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441.
Kenneth L. McCormick Gail J. Mick Lisa Butterfield Hugh Ross Elaine Parton Joan Totka 《Experimental diabetes research》2001,2(2):121-127
Leptin, the gene product of adipose tissue that signals
caloric plentitude via central nervous system
receptors, may also have diverse peripheral metabolic
actions. Of paramount interest has been the
potential interaction(s) between leptin and insulin.
Insofar as insulin alters leptin secretion/action (or
vice versa), dysregulation of this system could contribute
to disease states such as diabetes.The purpose of this study was to examine the
effect of exogenous insulin on serum leptin in
children with newly-diagnosed Type 1 diabetes.
Since these patients are hypoinsulinemic (insulindeplet.
ed) at diagnosis, they present an ideal
opportunity to examine the effect of insulin repletion
on serum leptin. Seventeen patients were
enrolled. At baseline (prior to insulin therapy),
leptin levels were 4.3 ± 1.1ng/ml; they were not statistically
related to the baseline serum insulin or
illness severity. There was no significant change in
serum leptin before, shortly (1–6 days) or several
weeks (3–26 weeks) after insulin treatment even
when the data was corrected for changes in BMI,
hemoglobin A1C, and daily insulin dose. Since
repletion of the insulin deficiency that is present
in non-acidotic, ambulatory patients with new
onset Type 1 diabetes did not alter serum leptin,
these results argue against an effect of insulin on
serum leptin in the absence of the acute diabetic
ketoacidosis. Because as the recuperative months
following the diagnosis of new onset Type 1
diabetes are marked by weight gain, the absence
of a rise in serum leptin might also indicate
either an adaptive (weight permissive) or pathologic
(impaired secretory) deficit. 相似文献
442.
The effect of secreted virulence components of Bordetella pertussis on chemiluminescence (CL) of rabbit peritoneal neutrophils was determined with the chemotactic peptide N'-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) or intact B. pertussis as the stimulus. Pertussis toxin (PT) inhibited the response to fMLP in a dose-dependent manner, although only after the neutrophils had been exposed to the toxin for greater than 15 min. Both filamentous haemagglutinin (FHA) and lipopolysaccharide (LPS) markedly enhanced the CL response to fMLP after greater than or equal to 15 min incubation with the neutrophils. Similar effects to those of B. pertussis LPS were also seen with smooth and rough LPS from Salmonella minnesota. With the lowest dose of each component which elicited a maximal effect on CL, the inhibitory effect of PT overrode the enhancing effect of FHA and B. pertussis LPS. Pre-incubation of neutrophils with PT, FHA or B. pertussis LPS caused a slight reduction in the subsequent CL response to virulent B. pertussis Tohama. Virulent (phase I, or X-mode) organisms of B. pertussis 18334 and B. pertussis Tohama induced greater neutrophil CL than their avirulent (C-mode) derivatives. There appeared to be an inverse correlation between bacterial hydrophilicity and the ability to induce neutrophil CL: X-mode bacteria were significantly less hydrophilic than C-mode organisms. Three mutants, the adenylate cyclase (AC)- and haemolysin (HLY)-deficient B. pertussis BP348, the FHA-deficient B. pertussis BP353, and the PT-deficient B. pertussis BP357, generated similar levels of CL and had similar hydrophilicity values. The hydrophilicity value of the avirulent mutant B. pertussis BP347 (deficient in AC, HLY, FHA and PT) and the CL induced by this strain were similar to those of B. pertussis C-mode organisms. Thus, the interaction of B. pertussis with neutrophils appears to be complex, reflecting both the alteration of leucocyte function by secreted virulence components of the organism and, in the absence of opsonins, the surface properties of the bacterium. 相似文献
443.
JÖRG THOMAS EPPLEN BRIGITTE KUNZ GERD WIECZOREK-ENGELKEN WOLFGANG ENGEL JÖRG SCHMIDTKE 《Differentiation; research in biological diversity》1981,20(1-3):124-130
Enzymatic digestion of the interstitial tissue of early juvenile and adult rat testes resulted in an enrichment of the Leydig cell population. The cells of the intertubular preparation from adult testes were separated by centrifugal elutriation, according to differences in sedimentation velocity, a counter-flow centrifugation technique leading to 70% Leydig cell purity. Using this approach, it was possible to demonstrate that Leydig cells from adult testes contain only low affinity isoenzymes of cyclic AMP phosphodiesterase (PDE; E.C.: 3.1.4.17), an intracellular regulator of cAMP. Starch gel electrophoresis showed that the isozyme of cAMP PDE of Leydig cells is masked in crude testis homogenates due to the relatively low level of these cells in the total population. In Leydig cells, there are two different electrophoretic forms expressed which resemble two of eleven different molecular forms of cAMP PDE demonstrated for comparison in 21 different organs of the adult rat.
An interstitial cell preparation from early juvenile testes, with a Leydig cell content of up to 20%, was also investigated electrophoretically with regard to molecular forms of cAMP PDE, the properties of which were characterized by kinetic analysis of cAMP hydrolysis. The results presented are discussed in relation to the onset of testosterone synthesis in Leydig cells of prepubertal rats leading to the initiation of male puberty. 相似文献
An interstitial cell preparation from early juvenile testes, with a Leydig cell content of up to 20%, was also investigated electrophoretically with regard to molecular forms of cAMP PDE, the properties of which were characterized by kinetic analysis of cAMP hydrolysis. The results presented are discussed in relation to the onset of testosterone synthesis in Leydig cells of prepubertal rats leading to the initiation of male puberty. 相似文献
444.
Abstract The optimal conditions for toxoiding a pertussis toxin (PT) preparation with 1-ethyl-3(3-dimethylaminopropyl) carbodiimide · HCl (EDAC) were determined. The prime factor affecting the toxoiding of PT was the EDAC to protein ratio. A ratio of 40–80 : 1 EDAC to protein by weight was optimal for abolishing the acute toxicity, histamine-sensitising and leucocytosis-promoting activities associated with PT, whilst maintaining the antigenicity of the vaccine antigens. An EDAC-toxoid also manifested no late histamine-sensitising activity. Duration of exposure to EDAC, temperature and pH value of the reaction were found not be be critical for toxoiding. The data indicated that the use of EDAC for toxoiding PT in a B. pertussis extract is a simple and reproducible procedure and should be considered as a method for the production of acellular pertussis vaccines. 相似文献
445.
Lei Wu Anastasia Parton Ling Lu Mary Adams Peter Schafer J. Blake Bartlett 《Cancer immunology, immunotherapy : CII》2011,60(1):61-73
We evaluated the effect of combining lenalidomide with therapeutic antibodies on antibody-dependant cell-mediated cytotoxicity
(ADCC) of solid tumor cells, and the requirement for expression of natural killer (NK) cell-activating receptors and their
solid tumor surface ligands. Twenty-three human tumor cell lines (colon, breast, lung, head and neck, ovary, and bone sarcoma)
were analyzed. NK effector cells were isolated from healthy donors, pre-treated with and without lenalidomide, and incubated
with antibody-coated tumor cells to determine ADCC. In blocking experiments, NK cells were pre-incubated with anti-DNAM-1
or anti-NKG2D antibodies, and target colorectal cells were pre-incubated with anti-CD155 (PVR), anti-MIC-A/B, or anti-ULBP
3 antibodies. Differences between groups were assessed using unpaired and paired Student’s t test and one-way ANOVA. Lenalidomide enhanced NK cell-mediated ADCC of trastuzumab- and cetuximab-coated tumor cells. Activity
against colorectal cancer cells was dependent on target antigen expression, but independent of KRAS status and FcγRIIIa genotype. The extent of ADCC and its enhancement by lenalidomide correlated with NK cell expression of
NKG2D and DNAM-1, and tumor cell expression of PVR and MIC-A. Blocking of NKG2D and, to a lesser extent, DNAM-1 inhibited
ADCC. Anti-MIC-A/B monoclonal antibody blocked natural cytotoxicity, but not ADCC. Lenalidomide enhances the ability of IgG1-isotype
antibodies to mediate ADCC of solid tumor cells, the extent of which is largely dependent on NKG2D–NKG2D ligand interactions,
but appears to be independent of MIC-A/B. This provides a rationale for exploratory clinical studies and an assessment of
potential biomarkers predictive of clinical benefit. 相似文献
446.
447.
448.
Summary Prescribed burning is a major control over element cycles in Tallgrass prairie (Eastern Kansas, USA). In this paper we report potential effects of fire on nonsymbiotic nitrogen fixation. Fire resulted in additions of available P in ash, which may stimulate nitrogen fixation by terrestrial cyanobacteria. Cyanobacterial nitrogenase activity and biomass responded positively to additions of ash or P in laboratory assays using soil. Further assays in soil showed that cyanobacteria responded to changes in available N:available P ratio (aN:P) across a range of concentrations. Nitrogen fixation rate could be related empirically to aN:P via a log-linear relationship. Extrapolation of laboratory results to the field yielded a maximal estimate of 21 kg N ha-1 y-1. Results support arguments from the marine and terrestrial literature that P availability is central to regulation of ecosystem N budgets. 相似文献