SHIBR—The Swedish Historical Birth Records: a semi-annotated dataset

This paper presents a digital image dataset of historical handwritten birth records stored in the archives of several parishes across Sweden, together with the corresponding metadata that supports the evaluation of document analysis algorithms’ performance. The dataset is called SHIBR (the Swedish Historical Birth Records). The contribution of this paper is twofold. First, we believe it is the first and the largest Swedish dataset of its kind provided as open access (15,000 high-resolution colour images of the era between 1800 and 1840). We also perform some data mining of the dataset to uncover some statistics and facts that might be of interest and use to genealogists. Second, we provide a comprehensive survey of contemporary datasets in the field that are open to the public along with a compact review of word spotting techniques. The word transcription file contains 17 columns of information pertaining to each image (e.g., child’s first name, birth date, date of baptism, father's first/last name, mother’s first/last name, death records, town, job title of the father/mother, etc.). Moreover, we evaluate some deep learning models, pre-trained on two other renowned datasets, for word spotting in SHIBR. However, our dataset proved challenging due to the unique handwriting style. Therefore, the dataset could also be used for competitions dedicated to a large set of document analysis problems, including word spotting.

Effect of anoxia on the electroretinogram of three anoxia-tolerant vertebrates

To survive anoxia, neural ATP levels have to be defended. Reducing electrical activity, which accounts for 50% or more of neural energy consumption, should be beneficial for anoxic survival. The retina is a hypoxia sensitive part of the central nervous system. Here, we quantify the in vivo retinal light response (electroretinogram; ERG) in three vertebrates that exhibit varying degrees of anoxia tolerance: freshwater turtle (Trachemys scripta), epaulette shark (Hemiscyllium ocellatum) and leopard frog (Rana pipiens). A virtually total suppression of ERG in anoxia, probably resulting in functional blindness, has previously been seen in the extremely anoxia-tolerant crucian carp (Carassius carassius). Surprisingly, the equally anoxia-tolerant turtle, which strongly depresses brain and whole-body metabolism during anoxia, exhibited a relatively modest anoxic reduction in ERG: the combined amplitude of turtle ERG waves was reduced by approximately 50% after 2 h. In contrast, the shark b-wave amplitude practically disappeared after 30 min of severe hypoxia, and the frog b-wave was decreased by approximately 75% after 40 min in anoxia. The specific A(1) adenosine receptor antagonist CPT significantly delayed the suppression of turtle ERG, while the hypoxic shark ERG was unaffected by the non-specific adenosine receptor antagonist aminophylline, suggesting adenosinergic involvement in turtle but not in shark.

Late onset of NMDA receptor-mediated ventilatory control during early development in zebrafish (Danio rerio)

Increased ventilation frequency (fV) in response to hypoxia in adult fish depends on ionotropic N-methyl-D-aspartate (NMDA) receptors. Nonetheless, the ontogeny of central control mechanisms mediating hypoxic ventilatory chemoreflexes in lower vertebrates has not been studied. Therefore, the aim of this study was to determine when the hypoxic ventilatory response during zebrafish (Danio rerio) development is mediated via NMDA receptors, by performing physiological experiments and western blot analysis of NMDA receptor subunits. Zebrafish larvae at stages 4-16 days post-fertilisation (dpf) were exposed to an hypoxic pulse in control groups and in groups treated with MK801 (NMDA receptor antagonist). The hypoxic increase in fV was present at all larval stages, and it matured during development. The reflex became MK801 sensitive at 8 dpf, but did not completely rely on a glutamatergic transmission until 13 dpf. This, together with changing subunit composition during the different stages (increasing amounts of NMDAR1 subunits and appearance of NMDAR2A subunits in adults), suggests that the amount of functional NMDA receptors needed to achieve a fully developed reflex is not attained until later stages. Furthermore, our results suggest that other non-NMDA receptor mechanisms are responsible for the hypoxia-induced increase in fV during the earlier developmental stages.

Endothelin receptors in teleost fishes: cardiovascular effects and branchial distribution

By observing gill blood flow using epi-illuminating microscopy, in parallel with cardiovascular recordings and immunohistochemistry, we have tried to identify the receptor mediating endothelin (ET) type 1 (ET1)-induced pillar cell contraction in the lamellae of the Atlantic cod ( Gadus morhua). Intra-arterial injection of the specific ETBreceptor agonist BQ-3020 induced dose-dependent increases in ventral aortic blood pressure, gill vascular resistance, and pillar cell area (indicating contraction). The specific ETAreceptor antagonist BQ-610 did not prevent either pillar cell contraction or increased gill vascular resistance induced by ET-1 injection. The cardiovascular responses were corroborated by the detection of ETBreceptor-like immunoreactivity (IR) associated with pillar cells in the lamellar region and in neuroendocrine cells. ETBreceptor-like IR was also found lining the muscle layer of lamellar arterioles and filament arteries. In contrast, strong ETAreceptor-like IR was found on branchial nerves throughout the filaments. In addition, ET-like IR was concentrated in neuroendocrine cells in the filament and lamellae. We also present data suggesting that ET-mediated pillar cell contraction is widespread among teleost fish, including Atlantic cod, rainbow trout ( Oncorhynchus mykiss), sculpin ( Myoxocephalus scorpius), and mackerel ( Scomber scombrus). Taken together, our results suggest that an ETB-like receptor mediates pillar cell contraction in fishes, whereas ETA-like receptors may serve another function in the gill, inasmuch as ETAreceptor-like IR is found on branchial nerves.

Organisational factors, individual characteristics and social support: what determines the level of social support?

A large body of research has linked social support to health, but there are fewer studies that have focused on factors that influence the level of social support available and/or perceived by employees in different organisations. This cross-sectional study therefore investigated the relationship between on the one hand, organisational, individual and socio-demographic factors and on the other, the level of social support at the workplace, i.e., the degree of supervisor support and a supportive work atmosphere. Organisational variables (job demands, job control, job content), individual (self-esteem, mistrust) and socio-demographic variables (type of employer, occupational position, age, gender and educational level) were used as independent variables in the analyses. The sample consisted of 16,144 individuals at a variety of different organisations in Sweden, who had responded to a questionnaire covering different psychosocial and psychological stress factors ("the Stress Profile"). Multiple hierarchical regression analyses were performed separately for each of the two dependent variables, which yielded almost identical results, and indicated that organisational determinants, particularly perceived job control, had the largest impact on the degree of social support.

Adenosinergic and cholinergic control mechanisms during hypoxia in the epaulette shark (Hemiscyllium ocellatum), with emphasis on branchial circulation

Coral reef platforms may become hypoxic at night during low tide. One animal in that habitat, the epaulette shark (Hemiscyllium ocellatum), survives hours of severe hypoxia and at least one hour of anoxia. Here, we examine the branchial effects of severe hypoxia (<0.3 mg oxygen l(-1) for 20 min in anaesthetized epaulette shark), by measuring ventral and dorsal aortic blood pressure (P(VA) and P(DA)), heart rate (fh), and observing gill microcirculation using epi-illumination microscopy. Hypoxia induced a flow of blood in two parallel blood vessels, termed longitudinal vessels, in the outer borders of the free tip of the gill filament. Hypoxia also induced significant falls in fh, P(VA) and P(DA), and a biphasic change in ventilation frequency (increase followed by decrease). Adenosine injection (1 micromol kg(-1)) also initiated blood flow in the longitudinal vessels, in addition to significant drops in P(VA), P(DA) and fh, and a biphasic response in ventilation frequency (decrease followed by increase) indicating that adenosine influences ventilation. Aminophylline (10 mg kg(-1)), an A(1) and A(2) adenosine receptor antagonist, blocked the effects of adenosine injection, and also significantly reduced blood flow in the longitudinal vessels during hypoxia. In the second part of the study, we examined the cholinergic influence on the cardiovascular circulation during severe hypoxia (<0.3 mg l(-1)) using antagonists against muscarinic (atropine 2 mg kg(-1)) and nicotinic (tubocurarine 5 mg kg(-1)) receptors. Injection of acetylcholine (ACh; 1 micromol kg(-1)) into the ventral aorta caused a marked fall in fh, a large increase in P(VA), but small changes in P(DA) (suggesting increased R(gill)). Atropine was able to inhibit the branchial vascular responses to ACh but not the hypoxic bradycardia, suggesting the presence of muscarinic receptors on the heart and gill vasculature, and that the hypoxia induced bradycardia is of non-cholinergic origin. The results suggest that adenosine mediates increases in the arterio-venous circulation in the gill during hypoxia. This may serve to increase blood supply to heart and gill tissue.

Pulsatile urea excretion in the gulf toadfish: mechanisms and controls

Opsanus beta expresses a full complement of ornithine-urea cycle (OUC) enzymes and is facultatively ureotelic, reducing ammonia-N excretion and maintaining urea-N excretion under conditions of crowding/confinement. The switch to ureotelism is keyed by a modest rise in cortisol associated with a substantial increase in cytosolic glutamine synthetase for trapping of ammonia-N and an upregulation of the capacity of the mitochondrial OUC to use glutamine-N. The entire day's urea-N production is excreted in 1 or 2 short-lasting pulses, which occur exclusively through the gills. The pulse event is not triggered by an internal urea-N threshold, is not due to pulsatile urea-N production, but reflects pulsatile activation of a specific branchial excretion mechanism that rapidly clears urea-N from the body fluids. A bidirectional facilitated diffusion transporter, with pharmacological similarity to the UT-A type transporters of the mammalian kidney, is activated in the gills, associated with an increased trafficking of dense-cored vesicles in the pavement cells. An 1814 kB cDNA ('tUT') coding for a 475-amino acid protein with approximately 62% homology to mammalian UT-A's has been cloned and facilitates phloretin-sensitive urea transport when expressed in Xenopus oocytes. tUT occurs only in gill tissue, but tUT mRNA levels do not change over the pulse cycle, suggesting that tUT regulation occurs at a level beyond mRNA. Circulating cortisol levels consistently decline prior to a pulse event and rise thereafter. When cortisol is experimentally clamped at high levels, natural pulse events are suppressed in size but not in frequency, an effect mediated through glucocorticoid receptors. The cortisol decline appears to be permissive, rather than the actual trigger of the pulse event. Fluctuations in circulating AVT levels do not correlate with pulses; and injections of AVT (at supraphysiological levels) elicit only minute urea-N pulses. However, circulating 5-hydroxytryptamine (5-HT) levels fluctuate considerably and physiological doses of 5-HT cause large urea-N pulse events. When the efferent cranial nerves to the gills are sectioned, natural urea pulse events persist, suggesting that direct motor output from the CNS to the gill is not the proximate control.

Identification of central mechanisms vital for breathing in the channel catfish, Ictalurus punctatus

To investigate central respiratory control mechanisms in channel catfish, microinjections of kainic acid (causing chemical lesion of neurons) or kynurenic acid (an antagonist of N-methyl-D-aspartate (NMDA), kainate and alpha-amino-3-OH-5-methyl-4-isooxazole-propionic-acid (AMPA) receptors) were made into the general visceral nucleus (nGV) of the medulla in anaesthetised spontaneously breathing animals. Kainic acid abolished the ventilatory movements, indicating that neurons in the nGV are crucial for maintaining normal breathing. Kynurenic acid did not affect normal breathing, but abolished the ventilatory responses to hypoxia, showing that ionotropic glutamate receptors in the nGV are vital for the production of oxygen chemoreceptor activated respiratory reflexes. In addition, immunohistochemistry of brain slices showed that interneurons and nerve fibres in the nGV display NMDA-immunoreactivity, which corroborates the physiological experiments. The results of this study suggest that neurons and glutamatergic pathways in the nGV are essential for ventilatory functions and hypoxic reflexes in channel catfish.

Effects of afferent input on the breathing pattern continuum in the tambaqui (Colossoma macropomum)

This study used a decerebrate and artificially-ventilated preparation to examine the roles of various afferent inputs in breathing pattern formation in the tambaqui (Colossoma macropomum). Three general breathing patterns were observed: (1) regular breathing; (2) frequency cycling and (3) episodic breathing. Under normoxic, normocapnic conditions, 50% of control fish exhibited regular continuous breathing and 50% exhibited frequency cycling. Denervation of the gills and oro-branchial cavity promoted frequency cycling. Central denervation of the glossopharyngeal and vagus nerves produced episodic breathing. Regardless of the denervation state, hyperoxia produced either frequency cycling or episodic breathing while hypoxia and hypercarbia shifted the pattern to frequency cycling and continuous breathing. We suggest that these breathing patterns represent a continuum from continuous to episodic breathing with waxing and waning occupying an intermediate stage. The data further suggest that breathing pattern is influenced by both specific afferent input from chemoreceptors and generalised afferent input while chemoreceptors specific for producing changes in breathing pattern may exist in fish.

N-methyl-D-aspartate receptors mediate chemoreflexes in the shorthorn sculpin Myoxocephalus scorpius

Glutamate microinjected into the vagal sensory area in the medulla produces cardiorespiratory responses mimicking oxygen chemoreflexes in fish. Here we directly investigate whether these reflexes are dependent on the ionotropic N-methyl-D-aspartate (NMDA) glutamate receptor. Fish were equipped with opercular, branchial and snout cannulae for measurements of cardiorespiratory parameters and drug injections. Oxygen chemoreceptor reflexes were evoked by rapid hypoxia, NaCN added into the blood (internal, 0.3 ml, 50 microg ml(-1)) and the mouth (external, 0.5 ml, 1 mg ml(-1)), before and after systemic administration of the NMDA receptor antagonist MK801 (3 mg kg(-1)). Hypoxia produced an MK801-sensitive increase in blood pressure and ventilation frequency, whereas the marked bradycardia and the increased ventilation amplitude were NMDA receptor-independent. The fish appeared more responsive to externally applied cyanide, but the injections and MK801 treatment did not distinguish whether external or internal oxygen receptors were differently involved in the hypoxic responses. In addition, using single-labelling immunohistochemistry on sections from the medulla and ganglion nodosum, the presence of glutamate and NMDA receptors in the vagal oxygen chemoreceptor pathway was established. In conclusion, these results suggest that NMDA receptors are putative central control mechanisms that process oxygen chemoreceptor information in fish.

Evidence for glutamatergic mechanisms in the vagal sensory pathway initiating cardiorespiratory reflexes in the shorthorn sculpin Myoxocephalus scorpius

Glutamate is a major neurotransmitter of chemoreceptor and baroreceptor afferent pathways in mammals and therefore plays a central role in the development of cardiorespiratory reflexes. In fish, the gills are the major sites of these receptors, and, consequently, the terminal field (sensory area) of their afferents (glossopharyngus and vagus) in the medulla must be an important site for the integration of chemoreceptor and baroreceptor signals. This investigation explored whether fish have glutamatergic mechanisms in the vagal sensory area (Xs) that could be involved in the generation of cardiorespiratory reflexes. The locations of the vagal sensory and motor (Xm) areas in the medulla were established by the orthograde and retrograde axonal transport of the neural tract tracer Fast Blue following its injection into the ganglion nodosum. Glutamate was then microinjected into identified sites within the Xs in an attempt to mimic chemoreceptor- and baroreceptor-induced reflexes commonly observed in fish. By necessity, the brain injections were performed on anaesthetised animals that were fixed by 'eye bars' in a recirculating water system. Blood pressure and heart rate were measured using an arterial cannula positioned in the afferent branchial artery of the 3rd gill arch, and ventilation was measured by impedance probes sutured onto the operculum. Unilateral injection of glutamate (40-100 nl, 10 mmol l(-1)) into the Xs caused marked cardiorespiratory changes. Injection (0.1-0.3 mm deep) in different rostrocaudal, medial-lateral positions induced a bradycardia, either increased or decreased blood pressure, ventilation frequency and amplitude and, sometimes, an initial apnea. Often these responses occurred simultaneously in various different combinations but, occasionally, they appeared singly, suggesting specific projections into the Xs for each cardiorespiratory variable and local determination of the modality of the response. Response patterns related to chemoreceptor reflex activation were predominantly located rostral of obex, whereas patterns related to baroreceptor reflex activation were more caudal, around obex. The glutamate-induced bradycardia was N-methyl-D-aspartate (NMDA) receptor dependent and atropine sensitive. Taken together, our data provide evidence that glutamate is a putative player in the central integration of chemoreceptor and baroreceptor information in fish.

Branchial innervation

Inspection of the dorsal end of fish gills reveals an impressive set of nerve trunks, connecting the gills to the brain. These trunks are branches of cranial nerves VII (the facial) and especially IX (the glossopharyngeal) and X (the vagus). The nerve trunks carry a variety of nervous pathways to and from the gills. A substantial fraction of the nerves running in the branchial trunks carry afferent (sensory) information from receptors within the gills. There are also efferent (motor) pathways, which control muscles within the gills, blood flow patterns and possibly secretory functions. Undertaking a more careful survey of the gills, it becomes evident that the arrangement of the microanatomy (particularly the blood vessels) and its innervation are strikingly complex. The complexity not only reflects the many functions of the gills but also illustrates that the control of blood flow patterns in the gills is of crucial importance in modifying the efficiency of its chief functions: gas transfer and salt balance. The "respiratory-osmoregulatory compromise" is maintained by minimizing the blood/water exchange (functional surface area of the gills) to a level where excessive water loss (marine teleosts) or gain (freshwater teleosts) is kept low while ensuring sufficient gas exchange. This review describes the arrangement and mechanisms of known nervous pathways, both afferent and efferent, of fish (notably teleosts) gills. Emphasis is placed primarily on the autonomic nervous system and mechanisms of blood flow control, together with an outline of the afferent (sensory) pathways of the gill arches.

Cardiovascular effects of prostaglandin F(2 alpha) and prostaglandin E(2) in Atlantic cod (Gadus morhua)

Little is known of the cardiovascular functions of prostaglandins in non-mammalian vertebrates. There are indications that prostaglandins may have a function in haemostasis by constricting blood vessels in filament arteries in the fish gill after injury. Our aim was to examine the cardiovascular effect of the prostaglandins F(2 alpha) (PGF(2 alpha)) and E(2) (PGE(2)) with emphasis on branchial circulation. Intra-arterial injections of PGF(2 alpha) (10, 40, 160, 400 nmol kg(-1)) in cod caused a dose-dependent increase in ventral aortic blood pressure, a reduction in cardiac output, and an increase in gill vascular resistance. A contraction of filament arteries was observed with in vivo microscopy only seconds after injection. PGF(2 alpha) may therefore possibly be involved in a haemostatic vasoconstriction. In contrast, the most significant effects of PGE(2) appeared to be on the heart. PGE(2) also reduced dorsal aortic blood pressure.

Extrabranchial chemoreceptors involved in respiratory reflexes in the neotropical fishColossoma macropomum(the tambaqui)

In a previous study, complete denervation of the gills in the tambaqui Colossoma macropomum did not eliminate the increase in breathing amplitude seen during exposure of this species to hypoxia. The present study was designed to examine other sites of putative O2-sensitive receptors that could be involved in this reflex action. Superfusion of the exposed brain of decerebrate, spinalectomized fish did not reveal the presence of central chemoreceptors responsive to hyperoxic, hypoxic, hypercarbic,acidic or alkaline solutions. Subsequent central transection of cranial nerve IX and X, removing not only all innervation of the gills but also sensory input from the lateral-line, cardiac and visceral branches of the vagus nerve,did not eliminate the increase in breathing amplitude that remained following peripheral gill denervation alone. Administration of exogenous catecholamines(10 and 100 nmol kg-1 adrenaline) to fish with intact brains and minimal surgical preparation reduced both respiratory frequency and amplitude,suggesting that humoral release of adrenaline also could not be responsible for the increase in breathing amplitude that remained following gill denervation. Denervation of the mandibular branches of cranial nerve V and the opercular and palatine branches of cranial nerve VII in gill-denervated fish(either peripheral gill denervation or central section of cranial nerves IX and X), however, did eliminate the response. Thus, our data suggest that hypoxic and hyperoxic ventilatory responses as well as ventilatory responses to internal and external injections of NaCN in the tambaqui arise from O2-sensitive receptors in the orobranchial cavity innervated by cranial nerves V and VII and O2-sensitive receptors on the gills innervated by cranial nerves IX and X.

Our results also revealed the presence of receptors in the gills that account for all of the increase in ventilation amplitude and part of the increase in ventilation frequency during hyperoxic hypercarbia, a group or groups of receptors, which may be external to the orobranchial cavity (but not in the central nervous system), that contribute to the increase in ventilation frequency seen in response to hyperoxic hypercarbia and the possible presence of CO2-sensitive receptors that inhibit ventilation frequency,possibly in the olfactory epithelium.

Pulmonary receptors in reptiles: discharge patterns of receptor populations in snakes versus turtles

This study examines the effects of lung inflation/deflation with and without CO2 on the entire population of pulmonary receptors in the vagus nerve in two species of snakes and two species of turtles. We asked the question, "how does the response of the entire mixed population of pulmonary stretch receptors (PSR) and intrapulmonary chemoreceptors (IPC) in species possessing both differ from that in species with only PSR"? This was studied under conditions of artificial ventilation with the secondary goal of extending observations on the presence/absence of IPC to a further three species. Our results indirectly illustrate the presence of IPC in the Burmese python and South American rattlesnake but not the side necked turtle, adding support to the hypothesis that IPC first arose in diapsid reptiles. In both species of snake, CO2-sensitive discharge (presumably from IPC) predominated almost to the exclusion of CO2-insensitive discharge (presumably arising from PSR) while the opposite was true for both species of turtle. The data suggest that for animals breathing air under conditions of normal metabolism there is little to distinguish between the discharge profiles of the total population of receptors arising from the lungs in the different groups. Interestingly, however, under conditions of elevated environmental CO2 most volume-related feedback from the lungs is abolished in the two species of snakes, while under conditions of elevated metabolic CO2, it is estimated that volume feedback from the lungs would be enhanced in these same species.

Branchial and circulatory responses to serotonin and rapid ambient water acidification in rainbow trout

Although the branchial and cardiovascular effects of serotonin (5-hydroxytryptamine) have only partially been characterized, a physiological role for serotonin in the cardiorespiratory responses of fish to environmental changes such as reduced Ph has been suggested. Therefore, we have characterized and compared the effects of serotonin and a rapid reduction of Ph in the ambient water (from pH 8.8 to pH 4.0) on ventral and dorsal aortic blood pressures, heart rate, cardiac output, and arterial pH in rainbow trout, Onchorhynchus mykiss. In addition, the circulation in the branchial microvasculature was observed using in vivo epi-illumination microscopy. The fall in water Ph and injection of serotonin (100 nmol/kg) both increased the branchial resistance and reduced the efferent filamental artery (EFA) blood velocity. Nevertheless, quantitatively, the responses to the two stimuli were different. Although acid exposure caused a much more profound increase in branchial resistance compared with serotonin, the blood flow in the observable distal portion of the EFA was only reduced by 60% in acid water, while it stopped with serotonin. Regardless of the marked branchial resistance elevation, a constriction of the efferent filamental vasculature could not be seen during acid exposure, as occasionally was the case with serotonin. While methysergide completely abolished the serotonin-induced branchial events, it only modestly suppressed the acid-induced reduction of EFA blood velocity. In contrast, all of the systemic changes induced by serotonin and acidic water were insensitive to methysergide. In conclusion, acidic water and injected serotonin elevate the branchial resistance, but the involvement of a serotonergic component in the acidic response appears negligible.

Branchial receptors and cardiorespiratory reflexes in a neotropical fish, the tambaqui (Colossoma macropomum)

This study examined the location and physiological roles of branchial chemoreceptors involved in the cardiorespiratory responses to hypoxia and hypercarbia in a neotropical fish that exhibits aquatic surface respiration, the tambaqui (Colossoma macropomum). Fish were exposed to abrupt progressive environmental hypoxia (18. 6–1.3 kPa water P(O2)) and hypercarbia (water equilibrated with 5 % CO(2) in air, which lowered the water pH from 7.0 to 5.0). They were also subjected to injections of NaCN into the ventral aorta (to stimulate receptors monitoring the blood) and buccal cavity (to stimulate receptors monitoring the respiratory water). All tests were performed before and after selective denervation of branchial branches of cranial nerves IX and X to the gill arches. The data suggest that the O(2) receptors eliciting reflex bradycardia and increases in breathing frequency are situated on all gill arches and sense changes in both the blood and respiratory water and that the O(2) receptors triggering the elevation in systemic vascular resistance, breathing amplitude, swelling of the inferior lip and that induce aquatic surface respiration during hypoxia are extrabranchial, although branchial receptors also contribute to the latter two responses. Hypercarbia also produced bradycardia and increases in breathing frequency, as well as hypertension, and, while the data suggest that there may be receptors uniquely sensitive to changes in CO(2)/pH involved in cardiorespiratory control, this is based on quantitative rather than qualitative differences in receptor responses. These data reveal yet another novel combination for the distribution of cardiorespiratory chemoreceptors in fish from which teleologically satisfying trends have yet to emerge.

Cardiovascular and respiratory reflexes in the tropical fish, traira (Hoplias malabaricus): CO2/pH chemoresponses

To examine the distribution and physiological role of CO2/pH-sensitive chemoreceptors in the gills of the tropical fish, traira (Hoplias malabaricus), fish were exposed to acute environmental hypercarbia (1.25, 2.5 and 5.0% CO2 in air) and subjected to injections of HCl into the ventral aorta and buccal cavity. This was done before and after selective denervation of branchial branches of the IXth and Xth cranial nerves to various gills arches. Hypercarbia produced a significant decrease in heart rate, a mild hypotension as well as increases in both ventilation rate and ventilation amplitude. The data suggest that the hypercarbic bradycardia and increase in ventilation frequency arise from receptors exclusively within the gills but present on more than the first gill arch, while extra-branchial receptors may also be involved in controlling the increase in ventilation amplitude. With the exception of a decrease in heart rate in response to HCl injected into the ventral aorta, the acid injections (internal and external) did not mimic the cardiorespiratory responses observed during hypercarbia suggesting that changes in CO2 are more important than changes in pH in producing cardiorespiratory responses. Finally, the data indicate that chemoreceptors sensitive to CO2/pH and to O2 in the gills of this species involved in producing ventilatory responses are distributed in a similar fashion, but that those involved in producing the bradycardia are not.

Cardiovascular responses to adenosine in the antarctic fish pagothenia borchgrevinki

We have investigated the effects of adenosine on the cardiovascular system of the Antarctic fish Pagothenia borchgrevinki. Continuous measurements of ventral and dorsal aortic blood pressures, heart rate (fh) and ventral aortic blood flow (cardiac output, q_dot) were made using standard cannulation techniques and a single-crystal Doppler flowmeter. On line measurements of arterial P(O2) were made using an oxygen electrode connected to an extracorporeal loop. Adenosine (10 nmol kg(−)(1)) and the specific A(1)-receptor agonist N(6)-cyclopentyladenosine (CPA) elicited biphasic changes in the branchial and systemic resistances. While there was an initial decrease in the branchial resistance followed by an increase, the opposite was true for the systemic response. The resistance changes were significantly attenuated by aminophylline (a P(1)-receptor antagonist) and 8-cyclopentyltheophylline (CPT; an A(1)-receptor antagonist). In addition, adenosine induced an aminophylline-sensitive decrease in the arterial P(O2). The reduction was attenuated when pre-injection arterial P(O2) was low. Adenosine and CPA also caused a marked reduction in fh, with CPA being more potent. The bradycardia was blocked by aminophylline and CPT, demonstrating an involvement of A(1) receptors in this response.

Cardiovascular and gill microcirculatory effects of endothelin-1 in atlantic cod: evidence for pillar cell contraction

Endothelin-1 (ET-1) has been shown to cause a considerable increase in the vascular resistance of fish gills. In trout, recent evidence suggest that this is the result of pillar cell contraction in the gill lamellae. Using epi-illumination microscopy to observe the gill lamellae of anaesthetised Atlantic cod (Gadus morhua), we show that ET-1 (100 ng kg-1, injected into the ventral aorta) causes an increase in pillar cell diameter, consistent with pillar cell contraction, and a shift of intralamellar blood flow from the lamellar sheet to the outer marginal channels. Simultaneously, there was an increase in ventral aortic blood pressure, a reduction in cardiac output, an increase in gill vascular resistance and a reduction in the oxygen partial pressure of venous blood. All these effects were blocked by the ETA/ETB receptor antagonist bosentan (5 mg kg-1). Pillar cell contraction is likely to be a mechanism for matching the functional respiratory surface area with the instantaneous respiratory needs of the fish.

Acute defense mechanisms against hemorrhage from mechanical gill injury in rainbow trout

By cutting gill filaments in anesthetized rainbow trout (Oncorhynchus mykiss), observing the bleeding through a stereomicroscope, and using blockers of various known endogenous filament artery vasoconstrictors, we have here attempted to characterize hemostatic mechanisms in gills. The immediate hemostatic response to a cut in a gill filament artery was a local vasoconstriction, stopping the hemorrhage within approximately 20 s. In heparinized fish, the hemorrhage recommenced after approximately 8 min, suggesting that the vasoconstriction soon subsides and blood clotting becomes responsible for the hemostasis. Antagonists of acetylcholine, adenosine, and serotonin receptors were unable to block the hemostatic vasoconstriction. Also, tetrodotoxin was without effect, indicating a nonnervous origin. By contrast, indomethacin significantly affected the measured bleeding times, suggesting that eicosanoids play a significant role in this process (possibly by stimulating vasoconstriction and/or by inducing local thrombocyte aggregation). By possessing several hundred virtually identical filaments with readily observable vasculature, the fish gill appears to be a good experimental model for studying hemostatic mechanisms.

A role of 5-HT2 receptors in the gill vasculature of the antarctic fish Pagothenia borchgrevinki

This study was conducted to describe the cardiovascular responses to intra-arterial injections of serotonin in the Antarctic fish Pagothenia borchgrevinki and to elucidate the underlying mechanisms. Immunohistochemistry was used to localise serotonin-containing cells within the gills. Simultaneous and continuous recordings of ventral and dorsal aortic blood pressure, heart rate and ventral aortic blood flow (cardiac output) were made using standard cannulation procedures in combination with Doppler flow measurement. An extracorporeal loop with an in-line oxygen electrode allowed continuous measurements of arterial oxygen pressure PaO2. Pre-branchial injection of serotonin (5-hydroxytryptamine, 5-HT) or the 5-HT2 receptor agonist alpha-methylserotonin increased the branchial vascular resistance and ventral aortic pressure, while the 5-HT1 receptor agonist piperazine was without effect. The branchial vasoconstriction produced by serotonin injection was completely blocked by the 5-HT1/5-HT2 receptor antagonist methysergide and the branchial vasoconstriction produced by WIDTH="9" HEIGHT="12" ALIGN="BOTTOM" NATURALSIZEFLAG= alpha-methylserotonin injection was completely blocked by the specific 5-HT2 receptor antagonist LY53857. The results suggest that the 5-HT2 receptor alone mediates the branchial vasoconstriction. Serotonin also mediated a methysergide-sensitive reduction in PaO2, the reduction being greatest when the pre-injection PaO2 value was high. 5-HT-immunoreactive cells and nerve fibres were present within the gill tissues. All the 5-HT-immunoreactive cells were located on the efferent side of the filaments, but 5-HT-immunoreactive nerve fibres were found lining both of the branchial arteries. Our findings demonstrate a potential serotonergic control system for the gills in Pagothenia borchgrevinki. In contrast to its effects on the branchial vasculature, serotonin produced a methysergide-insensitive decrease in the systemic vascular resistance. However, neither the specific 5-HT1 nor 5-HT2 receptor agonists produced a decrease in the resistance of the systemic vasculature. The nature of the serotonergic receptor(s) inducing vasodilation in teleost fish is uncertain.

Gill blood flow control

The arrangement of the fish gill vasculature is quite complex, and varies between the different fish groups. The use of vascular casting techniques has greatly enhanced our knowledge of the anatomy of the branchial microcirculation, not least through the contributions of Pierre Laurent and co-workers at Strasbourg. At different physiological situations, the contact surface between water and blood (functional surface area) varies to balance oxygen uptake against osmotic water flow ("respiratory-osmoregulatory compromise"). This is controlled by nerves and by blood-borne or locally released substances that affect blood flow patterns in the gill. Histochemical techniques have been used to demonstrate neurotransmitter substances in the branchial innervation. In combination with physioly-osmoregulatory compromise" at different physiological situations.

Neurochemical mechanisms behind gill microcirculatory responses to hypoxia in trout: in vivo microscopy study

In vivo microscopy combined with systemic blood flow and pressure measurements were used to examine the hemodynamic and microcirculatory responses to hypoxia in gills of rainbow trout and to clarify if the underlying mechanisms are adrenergic, cholinergic, serotonergic, or adenosinergic. Hypoxia (P(O2) 1.07-1.33 kPa) reduced, halted, or reversed the blood flow in the distal portion of the efferent filamental artery (EFA). Simultaneously, a large overflow to the central venous system appeared, allowing a continuous flow through many of the secondary lamellae. No vasoconstriction could be observed in this portion of the filament, showing that a vasoconstriction occurred elsewhere, possibly at the EFA sphincter, because the gill resistance (R(G)) increased. These effects were mimicked by prebranchial injection of acetylcholine, a treatment that also strongly constricted the distal efferent filamental vasculature. Atropine blocked most of the hypoxia-induced hemodynamic changes, although a minor increase in R(G) remained. The latter appeared to be of a nonadrenergic noncholinergic origin, being unaffected by additional treatment with an alpha-adrenoreceptor antagonist. It was also unaffected by blockers of serotonin and adenosine-A1 receptors. Other responses seen included a cholinergic maintenance of the systemic resistance during hypoxia and an alpha-adrenoceptor-mediated posthypoxic hypertension. This study demonstrates that hypoxia evoked a cholinergic reflex vasoconstriction located at proximal parts of the efferent filamental vasculature.

Branchial and systemic roles of adenosine receptors in rainbow trout: an in vivo microscopy study

The purinergic branchial vasomotor control in rainbow trout (Oncorhynchus mykiss) was studied using an epi-illumination microscope equipped with a water-immersion objective. Cardiac output (Q), heart rate, and dorsal (PDA) and ventral (PVA) aortic pressures were recorded simultaneously. Prebranchial injection of adenosine or the A1-receptor agonist N6-cyclopentyl-adenosine (CPA) constricted the distal portion of the filament vasculature, which coincided with an increase of PVA. The A2-receptor agonist PD-125944 was without effect. After adenosine and CPA injection, an overflow of blood to the secondary system was repeatedly observed unless blood flow came to a complete stop. The lack of a concomitant reduction of Q suggested a redistribution of blood to the secondary system and to more proximal parts of the filament. The branchial effects of adenosine and CPA were completely blocked by the unspecific adenosine receptor antagonist amino-phylline and the specific A1-receptor antagonist N6-cyclopen-tyltheophylline. The results suggest that A1-receptors alone mediate the branchial vasoconstriction observed. Thus the responses of the branchial vasculature to adenosine include a vasoconstriction of the filament vasculature mediated via specific A1 receptors and a redistribution of blood flow to the secondary system and to proximal parts of the filament. Additional cardiovascular effects of adenosine included decreased systemic vascular resistance and heart rate.

Serotonergic vasomotor control in fish gills

Serotonin (5-hydroxytryptamine,5-HT)-containing neuroepithelial cells (NECs) have been discovered in the gills of fish belonging to different phylogenetic groups, and an additional serotonergic innervation of the gill filaments is present in teleosts. The most apparent effect of serotonin is a branchial vasoconstriction. For teleosts, it has been postulated that the serotonergic innervation of the proximal portion of the efferent filamental artery (EFA) and adjacent efferent lamellar arterioles (ELA) acts to constrict the vasculature. Thus, as perfusion pressure increases, more lamellae are recruited. In contrast, recent results from rainbow trout show that one precise action of serotonin is a vasoconstriction on the distal portion of the filament vasculature. This may explain why exogenously added serotonin impairs gas exchange in rainbow trout. In addition to constricting the respiratory (arterio-arterial) pathway, injection of serotonin into the Atlantic cod dilates the arterio-venous pathway, diverting blood flow to the arterio-venous pathway. The vasoconstrictory effects of serotonin can be blocked by the 5-HT-receptor antagonist methysergide, whereas the vasodilatory effects cannot.

Control of gill filament blood flow by serotonin in the rainbow trout, Oncorhynchus mykiss

The effects of exogenously applied serotonin [5-hydroxytryptamine (5-HT)] on the distal arterial vasculature of gill filaments were observed using an epi-illumination microscope equipped with a water-immersion objective and connected to a video camera. In addition, ventral aortic flow (Q) and celiac artery pressure (PCA) were measured. Intra-arterial injection of serotonin (100 nmol/kg) completely stopped the blood flow in the distal part of the filaments and caused a rapid decrease of PCA. Repeatedly, the flow reduction was found to coincide with a constriction of the distal portion of the efferent filamental vasculature. Because there was no concomitant reduction in Q, it is concluded that a redistribution of blood to more proximal parts of the filaments occurred. After treatment with the serotonergic receptor antagonist methysergide, the vasoconstrictor effect of serotonin on the filamental vasculature was eliminated, while a decrease in PCA was still observed. The results demonstrate a specific site(s) for the serotonergic vasoconstriction in the distal portion of the filament.

EVIDENCE OF REGULATORY MECHANISMS FOR THE DISTRIBUTION OF BLOOD BETWEEN THE ARTERIAL AND THE VENOUS COMPARTMENTS IN THE HAGFISH GILL POUCH

Of the extant vertebrate animals, the hagfishes are generally considered to be the group which diverged first from the ancestral vertebrate lineage, although molecular sequence analysis has recently suggested that they form a monophyletic group with lampreys (Stock and Whitt, 1992). The circulatory system of hagfishes has features that have been described as 'primitive' (Burggren et al. 1985), but their gills are effective gas exchangers. The gills are contained within discrete muscular pouches, and the anatomy of the blood system and ventilatory ducts has an ideal countercurrent arrangement (Mallatt and Paulsen, 1986; Elger, 1987). Reite (1969) first reported effects of catecholamines and other drugs on the branchial vasculature of hagfish. Recent studies of both perfused gills in situ and of blood flow in vivo have suggested that blood flow through the gills of hagfish is under tonic control by catecholamines (Axelsson et al. 1990; Forster et al. 1992). In teleosts, several studies have shown that adrenergic control mechanisms are involved in the distribution of blood between the arterio-arterial and the arterio-venous pathways of the gill vasculature (see Nilsson, 1983). Anatomical and ultrastructural studies have demonstrated the existence of similar pathways in hagfish (Cole, 1925; Mallatt and Paulsen, 1986; Elger, 1987). The experiments reported here demonstrate that, in the hagfish gill pouch, both adrenaline and isoprenaline can increase the proportion of fluid leaving via the efferent arterial route, at the expense of the venous outflow. Hagfish (Eptatretus cirrhatus Forster) were collected off Motunau, North Canterbury, New Zealand, and held in seawater aquaria until used. The masses of the 11 animals used in these experiments ranged from 680 to 1720 g with a mean of 1140&plusmn;110 g (s.e.m.). Animals were anaesthetized in a 0.4 % solution of benzocaine in sea water. The hagfish were opened ventrally to expose the gills and their blood supply. Individual gill pouches were prepared for perfusion studies.