Massive lindane overdose with toxicokinetics analysis

BACKGROUND

Lindane is a possible carcinogen with known teratogenicity and immunologic and neurotoxic properties. Despite reports of seizures, coma, and death associated with its use as well as banning of its environmental use by the Environmental Protection Agency (EPA), the US Food and Drug Administration (FDA) still allows treatment with lindane as a second-line scabicide and pediculicide. We present a case of a massive suicidal ingestion of lindane in which the patient survived the ingestion, though he did expire shortly thereafter from an unrelated cause pre-discharge.

METHODS

Pharmacokinetic analysis of serum lindane concentrations was performed with Phoenix® WinNONLIN®. The estimated distribution half-life for lindane was 10.3 h, and the terminal half-life was 162.9 h, much longer than the previously reported terminal half-life of 25-36 h. Because of this long half-life, repeated lindane exposures may lead to accumulation of lindane in the tissues.

RESULT

After overdose, toxicity may be delayed and full recovery may be prolonged.

'Crazy Monkey' poisons man and dog: Human and canine seizures due to PB-22, a novel synthetic cannabinoid

CONTEXT

Synthetic cannabinoids have been manufactured, sold, and consumed for recreational purposes since at least 2004; their use has been associated with adverse psychiatric, cardiovascular, renal, pulmonary, and neurologic effects. We report simultaneous canine and human clinical cases associated with exposure to a novel synthetic cannabinoid, PB-22 (QUPIC).

CASE REPORT

A 22-year-old man brought his dog to a veterinary clinic after it had a seizure. During the course of the canine's evaluation, the human patient was witnessed to have a generalized tonic-clonic seizure. He was intubated for agitation and combativeness after his arrival to the emergency department (ED). He was extubated the next day without discernable sequelae. The canine patient received intravenous hydration and was also discharged to home after a period of close observation. The man later endorsed smoking three containers of a substance called "Crazy Monkey" daily for several weeks, but would not disclose how his dog had been exposed. The convulsant effects of "Crazy Monkey" were confirmed in this patient when, three months later, he was sedated, paralyzed, intubated, and admitted to another local hospital for seizures in the context of smoking the same product.

DISCUSSION

Laboratory analysis of samples obtained from the human and canine patients. A sample of the product (labeled "Crazy Monkey") revealed the presence of PB-22 (QUPIC), a novel synthetic cannabinoid. Additionally, serum and urine samples from the human patient contained metabolites of a second compound, UR-144.

CONCLUSION

We present a laboratory-confirmed case report of human and canine neurotoxicity associated with a novel synthetic cannabinoid, PB-22 (QUIPIC).

No one likes a copycat: a cross-cultural investigation of children's response to plagiarism

Copying other people's ideas is evaluated negatively by American children and adults. The current study investigated the influence of culture on children's evaluations of plagiarism by comparing children from three countries--the United States, Mexico, and China--that differ in terms of their emphasis on the protection of intellectual property and ideas. Children (3- to 6-year-olds) were presented with videos involving two characters drawing pictures and were asked to evaluate the character who drew unique work or the character who copied someone else's drawing. The study showed that 5- and 6-year-olds from all three cultures evaluated copiers negatively compared with unique drawers. These results suggest that children from cultures that place different values on the protection of ideas nevertheless develop similar concerns with plagiarism by 5-year-olds.

Alternative Models for Telephone Response to Pediatric Poisonings

BACKGROUND

Poison Control Centers (PCCs) provide telephone consultations to manage poisonings. They are threatened with funding loss. Policy decision-makers have requested an evaluation of alternate models for telephone management of poisonings.

OBJECTIVE

We examined the feasibility of alternative models for the telephone management of poisonings from the public.

METHODS

Alternative models evaluated included emergency medical dispatchers (EMDs), advice nurses (RNs), and poison information providers (PIPs) to manage real and hypothetical poisonings with protocols or computerized references (Poisindex) with and without PCC backup.

RESULTS

EMDs and RNs with a structured protocol and access to a PCC specialist were able to manage a small subset of poisoning calls. EMDs and RNs managed 6% and 12% of poisoning calls respectively. Non-protocol management of hypothetical cases using Poisindex resulted in mismanagement of cases and longer periods of time to manage cases. PIPs within a PCC were able to manage a substantially greater proportion of calls, but had a significant portion of non-productive time waiting for a PCC call.

CONCLUSION

EMDs, RNs, and technician-level PIPs can manage a subset of poisoning cases using structured protocols. Alternative providers were dependent on PCC staff for consultation of the majority of poisoning calls. There are several obstacles to these models and their cost-effectiveness needs to be determined. These studies were the basis of a new staffing model with the integration of PIPs into the call response system in California.

Yam bean seed poisoning mimicking cyanide intoxication*

BACKGROUND

Yam bean is a common food in southern Taiwan. However, its seeds are rarely consumed. We describe five patients of yam bean seed poisoning in Taiwan, one of them life-threatening.

CLINICAL PRESENTATION

The five patients presented with perioral numbness, nausea and vomiting after eating a same soup made from yam bean seeds. One of them, a 54-year-old woman, had difficulty breathing and lost consciousness. Physical examination showed dilated pupils and coma with no focal neurological signs. The initial blood pressure was normal. Laboratory data showed a severe anion gap metabolic acidosis, with a serum lactate level of 185 mg/dL. An initial diagnosis of cyanide intoxication was considered and she was given sodium nitrite and sodium thiosulfate i.v. Hypotension ensued shortly afterwards and pulmonary artery catheterization showed a decreased cardiac index. Aggressive fluid and inotropic therapy were given and the patient eventually recovered. The other four patients suffered only minor gastrointestinal and neurological symptoms and received supportive treatment. Cyanide levels were negative in all five patients.

CONCLUSION

Yam bean seed poisoning can cause acute metabolic acidosis and altered mental status, which could be confused with acute cyanide intoxication from a cyanogenic glycoside-containing plant. To our knowledge, this is the first outbreak of yam bean seed poisoning reported in the English published work.

Intracellular and extracellular calcium utilization during hypoxic vasoconstriction of cyclostome aortas

Hypoxic vasoconstriction (HV) is an intrinsic response of mammalian pulmonary and cyclostome aortic vascular smooth muscle. The present study examined the utilization of calcium during HV in dorsal aortas (DA) from sea lamprey and New Zealand hagfish. HV was temporally correlated with increased free cytosolic calcium (Ca2+c) in lamprey DA. Extracellular calcium (Ca2+o) did not contribute significantly to HV in lamprey DA, but it accounted for 38.1 +/- 5.3% of HV in hagfish DA. Treatment of lamprey DA with ionomycin, ryanodine, or caffeine added to thapsigargin-reduced HV, whereas HV was augmented by BAY K 8644. Methoxyverapamil (D600) in zero Ca2+o did not affect HV in lamprey DA, nor did it prevent further constriction when Ca2+o was restored during hypoxia in hagfish DA. Removal of extracellular sodium (Na+o) caused a constriction in both species. Lamprey DA relaxed to prehypoxic tension following return to normoxia in zero Na+o, whereas relaxation was inhibited in hagfish DA. Relaxation following HV was inhibited in lamprey DA when Na+o and Ca2+o were removed. These results show that HV is correlated with [Ca2+]c in lamprey DA and that Na+/Ca2+ exchange is used during HV in hagfish but not lamprey DA. Multiple receptor types appear to mediate stored intracellular calcium release in lamprey DA, and L-type calcium channels do not contribute significantly to constriction in either cyclostome.

The effects of endothelin-1 on the cardiorespiratory physiology of the freshwater trout (Oncorhynchus mykiss) and the marine dogfish (Squalus acanthias)

The aim of the present study was to evaluate the effects of endothelin-l-elicited cardiovascular events on respiratory gas transfer in the freshwater rainbow trout (Oncorhynchus mykiss) and the marine dogfish (Squalus acanthias). In both species, endothelin-1 (666 pmol kg(-1)) caused a rapid (within 4 min) reduction (ca. 30-50 mmHg) in arterial blood partial pressure of O2. The effects of endothelin-1 on arterial blood partial pressure of CO2 were not synchronised with the changes in O2 partial pressure and the responses were markedly different in trout and dogfish. In trout, arterial CO2 partial pressure was increased transiently by approximately 1.0 mmHg but the onset of the response was delayed and occurred 12 min after endothelin-1 injection. In contrast, CO2 partial pressure remained more-or-less constant in dogfish after injection of endothelin-1 and was increased only slightly (approximately 0.1 mmHg) after 60 min. Pre-treatment of trout with bovine carbonic anhydrase (5 mg ml(-1)) eliminated the increase in CO2 partial pressure that was normally observed after endothelin-1 injection. In both species, endothelin-1 injection caused a decrease in arterial blood pH that mirrored the changes in CO2 partial pressure. Endothelin-1 injection was associated with transient (trout) or persistent (dogfish) hyperventilation as indicated by pronounced increases in breathing frequency and amplitude. In trout, arterial blood pressure remained constant or was decreased slightly and was accompanied by a transient increase in systemic resistance, and a temporary reduction in cardiac output. The decrease in cardiac output was caused solely by a reduction in cardiac frequency; cardiac stroke volume was unaffected. In dogfish, arterial blood pressure was lowered by approximately 10 mmHg at 6-10 min after endothelin-1 injection but then was rapidly restored to pre-injection levels. The decrease in arterial blood pressure reflected an increase in branchial vascular resistance (as determined using in situ perfused gill preparations) that was accompanied by simultaneous decreases in systemic resistance and cardiac output. Cardiac frequency and stroke volume were reduced by endothelin-1 injection and thus both variables contributed to the changes in cardiac output. We conclude that the net consequences of endothelin-1 on arterial blood gases result from the opposing effects of reduced gill functional surface area (caused by vasoconstriction) and an increase in blood residence time within the gill (caused by decreased cardiac output.

Blood and extracellular fluid volume in whole body and tissues of the Pacific hagfish, Eptatretus stouti

Whole-body and 20 individual-tissue (51)Cr-RBC (red cell space; RCS) and (99)Tc-diethylenetriaminepentaacetic acid (extracellular space; ECS) spaces were measured in seven unanesthetized Pacific hagfish (Eptatretus stouti). Volume indicators were administered via a dorsal aortic cannula implanted the previous day. Blood samples were collected at 6, 12, 18, and 24 h after injection. Tissues were removed at 24 h and radioactivity was measured; tissue water content (percent of wet weight) was determined by desiccation at 95 degrees C for 48 h. Mixing rates of both indicators were identical and were essentially complete by 12 h, indicating that blood convection is the rate-limiting process. At 24 h, the whole-body RCS was 19.3+/-2.1 mL kg(-1) body weight, and the ECS was 338.5+/-15.2 mL kg(-1) body weight. Blood volume estimated from the 24-h RCS and the mean central hematocrit (14%) was 137.9 mL kg(-1) body weight. Liver RCS (118.6+/-30.5 microL g(-1) tissue weight) was twice that of any other tissue and was also the most variable, ranging from 59 to 263 microL g(-1), whereas liver ECS (406.0+/-34.3 microL g(-1)) was in the range of other tissues, and water content (66.9%+/-3.5%) was low. Gill RCS (55.9+/-5.7 microL g(-1)), ECS (415.3+/-37.7 microL g(-1)), and percent water (83.1%+/-0.8%) were higher than most other tissues. RCS, ECS, and percent water were consistently lowest in ovum (1.1+/-0.02 microL g(-1), 111.1+/-4.3 microL g(-1), 51.3%+/-3.5%, respectively). Tongue, notocord, and myotome had generally lower RCS (2.1+/-0.4, 2.2+/-0.5, 7.1+/-0.1 microL g(-1), respectively) and ECS (121.2+/-7.0, 246.3+/-17.4, 185.3+/-16.7 microL g(-1), respectively), although their water content was in the midrange (74.7+/-0.5, 81.2+/-1.6, 74.4%+/-0.6%, respectively). Skin had a low RCS (6.8+/-1.1) and midrange ECS (387.5+/-28.0) but very low water content (61.2%+/-2.1%). These findings confirm that hagfish blood volume is at least twice as large as other fish, whereas our estimate of extracellular fluid volume is larger than previously reported and more in line with the predicted interstitial volume. RCS, ECS, and water content vary, often independently, between tissues, which may perhaps be indicative of specific tissue needs or functions. A distinct spleen is lacking in hagfish, and the liver appears to serve this function by sequestering red cells. To our knowledge, this is the first report of tissue ECS in Myxiniformes.

Effects of hypoxia on isolated vessels and perfused gills of rainbow trout

Local hypoxia dilates systemic and constricts pulmonary blood vessels in mammals without neural or humoral involvement. The direct effects of hypoxia on isolated vessels from bony fish have not been examined. In the present study, isolated vessels (efferent branchial artery, EBA; coeliacomesenteric artery, CMA; ventral aorta, VA; and anterior cardinal vein, ACV) from rainbow or steelhead trout (Oncorhynchus mykiss) were subjected to either passive load (resting tension) or contracted with a ligand or 50 mM KCl and then subjected to 60 min of hypoxia by N(2) administration and an additional 30 min of normoxia. All vessels were usually refractory to hypoxia under conditions of resting tension. EBAs, CMAs and VAs pre-contracted with a receptor-mediated ligand were all significantly relaxed by hypoxia and only VAs recovered significantly upon subsequent restoration of normoxia. In contrast, tension in all arteries pre-contracted with 50 mM KCl was elevated further in response to hypoxia. Conversely, ligand-contracted ACVs responded to hypoxia with a further increase in tension, whereas KCl-contracted ACVs relaxed. During apparently random 2-3-week periods EBA and CMA from steelhead and EBA from rainbow trout were hyper-reactive to hypoxia. Steelhead vessels responded to hypoxia with a rapid contraction that increased in magnitude over 3 days. These contractions were independent of pre-stimulation and they were dose-dependent upon PO(2). In isolated gills, hypoxic perfusate produced an immediate but transient elevation of resistance (R(GILL)) in all four gill arches. R(GILL) increased by as much as 30% of initial values and this response was unaltered upon a second hypoxic exposure. These studies demonstrate that isolated vascular segments of rainbow trout are indeed responsive to hypoxia and that these differential responses are vessel and tone dependent and the overall response may be altered by as yet unknown seasonal or environmental factors. Hypoxia-induced arterial relaxation is blocked by elevated external [K(+)], implicating alteration of transmembrane K(+) conductance and/or membrane potential in this depressor response. K(+)-channel closure or voltage-gated Ca(2+) influx cannot account for arterial vasoconstriction due to hypoxia during KCl contractions. Vascular responses to hypoxia could have a profound impact on local flow in vivo and could mediate ventilation-perfusion matching in the branchial circulation of fish.

Computerized psychological test usage in APA-accredited training programs

Despite the advantages of computerized psychological assessment and the proliferation of assessment software, many psychologists still do not use computerized assessment, and its utilization has not increased during the past decade. Two-hundred-fifty-one APA-accredited training programs in clinical and counseling psychology were surveyed concerning their use of computerized psychological assessment. Directors reported a median of only three computerized tests used in their training programs. Twenty-five percent of the respondents reported no computerized psychological tests in their training programs. The computerized tests most-often used in psychology programs were compared to results of surveys of psychological tests most-often used in clinical practice.

Hypoxic vasoconstriction of cyclostome systemic vessels: the antecedent of hypoxic pulmonary vasoconstriction?

Hypoxic vasoconstriction (HV) is an intrinsic response of mammalian pulmonary vascular smooth muscle (VSM). In the present study, HV was examined by myography of vessel rings from three primitive vertebrates: New Zealand hagfish (NZH), Pacific hagfish (PH), and sea lamprey (SL). Hypoxia dilated pre-gill arteries (ventral aorta, afferent branchial) from all species, whereas it contracted systemic arteries [dorsal aorta (DA), efferent branchial, celiacomesenteric]. DA HV was reproducible over several days, and it could be sustained in NZH for 8 h without adverse effects. Tension was proportional to PO(2), and half-maximal HV was obtained at PO(2) (mmHg) of 4.7 +/- 0. 2 (NZH), 0.8 +/- 0.1 (PH), and 10.7 +/- 1.9 (SL). HV did not require preconditioning (preexisting contractile stimulus) and was unaffected by elevated extracellular potassium (200 mM NZH; 80 mM SL); removal of the endothelium (NZH); or inhibitors of cyclooxygenase, lipoxygenase, cytochrome P-450 or antagonists of alpha-adrenergic, muscarinic, nicotinic, purinergic, or serotoninergic receptors. These results show that HV is an intrinsic feature of systemic VSM in cyclostomes and suggest that HV has been in the repertoire of VSM responses, since the origin of vertebrates. The exceptionally hardy HV in cyclostome DA may provide a useful model with which to examine both the phylogeny and mechanisms of this response.

Angiotensin signaling and receptor types in teleost fish

Despite advances characterizing mammalian angiotensin receptors, the phylogeny of fish angiotensin receptors remains unclear. Three aspects of receptor function: (1) the nature of the ligand; (2) the second messenger system activated by it; and (3) the pharmacological profile of specific antagonists, are examined to provide insight into the fish receptor. (1) The octapeptide sequences of fish and mammalian angiotensin II (ANG II) are nearly homologous, differing only at the first and fifth residues. Both peptides are almost equally efficacious and equipotent in heterologous systems and both contain key agonist switches Tyr(4) and Phe(8) necessary to activate mammalian AT(1)-type receptors. (2) ANG II increases inositol trisphosphate production, and elevates intracellular calcium in fish tissues consistent with activation of the AT(1) receptor. (3) However, the specific mammalian sartan-type AT(1) antagonists, e.g. losartan, produce inconsistent results in fish often acting as partial agonists, or inhibiting only at elevated concentrations. Because sartans and ANG II act at distinct sites on the AT(1) receptor, we propose that the teleost receptor is an AT(1)-type receptor that is fairly well conserved with respect to both the ANG binding site and coupling to the second messenger system, whereas the sartan binding site has been poorly conserved. The evidence for non-AT(1) type ANG II receptors in teleosts is limited. Mammalian AT(2) receptor antagonists are generally ineffective but may block at elevated, non-specific doses. Truncated ANG II fragments, ANG III and ANG IV, are often less potent than ANG II, however, their receptors have not been examined. Preliminary studies in trout indicate that angiotensin 1-7 may have a mild vasodilatory effect; additional work is needed to determine if non-AT(1)-type receptors are involved.

Similarity of vasorelaxant effects of natriuretic peptides in isolated blood vessels of salmonids

Natriuretic peptides (NPs) have been implicated in cardiovascular regulation in rainbow trout (Oncorhyncus mykiss), and it has been observed that the vasorelaxant activity of distinct trout and human NPs is similar in isolated trout arteries. This study characterizes the response of a variety of vessels from rainbow trout and other salmonids to different NPs. The effects of heterologous (rat atrial and human atrial) and homologous (rainbow trout atrial and rainbow trout ventricular) NPs were examined in precontracted efferent branchial arteries from rainbow trout (O. mykiss, Kamloops strain), lake whitefish (Coregonus clupeaformis), and in rainbow trout celiacomesenteric arteries and anterior cardinal veins. The response to mammalian NPs was also examined in efferent branchial arteries from the steelhead (O. mykiss, Skamania strain), coho salmon (Oncorhyncus kisutch), brook trout (Salvelinus fontinalis), and brown trout (Salmo trutta). In general, there were relatively few differences that were species, peptide, or vessel specific. There was no difference in the sensitivity (concentration producing a half-maximal response EC(50)) or efficacy (percent relaxation, i.e., E(max)) of trout or whitefish efferent branchial arteries to any NP, except human NP, which was significantly less effective (greater EC(50) and lower E(max)) in whitefish arteries. There were no differences in E(max) of mammalian NPs in efferent branchial arteries from any species, and only coho and brook trout had significantly different EC(50)'s (coho, 1.0+/-0.2 nM; brook trout, 4. 2+/-0.6 nM; and other species, from 1.9 to 3.5 nM). Rainbow and coho anterior cardinal veins were less sensitive than arteries to mammalian NPs (EC(50)'s; 8.8+/-2.0, 2.0+/-0.1 vs. 3.0+/-0.9, 1.0+/-0. 2, respectively), whereas brown trout veins were more sensitive (1. 0+/-0.2, 3.5+/-1.3, respectively). Sodium nitroprusside (SNP), which activates soluble guanylate cyclase, was vasodilatory, albeit significantly less potent than all NPs, in efferent branchial arteries of all species. SNP was significantly more potent in trout than whitefish efferent branchial arteries, whereas it was equally efficacious in these vessels. These results demonstrate that multiple vessels from various salmonids are similarly responsive to the vasorelaxant effects of a variety of NPs and that the salmonid NP receptor has relatively little ability to discriminate between homologous and heterologous peptides. We conclude that the vascular NP receptor complex is highly conserved among salmonids. Further, salmonids utilize cyclic guanosine monophosphate (cGMP) elevations for reductions of vascular tonus by both particulate and soluble guanylate cyclase pathways.

Spontaneous contractions in elasmobranch vessels in vitro

Isolated vessels from four elasmobranchs, yellow stingray (Urolophus jamaicensis), clearnose skate (Raja eglanteria), ghost shark (Hydrolagus novaezelandiae), and spiny dogfish (Squalus acanthias), were examined for the presence of spontaneous contractions (SC). SC were observed in otherwise unstimulated dorsal aortas (DA) from stingray and ghost shark, but not in skate DA. Unstimulated ventral aortas (VA) did not exhibit SC. After treatment of VA with a contractile agonist, SC appeared in stingray and skate but not ghost shark or dogfish. SC in stingray VA were subsequently inhibited by either epinephrine (10(-5) M) or indomethacin (10(-4) M). Agonist contraction also elicited strong SC in ductus Cuvier from stingray, but not from ghost shark or dogfish. SC in dogfish hepatic portal veins (HPV) produced a rhythmical oscillation in tension. The frequency of HPV SC was highest (approximately 1 min(-1)) in intact veins and lower (approximately 3 min(-1)) in vein segments, indicative of a dominant pacemaker in the intact vessel. SC in HPV were depressed during the first 30 min of hypoxia, but there was substantial recovery over an additional 30 min of hypoxia and complete recovery upon return to normoxia. Addition of 80 mM KCl completely inhibited HPV SC and lowered resting tone. These results show that SC are a common feature of elasmobranch vessels and there appears to be a correlation between swimming behavior and the propensity for SC. KCl inhibition of SC and tonus in HPV is highly unusual for vascular smooth muscle.

Shorter duration of oral N-acetylcysteine therapy for acute acetaminophen overdose

STUDY OBJECTIVE

We sought to evaluate the safety and efficacy of a shorter N-acetylcysteine (NAC) regimen in the treatment of acute acetaminophen overdose.

METHODS

We performed a retrospective case series in a large urban county hospital. Of 305 patients identified through the emergency department, 75 patients met the criteria inclusion: an acute overdose ingestion, serum acetaminophen concentration in toxic range according to the Rumack-Matthew nomogram, and oral NAC treatment initiated within 24 hours of the ingestion. The regional poison control center recommended oral treatment with NAC 140 mg/kg, followed by maintenance doses of 70 mg/kg every 4 hours until the serum acetaminophen level was no longer detectable, rather than the standard 72-hour treatment regimen.

RESULTS

The primary outcome measure was the development of hepatotoxicity. Twenty-five (33.3%) patients were treated for a period of less than 24 hours, 25 (33.3%) were treated for 24 to 36 hours, and 25 (33.3%) were treated for 37 to 64 hours; the mean and median duration of treatment was 31 hours. None of the patients treated for less than 24 hours had evidence of hepatotoxicity (aspartate aminotransferase [AST] or alanine aminotransferase [ALT] level >1,000 IU/L); hepatotoxicity developed in 2 (8%) patients treated for 24 to 36 hours and 4 (16%) patients treated for 37 to 64 hours. There were no deaths or patients who received liver transplantation. The overall incidence of hepatotoxicity in our patients was similar to that found in other protocols with administration of oral NAC for 72 hours or intravenous NAC for 20 or 48 hours.

CONCLUSION

This observational study suggests that a shorter course of oral NAC therapy in patients who do not show evidence of hepatotoxicity within 36 hours of an acute acetaminophen overdose is safe and effective.

Effects of endothelin-1 and homologous trout endothelin on cardiovascular function in rainbow trout

The cardiovascular effects of endothelin (ET)-1 and the recently sequenced homologous trout ET were examined in unanesthetized trout, and vascular capacitance curves were constructed to evaluate the responsiveness of the venous system to ET-1. A bolus dose of 667 pmol/kg ET-1 doubled ventral aortic pressure; produced a triphasic pressor-depressor-pressor response in dorsal aortic pressure (P(DA)); increased central venous pressure, gill resistance, and systemic resistance; and decreased cardiac output, heart rate, and stroke volume. These responses were dose dependent. Bolus injection of trout ET (333 or 1,000 pmol/kg) produced essentially identical, dose-dependent cardiovascular responses as ET-1. Dorsal aortic infusion of 1 and 3 pmol. kg(-1). min(-1) ET-1 and central venous infusion into the ductus Cuvier of 0.3 and 1 pmol. kg(-1). min(-1) produced similar dose-dependent cardiovascular responses, although the increase in P(DA) became monophasic. The heightened sensitivity to central venous infusion was presumably due to the more immediate exposure of the branchial vasculature to the peptide. Infusion of 1 pmol. kg(-1). min(-1) ET-1 decreased vascular compliance but had no effect on unstressed blood volume. These results show that ETs affect a variety of cardiovascular functions in trout and that branchial vascular resistance and venous compliance are especially sensitive. The multiplicity of effectors stimulated by ET suggests that this peptide was extensively integrated into cardiovascular function early on in vertebrate phylogeny.

Clinical course of a fatal ingestion of diquat

CASE REPORT

A 28-year-old male ingested the herbicide diquat. The patient rapidly developed severe gastrointestinal and metabolic disturbances, airway compromise, respiratory failure, renal failure, hemodynamic collapse, and seizures. We describe multiple metabolic abnormalities, an apparent artifact introduced by diquat in the laboratory assay for serum creatinine, serum diquat levels, and the need for emergency airway management.

Cardiac natriuretic peptides: a physiological lineage of cardioprotective hormones?

Vertebrate hearts from fish to mammals secrete peptide hormones with profound natriuretic, diuretic, and vasodilatory activity; however, the specific role of these cardiac natriuretic peptides (NPs) in homeostasis is unclear. NPs have been suggested to be involved in salt excretion in saltwater teleosts, whereas they are proposed to be more important in volume regulation in mammals. In this review, we consider an alternative (or perhaps complementary) function of NPs to protect the heart. This hypothesis is based on a number of observations. First, evidence for NPs, or NP-like activity has been found in all vertebrate hearts thus far examined, from osmoconforming saltwater hagfish to euryhaline freshwater and saltwater teleosts to terrestrial mammals. Thus the presence of cardiac NPs appears to be independent of environmental conditions that may variously affect salt and water balance. Second, cardiac stretch is a universal, and one of the most powerful, NP secretagogues. Furthermore, stretch-induced NP release in euryhaline teleosts appears relatively independent of ambient salinity. Third, excessive cardiac stretch that increases end-diastolic volume (EDV) can compromise the mechanical ability of the heart by decreasing actin-myosin interaction (length-tension) or through Laplace effects whereby as EDV increases, the wall tension necessary to maintain a constant pressure must also increase. Excessive cardiac stretch can be produced by factors that decrease cardiac emptying (i.e., increased arterial pressure), or by factors that increase cardiac filling (i.e., increased blood volume, increased venous tone, or decreased venous compliance). Fourth, the major physiological actions of cardiac NPs enhance cardiac emptying and decrease cardiac filling. In fish, NPs promote cardiac emptying by decreasing gill vascular resistance, thereby lowering ventral aortic pressure. In mammals a similar effect is achieved through pulmonary vasodilation. NPs also decrease cardiac filling by decreasing blood volume and increasing venous compliance, the latter producing a rapid fall in central venous pressure. Fifth, the presence of NP clearance receptors in the gill and lung (between the heart and systemic circulation) suggest that these tissues may be exposed to considerably higher NP titers than are systemic tissues. Thus, a decrease in outflow resistance immediately downstream from the heart may be the first response to increased cardiac distension. Because the physiology of cardiac NPs is basically the same in fish and mammals, we propose that the cardioprotective effects of NPs have been well preserved throughout the course of vertebrate evolution. It is also likely that the cardioprotective role of NPs was one of the most primordial homeostatic activities of these peptides in the earliest vertebrates.

Do the DSM decision trees improve diagnostic ability?

Experiment 1 examined whether the use of the DSM-III-R decision trees increased the accuracy of DSM-III-R diagnoses. Results indicated that the use of the decision trees interacted with the level of DSM-III-R experience to affect diagnostic accuracy. The use of the decision trees resulted in a modest increase in diagnostic accuracy for participants with less DSM-III-R experience; for participants with more DSM-III-R experience, the use of the decision trees had no significant effect on diagnostic accuracy. Experiment 2 examined whether the use of the DSM-III-R decision trees increased the accuracy and confidence and decreased the time of DSM-IlI-R diagnosis across participants with varying levels of DSM-III-R experience. The primary analyses consisted of a 3 x 2 x 2-multivariate analysis of variance (MANOVA) to determine whether the use of the decision trees increased diagnostic accuracy and diagnostic confidence and decreased diagnostic time. Results indicated (1) the experienced participants made more accurate diagnoses than the less-experienced and no-experience participants: (2) the decision trees, combined with practice, increased class diagnostic accuracy and decreased diagnostic time; and (3) participants were more confident in their diagnosis when they used the decision trees than when they did not use the decision trees. Supplementary analyses consisted of two one-way analysis of variance (ANOVA) procedures and indicated that participants' preference for and knowledge of how to use the decision trees did not significantly affect their diagnostic accuracy.

Purification, structural characterization, and myotropic activity of endothelin from trout, Oncorhynchus mykiss

Endothelin (ET) from a nontetrapod species has never been characterized, either structurally or biologically. A single molecular form of trout ET with 21-amino-acid residues was isolated in pure form from an extract of the kidney of the steelhead trout, Oncorhynchus mykiss and its primary structure established as Cys-Ser-Cys-Ala-Thr-Phe-Leu-Asp-Lys-Glu10-Cys-Val-Tyr-Phe-Cys-His- L eu-Asp-Ile-Ile20-Trp. This amino acid sequence shows only three substitutions (Ala4-->Ser, Thr5-->Ser, and Phe6-->Trp) compared with human ET-2, demonstrating that the structure of the peptide has been well conserved during evolution and that the pathway of posttranslational processing of preproendothelin in the trout is probably similar to that in mammals. Synthetic trout ET produced concentration-dependent constrictions of isolated rings of vascular tissue from trout efferent branchial artery (EBA; pD2 = 7. 90 +/- 0.06, n = 5), caeliacomesenteric artery (pD2 = 8.03 +/- 0. 04, n = 4), anterior cardinal vein (ACV; pD2 = 8.57 +/- 0.25, n = 4), and rat abdominal aorta (AO; pD2 = 8.86 +/- 0.08, n = 7). Trout and rat vessels were more sensitive to mammalian ET-1 than to trout ET (pD(2) for human ET-1 in: EBA = 9.12 +/- 0.14; ACV = 9.90 +/- 0.15; AO = 8.86 +/- 0.08), but there was no significant difference in the maximum tension produced by either peptide in these vessels.

The control of blood pressure during external hypercapnia in the rainbow trout (Oncorhynchus mykiss)

Adult freshwater rainbow trout (Oncorhynchus mykiss) were exposed acutely (approximately 20 min) in a stepwise manner to increasing levels of environmental carbon dioxide ranging between 1.7 and 9.0 mmHg (0.23-1.2 kPa). Experiments were performed to examine, for the first time, the influence of hypercapnic acidosis on aspects of cardiovascular physiology including blood pressure, cardiac output and vascular resistance. Fish displayed dose (water CO(2) partial pressure) -dependent increases in ventral aortic (13–39 %) and dorsal aortic (17–54 %) blood pressures that reflected marked increases in systemic vascular resistance (16–78 %); branchial vascular resistance was unaffected by hypercapnia. At the highest level of hypercapnia (9.0 mmHg), central venous pressure was significantly elevated by 54 %. Although cardiac output remained constant, heart rate was significantly lowered by 4–7 beats min(−)(1) at the two highest levels of hypercapnia. To determine whether the cardiovascular responses to hypercapnia were being blunted by the stepwise increase in external P(CO2), a separate group of fish was exposed directly to a single step of hypercapnia (water P(CO2) 8.0 mmHg). The cardiovascular responses were similar to those exhibited by the more gradually exposed fish except that central venous pressure did not increase and the extent of the bradycardia was greater (13 beats min(−)(1)). After confirming the effectiveness of yohimbine in blocking the vasoconstrictory (α)-adrenoreceptors of the systemic vasculature, this antagonist was used as a tool to assess the importance of (α)-adrenoreceptor stimulation in promoting the cardiovascular responses during hypercapnia. Prior treatment of fish with yohimbine prevented the increased blood pressures and systemic vascular resistance during hypercapnia but did not influence the CO(2)-induced bradycardia. Plasma levels of catecholamines did not change during hypercapnia, and therefore the stimulation of the systemic (α)-adrenoreceptors presumably reflected increased sympathetic nerve activity. To determine whether the cardiovascular changes elicited by hypercapnia were related to acidosis-induced hypoxaemia, fish were exposed to hypoxia in a stepwise manner (water P(O2) 65–151 mmHg). The cardiovascular responses to hypoxia were markedly different from those to hypercapnia and consisted of pronounced increases in systemic and branchial vascular resistance, but only at the most severe level of hypoxia; ventral and dorsal aortic pressures were unaffected. The differences between the responses to hypercapnia and hypoxia, coupled with the smaller reductions in blood oxygen content during hypercapnia, support the hypothesis that the cardiovascular responses to CO(2) are direct and are unrelated to hypoxaemia.

Pharmacological characterization of arginine vasotocin vascular smooth muscle receptors in the trout (Oncorhynchus mykiss) in vitro

Arginine vasotocin (AVT) is present in the neurohypophysis of all nonmammalian vertebrates and it appears to be the antecedent of the neurohypophysial nonapeptide hormones. Relatively little is known about AVT receptors in lower vertebrates, especially fish, and the present study was designed to examine AVT receptor interactions in trout vascular and nonvascular smooth muscle in vitro. AVT produced dose-dependent contraction of isolated rings from celiacomesenteric, coronary, and efferent branchial arteries, ventral aorta, anterior cardinal vein, and strips of ductus Cuvier. The greatest efficacy (magnitude of contraction per unit tissue weight) and sensitivity (effective concentration for half-maximal response, EC50) to AVT was found in the efferent bronchial artery (EBA) and its receptors were characterized further. Other neurohypophysial peptides, including arginine vasopressin (AVP), lysine vasopressin (LVP), isotocin (IST), and oxytocin (OXY), contracted EBA with an efficacy order of (most to least) AVT = AVP = OXY > LVP > IST and a sensitivity order of AVT > OXY >/= AVP > IST > LVP. Neither Desmopressin, an AVP V2-receptor agonist, nor the AVP ring fragment, AVP4-9, contracted EBA nor did they inhibit AVT contraction. Pretreatment of EBA rings with the selective AVP V1-receptor antagonists (deamino-Pen1, O-Me-Tyr2, Arg8-vasopressin and deamino-Pen1, Val4, Arg8-vasopressin), the selective V2-receptor antagonist (adamantaneacetyl1, O-Et-D-Tyr0, Val4, aminobutyryl6, Arg8,9-vasopressin), or the combined V1-oxytocin receptor antagonist (d(CH2)5[Tyr(Me)2, Orn8-AVT]) competitively inhibited AVT contractions without affecting AVT efficacy. Receptor affinity constants (pA2) determined by Schild analysis were in the range of 6.8-7.3, with slightly higher constants for the AVP V1-/oxytocin receptor antagonists than for the selective V2-receptor antagonist. Endothelium removal had no effect on EBA sensitivity to AVT. EBA rings were an order of magnitude more sensitive to AVT than nonvascular gastrointestinal and urinary bladder smooth muscle rings or strips. However, AVT (10(-7) M) was as efficacious as acetylcholine (10(-5) M) in gastrointestinal, gallbladder, and urinary bladder smooth muscle. It is concluded that trout EBA possess an AVT smooth muscle receptor that shares a similar pharmacological profile with the mammalian vascular AVP V1a-receptor and the OXY-receptor, but it is distinct from the previously reported gill epithelial cell receptor.

Mushroom poisoning due to amatoxin. Northern California, Winter 1996-1997

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Catecholaminergic regulation of venous function in the rainbow trout

The significance of the sympathetic nervous system (SNS) in regulating peripheral vascular resistance and cardiac function in fish has been well established, whereas its effect on venous function in vivo is unknown. Two protocols were employed in the present study to evaluate SNS effects on the venous system in intact, unanesthetized trout. In the first, trout were instrumented with pressure cannulas in the ventral (PVA) and dorsal (PDA) aortas and ductus Cuvier (PVEN), and cardiac output (CO) was measured with a flow probe around the ventral aorta. Heart rate, stroke volume, and gill and systemic resistances were calculated from the measured parameters. In the second group, vascular capacitance curves were obtained by monitoring mean circulatory filling pressure (PVEN) during transient interruption of CO and while blood volume was adjusted between 80 and 120% of normal. Unstressed blood volume (USBV) and vascular compliance (C) were derived from the capacitance curves. Infusion of epinephrine (Epi; 3.3 nmol.min-1.kg body wt-1) increased PVA, PDA, and PVEN, whereas norepinephrine (NE) infusion (3.3 nmol.min-1.kg body wt-1) increased PVA and PDA but did not affect PVEN. Epi (1.0 nmol.min-1.kg body wt-1), but not NE (2.6 or 10.4 nmol.min-1.kg body wt-1), displaced the capacitance curve to the right and significantly decreased USBV. Inhibition of alpha 1-adrenoceptors with prazosin, or ganglionic nicotinic receptor blockade with hexamethonium, produced a left shift in the capacitance curve, and both treatments increased USBV and C. Conversely, the alpha-adrenoceptor antagonist phentolamine did not effect vascular capacitance. These results show that Epi has potent effects on trout veins in vivo and that it mobilizes blood from the unstressed into the stressed vascular compartment and augments central venous pressure by decreasing venous compliance. These results also show that the SNS is an active effector of venous tone and compliance in trout; this is the first demonstration of tonic regulation of vascular capacitance in any fish.

The costs and outcomes of restricting public access to poison control centers. Results from a natural experiment

OBJECTIVES

The authors examined the costs and outcomes resulting from a natural experiment during which direct public access to poison control centers was restricted and then restored.

METHODS

Both societal and health care purchaser perspectives were used. Probability data were obtained from a natural experiment during which public callers from a large county in California were electronically blocked from directly accessing the poison control center. Callers were referred to 911, which had direct access to the poison control center, if they thought they had a poisoning emergency. We conducted telephone interviews of: (a) persons who attempted to call the poison control center for a child's poisoning exposure but who did not have direct access (n = 270) and (b) persons who called the poison control center after direct access was restored (n = 279). Cost data were obtained from primary data collection and from other sources. The outcome measure was the appropriateness of the treatment location (at home or at a health care facility). Caller-reported outcomes were also examined.

RESULTS

The average additional cost per blocked call was $10.89 from a societal perspective, or $33.14 from a health care purchaser perspective. Fourteen percent of callers with restricted access were treated at an inappropriate location, compared with only 2% of callers with direct poison control center access. Also, 14% did not obtain any professional advice after they attempted to call the poison control center, although 66% of these cases involved potentially toxic substances. Results were robust across a range of sensitivity analyses.

CONCLUSION

Restricting direct public access to poison control centers created additional costs to society, the health care sector, and callers.

Hormone metabolism by the fish gill

The fish gill, like the mammalian lung, is ideally situated to process circulating biomolecules because: 1) the gill is the only organ perfused by the entire cardiac output, 2) the in-series positioning of branchial and systemic circulations permits "conditioning" of blood immediately before systemic perfusion and 3) gill microcirculation is extensive, providing substantial endothelial/pillar cell surface in contact with plasma. In addition, two or three distinct circulatory pathways within the gill may differentially affect plasma substrates, raising the possibility of vasoactive control of hormone titers. Hormones may be activated or inactivated by the gill, the latter involving extraction (uptake) from the plasma, metabolism by enzymes on the endothelial surface without uptake or uptake plus intracellular metabolism. Over 60% of angiotensin I (ANG I) is activated to angiotensin II (ANG II) in a single transit through the gill lamellae by pillar cell angiotensin-converting enzyme, whereas both ANG I and II are inactivated by the non-lamellar filamental vasculature. Gills may accumulate and store (uptake 1) or degrade (uptake 2) catecholamines via intracellular monoamine oxidase and catechol-O-methyl transferase enzymes, and they show substrate preference for norepinephrine over epinephrine. Similar processes may exist for serotonin. Atrial natriuretic peptides are efficiently (60-90%) extracted from plasma in vivo by C-type clearance receptors. Fifty percent of an endothelin-1 bolus is removed in a single transit through the gill circulation, arginine vasotocin extraction is modest and bradykinin is virtually unaffected. Arachidonic acid is completely extracted by the gill, whereas extraction of prostaglandins I2 and E2 is only 13 and 5%, respectively. Intense cytochrome P450 immunofluorescence in the pillar cells suggests that the gill vasculature may be an important site of detoxification and production of biologically active epoxides. Thus, gills appear to be potent and selective effectors of hormonal signals.

Purification and cardiovascular activity of [Met1, Met5]-bradykinin from the plasma of a sturgeon (Acipenseriformes)

The sturgeons (Order Acipenseriformes) are extant representatives of a group of primitive Actinopterygian (ray-finned) fish that probably shared a common ancestor with present-day teleosts. Incubation of heat-denatured plasma from a sturgeon (a hybrid of the shovelnosed sturgeon Scaphirhynchus platorynchus and the pallid sturgeon Scaphirhynchus albus) with either trypsin or porcine pancreatic kallikrein generated bradykinin-like immunoreactivity. The primary structure of sturgeon bradykinin was established as Met-Pro-Pro-Gly-Met-Ser-Pro-Phe-Arg. This amino acid sequence contains two amino acid substitutions (Arg1 --> Met and Phe5 --> Met) compared with mammalian bradykinin. Bolus injections of synthetic sturgeon bradykinin in doses as low as 1 pmol/kg into the dorsal aorta of unanesthetized sturgeon resulted in an immediate and significant fall in arterial blood pressure with a maximum depressor response at 300 pmol/kg. Thus, the cardiovascular response of the sturgeon to bradykinin resembles more closely the response of mammals rather than the predominantly pressor response seen in teleost fish. Sturgeon bradykinin produced a strong and concentration-dependent (EC50 = 4.7 +/- 0.7 x 10(-10) M) relaxation of rings of vascular tissue from the sturgeon ventral aorta that had been pre-contracted with acetylcholine. The data indicate that sturgeon tissues are particularly responsive to native bradykinin and suggest that the kallikrein-kinin system may have evolved before the appearance of the neopterygians (gars, bowfin and teleosts).

Cardiovascular effects of arginine vasotocin in the rainbow trout Oncorhynchus mykiss

The physiological functions of the neurohypophyseal hormone arginine vasotocin (AVT) in teleosts are not clear. In the present studies, the sites and mechanisms of action of AVT on the rainbow trout Oncorhynchus mykiss cardiovascular system were examined in unanesthetized instrumented fish, perfused organs and isolated vessels. Injection of AVT (1, 10 or 100 pmol kg-1 body mass) into trout with dorsal aortic cannulas produced a modest, but dose-dependent, increase in dorsal aortic pressure (PDA). Bolus injection of AVT (100 pmol kg-1 body mass), or continuous infusion (6.7 pmol kg-1 min-1), into trout instrumented with dorsal aortic, ventral aortic and central venous cannulas and a ventral aortic flow probe significantly increased PDA as well as ventral aortic (PVA) and central venous (PVEN) blood pressure. Bradycardia accompanied the rapid rise in PVA while gill resistance (RG) increased. Maximum response to the AVT bolus was reached within 13­21 min and the response decayed slowly over the ensuing 90 min. AVT infusion (6.7 pmol kg-1 min-1) significantly increased PVEN and mean circulatory filling pressure and decreased unstressed blood volume, whereas venous compliance was unaffected. These in vivo studies indicate that AVT increases venous tone, thereby mobilizing blood from the unstressed compartment into the stressed compartment. This increases PVEN, which increases venous return and helps maintain, or slightly elevate, cardiac output. This, combined with an elevated RG and slightly elevated systemic resistance (RS), increases both PVA and PDA; however, the rise in PDA is mitigated by a disproportionate increase in RG relative to RS. In vitro, the effects of AVT are consistent with in vivo responses. AVT increased vascular resistance in the perfused gill and perfused trunk and contracted isolated vascular rings from both rainbow and steelhead trout. The general order of sensitivity of isolated vessels to AVT was (in decreasing order): anterior cardinal vein, celiacomesenteric artery, ductus Cuvier, efferent branchial artery, ventral aorta and coronary artery. Extracellular Ca2+ accounted for over 70 % of the tension in the AVT-contracted efferent branchial artery, but only 57 % of the tension in the anterior cardinal vein. Vascular AVT receptor sensitivity (EC50) in vitro ranged from 0.3 to 6 nmol l-1 and was similar to the estimated ED50 for the dose-dependent increase in PDA in vivo (approximately 1 nmol l-1). AVT was not inotropic in paced ventricular rings nor did it exhibit vasorelaxant activity in perfused organs or vascular rings. These results show that AVT is a potent vasoconstrictor in trout and that its two primary cardiovascular targets are the systemic veins and the branchial vasculature.

A new natriuretic peptide isolated from cardiac atria of trout, Oncorhynchus mykiss

Atrial and brain natriuretic peptides (ANP and BNP, respectively) are two cardiac natriuretic peptides (NPs) found in tetrapods from amphibians to mammals, whereas ANP and ventricular NP (VNP) have been identified in eel hearts. Because VNP has also been found in the rainbow trout ventricle, we attempted to isolate NP from trout cardiac atria in order to determine whether ANP and VNP are common cardiac NPs in teleosts. In the present experiments, we isolated VNP and a novel atrial NP consisting of 29 amino acid residues from the atria. This new trout NP exhibited similar sequence identity to mammalian ANP and BNP (50-60%). Its homology to eel ANP was low (52%) compared with high homology of trout and eel VNP (78%). Based on yield, the content of this new NP in trout atria may be even smaller than that of VNP. The new trout atrial NP exhibited low relaxant activity in the chick rectum (only 1/10 of that of trout VNP), and extremely low vasorelaxant activity in the rat aortic strip (only 1/400 of that of human ANP). However, the new trout NP was equipotent with trout VNP and human ANP in relaxing trout epibranchial artery. Based on the sequence similarity with other NPs and on atrial content, the new NP isolated from trout atria cannot yet be assigned to a known member of the NP family.

Effects of natriuretic peptides and nitroprusside on venous function in trout

Active venous regulation of cardiovascular function is well known in mammals but has not been demonstrated in fish. In the present studies, the natriuretic peptides (NP) rat atrial natriuretic peptide (ANP) and trout ventricular natriuretic peptide (VNP), clearance receptor inhibitor SC-46542, and sodium nitroprusside (SNP) were infused into unanesthetized trout fitted with pressure cannulas in the ventral aorta, dorsal aorta, and ductus Cuvier, and a ventral aorta (VA) flow probe was used to measure cardiac output (CO). In another group, in vivo vascular (venous) capacitance curves were obtained during ANP or SNP infusion. The in vitro effects of NP on vessels and the heart were also examined. ANP, VNP, and SC-46542 decreased central venous pressure (PVen), CO, stroke volume (SV), and gill resistance (RG), whereas systemic resistance (RS) and heart rate (HR) increased. Dorsal aortic pressure (PDA) transiently increased and then fell even though RS remained elevated. ANP decreased mean circulatory filling pressure (MCFP), increased vascular compliance at all blood volumes, and increased unstressed volume in hypovolemic fish. ANP had no direct effect on the heart. ANP responses in vivo were not altered in trout made hypotensive by prior treatment with the angiotensin-converting enzyme inhibitor lisinopril. SNP reduced ventral aortic pressure (PVA), PDA, and RS, increased CO and HR, but did not affect PVen, SV, or RG. SNP slightly decreased MCFP but did not affect compliance or unstressed volume. In vitro, large systemic arteries were more responsive than veins to NP, whereas SNP relaxed both. These results show that, in vivo, NP decrease venous compliance, thereby decreasing venous return, CO, and arterial pressure. Conversely, SNP hypotension is due to decreased RS. This is the first evidence for active regulation of venous capacitance in fish, which probably occurs in small veins or venules. The presence of venous baroreceptors is also suggested.

Willingness to pay for poison control centers

We used the willingness-to-pay (WTP) method to value the benefits of poison control centers when direct access was blocked, comparing WTP among: (1) blocked callers (n = 396), (2) callers after access was restored (n = 418), and (3) the general population (n = 119). Mean monthly WTP was $6.70 (blocked callers), $6.11 (non-blocked callers), and $2.55 (general population). Blocked and non-blocked callers had a significantly higher WTP than general population respondents (p < 0.001). We conclude that the WTP method measured benefits that are difficult to quantify; however, WTP surveys need to be carefully conducted to minimize bias. We discuss how this approach could be useful for other health care services.

Cardiovascular effects of homologous bradykinin in rainbow trout

Bradykinins have only recently been identified in fish, and a detailed analysis of their cardiovascular actions is lacking. The present study examines the cardiovascular effects of trout bradykinin ([Arg0,Trp5,Leu8]bradykinin; tBK) in conscious trout, Oncorhynchus mykiss. tBK (1-10 nmol/kg body wt bolus) produced triphasic pressor-depressor-pressor responses. In phase 1, cardiac output (CO), ventral aortic (P(VA)), dorsal aortic (P(DA)), and central venous pressure increased, whereas systemic (R(S)) and gill resistance (R(G)) were unchanged. In phase 2, R(G) increased, whereas R(S), CO, and heart rate decreased, reducing P(VA) and P(DA). Plasma prostaglandin E2 and the prostacyclin metabolite, 6-ketoprostaglandin F1alpha, were significantly elevated during phase 2, whereas leukotrienes C4 and B4 and thromboxane B2 were unaffected. Phase 3 was produced by an increased CO and R(S) and the return of R(G) to control. Phase 1 pressor response was not blocked by inhibitors of cyclooxygenase, angiotensin-converting enzyme (ACE) or alpha-adrenoceptors (alpha-AD), whereas phase 2 depressor and plasma prostaglandin responses were prevented by cyclooxygenase inhibition. Phase 3 was partially blocked by ACE and alpha-AD inhibitors and is a response to the preceding hypotension. In vitro, tBK only decreased vascular resistance in the perfused splanchnic or skeletal muscle-kidney preparations. These results show that although tBK has multiple effects on the trout cardiovascular system, none of the effects are due to direct tBK stimulation of vascular smooth muscle. Phase 2 vasodilation has features consistent with release of vasodilator prostaglandins while the mechanism of phase 1 constriction is unknown.

Incorrect overdose management advice in the Physicians' Desk Reference

STUDY HYPOTHESIS

Physicians may consult references such as Physicians' Desk Reference (PDR) for overdose management advice. Although PDR recommendations are approved by the US Food and Drug Administration (FDA), we hypothesized that they are often outdated and potentially hazardous.

METHODS

We surveyed physicians who consulted our poison center during a 1-month period with regard to their use of the PDR for overdose information and also compared PDR overdose treatment recommendations with those of five current major toxicology references. For the PDR overdose information review we examined data from the American Association of Poison Control Centers to identify pharmaceutical categories with the largest number of deaths. We reviewed the four leading drugs with at least 1,000 reported exposures in each category and identified 20 PDR-listed brand-name products for analysis. We obtained the consensus from five current toxicology references on contraindicated treatments, ineffective treatments, and specific recommended treatments or antidotes. Finally, we compared the overdose management advice provided in the 1994 PDR with the toxicology reference consensus.

RESULTS

Forty of 80 of physicians surveyed (50%) reported use of the PDR for overdose information in the preceding 12 months. Of the 20 PDR entries, 16 (80%) had at least one deficiency, and 5 (25%) had two or more deficiencies. Thirteen (65%) omitted an indicated specific treatment, three (15%) recommended contraindicated treatments, and four (20%) advised ineffective treatments with potential for harm. Only four entries (20%) had no deficiencies by our survey criteria.

CONCLUSION

We found serious discrepancies in overdose treatment advice in the PDR compared with a consensus of current toxicology references. Altogether, four of five PDR entries were deficient, and almost half advised ineffective or frankly contraindicated therapies. Despite FDA approval, the use of PDR overdose advice in a serious poisoning case could result in unnecessary morbidity or mortality.

Cardiovascular actions of trout urotensin II in the conscious trout, Oncorhynchus mykiss

The central and peripheral cardiovascular effects of synthetic trout urotensin II (UII) were investigated in the conscious rainbow trout. Intracerebroventricular injection of 50 pmol UII produced a slight (3%) but significant (P < 0.05) increase in heart rate but had no effect on mean arterial blood pressure. Injection of 500 pmol UII icv produced a significant (P < 0.05) rise (8%) in blood pressure with no change in heart rate. In contrast to the weak pressor effect of centrally administered UII, intra-arterial injection of UII produced a dose-dependent increase in arterial blood pressure and decrease in heart rate with significant (P < 0.05) effects on both parameters observed at a dose of 25 pmol. Higher doses of the peptide produced a sustained decrease in cardiac output that accompanied the bradycardia and rise in arterial blood pressure. The UII-induced bradycardia, but not the increase in pressure, was abolished by pretreatment with phentolamine. Trout UII produced a sustained and dose-dependent contraction of isolated vascular rings prepared from trout efferent branchial [-log 50% of the concentration producing maximal contraction (pD2) = 8.30] and celiacomesenteric (pD2 = 8.22) arteries but was without effects on vascular rings from the anterior cardinal vein. The data indicate that the pressor effect of UII in trout is mediated predominantly, if not exclusively, by an increase in systemic vascular resistance. The UII-induced hypertensive response does not seem to involve release of catecholamines, but the bradycardia may arise from adrenergic-mediated activation of cardioinhibitory baroreflexes.

Arginine vasotocin relaxation of gar (Lepisosteous spp.) hepatic vein in vitro

The effects of arginine vasotocin (AVT) were examined in isolated gar arteries (afferent branchial, ABA; conus arteriosus, CA; ventral aorta, VA) and veins (hepatic, HV; intestinal; ovarian). AVT (10(-11) - 10(-7) M) had no effect in CA, produced contraction in ABA and VA and stimulated relaxation in veins. In precontracted HV, AVT relaxation was dose-dependent, long-lived (> 30 min) and reduced total tension by 49.0 +/- 10.7%. EC50s for AVT, arginine vasopressin, oxytocin, desmopressin, and isotocin in gar HV were 1.4 +/- 0.3, 3.6 +/- 0.2, 5.3 +/- 1.7, 11.0 +/- 6.5, and 19.0 +/- 0.4 nM, respectively. AVT was more potent compared with isotocin. Strength of relaxation (percentage decrease in total tension) of AVT and structural analogs was similar (range = 32.5 to 55%). Endothelium removal did not alter percentage relaxation or sensitivity to AVT in HV. AVT relaxation was not inhibited by nitric oxide synthase inhibitors or propranolol or reversed by addition of methylene blue but it was significantly enhanced by indomethacin (10(-5) M). Arginine vasopressin-receptor antagonists (V1- or V2-type selectivity; 10(-6) M) were equally effective inhibitors, each blocked 99% of AVT relaxation. Forskolin (10(-6) M) and papaverine (10(-4) M) relaxed precontracted gar arteries and veins. The adenylyl cyclase inhibitors SQ 22536 and MDL 12,330A (10(-5) M) produced transient contraction and stable relaxation, respectively, but did not inhibit AVT-induced relaxation in HV. Atrial natriuretic peptide (3 x 10(-8) M) and sodium nitroprusside (10(-4) M) had no effect in precontracted HV. AVT acts directly on gar venous smooth muscle cells via a nonclassical AVP receptor, possibly by increasing [cAMP]. AVT is a potent vasoconstrictor in vertebrate vasculature but produces a novel relaxation in gar veins.

Isolation and cardiovascular activity of a second bradykinin-related peptide ([Arg0, Trp5, Leu8]bradykinin) from trout

Previous work has shown that incubation of heat-denatured plasma from the rainbow trout Oncorhynchus mykiss with porcine pancreatic kallikrein generates [Lys0, Trp5, Leu8]bradykinin (trout [Lys0]BK). We have now isolated a second BK-related peptide from kallikrein-treated trout plasma with the primary structure: Arg-Arg-Pro-Gly-Trp-Ser-Pro-Leu-Arg (trout [Arg0]BK). Bolus injections of both trout [Arg0]BK and [Lys0]BK (> 100 pmol/kg) into the dorsal aorta of conscious trout produced multiphasic effects on arterial blood pressure. An initial pressor response of short duration (1-2 min) was followed by a fall in pressure (to below basal values in 11 out of 15 animals) and then by a sustained rise in pressure lasting up to 60 min. The maximum rise in pressure produced by trout [Arg0]BK (10 nmol/kg) was approximately one-fourth of the maximum rise produced by angiotensin II in the same animals. Intracerebroventricular injections of trout [Arg0]BK (500 pmol) into conscious trout had no effect on arterial blood pressure or heart rate. Trout [Arg0]BK did not affect the tension of vascular rings from trout efferent branchial and caeliacomesenteric arteries and anterior cardinal vein. Trout des [Arg9]BK had no effect on cardiovascular parameters, either in vivo or in vitro, indicating that the C-terminal arginine residue of the peptide is important in interaction with the trout kinin receptor(s).

Vasoconstrictive effects of native tachykinins in the rainbow trout, Oncorhynchus mykiss

The role of trout substance P (tSP) and neurokinin A (tNKA) in cardiovascular regulation was investigated in the rainbow trout, Oncorhynchus mykiss, in vivo and in vitro. In vivo, the coeliac arterial and ventral aortic relative blood flows were measured with Doppler flow probes, and blood pressure was measured via a cannula inserted into the dorsal aorta. tSP (0.1 and 1 nmol kg-1) and tNKA (1 nmol kg-1) increased both systemic and coeliac vascular resistances, leading to hypertension and bradycardia. In addition, cardiac output was decreased. The mammalian NK1 tachykinin receptor antagonist CP-96,345 did not affect the responses to tSP or tNKA. In vitro perfusions of the dorsal aortic and coeliacomesenteric vascular beds were performed using peristaltic pumps. The dorsal aortic vascular resistance was dose-dependently increased following infusion of the two peptides (pD2 values 7.6 +/- 0.1 and 7.3 +/- 0.1 for tSP and tNKA, respectively). Tetrodotoxin did not affect the tSP-induced hypertension. Increases in coeliac vascular resistance caused by tSP was correlated with stomach contractions when measurement of intragastric pressure was made using an inserted balloon. In conclusion, native SP and NKA are potent vasoconstrictors of rainbow trout vasculature, a property quite unusual to tachykinins compared with the vasodilation normally seen in mammals.

Production of [Asn1, Val5] angiotensin II and [Asp1, Val5] angiotensin II in kallikrein-treated trout plasma (T60K)

Incubation of heat-denatured plasma from the rainbow trout Oncorhynchus mykiss with porcine pancreatic kallikrein generates, in addition to bradykinin-related peptides, previously uncharacterized peptides that contract mammalian and amphibian vascular smooth muscle. Using rings of vascular smooth muscle from the bullfrog systemic arch as bioassay, we have isolated two myotropic peptides whose primary structures were established as: Asn-Arg-Val-Tyr-Val-His-Pro-Phe ([Asn1, Val5]angiotensin II) and Asp-Arg-Val-Tyr-Val-His-Pro-Phe ([Asp1, Val5]angiotensin II). These peptides are the same as those generated in salmon plasma by an extract of kidney. The data raise the possibility that activation of the kallikrein-kinin system in trout generates both bradykinin-related and angiotensin II-related peptides that may act synergistically in the regulation of blood pressure.