Oculoparalytic illusion: visual-field dependent spatial mislocalizations by humans partially paralyzed with curare.

In darkness, observers partially paralyzed with curare make large (greater thn 20 degrees) gaze- and dosage-dependent errors in visually localizing eye-level-horizontal and median planes, in matching the location of a sound to a light, and in pointing at a light. In illuminated, structured visual localization and pointing are accurate but errors in auditory-to-visual matches remain. Defects in extraretinal eye position information are responsible for all errors. The influence of extraretinal eye position information on visual localization is suppressed by a structured visual field but is crucial both in darkness and for intersensory localization if visual capture is prevented.

Widespread occurrence in frogs and toads of skin compounds interacting with the ouabain site of Na+, K+-ATPase.

Amphibians of the family Bufonidae contain high levels of skin compounds that both inhibit Na+- and K+-dependent adenosinetriphosphatase and antagonize the binding of ouabain to the enzyme. In species of Bufo and Atelopus, these compounds are relatively nonpolar bufodienolides, whereas Dendrophryniscus and Melanophryniscus contain more polar compounds of unknown structure. Skin extracts from 30 of 48 species of frogs representing an additional eight families contained relatively low levels of compounds that inhibit binding of ouabain to Na+,K+-adenosinetriphosphatase. The widespread occurrence of low levels of inhibitory compounds is consonant with the role for these compounds as physiological regulators of Na+,K+-adenosinetriphosphatase in amphibian skin; high levels in the Bufonidae probably also serve as a defense against some predators.

High-dose estrogen inhibits bone resorption and stimulates bone formation in the ovariectomized mouse.

In this study, we have investigated estrogen's capacity to regulate bone formation and resorption in the ovariectomized mouse, evaluating the dose and site dependence of estrogen action on bone modeling and remodeling surfaces. To quantitate bone resorption, the skeletons of fifty 8-week-old Swiss-Webster mice were prelabeled with [3H]tetracycline (3H-T) before initiation of treatment protocols. Ovariectomies (OVX) and sham surgeries were performed 3 days after the final 3H-T injection, and the animals were assigned to treatment groups and injected once per week for 4 weeks with one of the following doses of 17 beta-estradiol (E2): sham/oil vehicle (SV), OVX/oil vehicle, OVX/50 micrograms E2, OVX/250 micrograms E2, and OVX/500 micrograms E2. To assess bone formation, fluorochrome labels were administered 9 and 2 days before sacrifice. At the conclusion of the 4 week protocol, the femora and thoracic vertebrae were removed to quantitate the levels of bone resorption based on the skeletal retention of 3H-T. The tibiae were excised for histomorphometric evaluation of the proximal metaphyses and middiaphyses. Indicative of increased bone resorption, vehicle-treated OVX animals had significantly reduced levels of 3H-T in femora and vertebrae compared to SV mice. This result was consistent with histomorphometric data showing a 49% decrease in cancellous bone area of the proximal tibiae in the OVX/oil-treated group. Treatment of OVX animals with 50 micrograms E2 was sufficient to maintain 3H-T levels in vertebrae at SV values, with higher E2 doeses leading to a dose-dependent increase in the retention of 3H-T at this site.(ABSTRACT TRUNCATED AT 250 WORDS)

High-dose gestagens modulate bone resorption and formation and enhance estrogen-induced endosteal bone formation in the ovariectomized mouse.

To determine if gestagens of two separate classes have differing skeletal actions, we studied the effects of pharmacologic doses of norethisterone acetate (NETA), a 19-nortestosterone, and megestrol acetate (MA), a 17 alpha-hydroxyprogesterone, on bone formation and resorption in intact and in ovariectomized mice. In the same set of experiments, we also attempted to determine if these gestagens can alter the skeletal activity of 17 beta-estradiol (E2). Experimentally, the skeletons of 78 female BALB/c mice were prelabeled with [3H]tetracycline (3H-T). The animals were randomized to 13 groups of 6 mice each 3 days after the final 3H-T injection. Ovariectomies (OVX) were performed on 8 groups and sham operations (SO) on 5 groups. To study the skeletal effects of the gestagens, 4 groups each of the OVX and SO mice were treated with controlled-release pellet implants calculated to deliver 80 or 250 micrograms of NETA or MA per day. To study gestagen interactions with E2, 3 groups of OVX mice were treated with either 40 micrograms/day of E2 or 40 micrograms/day of E2 plus 250 micrograms/day of NETA or MA. One group of OVX and one group of SO animals received placebo pellets. Fluorochrome labels were administered 10 and 11 and 3 and 4 days before sacrifice to allow histomorphometric evaluation of bone formation. At the end of the 60 day protocol, tibiae and thoracic vertebrae were removed and processed for quantitating the levels of bone resorption based on the amounts of 3H-T retained in the bones. The femora were fixed and embedded for comparison of diaphyseal bone histomorphometry, and the humeri and lumbar vertebrae were prepared for bone density determinations. Reflecting an increase in bone resorption, 3H-T levels in tibiae and vertebrae were decreased in placebo-treated OVX animals compared to the placebo-treated SO group (p < 0.01). Treatment of both SO and OVX mice with NETA decreased bone resorption in a dose-dependent manner, but MA had no significant effects on vertebral bone resorption and increased bone resorption in the tibiae (p < 0.01). E2 treatment of OVX mice reduced bone resorption, but there were no significant interactions between the E2 and gestagen treatments on resorptive activity. Based on bone histomorphometry of in vivo fluorochrome labels, both gestagens increased periosteal bone formation rates but had no effect on endosteal bone formation (BFRe). In contrast, E2 treatment of the OVX mice stimulated bone formation at the endosteal surface.(ABSTRACT TRUNCATED AT 400 WORDS)

17 beta estradiol stimulation of endosteal bone formation in the ovariectomized mouse: an animal model for the evaluation of bone-targeted estrogens.

To evaluate the potential of an animal model as a means to identify bone-targeted estrogens, we have studied the response of the skeleton of ovariectomized mice to prolonged estrogen treatment. Seventy female Swiss-Webster mice were randomly divided into ten groups, with nine groups undergoing bilateral ovariectomy and one group a sham procedure. Mice were injected subcutaneously once per week for nine weeks with one of the following doses of estrogen (17 beta-E2) in oil vehicle: 19.3, 38.5, 75, 150, 300, 500, 1000, or 3000 micrograms. One group of ovariectomized (OVX) mice and the sham operated animals received vehicle injections only. At the end of the nine-week experimental protocol, there were no significant differences in body weights among any treatment groups. However, when compared to control values, spleen weights in vehicle-treated OVX mice and in mice treated with 1000 micrograms or 3000 micrograms of 17 beta-E2 were significantly elevated (p less than .01). Liver weights in the OVX mice treated with 1000 or 3000 micrograms 17 beta-E2 were also increased significantly (p less than .05). Comparisons of uterine weights and cortical bone areas were strongly correlated with 17 beta-E2 dose (r2 = .86 and .94, respectively), with maximal increases observed at estradiol doses in excess of 500 micrograms per week. Furthermore, based on bone histomorphometry of in vivo fluorochrome labels, increases in cortical bone area could be attributed to accelerated rates of endosteal mineral apposition and bone formation. These results indicate that the comparison of the response of endosteal bone and uterine tissue in the OVX mice to chronic estrogen treatment offers the potential to identify estrogen and/or estrogen-like compounds with bone-specific activity.

5-Cyano-2'-deoxyuridine 5'-phosphate: a potent competitive inhibitor of thymidylate synthetase.

The 5'-phosphate (1) of the antiviral nucleoside 5-cyano-2'-deoxyuridine was synthesized and evaluated for inhibition of thymidylate synthetase purified from methotrexate-resistant Lactobacillus casei. Compound 1 was a potent competitive inhibitor with a K1 of 0.55 microns. Irreversible enzyme inhibition by this compound could not be detected.

Extracorporeal membrane oxygenation during bronchopulmonary lavage.

Extracorporeal membrane oxygenation (ECMO) in a venoarterial perfusion circuit was used to provide support of gas exchange during bronchopulmonary lavage in a 32-year-old man with pulmonary alveolar proteinosis and severe arterial hypoxemia. Prior to the lavage, Pao2 during mechanical ventilation with 100% oxygen and positive end-expiratory pressure was only 125 mm Hg. Extracorporeal perfusion at a flow rate of 3 liters/min, with oxygen delivery of 244 ml/min, increased the Pao2 to 227 mmHg and lowered the mean pulmonary artery pressure from 28 to 24 mm Hg. During bronchopulmonary lavage and ECMO, the Pao2 ranged between 46 and 96 mm Hg. After the procedure, pulmonary performance decidely improved. By reducing the chances of fatal hypoxemia, ECMO allowed treatment to be instituted for this potentially reversible disorder and proved helpful as a form of support during the management of pulmonary alveolar proteinosis when severe hypoxemia may have other wise precluded bronchopulmonary lavage.

Prevention of postoperative intracerebral hemorrhage with topical recombinant factor XIII in the rat.

Factor XIII is an endogenous clotting factor that retards thrombus degradation by cross-linking fibrin. To determine the efficacy of Factor XIII as a topical clot-stabilizing agent in preventing postoperative hemorrhage associated with coagulopathy, a rat model of experimental craniotomy and standardized bilateral frontal corticectomy was developed. In 25 rats (50 lesions), recombinant human Factor XIII or placebo solution was topically applied to corticectomy cavities after hemostasis was achieved; each animal served as its own control. In 20 rats, heparin sulfate (100 U/kg.h) was initiated intraperitoneally 3 days after surgery and was continually administered by an Alzet pump for 7 days, compared with a control group of 5 rats receiving saline intraperitoneally. The volume of intracranial hemorrhage was quantitatively determined from coronal sections by use of automated image analysis. Large (> 50 mm3) intracerebral hemorrhages were significantly more frequent in placebo (60%)- compared with recombinant Factor XIII (15%)-treated lesions (P < 0.01) in animals receiving heparin. The topical application of clot-stabilizing agents such as Factor XIII may reduce the risk of postoperative intracranial hemorrhage, especially in high-risk patients with coagulopathy.

Medullary relay neurons in the carotid-body chemoreceptor pathway of cats.

Central terminations of the carotid body chemoreceptor afferents were localized by recording field potentials and unit activity evoked by electrical stimulation of the carotid sinus nerve, and unit activity during chemical stimulation of the chemoreceptors. Areas where evoked responses with short latency could be recorded and which contained neurons that responded to carotid body excitation were located in two regions of the medulla, about the level of the obex: a dorsal region which included the nucleus tractus solitarius and the reticular formation just below this nucleus; and a ventrolateral region which included the nucleus ambiguus and the ventrolateral reticular formation around that nucleus. The evoked field responses in the two regions were similar. In these two regions, the only neurons which increased their firing both to NaCN and a decreased PIO2 had a respiratory, bursting activity which was phase locked with phrenic nerve firing. The authors' findings suggest that there is a direct synaptic input from carotid body chemoreceptor afferents onto medullary respiratory neurons.

The anabolic effect of estrogen on endosteal bone formation in the mouse is attenuated by ovariohysterectomy: a role for the uterus in the skeletal response to estrogen?

In the mouse, the anabolic effect of estrogen on the uterus and its stimulatory effect on endosteal bone formation are well documented. When these observations are coupled with the recent description of uterine-derived bone cell mitogens, it raises the possibility that uterine hypertrophy in response to estrogen might lead to the production and release of factors that participate in the skeleton's anabolic response to estrogen. To determine if the stimulatory effects of estrogen on endosteal bone formation and uterine tissue in the mouse are related, we have studied this specific skeletal response to ovariectomy (OVX) and ovariohysterectomy (OHTX), and to two levels of 17 beta-estradiol (17 beta-E2). To assess treatment effects, 48 Swiss-webster mice were assigned to six groups: OHTX/oil vehicle, OVX/oil vehicle, OHTX/150 micrograms 17 beta-E2, OHTX/300 micrograms 17 beta-E2, OVX/150 micrograms 17 beta-E2, and OVX/300 micrograms 17 beta-E2. Animals were treated once per week with vehicle or the respective 17 beta-E2 dose. To quantitate bone formation, fluorochrome labels were administered at the beginning and end of the experimental period. At the conclusion of the 5-week study, tibiae were processed undecalcified for embedding in methyl methacrylate plastic. Cross-sectional areal properties and bone formation rates were quantitated from 30 microns mid-diaphyseal sections using a Bioquant Bone Morphometry system. Compared with the vehicle-treated OVX and OHTX mice, 150 micrograms of 17 beta-E2 administered once per week significantly increased cortical bone areas (P less than 0.05) but cortical bone widths and the ratio of cortical bone area to total bone area was increased only in estrogen-treated OVX mice (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Halothane depresses the response of carotid body chemoreceptors to hypoxia and hypercapnia in the cat.

Halothane is known to inhibit the ventilatory responses to hypoxia and hypercapnia. In order to determine whether this inhibition was mediated by peripheral chemoreceptors, the authors measured the effect of halothane on the response of carotid body chemoreceptors to these stimuli. Cats were decerebrated under brief halothane anesthesia, paralyzed, and ventilated. Chemoreceptor activity was recorded from single- or few-fiber preparations of carotid sinus nerve, and the inspiratory drive was recorded from the whole phrenic nerve. Steady-state responses were measured at three levels of CO2 tension (19-92 mmHg) during hyperoxia, and at four levels of O2 tension (35-450 mmHg) at a fixed PaCO2. Both responses were measured before, during, and after 0.5-1.0 per cent halothane was inspired. The halothane inhalation was maintained for at least 30 min before the responses were obtained. Halothane reduced the slope of chemoreceptor response to hypercapnia to about 48 per cent of the control slope. The response to hypoxia was reduced to about 58 pr cent of the control response. The increase in firing after intravenous nicotine (100 micrograms), summed for 20 s, was reduced to 25 per cent of the prehalothane control values; that after NaCN (25 micrograms) was reduced to 17 per cent of the control value. The effect of halothane was prompt (half complete in 1-2 min) and reversible. This finding explains some of the inhibition of the ventilatory responses to hypoxia and hypercapnia caused by halothane.

Impairment of effects of vasopressin on [1-14C]oleate metabolism in hepatocytes from obese (ob/ob) mice.

In hepatocytes from lean mice vasopressin decreased ketogenesis and increased 14CO2 production from [1-14C]oleate and glucose release; these effects were Ca2+-dependent. None of these effects of vasopressin were obtained with hepatocytes from obese (ob/ob) mice. Similarly, adrenaline did not increase 14CO2 production in these hepatocytes, but it stimulated glucose release. Possible reasons for the impairment of vasopressin action are discussed.

Audit of abdominal pain in general practice.

An audit of 150 consecutive cases of abdominal pain presenting to an urban teaching practice between October 1983 and May 1984 was performed. The median duration of pain prior to presentation was two days. Females predominated in all age groups.Eighty-nine per cent of these patients were managed entirely in the practice and of these, 52 per cent were managed with reassurance and advice alone, while 48 per cent also received a prescription. Only 15 per cent of patients were investigated in any way by the practice. Of the 17 patients (11 per cent) referred, nine were referred as emergencies and eight were admitted that day. However, there were only three true surgical emergencies in the entire series (one appendicitis, one intussusception and one fulminating pancreatitis).

Induction dose-response curves for midazolam and ketamine in premedicated ASA class III and IV patients.

Using probit analysis, dose-response curves for induction of anesthesia with midazolam or ketamine were constructed in ASA class III and IV patients premedicated with morphine, 0.1 mg/kg, and glycopyrrolate, 4 micrograms/kg. For ketamine, ED50 values for abolition of the response to verbal commands, eyelash stimulation, and painful stimulation were 0.9, 1.3, and 1.3 mg/kg, respectively; corresponding ED95 values were 1.6, 2.3, and 4.3 mg/kg, which are within the range of clinically recommended doses. For midazolam, ED50 values for verbal commands, eyelash stimulation, and painful stimulation were 0.19, 0.24, and 0.36 mg/kg, significantly greater than those previously reported for unpremedicated ASA class I and II patients. The corresponding ED95 values, 0.35, 0.43, and 1.04 mg/kg exceed previously reported values and are appreciably greater than the doses used in most previous studies of midazolam induction. Midazolam decreased systolic blood pressure slightly but significantly (from 138 +/- 4 to 128 +/- 4 mm Hg, mean +/- SEM, P less than 0.005), while diastolic blood pressure and heart rate remained unchanged. In contrast, ketamine increased systolic blood pressure (from 141 +/- 4 to 164 +/- 5 mm Hg, P less than 0.005), diastolic blood pressure (from 71 +/- 3 to 88 +/- 4 mm Hg, P less than 0.005), and heart rate (from 84 +/- 2 to 102 +/- 4 beats/min, P less than 0.005). On the basis of these data, we conclude that in ASA class III and IV patients, midazolam induction allows for hemodynamic stability and avoids the significant tachycardia and hypertension associated with equipotent doses of ketamine.

Calcium-dependent desensitization of adenylate cyclase in rat cerebral cortical slices.

Incubation of slices of rat cerebral cortical grey matter in Krebs-Ringer bicarbonate-glucose buffer induced a rapid decline in the responsiveness of the adenylate cyclase in subsequently prepared membrane preparations to stimulation by various activators of the enzyme. The loss of responsiveness was time- and temperature-dependent, showed an absolute dependence on extracellular calcium ions, and was mimicked by the presence of serine proteases in the incubation medium. The resultant adenylate cyclase preparation was partially responsive to activation by fluoride and guanylylimidodiphosphate but had become virtually unresponsive to activation by ganglioside, trypsin, or beta-adrenergic agonists. The loss of responsiveness of adenylate cyclase was not altered if slices were incubated with depolarizing agents, putative neurotransmitters, receptor blockers, serine protease inhibitors, or adenosine deaminase. The nature of the calcium-dependent mechanism involved in the loss responsiveness of membranal adenylate cyclase is unknown. A suggested mechanism for the loss of sensitivity is the action of a membrane-bound, calcium-dependent protease.

Regulation of cyclic AMP formation in brain tissue by alpha-adrenergic receptors: requisite intermediacy of prostaglandins of the E series.

The accumulations of cyclic AMP elicited by norepinephrine in slices of rat cerebral cortex or hypothalamus were markedly reduced after incubations with prostaglandin synthetase (8,11,14-eicosatrienoate, hydrogen-donor:oxygen oxidoreductase, EC 1.14.99.1) inhibitors such as indomethacin, aspirin, flufenamic acid, and acetoaminophen. Responses of cyclic AMP-generating systems to beta-adrenergic agonists or adenosine were unchanged by treatment with indomethacin and the reduction in the norepinephrine response appeared due primarily to a loss of the alpha-adrenergic component. The accumulation of cyclic AMP elicited by prostaglandin E2 [mean effective dose (EC50) 4 micro M] was increased by 2-fold by treatment with indomethacin. The alpha-adrenergic component of the norepinephrine response was fully restored by very low concentrations of prostaglandin E2 (EC50 20 nM). Prostaglandins of the F series had no effect on cyclic AMP generation under a variety of conditions. It appears that low levels of prostaglandins of the E series are required--perhaps by a calcium-dependent mechanism--for the expression of alpha-adrenergic receptor-mediated activation of cyclic AMP formation in brain tissue.

Alkaloids from a panamanian poison frog, Dendrobates speciosus: identification of pumiliotoxin-A and allopumiliotoxin class alkaloids, 3,5-disubstituted indolizidines, 5-substituted 8-methylindolizidines, and a 2-methyl-6-nonyl-4-hydroxypiperidine.

Dendrobates speciosus is a small red or orange frog that occupies a small geographic range in the highlands of western Panama, where it occurs abundantly in some cloud forest habitats. Gc-ms analysis indicated the presence of at least 30 alkaloids in MeOH skin extracts from population samples at the extreme eastern end of the known geographic range. Eleven alkaloids were isolated by cc in quantities sufficient for 2D-nmr spectral analysis, which in some cases confirmed their identity with alkaloids known from other species and in other cases led to assignment of structures. Pumiliotoxin 251D, pumiliotoxin A [307A], pumiliotoxin B [323A], and allopumiliotoxin 267A were identified as major constituents. N-Oxides of 323A and 267A were also isolated. Indolizidines 195B and 223AB with 3-butyl-5-methyl and 3-butyl-5-propyl substituents, respectively, were identified. The 5-substituents of the 8-methyl-indolizidines 207A and 235B' were assigned as -(CH2)3CH = CH2 and -(CH2)5CH = CH2, respectively; indolizidine 235B' from D. speciosus is, thus, a positional double-bond isomer of indolizidine 235B previously isolated from a closely related poison frog, Dendrobates pumilio. A piperidine 241D was isolated and assigned the structure cis-cis-2-methyl-6-nonyl-4-hydroxypiperidine.