A critical appraisal on the treatment of acute appendicitis in pediatric population during the COVID-19 pandemic

Acute appendicitis is one of the most common causes of abdominal pain in children. During the coronavirus disease 2019 (COVID-19) pandemic, a delay in presentation to the emergency department and a higher rate of complicated appendicitis were observed. Traditionally, operative management (laparoscopic or open appendectomy) was thought to be the best treatment strategy for acute appendicitis. However, nonoperative management with antibiotics has gained popularity in managing pediatric appendicitis during the COVID-19 era. The pandemic has posed significant challenges in the management of acute appendicitis. Cancellation of elective appendectomies, delay in seeking care due to fear of contracting COVID-19 infection, and impact of COVID-19 infection in the pediatric population have resulted in higher rates of complications. Furthermore, multiple studies have reported multisystem inflammatory syndrome in children mimicking acute appendicitis, subjecting patients to unnecessary surgery. Therefore, it is imperative to update the treatment guidelines for the management of acute appendicitis in the pediatric population during and after COVID-19 times.

Effect of preweaned dairy calf housing system on antimicrobial resistance in commensal Escherichia coli

Group housing of preweaned dairy calves is a growing practice in the United States. The objective of this practice is to increase the average daily gain of calves in a healthy and humane environment while reducing labor requirements. However, feeding protocols, commingling of calves, and occurrence of disease in different calf-housing systems may affect the prevalence of antimicrobial drug-resistant bacteria. This study evaluated the effect of a group pen-housing system and individual pen-housing system on antimicrobial resistance trends in fecal Escherichia coli of preweaned dairy calves and on the prevalence of environmental Salmonella. Twelve farms from central New York participated in the study: 6 farms using an individual pen-housing system (IP), and 6 farms using a group pen-housing system (GP). A maximum of 3 fecal E. coli isolates per calf was tested for susceptibility to 12 antimicrobial drugs using a Kirby-Bauer disk diffusion assay. Calves in GP had a significantly higher proportion of E. coli resistant to ciprofloxacin and nalidixic acid, whereas calves in IP had a significantly higher proportion of E. coli resistant to ampicillin, ceftiofur, gentamycin, streptomycin, and tetracycline. Calf-housing system had an effect on resistance to individual antimicrobial drugs in E. coli, but no clear-cut advantage to either system was noted with regard to overall resistance frequency. No outstanding difference in the richness and diversity of resistant phenotypes was observed between the 2 calf-housing systems.

Effect of on-farm use of antimicrobial drugs on resistance in fecal Escherichia coli of preweaned dairy calves

Respiratory disease and diarrhea are the 2 most common diseases that result in the use of antimicrobial drugs in preweaned calves. Because the use of drugs in food animals, including dairy calves, has the potential for generating cross-resistance to drugs used in human medicine, it is vital to propose farm practices that foster the judicious use of antimicrobials while assuring animal health and productivity. The objective of this study was to use dairy farm calf treatment records to identify antimicrobial drug treatments in calves and to evaluate their effects on the prevalence of antimicrobial-resistant Escherichia coli from rectal swabs of preweaned dairy calves. Eight farms from central New York participated in the study, 3 farms using individual pen housing management and 5 farms using group pen housing management. Eligible study farms could not add antimicrobial drugs to the milk fed to preweaned calves and were required to have farm records documenting antimicrobial drug treatment of calves from birth to weaning. Three fecal E. coli isolates per calf were tested for susceptibility to 12 antimicrobial drugs using a Kirby-Bauer disk diffusion assay. A total of 473 calves were sampled, from which 1,423 commensal E. coli isolates were tested. Of the 9 antimicrobial drugs used on study farms, only enrofloxacin was significantly associated with reduced antimicrobial susceptibility of E. coli isolates, although treatment with ceftiofur was associated with reduced susceptibility to ceftriaxone. The median numbers of days from treatment with ceftiofur and enrofloxacin to rectal swab sampling of calves were 16 d (range: 1-39) and 12 d (range: 6-44), respectively. At the isolate level, treatment with enrofloxacin resulted in odds ratios of 2 [95% confidence interval (CI): 1-4] and 3 (95% CI: 2-6), respectively, for isolation of nonsusceptible E. coli to nalidixic acid and ciprofloxacin compared with calves not treated with enrofloxacin. Treatment with ceftiofur resulted in an odds ratio of 3 (95% CI: 0.9-12) for isolation of nonsusceptible E. coli to ceftriaxone compared with calves not treated with ceftiofur. Treatment with enrofloxacin resulted in selection of isolates that presented phenotypic resistance to both ciprofloxacin and ceftriaxone. Treatment with ceftiofur resulted in a higher prevalence of isolates resistant to ≥3 antimicrobial drugs (97%) compared with no treatment with ceftiofur (73%). These findings reinforce the necessity for continued implementation of practices at the dairy farm that support the sustainable and judicious use of antimicrobial drugs in dairy calves.

A field study conducted at Kidston Gold Mine, to evaluate the impact of arsenic and zinc from mine tailing to grazing cattle

The grazing trial at Kidston Gold Mine, North Queensland, was aimed specifically to assess the uptake of metals from the tailing and the potential for unacceptable contamination of saleable meat. Further aims included estimating metal dose rates and identifying potential exposure pathways including plant uptake of heavy metals, mine tailings adhered to plants and direct ingestion of mine tailing. It was found that of the 11 metals analysed (As, Zn, Co, Cd, Cr, Sn, Pb, Sb, Hg, Se and Ni) in the animal's liver, muscle and blood during the 8-month trial period, only accumulation of arsenic and zinc occurred. A risk assessment including these two metals was conducted to determine the potential for chronic metal toxicity and long-term contamination, using the estimates of metal dose rate. It was concluded that no toxicity or long-term contamination in cattle was likely at this site. Management procedures were therefore not required at this site; however, the results highlight percent ground cover and standing dry matter (DM) as important factors in decreasing metal exposure from direct ingestion of tailings and dust adhered to plants.

Porphyrins as early biomarkers for arsenic exposure in animals and humans

We studied the effect of arsenic exposure on the haem biosynthetic pathway in the rat and humans. Significant increases in protoporphyrin IX, coproporphyrin III, coproporphyrin I were observed in the blood, liver and kidney, and in the urine of rats after a single dose of arsenic. The level of increase was dependent on the arsenic species present. Most of porphyrin concentrations in the tissues increased within 24 hr and urinary excretion elevated within 48 hr. In the human study, we collected urine samples from 113 people who live in Xing Ren of Guizhou Province, a coal-borne arsenicosis endemic area in southwest of PR China and from 30 people who live in Xing Yi (about 80 km southwest of Xing Ren) where arsenicosis is not prevalent. We analyzed the urinary porphyrins using HPLC. Results indicate that all urinary porphyrins were higher in the arsenic exposed group than those in the control group. Women, children and older age people spend much of their time indoors, they had greater increases of urinary arsenic and porphyrins. They were the higher risk groups among the study subjects. A positive correlation between the urinary arsenic levels and porphyrin concentrations demonstrated the effect of arsenic on haem biosynthesis. Significant alteration in the porphyrin excretion profiles of the younger age (<20 y) arsenic exposed group suggested that porphyrins could be used as early warning biomarkers for chronic exposure to arsenic.

A case of severe actinic prurigo successfully treated with thalidomide

Actinic prurigo is an uncommon and usually persistent idiopathic photodermatosis with typical human leukocyte antigen (HLA) associations (HLA-DR4, particularly subtypes DRB1*0407 and DRB1*0401). Although its mechanism of action is not clearly understood, thalidomide has been shown to be particularly efficacious in treating actinic prurigo, among other conditions. A 31-year-old Australian woman who had suffered actinic prurigo for most of her life was treated with two courses of thalidomide (50-100 mg nocte) over consecutive summers. Remission was observed after cessation of the second course of thalidomide and had continued 4 years later. Abnormalities in the cutaneous response to ultraviolet radiation at the time of diagnosis, detected by monochromator phototesting, reverted to normal following treatment.

Regulation of cellular growth by the Drosophila target of rapamycin dTOR

The TOR protein kinases (TOR1 and TOR2 in yeast; mTOR/FRAP/RAFT1 in mammals) promote cellular proliferation in response to nutrients and growth factors, but their role in development is poorly understood. Here, we show that the Drosophila TOR homolog dTOR is required cell autonomously for normal growth and proliferation during larval development, and for increases in cellular growth caused by activation of the phosphoinositide 3-kinase (PI3K) signaling pathway. As in mammalian cells, the kinase activity of dTOR is required for growth factor-dependent phosphorylation of p70 S6 kinase (p70(S6K)) in vitro, and we demonstrate that overexpression of p70(S6K) in vivo can rescue dTOR mutant animals to viability. Loss of dTOR also results in cellular phenotypes characteristic of amino acid deprivation, including reduced nucleolar size, lipid vesicle aggregation in the larval fat body, and a cell type-specific pattern of cell cycle arrest that can be bypassed by overexpression of the S-phase regulator cyclin E. Our results suggest that dTOR regulates growth during animal development by coupling growth factor signaling to nutrient availability.

Cucumber mosaic virus mutants with altered physical properties and defective in aphid vector transmission

Two mutant strains of cucumber mosaic virus (CMV) were investigated with respect to virion stability and molecular determinants of aphid vector transmission. The mutant 2A1-MT-60x, derived from the mechanically passaged wild type 2A1-AT, is poorly transmissible by the aphid Aphis gossypii and not transmissible by the aphid Myzus persicae, whereas the wild type virus is transmissible by both aphid species. The mutant phenotype was shown to be conferred by a single encoded amino acid change of alanine to threonine at position 162 of the coat protein (CP). Modifying the mutant CP gene to encode the wild type sequence (alanine) at position 162 restored aphid transmission. To test for a correspondence between changes in the physical stability of virions and defects in aphid transmission, a urea disruption assay was developed. Virions of aphid-transmissible strains 2A1-AT and CMV-Fny were stable with treatments of up to between 3 and 4 M urea. In this assay mutant viruses 2A1-MT-60x and CMV-M were less stable, as they were completely disrupted at urea concentrations of 2 and 1 M urea, respectively. The mutant 2A1-MT-60x also accumulated at a reduced level in infected squash relative to the wild type virus. These studies suggest that a primary factor in the loss of aphid transmissibility of some strains of CMV is a reduction in virion stability.

Immunosuppressant PG490 (triptolide) inhibits T-cell interleukin-2 expression at the level of purine-box/nuclear factor of activated T-cells and NF-kappaB transcriptional activation

PG490 (triptolide) is a diterpene triepoxide with potent immunosuppressive and antiinflammatory properties. PG490 inhibits interleukin(IL)-2 expression by normal human peripheral blood lymphocytes stimulated with phorbol 12-myristate 13-acetate (PMA) and antibody to CD3 (IC50 of 10 ng/ml), and with PMA and ionomycin (Iono, IC50 of 40 ng/ml). In Jurkat T-cells, PG490 inhibits PMA/Iono-stimulated IL-2 transcription. PG490 inhibits the induction of DNA binding activity at the purine-box/antigen receptor response element (ARRE)/nuclear factor of activated T-cells (NF-AT) target sequence but not at the NF-kappaB site. PG490 can completely inhibit transcriptional activation at the purine-box/ARRE/NF-AT and NF-kappaB target DNA sequences triggered by all stimuli examined (PMA, PMA/Iono, tumor necrosis factor-alpha). PG490 also inhibits PMA-stimulated activation of a chimeric transcription factor in which the C-terminal TA1 transactivation domain of NF-kappaB p65 is fused to the DNA binding domain of GAL4. In 16HBE human bronchial epithelial cells, IL-8 expression is regulated predominantly by NF-kappaB, and PG490 but not cyclosporin A can completely inhibit expression of IL-8. The mechanism of PG490 inhibition of cytokine gene expression differs from cyclosporin A and involves nuclear inhibition of transcriptional activation of NF-kappaB and the purine-box regulator operating at the ARRE/NF-AT site at a step after specific DNA binding.

Unique toxic peptides isolated from sawfly larvae in three continents

D-Amino acid containing peptides have been found to be responsible for sawfly larvae poisoning in many parts of the world. These compounds, unique in the animal kingdom, were isolated from three different species of sawfly indigenous to Australia, Denmark and South America. The octapeptide, lophyrotomin, is the major toxin in the Australian and Danish species and is present in small amounts in the South American sawfly. Pergidin, the main toxin in the South American sawfly, is a heptapeptide containing a phosphoseryl residue. This, as far as we are aware, is the first example of such a peptide to be isolated from an animal source. Small amounts of pergidin have been found in the other two species. All available evidence suggests that both peptides are biosynthesised 'de novo' possibly as a protective device, however it cannot be excluded that microorganisms may be responsible. These compounds are stable to enzymatic breakdown because of their configuration and their strong chemical bonding and lipophilic character provide a potential for residues to remain in the host animal and cause significant changes.

Environmental poisoning: presentation and management

Environmental poisoning is most commonly associated with chronic long-term exposure to toxins rather than to acute exposure. Such repeated exposure to sublethal doses of compounds and elements presents problems in risk assessment. This is primarily because the data are unavailable to describe relationships between dose and effect at lower levels of exposure to toxins. Bioavailability of toxins also presents a problem because the data on bioavailability are sparse and seldom as high as the default of 100% bioavailability commonly used in risk assessment. Examples are presented of two toxins: arsenic as an elemental anthropogenic and geologic poison and ciguatoxin, a polyether ladder compound, as a toxin produced naturally by dinoflagellates. Bioavailability drives the toxicity of arsenic from contaminated sites, whereas tissue accumulation drives the toxicity of ciguatoxin. Considerable benefit is derived from the harmonization of regulatory processes where there is linkage of health and environmental factors in the derivation of credible risk assessment.

Speciation of arsenic metabolites in the urine of occupational workers and experimental rats using an optimised hydride cold-trapping method

A hydride cold-trapping technique was developed and optimised for the measurement of urinary arsenic metabolites. The analytical precision of the method was found to be 6.1, 4.0 and 4.8% (n = 5) for inorganic arsenic (ASi), monomethylarsonate (MMA) and dimethylarsinate (DMA), respectively, with recoveries close to 100%. The detection limits were 1.0, 1.3 and 3 ng for ASi, MMA and DMA, respectively. The method was then used to analyse urine samples obtained from three groups of workers for occupational exposure in three companies where copper chrome arsenate was used for timber treatment. The results were compared with those for a normal control group of laboratory workers. Arsenic and its metabolites were also measured in experimental rats given 5 mg As kg-1 body mass by oral gavage in the form of sodium arsenite, calcium arsenite or sodium arsenate. Occupational workers showed a significantly higher excretion of ASi. Up to two fold increases of urinary ASi excretion in rats compared with control rats were also observed in animals dosed with various forms of arsenicals. The method is suitable for the measurement of arsenic metabolites in urine of both humans and experimental animals.

Speciation and absolute bioavailability: risk assessment of arsenic-contaminated sites in a residential suburb in Canberra

Watson is a fully developed suburb of some 30 years in Canberra (the capital city of Australia). A plunge dip using arsenical pesticides for tick control was operated there between 1946 and 1960. Chemical investigations revealed that many soil samples obtained from the study area contained levels of arsenic exceeding the current health-based investigation levels of 100 mg kg-1 set by the National Healthy and Medical Research Council in Australia. For the speciation study, nine composite samples of surface and sub-surface soils and a composite samples of rocks were selected. ICP-MS analysis showed that arsenic levels in these samples ranged from 32 to 1597 mg kg-1. Chemical speciation of arsenic showed that the arsenite (trivalent) components were 0.32-56% in the soil and 44.8% in the rock composite samples. Using a rat model, the absolute bioavailability of these contaminated soils relative to As3+ or As5+ ranged from 1.02 to 9.87% and 0.26 to 2.98%, respectively. An attempt was made to develop a suitable leachate test as an index of bioavailability. However, the results indicated that there was no significant correlation between the bioavailability and leachates using neutral pH water or 1M HC1. Our results indicate that speciation is highly significant for the interpretation of bioavailability and risk assessment data; the bioavailability fractions of arsenic in soils from Watson are small and therefore the healthy impact upon the environment and humans due to this element is limited.

Effects of inflammation-associated acute-phase response on hepatic and renal indices in the horse

OBJECTIVES

To determine the effect of an acute soft tissue inflammatory response on biochemical and haematological indices of hepatic and renal function in the Thoroughbred horse.

PROCEDURE

Soft tissue inflammation was induced in four Thoroughbred horses by intramuscular injections of Freund's complete adjuvant. The horses were clinically examined and blood and urine samples were collected before and after the adjuvant injections. Biochemical and haematological indices were measured in samples collected and used to determine the onset of the acute-phase response and to assess hepatic and renal function at this time.

RESULTS

After adjuvant injection, significant increases (P < 0.01) in total white (13.1 +/- 1.4 x 10(9)/L) and neutrophil (10.2 +/- 1.2 x 109/L) cell counts, rectal temperature (39.7 +/- 0.5 degrees C) and various plasma protein concentrations, including fibrinogen (6.6 +/- 1.2 g/L), haptoglobin (1.3 +/- 0.1 g/L) and total protein (88.1 +/- 2.7 g/L), indicated the induction of an acute-phase response. This corresponded with significant reductions (P < 0.01) in the plasma elimination half-lives (t1/2 beta) sodium bromosulphthalein (3.13 +/- 0.05 to 2.82 +/- 0.07 min) and sodium sulphanilate (38.29 +/- 4.04 to 19.60 +/- 5.68 min) and reductions in the plasma activities of aspartate aminotransferase, glutamate dehydrogenase, creatine kinase, alkaline phosphatase, gamma glutamyl transferase; the urinary creatinine clearance ratios of sodium, chloride and potassium; and the urinary gamma glutamyl transferase-to-creatinine clearance ratios. (All values mean +/- SD.)

CONCLUSIONS

The effects of the acute-phase response on indices of hepatic and renal function in the horse suggest that the disposition of pharmacological agents administered at this time may be altered and that indices of acute inflammation should be interpreted cautiously.

Stress response to chronic inflammation in the horse

Five clinically healthy Thoroughbred geldings were injected with Freund's adjuvant 3 times to induce a chronic inflammatory response. Blood was collected at various times before and after adjuvant administration. Clinical responses (rectal temperature and general demeanor) were also monitored. Adjuvant injection induced increases in rectal temperature and plasma fibrinogen concentration (maximum levels measured were mean +/- s.d. 39.7 +/- 0.5 degrees C and 8.2 +/- 0.3 g/l, respectively), indicative of an inflammatory response. A mild clinical depression was also observed in the horses for 24 h after the first injection of adjuvant only. Plasma cortisol levels decreased significantly from control levels of mean +/- s.d. 187.7 +/- 24.3 nmol/l to a minimum of 80.2 +/- 22.1 nmol/l (P < 0.01) 9 days after the first injection of adjuvant. Conversely, plasma insulin levels increased after the first injection of adjuvant to a maximum (96.7 +/- 15.2 iu/ml; P < 0.01) 12 days later, while plasma glucose concentrations tended to decline. A control group of horses to rule out contemporary environmental influences on the physiological and biochemical indices measured was not included in this study. The results show that chronic inflammation in the horse depressed resting plasma cortisol concentrations.

The effect of the acute-phase response on in vitro drug metabolism and plasma protein binding in the horse

The effect of the acute-phase response (APR) on the activity of the hepatic drug-metabolizing system (DMS) and on the binding of phenylbutazone to plasma proteins was investigated in the horse. An APR was induced by intramuscular injections of Freund's complete adjuvant in five horses and, five days later, these horses together with five clinically normal horses were shot and the right ventral lobe of each liver removed. The hepatic microsomal fractions from the liver samples were isolated and significantly lower (p < 0.01) concentrations of cytochromes P450 and b5 and activities of aniline-p-hydroxylase and aminopyrine N-demethylase (43%, 55%, 45% and 30%, respectively) were measured in the livers from the adjuvant-inflamed horses, compared to the controls. Phenylbutazone (PBZ) was administered intravenously (4.4 mg/kg) to a further four horses and plasma protein binding was measured by ultracentrifugation. Five weeks later, these horses were injected with Freund's complete adjuvant and the intravenous administration of PBZ (4.4 mg/kg) was repeated. Inflammation induced a significant increase (p < 0.01) in the unbound fraction of PBZ (5.2 +/- 0.5 as against 1.4 +/- 0.6%). These results suggest that the APR depresses the hepatic DMS and reduces the binding of PBZ to plasma proteins.

Isolation and characterisation of urushiol components from the Australian native cashew (Semecarpus australiensis)

Native cashew (Semecarpus australiensis) is a well-known food source for aboriginal people of northeastern Queensland and the Northern Territory. It is also well known that contact with the seeds at a certain stage of growth can cause sever dermatitis in susceptible individuals. To prepare the fruits for eating, they are commonly treated by leaching for 2-7 days with water followed by heating in bark, and this treatment apparently produces an edible cashew nut. Recently, attempts have been made to use this valuable source of food by a commercial company. It was necessary to identify the active principle(s) in the seeds to determine the most effective way of rendering the seed suitable for human consumption without altering the flavour. By using solvent extraction and silica-gel chromatography, a fraction containing one major urushiol was obtained. Its structure was confirmed by comparison of its NMR and mass spectral (MS) data with that previously reported. This compound, which is found in high yield, is also found in poison ivy (Toxiodenron radicans) and is responsible for dermatitis in susceptible individuals. A method of removing the active principle from the seed has been suggested.

The effect of inflammation on the disposition of phenylbutazone in thoroughbred horses

The effect of inflammation on the disposition of phenylbutazone (PBZ) was investigated in Thoroughbred horses. An initial study (n = 5) in which PBZ (8.8 mg/kg) was injected intravenously twice, 5 weeks apart, suggested that the administration of PBZ would not affect the plasma kinetics of a subsequent dose. Two other groups of horses were given PBZ at either 8.8 mg/kg (n = 5) or 4.4 mg/kg (n = 4). Soft tissue inflammation was then induced by the injection of Freud's adjuvant and the administration of PBZ was repeated at a dose level equivalent to, but five weeks later than, the initial dose. Inflammation did not appear to affect the plasma kinetics or the urinary excretion of PBZ and its metabolites, oxyphenbutazone (OPBZ) or hydroxyphenylbutazone (OHPBZ) when PBZ was administered at 8.8 mg/kg. However, small but significant increases (P < 0.05) in total body clearance (CLB; 29.2 +/- 3.9 vs. 43.8 +/- 8.1 mL/ h.kg) and the volume of distribution, calculated by area (Vd(area); 0.18+/- 0.05 vs. 0.25 +/- 0.03 L/kg) or at steady-state (Vd(SS); 0.17 +/- 0.04 vs. 0.25 +/- 0.03 L/ kg), were obtained in horses after adjuvant injection, compared to controls, when PBZ was administered at 4.4 mg/kg which corresponded to relatively higher tissues concentrations and lower plasma concentrations (calculated) at the time of maximum peripheral PBZ concentration. Soft tissue inflammation also induced a significantly (P < 0.05) higher amount of OPBZ in the urine 18 h after PBZ administration but the total urinary excretion of analytes over 48 h was unchanged. These results have possible implications regarding the administration of PBZ to the horse close to race-day.

Disposition and urinary excretion of phenylbutazone in normal and febrile greyhounds

Five days after the induction of acute systemic inflammation in greyhounds by intramuscular and subcutaneous injections of Freund's adjuvant, the hepatic concentrations of cytochromes P-450 and b5, the activities of the hepatic microsomal enzymes aniline p-hydroxylase and aminopyrine n-demethylase and the disposition and urinary excretion of phenylbutazone were determined. The mean plasma concentrations of phenylbutazone after intravenous administration were described by the bi-exponential equations: Cp = 144.2e-34.6t + 171.5e-0.104t for five normal greyhounds and Cp = 113.6e-16.13t + 163.1e-0.108t for five febrile greyhounds. The elimination half-lives, total body clearances and apparent volumes of distribution were 6.7 hours, 18.4 ml kg-1 hour-1 and 0.18 litre kg-1, for the normal greyhounds, and 6.4 hours, 19.5 ml kg-1 hour-1 and 0.18 litre kg-1, for the febrile greyhounds. There were no significant differences between the pharmacokinetic parameters describing the distribution and elimination of phenylbutazone, or between the quantities of phenylbutazone, oxyphenbutazone and hydroxyphenylbutazone excreted in the urine. In the febrile greyhounds, there were significant decreases in the hepatic microsomal concentrations of cytochromes P-450 and b5 and in the activities of aniline p-hydroxylase and aminopyrine n-demethylase.

Phenylbutazone in racing greyhounds: plasma and urinary residues 24 and 48 hours after a single intravenous administration

The concentrations of phenylbutazone (PBZ), oxyphenbutazone (OPBZ) and gammahydroxyphenylbutazone (OHPBZ) in plasma and urine from 50 Greyhounds 24 and 48 h after the intravenous administration of a single dose of PBZ (30 mg/kg) were measured. The 24 h plasma concentrations of OPBZ and OHPBZ, the 48 h plasma concentration of OHPBZ and the 24 h urinary concentration of PBZ were normally distributed, while log transformations were required before the 24 h plasma concentration of PBZ and the 24 and 48 h urinary concentrations of OPBZ and OHPBZ became normally distributed. The 95%, 99%, 99.9% and 99.99% upper predicted confidence intervals for both 24 h and 48 h plasma and urinary concentrations demonstrated wide potential variation in the concentration of the analytes should PBZ be administered to Greyhounds. The 24 h plasma and urinary concentrations of PBZ were weakly correlated, but no similar relationship existed for OPBZ or OHPBZ. The urinary concentrations of each analyte were not affected by the trainer or sex of the Greyhound or the urinary pH. We conclude that it would be impossible to predict the timing of the PBZ administration or the plasma concentration of PBZ from the measurement of the concentration of PBZ in a single sample of urine.

Kinetics, dose response, tachyphylaxis and cross-tachyphylaxis of vascular leakage induced by endotoxin, zymosan-activated plasma and platelet-activating factor in the horse

Vascular leakage induced by intradermal injection of endotoxin, zymosan-activated plasma (ZAP) and platelet-activating factor (PAF) was measured in nine Thoroughbreds using 125-iodine human serum albumin (125I-HSA) as a marker in the blood. ZAP and PAF produced dose-dependent increases in vascular permeability with the maximum occurring within the first 15 min after injection. The vascular leakage induced by endotoxin was also dose-dependent, but the maximum occurred 2 h after intradermal injection. Intradermal sites previously injected with endotoxin were refractory to a second injection of endotoxin for up to 5 days. However, sites injected with endotoxin and re-injected with either ZAP or PAF remained responsive with increased vascular leakage compared to saline injected control sites re-injected with either ZAP or PAF. Diminished response to endotoxin challenge may contribute to the poor prognosis of endotoxaemia in the horse.

Isolation and identification of a compound from avocado (Persea americana) leaves which causes necrosis of the acinar epithelium of the lactating mammary gland and the myocardium

It is well known that when lactating livestock eat avocado (Persea americana) leaves they may develop non-infectious mastitis and agalactia. This is associated with extensive coagulation necrosis of the secretory acinar epithelium and interstitial oedema, congestion, and haemorrhage. Similar lesions have been produced in mammary glands of lactating mice fed a diet containing a small percentage of freeze-dried avocado leaf. Tests using these animals have been used to isolate the active principle, termed "persin," from avocado leaves. The purified persin was examined using IR, NMR, and UV spectroscopy and mass spectrometry, and identified as (Z,Z)-1-(acetyloxy)-2-hydroxy-12,15-heneicosadien-4-one. Persin has previously been isolated from avocado leaves and shown to have antifungal properties and to be toxic to silkworms. Our tests have shown that persin at the dose rate of 60-100 mg/kg has the same effect on mammary glands in lactating mice as leaves from avocado. Enantioselective syntheses of the R and the S isomers of persin and related derivatives were carried out. These compounds were tested for activity required to induce widespread lactating mammary gland necrosis in mice, and only the R isomer was found active. At doses of persin above 100 mg/kg necrosis of myocardial fibres may occur and hydrothorax may be present in severely affected animals. The mechanism of action of persin on both the mammary gland and the myocardium remain to be resolved.

Isolation of a compound from Eupatorium adenophorum (Spreng.) [Ageratina adenophora (Spreng.)] causing hepatotoxicity in mice

Regular ingestion of Eupatorium adenophorum [Ageratina adenophora (Spreng.)] or Crofton weed causes chronic pulmonary disease in horses mainly in Australia, New Zealand, and the Himalayas. The disease is characterized by pulmonary interstitial fibrosis, emphysema, alveolar epithelisation and reduced tolerance to exercise. Horses apparently are the only animals affected and there are numerous reports of farms losing all their horses. The disorder was produced experimentally in horse feeding trials, and it was shown that characteristic lesions occurred in the lungs. In studies with laboratory animals, mice were shown to be suitable test animals, but in this species lesions occur in the liver rather than the lungs. The hepatic injury in these animals is characterized by multiple areas of focal necrosis of the parenchyma associated with degeneration and loss of the epithelium lining the small bile ducts. The active principle 9-oxo-10,11 dehydroagerophorone responsible for these lesions in mice has been isolated from E. adenophorum. Although the compound has been shown to exhibit toxicity to larvae of invertebrate species, no mammalian toxicity studies have been previously reported involving the isolated toxin. The mechanism of the toxic effect of the compound as well as its possible relevance to the respiratory disease in the horse remain to be investigated.

The magical and medicinal usage of Stangeria eriopus in South Africa

The underground caudex of the cycad Stangeria eriopus is used extensively by several ethnic groups in South Africa, mainly as an ingredient in magical potions but also as an emetic. An assessment of two main outlets showed that 3410 plants were sold in the month of July 1992; continued usage of this material now threatens the remaining plant populations. A proximate analysis of the caudex material gives high carbohydrate content with only small percentages of fat, protein, fibre and ash. An unusually high content of sodium sulphate may explain the efficacy of Stangeria-containing preparations as an emetic. The phytosterols sitosterol and stigmasterol are present in a 4:1 ratio while the fatty acid component comprises palmitic, oleic, stearic and arachidic acids. Twelve amino acids were identified in the material, including the non-protein amino acids beta-alanine, gamma-aminobutyric acid and pyroglutamic acid. The candidate neurotoxin beta-N-methylamino-L-alanine could not be detected but cycasin is present at the levels of 0.17% and 0.21% in fresh and dry caudex material, respectively and appears to be accompanied by the related toxin, macrozamin.

Concentration of ptaquiloside, a major carcinogen in bracken fern (Pteridium spp.), from eastern Australia and from a cultivated worldwide collection held in Sydney, Australia

Two surveys of bracken fern for the concentration of the carcinogen ptaquiloside (PT) have been carried out, one of bracken fern from the eastern side of Australia and the other from a worldwide collection of bracken clones held in Sydney Australia. Bracken from eastern Australia contained concentrations of ptaquiloside ranging from 0 to 12,945 micrograms PT/g. From 91 samples 15% contained greater than 5,000 micrograms PT/g and 57% of samples contained more than 1,000 micrograms PT/g bracken on the dry weight basis. Ptaquiloside concentrations were highest in Pteridium revolutum and from P. esculentum from areas where bovine enzootic haematuria was known to occur. Bracken from the cultivated bracken clone collection from world-wide sources tended to have lower concentrations of ptaquiloside ranging from 0 to 9,776 micrograms PT/g. From 77 samples, 8% contained more than 5,000 micrograms PT/g and 35% contained more than 1,000 micrograms PT/g bracken. Samples from both the eastern Australia survey and the Australian representatives in the worldwide collection showed significantly higher concentrations of PT in the P. esculentum collected from the more southern states. In samples from the worldwide collection there were no statistical differences in the concentrations of PT in bracken between taxa.

Exercise-induced connective tissue turnover and lipid peroxidation in horses

Four unfit thoroughbred horses were exercised on a treadmill twice, 5 weeks apart. Exercise consisted of stepwise increments in treadmill speed up to a maximum of 12 m s-1 and then maintained at this speed until the horses were fatigued. Two of the horses were administered phenylbutazone (4.4 mg kg-1) intravenously immediately before the first exercise period and the other two horses immediately before the second exercise period. Clinical observation revealed stiffness of gait and palpable soreness over the lumbar-sacral region in the horses 24 h after the exercise concluded. Mean plasma aspartate aminotransferase and creatine kinase activities and urinary creatinine clearance did not change as a result of exercise. The mean urinary excretion and clearance of hydroxyproline significantly increased in the 24 h following exercise (P < 0.001). A concurrent increase in the urinary excretion of malondialdehyde also occurred (P < 0.001). Prior administration of phenylbutazone did not affect hydroxyproline or malondialdehyde excretion or clearance, nor did it appear to reduce the severity of soreness after exercise. The results indicate that lipid peroxidation and the excretion and clearance of hydroxyproline increase when unfit thoroughbreds are strenuously exercised on a treadmill.

Free radical oxidation products in plasma and synovial fluid of horses with synovial inflammation

Free radical oxidation products, namely conjugated dienes, ultraviolet fluorescence (excitation 325 nm, emission 395 nm) and visible fluorescence (excitation 360 nm, emission 460 nm) were measured in equine synovial fluid exposed to free radicals in vitro and in the plasma and synovial fluids of horses with synovial effusions. The synovial effusions were induced by intra-articularly administered carrageenin (0.3 ml, 1%), which rarely resulted in clinical lameness. The free radicals were generated in vitro by mixtures of iron and ethylene diamine tetra acetate (Fe/EDTA) or mixtures of hypoxanthine and xanthine oxidase (HX/XO). The conjugated diene concentrations and intensity of ultraviolet fluorescence were negligible in plasma and synovial fluid specimens. No increase resulted from incubation of synovial fluids with either a free radical generating system or as a result of the induced inflammation. The intensity of visible fluorescence did not increase in specimens incubated with Fe/EDTA. However, the intensity of visible fluorescence increased in specimens incubated with HX/XO, in synovial effusions induced by carrageenin, in plasma and in synovial fluids aspirated from saline injected controls. The results indicate that the intensity of visible fluorescence of equine synovial fluid increases after exposure to free radicals and during synovitis in the horse, suggesting a possible role for free radicals in the pathogenesis of equine inflammatory joint disease.

Vascular leakage induced by histamine, bradykinin, serotonin and prostaglandin E2 in greyhounds

Vascular leakage induced by intradermal injection of histamine, bradykinin and serotonin alone and co-injected with prostaglandin E2 was measured in Greyhounds using 125iodine-labelled human serum albumin (125I-HSA) as a marker in the blood. Histamine and bradykinin produced dose-dependent vascular leakage. At equimolar concentrations, histamine was more than twice as potent as bradykinin. Serotonin did not induce vascular leakage and was irritant. Prostaglandin E2 did not induce significant vascular leakage (maximum 5 microL) when injected alone, but when co-injected with histamine and bradykinin, the vascular leakage of both histamine and bradykinin was increased. This effect was more pronounced if lower concentrations of histamine and bradykinin were injected. The induced vascular leakage was greatest during the first five minutes of lesion development for histamine, during the second five minutes of lesion development for bradykinin, and the synergistic effect of prostaglandin E2 was maximal during the third five minute period of lesion development.

Specific activation of glucuronide prodrugs by antibody-targeted enzyme conjugates for cancer therapy

Cancer chemotherapy may be improved by increasing antineoplastic drug specificity for tumor cells. We have synthesized a glucuronide prodrug that can be enzymatically converted to an antineoplastic agent at tumor cells that are able to bind beta-glucuronidase-monoclonal antibody conjugates. The glucuronide prodrug BHAMG, the tetra-n-butyl ammonium salt of (p-di-2-chloroethylaminophenyl-beta-D-glucopyranoside) uronic acid, was 150 times less toxic than the parent drug, N,N-di-(2-chloroethyl)-4-hydroxyaniline, to HepG2 human hepatoma cells and over 1000-fold less toxic than the parent drug to AS-30D rat hepatoma cells in vitro. In the presence of beta-glucuronidase, BHAMG was activated and became as toxic as the parent drug N,N-di-(2-chloroethyl)4-hydroxyaniline. A conjugate (RH1-beta G) was formed by linking beta-glucuronidase to a monoclonal antibody which binds to an antigen expressed on the surface of AS-30D cells. The concentration of BHAMG causing 50% inhibition of AS-30D cellular protein synthesis was reduced over 1000-fold, from greater than 770 microM to less than 0.74 microM after these cells were preincubated with RH1-beta G. Specificity of BHAMG activation at antigen-positive cells was shown by monoclonal antibody RH1 blocking of RH1-beta G conversion of BHAMG to toxic drug and by the inability of BHAMG to be converted to active drug when antigen-negative control cells were preincubated with RH1-beta G. Our results show that the targeted-beta-glucuronidase activation of BHAMG can increase the specificity of chemotherapy for rat hepatoma in vitro and suggest that the targeted activation of glucuronide prodrugs may be useful for cancer therapy.

Assessment of histamine, bradykinin, prostaglandins E1 and E2 and carrageenin as vascular permeability agents in the horse

The vascular leakage induced by histamine, bradykinin, serotonin and prostaglandin E1 and E2 was assessed. The test agents were injected intradermally into the shaved thoracic skin of horses and the vascular leakage estimated either semi-quantitatively by recording the diameter of the lesions or by measuring the actual volume of extravasated plasma in microliters using iodine-125-labelled human serum albumin (125I-HSA) as a marker in the blood plasma. Using the latter method, the vascular leakage induced by carrageenin and the effect of coadministered prostaglandins E1 and E2 upon the vascular leakage of both histamine and bradykinin were also investigated. No obvious lesions resulted when serotonin (10(-2) mol/l) was injected but histamine and bradykinin produced circular lesions which increased in diameter for approximately 30 min. The size of the lesions and volume of extravasated plasma was dose dependent. On a molar basis, bradykinin (10(-6) mol/l, 10(-5) mol/l) was more potent than histamine but they were equipotent at 10(-4) mol/l. The size of the lesions induced by carrageenin were independent of their anatomical location on the thorax. Except for the second hour, the hourly volume of vascular leakage increased until the fifth hour when the experiment was concluded. The maximum vascular leakage resulting from the injection of prostaglandin E1 or E2 (1, 10, 100 or 1000 ng) was 7 microliters but when co-administered with bradykinin (10(-6) mol/l), the volume of leaked plasma increased from 29 to 78 microliters. No synergy was observed when either prostaglandin was co-administered with histamine (10(-5) mol/l).

Copper salicylate and copper phenylbutazone as topically applied anti-inflammatory agents in the rat and horse

Topically applied copper phenylbutazone, phenylbutazone, copper salicylate, salicylate and dimethylsulfoxide glycerol (80:20) were investigated as anti-inflammatory agents in rats and horses. Dimethylsulfoxide and glycerol (80:20) or dimethylsulfoxide, ethanol and glycerol (60:20:20) were used as the drug solvents. Subcutaneously administered carrageenin was used to induce inflammatory oedema, either in the paws of rats or the alar fold of the horse. The severity of the oedema and the anti-inflammatory effect of the drugs were assessed by measuring changes in the paw or alar-fold diameters. Copper salicylate and copper phenylbutazone were effective inhibitors of the inflammatory oedema in both species, but dimethylsulfoxide:glycerol (80:20) was not. In the rat, copper salicylate and copper phenylbutazone were superior anti-inflammatory agents compared to either salicylate or phenylbutazone, respectively. Following the topical application of four times the recommended daily dose of copper phenylbutazone to the horse for 5 days, minor skin irritation occurred and trace concentrations of phenylbutazone (maximum 0.6 microgram/ml) and negligible concentrations of oxyphenbutazone and gamma-hydroxyphenylbutazone were detected in the plasma.

Superoxide production by stimulated equine polymorphonuclear leukocytes--inhibition by anti-inflammatory drugs

Polymorphonuclear leukocytes (PMNLs) were isolated from an inflammatory exudate induced in the intercarpal joints of horses by an administration of carrageenin. Their superoxide production at rest and following stimulation with either serum-treated zymosan (STZ) or phorbol myristate acetate (PMA) was measured by cytochrome-c reduction. Stimulation of the cells increased the cytochrome-c reduction 10-15 times that of resting cells. The maxima were 20 nmol of reduced cytochrome-c per 10(6) cells per ml at 120 min (STZ) and 35 nmol of reduced cytochrome-c per 10(6) cells per ml at 60 min (PMA). The maximum inhibition of the cytochrome-c reduction by superoxide dismutase (Palosein) was 83.6% (STZ stimulation) and 72.1% (PMA stimulation). The non-steroidal anti-inflammatory drugs, phenylbutazone, salicylic acid, aspirin, sodium salicylate in addition to D-penicillamine and dimethylsulfoxide caused dose-dependent inhibition of the cytochrome-c reduction when the cells were stimulated by PMA. The maximum inhibitions were 64% and 36% for aspirin (10(-2) M), 32% and 17% for phenylbutazone (10(-3) M), 15% and 31% for dimethylsulfoxide (6.4 x 10(-1) M), 32% and 19% for salicylic acid (10(-2) M), 0% and 17% for sodium salicylate (10(-2) M) and 2.2% and 2.5% for D-penicillamine (10(-4) M) when the cells were stimulated by STZ and PMA, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of palosein (superoxide dismutase) and catalase upon oxygen derived free radical induced degradation of equine synovial fluid

The effect of oxygen derived free radicals (ODFR) upon the specific viscosity of equine synovial fluid was studied. ODFR were generated either by a mixture of ferrous iron and EDTA (Fe/EDTA) or by a mixture of hypoxanthine and xanthine oxidase (HX/XO). Incubation of the synovial fluid with both free radical generating systems decreased its specific viscosity. When the synovial fluid was incubated with Fe/EDTA the specific viscosity of the synovial fluid was reduced rapidly. By 2 mins, it was 53 +/- 3 per cent of the original specific viscosity and by 30 mins it was reduced to 39 +/- 5 per cent. In the HX/XO system, the specific viscosity was 75 +/- 4 per cent of the original specific viscosity at 10 mins and by 50 mins it was reduced to 55 +/- 3 per cent. Palosein (superoxide dismutase) was an effective inhibitor of the free radical induced reduction of the viscosity of the synovial fluid when the free radicals were generated with HX/XO but not with Fe/EDTA. Catalase was moderately effective as an inhibitor of reduction in specific viscosity of the synovial fluid when the free radicals were generated by either system. Only minor synergy resulted when mixtures of Palosein and catalase were tested for inhibition of Fe/EDTA induced reduction in the specific viscosity of equine synovial fluid. The results indicate that Palosein may protect equine synovial fluid from the effects of the superoxide radical (O2-) but not from the hydroxyl radical (OH.).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute phase response in horses: changes in plasma cation concentrations after localised tissue injury

An acute phase reaction was elicited in four horses to which Freund's adjuvant was administered intramuscularly. The localised inflammation was accompanied by changes in the plasma concentrations of copper, iron and zinc. The plasma copper concentration, the plasma ceruloplasmin copper concentration and the ceruloplasmin oxidase activity in the plasma steadily increased to a maximum 24 days after the administration of the adjuvant. At this time, the plasma copper concentration was 2.2 micrograms/ml, a 90 per cent increase over the baseline concentration. The ratio of the concentration of plasma ceruloplasmin copper to plasma copper remained constant, indicating that the non-ceruloplasmin bound copper component of the plasma is also an acute phase reactant in the horse. The plasma zinc and iron concentrations decreased to 59 per cent and 30 per cent of their respective baseline concentrations and the severity of the inflammation appeared to influence the plasma concentrations of each metal. Weak correlations between the plasma fibrinogen concentration and the plasma copper and zinc concentrations of 25 horses with plasma fibrinogen concentrations of 5 g/litre or greater indicated that a single measurement of plasma copper concentration is not useful in the diagnosis of non-specific inflammatory disorders of the horse. However, the results suggest that the plasma copper concentrations in serial samples may be used to monitor the resolution of inflammatory disorders in the horse.

Assessment of copper and zinc status of farm horses and training thoroughbreds in south-east Queensland

The copper and zinc concentrations in the blood of stabled thoroughbred horses and in Australian Stock Horses mares at pasture, either late pregnant or lactating were determined by an atomic absorption spectroscopic method. The plasma concentration of the trace elements in these apparently normal horses were generally below the "normal" range. The plasma copper, caeruloplasmin copper, whole blood copper and plasma zinc concentrations in the stabled thoroughbreds were 0.76 +/- 0.19 micrograms/ml (n = 82), 0.56 +/- 0.14 micrograms/ml (n = 83), 0.75 +/- 0.18 micrograms/ml (n = 82) and 0.47 +/- 0.09 micrograms/ml (n = 83) respectively. The plasma copper and zinc concentrations of all the brood mares at pasture (pregnant and lactating) were 0.56 +/- 0.20 micrograms/ml and 0.47 +/- 0.11 micrograms/ml (n = 30). The plasma copper concentration of the pregnant group of mares (0.64 +/- 0.18 micrograms/ml; (n = 14) was greater than that of the lactating mares (0.49 +/- 0.21; (n = 16). Variation in the plasma copper concentration was also identified between stabled and farm horses, between horses of different stables and between horses of different ages. The proportion of plasma copper bound to caeruloplasmin was 73 +/- 11.8%. These low concentrations of copper and zinc in the plasma of apparently normal horses are of clinical significance since recent evidence has indicated that copper deficiency appears to promote the development of skeletal abnormalities in foals. An alternative to the use of a single plasma sample to identify the copper or zinc deficient horse was discussed.

The nifH gene product is required for the synthesis or stability of the iron-molybdenum cofactor of nitrogenase from Klebsiella pneumoniae

The MoFe protein of nitrogenase from Klebsiella pneumoniae contains an iron-molybdenum cofactor, FeMoco, the synthesis or processing of which involves the products of at least five genes, nifQ, nifB, nifN, nifE and nifV. We have detected FeMoco activity in extracts of strains which synthesise neither of the MoFe protein subunits, indicating that FeMoco can be synthesised prior to combination with the MoFe protein polypeptides. Expression of the nifH gene (or a large part of it), was essential for FeMoco activity to be observed either in the presence or in the absence of the MoFe protein subunits. The nifH gene product was not involved in the control of the transcription of other nif gene products known to be involved in FeMoco synthesis or processing, nor was it essential for the stability of performed FeMoco before its combination with the MoFe protein polypeptides.

Some effects of chronic mercuric chloride intoxication on renal function in a horse

Chronic mercuric chloride intoxication in an aged horse given 0.8 mg Hg/kg/day for 14 weeks was manifest by signs of progressive respiratory difficulty and renal disease. The effects were not self-limiting after mercury was withdrawn, and the animal was destroyed six weeks later. Renal function changes included heavy glycosuria, modest proteinuria, phosphaturia, reduced urine osmolality, gradually increasing urine production, reduced glomerular filtration rate, and terminally, azotemia. The condition bore similarities to the Fanconi syndrome in man. Urinary gamma-glutamyl transpeptidase, alkaline phosphatase and amino-aspartate transferase activities were inconsistent indicators of tubular damage in random samples at this dose rate. The pathologic response was characterized by extensive granulomatous infiltration throughout the lungs, in particular, and to a lesser extent in the kidneys, liver and bone marrow. The renal changes included this marked interstitial reaction and proximal tubular degeneration. Mercury levels were negligible in the lungs and highest in the renal cortex. The granulomatous reaction was not encountered in previous mercury toxicity studies in horses and may indicate an individual sensitivity to the agent.

Chronic phenylmercuric acetate toxicity in a horse

Phenylmercuric acetate (PMA) was administered orally to a horse over a period of 27 weeks (190 days) at a dose rate of 0.4 mg Hg/kg per day. The effects produced were consistent with those of chronic inorganic mercury intoxication. The clinical features included masseter muscle atrophy, difficulty in prehension and mastication, malodorous breath, reduced appetite and weight loss, and reflected significant pathological changes involving the buccal, mandibular and dental tissues. Renal dysfunction was evident terminally and there was degeration and necrosis of the proximal tubular epithelium. Necrotic and mineralized foci were found in facial and masticatory msucles, splenic trabecuale and the myocardium. The central nervous system and the intestinal tract were unaffected. The approximate mean plasma inorganic mercury concentration was 500 ng/ml whereas organic mercury levels in blood were much lower. The renal cortex had the highest inorganic mercury content, three times greater than in the liver and cecum, while organic mercury was highest in those tissues and absent from the kidney. The difference in the effects produced in this horse as compared to those in a horse receiving mercuric chloride at the same mercury dose rate, could be attributed to the more rapid and complete absorption of PMA from the gastrointestinal tract.