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At least 19 recordsLinked to original sources

PubMed1979

Neurotransmitter receptors on gill muscle fibers and the gill peripheral nerve plexus in Aplysia.

Isolated pinnules of the gill of Aplysia contract when dopamine (DA) is perfused through the bath. The contraction is not blocked by high-Mg2+ seawater, and reflects excitatory receptors for DA on the smooth muscle cells of the gill. The pinnule often shows irregular, spontaneous contractions which are blocked by high-Mg2+ seawater and 30 mM CoCl2. These contractions reflect spontaneous activity of a peripheral nerve plexus. No other transmitter was found to be directly excitatory on the muscle fibers, although there are inhibitory receptors for serotonin (5-HT). Tactile stimulation of the pinnule evoked a two-component contractile reflex contraction due to activation of the peripheral nerve plexus. Acetylcholine, octopamine, and 5-HT but not several other transmitters depressed these responses, presumably due to inhibitory receptors on the neurons of the peripheral plexus.

Animals↗

PubMed2026

Proteobacteria with chemosynthetic potential are highly prevalent in the gills of Hypoplectrus reef fishes.

Fishes host a diverse microbiome in their gills, but a broad characterization of this microbiome at the metagenomic level is lacking. Here, we apply genome-resolved metagenomics to the gills of the hamlets (Hypoplectrus spp), a group of reef fishes from the Greater Caribbean. The analysis of 353 gill samples from 15 hamlet species collected at eight locations over 13 years revealed a stark contrast between the gill microbiota and reef water microbial communities, indicating a distinct and specific gill microbiome. A total of 70 gill-associated metagenome-assembled genomes (MAGs) were recovered. These MAGs belong to 17 lineages, most of which are novel. They relate to known fish gill pathogens, fish gut microbes, free-living and biofilm-associated taxa, indicating that the gill microbiome was assembled from a collection of distinct eco-evolutionary trajectories. The MAGs harbor diverse metabolic modules, involved notably in nitrogen cycling, antibiotic production and biofilm formation, revealing a highly dynamic microbial ecosystem. One lineage in the Burkholderiaceae family was outstandingly prevalent across fish host species, sampling locations and years. Its genome encoded complete metabolic modules for carbon fixation and sulfur oxidation, indicating chemosynthetic potential. To the best of our knowledge, this is the first line of evidence that fishes may host sulfur-oxidizing chemosynthetic bacteria in their gills. The functional significance of this chemosynthetic potential for the fish host or other members of the gill microbiome remains to be established. The high prevalence of this lineage allowed to build a pangenome. It revealed large-scale geographic structure (western Caribbean, eastern Caribbean and Gulf of Mexico), which parallels the phylogenomic pattern observed in the hamlets. Overall, our findings point to complex fish host-microbe and microbe-microbe eco-evolutionary interactions in the gills that may influence fish physiology, homeostasis and immune response.

Animals↗

PubMed1979

L9 modulation of L7's elicited gill withdrawal response in Aplysia.

The effects of induced L9 activity on gill motor neuron L7's ability to elicit a gill withdrawal response were studied. It was found that L9 was a modulator of L7's effectiveness to elicit gill movements. Following L9 activity, L7's ability to elicit a gill withdrawal response was significantly potentiated by up to 240% of control. L9 activity potentiated L7's elicited gill withdrawal response when frequencies of L7 activity were used which would result in decrement of the response or when frequencies were used in which decrement does not occur. Induced L9 activity may also have a minor potentiating effect on LDG1's ability to elicit gill movements. L9 was the only neuron found to possess these modulatory abilities. The interposition of the activity in the other gill motor neurons failed to have any effect. L9's modulatory role is separate and independent from its role as a gill motor neuron. L9's modulation of L7 is mediated peripherally in the gill and not in the CNS.

Animals↗

PubMed2026

Comparative transcriptomic analysis of the gills and hepatopancreas of freshwater-cultured Litopenaeus vannamei under chronic nitrite stress.

To investigate the differences in molecular responses between the gills and hepatopancreas of freshwater-cultured Litopenaeus vannamei under chronic nitrite stress, a 30-day chronic stress experiment was conducted with a control group and a stress group. Transcriptomic analysis of the gills and hepatopancreas was performed using Illumina sequencing; differentially expressed genes (DEGs) were identified, and GO, KEGG, GSEA, PPI, and RT-qPCR validation were carried out. The results showed that 196 DEGs (161 up-regulated and 35 down-regulated) were identified in the gills, and 287 DEGs (199 up-regulated and 88 down-regulated) in the hepatopancreas, with only 18 DEGs shared between the two tissues. DEGs in the gills were enriched in oxidoreductase activity, glycerophospholipid metabolism, and tyrosine metabolism; DEGs in the hepatopancreas were enriched in lipid transporter activity, phagosome, ECM-receptor interaction, and riboflavin metabolism. GSEA revealed significant suppression of the mTOR pathway in the gills and the Polycomb complex pathway in the hepatopancreas. PPI network analysis identified hub genes P5CS and eEF2 in the gills, and PER, TUBB1, SHMT, and TUBB4B in the hepatopancreas. RT-qPCR validation was consistent with the RNA-seq results (R2 = 0.764). This study indicates that, under chronic nitrite stress, the gill response is centered on redox regulation and inhibition of growth metabolism, whereas the hepatopancreas response primarily involves lipid transport, cytoskeletal remodeling, and phagosome activation. The two tissues synergistically adapt through fundamental biosynthetic and motor protein pathways. This research provides molecular evidence for deciphering the nitrite tolerance mechanisms in freshwater-cultured shrimp.

Animals↗

PubMed1977

CNS control of the PNS-mediated gill withdrawal reflex and its habituation.

Removal of the branchial (Br) nerve input to the gill significantly reduced the latency and increased the amplitude of the gill withdrawal reflex evoked by siphon stimulation. Further, after Br removal repeated siphon stimulation which previously resulted in habituation now resulted in facilitation of the flex. However, the synaptic input to gill motor neurons in the abdominal ganglion continued to decrement as before. In preparations without the peripheral nervous system (PNS), removal of Br did not produce similar results. The gill withdrawal reflex and its habituation are mediated by the PNS, but the CNS exerts facilitatory and suppressive control. Thus, changes in synaptic efficacy to gill motor neurons in the abdominal ganglion are not the ultimate cause of gill reflex habituation. Habituation is the result of adaptive neural processes which occur together in the abdominal ganglion, the PNS, and the peripheral terminations of the central motor pathways to the gill. Therefore, in any analysis of the underlying neural mechanisms of habituation all these loci must be included and taken into account.

Animals↗

PubMed2026

Low-salinity stress alters growth, histology, physiology, and transcriptomic profiles of the gills and antennal glands in Macrobrachium rosenbergii.

Salinity is a major abiotic constraint in freshwater aquaculture of the giant freshwater prawn Macrobrachium rosenbergii, yet the coordinated roles of the gills and antennal glands, the two primary osmoregulatory organs in decapod crustaceans, under low-salinity stress remain poorly characterized. Here, we integrated histological, physiological, and transcriptomic analyses to characterize the adaptive responses of M. rosenbergii to acute (96 h) and chronic (8 weeks) exposure to salinity 5. Chronic low-salinity stress significantly impaired growth performance and decreased the survival rate. Acute stress induced thinning of the gill filaments, partial disorganization of pillar cells, and dilation of the intermicrovillar space in the antennal glands, whereas chronic stress caused gill vacuolization, cuticle thinning, and adaptive folding of antennal gland microvilli. In parallel, acute exposure significantly decreased hemolymph sodium and potassium ion concentrations but increased magnesium ion concentration, whereas chronic exposure increased hemolymph sodium and potassium ion concentrations, upregulated gill Na+/K+-ATPase activity, and enhanced hepatopancreatic antioxidant capacity. Transcriptomic analyses revealed distinct tissue-specific responses. Under acute stress, the gills preferentially activated pathways associated with cytoskeletal remodeling, motor proteins, and tight junctions, whereas chronic acclimation shifted the transcriptional response toward the renin-angiotensin system and glutathione metabolism. In the antennal glands, acute stress rapidly activated the renin secretion pathway, whereas chronic exposure promoted membrane remodeling by enriching pathways related to lipid and glycan metabolism. These findings reveal tissue-specific functional differentiation and synergistic coordination between the gills and antennal glands that underpin M. rosenbergii's adaptive response to low-salinity stress.

Animals↗

PubMed2026

Integrated physiological and transcriptomic analyses reveal coordinated gill responses to heat stress in pikeperch (Sander lucioperca).

Climate change-driven warming of aquatic environments has made thermal stress an increasingly important factor influencing fish physiological homeostasis. Given their central roles in respiration and osmoregulation, gills are particularly responsive to variations in ambient temperature. Histological examination, physiological measurements, and transcriptome profiling were integrated to investigate the mechanisms associated with heat stress-induced gill injury in pikeperch (Sander lucioperca). Histological analysis revealed that exposure to 29 °C directly caused structural damage to the gills of pikeperch. Oxidative status was evaluated by measuring malondialdehyde (MDA) levels and the activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). MDA accumulation was significantly enhanced under heat stress, while antioxidant enzyme activities (SOD, POD, and CAT) displayed a transient increase followed by a subsequent decline. Transcriptome profiling showed marked enrichment of the protein processing in endoplasmic reticulum pathway after heat stress, suggesting activation of endoplasmic reticulum (ER) stress in pikeperch gills. With increasing stress duration, the unfolded protein response (UPR) appeared unable to re-establish ER homeostasis, shifting ire1 and atf6 toward a pro-apoptotic state. Protein-protein interaction (PPI) analysis further highlighted hub genes potentially involved in heat stress-induced ER stress and apoptosis. TUNEL staining and western blotting collectively confirmed that heat stress triggered apoptosis in pikeperch gill tissue. Overall, this study provides new insights into the physiological and molecular responses of pikeperch gills to heat stress and enhances our understanding of thermal stress adaptation in cold-water aquaculture species under climate change.

Animals↗

PubMed2026

Chemoproteomics Prioritizes Mitochondrial ADP/ATP Translocase as a Candidate Target Associated with 6PPDQ-Induced Respiratory Toxicity in Rainbow Trout Gill.

6PPD quinone (6PPDQ) is an emerging contaminant that induces acute respiratory toxicity in rainbow trout (Oncorhynchus mykiss), yet its underlying molecular mechanisms remain poorly understood. In the present study, short-term in vivo exposure of rainbow trout to 6PPDQ resulted in substantial accumulation and limited biotransformation of 6PPDQ in the gill, accompanied by pronounced gill structural damage and increased whole-fish oxygen consumption. Taking advantage of the electrophilic reactivity of the quinone moiety of 6PPDQ toward cysteine residues, we applied activity-based protein profiling (ABPP) to gill tissue. ABPP revealed marked alterations in mitochondrial cysteine reactivity and highlighted ADP/ATP translocase (ANT) as a candidate 6PPDQ-interacting mitochondrial protein. A Cys-160-containing ANT peptide within the nucleotide-binding domain of ANT was pinpointed as the covalent binding site through ABPP, Peptide-centric Local Stability Assay (PELSA), and molecular docking. Functional assays using isolated gill mitochondria showed that 6PPDQ elicited an uncoupling-like mitochondrial respiratory response that was partially attenuated by the ANT inhibitor carboxyatractyloside (CATR), supporting the functional involvement of ANT in this gill-based model. Together, these findings nominate ANT as a candidate gill mitochondrial target associated with 6PPDQ-induced acute respiratory toxicity and demonstrate the utility of chemoproteomics for prioritizing mechanistically relevant protein interactions of emerging pollutants.

Animals↗

PubMed1979

L9 modulation of gill withdrawal reflex habituation in Aplysia.

Repeated tactile stimulation of the siphon in Aphysia normally results in habituation of the gill withdrawal reflex and a concomitant decrease in the amplitude of the excitatory synaptic input ot gill motor neurons in the abdominal ganglion. It was found, however, that induced low-level tonic activity in motor neuron L9, which does not itself elicit a gill withdrawal movement, prevented habituation of the reflex from occurring. Further, in preparations already habituated, this tonic low-level activity brought about a reversal of habituation. Although tonic L9 activity prevented the occurrence of habituation or brought about its reversal, it did not interfere with the synaptic decremental process which normally accompanies gill reflex habituation. Motor neurons L7 and LDG1 were found not to possess this ability of L9 to modulate gill reflex habituation. Evidence suggests that L9's modulatory effect is mediated in the periphery, in the gill and not centrally in the abdominal ganglion.

Animals↗

PubMed1979

Hydrogen shuttles in gills of water versus air breathing osteoglossids.

1. Using subcellular preparations of gills from Arapaima, an obligate air breather, and aruana, a related osteoglossid that is an obligate water breather, a comparison was made of the relative roles of the malate-aspartate cycle and the alpha-glycerophosphate (alpha-GP) cycle in transferring reducing equivalents from the cytosol to the mitochondria. 2. In aruana gill preparations, the alpha-GP cycle could be most clearly demonstrated by reconstructing it with purified isolated mitochondria, using the oxidation rate of exogenous NADH as a measure of the cycling activity. 3. Subcellular preparations of Arapaima gill, in contrast to the aruana gill, were not responsive to exogenous alpha-glycerophosphate, but a glutamate-malate stimulated O2 uptake was sensitive to aminooxyacetate, an aminotransferase inhibitor, a result that would be expected if the respiration were based on malate-aspartate cycling. 4. It was concluded that, compared to the alpha-glycerophosphate cycle, the malate-aspartate cycle was relatively more active in Arapaima gill than in aruana gill, and possible implications were discussed.

Air↗

PubMed1976

Teleost chloride cell. I. Response of pupfish Cyprinodon variegatus gill Na,K-ATPase and chloride cell fine structure to various high salinity environments.

Certain euryhaline teleosts can tolerate media of very high salinity, i.e. greater than that of seawater itself. The osmotic gradient across the integument of these fish is very high and the key to their survival appears to be the enhanced ability of the gill to excrete excess NaCl. These fish provide an opportunity to study morphological and biochemical aspects of transepithelial salt secretion under conditions of vastly different transport rates. Since the cellular site of gill salt excretion is believed to be the "chloride cell" of the branchial epithelium and since the enzyme Na,K-ATPase has been implicated in salt transport in this and other secretory tissues, we have focused our attention on the differences in chloride cell structure and gill ATPase activity in the variegated pupfish Cyprinodon variegatus adapted to half-strength seawater (50% SW), seawater (100% SW), or double-stregth seawater (200% SW). The Na,K-ATPase activity in gill homogenates was 1.6 times greater in 100% SW. When 50% SW gills were compared to 100% SW gills, differences in chloride cell morphology were minimal. However, chloride cells from 200% SW displayed a marked hypertrophy and a striking increase in basal-lateral cell surface area. These results suggest that there are correlations among higher levels of osmotic stress, basal-lateral extensions of the cell surface, and the activity of the enzyme Na,K-ATPase.

Adenosine Triphosphatases↗

PubMed1979

Non-electrolyte permeability of trout gills: effect of temperature and adrenaline.

1. The gill permeability to various non-electrolytes (P(s)) was measured in fresh-water and sea-water adapted trout (Salmo gairdneri). This study was performed in vitro using a ;head-perfused' preparation. The influence of temperature and adrenaline (10(-6)M) on permeability to non-electrolytes was also investigated.2. During salt adaptation P(butanol) and P(water) decrease, P(mannitol) rises and P(dextran) stays constant. In view of recently acquired morphological data these results back up the hypothesis of different pathways across the gill epithelium (transcellular, vesicular and paracellular) according to the physico-chemical characteristics of the molecules. The low selectivity of the gill epithelium as a function of the liposolubility of the molecules used testifies to the hydrophilic nature of diffusion across this epithelium, a feature becoming more pronounced during salt adaptation.3. The activation energies are about 4 kcal/mol, an energy comparable to diffusion in water for most of the substances tested, exceptions being butanol for fresh-water adapted gills and water for fresh-water and sea-water adapted gills. Arrhenius plots for butanol in fresh water gills show a transition temperature at 15 degrees C, suggesting an increased membrane lipid fluidity above this temperature.4. Adrenaline has no effect on P(mannitol) and P(dextran), but increases P(butanol) and P(water) selectively according to the adaptation medium (+ 160% and + 100% in fresh water and + 25% and + 20% in sea water respectively). These results point to an effect of this catecholamine on the membrane lipid fluidity.

Animals↗

PubMed1978

Stimulus-response relations and stability of mechanoreceptor and motor neurons mediating defensive gill-withdrawal reflex in Aplysia.

1. A weak or moderate-intensity tactile stimulus delivered to the siphon skin of Aplysia californica elicits a defensive reflex withdrawal of the gill and siphon into the mantle cavity. The reflex undergoes both short- and long-term habituation and sensitization and has, therefore, been used as a model system to examine various forms of learning. In this paper we describe studies of the response properties of the sensory and motor neurons of the reflex during repeated stimulation at rates that produce habituation. 2. The sensory neurons are slowly adapting mechanoreceptor cells whose frequency of discharge is a monotonic function of controlled-force punctate stimuli delivered to the skin. The majority of the stimulus-response relations could best be described by exponential functions. 3. We examined the stability of the sensory neuron responses in two ways; with punctate stimuli of varying intensity and with water jets of varying intensity. 4. With repeated punctate stimulation at rates which produce habituation in the intact animal the mechanoreceptor discharge showed no decrement. This stability was observed over a 10-fold range of intensities. 5. Weak or moderate intensity water-jet stimuli to the skin also gave stable responses but stronger stimuli caused the mechanoreceptor response to fatigue. 6. We examined the stability of the motor responses by using intracellular depolarizing current pulses to produce repetitive bursts of action potentials in gill motor neurons while monitoring the gill contractions with a strain gauge, photocell, or videotape recorder. The photocell and strain gauge were alternatively used in the same experiment. Gill contractions monitored with the photocell were stable, whereas those monitored by the strain gauge showed decrement. An independent measure of gill contraction, videotape recording, confirmed the results obtained with the photocell and showed that the gill contractions following repeated intracellular depolarization of the motor neurons were stable.

Action Potentials↗

PubMed1977

Microtubules in the "chloride cell" of the gill and disruptive effects of colchicine on the salt balance of the sea water adapted Mugil capito.

Electron-microscopic examination of the gill of the grey mullet, Mugil capito adapted to sea water, reveals the presence of numerous microtubules in the apical region of the mitochondria-rich cells. No microtubules are found in other types of epithelial cell. Exposure of the fish to colchicine (10(-4)M) for four hours induces a 20% increase of plasma Na and Cl. Colchicine leaves the water permeability of the gill unchanged but Cl and Na exchange fluxes are inhibited by 30-50% and the gill potential pattern is altered. Salt gain replaces salt excretion across the gill. The K dependent Na and Cl efflux components, independent of the gill potential shift produced by K, are totally inhibited by colchicine. Exposure to lumicolchicine is not followed by a significant change of these Na and Cl efflux-components and potential pattern. The possibility that microtubules intervene in the salt excretion process across the chloride cells is discussed.

Adaptation, Physiological↗

PubMed1977

Ouabain inhibition of gill Na-K-ATPase: relationship to active chloride transport.

Ouabain circulating in blood inhibits Na-K-ATPase in the gills of seawater eels at a concentration similar to that necessary for inhibition in vitro. By contrast, a much higher concentration is required when ouabain is applied to the exterior of the gill. Inhibition by external ouabain occurs only when the drug gains access to the circulation of the fish, as evidenced by simultaneous inhibition of Na-K-ATPase in the kidney. These results suggest that the Na-K-ATPase of gill chloride cells faces inward, lining intracytoplasmic tubular channels continuous with the extracellular fluid. Inhibition of gill Na-K-ATPase by ouabain in intact salt water eels results in almost complete inhibition of the efflux of both Na+ and Cl-. The efflux is tritiated water was much less reduced, to 60% of normal. Since chloride is actively transported outward across the gill of seawater teleosts, it is suggested that active chloride transport is coupled to Na-K-ATPase. A neutral sodium chloride carrier is postulated that is energized by the movement of sodium from extracellular fluid down its electrochemical gradient into the chloride cell.

Adenosine Triphosphatases↗

PubMed1977

Changes in the levels of chloride cells and (Na+ + K+)-dependent ATPase in the gills of yellow and silver eels adapting to seawater.

Changes were measured in the numbers of chloride cells and the levels of (Na+ + K+)-DEPENDENT ATPase in the gills of immature, yellow eels and mature, silver eels during adaptation from freshwater to seawater. The percentage of chloride cells in yellow eels more than doubled after six days in seawater; at this time the specific activity and concentration of (Na+ + K+)-dependent ATPase in gills start to increase in parallel to reach maxima after two weeks that are 2.5 times the starting values. It is concluded that adaptation of yellow eels to seawater involves an increase in the numbers of chloride cells in gills as well as an increased amount of (Na+ + K+)-dependent ATPase per chloride cell. Mature silver eels in freshwater had essentially the same numbers of chloride cells and the same specific activity of the enzyme in the gills as yellow eels fully adapted to seawater. Transferring silver eels to seawater did not alter the percentage of chloride cells in gills although the level of (Na+ + K+)-dependent ATPase and its specific activity increased slightly. Thus, although the silver eel is better prepared for life in seawater than the yellow eel, it still has to attain an increased level of (Na+ + K+)-dependent ATPase in its chloride cells to be fully adapted to seawater.

Adaptation, Physiological↗

PubMed1979

Accumulation of cadmium and lead in the gills of Mytilus edulis: X-ray microanalysis and chemical analysis.

The accumulation of Cd and Pb in the gills of the lamellibranch mollusc Mytilus edulis has been studied by electron microscopy, X-ray microanalysis, atomic absorption spectroscopy and radionuclide monitoring. The patterns of accumulation of the two elements differ markedly as do the sites of deposition whithin the gills. Lead is found extracellularly as crystalline deposits in the basal lamina which forms the capillary walls of the gill lamellae. The Pb is found associated with Ca in equiatomic ratios and occurs either as a mixed or complex carbonate. Cadmium is always associated with S and frequently with P in membrane bound vesicles within the cells of the gill epithelium and in the amoebocytes. The S is probably attributable to the presence of cysteine residues in a metal binding protein which can be extracted from the gills. Analysis of the metal binding protein shows that it binds Ag, Cd, Cu, Fe, Hg, Sn and Zn. Its amino acid composition is similar to that reported for eels and limpets but has a lower cysteine content than mammalian metal binding protein.

Amino Acids↗

PubMed1976

Teleost chloride cell. II. Autoradiographic localization of gill Na,K-ATPase in killifish Fundulus heteroclitus adapted to low and high salinity environments.

The specific binding and inhibitory action of (3H)ouabain were employed to localize transport Na,K-ATPase in the euryhaline teleost gill, a NaCl-transporting osmoregulatory tissue in which both enzyme activity and transepithelial transport vary with environmental salinity. In killifish fully adapted to 10%, 100%, or 200% seawater, the gills were internally perfused and externally irrigated in situ. After suitable internal or external exposure to (3H)ouabain, individual gill arches were excised for Na,K-ATPase assay, measurement of radiolabel binding, or quantitative high-resolution autoradiography. Internal exposure to 50 muM ouabain resulted in essentially complete enzyme inhibition, and binding paralleled the increases in enzyme activity at higher salinities; in contrast, external exposure gave minimal and erratic results consistent with leakage of external ouabain into interstitial fluid. (3H)Ouabain autoradiographs demonstrated that, irrespective of exposure or salinity, most of the gill binding was associated with chloride cell. These cells increased in size and number with salinity and, at the subcellular level, the distribution pattern for bound ouabain was always identical to that for the amplified basal-lateral (tubular system) membrane. The combined physiologicmorphologic results constitute final direct proof that chloride cells are the primary site of gill Na,K-ATPase. More important, they provide convincing evidence for unexpected increases in basal-lateral enzyme at higher salinities and thus raise a fundamental objection to the long-postulated role of the Na pump in secretory NaCl transport.

Adenosine Triphosphatases↗