Publications by authors named "Olga Larina"

6 Publications

  • Page 1 of 1

Scintigraphy false-positive results for cardiac amyloidosis in a patient with Danon disease.

Clin Case Rep 2021 Aug 16;9(8):e04652. Epub 2021 Aug 16.

Sechenov University Moscow Russia.

Common diagnostic approach in patients with suspected cardiac amyloidosis includes cardiac magnetic resonance imaging and scintigraphy. We report the first clinical case of false-positive results of scintigraphy in a patient with Danon disease.
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http://dx.doi.org/10.1002/ccr3.4652DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8365861PMC
August 2021

Differential sensitivity of brainstem versus cortical astrocytes to changes in pH reveals functional regional specialization of astroglia.

J Neurosci 2013 Jan;33(2):435-41

Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, United Kingdom.

Astrocytes might function as brain interoceptors capable of detecting different (chemo)sensory modalities and transmitting sensory information to the relevant neural networks controlling vital functions. For example, astrocytes that reside near the ventral surface of the brainstem (central respiratory chemosensitive area) respond to physiological decreases in pH with vigorous elevations in intracellular Ca(2+) and release of ATP. ATP transmits astroglial excitation to the brainstem respiratory network and contributes to adaptive changes in lung ventilation. Here we show that in terms of pH-sensitivity, ventral brainstem astrocytes are clearly distinct from astrocytes residing in the cerebral cortex. We monitored vesicular fusion in cultured rat brainstem astrocytes using total internal reflection fluorescence microscopy and found that ∼35% of them respond to acidification with an increased rate of exocytosis of ATP-containing vesicular compartments. These fusion events require intracellular Ca(2+) signaling and are independent of autocrine ATP actions. In contrast, the rate of vesicular fusion in cultured cortical astrocytes is not affected by changes in pH. Compared to cortical astrocytes, ventral brainstem astrocytes display higher levels of expression of genes encoding proteins associated with ATP vesicular transport and fusion, including vesicle-associated membrane protein-3 and vesicular nucleotide transporter. These results suggest that astrocytes residing in different parts of the rat brain are functionally specialized. In contrast to cortical astrocytes, astrocytes of the brainstem chemosensitive area(s) possess signaling properties that are functionally relevant-they are able to sense changes in pH and respond to acidification with enhanced vesicular release of ATP.
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http://dx.doi.org/10.1523/JNEUROSCI.2813-12.2013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3690976PMC
January 2013

Dynamic regulation of the large exocytotic fusion pore in pancreatic acinar cells.

Mol Biol Cell 2007 Sep 27;18(9):3502-11. Epub 2007 Jun 27.

Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD, United Kingdom.

Loss of granule content during exocytosis requires the opening of a fusion pore between the secretory granule and plasma membrane. In a variety of secretory cells, this fusion pore has now been shown to subsequently close. However, it is still unclear how pore closure is physiologically regulated and contentious as to how closure relates to granule content loss. Here, we examine the behavior of the fusion pore during zymogen granule exocytosis in pancreatic acinar cells. By using entry of high-molecular-weight dyes from the extracellular solution into the granule lumen, we show that the fusion pore has a diameter of 29-55 nm. We further show that by 5 min after granule fusion, many granules have a closed fusion pore with evidence indicating that pore closure is a prelude to endocytosis and that in granules with a closed fusion pore the chymotrypsinogen content is low. Finally, we show that latrunculin B treatment promotes pore closure, suggesting F-actin affects pore dynamics. Together, our data do not support the classical view in acinar cells that exocytosis ends with granule collapse. Instead, for many granules the fusion pore closes, probably as a transition to endocytosis, and likely involving an F-actin-dependent mechanism.
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http://dx.doi.org/10.1091/mbc.e07-01-0024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1951744PMC
September 2007

Ca2+ dynamics in salivary acinar cells: distinct morphology of the acinar lumen underlies near-synchronous global Ca2+ responses.

J Cell Sci 2005 Sep 23;118(Pt 18):4131-9. Epub 2005 Aug 23.

Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.

In salivary acinar cells, the pattern of the Ca2+ signals that regulates fluid and enzyme secretion has yet to be resolved, as there are conflicting reports in the literature. We have used a two-photon technique to directly visualize the acinar cell lumen in living fragments of exocrine tissue and simultaneously recorded agonist-induced changes in intracellular Ca2+. We show near-synchronous global Ca2+ responses in submandibular acinar cells, distinct from the typical apical to basal Ca2+ wave usually seen in rodent pancreatic acinar cells. In an effort to explain the basis of these near-synchronous global Ca2+ responses we used immunocytochemical experiments to localize luminal proteins and inositol trisphosphate receptors (InsP3Rs) in tissue fragments. Zona occludens 1 (ZO-1), a tight junction protein, shows that individual submandibular acinar cells are often nearly completely encircled by a narrow luminal structure. By contrast, in pancreatic fragments, ZO-1 staining shows short luminal branches terminating abruptly at the apical pole of single acinar cells. Co-immunostaining of InsP3Rs type 2 and type 3 showed them in the same region as ZO-1 in both exocrine tissues. Functional experiments showed that the near-synchronous global Ca2+ responses were still observed in the absence of extracellular Ca2+ and also in the presence of ryanodine. We conclude that the elaborate luminal region of submandibular cells leads to a hitherto unrecognized extensive distribution of InsP3Rs in a band around the cell and that this underlies the near-synchronous global Ca2+ response to agonists. We suggest that this may be a structural adaptation in submandibular cells to support the copious amounts of fluid secreted.
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http://dx.doi.org/10.1242/jcs.02533DOI Listing
September 2005

Syncollin is required for efficient zymogen granule exocytosis.

Biochem J 2005 Feb;385(Pt 3):721-7

Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.

Syncollin is a 13 kDa protein that is present in the exocrine pancreas, where the majority of the protein is tightly attached to the luminal surface of the zymogen granule membrane. We have addressed the physiological role of syncollin by studying the phenotype of syncollin KO (knockout) mice. These mice show pancreatic hypertrophy and elevated pancreatic amylase levels. Further, secretagogue-stimulated amylase release from pancreatic lobules of syncollin KO mice was found to be reduced by about 45% compared with wild-type lobules, and the delivery of newly synthesized protein to zymogen granules was delayed, indicating that the mice have a pancreatic secretory defect. As determined by two-photon imaging, the number of secretagogue-stimulated exocytotic events in acini from syncollin KO mice was reduced by 50%. This reduction was accounted for predominantly by a loss of later, 'secondary' fusion events between zymogen granules and other granules that had already fused with the plasma membrane. We conclude that syncollin is required for efficient exocytosis in the pancreatic acinar cell, and that it plays a particularly important role in compound exocytosis.
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http://dx.doi.org/10.1042/BJ20041064DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1134747PMC
February 2005
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