Lysis

About: Lysis is a research topic. Over the lifetime, 6072 publications have been published within this topic receiving 216978 citations.

Microcinematographic and electron microscopic analysis of target cell lysis induced by cytotoxic T lymphocytes.

Abstract: A study was carried out to determine the sequence of events of T-cell mediated target cell lysis in microcinematography and electron microscopy. Highly efficient cytotoxic T lymphocytes (CTL) were generated in vivo and in vitro using preimmunized spleen cells and purification procedures. Such CTL were highly specific. This specificity correlated well with the number of adhesions formed between CTL and targets and this criterion was used to study killer-target cell interaction. Microcinematography showed that target cell lysis at the single cell level, despite time variations, could be clearly separated into three phases: (a) a recognition phase, visible by random crawling of CTL over the target cell surface until firm contact was established; (b) a post-recognition phase, during which firm contact between CTL and target was maintained without gross modification of either cell; (c) a phase of target cell disintegration, mainly characterized by vigorous blebbing of the cell membrane resulting in a motionless carcass of the target cell but not in its total dissolution. Only later this carcass decayed and formed a necrotic ghost. Electron microscopic observations were put into sequence according to microcinematography. Post-recognition phase was characterized by a tight apposition of the membranes of CTL and target cell. No gap junctions could be observed. During target cell disintegration, profound cytoplasmic and nuclear changes occurred simultaneous with surface blebbing. Most noticeable were extensive internal vacuolization, mitochondrial swelling, nuclear pycnosis and dissolution of the nucleolus. These observations suggested that target cell lysis does not start with a surface phenomenon similar to complement lysis, but a process involving practically the whole cell simultaneously. It is conceivable, therefore, that the signal from the CTL is transmitted across the target cell, and that the switch to sudden cell death is manipulated deep inside the cell.

Lysis of Escherichia coli by induction of cloned ϕX174 genes

Abstract: The largest of the fragments produced by AluI digestion of ϕX174 RFI DNA comprises genes E and J as well as parts of genes D and F. This DNA fragment (1007 bp) was cloned into the lac z′ gene of plasmid pUR222. In the recombinant plasmid pUH12, transcription of the ϕX174 genes is controlled by the lac p-o region. Induction of the cloned genes by addition of the lac inducer, IPTG, resulted in lysis of the bacteria. Cloning of the corresponding AluI-fragment from ϕX174am3 DNA, carrying an amber mutation in gene E, showed that the expression of this gene alone is sufficient to trigger cell lysis. The time interval between the addition of IPTG and the onset of lysis depended on the concentration of the inducer, however, the rate of lysis was similar at all IPTG concentrations used.

ATP in soil: A new extractant and extraction procedure

Abstract: An extraction mixture comprised of 0.67 m H3PO4, 2 m urea, 20% DMSO, 1.8 mg of adenosine, 20 mM EDTA, and 1% Zwittergent 3,10 and a procedure to extract ATP from soil have been developed. The reagents and method were tested on six different Oklahoma soils and yielded a recovery of 99% of the ATP from added Escherichia coli cells. The extraction mixture was designed to minimize interference from soil-derived materials. The phosphoric acid provides acid to extract ATP and to inactivate proteins, and phosphate to saturate phosphate-binding sites. It also complexes or precipitates metal ions. The EDTA chelates metal ions, prevents inhibition of luciferase, and aids lysis of bacterial cells. The adenosine serves to saturate ATP binding-sites. Urea denatures proteins and prevents hydrogen bonding of the released ATP. DMSO, the Polytron treatment, and Zwittergent 3,10 remove cells from surfaces and lyse them. An internal standard of E. coli cells is used to determine efficiency of extraction and assay. When compared with the 12 best methods suggested by previous studies, the newly-formulated extractant and procedure yielded the greatest amount of ATP from soil.

Human adenovirus type 5 induces cell lysis through autophagy and

Abstract: ABSTRACT Oncolytic adenoviruses, such as Delta-24-RGD, are promising therapies for patients with brain tumor. Clinical trials have shown that the potency of these cancer-selective adenoviruses should be increased to optimize therapeutic efficacy. One potential strategy is to increase the efficiency of adenovirus-induced cell lysis, a mechanism that has not been clearly described. In this study, for the first time, we report that autophagy plays a role in adenovirus-induced cell lysis. At the late stage after adenovirus infection, numerous autophagic vacuoles accompany the disruption of cellular structure, leading to cell lysis. The virus induces a complete autophagic process from autophagosome initiation to its turnover through fusion with the lysosome although the formation of the autophagosome is sufficient for virally induced cell lysis. Importantly, downmodulation of autophagy genes (ATG5 or ATG10) rescues the infected cells from being lysed by the virus. Moreover, autophagy triggers caspase activity via the extrinsic FADD/caspase 8 pathway, which also contributes to adenovirus-mediated cell lysis. Therefore, our study implicates autophagy and caspase activation as part of the mechanism for cell lysis induced by adenovirus and suggests that manipulation of the process is a potential strategy to optimize clinical efficacy of oncolytic adenoviruses.

Susceptibility of HIV-1 plasma virus to complement-mediated lysis. Evidence for a role in clearance of virus in vivo.

Abstract: This study was undertaken to directly assess the susceptibility of HIV-1 plasma virus to C-mediated lysis. Plasma from HIV-infected individuals was collected and ultracentrifuged over 20% sucrose to isolate virions from plasma components including anticoagulants, which inhibit C activity. Treatment with C alone in the absence of exogenously added Ab caused lysis of virus from all patients (n = 18) (range 14 to 86%). This lysis occurred via the classical C pathway and was not due to cross-reactive Abs in the C source. Protein A bound a fraction of isolated plasma virus and this binding was blocked by purified human Ig suggesting that anti-HIV Abs bound to plasma virus could be responsible for inducing C activation. A portion of virus bound to CR2 on cells in the absence of exogenously added C indicating that virus activated C in vivo. C levels from six of six patients were determined to be sufficient to lead to lysis of virus in vivo. Since plasma virus appeared more sensitive to C than primary isolates, isolated virus was evaluated for the presence of C control proteins. While primary isolate virions contained CD46, CD55, and CD59, only CD59 was detected on plasma virus. The results of this study strongly suggest that C is activated by a portion of plasma virus in vivo due to the binding of Ab. The resultant opsonization plus subsequent lysis may be important routes of clearance and destruction of plasma virus in infected persons.