江滩与兴林垦种区钉螺体内几种酶活性的比较

在自动化分析仪上分析了兴林垦种林区内钉螺和草和滩钉螺的总蛋白（ＴＰｒ）含量和谷丙转氨酶（ＧＰＴ）、谷草转氨酶（ＧＯＴ）以及碱性磷酸脂酶（ＡＬＰ）的活力和比活力,及其受林地地下水位高度的影响,结果表明,林地钉螺的ＧＯＴ、ＧＰＴ酶活力和比活力均比滩于钉螺显著提高,ＡＬＰ活力较稳定,但比活力增加,林地内随地下水位降低,钉螺体内总蛋白含量下降,ＧＯＴ、ＧＰＴ比活力均显著升高。     

Mechanics of increased support of weight by the hindlimbs in primates

Quadrupedal primates support most of their weight on their hindlimbs during locomotion. Neither the position of their center of gravity nor the average position of their foot contacts is substantially different from that of other quadrupeds supporting most of their weight on their forelimbs. Arguments are presented to support the theory that high levels of hindlimb retractor activity will produce this shift of support to the hindlimbs. If this muscular activity is appropriately timed, it will generate only low horizontal accelerations, which can be offset by small changes in the average position of the limbs. Estimates of muscular force are derived from force plate and kinematic data, which indicate that primates in fact do exhibit the postulated pattern of muscular activity. It is suggested that this shift occurs to reduce the compressive forces on the forelimbs.     

Electrical connection between two bursting neurons inHelix pomatia

In some preparations of the CNS ofHelix pomatia, two neurons with bursting activity may be present in the right parietal ganglion, where usually there is only one bursting neuron RPal. If electrical activity of these neurons is recorded simultaneously, fluctuations of membrane potential are almost completely synchronized. Artificial depolarization and hyperpolarization of the membrane of one neuron caused depolarization or hyperpolarization of the other neuron. During long-term recording of the activity of both neurons synchronous modulation of their bursting activity was observed. Modulating factor (a peptide fraction obtained from the water-soluble part of snail brain homogenate) led to potentiation of the bursting activity of both neurons. It is concluded from the results of these experiments that two bursting RPal neurons, connected electrically with one another, may exist in the snail nervous system. In cases when the parameters of pacemaker activity of these two neurons are closely similar, electrical connection guarantees synchronization of their bursting activity and ensures a common frequency of changes in their membrane potential.     

Enzymatic preparation of chitooligosaccharides and their anti-obesity application

ABSTRACT

Chitooligosaccharides (COS) are derived from chitosan, which can be used as nutraceuticals and functional foods. Because of their various biological activities, COS are widely used in the food, medicine, agriculture, and other fields. COS were prepared by chitosanase from Pseudoalteromonas sp. SY39 and their anti-obesity activity was researched in mice in this study. The effects of hydrolysis time, temperature, the ratio of enzyme to chitosan, and pH on the productivity of COS were discussed. Preparation process of COS was established in a 5-L fermenter. COS were characterized and their anti-obesity activity was studied in animal experiments. The results showed that COS could effectively reduce serum lipid levels and obesity in mice, and have a good anti-obesity activity. The preparation technology and remarkable anti-obesity activity of COS further expand their applications in the food and pharmaceutical industries.     

Cloning and expression of two plant proteins: similar antimicrobial activity of native and recombinant form

Antimicrobial peptides and proteins are being studied with increasing interest because of their broad range antimicrobial activity. Among plant antimicrobial proteins, the wheat seed polypeptides, puroindoline a and puroindoline b, are particularly interesting because of their established antibacterial activity. In this paper we describe different strategies used to clone His tagged and GST tagged puroindolines obtaining 1.5 mg recombinant protein from 1 l culture. The antimicrobial activity of recombinant and native puroindolines was comparable.     

抗补体活性多糖

补体系统在宿主免疫中具有重要的作用。近年来,由某些中药中纯化的多糖具有明显的抗补体作用。这些多糖大多数含有阿拉伯糖、半乳糖和半乳糖醛酸,分子量范围6.000到500.000。它们的结构很复杂,多为具聚鼠李半乳糖醛酸结构中心的酸性杂多糖和果胶类多糖。这些多糖的抗补体活性可能和整个大分子的结构有关。一旦发生降解活性就大为下降甚至消失。它们都可以经典的方式激活补体系统。大部分也可以改变的方式激活补体系统。     

Identification of the carboxyl-terminal amino acids important for the ADP-ribosylation activity of Pseudomonas exotoxin A

The ADP-ribosylation domain of Pseudomonas exotoxin A (PE) has been identified to reside in structural domain III (residues 405-613) and a portion of domain Ib (residues 385-404) of the molecule (Hwang, J., FitzGerald, D. J., Adhya, S., and Pastan, I. (1987) Cell 48, 129-136). To further determine the carboxyl end region essential for ADP-ribosylation activity, we constructed sequential deletions at the carboxyl-terminal of PE. Our results show that a clone with a deletion of the carboxyl-terminal amino acid residues from Arg-609 to Lys-613 and replaced with Arg-Asn retained wild-type PE ADP-ribosylation activity. Deletion of the terminal amino acid residues from Ala-596 to Lys-613 and replaced with Val-Ile-Asn reduced ADP-ribosylation activity by 75%, while deletions of 36 or more amino acids from the carboxyl terminus completely lose their ADP-ribosylation activity. These modified PEs were also examined for their ability to block PE cytotoxicity. Our results shown that modified PEs which lost their ADP-ribosylation activity correspondingly lost their cytotoxicity. Furthermore, extracts containing PE fragments without ADP-ribosylation activity were able to block the cytotoxic activity of intact PE. Our results thus indicate that carboxyl-terminal amino acids in the Ser-595 region are crucial for ADP-ribosylation activity and, consequently, cytotoxicity of PE. The modified PEs which have lost their ADP-ribosylation activity may also be a route to new PE vaccines.     

Varietal differences in root phosphatase activity as related to the utilization of organic phosphates

This paper presents results of a comparative study of phosphorus utilization from inositol hexaphosphate by various varieties of Phaseolus vulgaris in relation to the activity and characteristics of their root phosphatases. Bean varieties show significant differences in their uptake of phosphorus from inositol hexaphosphate with a clear dependency on the phosphatase activity of their roots at pH 5. The results which are discussed in connection with the phosphorus turnover in the rhizosphere suggest that root phosphatase activity is a significant factor of nutritional efficiency under limited mineral phosphorus supply.     

Small,basic antifungal proteins secreted from filamentous ascomycetes: a comparative study regarding expression,structure, function and potential application

Peptides and proteins with antimicrobial activity are produced throughout all kingdoms in nature, from prokaryotes to lower and higher eukaryotes, including fungi, plants, invertebrates and vertebrates. These proteins contribute to an important constitutive or induced defense mechanism of the producer against microorganisms. According to their variety in structure and function, these proteins are classified arbitrarily into groups that are based on their mechanism of action, their structure and their similarity to other known proteins. The present review focuses on a new group of antimicrobial proteins, namely small, basic and cysteine-rich antifungal proteins, which are secreted from filamentous fungi of the group Ascomycetes. These proteins are encoded by orthologous genes and exhibit both similarities and differences concerning their species-specificity, primary structure, protein activity and target sites. The properties of these proteins, their possible mode of action and their potential application for human benefits are discussed in comparison with other already well known antimicrobial proteins.     

Alcohol dehydrogenase thermostability variants in Drosophila melanogaster: Comparison of activity ratios and enzyme levels

Representatives of five allozymic classes of Drosophila alcohol dehydrogenase have been compared with respect to their activity levels on two alcohol substrates, quantities of ADH protein, and stability in crude extracts. Within each allozymic class, strains from widely diverse geographic locations differ in their enzyme activity levels but are identical for a measure known as "activity ratio," which is obtained by dividing the average activity reading on isopropanol by that obtained with ethanol. They are also similar in the rate at which ADH activity declines in crude extracts held at 25 degrees C. For several of the fast-resistant and fast-moderate strains, differences in ADH activity are associated with differences in the amount of enzyme present. The catalytic efficiencies of the fast-resistant forms are considerably lower than those of the fast-moderate allozymes. The origin and persistence of the rare but ubiquitous fast-resistant allozyme is discussed.     

Ancient weapons for attack and defense: the pore-forming polypeptides of pathogenic enteric and free-living amoeboid protozoa

Pore-forming polypeptides have been purified from several amoeboid protozoans that are well-known human pathogens. Obligate enteric parasites, such as Entamoeba histolytica, and free-living but potentially highly pathogenic species, such as Naegleria fowleri, contain these cytolytic molecules inside cytoplasmic granules. Comprehensive functional and structural studies have been conducted that include isolation of the proteins from their natural sources, monitoring of their biological activity towards different targets, and molecular cloning of the genes of their precursors. In the case of the most prominent member of the protein family, with respect to protozoans, the three-dimensional structure of amoebapore A was solved recently. The amoebic pore-forming polypeptides can rapidly perforate human cells. The antibacterial activity of amoebapores and of related polypetides from free-living protozoa points to a more vital function of these molecules: inside the digestive vacuoles they combat growth of phagocytosed bacteria which are killed when their cytoplasmic membranes are permeabilized. The concommitant activity of these proteins towards host cells may be due to a coincidental selection for an efficient effector molecule. Nonetheless, several lines of evidence indicate that these factors are involved in pathogenesis of fatal diseases induced by amoeboid protozoa.     

Recombinant expression and range of activity of penaeidins, antimicrobial peptides from penaeid shrimp.

Penaeidins are 5.5- to 6.6-kDa antimicrobial peptides recently isolated from the plasma and haemocytes of the tropical shrimp Penaeus vannamei. These molecules differ from the other classes of antimicrobial peptides in that they are composed of a proline-rich N-terminus and of a C-terminus containing six cysteine residues engaged in three disulfide bridges. In order to gain information on their antimicrobial activity, two penaeidins (Pen-2 and Pen-3a) were expressed in Saccharomyces cerevisiae. The recombinant Pen-2 and -3a were characterized in terms of primary structure by Edman degradation, mass spectrometry and gas chromatography. A protocol was then established to purify the amount of penaeidins required for the determination of their activity spectrum. We demonstrate in this study that expression in yeast is appropriate for the large-scale production of functional penaeidins, whose activities are almost indistinguishable from those of the native molecules. Data on Pen-2 and -3a activity demonstrate that penaeidins have a broad spectrum of antifungal properties associated with a fungicidal activity, and that their antibacterial activities are essentially directed against Gram-positive bacteria, with a strain-specific inhibition mechanism. Despite a better efficiency of Pen-3a on most of the tested strains, similar activity spectra and inhibition mechanisms were observed for both Pen-2 and -3a. Finally, no synergistic effect could be observed between the two molecules.     

The effects of partner togetherness on salivary testosterone in women in long distance relationships

The present study examined whether women's testosterone levels are influenced by being with a sexual and romantic partner after a period of sexual abstinence. Women in long distance relationships (n = 15) provided five saliva samples: at least 1 week before seeing their partner (and at least 2 weeks since their last visit), the day before seeing their partner, when they were with their partner but prior to engaging in sexual activity, the day after their first sexual activity, and 3 days after they were separated from their partners. Salivary testosterone was lowest when participants had been away from their partners for at least 2 weeks and highest the day before they were to see their partners and the day after sexual activity. Results from this study indicated that women's testosterone increased both the day before they were with their partners and they day after they first engaged in sexual activity. However, something about initially reuniting with their partners returned their testosterone to baseline levels, which may be an effect of being in the same location as a partner, or just a state fluctuation due to nervousness or other psychological state.     

Natural killer-like activity mediated by activated T lymphocytes

Diverse types of lymphocytes mediate in vitro cytotoxic activity. In addition to CTLs (cytotoxic T lymphocytes) and NK (natural killer) cells which differ in their activation requirements, target specificities, and lytic mechanisms, a natural killer-like activity of activated cells (A-NK) has recently been described. The data presented here suggest that an activated T lymphocyte can mediate A-NK activity. A-NK activity can be separated from resting NK activity by its requirement for activation and an effector phenotype (T12+,Ia+,Mol-) which includes the presence of the T12 and Ia antigens and the absence of the Mol antigen. In contrast, resting NK activity is mediated by T12-,Ia-,Mol+ cells. Cells that mediate A-NK activity can be differentiated from CTLs by their differing kinetics of activation and susceptibility to inhibition by monoclonal antibodies. An additional distinguishing feature is the fact that A-NK cells are predominantly Ia+ and are derived from either the T4+ or T8+ T-cell subsets whereas CTLs generated under similar conditions are predominantly T8+,T4-,Ia-. The in vivo relevance of this newly defined T-cell cytolytic activity remains to be defined.     

Importance of the unsaturated fatty acyl group of phospholipids in their stimulatory role on rat adrenal mitochondrial steroidogenesis

We have investigated the relationship between chemical properties of various phospholipids and their steroidogenic activity for adrenal mitochondria prepared from dexamethasone/cycloheximide-treated quiescent rats. Phospholipids studied include those purified from bovine and rat adrenal mitochondria, obtained from commercial sources, and reduced by catalytic hydrogenation. All phospholipids were subjected to analysis of their fatty acyl groups and examined for their steroidogenic activities. From these experiments, we came to the following conclusions: The degree of unsaturation in the fatty acyl moiety correlates with their steroidogenic activities regardless of head groups. Namely, polyunsaturation appears to be more important than monounsaturation with a relative insensitivity toward their head groups. Saturated phospholipids exhibit an inhibition for steroidogenic activity. Cardiolipins, which are steroidogenic, appear exceptional. Their head groups may partially participate in the activity in addition to their high content of unsaturated fatty acids. The importance of the adrenoyl (C22:4) group in phospholipids is suggested.     

In vitro scavenger activity of some flavonoids and melanins against O2-(.).

The scavenger activity against O2-. of some flavonoids and melanins (synthetic melanins and melanins isolated from animal tissues, vegetable seeds, and mushroom spores) has been studied by ESR spectrometry. All these substances, except flavon and flavanone, diminish the signal of O2-. generated in vitro by a system containing H2O2 and acetone in an alkaline medium. It is shown that the presence of hydroxyl groups in the B ring of flavonoids is essential for their scavenger activity. Moreover, the presence of a hydroxyl at C-3 enhances the scavenger ability of flavonoids. Generally, aglycons are more active than their glycosides. It seems plausible that the antioxidant property of these substances comes from their scavenger activity against O2-(.). It is also pointed out that the scavenger activity shown by melanins, is strictly correlated with their nature of stable free radical.     

Proteolytic activity of lectins from the nitrogen-fixing bacterium Bacillus polymyxa

Two lectins (LI and LII) stripped from the surface of Bacillus polymyxa 1460 cells were found to possess proteolytic activity, which was associated with their hemagglutinating activity. The inhibition of the hemagglutinating activity of lectins by specific carbohydrate haptens changed their enzyme activities. The inhibition of hemagglutinating activity by glucuronic acid or fructose 1,6-diphosphate decreased the proteolytic activities of both lectins, whereas the blocking of this activity with D-glucosamine or D-galactosamine increased the proteolytic activity of LII. The molecules of the B. polymyxa lectins are suggested to contain two active centers responsible for hemagglutinating and proteolytic activities.     

The relationship between the golden spiny mouse circadian system and its diurnal activity: an experimental field enclosures and laboratory study

Examples of animals that switch activity times between nocturnality and diurnality in nature are relatively infrequent. Furthermore, the mechanism for switching activity time is not clear: does a complete inversion of the circadian system occur in conjunction with activity pattern? Are there switching centers downstream from the internal clock that interpret the clock differently? Or does the switch reflect a masking effect? Answering these key questions may shed light on the mechanisms regulating activity patterns and their evolution. The golden spiny mouse (Acomys russatus) can switch between nocturnal and diurnal activity. This study investigated the relationship between its internal circadian clock and its diurnal activity pattern observed in the field. The goal is to understand the mechanisms underlying species rhythm shifts in order to gain insight into the evolution of activity patterns. All golden spiny mice had opposite activity patterns in the field than those under controlled continuous dark conditions in the laboratory. Activity and body temperature patterns in the field were diurnal, while in the laboratory all individuals immediately showed a free-running rhythm starting with a nocturnal pattern. No phase transients were found toward the preferred nocturnal activity pattern, as would be expected in the case of true entrainment. Moreover, the fact that the free-running activity patterns began from the individuals' subjective night suggests that golden spiny mice are nocturnal and that their diurnality in their natural habitat in the field results from a change that is downstream to the internal clock or reflects a masking effect.     

Inhibition of Helicobacter pylori haemagglutination activity by human salivary mucins

Thirty isolates of Helicobacter pylori from gastric biopsies agglutinated human erythrocyte suspensions. Crude mucin preparations derived from saliva of 20 different donors were examined for their ability to inhibit haemagglutination. All mucin preparations exhibited strong inhibitory activity. Removal of sialic residues from mucin preparations by treatment with neuraminidase resulted in a substantial reduction of their inhibitory activity. The mucin preparations had no bactericidal or aggregation activity for H. pylori. These results are discussed in the context of the role of mucins in colonization of the gastric mucosa by H. pylori.