Research Note: Detection of antibiotic-resistance genes in commercial poultry and turkey flocks from Italy.

Antibiotics are routinely used in commercial poultry farms for the treatment of economically important bacterial diseases. Repeated use of antibiotics, usually administered in the feed or drinking water, may also result in the selection of resistant bacteria in animal feces, able to transfer their antimicrobial-resistance genes (ARG), residing on mobile elements, to other microorganisms, including human pathogens. In this study, single and multiplex PCR protocols were performed to detect tetracycline-, lincomycin-, chloramphenicol-, aminoglycoside-, colistin-, vancomycin-, and carbapenem-resistance genes, starting from 38 litter samples collected from 6 poultry and 2 turkey Italian flocks. The ARG were confirmed for all investigated classes of antimicrobials, except for colistin (mcr-1, mcr-2, mcr-3,mcr-4 mcr-5) and carbapenem (IMP, OXA-48, NDM, KPC), while the vanB gene was only detected for vancomycin. The highest positivity was obtained for tetracycline (tet[L], tet[M], tet[K], tetA[P]] and aminoglycoside (aadA2) ARG, confirming the predominant use of these antimicrobials in the veterinary practice and their potential to enhance the resistance patterns also in humans as a consequence of environmental contamination. On the contrary, the dissemination by poultry of ARG for critically important antimicrobials seems to be of minor concern, suggesting a negligible environmental dissemination by these genes in the Italian poultry industry. Finally, the molecular screening performed in this study using a noninvasive sampling method represents a simple and rapid tool for monitoring the ARG patterns at the farm level.

Aetiology of Canine Infectious Respiratory Disease Complex and Prevalence of its Pathogens in Europe.

The canine infectious respiratory disease complex (CIRDC) is an endemic worldwide syndrome involving multiple viral and bacterial pathogens. Traditionally, Bordetella bronchiseptica (Bb), canine adenovirus type 2 (CAV-2), canine distemper virus (CDV), canine herpesvirus (CHV) and canine parainfluenza virus (CPiV) were considered the major causative agents. Lately, new pathogens have been implicated in the development of CIRDC, namely canine influenza virus (CIV), canine respiratory coronavirus (CRCoV), canine pneumovirus (CnPnV), Mycoplasma cynos and Streptococcus equi subspecies zooepidemicus. To better understand the role of the different pathogens in the development of CIRDC and their epidemiological relevance in Europe, prevalence data were collected from peer-reviewed publications and summarized. Evidence of exposure to Bb is frequently found in healthy and diseased dogs and client-owned dogs are as likely to be infected as kennelled dogs. Co-infections with viral pathogens are common. The findings confirm that Bb is an important cause of CIRDC in Europe. CAV-2 and CDV recovery rates from healthy and diseased dogs are low and the most likely explanation for this is control through vaccination. Seroconversion to CHV can be demonstrated following CIRDC outbreaks and CHV has been detected in the lower respiratory tract of diseased dogs. There is some evidence that CHV is not a primary cause of CIRDC, but opportunistically re-activates at the time of infection and exacerbates the disease. The currently available data suggest that CIV is, at present, neither a prevalent nor a significant pathogen in Europe. CPiV remains an important pathogen in CIRDC and facilitates co-infection with other viral and bacterial pathogens. CnPnV and CRCoV are important new elements in the aetiology of CIRDC and spread particularly well in multi-dog establishments. M. cynos is common in Europe and is more likely to occur in younger and kennelled dogs. This organism is frequently found together with other CIRDC pathogens and is significantly associated with more severe respiratory signs. S. zooepidemicus infection is not common and appears to be a particular problem in kennels. Protective immunity against respiratory diseases is rarely complete, and generally only a reduction in clinical signs and excretion of pathogen can be achieved through vaccination. However, even vaccines that only reduce and do not prevent infection carry epidemiological advantages. They reduce spread, increase herd immunity and decrease usage of antimicrobials. Recommending vaccination of dogs against pathogens of CIRDC will directly provide epidemiological advantages to the population and the individual dog.

Detection of 'Candidatus Neoehrlichia mikurensis' and other Anaplasmataceae and Rickettsiaceae in Canidae in Switzerland and Mediterranean countries.

INTRODUCTION: 'Candidatus Neoehrlichia mikurensis' is an emerging tick-borne zoonotic agent that primarily affects immunocompromised human patients. Dogs and foxes are frequently exposed to ticks, and both species are in close proximity to humans. This is the first study to systematically investigate the occurrence of 'Candidatus Neoehrlichia mikurensis' in Canidae in Europa. We analyzed 1'739 blood samples from dogs in Switzerland, Italy, Spain and Portugal and 162 blood samples from free-ranging red foxes (Vulpes vulpes) in Switzerland. All samples were tested using a previously described multiplex real-time PCR for the Anaplasmataceae family, the 'Candidatus Neoehrlichia' genus and the 'Candidatus Neoehrlichia mikurensis' species. All Anaplasmataceae positive samples were subsequently tested using specific real-time PCRs for Anaplasma phagocytophilum, Anaplasma platys, Ehrlichia canis and Rickettsia helvetica. Among the tested animals, one dog from Zurich tested positive for 'Candidatus Neoehrlichia mikurensis'. The 12-year old West Highland white terrier had been splenectomized 3 months prior to the blood collection and presented with polyuria/polydipsia. Fanconi syndrome was diagnosed based on glucosuria with normoglycemia and hyperaminoaciduria. A. platys and E. canis were detected in 14/249 dogs from Sicily and Portugal; two of the dogs were coinfected with both agents. Four Swiss foxes tested positive for A. phagocytophilium. R. helvetica was detected for the first time in a red fox. In conclusion, 'Candidatus Neoehrlichia mikurensis' infection should be considered in sick dogs, particularly when immunocompromised. The pathogen seems not to be widespread in Canidae in the investigated countries. Conversely, other Anaplasmataceae were more readily detected in dogs and foxes.

INTRODUCTION: 'Candidatus Neoehrlichia mikurensis' est un agent de zoonose transmis par les tiques qui gagne en importance et concerne principalement les patients immunosupprimés. Les chiens comme les renards sont souvent concernés par des morsures de tiques et vivent en contact étroit avec les êtres humains. Dans le présent travail, nous étudions pour la première fois systématiquement la présence de 'Candidatus Neoehrlichia mikurensis' chez les canidés en Europe. Les échantillons sanguins analysés provenaient de 1'739 chiens de Suisse, d'Italie, d'Espagne et du Portugal ainsi que de 162 renards (Vulpes vulpes) de Suisse. Tous les échantillons ont été examinés avec un test de PCR multiplex en temps réel déjà publié quant à la présence d'agents de la famille des Anaplasmataceae, du genre 'Candidatus Neoehrlichia' et de l'espèce 'Candidatus Neoehrlichia mikurensis'. Les échantillons positifs aux Anaplasmataceae ont ensuite été testés avec un test PCR en temps réel spécifique quant à Anaplasma phagocytophilum, Anaplasma platys, Ehrlichia canis und Rickettsia helvetica. Parmi les échantillons examinés se trouvait celui d'un chien de Zürich qui était infecté par 'Candidatus Neoehrlichia mikurensis'. Ce West Highland White Terrier de 12 ans avait été présenté pour polyurie/polydipsie; il avait été splénectomisé trois mois avant la prise de l'échantillon. Au vu d'une glycosurie et d'une hyperaminoacidurie accompagnées d'une glycémie normale, on a posé le diagnostic de syndrome de Fanconi. A. platys et E. canis ont été mis en évidence chez 14/249 chiens provenant de Sicile et du Portugal; deux chiens étaient infectés par les deux agents pathogènes. Quatre renards suisses étaient positifs à A. phagocytophilium et R. helvetica a été trouvé pour la première fois chez un renard. En résumé, on peut dire qu'une infection à 'Candidatus Neoehrlichia mikurensis' chez un chien malade doit être prise en considération comme diagnostic différentiel, particulièrement chez les anomaux immunosupprimés. Toutefois cet agent n'est pas très répandu chez les canidés des pays examinés, contrairement aux autres Anaplasmataceae spp. qui ont été trouvées plus souvent chez les chiens et les renards.

Feline calicivirus VP2 is involved in the self-assembly of the capsid protein into virus-like particles.

Feline calicivirus (FCV) is considered the most common upper respiratory tract disease (URTD) associated pathogen in cats. We previously expressed FCV VP1 capsid protein in insect cells by baculovirus system and we observed that this protein self-assemble into virus-like particles (VLPs) different in size and lacking the typical cup-like depressions of caliciviruses. In the present study, VP1 and the small basic structural protein VP2 of FCV were individually expressed by baculovirus system. Coinfection of insect cells with both recombinant viruses resulted in VP1 and VP2 self-assembly to form depressions similar to native capsids in size and appearance, demonstrating that VP2 interacts with the VP1 protein in the formation of VLPs.

Cerebral toxoplasmosis in striped dolphins (Stenella coeruleoalba) stranded along the Ligurian Sea coast of Italy.

This article reports the results of necropsy, parasitologic, microbiologic, histopathologic, immunohistochemical, indirect immunofluorescence, biomolecular, and serologic investigations on 8 striped dolphins (Stenella coeruleoalba) found stranded from August to December 2007 on the Ligurian Sea coast of Italy. Severe, nonsuppurative meningoencephalitis was found in 4 animals, as characterized by prominent perivascular mononuclear cell cuffing and macrophage accumulations in neuropil. These lesions were associated with mild lymphocytic-plasmacytic infiltration of choroid plexuses in 1 dolphin. Toxoplasma gondii cysts and zoites, confirmed by immunohistochemical labeling, were scattered throughout the brain parenchyma of 2 of the 4 dolphins. No viral inclusions were seen in the brain of any animal. Other findings included severe bronchointerstitial pneumonia and pulmonary atelectasis, consolidation, and emphysema. Parasites were identified in a variety of organs, including lung (Halocerchus lagenorhynchi). Microbiologic and serologic examinations for Brucella spp were negative on all 8 dolphins. The 4 animals with meningoencephalitis had serum antibodies against T gondii (titers ranging from 1:80 to 1:320) but not against morbillivirus. In contrast, the other 4 dolphins were seropositive for morbillivirus (with titers ranging from 1:10 to 1:40) but seronegative for T gondii. No morbillivirus antigen or nucleic acid was detected in the tissues of any dolphin. It is concluded that the severe lung and brain lesions were the cause of death and that T gondii was the likely etiologic agent of the cerebral lesions. Morbillivirus infection was not considered to have contributed to death of these animals.

Etiological investigation of multiple respiratory infections in cats.

In order to evaluate the relevance of multiple infections in domestic cats with Upper Respiratory Tract Disease (URTD) one hundred animals with clinical signs were investigated for detection of Feline Herpesvirus type-1 (FHV-1), Chlamydophila felis, Feline Calicivirus (FCV) and Bordetella bronchiseptica from mucosal swabs. Forty-seven cats were positive for FCV, 42 cats for FHV-1, 26 for B. bronchiseptica and 8 for C. felis. Dual or multiple infections were found in 33 of examined animals. Our results document that FCV and FHV-1 are the major recognized cause of URTD, although infections associated with other pathogens such as B. bronchiseptica or C. felis are also common in cats.

Diagnosis of ovine chlamydial abortions by PCR-RFLP performed on vaginal swabs.

Ovine enzootic abortion is an infectious and contagious disease clinically characterized by abortion and weak neonates, affecting sheep and goats. The etiological agent is Chlamydophila (C.) abortus, which is considered one of the most common animal pathogens of small ruminants; it has important economic implications and represents a significant zoonotic risk. Clinical diagnosis is often difficult because the clinical signs and the pathological lesions are not specific for C. abortus infection, in fact they can also be observed as a result of infections with other abortifacient agents. Moreover, the involvement of the laboratory is necessary to perform the definitive diagnosis. One hundred and seventeen vaginal swabs from sheep with clinical signs related to chlamydial infection were examined by a PCR-RFLP assay that demonstrated high specifity and sensitivity. Six samples were positive for C. abortus. Vaginal swabs are easy to handle and allow to deal with biohazardous material in safety conditions.

Use of a duplex-PCR assay to screen for Feline Herpesvirus-1 and Chlamydophila spp. in mucosal swabs from cats.

Fifty-four ocular and forty-six pharyngeal swabs, collected from 54 cats with respiratory syndrome, were analyzed by duplex-PCR to evaluate the presence of Feline Herpesvirus type 1 and Chlamydophila spp. Both pathogens are in the population of cats and as four cats were positive only in ocular swabs and three only in pharyngeal ones, it is deduced that a correct diagnostic approach has to foresee the dispatch to the laboratory of both swabs. Furthermore, all chlamydophila strains analysed by endonuclease restriction were classified as Chlamydophila felis.

Slow release of two antibiotics of veterinary interest from PVA hydrogels.

Two antibiotics, tylosin tartrate and oxytetracycline hydrochloride, were entrapped in poly(vinyl alcohol) (PVA) hydrogels (MW 31,000-50,000) by a cryogen procedure obtaining a controlled release system suitable for veterinary application. It was found that at a low drug matrix loading (10 mg/ml), the in vitro release rate of both antibiotics could be reduced by a previous freeze drying of the gel, while no reduction in drug rate took place in heavily loaded matrices (300 mg/ml). When PVA hydrogels containing tylosin were administered to rats per os the drug could not be detected in the blood, but it was found in organs,: liver, kidneys, and muscles, for up to 120 h. On the other hand, when the same amount of drug was administered orally as powder, no appreciable organ accumulation was detected, while the drug was found in faeces and urine. These data show that PVA hydrogels can be a suitable slow release system for tylosin administration. Oxytetracycline could also be quantitatively entrapped and released from PVA hydrogels, but once administered per os to rats, it was not detected in blood or organs.

M gene evolution of canine coronavirus in naturally infected dogs.

Two stray pups (A and B), three and five months old, respectively, both naturally infected with canine coronavirus (CCoV), were studied for 180 days. The virus was detected intermittently in the pups' faeces by PCR for periods of 156 and 146 days, respectively. Sequence analysis of a fragment of the gene encoding the M protein revealed that the viruses detected at the onset of the infection were very similar to typical strains of CCoV, whereas from 42 days after infection in pup A and 40 days after infection in pup B the viruses had nucleotide and amino acid mutations resembling sequences in feline coronavirus.

Plain and drug loaded polyphosphazene membranes and microspheres in the treatment of rabbit bone defects.

The healing of periodontal surgical defects was studied in rabbits, using polyphosphazenes (POP) membranes and microspheres, both plain or drug-enriched. POP polymers having amino acid ester as backbone substituents, are used since they resorb and undergo hydrolytic degradation to ammonia, phosphate and amino acids. Fourteen animal were operated in tibia, and other fourteen at angle of the mandible, that was reached by extraoral access. Bone defects were performed in tibiae, and covered either with POP or with poly-tetrafluoroethylene (PTFE) membranes, while other rabbits served as controls. The animals were sacrificed after one and two months, and the tibiae taken and processed for optical microscopy. Similar surgical defects were made in mandible, and POP membranes were placed over the breaches, some of which were filled with POP microspheres, both alone or mixed with granular hydroxyapatite. For comparison, two rabbits were treated with PTFE membranes, while other two served as controls. The animals operated at the mandible were all sacrificed after one month, and the operated bones taken and processed for histology. It was found that POP membranes were very effective in promoting the healing in tibiae, while less satisfactory results were found in the animals treated with PTFE membranes and in controls. In mandible, the healing occurred without a clear relationship with the grafted microgranular material or the membrane, since repairing bone was found also in controls. In any case, both POP membranes and microspheres showed excellent biocompatibility, as no inflammatory cells or macrophages were found in the surrounding tissue. This property was completely independent from the presence of drug, since the matrix-entrapped drugs, released in the tissue, did not hamper the bone healing. It was also found that POP, by itself, has a positive effect in stimulating the bone repair.

Polyphosphazene membranes and microspheres in periodontal diseases and implant surgery.

Membranes or microcapsules made from polyphosphazenes bearing amino acid side groups are proposed for the treatment of periodontal diseases. Polyphosphazene membranes, prepared with alanine ethyl ester and imidazole in the molar ratio of 80:20 as phosphorus substituents, gave a degradation rate that corresponded to the healing of the bone defect. These membranes were much more successful in promoting healing of rabbit tibia defects than polytetrafluoroethylene membranes. Antibacterial or anti-inflammatory drugs, useful in periodontal tissue regeneration, could be entrapped in the polyphosphazene membranes and released both in vitro and in vivo at a rate that ensured therapeutic concentrations in the surrounding tissue. Polyphosphazene microspheres, prepared with phenylalanine ethyl ester as a phosphorus substituent and loaded with succinylsulphathiazole or naproxen, were also obtained. The kinetics of release from these matrices were very convenient in yielding local concentrations of the two drugs that are useful per se or when mixed with hydroxyapatite for better bone formation.

Crystallization and preliminary X-ray analysis of the Escherichia coli UDP-MurNAc-tripeptide D-alanyl-D-alanine-adding enzyme (MurF).

Crystals of the Escherichia coli UDP-MurNAc-tripeptide D-Ala-D-Ala-adding protein (MurF), which catalyzes the formation of the last metabolite of the bacterial cell-wall building block, have been grown in hanging-drop vapor-diffusion trials using PEG 8K as a precipitating agent. The crystals belong to hexagonal space group P6(1) or P6(5), with unit-cell dimensions a = b = 74, c = 425 A. The asymmetric unit contains two molecules, with a crystal volume per protein mass (V(m)) of 3.4 A(3) Da(-1) and a solvent content of about 64% by volume. A native data set to 2.8 A resolution has been obtained from a frozen crystal using a synchrotron X-ray source.

Polyorganophosphazene microspheres for drug release: polymer synthesis, microsphere preparation, in vitro and in vivo naproxen release.

Microsphere preparation for naproxen slow release was investigated using two newly prepared biodegradable polyorganophosphazenes, derivatized at the phosphorus atoms with phenylalanine ethyl ester and imidazole at molar ratios of 71/29 and 80/20. The polymers were prepared by substitution of the chloride atoms of polydichlorophosphazene with a phenylalanine ethyl ester-imidazole mixture followed, after 7 or 48 h reaction, by the addition of excess imidazole. Three methods of microsphere preparation have been considered: spray-drying, emulsion/solvent evaporation and emulsion/solvent evaporation-extraction. Microparticles obtained by spray-drying were found to possess a narrow distribution size with a mean diameter of 2-5 microm. Their internal structure consisted of a porous or empty core depending upon the solvent used for the preparation. Furthermore the microspheres prepared with this technique rapidly released the entrapped naproxen independently of the used polymer, the drug loading or the preparation process. On the other hand microspheres prepared by solvent evaporation or solvent evaporation-extraction showed a distribution size ranging between 10 and 100 microm. By the appropriate choice of pH and solvent composition of the external phase, naproxen could be entrapped, in these microspheres, with a yield higher of 80%. The polymer composition dictates the in vitro release rate of naproxen from the particles, which was faster when the microspheres were prepared with the polymer at higher imidazole content. In vivo experiments, carried out by subcutaneous implantation in rats of microspheres prepared by solvent evaporation, demonstrated that a constant level of naproxen in plasma could be maintained up to 400 h at a suitable concentration for antinflammatory activity.

Predictable deuteration of recombinant proteins expressed in Escherichia coli.

Random deuteration of recombinant proteins in Escherichia coli is widely used for protein structure determination by nuclear magnetic resonance (NMR). It is desirable to predict accurately the degree of deuteration because each NMR experiment benefits from a different level of deuteration. The method described here which uses [2H]2O and glucose as the sole carbon and deuterium sources is an alternative for a previously published procedure using acetate and [2H]2O (Venter et al., J. Biomol. NMR 5, 339-344, 1995) and it is of advantage for proteins that do not express well using acetate. While the deuteration degree with acetate is approximately linear with the [2H]2O content in the medium, the use of glucose leads to deviations up to 19%, which is analyzed systematically here. With [2H]2O as the sole deuterium source 0-86% of the chemically nonexchangeable hydrogen atoms can be deuterated. Higher levels of deuteration require perdeuterated glucose in combination with [2H]2O. As an example, recombinant peptide deformylase from Bacillus subtilis was overexpressed, deuterated to various degrees, purified, and analyzed by mass spectrometry and NMR.

Serologic survey for selected viral pathogens in brown bears from Italy.

Blood samples were collected from six captive bears and nine free-ranging Marsican brown bears (Ursus arctos marsicanus) in the Abruzzo National Park, Italy, between 1991 and 1995. Sera were tested for evidence of exposure to canine distemper virus (CDV), canine adenovirus type 2, canine coronavirus, and canine parvovirus type 2 (CPV-2). Serologic evidence of CDV and CPV-2-exposure was found in both captive and free-ranging bears. This may be the first report of CDV exposure in free-ranging bears.

Anti-inflammatory activity of polyphosphazene-based naproxen slow-release systems.

A biocompatible and biodegradable polyphosphazene bearing phenylalanine ethyl ester, imidazole and chlorine (10.7:1:2.5 molar ratio) as substituents of the phosphorus atoms of the polymer backbone was studied for the preparation of polymeric naproxen slow-release systems. Discs 2.5 cm in diameter and 0.5 mm (thin) or 0.65 mm (thick), loaded, respectively, with 20 and 13.5% naproxen, showed different drug release kinetics, the thin matrices releasing naproxen at a faster rate and for a shorter time. In-vivo studies in rats demonstrated the pharmacological efficacy of these two different delivery systems in the inhibition of acute or chronic inflammatory diseases. Subcutaneous implantation of the thin matrices in rats was found to reduce carrageenan oedema induced both 1 h and 7 days after implantation. Rats implanted with thick matrices showed a reduction in chronic inflammation caused by adjuvant arthritis. Approximately 78% inhibition of arthritic oedema was found 28 days after subcutaneous administration of the matrices whereas 28.7% inhibition was found after daily oral administration of naproxen. Blood levels of naproxen in arthritic rats after matrix implantation showed the presence of drug up to day 28. These positive results have encouraged us to study a controlled-release system suitable for use in man.

Preparation and characterisation of polyphosphazene-based controlled release systems for naproxen.

A new polyphosphazene polymer suitable for preparation of naproxen controlled release systems has been prepared by non complete substitution of the chlorine at the phosphorus atoms of polydichlorophosphazene with phenylalanine ethyl ester and imidazole. Polymeric disks obtained by solvent evaporation were found to maintain their integrity for months either "in vivo" and "in vitro" after incubation in buffer, although the intrinsic viscosity undergoes a rapid decrease. The release rate of naproxen from the films was found to depend on thickness of the matrixes and amount of entrapped drug. "In vitro" release spikes, corresponding to initial in plasma burst after subcutaneous implantation of the films in rats, have been observed with high concentrations of drug in the matrixes. On the other end decreasing the drug concentrations in the polymer matrixes, the naproxen release approximates a zero order kinetic and a controlled release is obtained for weeks. Scanning electron microscopy showed that the disks giving spikes in drug release are characterised by the presence of naproxen crystals on the matrix surface. "In vivo" studies are demonstrating that the initial naproxen concentration spike is useful in the treatment of acute models of inflammation, while a more constant and lasting release is successful in chronic inflammation models. The degradation profile of this new polyphosphazene as well as preliminary pharmacological data are also reported.

Activity of a novel nonpeptidyl growth hormone secretagogue, L-700,653, in swine.

L-700,653 is a potent nonpeptidyl GH secretagogue consisting of a benzolactam structure: (4'-[[3(R)-[[3-[(2(S),3-dihydroxypropyl) amino]3-methyl-1-oxobutyl]amino]2,3,4,5-tetrahydro-2-oxo-1H-1-benzaze pin- 1-yl]methyl][1,1'-biphenyl]2-carboxamide hydrochloride). When administered sc by a Medi-Jector device at 0, 0.003, 0.01, 0.03, and 0.1 mg/kg BW to male castrated swine (approximately 50 kg BW), L-700,653 stimulated dose-related increases in peak plasma GH concentrations by 20% (P = NS), 150% (P = NS), 250% (P < 0.05), and 340% (P < 0.05), respectively, over the saline vehicle control value (11.3 +/- 6.5 ng/ml) and stimulated increases in GH areas under the curve (AUCs) by 10% (P = NS), 30% (P = NS), 90% (P < 0.05), and 100% (P < 0.01), respectively, over the saline vehicle control value (799 +/- 145 ng/min.ml). After sc administration of L-700, 653, there were no significant changes in plasma LH levels. Subcutaneous dose of 0.03 or 0.1 mg/kg increased plasma cortisol AUCs by 60% (P = NS) and 150% (P < 0.03) over the control value (2461 +/- 935 ng/min.ml) and increased cortisol peaks by 80% (P = NS) and 200% (P < 0.01), respectively, over the control value (38.3 +/- 12.3 ng/ml). Repeated sc administration of L-700,653 (0.03 or 0.1 mg/kg) at 0800, 1400, and 2000 h daily over 3 days consistently increased mean GH peak and GH AUC at each treatment period, with minimal and maximal increases of 40% and 190% in GH peak level at the 0.03 mg/kg dose and 100% and 400% increases in GH peak level at the 0.01 mg/kg dose, respectively. Continuous i.v. infusion of L-700,653, at either 0.01 or 0.1 mg/kg BW.h over a 180-min period, increased GH AUCs by 60% (P = NS) or 470% (P < 0.01) and GH peaks by 190% (P = NS) or 1520% (P < 0.01), respectively, over the control value (589 +/- 313 ng/min.ml; 7.0 +/- 11.1 ng/ml). After a 180- to 300-min saline infusion, an iv bolus dose of 0.1 mg/kg L-700,653 resulted in GH responses inversely proportional to the previous infusion dose, i.e. 0, 0.01, or 0.1 mg/kg.(ABSTRACT TRUNCATED AT 400 WORDS)