A meta-analysis of the executive function components inhibition, shifting, and attention in intellectual disabilities

BACKGROUND

Executive function is a concept for higher-order cognitive functions, which have the role of controller and modulator of cognitive abilities. The consensus in the literature is that people with an intellectual disability perform significantly lower on executive function tasks than groups matched on chronological age. The comparison with groups matched on mental age is less clear. Therefore, the objective of this meta-analysis was to investigate to what extent executive function is impaired in people with intellectual disability compared with a typically developing control group matched on mental age. It was also investigated if the executive function component and intellectual disability aetiology moderated the effect.

METHODS

Eligibility criteria were participants with intellectual disability (IQ ≤ 75) without a dual diagnosis; a comparison group matched on mental age; executive function outcome reported in a group comparison study design with n ≥ 10. Working memory tasks and ratings of executive function were not included. The literature search yielded 6637 potentially interesting articles. Twenty-six studies (with 99 effect sizes) including 1395 participants were included in the quantitative synthesis.

RESULTS

A multilevel random-effects meta-analysis found that people with intellectual disability performed statistically significantly lower than the mental age-matched group on the executive function tasks, g = -0.34, 95% confidence interval = [-0.53, -0.16]. However, the heterogeneity between effect sizes was large. The intellectual disability aetiology moderator was significant, but it only reduced the heterogeneity marginally.

CONCLUSION

The overall conclusion is that individuals with an intellectual disability have more problems with executive function tasks than mental age-matched controls. Limitations are the large unexplained variance and the remarkably high number (69) of different tests that were used, which make more detailed conclusions problematic. This meta-analysis implies that future studies need to be of better quality, to have higher power, and to a higher degree use the same executive function tests.

OUP accepted manuscript

Objectives

Methods

Results

Conclusions

Search for Lepton Number and Flavor Violation in K^{+} and π^{0} Decays

Searches for the lepton number violating K^{+}→π^{-}μ^{+}e^{+} decay and the lepton flavor violating K^{+}→π^{+}μ^{-}e^{+} and π^{0}→μ^{-}e^{+} decays are reported using data collected by the NA62 experiment at CERN in 2017-2018. No evidence for these decays is found and upper limits of the branching ratios are obtained at 90% confidence level: B(K^{+}→π^{-}μ^{+}e^{+})<4.2×10^{-11}, B(K^{+}→π^{+}μ^{-}e^{+})<6.6×10^{-11} and B(π^{0}→μ^{-}e^{+})<3.2×10^{-10}. These results improve by 1 order of magnitude over previous results for these decay modes.

Cognitive abilities and life experience in everyday planning in adolescents with intellectual disabilities: Support for the difference model

BACKGROUND

The literature on planning ability in individuals with intellectual disability (ID) provides no clarity on whether their ability matches their mental age (MA) or not. Perhaps can planning experience explain the mixed results. The current study investigated to what extent cognitive abilities and life experience can explain everyday planning ability in individuals with ID and to what extent results from everyday planning tasks support the developmental or the difference model of ID.

METHOD

Planning tests, cognitive ability tasks and a self-rated life experience form were administered to 71 adolescents with ID and 62 children with a typical development matched on MA.

RESULTS

Adolescents with ID exhibited planning ability according to their MA. Regression analyses showed that the predictors of planning differed between the groups. The cognitive measures could predict planning in both groups, but life experience only contributed positively to planning in the MA group, whereas chronological age was negatively correlated with successful planning in the ID group.

CONCLUSIONS AND DISCUSSION

The results support the difference model of ID. When matched on MA, the individuals with ID will solve the planning task in a qualitatively different manner. Additionally, the participants with ID could not utilise their life experience when solving the planning task, contrary to the MA group. Practitioners should be aware that individuals with ID might need more everyday planning training throughout adolescence. To support adolescents with ID, practitioners may focus on supporting the individual's cognitive abilities rather than relying on their prior knowledge.

Construction and Performance Studies of Large Resistive Micromegas Quadruplets

In view of the use of Micromegas detectors for the upgrade of the ATLAS muon system, two detector quadruplets with an area of 0.3 m2 per plane serving as prototypes for future ATLAS chambers have been constructed. They are based on the resistive-strip technology and thus spark tolerant. The detectors were built in a modular way. The quadruplets consist of two double-sided readout panels and three support (or drift) panels equipped with the micromesh and the drift electrode. The panels are bolted together such that the detector can be opened and cleaned, if required. Two of the readout planes are equipped with readout strips inclined by 1.5 degree. In this talk, we present the results of detailed performance studies based on X-Ray and cosmic ray measurements as well as measurements with 855 MeV electrons at the MAMI accelerator. In particular, results on reconstruction efficiencies, track resolution and gain homogeneity is presented.

NA62 and NA48/2 results on search for Heavy Neutral Leptons

In this paper we present new results on upper limits for the search of Heavy Neutral Leptons (HNL) with data collected by NA48/2 (2003-2004), NA62-RK (2007) and NA62 (2015) CERN experiments. The data collected with different trigger configuration allow to search for both long and short living heavy neutrinos in the mass range below the kaon mass. In addition the status of the search for K+ → π+vv with the NA62 detector will be briefly presented.

Digital Support for Persons with Cognitive Impairment

Cognitive impairment may cause difficulties in planning and initiating daily activities, as well as remembering to do what is scheduled. This study investigates the effectiveness of an interactive web-based mobile reminder calendar that sends text messages to the users mobile phone as support in everyday life, for persons with cognitive impairment due to neurological injury/diagnoses. The study has a randomised controlled trail design with data collection at baseline and at follow-up sessions after two and four months. Data collection started in August 2016 and continues until December 2017. The interactive web-based mobile reminder calendar may give the needed support to remind the person and thus increase the ability to perform activities and to be independence in everyday life. Preliminary results will be presented regarding what effect the interactive web-based mobile reminder calendar have for the participants performance of everyday life activities as well as perceived quality of life.

Spatially valid data of atmospheric deposition of heavy metals and nitrogen derived by moss surveys for pollution risk assessments of ecosystems

For analysing element input into ecosystems and associated risks due to atmospheric deposition, element concentrations in moss provide complementary and time-integrated data at high spatial resolution every 5 years since 1990. The paper reviews (1) minimum sample sizes needed for reliable, statistical estimation of mean values at four different spatial scales (European and national level as well as landscape-specific level covering Europe and single countries); (2) trends of heavy metal (HM) and nitrogen (N) concentrations in moss in Europe (1990-2010); (3) correlations between concentrations of HM in moss and soil specimens collected across Norway (1990-2010); and (4) canopy drip-induced site-specific variation of N concentration in moss sampled in seven European countries (1990-2013). While the minimum sample sizes on the European and national level were achieved without exception, for some ecological land classes and elements, the coverage with sampling sites should be improved. The decline in emission and subsequent atmospheric deposition of HM across Europe has resulted in decreasing HM concentrations in moss between 1990 and 2010. In contrast, hardly any changes were observed for N in moss between 2005, when N was included into the survey for the first time, and 2010. In Norway, both, the moss and the soil survey data sets, were correlated, indicating a decrease of HM concentrations in moss and soil. At the site level, the average N deposition inside of forests was almost three times higher than the average N deposition outside of forests.

Updated stomatal flux and flux-effect models for wheat for quantifying effects of ozone on grain yield, grain mass and protein yield

Field measurements and open-top chamber experiments using nine current European winter wheat cultivars provided a data set that was used to revise and improve the parameterisation of a stomatal conductance model for wheat, including a revised value for maximum stomatal conductance and new functions for phenology and soil moisture. For the calculation of stomatal conductance for ozone a diffusivity ratio between O(3) and H(2)O in air of 0.663 was applied, based on a critical review of the literature. By applying the improved parameterisation for stomatal conductance, new flux-effect relationships for grain yield, grain mass and protein yield were developed for use in ozone risk assessments including effects on food security. An example of application of the flux model at the local scale in Germany shows that negative effects of ozone on wheat grain yield were likely each year and on protein yield in most years since the mid 1980s.

Lead exposure and biological effects in pied flycatchers (Ficedula hypoleuca) before and after the closure of a lead mine in northern Sweden

Mining activities affect the surrounding environment by increasing exposure to metals. In this study, metal accumulation and its effects on reproduction and health of pied flycatcher (Ficedula hypoleuca) nestlings were monitored before and up to five years after a lead mine and enrichment plant closed down. The lead concentration in moss, nestling blood, liver and feces all indicated decreased lead exposure by at least 31% after closure, although only blood lead decreased significantly. Although the birds responded fairly well to the changed atmospheric deposition (based on moss samples), concentrations were still higher compared with birds in a reference area, and breeding was affected at the mine (smaller clutches and higher mortality). Surviving nestlings suffered from lower hemoglobin levels, mean cell hemoglobin concentrations and inhibited delta-aminolevulinic acid dehydratase activity. Lead poisoning contributed to poor health and adverse reproductive effects, but other factors (e.g. increased parasitic load) probably also affected the birds.

Evidence for impacts of near-ambient ozone concentrations on vegetation in southern Sweden

Substantial impacts of near-ambient ozone concentrations on agricultural crops, trees, and seminatural vegetation are demonstrated for southern Sweden. Impacts of ambient ozone levels (2-15 microL L(-1) hr annual accumulated ozone exposure over a threshold of 40 nL L(-1) [AOT40]) range from a 2%-10% reduction for trees (e.g., leaf chlorophyll, tree growth) up to a 15% reduction for crops (e.g., yield, wheat/potato). Visible leaf injury on bioindicator plants caused by ambient ozone levels has been clearly demonstrated. The humid climatic conditions in Sweden promote high rates of leaf ozone uptake at a certain ozone concentration. This likely explains the comparatively large ozone impacts found for vegetation in southern Sweden at relatively low ozone concentrations in the air. It is important that the future methods used for the representation of ozone impacts on vegetation across Europe are based on the leaf ozone uptake concept and not on concentration-based exposure indices, such as AOT40.

Repetition of contaminating question types when children and youths with intellectual disabilities are interviewed

BACKGROUND

The present study examined the effects of repeating questions in interviews investigating the possible sexual abuse of children and youths who had a variety of intellectual disabilities. We predicted that the repetition of option-posing and suggestive questions would lead the suspected victims to change their responses, making it difficult to understand what actually happened. Inconsistency can be a key factor when assessing the reliability of witnesses.

MATERIALS

Case files and transcripts of investigative interviews with 33 children and youths who had a variety of intellectual disabilities were obtained from prosecutors in Sweden. The interviews involved 25 females and 9 males whose chronological ages were between 5.4 and 23.7 years when interviewed (M = 13.2 years).

RESULTS

Six per cent of the questions were repeated at least once. The repetition of focused questions raised doubts about the reports because the interviewees changed their answers 40% of the time.

CONCLUSIONS

Regardless of the witnesses' abilities, it is important to obtain reports that are as accurate and complete as possible in investigative interviews. Because this was a field study, we did not know which responses were accurate, but repetitions of potentially contaminating questions frequently led the interviewees to contradict their earlier answers. This means that the interviewers' behaviour diminished the usefulness of the witnesses' testimony.

Comparison of modelled and measured ozone concentrations and meteorology for a site in south-west Sweden: implications for ozone uptake calculations

Measurements of ground-level ozone concentrations and meteorology (temperature, vapour pressure deficit (VPD), solar radiation) at the monitoring site Ostad (south-west Sweden) were compared to data from the corresponding grid in the EMEP photo-oxidant model for 1997, 1999 and 2000. The influence of synoptic weather on the agreement between model and measurements was studied. Implications of differences between modelled and observed inputs for ozone flux calculations for wheat and potato were investigated. The EMEP model output of ozone, temperature and VPD correlated well with measurements during daytime. Deviations were larger during the night, especially in calm conditions, attributed to local climatological conditions at the monitoring site deviating from average conditions of the grid. These differences did not lead to significant differences in calculated ozone uptake, which was reproduced remarkably well. The uptake calculations were sensitive to errors in the ozone and temperature input data, especially when including a flux threshold.

What am I doing in Timbuktu: person-environment picture recognition for persons with intellectual disability

BACKGROUND

The aim of this study was to examine the effects of familiarity of depicted persons and environments in recognition of photographs for pupils with different degrees of intellectual disability (ID).

METHOD

Forty-five pupils with ID participated.

RESULTS

An interaction effect between the two variables, person and environment, was found in addition to main effects for both the variables. Pictures of the test person himself or herself in familiar environments were easier to recognize than in unfamiliar environments, whereas the opposite was found for pictures of other familiar persons. No interaction effects of degree of ID were found.

CONCLUSIONS

The interaction pattern is explained in terms of absent, present or implausible semantic associations between the person and the environmental context. The results are discussed in relation to augmentative and alternative communication with photographs.

Economic assessment of the negative impacts of ozone on crop yields and forest production. A case study of the estate Ostads Säteri in southwestern Sweden

Ground level ozone concentrations, in combination with the prevailing climate, at the estate Ostads Säteri in southwestern Sweden were estimated to reduce the yield of wheat and potato ranging between 5% and 10%. Occasionally, in years with the highest ozone concentrations and/or climatic conditions favoring high rates of ozone uptake to the leaves, yield loss levels above 10% may occur. Based on simple extrapolation, these ozone-induced reductions of crop yields at Ostads Säteri represent a potential total annual yield loss in Sweden in the range of 24.5 million Euro for wheat and 7.3 million Euro for potato, respectively. A simulation of forest growth at Ostad Säteri predicted that prevailing mean ozone exposure during 1993-2003 had the potential to reduce forest growth by 2.2% and the economic return of forest production by 2.6%. Using this value for extrapolation to the national level, the potential annual economic loss for Sweden due to negative impacts of ozone on forest production would be in the range of 56 million Euro (2004 prices).

The effects of tropospheric ozone and elevated carbon dioxide on potato (Solanum tuberosum L. cv. Bintje) growth and yield

An open-top chamber experiment with field grown potato (Solanum tuberosum L. cv. Bintje) was performed in the south-west of Sweden in 1998. The experiment was aimed to investigate individual and interactive impacts of elevated ozone (O(3)) and carbon dioxide (CO(2)) on potato growth and yield. Treatments were ambient and elevated CO(2) with or without the addition of 20 nmol mol(-1) O(3). In addition, plants were grown in ambient air plots. Plants grown in elevated CO(2) and O(3) had a reduced tuber yield, compared to control, by 2% and 8%, respectively. These effects were, however, not statistically significant. Elevated CO(2) caused a significantly larger number of tubers of lower average size, while elevated O(3) induced significantly lower tuber dry matter content. The number of tuber initials (tubers <15 mm) found at harvest was significantly lower in elevated O(3). Visible O(3) leaf injury appeared earlier and the number of yellow leaves 89 days after emergence was significantly larger in elevated O(3). In elevated CO(2), haulm dry weight was significantly (15%) lower at harvest and the haulm/tuber ratio was significantly reduced. There were significant interactive effects of O(3) and CO(2) on the final number of leaves and on stem height. Plants in elevated CO(2) reached final stem height earlier than in the other treatments. In summary, it was concluded: (a) that anticipated future O(3) levels are likely to have a negative impact on potato growth, although tuber yield effects may be hard to demonstrate experimentally in this plant due to large variation; (b) that whether any possible beneficial effect of elevated CO(2) on the magnitude of tuber yield will be expressed, depend on the climatic conditions prevailing; and (c) that potato growth responses to CO(2) and O(3) are not simply additive.

Clover as a tool for bioindication of phytotoxic ozone--5 years of experience from southern Sweden--consequences for the short-term critical levels

Critical levels (CLs) for ozone effects on plants in Europe have been defined within the UN-ECE Convention on Long-Range Transboundary Air Pollution, CLRTAP. The purpose of the short-term CLs is to ensure protection of all crops to acute ozone injury. The currently used CLs are based on the ozone exposure of the plants during daylight hours expressed as AOT40 (Accumulated exposure Over the Threshold 40 nmol mol(-1) ozone). The aims of this study were: to test the performance of the current short-term CLs, to test alternative ozone exposure indices and to test if changes in the ozone cut-off concentration, the inclusion of a lag-period (LP) between exposure and identification of visible ozone injury or the duration of the ozone integration period improved the performance of the exposure index. The analysis was based on 38 different datasets from experiments with subterranean clover, Trifolium subterraneum in southern Sweden. AOT indices generally performed better than averaged ozone concentrations or SUM (Sum of ozone concentrations when a threshold is exceeded) indices. Regression analysis showed that the current short-term CL, AOT40 with a VPD (water vapour pressure deficit) threshold of 1.5 kPa, explained 56% of the variation in visible injury. A longer exposure period and the introduction of a LP, admitting visible ozone injury time to develop after exposure, improved the performance of the exposure index. AOT30 accumulated over 10 days before harvest, excluding a LP of 3 days before injury observation, performed best and explained 88% of the variation in visible injury. AOT40 indices left a rather large amount of visible injury unexplained indicating that a lower cut-off concentration for ozone is preferable. The results of the investigation indicated that a visible injury threshold of 10% improved the distinction between harmful and less harmful exposure.

An ozone flux-response relationship for wheat

Six open-top chamber experiments with field-grown wheat Triticum aestivum L. (five with spring wheat and one with winter wheat) were combined to test which of the two ozone exposure indices, AOT40 and CFO(3), that provided the most consistent relationship between relative yield loss and ozone exposure. AOT40 is the accumulated exposure over a threshold ozone concentration of 40 nl l(-1), while CFO(3) is the cumulative flux of ozone (uptake) to the flag leaves. The ozone uptake of the flag leaves was estimated using a stomatal conductance model, sensitive to phenology, light, vapour pressure deficit (VPD) and temperature in combination with measurements of the boundary layer conductance in the open-top chambers. Both indices were calculated for the grain-filling period, defined as the time from anthesis until 2 weeks before harvest. The duration of the grain-filling period was shown to be closely related to the rate of accumulation of thermal time above a base temperature of 0 degrees C. The CFO(3) index provided a much more consistent pattern in terms of ozone effects compared to the AOT40 index. This was especially the case for spring wheat, for which a linear regression between relative yield and CFO(3) using all five data sets is presented. According to the stomatal conductance model, VPD limited daytime stomatal conductance in warm and dry years, while temperature was the most important limiting factor during daytime in cool and humid years. The effect of light was mainly to delimit the time period of the day during which substantial uptake of ozone took place. It is concluded that, compared to the AOT40 index, the more mechanistically relevant flux-based index CFO(3) will estimate larger yield loss in the relatively humid parts of western and northern Europe, while smaller yield loss will be estimated for the dry summer climates in south and central Europe. The use of an ozone flux threshold, similar to the cut-off concentration 40 nl l(-1) in AOT40, did not improve the performance of the CFO(3) index.

Limitations of a pencil beam approach to photon dose calculations in the head and neck region

The inherent limitations of a specific pencil beam model have been studied when applied to a cylindrical geometry simulating the neck region. A comparison is made between measured and calculated absorbed dose in a cylindrical phantom. The goal is to quantify the deviations in the absorbed dose level, i.e., the dose per monitor unit, when photons are used for the treatment of head and neck tumours. Square fields ranging from 5 x 5 up to 30 x 30 cm2 are studied for photon beam energies of 60Co, 4, 6 and 18 MV. Ionisation chamber measurements have been performed in the cylinder as well as in two other configurations in order to trace the origin of possible deviations. For 18 MV no significant deviations are found between measurement and calculation in the cylindrical configuration. For the lower energies, an overestimation of the calculated dose in the cylindrical configuration up to about 6% for a 20 x 20-cm2 60Co field has been found. These deviations have been traced to the basic approximation for the integration volume for phantom scatter calculations inherent in this pencil beam implementation.

Conversion of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 26-tetrol into 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestanoic acid by rabbit liver mitochondria

Rabbit liver mitochondria in the presence of NAD+ were found to catalyze the conversion of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 26-tetrol into 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestanoic acid. The peroxisomal fraction did not catalyze the reaction. Sonication of the mitochondria or dialysis overnight against a hypotonic buffer increased the rate of oxidation twofold. Most of the enzyme activity was recovered in the supernatant fraction after centrifugation at 100,000xg of sonicated mitochondria. 4-Heptylpyrazole, an inhibitor of cytosolic ethanol dehydrogenase, inhibited the mitochondrial formation of 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestanoic acid by 70%. Disulfiram, an inhibitor of cytosolic acetaldehyde dehydrogenase, did not inhibit the reaction. The role of the mitochondrial dehydrogenase system in bile acid biosynthesis is discussed.

Regulation of hydroxylations in biosynthesis of bile acids. Isolation of a protein from rat liver cytosol stimulating reconstituted cholesterol 7 alpha-hydroxylase activity

Modulation of cholesterol 7 alpha-hydroxylase activity was studied in a purified, reconstituted system from rat liver microsomes. Cysteine, dithiothreitol, reduced glutathione, and thioredoxin activated the system whereas glutathione disulfide inactivated it. A protein, which stimulated cholesterol 7 alpha-hydroxylase activity in the presence of glutathione or thioredoxin, was purified to apparent homogeneity from rat liver cytosol. It has a minimum Mr of 25,000. The protein had no effect on 12 alpha-hydroxylation of 7 alpha-hydroxy-4-cholesten-3-one or 25-hydroxylation of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol. The cholesterol 7 alpha-hydroxylase stimulatory protein could not be replaced by the thioltransferase-dependent disulfide-reducing system nor by glutathione S-transferase A, B, or C. Neither ATP and MgCl2 nor sodium fluoride had any effect on the activity of the cholesterol 7 alpha-hydroxylase stimulatory protein. The results show that purified cholesterol 7 alpha-hydroxylase can be regulated by a mechanism involving disulfide bonds in the cytochrome P-450 molecule.

Regulation of hydroxylations in biosynthesis of bile acids: modulation of reconstituted 12 alpha-hydroxylase activity by protein fractions from rabbit liver cytosol and microsomes

The activity of purified 12 alpha-hydroxylase from rabbit liver microsomes was modulated by including protein fractions from rabbit liver microsomes and cytosol into the system. The microsomal protein fraction stimulated 12 alpha-hydroxylation two times. The cytosolic fraction inhibited the reaction markedly. The microsomal 12 alpha-hydroxylase stimulatory activity was labile and the cytosolic 12 alpha-hydroxylase inhibitory activity was stable to mild heat treatment. Addition of ATP and MgCl2 or NaF had no effect on the activities of the two protein fractions. The activity of the microsomal stimulatory fraction decreased upon storage but could be reactivated by addition of reduced glutathione to the system.

Bile acid synthesis in humans

Metabolic pathways involved in the conversion of cholesterol to cholic and chenodeoxycholic acids have been investigated in bile fistula patients treated with a number of labeled potential bile acid intermediates. The findings of the present report indicate that the human liver cell has the capacity to synthesize both primary bile acids via multiple routes from cholesterol and 7 alpha-hydroxycholesterol. Evidence has been obtained for the existence of a major pathway to chenodeoxycholic acid via the 26-hydroxylation of 7 alpha-hydroxycholest-4-en-3-one. Cholic acid is synthesized preferentially via pathways from 5 beta-cholestane 3 alpha, 7 alpha-diol and a pathway from cholesterol not involving an initial 7 alpha-hydroxylation.

A quantitative evaluation of the conversion of 25-hydroxycholesterol to bile acids in man

The present study was directed toward providing additional information in man on the nature of a potential alternative pathway to cholic acid not involving an initial 7 alpha-hydroxylation of cholesterol. Two bile fistula patients and one normal subject each received 25-hydroxy[G-3H]cholesterol; [14C]cholic and [14C]chenodeoxycholic acids were also simultaneously administered to one bile fistula patient and normal subject. The labeled 25-hydroxycholesterol was found to be poorly converted to primary bile acids by all three patients; the range of conversion was 9.7 to 18.9%. Cholic acid was favored over chenodeoxycholic acid by a margin of about 1.4/1. It is concluded that a pathway to primary bile acid via the 25-hydroxylation of cholesterol is of minor importance under conditions of normal or accelerated synthesis in man.

Biosynthesis of bile acids in man. An in vivo evaluation of the conversion of R and S 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestanoic and 3 alpha, 7 alpha, 12 alpha-24 xi-tetrahydroxy-5 beta-cholestanoic acids to cholic acid

In vivo studies were carried out on three bile fistula patients to further elucidate the side chain oxidation pathways from C-27 bile acids to cholic acid in man. Two patients each received (25-R)- and (25-S)-3 alpha, 7 alpha,-12 alpha-trihydroxy-5 beta-[7 beta-3H]cholestanoic acid (THCA) on consecutive days and three patients wee administered 3 alpha, 7 alpha, 12 alhpa, 24 xi-tetrahydroxy-5 beta-[7 beta-3H]cholestanoic acid (varanic acid). The varanic acid was biosynthetically prepared with rat liver microsomes and was probably the 24 alpha isomer. The patients efficiently (84 to 97%) converted both (R)- and (S)-THCA to cholic acid. There was no apparent significant difference in the ability of either (R)- or (S)-THCA to form cholic acid. Varanic acid was poorly converted (20 to 27%) to cholic acid in all three patients. From 49 to 75% of the administered 3H activity was recovered in the bile as other labeled products. The bulk (30 to 35%) of this 3H activity was identified by thin layer chromatography as varanic acid. The rate of conversion of (R)-THCA, (S)-THCA, and varanic acid was extremely rapid in all three patients with a t 1/2 of 35 to 74 min. The findings suggest that (a) the stereospecific configuration at C-25 of THCA has no significant effect on the efficiency of side chain oxidation to cholic acid; and (b) side chain cleavage pathways may exist which do not pass through varanic acid, or the oxidation of varanic acid in man is highly stereospecific with respect to the hydroxyl group at C-24. To prove the latter, it will be necessary to compare the metabolism of the 24 alpha and 24 beta isomers of varanic acid.

An in vivo evaluation of the quantitative significance of several potential pathways to cholic and chenodeoxycholic acids from cholesterol in man

The present study was designed to obtain more definitive information in man on the metabolic pathways to chenodeoxycholic acid and to cholic acid via a pathway not involving an initial 7 alpha-hydroxylation of cholesterol. Four bile fistula patients were administered consecutively two or more of the following 3H-labeled bile acid intermediates: 7 alpha-hydroxycholesterol, 7 alpha-hydroxy-4-cholesten-3-one, 5 beta-cholestane 3 alpha,7 alpha,26-triol, 26-hydroxycholesterol,7 alpha,26-dihydroxy-4-cholesten-3-one, and 5-cholestene-3 beta,12 alpha-diol. Both 7 alpha-hydroxy[7 beta-3H]cholesterol and 7 alpha-hydroxy-4-[6 beta-3H]cholesten-3-one were efficiently converted to bile acids and preferred chenodeoxycholic acid over cholic acid. The specific activity time curves indicated that a portion of cholic acid synthesis did not pass through 7 alpha-hydroxycholesterol. [3H]26-Hydroxycholesterol and [3H]-5-cholestene 3 beta,12 alpha-diol, two potential intermediates of this bypass pathway to cholic acid, were poorly converted to primary bile acids (10 to 27%). The [3H]26-hydroxycholesterol preferred chenodeoxycholic over cholic acid by about 4 to 1. The [3H]5-cholestene 3 beta,12 alpha-diol formed cholic acid in low yield (10 to 20%). It is concluded that pathways to primary acids from cholesterol through 26-hydroxycholesterol and 5-cholestene 3 beta,12 alpha-diol are probably of minor quantitative significance. A selective pathway to chenodeoxycholic acid via 26-hydroxylation of 7 alpha-hydroxy-4-cholesten-3-one was also investigated. The 5 beta-cholestane 3 alpha,7 alpha,26-triol was converted in about equal amounts to cholic and chenodeoxycholic acids. The 7 alpha-hydroxy-4-cholesten-3-one was also efficiently converted to both bile acids but preferred chemodeoxycholic acid. The most efficient precursor of chenodeoxycholic acid was 7 alpha,26-dihydroxy-4-cholesten-3-one, which was efficiently converted to primary bile acids; chenodeoxycholic acid was preferred over cholic acid by approximately 7 to 1. These findings suggest the presence of a major pathway to chenodeoxycholic acid via the 26-hydroxylation of 7 alpha-hydroxy-4-cholesten-3-one and intermediate formation of 7 alpha,26-dihydroxy-4-cholesten-3-one.

Side chain hydroxylations in biosynthesis of cholic acid. 25- and 26-Hydroxylation of 5beta-cholestane-3alpha, 7alpha, 12alpha-triol by reconstituted systems from rat liver microsomes

25- and 26-Hydroxylation of 5beta-cholestane-3alpha, 7alpha, 12alpha-triol was studied with reconstituted systems from rat liver microsomes consisting of partially purified cytochrome P -450, NADPH-cytochrome P -450 reductase, a phospholipid, and an NADPH -generating system. Cytochrome P -450 was prepared either by sodium cholate treatment and ammonium sulfate fractionation or by subtilisin and sodium deoxycholate treatment followed by DEAE-cellulose chromatography. No side chain hydroxylation was observed when cytochrome P-450 was omitted. With ammonium sulfate-fractionated cytochrome P-450 25- and 26-hydroxylation was stimulated 5- to 8-fold by addition of NADPH-cytochrome P-450 reductase. With subtilisin-treated cytochrome P-450 an almost absolute requirement for NADPH-cytochrome P-450 reductase was observed. Omission of lipid did not reduce the rate of hydroxylation. Centrifugation of the cytochrome P-450 preparation at 100,000 X g for 1 hour just before incubation increased markedly lipid dependency. A significant difference between 25- and 26-hydroxylation was observed with respect to substrate saturation. The stimulatory effect of phenobarbital treatment on 25-hydroxylation and the inhibitory effect of this treatment on 26-hydroxylation were associated with the cytochrome P-450 fraction. The use of increasing amounts of sodium cholate in the solubilization of cytochrome P -450 resulted in a gradual decrease of 25-hydroxylase activity and a gradual increase of 26-hydroxylase activity. 25- and 26-Hydroxylase activities were separated partially by chromatography of subtilisintreated cytochrome P-450 fraction on DEAE-cellulose. The question whether different species of cytochrome P-450 are involved in 25- and 26-hydroxylation is discussed.