A self-organizing model of walking patterns of insects

It is well known that the motor systems of animals are controlled by a hierarchy consisting of a brain, central pattern generator, and effector organs. An animal's walking patterns change depending on its walking velocities, even when it has been decerebrated, which indicates that the walking patterns may, in fact, be generated in the subregions of the neural systems of the central pattern generator and the effector organs. In order to explain the self-organization of the walking pattern in response to changing circumstances, our model incorporates the following ideas: (1) the brain sends only a few commands to the central pattern generator (CPG) which act as constraints to self-organize the walking patterns in the CPG; (2) the neural network of the CPG is composed of oscillating elements such as the KYS oscillator, which has been shown to simulate effectively the diversity of the neural activities; and (3) we have introduced a rule to coordinate leg movement, in which the excitatory and inhibitory interactions among the neurons act to optimize the efficiency of the energy transduction of the effector organs. We describe this mechanism as the least dissatisfaction for the greatest number of elements, which is a self-organization rule in the generation of walking patterns. By this rule, each leg tends to share the load as efficiently as possible under any circumstances. Using this self-organizing model, we discuss the control mechanism of walking patterns.     

Isolation,characterization, and transmission of human T-lymphotropic virus types I and II in culture

Highly sensitive coculture methods were developed both for isolation of human T-lymphotropic virus types I and II (HTLV-1 and HTLV-II) from infected individuals and for productive infection of lymphoid cells. Mitogen-activated peripheral blood mononuclear cells (PBMC) from 13 HTLV-I- and 20 HTLV-II-positive specimens were cocultured with an equal number of mitogen-activated PBMC from HTLV-seronegative individuals, and culture supernatants were tested for the presence of soluble p24^gag antigens at weekly intervals for 4 weeks. Eleven of 13 (85%) HTLV-I and 14 of 20 (70%) HTLV-II cultures were positive for p24 antigens. None of the 17 HTLV-seroindeterminate or six HTLV-seronegative specimens were positive for the presence of p24 antigen. The isolation rates for HTLV-I and HTLV-II by an alternative whole-blood lysis procedure were comparable to those obtained by standard PBMC cultures. Furthermore, cocultivation of PHA-stimulated PBMC from healthy donors with lethally irradiated HTLV-I- and HTLV-II-infected cell lines (SP and Mo-T, respectively) resulted in productive viral infection, as reflected by the appearance of p24^gag antigens concomitant with specific genomic amplification of HTLV proviral DNA after 3 weeks of cocultivation. Thus, the cocultivation technique provides a highly sensitive and specific procedure both for HTLV isolation and for infection of target cells.     

Deletion of the immunoglobulin kappa chain intron enhancer abolishes kappa chain gene rearrangement in cis but not lambda chain gene rearrangement in trans.

Immunoglobulins (Ig) secreted from a plasma cell contain either kappa or lambda light chains, but not both. This phenomenon is termed isotypic kappa-lambda exclusion. While kappa-producing cells have their lambda chain genes in germline configuration, in most lambda-producing cells the kappa chain genes are either non-productively rearranged or deleted. To investigate the molecular mechanism for isotypic kappa-lambda exclusion, in particular the role of the Ig kappa intron enhancer, we replaced this enhancer by a neomycin resistance (neoR) gene in embryonic stem (ES) cells. B cells heterozygous for the mutation undergo V kappa-J kappa recombination exclusively in the intact Ig kappa locus but not in the mutated Ig kappa locus. Homozygous mutant mice exhibited no rearrangements in their Ig kappa loci. However, splenic B cell numbers were only slightly reduced as compared with the wild-type, and all B cells expressed lambda chain bearing surface Ig. These findings demonstrate that rearrangement in the Ig kappa locus is not essential for lambda gene rearrangement. We also generated homozygous mutant mice in which the neoR gene was inserted at the 3' end of the Ig kappa intron enhancer. Unexpectedly, mere insertion of the neoR gene showed some suppressive effect on V kappa-J kappa recombination. However, the much more pronounced inhibition of V kappa-J kappa recombination by the replacement of the Ig kappa intron enhancer suggests that this enhancer is essential for V kappa-J kappa recombination.     

A cDNA Encoding the 57 kDa Subunit of a Cytokinin-Binding Protein Complex from Tobacco: the Subunit Has High Homology to S-Adenosyl-L-Homocysteine Hydrolase

130 kDa cytokinin-binding protein complex (CBP130) is a majorcytokinin binding entity in tobacco leaves (Nicotiana sylvestris)and contains two protein species of 57 and 36 kDa [CBP57 andCBP36, Mitsui and Sugiura (1993) Plant Cell Physiol. 34: 543].We have determined partial amino acid sequences of CBP57 andisolated cDNAs encoding the protein from a tobacco cDNA libraryusing an oligonucleotide probe. Sequence analysis revealed significanthomology between CBP57 and S-adenosyl-L-homocysteine hydrolasefrom other organisms, which catalyzes the reversible hydrolysisof S-adenosyl-L-homocysteine, a methyltransferase inhibitor.CBP57 contains an additional sequence of 41 amino acids whichis not present in animal and slime mold Sadenosyl-L-homocysteinehydrolases. This additional sequence is also found in the parsleyand Rhodobacter enzymes, suggesting that it is unique to photosyntheticorganisms. CBP57 is encoded by more than one nuclear genes intobacco. Northern and western blot analyses revealed that thelevel of expression of the genes is high in roots and low inleaves. They are also expressed in cultured tobacco cells. Wediscuss the possibility that at least some of the physiologicaleffects of cytokinin are mediated through the control of methylation/demethylationby regulating the intracellular concentration of S-adenosyl-L-homocysteinevia the hydrolase. (Received June 24, 1993; Accepted August 14, 1993)     

Stimulatory Effects of Protein Kinase C and Calmodulin Kinase II on N-Methyl-d-Aspartate Receptor/Channels in the Postsynaptic Density of Rat Brain

Abstract: To clarify the regulatory mechanism of the N -methyl- d -aspartate (NMDA) receptor/channel by several protein kinases, we examined the effects of purified type II of protein kinase C (PKC-II), endogenous Ca²⁺/calmodulin-dependent protein kinase II (CaMK-II), and purified cyclic AMP-dependent protein kinase on NMDA receptor/ channel activity in the postsynaptic density (PSD) of rat brain. Purified PKC-II and endogenous CaMK-II catalyzed the phosphorylation of 80–200-kDa proteins in the PSD and l -glutamate-(or NMDA)-induced increase of (+)-5-[³H]methyl-10, 11-dihydro-5 H -dibenzo[a, d]cyclohepten-5, 10-imine maleate ([³H]MK-801; open channel blocker for NMDA receptor/channel) binding activity was significantly enhanced. However, the pretreatment of PKC-II-and CaMK-II-catalyzed phosphorylation did not change the binding activity of l -[³H]glutamate, cis -4-[³H](phospho-nomethyl)piperidine-2-carboxylate ([³H]CGS-19755; competitive NMDA receptor antagonist), [³H]glycine, α-[³H]-amino-3-hydroxy-5-methyl-isoxazole-4-propionate, or [³H]-kainate in the PSD. Pretreatment with PKC-II-and CaMK-II-catalyzed phosphorylation enhanced l -glutamate-induced increase of [³H]MK-801 binding additionally, although purified cyclic AMP-dependent protein kinase did not change l -glutamate-induced [³H]MK-801 binding. From these results, it is suggested that PKC-II and/or CaMK-II appears to induce the phosphorylation of the channel domain of the NMDA receptor/channel in the PSD and then cause an enhancement of Ca²⁺ influx through the channel.     

Mechanism for the increased permeability in endothelial monolayers induced by elastase

The aim of this study was to investigate the mechanism for the increase in endothelial permeability induced by human neutrophil elastase (HNE). Pretreatment of bovine pulmonary artery endothelial cells (BPAEC) with HNE(0-30 mug/ml) for 1 h produced a concentration dependent increase in (125)I-albumin clearance. The effect was reversible and was not due to cytolysis. Pretreatment of BPAEC with sodium tungstate, which depletes xanthine oxidase, or with oxypurinol, did not prevent HNE induced increased permeability. Heparin, which neutralizes the cationic charge of HNE, also had no protective effect. Pretreatment with heat inactivated HNE, which still had positive charge sites, did not result in increased endothelial permeability. Also, ONO-5046, a novel specific inhibitor of HNE, did prevent increased permeability. These results suggest that elastase increases endothelial permeability mainly through its proteolytic effects.     

Theste13 + gene encoding a putative RNA helicase is essential for nitrogen starvation-induced G1 arrest and initiation of sexual development in the fission yeastSchizosaccharomyces pombe

When the fission yeastSchizosaccharomyces pombe is starved for nitrogen, the cells are arrested in the G1 phase, enter the G0 phase and initiate sexual development. Theste13 mutant, however, fails to undergo a G1 arrest when starved for nitrogen and since this mutant phenotype is not suppressed by a mutation in adenylyl cyclase (cyr1), it would appear thatste13 ⁺ either acts independently of the decrease in the cellular cAMP level induced by starvation for nitrogen, or functions downstream of this controlling event. We have used functional complementation to clone theste13 ⁺ gene from anS. pombe genomic library and show that its disruption is not lethal, indicating that, while the gene is required for sexual development, it is not essential for cell growth. Nucleotide sequencing predicts thatste13 ⁺ should encode a protein of 485 amino acids in which the consensus motifs of ATP-dependent RNA helicases of the DEAD box family are completely conserved. Point mutations introduced into these consensus motifs abolished theste13 ⁺ functions. The predicted Ste13 protein is 72% identical to theDrosophila melanogaster Me31B protein over a stretch of 391 amino acids. ME31B is a developmentally regulated gene that is expressed preferentially in the female germline and may be required for oogenesis. Expression of ME31B cDNA inS. pombe suppresses theste13 mutation. These two evolutionarily conserved genes encoding putative RNA helicases may play a pivotal role in sexual development.     

Protein polymorphism in two populations of the wild quail Coturnix coturnix japonica

To evaluate genetic variability in two populations of the wild quail Cofurnix coturnix japonica , proteins and enzymes were examined by starch gel electrophoresis.
Rare variants so far not observed in domestic quail were found in the following five enzymes; aspartate aminotransferase, acid phosphatase, pancreatic esterase, isocitrate dehydrogenase and lactate dehydrogenase. The proportion of polymorphic loci ( P _poly) and the expected average heterozygosity ( H ) in one of the two populations were estimated to be 0.484 (15/31) and 0.085, respectively. Those in another population were 0.433 (13/30) and 0.086, respectively. The genetic distance (Nei, 1975) between the two wild quail populations was D = 0.0074. D values of 0.0321 and 0.0189 were estimated between the laboratory quail population previously examined (Kimura et al., 1982) and each of these two wild populations.