The Growth arrest specific 1 (Gas1) gene is transcriptionally regulated by NeuroD1 via two distal E-boxes.

Growth arrest specific 1 (GAS1) is a signaling mediator for the development of the central nervous system that works as a co-receptor for sonic hedgehog (SHH) to induce the amplification of neural progenitors during the patterning of the mammalian neural tube and establishing granular cells in the cerebellum. Recently, we confirmed that Gas1 is also expressed by neural progenitors of the developing cortex and the dentate gyrus of the hippocampus. The presence of GAS1 in progenitor stages indicates that one of its principal roles is the maintenance of these cells during neurogenic events. However, the signals responsible for the expression of Gas1 in progenitor cells are unknown, an aspect that is relevant to understand its functions during neurogenesis. Here, we focused on elucidating the mechanisms of the transcriptional regulation of Gas1 and using comparative genomics methods found two highly conserved E-boxes in the Gas1 promoter which mediate its up-regulation by NeuroD1. Additionally, we found that GAS1 and NeuroD1 co-localize in the neocortex, the dentate gyrus of the hippocampus and the external granular layer of the cerebellum, suggesting a previously unsuspected regulatory relationship. Our data indicate that Gas1 is a direct target of NeuroD1 during the induction of the neurogenic program.

Identifying barriers to the use of ultrasound in the perioperative period: a survey of southwestern Ontario anesthesiologists.

BACKGROUND: Ultrasound (US) can be used for many perioperative procedures, but evidence is lacking as to its frequency of use and barrier of application. The objectives of this survey were to determine i) how often US guidance was used perioperatively for vascular access placement, nerve blocks, and heart and lung assessment, and ii) to identify the barriers and the limitations of using US amongst anesthesiologists in southwestern Ontario. METHODS: We conducted a web-based survey in over 40 academic or community hospitals at southwestern Ontario. RESULTS: Of 266 surveys sent, 66 complete surveys were obtained (response rate of 25%). Most respondents (> 80%) reported that US was commonly used for central venous catheter (CVC) insertion, followed by regional blocks; the uses were less frequent for neuraxial blockade and cardiopulmonary assessment. Most respondents wanted to use US more frequently as part of their practice and felt that they already had adequate US training. However, most respondents (59%) reported limited access to US machines in their working institutes as being the major barrier to incorporating US in their daily practice. CONCLUSION: The most common uses of US in anesthesia practice in southwestern Ontario were for CVC insertion and regional blocks. Most anesthesiologists in southwestern Ontario are interested to incorporate US in their daily practice but most were limited by the lack of US resources. Apparently, only providing knowledge and skills teaching may not be sufficient to further improve the US utilization in our region; a matched administrative effort appears to be the next challenge.

Comparison of PrestoBlue® and plating method to evaluate antimicrobial activity of ascorbic acid, boric acid and curcumin in an in vitro gastrointestinal model.

AIMS: To compare the conventional plating method vs a fluorometric method using PrestoBlue® as a dye by determining the antimicrobial activity of two organic acids and curcumin (CUR) against Salmonella Enteritidis in an avian in vitro digestion model that simulates the crop, proventriculus and intestine. METHODS AND RESULTS: A concentration of 108  CFU per ml of S. Enteritidis was exposed to groups with different rates of ascorbic acid (AA), boric acid (BA) and CUR. Significant differences were observed when the means of the treatments were compared with the controls in the compartments that simulate the crop and intestine (P < 0·05). Ascorbic acid alone and high rates of AA in the mixtures were the most efficient treatments in the crop compartment. However, in the intestinal compartment BA alone and at different rates in the mixture BA-CUR (1 : 1) were the best treatments to decrease the concentration of S. Enteritidis. CONCLUSIONS: The results of this study suggest that there could be an antagonistic bactericidal effect between AA and CUR and AA and BA as well as a synergistic bactericidal effect between BA and CUR. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings may contribute to the development of a formulation with microencapsulated compounds to liberate them in different compartments to combat S. Enteritidis infections in broiler chickens.

Image-guided percutaneous management of duodenal perforation following endoscopic retrograde cholangiopancreatography (ERCP): assessment of efficacy and safety.

AIM: To evaluate the efficacy and safety of image-guided percutaneous drain placement for duodenal perforation following endoscopic retrograde cholangiopancreatography (ERCP). MATERIALS AND METHODS: A retrospective review of 7,249 ERCP examinations over a 10-year period was performed to identify cases of duodenal perforation. Indications for ERCP were documented, along with the clinical, laboratory, and imaging findings following perforation. Technical and clinical success of percutaneous drain placement was reviewed. RESULTS: Duodenal perforation occurred in 35 of 7,249 patients during the study period. Management included primary surgical debridement (n=2), conservative management consisting of bowel rest, nasogastric/nasojejunal tube placement (n=20), and percutaneous catheter drainage (n=13). Twenty-seven percutaneous drainage catheters were placed in 13 patients, with a mean duration of catheter drainage of 30.9 days (range 4-108 days). Ten patients were successfully treated with percutaneous management alone, and three required subsequent surgical intervention. CONCLUSION: Percutaneous management of duodenal perforation related to ERCP is associated with high technical and clinical success, and may obviate the need for surgical intervention.

Differential expression of the P2X7 receptor in ovarian surface epithelium during the oestrous cycle in the mouse.

Purinergic signalling has been proposed as an intraovarian regulatory mechanism. Of the receptors responsible for purinergic transmission, the P2X7 receptor is an ATP-gated cationic channel that displays a broad spectrum of cellular functions ranging from apoptosis to cell proliferation and tumourigenesis. In the present study, we investigated the functional expression of P2X7 receptors in ovarian surface epithelium (OSE). P2X7 protein was detected in the OSE layer of the mouse, both in situ and in primary cultures. In cultures, 2'(3')-O-(4-Benzoylbenzoyl)adenosine-5'-triphosphate (BzATP) activation of P2X7 receptors increased [Ca(2+)]i and induced apoptosis. The functionality of the P2X7 receptor was investigated in situ by intrabursal injection of BzATP on each day of the oestrous cycle and evaluation of apoptosis 24h using the terminal deoxyribonucleotidyl transferase-mediated dUTP-fluorescein nick end-labelling (TUNEL) assay. Maximum effects of BzATP were observed during pro-oestrus, with the effects being blocked by A438079, a specific P2X7 receptor antagonist. Immunofluorescence staining for P2X7 protein revealed more robust expression during pro-oestrus and in OSE regions behind the antral follicles, strongly supporting the notion that the differences in apoptosis can be explained by increased receptor expression, which is regulated during the oestrous cycle. Finally, P2X7 receptor expression was detected in the OSE layer of human ovaries, with receptor expression maintained in human ovaries diagnosed with cancer, as well as in the human ovarian carcinoma SKOV3 cell line.

An updated protocol to assess arm swimming power in front crawl.

Mechanical power output is a reliable predictor of swim speed in front crawl. However, a complete power curve (power vs. load) has not been described for swimming, and intra-cycle power has not been assessed. The purpose of this study was to examine intra-cycle power output at propulsive phases and to determine maximum swimming power, the corresponding load and swimming speed. 18 swimmers (age 22.10±4.31years, height 1.79±0.07 m, arm span 1.85±0.08 m and body mass 76.74±9.00 kg) performed a swim power test. It consisted of 12.5 m all-out swims with only the arms, with a load attached to the swimmer. A linear encoder and a load cell recorded intra-cycle speed and force in each trial. The test was recorded with 2 underwater cameras. Intra-cycle power was obtained for propulsive stroke phases (pull: 60.32±18.87 W; push: 71.21±21.06 W). Peak power was 114.37±33.16 W. Mean maximum swim power was 66.49 W (0.86 W/kg), which was reached at a swimming velocity of 0.75 m/s with a 47.07% of the individual maximal load. Significant positive correlation (r=0.76, p<0.01) between maximum swim power and maximum swim speed was observed. These results suggest that the proposed test may be a training tool that is relatively simple to implement and would provide swimmers and coaches with quick feedback.

The D-repeat polymorphism in the ASPN gene and primary knee osteoarthritis in a Mexican mestizo population: a case-control study.

BACKGROUND: A genetic association between osteoarthritis (OA) and a polymorphism in the aspartic acid (D) repeat of the asporin (ASPN) gene has been reported in Japanese, Han Chinese, Greek and UK Caucasian populations of patients having knee and hip OA. Such an association has not been previously described among the Mexican mestizo population. The aim of this study was to analyze the association of the ASPN gene D-repeat polymorphism in a Mexican mestizo population with primary knee OA as well as in healthy controls. MATERIALS AND METHODS: A case-control study was conducted on a Mexican mestizo population of northern Mexico. The repeat polymorphism was genotyped in 440 subjects (218 cases and 222 healthy controls). Primary knee OA was diagnosed according to American College of Rheumatology and Kellgren-Lawrence criteria, and allelic association was examined adjusting for other risk variables. RESULTS: After adjusting for some covariates, menopause and the D16 allele showed a trend toward being risk factors for knee OA in a Mexican mestizo population. Also, the D12 allele could be considered as a protective factor. CONCLUSIONS: These findings suggest that polymorphisms within the ASPN gene could influence knee OA susceptibility, but these associations must be confirmed by independent studies in larger samples and different ethnic groups to support the role of the D-repeat polymorphism in the ASPN gene as risk or protection factors for knee OA in a Mexican population.

Image-guided Ablative Procedures.

Various image-guided ablative procedures include chemical and thermal ablation techniques and irreversible electroporation. These have been used for curative intent for small tumours and palliative intent for debulking, immunogenicity and pain control. Understanding these techniques is critical to avoiding complications and achieving superior clinical outcomes. Additionally, combination with immunotherapy and chemotherapies is rapidly evolving. There are numerous opportunities in interventional radiology to advance ablation techniques and seamlessly integrate into current treatment regimens for both benign and malignant tumours.

Clinical and thyroid profile in patients with COVID-19 hospitalized in an intensive care unit.

OBJECTIVE: This study aimed to summarize the epidemiological and clinical features of thyroid function in COVID-19 patients in the intensive care unit (ICU) of Civil Fray Antonio Alcalde Hospital in Mexico. PATIENTS AND METHODS: This is a cross-sectional study that included 63 ICU patients with COVID-19 from August 2021 to December 2021. Thyroid function was evaluated through the TSH, T4, T3, and FT3 measures. Comorbidities such as diabetes mellitus type 2 (T2DM), arterial hypertension (HT), body mass index (BMI), and biochemical biomarkers, including procalcitonin (PCT) and C reactive protein (CRP), were also analyzed. RESULTS: A total of 63 patients with COVID-19 were hospitalized in the ICU; 42 (67%) were male, and 21 (33%) were female, with a mean age of 47 (range of 26-76 years). A total of 49 (78%) patients were non-vaccinated, 5 (8%) had an incomplete vaccination schedule, and 4 (6%) had completed the vaccination schedule. Regarding BMI, 10 (16%) were overweight, and 26 (40%) reported obesity. When assessing thyroid function, 8 (13%) patients were euthyroid, and 55 (87%) showed alterations on the thyroid hormonal axis, mainly a low concentration of TSH (0.56±0.79; p=0.0001) and FT3 (2.34±0.52; p=0.0006). In addition, increased PCT concentrations were associated with a higher risk to decease (1.22 vs. 8.21; p=0.0001) in this group of patients. CONCLUSIONS: Based on our findings, it appears that COVID-19 patients with low TSH and FT3 levels, who have not been vaccinated against SARS-CoV-2, are overweight or obese, and exhibit high levels of PCT are more likely to experience a poor prognosis and even mortality.

Progression and variation of competitive 100 and 200m performance at the 2021 European Swimming Championships.

Competitive progressions are necessary to ensure that peak performance occurs when medals are decided. This study aimed to: i) study the coefficient of variation (CV) and performance changes (%Δ) among swimmers who participated in different rounds (i.e., heats, semi-finals and finals); ii) study the CV changes as a function of FINA-points. A total of 1447 performances were analysed in the 100 and 200 m-races during the Budapest 2021 European-Championships. Linear mixed-effects models were applied for total and split-times to obtain intra-athlete CV and %Δ. The FINA-points were studied with two-way ANOVA and Pearson's correlation assessed the relations with CV. The CV in 100 m-races was: 0.48 ± 0.21% for males and 0.50 ± 0.20% for females (Δ = -0.66%); in 200 m-races: 0.63 ± 0.36% and 0.60 ± 0.34% (Δ = -0.82%). There were differences in FINA-points between strokes and distances (p < 0.02) associated with higher CV for the 200 m-races (r = 0.37; p = 0.003), indicating changes in performance over the rounds. Swimmers' finalists performed easier during the heats by going slower in the first 50 m-lap; however, some of them would have little chance of qualifying during major championships because some events were below FINA-points world-standards.

Effect of fatigue on the intra-cycle acceleration in front crawl swimming: a time-frequency analysis.

The present study analyzes the changes in acceleration produced by swimmers before and after fatiguing effort. The subjects (n = 15) performed a 25-m crawl series at maximum speed without fatigue, and a second series with fatigue. The data were registered with a synchronized system that consisted of a position transducer (1 kHz) and a video photogrametry (50 Hz). The acceleration (ms(-2)) was obtained by the derivative analysis of the variation of the position with time. The amplitude in the time domain was calculated with the root mean square (RMS); while the peak power (PP), the peak power frequency (PPF) and the spectrum area (SA) were calculated in the frequency domain with Fourier analysis. On the one hand, the results of the temporal domain show that the RMS change percentage between series was 67.5% (p < 0.001). On the other hand, PP, PPF, and SA show significant changes (p < 0.001). PP and SA were reduced by 63.1% and 59.5%, respectively. Our results show that the acceleration analysis of the swimmer with Fourier analysis permits a more precise understanding of which propulsive forces contribute to the swimmer performance before and after fatigue appears.

Kca3.1 Activation Via P2y2 Purinergic Receptors Promotes Human Ovarian Cancer Cell (Skov-3) Migration.

Disorders in cell signaling mediated by ATP or histamine, activating specific membrane receptors, have been frequently associated with tumorigenesis. Among the elements of response to purinergic (and histaminergic) signaling, ion channel activation controls essential cellular processes in cancer, such as cell proliferation, motility, and death. Here, we studied the effects that ATP had on electrical properties of human ovarian adenocarcinoma cells named SKOV-3. ATP caused increase in intracellular Ca2+ concentration ([Ca2+]i) and, concurrently, it evoked a complex electrical response with a conspicuous outward component. This current was generated through P2Y2 receptor activation and opening of K+ channels, KCa3.1, as indicated by electrophysiological and pharmacological analysis, as well as by immunodetection and specific silencing of P2Y2 or KCa3.1 gene by esiRNA transfection. Low µM ATP concentration increased SKOV-3 cell migration, which was strongly inhibited by KCa3.1 channel blockers and by esiRNA-generated P2Y2 or KCa3.1 downregulation. Finally, in human ovarian tumors, the P2Y2 and KCa3.1 proteins are expressed and co-localized in neoplastic cells. Thus, stimulation of P2Y2 receptors expressed in SKOV-3 cells promotes motility through KCa3.1 activation. Since P2Y2 and KCa3.1 are co-expressed in primary tumors, our findings suggest that they may play a role in cancer progression.

Interplay between ryanodine and IP3 receptors in ATP-stimulated mouse luteinized-granulosa cells.

In mouse luteinized-granulosa cells (MGLC), ATP induces an increase in intracellular Ca2+ concentration by stimulating phospholipase C (PLC) associated with purinergic receptors, leading to production of inositol 1,4,5-trisphosphate (IP3) and subsequent release of Ca2+ from intracellular stores. In this study, we examined the cross-talk between the ryanodine receptors (RyR) and IP3 receptors (IP3R) in response to ATP in MGLC. Specifically, the effect of RyR modulators on ATP response was examined. The results showed that ATP-induced intracellular calcium elevation was abolished by inhibitors of the RyR, such as dantrolene (25 microM) and ryanodine (80 microM). When the MGLC were stimulated with activators of RyR, 2 microM ryanodine and 10 mM caffeine, the ATP-elicited response was decreased. These actions were independent of IP3 production stimulated by ATP. Hence, ATP-induced intracellular Ca2+ mobilization involves the coordinated action of both types of calcium release channels (CRCs). Using fluorescent probes, it was shown that IP3R is uniformly distributed throughout the cell; in contrast, RyR is mainly found around the nuclei. It is concluded that the IP3R and the RyR are functionally associated, and both play a role in the pattern of Ca2+ increase observed during purinergic stimulation of MGLC. This coupling may provide a highly efficient amplification mechanism for ATP stimulation of Ca2+ mobilization.

Novel Cl- currents elicited by follicle stimulating hormone and acetylcholine in follicle-enclosed Xenopus oocytes.

Voltage-clamp techniques were used to study the membrane currents elicited by follicle stimulating hormone (FSH) and acetylcholine (ACh) in follicle-enclosed oocytes of Xenopus laevis (follicles). Both agonists caused complex responses that were more evident when the follicles were in hypotonic Ringer solution (HR; 190.4 mosM). In this medium, currents activated by FSH regularly showed three phases whereas currents activated by ACh displayed three to six phases. At a holding potential of -60 mV, FSH, and ACh responses involved combinations of inward and outward currents. Both FSH and ACh responses included a slow smooth inward component that was associated with an increase in membrane conductance, mainly to Cl- (S(in)). This current was strongly dependent on the osmolarity of the external solution: an increase in osmolarity of the HR solution of 18-20 mosM caused a 50% decrease in S(in). In contrast, a fast and transient Cl- current (F(in)) specifically elicited by ACh was not dependent on osmolarity. Both, F(in) and S(in) currents required the presence of follicular cells, since defolliculation using three different methods abolished all the response to FSH and at least four components of the ACh responses. The membrane channels carrying F(in) and oscillatory Cl- currents elicited by stimulation of ACh or serum receptors, were much more permeable to I- and Br- than Cl-, whereas S(in) channels were equally permeable to these anions. Unlike the oscillatory Cl- currents generated in the oocyte itself, S(in) and F(in) currents in follicle-enclosed oocytes were not abolished by chelation of intracellular Ca2+, either with EGTA or BAPTA, which suggests that intracellular Ca2+ does not play a critical role in the activation of these currents. Our experiments show that S(in) and F(in) currents are quite distinct from the previously characterized oscillatory Cl- responses of oocytes. Moreover, the results strongly suggest that the FSH and ACh receptors, the Cl- channels mediating the F(in) and S(in) currents, together with the necessary elements for their activation, are all located in the follicular cells and not in the oocyte. Many aspects of follicular cell physiology in Xenopus laevis, and other species, are regulated by hormones and neurotransmitters, including FSH and ACh. The follicular Cl- currents described in this paper may play an important role in the follicular cell-oocyte development.

Role of isoprenylation in intracellular pH regulation of granulocytes.

Lovastatin was used to study the role of isoprenylated GTP-binding proteins in the regulation of intracellular pH in granulocytic HL-60 cells. The cytosolic acidification that accompanies stimulation by chemoattractants was completely eliminated by lovastatin. The subsequent activation of Na+/H+ exchange was partially inhibited by the isoprenylation antagonist. In contrast, the osmotic activation of the Na+/H+ antiport was unaffected. The data indicate that the osmotically- and receptor-induced activation of the antiport utilize divergent signalling pathways. The results also provide evidence supporting the notion that cytosolic acidification by chemoattractants results from accumulation of metabolic acid generated during the respiratory burst.

HDL clearance and receptor-mediated catabolism of LDL are reduced in hypothyroid rats.

Hypercholesterolemia associated with hypothyroidism is due partly to increased plasma LDL and partly to increased HDL cholesterol concentrations. The increase in LDL cholesterol has been shown to be secondary to reduced plasma clearance of LDL. To determine which catabolic route was thyroid dependent, the present study examined the effects of hypothyroidism on the receptor-mediated pathway and the 'receptor-independent' pathway of LDL metabolism. Wistar rats (327 +/- 22 g; mean +/- SD) were made hypothyroid by feeding propylthiouracil (0.1%, w/w) and rat 131I-LDL (rLDL; d = 1.019-1.050) and 125I-methylated-LDL (rLDL-CH3) were simultaneously injected i.v. after which the rates of clearance of labelled LDL in plasma were determined over 0-54 h. Total LDL and 'receptor-independent' clearances were represented by clearance of 131I-rLDL and 125I-rLDL-CH3 respectively and the difference between the two represented high affinity receptor-mediated clearance. The data were analyzed using Matthews' model and the fractional catabolic rates (FCR) were calculated. The FCR of rLDL clearance via the receptor-mediated pathway was 0.1042 +/- 0.0112 pools/h (n = 6) in controls vs. 0.0613 +/- 0.0079 pools/h (n = 6) in hypothyroid animals (P less than 0.01). The FCR via the 'receptor-independent' pathway was 0.0642 +/- 0.0040 pools/h (n = 6) in controls vs. 0.0561 +/- 0.0036 pools/h (n = 6) in hypothyroid animals (not significant). The plasma HDL cholesterol concentration was also increased in hypothyroid rats (70.4 +/- 6.7 mg/dl) compared to control (53.3 +/- 3.1 mg/dl) (P less than 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)

Osmo-dependent Cl- currents activated by cyclic AMP in follicle-enclosed Xenopus oocytes.

The role of adenosine 3',5'-cyclic monophosphate (cAMP) in generating the osmo-dependent slow inward membrane currents (S(in)) elicited by activation of follicle stimulating hormone (FSH) or acetylcholine (ACh) receptors was studied in voltage-clamped, follicle-enclosed oocytes of Xenopus laevis (follicles). Forskolin (FSK) also generated S(in) currents, and in low concentrations it potentiated the S(in) currents elicited by FSH but not those elicited by ACh. Moreover, intra-oocyte injections of cAMP elicited similar slow inward currents (cAMP-S(in)) that: (i) were carried mainly by chloride ions; (ii) were abolished by defolliculating the oocytes; and (iii) were dependent on the osmolarity of the external medium. Compared with the Ca(2+)-dependent chloride channels that are located in the oocyte membrane; the cAMP-activated S(in) channels were less permeable to I- and Br-, and their current-voltage relation did not rectify strongly at negative potentials. Generation of cAMP-S(in) desensitized the FSH-S(in) currents, but did not have effects on both the S(in) and the fast chloride current (F(in)) specifically elicited by ACh. Furthermore, follicular phospholipase C activation through stimulation of angiotensin II (AII) receptors failed to generate the current responses elicited by ACh. We conclude that cAMP acts as a potent second messenger in generating the osmo-dependent Cl- currents elicited by FSH but not those elicited by ACh. The mechanisms underlying the ACh responses remain unknown. The osmo-dependent chloride channels activated by cAMP may play a role in the control of volume of the follicular cells-oocyte complex.

Glucocorticoid prevention of neonatal hypoxic-ischemic damage: role of hyperglycemia and antioxidant enzymes.

Recently, we observed that pre-treatment of neonatal rats with dexamethasone prevents brain damage associated with cerebral hypoxia-ischemia (unilateral carotid occlusion + 3 h hypoxia). Presently, we investigate whether hyperglycemia or an induction of endogenous free radical scavengers explains dexamethasone's neuroprotective effect. Pathological damage was examined in rats maintained hyperglycemic during hypoxia-ischemia by the repeated administration of 10% glucose (10 ml/kg, i.p.) at 0, 1, 2 and 3 h of hypoxia (n = 14) and this damage was compared to that in control (n = 15) or dexamethasone (0.1 mg/kg, i.p., n = 15) treated animals. Despite similar elevations in blood glucose at the end of hypoxia, glucose treated animals had greater damage than dexamethasone treated animals and both of these groups had less damage than controls (volumes of damage of approx. 30.9 +/- 10, 3.4 +/- 2.3 and 60.4 +/- 7.1% of the hemisphere, respectively; P < 0.0001). Anti-oxidant enzyme activities were measured within brains of animals treated with dexamethasone or vehicle (n = 44). Activities of the enzymes catalase, glutathione peroxidase and CuZn- or Mn-superoxide dismutase were similar in both treatment groups, with or without exposure to hypoxia-ischemia. Thus, an induction of antioxidant enzymes does not explain dexamethasone's effects whereas the relative hyperglycemia associated with glucocorticoid treatment may contribute partially. Neither account fully for dexamethasone's protective effect suggesting an additional glucocorticoid mediated mechanism must be involved.

Electrophysiological and hemolytic activity elicited by the venom of the jellyfish Cassiopea xamachana.

In this study, we determined hemolysis activity in human and sheep erythrocytes, and characterized the electrical responses in Xenopus oocyte membrane elicited by the venom of the jellyfish Cassiopea xamachana (Cx). The Cx venom produced hemolysis in both species, being more potent on human red cells. The electrophysiological study showed that the Cx venom elicited three different responses in the oocytes. One current was generated in all the oocytes tested and corresponded with a slow inward current (I(Cx)) associated with an increase in membrane conductance. I(Cx) was concentration-dependent and had a reversal potential of -10.3+/-0.4 mV. Ionic substitution studies indicated that the conductive pathway was mainly permeable to cations and non-selective. The oocyte membrane resistance was completely recovered after washout of the venom, this suggested that the effect was due to generation of a specific membrane conductance as opposed to a possible non-specific membrane breakdown. A comparative study with three distinct native cationic channels present in the oocyte membrane [i.e. (1) hemi-gap-junction channels, (2) mechanosensitive channels, and (3) the ouabain-sensitive channel activated by palytoxin], showed that I(Cx) might correspond to opening of mechanosensitive channels or to activation of an unknown cationic channel located in the oocyte membrane. The bioactive fraction eliciting I(Cx) were peptides and was separated from two other peptidic hemolytic fractions by chromatography.

Renal resistive index in experimental partial and complete ureteral obstruction.

RATIONALE AND OBJECTIVES: Recent clinical work suggests that the Doppler resistive index (RI) may be useful in distinguishing obstructive from nonobstructive hydronephrosis. We evaluated the usefulness of the RI in a rabbit model of hydronephrosis. METHODS: Unilateral partial ureteral obstruction was produced in nine rabbits and complete obstruction in another nine. Three sham operations were performed, and these animals served as control subjects. The RI was measured in all kidneys before and 6 hr after surgery and on days 1, 4, and 7 postoperatively. The RI and the difference in RI (delta RI) between the obstructed and normal kidney were evaluated over time using a two-way analysis of variance. The intravenous urography and Whitaker tests served as gold standards. RESULTS: Hydronephrosis was observed on sonograms in all obstructed kidneys. Comparing groups, there was no significant difference in mean RI or delta RI between the three groups at any time point. Looking at individual groups over time, there was no significant change in mean delta RI, whereas the change in mean RI was significantly elevated above baseline only in the complete obstruction group at 6 hr (p = .002) and on days 4 (p = .008) and 7 (p = .006). In evaluating varying thresholds of RI and delta RI, we could not consistently discriminate between normal and obstructed kidneys. CONCLUSION: Although complete obstruction caused a significant increase in RI, partial obstruction failed to do so. RI and delta RI values proved to be insensitive predictors of obstruction in this rabbit model.