Control of cardiorespiratory function in response to hypoxia in an air-breathing fish, the African sharptooth catfish, Clarias gariepinus.

We evaluated the role of the first pair of gill arches in the control of cardiorespiratory responses to normoxia and hypoxia in the air-breathing catfish, Clarias gariepinus. An intact group (IG) and an experimental group (EG, bilateral excision of first gill arch) were submitted to graded hypoxia, with and without access to air. The first pair of gill arches ablations reduced respiratory surface area and removed innervation by cranial nerve IX. In graded hypoxia without access to air, both groups displayed bradycardia and increased ventilatory stroke volume (VT), and the IG showed a significant increase in breathing frequency (fR). The EG exhibited very high fR in normoxia that did not increase further in hypoxia, this was linked to reduced O2 extraction from the ventilatory current (EO2) and a significantly higher critical O2 tension (PcO2) than the IG. In hypoxia with access to air, only the IG showed increased air-breathing, indicating that the first pair of gill arches excision severely attenuated air-breathing responses. Both groups exhibited bradycardia before and tachycardia after air-breaths. The fH and gill ventilation amplitude (VAMP) in the EG were overall higher than the IG. External and internal NaCN injections revealed that O2 chemoreceptors mediating ventilatory hypoxic responses (fR and VT) are internally oriented. The NaCN injections indicated that fR responses were mediated by receptors predominantly in the first pair of gill arches but VT responses by receptors on all gill arches. Receptors eliciting cardiac responses were both internally and externally oriented and distributed on all gill arches or extra-branchially. Air-breathing responses were predominantly mediated by receptors in the first pair of gill arches. In conclusion, the role of the first pair of gill arches is related to: (a) an elevated EO2 providing an adequate O2 uptake to maintain the aerobic metabolism during normoxia; (b) a significant bradycardia and increased fAB elicited by externally oriented O2 chemoreceptors; (c) increase in the ventilatory variables (fR and VAMP) stimulated by internally oriented O2 chemoreceptors.

Cardioprotective effects of alternagin-C (ALT-C), a disintegrin-like protein from Rhinocerophis alternatus snake venom, on hypoxia-reoxygenation-induced injury in fish.

Alternagin-C (ALT-C) is a disintegrin-like peptide purified from Rhinocerophis alternatus snake venom with the property of inducing vascular endothelial growth factor (VEGF) expression, endothelial cell proliferation and migration, and angiogenesis. Therefore, this protein could be interesting as a new approach for ischemic heart diseases, an imbalance between myocardial oxygen supply and demand, leading to cardiac dysfunction. We investigated the effects of a single dose of alternagin-C (0.5 mg kg-1, via intra-arterial), after 7 days, on hypoxia/reoxygenation challenge in isolated ventricle strips and on morphological changes and density of blood vessels of the heart, using fish as an alternative experimental model. ALT-C treatment provided protection of cardiomyocytes against hypoxia/reoxygenation-induced negative inotropism. ALT-C also stimulated angiogenesis and improved excitation-contraction coupling during hypoxic conditions. Our results provide a new insight into a functional role of ALT-C against hypoxia/reoxygenation-induced cardiomyocyte injury pointing out to a potential therapeutic strategy for ischemia-related diseases.

Alternagin-C (ALT-C), a disintegrin-like protein from Rhinocerophis alternatus snake venom promotes positive inotropism and chronotropism in fish heart.

Alternagin-C (ALT-C) is a disintegrin-like protein purified from the venom of the snake, Rhinocerophis alternatus. Recent studies showed that ALT-C is able to induce vascular endothelial growth factor (VEGF) expression, endothelial cell proliferation and migration, angiogenesis and to increase myoblast viability. This peptide, therefore, can play a crucial role in tissue regeneration mechanisms. The aim of this study was to evaluate the effects of a single dose of alternagin-C (0.5 mg kg(-1), via intra-arterial) on in vitro cardiac function of the freshwater fish traíra, Hoplias malabaricus, after 7 days. ALT-C treatment increased the cardiac performance promoting: 1) significant increases in the contraction force and in the rates of contraction and relaxation with concomitant decreases in the values of time to the peak tension and time to half- and 90% relaxation; 2) improvement in the cardiac pumping capacity and maximal electrical stimulation frequency, shifting the optimum frequency curve upward and to the right; 3) increases in myocardial VEGF levels and expression of key Ca(2+)-cycling proteins such as SERCA (sarcoplasmic reticulum Ca(2+)-ATPase), PLB (phospholamban), and NCX (Na(+)/Ca(2+) exchanger); 4) abolishment of the typical negative force-frequency relationship of fish myocardium. In conclusion, this study indicates that ALT-C improves cardiac function, by increasing Ca(2+) handling efficiency leading to a positive inotropism and chronotropism. The results suggest that ALT-C may lead to better cardiac output regulation indicating its potential application in therapies for cardiac contractile dysfunction.

Electrocardiographic characterization of myocardial function in normoxic and hypoxic teleosts.

Electrocardiography was applied to analyze cardiac function of four teleost species (Piaractus mesopotamicus, Hoplias malabaricus, Hoplias lacerdae and Cyprinus carpio) during normoxia and graded hypoxia. In these species, hypoxic bradycardia consistently occurred during severe hypoxia (below the critical oxygen tension--PCO2) and was accompanied by alterations in the ECG recordings. Three basic ECG alterations were demonstrable: 1) increase in the T wave area and amplitude, being more positive and with symmetrical morphology during severe hypoxia (P. mesopotamicus); 2) negative T wave in normoxia, changing to isodiphasic (just above the PCO2) and positive (below the PCO2; H. malabaricus and H. lacerdae); 3) positive T wave in normoxia, changing to negative in severe hypoxia (5 mmHg; Cyprinus carpio). These findings indicate changes in the direction of ventricular repolarization during exposure to severe hypoxia, and the analysis of the ECGs in relation to the derivation line permitted the estimation of these drifts to be 17 degrees in P. mesopotamicus, 46 degrees in H. malabaricus, 43 degrees in H. lacerdae, and 32 degrees in C. carpio. The changes in the direction of ventricular repolarization were attributed to myocardial impairment due to insufficient oxygen supply, and support the idea of a relationship between cardiac dysfunction and the bradycardia developed during severe hypoxia.

Changes in gut gross morphology of traíra, Hoplias malabaricus (Teleostei, Erythrinidae) during long-term starvation and after refeeding.

Adult traíra (Hoplias malabaricus) were submitted to different periods of food deprivation (from 30 to 240 days) and refed for 30 days after 90 and 240 days of starvation. Stomach length remained constant during all the experimental period. However, the intestine length was significantly reduced after 30 days of food deprivation. Normal length was not recovered after refeeding. The number of pyloric caeca did not change significantly. Conversely, caeca thickness decreased after 150 days of starvation and their length decreased after 180 days. After refeeding, however, the pyloric caeca recovered original thickness. In fish refed after 240 days of starvation the length of these structures seemed to present compensatory growth, becoming longer than in the control group.

[Detection of type specific antibodies to hepatitis C virus NS4 protein in hepatitis C patients by enzyme immunoassay]. / Vyiavlenie tipospetsificheskikh anti-HCNS4-antitel u bol'nykh gepatitom C metodom immunofermentnogo analiza.

A multi-enzyme immmune-assay test system was designed for serotyping of genotypes hepatitis C virus (HCV) and a method of such typing of the serum of patients with hepatitis C was worked out. The above test-system was worked out on the basis of a study of 10 type-specific peptides modeling different fragments from NS4-protein variable region of HCV. The designed test system was evaluated by using a set of 42 serum samples obtained at random from patients with chronic hepatitis C, which had been preliminarily genotyped by polymerase chain reaction. The serotyping makes it possible to identify the type-specific antibodies in the blood sera of patients, including those cases when viremia was absent. Differences in the circulation of HCV in Moscow (Russia) and Vitebsk (Byelorussia) were established by using the designed test-system.

[Viral hepatitis delta in the republic of Belarus]. / Virusnyi gepatit del'ta v Respublike Belarus'.

26,740 blood donors and persons of high risk groups with respect to HBV infection, residing in different regions of Belarus, were examined for the presence of HBsAg in 1983-1997. Of these, 1372 persons (5.1%) were found to have HBsAg, and out of 1081 HBsAg-positive persons anti-HDV antibodies (Ab) were detected in 96 persons (8.9%). In spite of a decrease in acute virus hepatitis B morbidity and in HBsAg carriership, the occurrence of anti-HBV Ab remained stable during the period of 16 years and was equal, on the average, about 4% among asymptomatic HBsAg carriers. Patients having tuberculosis, rheumatoid arthritis, diabetes mellitus, hematological diseases, chronic hepatitides and cirrhosis of the liver were an important reservoir of HBV and HDV infections for regions with the low level of the spread of HBV. A decrease in the detection rate of anti-HDV Ab in patients with cirrhosis of the liver from 47.6% to 15.4% was noted. In 1991-1997 a decrease in the detection rate of anti-HDV Ab in patients with chronic hepatic lesions in comparison with 1983-1990 was observed, and in the age group older than 50 years this decrease was from 33.3% to 8.3%. This difference was particularly pronounces in patients with cirrhosis of the liver: 53.9% and 7.7% respectively.

[The efficacy of proxodolol in patients with stable arterial hypertension]. / Effektivnost' proksodolola u bol'nykh stabil'noi arterial'noi gipertenziei.

The new original Russian drug proxodolol having alpha- and beta-adrenoblocking activities in a ratio of 1:100 was examined at Stages I and II of clinical trials. The drug was given to 29 male patients aged 30-63 years who suffered from Stages I and II persistent hypertensive disease with a baseline diastolic blood pressure of >95 mm Hg. Proxodolol as 10- and 40-mg tablets was demonstrated to be an effective antihypertensive agent, its antihypertensive effects being revealed in acute and chronic uses. The drug was well tolerated by the patients, causing no significant adverse reactions. Further comprehensive comparative controlled studies of proxodolol including larger patient groups will define the contribution of the drug in long-term antihypertensive prophylaxis.

[Autopsy-based data on radionuclide concentrations in selected endocrine organs (Vitebsk region, Belarus)]. / Soderzhanie radionuklidov v nekotorykh éndokrinnykh organakh po materialu autopsii v vitebskoi oblasti.

Gamma spectometry was used to compare 137Cs levels in certain endocrine organs of victims of general and oncological diseases of different localizations. The radionuclide distribution in the thyroid, adrenals and pancreas was studied. Elevated concentrations were found in the endocrine system of cancer patients.

[Use of the psychophysiological complex PFK-01 in patients after replantation of the segment of the upper extremity]. / Primenenie psikhofiziologicheskogo kompleksa PFK-01 u bol'nykh posle replantatsii segmenta verkhnei konechnosti.

The use of the psychophysiological complex PFK-01 permits the psychoemotional status to be examined in patients who underwent replantation of a segment of the upper limb after traumatic amputation. The method makes it possible to establish what kind of the psychic stage, tension or depression, is experienced by the examined patient. The data obtained can be used by the treating physician or by the psychotherapist in a complex of rehabilitation measures for goal-oriented psychotherapeutic correction of patients.

Cardiorespiratory responses to hypoxia in the African catfish, Clarias gariepinus (Burchell 1822), an air-breathing fish.

The African catfish, Clarias gariepinus, possesses a pair of suprabranchial chambers located in the dorsal-posterior part of the branchial cavity having extensions from the upper parts of the second and fourth gill arches, forming the arborescent organs. This structure is an air-breathing organ (ABO) and allows aerial breathing (AB). We evaluated its cardiorespiratory responses to aquatic hypoxia. To determine the mode of air-breathing (obligate or accessory), fish had the respiratory frequency (f (R)) monitored and were subjected to normoxic water (PwO(2) = 140 mmHg) without becoming hyperactive for 30 h. During this period, all fish survived without displaying evidences of hyperactivity and maintained unchanged f (R), confirming that this species is a facultative air-breather. Its aquatic O(2) uptake ([Formula: see text]) was maintained constant down to a critical PO(2) (PcO(2)) of 60 mmHg, below which [Formula: see text] declined linearly with further reductions of inspired O(2) tension (PiO(2)). Just above the PcO(2) the ventilatory tidal volume (V (T)) increased significantly along with gill ventilation ([Formula: see text]), while f (R) changed little. Consequently, the water convection requirement [Formula: see text] increased steeply. This threshold applied to a cardiac response that included reflex bradycardia. AB was initiated at PiO(2) = 140 mmHg (normoxia) and air-breathing episodes increased linearly with more severe hypoxia, being significantly higher at PiO(2) tensions below the PcO(2). Air-breathing episodes were accompanied by bradycardia pre air-breath, to tachycardia post air-breath.

Gill chemoreceptors and cardio-respiratory reflexes in the neotropical teleost pacu, Piaractus mesopotamicus.

This study examined the location and distribution of O(2) chemoreceptors involved in cardio-respiratory responses to hypoxia in the neotropical teleost, the pacu (Piaractus mesopotamicus). Intact fish and fish experiencing progressive gill denervation by selective transection of cranial nerves IX and X were exposed to gradual hypoxia and submitted to intrabuccal and intravenous injections of NaCN while their heart rate, ventilation rate and ventilation amplitude were measured. The chemoreceptors producing reflex bradycardia were confined to, but distributed along all gill arches, and were sensitive to O(2) levels in the water and the blood. Ventilatory responses to all stimuli, though modified, continued following gill denervation, however, indicating the presence of internally and externally oriented receptors along all gill arches and either in the pseudobranch or at extra-branchial sites. Chemoreceptors located on the first pair of gill arches and innervated by the glossopharyngeal nerve appeared to attenuate the cardiac and respiratory responses to hypoxia. The data indicate that the location and distribution of cardio-respiratory O(2) receptors are not identical to those in tambaqui (Colossoma macropomum) despite their similar habitats and close phylogenetic lineage, although the differences between the two species could reduce to nothing more than the presence or absence of the pseudobranch.

Erythrocyte senescence and haematological changes induced by starvation in the neotropical fish traíra, Hoplias malabaricus (Characiformes, Erythrinidae).

Adult specimens of traira (Hoplias malabaricus Bloch) were subjected to long-term starvation (30 to 240 days) and re-fed for 30 days after 90 and 240 days of food deprivation. Counting of immature erythrocytes in peripheral blood showed that erythropoiesis decreased significantly during the first 30 days of food deprivation. The results suggest that a process of senescence takes place in the pre-existent red blood cells and that the cells are not replaced during starvation. After 240 days of starvation, H. malabaricus had a significantly reduced number of red blood cells, causing changes in hematocrit and blood indices (mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration). Furthermore, during this period, the fish presented leukopenia (lymphocytopenia) and thrombocytopenia. After re-feeding, the number of leukocytes and thrombocytes recovered, but the red blood cell number remained reduced and there was a significant increase in abnormal red cell nuclei.

Dependence on body size of respiratory function in Hoplias malabaricus (Teleostei, Erythrinidae) during graded hypoxia.

Oxygen uptake and ventilatory responses to environmental hypoxia were assessed for two groups of Hoplias malabaricus of nearly tenfold different body weights (mean weights, group I = 39 g; group II = 365 g). The main purpose of the study was to evaluate the relationships between body weight and the critical O2 tension (PCO2) for maintenance of normal resting O2 uptake. The smaller specimens had a threefold larger weight-specific O2 uptake compared to that of the larger specimens. Moreover, smaller size coincided with a higher PCO2, i.e., a more limited range for maintenance of O2 uptake during hypoxia. Likewise, at any inspired PO2 the weight-specific gill ventilation was largest for group I. This was most pronounced during severe hypoxia where both tidal volume and respiratory frequency increased markedly. In addition, the oxygen cost of breathing tended to be highest in the smaller individuals. The results open questions as to correlations between development, weight-dependent O2 demands, and tolerance to hypoxia on an intraspecific level.

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.

[The development and a clinical trial of an erythrocytic diagnostic agent for determining antibodies to the liver-specific lipoprotein]. / Razrabotka i klinicheskoe ispytanie éritrotsitarnogo diagnostikuma dlia opredeleniia antitel k spetsificheskomu lipoproteinu pecheni.

A simple method for the preparation of purified liver-specific protein has been developed and a sensitive and specific test-system has been created on its basis for the detection of antiLSP. The titres of antiLSP correlate with the activity of the pathological processes in patients with acute and chronic hepatitides. Immunosuppressive therapy results in elimination of antiLSP.

Cardiorespiratory responses of the facultative air-breathing fish jeju, Hoplerythrinus unitaeniatus (Teleostei, Erythrinidae), exposed to graded ambient hypoxia.

The jeju, Hoplerythrinus unitaeniatus, is equipped with a modified part of the swim bladder that allows aerial respiration. On this background, we have evaluated its respiratory and cardiovascular responses to aquatic hypoxia. Its aquatic O2 uptake (V(O2)) was maintained constant down to a critical P(O2) (P(cO2)) of 40 mm Hg, below which V(O2) declined linearly with further reductions of P(iO2). Just below P(cO2), the ventilatory tidal volume (V(T)) increased significantly along with gill ventilation (V(G)), while respiratory frequency changed little. Consequently, water convection requirement (V(G)/V(O2)) increased steeply. The same threshold applied to cardiovascular responses that included reflex bradycardia and elevated arterial blood pressure (P(a)). Aerial respiration was initiated at water P(O2) of 44 mm Hg and breathing episodes and time at the surface increased linearly with more severe hypoxia. At the lowest water P(O2) (20 mm Hg), the time spent at the surface accounted for 50% of total time. This response has a character of a temporary emergency behavior that may allow the animal to escape hypoxia.

Cardiovascular and respiratory reflexes: the tropical fish, traira (Hoplias malabaricus) O2 chemoresponses.

To determine the location and distribution of chemoreceptors involved in the cardiovascular and respiratory responses to hypoxia of traira (Hoplias malabaricus), we measured heart rate, arterial blood pressure, ventilation frequency and amplitude of opercular movements during exposure to hypoxia and application of NaCN to either water bathing the gills (external) or the ventral aortic blood (internal). This was done before and after selective denervation of branchial branches of the IXth and Xth cranial nerves to various gill arches. The data suggest that hypoxia elicits a bradycardia that arises from internal receptors located in the first gill arch. They also indicate the presence of branchial and extra branchial O2-chemoreceptors that reflexively elevate systemic vascular resistance during hypoxia. Hypoxia induced increases in ventilation frequency arose primarily from external receptors located exclusively within the gills while increases in breathing amplitude also involved extra branchial receptors. In addition, the data suggest there are O2 sensitive chemoreceptors located in the first gill arch that attenuate the respiratory responses.

Changes in gut gross morphology of traíra, Hoplias malabaricus (Teleostei, Erythrinidae) during long-term starvation and after refeeding

Traíras (Hoplias malabaricus) adultas foram submetidas a diferentes períodos de privação de alimento (de 30 a 240 dias) e realimentadas por 30 dias após 90 e 240 dias de jejum. O comprimento do estômago permaneceu constante durante todo o tempo experimental. No entanto, o comprimento do intestino reduziu significativamente após 30 dias de jejum. O comprimento normal não foi recuperado após a realimentação. O número de cecos pilóricos não sofreu modificações significativas. Por outro lado, a espessura dos cecos diminuiu após 150 dias de privação de alimento e seu comprimento diminuiu após 180 dias. Após a realimentação, porém, os cecos pilóricos recuperaram a espessura original. Nos peixes realimentados após 240 dias de jejum, os comprimentos dessas estruturas aparentemente apresentaram crescimento compensatório, tornando-se mais longas que as do grupo controle.