Analysis of any point mutation in DNA. The amplification refractory mutation system (ARMS)

We have improved the "polymerase chain reaction" (PCR) to permit rapid analysis of any known mutation in genomic DNA. We demonstrate a system, ARMS (Amplification Refractory Mutation System), that allows genotyping solely by inspection of reaction mixtures after agarose gel electrophoresis. The system is simple, reliable and non-isotopic. It will clearly distinguish heterozygotes at a locus from homozygotes for either allele. The system requires neither restriction enzyme digestion, allele-specific oligonucleotides as conventionally applied, nor the sequence analysis of PCR products. The basis of the invention is that unexpectedly, oligonucleotides with a mismatched 3'-residue will not function as primers in the PCR under appropriate conditions. We have analysed DNA from patients with alpha 1-antitrypsin (AAT) deficiency, from carriers of the disease and from normal individuals. Our findings are in complete agreement with allele assignments derived by direct sequencing of PCR products.

The murine and Drosophila homeobox gene complexes have common features of organization and expression

In situ hybridization analysis of mouse embryos shows the seven members of the Hox-2 complex to be differentially expressed in the central and peripheral nervous system and in mesodermal derivatives (somites and lung). Beginning at the 5' end of the cluster, each successive gene displays a more anterior boundary of expression in the central nervous system. A gene's position in the Hox-2 cluster therefore reflects its relative domain of expression along the anteroposterior axis of the embryo, a feature observed with Drosophila homeotic genes. Sequence comparisons of the Hox-2 cluster with other mouse and Drosophila homeobox genes have defined subgroups of related genes; in the mouse there are four clusters related by duplication and divergence. Alignment shows a clear relationship among genes in the mouse and Drosophila complexes, based on relative position, sequence identity, and domains of expression along the rostral-caudal axis. Our results argue that these complexes arose from a common ancestor, present before the divergence of lineages that gave rise to arthropods and vertebrates.

Segmental origin and migration of neural crest cells in the hindbrain region of the chick embryo

A vital dye analysis of cranial neural crest migration in the chick embryo has provided a positional fate map of greater resolution than has been possible using labelled graft techniques. Focal injections of the fluorescent membrane probe DiI were made into the cranial neural folds at stages between 3 and 16 somites. Groups of neuroepithelial cells, including the premigratory neural crest, were labelled by the vital dye. Analysis of whole-mount embryos after 1–2 days further development, using conventional and intensified video fluorescence microscopy, revealed the pathways of crest cells migrating from mesencephalic and rhombencephalic levels of the neuraxis into the subjacent branchial region. The patterns of crest emergence and emigration correlate with the segmented disposition of the rhombencephalon. Branchial arches 1, 2 and 3 are filled by crest cells migrating from rhombomeres 2, 4 and 6 respectively, in register with the cranial nerve entry/exit points in these segments. The three streams of ventrally migrating cells are separated by alternating regions, rhombomeres 3 and 5, which release no crest cells. Rostrally, rhombomere 1 and the caudal mesencephalon also contribute crest to the first arch, primarily to its upper (maxillary) component. Both r3 and r5 are associated with enhanced levels of cell death amongst cells of the dorsal midline, suggesting that crest may form at these levels but is then eliminated. Organisation of the branchial region is thus related by the dynamic process of neural crest immigration to the intrinsic mechanisms that segment the neuraxis.

The signalling molecule BMP4 mediates apoptosis in the rhombencephalic neural crest

The pattern of skeletal structures and muscles in the branchial region of the head is profoundly influenced by the neural crest, whose cells arise at discrete segmental levels of the chick hindbrain: specifically, rhombomeres (r)1+2, r4 and r6, whereas r3 and r5 are crest-depleted. We have demonstrated that an interaction between even-numbered rhombomeres and r3/r5 effects this depletion of neural crest, resulting in the sculpting of discrete migratory streams of neural crest. This mechanism acts through increased expression of msx2 and the induction of apoptosis in dorsal cells of r3 and r5 (ref. 3) (Fig. 1A). Here we demonstrate that the signalling molecule Bmp4 is expressed in r3 and r5 and is dependent on the neighbouring rhombomeres. Addition of recombinant BMP4 protein to explant cultures of r3 or r5, which produce neural crest when isolated from their neighbouring rhombomeres, upregulates msx2 and reinstates apoptosis in the neural crest population.

The regulation of tyrosine kinase signalling pathways by growth factor and G-protein-coupled receptors

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Peroxynitrite modification of low-density lipoprotein leads to recognition by the macrophage scavenger receptor

Peroxynitrite is an oxidant which could be formed in the vasculature by the reaction of superoxide with nitric oxide. It is capable of modifying amino acid residues and of initiating lipid peroxidation. In the present study we have shown that peroxynitrite converts low density lipoprotein to a form recognized by the macrophage scavenger receptor and that this process is associated with modification of the protein and lipid, and with the oxidation of alpha-tocopherol to alpha-tocopherol quinone.

Even-numbered rhombomeres control the apoptotic elimination of neural crest cells from odd-numbered rhombomeres in the chick hindbrain

Neural crest cells originate at three discontinuous levels along the rostrocaudal axis of the chick rhombencephalon, centred on rhombomeres 1 and 2, 4 and 6, respectively. These are separated by the odd-numbered rhombomeres r3 and r5 which are depleted of migratory neural crest cells. Here we show elevated levels of apoptosis in the dorsal midline of r3 and r5, immediately following the formation of these rhombomeres at the developmental stage (10–12) when neural crest cells would be expected to emerge at these neuraxial levels. These regions are also marked by their expression of members of the msx family of homeobox genes with msx-2 expression preceding apoptosis in a precisely colocalised pattern. In vitro and in ovo experiments have revealed that r3 and r5 are depleted of neural crest cells by an interaction within the neural epithelium: if isolated or distanced from their normal juxtaposition with even-numbered rhombomeres, both r3 and r5 produce migrating neural crest cells. When r3 or r5 are unconstrained in this way, allowing production of crest, msx-2 expression is concomitantly down regulated. This suggests a correlation between msx-2 and the programming of apoptosis in this system. The hindbrain neural crest is thus produced in discrete streams by mechanisms intrinsic to the neural epithelium. The crest cells that enter the underlying branchial region are organised into streams before they encounter the mesodermal environment lateral to the neural tube. This contrasts sharply with the situation in the trunk where neural crest production is uninterrupted along the neuraxis and the segmental accumulation of neurogenic crest cells is subsequently founded on an alternation of permissive and non-permissive qualities of the local mesodermal environment.

Evidence for collapsin-1 functioning in the control of neural crest migration in both trunk and hindbrain regions

Collapsin-1 belongs to the Semaphorin family of molecules, several members of which have been implicated in the co-ordination of axon growth and guidance. Collapsin-1 can function as a selective chemorepellent for sensory neurons, however, its early expression within the somites and the cranial neural tube (Shepherd, I., Luo, Y., Raper, J. A. and Chang, S. (1996) Dev. Biol. 173, 185–199) suggest that it might contribute to the control of additional developmental processes in the chick. We now report a detailed study on the expression of collapsin-1 as well as on the distribution of collapsin-1-binding sites in regions where neural crest cell migration occurs. collapsin-1 expression is detected in regions bordering neural crest migration pathways in both the trunk and hindbrain regions and a receptor for collapsin-1, neuropilin-1, is expressed by migrating crest cells derived from both regions. When added to crest cells in vitro, a collapsin-1-Fc chimeric protein induces morphological changes similar to those seen in neuronal growth cones. In order to test the function of collapsin-1 on the migration of neural crest cells, an in vitro assay was used in which collapsin-1-Fc was immobilised in alternating stripes consisting of collapsin-Fc/fibronectin versus fibronectin alone. Explanted neural crest cells derived from both trunk and hindbrain regions avoided the collapsin-Fc-containing substratum. These results suggest that collapsin-1 signalling can contribute to the patterning of neural crest cell migration in the developing chick.

Mutations in the gene encoding peroxisomal alpha-methylacyl-CoA racemase cause adult-onset sensory motor neuropathy

Sensory motor neuropathy is associated with various inherited disorders including Charcot-Marie-Tooth disease, X-linked adrenoleukodystrophy/adrenomyeloneuropathy and Refsum disease. In the latter two, the neuropathy is thought to result from the accumulation of specific fatty acids. We describe here three patients with elevated plasma concentrations of pristanic acid (a branched-chain fatty acid) and C27-bile-acid intermediates. Two of the patients suffered from adult-onset sensory motor neuropathy. One patient also had pigmentary retinopathy, suggesting Refsum disease, whereas the other patient had upper motor neuron signs in the legs, suggesting adrenomyeloneuropathy. The third patient was a child without neuropathy. In all three patients we discovered a deficiency of alpha-methylacyl-CoA racemase (AMACR). This enzyme is responsible for the conversion of pristanoyl-CoA and C27-bile acyl-CoAs to their (S)-stereoisomers, which are the only stereoisomers that can be degraded via peroxisomal beta-oxidation. Sequence analysis of AMACR cDNA from the patients identified two different mutations that are likely to cause disease, based on analysis in Escherichia coli. Our findings have implications for the diagnosis of adult-onset neuropathies of unknown aetiology.

Pharyngeal arch patterning in the absence of neural crest

Pharyngeal arches are a prominent and critical feature of the developing vertebrate head. They constitute a series of bulges within which musculature and skeletal elements form; importantly, these tissues derive from different embryonic cell types [1]. Numerous studies have emphasised the role of the cranial neural crest, from which the skeletal components derive, in patterning the pharyngeal arches [2-4]. It has never been clear, however, whether all arch patterning is completely dependent on this cell type. Here, we show that pharyngeal arch formation is not coupled to the process of crest migration and, furthermore, that pharyngeal arches form, are regionalized and have a sense of identity even in the absence of the neural crest. Thus, vertebrate head morphogenesis can now be seen to be a more complex process than was previously believed and must result from an integration of both neural-crest-dependent and -independent patterning mechanisms. Our results also reflect the fact that the evolutionary origin of pharyngeal segmentation predates that of the neural crest, which is an exclusively vertebrate characteristic.

Myasthenia gravis and neuromyelitis optica spectrum disorder: a multicenter study of 16 patients

OBJECTIVE

To describe 16 patients with a coincidence of 2 rare diseases: aquaporin-4 antibody (AQP4-Ab)-mediated neuromyelitis optica spectrum disorder (AQP4-NMOSD) and acetylcholine receptor antibody (AChR-Ab)-mediated myasthenia gravis (AChR-MG).

METHODS

The clinical details and antibody results of 16 patients with AChR-MG and AQP4-NMOSD were analyzed retrospectively.

RESULTS

All had early-onset AChR-MG, the majority with mild generalized disease, and a high proportion achieved remission. Fifteen were female; 11 were Caucasian. In 14/16, the MG preceded NMOSD (median interval: 16 years) and 11 of these had had a thymectomy although 1 only after NMOSD onset. In 4/5 patients tested, AQP4-Abs were detectable between 4 and 16 years prior to disease onset, including 2 patients with detectable AQP4-Abs prior to thymectomy. AChR-Abs decreased and the AQP4-Ab levels increased over time in concordance with the relevant disease. AChR-Abs were detectable at NMOSD onset in the one sample available from 1 of the 2 patients with NMOSD before MG.

CONCLUSIONS

Although both conditions are rare, the association of MG and NMOSD occurs much more frequently than by chance and the MG appears to follow a benign course. AChR-Abs or AQP4-Abs may be present years before onset of the relevant disease and the antibody titers against AQP4 and AChR tend to change in opposite directions. Although most cases had MG prior to NMOSD onset, and had undergone thymectomy, NMOSD can occur first and in patients who have not had their thymus removed.

Nicotinic receptor abnormalities in the cerebellar cortex in autism

Autism is a common developmental disorder associated with structural and inferred neurochemical abnormalities of the brain. Cerebellar abnormalities frequently have been identified, based on neuroimaging or neuropathology. Recently, the cholinergic neurotransmitter system has been implicated on the basis of nicotinic receptor loss in the cerebral cortex. Cerebellar cholinergic activities were therefore investigated in autopsy tissue from a series of autistic individuals. The presynaptic cholinergic enzyme, choline acetyltransferase, together with nicotinic and muscarinic receptor subtypes were compared in the cerebellum from age-matched mentally retarded autistic (eight), normal control (10) and non-autistic mentally retarded individuals (11). The nicotinic receptor binding the agonist epibatidine (the high affinity receptor subtype, consisting primarily of alpha3 and alpha4, together with beta2 receptor subunits) was significantly reduced by 40-50% in the granule cell, Purkinje and molecular layers in the autistic compared with the normal group (P < 0.05). There was an opposite increase (3-fold) in the nicotinic receptor binding alpha-bungarotoxin (to the alpha7 subunit) which reached significance in the granule cell layer (P < 0.05). These receptor changes were paralleled by a significant reduction (P < 0.05) and non-significant increase, respectively, of alpha4 and alpha7 receptor subunit immunoreactivity measured using western blotting. Immunohistochemically loss of alpha(4 )reactivity was apparent from Purkinje and the other cell layers, with increased alpha7 reactivity in the granule cell layer. There were no significant changes in choline acetyltransferase activity, or in muscarinic M1 and M2 receptor subtypes in autism. In the non-autistic mentally retarded group, the only significant abnormality was a reduction in epibatidine binding in the granule cell and Purkinje layers. In two autistic cases examined histologically, Purkinje cell loss was observed in multiple lobules throughout the vermis and hemispheres. This was more severe in one case with epilepsy, which also showed vermis folial malformation. The case with less severe Purkinje cell loss also showed cerebellar white matter thinning and demyelination. These findings indicate a loss of the cerebellar nicotinic alpha4 receptor subunit in autism which may relate to the loss of Purkinje cells, and a compensatory increase in the alpha7 subunit. It remains to be determined how these receptor abnormalities are involved in neurodevelopment in autism and what is the relationship to mental function. Since nicotinic receptor agonists enhance attentional function and also induce an elevation in the high affinity receptor, nicotinic therapy in autism may be worth considering.

Apolipoprotein E inhibits platelet aggregation through the L-arginine:nitric oxide pathway. Implications for vascular disease

We have previously reported that plasma apolipoprotein (apo) E-containing high density lipoprotein particles have a potent anti-platelet action, apparently by occupying saturable binding sites in the cell surface. Here we show that purified apoE (10-50 microg/ml), complexed with phospholipid vesicles (dimyristoylphosphatidylcholine, DMPC), suppresses platelet aggregation induced by ADP, epinephrine, or collagen. This effect was not due to sequestration of cholesterol from platelet membranes; apoE x DMPC chemically modified with cyclohexanedione (cyclohexanedione-apoE x DMPC) did not inhibit aggregation but nevertheless removed similar amounts of cholesterol as untreated complexes, about 2% during the aggregation period. Rather we found that apoE influenced intracellular platelet signaling. Thus, apoE x DMPC markedly increased cGMP in ADP-stimulated platelets which correlated with the resulting inhibition of aggregation (r = 0.85; p < 0.01, n = 10), whereas cyclohexanedione-apoE x DMPC vesicles had no effect. One important cellular mechanism for up-regulation of cGMP is through stimulation of nitric oxide (NO) synthase, the NO generated by conversion of L-arginine to L-citrulline, binds to and activates guanylate cyclase. This signal transduction pathway was implicated by the finding that NO synthase inhibitors of distinct structural and functional types all reversed the anti-platelet action of apoE, whereas a selective inhibitor of soluble guanylate cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (100 nM), had a similar reversing action. Direct confirmation that apoE stimulates NO synthase was obtained by use of L-[3H]arginine; platelets pretreated with apoE x DMPC produced markedly more L-[3H]citrulline (0.71 +/- 0.1 pmol/h/10(9) platelets) than controls (0.18 +/- 0.03; p < 0.05). In addition, hemoglobin which avidly binds NO also suppressed the anti-aggregatory effect, indicating that apoE stimulated sufficient production of NO by platelets for extracellular release to occur. We conclude that apoE inhibits platelet aggregation through the L-arginine:NO signal transduction pathway.

Characterisation of ACTH peptides in human skin and their activation of the melanocortin-1 receptor

Alpha-Melanocyte-stimulating hormone (alpha-MSH) is a proopiomelanocortin (POMC)-derived peptide, which is produced in the pituitary and at other sites including the skin. It has numerous effects and in the skin has a pigmentary action through the activation of the melanocortin-1 (MC-1) receptor, which is expressed by melanocytes. Recent evidence suggests that the related POMC peptides such as adrenocorticotrophin (ACTH), which is the precursor of alpha-MSH, is also an agonist at the MC-1 receptor. By using immunocytochemistry, we confirmed the presence of alpha-MSH in human skin where staining was evident in keratinocytes and especially strong in melanocytes and possibly Langerhans cells. ACTH was also present and tended to show the strongest reaction in differentiated keratinocytes. Immunostaining was also observed for the prohormone convertases, PC1 and PC2, which are involved in the formation of ACTH and its cleavage to alpha-MSH, respectively. The amounts of immunoreactive ACTH exceeded those of alpha-MSH. Using HPLC we identified for the first time the presence of ACTH1-39, ACTH1-17, ACTH1-10, acetylated ACTH1-10, alpha-MSH, and desacetyl alpha-MSH in epidermis and in cultured keratinocytes. The ability of these peptides to activate the human MC-1 receptor was examined in HEK 293 cells that had been transfected with the receptor. All peptides increased adenylate cyclase in these cells with the following order of potency: ACTH1-17 > alpha-MSH > ACTH1-39 > desacetyl alpha-MSH > acetylated ACTH1-10 > ACTH1-10. ACTH1-17 also increased the dendricity and melanin content of cultured human melanocytes indicating that the peptide was able to activate MC-1 receptors when present in their normal location. However, as found with alpha-MSH, not all cultures were responsive and, as we have previously suggested, we suspect that this was the result of changes at the MC-1 receptor. Nevertheless, it would appear that ACTH peptides can serve as natural ligands of the MC-1 receptor on human melanocytes and their presence in the skin suggests that, together with alpha-MSH, they may have a role in the regulation of human melanocytes.

Nicotinic receptors in human brain: topography and pathology

Brain nicotinic acetylcholine receptors (nAChR) are a class of ligand-gated channels composed of alpha and beta subunits with specific structural, functional and pharmacological properties. They participate in the physiological and behavioural effects of acetylcholine and mediate responses to nicotine. They are associated with numerous transmitter systems and their expression is altered during development and ageing as well as in diseases such as autism, schizophrenia, Alzheimer's disease, Parkinson's disease and Lewy body dementia. Nicotinic receptors containing a number of different subunits are highly expressed during early human development. Disorders believed to be associated with abnormal brain maturation involve deficits in both alpha4beta2, in the case of autism, and alpha7 possibly in addition to alpha4beta2 nAChRs in the case of schizophrenia. In ageing and age-related neurodegenerative disorders nAChR deficits are predominantly associated with alpha4-containing receptors, although some studies also indicate the involvement of alpha3 and alpha7 subunits. Whilst ageing appears to be associated with reductions in subunit mRNA as well as protein expression, in Alzheimer's disease only protein loss is apparent. Nicotinic therapy may be of benefit in a number of neurological conditions, however studies evaluating further both the distribution of specific subunit involvement and the correlation of nAChR deficits with clinical symptoms are required to inform therapeutic strategy.

Induction of the epibranchial placodes

The cranial sensory ganglia, in contrast to those of the trunk, have a dual embryonic origin arising from both neurogenic placodes and neural crest. Neurogenic placodes are focal thickenings of ectoderm, found exclusively in the head of vertebrate embryos. These structures can be split into two groups based on the positions that they occupy within the embryo, dorsolateral and epibranchial. The dorsolateral placodes develop alongside the central nervous system, while the epibranchial placodes are located close to the top of the clefts between the branchial arches. Importantly, previous studies have shown that the neurogenic placodes form under the influence of the surrounding cranial tissues. In this paper, we have analysed the nature of the inductive signal underlying the formation of the epibranchial placodes. We find that epibranchial placodes do not require neural crest for their induction, but rather that it is the pharyngeal endoderm that is the source of the inductive signal. We also find that, while cranial ectoderm is competent to respond to this inductive signal, trunk ectoderm is not. We have further identified the signalling molecule Bmp7 as the mediator of this inductive interaction. This molecule is expressed in a manner consistent with it playing such a role and, when added to ectoderm explants, it will promote the formation of epibranchial neuronal cells. Moreover, the Bmp7 antagonist follstatin will block the ability of pharyngeal endoderm to induce placodal neuronal cells, demonstrating that Bmp7 is required for this inductive interaction. This work answers the long standing question regarding the induction of the epibranchial placodes, and represents the first elucidation of an inductive mechanism, and a molecular effector, underlying the formation of any primary sensory neurons in higher vertebrates.

Activities of daily living in frontotemporal dementia and Alzheimer disease

OBJECTIVE

To evaluate activities of daily living (ADLs) in three clinical variants of frontotemporal dementia and the relationship to cognitive dysfunction.

METHODS

Fifty-nine patients and caregivers participated in this cross-sectional study: behavioral variant frontotemporal dementia (bv-FTD, n = 15), progressive nonfluent aphasia (PNFA, n = 10), semantic dementia (n = 15), and Alzheimer disease (AD, n = 19). Caregivers were interviewed with the Disability Assessment for Dementia (DAD) to provide two outcome measures about ADLs: basic and instrumental ADLs (BADLs, IADL). In addition, patients were rated on the Clinical Dementia Rating Scale (CDR), and performance on cognitive measures (Addenbrooke's Cognitive Examination Revised [ACE-R]) was assessed.

RESULTS

On the DAD, the bv-FTD group was most affected (56% of normal), whereas PNFA and semantic dementia patients were least impaired (83% and 85%); AD was intermediate (76%). The opposite pattern was seen on the ACE-R, where PNFA and semantic dementia groups were most affected, and bv-FTD showed least impairment; AD was again intermediate. Scores on the DAD did not correlate with cognitive measures, CDR, or disease duration. We further analyzed which aspect of ADLs was most affected, and a unique pattern of deficits emerged for the bv-FTD group (initiation affected > planning > execution for BADLs).

CONCLUSION

Frontotemporal dementia has a devastating effect on activities of daily living, which is of considerable importance to caregivers and not captured by bedside cognitive tests.

Neural Crest Apoptosis and the Establishment of Craniofacial Pattern: An Honorable Death

During development of the vertebrate head neural crest cells emigrate from the hindbrain and populate the branchial arches, giving rise to distinct skeletal elements and muscle connective tissues in each arch. The production of neural crest from the hindbrain is discontinuous and crest cells destined for different arches, carrying different positional cues, are separated by regions of apoptosis centered on rhombomeres (r) 3 and r5. This cell death program is under the interactive control of the neighboring hindbrain segments. Both r3 and r5 produce large numbers of crest cells when freed from their flanking rhombomere, but when conjoined with their neighbor the cell death program is restored. Two key components of this program are Bmp 4 and msx-2, both of which are expressed in the apoptotic foci of r3 and r5 and which are also regulated by neighbor interactions. Importantly, the addition of recombinant Bmp 4 to isolated cultures of r3 and r5 induces the expression of Bmp 4 and msx-2 and restores the cell death program. This early neural crest segregation is maintained during development and it has profound effects upon the final craniofacial pattern. Even though crest cells from different axial origins will contribute to compound skeletal elements, these distinct populations do not intermingle. Furthermore head muscle connective tissues are exclusively anchored to skeletal domains arising from neural crest from the same axial level. Thus the discontinuous production of neural crest sculpts the crest into nonmixing streams and consequently ensures the fidelity of patterning.

Characterization of a murine homeo box gene, Hox-2.6, related to the Drosophila Deformed gene

The Hox-2 locus on chromosome 11 represents one of the major clusters of homeo-box-containing genes in the mouse. We have identified two new members (Hox-2.6 and Hox-2.7), which form part of this cluster of seven linked genes, and it appears that the Hox-2 locus is related by duplication and divergence to at least one other mouse homeo box cluster, Hox-1. The Hox-2.6 gene encodes a predicted protein of 250 amino acids, which displays extensive similarity in multiple regions to certain mouse, human, Xenopus, and zebra fish homeo domain proteins. The Drosophila Deformed (Dfd) gene also shares these same regions of similarity, and based on this sequence conservation, we suggest that Hox-2.6 forms part of a vertebrate 'Dfd-like' family. Hox-2.6 is expressed in fetal and adult tissues and is modulated during the differentiation of F9 teratocarcinoma stem cells. In situ hybridization analysis of mouse embryos shows that the Hox-2.6 is expressed in ectodermal derivatives: spinal cord, hindbrain, dorsal root ganglia, and the Xth cranial ganglia. In the central nervous system, expression is observed in the most posterior parts of the spinal cord, with the anterior limit residing in a region of the hindbrain and no expression in the mid- or forebrain. In mesodermal structures, Hox-2.6 is expressed in the kidney, the mesenchyme of the stomach and lung, and the longitudinal muscle layer of the gut. Expression has not been observed in derivatives of embryonic endoderm. The patterns of Hox-2.6 expression in both mesoderm and ectoderm are spatially restricted and may reflect a role for the gene in the response to or establishment of positional cues in the embryo.

Epidemiological, social, diagnostic and economic evaluation of population screening for genital chlamydial infection

OBJECTIVES

To investigate epidemiological, social, diagnostic and economic aspects of chlamydia screening in non-genitourinary medicine settings.

METHODS

Linked studies around a cross-sectional population-based survey of adult men and women invited to collect urine and (for women) vulvovaginal swab specimens at home and mail these to a laboratory for testing for Chlamydia trachomatis. Specimens were used in laboratory evaluations of an amplified enzyme immunoassay (PCE EIA) and two nucleic acid amplification tests [Cobas polymerase chain reaction (PCR), Becton Dickinson strand displacement amplification (SDA)]. Chlamydia-positive cases and two negative controls completed a risk factor questionnaire. Chlamydia-positive cases were invited into a randomised controlled trial of partner notification strategies. Samples of individuals testing negative completed psychological questionnaires before and after screening. In-depth interviews were conducted at all stages of screening. Chlamydia transmission and cost-effectiveness of screening were investigated in a transmission dynamic model.

SETTING AND PARTICIPANTS

General population in the Bristol and Birmingham areas of England. In total, 19,773 women and men aged 16-39 years were randomly selected from 27 general practice lists.

RESULTS

Screening invitations reached 73% (14,382/19,773). Uptake (4731 participants), weighted for sampling, was 39.5% (95% CI 37.7, 40.8%) in women and 29.5% (95% CI 28.0, 31.0%) in men aged 16-39 years. Chlamydia prevalence (219 positive results) in 16-24 year olds was 6.2% (95% CI 4.9, 7.8%) in women and 5.3% (95% CI 4.4, 6.3%) in men. The case-control study did not identify any additional factors that would help target screening. Screening did not adversely affect anxiety, depression or self-esteem. Participants welcomed the convenience and privacy of home-sampling. The relative sensitivity of PCR on male urine specimens was 100% (95% CI 89.1, 100%). The combined relative sensitivities of PCR and SDA using female urine and vulvovaginal swabs were 91.8% (86.1, 95.7, 134/146) and 97.3% (93.1, 99.2%, 142/146). A total of 140 people (74% of eligible) participated in the randomised trial. Compared with referral to a genitourinary medicine clinic, partner notification by practice nurses resulted in 12.4% (95% CI -3.7, 28.6%) more patients with at least one partner treated and 22.0% (95% CI 6.1, 37.8%) more patients with all partners treated. The health service and patients costs (2005 prices) of home-based postal chlamydia screening were 21.47 pounds (95% CI 19.91 pounds, 25.99) per screening invitation and 28.56 pounds (95% CI 22.10 pounds, 30.43) per accepted offer. Preliminary modelling found an incremental cost-effectiveness ratio (2003 prices) comparing screening men and women annually to no screening in the base case of 27,000 pounds/major outcome averted at 8 years. If estimated screening uptake and pelvic inflammatory disease incidence were increased, the cost-effectiveness ratio fell to 3700 pounds/major outcome averted.

CONCLUSIONS

Proactive screening for chlamydia in women and men using home-collected specimens was feasible and acceptable. Chlamydia prevalence rates in men and women in the general population are similar. Nucleic acid amplification tests can be used on first-catch urine specimens and vulvovaginal swabs. The administrative costs of proactive screening were similar to those for opportunistic screening. Using empirical estimates of screening uptake and incidence of complications, screening was not cost-effective.

Synthesis of beta-galactose-conjugated chlorins derived by enyne metathesis as galectin-specific photosensitizers for photodynamic therapy

A first report on the synthesis and biological evaluation of the beta-galactose-conjugated purpurinimides (a class of chlorins containing a six-membered fused imide ring system) as Gal-1 (galectin-1) recognized photosensitizers, prepared from purpurin-N-propargylimide via enyne metathesis, is discussed. On the basis of examination of the available crystal structure of the galectin-1 N-acetyllactose amine complex, it was considered that the chlorin-based photosensitizers could be introduced into a carbohydrate skeleton to expand the repertoire of the galectin-1-specific ligands. Preliminary molecular modeling analysis utilizing the modeled photosensitizers and the available crystal structures of galectin-carbohydrate complexes indicated that addition of the photosensitizer to the carbohydrate moiety at an appropriate position does not interfere with the galectin-carbohydrate recognition. Under similar drug and light doses, compared to the free purpurinimide analogue, the purpurinimides conjugated either with galactose or with lactose (Gal(beta1-4)-Glc) produced a considerable increase in photosensitizing efficacy in vitro. This indicates the possibility for development of a new class of specific photosensitizers for photodynamic therapy (PDT) based on recognition of a cellular receptor.

Domains of cellular retinoic acid-binding protein I (CRABP I) expression in the hindbrain and neural crest of the mouse embryo

We describe here the distribution of cellular retinoic acid-binding protein I (CRABP I) in the head of the early mouse embryo from day 8 to day 13 of gestation, using both in situ hybridisation to localise mRNA and immunocytochemistry to localise protein. The distribution of mRNA and protein was found to be identical. CRABP I first appeared in part of the presumptive hindbrain of the presomite embryo and then became localised to rhombomeres 2, 4, 5 and 6. The only other area of expression in the cephalic neuroepithelium was in a part of the midbrain roof. The neural crest and its mesenchymal derivatives, the branchial arches, expressed CRABP I and crest could be seen streaming from the neuroepithelium of individual rhombomeres into particular branchial arches. This suggested a fate map could be constructed describing the rhombomeric origin of branchial arch mesenchyme. Later in development, axons throughout the hindbrain expressed CRABP I. The results are considered in terms of the role of retinoic acid in the specification of neuronal phenotype in the hindbrain and in axon outgrowth.

Integration between the epibranchial placodes and the hindbrain

Developmental integration results from coordination among components of different embryonic fields to realize the later anatomical and functional relationships. We demonstrate that in the chick head, integration between the epibranchial placodes and the hindbrain is achieved as the neuroglial hindbrain crest cells guide the epibranchial neuronal cells inward to establish their central connections. This work defines a role for the neuroglial hindbrain crest in organizing the afferent innervation of the hindbrain.

Diagnosis of alpha 1-antitrypsin deficiency by enzymatic amplification of human genomic DNA and direct sequencing of polymerase chain reaction products

We have compared sequencing of cloned "polymerase chain reaction" (PCR) products and the direct sequencing of PCR products in the examination of individuals from six families affected with alpha 1-antitrypsin (AAT) deficiency. In families where paternity was in question we confirmed consanguinity by DNA fingerprinting using a panel of locus-specific minisatellite probes. We demonstrate that direct sequencing of PCR amplification products is the method of choice for the absolutely specific diagnosis of AAT deficiency and can distinguish normals, heterozygotes and homozygotes in a single, rapid and facile assay. Furthermore, we demonstrate the reproducibility of the PCR and a rapid DNA isolation procedure. We have also shown that two loci can be simultaneously amplified and that the PCR product from each locus can be independently examined by direct DNA sequencing.

Physical fitness of adults with an intellectual disability: a 13-year follow-up study

The purpose of this study was to describe the change in physical fitness of middle-aged adults with an intellectual disability over a period of 13 years. Participants were 32 adults who worked in a supported work environment in Montreal and had been participants in a physical fitness study in 1983. Using the Canadian Standardized Test of Fitness, the participants were evaluated for cardiovascular endurance, muscular strength, muscular endurance, flexibility, and body composition. A home visit prior to the testing session refamiliarized the participants with the test procedures. Two forms of analysis were used to describe the change in fitness over 13 years. First, a 2 x 2 (Group x Time) analysis of variance for each dependent variable assessed change over time. Second, effect sizes were calculated to measure the magnitude of change in fitness over the 13-year period in comparison to those without an intellectual disability. As expected, the physical fitness levels of the participants were low when compared to those without a disability and declined over the 13 years. In addition, the magnitude of change over the 13 years, as compared to those without a disability, was greater for male and female participants for body mass index and percentage of body fat and for female participants for cardiovascular endurance and sit-ups. It appears that adults with an intellectual disability may be particularly at risk for declining health associated with aging and low physical fitness.