Structure-function analysis of tissue-type plasminogen activator by linker-insertion, point and deletion mutagenesis

We undertook a structure--function analysis of human tissue plasminogen activator (tPA) using linker-scanning and deletion mutagenesis. Synthetic oligonucleotide linkers were introduced into the tPA cDNA at pre-existing restriction enzyme sites. This generated a series of tPA variants which contained small primary sequence alterations consisting of point mutations, deletions or insertions. The majority of the linker-insertion variants demonstrate a significant reduction in amidolytic and fibrinolytic activity in comparison to wild-type tPA. The exceptions are the variants with linker-inserts placed at the BglII(115) and StyI(277) sites of the tPA cDNA (4SLEG5 and 57LEA58 respectively), which encode insertions at the boundaries of the finger domain. The variants with linker-inserts in the light chain (protease domain) of tPA are the lowest in enzymatic activity. Particularly sensitive to mutation are highly conserved amino acids. Heavy chain deletion variants were constructed from point mutants at the domain boundaries of tPA. Deletion of the kringle domains lowers the fibrinolytic activity to a greater extent than deletion of the finger or growth factor domains. We conclude that alterations in any domain of the tPA molecule, and particularly in the highly conserved residues within these domains, can affect fibrinolytic activity.     

Perivascular regions of the rat neural lobe

Summary Neural lobes and portions of occipital cortex from rats were examined electron microscopically following fixation in 4% tannic acid in 2.5% glutaraldehyde. The procedure allowed a clear demonstration of the perivascular space and intercellular spaces in both tissues. The perivascular spaces in the neurosecretory tissue was far more extensive than in the neural tissue and the role of this region in relation to the process of neurosecretion is discussed.     

Field evaluation of a nuclear polyhedrosis virus of Neodiprion taedae linearis

Aerial applications of a nuclear polyhedrosis virus were evaluated for control of Neodiprion taedae linearis. Based on colony size, cocoon counts, and defoliation, rates of 5 × 10⁷, 1 × 10⁷, and 5 × 10⁶ PIB/ml of spray concentration were most effective in reducing sawfly populations. Sex ratio of cocoons recovered from the treated plots indicated a greater percentage of females succumbed to the virus than did males.     

A new procedure for the ultrastructural localization of acid phosphatases

Summary The synthesis and properties of two new lead-containing diazonium chlorides are described. The use of these reagents for the electron microscopical localization of acid phosphatases in animal cells has been assessed.