Bilgi Merkezi
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Toprakların doygun koşullardaki hidrolik iletkenlik değerlerinin pedotransfer eşitlikler ile tahminlenmesi
No full textÜç fazlı ve gözenekli bir sistem olan toprakta suyun hareketinin bilinmesi S-matriksin karakteri hakkında önemli ipuçları vermektedir. Bu nedenle toprak fizikokimyasal özelliklerine doğrudan etki eden suyun toprakta iletiminin ölçümü son derece önemlidir. Laboratuarda Mariotte düzeneği ile doygun koşullarda yapılan kullanışsız hidrolik iletkenlik testleri araştırmacı için çoğunlukla zaman alıcı ve usandırıcı olmaktadır. Bu çalışmanın amacı, bazı temel toprak fiziksel özellikleri ve nem sabiteleri kullanılarak oluşturulan pedotransfer eşitlikler (PTFs) yardımıyla toprakta doygun koşullardaki düşey hidrolik iletkenlik değerinin (Ks) tahminlenmesidir. Bu amaç doğrultusunda Kahramanmaraş-Narlı Ovası’ndan 25 adet yüzey toprak örneği (0-15 cm) alınmıştır. Rutin toprak özellikleri, nem sabiteleri ve Ks bilinen yöntemlerle ölçülmüştür. Daha sonra veri kümesi istatistiksel olarak değerlendirilmiş ve çoklu lineer regresyon yöntemi kullanılarak Ks’yi tahminlemede kullanılacak PTFs oluşturulmuştur. Bilinen yöntemlerle ölçülen ve geliştirilen PTFs ile tahminlenen Ks değerlerinin karşılaştırılmasında determinasyon katsayısı (R2) kullanılmış ve en yüksek R2 değeri 0.846 olarak elde edilmiştir. Bu araştırmanın sonuçları Kahramanmaraş-Narlı Ovası’nda Ks değerlerinin tahmin edilmesinde geliştirilen pedotransfer modellerin kullanılabileceğini göstermektedir
Bazı Pestisitlerin Avcı Akar Phytoseiulus persimilis A.-H. (Acari:Phytoseiidae)'e Laboratuar Koşullarında Yan Etkilerinin Belirlenmesi
No full textBu çalışmada, Süleyman Demirel Üniversitesi, Ziraat Fakültesi, Bitki koruma bölümünde 2010-2011 yılları arasında avcı akar Phytoseiulus persimilis A.-H. (Acarina: Phytoseiidae)'de ilaçlama kulesi-yaprak disk metodu kullanılarak 6 faklı pestisitin yan etkileri laboratuar koşullarında araştırılmıştır. Çalışmalarda, insektisitlerden indoxacarb, insektisit-akarisitlerden spiromesifen, abamectin ve akarisitlerden ise hexythiazox , spirodiclofen ve cyhexatin etkili maddeye sahip pestisitler kullanılmıştır. Bu pestisitlerin, tarla uygulama dozunun yarısı (T/2), tarla uygulama dozu (T), ve iki katı (2T) olmak üzere üç farklı dozu uygulanmıştır. Ölü-canlı sayımları uygulamadan 1, 3, 5 ve 7 gün sonra yapılmıştır. Ayrıca pestisitlerin Phytoseiulus persimilis dişilerinin yumurta verimi üzerindeki etkisini belirlemek için günlük bırakılan yumurta sayımları yapılmıştır. Avcı akarda indoxacarb ve hexythiazox'un tüm dozları orta derece zararlı bulunmuştur. Phytoseiulus persimilis'de abamectin, spiromesifen ve spirodiclofen'in 2T ve T dozları zararlı, cyhexatin'in 2T ve T dozu ise orta derecede zararlı bulunmuştur. Abamectin, spiromesifen ve spirodiclofen'in T/2 dozu orta derecede zararlı , cyhexatin'in T/2 dozu ise zararsız bulunmuştur. Dişi başına bırakılan yumurta sayısında kontrol grubuyla indoxacarb'ın 2T ve T dozları ile abamectin, cyhexatin ve spirodiclofen'in tüm dozlarında istatistiki olarak önemli faklılık belirlenmiştir. İlaçların diğer dozlarında ise yumurta verimi bakımından kontrol grubu ile karşılaştırıldığında önemli bir farklılık bulunmamıştır
The Potential Effects of Electromagnetic Field: A Review
No full textStudies about the potential effects of electromagnetic field on human body are increasing day by day. In this
study; new investigations on this field were tried to be explained by the help of literature. An exclusive search
was conducted in medical databases and these findings were compared with literatures in the world. It is
shown, in many studies around the world, that electromagnetic waves as well as the electromagnetic field that
is given out by some of the equipment we use, create negative effects on biological systems of humans. Moreover;
it had concluded that there are roles of molecular pathways such as oxidative stress on electromagnetic
field induced diseases. These effects are the short term effects and long term effects. Decreasing of the area
of vision, heavy stress and feeling of tiredness, loosing of concentration and attention, voices in the ears and
warming of ears, reversible hearing problems, headache and such can be seen as the short term effects. The
long term effects that are commonly encountered are; irreversible hearing problems, damaging of the embryonic
development, increasing risk of miscarriage, decrease in the number of sperms, damaging of the brain
tissue, heart related problems, weakening of the memory, lymphoma, and damaging of the genetic structure.
We cannot stop using electricity. Electromagnetic field related health problems could take many years to present
symptoms. Hence, public sensitivity to these issues is a necessity. Preventative measures should be high
priority and risks should be minimized
Recent Progress in the Regulation of TRPC1 by Store Depletion
No full textStore-operated Ca entry (SOCE) is activated in response to depletion of the ER-Ca stores. The ER-Ca
2+
sensor protein, STIM1, oligomerizes when [Ca ] in the store is decreased and moves to ER/PM junctional
domains where it interacts with and activates channels involved in SOCE, namely Orai and TRPC channels.
2+
Orai1 is the primary pore-forming component of the highly Ca selective CRAC channel. It is recruited to ER/
PM junctional domains by STIM1 where it is gated via interaction with a specific C-terminal domain of STIM1.
Thus Orai1 and STIM1 are sufficient for generation of functional CRAC channels. Store depletion also leads
to activation of relatively non-selective cation channels, referred to as SOC channels that contribute to SOCE
in several other cell types. TRPC1 has been proposed as a possible candidate component of SOC channels.
2+
TRPC1 contributes to endogenous SOCE in many cells types. In these cells, TRPC1-mediated Ca entry and
3+
cation currents are stimulated with either agonist or thapsigargin, and inhibited by low [Gd ] and 10-20 µM
2APB (conditions that block SOCE). STIM1 also associates with and gates TRPC1 via electrostatic interaction
between STIM1 (684KK685) and TRPC1 (639DD640). Further, functional Orai1 is required for activation of
TRPC1-SOCE and this has been associated with recruitment of a TRPC1/STIM1/Orai1 complex. However,
there is ongoing debate regarding the activation of TRPC1 by store depletion as well as the role of Orai1 and
STIM1 in regulating its function. This chapter will summarize recent studies and concepts regarding the contri-
butions of Orai1 and TRPC1 to SOCE. We will discuss major unresolved questions regarding functional inter-
action between Orai1 and TRPC1 as well as possible mechanisms involved in the regulation of TRPC channels
Ascorbic Acid Mediated Iron Toxicity in Caco-2 Cells:Effects of Different Iron Species
No full textAim of the presented study was to investigate whether scorbic acid enhances iron uptake and/or toxicity in Caco-2 cells. Cells were incubated with 1.5 mM of different iron species combined with increasing doses of ascorbic acid (1-3 mM). Thereafter viability, membrane damage, lipid peroxidation, and intracellular iron concentrations were measured. No effects on iron-induced damage to cells were found regarding viability.
Lipid peroxidation significantly increased when ascorbic acid was added to cells incubated with FeSO. In 4 contrast lactate dehydrogenase (LDH)-release decreased by addition of ascorbic acid in Caco-2 cells treated with FeCl : nitrilotriacetic acid (NTA) and FeCl : citric acid. Iron uptake was enhanced by ascorbic acid, when 3 3
FeCl : citric acid (1:2) or FeSO were used.
We suggested that, especially dependent on the iron species used, 3 4 a combination of ascorbic acid and iron favours lipid peroxidation in Caco-2 cells. But on the other hand we also found beneficial effects of this type of co-treatment, like an enhanced iron uptake and decreased plasma membrane damage
Melatonin: Helping cells cope with oxidative disaster
No full textMelatonin possesses the capability of donating electrons, consequently reducing the reactivity of molecules with an unpaired electron in their valence orbital, i.e. free radicals. A plethora of studies support the role of this indoleamine in diminishing molecular damage associated with massive free radical generation both in vitro and in vivo. Melatonin protects against neurodegenerative disorders, ischemia/reperfusion injury, acts as a radio protector, and counteracts herbicide and metal toxicity due to its essential role in antioxidant protection. At the intracellular level, it reduces electron leakage from the mitochondrial respiratory chain complexes as well as scavenging radicals generated in the cytosol (exclusive of its actions in mitochondria) and nucleus. Comparative studies with other well-known naturally occurring antioxidants show that melatonin’s efficacy is equal to or better in neutralizing highly toxic oxygen and nitrogen-reactants. However, not only melatonin but a series of its metabolites are also capable of detoxifying free radicals and related species in what is referred to as the antioxidative cascade. Thus, melatonin may be actually seen as a prodrug for a family of other molecules that also have the capability of reducing oxidative/nitrosative stress. Taken together, the results reviewed here indicate that melatonin is a key element in antioxidative medicine in the context of the antioxidative defense system
Multivitamin-mineral supplement is more efficacious than vitamins (E+C) in the prevention of chronic unpredictable stress induced oxidative damage in mice
No full textStress triggers a physiological response by increasing the
metabolic rate which translates into oxidative stress, resulting in the etiopathogenesis of many diseases. Several micronutrients like antioxidant vitamins and minerals can modulate the state of oxidative stress. This study tests whether an MM (consisting of functionally diverse dietary antioxidants) compares favourably with a combination of vitamins E and C, in providing increased anti-oxidative protection against chronic unpredictable stress (CUS) induced oxidative damage in mice. Thirty-two Swiss albino mice were randomized to one of the following groups: control+vehicle, CUS+ vehicle, CUS+ MM, and CUS+ vitamins (C+E). CUS was applied for 4 weeks and MM and vitamins (C+E) were administered orally for the same period. CUS led to a negative impact on all the biochemical parameters analyzed in circulation, liver and kidney with elevation of malondialdehyde
and reduction of glutathione levels. The activities of superoxide dismutase, catalase, glutathione S-transferase, and glutathione reductase were decreased by CUS, with an elevation of liver marker enzymes, glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) in the circulation and liver. Supplementation with MM and vitamins (C+E) restored the disturbed antioxidant status in the stress exposed mice. However, MM was found more effective than vitamins (C+E) in reinstating the altered parameters. The results of the study suggest that the cumulative action of diverse vitamins and minerals in an MM exert greater antioxidative effect than vitamins (C+E) in combating the CUS induced oxidative stress, thus supplementation of MM alone can be an effective measure to combat stress induced oxidative derangements both under normal and pathological conditions
Hypoglycemia and nitro-oxidative stress in the neonatal period
No full textPeroxynitrite generation and subsequent nitration and/or oxidation of proteins, lipids and DNA are implicated in neuronal death. In animal models, peroxynitrite generation is increased by hypoglycemia, a condition occurring frequently in low birth weight newborns. In order to detect systemic nitro-oxidative stress, we developed an assay to measure plasma nitroalbumin (PNA) concentration and investigated its variations according to the occurrence and recurrence of hypoglycemic events (HG: glycemia < 2.5 mmol/l) during the first day of life. PNA concentrations were measured at days 0, 1 and/or 4 of life in 120 low birth weight newborns (27 small for gestational age term and 93 preterm infants). PNA concentrations at days 0, 1 and 4 were significantly higher in infants who developed at least one HG than in normoglycemic patients. PNA concentration at D1 increased with the number of hypoglycemic events and was correlated to the area under curve of glycemia measured 12-24 hours before sampling. We conclude that hypoglycemia during the first 24 hours of life is associated with increased albumin nitration in newborns. Our results suggest that significant nitro-oxidative stress occurs promptly after hypoglycemia implying a risk of end-organ damage due to protein nitration, lipid peroxidation and DNA damage. Evidence of nitro-oxidative stress in hypoglycemic neonates may open new and exciting perspectives in neuroprotection
Geleneksel Asfalt Beton ve Genleştirilmiş Kil Agrega ile Üretilmiş Hafif Asfalt Betonun Çok Yönlü Karşılaştırılması
Get PDFBu çalışmada kırma taş agrega (KTA) kullanılarak geleneksel olarak üretilmiş asfalt beton numuneler ve yapay bir hafif agrega olan genleştirilmiş kil agrega (GKA) ile üretilmiş hafif asfalt beton numuneler üzerinde çok yönlü incelemeler yapılarak bir takım özellikler karşılaştırılmıştır. Üretilen numuneler üzerinde öncelikle bazı fiziksel deneyler yapılmış ve her bir numunenin fiziksel özelliği tayin edilmiştir. Daha sonra tahribatlı ve tahribatsız bir takım deneyler ile numunelerin mekanik özellikleri belirlenmiştir. Tüm bu deneyler ve son olarak da malzeme kullanımı ve temini gibi durumlar göz önünde bulundurularak ekonomik, fiziksel ve mekanik özellikler karşılaştırılmış ve sonuçlar değerlendirilmiştir