Incorporation of L-3H-fucose in the rete and ovary of the fetal mouse

The concept of Byskov which hypothesizes a glycoprotein inducer of meiosis for the mammalian fetal ovary has been tested by examining the incorporation of the specific precursor ³H-fucose into the rete ovarii of day 14 mouse ovaries. Semiquantitation of grains in autoradiographs has documented a concentration over the rete ovarii which exceeded that over the oogonia, ovarian fibroblasts, or surface epithelia. These data support the concept that the cytoplasm of mouse rete ovarii is capable of synthesizing a glycoprotein that may be the meiosis-inducing substance.     

Phospholipids of Nocardia coeliaca

The lipids of Nocardia coeliaca were separated into at least 10 components by the use of thin-layer chromatography. Phosphatidylcholine was the most abundant phospholipid in this organism, accounting for 25 to 40% of the total phospholipids. The major fatty acid components of the phosphatidylcholine were 14-methyl-pentadecanoic acid (41%), the other C(15) and C(17) iso- and anteiso-fatty acids (29%), and palmitic acid (13.5%). The next most abundant phospholipid was phosphatidylethanolamine (25 to 30%), followed by phosphatidylinositol (11 to 14%) and cardiolipin (7 to 15%). Phosphatidylethanolamine and phosphatidylinositol were very similar to the phosphatidylcholine in fatty acid composition, whereas cardiolipin was characterized by a higher content of palmitic acid (30%). In all of the phospholipids examined, only trace amounts of monounsaturated fatty acids were present. When washed cells of N. coeliaca were incubated with methionine-methyl-(14)C for 1 to 3 hr, the radioactivity was mainly incorporated into the choline moiety of the phosphatidylcholine. In contrast, acetate-1-(14)C or glycerol-1-(14)C was incorporated much more slowly into the phosphatidylcholine than into the other phospholipids and neutral lipids. No phosphatidylcholine was detected in 10 other species of Nocardia examined.     

Fine structure of ocelli of an anthomedusan,Nemopsis dofleini,with special reference to synaptic organization

Summary An ocellus of an anthomedusan, Nemopsis dofleini, is composed of sensory and pigment cells and underlain by a nerve plexus and a muscle sheet. A sensory cell is divided into three parts: an apical part from which a single cilium arises, a slender middle part with numerous microtubules and an enlarged basal part that contains an oval nucleus but does not send out an axon. The ocellar cup is occupied by variously remodelled ciliary sheaths that are covered by a few lysosomal projections from the pigment cells. Three modes of synaptic connections — centripetal, centrifugal and two-way — are found between sensory cells and either dendrites or somata of second order neurons. Synaptic vesicles in sensory cells are larger in number, smaller in size and more uniform in shape than those of second order neurons. The soma of a second order neuron lies below the surface layer of an ocellar cup and gives rise to a single cilium that lacks rootlets and the second centriole. The possibility of multimodal sensory perception in and around the ocellar region is discussed.The work was supported by research grants from the Ministry of EducationFormerly Tamano Marine Laboratory     

Distribution of post-proline cleaving enzyme in human brain and the peripheral tissues

Summary We have studied the distribution of post-propline cleaving enzyme activity in the various tissues in humans using 7-(succinyl-Gly-Pro)-4-methylcoumarinamide as substrate. The post-propline cleaving enzyme activity was high in muscle, testes, kidney and submandibular gland, but was low in the heart, mesenterium and aorta. In the brain, relatively high post-propline cleaving enzyme activity was observed in the cerebral cortex, but other brain regions showed a very low enzyme activity.On Sephadex G-100 column chromatography, enzyme activity in human kidney showed a major peak and a minor peak. The major peak coincided with the enzyme in human cerebral cortex, but was different from human serum enzyme. Diisopropylfluorophosphate, a serine protease inhibitor, strongly inhibited the enzyme activity of each active fraction. The enzyme in the cerebral cortex and kidney was inhibited by heavy metals and thiol blocking agents. However, inhibition of enzyme activity in the serum was not observed with such inhibitors. Therefore, we suppose that post-proline cleaving enzyme activity in the brain is similar, if not identical, to that in the kidney.     

Retinal-protein interactions in bacteriorhodopsin monomers,dispersed in the detergent L-1690

Bacteriorhodopsin monomer dispersed in a solution of the detergent L-1690 could maintain the specific interaction between retinal and protein in the pH range 9.0-0.0 at 25°C. λ_max of the absorbance spectrum was 550 nm at pH 9.0, 556 nm at pH 5.5, 609 nm at pH 2.1 and 570 nm at pH 0.0. Increasing the NaCl concentration in the solution promoted formation of the 609 nm product at pH 5.0-3.0 and also its transition to the 570 nm product at pH 2.5-1.0. Retinal isomer analysis gave a ratio of 13-cis- to all-trans-retinal of 53 : 47 at pH 5.5. When the pH of the solution was reduced, the relative content of all-trans-retinal increased and the ratio of 13-cis- to all-trans-retinal was 14 : 86 at pH 0.0. Illumination of the solution at pH 7.2 yielded a product containing 9-cis-retinal or 9-cis, 13-cis-retinal, which may be due to a reaction other than the photoreaction cycle.     

Degradation of Ethylbenzene by Pseudomonas putida Harboring OCT Plasmid

We have investigated the utilization of a variety of alkylbenzenes by P. putida strains and found that a strain harboring the OCT plasmid assimilated ethylbenzene. The linkage between the determinant for the degradation of ethylbenzene (Etb⁺ phenotype) and the OCT plasmid was inferred from conjugation experiments. The growth characteristics of the strains carrying mutations in the alk genes of the OCT plasmid which determine the assimilation of /t-alkanes indicated that alkB, alkA, and alkR should be responsible for the degradation of ethylbenzene. The exposure of ethylbenzene to the P. putida strain harboring the CAM-OCT plasmid resulted in the accumulation of β-phenylethyl alcohol. A possible degradation pathway for ethylbenzene including the terminal oxidation of the alkyl side chain was proposed.     

Fine structure of the erythrocytic stages of Plasmodium knowlesi

Summary The fine structure of erythrocytic stages of Plasmodium knowlesi was compared with that of the same parasite isolated from its host cell by a saponin technique. Rhesus monkeys experimentally infected with Plasmodium knowlesi were the source of parasitized red cells. The erythrocytic stages of this Plasmodium showed all the organelles described in other mammalian forms; the nucleus lacked a typical nucleolus but contained a cluster of granules. P. knowlesi did not have protozoan-type mitochondria as do the avian and reptilian forms, but had double-membrane-bounded bodies as observed in other mammalian malarial parasites.The isolation procedure caused a slight swelling of the parasite, but in general, the structure and structural relationships of the parasite were preserved. However, the isolation technique gave a new insight into the connection of the host cell cytoplasm with the large, so-called food vacuoles of the parasite. The parasite freed from its host cell showed clear spaces where the large vacuoles had been. The content of these vacuoles had been removed together with the red cell cytoplasm. As the nature of the isolation procedure precluded any disruption of the parasite itself, these findings support our view that the vacuoles are not true food vacuoles. If these were true food vacuoles, they would be completely enclosed by a parasite membrane within the parasite cytoplasm. However, we have demonstrated that they represent extensions of host cell cytoplasm in direct communication with the rest of the red cell. The outer membrane surrounding the intra-erythrocytic parasites disappeared after isolation of the parasite from the host cell. This strongly suggested that the outer membrane is of host cell origin. The budding process of the merozoites from a schizont was also described and discussed.This paper is contribution No. 558 from the Army Research Program on Malaria and was supported in part by Research Grant AI 08970-01 from the United States Public Health Service.     

Crystal structure of α5β1 integrin ectodomain: atomic details of the fibronectin receptor

Integrin α5β1 is a major cellular receptor for the extracellular matrix protein fibronectin and plays a fundamental role during mammalian development. A crystal structure of the α5β1 integrin headpiece fragment bound by an allosteric inhibitory antibody was determined at a 2.9-Å resolution both in the absence and presence of a ligand peptide containing the Arg-Gly-Asp (RGD) sequence. The antibody-bound β1 chain accommodated the RGD ligand with very limited structural changes, which may represent the initial step of cell adhesion mediated by nonactivated integrins. Furthermore, a molecular dynamics simulation pointed to an important role for Ca²⁺ in the conformational coupling between the ligand-binding site and the rest of the molecule. The RGD-binding pocket is situated at the center of a trenchlike exposed surface on the top face of α5β1 devoid of glycosylation sites. The structure also enabled the precise prediction of the acceptor residue for the auxiliary synergy site of fibronectin on the α5 subunit, which was experimentally confirmed by mutagenesis and kinetic binding assays.