Some factors affecting the accuracy and variability of measurements of the height of ponies

Height is the only factor used to differentiate horses and ponies for competitive purposes; any horse without shoes that is less than 148 cm at the highest point of the withers can be classified as a pony. However, variations in height associated with anatomical and other factors can occur. In this study the accuracy of the most commonly used measuring procedure and seven independent factors that might affect apparent height were evaluated in skeletally mature horses that were less than 155 cm in height. The results indicated that there was an improvement of 57 per cent in the accuracy of measurement when a second spirit level was added to the traditional measuring stick. The spread of values recorded for a series of repeated measurements by one person was +/-1.06 cm, but the spread increased to +/-1.89 cm when three different people made the measurements. Some variation in height occurred when the position of the pony's head was changed, but none occurred after a period of exercise. There was a reduction in height of 0.84 cm when the animals were allowed to adapt to their surroundings, and there was some reduction after they had been tranquillised.

Reduced tear production in three canine endocrinopathies

OBJECTIVES

Previous reports have suggested that hypothyroid and diabetic patients can be predisposed to keratoconjunctivitis sicca. This study aimed to measure tear production in dogs with diabetes, hypothyroidism and hyperadrenocorticism using the Schirmer tear test and to compare these results with Schirmer tear test values for a group of normal dogs.

METHODS

Schirmer tear tests were performed on 16 dogs with hyperadrenocorticism, 18 with diabetes and 12 with hypothyroidism together with 100 control dogs. Corneal sensitivity was also measured in 12 of the 18 diabetic dogs with a Cochet Bonnet aesthesiometer and compared with age- and breed-matched normal dogs.

RESULTS

Schirmer tear test values in dogs with hypothyroidism, hyperadrenocorticism and diabetes were 12.3+/-3.2, 14.0+/-4.0 and 12.3+/-5.3 mm/minutes, respectively. Schirmer tear test values were significantly lower than that for the control group (19.6+/-4.2 mm/minutes) in all dogs with an endocrinopathy. Only in two hypothyroid dogs and three diabetics, this was manifested as profound keratoconjunctivitis sicca with Schirmer tear test value lower than 5 mm/minutes. Diabetic dogs had significantly reduced corneal sensitivity compared with a matched set of control dogs.

CLINICAL SIGNIFICANCE

This study shows a significant reduction in tear production in animals with diabetes mellitus, hypothyroidism and hyperadrenocorticism. Further research is needed to elucidate the mechanisms by which this reduction in tear production occurs. Assessment of tear production should be undertaken in animals diagnosed with these endocrinopathies, as these animals may progress to clinical keratoconjunctivitis sicca.

Controlled clinical trial of the effect of a homoeopathic nosode on the somatic cell counts in the milk of clinically normal dairy cows

Cows in a 250-cow Holstein-Friesian herd were allocated at random to be treated with either a homoeopathic nosode or a negative control, both treatments being applied by means of an aerosol spray to the vulval mucous membranes. A total of six treatments were given over a period of three days and milk samples were taken for the determination of somatic cell counts (SCC) on days -3, 3, 7, 9, 14, 21 and 28. Individuals applying the treatments or carrying out the SCC determination were unaware of which animals were receiving which treatment. Owing to the wide natural variations in SCC, the trial had only a 71 per cent possibility of detecting a 30 per cent difference in SCC between the two groups. There were no significant differences between the SCC of the two groups on any sample day, but there were significant variations between the SCC on different days (P=0.003) in both groups.

Platelets enhance endotoxin-induced monocyte tissue factor (TF) activity in the horse

Endotoxaemia is the leading cause of death in horses. Disseminated intravascular coagulation (DIG), stimulated by induced monocyte proteins, is a prominent feature. Monocyte-platelet cellular interactions are central to the vascular dysfunction produced by circulating endotoxin and are implicated in many thrombotic diseases in the horse. This study reports that endotoxin (0.01-10 microg ml(-1)) and blood platelets (2.5 x 10(7) - 1 x 10(8) ml(-1)) are potent inducers of expression and activity of monocyte tissue factor (TF), the primary activator of the blood coagulation protease cascade. The co-incubation of endotoxin-stimulated monocytes with platelets resulted in greater production of this protein. Cycloheximide (1 mM) inhibited part of the stimulatory effect of endotoxin and/or platelets, the uninhibited part indicating de-encryption of cell-surface TF. Hence, platelets are considered to be an important component of the endotoxin-stimulated response of equine monocytes. The role of platelets as potent stimulators of endotoxin-stimulated monocyte proteins and mediators in vitro is likely to be of significance in vivo in the clinical manifestations and management of endotoxaemia in the horse.

Prevalence of canine cataract: preliminary results of a cross-sectional study

OBJECTIVE

In this study 2000 dogs were examined ophthalmoscopically to determine presence of cataract.

MATERIALS AND METHODS

The dogs examined were predominantly from veterinary hospital populations but also from the Waltham Center For Pet Nutrition, rehoming charities and breeding kennels. Prevalence of cataract was thus determined for different age groups (year cohorts). The age at which prevalence of cataract was 50% (C50) was determined indirectly from a fitted prevalence curve.

RESULTS

The mean +/- standard deviation of C50 for all dogs in the study was 9.4 +/- 3.3 years. All dogs over 13.5 years were affected by some degree of lens opacity. C50 was determined for animals of different genders and different breeds. For dogs of six breeds sufficient data were available for calculation of breed-specific C50. In these dogs C50 was positively correlated with longevity with a least squares correlation coefficient of 0.74.

CONCLUSION

The study yields novel findings regarding the prevalence and incidence of cataract in the dog and forms the basis for considerable further work on the epidemiology and pathophysiology of age-related cataract in the dog.

Effects of a P2Y(12) receptor antagonist on the response of equine platelets to ADP. Comparison with human platelets

Horses show susceptibility to platelet-related disorders. Equine platelets differ from human platelets in some of their responses, so information available about human platelets must be validated in the horse. Aggregation of platelets by ADP involves both P2Y(1) and P2Y(12) receptors on the platelet surface. We have compared the effect of the P2Y(12) antagonist, AR-C67085, on equine and human platelets in vitro using turbidimetric aggregometry to measure the rate and final extent of aggregation. Aggregation profiles, concentration-response curves and pA(2) values show that the rate of aggregation of equine platelets is much more susceptible to inhibition by AR-C67085 than that of human platelets. This species difference may reflect differences in the relative numbers of P2Y(1) and P2Y(12) receptors, or in intracellular signalling pathways, but will need to be considered by equine clinicians before using P2Y(12) antagonists in the treatment of thrombotic conditions.

Effects of P2Y(1) and P2Y(12) receptor antagonists on ADP-induced shape change of equine platelets: comparison with human platelets

Platelet activation by adenosine 5' -diphosphate (ADP) is via both P2Y(1 )and P2Y(12) receptors and leads to shape change and aggregation. The effects on ADP-induced platelet shape change of two P2Y(1) antagonists, adenosine 3'-phosphate, 5'-phosphosulfate (A3P5PS) and 2-deoxy-N(6)-methyladenosine 3', 5'-diphosphate (MRS-2179) and a P2Y(12) antagonist 2-propylthio-D-beta,gamma-dichloromethylene-adenosine 5'-triphosphate (AR-C67085MX) were determined by turbidimetric aggregometry and scanning electron microscopy (SEM) on equine and human platelets. The platelet aggregation was inhibited during aggregometry by 4-[4-[4(aminoiminomethyl)phenyl]-1-piperazinyl]-1-piperidin acid hydrochloride trihydrate (GR 144053F), an inhibitor of fibrinogen binding. From aggregation profiles, concentration-response curves and SEM we conclude that the shape change of equine platelets was susceptible to inhibition by the P2Y(1) antagonists A3P5PS and MRS-2179, but less so than human platelets. The P2Y(12) antagonist AR-C67085 did not influence significantly the shape change of either equine or human platelets.

Agricultural intensification and the collapse of Europe's farmland bird populations

The populations of farmland birds in Europe declined markedly during the last quarter of the 20th century, representing a severe threat to biodiversity. Here, we assess whether declines in the populations and ranges of farmland birds across Europe reflect differences in agricultural intensity, which arise largely through differences in political history. Population and range changes were modelled in terms of a number of indices of agricultural intensity. Population declines and range contractions were significantly greater in countries with more intensive agriculture, and significantly higher in the European Union (EU) than in former communist countries. Cereal yield alone explained over 30% of the variation in population trends. The results suggest that recent trends in agriculture have had deleterious and measurable effects on bird populations on a continental scale. We predict that the introduction of EU agricultural policies into former communist countries hoping to accede to the EU in the near future will result in significant declines in the important bird populations there.

Dextran-70 inhibits equine platelet aggregation induced by PAF but not by other agonists

Dextrans of mean molecular weight 70 kDa (dextran-70) have had clinical use as anti-thrombotics in man. A major part of the anti-thrombotic action is mediated via inhibition of platelet function. Greatorex (1975, 1977) treated thromboembolic colic in horses with infusions of dextran-70 and reported a 90% recovery rate, but this treatment is nonetheless rarely used. We have used an in vitro method to examine the effect of dextran-70 on equine platelet suspensions, in the hope that understanding the mechanism of action of dextran-70 might lead to the development of alternative therapeutic agents. The effects of dextran-70 on equine platelets occurred immediately in vitro with an initial activation and shape change. Subsequent assessment of aggregation revealed a dose-dependent specific inhibition of platelet-activating factor (PAF)-induced aggregation, significant in rate of aggregation at dextran-70 concentrations >40 g/l (P<0.05) and in extent of aggregation at dextran-70 concentrations >50 g/l (P<0.05). Pre-incubation with 60 g/l dextran-70 significantly inhibited the rate and extent of aggregation in response to PAF (1 nmol/l) (P<0.001 and P = 0.003, respectively) but this was not dependent on the duration of pre-incubation (from 0 to 150 min). No effects were seen when the agonist was adenosine 5'-diphosphate (200 nmol/l), collagen (10 mg/l), 5-hydroxytryptamine (100 micromol/l) or U44069 (600 nmol/l) (all P>0.1). Analysis of PAF concentration-aggregation curves after pre-incubation with 60 g/l dextran-70 indicated significant noncompetitive inhibition by dextran-70 (P<0.001 for rate and extent of aggregation). The ability of dextran-70 to inhibit responses of equine platelets to PAF is probably an important component of its beneficial effect as an anti-thrombotic in colic cases.

Identification of a P2X1 purinoceptor expressed on human platelets

It has been proposed that platelets possess a P2X1-purinoceptor-like ligand-gated cation channel, through which Ca2+ enters platelets from the extracellular medium upon ADP or ATP stimulation. In this paper we describe the cloning of human P2X1-specific cDNA from human platelets, K562 and human erythroleukaemic cell lines. Sequence analyses of these cDNAs show 100% nucleotide sequence identity with that of human P2X1 cloned from urinary bladder. Western blotting of platelet lysates separated by SDS-PAGE and probed with anti-P2X1 IgG shows the expected protein with a molecular mass of 60 kDa and a second protein of 45 kDa. These data confirm that platelets possess at least two distinct purinoceptors: a P2T purinoceptor which mediates platelet aggregation, inhibition of adenylate cyclase, and release of intracellular Ca2+ stores and a platelet P2X1 purinoceptor which upon ATP and ADP stimulation mediates the rapid entry of extracellular Ca2+ into platelets.

The role of ADP in endotoxin-induced equine platelet activation

We have shown previously that endotoxin induces platelet aggregation in equine heparinised whole blood in a platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) dependent manner. ADP is an agonist of platelets and is present in platelet dense granules with ATP in high concentrations. An investigation was carried out to establish whether endotoxin-induced platelet activation was associated with release of platelet ATP and ADP. ADP-scavenging enzyme systems significantly inhibited endotoxin-induced aggregation. Plasma levels of adenine nucleotides were measured using a luminometric assay following incubation of heparinised equine whole blood with endotoxin (300 ng/ml). After addition of endotoxin ATP and ADP were released from the platelets and then subsequently degraded to AMP. WEB2086 (4-[3-[4-(o-chlorophenyl)-9-methyl-6H-thieno[3,2-f]-s-triazolo[4,3-a][1, 4] diazepin-2-yl]proprionyl]-morpholine) (100 nM), a competitive PAF receptor antagonist, inhibited endotoxin-induced aggregation and also inhibited the release of adenine nucleotides from the platelets. It is concluded that endotoxin-induced aggregation is dependent upon ADP released from platelet dense granules.

Protein tyrosine phosphorylation in equine platelets: the effect of stimulation by thrombin and platelet-activating factor (PAF)

Protein tyrosine phosphorylation (PTP) in thrombin- and platelet-activating factor (PAF)-stimulated equine platelet activation was investigated in the absence and presence of 2 protein tyrosine kinase inhibitors (PTKIs), methyl 2,5-dihydroxycinnamate (MDHC) and genistein. Washed equine platelets aggregated irreversibly in response to thrombin or PAF in an agonist concentration dependent fashion. MDHC produced an MDHC concentration and time dependent inhibitory effect on rate and extent of thrombin- and PAF-induced aggregations, whereas the effect of genistein on the same parameters was only genistein concentration dependent. Western blotting demonstrated tyrosine phosphorylated proteins in resting platelets. Changes in the PTP pattern occurred both when platelets were stimulated with varying concentrations of thrombin or PAF for a standard time (3 min) or with a standard agonist concentration (0.17 u/ml thrombin or 10(-10) mol/l PAF) for varying times. Different patterns of PTP were produced by thrombin and PAF. 500 mumol/l MDHC and 300 mumol/l genistein each affected the PTP patterns produced in response to thrombin or PAF, but in different ways. PTP results with thrombin and PAF in the presence of 500 mumol/l MDHC were similar, as were those in the presence of 300 mumol/l genistein. However, there were many differences in the PTP results between thrombin (or PAF) in the presence of MDHC and between thrombin (or PAF) in the presence of genistein. Therefore, although both inhibitors are PTKIs, they have different effects on the PTP induced by either agonist. Our work has produced the first evidence of PTP in equine platelets. It is probable that the changes in PTP are related to events in the signal transduction pathway.

The effects of tyrphostins B42 and B46 on equine platelet function and protein tyrosine phosphorylation

The effects of the protein tyrosine kinase inhibitors tyrphostins B42 and B46 on equine platelet function and protein tyrosine phosphorylation (PTP) were assessed. Tyrphostins B42 and B46 (both at 100 microM concentration) produced significant inhibition of thrombin-stimulated equine platelet aggregation. The effect of tyrphostin B46 was also time-dependent. The same concentration of these inhibitors produced very little or no inhibition of platelet-activating factor (PAF)-induced aggregation. The effects of tyrphostins B42 and B46 on thrombin- and PAF-stimulated PTP were generally similar, although some bands were more strongly inhibited when thrombin was the agonist. Therefore, although thrombin and PAF both act via G-protein coupled receptors, PAF may be capable of utilising an alternative signal transduction pathway to that used by thrombin.

The effects of aspirin and paracetamol on the aggregation of equine blood platelets

The responses of equine blood platelets in citrated platelet-rich plasma to arachidonic acid, U44069 (prostaglandin endoperoxide analogue), adenosine 5'-diphosphate, platelet-activating factor or collagen were investigated by turbidimetric aggregometry. Pre-treatment of the platelets with aspirin (1 mmol/l) or paracetamol (1.3 mmol/l) abolished shape change and aggregation in response to arachidonic acid; decreased the rate of aggregation in response to collagen, with no separate effect on shape change; had no marked effect on aggregation caused by the other agonists; but in no case transformed irreversible aggregation to reversible aggregation. We conclude that thromboxane A2 generation is of minor importance in the aggregation of equine platelets, and in particular that thromboxane A2 is not a significant mediator of irreversible aggregation.

Changes in fetal thyroid hormone levels in adrenalectomized fetal sheep following continuous cortisol infusion 72 h before delivery

Continuous infusion of cortisol into adrenalectomized fetal sheep during the last 72 h of gestation (term = 145 +/- 2 days) produced a significant (P < 0.05) rise in fetal serum tri-iodothyronine (T3) mean +/- S.E.M. concentrations from 398 +/- 65 to 1340 +/- 238 ng/l. A concurrent decrease in plasma thyroxine (T4) levels was observed in three out of four animals. No significant changes in the concentrations of either hormone were noted prior to the start of cortisol infusion. The plasma concentrations of cortisol, T3 and T4 at term were similar to those in untreated full-term lambs. Adrenalectomized fetuses not given cortisol infusions still had low levels of T3 at term, with no increase being observed. The results suggest that cortisol plays an important role in the increase of fetal plasma T3 observed towards the end of gestation. This is probably achieved by the stimulation of the monodeiodination of T4 to T3 in the peripheral tissues.

ADP induces desensitisation of equine platelet aggregation responses: studies using ADP beta S, a stable analogue of ADP

Pre-incubation of equine platelets in platelet-rich plasma with adenosine 5'-diphosphate (ADP) induced a reduction in aggregation responsiveness to subsequent additions of ADP. The desensitisation was shown to be homologous since the responsiveness to platelet-activating factor, thrombin, collagen, 5-hydroxytryptamine or ionomycin remained unchanged. Adenosine 5'-(beta-thio)-diphosphate (ADP beta S), a non-hydrolysable analogue of ADP, was shown to act as an agonist inducing aggregation by interaction with the ADP receptor. ADP beta S was then used in the desensitisation studies in which residual ADP was degraded by the addition of apyrase. The desensitisation to ADP beta S fully recovered by one hour after pre-treatment with ADP and was not induced by an extracellular mediator. The mechanism of desensitisation is therefore likely to involve the ADP receptor or proximal intermediates in the signal transduction pathway for ADP.

A method for loading equine platelets with the fluorescent calcium indicator Fura-2: ADP induces a rise in the cytosolic free calcium ion concentration

Equine platelets in platelet-rich plasma were incubated with the fluorescent indicator dye, Fura-2-AM (Fura-2-acetoxymethyl ester) and the degree of loading of the cells with the dye and the extent of hydrolysis of the ester was assessed by quantitative fluorimetry and by thin-layer chromatography respectively. Under these conditions the cells loaded poorly with Fura-2 to a concentration of 4 microM. The technique was validated by demonstrating adequate loading of human platelets with Fura-2, to a concentration of 250-300 microM, using the same method. The removal of plasma from the extracellular medium was important for successful loading of the cells with the dye since washed cells resuspended in a physiological salt solution loaded adequately with Fura-2 to a concentration of 190 microM. Cells loaded as such showed a resting [Ca2+]i of 129 nM and a concentration-dependent rise in [Ca2+]i to a transient maximum of 350 nM when stimulated by the pro-aggregatory agonist adenosine 5'-diphosphate (ADP).

A modified helium dilution technique for measuring small lung gas volumes

The present study was undertaken to devise an accurate method for measuring functional residual capacity, FRC, in small and lively newborn animals such as lambs and piglets under flexible laboratory conditions using relatively simple equipment. This was achieved by adapting the standard helium dilution method so that FRC could be calculated from the helium equilibration concentration reached when the subject, having breathed a gas mixture with a high helium concentration, rebreathed from an air-filled spirometer. Using this technique, typical results for test volumes of 10, 20, 30 and 40 ml were measured as 10.7 +/- 0.34, 20.2 +/- 0.19, 30.5 +/- 0.40 and 40.6 +/- 0.75 ml respectively with corresponding coefficients of variation of 6.4%, 1.9%, 2.6% and 3.7%. Repeat measurements made on each of 3 urethane anaesthetised rabbits gave values for FRC of 45.64 +/- 0.9 ml (5 measurements), 37.22 +/- 0.8 ml (8 measurements) and 48.95 +/- 0.99 ml (8 measurements) confirming the reproducibility of results from animal preparations. The FRC of newborn lambs (12 animals) was 81.4 +/- 9.2 ml. The technique also allowed clear recordings of respiratory pattern essential to the analysis of variations in FRC.

Interaction of Ostertagia and Nematodirus species in sheep and the potential of serum fructosamine determination in monitoring gastrointestinal parasitism

Serum fructosamine concentration falls with an increase in plasma protein turnover. Since this increase is a feature of gastrointestinal parasite infection at all sites, a falling serum fructosamine level may be of general application in the interpretation of parasite-related events. The circulating fructosamine level was investigated in the lamb as an indicator of protein-losing gastroenteropathy associated with two parasites at different sites, Ostertagia circumcincta (abomasum) and Nematodirus spathiger (small intestine). Infection with 10,000 N spathiger infective larvae daily for seven weeks produced only slight clinical signs, and only a small change in serum fructosamine levels. 2500 O circumcincta L3 daily gave no clinical signs in most animals, but serum fructosamine was more strongly affected in this group. Concurrent infection with both organisms caused some degree of diarrhoea in all lambs, and a sustained fall in serum fructosamine, more accentuated than that observed in either of the single infection groups, supporting the value of serum fructosamine determination in monitoring gastrointestinal parasitism.

Blood biochemical reference ranges for sows under modern management conditions

Published reference ranges for blood biochemistry in swine generally do not relate to sows in modern breeding units, and results were often obtained by methods that are now outdated. The ranges widely used in clinical practice reflect these inappropriate sources. The data presented here were obtained using modern methods of analysis on blood samples from healthy, conventionally managed sows from six breeding herds of known disease status in eastern England, and thus represent appropriate ranges for this class of swine. The values differ from earlier reports principally in higher values for total bilirubin, creatine kinase, and more particularly of total plasma and serum proteins. The latter are shown to be due to higher immunoglobulin concentrations than those previously reported.

Pretreatment with pentoxifylline improves the hemodynamic and histologic changes and decreases neutrophil adhesiveness in a pig fecal peritonitis model

We investigated pentoxifylline (PTF) as a pretreatment of septic syndrome in pigs with fecal peritonitis. In the untreated group there was a progressive decrease in mean arterial pressure (MAP), cardiac output, mean pulmonary artery wedge pressure (WP), and a progressive rise in mean pulmonary artery pressure (MPAP), pulmonary vascular resistance (PVR), systemic vascular resistance (SVR), heart rate (HR), and core temperature (T). In those pigs given PTF there was a significantly smaller increase in SVR throughout and in PVR after 270 min. No significant differences were seen in MAP, MPAP, WP, HR, and T. Neutrophil adhesiveness did not change in the untreated group. However, it decreased markedly with PTF, both before and after peritonitis induction. Electron microscopy of the lungs, liver, and spleen in the test group showed severe damage, with endothelial disruption, capillary or sinusoidal occlusion, leukostasis, and neutrophil degranulation. Pretreatment with PTF attenuated these changes.

Primary hyperoxaluria (L-glyceric aciduria) in the cat: a newly recognised inherited disease

The clinical features of a newly recognised inherited disease, primary hyperoxaluria in the cat, are reported. Affected cats developed acute renal failure between five and nine months old owing to the deposition of oxalate crystals in the tubules of the kidney. In addition to the signs attributable to kidney failure the affected animals became profoundly weak; there was evidence of denervation atrophy in skeletal muscle, and accumulations of neurofilaments were found in the proximal axons of the ventral horn cells and dorsal root ganglion cells of the spinal cord. Examination of urine from affected cats revealed L-glyceric aciduria and intermittent hyperoxaluria suggesting that the disease is a feline analogue of the human disorder, primary hyperoxaluria type 2. This supposition was confirmed by liver enzyme studies.

Pentoxifylline reduces pulmonary leucostasis and improves capillary patency in a rabbit peritonitis model

This study examines the changes in pulmonary leucostasis and capillary ultrastructure in 18 rabbits divided into three groups. Those in the first group were sham operated, and those in the second and third groups underwent peritonitis induction; those in the latter group were treated with pentoxifylline (PTF). White blood cells (WBC) were counted, and tissue area, total capillary area, and capillary patency were measured from electron micrographs of lung tissue. Pulmonary WBCs were 1.2 per unit field in the sham group, 9.7 in the test group (P less than 0.001 compared with sham), and 2.5 in the PTF group (P less than 0.001 compared with sham). Capillary patency was 53 +/- 5% in the sham group, 12 +/- 4% (P less than 0.001 compared with sham) in the test group, and 24 +/- 2% (P less than 0.001 compared with sham) in the PTF group. Pentoxifylline treatment attenuates pulmonary leucostasis, pulmonary capillary occlusion, and endothelial and epithelial damage associated with peritonitis in rabbits. This study shows that PTF warrants investigation into its potential protective effects on the lungs in clinical sepsis.

Multi-organ damage resulting from experimental faecal peritonitis

1. Using specific-pathogen-free New Zealand White rabbits, we have compared the effects of faecal peritonitis over a period of 5 h in eight test animals with eight controls in which a sham operation was performed. 2. There was morphological damage to lungs, liver and spleen of test animals. Lung capillaries and sinusoids of the liver showed occlusion by cell debris and leucocytes, with endothelial damage. The lungs also showed alveolar epithelial disruption, basement membrane exposure and type II pneumocytes lacking lamellar bodies. In the liver there was fibrin deposition and swollen Kupffer cells. The spleen showed degranulating neutrophils, fibrin deposits, platelet aggregates and activated macrophages, with no damage to the endothelium. 3. There was no morphological damage to the kidney or heart of test animals or to any organs of sham-operated animals. 4. There were mixed anaerobes and aerobes in faecal material used to induce peritonitis. Cultures of liver, spleen and kidney isolated four different types of micro-organisms. Blood cultures showed two types of micro-organisms. Cultures of lung and heart showed one type of micro-organism. 5. The presence of micro-organisms in an organ could not be correlated with the degree of histological damage to that organ. 6. In test animals an early significant reduction in circulating leucocytes and platelets was sustained for the duration of the experiment with significant diffuse intravascular coagulation. 7. There was no change in test animal neutrophil adhesiveness until 120 min, when significant reduction was observed. 8. Serum phospholipase A2 (EC 3.1.1.4) activity in the test group showed a threefold increase at 300 min.

Enzymological characterization of a feline analogue of primary hyperoxaluria type 2: a model for the human disease

This paper concerns an enzymological investigation into a putative feline analogue of the human autosomal recessive disease primary hyperoxaluria type 2. The hepatic activities of D-glycerate dehydrogenase, using both D-glycerate and hydroxypyruvate as substrates, and glyoxylate reductase, which are the deficient enzyme activities in human primary hyperoxaluria type 2, were markedly depleted in four affected cats (0-6% of controls). The activities of a number of other enzymes, lactate dehydrogenase, glutamate dehydrogenase, D-amino acid oxidase, aspartate:2-oxoglutarate amino-transferase, glutamate:glyoxylate aminotransferase and alanine:glyoxylate aminotransferase (the deficient enzyme in primary hyperoxaluria type 1) were unaltered. The intracellular distribution of D-glycerate dehydrogenase and glyoxylate reductase in cat liver was shown to be cytosolic, as they are in human liver. The activities of D-glycerate dehydrogenase and glyoxylate reductase were determined in unaffected related cats and putative heterozygotes were identified. The correlation between D-glycerate dehydrogenase and glyoxylate reductase activities in the related cats and their combined deficiency in the affected cats confirmed previous suggestions that they are identical gene products.

The induction of pulmonary phospholipidosis and the inhibition of lysosomal phospholipases by amiodarone

Administration of high doses of amiodarone to young adult rats leads to phospholipidosis of the lung, with extensive phospholipid storage by type II pneumonocytes and alveolar macrophages. Biochemical analysis reveals an increase in the total phospholipid content of the lung and in the proportion of phosphatidylcholine. The cause of the phospholipidosis is suggested to be the inhibition of lysosomal phospholipases, responsible for catabolizing phospholipids. It is shown that amiodarone is a potent inhibitor of phospholipases prepared from the soluble fraction of adult rabbit lung lysosomes.

Developmental changes in enzyme activities in fetal and neonatal rabbit lung. Cytidylyltransferase, cholinephosphotransferase, phospholipases A1 and A2, beta-galactosidase, and beta-glucuronidase

Lungs were obtained from rabbit fetuses (on each day from d 24 to d 30 of gestation), neonates and adults, and were fractionated for enzyme assays. The developmental profile of cytidylyltransferase shows a decrease in specific activity from d 25 to d 29 (P less than 0.05) then a sharp rise from d 30 to adult values in d 0 neonates (P less than 0.05). Cholinephosphotransferase specific activity changes little from d 25 to birth, apart from a non-significant peak on d 29. There is a sharp rise from neonatal d 0 to adult values on d 1 (P less than 0.01). The specific activity of microsomal phospholipase A2 declines from d 25 to reach adult values in the neonate (P = 0.05). In contrast, the specific activity of lysosomal phospholipase A2 rises from d 24-28 then falls in the neonate (P less than 0.05). Adult values are higher than those in the fetus and neonate. Three other lysosomal enzyme specific activities rise to d 28 then decline: phospholipase A1, beta-galactosidase, and beta-glucuronidase. The results demonstrate that the level of microsomal phospholipase A2 does not control the extent of remodelling of phosphatidylcholine for surfactant production. Lysosomal phospholipase A2 only increases in parallel with the other lysosomal enzymes, indicating an increase in the number of lysosomes in the lung.

The effect of components of rabbit pulmonary surfactant on the activity of phospholipases

This study investigates the ability of two components of pulmonary surfactant, protein and phosphatidylglycerol, to inhibit the action of phospholipases against phosphatidylcholine. Broncho-alveolar protein, prepared by de-lipidation of rabbit lung lavage material had an inhibitory effect on phospholipases A1 and A2 from rabbit lung lysosomes, comparable to the effect of bovine serum albumin. The degree of inhibition was found to increase with increasing enzyme activity. De-lipidated broncho-alveolar protein was separated into two fractions by gel chromatography. Inhibitory activity was associated only with the second peak, corresponding to rabbit albumin. The effect of phosphatidylglycerol (PG) on the activity of phospholipases A against dipalmitoyl phosphatidylcholine and unsaturated phosphatidylcholine (USPC) was investigated, and compared with the effects of two substrate analogues on the hydrolysis of USPC. There was no indication of true inhibition by PG, but some stimulation of USPC hydrolysis by 10 mol % PG. The relevance of these findings to the fate of surfactant in vivo is discussed.

The nature of the phospholipases A of lung lamellar bodies

Phospholipases A1 and A2 from rabbit lung lysosomes have maximal activity at pH 4.0 (Fig. 1). Lamellar bodies from rabbit lung contain phospholipases A which resemble the lysosomal enzymes in being active at pH 4 and showing sensitivity to inhibition by calcium ions (80% inhibition at 10 mM Ca2+). Lamellar body phospholipases hydrolyse dipalmitoyl phosphatidylcholine (containing 10% phosphatidylglycerol and thus approximating the phospholipid composition of mature lamellar bodies) at only 1% of their rate of hydrolysis of unsaturated molecules (Tables 1 and 2). This substrate preference corresponds to that shown by phospholipases from lysosomes.

The action of lung lysosomal phospholipases on dipalmitoyl phosphatidylcholine and its significance for the synthesis of pulmonary surfactant

Subcellular fractions were prepared from rabbit lung and characterized by marker enzyme assays. Phospholipases A of lysosomal type (activity at pH 4.0 in the absence of Ca2+) show a peak of specific activity in fraction P3 (13000 x g; 20 min; pellet). About 70% of the phospholipase A activity of P3 can be obtained in a soluble extract. The rates of hydrolysis of dipalmitoyl (saturated) and unsaturated phosphatidylcholine molecules, presented to enzyme preparations in liposomes of varying composition, are shown in Tables 3 to 5. Although the rate of unsaturated molecules is unaffected by liposome composition, saturated molecules are hydrolyzed significantly faster in 5 mol % dipalmitoyl phosphatidylcholine liposomes than in 95 mol %. With enzyme preparation I (60% A1: 40% A2) the increase was 6-fold (P less than 0.01). Preparations I and II hydrolyzed both kinds of molecules at similar rates in 50 mol % dipalmitoyl phosphatidylcholine liposomes, but preparation III, with a higher proportion of A2 (80%), gave a notably lower rate of hydrolysis of saturated molecules. Phosphatidylglycerol (10 mol %) also decreased the rate of hydrolysis of saturated molecules. These results are discussed in relation to fluidity of the liposomes and to the functions of the lysosomal-type phospholipases A of the lamellar inclusion bodies of the lung.

Phospholipase A2 activity of the regularly arranged surface protein of Acinetobacter sp.199A

The regularly arranged surface protein, the a-protein, of Acinetobacter 199A has been shown to have phospholipase A2 activity. Since half of the a-protein synthesised by Acinetobacter 199A is secreted into the growth medium, the bacteria are producing extracellular phospholipase A2.

Phospholipases A1 and A2 in lamellar inclusion bodies of the alveolar epithelium of rabbit lung

1. A lamellar body-enriched fraction was prepared from rabbit lung and characterized by electron microscopy, surface activity studies, phospholipid assay and marker enzymes. 2. Both phospholipases A1 and A2 were found to be present in lamellar bodies. After these had been ruptured both enzymes were found to be principally in the soluble phase. 3. The possible roles for phospholipases in lamellar body development and in the respiratory distress syndrome of the newborn are discussed.

A hydroxyproline-containing glycopeptide released from the walls of sycamore tissue-culture cells by hydrazinolysis

Degradation of the sycamore cell wall by hydrazinolysis yielded soluble glycopeptides. The peptide portion of the predominant glycopeptide was shown to be cyclic (4-trans-hydroxy-l-prolyl)-4-trans-hydroxy- l-proline. From this structure and the composition of the major glycopeptide it was deduced that only short oligosaccharides are attached to the hydroxyprolyl residues of the wall glycoprotein. Detailed evidence for the structure of the peptide is given in a supplementary paper that has been deposited as Supplementary Publication SUP 50020, at the National Lending Library for Science and Technology, Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1973) 131, 5.

Glycoprotein of the wall of sycamore tissue-culture cells

1. A glycoprotein containing a large amount of hydroxyproline is present in the cell walls of sycamore callus cells. This protein is insoluble and remained in the alpha-cellulose when a mild separation procedure was used to obtain the polysaccharide fractions of the wall. The glycoprotein contained a high proportion of arabinose and galactose. 2. Soluble glycopeptides were prepared from the alpha-cellulose fraction when peptide bonds were broken by hydrazinolysis. The soluble material was fractionated by gel filtration and one glycopeptide was further purified by electrophoresis; it had a composition of 10% hydroxyproline, 35% arabinose and 55% galactose, and each hydroxyproline residue carried a glycosyl radical so that the oligosaccharides on the glycopeptide had an average degree of polymerization of 9. 3. The extraction of the glycopeptides was achieved without cleavage of glycosyl bonds, so that the glycoprotein cannot act as a covalent cross-link between the major polysaccharides of the wall. 4. The wall protein approximates in conformation to polyhydroxyproline and therefore it probably has similar physicochemical properties to polyhydroxyproline. This is discussed in relation to the function of the glycoprotein and its effect on the physical and chemical nature of the wall.