Electrostatic depletion forces between planar surfaces.

The interaction between two dielectric plates immersed in an electrolyte solution is examined by using a variational perturbation approximation for the grand partition function. This approach differs from previous treatments in that the screening length between the plates is treated as a variational parameter. A key finding is that adjacent to each plate is a layer of ion depletion with thickness given by about one-half of a Bjerrum length. Consequently, for plate-plate separations less than the Bjerrum length, nearly all the electrolyte is excluded from between the plates, and the interaction is given by the sum of a van der Waals interaction and an attractive osmotic depletion force. In contrast to the predictions of previous theories, the interaction between the plates at short range increases with increasing electrolyte concentration and may provide an important contribution to the salt-induced attraction, commonly referred to as salting out. Because the range of the osmotic depletion force is roughly equal to the Bjerrum length, it increases with the square of the valency of the electrolyte. At larger plate-plate separations, the van der Waals interaction is screened as electrolyte enters the space between the plates, leading to an exponential decay of the interactions, as has been previously observed. However, this interaction is slightly stronger than that previously predicted, due to ion depletion from the surface of the interface, also this effect increases with increasing electrolyte concentration.

Observations on respiratory flow strategies during and after intense treadmill exercise to fatigue in thoroughbred racehorses.

REASONS FOR PERFORMING STUDY: Locomotor-respiratory coupled (LRC) breath types are a feature of galloping exercise in horses. Differences in breath type have been demonstrated during exercise in particular the 'big respiratory cycle' (BRC) and 'flow hesitation'. To investigate breath types during recovery and quantitatively investigate BRCs during exercise to understanding the mechanism driving BRCs. OBJECTIVES: To investigate the occurrence of different breath types during and after intense treadmill exercise, and test the hypothesis that large breaths (BRCs) were a function of respiratory frequency. METHODS: Six trained and clinically normal Thoroughbred horses were exercise tested on a treadmill (slope 10%). Breath-by-breath pulmonary ventilation was measured continuously during exercise and recovery using a Quadflow mask. RESULTS: Five different breath types were identified, and classified as normal monophasic, normal biphasic, deglutition, effort pause, or large breaths. Exercising at 10 m/sec, the number of large breaths was significantly related to Rf (r = -0.86, P = 0.03). During 120 sec after exercise there were 2 distinct populations of breaths, large and normal monophasic. CONCLUSIONS: BRC type breaths are a normal feature of ventilation during and after intense exercise. In recovery there are two distinct breath populations. During exercise BRC frequency is inversely associated with respiratory frequency and highly dependant on the individual horse. From intense exercise to recovery, high flow rates and LRC limited tidal volumes are replaced by high tidal volumes and progressively decreasing flow rates. There is a temporal association between BRC occurrence and PECO2. POTENTIAL RELEVANCE: Breath types and the physiological mechanism for driving each type is important in the clinical interpretation of respiratory disease or dysfunction. The demonstration of BRC association with PECO2 may help understand the driving mechanism for the BRC. In pulmonary function testing, breath type is important in quantitative results. The demonstration that high tidal flows with limited tidal volumes during intense exercise being replaced by high tidal volumes and progressively decreasing flows in recovery has potential clinical relevance.

Electrolytes at spherical dielectric interfaces.

A variational theory is developed and applied to study the properties of dielectric spheres immersed in a symmetric electrolyte solution. In the limit that the radius of the sphere becomes much larger than the Debye screening length, the system reduces to that of a planar dielectric interface. For this case, the excess surface tension obtained by the variational theory reduces to the Onsager-Samaras [J. Chem. Phys. 2, 528 (1934)] limiting law at low electrolyte concentrations. As the radius of the dielectric sphere decreases, the excess surface tension also decreases. The implications of this work to protein-salt interactions and the salting out of proteins are discussed.

Thoracolaryngeal reflex latencies in Thoroughbred horses with recurrent laryngeal neuropathy.

Electrolaryngeography was used to study the latencies of the thoracolaryngeal adductor reflex in Thoroughbred horses with and without recurrent laryngeal neuropathy (RLN). Latencies were compared in horses with grades 1 and 2 RLN, diagnosed by endoscopy in resting horses. The reliability of the measurements, effect of sedation and correlations of latencies with age of the horse were also studied. There was no effect of sedation on reflex latency periods. The latency of the reflex period measured to a convolved peak of the electromyographic response was significantly different in horses with grades 1 and 2 disease; medians and quartile ranges were 0.067 (0.065-0.073) and 0.072 (0.068-0.074) s, respectively (P<0.05). Significant associations were found between reflex latencies and both horse age and the grade of RLN. Reflex latency measurements are reliable and sensitive, and may assist with the clinical appraisal of Thoroughbred horses with RLN.

Reliability of cardiorespiratory measurements with a new ergospirometer during intense treadmill exercise in Thoroughbred horses.

This study investigated the reliability of measurements with a new equine ergospirometer (Quadflow). Heart rate and blood lactate responses during exercise in horses wearing the Quadflow and an open flow mask were also compared. The mean percentage error of the oxygen uptake measurements was 8.2% (range 2.1-12.5%). Percent error for peak expiratory flow rates ranged from 6.1% to 9.4 %, and for minute ventilation from 2.5% to 7.4%. The coefficients of variation of the means of four measurements in two horses exercising continuously at 9.0 m/s were <5% for variables related to pulmonary ventilation, and was 7.7% for oxygen uptake. The Quadflow mask resulted in small increases in blood lactate concentration and relative heart rate during submaximal exercise. It was concluded that between- and within-test reliability statistics for important measurements in equine clinical exercise testing were acceptable for routine use in a veterinary practice or research laboratory.

Protein-protein interactions in concentrated electrolyte solutions.

Protein-protein interactions were measured for ovalbumin and for lysozyme in aqueous salt solutions. Protein-protein interactions are correlated with a proposed potential of mean force equal to the free energy to desolvate the protein surface that is made inaccessible to the solvent due to the protein-protein interaction. This energy is calculated from the surface free energy of the protein that is determined from protein-salt preferential-interaction parameter measurements. In classical salting-out behavior, the protein-salt preferential interaction is unfavorable. Because addition of salt raises the surface free energy of the protein according to the surface-tension increment of the salt, protein-protein attraction increases, leading to a reduction in solubility. When the surface chemistry of proteins is altered by binding of a specific ion, salting-in is observed when the interactions between (kosmotrope) ion-protein complexes are more repulsive than those between the uncomplexed proteins. However, salting-out is observed when interactions between (chaotrope) ion-protein complexes are more attractive than those of the uncomplexed proteins.

Hydrophobic forces between protein molecules in aqueous solutions of concentrated electrolyte.

Protein-protein interactions have been measured for a mutant (D101F) lysozyme and for native lysozyme in concentrated solutions of ammonium sulfate at pH 7 and sodium chloride at pH 4.5. In the mutant lysozyme, a surface aspartate residue has been replaced with a hydrophobic phenylalanine residue. The protein-protein interactions of D101F lysozyme are more attractive than those of native lysozyme for all conditions studied. The salt-induced attraction is correlated with a solvation potential of mean force given by the work required to desolvate the part of the protein surfaces that is buried by the protein-protein interaction. This work is proportional to the aqueous surface-tension increment of the salt and the fractional non-polar surface coverage of the protein. Experimental measurements of osmotic second virial coefficients validate a proposed potential of mean force that ascribes the salt-induced attraction between protein molecules to an enhancement of the hydrophobic attraction. This model provides a first approximation for predicting the protein-protein potential of mean force in concentrated aqueous electrolyte solutions; this potential is useful for determining solution conditions favorable for protein crystallization.

Locomotion evaluation for racing in thoroughbreds.

The potential racing and locomotory profile of a Thoroughbred yearling should be taken into account for its training programme and racing career. A gait test has been designed to assist the trainer in this task. The aim of this study was to investigate the temporal and kinetic locomotory variables of Thoroughbreds at the gallop, in relationship to their racing ability. Thirty Thoroughbred horses in race training were tested at maximal speed during a training session. The training exercise consisted of a warming-up session at trot and canter for 10 min followed by a gallop session at increasing speed on a dirt track 1942 m long. The maximal speed was measured for the last 800 m before the finishing post. An acclerometric device attached to the girth provided quantitative information about the kinetic and temporal variables of the gallop such as: stride length (SL), stride frequency (SF), times elapsed between each hoof midstance phase (HIND, DIAGO, FORE), regularity of the strides (REG), mean vector of propulsion (VPROP), energy of propulsion (EPROP) and energy of loading (ELOAD). The performance records (number of wins, placings and average earning/start [PERF]) were used to analyse the relationship with the gait measurements. The mean maximum speed was 15.26 m/s. Several locomotory variables were significantly (P < 0.05) correlated to the gallop speed: SL (0.90), SF (0.75), DIAGO (0.42), REG (-0.47), VPROP (0.52), ELOAD (0.56) and EPROP (0.65). There were significant correlations between PERF and the following gait variables: REG (0.79), DIAGO (0.43), SF (0.42), SL (-0.32) and ELOAD (-0.40). The horses that won short distance races (< 1400 m) had a larger relative ground contact duration and higher stride frequency than horses that won in longer distance races. The gait test was easy to perform and provided useful locomotory variables that may be used to evaluate the racing ability of the Thoroughbreds in training.

Protein-protein and protein-salt interactions in aqueous protein solutions containing concentrated electrolytes.

Protein-protein and protein-salt interactions have been obtained for ovalbumin in solutions of ammonium sulfate and for lysozyme in solutions of ammonium sulfate, sodium chloride, potassium isothiocyanate, and potassium chloride. The two-body interactions between ovalbumin molecules in concentrated ammonium-sulfate solutions can be described by the DLVO potentials plus a potential that accounts for the decrease in free volume available to the protein due to the presence of the salt ions. The interaction between ovalbumin and ammonium sulfate is unfavorable, reflecting the kosmotropic nature of sulfate anions. Lysozyme-lysozyme interactions cannot be described by the above potentials because anion binding to lysozyme alters these interactions. Lysozyme-isothiocyanate complexes are strongly attractive due to electrostatic interactions resulting from bridging by the isothiocyanate ion. Lysozyme-lysozyme interactions in sulfate solutions are more repulsive than expected, possibly resulting from a larger excluded volume of a lysozyme-sulfate bound complex or perhaps, hydration forces between the lysozyme-sulfate complexes.

Human tumor models in the severe combined immune deficient (scid) mouse.

PURPOSE: To test a number of established human tumor cell lines and early passage breast cancer (UACC2150) and melanoma cells (UACC1273) for growth in the scid mouse and the tumors' response to conventional chemotherapeutic drugs. METHODS: Established melanoma (A375, C81-61), colon (SW480), lung (A549), lymphomoblastoid leukemia (LCL-B), promyelocytic leukemia (HL60), prostate (PC-3, DU145), and breast (MCF7) cell lines were injected at subcutaneous (s.c.), intraperitoneal (i.p.), or mammary fat pad (MFP) sites. Tumor volume growth curves and survival curves were established for the various tumor cell lines. Carmustine (BCNU), cisplatin (CDDP), cyclophosphamide (CPA), doxorubicin, dacarbazine (DTIC), tamoxifen and vincristine were injected s.c. or i.p.. The chemotherapeutic drug effects on tumor volumes and survival were determined. RESULTS: Tumor growth occurred with each cell type. After i.p. injection, 90% mortality occurred within 26 to 60 days except for the early passage melanoma cell line UACC1273 with which mortality occurred within approximately 90 days. In the MCF7 breast model, treatment with tamoxifen (P < 0.001) and CPA (P < 0.0001) resulted in significant tumor growth delay compared with control groups. BCNU and CDDP resulted in significant tumor growth delays relative to control in SW480 colon cancer (P < 0.0014) and A375 melanoma (P < 0.0001) models, respectively. CPA and doxorubicin improved survival in the HL60 leukemia model (P = 0.0018). CONCLUSIONS: These scid mouse human tumor models appear to reflect the clinical situation in that clinically active chemotherapeutic drugs are similarly active in the scid mouse models. Therefore, the scid mouse models may be useful for testing new chemotherapeutic agents against various human cancer types.

Aspects of the epidemiology of nematode infections in a cow-calf herd in Ontario.

On May 29, 1980, 108 cows and calves were placed on a 20 hectare pasture until October 26, except that from September 18 to October 2 they were in a barn. Every two weeks during the total period, fecal samples were taken from 17 cows and 14 calves and herbage samples were collected from the pasture. Parasite fecal egg counts were estimated using the Cornell-Wisconsin centrifugation technique and herbage infective larvae by a modified Sandwich technique. Daily maximum and minimum air temperature and precipitation were recorded. The principal parasite egg found was the trichostrongyle-strongyle morulate, oval-shaped egg referred to as a gastrointestinal nematode (GIN) egg. The mean GIN egg/g of feces for cows varied from 14.2 to 23.9 and for calves it rose from 0.2 in the spring to 134.8 in the fall. Nematodirus, Trichuris, Strongyloides, Moniezia and coccidia were also found. Larvae were recovered first in July, with the greatest number, over 2000/kg of dry weight of herbage, in September and were primarily Cooperia and Ostertagia.

Effect of prepartum energy, body condition, and sodium bicarbonate on health and blood metabolites of holstein cows in early lactation.

Effects of prepartum energy and of postpartum sodium bicarbonate (0, .75% DM) on health were studied in two trials. In trial 1, 36 cows consumed either 102, 131, or 162% of their energy requirement in the dry period. Postpartum glucose and D(-)-3-hydroxybutyrate levels indicated that 131% group (between wk 1 and 2) and 162% group (over the first 4 wk) were closer to a ketotic state than treatment groups at other times. Displaced abomasums occurred more frequently in the 162% group than either the 102 or 131 group. Sodium bicarbonate did not alter the health. In trial 2, 40 cows were used to evaluate the effects of prepartum energy for a longer period. Energy treatments imposed in late lactation and in the dry period were 1) cows fed to requirement in both periods; 2) cows overfed in the first and underfed in the second period; 3) cows fed to requirement in the first and overfed in the second; 4) cows overfed in both periods. Blood metabolites and health measures were not affected by energy or sodium bicarbonate treatments. Overconsumption of energy by prepartum cows should be avoided; however, for a short period, overconsumption did not produce major health problems.

Clinical pharmacy on-call program in the emergency department.

This is a descriptive and evaluative report regarding a clinical pharmacy residency in-house on-call program that facilitates the provision of 24-hour clinical pharmacy consultative services within the emergency department. During the two-year evaluation period, clinical pharmacy residents completed 3.1 consultations per 14-hour call period. Additionally, greater than 90% of the clinical pharmacy recommendations were accepted and completely followed by physician cohorts. These consultations were usually solicited by internal medicine physicians within the emergency department, involved patient-specific drug therapy recommendations, and required about 100 minutes (mean per consultation) of the clinical pharmacist's time. Thus, clinical pharmacy consultative services can be a useful addition to health care within the emergency department in teaching hospitals.

Verminous Pneumonia in Adult Dairy Cows in Southern Ontario due to Dictyocaulus viviparus.

An outbreak of verminous pneumonia due to Dictyocaulus viviparus in a herd of mature, lactating, dairy cows in southern Ontario is described. The fact that the herd had been closed to new additions for ten years and had never experienced clinical disease due to D. viviparus in the past makes the occurrence of this herd problem difficult to explain. Correlation of fecal Baermann analysis for D. viviparus larvae with the progress of anthelmintic treatment is discussed. It is suggested that certain climatological variations in combination with unique, immunological aspects of D. viviparus infection may have contributed to the development of clinical disease in this herd.

Lung sounds in cattle, horses, sheep and goats.

The purpose of this paper is to emphasize the importance of pulmonary auscultation for the clinician. It suggests a clarification and simplification of the terminology to be used which would be helpful to veterinary students and allow better communications between veterinarians. The interpretation of these sounds and the relationships to conditions and diseases of the lungs in cattle, horses, sheep and goats are discussed.

A survey of sheep diseases in Canada.

A mail survey of disease occurrence in Canadian sheep flocks was conducted. The survey, which covered the period from September 1982 to August 1983, utilized flocks on the Record of Performance (ROP) sheep program and relatively complete data were available from 116 flocks. Data about lambing rates, incidence of a variety of lamb and ewe diseases and reasons for culling were obtained. At the same time a retrospective evaluation of records of diagnoses of sheep diseases recorded at diagnostic laboratories across the country was performed. Data from the years 1978 to 1982 were obtained and summarized. A lambing percentage of 153% (1.53 lambs live born per ewe lambing) was observed and an additional 0.05 lambs were stillborn. The major identified causes of mortality amongst lambs were starvation, pneumonia, scours and accidents. Pasteurella spp. were the etiological agents most commonly associated with pneumonia in lambs and Escherichia coli had the same predominant position with regards to nonparasitic scours. A large discrepancy existed between the proportional mortality rates for internal parasites and coccidiosis as determined from the farm survey data compared to diagnostic laboratory data. This suggests that clinical parasitism may not be adequately recognized at the farm level. Abortions in ewes occurred in approximately half the flocks, but generally at a low level and no severe abortion storms occurred. Pneumonia was the most commonly identified cause of mortality in ewes and although Pasteurella spp. appear to be the most important etiological agents, regional differences were apparent.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of empiric dosing on blood levels of theophylline and phenytoin.

To evaluate empiric dosing guidelines for aminophylline and phenytoin in the management of acute exacerbations of obstructive lung disease and seizure disorders, we utilized an emergency department (ED)-based EMIT system to measure stat plasma theophylline and phenytoin levels in patients intended to receive these drugs. Plasma drug level results were available prior to initiation of therapy. Of the patients evaluated, 45 of 163 (27.6%) aminophylline patients and 21 of 73 (28.7%) phenytoin patients were projected to have plasma concentrations below the recommended therapeutic range if empiric dosing schedules were employed. In addition, 39 of 163 (23.9%) aminophylline and 10 of 73 (13.7%) phenytoin patients, had they received these drugs empirically, would have had plasma theophylline and phenytoin levels in excess of the recommended therapeutic range using empiric dosing. We conclude that the use of empiric dosing guidelines for aminophylline and phenytoin in the ED do not reliably produce therapeutic plasma concentrations. The development of a stat drug analysis laboratory in the hospital or within the ED would improve the effectiveness and safety of these acutely used drugs with narrow therapeutic ranges.

Volume of distribution of theophylline in acute exacerbations of reversible airway disease. Effect of body weight.

The literature is unclear as to whether theophylline loading doses should be based on total body weight (TBW) or ideal body weight (IBW). The objective of this study was to determine the most appropriate body weight for estimation of volume of distribution (Vd) in calculating theophylline loading dose in patients with acute bronchospasm. Fifty-four adult patients with acute bronchospasm requiring intravenous (IV) theophylline therapy were entered into the study. Patients were randomized into three theophylline loading dose groups based on (1) TBW, (2) IBW, and (3) adjusted body weight (ABW). Initial serum theophylline concentrations were used to determine an IV loading dose to reach a plasma concentration of 12 to 15 micrograms/ml. Percent prediction error was used to determine the appropriateness of each dosing group. Volumes of distribution were also determined for each group. There was a statistically significant difference at p less than 0.01 in the percent prediction error when patients in the TBW group were compared to the IBW and ABW groups. A statistically significant difference in the Vd was observed between the TBW and IBW group (p less than 0.01). We conclude that IBW is more appropriate than TBW or ABW for determining theophylline loading dose in patients with acute bronchospasm.