Flagellin as an object for supramolecular engineering

A model of tertiary and quaternary structure of E. coli flagellin is suggested. According to this model, the molecule consists of two independent parts. One of them is formed by the N- and C-terminal regions of the polypeptide chain and is responsible for polymerization properties. The other consists of the central region of the polypeptide chain and composes that part of the molecular globule that forms the flagella surface. It is suggested that different artificial supramolecular structures can be constructed from flagellin molecules by varying the surface domain, i.e. the central part of the polypeptide chain, and by using the domain responsible for polymerization properties as a universal block for assembly. The simplest possible artificial supramolecular structures that can be constructed from flagellins of different strains are discussed.     

Intestinal lactase in the neonatal rat. Maturational changes in intracellular processing and brush-border degradation

The mechanism of decline in the catalytic activity of intestinal lactase during neonatal maturation has not been defined, but a shift in the lactase subunit synthesis from an active 130-kDa subunit to an inactive 100-kDa species has now been noted in the adult rat (Quan, R., Santiago, N. A., Tsuboi, K. K., and Gray, G. M. (1990) J. Biol. Chem. 265, 15882-15888). The subunit structure, synthesis, intracellular assembly, and subsequent degradation of lactase from the brush-border surface membrane was examined in 15-day-old pre-weaned and 30-day-old post-weaned intact rats. Lactase was labeled intraintestinally with [35S]methionine, isolated from Triton-solubilized membranes with monospecific polyclonal anti-lactase, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. The protein-stained gel revealed subunits of 225 and 130 kDa, the latter species predominating in both the pre- and post-weaned state. The distinct adult-type 100-kDa moiety was present in post-weaned animals while only a trace of a slightly larger (approximately 110 kDa) species was observed in pre-weaned animals. Quantitation of radioactivity in newly synthesized lactase revealed an increasing prominence of the 100-kDa species in post-weaned rats (130/100 incorporation ratio: pre-weaned 6.2; post-weaned 3.3). Accumulation of newly labeled lactase in brush-border membranes after intraperitoneal [35S]methionine labeling was similar in both groups at 3 h. Despite these comparable rates of lactase synthesis, assembly and insertion in the pre- and post-weaned state, subsequent removal of the 130-kDa unit was more rapid in post-weaned animals (t1/2 = 11 h; pre-weaned t1/2 = 37 h). In intact rats, the neonatal maturational decline in lactase catalytic activities involves both a shift to production of the inactive 100-kDa subunit and increased membrane surface degradation of the active 130-kDa subunit.     

Effects of high and low molecular soluble factors of the bone marrow on antibody formation and pain sensitivity in animals

In addition to the immunostimulating activity, bone marrow mediators, myelopeptides (MP) show the dose-dependent effect on the development of pain sensitivity in mice. When injected in nanogram amounts, MP induce hyperalgesia and 3-9 fold higher production of antibodies against SREC. When injected in milligram amounts, they exhibit hypoalgesic effect and no influence on antibody production. Immunostimulating effect in MP (mol, mass less than 1 KD, fraction 3) is accompanied with hypoalgesia. Bone marrow factors of mol. masses 40-150 KD (fraction 1) eluted at Sephadex G-25 gel-filtration before MP enhance the pain sensitivity tHreshold and show a potent immunodepressive effect. Thus the bone marrow factors are capable of exhibiting the opposite effects on the immune system in the pain control system that evidences the tight interrelation between these systems.     

The participation of cholinergic structures at different levels in shaping the immediate adaptation of the pancreas to food quality in ontogeny

The experiments on rats showed that the urgent enzymatic adaptations of the pancreas to the quality of food have not been inherent, but have been created in the ontogeny. These adaptations are usually absent during transition to the definitive feeding (23rd day of life). Adaptation for protein stimulant appears in the moment of taking away of mother (30th day of life) and becomes persistent for protein and fat stimulants by the 90th day of life (adult rats). The blockade of different levels' cholinergic structures prevents the normal development of urgent specific pancreas adaptations in all investigated ages.     

Ancient butterfly-ant symbiosis: direct evidence from Dominican amber

Although symbiotic association with ants is pervasive in the butterfly families Lycaenidae and Riodinidae the age of these symbioses has never been estimated explicitly. Here we report the first known fossil riodinid caterpillar. This fossil can be dated minimally between 15 and 20 Ma old, and confidently placed in the extant genus Theope. Differing little from modern day Theope, this fossil from Dominican amber provides direct evidence that secretory and acoustical organs used by modern caterpillars to mediate symbioses with ants have been highly developed at least since the Miocene. This fossil therefore becomes the point of reference for future studies using molecular clock methods for dating these symbioses within the riodinid butterflies. Modern evidence, and the abundance of dolichoderine ants in Dominican amber (now extinct in the West Indies) imply that specialized symbiotic relationships between Theope caterpillars and these ants were likely in existence at least 15 Ma ago. The current distribution of neotropical riodinid butterfly and ant faunas indicates the extinction in the West Indies of at least two unrelated taxa that formed a tightly linked symbiotic association, which persisted to the present elsewhere. <br>     

Pilot study of the Urals population by tooth electron paramagnetic resonance dosimetry

During 1949–1956, about 76 × 10⁶ m³ of radioactive liquid waste containing a total activity of 10¹⁷ Bq was discharged into the Techa River by the first Russian industrial nuclear facility Mayak. As a consequence, the population living in the river valley received considerable internal and external radiation doses. The results of a first application of electron paramagnetic resonance (EPR) of tooth enamel for a retrospective individual dose evaluation of the residents of the Techa riverside are presented. Three main contributions to the dose absorbed in tooth enamel have been considered: external exposure mainly from the Techa River sediments, internal exposure mainly due to ⁹⁰Sr; and background radiation including all other sources of exposure except the Techa River. The teeth of 86 inhabitants of the town Kamensk-Uralskii were analysed to determine the age-dependent contribution of the background radiation to the enamel dose. For 22 residents of the middle and lower Techa riverside, measurements of the ⁹⁰Sr whole-body content and EPR measurements of the absorbed dose in enamel were used to establish a correlation between these two quantities. Finally, absorbed doses in the enamel of five residents of the upper Techa riverside were determined by the EPR method. Contributions of the background radiation and the internal ⁹⁰Sr contamination were subtracted to determine the external exposure of the residents.     

Development of baking yeast from Nigerian palm-wine yeasts

Two local strains of Saccharomyces cerevisiae, Nk, and Nk₂, showed leavening activities of 103% and 102% of that of a commercial yeast strain on wheat flour and of 114% and 113% on composite dough with 40% (w/v) maize substitution. Yeast fusion products Nk/Ng, Nk/Nk₁ and Nk/Nk₂ showed activities of 104% to 113% on wheat flour and 111% to 131% on the composite dough. These advantages were maintained in the yeasts' baking properties and organoleptic qualities. The fusion products also showed enhanced osmotic tolerance, as indicated by good growth in 3%, 6% and 10% (w/v) NaCl and 50% (w/v) glucose. Viability of the fusion products, preserved by drying at 30 to 35°C, dropped to between 62% and 72% after 3 months.A.O. Ejiofor was and N. Okafor and E.N. Ugwueze are with the Department of Applied Microbiology and Brewing, Nnamdi Azikiwe University, P.M.B. 5025, Awka, Nigeria. A.J. Ejiofor is now with the Abteilung Biovertahrenstechnik, Gesellschaft für Biotechnologische Forschung, Mascheroder Weg 1, D-38124 Braunschweig, Germany     

Experimental and theoretical investigations of submerged fermentation and synthesis of pectinolytic enzymes by Aspergillus niger

The growth of the microorganism and the production of the pectinolytic enzyme complex in a stirred 30-l biofermentor using the Aspergillus niger Rehbrücke strain were studied. The time courses of fermentation parameters (formation of biomass, consumption of carbon and inorganic nitrogen source, formation of pectinolytic enzymes) were measured. The formation of biomass showed a distinct lag phase, followed by a log phase with exponential growth and finally a stationary period when cell lysis was beginning. The uptake of the carbon source and inorganic nitrogen source by the A. niger cells corresponded to the time course of growth. The formation of pectinolytic enzymes took place in two steps. The first one was growth-bounded and finished with the end of the log phase of biomass growth. The second step of pectinolytic enzyme formation took place after the end of the catabolite repression of the carbon source and was not growth-bounded. On the basis of the experimental data a mathematical model of the fermentation process was developed. Comparison of the kinetics of the measured fermentation curves and the solution curves of the model showed qualitatively good agreement.     

Decrease in rat cardiac beta 1- and beta 2-adrenoceptors by training and endurance exercise

The cardiac beta-adrenoceptor adaptation to physical activity was investigated in rats which were subjected to a six-week endurance swimming training (ET; n = 7) and a training of high intensity (MT; n = 7). In addition, the effect of a single bout of endurance exercise without preceding training (EE; n = 7) was evaluated. These groups were compared with a sedentary control group (C; n = 9). Beta-adrenergic receptors in rat myocardial membranes were labelled using the high affinity antagonist radioligand (-)125iodocyanopindolol (ICYP). Computer modelling techniques provided estimates of the maximal binding capacity (Bmax) and the dissociation constants (KD). Tissue was constantly kept at temperatures of less than or equal to 4 degrees C and incubated at 4 degrees C for 18 h in buffer containing 100 microM GTP so as to prevent masking of beta-adrenoceptors by endogenous norepinephrine. In comparison with the C group (Bmax = 43.2 +/- 1.6 fmol/mg protein, KD = 11.7 +/- 1.5 pM) computerized coanalyses of saturation binding data of ET, MT, and EE revealed a 13.0%, 25.5%, and 16.6% decrease in Bmax (P less than 0.01), respectively, without significantly differing KD values (10.6 pM, 9.0 pM, 10.5 pM, respectively). We provide the first evidence that acute exercise lowers the sarcolemmal beta-adrenoceptor number in the rat heart. In the competition radioligand binding, CGP20712A and ICI118.551 were employed as subtype-selective antagonists of beta 1- and beta 2-adrenoceptors, respectively, to determine the relative proportions of the receptor subtypes. The ratio of beta 1-/beta 2-adrenoceptors in C was 67.5:32.5 and no statistically significant variation occurred in animals subjected to physical activity. On the basis of published data we assume that acute exercise induces a sequestration of beta-adrenoceptors from the cell surface to some intracellular compartment, whereas the molecular basis of the chronic beta-adrenoceptor down-regulation may involve a training-induced reduction in receptor synthesis. Our findings on cardiac beta-adrenoceptor adaptation to physical activity may represent one of the mechanisms underlying the relative bradycardia in trained subjects.