Isolubimin: A possible precursor of lubimin in infected potato slices

Potato slices treated with spirovetiva-1(10),11-diene-2-one yield lubimin and rishitin within 24 hr. A vetispirane which has not been detected in fungally infected potatoes was also isolated. This compound, isolubimin, appears to be an intermediate in the conversion of the above spirovetivone to lubimin.     

Morphology,morphometry and electron microscopy of HeLa cells infected with bovine Mycoplasma

Summary The host-parasite relationship of HeLa M cells artificially infected with a bovine species of Mycoplasma was studied by light microscopy, transmission electron microscopy and scanning electron microscopy. The use of morphometry to quantitate some of the findings was explored. The parasites were seen in locations extracellular to the cell surface. The detection of small numbers of organisms by light microscopy was well demonstrated by use of the fluorescent antibody technique. Scanning electron microscopy proved to be an excellent method for revealing the surface details of cell-parasite morphology. Ultra-thin sections showed that the parasites are aligned mostly parallel to the plasma membrane of the host cell but separated by a gap of 10 nm. Morphometry indicated an average of 69 organisms per cell surface occupying 1.7% of the surface area. An increase of 26% in diameter of the HeLa cells, possibly as a result of infection, was observed.The authors wish to thank Christiana Ulness and Andrea Erickson for expert technical assistance and Arnold Schmidt for the operation of the scanning electron microscope. This work was supported by grants from the U.S.P.H.S.: AI 09586, AI 10743, and AI 06720     

Characterization of a monoclinic crystal form of an enzyme of steroid metabolism, Δ5-3-ketosteroid isomerase

A monoclinic crystal form ($\text{P2}{}_1\text{, a = 140.4}\text{A}\text{?}\text{, b = 85.0}\text{A}\text{?}\text{, c = 94.5}\text{A}\text{?}$, β= 130.1 °) of Δ⁵-3-ketosteroid isomerase from Pseudomonas testosteroni (EC 5.3.3.1), grown at pH 7.0, has been characterized. Crystal-density measurements show that the asymmetric unit contains 12 protomers (M_r = 13,394).     

Interralation of prostaglandin endoperoxide (prostaglandin G2) and cyclic 3′,5′-adenosine monophosphate in human blood platelets

The prostaglandin endoperoxide, prostaglandin G₂, in platelet-rich plasma may produce reversible platelet aggregation without secretion, irreversible aggregation with secretion of platelet constituents inhibited by indomethacin, or the latter effects despite indomethacin, depending on the concentration of the endoperoxide. Irreversible aggregation and platelet secretion induced by prostaglandin G₂ apparently result from the action of ADP, since these responses are inhibited by 2-n-amylthio-5′-AMP (an inhibitor of the actions of ADP on platelets) and they do not occur in heparinized platelet-rich plasma. Prostaglandin G₂ lowers the platelet level of cyclic 3′,5′-AMP. Its actions are inhibited by elevation of cyclic AMP levels by prostaglandin E₁ or dibutyryl cyclic AMP or adenosine. Like malondialdehyde production induced by thrombin, ADP, or arachidonic acid, prostaglandin G₂-induced malondialdehyde production is reduced by dibutyryl cyclic AMP and prosraglandin E₁. Platelet activation by prostaglandin G₂ is enhanced by the adenylate cyclase inhibitor, 9-(tetrahydro-2-furyl)-adenine.The action of prostaglandin G₂ on platelets is more complex then previously reported.     

POLLEN COMPETITION AND RELATEDNESS IN HAPLOPAPPUS SECTION ISOPAPPUS (COMPOSITAE). II.

Pollen competition in mixed pollinations involving a time handicap was studied among the five aneuploid members of section Isopappus of Haplopappus. Foreign pollen was applied to the stigmas of a plant followed after a delay of 0–180 min by domestic pollen. Domestic pollen was prepotent over foreign pollen in all cases, but with increasing delay an increasing percentage of hybrids appeared in the progeny. The time interval required to produce 50% of hybrids in the progeny (at which time the two pollen types were competitively matched in potency) was determined for each cross. The interval is correlated with relatedness, with chromosome number, and with length of the style of the pollen parent. It can be used as an estimate of the potential frequency of hybridization in nature, with all other factors being equal.