Proximate ferromagnetic state in the Kitaev model material α-RuCl3

α-RuCl₃ is a major candidate for the realization of the Kitaev quantum spin liquid, but its zigzag antiferromagnetic order at low temperatures indicates deviations from the Kitaev model. We have quantified the spin Hamiltonian of α-RuCl₃ by a resonant inelastic x-ray scattering study at the Ru L₃ absorption edge. In the paramagnetic state, the quasi-elastic intensity of magnetic excitations has a broad maximum around the zone center without any local maxima at the zigzag magnetic Bragg wavevectors. This finding implies that the zigzag order is fragile and readily destabilized by competing ferromagnetic correlations. The classical ground state of the experimentally determined Hamiltonian is actually ferromagnetic. The zigzag state is stabilized by quantum fluctuations, leaving ferromagnetism – along with the Kitaev spin liquid – as energetically proximate metastable states. The three closely competing states and their collective excitations hold the key to the theoretical understanding of the unusual properties of α-RuCl₃ in magnetic fields.

RuCl₃ has stood out as a prime candidate in the search for quantum spin liquids; however, its antiferromagnetic ordering at low temperature suggests deviations from typical QSL models. Here, using resonant inelastic x-ray scattering, the authors provide a comprehensive determination of the low energy effective Hamiltonian.

Risk factors associated with major cerebrovascular complications after intracranial stenting

BACKGROUND

There are limited data on the relationship between patient and site characteristics and clinical outcomes after intracranial stenting.

METHODS

We performed a multivariable analysis that correlated patient and site characteristics with the occurrence of the primary endpoint (any stroke or death within 30 days of stenting or stroke in the territory of the stented artery beyond 30 days) in 160 patients enrolled in this stenting registry. All patients presented with an ischemic stroke, TIA, or other cerebral ischemic event (e.g., vertebrobasilar insufficiency) in the territory of a suspected 50-99% stenosis of a major intracranial artery while on antithrombotic therapy.

RESULTS

Cerebral angiography confirmed that 99% (158/160) of patients had a 50-99% stenosis. In multivariable analysis, the primary endpoint was associated with posterior circulation stenosis (vs anterior circulation) (hazard ratio [HR] 3.4, 95% confidence interval [CI] 1.2-9.3, p = 0.018), stenting at low enrollment sites (< 10 patients each) (vs high enrollment site) (HR 2.8, 95% CI 1.1-7.6, p = 0.038), < or = 10 days from qualifying event to stenting (vs > or = 10 days) (HR 2.7, 95% CI 1.0-7.8, p = 0.058), and stroke as a qualifying event (vs TIA/other) (HR 3.2, 95% CI 0.9-11.2, p = 0.064). There was no significant difference in the primary endpoint based on age, gender, race, or percent stenosis (50-69% vs 70-99%).

CONCLUSIONS

Major cerebrovascular complications after intracranial stenting may be associated with posterior circulation stenosis, low volume sites, stenting soon after a qualifying event, and stroke as the qualifying event. These factors will need to be monitored in future trials of intracranial stenting.

Evidence for two separate energy gaps in underdoped high-temperature cuprate superconductors from broadband infrared ellipsometry

We present broadband infrared ellipsometry measurements of the c-axis conductivity of underdoped RBa_{2}Cu_{3}O_{7-delta} (R=Y, Nd, and La) single crystals. Our data show that separate energy scales are underlying the redistributions of spectral weight due to the normal state pseudogap and the superconducting gap. Furthermore, they provide evidence that these gaps do not share the same electronic states and do not merge on the overdoped side. Accordingly, our data are suggestive of a two gap scenario with a pseudogap that is likely extrinsic with respect to superconductivity.

The NIH registry on use of the Wingspan stent for symptomatic 70-99% intracranial arterial stenosis

BACKGROUND

The Warfarin-Aspirin Symptomatic Intracranial Disease (WASID) trial showed that patients with symptomatic 70% to 99% intracranial arterial stenosis are at particularly high risk of ipsilateral stroke on medical therapy: 18% at 1 year (95% CI = 3% to 24%). The Wingspan intracranial stent is another therapeutic option but there are limited data on the technical success of stenting and outcome of patients with 70% to 99% stenosis treated with a Wingspan stent.

METHODS

Sixteen medical centers enrolled consecutive patients treated with a Wingspan stent in this registry between November 2005 and October 2006. Data on stenting indication, severity of stenosis, technical success (stent placement across the target lesion with <50% residual stenosis), follow-up angiography, and outcome were collected.

RESULTS

A total of 129 patients with symptomatic 70% to 99% intracranial stenosis were enrolled. The technical success rate was 96.7%. The mean pre and post-stent stenoses were 82% and 20%. The frequency of any stroke, intracerebral hemorrhage, or death within 30 days or ipsilateral stroke beyond 30 days was 14.0% at 6 months (95% CI = 8.7% to 22.1%). The frequency of >or=50% restenosis on follow-up angiography was 13/52 (25%).

CONCLUSION

The use of a Wingspan stent in patients with severe intracranial stenosis is relatively safe with high rate of technical success with moderately high rate of restenosis. Comparison of the event rates in high-risk patients in Warfarin-Aspirin Symptomatic Intracranial Disease (WASID) vs this registry do not rule out either that stenting could be associated with a substantial relative risk reduction (e.g., 50%) or has no advantage compared with medical therapy. A randomized trial comparing stenting with medical therapy is needed.

[Obesity--a risk factor]

The nutritional status of a selected population--859 male members of the Fire Rescue Service from 12 districts in the Czech Republic--was assessed in 1997 and 1998. The study provides extensive information on selected anthropometrical and biochemical parameters, especially on those, which are generally used as risk indices for the origin and development of cardiovascular disease (CVD): body mass index (BMI), body fat percentage (b. fat), waist circumference (waist), serum concentrations of total cholesterol (Tchol), HDL- and LDL-cholesterol (HDL-chol, LDL-chol), triacylglyceroles (TAG) and the atherogenic index (AI). As far as lipid parameters were concerned, increased serum levels were estimated in 30.4% (TAG), 54% (Tchol) and 60.9% (LDL-chol) of volunteers. Decreased serum levels of HDL-chol were found in 38.2% of volunteers. An AI higher than 3.5 a.u. was calculated for 79.9% of all subjects in study while an AI higher than 5.0 a.u. was calculated for 45.3% of all subjects. An AI higher than 3.5 a.u. was found in 62% of males with normal weight, in 85% of overweight males and in 92% of obese males. The results of the study proved the considerable prevalence of the overweightness and obesity in the male population group that was followed: according to the calculated BMI, 49.5% of volunteers were estimated to be overweight and 16.3% to be obese. The study concept made it possible to reveal the relationships among the anthropometrical and biochemical parameters followed. The correlation matrix documents a statistically significant dependence among the BMI or waist values and the serum concentrations of Tchol, LDL-chol, TAG and AI. A significant negative correlation was found between the HDL-chol serum concentration and the BMI or waist values. The variance analysis results (the estimated lipid parameter values were divided into groups according to BMI and waist categories) document a statistically significant increase in serum Tchol, LDL-chol, TAG and AI in age categories over 35 years in comparison with the category of men under 25 years of age. For Tchol and LDL-chol a statistically significant increase had already been found in the 25-35 year age category. In comparison with the normal weight category, Tchol serum levels and AI values were statistically significantly higher in both the overweight and obese categories. Statistically significant increase was proven for the TAG and LDL-chol serum levels in both the overweight II. gr. and obese categories. A statistically significant decrease in comparison with the normal weight category was found in the HDL-chol serum levels of both the overweight and obesity categories. In the same way, an increase in Tchol and LDL-chol, TAG serum concentrations and AI values in higher and high risk CVD categories (according to the waist circumference value) was found in comparison with the low CVD risk category.

Strong-field double ionization of rare gases

We have studied the double ionization of helium and other rare gases using an electron-ion coincidence technique. With this scheme, the electron energy spectrum correlated to the creation of a doubly charged ion may be compiled. In all cases, the observed double ionization electron distributions are similar and enhanced at high energies, while the single ionization spectra exhibit distinct differences.

Differences in the regulation of the intracellular Ca2+-dependent serine proteinase activity between Bacillus subtilis and B. megaterium

A rise of the intracellular serine proteinase activity (ISP) during postexponential growth of Bacillus subtilis was decreased by a temperature upshift from 35 degrees to 42 degrees C. However, the amount of both molecular forms of the major intracellular serine proteinase ISP1 determined by immunoblotting was similar at both temperatures or even slightly increased at 42 degrees C. The evolution of the ISP activity in B. megaterium showed an opposite temperature dependence, being faster during growth at 42 degrees C. The amount of immunologically detected ISP1 again did not correlate well with the enzyme activity. Moreover, most of the ISP1 molecules in cell-free extracts from B. megaterium were inactive and were activated by increasing the CaCl2 concentration up to 30 mM--unlike B. subtilis, where the enzymic activity was unaffected by Ca2+ concentration. These data suggest that the ISP1 activity in the two bacillar species during postexponential growth is regulated posttranscriptionally, but that the regulatory mechanisms differ.

[Prevalence of obesity in selected subpopulations in the Czech Republic]

The authors present the results of an epidemiological study focused on monitoring selected anthropometric parameters which characterize the nutrition state. 933 volunteers altogether, in age group 19-60 years, were tested in the study. Anthropometric parameters such as weight, height, skinfold thickness and abdomen circumference were measured. BMI and fat tissue percentage were calculated on the basis of gathered data. Overweight was detected in 67.5% of monitored men, obesity in 17.0% of them. Overweight was detected in 50.0% of women, obesity in 18.9% of them. Waist circumference exceeding 102 cm was measured in 41.2% of men and waist circumference exceeding 88 cm in 41.7% of monitored women. The unfavourable nutrition state correlates with a high occurrence of cardiovascular and metabolic diseases appearing within the Czech population.

Effect of pH on proteinase secretion by transformed fibroblast populations

Effect of pH on secretion of proteolytic enzymes in cell cultures of three clonal lines of transformed fibroblasts (K2, T15 and K4) was studied by using 14C-labelled denatured proteins as substrate. One line of malignant macrophages derived from mouse reticulum cell sarcoma (J774.1) was used for comparison. The relative motility index of all cell lines was derived by computer analysis of quantitative estimations of cell dispersion in single-cell-derived colonies. Cultivation at pH 6.5 decreased the growth rate in most experiments as compared with that at pH 7.4, and stimulated cell motility to a different extent. The population of mouse malignant macrophages produced several-fold higher extracellular proteolytic activity than the fibroblast lines. Secretion of proteinases by the malignant macrophages was significantly stimulated by the lower pH. Enzyme secretion by two of the three fibroblast derivatives was also stimulated by acidic pH but to a lesser extent than the secretion of the malignant macrophages. The assessment of motility done by measurement of dispersion of cells in colony proved a positive correlation between motility and proteinase secretion in J774.1 cells and one transformed fibroblast clone (T15) but not in the two other clonal lines.

Protein catabolism in growing Bacillus megaterium during adaptation to salt stress

Elevated concentration of NaCl in liquid medium caused a concentration-dependent growth delay (adaptation lag) and decrease in the maximal growth rate of Bacillus megaterium. The adaptation to salt stress was accompanied by transformation of some otherwise stable (long-lived; LLP) cell proteins into quickly degraded (short-lived; SLP) ones. Exposure to the strongly growth-reducing 1 M NaCl increased the size of the SLP 'pool' of intracellular proteins from about 5 to about 15% of total protein. The major intracellular proteolytic capacity of B. megaterium is represented by intracellular serine proteinases (ISP). Paradoxically, their specific activity was lowered or masked during the adaptation phase marked by increased catabolism of short-lived and/or destabilized proteins by the stress. This documents that intracellular proteolytic activity cannot be a key regulator of protein catabolism during adaptation to stress.

Cell viability and protein turnover in nongrowing Bacillus megaterium at sporulation suppressing temperature

In Bacillus megaterium, a temperature that suppresses sporulation (43 degrees C) only slightly exceeds both the optimum growth temperature and the temperature still permitting sporulation (40-41 degrees C). Here we show that, when cells grown at 35 degrees C and transferred to a sporulation medium, were subjected to shifts between 35 degrees C and the sporulation suppressing temperature (SST, 43 degrees C), their development and proteolytic activities were deeply affected. During the reversible sporulation phase that took place at 35 degrees C for 2-3 h (T2-T3), the cells developed forespores and their protein turnover was characterized by degradation of short-lived proteins and proteins made accessible to the proteolytic attack because of starvation. During the following irreversible sporulation phase refractile heat-resistant spores appeared at T4-T5. Protein turnover rate increased again after T2 and up to T8 60-70% prelabelled proteins were degraded. The SST suppressed sporulation at its beginning; at T3 no asymmetric septa were observed and the amount of heat-resistant spores at T8 was by 4-5 orders lower than at 35 degrees C. However, the cells remained viable and were able to sporulate when transferred to a lower temperature. Protein degradation was increased up to T3 but then its velocity sharply dropped and the amount of degraded protein at T8 corresponded to slightly more than one-half of that found at 35 degrees C. The cytoplasmic proteolytic activity was enhanced but the activity in the membrane fraction was decreased. When a temperature shift to SST was applied at the beginning of the irreversible sporulation phase (T2.5), the sporulation process was impaired. A portion of forespores lyzed, the others were able to complete their development but most spores were not heat-resistant and their coats showed defects. Protein degradation increased again because an effective proteolytic system was developed during the reversible sporulation phase but the amount of degraded protein was slightly lower than at 35 degrees C. A later (T4) shift to SST had no effect on the sporulation process.

Contrast-enhanced ultrasound for guidance of local tumor ablation

The objective was to assess the efficacy of sonography with and without contrast medium enhancement in guiding and monitoring percutaneous ethanol ablation of tumors in an animal model. VX-2 carcinoma was implanted into the thighs of New Zealand white rabbits and examined by grey-scale ultrasound, color, power, and pulse Doppler, before and after injection of 95% ethanol into the tumors. Injections of ethanol were guided by ultrasound to sites of tumor vascularity, until all tumor vascularity had been obliterated. Microbubble contrast medium or saline was injected i.v. prior to each of the ultrasonic interrogations. Arteriography was performed before and after ablation. Selected tumor samples were submitted for histologic examination. Contrast enhanced tumor vascularity over saline controls in all cases. In some, incompletely ablated foci of tumor could only be identified with contrast medium enhancement. Arteriography showed complete ablation of all but 1 tumor. We conclude that ultrasound enhanced by contrast better shows the presence or absence of tumor vascularity. Ultrasound enhanced by contrast might offer an accurate means of guiding and monitoring percutaneous ethanol injection for tumor ablation.

[Non-invasive methods for evaluation of body composition during weight reduction]

As a result of positive energetic balance of organism, there is a cumulation of an excessive energy in the adipose tissue. Adipose tissue repletion represents the main characteristic of obesity. The objective of our work was to perform the comparative study for the evaluation of selected noninvasive methods used for the determination of body composition. We analysed the results of 4 methods of the body composition measurement: bioelectrical impedance (BIA), physical anthropometry (ANTHR), Deurenberg's calculation (FORM) and dual energy X-ray absorptiometry (DEN). The most statistically significant correlation was proved between the results of BIA and results of DEN method (r = 0.9145), and results of BIA and FORM method (r = 0.9014).

[Changes in autonomic nervous system activity in obese individuals during weight reduction]

The frequency analysis (fast Fourier transformation) of heart rate variability follow-up during modified orthostatic test is the non-invasive method used to the evaluation of vegetative nervous system (NS) activity. There are only few data about the changes of the parameters in the groups with civilization diseases or with the presence of the risk factors of coronary heart disease. In the groups of 82 volunteers (BMI 24.9 +/- 2.7 kg/m2) and 37 healthy obese people (BMI 36.1 +/- 4.9 kg/m2) we compare some of the vegetative NS parameters. In 16 volunteers we measured the vegetative NS activity changes during the weight reduction regimen (10 day's hospitalization, daily energy intake 3300 kJ, weight before 101.5 +/- 18.1 kg, after 97.5 +/- 17.1 kg, p < 0.0001). Acute reactions to the energy restriction were evaluated in 3 groups of 10 volunteers during 3 days of the energy intake 3200, 6600 and 13400 kJ. Obese persons show a slight decrease of both sympathetic and parasympathetic NS activity. In the supine position only few changes in the sympathetic/parasympathetic NS activity ration were observed. In the standing position in obese group drop of the most indexes and decrease of sympathetic/parasympathetic NS activity ratio were described. Significant correlations between sympathetic NS activity and lipid oxidation (r = 0.329, p < 0.01) as well as saccharide oxidation (r = -0.258, p < 0.05) were observed. During the weight reduction slight increase of the parasympathetic NS activity and higher one in the sympathetic NS activity were measured. The values after weight reduction regime are comparable with the control group of the lean persons. Different changes of the parameters were described in standing and in supine position. Acute reaction on the low-energy diet was observed in a few days. It shows a slight increase of the NS activity parameters. Relative increase mainly in the sympathetic nervous system activity doesn't depend on the degree of energy deficit only, but some subjective factors may play a role (age, psychological and psychosocial factors, agreeability of the diet, behavioral factors ...). In the group of obese persons non-specific changes of the vegetative NS activity were observed. They are modulated by some behavioral factors. The tendency to the higher parasympathetic NS activity confirms the MONA LISA theory of the origin of obesity. Important are the informations of the return of the indexes after overweight reduction.

Oxidative stress in microorganisms--I. Microbial vs. higher cells--damage and defenses in relation to cell aging and death

Oxidative stress in microbial cells shares many similarities with other cell types but it has its specific features which may differ in prokaryotic and eukaryotic cells. We survey here the properties and actions of primary sources of oxidative stress, the role of transition metals in oxidative stress and cell protective machinery of microbial cells, and compare them with analogous features of other cell types. Other features to be compared are the action of Reactive Oxygen Species (ROS) on cell constituents, secondary lipid- or protein-based radicals and other stress products. Repair of oxidative injury by microorganisms and proteolytic removal of irreparable cell constituents are briefly described. Oxidative damage of aerobically growing microbial cells by endogenously formed ROS mostly does not induce changes similar to the aging of multiplying mammalian cells. Rapid growth of bacteria and yeast prevents accumulation of impaired macromolecules which are repaired, diluted or eliminated. During growth some simple fungi, such as yeast or Podospora spp., exhibit aging whose primary cause seems to be fragmentation of the nucleolus or impairment of mitochondrial DNA integrity. Yeast cell aging seems to be accelerated by endogenous oxidative stress. Unlike most growing microbial cells, stationary-phase cells gradually lose their viability because of a continuous oxidative stress, in spite of an increased synthesis of antioxidant enzymes. Unlike in most microorganisms, in plant and animal cells a severe oxidative stress induces a specific programmed death pathway--apoptosis. The scant data on the microbial death mechanisms induced by oxidative stress indicate that in bacteria cell death can result from activation of autolytic enzymes (similarly to the programmed mother-cell death at the end of bacillary sporulation). Yeast and other simple eukaryotes contain components of a proapoptotic pathway which are silent under normal conditions but can be activated by oxidative stress or by manifestation of mammalian death genes, such as bak or bax. Other aspects, such as regulation of oxidative-stress response, role of defense enzymes and their control, acquisition of stress tolerance, stress signaling and its role in stress response, as well as cross-talk between different stress factors, will be the subject of a subsequent review.

[Sporicidal effect of Presept and Chloramine B on Bacillus cereus spores]

The sporicidal effect of Presept was compared with Chloramine B on the spores of Bacillus cereus. Either compound was calibrated to the same concentration of active chlorine. While a portion of spore population after 4 hrs of treatment by Chloramine germinated and started to divide in a rich nutrient medium, the optical density of the culture inoculated with spores treated by Presept did not increase even after 7 hrs when exposed to the nutrient medium. Significant morphological differences were found in either population of spores. Spores treated by Presept lost the impermeability within 3 hrs in the nutrient medium but almost no postgerminative development was observed. However, a portion of spores treated by Chloramine B developed after germination within 3 hrs into vegetative cells. It seems that Presept does not block germination and/or loss of impermeability of spores, but prevents their postgerminative development and division.

Occipital lobe vascular malformations: prevalence of visual field deficits and prognosis after therapeutic intervention

BACKGROUND

The prevalence of visual field (VF) deficits in association with vascular malformations of the occipital lobe is not known, and the prognosis of the VF after therapeutic intervention has not been systematically documented.

METHODS

We reviewed the clinical records of 23 consecutive patients who were managed at a single institution during a 3-year period with intracranial vascular malformations extending within the anatomic borders of the occipital lobe. Lesion location and treatment rendered were correlated with formal VF testing performed before and after therapeutic intervention.

RESULTS

Twenty-one of the 23 patients underwent treatment of their lesions. Treatment included resection after preoperative embolization (12 patients), resection alone (2 patients with arteriovenous malformations and 3 patients with cavernous malformations), and stereotactic radiosurgery (4 patients; preceded by embolization in 3 of the 4). One patient was followed expectantly, and another died as a result of hemorrhage soon after undergoing endovascular embolization. The VFs were assessed before and after therapeutic intervention (follow-up assessment, 2-29 mo). New VF deficits or worsening of preexisting VF deficits were documented in 5 of the 21 treated patients (24%), but only 2 of these patients (9.5%) had persistent deficits at the time of their follow-up examinations. Among the 10 patients with pretreatment VF deficits, 5 improved and the other 5 were unchanged after treatment.

CONCLUSION

Patients with occipital lobe vascular malformations frequently present with associated VF deficits. Surgical resection or stereotactic radiosurgery (with or without previous embolization) of these lesions can be performed with little risk of causing new VF deficits or worsening of preexisting ones. Many VF deficits can be expected to improve or resolve after therapy.

Asporogenic Bacillus megaterium mutant 27-36 degrades intrinsically short-lived proteins but fails to convert most of other proteins to a short-lived fraction

Asporogenic mutant blocked in the 0-II sporulation stage degraded pulse-labelled proteins in the sporulation medium at the same rate as the parental strain for the first two hours. The degraded fraction was mostly composed of intrinsically short-lived proteins which were degraded even after enriching the medium with amino acids and growth resumption. Proteins accessible to degradation because of nutritional shift down formed a lesser proportion of this fraction. The acceleration of protein turnover in the parent strain during the irreversible sporulation phase was not developed in the mutant. A first order kinetic model of protein degradation was used for parameter estimation. Ca(2+)-dependent intracellular serine proteinase was synthesized in an inactive form, which was activated by increasing Ca2+ concentration to 30 mM.

Computer modeling of cerebral blood flow following internal carotid artery occlusion

It is difficult to predict the adequacy of the collateral blood flow in patients who undergo internal carotid artery occlusion. In order to address this difficulty, the authors have created a computer model of the cerebral circulation. This model features individualized simulations of the Circle of Willis and its afferent and efferent branches which can predict changes in flow that will occur during internal carotid artery occlusion. Analysis of the flow predictions suggests that in patients with a symmetric Circle of Willis the anterior communicating artery is the major conduit of collateral blood supply. In patients with a small anterior communicating artery, the posterior communicating arteries become more important as sources of collateral flow, but they cannot supply as much flow as in the case of a normal anterior communicating artery. Sensitivity studies show that changes in the dimensions of each artery affect the flow throughout the system, such that the arteries in the cerebral circulation must be analyzed as a network rather than as isolated elements. This computer model of the cerebral circulation may help clinicians predict the adequacy of collateral blood supply in patients who undergo internal carotid artery occlusion.

[Proteolytic enzymes in cell physiology and pathophysiology]

Extracellular proteases (proteinases, endopeptidases) are usually synthesized as larger precursors containing a signal sequence in the N-terminal part of their molecule. The signal sequence contains a sequence composed of hydrophobic amino acids which facilitate the transport of the polypeptide through membranes of the secretory apparatus. Extracellular proteinases play an important role in reproduction and spreading of tumor cells and in tissue remodelling in addition to their function in digestion food proteins. Intracellular proteinases are mostly localized in the cytoplasm and in specialized organelles (lysosomes) but are present also in nuclei and in mitochondria. They degrade or modify cell proteins and are thus involved in protein turnover which is necessary for cell viability. Intracellular proteinases are important components of the cell defense system which protects the cell against the effect of different stress factors by removing damaged and nonfunctional proteins. They modify different proteins and are thus involved in virus reproduction because some proteins are synthesized as nonfunctional virus precursors. Intracellular proteinases also play a role in the cell cycle control and in cytodifferentiation. Rather complex proteolytic enzymes were found even in very primitive organisms (archebacteria).

Intracellular serine proteinase behaves as a heat-stress protein in nongrowing but as a cold-stress protein in growing populations of Bacillus megaterium

A temperature increase from 35 degrees to 40-42 degrees C enhances the rise of cytoplasmic serine proteinase (ISP1) activity in Bacillus megaterium incubated in a sporulation medium. A temperature shift from 27 degrees C in the growth medium to 35 degrees C in the sporulation medium has the same effect. Elevated temperature stimulates the increase of ISP1 level when applied immediately after the transfer of cells from the growth to the sporulation medium (at T0) or at T3, when sporulation becomes irreversible. The cytoplasmic PMSF-resistant activity or the proteolytic activity associated with the membrane fraction is stimulated only slightly or not at all. A temperature increase to 45-47 degrees C suppresses the rise of proteolytic activities in all cell fractions. In addition to the elevation of the ISP1 activity by an upward temperature shift, the rise of this enzyme in nongrowing cells is also stimulated by osmotic stress. In growing populations, in contrast to the rise of the ISP1 activity caused by elevated temperature in nongrowing cells, this proteinase is induced by low temperatures (24-27 degrees C). The ISP1 activity roughly correlates with the enzyme protein concentration determined by immunoblotting.

Heat and osmotic stress enhance the development of cytoplasmic serine proteinase activity in sporulating Bacillus megaterium

The intracellular Ca(2+)-dependent serine proteinase (ISP1) activity in the cytoplasm of nongrowing Bacillus megaterium incubated in a sporulation medium was determined at 35 degrees C and at temperatures decreasing the sporulation frequency (42 degrees C) or suppressing sporulation (43.5 degrees C). The enzyme in the crude cytoplasmic fraction was partially inhibited by a loosely bound inhibitor(s) because the ISP1 activity rose after protein fractionation by HPLC. Temperature shift-up or osmotic stress applied at 35 degrees C increased the development of the ISP1 activity several times. The increase was caused at least partially by the synthesis of the enzyme protein, as proved by SDS-PAGE and immunoblotting of the cytoplasm. This enzyme thus probably belongs among heat-shock proteins.

Heat shock applied early in sporulation affects heat resistance of Bacillus megaterium spores

Cells of Bacillus megaterium 27 were challenged by a 30-min heat shock at 45 degrees C during various sporulation stages and then shifted back to a temperature permissive for sporulation (27 degrees C), at which they developed spores. Heat shock applied at 120 min after the end of the exponential phase induced synthesis of heat shock proteins (HSPs) in the sporangia and delayed the inactivation of spores at 85 degrees C. Several HSPs, mainly HSP 70, could be detected in the cytoplasm of these spores. An analogous HSP, the main HSP induced by increased temperature during growth, belongs to the GroEL group according to its N-terminal sequence. The identity of this protein was confirmed by Western blot (immunoblot) analysis with polyclonal antibodies against B. subtilis GroEL. Sporangia treated by heat shock immediately or 240 min after exponential phase also synthesized HSPs, but none of them could be detected in the spores in an appreciable amount. These spores showed only a slightly increased heat resistance.

Turnover of canavanine-containing proteins in Saccharomyces cerevisiae

Saccharomyces cerevisiae grown for 2 h in the presence of 0.5 mmol/L canavanine in a synthetic medium with ethanol as the sole carbon source (OEC) exhibited a slowing down of protein synthesis for 3-4 h after a shift to fresh ethanol-based medium containing 1.0 mmol/L arginine (OEA) in comparison with untreated cells grown on OEA. The change of carbon source from ethanol to glucose (OGA) after growth in the OEC medium resulted in an even deeper decline of protein synthesis. The degradation of canavanine-containing proteins in cells pregrown and labelled in an OEC medium after transfer to OEA was more rapid than in the OGA medium. The initial rate of protein degradation during the first hour in the OGA medium was less than 1%/h whereas in the OEA medium it reached almost 10%/h. The fraction of proteins with high turnover (half-life 0.46 h) constituted 8.3% on OEA, while during subsequent growth on OGA it was only 0.75% with a half-life of 0.12 h.

Sporulation and synthesis of extracellular proteinases in Bacillus subtilis are more temperature-sensitive than growth

Bacillus subtilis 115 grew in a medium with amino acids and glucose with the maximum specific growth rates mu of 1.20-1.10/h in the temperature range of 45-48 degrees C. Activity of the extracellular neutral proteinase excreted by 1.3 mg/mL dry mass during 8 h of the postexponential and stationary growth phases decreased from its maximum value of 0.23 TU/mL at 40 degrees C to 0.13 and 0.06 TU/mL at 45 and 48 degrees C, respectively. Formation of the extracellular serine proteinase decreased even more - from 0.18 TU/mL at 40 degrees C to 0.06 and 0.03 TU/mL at 45 and 48 degrees C, respectively. Sporulation, expressed as the portion of sporangia with refractile spores at the 6th h of the stationary phase decreased from 46% at 40 degrees C to 17 and 3% at 45 and 48 degrees C, respectively.

Netropsin inhibits the increase of intracellular Ca(2+)-dependent serine proteinase activity in sporulating Bacillus megaterium

Netropsin suppressed the increase of intracellular proteolytic activity when added to B. megaterium incubated in a sporulation medium. The inhibited enzyme was a Ca(2+)-dependent serine proteinase. Sporulation and protein turnover in later sporulation phases were inhibited as well. Different concentrations of netropsin affected various aspects of protein catabolism differently.

Characteristics of intracellular proteolytic activities of Bacillus megaterium

Intracellular proteolytic activities of B. megaterium KM occur soluble in the cytoplasm and periplasm and insoluble in the membrane. Two proteolytic enzymes were found in the cytoplasmic fraction by gel filtration on Sephadex G 150 and by polyacrylamide gel electrophoresis. The first enzyme called CI was stable, had a relative molecular mass of Mr = 105,000 (M = 105 kg/mol) and was inhibited by EDTA and PMSF, whereas the second, designated CII, was labile and had a relative molecular mass of Mr = 46,000 (M = 46 kg/mol). Because of its lability it could not be characterized in detail. In the "periplasm" only a single proteolytic enzyme P (Mr = 28,000; M = 28 kg/mol) inhibited by EDTA could be demonstrated. The extracellular enzyme exhibited similar properties. The membrane proteolytic activity was sensitive to PMSF and EDTA. The membrane enzymes have not yet been solubilized. In cells of the mutant KM 12 that does not produce the extracellular proteinase, only one type of proteinase, in all its properties identical with the cytoplasmic proteinase CI, could be demonstrated.

Effect of actinomycin D on viability, sporulation and nucleotide pool of Bacillus megaterium

A transient 7-fold rise of ppGpp concentration, 2-3-fold increase of pppGpp concentration and 50% drop of the concentration of GTP in Bacillus megaterium cells immediately after their transfer to the sporulation medium were observed. Actinomycin D, in concentrations inhibiting RNA synthesis by 95%, blocked the rise of the (p)ppGpp pool and caused an instant several-fold increase of the GTP level. When the cells were exposed to actinomycin D in the sporulation medium for a 1-h period (time 0-1 h, 1-2 h or 2.20-3.20-h), they were able to form colonies on nutrient agar after being kept, in addition for 1-2 h in the sporulation medium free of the antibiotic. The ability of sporulation was, however, markedly limited. The share of cells that could sporulate increased when the irreversible sporulation phase was reached.

Regulation of extracellular proteins and alpha-amylase secretion by temperature in Bacillus subtilis

alpha-Amylase was found to be the main protein secreted by Bacillus subtilis, corresponding to 90, 87 and 60% of total extracellular proteins at 30, 40 and 45 degrees C, respectively. A change in temperature can affect the pattern of proteins secreted as detected by gel electrophoresis. 14C-Leucine incorporation into extracellular proteins and their proportion at the end of the growth phase was higher at 30 degrees C than that at 40 or 45 degrees C. The effect of temperature on alpha-amylase synthesis as determined by its enzymic activity and on the extracellular protein synthesis followed a similar pattern.