Striving for the development of biology—— The celebration of Biomagnetisnt formally changed into Progress in Modern Biomedicine

Time flies! Biomagnetism magazine has been gradually growing up since it was started publication, which was firstly sponsored by China Biomagnetism Society in 1987 as a restricted publication. The publication was given official number by Ministry of Science and Technology in April, 2001, issued by post office in 2003; it was chosen as one of the core periodicals of science and technology in 2004, with influence factor（0.734） and being classified as ninth- rate in periodicals of biology. Upon the approval of Press and Publication Administration（2006 - 4）,this periodical has been formally changed into Progress in Modern Biomedicine.     

Presowing Seed Treatment with Cytokinins and Its Effect on Growth, Photosynthetic Rate, Ionic Levels and Yield of Two Wheat Cultivars Differing in Salt Tolerance

The effects of presowing seed treatment with different concentrations of cytokinins （kinetin and benzylaminopurine; 100, 150, and 200 mg/L） on growth, photosynthetic capacity, and ion homeostasis were investigated in two spring wheat （Triticum aestivum L.） cultivars, namely MH-97 （salt sensitive） and Inqlab- 91 （salt tolerant）. Primed and non-primed seeds were sown in a field in which NaC1 salinity of 15 dS/m was developed. Of the different concentrations of priming agents tested, the effect of a moderate concentration of kinetin （150 mg/L） was very pronounced, particularly in improving growth and grain yield, in both cultivars. In addition, priming with kinetin alleviated the adverse effect of salt stress on gaseous exchange characteristics （net CO2 assimilation rate and water use efficiency） in both cultivars. Seed priming with a moderate concentration of kinetin also altered the pattern of accumulation of Na^＋ and Clˉ in the shoots, irrespective of the wheat cultivar, under conditions of salt stress. However, all other priming agents at the different concentrations tested did not show any consistent effect on ion levels, except hydropriming, which increased K^＋ levels in the shoots of both cultivars under salt stress. In conclusion, a moderate concentration of kinetin showed a consistent effect in altering the growth and grain yield of both wheat cultivars, which was related to the beneficial effects of kinetin priming on water use efficiency and photosynthetic rate under conditions of salt stress.     

Photosynthetic, Physiological and Biochemical Responses of Tomato Plants to Polyethylene Glycol-Induced Water Deficit

Polyethylene glycol （PEG 6000）-induced water deficit causes physiological as well as biochemical changes in plants. The present study reports on the results of such changes in hydroponically grown tomato plants （Lycopersicon esculentum Mill. cv. Nikita）. Plants were subjected to moderate and severe levels of water stress （i.e. water potentials in the nutrient solution of- 0.51 and -1.22 MPa, respectively）. Water stress markedly affected the parameters of gas exchange. Net photosynthetic rate （Pn） decreased with the induction of water stress. Accordingly, a decrease in the transpiration rate （E） was observed. The ratio of both （Pn/E） resulted in a decrease in water use efficiency. One of the possible reasons for the reduction in Pn is structural damage to the thylakoids, which affects the photosynthetic transport of electrons. This was indicated by an increase in non-photochemical quenching and a reduction in the quantum yield of photosystem Ⅱ. Furthermore, a decrease in both leaf water potential and leaf osmotic potential was observed, which resulted in a significant osmotic adjustment during stress conditions. Analysis of the physiological responses was complemented with a study on changes in proline content. In stressed plants, a 10-fold increase in proline content was detected compared with control plants. It is clear that water stress tolerance is the result of a cumulative action of various physiological and biochemical processes, all of which were affected by PEG 6000-induced water stress.     

Distribution of gamasid mites on small mammals in Yunnan Province, China

An investigation of gamasid mites on the body surface of small mammals was carried out in Yunnan Province of China from 1990 to 2004. The small mammal hosts were captured from 25 counties which represent five geographical subregions, namely Middle Subregion of Hengduan Mountains, Southern Subregion of Hengduan Mountains, Eastern Plateau Subregion of Yunnan, Western Plateau Subregion of Yunnan and Southern Moun- tainous Subregion of Yunnan. The captured 10 803 small mammal hosts belong to nine families, 29 genera and 52 species in four orders （Rodentia, Insectivora, Scandentia and Lagomorpha）. A total of 68 571 gamasid mites were collected from the body surface of the captured small mammal hosts and all the gamasid mites were identified to 10 families, 33 genera and 112 species. This paper lists all the mite species, together with their taxonomic position （genera and families） and their corresponding hosts. Much more mite species were found in the Middle Subregion of Hengduan Mountains than in other geographical subregions. The total individuals of mites and small mammals in the Middle Subregion of Hengduan Mountains are also the most plentiful in the five geographical subregions. Three dominant mite species and three dominant small mammal hosts were determined as the dominant species in the investigated areas of Yunnan Province. The dominant hosts are Rattus flavipectus （which accounts for 34.85% of the total individuals）, Apodemus chevrieri （13.43%） and Rattus norvegicus （10.40%） while the dominant gamasid mite species are Laelaps nuttalli （Hirst, 1915） （27.84%）, Laelaps echidninus （Berlese, 1887） （18.38%） and Laelaps guizhouensis （Gu et Wang, 1981） （14.79%）. The results showed the high species diversity of gamasid mites in Yunnan Province and the uneven distribution feature in different subregions.     

（1,3;1,4）-β-D-Glucans in Cell Walls of the Poaceae,Lower Plants,and Fungi： A Tale of Two Linkages

（1,3;1,4）-β-D-Glucans consist of unbranched and unsubstituted chains of （1,3）- and （1,4）-β-glucosyl residues, in which the ratio of （1,4）-β-D-glucosyl residues to （1,3）-β-D-glucosyl residues appears to influence not only the physicochemical properties of the polysaccharide and therefore its functional properties in cell walls, but also its adoption by different plant species during evolution. The （1,3; 1,4）-β-D-glucans are widely distributed as non-cellulosic matrix phase polysaccharides in cell walls of the Poaceae, which evolved relatively recently and consist of the grasses and commercially important cereal species, but they are less commonly found in lower vascular plants, such as the horsetails, in algae and in fungi. The （1,3;1,4）-β-D-glucans have often been considered to be components mainly of primary cell walls, but recent observations indicate that they can also be located in secondary walls of certain tissues. Enzymes involved in the depolymerisation of （1,3;1,4）-β-D-glucans have been well characterized. In contrast, initial difficulties in purifying the enzymes responsible for （1,3;1,4）-β-D-glucan biosynthesis slowed progress in the identification of the genes that encode （1,3;1,4）-β-D-glucan synthases, but emerging comparative genomics and associated techniques have allowed at least some of the genes that contribute to （1,3;1,4）-β-D-glucan synthesis in the Poaceae to be identified. Whether similar genes and enzymes also mediate （1,3;1,4）-β-D-glucan biosynthesis in lower plants and fungi is not yet known. Here, we compare the different fine structures of （1,3;1,4）-β-D-glucans across the plant kingdom, present current information on the genes that have been implicated recently in their biosynthesis, and consider aspects of the cell biology of （1,3;1,4）-β-D-glucan biosynthesis in the Poaceae.     

Regulation of enzyme turnover during tissue differentiation. Studies on 6-phosphogluconate dehydrogenase in rabbit mammary gland in organ culture.

(1) Explants of mammary gland from mid-pregnant rabbits were cultured in Medium 199 in the presence or absence of insulin, prolactin and cortisol. (2) Antiserum to 6-phosphogluconate dehydrogenase was raised in sheep and used to titrate the amount of enzyme activity present in explant extracts. Changes in enzyme activity were found to be due to corresponding changes in amount of the enzyme. The greatest increases in the amount of the enzyme were only brought about by culture of explants in the presence of hormones (insulin, prolactin and cortisol) in Medium 199 which contained glucose. (3) The increases in the amount of the enzyme were similar in explants cultured with hormones in Medium 199 which contained 1.39 mM, 5.55 mM or 55.5 mM glucose. (4) When explants were cultured with hormones in Medium 199 which contained glucose (5.55 mM) for 24 h and then cultured with hormones in Medium 199 which contained glycerol (10.9 mM), a decrease in the amount of the enzyme occurred. In contrast, the culture of explants with hormones in Medium 199 which contained glycerol (10.9 mM) for 24 h followed by transfer of the explants to medium which contained glucose (5.55 mM) resulted in an increase in the amount of the enzyme to reach values which were not different from those found in explants cultured throughout with hormones in Medium 199 which contained glucose.     

POLYADENYLIC ACID-CONTAINING RNA FROM RAT BRAIN

A portion of rat brain RNA contains poly(A) sequences and binds to oligo(dT)-cellulose. Young rats have a greater amount of brain RNA which contains poly(A) than do adult animals. The length of the poly(A) sequence from the brain RNA of young animals was shown to be somewhat longer than that from the RNA of adults. The RNA which bound to the oligo(dT)-cellulose was found to be large and heterogeneous, and to be almost free of ribosomal or of small mol. wt. RNAs. When the polysomal RNA which bound to the oligo(dT)-cellulose columns and that which did not were used to prime a cell-free protein synthesizing system there was a noticeable difference in their‘messenger’activity; the RNA which bound to the oligo(dT)-cellulose was much more active than the unbound material. However, in the case of the nuclear RNA there was not as great a difference between the material which was bound and that which was not bound.     

Isolation and characterization of developmental variants in fruiting using a homokaryotic fruiting strain ofCoprinus cinereus

Developmental variants in fruiting ofCoprinus cinereus were induced by mutagenizing oidia of the homokaryotic fruiting strain CopD5-12 with UV light. Through screening of 2,696 isolates, 1,018 strains exhibited defects in fruiting and were classified into 8 groups: (1) knotless variants, which fail to form hyphal knots, the first visible sign of fruiting; (2) primordiumless variants, which form hyphal knots but fail to develop fruit-body primordia; (3) maturationless variants, which form fruit-body primordia but do not form mature fruit bodies; (4) elongationless variants, which form mature fruit bodies with short stipes; (5) expansionless variants, which form mature fruit bodies with unexpanded pilei; (6) sporeless variants, which fail to produce black basidiospores, resulting in fruit bodies with white pilei after maturation; (7) compound type, which includes variants exhibiting several of the phenotypes described above; (8) others, including variants that produce a “dark stipe” even under in light/dark conditions, which is formed under continuous darkness in the wild-type. Two elongationless variants were characterized histologically.     

Bundle sheath diffusive resistance to CO(2) and effectiveness of C(4) photosynthesis and refixation of photorespired CO(2) in a C(4) cycle mutant and wild-type Amaranthus edulis

A mutant of the NAD-malic enzyme-type C(4) plant, Amaranthus edulis, which lacks phosphoenolpyruvate carboxylase (PEPC) in the mesophyll cells was studied. Analysis of CO(2) response curves of photosynthesis of the mutant, which has normal Kranz anatomy but lacks a functional C(4) cycle, provided a direct means of determining the liquid phase-diffusive resistance of atmospheric CO(2) to sites of ribulose 1,5-bisphosphate carboxylation inside bundle sheath (BS) chloroplasts (r(bs)) within intact plants. Comparisons were made with excised shoots of wild-type plants fed 3,3-dichloro-2-(dihydroxyphosphinoyl-methyl)-propenoate, an inhibitor of PEPC. Values of r(bs) in A. edulis were 70 to 180 m(2) s(-1) mol(-1), increasing as the leaf matured. This is about 70-fold higher than the liquid phase resistance for diffusion of CO(2) to Rubisco in mesophyll cells of C(3) plants. The values of r(bs) in A. edulis are sufficient for C(4) photosynthesis to elevate CO(2) in BS cells and to minimize photorespiration. The calculated CO(2) concentration in BS cells, which is dependent on input of r(bs), was about 2,000 microbar under maximum rates of CO(2) fixation, which is about six times the ambient level of CO(2). High re-assimilation of photorespired CO(2) was demonstrated in both mutant and wild-type plants at limiting CO(2) concentrations, which can be explained by high r(bs). Increasing O(2) from near zero up to ambient levels under low CO(2), resulted in an increase in the gross rate of O(2) evolution measured by chlorophyll fluorescence analysis in the PEPC mutant; this increase was simulated from a Rubisco kinetic model, which indicates effective refixation of photorespired CO(2) in BS cells.     

Contribution of polyol pathway to arteriolar dysfunction in hyperglycemia. Role of oxidative stress, reduced NO, and enhanced PGH(2)/TXA(2) mediation

Hyperglycemia increases glucose metabolism via the polyol pathway, which results in elevations of intracellular sorbitol concentration. Thus we hypothesized that elevated level of sorbitol contributes to the development of hyperglycemia-induced dysfunction of microvessels. In isolated, pressurized (80 mmHg) rat gracilis muscle arterioles (approximately 150 microm), high glucose treatment (25 mM) induced reduction in flow-dependent dilation (from maximum of 39 +/- 2% to 15 +/- 1%), which was significantly mitigated by an aldose reductase inhibitor, zopolrestat (maximum 27 +/- 2%). Increasing doses of sorbitol (10(-10)-10(-4) M) elicited dose-dependent constrictions (maximum 22 +/- 3%), which were abolished by endothelium removal, a prostaglandin H(2)/thromboxane A(2) (PGH(2)/TXA(2)) receptor (TP) antagonist SQ-29548, or superoxide dismutase (SOD) plus catalase (CAT). Incubation of arterioles with sorbitol (10(-7) M) reduced flow-dependent dilations (from maximum of 39 +/- 2% to 20 +/- 1.5%), which was not further affected by inhibition of nitric oxide synthase by N(omega)-nitro-l-arginine methyl ester but was prevented by SOD plus CAT and mitigated by SQ-29548. Nitric oxide donor sodium nitroprusside-induced (10(-9)-10(-6) M) dilations were also decreased in a SQ-29548 and SOD plus CAT-reversible manner, whereas adenosine dilations were not affected by sorbitol exposure. Sorbitol significantly increased arterial superoxide production detected by lucigenin-enhanced chemiluminescence, which was inhibited by SOD plus CAT. Sorbitol treatment also increased arterial formation of 3-nitrotyrosine. We suggest that hyperglycemia by elevating intracellular sorbitol induces oxidative stress, which interferes with nitric oxide bioavailability and promotes PGH(2)/TXA(2) release, both of which affect regulation of vasomotor responses of arterioles. Thus increased activity of the polyol pathway may contribute to the development of microvascular dysfunction in diabetes mellitus.     

Roles of Lignin Peroxidase and Manganese Peroxidase from Phanerochaete chrysosporium in the Decolorization of Olive Mill Wastewaters

The relative contributions of lignin peroxidase (LiP) and manganese peroxidase (MnP) to the decolorization of olive mill wastewaters (OMW) by Phanerochaete chrysosporium were investigated. A relatively low level (25%) of OMW decolorization was found with P. chrysosporium which was grown in a medium with a high Mn(II) concentration and in which a high level of MnP (0.65 (mu)M) was produced. In contrast, a high degree of OMW decolorization (more than 70%) was observed with P. chrysosporium which was grown in a medium with a low Mn(II) concentration but which resulted in a high level of LiP activity (0.3 (mu)M). In this culture medium, increasing the Mn(II) concentration resulted in decreased levels of OMW decolorization and LiP activity. Decolorization by reconstituted cultures of P. chrysosporium was found to be more enhanced by the addition of isolated LiP than by the addition of isolated MnP. The highest OMW decolorization levels were obtained at low initial chemical oxygen demands combined with high levels of extracellular LiP. These data, plus the positive effect of veratryl alcohol on OMW decolorization and LiP activity, indicate that culture conditions which yield high levels of LiP activity lead to high levels of OMW decolorization.     

Superoxide Dismutases of Escherichia coli: Intracellular Localization and Functions

Escherichia coli B contains two superoxide dismutases which differ with respect to their localization within the cell, the nature of their prosthetic metals, their responses to changes in (p)O(2), and their functions. One of these enzymes, which was liberated from the cells by osmotic shock and which was therefore presumed to be localized in the periplasmic space, is an iron-containing superoxide dismutase. The amount of this iron enzyme did not vary in response to changes in (p)O(2) during growth. In contrast, the other superoxide dismutase was not solubilized by osmotic shock, was a mangano-protein, and was found in greater amounts in cells which had been grown at high (p)O(2). E. coli, which had low levels of the iron-enzyme and high levels of the mangano-enzyme, as a consequence of growth in iron-deficient aerated medium, was killed by exposure to an exogenous flux of O(2) (-) which was generated either photochemically or enzymatically. The addition of bovine superoxide dismutase to the suspending medium protected these cells against this stress. On the other hand, E. coli, which had high levels of the iron-enzyme and low levels of the mangano-enzyme, as a consequence of growth in iron-rich anaerobic medium, was resistant to exogeneous O(2) (-). On the basis of these and of previously reported results (4a, Yost, F. J. and I. Fridovich, J. Biol. Chem., 1973, in press), it appears that the iron superoxide dismutase, of the periplasmic space, serves as a defense against exogenous O(2) (-), whereas the mangano-superoxide dismutase, in the matrix of these cells, serves to counter the toxicity of endogenous O(2) (-).     

A new phosphatidylinositol 4,5-bisphosphate-binding site located in the C2 domain of protein kinase Calpha

In view of the interest shown in phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)) as a second messenger, we studied the activation of protein kinase Calpha by this phosphoinositide. By using two double mutants from two different sites located in the C2 domain of protein kinase Calpha, we have determined and characterized the PtdIns(4,5)P(2)-binding site in the protein, which was found to be important for its activation. Thus, there are two distinct sites in the C2 domain: the first, the lysine-rich cluster located in the beta3- and beta4-sheets and which activates the enzyme through direct binding of PtdIns(4,5)P(2); and the second, the already well described site formed by the Ca(2+)-binding region, which also binds phosphatidylserine and a result of which the enzyme is activated. The results obtained in this work point to a sequential activation model, in which protein kinase Calpha needs Ca(2+) before the PtdIns(4,5)P(2)-dependent activation of the enzyme can occur.