Dominant-negative subunits reveal potassium channel families that contribute to M-like potassium currents

M-currents are K+ currents generated by members of the KCNQ family of K+ channels (Wang et al., 1998). However, in some cells, M-like currents may be contaminated by members of other K+ channel gene families, such as the erg family (Meves et al., 1999; Selyanko et al., 1999). In the present experiments, we have used the acute expression of pore-defective mutants of KCNQ3 (DN-KCNQ3) and Merg1a (DN-Merg1a) as dominant negatives to separate the contributions of these two families to M-like currents in NG108-15 neuroblastoma hybrid cells and rat sympathetic neurons. Two kinetically and pharmacologically separable components of M-like current could be recorded from NG108-15 cells that were individually suppressed by DN-Merg1a and DN-KCNQ3, respectively. In contrast, only DN-KCNQ3, and not DN-Merg1a, reduced currents recorded from sympathetic neurons. Pharmacological tests suggested that the residual current in DN-KCNQ3-treated sympathetic neurons was carried by residual KCNQ channels. Ineffectiveness of DN-Merg1a in sympathetic neurons was not caused by lack of expression, as judged by confocal microscopy of Flag-tagged DN-Merg1a. These results accord with previous inferences regarding the roles of erg and KCNQ channels in generating M-like currents. This experimental approach should therefore be useful in delineating the contributions of members of these two gene families to K+ currents in other cells.

Dental caries-protective agents in milk and milk products: investigations in vitro

OBJECTIVES

To characterise and identify the anti-dental caries components that exist in milk and milk products.

METHODS

Standard enamel or hydroxyapatite demineralisation tests were devised to simulate the action of acid on tooth mineral, and they were used to show which constituents of milk possessed a potential protective action against acid attack.

RESULTS

Milk and milk products were fractionated and tested, revealing that minerals, including calcium and phosphorus, played a part in this protective process. The findings also drew attention to the effectiveness of minor milk protein or protein-associated components, the structures of which are mostly known, which were separated and characterised by gel electrophoresis as proteose-peptone fractions 3 and 5. The strength of adsorption of the protein or polypeptides in these fractions to dental enamel was measured and found to be sufficient to reduce the extent of demineralisation of enamel by acid buffer solutions.

CONCLUSIONS

The removal of lactose, fat, casein and other proteins had little influence on the protective effect of the milk fractions. Besides calcium and phosphorus, milk contains other more powerful protective factors, which were identified as proteose-peptone fractions 3 and 5. Details of their composition and the strength of their adherence to the surface of dental mineral are given.

Apolipoprotein J/clusterin limits the severity of murine autoimmune myocarditis

Apolipoprotein J/clusterin (apoJ/clusterin), an intriguing protein with unknown function, is induced in myocarditis and numerous other inflammatory injuries. To test its ability to modify myosin-induced autoimmune myocarditis, we generated apoJ-deficient mice. ApoJ-deficient and wild-type mice exhibited similar initial onset of myocarditis, as evidenced by the induction of two early markers of the T cell-mediated immune response, MHC-II and TNF receptor p55. Furthermore, autoantibodies against the primary antigen cardiac myosin were induced to the same extent. Although the same proportion of challenged animals exhibited some degree of inflammatory infiltrate, inflammation was more severe in apoJ-deficient animals. Inflammatory lesions were more diffuse and extensive in apoJ-deficient mice, particularly in females. In marked contrast to wild-type animals, the development of a strong generalized secondary response against cardiac antigens in apoJ-deficient mice was predictive of severe myocarditis. Wild-type mice with a strong Ab response to secondary antigens appeared to be protected from severe inflammation. After resolution of inflammation, apoJ-deficient, but not wild-type, mice exhibited cardiac function impairment and severe myocardial scarring. These results suggest that apoJ limits progression of autoimmune myocarditis and protects the heart from postinflammatory tissue destruction.

Properties of maltodextrins and glucose syrups in experiments in vitro and in the diets of laboratory animals, relating to dental health

The objective of the study was to examine the cariogenic potentials of maltodextrins and glucose syrups (two glucose polymers derived from starch) using a range of techniques in vitro and in laboratory animals. The experimental methods used were: (1) measurement of acid production from glucose syrups and maltodextrins by human dental plaque micro-organisms; (2) evaluation of the role salivary alpha-amylase in degrading oligosaccharides (degree of polymerisation > 3) in the glucose polymers, estimating the products by HPLC; (3) assessment of the fermentability of trioses relative to maltose; (4) measurement of dental caries levels in three large-scale studies in laboratory rats fed on diets containing the glucose polymers. It was found that acid production from the glucose polymers increased as their higher saccharide content fell. Salivary alpha-amylase rapidly degraded the oligosaccharides (degree of polymerisation > 3), mainly to maltose and maltotriose. In the presence of oral micro-organisms, maltotriose took longer to ferment than maltose, but by the end of a 2 h period the total amount of acid produced was the same from both. Incorporated into the diets in solid form, the glucose syrups and maltodextrins were associated with unexpectedly high levels of dental caries. In conclusion, the findings were unforeseen in the light of earlier data that a glucose syrup was less cariogenic than sucrose.

Transmission of IgA and IgG monoclonal antibodies to mucosal fluids following intranasal or parenteral delivery

BACKGROUND

The efficacy by which passive antibodies can reach the lungs could be important for the outcome of immunotherapy of respiratory pulmonary infections. We examined how transmission to a number of mucosal sites is affected by the route of inoculation.

METHODS

Transmission of newly raised IgA class Mabs against mycobacterial surface antigens to saliva, lung or vaginal lavage, bile and serum of BALB/c mice was compared with existing IgG Mabs. ELISA was used for testing body fluids obtained 1-24 h after intranasal or intravenous inoculation and 1-7 days following back-pack tumour growth of hybridomas.

RESULTS

Intranasal inoculation resulted in a rapid rise and high levels of both IgA and IgG class Mabs in lung lavage. In contrast, following intravenous Mab injection or back-pack tumour growth of hybridoma cells, effective lung transmission was observed for the IgG1 and IgG2b MAbs, but not for the IgA Mabs. The secretory component was acquired by the transmitted IgA MAbs in the mucosal fluids, but not in the serum. Nevertheless, the time course of mucosal IgA antibody levels was similar to that of the tested IgG Mabs. Furthermore, the relative proportion of transmission to saliva and bile varied between individual Mabs indicating a role of tissue-specific, immunoglobulin class-unrelated mechanisms.

CONCLUSIONS

Intranasal, rather than parenteral inoculation of mice is required for the efficient delivery of IgA antibodies against respiratory pulmonary pathogens. Interestingly, IgA-secretory component complexing of intranasally applied Mabs did not significantly influence their persistence in the lungs.

The effect of extended family living on the mental health of three generations within two Asian communities

BACKGROUND

A study by Shah & Sonuga-Barke (1995) identified a relationship between family structure and the mental health of Pakistani Muslim mothers and their children. Children in extended families fared better, but their mothers fared worse than their nuclear family counterparts. The present study replicates and extends this study by exploring the impact of nuclear and extended family living on the mental health of three generations (children, mothers and grandmothers) in British Hindu as well as Muslim communities.

METHOD

44 Muslim and 42 Hindu families participated in the study. The mental health of mothers and grandmothers and the behavioural problems of children (aged 5-11) were examined. Both mothers and grandmothers completed the Hospital Anxiety and Depression Scale. The children's behavioural adjustment was rated by their teachers using the Rutter Scale. Other relevant variables such as acculturation levels were also measured.

RESULTS

Children and grandmothers were better adjusted in extended families than nuclear families. In contrast, mothers were better adjusted in nuclear families. This interaction between family type and generation was evident in both Muslim and Hindu families and did not appear to be mediated by other variables such as acculturation. Furthermore, mothers' and childrens' adjustment was significantly correlated with grandmothers', but not mothers', mental health in extended families (although not in nuclear families).

DISCUSSION

These results provide further evidence for the link between family structure and mental health in Asian communities. They also challenge some of the assumptions about maternal mental health, its effects on child adjustment and its links to systems of social support. In extended families where social support was likely to be most available mothers were at greatest risk, while their children profited and this advantage seemed to be linked to the grandmaternal presence.

Repression and activation of muscarinic receptor genes

The specific cellular response to muscarinic receptor activation is dependent upon appropriate expression of each of the five muscarinic receptor genes by individual cells. Here we summarise recent work describing some of the genomic regulatory elements and transcriptional mechanisms that control expression of the M1 and M4 genes.

The mental health of Muslim mothers in extended families living in Britain: the impact of intergenerational disagreement on anxiety and depression

OBJECTIVES

The study assessed the impact of intergenerational differences of opinion over child rearing on the mental health of Muslim mothers living in extended families.

DESIGN

The study adopted a correlational design in an attempt to identify factors that accounted for mental health problems.

METHODS

The child-rearing attitudes of mothers and grandmothers, mothers' mental health, levels of family acculturation and a range of other background and demographic information was collected from 54 extended families living in two Muslim communities in London using Urdu versions of standard questionnaires.

RESULTS

Rates of depression and anxiety among the mothers in the study were high. Grandmothers had more traditional attitudes to child rearing than did mothers. Intergenerational discrepancy over child rearing was more marked in more acculturated families. Discrepancy was associated with higher levels of mothers' anxiety and depression.

CONCLUSIONS

The unusually high levels of depression and anxiety displayed by Muslim mothers living in extended families can in part be accounted for by patterns of intergenerational discrepancy. These possibly reflect discordant world views within those families that have been assimilated into the dominant British culture.

Beneficial action of beraprost sodium, a prostacyclin analog, in stroke-prone rats

Beraprost sodium is a stable analog of the vasodilator, platelet antiaggregatory eicosanoid, prostacyclin. Experiments were performed to determine whether long-term therapy with beraprost produces vascular protective effects in saline-drinking stroke-prone spontaneously hypertensive rats (SHRSPs). Oral beraprost at 30, 100, or 300 micrograms/kg/day starting at 8.4 weeks of age did not affect the progressive increase of systolic blood pressure (measured by tail-cuff plethysmography) in these rats. Additional experiments in SHRSPs, prepared for continuous monitoring of blood pressure by radiotelemetry, revealed that oral beraprost administration reduced mean arterial pressure but that these hypotensive responses were not sustained (< 4 h). In all SHRSPs receiving oral beraprost, proteinuria and cerebrovascular lesions developed. In contrast, continuous subcutaneous infusion of beraprost at 2.8 mg/kg/day from age 8.3-12.3 weeks reduced systolic blood pressure and markedly diminished the development of renal lesions and the occurrence of stroke in saline-drinking SHRSPs. Beraprost at 0.9 mg/kg/day reduced blood pressure less than did 2.8 mg/kg/day and provided partial protection against cerebral and renal lesions after a 4-week infusion period. These results indicate that long-term subcutaneous infusion of beraprost can protect saline-drinking SHRSPs against stroke and renal damage. This effect is not readily dissociated from the ability of beraprost to reduce blood pressure in SHRSPs.

Laboratory studies of sweets re-formulated to improve their dental properties

OBJECTIVES

To evaluate the potential dental effects of ten new types of sugar-free sweets formulated with Lycasin or isomalt as bulk sweeteners instead of sugars.

METHODS

Examination of the sweets for their acidity, fermentability by oral microorganisms, influence on the demineralisation of dental enamel, and their influence on human interdental plaque pH, compared with conventional sugar-containing sweets.

FINDINGS

The importance of reducing the levels of flavouring acids in the sweets was demonstrated. It was not straightforward to evaluate chocolate products in this system, but the potential benefits of re-formulating fruit gums, lollipops, chew-bars, toffee and fudge with Lycasin or isomalt in place of sugars were shown by determining their reduced acidogenicity and fermentability compared with conventional confectionery.

CONCLUSIONS

The extent of demineralisation of dental enamel was related to both the acidity and the fermentability of the sweets. Re-formulating sweets with reduced acidity levels and bulk sweeteners not fermentable by dental plaque microorganisms can provide a basis for improving their potential dental effects.

Precise control of the frequency and amount of food provided for small laboratory animals by a new electronic metering technique, used to evaluate the cariogenic potential of chocolate

A new electronic system was set up for accurately regulating the amount and frequency of food dispensed to laboratory rats so that investigations of the cariogenic potential of foods can be carried out under strictly controlled conditions according to the stipulations of the San Antonio Consensus Conference, 1985. The system was used to evaluate the cariogenicity of sucrose incorporated into plain and milk chocolate. The results suggested that 18.75% of sucrose in the diet had the same cariogenic potential no matter whether it was in the form of fine crystals or incorporated into plain chocolate, but mean caries scores were nearly 30% higher on a plain chocolate than on a milk chocolate regime.

Erosion by soft drinks of rat molar teeth assessed by digital image analysis

A digital imaging analysis (DIA) procedure for recording and assessing erosive changes on teeth was developed and evaluated against an older subjective method. Results after exposure of rats' teeth to various soft drinks showed that the DIA system was superior to the conventional method, with improved precision. The system provided a direct and highly sensitive means of quantifying the erosion of dental hard tissues by three different soft drinks, showing that it could be used to evaluate erosiveness and other dental damage. After 6 weeks' exposure to soft drinks in the diet, the area of intact enamel on the lingual surface of the first mandibular molar averaged 47% on apple juice, 27% on still orange and 6% on carbonated orange. The greatest exposure of dentine (36%) was on the still orange drink. Eroded enamel accounted for 72.5% of the tooth surface on the carbonated drink.

Effect of clentiazem on arterial pressure and renal function in normotensive and hypertensive rats

The present study evaluated the effects of a new benzothiazepine calcium channel antagonist, clentiazem, on arterial pressure and renal function in spontaneously hypertensive rats (SHR), normotensive Wistar-Kyoto (WKY) and Munich-Wistar rats (MWR). Administration of clentiazem in doses from 1 to 20 micrograms/kg/min produced dose-dependent increases in sodium and water excretion in MWR, reaching maximum values of 292 and 376% of control, respectively, at the 20-micrograms/kg/min dose. Clentiazem (10 micrograms/kg/min) lowered arterial pressure by 16% and doubled glomerular filtration rate (GFR) in MWR. The rise in GFR was associated with an increase in glomerular capillary pressure of 16 mm Hg, produced by a combination of preglomerular vasodilation and efferent arteriolar vasoconstriction. In SHR, administration of clentiazem (10 micrograms/kg/min) lowered arterial pressure by 30 mm Hg and increased urine flow and sodium excretion by 137 and 200%, respectively. In WKY rats, the same dose of clentiazem decreased arterial pressure by only 10 mm Hg, whereas urine flow and sodium excretion increased 62 and 38%, respectively. A high dose of clentiazem (1 mg/kg bolus plus 1 mg/kg/hr infusion i.v.) lowered arterial pressure by 63 mm Hg in SHR. Renal vascular resistance fell by 39% and there was a 5-fold increase in sodium excretion. In WKY rats, the same dose of clentiazem reduced arterial pressure by 20 mm Hg, but it had no significant effect on sodium excretion. These results indicate that clentiazem increases sodium excretion and GFR in normotensive rats in part by preferentially dilating the renal preglomerular vasculature. This compound is also an antihypertensive agent that lowers arterial pressure and promotes sodium excretion in SHR.

Role of prostanoids in renin-dependent and renin-independent hypertension

We investigated the role of prostanoid-mediated pressor mechanisms in setting the level of blood pressure in renin-dependent and renin-independent models of hypertension in unanesthetized rats. Intravenous administration of a blocker of thromboxane A2/prostaglandin endoperoxide receptors, SQ29548 (2 mg/kg bolus injection plus 2 mg/kg/hr for 3 hours), reduced from 162 +/- 4 to 144 +/- 5 mm Hg (p less than 0.05) the blood pressure of rats with aortic coarctation-induced hypertension at 7-14 days after coarctation when plasma renin activity is greatly increased. In contrast, treatment with SQ29548 was without effect on the blood pressure of either normotensive or hypertensive rats (i.e., aortic coarctation-induced hypertension at 90-113 days after coarctation, deoxycorticosterone-salt-induced hypertension) having normal or depressed values of plasma renin activity. The blood pressure-lowering effect of SQ29548 in the early phase of aortic coarctation-induced hypertension was positively correlated with the prevailing plasma renin activity and could not be demonstrated in hypertensive rats pretreated with indomethacin. We attribute the hypotensive effect of SQ29548 to interference with pressor mechanisms that depend on activation of thromboxane A2/prostaglandin endoperoxide receptors and suggest that such prostanoid-mediated mechanisms are operational and contribute to an increase in blood pressure in angiotensin-dependent forms of hypertension. Also prostanoid-mediated vasodepressor mechanisms are operational in the early phase of aortic coarctation-induced hypertension since the blood pressure of rats pretreated with SQ29548 was increased by the subsequent administration of indomethacin. Accordingly, the blood pressure of rats with aortic coarctation-induced hypertension is influenced by the interplay of prostanoid-mediated pressor and vasodepressor mechanisms.

Potential dental effects of infants' fruit drinks studied in vitro

Eighteen different infants' drinks from five manufacturers were examined for their carbohydrate, calcium, phosphorus and acid contents, and their attack on tooth mineral. Seven of the drinks were compared with nine varieties of adults' soft drinks, and demineralization was studied with and without the presence of a cariogenic oral streptococcus. The influence of the acids already in the drinks in dissolving Ca and P outstripped that of any acid generated in these studies in vitro by microbial fermentation of the sugars they contained, giving an indication of their relative erosiveness rather than their cariogenic action. Various other features of the drinks relevant to dental health were identified. Titratable acid was a better guide than pH to their dental properties. Although there were considerable differences between the various infants' drinks, taken as a group, their acidity levels and demineralizing powers were generally lower than those of the adults' drinks.

Contrasting effect of thromboxane synthase inhibitors and a thromboxane receptor antagonist on the development of angiotensin II-salt-induced hypertension in rats

This study was designed to contrast the effects of prolonged treatment with a thromboxane (Tx) synthase inhibitor (UK 38485 or SC 41156) and a Tx receptor antagonist (SQ 29548) on the development of angiotensin II (Ang II)-salt-induced hypertension. Ang II infusion (125 ng/min i.p. for 12 days) in rats drinking 0.15 M NaCl resulted in severe hypertension accompanied by proteinuria, reduction of urinary creatinine excretion and augmentation of urinary TxB2 excretion and TxB2 release from aortic rings and renal cortex slices. In saline-drinking rats undergoing Ang II infusion, the concomitant administration by gavage of UK 38485 (100 mg/kg/day) or SC 41156 (25 mg/kg/day) reduced serum and urinary TxB2 and TxB2 release from aortic rings and/or renal cortex slices, but it was without effect on the development of hypertension. In contrast, concomitant infusion of SQ 29548 (4.2 mg/24 hr s.c.) significantly attenuated the increase of blood pressure produced by the infusion of Ang II in saline-drinking rats. This effect of SQ 29548 may be the consequence of blockade of the actions of one or more endogenous eicosanoids that increase blood pressure by a mechanism(s) involving interaction with TxA2 receptors. This implies that pressor eicosanoids play a contributory role in the development of severe Ang II-salt hypertension.

Renal function in rats with angiotensin II-salt-induced hypertension: effect of thromboxane synthesis inhibition and receptor blockade

This study was designed to assess the contribution of thromboxane (Tx) A2 to the pathogenesis of renal dysfunction in rats with angiotensin II (Ang II)-salt hypertension. Hypertension was induced in rats drinking 0.15 mol/l NaCl by infusion of Ang II (125 ng/min, intraperitoneally) for 12 days. Relative to values in water- and saline-drinking rats without Ang II infusion, rats with Ang II-salt hypertension exhibited increased renal vascular resistance, decreased renal blood flow, and increased renal excretion and glomerular synthesis of TxB2. Treatment with an inhibitor of TxA2 synthesis, UK 38,485, had no effect on renal function in normotensive and hypertensive rats. Similarly, the TxA2 and prostaglandin endoperoxide antagonist SQ 29,548 did not affect renal function in normotensive rats. In contrast, in rats with Ang II-salt hypertension of 12 days' duration, SQ 29,548 caused a reduction in renal vascular resistance, allowing for maintenance of renal blood flow in the face of an accompanying reduction in blood pressure. A comparable reduction in renal perfusion pressure, produced by constriction of the abdominal aorta above the renal arteries, was not accompanied by a reduction in renal vascular resistance in Ang II-salt hypertensive rats. Therefore, the SQ 29,548-induced lowering of renal vascular resistance is attributable not to renal blood flow autoregulation, but to blockade of the renal vasoconstrictor actions of TxA2 and/or prostaglandin endoperoxides. This interpretation implies that pressor eicosanoids contribute to increase renal vascular resistance in rats with severe Ang II-salt hypertension.

Laboratory studies of the dental properties of soft drinks

The composition and dental properties of eight different soft drinks, representing some of the most popular types used in the UK, were examined. Demineralization experiments were conducted on hydroxylapatite, the basic component of dental enamel, determining calcium dissolving by atomic absorption spectroscopy and phosphorus by u.v. visual spectrophotometry. The titratable acid content of the drinks was found to give a better guide than their pH to their potential dental erosiveness. The sugar content, in their ready-to-drink form, varied from zero in a low-calorie product up to almost 14% in a blackcurrant drink, but using a technique with a relatively long contact time, and in the absence of intact dental plaque, the demineralizing action on hydroxylapatite of the acids already in the drinks eclipsed the effects of the acid generated by oral micro-organisms from the sugars in the drinks. The pure citrus juices showed potentially the worst dental properties, followed by the orange and blackcurrant concentrates after dilution to their ready-to-drink form, with least demineralization from the carbonated drinks, and a cola drink giving especially low values.

Studies of the dental properties of lactitol compared with five other bulk sweeteners in vitro

Standardized mixed cultures of dental plaque microorganisms were incubated for 24 h in media containing six different bulk sweeteners as energy source. The attack of the acid generated on tooth mineral was measured by calcium and phosphorus analyses. Demineralization was most severe with glucose and sucrose. Less acid was generated from sorbitol and mannitol, with much reduced demineralization. Fermentation of lactitol and xylitol was only very slight, leaving the final pH high and leading to extremely low enamel demineralization figures. The amounts of polysaccharide synthesized by the microorganisms in the incubations decreased in the order: glucose greater than sucrose greater than sorbitol greater than mannitol greater than lactitol greater than xylitol.

Influence of eicosanoids on renal function of DOCA-salt hypertensive rats

The present study examined the contribution of changes in the synthesis or degradation (or both) of renal eicosanoids to the alterations in renal hemodynamics observed in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Renal blood flow and glomerular filtration rate were markedly reduced in DOCA-salt hypertensive rats compared with values observed in control rats given water or saline to drink. The abnormalities in renal hemodynamics in the hypertensive rats were associated with an increase in the excretion of thromboxane B2, an increase in the release of thromboxane B2 from renal cortical tissue slices, and a diminished release of prostaglandin E2 (PGE2) from renal medullary tissue. Additionally, the urinary excretion of PGE2 and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and the release of 6-keto-PGF1 alpha from renal cortical and medullary tissue were elevated in rats with DOCA-salt hypertension. Since the excretion of PGE2 and 6-keto-PGF1 alpha and the release of 6-keto-PGF1 alpha by medullary tissue were also elevated in normotensive rats given 1% NaCl solution to drink, these latter changes probably were related to an elevation of sodium intake rather than to the development of hypertension. The functional significance of the alterations in the renal production of thromboxane in DOCA-salt hypertensive rats was evaluated by comparing the effects of a thromboxane synthesis inhibitor and a receptor antagonist on renal function in normotensive and DOCA-salt hypertensive rats. The administration of the thromboxane synthetase inhibitor furegrelate and the thromboxane receptor blocker SQ 29548 had no effect on renal hemodynamics in either group.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of pressor prostanoids in rats with angiotensin II-salt-induced hypertension

This study was designed to assess the contribution of thromboxane A2 to high blood pressure in rats with angiotensin II (Ang II)-salt hypertension. Hypertension was induced in rats drinking 0.15 M NaCl by infusion of Ang II (125 ng/min i.p.) for 12 days. Relative to values in water-drinking rats without Ang II infusion, Ang II-salt hypertensive rats exhibited augmentation (p less than 0.05) of blood pressure (from 129 +/- 3 to 217 +/- 12 mm Hg), urinary thromboxane B2 excretion (from 5.4 +/- 0.9 to 25.4 +/- 2.1 ng/day), and thromboxane B2 release from renal cortex slices (from 71.3 +/- 6.7 to 121.1 +/- 14.4 pg/mg) and aortic rings (from 28.8 +/- 2.9 to 115.8 +/- 12.8 pg/mg). Treatment with an inhibitor of thromboxane A2 synthetase, UK 38485, had no effect on blood pressure in normotensive and Ang II-salt hypertensive rats. Treatment with a thromboxane A2 receptor blocker, SQ 29548, decreased blood pressure in Ang II-salt hypertensive rats from 191 +/- 9 to 152 +/- 9 mm Hg after 3 hours, but it had no effect on blood pressure in normotensive rats. Since SQ 29548 interfered with the pressor effects of the prostaglandin endoperoxide analogue U-46619, prostaglandin F2 alpha, and 9 alpha,11 beta-prostaglandin F2, we suggest that the SQ 29548-induced blood pressure reduction in Ang II-salt hypertensive rats is the manifestation of blockade of the vascular actions of one or more endogenous prostanoids including thromboxane A2 and prostaglandin endoperoxides. If so, pressor prostanoids may be contributory factors in the pathogenesis of severe Ang II-salt hypertension in rats.

Glucuronidation in vitro and in vivo. Comparison of intestinal and hepatic conjugation of morphine, naloxone, and buprenorphine

The glucuronidation of morphine, naloxone, and buprenorphine by the liver and intestine has been assessed both in vitro and in vivo in the rat. Using microsomes, Vmax/Km ratios were estimated as measures of intrinsic enzyme activity, and a wide range of ratios were obtained (500-fold). The ratio for the intestine was consistently less than for the liver, and the rank order of activities within each tissue was morphine less than naloxone less than buprenorphine. Using various routes of administration, plasma concentration-time profiles for each compound were determined and used to estimate hepatic and intestinal extraction ratios. These extraction ratios were dose-independent and more substantial for the liver than the intestine. For each tissue, buprenorphine and naloxone showed similar extraction, whereas morphine was less. Plasma binding and blood/plasma concentration ratios were determined, and perfusion models were used to calculate intrinsic clearance. This in vivo parameter of enzyme activity showed a wide range (200-fold), comparable to the spread of microsomal Vmax/Km ratios. Although the in vivo parameters consistently gave measures 10- to 30-fold higher than the in vitro parameters, the rank order was identical for the two sets. These data suggest that a comparative approach to correlate in vitro and in vivo data has advantages over the use of absolute drug characteristics.

A sensitive method for demonstration of decarboxylase activities amongst Enterobacteriaceae without use of pH indicators

Lysine decarboxylase and ornithine decarboxylase activities have been demonstrated in a range of Enterobacteriaceae and related taxa by methods not involving pH indicators. Detection of the diamines produced, cadaverine and putrescine, was achieved by use of reagents based on 5-nitrosalicylaldehyde in the presence of triethanolamine and nickel ions. The method has been shown to be a simple and sensitive means for demonstration of decarboxylase activities when organisms were grown in the presence of the appropriate amino acid. Formation of highly coloured insoluble metal chelates was indicative of enzymatic activity. Results correlated well with existing indicator methods while being superior to the latter with respect to interpretation.

Effects of a fish oil supplement on platelet function, haemostatic variables and albuminuria in insulin-dependent diabetics

A randomised trial of the effects of 15 gm per day of a fish oil supplement (MaxEPA) on blood lipids, haemostatic variables (including platelet function) and albuminuria was undertaken in 41 insulin dependent diabetics. Compared with the control group there was a significant reduction in thromboxane production by platelets stimulated by collagen in vitro in the group who took the fish oil supplement. The extent of platelet aggregation was not altered but the lag phase before aggregation was prolonged. There were also statistically significant increases in plasma LDL cholesterol, fibrinogen and clotting factor X in the group who took the fish oil supplement. No other significant differences were noted.