Do women referred for colposcopy receive adequate information from the primary care team?

The objective of this study was to assess whether women had been counselled by their primary health care team and whether or not they had received any information about colposcopy. We also asked where the best information had been obtained. The setting was the colposcopy clinic of a large district general hospital, the design of which was a cross-sectional audit using a questionnaire. The subjects were 100 women attending the colposcopy clinic. The results show that 63% of women were seen by their primary health care team before the colposcopy visit and that counselling was associated with knowledge about colposcopy (P = 0.017). However, 43% of women felt that they knew nothing about colposcopy whilst 19% of women thought that the information they had obtained was not useful. We conclude that there is scope for improving the quality, timing and provision of information for women undergoing colposcopy.

Dynamics of the filarial surface

The surface of the filarial worm consists of an extracellular cuticle which overlies the outer plasma membrane of the hypodermis. The cuticle is permeable to a wide range of molecules of low molecular weight, and L-amino acid and D-glucose uptake occurs transcuticularly by active transport and diffusion in physiologically significant amounts. Transport mechanisms are associated with the plasma membrane of the hypodermis, and the cuticle may be considered an 'unstirred layer' distal to the transport loci. The outermost layer of the cuticle, or epicuticle, consists of a lipid bilayer which differs from a typical plasma membrane. There is no conclusive evidence for turnover of the epicuticular materials between the larval moults and in the adult stage. It is proposed that the filarial surface does not show the dynamic properties associated with the surface membranes of parasitic cestodes and trematodes.

Audit of the views of gynaecological cancer patients regarding follow-up

The purpose of this study was to audit patients opinions on routine follow-up and discharge from the gynaecology clinic. The setting was the gynaecology clinic of a large district general hospital and the design was a cross-sectional audit analysis using a written questionnaire. The subjects were 103 women attending the gynaecological out patients for review following previous treatment for various gynaecological cancers. Ninety patients took part in the study, of these 36 (40%) wished for 'free access', 29 (32%) wished for routine hospital follow-up, and 25 (28%) wished for discharge but with follow-up by their general practitioner. There were no statistically significant differences in choices between cancer groups. The choice of 'free access'seemed to be an important choice for women. We conclude that routine hospital follow-up of women treated for gynaecological cancer is not the desire of the majority and it appears the women may have different inherent psychological characteristics.

Glutathione S-transferase GSTM1 and GSTT1 genotypes in ovarian cancer: association with p53 expression and survival

The objective of this study was to determine whether the association between GSTM1 null/GSTTI null and survival in ovarian cancer is mediated by the influence of these genes on p53 expression. In 81 women with pure invasive ovarian cancer, GSTM1 null and GSTT1 null genotypes were identified using polymerase chain reaction and p53 expression was assessed using immunohistochemistry. The association of these factors with survival was examined using Cox's proportional hazards regression models. Performance status (P < 0.001), operative stage (P = 0.004), residual disease (P = 0.001), histologic subtype (P = 0.05), tumor grade (P = 0.007), and the combined GSTMI null/GSTTl null genotype (P = 0.023) were all individually associated with survival. p53 expression was not associated with survival (P = 0.45). In a multivariate analysis, the effects of GSTM1 null/GSTT1 null on survival were lost when residual disease and tumor grade were included. The effects of p53 expression on survival were unchanged when residual disease, tumor grade, operative stage, and performance score were included. GSTM1 null/GSTT1null did not influence the effects of p53 expression on survival and vice versa. The GSTM1 null/GSTT1 null genotype was associated with response to primary chemotherapy (P = 0.007) but p53 expression was not. We conclude that the association of GSTM1 null/GSTTl null with survival appears to be mediated through different mechanisms to p53 expression in ovarian cancer and in addition, may be a better predictor of outcome.

How can the incidence of negative specimens resulting from large loop excision of the cervical transformation zone (LLETZ) be reduced? An analysis of negative LLETZ specimens and development of a predictive model

OBJECTIVE

To analyse biopsies of large loop excision of the transformation zone of the cervix; to identify factors associated with negative histology; and to develop predictive models in order to reduce the number of negative loop excisions.

DESIGN

Retrospective analysis of patient notes and audit database.

SETTING

Colposcopy clinic of a large district general hospital in North Staffordshire.

POPULATION

Four hundred and fifty-two women who underwent a large loop excision of the transformation zone (LLETZ) procedure for suspected cervical intraepithelial neoplasia.

METHODS

Women who underwent a LLETZ procedure were placed in two different groups, one positive for cervical intra epithelial neoplasia and the other negative for cervical intra epithelial neoplasia. Information was obtained on a number of clinical and colposcopic variables. Analysis was undertaken to determine if there were any differences between the two groups. These factors were then identified and three predictive models generated. Receiver-operator characteristic curves were used to assess and test these models.

MAIN OUTCOMES MEASURES

To identify factors associated with negative histology on a LLETZ specimen. To predict how to reduce the number of negative LLETZ specimens.

RESULTS

Four hundred and fifty-two women underwent a LLETZ procedure, 88 were negative (19%) and 364 were positive (81%). In women who were treated at their first visit, 56/316 (18%) had negative histology. There were significant associations between negative histology in the LLETZ and negative or low grade cytological atypia, negative colposcopic findings and years of age > 50 in both bivariate analysis and stepwise logistic regression. In the predictive models, the sensitivity ranged between 72% and 80%, the specificity 59%-72%, and the area under the receiver-operator characteristic was 0.75-0.77. If we had used the predictor models and managed women with negative or low grade cervical atypia and negative colposcopy findings conservatively, we would have reduced the negative biopsy rate from 19% to 14%, but five cases of high grade disease and 25 cases of low grade disease would have been missed. If we had also included women aged > 50 years in this model, the negative biopsy rate would have dropped from 19% to 15%, with only one case of high grade disease and 11 cases of low grade disease missed. All these women would require continued cytological and colposcopic surveillance. Importantly, no cases of invasion would have been missed.

CONCLUSION

Using a predictive model can reduce the number of negative LLETZ specimens, but at the expense of continued cytological and colposcopic surveillance and cannot be recommended in normal practice. This raises the question whether current standards for negative histology in LLETZ specimens are set unrealistically high.

A comparison of the side effects of prilocaine with felypressin and lignocaine with adrenaline in large loop excision of the transformation zone of the cervix: results of a randomised trial

OBJECTIVE

To test the hypothesis that prilocaine with felypressin causes fewer side effects than lignocaine with adrenaline when performing large loop excision of the transformation zone of the cervix.

DESIGN

Randomised trial.

SETTING

Colposcopy clinic in a large district general hospital.

PARTICIPANTS

Two hundred consecutive women undergoing large loop excision of the transformation zone of the cervix.

METHODS

Two different local anaesthetic combinations (prilocaine with felypressin and lignocaine with adrenaline) were compared in women undergoing large loop excision of the transformation zone. Prospective collection of clinical and treatment data was undertaken with scoring using an ordinal scale of pain experienced by the women during the procedure. Peri-operative blood loss and any side effects were also recorded.

MAIN OUTCOME MEASURES

Side effects associated with the local anaesthetic agents.

RESULTS

Lignocaine with adrenaline resulted in less blood loss (P = 0.006) but was more likely to cause side effects, such as feeling faint (P = 0.017) and shaking (P < 0.001).

CONCLUSION

Prilocaine with felypressin causes fewer side effects than lignocaine with adrenaline and is therefore the preferred local anaesthetic combination for large loop excision of the transformation zone.

Expression and subcellular localization of cyclin D1 protein in epithelial ovarian tumour cells

The expression of cyclin D1 protein in tumour sections from 81 patients with epithelial ovarian cancer was analysed using immunohistochemistry. The tumours that overexpressed cyclin D1 in more than 10% of neoplastic cells were considered positive. Thus overexpression of cyclin D1 was observed in 72/81 (89%) of the cases examined. Protein was detected in both the nucleus and the cytoplasm in 24/81 (30%) and localized exclusively in the cytoplasm in 48/81 (59%) of the tumours. Cyclin D1 was overexpressed in both borderline and invasive tumours. There was no association between protein overexpression and tumour stage and differentiation. Furthermore, no correlation between cyclin D1 expression and clinical outcome was observed. However, in tumours overexpressing cyclin D1 (n = 72), the proportion displaying exclusively cytoplasmic localization of protein was higher in those with serous compared with non-serous histology (P = 0.004, odds ratio 4.8, 95% confidence interval 1.4-19.1). Western analysis using a monoclonal antibody to cyclin D1 identified a 36 kDa protein in homogenates from seven tumours displaying cytoplasmic only and one tumour demonstrating both nuclear and cytoplasmic immunostaining. Using restriction fragment length polymorphism polymerase chain reaction and PCR-multiplex analysis, amplification of the cyclin D1 gene (CCND1 was detected in 1/29 of the tumours demonstrating overexpression of cyclin D1 protein. We conclude that deregulation of CCND1 expression leading to both cytoplasmic and nuclear protein localization is a frequent event in ovarian cancer and occurs mainly in the absence of gene amplification.

Is the provision of information leaflets before colposcopy beneficial? A prospective randomised study

OBJECTIVE

To assess the usefulness of a leaflet distributed to women before colposcopy designed to reduce their anxiety and psychosexual morbidity by providing information.

DESIGN

Prospective randomised study.

SETTING

Colposcopy clinic of a large district general hospital.

SAMPLE

Two hundred consecutive women undergoing colposcopy for the first time for a cervical cytological abnormality of severity no greater than moderate dyskaryosis.

METHODS

Women were randomised into one of two groups (leaflet or control). Those in the leaflet group were sent an information leaflet prior to attending the clinic. In the colposcopy clinic all the women completed a State/Trait Anxiety Inventory (StAI/TrAI) and a modified psychosexual questionnaire before undergoing colposcopy. This was repeated at the six-month follow up visit. Women in the leaflet group also completed a further questionnaire on the leaflet.

MAIN OUTCOME MEASURES

Differences of anxiety and psychosexual scores between leaflet and control groups.

RESULTS

The leaflet was well received. There were no statistical differences in StAI and TrAI scores between the study group and the control group at either visit, although in the whole study population StAI and TrAI scores were reduced at the second visit. The leaflet group had significantly more psychosexual problems but by the second visit, the scores had improved and the two groups were similar. When the mean differences in anxiety and psychosexual scores at the initial and second visits were compared between the groups, the reduction in negative sexual feelings and deterioration of TrAI scores experienced by the leaflet group was significant.

CONCLUSIONS

This study suggests that the provision of sending an information leaflet prior to colposcopy is not beneficial in isolation. Other approaches need to be considered.

Association of glutathione S-transferase GSTM1 and GSTT1 null genotypes with clinical outcome in epithelial ovarian cancer

Epithelial ovarian cancer is generally associated with a poor outcome, although the mechanisms that determine survival and progression-free interval (PFI) are unclear. Data from ovarian tumors showing associations between (a) null genotypes at the glutathione S-transferase GSTM1 and GSTT1 loci and expression of p53 protein and (b) outcome and expression of p53 suggest that polymorphism at these loci is a factor determining outcome. Accordingly, we have studied the association between the GSTM1 null and GSTT1 null genotypes and survival and PFI in 148 women with epithelial ovarian cancer. Although we did not find an association between individual genotypes and outcome, women with both GSTM1 null and GSTT1 null genotypes demonstrated poorer survival (P = 0.001) and reduced PFI (P = 0.003). Thus, no cases with both these genotypes survived past 42 months postdiagnosis. In contrast, 43% of the women without this combination survived beyond this time. Because response to chemotherapy is a major factor determining outcome in ovarian cancer, we also examined the data for associations between the glutathione S-transferase genotypes and response to such treatment. Thus, in 78 patients treated with chemotherapy, the combination of GSTM1 null and GSTT1 null was associated with unresponsiveness to primary chemotherapy (P = 0.004); none of the eight patients with both these genotypes responded, compared with 38 of 70 (54%) of patients with other genotype combinations. The effect of the combination of genotypes on survival and PFI was lost in a multivariate model that included response to chemotherapy as a confounding factor. This suggests that the combination of GSTM1 null/GSTT1 null is associated with outcome because of its influence on response to chemotherapy. These preliminary findings may provide a basis for the selection of patients for treatment with chemotherapeutic agents.

A comparison of two alginate dressings used in surgical wounds

A report of a study that examined some clinical characteristics of two commonly used wound dressings

Relationship of global chloroquine transport and reversal of resistance in Plasmodium falciparum

Control of falciparum malaria has become almost impossible in many areas due to the development of resistance to chloroquine and other antimalarial drugs. Verapamil and a number of unrelated compounds which chemosensitise multi-drug resistant cancer cells also enhance chloroquine susceptibility in Plasmodium falciparum. Chloroquine is accumulated to lower levels in resistant plasmodia, hence the reversal of chloroquine resistance has been attributed to the ability of chemosensitising agents to increase the amount of chloroquine accumulated by the resistant parasite. We have conducted a detailed examination of the effect of verapamil on chloroquine sensitivity and its relationship to chloroquine accumulation. The ability of verapamil to increase steady-state chloroquine accumulation was found to be totally insufficient to explain the increase in chloroquine sensitivity caused by the drug. In contrast, when chloroquine accumulation was increased by raising the pH gradient, the corresponding shifts in sensitivity to chloroquine could be accurately predicted. These results were confirmed with other classes of chemosensitisers and we conclude that an alternative mechanistic explanation is required to completely explain the reversal of chloroquine resistance in P. falciparum.

The effect of invertebrate hormones and potential hormone inhibitors on the third larval moult of the filarial nematode, Dirofilaria immitis, in vitro

The effects of the insect hormones, ecdysone and 20-hydroxyecdysone, certain non-steroidal ecdysteroid agonists (RH compounds) and the inhibitor, azadirachtin, on the timing of the 3rd-stage moult of Dirofilaria immitis were investigated. 20-Hydroxyecdysone and RH 5849 when used at a concentration of 10(-5) M, resulted in a premature timing of this moult. Azadiracthin, at a similar concentration, prevented moulting of most of the larvae to the 4th stage. The results are discussed in relation to the possibility of a hormonal role for ecdysteroids and neuropeptide-like compounds in the control of ecdysis in filarial nematodes, that maybe somewhat comparable to the system which is found in insects.

Development of halofantrine resistance and determination of cross-resistance patterns in Plasmodium falciparum

Intermittent exposure to halofantrine (HF) of both chloroquine-susceptible (T9.96) and chloroquine-resistant (K1) isolates of Plasmodium falciparum in vitro resulted in a rapid reduction in susceptibility to HF. After 6 months, the 50% inhibitory concentration (IC50) of HF, determined with [G-3H]hypoxanthine incorporation as a marker, increased ninefold for the chloroquine-resistant (K1) isolate and threefold for the cloned chloroquine-susceptible (T9.96) isolate, the derived isolates being termed the K1HF3 and T9.96HF4 isolates, respectively. By microscopic examination of cultured erythrocytes, we determined that there was a fivefold increase in the IC50 for isolate T9.96HF4. The responses of the parental isolates and the HF-resistant isolates to chloroquine, mefloquine, quinine, amodiaquine, qinghaosu, and pyrimethamine were determined. In comparison with the parental K1 isolate, HF-resistant isolate K1HF3 was significantly more susceptible to the action of chloroquine and exhibited a significantly reduced susceptibility to quinine and mefloquine. The other HF-resistant isolate, T9.96HF4, showed no alteration in susceptibility to amodiaquine or chloroquine but a significantly decreased susceptibility to mefloquine. Resistance was stable in the two isolates, both in the absence of drug pressure or when kept frozen in liquid nitrogen. In contrast, continuous exposure to HF had no effect on the susceptibility of the parasites to this drug above HF concentrations of 3.2 x 10(-9) M.

Enhancement of drug susceptibility in Plasmodium falciparum in vitro and Plasmodium berghei in vivo by mixed-function oxidase inhibitors

A number of compounds, as exemplified by verapamil and desipramine, have been shown to enhance the susceptibility of resistant malaria parasites to chloroquine. The mechanism by which these agents reverse resistance is still controversial but is though to involve alterations in drug transport causing an increase in steady-state drug concentrations. We have proposed that an alternative resistance mechanism may involve the metabolic deactivation of the drug in some resistant parasites via cytochrome P-450 mixed-function oxidases. If the hypothesis is true, it should be possible to alter drug susceptibility in malaria parasites by the use of agents known to inhibit or induce cytochrome P-450 activities. We have assessed the ability of known inhibitors of cytochrome P-450 enzymes (cimetidine, metyrapone, and alpha-naphthoflavone) to enhance chloroquine susceptibility in Plasmodium falciparum culture-adapted and wild-type isolates in vitro and P. berghei in vivo. In all three systems, the inhibitor cimetidine enhanced parasite susceptibility to chloroquine, and this increase in susceptibility was unrelated to changes in chloroquine steady-state concentrations in vitro or to alterations in host pharmacokinetics in vivo. Additionally, the cytochrome P-450 inducer phenobarbital produced slight decreases in P. falciparum drug susceptibility in vitro. We have compared the ability of the cytochrome P-450 inhibitors cimetidine and metyrapone to enhance drug susceptibility with that of verapamil by using wild-type malaria isolates obtained from Cameroon. Verapamil completely reversed resistance, i.e., to below the cutoff point of 70 nM, in all the resistant isolates. Cimetidine enhanced chloroquine susceptibility in 60% of the isolates and reduced 50% inhibitory concentrations by at least 43% in all the resistant isolates. The compounds tested had little or no effect on the 50% inhibitory concentrations for the susceptible isolates. The data support a possible role for detoxification in chloroquine resistance, and even in the absence of such a process we have observed apparent chemosensitization by agents whose common biological feature is the inhibition of cytochrome P-450 enzymes. Additionally, sensitization has been observed in wild-type isolates of P. falciparum obtained form immune residents of an area of endemicity as well as culture-adapted parasites.

Rapid chloroquine efflux phenotype in both chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum. A correlation of chloroquine sensitivity with energy-dependent drug accumulation

Recent reports suggest that lower levels of chloroquine accumulation in chloroquine-resistant isolates of Plasmodium falciparum are achieved by energy-dependent chloroquine efflux from resistant parasites. In support of this argument, a rapid chloroquine efflux phenotype has been observed in some chloroquine-resistant isolates of P. falciparum. In this study, no relationship was found between chloroquine sensitivity and the rate of [3H]chloroquine efflux from four isolates of P. falciparum with a greater than 10-fold range in sensitivity to chloroquine. All the isolates tested displayed the rapid efflux phenotype, irrespective of sensitivity. However, chloroquine sensitivity of these isolates was correlated with energy-dependent rate of drug accumulation into these parasites. Verapamil and a variety of other compounds reverse chloroquine resistance. The reversal mechanism is assumed to result from competition between verapamil and chloroquine for efflux protein translocation sites, thus causing an increase in steady-state accumulation of chloroquine and hence a return to sensitivity. Verapamil accumulation at a steady-state is increased by chloroquine, possibly indicating competition for efflux of the two substrates. Increases in steady-state verapamil concentrations caused by chloroquine were identical in sensitive and resistant strains, suggesting that similar capacity efflux pumps may exist in these isolates. These data suggest that differences in steady-state chloroquine accumulation seen in these isolates can be attributed to changes in the chloroquine concentrating mechanism rather than the efflux pump. It seems likely that chloroquine resistance generally in P. falciparum, results at least in part from a change in the drug concentrating mechanism and that changes in efflux rates per se are insufficient to explain chloroquine resistance.

Chloroquine sensitivity of Plasmodium falciparum in vivo in a savanna town in Cameroon

Chloroquine-resistant Plasmodium falciparum has been reported in the Sahel and forest regions of Cameroon since 1985. In vivo response to chloroquine treatment (25 mg/kg) was assessed in 19 patients with malaria in the savanna North-West province. 58% of the cases showed RII resistance to chloroquine. RIII resistance was suspected in one patient. Only 35% of cases showed complete parasite clearance by day 5 of treatment. Chloroquine reduced parasite counts by at least 87% in all patients. Chloroquine resistance now seems to be well established and widespread in Cameroon. Its rapid spread and the prevalence of resistance suggest the existence of sustained drug pressure resulting in rapid selection of less sensitive strains. Unfortunately, similar pressure is also being exerted with quinine.

Vacuolar acidification and chloroquine sensitivity in Plasmodium falciparum

The antimalarial chloroquine concentrates in the acid vesicles of Plasmodium falciparum partially as a result of its properties as a weak base. Chloroquine-resistant parasites accumulate less drug than sensitive parasites. A simple hypothesis is that the intravacuolar pH of resistant strains is higher than that for sensitive strains, as a consequence of a weakened proton pump in the vacuoles of resistant strains, thereby explaining the resistance mechanism. We have attempted to test this hypothesis by the use of bafilomycin A1, a specific inhibitor of vacuolar proton pumping ATPase systems in plant cells, animal cells and microorganisms. Bafilomycin A1 significantly reduces uptake of [3H]chloroquine into both chloroquine-sensitive and -resistant strains of P. falciparum, at concentrations of inhibitor which have no antimalarial effect. Additionally, chloroquine-resistant strains of P. falciparum are more sensitive to bafilomycin A1 than chloroquine-sensitive strains. The use of bafilomycin A1 in combination with chloroquine in the standard in vitro sensitivity assay, produced an apparent reduction in sensitivity of both strains to chloroquine. The reported data support the hypothesis that chloroquine resistance in P. falciparum is associated with increased vacuolar pH, possibly due to a weakened vacuolar proton pumping ATPase.

Immunocytochemical localisation of an FMRFamide-like peptide in the filarial nematodesDirofilaria immitis andBrugia pahangi

Immunocytochemical techniques were used to detect FMRFamide-like immunoreactivity in adults of the filarial nematodes Dirofilaria immitis and Brugia pahangi. An FMRFamide-like peptide was also located in third- and fourth-stage larvae of D. immitis. Positive immunoreactivity was observed in all parasites examined, irrespective of developmental stage. The major areas of positive immunoreactivity were located in the anterior nerve ring, lateral/dorso-ventral nerves, cephalic papillary ganglia and lateral ganglia. No staining was seen in the intestine or gonads of any parasite. These results indicate that filarial worms possess a peptidergic component in their nervous system. The possible role of an FMRFamide-like peptide in the control of certain physiological events is discussed.

Metabolism and fate of ecdysteroids in the nematodes Ascaris suum and Parascaris equorum

When injected with [3H]ecdysone and maintained in vitro, the parasitic nematodes, Ascaris suum and Parascaris equorum each produced a series of polar and relatively apolar metabolites. A. suum metabolised the compound into ecdysonoic acid ([3H]EOIC), ecdysone 25-glucoside ([3H]E25gluc), putative ecdysone 22-phosphate ([3H]E22P) and a series of at least six relatively apolar metabolites. All of these, except ecdysonoic acid, were hydrolysed by a crude enzyme preparation from Helix pomatia, releasing ecdysone. In a similar study, P. equorum produced ecdysone 25-glucoside, putative ecdysone 22-phosphate and a series of relatively apolar compounds all of which were hydrolysed by H. pomatia enzymes, releasing ecdysone. [3H]Ecdysone 25-glucoside was the most abundant single metabolite in both species, and in P. equorum, at least, was released into the culture medium in relatively large amounts. Apolar metabolites were present in worm samples and were the major, if not the only radiolabelled compounds detected in eggs of both species. Data indicated a metabolic relationship between some of the apolar conjugates found in both nematode species and ecdysone 25-glucoside.

The effect of ecdysteroids on the microfilarial production of Brugia pahangi and the control of meiotic reinitiation in the oocytes of Dirofilaria immitis

The effects of the ecdysteroids ecdysone and 20-hydroxyecdysone on microfilarial release in Brugia pahangi and on meiotic reinitiation in the oocytes of Dirofilaria immitis were studied. Ecdysone was found to stimulate microfilarial release at 2 x 10(-6) M, but this effect was reduced at higher and lower concentrations. 20-Hydroxyecdysone was found to have no such effect. In D. immitis, ecdysone at 10(-5) M was also found to overcome the period of meiotic arrest that occurs during the pachytene stage of prophase 1. This effect was reduced when 10(-6) M ecdysone was used. These results help support the theory that the ecdysteroids play a hormonal role in filarial worms similar to that found in insects.

The pharmacokinetics and activation of proguanil in man: consequences of variability in drug metabolism

1. Based on the ratio of drug to active metabolite excreted in urine approximately 3% of a healthy Caucasian population showed a reduced ability to convert proguanil to cycloguanil. 2. Pharmacokinetic analysis showed that this observation resulted from a reduced oral clearance of proguanil in these individuals (245, 534 and 552 ml min-1) compared with the rest of the population (858 +/- 482 ml min-1). 3. Peak plasma concentrations of active metabolite were significantly lower in these subjects (54.2, 26.8 and 51.7 ng ml-1) compared with the rest of the population (141 +/- 45.2 ng ml-1). 4. The observed variability may result from the polymorphic metabolism of proguanil in man.

In vitro metabolism of the biguanide antimalarials in human liver microsomes: evidence for a role of the mephenytoin hydroxylase (P450 MP) enzyme

The metabolic activation of the arylbiguanide antimalarials proguanil (PG) and chlorproguanil (CPG) has been investigated in liver microsomes from three human livers. All three microsomal preparations activated the biguanides. The kinetic parameters for PG metabolism to cycloguanil (CG) were Km 21.8, 29.6 and 26.4 microM and Vmax 1.5, 5.9, and 8.2 pmol min-1 mg-1. The values for CPG conversion to chlorcycloguanil (CCG) were Km 12.9, 19.7 and 26.1 microM and Vmax 5.7, 4.8 and 3.6 pmol min-1 mg-1. The metabolic activation of both biguanides was competitively inhibited by the anticonvulsant mephenytoin. Sparteine and tolbutamide had no effect on biguanide metabolism. These data suggest an involvement of the mephenytoin hydroxylase enzyme, which exhibits a genetic polymorphism in man, in the metabolic activation of the biguanide antimalarials.

Cytochrome P-450 activity in malarial parasites and its possible relationship to chloroquine resistance

Cytochrome P-450-dependent enzyme activities have been determined in malarial parasites. Both Plasmodium berghei and Plasmodium falciparum parasites exhibited activity and these activities were greater in chloroquine resistant parasites than in sensitive strains. This enzyme activity could be induced by phenobarbitone and inhibited by specific inhibitors of the cytochrome P-450 family of enzymes. The significance of these observations in parasite drug resistance is discussed.

Investigation of ecdysteroid excretion by adult Dirofilaria immitis and Brugia pahangi

The excretion of ecdysteroids by the filarial nematode species, Dirofilaria immitis and Brugia pahangi, was examined both in vitro, by the analysis of culture medium, and in vivo, through analysis of serum samples from experimentally infected hosts. There was no evidence of ecdysteroid excretion by intact parasites of either species in vitro. Free ecdysteroids were detected in the serum of ferrets and dogs infected with D. immitis, but concentrations would be at or below the limit of detection in sub-millilitre serum samples. The detection of ecdysteroids in the serum of potential hosts is unlikely to be of value in the diagnosis of filarial infections due to a combination of low titre in the presence of current infection and measurable titre in its absence. Ecdysteroids of dietary origin may contribute to the latter.

Studies on the biosynthesis and fate of ecdysteroids in filarial nematodes

Experiments were performed to investigate whether adult Dirofilaria immitis and Brugia pahangi were capable of synthesising ecdysteroids from cholesterol or various intermediates from the biosynthetic pathway functioning in insects. Metabolites of radioactively-labelled cholesterol and 5 beta-ketodiol (2,22,25-trideoxy-ecdysone) were detected in the filarial nematodes, but there was no radioactivity corresponding to ecdysteroid. Uptake of tritiated 2-deoxyecdysone was poor and metabolism was not observed. [3H]Ecdysone was absorbed sparingly by adult D. immitis, but was metabolised efficiently to several less polar products. There was no evidence of C-20 hydroxylation capability.

Analysis of ecdysteroids in Onchocerca gibsoni, O. volvulus and nodule tissues

Free ecdysteroids were detected in Onchocerca gibsoni, in tissues constituting O. volvulus and O. gibsoni nodules and in unrelated bovine tissues. Ecdysone and 20-hydroxyecdysone were identified by HPLC-RIA and GC/MS(SIM). The concentration of free ecdysteroids in the nodule tissue immediately surrounding the parasites was at least an order of magnitude higher than that detected in the worms themselves, or in adjacent nodular tissues or other bovine tissues.

Effects of potential inhibitors on Brugia pahangi in vitro: macrofilaricidal action and inhibition of microfilarial production

A series of compounds that apparently disrupt hormonally regulated processes in insects have been examined for effects on the viability and microfilarial production of adult Brugia pahangi cultured in vitro. The azasteroids, 25-azacoprostane and 25-azacholestane, inhibited the production of microfilariae at 5 ppm, the former also exhibiting macrofilaricidal activity at this concentration. The brassinosteroids examined inhibited microfilarial production at 5 ppm but did not affect worm viability. Azadirachtin also proved to be a significant inhibitor of microfilarial release without effect on worm motility or viability. Of all the compounds tested, the non-steroidal amines appeared to be the most promising as potential filaricides, several of them proving to be macrofilaricidal at 1 ppm and affecting microfilarial production at even lower concentrations.

Neurosecretory-like material in 3rd- and 4th-stage Dirofilaria immitis larvae (Nematoda: Filarioidea)

Phase-interference microscopic examination of the infective, post-infective 3rd-stage and 4th-stage larvae of Dirofilaria immitis has identified a single cell body in each of the paired lateral amphidial nerves which undergoes characteristic morphological change during the development from 3rd- to 4th-stage larvae. Acetaldehyde-fuchsin staining of worm sections revealed fuchsinophilic material in the precise location of the amphidial nerve-cell bodies observed by phase-interference microscopy. This material was found in 70% of infective larvae recovered from mosquitoes and in 100% of larvae recovered from micropore chambers 24 h after implantation into BALB/C mice. In pre-moult larvae recovered at 42 h (Experiment 1) and at 48 h (Experiment 2) fuchsinophilic material was demonstrable, but no staining was observed in those larvae in which separation of the 3rd- and 4th-stage cuticles had occurred. No such material was observed in 4th-stage larvae recovered from chambers after 74 h, and in these larvae the amphidial nerve-cell bodies were not discernible. These cytological observations are consistent with a cycle of elaboration and release of neurosecretion associated with moulting in D. immitis.

The efficacy of 22,23-dihydroavermectin B1 (Ivermectin) acting singly or in combination with a benzodiazepine on microfilariae of Onchocerca species and Brugia pahangi (an in vitro study)

An in vitro study of the antinematodal action of two groups of compounds which act on the receptor complex of the inhibitory neurotransmitter, Gamma-aminobutyric acid (GABA) in mammalian systems is described. The compounds, Ivermectin and two benzodiazepines, Diazepam and a water soluble Midazolam were tested singly or in combination against two microfilarial parasites Onchocerca lienalis (closely related to Onchocerca volvulus) and Brugia pahangi. The combination of ivermectin and diazepam at a concentration of 0.1 microgram/ml and 33 micrograms/ml respectively achieved the same effect on microfilarial motility as when ivermectin was given at 1 microgram/ml alone or diazepam at 66 micrograms/ml alone. Similarly when the combination of ivermectin at 0.1 microgram/ml and midazolam at 10 micrograms/ml was used it achieved the same effect as ivermectin at 1 microgram/ml alone or midazolam at 33 micrograms/ml alone. This showed that both benzodiazepines had a synergistic effect on the activity of ivermectin. The microfilariae of B. pahangi were insensitive to both groups of compounds at all concentrations used.

Inter-subject variability in the metabolism of proguanil to the active metabolite cycloguanil in man

1. The metabolism of proguanil to the active metabolite cycloguanil has been evaluated in 135 British Troops and 26 Kenyan schoolchildren. 2. Large inter-subject variability was observed in both plasma and urinary concentrations of proguanil and cycloguanil after standard doses of drug. 3. Based on the ratio of proguanil to cycloguanil (P/C) in urine the British troops formed a non-normal distribution. 90% of the population formed a discrete distribution with P/C ranging from 0.5 to 9.0 while the remaining 10% were scattered throughout the distribution to an extreme value of 39. A similar pattern of variability was observed using P/C from a 6 h plasma sample. 4. This variability was due to differences in the ability of individuals to metabolise proguanil to cycloguanil. 5. Thirteen schoolchildren who had experienced malaria during prophylaxis with proguanil and thirteen matched controls each received proguanil (100 mg). We could not discriminate between the two groups based on P/C ratio in either a 6 h plasma or 0-6 h urine sample.

Egg production in Brugia pahangi (Nematoda: Filarioidea)

Oogenesis in Brugia pahangi has been studied by means of the aceto-orcein chromosomal squash technique and light-microscope autoradiography. The use of colchicine has demonstrated a 2-3 mm terminal germinative zone within the ovary, in which continuous and rapid mitotic division of germ cells occurs. In 80% of the gonads, oocytes within a 1-2 mm length of the ovary proximal to the germinative zone were at the prophase of meiosis I. Primary oocytes with markedly less condensed chromatin, apparently interphase cells, were observed in the corresponding region of the ovary in the remaining 20% of material examined. A cyclical or phased development of primary oocytes is suggested. Autoradiographic studies, concerned with the incorporation of [5-3H]uridine into germ cells of B. pahangi in vitro, further suggest that the onset of meiotic prophase is associated with the initiation of high RNA synthetic activity. Following meiotic prophase, oocytes complete meiosis I before entering a period of growth during which the chromatin material is decondensed. Recondensation of chromosomes prior to meiosis II is only observed after fertilization within the seminal receptacle. On completion of meiosis II, with the extrusion of a polar body, the haploid chromosome complement of the female unites with that of the male, re-establishing the diploid number of the zygote (2n = 10).

Chlorproguanil/dapsone for the treatment of non-severe Plasmodium falciparum malaria in Kenya: a pilot study

Chlorocycloguanil, the active metabolite of chlorproguanil, was synergistic in vitro with dapsone against 2 culture-adapted Plasmodium falciparum isolates from Kenya; maximal synergy occurred at lower concentrations that it did with pyrimethamine and sulfadoxine. 48 children with asymptomatic P. falciparum infections were treated with chlorproguanil (at a target dose of 1.2 mg/kg) and dapsone (target dose of 1.2 or 2.4 mg/kg); all were free of parasitaemia by day 7. The following numbers had recurrences on days 14, 21, and 28, respectively: 1 of 48, 7 of 47, and 7 of 40. All 39 children treated with pyrimethamine (target dose 1.2 mg/kg) and sulfadoxine (target dose 24 mg/kg) were cleared of infection, while the following had recurrences on days 14, 21, and 28: 1 of 39, 2 of 38, and 2 of 36. The rate of decrease in parasitaemia was the same in the 2 groups, and there was no change in haematocrit or haemoglobin during the follow-up. The rate of recurrence in the children receiving chlorporguanil/dapsone was higher, probably because these drugs have a much shorter clearance time than pyrimethamine/sulfadoxine. Chlorproguanil/dapsone is an effective combination for treating P. falciparum malaria and deserves further study.

The changing response of Plasmodium falciparum to antimalarial drugs in east Africa

For the past 20 years, chloroquine chemotherapy has been the single most effective malaria control measure in East Africa. The advent of chloroquine-resistant Plasmodium falciparum has reduced the clinical effectiveness of chloroquine and this trend is likely to continue. Combinations of antifol drugs are at present effective inhibitors of most P. falciparum infections in the region, in spite of widespread resistance to pyrimethamine. The development of (i) sensitive methods for monitoring changes in sensitivity to antifol combinations, (ii) more effective and less costly alternatives to commercially available combinations, and (iii) investigation of host and parasite factors leading to drug treatment failure in P. falciparum infections has been the primary goal of the Wellcome Trust Research Laboratories in Kenya (directed by Dr W.M. Watkins) within the malaria programme of the Kenya Medical Research Institute, and collaborating laboratories at the School of Tropical Medicine and the University of Liverpool.

In vitro susceptibility of Plasmodium falciparum isolates from Jilore, Kenya, to antimalarial drugs

Twenty-six Plasmodium falciparum isolates obtained during a prophylaxis study at Jilore primary school, Malindi, Kenya, were adapted to in vitro culture and their susceptibility to 13 antimalarial drugs was tested by a modified radioisotopic method. Pyrimethamine, chloroquine, amodiaquine, cycloguanil, chlorcycloguanil, quinine, quinidine and sulfadoxine, and the experimental compounds MB 35769, mefloquine, WR 184806, parvoquone, and menoctone were used. The isolates could be divided into two groups with significantly different susceptibility to pyrimethamine, shown by a 755-fold difference in the mean ID50 values (2.77 +/- 1.98 x 10(-10) mol/l and 2.09 +/- 1.64 x 10(-7) mol/l). The mean susceptibility of the two groups differed 7.7-fold for chlorcycloguanil and 14.6-fold for cycloguanil, but were not significantly different for the other drugs. All isolates were more sensitive to amodiaquine than to chloroquine in vitro. The ratio of the geometric mean ID50 values of chloroquine to amodiaquine was 3.13. The ratio for the chemically related compounds parvoquone to menoctone was 5.63, quinine to quinidine was 5.58, and mefloquine to WR 184806 was 12.16.

Identity and tissue localization of free and conjugated ecdysteroids in adults of Dirofilaria immitis and Ascaris suum

Adult males and females of the dog heartworm, Dirofilaria immitis, and of the swine parasite, Ascaris suum, were extracted, the free and polar conjugated ecdysteroid fractions separated and the latter hydrolysed enzymically. The ecdysteroids released by hydrolysis of the conjugates and the free hormones were analysed by radioimmunoassay, high-performance liquid chromatography on reversed phase and adsorption columns monitoring fractions by radioimmunoassay, and by gas-liquid chromatography/mass spectrometry (selected ion monitoring). In both species, males and females contained free and polar conjugated ecdysteroids, with evidence for the presence primarily of ecdysone and 20-hydroxyecdysone together with smaller amounts of 20,26-dihydroxyecdysone. Males and females of both species were then dissected into body fluid, reproductive system, gut and remaining body wall compartments, the ecdysteroids extracted, fractionated and analysed by radioimmunoassay and high-performance liquid chromatography monitoring fractions by radioimmunoassay. The results for both sexes in the two species were similar and indicated that ecdysteroids were not detectable in body fluids and that free ecdysteroids occurred in the reproductive system and the body wall, whereas polar conjugated ecdysteroids were detected in the reproductive system and the gut; a minor portion of the free ecdysteroids in A. suum was also apparently present in the gut. Further localization of the ecdysteroids in the body wall of A. suum females suggested that negligible immunoreactivity was associated with the circumpharyngeal nerve ring. The possible significance of the results is discussed.

A preliminary pharmacokinetic study of the antimalarial drugs, proguanil and chlorproguanil

Pharmacokinetic parameters for cycloguanil and chlorcycloguanil, the active metabolites of proguanil (Paludrine] and chlorproguanil (Lapudrine) have been measured in a bioassay which assesses the in-vitro growth inhibition of a cycloguanil- and chlorcycloguanil-sensitive strain of Plasmodium falciparum produced by dilutions of plasma collected after oral administration of the pro-drugs. A single compartment model is applicable for cycloguanil with mean rate constants of elimination of 0.0624 h-1 and availability of 0.2398 h-1. The elimination profile for chlorcycloguanil indicates partition of drug into more than one compartment. In 2 of 10 subjects dosed with proguanil and 1 of 11 subjects dosed with chlorproguanil, the active metabolite levels were significantly lower than the mean for the other subjects. Abnormally low cycloguanil or chlorcycloguanil plasma levels may be of importance in relation to effective prophylaxis against malaria.

Inadequacy of chlorproguanil 20 mg per week as chemoprophylaxis for falciparum malaria in Kenya

After treatment with chloroquine and pyrimethamine/sulfadoxine, 118 school children aged 6 to 10 years living near the Kenyan coast were enrolled in a malaria chemoprophylaxis study and followed up for 20 weeks. Children were randomly assigned to receive either chlorproguanil 20 mg weekly (n = 78) or placebo (n = 37). The attack rate of Plasmodium falciparum infection was 42% in chlorproguanil recipients (39.8 episodes per 1000 person-weeks of prophylaxis) and 73% in placebo recipients (69.2 episodes per 1000 person-weeks, p less than 0.02). Sensitivity tests on 36 isolates successfully cultured in vitro showed that all 21 isolates from chloroproguanil recipients were resistant to dihydrofolate-reductase inhibitors, whereas only 3 of 15 isolates from the placebo group were resistant (p less than 10(-6)). Chlorproguanil in a weekly adult dose of 40 mg does not provide adequate prophylaxis against P falciparum in Kenya, probably because drug levels between doses fall below those required to suppress parasites resistant to dihydrofolate-reductase inhibitors.

The disposition of pyrimethamine base and pyrimethamine pamoate in the mouse: effect of route of administration

We have investigated the plasma pharmacokinetics and mass fate in mice, of pyrimethamine administered as either the base or as the poorly soluble pamoate salt, in each case by the intraperitoneal (i.p.) and subcutaneous (s.c.) routes. Following the administration of pyrimethamine base (i.p. and s.c.) and pyrimethamine pamoate (i.p.), maximum measured plasma levels of pyrimethamine were attained within 1 h, before declining monoexponentially. There was no significant difference between these three groups in the clearance (0.29 +/- 0.05, 0.30 +/- 0.03, 0.26 +/- 0.05 ml min-1), elimination half-life (4.5 +/- 0.5, 4.8 +/- 0.8, 4.9 +/- 0.5 h) and AUC (19.4 +/- 4.4, 17.3 +/- 2.2, 21.1 +/- 4.4 micrograms.h ml-1). By contrast, after s.c. dosage of pyrimethamine pamoate, drug absorption was significantly delayed, maximum plasma levels being reached after 4 h, these levels being approximately one-third of those in the other three groups. Absorption was however complete, as the values for AUC and clearance were not significantly different from the other groups. The pattern of faecal and urinary elimination of 14C radioactivity was unaffected by either dose site or formulation of pyrimethamine. The majority of the dose (44.5-64.2 per cent) was eliminated in the faeces suggesting extensive biliary excretion. Localization of 14C radioactivity in the major organs was negligible in all groups. Following each dose, between 85 and 98 per cent of the dose was accounted for. These studies indicate that of the four treatment groups only pyrimethamine pamoate on s.c. administration demonstrates a sustained release action from the dose site.(ABSTRACT TRUNCATED AT 250 WORDS)

Gametogenesis and fertilization in Dirofilaria immitis (Nematoda: Filarioidea)

Gametogenesis in Dirofilaria immitis has been studied principally by means of the aceto-orcein chromosomal squash technique, but with additional ultrastructural observations. A terminal germinative zone, in which a continuous and rapid division of germ cells occurs, has been identified in the gonoduct of both male and female worms. Approximately 20% of cells within these germinative zones were in arrested mitotic division following the incubation in vitro of excised gonads in 0.01% colchicine for 4 h. All primary spermatocytes within a 1-2 cm length of the testis proximal to the germinative zone were at the prophase of the 1st meiotic division. In the corresponding region of the ovary, the primary oocytes were similarly at the prophase of the 1st meiotic division in 75% of female worms examined but in the remaining 25% all primary oocytes possessed markedly less condensed, probably interphase nuclei. A possible hormonal control of the cyclical development of primary oocytes, but not primary spermatocytes in D. immitis is suggested. In most of the remaining length of the gonoducts beyond this region of cells at meiotic prophase, the chromatin material of both primary spermatocytes and oocytes is decondensed. Recondensation of chromosomes in the spermatocytes is observed just prior to entry into the seminal vesicle, where meiosis I is completed and meiosis II takes place. In the primary oocyte, completion of meiosis only occurs after fertilization within the seminal receptacle by an entire male gamete. Following the 2 meiotic divisions in the oocyte and subsequent extrusion of the 2 polar bodies, the haploid chromosome complement of the female unites with that of the male, re-establishing the diploid number of the zygote (2n = 10). Male chromosomes within the oocyte remain visible throughout late oogenesis and fusion occurs without the formation of pronuclei.