Does the presence of a true radiological rectocele increase the likelihood of symptoms of prolapse?

INTRODUCTION AND HYPOTHESIS: Posterior compartment prolapse is commonly due to a 'true' rectocele, i.e., a diverticulum of the rectal ampulla. This condition is associated with symptoms of obstructed defecation and may contribute to prolapse symptoms. We tested the hypothesis: 'A true rectocele is an independent predictor of symptoms of prolapse.' METHODS: This was a retrospective cohort study of patients presenting to a urogynecology unit for symptoms of pelvic floor dysfunction between September 2011 and June 2016. Assessment included a structured interview, POP-Q examination and 4D TLUS. Ultrasound volume data were acquired on Valsalva. Offline measurements were performed by analysis of stored volume data sets at a later date, blinded to all clinical data. RESULTS: One hundred six patients were excluded because of incomplete data. Of the remainder, Bp was the most distal point on POP-Q in 348. Statistical analysis was performed on this cohort. Mean age was 60 (33-86) years and mean BMI 31 (18-55) kg/m². One hundred fifty-three patients (44%) presented with symptoms of prolapse; 272 were diagnosed with a true rectocele on TLUS. Bp on POP-Q and true rectocele on TLUS were both significantly associated with prolapse symptoms; however, on multivariate analysis the latter became nonsignificant (p = 0.059). Receiver-operating characteristic (ROC) analysis confirmed that the presence of a true rectocele on TLUS did not contribute significantly to symptoms of prolapse (AUC 0.66 for model with rectocele, AUC 0.65 without). CONCLUSIONS: The presence of a true rectocele on TLUS does not seem to contribute substantially to the manifestation of clinical symptoms of prolapse.

Vaginal laxity: which measure of levator ani distensibility is most predictive?

OBJECTIVE: To assess the predictive value of measures of levator hiatal distension at rest and on maximum Valsalva maneuver for symptoms of vaginal laxity. METHODS: This was a retrospective study of women seen at a tertiary urogynecological unit. All women underwent a standardized interview, clinical examination and four-dimensional translabial ultrasound examination. Area, anteroposterior diameter (APD) and coronal diameter (CD) of the levator hiatus were measured at rest and on maximum Valsalva maneuver in the plane of minimal hiatal dimensions using the rendered volume technique, by an operator blinded to all clinical data. The association between levator hiatal measurements and vaginal laxity was assessed, and receiver-operating-characteristics (ROC)-curve analysis was used to determine their predictive value. RESULTS: Data from 490 patients were analyzed. Mean age was 58 (range, 18-88) years, and vaginal laxity was reported by 111 (23%) women. Measurements obtained on maximum Valsalva were significantly larger in women who reported vaginal laxity than in those who did not, with mean levator hiatal area, APD and CD of 30.45 ± 8.74 cm2 , 7.24 ± 1.16 cm and 5.60 ± 0.89 cm, respectively, in the vaginal-laxity group, compared with 24.84 ± 8.63 cm2 , 6.64 ± 1.22 cm and 5.01 ± 0.97 cm in the no-laxity group (P < 0.001 for all). Measurements obtained at rest were not significantly different between the groups. Multiple logistic regression analysis controlling for age, body mass index, vaginal parity and levator avulsion confirmed these results. The best regression model for the prediction of vaginal laxity included age, vaginal parity and levator hiatal area on maximum Valsalva. ROC-curve analysis of levator hiatal measurements on maximum Valsalva in the prediction of vaginal laxity demonstrated areas under the curve of 0.68 (95% CI, 0.63-0.73) for area, 0.63 (95% CI, 0.57-0.68) for APD and 0.68 (95% CI, 0.62-0.73) for CD. CONCLUSIONS: Levator hiatal area on maximum Valsalva seems to be the measure of levator ani distensibility that is most predictive of symptoms of vaginal laxity. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Is levator trauma an independent risk factor for anal incontinence?

AIM: To determine the role of levator ani trauma in anal incontinence (AI), whilst controlling for anal sphincter injury. METHODS: The records of 1273 patients who had attended a tertiary urogynaecology unit between 1st of January to 31st December 2016 were reviewed. AI was assessed using St Mark's score and visual analogue scale (VAS). Levator muscle and anal sphincter trauma were examined by translabial ultrasound using tomographic imaging, with archived data sets investigated blinded against all clinical data. A complete avulsion was diagnosed if at least three central tomographic slices showed an abnormal muscle insertion, rated separately for each side. A significant anal sphincter defect was diagnosed if at least four out of six slices showed a defect of ≥ 30°. RESULTS: Avulsion was associated with St Mark's score (P = 0.005) and VAS bother of AI (P = 0.022) both on univariate analysis and when controlling for external anal sphincter (EAS) trauma on translabial imaging, forceps, body mass index (BMI) and age (P = 0.011 and P = 0.04, respectively). AI expressed as a binary variable was significantly associated with avulsion on univariate analysis (P = 0.011), although the association became nonsignificant after controlling for anal sphincter trauma, age, BMI and forceps delivery (P = 0.084). CONCLUSION: In this retrospective observational study, we found a weak association between levator ani avulsion and measures of AI, which largely remained significant when controlling for anal sphincter trauma. However, given the large data set, any clinical effect of levator trauma on AI is likely to be minor.

Levator avulsion and vaginal parity: do subsequent vaginal births matter?

INTRODUCTION AND HYPOTHESIS: Tears of the levator ani muscle are common after vaginal birth and associated with pelvic organ prolapse (POP). Although such trauma is usually attributed to the first vaginal birth, epidemiological evidence suggests an additional effect of subsequent vaginal deliveries. Our hypothesis was: "The prevalence of avulsion increases with the number of vaginal births". METHODS: We conducted a retrospective cohort study in patients who presented to a tertiary urogynaecology clinic. Assessment included a physician-directed interview, POP-Q and 4D translabial ultrasound (TLUS), supine, after voiding, at rest, on maximum pelvic floor muscle contraction (PFMC) and Valsalva. Offline analysis of levator integrity was undertaken by tomographic imaging (TUI) at a later date, blinded against all other data. RESULTS: A total of 1,124 patients had been seen between 1 January 2014 and 30 June 2016, on average 33 (0.32-69.7) years after their first birth. Mean age was 56 (19-90) years. 1,012 (90%) were vaginally parous with a median vaginal parity of 2 (1-8). On TUI, avulsion was diagnosed in 257 (23%) women, all of whom were vaginally parous. On univariate analysis, there was no significant difference in the prevalence of avulsion on comparing vaginally primiparous and multiparous women (P = 0.6), nor was there any difference between vaginal parity groups (one, two, three, and ≥4 births; p = 0.7). This remained true after controlling for potential confounding factors using multivariate regression (p = 0.6). CONCLUSIONS: There was no significant difference in the prevalence of avulsion between vaginally primiparous and multiparous women. Vaginal deliveries after a first vaginal birth are unlikely to cause avulsion.

Does levator ani hiatal area configuration affect pelvic organ prolapse?

OBJECTIVE: Levator ani trauma and hiatal overdistension have been shown to be associated with female pelvic organ prolapse (POP); however, the role of the shape of the levator hiatus in POP has not been examined to date. The aim of this study was to investigate the association between the configuration of the levator ani hiatus and POP. METHODS: This was a retrospective study of 547 women who attended a tertiary urogynecological center for symptoms of pelvic floor and lower urinary tract dysfunction between October 2014 and August 2016. All women underwent a standardized interview and prolapse assessment using the International Continence Society (ICS) Pelvic Organ Prolapse Quantification (POP-Q) method and four-dimensional translabial ultrasound (TLUS). Measurements of the hiatal anteroposterior diameter (APD), coronal diameter (CD) and hiatal area (HA), at rest and on maximal Valsalva maneuver, and those of organ descent were performed offline at a later date by an investigator blinded to all other data. Hiatal configuration was defined as the ratio APD/CD. Associations between HA and HA adjusted by APD/CD at rest and on maximal Valsalva and symptoms and signs of prolapse were analyzed statistically using logistic regression modelling. RESULTS: The mean age of the women was 54 ± 13.6 (range, 16-89) years. Of the 547 women included, 241 (44%) presented with prolapse symptoms. Clinically significant POP was detected in 406 (74%) patients and significant prolapse on TLUS was detected in 331 (61%). Hiatal ballooning was observed in 310 (57%) women and this was strongly associated with signs and symptoms of POP. HA at rest and on Valsalva was associated with significant POP both on clinical examination and on TLUS. Adjusted odds ratios for hiatal shape showed no effect of the hiatal configuration on the association between HA and POP. CONCLUSION: Hiatal shape does not seem to influence the association between HA and symptoms and signs of prolapse. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

How repeatable is assessment of external anal sphincter trauma by exoanal 4D ultrasound?

OBJECTIVE: Three-/four-dimensional translabial ultrasound (TLUS) is gaining popularity for the assessment of anal sphincter trauma, although repeatability data are lacking. This study aimed to determine the repeatability of tomographic ultrasound imaging (TUI) on TLUS for the diagnosis of external anal sphincter (EAS) trauma and compare the performance of a novice with that of an experienced investigator. METHODS: This was a retrospective study of archived ultrasound datasets of patients who presented with symptoms of pelvic floor dysfunction and were examined twice between 2012 and 2016 at an average interval of 260 (range, 1-1100) days. All volumes were obtained using a GE Medical Systems Voluson 730 Expert or E8 ultrasound system. Post-processing of volumes was performed independently by two investigators, one with over 1 year's experience and another with no prior experience in using TUI, who were blinded to clinical data, each other's results and the results obtained at the first timepoint. Significant trauma on EAS was diagnosed if four of the six TUI slices showed a defect of ≥ 30°. Intra- and interobserver agreement were determined using Cohen's kappa (κ) and intraclass correlation coefficients. RESULTS: During the study period, 105 women underwent two TLUS assessments of the anal sphincter. Of these, 103 patients with ultrasound volumes available for both timepoints were included in the analysis. The novice investigator demonstrated average repeatability for assessment of significant EAS trauma and single-slice defect (κ, 0.30 and 0.22, respectively) despite relatively high agreement between measurements obtained at the two timepoints (84.5% and 79.3%, respectively). The experienced investigator demonstrated good to very good repeatability for significant EAS trauma and single-slice defect (κ, 0.91 and 0.78, respectively) between the two assessments, which equates to 98.1% and 94.7% agreement, respectively. CONCLUSION: The repeatability of TLUS measurements for diagnosis of EAS trauma seems to be very good when imaging is undertaken with state-of-the-art equipment and the analysis is performed by an experienced observer; however, the performance of a novice investigator is much poorer. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Mutations of SGO2 and CLDN14 collectively cause coincidental Perrault syndrome.

Perrault syndrome (PS) is a genetically heterogeneous disorder characterized by primary ovarian insufficiency (POI) in females and sensorineural hearing loss in males and females. In many PS subjects, causative variants have not been found in the five reported PS genes. The objective of this study was to identify the genetic cause of PS in an extended consanguineous family with six deaf individuals. Whole exome sequencing (WES) was completed on four affected members of a large family, and variants and co-segregation was confirmed by Sanger sequencing. All hearing impaired individuals, including the proband, are homozygous for a pathogenic variant of CLDN14, but this only explains the deafness. The PS proband is also homozygous for a frameshift variant (c.1453_1454delGA, p.(Glu485Lysfs*5)) in exon 7 of SGO2 encoding shugoshin 2, which is the likely cause of her concurrent ovarian insufficiency. In mouse, Sgol2a encoding shugoshin-like 2a is necessary during meiosis in both sexes to maintain the integrity of the cohesin complex that tethers sister chromatids. Human SGO2 has not previously been implicated in any disorder, but in this case of POI and perhaps others, it is a candidate for unexplained infertility.

Unresolved questions regarding human hereditary deafness.

Human hearing loss is a common neurosensory disorder about which many basic research and clinically relevant questions are unresolved. This review on hereditary deafness focuses on three examples considered at first glance to be uncomplicated, however, upon inspection, are enigmatic and ripe for future research efforts. The three examples of clinical and genetic complexities are drawn from studies of (i) Pendred syndrome/DFNB4 (PDS, OMIM 274600), (ii) Perrault syndrome (deafness and infertility) due to mutations of CLPP (PRTLS3, OMIM 614129), and (iii) the unexplained extensive clinical variability associated with TBC1D24 mutations. At present, it is unknown how different mutations of TBC1D24 cause non-syndromic deafness (DFNB86, OMIM 614617), epilepsy (OMIM 605021), epilepsy with deafness, or DOORS syndrome (OMIM 220500) that is characterized by deafness, onychodystrophy (alteration of toenail or fingernail morphology), osteodystrophy (defective development of bone), mental retardation, and seizures. A comprehensive understanding of the multifaceted roles of each gene associated with human deafness is expected to provide future opportunities for restoration as well as preservation of normal hearing.

Increased glycogen synthase kinase-3ß and hexose-6-phosphate dehydrogenase expression in adipose tissue may contribute to glucocorticoid-induced mouse visceral adiposity.

BACKGROUND: Increased adiposity in visceral depots is a crucial feature associated with glucocorticoid (GC) excess. The action of GCs in a target tissue is regulated by GC receptor (GR) and 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) coupled with hexose-6-phosphate dehydrogenase (H6pdh). Glycogen synthase kinase-3ß (GSK3ß) is known to be a crucial mediator of ligand-dependent gene transcription. We hypothesized that the major effects of corticosteroids on adipose fat accumulation are in part mediated by changes in GSK3ß and H6pdh. METHODS: We characterized the alterations of GSK3ß and GC metabolic enzymes, and determined the impact of GR antagonist mifepristone on obesity-related genes and the expression of H6pdh and 11ß-HSD1 in adipose tissue of mice exposed to excess GC as well as in in vitro studies using 3T3-L1 adipocytes treated with GCs. RESULTS: Corticosterone (CORT) exposure increased abdominal fat mass and induced expression of lipid synthase acetyl-CoA carboxylase and ATP-citrate lyase with activation of GSK3ß phosphorylation in abdominal adipose tissue of C57BL/6J mice. Increased pSer(9) GSK3ß was correlated with the induction of H6pdh and 11ß-HSD1. In addition, mifepristone treatment reversed the production of H6pdh and attenuated CORT-mediated production of 11ß-HSD1 and lipogenic gene expression with reduction of pSer(9) GSK3ß, thereby leading to improvement of phenotype of adiposity within adipose tissue in mice treated with excess GCs. Suppression of pSer(9) GSK3ß by mifepristone was accompanied by activation of pThr(308) Akt and blockade of CORT-induced adipogenic transcriptor C/EBPα and PPARγ. In addition, mifepristone also attenuated CORT-mediated activation of IRE1α/XBP1. In addition, reduction of H6pdh by shRNA showed comparable effects to mifepristone on attenuating CORT-induced expression of GC metabolic enzymes and improved lipid accumulation in vitro in 3T3-L1 adipocytes. CONCLUSION: These findings suggest that elevated adipose GSK3ß and H6pdh expression contribute to 11ß-HSD1 mediating hypercortisolism associated with visceral adiposity.

Effect of long term vitamin D supplementation on biomarkers of inflammation in Latino and African-American subjects with pre-diabetes and hypovitaminosis D.

Low vitamin D levels are associated with minority subjects, the metabolic syndrome, and inflammation. The effect of vitamin D supplementation on markers of inflammation has not been well studied. The aim of the study was to evaluate the effects of high doses of vitamin D supplementation for 1 year on serum biomarkers of inflammation in Latino and African-American subjects with pre-diabetes and hypovitaminosis D. Latino (n=69) and African-American (n=11) subjects who had both pre-diabetes and hypovitaminosis D with a mean age of 52.0 years, a BMI of 32.7 kg/m(2), and 70% of whom were females, were randomized to receive weekly doses (mean±SD) of vitamin D (85 300 IU±16 000) or placebo oil for 1 year. Serum levels of interleukin-6, tumor necrosis factor, highly sensitive C-reactive protein), plasminogen activator inhibitor 1, and insulin-like growth factor-1 were measured at baseline, 6, and 12 months. Serum 25-OH vitamin D levels of 22 ng/ml at baseline quickly rose to nearly 70 ng/ml in subjects receiving vitamin D and did not change in the placebo group. Two-way repeated measures ANOVA showed no differences between the 2 groups in any of the 5 selected parameters. High dose vitamin D supplementation for 1 year in minority subjects with pre-diabetes and hypovitaminosis D failed to affect serum biomarkers of inflammation.Clinical trial reg. no.: NCT00876928, clinicaltrials.gov.

Additive effects of nicotine and high-fat diet on hepatocellular apoptosis in mice: involvement of caspase 2 and inducible nitric oxide synthase-mediated intrinsic pathway signaling.

Smoking is a major risk factor for diabetes and cardiovascular disease and may contribute to nonalcoholic fatty liver disease (NAFLD). The health risk associated with smoking is exaggerated by obesity and is the leading causes of morbidity and mortality worldwide. We recently demonstrated that combined treatment with nicotine and a high-fat diet (HFD) triggers greater oxidative stress, activates hepatocellular apoptosis, and exacerbates HFD-induced hepatic steatosis. Given that hepatocellular apoptosis plays a pivotal role in the pathogenesis of NAFLD, using this model of exacerbated hepatic steatosis, we elucidated the signal transduction pathways involved in HFD plus nicotine-induced liver cell death. Adult C57BL6 male mice were fed a normal chow diet or HFD with 60% of calories derived from fat and received twice daily IP injections of 0.75 mg/kg BW of nicotine or saline for 10 weeks. High-resolution light microscopy revealed markedly higher lipid accumulation in hepatocytes from mice received HFD plus nicotine, compared to mice on HFD alone. Addition of nicotine to HFD further resulted in an increase in the incidence of hepatocellular apoptosis and was associated with activation of caspase 2, induction of inducible nitric oxide synthase (iNOS), and perturbation of the BAX/BCL-2 ratio. Together, our data indicate the involvement of caspase 2 and iNOS-mediated apoptotic signaling in nicotine plus HFD-induced hepatocellular apoptosis. Targeting the caspase 2-mediated death pathway may have a protective role in development and progression of NAFLD.

A gene for congenital, recessive deafness DFNB3 maps to the pericentromeric region of chromosome 17.

Two percent of the residents of Bengkala, Bali, have profound, congenital, neurosensory, nonsyndromal deafness due to an autosomal recessive mutation at the DFNB3 locus. We have employed a direct genome-wide disequilibrium search strategy, allele-frequency-dependent homozygosity mapping (AHM), and an analysis of historical recombinants to map DFNB3 and position the locus relative to flanking markers. DFNB3 maps to chromosome 17, closest to D17S261, pRM7-GT and D17S805. In individuals homozygous for DFNB3, historical recombinant genotypes for the flanking markers, D17S122 and D17S783, place DFNB3 in a 5.3 cM interval of the pericentromeric region of chromosome 17 on a refined linkage map of 17p-17q12. Based on conserved synteny, the murine sh2 gene may be the homologue of DFNB3.

Dominant modifier DFNM1 suppresses recessive deafness DFNB26.

More than 50% of severe childhood deafness is genetically determined, approximately 70% of which occurs without other abnormalities and is thus termed nonsyndromic. So far, 30 nonsyndromic recessive deafness loci have been mapped and the defective genes at 6 loci, DFNB1, DFNB2, DFNB3, DFNB4, DFNB9 and DNFB21, have been identified, encoding connexin-26 (ref. 3), myosin VIIA (ref. 4), myosin XV (ref. 5), pendrin, otoferlin and alpha-tectorin, respectively. Here we map a new recessive nonsyndromic deafness locus, DFNB26, to a 1.5-cM interval of chromosome 4q31 in a consanguineous Pakistani family. A maximum lod score of 8.10 at theta=0 was obtained with D4S1610 when only the 8 affected individuals in this family were included in the calculation. There are seven unaffected family members who are also homozygous for the DFNB26-linked haplotype and thus are non-penetrant. A dominant modifier, DFNM1, that suppresses deafness in the 7 nonpenetrant individuals was mapped to a 5.6-cM region on chromosome 1q24 with a lod score of 4.31 at theta=0 for D1S2815.

Tissue-specific dysregulation of hexose-6-phosphate dehydrogenase and glucose-6-phosphate transporter production in db/db mice as a model of type 2 diabetes.

AIMS/HYPOTHESIS: Tissue-specific amplification of glucocorticoid action through 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) affects the development of the metabolic syndrome. Hexose-6-phosphate dehydrogenase (H6PDH) mediates intracellular NADPH availability for 11ß-HSD1 and depends on the glucose-6-phosphate transporter (G6PT). Little is known about the tissue-specific alterations of H6PDH and G6PT and their contributions to local glucocorticoid action in db/db mice. METHODS: We characterised the role of H6PDH and G6PT in pre-receptor metabolism of glucocorticoids by examining the production of the hepatic 11ß-HSD1-H6PDH-G6PT system in db/db mice. RESULTS: We observed that increased production of hepatic H6PDH in db/db mice was paralleled by upregulation of hepatic G6PT production and responded to elevated circulating levels of corticosterone. Treatment of db/db mice with the glucocorticoid antagonist RU486 markedly reduced production of both H6PDH and 11ß-HSD1 and improved hyperglycaemia and insulin resistance. The reduction of H6PDH and 11ß-HSD1 production by RU486 was accompanied by RU486-induced suppression of hepatic G6pt (also known as Slc37a4) mRNA. Incubation of mouse primary hepatocytes with corticosterone enhanced G6PT and H6PDH production with corresponding activation of 11ß-HSD1 and PEPCK: effects that were blocked by RU486. Knockdown of H6pd by small interfering RNA showed effects comparable with those of RU486 for attenuating the corticosterone-induced H6PDH production and 11ß-HSD1 reductase activity in these intact cells. Addition of the G6PT inhibitor chlorogenic acid to primary hepatocytes suppressed H6PDH production. CONCLUSIONS/INTERPRETATION: These findings suggest that increased hepatic H6PDH and G6PT production contribute to 11ß-HSD1 upregulation of local glucocorticoid action that may be related to the development of type 2 diabetes.

High prevalence of normal tests assessing hypercortisolism in subjects with mild and episodic Cushing's syndrome suggests that the paradigm for diagnosis and exclusion of Cushing's syndrome requires multiple testing.

Many Endocrinologists believe that a single determination of eucortisolism or a single demonstration of appropriate suppression to dexamethasone excluded Cushing's syndrome, except in what was previously thought to be the rare patient with episodic or periodic Cushing's syndrome. We hypothesize that episodic Cushing's syndrome is relatively common and a single test assessing hypercortisolism may not be sufficient to accurately rule out or diagnose Cushing's syndrome and retrospectively examined the number of normal and abnormal tests assessing hypercortisolism performed on multiple occasions in 66 patients found to have mild and/or episodic Cushing's syndrome compared to a similar group of 54 patients evaluated for, but determined not to have Cushing's syndrome. We found that 65 of the 66 patients with Cushing's syndrome had at least one normal test of cortisol status and most patients had several normal tests. The probability of having Cushing's syndrome when one test was negative was 92% for 23:00 h salivary cortisol, 88% for 24-h UFC, 86% for 24-h 17OHS, and 54% for nighttime plasma cortisol. These results demonstrated that episodic hypercortisolism is highly prevalent in subjects with mild Cushing's syndrome and no single test was effective in conclusively diagnosing or excluding the condition. Rather, the paradigm for the diagnosis should be a careful history and physical examination and in those patients in whom mild Cushing's syndrome/disease is strongly suspected, multiple tests assessing hypercortisolism should be performed on subsequent occasions, especially when the patient is experiencing signs and symptoms of short-term hypercortisolism.

USH1H, a novel locus for type I Usher syndrome, maps to chromosome 15q22-23.

Usher syndrome (USH) is a hereditary disorder associated with sensorineural hearing impairment, progressive loss of vision attributable to retinitis pigmentosa (RP) and variable vestibular function. Three clinical types have been described with type I (USH1) being the most severe. To date, six USH1 loci have been reported. We ascertained two large Pakistani consanguineous families segregating profound hearing loss, vestibular dysfunction, and RP, the defining features of USH1. In these families, we excluded linkage of USH to the 11 known USH loci and subsequently performed a genome-wide linkage screen. We found a novel USH1 locus designated USH1H that mapped to chromosome 15q22-23 in a 4.92-cM interval. This locus overlaps the non-syndromic deafness locus DFNB48 raising the possibility that the two disorders may be caused by allelic mutations.

DFNB74, a novel autosomal recessive nonsyndromic hearing impairment locus on chromosome 12q14.2-q15.

Autosomal recessive nonsyndromic hearing impairment (ARNSHI) segregating in three unrelated, large consanguineous Pakistani families (PKDF528, PKDF859 and PKDF326) is linked to markers on chromosome 12q14.2-q15. This novel locus is designated DFNB74. Maximum two-point limit of detection (LOD) scores of 5.6, 5.7 and 2.6 were estimated for markers D12S313,D12S83 and D12S75 at theta = 0 for recessive deafness segregating in these three families. Haplotype analyses identified a critical linkage interval of 5.35 cM (5.36 Mb) defined by D12S329 at 74.58 cM and D12S313 at 79.93 cM. DFNB74 is the second ARNSHI locus mapped to chromosome 12, but the physical intervals do not overlap with one another. A locus contributing to the early onset, rapidly progressing hearing loss of A/J mice (ahl4, age-related hearing loss 4) was reported to map to chromosome 10 in a region of conserved synteny to DFNB74, suggesting that ahl4 and DFNB74 may be due to mutations of the same gene in these two species.

Identities and frequencies of mutations of the otoferlin gene (OTOF) causing DFNB9 deafness in Pakistan.

Mutations in OTOF, encoding otoferlin, cause non-syndromic recessive hearing loss. The goal of our study was to define the identities and frequencies of OTOF mutations in a model population. We screened a cohort of 557 large consanguineous Pakistani families segregating recessive, severe-to-profound, prelingual-onset deafness for linkage to DFNB9. There were 13 families segregating deafness consistent with linkage to markers for DFNB9. We analyzed the genomic nucleotide sequence of OTOF and detected probable pathogenic sequence variants among all 13 families. These include the previously reported nonsense mutation p.R708X and 10 novel variants: 3 nonsense mutations (p.R425X, p.W536X, and p.Y1603X), 1 frameshift (c.1103_1104delinsC), 1 single amino acid deletion (p.E766del) and 5 missense substitutions of conserved residues (p.L573R, p.A1090E, p.E1733K, p.R1856Q and p.R1939W). OTOF mutations thus account for deafness in 13 (2.3%) of 557 Pakistani families. This overall prevalence is similar, but the mutation spectrum is different from those for Western populations. In addition, we demonstrate the existence of an alternative splice isoform of OTOF expressed in the human cochlea. This isoform must be required for human hearing because it encodes a unique alternative C-terminus affected by some DFNB9 mutations.

Taxol induces postmitotic myoblasts to assemble interdigitating microtubule-myosin arrays that exclude actin filaments.

Taxol has the following effects on myogenic cultures: (a) it blocks cell replication of presumptive myoblasts and fibroblasts. (b) It induces the aggregation of microtubules into sheets or massive cables in presumptive myoblasts and fibroblasts, but not in postmitotic, mononucleated myoblasts. (c) It induces normally elongated postmitotic myoblasts to form stubby, star-shaped cells. (d) It reversibly blocks the fusion of the star-shaped myoblasts into multinucleated myotubes. (e) It augments the number of microtubules in postmitotic myoblasts, and these are assembled into interdigitating arrays of microtubules and myosin filaments. (f) Actin filaments are largely excluded from these interdigitating microtubule-myosin complexes. (g) The myosin filaments in the interdigitating microtubule-myosin arrays are aligned laterally, forming A-bands approximately 1.5 micrometers long.

Purine resistant mutants of Drosophila are adenine phosphoribosyltransferase deficient.

A deficiency for adenine phosphoribosyltransferase activity is the primary biochemical defect in mutants of Drosophila selected for resistance to purine-induced lethality.