Desmosomes: Their occurrence between adjacent primary oocytes in polyovular follicles in the rabbit

Summary In polyovular, primordial follicles in the rabbit, desmosomes are found between apposing oocyte surfaces. Morphologically these desmosomes correspond closely to those described in epithelia of vertebrates. The desmosomes alternate with other junctions which are probably gap junctions.This work was supported in part by the G.R.S.T. Grant n 75.7.1313     

The relative effectiveness of three techniques to induce the trophotropic response

The purpose of this study was to examine the relative effectiveness of electromyographic biofeedback training(EMG BFT), remeditation, and progressive muscle relaxation(PMR) in eliciting a relaxation or trophotropic response as measured by frontalis muscle tension, heart rate, electrodermal response, respiration rate, and skin temperature. Fifty-four college students were randomly assigned to one of five groups:(1) control,(2) placebo control,(3) EMG BFT,(4) meditation,(5) PMR. After baseline measures were obtained subjects were trained in 10 30-minute training sessions and posttested. Comparisons by ANOVAs indicated there was a significant decrease in muscle tension in the EMG BFT and meditation groups and significant decreases in respiration rate in the meditation and PMR groups. No other changes were attributed to treatment.     

Built-in co-operativity of oxygen binding by arthropod hemocyanins

Oxygen binding by arthropod hemocyanin from the scorpion Leirus quinquestriatus and the crabs Telphusa fluviatilis and Ocypoda cursor was studied in Ca²⁺, Mg²⁺-free solutions. The binding was found to be co-operative in all three cases. Our results and a re-examination of the literature lead us to conclude that co-operative oxygen binding is a built-in feature common to arthropod hemocyanins, distinguishing them from mollusc hemocyanins where co-operativity is conditional upon the presence of Ca²⁺ or Mg²⁺.     

Neurotubule assembly at substoichiometric nucleotide levels using a GTP regenerating system

Tubulin derived from cold depolymerized bovine microtubules has been gel filtered to obtain a tubulin preparation with only 3% of the tubulin dimers containing exchangeable [³H]-guanine nucleotide. In the presence of acetyl-P and bacterial acetate kinase, this preparation polymerizes to form microtubules which are morphologically indistinguishable from microtubules formed in the presence of excess GTP. The extent of microtubule formation at substoichiometric nucleotide levels using the GTP regenerating system exceeds the extent of assembly obtained with excess GTP. It is concluded that the exchangeable guanine nucleotide site can be virtually unoccupied in intact neurotubules and this finding indicates that GDP can “catalyze” tubule assembly in the presence of a GTP regenerating system.     

THE THICKENED LEPTOID (SIEVE ELEMENT) WALL OF DENDROLIGOTRICHUM (BRYOPHYTA): CYTOCHEMISTRY AND FINE STRUCTURE

Leptoids (sieve elements) of Dendroligotrichum exhibit unevenly thickened lateral walls. The thickened wall areas are predominantly confined to the radial walls. With the light microscope the thickened wall cannot be resolved into distinct layers, but rather is optically homogeneous. Standard histochemical tests reveal that these walls are rich in cellulose (birefringent; IKI-H₂SO₄-positive) with small amounts of polyuronides (toluidine blue-positive) and pectins (hydroxylamine-positive) and are non-lignified. They also contain abundant natural aldehydes as revealed by the Schiff, silver hexamine, and silver proteinate reagents. Aldehyde blockades (sodium borohydrate, sodium chlorite) confirmed the presence of aldehyde groups in the cell wall. At the ultrastructural level, the lateral walls of sieve elements react strongly with uranyl and lead salts and yield little fine structural information. Electron cytochemical localization of aldehydes with silver proteinate revealed three distinct wall regions: outer, middle and inner. The outer and middle regions appeared polylamellate while the inner region contained no reaction product. The nacreous sieve elements of vascular plants are compared to the thickened sieve elements in bryophytes.     

Resolution of optical isomers by high-pressure liquid chromatography: The separation of benzo[a]pyrene trans-diol derivatives

The optical isomers of (±)r-7,t-8-dihydroxy-7,8-dihydrobenzo[a]pyrene and its synthetic precursor (±)r-7,t-8-dihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene were resolved as their di-(−)menthoxyacetates using high-pressure liquid chromatography. Saponification of the resolved diesters yielded the corresponding enantiomers. The specific rotation, CD spectra, and ORD curves are reported. The resolution of these optical isomers permits detailed studies on the enzymatic intermediates and the mechanism of benzo[a]pyrene activation to its carcinogenic form. The method is of general usefulness for the resolution of optical isomers.     

Viruses of Entamoeba histolytica. VII. Novel beaded virus.

A third amoebal virus type was isolated from four different strains of Entamoeba histolytica. The virus was most frequently seen as a linear structure about 235 nm long and consisting of 14 beadlike structures about 19 nm in diameter. A "dimer" of twice the length and consisting of 28 beads was occationally encountered. The virus replicated in the nucleus, forming ordered arrays. Acridine orange staining of viral aggregates in infected nuclei suggested the presence of double-stranded nucleic acid.     

Decrease in ribosomal proteins 1, 2/3, L4, and L7 in Drosophila melanogaster in the absence of X rDNA

Summary The rRNA genes (rDNA) in Drosophila melanogaster are found in two clusters, one on the X and one on the Y chromosome. We have compared the ribosomal protein composition of wild-type Oregon-R flies containing both X-linked and Y-linked rDNA with that of flies containing only the Y-linked rDNA by two-dimensional polyacrylamide gel electrophoresis. Four basic proteins (1, 2/3, L4, and L7) normally present in wild-type flies were either electrophoretically not detectable (1, 2/3, and L4) or marginally detectable (L7) in flies with only Y-linked rDNA. No additional proteins were observed in these flies. However, immunodiffusion assays using specific antibodies raised against purified protein L4 confirmed that L4 was present but in relatively lower amounts in these Y-linked rDNA flies. An investigation was carried out to determine whether these electrophoretically undetectable proteins were more readily lost during ribosome preparation and hence were not readily detectable in the 80S particles by gel electrophoresis or whether they had been modified. Thus the proteins in the post-ribosomal cell supernatant and the high salt sucrose gradient were analyzed by two-dimensional gel electrophoresis and immunochemical assays with antibodies raised against protein L4 and total 80S ribosomal proteins. The experimental evidence indicates that there is a small amount of protein L4 and probably proteins 1, 2/3, and L7 in flies with only Y-linked rDNA but significantly less of these proteins than in wild-type flies.     

Germacranolides from Melampodium americanum and Melampodium pilosum

Chemical analysis of Melampodium americanum yielded, besides the known melampodinin A, four new melampolides, melampodinin B, melampodinin C, 9-des     

Stimulation of deacylation in Madin-Darby canine kidney cells. Specificity of deacylation and prostaglandin production in 12-O-tetradecanoylphorbol-13-acetate-treated cells

Madin-Darby canine kidney cells deacylate arachidonic acid from cellular phospholipid in response to 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and convert the free arachidonic acid to prostaglandins. We have used this system to characterize the acyl specificity of deacylation. Cells were labeled with either [14C]linoleic, [14C]eicosatrienoic (delta 8,11,14 or delta 5,8,11), or [14C]arachidonic acid and stimulated with 10 nM TPA. We found that TPA stimulated the deacylation of all four acids, primarily from phosphatidylethanolamine and phosphatidylcholine.l Only products from linoleic (presumably through chain elongation and desaturation), eicosatrienoic (delta 8,11,14), and arachidonic acids produced prostaglandins. Those produced from linoleic and eicosatrienoic acid (delta 8,11,14)-labeled cells were determined to be primarily of the 1-series, while arachidonic acid-labeled cells produced prostaglandins of the 2-series. Together these results indicate that the stimulated deacylation of phospholipids is not specific for arachidonic acid and that the membrane acyl composition controls the particular series of prostaglandin which is produced.