Preoperative and postoperative L-lactatemia assessment for the prognosis of right abomasal disorders in dairy cattle

BACKGROUND

Preoperative L-lactatemia and heart rate have been suggested as prognostic indicators of outcome for cows with right dilatation of the abomasum or volvulus (RDA/AV). However, postoperative L-lactatemia has not been assessed as a potential prognostic tool.

OBJECTIVES

To determine the prognostic value of postoperative L-lactatemia (LAC2 ), duration of treatment (Dt), relative L-lactatemia difference (compared with preoperative L-lactatemia [LAC1 ]) ([LAC2 - LAC1 ]/LAC2 ) and change in L-lactate over time ([LAC2 - LAC1 ]/Dt) as compared to preoperative findings (LAC1 and heart rate [HR]) as prognostic factors in dairy cows with RDA/AV.

ANIMALS

A total of 41 dairy cows were included: 19 with AV and 22 with RDA; 11 cows had a negative outcome (NO) and 30 cows had a positive outcome (PO) based on telephone follow-up with owners 30 days after surgery.

METHODS

Prospective cohort study. Analysis was performed using logistic regression and comparison of area under the receiver operating characteristics curve (AUC) using nonparametric tests.

RESULTS

LAC1 > 1.4 mmol/L or LAC2 > 2.2 mmol/L had the same accuracy with sensitivity of 100% (95% CI, 75.1-100%) and specificity of 80% (95% CI, 61.4-92.3%) for predicting NO. The relative L-lactatemia difference ([LAC2 - LAC1 ]/LAC1 ) or lactate kinetics ([LAC2 - LAC1 ]/Dt) were not associated with prognosis. The AUC of the preoperative model (which included HR and lnLAC1 ) was 0.92 (95% CI, 0.83-1.0) and that of the postoperative model (including only lnLAC2 ) was 0.95 (95% CI, 0.88-1.0); these were not significantly different.

CONCLUSIONS AND CLINICAL IMPORTANCE

Postoperative L-lactatemia is helpful to predict outcome in cows with RDA/AV. The short-term change in blood L-lactate is not a useful prognostic indicator, at least during the period of time spent on the farm for surgery and treatment.

Preoperative cow-side lactatemia measurement predicts negative outcome in Holstein dairy cattle with right abomasal disorders

The objectives of the current study were (1) to determine the gain in prognostic accuracy of preoperative l-lactate concentration (LAC) measured on farm on cows with right displaced abomasum (RDA) or abomasal volvulus (AV) for predicting negative outcome; and (2) to suggest clinically relevant thresholds for such use. A cohort of 102 cows with on-farm surgical diagnostic of RDA or AV was obtained from June 2009 through December 2011. Blood was drawn from coccygeal vessels before surgery and plasma LAC was immediately measured by using a portable clinical analyzer. Dairy producers were interviewed by phone 30 d following surgery and the outcome was determined: a positive outcome if the owner was satisfied of the overall evolution 30 d postoperatively, and a negative outcome if the cow was culled, died, or if the owner reported being unsatisfied 30 d postoperatively. The area under the curve of the receiver operating characteristic curve for LAC was 0.92 and was significantly greater than the area under the curve of the receiver operating characteristic curve of heart rate (HR; 0.77), indicating that LAC, in general, performed better than HR to predict a negative outcome. Furthermore, the ability to predict a negative outcome was significantly improved when LAC measurement was considered in addition to the already available HR data (area under the curve: 0.93 and 95% confidence interval: 0.87, 0.99). Important inflection points of the misclassification cost term function were noted at thresholds of 2 and 6 mmol/L, suggesting the potential utility of these cut-points. The 2 and 6 mmol/L thresholds had a sensitivity, specificity, positive predictive value, and negative predictive value for predicting a negative outcome of 76.2, 82.7, 53.3, and 93.1%, and of 28.6, 97.5, 75, and 84%, respectively. In terms of clinical interpretation, LAC ≤2 mmol/L appeared to be a good indicator of positive outcome and could be used to support a surgical treatment decision. The treatment decision for cows with LAC between 2 and 6 mmol/L, however, would depend on the economic context and the owner's attitude to risk in regard to potential return on its investment. Finally, performing a surgical correction on commercial cows with RDA or AV and a LAC ≥6 mmol/L appeared to be unjustified and these animals should be culled based on their high probability of negative outcome.

Molecular determinants of TRP channel assembly

Calcium channels play important roles in cellular signalling. TRP (transient receptor potential) channels form a superfamily of calcium channels through which Ca(2+) enters the cell. TRPs have six transmembrane segments with a putative pore between the fifth and the sixth segments, and assemble in tetrameric complexes to form functional Ca(2+) channels. They are thus similar to K(V) (voltage-gated potassium channel) channels in terms of structure and molecular determinants that promote subunit assembly. In this review, the molecular determinants mediating the assembly of Drosophila TRP, TRPC (TRP canonical), TRPV (TRP vanilloid) and K(V) channels are described.

Endoscopic screening for esophageal squamous-cell carcinoma in high-risk patients: a prospective study conducted in 62 French endoscopy centers

BACKGROUND AND STUDY AIMS

The prevalence of esophageal squamous-cell carcinoma in high-risk patients and the advantages of systematic Lugol staining during esophagoscopy have not yet been evaluated in a large prospective study. In this study we aimed to assess the prevalence of this type of tumor in high-risk patients, to examine the role of Lugol staining in endoscopic screening for esophageal squamous-cell carcinoma, and to establish whether it is possible to identify a particularly high-risk group which would benefit from systematic screening.

PATIENTS AND METHODS

A prospective study was undertaken in 62 endoscopy centers. A total of 1095 patients were enrolled, none of whom had any esophageal symptoms. These patients had presented with either a past history of or a recent head and neck or tracheobronchial squamous-cell carcinoma (group 1), with alcoholic chronic pancreatitis (group 2), with alcoholic cirrhosis (group 3), or were alcohol and tobacco addicts (group 4). The patients underwent a meticulous endoscopic examination of the esophagus, followed by Lugol staining.

RESULTS

The prevalence of esophageal squamous-cell carcinoma was 3.2 %. The group 1 patients showed the highest prevalence of carcinoma (5.3 %) and the highest prevalence of dysplasia (4.5 %). Of the 35 carcinomas detected in the 1095 patients, seven (20 %) were early lesions, and 20 % were only detected after Lugol staining (P = 0.02). High-grade dysplasia was only observed in group 1 patients and two-thirds of these lesions were only diagnosed after Lugol staining. The overall prevalence of low-grade dysplasia was 2.4 %, and 77 % of these were detected only after Lugol staining (P < 0.001).

CONCLUSIONS

Lugol dye staining increases the sensitivity of esophageal endoscopy for the detection of high-grade dysplasia and cancer. The prevalence of dysplasia and cancer reached 9.9 % in group 1, and we therefore believe that an endoscopic screening program could be justified for patients with head and neck or tracheobronchial cancer.

[Anesthesic practices in patients with severe postpartum hemorrhage with persistent or worsening bleeding]

Severe postpartum hemorrhage (PPH) is a rare and critical situation which requires fast and well-planned management where close collaboration between obstetricians and anesthesiologists is essential. In case of persisting or worsening bleeding in spite of initially adequate management, the main goal of the anesthesiologist is to maintain hemodynamic stability (fluid resuscitation, transfusion, vasoactive drugs) and optimal respiratory state (oxygenation) and to correct the frequent clotting disorders, whereas the obstetrician and/or the radiologist have to achieve definitive hemostasis. Assessment of the severity of PPH is determined from: quantity of blood loss and/or duration of bleeding, difficulty in maintaining a correct hemodynamic state in spite of active vascular fluid resuscitation, need for vasoactive therapy and transfusion, occurrence and worsening of clotting disorders. Continuous drip Sulprostone requires close clinical surveillance and continuous monitoring (electrocardiography, non-invasive blood pressure monitor, pulse oximetry). When this treatment does not enable sufficiently rapid control of the bleeding (consensus = within 30 minutes), invasive therapy (arterial embolization, vascular ligation even hysterectomy) should be started promptly. When the bleeding continues despite aggressive medical treatments, general anesthesia (even if an epidural catheter is already in place) is needed to proceed with the invasive surgical procedure. This anaesthesia of a "full stomach" patient justifies a rapid-sequence induction with cricoid pressure and intubation. The risk is particularly high in case of hemorrhagic shock. Angiographic embolization should be carried out in an angiography suite which must be equipped for this kind of situation (anesthesia and resuscitation material, adapted monitoring). A member of the anesthesia team must be present throughout this procedure. At best, a multidisciplinary team, specially trained for this purpose, including obstetrician, anesthesiologist, radiologist and biologist should be available. When one or several invasive treatments were necessary to control the bleeding, it is recommended to transfer the patient to a specialized unit (intensive care unit or recovery room).

Ca(2+)-calmodulin regulates receptor-operated Ca(2+) entry activity of TRPC6 in HEK-293 cells

Mammalian homologues of the Drosophila transient receptor potential channel (TRPC) are involved in Ca(2+) entry following agonist stimulation of nonexcitable cells. Seven mammalian TRPCs have been cloned but their mechanisms of activation and/or regulation are still the subject of intense research efforts. It has already been shown that calmodulin (CaM) can regulate the activity of Drosophila TRP and TRPL and, more recently, CaM has been shown to interact with mammalian TRPCs. In this study, TRPC6 stably transfected into HEK-293 cells was used to investigate the possible influence of CaM on TRPC6-dependent Ca(2+) entry. Overexpression of TRPC6 in mammalian cells is known to enhance agonist-induced Ca(2+) entry, but not thapsigargin-induced Ca(2+) entry. Here, we show that CaM inhibitors (calmidazolium and trifluoperazine) abolish receptor-operated Ca(2+) entry (ROCE) without affecting thapsigargin-operated Ca(2+) entry and that the activity of CaM is dependent on complexation with Ca(2+). We also show that Ca(2+)-CaM binds to TRPC6 and that the binding can be abolished by CaM inhibitors. These results indicate that CaM is involved in the modulation of ROCE.

Dose of prophylactic intravenous ephedrine during spinal anesthesia for cesarean section

STUDY OBJECTIVE

To compare the incidence of maternal hypotension associated with spinal anesthesia for cesarean section when 10-, 15-, or 20-mg prophylactic boluses of intravenous (IV) ephedrine are used.

DESIGN

Prospective observational study.

SETTING

Teaching hospital.

PATIENTS

108 women admitted for elective cesarean section.

INTERVENTIONS

Spinal anesthesia was performed using hyperbaric bupivacaine 10 mg, sufentanil 2 microg, and morphine 0.2 mg (volume 4 mL). Ephedrine (10, 15, or 20 mg) was administered 2 minutes after the intrathecal injection. Maternal blood pressure was checked every 2 minutes. Hypotension was promptly treated with 5-mg ephedrine boluses.

MAIN RESULTS

Incidence of hypotension was significantly higher in women receiving a 10-mg prophylactic dose of ephedrine than in those receiving either a 15-mg or a 20-mg prophylactic dose of ephedrine [23/36 in the 10-mg ephedrine group vs. 13/36 and 10/36 in the 15-mg and 20-mg ephedrine groups, respectively (p< 0.05)].

CONCLUSION

In the conditions of this study, a single bolus of IV ephedrine with doses of either 15 or 20 mg decreased significantly the incidence of maternal hypotension as compared to a single 10-mg bolus of ephedrine.

Most central nervous system D2 dopamine receptors are coupled to their effectors by Go

We reported previously that Go-deficient mice develop severe neurological defects that include hyperalgesia, a generalized tremor, lack of coordination, and a turning syndrome somewhat reminiscent of unilateral lesions of the dopaminergic nigro-striatal pathway. By using frozen coronal sections of serially sectioned brains of normal and Go-deficient mice, we studied the ability of several G protein coupled receptors to promote binding of GTPgammaS to G proteins and the ability of GTP to promote a shift in the affinity of D2 dopamine receptor for its physiologic agonist dopamine. We found a generalized, but not abolished reduction in agonist-stimulated binding of GTPgammaS to frozen brain sections, with no significant left-right differences. Unexpectedly, the ability of GTP to regulate the binding affinity of dopamine to D2 receptors (as seen in in situ [(35)S]sulpiride displacement curves) that was robust in control mice, was absent in Go-deficient mice. The data suggest that most of the effects of the Gi/Go-coupled D2 receptors in the central nervous system are mediated by Go instead of Gi1, Gi2, or Gi3. In agreement with this, the effect of GTP on dopamine binding to D2 receptors in double Gi1 plus Gi2- and Gi1 plus Gi3-deficient mice was essentially unaffected.

Mechanism of capacitative Ca2+ entry (CCE): interaction between IP3 receptor and TRP links the internal calcium storage compartment to plasma membrane CCE channels

Activation of cells by agents that stimulate inositol trisphoshate (IP3) formation causes, via IP3 receptor (IP3R) activation, the release of Ca2+ from internal stores and also the entry of Ca2+ via plasma membrane cation channels, referred to as capacitative Ca2+ entry or CCE channels. Trp proteins have been proposed to be the unitary subunits forming CCE channels; however, there is no definitive proof for this hypothesis. We have now identified amino acid sequences of a Trp and of an IP3R that interact to form stable complexes. These complexes appear to form in vivo, as evidenced by co-immunoprecipitation of Trp with IP3R and by the fact that expression of the respective interacting sequences modulates development of CCE brought about by store depletion. The finding that a Trp-interacting sequence of IP3R interferes with natural CCE leads us to conclude that Trp proteins are, indeed, structural members of CCE channels. We conclude further that direct coupling of IP3R to Trp is a physiological mechanism by which cells trigger CCE in response to signals that stimulate phosphoinositide hydrolysis and IP3 formation. Pros and cons of various CCE activation models are discussed.

Effect of injection rate on hypotension associated with spinal anesthesia for cesarean section

Maternal hypotension is a common problem during cesarean section under spinal anesthesia. We evaluated in a prospective observational study the influence of injection speed on maternal hypotension. Hyperbaric bupivacaine 10 mg, sufentanil 2 microg and morphine 200 microg (total volume 4 mL) were injected either quickly (<15 s) or slowly (=120 s) in 50 women scheduled for elective cesarean section. Hypotension (systolic arterial pressure (SAP) <100 mmHg or <70% of baseline) was promptly treated with 5 mg ephedrine boluses. Slow injection significantly reduced the incidence of hypotension (68% in the 120 s group and 92% in the other, P =0.03). In addition, onset of hypotension was delayed, had a shorter duration and required less ephedrine for hypotension in the 120 s group (11.6 mg vs. 19.6 mg, P =0.019). Anesthesia was satisfactory for all women. We conclude that a 2 mL/min injection rate may be a simple and effective way to reduce the incidence and severity of hypotension during cesarean section under spinal anesthesia.

Central venous catheter placement in children: evaluation of electrocardiography using J-wire

Misplacement of a central venous catheter may lead to myocardial perforation and dysrhythmia. Atrial electrocardiography (ECG) through a saline column is an effective but complex method to determine the accurate location of catheters. We evaluated a simplified variant of this technique using the guidewire as an internal electrode in 23 children (5-16 years old) undergoing spinal surgery. Catheters were placed using a Seldinger technique after jugular or subclavian venous puncture. Each time the operator recognized the atrial signal, the catheter was found to be correctly placed on the chest radiograph (20/23). In three patients, the atrial signal was not obtained. A technical error was responsible in one case whereas the two others were related to aberrant migrations of the catheter either into a subclavian vein or into the pleura. In this latter case, the complication was unrecognized on the first radiograph despite malposition having been predicted by atrial ECG. We conclude that a method using atrial ECG guidance is sensitive and specific, and may be an alternative to the classical chest radiograph to detect accurate placement of central venous catheters in children.

Modulation of Ca(2+) entry by polypeptides of the inositol 1,4, 5-trisphosphate receptor (IP3R) that bind transient receptor potential (TRP): evidence for roles of TRP and IP3R in store depletion-activated Ca(2+) entry

Homologues of Drosophilia transient receptor potential (TRP) have been proposed to be unitary subunits of plasma membrane ion channels that are activated as a consequence of active or passive depletion of Ca(2+) stores. In agreement with this hypothesis, cells expressing TRPs display novel Ca(2+)-permeable cation channels that can be activated by the inositol 1,4,5-trisphosphate receptor (IP3R) protein. Expression of TRPs alters cells in many ways, including up-regulation of IP3Rs not coded for by TRP genes, and proof that TRP forms channels of these and other cells is still missing. Here, we document physical interaction of TRP and IP3R by coimmunoprecipitation and glutathione S-transferase-pulldown experiments and identify two regions of IP3R, F2q and F2g, that interact with one region of TRP, C7. These interacting regions were expressed in cells with an unmodified complement of TRPs and IP3Rs to study their effect on agonist- as well as store depletion-induced Ca(2+) entry and to test for a role of their respective binding partners in Ca(2+) entry. C7 and an F2q-containing fragment of IP3R decreased both forms of Ca(2+) entry. In contrast, F2g enhanced the two forms of Ca(2+) entry. We conclude that store depletion-activated Ca(2+) entry occurs through channels that have TRPs as one of their normal structural components, and that these channels are directly activated by IP3Rs. IP3Rs, therefore, have the dual role of releasing Ca(2+) from stores and activating Ca(2+) influx in response to either increasing IP3 or decreasing luminal Ca(2+).

Mouse trp2, the homologue of the human trpc2 pseudogene, encodes mTrp2, a store depletion-activated capacitative Ca2+ entry channel

Capacitative Ca2+ entry (CCE) is Ca2+ entering after stimulation of inositol 1,4,5-trisphosphate (IP3) formation and initiation of Ca2+ store depletion. One hallmark of CCE is that it can also be triggered merely by store depletion, as occurs after inhibition of internal Ca2+ pumps with thapsigargin. Evidence has accumulated in support of a role of transient receptor potential (Trp) proteins as structural subunits of a class of Ca2+-permeable cation channels activated by agonists that stimulate IP3 formation-very likely through a direct interaction between the IP3 receptor and a Trp subunit of the Ca2+ entry channel. The role of Trp's in Ca2+ entry triggered by store depletion alone is less clear. Only a few of the cloned Trp's appear to enhance this type of Ca2+ entry, and when they do, the effect requires special conditions to be observed, which native CCE does not. Here we report the full-length cDNA of mouse trp2, the homologue of the human trp2 pseudogene. Mouse Trp2 is shown to be readily activated not only after stimulation with an agonist but also by store depletion in the absence of an agonist. In contrast to other Trp proteins, Trp2-mediated Ca2+ entry activated by store depletion is seen under the same conditions that reveal endogenous store depletion-activated Ca2+ entry, i.e., classical CCE. The findings support the general hypothesis that Trp proteins are subunits of store- and receptor-operated Ca2+ channels.

[Acute cardiogenic postoperative edema after doxorubicin (adriamycin) chemotherapy]

We describe a case of postoperative congestive heart failure in a young woman of physical class ASA 1, following breast cancer surgery. Preoperatively she had been treated with doxorubicin (Adriamycin) 450 mg.m-2, total dose, associated with breast and ovarian radiotherapy. This association was probably the cause of postoperative heart failure. Twenty-four hours after surgery, a two-dimensional echocardiography showed a severe left ventricular dysfunction, whereas preoperative clinical assessment was unremarkable. Doxorubicin cardiotoxicity can be acute, subacute and delayed as in our case. Clinical assessment and ECG are not sensitive indicators of such cardiac damage. Preoperative echography is the technique of choice for the evaluation of the cardiac status of a patient treated with a high cumulative dose of doxorubicin and mediastinal irradiation.

Inactivation of the G alpha i2 and G alpha o genes by homologous recombination

G proteins couple receptors to effectors and thus regulate multiple biological processes. Here we report on the phenotypes of G alpha i2-deficient and G alpha o-deficient mice. G alpha i2-deficient mice display a blunted inhibitory regulation of adenylyl cyclase, alterations in T cell maturation and function, a growth retardation and also develop a lethal diffuse colitis with clinical and histopathological features closely resembling ulcerative colitis in humans, including the development of adenocarcinoma of the colon. G alpha o-deficient mice are also viable, but significantly smaller than wild-type controls.

Multiple neurological abnormalities in mice deficient in the G protein Go

The G protein Go is highly expressed in neurons and mediates effects of a group of rhodopsin-like receptors that includes the opioid, alpha2-adrenergic, M2 muscarinic, and somatostatin receptors. In vitro, Go is also activated by growth cone-associated protein of Mr 43,000 (GAP43) and the Alzheimer amyloid precursor protein, but it is not known whether this occurs in intact cells. To learn about the roles that Go may play in intact cells and whole body homeostasis, we disrupted the gene encoding the alpha subunits of Go in embryonic stem cells and derived Go-deficient mice. Mice with a disrupted alphao gene (alphao-/- mice) lived but had an average half-life of only about 7 weeks. No Goalpha was detectable in homogenates of alphao-/- mice by ADP-ribosylation with pertussis toxin. At the cellular level, inhibition of cardiac adenylyl cyclase by carbachol (50-55% at saturation) was unaffected, but inhibition of Ca2+ channel currents by opioid receptor agonist in dorsal root ganglion cells was decreased by 30%, and in 25% of the alphao-/- cells examined, the Ca2+ channel was activated at voltages that were 13.3 +/- 1.7 mV lower than in their counterparts. Loss of alphao was not accompanied by appearance of significant amounts of active free betagamma dimers (prepulse test). At the level of the living animal, Go-deficient mice are hyperalgesic (hot-plate test) and display a severe motor control impairment (falling from rotarods and 1-inch wide beams). In spite of this deficiency, alphao-/- mice are hyperactive and exhibit a turning behavior that has them running in circles for hours on end, both in cages and in open-field tests. Except for one, all alphao-/- mice turned only counterclockwise. These findings indicate that Go plays a major role in motor control, in motor behavior, and in pain perception and also predict involvement of Go in Ca2+ channel regulation by an unknown mechanism.

Ionic currents underlying HTRP3 mediated agonist-dependent Ca2+ influx in stably transfected HEK293 cells

hTrp3 is a human homologue of the Drosophila gene responsible for a transient receptor potential (trp) mutation. When stably expressed in HEK293 cells, hTrp3 formed ion channels that were active under resting conditions but could be further stimulated by carbachol or ATP via endogenous muscarinic or purinergic receptors, respectively. Agonist evoked currents reversed polarity near 0 mV in physiological ionic conditions and were associated with a significant increase in the current variance. These results suggest the involvement of a non-selective cation channel with relatively large unitary amplitude. Consistent with this, resolved unitary events had a conductance of approximately 60 pS in the negative voltage range and an extrapolated reversal potential near 0 mV.

Cloning and expression of a novel mammalian homolog of Drosophila transient receptor potential (Trp) involved in calcium entry secondary to activation of receptors coupled by the Gq class of G protein

Hormonal stimulation of Gq-protein coupled receptors triggers Ca2+ mobilization from internal stores. This is followed by a Ca2+ entry through the plasma membrane. Drosophila Trp and Trpl proteins have been implicated in Ca2+ entry and three mammalian homologues of Drosophila Trp/Trpl, hTrp1, hTrp3 and bTrp4 (also bCCE) have been cloned and expressed. Using mouse brain RNA as template, we report here the polymerase chain reaction-based cloning and functional expression of a novel Trp, mTrp6. The cDNA encodes a protein of 930 amino acids, the sequence of which is 36.8, 36.3, 43.1, 38.6, and 74. 1% identical to Drosophila Trp and Trpl, bovine Trp4, and human Trp1 and Trp3, respectively. Transient expression of mTrp6 in COS.M6 cells by transfection of the full-length mTrp6 cDNA increases Ca2+ entry induced by stimulation of co-transfected M5 muscarinic acetylcholine receptor with carbachol (CCh), as seen by dual wavelength fura 2 fluorescence ratio measurements. The mTrp6-mediated increase in Ca2+ entry activity was blocked by SKF-96365 and La3+. Ca2+ entry activity induced by thapsigargin was similar in COS cells transfected with or without the mTrp6 cDNA. The thapsigargin-stimulated Ca2+ entry could not be further stimulated by CCh in control cells but was markedly increased in mTrp6-transfected cells. Records of whole cell transmembrane currents developed in response to voltage ramps from -80 to +40 mV in control HEK cells and HEK cells stably expressing mTrp6 revealed the presence of a muscarinic receptor responsive non-selective cation conductance in Trp6 cells that was absent in control cells. Our data support the hypothesis that mTrp6 encodes an ion channel subunit that mediates Ca2+ entry stimulated by a G-protein coupled receptor, but not Ca2+ entry stimulated by intracellular Ca2+ store depletion.

On the molecular basis and regulation of cellular capacitative calcium entry: roles for Trp proteins

During the last 2 years, our laboratory has worked on the elucidation of the molecular basis of capacitative calcium entry (CCE) into cells. Specifically, we tested the hypothesis that CCE channels are formed of subunits encoded in genes related to the Drosophila trp gene. The first step in this pursuit was to search for mammalian trp genes. We found not one but six mammalian genes and cloned several of their cDNAs, some in their full length. As assayed in mammalian cells, overexpression of some mammalian Trps increases CCE, while expression of partial trp cDNAs in antisense orientation can interfere with endogenous CCE. These findings provided a firm connection between CCE and mammalian Trps. This article reviews the known forms of CCE and highlights unanswered questions in our understanding of intracellular Ca2+ homeostasis and the physiological roles of CCE.

trp, a novel mammalian gene family essential for agonist-activated capacitative Ca2+ entry

SUMMARY

Capacitative calcium entry (CCE) describes CA2+ influx into cells that replenishes CA2+ stores emptied through the action of IP3 and other agents. It is an essential component of cellular responses to many hormones and growth factors. The molecular basis of this form of Ca2+ entry is complex and may involve more than one type of channel. Studies on visual signal transduction in Drosophila led to the hypothesis that a protein encoded in trp may be a component of CCE channels. We reported the existence of six trp-related genes in the mouse genome. Expression in L cells of small portions of these genes in antisense orientation suppressed CCE. Expression in COS cells of two full-length cDNAs encoding human trp homologs, Htrp1 and Htrp3, increased CCE. This identifies mammalian gene products that participate in CCE. We propose that trp homologs are subunits of CCE channels, not unlike those of classical voltage-gated ion channels.

[Combined spinal and epidural analgesia for labor. Prolongation by addition of a minidose of clonidine to sufentanil. An initial study]

The effect of adding a minidose of clonidine to intrathecal sufentanil during the early first stage of a painful labour was evaluated in this preliminary open-label, non-randomised trial. Group 1 received sufentanil 5 micrograms + clonidine 30 micrograms intrathecally (n = 10) and group 2 only intrathecal sufentanil 5 micrograms (n = 11). The two groups were not statistically different regard-ing age, weight, height, primiparity (67 vs 50%), oxytocin use (37 vs 60%), initial cervical dilation (m +/- DS: 2.9 +/- 1.1 vs 2.9 +/- 1 cm) and VAS pain scores (70 +/- 14 vs 68 +/- 19 mm). In group 1, analgesia was markedly prolonged with a reduced variability in duration: 146 +/- 27 min vs 95 +/- 44 min, (P = 0.006). VAS pain scores were: 14 +/- 20 vs 19 +/- 13, 1 +/- 3 vs 9 +/- 12, 0 vs 5 +/- 7, 48 +/- 12 vs 65 +/- 15, five and fifteen minutes after intrathecal injection, during maximum efficacy, and at the time additional analgesia was required, in group 1 and group 2, respectively. Analgesia evaluated with the VAS pain scores was better in group 1 compared with group 2 (P = 0.02) and decreased somewhat slower. Side effects, such as hypotension, pruritus and sedation, were not statistically different between groups. Nausea and motor blockade did not occur. In conclusion, the addition of a minidose (30 micrograms) of clonidine to sufentanil 5 micrograms given intrathecally seems to potentiate markedly the analgesia obtained during the early first stage of labour.

Leukotriene C4 receptors on guinea pig tracheocytes

Leukotriene (LT) C4 receptors have been characterized on freshly isolated guinea pig tracheal epithelial cells (tracheocytes). The [3H]LTC4 receptor affinity was enhanced by increasing the sodium (60-160 mM) and the magnesium (0-10 mM) concentrations. Low concentrations of calcium (0-3 mM) increased [3H]LTC4 binding, but high concentrations (3-10 mM) decreased it. The pH (6.5-8.0) had no effect on [3H]LTC4 binding to tracheocytes. Under our experimental conditions, binding equilibrium was reached after 20 min. The association and the dissociation rate constants were estimated to be 2.75 +/- 0.25 x 10(6) M-1.min-1 and 0.093 +/- 0.008 min-1, respectively. The Kd (35.4 +/- 8.6 nM) and the Bmax values (2.4 +/- 0.6 x 10(5) receptors/cell) were determined by Scatchard analysis. LTB4, LTD4 and LTE4 did not inhibit [3H]LTC4 binding to the receptors. However, the compound FPL 55712 inhibited the binding of [3H]LTC4 with an IC50 value of 9.0 +/- 1.0 microM. [3H]LTC4 was not metabolized during the binding assays, as confirmed by reverse-phase high-performance liquid chromatography. The lack of [3H]LTC4 binding to glutathione-S-transferase was demonstrated in the presence of an excess of reduced glutathione. LTC4 produced a concentration-dependent increase of free Ca++ in tracheocytes. Our results suggest that guinea pig tracheocytes possess a specific LTC4 receptor coupled to a Ca++ signaling pathway. This LTC4 receptor may play a key role in the epithelium-dependent responses of airway smooth muscle.

Ulcerative colitis and adenocarcinoma of the colon in G alpha i2-deficient mice

G proteins are involved in cellular signalling and regulate a variety of biological processes including differentiation and development. We have generated mice deficient for the G protein subunit alpha i2 (G alpha i2) by homologous recombination in embryonic stem cells. G alpha i2-deficient mice display growth retardation and develop a lethal diffuse colitis with clinical and histopathological features closely resembling ulcerative colitis in humans, including the development of adenocarcinoma of the colon. Prior to clinical symptoms, the mice show profound alterations in thymocyte maturation and function. The study of these animals should provide important insights into the pathogenesis of ulcerative colitis as well as carcinogenesis.

Short-term desensitization of the angiotensin II receptor of bovine adrenal glomerulosa cells corresponds to a shift from a high to a low affinity state

Angiotensin II (Ang II) is an important regulator of aldosterone production by bovine adrenal glomerulosa (BAG) cells. Ang II interacts with a specific receptor coupled to a guanyl nucleotide-binding protein (G protein) that controls the activity of phospholipase C. A primary culture of BAG cells was used to study short-term desensitization of the Ang II receptor. After short exposures to Ang II, BAG cells lost some [125I]Ang II binding capacity. This loss was dependent on the duration of the pretreatment and on the concentration of Ang II used. A maximal loss of [125I]Ang II binding of 55 +/- 10% was observed after a pretreatment of 30 min with 30 nM Ang II. The EC50 was 1.3 +/- 0.6 nM (mean +/- SD of three experiments). The desensitization was readily reversible, since most of the binding capacity (higher than 90%) was recovered after a 60-min incubation, at 37 C, in the absence of Ang II. Scatchard studies revealed that the Ang II receptor of BAG cells exists under two affinity states with one dissociation constant of 0.2 nM and another dissociation constant of 1.5 nM. After a 30-min exposure of BAG cells to 10 nM Ang II, an important decrease of high affinity binding sites was observed. The maximal amount of binding sites was similar on control and desensitized cells (around 52,000 receptors per cell). GTP gamma S, a potent activator of G proteins, decreased [125I]Ang II binding to permeabilized BAG cells. This GTP gamma S effect was not observed on permeabilized BAG cells that had previously been desensitized with 10 nM Ang II. These results suggested that, similarly to GTP gamma S, short exposure to 10 nM Ang II caused the uncoupling of Ang II receptor from its G protein. DuP-753 (a selective AT1 angiotensin II type 1 receptor antagonist) markedly unhibited, whereas PD-123319 (a selective AT2 angioten II type 2 receptor antagonist) had no effect on Ang II receptor desensitization, indicating that the AT1 receptor subtype was responsible for the observed phenomenon. Pretreatment of BAG cells with staurosporine (a protein kinase C inhibitor) and R24571 (a calmodulin inhibitor) did not modify Ang II-induced desensitization of AT1 receptor.(ABSTRACT TRUNCATED AT 400 WORDS)

Protection of mice and swine against infection with Actinobacillus pleuropneumoniae by vaccination

CaCl2 and LiCl cell extracts and a crude hemolysin preparation were isolated from Actinobacillus pleuropneumoniae serotype 1 strain 4074 and tested for protection against A. pleuropneumoniae serotype 1 and 5 in mice. The LiCl cell extract adsorbed on AlPO4 and the crude hemolysin preparation adsorbed on Al(OH)3 showed a highly significant protection (P < 0.01) against both serotypes. Different vaccine preparations were used to immunize pigs by intra-muscular injection at days 0 and 14; the pigs were then challenged at day 21 by intra-tracheal inoculation of 1 x 10(8) colony forming units (CFU) of a serotype 1 strain 4074. A vaccine which combined the LiCl extract and the crude hemolysin preparation adsorbed on Al(OH)3 gave the best protection with no mortality and no sign of morbidity in the vaccinated pigs. In the other experimental groups which included a group immunized with a commercial bacterin, mortality, respiratory disease and extensive pulmonary lesions were noted. This mixture shows good potential as a vaccine against pleuropneumonia in pigs.

Selective interaction of chemical dyes with inositol 1,4,5-trisphosphate recognition sites

Inositol 1,4,5-trisphosphate (InsP3) is an important second messenger that interacts with a specific intracellular receptor and triggers a release of Ca2+ from intracellular stores. InsP3 is preferentially metabolized by two enzymes. A specific 5-phosphatase (InsP3 phosphatase) produces an inactive metabolite, inositol 1,4-bisphosphate, while a specific 3-kinase (InsP3 kinase) produces an active metabolite, inositol 1,3,4,5-tetrakisphosphate. With the goal of developing selective ligands of the diverse InsP3 recognition sites, we have studied the effects of some chemical dyes on the binding of InsP3 to its receptor and on the activity of its metabolic enzymes. Although these dyes possess similar chemical structures, they showed varied selectivities towards the three recognition sites. Thymol Blue was the most potent inhibitor of InsP3 binding activity, with an IC50 of 105 microM. Phenol Red demonstrated a higher selectivity for InsP3 phosphatase inhibition, with an IC50 of 100 microM. 3',3",5',5"-Tetraiodophenolsulfonephthalein showed its most potent inhibitory effect on InsP3 kinase activity, with an IC50 of 35 microM. Tetrabromophenol Blue potently inhibited InsP3 phosphatase and InsP3 kinase activities, with respective IC50 values of 25 and 12 microM. Phenolphthalein Diphosphate and Phenolphthalein Carbinol Disulfate demonstrated weak inhibitory effects towards the three recognition sites for InsP3. These results reveal certain structural clues that should help in the development of more selective inhibitors.

The important discrepancy between the apparent affinity observed in Ca2+ mobilization studies and the Kd measured in binding studies is a consequence of the quantal process by which inositol 1,4,5-trisphosphate releases Ca2+ from bovine adrenal cortex microsomes

Inositol 1,4,5-trisphosphate (InsP3) is a second messenger responsible for Ca2+ release from a non-mitochondrial intracellular store. An important discrepancy has been observed between the affinity measured in binding studies (Kd) and the apparent affinity obtained in Ca2+ mobilization studies (EC50). It has been proposed that this discrepancy could be due to different experimental conditions used for Ca2+ mobilization studies and for InsP3 binding studies. With the fluorescent indicator Fura-2, we studied InsP3-induced Ca2+ release activity at 7 degrees C and at 37 degrees C, in bovine adrenal cortex microsomes. Under both conditions, the Ca2+ releasing effect of InsP3 (1 microM) was completed within about 2 s, as a result of the quantal process of InsP3 receptor action. The apparent affinity (EC50) observed for InsP3-induced Ca2+ release at 7 degrees C and at 37 degrees C were 0.64 +/- 0.2 microM and 0.9 +/- 0.2 microM respectively. InsP3 degradation studies, at 37 degrees C, indicated that less than 10% of [3H]-InsP3 was degraded within the first 10 s of incubation. InsP3 association rates were evaluated, at low temperature, with increasing concentrations of [3H]-InsP3. These kinetic studies revealed a direct relationship between the initial rate of association (Vi) and InsP3 concentration. From this relationship, we evaluated that the concentration of InsP3 needed to occupy half of the binding sites within the first second of incubation was 271 nM. We conclude that the discrepancy between Kd and EC50 is related to a kinetic constraint dictated by the quantal process by which InsP3 releases Ca2+.

The high affinity state of inositol 1,4,5-trisphosphate receptor is a functional state

Inositol 1,4,5-trisphosphate (InsP3) is a second messenger responsible for the rapid and discontinuous release of Ca2+ from intracellular stores. In this study, the effects of the sulfhydryl reagent thimerosal were investigated on Ca2+ mobilization and on InsP3 binding. Thimerosal was shown to release Ca2+, in a dose-dependent manner, with an EC50 of 135.8 +/- 5.2 microM, from bovine adrenal cortex microsomes. Thimerosal-induced Ca2+ release was not prevented by heparin (250 micrograms/ml), ruling out a participation of InsP3 receptor in that effect. The slow rate of thimerosal-induced Ca2+ release rather suggested an inhibition of microsomal Ca2+ ATPase. At submaximal concentration, thimerosal (100 microM) was also shown to potentiate the release of Ca2+ induced by InsP3. Dose-response experiments revealed that thimerosal enhanced the apparent affinity of InsP3 by a factor 2.21 +/- 0.28, without modifying the maximal amount of Ca2+ released by InsP3. Thimerosal also enhanced, in a dose-dependent manner, [3H]InsP3 binding to adrenal cortex microsomes (EC50 = 43.3 +/- 7.6 microM). A similar effect was also observed on [3H]InsP3 binding to solubilized receptors, suggesting a direct modification of the receptor protein by thimerosal. The effects of thimerosal on Ca2+ release and [3H]InsP3 binding were abolished in the presence of the reducing agent dithiothreitol (1 mM), suggesting a modification by thimerosal of specific thiol groups on these microsomal proteins. Scatchard analysis revealed that thimerosal (100 microM) increased InsP3 receptor affinity by 1.87 +/- 0.26-fold. Kinetic analysis indicated that this increased affinity was due to an enhancement of InsP3 association rate constant. The concomitant increases of binding affinity and Ca2+ releasing potency suggest that the high affinity state of InsP3 receptor is a functional state.

Photoaffinity labeling of subtype 2 angiotensin receptor of human myometrium

Angiotensin II (AII) binding sites were characterized in human myometrium membrane preparations. The sites were saturable and of high affinity (Kd of 0.09 nM and Bmax of about 200 fmol/mg of protein). PD 123319 completely inhibited 125I-AII binding, with an IC50 of 30 nM, whereas L-158,809 (1 microM) had no significant effect on 125I-AII binding. These results indicate that human myometrium contains almost exclusively the AT2 receptor subtype. Association and dissociation studies performed with 125I-AII on human myometrium membranes revealed that AII had a very high affinity for AT2 receptors, with a Kd of 0.01 nM (association rate constant K1 = 1.056 x 10(12) mol-1 min-1; dissociation rate constant K2 = 0.003 min-1). The photoactivable AII analogue [Sar1, Val5, D-Phe8(N3)]AII displayed a high affinity for AT2 receptors (IC50 of 0.18 nM), but its radioiodinated form showed poor efficiency in photoaffinity labeling experiments. A newly synthesized photoactivatable analogue of AII, [Sar1, p-benzoyl-Phe8]AII, (AII-Bpa), also displayed a high affinity for AT2 receptors of human myometrium (IC50 of 0.3 nM). Photoaffinity labeling experiments were performed with 125I-AII-Bpa, and a high yield (70%) of covalent incorporation to human myometrium membranes was obtained upon photolysis. Covalently labeled receptors were solubilized, denatured, and subjected to polyacrylamide gel electrophoresis. Autoradiography of the polyacrylamide gel revealed a single band, of 68 kDa, and the labeling of this band was completely abolished in the presence of 1 microM PD 123319, indicating selective labeling of the AT2 receptor subtype. These results demonstrate that AII-Bpa is a very efficient tool for selective photoaffinity labeling of the AT2 receptor.

Sar1-p-benzoylphenylalanine-angiotensin, a new photoaffinity probe for selective labeling of the type 2 angiotensin receptor

Previous photoaffinity labeling of angiotensin II (Ang) receptors with azidophenylalanine containing Ang analogs produced high yield labeling of a 60 kDa protein on bovine adrenocortical membranes. This preparation is mostly enriched in the type 1 Ang receptor (AT1) and AT1 selective ligands (L158,809) totally prevented labeling, therefore confirming the AT1 nature of the labeled protein. Our attempt to photolabel the type 2 Ang receptor (AT2) of human myometrium with [Sar1,D-Phe(N3)8]Ang was unsuccessful, revealing a high degree of photolabeling selectivity. An Ang analog, [Sar1,Bpa8]Ang (or BpaAng) was prepared containing the photosensitive amino acid p-benzoylphenylalanine (Bpa). This compound was a specific but non-competitive Ang antagonist on rabbit aorta with a pA2 of 8.5. It displayed good binding affinities for bovine adrenocortical membranes (Kd = 6.5 nM), a predominantly AT1 preparation, and for human myometrium membranes (Kd = 0.39 nM), a predominantly AT2 preparation. Photolabeling experiments with iodinated BpaAng showed that AT1 was not covalently labeled whereas AT2 was covalently labeled with high yield. Labeling specificity was verified with the AT2-selective ligand PD123319 and with the AT1-selective antagonist L158,809. Our results indicate that 125I-BpaAng is exclusively labeling AT2 sites. This compound should be a useful tool for further biochemical characterization of the AT2 binding site.

Interaction of benzene 1,2,4-trisphosphate with inositol 1,4,5-trisphosphate receptor and metabolizing enzymes

In a wide variety of cells, inositol 1,4,5-trisphosphate (InsP3) is an important second messenger involved in the regulation of intracellular Ca2+ concentration. InsP3 interacts with specific receptors and triggers the release of sequestered Ca2+ from an internal store. We have synthesized a structural analogue of InsP3 by phosphorylation of the free hydroxyl groups of 1,2,4-benzenetriol with dibenzylphosphorochloridate. The product benzene 1,2,4-trisphosphate (BzP3) was shown to interact with InsP3 receptor and InsP3 metabolizing enzymes of bovine adrenal cortex. BzP3 competitively blocked InsP3 binding to adrenal cortex microsomes with a half-maximal efficiency at 34 microM. This affinity was about 10,000 times lower than that of InsP3 for its receptor. The Ca2+ releasing activity of BzP3 on the same microsomal preparation was monitored with the fluorescent indicator fura-2. BzP3 had no agonistic effect on this activity but it was able to inhibit InsP3-induced Ca2+ release in a dose-dependent manner. The activity of InsP3 phosphatase was also studied. BzP3 inhibited the activity of the phosphatase with a half-maximal efficiency of 32 microM. BzP3 was also able to inhibit the activity of the cytosolic InsP3 kinase with a half-maximal efficiency of 6.1 microM. These results show that BzP3 is interacting with the three specific recognition sites for InsP3 in the bovine adrenal cortex. The inhibitory effect of this compound is relatively more potent on the metabolizing enzymes than on the Ca(2+)-mobilizing receptor.

Crystal structure of tert.-butyloxycarbonyl-L-prolyl-D-alanyl-D-alanyl-N-methylamide. Dimeric beta-sheet formation

The crystal structure of the tripeptide t-Boc-L-Pro-D-Ala-D-Ala-NHCH3, monohydrate, (C17H30N4O5.H2O, molecular weight = 404.44) has been determined by single crystal X-ray diffraction. The crystals are monoclinic, space group P2(1), a = 9.2585(4), b = 9.3541(5), c = 12.4529(4)A, beta = 96.449(3) degrees, Z = 2. The peptide units are in the trans and the tBoc-Pro bond in the cis orientation. The first and third peptide units show significant deviations from planarity (delta omega = 5.2 degrees and delta omega = 3.7 degrees, respectively). The backbone torsion angles are: phi 1 = -60 degrees, psi 1 = 143.3 degrees, omega 1 = -174.8 degrees, phi 2 = 148.4 degrees, psi 2 = -143.1 degrees, omega 2 = -179.7 degrees, phi 3 = 151.4 degrees, psi 3 = -151.9 degrees, omega 3 = -176.3 degrees. The pyrrolidine ring of the proline residue adopts the C2-C gamma conformation. The molecular packing gives rise to an antiparallel beta-sheet structure formed of dimeric repeating units of the peptide. The surface of the dimeric beta-sheet is hydrophobic. Water molecules are found systematically at the edges of the sheets interacting with the urethane oxygen and terminal amino groups. Surface catalysis of an L-Ala to D-Ala epimerization process by water molecules adsorbed on to an incipient beta-sheet is suggested as a mechanism whereby crystals of the title peptide were obtained from a solution of tBoc-Pro-D-Ala-Ala-NHCH3.

Study on the stereoselectivity of inositol 1,4,5-trisphosphate recognition sites of bovine adrenal cortex

Inositol 1,4,5-trisphosphate (InsP3) is an intracellular messenger generated from the hydrolysis of phosphatidylinositol 4,5-bisphosphate by phospholipase C in response to Ca(2+)-mobilizing stimuli. InsP3 interacts with a specific receptor responsible for the release of sequestered Ca2+ from an intracellular store. The purpose of the present study was to evaluate the relative affinities of the naturally occurring D-isomer of InsP3 and that of its L-stereoisomer for the InsP3 receptor and the InsP3 metabolizing enzymes from bovine adrenal cortex. The InsP3 receptor recognized D- and L-isomers with respective affinities of 4.8 nM and 7.3 microM. This high degree of selectivity was also reflected in the capacity of both isomers to mobilize Ca2+ from the microsomal preparation. The partially purified InsP3 kinase preparation was also able to discriminate between the two stereoisomers. The activity of the kinase was half-maximally inhibited in the presence of 11 microM L-InsP3, a value much higher than the Km of the kinase for D-InsP3 (0.4 microM). Both stereoisomers exhibited equipotent affinities (around 17 microM) for the particulate preparation of InsP3 phosphatase. The enzyme, however, appeared to hydrolyze L-InsP3 at a much slower rate. These results demonstrated that the different recognition sites for InsP3 were expressing distinct levels of stereoselectivity. This property, which is an important aspect of ligand-receptor interaction, could be exploited for the design of new selective drugs interfering with InsP3 action and metabolism.

Modulation of angiotensin II binding affinity by allosteric interaction of polyvinyl sulfate with an intracellular domain of the DuP-753-sensitive angiotensin II receptor of bovine adrenal glomerulosa

Angiotensin II (AII) is an important regulator of aldosterone secretion by adrenal glomerulosa cells. All interacts with a specific receptor coupled to a guanine nucleotide-binding protein that controls the activity of phospholipase C. Recently, novel All nonpeptide antagonists (DuP-753 and PD-123319) have been shown to discriminate between two subclasses of All receptors in many different tissues. Our studies confirmed that 125I-All specifically labeled two classes of binding sites for All in a membrane preparation of bovine adrenal glomerulosa cells. The first class (DuP-753 sensitive) represented approximately 85% of the total binding sites for All and possessed a high affinity (IC50 of 92.9 +/- 19.5 nM) for DuP-753. PD-123319 did not have any effect on 125I-All binding to this site. The second class of binding sites was more sensitive to PD-123319, with an IC50 of 6.9 +/- 3.7 nM, and had a much lower affinity for DuP-753 (IC50 around 10 microM). The two classes of receptors had different affinities for All. All showed an affinity around 2 nM for All type 1 receptor (AT1)(DuP-753 sensitive) and a higher affinity, around 0.3 nM, for All type 2 receptor (AT2) (PD-123319 sensitive). All-induced steroidogenesis was completely abolished in the presence of 3 microM DuP-753, indicating that this activity was mediated through a DuP-753-sensitive receptor. We also found that polyvinyl sulfate (PVS), a polyanion, could partly inhibit the binding of 125I-All to bovine adrenal glomerulosa cell membranes, with half-maximal efficiency at 17.3 +/- 8.2 nM. The inhibitory effect of PVS was selective for AT1. The inhibitory effect of PVS was due to a change in the affinity state of the receptor. Unexpectedly, PVS had no effect on All-induced steroidogenesis or on All binding to intact bovine adrenal glomerulosa cells. However, the inhibitory effect of PVS on All binding was recovered after permeabilization of cells. Direct interaction of polyanions with AT1 was suggested by the capacity of solubilized photoaffinity-labeled 125I-AT1 to adsorb to heparin-agarose gels. The adsorption of 125I-AT1 to heparin-agarose was inhibited by prior incubation of solubilized receptor with heparin or PVS. These results suggest that All-induced steroidogenesis is mediated by a DuP-753-sensitive receptor and that PVS decreases the affinity of this receptor by interacting with an intracellular domain (possibly the positively charged domain responsible for coupling with guanine nucleotide-binding proteins).

Interaction of polyanions with the recognition sites for inositol 1,4,5-trisphosphate in the bovine adrenal cortex

Inositol 1,4,5-trisphosphate (InsP3) serves as a second messenger for Ca2+ mobilization in a wide variety of cells. InsP3 activates a specific receptor/channel located on an internal Ca2+ store. Because heparin has already been shown to block the action of InsP3, we have looked at the influence of other polyanions (dextran sulfate and polyvinyl sulfate) on the action and metabolism of InsP3 in the bovine adrenal cortex. Polyvinyl sulfate blocked InsP3 binding to adrenal cortex microsomes with a half-maximal efficiency of 250 nM. Scatchard analyses revealed that this effect was not competitive. The Ca2+ releasing activity of InsP3 on the same microsomal preparation was monitored with the fluorescent indicator, fura-2. Polyvinyl sulfate blocked this activity with a half-maximal efficiency of 80 nM. The effect of polyvinyl sulfate could not be overcome by supramaximal doses of InsP3, suggesting a non-competitive inhibitory effect. The activity of InsP3 phosphatase from bovine adrenal cortex microsomes was also studied. Polyvinyl sulfate inhibited the activity of the phosphatase with a half-maximal efficiency of 5 microM. Lineweaver-Burk plots revealed that this effect was not competitive. Polyvinyl sulfate was able to inhibit the activity of InsP3 kinase from bovine adrenal cortex cytosol. The half-maximal dose was 15 nM and the Lineweaver-Burk analysis showed that the inhibition was not competitive. The effect of dextran sulfate 5000 (DS-5000) on these activities was also studied. DS-5000 inhibited in a competitive manner the binding of InsP3 to its receptor (IC50 of 34 microM), the release of Ca2+ induced by InsP3 (IC50 of 6.5 microM) and the activity of InsP3 phosphatase (IC50 of 57 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Two Ca2+ transport systems are distinguished on the basis of their Mg2+ dependency in a post-nuclear particulate fraction of bovine adrenal cortex

Inositol 1,4,5-trisphosphate (InsP3) is a second messenger responsible for Ca2+ release from an internal store whose nature and location remains undefined. To get more information on this intracellular Ca2+ store, a post-nuclear particulate fraction was prepared from bovine adrenal cortex and its Ca2+ uptake and release activities were monitored with the fluorescent indicator Fura-2. In the presence of Mg2+ (2 mM), the particulate preparation showed high ATP-dependent Ca2+ sequestering activity and decreased the ambient Ca2+ concentration to about 150 nM. In the absence of Mg2+, Ca2+ was still sequestered but less efficiently, reaching a level around 170 nM. In the presence of Mg2+, the Ca2+ released by a maximal dose of InsP3 (2 microM) was completely resequestered whereas in the absence of Mg2+, no resequestration occurred even after complete degradation of InsP3. The use of selective agents such as oligomycin, saponin, ionomycin and biliary salts indicated that Ca2+ was stored in three different pools which are distinct from the mitochondria and from inside-out membrane vesicles. Our data also indicate that InsP3 releases Ca2+ from a pool which is filled up by a Mg2(+) -dependent Ca2+ ATPase.

Solubilization and partial characterization of inositol 1,4,5-trisphosphate receptor of bovine adrenal cortex reveal similarities with the receptor of rat cerebellum

Inositol 1,4,5-trisphosphate (InsP3) is an intracellular messenger generated upon stimulation of a wide variety of cells by Ca2(+)-mobilizing stimuli. Specific binding sites for InsP3 have been identified in the adrenal cortex and many other tissues. The purpose of the present study was to solubilize and further characterize InsP3 receptors of bovine adrenal cortex. When adrenal cortex microsomes were incubated with Triton X-100 (1%) for 45 min and centrifuged at 100,000 x g for 1 hr, substantial InsP3-binding activity was recovered in the pellet fraction (82 +/- 46 fmol/mg of protein; Kd of 2.7 +/- 1.2 nM), suggesting a possible association with the cell skeleton. Similar results were also obtained with a microsomal preparation of rat cerebellum. On the other hand, the supernatant fraction also displayed important InsP3-binding activity (188 +/- 67 fmol/mg of protein; Kd of 10.4 +/- 2.2 nM). InsP3 binding in both fractions was inhibited by heparin and was increased upon pH elevations from 6 to 9. These are two characteristic properties of InsP3 receptors. Solubilized InsP3 receptors displayed a molecular size around 1,000,000, as estimated by gel filtration through Sepharose-4B column. Radiation inactivation analyses of the receptors of bovine adrenal cortex and rat cerebellum revealed unusual inactivation curves, indicating binding domains of Mr 65,000, much smaller than the smallest covalent structure (subunit) of Mr 260,000 estimated by gel electrophoresis. These results suggest that the binding domain of the receptor behaves independently from the rest of the molecule and that a direct hit on the domain is needed for inactivation. Our data show that the binding sites for InsP3 in the adrenal cortex have properties similar to those of sites recently purified from rat cerebellum, and they suggest that InsP3 receptors from both sources might be the same molecular entity.

Implication of phospholipase C in the steroidogenic action of angiotensin II

Angiotensin II (AII) is a major regulator of aldosterone synthesis and secretion by the adrenal zona glomerulosa. Although it has been suggested by many authors that AII acts by increasing the turnover of inositol-lipids, these studies were mainly focussed on the identity and on the kinetics of appearance of inositol phosphates. The purpose of the present study was to establish a relationship between phospholipase C activation and steroidogenesis in the adrenal cortex. A primary culture of bovine adrenal glomerulosa cells was used. Dose-response curves for receptor occupation, inositol phosphate production and aldosterone secretion were made under the same experimental conditions, on the third day of culture. 125I-[Sar1, Val5, D-Phe8]AII binding to glomerulosa cells was progressively inhibited by increasing concentrations of AII up to 30 nM. Scatchard analyses showed a Kd of 1.9 +/- 1.1 nM and a maximal binding capacity of 49,000 +/- 4,500 receptors/cell (six experiments). Dose-response curves for AII-induced inositol 1,4,5-trisphosphate production showed an EC50 of 0.5 +/- 0.1 nM (five experiments). The threshold dose for AII-induced inositol phosphates was around 0.1 nM and the maximal effect was obtained with 30 nM AII. The AII-stimulated steroidogenesis occurred at a threshold dose around 0.03 nM and the maximal effect was obtained with 10 nM AII with an EC50 of 0.5 +/- 0.1 nM (five experiments). These results support previous suggestions that phospholipase C is involved in the steroidogenic action of angiotensin II.

2,3-Diphosphoglycerate is a nonselective inhibitor of inositol 1,4,5-trisphosphate action and metabolism

Inositol 1,4,5-trisphosphate (InsP3) is an important second messenger generated from the hydrolysis of phosphatidylinositol 4,5-bisphosphate by phospholipase C in response to Ca2(+)-mobilizing stimuli. InsP3 interacts with specific intracellular receptors and triggers the release of sequestered Ca2+ from an intracellular store. We have looked at the influence of 2,3-diphosphoglycerate on the action and metabolism of InsP3 in the bovine adrenal cortex. 2,3-Diphosphoglycerate blocked InsP3 binding to adrenal cortex microsomes with a half-maximal efficiency of 0.5 mM. Scatchard analyses revealed that 2,3-diphosphoglycerate did not change the maximal capacity of the microsomes, but decreased their binding affinity for InsP3. The Ca2(+)-releasing activity of InsP3 on the same microsomal preparation was monitored with the fluorescent indicator, Fura-2. 2,3-Diphosphoglycerate blocked this activity with a half-maximal efficiency of 2 mM. The effect of 2,3-diphosphoglycerate could be overcome by supramaximal doses of InsP3, indicating a competitive inhibitory effect. The activity of InsP3 phosphatase from bovine adrenal cortex microsomes was also studied. 2,3-Diphosphoglycerate inhibited the activity of the phosphatase with a half-maximal efficiency of 0.3 mM. Lineweaver-Burke plots revealed that this effect was competitive. Finally, 2,3-diphosphoglycerate was also able to inhibit the activity of a partially purified preparation of InsP3 kinase from bovine adrenal cortex cytosol. The half-maximal dose was around 10 mM and the Lineweaver-Burke plot showed that the inhibition was competitive. These results show that 2,3-diphosphoglycerate can be considered as a structural analog of InsP3. Its inhibitory effects, however, are not selective enough to use it as an InsP3 protective agent in Ca2(+)-mobilization studies.

[The influence of previous infections on the development of experimental swine pleuropneumonia in specific pathogen free pigs]

This study was designed to determine in six-week old specific pathogen free pigs, the effect of previous experimental exposure to Mycoplasma hyopneumoniae and transmissible gastroenteritis virus on a challenge infection with Actinobacillus pleuropneumoniae. Pigs exposed simultaneously to M. hyopneumoniae and transmissible gastroenteritis virus appeared more resistant to challenge (one week later) with A. pleuropneumoniae. Four pigs out of a group of ten died following the challenge infection, compared to all ten pigs in the control group not submitted to previous infections. Clinical signs and lesions were also less severe in the previously infected group than in the control group. Pigs submitted to a single previous infection with M. hyopneumoniae only appeared to be less resistant to the challenge infection than pigs submitted to the dual previous infection with M. hyopneumoniae and the transmissible gastroenteritis virus. A correlation was found between the resistance of pigs to the challenge infection and their serum gammaglobulin levels.

Enzootic pneumonia in feeder pigs: Association with transmissible gastroenteritis virus infection

Infection with transmissible gastroenteritis virus (TGEV) was present in some pigs on arrival at a feeder pig farm and was well established three weeks later. TGE infection preceded Mycoplasma hyopneumoniae infection, which was not detected until three weeks after arrival. Severe lesions of enzootic pneumonia were observed at the end of the fattening period.A trial was subsequently done in six-week-old-pigs in order to evaluate the potentiating effect of TGEV infection on experimental M. hyopneumoniae infection. The effects of mycoplasmal infection were aggravated when associated with TGEV infection as determined by the extent of pneumonic lesions observed two weeks later.

Differential effects of heparin on inositol 1,4,5-trisphosphate binding, metabolism, and calcium release activity in the bovine adrenal cortex

In a wide variety of cells, inositol-1,4,5-triphosphate is a second messenger that interacts with specific intracellular receptors and triggers the release of sequestered Ca2+ from an intracellular store. We have looked at the influence of heparin on the action and metabolism of inositol-1,4,5-triphosphate in the bovine adrenal cortex. Heparin blocked inositol-1,4,5-trisphosphate binding with half-maximal efficiency around 10 micrograms/ml. Scatchard analyses revealed that heparin did not change the affinity but decreased the number of available binding sites. The Ca2+-releasing activity of inositol-1,4,5-trisphosphate was monitored with the fluorescent indicator, fura-2. Heparin blocked this activity with half-maximal effeciency around 10 micrograms/ml. The effect of heparin could be overcome by a supramaximal dose of inositol-1,4,5-trisphosphate (25 microM). The activity of inositol-1,4,5-trisphosphate-3-kinase from bovine adrenal cortex cytosol was also studied. Heparin inhibited the activity of the kinase with a half-maximal effeciency around 0.4 microgram/ml. Lineweaver-Burk plots revealed that this potent effect was noncompetitive. Finally, we observed that heparin is without effect on inositol-1,4,5-trisphosphate-5-phosphatase (at concentrations as high as 2 mg/ml). These results are consistent with the suggestion that the binding sites for inositol-1,4,5-trisphosphate are the intracellular receptors responsible for the Ca2+-mobilizing effects of inositol-1,4,5-trisphosphate. These results also show that the kinase, the phosphatase, and the receptor are three different molecular entities, which are affected in a different manner by heparin.

Immune response to an Actinobacillus pleuropneumoniae vaccine in swine

Piglets vaccinated with an inactivated tetravalent vaccine (Pleurovac 4) against Actinobacillus pleuropneumoniae serotypes 1, 2, 5 and 7, produced circulating antibodies after a first intramuscular injection and showed an anamnestic reaction after a second. The rise in antibody levels in vaccinated piglets was statistically significant when compared with those of the control group. The administration of 1 or 2 mL of vaccine did not lead to significantly different antibody levels. The specificity of the immune response is demonstrated by an increase in titer to all four serotypes in pigs given the tetravalent vaccine, but an increase in titer to only two serotypes in pigs given a bivalent vaccine (Pleurovac).