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1.
Digestion in the cattle-tick Boophilus microplus: light microscope study of the gut cells in nymphs and females 总被引:3,自引:0,他引:3
The gut caeca of B. microplus were studied by light microscopy using paraffin and methacrylate embedded material. It has been shown that during feeding of nymphs and adults, the midgut consists of five cell types, stem cell, digest cell, secretory cells (s1) and (s2) and basophilic cell. The stem cell differentiates into any of the other cell types. The digest cell matures through a series of stages and has up to three generations during feeding on the host. The final generation has two distinct cell types, the first type is thought to be capable of both phagocytosis and pinocytosis. Cells of the second type are predominant at the end of feeding, and may be specialized to ingest and digest haemoglobin. The final stage of the digest series is the spent digest cell which discharges its content into the gut lumen or is excreted whole. The basophilic cell has structures which suggest that one of its functions is to transport digested materials, water and ions across the gut. Secretory cell (s1) secretes a glycoprotein which may be a haemolysin and secretory cell (s2) secretes the gut “colloid” mass, an acid mucopolysaccharide, which may function as an anticoagulant. Intracellular digestion leads to the breakdown of host blood and storage of lipid and glycogen in the digest cells. 相似文献
2.
Background
Radial chromosome positioning in interphase nuclei is nonrandom and can alter according to developmental, differentiation, proliferation, or disease status. However, it is not yet clear when and how chromosome repositioning is elicited. 相似文献3.
4.
Joanna Nakonieczna Ewelina Michta Magda Rybicka Mariusz Grinholc Anna Gwizdek-Wiśniewska Krzysztof P Bielawski 《BMC microbiology》2010,10(1):323
Background
Staphylococcus aureus, a major human pathogen causes a wide range of disease syndromes. The most dangerous are methicillin-resistant S. aureus (MRSA) strains, resistant not only to all β-lactam antibiotics but also to other antimicrobials. An alarming increase in antibiotic resistance spreading among pathogenic bacteria inclines to search for alternative therapeutic options, for which resistance can not be developed easily. Among others, photodynamic inactivation (PDI) of S. aureus is a promising option. Photodynamic inactivation is based on a concept that a non toxic chemical, called a photosensitizer upon excitation with light of an appropriate wavelength is activated. As a consequence singlet oxygen and other reactive oxygen species (e.g. superoxide anion) are produced, which are responsible for the cytotoxic effect towards bacterial cells. As strain-dependence in photodynamic inactivation of S. aureus was observed, determination of the molecular marker(s) underlying the mechanism of the bacterial response to PDI treatment would be of great clinical importance. We examined the role of superoxide dismutases (Sod) in photodynamic inactivation of S. aureus as enzymes responsible for oxidative stress resistance. 相似文献5.
6.
Nathan Downs Alfio Parisi Joanna Turner David Turnbull 《Photochemical & photobiological sciences》2008,7(6):700-710
A technique has been developed to represent erythemally effective ultraviolet radiation exposure within a school environment. The technique models the erythemally effective exposure onto a horizontal plane representation of a mapped school environment located in Hervey Bay (25 degrees S, 153 degrees E), Australia. The input parameters used to model the ultraviolet exposures received within the school playground included the measured sky view, ground albedo and standing surface albedo. Estimates of the erythemally effective ultraviolet exposure received within the school playground during morning tea and lunch time meal breaks during a winter and summer school day are presented. The influence of tree shade and building structure was found to vary significantly with solar zenith angle modelled over the winter and summer school meal break times with horizontal plane exposures predicted to vary from between 0 and 7 SED at different locations within the playground. The technique presented provides a method that can be followed to examine the effect of surrounding buildings and surface structures of real environments on the predicted horizontal plane ultraviolet exposure. 相似文献
7.
Basophilic cells in the guts of female ticks are derived from the basal remnants of type 2 secretory cells. As viewed by electron microscopy, these cells have microvilli uniformly distributed on the luminal surface, but they lack the abundant pinocytotic vesicles and lysosomes characteristic of digest cells. The cytoplasm is filled with well organized rough endoplasmic reticulum, Golgi complexes and secretory granules. Infoldings of a basal labyrinth extend the contact of the cell with the underlying haemolymph, and there are many mitochondria in the cell processes between folds. This morphology appears to fit the cell for functioning in active water transport across the gut wall. Subsequent to a final rapid phase of engorgement, the basophilic cell reorganizes its cisternae of rough endoplasmic reticulum into whorls and parallel arrays and resumes a secretory role. 相似文献
8.
Carroll D. Arnett Joanna S. Fowler Robert R. MacGregor David J. Schlyer Alfred P. Wolf Bengt Långström Christer Halldin 《Journal of neurochemistry》1987,49(2):522-527
The distribution of carbon-11-labeled L-deprenyl, an irreversible inhibitor of monoamine oxidase type B (MAO-B), was determined in the baboon brain by positron emission tomography. The irreversible blood-to-brain transfer constant (influx constant, Ki) was measured using a complete metabolite-corrected arterial plasma concentration curve. This influx constant was used as a measure of functional enzyme activity for sequential determinations of MAO-B recovery following a single high dose of unlabeled l -deprenyl. The half-life for turnover of MAO-B was thus determined to be 30 days. Using appropriate irreversible inhibitors, this procedure should be generally useful for determining enzyme turnover rates in any organ in vivo and can be applied to some human studies as well. 相似文献
9.
Analysis of the lesions in several drug-resistant DNA polymerase mutants of herpes simplex virus along with comparative analysis of the published polymerase sequences of other human herpesviruses has shown that most lesions (five out of six) are substitutions at amino acid residues conserved in all four polymerases. Furthermore, the majority of lesions are in regions of the polypeptide where there are marked clusterings of conserved residues. On the basis of these data we have identified several domains within the polypeptide which we believe may have important functional roles in the action of the enzyme. The apparent restriction in the potential sites of lesions conferring drug resistance may explain the difficulty in selecting such mutants using acyclovir (ACV) in culture and their failure to emerge so far during ACV therapy. Extension of the comparative analysis to the polymerases of adenovirus type 2, vaccinia virus and phage phi 29 suggests that these enzymes also possess domains homologous to those most conserved in the herpes polymerases (regions I-III) and that these domains have a similar linear spatial distribution on the polypeptides. The results are discussed in relation to the known function of the DNA polymerases. 相似文献
10.
Calcitonin receptors of human osteoclastoma 总被引:2,自引:0,他引:2
G C Nicholson M A Horton P M Sexton C S D'Santos J M Moseley B E Kemp J A Pringle T J Martin 《Hormones et métabolisme》1987,19(11):585-589
Osteoclast-rich cultures were prepared by disaggregation of osteoclastomas (giant cell tumour of bone) and settlement onto glass or plastic surfaces. Autoradiography using [125I]-salmon calcitonin ([125I]-sCT) revealed specific binding only to multinucleate giant cells (osteoclasts) and a minor population of mononuclear cells. [125I]-sCT competitive binding studies indicated a Kd of 5 x 10(-10) M and receptor number of approximately 1 million sites/osteoclast. sCT treatment resulted in a dose-dependent rise in cAMP (EC50 10(-10) M). Homogenates of an osteoclastoma also demonstrated specific binding of [125I]-sCT. Chemical cross-linking of a labelled synthetic sCT derivative. [125I]-[Arg11,18,Lys14]-sCT, using disuccinimidyl suberate, resulted in labelling of a receptor component of approximate Mr 85-90,000. The multinucleate giant cells (osteoclasts) of human osteoclastomas possess large number of CT receptors which exhibit the same binding kinetics and apparent Mr as those of other CT target cells. 相似文献