scholarly journals The role of retinal photoisomerase in the visual cycle of the honeybee.

1991 ◽  
Vol 97 (1) ◽  
pp. 143-165 ◽  
Author(s):  
W C Smith ◽  
T H Goldsmith
Keyword(s):  
Visual Pigment ◽  
Compound Eye ◽  
Rod Outer Segments ◽  
Visual Cycle ◽  
In Vitro Techniques ◽  
The Third ◽  
Isomerization Processes

The compound eye of the honeybee has previously been shown to contain a soluble retinal photoisomerase which, in vitro, is able to catalyze stereospecifically the photoconversion of all-trans retinal to 11-cis retinal. In this study we combine in vivo and in vitro techniques to demonstrate how the retinal photoisomerase is involved in the visual cycle, creating 11-cis retinal for the generation of visual pigment. Honeybees have approximately 2.5 pmol/eye of retinal associated with visual pigments, but larger amounts (4-12 pmol/eye) of both retinal and retinol bound to soluble proteins. When bees are dark adapted for 24 h or longer, greater than 80% of the endogenous retinal, mostly in the all-trans configuration, is associated with the retinal photoisomerase. On exposure to blue light the retinal is isomerized to 11-cis, which makes it available to an alcohol dehydrogenase. Most of it is then reduced to 11-cis retinol. The retinol is not esterified and remains associated with a soluble protein, serving as a reservoir of 11-cis retinoid available for renewal of visual pigment. Alternatively, 11-cis retinal can be transferred directly to opsin to regenerate rhodopsin, as shown by synthesis of rhodopsin in bleached frog rod outer segments. This retinaldehyde cycle from the honeybee is the third to be described. It appears very similar to the system in another group of arthropods, flies, and differs from the isomerization processes in vertebrates and cephalopod mollusks.

scholarly journals Assessing Democracy In Vitro, In Vivo, and In Actu and the Role of Democratic Theory Today

2019 ◽  
Vol 6 (2) ◽  
pp. 70-84
Author(s):  
Anastasia Deligiaouri ◽  
Jane Suiter
Keyword(s):  
Democratic Theory ◽  
Discourse Theory ◽  
Second Step ◽  
The Third ◽  
The Core ◽  
Ongoing Project

How can we define democracy today given the continuous changes that modern societies are undergoing? What is the role of a democratic theorist? This paper articulates a threefold argument in responding to these questions by analyzing the term of democracy in vitro, in vivo, and in actu. The first step is to secure a democratic minimum and the core principles of democracy. The second step involves studying democracy as an ongoing project and examining how the principles of this democratic minimum are encoded. In the third step we deploy the basic premises of discourse theory of Laclau and Mouffe when evaluating a specific discourse of democracy, as this approach encompasses both discursive and nondiscursive practices. Utilizing this three-level evaluative framework for democratic theory will allow us to not only articulate normative principles but also evaluate them according to their mode of implementation.

Functional role of intrahypothalamic release of oxytocin and vasopressin: consequences and controversies

1995 ◽  
Vol 268 (4) ◽  
pp. E537-E545 ◽  
Author(s):  
M. Ludwig
Keyword(s):  
Milk Ejection ◽  
In Vitro Techniques ◽  
Hypothalamic Nuclei ◽  
Peptide Release ◽  
Functional Consequences ◽  
Milk Ejection Reflex ◽  
And Behavior

This brief review of vasopressin (VP) and oxytocin (OT) release into the extracellular space of the supraoptic (SON) and paraventricular (PVN) nuclei focuses on recent data illustrating the significance of their intranuclear release and the potential functional consequences. With the use of in vitro techniques, it has been demonstrated that administration of exogenous OT causes local peptide release and that, in vivo, this facilitates the milk ejection reflex. These findings lead to the idea that endogenous peptides are released into the hypothalamic nuclei. Microperfusion techniques have been used to monitor the dynamics of intranuclear OT and VP release in response to distinct stimuli. It is clear that intranuclear release of OT plays a role during reproductive states (parturition and lactation) and that intranuclear release of VP and OT is involved in osmoregulation. This review discusses 1) the origin of the intranuclearly released peptides, 2) stimuli which cause release into the hypothalamic nuclei, and 3) the function of intranuclear VP and OT, e.g., regulation of local morphology, feedback mechanisms and synchronization, and the possible role in regulating autonomic function and behavior.

Relationships Between Factor XII-Dependent Systems And The “Prorenin”-Renin System In Human Plasma

1981 ◽  
Author(s):  
E A Wilczynski ◽  
A D Purdon ◽  
D H Osmond
Keyword(s):  
Clotting Factor ◽  
Factor Xii ◽  
Clotting Factors ◽  
In Vitro Techniques ◽  
Subsequent Exposure ◽  
Control Plasma ◽  
Free Plasma

Treatment of plasma with cold (-4°C,72 hr), and with trypsin (0.5 mg trypsin/ml plasma), are well established in-vitro techniques used to activate plasma prorenin. Various clotting factor deficiencies have been found to impair the conversion of prorenin to renin in plasma. Studies with factor XII deficient plasma, in which marked reduction in both cold and tryptic activation was seen, led to further studies on the role of clotting factors and other factor XI I-dependent systems in prorenin activation. Removal of factors II, VII, IX, and X by adsorption onto BaSO4, and subsequent exposure of the residual plasma to cold (-4°C, 48 hr) and trypsin (1 mg/ml), resulted in a decreased capacity for prorenin activation when compared to control plasma, more so in cold than in trypsin-treated plasma. Plasminogen-free plasma responded similarly and, while increased concentrations of trypsin could enhance its prorenin activation to near-normal levels, prolonged cold incubation could not. This suggests that trypsin, added in an appropriate concentration to deficient plasma, may be able to substitute for the missing factor(s), while cold activation is limited by availability of one or more crucial factors. Unmanipulated Fletcher plasma (prekallikrein deficient) has a low level of active renin, and elevated prorenin, symptomatic of a block of prorenin conversion in-vivo. However, cold and tryptic activation were, if anything, relatively greater than normal, especially for trypsin, suggesting that enzymes other than kallikrein are important activators, in-vitro, and can substitute for the missing kallikrein. Thus, neither kallikrein, nor any other single factor studied here, including factor XII, is solely responsible for the activation of plasma prorenin.

scholarly journals Component Permeabilities and Water Contents in periplaneta Integument: Role Of The Epidermis Re-Examined

1985 ◽  
Vol 117 (1) ◽  
pp. 155-169 ◽  
Author(s):  
J. MACHIN ◽  
G. J. LAMPERT ◽  
M. J. O'DONNELL
Keyword(s):  
In Vitro Techniques ◽  
Linear Relationships ◽  
Before And After ◽  
Pressure Lowering ◽  
First Time ◽  
Water Contents

Improved in vivo and in vitro techniques for measuring cuticular water permeability are described. Air flowing over a cuticle disc mounted in a holder, permitted elimination of unstirred layers, or corrections for them, for the first time. Conditions inside the holder were incompatible with the long-term health of the epidermal cells. Significantly, mean permeabilities of these discs did not differ from values obtained in vivo on the same cuticular plate. Overall cuticular permeability was apportioned between endocuticle and combined epicuticle and exocuticle on the basis of measurements made before and after solvent extraction of lipids. Under identical activity gradients, endocuticle permeability was 35 to 40 times greater than the value for the other layer. Permeability of both component layers showed strongly non-linear relationships with ambient activity, with empirical proportionality to the reciprocal of vapour pressure lowering. Cuticle water contents measured in activity gradient conditions showed significantly higher values in vivo than in vitro. The amount of water contained in the combined epicuticle and exocuticle was too small to measure. We conclude that neither permeability nor water content data support the existence of a significant water barrier in the region of the epidermis.

The Role of Polyphenols in the Modulation of Plasma Non-Enzymatic Antioxidant Capacity (NEAC)

2012 ◽  
Vol 82 (3) ◽  
pp. 228-232 ◽  
Author(s):  
Mauro Serafini ◽  
Giuseppa Morabito
Keyword(s):  
Antioxidant Capacity ◽  
Dietary Intervention ◽  
Ex Vivo ◽  
The Body ◽  
Dietary Polyphenols ◽  
Enzymatic Antioxidant ◽  
Endogenous Antioxidant

Dietary polyphenols have been shown to scavenge free radicals, modulating cellular redox transcription factors in different in vitro and ex vivo models. Dietary intervention studies have shown that consumption of plant foods modulates plasma Non-Enzymatic Antioxidant Capacity (NEAC), a biomarker of the endogenous antioxidant network, in human subjects. However, the identification of the molecules responsible for this effect are yet to be obtained and evidences of an antioxidant in vivo action of polyphenols are conflicting. There is a clear discrepancy between polyphenols (PP) concentration in body fluids and the extent of increase of plasma NEAC. The low degree of absorption and the extensive metabolism of PP within the body have raised questions about their contribution to the endogenous antioxidant network. This work will discuss the role of polyphenols from galenic preparation, food extracts, and selected dietary sources as modulators of plasma NEAC in humans.

Anti-obesity role of Aster glehni extract: in vivo and in vitro effects

Planta Medica ◽  
2012 ◽  
Vol 78 (11) ◽  
Author(s):  
HM Lee ◽  
TG Ahn ◽  
CW Kim ◽  
HJ An
Keyword(s):  
In Vitro Effects

A Molecular Approach to Immunoscintigraphy: A Study of the T-Antigen Conformation on the Surface of Tumors

1987 ◽  
Vol 26 (01) ◽  
pp. 1-6 ◽  
Author(s):  
S. Selvaraj ◽  
M. R. Suresh ◽  
G. McLean ◽  
D. Willans ◽  
C. Turner ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Tumor Cell ◽  
T Antigen ◽  
Human Carcinomas ◽  
Animal Tumor ◽  
Synthetic Antigens

The role of glycoconjugates in tumor cell differentiation has been well documented. We have examined the expression of the two anomers of the Thomsen-Friedenreich antigen on the surface of human, canine and murine tumor cell membranes both in vitro and in vivo. This has been accomplished through the synthesis of the disaccharide terminal residues in both a and ß configuration. Both entities were used to generate murine monoclonal antibodies which recognized the carbohydrate determinants. The determination of fine specificities of these antibodies was effected by means of cellular uptake, immunohistopathology and immunoscintigraphy. Examination of pathological specimens of human and canine tumor tissue indicated that the expressed antigen was in the β configuration. More than 89% of all human carcinomas tested expressed the antigen in the above anomeric form. The combination of synthetic antigens and monoclonal antibodies raised specifically against them provide us with invaluable tools for the study of tumor marker expression in humans and their respective animal tumor models.

THYROID STIMULATORS AND THYROID STIMULATION

1971 ◽  
Vol 66 (3) ◽  
pp. 558-576 ◽  
Author(s):  
Gerald Burke
Keyword(s):  
Regulatory System ◽  
Control Site ◽  
Thyroid Cell ◽  
Primary Control ◽  
Physico Chemical ◽  
Site Of Action ◽  
Long Acting

ABSTRACT A long-acting thyroid stimulator (LATS), distinct from pituitary thyrotrophin (TSH), is found in the serum of some patients with Graves' disease. Despite the marked physico-chemical and immunologic differences between the two stimulators, both in vivo and in vitro studies indicate that LATS and TSH act on the same thyroidal site(s) and that such stimulation does not require penetration of the thyroid cell. Although resorption of colloid and secretion of thyroid hormone are early responses to both TSH and LATS, available evidence reveals no basic metabolic pathway which must be activated by these hormones in order for iodination reactions to occur. Cyclic 3′, 5′-AMP appears to mediate TSH and LATS effects on iodination reactions but the role of this compound in activating thyroidal intermediary metabolism is less clear. Based on the evidence reviewed herein, it is suggested that the primary site of action of thyroid stimulators is at the cell membrane and that beyond the(se) primary control site(s), there exists a multifaceted regulatory system for thyroid hormonogenesis and cell growth.

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