Sea to land transfer of anthropogenic radionuclides to the North Wales coast, Part I: external gamma radiation and radionuclide concentrations in intertidal sediments, soil and air

Previous projects specifically aimed at performing radiological assessments in the vicinity of North Wales, investigating the presence and transfer of radionuclides from sea to land, were in 1986 and 1989. Since then, changes have occurred in the radioactive discharges from the British Nuclear Group Sellafield site. Annual discharges of (137)Cs, (238)Pu, (239,340)Pu and (241)Am have decreased markedly whereas, up until recent years, discharges of (99)Tc have increased. It is therefore desirable to quantify current transfer processes of radionuclides in the North Wales region and thus provide an update on 15-year-old studies. A field campaign was conducted collecting soil samples from 10 inland transects and air particulates on air filters from three High Volume Air Samplers, along the northern coast of Wales at Amlwch, Bangor Pier and Flint. Complementary field data relating to external gamma dose rates were collected at the soil sites. The field data generated for (137)Cs, (238)Pu, (239,340)Pu and (241)Am were consistent with what had been reported 15 years previously. Therefore, there has been no increase in the supply of these Sellafield-derived radionuclides to the terrestrial environment of the North Wales coast. The (99)Tc data in sediments were consistent with reported values within annual monitoring programmes, however, a relatively high activity concentration was measured in one sediment sample. This site was further investigated to determine the reason why such a high value was found. At present there is no clear evidence as to why this elevated concentration should be present, but the role of seaweed and its capacity in accumulating (99)Tc and transferring it to sediment is of interest. The analysis of the field samples for (99)Tc, (137)Cs, (238)Pu, (239,240)Pu and (241)Am has provided a data set that can be used for the modelling of the transfer of anthropogenic radionuclides from sea to land and its subsequent radiological implications and is reported in an accompanying paper.

Sea to land transfer of anthropogenic radionuclides to the North Wales coast, Part II: aerial modelling and radiological assessment

Modelling calculations have been performed to predict the radiological impact of the sea to land transfer pathway to members of the public in North Wales from 1952 to 2004. The radionuclides of interest were (99)Tc, (137)Cs, (239,240)Pu and (241)Am and the exposure routes considered were food consumption, external and inhalation. The consumption of locally grown terrestrial food in the early to mid 1980s was the most significant source of exposure to all of the groups considered, with (239,240)Pu being the radionuclide contributing most to the dose. A maximum dose of 1.46microSvy(-1) was calculated for adult members of the critical consumption group in 1985, with doses for 2004 reducing to 0.59microSvy(-1). Despite the conservative approach of the dose calculations, the dose rate values are very low, less than 0.15% of the annual limit of 1000microSvy(-1) for the UK public from controlled radiation sources (excluding medical).

Allometric methodology for the calculation of biokinetic parameters for marine biota

Biological half-lives of elimination (T(B1/2)) and concentration factors (CF) for different radionuclides and marine organisms were analysed. Tests were carried out in order to investigate the cases in which these parameters can be described by a simple power equation as a function of the volume of the organism, to verify the hypothesis of allometric scaling. Statistically significant trends were found for the CF of plutonium and americium and the T(B1/2) of technetium and radiocaesium across organisms. Some of these trends satisfy the theoretical expectation that allometric relations are a power function of the volume of the organism. For the CF, which relates to retention of a radionuclide, the mean exponent of the power function, -0.29+/-0.02, is close to the theoretical value of -0.25. For the T(B1/2) the mean exponent of the power function is lower at 0.16+/-0.01. The work improves the understanding of the metabolism of radionuclides within organisms for which no direct biokinetic information exists. The allometric relationships derived can be applied to calculate a T(B1/2) for caesium or technetium and a CF for plutonium and americium for any marine species. For the elements N, K, Np and Cm, the same allometric relationships as those derived for their analogues (99)Tc, (137)Cs, (239,240)Pu and (241)Am, respectively, can be applied, when no other data are available.

Ethnic-specific distribution of mutations in 716 patients with congenital adrenal hyperplasia owing to 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21OHD) occurs worldwide. The most common mutations in the CYP21A2 gene in 716 unrelated patients were analyzed and the mutations were grouped by ethnicity, as defined through self-declaration corroborated by review of pedigrees extending to two or three generations. Prevalent allelic mutations and genotypes were found to vary significantly among ethnic groups, and the predominance of the prevalent mutations and genotypes in several of these populations was significant. There are ethnic-specific mutations in the CYP21A2 gene. A large deletion is prevalent in the Anglo-Saxons; a V281L (1685 G to T) mutation is prevalent in Ashkenazi Jews; an R356W (2109 G to A) mutation is prevalent in the Croatians; an IVS2 AS -13 (A/C to G) mutation is prevalent in the Iranians and Yupik-speaking Eskimos of Western Alaska; and a Q318X (1994 C to T) mutation is prevalent in East Indians. Genotype/phenotype non-correlation was seen when at least one IVS2 AS -13 (A/C to G) mutation in the CYP21A2 gene was present.

Aldosterone-to-renin ratio as a marker for disease severity in 21-hydroxylase deficiency congenital adrenal hyperplasia

CONTEXT

Congenital adrenal hyperplasia (CAH) owing to 21-hydroxylase deficiency (21 OHD) is classified clinically in decreasing order of severity into salt-wasting, simple-virilizing, and nonclassical forms. Causative mutations in the CYP21A2 gene dictate the degrees of adrenal enzyme defect. Salt-wasting crises due to aldosterone deficiency are clinically apparent in the salt-wasting form but not in other forms of 21 OHD.

OBJECTIVES

This study examined the ratio of serum aldosterone to plasma renin activity as an index of sodium wasting in patients with 21 OHD CAH, heterozygotes, and normal individuals.

DESIGN

This was a cross-sectional, retrospective, noninterventional study.

PATIENTS AND OTHER PARTICIPANTS

A total of 402 individuals were included: 224 patients affected with 21 OHD CAH and 178 unaffected subjects. Classification into each diagnostic group was made primarily on the basis of clinical and hormonal features. Affected or unaffected status was confirmed by genotype of CYP21A2. All subjects were on ad lib diets without restrictions. Salt-wasting status was examined by sodium deprivation testing in 32 salt-wasting subjects and 14 simple virilizing subjects.

RESULTS

The ratio of serum aldosterone to plasma renin activity was found to discriminate well between the different groups of disease severity. The lowest ratios, indicative of the least sodium conservation, were seen in the salt-wasting group with increasing ratios in the simple virilizing, nonclassical, and unaffected groups. This ratio remained stable with age.

CONCLUSION

The ratio of serum aldosterone to plasma renin activity provides a simple index to compare groups of patients with varying degrees of 21 OHD.

Uptake and depuration of 131I from labelled diatoms (Skeletonema costatum) to the edible periwinkle (Littorina littorea)

Uptake and depuration of (131)I into winkles through consumption of the diatom Skeletonema costatum is described. The work follows on from previous studies that investigated the uptake of iodine into winkles from seawater and seaweed. Incorporation of (131)I in S. costatum from labelled seawater followed linear first-order kinetics with an uptake half-time of 0.40 days. Iodine uptake in winkles from labelled S. costatum also followed linear first-order kinetics, with a calculated equilibrium concentration (C(infinity)) of 42Bqkg(-1) and a transfer factor (TF) of 1.1x10(-4) with respect to labelled diatom food. This TF is lower than that observed for uptake of (131)I in winkles from labelled seaweed. For the depuration stage, a biphasic sequence with biological half-lives of 1.3 and 255 days was determined. The first phase is biokinetically important, given that winkles can lose two-thirds of their activity during that period. This study shows that, whilst winkles can obtain radioactive iodine from phytoplankton consumption, they do not retain the majority of that activity for very long. Hence, compared with other exposure pathways, such as uptake from seawater and macroalgae, incorporation from phytoplankton is a relatively minor exposure route.

Relationship between susceptibility induced field inhomogeneities, restricted diffusion, and relaxation in sedimentary rocks

Low field relaxation and diffusion measurements have become essential tools to study the pore space of sedimentary rocks with important practical applications in the field of well logging and hydrocarbon extractions. Even at Larmor frequencies below 2 MHz, diffusion measurements are often affected noticeably by internal field inhomogeneities. These field inhomogeneities are induced by susceptibility contrast between the rock and the fluid and are evident in most sandstones. Using sets of two-dimensional diffusion-relaxation measurements in applied and internal gradients, we study in detail the correlation between the field inhomogeneities, restricted diffusion, and relaxation time in three rocks of different susceptibility. We find that in the sandstone cores, the field inhomogeneities in large pores can be described by a local gradient that scales inversely with relaxation time above 250 ms. At shorter relaxation times, the extracted internal gradients deviate from this scaling relationship and we observe a dependence on diffusion time. This demonstrates that in this case, the internal field has structure on a length scale of a few microns.

Two novel mutations found in a patient with 17alpha-hydroxylase enzyme deficiency

CONTEXT

Congenital adrenal hyperplasia resulting from 17alpha-hydroxylase deficiency (17OHD) is a rare disorder associated with hypertension.

SUBJECT AND METHODS

We describe a phenotypically and hormonally affected female patient with 17OHD. DNA sequencing of her CYP17 gene revealed a maternal heterozygous mutation in exon 2 (R125Q) and a paternal heterozygous mutation in exon 8 (R416H). These are novel mutations in the CYP17 gene that completely eliminate enzyme activity.

CONCLUSION

Identification of novel mutations in the CYP17 gene is vital in understanding the molecular mechanisms of its deficiency and in providing additional information about the structure and enzymatic functions of P450c17.

Effect of maternal facial oxygen on neonatal behavioural scores during elective Caesarean section with spinal anaesthesia

BACKGROUND AND OBJECTIVE

For many, the administration of additional oxygen to the women receiving regional anaesthesia for Caesarean section is traditional, but for others it is controversial because of doubts about its efficacy. The aim of our study was to determine if beneficial effects of maternal oxygen therapy on the fetus could be revealed using a neonatal behavioural scoring system.

METHODS

Sixty women with a normal singleton pregnancy beyond 36 weeks gestation, undergoing elective Caesarean section under spinal anaesthesia were randomized into two groups: Group 1 received air and oxygen mixture through a Hudson style face mask (FiO2 of 0.21-0.25). Group 2 received FiO2 of 0.40-0.60 through an identical Hudson style face mask. Neurologic Adaptive Capacity Score on all the infants within 5 min of birth and between 10 and 24 h after the Caesarean delivery was performed. Apgar score, umbilical venous blood oxygen tension and umbilical artery standardized base excess were recorded.

RESULTS

Initial Neurologic Adaptive Capacity Scores at birth in Groups 1 and 2 were 32.6 (SD 4.6) and 31.3 (SD 4.3), respectively. Latter scores were 36.0 (SD 3.0) and 36.5 (SD 1.9), respectively. Neither were statistically significant. There were no significant differences between the groups for any of the recorded variables.

CONCLUSIONS

Administering maternal oxygen using a standard commercial Hudson style face mask does not appear to significantly improve oxygen delivery to, nor does it influence acidosis or behavioural effects in, the normal neonate at elective Caesarean delivery with spinal anaesthesia.

Equivalent dose of ephedrine and phenylephrine in the prevention of post-spinal hypotension in Caesarean section

BACKGROUND

Comparative studies of ephedrine and phenylephrine in prevention of hypotension after spinal anaesthesia for Caesarean section have lacked a consensus on dose equivalence. The aim of this study was to determine the minimum vasopressor dose for each of these drugs to calculate the dose ratio for clinical equivalence in the prevention of hypotension.

METHODS

Patients with a normal singleton pregnancy beyond 36 weeks gestation undergoing elective Caesarean section under spinal anaesthesia were randomized into two groups. The first patient in Group A received 50 mg of ephedrine in saline 0.9% w/v, 500 ml, at 999 ml h(-1), the maximum rate possible on the pump and the first patient in Group B received 500 microg of phenylephrine in saline 0.9% w/v, 500 ml, at the same rate. The initial dose for dilution was an arbitrary choice. The dose of vasopressor in the saline bag for every subsequent patient was established by the efficacy of the dose in preventing hypotension in the previous patient according to the technique of up-down sequential allocation. Minimum vasopressor dose for each drug was determined according to the Dixon-Massey formula.

RESULTS

The minimum vasopressor dose in saline 500 ml was 532.9 microg (95% CI 506.0-559.8) for phenylephrine and 43.3 mg (95% CI 39.2-47.3) for ephedrine. The concentration needed for equivalence at an infusion rate of 999 ml h(-1) was 1.07 microg ml(-1) for phenylephrine and 86.66 microg ml(-1) for ephedrine. Mean (sd) dose used for phenylephrine was 496.45 (78.3) microg and for ephedrine 39.64 (6.33) mg.

CONCLUSION

This study demonstrates a potency ratio of 81.2 (95% CI 73.0-89.7) for equivalence between phenylephrine and ephedrine in prevention of hypotension after spinal anaesthesia for Caesarean section.

Validation and clinical application of a locus-specific polymerase chain reaction- and minisequencing-based assay for congenital adrenal hyperplasia (21-hydroxylase deficiency)

Congenital adrenal hyperplasia is an autosomal recessive disorder caused by defective adrenal steroid biosynthesis, resulting in reduced glucocorticoid and increased androgen production. The majority of cases are due to inactivation of the 21-hydroxylase gene (CYP21A2), most commonly caused by genomic rearrangements with the adjacent, highly homologous pseudogene CYP21A. The most common deletions and gene conversion events have been defined and are typically detected by Southern hybridization detection of CYP21 rearrangements and/or polymerase chain reaction (PCR). However, Southern hybridization is laborious, and allele-specific PCR results may be difficult to interpret. We have therefore developed a locus-specific, PCR-based, minisequencing method for detecting the 12 most common CYP21A2 mutations. We validated the assay using a panel of 20 previously genotyped samples obtained from individuals who collectively have a broad spectrum of mutations causing 21-hydroxylase deficiency. We also used 19 control samples having no CYP21 mutations. All validation samples were correctly typed, and we identified haplotypes that may be useful for clinical diagnosis. Results from 102 clinical samples demonstrate that this assay is a rapid, reliable, and robust method for locus-specific identification of mutations and is suitable for routine clinical use and prenatal diagnosis.

Monogenic low renin hypertension

Monogenic forms of low renin hypertension can now be identified in a large and heterogeneous family of hypertensive patients with highly specific etiologies and similar clinical manifestations. These include the following well-characterized disorders: apparent mineralocorticoid excess, Liddle's Syndrome, steroid 11beta-hydroxylase (11beta-OHD) and steroid 17-hydroxylase (17-OHD) deficiencies, glucocorticoid-remediable hyperaldosteronism (familial hyperaldosteronism type I), familial hyperaldosteronism type II, hypertension exacerbated by pregnancy and primary hyperaldosteronism (Conn's syndrome). The successful elucidation of specific DNA mutations in most of these conditions has emphasized the role of molecular genetics in hypertension, a field in which diagnosis can now be made on proven genetic evidence. The current knowledge of these genetic markers enables practitioners to make precise diagnoses, and to initiate specific therapy, in patients with these relatively uncommon but interesting and often treatable forms of hypertension.

Which patients spend more than 4 hours in the Accident and Emergency department?

OBJECTIVES

The NHS Plan has a target that no patient should spend longer than 4 hours in Accident and Emergency (A & E) by the end of 2004. The aim of this study is to describe the attendance characteristics of patients spending less than and more than 4 hours total time in A & E.

METHODS

Data were collected from 10 A & E departments in the West Midlands NHS region for the period 1 April 2001 to 31 March 2002. Patients were split into three groups; those spending less than 4 hours, between 4 and 8 hours and over 8 hours in A & E. The groups were compared in terms of their attendance characteristics, these being demography, temporal patterns, arrival mode and disposal. The data were also entered into a multinomial logistic regression using SPSS.

RESULTS

Overall, 83.0 per cent (range 76.7 - 94.0 per cent) of patients spent less than 4 hours in A & E ; 3.6% per cent (range 0.3-8.6 per cent) spent longer than 8 hours in A & E. The risk factors for spending over 4 hours in A & E were requiring admission, arriving by ambulance, arriving during the night, increasing age and higher levels of deprivation. Being admitted had the greatest effect on time spent in A & E, with a patient being 2.64 times more likely to spend 4-8 hours and 4.84 times more likely to spend over 8 hours in the department.

CONCLUSIONS

This study points to admission and service provision at night as factors leading to long periods in A & E. However, these results can only act as a guide as the problems are different in different Trusts and each should analyse their problem before taking action.

Update on the prenatal diagnosis and treatment of congenital adrenal hyperplasia due to 11beta-hydroxylase deficiency

11beta-Hydroxylase deficiency is a common form of congenital adrenal hyperplasia causing virilization of the female fetus and hypertension. DNA analysis of the gene (CYP11B1) encoding 11beta-hydroxylase has been reported previously to be effective in the prenatal diagnosis of one affected female fetus. In that case, prenatal treatment with dexamethasone resulted in normal female genitalia. We now report five new pregnancies that underwent prenatal diagnosis for 11beta-hydroxylase deficiency. In the first family, the proband is homozygous for a T318M mutation and all fetuses from four subsequent pregnancies are carriers. In a second family, the mother is homozygous for a A331V mutation and was started on dexamethasone, but identification of a homozygous normal fetus led to the discontinuation of treatment. In another family, the fetus was a male homozygous for R384Q and treatment was discontinued. Lastly, a novel G444D mutation in exon 8 was identified and proven to reduce 11beta-hydroxylase activity.

The natural history and genotype-phenotype nonconcordance of HLA identical siblings with the same mutations of the 21-hydroxylase gene

The correlation of genotype to phenotype in congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency has been investigated thoroughly since the mapping of the CYP21 gene to the short arm of chromosome 6. In most instances, it is possible to accurately predict the phenotype based on genoytpe; however, in a small number of patients, individuals with identical mutations demonstrate variable phenotypes. We report two HLA-identical brothers who represent a striking case of genotype-phenotype nonconcordance in CAH. Molecular genetic analysis showed both patients had mutations in intron 2 and exon 10 of CYP21. Both brothers underwent salt-deprivation tests at similar ages over three separate hospital admissions. Patient 1 was diagnosed with simple virilizing CAH and was able to maintain sodium balance during salt deprivation tests. Patient 2, 3 years younger, was diagnosed with salt-wasting CAH and was unable to maintain sodium balance but progressively increased his aldosterone secretion with age.

Uptake and depuration of 131I by the edible periwinkle Littorina littorea: uptake from seawater

Uptake and depuration experiments for the edible periwinkle Littorina littorea have been performed using 131I-labelled seawater. Throughout the experimental phase the winkles were fed on unlabelled Chondrus crispus. 131I concentrations in winkles during uptake followed linear first-order kinetics with an uptake half-time of 11 days, whereas for depuration a triphasic sequence with biological half-lives of 4, 23 and 56 days was determined. In general, iodine turnover in winkles via labelled seawater appears to be slower than observed for other molluscs (2-3 days). Most of the activity prior to and after depuration is found to be in the shell, with indications that shell and soft parts accumulate and depurate 131I at a similar rate. The operculum displays the highest specific activity of all fractions with a concentration factor of 750 l kg(-1). Concentration factors for whole winkle, shell, soft parts and digestive gland are in the order of 40-60 l kg(-1), higher than the IAEA recommended CF value for iodine in molluscs of 10 l kg(-1). The 131I CF in winkles is closer to that of the conservative radionuclides 99Tc and 137Cs than the CF of the particle reactive radionuclides (239,240)Pu and 241Am.

Uptake and depuration of 131I by the edible periwinkle Littorina littorea: uptake from labelled seaweed (Chondrus crispus)

Uptake and depuration experiments of (131)I from labelled seaweed (Chondrus crispus) by the edible periwinkle Littorina littorea have been performed. Radioiodine concentrations in winkles during uptake followed first-order kinetics with an uptake half-time of 1 day, and a calculated equilibrium concentration (C(infinity)) of 21 000 Bq kg(-1) resulting in a transfer factor of 0.07 with respect to the labelled seaweed used as food. For depuration, a biphasic sequence with biological half-lives of 1 and 24 days was determined. The results suggest that in general, iodine turnover in periwinkles is slower than observed for other molluscs (monophasic biological half-lives in the order of 2-3 days). Both environmental media, food and seawater, can be significant sources of radioiodine for the winkle.

Influence of material deprivation on hospital admissions for gynaecologic infections

This study was conducted to examine the relationship between age, material deprivation, and hospital admissions for selected gynaecologic infections in an English health region. Data from hospital episode statistics relating to hospital admissions for pelvic inflammatory disease (PID), infections of the uterus, and infections of the cervix, vagina, and vulva were obtained. Townsend deprivation scores (based on 1991 census data) were allocated by linking postcodes of cases to enumeration districts (EDs) and then assigning the EDs to appropriate quintiles of material deprivation. Both single variable and multivariable (Poisson regression) analyses were performed. For women with PID, the risk of hospitalisation increased with increasing deprivation (P<0.0001), and women in the most deprived quintile were at increased risk (relative risk [RR] 1.31; 95% confidence interval [95%CI] 1.24-1.39) for hospitalisation. Multivariable analysis identified an elevated risk of hospital admission in women aged 25-44 years for PID (RR 2.03; 95%CI 0.84-4.87) and infections of the cervix, vagina, and vulva (RR 1.47; 95%CI 1.16-1.87), and the incidence of both conditions increased significantly with age. In summary, the results obtained suggest that women from the most deprived areas are at greatest risk of hospitalisation for gynaecologic infections, particularly PID. Preventive measures together with earlier diagnostic, treatment, and referral procedures are required to reduce morbidity.

In vitro expression studies of a novel mutation delta299 in a patient affected with apparent mineralocorticoid excess

Apparent mineralocorticoid excess syndrome (AME) is an autosomal recessive disorder that results in low renin hypertension and other characteristic clinical features. Typical patients present with severe hypertension, hypokalemia, and undetectable aldosterone. Most patients also have low birth weight, failure to thrive, and nephrocalcinosis. The 11betahydroxysteroid dehydrogenase type 2 (11betaHSD2) defect is documented by demonstrating a failure to convert cortisol to cortisone. Here, we report a patient with typical phenotypic features of AME who does not carry any of the previously described mutations in the HSD11B2 gene. This female patient from a consanguineous Pakistani family presented at age 9 yr. She had a low birth weight compared with her siblings and presented with hypertension (225/120 mm Hg), low plasma renin activity, hypokalemic metabolic alkalosis, suppressed aldosterone, and bilateral nephrocalcinosis. Echocardiogram did not reveal left ventricular hypertrophy, and baseline ophthalmological evaluation did not demonstrate hypertensive retinopathy. However, at age 12 yr, she developed mild to moderate hypertensive retinopathy. Biochemical analysis showed an elevated urinary cortisol to cortisone metabolites ratio (tetrahydrocortisol and 5alpha-tetrahydrocortisol/tetrahydrocortisone) of 28 (normal, 0.66-2.44). She had a cortisol secretion rate of 0.43 mg/d (normal, 5-25 mg/d). Sequence analysis of the HSD11B2 gene revealed a novel homozygous delta299 mutation in exon 5. In vitro expression in Chinese hamster ovary cells revealed that this mutation resulted in no activity.

Nonclassic 21-hydroxylase deficiency in Croatia

This is the first report of nonclassic congenital adrenal hyperplasia due to 21-hydroxylase (21-OH) deficiency in Croatia in which the patients have been evaluated clinically, hormonally, and by molecular genetic analysis. Genetic analysis was performed on 18 Croatian patients with nonclassic CAH due to 21-OH deficiency using allele-specific PCR. ACTH stimulation testing and HLA typing were used to evaluate patients hormonally. Molecular genetic analysis revealed a variety of mutations in individuals with different clinical symptoms, including precocious pubarche, hirsutism, (dysmenorrhea, subfertility and clitoromegaly. Serum stimulated 17-hydroxyprogesterone (17-OHP) levels indicated that all patients fell within the acceptable range for nonclassic congenital adrenal hyperplasia. Clinical and genetic analysis confirmed nonclassic 21-OH deficiency in our Croatian sample of ten males and eight females. This study shows that genotype does not necessarily predict fertility status in our group of affected patients.

Hypertension and adrenal disorders

Adrenal disorders causing hypertension can be related to the dysfunction of either the adrenal cortex or the adrenal medulla. These disorders, including congenital adrenal hyperplasia (CAH), owing to 11B-hydroxylase deficiency and to 17alpha-hydroxylase deficiency; apparent mineralocorticoid excess; familial hyperaldosteronism type I; primary aldosteronism; Cushing's syndrome; and familial glucocorticoid resistance, primarily affect the adrenal cortex and cause low-renin hypertension. The classic disorder of the adrenal medulla resulting in hypertension is pheochromocytoma, although hypertension in obesity might also be associated with catecholamine secretion. In this review, we discuss these etiologies and the most recent advances in our knowledge of their pathophysiology, diagnosis, and treatment.

A novel semiquantitative polymerase chain reaction/enzyme digestion-based method for detection of large scale deletions/conversions of the CYP21 gene and mutation screening in Turkish families with 21-hydroxylase deficiency

21-Hydroxylase deficiency is a recessively inherited disorder resulting from mutations in the CYP21 gene. The CYP21 gene is located along with the CYP21P pseudogene in the human leukocyte antigen major histocompatibility complex region on chromosome 6. Molecular diagnosis is difficult due to the 98% similarity of CYP21 and CYP21P genes and the fact that almost all frequently reported mutations reside on the pseudogene. Allele-specific PCR for the 8 most frequently reported point mutations was performed in 31 Turkish families with at least a single 21-hydroxylase-deficient individual. The allele frequencies of the point mutations were as follows: P30L, 0%; IVS2 (AS,A/C-G,-13), 22.5%; G110delta8nt, 3.2%; I172N, 11.4%; exon 6 cluster (I236N, V237E, M239K), 3.2%; V281L, 0%; Q318X, 8%; and R356W, 9.6%. Large deletions and gene conversions were detected by Southern blot analysis, and the allele frequencies were 9.6% and 22.5%, respectively. Sequence analysis of the gene, performed on patients with only 1 mutated allele, revealed 2 missense mutations (R339H and P435S). A novel semiquantitative PCR/enzyme digestion-based method for the detection of large scale deletions/conversions of the gene was developed for routine diagnostic purposes, and its accuracy was shown by comparison with the results of Southern blot analysis.

Regional blockade for delivery in women with scoliosis or previous spinal surgery

We conducted a prospective observational study between 1992 and 2001 identifying obstetric patients with untreated or surgically corrected scoliosis or lumbar-sacral fusion surgery. The regional techniques for labour and delivery that were offered were epidural analgesia, combined spinal epidural anaesthesia (CSE), single shot spinal or continuous spinal anaesthesia (CSA) depending on the degree of scoliosis, previous surgery, cardio-respiratory compromise and planned mode of delivery. Forty women were included in the study, one woman with two separate deliveries, giving 41 cases for analysis. Twenty-four women presented in labour: 11 required no regional technique, seven received effective epidural analgesia and six received CSA. Seventeen women presented for elective caesarean delivery: two received a CSE technique, two received single shot spinal and 13 had CSA. From a total of 19 CSA techniques attempted sixteen catheters were successfully inserted and produced good analgesia or anaesthesia for vaginal or operative delivery in 12 women (63%). There was one case of post dural puncture headache following a CSA for labour and delivery. We discuss the choices available for regional anaesthetic techniques in scoliotic women and the relative merits of each.

A mixture model for population codes of Gabor filters

Population coding is a coding scheme which is ubiquitous in neural systems, and is also of more general use in coding stimuli, for example in vision problems. A population of responses to a stimulus can be used to represent not only the value of some variable in the environment, but a full probability distribution for that variable. The information is held in a distributed and encoded form, which may in some situations be more robust to noise and failures than conventional representations. Gabor filters are a popular choice for detecting edges in the visual field for several reasons. They are easily tuned for a variety of edge widths and orientations, and are considered a close model of the edge filters in the human visual system. In this paper, we consider population codes of Gabor filters with different orientations. A probabilistic model of Gabor filter responses is presented. Based on the analytically derived orientation tuning function and a parametric mixture model of the filter responses in the presence of local edge structure with single or multiple orientations a probability density function (pdf) of the local orientation in any point (x, y) can be extracted through a parameter estimation procedure. The resulting pdf of the local contour orientation captures not only angular information at edges, corners or T-junctions but also describes the certainty of the measurement which can be characterized in terms of the entropy of the individual mixture components.