The action of ribonuclease on neoplastic growth. III. Studies by interference microscopy

Sialic acid-binding lectin (leczyme) induces caspase-dependent apoptosis-mediated mitochondrial perturbation in Jurkat cells

Sialic acid binding lectin (SBL) isolated from Rana catesbeiana oocytes is a multifunctional protein which has lectin activity, ribonuclease activity and antitumor activity. However, the mechanism of antitumor effects of SBL is unclear to date and the validity for human leukemia cells has not been fully studied. We report here that SBL shows cytotoxicity for some human leukemia cell lines including multidrug-resistant (MDR) cells. The precise mechanisms of SBL-induced apoptotic signals were analyzed by combinational usage of specific caspase inhibitors and the mitochondrial membrane depolarization detector JC-1. It was demonstrated that SBL causes mitochondrial perturbation and the apoptotic signal is amplified by caspases and cell death is executed in a caspase-dependent manner. The efficacy of this combinational usage was shown for the first time, to distinguish the apoptotic pathway in detail. SBL selectively kills tumor cells, is able to exhibit cytotoxicity regardless of P-glycoprotein expression and has potential as an alternative to conventional DNA-damaging anticancer drugs.

Stain-free quantification of chromosomes in live cells using regularized tomographic phase microscopy

Refractive index imaging is a label-free technique that enables long-term monitoring of the internal structures and molecular composition in living cells with minimal perturbation. Existing tomographic methods for the refractive index imaging lack 3-D resolution and result in artifacts that prevent accurate refractive index quantification. To overcome these limitations without compromising the capability to observe a sample in its most native condition, we have developed a regularized tomographic phase microscope (RTPM) enabling accurate refractive index imaging of organelles inside intact cells. With the enhanced accuracy, we quantify the mass of chromosomes in intact living cells, and differentiate two human colon cancer lines, HT-29 and T84 cells, solely based on the non-aqueous (dry) mass of chromosomes. In addition, we demonstrate chromosomal imaging using a dual-wavelength RTPM, which shows its potential to determine the molecular composition of cellular organelles in live cells.

[Fibre formation by cellular systems]

In order to study possible mechanisms of fibrogenesis within living cells, experiments have been carried out using solutions of nucleo-proteins to determine the conditions which lead to the building up of spontaneously ordered structures. Nucleo-protein solutions which separate into a two-phase system produce orientated fibres by a process of aggregation. These fibres are birefringent and show visual dichroism after staining with vital stains. A method of measuring concentrations by interference microscopy in the living cell has shown that the concentration of high molecular-weight material within the nucleus would be expected to maintain ordered structures of the type observed in the solutions of isolated nucleoprotein. It is shown that the formation of fibres takes place by a similar process in the cytoplasm during spermatogenesis. These fibres also undergo a process of spiralization which is analogous to the behaviour of chromosomes.