Procedures utilizing Chelex 100 chelating resin have been developed for extracting DNA from forensic-type samples for use with the PCR. The procedures are simple, rapid, involve no organic solvents and do not require multiple tube transfers for most types of samples. The extraction of DNA from semen and very small bloodstains using Chelex 100 is as efficient or more efficient than using proteinase K and phenol-chloroform extraction. DNA extracted from bloodstains seems less prone to contain PCR inhibitors when prepared by this method. The Chelex method has been used with amplification and typing at the HLA DQ alpha locus to obtain the DQ alpha genotypes of many different types of samples, including whole blood, bloodstains, seminal stains, buccal swabs, hair and post-coital samples. The results of a concordance study are presented in which the DQ alpha genotypes of 84 samples prepared using Chelex or using conventional phenol-chloroform extraction are compared. The genotypes obtained using the two different extraction methods were identical for all samples tested.

Chelex 100 as a Medium for Simple Extraction of DNA for PCR-Based Typing from Forensic Material

A simple, rapid, and sensitive DNA assay procedure.

It has been suggested that cancer represents an alteration in DNA, heritable by progeny cells, that leads to abnormally regulated expression of normal cellular genes; DNA alterations such as mutations, rearrangements and changes in methylation have been proposed to have such a role. Because of increasing evidence that DNA methylation is important in gene expression (for review see refs 7, 9-11), several investigators have studied DNA methylation in animal tumours, transformed cells and leukaemia cells in culture. The results of these studies have varied; depending on the techniques and systems used, an increase, decrease, or no change in the degree of methylation has been reported. To our knowledge, however, primary human tumour tissues have not been used in such studies. We have now examined DNA methylation in human cancer with three considerations in mind: (1) the methylation pattern of specific genes, rather than total levels of methylation, was determined; (2) human cancers and adjacent analogous normal tissues, unconditioned by culture media, were analysed; and (3) the cancers were taken from patients who had received neither radiation nor chemotherapy. In four of five patients studied, representing two histological types of cancer, substantial hypomethylation was found in genes of cancer cells compared with their normal counterparts. This hypomethylation was progressive in a metastasis from one of the patients.

Hypomethylation distinguishes genes of some human cancers from their normal counterparts.

Extraction of extracellular polymers from activated sludge using a cation exchange resin

A tool changer is disclosed for automatically removing a working tool after having been used from the spindle of a machine tool such as a vertical milling machine, transferring the used working tool to a rack which stores a plurality of working tools, picking up from the rack another working tool for the next machining operation, transferring such new working tool to the spindle, and operatively mounting such new working tool on the spindle.

Temperature and Organism Size—A Biological Law for Ectotherms?

Assay for nanogram quantities of DNA in cellular homogenates

Culturing of Amoeba proteus on Tetrahymena.

Synchronization of cell division in Astasia longa on a chemically defined medium.

Light-induced division synchrony in Euglena gracilis var. Bacillaris

THE physiological reality and profound ecological significance of the phenomenon of regulation of rate functions towards a constant, in response to maintained temperature differences, within the species in poikilotherms, has been widely recognized in recent times. Much attention has been directed in this connexion to a study of populations spatially separated by a wide range of latitude1–3 or temporally separated by the annual cycle of seasons4,5. Indications of the existence of similar intraspecific differences between high and low members of populations of intertidal invertebrates are reported in the present communication.

Thomas W. James

Papers

Assay for nanogram quantities of DNA in cellular homogenates

Culturing of Amoeba proteus on Tetrahymena.

Synchronization of cell division in Astasia longa on a chemically defined medium.

Light-induced division synchrony in Euglena gracilis var. Bacillaris

Rate of Activity as a Function of Intertidal Height within Populations of some Littoral Molluscs