Efficacy of fenbendazole and ivermectin in treating gastrointestinal nematode infections in an Ontario cow-calf herd

The objective of this randomized clinical trial was to compare performance of cow-calf pairs in southern Ontario treated with fenbendazole or ivermectin, or not treated, for gastrointestinal nematode infections. Treatments were administered to 128 cow-calf pairs over 2 years. Weights, body condition score, and fecal egg counts (FEC) were collected at treatment and at 28-day intervals. Treating calves with an anthelmintic was significantly advantageous compared with not treating, and there was no significant difference between treatment with fenbendazole or ivermectin. Neither treatment nor calf FEC had a significant effect on calf weaning weight. This could be the result of time of treatment, low initial FEC, or lack of power. Treatment affected cow FEC (P = 0.003). Cows in the ivermectin groups had the lowest FEC (P < 0.05), but because FEC were all low, biological significance is questionable. Additional work is needed to provide recommendations on when an anthelmintic should be used.

ADP Plays a Key Role in Thrombogenesis in Rats

The relative importance of ADP, arachidonic acid metabolites and serotonin as thrombogenic factors was evaluated in rats by comparing, after oral administration, the effects of two inhibitors of ADP-induced platelet aggregation (ticlopidine and PCR 4099), three cyclo-oxygenase inhibitors (aspirin, triflusal and indobufen) and a selective serotonin 5HT2 receptor antagonist (ketanserin) on platelet aggregation, in four platelet-dependent thrombosis models and on bleeding time. Platelet aggregation induced by ADP and collagen was completely inhibited by ticlopidine and PCR 4099 whereas only the collagen aggregation was reduced by the cyclo-oxygenase inhibitors. Ketanserin or a depletion of platelet serotonin by reserpine did not affect platelet aggregation. Ticlopidine and PCR 4099 greatly prolonged rat tail transection bleeding time. This is probably related to their known ability to inhibit ADP-mediated platelet aggregation. In contrast, the cyclooxygenase inhibitors did not affect bleeding time at all. Reserpine and ketanserin prolonged bleeding time by interfering with the action of serotonin on the vascular wall. Ticlopidine and PCR4099 were very potent antithrombotics in all the models. Aspirin, only at a high dose, inhibited poorly thrombus formation on a silk thread in an arterio-venous shunt, suggesting that the inhibition of cyclo-oxygenase was not responsible. Triflusal was inactive in all models while indobufen slightly reduced thrombus formation in the silk thread and metallic coil models. Ketanserin and reserpine reduced thrombus only in the metallic coil model. Thrombus formation was greatly reduced in fawn-hooded rats, which lack ADP in their platelet dense granules because of a genetic storage pool deficiency. Taken together, the results obtained with the drugs and with the fawn-hooded rats support the concept that ADP plays a key role in thrombogenesis in rats.

Effects of a combination butaphosphan and cyanocobalamin product and insulin on ketosis resolution and milk production

The objective of this study was to determine the effects of butaphosphan-cyanocobalamin (B+C), glargine insulin, and propylene glycol on resolution of ketosis and average daily milk yield after treatment. Cows from 16 herds in Ontario, Canada, and 1 herd in Michigan were tested at weekly intervals between 3 and 16 DIM. Ketosis was defined as blood β-hydroxybutyrate (BHB) ≥1.2 mmol/L. All ketotic cows were given a baseline treatment of 3 d of 300 g of propylene glycol orally. Animals were then randomly assigned to treatment with 3 doses of either 25 mL of B+C or 25 mL of saline placebo and 1 dose of either 2 mL (200 IU) of glargine insulin or 2 mL of saline placebo in a 2 × 2 factorial arrangement. Outcomes of interest on all farms were ketosis cure (blood BHB <1.2 mmol/L 1 wk postenrollment), maintenance of ketosis cure (blood BHB <1.2 mmol/L 1 and 2 wk postenrollment), and blood BHB concentrations at 1 and 2 wk postenrollment. Milk weights were collected daily in 1 large freestall herd. Repeated measures ANOVA was used to evaluate blood BHB concentrations 2 wk after treatment and milk production for 30 d after treatment. Poisson regression was used to examine the effect of treatment on cure and maintenance of cure. Due to a regulatory delay causing temporary unavailability of B+C in Canada, data were analyzed in 2 sets of models: one for insulin and the corresponding placebo (n = 620) and one for the full trial (n = 380). Animals with blood glucose concentrations ≤2.2 mmol/L at the time of ketosis diagnosis were 2.1 times more likely (95% CI = 1.2 to 3.7) to be cured if treated with B+C. Animals in lactation 3 or higher that had blood glucose concentrations <2.2 mmol/L at enrollment produced 4.2 kg/d (95% CI = 1.4 to 7.1) more milk if treated with insulin versus placebo and 2.8 kg/d (95% CI = 0.9 to 4.7) more milk if treated with B+C versus placebo. Animals in lactation 3 or higher with blood glucose ≥2.2 mmol/L that were treated with insulin produced 2.3 kg/d (95% CI = 0.3 to 4.4) less milk than untreated controls. No interaction was observed between treatments. This evidence suggests that B+C and insulin may be beneficial for ketosis treatment in animals with blood glucose <2.2 mmol/L at ketosis diagnosis. It also suggests that blood glucose concentration may be an important predictor of success of ketosis treatment.

Room temperature housing results in premature cancellous bone loss in growing female mice: implications for the mouse as a preclinical model for age-related bone loss

Room temperature housing (22 °C) results in premature cancellous bone loss in female mice. The bone loss was prevented by housing mice at thermoneutral temperature (32 °C). Thermogenesis differs markedly between mice and humans and mild cold stress induced by standard room temperature housing may introduce an unrecognized confounding variable into preclinical studies.

INTRODUCTION

Female mice are often used as preclinical models for osteoporosis but, in contrast to humans, mice exhibit cancellous bone loss during growth. Mice are routinely housed at room temperature (18-23 °C), a strategy that exaggerates physiological differences in thermoregulation between mice (obligatory daily heterotherms) and humans (homeotherms). The purpose of this investigation was to assess whether housing female mice at thermoneutral (temperature range where the basal rate of energy production is at equilibrium with heat loss) alters bone growth, turnover and microarchitecture.

METHODS

Growing (4-week-old) female C57BL/6J and C3H/HeJ mice were housed at either 22 or 32 °C for up to 18 weeks.

RESULTS

C57BL/6J mice housed at 22 °C experienced a 62 % cancellous bone loss from the distal femur metaphysis during the interval from 8 to 18 weeks of age and lesser bone loss from the distal femur epiphysis, whereas cancellous and cortical bone mass in 32 °C-housed mice were unchanged or increased. The impact of thermoneutral housing on cancellous bone was not limited to C57BL/6J mice as C3H/HeJ mice exhibited a similar skeletal response. The beneficial effects of thermoneutral housing on cancellous bone were associated with decreased Ucp1 gene expression in brown adipose tissue, increased bone marrow adiposity, higher rates of bone formation, higher expression levels of osteogenic genes and locally decreased bone resorption.

CONCLUSIONS

Housing female mice at 22 °C resulted in premature cancellous bone loss. Failure to account for species differences in thermoregulation may seriously confound interpretation of studies utilizing mice as preclinical models for osteoporosis.

Differential association of insulin resistance with cognitive and somatic symptoms of depression

AIM

To examine the associations of depressive symptoms with insulin resistance, evaluating somatic and cognitive depressive symptoms separately.

METHODS

A total of 328 individuals (mean age 60 years) referred for exercise stress testing, taking part in the Mechanisms and Outcomes of Silent Myocardial Ischemia study, completed the Beck Depression Inventory II. A fasting venous blood sample was collected for assessments of insulin and glucose level; the HOMA-IR (homeostatic model assessment of insulin resistance) was calculated. In principal component analysis, Beck Depression Inventory II items were forced to load onto two components (somatic and cognitive depressive symptoms). Adjusting for age, sex, BMI, medication use, smoking, physical activity, diabetes and cardiovascular disease, general linear model analyses were conducted to examine the associations between the components and log HOMA-IR .

RESULTS

Principal component analysis showed that nine items loaded onto a cognitive depressive symptoms component and 10 items loaded onto a somatic depressive symptoms component. When examined separately, both components were significantly associated with log HOMA-IR however, when including both components simultaneously in the model, only somatic depressive symptoms remained significantly associated with log HOMA-IR. Back-transformed, a one-unit change in somatic depressive symptoms was associated with a 1.07 (95% CI 1.002, 1.14) change in HOMA-IR and a one-unit change in cognitive depressive symptoms was associated with a 1.03 (95% CI 0.97, 1.14) change in HOMA-IR.

CONCLUSION

Somatic depressive symptoms seem to be more strongly associated with insulin resistance than do cognitive depressive symptoms. Monitoring somatic depressive symptoms may be more appropriate than monitoring cognitive depressive symptoms among depressed individuals with high insulin resistance.

Draft Genome Sequence of Xanthomonas axonopodis pv. allii Strain CFBP 6369

We report here the draft genome sequence of Xanthomonas axonopodis pv. allii strain CFBP 6369, the causal agent of bacterial blight of onion. The draft genome has a size of 5,425,942 bp and a G+C content of 64.4%.

Molecular basis for enantioselectivity of lipase from Chromobacterium viscosum toward the diesters of 2,3-dihydro-3-(4'-hydroxyphenyl)-1,1,3-trimethyl-1H-inden-5-ol

2,3-Dihydro-3-(4'-hydroxyphenyl)-1,1,3-trimethyl-1H-inden-5-ol, 1, is a chiral bisphenol useful for preparation of polymers. Previous screening of commercial hydrolases identified lipase from Chromobacterium viscosum (CVL) as a highly regio- and enantioselective catalyst for hydrolysis of diesters of 1. The regioselectivity was > or =30:1 favoring the ester at the 5-position, while the enantioselectivity varied with acyl chain length, showing the highest enantioselectivity (E = 48 +/- 20 S) for the dibutanoate ester. In this paper, we use a combination of nonsymmetrical diesters and computer modeling to identify that the remote ester group controls the enantioselectivity. First, we prepared nonsymmetrical diesters of (+/-)-1 using another regioselective, but nonenantioselective, reaction. Lipase from Candida rugosa (CRL) showed the opposite regioselectivity (>30:1), allowing removal of the ester at the 4'-position (the remote ester in the CVL-catalyzed reaction). Regioselective hydrolysis of (+/-)-1-dibutanoate (150 g) gave (+/-)-1-5-dibutanoate (89 g, 71% yield). Acylation gave nonsymmetrical diesters that varied at the 4'-position. With no ester at the 4'-position, CVL showed no enantioselectivity, while hindered esters (3,3-dimethylbutanoate) reacted 20 times more slowly, but retained enantioselectivity (E = 22). These results indicate that the remote ester group can control the enantioselectivity. Computer modeling confirmed these results and provided molecular details. A model of a phosphonate transition state analogue fit easily in the active site of the open conformation of CVL. A large hydrophobic pocket tilts to one side above the catalytic machinery. The tilt permits the remote ester at the 4'-position of only the (S)-enantiomer to bind in this pocket. The butanoate ester fits and fills this pocket and shows high enantioselectivity. Both smaller and larger ester groups show low enantioselectivity because small ester groups cannot fill this pocket, while longer ester groups extend beyond the pocket. An improved large-scale resolution of 1-dibutanoate with CVL gave (R)-(+)-1-dibutanoate (269 g, 47% yield, 92% ee) and (S)-(-)-1-4'-monobutanoate (245 g, 52% yield, 89% ee). Methanolysis yielded (R)-(+)-1 (169 g, 40% overall yield, >97% ee) and (S)-(-)-1 (122 g, 36% overall yield, >96% ee).

The impact of occupational injury on injured worker and family: outcomes of upper extremity cumulative trauma disorders in Maryland workers

BACKGROUND

Surveys have identified a dramatically rising incidence of work-related upper extremity cumulative trauma disorders (UECTDs). Outcome studies have addressed time lost from work and cost of compensation; omitting other significant consequences. We assess health, functional and family outcomes.

METHODS

We identified 537 Workers' Compensation UECTD claimants. A computer-assisted telephone questionnaire was used to elicit symptom prevalence, functional impairment, depressive symptoms (CES-D scale), employment status.

RESULTS

One to 4 years post-claim, respondents reported persistent symptoms severe enough to interfere with work (53%), home/recreation activities (64%) and sleep (44%). Only 64% of responses to the activities of daily living scale items indicated "normal" function. Job loss was reported by 38% of respondents, and depressive symptoms by 31%.

CONCLUSIONS

Work-related UECTDs result in persisting symptoms and difficulty in performing simple activities of daily living, impacting home life even more than work. Job loss, symptoms of depression, and family disruption were common.

Patterns and predictors of employer risk-reduction activities (ERRAs) in response to a work-related upper extremity cumulative trauma disorder (UECTD): reports from workers' compensation claimants

BACKGROUND

Despite being preventable, work-related upper extremity cumulative trauma disorders (UECTDs) remain problematic. This study is unique in its focus on predictors of employer risk-reduction activities (ERRAs) in response to a UECTD case.

METHODS

Workers' compensation claimants (N = 537) completed a telephone survey about employer risk-reduction activities, workplace characteristics, safety programs, and physician recommendations for job modifications.

RESULTS

Only 52% of respondents reported employer actions to investigate or reduce UECTD risk. Engineering and pace changes were prominent for keyboard workers and transfer to another job for manufacturing workers. Safety programs and physician recommendations increased the likelihood of risk-reduction activities.

CONCLUSIONS

An opportunity to intervene post-injury to reduce risks for the injured worker and prevent new UECTD cases is being missed. Physician recommendations are strongly associated with specific ERRAs thought to be most effective. Educating employers and physicians about ergonomics could result in prevention of UECTDs.

Evidence for independent feedback control of horizontal and vertical saccades from Niemann-Pick type C disease

We measured the eye movements of three sisters with Niemann-Pick type C disease who had a selective defect of vertical saccades, which were slow and hypometric. Horizontal saccades, and horizontal and vertical pursuit and vestibular eye movements were similar to control subjects. The initial movement of oblique saccades was mainly horizontal and most of the vertical component occurred after the horizontal component ended; this resulted in strongly curved trajectories. After completion of the horizontal component of an oblique saccade, the eyes oscillated horizontally at 10-20 Hz until the vertical component ended. These findings are best explained by models that incorporate separate feedback loops for horizontal and vertical burst neurons, and in which the disease selectively affects vertical burst neurons.

Evidence for an early inflammatory response in the central nervous system of mice with scrapie

In Alzheimer's disease, the most prevalent of the neurodegenerative diseases, inflammation of the CNS contributes to the pathology and is a target for therapy. In contrast, the group of neurodegenerative conditions known as the Prion Diseases have been widely reported as lacking any inflammatory elements despite the many similarities between the pathologies of Alzheimer's Disease and Prion Diseases We have found evidence for an inflammatory component in mouse scrapie, characterized by microglial activation and T-lymphocyte recruitment, which appears long before any clinical signs of the disease and spreads along well-defined anatomical pathways. These observations emphasize the potential value of murine scrapie as a model for studying the inflammatory pathology of other neurodegenerative diseases.

Genetic engineering of carbohydrate biosynthetic pathways in transgenic mice demonstrates cell cycle-associated regulation of glycoconjugate production in small intestinal epithelial cells

Proliferation, migration-associated differentiation, and cell death occur continuously and in a spatially well-organized fashion along the crypt-villus axis of the mouse small intestine, making it an attractive system for studying how these processes are regulated and interrelated. A pathway for producing glycoconjugates was engineered in adult FVB/N transgenic mice by expressing a human alpha 1,3/4-fucosyltransferase (alpha 1,3/4-FT; EC 2.4.1.65) along the length of this crypt-villus axis. The alpha 1,3/4-FT can use lacto-N-tetraose or lacto-neo-N-tetraose core chains to generate Lewis (Le) blood group antigens Le(a) or Le(x), respectively, and H type 1 or H type 2 core chains to produce Leb and Le(y). Single- and multilabel immunohistochemical studies revealed that expression of the alpha 1,3/4-FT results in production of Le(a) and Leb antigens in both undifferentiated proliferated crypt cells and in differentiated postmitotic villus-associated epithelial cells. In contrast, Le(x) antigens were restricted to crypt cells. Villus enterocytes can be induced to reenter the cell cycle by expression of simian virus 40 tumor antigen under the control of a promoter that only functions in differentiated members of this lineage. Bitransgenic animals, generated from a cross of FVB/N alpha 1,3/4-FT with FVB/N simian virus 40 tumor antigen mice, expand the range of Le(x) expression to include villus-associated enterocytes that have reentered the cell cycle. Thus, the fucosylations unveil a proliferation-dependent switch in oligosaccharide production, as defined by a monoclonal antibody specific for the Le(x) epitope. These findings show that genetic engineering of oligosaccharide biosynthetic pathways can be used to define markers for entry into, or progression through, the cell cycle and to identify changes in endogenous carbohydrate metabolism that occur when proliferative status is altered in a manner that is not deleterious to the system under study.

Supplementation of the human vestibulo-ocular reflex by visual fixation and smooth pursuit

In studies over the past 30 years, D. A. Robinson and colleagues established that the dynamic characteristics of smooth pursuit eye movements (SP) are different at the onset from those at the cessation of the response. They proposed that cessation of SP was due to a separate fixation system. During head movements, both fixation and SP may contribute to gaze stabilization. We investigated the relative contributions of fixation and SP to the "visually enhanced" vestibulo-ocular reflex (VVOR) using a paradigm requiring a transition from VVOR to combined eye-head tracking (CEHT). We found, in four normal subjects, that ringing typical of SP generally did not occur during VVOR, but that it often appeared after the transition to CEHT. The findings were different in two patients with absent peripheral vestibular function; ringing typical of SP occurred always during VVOR but disappeared during the onset of CEHT. These results can be explained by a model in which an internal representation of target velocity serves as input to parallel SP and fixation systems, and as the determinant of which of the two systems will provide the command signal. Interpretation of our data using this model indicates that either fixation or SP systems may "visually enhance" the VOR, depending on the magnitude of retinal error velocity that remains after vestibular eye movements have been generated.

Processing of tumour necrosis factor-alpha precursor by metalloproteinases

Tumour necrosis factor-alpha (TNF-alpha) is a potent pro-inflammatory and immunomodulatory cytokine implicated in inflammatory conditions such as rheumatoid arthritis, Crohn's disease, multiple sclerosis and the cachexia associated with cancer or human immunodeficiency virus infection. TNF-alpha is initially expressed as a 233-amino-acid membrane-anchored precursor which is proteolytically processed to yield the mature, 157-amino-acid cytokine. The processing enzyme(s) which cleave TNF-alpha are unknown. Here we show that the release of mature TNF-alpha from leukocytes cultured in vitro is specifically prevented by synthetic hydroxamic acid-based metalloproteinase inhibitors, which also prevent the release of TNF-alpha into the circulation of endotoxin challenged rats. A recombinant, truncated TNF-alpha precursor is cleaved to biologically active, mature TNF-alpha by several matrix metalloproteinase enzymes. These results indicate that processing of the TNF-alpha precursor is dependent on at least one matrix metalloproteinase-like enzyme, inhibition of which represents a novel therapeutic mechanism for interfering with TNF-alpha production.

The expression of the adhesion molecules ICAM-1, VCAM-1, PECAM, and E-selectin in human atherosclerosis

The expression of PECAM, ICAM-1, VCAM-1, and E-selectin was studied in 64 samples of human coronary arteries taken from 15 explanted hearts obtained within 5 min of transplantation. Normal artery (n = 12), predominantly fibrous plaques (n = 23), and plaques containing extracellular lipid (n = 26) and three segments showing recanalization channels were studied. All endothelial cells strongly and equally expressed PECAM; positive staining was used to check that artefactual denudation of the endothelial surface had not occurred. PECAM was also present in some lipid-filled macrophages. Normal arteries showed no VCAM-1 staining but focal segments of the endothelium were positive for ICAM-1 and E-selectin. ICAM-1 was strongly and constantly expressed by the endothelium over all types of plaques and in macrophages. E-selectin expression was confined to endothelial cells and occurred on the surface in 35 per cent of fibrous and 22 per cent of lipid-containing plaques. VCAM-1 staining of surface endothelium occurred in 39 per cent of fibrous and 20 per cent of lipid-containing plaques. A population of spindle-shaped cells of macrophage type (positive for EMB11 antigen) expressed VCAM-1 in lipid-containing plaques. Adventitial vessels adjacent to plaques showed endothelial expression of ICAM-1 and E-selectin. VCAM-1 staining of adventitial vessel endothelium was associated with local lymphoid aggregation. In conclusion, the expression of cell adhesion molecules is an important element in the inflammatory component of atherosclerosis and contributes to both monocyte and lymphocyte activation and recruitment from adventitial vessels and the arterial lumen.

Metalloproteinase inhibitors as therapeutics

Matrix metalloproteinases (MMPs) are a family of enzymes which contain zinc at their active site and can degrade most of the matrix macromolecules found in connective tissues. These MMPs are secreted by connective tissue cells and infiltrating leucocytes in response to inflammatory mediators. There is now widespread recognition that MMPs are the major class of proteinases responsible for the excessive degradation of cartilage that leads to joint dysfunction in rheumatoid arthritis. The properties of the MMPs are reviewed and a therapeutic role for synthetic, zinc-binding pseudopeptide MMP inhibitors in the treatment of arthritis is proposed.

The effects of radiographic contrast media on myocardial contractility and coronary resistance: osmolality, ionic concentration, and viscosity

With the ongoing development of new contrast agents, questions develop concerning the cardiac effects of these drugs. We used the perfused rat heart model to investigate the effects on cardiac and coronary function of hypertonic ionic (sodium chloride) and nonionic (glucose) solutions and conventional and low osmolality radiographic contrast media (RCM). We also evaluated the concurrent effects of RCM on prostacyclin and adenine nucleotide/nucleoside release. Hypertonic solutions of glucose had little effect on myocardial contraction (increase up to 7.7 +/- 0.9%), while NaCl solutions of similar osmolality were negatively inotropic (contractile force decreased up to 76.1 +/- 9.2%). Conventional RCM were negatively inotropic (decrease of 59.6 +/- 5.6% with Conray (Mallinckrodt Pharmaceuticals, St. Louis, MO), 32.2 +/- 3.2% with Angiovist 282 (Berlex Laboratories, Cedar Knolls, NJ]; two nonionic RCM, Iopamidol and Iotrol had little effect on myocardial contraction (reduction of 6.9 +/- 1.4% and increase of 12.0 +/- 2.9%, respectively). Hypertonic solutions of glucose and NaCl reduced coronary resistance in direct relationship to hyperosmolality. Conventional RCM also reduced coronary resistance, while the nonionic media caused minor alteration. None of the solutions tested altered prostacyclin or adenine nucleotide/nucleoside efflux from the heart. A solution of Ficoll 70 with a viscosity similar to that of RCM increased myocardial contraction by 9.6 +/- 3.6% and had no effect on coronary resistance, indicating that viscosity per se did not contribute to the negative inotropic effects or the reduction in coronary resistance. Hypertonic solutions, including conventional RCM, reduce coronary resistance as a result of their hyperosmolality Negative inotropic effects, however, are more related to high ionic concentration than to osmolality.

Reflections and remembrances

Two brief and very personal essays written by practicing nurses in the Rhode Island community. These commentaries reflect their remembrances of the human dimensions of dying and the role of hospice in easing the accompanying burdens of anguish and grief.

Kinetics of adenine nucleotide catabolism in coronary circulation of rats

We have used the rat isolated, perfused heart to study the metabolism of adenine nucleotides on a single passage through the coronary circulation. Low doses (3-30 nmol) of ATP, ADP, or AMP injected as a bolus were extensively catabolized by ectoenzymes. Increasing doses of each nucleotide demonstrated saturability of catabolism that occurred at significantly lower doses of AMP than of ADP or ATP. The patterns of catabolites formed in each case were consistent with the major pathway of metabolism being sequential dephosphorylation of ATP----ADP----AMP----adenosine, although from experiments in which [3H]ATP was co-injected with unlabeled ADP, it appears that some direct conversion of ATP----AMP can occur. Furthermore, particularly in the presence of excess unlabeled ATP, [3H]ADP was phosphorylated to [3H]ATP, indicating that ectoenzymes capable of interconverting nucleotides are present. By evaluating recovery and metabolism in serial samples collected rapidly after bolus injection, we were able to use the integrated form of the Michaelis-Menten equation as developed by Bronikowski et al. (Math. Biosci. 61: 237-266, 1982) to derive Michaelis constant (Km) and maximum velocity times capillary plasma volume (Amax) values for adenosinetriphosphatase, adenosine diphosphatase, and 5'-nucleotidase (450, 300, and 93 microM; and 5.3, 5.9, and 1.7 mumol/min, respectively). This analysis also indicated that there is a high degree of heterogeneity of path lengths within the coronary circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Lysosomal hydrolases of human vascular cells: response to agonists of endothelial function

Endothelial injury has been proposed as a feature of a wide variety of vascular diseases, and release of endothelial lysosomal hydrolases could contribute to the pathological changes seen. We have determined the relative activities of 14 glycosidases, two esterases and four peptide hydrolases in human umbilical vein endothelial cells and investigated whether known agonists of endothelial function, or materials known to modulate hydrolase secretion in other phagocytic cells, influenced the activity or secretion of these enzymes by human umbilical vein endothelial cells. Hexosaminidase, beta-galactosidase, beta-glucuronidase and alpha-iduronidase accounted for most of the measured glycosidase activity. Acid phosphatase activity greatly exceeded arylsulphatase activity, and most of the measured peptidase activity was due to acid peptidases. Optimum pH and apparent Km values were determined for the most abundant hydrolases. Exposure of human umbilical vein endothelial cells to bradykinin, thrombin or interleukin-1 resulted in negligible release of either hexosaminidase or lactate dehydrogenase (LDH), in contrast to phorbol myristate acetate, which caused a parallel, dose-dependent release of both enzymes. Treatment of these cells with calcium ionophore A23187, trypsin or platelet-activating factor, caused less than 10% release of either hexosaminidase or LDH. Agents known to modulate lysosomal enzyme secretion by other phagocytic cells failed to induce selective secretion of lysosomal enzymes by human umbilical vein endothelial cells.

Desensitization of agonist-stimulated prostacyclin release in human umbilical vein endothelial cells

Prostacyclin (PGI2) release was studied in perfused columns of human umbilical vein endothelial cells cultured on microcarrier beads. Substantial homologous desensitization of PGI2 release occurred when cells were exposed to agonist for 2 min after a previous exposure; the extent depended on the concentration and duration of the first challenge. Recovery from exposure to ATP or bradykinin was complete in less than 80 min; recovery from thrombin was incomplete after greater than 80 min, and this was apparently related to its proteolytic activity. Experiments with ibuprofen, a reversible inhibitor of cyclo-oxygenase, demonstrated that homologous desensitization did not involve inactivation of cyclo-oxygenase. ATP and bradykinin did not induce heterologous desensitization. Thrombin and trypsin induced cross-desensitization, but neither agonist significantly reduced responses to ATP or bradykinin, suggesting that a common proteolytic mechanism is responsible for their ability to induce PGI2 synthesis. We conclude that desensitization of PGI2 release in response to physiological agonists is generally agonist-specific and involves modulation of molecular events at or close to the receptors involved, rather than inactivation of prostanoid biosynthesis.

Endothelial functional responses and increased vascular permeability induced by polycations

Polycations such as poly-L-lysine powerfully stimulated cultured endothelial cells from pig aorta to release prostacyclin and cytoplasmic purines in a dose (charge)-dependent and molecular weight (size) dependent manner. Neutral or anionic polymers were inactive. Qualitatively similar findings were made in vivo where poly-L-lysine induced charge and size-dependent local edema formation after intradermal injection in the rabbit. Pretreatment of cultured endothelium with heparin or trypsin (but not neuraminidase) effectively reduced the response of the cells to subsequent exposure to poly-L-lysine suggesting an interaction of polycations with integral membrane proteins. Edema responses to poly-L-lysine were reduced in the presence of indomethacin suggesting that generation of an endogenous vasodilator prostaglandin, perhaps endothelial cell-derived, was an important component of the response. Poly-L-lysine-induced edema formation was not dependent on endogenous histamine release but was reduced by locally administered trasylol while soybean trypsin inhibitor failed to inhibit the response. Our results indicate that polycations such as poly-L-lysine can induce responses of vascular endothelium in vitro and in vivo and that the effects are not only charge-related but are also dependent on the size of the polycation. We suggest that naturally occurring polycations such as those derived from leukocytes and platelets may play an important role in various pathologic processes and that this may be closely related to their size.

ADP plays a key role in thrombogenesis in rats

The relative importance of ADP, arachidonic acid metabolites and serotonin as thrombogenic factors was evaluated in rats by comparing, after oral administration, the effects of two inhibitors of ADP-induced platelet aggregation (ticlopidine and PCR 4099), three cyclo-oxygenase inhibitors (aspirin, triflusal and indobufen) and a selective serotonin 5HT2 receptor antagonist (ketanserin) on platelet aggregation, in four platelet-dependent thrombosis models and on bleeding time. Platelet aggregation induced by ADP and collagen was completely inhibited by ticlopidine and PCR 4099 whereas only the collagen aggregation was reduced by the cyclo-oxygenase inhibitors. Ketanserin or a depletion of platelet serotonin by reserpine did not affect platelet aggregation. Ticlopidine and PCR 4099 greatly prolonged rat tail transection bleeding time. This is probably related to their known ability to inhibit ADP-mediated platelet aggregation. In contrast, the cyclooxygenase inhibitors did not affect bleeding time at all. Reserpine and ketanserin prolonged bleeding time by interfering with the action of serotonin on the vascular wall. Ticlopidine and PCR 4099 were very potent antithrombotics in all the models. Aspirin, only at a high dose, inhibited poorly thrombus formation on a silk thread in an arterio-venous shunt, suggesting that the inhibition of cyclo-oxygenase was not responsible. Triflusal was inactive in all models while indobufen slightly reduced thrombus formation in the silk thread and metallic coil models. Ketanserin and reserpine reduced thrombus only in the metallic coil model. Thrombus formation was greatly reduced in fawn-hooded rats, which lack ADP in their platelet dense granules because of a genetic storage pool deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of vascular smooth muscle cell proliferation in culture by pentosan polysulphate and related compounds

Pentosan polysulphate (PPS; SP 54; Hemoclar), a highly sulphated semi-synthetic polysaccharide of MW 4.7 kD, was tested in vitro as an inhibitor of rabbit aortic smooth muscle cell (SMC) proliferation and its effects were compared with those of dextran sulphate, laminarin sulphate and heparin fractions. When added to the cell cultures simultaneously with foetal calf serum, all sulphated polysaccharides inhibited cell growth. PPS was five fold more active than heparin and its low molecular weight fractions. A high molecular weight fraction of PPS was the most active inhibitor (IC50: 2.7 micrograms/ml vs 45 micrograms/ml for PPS, and 241 micrograms/ml for heparin). When PPS and heparin were pre-incubated with the cells for three days, then removed before foetal calf serum was added to stimulate growth, their inhibitory effects were comparable with those seen when the compounds were present throughout the growth phase, suggesting that they exert their effect by binding to the cell surface, and not by interacting with the growth factors in serum.

Characteristics of the P2 purinoceptor that mediates prostacyclin production by pig aortic endothelial cells

Release of prostacyclin was studied by superfusing small columns containing cells cultured on microcarrier beads. Transient dose-dependent stimulation of prostacyclin release by up to 500-fold was induced by adenosine 5'-triphosphate (ATP; 0.5-50 microM). Adenosine 5'-diphosphate (ADP) gave similar responses, whereas adenosine 5'-phosphate (AMP) and adenosine were essentially inactive. Of other natural nucleotides tested only uridine 5'-phosphate (UTP) was active. The L-enantiomers of ATP and ADP were inactive. 2-Cl-ATP was approximately 100 times more potent than ATP; 2-MeS-ATP was also more potent (threshold 0.05 microM) but its maximal effectiveness was less than 20% that of ATP; 2-EtS-ATP had a similar threshold to ATP but was even less effective than 2-MeS-ATP. Phosphorothioate nucleotide analogues of ATP or ADP were active, with no stereoselectivity between Rp and Sp diastereoisomers. No analogue tested showed antagonist activity. We conclude that ATP mediates endothelial prostacyclin release apparently via a P2Y receptor, although there are some striking differences from the previously described P2Y receptor mediating endothelium-dependent vasodilation in pig aorta.

Purinoceptors in the rat heart

The effects of an intracoronary bolus of adenosine triphosphate (ATP), alpha, beta-methylene ATP (APCPP), beta, gamma-methylene ATP (APPCP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and adenosine on coronary tone and ventricular myocardial contraction were investigated in the perfused rat heart. Adenine nucleotides, given by bolus injection were negatively inotropic in amounts greater than 3 X 10(-7) mol. The potency order was ATP greater than ADP greater than AMP. Adenosine (less than 1 X 10(-5)mol) had no effect on ventricular myocardial contraction. Adenine nucleotides and adenosine (1 X 10(-10)-1 X 10(-7) mol) reduced coronary tone. The potency order was ATP greater than ADP greater than AMP = adenosine. The ATP analogue APPCP was less active than ATP at reducing coronary tone, and APCPP had no vasodilator effect. This suggests the presence of a P2-purinoceptor, subclass P2Y, which mediates vasodilation. ATP and ADP increased the concentration of prostacyclin (measured as 6-keto prostaglandin F1 alpha) in the perfusate, but only after injection of greater than 3 X 10(-7) mol, suggesting that the vasodilator responses to ATP and ADP were not mediated by prostacyclin. AMP and adenosine had no effect, even at 1 X 10(-5) mol. At a dose of 3 X 10(-9) mol, approximately 40% of ATP and 70% of ADP was converted to AMP and adenosine whilst passing through the heart. The amounts of AMP and adenosine formed, however, were insufficient to account for the vasodilator effects of ATP and ADP. 6 Vasodilatation mediated by AMP and adenosine was inhibited by an infusion of 8-phenyltheophylline (8-PT; 2 x 10-5 M) indicating interaction with a P1-purinoceptor. Vasodilatation induced by ATP (at doses at which AMP and adenosine had no action) was also depressed by 8-PT indicating either an action of ATP on PI-purinoceptors, or an effect of 8-PT on P2y receptors. 7 Vasodilatation induced by AMP was unaltered during an infusion of alpha,beta-methylene ADP (2 x 10-6 M, which inhibited breakdown of AMP to adenosine by 54.2 +/- 1.5%, n = 4). This suggests that AMP acted directly, and it did not require conversion to adenosine to induce vasodilatation. 8 The ATP analogues APCPP (1 x 10-9_1 x 10-8 mol) and APPCP (1 x 10-8_l x 10-7mol) increased coronary tone, as did high doses (I x 10-5 mol) ofATP and ADP, indicating the presence of an additional P2-purinoceptor, subclass P2X, mediating vasoconstriction.

A model of the smooth pursuit eye movement system

Human, horizontal, smooth-pursuit eye movements were recorded by the search coil method in response to Rashbass step-ramp stimuli of 5 to 30 deg/s. Eye velocity records were analyzed by measuring features such as the time, velocity and acceleration of the point of peak acceleration, the time and velocity of the peaks and troughs of ringing and steady-state velocity. These values were averaged and mean responses reconstructed. Three normal subjects were studied and their responses averaged. All showed a peak acceleration-velocity saturation. All had ringing frequencies near 3.8 Hz and the mean steady-state gain was 0.95. It is argued that a single, linear forward path with any transfer function G(s) and a 100 ms delay (latency) cannot simultaneously simulate the initial rise of acceleration and ring at 3.8 Hz based on a Bode analysis. Also such a simple negative feedback model cannot have a steady-state gain greater than 1.0; a situation that occurs frequently experimentally. L.R. Young's model, which employs internal positive feedback to eliminate the built-in unity negative feedback, was felt necessary to resolve this problem and a modification of that model is proposed which simulates the data base. Acceleration saturation is achieved by borrowing the idea of the local feedback model for saccades so that one nonlinearity can account for the acceleration-velocity saturation: the main sequence for pursuit. Motor plasticity or motor learning, recently demonstrated for pursuit, is also incorporated and simulated. It was noticed that the offset of pursuit did not show the ringing seen in the onset so this was quantified in one subject. Offset velocity could be characterized by a single exponential with a time constant of about 90 ms. This observation suggests that fixation is not pursuit at zero velocity and that the pursuit system is turned on when needed and off during fixation.

Purines and prostaglandins as regulators in the coronary circulation

In the isolated rat heart perfused at constant flow a bolus injection of an adenine nucleotide reduced coronary perfusion pressure and was negatively inotropic (ATP greater than ADP greater than AMP). Adenosine had no effect on perfusion pressure or contractile force. ATP and ADP stimulated production of PGI2 from the coronary bed. Perfusion with indomethacin completely inhibited PGI2 production but had no effect on the reduction in perfusion pressure and cardiac function produced by ATP. Purinoceptors in the perfused rat heart are of the P2 type and responses produced by purinoceptor activation are not mediated by PGI2.

Specificity of P2-purinoceptor that mediates endothelium-dependent relaxation of the pig aorta

ATP (EC50 5 microM) induced endothelium-dependent relaxation of the isolated aorta of the newborn pig, but the other naturally occurring nucleotides CTP, GTP, ITP and UTP were more than 100 times less potent. 2-Methylthio-ATP (EC50 0.1 microM) was 50 times more potent than ATP, but the unnatural enantiomers L-ATP and 2-methylthio-L-ATP were virtually inactive. beta,gamma-Imido-ATP and beta,gamma-methylene-ATP, both of which are resistant to degradation by ectonucleotidases on cultured pig endothelial cells, were much less potent than ATP. ADP beta S, which is also resistant to degradation, was equipotent with ATP at low concentrations but achieved a maximal relaxation of only 50% that of ATP. The Rp and Sp diastereoisomers of ATP beta S were both equipotent with ATP at low concentrations and both achieved approximately 60% of the maximal relaxation of ATP. The Rp and Sp diastereoisomers of ADP alpha S were both less potent than ATP and achieved only approximately 25% of the maximal relaxation of ATP. These results demonstrate that the P2-purinoceptor mediating endothelium-dependent relaxation of the pig aorta exhibits a high degree of specificity for the adenine base, is stereospecific for the D-ribofuranosyl moiety, requires a phosphate chain of 2 or 3 units but is not stereoselective toward this phosphate chain. These structural requirements have some features in common with the P2-purinoceptors on smooth muscle and on platelets, and are quite different from those of the ectonucleotidases present on pig endothelial cells in culture.

Endothelium as a modulator of platelet reactivity

The pathways through which endothelial cells can modulate platelet reactivity (whether directly via the secretion of agents that affect platelet function or indirectly through the regulation of coagulation or vascular tone) are sufficiently varied and complex that the direction of individual reactions can be altered as the homeostatic balance requires--in other words, the balance can be shifted in favour of activation or inhibition depending on circumstances. For example, endothelium has the capacity to express pro- or anticoagulant activities, and to release or inactivate agents that either promote or inhibit platelet aggregation. The role of endothelial cells in modulating platelet function is important, complex and as yet poorly understood, but our understanding of the processes involved has advanced greatly over the past few years and continues to increase.

Effects of neutrophil elastase and other proteases on porcine aortic endothelial prostaglandin I2 production, adenine nucleotide release, and responses to vasoactive agents

The effects of neutrophil elastase on endothelial prostacyclin (PGI2) production, nucleotide release, and responsiveness to vasoactive agents were compared with the effects of cathepsin G (the other major neutral protease of neutrophils), pancreatic elastase, trypsin, chymotrypsin, and thrombin. PGI2 production by pig aortic endothelial cells cultured on microcarrier beads and perfused in columns was stimulated in a dose-dependent manner by trypsin, chymotrypsin, and cathepsin G (1-100 micrograms/ml for 3 min). Thrombin, while active at low concentrations (0.1-10 National Institutes of Health U/ml), induced smaller responses. Neutrophil and pancreatic elastase had little or no effect on PGI2 production. Dose-dependent, selective release of adenine nucleotides was induced by neutrophil elastase (3-30 micrograms/ml). The other proteases were much less active; for example, trypsin (100 micrograms/ml) induced a response only approximately 5% as great as did 30 micrograms/ml neutrophil elastase. After exposure to 30 micrograms/ml neutrophil elastase, cells did not exhibit the characteristic burst of PGI2 production in response to extracellular ATP; responsiveness gradually returned after 40-120 min. This effect was not seen with the other proteases. Elastase partly inhibited responses to bradykinin and had no effect on PGI2 production that was stimulated by ionophore A23187. There was no evidence of cytotoxicity, as measured by release of lactate dehydrogenase. Neutrophil degranulation can generate concentrations of elastase and cathepsin G comparable with those tested in the present study, and the effects of these enzymes on endothelial function lead us to suggest that they may play a role in vasoregulation and vascular pathology.

Stimulation of endothelial cells by protease activity in commercial preparations of xanthine oxidase

The oxygen radical generating system of xanthine oxidase plus xanthine, which has been used as a model for the oxidative burst of activated granulocytes, is known to damage endothelium in vivo and in vitro. We previously observed effects (inhibited by catalase, and thus associated with the formation of H2O2) on several parameters of endothelial function, using a non-commercial preparation of xanthine oxidase. Our present study demonstrates that xanthine oxidase from two different commercial sources has additional effects on endothelial morphology and ion flux that are substrate-independent (i.e. produced in the absence of added xanthine) and are attributable to the presence of pancreatin (a crude enzyme mixture used in the commercial preparation of xanthine oxidase from milk). These effects are related to the tryptic activity of pancreatin and extend previous observations on the effects of neutral proteases on endothelial cells. Our results emphasise the practical point that studies on the effects of commercial xanthine oxidase preparations on endothelial cells must take account of their trypsin-like activity as well as their capacity to generate oxygen products.

Differential effects of hydrogen peroxide on indices of endothelial cell function

The responses of pig aortic endothelial cells to sublethal doses of potentially toxic stimuli were investigated by monitoring K+ efflux, prostaglandin production, and the release of cytoplasmic purines. Xanthine plus xanthine oxidase reversibly stimulated these three parameters of endothelial cell function at doses that were not cytotoxic, as measured by chromium release, adenine uptake, and vital dye exclusion. The effects of xanthine plus xanthine oxidase were inhibited by catalase but not by superoxide dismutase, suggesting that H2O2 was responsible. Reagent H2O2 also reversibly stimulated K+ efflux, prostaglandin production, and the release of purines. The threshold concentration of H2O2 for these effects was approximately 10 microM, which was at least 30-fold lower than that which caused cytotoxicity. In addition to the direct effect of H2O2 in stimulating prostaglandin production (PGI2 and PGE2), prior exposure of endothelial cells to lower doses of H2O2 (less than 0.1 microM) at high oxygen tension inhibited the subsequent stimulation of prostaglandin production by ATP, A23187, and H2O2 itself. We conclude that H2O2 has substantial effects on endothelial physiology at doses up to 3,000-fold lower than those which induce cytotoxicity.

Stereoselectivity of ectonucleotidases on vascular endothelial cells

We have investigated the stereoselectivity of ectonucleotidases (nucleoside triphosphatase, EC 3.6.1.15; nucleoside diphosphatase, EC 3.6.1.6; 5'-nucleotidase, EC 3.1.3.5) on pig aortic endothelial cells using two classes of nucleotide analogue. In experiments with nucleotide enantiomers in which the natural D-ribofuranosyl moiety is replaced by an L-ribofuranosyl moiety, the rate of catabolism of 100 microM-L-ATP was one-fifth that of D-ATP, the rate of catabolism of 100 microM-L-ADP was one-fifteenth that of D-ADP and there was no detectable catabolism of 100 microM-L-AMP. Each of the L-enantiomers inhibited, apparently competitively, the catabolism of the corresponding D-enantiomer; Ki values were approx. 0.6 mM, 1.0 mM and 3.9 mM for L-ATP, L-ADP and L-AMP respectively. Experiments with adenosine 5'-[beta, gamma-imido]triphosphate and with D- and L-enantiomers of adenosine 5'-[beta, gamma-methylene]triphosphate revealed modest ectopyrophosphatase activity, undetectable in experiments with natural nucleotides, which was also stereoselective. Use of phosphorothioate nucleotide analogues demonstrated that ATP catabolism was virtually stereospecific with respect to the geometry of the thiol group substituted on the beta-phosphate: the Rp isomer was degraded, whereas there was little or no breakdown of the Sp isomer. ADP catabolism was also stereospecific with respect to the geometry of the thiol group substituted on the alpha-phosphate: the Sp isomer but not the Rp isomer was degraded. The geometry of thiol-group substitution on the alpha-phosphate had no effect on ATP catabolism to ADP. There was no detectable catabolism of analogues with thiol-group substitution on the terminal phosphate. Each of the phosphorothioate analogues that was catabolized broke down at a rate similar to that of the natural nucleotide from which it was derived. These results demonstrate that the ectonucleotidases on pig aortic endothelial cells exhibit a high degree of stereoselectivity, characteristic for each enzyme, both with respect to the ribofuranosyl moiety and to the phosphate side chain.