Low Molecular Weight Antioxidants Research Articles

Analytical Tools for the Determination of Antioxidants and Antioxidant Capacity in Biological Samples, Principles and Applications

Background: There are two types of antioxidants – high molecular weight antioxidants like glutathione peroxidase and superoxide dismutase and low molecular weight antioxidants like ascorbic acid, glutathione, uric acid, melatonin. Both types of antioxidants are necessary in the system keeping oxidative homeostasis and protecting against reactive oxygen and nitrogen species. Objective: This review is focused on low molecular weight antioxidant assay which can serve as an important tool for various diagnoses since the antioxidant level corresponds with pathological states and can indicate oxidative stress. The assay of antioxidants is also a tool for food quality control because the antioxidant level is decreasing due to aging and poor storage conditions. Disparate protocols were established in order to judge antioxidant capacity. Conclusion: In this review, spectrophotometric tests like 2,2'-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid) based assay (ABTS), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), like ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), electrochemical assays and instrumental analyses are described and discussed. Survey of actual literature and principle of the analyses are provided as well. Keywords: ABTS test, ascorbic acid, DPPH test, ferric reducing antioxidant power, flavonoid, FRAP, glutathione, oxidative stress.

Total reducing capacity in Arabidopsis thaliana cat2cat3 knockout mutants under heat stress

Aim. It was investigated whether the simultaneous loss of the two catalase isoforms CAT2 and CAT3 can be compensated by the increase in content of low-molecular weight antioxidants. To clarify this question, the total reducing capacity in Arabidopsis wild type and cat2cat3 knockout mutants was evaluated under optimal growth conditions and after heat stress. Methods. Leaves of Arabidopsis thaliana wild type and cat2cat3 knockout mutants were exposed to high temperatures. The content of water-soluble low molecular weight antioxidants was evaluated by determining the total reducing capacity using iodometry. Results. In intact cat2cat3 mutants there is an 1.7 times increase in the content of low-molecular weight antioxidants compared to wild type plants. A high content of these compounds in knockout plants was also observed upon heat stress. Patterns of changes in total reducing capacity differ between wild type and knockout lines. Conclusion. The loss of activity of the catalase isoforms CAT2 and CAT3 in knock-out mutants of Arabidopsis results in activation of non-enzymatic antioxidant defenses. The increase of the content of low-molecular weight antioxidants is one of the mechanisms that provide protection of mutant plants from chronic oxidative stress, both under optimal cultivation conditions and under the influence of elevated temperatures.Keywords: multigenic family, heat shock, total reducing capacity, knockout mutants, Arabidopsis thaliana.

Changes in protein abundance and activity induced by drought during generative development of winter barley (Hordeum vulgare L.)

The present study investigated drought-induced changes in proteome profiles of ten DH lines of winter barley, relatively varied in water deficit tolerance level. Additionally, the parameters describing the functioning of the photosynthetic apparatus and the activity of the antioxidative system were analysed. Water deficit (3-week growth in soil with water content reduced to ca. 35%) induced significant changes in leaf water relations and reduced photosynthetic activity, probably due to decreased stomatal conductance. It was associated with changes in protein abundance and altered activity of antioxidative enzymes. From 47 MS-identified proteins discriminating more tolerant from drought-sensitive genotypes, only two revealed distinctly higher while seven revealed lower abundance in drought-treated plants of tolerant DH lines in comparison to sensitive ones. The majority were involved in the dark phase of photosynthesis. Another factor of great importance seems to be the ability to sustain, during drought stress, relatively high activity of enzymes (SOD and CAT) decomposing reactive oxygen species and protecting plant cell from oxidative damages. Low molecular weight antioxidants seem to play less important roles. Our findings also suggest that high tolerance to drought stress in barley is a constitutively controlled trait regulated by the rate of protein synthesis and their activity level. Biological significanceAccording to our knowledge, this is the first comparative proteomic analysis of drought tolerance performed for the model set of several winter barley doubled haploid (DH) lines. We analysed both the drought impact on the protein pattern of individual winter barley DH lines as well as comparisons between them according to their level of drought tolerance. We have identified 47 proteins discriminating drought-tolerant from drought-sensitive genotypes. The majority was involved in the dark phase of photosynthesis. Another factor of great importance in our opinion seems to be the ability to sustain, during drought stress, relatively high activity of antioxidative enzymes (SOD and CAT) decomposing reactive oxygen species and protecting plant cell from oxidative damages. Our findings also suggest that high tolerance to drought stress in barley is a constitutively-controlled trait regulated by the rate of protein synthesis and their activity level.

Antioxidant defense system in tissues of semiaquatic mammals

Activity of antioxidant enzymes (superoxide dismutase and catalase) and low molecular weight antioxidants (tocopherol and retinol) was studied in tissues of 8 semiaquatic mammalian species. In animals from different taxa, the enhancement of antioxidant defense can be achieved either by increased enzymatic activity of tissues or elevated concentration of low molecular weight antioxidants. The level of enzymatic and nonenzymatic (low molecular weight) antioxidants, determined in tissues and organs of diving mammals, is likely to be considered as an integral complex, which has evolved to ensure the greatest efficiency of metabolic systems during adaptation to species-specific habitats.

P 014 - Rapid ascorbate response to bacterial elicitor treatment in Arabidopsis thaliana cells

An early event of the incompatible plant-pathogen interactions is an oxidative burst. The major water soluble, low molecular weight antioxidant, ascorbic acid plays a crucial role in Reactive Oxygen Species (ROS) balancing (scavenging). The regulation of ascorbate level therefore can be an important point of the fine tuning of ROS level during the early phase of plant-pathogen interaction. To evaluate how this interaction affects the biosynthesis, the recycling and the level of ascorbate, we challenged Arabidopsis thaliana cells with 2 different harpin proteins (HrpZpto and HrpWpto). HrpZpto and HrpWpto treatments caused a well-defined ROS peak. The expression of the alternative oxidase (AOX1a) and vtc5, one of the paralog genes that encode the rate limiting enzyme of ascorbate biosynthesis followed the elevation of ROS. Similarly the activity of ascorbate-peroxidase and galactono-1,4-lactone dehydrogenase (GLDH), the enzyme catalyzing the ultimate, mitochondria coupled step of ascorbate biosynthesis and the level of ascorbate and glutathione also followed the elevation of ROS due to harpin treatment. The enhanced expression of AOX1a, the elevated activity of GLDH and the increased level of ascorbate and glutathione all can contribute to the mitigation or absence of programmed cell death. Finally a new function, the fine tuning of redox balance during plant-pathogen interaction can be proposed to vtc5.

Lipid-Based Nanoparticles as Carriers for Dermal Delivery of Antioxidants.

The skin, being the outermost layer of our body, is constantly exposed to oxidative stress induced by UV-radiation, pollutants, smoke and xenobiotics. To counteract the deleterious effects of such exposure, the skin is equipped with a complex anti-oxidation system, involving both exogenous and endogenous antioxidants. As low molecular weight antioxidants undergo depletion in counteracting oxidative stress occurring in the skin, topical supplementation with these agents is regarded as a suitable strategy to restore skin oxidative balance. Unfortunately, most antioxidants show unfavorable physico-chemical properties (e.g. excessive lipophilicity or hydrophilicity, chemical instability) that strongly limit their skin penetration and hence their effectiveness after topical application. To overcome these drawbacks, nanocarriers such as liposomes, niosomes, nanoemulsions and nanoparticles have been widely investigated as dermal delivery systems for antioxidants. The present paper will review two different types of lipid-based nanocarriers, solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC), which represent the latest innovation in the field of nanoparticles designed as topical drug delivery systems. The effects of loading different topical antioxidants into SLN or NLC will be examined along with the usefulness of these antioxidant delivery systems in improving skin defenses against oxidative stress. In this review, recent studies regarding ability of solid lipid nanoparticles and nanostructured lipid carriers to improve dermal delivery of low molecular weight antioxidants have evidenced that these carriers show technological properties that make them particularly useful for topical delivery of antioxidants, both in pharmaceutical and cosmetic field.

АКТИВНЫЕ ФОРМЫ КИСЛОРОДА КАК ТРИГГЕРЫ ИНФАРКТ-ЛИМИТИРУЮЩЕГО ЭФФЕКТА РАННЕГО ГИПОКСИЧЕСКОГО ПРЕКОНДИЦИОНИРОВАНИЯ МИОКАРДА КРЫСЫ

It is believed that reactive oxygen species (ROS) are involved in the performance of this adaptive hepatoprotective effect phenomenon. However, the role of ROS in the signaling mechanism of the early hypoxic preconditioning (early HP) and the contribution of individual types of oxygen radicals in the infarct-limiting effect of early HP remains uncertain to the end. Objective was to investigate the role of various types of reactive oxygen species in the signaling mechanism of the infarct-limiting effect of early hypoxic preconditioning. We investigated the role of reactive oxygen species in the signaling mechanism of early HP in vivo. Adaptation of animals was conducted with 6 transient hypoxia-reoxygenation sessions before prolonged ischemia (45 min) and reperfusion (120 min). Low molecular weight antioxidants were administered 15 minutes prior to the HP. We found out that pretreatment with the nonselective antioxidant indirect action of N-(2-mercaptopropionyl)-glycine and "trap" of hydroxyl radicals 1,3-dimethylthiourea completely eliminated the infarct-limiting effect of adaptation. Administration of antioxidants tempol and trolox, as well as the use of N-(2-mercaptopropionyl)-glycine after HP had no effect on the protective effect of adaptation. Consequently, reactive oxygen species, including hydroxyl radical, operate as the trigger function in the signaling mechanism of early HP.

Effect of extremely low frequency magnetic fields on the seedlings of wild plants growing in Central Yakutia

It was shown that permanent (B = 50 μT, horizontal plane, direction to the north) and alternating magnetic fields (North–South direction) exerted influences on seed germination as well as on cytological and biochemical features of seedlings characteristic of investigated species (Lepidium apetalum, Artemisia vulgaris, A. jacutica, and A. dracunculus) of wild plants growing in Central Yakutia. Under the effect of permanent magnetic field (MF), germinating capacity of seeds decreased (except for A. vulgaris), whereas alternating MF of different frequencies improved their germinating capacity, except for L. apetalum and A. jacutica at frequencies of 200 and 300 Hz, respectively. Under permanent MF, the rate of lipid peroxidation in the tissues of the seedlings decreased, whereas the content of low molecular weight antioxidants rose; when the plants were exposed to an alternating magnetic field, the content of MDA and peroxidase activity increased, and the content of low molecular weight antioxidants followed an ambiguous pattern.

Circulating glutathione concentrations in marine, semiaquatic, and terrestrial mammals

AbstractAn important low molecular weight antioxidant in biological systems is glutathione; its efficiency depends on the equilibrium between its reduced (GSH) and oxidized (GSSG) forms. The oxidized:total glutathione (GSSG:GSH‐Eq) ratio can be used as an indicator of oxidative stress. Previous studies suggest that marine mammals, unlike terrestrial mammals, do not show adverse effects in tissues exposed to ischemia/reperfusion during the peripheral vasoconstriction associated with breath‐hold diving. This is due, in part, to higher antioxidant enzyme activities in marine mammals compared with terrestrial mammals. The objective of this study was to compare circulating glutathione levels among mammals with different diving capacities. Circulating GSH‐Eq, GSH, and GSSG concentrations in erythrocyte samples from northern elephant seals (Mirounga angustirostris), bottlenose dolphins (Tursiops truncatus), neotropical otters (Lontra longicaudis annectens), domestic pigs (Sus scrofa), and humans were quantified using spectrophotometry. Higher GSH‐Eq and GSH concentrations and a lower GSSG:GSH‐Eq index were found in erythrocytes from northern elephant seals and bottlenose dolphins as compared to otters, domestic pigs, and humans. Results suggest that marine mammals, independent of their diving capacity, possess a highly developed antioxidant system, including GSH; continuous availability of GSH could allow these species to avoid oxidative damage and tolerate ischemia/reperfusion and hypoxia/reoxygenation events associated with diving.

Extraction resistance and mechanism of a macromolecular hindered phenol antioxidant in natural rubber

ABSTRACTDue to low thermal stability, poor migration, and extraction resistances, the antioxidant with low molecular weight is easy to physically lose during processing and long‐term service, and its applications are severely restricted. To increase the molecular weight of antioxidant is one of the promising methods to overcome such drawbacks. In this study, the extraction resistance of a macromolecular antioxidant, namely polyhydroxylated polybutadiene containing thioether binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (PHPBT‐b‐TPH), was investigated by extraction resistance test and equilibrium swelling experiment. The results exhibited that the PHPBT‐b‐TPH offered much better extraction resistance in natural rubber (NR) than the low molecular weight antioxidant TPH. In addition, the extraction resistance of hydroxyl‐terminated polybutadiene (HTPB), polyethylene glycol (PEG), and polypropylene glycol (PPG) in NR were also compared to study the extraction mechanism of the PHPBT‐b‐TPH. It was found that the higher molecular weight of PHPBT‐b‐TPH and the co‐vulcanization between PHPBT‐b‐TPH and NR were the main reasons for the excellent extraction resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44905.

Rapid ascorbate response to bacterial elicitor treatment in Arabidopsis thaliana cells

An early event of the incompatible plant–pathogen interactions is an oxidative burst. On one hand, the ROS generated during oxidative burst is advantageous. ROS can serve as secondary messengers mediating defence gene activation and establishment of additional defences. On the other hand, the concentration of ROS must be carefully regulated to avoid undesired cellular cytotoxicity. The major water soluble, low molecular weight antioxidant, ascorbic acid plays a crucial role in ROS balancing (scavenging). The regulation of ascorbate level, therefore, can be an important point of the fine-tuning of ROS level during the early phase of plant–pathogen interaction. To evaluate how this interaction affects the biosynthesis, the recycling, and the level of ascorbate, we challenged Arabidopsis thaliana cells with two different harpin proteins (HrpZpto and HrpWpto). HrpZpto and HrpWpto treatments caused a well-defined ROS peak. The expression of the alternative oxidase (AOX1a) and vtc5, one of the paralog genes that encode the rate limiting enzyme of ascorbate biosynthesis, followed the elevation of ROS. Similarly, the activity of ascorbate peroxidase and galactono-1,4-lactone dehydrogenase (EC 1.3.2.3) (GLDH), the enzyme catalysing the ultimate, mitochondria coupled step of ascorbate biosynthesis and the level of ascorbate and glutathione also followed the elevation of ROS due to harpin treatment. The enhanced expression of AOX1a, the elevated activity of GLDH, and the increased level of ascorbate and glutathione all can contribute to the mitigation or absence of programmed cell death. Finally, a new function, the fine-tuning of redox balance during plant–pathogen interaction, can be proposed to vtc5.

Short-term and long-term effects of transient exogenous cortisol manipulation on oxidative stress in juvenile brown trout.

In the wild, animals are exposed to a growing number of stressors with increasing frequency and intensity, as a result of human activities and human-induced environmental change. To fully understand how wild organisms are affected by stressors, it is crucial to understand the physiology that underlies an organism's response to a stressor. Prolonged levels of elevated glucocorticoids are associated with a state of chronic stress and decreased fitness. Exogenous glucocorticoid manipulation reduces an individual's ability to forage, avoid predators and grow, thereby limiting the resources available for physiological functions like defence against oxidative stress. Using brown trout (Salmo trutta), we evaluated the short-term (2 weeks) and long-term (4 months over winter) effects of exogenous cortisol manipulations (versus relevant shams and controls) on the oxidative status of wild juveniles. Cortisol caused an increase in glutathione over a 2week period and appeared to reduce glutathione over winter. Cortisol treatment did not affect oxidative stress levels or low molecular weight antioxidants. Cortisol caused a significant decrease in growth rates but did not affect predation risk. Over-winter survival in the stream was associated with low levels of oxidative stress and glutathione. Thus, oxidative stress may be a mechanism by which elevated cortisol causes negative physiological effects.

The effect of biguanide derivatives on antioxidant status during the development of oxidative stress

The intensity of free radical processes, activity of antioxidant enzymes (superoxide dismutase, catalase), and the content of low molecular weight antioxidants (reduced glutathione, citrate) in skeletal muscle and liver from rats with experimental rheumatoid arthritis administered with biguanide synthetic derivatives (2,4-dicarbomethoxyphenyl-biguanide and 4-methyl-phenyl biguanide) selected by Prediction of Activity Spectra for Substances (PASS), a computer program for the prediction of biological activity, were studied. The observed changes in the studied parameters toward the reference values under the effect of tested compounds can be explained by their antioxidant and protective properties during pathology, which are accompanied by oxidative stress. The results can be used for the development of new methods for the prevention and treatment of rheumatoid arthritis.

Oxidative stress, free radicals, kidney disease and plant antioxidants

Over generation of reactive molecules leads to oxidative stress which is a causative agent of many diseases occurrence including kidney disease. Oxidative stress at kidney tissue induces the cellular signaling pathways which may activate construction of growth and pro-inflammatory mediators, finally, lead to glomerulosclerosis and renal fibrosis. Both enzymatic and low molecular weight antioxidants are able to ameliorate these injurious impacts. Therefore, antioxidants are chemoprotective agents that neutralize cellular macromolecules oxidative damages. Numerous components are recognized to exert antioxidative properties that are originated from medicinal plants and have been administering as resourceful therapeutic approach in various diseases such as kidney failure. Therefore, we summarized the nephron-protective effects of several medicinal plants which are recently investigated at clinical trials.

Alterations in Tear Biochemistry Associated with Postanesthetic Chronic Dry Eye Syndrome.

Perioperative dry eye syndrome (DES) is a common ocular complication of long-term general anesthesia. Chronic DES can lead to permanent damage to the cornea and disturbance of visual function, up to total loss of vision. Here, a relationship between the duration of general anesthesia and the risk of chronic DES in patients was demonstrated. Using an experimental model of perioperative corneal abrasions in rabbits, it was found that introduction of animals to 3-h general anesthesia resulted in clinically significant chronic damage to the cornea in 50% of cases. The development of the complication was not associated with irreversible or long-term impairment of tear secretion, but it was accompanied by a decrease in tear film stability and growth of the total protein content as well as decrease in total antioxidant activity of the tear induced by low molecular weight antioxidants. In addition, anesthesia-induced changes in activity of tear antioxidant enzymes including superoxide dismutase and enzymes providing homeostasis of reduced glutathione (glutathione peroxidase, glutathione-S-transferase, glutathione reductase) were observed. All these alterations were protracted (up to 1-2 weeks) and therefore might account for transition of the perioperative DES into the chronic form. These findings can be useful in the development of novel approaches for the prevention and treatment of chronic forms of DES in the postanesthetic period.

Why Have Clinical Trials of Antioxidants to Prevent Neurodegeneration Failed? - A Cellular Investigation of Novel Phenothiazine-Type Antioxidants Reveals Competing Objectives for Pharmaceutical Neuroprotection.

Only a fraction of the currently established low-molecular weight antioxidants exhibit cytoprotective activity in living cells, which is considered a prerequisite for their potential clinical usefulness in Parkinson's disease or stroke. Post hoc structure-activity relationship analyses have predicted that increased lipophilicity and enhanced radical stabilization could contribute to such cytoprotective activity. We have synthesized a series of novel phenothiazine-type antioxidants exhibiting systematic variation in their lipophilicity and radical stabilization. Phenothiazine was chosen as lead structure for its superior activity at baseline. The novel compounds were evaluated for their neuroprotective potency in cell culture, and for their primary molecular targets. Lipophilicity was associated with enhanced cytoprotective activity, but only to a certain threshold (logP ≈ 7). Benzannulation likewise produced improved cytoprotectants that exhibited very low EC50 values of ~8nM in cultivated neuronal cells. Inhibition of global protein oxidation was the best molecular predictor of cytoprotective activity, followed by the inhibition of membrane protein autolysis. In contrast, the inhibition of lipid peroxidation in isolated brain lipids and the suppression of intracellular oxidant accumulation were poor predictors of cytoprotective activity, primarily as they misjudged the cellular advantage of high lipophilicity. Lipophilicity, radical stabilization and molecular weight appear to form an uneasy triangle, in which a slightly faulty selection may readily abolish neuroprotective activity.

210 - Construction of Oxidative Stress-Free Cell Culture System for the Separation of Stem Cells and the Maintenance of Separated Cell Properties

Reactive oxygen species (ROS) play important roles in regulating cellular morphology. In particular, mitochondrial ROS are involved in the regulation of cellular physiology. The balance between generation and elimination of ROS is essential for signaling pathway maintenance. However, excessive ROS are generated during cell culture in response to high oxygen concentration, cell contact with cell culture instruments and pro-oxidants in culture medium also generate ROS. Redox balance disruptions lead to changes in cellular morphology and disturb cellular homeostasis. Therefore, suppression of excessively generated ROS during cell subculture and treatments is very important issue, especially in the field of cellular therapeutics where cellular morphology should be strictly controlled. Though addition of low molecular weight (LMW) antioxidants to culture media suppresses such effect to some extent, they cause unwanted morphological changes of cultivating cells after internalization into the cells. In this work, we constructed a new biocompatible instrument based on ROS scavenging character and demonstrated the utility of a ROS-scavenging polymer as a novel biocompatible material. A polymer (PEG-b-PMNT) composed of poly(ethylene glycol) (PEG) and polystyrene segment with a nitroxide radicals (TEMPO) as a side chain, which catalytically scavenges ROS, was coated onto the surface of a dish via covalent linkage. Differentiation and spontaneous apoptosis of several kinds of cells including hematopoietic stem cells were suppressed on the polymer-coated dish. In contrast, LMW antioxidants showed disruption of mitochondrial membrane potential and induction of cellular differentiations. These adverse effects were likely due to the internalization of LMW antioxidants into mitochondria, resulting in a disrupted redox balance. In contrast, ROS-scavenging polymer could not internalize in cells and, therefore, could not have any adverse effects within the cell or mitochondria. These results demonstrate the utility of our novel biocompatible material for actively scavenging ROS and thus maintaining cellular properties.

The transport activity of P-glycoprotein upon a change of the redox balance in lymphocytes of patients with chronic B-lymphocytic leukemia

The effect of drugs used in the treatment of chronic B-lymphocytic leukemia on the functional activity of P-glycoprotein, which is a membrane transporter associated with the phenomenon of multiple drug resistance, in B-lymphocytes of leukemia patients has been investigated. The level of reactive oxygen species and the content of low molecular weight antioxidants in the leukemic cells during the metabolic processing of chemotherapy drugs has been assessed. The degree of involvement of low molecular weight antioxidants in the maintenance of redox balance in the lymphocytes of drug-treated leukemia patients has been characterized. Variation of the levels of reactive oxygen species in leukemic B-lymphocytes within a certain range, as well as the subsequent return of these values to the levels of intact cells, was shown to enhance the P-glycoprotein transport activity. The viability of leukemic B-cells decreased upon exposure to antitumor compounds and depended on the redox balance. No statistically significant correlation between the P-glycoprotein transport activity and the viability of lymphocytes during the detoxification from drugs in B-cell chronic lymphocytic leukemia patients has been detected; however, the transport activity of the protein was directly correlated to the viability of leukemia cells within 15 h after exposure of the cells to H2O2.

Implication of metabolomic profiles to wide thermoneutral zone in Mongolian gerbils (Meriones unguiculatus).

Mongolian gerbils (Meriones unguiculatus) have evolved a wide thermoneutral zone (26.5-38.9 °C) and high upper critical temperature, and appear to have a high tolerance for heat exposure. Here, we use a metabolomic approach to measure global metabolite profiles for gerbils between lower (27 °C) and upper critical temperatures (38 °C) to investigate the role of metabolomic characterization in maintaining basal metabolic rates within a wide thermoneutral zone. We found that in serum and liver, 14 and 19 metabolites were significantly altered, respectively. In the aerobic respiration-related tricarboxylic cycle (TCA), 5 intermediates (isocitric acid, cis-aconitic acid, α-ketoglutaric acid, fumaric acid and malic acid) were increased in serum in 38 °C animals; however, no such increase was found in the liver. A stable level of hepatic TCA cycle intermediates may be related to the steady state of aerobic respiration at 38 °C. Metabolomic results also revealed that acute heat exposure caused increased oxidative stress and low molecular weight antioxidants in Mongolian gerbils. Increased methionine and 2-hydroxybutyrate suggest an accelerated synthesis of glutathione. Increased urate and its precursors, inosine and hypoxanthine, were detected at 38 °C. Glucuronate, threonate and oxalate involved in ascorbate synthesis and degradation were increased in serum at 38 °C. In conclusion, although dramatic metabolomic variation was found, a stable hepatic TCA cycle may contribute to maintaining a constant basal metabolic rate within a wide thermoneutral zone in Mongolian gerbils.

EFFECT OF BIO-STIMULATORS ON PRODUCTION OF COWPEA SEED FOR FOOD SECURITY AND WEALTH CREATION IN JUJA, KENYA

A study was done to evaluate the effect of bio-stimulators on seed production of cowpea crop in Juja, Kenya during short rains season 2014-15. Bio-stimulators are plant and animal derived substances that trigger plant processes when applied to the plants at very low concentrations. They contain amino acids, low molecular weight polypeptides, vitamins, enzymes, hormones, sugars, betaines and antioxidants. Drought causes slow rate of the majority of plant growth and development processes leading to discontinuation of cell growth, stomatal closures, increased abscisic acid and proline, drop in cytokinins levels, reduced protein synthesis and reduced activity of nitrate reductase leading to retarded growth and plant senescence. In reducing the impact of the water stress therefore, cytokinins in bio-stimulators promote growth and slow down plant senescence. Parameters investigated were germination rate, days to flowering and pod formation, number of seeds per pod, length of pods, total number of pods and weight of seeds. Results on the effect of bio-stimulators on cowpea seed production are discussed.