Functional genomics in Spiralia

Our understanding of the mechanisms that modulate gene expression in animals is strongly biased by studying a handful of model species that mainly belong to three groups: Insecta, Nematoda and Vertebrata. However, over half of the animal phyla belong to Spiralia, a morphologically and ecologically diverse animal clade with many species of economic and biomedical importance. Therefore, investigating genome regulation in this group is central to uncovering ancestral and derived features in genome functioning in animals, which can also be of significant societal impact. Here, we focus on five aspects of gene expression regulation to review our current knowledge of functional genomics in Spiralia. Although some fields, such as single-cell transcriptomics, are becoming more common, the study of chromatin accessibility, DNA methylation, histone post-translational modifications and genome architecture are still in their infancy. Recent efforts to generate chromosome-scale reference genome assemblies for greater species diversity and optimise state-of-the-art approaches for emerging spiralian research systems will address the existing knowledge gaps in functional genomics in this animal group.

Annelid functional genomics reveal the origins of bilaterian life cycles

Indirect development with an intermediate larva exists in all major animal lineages1, which makes larvae central to most scenarios of animal evolution2-11. Yet how larvae evolved remains disputed. Here we show that temporal shifts (that is, heterochronies) in trunk formation underpin the diversification of larvae and bilaterian life cycles. We performed chromosome-scale genome sequencing in the annelid Owenia fusiformis with transcriptomic and epigenomic profiling during the life cycles of this and two other annelids. We found that trunk development is deferred to pre-metamorphic stages in the feeding larva of O. fusiformis but starts after gastrulation in the non-feeding larva with gradual metamorphosis of Capitella teleta and the direct developing embryo of Dimorphilus gyrociliatus. Accordingly, the embryos of O. fusiformis develop first into an enlarged anterior domain that forms larval tissues and the adult head12. Notably, this also occurs in the so-called 'head larvae' of other bilaterians13-17, with which the O. fusiformis larva shows extensive transcriptomic similarities. Together, our findings suggest that the temporal decoupling of head and trunk formation, as maximally observed in head larvae, facilitated larval evolution in Bilateria. This diverges from prevailing scenarios that propose either co-option9,10 or innovation11 of gene regulatory programmes to explain larva and adult origins.

A study examining the relationship between alexithymia and challenging behaviour in adults with intellectual disability

BACKGROUND

Research suggesting that people with intellectual disabilities (ID) have difficulties in recognising emotions provides a rationale for studying alexithymia in this population. A number of studies have found a relationship between alexithymia and challenging behaviours in various populations and this study aims to discover if this is the case for people with ID.

METHOD

Cross-sectional data were collected from 96 participants with ID and 95 of their carers. The service user participants completed an alexithymia questionnaire for children while carers completed the checklist for challenging behaviour and the observer alexithymia scale. Correlational analyses were employed to explore relationships between the variables.

RESULTS

The relationship between service user and carer-rated alexithymia was very weak. The analysis did show significant associations between observer-rated alexithymia and challenging behaviour frequency, management difficulty and severity, but there was no significant relationship between challenging behaviour and alexithymia as rated by service users themselves.

CONCLUSIONS

This study suggests that observer-rated alexithymia is important in understanding challenging behaviour presented by people with ID. Service user-rated alexithymia had no association with challenging behaviour, in contrast to the results from similar research with other challenging populations.

The UK geochemical environment and cardiovascular diseases: magnesium in food and water

Cardiovascular diseases (CVDs) contribute approximately one-third to noncommunicable diseases in the UK. The central role of magnesium in CVDs (enzyme activity, cardiac signalling, etc.) is well established. Mortality and morbidity rates for CVDs may be inversely related to water hardness, suggesting a role for environmental magnesium. Published official and quasi-official data sources were evaluated to establish a model magnesium intake for a representative adult: standardised reference individual (SRI), standardised reference male (SRM) or standardised reference female (SRF). For typical dietary constituents, only tap water is probably locally derived and bottled water may not be. Fruits and vegetables are imported from many countries, while meat, dairy and cereal products represent a composite of UK source areas. Alcoholic beverages provide magnesium, there is doubt about its absorptive efficiency, and they are not locally derived. A simple model was devised to examine the effect of varying dietary contributions to total daily intake of magnesium. Omitting tap or bottled water, the combined intake, solid food plus alcoholic beverages, is 10.57 mmol Mg (84.5 % RNI) for the SRM and for the SRF, 8.10 mmol Mg (71.7 % RNI). Consumers drinking water derived from reservoirs or rivers, or supplementing it with the purest bottled water, improve their magnesium intake only slightly compared with water containing no magnesium. Choosing bottled water with high magnesium content when the public supply derives from rivers or reservoirs partially satisfies magnesium needs. Real improvement in SRI magnesium nutrition is seen only where water is hard. However, this conclusion cannot be validated until new measurement technologies for body magnesium become available.

Safety and pharmacokinetics of oseltamivir at standard and high dosages

Although clinical evidence is currently lacking, opinion in the literature on avian influenza A/H5N1 suggests that increased doses of the oral neuraminidase inhibitor oseltamivir may offer clinical benefits against highly pathogenic influenza where high levels of viral replication and disseminated infection cause severe disease. We assessed the pharmacokinetics and safety/tolerability of oseltamivir at dosages up to 450 mg twice daily. Healthy adult volunteers were randomised to receive placebo or oseltamivir 75, 225 or 450 mg every 12h for 5 days. Volunteers were followed up to Day 7 for pharmacokinetic parameters, vital signs, adverse events and cardiac safety. In total, 391 volunteers were randomised and evaluated. Pharmacokinetics were linear and dose-proportional, with no evidence of accumulation of oseltamivir or its active metabolite at any dosage. Headache was the most common adverse event (16.8-23.7% across groups), but its incidence was unrelated to dosage. Dosage-related events with oseltamivir included nausea (up to 31.3% of volunteers) and vomiting (up to 16.2%), which generally occurred on Day 1 and lasted <1 day, and possibly dizziness (up to 11.3%). Oseltamivir had no relevant effects on vital signs, laboratory parameters or cardiac function. In conclusion, oseltamivir was well tolerated, with dose-proportional pharmacokinetics and no accumulation. Possible clinical benefit in severe influenza infections could be investigated at dosages higher than those currently recommended.

A preliminary electron backscattered diffraction study of sintered NdFeB-type magnets

This paper reports, for the first time, the use of electron backscattered diffraction (EBSD) to study orientation in sintered NdFeB type magnets. The magnetic properties of NdFeB magnets are greatly improved if a strong crystallographic texture is firstly achieved, namely, the direction of the c-axis is along the direction of magnetization. A systematic survey of sample preparation techniques showed that samples that were mechanically polished and then etched gave the most reliable EBSD data. Analyses were made using both fully automated EBSD scans and by EBSD measurements taken after manual movement of the beam. The EBSD results are presented as secondary electron SEM micrographs, orientation images and 001 pole figures. For the selection of grains investigated, the deviation of the c-axis was shown to be between 10 degrees and 30 degrees from the ideal [001]//magnetization direction. It is demonstrated that EBSD is a valuable tool for characterizing the microstructure and texture relationships and for assessing the performance of the processing routes of NdFeB magnets.

Safety of intravenous gadolinium (Gd-BOPTA) infusion in patients with renal insufficiency

The safety of gadolinium (Gd-benzyloxypropionictetra-acetate [BOPTA] dimeglumine) infusion was evaluated in 32 patients with severe or moderate chronic renal failure in a prospective, randomized, double-blind, placebo-controlled study. Renal failure was defined as severe if creatinine clearance was between 10 and 29 mL/min, and as moderate if creatinine clearance was between 30 and 60 mL/min. Serum creatinine level and 24-hour urine samples for creatinine clearance were followed up serially for 7 days after the administration of either gadolinium (Gd-BOPTA dimeglumine), 0.2 mmol/kg, or a saline infusion. No patient experienced a significant change in renal function, defined as an increase in serum creatinine level greater than 0.5 mg/dL more than baseline, and no patient required hospitalization or dialysis during the study period. Gadolinium (Gd-BOPTA dimeglumine) appears to be well tolerated in patients with moderate to severe renal failure.

Safety and pharmacokinetic profile of gadobenate dimeglumine in subjects with renal impairment

RATIONALE AND OBJECTIVES

To determine the safety and pharmacokinetics of gadobenate dimeglumine in a group of subjects with moderate or severe renal impairment.

METHODS

The safety and pharmacokinetic profile of gadobenate dimeglumine, a gadolinium (Gd3+) chelate complex in development as a contrast agent for MRI, were evaluated in a placebo-controlled, double-blind, multicenter trial. Subjects with moderate or severe renal impairment (creatinine clearances of 31 to 60 or 10 to 30 mL/min, respectively) received a 0.2-mmol/kg intravenous bolus of Gd3+ or saline placebo. Blood samples (up to 72 hours) and urine and fecal samples (up to 216 hours) were assayed for total Gd3+ content by inductively coupled plasma atomic emission spectroscopy. Gd3+ blood concentration/time data were analyzed nonparametrically and parametrically using the software program WinNonlin VI.1.

RESULTS

Mean (SD) values for Gd3+ area under the curve, blood clearance, steady-state volume of distribution, renal clearance, and creatinine clearance for the moderate group were 862 (392) micrograms.h/mL, 56 (25) mL/min, 21 (5) L, 47 (23) mL/min, and 46 (16) mL/min. Values for the severe group were 1347 (366) micrograms.h/mL, 31 (7) mL/min, 19 (6) L, 22 (7) mL/min, and 21 (8) mL/min. No Gd(3+)-related adverse events occurred. Mean values for Gd3+ recovery in urine and feces for moderate and severe groups were 74% and 6%, and 69% and 8% of the dose, respectively. Linear regression analysis demonstrated a significant relation between the level of renal function and blood clearance of Gd3+.

CONCLUSIONS

Although mean blood clearance and renal clearance values progressively declined with increasing degree of renal impairment, based on the safety profile and the fact that the administered dose was double the standard dose used for MRI purposes, there appears to be no need for dose reduction in this population.

The pharmacokinetics of topotecan and its carboxylate form following separate intravenous administration to the dog

PURPOSE

To determine the relationship between topotecan and its ring opened hydrolysis product (SK&F 105,992) following intravenous administration of the two agents separately, and to determine the bio-availability of topotecan in female beagle dogs.

METHODS

The pharmacokinetics of topotecan and SK&F 105,992 were determined following separate administration as 30 minute intravenous infusions in a cross-over design. Topotecan was also administered orally to the same dogs.

RESULTS

When administered intravenously to dogs, SK&F 105,992 underwent interconversion to topotecan. Plasma concentrations of both topotecan and SK&F 105,992 appeared to decline multi-exponentially following i.v. infusion of either compound. A 2-compartment model was found to adequately characterize the data.

CONCLUSIONS

The clearance of topotecan by other routes proceeded at a faster rate than its interconversion to SK&F 105,992, whereas the clearance of SK&F 105,992 by other routes was slower than the rate of its interconversion to topotecan. Any SK&F 105,992 formed in the GI tract did not appear to be well absorbed following oral administration of topotecan to dogs. The steady-state volume of distribution for topotecan was approximately 8- to 9-fold greater than that for SK&F 105,992 in the dog. After intravenous administration of topotecan, the amount of topotecan in the dog was much greater than that of the carboxylate, even though their respective plasma concentrations were similar. The bioavailability of topotecan, calculated from oral topotecan data or from SK&F 105,992 data, was approximately 50%.

Pharmacokinetics and pharmacodynamics of topotecan given on a daily-times-five schedule in phase II clinical trials using a limited-sampling procedure

Topotecan is a novel semisynthetic derivative of the anticancer agent camptothecin and inhibits the intranuclear enzyme topoisomerase I. The lactone structure of topotecan, which is in equilibrium with the inactive ring-opened hydroxy acid, is essential for this activity. We performed a pharmacokinetics study as part of phase II clinical trials in patients with various types of solid tumors, giving topotecan at 1.5 mg/m2 per day by 30-min infusion for 5 consecutive days, with courses being repeated every 3 weeks. Previously validated limited-sampling models, using concentration measurements in samples obtained 2 h after infusion, were used to calculate the area under the plasma concentration-time curves (AUCs) for both chemical forms. Samples were obtained from a total of 36 patients over 136 treatment days. The mean AUC of the closed-ring form (AUC(closed)) was 8.74 (range 2.3-16.3 microM min per day, and the mean AUC of the ring-opened form (AUC(open)) was 11.5 (range 3.2-46.0) microM min per day (interpatient variability 34-61%). In each patient the AUC values achieved on the 1st day of administration were similar to and, thus, predictive for those achieved during the following days, with a day-to-day variation of 7.39% being recorded for the AUC(closed) and that of 12.6% for the AUC(open). There was no drug accumulation during the 5 consecutive treatment days of each cycle. However, despite the large interpatient pharmacokinetic variability, the importance of regular drug monitoring on this schedule can be questioned, as the pharmacodynamic variability was relatively small.

Interspecies pharmacokinetics of a novel hematoregulatory peptide (SK&F 107647) in rats, dogs, and oncologic patients

PURPOSE

To study the pharmacokinetics of SK&F 107647, a novel hematoregulatory agent, in rats, dogs, and patients with non-lymphoid solid tumor malignancy.

METHODS

Sprague Dawley rats and beagle dogs (n = 6 each; 3 M, 3 F) were given 25 mg/kg of SK&F 107467 as an iv bolus injection, and patients (n = 6; 4 M, 2 F) received 100 mg/kg as a 2 hour iv infusion. Plasma samples were assayed for drug using either HPLC (rat and dog) or RIA (human).

RESULTS

In each species the plasma clearance (CL) of SK&F 107647 was low in relation to hepatic blood flow, and the volume of distribution (Vd ss) was reflective of distribution to extracellular body water. The plasma CL in humans was near that of average glomerular filtration rate. Using allometric equations for interspecies scaling (Y = a.W(b)), body-weight normalized human pharmacokinetic data were reasonably predicted using either the body weight normalized rat or the dog data. The allometric exponents (b) for CL, Vd(ss), and T(1/2) of SK&F 107647 were 0.63, 0.94, and 0.29, respectively.

CONCLUSIONS

Use of a limited pool of available animal data allowed for reasonable predictions of human pharmacokinetics of SK&F 107647.

Phase I clinical and pharmacokinetic study of topotecan administered by a 24-hour continuous infusion

PURPOSE

To determine the maximum-tolerable dose (MTD) and to investigate the pharmacokinetics and pharmacodynamics of topotecan in a phase I study. Topotecan is a novel semisynthetic derivative of the anticancer agent camptothecin and inhibits the intranuclear enzyme topoisomerase I. Broad preclinical activity rationalized further clinical evaluation.

PATIENTS AND METHODS

In this phase I trial, topotecan was administered by 24-hour continuous infusion every 21 days to patients with solid malignant tumors.

RESULTS

A total of 25 eligible patients, of whom 22 were pretreated, entered the study. They received the following dosages of topotecan: 2.5, 3.75, 5.60, 8.4, and 10.5 mg/m2 by 24-hour infusion. Reversible leukopenia and thrombocytopenia were dose-limiting, with mild anemia occurring regularly. Other toxicities, such as alopecia, mucositis, nausea, and vomiting were sporadic and mild. Responses were not observed. However, eight patients had stable disease. The plasma concentration-time curves were not compatible with standard linear pharmacokinetic models, and indications were found for the occurrence of nonlinear (saturation) kinetics at the dosages studied.

CONCLUSION

The recommended dose for phase II studies is 8.4 mg/m2 when administered as a 24-hour infusion, which is well tolerated. Further studies will be necessary to account for the putative nonlinear behavior of the drug.

High-performance liquid chromatographic determination of the novel antitumour drug topotecan and topotecan as the total of the lactone plus carboxylate forms, in human plasma

A sensitive high-performance liquid chromatographic (HPLC) assay has been developed and validated for the quantitation of the novel anticancer agent topotecan and topotecan as the total of its lactone and carboxylate forms in human plasma. Linear response in analyte standard peak area were observed over the concentration range 0.05-10 ng/ml using 100-microliters plasma samples. The instability of the drug in the biological matrix necessitated that the plasma fraction was obtained within 5 min after blood sampling by centrifugation, immediately followed by protein precipitation with cold methanol (-30 degrees C). Stability studies have indicated that topotecan is stable in these methanolic extracts for at least 4.5 months at -30 degrees C and 2 months at -70 degrees C. For the total determination of the lactone plus lactone ring-opened forms of the drug as topotecan, plasma samples were deproteinated with methanol and, subsequently, acidified with 7% (v/v) perchloric acid. Plasma samples for the measurement of total levels of the lactone and the ring-opened forms of topotecan were stable for at least 4.5 months when stored at -30 degrees C. After centrifugation, the supernatants were analysed by HPLC using a Zorbax SB-C18 Stable Bond column and methanol-0.1 M hexane-1-sulfonic acid in methanol-0.01 M N,N,N',N'-tetramethylethylenediamine (TEMED) in distilled water pH 6.0 (25:10:65, v/v) as the mobile phase. Detection was performed fluorimetrically. Within-run and between-run precision was always less than 12.1% in the concentration range of interest (0.05-10.0 ng/ml). The limit of quantitation is 0.05 ng/ml. Accuracy measurements ranged between 87.6 and 113.5%.

Distribution of metals in mechanical fractions of soils from a lake catchment in Venezuela

Soil samples were collected from both the surface and at depth from the lowlands around Lake Valencia and from the adjacent mountains. This paper reports results for Al, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb and Zn in mechanical fractions of the soils. Lowland soils, developed on lacustrine sediments, show a predominance of medium- to fine-grain size fractions whereas the shallow mountain soils show the highest percentage of particles in the coarse to medium fractions. Concentrations of most of the elements investigated increased toward finer particle sizes. The generally higher metal concentrations in lowland soils compared with mountain soils are consistent with release by weathering in the uplands and accumulation in the lowlands. The presence of carbonates derived from ubiquitous shelly material in the lowland soils may explain increases of Ca and Mg in labile fractions. In the lowland area, there is little evidence for the translocation of metals in the soil profiles, despite the high rainfall of a tropical climate, and the calcareous nature of these soils could account for the immobility of metals.

Pharmacokinetics and pharmacodynamics of topotecan administered daily for 5 days every 3 weeks

Topotecan is a novel semisynthetic derivative of the anticancer agent camptothecin and inhibits the intranuclear enzyme topoisomerase I. The lactone structure of topotecan, which is in equilibrium with the inactive ring-opened hydroxy acid, is essential for this activity. The open form predominates at physiological pH. We performed a pharmacokinetic study as part of a phase I study in patients with various types of solid tumors, where topotecan was administered in a 30-min infusion daily on 5 consecutive days every 3 weeks. The plasma kinetics of topotecan could be described best using an open two-compartment model with t1/2(alpha) and t1/2(beta) of 8.1 (range 0.3 to 40.7) min and 132 (range 49 to 286) min, respectively. The plasma concentration-time profiles of the metabolite, however, could be described using a one-compartment model with t1/2(formation) of 29.0 (range 5.6-99.5) min and t1/2 (elimination of 123.2 (range 32-265) min, respectively. The lactone was the predominate form during the first hour from the start of infusion, but was rapidly converted into its ring-opened structure. The elimination rate of topotecan was independent of the dose. There were linear relationships between the dose (mg m-2 day-1), the area under the plasma concentration versus time curve (AUC) of topotecan and its metabolite, the total AUC, peak plasma lactone concentrations, and the time period that the topotecan concentrations remained above 10 nM. Different models were used to correlate pharmacokinetic and pharmacodynamic parameters. The percentage decrease in absolute neutrophil count (ANC) was related to these parameters and plots were well fitted by linear and sigmoidal Emax models.

Trace elements in the human environment: Problems and risks

Early studies on the possible influences of environmental geochemistry and health were concerned with major diseases such as cancer or multiple sclerosis. They were generally confined to simple comparisons of geochemical and epidemiological maps and corresponding rural areas. Subsequently, studies of dental health produced evidence for the roles of environmental fluoride, selenium, molybdenum and lead in the aetiology of caries. In recent decades lead has been closely studied. Most people in the western world live in urban areas, rather than rural areas, and research on lead has yielded much information on the distribution of the element in streets, parks and gardens of cities and in the home environment. The role of lead in human health has thereby been better understood. Cadmium, selenium and aluminium are good candidates for future study but success will depend on applying appropriate methods of investigation and here the experiences from research on lead are a valuable model to follow.

Leaded windows as a source of lead within homes

Corrosion of 'cames', i.e., the lead binding or decorative strips in leaded windows, is a significant, but previously unreported source of lead within older homes. Surfaces close to the leaded windows are highly contaminated with lead but the content of lead in dust diminishes rapidly within the first 2 m away from the window and is minimal after 3 m. The dust near the window was identified, using X-ray diffraction, as mainly composed of basic lead carbonate. Condensation water on leaded windows contains appreciable lead whereas for unleaded windows it is negligible. The exterior surface of unleaded windows contains more lead than the interior surface but the converse is true for leaded windows. A laboratory simulation suggested that corrosion by window condensate was likely to be the principal mechanism by which lead entered the home environment.

Heavy metals in soils in north Somerset, England, with special reference to contamination from base metal mining in the Mendips

A 2 × 2 km grid survey of surface soils was conducted over 600 km of North Somerset, England, to investigate the role of pollution from former base metai mines on soil heavy metal content. Soil contents of Pb, Zn, Cu and Cd were determined by atomic absorption spectrometry after extraction in hot, concentrated nitric acid. Most of the soils were contaminated by lead, zinc and cadmium. Isoline maps and perspective block diagrams showed this contamination to be most severe on the Mendip plateau, especially in the vicinity of Shipham, Wells and Priddy districts. Resurgences, polluted from mine drainage, also contaminated soils at the base of the Mendip slopes and, over the lowlands, trace element enriched Liassic shales caused significant local anomalies.

Temocillin: lymph penetration and protein binding

Temocillin, a novel betalactam antibiotic, was administered in doses of 1,2 and 4 g i.v. to 12 healthy subjects and the plasma concentrations of free and protein bound temocillin assayed and protein binding parameters were calculated. In a second study 2 g of temocillin was administered i.v. to 12 healthy subjects and samples of lymph were collected and assayed for total temocillin. Using the protein binding parameters so obtained the corresponding free temocillin in lymph was calculated. The clinical significance of the lymph penetration is discussed.

Data handling and pattern recognition for metal contaminated soils

In the laboratory sciences good experimental design minimises the effects of any disturbing variables so that hypotheses are amenable to to relatively unambiguous testing. But in the field sciences such variables cannot be controlled and data are inherently variable. Subsequent hypothesis testing must rely on a careful statistical interpretation of noisy data. This paper describes one systematic approach to interpreting the results from surveys of metal contaminated soils. Since contaminating metals are also present naturally in soil, anthropogenic excesses are recognised through statistical tests on the data. The nature of pollution processes also leads to the generation of distinct spatial patterns which may be evaluated through appropriate computergraphic techniques.

Pharmacokinetics of amoxycillin and clavulanic acid in haemodialysis patients following intravenous administration of Augmentin

1. Serum concentrations of amoxycillin and clavulanic acid were measured in patients with end-stage renal disease (ESRD) following intravenous administration of 1.2 g Augmentin. Augmentin was administered on a non-dialysis day and 2 h prior to a 4 h dialysis session. 2. The mean values of total serum clearance, mean residence time, volume of distribution at steady state, and terminal half-life for amoxycillin on the non-dialysis day were 14.4 ml min-1, 19.2 h, 14.9 l and 13.6 h, respectively. 3. The mean values of dialysis clearance, total serum clearance during dialysis, fractional drug removal during haemodialysis and half-life during dialysis for amoxycillin were 77.1 ml min-1, 91.5 ml min-1, 0.64 and 2.30 h, respectively. 4. The mean values of total serum clearance, mean residence time, volume of distribution at steady state, and terminal half-life for clavulanic acid on the non-dialysis day were 43.6 ml min-1, 4.4 h, 11.0 l and 3.05 h, respectively. 5. The mean values of dialysis clearance, total serum clearance during dialysis, fractional drug removal during haemodialysis and half-life during dialysis for clavulanic acid were 92.8 ml min-1, 136 ml min-1, 0.65 and 1.19 h, respectively. 6. The total serum clearance on the non-dialysis day, which represents non-renal clearance, was lower than that in normal subjects for both amoxycillin and clavulanic acid. These data would suggest some degree of hepatic impairment in patients with ESRD.(ABSTRACT TRUNCATED AT 250 WORDS)

On the absorption of clavulanic acid

It was not possible to computer fit oral clavulanic acid data using exponential or model equations incorporating a single exponential defining the absorption phase. Using the Loo-Riegelman method three phases of the absorption process became apparent, an initial slow phase, a more rapid phase and a final slow phase, contributing approximately 20, 70, and 5%, respectively, to the overall absorption process. Statistical moment analysis of clavulanic acid data following intravenous and oral solution administration gave mean values for the mean residence time, mean absorption time, and volume of distribution steady-state of 56 min, 43 min, and 14.01, respectively. Weibull analysis of the oral solution data gave mean values for lag-time and mean absorption time of 8 min and 46.8 min, respectively. Administration of clavulanic acid in a capsule formulation increased the lag-time before absorption but had no significant effect on the mean absorption time.

The epidemiology of dental caries in relation to environmental trace elements

This paper reviews the influence of the geochemical environment on the epidemiology of human dental caries. The best documented association is that between water borne fluoride and reduced caries prevalence. The influence of fluoride was first reported during the early decades of this century in Colorado, USA, and led to the fluoridation of some public water supplies in several countries. In all cases, fluoridation has been followed by significant improvements in dental health and no adverse effects in general health. Other trace elements in food and water have now been linked with dental caries. Molybdenum has been associated with reduced caries prevalence whereas selenium and lead appear to have adverse effects. Cavity formation in teeth probably involves a localised dissolution of the enamel surface by the products of bacterial activity. It is possible that the incorporation of trace metals into the apatite microcrystals of enamel may alter their physical properties, especially solubility, and hence their susceptibility to degradation.

The disposition of clavulanic acid in man

Following oral administration of potassium 14C-clavulanate to four human subjects, at least 73% of the radioactive dose was absorbed. The mean absolute bioavailability was 64%. Absorption was rapid with peak plasma concentrations of radioactivity and clavulanic acid (2-6 micrograms/ml) occurring between 45 min and three hours after dosing. Values for the volume of distribution at steady-state and terminal half-life of clavulanic acid in the plasma were 12.01 and 0.8 h respectively. Following intravenous administration of clavulanic acid to the same subjects, the clearance, and volume of distribution at steady-state were 0.21 l/min, and 12.01, respectively. Clavulanic acid was the major radioactive component present in 0-24 h urine following oral dosing (23% of the dose). The two major metabolites were 2,5-dihydro-4-(2-hydroxyethyl)-5-oxo-1H-pyrrole-3-carboxylic acid (15% of the dose) and 1-amino-4-hydroxybutan-2-one (8.8% of the dose). Clavulanic acid and 1-amino-4-hydroxybutan-2-one were the major components in plasma following oral administration (52 and 21% of plasma radioactivity respectively at two hours after dosing). The major route of excretion of radioactivity following oral administration was via the urine (73% of the dose). Most of this radioactivity was excreted in the first 24 h after dosing (68% of the dose). The renal clearance of clavulanic acid was 0.1 l/min. Elimination of radioactivity also occurred via the expired air (17% of the dose) and the faeces (8% of the dose).

Pharmacokinetics of parenteral ticarcillin formulated with clavulanic acid: Timentin

The pharmacokinetics of a formulation of clavulanate potentiated ticarcillin (Timentin) have been investigated following a bolus intravenous injection of 1.2 g, infusions of 3.2 g over periods ranging from 30 minutes to three hours, and a bolus dose of 1.2 g followed by an infusion of 3.2 g. The effect of probenecid has also been investigated. The serum levels of clavulanic acid are discussed in relation to the microbiology and therapeutic implications.

Displacement of bilirubin from cord serum by sulphadimethoxine, amoxycillin, clavulanic acid in combination with either amoxycillin or ticarcillin, temocillin and cloxacillin

The displacement of bilirubin from its binding sites in cord serum by sulphadimethoxine and various penicillins was studied using Sephadex gel filtration. Sulphadimethoxine displaced bilirubin at concentrations well within the normal therapeutic range of sulphonamide concentrations. Amoxycillin, clavulanic acid in combination with either amoxycillin or ticarcillin, temocillin and cloxacillin displaced bilirubin at concentrations much higher than those found clinically. It was concluded that the primary binding site/s of sulphadimethoxine and the secondary binding site/s of the penicillins were at or near the primary bilirubin binding site.

Lead levels on traffic-less islands

Surveys were conducted on three traffic-less islands: Tory and Aran, off the coast of Ireland, and Sark, one of the Channel Islands off the coast of France. Identical methods were used in surveys in three other areas, all of which have heavy gasoline driven traffic. These were Jersey, another of the Channel Islands, Ebbw Vale--a mixed industrial area, and Cardiff--the capital city of Wales. Environmental lead levels were very low in two of the traffic-less islands, but on the third, house dust lead levels were comparable with levels found throughout Wales. Blood lead levels on one of the islands were similar to those which have been reported for unaccultured remote tribes, but on the other two traffic-less islands blood lead levels were comparable with those of areas on the mainland of Wales.

Bioavailability and pharmacokinetics of clavulanic acid in healthy subjects

The bioavailability and pharmacokinetics of clavulanic acid were studied following oral solution and rapid intravenous administration to healthy volunteers. Plasma and urine samples were collected at frequent intervals following dose administration and were assayed for clavulanic acid by an enzyme inhibition method. Plasma data after intravenous administration were subjected to pharmacokinetic analysis using a two-compartment open model. The mean absolute bioavailability of clavulanic acid from oral solution was 0.75, derived from both urine and plasma data. No changes in the disposition pharmacokinetics of clavulanic acid with route were found, with a mean renal clearance of 0.1051 X min-1 and mean terminal elimination rate constant of 0.0134 min-1.

Greater contribution to blood lead from water than from air

Concern about the levels of lead in blood is widespread. There is uncertainty, however, about the relative importance of the various environmental sources. Lead in petrol is widely assumed to be one of the most important sources and air and dust have been identified as the main routes to man. Water is regarded as an important source in areas with a plumbosolvent water supply, but of little or no importance in other areas. In order to evaluate the contribution to blood lead by various environmental sources, we have conducted surveys of random samples of women in areas of Wales chosen to represent very different levels of exposure to traffic. We report here that lead in air makes a small, but significant, contribution to blood lead but there is no evidence of any contribution from dust. Although in none of the areas were high levels of lead detected in water, water emerges as an important contributor to blood lead.

Vegetable consumption and blood lead concentrations

Women resident in an area heavily contaminated by spoil from old lead mining have blood lead concentrations that are about 50% higher (p less than 0.001) than those of women living in a "control" area some distance away. Blood lead concentrations were related to the consumption of home grown produce. Those with the highest consumptions had blood lead concentrations that were 28% higher (p less than 0.001) than those of women who consumed no locally grown vegetables. Nevertheless, in the total population in the area this effect seemed likely to account for only about 5% of the population mean blood lead concentration. The data suggested that an increase in soil lead of 1000 micrograms/g is associated with an increase in blood lead of about 0.20 microM/1 (4.2 micrograms/dl).

Relation between pica and blood lead in areas of differing lead exposure

Surveys were conducted in four areas in Wales with differing degrees of environmental lead. In two areas the source of the lead was traffic and in one it was spoil from lead mining in the past. The fourth area, which served as a control, was a village remote from heavy traffic, industry, and lead mining. Various environmental samples were taken, and children aged 1-3 years and their mothers were studied. Blood lead concentrations were raised in the lead mining area, and within the areas defined by traffic flow the blood lead concentrations of the mothers showed a gradient. Pica in the children, assessed by a questionnaire, showed no relation with blood lead, but the amount of lead removed from the children's hands with 'wet wipes' was an important contributor to blood lead concentrations.

The contribution of heavy metals in potato peel to dietary intake

For potatoes grown in soil contaminated by Pb/Zn smelter smoke it was observed that Cd and Pb accumulated in the peel. When potatoes are baked both skin and tuber may be eaten. From an investigation of the relative contributions of peel and tuber to diet it was concluded that normally when both are eaten together there is no risk to health from ingesting excess of toxic metals.

Pharmacokinetics of ticarcillin in man

The excretion of radioactivity has been investigated in 3 healthy volunteers following rapid intravenous administration of 5 g of [35S]-ticarcillin. The radioactive dose was rapidly and completely excreted, since within 4 days 98.5% was recovered, 95% in the urine and 3.5% in faeces. All the urine radioactivity was accounted for as ticarcillin and its penicilloic acid. Plasma and urine samples collected from the volunteers at frequent intervals during the first 6 h of the experiment were assayed for penicillin by an automated chemical method and also for radioactivity. The results obtained by the chemical autoanalyser method were in excellent agreement with the plasma levels of radioactivity. From the data it was possible to calculate the renal clearance of the penicillin, a mean value of 104 ml/min was observed in the 3 volunteers. A further three volunteers were dosed intravenously with a 5 g bolus of non-radiolabelled ticarcillin in a cross-over study with and without predosing with probenecid. Serum samples were analysed by the chemical method for penicillin and the data subjected to pharmacokinetic analysis using a two compartment open model. The results indicate a shift of the distribution equilibrium of ticarcillin from the serum into the peripheral compartment after predosing with probenecid. Furthermore, the mean half-life of ticarcillin in the serum of the three volunteers was significantly increased from 1.3 h to 2.1 h by predosing with probenecid.