The Properties and Subcellular Localization of Acid Phosphatases in the Colourless Alga, Polytomella Caeca

The acid p-nitrophenyl phosphatase of homogenates of Polytomella caeca is a latent acid hydrolase, which is partially inhibited by NaF. Its distribution profile in density gradients (which is similar to that of naphthyl AS-TR phosphatase) suggests that this enzyme is partially lysosomal in location. Cytochemical evidence for the localization of acid phosphatases in fine subcellular structures is presented. Naphthyl AS-TR phosphatase is localized in vacuoles, points of focal degradation, Golgi bodies and dispersed throughout the cytosol. β-Glycerophosphatase is confined to large vacuoles and the cytosol. The nature of acid phosphatase-containing organelles in P. caeca is discussed in view of the inability to detect eleven other latent acid hydrolases in cell-free homogenates.

Genetic studies on ribose 5-phosphate isomerase mutants of Escherichia coli K-12

A gene for the constitutive ribosephosphate isomerase (rpiA) is highly cotransducible with serA at 56.2 min on the genetic linkage map of Escherichia coli K-12. Suppression of ribosephosphate isomerase A-negative mutants can occur by a regulator gene mutation permitting constitutive synthesis of the normally inducible ribosephosphate isomerase B.

A furosemide-sensitive cotransport of sodium plus potassium in the human red cell

The influxes of Na(+) and K(+) into the human red cell appear to be interrelated. This relationship was investigated under conditions in which either Na(+) or K(+) concentration outside the cell was varied or one cation was replaced by Mg(2+), choline(+), or Li(+). The effects of furosemide on Na(+) and K(+) movements were studied in the presence of ouabain. When ouabain was present, Na(+) influx was higher with K(+) ions externally than with other cations externally. Furosemide inhibited this K(+)-stimulated Na(+) influx, but it had little effect when K(+) was absent. Ouabain-insensitive K(+) influx was stimulated two-fold by external Na(+) compared with other cations. Furosemide also inhibited this stimulation, but it had little effect when Mg(2+) or choline(+) replaced external Na(+). Thus it was confirmed that synergism exists between the ouabain-insensitive influxes of Na(+) and K(+) and it was demostrated that furosemide inhibits this cooperative effect. The ouabain-insensitive influx of both K(+) and Na(+) showed a hyperbolic "saturating" dependence on the external concentration of the transported cation. Furosemide therefore eliminates a saturable component of influx of each cation. The net uptake of Na(+) in the presence of ouabain was stimulated by K(+) ions. A similar effect was observed with red cells, in which Li(+) replaced nearly all the internal Na(+) plus K(+) ions. In these cells, net Na(+) uptake was stimulated by external K(+), and net K(+) uptake was stimulated by external Na(+). Furosemide inhibited this mutual stimulation of net cation entries. The inhibitory action of furosemide was not limited to inward flux and net movement of Na(+) and K(+). Furosemide also inhibited the efflux of Na(+) into Na(+)-free media and the efflux of K(+) into K(+)-free media. It appeared, therefore, that the action of furosemide was not explained by inhibition of exchange diffusion. These data are consistent with an ouabain-insensitive transport process that facilitates the inward cotransport of Na(+) plus K(+)-ions, and that can produce a net movement of both ions. Although this process under some conditions mediates an equal bidirectional flux of both Na(+) and K(+), it cannot be defined as exchange diffusion. The contransport process is inhibited by furosemide.

An analysis of lipoproteins, bile acids, and red cell membranes associated with target cells and spur cells in patients with liver disease

Most patients with stable cirrhosis of the alcoholic have "target" red cells; however, a minority have "spur" cells and severe hemolytic anemia. These two syndromes were studied in 27 patients with target cells and 17 patients with spur cells, all of whom had advanced cirrhosis. The cholesterol and phospholipid content of red cell membranes effectively distinguished target cells from spur cells. Target cells alone were rich in lecithin, and both the cholesterol/phospholipid and cholesterol/lecithin mole ratios were greater in spur cells. The cholesterol/phospholipid mole ratio of both types of red cells correlated closely with the free cholesterol saturation of serum lipoproteins, as defined by the amount of free cholesterol relative to phospholipid and protein in these lipoproteins. Lecithin: cholesterol acyltransferase (LCAT) activity was decreased in most patients with target cells and spur cells; however, the relationship between this activity and the lipid abnormalities observed was weak. Serum bile acid levels also correlated poorly with serum and cell lipids. However, in patients with target cells the amount of cholic and deoxycholic acids in serum was approximately equal to the amount of chenodeoxycholic acid, whereas in patients with spur cells chenodeoxycholic acid (the precursor of lithocholic acid) predominated.

The purification and properties of Escherichia coli methylglyoxal synthase

1. Methylglyoxal synthase was purified over 1500-fold from glycerol-grown Escherichia coli K 12 strain CA 244. The purified enzyme was inactivated by heat or proteolysis, had a molecular weight of approx. 67000, a pH optimum of 7.5 and was specific for dihydroxyacetone phosphate with K(m) 0.47mm. 2. The possibility that a Schiff-base intermediate was involved in the reaction mechanism was investigated but not confirmed. 3. The purified enzyme lost activity, especially at low temperature, but could be stabilized by P(i). Two binding sites for P(i) may be present on the enzyme. Of other compounds tested only the substrate, dihydroxyacetone phosphate, and bovine serum albumin showed any significant stabilizing effect. 4. Phosphoenolpyruvate, 3-phosphoglycerate, PP(i) and P(i) were potent inhibitors of the enzyme. Kinetic experiments showed that PP(i) was apparently a simple competitive inhibitor, but inhibition by the other compounds was more complex. In the presence of P(i) the enzyme behaved co-operatively, with at least three binding sites for dihydroxyacetone phosphate. 5. It is proposed that methylglyoxal synthase and glyceraldehyde 3-phosphate dehydrogenase play important roles in the catabolism of the triose phosphates in E. coli. Channelling of dihydroxyacetone phosphate via methylglyoxal would not be linked to ATP formation and could be involved in the uncoupling of catabolism and anabolism.

Loss of membrane components in the pathogenesis of antibody-induced spherocytosis

The infusion of hyperimmune agglutinating antibodies into man or animals causes spherocytosis and hemolysis. The mechanism of spherocytosis was studied in rats given rabbit anti-rat red cell antiserum intravenously. During the 18 hr after antibody infusion, a time before the onset of reticulocytosis, hematocrits fell from 40.6 to 27.6%. However, no change occurred in mean cell volume, mean cell hemoglobin content, or the red cell concentrations of potassium or adenosine triphosphate (ATP). There was a progressive loss of membrane constituents and membrane surface area which followed first order kinetics. At 18 hr membrane cholesterol had decreased 23.5%, phospholipid 26.3%, protein 4.7%, and surface area (calculated from a measure of osmotic fragility) 14.2%. There was no change in the per cent composition of the various phospholipids. Similar changes occurred in animals splenectomized before receiving antibody.These studies demonstrate that spherocytosis induced by heterologous agglutinating antibodies in vivo results from a loss of surface area with no accompanying change in cell volume or in the concentration of the major intracellular constituents. It is caused by a process acting at the cell surface leading to the loss of lipid-rich, protein-poor components of the red cell membrane.

Migrations and growth of deep-sea lobsters, Homarus americanus

In distinct contrast to the restricted movements of coastal stocks of lobsters (Homarus americanus), those inhabiting the outer continental shelf undertake extensive seasonal migrations. Of 5710 tagged lobsters released on the outer continental shelf off New England from April 1968 to June 1969, 400 had been recaptured by April 1970. The distribution of the recoveries demonstrated shoalward migration in spring and summer and a return to the edge of the shelf in fall and winter. Deep-sea lobsters have a faster rate of growth than coastal lobsters; growth increments at molting and the frequency of molting are greater.

Anemia with spur cells: a red cell defect acquired in serum and modified in the circulation

The sera and red cells of three patients with severe liver disease and "spur cells" were studied. In each case the per cent of serum cholesterol which was free (unesterified) was elevated, and the serum lecithin: cholesterol acyltransferase activity was depressed. Lipoproteins with beta mobility were increased, but exhibited immune reactivity with antisera to both alpha- and beta-lipoproteins. Serum bile salt concentrations were markedly elevated and consisted primarily of chenodeoxycholic acid, with small amounts of lithocholic acid present as well.SPUR CELLS MANIFESTED A STRIKING INCREASE IN CHOLESTEROL CONTENT AND IN THE CHOLESTEROL: phospholipid ratio, but a normal osmotic fragility. When incubated in heated normal serum, spur cells lost their excess cholesterol and became spherocytic and osmotically fragile. Conversely, sera from patients with spur cells readily transferred up to one-third of their free cholesterol to normal red cells, causing normal cells to become resistant to osmotic lysis. In addition, these sera caused normal red cells to acquire thorny membrane projections. Cholesterol transfer to normal cells also occurred from normal serum which had previously been incubated with spur cells. Changes in cell cholesterol were induced by all of the lipoprotein fractions of spur serum. When transfused into a patient with spur cells, normal red cells became more resistant to osmotic lysis over the course of 24 hr. However, over the subsequent 7 days they underwent a progressive increase in osmotic fragility. These normal cells, as well as the patient's own cells, had a shortened survival. Correlating with the moderate decrease in the filterability of red cells spurred in vitro, red cell destruction occurred predominently in the spleen. Red cells in this disorder appear to serve as repositories for free cholesterol loosely bound to serum lipoproteins. Cholesterol acquisition by the red cell membrane increases its surface area and causes the red cell to be resistant to osmotic lysis. The associated alteration in red cell shape leads to further changes in the cell membrane during circulation in vivo resulting in the loss of membrane surface area and culminating in the cell's premature destruction in the spleen.