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991.
Lac repressor protein was purified from E. coli BMH8117 harboring plasmid pWB1000 and E. coli K12BMH 71-18 strains. Displacement of the protein with poly(ethyleneimine) (PEI) from phosphocellulose cation exchange column was shown to be an effective elution strategy. It resulted in better recoveries and sharper elution profiles than traditional salt elution without effecting the purity of the protein. The elution is assumed to proceed via displacement of bound protein by PEI when the polymer binds to the ion exchanger. The minor impurities in the protein solution were finally removed by chromatography on immobilized metal affinity column. The repressor protein undergoes distinct conformational changes upon addition of specific inducer isopropyl--D-thiogalactoside (IPTG), which is evidenced by changes in ultraviolet absorption spectrum. The protein was immobilized covalently to the Sepharose matrix. The intact biological activity of the protein after immobilization was shown by binding of genomic DNA and lac operator plasmid DNA from E. coli to the immobilized lac repressor. 相似文献
992.
A new group of potent antibacterial compounds, non-iron metalloporphyrins (MPs), is described. MPs possess a strong antibacterial activity against Gram-positive bacteria, Gram-negative bacteria and mycobacteria. Anaerobically grown bacteria and microorganisms that do not respire and/or express haem uptake systems were resistant to MPs. Antibacterial activity of MPs was not affected by known antibiotic resistance mechanisms operating in bacteria. The most potent MP against Y. enterocolitica, methicillin-resistant S. aureus and M. smegmatis was gallium protoporphyrin IX (Ga-PPIX). When tested alone, Ga ions and metal-free porphyrins had approximately 100-fold higher minimum inhibitory concentration (MIC) values for these organisms. Ga-PPIX was not degraded by MP-sensitive bacteria, indicating that the whole molecule is responsible for antibacterial activity. MPs are antibacterial 'Trojan horses', as they exploit haem transport systems of Gram-negative bacteria as portals of entry into the cell. Bacterial mutants in superoxide dismutases, catalases and stationary-phase sigma factors were hypersensitive to Ga-PPIX. The extreme sensitivity of sod mutants to MPs and the requirement for active respiration for MP activity suggests that these compounds stimulate the production of reactive oxygen radicals in bacteria. Ga-PPIX was not toxic to primary human fibroblasts, several established cell lines and experimental animals at concentrations > 100-fold higher than the MIC for sensitive bacteria. 相似文献
993.
Vijaya Kumar M Sambaiah K Lokesh BR 《Prostaglandins, leukotrienes, and essential fatty acids》1999,61(4):249-254
Ghee, the anhydrous milk fat, is one of the most important sources of dietary fat in India. Male Wistar rats were fed diets containing 2.5, 5.0 and 10 wt% ghee for a period of 8 weeks. The diets were made isocaloric with groundnut oil. The results showed that serum thromboxane levels decreased by 27-35%, and 6-keto-prostaglandin F1alpha by 23-37% when ghee was incorporated at level of 10% in the diet. Prostaglandin E2 levels in serum and secretion of leukotrienes B4, C4 and D4 by peritoneal macrophages activated with calcium ionophore decreased when increased amounts of ghee from 2.5 to 10% were included in the diet. Arachidonic acid levels in macrophage phospholipids decreased when incremental amounts of ghee were fed to rats. These studies indicate that ghee in the diet not only lowers the prostaglandin levels in serum but also decreases the secretion of leukotrienes by macrophages. 相似文献
994.
A polygalacturonase was purified from the thermophilic fungus, Thermomyces lanuginosus to apparent homogeneity by ultrafiltration, acetone precipitation and ion-exchange chromatography. The enzyme was maximally active at pH 5.5 and 60 °C. The apparent KM with potassium pectate was 0.67 mg/ml and the Vmax was 7.2 × 105 mol/min/mg protein. The apparent molecular weight of the enzyme was 59 kDa and it contained approximately 10% carbohydrate. The enzyme was completely stable at room temperature (32 ± 3 °C) and retained about 50% activity at 50 °C for 6 h. The zymogram of the purified enzyme revealed two activity bands, one of which was a major one. Polyclonal antibodies raised against the enzyme did not show any immunological relatedness with other mesophilic polygalacturonases. 相似文献
995.
996.
997.
Most species use daily light in one way or the other in regulation of their short and/or long term activities. Light is perceived by pigment(s) present in the retinal (RP) and/or extra-retinal photoreceptors (ERPs). ERPs may be located at various sites in the body but in non-mammalian vertebrates they are found predominantly in the pineal body and hypothalamic region of the brain, Light radiations directly penetrate brain tissues to reach and stimulate the hypothalamic (deep-brain) photoreceptors. How does light information finally reach to the clock is not fully understood in many vertebrate groups? In mammals, however, the light information from the retina to the clock (the hypothalamic suprachiasmatic nuclei, SCN) is relayed through the retino-hypothalamic tract (RHT) which originates from the retinal ganglion cells, and through the geniculo-hypothalamic tract (GHT) which originates from the photically responsive cells of a portion of the lateral geniculate nucleus (LGN), called the intergeniculate leaflet (IGL). A response to light (the photoperiodic response) is the result of the interpretation of light information by the photoperiodic system. Apart from the duration, the animals use the gradual shifts in the intensity and wavelength of daily light to regulate their photoperiodic clock system. The wavelengths to which photoreceptors are maximally sensitive or the wavelengths which have greater access to the photoreceptors can induce a maximal response. There can also be differential effects of wavelength and intensity of light on circadian process(es) involved in the entrainment and induction of the photoperiodic clock. This may have some adaptive implications. Entrainment to daily light-dark (LD) cycle may be achieved at dawn or dusk, depending whether the animal is day- or night-active, when there is relatively low intensity of light. By contrast, photoperiodic induction in many species occurs during long days of spring and summer when plenty of daylight at higher intensity is available later in the day. 相似文献
998.
Kumar D Bansal A Thomas P Sairam M Sharma SK Mongia SS Singh R Selvamurthy W 《International journal of biometeorology》1999,42(4):201-204
High altitude stress leads to lipid peroxidation and free radical formation which results in cell membrane damage in organs
and tissues, and associated mountain diseases. This paper discusses the changes in biochemical parameters and antibody response
on feeding glutamate to male albino Sprague Dawley rats under hypoxic stress. Exposure of rats to simulated hypoxia at 7576
m, for 6 h daily for 5 consecutive days, in an animal decompression chamber at 32±2° C resulted in an increase in plasma malondialdehyde
level with a concomitant decrease in blood glutathione (reduced) level. Supplementation of glutamate orally at an optimal
dose (27 mg/kg body weight) in male albino rats under hypoxia enhanced glutathione level and decreased malondialdehyde concentration
significantly. Glutamate feeding improved total plasma protein and glucose levels under hypoxia. The activities of serum glutamate
oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) and the urea level remained elevated on
glutamate supplementation under hypoxia. Glutamate supplementation increased the humoral response against sheep red blood
cells (antibody titre). These results indicate a possible utility of glutamate in the amelioration of hypoxia-induced oxidative
stress.
Received: 23 March 1998 / Accepted: 19 October 1998 相似文献
999.
All-trans-retinoic acid (RA), an active metabolite of vitamin A, induces the gene expression of uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) and suppresses leptin gene expression in white adipose tissue (WAT) when given as an acute dose. These contrasting effects of RA leave in doubt the overall effect of chronic RA or vitamin A supplementation on energy homeostasis. To investigate the effects of dietary vitamin A supplementation on leptin and UCP1 gene expression, rats were fed either a normal diet (2.6 retinol/kg diet) or a vitamin A-supplemented diet (129 mg retinol/kg diet) for 8 weeks, and adiposity, serum leptin levels, leptin mRNA levels in perirenal WAT, UCP1 and UCP2 mRNA levels in BAT, and beta3-adrenergic receptor mRNA levels in BAT and WAT were examined. Rats on both diets gained a similar amount of weight, but there was a small 9% decrease in the adiposity index in the vitamin A-supplemented rats. Dietary vitamin A supplementation increased UCP1 gene expression in BAT by 31%, but suppressed leptin gene expression by 44% and serum leptin levels by 65%. UCP2 and beta3-adrenergic receptor gene expression in BAT and perirenal WAT were unchanged by the vitamin A diet. These data suggest that dietary vitamin A has a role in regulating energy homeostasis by enhancing UCP1 gene expression and decreasing serum leptin levels. 相似文献
1000.
Split flexor carpi radialis muscle 总被引:7,自引:0,他引:7
Hua J Kumar VP Pereira BP Lim AY Pho RW Liu J 《Plastic and reconstructive surgery》1999,103(3):930-934
A detailed anatomic and intramuscular neural staining study in 22 human and 5 monkey upper limbs revealed that the flexor carpi radialis can be raised on its proximal neurovascular pedicle and that the muscle can be split along its tendon into two independently functioning neuromuscular compartments, each with its own nerve and blood supply. A study of the muscle architecture in the human specimens found the radial compartment to have significantly longer fiber length and a larger physiologic cross-sectional area than the ulnar compartment. Independence of function of each compartment was demonstrated in electrical stimulation studies in six monkeys (Macaca fascicularis), but no significant difference was noted in the peak isometric load between the two compartments (p = 0.68) in the monkey. The extra functioning muscle units become important in local transfers for restoring function in multiple nerve palsies as in Hansen's disease, severe traumatic loss of muscle in crush injuries and compartment syndromes, and after wide resection in infective and neoplastic conditions in the forearm and hand. 相似文献