The effects of experimentally induced bronchopneumonia on the pharmacokinetics and tissue depletion of gentamicin in healthy and pneumonic calves

The effects of a bovine bronchopneumonia model on the pharmacokinetics and tissue residue depletion profiles of gentamicin in calves weighing 90-140 kg was explored. Two groups of heifer calves were used. The first was a normal group, while the second group had bronchopneumonia induced. A scoring system was developed to evaluate the extent of disease in the groups. A bimodal distribution of the serum pharmacokinetic parameters in the pneumonic group was caused by the effects of dehydration. When the severely dehydrated calves were omitted from the analysis, serum clearance of gentamicin was significantly higher in the pneumonic group than in the normal group (P less than 0.05). The pharmacokinetic equations used to fit the tissue concentrations varied from tissue to tissue and between groups. Because the best equation of a particular tissue's concentrations varied between groups, withdrawal periods, which are normally determined in healthy animals, may be inappropriate in diseased animals. Addition of several parameters (serum creatinine, serum urea nitrogen, albumin, fibrinogen, and total protein concentrations, white blood cell counts, central fluid volume, volume of distribution at steady state, area under the serum concentration vs time curve, serum clearance, and elimination rate constant) to these tissue-depletion models using multiple regression improved the prediction of a concentration in a given tissue.     

An in vitro method for testing synergistic action of parasiticides using malachite green and formalin as a model system

Abstract. An in vitro technique was developed to screen drugs for toxicity to laboratory cultured protozoans. Drugs were diluted using standard microtitration equipment. An easily cultured protozoan, Tetrahymena pyriformis , was added to the dilutions of drugs and viability was checked daily for 10 days. Drugs used as a model system to test the technique were formalin and malachite green. Effective concentrations of formalin determined by this in vitro technique were close to recommended therapeutic treatment levels for Ichthyophthirius . Malachite green was effective at concentrations in excess of recommended therapeutic treatment levels for Ichthyophthirius . The synergistic effect of formalin and malachite green was demonstrated. This technique can he of use in determining effectiveness of new drugs as parasiticides.     

Re-defining native woodland

The term ‘native’ is widely used to refer to a smallnumber of British tree species and naturally regenerating woodland.This paper proposes that the concept is rooted in an out-datedunderstanding of vegetation dynamics. Consequently, its definitionis arbitrary and ecologically flawed, and should be replacedby terms that make clear the different but important aspectsof biogeographical origin, local distinctiveness and conservationvalue.     

RELIABILITY OF T2‐WEIGHTED SAGITTAL MAGNETIC RESONANCE IMAGES FOR DETERMINING THE LOCATION OF COMPRESSIVE DISk HERNIATION IN DOGS

Magnetic resonance imaging is used commonly to diagnose intervertebral disk herniation in dogs. It is common to locate areas of suspected compression on sagittal T2‐weighted (T2‐W) images and then obtain limited transverse images in these areas to reduce the acquisition time (a step‐by‐step approach). Our objective was to assess the frequency of correct localization of spinal cord compression due to disk herniation using only the sagittal images. The results from isolated readings of the sagittal T2‐W images alone or combined with a single‐shot fast spin echo (SSFSE) slab in 118 dogs were compared with a gold standard, based on a consensual reading of all images available, including complete transverse images across the entire spinal segments under study. The sites of compression were localized correctly from the sagittal images in 89.8% of dogs. If only the most significant lesions were accounted for, the percentage increased up to 95.2%. In 54.9% of the readings with incorrect localization, the actual compressive site was immediately adjacent to the one suspected from review of the sagittal images. The frequency of correct localization was higher in the cervical region, and was increased by examination of the SSFSE slab. The most common cause of disagreement was the presence of multiple degenerate bulging disks. Based on these results we recommend obtaining transverse images across the entire segment when multiple bulging disks are present. It is also recommended to obtain transverse images across the spaces immediately adjacent to the suspected site of herniation from review of the sagittal images.     

The Self-Assembly Mechanism of Alkanethiols on Au(111)

The self-assembly mechanism of alkanethiol monolayers on the (111) surface of gold was discovered with the use of an ultrahigh-vacuum scanning tunneling microscope. Monolayer formation follows a two-step process that begins with condensation of low-density crystalline islands, characterized by surface-aligned molecular axes, from a lower density lattice-gas phase. At saturation coverage of this phase, the monolayer undergoes a phase transition to a denser phase by realignment of the molecular axes with the surface normal. These studies reveal the important role of molecule-substrate and molecule-molecule interactions in the self-assembly of these technologically important material systems.     

Non-destructive measurement of sunshine bass, Morone chrysops (Rafinesque) ×Morone saxatilis (Walbaum), body composition using electrical conductivity

Abstract. We describe a rapid, non-destructive method for determining lean body mass (LBM; i.e. total body mass — total lipid mass) and lipid content in live fish. This method provides non-invasive determination of body composition by measuring the total body electrical conductivity (TOBEC) of an animal placed within a low-frequency electromagnetic field. This principle is governed by the different electrical properties of body fat and fat-free tissues. Relationships between TOBEC analysis and body composition were examined using juvenile sunshine bass (hybrid striped bass, Morone chrysops (Rafinesque) ♀× M. saxatilis (Walbaum) ♂) in a size range of 24–124g. Whole-body conductivity was significantly correlated to LBM, lipid, protein, water, and ash content. Analyses of an independent group of fish indicated TOBEC to be a reliable indicator of body composition. This method should prove useful for deriving body composition data at various phases of an experiment or a life cycle, rather than a single point in time as with destructive methods.     

Primary lung tumours in the cat

Seventeen cats with primary lung tumours were referred to the University of Bristol Veterinary School between 1970 and 1986. Clinical, radiographic and pathological findings were recorded in each case. Analysis of these findings allowed assessment of those features most helpful in reaching a definitive diagnosis.     

Oral clindamycin disposition after single and multiple doses in normal cats

Eighteen normal cats were randomly allocated into three treatment groups and dosed with clindamycin aqueous solution for 10 days at a dosage rate of: (1) 5.5 mg/kg b.i.d.; (2) 11 mg/kg b.i.d.; or (3) 22 mg/kg once daily. Serum disposition of clindamycin was determined after the first and last dose of clindamycin was given, and was analyzed using model-independent pharmacokinetics by both the trapezoidal rule method and the predictive equation method. Complete blood counts and clinical chemistries were determined before and after the study. The trapezoidal rule method produced similar mean results with much less variance than the predictive equation method. Mean residence time was longer (P less than 0.05) after the high dose (393 +/- 77 min) than after either the low or medium doses (276 +/- 51 and 274 +/- 45 min, respectively). Oral volume of distribution (Vd(ss)/F) after the high dose (3.06 +/- 0.92 l/kg) was larger (P less than 0.05) than that after the low or medium doses (1.62 +/- 0.30 and 1.76 +/- 0.53 l/kg, respectively). Oral Vd(ss)/F was significantly smaller (P less than 0.001) after the last dose than after the first dose when analyzed by treatment group. Significant (P less than 0.01) decreases in the leukogram and erythrogram were observed, due to the large amount of blood collected for drug analysis. No clinical signs of drug intoxication were observed, and no drug-related necropsy findings were found.