scholarly journals Role of internal convection in respiratory gas transfer and aerobic metabolism in larval zebrafish (Danio rerio)

2019 ◽  
Vol 316 (3) ◽  
pp. R255-R264 ◽  
Author(s):  
Malcolm C. Hughes ◽  
Alex M. Zimmer ◽  
Steve F. Perry
Keyword(s):  
Danio Rerio ◽  
Troponin T ◽  
High Surface ◽  
Volume Ratio ◽  
Aerobic Metabolism ◽  
Whole Body ◽  
Gas Transfer ◽  
Larval Zebrafish ◽  
Respiratory Gases ◽  
Internal Convection

Purely diffusive O2 transport typically is insufficient to sustain aerobic metabolism in most multicellular organisms. In animals that are small enough, however, a high surface-to-volume ratio may allow passive diffusion alone to supply sufficient O2 transfer. The purpose of this study was to explore the impacts of internal convection on respiratory gas transfer in a small complex organism, the larval zebrafish ( Danio rerio). Specifically, we tested the hypothesis that internal convection is required for the normal transfer of the respiratory gases O2 and CO2 and maintenance of resting aerobic metabolic rate in larvae at 4 days postfertilization (dpf). Morpholino knockdown of the vascular endothelial growth factor (VEGF) or cardiac troponin T (TNNT2) proteins allowed an examination of gas transfer in two independent models lacking internal convection. With the use of a scanning micro-optrode technique to measure regional epithelial O2 fluxes ( Jo2), it was demonstrated that larvae lacking convection exhibited reduced Jo2 in regions spanning the head to the trunk. Moreover, the acute loss of internal convection caused by heart stoppage resulted in reduced rates of cutaneous Jo2, an effect that was reversed upon the restoration of internal convection. With the use of whole body respirometry, it was shown that loss of internal convection was associated with reduced resting rates of O2 consumption and CO2 excretion in larvae at 4 dpf. The results of these experiments clearly demonstrate that internal convection is required to maintain resting rates of respiratory gas transfer in larval zebrafish.

scholarly journals Respirometry and cutaneous oxygen flux measurements reveal a negligible aerobic cost of ion regulation in larval zebrafish (Danio rerio)

2020 ◽  
Vol 223 (18) ◽  
pp. jeb226753
Author(s):  
Julian J. Parker ◽  
Alex M. Zimmer ◽  
Steve F. Perry
Keyword(s):  
Danio Rerio ◽  
Oxygen Flux ◽  
Whole Body ◽  
Uptake Capacity ◽  
Ion Regulation ◽  
Larval Zebrafish ◽  
Morpholino Knockdown ◽  
Rearing Conditions ◽  
Flux Measurements ◽  
Energy Consuming

ABSTRACTFishes living in fresh water counter the passive loss of salts by actively absorbing ions through specialized cells termed ionocytes. Ionocytes contain ATP-dependent transporters and are enriched with mitochondria; therefore ionic regulation is an energy-consuming process. The purpose of this study was to assess the aerobic costs of ion transport in larval zebrafish (Danio rerio). We hypothesized that changes in rates of Na+ uptake evoked by acidic or low Na+ rearing conditions would result in corresponding changes in whole-body oxygen consumption (ṀO2) and/or cutaneous oxygen flux (JO2), measured at the ionocyte-expressing yolk sac epithelium using the scanning micro-optrode technique (SMOT). Larvae at 4 days post-fertilization (dpf) that were reared under low pH (pH 4) conditions exhibited a higher rate of Na+ uptake compared with fish reared under control conditions (pH 7.6), yet they displayed a lower ṀO2 and no difference in cutaneous JO2. Despite a higher Na+ uptake capacity in larvae reared under low Na+ conditions, there were no differences in ṀO2 and JO2 at 4 dpf. Furthermore, although Na+ uptake was nearly abolished in 2 dpf larvae lacking ionocytes after morpholino knockdown of the ionocyte proliferation regulating transcription factor foxi3a, ṀO2 and JO2 were unaffected. Finally, laser ablation of ionocytes did not affect cutaneous JO2. Thus, we conclude that the aerobic costs of ion uptake by ionocytes in larval zebrafish, at least in the case of Na+, are below detection using whole-body respirometry or cutaneous SMOT scans, providing evidence that ion regulation in zebrafish larvae incurs a low aerobic cost.

scholarly journals Angiotensin-II promotes Na+ uptake in larval zebrafish, Danio rerio, in acidic and ion-poor water

2013 ◽  
Vol 220 (3) ◽  
pp. 195-205 ◽  
Author(s):  
Yusuke Kumai ◽  
Nicholas J Bernier ◽  
Steve F Perry
Keyword(s):  
Angiotensin Ii ◽  
Danio Rerio ◽  
Glucocorticoid Receptors ◽  
Enzyme Inhibitor ◽  
Renin Angiotensin System ◽  
Whole Body ◽  
Ang Ii ◽  
Larval Zebrafish ◽  
Rapid Activation ◽  
Stimulation Of

The contribution of the renin–angiotensin system (RAS) to Na+uptake was investigated in larval zebrafish (Danio rerio). At 4 days post fertilization (dpf), the level of whole-body angiotensin-II (ANG-II) was significantly increased after 1- or 3-h exposure to acidic (pH=4.0) or ion-poor water (20-fold dilution of Ottawa tapwater), suggesting rapid activation of the RAS. Long-term (24 h) treatment of 3 dpf larvae with ANG-I or ANG-II significantly increased Na+uptake which was accompanied by an increase in mRNA expression of the Na+-Cl−cotransporter (zslc12a10.2). Induction of Na+uptake by exposure to ANG-I was blocked by simultaneously treating larvae with lisinopril (an angiotensin-converting enzyme inhibitor). Acute (2 h) exposure to acidic water or ion-poor water led to significant increase in Na+uptake which was partially blocked by the ANG-II receptor antagonist, telmisartan. Consistent with these data, translational knockdown of renin prevented the stimulation of Na+uptake following exposure to acidic or ion-poor water. The lack of any effects of pharmacological inhibition (using RU486), or knockdown of glucocorticoid receptors on the stimulation of Na+uptake during acute exposure to acidic or ion-poor environments, indicates that the acute effects of RAS occur independently of cortisol signaling. The results of this study demonstrate that the RAS is involved in Na+homeostasis in larval zebrafish.

scholarly journals Involvement of the calcium-sensing receptor in calcium homeostasis in larval zebrafish exposed to low environmental calcium

2014 ◽  
Vol 306 (4) ◽  
pp. R211-R221 ◽  
Author(s):  
Raymond W. M. Kwong ◽  
Dan Auprix ◽  
Steve F. Perry
Keyword(s):  
In Situ Hybridization ◽  
Confocal Microscopy ◽  
Mrna Expression ◽  
Danio Rerio ◽  
Whole Body ◽  
Calcium Sensing Receptor ◽  
Larval Zebrafish ◽  
Calcium Sensing ◽  
Normal Water

The involvement of the calcium-sensing receptor (CaSR) in Ca2+ homeostasis was investigated in larval zebrafish, Danio rerio. The expression of CaSR mRNA was first observed at 3 h posfertilization (hpf) and increased with development until plateauing at ∼48 hpf. At 4 dpf, CaSR mRNA was increased in fish acclimated to low Ca2+ water (25 μM vs. 250 μM in normal water). Using immunohistochemistry and confocal microscopy, we demonstrated that the CaSR is expressed in the olfactory epithelium, neuromasts, ionocytes on the yolk sac epithelium, and corpuscles of Stannius. Results of double immunohistochemistry and/or in situ hybridization indicated that the CaSR is localized to a subset of mitochondrion-rich ionocytes enriched with Na+/K+-ATPase and epithelial Ca2+ channel ( ecac). Translational knockdown of the CaSR prevented 4 dpf larvae from regulating whole body Ca2+ levels when exposed to a low Ca2+ environment. Further, the increases in ecac mRNA expression and Ca2+ influx, normally associated with exposure to low-Ca2+ water, were prevented by CaSR knockdown. These findings demonstrate that larval zebrafish lacking the CaSR lose their ability to regulate Ca2+ when confronted with a low-Ca2+ environment. Results from real-time PCR suggested that the mRNA expression of the hypocalcemic hormone stanniocalcin ( stc-1) remained elevated in the CaSR morphants following acclimation to low-Ca2+ water. Overall, the results suggest that the CaSR is critical for Ca2+ homeostasis in larval zebrafish exposed to low environmental Ca2+ levels, possibly owing to its modulation of stanniocalcin mRNA expression.

scholarly journals The tight junction protein claudin-b regulates epithelial permeability and sodium handling in larval zebrafish, Danio rerio

2013 ◽  
Vol 304 (7) ◽  
pp. R504-R513 ◽  
Author(s):  
Raymond W. M. Kwong ◽  
Steve F. Perry
Keyword(s):  
Tight Junction ◽  
Danio Rerio ◽  
Free Water ◽  
Yolk Sac ◽  
Tight Junction Protein ◽  
Whole Body ◽  
Epithelial Permeability ◽  
Pericardial Cavity ◽  
Larval Zebrafish ◽  
Junction Protein

The functional role of the tight junction protein claudin-b in larval zebrafish ( Danio rerio) was investigated. We showed that claudin-b protein is expressed at epithelial cell-cell contacts on the skin. Translational gene knockdown of claudin-b protein expression caused developmental defects, including edema in the pericardial cavity and yolk sac. Claudin-b morphants exhibited an increase in epithelial permeability to the paracellular marker polyethylene glycol (PEG-4000) and fluorescein isothiocyanate-dextran (FD-4). Accumulation of FD-4 was confined mainly to the yolk sac and pericardial cavity in the claudin-b morphants, suggesting these regions became particularly leaky in the absence of claudin-b expression. Additionally, Na+ efflux was substantially increased in the claudin-b morphants, which contributed to a significant reduction in whole-body Na+ levels. These results indicate that claudin-b normally acts as a paracellular barrier to Na+. Nevertheless, the elevated loss of Na+ in the morphants was compensated by an increase in Na+ uptake. Notably, we observed that the increased Na+ uptake in the morphants was attenuated in the presence of the selective Na+/Cl−-cotransporter (NCC) inhibitor metolazone, or during exposure to Cl−-free water. These results suggested that the increased Na+ uptake in the morphants was, at least in part, mediated by NCC. Furthermore, treatment with an H+-ATPase inhibitor bafilomycin A1 was found to reduce Na+ uptake in the morphants, suggesting that H+-ATPase activity was essential to provide a driving force for Na+ uptake. Overall, the results suggest that claudin-b plays an important role in regulating epithelial permeability and Na+ handling in zebrafish.

scholarly journals Electrospun Nanofibers for Sensing and Biosensing Applications—A Review

2021 ◽  
Vol 22 (12) ◽  
pp. 6357
Author(s):  
Kinga Halicka ◽  
Joanna Cabaj
Keyword(s):  
High Surface ◽  
High Surface Area ◽  
Toxic Metal ◽  
Volume Ratio ◽  
Electrospun Nanofibers ◽  
Clinical Diagnostics ◽  
Loading Capacity ◽  
Electrospun Nanofiber ◽  
Sensing Platforms ◽  
Different Types

Sensors and biosensors have found applications in many areas, e.g., in medicine and clinical diagnostics, or in environmental monitoring. To expand this field, nanotechnology has been employed in the construction of sensing platforms. Because of their properties, such as high surface area to volume ratio, nanofibers (NFs) have been studied and used to develop sensors with higher loading capacity, better sensitivity, and faster response time. They also allow to miniaturize designed platforms. One of the most commonly used techniques of the fabrication of NFs is electrospinning. Electrospun NFs can be used in different types of sensors and biosensors. This review presents recent studies concerning electrospun nanofiber-based electrochemical and optical sensing platforms for the detection of various medically and environmentally relevant compounds, including glucose, drugs, microorganisms, and toxic metal ions.

scholarly journals Study of the geometry of open channels in a layer-bed-type microfluidic immobilized enzyme reactor

2021 ◽  
Author(s):  
Cynthia Nagy ◽  
Robert Huszank ◽  
Attila Gaspar
Keyword(s):  
Immobilized Enzyme ◽  
High Surface ◽  
Volume Ratio ◽  
Volumetric Flow Rate ◽  
Enzyme Reactor ◽  
Channel Pattern ◽  
Immobilized Enzyme Reactor ◽  
Split Flow ◽  
Parallel Streams ◽  
Enzymatic Microreactors

AbstractThis paper aims at studying open channel geometries in a layer-bed-type immobilized enzyme reactor with computer-aided simulations. The main properties of these reactors are their simple channel pattern, simple immobilization procedure, regenerability, and disposability; all these features make these devices one of the simplest yet efficient enzymatic microreactors. The high surface-to-volume ratio of the reactor was achieved using narrow (25–75 μm wide) channels. The simulation demonstrated that curves support the mixing of solutions in the channel even in strong laminar flow conditions; thus, it is worth including several curves in the channel system. In the three different designs of microreactor proposed, the lengths of the channels were identical, but in two reactors, the liquid flow was split to 8 or 32 parallel streams at the inlet of the reactor. Despite their overall higher volumetric flow rate, the split-flow structures are advantageous due to the increased contact time. Saliva samples were used to test the efficiencies of the digestions in the microreactors. Graphical abstract

scholarly journals A Review on Biosensors and Recent Development of Nanostructured Materials-Enabled Biosensors

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1109
Author(s):  
Varnakavi. Naresh ◽  
Nohyun Lee
Keyword(s):  
High Surface ◽  
Three Dimensional ◽  
Biological Response ◽  
Volume Ratio ◽  
Recent Decade ◽  
Disease Diagnosis ◽  
Electrical Signal ◽  
Detection Sensitivity ◽  
Wide Range ◽  
Color Tunability

A biosensor is an integrated receptor-transducer device, which can convert a biological response into an electrical signal. The design and development of biosensors have taken a center stage for researchers or scientists in the recent decade owing to the wide range of biosensor applications, such as health care and disease diagnosis, environmental monitoring, water and food quality monitoring, and drug delivery. The main challenges involved in the biosensor progress are (i) the efficient capturing of biorecognition signals and the transformation of these signals into electrochemical, electrical, optical, gravimetric, or acoustic signals (transduction process), (ii) enhancing transducer performance i.e., increasing sensitivity, shorter response time, reproducibility, and low detection limits even to detect individual molecules, and (iii) miniaturization of the biosensing devices using micro-and nano-fabrication technologies. Those challenges can be met through the integration of sensing technology with nanomaterials, which range from zero- to three-dimensional, possessing a high surface-to-volume ratio, good conductivities, shock-bearing abilities, and color tunability. Nanomaterials (NMs) employed in the fabrication and nanobiosensors include nanoparticles (NPs) (high stability and high carrier capacity), nanowires (NWs) and nanorods (NRs) (capable of high detection sensitivity), carbon nanotubes (CNTs) (large surface area, high electrical and thermal conductivity), and quantum dots (QDs) (color tunability). Furthermore, these nanomaterials can themselves act as transduction elements. This review summarizes the evolution of biosensors, the types of biosensors based on their receptors, transducers, and modern approaches employed in biosensors using nanomaterials such as NPs (e.g., noble metal NPs and metal oxide NPs), NWs, NRs, CNTs, QDs, and dendrimers and their recent advancement in biosensing technology with the expansion of nanotechnology.

scholarly journals Water uptake of various electrospun nonwovens

2020 ◽  
Vol 6 (3) ◽  
pp. 155-158
Author(s):  
Katharina Wulf ◽  
Volkmar Senz ◽  
Thomas Eickner ◽  
Sabine Illner
Keyword(s):  
Contact Angle ◽  
Surface Modification ◽  
Water Absorption ◽  
Water Uptake ◽  
Biomedical Applications ◽  
High Surface ◽  
Volume Ratio ◽  
Polymer Composition ◽  
Water Wetting ◽  
Morphology Changes

AbstractIn recent years, nanofiber based materials have emerged as especially interesting for several biomedical applications, regarding their high surface to volume ratio. Due to the superficial nano- and microstructuring and the different wettability compared to nonstructured surfaces, the water absorption is an important parameter with respect to the degradation stability, thermomechanic properties and drug release properties, depending on the type of polymer [1]. In this investigation, the water absorption of different non- and plasma modified biostable nanofiber nonwovens based on polyurethane, polyester and polyamide were analysed and compared. Also, the water absorption by specified water wetting, the contact angle and morphology changes were examined. The results show that the water uptake is highly dependent on the surface modification and the polymer composition itself and can therefore be partially changed.

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