。也有的背联体中背部皮层联接区有变化。无性分裂中背联两虫皮层纤毛结构的形态发生相似于正常棘尾虫,并且两者其皮层纤毛器如口围带、额腹横棘毛、左、右缘棘毛和背触毛等相应结构的发育是同步进行的,推测背联两虫的皮层发育既是相对独立的,又有某种机制控制着相互间的协调。背联体棘昆虫在无性生殖周期中总是经历着一个调节成单体的过程,认为这于背联两虫都具有一套结构功能正常的运动胞器(特别是口围带),而产生向不同方向运动的“不协调”的力有关。     

The effect of insecticides on the distribution of foracing parasitoids,Diaeretiella rapae [Hym.: Braconidae] on plants

Foraging aphid parasitoids,Diaeretiella rapae M'Intosh, were exposed to sublethal doses of the insecticides pirimicarb, permethrin and malathion on brusslls sprouts plants. Observations on wasp distribution over time revealed that wasps spent less time on sprayed plants, relative to controls and, while on these plants, tended to concentrate activity on unsprayed surfaces. For permethrin and malathion, pesticide residues reversed the stereotypic upward foraging pattern of the wasp. Negative consequences of sublethal pesticide doses for parasitoid foraging efficiency are discussed.      

Characterization of Inhibitor-Sensitive and -Resistant Adenosine Transporters in Cultured Human Fetal Astrocytes

Abstract: The kinetic characteristics of [³H]adenosine uptake, the extent to which accumulated [³H]adenosine was metabolized, the effects such metabolism had on measurements of apparent Michaelis-Menten kinetic values of K_T and V_max, and the sensitivities with which nucleoside transport inhibitors blocked [³H]adenosine accumulations were determined in cultured human fetal astrocytes. K_T and V_max values for accumulations of [³H]-labeled purines using 15-s incubations in the absence of the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) and the adenosine kinase inhibitor 5′-iodotubercidin (ITU) were 6.2 µM and 0.15 nmol/min/mg of protein for the high-affinity and 2.6 mM and 21 nmol/min/mg of protein for the low-affinity components respectively. In the presence of EHNA and ITU, where <4% of accumulated [³H]adenosine was metabolized, transport per se was measured, and kinetic values for K_T and V_max were 179 µM and 5.2 nmol/min/mg of protein, respectively. In the absence of EHNA and ITU, accumulated [³H]adenosine was rapidly metabolized to AMP, ADP, and ATP, and caused an appearance of “concentrative” uptake in that the intracellular levels of [³H]-labeled purines (adenosine plus its metabolites) were 1.4-fold higher than in the medium. No apparent concentrative accumulations of [³H]adenosine were found when assays were conducted using short incubation times in the absence or presence of EHNA and ITU. The nucleoside transport inhibitors dipyridamole (DPR), nitrobenzylthioinosine (NBI), and dilazep biphasically inhibited [³H]adenosine transport; for the inhibitor-sensitive components the IC₅₀ values were 0.7 nM for NBI, 1.3 nM for DPR, and 3.3 nM for dilazep, and for the inhibitor-resistant component the IC₅₀ values were 2.5 µM for NBI, 5.1 µM for dilazep, and 39.0 µM for DPR. These findings, in cultured human fetal astrocytes, represent the first demonstration of inhibitor-sensitive and -resistant adenosine transporters in nontransformed human cells.     

Isolation of a root-specific cDNA encoding a ns-LTP-like protein from the roots of bean (Phaseolus vulgaris L.) seedlings

A root-specific cDNA clone, PVR3, was isolated from a bean (Phaseolus vulgaris L.) root cDNA library by a differential screening procedure. The nucleotide sequence of PVR3 contains an open reading frame coding for an 11.14 kDa polypeptide of 102 amino acid residues; the first 25 amino acids correspond to the sequence characteristic of a signal peptide. Comparison of the deduced PVR3 polypeptide sequence with the polypeptide sequences of previously cloned genes indicates that PVR3 may encode a ns-LTP-like protein. Molecular modelling of the PVR3 protein predicts that it has a three-dimensional structure that is similar to the three-dimensional model determined from the maize ns-LTP. The PVR3 mRNA accumulated mainly in the roots of young seedlings. It can be detected at low levels in flowers, but it is not detected in other organs. Genomic Southern blot analysis indicates that the genomic DNA corresponding to PVR3 cDNA is encoded by a single gene or small gene family in the bean genome.     

包囊游仆虫皮层和营养核的超微结构研究

为研究纤毛虫在不同生理条件下结构的分化及其调节机理,本文应用透射电镜术显示,营养期包囊游仆虫背、腹面皮层表膜下含３种方式排列组成的纵微管层以及深部微管;口区皮层内含高电子密度的杆状小体;口围带小腹基部含电子致密带和小腹托架,棘毛基体基部及基体下微管束形成围棘纤维篮;背纤毛基体下方也含微管结构;大核染色质附着在核膜上,核膜其他区域有规则排列的核孔。     

Isolation and expression in Escherichia coli of hepB and hepC, genes coding for the glycosaminoglycan-degrading enzymes heparinase II and heparinase III, respectively, from Flavobacterium heparinum.

Upon induction with heparin, Flavobacterium heparinum synthesizes and secretes into its periplasmic space heparinase I (EC 4.2.2.7), heparinase II, and heparinase III (heparitinase; EC 4.2.2.8). Heparinase I degrades heparin, and heparinase II degrades both heparin and heparan sulfate, while heparinase III degrades heparan sulfate predominantly. We isolated the genes encoding heparinases II and III (designated hepB and hepC, respectively). These genes are not contiguous with each other or with the heparinase I gene (designated hepA). hepB and hepC were found to contain open reading frames of 2,316 and 1,980 bp, respectively. Enzymatic removal of pyroglutamate groups permitted sequence analysis of the amino termini of both mature proteins. It was determined that the mature forms of heparinases II and III contain 746 and 635 amino acids, respectively, and have calculated molecular weights of 84,545 and 73,135, respectively. The preproteins have signal sequences consisting of 26 and 25 amino acids. Truncated hepB and hepC genes were used to produce active, mature heparinases II and III in the cytoplasm of Escherichia coli. When these enzymes were expressed at 37 degrees C, most of each recombinant enzyme was insoluble, and most of the heparinase III protein was degraded. When the two enzymes were expressed at 25 degrees C, they were both present predominantly in a soluble, active form.     

包囊游仆虫休眠包囊的超微结构研究

包囊游仆虫休眠包囊中,各类纤毛器的纤毛基体上方的大部分纤毛杆退化,或仅保留毛基体,有时部分额腹棘毛的毛基体也瓦解消失。残留纤毛的纤毛杆周围微管和中央微管仍具有“9 2”结构特征,也有少数纤毛杆出现2套“9 2”微管共处于一层纤毛膜内的现象。毛基体中周围三联体微管的中央形成微管形结构聚合体,基体附属结构仅存在基体间连接及纤毛器托架的残余物;非纤毛区皮层表膜下未见微管层。纤毛区皮层含纤毛器腔周围微管层(相当于表膜下微管层)、纤毛器深部及附近的微管束和分散的微管群。并且,纤毛区皮层囊泡内含有呈不同形态的纤毛杆结构;大核核孔明显变大,核孔数目减少,核孔内膜附着染色质。