Reaction, Recognition, Relay: Anhydride Hydrolysis Reported by Conformationally Responsive Fluorinated Foldamers in Micelles

Natural membrane receptors are proteins that can report on changes in the concentration of external chemical messengers. Messenger binding to a receptor produces conformational changes that are relayed through the membrane into the cell; this information allows cells to adapt to changes in their environment. Artificial membrane receptors (R)-1 and (S)-1 are helical α-aminoisobutyric acid (Aib) foldamers that replicate key parts of this information relay. Solution-phase 19F NMR spectroscopy of zinc(II)-capped receptor 1, either in organic solvent or in membrane-mimetic micelles, showed messenger binding produced an enrichment of either left- or right-handed screw-sense; the chirality of the bound messenger was relayed to the other receptor terminus. Furthermore, in situ production of a chemical messenger in the external aqueous environment could be detected in real-time by a racemic mixture of receptor 1 in micelles. The hydrolysis of insoluble anhydrides produced carboxylate in the aqueous phase, which bound to the receptors and gave a distinct 19F NMR output from inside the hydrophobic region of the micelles.

α-Amino-iso-butyric acid foldamers terminated with rhodium(I) N-heterocyclic carbene catalysts

To investigate how remotely induced changes in ligand folding might affect catalysis by organometallic complexes, dynamic α‐amino‐iso‐butyric acid (Aib) peptide foldamers bearing rhodium(I) N‐heterocyclic carbene (NHC) complexes have been synthesized and studied. X‐ray crystallography of a foldamer with an N‐terminal azide and a C‐terminal Rh(NHC)(Cl)(diene) complex showed a racemate with a chiral axis in the Rh(NHC) complex and a distorted 3₁₀ helical body. Replacing the azide with either one or two chiral L‐α‐methylvaline (L‐αMeVal) residues gave diastereoisomeric foldamers that each possessed point, helical and axial chirality. NMR spectroscopy revealed an unequal ratio of diastereoisomers for some foldamers, indicating that the chiral conformational preference of the N‐terminal residue(s) was relayed down the 1 nm helical body to the axially chiral Rh(NHC) complex. Although the remote chiral residue(s) did not affect the stereoselectivity of hydrosilylation reactions catalysed by these foldamers, these studies suggest a potential pathway towards remote conformational control of organometallic catalysts.

Infant EEG theta modulation predicts childhood intelligence

Intellectual functioning is a critical determinant of economic and personal productivity. Identifying early neural predictors of cognitive function in infancy will allow us to map the neurodevelopmental pathways that underpin individual differences in intellect. Here, in three different cohorts we investigate the association between a putative neurophysiological indicator of information encoding (change in frontal theta during a novel video) in infancy and later general cognitive outcome. In a discovery cohort of 12-month-old typically developing infants, we recorded EEG during presentation of dynamic movies of people and objects. Frontal theta power (3-6 Hz) significantly increased during the course of viewing each video. Critically, increase in frontal theta during viewing of a video was associated with a differential response to repetition of that specific video, confirming relation to learning. Further, individual differences in the magnitude of change in frontal theta power were related to concurrent nonverbal cognitive level. We then sought to extend this association in two independent samples enriched for variation in cognitive outcome due to the inclusion of infants at familial risk for autism. We observed similar patterns of theta EEG change at 12 months, and found a predictive relation to verbal and nonverbal cognitive skills measured at 2, 3 and 7 years of age. For the subset of high-risk infants later diagnosed with autism, infant theta EEG explained over 80% of the variance in nonverbal skills at age 3 years. We suggest that EEG theta change in infancy is an excellent candidate predictive biomarker that could yield substantial insight into the mechanisms that underlie individual differences in childhood intelligence, particularly in high risk populations.

Replication of a rare risk haplotype on 1p36.33 for autism spectrum disorder

Hundreds of genes have been implicated in autism spectrum disorders (ASDs). In genetically heterogeneous conditions, large families with multiple affected individuals provide strong evidence implicating a rare variant, and replication of the same variant in multiple families is unusual. We previously published linkage analyses and follow-up exome sequencing in seven large families with ASDs, implicating 14 rare exome variants. These included rs200195897, which was transmitted to four affected individuals in one family. We attempted replication of those variants in the MSSNG database. MSSNG is a unique resource for replication of ASD risk loci, containing whole genome sequence (WGS) on thousands of individuals diagnosed with ASDs and family members. For each exome variant, we obtained all carriers and their relatives in MSSNG, using a TDT test to quantify evidence for transmission and association. We replicated the transmission of rs200195897 to four affected individuals in three additional families. rs200195897 was also present in three singleton affected individuals, and no unaffected individuals other than transmitting parents. We identified two additional rare variants (rs566472488 and rs185038034) transmitted with rs200195897 on 1p36.33. Sanger sequencing confirmed the presence of these variants in the original family segregating rs200195897. To our knowledge, this is the first example of a rare haplotype being transmitted with ASD in multiple families. The candidate risk variants include a missense mutation in SAMD11, an intronic variant in NOC2L, and a regulatory region variant close to both genes. NOC2L is a transcription repressor, and several genes involved in transcription regulation have been previously associated with ASDs.

Sensory hypersensitivity predicts enhanced attention capture by faces in the early development of ASD

Sensory sensitivity is prevalent among young children with ASD, but its relation to social communication impairment is unclear. Recently, increased sensory hypersensitivity has been linked to greater activity of the neural salience network (Green et al., 2016). Increased neural sensitivity to stimuli, especially social stimuli, could provide greater opportunity for social learning and improved outcomes. Consistent with this framework, in Experiment 1 we found that parent report of greater sensory hypersensitivity at 2 years in toddlers with ASD (N=27) was predictive of increased neural responsiveness to social stimuli (larger amplitude event-related potential/ERP responses to faces at P1, P400 and Nc) at 4 years, and this in turn was related to parent report of increased social approach at 4 years. In Experiment 2, parent report of increased perceptual sensitivity at 6 months in infants at low and high familial risk for ASD (N=35) predicted larger ERP P1 amplitude to faces at 18 months. Increased sensory hypersensitivity in early development thus predicted greater attention capture by faces in later development, and this related to more optimal social behavioral development. Sensory hypersensitivity may index a child's ability to benefit from supportive environments during development. Early sensory symptoms may not always be developmentally problematic for individuals with ASD.

Maternal experience raising girls with autism spectrum disorder: a qualitative study

BACKGROUND

A growing line of research has sought to characterize the different presentations of autism spectrum disorder (ASD) among boys and girls. Much less is known about maternal experience and mother-child relationship in children with ASD based on child gender. The present qualitative study aimed to investigate the mother-daughter relationship from the perspective of mothers who are raising girls with ASD with normal intelligence and functional verbal communication.

METHODS

Eleven in-depth interviews were conducted with mothers of girls with ASD, ages 10-19 years. Data were analysed in an interactive process commonly used in naturalistic inquiry. Results provide insight into the unique maternal experience of raising a daughter with ASD.

RESULTS

Mothers reported a sense of exclusion from the neurotypical population and male-dominant ASD population and transformation in relationship. Themes identified were skepticism and delayed diagnosis, disbelief from others, lack of information about girls with ASD, higher social demands in adolescence, puberty challenges around hygiene, disappointment about physical appearance, vulnerability in relationships and worries about future functioning. The mother-daughter relationship started with an early expectation of a close and intimate relationship that then underwent a transformation, which challenged maternal competence, reshaped expectations and created a different bond between mother and daughter.

CONCLUSIONS

The findings in this qualitative study highlight the impact of gender on the maternal experience of raising a daughter with ASD and contribute to a better understanding of the needs of both mothers and daughters. These results can help providers support the mother-daughter dyad by recognizing gender-specific challenges.

Reduced engagement with social stimuli in 6-month-old infants with later autism spectrum disorder: a longitudinal prospective study of infants at high familial risk

Background

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects more than 1 % of the population and close to 20 % of prospectively studied infants with an older sibling with ASD. Although significant progress has been made in characterizing the emergence of behavioral symptoms of ASD, far less is known about the underlying disruptions to early learning. Recent models suggest that core aspects of the causal path to ASD may only be apparent in early infancy. Here, we investigated social attention in 6- and 12-month-old infants who did and did not meet criteria for ASD at 24 months using both cognitive and electrophysiological methods. We hypothesized that a reduction in attention engagement to faces would be associated with later ASD.

Methods

In a prospective longitudinal design, we used measures of both visual attention (habituation) and brain function (event-related potentials to faces and objects) at 6 and 12 months and investigated the relationship to ASD outcome at 24 months.

Results

High-risk infants who met criteria for ASD at 24 months showed shorter epochs of visual attention, faster but less prolonged neural activation to faces, and delayed sensitization responses (increases in looking) to faces at 6 months; these differences were less apparent at 12 months. These findings are consistent with disrupted engagement of sustained attention to social stimuli.

Conclusions

These findings suggest that there may be fundamental early disruptions to attention engagement that may have cascading consequences for later social functioning.

Electronic supplementary material

The online version of this article (doi:10.1186/s11689-016-9139-8) contains supplementary material, which is available to authorized users.

Rule learning in autism: the role of reward type and social context

Learning abstract rules is central to social and cognitive development. Across two experiments, we used Delayed Non-Matching to Sample tasks to characterize the longitudinal development and nature of rule-learning impairments in children with Autism Spectrum Disorder (ASD). Results showed that children with ASD consistently experienced more difficulty learning an abstract rule from a discrete physical reward than children with DD. Rule learning was facilitated by the provision of more concrete reinforcement, suggesting an underlying difficulty in forming conceptual connections. Learning abstract rules about social stimuli remained challenging through late childhood, indicating the importance of testing executive functions in both social and non-social contexts.

Mechanisms of postnatal neurobiological development: implications for human development

This review focuses on the postnatal neuroanatomical changes that arise during the first years of human life. Development is characterized by 2 major organizational periods. The first period begins at conception and includes the major histogenetic events such as neurulation, proliferation, migration, and differentiation. It has been proposed that these events may be controlled by genetic and epigenetic events, which give rise to neural structures that are amenable to external influence. The second period is a time of reorganization in the human cortex. These events occur during gestation and continue postnatally, possibly through the 2nd decade of life. This stage is characterized by dendritic and axonal growth, synapse production, neuronal and synaptic pruning, and changes in neurotransmitter sensitivity. Although the initiation of these events is influenced by endogenous signals, further neural maturation is primarily influenced by exogenous signals. To illustrate both the progressive and regressive events during the postnatal period, we use examples from the development of the human cortex.

Prenatal neurobiological development: molecular mechanisms and anatomical change

During prenatal development, the central nervous system is transformed from a thin layer of unspecified tissue into a complex system that can process information and organize actions. There are 8 general mechanisms that permit this transformation: neural induction, neurulation, proliferation, migration, axonal outgrowth, synaptogenesis, differentiation, and apoptosis. These processes as well as the anatomical changes they cause are described. Future research with humans, such as in utero MRI as well as behavioral and electrophysiological testing of infants following specific prenatal perturbations, is suggested to link the findings from molecular approaches to developmental neuropsychology.

Regulation of TNF-alpha-induced IL-6 production in MG-63 human osteoblast-like cells

Tumor necrosis factor-alpha (TNF-alpha) stimulates osteoblast production of interleukin-6 (IL-6), an inflammatory cytokine implicated in osteoclastic bone resorption. Therefore, we tested the hypothesis that TNF-alpha-induced IL-6 production in MG-63 osteosarcoma cells occurs via the p38 mitogen-activated protein kinase (MAPK) pathway. TNF-alpha activated p38 MAPK and stimulated IL-6 secretion by MG-63 cells, and pre-incubation of cells with the p38 MAPK inhibitor abrogated TNF-alpha-dependent IL-6 secretion. Transfection of IL-6 full-length and 5-deletion gene promoter reporter constructs indicated that p38 MAPK activation by TNF-alpha enhanced IL-6 gene expression, and that the p38 MAPK-responsive region resided in the proximal 260-bp segment. Transfection of NFkappaB and C/EBPbeta-sensitive reporter promoter constructs demonstrated that NFkappaB activity was enhanced and that constitutive C/EBPbeta was inhibited by TNF-alpha, with both effects being p38 MAPK-dependent. In conclusion, although p38 MAPK activation by TNF-alpha stimulates IL-6 secretion by MG-63 cells, it has opposing effects on c/EBPbeta and NFkappaB activity.

DNA adduct levels and absence of tumors in female rapid and slow acetylator congenic hamsters administered the rat mammary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine

N-acetyltransferases (EC 2.3.1.5) catalyze O-acetylation of heterocyclic amine carcinogens to DNA-reactive electrophiles that bind and mutate DNA. An acetylation polymorphism exists in humans and Syrian hamsters regulated by N-acetyltransferase-2 (NAT2) genotype. Some human epidemiological studies suggest a role for NAT2 phenotype in predisposition to cancers related to heterocyclic amine exposures, including breast cancer. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a heterocyclic amine carcinogen prevalent in the human environment and induces a high incidence of mammary tumors in female rats. PhIP-induced carcinogenesis was examined in female rapid and slow acetylator Syrian hamsters congenic at the NAT2 locus. In both rapid and slow acetylators, PhIP-DNA adduct levels were highest in pancreas, lower in heart, small intestine, and colon, and lowest in mammary gland and liver. Metabolic activation of N-hydroxy-PhIP by O-acetyltransferase was highest in mammary epithelial cells, lower in liver and colon, and lowest in pancreas. Metabolic activation of N-hydroxy-PhIP by O-sulfotransferase was low in liver and colon and below the limit of detection in mammary epithelial cells and pancreas. Unlike the rat, PhIP did not induce breast or any other tumors in female rapid and slow acetylator congenic hamsters administered high-dose PhIP (10 doses of 75 mg/kg) and a high-fat diet.

Perceptual priming for upright and inverted faces in infants and adults

Based on recent models of the ontogeny of memory (Nelson, 1995), we hypothesize that 6-month-old infants should show evidence of repetition priming. Event-related potentials were recorded from 11 scalp sites to novel and primed upright and inverted faces. In Experiment 1 (n = 24), 6-month-old infants viewed faces that were repeated after 6 to 12 images. Overall, repeated faces demonstrated greater negativity than novel faces and upright faces demonstrated greater negativity than inverted faces. In order to ground these results in an adult model, a group of adults (n = 30) was tested in a similar experiment. Here we observed effects of repetition at an early positive component labeled the P150 as well as at the P300, with repeated images being more positive than novel images. These data support the idea that infants at 6 months are capable of revealing electrophysiological evidence of perceptual priming.

Oral administration of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) yields PhIP-DNA adducts but not tumors in male Syrian hamsters congenic at the N-acetyltransferase 2 (NAT2) locus

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a heterocyclic amine carcinogen present in well-done meat. PhIP must undergo host-mediated bioactivation to exert its mutagenic and carcinogenic effects. Following N-hydroxylation, N-acetyltransferases catalyze the O-acetylation (activation) of N-hydroxy-PhIP to an electrophile causing DNA damage. A well-defined genetic polymorphism in N-acetyltransferase 2 (NAT2) activity exists in humans and the Syrian hamster. Since some human epidemiological studies suggest an association between acetylator genotype and cancer susceptibility in individuals who consume well done meats, this study was designed to investigate the specific role of acetylator genotype in PhIP-induced tumors using a Syrian hamster model congenic at the NAT2 locus. Following oral administration of PhIP to male rapid and slow acetylator Syrian hamsters, DNA adducts were identified in each tissue examined with levels in the relative order: pancreas > heart and urinary bladder > prostate, small intestine and transverse colon > ascending colon, liver, cecum, descending colon, and rectum. However, no tumors were observed in male rapid and slow acetylator congenic hamsters administered 11 oral doses of PhIP (75 mg/kg) and maintained on a high fat diet for one year.

A tin(IV)-ruthenium(II)-tin(IV) cyclic porphyrin trimer with replaceable chiral linings

A series of cyclic metalloporphyrin trimers, Ru(CO)(py)[Sn(carboxylate)2](2)2, having cavities lined with different carboxylate groups are synthesized by adding the appropriate carboxylic acids to the mixed trimer Ru(CO)(py)-[Sn(OH)2](2)2. This methodology provides ready access to a wide range of cavities lined with substituents possessing chirality or hydrogen-bonding groups. The potential of such systems is illustrated by synergistic binding of a hydroxypyridine to the Ru(II)-CO center and to the hydroxyl groups of a D-quinate-lined cavity. The effect of changing the carboxylate lining of the cavity on the course of epoxidation reactions catalyzed by these trimers is also reported.

Synthesis and recognition properties of a ruthenium(II)-bis(zinc) cyclic porphyrin trimer

A series of cyclic metalloporphyrin trimers containing one Ru(II)-CO porphyrin center are synthesized. A stepwise convergent route is used to synthesize Ru(CO)Zn(2)2.Py3T, where tripyridyltriazine (Py3T) templates the formation of the trimer and forces the CO group to the outside of the cavity. Three mixed-metal trimers, Ru(CO)Zn(2)2, Ru(CO)Ni(2)2, and Ru(CO)Mg(2)2, are synthesized from Ru(CO)Zn(2)2.Py3T and are characterized by NMR, UV-visible, and fluorescence spectroscopy. The Ru(CO)Zn(2)2 trimer is found to bind Py3T very tightly (K approximately 10(12) M-1), the resultant complex dissociating very slowly (kdissoc approximately 3 x 10(-7) s-1) in CDCl3 at 60 degrees C. During the course of these studies, the binding selectivity of a ruthenium porphyrin monomer, Ru(CO)3, for pyridine over THF is estimated to be ca. 7 x 10(4):1.

Molecular genetics and epidemiology of the NAT1 and NAT2 acetylation polymorphisms

The focus of this review is the molecular genetics, including consensus NAT1 and NAT2 nomenclature, and cancer epidemiology of the NAT1 and NAT2 acetylation polymorphisms. Two N-acetyltransferase isozymes, NAT1 and NAT2, are polymorphic and catalyze both N-acetylation (usually deactivation) and O-acetylation (usually activation) of aromatic and heterocyclic amine carcinogens. Epidemiological studies suggest that the NAT1 and NAT2 acetylation polymorphisms modify risk of developing urinary bladder, colorectal, breast, head and neck, lung, and possibly prostate cancers. Associations between slow NAT2 acetylator genotypes and urinary bladder cancer and between rapid NAT2 acetylator genotypes and colorectal cancer are the most consistently reported. The individual risks associated with NAT1 and/or NAT2 acetylator genotypes are small, but they increase when considered in conjunction with other susceptibility genes and/or aromatic and heterocyclic amine carcinogen exposures. Because of the relatively high frequency of some NAT1 and NAT2 genotypes in the population, the attributable cancer risk may be high. The effect of NAT1 and NAT2 genotype on cancer risk varies with organ site, probably reflecting tissue-specific expression of NAT1 and NAT2. Ethnic differences exist in NAT1 and NAT2 genotype frequencies that may be a factor in cancer incidence. Large-scale molecular epidemiological studies that investigate the role of NAT1 and NAT2 genotypes and/or phenotypes together with other genetic susceptibility gene polymorphisms and biomarkers of carcinogen exposure are necessary to expand our current understanding of the role of NAT1 and NAT2 acetylation polymorphisms in cancer risk.

Cytochrome P-450 mRNAs are modulated by dehydroepiandrosterone, nafenopin, and triiodothyronine

Dehydroepiandrosterone (DHEA) is the only known naturally occurring compound that promotes peroxisome proliferation in rodent liver, and stimulates transcriptional induction of genes involved in lipid metabolism and peroxisomal beta-oxidation. Therefore, we examined mRNA for several such genes in rat liver, specifically acyl-CoA oxidase and the cytochromes P-450 (CYP4A1, CYP4A3, and CYP3A23), after 5 to 6 day treatments with either DHEA, or nafenopin, a known peroxisome proliferator. Acyl-CoA oxidase and CYP4A1 were induced nearly identically by DHEA and nafenopin, with induction being more pronounced in female rats. However, CYP3A23 was induced only by DHEA, suggesting an induction mechanism independent of the peroxisome proliferator activated receptor. Previously, we observed triiodothyronine (T3) suppression of peroxisome proliferator induced CYP4As and we sought to determine whether CYP3A23 might be regulated in a different manner. T3 was found to also suppress DHEA-dependent induction of CYP3A23. CYP4A2 expression in kidney was also negatively regulated by T3. To characterize a putative negative thyroid hormone response element (nTRE) in the 5' flanking region of this gene, a luciferase reporter gene containing a rat CYP4A2 flanking sequence extending to -1865 bp was transfected into HepG2 cells along with human thryroid hormone receptor expression vector. Expression of luciferase activity was unaffected by T3, suggesting the absence of a functional nTRE within this portion of CYP4A2. These data demonstrate gene regulatory activity by DHEA different from that of nafenopin, and a suppressive effect of T3, consistent with indirect regulatory mechanisms not involving an nTRE.

Caspase-mediated cleavage of APC results in an amino-terminal fragment with an intact armadillo repeat domain

During the effector phase of apoptosis, caspase activation appears to be responsible for the distinctive structural changes of apoptosis and perhaps for some of the changes in function of the doomed cells. There is therefore interest in identifying caspase substrates and the details of the cleavage events. Here we define precisely the event responsible for generation of a stable 90 kDa fragment from the oncosuppressor protein adenomatous polyposis coli (APC). Using synthetic radiolabeled APC peptides as substrate, we demonstrate cleavage by cytosolic extracts from preapoptotic cells. This cleavage was reproduced by recombinant caspase-3 and blocked by a tetrapeptide inhibitor Ac-DEVD-CHO, which is specific for caspase-3 family members. Inhibitors specific for caspase-1 and -8 however, were less effective in blocking APC cleavage. Mutation of a candidate DNID caspase-3 target site completely abolished cleavage. This cleavage may be of biological importance since the 90 kDa fragment consists of a sequence that is highly conserved in the human, rat, mouse, Xenopus, and Drosophila APC, although wide sequence divergence is observed in Drosophila immediately carboxy-terminal to the DNID site. Furthermore, cleavage at this site separates two significant functional domains: an amino-terminal armadillo repeat and an adjacent series of beta-catenin binding sites. Further circumstantial evidence for the significance of APC-related pathways in apoptosis is provided by the observation that apoptosis also induces cleavage of beta-catenin itself, a protein known to accumulate in cells depleted in functional APC and that appears to link cell-cell signaling to changes in transcription and cell movement.

Regulation of CYP4A expression in rat by dehydroepiandrosterone and thyroid hormone

Dehydroepiandrosterone (DHEA) is a peroxisome proliferating agent when administered in pharmacological dosages, but it has not been shown to function through the peroxisome proliferator-activated receptor in cell-based assays. Because members of the thyroid hormone/vitamins A and D nuclear receptor subfamily, including PPAR, are known to modulate each other's function in gene expression by heterodimerization, we sought to establish whether DHEA and thyroid hormone interact to regulate several of the hepatic and renal enzymes associated with peroxisome proliferation, i.e., peroxisomal beta-oxidation and microsomal NADPH:cytochrome P450 oxidoreductase and the cytochromes P450 4A. In rats administered exogenous T3 to attain a hyperthyroid state, induction of the three isozymes of CYP4A (4A1, 4A2, and 4A3) by DHEA was suppressed > 60-80% at the mRNA level, with induction of CYP4A2 mRNA being completely inhibited. Nuclear run-on transcription assays indicated that this inhibitory effect was regulated at the level of transcription. Induction of hepatic peroxisomal beta-oxidation by DHEA or the peroxisome proliferator nafenopin was in large part unaffected by treatment of animals with T3 under any condition tested. Microsomal NADPH:cytochrome P450 oxidoreductase activity was induced by either DHEA or T3; cotreatment resulted in an additive induction. When animals were treated with a lower dose of exogenous T3 that rendered the animals slightly hyperthyroid, only induction of hepatic CYP4A2 mRNA by DHEA or nafenopin was significantly inhibited (> 80%) compared with euthyroid control animals. Animals that had been rendered hypothyroid through removal of the thyroid gland showed normal induction of CYP4A genes by DHEA in liver, suggesting that their induction by DHEA was not dependent on the presence of thyroid hormone. The administration of exogenous T3 to thyroidectomized rats in the presence of DHEA potently suppressed hepatic induction of all three genes at the mRNA and protein level. In experiments with cultured rat hepatocytes, physiological concentrations of T3 potently inhibited the induction of CYP4A2 mRNA levels by nafenopin but had little effect on induction of CYP4A1 or 4A3 mRNA. At higher T3 concentrations, the induction of CYP4A1/4A3 mRNA and protein was also inhibited. These results suggest that T3 modulates the expression of CYP4A2 at the level of transcription in physiologically relevant concentrations but that hyperthyroid conditions are required to suppress expression of CYP4A1/4A3 genes. In euthyroid rodent kidney, which only expresses CYP4A2 under either basal or DHEA-induced conditions, near-physiological levels of T3 caused potent suppression of peroxisome proliferator-dependent induction of CYP4A2 mRNA levels by either DHEA or nafenopin. In thyroidectomized rats, basal expression of CYP4A2 mRNA was decreased relative to euthyroid controls, but DHEA was as effective an inducer of this mRNA as it is in euthyroid rats. As seen in euthyroid rats, T3 administration potently suppressed DHEA induction of CYP4A2 mRNA levels under either basal or induced conditions. Although CYP4A expression was not derepressed in liver or kidneys of hypothyroid animals, our results indicated that the thyroid status of the animal did affect basal expression of CYP4A2, suggesting involvement of thyroid hormone or some other factor regulated by the thyroid gland on its constitutive expression.

Induction of microsomal and peroxisomal enzymes by dehydroepiandrosterone and its reduced metabolite in rats

Dehydroepiandrosterone (DHEA) given to rodents in pharmacological doses induces several hepatic enzymes including cytochromes P4504A, NADPH:P450 oxidoreductase, palmitoyl coenzyme A oxidase, and other enzymes associated with the peroxisomal beta-oxidation pathway, leading to peroxisome proliferation and development of hepatocellular carcinoma in rodents. Comparison of the inductive potency of DHEA and other intermediates of the steroid biosynthetic path demonstrated that only DHEA, 5-ene-androstene-3 beta,17 beta-diol (ADIOL), and to a lesser extent, 17 alpha-hydroxypregnenolone, a precursor of DHEA, induce cytochromes P4504A protein and other enzymes associated with the peroxisome proliferative response in vivo. ADIOL exerted its inductive response at a somewhat lower dosage than DHEA, whereas ADIOL and DHEA both induced the microsomal enzymes (P4504A and its oxidoreductase) at somewhat lower dosages than those required to induce peroxisomal enzymes. Northern analysis demonstrated increases in the mRNAs encoding the cytochromes P4504A (> 20-fold) and NADPH:P450 oxidoreductase (> 10-fold) in the livers of DHEA- and ADIOL-treated rats. Run-on transcription analysis demonstrated that DHEA induces CYP4A gene expression 11-fold at the level of transcription initiation. Comparison of the responsiveness of individual rat CYP4A genes (4A1, 4A2, and 4A3) to DHEA and ADIOL in immature versus mature male rats revealed 2-3-fold higher levels of induced CYP4A1 and 4A3 mRNAs in immature rat livers. In contrast, hepatic CYP4A2 mRNA was induced to 6-10-fold higher levels in mature rats. No basal or significant inducible expression of mRNA for CYP4A1 and 4A3 was noted in rat kidney. Significant basal levels of kidney CYP4A2 mRNA were observed only in mature animals, where they were inducible by ADIOL and DHEA to a 3-5-fold greater extent than in the kidneys of immature rats. These studies demonstrate developmental differences in the responsiveness of CYP4A mRNA levels to DHEA and ADIOL in rat kidney and liver. Moreover, the striking inducibility of CYP4A protein and mRNAs, together with the increased rates of synthesis of nascent CYP4A mRNA transcripts in hepatic nuclei from DHEA-treated rats, establish that DHEA increases the expression of these microsomal enzymes at the transcriptional level.

Survey of general practice audit in Leeds

OBJECTIVE

To determine general practitioners' attitudes to medical audit and to establish what initiatives are already being undertaken; to define future ideas for audit and perceived difficulties in implementing audit in primary care.

DESIGN

Analysis of responses to a self administered postal questionnaire.

SETTING

Urban conurbation with a population of about 750,000.

PARTICIPANTS

386 general practitioners on the general medical list of Leeds Family Practitioner Committee.

MAIN OUTCOME MEASURES

Extent of recording of practice activity data and outcome measures and clinical data, use of data, and audit performed; ideas for audit and perceived difficulties.

RESULTS

317 doctors responded to the questionnaire (individual response rate 82%) from 121 practices (practice response rate 88%). In all, 206 doctors thought that audit could improve the quality of care; 292 collected practice activity data, though 143 of them did not use it. A total of 111 doctors recorded some outcome measures, though half of them did not use them. Varying proportions of doctors had registers, for various diseases (136 had at least one register), disease management policies (60 doctors), and prescribing policies. In all, 184 doctors met monthly with other members of the primary health care team.

CONCLUSIONS

Much poorly focused data collection is taking place. Some doctors have experience in setting up basic information systems and practice policies, and some audit is being performed. The family health services authorities need to take seriously the perceived difficulties of time, organisation, and resources concerned with audit.

Appendicitis and appendicectomy in a Melanesian population

A prospective study of patients with appendicitis has been conducted over a 3-year period in the Melanesian population of the North Solomons. Patients presented with suspected appendicitis at an annual rate of 39 per 100,000 population. Appendicitis was confirmed at operation at an annual rate of 22 per 100,000 population. The disease was considerably more frequent in male than in female patients. The annual appendicectomy rate was 29 per 100,000 population. Thirty per cent of patients presented with signs of late or complicated appendicitis, while 37 per cent of patients submitted to operation were found to have advanced appendicitis. The incidence and pattern of appendicitis in the North Solomons are quite different from those seen in the urbanized populations of developed countries.

Experimental murine herpes simplex encephalitis: immunohistochemical detection of virus antigens

Inbred Balb/c female mice were intranasally inoculated with 1 microliter of a suspension of herpes simplex virus type 1 adjusted to contain the required infectivity. Doses of virus inoculated ranged from 1 X 10(2) plaque forming units (p.f.u.) to 1 X 10(6) p.f.u. Humoral and cellular immunological response of the animals was studied for the acute phase of the disease, defined as being up to 14 days post infection. Localization of virus-antigen positive cells, detected by immunoperoxidase staining, was monitored daily for the acute phase. Immune responses directly reflected virus input, with the highest response to 1 X 10(6) p.f.u. of herpes simplex virus. The neuro-anatomical localization of virus-antigen positive cells was found mainly in the hippocampus and entorhinal cortex for inoculum doses of 1 X 10(6) p.f.u. and mainly in the brain stem for inoculum doses 5 X 10(2) p.f.u. The lower mortality rate of animals inoculated with 5 X 10(2) p.f.u. has identified this dose as suitable for use in the study of sites of latency within the central nervous system and in the investigation of reactivation of herpes simplex virus type 1 in causing encephalitis.

Skin cancer in the North Solomons

The Melanesians of the North Solomons are exposed to intense equatorial sunlight and yet have a very low incidence of skin cancer. This study reveals no proven cases of basal cell carcinoma in these people, and demonstrates the rarity of squamous cell carcinoma and melanoma arising in normal pigmented skin. Most, if not all squamous cell carcinomas, arise in skin damaged by tropical ulceration, burns or osteomyelitis. Melanoma arises from the unpigmented skin of the sole of the foot. North Solomon Islanders are very deeply pigmented. Presumably, dense cutaneous melanin in normal undamaged skin provides the highly effective protection against solar carcinogenesis which these people enjoy. Chronic or recurrent skin ulceration with subsequent repair, scarring and loss of pigment is the precursor to almost all non-melanoma skin cancer in these people. Most of these cancers could be prevented by split thickness skin grafting of chronic ulcers, and protection of ulcerated, depigmented and scarred skin from solar radiation.

The action of hydrolytic enzymes and vapor rehydration on semidried cells of Klebsiella pneumoniae

Airborne cells of Klebsiella pneumoniae have been found to develop a sensitivity to lethal actions of hydrolytic enzymes. The degree to which the cells become sensitive to enzymic damage is shown to depend on (a) the medium from which they are aerosolized, (b) the relative humidity (RH) at which they are stored, (c) the duration of their storage in aerosols, (d) the method by which they are rehydrated, and (e) the particular enzyme. When cells are aerosolized from suspensions in distilled water they develop their maximum sensitivity to lysozyme and DNase after storage at 55% and 80% relative humidity (RH) respectively. Sensitivity to RNase is small and independent of the storage RH. The addition of glycerol to the cells before their aerosolization results in the development of maximal sensitivities to lysozyme and RNase occurring after storage at 55% RH, while sensitivity to DNase remains at a maximal level after holding at 80% RH. If the cells are atomized from suspensions containing raffinose or myo-inositol their sensitivity to lysozyme, RNase, and DNase is greatest after storage at 30%, 55%, and 80% respectively. When the airborne cells either are rehydrated with water vapor before their collection, or held in buffer after collection, before being exposed to these enzymes, their susceptibility to enzymic damage is reduced. The possible bearing these findings have on the mechanisms of cell viability and loss of ability to infect a host, because of their semidehydration, is discussed.

Microwave absorption by normal and tumor cells

Energy levels exist in mammalian cells which result in the absorption of microwaves between 66 and 76 gigahertz. Many of these energy levels occur when water molecules associate with the various chemical groups of macromolecules. The absorption spectra of cells between 66 and 76 gigahertz, therefore, is determined by the structure of in vivo water lattices, and these seem to reflect indirectly the structural makeup of macromolecules or macromolecular complexes. Tumor cells absorb 66-, 68-, and 70-gigahertz microwaves less strongly and 69-, 72-, and 75-gigahertz microwaves more strongly than normal cells. These differences in the strength of attenuation at each frequency suggest that either the ratio of RNA to DNA or the relative number of certain types of chemical groups in tumor cells is different from that in normal cells.

An infrared study of the influence of growth media and myo-inositol on structural changes in DNA induced by dehydration and ultraviolet light

The infrared spectra of films of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and synthetic polynucleotides have been studied under varying degrees of relative humidity (R.H.) in the presence and absence of myo-inositol. In addition the effect of 2537 Å light (ultraviolet) on the hydration of DNA has been investigated. As other researchers have shown, when the R.H. is lowered shifts in the P=O and C=O absorption frequencies occur. These shifts seem to be associated with the removal of approximately 12 molecules of water/nucleotide and all are prevented by the presence of 2 molecules of inositol/nucleotide during desiccation. The irradiation of DNA at 75% R.H. with ultraviolet also produces spectral shifts which appear to arise as a result of bound water molecules moving from P=O and C=O groups.The response of bacterial DNA to desiccation appears to depend on the medium in which the cells are grown. The DNA from cells grown in a minimal salts medium is less hydrated at a given R.H. level than the DNA from cells grown in an enriched medium. This loss of water-adsorbing sites is considered to be due to a physiological replacement of water on the DNA of cells grown on minimal salt medium by amino acids or proteins. RNA and polynucleotides are less hydrated than DNA, which is assumed to be due to their lack of an ordered double helical structure. Of the synthetic polynucleotides poly-I was found to most closely resemble the behavior of DNA. The ability of inositol to prevent spectral shifts in DNA caused by desiccation and irradiation tends to substantiate the suggestion that it preserves the biological integrity of cells and viruses during stress by combining with DNA.

Infrared studies of DNA, water, and inositol associations

Ultraviolet and polarized infrared spectra of oriented films of bacterial DNA have been recorded over a range of relative humidities (R.H.) between 10 and 84%. The films were made from a DNA gel in H2O or D2O with and without 5% (w/v) myo-inositol. In the absence of inositol a large decrease in the dichroic ratio at 1670 cm−1 occurred as the R.H. was lowered between 70 and 30%, indicating the occurrence of considerable disorganization. This was not observed when the DNA was dehydrated in the presence of myo-inositol. A marked increase in absorbance at 2600 Å which occurred on lowering the R.H. from 70 to 50% was prevented also by inositol.These results indicate that myo-inositol can replace water molecules and maintain the DNA in the B configuration during dehydration. The possible significance of these observations in the explanation of certain biological phenomena is discussed.

Lethal and mutagenic action of 3200-4000 A light

Cells of a thymine-requiring auxotrophic mutant of Escherichia coli B have been irradiated with 2537 Å light (ultraviolet) and 3200–4000 Å light (black light) while being held in aerosols of various relative humidity (R.H.) levels. When cells were held in aerosols of 70% R.H. or lower they became susceptible to damage by black light and much of this damage could be prevented by the compound myo-inositol. The damage inflicted on cells by black light was not photorepairable by the usual methods, suggesting that the lesions produced are different from those produced by ultraviolet light. In addition, the ability of cells to undergo photorepair after irradiation with 2537 Å light was found to decrease rapidly when the cells were irradiated in a dry or near-dry state, indicating that the lesions produced under these conditions are different from those produced in wet cells.Sensitization of the cells to both kinds of radiations by the presence of bromodeoxyuridine (BUDR) in their deoxyribonucleic acid was apparent only when the cells were irradiated in a wet or semidry state, suggesting that sensitization involves a photostimulated hydrolysis of BUDR. Black light was found to be more mutagenic to cells held in a semidried state than was 2537 Å light. It is concluded that the irradiation of cells with 2537 Å light or with black light when they are in the dry state produces a lesion which is non-photorepairable and which is both lethal and mutagenic.

The effects of mutation and nucleic acid base analogues on the sensitivity of E. coli to partial dehydration

Investigations have been carried out on the effect of mutation and the incorporation of base analogues into the deoxyribonucleic acid (DNA) of cells on their resistance to dehydration. Auxotrophic mutant cells have been found to possess the same sensitivity or a greater sensitivity than the parent prototrophic organism. This suggests that mutant cells, previously found in populations surviving periods of desiccation, occurred as a result of induced mutation and not the concentration of mutants existing in the cell population before its dehydration. In addition, the incorporation of nucleic base analogues into the DNA of cells has been found to alter their sensitivity to dehydration. With some analogues, the sensitivity of cells is increased and with others it is decreased. Also, the presence of nucleic acid base analogues in the DNA of cells markedly inhibits the ability of myo-inositol to protect cells against dehydration damage. These results suggest that the dehydration of cells is mutagenic and inositol is able to preserve the integrity of desiccated cells by combining with specific areas of normal DNA.

The influence of cell water content on the inactivation of RNA by partial desiccation and ultraviolet light

The influence of the water content of cells of Escherichia coli K38 and Escherichia coli B on the inactivation of F2 phage RNA and β-galactosidase mRNA by partial desiccation and 2537 Å ultraviolet light (uv.) has been studied. Both types of RNA were found to resist desiccation and their inactivation by ultraviolet to require much larger doses than the destruction of the colony-forming ability of cells. The ability of non-induced cells to produce β-galactosidase was destroyed by desiccation and irradiation more easily in non-induced cells than in preinduced cells. The inactivation of RNA was found to occur more readily when the cells contained from 10 to 15 g H2O/100 g of cell solids than when the cells contained less water. Damage by desiccation and irradiation, however, was partially prevented by i-inositol.It is concluded that damage to existing cell RNA either by ultraviolet or desiccation is not involved in the loss of cell viability and that cell death occurs as a result of damage to the mechanism by which mRNA is manufactured.

The influence of oxygen and inositol on the survival of semidried microorganisms

Oxygen was found to have no effect on the induction of the λ prophage due to desiccation but enhanced cell death and the inactivation of the intracellular phages at relative humidity (R.H.) levels below 40%. The magnitude of the oxygen effect increased as the R.H. below 30% decreased. Inositol prevented cell death and phage inactivation due to both bound water reorientation and oxidations. Cells freeze-dried before aerosolization were more stable to storage in air at 30% R.H. and below than they were at 40% to 70% R.H. However, most of the killing of pre-dried cells held at 20% R.H. and below in air was found to be due to an effect of oxygen.

Some observations concerning DNA and beta-galactosidase synthesis in Escherichia coli B

When starved cells of thymine-requiring Escherichia coli B were placed in a complete induction medium there was an initial lag of 10 minutes before measurable amounts of the enzyme were detected. Cells exposed for 15 minutes to one inducer and then given an alternative inducer continued to manufacture the enzyme for 60 minutes at a rate characteristic of the initial inducer. After this period, enzyme manufacture assumed the characteristics of the second inducer. Glucose or mitomycin was found to inhibit enzyme synthesis only when they were added during the first 10 minutes or 45- to 60-minute periods of induction. Chloramphenicol stopped enzyme synthesis at any stage of induction. The synthesis of DNA was found to occur in two stages and enzyme synthesis was prevented by glucose or mitomycin only if they were added to the cells during a 10-minute period which immediately preceded DNA replication. It is concluded that a gene can express itself only once, and change in expression requires the synthesis of new DNA.