THE PYRUVATE METABOLISM OF SEA URCHIN EGGS DURING THE PROCESS OF CELL DIVISION

The eggs of Arbacia and starfish contained about 70 and 25 micrograms of pyruvate per gm. of dry cells respectively. Arbacia eggs utilized added pyruvate, although the O₂ uptake did not increase. On fertilization the utilization of pyruvate increased sevenfold. This pyruvate seems to be metabolized, as in other cells, with diphosphothiamine as coenzyme. The diphosphothiamine content of fertilized and non-fertilized eggs was about 16 micrograms; that of sperm, 30 micrograms. Penetration of sperm into the egg and fertilization with cell division to the pluteus stage did not bring forth appearance of succino-dehydrogenase. The possible mechanism of fertilization and cell division is discussed.     

Increased surfactant protein A content in human alveolar macrophages in hypersensitivity pneumonitis.

Surfactant protein A (SP-A) appears to have an important function in the assembly and maintenance of the alveolar surfactant monolayer. SP-A has also been implicated in modulating the activity of immunoactive cells, such as increasing the bactericidal capacity of alveolar macrophages. In this immunocytochemical study the SP-A content of alveolar macrophages from seven patients with hypersensitivity pneumonitis was compared with the results obtained from six healthy controls. A polyclonal rabbit antibody against human SP-A was used for detection of SP-A in the cytoplasm of alveolar macrophages, applying the immunoperoxidase adhesive slide assay. In hypersensitivity pneumonitis a significant increase in the percentage of SP-A+ alveolar macrophages was observed as compared with the percentage in healthy controls. The intensity of the staining reaction was also increased in the alveolar macrophages of hypersensitivity pneumonitis. We conclude that the observed abnormalities in SP-A content in alveolar macrophages may play a role in the pathogenesis of hypersensitivity pneumonitis.     

Effects of brief starvation on brain protease activity

Changes in the activity of proteases (cathepsin D and calpains) caused by 48-h food withdrawal were studied in the brain, liver, kidney, spleen, and heart of 3-, 12-, and 24-month-old Fischer rats. Cathepsin D activity was similar in brain, liver, and heart of control animals; in kidney it was 5-fold higher and in spleen about 10-fold higher. With age, activity increased in all organs tested except spleen. Brief starvation caused no change of cathepsin D activity in brain, but caused an increase in liver and a decrease in spleen. Neutral proteolytic activity in control was highest in the pons-medulla-cerebellum fraction of brain, and activity in liver and heart was below that in brain. Activity increased with age in brain and decreased in other organs. Brief starvation in young animals caused an increase in activity in brain, and a decrease in liver and spleen. Isolated calpain II activity was high in control brain. It increased with age in the cerebrum. Brief starvation resulted in a decrease in the brain. The results indicate that the protease content of the brain is altered with age and in malnutrition, with changes not being the same for all proteases, and changes in brain being different from those in other organs.Special issue dedicated to Dr. Louis Sokoloff.     

Use of glutaraldehyde-fixed Escherichia coli cells as a convenient support for radioimmune assays.

Escherichia coli were activated by incubation with 1% glutaraldehyde, and the activated bacteria were then conjugated by incubation with IgG. About 66,000 molecules of IgG were bound per cell. The Escherichia coli-antibody conjugates were then used in competitive radioimmune assays. When a specific IgG fraction was used to prepare the conjugate, each cell bound about 16,000 molecules of antigen. With an antigen which had a specific activity of about 300 cpm/ng (or about 4.8 × 10⁴ cpm/pmol), the assay was linear over a range of 40–300 ng/ml (0.3–2.0 pmol/ml). About 100 samples were assayed per day.