A tobacco protein kinase, NPK2, has a domain homologous to a domain found in activators of mitogen-activated protein kinases (MAPKKs)

A cDNA (cNPK2) that encodes a protein of 518 amino acids was isolated from a library prepared from poly(A)⁺ RNAs of tobacco cells in suspension culture. The N-terminal half of the predicted NPK2 protein is similar in amino acid sequence to the catalytic domains of kinases that activate mitogen-activated protein kinases (designated here MAPKKs) from various animals and to those of yeast homologs of MAPKKs. The N-terminal domain of NPK2 was produced as a fusion protein in Escherichia coli, and the purified fusion protein was found to be capable of autophosphorylation of threonine and serine residues. These results indicate that the N-terminal domain of NPK2 has activity of a serine/threonine protein kinase. Southern blot analysis showed that genomic DNAs from various plant species, including Arabidopsis thaliana and sweet potato, hybridized strongly with cNPK2, indicating that these plants also have genes that are closely related to the gene for NPK2. The structural similarity between the catalytic domain of NPK2 and those of MAPKKs and their homologs suggests that tobacco NPK2 corresponds to MAPKKs of other organisms. Given the existence of plant homologs of an MAP kinase and tobacco NPK1, which is structurally and functionally homologous to one of the activator kinases of yeast homologs of MAPKK (MAPKKKs), it seems likely that a signal transduction pathway mediated by a protein kinase cascade that is analogous to the MAP kinase cascades proposed in yeasts and animals, is also conserved in plants.     

Evolution of the LINE-like I element in the Drosophila melanogaster species subgroup

LINE-like retrotransposons, the so-called I elements, control the system of I-R (inducer-reactive) hybrid dysgenesis in Drosophila melanogaster. I elements are present in many Drosophila species. It has been suggested that active, complete I elements, located at different sites on the chromosomes, invaded natural populations of D. melanogaster recently (1920–1970). But old strains lacking active I elements have only defective I elements located in the chromocenter. We have cloned I elements from D. melanogaster and the melanogaster subgroup. In D. melanogaster, the nucleotide sequences of chromocentral I elements differed from those on chromosome arms by as much as 7%. All the I elements of D. mauritiana and D. sechellia are more closely related to the chromosomal I elements of D. melanogaster than to the chromocentral I elements in any species. No sequence difference was observed in the surveyed region between two chromosomal I elements isolated from D. melanogaster and one from D. simulans. These findings strongly support the idea that the defective chromocentral I elements of D. melanogaster originated before the species diverged and the chromosomal I elements were eliminated. The chromosomal I elements reinvaded natural populations of D. melanogaster recently, and were possibly introduced from D. simulans by horizontal transmission.     

Influence of muscle activity on the forces in the femur: An in vivo study

Experiments were performed on two patients with custom-made instrumented massive proximal femoral prostheses implanted after tumour resection. In vivo axial forces transmitted along the prostheses were telemetered during level walking, single- and double-leg stance, and isometric exercises of the hip muscles. These activities varied the lever arms available to the external loads: minimum for double-leg stance and maximum for hip isometric exercises. Kinematic, force plate, EMG and telemetered force data were recorded simultaneously. The force magnification ration (FMR; the ratio of the telemetered axial force to the external force) was calculated. The FMRs ranged from 1.3 (during double-leg stance) to 29.8 (during abductors test), indicating that a major part of the axial force in the long bones is a response to muscle activity, the strength of which depends on the lever arms available to the external loads. From these results, it was shown that the bulk of the bending moment along limbs is transmitted by a combination of tensile forces in muscles and compressive forces in bones, so moments transmitted by the bones are smaller than the limb moments. It was concluded that appropriate simulation of muscle forces is important in experimental or theoretical studies of load transmission along bones.     

SNARE Proteins-Why So Many,Why So Few?

Abstract: Both trafficking and secretion critically depend on accurate and specific membrane recognition and fusion. A key step in these processes is the assembly of a complex consisting of a small number of proteins, i.e., the exocytic core complex. In nerve terminals, this set consists of VAMP and synaptotagmin, which reside at membranes of synaptic vesicles, and syntaxin and SNAP-25 at the plasma membrane. In this survey, different secretory systems that depend on the exocytic core proteins are considered. The possibility that specificity in membrane recognition and fusion is achieved by the numerous variants of proteins of the exocytic core is discussed. Variability of the core complex proteins is determined by the complexity of gene families, isoform-specific localization, and posttranslational modifications. Basic biochemical properties depend on specific isoforms, and the possible protein-protein interactions are determined, in turn, by the compatibility of different isoforms. A correlation between specific variants and distinct biochemical or cellular properties is shown. The outcome of this survey is that heterogeneity in secretion may be dictated by the large number of possible combinations of variants of only a few proteins.     

AIDS in Africa: distinguishing fact and fiction

The data widely purporting to show the existence and heterosexual transmission in Africa of a new syndrome caused by a retrovirus which induces immune deficiency are critically evaluated. It is concluded that both acquired immune deficiency (AID) and the symptoms and diseases which constitute the clinical syndrome (S) are of long standing in Africa, affect both sexes equally and are caused directly and indirectly by factors other than human immunodeficiency virus (HIV). Seropositivity to HIV in Africans usually represents no more than cross-reactivity caused by an abundance of antibodies induced by the numerous infectious and parasitic diseases which are endemic in Africa. The apparently high prevalence of AIDS and HIV seropositives is therefore not surprising and is not proof of heterosexual transmission of either HIV or AIDS.E. Papadopulos-Eleopulos is with the Department of Medical Physics, The Royal Perth Hospital, Perth 6000, Western Australia, Australia; V.F. Turner is with the Department of Emergency Medicine, The Royal Perth Hospital, Perth 6000, Western Australia, Australia, J.M. Papadimitriou is with the Department of Pathology, University of Western Australia, Perth, Western Australia. H. Bialy is with Bio/Technology, 65 Becker St, New York, NY 10012, USA.     

Movement and distribution pattern of the residues of granular insecticides in tropical soil and okra plants

Summary The increased downward mobility of phorate, quinalphos and carbofuran residues was detected in soil with increase in depth of soil column whereas aldicarb was found to remain localised mainly in 0–7.5 cm and 7.5–15.0 cm layers. Persistence of organophosphate insecticides was higher as compared to carbamates in all the soil layers. Residues of all the four insecticides got distributed in all parts of okra plant through uptake but accumulated in higher amounts in fruits only. Contribution No. 312/83 from I.I.H.R. Bangalore (India)     

Paddle cilia and discocilia — Genuine structures?

Kinocilia of epidermal sensory cells in fixed marine Turbellaria often terminate as flattened biconcave discs. The distal part of the ciliary axoneme curves back upon itself forming a 360 degree loop which is enveloped by the plasmalemma. In living animals this structure can be induced by the addition of sodium cacodylate, monobasic sodium phosphate, dibasic sodium phosphate, sucrose, calcium chloride, or formaldehyde to the sea water. Specimens treated with sodium chloride, glutaraldehyde, or osmium tetroxide do not show modified cilia. In animals prepared for EM at low temperature and with a buffered hypotonic fixative less kinocilia are modified than in animals treated with a buffered iso- or hypertonic fixative and at a higher temperature. It is assumed that the unusually shaped cilia, described as "paddle cilia" or "discocilia" in other invertebrates, do not represent a genuine but an artificial structure.     

Influence of soil gas contamination on tree root growth

Summary Rooted-cuttings and saplings of green ash (Fraxinus lanceolata) and hybrid poplar (Populus spp) were planted on a former municipal refuse landfill and on a nearby nonlandfill control plot. The root systems of four trees of each species and size were excavated on the landfill plot-two growing in an area where the concentrations of anaerobic landfill gases were relatively high and two in a relatively low-gas area. Two trees of each species and size were also excavated on the control. The root systems of both species were significantly shallower on the landfill plot than on the control. Green ash appeared to avoid the adverse gas environment of the deeper soil layers on the landfill by producing adventitious roots. Hybrid poplar became adapted in a different manner, by redirecting root growth from the deepter soil layers to the soil surface.     

Origin of bipedalism

Human and chimpanzee locomotor behaviors are described and compared using field patterns derived from measurements of the motions at the joints. Field patterns of human and ape bipedalism are so different that it is doubted whether the nonhuman type could ever have been a precursor of the human type. Chimpanzee quadrupedal vertical climbing and human bipedalism are, on the other hand, similar and a particular variety of this kind of climbing probably was the precursor of human bipedalism. Animals adapted to this variation would have had some brachiation-like morphological traits in their pectoral limbs and some hominid-like morphological traits in their pelvic limbs, traits anticipating the human condition. The australopithecines possessed these traits and must have been adapted to arboreal quadrupedal vertical climbing, having the capacity, at the same time, to perform facultative terrestrial bipedalism, moving on the ground in a manner visually identical to that of humans.     

索曼中毒运动终板乙酰胆碱酯酶活性和接头传递功能的关系

用大鼠的在体膈肌局部索曼(Soman)中毒法,观察了乙酰胆碱酯酶(ACHE)在运动终板的再生和肌接头传递功能的恢复过程,以及肟类药物(HI-6)对两过程的促进作用。提出终板 AChE 活性与高频间接刺激(100次/秒)引起膈肌强直收缩幅度有一定的关系。中毒早期(30分钟以内)HI-6对索曼抑制的膈肌终板 AChE 有一定的重活化作用,并能相应地恢复肌接头的传递功能。