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1.
In order to investigate the special function of tryptophan in peptide hormones, six tryptophan analogues have been synthesized, in which structural resemblance has been grossly retained and potentially essential properties have only partially been varied. The L-enantiomers have been isolated after enzymatic digestion of racemic dipeptide derivatives, and charge-transfer properties of the compounds have been studied.  相似文献   

2.
Hybridoma cells which secrete colorectal carcinoma-specific antibodies have been produced and used to study the antigenic structure of these tumor cells. Nineteen antibodies have been studied in detail, and 15 of these are colorectal carcinoma specific. Only two antibodies reactive with carcinoembryonic antigen (CEA) have been discovered and five other antibodies that react with distinct epitopes on the cell surface have been defined. Several antigens with distinct molecular characteristics have been shown to exist by use of hybridoma antibodies. Six hybridoma antibodies have been shown to mediate antibody-dependent cell-mediated cytotoxicity (ADCC).  相似文献   

3.
The different invasive and noninvasive diagnostic tests for Helicobacter pylori have been applied mainly in emerging countries. Molecular methods have been developed, especially a test for detection of H. pylori and its clarithromycin resistance directly from stools. The long-term effects of eradication on histologic lesions have been studied in a meta-analysis and the prognostic value of post-treatment in gastric mucosa-associated lymphoid tissue lymphoma has been assessed. An operating link for gastritis assessment (the OLGA staging) has also been published. Attempts to simplify the urea breath test protocol have been made, and new stool antigen tests have been proposed and compared to those previously available.  相似文献   

4.
The measurement of 13 items in the face and nose of 220 young adults (110 males and 110 females) of the Han nationality between the ages of 18 and 21 years has been done in the Henan Province of China. The means and standard deviations have been obtained, and the significant differences in many items between males and females have been proved. Some items influencing outer nasal shape have been analyzed. The correlations between nose height, nose length, and morphologic facial height and physiognomic facial height have been discussed. The ratio and amount of nasal breadth to facial breadth and nasal breadth to interocular breadth have been compared and analyzed, and the differences among the different races and between the sexes have been explained.  相似文献   

5.
Gas chromatography mass spectrometry has been used for over a decade for the determination of the amino acid sequences of fragment peptides derived from larger parent molecules. The majority of these fragments have from four to seven residues and several different methods of derivatization have been devised. Few reports have been published in which similar techniques have been used for the quantification of such peptides, but there is a growing list of small peptides which have been shown to have biological activity in their own right. This report is concerned with the development of a gas chromatographic mass spectrometric assay for the two eosinophil chemotactic peptides, Val-Gly-Ser-Glu and Ala-Gly-Ser-Glu, which appear to have a role to play in the course of the inflammatory process in skin disorders.  相似文献   

6.
7.
Since its invention in the mid 1980s atomic force microscopy has revolutionised the way in which surfaces can be imaged. Close to atomic resolution has been achieved for some materials and numerous images of molecules on surfaces have been recorded. Atomic force microscopy has also been of benefit to biology where protein molecules on surfaces have been studied and even whole cells have been investigated. Here we report a study of red blood cells which have been imaged in a physiological medium. At high resolution, the underlying cytoskeleton of the blood cell has been resolved and flaws in the cytoskeleton structure may be observed. Comparison of the normal 'doughnut' shaped cells with swollen cells has been undertaken. Differences in both the global properties of the cells and in the local features in cytoskeleton structure have been observed.  相似文献   

8.
The breeder and the chemostat have been used to measure mutation rates for two mutations under a variety of steady state growth conditions. These rates have been found to be higher in complex medium than in minimal (F) medium. The effects of changes in nutritional conditions on these high rates have been described. In addition, the mutation rates at short generation times, in complex medium, have been shown to decrease with increasing generation time.  相似文献   

9.
The technique of sedimentation equilibrium in density gradients in the analytical ultracentrifuge has been applied to the study of proteins. A variety of effects and procedures including the use of density marker beads, the effects of pressure on buoyant density and pH, and the calculation of compositional density gradient proportionality constants and density--refractive index relations have been developed. The buoyant densities of twenty-four proteins have been measured and hydration values computed. The buoyant titrations of six proteins have been measured. These data have been interpreted in terms of the buoyant titrations which have been obtained for six ionizable homopolypeptides, five copolypeptides, two non-ionizable homopolypeptides and three chemically modified proteins. Spectropolarimetry and potentiometric titrations were employed to further interpret these data. Approximate values for dissociation constants, numbers of ionizable residues, and the nature of ions bound or dissociated upon ionization have been obtained. The relation between potentiometric and buoyant titrations and the use of density gradient centrifugation as a probe for protein structure have been explored.  相似文献   

10.
Supercritical fluid technology offers the possibility to produce dry powder formulations of biocompatible materials, overcoming the drawbacks of classical micronization processes. In this work, Supercritical Assisted Atomization (SAA) has been used to micronize alpha-cyclodextrin (alpha-CD) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD). Some process parameters, such as precipitation temperature and solute concentration in the liquid solution, have been studied to evaluate their influence on morphology and size of precipitated particles. Cyclodextrins (CDs) micronization has been successful: well-defined spherical microparticles of alpha-CD and HP-beta-CD have been produced. Particle size analysis revealed that sharp distributions have been obtained: 95% of particles have diameters ranging between 0.1 and 5 microm for both CDs. X-ray and DSC analyses have been also performed to investigate CDs modifications induced by SAA processing: amorphous particles have been obtained in both cases, whereas raw alpha-CD was crystalline and raw HP-beta-CD was amorphous.  相似文献   

11.
The results of cytogenetic examination carried out in 255 couples with a history of infertility have been analysed. Chromosomal aberrations have been detected in 15 examinations (6.7%) with predominance of translocations (mutual - 3.6%; Robertson' - 1.3%). Identified aberrations have been noted in 9 women and 6 men. The obtained results have been analysed in relation to the number of abortions, dead and live newborn babies with inherited abnormalities. It was found that the incidence of chromosomal aberrations increases with the number of the spontaneous abortions in anamnesis. Such aberrations have also been more frequent in the families in which spontaneous abortions have been accompanied by other fertility disorders.  相似文献   

12.
The presence or absence of a chemoreceptive capacity in marine mammals has drawn relatively little attention from the research community outside the Soviet Union. Toothed whales are typically labelled anosmic (lacking a sense of smell) since they do not have the peripheral olfactory structures typically associated with terrestrial mammals. Baleen whales are known to possess reduced olfactory tracts; their olfactory bulbs also may be reduced or absent. Although the neural structures that mediate taste in terrestrial mammals have been reported to be present in both groups of whales, cetaceans have been considered to have a poor sense of taste because typical mammalian taste receptors have been thought to be absent. Soviet researchers, however, recently have reported that gustatory receptors are present on some cetacean tongues and that the tongue of Tursiops truncatus appear to be well innervated. These workers also have been conducting investigations which seem to be aimed at describing a specialized gustatory capability in cetaceans. No experimental work has been reported by Western scientists. Little work has been done by either Western or Soviet researchers with regard to chemoreception among the other orders of marine mammals (Pinnipedia, Carnivora and Sirenia). Pinnipedia are typically labelled microsmatic (having a poor sense of smell); research has been restricted to histological examination of the nasal pathways, and neural anatomy. Sea otters are credited with a keen sense of smell, but no quantitative work has been reported. The chemosensory abilities of Sirenia remain unknown. The tongues of non-cetacean marine mammals have been histologically examined and found to resemble those of terrestrial mammals. No other investigations of gustation in non-cetacean marine mammals have been reported.  相似文献   

13.
Humoral and cellular mechanisms of defense have been described for cephalopods, a relatively advanced group of mollusks. Typical of other mollusks, cephalopod agglutinins are the most documented component of humoral immunity. Lectins, which have agglutinating properties, have been described and characterized from octopuses. Agglutinins from cephalopod hemolymph have also been shown to agglutinate a variety of vertebrate red blood cells, as well as potential bacterial pathogens. Hemocytes are the primary component of cellular immunity. Although the hemocyte role in phagocytosis has been extensively studied in other mollusks, the mechanisms of phagocytosis have not been described extensively for cephalopods. Cephalopod hemocytes have phagocytic capabilities and may function in encapsulation and neutralization of foreign substances; however, the effects of environmental factors and the full extent of phagocytic capabilities of cephalopod hemocytes have not been reported. Hemocytes from cephalopods have a role in wound healing and inflammation which have been reported in detail by several investigators.  相似文献   

14.
The extent of rotting of commercially stored Cox's Orange Pippin apples by Gloeosporium species has been severe in recent years. G. perennans has been found to be mainly responsible.
Tree infections of this fungus have usually been found to be prevalent in the orchards on farms where storage losses of fruit have occurred, and conidia of G. perennans have been found on cankers at all seasons during the year. Winter as well as summer pruning cuts have been found to become infected. Detached leaves of Cox's Orange Pippin have been successfully inoculated with G. perennans in the laboratory and the fungus has also been found on dead detached leaves in the orchard after picking time. Considerable variations have been found in the susceptibility to rotting of samples of different varieties of apple and samples of Cox's Orange Pippin apples from different orchards. Periodic loading of fruit with spores after picking has shown that resistance declines with length of storage. Wide variation in the time at which rotting commences in commercially stored samples has been observed. A series of inoculations on picked and unpicked immature fruit has shown that the apple loses its resistance to attack on picking. Lenticels which are impermeable to gaseous exchange have been shown to be resistant to penetration by the fungus. Temperature affects the development of lenticel rotting by G. perennans , infection being most rapid at temperatures of about 20°. Rotting can occur at 0° C.  相似文献   

15.
In this, a preliminary report, the advantages and disadvantages of upper lobe lobectomy and concomitant thoracoplasty in tuberculosis have been summarized. There has been no undue increase in the operative hazard, there have been no complications, and the immediate results have been entirely satisfactory.Twenty-six patients were subjected to a combined operation (17 upper lobectomy-thoracoplasty and nine pneumonectomy-thoracoplasty) with one postoperative death. Indications for primary lobectomy have been discussed. The technique of resection and concomitant thoracoplasty has been briefly described.  相似文献   

16.
Debeljuk L  Lasaga M 《Peptides》2006,27(11):3007-3019
Tachykinins are present in the pituitary gland and in brain areas involved in the control of the secretion of pituitary hormones. Tachykinins have been demonstrated to stimulate prolactin release acting directly on the anterior pituitary gland. These peptides have also been revealed to be able to act at the hypothalamic level, interacting with neurotransmitters and neuropeptides that have the potential to affect prolactin secretion. Tachykinins seem to act by stimulating or inhibiting the release of the factors that affect prolactin secretion. Among them, tachykinins have been demonstrated to stimulate oxytocin and vasopressin release, which in turn results in prolactin release. Tachykinins also potentiated the response to vasoactive intestinal peptide (VIP) and reinforced the action of glutamate, which in turn result in prolactin release. They have also been shown to interact with serotonin, a neurotransmitter involved in the control of prolactin secretion. In addition, tachykinins have been shown to inhibit GABA release, a neurotransmitter with prolactin-release inhibiting effect. This inhibition may result in an increased prolactin secretion by removal of the GABA inhibition. On the other hand, tachykinins have also been shown to stimulate dopamine release by the hypothalamus, an action that results in an inhibition of prolactin release. Dopamine is a well known inhibitor of prolactin secretion. In conclusion, although tachykinins have been shown to have a predominantly stimulatory effect on prolactin secretion, especially at the pituitary level, under some circumstances they may also exert an inhibitory influence on prolactin release, by stimulating dopamine release at the hypothalamic level.  相似文献   

17.
In this, a preliminary report, the advantages and disadvantages of upper lobe lobectomy and concomitant thoracoplasty in tuberculosis have been summarized. There has been no undue increase in the operative hazard, there have been no complications, and the immediate results have been entirely satisfactory.Twenty-six patients were subjected to a combined operation (17 upper lobectomy-thoracoplasty and nine pneumonectomy-thoracoplasty) with one postoperative death.Indications for primary lobectomy have been discussed.The technique of resection and concomitant thoracoplasty has been briefly described.  相似文献   

18.
Chlorinated nitroaromatic compounds (CNAs) are persistent environmental pollutants that have been introduced into the environment due to the anthropogenic activities. Bacteria that utilize CNAs as the sole sources of carbon and energy have been isolated from different contaminated and non-contaminated sites. Microbial metabolism of CNAs has been studied, and several metabolic pathways for degradation of CNAs have been proposed. Detoxification and biotransformation of CNAs have also been studied in various fungi, actinomycetes and bacteria. Several physicochemical methods have been used for treatment of wastewater containing CNAs; however, these methods are not suitable for in situ bioremediation. This review describes the current scenario of the degradation of CNAs.  相似文献   

19.
The cloning of all the eleven fragments obtained by degrading the phage lambdarifd18 by the restriction enzyme EcoRI into the plasmid pSF2124 has been achieved: nine of these fragments have been cloned individually, whereas two others have been cloned jointly in the same plasmid. These fragments harbor, in addition of lambda genes, the genes for ribosomal proteins, the elongation factor Tu, the beta and beta' subunits of RNA polymerase and the ribosomal RNAs. The clones carrying the ribosomal RNA genes have been constructed to provide convenient plasmids to determine the primary structure of ribosomal RNAs. Some further genetic manipulations in vitro have been performed on two of them to remove extraneous non-ribosomal RNA gene sequences; the ribosomal genes purified this way have been subcloned into the plasmid pBR322. Other clones of interest have been obtained which carry the genes for the elongation factor Tu, a number of 50-S ribosomal proteins and the beta subunit of RNA polymerase.  相似文献   

20.
Small, non-coding bacterial RNAs (sRNAs) have been shown to regulate a plethora of biological processes. Up until recently, most sRNAs had been identified and characterized in E. coli. However, in the past few years, dozens of sRNAs have been discovered in a wide variety of bacterial species. Whereas numerous sRNAs have been isolated or detected through experimental approaches, most have been identified in predictive bioinformatic searches. Recently developed computational tools have greatly facilitated the efficient prediction of sRNAs in diverse species. Although the number of known sRNAs has dramatically increased in recent years, many challenges in the identification and characterization of sRNAs lie ahead.  相似文献   

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