Modeling mechanical stresses as a factor in the etiology of benign vocal fold lesions

Vocal fold tissue lesions such as nodules and polyps are thought to develop in response to mechanical stress that occurs during vocal fold collision. Two computational models of vocal fold collision during voice production are used to investigate this hypothesis. A one-dimensional lumped mass model, whose parameters are derived from vocal fold tissue dimensions and material properties, predicts stress perpendicular to the direction of impact (normal stress). A previously published three-dimensional finite element model that incorporates the same dimensions and properties predicts the entire stress tensor. The hypothesis is supported by predictions from the finite element model that three components of normal stress and one component of shear stress are increased during collision in the typical location of lesions (i.e. the center of the superior medial edge of the vocal fold in the middle of the vibrating and contact region). The lumped mass model predicts that mechanical stress is negatively correlated with mucosal thickness (increased by voice warm-up and hydration), is positively correlated with driving force (proportional to voice intensity), and is affected by voice production method. These relationships are consistent with clinical observations of vocal fold lesion risk factors and have implications for improving prevention and treatment of benign vocal fold lesions.     

Conformational changes induced by nucleotide binding in Cdc6/ORC from Aeropyrum pernix

Archaea contain one or more proteins with homology to eukaryotic ORC/Cdc6 proteins. Sequence analysis suggests the existence of at least two subfamilies of these proteins, for which we propose the nomenclature ORC1 and ORC2. We have determined crystal structures of the ORC2 protein from the archaeon Aeropyrum pernix in complexes with ADP or a non-hydrolysable ATP analogue, ADPNP. Between two crystal forms, there are three crystallographically independent views of the ADP complex and two of the ADPNP complex. The protein molecules in the three complexes with ADP adopt very different conformations, while the two complexes with ADPNP are the same. These structures indicate that there is considerable conformational flexibility in ORC2 but that ATP binding stabilises a single conformation. We show that the ORC2 protein can bind DNA, and that this activity is associated with the C-terminal domain of the protein. We present a model for the interaction of the winged helix (WH) domain of ORC2 with DNA that differs from that proposed previously for Pyrobaculum aerophilum ORC/Cdc6.     

Naiadocystis phykoterion n. gen., n. sp. (Apicomplexa: Eugregarinida: Hirmocystidae), from the Mexican pygmy grasshopper, Paratettix mexicanus (Orthoptera: Tetrigidae), in the Texas big thicket with recognition of three previously described species of Naiadocystis

Naiadocystis phykoterion n. gen., n. sp. (Apicomplexa: Eugregarinida: Hirmocystidae), is described from the Mexican pygmy grasshopper, Paratettix mexicanus (Orthoptera: Tetrigidae), collected from sandbars along Harmon Creek, Walker County, Texas, in the western edge of the Texas Big Thicket. Naiadocystis n. gen. is distinguished by the form of the epimerite complex, a simple cordoid or toroid epimerite with an interior obconoid structure resembling a funnel that tapers to a distinct axial canal bisecting the protomerite, which is conspicuous in all stages of development, and a satellite protomerite reduced to a linearly crateriform cup or sucker that receives and enfolds posterior end of primite deutomerite. Association is precocious, caudofrontal, and biassociative. Gametocysts are spherical. Sporoducts are present but vestigial and irregular in number. Oocysts are broadly elliptoid with 4 small spherical polar knobs, 1 each at 30 degrees, 150 degrees, 210 degrees, and 330 degrees, and dehisce en masse. The species described herein are differentiated by their overall size and relative proportion of cellular structures. Naiadocystis acantholobae (Hoshide, 1952) n. comb., Naiadocystis acrydiinarum (Semans, 1939) n. comb., and Naiadocystis tetrigis (Corbel, 1968) n. comb. are recognized as members of Naiadocystis previously placed within Gregarina (Apicomplexa: Eugregarinida: Gregarinidae).     

Possible involvement of neuronal nitric oxide synthase enzyme in early-phase isoflurane-induced hypotension in rats

This study was conducted to demonstrate the involvement of nitric oxide synthase (NOS) in the early-phase isoflurane-induced hypotension and to ascertain whether this NOS is neuronal NOS (nNOS) or endothelial NOS (eNOS). Mean arterial pressures (MAPs) were directly measured from the femoral arteries of urethane-anesthetized rats. Isoflurane-induced changes in MAP were monitored in rats following pretreatment with vehicle or one of the following NOS inhibitors: L-N^G-monomethyl-L-arginine (L-NMMA), which is non-selective; L-N^G-nitro arginine (L-NOARG), which is more selective for nNOS and eNOS; and 7-nitroindazole (7-NI), which is selective for nNOS. Exposure to 2% isoflurane in oxygen produced a triphasic reduction in MAP, including an early phase in which mean arterial pressure (MAP) fell by 25-30% during the initial 2½ min. This early hypotensive response, but not subsequent phases, was abolished by i.v. pretreatment with either L-NMMA or L-NOARG. The early-phase hypotension was also significantly attenuated by i.p. pretreatment with 7-NI; however, the blockade was not as complete as with L-NMMA or L-NOARG. Cerebella and aorta were removed from vehicle- and 7-NI pretreated rats and assayed for NOS activity by determining the conversion of [¹⁴C]L-arginine to [¹⁴C]L-citrulline. The 7-NI pretreatment significantly reduced NOS activity in the cerebellum but not the aorta. These findings indicate that the early-phase isoflurane-induced hypotension may involve nNOS as well as eNOS. The nNOS may participate in regulation of isoflurane-induced neuronal release of endogenous opioid peptide, which produces a vasodilation that is dependent on NO derived from an action of eNOS.     

Phosphorylation and nuclear accumulation are distinct events contributing to the activation of p53

It has been recently shown that ionizing radiation (IR) and the mRNA synthesis inhibitor 5,6-dichloro-1-b-D-ribofuranosylbenzimidazole (DRB) act in synergy to induce p53-mediated transactivation of reporter plasmids in human cells [Oncogene 19 (2000) 3829]. We have extended these studies and show that ionizing radiation and DRB also act in synergy to induce ATM-mediated phosphorylation of the ser15 site of p53 and enhance the expression of endogenous p21 protein. Examination of the localization of p53 revealed that while DRB did not induce phosphorylation of the ser15 site of p53 but efficiently accumulated p53 in the nucleus, ionizing radiation induced phosphorylation of the ser15 site of p53 without prolonged nuclear accumulation. Importantly, the combination of DRB and IR resulted in a strong accumulation of phosphorylated p53 in the nucleus that was more persistent then p53 accumulation after IR alone. Furthermore, the nuclear export inhibitor leptomycin B showed a similar synergy with IR as did DRB regarding ser15 phosphorylation of p53 and p21 induction. These results suggest that the synergistic activation of the p53 response by the combination treatment is due to the activation of two distinct pathways where DRB causes the prolonged nuclear accumulation of p53 while ionizing radiation activates p53 by ATM-mediated phosphorylation.     

Increased conidiation associated with progression along the sterigmatocystin biosynthetic pathway

The Aspergillus nidulans sterigmatocystin (ST) gene cluster contains both regulatory (aflR) and biosynthetic genes (stc genes) required for ST production. A total of 26 genes are in the cluster, 13 of which have been assigned a known function in the biosynthetic pathway. This complex secondary pathway represents a physiological cost to the fungus. We tested the amount of asexual spore production using a series of isogenic lines of A. nidulans, differing only in a mutation in aflR (resulting in a strain containing no ST intermediates) or a mutation in three stc genes that produced either no ST intermediates (ΔstcJ), an early ST intermediate, norsoloroinic acid (ΔstcE) or a late ST intermediate, versicolorin A (ΔstcU). In two independently replicated experiments we compared the numbers of conidia produced by each of these mutant strains and a wild type ST producer in a neutral (growth media) and a host (corn seed) environment. A stepwise increase in asexual spore production was observed with each progressive step in the ST pathway. Thus, the data suggest that recruitment or loss of these secondary metabolite pathway genes has a selective advantage apart from the physiological activity of the metabolite.     

Temporal characteristics of laboratory screening errors in cervical cytology

OBJECTIVE: To explore the temporal characteristics of laboratory false negative reports in cervical cytology. STUDY DESIGN: The temporal characteristics of 198 false negative cervical cytology cases were compared with those of 750,805 control cases. RESULTS: The false negative rate did not vary significantly by month, day of the week or time of day. The false negative rate was lowest for slides that took between 4 and 5 minutes to screen and increased significantly with screening times that were longer than 5 minutes. The false negative rate did not vary by the number of cases already authorized in a given day. After 40 cases had been authorized in a given day, the false negative rate fell for subsequent cases, but this did not reach statistical significance. The false negative rate was higher during periods when prescreening was performed. CONCLUSION: Further studies of the relationship between time and false negative reports are needed. These would provide an evidence base to help promote safe working practices within laboratories and a more objective setting of maximum daily productivity levels for cytotechnologists.     

New complexities in the genetics of stuttering: significant sex-specific linkage signals

Stuttering is a speech disorder long recognized to have a genetic component. Recent linkage studies mapped a susceptibility locus for stuttering to chromosome 12 in 46 highly inbred families ascertained in Pakistan. We report here on linkage studies in 100 families of European descent ascertained in the United States, Sweden, and Israel. These families included 252 individuals exhibiting persistent stuttering, 45 individuals classified as recovered from stuttering, and 19 individuals too young to classify. Primary analyses identified moderate evidence for linkage of the broader diagnosis of "ever stuttered" (including both persistent and recovered stuttering) on chromosome 9 (LOD = 2.3 at 60 cM) and of the narrower diagnosis of persistent stuttering on chromosome 15 (LOD = 1.95 at 23 cM). In contrast, sex-specific evidence for linkage on chromosome 7 at 153 cM in the male-only data subset (LOD = 2.99) and on chromosome 21 at 34 cM in the female-only data subset (LOD = 4.5) met genomewide criteria for significance. Secondary analyses revealed a significant increase in the evidence for linkage on chromosome 12, conditional on the evidence for linkage at chromosome 7, with the location of the increased signal congruent with the previously reported signal in families ascertained in Pakistan. In addition, a region on chromosome 2 (193 cM) showed a significant increase in the evidence for linkage conditional on either chromosome 9 (positive) or chromosome 7 (negative); this chromosome 2 region has been implicated elsewhere in studies on autism, with increased evidence for linkage observed when the sample is restricted to those with delayed onset of phrase speech. Our results support the hypothesis that the genetic component to stuttering has significant sex effects.