Crystallization of salt-free chymotrypsinogen and chymotrypsin from solution in dilute ethyl alcohol

Chymotrypsinogen and chymotrypsin crystallize readily from dilute solutions of ethyl alcohol in the absence of salts. The crystals formed in the presence of alcohol differ in appearance from those formed in the presence of ammonium sulfate. Chymotrypsinogen yields well formed polyhedrons instead of fine needles usually produced in ammonium sulfate solution. Chymotrypsin yields fine needles in the presence of alcohol and rhombohedrons in the presence of ammonium sulfate. The enzymatic properties of the crystals formed in the presence of alcohol are identical with those of the crystals isolated in the presence of ammonium sulfate.     

In vitro effects of gossypol and lactic acid on rat uterus and ovary during implantation and antiimplantation

ATPase activity of uterus and ovary was markedly elevated in presence of gossypol and decreased in presence of lactic acid indicating activation and inhibition of energy metabolism by gossypol and lactic acid respectively. The elevated levels of glycogen in uterus indicate inhibition of glycogenolysis as supported by phosphorylase activity. Whereas in ovary the glycogen depletion indicates activation of glycogenolysis supported by phosphorylase activity. The activity levels of aldolase and G-6-PDH decreased in the uterus in presence of gossypol and increased in presence of lactic acid. The same were elevated in ovary indicating the activation of hexose mono and diphosphate pathways. Lactic acid accumulated in presence of both gossypol and lactic acid with a depletion in level of pyruvic acid in both the tissues. This situation in the uterus indicates the condition of anti-implantation in presence of both gossypol and lactic acid. The NAD-LDH activity was inhibited in presence of gossypol and activated in presence of lactic acid in both tissues.     

Reduction of trimethylamine N-oxide by Escherichia coli as anaerobic respiration.

E. coli was found to grow anaerobically on lactate in the presence of trimethylamine N-oxide (TMANO), reducing it to trimethylamine. Anaerobic growth on glucose was promoted in the presence of TMANO. When a culture grown in complex medium was transferred to defined medium, growth on glucose and ammonia took place in the presence of TMANO after consumption of complex nutrients introduced with the preculture, in contrast to growth in nitrate respiration. The amounts of ethanol, succinate, and lactate among the fermentation products were decreased and that of acetate was increased in the presence of TMANO. Formate generation was much reduced at pH 7.4, whereas stoichiometric formation of formate was observed in the absence of TMANO. Cells grown anaerobically in the presence of TMANO had a higher activity of amine N-oxide reductase than cells grown under other conditions. The content of cytochrome-558 was elevated in the presence of TMANO during growth in complex medium. Cytochrome c-552 found in cells grown in diluted complex medium or defined medium in the presence of TMANO was oxidized by TMANO in cell extracts. The molar growth yield on glucose was higher in the presence of TMANO than in its absence and lower than that in the presence of nitrate.     

Can we model the probability of presence of species without absence data?

In ecological studies, it is useful to estimate the probability that a species occurs at given locations. The probability of presence can be modeled by traditional statistical methods, if both presence and absence data are available. However, the challenge is that most species records contain only presence data, without reliable absence data. Previous presence‐only methods can estimate a relative index of habitat suitability, but cannot estimate the actual probability of presence. In this study, we develop a presence and background learning algorithm (PBL) that is successful in modeling the conditional probability of presence of a simulated species. The model is trained by two completely separate sets: observed presence and background data. Assuming that the probability of presence is one for ‘prototypical presence’ locations where the habitats are maximally suitable for a species, we can estimate a constant that can calibrate the trained model into the actual probability of presence. Experimental results show that the PBL method performs similarly to a presence‐absence method, and significantly better than the widely used maximum entropy method. The new algorithm enables us to model the probability that a species occurs conditional on environmental covariates without absence data. Hence, it has potential to improve modeling of the geographical distributions of species.     

Regulation of growth and polyamine biosynthesis of the ciliated protozoan Tetrahymena thermophila. Effects of L-arginine metabolites and polyamines

Growth of Tetrahymena thermophila in a synthetic nutrient medium with or without the essential amino acid L-arginine was studied in the presence or absence of the arginine metabolites L-citrulline and L-ornithine and the polyamines putrescine, spermidine, and spermine. The effects of the growth conditions on the stimulations of the enzymes of the arginine metabolic and polyamine biosynthetic pathway, arginine deiminase (ADI), citrulline hydrolase (CH), ornithine decarboxylase (ODC), and ornithine-oxo-acid aminotransferase were determined. Tetrahymena cells were unable to grow in the absence of L-arginine and the amino-acid utilization was greatly impaired. None of the metabolites or polyamines was able to substitute for arginine. In the presence of arginine, Tetrahymena cultures grew well and citrulline and ornithine did not alter the growth behaviour in any way. In the presence of putrescine, the lag period was decreased from 3 h to 2 h. Spermidine and spermine acted similar to putrescine but less pronounced. The stimulation of the activity of ADI, the key enzyme of arginine degradation, was absolutely dependent upon the presence of arginine in the medium: in the absence of arginine, the low ADI activity which was present in the cells before inoculation was decreased to zero levels within 30 min. In the presence of arginine, the stimulation of ADI was not altered by citrulline and ornithine but putrescine, spermidine, and spermine decreased ADI-stimulation to half of the control values. The stimulation of CH activity in the presence of arginine was not altered by any added metabolite or polyamine. In the media without arginine, stimulation of CH was greatly reduced, in the presence of ornithine more than in its absence, and even more in the presence of putrescine and spermidine. Stimulation of ODC activity in the presence of arginine was not affected by citrulline and ornithine but in the presence of polyamines it was rapidly decreased to unstimulated levels after an initial ca. 10-fold increase. The "hyperstimulation" of ODC in the absence of free arginine was reduced to normal in the presence of citrulline, the stimulation was decreased even below normal levels in the presence of ornithine and polyamines decreased ODC activity to zero levels. O delta T activity was stimulated more in the presence of arginine than in its absence. In both cases the stimulation was enhanced in the presence of polyamines and only in the absence of arginine--by ornithine.(ABSTRACT TRUNCATED AT 400 WORDS)     

Strategic mate‐guarding behaviour in ladybirds

Mate‐guarding behaviour is regarded as a means of increasing paternity share by reducing sperm competition. It is known to be a plastic response which varies with operational sex ratios and competitor presence in the vicinity. In a recent study, prolonged mating duration in Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae) has been found to incorporate mate‐guarding behaviour. The present investigation was conducted to assess its plasticity in the presence of competitors. The physical and chemical presence of competitors of both sexes at varying densities was provided to a pair of ladybirds, and their time to commence mating, latent period and mate‐guarding duration was observed. These were compared to a control treatment where other partners were absent. All treatments were conducted with sibling as well as non‐sibling competitors. It was our hypothesis that mate guarding would be increased in the presence of male competitors and would be reduced by female presence. The results revealed that while mate‐guarding duration was increased by the chemical presence of males it was decreased by their physical presence. The latter result was attributed to interference by other males who dislodge the mating male in order to access the female. Female chemical presence had no effect on mate guarding, while physical presence increased the duration of mate guarding. The reasons for the latter behaviour require further investigation. Responses were not significantly affected by the relationship between the focal pair and the competitor. The authenticity of the mate guarding in this ladybird is strongly affirmed by our results.     

Asymmetrical costs of sexual conflict in the seaweed fly, Coelopa frigida

Abstract.  1. Sexual conflict can play an important role in the evolution of animal life-history characteristics, including lifespan. Seaweed flies show an increase in mortality rates when exposed to brown algae. The seaweed stimulates females to oviposit and males to mount females. Females typically respond to male mounts by performing a violent rejection response.
2. Here the contribution of sexual conflict to the increase in mortality seen in the presence of seaweed was determined. The survival of single and mixed sex pairs of flies was followed in the presence and absence of seaweed.
3. The two sexes showed differential survival rates, with females living longer in the absence of seaweed. The presence of seaweed reduced survival in both sexes. In the presence of seaweed, female survival was lower when paired with a male. Over 40% of the reduction in survival in females in the presence of seaweed appears to be attributable to sexual conflict.
4. The presence of a female did not significantly affect male survival. Thus the mortality cost of being in the presence of the opposite sex and seaweed appears highly asymmetric.
5. In the presence of seaweed, female survival was lower when females were paired with small males. Small males exhibit higher levels of harassment of females, thus it is argued that pre-copulatory sexual conflict is the probable cause of the increased mortality cost to females of being in the presence of both males and seaweed.     

Binding of Chlorpromazine to S-100 Protein

Chlorpromazine (CPZ) induces in S-100 conformational changes resulting in the exposure of titratable SH groups of the protein to the solvent. This effect is even greater in the presence of Mg2+ +/- Ca2+. S-100 possesses binding sites for CPZ. The binding of CPZ to 3 microM S-100 is half-saturated by 0.18 microM CPZ in the presence of Mg2+ plus Ca2+ and by 0.24 microM CPZ in the presence of Mg2+ plus EGTA. The extent of the binding is greater in the presence of Ca2+ than in the presence of EGTA, especially at low CPZ concentrations.     

有机酸对Pb、Cd的土壤化学行为和植株效应的影响

有机酸对Pb、Cd的络合作用将其对土壤吸附Pb、Cd的影响和植株效应差异的研究表明,柠檬酸、草酸与Pb、Cd络合能力的大小与重金属本身的性质有关,络合作用影响土壤对Pb、Cd的吸附量,柠檬酸降低土壤对Pb、Cd的吸附,草酸则增加土壤对Pb、Cd的吸附.水培试验表明,柠檬酸可减轻Pb对小麦、水稻幼苗的毒害.柠檬酸对Cd的植株外观毒性效应影响不显著,但能促使植株茎叶、根中Cd含量下降.Pb和Cd复合处理条件下,Cd存在促使水稻植株对Pb吸收量增加,Pb存在抑制水稻植株对Cd的吸收.     

Evidence of brain-warming in the mobulid rays, Mobula tarapacana and Manta birostris (Chondrichthyes: Elasmobranchii: Batoidea: Myliobatiformes)

The presence of cranial retia mirabilia in rays of the genus Mobula is well established. Although previously regarded as consisting exclusively of arteries, the presence of veins has now been established in gross dissections of the rete in the mobulid, Manta birostris. Histological examination of the retia in Manta birostris and Mobula tarapacana confirms the presence of veins. These findings suggest the presence of a counter-current heat-exchanger that warms the brain.     

Spectroscopic studies on the protective effect of a specific sugar on concanavalin A at acidic, neutral and alkaline pH

A Systematic investigation of the effect of pH on concanavalin A in the presence of specific and non-specific sugars is made using CD (circular dichroism) and fluorescence. The specific and non-specific sugars for concanavalin A were methyl alpha-D-glucopyranoside and methyl alpha-D-galactopyranoside respectively. Far-UV CD showed changes in the MRE value at 217 nm in the presence of the above-mentioned sugars. At pH 7, the CD and fluorescence spectra obtained in the presence of methyl alpha-D-glucopyranoside were slightly different from those for the native state and a significant difference was obtained in the presence of methyl alpha-D-galactopyranoside. Near-UV CD spectra showed the retention of a native-like tertiary structure in the presence of the specific sugar upon pH denaturation. Tryptophan fluorescence studies indicated a change in the tryptophan enviornment. The results obtained from our CD data are consistent with those obtained from fluorescence studies. Upon pH exposure of concanavalin A in the presence of methyl alpha-D-glucopyranoside and methyl alpha-D-galactopyranoside, the former acted as a protector preventing conformational alteration at different pH while the presence of latter induced a different stable conformational state and this state persists over the pH range from 2 to 10.     

ACTIVITY OF AMINOACYL-TRANSFER RNA SYNTHETASES IN BRAIN MITOCHONDRIA 1

Abstract— The binding capacity for amino acids of low molecular wt. RNAs isolated from mitochondrial and cytoplasmic fractions from brain was studied in the presence of partially purified aminoacyl-tRNA synthetases obtained from both subcellular fractions. The ability of mitochondrial tRNAs to bind amino acids was greater by about three times in the presence of mitochondrial aminoacyl-tRNA synthetases than in the presence of cytoplasmic enzymes. In contrast, the amino acid-binding ability of cytoplasmic tRNA was the same in the presence of mitochondrial enzymes as in the presence of those from the cytoplasm. When homologous (rabbit) and heterologous (calf) tRNAs were tested in the presence of mitochondrial or cytoplasmic enzymes obtained from rabbit brain and a mixture of amino acids, a significant species specificity was seen: in both heterologous systems the highest amount of tRNA binding was only 44-66 per cent of that obtained with the homologous enzyme system.     

Effect of actinomycin D on purified DNA-dependent RNA polymerases from normal and neoplastic tissues

The effect of low concentrations of actinomycin D was investigated, using two forms of DNA-dependent RNA polymerase (A and B) purified from normal tissues and experimental tumours, in the presence either of Mn2+ or Mg2+, and homologous DNA. The A enzyme activity was strongly inhibited by the antibiotic in presence of Mg2+ and much less in presence of Mn2+. The B enzyme activity was almost suppressed in presence of both cations. The results here reported provide support that the actinomycin D induce a cellular damage of the same extent in normal and tumour tissues.     

Stabilities and conformational transitions of various proteases in the presence of an organic solvent

The half-life of the activity of the PST-01 protease that was secreted by organic solvent-tolerant Pseudomonas aeruginosa PST-01 was very long in the presence of methanol as compared to that in the absence of methanol. The conformational transitions of the PST-01 protease, alpha-chymotrypsin, thermolysin, and subtilisin in the presence and absence of methanol were monitored by measuring the CD spectra. The conformational stabilities of the PST-01 protease and subtilisin in the presence of methanol were higher than those in the absence of methanol. This resulted in high stability of these proteases in the presence of methanol. Furthermore, it was suggested that the organic solvent stabilities of enzymes were closely related to the secondary structure by monitoring the conformational transitions of polyamino acids, which form the particular conformations, in the presence and absence of methanol.     

Effects of the chaperonin GroE on the refolding of tryptophanase from Escherichia coli. Refolding is enhanced in the presence of ADP.

The refolding of the tetrameric enzyme tryptophanase was facilitated by the chaperonin GroE. Maximum refolding yield of tryptophanase molecules (about 80%) was attained in the presence of a 15-fold excess of GroE 21-mer over tryptophanase monomer. The GroEL subunit was required for this improvement in refolding yield, whereas the GroES subunit was not. Light scattering experiments of the refolding reaction revealed that GroE bound to tryptophanase folding intermediates and suppressed their aggregation. The presence of ATP was required for the efficient dissociation of tryptophanase from GroEL. However, our experiments indicated that tryptophanase dissociated readily from GroEL in the presence of not only ATP, but also in the presence of non-hydrolyzable ATP analogues such as ATP gamma S (adenosine 5'-O-(3-thiotriphosphate)) and AMP-PNP (adenyl-5'-yl imidodiphosphate) as well. Surprisingly, the release of tryptophanase from GroEL was facilitated in the presence of ADP as well. We concluded that the binding of nucleotides such as ATP and ADP changed the conformation of GroEL and facilitated the dissociation of tryptophanase molecules. The conformation formed in the presence of ADP was distinct from the conformation formed in the presence of ATP, as shown by the selective dissociation of various folding proteins from the two conformations.     

Dynamics of the NADP+ and NAD+ levels in the mycelium of P. nigricans Thom strains of varying productivity depending on the carbon source]

The levels of NADP+ and NAD+ in the mycelium of the highly productive strain 117 and low productive strain B of P. nigricans were studied by the 2nd, 5th, 9th and 13th days of development on the mineral medium in the presence of glucose, succinate or acetate. It was found that at the beginning of the growth the levels of NADP+ in both strains in the presence of the same carbon source were the same, just as the levels of NAD+ in the presence of glucose or succinate. The same strain had different levels of NADP+ in the presence of different carbon sources. The levels of NAD+ depended on both the carbon source and the strain. In the presence of glucose both nucleotides were accumulated by the end of the culture development and in greater amounts by strain 117. In the presence of succinate the maximum levels were observed at the beginning of the culture growth, while in the presence of accetate the maximum levels were recorded by the end of the culture development (strain 117) and by the 19th day (strain B). It is supposed that NAD+ is transformed into adenylates in the fungi.     

Impacts of male and food density on female performance in the brackish cladoceran Daphniopsis australis

The roles of male and food density in regulating female performance were investigated in the brackish cladoceran, Daphniopsis australis. Parthenogenetic females and ephippial females were tested using a 2 × 4 factorial experiment involving the presence and the absence of a male cross-classified with nil, low, medium and high food densities. For parthenogenetic females, the male presence and food density failed to trigger the switch from asexual to sexual reproduction, but the presence of male negatively affected parthenogenesis through egg abortion. Food density affected the animal longevity but depended on the male presence. The reproductive output was favoured by increasing food densities, but the male presence increased egg abortion, suggesting male being an added stress factor to parthenogenetic females. For ephippial females, food densities affected the frequency of switch from sexual to asexual modes in the absence and the presence of a male. However, the male enhanced switch frequency under low and high food densities. Longevity was increased with the male presence but was unaffected by food density. The ephippial females successfully produced diapausing eggs with the male presence. Although, ephippial females could switch to parthenogenesis but the reproductive output of switched ephippial females was inferior to that of parthenogenetic females since birth. The results reveal that the male presence and food density can impact the performance of female D. australis. Hence, this study provides an insight into the understanding of the reproductive biology of cladocerans and a possible alternative explanation for population dynamic of this species and other cladocerans in the field.     

Glycine uptake in brush border vesicles isolated from the rat intestinal cells

The uptake of glycine in osmotically active brush border membrane vesicles (obtained by the Mg++ precipitation method) has been studied and a partial characterization of its transport system has been established. The glycine uptake in these vesicles was stimulated by the presence of sodium and in the presence of an inwardly directed Na+ -gradient glycine was accumulated inside the vesicles. The effect of Na+ was specific; other monovalent cation as Li+, K+, Rb+ and choline were uneffective in the stimulation of glycine uptake, under the same experimental conditions. Preliminary experiments show an important role of some anions on the glycine uptake. A strong inhibition in the uptake rate was found when the measurements were carried out in the presence of sodium cyclamate, while in the presence of NaSCN the measured uptake values were similar to those observed in the presence of NaCl.     

Enhanced production of hydroperoxides by immobilized lipoxygenase in the presence of cyclodextrins

The advantages of the presence of cyclodextrins in a reaction catalyzed by immobilized lipoxygenase at neutral pH are reported for the first time. The steady-state rate in the presence of beta-cyclodextrins was seven times higher than in control experiments using the same concentration of linoleic acid; furthermore the percentage of substrate conversion (and product accumulation) obtained in the presence of beta-cyclodextrins was higher than in the control assays. The optimum concentration of free linoleic acid coincided with the critical micellar concentration for linoleic acid at neutral pH. The operational stability of the immobilized enzyme increased in the presence of beta-cyclodextins, while an increase in the percentage of 13-HPOD was also observed.