HETEROTROPHY OF FOUR MARINE PHYTOPLANKTERS AT LOW SUBSTRATE CONCENTRATIONS1

Three pelagic marine phytoplankters, Coccolithus huxleyi, Skeletonema costatum, and Thalassiosira ro-tula, and a facultative heterotroph, Cyclotella cryp-tica, have been exposed to three organic substrates, viz, glucose, acetate, and glutamate, at low concentrations (organic carbon 0.25 mg/liter). Experiments were performed in the dark and light and the net assimilation of substrate was measured by using radiocarbon. The dark uptake of carbon dioxide was also determined, together with photosynthesis at near optimum light intensity. The expected heterotrophy was detected with Cyclotella cryptica. Thalassiosira rotula was found to assimilate glutamate at an appreciable rate. In all cases, however, the short-term uptake of carbon dioxide in the dark was the greatest assimilation rate measured. Values are discussed in relation to their ecological significance and it is concluded that heterotrophic survival of these and probably most other algae in the open ocean xuould be impossible unless they were in contact with a high concentration of substrate in the form of particulate matter.     

Construction of a sequencedClostridium perfringens-Escherichia coli shuttle plasmid

A newClostridium perfringens-Escherichia coli shuttle plasmid has been constructed and its complete DNA sequence compiled. The vector, pJIR418, contains the replication regions from theC. perfringens replicon pIP404 and theE. coli vector pUC18. The multiple cloning site and lacZ gene from pUC18 are also present, which means that X-gal screening can be used to select recombinants inE. coli. Both chloramphenicol and erythromycin resistance can be selected inC. perfringens andE. coli since pJIR418 carries theC. perfringens catP and ermBP genes. Insertional inactivation of either the catP or ermBP genes can also be used to directly screen recombinants in both organisms. The versatility of pJIR418 and its applicability for the cloning of toxin genes fromC. perfringens have been demonstrated by the manipulation of a cloned gene encoding the production of phospholipase C.     

Conformationally restricted homotryptamines 3. Indole tetrahydropyridines and cyclohexenylamines as selective serotonin reuptake inhibitors

A series of indole tetrahydropyridine and indole cyclohexenylamines was prepared, and their binding affinities at the human serotonin transporter (SERT) were determined. In particular, a nitrile substituent at the C5 position of the indole ring gave potent SERT activity. The stereochemistry of the N,N-dimethylamine substituent was determined for the most potent indole cyclohexenylamine, 6a. The enantiomers of 6a were energy minimized and compared to other conformationally restricted SSRIs. Compound 6a was found to give a dose-response similar to the SSRI fluoxetine in microdialysis studies in rats.     

How was teleology eliminated in early molecular biology?

This paper approaches the issue of the status of teleological reasoning in contemporary biology through a historical examination of events of the 1930s that surrounded Niels Bohr’s efforts to introduce ‘complementarity’ into biological discussions. The paper examines responses of three theoretical physicists who engaged boundary questions between the biological and physical sciences in this period in response to Bohr—Ernst Pascual Jordan (1902–80), Erwin Schrödinger (1887–1961), and Max Delbrück (1906–81). It is claimed that none of these physicists sufficiently understood Bohr’s ‘critical’ teleological arguments, which are traced to the lineage of Kant and Harald Høffding and their respective resolutions of the Antinomy of Teleological Judgment. The positions of these four historical actors are discussed in terms of Ernst Mayr’s distinction of ‘teleological,’ ‘teleomatic,’ and ‘teleonomic’ explanations. A return to some of the views articulated by Bohr, and behind him, to Høffding and Kant, is claimed to provide a framework for reintroducing a ‘critical’ teleology into biological discussions.     

禽流感H5N1病毒感染BALB/c小鼠后多器官病变初探

为了研究禽流感H5N1病毒在各个器官的增殖和病理变化,在生物安全实验室,我们将禽流感H5N1病毒通过尾静脉接种BALB/C小鼠。结果小鼠在不经过适应的情况下,直接感染发病,甚至死亡。在观察的7天内,感染小鼠临床症状主要表现呼吸急促,体温、体重下降。尸检表现肺出血,心外膜坏死以及肝脏的坏死。组织病理检查表现心、肝、肺等多器官的病变。肺的病变伴有纤维化的弥漫性肺泡损伤;心肌外膜大量淋巴细胞浸润、坏死;肝细胞大量坏死,淋巴细胞浸润。心、肝的坏死病变在H5N1禽流感病毒相关的研究中未见报道。经过对各个组织器官的病毒载量的检测,未发现病毒在各个病变组织中的复制。免疫组化的检测,各个组织中也未检出阳性的细胞反应。因此,我们认为H5N1禽流感病毒感染小鼠引起多个器官组织的损伤,甚至死亡,不是病毒在器官的复制,而可能是病毒感染小鼠,产生炎症细胞因子的高度表达,损伤多个器官组织所致。     

Characterization of pACK4, a mobilizable plasmid from Staphylococcus simulans biovar staphylolyticus

Staphylococcus simulans biovar staphylolyticus, the lysostaphin-producing organism, contains five plasmids designated pACK1–pACK5. pACK4 was found to be relaxable and to share sequence similarity with a number of well-characterized mobilizable plasmids from other staphylococci. All mobilizable staphylococcal plasmids characterized to date mediate resistance to various antibiotics, but pACK4 is unique because it contains no recognizable antibiotic resistance genes. pACK4 was found to contain an origin of transfer (oriT) region that shares inverted repeat regions and the same nic site as several other mobilizable staphylococcal plasmids. The presence of this conserved oriT region suggested that pACK4 might be mobilized in the presence of a conjugative plasmid. Filter mating studies revealed that pACK4 was mobilized by the conjugative plasmid pGO1. In addition, pACK4 was found to be virtually identical to the recently described plasmid pVGA from Staphylococcus aureus, except that pVGA contains an additional region (vgaA) that confers resistance to pleuromutilin, streptogramin A, and lincosamide. The high sequence similarity among pACK4, pVGA, and several previously described mobilizable staphylococcal plasmids suggests a common origin for these plasmids.