scholarly journals The role of the inositol phosphate cascade in visual excitation of invertebrate microvillar photoreceptors.

1991 ◽  
Vol 97 (4) ◽  
pp. 697-723 ◽  
Author(s):  
T M Frank ◽  
A Fein
Keyword(s):  
Calcium Release ◽  
Inositol Phosphate ◽  
Light Response ◽  
Parallel Process ◽  
Visual Transduction ◽  
Direct Role ◽  
Transient Component ◽  
Calcium Buffer ◽  
Inositol 1,4,5 Trisphosphate

The identity of the transmitter(s) involved in visual transduction in invertebrate microvillar photoreceptors remains unresolved. In this study, the role of inositol 1,4,5-trisphosphate (IP3) was examined in Limulus ventral photoreceptors by studying the effects on the light response of heparin and neomycin, agents that inhibit the production or action of IP3. Both heparin and neomycin reduce responses to brief flashes of light and the transient component of responses to steps of light, and also inhibit IP3-induced calcium release, indicating that IP3 plays a direct role in invertebrate visual excitation. The effects of BAPTA, a calcium buffer, were also examined and shown to be consistent with a role for IP3-mediated calcium release in visual excitation. However, all three agents fail to block the plateau component of the response to a step of light, indicating that a single pathway involving IP3 and calcium cannot solely be responsible for visual excitation in invertebrates. We suggest that the inositol phosphate cascade and a second parallel process that is not dependent on IP3 are involved in the production of the light response.

scholarly journals Inositol 1,4,5-trisphosphate–induced Calcium Release Is Necessary for Generating the Entire Light Response of Limulus Ventral Photoreceptors

2003 ◽  
Vol 121 (5) ◽  
pp. 441-449 ◽  
Author(s):  
Alan Fein
Keyword(s):  
Calcium Release ◽  
Cyclopiazonic Acid ◽  
Light Response ◽  
Calcium Stores ◽  
Ip3 Receptor ◽  
Treatment Results ◽  
Light Responses ◽  
Calcium Buffer ◽  
Pressure Injection ◽  
Inositol 1,4,5 Trisphosphate

The experiments reported here were designed to answer the question of whether inositol 1,4,5-trisphosphate (IP3)-induced calcium release is necessary for generating the entire light response of Limulus ventral photoreceptors. For this purpose the membrane-permeable IP3 receptor antagonist 2-aminoethoxydiphenyl borate (2APB) (Maruyama, T., T. Kanaji, S. Nakade, T. Kanno, and K. Mikoshiba. 1997. J. Biochem. (Tokyo). 122:498–505) was used. Previously, 2APB was found to inhibit the light activated current of Limulus ventral photoreceptors and reversibly inhibit both light and IP3 induced calcium release as well as the current activated by pressure injection of calcium into the light sensitive lobe of the photoreceptor (Wang, Y., M. Deshpande, and R. Payne. 2002. Cell Calcium. 32:209). In this study 2APB was found to inhibit the response to a flash of light at all light intensities and to inhibit the entire light response to a step of light, that is, both the initial transient and the steady-state components of the response to a step of light were inhibited. The light response in cells injected with the calcium buffer 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) was reversibly inhibited by 2APB, indicating that these light responses result from IP3-mediated calcium release giving rise to an increase in Cai. The light response obtained from cells after treatment with 100 μM cyclopiazonic acid (CPA), which acts to empty intracellular calcium stores, was reversibly inhibited by 2APB, indicating that the light response after CPA treatment results from IP3-mediated calcium release and a consequent rise in Cai. Together these findings imply that IP3-induced calcium release is necessary for generating the entire light response of Limulus ventral photoreceptors.

scholarly journals Inositol 1,4,5-Trisphosphate Receptors in Human Disease: A Comprehensive Update

2020 ◽  
Vol 9 (4) ◽  
pp. 1096
Author(s):  
Jessica Gambardella ◽  
Angela Lombardi ◽  
Marco Bruno Morelli ◽  
John Ferrara ◽  
Gaetano Santulli
Keyword(s):  
Human Disease ◽  
Calcium Release ◽  
Current Knowledge ◽  
Association Studies ◽  
Genome Wide Association Studies ◽  
Loss Of Function ◽  
Genome Wide ◽  
Inositol 1,4,5 Trisphosphate ◽  
Human Disorders

Inositol 1,4,5-trisphosphate receptors (ITPRs) are intracellular calcium release channels located on the endoplasmic reticulum of virtually every cell. Herein, we are reporting an updated systematic summary of the current knowledge on the functional role of ITPRs in human disorders. Specifically, we are describing the involvement of its loss-of-function and gain-of-function mutations in the pathogenesis of neurological, immunological, cardiovascular, and neoplastic human disease. Recent results from genome-wide association studies are also discussed.

scholarly journals Role of the Phospholipase C-Inositol 1,4,5-Trisphosphate Pathway in Calcium Release-activated Calcium Current and Capacitative Calcium Entry

2001 ◽  
Vol 276 (19) ◽  
pp. 15945-15952 ◽  
Author(s):  
Lisa M. Broad ◽  
Franz-Josef Braun ◽  
Jean-Philippe Lievremont ◽  
Gary St. J. Bird ◽  
Tomohiro Kurosaki ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Calcium Current ◽  
Calcium Release ◽  
Calcium Entry ◽  
Capacitative Calcium Entry ◽  
Inositol 1,4,5 Trisphosphate

Electrically Elicited Neurosecretory and Electrical Responses of the Isolated Crab Sinus Gland in Normal and Reduced Calcium Salines

1977 ◽  
Vol 70 (1) ◽  
pp. 125-149
Author(s):  
IAN M. COOKE ◽  
BEVERLEY A. HAYLETT ◽  
TINA M. WEATHERBY
Keyword(s):  
Calcium Release ◽  
Electrical Response ◽  
Compound Action Potential ◽  
Hormone Release ◽  
Sinus Gland ◽  
Direct Role ◽  
Unstimulated Control ◽  
Neurohaemal Organ ◽  
Electrical Responses

The sinus gland (a neurohaemal organ) and its nerve have been isolated from the eyestalk of the crabs Cardisoma carnifex and Portunus sanguinolentus for studies correlating electrical responses recorded extra-cellularly from the sinus gland with hormone release. The appearance of erythrophore concentrating hormone (ECH) in the perfusate was followed by bioassay on leg segments of Ocypode pallidula. Electrical stimulation of the sinus gland nerve (175 pulses in trains of 5 at 5/s, every 10 s) results in significant amounts of hormone appearing in the perfusate, provided that a propagated compound action potential is recorded from the sinus gland. Release is normally below assayable levels in equivalent unstimulated control periods. A single preparation will release in excess of the equivalent of 20 pg of synthetic ECH in response to the standard routine of 175 stimuli. Many such secretory responses can be obtained over periods extending to as long as 30 h. Addition of tetrodotoxin (3 × 10-7 M) rapidly abolishes propagated electrical responses and secretion; the effects are reversible. Perfusion with saline having 30% (7.5 mM) of normal (25 mM) calcium reduces hormone release to about 10%, while the electrical response is often augmented. In 10% normal calcium, release is further decreased, and in 1% is indistinguishable from unstimulated release; electrical responses are reduced. Reduced calcium salines also induce spontaneous unit potentials, which persist in 30% calcium saline but subside after 10 min or longer exposure to salines of lower calcium concentration. All the effects of reduced calcium salines are reversible. Inhibition of secretion without reduction of electrical responses in 30% calcium saline provides evidence for a direct role of calcium in excitationsecretion coupling. In salines that are more calcium deficient, failure of terminal electrical responses may also contribute to reduction of secretion. In the crab sinus gland, as in other neurosecretory systems, propagation of action potentials to the terminals causes hormone release for which the presence of external calcium is essential.

scholarly journals The Association of Human Herpesviruses with Malignant Brain Tumor Pathology and Therapy: Two Sides of a Coin

2021 ◽  
Vol 22 (5) ◽  
pp. 2250
Author(s):  
Evita Athanasiou ◽  
Antonios N. Gargalionis ◽  
Fotini Boufidou ◽  
Athanassios Tsakris
Keyword(s):  
Brain Tumor ◽  
Brain Tumors ◽  
Comprehensive Evaluation ◽  
Tumor Development ◽  
Scientific Data ◽  
Malignant Brain Tumor ◽  
Direct Role ◽  
Tumor Pathology ◽  
Human Herpesviruses

The role of certain viruses in malignant brain tumor development remains controversial. Experimental data demonstrate that human herpesviruses (HHVs), particularly cytomegalovirus (CMV), Epstein–Barr virus (EBV) and human herpes virus 6 (HHV-6), are implicated in brain tumor pathology, although their direct role has not yet been proven. CMV is present in most gliomas and medulloblastomas and is known to facilitate oncomodulation and/or immunomodulation, thus promoting cancer cell proliferation, invasion, apoptosis, angiogenesis, and immunosuppression. EBV and HHV-6 have also been detected in brain tumors and high-grade gliomas, showing high rates of expression and an inflammatory potential. On the other hand, due to the neurotropic nature of HHVs, novel studies have highlighted the engagement of such viruses in the development of new immunotherapeutic approaches in the context of oncolytic viral treatment and vaccine-based strategies against brain tumors. This review provides a comprehensive evaluation of recent scientific data concerning the emerging dual role of HHVs in malignant brain pathology, either as potential causative agents or as immunotherapeutic tools in the fight against these devastating diseases.

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