Catalytic properties and stability of three common variants of placental alkaline phosphatase

Three placental alkaline phosphatases purified to homogeneity, i.e., the F, I, and S variants, were investigated for catalytic and stability properties. All three forms of the enzyme were found to have almost identical pH optima (10.7–10.8), similar sensitivity to the uncompetitive inhibitors L-phenylalanine (70%) and L-leucine (30%), and identical K_m values against p-nitrophenylphosphate, -glycerophosphate, and -naphthylphosphate. Significant differences among the three types were observed in thermal stability. The F variant was found to be most stable and the I variant most labile at 79 C. At 70 C all three forms were stable.This investigation was supported by grants from the Swedish Medical Research Council (Projects No. 4217 and 03X-2725), from the Medical Faculty, University of Umeå, and Jubileumsklinikens i Umeå forskningsfond.     

Effect of prostaglandin E2 on vascular responses of the rabbit kidney to nerve stimulation and noradrenaline, in vitro and in situ

The effect of prostaglandin E₂ on vascular responses of the rabbit kidney to renal nerve stimulation and noradrenaline was examined $\text{in}$$\text{vitro}$ and $\text{in}$$\text{situ}$ as a test of the hypthesis that prostaglandins of the E series may be involved in the regulation of adrenergic neuroeffector transmission. Intraarterial administration of prostaglandin E₂ to the $\text{in}$$\text{vitro}$ kidney caused marked inhibition of vascular responses to nerve stimulation whereas the responses to noradrenaline were not significantly altered. In the $\text{in}$$\text{situ}$ preparation, vascular responses to both nerve stimulation and noradrenaline were inhibited by prostaglandin E₂ infusion, although its effect on responses to nerve stimulation was approximately twice that observed on responses to noradrenaline.It is concluded that prostaglandin E₂ acts primarily at a prejunctional level of adrenergic neuroeffector transmission in the kidney, although a postjunctional effect has also been observed.     

Endogenous γ-l-glutamylglutamate is a partial agonist at the N-methyl-d-aspartate receptors in cultured cerebellar granule cells

-l-Glutamylglutamate (LGG), an endogenous constituent of the brain, reduced the glutamateevoked increase in intracellular Ca²⁺ in cultured cerebellar granule cells. The extent and properties of this inhibition were different at different Mg²⁺ concentrations. The intracellular Ca²⁺ response to NMDA was slightly enhanced by 0.1 mM LGG in normal (1.3 mM) Mg²⁺ medium, but in Mg²⁺-free medium LGG was stimulatory at low (0.1–1 M) NMDA and inhibitory at high (0.1–1 mM) NMDA concentrations. In the absence of Mg²⁺, LGG alone increased cytosolic free Ca²⁺ and depolarized the cells. These effects were potentiated by glycine and blocked by extracellular Mg²⁺, 2-amino-5-phosphonopentanoate (APV), 7-chlorokynurenate, 3-amino-1-hydroxypyrrolidin-2-one (HA-966) and 5,7-dinitroquinoxaline-2,3-dione (MNQX). The results indicate that LGG is a partial NMDA agonist. On the other hand, the non-NMDA antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6,7-dinitroquinoxaline-2,3-dione (DNQX) also inhibited the effects of LGG. This indicates an involvement of non-NMDA receptors in the actions of LGG. The consequent depolarization may also contribute to the activation of NMDA receptor-governed ionophores.     

Role of microtubules in the movement of the vegetative nucleus and generative cell in tobacco pollen tubes

The germination and growth of pollen grains of Nicotiana tabacum and N. alata with the anti-microtubule drug oryzalin retarded significantly the movement of the vegetative nucleus (VN) and the generative cell (GC) from the grain to the tube apex but had no effect on pollen tube elongation. In N. tabacum, only 11% and 48% of the pollen tubes treated with oryzalin for 6 h and 12 h, respectively, had the VN and GC in the tube mainly in its middle part. In corresponding control materials, 79% and 99% of pollen tubes contained the VN and GC close to the apex. Indirect immunofluorescence microscopy and related studies of the tubes grown in the presence of oryzalin revealed complete absence of microtubules (MTs) but apparently intact microfilaments (MFs). These results suggested that the movement of VN and GC from the grain into the tube is possible when no MTs but only MFs are present, but the movement is then slow. In control tubes, the parallel orientation of MT bundles and extensions of VN were interpreted to represent the structural organization needed for the MT-dependent movement of VN.     

Hydrophobic surface properties of erythrocytes studied by affinity partition in aqueous two-phase systems

Summary Erythrocytes from various species have been partitioned in aqueous two-phase systems consisting of water, dextran, poly-(ethylene glycol), salt and buffer. The terminal hydroxyl groups of the latter polymer were esterified with palmitic, oleic, linoleic and linolenic acids, as well as with deoxycholic acid. In a two-phase system containing unesterified poly(ethylene glycol) the erythrocytes are exclusively in the dextran-rich lower phase. When the poly(ethylene glycol) is esterified the red blood cells collect at the interface and/or in the poly(ethylene glycol)-rich upper phase depending on the type and concentration of esterified acid. Palmitate ester is most effective in increasing the affinity of the cells for the upper phase, followed by oleate, linolate, linolenate, and deoxycholate esters. The partition behaviour of erythrocytes from various species differs considerably. Two groups can be distinguished: one consisting of erythrocytes from dog, guinea pig and rat, the other from human, sheep and rabbit. This division can be correlated to the content of sphingomyelin and phosphatidyl choline in the erythrocyte membranes.     

Reproduction mode and crop improvement

Summary The author has tried to accumulate data on the reproduction modes of crop plants: autogamy and allogamy in the case of sexuality, involving self-fertility and self-sterility, and different means of vegetative propagation and apomixis. In combination with the state of ploidy and the basic chromosome number the different modes of reproduction exert a considerable influence on population structure and the success or failure of different methods applied in plant breeding. This relates to the use of selection, hybrid vigour (F₁ heterosis), gene recombination, as well as polyploidy and induced or spontaneous mutation. It is pointed out that extranuclear (cytoplasmic) inheritance should not be neglected as a device also in the case of polyploidy and mutation.Transitional stages exist between autogamy and allogamy. Autogamy is obligate in no or at least very few cases. In allogamous species inbreeding and subsequent outcrossing are important features in their improvement by breeding. In dioecious, monoecious and hermaphroditic species the modes of reproduction can be switched into one another by appropriate methods of gene recombination, mutation and selection. Apomictic species, for instance several grasses, display a series of transitions between more or less obligatory apomixis (parthenogenesis and vivipary) and partial or complete sexuality.At the end of the article data are presented to indicate how various modes of reproduction influence the methods applied in the exploration and conservation of plant gene pools.Finally, the pioneer work on plant exploration carried out byVavilov, Zhukovsky and their co-workers is emphasized. Favourable genes, chromosomes and cytoplasms present in natural populations have to be preserved. New favourable genes etc. should be continually produced by mutation. Preservation of old genes and induction of new genes are means of augmenting the breeders' resources in their efforts of continuous crop plant improvement.

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Zusammenfassung Es werden die verschiedenen Formen der Fortpflanzung bei Kulturpflanzen behandelt, wie Auto-und Allogamie bei geschlechtlicher Vermehrung, einschließlich Selbstfertilität und Selbststerilität, und die verschiedenen Möglichkeiten der vegetativen Vermehrung und Apomixis. In Verbindung mit dem Ploidiegrad und der Chromosomengrundzahl haben die verschiedenen Fortpflanzungsformen einen erheblichen Einfluß auf die Populationsstruktur und auf den Erfolg oder Mißerfolg der einzelnen in der Pflanzenzüchtung angewandten Methoden. Das gilt für die Anwendung von Selektion, F₁-Heterosis und Genrekombination ebenso wie für Polyploidie und induzierte oder spontane Mutation. Es wird betont, daß die plasmatische Vererbung, auch im Falle von Polyploidie und Mutation, nicht außer acht gelassen werden sollte.Zwischen Auto- und Allogamie sind Übergangsstadien vorhanden. Autogamie ist in keinem Fall oder wenigstens in sehr wenigen Fällen obligatorisch. Bei allogamen Species sind Inzucht und nachfolgende Kreuzung wesentliche Möglichkeiten für eine Leistungssteigerung durch Züchtung. Bei diözischen, monözischen und hermaphroditen Species kann die Fortpflanzungsform durch geeignete Methoden der Genrekombination, Mutation und Selektion geändert werden. Apomiktische Species, z. B. verschiedene Gräser, zeigen Übergänge zwischen mehr oder weniger obligatorischer Apomixis (Parthenogenesis und Viviparie) und teilweiser oder völliger Sexualität.Am Schluß der Arbeit werden Beispiele gebracht, wie die verschiedenen Fortpflanzungsformen die Methoden beeinflussen, die bei der Erforschung und Erhaltung der pflanzlichen Gen-Pools angewendet werden.Schließlich wird die Pionierarbeit vonVavilov, Zhukovsky und ihren Mitarbeitern gewürdigt.Günstige Gene, Chromosomen und Cytoplasmen, die in natürlichen Populationen vorhanden sind, müssen erhalten bleiben. Neue günstige Gene usw. sollten laufend durch Mutation geschaffen werden. Die Erhaltung der alten Gene und die Induktion neuer sind Hilfsquellen für den Züchter in seinem Bemühen um fortgesetzte Leistungssteigerung der Kulturpflanzen.

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In condensed form this article was presented at the FAO technical conference on Exploration, utilization and conservation of plant gene resources, Rome, September 1967. It is here, with all reverence, dedicated to the memory ofN. I. Vavilov and the noble spirit of his friend and successorP. M. Zhukovsky.     

Spermiogenesis in two species ofNebalia leach (crustacea,malacostraca, phyllocarida)

Summary Spermiogenesis inNebalia pugettensis andN. sp. of the subclass Phyllocarida was investigated by transmission electron microscopy. Spermiogenesis is almost identical in the two species. Early spermatids are found in groups with several nuclei in a common cytoplasm. Specializations of the cell surface appear as small, scattered dense knobs underlying the cell membrane. The spermatids become separated but are kept together by a surrounding vegetative cell, which produces a hyaline secretion. The secretion hardens to a capsule surrounding a number of spermatids. Maturation of the spermatids takes place within the secretion. The cells become dense and compact, the cytoplasm vacuolizes, and the mitochondria show signs of degeneration. The centrioles disappear and the surface of the cell becomes irregular and spiny, as the knobs, present in the early spermatids, develop into small spines. Spermatozoa from a spermatophore are small and compact spiny cells without polarity, with a vacuolized cytoplasm and degenerating mitochondria. Acrosomal structures and axonema or flagellum are absent in all developmental stages of theNebalia sperm.     

Plasmodium lophurae: Membrane Proteins of Erythrocyte-free Plasmodia and Malaria-Infected Red Cells*

SYNOPSIS. Plasma membranes of normal duckling erythrocytes were prepared by blender homogenization and nitrogen decompression. Surface membrane vesicles of red cells infected with the avian malaria Plasmodium lophurae were produced by nitrogen decompression. Membranes of erythrocyte-free malaria parasites were removed from cytoplasmic constituents by Dounce homogenization. These membranes were collected by centrifugation in a sucrose step gradient and purified on a linear sucrose gradient. Red cell membranes had a buoyant density of 1.159 g/cm³, whereas plasmodial membranes banded at 2 densities: 1.110 g/cm³ and 1.158 g/cm³. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the isolated red cell membranes revealed 7 major protein bands with molecular weights (MW) ranging from 230,000 to 22,000, and 3 glycoprotein bands with MW of 160,000, 88,000 and 37,000. Parasite membranes also had 7 major bands with MW ranging from 100,000 to 22,000. No glycoproteins were identifiable in these membranes. The proteins of the surface membranes from infected red cells had MW similar to those from normal red cells; however, there was some evidence of a reduction in the amount of the high MW polypeptides. The red cell membrane contained 79 nmoles sialic acid/mg membrane protein, whereas plasmodial membranes had 8 nmoles sialic acid/mg membrane protein. The sialic acid content of the surface membranes of infected red cells was significantly smaller than that of normal cells. Lactoperoxidase-glucose oxidase-catalyzed iodination of intact normal and malaria-infected erythrocytes labeled 7 surface components. Although no observable differences in iodinatable proteins were seen in these preparations, there was a striking reduction in the iodinatability of erythrocytic membranes obtained from P. lophurae-infected cells. Erythrocyte-free plasmodia bound very little radioactive iodine; the small amount of radioactivity was distributed among 3 major bands with MW of 42,000, 32,000 and 28,000. It is suggested that the alterations of the surface of the P. lophurae-infected erythrocyte do not occur by a wholesale insertion of plasmodial membrane proteins into the red cell plasma membrane, but rather that there are parasite-mediated modifications of existing membrane polypeptides.     

A Modified Method for the Detection of Antibiotic Residues in Slaughter Animals

Biological methods in current use for the detection of antibiotic residues in slaughter animals are reviewed. A modified method is suggested in which the conditions for the control have been standardized. By the use of a semi-defined medium, the batch-to-batch variations are minimized. In order to facilitate the detection of sulfonamides the medium is supplemented with trimethoprim. The standardized conditions included the use of a sporulating organism, Bacillus subtilis, an inoculum size of 0.5 × 105 spores per ml medium, and 5 ml medium of pH 6.0 per plate. A preincubation-diffusion time of 1 h in room temperature is recommended before incubation. The modified method was compared with the currently prescribed Swedish method. The new method was easier to perform and showed a more uniform sensitivity to most of the antibiotics used.