Concentrations and origin of oxytocin in breast milk

Samples of human milk obtained from lactating women in the early postpartum period were assayed for oxytocin concentrations by specific RIA, following extraction procedures with Florisil. Mean oxytocin concentrations in human milk at postpartum day 1 to 5 were 4.5 +/- 1.1, 4.7 +/- 1.1, 4.0 +/- 1.3, 3.2 +/- 0.4, 3.3 +/- 0.6 microunits/ml (+/- SE), respectively. Oxytocin levels in milk were significantly increased by nursing (3.1 +/- 0.6, 5.3 +/- 1.0 microunits/ml, respectively). 3H-oxytocin in human milk was stable even after incubation at 37 degrees C for 2 hours. The dilution curve for milk was parallel to the curve for the standard oxytocin. The chromatographic fraction of immunoreactive oxytocin was identical to that of 3H-oxytocin. 3H-oxytocin was administered to lactating rats. Radioactivity in the neonatal gastric contents and plasma were 12.8% and 4.4% of the counts in the maternal plasma. It was made clear that oxytocin is stable in milk and that oxytocin in maternal blood can be transferred to mik and then to neonates.     

OH-induced free radicals in purine nucleosides and their homopolymers: e.s.r. and spin-trapping with 2-methyl-2-nitrosopropane

Free radicals produced by X-irradiation of N2O-saturated aqueous solutions of purine nucleosides (2'-deoxyadenosine, adenosine, 2'-deoxyguanosine, 3'-deoxyadenosine, guanosine and inosine) and the corresponding homopolymers (poly A and poly I) have been investigated by the technique of spin-trapping and e.s.r. spectroscopy. 2-Methyl-2-nitrosopropane was used as a spin-trap. For 2'-deoxyadenosine and 2'-deoxyguanosine, the resulting spin-adducts were separated by Bio-Gel P-2 column chromatography and analysed by e.s.r. spectroscopy. For homopolymers, e.s.r. spectra were recorded at 50 degrees C after enzymatic digestion to obtain signals with narrower line width. The e.s.r. signal consisting of only a primary triplet without further splittings, which is consistent with assignment to the trapping of an H-abstraction radical at the C4' position of the sugar moiety, was observed in all cases. For 2'-deoxyguanosine an e.s.r. signal consisting of a secondary triplet was observed. Examinations using other spin-trapping reagents such as PBN, 4-PyOBN and DMPO provided no positive evidence supporting the proposal that this was due to an alpha-nitrogen. The e.s.r. signal consisting of a secondary doublet which further splits into a doublet was observed for 2'-deoxyadenosine, adenosine, 3'-deoxyguanosine, 2'-deoxyguanosine, and inosine, and tentatively associated with a radical centered in the sugar moiety.     

Inactivation and sedimentation of mercury from organomercurials by Klebsiella pneumoniae

Abstract A susceptibility of 63 clinical isolates of Klebsiella pneumoniae to inorganic and organic mercuric compounds was determined. 18 of them were found to be resistant to fluorescein mercuric acetate (FMA) and merbromin (MB). Moreover, all the resistant strains inactivate the antibacterial effect of FMA. The changes in the amount of organic mercury at the time of inactivation of the drug and the structures of the end products were examined in detail with the plasmid-bearing strain JK9 and its transconjugants of Escherichia coli .
The results showed that FMA was inactivated by an intracellular enzyme produced inducively and was degraded to fluorescein (sodium salt, uranine), which led to the sedimentation of metallic mercury. The discovery of the genes conferring inducible organic mercury-inactivating enzymes determined by plasmids was the next step and their application in the recovery of metallic mercury from organomercurials is now imminent.     

Reactions of the hydrated electron with pyrimidine nucleosides halogenated at the sugar moiety: e.s.r. and spin-trapping with 2-methyl-2-nitrosopropane

Free radicals produced by the reactions of hydrated electrons with pyrimidine nucleosides halogenated at the sugar moiety (2'-chloro-2'-deoxyuridine and 2'-chlorothymidine) were studied by e.s.r. and spin-trapping. 2-Methyl-2-nitrosopropane was used as the spin-trap. The usual spin-trapping technique was extended to frozen and deoxygenated systems to avoid contamination of the trapped radicals with side-products by spin-trapping 2-methyl-2-nitrosopropane itself. When this method was applied to 2'-chloro-2'-deoxyuridine, a free radical at the C-2' position of the sugar moiety was spin-trapped together with a free radical at the C-5 position of the base moiety. This indicates that hydrated electrons both add to the base moiety and eliminate halogen anions from the halogenated sugar moiety. In the case of 2'-chlorothymidine, however, only a free radical attributed to H-addition at the C-6 position of the thymine base was observed. No radicals produced by the reaction of hydrated electrons with the halogenated sugar could be spin-trapped.     

Quantitative Analysis of the Inactivation of Photosynthetic Oxygen Evolution and the Release of Polypeptides and Manganese in the Photosystem II Particles of Spinach Chloroplasts

Photosynthetic oxygen evolution by photosystem II particleswas inactivated by treatment with NaCl, NH₂OH or high pH. Whenthe degree of inactivation was compared with the degree of releasefrom the particles of Mn and three polypeptides having molecularmasses of 33, 24 and 18kdaltons, two types of inactivation werefound: one, brought about with 960 mM NaCl, was related to therelease of the 24 kdalton polypeptide, and the other, broughtabout with 1.5 mM NH₂OH or high pH, seemed to be related tothe release of Mn. ¹Present address: Department of Chemistry, Faculty of Science,Toho University, Miyama 2-2-1, Funabashi 274, Japan. (Received January 31, 1983; Accepted March 28, 1983)     

R-Factor Mutant Capable of Specifying Hypersynthesis of Penicillinase

The physical characteristics of a mutant, R(M201-2), capable of conferring high and stable ampicillion resistance was analyzed. The R(M201-2) and its parent R-factor deoxyribonucleic acid (DNA) could be isolated as an extrachromosomal and covalently closed circular form. Their buoyant densities were both 1.712 g/cm(3), and their molecular weights were about 82 x 10(6) and 64 x 10(6), respectively, when measured by CsCl and sucrose density gradient analyses. The contour lengths by electron microscopy were 35.9 +/- 0.6 and 31.0 +/- 0.6 mum, respectively. By using the extracted R-factor DNA, the mutant and parent characters were transformable to another Escherichia coli strain. The mutant R factor showed an increased amount of DNA even after conjugal transfer to Proteus. An increase in the size of R-factor DNA was thus considered to be the cause of the high level of ampicillin resistance.     

Fine structure of the dorsal ocellus of the worker honeybee

The three dorsal ocelli of worker honeybees have been studied by light and electron microscopy. Each ocellus has a single flattened spheroidal lens and about 800 elongated retinular cells. Retinular cells are paired and form a two-part plate-like rhabdom between their distal processes. Each rhabdomere comprises parallel microvilli projecting laterally from the apposed retinular cells. Primary receptor cell axons synapse within the ocellus with ocellar nerve fibers of two different calibers. Each ocellus has eight thick fibers ca 10 m?m in diameter and several thinner ones less than 3 m?m in diameter. Fine structural evidence suggests that retinular axons end presynaptically on both types of ocellar nerve fibers. Since all retinular cells apparently synapse repeatedly with the thick fibers this involves a convergence of about 100:1. Thick fibers always terminate postsynaptically within the ocellus while thin fibers terminate presynaptically on other thin fibers, thick fibers or retinular axons. Structural evidence for synaptic polarization indicates that retinular cells and thick fibers are afferent, thin fibers efferent. Thus complex processing of the ocellar visual input can occur before the secondary neurons of the three ocelli converge to form the single short ocellar nerve which runs to the posterior forebrain.     

The Development of the Rhabdom and the Appearance of the Electrical Response in the Insect Eye

Electron microscopic studies on the development of the rhabdom in the compound eye of the silkworm moth and pupa (Bombyx mori) were carried out in parallel with the recording of the electrical response to photic stimulation. No electrical response to photic stimulation was recorded from the pupal compound eye which had no trace of differentiation of the rhabdom. With the differentiation of development of the rhabdom in the pupal compound eye, electrical responses could be recorded, and the amplitude of such electrical responses increased with the progress of development of the rhabdom. These observations suggest that the rhabdom is probably the site of the photochemical reaction which leads to the generation of the slow retinal action potentials.