This study aims to evaluate in detail the biological osteoconductive properties of the low-temperature synthetic porous calcium-deficient hydroxyapatite and to compare it with the biological apatite. Bone reactions to granules of similar sizes of the low-temperature hydroxyapatite and commercially available non-sintered deproteinized bovine bone were compared. Two different temperatures were used to fabricate two batches of newly developed porous hydroxyapatite with different carbonate groups content and specific surface area. The histological analysis of specimens with histomorphometry was performed at different time after in vivo implantation. Based on histological analysis, the level of bone formation in the spaces between the implanted granules and through the interconnected pores of all implanted materials within a cortical region (bone area ingrowth 72-85 %) was several-fold higher than within a cancellous bone site (bone area ingrowth 16-28 %) at three and six months after implantation. Within the cancellous bone site, bone coverage of the implanted material at six months was significantly higher in hydroxyapatite material fabricated using low-temperature synthesis and subsequent processing at 150°C than in hydroxyapatite scaffold developed using low-temperature synthesis with subsequent processing at 700°C or deproteinized bovine bone. According to our study, the bioactive properties of the low-temperature calcium-deficient hydroxyapatite are comparable with the biological apatite. The favourable influence of a high specific surface area of a low-temperature calcium-deficient hydroxyapatite on in vivo bone formation was emphasized.

The course of protein degradation during growth of a [14C]leucine-labelled population of BaciZZus megaterium with a surplus of the non-radioactive amino acid indicated the presence of a labile protein fraction decaying with a half-life of less than 1 h. The half-life of the remaining 'stable' fraction was much longer (40 h or more). A nutrient shift-down increased, and a shift-up decreased the relative size of the labile fraction and the rate of degradation of the 'stable' fraction. When bacteria were prelabelled in the presence of ethionine, both the size of the labile fraction and the rate of degradation of the 'stable' fraction were increased. A shift-up in temperature caused a large increase in the size of the labile fraction while the rate of degradation of 'stable' proteins increased only slightly. The rate of degradation of the labile fraction was not changed significantly by any treatment. The results suggest that the main target of regulation of protein turnover by environmental conditions is the relative size of the labile protein fraction. I N T R O D U C T I O NPartial or complete degradation of protein molecules in growing bacterial populations appears to play a role primarily in protein processing or the removal of abnormal proteins, such as the products of translational errors. The half-lives of such processes are probably no longer than several minutes (Pine, 1970; Goldberg, 1972; Bukhari & Zipser, 1973). In a special case, the germination of spores of bacilli, the labile protein fraction is formed by several kinds of proteins, synthesized during sporogenesis; their degradation supplies the germinated spore with amino acids making possible a rapid onset of protein synthesis (Setlow, 1975). However, most proteins in growing bacteria are relatively stable and their degradation rates do not usually exceed 1 % h-' (Goldberg & St John, 1976).The general rate of protein turnover in Escherichia coli is regulated by nutrition as well as by temperature (Pine, 1973). These conclusions were derived mostly from experiments in which the turnover rate was calculated from samples taken at one or two time intervals. Our study of protein turnover in Bacillus megaterium is based on the measurement of the kinetics of protein degradation, from which the proportions of the labile and 'stable' fractions and their degradation constants could be separately determined. We found that the size of the labile fraction, with a half-life of less than 1 h, and to a lesser extent the degradation rate of the 'stable' fraction, are influenced by cultivation conditions. M E T H O D SThe asporogenous strain of Bacillus megaterium KM, and the composition of mineral C medium were described previously (Chaloupka et al., 1975). The medium was supplemented with glucose ( 5 mg ml-I). When the influence of different media was studied, either NH,Cl was omitted and replaced with m-leucine (5 mM) as the sole nitrogen source (C -N + L), or casein hydrolysate (Oxoid; 10mgml-I) was added (C + AA). The media were supplemented with m-leucine (+L; ...

Differences in the regulation of exocellular proteinase synthesis during growth and sporogenesis of Bacillus megaterium. Can. J. Microbiol. 28: 1214-121 8. Bacillus megaterium 27 produces one exocellular metalloproteinase during growth as well as during sporogenesis. The formation of the enzyme during growth is repressed by the addition of amino acids of the leucine-isoleucine group. Its synthesis during sporogenesis is rather insensitive to repression. The enzyme is formed during the first 90 min after transfer to a sporulation medium, amino acids delaying only the onset of its synthesis as well as the onset of sporogenesis. The synthesis of the proteinase in asporogenic B. megaterium KM1 is repressed by amino acids during growth as well as during incubation in the sporulation medium and proceeds for a longer time under the latter condition. The results suggest that the formation of the proteinase during growth may be controlled differently from that during sporulation. CHALOUPKA, J., A. I. SEVERIN, K. J. SASTRY, H. KUEEROVA et M. STRNADOVA. 1982. Differences in the regulation of exocellular proteinase synthesis during growth and sporogenesis of Bacillus megaterium. Can. J. Microbiol. 28: 1214-121 8. Bacillus megaterium 27 produit une mttallo-prottinase exocellulaire durant sa croissance tout c o m e durant la sporogenkse.La formation de l'enzyme pendant la croissance est riprimie par l'addition d'acides amints du groupe leucine-isoleucine. Sa synthkse durant la sporogenbe est plutSt insensible h la ripression. L'enzyme est form6 au cours des 90 premikres min aprks le transfert dans un milieu de sporulation; les acides amints retardent seulement le dtclenchement de sa synthkse tout c o m e le diclenchement de la sporogenbse. La synthkse de la prottinase chez l'asporogbne B. megaterium KM1 est riprimie par les acides aminis durant sa croissance ainsi que durant l'incubation dans le milieu de sporulation et sous cette condition, elle se poursuit plus longtemps. Les rtsultats suggkrent que la formation de la prottinase durant la croissance pourrait Etre sous un contr6le qui differe de celui de la sporulation.[Traduit par le journal]

No abstract

The ARRHENIUS plot of the specific growth rate p of an asporogenic mutant of Bacillus nlegaterium, growing in the range of 17-37 "C followed a straight line, whose slope was affected by the composition of the medium. The maximal p was found a t 40 "C in all media tested and decreased rapidly above 42 "C. The portion of protein degraded also followed a straight line but reached its maximal value a t 45-47 "C. I t s slope was affected substantially by the composition of the medium; the mixture of amino acids suppressed protein degradation a t temperature lower than 37 "C. The extent of the short-lived protein fraction, degraded with the half-time of about 1 h, was mostly affected by both -the temperature and the medium. The amount of proteins degraded per one biomass doubling was almost constant up to 37 "C but was affected by the composition of the medium. At higher temperatures it increased rapidly and reached values of 20-40% of pulselabelled proteins degraded per one cell cycle. The degradation of ethionine-containing proteins was similarly dependent on the temperature but the extent of proteins degraded was increased.The effect of temperature on protein synthesis and growth is inteiisively studied a t present, because temperature is considered to be an important factor regulating various biological processes (SCHLESINGER et al. 1982 (RATKOWSKY et al. 1982 and1983) tried to overcome this problem by using the square root plot.Within a narrow range around the optimal temperature (Topt, i. e. the temperature of the maximal value of p), the ARRHENIUS plot of p usually deviates from the straight line. One of the factors responsible for this deviation could be an increased protein turnover, which could result in a disharmony between protein synthesis and degradation.The effect of temperature on protein turnover in Escherichia coli was first studied by PINE (1967, 1973). He found that an increased temperature stimulated protein turnover and that the estent of protein degradation in growing and starving populations was similar a t supraoptimal temperatures. The extensive protein turnover at high temperatures might be explained by a recent observation that one of the intracellular proteinases is a heat-shock protein (PHILLIPS et al. 1984). Also in Bacillus megaterium, an increased temperature stimulated the initial rate of protein degradation during growth and sporogenesis. However, a slightly supraoptimal temperature may I ) Participant of the UNESCO Course on Modern Problems in Biology and Biotechnology.