Local negative permittivity and topological phase transition in polar skyrmions.

Topological solitons such as magnetic skyrmions have drawn attention as stable quasi-particle-like objects. The recent discovery of polar vortices and skyrmions in ferroelectric oxide superlattices has opened up new vistas to explore topology, emergent phenomena and approaches for manipulating such features with electric fields. Using macroscopic dielectric measurements, coupled with direct scanning convergent beam electron diffraction imaging on the atomic scale, theoretical phase-field simulations and second-principles calculations, we demonstrate that polar skyrmions in (PbTiO3)n/(SrTiO3)n superlattices are distinguished by a sheath of negative permittivity at the periphery of each skyrmion. This enhances the effective dielectric permittivity compared with the individual SrTiO3 and PbTiO3 layers. Moreover, the response of these topologically protected structures to electric field and temperature shows a reversible phase transition from the skyrmion state to a trivial uniform ferroelectric state, accompanied by large tunability of the dielectric permittivity. Pulsed switching measurements show a time-dependent evolution and recovery of the skyrmion state (and macroscopic dielectric response). The interrelationship between topological and dielectric properties presents an opportunity to simultaneously manipulate both by a single, and easily controlled, stimulus, the applied electric field.

Optimizing the linearity in high-speed photodiodes.

Analog photonic links require high-fidelity, high-speed optical-to-electrical conversion for applications such as radio-over-fiber, synchronization at kilometer-scale facilities, and low-noise electronic signal generation. Photodetector nonlinearity is a particularly vexing problem, causing signal distortion and excess noise, especially in systems utilizing ultrashort optical pulses. Here we show that photodetectors designed for high power handling and high linearity can perform optical-to-electrical conversion of ultrashort optical pulses with unprecedented linearity over a large photocurrent range. We also corroborate and expand upon the physical understanding of how the broadband, complex impedance of the circuit following the photodiode modifies the linearity - in some cases quite significantly. By externally manipulating the circuit impedance, we extend the detector's linear range to higher photocurrents, with over 50 dB rejection of amplitude-to-phase conversion for photocurrents up to 40 mA. This represents a 1000-fold improvement over state-of-the-art photodiodes and significantly extends the attainable microwave power by a factor of four. As such, we eliminate the long-standing requirement in ultrashort pulse detection of precise tuning of the photodiode's operating parameters to coincide with a nonlinearity minimum. These results should also apply more generally to reduce nonlinear distortion in a range of other microwave photonics applications.

Accelerated resolution therapy and a thematic approach to military experiences in US Special Operations Veterans.

Accelerated Resolution Therapy (ART) is an emerging therapeutic intervention that has demonstrated effectiveness in treating post-traumatic stress, anxiety and depression. The ART protocol aligns with first-line trauma-focused psychotherapies and clinical guides in the USA and UK. This review addresses previous ART research that includes members of US Special Operations Forces. Observations from that research has led to a thematic conceptualisation of trauma through ART interventions. These include three clusters of traumatic memories and several themes relevant to individual distress but not necessarily symptoms that meet diagnostic criteria for PTSD. ART represents a movement in treatment away from the symptoms, to the individuals' story. Not only the story of an event, but how that experience becomes incorporated into one's sense of identity. The themes identified (and treated with ART) appear to have broader application to the entirety of one's military experience, not just PTSD. These themes may be helpful in directing treatment and may help to focus on significant aspects of service not traditionally associated with PTSD. Theoretically, some of these areas may have protective implications in suicide.

Why are pediatric urologists unable to predict renal deterioration using urodynamics? A focused narrative review of the shortcomings of the literature.

In this focused narrative review we set out to review the current literature addressing the utilization of UDS in patients with spina bifida (SB). We specifically analyzed 6 urodynamic parameters and their roles as predictors of upper tract deterioration in pediatric SB patients. The material available did not allow a systematic analysis or the usage of metanalysis methodology, due to the predominance of small retrospective cohorts, and high heterogeneity. We identified 10 retrospective chart reviews that met our study criteria. The results of each of these papers, as well as other studies deemed relevant to the discussion, are included in our narrative review of the literature. We summarize the current literature, offer explanations for divergences in opinion, and identify future research directions and emerging solutions with a focus on machine learning.

Back to the future: The Cecil-Culp technique for salvage penile reconstructive procedures.

INTRODUCTION: Re-operative penile reconstruction is challenging and requires tension-free skin closure. The repair popularized by Cecil and Culp in the 1940s, using the scrotum to provide a temporary vascularized bed for complex hypospadias repairs, fell out of favor due to temporal trends towards single-stage repairs and concern for utilizing hair-bearing skin on the penile shaft. OBJECTIVE: It was hypothesized that a modified Cecil-Culp (CC) concept of penile scrotalization, leaving the penis attached to the scrotum for 1 year rather than 6 weeks as originally described, improves outcomes with this reconstruction for ventral skin deficiency or poor vascular support. METHODS: Institutional Review Board-approved registries were reviewed to identify patients who underwent a CC repair during 1987-2016 at two institutions. Cecil-Culp technique was utilized in multi-stage hypospadias complication repairs or for insufficient ventral penile shaft skin coverage. Anatomic abnormality, number and type of prior surgeries, and complications before and after CC were recorded. RESULTS: Thirty-nine patients underwent CC: 23 failed hypospadias repairs, three hypospadias after bladder exstrophy, 10 penile curvature following circumcision, and three with skin loss from trauma. Mean age at CC was 61.8 months (hypospadias), and 59.8 months (non-hypospadias). Hypospadias patients underwent a mean of 3.6 surgeries (range 1-9) prior to CC. Four of the 39 patients (10.3%) had perioperative complications after CC, including scrotal abscess, skin infections, and difficulty removing the urethral stent. Eight of 37 (21.6%) patients had longer-term complications related to their hypospadias repair, including fistulae, diverticula, dehiscence, and stricture. Mean time from CC placement to release was 345 and 473 days for hypospadias and non-hypospadias cases, respectively. There was no apparent scrotal skin transferred to the penile shaft at the final take-down. Mean follow-up was 22.3 months. DISCUSSION: Embedding the penis into the scrotum for added vascularity and ventral skin coverage has been used effectively in cases of the most tenacious fistulas and for significant skin loss and trauma. Limitations of this study were its retrospective approach at two institutions over an extended period of time by multiple surgeons, so patient selection and procedure may have varied. CONCLUSIONS: Modification of CC repair by delaying 9-12 months before CC take-down enhanced the benefits of a robust vascular bed for wound healing, and helped to avoid transfer of hair-bearing scrotal skin to the penile shaft. The CC technique is an important tool for penile reconstructive surgery of complex hypospadias repairs with inadequate skin, and for traumatic injuries.

Outcomes of externalized pyeloureteral versus internal ureteral stent in pediatric robotic-assisted laparoscopic pyeloplasty.

INTRODUCTION: After pyeloplasty, urinary drainage options include internal double-J (DJ) ureteral stents or externalized pyeloureteral (EPU) stents, which can avoid bladder symptoms and additional anesthetic exposure from stent removal. Comparative outcome studies, however, are lacking following primary pediatric robotic-assisted laparoscopic pyeloplasty (RALP). OBJECTIVE: To compare operative success, operative time, hospitalization, and postoperative complications of EPU versus DJ stents following RALP. STUDY DESIGN: Consecutive children undergoing primary RALP from 10/2013 to 9/2015 were retrospectively identified. Data collected included patient demographics, stent type and duration, postoperative complications, and operative success. To control for confounding by indication for EPU stent, propensity score weighting was used to balance baseline covariates. Weighted regression analyses compared between-group differences in study outcomes. RESULTS: At median follow-up of 12.3 months, 44 and 17 patients underwent DJ and EPU stenting, respectively. At baseline, DJ stent patients were older than EPU stent patients (median 7.7 vs 1.2 years, P = 0.01) and were less likely to be on postoperative antibiotic prophylaxis (25 vs 76%, P < 0.001). After weighting, these differences disappeared. All EPU stents were removed in the outpatient clinic; all DJ stents were removed under anesthesia. On weighted regression analyses (Summary Fig.), EPU stents had no different associations than DJ stents with operative success (95 vs 94%, between-group difference 1%, 95% CI -11, 13; P = 0.86), complications, or operative time, but did have 0.6 of a day more hospitalization (95% CI 0.04, 1.2; P = 0.04). DISCUSSION: Patients receiving EPU stents were different at baseline from those receiving DJ stents. After propensity score weighting balanced these covariates, EPU stents were associated with similar operative success, complications, and operative time to DJ stents. Further study is warranted in larger prospective cohorts. CONCLUSION: Use of EPU stents provided a viable alternative, particularly in younger patients, to DJ stenting with comparable success and complications, while avoiding the need for an additional anesthetic.

Disruption of the cathepsin K gene reduces atherosclerosis progression and induces plaque fibrosis but accelerates macrophage foam cell formation.

BACKGROUND: Cathepsin K (catK), a lysosomal cysteine protease, was identified in a gene-profiling experiment that compared human early plaques, advanced stable plaques, and advanced atherosclerotic plaques containing a thrombus, where it was highly upregulated in advanced stable plaques. METHODS AND RESULTS: To assess the function of catK in atherosclerosis, catK(-/-)/apolipoprotein (apo) E(-/-) mice were generated. At 26 weeks of age, plaque area in the catK(-/-)/apoE(-/-) mice was reduced (41.8%) owing to a decrease in the number of advanced lesions as well as a decrease in individual advanced plaque area. This suggests an important role for catK in atherosclerosis progression. Advanced plaques of catK(-/-)/apoE(-/-) mice showed an increase in collagen content. Medial elastin fibers were less prone to rupture than those of apoE(-/-) mice. Although the relative macrophage content did not differ, individual macrophage size increased. In vitro studies of bone marrow derived-macrophages confirmed this observation. Scavenger receptor-mediated uptake (particularly by CD36) of modified LDL increased in the absence of catK, resulting in an increased macrophage size because of increased cellular storage of cholesterol esters, thereby enlarging the lysosomes. CONCLUSIONS: A deficiency of catK reduces plaque progression and induces plaque fibrosis but aggravates macrophage foam cell formation in atherosclerosis.

Rapid structural mapping of ternary metallic alloy systems using the combinatorial approach and cluster analysis.

We are developing a procedure for the quick identification of structural phases in thin film composition spread experiments which map large fractions of compositional phase diagrams of ternary metallic alloy systems. An in-house scanning x-ray microdiffractometer is used to obtain x-ray spectra from 273 different compositions on a single composition spread library. A cluster analysis software is then used to sort the spectra into groups in order to rapidly discover the distribution of phases on the ternary diagram. The most representative pattern of each group is then compared to a database of known structures to identify known phases. Using this method, the arduous analysis and classification of hundreds of spectra is reduced to a much shorter analysis of only a few spectra.

Effects of exogenous phytase supplementation on phosphorus metabolism and digestibility of beef cattle.

Objectives were to determine interactions between phytase inclusion and dietary P concentration on P utilization by beef cattle fed a starch-based diet. Six ruminally-fistulated steers (BW = 750 ± 61 kg) were allotted to a 6 × 6 Latin square design with a 3 × 2 factorial arrangement of treatments. Factors included phytase inclusion, at 0, 500, or 2,000 phytase units (FTU)/kg of diet DM, and dietary P concentrations, at 0.10% and 0.30% of total diet DM. Feed ingredients, fecal samples, and orts were composited within period, lyophilized and ground. Samples were analyzed for NDF, ADF, CP, fat, ash, total P, and other minerals. Data were analyzed using the MIXED procedure of SAS with animal as the experimental unit. The CORR procedure was used to compare blood and urinary P concentrations. There were no treatment interactions (P ≥ 0.30) for any parameter measured. There were no main effects (P ≥ 0.45) of phytase inclusion on DMI, total fecal output, apparent DM digestibility, water intake, or urinary output. Steers fed 0.10% P had decreased (P < 0.01) DMI and total fecal output, but increased (P < 0.01) apparent DM digestibility compared with steers fed 0.30% P. Although N intake and retention were not affected by treatment, steers fed the 0.10% P diet tended (P = 0.10) to absorb more N compared with steers fed 0.30% P; and, steers fed the 0.10% P diets excreted more N in the urine (P = 0.02) and less N in the feces (P < 0.01) compared with steers fed the 0.30% P diets. Steers fed the 0.10% P diets also consumed 70.1% less (P < 0.01) total P each day, and excreted 51.9% less (P < 0.01) P in feces and 94.6% less P in the urine (P < 0.01) compared with steers fed 0.30% P. Excretion of water-soluble P in the feces was greater (P < 0.01) on a g/d basis for steers fed 0.30% P when compared with steers fed 0.10% P. However, the proportion of total fecal P excreted as water-soluble P increased (P < 0.05) by 23.0% in steers fed 0.10% P compared with steers fed 0.30% P, regardless of phytase inclusion level. There was no effect of dietary phytase concentration on blood or urinary (P ≥ 0.27) P concentrations. Blood P concentration was positively correlated (r = 0.60; P < 0.01) to urinary P concentration when steers were fed 0.10% P; however, when steers were fed 0.30% P, there was no correlation (r = 0.36; P = 0.16) between blood and urine P. Regardless of dietary P concentration, phytase supplementation did not increase calculated P absorption or retention.

Genitourinary involvement and management in children with Stevens-Johnson syndrome and toxic epidermal necrolysis.

BACKGROUND: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are devastating hypersensitivity disorders that cause epidermal cell death and can affect all epidermal surfaces, including the urethra, vagina, labial and scrotal skin. Despite the well-described ocular and orofacial manifestations of SJS/TEN, there is a paucity of reports on the genitourinary (GU) symptoms and their management. Specifically, consulting services often ask the pediatric urology team if it is safe to place a urethral catheter, but there is no data in the literature to help guide management. The present study sought to review all pediatric cases of SJS/TEN in a tertiary care hospital to determine the incidence and optimal management of GU manifestations, including the use of urethral catheters. METHODS: With IRB approval, cases of SJS and TEN that were managed as an inpatient between January 2008 and June 2015 were retrospectively reviewed in order to identify the extent of GU involvement/manifestations, the treatment provided, use of urethral catheterization and long-term follow-up or complications. RESULTS: Thirty-one patients (15 female, 16 male; age range 2-18 years) presented with SJS or TEN over the study period. Etiologies for SJS/TEN included mycoplasma infection (48%) and medications (45%). Incidences of GU manifestations at presentation and their management are shown in Summary Table. Overall, 74% of patients had genital involvement of skin lesions. In 12 cases (39%), urology consultation was obtained. Twenty patients (61%) complained of dysuria and one child had gross hematuria in the setting of meatal lesion. Petroleum jelly was used in the majority of patients. A urethral catheter was placed in eight patients (25.8%, four female, four male) with a range of duration of 7-23 days. No patient developed hematuria or any other complications (i.e. strictures or urinary symptoms) after catheter removal. One boy required lysis of penile adhesions in the short-term. One of each gender developed penile and labial adhesions on long-term follow-up that self-resolved. CONCLUSIONS: GU involvement in SJS/TEN occurred in almost three-quarters of patients and was managed conservatively like other skin/mucosal manifestations. Long-term sequelae were rare and urethral catheterization appeared to be safe, without any short-term or long-term complications.

Hypospadias: Are we as good as we think when we correct proximal hypospadias?

OBJECTIVE: Hypospadias surgery is a humbling art form. Although outcomes with distal hypospadias are favorable, recent publications have suggested that the complication rates are much higher than previously anticipated for proximal hypospadias. The present review examined the literature concerning proximal hypospadias, to explore some of the inadequacies and identify some of the reasons behind these shortfalls in the reported data. METHODS: A systematic review of the published literature was conducted using keywords relevant to proximal hypospadias and long-term outcomes. RESULTS: The literature for hypospadias was reviewed, and outcomes for distal vs proximal variants were compared. The quality of the literature for proximal hypospadias was examined, and the shortcomings that led to underreporting of the surgical outcomes were identified. Special focus was on the lack of standardized documentation, the subsequent inability to objectify the severity of the phenotype, and the underestimation of complications due to lack of long-term follow-up. There was also a great deal of variability in the utilized techniques, and the literature was filled with small case series from single institutions. To enable scientific assessment of outcomes, it is proposed that the following be implemented: acceptance and incorporation of standardized phenotype assessment scores in the pre-operative period, objective intraoperative hypospadias characterization, and postoperative score assessment. CONCLUSIONS: Treatment of proximal hypospadias is much less successful than the distal variant. A specialty wide commitment to standardize the hypospadias language is required to make advancement in surgical outcomes. Boys need to be followed through puberty into adulthood, and honest reporting of outcomes must be discussed so that surgical techniques for this complicated disease process can be advanced.

Pediatric calyceal diverticulum treatment: An experience with endoscopic and laparoscopic approaches.

INTRODUCTION: The symptomatic calyceal diverticulum is a rare event in the pediatric population. In adults, surgical options include ureteroscopy, percutaneous ablation, and laparoscopic decortication but there is a lack of experience in the literature with these techniques. OBJECTIVE: We present our experience with both the ureteroscopic and laparoscopic approach to treating the pediatric calyceal diverticulum. STUDY DESIGN: We performed a retrospective case series looking at patients who underwent treatment for calyceal diverticulum at our institution from January 2009 to May 2014. We reviewed patient demographics, indications for intervention, radiographic appearance, type of intervention, and perioperative outcomes. Ureteroscopic approach included dilation of infundibulum and ablation of diverticular cavity. Laparoscopic approach included ablation of the diverticulum with argon diathermy with or without surgical closure of the ostium. RESULTS: There were 13 patients who underwent 15 procedures for symptomatic calyceal diverticulum (Table). Median age was 11 years. Indications for intervention were: pain and increasing size of diverticulum (8/15, 55%), hematuria (3/15, 20%), UTI (3/15, 20%), and calculi (1/15, 5%). 11/15 (73%) procedures were managed endoscopically and 4/15 (27%) were managed with laparoscopic decortication. Ureteral stent was left in all patients for a mean duration of 51 days (15-120 days). Follow up imaging at median of 2.1 years (0.5-4 years) revealed an initial success rate of 85% (11/13 patients). Two patients failed initial intervention (persistent pain/increasing size) necessitating successful secondary minimally invasive procedures. There were 2 (13%) complications: a perinephric hematoma post endoscopic ablation which resolved spontaneously and a deep venous thrombosis in a patient with a coagulation disorder in the laparoscopic group. DISCUSSION: Limitations of our study include its retrospective design, lack of standardization of the treatment approach amongst the four treating surgeons, and the small number of patients requiring intervention for this relatively rare diagnosis. Our study is the largest to date in the pediatric population and is the first to report outcomes with ureteroscopic management of the calyceal diverticulum. CONCLUSIONS: We found that the pediatric calyceal diverticulum can be successfully treated in a minimally invasive manner. The endoscopic approach should be the first line option for patients with small, endophytic diverticula, particularly those located in the upper and mid pole. The laparoscopic approach is more invasive but should be considered for large diverticula that are exophytic with thin overlying parenchyma.

Inhibition of human immunodeficiency virus-1 production resulting from transduction with a retrovirus containing an HIV-regulated diphtheria toxin A chain gene.

Expression of a gene encoding the diphtheria toxin A (DT-A) chain, under the control of human immunodeficiency virus-1 (HIV-1) proteins Tat and Rev, has previously been shown to confer on cells an impaired ability to produce HIV. That work was done in HeLa cell lines that had stably integrated the regulated DT-A gene in a plasmid context. To increase the efficiency with which the HIV-regulated DT-A gene could be introduced into cells, we studied a recombinant, amphotropic murine leukemia virus containing the HIV-regulated DT-A transcription unit. Here we demonstrate that such recombinant retroviruses can be packaged, for both wild-type DT-A and an attenuated version, tox 176. In transient transfection assays, the proviral constructs exhibited similar basal and trans-activated levels of DT-A expression to the parental plasmids. Transduced H9 cells expressed the integrated DT-A gene upon transfection with plasmids encoding Tat and Rev, as assayed by decreased expression of a cotransfected luciferase reporter gene. Furthermore, the transduced H9 cells were substantially impaired in their ability to produce HIV, as demonstrated by p24 assays of culture supernatants following either transfection with an HIV proviral clone or infection with HIV-IIIB. These data demonstrate that basal expression of the regulated DT-A gene has been reduced to a tolerable level, both in packaging cells and transduced H9 cells. The use of HIV-regulated retroviruses encoding the highly lethal DT-A product may eventually be applicable as a gene therapy approach for the acquired immunodeficiency syndrome (AIDS).

Activation of a diphtheria toxin A gene by expression of human immunodeficiency virus-1 Tat and Rev proteins in transfected cells.

Expression of a gene encoding the diphtheria toxin A (DT-A) fragment, controlled by tissue specific regulatory elements, has previously been used to kill selected cell populations. Here, we have examined the feasibility of controlling DT-A expression using regulatory systems from the human immunodeficiency virus (HIV-1) genome. Plasmids were constructed which express either DT-A or, as a model system, the luciferase (luc) reporter gene, under control of HIV-1 long terminal repeat (LTR) sequences (-167 to +80). While trans-activation by expression of the viral protein Tat was demonstrated, significant basal expression was observed. To reduce basal expression, cis-acting negative regulatory elements from the env region of the HIV-1 genome were inserted in the 3' untranslated region of both the luc and DT-A constructs. This dramatically reduced basal expression from the HIV LTR, and now both viral regulatory proteins Tat and Rev were required for maximal trans-activation. Such regulation of DT-A expression might be therapeutically applied to selectively kill HIV-infected cells in acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC).

Thromboxane modulating agents. 3. 1H-imidazol-1-ylalkyl- and 3-pyridinylalkyl-substituted 3-[2-[(arylsulfonyl)amino]ethyl]benzenepropanoic acid derivatives as dual thromboxane synthase inhibitor/thromboxane receptor antagonists.

The design of a series of dual thromboxane synthase inhibitor/thromboxane receptor antagonists based on a 3-[2-[(arylsulfonyl)amino]ethyl]benzenepropanoic acid thromboxane receptor antagonist template is described. Introduction of a 5-(1H-imidazol-1-ylmethyl), a 5-(3-pyridinyl-methyl), or a 5-(3-pyridinyloxy) substituent leads to dual agents with thromboxane synthase inhibitory activity comparable with that of dazmegrel (7). In addition, 3-pyridinylalkyl substituents also make a significant contribution to thromboxane receptor binding. Oral administration of compound 74 (5 mg/kg) to conscious dogs produces long-lasting thromboxane synthase inhibition and thromboxane receptor blockade as measured by inhibition of U46619-induced platelet aggregation ex vivo.

The inhibition of release of endothelium-derived relaxant factor by manoalide, a potent inhibitor of phospholipase A2.

1 The inhibitory action of manoalide on vascular relaxation was characterized. Manoalide was a potent inhibitor of endothelium-dependent relaxations in the isolated aorta of the rabbit. Responses to acetylcholine (ACh), A23187 and substance P were reduced by manoalide in a dose-dependent manner whilst those to nitroglycerin were unaffected. 2 Repeated washing of manoalide-treated tissues did not restore the relaxant response to ACh, indicating an irreversible action of manoalide. Scanning electron microscopic studies revealed that the endothelium remained intact on manoalide-treated tissues. 3 Rabbit aortae from which the endothelium had been removed relaxed in response to perfusion with ACh when delivered via an upstream endothelium-bearing tissue, indicating release of an endothelium-derived relaxant factor (EDRF). Incubation of the tissue without endothelium with manoalide (100 nM; 30 min) or inclusion of manoalide in the superfusate at a point just distal to the endothelium bearing tissue did not reduce the relaxant potency of EDRF. 4 Contractile responses of the guinea-pig isolated ileum to ACh were not affected by manoalide and, furthermore, binding of [3H]-quinuclidinyl benzilate to striatal membranes was not reduced by manoalide except at very high concentrations. 5 Manoalide therefore appears to inhibit vascular relaxation with a selectivity directed towards that mediated by EDRF. A direct antagonism of neither cholinoceptors nor EDRF receptors occurs and it is suggested that manoalide acts at a site within the endothelium to inhibit the synthesis and/or release of EDRF. Based upon these and previous data the possibility that EDRF is lipid-like or controlled by an arachidonic acid metabolite must continue to be considered.

Inhibition of HIV production in cells containing an integrated, HIV-regulated diphtheria toxin A chain gene.

Construction of a DNA plasmid that expresses a diphtheria toxin A chain (DT-A) gene under control of human immunodeficiency virus (HIV-1) proteins Tat and Rev has been described. Here the generation of HeLa cell clones containing integrated, HIV-regulated DT-A sequences is reported. Five such clones were identified by their decreased expression of a luciferase reporter gene transiently cotransfected with Tat- and Rev-encoding plasmids. The decreased luciferase expression most probably was due to activation of the integrated DT-A gene because higher luciferase activity could be restored by introducing either DT antitoxin or a gene encoding a mutant, DT-resistant elongation factor 2 (the intracellular target for DT-A). Analysis by polymerase chain reaction (PCR) indicated that all clones expressed DT-A encoding RNA. The clones were then transfected with an HIV proviral clone and were tested for HIV production; all five clones demonstrated substantially impaired HIV production compared with parental HeLa cells, as shown by p24 assays of culture supernatants. Our success in generating these cell lines indicates that extremely low basal expression has been achieved in view of the high cellular lethality of DT-A. HIV-regulated expression of DT-A may be applicable as a gene therapy approach for the acquired immune deficiency syndrome (AIDS), to bring about selective suicide of HIV-infected cells before production of viral progeny.

The effects of adenosine on receptor sensitivity in the rat vas deferens.

In the guinea-pig isolated vas deferens adenosine augments the contractile response to noradrenaline (NA). Adenosine also augments the contractile response to NA and phenylephrine in the prostatic portion of the transversely bisected rat vas deferens. However, adenosine appeared to neither augment nor diminish the responses to carbachol, 5HT or high K+. Repetitive exposure of the vas to various agonists induced a desensitisation specific to the particular agonist used. The rate of return of responsiveness (the rate of resensitization) was investigated and, in particular, the effect of adenosine on that rate. In the rat vas deferens the rate of resensitization of responses to NA was retarded by adenosine and this effect was abolished by 8-phenyltheophylline and by yohimbine, but not by atropine or propranolol. Neither 8-phenyltheophylline, yohimbine, propranolol nor atropine by themselves affected the rate of resensitization of the rat alpha-adrenoceptor. Adenosine had no effect on the rate of resensitization of responses to phenylephrine, 5HT, carbachol or high K+. It is considered that the potentiation of catecholamine responses by adenosine involves solely alpha 1-receptors but that the retardation of resensitization may involve alpha 2-receptors which do not contribute directly to contraction.