Studies on the chemical modification of potato (Solanum tuberosum) lectin and its effect on haemagglutinating activity

1. Modification of potato (Solanum tuberosum) lectin with acetic anhydride blocked 5.1 amino and 2.7 tyrosyl groups per molecule of lectin and decreased the haemagglutinating activity of the lectin. De-O-acetylation regenerated 2.0 of the tyrosyl groups and resulted in a recovery of activity. 2. Modification with citraconic anhydride or cyclohexane-1,2-dione did not greatly affect activity, although modification of amino and arginyl groups could be demonstrated. 3. Treatment with tetranitromethane nitrated 3.7 tyrosine residues per molecule of lectin with concomitant loss of activity. The presence of 0.1m-NN′N″-triacetylchitotriose (a potent inhibitor of the lectin) in the reaction medium protected all the tyrosyl residues from nitration and the lectin was fully active. 4. Modification of tryptophyl groups with 2-hydroxy-5-nitrobenzyl bromide and 2,3-dioxoindoline-5-sulphonic acid modified 0.9 and 2.6 residues per molecule of lectin respectively with a loss of activity in each case. Reaction of potato lectin with 2,3-dioxoindoline-5-sulphonic acid in the presence of inhibitor protected 2.4 residues of tryptophan from the reagent. Loss of haemagglutination activity was prevented under these conditions. 5. Reaction of carboxy groups, activated with carbodi-imide, with α-aminobutyric acid methyl ester led to the incorporation of 5.3 residues of the ester per molecule of lectin. Presence of inhibitor in this case, although protecting activity, did not prevent modification of carboxy groups; in fact an increase in the number of modified residues was seen. This effect could be imitated by performing the reaction in 8m-urea. In both cases the number of carboxy groups modified was close to the total number of free carboxy groups as determined by the method of Hoare & Koshland [(1967) J. Biol. Chem. 242, 2447–2453]. Guanidination of lysine residues after carboxy-group modification gave less homoarginine than did the unmodified lectin under the same conditions, suggesting the formation of intramolecular cross-links during carbodi-imide activation. 6. It is suggested from the results presented that amino, arginyl, methionyl, histidyl and carboxyl groups are not involved in the activity of the lectin and that tyrosyl and tryptophyl groups are very closely involved. These findings are similar to those reported for other proteins that bind N-acetylglucosamine oligomers and also fit the general trend in other lectins.     

A light- and electron-microscopic investigation of gametogenesis in Typosyllis pulchra (Berkeley and Berkeley) (polychaeta: Syllidae)

Summary Typosyllis pulchra reproduces by the production of three to four gamete-bearing stolons (schizogamy) during consecutive 30-day periods. Although gonads are found in a large number of segments, only those in the posterior-most segments produce gametes and become incorporated into the developing stolon. The more anterior gonads remain undifferentiated and probably sexually undetermined until they are needed in future stolonizations. Gonial cells, which will eventually become either male or female, are ultrastructurally identical at the onset of each stolonization period. Spermatogenesis is marked by a short proliferative period followed by differentiation and spermiogenesis. The first ultrastructural signs of spermatogenesis were found in coelomic spermatogonia on day 10 of stolon formation. Spermatogonia are joined by intercellular bridges, which are maintained until the early spermatid stage. Synaptonemal complexes mark the onset of meiosis, which is apparently synchronized in the syncytial clusters of primary spermatocytes. Spermiogenesis occurs during the final 10 days of stolonization and a variety of stages is present within a single animal. All sperm mature by the time the stolon detaches. Acrosome formation and nuclear condensation are described in addition to the ultrastructure of mature sperm.     

The effect of prostaglandins A2,E1,E2,15 methyl E2, 16, 16 dimethyl E2 and F2α on erythropoiesis

Prostaglandins A₂, E₁, E₂, methylated E₂s and F₂α affected erythropoiesis and/or erythropoietin (Ep) production. This action is indicated in the exhypoxic, polycythemic mouse where radioiron incorporations into RBC increased after administration of these compounds. The kidney and liver have been indicated through previous studies, to actively participate in Ep production. By the removal of one of these active sites in a murine system treated with prostaglandins it is shown that a response is reflected in Ep levels. Interference of the action of prostaglandins (PG) is altered by the removal of one of these target sites of Ep production. The erythropoietic responses elicited by PGA₂, E₁, and perhaps the methylated PGE₂s act through the liver whereas PGE₂ may operate through a renal pathway for its response. PGF_2α reveals no effect on erythropoietic activity and is no different than that observed for vehicle-treated controls. The prostaglandins tested appear to act primarily through the kidney or liver but the possibility exists that some yet undetermined organ site may also be involved.     

Fine structure of seminiferous tubules in antarctic seals

Summary The fine structure of seminiferous tubules from 5 crabeater, 2 leopard and 2 Ross seals showed that during the nonbreeding season the tubules were essentially similar in possessing spermatogenic and Sertoli cells. However, the tubules of leopard and Ross seals had more primary and secondary spermatocytes and spermatids than the crabeater seals. In general, the tubules were devoid of spermatozoa. The spermatids showed stages of maturation such as Golgi phase of acrosome formation, acrosomal cap formation and condensation of nuclei. Some spermatids degenerated in tubules. Both maturing and degenerating spermatids were closely associated with Sertoli cells. Junctional complexes with plaques of filaments were observed between Sertoli cells and the spermatogenic cells. Sertoli cells, irregular and polygonal, contained highly convoluted nuclei, strands of rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi complexes, small mitochondria, variable amounts of lipid droplets, lysosomes, lipofuscin granules and highly plicated plasma membranes. In brief, the spermatogenic activity had practically ceased in the testes and the animals probably secreted low levels of testosterone during the nonbreeding season.This research was supported in part by National Science Foundation Grants G.U. 30270 and G.U. 29829X from the Office of Polar Program and by NIH Grant 5 R01 AM11-376     

Clozapine-induced agranulocytosis

Summary An epidemic of agranulocytosis and granulocytopenia occurred in 1975 in conjunction with clozapine treatment of mental patients in Finland. An attempt was made to assess the epidemiologic and genetic factors contributing to the adverse drug effect. The estimated incidence rate in Finland was 2.1/1000 patient-months. This figure could not be compared with rates from other countries because of the inexact nature of the figures reported so far. All 16 cases occurred in seven hospitals in southwestern Finland, whereas the overall hospital net use of the drug was geographically evenly distributed. The difference between the observed and the proportionally expected incidence of cases amongst the hospitals where clozapine was used was statistically significant. The average consumption of the drug did not differ between the hospitals where cases occurred and those where no definite cases could be diagnosed. Six-generation pedigree analyses failed to reveal significant parental consanguinity or genetic kinship between probands. Neither did the birth places of the ancestors of the probands disclose a typical isolate pattern. In conclusion, the cases appeared to be confined to a few hospitals in southwestern Finland. Although a genetic factor is not excluded, we found no evidence in support of a genetic mechanism.     

Amber mutations in Escherichia coli essential genes: isolation of mutants affected in the ribosomes.

Summary A method to obtain amber mutations in ribosomal protein genes is described. It relies on the P1-mediated localized mutagenesis (Hong and Ames, 1971) and on the fact that the recipient strain contains (a) an efficient but genetically unstable suppressor, (b) a particular thermoinducible prophage which kills suppressor hosts at 42° C. Exposure of these bacteria to the high temperature yields frequent suppressor-free derivatives while none will be found if the strain carries an amber mutation in an essential gene. Eleven mutants have been isolated by this method, of which at least six appear to carry amber mutations. All of them map close to, and to the right of spcA, in a region which codes mostly for ribosomal proteins. Three mutants were studied biochemically; all three show defective ribosomal assembly in vivo upon loss of suppression.     

Terpen-derivate aus Senecio-arten

Investigation of about 50 Senecio species has afforded many new substances, in addition to known compounds. Present in these plants are 23 fura