Morphological variations of isolated liver mitochondria during spontaneous deterioration

Summary The effects of mitochondrial concentration, incubation temperature and composition of suspension medium on spontaneous swelling of rat liver mitochondria were investigated. The swelling was measured simultaneously by four different methods — optical density changes at 520 m, mitochondrial diameter measurements and differential counts made on phase contrast micrographs of fixed suspensions, and electron microscopical examination of the fine structural alterations.The findings indicate that, in isosmotic sucrose and KCl media, both mitochondrial concentration and incubation temperature influence the course of spontaneous swelling. It was also found that the ratio of Tris (hydroxymethyl) aminomethane to mitochondria concentration profoundly affects the morphological transformations.Correlation of the results obtained with the four methods shows that measurement of optical density changes alone is insufficient for full assessment of mitochondrial swelling and that this method therefore is best used in conjunction with electron microscopical studies.The authors wish to thank Mr. George O'Shea for valuable technical assistance.     

A Service for Human Chromosome Studies in Saskatchewan

A service has been developed in Saskatchewan to make available the results of studies of human chromosomes, the material being forwarded to the laboratory by local transport facilities. During the first year of this project chromosome studies were requested for five doubtful cases of trisomy-21 (two were found to be normal) and for 20 definite cases of trisomy-21 in young patients (two had translocations but the parents of both these children had normal karyotypes). Eleven confirmed cases of Turner''s syndrome, two of Klinefelter''s syndrome, and one each of the D and E syndromes were also studied. The largest group for which studies were requested comprised 36 patients with mental retardation; only two abnormal karyotypes were encountered in this group.     

BIOSYNTHESIS OF COLLAGEN AND NON-COLLAGEN PROTEIN DURING DEVELOPMENT OF THE CHICK CORNEA

The relationship between the rates of increase of corneal protein fractions and incorporation of labeled precursors has been examined during embryonic and early posthatching development of the chick corneal stroma. Non-collagen protein increased gradually from 9 through 20 days of incubation. Collagen accumulated approximately logarithmically through the 19th day, the most rapid rate occurring between 13 and 20 days of incubation. The rates at which labeled amino acids are incorporated into collagen in vivo and in vitro undergo marked changes during the last week of embryonic development, corresponding closely to the rate of collagen accumulation in vivo; whereas incorporation into non-collagen protein changes much less markedly. Changes in the rate of incorporation of precursors into collagen are not due to changes in the rate of conversion of collagen from the soluble to insoluble form, or to changes in the endogenous amino acid pool size. Chick embryo corneal stroma collagen turns over very slowly, if at all. Non-collagen protein turns over more rapidly. An increase in cell number, as indicated by DNA content, does not account for the increased rate of collagen synthesis between the 9th and 16th day of incubation. It is concluded that the observed changes in collagen synthesis reflect changing activities in the individual cornea fibroblasts. These activities are comparable in the intact tissue in vivo and in isolated corneas in vitro.     

LOCALIZATION OF A BASIC PROTEIN IN THE MYELIN OF VARIOUS SPECIES WITH THE AID OF FLUORESCENCE AND ELECTRON MICROSCOPY

In this study, alanine was shown to be the N-terminal amino acid of a basic protein of low molecular weight that was isolated from either human or guinea pig brain. Antibodies prepared against the guinea pig protein were labeled with either fluorescein or ferritin. Studies with the labeled antibodies showed that an immunohistochemically similar protein is found in the myelin sheaths of central and peripheral nervous tissues of chicken and frog and a variety of mammalian species. Loss of integrity of the myelin during processing was shown to enhance markedly the antigen-antibody reaction.