Schistosoma mansoni tetraspanning orphan receptor (SmTOR): a new vaccine candidate against schistosomiasis

One approach to fight against schistosomiasis is to develop an efficient vaccine. Schistosoma mansoni tetraspanning orphan receptor (SmTOR) might be a vaccine candidate, as it is a tegument membrane protein expressed most highly in cercariae. In this study we characterized the recombinant first extracellular domain of SmTOR (rSmTORed1) as having the expected property to bind C2 of complement similarly to a smaller peptide of the same domain, and to produce specific and high-titre antibodies in BALB/c mice immunized using complete Freund's adjuvant/incomplete Freund's adjuvant (CFA/IFA). Immunization was protective against parasite infection, as demonstrated by a significant decrease in worm burden in immunized BALB/c mice versus the control groups over two independent trials [64 and 45% reduction for mean adult worm burden in immunized versus phosphate-bufferd saline (PBS) injected mice]. Interestingly, infection by itself did not lead to the generation of anti-rSmTORed1 antibodies, corresponding to the low frequency of specific anti-rSmTORed1 antibodies detected in the sera of patients infected with S. mansoni (2/20; 10%). These data suggest that, as opposed to the natural infection during which SmTOR induces antibodies only rarely, immunization with its smaller first extracellular domain might be more efficient.

In vitro synergistic interaction between amide piplartine and antimicrobial peptide dermaseptin against Schistosoma mansoni schistosomula and adult worms

Schistosomiasis is one of the world's major public health problems, and praziquantel is the only available drug to treat this notable neglected disease. Drug combinations have been considered an important strategy for treatment of infectious diseases, which might enhance therapeutic efficacy and delaying resistance. In this study, we have examined the in vitro activities of the amide piplartine and the antimicrobial peptide dermaseptin 01 administered singly or in combination against Schistosoma mansoni of different ages including 3-hour-old and 7-day-old schistosomula and 49-day-old adult schistosomes as well as on egg output by adult worms. We calculated the median lethal concentrations (LC(50)) of 7.87 and 17.99 μM on 49-day-old adults, 11.02 and 71.58 μM on 7-day-old schistosomula, and 70.87 and 98.42 μM on 3-hour-old schistosomula for piplartine and dermaseptin, respectively. Most Piplartine/dermaseptin combinations showed synergistic effect, with combination index (CI) values less than 0.9 when S. mansoni adults or schistosomula were simultaneously incubated with both drugs in vitro; synergy between these two compounds was also indicated using isobolograms. Additionally, we observed alterations on the tegumental surface of schistosomula and adult schistosomes by means of laser scanning confocal microscopy. Furthermore, egg laying of surviving worms was considerably more reduced when exposed to the piplartine/dermaseptin combinations than each drug alone, and this inhibition was irreversible. This is the first report on the synergistic effect between piplartine and dermaseptin against S. mansoni and opens the route to further studies (e.g. in vivo) to characterize this combination in greater detail.

Effect of dengue vector control interventions on entomological parameters in developing countries: a systematic review and meta-analysis

The aim of this review was to compare the effects of different dengue vector control interventions (i.e. biological control, chemical control, environmental management and integrated vector management) with respect to the following entomological parameters: Breteau index (BI), container index (CI), and house index (HI). We systematically searched PubMed, ISI Web of Science, Science Direct, the Dengue Bulletin of the World Health Organization and reference lists of retrieved articles on dengue vector control interventions in developing countries. We extracted data on the effectiveness of different dengue vector control interventions (defined as the relative reduction of an entomological measure caused by the intervention compared with the control or pre-intervention phase) and calculated a measure of combined relative effectiveness, with 95% confidence intervals (95% c.i.). We identified 56 publications covering 61 dengue vector control interventions. Integrated vector management was found to be the most effective method to reduce the CI, HI and BI, resulting in random combined relative effectiveness values of 0.12 (95% c.i. 0.02-0.62), 0.17 (95% c.i. 0.02-1.28) and 0.33 (95% c.i. 0.22-0.48), respectively. Environmental management showed a relatively low effectiveness of 0.71 (95% c.i. 0.55-0.90) for the BI, 0.49 (95% c.i. 0.30-0.79) for the CI and 0.43 (95% c.i. 0.31-0.59) for the HI. Biological control (relative effectiveness for the CI: 0.18) usually targeted a small number of people (median population size: 200; range 20-2500), whereas integrated vector management focused on larger populations (median: 12 450; range: 210-9 600 000). In conclusion, dengue vector control is effective in reducing vector populations, particularly when interventions use a community-based, integrated approach, which is tailored to local eco-epidemiological and sociocultural settings and combined with educational programmes to increase knowledge and understanding of best practice. New research should assess the density-dependent effectiveness of each control measure in order to estimate whether reducing vector numbers has an impact on dengue transmission when populations are at a critical threshold.

Urbanization and tropical health--then and now

Since the launch of the Annals of Tropical Medicine and Parasitology 100 years ago, the percentage of the world's population living in urban settings has more than tripled and is now approaching 50%. Urbanization will continue at a high pace, particularly in the less developed regions of Africa and Asia. The profound demographic, ecological and socio-economic transformations that accompany the process of urbanization have important impacts on health and well-being. In industrialized countries, urbanization led to the so-called 'epidemiological transition', from acute infectious and deficiency diseases to chronic non-communicable diseases, many decades ago. In the developing world, surprisingly little research has been carried out on the health-related aspects of urbanization. In a temporal analysis of publications in the Annals of Tropical Medicine and Parasitology, for example, in which the first volume in every decade from 1907 was examined, only 16 (2.6%) of the 604 articles investigated focused on epidemiological and/or public-health issues in urban tropical settings. This review begins with the question 'what is urban?' and then provides a summary of the trends seen in urbanization, and its impacts on human health, over the past century, on both a global and regional scale. For the main tropical diseases, estimates of the at-risk populations and the numbers of cases are updated and then split into urban and non-urban categories. The inhabitants of urban slums are particularly vulnerable to many of these diseases and require special attention if internationally-set targets for development are to be met. Heterogeneity, a major feature of urban settings in the tropics that complicates all efforts at health improvement, is demonstrated in an exploration of a densely populated municipality of a large West African town. Urban planners, public-health experts and other relevant stakeholders clearly need to make much more progress in alleviating poverty and enhancing the health and well-being of urban residents, in an equity-effective and sustainable manner.

Malaria transmission dynamics in central Côte d'Ivoire: the influence of changing patterns of irrigated rice agriculture

The dynamics of malaria transmission was studied comparatively in the villages of Zatta and Tiemelekro, central Cote d'Ivoire, from February 2002 to August 2003. Prominent agroecosystems in these villages are irrigated rice growing and vegetable farming, respectively. Mosquitoes (Diptera: Culicidae) were collected on human bait at night and by pyrethrum knock-down spray sheet collections at four randomly selected sentinel sites in each village. In 2002, for a total of 96 man-nights per village, 7716 mosquitoes were collected in Zatta and 3308 in Tiemelekro. In 2003, with half the sampling effort, 859 and 2056 mosquitoes were collected in Zatta and Tiemelekro, respectively. Anopheles gambiae Giles s.l. was the predominant mosquito and the key malaria vector throughout, followed by An. funestus Giles. Anthropophily among adult female Anopheles exceeded 95% in both villages. Comparison between years revealed that the biting rate of An. gambiae s.l. in Zatta decreased several-fold from 49.3 bites per person per night (b/p/n) in 2002 to 7.9 b/p/n in 2003 (likelihood ratio test (LRT) = 1072.66; P < 0.001). Although the biting rate remained fairly constant in Tiemelekro, the difference between years was significant (16.1 vs. 18.2 b/p/n; LRT = 148.06; P < 0.001). These observations were paralleled by a marked decrease in the infective rate of An. gambiae s.l. in Zatta (4.6-1.2%), and an increase in Tiemelekro (3.1-7.6%). Meanwhile, the entomological inoculation rate of An. gambiae s.l. decreased 21-fold in Zatta, from 789 to 38 infective bites per person per year (ib/p/y), whereas it remained high in Tiemelekro (233 vs. 342 ib/p/y). The interruption of irrigated rice growing in Zatta in 2003, consequential to a farmers' conflict over land, might be the underlying cause for the significant reduction in malaria transmission, whereas more stable conditions occurred in Tiemelekro.

Acridine Orange for malaria diagnosis: its diagnostic performance, its promotion and implementation in Tanzania, and the implications for malaria control

One hundred years ago, Giemsa's stain was employed for the first time for malaria diagnosis. Giemsa staining continues to be the method of choice in most malarious countries, although, in the recent past, several alternatives have been developed that exhibit some advantages. Considerable progress has been made with fluorescent dyes, particularly with Acridine Orange (AO). The literature on the discovery, development and validation of the AO method for malaria diagnosis is reviewed here. Compared with conventional Giemsa staining, AO shows a good diagnostic performance, with sensitivities of 81.3%-100% and specificities of 86.4%-100%. However, sensitivities decrease with lower parasite densities, and species differentiation may occasionally be difficult. The most notable advantage of the AO method over Giemsa staining is its promptness; results are readily available within 3-10 min, whereas Giemsa staining may take 45 min or even longer. This is an important advantage for the organization of health services and the provision of effective treatment of malaria cases. The national malaria control programme of Tanzania, together with the Japan International Co-operation Agency, began to introduce the AO method in Tanzania in 1994. So far, AO staining has been introduced in 70 regional and district hospitals, and 400 laboratory technicians have been trained to use the method. The results of this introduction, which are reviewed here and have several important implications, indicate that AO is a viable alternative technique for the laboratory diagnosis of malaria in highly endemic countries.

Current progress in the development and use of artemether for chemoprophylaxis of major human schistosome parasites

Human schistosomiasis, a chronic and debilitating parasitic disease of the tropics, is ranked second after malaria in terms of public health importance. At present, there is no vaccine available, and chemotherapy is the cornerstone of schistosomiasis control. Praziquantel is the drug of choice. Oxamniquine has become difficult to obtain and metrifonate has recently been withdrawn from the market. Rapid re-infection following treatment and concern about praziquantel resistance called for the search of novel drugs for prevention and cure of schistosomiasis. Significant progress has been made with artemether, the methyl ether of dihydroartemisinin, already widely used for the treatment of malaria. The present article reviews the literature that led to the development of artemether for chemoprophylaxis in schistosomiasis, and it summarises the experiences so far obtained with its use to control schistosomiasis in different endemic settings. Topics covered include an overview of the global burden of schistosomiasis and approaches for its control; the nature and features of artemisinin and related derivatives, initially discovered as antimalarials, other bioactivities, and their recent discovery of antischistosomal properties; a historic account disclosing the antischistosomal activity of artemether; in vivo assessment of drug susceptibility of different developmental stages of schistosome parasites; artemether-induced pathology evidenced by scanning and transmission electron microscopy; the possible mechanism of action; in vivo studies with combination therapy of artemether and praziquantel; results of randomised controlled clinical trials of oral artemether for the prevention of patent infection and morbidity; and, ultimately the translation of this knowledge into public health action in different endemic settings towards a more integrated approach of schistosomiasis control.

Pharmacokinetic investigations in patients from northern Angola refractory to melarsoprol treatment

Melarsoprol, an organo-arsenical drug, has been the drug of choice for late-stage trypanosomiasis for 50 years. Because of the lack of alternatives any abatement of this medication will have a dramatic negative impact on the perspectives for patients. As a large number of patients refractory to melarsoprol treatment was recently reported from northern Uganda and northern Angola, we investigated in northern Angola whether interpatient pharmacokinetic differences influence the outcome of melarsoprol treatment. Drug levels were determined by a biological assay in serum and cerebrospinal fluid (CSF) of 22 patients. Nine patients could be successfully treated, eight were refractory and the outcome was unclear or no adequate follow-up information was available for five patients. No differences in the pharmacokinetic parameters (maximum serum concentration Cmax, half-life t1/2 beta, total clearance CL and the volume of distribution Vss) could be detected between the groups. Serum and CSF concentrations for all patients were in the expected range. This result indicates that other underlying factors are responsible for treatment failures.

Evaluation of quinolone derivatives for antitrypanosomal activity

About 160 fluoroquinolones and derivatives were tested for antitrypanosomal activity in a drug sensitivity assay followed by fluorometric evaluation. The most active quinolone compounds had IC50 values in the range from 100 to 900 ng/ml, while several derivatives were not active at a concentration of 100 microg/ml. In a structure activity relationship study, modification of the quinolones at position R1, R2, R3 and R8 did not influence trypanocidal activity. An exchange of the fluor at position 6 may contribute to an increase in activity but does not entirely control it. Pyrrolidine substituents at position R7 generally were more active than other substituents at this position. Tetracyclic quinolone derivatives were amongst the most active compounds with IC50 values in the range of 0.3-8.8 microg/ml. The in vitro cytotoxicity on HT-29 cells was determined for active compounds with IC50 values below 1 microg/ml. In addition, six drugs with an IC50 below 1 microg/ml and a selectivity index of more than 10 were chosen for in vivo experiments. Dose escalation experiments with a maximum dose of 100 mg/kg/bid were performed in a mouse model without central nervous system involvement. For unknown reasons the in vitro effect of the drugs could not be confirmed in vivo, but the class of compound remains of interest for their mode of action, the low toxicity, pharmacological properties and the availability of a large number of synthesized compounds.

New drugs for the treatment of human African trypanosomiasis: research and development

Chemotherapy of human African trypanosomiasis is problematic because of the high frequency of severe adverse events, the long duration and high cost of treatment, and an increasing number of treatment-refractory cases. New cost-efficient, easy-to-use drugs are urgently needed. Whereas basic research on potential drug targets is anchored in academia, the complex, highly regulated and very expensive process of preclinical and clinical drug development is almost exclusively in the hands of pharmaceutical companies. Jennifer Keiser, August Stich and Christian Burri here review, from the angle of industrial drug research and development, the past ten years of research activities at different stages of the development of trypanocidal drugs, and assess future prospects. The absence of compounds in clinical development Phases I-III indicates no new drugs will become available in the next few years.

Investigations of the metabolites of the trypanocidal drug melarsoprol

BACKGROUND

Melarsoprol remains the first-choice drug for trypanosomiasis (human African sleeping sickness). To contribute to the sparse pharmacologic data and to better understand the cause of the frequent serious adverse reactions, we investigated the metabolism of this 50-year-old organoarsenic compound.

RESULTS

The half-life of melarsoprol determined by HPLC was <1 hour compared with 35 hours determined by bioassay and atomic absorption spectroscopy, indicating the existence of active metabolites. One metabolite, melarsen oxide, was identified by ultraviolet HPLC after incubation of melarsoprol with microsomes. The maximum plasma concentration of melarsenoxide was reached 15 minutes after administration; the clearance was 21.5 mL/min/kg and the half-life of free melarsen oxide was 3.9 hours. Either melarsen oxide or a yet-undiscovered active metabolite is irreversibly bound to proteins, as shown by ultrafiltration, precipitation experiments, and atomic absorption spectroscopy. Because of the poor pharmaceutical properties of melarsoprol, the therapeutic potential of melarsen oxide was investigated. In a rodent model of acute infection, 20 of 20 mice were cured (0.1 to 1 mg/kg intravenously or 2.2 mg/kg intraperitoneally). In a rodent model of central nervous system infection, five of six mice survived for more than 180 days (5 mg/kg intravenously), indicating a sufficient melarsen oxide penetration across the blood-brain barrier.

CONCLUSION

The prospects for the future of trypanosomiasis treatment are deplorable. Investigations on the improvement of the use of the old drugs are therefore required. The results of this study may build a basis for further research on the cause of severe adverse reactions.

Detection of cytomegalovirus proteins by flow cytometry in the blood of patients undergoing hematopoietic stem cell transplantation

Cytomegalovirus (CMV) infection and associated diseases continue to be a major complication encountered by patients undergoing high-dose chemoradiotherapy and hematopoietic stem cell transplantation (HSCT). A number of studies revealed that identification of CMV in the blood of HSCT patients was a predictor of future CMV disease. The purpose of this study was to determine if CMV proteins detected by flow cytometry could be a rapid and more quantitative way to monitor CMV infections and CMV antigenemia in HSCT patients. Preliminary studies showed that CMV immediate early (IE), early (E), and late (L) tegument proteins were specifically identified in CMV-infected cell lines and not in uninfected cells. We evaluated CMV antigen detection by flow cytometry in blood samples collected before and after transplantation in 56 serially collected blood samples from 17 HSCT patients and CMV protein expression was compared to CMV isolation. CMV IE and E proteins were not detected in any of the samples analyzed. However, CMV L protein detection by flow cytometry correlated with virus isolation in serially collected blood samples. Samples from 14 patients were evaluated by both techniques, at the same time intervals. There was a 100% correlation (8/8) between the lack of CMV antigen detection by flow cytometry and the failure to isolate infectious virus. Moreover, 5 of 6 patients who were positive for CMV L antigen by flow cytometry also were positive by virus isolation techniques. When flow cytometry and virus isolation did not detect CMV antigen on the same day, CMV positivity was first detected by flow cytometry. Then, 1-2 weeks later, positive virus isolation was documented. This study indicates that flow cytometric identification of CMV antigenemia correlates with isolation of CMV in HSCT patients and may be a predictive test for the rapid detection of CMV in the blood.

Discrepancy in plasma melarsoprol concentrations between HPLC and bioassay methods in patients with T. gambiense sleeping sickness indicates that melarsoprol is metabolized

OBJECTIVE

With the use of a specific high-performance liquid chromatography (HPLC) method and a bioassay which determines trypanocidal activity, concentrations of melarsoprol were assessed in plasma, urine and cerebrospinal fluid (CSF) from 8 patients with late-stage Trypanosoma gambiense sleeping sickness. The aim was to unravel to what extent the bioassay codetermines biologically active metabolites of melarsoprol.

METHODS

Subjects were given one dose of melarsoprol i.v. per day for 4 days (1.2, 2.4, 3.0-3.6, 3.0-3.6 mg per kg b.w., respectively). Plasma samples were obtained before the first melarsoprol injection, immediately after and at 1 h, 24 h and 5 days after the 4th injection. Urine was collected before melarsoprol therapy and at 24 h after the 4th injection. CSF samples were taken once before treatment and at 24 h after the 4th injection.

RESULTS

HPLC analyses showed that plasma concentrations immediately after the 4th injection varied from 2200 to 15,900 nmol/l; dropping to 0-1800 nmol/l at 1 h; and to undetectable levels at 24 h. In urine small amounts of melarsoprol were recovered. Melarsoprol could not be detected in CSF by HPLC. Immediately after injection, bioassay analyses showed plasma concentrations of the same magnitude as HPLC assays but at 1 h they were 4-65-fold higher than the levels assessed by HPLC. Even 24 h and 5 days after the 4th injection there was significant but decreasing activity. Urine levels were 40-260-fold higher than the measured HPLC concentrations, whereas there was low but detectable activity in CSF.

CONCLUSION

Results indicate that melarsoprol is rapidly eliminated from plasma. The significant trypanocidal activity determined by bioassay and simultaneous low or undetectable levels of melarsoprol assayed by HPLC indicate that the compound is transformed into metabolites with parasiticidal activity.

Synthesis and tyrosine kinase inhibitory activity of a series of 2-amino-8H-pyrido[2,3-d]pyrimidines: identification of potent, selective platelet-derived growth factor receptor tyrosine kinase inhibitors

Screening of a compound library led to the identification of 2-amino-6-(2,6-dichlorophenyl)-8-methylpyrido[2,3-d]pyrimidine (1) as a inhibitor of the platelet-derived growth factor receptor (PDGFr), fibroblast growth factor receptor (FGFr), and c-src tyrosine kinases (TKs). Replacement of the primary amino group at C-2 of 1 with a 4-(N,N-diethylaminoethoxy)phenylamino group yielded 2a, which had greatly increased activity against all three TKs. In the present work, variation of the aromatic group at C-6 and of the alkyl group at N-8 of the pyrido[2,3-d]pyrimidine core provided several analogues that retained potency, including derivatives that were biased toward inhibition of the TK activity of PDGFr. Analogues of 2a with a 3-thiophene or an unsubstituted phenyl group at C-6 were the most potent inhibitors. Compound 54, which had IC50 values of 31, 88, and 31 nM against PDGFr, FGFr, and c-src TK activity, respectively, was active in a variety of PDGF-dependent cellular assays and blocked the in vivo growth of three PDGF-dependent tumor lines.

Efficacy of CI-1020, an endothelin-A receptor antagonist, in hypoxic pulmonary hypertension

We previously showed that CI-1020, an endothelin (ET)-A-selective receptor antagonist, dose-dependently blocked acute hypoxic pulmonary hypertension (PH) in rats. In this study we show that CI-1020 can reverse existing PH and prevent progression of right ventricular hypertrophy (RVH) in rats exposed to chronic hypoxia. Male Sprague-Dawley rats were exposed to 20 days of hypoxia (10% O2) with CI-1020 treatment (20 or 40 mg/kg/day) starting on day 10. On day 20 of hypoxia, the rats were instrumented under anesthesia with a pulmonary artery cannula and allowed to recover to consciousness before measurement of mean pulmonary arterial pressure (MPAP). Blood samples were then collected for plasma ET-1 measurements, the rats killed, and their hearts dissected, dried, and weighed. RV/LV + septum ratio (g/g) was used as an index of RVH (RVHi). Normoxic rats and rats exposed to hypoxia for only 10 days were also evaluated as controls. Normoxic rats had MPAPs of 13 +/- 1 mm Hg, plasma ET-1 levels of 2.1 +/- 0.1 pg/ml, and an average RVHi of 0.29 +/- 0.03. Rats exposed to 10 or 20 days of hypoxia had MPAPs of 33 +/- 2 and 44 +/- 0 mm Hg, plasma ET-1 levels of 4.2 +/- 0.8 and 4.6 +/- 0.8 pg/ml, and average RVHis of 0.47 +/- 0.05 and 0.52 +/- 0.03, respectively. In comparison, rats treated with CI-1020 had MPAPs that were 37% (20 mg/kg/day) and 44% (40 mg/kg/day) lower than untreated 20-day hypoxic rats. Furthermore, rats dosed with 40 mg/kg/day of CI-1020 had MPAPs that were significantly lower (24%) than control 10-day hypoxic rats, indicating a significant reversal of PH. Along with this reversal in PH, their average RVHi was 23% lower (p < 0.05) relative to untreated 20-day hypoxic rats.

Structure-activity relationships for a novel series of pyrido[2,3-d]pyrimidine tyrosine kinase inhibitors

Screening of a compound library for inhibitors of the fibroblast growth factor (FGFr) and platelet-derived growth factor (PDGFr) receptor tyrosine kinases led to the development of a novel series of ATP competitive pyrido[2,3-d]pyrimidine tyrosine kinase inhibitors. The initial lead, 1-[2-amino-6-(2,6-dichlorophenyl)pyrido[2,3-d]pyrimidin-7-yl]-3- tert-butylurea (4b, PD-089828), was found to be a broadly active tyrosine kinase inhibitor. Compound 4b inhibited the PDGFr, FGFr, EGFr, and c-src tyrosine kinases with IC50 values of 1.11, 0.13, 0.45, and 0.22 microM, respectively. Subsequent SAR studies led to the synthesis of new analogs with improved potency, solubility, and bioavailability relative to the initial lead. For example, the introduction of a [4-(diethylamino)butyl]amino side chain into the 2-position of 4b afforded compound 6c with enhanced potency and bioavailability. Compound 6c inhibited PDGF-stimulated vascular smooth muscle cell proliferation with an IC50 of 0.3 microM. Furthermore, replacement of the 6-(2,6-dichlorophenyl) moiety of 4b with a 6-(3',5'-dimethoxyphenyl) functionality produced a highly selective FGFr tyrosine kinase inhibitor 4e. Compound 4e inhibited the FGFr tyrosine kinase with an IC50 of 0.060 microM, whereas IC50s for the inhibition of the PDGFr, FGFr, EGFr, c-src, and InsR tyrosine kinases for this compound (4e) were all greater than 50 microM.

Role for endothelin-1 in angiotensin II-mediated hypertension

Experiments in cultured vascular smooth muscle cells have shown that angiotensin II (Ang II) stimulates expression of endothelin-1. We sought to examine role of endothelin-1 in the effects of Ang II in vivo. Ang II infusion in rats (0.7 mg/kg per day for 5 days) was associated with marked increases in vascular smooth muscle endothelin-1 levels, as assessed by immunostaining. Administration of the selective endothelin type A (ET(A)) receptor antagonist PD 155080 (50 mg/kg per day) abrogated the hypertensive response to a 5-day infusion of Ang II (0.7 mg/kg per day), as did losartan (25 mg/kg per day). ET(A) receptor blockade during Ang II-mediated hypertension was associated with marked elevations of plasma endothelin-1 levels. Ang II-mediated hypertension was associated with heightened vascular responsiveness to a variety of vasoconstrictor agents except endothelin-1. Blockade of ET(A) receptor invariably corrected this vasoconstrictor hyperresponsiveness. We conclude that some of the vascular effects of Ang II thought to be unique to this hormone are likely mediated by endothelin-1.

Mycobacterium kansasii bacteremia in patients infected with human immunodeficiency virus

In a retrospective review of microbiology records at the George Washington University Hospital from 1980 through 1990, Mycobacterium kansasii bacteremia was identified in 10 patients; this finding represented 4.5% of nontuberculous mycobacterial blood cultures. M. kansasii was isolated from respiratory specimens from all 10 patients, and pulmonary parenchymal changes were noted in five patients. The median survival time was 14 weeks; however, only five patients received therapy with two or more drugs active against M. kansasii.

Evaluation of physicochemical parameters important to the oral bioavailability of peptide-like compounds: implications for the synthesis of renin inhibitors

A series of radiolabeled compounds related to renin inhibitor structures was synthesized to represent a range of physicochemical properties. These compounds were tested in assays for intestinal absorption and hepatic clearance in order to define parameters conducive to optimizing bioavailability. In general, compounds with higher lipophilicity were better absorbed from the intestine. Absorption may also be dependent on molecular charge, as compounds with ionizable functionality were less well-absorbed than neutral compounds. Neutral compounds showed some dependency on molecular weight, with smaller compounds exhibiting better absorption. While uptake into hepatic cells was rapid regardless of partition coefficient or molecular weight, rate of appearance in bile was dependent on the molecular weight of the compounds.

Endothelin antagonists improve renal function in spontaneously hypertensive rats

Hypertension in the spontaneously hypertensive rat (SHR) is associated with reduced renal excretory function, low renal plasma flow, reduced glomerular filtration rate, and reduced renal interstitial hydrostatic pressure. The mechanisms responsible for these abnormalities in renal function are unknown. The purpose of this study was to determine the role of intrarenal endothelin in altering renal hemodynamic and excretory function in the SHR. Both PD 145065 (an endothelin A and B receptor antagonist) and FR 139317 (a selective endothelin A receptor antagonist) or saline was infused into the renal interstitium of 14- to 16-week-old SHR (n = 7) and age-matched Wistar-Kyoto rats (WKY) (n = 7). Renal perfusion pressure in some SHR was reduced to that of the WKY by a servocontrol system. At a renal perfusion pressure of 124 +/- 4 mm Hg, infusion of PD 145065. (0.03 mg.kg-1.min-1) and FR 139317 (0.02 mg.kg-1.min-1) significantly increased glomerular filtration rate (delta 22%), renal plasma flow (delta 37%), and renal interstitial hydrostatic pressure (from 3.2 +/- 0.5 to 5.4 +/- 0.6 mm Hg) in the SHR. These changes were associated with significant increases in urine flow, absolute sodium excretion, and fractional excretion of sodium. Similar improvements in renal plasma flow, renal interstitial hydrostatic pressure, and renal excretory function were obtained in the SHR whose renal perfusion pressure was not reduced (n = 7). Renal interstitial infusion of endothelin receptor antagonists had no effect on renal hemodynamic or excretory function in the WKY. These data demonstrate that endothelin receptor blockade within the kidney improves renal hemodynamic and excretory function in the SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel angiotensin receptor subtypes in fowl

We reported previously that blood vessels of domestic fowl contain angiotensin (ANG) receptors on 1) endothelium, mediating vasorelaxation via endothelium-derived relaxing factor and guanosine 3',5'-cyclic monophosphate; 2) vascular smooth muscles, mediating neither relaxation nor contraction; and 3) presumably adrenergic nerve endings, transmitting vasopressor action via a release of norepinephrine. We aimed in the present study to determine fowl vascular ANG receptor subtypes and relate them to function. [Val5]ANG II (native fowl ANG II) increased mean arterial pressure of anesthetized, ganglion-blocker-treated fowl. The dose-pressor response curve for fowl ANG II was not altered by pretreatment (i.v.) with the ANG receptor subtype 1 (AT1) antagonist Dup-753 (losartan, 10 mg/kg) or the subtype 2 (AT2) antagonist PD-123319 (10 mg/kg). Furthermore, cumulative doses (1-20 mg/kg) of losartan or PD-123319 did not selectively inhibit ANG II-induced pressor responses. In reserpine- and prazosin-treated anesthetized fowl, [Val5]ANG II caused dose-dependent vasodepressor actions inhibited by neither losartan (10 mg/kg) nor PD-123319 (10 mg/kg). Likewise, [Val5]ANG II-induced vasorelaxation of fowl aortic rings in vitro was not inhibitable by PD-123319 or losartan (10(-5) M). Specific binding of 125I-labeled ANG II to the aortic endothelium was markedly displaced by ANG II, but not selectively by PD-123319 or losartan. Specific binding of 125I-ANG II ligand to the membrane fraction of aortic smooth muscles was displaced (50% inhibitory concentration) by [Val5]ANG II (3.3 x 10(-8) M) and slightly by PD-123319 (3.7 x 10(-5) M), but not by losartan or EXP-3174, an active metabolite of losartan.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of renin-angiotensin system in mediating endothelin-induced renal vasoconstriction: therapeutic implications

PURPOSE

Experiments were designed to determine whether angiotensin converting enzyme inhibition with quinaprilat can prevent endothelin-mediated decreases in renal blood flow and the glomerular filtration rate in the anesthetized dog.

METHODS

To mimic the activation of the renal endothelin system that occurs in a number of cardiorenal disease states, endothelin was administered intrarenally in a group of mongrel dogs. Quinaprilat, the major active metabolite of quinapril, was infused in a separate group. One kidney (group 1) or both kidneys (group 2) were exposed in order to measure renal blood flow by an electromagnetic flow probe. Mean arterial blood pressure was measured through a catheter in a femoral vein. Blood samples were taken to determine plasma renin activity. Urine was collected.

RESULTS

The infusion of endothelin decreased renal blood flow and the glomerular filtration rate and increased renal vascular resistance. These renal vascular responses were associated with increased plasma renin activity, indicating activation of the renal renin-angiotensin system. Quinaprilat attenuated the renal vascular responses.

CONCLUSIONS

These studies provide further evidence of the importance of the renal renin-angiotensin system in mediating the renal vasoconstrictor actions of endothelin and indicate the therapeutic potential for quinapril in opposing the actions of endothelin in states of excessive endothelin activation.

Sequential culturing method improves recovery of Legionella spp. from contaminated environmental samples

Investigations were undertaken to improve detection and isolation of Legionella spp. from samples containing a large number of non-legionellae isolates. The direct fluorescent antibody staining technique was used in conjunction with a sequential culturing method which was developed to improve the recovery rate of Legionella spp. from such samples. The technique for enrichment and isolation of Legionella spp. from environmental samples includes storage at 4 degrees C and repeated culture on freshly prepared media. Heat and acid treatments were included when deemed appropriate. A DNA probe was used for confirmation of Legionella. Treatment of the water samples, as described, and co-cultivation with amoebae naturally present in the samples are concluded to be responsible for increased success in recovery of Legionella isolates.

An Analysis of the Predictability of Hypoxemia Following Vertical Banded Gastroplasty

Postoperative (post-op) hypoxemia is unpredictable, often undetected by physical examination, sometimes fatal. We studied 45 morbidly obese patients with an average age of 37, including 16 smokers, having vertical banded gastroplasty (VBG) for useful preoperative (preop) predictor(s) of post-op hypoxemia during the first five days following VBG. Patient blood gases (arterial blood oxygen, P&infa;O&inf2; in mmHg), pre-op and five post-op days (POD), after 30 min in room air were: pre-op, 85 +/- 9; POD1, 63 +/- 9*; POD2, 61 +/- 9*; POD3, 63 +/- 10*; POD4, 63 +/- 9* POD5, 64 +/- 1 * (* p < 0.05, Student's t-test compared with pre-op). Linear regression showed no practical, predictive value for P.02 for age, Body Mass Index (BMI), pulmonary function tests (PFTs), smokers or preop P&infa;O&inf2;. Post-op atelectasis occurred in 84% of patients, mostly the posterior basilar regions on chest X-ray. No patient developed clinically diagnostic pneumonia. VBG patients experienced profound hypoxemia post-op, the lowest on POD2. There is no reliable method to predict which patient may develop severe hypoxemia. It is, therefore, extremely helpful to uniformly monitor P&infa;O&inf2; post-op in morbidly obese patients.

Subclasses of cyclic GMP-specific phosphodiesterase and their role in regulating the effects of atrial natriuretic factor

Two subclasses of cyclic guanosine monophosphate (GMP)-specific phosphodiesterases were identified in vascular tissue from several beds. The activity of one subclass (phosphodiesterase IB) was stimulated severalfold by calmodulin and selectively inhibited by the phosphodiesterase inhibitor TCV-3B. The activity of the other subclass (phosphodiesterase IC) was not stimulated by calmodulin and was selectively inhibited by the phosphodiesterase inhibitor M&B 22,948. To assess the involvement of both subclasses in regulating cyclic GMP-dependent responses, the ability of TCV-3B and M&B 22,948 to potentiate the in vitro and in vivo responses to the endogenous guanylate cyclase stimulator atrial natriuretic factor (ANF) was evaluated. Both TCV-3B and M&B 22,948 relaxed isolated rabbit aortic and pulmonary artery rings and also potentiated the relaxant effect of ANF. In addition, both inhibitors produced small increases in urine flow and sodium excretion in anesthetized rats and potentiated the diuretic and natriuretic responses to exogenous ANF. M&B 22,948 (30 micrograms/kg/min) produced a threefold increase in the natriuretic response to simultaneously administered ANF, and TCV-3B (10 micrograms/kg/min) produced a twofold increase in the response to ANF. The results of the present experiments suggest that both the calmodulin-sensitive and calmodulin-insensitive subclasses of cyclic GMP-specific phosphodiesterase play a role in regulating the in vitro and in vivo response to ANF.

Comparison of in situ hybridization and monoclonal antibodies for early detection of cytomegalovirus in cell culture

The abilities of each of four diagnostic tests--direct fluorescent monoclonal antibody (direct FA) staining, indirect fluorescent monoclonal antibody (indirect FA) staining, in situ hybridization with biotinylated DNA probes, and in situ hybridization with DNA probes directly linked to enzymatically active horseradish peroxidase-to detect cytomegalovirus soon after culture were compared. Only the indirect FA test and the in situ hybridization method with directly linked HRP-DNA probes provided consistent and reliable cytomegalovirus detection as early as 15 h postinfection.

Increased vasodilator responsiveness to BRL 34915 in spontaneously hypertensive versus normotensive rats: contrast with nifedipine

The blood pressure-lowering potency and activity of BRL 34915, a new vasodilator and putative stimulator of potassium efflux from vascular smooth muscle, was investigated in conscious spontaneously hypertensive rats (SHR) and normotensive rats (NTR) after intravenous administration and compared with that of the calcium channel blocker, nifedipine. In SHR, BRL 34915 (3-100 micrograms/kg) or nifedipine (10-3000 micrograms/kg) produced similar reductions in mean arterial pressure of 58 +/- 3% and 55 +/- 3%, respectively. BRL 34915 (ED30% = 13.8 micrograms/kg) was 15.3 times more potent than nifedipine (ED30% = 207 micrograms/kg) in SHR. In contrast, only a 1.7-fold difference in potency was observed in NTR between BRL 34915 (ED30% = 123 micrograms/kg) and nifedipine (ED30% = 182 micrograms/kg). The potency ratio (ED30% NTR/ED30% SHR) for BRL 34915 was 8.83 whereas nifedipine had a ratio of 0.88, reflecting the greater responsiveness of the SHR to BRL 34915. Systemic hemodynamics were monitored in anesthetized SHR and NTR to determine the basis for the reductions in blood pressure. BRL 34915 (3-100 micrograms/kg iv) lowered mean arterial pressure in both groups solely by decreasing total peripheral vascular resistance, since no changes in cardiac output were observed. Relaxation responses were also obtained in phenylephrine-contracted isolated aortic strips from both strains of rat to ascertain whether differences in responsiveness existed at this level of the vasculature. No significant difference in the potency of BRL 34915 (3-10 microM) as a vasodilator was found in aortas from SHR or NTR. These results indicate that, unlike nifedipine, BRL 34915 is a more potent vasodepressor agent in SHR than in NTR and suggests that the potassium efflux stimulator may preferentially relax resistance vessels in the hypertensive rat.

Comparative leukocyte esterase-nitrite and BAC-T-SCREEN studies using single and multiple urine volumes

The Chemstrip LN and BAC-T-SCREEN filtration systems were used to evaluate 980 urine specimens rapidly for the presence of microorganisms. Multiple volumes of individual specimens were also tested using the BAC-T-SCREEN to determine whether this procedure enhanced test performance. Ninety-nine specimens (10%) could not be processed because of interfering substances or clogging of the BAC-T-SCREEN. Analysis of the remaining 881 samples showed these test results for the Chemstrip LN system: sensitivity, 48%; specificity, 93%; positive predictive value (PPU), 88%; and negative predictive value (NPV), 71%. The BAC-T-SCREEN results using multiple urine volumes were (for 1 mL) sensitivity, 88%; specificity, 98%; PPV, 97%; NPV, 92%; for 2 mL, sensitivity, 94%; specificity, 96%; PPV, 94%; NPV, 96%; for 3 mL, sensitivity, 98%; specificity, 95%; PPV, 93%; NPV, 98%. Analyzing multiple urine volumes permitted detection of 92% of urine samples with colony-forming units of 10(4) or less. The BAC-T-SCREEN system proved superior to Chemstrip LN for detecting microorganisms in urine specimens, and analyzing multiple urine volumes enhanced test sensitivity.

Antimicrobial therapy of Broviac catheter infections in pediatric hematology oncology patients

Long-term therapy of pediatric oncology patients has been facilitated by permanent indwelling venous catheters. Over a 3-year period, 54 Broviac catheters were placed in 43 oncology patients and two hemophiliacs. There were 20 episodes of sepsis in 14 patients and the most common bacteria were S epidermidis (4), S aureus (4), and K pneumoniae (3). Catheter exit site infections occurred ten times in six patients; S aureus eight of ten. Antibiotic therapy without catheter removal was successful in 18 of 20 children with catheter sepsis and 8 of 10 patients with exit site infections. These data strongly suggest that although catheter-related infections are common, removal of Broviac catheters is not required for successful treatment of the infection.

Colonization of newly arrived house staff by virulent staphylococcal phage types endemic to a hospital environment

The acquisition of hospital strains of Staphylococcus aureus by new house officers was studied in an 800-bed referral hospital over a 1-year period. S. aureus isolates, including three strains with characteristic phage patterns that had previously been documented to cause disease in patients and colonize hospital personnel, were recovered from the anterior nares of 35 of 54 newly arrived house officers. There was a significant correlation (r = 0.7475; P less than 0.02) between colonization with the dominant hospital strain (S) and exposure to the hospital environment over 12 months. No hospital-wide increase in infections owing to the S strain was seen during this period, which suggests that house staff acquired this strain from reservoirs within the hospital. The finding of colonization with virulent endemic S. aureus strains in house officers working on every ward of the hospital suggests that new strategies for control of S. aureus nosocomial infections must be considered and evaluated.

Comparison of the Phadebact Gonococcus Test with the rapid fermentation method

The Phadebact Gonococcus Test (Pharmacia Diagnostics, Piscataway, N.J.), a coagglutination technique, was compared with the rapid fermentation method of Kellogg and Turner (D. S. Kellogg, Jr., and E. M. Turner, Appl. Microbiol. 25: 550--552, 1973). A total of 93 organisms isolated on Martin-Lewis media were determined to be Neisseria gonorrhoeae based on the following criteria: presence of gram-negative diplococci, oxidase positivity, and appropriate reaction in the rapid fermentation method. These 93 isolates were then serologically tested with the Phadebact test. The direct method was attempted on the first 46 N. gonorrhoeae isolates. Difficulty in interpreting results was encountered in 39%. Thereafter, the alternate method of boiling was instituted on an additional 47 N. gonorrhoeae isolates, with 2 isolates producing noninterpretable results. All 93 isolates were frozen for a maximum of 2 months in skim milk at -25 degrees C. These isolates were thawed and retyped with the alternate boiling procedure, with 97% being confirmed as N. gonorrhoeae. In addition, 33 Neisseria meningitidis isolates, 14 Neisseria species, and 7 Moraxella species were tested with similar techniques. No positive reactions were observed. A cost effectiveness study using 5, 10, and 20 microliters of the gonococcal reagent was undertaken to reduce the cost of the test. When 10 and 20 microliters of reagent were used, no difficulty was encountered in interpreting the reaction. The coagglutination technique was difficult to read when 5 microliters of reagent was used.

Multiple short-term effects of lead on the renin-angiotensin system

We previously demonstrated that lead (3 mg/kg iv) sharply raises PRA in dogs. In the present study, the short-term effects of the same dose of lead on renin secretion, hepatic removal of renin, and arterial AII levels were measured in anesthetized dogs. Despite large increases in PRA in all nine lead-treated dogs, renin secretion increased in only three out of nine lead-treated animals (those with the lowest baseline renin secretion). Hepatic extraction of renin was eliminated by lead, and so total hepatic removal of renin became zero by 2 or 3 hr after lead administration. Finally, despite large increases in PRA, AII levels did not rise after lead. The linear relationship of AII to PRA seen in animals not treated with lead was changed, so that after lead, AII levels were disproportionately low for the corresponding level of PRA. It is concluded that lead may increase renin secretion in animals otherwise unstimulated to secrete but that the major mechanism for the short-term rise in PRA after lead is elimination of hepatic removal of renin; further, lead prevents AII from rising proportionately with PRA, presumably by inhibiting angiotensin-converting enzyme.

Cortical bone density of adult lacto-ovo-vegetarian and omnivorous women

Lacto-ovo-vegetarian women fifty to eighty-nine years of age lost 18 per cent bone mineral mass while omnivorous women lost 35 per cent. This study established that this difference could not be explained by a greater bone density in the lacto-ovo-vegetarians during the third, fourth, and fifth decades of life. The possibility of higher sulfur content in the meat-containing diet, the effect of excess phosphorus, and the effect of an acid-ash diet are discussed. From the standpoint of a general survey, comsumption of calcium-containing foods was not appreciably different in the two groups. It is, therefore, concluded that lacto-ovo-vegetarian diet may be beneficial in extended protective health care in terms of defense against, or control of, bone mineral loss in the later years of a woman's life.

Selection of materials for ventricular assist pump development and fabrication

A study was undertaken to select 2 of the most promising bladder materials from a list of 8 carefully chosen polymers. The polymers chosen for testing included a wide spectrum of urethanes, as well as a polyester resin and a millable polyolefin rubber. The following materials were studied: Adiprene LW-500, Avcothane 51, Biomer, Hexsyn, Hytrel 4055, Mobay 240313, Pellethane 2103-80 AE, and Tecoflex HR. The selection process was based on a test matrix which was divided into segmented steps, each a logical sequel from its predecessor, and each of increasing technical complexity. Hydrolytic stability, flexure endurance, fabricability, tissue compatibility, hemocompatibility and chronic tissue compatibility were evaluated, forming the basis for the acceptance/rejection criteria. As a result of this search, 2 biomaterials were identified as most suitable for use in conventionally flocked bladders; Biomer and Tecoflex HR. Both Biomer and Tecoflex HR bladders have demonstrated impressive results in circulatory analog loop endurance tests, with Tecoflex bladders surpassing 50 million flexes to date, and Biomer bladders (the longest running bladders) exceeding 150 million flexes. Tests are continuing.