Nif-hybrids of Enterobacter: selection for nif gene integration with chlorate

The nif gene group from Klebsiella can be transferred into Enterobacter cloacae by conjugation using Escherichia coli donor cells carrying the composite self-transmissible nif-plasmid pRD1. A small fraction of the hybrids obtained is stable upon prolonged passaging without selection. Their stability is due to integration of pRD1 into the chromosome. Such integration hybrids were chlorate resistant, and nitrate reductase negative, which indicated that integration preferentially occurred within one of the genes for the production or functioning of this enzyme. Chlorate resistance could, therefore, be used to select for additional nitrate reductase-negative sublines with pRD1 in their chromosome. Such sublines have been analyzed further for the presence of nif genes, other pRD1 markers, and for stability. In all except one the complete plasmid seems to have been integrated. Some tend to revert to nitrate utilisation (chlorate sensitivity).     

Advantages of arthroscopy of the knee joint]

Arthroscopic surgery causes considerably less soft tissue damage than conventional surgery. As the result of the development of an optical system employed with a chip camera and a video chain arthroscopic knee surgery can be ideally documented with excellent picture quality. Besides the advantage of soft-tissue sparing procedures, diagnosis is substantially improved and operative procedures can be kept to a minimum. This means, in particular in the case of meniscus procedures, that only the damaged areas are removed, this minimising changes to the biomechanics of the knee. The technical equipment, the arthroscopic surgery technic and the advantages of the knee arthroscopy are discussed.     

Synthesis of thiol-functionalized N-acetylmuramyl peptide congeners suitable for their conjugation to target molecules

N-Acetylmuramyl-dipeptide and tripeptide derivatives containing at the C-terminus a masked thiol function, i.e. the S-tert-butylthiocysteamine residue, were synthesized via direct condensation of N-acetylmuramic acid with the peptide moiety using the dicyclohexylcarbodiimide/N-hydroxysuccinimide procedure. Reduction with tributylphosphine in aqueous organic media generates the free thiol function for a selective conjugation of these immunomodulants with target molecules via unsymmetrical disulfide bridging with a second thiol group by the sulfenohydrazide procedure or via thio-ether linkage by the addition to maleimido--or aziridine-derivatives.     

Dark starvation and chloroplast function

Summary Mature spinach plants were held in the dark for several days. The photochemical activities and the activity of some enzymes related to NADP reduction were follwed in the chloroplasts isolated from leaves after dark starvation. Photosystem-II, measured by reduction of DPIP, remained stable during 6 days of darkening. The decrease of NADP reduction which appeared after 2 days of starvation was found to be due to protein autolysis rather than inactivation of the photosystems. The stability of photosystem-I was demonstrated by reactivation of NADP reduction after addition of purified ferredoxin and ferredoxin-NADP-reductase. After 4 days of starvation the restoration of the NADP reduction required in addition another, low-molecular-weight factor. From the isolation procedure and from its properties this factor is assumed to be identical with FRS. However, even in the presence of FRS only half of the total activity is restored after 7 days. The activity of the NADP-reducing system is restored in vivo when plants kept for 7 days in the dark are again illuminated.Abbreviations NADP nicotinamide-adenine-dinucleotide phosphate - DPIP 2,6-dichlorophenolindophenol - DCMU (3,4-dichlorophenyl)-1,1-dimethylurea - FRS ferredoxin-reducing-substance     

Eicosanoid-mediated increase in glucose and lactate output as well as decrease and redistribution of flow by complement-activated rat serum in perfused rat liver

Rat serum, in which the complement system had been activated by incubation with zymosan, increased the glucose and lactate output, and reduced and redistributed the flow in isolated perfused rat liver clearly more than the control serum. Heat inactivation of the rat serum prior to zymosan incubation abolished this difference. Metabolic and hemodynamic alterations caused by the activated serum were dose dependent. They were almost completely inhibited by the cyclooxygenase inhibitor indomethacin and by the thromboxane antagonist 4-[2-(4-chlorobenzesulfonamide)-ethyl]-benzene-acetic acid (BM 13505), but clearly less efficiently by the 5'-lipoxygenase inhibitor nordihydroguaiaretic acid and the leukotriene antagonist N-(3-[3-(4-acetyl-3-hydroxy-2-propyl-phenoxy)-propoxy]-4-chlorine-6-meth yl- phenyl)-1H-tetrazole-5-carboxamide sodium salt (CGP 35949 B). Control serum and to a much larger extent complement-activated serum, caused an overflow of thromboxane B2 and prostaglandin F2 alpha into the hepatic vein. It is concluded that the activated complement system of rat serum can influence liver metabolism and hemodynamics via release from nonparenchymal liver cells of thromboxane and prostaglandins, the latter of which can in turn act on the parenchymal cells.     

Uptake of the aromatic retinoids Ro 10-9359 (etretinate) and Ro 10-1670 (acitretin), its main metabolite, delivered to cultured human fibroblasts by serum proteins. Lack of evidence for perturbation of LDL catabolism

Etretinate or acitretin are efficiently delivered to cultured human fibroblasts in the presence of low density lipoproteins, high density lipoproteins or human serum albumin. In contrast to acitretin, delivery of etretinate to fibroblasts is more efficiently achieved with human serum albumin than with lipoproteins. The uptake of etretinate and acitretin via low density lipoproteins delivery, does not take place via the low density lipoprotein-receptor endocytotic pathway but mostly through a passive exchange with the plasma membrane. However, in contrast to acitretin, the exchange of etretinate seems to occur alter binding of etretinate-loaded low density lipoproteins to the apolipoprotein B receptors. No differences are observed in binding, internalization and degradation of native, etretinate-loaded low density lipoproteins and acitretin-loaded low density lipoproteins, suggesting that the presence of these retinoids in low density lipoproteins does not alter their processing by the cells. Furthermore, the presence of these retinoids in the cells does not notably affect, under our experimental conditions, the catabolism of native low density lipoproteins.     

Bacteriophage-resistance mechanisms examined by transfection of Lactococcus lactis subsp. lactis 4513-5 mediated by high voltage electroporation

Summary Phage adsorption tests and transfection by electroporation were carried out to decide whether phage-resistance in Lactococcus lactis subsp. lactis strain 4513-5 is based on intracellular or extracellular mechanisms. Using high voltage (12.5 kV/cm) electroporation, untreated phage DNA was introduced into phage-sensitive and phage-resistant cells. Since phages showed low adsorption frequencies on resistant bacteria, resistance is localized in the cell wall preventing phage DNA from entering the cell. This is the only mechanism responsible for the resistance of L. lactis subsp. lactis 4513-5 against its homologous phage P4513-K12 and non-homologous phages P05M-13 and P05M-47, but not against phage P530-7 and phage P530-12. In the case of the latter two phage strains, intracellular resistance mechanisms are involved and discussed.     

Methods in clinical hemorheology: the continuous measurement of arterial blood density and blood sound speed in man

Both blood density and sound speed are closely related to total protein concentration in blood and, as a consequence, to rheologically important parameters of blood. Two methods that permit continuous measurement of these properties, the mechanical oscillator technique and the new ultrasonic technique, were used for measuring blood protein concentration over a continuous period of time in a group of hemodialysis patients and in volunteers. It was seen that the concentration of the components of blood varies considerably. This variability is related to transport phenomena within as well as to the flow of masses across the cardiovascular compartment. From the continuous measurement of concentrations during hemodialysis treatment, relative changes in blood volume can be recorded in order to control the fluid balance of the patient. Rapid fluctuations at the macroscopic scale with periods of 5 to 30 seconds are due to heterogeneities at the microscopic scale and to the particular rheological behaviour of the red blood cells at the level of the capillaries and the small blood vessels. The amplitude of rapid oscillations increased up to 1.2% in terms of hematocrit values when there was rhythmic, spontaneous breathing at various frequencies. The measurement of concentrations at an accessible measuring site may be used to investigate the rheology of blood in the human microvasculature.