Urea inhibits Na-K-2Cl cotransport in medullary thick ascending limb cells

We examined the effect of physiological concentrations of urea (100-500 mM) on Na-K-2Cl cotransport in cultured cells from mouse medullary thick ascending limb (mTAL). Urea acutely inhibited bumetanide-sensitive K influx in mTAL cells in a concentration-dependent fashion, with a statistically significant inhibition (19%) at 100 mM and 86% inhibition at 500 mM. The effect of urea was entirely reversible and was blocked by prior treatment with okadaic acid, a phosphatase inhibitor, suggesting that urea exerts its action upstream of the phosphorylation-dephosphorylation step. Cell volume was unchanged in the presence of 500 mM urea. The number of [3H]bumetanide binding sites, a measure of the number of functioning cotransporter sites, was decreased in the presence of urea, and the decrease in bumetanide binding was proportional to the decrease in bumetanide-sensitive K influx. Urea also stimulated the Ba-sensitive swelling-activated K efflux from mTAL cells. Thus urea, in concentrations that prevail in the renal medulla, alters ion transport in mTAL cells.

Effect of Anapsos (Polypodium leucotomos extract) on in vitro production of cytokines

AIMS

The aim of the study was to test the immunomodulating capacity of Anapsos, Polypodium leucotomos extract, in vitro in an attempt to explore how this extract acts from an immunological point of view and thus to identify a common link capable of explaining most of its effects.

METHODS

Polypodium leucotomos rhizomes were harvested in Guatemala and the extract, Anapsos, obtained. Mononuclear cells were obtained by density gradient centrifugation from healthy donors, and stimulated with phytohemagglutinin or Pokeweed with and without Anapsos and with Anapsos alone. Cell proliferation was determined by thymidine incorporation. Cells were also stimulated and the following cytokines determined by ELISA at 0, 12, 24, 48, 72, and 96 h: IL-1 beta, TNF-alpha, IL-2, INF-8, IL-4 and IL-10.

RESULTS

Anapsos, Polypodium leucotomos extract, has a modulating effect on the in vitro production and release of cytokines by peripheral blood mononuclear cells of healthy subjects. At doses effective in vivo, Anapsos can stimulate PBMNc proliferation, delay IL-1 beta secretion and at the same time increase that of IL-2, IL-10, and INF-gamma.

CONCLUSIONS

Anapsos may have an antagonistic effect on some of the cytokines released on cell stimulation with LPS and/or PHA, which suggests that this product has a pleiotropic effect on different populations in the immune system.

The use of vaginal ultrasound to identify copper T IUDs at high risk of expulsion

A total of 235 women who had a TCu 380A IUD inserted had a vaginal ultrasound scan performed to identify if the IUDs were correctly placed in the uterine fundus. Women identified as having a misplaced IUD had it removed. The remaining women were compared to 201 women who had an IUD inserted and had no ultrasound evaluation, matched by age and parity. Women were followed-up for one year. Gross cumulative discontinuation rates and continuation rates were calculated by life table analysis. Comparison between groups was done by the Gehan test. The study group had 34 IUDs removed because they were misplaced according to the established criteria. The expulsion rate was significantly higher in the control group, also influencing the continuation rate which was lower in the same group. Of the 34 women who had their IUD removed because it was not correctly placed, only 22 requested and had another IUD inserted. The removal of IUD determined by an ultrasound to be incorrectly placed significantly decreased expulsion rates. However, many IUDs may have been removed unnecessarily, probably resulting in many women not returning to the clinic or deciding to use another contraceptive method.

Spacial compartmentalization of Ca2+ signaling complexes in pancreatic acini

Imaging [Ca2+]i at high temporal resolution and measuring the properties of Ca2+ signaling in streptolysin O (SLO)-permeabilized cells were used to study the spacial organization of signaling complexes. Sequential stimulation of single cells within pancreatic acini with several Ca2+-mobilizing agonists revealed an agonist-specific pattern and propagation rate of Ca2+ waves in the same cells, with CCK8 stimulating the fastest and bombesin the slowest waves. More importantly, each agonist initiated the wave in a different region of the same cell. On the other hand, repetitive stimulation with the same agonist induced Ca2+ waves of the same pattern that were initiated from the same region of the cell. The agonist-specific Ca2+ signaling does not appear to be the result of coupling to different G proteins as infusion of an anti-Galphaq antibody into the cells through a patch pipette equally inhibited Ca2+ signaling by all agonists. Further evidence for compartmentalization of signaling complexes was developed in permeabilized cells. The time-dependent loss of Ca2+ signaling due to SLO permeabilization occurred in an agonist-specific manner in the sequence cabachol > bombesin > cholecystokinin. Signaling by all agonists could be completely restored with as low as 2 micro guanosine 5'-3-O-(thio)triphosphate (GTPgammaS). At this low concentration GTPgammaS recoupled inositol 1,4,5-trisphosphate production and Ca2+ release, rather than enhancing phospholipase C activity. Priming of Ca2+ signaling by GTPgammaS was agonist-specific. Guanosine 5'-O-(thio)diphosphate (GDPbetaS) uncoupled the ability of signaling complexes to release Ca2+ much better than stimulating inositol 1,4,5-trisphosphate production. The uncoupling of Ca2+ signaling by GDPbetaS was also agonist-specific. The combined findings of agonist-specific initiation sites of the Ca2+ wave and differential access of guanine nucleotides to signaling complexes suggest spacial compartmentalization of Ca2+ signaling complexes. Each complex must include a receptor, G protein, and phospholipase C that are coupled to a specific portion of the Ca2+ pool.

Laparoscopic resection of accessory spleen for recurrent immune thrombocytopenic purpura 19 years after splenectomy

Routine identification and resection of accessory splenic tissue, an integral part of splenectomy for immune thrombocytopenic purpura (ITP), is not necessarily a "blind spot" of the laparoscopic technique. This case report of laparoscopic resection of accessory spleen for recurrent ITP 19 yr after splenectomy supports this view.

Consequences of electroencephalographic-suppressive doses of propofol in conjunction with deep hypothermic circulatory arrest

BACKGROUND

Some patients who undergo cerebral aneurysm surgery require cardiopulmonary bypass and deep hypothermic circulatory arrest. During bypass, these patients often are given large doses of a supplemental anesthetic agent in the hope that additional cerebral protection will be provided. Pharmacologic brain protection, however, has been associated with undesirable side effects. These side effects were evaluated in patients who received large doses of propofol.

METHODS

Thirteen neurosurgical patients underwent cardiopulmonary bypass and deep hypothermic circulatory arrest to facilitate clip application to a giant or otherwise high-risk cerebral aneurysm. Electroencephalographic burst suppression was established before bypass with an infusion of propofol, and the infusion was continued until the end of surgery. Hemodynamic and echocardiographic measurements were made before and during the prebypass propofol infusion and again after bypass. Emergence time also was determined.

RESULTS

Prebypass propofol at 243 +/- 57 micrograms.kg-1.min-1 decreased vascular resistance from 34 +/- 8 to 27 +/- 8 units without changing heart rate, arterial or filling pressures, cardiac index, stroke volume, or ejection fraction. Propofol blood concentration was 8 +/- 2 micrograms/ml. Myocardial wall motion appeared hyperdynamic at the end of cardiopulmonary bypass, and all patients were weaned therefrom without inotropic support. After bypass, vascular resistance decreased further, and cardiovascular performance was improved compared to baseline values. Nine of the 13 patients emerged from anesthesia and were able to follow commands at 3.1 +/- 1.4 h. Three others had strokes and a fourth had cerebral swelling.

CONCLUSIONS

Propofol infused at a rate sufficient to suppress the electroencephalogram does not depress the heart or excessively prolong emergence from anesthesia after cardiopulmonary bypass and deep hypothermic circulatory arrest.

Prostaglandin E2 inhibits Na-K-2Cl cotransport in medullary thick ascending limb cells

Prostaglandin E2 (PGE2) is known to inhibit transepithelial Cl transport in medullary thick ascending limb (mTAL), but the mechanism of inhibition or the transport pathway affected has not been identified. We undertook this study to examine the effect of PGE2 on Na-K-2Cl cotransport in mouse mTAL cells in culture. In nanomolar concentrations, PGE2 inhibited the Na- and Cl-dependent, bumetanide-sensitive K influx by 45%, and this inhibition was also observed in the presence of 3 mM ouabain. Although PGE2 also inhibited ouabain-sensitive K flux, that inhibition was abolished in the presence of apical nystatin, suggesting that the pump inhibition was secondary to diminished Na entry into the cells. The effect of PGE2 was concentration dependent. Inhibition was observed at a concentration of < 1 nM, and half-maximal effect was observed at 2.5 nM. The effect of PGE2 was not mediated by an action on cytosolic Ca because cytosolic Ca was unchanged after the addition of PGE2. PGE2 reduced the maximal velocity for the cotransporter but had no effect on the affinity of the cotransporter for external Na, K, or Cl. Specific [3H]bumetanide binding was reduced in the presence of PGE2, suggesting that PGE2 affected bumetanide-sensitive K influx by downregulating the number of functioning Na-K-2Cl cotransporters. These results suggest that Na-K-2Cl cotransport in the mTAL cells may be under tonic inhibitory control of PGE2.

Diaphragmatic fatigue following voluntary hyperpnea

The purpose of this study was to determine whether diaphragmatic fatigue occurs after voluntary hyperpnea to task failure. Ten male subjects were asked to breathe at minute ventilation (V1) equal or slightly greater than 60% of their 12-s maximum voluntary ventilation (MVV) until task failure. Transdiaphragmatic pressure (Pdi) was measured during bilateral supramaximal stimulation of the phrenic nerves before and 10, 30, 60, and 120 min after hyperpnea. For the group, V1 averaged 107.1 +/- 7.1 L/min (SE) (range, 71-154 L/min), which represented 60 +/- 2% of the MVV. After voluntary hyperpnea, seven of the 10 subjects displayed at least a 10% reduction in twitch Pdi during transcutaneous stimulation, while all 10 subjects had a greater than 10% reduction in twitch Pdi during cervical magnetic stimulation. For the group, transcutaneous twitch Pdi was significantly decreased from 27.0 +/- 1.9 at baseline to 21.4 +/- 1.7 cm H2O (p < 0.0001) at 10 min posthyperpnea. Magnetic twitch Pdi was also significantly decreased from 36.0 +/- 2.1 at baseline to 28.7 +/- 1.9 cm H2O (p < 0.0001) at 10 min posthyperpnea. Twitch Pdi remained significantly decreased from baseline for at least 1 h after hyperpnea. After hyperpnea, the mean percentage decrease from baseline in twitch Pdi was virtually identical with the two stimulation techniques. The percentage fall in twitch Pdi after hyperpnea with the two techniques was not significantly correlated (r = 0.4). In conclusion, long-lasting contractile fatigue of the diaphragm reliably occurs after voluntary hyperpnea at levels sufficient to induce task failure. Cervical magnetic stimulation can detect diaphragmatic fatigue after a fatiguing task, but the results obtained with this technique may differ from those obtained with transcutaneous stimulation in individual subjects.

[in vitro comparison of liquid antacids of commercial use]

The aim of our study was to compare the capacity of several liquid antacids to elevate the pH of a hydrochloric acid solution. An experimental model was designed to measure this capacity in different commercially available liquid antacids. Change in pH of an HCl solution was registered when each of the liquid antacids was added. We found differences between the 4 MgOH - ALOH antacids. Minimal difference was found between the 2 commercially available magaldrates.

Factors influencing physicians' prescribing behaviour in the treatment of childhood diarrhoea: knowledge may not be the clue

Proper diarrhoea treatment has received greater attention during the last 10 years. However, the unjustified use of medicines to treat simple episodes of acute diarrhoea continues to divert attention and available resources away from appropriate treatment. A study to identify the factors determining prescribing practices for diarrhoea treatment was carried out in a peri-urban part of Lima, Peru in 1991. Physicians were interviewed, and then their practice was assessed by visits of confederates with healthy children described as ill, by interviews with mothers of sick children leaving the clinic, or by both of these methods. Physicians' reported practices in treating diarrhoea cases were compared to their actual practices. Although physicians' knowledge of drug management seemed to influence the low frequency of prescription of antidiarrhoeal drugs, it did not have the same influence on prescription of antimicrobials. Our results suggest that the diagnostic process and consequently the treatment decision do not follow a scientific rationale for this illness. The physicians' prescribing practices seemed to be more related to agreement with social expectations and the caretakers' perception of the physicians' role than they were to the standard biomedical rules of diarrhoea management.

Serum ionized magnesium monitoring during orthotopic liver transplantation

During orthotopic liver transplantation (OLT) citrate accumulates and magnesium can be chelated, which can lead to ionized hypomagnesemia and cardiovascular dysfunction. Our aim was to study the serum ionized magnesium (Me2+) evolution and establish its relation to serum total Mg and citrate levels during OLT. We studied 58 adult patients undergoing OLT. The serum Me2+ level dropped significantly at the end of the preanhepatic phase, and remained low until the end of the procedure. Furthermore, the Me2+ levels remained below the range of reference from the beginning of the anhepatic phase onward. There was an inverse correlation between Me2+ and citrate for all patients. Me2+, like ionized calcium (Ca2+), is chelated by citrate and its evolution is a mirror image of that of citrate. In our patients, we did not observe any significant dysrhythmias that could be directly attributed to ionized hypomagnesemia. In conclusion, low preoperative levels, together with the massive transfusion of blood products and the increase in renal losses, cause progressive ionized hypomagnesemia in OLT patients. We propose that it he routinely monitored and treated accordingly, as is already done with Ca2+.

Characterization, localization and axial distribution of Ca2+ signalling receptors in the rat submandibular salivary gland ducts

1. To characterize [Ca2+]i signalling in salivary duct cells a procedure was developed for the rapid preparation and isolation of intralobular ducts, some of which had attached intercalated ducts. The isolated ducts retained agonist-induced Ca2+ signalling after permeabilization with streptolysin O (SLO). 2. The improved cell preparation technique was reflected in the repertoire and intensity of agonist responsiveness of the cells. Measurements of [Ca2+]i in intact cells showed that all agonists previously reported to affect electrolyte transport by the submandibular salivary gland (adrenaline, carbachol, isoprenaline and forskolin) mobilized Ca2+ from internal stores and increased Ca2+ influx across the plasma membrane. 3. The use of the SLO-permeabilized ducts showed that all agonists, including isoprenaline and forskolin, mobilized Ca2+ exclusively from the inositol 1,4,5 trisphosphate (IP3)-sensitive pool. However, in granular ducts only adrenaline mobilized the entire IP3-sensitive pool whereas all other agonists mobilized only part of the pool. 4. All regions of the duct responded to substance P and the luminally secreted agonist ATP. Interestingly, the intercalated duct was most responsive to ATP and demonstrated only a minimal response to all other agonists. The granular region of the same duct and the extralobular duct always responded best to stimulation by adrenaline. 5. The perfused extralobular duct was used to show that adrenaline and carbachol stimulated the duct through the basolateral membrane whereas the receptors for ATP were localized in the luminal membrane of the duct. This suggests the presence of an ATP-dependent positive feedback loop in salivary duct with decreased activity along the ductal tree.

Pharmacodynamics and pharmacokinetics of cisatracurium in geriatric surgical patients

BACKGROUND

Cisatracurium, one of ten stereoisomers that comprise atracurium, is more potent than atracurium and has less propensity to release histamine. This study compares the pharmacokinetics and pharmacodynamics of cisatracurium in elderly and young patients.

METHODS

Twelve elderly (aged 65-82 yr) and 12 younger patients (aged 30-49 yr) were anesthetized with nitrous oxide, fentanyl, and isoflurane (0.7%, end-tidal). The mechanomyographic response to train-of-four stimulation was assessed every 15 s after the administration of cisatracurium (0.1 mg/kg). Arterial samples were obtained over 6 h. Plasma cisatracurium concentration versus time data were fit to compartmental models. Pharmacokinetic parameters were determined assuming that elimination occurred from the central compartment only. This provides accurate clearance and half-life estimates but underestimates V(ss) (reported herein as V(ss). The pharmacodynamic response was described by the neuromuscular blocking profile.

RESULTS

Onset to 90% paralysis (mean +/- SD) was delayed in the elderly (3.4 +/- 1.0 vs. 2.5 +/- 0.6 min). Recovery profiles were the same for both groups. Elimination half-life was minimally prolonged in the elderly (25.5 +/- 3.7 vs. 21.5 +/- 2.4 min). The Vss was larger in the elderly (126 +/- 16 vs. 108 +/- 13 ml/kg), although the clearances were the same for the two groups (5.0 +/- 0.9 vs. 4.6 +/- 0.8 ml.kg(-1).min(-1).

CONCLUSIONS

There are minor differences in the pharmacokinetics of cisatracurium between elderly and young patients. These differences are not associated with changes in recovery profile after a single bolus dose, although the mean time to onset was approximately 1 min longer in elderly patients.

Comparison of five plating media for isolation of Salmonella species from human stools

A comparative study was carried out to evaluate the performances of different culture media for the recovery of Salmonella spp. from 1,000 routine samples of human stools. By direct plating we tested Salmonella-Shigella agar (SS), Hektoen enteric agar (HE), bismuth sulfite agar (BS), novobiocin-brilliant green-glycerol-lactose agar (NBGL) and SM-ID medium (SM), and after selenite enrichment, we tested all of the media except HE. C8-esterase and oxidase tests were used for the screening of Salmonella spp. on SS and HE. The total number of Salmonella isolates from direct culture was 74, with respective sensitivities and positive predictive values (PPVs) of 78.4 and 61%, 64.9 and 18.7%, 36.5 and 34.2%, 55.4 and 20.7%, and 39.2 and 43.9% for NBGL, SS, HE, BS, and SMID, respectively. After enrichment, the total number of Salmonella isolates was 88. The respective sensitivities and PPVs obtained were 90.9 and 62.5%, 92 and 17%, 90.9 and 32% and 93.2 and 71.3% for NBGL, SS, BS, and SM, respectively. According to our results, NBGL in direct plating was the medium with the highest sensitivity with respect to the sensitivities of the other media, with significant statistical differences (P < 0.05). Likewise, the PPV for NBGL was also the highest (61%). After enrichment in selenite broth, the sensitivities of the four media tested were similar, with the best PPV obtained with SM (71.3%); this was followed by NBGL (62.5%). When C8-esterase was used on SS or HE, the PPVs improved from less than 40% to about 100%.

Bleeding complaints during the first year of norplant implants use and their impact on removal rate

The frequency of bleeding complaints during the first year of use and their influence on removal rate were analyzed in a retrospective cohort study of 491 Norplant implants acceptors. Removal rates were significantly higher in women having menstrual complaints (1.98% and 29.23% in the first and fourth trimester) than in those who did not mention them (0.79 and 5.07% in the same periods). In all periods of observation, most women who mentioned menstrual problems decided to continue using the method. Two possible explanations for this are that 1) the complaints did not persist for very long, and 2) the most frequent complaint mentioned was bleeding irregularity, which was not as strongly associated with removals as increased or decreased bleeding. The authors conclude that bleeding problems are the most important factor limiting the acceptability of Norplant implants, either being the main reason for removal (3.9 per 100 women) or influencing the rate of removal for other reasons. Adequate counseling appears to be critical for reducing the impact of bleeding problems on removal rates, and thereby increasing the acceptability of the method. The importance of research aimed at preventing or treating menstrual problems to improve the acceptability of the method is emphasized.

Aging alters the pharmacokinetics of pyridostigmine

The duration of the antagonism to neuromuscular blockade produced by pyridostigmine is prolonged in elderly patients, and a pharmacokinetic explanation was sought. Ten elderly (71-85 yr) and 10 younger (21-51 yr) patients were anesthetized with thiopental, nitrous oxide, and isoflurane and paralyzed with a combination of d-tubocurarine and pancuronium. When twitch height returned to 5% of baseline, pyridostigmine 0.25 mg/kg was administered and blood samples were collected intermittently for 6 h. Pyridostigmine plasma concentrations were determined by radioimmunoassay and after an hour were always greater in the elderly than in the younger patients. In both groups, plasma pyridostigmine decrement curves were best described by triexponential equations. Pharmacokinetic analysis revealed that plasma clearance in the elderly group was significantly decreased compared to that in the younger group (6.7 +/- 2.2 vs 9.5 +/- 2.7 mL.kg-1.min-1, P < 0.05). Elimination half-lives and volumes of distribution were not significantly different between groups. We conclude that a possible explanation for the prolonged duration of action of pyridostigmine in the elderly is its slow plasma clearance.

Creatine kinase BB and neuron-specific enolase in cerebrospinal fluid in the diagnosis of brain insult

Cerebrospinal fluid (CSF) markers provide useful information about the extent of brain damage. These biochemical indices may also be used when postmortem histopathological examination does not confirm antemortem brain insult. Seven biochemical parameters--creatine kinase (CK), creatine kinase BB isoenzyme (CK-BB), lactate dehydrogenase (LDH), gamma-glutamyltransferase, aldolase, leucine aminopeptidase (LAP), and neuron-specific enolase (NSE)--were analyzed in CSF from 82 cadavers. Case studies were categorized into one of four diagnostic groups. There were 15 cases of head trauma, 23 of hypoxia (hangings, carbon monoxide, and drug poisonings), 23 sudden cardiac death, and 21 miscellaneous cases. The degree of craniocerebral trauma was graded. In CSF there was a statistically significant correlation between the severity of craniocerebral trauma and levels of CK, CK-BB, aldolase, LDH, and LAP. CSF CK-BB [median U/L (range)] for the groupings of head trauma, hypoxia, sudden cardiac death, and miscellaneous were, respectively, 873 (1-12,100), 26 (2-2,780), 16 (1-42), and 18 (0-2,780). Corresponding CSF CK levels were 9,370 (28-67,842), 101 (18-36,840), 180 (10-29,622), and 264 (17-26,556). There were no statistical significant differences among the NSE concentrations in the four diagnostic groups. The testing of biochemical markers could be a reliable indicator of the degree of brain insult in support of morphological studies.

The D3 receptor and its relevance in psychiatry

A large fraction of neurotensin neurons in the ventromedial shell subdivision of nucleus accumbens express D3 receptors. Blockade of D2/D3 receptors by antipsychotic agents paradoxically decreases neurotensin gene expression in these neurons whereas it enhances it in other striatal areas expressing the D2 receptor. This suggests that D2 and D3 receptors mediate opposite actions of dopamine. In support of this view low doses of nafadotride, a novel D3 receptor-preferring antagonist, enhances locomotor activity in rodents, a behavioral response opposite to that of current neuroleptics. The action of D3 receptor-preferring agonists was characterized by the mitogenic response they elicit in transfected NG 108-15 cells. Finally, gene expression of the D3 receptor is in opposition to that of the D2 receptor, being decreased by denervation and unaffected by chronic blockade by neuroleptics.

Regulation of [Na+]i in resting and stimulated submandibular salivary ducts

In the preceding manuscript (Zhao, H., Xu, X., Diaz, J., and Muallem, S. (1995) J. Biol. Chem. 270, 19599-19605), we described a Kout(+)-dependent H+/HCO3- and Na+ influx pathway in the luminal membrane of salivary duct cells. In the present studies, we further characterized this pathway to show that the Kout(+)-dependent Na+ influx was not mediated by the luminal amiloride-sensitive Na+ channel, the Na+/H+ exchangers, or any electroneutral or conductive Cl(-)-dependent transport pathway. Thus, K+ efflux probably maintained electroneutrality during Na+ influx induced by removal of Kout+. Accordingly, Na+ influx was largely inhibited by 2.5mM external Ba2+. The K+ site of the Kout(+)-dependent Na+ influx showed the selectivity sequence Cs+ > K+ > NH4+ >> > Li+ which is different from that of several known K+ channels. More importantly, Na+ influx is 50% inhibited at about 20 mM Kout+, and significant Na+ influx occurred even at 80 mM Kout+. This is a critical property for the pathway to play a role in Na+ reabsorption and K+ secretion by the duct. The large Na+ influx in resting duct cells is matched by high activity of the ductal Na+ pump which is about 8-fold faster than that of acinar cells. Stimulation of submandibular ducts with various agonists increased [Na+]i in an agonist-specific manner. The parasympathetic agonist epinephrine was more effective than isoproterenol and sympathetic agonist carbachol. The use of various inhibitors of Na+ and K+ transporters suggests that different pathways mediate Na+ influx in stimulated acinar and duct cells of the gland. In duct cells, Na+ influx was inhibited only by extracellular Cs+ and Ba2+. The overall findings support a significant role for the Kout(+)-dependent pathway(s) in Na+ reabsorption and K+ and HCO3- secretion and explain several features of transepithelial electrolyte transport by salivary ducts.

Na+, K+, and H+/HCO3- transport in submandibular salivary ducts. Membrane localization of transporters

The mechanisms mediating transepithelial ion transport in salivary ducts were characterized and localized by studying the regulation of [Na+]i, [K+]i, and pHi in isolated intralobular ducts and perfused main ducts of the submandibular salivary gland. A new procedure was developed for the rapid preparation of intralobular ducts. Measurements of pHi revealed the presence of Na+/H+ and Cl-/HCO3- exchange activities in intralobular duct cells. We could not obtain evidence for a coupled K+/H+ exchange activity which was postulated to exist in the luminal membrane of duct cells. Rather, a Kout+-dependent pathway which mediates the transport of H+/HCO3- and Na+ was found. This pathway was absent from acinar cells of the same gland and was active in unstimulated duct cells incubated in 5mM Kout+. Accordingly, inhibition of the Na+ pump with ouabain resulted in rapid and large Na+ influx in duct but not acinar cells. Perfusion experiments with the experimentally accessible main duct and measurements of pHi were used to provide the first direct localization of ion transporters in salivary ducts. The luminal and basolateral membranes of the duct express separate Na+/N+ and Cl-/HCO3- exchangers. Na+/H+ exchange activity in both membranes was similar, whereas the luminal Cl-/HCO3- exchange activity was higher than that in the basolateral membrane. The perfused main dust was also used to localize the newly discovered Kout(+)-dependent H+/HCO3- and Na+ transport pathway to the luminal membrane, which suggests that this pathway may play an important role in Na+ reabsorption of K+ and HCO3- secretion by the salivary ductal system.

Are all effects of esmolol equally rapid in onset?

The purpose of this study was to compare the time course of the bradycardic and hypotensive effects of esmolol. Ten patients undergoing craniotomy requiring hypotension were anesthetized with nitrous oxide and isoflurane. During steady state anesthesia, the response to an infusion of esmolol 500 micrograms.kg-1.min-1 for 90 s followed by 300 micrograms.kg-1.min-1 was measured over 60 min. Heart rate (HR), mean arterial pressure (MAP), and plasma renin activity (PRA) responses did not occur with equal rapidity. The half-time for the 14% decrease in HR (81 +/- 13 bpm to 70 +/- 9 bpm) was 1.2 min. MAP decreased by 26% (85 +/- 7 mm Hg to 63 +/- 6 mm Hg) with a 17.8 min half-time. This delay in MAP response may, in part, be related to the gradual 44% decline in PRA (9.5 +/- 4.5 ng.mL-1.h-1 to 5.3 +/- 2.5 ng.mL-1.h-1) occurring with a half-time of 11.9 min. The times to attainment of 90% maximum decreases were 4.8 +/- 3.0 min for HR, 42.5 +/- 8.9 min for MAP, and 32.1 +/- 15.0 min for PRA. Thus although esmolol has an ultrashort kinetic half-life, only the HR effect can be considered to have an ultrashort onset.

The value of polymorphonuclear elastase in adult respiratory distress syndrome

The clinical usefulness of quantitative plasma polymorphonuclear elastase (PMN-elastase) determinations as prognostic markers of adult respiratory distress syndrome (ARDS) in polytraumatized patients was analyzed. PMN-elastase and C-reactive protein (CRP) levels were determined in 55 polytraumatized patients admitted into the Intensive Care Unit. Eight patients developed ARDS and 47 patients did not. These parameters were also analyzed in a control group (n = 34). PMN-elastase levels in ARDS cases reached significantly higher values than in patients who did not develop this syndrome (P < 0.01). We conclude that the increase in plasma PMN-elastase levels can be useful in predicting the development of ARDS in polytraumatized patients, in instituting prophylactic actions and monitoring the course of the disease in these high risk patients. This test is easily adaptable to the routine of any hospital laboratory.

Estrogen dependent expression of heat shock transcription factor: implications for uterine synthesis of heat shock proteins

Transcriptional induction of heat shock protein genes is generally mediated by binding of heat shock transcription factor(s) to the heat shock element present in the promoters of heat shock genes. Although the steady-state levels of heat shock factor mRNAs vary among different tissues, at present virtually nothing is known regarding the cellular signals responsible for their synthesis and hence the observed variations. In this report we demonstrate that the heat shock transcription factor (HSTF or HSF) is under positive regulation by estrogen. The effect of estrogen was observed with both types of heat shock factors (HSF-1 and HSF-2) and occurred at both the mRNA and protein level. Immunolocalization studies emphasized the potential biological importance of these observations whereby the increase in uterine HSF-1 and HSF-2 due to estrogen was found to be associated with the endometrium, the primary tissue component which is targeted for estrogen action. This is the first demonstration of a cellular factor which can regulate HSF-1 and HSF-2 gene expression. The implications of these findings to uterine heat shock protein gene expression are discussed.

Synaptic transmission blockade increases plasminogen activator activity in mouse skeletal muscle poisoned with botulinum toxin type A

Experimental denervation, either by nerve crush or axotomy, leads to a dramatic increase in muscle plasminogen activator (PA) activity, suggesting a regulation of muscle PA levels by some neural influence (Festoff et al., 1986, J. Cell Biol., 103:1415-1421; Hantaï et al., 1990, Proc. Natl. Acad. Sci. U.S.A., 87:2926-2930). The Botulinum toxin (BoTx) type A is known to selectively interrupt the release of acetylcholine without structurally altering synaptic morphology. In the present study we have used acute BoTx poisoning of hind limb muscles to further explore the neural regulation of muscle PA activities directly after poisoning and during the process of collateral reinnervation. Electromyographic recording and study of ultraterminal sprouting after zinc iodideosmium and silver-cholinesterase staining were used to monitor "denervation" and reinnervation. Muscle choline acetyltransferase activity did not decrease, as is observed after experimental denervation, but in contrast increased and, therefore, reflected the functional integrity of intramuscular nerve endings. Within 2 days of BoTx poisoning, muscle urokinase-PA, and to a lesser extent, tissue-PA activities, rose in muscle extracts as shown by an amidolytic assay and fibrin zymography. When reinnervation occurred, muscle urokinase-PA activity decreased but did not return to baseline levels within the 80 days of our study. These results suggest that cholinergic transmission-regulated events determine activity of muscle PAs and that PAs likely have a role in neuromuscular formation and plasticity.

Phenotypical characterization of neurons expressing the dopamine D3 receptor in the rat brain

We have established the cellular distribution of the dopamine D3 receptor using tritiated 7-hydroxy-N-N-di-n-propyl-2-aminotetralin and a complementary RNA probe to visualize autoradiographically the protein in binding studies and the gene transcripts by in situ hybridization, respectively. Studies with these two markers confirm the restricted expression of the D3 receptor in few brain areas, i.e. mainly the ventral striatal complex, the substantia nigra-ventral tegmental area and the cerebellum. In nucleus accumbens, the D3 receptor was mainly expressed in medium-sized neurons of the rostral pole and ventromedial shell subdivisions, but not of the core or septal pole, i.e. accumbal subdivisions expressing the D2 receptor. In the ventromedial shell, about 60% of the D3 receptor-expressing neurons were neurotensin neurons, presumably projecting to the ventral pallidum. In the islands of Calleja, both D3 receptor binding and messenger RNA were abundant in the entire population of granule cells. These cells are known to make sparse contacts with dopaminergic axons and also to express the D1 receptor. In the mesencephalon, low levels of D3 messenger RNA were detected in few dopamine neurons of substantia nigra pars lateralis and ventral tegmental area. In addition, some D3 receptor binding but not messenger RNA was detected in medial substantia nigra and lateral ventral tegmental area, where the receptor is presumably located presynaptically on afferents. In the archicerebellum, Purkinje cell perikarya in lobules 9 and 10 expressed the D3 receptor messenger RNA, whereas binding sites were found in the molecular layer, where corresponding dendrites but no known dopaminergic projection from mesencephalon are found. The occurrence of D3 receptor gene expression in some brain areas receiving low dopamine innervation supports the hypothesis that this receptor may mediate non-synaptic actions of dopamine.

Tumor embolism after pneumonectomy for primary pulmonary neoplasia

We report a case of tumor embolism of the lower right extremity after right pneumonectomy. This is an infrequent complication and in most cases occurs during the intraoperative or immediate postoperative period. Our patient underwent surgery for primary pulmonary neoplasia (squamous cell carcinoma) and 4 hours later showed clinical signs of acute arterial occlusion in the lower right extremity. An emergency embolectomy was performed and a thrombus with tumor characteristics was extracted from the right common femoral artery. The pathologic features of this thrombus were identical to those of the pulmonary tumor.

Cell proliferation and apoptosis during development and aging of the rabbit corpus luteum

Corpora lutea (CL) are endocrine ovarian structures that regulate fundamental reproductive events in mammals. The functional lifespan of these structures is finite as CL regress and cease secreting progesterone after species-dependent intervals during nonfertile postovulatory cycles or pregnancy. The signals that regulate CL aging are poorly understood. This study investigates cell growth and programmed cell death or apoptosis in corpora lutea of New Zealand White rabbits. To study cell growth, CL were obtained at various postovulatory days (POD) from animals injected with the deoxyribonucleic acid (DNA) precursor analog bromodeoxyuridine (BUdR). The BUdR-labeled cells were identified by avidin-biotin-complex immunocytochemistry, and the mean proliferation index area computed by image analysis. Apoptotic cells were scored and further identified by in situ demonstration of DNA fragmentation. Proliferation in parenchymal, stromal, and endothelial CL cells was significantly elevated at POD 3, 5, 18, and 21 and highest at POD 3 (P < 0.001). The number of apoptotic cells was elevated (P < 0.001) at POD 18 and 21, while 1 percent or less of CL cells were apoptotic at POD 3, 5, and 12. Apoptosis was accompanied by shrinkage or vacuolization of CL cells and increased mean number (P < 0.001) of heterophilic leucocytes at POD 18. These data demonstrate that cell growth is more intense during early luteal development and that cell deletion via apoptosis plays an important role in CL regression. The role of paracrine signals such as microphagic cytokines in CL aging remains to be elucidated.

A paradoxical regulation of the dopamine D3 receptor expression suggests the involvement of an anterograde factor from dopamine neurons

The effects of interruption of dopaminergic transmission or sustained blockade of dopamine receptors by neuroleptics on the dopamine D3 receptor in the shell of the nucleus accumbens were investigated in rats. In this brain area the D3 receptor is abundant and may mediate antipsychotic drug effects. The D3 receptor density and mRNA abundance were evaluated with 7-[3H]hydroxy-N,N-di-n-propyl-2-aminotetralin and by quantitative PCR or image analysis of in situ hybridization signals, respectively. Unilateral dopamine neuron degeneration by 6-hydroxydopamine or sections triggered, after a few days, a marked decrease (up to 50%) in D3 receptor binding and mRNA in the nucleus accumbens. In contrast, a 2-week treatment with the neuroleptic haloperidol (20 mg/kg) had no effect on D3 receptor density and mRNA but enhanced D2 receptor density and mRNA level by > 50%. In addition, tolerance to the haloperidol-induced change of neurotensin mRNA mediated by the D2 receptor developed, but there was no tolerance to the opposite change mediated by the D3 receptor. Reserpine, a monoamine-depleting drug with antipsychotic activity, did not modify D3 receptor mRNA. These observations reinforce the idea that the D3 receptor may be an important target for neuroleptics whose antipsychotic actions, but not extrapyramidal motor actions, do not display tolerance. The D3 receptor mRNA level was also decreased by a unilateral injection in dopamine cell body areas of colchicine, a drug blocking the anterograde axonal transport, or by baclofen, a type A gamma-aminobutyric acid receptor agonist reducing dopamine neuron activity, but not by sustained blockade of D1-like and D2-like, neurotensin, or cholecystokinin receptors. We therefore propose that an anterograde factor present in mesolimbic dopaminergic neurons, but distinct from dopamine and known peptide cotransmitters, plays a positive role on transcription of the D3 receptor gene.

Arteriosclerotic histologic evaluation of the internal mammary artery in patients undergoing coronary artery bypass grafting

During 1991, 52 patients undergoing myocardial revascularization had a biopsy of the distal internal left mammary artery (IMA) taken. There were 48 male and 4 female patients with a medium age of 58 years. Arteriosclerotic involvement of the IMA was assessed according to the scale of Kay. Using this index, grade 0 corresponds to a normal artery without atherosclerosis, grade 1 represents minimal disease, grade 2 a narrowing of less than 25% of the lumen, grade 3 narrowing between 25 and 50%, and grade 4 narrowing of 50% or greater of the lumen. Of the 52 IMA examined, the arteries with degree 0, 1, 2, 3, and 4 were: 19 (36.5%), 20 (38.4%), 9 (17.6%), 4 (7.6%) and zero. Thirty-three arteries (63.4%) had some degree of atherosclerosis. Considering the arteries with some atherosclerotic narrowing, 13 (25%) of the whole group had this pathological alteration. The IMA has a low but consistent incidence of arteriosclerosis involvement. Preoperative angiographic investigation of the IMA could be routinely performed.

The dopamine D3 receptor and schizophrenia: pharmacological, anatomical and genetic approaches

Antipsychotic drug therapy mainly rests on the use of antagonists of dopamine D2-like (D2, D3 and D4) receptors, for which all clinically active compounds have high affinity. The D3 receptor has a restricted expression in brain limbic areas, associated with cognitive functions and motivated behavior. D3 selective agonists and antagonists reveal an inhibitory role on motor behaviors for the D3 receptor, opposite to that of the D2 receptor. An opposing role for D2 and D3 receptors is also suggested by the contrasted effects of D2/D3 antagonists on neurotensin expression in discrete subdivisions of nucleus accumbens, where D2 and D3 receptors are selectively expressed. Tolerance to the motor but not to the therapeutic effects of neuroleptics is observed after repeated administration, which upregulates the D2, but not the D3 receptor in animals. In genetic association studies, an excess of homozygosity for both alleles of the BalI polymorphism at the D3 receptor gene was found in schizophrenic patients, suggesting that this gene may have subtle influence on the liability to develop schizophrenia. These results suggest the D3 receptor as an important target for antipsychotic drug action, and D3 receptor selective antagonists as promising therapeutic agents.

[125I]iodoproxyfan, a new antagonist to label and visualize cerebral histamine H3 receptors

Iodoproxyfan, i.e., 3-(1H-imidazol-4-yl)propyl-(4-iodophenyl)-methyl ether, is a novel potent and selective histamine H3 receptor antagonist. [125I]Iodoproxyfan binding to membranes of the rat striatum was reversible and saturable. Specific binding defined with 1 microM (R)-alpha-methylhistamine corresponded to 65% of the total at 30 pM. Scatchard analysis indicated a Kd of 65 pM and maximal binding capacity of 78 fmol/mg of protein. The specificity of [125I]Iodoproxyfan binding to H3 receptors was demonstrated by its pharmacological profile. A series of H3 receptor agonists inhibited [125I]iodoproxyfan binding with a similar maximal effect and with the expected order of potency and stereoselectivity ratio. H3 receptor antagonists inhibited the specific binding with the expected Ki values. In the presence of guanylnucleotides, 40% of sites exhibited a approximately 40-fold lower affinity for histamine, indicating that the H3 receptor belongs to the superfamily of G protein-coupled receptors and revealing the existence of two populations of sites. Well contrasted autoradiographic pictures of total [125I]iodoproxyfan binding to sections of the rat brain were obtained in a short time and over a low nonspecific binding. The heterogenous distribution of H3 receptors with high labeling of anterior cerebral cortex, ventral striatum and other limbic areas was confirmed. In addition, a clearly distinguishable laminated pattern of labeling was evidenced in the cerebral cortex and hippocampal formation. Hence, this new probe should be useful for sensitive assay and localization of the H3 receptor.