Quinoline Thiourea-Based Zinc Ionophores with Antibacterial Activity

The increasing resistance of bacteria to commercially available antibiotics threatens patient safety in healthcare settings. Perturbation of ion homeostasis has emerged as a potential therapeutic strategy to fight against antibacterial resistance and other channelopathies. This study reports the development of 8-aminoquinoline (QN) derivatives and their transmembrane Zn2+ transport activities. Our findings showed that a potent QN-based Zn2+ transporter exhibits promising antibacterial properties against Gram-positive bacteria with reduced hemolytic activity and cytotoxicity to mammalian cells. Furthermore, this combination showed excellent in vivo efficacy against Staphylococcus aureus. Interestingly, this combination prevented bacterial resistance and restored susceptibility of gentamicin and methicillin-resistant S. aureus to commercially available β-lactam and other antibiotics that had lost their activity against the drug-resistant bacterial strain. Our findings suggest that the transmembrane transport of Zn2+ by QN derivatives could be a promising strategy to combat bacterial infections and restore the activity of other antibiotics.

Salinomycin alleviates osteoarthritis progression via inhibiting Wnt/β-catenin signaling

Osteoarthritis (OA) is the most prevalent degenerative whole-joint disease characterized by cartilage degeneration, synovial hyperplasia, osteophyte formation, and subchondral bone sclerosis. Currently there are no disease-modifying treatments available for OA because its etiology and pathogenesis are largely unknown. Here we report that a natural carboxylic polyether ionophore that is used as an anti-tumor drug, salinomycin (SAL), may be a promising therapeutic drug for OA in the future. We found that SAL showed no cytotoxicity on mouse chondrocytes and displayed a protective effect against interleukin-1β (IL-1β), in cultured mouse chondrocytes and cartilage explants. Treatment with low SAL concentrations directly upregulated the anabolism factors collagen II and aggrecan, while it inhibited the catabolic factors matrix metalloproteinase-13 (MMP13) and metalloproteinase with thrombospondin motifs-5 (ADAMTS5) to protect against extracellular matrix (ECM) degradation, and also suppressed inflammatory responses in mouse chondrocytes. Furthermore, SAL reduced the severity of OA-associated changes and delayed cartilage destruction, subchondral bone sclerosis, and osteophyte formation in a destabilized medial meniscus (DMM) surgery-induced mouse OA model. Mechanistically, a low SAL concentration induced anabolism and inhibited catabolism in chondrocytes via inhibiting Lrp6 phosphorylation and Wnt/β-catenin signaling. Our results suggested that SAL may serve as a potential disease-modifying therapeutic against OA pathogenesis.

The Zinc Ionophore Clioquinol Reduces Parkinson's Disease Patient-Derived Brain Extracts-Induced Neurodegeneration

Parkinson's disease (PD) is pathologically characterized by intracellular α-synuclein-rich protein aggregates, named Lewy bodies (LB), and by the progressive loss of dopaminergic neurons in the substantia nigra. Several heavy metals, including zinc (Zn), have been suggested to play a role in PD progression, although the exact role of Zn in neurodegeneration remains to be fully elucidated. To address this gap, we investigated the effects of Zn modulation on the progression of degeneration in mice injected with PD patient-derived LB-extracts carrying toxic α-synuclein aggregates. Zn modulation was achieved using either a clioquinol-enriched diet, a Zn ionophore that redistributes cellular Zn, or a Zn-enriched diet that increases Zn levels. Clioquinol treatment significantly prevented dopaminergic neurodegeneration and reduced α-synuclein-associated pathology in LB-injected mice, while no differences were observed with Zn supplementation. Biochemical analyses further demonstrate that the expression levels of vesicle-specific Zn transporter ZnT3 in the striatum of LB-injected mice treated with clioquinol were decreased, suggesting an intracellular redistribution of Zn. Additionally, we found that clioquinol modulates the autophagy-lysosomal pathway by enhancing lysosomal redistribution within the neuronal compartments. Collectively, we found that in vivo pharmacological chelation of Zn, by dampening Zn-mediated cytotoxicity, can result in an overall attenuation of PD-linked lysosomal alterations and dopaminergic neurodegeneration. The results support zinc chelation as a disease-modifying strategy for treating PD.

Evidence of Metallic and Polyether Ionophores as Potent Therapeutic Drug Candidate in Cancer Management

Cancer remains one of the most crucial human malignancies with a higher mortality rate globally, and is predicted to escalate soon. Dysregulated ion homeostasis in cancerous cells prompted the researchers to investigate further ion homeostasis impeding agents as potent anticancerous agents. Reutilization of FDA-approved non-cancerous drugs has emerged as a practical approach to developing potent, cost-effective drugs for cancer treatment. Across the globe, most nations are incapable of fulfilling the medical demands of cancer patients due to costlier cancerous drugs. Therefore, we have inclined our review towards emphasizing recent advancements in cancer therapies involving ionophores utilization in exploring potent anticancer drugs. Numerous research reports have established the significant anticancerous potential of ionophores in several pre-clinical reports via modulating aberrant cell signaling pathways and enhancing antitumor immunity in immune cells. This review has mainly summarized the most significant ion homeostasis impeding agents, including copper, zinc, calcium, and polyether, that presented remarkable potential in cancer therapeutics via enhanced antitumor immunity and apoptosis induction. Altogether, this study could provide a robust future perspective for developing cost-effective anticancerous drugs rapidly and cost-effectively, thereby combating the limitations of currently available drugs used in cancer treatment.

Can food and food supplements be deployed in the fight against the COVID 19 pandemic?

BACKGROUND

Due to lack of approved drugs and vaccines, the medical world has resorted to older drugs, produced for viral infections and other diseases, as a remedy to combat COVID-19. The accumulating evidence from in vitro and in vivo studies for SARS-CoV and MERS-CoV have demonstrated that several polyphenols found in plants and zinc- polyphenol clusters have been in use as herbal medicines have antiviral activities against viruses with various mechanisms.

SCOPE OF REVIEW

Curcumin, zinc and zinc-ionophores have been considered as nutraceuticals and nutrients showing great antiviral activities with their medicinal like activities.

MAJOR CONCLUSIONS

In this work, we discussed the potential prophylactic and/or therapeutic effects of curcumin, zinc and zinc-ionophores in treatment of viral infections including COVID-19.

GENERAL SIGNIFICANCE

Curcuminoids and Zinc classified as nutraceuticals under GRAS (Generally Recognized As Safe) by FDA can provide complementary treatment for COVID 19 patients with their immunity-boosting and antiviral properties.

Salinomycin inhibits proliferative vitreoretinopathy formation in a mouse model

Proliferative vitreoretinopathy (PVR) is a progressive disease that develops in a subset of patients who undergo surgery for retinal detachment repair, and results in significant vision loss. PVR is characterized by the migration of retinal pigment epithelial (RPE) cells into the vitreous cavity, where they undergo epithelial-to-mesenchymal transition and form contractile membranes within the vitreous and along the retina, resulting in recurrent retinal detachments. Currently, surgical intervention is the only treatment for PVR and there are no pharmacological agents that effectively inhibit or prevent PVR formation. Here, we show that a single intravitreal injection of the polyether ionophore salinomycin (SNC) effectively inhibits the formation of PVR in a mouse model with no evidence of retinal toxicity. After 4 weeks, fundus photography and optical coherence tomography (OCT) demonstrated development of mean PVR grade of 3.5 (SD: 1.3) in mouse eyes injected with RPE cells/DMSO (vehicle), compared to mean PVR grade of 1.6 (SD: 1.3) in eyes injected with RPE cells/SNC (p = 0.001). Additionally, immunohistochemistry analysis showed RPE cells/SNC treatment reduced both fibrotic (αSMA, FN1, Vim) and inflammatory (GFAP, CD3, CD20) markers compared to control RPE cells/DMSO treatment. Finally, qPCR analysis confirmed that Tgfβ, Tnfα, Mcp1 (inflammatory/cytokine markers), and Fn1, Col1a1 and Acta2 (fibrotic markers) were significantly attenuated in the RPE cells/SNC group compared to RPE/DMSO control. These results suggest that SNC is a potential pharmacologic agent for the prevention of PVR in humans and warrants further investigation.

Zinc sulfate in combination with a zinc ionophore may improve outcomes in hospitalized COVID-19 patients

Introduction. COVID-19 has rapidly emerged as a pandemic infection that has caused significant mortality and economic losses. Potential therapies and prophylaxis against COVID-19 are urgently needed to combat this novel infection. As a result of in vitro evidence suggesting zinc sulphate may be efficacious against COVID-19, our hospitals began using zinc sulphate as add-on therapy to hydroxychloroquine and azithromycin.Aim. To compare outcomes among hospitalized COVID-19 patients ordered to receive hydroxychloroquine and azithromycin plus zinc sulphate versus hydroxychloroquine and azithromycin alone.Methodology. This was a retrospective observational study. Data was collected from medical records for all patients with admission dates ranging from 2 March 2020 through to 11 April 2020. Initial clinical characteristics on presentation, medications given during the hospitalization, and hospital outcomes were recorded. The study included patients admitted to any of four acute care NYU Langone Health Hospitals in New York City. Patients included were admitted to the hospital with at least one positive COVID-19 test and had completed their hospitalization. Patients were excluded from the study if they were never admitted to the hospital or if there was an order for other investigational therapies for COVID-19.Results. Patients taking zinc sulphate in addition to hydroxychloroquine and azithromycin (n=411) and patients taking hydroxychloroquine and azithromycin alone (n=521) did not differ in age, race, sex, tobacco use or relevant comorbidities. The addition of zinc sulphate did not impact the length of hospitalization, duration of ventilation or intensive care unit (ICU) duration. In univariate analyses, zinc sulphate increased the frequency of patients being discharged home, and decreased the need for ventilation, admission to the ICU and mortality or transfer to hospice for patients who were never admitted to the ICU. After adjusting for the time at which zinc sulphate was added to our protocol, an increased frequency of being discharged home (OR 1.53, 95 % CI 1.12-2.09) and reduction in mortality or transfer to hospice among patients who did not require ICU level of care remained significant (OR 0.449, 95 % CI 0.271-0.744).Conclusion. This study provides the first in vivo evidence that zinc sulphate may play a role in therapeutic management for COVID-19.

Structures and properties of naturally occurring polyether antibiotics

Polyether ionophores represent a large group of natural, biologically active substances produced by Streptomyces spp. They are lipid soluble and able to transport metal cations across cell membranes. Several of polyether ionophores are widely used as growth promoters in veterinary. Polyether antibiotics show a broad spectrum of bioactivity ranging from antibacterial, antifungal, antiparasitic, antiviral, and tumour cell cytotoxicity. Recently, it has been shown that some of these compounds are able to selectively kill cancer stem cells and multidrug-resistant cancer cells. Thus, they are recognized as new potential anticancer drugs. The biological activity of polyether ionophores is strictly connected with their molecular structure; therefore, the purpose of this paper is to present an overview of their formula, molecular structure, and properties.

Correction of failed fertilization despite intracytoplasmic sperm injection with oligoasthenoteratozoospermia but with acrosomes present by oocyte activation with calcium ionophore--case report

PURPOSE

To determine if fertilization and embryo cleavage can be achieved by artificial oocyte activation in circumstances of repeated failed fertilization with sperm that have an acrosome.

METHODS

A woman with three IVF cycles with intracytoplasmic sperm injection (ICSI) failed to fertilize any eggs. The sperm had severe oligoasthenoteratozoospermia with no sperm with normal morphology. In the fourth IVF cycle fertilization was evaluated by performing ICSI with the husband's sperm and egg activation with calcium ionophore, ICSI with the husband's sperm without artificial oocyte activation, and ICSI with donor sperm.

RESULTS

Five mature oocytes were retrieved. Of the four eggs having ICSI with the husband's sperm only one of the two activated by calcium ionophore fertilized and resulted in a cleaved day 3 embryo. Interestingly, the one egg fertilized by donor sperm did not fertilize.

CONCLUSIONS

The data could be consistent with conclusions that in some cases the failure to fertilize may be related to an oocyte activation factor/receptor problem in the oocyte that can be overcome by the use of calcium ionophore.

[Cryptosporidiosis in newborn calves in Ankara region: clinical, haematological findings and treatment with Lasalocid-NA]

In the first part of the present study, a total of 109 faeces samples collected from calves suffering from diarrhoea were examined for Cryptosporidium parvum oocytes and 39 (35.8%) of them were found to be positive. On the basis of oocyte counts, 14 (36%) samples were assessed as mildly infected and 25 (64%) samples as heavily infected. The occurrence of the disease was more common in winter (56.4%) than during other seasons (autuma 0%, summer 15.4% spring 28.2%. In the present study, the ionophore polyetherantibiotic Lasalocid-Na, that is licensed as a feed additive (Bovatec, 15% Lasalocid-Na, Roche AG) in Turkey, was administered to 11 calves naturally infected with Cryptosporidium and its therapeutic effect was evaluated. Lasalocid-Na (8 mg/ kg BW) was given once daily for 3 days added to the milk. The clinical parameters of infected calves were evaluated before and 3 days after the treatment in 24 hour intervals. The oocyst counts of faeces of calves with cryptosporidiosis were between 15 x 10(6) and 96 x 10(6)/mL before treatment. No oocystes were found in faecal samples of 3 calves (27.3%) after 48 hours and 4 (40%) calves after 72 hours of treatment, respectively. The number of oocytes in the faeces of the remaining calves varied between 90 and 1.2 x 10(6)/mL during the respective period. The number of oocystes before treatment was significantly higher than the number of oocytes after treatment. One of the calves died 56 h after the first treatment despite the treatment. The pH of venous blood was decreased prior to treatment as expected. The lowest pH was 6.83, the lowest bicarbonate concentration was 3.80 mmol/l and the lowest base excess was -31.2 mmol/l. After the treatment, pH, pCO2, HCO3- and BE values of the venous blood increased significantly and reached physiological values before discharge. The differences between the values assessed before the treatment and at the 2nd, 3rd, and 4th sampling time were statistically significant. Number of leucocyte and haemoglobin concentration before the treatment were significantly higher than the values after treatment (p < 0.01). These values returned back to physiological ranges 72 hours after first treatment. Lasalocid-Na was rather well tolerated. Side effects such as the decline of the suckling reflex and intoxication symptoms in respect to present administration form and dosage were found only in one calf (9%). Treatment procedure in the present study with Lasalocid-Na was found to be suitable in combination with an adequate infusion therapy for the treatment of calves on farms with problems related to cryptosporidiosis. Although the use of Lasolacid-Na for the treatment of Cryptosporidium infection in the EU is banned, it might be used as an alternative drug outside of the EU since it has a successful effect for preventing reinfections.

Effect of ionophore monensin on anaesthetized dogs in hemorrhagic hypotension

AIM

Progressive decompensation and irreversible cellular injury from the severe hemorrhagic shock can be reversed therapeutically with aggressive and timely resuscitation by administering volume expanding fluids. The possibility of the use of rapidly acting pressor agents which can effectively maintain the blood pressure and peripheral perfusion (without volume resuscitation) and prevent the progression of shock and providing in regular time interval for volume replacement has not been looked into. In the present investigation, two pressor agents, dopamine and a long acting carboxylic ionophore monensin, were examined for their potential role in hemorrhagic hypotension produced experimentally in dogs.

METHODS

Two groups of animals were studied: (a) In the first group (n=10) 20% of the total blood volume i.e. moderate hemorrhage was induced. (b) In the second group (n=10) 35% of the total blood volume i.e. severe hemorrhage was induced. After 30 min of induction of hemorrhage both the groups were given intravenous infusion of dopamine (20 microgm/kg/min) for 10 min. Then after 30 min of stopping dopamine infusion, both the groups were given intravenously a single bolus dose (50 microgm/kg) of monensin.

RESULTS

In both moderate and severe hemorrhage monensin injection produced significant increases in systolic arterial blood pressure, mean arterial blood pressure, cardiac output and stroke volume. The effects persisted for 1 h of administration. In severe hemorrhage dopamine infusion produced significant decrease in mean arterial blood pressure, diastolic blood pressure and pH. Dopamine produced a significant rise in heart rate also while monensin did not have such an effect.

CONCLUSION

Monensin produced a rapid and sustained recovery of the arterial blood pressure without requiring adequate preload. Dopamine failed to produce such an effect because it requires adequate circulating blood volume for its pressor action. Thus monensin has the potential to prevent progression of shock and improving the prognosis in management of hemorrhagic hypotension.

Successful fertilization and pregnancy after intracytoplasmic sperm injection and oocyte activation with calcium ionophore in a normozoospermic patient with extremely low fertilization rates in intracytoplasmic sperm injection cycles

OBJECTIVE

To investigate the effect of calcium ionophore on the fertilization rate of a patient with normozoospermia who nonetheless exhibited a low fertilization rate in intracytoplasmic sperm injection (ICSI).

DESIGN

Case report.

SETTING

In vitro fertilization center.

PATIENT(S)

A male patient whose sperm, though diagnosed as normal by semen analysis, exhibited a severely low fertilization rate in ICSI cycles.

INTERVENTION(S)

Oocytes were activated by calcium ionophore after ICSI.

MAIN OUTCOME MEASURE(S)

Fertilization rate after oocyte activation; ultrastructure and protein expression of the patient's sperm.

RESULT(S)

The fertilization rate of oocytes activated with calcium ionophore (12 of 15, 80.0%) was higher than that of the nonactivated oocytes (4 of 16, 25.0%). Four embryos derived from the activated oocytes were transferred, resulting in a twin pregnancy. Further investigation revealed abnormalities in the patient's sperm: many nuclear vacuoles were observed and the expression of some proteins was absent.

CONCLUSION(S)

Oocyte activation with calcium ionophore was effective at increasing the fertilization rate of dysfunctional sperm characterized by ultrastructural and protein expression anomalies.

Pregnancy following chemical activation of oocytes in a couple with repeated failure of fertilization using ICSI: Case report

We report our attempts to achieve a successful pregnancy outcome with calcium ionophore A23187 and puromycin oocyte activation using sperm from a normozoospermic husband of a patient with previous repeated failed fertilization following ICSI. Oocytes from the female partner of a couple with a 4 year history of unexplained primary infertility with repeated failed fertilization following ICSI were used. In the latest ICSI attempt, oocytes were activated by treatment with calcium ionophore (5 min) and puromycin (5 h), then cultured. In this cycle, assisted oocyte activation with calcium ionophore and puromycin after ICSI resulted in a satisfactory fertilization rate (8/12; 66.7%); in prior cycles only one of 71 oocytes (1.4%) was fertilized. The outcome was a Caesarean section delivery of a healthy male infant without congenital abnormalities at 41 weeks, 2 days of gestation. In conclusion, the use of calcium ionophore and puromycin for oocyte activation was found to be a useful method in a case of repeated failed fertilization after ICSI.

Short Communication: Effects of a Monensin Premix on Milk Fatty Acid Content During Subacute Ruminal Acidosis in Dairy Cows

The effects of a monensin premix on milk fatty acid content during grain-induced subacute ruminal acidosis (SARA) in Holstein cows receiving a total mixed ration was investigated. Six multiparous, rumen-fistulated Holstein cows were used in a two-treatment, two-period crossover design with 6-wk periods. Experimental treatments were either a monensin premix or a placebo premix. At the beginning of wk 4, SARA was induced in experimental cows for a 10-d period using a grain challenge model. The administration of a monensin premix elevated milk fat proportion of total short-chain saturated fatty acids (sum of C4 to C15). Milk fat proportions of conjugated linoleic acid isomers were unaffected. Linolenic acid (C18:3n3) proportion in milk fat of monensin-treated cows were lower when compared with placebo-treated cows during the SARA period. Results from this study indicate that dietary supplementation with monensin during SARA had little effect on milk fatty acid content.

Ionophores: their use as ruminant growth promotants and impact on food safety

Ionophores (such as monensin, lasalocid, laidlomycin, salinomycin and narasin) are antimicrobial compounds that are commonly fed to ruminant animals to improve feed efficiency. These antimicrobials specifically target the ruminal bacterial population and alter the microbial ecology of the intestinal microbial consortium, resulting in increased carbon and nitrogen retention by the animal, increasing production efficiency. Ionophores transport ions across cell membranes of susceptible bacteria, dissipating ion gradients and uncoupling energy expenditures from growth, killing these bacteria. Not all bacteria are susceptible to ionophores, and several species have been shown to develop several mechanisms of ionophore resistance. The prophylactic use of antimicrobials as growth promotants in food animals has fallen under greater scrutiny due to fears of the spread of antibiotic resistance. Because of the complexity and high degree of specificity of ionophore resistance, it appears that ionophores do not contribute to the development of antibiotic resistance to important human drugs. Therefore it appears that ionophores will continue to play a significant role in improving the efficiency of animal production in the future.

Effect of 3M™ Coban™ Self-Adherent Wraps on Edema and Function of the Burned Hand: A Case Study

Edema and limited function are common acute problems associated with hand burns. This case study examined the effects of 3M Coban Self-Adherent Wraps on edema and function in a 59-year-old male (46% TBSA flame injury) with newly skin grafted dorsally burned hands. At the time of each dressing change, circumferential measurements were taken of both hands and weekly active range of motion and grip strength measurements were recorded. The nine-hole peg test was used to appraise dexterity. During the 4-week study period, there was less edema, greater active range of motion and grip strength, and greater dexterity in the hand with 3M Coban Self-Adherent Wraps as compared with the control hand. This case study suggests that 3M Coban Self-Adherent Wraps were effective in reducing edema in the skin-grafted hand after skin grafting. It further appeared that the reduced edema may have contributed to improved hand function and that 3M Coban Self-Adherent Wraps as a compressive dressing do not impede hand function

Prepartum monensin for the reduction of energy associated disease in postpartum dairy cows

A total of 1317 Holstein cows from 45 farms in the Canadian provinces of Quebec, Prince Edward Island (PEI) and Ontario were enrolled in a randomized trial during 1998 and 1999 to further confirm the efficacy of a monensin controlled release capsule in preventing periparturient disease in lactating dairy cows. Cows were randomized on the farms to receive either a monensin controlled release capsule (CRC) 2 to 4 wk before expected calving or to serve as negative controls. Health data were collected for 90 d postcalving and were analyzed with logistic regression accounting for the intraherd correlation with generalized estimating equations. Monensin CRC significantly reduced the incidence of both clinical ketosis and abomasal displacement post-calving. There was a numerical but nonsignificant decrease in the incidence of retained placenta in cows receiving a monensin CRC. A pooled analysis of two separate but similar studies (conducted in 1995 and 1998) demonstrated a strengthened association between monensin CRC administration precalving and reduced periparturient disease. A 40% reduction in both abomasal displacement and clinical ketosis was observed with precalving administration of a monensin CRC. In addition, the larger dataset highlighted a trend for a 25% reduction in the incidence of retained placenta in monensin-treated cows. Improved energy metabolism as a result of monensin treatment is likely the mechanism for the reduction in incidence of all three of these diseases. Thus the term "energy associated disease" was created to assess the combined impact of the precalving monensin treatment on the incidence of retained placenta, displaced abomasum, and clinical ketosis. The monensin controlled release capsule reduced the incidence of energy associated disease by 30%.

Study of resistance against some ionophores in Eimeria tenella field isolates

Three Eimeria tenella field isolates from Gurgaon district of Haryana (north India) were studied in a battery test for evaluating drug resistance against two currently used ionophores; maduramicin (5ppm) and salinomycin (60ppm). Broiler birds (Ross strain) were infected with 10(5) sporulated oocysts each at the age of 2 weeks and prophylactic medication commenced 2 days prior to infection. Drug resistance was assessed by calculating the global index for individual ionophore compounds based on weight gain, feed conversion ratio, oocyst index, lesion score and mortality. Present studies revealed no resistance of the ionophores in any of the field isolates. Both the drugs showed varying degree of efficacy, e.g. maduramicin exhibited limited efficacy against all the three field isolates, whereas salinomycin showed limited efficacy against Gurgaon isolate (GrI)-I, good efficacy against GrI-II and partial resistance against GrI-III.

Use of Anticoccidial Drugs in Broiler Chickens in the USA: Analysis for the Years 1995 to 1999

Data collected by Agri Stats Inc. in the US for the years 1995 to 1999 was evaluated to determine the types of anticoccidial drug programs used by broiler plants, their frequency and duration, and whether there was any correlation with performance of the birds. Information was available for five feed types (prestarter, starter, grower, first withdrawal, and final withdrawal). The most popular program was an ionophore (ION; principally salinomycin) in starter and grower feeds. A chemical (principally nicarbazin) was also used in the starter feed followed by an ION in the grower feed, or two different ION in the starter and grower feeds. Seasonal differences were apparent in the type of program and in the frequency of program changes. There was no consistent pattern in the sequence with which different programs were employed. There were no significant differences in calorie conversion or the number of days to produce a 2.27 kg bird, whether a single ION or a chemical followed by an ION was used, but mortality was significantly higher for the latter. For 1999, calorie conversion and mortality were higher in plants where chemical-ION programs had been used for more than 40% of the time during the previous 4 yr. The duration and frequency with which different programs were employed were similar whether birds were raised to final weights of 1.5 to 2.0 kg, 2.0 to 2.5 kg, or more than 2.5 kg. There were significant differences in the use of salinomycin and nicarbazin in different regions of the US.

Synergistic antitumor effect of ionomycin and cisplatin against renal cell carcinoma in vitro and in vivo

Objectives. To characterize the synergistic antitumor effects of the calcium ionophore, ionomycin, and of cisplatin against human renal cell carcinoma cell line, ACHN, both in vitro and in vivo.Methods. The in vitro growth rate of ACHN after exposure to these compounds was measured, using the MTT assay. The apoptotic features in ACHN were evaluated by DNA ladder analysis and flow cytometric analysis. Bcl-2 and Bax expression levels in ACHN after treatment were examined by Western blot. The synergistic antitumor effects of ionomycin and cisplatin against the growth of established ACHN tumors in athymic nude mice were then tested.Results. The in vitro growth rate of ACHN was suppressed more by ionomycin and cisplatin in combination than by either alone. DNA ladder and fragmentation were more obvious when the cells were incubated with ionomycin and cisplatin together than with either reagent alone. Ionomycin treatment increased the expression level of Bax protein, whereas Bcl-2 expression was not influenced. Although an intraperitoneal injection of cisplatin or an intratumoral injection of ionomycin against subcutaneous ACHN tumors somewhat reduced tumorigenicity in nude mice, the effect was significantly enhanced by a combination of these drugs.Conclusions. The synergistic antitumor effects suggest that ionomycin-based therapy could be a novel therapeutic strategy with which to treat advanced renal cell carcinoma.

Reduced incidence of Clostridium perfringens-associated lesions and improved performance in broiler chickens treated with normal intestinal bacteria from adult fowl

The dosing of young chicks with cultures of normal gut flora has been termed "competitive exclusion" (CE). This study was undertaken to examine, under field conditions, the effect of CE treatment on counts of intestinal Clostridium perfringens (CP) and on the occurrence of CP-associated disease in broiler chickens. A farm having recurrent CP-associated health problems was selected as study site. The study comprised four broiler houses, with one treated and one untreated flock per house. Treated birds were sprayed with the CE product Broilact upon arrival at the farm. All flocks were offered feed containing the ionophorous anticoccidial agent narasin. The feed did not contain growth promoters. Treatment was associated with positive but statistically nonsignificant effects on gut health. Delayed intestinal proliferation of CP and delayed appearance of CP-associated gut lesions were found in CE-treated flocks. This delay was associated with improved production performance at slaughter.

Use of ionophores in lactating dairy cattle: a review

Ionophores are feed additives that alter rumen microbial populations through ion transfer across cell membranes. Although ionophores have been used widely in the beef industry for improved feed efficiency and control of coccidiosis, there has been limited use by the dairy industry. In Canada, the label warning prohibiting the use of monensin premix in lactating dairy cattle was removed in June 1996. Following this, in December 1997, a controlled release capsule containing monensin was approved for use in dairy cattle as an aid to prevent subclinical ketosis. Monensin may have several advantages for dairy cattle, including improved energy metabolism, increased milk production, and altered milk components. This literature review was primarily conducted in 1996 by using the Agricola and CAB search databases. Other relevant articles published since the search (up to 1998) have been added. This review will provide practitioners with relevant references in the published literature regarding ionophore use in dairy cattle. It should also give some guidance as to what effects might be anticipated with the use of ionophores in lactating dairy animals.

Tissue factor de-encryption: ionophore treatment induces changes in tissue factor activity by phosphatidylserine-dependent and -independent mechanisms

Coagulation is initiated on tissue-factor-bearing cells when factor VIIa complexes with membrane-bound tissue factor and activates factors X and IX. Cellular tissue factor activity does not correlate with tissue factor antigen; treatment with calcium ionophore rapidly increases tissue factor activity without increasing tissue factor antigen. Our study examined the effect of calcium ionophore A23187 on tissue factor activity of freshly isolated, lipopolysaccharide-stimulated monocytes and non-transformed human dermal fibroblasts. A23187 increased tissue factor activity on monocytes and fibroblasts in a dose-dependent fashion between 0.1 and 50 micromol/l ionophore. This increase in activity was proportional to an increase in intracellular calcium in monocytes. The increase in tissue factor activity was partially attributable to an increase in phosphatidylserine expression, as measured by increased prothrombinase activity (1.1- to 4-fold) on ionophore-treated cells. The phosphatidylserine-binding protein annexin V decreased tissue factor activity on both ionophore-treated and untreated cells, reflecting the role of phosphatidylserine in tissue factor activity. However, even in the presence of saturating concentrations of annexin V, the tissue factor activity of ionophore-treated cells was 1.3- to 11.3-fold higher than that of untreated cells, indicating that the increase in tissue factor activity did not result solely from increased expression of phosphatidylserine. A23187 increased tissue-factor-dependent activation of factors IX and X 1.4- to 7-fold on both cell types, indicating that ionophore treatment did not alter factor VIIa/tissue factor substrate specificity. We conclude that the mechanism by which calcium ionophore increases tissue factor activity is not unique to monocytoid or transformed cells. Furthermore, the ionophore-induced increase in activity is not solely the result of increased exposure to phosphatidylserine. Finally, tissue factor de-encryption by A23187 does not alter factor VIIa/tissue factor substrate specificity.

Diverse stimuli induce calpain overexpression and apoptosis in C6 glioma cells

Calpain, a Ca2+-activated cysteine protease, has been implicated in apoptosis of immune cells. Since central nervous system (CNS) is abundant in calpain, the possible involvement of calpain in apoptosis of CNS cells needs to be investigated. We studied calpain expression in rat C6 glioma cells exposed to reactive hydroxyl radical (.OH) [formed via the Fenton reaction (Fe2++H2O2+H+-->Fe3++H2O+.OH)], interferon-gamma (IFN-gamma), and calcium ionophore (A23187). Cell death, cell cycle, calpain expression, and calpain activity were examined. Diverse stimuli induced apoptosis in C6 cells morphologically (chromatin condensation as detected by light microscopy) and biochemically [DNA fragmentation as detected by TdT-mediated dUTP Nick-End Labeling (TUNEL) assay]. Oxidative stress arrested a population of C6 cells at the G2/M phase of cell cycle. The levels of mRNA expression of six genes were analyzed by the reverse transcriptase-polymerase chain reaction (RT-PCR). Diverse stimuli did not alter beta-actin (internal control) expression, but increased calpain expression, and the upregulated bax (pro-apoptotic)/bcl-2 (anti-apoptotic) ratio. There was no significant increase in expression of calpastatin (endogenous calpain inhibitor). Western blot analysis showed an increase in calpain content and degradation of myelin-associated glycoprotein (MAG), a calpain substrate. Pretreatment of C6 cells with calpeptin (a cell-permeable calpain inhibitor) blocked calpain overexpression, MAG degradation, and DNA fragmentation. We conclude that calpain overexpression due to.OH stress, IFN-gamma stimulation, or Ca2+ influx is involved in C6 cell death, which is attenuated by a calpain-specific inhibitor.

Comparison between a live, attenuated anticoccidial vaccine and an anticoccidial ionophore, on performance of broilers raised with or without a growth promoter, in an initially Eimeria-free environment

An experiment was carried out to study the effects of vaccination with Paracox, a live, attenuated vaccine against avian coccidiosis, on broilers isolated from extraneous Eimeria parasites. The study involved 3200 broiler chickens raised in floor pens similar to commercial conditions, but in an initially Eimeria-free environment. Forty percent of the chickens were vaccinated at 3 days of age and given either a basal unmedicated feed or a feed supplemented with the feed antibiotic virginiamycin. Unvaccinated birds were given either the basal feed or feed supplemented either with virginiamycin or the anticoccidial ionophore narasin. At slaughter at 36 days of age vaccinated birds had a lower live weight than non-vaccinated birds. The difference was 4.6% in unmedicated, and 6.0% in virginiamycin medicated chickens. Feed conversion ratio at slaughter was 2.5% higher for unmedicated vaccinated birds, and 1.3% higher for virginiamycin medicated vaccinated birds, compared to respective non-vaccinated groups. There was no significant difference in overall performance of unvaccinated birds given narasin as compared to virginiamycin. At 10 days post vaccination vaccinated birds had a higher number of Clostridium perfringens in the caeca, but there was no difference thereafter. Throughout the experiment, caecal clostridial counts were considerably higher in vaccinated unmedicated birds than in unvaccinated birds given narasin. The number of oocysts shed in the vaccinated groups was very low, but during a subsequent challenge with E. maxima and E. tenella the birds' immunity was found to be satisfactory.

Multiple and multigeneric anthelmintic resistance on a sheep farm in Kenya

The anthelmintic efficacy of benzimidazoles (albendazole, fenbendazole and oxfendazole), levamisole, oral ivermectin and closantel was evaluated on a farm in Kenya using faecal egg count reduction test, larval cultures and a controlled slaughter trial. The results of this study indicated simultaneous resistance of Haemonchus contortus against benzimidazoles, levamisole and ivermectin, and of Trichostrongylus colubriformis and Oesophagostomum spp. against levamisole on the same farm. Ivermectin resistance developed to 47% within 15 months of first use. Closantel was effective against the benzimidazoles, levamisole and ivermectin resistant H. contortus.

Comparative efficacy of anticoccidials under the conditions of commercial broiler production and in battery trials

Coccidia were isolated from a commercial broiler farm with a history of suspected drug resistance. The sensitivity profiles of the Eimeria spp. isolates against the anticoccidial drugs nicarbazin (NIC), narasin (NAR), halofuginone (HAL), salinomycin (SAL), meticlorpindol plus methylbenzoquate (MET), and monensin (MON) at the recommended dose levels were followed in three battery trials (B1, B2, B3) corresponding to a field study over three periods of commercial broiler keeping (F1, F2, F3). Shuttle programs were performed in F1 (NIC/MON) and in F2 (MET/MON) while only SAL was used in F3. Eimeria acervulina and E. tenella were isolated from indicator birds in F1 while only E. acervulina could be found during F2 and F3. In trial B1 the isolate from F1 was identified as resistant against HAL and partly resistant against NIC and MON, the two drugs that were used in F1. Following the replacement of NIC in the starter feed by MET the respective isolate from F2 showed no resistance against ionophores (trial B2) while partial resistance against HAL was still present. Since SAL was the most efficient drug in B1 and B2 only this drug was applied in F3. Apart from a resistance against HAL no resistance against any of the other tested anticoccidials was found in the isolate from F3. SAL controlled coccidiosis efficiently in the field and best productivity was recorded in F3. This study shows that battery trials have a good predictive value in respect to the efficacy of anticoccidials under the conditions of commercial broiler production.

Calcium ionophore-induced acrosome reaction correlates with fertilization rates in vitro in patients with teratozoospermic semen

The aim of this study was to determine the relationship between calcium ionophore A23187-induced acrosome reaction (AR) and sperm fertilizing ability. Semen samples remaining after preparation for standard IVF were studied in 109 patients who had sperm concentrations > or =20 x 10(6)/ml. Ionophore-induced AR was performed on motile spermatozoa selected by centrifugation on a Percoll gradient. Semen analysis was performed using standard methods. Patients with higher (>50%, n = 76) fertilization rates had significantly higher ionophore-induced AR than patients with lower (<50%, n = 33) fertilization rates (49 +/- 14 versus 38 +/- 21%, P < 0.05). When the data from all patients were analysed by logistic regression, only the percentage sperm motility in insemination medium and ionophore-induced AR were significantly related to fertilization rates. Similar results were also obtained when the data from a subgroup of patients with poor (<15% normal) sperm morphology were analysed. However, when patients with normal sperm morphology > or =15% were analysed separately, only sperm count and the percentage of spermatozoa with progressive motility in semen were significantly related to fertilization rates. In conclusion, ionophore-induced AR was significantly related to fertilization rates in vitro mainly in patients with teratozoospermic semen. Tests for ionophore-induced AR may provide additional information about sperm fertilizing ability but may not indicate specific defects of the physiological AR.

Sheep fed grain prefer foods and solutions that attenuate acidosis

We conducted experiments to determine whether lambs fed grain prefer foods and solutions containing sodium bicarbonate (NaHCO3) and lasalocid, compounds capable of attenuating acidosis. In Exp. 1, we determined whether lambs fed barley preferred flavored rabbit pellets (RP) containing NaHCO3 and lasalocid. Lambs in two groups (n = 10/group) were fed increasing amounts of barley on d 1 to 12 (300 to 1,100 g) and again on d 23 to 34 (300 to 1,350 g). After ingesting barley on d 1 to 12, lambs were fed ground RP containing lasalocid and NaHCO3 (i.e., medicated) and flavored with either 2% onion (group 1) or 2% oregano (group 2). During d 23 to 34, lambs were fed unmedicated RP containing NaCl and flavored with either 2% oregano (group 1) or 2% onion (group 2). During preference tests on d 35 to 40, lambs fed grain preferred RP with NaHCO3 to RP with NaCl (151 vs. 96 g; P < .01). In the Exp. 2, we determined whether wheat ingestion affected consumption of aqueous solutions containing NaHCO3. In trial 1, 28 lambs were assigned to four treatments: 1) low-wheat + 2% NaHCO3, 2) high-wheat + 2% NaHCO3, 3) low-wheat + water, and 4) high-wheat + water. For 12 d from 0800 to 0830, lambs in treatments 1 and 3 were fed 300 g of wheat and lambs in treatments 2 and 4 were fed up to 1,300 g of wheat; fluids (NaHCO3 and water) were then offered from 0930 to 1230 daily. Lambs drank more NaHCO3 on the high- than on the low-wheat diet (1,332 vs 890 g; P = .03); water consumption was similar for lambs on the high- and low-wheat diets (1,675 vs 1,700 g; P > .10). In trial 2, lambs in treatments 3 and 4 were offered a solution containing 1.4% NaCl. For 13 d from 0800 to 0830, lambs in treatments 1 and 3 were fed 500 g of wheat and lambs in treatments 2 and 4 were fed up to 1,700 g of wheat. Lambs had access to fluids from 0800 to 1200 daily. Lambs drank nearly twice as much NaHCO3 solution on the high- than on the low-wheat diet (1,066 vs 572 g), whereas they drank only 1.4 times more NaCl solution on the high- than on the low-wheat diet (888 vs. 634 g; P < .001). Fewer lambs showed signs of acidosis in treatment 2 than in treatment 4 in trials 1 (2 vs 9) and 2 (7 vs 17). Collectively, these results are consistent with the hypothesis that lambs fed grain prefer substances that attenuate acidosis.

Effect of antibiotic growth promoters and anticoccidials on growth of Clostridium perfringens in the caeca and on performance of broiler chickens

The effects of the growth promoters avoparcin and avilamycin and the ionophore anticoccidials maduramicin, narasin and monensin on the growth of Clostridium perfringens (Cp) in the caeca and on performance of broiler chickens were tested in 2 experiments. The supplements were fed as single feed additives or in some combinations. No clinical signs or lesions caused by coccidia were observed in any of the studies. All supplements had an antibacterial effect on Cp and improved growth rate significantly. Carcass yield of birds fed growth promoters avilamycin or avoparcin was significantly higher compared with birds fed anticoccidials. These data indicate that, what concerns bird performance, during good hygienic conditions supplementation with antibiotic growth promoters may not be necessary when the diet is supplemented with an anticoccidial with antibacterial effects.

Dissociation between intracellular calcium elevation and development of human oocytes treated with calcium ionophore

OBJECTIVE

To develop an acceptable model system to study calcium activation of human oocytes.

DESIGN

Study of oocyte development and intracellular calcium [Ca]i dynamics of activated oocytes.

SETTING

Research center affiliated with infertility service.

MAIN OUTCOME MEASURE

Morphologic evidence of meiotic maturation and cell division under high-power Hoffman optics with an inverted microscope. Meiotic maturation was determined by the number of polar bodies or the presence of a pronucleus, and cell division was determined by evidence of a cleavage furrow or presence of blastomeres. To monitor the effect of calcium ionophore on [Ca]i levels, oocytes were incubated with fura-2 (2 microM) for 30 minutes and [Ca]i was determined by rationing the emission fluorescence (510-nm long-pass filter) during simultaneous excitation at 340 and 380 nm with a microspectrofluorimeter.

RESULT(S)

All oocytes loaded with fura-2 and then exposed to ionophore exhibited an isolated elevation of [Ca]i, followed by prompt return to baseline levels. None of the oocytes showed signs of cleavage or of meiotic maturation after treatment with calcium ionophore.

CONCLUSION(S)

Human oocytes activated with calcium ionophore A23187 or ionomycin exhibited elevated [Ca]i but remained resistant to subsequent meiotic maturation and cleavage. Our results differ from some reports of parthenogenetic activation of human oocytes. These differences may result from different activation protocols or culture conditions. Because none of the 126 oocytes cleaved after the activation protocols used in these experiments, this approach should provide an ethically acceptable model system to study calcium dynamics in human oocytes.

Modes of action of anthelmintic drugs

Modes of action of anthelmintic drugs are described. Some anthelmintic drugs act rapidly and selectively on neuromuscular transmission of nematodes. Levamisole, pyrantel and morantel are agonists at nicotinic acetylcholine receptors of nematode muscle and cause spastic paralysis. Dichlorvos and haloxon are organophosphorus cholinesterase antagonists. Piperazine is a GABA (gamma-amino-butyric acid) agonist at receptors on nematode muscles and causes flaccid paralysis. The avermectins increase the opening of glutamate-gated chloride (GluCl) channels and produce paralysis of pharyngeal pumping. Praziquantel has a selective effect on the tegument of trematodes and increases permeability of calcium. Other anthelmintics have a biochemical mode of action. The benzimidazole drugs bind selectively to beta-tubulin of nematodes, cestodes and fluke, and inhibit microtubule formation. The salicylanilides: rafoxanide, oxyclozanide, brotianide and closantel and the substituted phenol, nitroxynil, are proton ionophores. Clorsulon is a selective antagonist of fluke phosphoglycerate kinase and mutase. Diethylcarbamazine blocks host, and possibly parasite, enzymes involved in arachidonic acid metabolism, and enhances the innate, nonspecific immune system.

Characterization of the potent in vitro and in vivo antimalarial activities of ionophore compounds

Large-scale in vitro screening of different types of ionophores previously pinpointed nine compounds that were very active and selective in vitro against Plasmodium falciparum; their in vitro and in vivo antimalarial effects were further studied. Addition of the ionophores to synchronized P. falciparum suspensions revealed that all P. falciparum stages were sensitive to the drugs. However, the schizont stages were three- to ninefold more sensitive, and 12 h was required for complete parasite clearance. Pretreatment of healthy erythrocytes with toxic doses of ionophores for 24 to 48 h showed that the activity was not due to an irreversible effect on the host erythrocyte. No preferential ionophore adsorption in infected or uninfected erythrocytes occurred. On the other hand, ionophore molecules strongly bound to serum proteins since increasing the serum concentration from 2 to 50% led to almost a 25-fold parallel increase in the ionophore 50% inhibitory concentration. Mice infected with the malaria parasites Plasmodium vinckei petteri or Plasmodium chabaudi were successfully treated with eight ionophores in a 4-day suppressive test. The 50% effective dose after intraperitoneal administration ranged from 0.4 to 4.1 mg/kg of body weight, and the therapeutic indices were about 5 for all ionophores except monensin A methyl ether, 5-bromo lasalocid A, and gramicidin D, whose therapeutic indices were 12, 18, and 344, respectively. These three compounds were found to be curative, with no recrudescence. Gramicidin D, which presented impressive antimalarial activity, requires parenteral administration, while 5-bromo lasalocid A has the major advantage of being active after oral administration. Overall, the acceptable levels of toxicity and the good in vivo therapeutic indices in the rodent model highlight the interesting potential of these ionophores for the treatment of malaria in higher animals.

Efficacy of lasalocid against murine Pneumocystis carinii pneumonitis

The efficacy of the ionophore lasalocid against Pneumocystis carinii pneumonitis in corticosteroid-immunosuppressed Sprague-Dawley rats was investigated. Lasalocid was effective in the prevention of the pneumonitis in a dose-dependent manner. At dosages of 0, 5, 10, and 20 mg/kg/day, P. carinii infection rates were 92, 60, 20, and 0%, respectively, during dexamethasone immunosuppression. Also, lasalocid compared favorably with other drugs known to have anti-P. carinii activity, including trimethoprim-sulfamethoxazole, atovaquone, and dapsone-trimethoprim.

Magnesium attenuates the neutrophil respiratory burst in adult asthmatic patients

INTRODUCTION

IV magnesium (Mg2+) has been proposed as an emergent treatment for acute asthma exacerbations. Recent studies have focused on the effects of Mg2+ on bronchial smooth muscle, yet asthma is primarily an inflammatory disease.

OBJECTIVE

To assess the effects of Mg2+ on the neutrophil respiratory burst of adult patients with asthma.

METHODS

A prospective, blind study of volunteer adult asthmatic patients was performed. The patients' polymorphonuclear neutrophils (PMNs) were isolated, purified, and placed into phosphate-buffered saline with the following test conditions: concentrations of magnesium chloride (MgCl2) added: 0 mmol MgCl2, 1 mmol MgCl2 (low), and 10 mmol MgCl2 (high) both with and without the calcium (Ca2+) ionophore A23187 (0.1 mmol). PMNs were activated using N-formyl-methionyl-leucyl-phenylalanine (fMLP) (10 mumol), and the production of superoxide (O2-) was measured by the spectrophotometric reduction of cytochrome c.

RESULTS

Mg2+ reduced activated PMN O2- production compared with that for no Mg2+ (1.0 +/- 0.1 nmol O2-/5 x 10(5) PMN/min) in both low (-0.52* +/- 0.3 nmol O2-/5 x 10(5) PMN/min) and high (-0.76* +/- 0.3 nmol O2-/5 x 10(5) PMN/min; *p < 0.05) concentrations. The addition of A23187 increased O2- production in both the high (0.53* +/- 0.02 nmol O2-/5 x 10(5) PMN/min) and the low (1.5* +/- 0.6 nmol O2-/5 x 10(5) x 10(5) PMN/min) Mg2+ groups, with no change in the control group (1.2 +/- 0.2 nmol O2-/10(5) PMN/min).

CONCLUSIONS

In clinically relevant concentrations, Mg2+ attenuates the neutrophil respiratory burst in adult asthmatic patients. Mg2+ appears to affect PMNs by interfering with extracellular Ca2+ influx. Mg2+ may have a beneficial anti-inflammatory effect in asthmatic individuals.

Efficacy of laidlomycin propionate to reduce ruminal acidosis in cattle

Three trials were conducted to evaluate the efficacy of laidlomycin propionate (LP) to reduce the incidence and severity of ruminal acidosis in cattle fed high-grain finishing diets. In each trial, LP was fed at 0, 6, or 12 mg/kg of diet DM. In two acidosis-challenge trials, ruminally fistulated steers were fed (DM basis) a 50% concentrate diet and then fed a 95% concentrate diet at a specific intake (2.75% BW) or steers were dosed intraruminally with a 100% concentrate diet. Laidlomycin propionate did not alter ruminal pH or total acid concentrations, but in Trial 1 the 6 mg/kg level altered (P < .10) the molar proportions of the acids, increasing total ruminal VFA and decreasing ruminal lactate. In Trial 3, a finishing trial, LP reduced (P < .10) intake day-to-day variation of individually fed steers during a 13-d adaptation period from a 65 to a 100% concentrate diet, suggesting reduced incidence of subacute acidosis. Feed intake was lower (P < .05) during the first 13 d of the trial due to LP but was not affected over the entire trial. Laidlomycin propionate improved feed efficiency (gain/feed) when calculated on a live weight basis (linear, P = .05) or carcass weight basis (linear, P = .20). Laidlomycin propionate does not prevent ruminal acidosis, but it may reduce the severity of ruminal acidosis during adaptation to a 100% concentrate diet.

Potentiation of ionophorous anticoccidials with duokvin: battery trials against Cryptosporidium baileyi in chickens

Three battery tests, employing 444 Arbor Acres chickens, were conducted to study the anticryptosporidial efficacy of the polyether ionophorous anticoccidials alone and in combination with a new dihydroquinoline antioxidant, duokvin. The following efficacy percentages for the ionophores at the recommended level were established on the basis of oocyst output: lasalocid 45, monensin 37, semduramicin 29, narasin 23, and maduramicin and salinomycin 21. The efficacy of the ionophores, with the exception of lasalocid, could be increased to 36-88% by combination with duokvin. However, these combinations resulted in a significant weight gain reduction due to toxic interaction. Efficacy showed a strong negative correlation with body weight gain and bursa weight, suggesting an indirect mode of action against the parasite. It has been concluded that neither ionophorous anticoccidials nor their combinations with duokvin can be recommended for chemoprophylaxis against avian cryptosporidiosis.

Potentiation of ionophorous anticoccidials with dihydroquinolines: battery trials against Eimeria tenella in chickens

Seven battery tests, employing a total of 1344 Hybro cockerels, were conducted in order to study the interaction between ionophorous anticoccidials and a new dihydroquinoline-type antioxidant known as duokvin. A significant, non-selective, toxic interaction was established, resulting in growth depression and improved anticoccidal efficacy against Eimeria tenella and E. mitis in these chickens. The duokvin itself showed no appreciable activity against the coccidia. The adverse effects of the interaction were eliminated, and the anticoccidial efficacy of the approved levels of ionophores was maintained, when the dietary levels of monovalent cation ionophorous monensin, salinomycin and narasin were reduced to approximately 12% in the presence of 120 p.p.m. duokvin. No adverse effects on the growth of chickens appeared in the combination with maduramicin, yet the enhancement of anticoccidial activity allowed an approx. 50% reduction of this ionophore as well.

[Ketorolac protection in damage due to myocardial ischemia and reperfusion]

This study shows that the nonsteroidal anti-inflammatory drug. Ketorolac, has an ionophore-like action for calcium, such a drug may transfer calcium through an hydrophobic phase. This property does not affect the respiratory rate of mitochondria. These results indicate that the ionophoretic effect is not due to an uncoupling action of Ketorolac. The effect of this compound was tested in a reperfusion model where it was observed that Ketorolac (1 mg/Kg weight) administered 30 min before an ischemic period was induced, reverts the arrhythmic effect of reperfusion. These results are in agreement with the analysis of the plasmatic concentrations of the enzymes creatine kinase and lactic dehydrogenase. It was found that the levels of such enzymes were lower in Ketorolac treated group, than in the untreated one. The results clearly indicate that Ketorolac prevents from the myocardial damage induced by reperfusion, probably by avoiding calcium overload in myocytes.

Anticryptosporidial activity of lasalocid and other ionophorous antibiotics in immunosuppressed rats

The anticryptosporidial activities of three ionophorous antibiotics were assessed in dexamethasone-immunosuppressed rats infected with Cryptosporidium parvum. When administered prophylactically, lasalocid prevented infection in a dose-dependent manner, whereas monensin and salinomycin were ineffective. Therapeutically, lasalocid eliminated established overt infections of the intestine, although infection persisted in the common bile duct and intestinal infection recurred after lasalocid treatment was stopped. These findings suggest that lasalocid is a potentially useful anticryptosporidial agent but that long-term continuous administration may be necessary in the immunocompromised host.

Efficacy of semduramicin and salinomycin against different stages of Eimeria tenella and E. acervulina in the chicken

The efficacy of a new ionophore, semduramicin, was compared with salinomycin in a series of in ovo and in vivo trials. Semduramicin was more efficacious than salinomycin against Eimeria tenella sporozoites as judged by oocyst production in embryonated eggs. When the two drugs were given in ovo at 93 h post inoculation (PI), both drugs exerted some effect against late schizogonous stages of E. tenella. In three battery studies, semduramicin (25 ppm) and salinomycin (60 and 66 ppm) were tested against E. tenella and E. acervulina. Medicated feed was withdrawn at 24-h intervals PI to study the stage of action of the anticoccidials. In E. tenella infected chickens, both anticoccidials exerted their maximum effect on weight gain and feed:gain ratio through the first 72 h PI. Semduramicin was more effective than salinomycin in controlling E. tenella lesions and coccidiosis mortality. With E. acervulina, both drugs acted similarly on early life cycle stages and no improvement in performance was recorded when medicated feed was given for longer than 72 h. Semduramicin was more effective than salinomycin in controlling E. acervulina lesions.

Characterization in vitro and in vivo of resistance to ionophores in a strain of Eimeria tenella

A field isolate of Eimeria tenella (FS139) was propagated several times in chickens medicated with 200 ppm of dietary monensin. In a laboratory test with 2-wk-old-chickens, the strain was resistant to monensin, salinomycin, and lasalocid given at double use level and was resistant to narasin and maduramicin at the normal use level. In comparison, a laboratory strain (WIS) was controlled by the normal use level of each product. When free WIS sporozoites were treated in vitro with 1.0 microgram/ml of monensin for 0.5 or 4.0 hr at 41 C and inoculated into primary cultures of chicken kidney cells the invasion was reduced by 35.6% or 96.3%, but invasion of FS139 sporozoites was increased by 18.5% by 0.5 hr treatment and was about the same as controls after 2 hr of treatment. Few sporozoites from the WIS strain developed into schizonts, but numerous sporozoites from the FS139 strain developed into normal first and second generation schizonts. The structure of free WIS sporozoites was distorted after 3 hr of treatment with 2.5 micrograms/ml of monensin at 41 C, as observed by light and scanning electron microscopy, whereas there was no change in structure of most treated FS139 sporozoites.

Anticoccidial efficacy of semduramicin in battery studies with laboratory isolates of coccidia

The anticoccidial activity of semduramicin against laboratory isolates of five species of poultry Eimeria was investigated. In laboratory scale battery trials, semduramicin at 20 to 30 ppm demonstrated broad-spectrum anticoccidial efficacy equivalent to salinomycin at 60 ppm. Also, semduramicin at 25 ppm was fed to uninfected cockerels in batteries for 21 days, and growth rate and feed efficiency were found to be equivalent to birds fed salinomycin at 60 ppm. Semduramicin was well tolerated when coadministered with tiamulin. Semduramicin demonstrated the same activity whether produced by semisynthesis or by direct fermentation.

Interactive effects of sodium zeolite A (Ethacal) and monensin in uninfected and Eimeria acervulina-infected chicks

An experiment was conducted with 5- to 18-day-old Arbor Acres broiler chicks to evaluate the interaction of sodium zeolite A (NZA) and monensin in uninfected and in coccidiosis-infected chicks. Sodium zeolite A (0 and .75%) or monensin (0 and 121 ppm), or both, were fed to uninfected chicks or to chicks infected with 4 x 10(5) sporulated, Eimeria acervulina oocysts, resulting in a 2-by-2-by-2 factorial arrangement of treatments. Coccidial infection reduced (P less than .01) weight gain, feed intake, feed efficiency, percentage of bone ash and of bone calcium; but the infection increased (P less than .05) bone Zn percentage. Monensin alleviated (or at least partially so) the adverse effects of the coccidial infection on weight gain, feed intake, feed efficiency and percentage of bone ash (coccidiosis by monensin, P less than .01). In addition, monensin increased the bone-calcium (P less than .06) and zinc content (P less than .02) in uninfected chicks and in those infected with coccidiosis. Sodium zeolite A tended to reduce feed intake by coccidiosis-infected chicks (coccidiosis by NZA, P less than .07), but increased (P less than .01) the bone zinc and decreased (P less than .01) serum inorganic phosphorus in uninfected chicks and in those infected with coccidiosis.

Cross resistance to the ionophorous polyether anticoccidial drugs in Eimeria tenella isolates from Czechoslovakia

Two field isolates of Eimeria tenella were isolated on farms where continuous outbreaks of coccidiosis in broilers had occurred over several years. The isolates were repeatedly tested for their sensitivity to ionophorous polyether drugs in floor pen trials lasting 7 wk. Hybro cockerels were inoculated with 25 x 10(3) oocysts/chicken at the age of 23 to 24 days. Total mortality, mortality caused by coccidia, live weights, feed conversion ratios, number of oocysts in litter, and titers of circulating antibodies against E. tenella were followed. Tested isolates were not controlled by the monovalent polyether drugs monensin, narasin, and salinomycin, but maduramicin, which is a monovalent monoglycoside polyether, and the bivalent polyether lasalocid controlled them effectively. This study indicates that coccidia that lose their sensitivity to a monovalent polyether drug lose the sensitivity to other monovalent polyethers, also, but might yet be effectively controlled by drugs from other classes of polyether antibiotics. This supports the hypothesis that there are differences in the mechanisms of anticoccidial activity of different classes of polyether antibiotics.

Field trials with closantel and Haemonchus contortus in sheep in Papua New Guinea

Sheep treated once with closantel at 7.5 or 15.0 mg/kg and grazing with untreated sheep remained free of Haemonchus contortus for at least 4 to 5 weeks and 6 to 7 weeks respectively after treatment. When the whole flock was treated with 15.0 mg/kg, H. contortus began to become re-established 7 to 8 weeks later. Maximum benefit of the residual anthelmintic effect of closantel against H.contortus was obtained only when all sheep in the flock were treated; it took 10 weeks longer for H.contortus to form 50% of larval cultures when the whole flock was treated than when only a part of the flock was treated.

Anticoccidial evaluation of halofuginone, lasalocid, maduramicin, monensin and salinomycin

The activities of five anticoccidials were compared against Eimeria species in/of chickens, in controlled in vivo and in vitro laboratory studies. Two more recent and potent market entries (maduramicin and halofuginone) were compared with three older polyether antibiotic anticoccidials (monensin, lasalocid and salinomycin). Halofuginone, lasalocid, maduramicin, monensin and salinomycin were evaluated at 3, 125, 5, 120 and 66 ppm, respectively, of active drug in the diets. At these levels, all five drugs demonstrated significant activity against Eimeria tenella, E. maxima, E. necatrix, E. brunetti and E. acervulina (in vivo). Monensin was least effective against E. tenella, and one of the lesser efficacious drugs against E. necatrix, maduramicin, was least effective against E. maxima. In studies of single Eimeria species infections, comparable weight gains were noted for the drugs. In the mixed Eimeria species infections, however, birds treated with maduramicin had significantly higher weight gains than did birds medicated with monensin. Unlike in vivo potencies, titration in vitro indicated that monensin was most potent (active at 10(-6) mcg ml-1), and maduramicin and lasalocid least potent (inactive at less than or equal to 10(-3) mcg ml-1).