The integument of the Queensland fruit fly,Dacus tryoni (Frogg.)

Summary Testes of the Japanese freshwater turtle Clemmys japonica Temmnick et Schlegel were fixed in 3% potassium permanganate buffered to pH 7.2 with Veronal-acetate buffer, and thin sections of the tissue, embedded in epoxy Epon resin, were studied under the electron or light microscope.At the early stage of differentiation of the spermatid, the cytoplasm contains a few mitochondria provided with cristae which are oriented transversely or longitudinally. As the differentiation of spermatids proceeds, the mitochondrion has been modified into a cupshaped body with a wall consisting of several concentric layers. Such body has been referred to the mitochondrial lamellar body. The formation of such a body is mainly attributed to the mitochondrial cristae, and subsequently to the membrane system of the endoplasmic reticulum. In a more advanced stage of differentiation, the mitochondrial lamellar bodies appear wrapped around a bundle of tail filaments, and seem to present a very wide surface available for the localization of organized enzyme systems to facilitate the motion of spermatozoa.Prior to the formation of the mitochondrial lamellar bodies, the Golgi apparatus has been reorganized into a peculiar body with a floral appearance, consisting of numerous tubular elements, and revealing to be positive in PAS-reaction. The body has been designated as the tubular body which has never been demonstrated in any spermatogenic cells through animal kingdom.One to three tubules oval in cross section, approximately 430 × 700 Å in diameter, have been found in the nucleoplasm along the longitudinal axis of a greatly elongated, cone-shaped nucleus of the spermatid. The tubules open on the apex surface of the nucleus, but they are not encountered in the acrosome. A possible physiological significance of the tubules has been discussed in view of the function of the acrosomal tubules in the decapod and other species spermatozoa as well as on the basis of the metabolism of nucleus.This study was supported by Grant GM-8327 from the United States Public Health Service.We wish to express our gratitude to Dr. B. A. Afzelius, Wenner-Gren Institute, University of Stockholm, for his valuable suggestion to the present work.     

The photo-oxidation of succinate by chromatophores of Rhodospirillum rubrum

1. The stoicheiometry of the photo-oxidation of succinate by chromatophores has been investigated with [2,3-¹⁴C₂]succinate. It was found that there is a stoicheiometric relationship between the amount of succinate oxidized and the NAD reduced, and that fumarate is the only product of succinate oxidation. 2. The possibility of a direct hydrogen transfer from succinate to NAD in this reaction was investigated with tritiated substrates. With tritiated succinate less than 3% of the activity expected if direct hydrogen transfer occurred was recovered in the NADH₂, and this was due to contamination with the substrate. In experiments with tritiated water, NADH₂ was labelled, and had half the specific activity of the water, as expected if water was the source of protons. It was also found that chromatophores catalyse an exchange reaction between NADH₂ and water. 3. It is concluded that the exchange reaction makes it impossible to interpret these results as indicating either a hydrogen-transfer or an electron-transfer mechanism for the photoreduction reaction.     

Kinetics of granulocyte phagocytosis: rate limited by cytoplasmic viscosity and constrained by cell size

Micromanipulation of yeast particles and blood granulocytes has been used to study the kinetics of single phagocytosis events. The ingestion process was quantitated by observation of sequential adhesion and encapsulation times. Both adherence and encapsulation times were found to increase greatly as the temperature was reduced below 37 degrees C; calcium in solution facilitated adhesion of the particle to the phagocyte but not encapsulation; both adhesion and encapsulation processes required a minimum level of plasma components (presumably complement). The general nature of these observations were confirmatory of previous studies, but this study is unique in that the specific time course of single particle ingestion was quantitated. It was immediately apparent that the phagocytosis process was 100% efficient above the threshold concentrations required for plasma and temperature, but variations in times from cell to cell indicated heterogeneity in the population. The total time for ingestion varied from as low as 2 sec/particle at 37 degrees C to above several min/particle below 15 degrees C. Encapsulation times for particles were normalized by estimates of particle surface areas to establish a specific time/unit area of particle surface: from 0.5 sec/10(-8) cm2 at 37 degrees C to greater than 8 sec/10(-8) cm2 at 15 degrees C. The temperature dependence of the encapsulation time correlated well with the temperature dependence of the "apparent" viscosity for granulocytes measured by micropipet aspiration. As such, the kinetic properties observed in these phagocytosis tests are consistent with a model that both assembly of the contractile system and the displacement of the surface by active contraction in phagocytosis are limited by viscous dissipation in the cell.(ABSTRACT TRUNCATED AT 250 WORDS)     

Do all human urinary infections with Schistosoma mattheei represent hybridization between S. haematobium and S. mattheei?

Enzyme electrophoresis indicated that all Schistosoma mattheei eggs passed in the urine of humans derive from S. mattheei females in copula with S. haematobium males. It appears that S. mattheei males do not reach sexual maturity in man; however, S. haematobiumxS. mattheei males possibly do.     

Temperature-sensitive vaccinia virus mutants identify a gene with an essential role in viral replication.

Vaccinia virus mutants ts2 and ts25, members of the same complementation group, exhibit a temperature-dependent arrest at the stage of viral DNA replication. The lesions responsible for the mutant phenotypes have been localized to the far left region of the HindIII B genomic fragment by marker rescue studies. Hybrid selection analyses established that the DNA fragments positive for rescue represented the first open reading frame of the HindIII B fragment and encoded a 30-kilodalton protein. The gene is expressed early after infection as a rightwardly transcribed 1-kilobase-pair mRNA whose coordinates were determined by S1 nuclease mapping. To further the phenotypic analysis of the mutants, the accumulation of viral DNA sequences during permissive and nonpermissive infections was quantitated. The extent of the DNA- phenotype was shown to vary in different cell types. In mouse L cells at either high or low multiplicity of infection, nonpermissive DNA synthesis was less than 5% of that seen in permissive infections. This severe defect was mirrored by correspondingly low viral yields. In infections of BSC40 monkey cells, however, the deficiencies in both DNA synthesis and virus production were far less severe. For one mutant (ts2), the temperature sensitivity in BSC40 cells varied inversely with the multiplicity of infection.     

Characterization of the total lipid and fatty acid composition of rat olfactory mucosa

Phospholipid accounted for 81% (by weight) of the total lipid of rat olfactory mucosa. Phosphatidylcholine (46% of total phospholipids) and phosphatidylethanolamine (26%) were the predominant phospholipids. Phosphatidylinositol (8%), sphingomyelin (6%), and phosphatidylserine (7%) were the next most abundant phospholipids, with cardiolipin (4%) and phosphatidic acid (1%) present in lesser amounts. Only trace amounts of the polyphosphoinositides, phosphatidylinositol monophosphate, and phosphatidylinositol bisphosphate were detected. Sterol was the major neutral lipid present (83% of the total neutral lipid mass) with lesser amounts of triacylglycerols (7%), steryl esters (6%), free fatty acids (4%), and diacylglycerols (1%). Monoacylglycerols were detected only in trace amounts. The sterol to phospholipid ratio was 0.39:1. Most of the phospholipids of the olfactory mucosa showed a high polyunsaturated fatty acid content, with the arachidonic acid (20:4) and docosahexaenoic acid (22:6) residues predominating. The fatty acids in sphingomyelin, however, were almost totally saturated and included the 24:0 and 24:1 residues, which were not detected in other phospholipids. Polyunsaturated fatty acids accounted for less than 25% of the total fatty acid of any individual neutral lipid and comprised largely linoleic and arachidonic acids. The results are discussed in relation to the putative role of lipids in olfactory signal transduction.     

Crystal structure of unliganded phosphofructokinase from Escherichia coli

In an attempt to characterize the mechanism of co-operativity in the allosteric enzyme phosphofructokinase from Escherichia coli, crystals were grown in the absence of activating ligands. The crystal structure was determined to a resolution of 2.4 A by the method of molecular replacement, using the known structure of the liganded active state as a starting model, and has been refined to a crystallographic R-factor of 0.168 for all data. Although the crystallization solution would be expected to contain the enzyme in its inactive conformation, with a low affinity for the co-operative substrate fructose 6-phosphate, the structure in these crystals does not show the change in quaternary structure seen in the inactive form of the Bacillus stearothermophilus enzyme (previously determined at low resolution), nor does it show any substantial change in the fructose 6-phosphate site from the structure seen in the liganded form. Compared to the liganded form, there are considerable changes around the allosteric effector site, including the disordering of the last 19 residues of the chain. It seems likely that the observed conformation corresponds an active unliganded form, in which the absence of ligand in the effector site induces structural changes that spread through much of the subunit, but cause only minor changes in the active site. It is not clear why the crystals should contain the enzyme in a high-affinity conformation, which presumably represents only a small fraction of the molecules in the crystallizing solution. However, this structure does identify the conformational changes involved in binding of the allosteric effectors.     

Studies on the Formation of 6-Hydroxydopamine in Mouse Brain After Administration of 2,4,5-Trihydroxyphenylalanine (6-HydroxyDOPA)

2,4,5-Trihydroxyphenylalanine (6-OH-DOPA) destroys central and peripheral noradrenergic neurons, while sparing dopaminergic neurons. Previous studies indicate that 6-OH-DOPA toxicity is mediated by the formation of 6-hydroxydopamine. However, levels of 6-hydroxydopamine in brain following peripheral administration of 6-OH-DOPA have not been documented. In the current study, 6-OH-DOPA and 6-hydroxydopamine were measured in brain by HPLC with electrochemical detection after intraperitoneal injection of 6-OH-DOPA. When mice were injected with 100 mg 6-OH-DOPA/kg, 6-hydroxydopamine levels in the striatum were highest (1.9 microgram/g) at 15 min and fell slowly to 24% of the peak value at 4 h. Experiments with reserpine indicated that the relatively stability of 6-hydroxydopamine was largely dependent upon storage in synaptic vesicles. Reserpine (10 mg/kg) lowered striatal 6-hydroxydopamine levels to 21.6% of control (non-reserpine-treated) values at 1 h, and to 8.9% of control values at 4 h. Levels of 6-hydroxydopamine in the striatum at 1 h were increased 113% by pargyline (100 mg/kg), 145% by alpha-methyldopahydrazine (carbidopa; 25 mg/kg), and 261% by pargyline and carbidopa together. Levels of dopamine in the striatum were unchanged at 2.5 h after 200 mg 6-OH-DOPA/kg (with pargyline and 50 mg carbidopa/kg), whereas levels of norepinephrine in the frontal cortex fell by 77%. At the same time, 6-hydroxydopamine levels were 8.8-fold higher in the striatum (5.54 micrograms/g) than in the cortex (0.63 micrograms/g).(ABSTRACT TRUNCATED AT 250 WORDS)