The syntaxin Tlg1p mediates trafficking of chitin synthase III to polarized growth sites in yeast

Tlg1p and Tlg2p, members of the syntaxin family of SNAREs in yeast, have been implicated in both endocytosis and the retention of late Golgi markers. We have investigated the functions of these and the other endocytic syntaxins Pep12p and Vam3p. Remarkably, growth is possible in the absence of all four proteins. In the absence of the others, Pep12p and Tlg1p can each create endosomes accessible to the endocytic tracer dye FM4-64. However, although Pep12p is required for the ligand-induced internalization of the alpha factor receptor and its passage via Pep12p-containing membranes to the vacuole, Tlg1p is not. In contrast, Tlg1p is required for the efficient localization of the catalytic subunit of chitin synthase III (Chs3p) to the bud neck, a process that involves endocytosis and polarized delivery of Chs3p. In wild-type cells, internalized Chs3p cofractionates with Tlg1p and Tlg2p, and in a strain lacking the other endocytic syntaxins, either Tlg1p or Tlg2p is sufficient for correct localization of the enzyme. Pep12p is neither necessary nor sufficient for this process. We conclude that there are two endocytic routes in yeast that can operate independently and that Tlg1p is located at the junction of one of these with the polarized exocytic pathway.     

Inhibition of motor axon growth by T-cadherin substrata

As spinal motor neurons project to their hindlimb targets, their growth cones avoid particular regions along their pathway. T-cadherin is discretely distributed in the avoided caudal sclerotome and on extrasynaptic muscle surfaces (B. J. Fredette and B. Ranscht (1994) J. Neurosci. 14, 7331-7346), and therefore, the ability of T-cadherin to inhibit neurite growth was tested in vitro. T-cadherin inhibited neurite extension from select neuron populations both as a substratum, and as a soluble recombinant protein. Anti-T-cadherin antibodies neutralized the inhibition. Spinal motor neurons were inhibited only during the stages of axon growth across the sclerotome and muscle innervation. Inhibitory responses corresponded to neuronal T-cadherin expression, suggesting a homophilic binding mechanism. These results suggest that T-cadherin is a negative guidance cue for motor axon projections.     

Seminar planning guidelines. As I see it

Small local chapter groups can present quality cost effective regional seminars. Key components are dedication of members, teamwork, and a sense of direction. The following guidelines and information can provide a framework for planning and coordinating a seminar.     

Concentration-dependent changes in the latency and amplitude of somatosensory-evoked potentials by desflurane, isoflurane and sevoflurane

Despite improvement in early diagnosis, surgical techniques, and general patient care, most deaths of cancer patients result from metastases. Recent studies have revealed that cytokines produced by cancer cells or by stromal cells play an important role into development the cancer metastasis. The formation of a cancer metastasis involves several major steps: 1) extensive vascularization; 2) local invasion; 3) adherence either to capillary endothelial cells or to subendothelial basement membrane; 4) extravasation; and 5) proliferation. In colon cancer, several cytokines such as growth factors, inflammatory cytokines, and angiogenic factors have been confirmed to be involved in each step of metastasis. This paper summarizes the involvement of cytokines in the development of invasion and metastasis in colon cancer.     

A new class of tobacco chitinases homologous to bacterial exo-chitinases displays antifungal activity

A novel chitinase gene of tobacco was isolated and characterized by DNA sequence analysis of a genomic clone and a cDNA clone. Comparative sequence analysis of both clones showed an identity of 94%. The proteins encoded by these sequences do not correspond to any of the previously characterized plant chitinases of classes I-IV and are designated as class V chitinases. Comparison of the chitinase class V peptide sequence with sequences in the Swiss Protein databank revealed significant sequence similarity with bacterial exo-chitinases from Bacillus circulans, Serratia marcescens and Streptomyces plicatus. It was demonstrated that class V chitinase gene expression is induced after treatment of tobacco with different forms of stress, like TMV-infection, ethylene treatment, wounding or ultraviolet irradiation. Two related chitinase class V proteins of 41 and 43 kDa were purified from Samsun NN tobacco leaves inoculated with tobacco mosaic virus. The proteins were purified by Chelating Superose chromatography and gel filtration. In vitro assays demonstrated that class V chitinases have endo-chitinase activity and exhibit antifungal activity toward Trichoderma viride and Alternaria radicina. In addition, it was shown that class V chitinase acts synergistically with tobacco class I beta-1,3-glucanase against Fusarium solani germlings.     

A closed-loop cross-correlation method for detecting model mismatch in MIMO model-based controllers

Correlation between a dithering signal and the prediction error has been used for detecting model mismatch in univariate model based control systems. This paper extends that approach to MIMO control systems. A closed-loop cross-correlation method is presented to detect which specific input-output pairings of a model-based controller are mismatched. This method may be used in screening the complete set of models and in selecting candidate models for re-identification. The method first finds the rows and columns of the transfer function matrix that contain mismatch, and then the candidates are found by the intersection of the said rows and columns. Placing the system under partial control, whereby one or more of the manipulated variables are held constant, can be used to further reduce the set of candidate models.     

Concerted evolution at the population level: pupfish HindIII satellite DNA sequences

The canonical monomers (approximately 170 bp) of an abundant (1.9 x 10(6) copies per diploid genome) satellite DNA sequence family in the genome of Cyprinodon variegatus, a "pupfish" that ranges along the Atlantic coast from Cape Cod to central Mexico, are divergent in base sequence in 10 of 12 samples collected from natural populations. The divergence involves substitutions, deletions, and insertions, is marked in scope (mean pairwise sequence similarity = 61.6%; range = 35-95.9%), is largely confined to the 3' half of the monomer, and is not correlated with the distance among collecting sites. Repetitive cloning and direct genomic sequencing experiments failed to detect intrapopulation and intraindividual variation, suggesting high levels of sequence homogeneity within populations. The satellite sequence has therefore undergone "concerted evolution," at the level of the local population. Concerted evolution has previously almost always been discussed in terms of the divergence of species or higher taxa; its intraspecific occurrence apparently has not been reported previously. The generality of the observation is difficult to evaluate, for although satellite DNAs from a large number of organisms have been studied in detail, there appear to be little or no other data on their sequence variation in natural populations. The relationship (if any) between concerted, population level, satellite DNA divergence and the extent of gene flow/genetic isolation among conspecific natural populations remains to be established.