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71.
Follower neurons in lobster (Panulirus interruptus) pyloric network regulate pacemaker period in complementary ways 总被引:2,自引:0,他引:2
Distributed neural networks (ones characterized by high levels of interconnectivity among network neurons) are not well understood. Increased insight into these systems can be obtained by perturbing network activity so as to study the functions of specific neurons not only in the network's "baseline" activity but across a range of network activities. We applied this technique to study cycle period control in the rhythmic pyloric network of the lobster, Panulirus interruptus. Pyloric rhythmicity is driven by an endogenous oscillator, the Anterior Burster (AB) neuron. Two network neurons feed back onto the pacemaker, the Lateral Pyloric (LP) neuron by inhibition and the Ventricular Dilator (VD) neuron by electrical coupling. LP and VD neuron effects on pyloric cycle period can be studied across a range of periods by altering period by injecting current into the AB neuron and functionally removing (by hyperpolarization) the LP and VD neurons from the network at each period. Within a range of pacemaker periods, the LP and VD neurons regulate period in complementary ways. LP neuron removal speeds the network and VD neuron removal slows it. Outside this range, network activity is disrupted because the LP neuron cannot follow slow periods, and the VD neuron cannot follow fast periods. These neurons thus also limit, in complementary ways, normal pyloric activity to a certain period range. These data show that follower neurons in pacemaker networks can play central roles in controlling pacemaker period and suggest that in some cases specific functions can be assigned to individual network neurons. 相似文献
72.
Kim W Koo H Richman AM Seeley D Vizioli J Klocko AD O'Brochta DA 《Journal of medical entomology》2004,41(3):447-455
Genetically altering the disease vector status of insects using recombinant DNA technologies is being considered as an alternative to eradication efforts. Manipulating the endogenous immune response of mosquitoes such as the temporal and special expression of antimicrobial peptides like cecropin may result in a refractory phenotype. Using transgenic technology a unique pattern of expression of cecropin A (cecA) in Anopheles gambiae was created such that cecA was expressed beginning 24 h after a blood meal in the posterior midgut. Two independent lines of transgenic An. gambiae were created using a piggyBac gene vector containing the An. gambiae cecA cDNA under the regulatory control of the Aedes aegypti carboxypeptidase promoter. Infection with Plasmodium berghei resulted in a 60% reduction in the number of oocysts in transgenic mosquitoes compared with nontransgenic mosquitoes. Manipulating the innate immune system of mosquitoes can negatively affect their capacity to serve as hosts for the development of disease-causing microbes. 相似文献
73.
Lyashchenko K Whelan AO Greenwald R Pollock JM Andersen P Hewinson RG Vordermeier HM 《Infection and immunity》2004,72(5):2462-2467
Vaccine development and our understanding of the pathology of bovine tuberculosis in cattle would be greatly facilitated by definition of the immunological correlates of protection and/or pathology. In this study we analyzed humoral immune responses in Mycobacterium bovis BCG-vaccinated and control cattle (in particular, the relationship between the intradermal comparative tuberculin skin test and serum immunoglobulin G [IgG] responses) against a range of mycobacterial antigens (MPB59, MPB64, MPB70, MPB83, ESAT-6, CFP-10, Acr1, and PstS-1) by multiantigen print immunoassay and conventional enzyme-linked immunosorbent assay. Following M. bovis infection, the comparative tuberculin skin test strongly boosted IgG, IgG1, and IgG2 antibody responses, particularly against MPB83 and MPB70, in unvaccinated cattle but failed to boost these responses, or did so only weakly, in BCG-vaccinated calves. In addition, the skin test-induced increases in MPB83-specific IgG responses correlated positively with bacterial loads and ESAT-6-induced in vitro gamma interferon responses. In conclusion, both the negative correlation of skin test-enhanced MPB83-specific antibody responses with BCG-induced protection and their positive correlation with bacterial loads can serve as useful markers for vaccine efficacy after challenge. 相似文献
74.
75.
Delayed angiogenesis in aging rats and therapeutic effect of adenoviral gene transfer of VEGF 总被引:4,自引:0,他引:4
Wang H Keiser JA Olszewski B Rosebury W Robertson A Kovesdi I Gordon D 《International journal of molecular medicine》2004,13(4):581-587
We have studied an age-related impairment in angiogenesis and evaluated the effect of overexpressing VEGF in this situation. Polyvinyl alcohol sponges were implanted subcutaneously into aged (24-month), adult (12-month), and young (2-month) rats. Blood vessel ingrowth and proliferative activity in the sponges were assessed by histology with immunostaining for von Willebrand's factor and proliferating cell nuclear antigen (PCNA), respectively. The percentage of total sponge area filled with ingrowing fibrovascular tissue was minimal in aged rats, intermediate in adult rats and highest in young rats. A similar pattern was observed for the total blood vessel numbers in the sponges from old to young animals. The percentage of total sponge endothelial cells (ECs) showing proliferative activity (PCNA positive) was lowest in the aged animals, intermediate in the adult rats and highest in the young rats. To further explore the mechanism of impaired angiogenesis in aged animals, we investigated and found a reduced level of endogenous VEGF protein expression in 12-month-old rats compared to that in 2-month-old rats. VEGF121 gene transfer significantly enhanced blood vessel and fibrovascular tissue ingrowth in adult/aged rats. Adenoviral-VEGF gene transfer also significantly stimulated EC proliferation in aged and adult rats. However, identical treatment failed to further stimulate the already more robust angiogenesis in young animals. The different angiogenic response in adult vs. young rats was not due to differences in gene transfer efficiency, since similar levels of human VEGF121 protein was detected in adult and young rats. Our results indicate that the decreased angiogenic response with aging is associated with reduced EC proliferation and reduced endogenous VEGF production. Adenoviral-VEGF121 gene transfer is effective in augmenting angiogenesis, particularly in older animals. 相似文献
76.
Terminal bronchioles harbor a unique airway stem cell population that localizes to the bronchoalveolar duct junction 总被引:14,自引:0,他引:14 下载免费PDF全文
Cellular mechanisms contributing to renewal of terminal bronchioles remain poorly defined. Our previous studies identified pollutant-resistant Clara cell secretory protein (CCSP)-expressing stem cells that localize to the neuroepithelial body (NEB) and contribute to renewal of the proximal bronchiolar epithelium. However, activation of NEB-associated stem cells is unlikely to contribute to renewal of terminal bronchiolar epithelium because of the paucity of NEBs at this location. Goals of this study were to determine the location and properties of cells contributing to renewal of terminal bronchioles after Clara cell depletion. Pollutant-resistant CCSP-expressing cells were identified that localized to the bronchoalveolar duct junction (BADJ) and contribute to restoration of a phenotypically diverse epithelium. CCSP-expressing cells comprise the predominant proliferative population in initial terminal bronchiolar repair and include a population of label-retaining cells suggesting that they maintain characteristics of a stem cell population. Furthermore, immunohistochemical co-localization studies involving CCSP and the NEB-specific marker calcitonin gene-related peptide indicate that BADJ-associated CCSP-expressing stem cells function independently of NEB microenvironments. These studies identify a BADJ-associated, NEB-independent, CCSP-expressing stem cell population in terminal bronchioles and support the notion that regiospecific stem cell niches function to maintain epithelial diversity after injury. 相似文献
77.
In vitro degradation of silk fibroin 总被引:14,自引:0,他引:14
Horan RL Antle K Collette AL Wang Y Huang J Moreau JE Volloch V Kaplan DL Altman GH 《Biomaterials》2005,26(17):3385-3393
A significant need exists for long-term degradable biomaterials which can slowly and predictably transfer a load-bearing burden to developing biological tissue. In this study Bombyx mori silk fibroin yarns were incubated in 1mg/ml Protease XIV at 37 degrees C to create an in vitro model system of proteolytic degradation. Samples were harvested at designated time points up to 12 weeks and (1) prepared for scanning electron microscopy (SEM), (2) lyophilized and weighed, (3) mechanical properties determined using a servohydraulic Instron 8511, (4) dissolved and run on a SDS-PAGE gel, and (5) characterized with Fourier transform infrared spectroscopy. Control samples were incubated in phosphate-buffered saline. Fibroin was shown to proteolytically degrade with predictable rates of change in fibroin diameter, failure strength, cycles to failure, and mass. SEM indicated increasing fragmentation of individual fibroin filaments from protease-digested samples with time of exposure to the enzyme; particulate debris was present within 7 days of incubation. Gel electrophoresis indicated a decreasing amount of the silk 25 kDa light chain and a shift in the molecular weight of the heavy chain with increasing incubation time in protease. Results support that silk is a mechanically robust biomaterial with predictable long-term degradation characteristics. 相似文献
78.
Paul K. Hildebrandt James D. Conroy Adam E. McKee M. B. A. Nyindo David L. Huxsoll 《Infection and immunity》1973,7(2):265-271
The ultrastructure of Ehrlichia canis was examined in both pulmonary mononuclear cells and in monocytes cultured from an infected dog. The cytoplasmic inclusions, or morulae, of E. canis consisted of a membrane-lined vacuole-containing elementary bodies which varied in size and number. The elementary bodies were bound by two trilamellar membranes. The organism shared morphological properties of both the genus Rickettsia and genus Chlamydia. 相似文献
79.
Jones HE Andolina IM Oakely NM Murphy PC Sillito AM 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2000,135(2):279-284
We have compared the spatial summation characteristics of cells in the primary visual cortex with those of cells in the dorsal lateral geniculate nucleus (LGN) that provide the input to the cortex. We explored the influence of varying the diameter of a patch of grating centred over the receptive field and quantitatively determined the optimal summation diameter and the degree of surround suppression for cells at both levels of the visual system using the same stimulus parameters. The mean optimal summation size for LGN cells (0.90 degrees) was much smaller than that of cortical cells (3.58 degrees). Virtually all LGN cells exhibited strong surround suppression with a mean value of 74%+/-1.61% SEM for the population as a whole. This potent surround suppression in the cells providing the input to the cortex suggests that cortical cells must integrate their much larger summation fields from the low firing rates associated with the suppression plateau of the LGN cell responses. Our data suggest that the strongest input to cortical cells will arise from geniculate cells representing areas of visual space located at the borders of a visual stimulus. We suggest that analysis of response properties by patterns centred over the receptive fields of cells may give a misleading impression of the process of the representation. Analysis of pattern terminations or salient borders over the receptive field may provide much more insight into the processing algorithms involved in stimulus representation. 相似文献
80.
The complete sequence of the coding region of the ATM gene reveals similarity to cell cycle regulators in different species 总被引:30,自引:3,他引:30
Savitsky Kinneret; Sfez Sharon; Tagle Danilo A.; Ziv Yael; Sartiel Adam; Collins Francis S.; Shiloh Yosef; Rotman Gallt 《Human molecular genetics》1995,4(11):2025-2032
Ataxia-telangiectasia (A-T) is an autosomal recessive disorderinvolving cerebellar degeneration, immunodeficiency, radiationsensitivity, and cancer predisposition. A-T heterozygotes aremoderately cancer prone. The A-T gene, designated ATM, was recentlyidentified in our laboratory by positional cloning, and a partialcDNA clone was found to encode a polypeptide with a PI-3 kinasedomain. We report here the molecular cloning of a cDNA contigspanning the complete open reading frame of the ATM gene. Thepredicted protein of 3056 amino acids shows significant sequencesimilarities to several large proteins in yeast, Drosophilaand mammals, all of which share the PI-3 kinase domain. Manyof these proteins are involved in the detection of DNA damageand the control of cell cycle progression. Mutations in theirgenes confer a variety of phenotypes with features similar tothose observed in human A-T cells. The complete sequence ofthe ATM gene product provides useful clues to the function ofthis protein, and furthers understanding of the pleiotropicnature of the A-T mutations. 相似文献