Engineered cocultures of iPSC-derived atrial cardiomyocytes and atrial fibroblasts for modeling atrial fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia treatable with antiarrhythmic drugs; however, patient responses remain highly variable. Human induced pluripotent stem cell-derived atrial cardiomyocytes (iPSC-aCMs) are useful for discovering precision therapeutics, but current platforms yield phenotypically immature cells and are not easily scalable for high-throughput screening. Here, primary adult atrial, but not ventricular, fibroblasts induced greater functional iPSC-aCM maturation, partly through connexin-40 and ephrin-B1 signaling. We developed a protein patterning process within multiwell plates to engineer patterned iPSC-aCM and atrial fibroblast coculture (PC) that significantly enhanced iPSC-aCM structural, electrical, contractile, and metabolic maturation for 6+ weeks compared to conventional mono-/coculture. PC displayed greater sensitivity for detecting drug efficacy than monoculture and enabled the modeling and pharmacological or gene editing treatment of an AF-like electrophysiological phenotype due to a mutated sodium channel. Overall, PC is useful for elucidating cell signaling in the atria, drug screening, and modeling AF.

Delayed boosting improves human antigen-specific Ig and B cell responses to the RH5.1/AS01B malaria vaccine

Modifications to vaccine delivery that increase serum antibody longevity are of great interest for maximizing efficacy. We have previously shown that a delayed fractional (DFx) dosing schedule (0-1-6 month) - using AS01B-adjuvanted RH5.1 malaria antigen - substantially improves serum IgG durability as compared with monthly dosing (0-1-2 month; NCT02927145). However, the underlying mechanism and whether there are wider immunological changes with DFx dosing were unclear. Here, PfRH5-specific Ig and B cell responses were analyzed in depth through standardized ELISAs, flow cytometry, systems serology, and single-cell RNA-Seq (scRNA-Seq). Data indicate that DFx dosing increases the magnitude and durability of circulating PfRH5-specific B cells and serum IgG1. At the peak antibody magnitude, DFx dosing was distinguished by a systems serology feature set comprising increased FcRn binding, IgG avidity, and proportion of G2B and G2S2F IgG Fc glycans, alongside decreased IgG3, antibody-dependent complement deposition, and proportion of G1S1F IgG Fc glycan. Concomitantly, scRNA-Seq data show a higher CDR3 percentage of mutation from germline and decreased plasma cell gene expression in circulating PfRH5-specific B cells. Our data, therefore, reveal a profound impact of DFx dosing on the humoral response and suggest plausible mechanisms that could enhance antibody longevity, including improved FcRn binding by serum Ig and a potential shift in the underlying cellular response from circulating short-lived plasma cells to nonperipheral long-lived plasma cells.

Reanalysis of Trichloroethylene and Tetrachloroethylene Metabolism to Glutathione Conjugates Using Human, Rat, and Mouse Liver in Vitro Models to Improve Precision in Risk Characterization

BACKGROUND

Both trichloroethylene (TCE) and tetrachloroethylene (PCE) are high-priority chemicals subject to numerous human health risk evaluations by a range of agencies. Metabolism of TCE and PCE determines their ultimate toxicity; important uncertainties exist in quantitative characterization of metabolism to genotoxic moieties through glutathione (GSH) conjugation and species differences therein.

OBJECTIVES

This study aimed to address these uncertainties using novel in vitro liver models, interspecies comparison, and a sensitive assay for quantification of GSH conjugates of TCE and PCE, S-(1,2-dichlorovinyl)glutathione (DCVG) and S-(1,2,2-trichlorovinyl) glutathione (TCVG), respectively.

METHODS

Liver in vitro models used herein were suspension, 2-D culture, and micropatterned coculture (MPCC) with primary human, rat, and mouse hepatocytes, as well as human induced pluripotent stem cell (iPSC)-derived hepatocytes (iHep).

RESULTS

We found that, although efficiency of metabolism varied among models, consistent with known differences in their metabolic capacity, formation rates of DCVG and TCVG generally followed the patterns human ≥ rat ≥ mouse , and primary hepatocytes > iHep . Data derived from MPCC were most consistent with estimates from physiologically based pharmacokinetic models calibrated to in vivo data.

DISCUSSION

For TCE, the new data provided additional empirical support for inclusion of GSH conjugation-mediated kidney effects as critical for the derivation of noncancer toxicity values. For PCE, the data reduced previous uncertainties regarding the extent of TCVG formation in humans; this information was used to update several candidate kidney-specific noncancer toxicity values. Overall, MPCC-derived data provided physiologically relevant estimates of GSH-mediated metabolism of TCE and PCE to reduce uncertainties in interspecies extrapolation that constrained previous risk evaluations, thereby increasing the precision of risk characterizations of these high-priority toxicants. https://doi.org/10.1289/EHP12006.

Reduced blood-stage malaria growth and immune correlates in humans following RH5 vaccination

BACKGROUND

Development of an effective vaccine against the pathogenic blood-stage infection of human malaria has proved challenging, and no candidate vaccine has affected blood-stage parasitemia following controlled human malaria infection (CHMI) with blood-stage Plasmodium falciparum.

METHODS

We undertook a phase I/IIa clinical trial in healthy adults in the United Kingdom of the RH5.1 recombinant protein vaccine, targeting the P. falciparum reticulocyte-binding protein homolog 5 (RH5), formulated in AS01B adjuvant. We assessed safety, immunogenicity, and efficacy against blood-stage CHMI. Trial registered at ClinicalTrials.gov, NCT02927145.

FINDINGS

The RH5.1/AS01B formulation was administered using a range of RH5.1 protein vaccine doses (2, 10, and 50 μg) and was found to be safe and well tolerated. A regimen using a delayed and fractional third dose, in contrast to three doses given at monthly intervals, led to significantly improved antibody response longevity over ∼2 years of follow-up. Following primary and secondary CHMI of vaccinees with blood-stage P. falciparum, a significant reduction in parasite growth rate was observed, defining a milestone for the blood-stage malaria vaccine field. We show that growth inhibition activity measured in vitro using purified immunoglobulin G (IgG) antibody strongly correlates with in vivo reduction of the parasite growth rate and also identify other antibody feature sets by systems serology, including the plasma anti-RH5 IgA1 response, that are associated with challenge outcome.

CONCLUSIONS

Our data provide a new framework to guide rational design and delivery of next-generation vaccines to protect against malaria disease.

FUNDING

This study was supported by USAID, UK MRC, Wellcome Trust, NIAID, and the NIHR Oxford-BRC.

Adoptive Transfer of Serum Samples From Children With Invasive Staphylococcal Infection and Protection Against Staphylococcus aureus Sepsis

A successful Staphylococcus aureus vaccine remains elusive, and one controversy in the field is whether humans generate a protective adaptive immune response to infection. We developed a bacterial challenge murine assay that directly assesses the protective capacity of adoptively transferred human serum samples. We first validated the model by showing that postpneumococcal vaccine serum samples from humans induced effective clearance of Streptococcus pneumoniae in mice. We then found that human serum samples adoptively transferred from children with invasive S. aureus infections exhibited protection from disease in a murine model, with some samples conferring near complete protection. These findings demonstrate that human serum samples are capable of conferring a protective adaptive response generated by humans during invasive staphylococcal disease, allowing for the study of protective factors in a murine model. Identification of the protective factors present in the most efficacious serum samples would be of high interest as potential staphylococcal vaccine candidates or passive therapeutics.

Loss of Bcl-6-Expressing T Follicular Helper Cells and Germinal Centers in COVID-19

Humoral responses in coronavirus disease 2019 (COVID-19) are often of limited durability, as seen with other human coronavirus epidemics. To address the underlying etiology, we examined post mortem thoracic lymph nodes and spleens in acute SARS-CoV-2 infection and observed the absence of germinal centers and a striking reduction in Bcl-6⁺ germinal center B cells but preservation of AID⁺ B cells. Absence of germinal centers correlated with an early specific block in Bcl-6⁺ T_FH cell differentiation together with an increase in T-bet⁺ T_H1 cells and aberrant extra-follicular TNF-α accumulation. Parallel peripheral blood studies revealed loss of transitional and follicular B cells in severe disease and accumulation of SARS-CoV-2-specific "disease-related" B cell populations. These data identify defective Bcl-6⁺ T_FH cell generation and dysregulated humoral immune induction early in COVID-19 disease, providing a mechanistic explanation for the limited durability of antibody responses in coronavirus infections, and suggest that achieving herd immunity through natural infection may be difficult.

The Loss of Bcl-6 Expressing T Follicular Helper Cells and the Absence of Germinal Centers in COVID-19

Humoral responses in COVID-19 disease are often of limited durability, as seen with other human coronavirus epidemics. To address the underlying etiology, we examined postmortem thoracic lymph nodes and spleens in acute SARS-CoV-2 infection and observed the absence of germinal centers, a striking reduction in Bcl-6+ germinal center B cells but preservation of AID+ B cells. Absence of germinal centers correlated with an early specific block in Bcl-6+TFH cell differentiation together with an increase in T-bet+TH1 cells and aberrant extra-follicular TNF-a accumulation.  Parallel peripheral blood studies revealed loss of transitional and follicular B cells in severe disease and accumulation of SARS-CoV-2-specific "disease-related" B cell populations. These data identify defective Bcl-6+TFH cell generation and dysregulated humoral immune induction early in COVID-19 disease, providing a mechanistic explanation for the limited durability of antibody responses in coronavirus infections and suggest that achieving herd immunity through natural infection may be difficult. Funding: This work was supported by NIH U19 AI110495 to SP, NIH R01 AI146779 to AGS, NIH R01AI137057 and DP2DA042422 to DL, BMH was supported by NIGMS T32 GM007753, TMC was supported by T32 AI007245. Funding for these studies from the Massachusetts Consortium of Pathogen Readiness, the Mark and Lisa Schwartz Foundation and Enid Schwartz is also acknowledged. Conflict of Interest: None. Ethical Approval: This study was performed with the approval of the Institutional Review Boards at the Massachusetts General Hospital and the Brigham and Women's Hospital.

A high-throughput, bead-based, antigen-specific assay to assess the ability of antibodies to induce complement activation

The complement system plays a critical role in innate immune defense against pathogens, both via non-specific direct pathogen recognition and killing or via antigen-specific indirect recruitment by complement fixing antibodies. While various assays for measuring complement activation have been developed, few provide a high-throughput, sample-sparing approach to interrogate the qualitative differences in the ability of antibodies to drive complement activation. Here we present a high-throughput, sample-sparing, bead-based assay to evaluate antigen-specific antibody-dependent complement activation against nearly any antigen. Optimization of buffer composition, kinetics of immune complex formation, as well as complement source all contribute critically to the development of a robust, highly flexible and high-throughput approach to analyze antibody-dependent complement deposition (ADCD). Thus, the optimized bead-based, antigen-specific assay represents a simple, highly adaptable platform to profile antibody-dependent complement activation across pathogens and diseases.

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Optimized flow-based assay for the detection of antibody-mediated complement deposition

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Robust, rapid and reproducible high-throughput bead-based assay applicable to various diseases, including HIV and influenza

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Lot controlled complement is a controlled source for exogenous complement that correlates with human complement activity

Glomerular filtration rate estimated by 3-sample plasma clearance of iohexol in 118 healthy dogs

BACKGROUND

Glomerular filtration rate (GFR) decreases in the aging human kidney, but limited data exist in dogs.

HYPOTHESIS

There is an effect of age and body size on estimated GFR in healthy dogs.

ANIMALS

One hundred and eighteen healthy dogs of various breeds, ages, and body weights presenting to 3 referral centers.

METHODS

GFR was estimated in clinically healthy dogs between 1 and 14 years of age. GFR was estimated from the plasma clearance of iohexol, by a compartmental model and an empirical correction formula, normalized to body weight in kilograms or liters of extracellular fluid volume (ECFV). For data analysis, dogs were divided into body weight quartiles 1.8-12.4, 13.2-25.5, 25.7-31.6, and 32.0-70.3 kg.

RESULTS

In the complete data set, there was no trend toward lower estimated GFR/kg or GFR/ECFV with increasing age. GFR decreased with age in dogs in the smallest weight quartile only. A significant negative linear relationship was detected between body weight and estimated GFR/kg and GFR/ECFV. Reference ranges in different weight quartiles were 1.54-4.25, 1.29-3.50, 0.95-3.36, and 1.12-3.39 mL/min/kg, respectively. Standardization to ECFV rather than kilogram body weight did not produce substantial changes in the relationships between GFR estimates and age or weight.

CONCLUSIONS AND CLINICAL IMPORTANCE

Interpretation of GFR results for early diagnosis of renal failure should take into account the weight and the age of the patient for small dogs.

Reliability of the MDRD method for estimating glomerular filtration rate in relation to gender, body mass index and extracellular fluid volume

BACKGROUND

The accuracy of estimating glomerular filtration rate from plasma creatinine (eGFR) has been questioned but it is unclear how much covert error in several reference methods that have been used has contributed to this perceived inaccuracy. The aim of the study was to evaluate eGFR in comparison with a second 'gold standard' to test the performance of the primary gold standard and to examine the influence of patient demographics (age, body mass index (BMI), extracellular fluid volume (ECV) and gender).

DESIGN

Non-fasting multisample GFR and ECV were measured in 80 subjects simultaneously and independently with Cr-51-EDTA (GFR(EDTA)) and iohexol (GFR(iohexol)). Percentage bias and imprecision in the prediction of, and disagreement with, GFR(EDTA) were compared between eGFR and GFR(iohexol). Another simplified method for measuring GFR, the slope-only method ((SO)GFR), was also evaluated against multisample GFR (measured with the opposing indicator). Accuracies were assessed in all subjects and across age, BMI and ECV boundaries of 65 y, 29 kg m(-2) and 14 L.

RESULTS

eGFR was less precise than GFR(iohexol) (imprecisions of 22.3% and 12.9%; P < 0.01). The precision of (SO)GFR was intermediate between eGFR and GFR(iohexol). Both GFR(iohexol) and eGFR were less precise in the elderly, the obese and men, but minimally influenced by ECV. (SO)GFR was minimally influenced by subject demographics.

CONCLUSION

Although eGFR does not predict GFR (based on a primary gold standard) as accurately as a second gold standard, a significant component of its poor performance is the result of inaccuracy in the primary gold standard. (SO)GFR measured with Cr-51-EDTA is superior to eGFR.

Why has oral rehydration for calves and children diverged: direct vs. indirect criteria of efficacy

Oral rehydration therapy (ORT) for acute diarrhoea has advanced in contrary directions in humans and animals; the unresolved question is whether this reflects species differences or a divergence in scientific outlook. This review suggests that the explanation lies in the fact that developments in veterinary ORT have the advantage of utilising more reliable criteria than those available from human patients. The dilemma for human ORT is that the validity of systematic reviews and meta-analyses are undermined when the underlying data only reflect crucial variables indirectly and unreliably. It is therefore possible that the approaches currently used to treat calves, which are radically different from those used by paediatricians, could potentially benefit children and the necessary additional research should be initiated. At a time when the value of animal models of human disease is frequently questioned, the benefits of being able to utilise disease models in the target species for clinical research deserve to be emphasised.

Comparative clinical science: The medicine of the future

This review explores the emergence of Comparative Medicine in the late 19th Century as 'the medicine of the future', its failure to realise these expectations during the 20th century as it became increasingly equated with laboratory animal models of human disease, and explains why there is now an unprecedented opportunity for this latent potential to be fully realised. Comparative medicine no longer rests on apparent similarities between disease mechanisms in different species but on the rapidly maturing ability to relate these similarities to a remarkably rich shared genetic heritage. In the United Kingdom, the creation of the new Medical Research Council Comparative Clinical Science Panel, once securely funded, will provide the infrastructure and strategic focus to foster comparative clinical research, encouraging collaboration between veterinary and human medicine and between investigators in institutes and in practice. This will generate the necessary evidence base for veterinary practice, raise the standard of veterinary research, broaden the horizons of human medicine and create real opportunities for veterinary surgeons to reconcile research with practice. The review explores the broad scope of the science which will flourish in this new environment and examines specific areas in greater depth as examples, notably multifactorial disease such as hypertension and diarrhoea, also aspects of comparative endocrinology and oncology, with emphasis on the growing power conferred by comparative molecular genetics.

The Shipman reports: lessons and warnings

The reports from the Shipman inquiry will lead to changes in the way the medical profession is regulated. Bob Michell fears that the veterinary profession will be affected, too.

In the still of the night

With medical general practitioners soon being able to buy themselves out of the requirement to provide overnight cover for their patients, for how much longer will the veterinary profession be able to sustain its 24-hour commitment? Here, Professor Bob Michell argues that it is time for the profession to rethink how it provides out-of-hours services--and, with the RCVS about to review the situation, concludes that something will have to change.

Iatrogenic hypocalcaemia during parenteral fluid therapy of diarrhoeic calves

Acid-base balance and electrolyte concentrations, including ionised calcium, were monitored during intravenous fluid therapy of 11 collapsed diarrhoeic suckler calves aged five to 10 days. Six healthy calves of similar age and type were used to provide control data. All the diarrhoeic calves were severely acidotic (TCO2<12 mmol/litre). Isotonic sodium bicarbonate (1-3 per cent) was administered until the metabolic acidosis was half corrected, as indicated by the TCO2 increasing to 17 to 24 mmol/litre when the infusion was changed to an extracellular volume replacement fluid containing 144 mmol/litre Na+, 35 mmol/litre HCO3-, 4 mmol/litre K+ and 113 mmol/litre Cl- which was administered until the calf was discharged. Milk feeding was started as soon as the calf had a suck reflex. The treatment was successful in 10 calves. At admission the diarrhoeic calves were hypocalcaemic compared with the control calves, but their ionised calcium was significantly higher, with significantly less calcium being protein bound. Treatment with isotonic sodium bicarbonate resulted in a significant improvement in acid-base balance, but both total and ionised calcium decreased significantly, the decrease in ionised calcium being proportionately greater owing partly to a significant increase in the protein binding of calcium. The mean total, bound and ionised calcium concentrations were all significantly lower in the treated calves after they had received isotonic sodium bicarbonate than in the control calves. Further treatment with replacement fluid had no significant effect on any of the parameters apart from pCO2 which increased significantly. Milk feeding had no significant effect on plasma calcium concentrations. The calves' mean ionised calcium concentration was significantly lower at the end of the treatment than before it, but there was no difference in the mean total and bound calcium concentrations. The calves' mean plasma potassium and magnesium concentrations decreased significantly during the course of the treatment.

Comparison of the measurement of total carbon dioxide and strong ion difference for the evaluation of metabolic acidosis in diarrhoeic calves

Eighty-four calves with diarrhoea were treated with fluids and 13 apparently healthy calves of similar ages were sampled as controls. Their total blood carbon dioxide (TCO2) was measured with a Harleco apparatus and 31 of the calves were treated with oral fluids and 53 with parenteral fluids. The oral fluid contained 118 mmol/litre Na+, 25 mmol/litre K+, 110 mmol/litre glucose, 108 mmol/litre bicarbonate (HCO3- as citrate), 43 mmol/litre Cl-, 4 mmol/litre Ca++, 4 mmol/litre Mg++ and 20 mmol/litre glycine, and the parenteral fluid contained 144 mmol/litre Na+, 4 mmol/litre K+, 35 mmol/litre HCO3- and 113 mmol/litre Cl-. Both treatments resulted in significant improvements in acid-base status as demonstrated by an increase in TCO2, and the treatment was successful in 27 of the 31 calves receiving oral fluids and in 45 of the 53 calves receiving parenteral fluids. Thirty-seven of the calves treated parenterally were very severely acidotic (TCO2 <8 mmol/litre) initially and they received an additional 400 mmol HCO3- added to the first 5 litres of infusion. Treatment was successful in 33 of these calves. The decision to administer additional bicarbonate was made on the basis of their acid-base status as measured with a Harleco apparatus. The strong ion difference (Na++K+-Cl-) (SID) of the calves was calculated retrospectively. There was a significant correlation between the SID and TCO2 of the calves treated with oral fluids but not among the control calves or the calves treated parenterally. Furthermore, measurements of the change in SID during therapy gave little indication of the change in acid-base status as measured by the Harleco apparatus, with the SID decreasing (suggesting a worsening of acid-base status) in 16 calves in which the TCO2 increased (suggesting an improvement in acid-base status). There was a significant correlation between the change in SID and the change in TCO2 during treatment in the calves receiving oral fluids but not in the calves treated parenterally.

Reduction of renal function in exercising horses

Glomerular filtration rate (GFR) and extracellular volume (ECFV) were measured before, during and after treadmill exercise in 5 trained Thoroughbred horses (mean weight 483 kg). GFR/ECFV was determined by plasma disappearance of Tc-DTPA and ECFV was measured independently as thiocyanate space. Resting GFR averaged 1.6 l/min (3.3 ml/kg/min) and fell by over 40% during exercise, moreover the fall was severe even during the first walk, prior to trotting. The results suggest that rather than being protected, GFR is allowed to fall, even with mild exercise and that this is probably an adaptation to allow greater perfusion of muscle and skin. In man, GFR appears to be more resistant to the effects of exercise but it is hard to compare intensity of exercise between such different species.

Longevity of British breeds of dog and its relationships with sex, size, cardiovascular variables and disease

The results of a questionnaire provided data about owners' perceptions of the cause of death of over 3000 British dogs. The mean age at death (all breeds, all causes) was 11 years one month, but in dogs dying of natural causes it was 12 years eight months. Only 8 per cent of dogs lived beyond 15, and 64 per cent of dogs died of disease or were euthanased as a result of disease. Nearly 16 per cent of deaths were attributed to cancer, twice as many as to heart disease. Neutered females lived longer than males or intact females, but among dogs dying of natural causes entire females lived slightly longer. In neutered males the importance of cancer as a cause of death was similar to heart disease. Mongrels lived longer than average but several breeds lived longer than mongrels, for example, Jack Russells, miniature poodles and whippets. There was no correlation between longevity and cardiovascular parameters (heart rate, systolic, diastolic, pulse and mean arterial pressure, or the combination of heart rate and pulse pressure) but smaller dogs had longer lifespans. The results also include breed differences in lifespan, susceptibility to cancer, road accidents and behavioural problems as a cause of euthanasia.

Use of a three-blood-sample plasma clearance technique to measure GFR in horses

Measurement of renal function in horses poses a particular challenge because plasma creatinine is influenced by muscle mass which is highly developed and variable between individuals, while conventional clearance methods involve potentially daunting problems, particularly urine collection and bladder washout. This paper provides data which enable technetium-diethyleneaminopentacetic acid (Tc-DTPA) clearance to be used to calculate glomerular filtration rate (GFR)/extracellular fluid volume (ECFV) as an expression of GFR in horses, as previously validated in humans, dogs and calves. Apart from being arguably a more physiological expression of GFR than using derivatives of body weight, the use of GFR/ECFV eliminates a source of delay and error, namely measurement of the injected dose, and offers the convenience of requiring only three blood samples. It therefore has advantages for both research and clinical applications.

Detrimental effects on villus form during conventional oral rehydration therapy for diarrhoea in calves; alleviation by a nutrient oral rehydration solution containing glutamine

This paper examines the possibility that treatment of diarrhoea with conventional oral rehydration solutions (ORSs) may be detrimental to villus structure by imposing nutrient deprivation and that such detrimental effects may be reduced or avoided by using a nutrient ORS. A conventional WHO-type ORS (W) was compared with two nutrient solutions (N and G) both containing high glucose concentrations and the latter containing glutamine; their effects on enteric structure were assessed by morphometric analysis of samples obtained from diarrhoeic calves after 96 h treatment. Comparisons were also made with samples from controls and diarrhoeic calves at the stage where oral rehydration would have begun in the treated groups. As in our previous ORS studies, diarrhoea was induced with enterotoxigenic Escherichia coli (09:K30:K99). We measured villus length and width, crypt depth and width and calculated villus surface area in proximal, mid and distal small intestine (PSI, MSI, DSI), using standard morphometric techniques. Proximal and distal spiral colon samples (PC, DC) were examined for crypt depth and width; mitoses per crypt were counted in samples from all regions. Non-diarrhoeic calves showed the expected gradient of villus length through PSI, MSI and DSI, hence data for each region are normalized as a percentage of the control value for that region. PSI showed the greatest loss of villus length and surface area (50%) with diarrhoea. In MSI and DSI the villus loss was greater with solution W and N or G, as were increased mitoses and crypt depth. Crypt depth and mitoses also increased in the colon with solution W. Colonic crypt width increased with diarrhoea and conventional oral rehydration but less so with G; there is reason to believe that such changes have functional significance. Crypt changes in colon, MSI and DSI were least with solution G. The changes developing in diarrhoeic calves prior to treatment were thus less apparent in those treated with a nutritional ORS, particularly if it contained glutamine.

Longitudinal studies of reproducibility and variability of indirect (oscillometric) blood pressure measurements in dogs: evidence for tracking

To be clinically reliable, blood pressure readings taken in quiet surroundings with good technique from healthy, unstressed subjects accustomed to the procedure, should be reasonably constant between occasions. Apart from changes attributable to age or stress, sustained rises suggest hypertension. Yet it is increasingly realised that arterial pressure shows great short-term lability. Despite this, 'tracking' occurs in groups of humans, i.e. when ranked by blood pressure they tend to maintain their rank order. This paper examines month-on-month variability of arterial pressure, measured by non-invasive oscillometry (Dinamap) in both pet dogs and kennel populations. 'Tracking' occurred and there was also evidence of 'white coat' effects. Heart rate was more variable than arterial pressure and should not be used to reject pressure readings unless changes are extreme. There was further evidence that canine blood pressure rises with age.

Fallibility of plasma urea and creatinine as indices of renal function in diarrhoeic calves treated with conventional or nutritional oral rehydration solutions

Changes in plasma urea, creatinine and glomerular filtration rate (GFR) were measured in calves before and after development of diarrhoea and during treatment with a conventional (WHO-type) or a nutritional oral rehydration solution (ORS). Changes in urea and creatinine failed to represent the extent of pre-renal failure. The two ORSs differed in their impact on GFR with the nutritional ORS improving GFR whereas with the WHO-type solution it deteriorated further.

Evaluation of a glutamine-containing oral rehydration solution for the treatment of calf diarrhoea using an Escherichia coli model

A high-calorie oral rehydration solution (ORS) with glutamine (n=11) was more effective in correcting plasma, extracellular fluid and blood volume than solutions without (one WHO-type solution, n=6, and two high-glucose but glutamine-free solutions, n=7, n=12). It was the only solution to improve plasma volume significantly within 48 h and sustain the improvement throughout treatment; similarly, it was the only solution to correct packed-cell volume within 48 h and sustain the benefit to the end of treatment. At the end of treatment, the glutamine-treated calves were the only ones to avoid a significant weight loss compared with their pre-diarrhoeic values. The crucial difference between this solution and those used with glutamine previously is that it gave significant nutritional support whereas WHO type solutions did not. It also had more favourable effects on hyponatraemia and metabolic acidosis than a standard ORS. Use of a high-calorie ORS for 4 days (rather than 2 days of 50:50 admixture with milk replacer) brought additional beneficial effects on blood glucose and body weight.

Absence of hypertension in dogs with renal insufficiency

Dogs have provided classic models of induced hypertension. This paper shows that despite being susceptible to hypertension, they are naturally resistant to its development even when renal function is severely compromised. The proportion of hypertensive dogs was almost as low among those with reduced glomerular filtration rate (GFR) (9%) as those with normal GFR (6%). Dogs with GFR less than 33% of the normal lower limit (with an average GFR equivalent to 10 mL min-1 in a 70-kg patient) had arterial pressures not significantly above normal. Only dogs with a GFR 33-75% of the lower limit of normal had significantly elevated systolic pressure, though none was actually hypertensive. Since there was no correlation between arterial pressure and GFR below 33% of lower limit, the dogs in the 33-75% range may be showing an effect of increased pressure, rather than a cause. In humans with GFR less than 33% of normal, the majority are hypertensive. Since various aspects of canine cardiovascular and renal function are comparable with humans, the question is why dogs, despite being capable of developing hypertension, are resistant to it, even when they have chronic renal insufficiency.

Evaluation of a nutritive oral rehydration solution for the treatment of calf diarrhoea

The essential constituents of a conventional oral rehydration solution (ORS) are sodium, glucose and a bicarbonate precursor. The glucose promotes sodium uptake but because these solutions are isotonic, it is insufficient to sustain calorie requirements. This paper examines the performance of a novel ORS with over three times the conventional glucose concentration, by comparing it with two leading commercial ORSs in calves with induced Escherichia coli diarrhoea. This solution showed greater ability than the current market-leading ORS to repair extracellular fluid and plasma volume and to correct both hyponatraemia and metabolic acidosis, especially in more severely affected calves. In acidotic calves it was more effective in correcting hyperkalaemia, probably by supplying glucose to promote cellular potassium uptake as well as by correcting the acidosis. It therefore appears possible to depart from the traditional isotonic formulations for calf ORSs and gain significant nutritional support while retaining effective rehydration and correction of acid-base and electrolyte disturbances. This seems especially important in young animals where energy deprivation imposes a particular penalty; the use of hypertonic ORSs should not, however, be extended to other species without further research.

Comparison of direct and indirect (oscillometric) measurements of arterial blood pressure in conscious dogs

Oscillometric measurements of arterial blood pressure were compared with direct measurements made on seven dogs fitted with catheters. Tail and limb cuff sites were used while the dogs were gently restrained either standing or in lateral recumbency. The accuracy of the readings for the various cuff sites was compared with the direct (gold standard) readings. The accuracy of the indirect readings was improved by using mean values from a series of readings rather than individual values and when the dogs were in lateral recumbency rather than standing. The differences between the direct and indirect values were greatest with high pressures, and with systolic rather than diastolic values. In standing dogs, the proximal forelimb readings (when obtainable) correlated most closely with the direct readings. The tail cuff readings correlated significantly with the direct readings, though less closely. The tail cuff readings were the most easily recorded in the standing dogs. In the laterally recumbent dogs, the readings from all the cuff sites correlated closely with the direct values except for diastolic readings from the distal hindlimb.

Relationship between blood pressure and stress-prone temperament in dogs

As part of an assessment of stress during the training of guide dogs for the blind, blood pressures have been monitored in their main breeds. For this article a population of 227 Labradors, between 9 and 24 months of age, had indirect arterial blood pressures measured and means taken of five readings. They were ranked according to their pressures. Prior to the measurements, their character was independently assessed as "stress-prone" or "non-stress-prone" by their highly experienced and trained handlers. The pressure data distribution of stress-prone animals in the ranking was analysed; they were significantly more likely to be found at the high end of the blood pressure range for that population.