Fatal respiratory infection due to ST308 VIM-1-producing Pseudomonas aeruginosa in a lung transplant recipient: case report and review of the literature.

BACKGROUND: Data regarding the prevalence of metallo-ß-lactamases (MBLs) among Pseudomonas aeruginosa isolates in cystic fibrosis patients are scarce. Furthermore, there is limited knowledge on the effect of MBL production on patient outcomes. Here we describe a fatal respiratory infection due to P. aeruginosa producing VIM-type MBLs in a lung transplant recipient and the results of the subsequent epidemiological investigation. CASE PRESENTATION: P. aeruginosa isolates collected in the index patient and among patients temporally or spatially linked with the index patient were analyzed in terms of antibiotic susceptibility profile and MBL production. Whole-genome sequencing and phylogenetic reconstruction were also performed for all P. aeruginosa isolates producing VIM-type MBLs. A VIM-producing P. aeruginosa strain was identified in a lung biopsy of a lung transplant recipient with cystic fibrosis. The strain was VIM-1-producer and belonged to the ST308. Despite aggressive treatment, the transplant patient succumbed to the pulmonary infection due to the ST308 strain. A VIM-producing P. aeruginosa strain was also collected from the respiratory samples of a different cystic fibrosis patient attending the same cystic fibrosis center. This isolate harbored the blaVIM-2 gene and belonged to the clone ST175. This patient did not experience an adverse outcome. CONCLUSIONS: This is the first description of a fatal infection due to P. aeruginosa producing VIM-type MBLs in a lung transplant recipient. The circulation of P. aeruginosa isolates harboring MBLs pose a substantial risk to the cystic fibrosis population due to the limited therapeutic options available and their spreading potential.

Artificial Intelligence for Caries Detection: Value of Data and Information.

If increasing practitioners' diagnostic accuracy, medical artificial intelligence (AI) may lead to better treatment decisions at lower costs, while uncertainty remains around the resulting cost-effectiveness. In the present study, we assessed how enlarging the data set used for training an AI for caries detection on bitewings affects cost-effectiveness and also determined the value of information by reducing the uncertainty around other input parameters (namely, the costs of AI and the population's caries risk profile). We employed a convolutional neural network and trained it on 10%, 25%, 50%, or 100% of a labeled data set containing 29,011 teeth without and 19,760 teeth with caries lesions stemming from bitewing radiographs. We employed an established health economic modeling and analytical framework to quantify cost-effectiveness and value of information. We adopted a mixed public-private payer perspective in German health care; the health outcome was tooth retention years. A Markov model, allowing to follow posterior teeth over the lifetime of an initially 12-y-old individual, and Monte Carlo microsimulations were employed. With an increasing amount of data used to train the AI sensitivity and specificity increased nonlinearly, increasing the data set from 10% to 25% had the largest impact on accuracy and, consequently, cost-effectiveness. In the base-case scenario, AI was more effective (tooth retention for a mean [2.5%-97.5%] 62.8 [59.2-65.5] y) and less costly (378 [284-499] euros) than dentists without AI (60.4 [55.8-64.4] y; 419 [270-593] euros), with considerable uncertainty. The economic value of reducing the uncertainty around AI's accuracy or costs was limited, while information on the population's risk profile was more relevant. When developing dental AI, informed choices about the data set size may be recommended, and research toward individualized application of AI for caries detection seems warranted to optimize cost-effectiveness.

Nerve gaps repaired with acellular nerve allografts recellularized with Schwann-like cells: Preclinical trial.

BACKGROUND: Acellular nerve allografts (ANA) recellularized with mesenchymal stem cells (MSC) or Schwann cells (SC) are, at present, a therapeutic option for peripheral nerve injuries (PNI). This study aimed to evaluate the regenerative and functional capacity of a recellularized allograft (RA) compared with autograft nerve reconstruction in PNI. METHODS: Fourteen ovines were randomly included in two groups (n=7). A peroneal nerve gap 30 mm in length was excised, and nerve repair was performed by the transplantation of either an autograft or a recellularized allograft with SC-like cells. Evaluations included a histomorphological analysis of the ANA, MSC pre differentiated into SC-like cells, at one year follow-up functional limb recovery (support and gait), and nerve regeneration using neurophysiological tests and histomorphometric analysis. All evaluations were compared with the contralateral hindlimb as the control. RESULTS: The nerve allograft was successfully decellularized and more than 70% of MSC were pre differentiated into SC-like cells. Functional assessment in both treated groups improved similarly over time (p <0.05). Neurophysiological results (latency, amplitude, and conduction velocity) also improved in both treated groups at twelve months. Histological results demonstrated a less organized arrangement of nerve fibers (p <0.05) with an active remyelination process (p <0.05) in both treated groups compared with controls at twelve months. CONCLUSIONS: ANA recellularized with SC-like cells proved to be a successful treatment for nerve gaps. Motor recovery and nerve regeneration were satisfactorily achieved in both graft groups compared with their contralateral nontreated nerves. This approach could be useful for the clinical therapy of PNI.

[Relationship between technical difficulty to cannulate papila of Vater and fluoroscopy time]. / Relación entre grado de dificultad para canular papila de Vater, realización del procedimiento y tiempo de fluoroscopia.

BACKGROUND: Exposure to radiation during endoscopic retrograde cholangiopancreatography (ERCP) could have adverse effects on the endoscopic team members and patients. There is an inverse relationship between fluoroscopy time and endoscopist experience. OBJECTIVE: To determine the relationship between the technical difficulty to cannulate Vater's papilla, and time to perform the procedure and fluoroscopy time. METHODS: Patients scheduled for ERCP were divided in two groups depending on the degree of difficulty of the process according to Schutz classification: group A (grades 1-3) and group B (grades 4 and 5). We registered demographic variables, reference diagnosis, endoscopic and radiological diagnoses, degree of difficulty to cannulate Vater's papilla (Freeman scale), duration of procedure, fluoroscopy time and endoscopic complications. RESULTS: 213 patients were included: 101 in group A and 112 in group B. Mean fluoroscopy time was 59.15 seconds in group A and 93.59 seconds in group B (p <0.0001). Mean time to perform the procedure was 13.18 minutes in group A and 20.23 minutes in group B (p <0.0001). Factors related to increased fluoroscopy time were technical difficulty for the CPE according to Schutz (p <0.0001), stent placement (p = 0.021) and hydrostatic dilation (p <0.0001). CONCLUSIONS: The fluoroscopy time increased proportionally to technical difficulty to perform the procedure.

[Epidemiology of bilio-pancreatic cancer in Specialty Hospital UMAE N°71 IMSS in Torreón, Coahuil]. / Epidemiología de neoplasias bilio-pancreáticas en el Hospital de Especialidades UMAE No. 71, IMSS. Torreón, Coahuila.

BACKGROUND: There is a worldwide increase in the incidence of cancer of the biliopancreatic ducts; early diagnosis is difficult and prognosis is poor. OBJECTIVE: To analyze the frequency of malignant biliary strictures diagnosed by Endoscopio Retrograde Cholangiopancreatography (ERCP) at the "Hospital de Especialidades No. 71 UMAE IMSS", Torreon, Coahuila, Mexico. METHODS: A 5-year retrospective study of consecutive patients referred for ERCP at our institution was performed. Medical records from patients with malignant neoplasms were reviewed. Demographic variables, post-ERCP and final diagnosis, based on cytological and endoscopic or surgical biopsies, imaging studies and clinical outcome were registered. RESULTS: The frequency of biliary-pancreatic neoplasm was 15.6% (301 cases in 1924 ERCP) determined by bile duct cancer (40.7%), pancreas (27.9%) and Vater´s ampulla (12.3%). Brushing was performed for histopathological analysis in 86.7% of cases. The cytology was positive in 91.2%, negative 8.8%, and it was no possible in 13.3% of cases. Therapeutic endoscopy was performed in 273 patients with complications in 1.3% and no procedure-related mortality. Patients with malignant strictures had a higher risk for unsuccessful ERCP (RR 3.01, 95% CI 1.77 - 5.11) and carrying out pre-cut sphincterotomy (RR 1.80, 95% CI 1.38 - 2.35). CONCLUSION: In our center the incidence of biliary-pancreatic neoplasm was 15.6% among patients sent to ERCP and its presence increases the degree of difficulty in performing diagnostic and therapeutic endoscopic procedures.

[Effect of different doses of fentanyl and butylhyoscine on the rabbit's sphincter of Oddi]. / Efecto del fentanilo a diferentes dosis y de la butilhioscina en el esfínter de Oddi del conejo.

BACKGROUND: It was not until the advent of endoscopic retrograde cholangiopancreatography (ERCP) that Oddi's sphincter manometry was performed directly. Use of opioids for the intravenous (IV) sedation of these patients is controversial. OBJECTIVE: To evaluate with manometry the effect of fentanyl at different doses as well as the effect of butylhyoscine on the rabbit's Oddi's sphincter. METHODS: This is an experimental, randomized, double-blind study conducted in New Zealand rabbits distributed in 4 groups (control, fentanyl at doses of 1, 5 and 10 µg/kg of weight) that, after laparotomy and duodenotomy, underwent direct Oddi's sphincter manometry. The analyzed variables included sphincter pressure, wave frequency, amplitude and duration. RESULTS: The baseline measurements of the study variables did not show any differences among the groups. The administration of fentanyl at 1 µg/kg reduced Oddi's sphincter pressure compared with the baseline value (p = 0.003), while the doses of 5 and 10 µg/kg significantly increased it (p <0.0001). Butylhyoscine decreased the sphincter pressure, frequency, amplitude and duration of the waves in all the groups and antagonized the increase in pressure produced by fentanyl. CONCLUSIONS: Fentanyl at 1 µg/kg of body weight relaxes the rabbit's Oddi's sphincter and butylhyoscine can antagonize the increased pressure of the sphincter caused by fentanyl at 5 and 10 µg/kg of weight. These finding suggest a potential beneficial for the ERCP in clinical controlled trials in humans.

Cost-effectiveness of Artificial Intelligence for Proximal Caries Detection.

Artificial intelligence (AI) can assist dentists in image assessment, for example, caries detection. The wider health and cost impact of employing AI for dental diagnostics has not yet been evaluated. We compared the cost-effectiveness of proximal caries detection on bitewing radiographs with versus without AI. U-Net, a fully convolutional neural network, had been trained, validated, and tested on 3,293, 252, and 141 bitewing radiographs, respectively, on which 4 experienced dentists had marked carious lesions (reference test). Lesions were stratified for initial lesions (E1/E2/D1, presumed noncavitated, receiving caries infiltration if detected) and advanced lesions (D2/D3, presumed cavitated, receiving restorative care if detected). A Markov model was used to simulate the consequences of true- and false-positive and true- and false-negative detections, as well as the subsequent decisions over the lifetime of patients. A German mixed-payers perspective was adopted. Our health outcome was tooth retention years. Costs were measured in 2020 euro. Monte-Carlo microsimulations and univariate and probabilistic sensitivity analyses were conducted. The incremental cost-effectiveness ratio (ICER) and the cost-effectiveness acceptability at different willingness-to-pay thresholds were quantified. AI showed an accuracy of 0.80; dentists' mean accuracy was significantly lower at 0.71 (minimum-maximum: 0.61-0.78, P < 0.05). AI was significantly more sensitive than dentists (0.75 vs. 0.36 [0.19-0.65]; P = 0.006), while its specificity was not significantly lower (0.83 vs. 0.91 [0.69-0.98]; P > 0.05). In the base-case scenario, AI was more effective (tooth retention for a mean 64 [2.5%-97.5%: 61-65] y) and less costly (298 [244-367] euro) than assessment without AI (62 [59-64] y; 322 [257-394] euro). The ICER was -13.9 euro/y (i.e., AI saved money at higher effectiveness). In the majority (>77%) of all cases, AI was less costly and more effective. Applying AI for caries detection is likely to be cost-effective, mainly as fewer lesions remain undetected. Notably, this cost-effectiveness requires dentists to manage detected early lesions nonrestoratively.

How appropriate is the use of rehabilitation facilities? Assessment by an evaluation tool based on the AEP protocol.

BACKGROUND: During the last few decades, an increasing attention has been drawn to public health expenditure and resource use. The increasing aging population has highlighted the need to deliver post-acute care and to assess its appropriateness. The "PRUO rehab" (Protocollo di Revisione dell'Utilizzo dell'Ospedale riabilitativo) protocol was realized and validated to assess the appropriateness of use of rehabilitation units. The aims of this study were to test the validity of the PRUO-rehab tool and to analyse the causes for Inappropriate Hospital Stay (IPS) in rehabilitation units. METHODS: The PRUO rehab tool was retrospectively applied to the medical records of 502 patients who stayed at least overnight in one of ten different rehabilitation units set in Northern Italy, during 2007. RESULTS: The tool was valid and the inappropriate patient stay (IPS) score was 25.0%. CONCLUSION: Although reasonably low, the IPS indicates that the rehabilitation structures analysed could be used more efficiently.

[Does the use of fentanyl make Vater's ampulla cannulation difficult? A prospective and comparative study]. / ¿Dificulta la canulación del ámpula de Vater el uso de fentanilo? Un estudio prospectivo y comparativo.

BACKGROUND: Fentanyl is a synthetic opioid with excellent results in perioperative analgesia. It is commonly used for proximal and distal gastrointestinal endoscopic procedures, but its contracting action on the sphincter of Oddi, similar to that of morphine, makes its use for endoscopic cholangiopancreatography (ERCP) controversial. OBJECTIVE: To determinate if intravenous fentanyl as part of deep sedation hinders the cannulation of Vater's papilla during ERCP. MATERIAL AND METHODS: Prospective, comparative, randomized and double-blind trial that enrolled patients undergoing ERCP in 2008, > 18 years old, without previous endoscopic or surgical procedures related with Vater s papilla. Patients were randomized into two groups: patients in whom ERCP was performed with intravenous propofol (group A), and patients in whom the procedure was performed with intravenous fentanyl and propofol (group B). Gender, age, comorbid conditions, reasons for referral, difficulty of cannulation, diagnosis, therapeutic procedures, procedure time and endoscopic complications were all documented. RESULTS: 432 were included: 214 in group A and 218 in group B. Both groups were similar in relation with demographic characteristics, time of sedation and endoscopic procedure. Difficulty in cannulation had not a statistical significance (p = 0.163). The administered dose of propofol were less for group B (p < 0.001). No procedure-related mortality was documented. CONCLUSION: The combination of fentanyl and propofol may be used during ERCP, since it does not hinder the cannulation of Vater's papilla.

[Foreign body reaction to biodegradable esophageal prosthesis. A case report]. / Reacción a cuerpo extraño de una prótesis esofágica biodegradable. Informe de un caso.

Although benign esophageal stricture induced by various factors can often be managed with dilatations using hydrostatic balloons or different dilators, some patients have esophageal stenosis that is refractory to such treatment. Endoprothesis have facilitated the palliation of malignant esophageal strictures. However, the indications for permanent esophageal stenting in patients with benign esophageal strictures have not been established. Everyday, the use of plastic self-expanding endoprosthesis is more common in esophageal strictures because of their advantages over metallic stents, ease of placement and retrieval, and limited local tissue reaction. More recently, biodegradable stents have been used to manage benign esophageal stenosis. We report a case of a 72 years woman who was attended because of the presence of esophageal stenosis secondary to caustic ingestion refractory to dilatation, was placed a biodegradable stent and developed a foreign body reaction.

[Endoscopic cholangiopancreatography in the elderly: a prospective comparative study in northern Mexico]. / Colangiopancreatografía endoscópica en la tercera edad; un estudio prospectivo y comparativo en el norte de México.

BACKGROUND: Endoscopic retrograde cholangiopancreatography (ERCP) is a widely used technique for the diagnosis and treatment of bilio-pancreatic diseases. According to Mexican Statistics, there is increasing life expectancy in Mexican population. The incidence of biliary tract pathologies is also increasing, leading to an increased demand of ERCP. AIM: Compare the utility and safety of ERCP in elderly and younger patients. METHODS: Prospective and comparative study including 450 patients who underwent ERCP during 2007. Patients were divided into two groups: 65 years age and older (group A) and less than 65 years old (group B). We registered gender, age, indication and length of the endoscopic procedure, morbidity and mortality. RESULTS: Mean patient age was 74.5 ± 6.9 and 43.0 ± 13.5 years old in groups A and B respectively. Choledocholithiasis was the more frequent diagnosis in both groups (48.62 %), followed by benign biliary stenosis (22.02 %) and malignant biliary obstruction (16.28 %). In 428 patients (98.16%) therapeutic procedures were performed. Endoscopic complications occurred in 1.37 % and there were not significant differences between groups (p = 0.218). There was no mortality. CONCLUSION: ERCP is a safe procedure in elderly patients with a very low rate of complications and excellent therapeutic efficacy.

[Difficulty to cannulate papilla of Vater in the presence of periampullary duodenal diverticulum]. / Grado de dificultad para canular papila de Vater en presencia de divertículo duodenal periampular.

BACKGROUND: There are conflicting results in the literature regarding the impact of duodenal diverticula on the technical success and complications of endoscopic retrograde cholangiopancreatography (ERCP). AIM: To evaluate if the presence of periampullary duodenal diverticulum increases the risk of failure of ampulla cannulation. METHODS: Patients who underwent ERCP between January 2008 and December 2009 were evaluated. They were divided in group A (without duodenal diverticulum) or group B (with duodenal diverticulum). Gender, age, endoscopic and radiological diagnosis, difficulty to cannulate, endoscopic sphincterotomy, precut technique, therapeutic procedure and complications were documented. RESULTS: 1159 patients were included: 1100 in group A and 59 in group B. A successful cannulation was obtained in 1061 patients of group A and 53 of group B (96.46 vs. 89.83%, p < 0.0001, OR 0.03). The failure of cannulation was observed in 39 patients of group A and 6 of group B (3.54 vs. 10.17%, p= 0.021, OR 2.94). The presence of intradiverticular papilla was the cause of failure in all cases. The therapeutic procedures showed statistical differences in choledocholithiasis clearance as well as endoscopic sphincterotomy and biliary stents insertion, but there was no significant difference in complications. We found statistical significant differences in biliary lithiasis, malignant stenosis, mechanical lithotripsy and insertion of biliary stents. CONCLUSIONS: Periampullary duodenal diverticula increase the risk of failure for cannulation of ampulla. However, it should not be considered as contraindication for ERCP.

Characteristics of 1573 healthcare workers who underwent nasopharyngeal swab testing for SARS-CoV-2 in Milan, Lombardy, Italy.

OBJECTIVES: The management of healthcare workers (HCWs) exposed to confirmed cases of coronavirus disease 2019 (COVID-19) is still a matter of debate. We aimed to assess in this group the attack rate of asymptomatic carriers and the symptoms most frequently associated with infection. METHODS: Occupational and clinical characteristics of HCWs who underwent nasopharyngeal swab testing for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a university hospital from 24 February 2020 to 31 March 2020 were collected. For those who tested positive and for those who tested positive but who were asymptomatic, we checked the laboratory and clinical data as of 22 May to calculate the time necessary for HCWs to then test negative and to verify whether symptoms developed thereafter. Frequencies of positive tests were compared according to selected variables using multivariable logistic regression models. RESULTS: There were 139 positive tests (8.8%) among 1573 HCWs (95% confidence interval, 7.5-10.3), with a marked difference between symptomatic (122/503, 24.2%) and asymptomatic (17/1070, 1.6%) workers (p < 0.001). Physicians were the group with the highest frequency of positive tests (61/582, 10.5%), whereas clerical workers and technicians had the lowest frequency (5/137, 3.6%). The likelihood of testing positive for COVID-19 increased with the number of reported symptoms; the strongest predictors of test positivity were taste and smell alterations (odds ratio = 76.9) and fever (odds ratio = 9.12). The median time from first positive test to a negative test was 27 days (95% confidence interval, 24-30). CONCLUSIONS: HCWs can be infected with SARS-CoV-2 without displaying any symptoms. Among symptomatic HCWs, the key symptoms to guide diagnosis are taste and smell alterations and fever. A median of almost 4 weeks is necessary before nasopharyngeal swab test results are negative.

[Intravenous sedation in endoscopic cholangiopancreatography: a prospective and comparative trial.]. / Sedación endovenosa en colangiopancreatografía endoscópica; un estudio prospectivo y comparativo.

INTRODUCTION: Endoscopic cholangiopancreatography (ECP) has an established role in the diagnostic and treatment of biliopancreatic diseases. It is performed in supine position, under intravenous sedation to avoid movements and discomfort of the patient. OBJECTIVE: To evaluate the safety of anesthetic procedure in elderly and younger patients who underwent ECP. PATIENTS AND METHODS: A prospective, comparative study enrolling 450 consecutive patients who underwent ERCP in 2007 was performed. The following variables were documented: gender, age, comorbid conditions, reason for referral, diagnostic, therapeutic procedures, American Society of Anesthesiology (ASA) classification, anesthetic drugs, duration of the procedure and complications. RESULTS: Patients were divided into two groups: 126 patients >65 years of age and 324 <65 years of age. Group A had a higher incidence of comorbid conditions (p <0.001). All procedures were performed under sedation with propofol. Anesthetic complications were detected in 6% of patients, without a statistical significance between ASA group (p = 0.7) or age groups (p = 0.1). No procedure-related mortality was documented. CONCLUSION: ECP under deep IV sedation is a safe procedure in elderly patients and has a low anesthetic complication rate.

Efficiency of trapping processes in regular and disordered networks.

We use a Markov method to study the efficiency of trapping processes involving both a random walker and a deep trap in regular and disordered networks. The efficiency is gauged by the mean absorption time (average of the mean number of steps performed by the random walker before being absorbed by the trap). We compute this quantity in terms of different control parameters, namely, the length of the walker jumps, the mobility of the trap, and the degree of spatial disorder of the network. For a proper choice of the system size, we find in all cases a nonmonotonic behavior of the efficiency in terms of the corresponding control parameter. We thus arrive at the conclusion that, despite the decrease of the effective system size underlying the increase of the control parameter, the efficiency is reduced as a result of an increase of the escape probability of the walker once it finds itself in the interaction zone of the trap. This somewhat anti-intuitive effect is very robust in the sense that it is observed regardless of the specific choice of the control parameter. For the case of a ring lattice, results for the mean absorption time in systems of arbitrary size are given in terms of a two-parameter scaling function. For the case of a mobile trap, we deal with both trapping via a single channel (walker-trap overlap) and via two channels (walker-trap overlap and walker-trap crossing), thereby generalizing previous work. As for the disordered case, our analysis concerns small world networks, for which we see several crossovers of the absorption time as a function of the control parameter and the system size. The methodology used may be well suited to exploring characteristic time scales of encounter-controlled phenomena in networks with a few interacting elements and the effect of geometric constraints in nanoscale systems with a very small number of particles.

12-O-tetradecanoylphorbol-13-acetate-dependent induction of xanthine dehydrogenase and conversion to xanthine oxidase in murine epidermis.

Both xanthine dehydrogenase (XD) and xanthine oxidase (XO) catalyze the conversion of hypoxanthine to xanthine, and xanthine to uric acid. Topical application of a promoting dose of 12-O-tetradecanoylphorbol-13-acetate (TPA) to the dorsal skin of female SENCAR mice resulted in a 3.0-3.5-fold elevation of epidermal XO specific activity. Epidermal XO specific activity was maximally elevated 48-96 h after TPA treatment, and required 11 days to return to control levels. Although TPA increased the XO/(XD + XO) ratio from 0.45 to 0.7, the conversion of preexisting XD to XO could not solely account for the TPA-dependent elevation in XO specific activity since control XD plus XO activity was less than just the XO activity in TPA-treated epidermis. Topical application of cycloheximide simultaneously with, or 12 h after, TPA treatment inhibited the TPA-dependent increases in the XO/(XD + XO) ratio and XO specific activities. Collectively, these results suggest that the increased XO activity detected following TPA treatment is the consequence of TPA-induced XD synthesis, and a conversion of existing and newly synthesized XD to XO. In addition, the in vivo promoting activities of analogues of TPA could be correlated with their abilities to elevate XO activity (TPA greater than phorbol-12,13-dibenzoate much greater than 4-O-methyl-TPA = phorbol).

Tumor copromoting activity of gamma-interferon in the murine skin multistage carcinogenesis model.

Recombinant DNA-derived murine gamma-interferon (rMuIFN-gamma) was tested in the murine skin multistage carcinogenesis model as a modulator of 12-O-tetradecanoylphorbol-13-acetate (TPA) promotion. Female SENCAR mice were topically initiated with 7,12-dimethylbenz(a)anthracene and promoted twice weekly with TPA for 20 weeks. Intraperitoneal administration of rMuIFN-gamma 1 day prior to TPA treatment affected neither the kinetics of papilloma development nor the percentage of mice that developed tumors. However, papilloma multiplicities could be either inhibited or increased depending upon the dose of rMuIFN-gamma. Papilloma multiplicities for mice receiving 100, 500, 1000, and 5000 units of rMuIFN-gamma were 184, 122, 105, and 84% of TPA control values, respectively. In contrast, twice weekly i.p. treatments of 7,12-dimethylbenz(a)anthracene initiated mice with only rMuIFN-gamma for 20 weeks did not promote the development of any tumors. Consequently, TPA functioned as a copromoter in those situations in which combined TPA and IFN-gamma treatments elevated papilloma multiplicities. Collectively, the current study demonstrates that rMuIFN-gamma can systemically modulate TPA-dependent promotion in mouse skin.

Redox agents regulate ion channel activity in vacuoles from higher plant cells.

The ability of redox agents to modulate certain characteristics of voltage- and calcium-activated channels has been recently investigated in a variety of animal cells. We report here the first evidence that redox agents regulate the activation of ion channels in the tonoplast of higher plants. Using the patch-clamp technique, we have demonstrated that, in tonoplasts from the leaves of the marine seagrass Posidonia oceanica and the root of the sugar beet, a variety of sulphydryl reducing agents, added at the cytoplasmic side of the vacuole, reversibly favoured the activation of the voltage-dependent slow vacuolar (SV) channel. Antioxidants, like dithiothreitol (DTT) and the reduced form of glutathione, gave a reversible increase of the voltage-activated current and faster kinetics of channel activation. Other reducing agents, such as ascorbic acid, also increased the SV currents, although to a lesser extent in comparison with DTT and glutathione, while the oxidising agent chloramine-T irreversibly abolished the activity of the channel. Single channel experiments demonstrated that DTT reversibly increased the open probability of the channel, leaving the conductance unaltered. The regulation of channel activation by glutathione may correlate ion transport with other crucial mechanisms that in plants control turgor regulation, response to oxidative stresses, detoxification and resistance to heavy metals.

Ion channels in the vacuoles of the seagrass Posidonia oceanica.

Voltage-dependent ionic channels were investigated by the patch-clamp technique in the vacuolar membrane from the leaves of the seagrass Posidonia oceanica. Vacuoles extruded from the meristematic white part of the leaves displayed rectifying slow currents which activated in several seconds at positive potentials and deactivated at negative voltages within a few hundreds of ms. Like the Slow Vacuolar (SV) channel already identified in the tonoplast of terrestrial plants, the SV voltage-dependent channel of Posidonia leaves was activated by micromolar concentrations of Ca2+ and was equally permeable to K+ and Na+. The single-channel conductance of the Posidonia SV-type channel was 106 +/- 12 pS (in symmetric 400 mM K+). In the same ionic solutions, another channel, occasionally observed in vacuoles from the green part of the leaves, displayed a single-channel conductance of 47 +/- 4 pS. To our knowledge, this is the first electrophysiological characterization of ion transport pathways in Posidonia, a marine plant of crucial importance for the ecology of the Mediterranean sea.

Temperature and non-aromatizable androgens: a common pathway in male sex determination in a turtle with temperature-dependent sex determination?

This study addressed the hypothesis that, in the red-eared slider turtle, Trachemys scripta, non-aromatizable androgens are the physiological equivalent of temperature in determining male development. In the first experiment, eggs were treated in the middle of the temperature-sensitive period with 1.0 or 10.0 micrograms androsterone, 5 alpha-dihydrotestosterone, 3 alpha-androstanediol, or 3 beta-androstanediol, while at an all-male, male-biased, or one of two female-biased incubation temperatures. In the second experiment, eggs were treated with the same dosages of dihydrotestosterone at different stages of embryonic development while at a male-biased, threshold, or a female-biased incubation temperature. Results of experiment one indicated that hormone-induced masculinization is specific to non-aromatizable androgens. Results of experiment two indicated that the sensitivity to dihydrotestosterone corresponds to the temperature-sensitive window during development. Further, there is a dose-response relationship but no apparent synergism between exogenous dihydrotestosterone and incubation temperature. When considered with other research, it is suggested that non-aromatizable androgens and their products are involved in the initiation of male sex determination whereas oestrogens and their aromatizable androgen precursors are involved in the initiation of female sex determination.