Chromosomal rearrangements by an IS2 insertion in phage Mu-1

We have isolated and characterized a mutant of temperate phage Mu-1 carrying an IS2 insertion in the middle of its β region. This mutant gives rise spontaneously to secondary mutants which have deletions of different sizes adjacent to IS2. One particular derivative however, was found to have acquired an additional insertion sequence adjacent to IS2. This derivative gave rise to tertiary mutants carryinh a deletion next to the tandem insertion. The tandem insertion was located at the same place in the Mu β region as another 2.6 kb insertion independently isolated by Chow et al. (1977) and was found to be homologous to that insertion. The properties of this particular secondary mutant show that Mu phage particles lacking their S end are defective for growth and lysogenisation.     

How obstetricians manage hypertension in pregnancy.

One thousand and ninety-three obstetricians answered a questionnaire on the management of pregnant women with pre-existing hypertension and pre-eclampsia. They reported that they frequently used antihypertensive drugs (most often methyldopa and diuretics) in severe essential hypertension but tended to give sedatives in mild cases. Renal impairment was considered more important that raised blood pressure as an indication for terminating pregnancy; but even without a raised blood urea concentration over a quarter of respondents (especially the more senior obstetricians) would have considered it. The more junior obstetricians were more likely to admit the least severely affected patients to hospital. Pre-eclampsia was usually treated with bed rest and sedatives (most frequently diazepam); but the choice of drug varied with the seniority of the respondents, the more senior obstetricians tending to confine themselves to the more familial drugs. There was considerable unanimity in the replies, even though most of the treatments and practices have not been validated by controlled trials, and two-thirds of the obstetricians gave the same answers to most of the questions.     

Aspects of population dynamics in Halimione portulacoides communities

Summary Studies on sample plots inHalimione portulacoides communities show that environmental disturbances, either natural or induced by man, start a sequence of partly overlapping density maxima inSuaeda maritima, Aster tripolium andPuccinellia maritima successively, before the originalHalimione community totally recovers. When succession time before recovering is long enough, there are tendencies in redundancy of this sequence stressing the unilinear character of the succession. Minor environmental impacts induce a longer time-lag period of theSuaeda density maximum, suggesting threshold values of these impacts for the species to maintain minimal population densities or to become locally extinct. This sequence of interim species starting after an environmental disturbance, suggests also a gradient character in various biological attributes, for instance in life-time, propagation, nutrient and genetic plasticity strategies. The mechanism described can therefore be interpreted as a complex of mostly well-adapted and well-integrated inherent species strategies capable of absorbing environmental shocks. It is suggested that in the salt-marsh ccosystem the pattern of spatial variation in densities and that of temporal variation in fluctuations of the three species populations under natural conditions reflect corresponding patterns of environmental disturbances in the vegetation taking into account a timelag associated with the magnitude of the impact concerned.Contribution to the Symposium on Plant species and plant communities held at Nijmegen, 11–12 November 1976, on the occasion of the 60th birthday of Professor Victor Westhoff.Nomenclature follows Heukels-van Ooststroom. Flora van Nederland, 18e druk, 1975. Wolters-Noodhoff, Groningen.The authors are greatly indebted to Dr K.F. Vaas (Yerseke) for reviewing the English text.Communication Nr. 160.     

Stored and polysomal ribosomes of mouse ova

RNP particles of ovulated mouse ova, labeled by exposure of growing oocytes to [³H]uridine, were displayed on sucrose gradients. Under standard salt conditions, radioactivity was observed coinciding with liver ribosomal subunits, monomers, and polysomes. The RNA from each region of the gradient was isolated and was found to contain the expected species of labeled 18S and/or 28S ribosomal RNA. Heterogeneous RNP particles were widely distributed in the gradient. From data on RNase sensitivity and resistance to dissociation in high salt, it was estimated that 20–25% of the total ribosomes were in polysomes. No difference in the distribution was observed when ribosomes were labeled in the early or late growth phase of the oocyte. The evidence suggested that the nonpolysomal subunits and monomers were unable to form a high salt-stable complex in the presence of poly(U) and factors for protein synthesis. Thus, the bulk of the ribosomes are inactive in protein synthesis in ovulated ova and are apparently stored for use in embryonic development.     

Purification and characterization of a complex between cloacin and its immunity protein isolated from Enterobacter cloacae (Clo DF13). Dissociation and reconstitution of the complex.

Cell of Enterobacter cloacae (Clo DF13) produce a bacteriocin which is characterized by its very effective killing activity against sensitive bacteria. Purification and characterization of the excreted bacteriocin has revealed that this bacteriocin consists of an equimolar complex of two plasmid-specific gene products: the cloacin and its inhibitor the immunity protein. Dissociation of the complex by treatment with sodium dodecylsulfate induces the endonucleolytic activity of the cloacin but strongly reduces the killing activity. The purified complex possesses no activity in vitro. Both cloacin and immunity protein isolated from the complex were functionally identical to cloacin and immunity protein purified from the bacteriocinogenic cells by other methods. Reconstitution of the complex results in a partial restoration of killing activity.     

Assembly of Bacillus subtilis phage phi29. 1. Mutants in the cistrons coding for the structural proteins.

The effect of mutations in the cistrons coding for the phage structural proteins has been studied by analyzing the phage-related structures accumulated after restrictive infection. Infection with susmutants in cistron 8, lacking both the major head and the fiber protein, does not produce any phage-related structure, suggesting a single route for the assembly of phage phi29; infection with ts mutants in this cistron produces isometric particles. Mutants is cistron 9, coding for the tail protein, TP1, produce DNA-free prolate heads with an internal core; these particles are abortive and contain the head proteins HPO, HP1 and HP3, the upper collar protein NP2 and the nonstructural proteins p7, p15 and p16. Mutants in cistron 10, coding for the upper collar protein, NP2, produce DNA-free isometric heads also with an internal core; they contain the head proteins and the nonstructural protein p7, suggesting that this protein forms the internal core. Mutants in cistrons 11 and 12, coding for the lower collar protein, NP3, and the neck appendages, NP1, respectively, give rise to the formation of DNA-containing normal capsids and DNA-free prolate particles, more rounded at the corners than the normal capsids and with an internal core; the DNA-containing 11-particles are formed by the head proteins and the upper collar protein; the DNA-free 11-particles contain, besides these proteins, the nonstructural protein p7 and a small amount of proteins p15 and 16. The DNA-containing 12-particles have all the normal phage structural proteins except the neck appendages, formed by protein NP1; the DNA-free particles are similar to the DNA-free 11-particles. After restricitive infection mutant sus14(1241) has a delayed lysis phenotype and produces a phage burst higher than normal, after artificial lysis. It produces DNA-containing particles, identical to wild-type phage, which have all the normal phage structural proteins, and DNA-free prolate particles, more rounded at the corners than the final phage particles and with an internal core; the last particles contain the same proteins as the DNA-free 11 or 12-particles. These particles could represent a prohead state, ready for DNA encapsulation. None of the DNA-containing particles have the nonstructural proteins p7, p15 or p16, suggesting that these proteins are released from the proheads upon DNA encapsulation.     

Control of galactosyl diglycerides in wheat endosperm by group 5 chromosomes

Lower levels of monogalactosyl diglyceride (MGDG) and digalactosyl diglyceride (DGDG) have been found in tetraploid wheats as compared with those in hexaploid wheats. The same difference has been found between hexaploid cultivars and tetraploid lines derived from them by D genome extraction. A lower level of MGDG and DGDG is also present in Triticum carthlicum (AABB) as compared with Aegilops squarrosa (DD) or with the synthetic T. spelta (AABBDD) obtained from them. Analysis of the appropriate nullitetrasomic and ditelosomic lines indicates that a gene or genes located in the short arm of chromosome 5D are responsible for the observed difference and that group 5 chromosomes can be ranked as to their influence on the MGDG and DGDG levels in the order 5B > 5D > 5A and 5D > 5B > 5A, respectively. These results further support our previous identification of DGDG as the lipid factor responsible for petroleum ether solubility of lipopurothionins. Since DGDG contributes to baking quality by improving the retention of fermentation gases, the present observations imply that the difference in bread-making quality between the two types of wheat is not due only to proteins contributed by the D genome.