Publisher Summary The classification of cell death can be based on morphological or biochemical criteria or on the circumstances of its occurrence. Currently, irreversible structural alteration provides the only unequivocal evidence of death; biochemical indicators of cell death that are universally applicable have to be precisely defined and studies of cell function or of reproductive capacity do not necessarily differentiate between death and dormant states from which recovery may be possible. It has also proved feasible to categorize most if not all dying cells into one or the other of two discrete and distinctive patterns of morphological change, which have, generally, been found to occur under disparate but individually characteristic circumstances. One of these patterns is the swelling proceeding to rupture of plasma and organelle membranes and dissolution of organized structure—termed “coagulative necrosis.” It results from injury by agents, such as toxins and ischemia, affects cells in groups rather than singly, and evokes exudative inflammation when it develops in vivo. The other morphological pattern is characterized by condensation of the cell with maintenance of organelle integrity and the formation of surface protuberances that separate as membrane-bounded globules; in tissues, these are phagocytosed and digested by resident cells, there being no associated inflammation.

Cell death : the significance of apoptosis

The protease responsible for the cleavage of poly(ADP-ribose) polymerase and necessary for apoptosis has been purified and characterized. This enzyme, named apopain, is composed of two subunits of relative molecular mass (M(r)) 17K and 12K that are derived from a common proenzyme identified as CPP32. This proenzyme is related to interleukin-1 beta-converting enzyme (ICE) and CED-3, the product of a gene required for programmed cell death in Caenorhabditis elegans. A potent peptide aldehyde inhibitor has been developed and shown to prevent apoptotic events in vitro, suggesting that apopain/CPP32 is important for the initiation of apoptotic cell death.

Identification and inhibition of the ICE/CED-3 protease necessary for mammalian apoptosis

In vitro disassembly of the nuclear lamina and M phase-specific phosphorylation of lamins by cdc2 kinase

Chicken hematopoietic cells transformed by seven strains of defective avian leukemia viruses display three distinct phenotypes of differentiation.

Publisher Summary This chapter highlights how the current understanding of the mechanisms and factors influencing virus adsorption can be used to interpret and control virus behavior in the environment. An understanding of factors controlling the interaction has already led to new and improved methods for the concentration of viruses from water, and their isolation from the environment. It is evident that not all viruses behave alike toward a solid under identical conditions. Under most natural conditions viruses with a low isoelectric point appear to be more poorly adsorbed to most solid surfaces. This must be taken into consideration when evaluating concentration or treatment systems which involve adsorption. This phenomenon is also important in determining the transport of viruses in the environment. Certain enteric viruses appear to adsorb less readily to soils and aquatic sediments than others. Thus their potential transport to groundwater may be greater and they may be less likely to settle in surface waters. To take into consideration these differences in virus behavior, it is perhaps best to use viruses with widely varying isoelectric points or marked differences in hydrophobicity to evaluate the extremes in virus interaction with a given surface which could occur.

Applied and Theoretical Aspects of Virus Adsorption to Surfaces

SummaryA simple and accurate colorimetric method is described for the routine determination of quantities of nitrogen in the range from 5 to 80 y. The method, which is a modification of the direct-nesslerization procedure of Koch and McMeekin, has been developed especially for the analysis of serological precipitates, but is adapted readily to the analysis of protein solutions.

Determination of small quantities of nitrogen in serological precipitates and other biological materials.

Sucrose-density-gradient centrifugation of RNA extracted from BAI strain A virus with phenol revealed 4 distinct components in continuous-flow spectrophotometer diagrams. Two of these, not previously described, sedimented at about 16 S and 26 S in association with the components of about 60 S and 5 S reported by others. The 5 S material, like cell transfer RNA, exhibited the amino-acid-acceptor activity already observed with whole virus RNA. Experiments indicated that the RNA's were not derived from external contaminating particulate or low molecular weight materials but that all were intrinsic to the agent. Comparative sedimentation studies showed that the 16 S and 26 S components were similar to cell ribosome RNA. Evidence indicated that the 16 S, 26 S, and a part of the 5 S materials were present in the cell cytoplasm and included in the virus during budding. The remainder of the 5 S appeared to be degradation products of the 60 S specific virus RNA component. The possible origin and biologic significance of the components are discussed, particularly with respect to mechanisms of virus formation.

https://cancerres.aacrjournals.org/content/canres/27/6_Part_1/1138.full.pdf

Ribonucleic Acid Components of BAI Strain A (Myeloblastosis) Avian Tumor Virus

Strain MC29 Avian Leukosis Virus. Myelocytoma, Endothelioma, and Renal Growths: Pathomorphological and Ultrastructural Aspects

From lots of 20 to 30 g of avian myeloblastosis virus RNA-dependent DNA polymerase was obtained in preparations of purity greater than 95% by using a two-step column chromatographic procedure employing DEAE (DE 52) and carboxymethylcellulose (CM 52.). Yields of RNA-dependent DNA polymerase varied from approximately 20,000 to 35,000 U/g of virus. Specific activity of the enzyme was about 35,000 to 60,000 U/mg of protein. Free of detectable RNase activity, the product exhibited a molecular weight of about 160,000, an isoelectric point of 6.5, and approximately 2 mol of fatty acid per mol of enzyme.

J. W. Beard

Papers

Determination of small quantities of nitrogen in serological precipitates and other biological materials.

Ribonucleic Acid Components of BAI Strain A (Myeloblastosis) Avian Tumor Virus

Strain MC29 Avian Leukosis Virus. Myelocytoma, Endothelioma, and Renal Growths: Pathomorphological and Ultrastructural Aspects

Reverse transcriptase from avian myeloblastosis virus.

SEDIMENTATION CHARACTERS AND pH STABILITY OF THE T2 BACTERIOPHAGE OF ESCHERICHIA COLI