DEVELOPMENT OF AN EXPRESSION WHICH RELATES THE EXCITABLE STATE OF THE BRAIN TO THE LEVEL OF GAD ACTIVITY AND GABA CONTENT, WITH PARTICULAR REFERENCE TO THE ACTION OF HYDRAZINE AND ITS DERIVATIVES

—The effect of hydrazine, unsymmetrical dimethylhydrazine (UDMH) and symmetrical dimethyl hydrazine (SDMH) on GABA metabolism in mouse brain was studied. All three compounds inhibited the activity of glutamic acid decarboxylase, although to different extents. In contrast, very different effects were observed on GABA levels; UDMH causing a decrease, SDMH no effect, and hydrazine a marked increase in the content of the amino acid. These results together with previous data obtained by the authors were used to develop an equation which related the excitable state of the brain to changes in overall GABA metabolism. The major factor affecting brain excitability was a change in the activity of glutamic acid decarboxylase, with a change in the concentration of GABA playing a more minor role. It was suggested that the values obtained from the equation might reflect the content of GABA in a critical subcellular location such as the synaptic cleft.     

METHODS OF STUDYING THE RESPIRATORY EXCHANGE IN SMALL AQUATIC ORGANISMS,WITH PARTICULAR REFERENCE TO THE USE OF FLAGELLATES AS AN INDICATOR FOR OXYGEN CONSUMPTION

1. Flagellates are positively chemotactic to a certain concentration of dissolved oxygen which is lower than that in water saturated with oxygen under atmospheric partial pressure. Consequently, when a small aquatic animal is held motionless between cover-slip and slide in a suspension of flagellates in water saturated with oxygen, the flagellates are attracted to those parts of the animal which are absorbing oxygen. The relative sizes of the flagellate aggregations then show the relative activities of the different surfaces of the animal in absorbing oxygen. 2. Applying this method to the red Chironomus larva it was found that the animal respires by the whole body surface except by the head and the "ventral gills" and that the relative intensity of oxygen intake by the different parts of the body varies in different individuals and in the same individual at different times. 3. The absence of oxygen intake by the "ventral gills" was confirmed with the microspectroscope. In oxygen-free water all the hemoglobin of the blood becomes reduced. When an air bubble is now introduced so that it touches the "ventral gills" oxyhemoglobin first appears in the nearest body segment to the bubble, not in the "gills." 4. When a small aquatic animal is held motionless between cover-slip and slide in a solution of an indicator which changes color about the neutral point of water the relative extent of color change at different surfaces of the animal''s body indicates the relative amounts of carbon dioxide given off by these surfaces. 5. Using this method with the red Chironomus larva similar conclusions were reached for carbon dioxide output as for oxygen intake.     

MEMBRANES OF MESOPHYLL CELLS OF NICOTIANA RUSTICA AND PHASEOLUS VULGARIS WITH PARTICULAR REFERENCE TO THE CHLOROPLAST

Weier , T. E., and W. W. Thomson . (U. California, Davis.) Membranes of mesophyll cells of Nicotiana rustica and Phaseolus vulgaris with particular reference to the chloroplast. Amer. Jour. Bot. 49(8): 807–820. Illus. 1962.—The endoplasmic reticulum in mesophyll cells is represented by short lengths of irregularly disposed, paired membranes. It is occasionally associated with a typically double nuclear envelope. Groups of irregularly parallel, paired membranes suggesting disorganized dictyosomes occur infrequently. Mitochondria are unevenly distributed in mesophyll; they are large and have sparse tubular cristae around their periphery. In the great majority of instances the bounding membrane is diffusely stained with KMnO₄. When it is sharp and distinct, it may be double as usually pictured, or it may have well-delineated stretches of a single membrane bounding 25–50% of its circumference. The tonoplast and ectoplast are very fragile, the former appearing as a single dark line. In young leaves the ectoplast is visualized as a continuous single membrane adjacent to the cell wall, but in our micrographs of mature leaves it is always discontinuous. The plastid membrane sometimes is distinctly double, having 2 dark components bounding a light component. In the great majority of cases, however, this membrane is either a solid dark line, or the clear component of the double membrane is crossed by delicate dark lines giving the membrane a braided, or scalariform appearance. The various appearances of the membrane may intergrade with each other. The width of the plastid membrane is variable, ranging from 200 to 400 A. The inner component may invaginate into the stroma, and bodies may form in the clear space between the 2 outer membrane components. Micrographs suggest that these bodies, and others formed by small masses of stroma, may be expelled into the hyaloplasm, where they exist as spherical single-membraned particulates. The reality of the variable structure of the plastid membrane is discussed in light of concepts of membrane activity, molecular structure, and the relation of these factors to possible artifacts.