Prehensile control of a hand prosthesis by a microcontroller

The functional replacement of a natural hand and wrist is usually achieved by a split hook or an electrically powered and myoelectrically controlled artificial hand with one degree of freedom. In contrast to the commercial devices, this paper describes an experimental hand with four electric motors, nineteen sensors, and control algorithms which are written for a microcontroller. The hand significantly improves the prehension capabilities of an artificial device and leads to a design which is easily controlled by a user as it mimics the control system of the natural hand.     

Biosynthesis of a prostaglandin by a plant enzyme.

Lipoxygenase-2 from soybeans catalyzes the oxygenation of arachidonic acid to form significant amounts of a prostaglandin product. Results obtained with the dithionite-reduced derivatized product upon combined gas chromatography-mass spectroscopy are consistent with structures of the stereoisomers of 9,11,15-trihydroxyprosta-5,13-dienoic acid. A portion of the material formed by reduction of the enzyme product with dithionite reacts positively in a radioimmunoassay against rabbit anti-prostaglandin F2alpha antibody. This appears to be the first report of the synthesis of a prostaglandin by a non-animal enzyme.     

Disruption of a Silencer Domain by a Retrotransposon

A galactose-inducible Ty element carrying the HIS3 gene has been used as an insertional mutagen to generate alpha-factor resistant mutants. This collection of Ty-induced mutations includes insertions into the gene for the alpha-factor receptor (STE2), several nonspecific STE genes, and mutations that lead to the expression of the normally silent HML alpha locus. The hml alpha "on" mutations fall into two classes, those that disrupt trans-acting regulators involved in silencing HML alpha and a novel class of mutations that activate HML alpha by insertion at that locus. The hml alpha::Ty "on" mutations illustrate the unusual ability of these retrotransposons to activate genes by overcoming gene silencing mechanisms. The hml alpha::Ty "on" mutations include examples of multimeric Ty arrays. Single Ty and solo delta insertion derivatives of these Ty multimers restore the ability of the silencing mechanism to repress HML alpha.     

Exploitation of a specialized mutualism by a deceptive orchid

Plants that lack floral rewards may nevertheless attract pollinators through mimetic resemblance to the flowers of co-occurring rewarding plants. We show how a deceptive orchid (Disa nivea) successfully exploits a reciprocally specialized mutualism between a nectar-producing plant (Zaluzianskya microsiphon) and its long-proboscid fly pollinator (Prosoeca ganglbaueri). Disa nivea is a rare southern African orchid known only from habitats that support large populations of Z. microsiphon, which it closely resembles in both general morphology and floral spectral reflectance. Significant covariation in floral traits of Z. microsiphon and D. nivea was detected among populations. Where mimics are uncommon, flies do not appear to discriminate between the flowers of the two species. Pollination success in D. nivea was much higher at a site with abundant Z. microsiphon plants than at a site where Z. microsiphon was rare. Exploitation of a highly specialized mutualism appears to demand a high degree of phenotypic resemblance to a rewarding model by a deceptive mimic, as exemplified by D. nivea. The majority of deceptive orchids, on the other hand, exploit relatively generalized pollination systems and thus require only a vague resemblance to rewarding plants in the community in order to attract pollinators.     

Diagnostics of a magnetized plasma by the field of surface waves guided by a discharge channel

A diagnostic method for determining plasma density from the dispersion of surface waves guided by a discharge channel in an axial magnetic field is discussed. The diagnostic characteristics that are the easiest to record experimentally are determined by analyzing the theoretical dispersion curves, and the ways of exploiting these characteristics for plasma diagnostics are suggested. To determine the slowing-down factor of a probing wave in a plasma channel, it is proposed to use diagnostic-signal resonances that occur when the wavelength of the slowed wave becomes equal to the length of the emitting or receiving antenna. The dependence of the plasma density averaged over the cross section of the plasma column on the strength of the external magnetic field is determined for a discharge channel formed as a result of the ionization self-channeling of plasma (lower hybrid) waves and whistlers.     

Diel infection of a cyanobacterium by a contractile bacteriophage

Light was found to strongly influence the infection of a freshwater cyanobacterium (Synechococcus elongatus PCC 7942) by a contractile DNA phage named AS-1. Phage progeny production was correlated with the amount of light in the laboratory and occurred in a diel pattern under natural light. At least one effect of light on AS-1 infection is at the level of adsorption.     

Metabolism of beta-methylaspartate by a pseudomonad

A bacterium was isolated from soil which utilizes threo-beta-methyl-l-aspartate, certain other amino acids, and a variety of organic substances as single energy sources. It is, or closely resembles, Pseudomonas putida biotype B. The ability of this organism to rapidly decompose such amino acids is dependent on inducible enzyme systems. Dialyzed cell-free extracts of this bacterium metabolize beta-methylaspartate only when catalytic amounts of alpha-ketoglutarate, or pyruvate, and pyridoxal phosphate are also present. The main products formed from beta-methylaspartate under these conditions are alpha-aminobutyrate, carbon dioxide, and alpha-ketobutyrate. When l-aspartate is substituted for beta-methylaspartate in this system, it is converted mainly to alanine and carbon dioxide. beta-Methyloxalacetate is decarboxylated, and the resulting alpha-ketobutyrate is converted enzymatically in the presence of glutamate to alpha-aminobutyrate which accumulates. The added keto acids are converted, in part, to the corresponding amino acids probably by transamination. The data indicate that beta-methylaspartate is converted to alpha-aminobutyrate, and aspartate to alanine, by a circuitous transamination-beta-decarboxylation-transamination sequence rather than by a direct beta-decarboxylation.     

Activation of a flavoprotein by proteolysis

Chymotryptic digestion of brain pyridoxine-5-P oxidase brings about a 4-fold enhancement of the catalytic power (Vmax/KM) using pyridoxine-5-P as substrate in the assay mixtures. The chymotrypsin-treated enzyme is less susceptible to inhibition by pyridoxal-5-P than the native enzyme. Fragments arising from limited proteolysis were separated by affinity chromatography using P-pyridoxal-Sepharose as supporting matrix. Catalytically active fractions, eluted by pyridoxine-5-P (5mM), displayed three bands when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular masses of the three protein bands are considerably lower than 28 kDa, the molecular mass of monomeric pyridoxine-5-P oxidase. Spectroscopic studies, absorption, fluorescence, and circular dichroism revealed that the microenvironment surrounding the cofactor flavin mononucleotide is not perturbed by limited proteolysis.     

Diel Infection of a Cyanobacterium by a Contractile Bacteriophage

Light was found to strongly influence the infection of a freshwater cyanobacterium (Synechococcus elongatus PCC 7942) by a contractile DNA phage named AS-1. Phage progeny production was correlated with the amount of light in the laboratory and occurred in a diel pattern under natural light. At least one effect of light on AS-1 infection is at the level of adsorption.     

Bacterial cell-body rotation driven by a single flagellar motor and by a bundle

Using self-trapped Escherichia coli bacteria that have intact flagellar bundles on glass surfaces, we study statistical fluctuations of cell-body rotation in a steady (unstimulated) state. These fluctuations underline direction randomization of bacterial swimming trajectories and plays a fundamental role in bacterial chemotaxis. A parallel study is also conducted using a classical rotation assay in which cell-body rotation is driven by a single flagellar motor. These investigations allow us to draw the important conclusion that during periods of counterclockwise motor rotation, which contributes to a run, all flagellar motors are strongly correlated, but during the clockwise period, which contributes to a tumble, individual motors are uncorrelated in long times. Our observation is consistent with the physical picture that formation and maintenance of a coherent flagellar bundle is provided by a single dominant flagellum in the bundle.     

Electron acceleration by Langmuir waves excited by a laser pulse in a semi-infinite plasma

Results are presented from a theoretical investigation of the acceleration of test electrons by a Langmuir wave excited by a short laser pulse at half the electron plasma frequency. Such a pulse penetrates into the plasma over a distance equal to the skin depth and efficiently excites Langmuir waves in the resonant interaction at the second harmonic of the laser frequency. It is shown that the beam of electrons accelerated by these waves is modulated into a train of electron bunches, but because of the initial thermal spread of the accelerated electrons, the bunches widen and begin to overlap, with the result that, at large distances, the electron beam becomes unmodulated.     

Dispersion properties of a plasma produced by a short X-ray pulse

A collisionless plasma produced by a short ionizing pulse from an X-ray laser is characterized by an anisotropic monoenergetic electron distribution governed by the classical photoeffect. The dispersion properties of such a photoionized plasma are studied. The spectra of high-frequency plasma waves and their damping, as well as the parameters of the aperiodic instability of a photoionized plasma, are described. The relationship between the electrostatic and magnetic perturbations generated by this instability is investigated, and an analysis is made of how the instability transforms into a purely longitudinal (two-stream-like) instability and into a purely transverse (Weibel-like) instability, depending on the absolute value and direction of the wave vector.     

Virilization of a female infant by a maternal adrenocortical carcinoma

ObjectiveTo describe a possible mechanism underlying the partial virilization of a 46, XX infant by a functional maternal adrenocortical carcinoma (ACC).MethodsWe performed immunocytochemical staining of tumor sections for luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptors. In addition, related reports in the literature are discussed.ResultsA previously healthy mother developed a large cortisoland androgen-producing stage III adrenal tumor that did not interfere with conception or early morphogenesis. The tumor eluded detection until after delivery of a partially virilized 46, XX female infant with ambiguous genitalia. Immunohistochemical staining of tumor sections revealed overexpression of the LH/hCG receptor. Virilization of the genetically female fetus may have resulted from hCG-stimulated steroid secretion by the ACC.ConclusionBecause hypercortisolism and hyperandrogenism are associated with menstrual disturbances and spontaneous abortion, pregnancy in patients with functional adrenal tumors is uncommon. Rarely, maternal steroid excess from a functional adrenal tumor has caused 46, XX disordered sex differentiation. This unusual case demonstrates the influence of hCG on the functionality of an ACC and demonstrates the rare phenomenon of virilization of a female infant by a functional maternal adrenal tumor. (Endocr Pract. 2011;17:e26-e31)     

一株奇异变形杆菌对铜绿假单胞菌多细胞行为的抑制作用*

摘要目的：抗生素耐药性成为了全球性的健康问题。研究发现病原菌的多细胞行为在抗生素的耐药性中起着至关重要的作用 （尤其是生物膜）,因而通过抑制多细胞行为而控制耐药性成为当务之急。本文以奇异变形杆菌（Proteus Mirabilis ）为研究对象,考 察它的发酵滤液对一种机会致病菌———铜绿假单胞菌（ Pseudomonas aeruginose）多细胞行为的作用,以期得到一株多细胞行为抑 制菌：在不影响 P.aeruginosa 生长的前提下,抑制生物膜形成、EPS 产生以及定向丛集运动,解除保护,减缓扩散,为降低P.aeruginosa 耐药性,增强抗生素作用效果提供可能。方法：采用结晶紫生物膜测定法、蒽酮-硫酸法、平板检测法,探究P.aeruginosa 发酵滤 液对P.aeruginosa 生物膜、胞外多聚物、定向丛集运动和生长的影响。结果： P.aeruginosa 发酵滤液能显著抑制生物膜 量,在体积百分比浓度为1 %时,抑制率可达60.9 %。该菌的发酵滤液还能阻碍的定向丛集运动,减弱它的吸附和扩 散运动;同时,也减少了P.aeruginosa 胞外多聚物的产量,在滤液体积百分比浓度为1 %时,抑制率达到45.9%。更重要的是,固体 平板实验证明该发酵滤液对P.aeruginosa 的生长没有影响。结论： 在不影响病原菌生长的前提下,对病原菌的多细胞 行为有一定的控制作用。其发酵滤液中存在着抑制微生物膜、定向丛集运动等的成分,在治疗细菌感染性疾病和降低抗生素耐药 性方面有潜在应用价值。     

Behavioural modification of a social spider by a parasitoid wasp

1. Manipulation of host behaviour by parasitoids has long captured the imagination of ecologists. Parasitoid wasps in the Polysphincta group of genera develop as external parasitoids of spiders. 2. In the present study, the previously undescribed interaction between a Zatypota sp. wasp (Ichneumonidae) and a social spider Anelosimus eximius (Theridiidae) is described. The larva of this Zatypota wasp is found to induce its host to disperse from their communal web and build an entirely enclosed web consisting of densely spun silk. 3. The wasp is observed to target primarily immature A. eximius individuals, with 37.5–44% of nests in a given area being parasitised. Of those nests, approximately 1.3–2.0% of individuals are hosts to the parasitoid larvae. Larger spider colonies had a significantly higher probability of harbouring parasitoids. 4. This interaction results in unusual behaviours for A. eximius induced by the parasitoid: (i) leaving the protection of the social nest and (ii) building a unique, altered web that it would not otherwise build. It is suggested that the wasp may be tapping into ancestral dispersal behaviours in its host and that a social species provides this wasp an evolutionary advantage by allowing a stable host source.     

Marker rescue by a homologous recipient plasmid during transformation of gonococci by a hybrid Pcr plasmid

A 42-kilobase hybrid Pcr plasmid (pFA14) was formed when the naturally occurring 7.2-kilobase Pcr plasmid pFA3 was introduced by transformation into a competent gonococcal recipient containing the 36-kilobase conjugative plasmid pFA2 (Sox et al., J. Bacteriol. 138:510-518). Analysis of the structure of pFA14 showed that it was a stable recombinant between pFA3 and pFA2. The transformation efficiency of pFA14 was increased 300- to 10,000-fold by the presence in isogenic recipients of the homologous plasmid pFA2. The presence of a homologous plasmid in the recipient also markedly increased the likelihood of recovery of intact donor-size Pcr plasmids in the transformants. The presence of pFA2 had no effect on the competence of piliated or nonpiliated gonococci for transformation by either linear chromosomal DNA or a nonhomologous Pcr plasmid. Increased transformation efficiency of the hybrid Pcr plasmid pFA14 may have been due to recombination between the nicked or linearized donor plasmid and the homologous recipient plasmid (marker rescue).     

Catabolism of pentachlorophenol by a Flavobacterium sp

The pathway employed for pentachlorophenol (PCP) degradation by an aerobic, chlorophenol-utilizing Flavobacterium sp. was initiated by conversion of PCP to tetrachloro-p-hydroquinone (TCH). 18O labelling experiments demonstrated that the first dechlorination, where a hydroxyl replaced the chlorine at PCP ring position number 4, involved a hydrolytic reaction. Then two reductive dechlorinations of TCH followed to yield firstly trichlorohydroquinone (TrCH) and then 2,6-dichlorohydroquinone (DCH). Thus, the initial steps in catabolism of PCP by the Flavobacterium were: PCP----TCH----TrCH.     

Technique of surface modification of a cell-adhesion-resistant hydrogel by a cell-adhesion-available inorganic microarray

A microtransfer technique for micropattern fabrication using a dithiol macromolecular linker is suggested by transferring a conventionally photolithography-prepared gold microarray on a hard inorganic substrate to a polymeric substrate. The linker was synthesized by end-capping a poly(ethylene glycol) (PEG) chain by the thiol groups. The efficiency of this technique is demonstrated by the transfer of gold microdots from glass to a cell-adhesion-resistant PEG hydrogel, which was formed by polymerizing PEG diacrylate macromers. The stability and biocompatibility of the resulting polymeric-inorganic hybrid material and cell-adhesion contrast of the patterned surface is confirmed by preliminary cell experiments.