Search

Changes occurring in membrane saccharides during the in vivo aging of normal human erythrocytes have been evaluated after the fractionation of the red cells into five age groups by density gradient centrifugation. The glycoconjugate fractions studied included sialoglycoproteins, macroglycolipids, low-molecular-weight glycolipids, and Band 3 glycoproteins. All of the carbohydrate constituents of the membrane were found to decrease relative to the total ghost protein as a function of cell age, with the most substantial losses occurring in the macroglycolipids (50%) and Band 3 glycoprotein (30%); the smallest changes were observed in the sialoglycoproteins (13%). No preferential loss of sialic acid or other peripheral sugars was found, making unlikely the importance of glycosidase action in the removal of sugars from the membrane. It is suggested that the changes observed in the composition of the ghosts during aging are best explained by a loss of membrane segments enriched in glycoproteins and glycolipids and deficient in internally located molecules such as spectrin. Analyses were also performed on the glycoconjugate fractions from diabetic erythrocytes separated according to cell age. These erythrocytes, which had glycosylated hemoglobin values twice those of normals, had somewhat smaller amounts of membrane-bound carbohydrate. The difference between diabetic and normal erythrocytes was greatest when young cells were examined (diabetic to normal = 0.93), suggesting that the known increased turnover of red cells in diabetes leads to an early loss of membrane constituents.

Energy deprivation, induced in thyroid slices by incubation with an uncoupler of oxidative phosphorylation (carbonyl cyanide m-chlorophenylhydrazone) or inhibitors of respiration (N2 or antimycin A), led to a disturbance in oligosaccharide-lipid metabolism which was characterized by a pronounced depletion of the glucosylated (Glc3Man9GlcNAc2) dolichyl pyrophosphoryl saccharide with an attendant accumulation of the Man9GlcNAc2 and, to a lesser extent, the Man8GlcNAc2 lipid-linked species. A concomitant decrease in the N-glycosylation of proteins was furthermore observed. The distribution of lipid-derived oligosaccharides observed by thin layer chromatographic separation was similar whether radiolabeling was achieved by a metabolic ([14C]glucose or [2-3H]mannose incubation) or chemical ([3H]NaBH4) procedure. The latter method proved useful for measuring the levels of individual oligosaccharide-lipids in unincubated tissue, and in this way it was found that unless thyroid was rapidly frozen or immediately immersed in oxygenated medium a marked decrease of glucose-containing oligosaccharide-lipids occurred which could, however, be reversed by a short incubation. The addition of glucose to the slice incubations did not prevent the Man8-9GlcNAc2 accumulation brought about by the inhibitors of energy production, nor did it alter the oligosaccharide-lipid pattern of uninhibited slices. The effect of the inhibitors on metabolically labeled liver slices was similar to that observed in thyroid. The size of the total chloroform/methanol/water (10:10:3)-extractable oligosaccharide-lipid pool (Glc3-Man9GlcNAc2 to Man5GlcNAc2) of thyroid remained quite constant (about 2 nmol/g) regardless of the energy state, and no substantial change in the level of smaller oligosaccharide-lipids, primarily represented by Man2GlcNAc2 (0.5 nmol/g) was evident. Moreover, no change in the total pool sizes was observed in puromycin-treated slices. The possible mechanisms by which energy deprivation leads to an accumulation of the glucose-free oligosaccharide-lipids are evaluated. While it is likely that a selective impairment of glucosylation of newly formed molecules occurs, it is also possible that an imbalance occurs in a postulated glucosyltransferase-glucosidase shuttle with a trapping of the oligosaccharide-lipid in its unglucosylated form.

The task of selecting the electroacoustic characteristics of hearing aids for young hearing-impaired children continues to challenge many clinical audiologists. The rationale for a theoretically based approach to this problem is presented. Additionally, issues related to the choice of an idealized speech spectrum for a theoretical selection model are considered in relation to the acoustic environment and auditory needs of young hearing-impaired children. Finally, the preliminary version of a computer assisted speech spectrum approach, which facilitates the initial selection of frequency/gain and frequency/SSPL characteristics is presented.

In contrast to the thoroughness with which the respiratory enzymes of such tissues as heart muscle and liver have been studied, information concerning these enzymes in the adrenal gland is scant. Such information as is available suggests that an unusual pattern for the cytochromes exists in this tissue. Cohen and Elvehjem (2) commented on the "peculiar cytochrome spectrum"of the adrenal medulla of the cow. They concluded that a very strong cytochrome c component was present, and that cytochrome a and 6 were absent. Huszák (3) noted that the adrenal cortex possessed a nearly normal cytochrome pattern. In the medulla he could observe no cytochrome a or c bands, but reported a strong band in the region of 559 rnp which he attributed to cytochrome 5. Since Huszák could demonstrate no cytochrome oxidase activity in the medulla, he felt that oxidation of substrates proceeded by way of a peroxidative mechanism. Tsou (4), on the other hand, was able to demonstrate cytochrome oxidase activity in the medulla, but little if any cytochrome c. He observed the presence of a strong band at 561 millimicron which was referred to as cytochrome b. In view of these divergent conclusions and in the light of newer methods and knowledge, it seemed worth-while to reinvestigate some of the oxidative pathways in the adrenal gland. The present study deals with the adrenal medulla, and an accompanying paper deals with the cortex (5). It will be shown here that the adrenal medulla contains the regular mitochondrial cytochrome system. In addition, this tissue contains a hemochromogen which is apparently microsomal in origin and is abundantly present in the epinephrine-containing granules. The presence in the medulla of the enzymes succinate dehydrogenase,reduced di- and triphosphopyridine nucleotide-cytochrome c reductase,and transhydrogenase is also demonstrated.

On the basis of his observations with the hand spectroscope, Huszák (1) stated that the adrenal cortex contained cytochromes c, b, and a + a3, as well as an unknown cytochrome absorbing between cytochromes b and c. The present study has attempted to define both the cytochromes present in the beef adrenal cortex, as well as their distribution among the cell fractions. It confirms the presence of cytochromes c, b, and a + a3, and indicates the likelihood that cytochrome cl is the unknown cytochrome mentioned by Huszák. All of these cytochromes are present in the cortical mitochondria, and it has not been possible to demonstrate the presence of a microsomal cytochrome in the cortex such as is present in the microsomes of liver (2) or of the adrenal medulla (3). A survey has also been made of several of the respiratory enzymes of the cortex. Similar to what has already been reported for the adrenal medulla (3), it showed that the enzymes responsible for the transfer of electrons to O2 from reduced triphosphopyridine nucleotide are of much lower activity than those responsible for the production of this reduced coenzyme. Such a relationship is fitting in view of the synthetic requirements for reduced triphosphopyridine nucleotide in the various hydroxylation steps of steroid biosynthesis (4, 5).

A technique is described for the resolution and quantitative determination of the nitrogenous constituents of dog tissue lipids. Results of representative analyses are presented for seven different tissues. All but a few per cent of the total lipid nitrogen has been specifically accounted for as choline, ethanolamine, serine, other amino acids, ammonia, sphingosine, and hexosamine. Serine-containing lipids comprise a maximum of 2.6% to 7.7% of total lipid nitrogen of the tissues studied. Despite extensive purification of the lipid extracts, other amino acids and peptides are present in quantities comparable to serine. The ammonia content of the lipid hydrolyzates ranges from 4.3% to 5.9% of lipid nitrogen. From 1.0% to 9.4% of lipid nitrogen becomes water soluble after hydrolysis, and is neither choline, ammonia, nor primary amine. This is considered to be substituted amine, although no important fraction of this material has been identified.