Leguminosae plants play a key role in affecting soil physical-chemical and biological properties during grassland succession after farmland abandonment in the Loess Plateau,China

Leguminosae are an important part of terrestrial ecosystems and play a key role in promoting soil nutrient cycling and improving soil properties.However,plant composition and species diversity change rapidly during the process of succession,the effect of leguminosae on soil physical-chemical and biological properties is still unclear.This study investigated the changes in the composition of plant community,vegetation characteristics,soil physical-chemical properties,and soil biological properties on five former farmlands in China,which had been abandoned for 0,5,10,18,and 30 a.Results showed that,with successional time,plant community developed from annual plants to perennial plants,the importance of Leguminosae and Asteraceae significantly increased and decreased,respectively,and the importance of grass increased and then decreased,having a maximum value after 5 a of abandonment.Plant diversity indices increased with successional time,and vegetation coverage and above-and below-ground biomass increased significantly with successional time after 5 a of abandonment.Compared with farmland,30 a of abandonment significantly increased soil nutrient content,but total and available phosphorus decreased with successional time.Changes in plant community composition and vegetation characteristics not only change soil properties and improve soil physical-chemical properties,but also regulate soil biological activity,thus affecting soil nutrient cycling.Among these,Leguminosae have the greatest influence on soil properties,and their importance values and community composition are significantly correlated with soil properties.Therefore,this research provides more scientific guidance for selecting plant species to stabilize soil ecosystem of farmland to grassland in the Loess Plateau,China.

Biomedical rare-earth magnesium alloy:Current status and future prospects

Biomedical magnesium(Mg)alloys have garnered significant attention because of their unique biodegradability,favorable biocompatibility,and suitable mechanical properties.The incorporation of rare earth(RE)elements,with their distinct physical and chemical properties,has greatly contributed to enhancing the mechanical performance,degradation behavior,and biological performance of biomedical Mg alloys.Currently,a series of RE-Mg alloys are being designed and investigated for orthopedic implants and cardiovascular stents,achieving substantial and encouraging research progress.In this work,a comprehensive summary of the state-of-the-art in biomedical RE-Mg alloys is provided.The physiological effects and design standards of RE elements in biomedical Mg alloys are discussed.Particularly,the degradation behavior and mechanical properties,including their underlying action are studied in-depth.Furthermore,the preparation techniques and current application status of RE-Mg alloys are reviewed.Finally,we address the ongoing challenges and propose future prospects to guide the development of high-performance biomedical Mg-RE alloys.

Biological properties of differently-aged human keratinocytes:population doubling time growth curve and cell cycle analysis

Objective To explore the biological properties of keratinocytes from differently-aged healthy human beings. Methods Keratinocytes from fetus,teenager and middle-aged groups were separated and cultured. The population doubling time (PDT) and cell growth curve in different cells were compared,and the cell cycles were analyzed by flow cytometry. Results ① In primary culture of keratinocytes,the adherence time in middle-aged group was longer than that in fetus and teenager groups. However,all cell morphology showed no obvious differences. In subculture of keratinocytes,with donator’s age increasing,time of cell adherence prolonged,passage number decreased and differences in cell morphology were obvious. ② The average PDT of keratinocytes was shorter in fetus group than in teenager and middle-aged groups. But difference in cell growth curve between different passages was not observed. ③ Keratinocytes showed G2/M period in fetus group but G0/G1 period in teenager and middle-aged groups mainly. Conclusion As age increases,the biological properties of keratinocytes change obviously.

Recovery and Biological Properties of Nitrate Non-utilizing Mutants of Rice Blast,Magnaporthe grisea

Eleven nitrate non-utilizing (nit) mutants were recovered from six isolates of Magnaporthe grisea cultured on MM media -amended with 60 g/L potassium chlorate, with a frequency of 1.42 %. Some biological properties, such as growth rate, growth biomass, cultural characters, conidial production, sexual reproduction ability, and pathogenicity were compared between nit mutants and their parent isolates. Results showed that all the nit mutants were resistant to chlorate. Some important biological properties such as the growth rate on YPSA, conidial production ability on TPSA, pathogenicity, had no significant differences between nit mutants and their parent isolates. Mating type didn't change, but perithecia production ability of fertile isolates changed significantly as compared with that of their parent isolates. Therefore, the nit can be used as a genetic marker to study the genetics such as pathogenicity, fungicide resistance in Magnaporthe grisea.

Calcium phosphate cements for bone engineering and their biological properties

Calcium phosphate cements （CPCs） are frequently used to repair bone defects. Since their discovery in the 1980s, extensive research has been conducted to improve their properties, and emerging evidence supports their increased application in bone tissue engineering. Much effort has been made to enhance the biological performance of CPCs, including their biocompatibility, osteoconductivity, osteoinductivity, biodegradability, bioactivity, and interactions with cells. This review article focuses on the major recent developments in CPCs, including 3D printing, injectability, stem cell delivery, growth factor and drug delivery, and pre- vascularization of CPC scaffolds via co-culture and tri-culture techniques to enhance angiogenesis and osteogenesis.

Effects of shifting cultivation on biological and biochemical characteristics of soil microorganisms in Khagrachari hill district, Bangladesh

We collected soil samples from two representative sites at Aatmile of Khagarachari hill district in Chittagong Hill Tracts. One of the sites was under shifting cultivation and the other an adjacent 13-year old teak plantation. Both sites were in the same physiographic condition and same aspect with parable soil type, which enabled us to measure the effects of shifting cultivation on soil micro-flora. We studied soil phys-ico-chemical properties and the biochemical and biological properties of soil microbes. Moisture and organic matter content as well as fungi and bacterial populations, both in surface and subsurface soils, were signifi-cantly （p≤0.001） lower in shifting cultivated soils compared to soils not under shifting cultivation, i.e. the teak plantation site. The most abundant bacteria in surface （0-10 cm） and sub-surface （10-20 cm） soils under shifting cultivation were Pseudomonas diminuta and Shigella, respec-tively, while in corresponding soil layers of teak plantation, predominant microbes were Bacillus firmus （0-10 cm） and Xanthomonas （10-20 cm）. The microbial population differences cannot be explained by soil texture differences because of the textural similarity in soils from the two sites but could be related to the significantly lower moisture and organic mat-ter contents in soils under shifting cultivation.

Influence of bean rhizosphere on the biological properties and phosphorus fractionation in the calcareous soils amended with municipal sewage sludge

The biological and chemical conditions of the rhizosphere are known to considerably differ from those of the bulk soil, as a consequence of a range of processes that are induced either directly by the activity of plant roots or indirectly by the stimulation of microbial population and activity in the rhizosphere. Information about phosphorus （P） fractionation in the rhizosphere soils amended with municipal sewage sludge （MSS） is limited, were We carried out greenhouse experiments using a rhizobox in order to evaluate the effects of bean rhizosphere on the various inorganic P （Pi） fractions, organic P （Po）, P in particulate fraction （PF-P）, Olsen-P, dissolved organic C （DOC）, microbial biomass P （MBP） and alkaline phosphatase （ALP） enzyme in 10 calcareous soils amended with MSS （10 g MSS was added to 1 kg soil）. Non-occluded P, occluded P, calcium phosphate and residual P were also quantitated. The results showed that DOC, MBP and ALP activity strongly increased and PF-P and Olsen-P de- creased in the rhizosphere soils compared with in the bulk soils （P〈0.05）. The contents of non-occluded P, oc- cluded P and residuaI-P fractions in the rhizosphere soils were lower than in the bulk soils, while the contents of calcium phosphate and organic P in the rhizosphere soils were higher than in the bulk soils. Simple correlation coefficients showed that P uptake had positive relationship with non-occluded P, occluded P, calcium phosphate fractions and PF-P in the rhizosphere soils. The results suggest that the short-term application of MSS to the cal- careous soils may increase Po and calcium phosphate fractions in the rhizosphere soils, and calcium phosphate fraction is potentially available to crops.

Deforestation effects on biological and other important soil properties in an upland watershed of Bangladesh

Deforestation occurs at an alarming rate in upland watersheds of Bangladesh and has many detrimental effects on the environment. This study reports the effects of deforestation on soil biological proper- ties along with some important physicochemical parameters of a southern upland watershed in.Bangladesh. Soils were sampled at 4 paired sites, each pair representing a deforested site and a forested site, and having similar topographical characteristics. Significantly fewer （p〈0.001） fungi and bacteria, and lower microbial respiration, active microbial biomass, metabolic and microbial quotients were found in soils of the deforested sites. Soil physical properties such as moisture content, water holding capacity, and chemical properties such as organic matter, total N, avail- able P and EC were also lower in deforested soils. Bulk density and pH were significantly higher in deforested soils. Available Ca and Mg were inconsistent between the two land uses at all the paired sites. Re- duced abundance and＇biomass of soil mesofauna were recorded in defor- ested soils. However, soil anecic species were more abundant in defor- ested soils than epigeic and endogeic species, which were more abundant in forested soils than on deforested sites.

MEASUREMENT OF THE DIELECTRIC PROPERTIES OF BIOLOGICAL TISSUE

An open-ended coaxial line reflection method especially suitable for meas-uring the dielectric properties of biological tissue in vivo is described.This method offersthe advantage of not requiring any special preparation of the samples to be measured but aclose contact with the open end of a coaxial line.It is,therefore,very convenient to acquirea large number of measurement data in broad band rapidly.The method may also be usedto measure the properties of other substances.The measuring system consists of a networkanalyzer controlled by a microcomputer and calibrated by using ANA procedure to elimi-hate the influnce of error network introduced by the adapter,some connectors,etc.In or-der to reach higher accuracy,the iterative method is used to determine the parameters ofthe equivalent circuit.Measurements of permeativities of some living tissues have been per-formed in the frequency band of 0.5-2GHz.Compared with the results known in somepapers,the validity of this method has been confirmed.The difference in dielectric proper-ties between living and dead tissues,and the tissue permeativites(ε)versus frequency andduration of measurement after death have also been measured.

Construction of Burkholderia pseudomalleiΔrelA mutant and comparison of their biological characteristics

Objective: The relA gene,a gene associated with the synthesis of rigorous response signaling molecule (p)ppGpp in Burkholderia pseudomallei, was knocked out and its effects on the biological functions of bacterial growth, motility and biofilm formation were investigated. Methods: The plasmids with trimethoprim resistance (TPR) were modified by enzyme digestion and enzyme ligation method. The TPR fragment was linked to the suicide plasmid pK18mobSacB containing SacB sucrose killing gene by Bgl Ⅱ enzyme digestion site, and trimethoprim resistance was obtained Plasmid(TPR-pK18mobSacB);The relA gene of Burkholderia pseudomallei HNBP001 was knocked out by homologous recombinant gene knockout method, and the relA mutant was obtained. The growth, motility and biofilm phenotypes of Burkholderia pseudomallei HNBP001 were compared before and after the deletion of relA gene. Results: The relA mutant was successfully constructed. The growth rate, motility and biofilm formation of ΔrelA decreased. Conclusion: The modified plasmid TPR- pK18mobSacB can improve the knockout efficiency of HNBP001 strain, which can be widely used in the gene knockout of Burkholderia pseudomallei, and provide convenience for the laboratory to study the gene function of Burkholderia pseudomallei at the molecular level;The mutant of the relA gene inhibits the growth, motility and biofilm formation of HNBP001.

Design, Synthesis, Chemistry and Biological Evaluation of Some Polyfunctional Heterocyclic Nitrogen Systems—Overview

The synthesis, preparation, chemical reactivities and biological activity of simple heterocyclic and heteropolycyclic nitrogen systems as small units as functional pyrazoles, pyridine and pyrimidine, and the related fused systems are reviewed. Among the various possible routes to the formation, isomeric structures have been cited because of patented reaching advanced phases of clinical trials, from 2000 to 2020.

Porous metal implants: processing,properties, and challenges

Porous and functionally graded materials have seen extensive applications in modern biomedical devices—allowing for improved site-specific performance;their appreciable mechanical,corrosive,and biocompatible properties are highly sought after for lightweight and high-strength load-bearing orthopedic and dental implants.Examples of such porous materials are metals,ceramics,and polymers.Although,easy to manufacture and lightweight,porous polymers do not inherently exhibit the required mechanical strength for hard tissue repair or replacement.Alternatively,porous ceramics are brittle and do not possess the required fatigue resistance.On the other hand,porous biocompatible metals have shown tailorable strength,fatigue resistance,and toughness.Thereby,a significant interest in investigating the manufacturing challenges of porous metals has taken place in recent years.Past research has shown that once the advantages of porous metallic structures in the orthopedic implant industry have been realized,their biological and biomechanical compatibility—with the host bone—has been followed up with extensive methodical research.Various manufacturing methods for porous or functionally graded metals are discussed and compared in this review,specifically,how the manufacturing process influences microstructure,graded composition,porosity,biocompatibility,and mechanical properties.Most of the studies discussed in this review are related to porous structures for bone implant applications;however,the understanding of these investigations may also be extended to other devices beyond the biomedical field.

Additive manufacturing of biodegradable magnesium-based materials:Design strategies,properties,and biomedical applications

Magnesium(Mg)-based materials are a new generation of alloys with the exclusive ability to be biodegradable within the human/animal body.In addition to biodegradability,their inherent biocompatibility and similar-to-bone density make Mg-based alloys good candidates for fabricating surgical bioimplants for use in orthopedic and traumatology treatments.To this end,nowadays additive manufacturing(AM)along with three-dimensional(3D)printing represents a promising manufacturing technique as it allows for the integration of bioimplant design and manufacturing processes specific to given applications.Meanwhile,this technique also faces many new challenges associated with the properties of Mg-based alloys,including high chemical reactivity,potential for combustion,and low vaporization temperature.In this review article,various AM processes to fabricate biomedical implants from Mg-based alloys,along with their metallic microstructure,mechanical properties,biodegradability,biocompatibility,and antibacterial properties,as well as various post-AM treatments were critically reviewed.Also,the challenges and issues involved in AM processes from the perspectives of bioimplant design,properties,and applications were identified;the possibilities and potential scope of the Mg-based scaffolds/implants are discussed and highlighted.

Genetic Study on JS399-19 Resistance in Hyphal Fusion of Fusarium graminearum by Using Nitrate Nonutilizing Mutants as Genetic Markers

Twenty-two nitrate nonutilizing （nit） mutants were recovered from five wild-type isolates of Fusarium graminearum and fifty nit mutants were recovered from three JS399-19-resistant mutants of F. graminearum cultured on MMC medium. Some biological properties were compared between nit mutants and their parental isolates. The results showed that there were no significant differences in growth rate, cultural characters or pathogenicity between JS399-19-resistant nit mutants and their parental isolates. But the conidial production and the sexual reproduction ability changed to some extent. There was no cross resistance toward chlorate and JS399-19 in F. graminearum and the resistance could be stable through 20-time subcultures. Therefore, the nit could be used as a genetic marker for studying the genetics of JS399-19 resistance in E graminearum, which was used to study JS399-19 resistance transferability in hyphal fusion. Resistance in JS399-19 could not be transferred by hyphal fusion or could be transferred with low chance between two compatible isolates, which would delay the development of JS399-19 resistance in the field.

The Establishment and Characterization of a Continuous Cell Line of Mouse Cervical Carcinoma

OBJECTIVE To establish a murine uterine cervical cancer cell line and to define its biological characters. METHODS Transplanted tumor tissue was used for in vitro primary culture of U14 cervical carcinoma cells. After 20 passages, we examined its morphology, chromosomes, tumorigenicity and produced a growth curve. CK was detected by immunohistochemistry, the cell cycle determined by flow cytometry and the metastatic potential assessed in 615 and C57BL/c mice. We also transfected the cells with the pEGFP-N1 plasmid. RESULTS A newly established murine cell line was passaged 50 times over a period of 10 months. The cells grow as a partially suspended culture, and are immunohistochemically CK（＋）. The cell line is characterized by a hypotetraploid karyotype, a chromosomal number of 64-68 and a doubling time of 21.8 h. Exponential growth occurs by the third and forth day of culture. Cell cycle analysis showed G1 34%, G2 26%, and 40% in the S phase. The tumorigenicity was 100% upon implantation. No mycoplasma contamination was detected. A monoclonal continuous U14-GFP cell strain which was 100% GFP （＋） was also produced. CONCLUSION We successfully established a new murine cervical U14 carcinoma cell line and an U14-GFP monoclonal strain. These cell lines are ideal for combined in vivo and in vitro tumor research.

Recent advances in hydrothermal modification of calcium phosphorus coating on magnesium alloy

Magnesium(Mg) and its alloys have emerged as a favored candidate for bio-regenerative medical implants due to their superior biocompatibility, biodegradability and the elastic modulus close to that of human bone. Unfortunately, the rapid and uncontrollable degradation rate of Mg alloys in chloride-rich body microenvironments limits their clinical orthopedic applications. Recently, Calcium Phosphate(Ca-P)biomaterials, especially Hydroxyapatite(HA), have been broadly applied in the surface functional modification of metal-based biomaterials attributed to their excellent bioactivity and biocompatibility. Hydrothermal modification of Ca-P coatings on Mg alloys has been extensively exploited by researchers for its significant superiorities in controlling coating structure and improving interfacial bonding strength for better osseointegration and corrosion resistance. This work focuses on the up-to-the-minute advances in Ca-P coatings on the surface of Mg and its alloys via hydrothermal methods, including the strategies and mechanisms of hydrothermal modification. Herein, we are inclined to share some feasible and attractive hydrothermal surface modification strategies. From the perspectives of hydrothermal manufacturing technique innovation and coating structure optimization, we evaluate how to foster the corrosion resistance, coating bonding strength, osseointegration and antibacterial properties of Mg alloys with Ca-P coatings synthesized by hydrothermal method. The challenges and future perspectives on the follow-up exploration of Mg alloys for orthopedic applications are also elaborately proposed.

Micro and nano-enabled approaches to improve the performance of plasma electrolytic oxidation coated magnesium alloys

Magnesium(Mg)and its alloys have become a hot research topic in various industries owing to the specific physical and chemical properties.However,high corrosion rate is considered the key lifetime-limiting.Plasma electrolytic oxidation(PEO)method is a simple strategy to deposit an oxide layer on the surface of light metals such as magnesium alloys,to control corrosion rate and promote some other properties,depending on their performances.Nevertheless,their features including their micropore size,distribution,and interconnectivity,and microcracks have not been improved to an acceptable level to support long-term performances of the magnesium-based substrates.Studies have introduced micro/nano-enabled approaches to enhance various properties of PEO coatings such as corrosion resistance,tribological properties,self-healing ability,bioactivity,biocompatibility,antibacterial properties,or catalytic performances.These strategies consist of incorporating of micro and nanoparticles into the PEO layers to produce multi-functional surfaces or the formation of multi-layered coatings to cover the defects of PEO coatings.In this perspective,the present paper aims to overview various nano/micro-enabled strategies to promote the properties of PEO coatings on magnesium alloys.The main focus is given to the functional changes that occurred in response to the incorporation of various types of nano/micro-structures into the PEO coatings on magnesium alloys.

Shifting cultivation effects on soil fungi and bacterial population in Chittagong Hill Tracts, Bangladesh

A study was conducted at two pair sites of Chittagong Hill Tracts in Bangladesh to find out the effects of shifting cultivation on soil fungi and bacterial population. The first pair of sites with shifting culti-vation and village common forest-managed by indigenous community was at Madhya Para in Rangamati district and the second pair of sites with the shifting cultivated land and village common forest at Ampu Para in Bandarban district of Chittagong Hill Tracts. At both the locations with two different land uses, soil textures in surface （0？10 cm） and sub-surface （10？20 cm） soils varied from sandy loam to sandy clay loam. Soil pH and moisture content were lower in shifting cultivated land com-pared to village common forest. The results also showed that both fungal and bacterial population in surface and subsurface soils was significantly （p ≤ 0.05） lower, in most cases, in shifting cultivated land compared to village common forest at both Madhya Para and Ampu Para. At Ranga-mati and Bandarban in shifting cultivated lands, Colletrotrichum and Fusarium fungi were absent and all the bacterial genus viz. Coccus, Bacillus and Streptococcus common in two different locations with dif-ferent land uses. Common identified fungi at both the land uses and locations were Aspergillus, Rhizopus, Trichoderma and Penicillium. Further study can be done on the other soil biota to understand the extent of environmental deterioration due to shifting cultivation.

First isolation and characterization of a new species of Vibrio from diseased flounder(Paralichthys olivaceus Temminck et Schlegel)

Appropriate pathogenic bacteria were isolated from diseased (or dead) flounder (Paralichthys olivaceus L) occurring in a mariculture farms of Qinhuangdao, which all diseased fishes expressed bacterial septicaemia. The phenotypic information of the 12 pure cultures was studied extensively, including morphological characteristics, colony characteristics in different media, physiological and biochemi- cal characteristics, and the mole fraction G+C ratio of the DNA for representative strain. The results show that the isolates belong to a new species of Vibrio, and are designated as Vibrio qinhuangdaora sp.nov. by the area from which the diseased flounders are collected (Qinhuangdao) based on its biological properties following Rules of International Code of Nomenclature of Bacteria. At the same time, studies on the serum homology of isolates, and pathogenicity of isolates were conducted by experimental infection. The results show that all the isolates are of serologic similarity, and the isolates have strong pathogenicity to flounder. The studies can extensively reflect the main biological properties of this new species of Vibrio.

Nonlinearity of muscle stiffness

In this letter, a comparison between three types （two linear and one nonlinear） of models of skeletal muscle stiffness is shown. Results are compared with experimental data for biceps brachii in the case of muscle stretching and with the Hill equation for a biological muscle. It is shown that results for nonlinear stiffness model in case of length-force relationship fits to the experimental data.