生长抑素受体的生理功能及动力学特征

生长抑素受体家族(somatostatin receptors,SSTRs)是一类介导生长抑素及其类似物,具有多种生物学效应的G蛋白偶联受体家族,其生理功能和作用机制长期以来倍受关注.研究表明,这些细胞膜上存在的特定膜受体包括SSTR1、SSTR2、SSTR3、SSTR4以及SSTR5,可以通过cAMP、PTP和MAPK信号通路,在调控GH分泌、诱导细胞凋亡、抑制肿瘤细胞增生、抑制胰岛素作用和抑制细胞生长等生物学过程发挥重要的作用,同时表现出与其它G蛋白偶联受体性质相似的动力学特征.本文将SSTRs的结构、分布和生理功能、配体选择性、下游信号通路,以及该受体家族的动力学特征最新研究进展作一综述.     

Behavioral and Physiological Characteristics of the Antarctic Krill, Euphausia superba

The antarctic krill, Euphausia superba, is considered a successin the intensely seasonal environment of the Southern Oceanbecause of its abundance and central role as an important fooditem for many of the larger carnivores in the ecosystem. Thebehavioral and physiological characteristics that foster thissuccess are: (1) the ability to find concentrations of foodin several types of habitat and efficiently exploit whateverfood is available; (2) the close correspondence of the lifecycle with seasonal cycles of food availability; and (3) a combinationof physiological mechanisms that enable krill to survive thelong winter period of low food availability. We evaluated therelative importance of the following four major winter-overmechanisms that have been proposed for adult krill west of theAntarctic Peninsula. The three-fold reduction in metabolic rateis the most important winter-over mechanism for these adults,although lipid utilization and shrinkage also help satisfy energyrequirements in the winter. Alternate food sources did not appearto contribute significantly as a winter energy source. However,the extent, predictability and complexity of the ice cover ina region during winter may have a great influence on the relativeimportance of these winter-over mechanisms for different populations.Ice cover in the waters west of the Antarctic Peninsula is unpredictableand smooth surfaced when it occurs, providing the krill withlittle refuge from predation. In multi-year pack ice of theWeddell Sea, however, ice cover is predictable and extensive,and there is a complex undersurface that provides hiding places.In this multi-year ice, adult krill have been observed underthe ice feeding, whereas west of the Antarctic Peninsula mostadult krill are in the water column in the winter and are notfeeding. The balance between acquiring energy and avoiding predationmay be different in these two regions in the winter becauseof differences in predictability and complexity of the ice cover.     

Association of the Leptin Gene with Carcass Characteristics in Nellore Cattle

Advances in DNA technology have created biotechnological tools that can be used in animal selection and new strategies for increasing herd productivity and quality. The objective of the present work was to associate the genotypes of leptin gene exon 2 polymorphisms with productive traits in Nellore cattle. Blood was collected from Nellore males and PCR-RFLP reactions were performed with the restriction enzymes ClaI and Kpn2I. The gene frequencies resulting from digestion by ClaI were 0.60 and 0.40 for allele A and T, respectively; the genotypic frequencies were AA = 0.20 and AT = 0.80. The gene frequencies from digestion by Kpn2I were 0.81 for allele C and 0.194 for allele T; the genotypic frequencies were CC = 0.62 and CT = 0.38. The populations in both cases were not in Hardy-Weinberg equilibrium (p > 0.05), and the TT genotype was not found. Significant associations were noted between leptin gene exon 2 polymorphisms and five productive traits in Nellore cattle: carcass fat distribution, the intensity of red muscle coloration, pH, marbling, and post-slaughter fat thickness.     

Behavioral and Other Characteristics Associated with HIV Viral Load in an Outpatient Clinic

Persons living with HIV (PLWH) who are engaged in care, yet not virally suppressed, represent a risk for transmission and opportunity for risk reduction interventions. This study describes characteristics of an outpatient clinic cohort of PLWH by laboratory confirmed viral suppression status and examines associations with demographics and sexual and drug use behaviors gathered through questionnaire. From a sample of 500 clinic patients, 438 were prescribed antiretroviral treatment (ART) and 62 were not. Among the 438 on ART, 72 (16.4%) were not virally suppressed at the most recent lab draw. Compared to individuals with a suppressed viral load, those that were unsuppressed were more likely to: be black (79.2% vs. 64.2%; p = 0.014); earn below $25,000/year (88.9% vs. 65.0%; p < 0.001); be of a younger age (47.8 vs. 50.0 mean years; p = 0.009); be on opiate substitution (14.1% vs. 6.3%; p = 0.023); and acknowledge poly-substance (38.9% vs. 24.4%; p = 0.012) and excessive alcohol use (13.9% vs. 6.0%; p = 0.019). Conversely, a smaller proportion of those with an unsuppressed viral load had multiple sex partners in the previous 30 days (39.8% vs. 58.5%; p = 0.003). In multivariable regression of those on ART, the prevalence of an unsuppressed viral load was 3% lower with each increasing year of age (aPR: 0.97; 95% CI: 0.95, 0.99) and 47% lower with income over $25,000/year (aPR: 0.33; 95% CI: 0.16, 0.70). In a separate analysis of all 500 subjects, ART was less frequently prescribed to blacks compared to whites, heterosexuals, those with lower education and income, and persons with active substance use. Findings confirm that a large proportion of PLWH and engaged in care were not virally suppressed and continued behaviors that risk transmission, indicating the need for screening, prevention counseling and access to ancillary services to lower the incidence of HIV infections.     

Characteristics and Physiological Function of NADP-Malic Enzyme from Wheat

Kinetic and structural properties of NADP-malic enzyme (NADP-ME,EC 1.1.1.40 [EC] ) purified from stems and roots of wheat (Triticumaestivum), along with the possible physiological role of theenzyme were examined. Enzyme purification from stems sequentiallyinvolved precipitation with crystalline ammonium sulfate, anion-exchange,affinity and size exclusion chromatographies, while anion-exchangechromatography was omitted for the enzyme purification fromroots. SDS-PAGE of the purified enzyme showed a single proteinband with a molecular mass of 72-kDa. Enzyme activity was dependenton the presence of a bivalent metal cation, Mg²⁺ or Mn²⁺. Bindingcharacteristics of each metal ion suggest the existence of atleast two different binding sites with distinct affinities.Nonetheless, activity response to NADP⁺ and L-malate exhibitedMichaelis-Menten behavior with K_m values of 37 and 960 µM,respectively. The amount and activity of NADP-ME were increasedby GSH, cellulase and macerozyme. From these results we suggestthat NADP-ME of wheat could be implicated in defense-relateddeposition of lignin. ¹Both authors contributed equally to this work.     

Behavioral and Physiological Thermoregulation of Crocodilians

Crocodilians, like other reptiles, regulate their body temperaturesby a combination of behavioral and physiological mechanisms.Behaviorally, they seek warm surface water or bask when cooland avoid overheating by the evaporation of water from theirdorsum, evaporation of water by gaping or by retreating to deep,cool water. Physiologically, crocodilians increase cutaneousthermal conductance by increasing blood flow to the skin (andsubdermal musculature) during warming. This hastens the warmingprocess. Cutaneous blood flow is reduced during general coolingand locally if the body temperature exceeds skin temperature.This enables crocodilians to increase body temperature significantlywhile basking in cool shallow water. Large crocodilians appearto be able to alter their rates of heat exchange to a largerextent than small ones and they can do so with less cardiovascularinvolvement. Large crocodilians, with their lower surface/volumeratio, are capable of producing sufficient metabolic heat toelevate their body temperature above water temperature.     

Lack of Association of Diagonal Earlobe Crease With Other Cardiovascular Risk Factors

The relationship between diagonal earlobe crease and coronary risk factors, controlling for age and sex effects, was tested in 686 persons. A positive correlation (ρ=.86, P<.001) is obtained between age and percentage of persons with earlobe creases in each one-year age interval; no sex difference is seen. To test for associations between cardiovascular risk factors and earlobe creases, 67 persons with creases are compared with 67 controls (matched by age and sex) without creases, using the following variables: diastolic and systolic blood pressures, cigarette smoking, weight, height, scapular skinfold thickness, serum cholesterol level, high-density lipoprotein level, intracellular sodium, sodium-lithium countertransport, plasma renin level and the presence of diabetes and hypertension. None of these variables differs significantly between cases and controls, indicating that the previously documented association between earlobe crease and coronary heart disease may be independent of these risk factors. Although coronary heart disease has often been shown to aggregate in families, no familial aggregation is found for earlobe creases.     

Association of Obesity and Hypertension With Left Ventricular Geometry and Function in Children and Adolescents

Obesity, especially when complicated with hypertension, is associated with structural and functional cardiac changes. Recent studies have focused on the prognostic impact of the type of left ventricular (LV) geometric remodeling. This study looked at the prevalence and clinical correlates of LV geometric patterns and their relation to cardiac function in a sample of predominantly African‐American (AA) youth. Echocardiographic data was collected on 213 obese (BMI of 36.53 ± 0.53 kg/m²) and 130 normal‐weight subjects (BMI of 19.73 ± 0.21 kg/m²). The obese subjects had significantly higher LV mass index (LVMI; 49.6 ± 0.9 vs. 46.0 ± 1.0 g/m^2.7, P = 0.01), relative wall thickness (RWT; 0.45 ± 0.00 vs. 0.40 ± 0.00, P < 0.001), left atrial (LA) index (33.2 ± 0.7 vs. 23.5 ± 0.6 ml/m, P < 0.001), more abnormal diastolic function by tissue Doppler E/Ea septal (7.5 ± 0.14 vs. 6.5 ± 0.12 ms, P < 0.001), E/Ea lateral (5.7 ± 0.12 vs. 4.8 ± 0.1 ms, P < 0.001), myocardial performance index (MPI; 0.43 ± 0.00 vs. 0.38 ± 0.00, P < 0.001), and Doppler mitral EA ratio (2.0 ± 0.04 vs. 2.4 ± 0.07, P < 0.001) but similar systolic function. Concentric remodeling (CR) was the most prevalent pattern noted in the obese group and concentric hypertrophy (CH) in the obese and hypertensive group. Obesity, hypertension, and CH were independent predictor of diastolic dysfunction. Systolic (SBP) and diastolic blood pressures (DBP) were the prime mediators for CH whereas obesity and diastolic blood pressure were predictors of CR. No significant association was observed between the geometric patterns and systolic function. Tracking LV hypertrophy (LVH) status and geometric adaptations in obesity may be prognostic tools for assessing cardiac risk and therapeutic end points with weight loss.     

Behavioral and Physiological Responses to Emersion in Freshwater Bivalves

SYNOPSIS. Littoral lentic and shallow lotic freshwater habitatsare unpredictable in periodicity and duration of shore emersion.As a result, freshwater bivalves have evolved extensive capacitiesto withstand prolonged emersion. Valve movement behaviors allowemersed bivalves to control rate of water loss while maintainingat least partial aerial gas exchange; these behaviors are affectedby environmental variables such as temperature and relativehumidity. Aerial oxygen uptake is associated directly with valveventilatory behaviors and mantle edge exposure. Such behaviorsare often phasic, indicative of oxygen "debt" payment. Lackingeffective hemolymph buffer, respiratory acidosis during emersionis compensated by shell carbonate stores allowing hemolymphP_CO2 to rise to levels facilitating diffusion of CO₂ to theenvironment. During emersion, hemolymph calcium can increasefour fold while Na and Cl are tightly regulated. Ammonia productionceases in emersed bivalves. It resumes on reimmersion, indicativeof heavy reliance on non-protein catabolism during emersion.Some emersion adaptations of freshwater species appear to bemodifications of those displayed by intertidal and estuarinebivalves, while others appear independently evolved to allowsurvival of the extreme emersion periods associated with lifein shallow freshwaters.     

一类新携氧球蛋白--脑红蛋白

脑红蛋白是继血红蛋白、肌红蛋白之后发现的第三类具有运输与储存氧的球蛋白。脑红蛋白主要在脑中表达．能可逆性的结合氧,与氧有很高的亲和力,能够特异性地向脑组织供氧,在神经系统氧的摄取、运输和利用等生理过程中起着极其重要的作用。     

Air Ions and Physiological Function

Although gaseous ions possess no obvious physical properties which would predict a capability to influence living cells or tissues they can be shown to produce functional changes. The physiological effects so far demonstrated are limited in extent. In the mammalian trachea air ion action appears to depend upon the release of bound 5-hydroxytryptamine by CO₂⁺ and upon O^--induced acceleration of its metabolic destruction.     

Heavy Metals and Other Elements in Serum of Cattle from Organic and Conventional Farms

Concentrations of cadmium, lead, iron, zinc, copper, chromium, nickel, aluminium and arsenium were analysed in blood serum of cattle from organic (n = 20) and conventional (n = 21) farms. The elements were determined by inductively coupled plasma atomic emission spectrometry using an Optima 2000 DV instrument (Perkin Elmer Inc.). Animals from the organic farm were characterised by significantly lower (P < 0.01) serum concentrations of Pb, Zn, Fe, Cu, Cr, Ni, As and Al compared to animals from the conventional farm. The concentration of Cd was similar in animals from both organic and conventional farms. The concentration of toxic elements in cattle from organic and conventional farms studied was very low. The trace essential elements were generally within the adequate ranges except Zn and Cu, which were deficient. In organically reared animals, also serum Fe content was below the critical level for diagnosing iron deficiency. Pb was significantly correlated with Cd, Zn, Fe, Cu and Ni. A significant positive correlation between the concentration of Cd and Zn, Cu and Ni concentrations was only observed in cows from the organic farm. The present results suggest that organically raised animals are less exposed to harmful environmental influences such as the environmental pollution with heavy metals. On the other hand, these animals are at a greater risk of mineral deficiency compared to animals kept on conventional farms.     

Physiological Level Production of Antigen-Specific Human Immunoglobulin in Cloned Transchromosomic Cattle

Therapeutic human polyclonal antibodies (hpAbs) derived from pooled plasma from human donors are Food and Drug Administration approved biologics used in the treatment of a variety of human diseases. Powered by the natural diversity of immune response, hpAbs are effective in treating diseases caused by complex or quickly-evolving antigens such as viruses. We previously showed that transchromosomic (Tc) cattle carrying a human artificial chromosome (HAC) comprising the entire unrearranged human immunoglobulin heavy-chain (hIGH) and kappa-chain (hIGK) germline loci (named as κHAC) are capable of producing functional hpAbs when both of the bovine immunoglobulin mu heavy-chains, bIGHM and bIGHML1, are homozygously inactivated (double knockouts or DKO). However, B lymphocyte development in these Tc cattle is compromised, and the overall production of hpAbs is low. Here, we report the construction of an improved HAC, designated as cKSL-HACΔ, by incorporating all of the human immunoglobulin germline loci into the HAC. Furthermore, for avoiding the possible human-bovine interspecies incompatibility between the human immunoglobulin mu chain protein (hIgM) and bovine transmembrane α and β immunoglobulins (bIgα and bIgβ) in the pre-B cell receptor (pre-BCR) complex, we partially replaced (bovinized) the hIgM constant domain with the counterpart of bovine IgM (bIgM) that is involved in the interaction between bIgM and bIgα/Igβ; human IgM bovinization would also improve the functionality of hIgM in supporting B cell activation and proliferation. We also report the successful production of DKO Tc cattle carrying the cKSL-HACΔ (cKSL-HACΔ/DKO), the dramatic improvement of B cell development in these cattle and the high level production of hpAbs (as measured for the human IgG isotype) in the plasma. We further demonstrate that, upon immunization by tumor immunogens, high titer tumor immunogen-specific human IgG (hIgG) can be produced from such Tc cattle.     

Succinate Dehydrogenase and Other Respiratory Pathways in Thylakoid Membranes of Synechocystis sp. Strain PCC 6803: Capacity Comparisons and Physiological Function

Respiration in cyanobacterial thylakoid membranes is interwoven with photosynthetic processes. We have constructed a range of mutants that are impaired in several combinations of respiratory and photosynthetic electron transport complexes and have examined the relative effects on the redox state of the plastoquinone (PQ) pool by using a quinone electrode. Succinate dehydrogenase has a major effect on the PQ redox poise, as mutants lacking this enzyme showed a much more oxidized PQ pool. Mutants lacking type I and II NAD(P)H dehydrogenases also had more oxidized PQ pools. However, in the mutant lacking type I NADPH dehydrogenase, succinate was essentially absent and effective respiratory electron donation to the PQ pool could be established after addition of 1 mM succinate. Therefore, lack of the type I NADPH dehydrogenase had an indirect effect on the PQ pool redox state. The electron donation capacity of succinate dehydrogenase was found to be an order of magnitude larger than that of type I and II NAD(P)H dehydrogenases. The reason for the oxidized PQ pool upon inactivation of type II NADH dehydrogenase may be related to the facts that the NAD pool in the cell is much smaller than that of NADP and that the NAD pool is fully reduced in the mutant without type II NADH dehydrogenase, thus causing regulatory inhibition. The results indicate that succinate dehydrogenase is the main respiratory electron transfer pathway into the PQ pool and that type I and II NAD(P)H dehydrogenases regulate the reduction level of NADP and NAD, which, in turn, affects respiratory electron flow through succinate dehydrogenase.     

Cardiovascular and Other Physiological Correlates of Hibernation in Aquatic and Terrestrial Turtles

Recent research has provided new insight into the physiologyof hibernation in freshwater, marine, and terrestrial turtles.In this paper I review what is known about the mechanisms thatpermit the hearts of these turtles to withstand several monthsof hypoxia or anoxia. I also report new research that indicatesthat a terrestrial turtle, unlike freshwater and marine species,does not experience hypoxia in its winter burrow and thus doesnot rely on glycolysis to supply ATP, at least under moderatewinter conditions.     

Association of Thyroid Function During Pregnancy With the Risk of Pre-eclampsia and Gestational Diabetes Mellitus

ObjectiveTo estimate the association of maternal thyroid dysfunction with the risk of gestational hypertension and diabetes. Whether the association was affected by gestational age at diagnosis and thyroid autoimmunity was further explored.MethodsA cohort study of 41 647 participants was conducted. Thyroid function (ie, thyroid-stimulating hormone [TSH] and free thyroxine [FT4]) was measured by electrochemiluminescence immunoassay. Thyroid antibody positivity (eg, thyroperoxidase, thyroglobulin, and TSH receptor antibody) was indicated if the values of these antibodies exceeded the upper targets of the reference range. The relationship between maternal thyroid dysfunction and the risk of pre-eclampsia (PE) and gestational diabetes mellitus (GDM) was assessed by multivariate logistic regression.ResultsIsolated hypothyroxinemia (defined as 5th ≤ TSH ≤ 95th percentile, FT4 < 5th percentile) was associated with the risk of PE (odds ratio [OR], 1.32; 95% CI, 1.10-1.58). Overt hypothyroidism (TSH > 95th percentile; FT4 < 5th percentile) was related to the risk of severe PE (OR, 2.59; 95% CI, 1.05-6.37). Being positive for TSH receptor antibody was associated with a decreased risk of GDM (OR, 0.49; 95% CI, 0.35-0.70). A marginally significant association between overt hypothyroidism detected at the first trimester and the risk of GDM was found (OR, 1.60; 95% CI, 1.00-2.83). The association of thyroid dysfunction with the risk of PE and GDM was stronger among pregnant women who were negative for autoantibodies.ConclusionSome types of thyroid dysfunction during pregnancy were associated with the risk of PE and GDM. The associations varied by gestational age at diagnosis and by thyroid autoantibody status.     

脂肪细胞分泌蛋白质Acrp30及其生理功能

脂肪组织是人体最大的能量储存库,在需要时动用储存的脂肪,向机体供能。脂肪组织同时也是一个极其重要的分泌器官。Acrp30(adipocyte complete related protein 30 kD,)就是由脂肪组织分泌的一种活性蛋白质,参与能量代谢、炎症反应等生理过程,与肥胖、Ⅱ型糖尿病、动脉粥样硬化、心血管疾病等疾病有密切的关系。     

硅在植物中的生理功能

硅参与植物的许多生理活动和代谢作用,促进植物器官的形成、发育和健壮生长,改善叶的着生方式和冠层结构,缓解金属离子毒害和盐胁迫,增强植物的抗旱性、抗病性和抗虫性,提高经济产量和质量.该文就这些方面的研究进展作了介绍.     

The Physiological Function of Melatonin in Plants

Melatonin (N-acetyl-5-methoxytryptamine), a well-known animal hormone, was discovered in plants in 1995 but very little research into it has been carried out since. It is present in different parts of all the plant species studied, including leaves, stems, roots, fruits and seeds. This brief review will attempt to provide an overview of melatonin (its discovery, presence and functions in different organisms, biosynthetic route, etc.) and to compile a practically complete bibliography on this compound in plants. The common biosynthetic pathways shared by the auxin, indole-3-acetic, and melatonin suggest a possible coordinated regulation in plants. More specifically, our knowledge to date of the role of melatonin in the vegetative and reproductive physiology of plants is presented in detail. The most interesting aspects for future physiological studies are presented.Key Words: antioxidant, auxin, flowering, growth, IAA, melatonin, plant hormone, reproductive development, rooting, vegetative developmentMelatonin (N-acetyl-5-methoxytryptamine), an “old friend” and well known as an animal hormone but “new” to plant biology is arousing great interest due to its broad distribution in the biological kingdom and the recent data on its possible physiological role in plants. Many studies on melatonin, as a phytochemical compound with potentially interesting health-related properties, have recently appeared, but no more than 15–20 papers with a plant physiological focus have been published since 1995. Besides mentioning the most interesting data on melatonin related with plants, this review will hopefully trigger more studies into this molecule to deepen our understanding of the different physiological roles that it might play in plants. We shall briefly look at the well-known function of melatonin in vertebrates, its discovery in plants and other organisms, and its presence in plants as a possible medicinal phytochemical. The joint biosynthetic pathways of melatonin and the auxin indole-3-acetic acid (IAA) will be described. Thus, we reveal the new and emerging field of melatonin studies in plants, the limited physiological data available and its possible role in plants.