scholarly journals Binding in vitro to rat liver receptors does not correlate with activities in vivo of bovine somatotropin. Use of chemically modified derivatives as probes

1984 ◽  
Vol 224 (2) ◽  
pp. 535-540 ◽  
Author(s):  
L P Roguin ◽  
J M Delfino ◽  
N Vita ◽  
A C Paladini
Keyword(s):  
Rat Liver ◽  
Binding Sites ◽  
Specific Binding ◽  
The Body ◽  
Water Soluble ◽  
Bovine Somatotropin ◽  
Isolated Cells ◽  
Carboxylate Groups

Bovine somatotropin with an increasing number of its carboxylate groups modified by reaction with glycine methyl ester in the presence of a water-soluble carbodi-imide was tested for its activity in different bioassays. Only those derivatives which were known to be active in the body-weight-increase bioassay were able to compete with 125I-labelled bovine somatotropin for their specific binding sites in vivo. No difference was found in the rate of clearance of a poorly active derivative as compared with that of native somatotropin. In contrast, both active and inactive derivatives were found to be equally effective in displacing the tracer from its binding sites present in isolated cells and membrane preparations from rat liver. These results suggest that the liver somatogenic receptors studied in vitro are less discriminating than those detected in vivo.

Effects of vasopressin and aldosterone on amiloride binding in toad bladder epithelial cells

1975 ◽  
Vol 189 (1097) ◽  
pp. 543-575 ◽  
Keyword(s):  
Epithelial Cells ◽  
Sodium Transport ◽  
Binding Sites ◽  
Specific Binding ◽  
Sodium Concentration ◽  
Isolated Cells ◽  
The Right ◽  
Transepithelial Sodium Transport

Methods have been devised to measure the binding of [ 14 C]amiloride to isolated cells from bladders of toads, Bufo marinus . This agent blocks transepithelial sodium transport across bladders by preventing sodium entry to the transporting mechanism. A saturable binding component has been found with an affinity of 5.6 x 10 7 m -1 in the presence of 1.1 mM Na + , which corresponds to the affinity of amiloride when used as a transport inhibitor at the same sodium concentration. In freshly isolated cells the capacity of the binding sites is 3.6 x 10 5 sites/cell, but this value falls to about one third in aged suspensions. When cells are treated with vasopressin (100 mU/ml) somewhat less specific binding is measured at an amiloride concentration giving 50 % occupancy. The results are consistent with the view that vasopressin moves the binding curve to the right along the concentration axis, reducing the affinity of amiloride by a factor of approximately two, while leaving the total capacity unaffected. The affinity of amiloride when used as an inhibitor of transport is also found to be reduced by a factor of two by vasopressin, and complete inhibition of transport can still be achieved. d -Aldosterone in vitro increases the number of amiloride binding sites in isolated cells by approximately 115%, and results from transport studies indicate that there is no significant change in the affinity of amiloride after d -aldosterone treatment. Inhibitors of transcription and translation (actinomycin D and cycloheximide) prevent the increase in amiloride binding caused by d -aldosterone. In vivo the effects of d -aldosterone are more complex, but it is shown that the steroid increases the transport capacity of the tissue, when this is expressed as the number of amiloride binding sites per unit mass of tissue. The results are discussed in terms of the ways in which the two hormones may alter the entry of sodium into the epithelial cells, and so in turn affect transepithelial sodium transport.

Human Skin Binding and Absorption of Contaminants from Ground and Surface Water During Swimming and Bathing

1989 ◽  
Vol 8 (5) ◽  
pp. 853-859 ◽  
Author(s):  
Ronald C. Wester ◽  
Howard I. Maibach
Keyword(s):  
Surface Water ◽  
Stratum Corneum ◽  
Human Skin ◽  
The Body ◽  
Water Soluble ◽  
Exposure Effect ◽  
Human Stratum Corneum ◽  
Water Dilution

Contaminants exist in ground and surface water. Human skin has the capacity to bind and then absorb these contaminants into the body during swimming and bathing. Powdered human stratum corneum will bind both lipid-soluble (alachlor, polychlorinated biphenyls [PCBs], benzene) and water-soluble (nitroaniline) chemicals. In vitro (human skin) and in vivo (Rhesus monkey) studies show that these chemicals readily distribute into skin, and then some of the chemical is absorbed into the body. Linearity in binding and absorption exists for nitroaniline over a 10-fold concentration range. Multiple exposure to benzene is at least cumulative. Binding and absorption can be significant for exposures as short as 30 min, and will increase with time. Absorption with water dilution increased for alachlor, but not for dinoseb. Soap reversed the partitioning of alachlor between human stratum corneum and water. The PCBs could be removed from skin by soap and water (70% efficiency) for up to 3 h and then decontamination potential decreased, due to continuing skin absorption. The model in vitro and in vivo systems used should permit easy estimation of this area of extensive human exposure effect on risk assessment.

Polyphenols in Food: Cancer Prevention and Apoptosis Induction

2018 ◽  
Vol 25 (36) ◽  
pp. 4740-4757 ◽  
Author(s):  
Ashita Sharma ◽  
Mandeep Kaur ◽  
Jatinder Kaur Katnoria ◽  
Avinash Kaur Nagpal
Keyword(s):  
Cancer Prevention ◽  
Defense Mechanism ◽  
Antioxidant Property ◽  
The Body ◽  
Water Soluble ◽  
Stress Factors ◽  
In Vivo Studies ◽  
Hydroxyl Groups

Polyphenols are a group of water-soluble organic compounds, mainly of natural origin. The compounds having about 5-7 aromatic rings and more than 12 phenolic hydroxyl groups are classified as polyphenols. These are the antioxidants which protect the body from oxidative damage. In plants, they are the secondary metabolites produced as a defense mechanism against stress factors. Antioxidant property of polyphenols is suggested to provide protection against many diseases associated with reactive oxygen species (ROS), including cancer. Various studies carried out across the world have suggested that polyphenols can inhibit the tumor generation, induce apoptosis in cancer cells and interfere in progression of tumors. This group of wonder compounds is present in surplus in natural plants and food products. Intake of polyphenols through diet can scavenge ROS and thus can help in cancer prevention. The plant derived products can also be used along with conventional chemotherapy to enhance the chemopreventive effects. The present review focuses on various in vitro and in vivo studies carried out to assess the anti-carcinogenic potential of polyphenols present in our food. Also, the pathways involved in cancer chemopreventive effects of various subclasses (flavonoids, lignans, stilbenes and phenolic acids) of polyphenols are discussed.

Atrial natriuretic factor binding sites in the jejunum

1989 ◽  
Vol 256 (2) ◽  
pp. G436-G441 ◽  
Author(s):  
C. Bianchi ◽  
G. Thibault ◽  
A. De Lean ◽  
J. Genest ◽  
M. Cantin
Keyword(s):  
Binding Sites ◽  
Atrial Natriuretic Factor ◽  
Specific Binding ◽  
Rat Tissues ◽  
Rat Jejunum ◽  
Specific Binding Sites ◽  
Natriuretic Factor ◽  
Atrial Natriuretic

We have studied the localization and the characterization of atrial natriuretic factor (ANF) binding sites by radioautographic techniques. Quantitative in vitro radioautography with a computerized microdensitometer demonstrated the presence of high-affinity, low-capacity 125I-ANF-(99-126) binding sites (Kd, 48 pM; Bmax, 63 fmol/mg protein) mainly in the villi of 20-microns slide-mounted transverse sections of the rat jejunum. Competition curves showed 50% inhibitory concentrations of 55 and 1,560 pM for ANF-(99-126) and ANF-(103-123), respectively. In vivo electron microscope radioautography showed that 80% of the silver grains were localized on the lamina propria fibroblast-like cells, 18% on mature enterocytes, and 2% on capillaries. Bradykinin and adrenocorticotropin did not compete with ANF binding. These results demonstrate that ANF binding sites in the rat jejunum possess the pharmacological characteristics of functional ANF receptors encountered in other rat tissues, and ultrastructural radioautographs show their cellular distribution. Taken together, these results demonstrate the presence and the localization of specific binding sites for ANF in the jejunal villi of the rat small intestine.

scholarly journals Binding of disparate transcriptional activators to nucleosomal DNA is inherently cooperative.

1995 ◽  
Vol 15 (3) ◽  
pp. 1405-1421 ◽  
Author(s):  
C C Adams ◽  
J L Workman
Keyword(s):  
Transcription Factors ◽  
Dna Binding ◽  
Binding Sites ◽  
Specific Binding ◽  
General Mechanism ◽  
Nf Kappa B ◽  
Nucleosomal Dna ◽  
Nucleosome Binding

To investigate mechanisms by which multiple transcription factors access complex promoters and enhancers within cellular chromatin, we have analyzed the binding of disparate factors to nucleosome cores. We used a purified in vitro system to analyze binding of four activator proteins, two GAL4 derivatives, USF, and NF-kappa B (KBF1), to reconstituted nucleosome cores containing different combinations of binding sites. Here we show that binding of any two or all three of these factors to nucleosomal DNA is inherently cooperative. Thus, the binuclear Zn clusters of GAL4, the helix-loop-helix/basic domains of USF, and the rel domain of NF-kappa B all participated in cooperative nucleosome binding, illustrating that this effect is not restricted to a particular DNA-binding domain. Simultaneous binding by two factors increased the affinity of individual factors for nucleosomal DNA by up to 2 orders of magnitude. Importantly, cooperative binding resulted in efficient nucleosome binding by factors (USF and NF-kappa B) which independently possess little nucleosome-binding ability. The participation of GAL4 derivatives in cooperative nucleosome binding required only DNA-binding and dimerization domains, indicating that disruption of histone-DNA contacts by factor binding was responsible for the increased affinity of additional factors. Cooperative nucleosome binding required sequence-specific binding of all transcription factors, appeared to have spatial constraints, and was independent of the orientation of the binding sites on the nucleosome. These results indicate that cooperative nucleosome binding is a general mechanism that may play a significant role in loading complex enhancer and promoter elements with multiple diverse factors in chromatin and contribute to the generation of threshold responses and transcriptional synergy by multiple activator sites in vivo.

M2 muscarinic ([3H]N-methyl scopolamine) binding in micropunches of rat ventricular myocardium: characterization and modification by progesterone

1992 ◽  
Vol 70 (7) ◽  
pp. 943-948 ◽  
Author(s):  
M. Wilkinson ◽  
Alice Giles ◽  
Diane A. Wilkinson
Keyword(s):  
Muscarinic Receptor ◽  
Cardiac Tissue ◽  
Specific Binding ◽  
Ventricular Myocardium ◽  
Water Soluble ◽  
Intact Cells ◽  
Muscarinic Binding Sites ◽  
Methyl Scopolamine

A new technique is outlined for the characterization and quantification of M2 muscarinic binding sites (receptors) in micro-punches (1 mm diam.), cut from slices (350 μm), of fresh cardiac tissue using the hydrophilic antagonist [3H]N-methyl scopolamine. The use of this water-soluble ligand allows us to label, and quantify, M2 receptors on the cell surface of intact cells contained within the micropunch. We believe that cardiac micropunches offer a simple but powerful approach to the investigation of membrane receptor regulation in tissue that largely retains the in vivo cytoarchitecture. Specific binding is reversible, stereospecific, saturable, of high affinity, and has the drug specificity typical of an M2 muscarinic receptor. In rat left ventricle, Bmax was 151.2 ± 10.3 fmol/mg protein while KD was 1.0 ± 0.1 nM. Nonspecific binding of the ligand was very low, varying from 2.8% (at 0.27 nM) to 7.7% (at 3.58 nM). This micropunch assay was used to determine that progesterone can compete with the muscarinic ligand for the M2 receptor in vitro (IC50 = 50 × 10−6 M). The steroids estradiol and testosterone, as well as ouabain, were without effect. Progesterone inhibited [3H]N-methyl scopolamine binding competitively (KD reduced from 1.9 to 4.3 nM) without affecting the rate of association of the ligand. However, progesterone induced a rapid dissociation of the ligand from its receptor. We conclude that the micropunch assay described here is suitable for the continued study of sex hormone effects on cardiac function.Key words: cardiac micropunches, muscarinic receptor, progesterone, [3H]N-methyl scopolamine.

scholarly journals The behavior of transferrin iron in the rat

Blood ◽  
1981 ◽  
Vol 57 (2) ◽  
pp. 218-228 ◽  
Author(s):  
H Huebers ◽  
W Bauer ◽  
E Huebers ◽  
E Csiba ◽  
C Finch
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Ferrous Ammonium Sulfate ◽  
Iron Binding ◽  
Body Tissues ◽  
Iron Deficient ◽  
Diferric Transferrin ◽  
Iron Exchange

Abstract The behavior of rat transferrin has been investigated employing acrylamide gel electrophoresis and isoelectric focusing. In vitro trace labeling with iron chelates at 30 min was 93%-98% effective, whereas binding by simple ferric salts was reduced to 71%-76%. Complete and specific binding of 59FeSO4 by the iron binding sites of transferrin was demonstrated after in vitro or in vivo addition of ferrous ammonium sulfate in pH 2 saline up to the point of iron saturation. In vitro the radioriron transferrin complex in plasma was stable and its iron had a negligible exchange with other transferrin binding sites over several hours. The distribution of radioiron added in vitro or through absorption was shown to be random between the binding sites of slow and fast transferrin molecule. Iron distribution among body tissues was similar for mono- and diferric transferrin iron and was not affected by the site distribution of iron on the transferrin molecule. The only important aspect of transferrin iron binding was the more rapid tissue uptake of iron in the diferric form was compared to monoferric transferrin. Additional in vivo effects on internal iron exchange were produced by changes in the iron balance of the animal. In the iron loaded animal, monoferric transferrin injected into the plasma was rapidly loaded by iron from tissue and thereby converted to diferric transferrin. Injection of diferric transferrin in the iron deficient animal was associated with a rapid disappearance from circulation of the original complex and a subsequent appearance of monoferric transferrin as a result of iron returning from tissues. These observations support the concept that plasma iron behaves as a single pool except that diferric iron exchange occurs at a more rapid rate than dose monoferric iron exchange.

scholarly journals A yeast ARS-binding protein activates transcription synergistically in combination with other weak activating factors.

1990 ◽  
Vol 10 (3) ◽  
pp. 887-897 ◽  
Author(s):  
A R Buchman ◽  
R D Kornberg
Keyword(s):  
Dna Sequences ◽  
Transcriptional Activation ◽  
Binding Sites ◽  
Essential Gene ◽  
Specific Binding ◽  
Binding Protein ◽  
Point Mutations ◽  
Yeast Genes

ABFI (ARS-binding protein I) is a yeast protein that binds specific DNA sequences associated with several autonomously replicating sequences (ARSs). ABFI also binds sequences located in promoter regions of some yeast genes, including DED1, an essential gene of unknown function that is transcribed constitutively at a high level. ABFI was purified by specific binding to the DED1 upstream activating sequence (UAS) and was found to recognize related sequences at several other promoters, at an ARS (ARS1), and at a transcriptional silencer (HMR E). All ABFI-binding sites, regardless of origin, provided weak UAS function in vivo when examined in test plasmids. UAS function was abolished by point mutations that reduced ABFI binding in vitro. Analysis of the DED1 promoter showed that two ABFI-binding sites combine synergistically with an adjacent T-rich sequence to form a strong constitutive activator. The DED1 T-rich element acted synergistically with all other ABFI-binding sites and with binding sites for other multifunctional yeast activators. An examination of the properties of sequences surrounding ARS1 left open the possibility that ABFI enhances the initiation of DNA replication at ARS1 by transcriptional activation.

scholarly journals Combretastatins: An Overview of Structure, Probable Mechanisms of Action and Potential Applications

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2560 ◽  
Author(s):  
Gökçe Şeker Karatoprak ◽  
Esra Küpeli Akkol ◽  
Yasin Genç ◽  
Hilal Bardakcı ◽  
Çiğdem Yücel ◽  
...  
Keyword(s):  
South African ◽  
Water Solubility ◽  
The Body ◽  
Water Soluble ◽  
In Vivo Studies ◽  
Lead Compounds ◽  
Combretastatin A4 ◽  
Potential Applications

Combretastatins are a class of closely related stilbenes (combretastatins A), dihydrostilbenes (combretastatins B), phenanthrenes (combretastatins C) and macrocyclic lactones (combretastatins D) found in the bark of Combretum caffrum (Eckl. & Zeyh.) Kuntze, commonly known as the South African bush willow. Some of the compounds in this series have been shown to be among the most potent antitubulin agents known. Due to their structural simplicity many analogs have also been synthesized. Combretastatin A4 phosphate is the most frequently tested compounds in preclinical and clinical trials. It is a water-soluble prodrug that the body can rapidly metabolize to combretastatin A4, which exhibits anti-tumor properties. In addition, in vitro and in vivo studies on combretastatins have determined that these compounds also have antioxidant, anti-inflammatory and antimicrobial effects. Nano-based formulations of natural or synthetic active agents such as combretastatin A4 phosphate exhibit several clear advantages, including improved low water solubility, prolonged circulation, drug targeting properties, enhanced efficiency, as well as fewer side effects. In this review, a synopsis of the recent literature exploring the combretastatins, their potential effects and nanoformulations as lead compounds in clinical applications is provided.

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