How well tolerated are lipid-lowering drugs?

It has been clearly established that lipid-lowering treatments [such as 3-hydroxyl-3-methylglutamyl coenzyme A reductase inhibitors ('statins') or fibrates] can reduce cardiovascular events, and with one of the statins even total mortality, in high-risk populations. Intervention studies have not included the very old, but it is generally assumed that this patient group would benefit from these treatments to an extent similar to younger patients. Worries about the associations seen in observational studies between low cholesterol levels and cancer, cerebral haemorrhage or mood and behaviour change have been largely overcome by findings from the latest large drug intervention trials, which do not show any increase in these conditions with statin or fibrate treatments. The common adverse effects associated with these drugs are relatively mild and often transient in nature. Potentially more serious adverse effects, which are more clearly related to drug treatment and are probably dose-dependent, include elevations in hepatic transaminase levels and myopathy; however, these effects are uncommon and generally resolve rapidly when treatment is stopped. The risk of myopathy with fibrate treatment is increased in patients with renal impairment, and the risk of myopathy with statin treatment increases with co-administration of drugs that inhibit statin metabolism or transport. Other adverse effects are related to specific drugs, for example, clofibrate is associated with an increased risk of gallstones. Studies in elderly patients have not shown an increased risk of adverse effects with lipid-lowering drugs compared with younger patients, but in clinical practice there may be some increased risk, particularly with regards to drug interactions. Therefore, lipid-lowering drugs should be administered with extra caution to elderly patients.

Early introduction of clinical skills teaching in a medical curriculum--factors affecting students' learning

OBJECTIVE

To evaluate the effects of the early introduction of clinical skills teaching on students' learning following an overhaul of the curriculum of a traditional Asian medical school.

METHODS

Randomly selected medical students in Year I and II were invited to participate in 30 focus group interviews while all students were asked to assist with the questionnaire survey. Most students were contacted personally to help them understand the objectives of the study. Confidentiality was emphasised and a non-faculty interviewer was recruited for the interviews.

RESULTS

Two hundred and eight of Year I/Year II students attended the lunchtime focus group interviews (response rate=86.7%) while 252 (73.5%) students returned the questionnaire. The majority of them (87%) agreed or strongly agreed that it was good to introduce clinical skills in the early years of the curriculum. They reflected that the course enhanced their learning interest and made them feel like doctors. They also made many constructive suggestions on how the course could be improved during the interactive focus group interviews so that the negative effects could be minimised.

CONCLUSION

It is useful to introduce clinical skills in the early years of a medical curriculum. A comprehensive course evaluation, using both quantitative and qualitative methods, helps to collect useful information on how the course can be improved.

Latissimus dorsi mini-flap: a technique for extending breast conservation

The latissimus dorsi (LD) flap was first used in patients for breast reconstruction in 1896. More recently it has been used to fill defects after quadrantectomy or very wide excision. We have developed a two stage procedure for excision of large breast cancers which would otherwise require mastectomy. The first stage is a wide excision of the cancer without removal of the overlying skin. Thirty patients with large localized operable breast cancer underwent wide local excision followed 5 to 10 days later in 25 patients who had clear histological margins by an axillary dissection with transfer of the LD muscle and overlying fat into the defect in the breast (mini-flap). The cosmetic outcome of these 25 patients who underwent mini-flap were compared with age matched patients having a standard wide local excision and axillary node clearance or mastectomy and immediate breast reconstruction. The volume of tissue excised in patients having their defects filled by LD mini-flap was significantly greater than those women undergoing standard wide excision, p<0.001. Compared with patients who had a mastectomy and immediate breast reconstruction, patients who had mini-flaps reported a better treated breast shape, p=0.04, a greater resemblance to the opposite breast, less self consciousness and less change in attitude of their spouse, p=0.03 and they were more likely to choose the same operation in future compared with patients having immediate whole breast reconstruction, p=0.02. Results as rated by patients in the mini-flap group were similar to those women treated by standard wide local excision. Only one patient in the mini-flap group felt sexually inhibited. When wide local excision and LD mini-flap is performed as a two stage procedure, it is an oncologically safe technique and extends breast conservation to women with larger tumours. The cosmetic outcomes appear better than those following the alternative of mastectomy and immediate breast reconstruction.

Effects of rapid atrial pacing on the arrhythmogenic activity of single cardiomyocytes from pulmonary veins: implication in initiation of atrial fibrillation

BACKGROUND

Pulmonary veins (PVs) are important sources of paroxysmal atrial fibrillation. Long-term rapid atrial pacing (RAP) changes atrial electrophysiology and facilitates the maintenance of atrial fibrillation. It is not clear whether RAP alters the arrhythmogenic activity of PVs. The purpose of this study was to isolate single PV cardiomyocytes from control and RAP dogs and evaluate their electrophysiological characteristics.

METHODS AND RESULTS

The action potential and ionic currents were investigated in PV cardiomyocytes from control and long-term (6 to 8 weeks) RAP (780 bpm) dogs by use of the whole-cell clamp technique. Dissociation of PVs yielded rod-shaped single cardiomyocytes without (n=91, 60%) or with (n=60, 40%) pacemaker activity. Compared with the control group, the RAP dog PV cardiomyocytes had faster beating rates (0.86+/-0.28 versus 0.45+/-0.07 Hz, P<0.05) and shorter action potential duration. The RAP dog PV cardiomyocytes with pacemaker activity have a higher incidence of delayed (59% versus 7%, P<0.001) or early (24% versus 0%, P<0.005) after depolarization. The RAP dog PV cardiomyocytes with pacemaker activity had smaller slow inward and transient outward but larger transient inward (0.017+/-0.004 versus 0.009+/-0.002 pA/pF, P<0.05) and pacemaker (0.111+/-0.019 versus 0.028+/-0.008 pA/pF, P<0.001) currents. The RAP dog PV cardiomyocytes without pacemaker activity had only smaller slow inward and transient outward and larger pacemaker currents.

CONCLUSIONS

PVs contain multiple cardiomyocytes with distinct electrophysiological characteristics. RAP changes the electrophysiological characteristics and arrhythmogenic activity of PVs.

Inhibitory effect of stevioside on calcium influx to produce antihypertension

Stevioside is a sweet-tasting glycoside occurring abundantly in the leaves of Stevia rebaudiana (Compositae). It has been used popularly in Japan and Brazil as a sugar substitute for decades. Previous study has shown that it lowered blood pressure in spontaneously hypertensive rats (SHRs) when administered intravenously. This study shows that intraperitoneal injection of stevioside 25 mg/kg also has antihypertensive effect in SHRs. In isolated aortic rings from normal rats, stevioside could dose-dependently relax the vasopressin-induced vasoconstriction in both the presence and absence of endothelium. However, stevioside had no effect on phenylephrine- and KCl-induced phasic vasoconstriction. In addition, stevioside lost its influence on vasopressin-induced vasoconstriction in Ca(2+)-free medium. The results indicate that stevioside caused vasorelaxation via an inhibition of Ca(2+) influx into the blood vessel. This phenomenon was further confirmed in cultured aortic smooth muscle cells (A7r5). Using 10(-5) M methylene blue for 15 min, stevioside could still relax 10(-8) M vasopressin-induced vasoconstriction in isolated rat aortic rings, showing that this vasorelaxation effect was not related to nitric oxide. The present data show that the vasorelexation effect of stevioside was mediated mainly through Ca(2+) influx inhibition.

Controlled ovarian stimulation and ultrasound guided follicular aspiration in the baboon (Papio cynocephalus anubis)

The objective of this study was to investigate whether baboon females respond to an ovarian stimulation protocol incorporating pituitary suppression with a GnRH agonist (GnRHa) and highly purified human FSH (hphFSH) with follicular development and oocyte maturation. An ovulation induction protocol was applied to 5 adult female baboons with a history of regular menstrual cycles (33-34 days). A long-acting GnRHa implant containing goserelin acetate was placed s.c. on days 22-24 of their menstrual cycle. Daily hphFSH (75 IU im) treatments were started approximately 10 days following menses. When the majority of the follicles were > or = 5 mm in diameter and the E2 levels had reached a maximum, hCG (2000 IU i.m.) was administered to induce final maturation of the oocytes and ovulation. 30 to 34 h after hCG administration, transabdominal follicular aspiration was performed using a variable frequency transvaginal transducer with ultrasound. A total of 71 oocytes were collected (average: 17). 91% of the oocytes were morphologically normal indicating that they were appropriate for in vitro insemination.

[Association between DLST gene polymorphism and Alzheimer's disease]

OBJECTIVE

To investigate the association between the polymorphic alleles of dihydrolipoamide succinyltransferase (DLST) gene cDNA at position A19117G in intron 13 and C19183T in exon 14 and the risk for sporandic Alzheimer's disease (SAD).

METHODS

The polymorphism of DLST gene was detected using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) techniques in 105 patients with sporadic Alzheimer disease and 109 normal controls.

RESULTS

The frequency of AT/AC genotype was found to be significantly higher in SAD patients (21%) than in controls (10%) with an odds ratio of 2.36 (P < 0.05). The frequencies of AC/AC, AT/AT genotypes and AC allele were slightly decreased in cases with SAD as compared with controls. While the frequencies of the GC/GC genotype and GC allele were slightly higher in SAD patients than in controls. However, these differences were not statistically significant (P > 0.05).

CONCLUSION

The AT/AC genotype of DLST gene is associated with an increased risk for SAD.

Association of moderate polyglutamine tract expansions in the slow calcium-activated potassium channel type 3 with ataxia

BACKGROUND

The small-conductance calcium-activated potassium channel gene (hSKCa3) contains 2 CAG repeats, 1 of which is highly polymorphic. Although this repeat is not pathologically expanded in patients with schizophrenia, some studies have suggested an allelic association with schizophrenia. CAG expansions in other genes such as the alpha1 subunit of a brain-specific P/Q-type calcium channel gene cause spinocerebellar ataxia type 6, whereas the length of the CAG repeat in the RAI1 gene modifies the age of onset of spinocerebellar ataxia type 2.

OBJECTIVES

To evaluate expansions in the hSKCa3 polyglutamine domain as causative for ataxia, and to study the association between the length of the polyglutamine repeat and the presence of ataxia.

METHODS

We analyzed this repeat in 122 patients with autosomal dominant cerebellar ataxia, or sporadic ataxia, and compared allele distribution with 750 alleles seen in 2 healthy control groups and 172 alleles in patients with Parkinson disease.

RESULTS

The distribution of alleles in ataxia patients and controls was significantly different by Wilcoxon rank test (P <.001). Twenty-two or more polyglutamine tracts were more common in ataxia patients compared with controls by chi2 analysis (P<.001).

CONCLUSION

Longer stretches of polyglutamines in a human potassium channel are not causative for ataxia, but they are associated with the presence of ataxia. There is no association with the presence of Parkinson disease.

Increased risk of wasting syndrome in HIV-infected travellers: prospective multicentre study

HIV-infected patients from moderate regions who travel in tropical countries may experience clinical disease progression due to exposure to bacteria (including mycobacteria), fungi and parasites. In the Swiss HIV Cohort Study we examined the hypothesis that travelling increases the risk of tuberculosis, wasting syndrome, cryptosporidiosis, isosporiasis, cryptococcosis, coccidiomycosis, histoplasmosis and Salmonella septicaemia. A total of 4549 participants were included (in 1988-98) of whom 596 (13.1%) travelled at least once. During 16,800 person-years of follow-up 231 patients developed at least 1 of the diseases of interest. Wasting syndrome was the only diagnosis significantly associated with travelling (hazard ratio 2.16, 95% confidence interval 1.09 to 4.30). The risk of wasting syndrome ('slim disease') should be taken into account when counselling HIV-infected patients intending to travel in tropical regions.

The addition of fentanyl does not alter the extent of spread of intrathecal isobaric bupivacaine in clinical practice

PURPOSE

Fentanyl is commonly added to intrathecal local anesthetic solutions. In vitro data has shown fentanyl to render isobaric local anesthetics hypobaric, and alter the spread in artificial cerebrospinal fluid. This study examined whether the addition of fentanyl to isobaric bupivacaine with morphine leads to a clinically important alteration in the extent of spread of anesthesia.

METHODS

Forty-four ASA I-III patients undergoing lower limb orthopedic procedures completed this double-blind, placebo-controlled trial. Patients were randomized into one of two groups, receiving intrathecal bupivacaine 15 mg and preservative-free morphine 200 microg without (Control group), or with the addition of fentanyl 0.02 mg (Fentanyl group). Patients were maintained at a slight head-up tilt. Variables studied over three hours included sensory level to cold and pinprick, motor blockade (Bromage scale), and circulatory data.

RESULTS

No differences existed between the Fentanyl and Control groups with respect to highest level of block for cold: T4 (T2-T5) vs T3.5 (T3-T8) respectively (median, 95% confidence interval) or pinprick: T4 (T3-T6) vs T4.5 (T3-T8). Similarly, there was no difference in the time taken to reach maximum block height to cold (20 +/- 9 vs 23 +/- 13 min, mean +/- SD) or pinprick (20 +/- 9 vs 24 +/- 13 min).

CONCLUSION

The addition of fentanyl 0.02 mg to 0.5% bupivacaine with morphine does not affect the maximal block height or time to maximal block in clinical practice.

Lewy bodies and parkinsonism in families with parkin mutations

Previous work has established that compound mutations and homozygous loss of function of the parkin gene cause early-onset, autosomal recessive parkinsonism. Classically, this disease has been associated with loss of dopaminergic neurons in the substantia nigra pars compacta and locus ceruleus, without Lewy body pathology. We have sequenced the parkin gene of 38 patients with early-onset Parkinson's disease (<41 years). Two probands with mutations were followed up. Clinical evaluation of their families was performed, blinded to both genetic and pathological findings. Chromosome 6q25.2-27 haplotype analysis was carried out independently of the trait; parkin gene expression was examined at both the RNA and protein levels. Haplotype analysis of these families revealed a common chromosome 6, with a novel 40 bp exon 3 deletion that cosegregated with disease. In the proband of the smaller kindred, an exon 7 R275W substitution was identified in addition to the exon 3 deletion; RNA analysis demonstrated that the mutations were on alternate transcripts. However, Lewy body pathology typical of idiopathic Parkinson's disease was found at autopsy in the proband from the smaller kindred. These data suggest that compound heterozygous parkin mutations and loss of parkin protein may lead to early-onset parkinsonism with Lewy body pathology, while a hemizygous mutation may confer increased susceptibility to typical Parkinson's disease.

Effect of nitric oxide on strophanthidin-induced ventricular tachycardia

Nitric oxide (NO) has been demonstrated to have several effects on the heart. Through the stimulation of guanylate cyclase, NO increases cyclic GMP and decreases intracellular calcium. The purpose of this study was to evaluate the effects of NO on ventricular arrhythmia induced by strophanthidin in guinea pigs and dogs. In experiment 1, after strophanthidin-induced ventricular tachycardia, guinea pigs received different doses of L-arginine (0, 25, 50, 100, 200, and 400 mg/kg; n = 10 for each dose), 200 mg/kg L-arginine combined with 100 mg/kg N(G)-nitro-L-arginine methylester (L-NAME, n = 10), or 200 mg/kg D-arginine (n = 10). In experiment 2, after strophanthidin-induced ventricular tachycardia, dogs (n = 7) received 200 mg/kg L-arginine. By 12-lead ECG, monophasic action potentials in left and right ventricles were recorded throughout the study. In experiment 1, guinea pigs which received 200 mg/kg or 400 mg/kg L-arginine had greater incidences of ventricular tachycardia termination (60 and 80%, respectively) than those which received 0, 25, 50, and 100 mg/kg L-arginine (0, 0, 20, and 30%, respectively), those which received L-arginine with L-NAME (0%), and those which received D-arginine (0%). In experiment 2, 5 (71%) of the dogs had successful termination of ventricular tachycardia. These findings suggest that L-arginine was effective in treating strophanthidin-induced ventricular tachycardia in vivo and that the underlying mechanism is through a NO pathway.

The in vitro inhibitory effect of tannin derivatives on 3-hydroxy-3-methylglutaryl-coenzyme a reductase on vero cells

Coronary heart disease is still the major cause of death in industrialized countries. Multiple primary or secondary interventional trials to lower serum cholesterol in humans have resulted in significant reduction of coronary events and death, one of the major reasons attributed to developing a 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor such as pravastatin. Developing new inhibitors of cholesterol synthesis is still common in the pharmaceutical industry. Tannin comprises a large group of natural polyphenolic compounds possessing antioxidant effects. The methods for analysis of specific inhibitors of mevalonate biosynthesis have already been well established by using Vero cells, a cell line obtained from kidneys of African green monkeys. Tannin derivatives isolated from different traditional Chinese herbs were dissolved in DMSO and incubated with Vero cells with or without the addition of 1 mmol/l mevalonate or 5 mmol/l sodium acetate for 24 h in order to observe cell growth. Pravastatin, a specific HMG-CoA reductase inhibitor, was used as positive control which could inhibit Vero cells growth effectively and cell growth inhibition was reversible after adding 1 mmol/l mevalonate. More than 50 tannin derivatives were used for the study, but only two compounds - proanthrocyanidin A-2 (belonging to the flavan-3-ol group) and 1,2,3,6-tetra-O-galloyl-beta-D-glucose (belonging to the gallotannin group) - showed significant growth inhibition of Vero cells. This study showed that some isolated tannin derivatives from traditional herbs were effective HMG-CoA reductase inhibitors which might be developed into new hypocholesterolemic agents.

The in vitro inhibitory effect of flavonoid astilbin on 3-hydroxy-3-methylglutaryl coenzyme A reductase on Vero cells

BACKGROUND

Epidemiological studies have shown that hypercholesterolemia is a major risk factor for coronary heart disease. In clinical trials of lipid lowering therapy, 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase inhibitor has been shown to decrease cardiac events and mortality. Flavonoids are polyphenolic natural antioxidants existing in vegetables, fruits and beverages such as tea and wine. Previous studies have shown that some antioxidants had hypocholesterolemic effect, and flavonoid intake was associated with the decrease of mortality from coronary artery disease. The aim of this study was to evaluate the inhibitory effect of flavonoids on HMG-CoA reductase.

METHODS

The methods for analysis of specific inhibitors of mevalonate biosynthesis have been well-established, using Vero cells, a cell line obtained from kidneys of African green monkeys. Flavonoids isolated from different traditional Chinese herbs were dissolved in DMSO and incubated with Vero cells with or without the addition of 1 mM mevalonate or 5 mM sodium acetate in order to observe cell growth for 24 h.

RESULTS

Concentrations of 1 mM mevalonate or 5 mM sodium acetate were added into culture medium in order to observe the effect on cell growth. Different concentrations of pravastatin to inhibit cell growth were used as a positive control. About 40 flavonoid compounds were used for study, only one compound, astilbin (belonging to the flavonol group), showed significant inhibition of Vero cell growth.

CONCLUSIONS

This study shows that one flavonoid compound, isolated from traditional medicinal herbs, may be an effective HMG-CoA reductase inhibitor which might be developed into a new hypocholesterolemic agent.

Enhancement of the anti-herpetic effect of trichosanthin by acyclovir and interferon

Trichosanthin (TCS) is a type I ribosome-inactivating protein that has a wide range of pharmacological activities. The present study investigated the effectiveness of TCS on herpes simplex virus (HSV-1). The anti-viral activity and toxicity of TCS on Vero cells were measured. Results showed that the ED(50), TD(50) and the therapeutic indices were 38.5, 416.5 and 10.9 microg/ml, respectively. Anti-viral activity of TCS was substantially potentiated when it was used in conjunction with other anti-viral agents. The ED(50) of TCS was reduced 125-fold by acyclovir at a concentration of 0.001 microg/ml, which was practically devoid of significant anti-viral activity. Similarly, the ED(50) of TCS was reduced 100-fold by interferon-alpha2a at a concentration of 100 IU/ml. In conclusion, TCS is effective against HSV-1 and other anti-viral agents such as acyclovir or interferon can potentiate its action substantially.

The use of focus group interviews in Asian medical education evaluative research

OBJECTIVE

To evaluate the use of focus group interviews in Asian medical education evaluative research.

METHODS

Randomly selected medical students were invited to participate in 30 focus group interviews to provide in-depth data about the effect on their learning of the introduction of early clinical skills. Efforts were made to meet all the students to help them understand the objectives of the focus group. Confidentiality was emphasised and a non-faculty interviewer was recruited for the interviews.

RESULTS

The students considered the use of focus groups to be a more meaningful way of collecting students' opinions than other methods, for example structured questionnaire, because it allowed an interactive discussion. They also felt that having an independent non-faculty interview moderator had encouraged them to express their opinions more candidly during the interviews.

CONCLUSION

The use of focus group interviews among Asian medical students for evaluative research is practical and efficient.

Stimulatory effect of D-ephedrine on beta3-adrenoceptors in adipose tissue of rats

The effect of ephedrine on beta3-adrenoceptos (beta3-AR) was studied in the isolated adipose tissue of Wistar rat. Incubation with D-ephedrine (0.1-10 microM) induced a concentration-dependent decrease of uptake of [14C]-deoxy-D-glucose into white adipose tissues (WAT). The inhibitory effect of D-ephedrine was potentiated by BRL 37344, the agonist of beta3-AR and concentration-dependently inhibited by SR 59230A, the selective antagonist of beta3-AR. The action of D-ephedrine on beta3-AR was further blocked by the antibodies for beta3-AR, but not the immunoglobulin. in a concentration-dependent manner. Moreover, D-ephedrine increased glycerol release from the isolated brown adipose tissues (BAT) and this action was also abolished by SR 59230A at concentration sufficient to block beta3-AR. Thus, these results suggest that D-ephedrine has the ability to activate beta3-AR both in WAT and BAT of Wistar rats in vitro.

Efficacy study of video-assisted thoracoscopic surgery pleurodesis for spontaneous pneumothorax

BACKGROUND

This study aims to assess the efficacy of video-assisted thoracoscopic surgery pleurodesis in the treatment of spontaneous pneumothorax with particular reference to the rate of recurrence after abrasion pleurodesis and postoperative neuralgia.

METHODS

One hundred one patients who underwent 109 video-assisted thoracoscopic surgery pleurodesis procedures in the Austin & Repatriation Medical Centre between January 1992 and June 1998 were identified from a computerized database. The follow-up period was from 8 months to 7 years and 1 month (mean, 44.4 months). Patients were telephoned and asked as to whether recurrence occurred, and if so, when it occurred and how it was treated. They were asked to grade their current pain level from 0 to 6.

RESULTS

Eighty-two patients were contacted, corresponding to 88 video-assisted thoracoscopic surgery pleurodesis procedures that were followed up (80.7%). There were five recurrences (5.7%). The pain level was rated as 0 in 64 cases (72.7%), 1 in 27 cases (23.9%), 2 in 1 case (1.1%), and 3 in 2 cases (2.3%).

CONCLUSIONS

These data suggest that video-assisted thoracoscopic surgery pleurodesis is a valid alternative to thoracotomy with pleurectomy for treatment of spontaneous pneumothorax with an acceptable recurrence rate and minimal amount of postoperative neuralgia.

Development of a (32)P-postlabeling/HPLC method for detection of dehydroretronecine-derived DNA adducts in vivo and in vitro

Pyrrolizidine alkaloids are naturally occurring genotoxic chemicals produced by a large number of plants. Metabolism of pyrrolizidine alkaloids in vivo and in vitro generates dehydroretronecine (DHR) as a common reactive metabolite. In this study, we report the development of a (32)P-postlabeling/HPLC method for detection of (i) two DHR-3'-dGMP and four DHR-3'-dAMP adducts and (ii) a set of eight DHR-derived DNA adducts in vitro and in vivo. The approach involves (1) synthesis of DHR-3'-dGMP, DHR-3'-dAMP, and DHR-3',5'-dG-bisphosphate standards and characterization of their structures by mass and (1)H NMR spectral analyses, (2) development of optimal conditions for enzymatic DNA digestion, adduct enrichment, and (32)P-postlabeling, and (3) development of optimal HPLC conditions. Using this methodology, we have detected eight DHR-derived DNA adducts, including the two epimeric DHR-3',5'-dG-bisphosphate adducts both in vitro and in vivo.

Effects of trilinolein on superoxide dismutase activity and mrna levels in aortic smooth muscle cells

1. Atherosclerotic cardiovascular disease is still the leading cause of death in Western countries. Oxygen free radicals are considered to be intimately involved in the development of atherosclerosis. Anti-oxidants may help to protect mammalian cells from the damage induced by these reactive oxygen species. Many reports have indicated that anti-oxidants used in the treatment or prevention of disease could modify the levels of superoxide dismutase (SOD). However, the effects of long-term anti-oxidant treatment on the levels of SOD in smooth muscle cells (SMC) is still unclear. In the present study, the effects of the lipophilic anti-oxidant trilinolein on the activity and gene expression of SOD in SMC were evaluated. 2. After 2 days incubation with 0.1 micromol/L trilinolein, the activity and mRNA levels of SOD were increased in rat aortic SMC (A7r5), but there was no significant change in these parameters with a higher concentration of 1 micromol/L trilinolein. 3. In contrast, after 7 days incubation with trilinolein, both the activity and mRNA levels of SOD were lowered in a dose-dependent manner. 4. These data emphasize the importance of choosing an optimal dosage for supplementation with anti-oxidants in humans for the scavenging of oxygen free radicals.

Vasoactive and proliferative effects of parathyroid hormone and parathyroid hormone-related peptide on human vascular smooth muscle

BACKGROUND

Hyperparathyroidism is associated with an increased incidence of hypertension and cardiovascular disease. Experiments in rats suggest that this results from desensitization of the normally inhibitory effects of parathyroid hormone-related peptide (PTHrP) on vascular smooth muscle cells (VSMCs) by previous exposure to parathyroid hormone (PTH).

METHODS

Isometric tension in vitro was measured in segments of vessels obtained at neck surgery from six normotensive patients with hyperparathyroidism and 12 eucalcaemic controls undergoing thyroid surgery. Vessels were precontracted with noradrenaline to allow the vasodilatory effects of PTH and PTHrP to be observed. Human VSMCs were cultured in 0.5, 5 and 15 per cent serum with or without PTH (10(-11) to 10(-7) nmol l-(1)) and proliferation was assessed by cell counts after 14 days.

RESULTS

Vasodilatation of arterial segments produced by both PTH 20 nmol l(-1) and PTHrP 100 nmol l(-1) did not differ significantly between control and hyperparathyroidism groups (P > 0.08, Mann-Whitney U test). Vasodilatation by PTHrP was not reduced by preincubation of vessels in vitro with PTH 50 nmol l(-1) for 1 h (P > 0.36, Wilcoxon test). No effects of PTH on serum-induced proliferation of human VSMCs were observed.

CONCLUSION

These data imply that homologous desensitization to PTHrP is not implicated in the pathogenesis of vascular disease in patients with hyperparathyroidism.