The genome of black cottonwood, Populus trichocarpa (Torr. & Gray)

We report the draft genome of the black cottonwood tree, Populus trichocarpa. Integration of shotgun sequence assembly with genetic mapping enabled chromosome-scale reconstruction of the genome. More than 45,000 putative protein-coding genes were identified. Analysis of the assembled genome revealed a whole-genome duplication event; about 8000 pairs of duplicated genes from that event survived in the Populus genome. A second, older duplication event is indistinguishably coincident with the divergence of the Populus and Arabidopsis lineages. Nucleotide substitution, tandem gene duplication, and gross chromosomal rearrangement appear to proceed substantially more slowly in Populus than in Arabidopsis. Populus has more protein-coding genes than Arabidopsis, ranging on average from 1.4 to 1.6 putative Populus homologs for each Arabidopsis gene. However, the relative frequency of protein domains in the two genomes is similar. Overrepresented exceptions in Populus include genes associated with lignocellulosic wall biosynthesis, meristem development, disease resistance, and metabolite transport.

Principles of protein-protein interactions

This review examines protein complexes in the Brookhaven Protein Databank to gain a better understanding of the principles governing the interactions involved in protein-protein recognition. The factors that influence the formation of protein-protein complexes are explored in four different types of protein-protein complexes--homodimeric proteins, heterodimeric proteins, enzyme-inhibitor complexes, and antibody-protein complexes. The comparison between the complexes highlights differences that reflect their biological roles.

CATH--a hierarchic classification of protein domain structures

BACKGROUND

Protein evolution gives rise to families of structurally related proteins, within which sequence identities can be extremely low. As a result, structure-based classifications can be effective at identifying unanticipated relationships in known structures and in optimal cases function can also be assigned. The ever increasing number of known protein structures is too large to classify all proteins manually, therefore, automatic methods are needed for fast evaluation of protein structures.

RESULTS

We present a semi-automatic procedure for deriving a novel hierarchical classification of protein domain structures (CATH). The four main levels of our classification are protein class (C), architecture (A), topology (T) and homologous superfamily (H). Class is the simplest level, and it essentially describes the secondary structure composition of each domain. In contrast, architecture summarises the shape revealed by the orientations of the secondary structure units, such as barrels and sandwiches. At the topology level, sequential connectivity is considered, such that members of the same architecture might have quite different topologies. When structures belonging to the same T-level have suitably high similarities combined with similar functions, the proteins are assumed to be evolutionarily related and put into the same homologous superfamily.

CONCLUSIONS

Analysis of the structural families generated by CATH reveals the prominent features of protein structure space. We find that nearly a third of the homologous superfamilies (H-levels) belong to ten major T-levels, which we call superfolds, and furthermore that nearly two-thirds of these H-levels cluster into nine simple architectures. A database of well-characterised protein structure families, such as CATH, will facilitate the assignment of structure-function/evolution relationships to both known and newly determined protein structures.

A Wnt5a pathway underlies outgrowth of multiple structures in the vertebrate embryo

Morphogenesis depends on the precise control of basic cellular processes such as cell proliferation and differentiation. Wnt5a may regulate these processes since it is expressed in a gradient at the caudal end of the growing embryo during gastrulation, and later in the distal-most aspect of several structures that extend from the body. A loss-of-function mutation of Wnt5a leads to an inability to extend the A-P axis due to a progressive reduction in the size of caudal structures. In the limbs, truncation of the proximal skeleton and absence of distal digits correlates with reduced proliferation of putative progenitor cells within the progress zone. However, expression of progress zone markers, and several genes implicated in distal outgrowth and patterning including Distalless, Hoxd and Fgf family members was not altered. Taken together with the outgrowth defects observed in the developing face, ears and genitals, our data indicates that Wnt5a regulates a pathway common to many structures whose development requires extension from the primary body axis. The reduced number of proliferating cells in both the progress zone and the primitive streak mesoderm suggests that one function of Wnt5a is to regulate the proliferation of progenitor cells.

Impaired osteoclastic bone resorption leads to osteopetrosis in cathepsin-K-deficient mice

Cathepsin K is a recently identified lysosomal cysteine proteinase. It is abundant in osteoclasts, where it is believed to play a vital role in the resorption and remodeling of bone. Pycnodysostosis is a rare inherited osteochondrodysplasia that is caused by mutations of the cathepsin-K gene, characterized by osteosclerosis, short stature, and acroosteolysis of the distal phalanges. With a view to delineating the role of cathepsin K in bone resorption, we generated mice with a targeted disruption of this proteinase. Cathepsin-K-deficient mice survive and are fertile, but display an osteopetrotic phenotype with excessive trabeculation of the bone-marrow space. Cathepsin-K-deficient osteoclasts manifested a modified ultrastructural appearance: their resorptive surface was poorly defined with a broad demineralized matrix fringe containing undigested fine collagen fibrils; their ruffled borders lacked crystal-like inclusions, and they were devoid of collagen-fibril-containing cytoplasmic vacuoles. Assaying the resorptive activity of cathepsin-K-deficient osteoclasts in vitro revealed this function to be severely impaired, which supports the contention that cathepsin K is of major importance in bone remodeling.

Il-6 and its soluble receptor orchestrate a temporal switch in the pattern of leukocyte recruitment seen during acute inflammation

During acute inflammation, leukocyte recruitment is characterized by an initial infiltration of neutrophils, which are later replaced by a more sustained population of mononuclear cells. Based on both clinical and experimental evidence, we present a role for IL-6 and its soluble receptor (sIL-6R) in controlling this pattern of leukocyte recruitment during peritoneal inflammation. Liberation of sIL-6R from the initial neutrophil infiltrate acts as a regulator of CXC and CC chemokine expression, which contributes to a suppression of neutrophil recruitment and the concurrent attraction of mononuclear leukocytes. Soluble IL-6R-mediated signaling is therefore an important intermediary in the resolution of inflammation and supports transition between the early predominantly neutrophilic stage of an infection and the more sustained mononuclear cell influx.

A physical map of the human genome

The human genome is by far the largest genome to be sequenced, and its size and complexity present many challenges for sequence assembly. The International Human Genome Sequencing Consortium constructed a map of the whole genome to enable the selection of clones for sequencing and for the accurate assembly of the genome sequence. Here we report the construction of the whole-genome bacterial artificial chromosome (BAC) map and its integration with previous landmark maps and information from mapping efforts focused on specific chromosomal regions. We also describe the integration of sequence data with the map.

Analysis of protein-protein interaction sites using surface patches

Protein-protein interaction sites in complexes of known structure are characterised using a series of parameters to evaluate what differentiates them from other sites on the protein surface. Surface patches are defined in protomers from a data set of 28 homo-dimers, 20 different hetero-complexes (segregated into large and small protomers), and antigens from six antibody-antigen complexes. Six parameters (solvation potential, residue interface propensity, hydrophobicity, planarity, protrusion and accessible surface area) are calculated for the observed interface patch and all other surface patches defined on each protein. A ranking of the observed interface, relative to all other possible patches, is calculated. With this approach it becomes possible to analyse the distribution of the rankings of all the observed patches, relative to all other surface patches, for each data set. For each type of complex, none of the parameters were definitive, but the majority showed trends for the observed interface to be distinguished from other surface patches.

Influenza vaccination of pregnant women and protection of their infants

BACKGROUND

There are limited data on the efficacy of vaccination against confirmed influenza in pregnant women with and those without human immunodeficiency virus (HIV) infection and protection of their infants.

METHODS

We conducted two double-blind, randomized, placebo-controlled trials of trivalent inactivated influenza vaccine (IIV3) in South Africa during 2011 in pregnant women infected with HIV and during 2011 and 2012 in pregnant women who were not infected. The immunogenicity, safety, and efficacy of IIV3 in pregnant women and their infants were evaluated until 24 weeks after birth. Immune responses were measured with a hemagglutination inhibition (HAI) assay, and influenza was diagnosed by means of reverse-transcriptase-polymerase-chain-reaction (RT-PCR) assays of respiratory samples.

RESULTS

The study cohorts included 2116 pregnant women who were not infected with HIV and 194 pregnant women who were infected with HIV. At 1 month after vaccination, seroconversion rates and the proportion of participants with HAI titers of 1:40 or more were higher among IIV3 recipients than among placebo recipients in both cohorts. Newborns of IIV3 recipients also had higher HAI titers than newborns of placebo recipients. The attack rate for RT-PCR-confirmed influenza among both HIV-uninfected placebo recipients and their infants was 3.6%. The attack rates among HIV-uninfected IIV3 recipients and their infants were 1.8% and 1.9%, respectively, and the respective vaccine-efficacy rates were 50.4% (95% confidence interval [CI], 14.5 to 71.2) and 48.8% (95% CI, 11.6 to 70.4). Among HIV-infected women, the attack rate for placebo recipients was 17.0% and the rate for IIV3 recipients was 7.0%; the vaccine-efficacy rate for these IIV3 recipients was 57.7% (95% CI, 0.2 to 82.1).

CONCLUSIONS

Influenza vaccine was immunogenic in HIV-uninfected and HIV-infected pregnant women and provided partial protection against confirmed influenza in both groups of women and in infants who were not exposed to HIV. (Funded by the Bill and Melinda Gates Foundation and others; ClinicalTrials.gov numbers, NCT01306669 and NCT01306682.).

Nicotinic receptors in the brain: correlating physiology with function

Nicotinic ACh receptors (nAChRs) have been implicated in a variety of brain functions, including neuronal development, learning and memory formation, and reward. Although there are substantial data indicating that nAChR subunits are found in many brain regions, the precise cellular roles of these subunits in neuronal functions have remained elusive. Until recently, nAChRs were thought primarily to serve a modulatory role in the brain by regulating neurotransmitter release from nerve terminals. However, new evidence has revealed that nAChRs also function in a postsynaptic role by mediating fast ACh-mediated synaptic transmission in the hippocampus and in the sensory cortex, and are found at somatodendritic as well as nerve terminal sites in the reward system. It is possible that presynaptic and postsynaptic nAChRs mediate changes in the efficacy of synaptic transmission in these brain regions. These changes could underlie the proposed functions of nAChRs in cognitive functions of the hippocampus and cerebral cortex, in neuronal development in the sensory cortex, and in reward.

Family factors in schizophrenic relapse. Replication in California of British research on expressed emotion

Our study of the emotional atmosphere of the homes of schizophrenic patients in southern California has replicated British findings concerning the influence of the family environment on the course of schizophrenia. As in the British studies, criticism and overinvolvement expressed by a key relative about the patient at the time of the key admission proved to be the best single predictor of symptomatic relapse in the nine months after discharge from the hospital. Replicating the British results, the association between relatives' expressed emotion and relapse was independent of all other variables investigated. Cross-cultural results concerning the prophylactic effects of medication suggest that clinicians should look to the emotional atmosphere in the home for explanations of medication failures.

Protein-DNA interactions: A structural analysis

A detailed analysis of the DNA-binding sites of 26 proteins is presented using data from the Nucleic Acid Database (NDB) and the Protein Data Bank (PDB). Chemical and physical properties of the protein-DNA interface, such as polarity, size, shape, and packing, were analysed. The DNA-binding sites shared common features, comprising many discontinuous sequence segments forming hydrophilic surfaces capable of direct and water-mediated hydrogen bonds. These interface sites were compared to those of protein-protein binding sites, revealing them to be more polar, with many more intermolecular hydrogen bonds and buried water molecules than the protein-protein interface sites. By looking at the number and positioning of protein residue-DNA base interactions in a series of interaction footprints, three modes of DNA binding were identified (single-headed, double-headed and enveloping). Six of the eight enzymes in the data set bound in the enveloping mode, with the protein presenting a large interface area effectively wrapped around the DNA.A comparison of structural parameters of the DNA revealed that some values for the bound DNA (including twist, slide and roll) were intermediate of those observed for the unbound B-DNA and A-DNA. The distortion of bound DNA was evaluated by calculating a root-mean-square deviation on fitting to a canonical B-DNA structure. Major distortions were commonly caused by specific kinks in the DNA sequence, some resulting in the overall bending of the helix. The helix bending affected the dimensions of the grooves in the DNA, allowing the binding of protein elements that would otherwise be unable to make contact. From this structural analysis a preliminary set of rules that govern the bending of the DNA in protein-DNA complexes, are proposed.

Protein-RNA interactions: a structural analysis

A detailed computational analysis of 32 protein-RNA complexes is presented. A number of physical and chemical properties of the intermolecular interfaces are calculated and compared with those observed in protein-double-stranded DNA and protein-single-stranded DNA complexes. The interface properties of the protein-RNA complexes reveal the diverse nature of the binding sites. van der Waals contacts played a more prevalent role than hydrogen bond contacts, and preferential binding to guanine and uracil was observed. The positively charged residue, arginine, and the single aromatic residues, phenylalanine and tyrosine, all played key roles in the RNA binding sites. A comparison between protein-RNA and protein-DNA complexes showed that whilst base and backbone contacts (both hydrogen bonding and van der Waals) were observed with equal frequency in the protein-RNA complexes, backbone contacts were more dominant in the protein-DNA complexes. Although similar modes of secondary structure interactions have been observed in RNA and DNA binding proteins, the current analysis emphasises the differences that exist between the two types of nucleic acid binding protein at the atomic contact level.

The two distinct phospholipases C of Listeria monocytogenes have overlapping roles in escape from a vacuole and cell-to-cell spread

Listeria monocytogenes secretes two distinct phospholipases C, a phosphatidylinositol-specific phospholipase C (PI-PLC) and a broad-range phospholipase C (PC-PLC). In this study, single in-frame deletion mutants with mutations in each PLC and a double mutant lacking both PLCs were characterized with regard to virulence in mice, escape from a primary vacuole, and cell-to-cell spread in cell culture. The mutant lacking PI-PLC, previously shown to be twofold less virulent than the wild type in mice, had a minor defect in escape from a primary vacuole but was not notably affected in cell-to-cell spread. The mutant lacking PC-PLC was 20-fold less virulent in mice and was defective in cell-to-cell spread but had no measurable defect in escape from a primary vacuole. The mutant lacking both PLCs was 500-fold less virulent in mice and was severely diminished in its ability to escape from the primary vacuole and to spread cell to cell. Cellular levels of diacylglycerol and ceramide, products of PLC activity, accumulated beginning 3 to 4 h after infection of cells with wild-type bacteria. The bacterial PLCs were partially responsible for this activity, since cells infected with the mutant lacking both PLCs had a reduced increase in diacylglycerol and no increase in ceramide. Elevation of diacylglycerol in the absence of bacterial PLCs indicated that host cell phospholipase(s) was activated during infection. The results of this study were consistent with the two bacterial PLCs having overlapping functions throughout the course of intracellular infection. Furthermore, the PC-PLC, and possibly PI-PLC, appeared to be enzymatically active intracellularly.

A functional genomic analysis of cell morphology using RNA interference

Background

The diversity of metazoan cell shapes is influenced by the dynamic cytoskeletal network. With the advent of RNA-interference (RNAi) technology, it is now possible to screen systematically for genes controlling specific cell-biological processes, including those required to generate distinct morphologies.

Results

We adapted existing RNAi technology in Drosophila cell culture for use in high-throughput screens to enable a comprehensive genetic dissection of cell morphogenesis. To identify genes responsible for the characteristic shape of two morphologically distinct cell lines, we performed RNAi screens in each line with a set of double-stranded RNAs (dsRNAs) targeting 994 predicted cell shape regulators. Using automated fluorescence microscopy to visualize actin filaments, microtubules and DNA, we detected morphological phenotypes for 160 genes, one-third of which have not been previously characterized in vivo. Genes with similar phenotypes corresponded to known components of pathways controlling cytoskeletal organization and cell shape, leading us to propose similar functions for previously uncharacterized genes. Furthermore, we were able to uncover genes acting within a specific pathway using a co-RNAi screen to identify dsRNA suppressors of a cell shape change induced by Pten dsRNA.

Conclusions

Using RNAi, we identified genes that influence cytoskeletal organization and morphology in two distinct cell types. Some genes exhibited similar RNAi phenotypes in both cell types, while others appeared to have cell-type-specific functions, in part reflecting the different mechanisms used to generate a round or a flat cell morphology.

Clinical practice guideline: Polysomnography for sleep-disordered breathing prior to tonsillectomy in children

OBJECTIVE

This guideline provides otolaryngologists with evidence-based recommendations for using polysomnography in assessing children, aged 2 to 18 years, with sleep-disordered breathing and are candidates for tonsillectomy, with or without adenoidectomy. Polysomnography is the electrographic recording of simultaneous physiologic variables during sleep and is currently considered the gold standard for objectively assessing sleep disorders.

PURPOSE

There is no current consensus or guideline on when children 2 to 18 years of age, who are candidates for tonsillectomy, are recommended to have polysomnography. The primary purpose of this guideline is to improve referral patterns for polysomnography among these patients. In creating this guideline, the American Academy of Otolaryngology--Head and Neck Surgery Foundation selected a panel representing the fields of anesthesiology, pulmonology medicine, otolaryngology-head and neck surgery, pediatrics, and sleep medicine.

RESULTS

The committee made the following recommendations: (1) before determining the need for tonsillectomy, the clinician should refer children with sleep-disordered breathing for polysomnography if they exhibit certain complex medical conditions such as obesity, Down syndrome, craniofacial abnormalities, neuromuscular disorders, sickle cell disease, or mucopolysaccharidoses. (2) The clinician should advocate for polysomnography prior to tonsillectomy for sleep-disordered breathing in children without any of the comorbidities listed in statement 1 for whom the need for surgery is uncertain or when there is discordance between tonsillar size on physical examination and the reported severity of sleep-disordered breathing. (3) Clinicians should communicate polysomnography results to the anesthesiologist prior to the induction of anesthesia for tonsillectomy in a child with sleep-disordered breathing. (4) Clinicians should admit children with obstructive sleep apnea documented on polysomnography for inpatient, overnight monitoring after tonsillectomy if they are younger than age 3 or have severe obstructive sleep apnea (apnea-hypopnea index of 10 or more obstructive events/hour, oxygen saturation nadir less than 80%, or both). (5) In children for whom polysomnography is indicated to assess sleep-disordered breathing prior to tonsillectomy, clinicians should obtain laboratory-based polysomnography, when available.

Prospective study of radioimmunoassay for antibodies against neutrophil cytoplasm in diagnosis of systemic vasculitis

The diagnosis and management of Wegener's granulomatosis and microscopic polyarteritis are complicated by the lack of specific diagnostic tests. The diagnostic performance of a solid-phase radioimmunoassay, which detects the autoantibodies against neutrophil cytoplasm present in these disorders, was assessed in a prospective study of patients with suspected vasculitis and/or rapidly progressive nephritis. The assay had a sensitivity and specificity of 96% when carried out in combination with a specific inhibition stage and indirect immunofluorescence staining of alcohol-fixed normal neutrophils.

The lux autoinducer regulates the production of exoenzyme virulence determinants in Erwinia carotovora and Pseudomonas aeruginosa

Erwinia carotovora and Pseudomonas aeruginosa secrete exoenzymes that contribute to the pathogenesis of plant and mammalian infections respectively. E.carotovora mutants defective in synthesis of the pectinase, cellulase and protease exoenzymes were isolated and classified into two groups. Group 2 mutants were found to be defective in the production of a small freely diffusible molecule, N-3-(oxohexanoyl)-L-homoserine, lactone (HSL), and were avirulent. Addition of exogenous HSL to these group 2 mutants restores synthesis of the exoenzymes and virulence in planta. Of the exoenzymes of P.aeruginosa the metalloprotease, elastase, is an established virulence determinant. Mutants of P.aeruginosa that are defective in elastase production have been isolated and were again found to fall into two groups. Analogous to the group 2 mutants of E.carotovora, group 2 mutants of P. aeruginosa are defective in the synthesis of HSL and exogenous HSL restores elastase production. HSL has now been linked to the control of bioluminescence in Vibrio fischeri, carbapenem antibiotic production of E.carotovora and the above exoenzyme virulence determinants. This information significantly enhances our understanding of the extent and nature of pheromone mediated gene expression control in prokaryotes.

Prediction of protein-protein interaction sites using patch analysis

A method for defining and analysing a series of residue patches on the surface of protein structures is used to predict the location of protein-protein interaction sites. Each residue patch is analysed for six parameters; solvation potential, residue interface propensity, hydrophobicity, planarity, protrusion and accessible surface area. The method involves the calculation of a relative combined score that gives the probability of a surface patch forming protein-protein interactions. Predictions are made for the known structures of protomers from 28 homo-dimers, large protomers from 11 hetero-complexes, small protomers from 14 hetero-complexes, and antigens from six antibody-antigen complexes. The predictions are successful for 66% (39/59) of the structures and the remainder can usually be rationalized in terms of additional interaction sites.

Comparative effect of paracetamol, NSAIDs or their combination in postoperative pain management: a qualitative review

BACKGROUND

Quantitative reviews of postoperative pain management have demonstrated that the number of patients needed to treat for one patient to achieve at least 50% pain relief (NNT) is 2.7 for ibuprofen (400 mg) and 4.6 for paracetamol (1000 mg), both compared with placebo. However, direct comparisons between paracetamol and non-steroidal anti-inflammatory drugs (NSAIDs) have not been extensively reviewed. The aims of this review are (i) to compare the analgesic and adverse effects of paracetamol with those of other NSAIDs in postoperative pain, (ii) to compare the effects of combined paracetamol and NSAID with those of either drug alone, and (iii) to discuss whether the adverse effects of NSAIDs in short-term use are justified by their analgesic effects, compared with paracetamol.

METHODS

Medline (1966 to January 2001) and the Cochrane Library (January 2001) were used to perform a systematic, qualitative review of postoperative pain studies comparing paracetamol (minimum 1000 mg) with NSAID in a double-blind, randomized manner. A quantitative review was not performed as too many studies of high scientific standard (27 out of 41 valid studies, including all major surgery studies) would have been excluded.

RESULTS

NSAIDs were clearly more effective in dental surgery, whereas the efficacy of NSAIDs and paracetamol seemed without substantial differences in major and orthopaedic surgery, although firm conclusions could not be made because the number of studies was limited. The addition of an NSAID to paracetamol may confer additional analgesic efficacy compared with paracetamol alone, and the limited data available also suggest that paracetamol may enhance analgesia when added to an NSAID, compared with NSAIDs alone.

CONCLUSION

Paracetamol is a viable alternative to the NSAIDs, especially because of the low incidence of adverse effects, and should be the preferred choice in high-risk patients. It may be appropriate to combine paracetamol with NSAIDs, but future studies are required, especially after major surgery, with specific focus on a potential increase in side-effects from their combined use.

Partial leptin deficiency and human adiposity

The adipocyte-derived hormone leptin is crucial for energy homeostasis in mammals; mice and humans without it suffer from a voracious appetite and extreme obesity. The effect on energy balance of variations in plasma leptin above a minimal threshold is uncertain, however, particularly in humans. Here we examine a group of individuals who are genetically partially deficient in leptin, and show that differences in circulating leptin levels within the range found in normal human populations can directly influence the laying down of fat tissue (adiposity).

Three-dimensional imaging of atomic four-body processes

To understand the physical processes that occur in nature we need to obtain a solid concept about the 'fundamental' forces acting between pairs of elementary particles. It is also necessary to describe the temporal and spatial evolution of many mutually interacting particles under the influence of these forces. This latter step, known as the few-body problem, remains an important unsolved problem in physics. Experiments involving atomic collisions represent a useful testing ground for studying the few-body problem. For the single ionization of a helium atom by charged particle impact, kinematically complete experiments have been performed since 1969 (ref. 7). The theoretical analysis of such experiments was thought to yield a complete picture of the basic features of the collision process, at least for large collision energies. These conclusions are, however, almost exclusively based on studies of restricted electron-emission geometries. Here, we report three-dimensional images of the complete electron emission pattern for the single ionization of helium by the impact of C6+ ions of energy 100 MeV per a.m.u. (a four-body system) and observe features that have not been predicted by any published theoretical model. We propose a higher-order ionization mechanism, involving the interaction between the projectile and the target nucleus, to explain these features.

Bladder surface glycosaminoglycans: an epithelial permeability barrier

Sulfated polysaccharide's ability to modulate the movement of small molecules was examined both in vivo and in vitro. For the in vivo test, the rabbit bladder was utilized and C-14 labeled urea 45-Ca, or 3H2O was placed into the lumen of control bladders, bladders pretreated with protamine sulfate (20 mg./cc) and bladders pretreated with protamine sulfate (20 mg./cc) plus pentosanpoly-sulfate (PPS), 10 mg./cc. After 45 minutes, the controls absorbed 21% of the urea, 16% of the calcium, and 38% of the 3H2O; the protamine treated group 40% urea, 23% calcium, and 51% H2O; the PPS only group 22% urea and the protamine plus PPS group absorbed 24% of urea, 18% calcium, and 44% water. Differences between the control and protamine groups were statistically significant, p less than 0.01 for urea 45-Ca and 3H2O. The bladder mucosa contained a significantly higher concentration of urea and calcium after protamine treatment which were both reversed by PPS (p less than 0.01) while 3H2O content went down significantly (p = 0.03), reflecting a loss of the hydrophilic effect of bladder GAG. The control mucosas had 250 cpm/mg. tissue urea for Ca 64 cpm/mg. and water 262 cpm/mg., the protamine group urea 498 cpm/mg., Ca 190 cpm/mg., and H2O 139 cpm/mg.; the protamine plus PPS group urea 344 cpm/mg., Ca 129 cpm/mg., and water 168 cpm/mg. For the in vitro studies, an Ussing chamber was employed. Normal rabbit bladder membranes were placed in the chambers and the potential difference was zeroed across the membrane. There were three groups, membranes that were treated only with the irrigating solution, membranes pretreated with protamine, and membranes pretreated with protamine plus PPS. At the end of 40 minutes, there was an approximately 1.2% movement of urea across the control membrane, a 3.5% movement across the protamine treated membrane (a significant increase p less than 0.001) and a 1.1% movement across the protamine plus PPS treated membrane. It would appear that the surface polysaccharide may play an important role as a bladder permeability barrier in modulating both charged and uncharged small molecule movement in that its ability to impair such movement can be inhibited by protamine and this protamine effect can be reversed by a treatment with an exogenous sulfated polysaccharide.

Functional nicotinic ACh receptors on interneurones in the rat hippocampus

1. Neuronal nicotinic ACh receptors (nAChRs) were studied in the rat hippocampal slice preparation using whole-cell patch-clamp recording techniques. 2. Responses to ACh (100 microM) were detected on inhibitory interneurones in the Ca1 field of the hippocampus proper and in the dentate gyrus, but not on principal excitatory neurones in either region. The different neuronal types were identified based on their morphology and location. 3. ACh excited interneurones in the hippocampus and dentate gyrus in current-clamp recordings. In voltage-clamp recordings, ACh-activated inward currents were recorded from interneurones in the presence of blockers of synaptic transmission and the muscarinic ACh receptor antagonist atropine. The zero current potential for this response to ACh was near 0 mV. 4. The effect of ACh was mimicked by the nAChR-selective agonists nicotine (100 microM) and 1,1-dimethyl-4-phenyl-piperazinium iodide (DMPP, 100 microM). The response to ACh was reversibly antagonized by the neuronal nAChR antagonist mecamylamine (10 microM). The nAChR alpha 7 subunit-selective antagonists alpha-bungarotoxin (100 nM) and methyllycaconitine (10 nM) also inhibited the response to ACh. 5. These observations demonstrate the presence of functional nAChRs on inhibitory interneurones in the rat hippocampus. Thus, a novel mechanism by which ACh can regulate neuronal activity in the hippocampus is revealed.