Population dynamics of a stoichiometric aquatic tri-trophic level model with fear effect.

In this paper, a stoichiometric aquatic tri-trophic level model is proposed and analyzed, which incorporates the effect of light and phosphorus, as well as the fear effect in predator-prey interactions. The analysis of the model includes the dissipativity and the existence and stability of equilibria. The influence of environmental factors and fear effect on the dynamics of the system is particularly investigated. The key findings reveal that the coexistence of populations is positively influenced by an appropriate level of light intensity and/or the dissolved phosphorus input concentration; however, excessive levels of phosphorus input can disrupt the system, leading to chaotic behaviors. Furthermore, it is found that the fear effect can stabilize the system and promote the chances of population coexistence.

[Acupoints compatibility rules of acupuncture for depression disease based on data mining technology].

Based on data mining technology, the acupoints compatibility rules of acupuncture for depression diseases were explored. The randomized controlled trial (RCT) articles regarding acupuncture for depression diseases published from establishment of database to September 2nd, 2022 were searched in CNKI database, Wangfang database, VIP database, SinoMed database, PubMed, EMbase, Web of Science and Cochrane Library. The use frequency of acupoints, meridian tropism, selection of special acupoints and acupoint association rules for five common depression diseases, including primary depression, post-stroke depression, menopausal syndrome, psychoneurosis and anxiety disorder, were analyzed by Python programming language. Cytoscape software was used to analyze the acupoint association and the disease-acupoint co-occurrence network. As a result, totally 387 articles were included, and 319 acupoints prescriptions for the above five common depression diseases were extracted, involving 159 acupoints. The use frequency of acupoints was 2 574 times in total. The frequently-used acupoints were Baihui (GV 20), Sanyinjiao (SP 6), Taichong (LR 3), Neiguan (PC 6), Shenmen (HT 7), Yintang (GV 24+), Zusanli (ST 36), Hegu (LI 4), Sishencong (EX-HN 1) and Taixi (KI 3), etc. The frequently involved meridians were the governor vessel, foot-taiyang bladder meridian, foot-taiyin spleen meridian, and foot-jueyin liver meridian. The frequency of the special acupoints from high to low was crossing points, five-shu points, yuan-primary points, back-shu points, luo-connecting points, and eight confluent points, etc, which were often used in combination with "Baihui (GV 20)-Yintang (GV 24+)" (the highest degree of association). At the same time, the analysis of the co-occurrence network of depression diseases and acupoints showed that the core acupoints group of acupuncture for depression diseases were Baihui (GV 20), Taichong (LR 3), Shenmen (HT 7), Zusanli (ST 36), Neiguan (PC 6) and Sanyinjiao (SP 6). In conclusion, acupuncture treatment for depression diseases has gradually formed a rule of acupoint compatibility, with special acupoint as the main body and "unblocking the governor vessel, and regulating the spirit and qi " as the main therapeutic principle.

Atractylenolide I ameliorates cancer cachexia through inhibiting biogenesis of IL-6 and tumour-derived extracellular vesicles.

BACKGROUND: Atractylenolide I (AI) is a natural sesquiterpene lactone isolated from Atractylodes macrocephala Koidz, known as Baizhu in traditional Chinese medicine. AI has been found to ameliorate cancer cachexia in clinic cancer patients and in tumour-bearing mice. Here, we checked the influence of AI on biogenesis of IL-6 and extracellular vesicles (EVs) in cancer cachexia mice and then focused on studying mechanisms of AI in inhibiting the production of tumour-derived EVs, which contribute to the ameliorating effects of AI on cancer cachexia. METHODS: C26 tumour-bearing BALB/c mice were applied as animal model to examine the effects of AI (25 mg/kg) in attenuating cachexia symptoms, serum IL-6 and EVs levels. IL-6 and EVs secretion of C26 tumour cells treated with AI (0.31-5 µM) was further observed in vitro. The in vitro cultured C2C12 myotubes and 3T3-L1 mature adipocytes were used to check the potency of conditioned medium of C26 cells treated with AI (0.625-5 µM) in inducing muscle atrophy and lipolysis. The glycolysis potency of C26 cells under AI (0.31-5 µM) treatment was evaluated by measuring the extracellular acidification rate using Seahorse XFe96 Analyser. Levels of related signal proteins in both in vitro and in vivo experiments were examined using western blotting to study the possible mechanisms. STAT3 overexpression or knockout C26 cells were also used to confirm the effects of AI (5 µM). RESULTS: AI ameliorated cancer cachexia symptoms (P < 0.05), improved grip strength (P < 0.05) and decreased serum EVs (P < 0.05) and IL-6 (P < 0.05) levels of C26 tumour-bearing mice. AI directly inhibited EVs biogenesis (P < 0.001) and IL-6 secretion (P < 0.01) of cultured C26 cells. The potency of C26 medium in inducing C2C12 myotube atrophy (+59.54%, P < 0.001) and 3T3-L1 adipocyte lipolysis (+20.73%, P < 0.05) was significantly attenuated when C26 cells were treated with AI. AI treatment inhibited aerobic glycolysis and the pathway of STAT3/PKM2/SNAP23 in C26 cells. Furthermore, overexpression of STAT3 partly antagonized the effects of AI in suppressing STAT3/PKM2/SNAP23 pathway, EVs secretion, glycolysis and the potency of C26 medium in inducing muscle atrophy and lipolysis, whereas knockout of STAT3 enhanced the inhibitory effect of AI on these values. The inhibition of AI on STAT3/PKM2/SNAP23 pathway was also observed in C26 tumour tissues. CONCLUSIONS: AI ameliorates cancer cachexia by decreasing the production of IL-6 and EVs of tumour cells. The decreasing effects of AI on EVs biogenesis are based on its inhibition on STAT3/PKM2/SNAP23 pathway.

[Influence of Land Use and Land Cover Patterns on Water Quality at Different Spatio-temporal Scales in Hehuang Valley].

Based on the measured water quality data of Huangyuan County, Huzhu Tu Autonomous County, and Minhe Hui Tu Autonomous County in Hehuang Valley of Qinghai province in the normal and wet seasons, the effects of land use and land cover patterns on regional seasonal water quality were analyzed using remote sensing technology and mathematical statistics. The results showed that:① the concentrations of total nitrogen and total phosphorus in the surface water of Hehuang Valley were high. Water pollution areas (Class Ⅳ and Ⅴ) were mainly concentrated in the lower reaches of the river and the junction of tributaries. ② The explanation rate of land use to water quality in the normal season was higher than that in the wet season. The optimal scale was the 200 m buffer scale in the normal season, and farmland and towns were the main influencing factors. The optimal scale in the wet season was the 5 km buffer scale, and the main influencing factor was the forest. ③ In the normal season, the proportion of farmland was positively correlated with the concentration of total nitrogen and permanganate index but negatively correlated with the concentration of total phosphorus. The proportion of town area was positively correlated with the water quality index. The proportion of grassland area in the wet season was positively correlated with the permanganate index. The proportion of forestland area was negatively correlated with water quality index in both periods. Farmland, grassland, and town areas were the "source" landscape of pollutants, but farmland also played a role in intercepting pollutants to a certain extent. Forest land was the "sink" landscape of pollutants. ④ The pattern of forestland in the 200 m buffer zone in the normal season had a high explanatory rate for water quality, and the largest patch index (LPI) and patch density (PD) were the main factors. The study showed that it is an important measure to purify the surface water quality of Hehuang Valley by rationally planning the proportion of residential land and cultivated land and improving the coverage rate and aggregation degree of forestland around the riparian zone.

Combined effectiveness of extracorporeal radial shockwave therapy and ultrasound-guided trigger point injection of lidocaine in upper trapezius myofascial pain syndrome.

OBJECTIVE: Myofascial pain syndrome (MPS) is a major musculoskeletal problem and a leading cause of disability worldwide. Extracorporeal shockwave therapy (ESWT) and trigger point injection (TPI) have shown positive results for MPS but no previous study has investigated the combined effects of radial shockwave and trigger point injection of lidocaine for upper trapezius myofascial pain syndrome. METHOD: For this purpose, forty-five participants were randomly divided into shockwave (n = 15), shockwave with ultrasound-guided trigger point injection (combined; n = 15), and control (standard care; n = 15) groups. Participants were assessed at baseline, one week and four weeks by using the visual analog scale, neck disability index, electromyography, infrared thermography, and sonoelastography. RESULTS: Compared with control group, both shockwave and combined groups showed a statistically significant reduction in pain (P<0.01), functional disability (P<0.01), skin temperature (P<0.01), and elastic stiffness, with greater reduction in the combined group (P<0.01) than shockwave group (P<0.05) at four weeks. However, no significant difference was found in electrical activity between the groups (P>0.05). The combined group also showed significant differences in pain (P<0.05) and elastic stiffness (P<0.01) compared with shockwave group at four weeks. CONCLUSION: Our study revealed that extracorporeal radial shockwave therapy combined with trigger point injection of lidocaine was more effective for decreasing pain and elastic stiffness in upper trapezius myofascial pain syndrome at four weeks.

[Study advance of depressive animal models and its application in traditional Chinese medicines].

Depression is a kind of mental disease with main symptoms of low mood and lack of pleasure, which seriously endangers human health. An appropriate depressive animal model is of great significance for the study of depression and new antidepressant drugs, while the suitable selection and matching of experimental animals, modeling methods and evaluation indexes are critical to eva-luate the scientificity and effectiveness of the depressive animal model. The study advance of depressive animal models in the aspects of experimental animal selection, modeling principle and method, characteristics, evaluation indexes and their application in traditional Chinese medicine are summarized through the systematic review of relevant literatures in PubMed, CNKI and other databases. The depressive animal modeling methods utilized in recent studies include stress, glucocorticoid induction, reserpine induction, lipopolysaccharide induction, surgical modeling, gene knockout, joint application modeling methods. Stress method is better to simulate the depressive symptoms of clinical patients, whereas there are some deficiencies, such as long modeling time and large cost. The depressive animal models induced by glucocorticoid, reserpine and lipopolysaccharide have the advantages of short modeling time and good controllability, but with a poor reliability. The pathogenesis of surgical modeling is highly matched with that of clinical depressive patients, whereas it has the defect of long postoperative recovery period. Gene knockout models can be used to study the precise role of specific genes in depression. However, its applicability may be restricted in studies on depression. The joint application modeling method can improve its reliability and accuracy, and attracts more and more attention. This paper provides a reference for the selection of animal models in future studies of pathological mechanism of depression, and screening and evaluation of antidepressant drugs.

A rapid strategy for screening high-efficiency PCSK9 inhibitors from Ginkgo biloba leaves by ligand fishing, HPLC-Q-TOF-MS and interdisciplinary assay.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an attractive target for new cholesterol-lowering drug development. Here, we developed a method integrating ligand fishing, HPLC-Q-TOF-MS and interdisciplinary assay, aiming to explore potential PCSK9 inhibitors from mixtures rapidly and accurately. PCSK9 was expressed and purified firstly, and then the recombined PCSK9 was coated on the surface of magnetic beads (MBs). The PCSK9-immobilized MBs (PCSK9-MBs) were used for ligand fishing combined with HPLC and Q-TOF-MS/MS. Ginkgo biloba leaves (GBL), an herbal medicine widely used in Asia and Europe with good efficacy in treatment of hypercholesterolemia, were chosen as an illustration for ligand fishing. Two PCSK9 ligands were discovered from GBL and identified as kaempferol-3-O-rutinoside (1) and kaempferol 3-O-26″-(6‴-p-coumaroyl) glucosylrhamnoside (KCGR) (2). In order to verify fishing results and pick out more powerful PCSK9 inhibitors, molecular docking assay was further performed and KCGR was optimized to be an excellent PCSK9 inhibitor by the confirmation of affinity and activity bioassay. These results suggested that the developed approach could be applied to screen and analysis potential bioactive constituents from mixtures, which may improve the efficiency of drug discovery. Moreover, KCGR separated from GBL was expected to be a potential candidate of PCSK9 inhibitors.

[Research progress on clinical diagnosis and treatment for external snapping hip].

External snapping hip(ESH) is a vague term used to describe palpable or auditory snapping with hip movements with or without pain. The pathogenesis of ESH is related to the specific anatomical structure and friction factor. The clinical symptom is auditory snapping during activities, physical examination, X-ray, magnetic resonance imaging(MRI), dynamic ultrasound and other imaging techniques can be used to diagnose. Conservative medical management includes rest, avoidance of aggravating activities, and antiinflammatory medications. Treatment Patients with mild symptoms can achieve good results by medication, rest and physiotherapy. Surgical treatment for patients with ineffective conservative treatment was performed. All kinds of open surgery method can achieve good clinical curative effect, arthroscopic surgery is gradually been promoted due to small trauma, less complications. Besides, there are some reports that traditional treatments such as massage, acupuncture and acupotomology have achieved good clinical results, which deserve further study and promotion.

Stoichiometric food chain model on discrete time scale.

Stoichiometry-based models can yield many new insights into producer - grazer systems. Many interesting results can be obtained from models continuous in time. There raises the question of how robust the model predictions are to time discretization. A discrete stoichiometric food-chain model is analyzed and compared with a corresponding continuous model. Theoretical and numerical results show that the discrete and continuous models have many properties in common but differences also exist. Stoichiometric impacts of producer nutritional quality also persist in the discrete system. Both types of models can exhibit qualitatively different behaviors with the same parameter sets. Discretization enlarges the parameter ranges for the existence of chaotic dynamics. Our results suggest that the stoichiometric mechanisms are robust to time discretization and the nutritional quality of the producer can have dramatic and counterintuitive impacts on population dynamics, which agrees with the existing analysis of pelagic systems.

GDP-D-mannose epimerase regulates male gametophyte development, plant growth and leaf senescence in Arabidopsis.

Plant GDP-D-mannose epimerase (GME) converts GDP-D-mannose to GDP-L-galactose, a precursor of both L-ascorbate (vitamin C) and cell wall polysaccharides. However, the genetic functions of GME in Arabidopsis are unclear. In this study, we found that mutations in Arabidopsis GME affect pollen germination, pollen tube elongation, and transmission and development of the male gametophyte through analysis of the heterozygous GME/gme plants and the homozygous gme plants. Arabidopsis gme mutants also exhibit severe growth defects and early leaf senescence. Surprisingly, the defects in male gametophyte in the gme plants are not restored by L-ascorbate, boric acid or GDP-L-galactose, though boric acid rescues the growth defects of the mutants, indicating that GME may regulate male gametophyte development independent of L-ascorbate and GDP-L-galactose. These results reveal key roles for Arabidopsis GME in reproductive development, vegetative growth and leaf senescence, and suggest that GME regulates plant growth and controls male gametophyte development in different manners.

Metabolic profile and underlying improved bio-activity of Fructus aurantii immaturus by human intestinal bacteria.

Fructus aurantii immaturus (FAI) is the dried young fruit of Citrus aurantium L. or Citrus sinensis L. Osbeck. The purpose of this paper was to investigate the metabolic fate of FAI upon incubation with human intestinal bacteria, meanwhile to evaluate the antioxidant and anti-inflammatory activities of FAI and the transformed Fructus aurantii immaturus (TFAI). The water extract of FAI was anaerobically incubated with human intestinal bacterial suspensions for 48 h at 37 °C. Liquid chromatography-hybridised with quadrupole-time-of-flight mass spectrometry (LC-Q-TOF/MS) was applied to identify FAI metabolites. A total of 45 compounds were identified in FAI, eleven of which were metabolized by human intestinal bacteria. Nine major metabolites were identified as eriodictyol, naringenin, hesperetin, luteolin, apigenin, chryseriol, isosakuranetin, phloretin and diosmetin. The metabolic profile of FAI was elucidated on the basis of metabolite information. We found that the concentrations of acetic, propionic and butyric acids in FAI culture were all increased during fermentation relative to those of the control. Further bioactive evaluations showed that TFAI exhibited more potent antioxidant and anti-inflammatory abilities than FAI in vitro. Additionally, in vivo experiment confirmed that FAI significantly attenuated the blood endotoxin and TNF-α levels in the conventional rats compared to those of pseudo-germ-free (PGF) rats. This study revealed that metabolites may play a key role in the antioxidant and anti-inflammatory capacities of FAI.

Protective effects of petroleum ether extracts of Herpetospermum caudigerum against α-naphthylisothiocyanate-induced acute cholestasis of rats.

ETHNOPHARMACOLOGICAL RELEVANCE: The ripe seeds of Herpetospermum caudigerum have been used in Tibetan folk medicine for treatment of bile or liver diseases including jaundice, hepatitis, intumescences or inflammation. Previously reports suggested that the seed oil and some lignans from H. caudigerum exhibited protective effects against carbon tetrachloride (CCl4)-induced hepatic damage in rats, which may be related to their free radical scavenging effect. However, the protective effect of H. caudigerum against cholestasis is still not revealed. The aim of the present study was to investigate the pharmacological effect and the chemical constituents of the petroleum ether extract (PEE) derived from H. caudigerum against α-naphthylisothiocyanate (ANIT)-induced acute cholestasis in rats. MATERIALS AND METHODS: Male cholestatic Sprague-Dawley (SD) rats induced by ANIT (60mg/kg) were orally administered with PEE (350, 700 and 1400mg/kg). Levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), γ-Glutamyl transpeptidase (γ-GTP), total bilirubin (TBIL), direct bilirubin (DBIL) and total bile acid (TBA), as well as bile flow, and histopathological assay were evaluated. Hepatic malondialdehyde (MDA), myeloperoxidase (MPO), superoxide dismutase (SOD), glutathione S-transferase (GST), and nitric monoxide (NO) in liver were measured to explore the possible protective mechanisms. Phytochemical analysis of PEE was performed by gas chromatography-mass spectrometer (GC-MS). RESULTS: PEE have exhibited significant and dose-dependent protective effect on ANIT-induced liver injury by reduce the increases in serum levels of ALT, AST, ALP, γ-GTP, TBIL, DBIL and TBA, restore the bile flow in cholestatic rats, and reduce the severity of the pathological tissue damage induced by ANIT. Hepatic MDA, MPO and NO contents in liver tissue were reduced, while SOD and GST activities were elevated in liver tissue. 49 compounds were detected and 39 of them were identified by GC-MS analysis, in which long-chain fatty acids were the main constituents. CONCLUSIONS: PEE exhibited a dose-dependently protective effect on ANIT-induced liver injury in cholestatic rats with the potential mechanism of attenuated oxidative stress in the liver tissue, and the possible active compounds were long-chain fatty acids.

Problems in novelty assessment of doctorial dissertations in Chinese Academy of Traditional Chinese Medi-cine and measures for their solution / 中华医学图书情报杂志

The novelty assessment of doctorial dissertations in Chinese Academy of Traditional Chinese Medicine was outlined, the selected topics and innovative characteristics of doctorial dissertations in Chinese Academy of Tra-ditional Chinese Medicine from 2012 to 2016 were summarized, the problems in their novelty assessment were ana-lyzed, and the following measures were put forward for improving the novelty assessment of doctorial dissertations, such as adjusting its timetable, finding its new model, carrying out its training for doctors, and attaching highly concern to it by the governments.

Dynamic Model for Life History of Scyphozoa.

A two-state life history model governed by ODEs is formulated to elucidate the population dynamics of jellyfish and to illuminate the triggering mechanism of its blooms. The polyp-medusa model admits trichotomous global dynamic scenarios: extinction, polyps survival only, and both survival. The population dynamics sensitively depend on several biotic and abiotic limiting factors such as substrate, temperature, and predation. The combination of temperature increase, substrate expansion, and predator diminishment acts synergistically to create a habitat that is more favorable for jellyfishes. Reducing artificial marine constructions, aiding predator populations, and directly controlling the jellyfish population would help to manage the jellyfish blooms. The theoretical analyses and numerical experiments yield several insights into the nature underlying the model and shed some new light on the general control strategy for jellyfish.

[Advances on chemical constituents and pharmacological activity of genus Scilla].

The genus Scilla consists of 90 species widely distributed in Europe, Asia and Africa, one and its variant of which can be found in China Some species of the genus have been used in traditional medicine to treat various diseases related to inflammation and pain. Phytochemical studies have demonstrated the presence of triterpene and tritepenoid saponins derived from eucosterol, bufadienolides, alkaloids, stilbenoids and lignan in the plants of this genus. Various bioactivities such as antimicrobial, anti-inflammatory, antioxidant, anti-tumor and glycosidase inhibitory activities, have been reported. In this review, the advance of chemical constituents and pharmacological activities of the Scilla species are summarized for further development and utilization of the resource.

[Homoisoflavanones and stilbenes from fresh bulb of Scilla scilloides].

Mian-Zao-Er was collected from the bulbs of Scilla scilloides (Lindl. ) Druce, belonging to the Hyacinthaceae family. 17 compounds were obtained using various column chromatographies on macroporus resin (HPD100), silica gel, Sephadex LH-20 and ODS, as well as semi-preparative HPLC. Their structures were elucidated on the basis of physicochemical properties and spectral data as 2-hydroxy-7-methoxyscillascillin (1), scillascillin (2), 5,7-dihydroxy-3',4'-dimethoxyspiro 2H-1-benzopyran-7'-bicyclo[4.2.0 ] octa [1,3,5 ] -trien } -4-one (3), socialinone (4), 4-methylresveratrol (5), (E)-resveratrol (6), scillavoneA (7), 3,9-di- hydroeucomnalin (8), 3-(3-hydroxy-4-methoxybenzyl) -5,7-dihydroxychroman-4-one (9), (3R)-5,7,3'-trihydroxy-4'-methoxyspiro (2H-1-benzopyran-7'-bicyclo[4, 2, 0] octa [1, 3, 5]-trien} -4-one (10), scillabene A (11), 2-hydroxyscillascillin (12), 3-(4-hydroxybenzyl) -5,7-dihydroxychroman-4-one (13), 3-( 4-hydroxybenzylidene) -5, 7-dihydroxychroman-4-one (14), 3-( 4-hydroxybenzyl) -5-hydroxy-7,8-dimethoxychroman-4-one (15), 3-(4-hydroxybenzyl) -5-hydroxy-6, 7-dimethoxychroman-4-one (16), and 3-(4-hydroxybenzyl)-5,8-hydroxy-7-methoxychroman-4-one (17). Among them, compounds 3, 4, 6, 9, 13 and 15-17 were isolated from this plant for the first time.

A new method of automatic analysis of tongue deviation using self-correction / 生物医学工程学杂志

The article analyzes the old analysis method of tongue deviation and introduces a new analysis method of it with self-correction avoiding the shortcomings of the old method. In this article, comparisons and analyses are made to current central axis extraction methods, and the facts proved that these methods were not suitable for central axis extraction of tongue images. To overcome the shortcoming that the old method utilized area symmetry to extract central axis so that it would lead to a failure to find central axis, we introduced a kind of shape symmetry analysis method to extract the central axis. This method was capable of correcting the edge of tongue root automatically, and it improved the accuracy of central axis extraction. In additional, in this article, a kind of mouth corner analysis method by analysis of variational hue of tongue images was introduced. In the experiment for comparison, this method was more accurate than the old one and its efficiency was higher than that of the old one.

Experimental animal models of osteonecrosis.

Osteonecrosis (ON) or avascular necrosis (AVN) is a common bone metabolic disorder, mostly affecting femoral head. Although many biological, biophysical, and surgical methods have been tested to preserve the femoral head with ON, none has been proven fully satisfactory. It lacks consensus on an optimal approach for treatment. This is due, at least in part, to the lack of ability to systematically compare treatment efficacy using an ideal animal model that mimics full-range osteonecrosis of femoral head (ONFH) in humans with high incidence of joint collapse accompanied by reparative reaction adjacent to the necrotic bone in a reproducible and accessible way. A number of preclinical animal ON models have been established for testing potential efficacy of various modalities developed for prevention and treatment of ON before introduction into clinics for potential applications. This paper describes a number of different methods for creating animal experimental ON models. Advantages and disadvantages of such models are also discussed as reference for future research in battle against this important medical condition.

Treatment of secondary hyperparathyroidism by high calcium diet is associated with enhanced resistance artery relaxation in experimental renal failure.

BACKGROUND: Vasorelaxation is impaired in renal failure (RF) and hypertension. A high calcium diet enhances vasodilatation and reduces blood pressure in experimental hypertension. Oral calcium salts are used as phosphate binders in RF. However, the effect of increased calcium intake on arterial tone in RF is unknown. METHODS: We investigated the influence of an 8-week high calcium diet (0.3 vs 3.0%) on resistance artery tone in 5/6 nephrectomized (NTX) rats. Calcium was supplemented as carbonate salt, blood pressure measured by tail-cuff, urine collected in metabolic cages, and samples taken for blood chemistry and parathyroid hormone (PTH). Functional studies of isolated third-order branches of the mesenteric artery in vitro were performed using the Mulvany multimyograph. RESULTS: Plasma urea was elevated 1.6-fold and systolic blood pressure by 10 mmHg after NTX, while increased calcium intake was without effect on these variables. Plasma PTH and phosphate were raised following NTX, and suppressed by high calcium diet. Vasorelaxations induced by K(+) channel agonists 11,12-epoxyeicosatrienoic acid and levcromakalim were impaired after NTX. Vasorelaxation induced by acetylcholine was also reduced following NTX, and experiments with N(G)-nitro-L-arginine methyl ester, diclofenac and charybdotoxin + apamin suggested that the K(+) channel-mediated component of endothelium-dependent relaxation was deficient after NTX. Increased calcium intake corrected all impairments of vasodilatation in NTX rats. CONCLUSIONS: Deficient vasorelaxation via K(+) channels was normalized by high calcium diet in experimental RF. This effect was independent of the degree of renal impairment and blood pressure, but was associated with improved calcium metabolism: plasma levels of PTH and phosphate were decreased and ionized calcium was increased.