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排序方式: 共有463条查询结果,搜索用时 109 毫秒
461.
Zaquer Suzana Munhoz Costa-Ferro Fernanda de Borba Cunha Bruno Solano de Freitas Souza Marcos Maurício Tosta Leal Adelson Alves da Silva Telma Ingrid Borges de Bellis Kühn Andresa Forte Eliseo Joji Sekiya Milena Botelho Pereira Soares Ricardo Ribeiro dos Santos 《Cytotechnology》2014,66(2):193-199
Status epilepticus (SE) is a condition of persistent seizure that leads to brain damage and, frequently, to the establishment of chronic epilepsy. Cord blood is an important source of adult stem cells for the treatment of neurological disorders. The present study aimed to evaluate the effects of human umbilical cord blood mononuclear cells (HUCBC) transplanted into rats after induction of SE by the administration of lithium and pilocarpine chloride. Transplantation of HUCBC into epileptic rats protected against neuronal loss in the hippocampal subfields CA1, CA3 and in the hilus of the dentate gyrus, up to 300 days after SE induction. Moreover, transplanted rats had reduced frequency and duration of spontaneous recurrent seizures (SRS) 15, 120 and 300 days after the SE. Our study shows that HUCBC provide prominent antiepileptic and neuroprotective effects in the experimental model of epilepsy and reinforces that early interventions can protect the brain against the establishment of epilepsy. 相似文献
462.
Marcus B. S. Forte Marcio A. Mazutti Francisco Maugeri Filho Maria Isabel Rodrigues 《Biotechnology and Bioprocess Engineering》2011,16(6):1223-1230
This work investigates the adsorption of clavulanic acid using natural six cationic forms (Na+, Ca+2, Ba+2, Sr2+, K+, and Mg2+) of the X and NZ zeolites in a stirred tank reactor since the separation is an important step of the biomolecule production.
A mathematical model was proposed taking into account the transport of CA molecules from the liquid phase to the surface of
the adsorbent and after diffusion into the particles. The estimated kinetic and mass transfer parameters were used to evaluate
adsorption rates and mass transfer resistances involved in the separation of clavulanic acid from the broth. It has been shown
that mass-transfer phenomena were a limiting step in the clavulanic acid adsorption process and that the adsorption rate should
be considered to evaluate the system. Amongst the materials, the synthetic zeolite NaX was selected as the most appropriate
material to separate clavulanic acid because this material presented the highest values for the observed reaction rate, compensating
for the external mass transfer resistance. Modeling and simulation of clavulanic acid purification using the zeolite NaX showed
a satisfactory fitting of experimental data. The model was used to simulate the process and it was evaluated for its technical
and economical viability by comparisons considering the influence of the solid:liquid ratio on the adsorption equilibrium
time and on the hydrolysed mass of biomolecule. 相似文献
463.
L R Forte 《Regulatory peptides》1999,81(1-3):25-39
The guanylin family of bioactive peptides consists of three endogenous peptides, including guanylin, uroguanylin and lymphoguanylin, and one exogenous peptide toxin produced by enteric bacteria. These small cysteine-rich peptides activate cell-surface receptors, which have intrinsic guanylate cyclase activity, thus modulating cellular function via the intracellular second messenger, cyclic GMP. Membrane guanylate cyclase-C is an intestinal receptor for guanylin and uroguanylin that is responsible for stimulation of Cl- and HCO3- secretion into the intestinal lumen. Guanylin and uroguanylin are produced within the intestinal mucosa to serve in a paracrine mechanism for regulation of intestinal fluid and electrolyte secretion. Enteric bacteria secrete peptide toxin mimics of uroguanylin and guanylin that activate the intestinal receptors in an uncontrolled fashion to produce secretory diarrhea. Opossum kidney guanylate cyclase is a key receptor in the kidney that may be responsible for the diuretic and natriuretic actions of uroguanylin in vivo. Uroguanylin serves in an endocrine axis linking the intestine and kidney where its natriuretic and diuretic actions contribute to the maintenance of Na+ balance following oral ingestion of NaCl. Lymphoguanylin is highly expressed in the kidney and myocardium where this unique peptide may act locally to regulate cyclic GMP levels in target cells. Lymphoguanylin is also produced in cells of the lymphoid-immune system where other physiological functions may be influenced by intracellular cyclic GMP. Observations of nature are providing insights into cellular mechanisms involving guanylin peptides in intestinal diseases such as colon cancer and diarrhea and in chronic renal diseases or cardiac disorders such as congestive heart failure where guanylin and/or uroguanylin levels in the circulation and/or urine are pathologically elevated. Guanylin peptides are clearly involved in the regulation of salt and water homeostasis, but new findings indicate that these novel peptides have diverse physiological roles in addition to those previously documented for control of intestinal and renal function. 相似文献