pAMβ1 resolvase has an atypical recombination site and requires a histone-like protein HU

The broad-host-range plasmid pAMβ1 from Gram-positive bacteria encodes a resolvase, designated Resβ, which shares homology with the proteins of the resolvase—invertase family. Here we report the purification and in vitro characterization of Resβ. This resolvase is particular in two aspects: it has an atypical binding site and requires a cofactor to promote resolution in vitro . Resβ binds to two regions within its resolution site res . One contains two inverted repeats (R1 and R2), the other contains only one repeat (R3). The cofactor required for resolution in vitro is present in crude extracts of both Bacillus subtilis and Escherichia coli and can be substituted by the E. coli histone-like protein HU. The possible mode of action of HU in the resolution process is discussed.     

Automatic gas meter for laboratory fermenters

Summary A versatile, cheap and automated system is designed for the measurement of small gas flows produced in laboratory-scale fermentation processes. An automatic sampling device for programmed times is linked to the flow meter. The displacement of a liquid by the gas being measured is the principle on which both the meter and the sampling device are based. The operation of the system is controlled by a simple electronic circuit.     

New food sources,conservation of biodiversity and sustainable development: can unconventional animal species contribute to feeding the world?

There is increasing interest in the potential of animal species that do not currently fall within the scope of conventional livestock farming to supplement the production of animal protein for human consumption. This paper provides an overview of the current situation and the conditions the led to it, and offers an analysis of the future of wildlife usage within the general framework of sustainable development.     

Roles for mannose-6-phosphate receptors in lysosomal enzyme sorting, IGF-II binding and clathrin-coat assembly

Two related transmembrane proteins in mammalian cells bind the mannose 6-phosphate recognition marker present on all soluble lysosomal hydrolases. Recent studies of cells that express only one or neither of these proteins have shed light not only on their function in directing lysosomal enzymes into the endocytic pathway but also on their critical role in transport vesicle formation in the trans Golgi network. One of these proteins also binds insulin-like growth factor II (IGF-II) and may be an important part of the IGF-dependent system that regulates development.     

Postjunctional Origin of the indirect-like sympathomimetic effect of metanephrine and normetanephrine on blood pressure

The effects of metanephrine and normetanephrine have been compared with those from equiactive doses of the origin compounds, adrenaline and noradrenaline, on the pressor responses in rat, in order to determine whether their effects are owed, at least partially, to a releasing presynaptic action of the catecholamines in normal animals as well as those pretreated with reserpine, guanethidine and 6-OH-dopamine. Their effects have likewise been studied in isolated perfused renal arteries both in normal and reserpinized rats. None of the adrenolytic agent used were able either to reduce the duration of the hypertensive response or to accelerate tachyphylaxis. Identical results were obtained in renal artery preparations. It is thus concluded that the catecholamines stored in presynaptic endings are not involved in the observed phenomena and it is suggested that they might depend on the high doses required to produce effects equiactive to those of the origin substances.     

Extracellular matrix and capillary ingrowth in interspecies chimeric kidneys

The migration of capillaries into mouse embryonic kidneys grafted on quail chorioallantoic membrane (CAM) was analyzed by two monoclonal antibodies against quail endothelial and haematopoietic cells. As shown by immunohistochemistry, the quail chorioallantoic vessels invaded the kidney explant. Initially, the capillaries were detected in the interstitial stroma and, soon thereafter, tightly adjacent to the branches of the ureteric bud. The induced mesenchymal cell condensates, the prospective nephric vesicles, were avascular, but when the early S-shaped body was formed, the capillaries invaded its lower crevice. Finally chimeric glomeruli consisting of mouse podocytes and quail endothelial cells, were formed and, contemporarily, the capillaries ceased to migrate. Within the endothelial-mesangial area of the chimeric glomeruli, all cells expressed the quail-type nuclear structure and were stained by the quail endothelial-specific antibodies. The pattern of migrating capillaries was compared to the distribution of the extracellular matrix (ECM) molecules by double staining with polyclonal antibodies against laminin or fibronectin, and monoclonal quail endothelial-specific antibodies. Initially, the capillaries migrated in a fibronectin-rich matrix, devoid of laminin, but when the epithelial kidney tubules formed, some capillaries attached to the newly formed epithelial basement membrane. At no stage were the capillaries seen to penetrate the epithelial basement membrane. The orderly branching of the ureteric bud, followed by the formation of nephrons and the shift in the ECM, might create pathways for an oriented capillary migration. The fibronectin-rich areas could be a scaffold for the capillary migration, and the attachment to the basement membranes a means for their cessation.     

Changes in calmodulin and its mRNA accompany reentry of quiescent (G0) cells into the cell cycle

Release of CHO-K1 cells from plateau or stationary phase and reentry into the cell cycle is specifically and reversibly blocked at two distinct sites by the anticalmodulin drug W13. The first block occurs early during release while the cells are still at G0/G1, whereas the second occurs later in reentry during early S phase. As determined by radioimmunoassay, calmodulin levels undergo changes at three distinct steps in plateau-phase entry and release. First, the entry of exponentially growing cells into plateau phase is accompanied by an increase in the calmodulin level. The second change is a reduction in the calmodulin content of cells within the first hour following release from plateau phase. The third change is the subsequent increase in calmodulin levels, which precedes entry of the cells into S phase. Analysis of calmodulin mRNA levels by dot-blot hybridization demonstrates that the changes in calmodulin protein are preceded by changes in calmodulin mRNA. Furthermore, whereas a decrease in CaM mRNA is observed within the first hour following plateau release, no such decrease is observed for beta-actin mRNA, suggesting that this decrease may be selective for calmodulin. This selectivity is further substantiated by the fact that identical changes in calmodulin and calmodulin mRNA are observed in cells released from plateau by two different techniques. Taken together, these data suggest that calmodulin may play an important role in the reentry of cells into the cell cycle.     

Entrapment of l-tryptophan producing Escherichia coli in different matrices: activity of immobilized cells

Cells of Escherichia coli induced for l-tryptophan synthase [l-serine hydro-lyase (adding indole-glycerol-phosphate), EC 4.2.1.20] have been assayed in DMF and DMSO aqueous solvents as reaction medium. Up to 20% DMF/water, cells retained 90% of their tryptophan synthase activity. Concentrations of 20 mM indole, which did not inhibit this reactivity, could be reached with 5% DMF/water. Four matrices were compared for cell immobilization: polyacrylamide, foam particles of bovine seum albumin, alginate and κ-carrageenan. The best activity was retained with the latter matrix, and the preparations thus obtained allowed high productivity of l-tryptophan. Various systems of production of l-tryptophan with κ-carrageenan and DMF/water were studied.     

A large transmissible plasmid is required for crystal toxin production in Bacillus thuringiensis variety israelensis

Bacillus thuringiensis var. israelensis (BTI), serotype 14, which produces parasporal crystals toxic to certain dipteran larvae, was analyzed by agarose gel electrophoresis and found to contain a complex plasmid array. Eight plasmids were detected, with approximate sizes of 3.3, 4.2, 4.9, 10.6, 68, 75, 105, and 135 MDa, as well as a plasmidlike linear DNA element of ~10 MDa. Partially cured mutants of BTI implicated the 75-MDa plasmid in crystal production. Fifteen independently isolated acrystalliferous (Cry^?) mutants were found to lack this plasmid. In plasmid transfer experiments, several of the BTI plasmids transferred into a plasmid-free, Cry^? BTI recipient, but only transfer of the 75-MDa plasmid converted the recipient to crystal toxin production. The presence or absence of mosquito-toxic activity in all Cry⁺ and Cry^? variants of BTI was confirmed by bioassay of sporulated cultures against larvae of Aedes aegypti. Southern blot analyses revealed that in one unusual Cry⁺ variant in which no 75-MDa plasmid band was detectable, plasmid sequences were still present, possibly integrated into the chromosome. The 75-MDa plasmid could also apparently recombine with the 68-MDa plasmid, to which it was partially homologous.