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91.
We investigate how a unique dietary specialist, the Gila monster (Heloderma suspectum), uses behavioral thermoregulation to elevate body temperature (Tb) after feeding. Lizards in a laboratory thermal gradient were fed rodent meals of three different sizes (5, 10, or 20% of body mass), or sham fed (meal of 0% body mass), and Tbs were recorded for three days before feeding and seven days after feeding. Gila monsters selected a mean Tb of 25.2 °C while fasting (set-point range 23.6–27.1), and increased Tbs after feeding. The magnitude and duration of post-prandial Tb increases are positively related to meal size, and Gila monsters selected mean Tbs up to 3.0 °C higher and maintain elevated Tbs for 3–6 days after feeding. Selection of Tb does not appear to differ between day and night time periods, and because the lizards are both diurnal and nocturnal (at different times of year), photoperiod may not be an important influence on Tb selection. 相似文献
92.
Oxidized alkyl phospholipids are specific, high affinity peroxisome proliferator-activated receptor gamma ligands and agonists 总被引:6,自引:0,他引:6
Davies SS Pontsler AV Marathe GK Harrison KA Murphy RC Hinshaw JC Prestwich GD Hilaire AS Prescott SM Zimmerman GA McIntyre TM 《The Journal of biological chemistry》2001,276(19):16015-16023
Synthetic high affinity peroxisome proliferator-activated receptor (PPAR) agonists are known, but biologic ligands are of low affinity. Oxidized low density lipoprotein (oxLDL) is inflammatory and signals through PPARs. We showed, by phospholipase A(1) digestion, that PPARgamma agonists in oxLDL arise from the small pool of alkyl phosphatidylcholines in LDL. We identified an abundant oxidatively fragmented alkyl phospholipid in oxLDL, hexadecyl azelaoyl phosphatidylcholine (azPC), as a high affinity ligand and agonist for PPARgamma. [(3)H]azPC bound recombinant PPARgamma with an affinity (K(d)((app)) approximately 40 nm) that was equivalent to rosiglitazone (BRL49653), and competition with rosiglitazone showed that binding occurred in the ligand-binding pocket. azPC induced PPRE reporter gene expression, as did rosiglitazone, with a half-maximal effect at 100 nm. Overexpression of PPARalpha or PPARgamma revealed that azPC was a specific PPARgamma agonist. The scavenger receptor CD36 is encoded by a PPRE-responsive gene, and azPC enhanced expression of CD36 in primary human monocytes. We found that anti-CD36 inhibited azPC uptake, and it inhibited PPRE reporter induction. Results with a small molecule phospholipid flippase mimetic suggest azPC acts intracellularly and that cellular azPC accumulation was efficient. Thus, certain alkyl phospholipid oxidation products in oxLDL are specific, high affinity extracellular ligands and agonists for PPARgamma that induce PPAR-responsive genes. 相似文献
93.
Duffy-null promoter heterozygosity reduces DARC expression and abrogates adhesion of the P. vivax ligand required for blood-stage infection 总被引:3,自引:0,他引:3
The Duffy blood group antigen is an essential receptor for Plasmodium vivax entry into erythrocytes in a process mediated by the parasite ligand, the Duffy binding protein (DBP). Recently, individuals living in a malaria endemic region of Papua New Guinea were identified as heterozygous for a new allele conferring Duffy negativity, which results in 50% less Duffy antigen on their erythrocytes. We demonstrate that DBP adherence to erythrocytes is significantly reduced for erythrocytes from heterozygous individuals who carry one Duffy antigen negativity allele. These data provide evidence that emergence of this new allelic form of Duffy negativity is correlated with resistance against vivax malaria. 相似文献
94.
Lysophosphatidylcholine and lyso-PAF display PAF-like activity derived from contaminating phospholipids 总被引:3,自引:0,他引:3
Marathe GK Silva AR de Castro Faria Neto HC Tjoelker LW Prescott SM Zimmerman GA McIntyre TM 《Journal of lipid research》2001,42(9):1430-1437
Lysophosphatidylcholine is an abundant component of plasma and oxidized LDL that displays several biological activities, some of which may occur through the platelet-activating factor (PAF) receptor. We find that commercial lysophosphatidylcholine, its alkyl homolog (lyso-PAF), and PAF all induce inflammation in a murine model of pleurisy. Hydrolysis of PAF to lyso-PAF by recombinant PAF acetylhydrolase abolished this eosinophilic infiltration, implying that lyso-PAF should not have displayed inflammatory activity. Saponification of lyso-PAF or PAF acetylhydrolase treatment of lyso-PAF or lysophosphatidylcholine abolished activity; neither lysolipid should contain susceptible sn-2 residues, suggesting contaminants account for the bioactivity. Lyso-PAF and to a lesser extent lysophosphatidylcholine stimulated Ca(2+) accumulation in 293 cells stably transfected with the human PAF receptor, and this was inhibited by specific PAF receptor antagonists. Again, treatment of lyso-PAF or lysophosphatidylcholine with recombinant PAF acetylhydrolase, a nonselective phospholipase A(2), or saponification of lyso-PAF destroyed the PAF-like activity, a result incompatible with lyso-PAF or lysophosphatidylcholine being the actual agonist.We conclude that neither lyso-PAF nor lysophosphatidylcholine is a PAF receptor agonist, nor are they inflammatory by themselves. We suggest that PAF or a PAF-like mimetic accounts for inflammatory effects of lysophosphatidylcholine and lyso-PAF. 相似文献
95.
Pisarri T. E.; Zimmerman M. P.; Adrian T. E.; Coleridge J. C.G.; Coleridge H. M. 《Journal of applied physiology》1999,86(1):105-113
Bronchialvasodilation in dogs is mediated largely by vagal pathways. To examinethe relative contribution of cholinergic and noncholinergicparasympathetic pathways and of sensory axon reflexes to vagalbronchial vasodilation, we electrically stimulated the peripheral vagusnerve in 10 chloralose-anesthetized dogs and measured bronchial arteryflow. Moderate-intensity electrical stimulation (which did not activateC-fiber axons) caused a rapid voltage- and frequency-dependentvasodilation. After atropine, vasodilation was slower in onset andreduced at all voltages and frequencies: bronchial vascular conductanceincreased by 9.0 ± 1.5 (SE)ml · min1 · 100 mmHg1 during stimulationbefore atropine and 5.5 ± 1.4 ml · min1 · 100 mmHg1 after(P < 0.02). High-intensitystimulation (sufficient to recruit C fibers) was not studied beforeatropine because of the resulting cardiac arrest. After atropine,high-intensity stimulation increased conductance by 12.0 ± 2.5 ml · min1 · 100 mmHg1. Subsequent blockadeof ganglionic transmission, with arterial blood pressure maintained bya pressure reservoir, abolished the response to moderate-intensitystimulation and reduced the increase to high-intensity stimulation by82 ± 5% (P < 0.01). In 13 other dogs, we measured vasoactive intestinalpeptide-like immunoreactivity in venous blood draining from thebronchial veins. High-intensity vagal stimulationincreased vasoactive intestinal peptide concentration from 5.7 ± 1.8 to 18.4 ± 4.1 fmol/ml (P = 0.001). The results suggest that in dogs cholinergic and noncholinergicparasympathetic pathways play the major role in vagal bronchial vasodilation. 相似文献
96.
Zimmerman TJ Jenks JA Holler LD Jacques CN Morlock WW 《Journal of wildlife diseases》2004,40(1):145-149
On 1 October 2001, a 4-mo-old male white-tailed deer (Odocoileus virginianus) fawn was collected in Day County, South Dakota (USA), by South Dakota Department of Game, Fish and Parks personnel. The fawn had sparse hair development on the ventral thorax, the lateral caudal and caudal aspects of the rear legs, the muzzle, around the eyes, and inside the ears. Remaining skin surfaces were devoid of hair. Histologic examination revealed normal hair follicle density although follicles were empty or contained keratin debris and fragments of hair shaft. The epidermis of the fawn was mildly thickened and melanin pigment was prominent within deep layers of the epidermis. Based on histologic examination, the deer was diagnosed with congenital hypotrichosis. Although this condition has been reported in domestic species and humans, this specimen represents the first documented case of congenital hypotrichosis in a cervid. 相似文献
97.
98.
Zimmerman SB 《Journal of structural biology》2004,147(2):146-158
The genomic DNA of Escherichia coli is contained in one or two compact bodies known as nucleoids. Isolation of typically shaped nucleoids requires control of DNA expansion, accomplished here by a modification of the polylysine-spermidine procedure. The ability to control expansion of in vitro nucleoids has application in nucleoid purification and in preparation of samples for high-resolution imaging, and may allow an increased resolution in gene localization studies. Polylysine of relatively low average molecular weight (approximately 3 kDa) is used to produce lysates containing nucleoids that are several-fold expanded relative to the sizes of in vivo nucleoids. These expanded forms can be converted to compact forms similar in dimensions to the cellular nucleoids by either a further addition of polylysine or by incubation of diluted lysates at 37 degrees C. The incubation at 37 degrees C is accompanied by autolytic degradation of most ribosomal RNA. Hyperchromism and circular dichroism spectra indicate that polylysine-DNA complexes are modified during the incubation. Compact forms of the nucleoid can be progressively reexpanded by exposure to salt solutions. Nucleoid compaction was similar in lysates made from rapidly or slowly growing cells or from cells that had been briefly treated with chloramphenicol to reduce linkages between DNA and cell envelope. 相似文献
99.
‘Indirect readout’ refers to the proposal that proteins can recognize the intrinsic three-dimensional shape or flexibility of a DNA binding sequence apart from direct protein contact with DNA base pairs. The differing affinities of human papillomavirus (HPV) E2 proteins for different E2 binding sites have been proposed to reflect indirect readout. DNA bending has been observed in X-ray structures of E2 protein–DNA complexes. X-ray structures of three different E2 DNA binding sites revealed differences in intrinsic curvature. DNA sites with intrinsic curvature in the direction of protein-induced bending were bound more tightly by E2 proteins, supporting the indirect readout model. We now report solution measurements of intrinsic DNA curvature for three E2 binding sites using a sensitive electrophoretic phasing assay. Measured E2 site curvature agrees well the predictions of a dinucleotide model and supports an indirect readout hypothesis for DNA recognition by HPV E2. 相似文献
100.