Delineating genetic groupings in continuously distributed species across largely homogeneous landscapes: a study of American black bears (Ursus americanus) in Ontario, Canada

There is a crucial need to understand the genetic consequences of landscape modifications on continuous populations that could become fragmented, and to evaluate the degree of differentiation of isolated populations that were historically part of the core. Using 15 microsatellite loci, we evaluated the genetic structure of American black bears ( Ursus americanus Pallas, 1780) across a vast, contiguous Ontario landscape (>1 × 106 km2) that largely represents their pre-European settlement distribution. Because geographic barriers are absent, we predicted that isolation by distance would drive genetic structure. We identified three genetic clusters (Northwest, Southeast, and Bruce Peninsula) that were less differentiated than when assessed with mtDNA, suggesting the influence of male-biased dispersal on large-scale genetic differentiation. Isolation by distance (r = 0.552, P = 0.001) was supported by a weak, clinal variation between Northwest and Southeast, illustrating the challenges to delineate populations in wide-ranging taxa. The Bruce Peninsula cluster, confined to a small area under strong anthropogenic pressures, was more differentiated from neighbouring clusters (FST > 0.13, P < 0.0001), with a genetic diversity corresponding to disjunct populations of black bears. Our results could be used in landscape genetics models to project the evolution of population differentiation based on upcoming landscape modifications in northern regions of North America.

Environmental risk factors for REM sleep behavior disorder: a multicenter case-control study

OBJECTIVE

Idiopathic REM sleep behavior disorder is a parasomnia characterized by dream enactment and is commonly a prediagnostic sign of parkinsonism and dementia. Since risk factors have not been defined, we initiated a multicenter case-control study to assess environmental and lifestyle risk factors for REM sleep behavior disorder.

METHODS

Cases were patients with idiopathic REM sleep behavior disorder who were free of dementia and parkinsonism, recruited from 13 International REM Sleep Behavior Disorder Study Group centers. Controls were matched according to age and sex. Potential environmental and lifestyle risk factors were assessed via standardized questionnaire. Unconditional logistic regression adjusting for age, sex, and center was conducted to investigate the environmental factors.

RESULTS

A total of 694 participants (347 patients, 347 controls) were recruited. Among cases, mean age was 67.7 ± 9.6 years and 81.0% were male. Cases were more likely to smoke (ever smokers = 64.0% vs 55.5%, adjusted odds ratio [OR] = 1.43, p = 0.028). Caffeine and alcohol use were not different between cases and controls. Cases were more likely to report previous head injury (19.3% vs 12.7%, OR = 1.59, p = 0.037). Cases had fewer years of formal schooling (11.1 ± 4.4 years vs 12.7 ± 4.3, p < 0.001), and were more likely to report having worked as farmers (19.7% vs 12.5% OR = 1.67, p = 0.022) with borderline increase in welding (17.8% vs 12.1%, OR = 1.53, p = 0.063). Previous occupational pesticide exposure was more prevalent in cases than controls (11.8% vs 6.1%, OR = 2.16, p = 0.008).

CONCLUSIONS

Smoking, head injury, pesticide exposure, and farming are potential risk factors for idiopathic REM sleep behavior disorder.

How does parkinsonism start? Prodromal parkinsonism motor changes in idiopathic REM sleep behaviour disorder

Parkinsonism, as a gradually progressive disorder, has a prodromal interval during which neurodegeneration has begun but cardinal manifestations have not fully developed. A systematic direct assessment of this interval has never been performed. Since patients with idiopathic REM sleep behaviour disorder are at very high risk of parkinsonism, they provide a unique opportunity to observe directly the development of parkinsonism. Patients with idiopathic REM sleep behaviour disorder in an ongoing cohort study were evaluated annually with several quantitative motor measures, including the Unified Parkinson's Disease Rating Scale, Purdue Pegboard, alternate-tap test and timed up-and-go. Patients who developed parkinsonism were identified from this cohort and matched according to age to normal controls. Their results on motor testing from the preceding years were plotted, and then assessed with regression analysis, to determine when markers first deviated from normal values. Sensitivity and specificity of quantitative motor markers for diagnosing prodromal parkinsonism were assessed. Of 78 patients, 20 developed parkinsonism. On regression analysis, the Unified Parkinson's Disease Rating Scale first intersected normal values at an estimated 4.5 years before diagnosis. Voice and face akinesia intersected earliest (estimated prodromal interval = 9.8 years), followed by rigidity (4.4 years), gait abnormalities (4.4 years) and limb bradykinesia (4.2 years). Quantitative motor tests intersected normal values at longer prodromal intervals than subjective examination (Purdue Pegboard = 8.6 years, alternate-tap = 8.2, timed up-and-go = 6.3). Using Purdue Pegboard and the alternate-tap test, parkinsonism could be detected with 71-82% sensitivity and specificity 3 years before diagnosis, whereas a Unified Parkinson's Disease Rating Scale score >4 identified prodromal parkinsonism with 88% sensitivity and 94% specificity 2 years before diagnosis. Removal of action tremor scores improved sensitivity to 94% and specificity to 97% at 2 years before diagnosis (cut-off >3). Although distinction between conditions was often difficult, prodromal dementia with Lewy bodies appeared to have a slower progression than Parkinson's disease (prodromal interval = 6.0 versus 3.8 years). Using a cut-off of Unified Parkinson's Disease Rating Scale >3 (excluding action tremor), 25% of patients with 'still-idiopathic' REM sleep behaviour disorder demonstrated evidence of possible prodromal parkinsonism. Therefore, using direct assessment of motor examination before parkinsonism in a REM sleep behaviour disorder, we have estimated a prodromal interval of ∼4.5 years on the Unified Parkinson's Disease Rating Scale; other quantitative markers may detect parkinsonism earlier. Simple quantitative motor measures may be capable of reliably detecting parkinsonism, even before a clinical diagnosis can be made by experienced movement disorders neurologists.

Variations in incubator temperature and humidity management: a survey of current practice

AIM

To describe and assess routine procedures and practices for incubator temperature and humidity management in France in 2009.

METHODS

A questionnaire was sent to all the 186 neonatal care units in France.

RESULTS

The questionnaire return rate was 86%. Seventy-five per cent of the units preferred skin servo-control to air temperature control in routine practice. Air temperature control was mainly used for infants with a gestational age of more than 28 weeks and aged over 7 days of life. In general, thermal management decisions did not depend on the infant's age but were based on a protocol applied specifically by each unit. All units humidified the incubator air, but there was a large difference between the lowest and highest reported humidity values (45% and 100% assumed to be a maximal value, respectively). More than 65% of the units used a fixed humidity value, rather than a variable, protocol-derived value.

CONCLUSION

We observed large variations in incubator temperature and humidity management approaches from one neonatal care unit to another. There is a need for more evidence to better inform practice. A task force should be formed to guide clinical practice.

Purification and Characterization of Three Chitosanase Activities from Bacillus megaterium P1

Bacillus megaterium P1, a bacterial strain capable of hydrolyzing chitosan, was isolated from soil samples. Chitosan-degrading activity was induced by chitosan but not by its constituent d-glucosamine. Extracellular secretion of chitosanase reached levels corresponding to 1 U/ml under optimal conditions. Three chitosan-degrading proteins (chitosanases A, B, and C) were purified to homogeneity. Chitosanase A (43 kilodaltons) was highly specific for chitosan and represented the major chitosan-hydrolyzing species. Chitosanases B (39.5 kilodaltons) and C (22 kilodaltons) corresponded to minor activities and possessed comparable specific activities toward chitosan, chitin, and cellulose. Chitosanase A was active from pH 4.5 to 6.5 and was stable on the basis of activity up to 45 degrees C. The optimum temperature for enzymatic chitosan hydrolysis was 50 degrees C. Kinetic studies on chitosanase A suggest that the enzyme is substrate inhibited. The apparent K(m) and V(max) determined at 22 degrees C and pH 5.6 were 0.8 mg/ml and 280 U/mg, respectively. End products of chitosan hydrolysis by each of the three chitosanases were identified as glucosamine oligomers, similar to those obtained for previously reported chitosanase digestions.

Inhibition of human papillomavirus DNA replication by small molecule antagonists of the E1-E2 protein interaction

Human papillomavirus (HPV) DNA replication is initiated by recruitment of the E1 helicase by the E2 protein to the viral origin. Screening of our corporate compound collection with an assay measuring the cooperative binding of E1 and E2 to the origin identified a class of small molecule inhibitors of the protein interaction between E1 and E2. Isothermal titration calorimetry and changes in protein fluorescence showed that the inhibitors bind to the transactivation domain of E2, the region that interacts with E1. These compounds inhibit E2 of the low risk HPV types 6 and 11 but not those of high risk HPV types or of cottontail rabbit papillomavirus. Functional evidence that the transactivation domain is the target of inhibition was obtained by swapping this domain between a sensitive (HPV11) and a resistant (cottontail rabbit papillomavirus) E2 type and by identifying an amino acid substitution, E100A, that increases inhibition by approximately 10-fold. This class of inhibitors was found to antagonize specifically the E1-E2 interaction in vivo and to inhibit HPV DNA replication in transiently transfected cells. These results highlight the potential of the E1-E2 interaction as a small molecule antiviral target.

IntI2 integron integrase in Tn7

Integrons can insert and excise antibiotic resistance genes on plasmids in bacteria by site-specific recombination. Class 1 integrons code for an integrase, IntI1 (337 amino acids in length), and are generally borne on elements derived from Tn5090, such as that found in the central part of Tn21. A second class of integron is found on transposon Tn7 and its relatives. We have completed the sequence of the Tn7 integrase gene, intI2, which contains an internal stop codon. This codon was found to be conserved among intI2 genes on three other Tn7-like transposons harboring different cassettes. The predicted peptide sequence (IntI2*) is 325 amino acids long and is 46% identical to IntI1. In order to detect recombination activity, the internal stop codon at position 179 in the parental allele was changed to a triplet coding for glutamic acid. The sequences flanking the cassette arrays in the class 1 and 2 integrons are not closely related, but a common pool of mobile cassettes is used by the different integron classes; two of the three antibiotic resistance cassettes on Tn7 and its close relatives are also found in various class 1 integrons. We also observed a fourth excisable cassette downstream of those described previously in Tn7. The fourth cassette encodes a 165-amino-acid protein of unknown function with 6.5 contiguous repeats of a sequence coding for 7 amino acids. IntI2*179E promoted site-specific excision of each of the cassettes in Tn7 at different frequencies. The integrases from Tn21 and Tn7 showed limited cross-specificity in that IntI1 could excise all cassettes from both Tn21 and Tn7. However, we did not observe a corresponding excision of the aadA1 cassette from Tn21 by IntI2*179E.

Chronic exposure to beta-hydroxybutyrate impairs insulin action in primary cultures of adult cardiomyocytes

Type 1 and type 2 diabetic patients often show elevated plasma ketone body concentrations. Because ketone bodies compete with other energetic substrates and reduce their utilization, they could participate in the development of insulin resistance in the heart. We have examined the effect of elevated levels of ketone bodies on insulin action in primary cultures of adult cardiomyocytes. Cardiomyocytes were cultured with the ketone body beta-hydroxybutyrate (beta-OHB) for 4 or 16 h, and insulin-stimulated glucose uptake was evaluated. Although short-term exposure to ketone bodies was not associated with any change in insulin action, our data demonstrated that preincubation with beta-OHB for 16 h markedly reduced insulin-stimulated glucose uptake in cardiomyocytes. This effect is concentration dependent and persists for at least 6 h after the removal of beta-OHB from the media. Ketone bodies also decreased the stimulatory effect of phorbol 12-myristate 13-acetate and pervanadate on glucose uptake. This diminution could not be explained by a change in either GLUT-1 or GLUT-4 protein content in cardiomyocytes. Chronic exposure to beta-OHB was associated with impaired protein kinase B activation in response to insulin and pervanadate. These results indicate that prolonged exposure to ketone bodies altered insulin action in cardiomyocytes and suggest that this substrate could play a role in the development of insulin resistance in the heart.

Characterization of recombinant HPV6 and 11 E1 helicases: effect of ATP on the interaction of E1 with E2 and mapping of a minimal helicase domain

To better characterize the enzymatic activities required for human papillomavirus (HPV) DNA replication, the E1 helicases of HPV types 6 and 11 were produced using a baculovirus expression system. The purified wild type proteins and a version of HPV11 E1 lacking the N-terminal 71 amino acids, which was better expressed, were found to be hexameric over a wide range of concentrations and to have helicase and ATPase activities with relatively low values for K(m)(ATP) of 12 microm for HPV6 E1 and 6 microm for HPV11 E1. Interestingly, the value of K(m)(ATP) was increased 7-fold in the presence of the E2 transactivation domain. In turn, ATP was found to perturb the co-operative binding of E1 and E2 to DNA. Mutant and truncated versions of in vitro translated E1 were used to identify a minimal ATPase domain composed of the C-terminal 297 amino acids. This fragment was expressed, purified, and found to be fully active in ATP hydrolysis, single-stranded DNA binding, and unwinding assays, despite lacking the minimal origin-binding domain.

[Games of chance and gambling in adolescents and in adolescents-at-risk]

A number of studies have established that adolescents are attracted to games of chance and gambling, and have confirmed that excessive gambling is not a phenomenon of adulthood alone. In Quebec, the proportion of high school students who are struggling with gambling problems is estimated at 2.6% (Ladouceur, Boudreault, Jacques, & Vitaro, 1999). So far, few researchers have studied adolescent populations that are at greater risk of developing gambling problems. The present study was carried out among 104 adolescents in difficulty, ranging in age from 12 to 19 and served by the Centre jeunesse de Québec. It assesses the prevalence of excessive gambling and the problems associated with it. The results indicate that 92.3% of adolescents had bet at least once during the previous year and 40.4% bet every week. The prevalence of excessive gambling was established at 7.7%. Girls were found to gamble as frequently as boys and to experience as many gambling problems. In addition, habitual gambling was found to be associated with the consumption of psychotropic substances, delinquent behaviour and school absenteeism. The discussion puts the results obtained in perspective and emphasizes the need for establishing gambling prevention programs among at-risk youth.

Identification of domains of the human papillomavirus type 11 E1 helicase involved in oligomerization and binding to the viral origin

The E1 helicase of papillomavirus is required, in addition to host cell DNA replication factors, during the initiation and elongation phases of viral episome replication. During initiation, the viral E2 protein promotes the assembly of enzymatically active multimeric E1 complexes at the viral origin of DNA replication. In this study we used the two-hybrid system and chemical cross-linking to demonstrate that human papillomavirus type 11 (HPV11) E1 can self-associate in yeast and form hexamers in vitro in a reaction stimulated by single-stranded DNA. Self-association in yeast was most readily detected using constructs spanning the E1 C-terminal domain (amino acids 353 to 649) and was dependent on a minimal E1-E1 interaction region located between amino acids 353 and 431. The E1 C-terminal domain was also able to oligomerize in vitro but, in contrast to wild-type E1, did so efficiently in the absence of single-stranded DNA. Sequences located between amino acids 191 and 353 were necessary for single-stranded DNA to modulate oligomerization of E1 and were also required, together with the rest of the C terminus, for binding of E1 to the origin. Two regions within the C-terminal domain were identified as important for oligomerization: the ATP-binding domain and region A, which is located within the minimal E1-E1 interaction domain and is one of four regions of E1 that is highly conserved with the large T antigens of simian virus 40 and polyomavirus. Amino acid substitutions of highly conserved residues within the ATP-binding domain and region A were identified that reduced the ability of E1 to oligomerize and bind to the origin in vitro and to support transient DNA replication in vivo. These results support the notion that oligomerization of E1 occurs primarily through the C-terminal domain of the protein and is allosterically regulated by DNA and ATP. The bipartite organization of the E1 C-terminal domain is reminiscent of that found in other hexameric proteins and suggests that these proteins may oligomerize by a similar mechanism.

Role of p97 and syntaxin 5 in the assembly of transitional endoplasmic reticulum

Transitional endoplasmic reticulum (tER) consists of confluent rough and smooth endoplasmic reticulum (ER) domains. In a cell-free incubation system, low-density microsomes (1.17 g cc(-1)) isolated from rat liver homogenates reconstitute tER by Mg(2+)GTP- and Mg(2+)ATP-hydrolysis-dependent membrane fusion. The ATPases associated with different cellular activities protein p97 has been identified as the relevant ATPase. The ATP depletion by hexokinase or treatment with either N-ethylmaleimide or anti-p97 prevented assembly of the smooth ER domain of tER. High-salt washing of low-density microsomes inhibited assembly of the smooth ER domain of tER, whereas the readdition of purified p97 with associated p47 promoted reconstitution. The t-SNARE syntaxin 5 was observed within the smooth ER domain of tER, and antisyntaxin 5 abrogated formation of this same membrane compartment. Thus, p97 and syntaxin 5 regulate assembly of the smooth ER domain of tER and hence one of the earliest membrane differentiated components of the secretory pathway.

Cryptogenic organizing pneumonia. Characteristics of relapses in a series of 48 patients. The Groupe d'Etudes et de Recherche sur les Maladles "Orphelines" Pulmonaires (GERM"O"P)

Cryptogenic organizing pneumonia (COP) is a clinicopathologic syndrome characterized by rapid resolution with corticosteroids, but frequent relapses when treatment is tapered or stopped. We retrospectively studied relapses in 48 cases of biopsy-proven COP. One or more relapses (mean 2.4 +/- 2.2) occurred in 58%. At first relapse, 68% of patients were still under treatment for the initial episode. Compared with the no-relapse group, nine patients with multiple (>/= 3) relapses had longer delays between first symptoms and treatment onset (22 +/- 17 versus 11 +/- 8 wk, p = 0.02), and elevated gamma-glutamyltransferase (124 +/- 98 versus 29 +/- 13 IU/L, p = 0.001) and alkaline phosphatase (190 +/- 124 versus 110 +/- 68 IU/L, p = 0.04) levels. Relapses did not adversely affect outcome. Corticosteroid treatment side effects occurred in 25% of patients. Standardized treatment in 14 patients allowed a reduction of prednisone cumulated doses (p < 0.05) without affecting outcome or relapse rate. We conclude that: (1) delayed treatment increases the risk of relapses; (2) mild cholestasis identifies a subgroup of patients with multiple relapses; (3) relapses do not affect outcome, and prolonged therapy to suppress relapses appears unnecessary; (4) a standardized treatment allows a reduction in steroid doses.

Identification of domains of the HPV11 E1 protein required for DNA replication in vitro

The HPV E1 and E2 proteins along with cellular factors, are required for replication of the viral genome. In this study we show that in vitro synthesized HPV11 E1 can support DNA replication in a cell-free system and is able to cooperate with E2 to recruit the host polymerase alpha primase to the HPV origin in vitro. Deletion analysis revealed that the N-terminal 166 amino acids of E1, which encompass a nuclear localization signal and a cyclin E-binding motif, are dispensable for E1-dependent DNA replication and for recruitment of pol alpha primase to the origin in vitro. A shorter E1 protein lacking the N-terminal 190 amino acids supported cell-free DNA replication at less than 25% the efficiency of wild-type E1 and was active in the pol alpha primase recruitment assay. An even shorter E1 protein lacking a functional DNA-binding domain due to a truncation of the N-terminal 352 amino acids was inactive in both assays despite the fact that it retains the ability to associate with E2 or pol alpha primase in the absence of ori DNA. We provide additional functional evidence that E1 interacts with pol alpha primase through the p70 subunit of the complex by showing that p70 can be recruited to the HPV origin by E1 and E2 in vitro, that the domain of E1 (amino acids 353-649) that binds to pol alpha primase in vitro is the same as that needed for interaction with p70 in the yeast two-hybrid system, and that exogenously added p70 competes with the interaction between E1 and pol alpha primase and inhibits E1-dependent cell-free DNA replication. On the basis of these results and the observation that pol alpha primase competes with the interaction between E1 and E2 in solution, we propose that these three proteins assemble at the origin in a stepwise process during which E1, following its interaction with E2, must bind to DNA prior to interacting with pol alpha primase.

Role of the ATP-binding domain of the human papillomavirus type 11 E1 helicase in E2-dependent binding to the origin

Replication of the genome of human papillomaviruses (HPV) is initiated by the recruitment of the viral E1 helicase to the origin of DNA replication by the viral E2 protein, which binds specifically to the origin. We determined, for HPV type 11 (HPV-11), that the C-terminal 296 amino acids of E1 are sufficient for interaction with the transactivation domain of E2 in the yeast two-hybrid system and in vitro. This region of E1 encompasses the ATP-binding domain. Here we have examined the role of this ATP-binding domain, and of ATP, on E2-dependent binding of E1 to the origin. Several amino acid substitutions in the phosphate-binding loop (P loop), which is implicated in binding the triphosphate moiety of ATP, abolished E2 binding, indicating that the structural integrity of this domain is essential for the interaction. The structural constraints imposed on the E1 P loop may differ between HPV-11 and bovine papillomavirus type 1 (BPV-1), since the P479S substitution that inactivates BPV-1 E1 is tolerated in the HPV-11 enzyme. Other substitutions in the E1 P loop, or in two other conserved motifs of the ATP-binding domain, were tolerated, indicating that ATP binding is not essential for interaction with E2. Nevertheless, ATP-Mg stimulated the E2-dependent binding of E1 to the origin in vitro. This stimulation was maximal at the physiological temperature (37 degrees C) and did not require ATP hydrolysis. In contrast, ATP-Mg did not stimulate the E2-dependent binding to the origin of an E1 protein containing only the C-terminal domain (353 to 649) or that of mutant E1 proteins with alterations in the DNA-binding domain. These results are discussed in light of a model in which the E1 ATP-binding domain is required for formation of the E2-binding surface and can, upon the binding of ATP, facilitate and/or stabilize the interaction of E1 with the origin.

Cardiopulmonary bypass pumps and thrombin generation: what goes around comes around

Thrombin generation and subsequent fibrin deposition occur during cardiopulmonary bypass (CPB) using roller pumps (RPs) despite the administration of high dose heparin. The authors attempted to determine if less thrombin is generated and less fibrin is deposited during CPB using a centrifugal pump (CP). In Part 1 of the experiment, 12 pigs receiving 400 U/kg heparin underwent CPB, including hypothermia, cardioplegia, and aortic cross-clamping, using a CP or RP. Blood samples were collected throughout CPB to measure thrombin generation. At the end of CPB, the amount of fibrin deposited onto each filter was assessed spectrophotometrically. In Part 2, blood samples and arterial in-line filters were obtained from 20 patients undergoing CPB, using either RP or CP, and studied as described previously. The Part 1 results showed that thrombin generation and fibrin deposition in CP pigs were <50% of those seen in the RP pigs (p < 0.01 and p < 0.01, respectively). In Part 2, thrombin generation was significantly attenuated both during and after CPB in the CP patients (p < 0.01 and p < 0.01, respectively). However, there was no significant difference in fibrin deposition between the two types of pumps after their use in the patients undergoing cardiopulmonary bypass. It is concluded that there is less thrombin generation and subsequent fibrin deposition during CPB when using a CP instead of RP in a defined experimental in vivo situation, suggesting that there is less hypercoagulability during CPB when using a CP instead of an RP. However, a large study in more patients undergoing CPB for longer pump runs is required to determine the relevance of these observations on subsequent clinical endpoints.

Characterization of a tight molecular complex between integrin alpha 6 beta 4 and laminin-5 extracellular matrix

In many adult epithelia, e.g., epidermis or intestine, adhesion of epithelial cells to basement membrane requires the integrin alpha6 beta4 and laminin-5 (Ln-5). In the absence of one or the other, extensive blistering and exfoliation occur. While alpha6 beta4 was reported to be a receptor for Ln-5, this interaction is poorly understood. We characterize complexes between alpha6 beta4 and Ln-5 in cell-free preparations of extracellular matrix (ECM) from the epithelial cell line, 804G. By microsequencing, Ln-5 and alpha6 beta4 were the major proteins in this ECM and were likely engaged in receptor/ligand complexes because, by immunofluorescence, alpha6 beta4 was colocalized with Ln-5 both in cell monolayers and in cell-free ECM preparations, but they disappeared after preincubation of the monolayers with alpha6 beta4 or Ln-5 function-blocking antibodies. The alpha6 beta4/Ln-5 complexes were resistant to dissociation by extreme pH, urea, chaotropes, eDTA, non-ionic detergents, and b-mercaptoethanol. They were only dissociated by strong anionic detergents, e.g., 1% SDS, suggesting receptor/ligand interactions based on high affinity or avidity. We propose that these alpha6 beta4/Ln-5 complexes may provide links between plasma membrane and basement membrane that resist mechanical stress and support epithelial integrity.

Design of fluorogenic peptide substrates for human cytomegalovirus protease based on structure-activity relationship studies

Human cytomegalovirus (HCMV) protease is a slow-processing enzyme in vitro and its characterization would be facilitated if more efficiently cleaved substrates were available. Here we describe the development of improved fluorogenic peptide substrates for this protease and demonstrate that its indolent nature can be overcome by appropriate modifications within existing substrates. Prior structure-activity studies have indicated that replacement of the Val-Val-Asn sequence corresponding to the P4-P2 residues of the maturation site of the enzyme by the optimized Tbg-Tbg-Asn(NMe2) sequence conferred significant binding to inhibitors (Tbg, t-butylglycine). Incorporation of this improved sequence in a variety of substrates invariably led to improved kinetic parameters compared to homologues containing the natural sequence only. For example, the substrate o-aminobenzoyl-Tbg-Tbg-Asn (NMe2)-Ala decreases Ser-Ser-Arg-Leu-Tyr(3-NO2)Arg-OH (2) displayed a kcat/K(m) value of 15,940 M-1 s-1 i.e., more than 60-fold greater than that of the equivalent, nonoptimized substrate 1 under identical conditions. This improved sequence also permitted the development of a sensitive 7-amino-4-methylcoumarin fluorogenic substrate 3 which represents the shortest HCMV protease substrate to date. The kinetic and photometric advantages of these various substrates are discussed along with specific applications.

Self-association of herpes simplex virus type 1 ICP35 is via coiled-coil interactions and promotes stable interaction with the major capsid protein

The ordered copolymerization of viral proteins to form the herpes simplex virus (HSV) capsid occurs within the nucleus of the infected cell and is a complex process involving the products of at least six viral genes. In common with capsid assembly in double-stranded DNA bacteriophages, HSV capsid assembly proceeds via the assembly of an outer capsid shell around an interior scaffold. This capsid intermediate matures through loss of the scaffold and packaging of the viral genomic DNA. The interior of the HSV capsid intermediate contains the viral protease and assembly protein which compose the scaffold. Proteolytic processing of these proteins is essential for and accompanies capsid maturation. The assembly protein (ICP35) is the primary component of the scaffold, and previous studies have demonstrated it to be capable of intermolecular association with itself and with the major capsid protein, VP5. We have defined structural elements within ICP35 which are responsible for intermolecular self-association and for interaction with VP5. Yeast (Saccharomyces cerevisiae) two-hybrid assays and far-Western studies with purified recombinant ICP35 mapped a core self-association domain between Ser165 and His219. Site-directed mutations in this domain implicate a putative coiled coil in ICP35 self-association. This coiled-coil motif is highly conserved within the assembly proteins of other alpha herpesviruses. In the two-hybrid assay the core self-association domain was sufficient to mediate stable self-association only in the presence of additional structural elements in either N- or C-terminal flanking regions. These regions also contain conserved sequences which exhibit a high propensity for alpha helicity and may contribute to self-association by forming additional short coiled coils. Our data supports a model in which ICP35 molecules have an extended conformation and associate in parallel orientation through homomeric coiled-coil interactions. In additional two-hybrid experiments we evaluated ICP35 mutants for association with VP5. We discovered that in addition to the C-terminal 25 amino acids of ICP35, previously shown to be required for VP5 binding, an additional upstream region was required. This region is between Ser165 and His234 and contains the core self-association domain. Site-directed mutations and construction of chimeric molecules in which the self-association domain of ICP35 was replaced by the GCN4 leucine zipper indicated that this region contributes to VP5 binding through mediating self-association of ICP35 and not through direct binding interactions. Our results suggest that self-association of ICP35 strongly promotes stable association with VP5 in vivo and are consistent with capsid formation proceeding via formation of stable subassemblies of ICP35 and VP5 which subsequently assemble into capsid intermediates in the nucleus.

Deaths among railroad trespassers. The role of alcohol in fatal injuries

OBJECTIVE

To describe the characteristics of persons killed by trains while trespassing (ie, using railroad property for activities unrelated to railroad operations).

DESIGN

Case series obtained from records of the state medical examiner.

SETTING

North Carolina, 1990 through 1994.

SUBJECTS

One hundred twenty-eight persons ranging in age from 7 to 84 years who were killed in 125 separate incidents.

RESULTS

Of 224 railroad-related deaths during the study period, 128 cases (57%) involved trespassers. Trespasser fatalities typically involved unmarried male pedestrians 20 to 49 years of age with less than a high school education. Eighty-two percent of incidents occurred in the trespassers' county of residence, indicating that few deaths involved transients. Fatalities among railroad trespassers exhibited both geographic and temporal clustering. Seventy-eight percent of trespassers were killed while intoxicated (median alcohol level, 56 mmol/L [260 mg/dL]).

CONCLUSIONS

Deaths among trespassers are the leading cause of railroad-related mortality in North Carolina. Greater efforts are needed to reduce this type of preventable injury. Prevention of trespasser fatalities is dependent on control of alcohol abuse, enforcement of existing laws, and education of the public regarding the dangers of railroad trespassing.