A sterol analog inhibits hedgehog pathway by blocking cholesterylation of smoothened

The hedgehog (Hh) signaling pathway has long been a hotspot for anti-cancer drug development due to its important role in cell proliferation and tumorigenesis. However, most clinically available Hh pathway inhibitors target the seven-transmembrane region (7TM) of smoothened (SMO), and the acquired drug resistance is an urgent problem in SMO inhibitory therapy. Here, we identify a sterol analog Q29 and show that it can inhibit the Hh pathway through binding to the cysteine-rich domain (CRD) of SMO and blocking its cholesterylation. Q29 suppresses Hh signaling-dependent cell proliferation and arrests Hh-dependent medulloblastoma growth. Q29 exhibits an additive inhibitory effect on medulloblastoma with vismodegib, a clinically used SMO-7TM inhibitor for treating basal cell carcinoma (BCC). Importantly, Q29 overcomes resistance caused by SMO mutants against SMO-7TM inhibitors and inhibits the activity of SMO oncogenic variants. Our work demonstrates that the SMO-CRD inhibitor can be a new way to treat Hh pathway-driven cancers.

Synthesis and Biological Evaluation of Heterocyclic Ring-Fused 20(S)-Protopanaxadiol Derivatives as Potent Antiosteoporosis Agents

A series of heterocyclic ring-fused derivatives of 20(S)-protopanaxadiol (PPD) were synthesized and evaluated for their inhibitory effects on RANKL-induced osteoclastogenesis. Among these compounds, 33 (SH491, IC50 = 11.8 nM) showed the highest potency with 100% inhibition at 0.1 μM and 44.4% inhibition at an even lower concentration of 0.01 μM, which was much more potent than the lead compound PPD (IC50 = 10.3 μM). Cytotoxicity tests indicated that the inhibitory effect of these compounds on RANKL-induced osteoclast differentiation was not due to their cytotoxicity. Interestingly, SH491 also exhibited a notable impact on the osteoblastogenesis of MC3T3-E1 preosteoblasts. Mechanistic studies revealed that SH491 inhibits the expression of osteoclastogenesis-related marker genes and proteins, including TRAP, CTSK, MMP-9, and ATPase v0d2. In vivo, SH491 could dramatically decrease the ovariectomy-induced osteoclast activity and relieve osteoporosis obviously. Thus, these PPD derivatives could be served as promising leads for the development of novel antiosteoporosis agents.

Synthesis of plant-derived cholesterol from bisnoralcohol

Currently, the market demand of the non-animal-derived cholesterol is increasing. A novel synthetic route of producing cholesterol was developed through multiple reactions from plant-sourced and commercially available bisnoralcohol (BA). The key reaction conditions, including solvents, reaction temperatures, bases and reducing agents of the route were investigated and optimized. In this straightforward synthetic pathway of cholesterol, most of the reaction steps possess high conversions with average yields of 94%, and the overall yield is up to 74% (5 steps) from the BA. The epicholesterol and were also synthesized. This promising route offers economical and efficient strategies for potential large-scale production of plant-derived cholesterol.

Targeting STAT3 by a small molecule suppresses pancreatic cancer progression

Pancreatic cancer is lethal in over 90% of cases since it is resistant to current therapeutic strategies. The key role of STAT3 in promoting pancreatic cancer progression has been proven, but effective interventions that suppress STAT3 activities are limited. The development of novel anticancer agents that directly target STAT3 may have potential clinical benefits for pancreatic cancer treatment. Here, we report a new small-molecule inhibitor (N4) with potent antitumor bioactivity, which inhibits multiple oncogenic processes in pancreatic cancer. N4 blocked STAT3 and phospho-tyrosine (pTyr) peptide interactions in fluorescence polarization (FP) assay, specifically abolished phosphor-STAT3 (Tyr705), and suppressed expression of STAT3 downstream genes. The mechanism involved the direct binding of N4 to the STAT3 SH2 domain, thereby, the STAT3 dimerization, STAT3-EGFR, and STAT3-NF-κB cross-talk were efficiently inhibited. In animal models of pancreatic cancer, N4 was well tolerated, suppressed tumor growth and metastasis, and significantly prolonged survival of tumor-bearing mice. Our results offer a preclinical proof of concept for N4 as a candidate therapeutic compound for pancreatic cancer.

Synthesis of ursodeoxycholic acid from plant-source (20S)-21-hydroxy-20-methylpregn-4-en-3-one

A novel synthetic route of producing ursodeoxycholic acid (UDCA) was developed through multiple reactions from cheap and commercially available bisnoralcohol (BA). The key reaction conditions, including solvents, bases and reaction temperatures of the route were investigated and optimized. In the straightforward route for preparation of UDCA, most of the reaction steps have high conversions with average yields of 91%, and overall yield up to 59% (6 steps) from the plant-source BA. Especially in the last step of reduction and hydrolysis, there are five functional groups converted with calcd 97% per conversion in one-pot reaction. This promising route offers economical and efficient strategies for potential large-scale production of UDCA.

Synthesis and Preliminary Evaluation of [11 C]GNE-1023 as a Potent PET Probe for Imaging Leucine-Rich Repeat Kinase 2 (LRRK2) in Parkinson's Disease

Leucine-rich repeat kinase 2 (LRRK2) is a large protein involved in the pathogenesis of Parkinson's disease (PD). It has been demonstrated that PD is mainly conferred by LRRK2 mutations that bring about increased kinase activity. As a consequence, selective inhibition of LRRK2 may help to recover the normal functions of LRRK2, thereby serving as a promising alternative therapeutic target for PD treatment. The mapping of LRRK2 by positron emission tomography (PET) studies allows a thorough understanding of PD and other LRRK2-related disorders; it also helps to validate and translate novel LRRK2 inhibitors. However, no LRRK2 PET probes have yet been reported in the primary literature. Herein we present a facile synthesis and preliminary evaluation of [¹¹ C]GNE-1023 as a novel potent PET probe for LRRK2 imaging in PD. [¹¹ C]GNE-1023 was synthesized in good radiochemical yield (10 % non-decay-corrected RCY), excellent radiochemical purity (>99 %), and high molar activity (>37 GBq μmol^-1 ). Excellent in vitro binding specificity of [¹¹ C]GNE-1023 toward LRRK2 was demonstrated in cross-species studies, including rat and nonhuman primate brain tissues by autoradiography experiments. Subsequent whole-body biodistribution studies indicated limited brain uptake and urinary and hepatobiliary elimination of this radioligand. This study may pave the way for further development of a new generation of LRRK2 PET probes.

Diastereoselective synthesis of 3,3-disubstituted 3-nitro-4-chromanone derivatives as potential antitumor agents

We report an efficient and highly diastereoselective protocol for the rapid construction of 3-nitro substituted 4-chromanones by an intramolecular Michael-type cyclization of α-nitro aryl ketones bearing unsaturated ester units.

Synthesis and biological evaluation of 3-nitro-4-chromanone derivatives as potential antiproliferative agents for castration-resistant prostate cancer

A series of novel 3-nitro-4-chromanones were synthesized and their in vitro cytotoxicity was evaluated on castration-resistant prostate cancer cell (CRPC) lines using the sulforhodamine B (SRB) assay. The amide derivatives showed more potent antitumor activity than their corresponding ester derivatives. Most of the tested compounds showed less toxicity towards human fibroblasts (HAF) compared with the tumor cell lines. The optimal compound 36 possessed much more potent antiproliferative activity than the positive compound cisplatin. The colony formation, cell cycle distribution, apoptosis, transwell migration and wound healing assays of 36 were performed on CRPC cell lines.

A series of novel 3-nitro-4-chromanones were synthesized and their in vitro cytotoxicity was evaluated on castration-resistant prostate cancer cell lines.

Discovery of methylpyrimidine ring-fused diterpenoid analogs as a novel testosterone synthesis promoter

We synthesized a series of methylpyrimidine ring-fused diterpenoid analogs, among them, compound 17 is a potent agent in promoting testosterone production in Leydig TM3 cells.

Discovery of a potent HMG-CoA reductase degrader that eliminates statin-induced reductase accumulation and lowers cholesterol

Statins are inhibitors of HMG-CoA reductase, the rate-limiting enzyme of cholesterol biosynthesis, and have been clinically used to treat cardiovascular disease. However, a paradoxical increase of reductase protein following statin treatment may attenuate the effect and increase the side effects. Here we present a previously unexplored strategy to alleviate statin-induced reductase accumulation by inducing its degradation. Inspired by the observations that cholesterol intermediates trigger reductase degradation, we identify a potent degrader, namely Cmpd 81, through structure-activity relationship analysis of sterol analogs. Cmpd 81 stimulates ubiquitination and degradation of reductase in an Insig-dependent manner, thus dramatically reducing protein accumulation induced by various statins. Cmpd 81 can act alone or synergistically with statin to lower cholesterol and reduce atherosclerotic plaques in mice. Collectively, our work suggests that inducing reductase degradation by Cmpd 81 or similar chemicals alone or in combination with statin therapy can be a promising strategy for treating cardiovascular disease.

A facile synthesis of ursodeoxycholic acid and obeticholic acid from cholic acid

A novel synthetic route of producing ursodeoxycholic acid (UDCA) and obeticholic acid (OCA) was developed through multiple reactions from cheap and readily-available cholic acid. The reaction conditions of the key elimination reaction of mesylate ester group were also investigated and optimized, including solvent, base and reaction temperature. In the straightforward synthetic route for preparation of UDCA and OCA, most of the reaction steps have high conversions with average yields of 94% and 92%, and overall yield up to 65% (7 steps) and 36% (11 steps) from cholic acid, respectively. This promising route offers economical and efficient strategies for potential large-scale production of UDCA and OCA.

Synthesis of Cyanoenone-Modified Diterpenoid Analogs as Novel Bmi-1-Mediated Antitumor Agents

Bmi-1 is overexpressed in colorectal cancer (CRC) and served as a novel therapeutic target for the treatment of CRC. A series of novel cyanoenone-modified diterpenoid analogs was synthesized and investigated for their antiproliferative activity against CRC cells. The results showed that most of these compounds exhibited potent antiproliferative and Bmi-1 inhibitory activity. Among them, the most active compound 33 (SH498) showed more potent antiproliferative activity than the positive control compound PTC-209. These synthetic diterpenoid analogs were less toxic for normal human fibroblasts (HAF) than for CRC cells. Especially 33, its selectivity index (SI) between HAF and tumor cells was 7.3-13.1, which was much better than PTC-209. The polycomb repressive complex 1 (PRC1) complex, transwell migration, colony formation, cancer stem cell proliferation, and apoptosis assays of 33 were performed on CRC cell lines. The in vivo antitumor effect of 33 was also observed in HCT116 tumor-bearing mice.

The synthesis and antitumor activity of lithocholic acid and its derivatives

In this paper, a new and concise synthetic route of lithocholic acid (LCA) using commercially available steroid source deoxycholic acid is reported. A series of amide derivatives of LCA were also synthesized and investigated for their activity against the growth of MCF-7 and MCF-7/ADR cells using the sulforhodamine B assay. For MCF-7, the most potent compound 20 showed a 20-fold higher antitumor activity than LCA. For MCF-7/ADR, the most potent compound 24 showed a 22-fold higher antitumor activity than LCA. The transwell migration assay of 20 was evaluated on MDA-MB-231 cells. The colony formation and apoptosis assays of 20 were performed on MCF-7 and MCF-7/ADR cell lines.

SH479, a Betulinic Acid Derivative, Ameliorates Experimental Autoimmune Encephalomyelitis by Regulating the T Helper 17/Regulatory T Cell Balance

CD4⁺ T helper cells, especially T helper 17 (T_H17) cells, combined with immune regulatory network dysfunction, play key roles in autoimmune diseases including multiple sclerosis (MS). Betulinic acid (BA), a natural pentacyclic triterpenoid, has been reported to be involved in anti-inflammation, in particular having an inhibitory effect on proinflammatory cytokine interleukin 17 (IL-17) and interferon-γ (IFN-γ) production. In this study, we screened BA derivatives and found a BA derivative, SH479, that had a greater inhibitory effect on T_H17 differentiation. Our further analysis showed that SH479 had a greater inhibitory effect on T_H17 and T_H1, and a more stimulatory effect on regulatory T (Treg) cells. To evaluate the effects of SH479 on autoimmune diseases in vivo, we employed the extensively used MS mouse model experimental autoimmune encephalomyelitis (EAE). Our results showed that SH479 ameliorated clinical and histologic signs of EAE in both prevention and therapeutic protocols by regulating the T_H17/Treg balance. SH479 dose-dependently reduced splenic lymphocyte proinflammatory factors and increased anti-inflammatory factors. Moreover, SH479 specifically inhibited splenic lymphocyte viability from EAE mice but not normal splenic lymphocyte viability. At the molecular level, SH479 inhibited T_H17 differentiation by regulating signal transducer and activator of transcription-3 (STAT3) phosphorylation, DNA binding activity, and recruitment to the Il-17a promoter in CD4⁺ T cells. Furthermore, SH479 promoted the STAT5 signaling pathway and inhibited the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway. Together, our data demonstrated that SH479 ameliorated EAE by regulating the T_H17/Treg balance through inhibiting the STAT3 and NF-κB pathways while activating the STAT5 pathway, suggesting that SH479 is a potential novel drug candidate for autoimmune diseases including MS.

A betulinic acid derivative SH479 inhibits collagen-induced arthritis by modulating T cell differentiation and cytokine balance

The ideal therapeutic drug for rheumatoid arthritis (RA) should not only inhibit inflammation, but also prevent articular joint damage and particularly inhibit osteoclastogenesis. Betulinic acid (BA) is a natural pentacyclic triterpene that has displayed moderate anti-inflammatory and anti-osteoclastogenesis activities in various experimental systems, suggesting that BA or its derivatives could have an inhibitory effect on RA. In this study, we screened BA derivatives and found a heterocyclic ring-fused BA derivative, SH479, which had greater inhibitory effect than BA on Th17 differentiation. Moreover, we investigated the immune regulatory activity and potential therapeutic effects of SH479 in an experimental model of rheumatoid arthritis, the collagen-induced arthritis (CIA) mouse model. SH479 significantly inhibited Th1 and Th17 polarization, antigen-specific T cell proliferation and splenic lymphocyte-induced osteoclastogenesis. Furthermore, it diminished arthritis scores as well as bone destruction and cartilage depletion in the CIA mouse model. The protective effect of SH479 was accompanied by decreased levels of pro-inflammatory cytokines IL-17 and IFN-γ, together with enhanced anti-inflammatory cytokine expression including IL-10 and IL-4, as well as elevated CD4⁺ Foxp3⁺ cell number. At the molecular level, our results indicated that SH479 alleviated CIA through regulation of CD4⁺ T cell subtypes by JAK-STAT pathways. In conclusion, this study demonstrates that SH479 has therapeutic potential for rheumatoid arthritis through an anti-inflammatory effect by shifting a pathogenic Th17/Th1 response to a Th2/Treg phenotype, and also through an additional articular bone protection effect.

Design, synthesis and biological evaluation of tricyclic diterpene derivatives as novel neuroprotective agents against ischemic brain injury

Lead compound 7 has neuroprotective effects, and it was discovered by screening a small synthetic natural product-like (NPL) library. Based on the lead, a series of tricyclic diterpene derivatives was designed and synthesized, and their neuroprotective effects were further evaluated against glutamate-, oxygen and glucose deprivation (OGD)- and nutrient deprivation-induced neuronal injury using cell-based assays. To our delight, most of these synthetic compounds exhibited increased neuroprotective effects and blood-brain barrier (BBB) permeability without cellular toxicity. The most potent compound, compound 30, showed significantly improved neuroprotection against neuronal injury in primary neurons. Furthermore, compound 30 exhibited remarkable neuroprotection in transient middle cerebral artery occlusion (tMCAO) rats by reducing their infarct sizes and neurological deficit scores. A mechanistic exploration using in vitro and in vivo experiments showed that the neuroprotection of these compounds was at least partly mediated by improving the levels of glutathione (GSH), superoxide dismutase (SOD) and heme oxygenase-1 (HO-1) protein. Therefore, these tricyclic diterpene derivatives could be used as promising leads for the development of a new type of neuroprotective agents against ischemic brain injury.

Synthesis of heterocycle-modified betulinic acid derivatives as antitumor agents

A series of novel heterocycle-modified betulinic acid (BA) derivatives were synthesized and investigated for their activity against the growth of eight non-drug resistant and one multidrug-resistant tumor cell line using a sulforhodamine B (SRB) assay. The most active compound 17 showed an average IC50 1.19 μM, which was about 20 times more potent than the lead compound BA. It is amazing that for most synthetic saturated N-heterocycle derivatives, MCF-7/ADR was the most sensitive tumor cells, especially 17 showed the most potent antitumor activity (IC50 = 0.33 μM) on this multidrug-resistant tumor cell line, that was 117 times more potent than BA. Most of the tested compounds displayed less toxic on human fibroblasts (HAF) in comparison with the tumor cell lines. The cytometry and transwell migration assays were used to test the ability of 17 to induce apoptosis and inhibit metastasis on tumor cell lines respectively.

Synthesis of novel heterocyclic ring-fused 18β-glycyrrhetinic acid derivatives with antitumor and antimetastatic activity

Glycyrrhetinic acid (GA) is one of the most important triterpenoic acids shows many pharmacological effects, especially antitumor activity. GA triggers apoptosis in various tumor cell lines. However, the antitumor activity of GA is weak, thus the synthesis of new synthetic analogs with enhanced potency is needed. By introducing various five-member fused heterocyclic rings at C-2 and C-3 positions, 18 novel GA derivatives were obtained. These compounds were evaluated for their inhibitory activity against the growth of eight different tumor cell lines using a SRB assay. The most active compound 37 showed IC50 between 5.19 and 11.72 μm, which was about 11-fold more potent than the lead compound GA. An apoptotic effect of GA and 37 was determined using flow cytometry and trypan blue exclusion assays. We also demonstrated here for the first time that GA and the synthetic derivatives exhibited inhibitory effect on migration of the tested tumor cells, especially 37 which was about 20-fold more potent than GA on antimetastatic activity.

Selective formation of six-membered oxa- and carbocycles by the In(III)-activated ring closure of acetylenic substrates

Fifteen examples are disclosed of efficient In(III)-catalyzed six-membered ring closure leading to bi-, tri-, and tetracyclic products.

Inhibition of SREBP by a small molecule, betulin, improves hyperlipidemia and insulin resistance and reduces atherosclerotic plaques

Sterol regulatory element-binding proteins (SREBPs) are major transcription factors activating the expression of genes involved in biosynthesis of cholesterol, fatty acid and triglyceride. In this study, we identified a small molecule, betulin, that specifically inhibited the maturation of SREBP by inducing interaction of SREBP cleavage activating protein (SCAP) and Insig. Inhibition of SREBP by betulin decreased the biosynthesis of cholesterol and fatty acid. In vivo, betulin ameliorated diet-induced obesity, decreased the lipid contents in serum and tissues, and increased insulin sensitivity. Furthermore, betulin reduced the size and improved the stability of atherosclerotic plaques. Our study demonstrates that inhibition SREBP pathway can be employed as a therapeutic strategy to treat metabolic diseases including type II diabetes and atherosclerosis. Betulin, which is abundant in birch bark, could be a leading compound for development of drugs for hyperlipidemia.

Synthesis and biological evaluation of heterocyclic ring-substituted maslinic acid derivatives as novel inhibitors of protein tyrosine phosphatase 1B

A series of maslinic acid derivatives have been synthesized by introducing various fused heterocyclic rings at C-2 and C-3 positions. Their inhibitory effects on PTP1B, TCPTP and related PTPs are evaluated. Most of the compounds exhibited a dramatic increase in inhibitory potency and selectivity, the two most potent PTP1B inhibitors 20 (IC(50)=0.61 microM) and 29 (IC(50)=0.64 microM) showed about 10-fold more potent than lead compound maslinic acid. More importantly, 29 possesses the best selectivity of 6.9-fold for PTP1B over TCPTP.

Design and synthesis of a biotin-tagged photoaffinity probe of paeoniflorin

A trifunctional probe (binding element-photoreactive group-affinity tag) of natural product paeoniflorin was designed and synthesized based on the previous primary structure-activity relationship. This new probe is a potential tool for labeling, purification, and identification of the target proteins.

Critical evaluation of neurolaryngological disorders

Otolaryngological examinations, videostroboscopic image analysis, and laryngeal electromyography were used as a test battery for a critical evaluation in 80 patients. Vocal fold movements were categorized into mobility, restricted mobility, immobility with different positions, and overactive movement. Laryngeal electromyographic examinations were conducted in all patients, and the results were classified into normal, neuropathic, and myopathic patterns. The electromyographic data were integrated with videostroboscopic findings, interpreted with knowledge of biomechanical and electrophysiological mechanisms of the larynx, and correlated clinically with underlying diseases. It is suggested that neurolaryngological procedures are most clinically useful when dictated by a decision-making algorithm.

Laryngeal reflexomyographic responses in rabbits: a neurolaryngological study of glottal movement

The role of the laryngeal reflex in glottal movement has been reported, but its mechanism remains unclear. To further investigate the neurophysiological characteristics of glottal movement, we recorded the laryngeal reflexomyographic responses (LRMRs) to electrical stimulation of the superior laryngeal nerve (SLN) in rabbits. The procedure involved simultaneous recording of the LRMRs from the thyroarytenoid muscles by means of bipolar hooked wire electrodes after electrical stimulation to the SLN. The results demonstrated characteristic patterns of the responses, consisting of R1 and R2, similar to those found in humans. The R1 response was obtained with a latency of 10.7 +/- 0.78 ms. The ipsilateral R2 response was obtained with a latency of 43.76 +/- 4.67 ms in all rabbits, and the contralateral R2 response with a latency from 42.6 to 50.2 ms in 4 rabbits. It was concluded that LRMRs may serve as a potential central laryngeal function test in the investigation of glottal movement control.

Critical evaluation of deafness

OBJECTIVE

The purpose of this study is to investigate the clinical aspects of profound hearing loss (PHL) and their significance for defining deafness.

METHODS

The audiological data were reviewed from 3660 patients who were evaluated in the Otolaryngology Clinic at Louisiana State University in Shreveport, LA, over a 5-year period. The medical charts from the patients were also reviewed for the information of medical diagnosis, surgical records and radiological findings.

RESULTS

There were 34 patients identified with bilateral PHL or deaf, 177 patients with unilateral PHL and 123 patients with borderline PHL. Congenital hearing loss and unknown-cause hearing loss in this series were predominant with 267 cases (79.9%). A surgical management was indicated in 39 cases (11.7%) including middle ear infection, ossicular chain abnormalities and auditory nerve/brainstem tumors.

CONCLUSION

This study suggests that audiometrically PHL should be thoroughly evaluated to detect reversible or remediable conditions by surgical and medical approaches. The diagnosis of deafness should be confirmed by an integration of the audiological data and medical documents including surgical and radiological findings. Aural rehabilitation program should be designed for deaf patients with varied etiology and degree of residual peripheral hearing sensitivity following medical clearance.

Neurotologic evaluation of facial nerve paralysis caused by gunshot wounds

Facial nerve injury is one of the most common neurotologic sequelae of a gunshot wound (GSW) to the head or neck. However, few neurotologic studies have been performed on the nature and time course of such facial nerve impairments. This study was designed to characterize the neurotologic manifestations and time course of facial nerve paralysis caused by GSWs to the head and neck. We conducted a battery of electrodiagnostic tests on 10 patients who had experienced traumatic facial paralysis due to a GSW to the head or neck. The etiologies of facial nerve paralysis--including direct injury, compression, fracture, and concussion of the temporal bone--were demonstrated by audiologic, radiologic, and surgical findings. Hearing loss and other cranial nerve injuries were also seen. Six of the 10 patients experienced a complete paralysis of the facial nerve and a poor recovery of its function. We also present a comprehensive case report on 1 patient as a means of discussing the evaluation of facial nerve function during the course of management.

Clinical interpretations of transient otoacoustic emissions

PURPOSE

The purpose of this study was to characterize the relation of different ordinal patterns of transient otoacoustic emissions (TEOAES) with respect to underlying otologic disorders and auditory status.

PATIENTS AND METHODS

The results of TEOAEs in 225 patients with various auditory disorders were investigated and compared with normative data established from 90 subjects of various ages. TEOAEs were categorized according to four patterns: (1) normal (general response level within 90% of normative data, (2) reduced amplitude (general response level was > or =2 dB peak sound pressure level (pSPL), but less than the mean -1.64 SD of the normative data), (3) abnormal morphology of frequency spectrum (general response level was within normal limits, but reduced at > or =2 individual octave frequencies between 1,000 and 5,000 Hz), and (4) total absence (response level <2 dB pSPL).

RESULTS

This study showed that the normal pattern of TEOAEs, in terms of response amplitude, varied with age. Our results further indicated that a reduced amplitude pattern of TEOAEs was noted in patients with a mild sensorineural hearing loss (SNHL), negative tympanometric pressure, a pressure-equalization tube, and Meniere's disease. TEOAEs provided good frequency-specific information for patients with a noise-induced hearing loss. All patients with ossicular chain abnormalities, more than moderate SNHL, and a middle ear mass or effusion had total absence of TEOAEs. Patients with acoustic neuroma and brainstem lesions presented a complex profile of TEOAEs. In the follow-up of auditory function in patients undergoing otologic surgery, different patterns of TEOAEs between the preoperative and postoperative recordings were evident, which correlated with the hearing thresholds and middle ear status. The abnormal findings of TEOAEs due to specific auditory diseases were discussed.

CONCLUSION

The interpretation of TEOAEs can be facilitated through an analysis of specific patterns and in combination with other audiologic tests.

Current evaluation of pseudohypacusis: strategies and classification

Some cases of pseudohypacusis may involve medicolegal aspects and require a confirmed and quantitative diagnosis. These challenging cases must be identified, and then evaluated with basic audiologic and sophisticated electrophysiologic tests. Data on 64 patients with pseudohypacusis collected over a 4-year period are reported. A classification system was developed from an analysis of these cases and is presented for clinical evaluation and diagnosis. In many cases, conventional audiologic evaluation involving pure tone and speech audiometry may be adequate and sufficient for diagnosis. In more complex cases, evoked otoacoustic emissions (EOAEs) and auditory brain stem responses (ABRs) are needed for confirmation of peripheral auditory sensitivity. We found that EOAEs were the most rapid economical, and objective method, and confirmed the diagnosis of hearing loss in 78.1% of cases. Fifteen percent of subjects required ABRs to substantiate the diagnosis. The reliability of basic audiologic tests based on previous clinical investigations and data from the literature are discussed. We conclude that a thorough knowledge and understanding of pseudohypacusis is essential to verify the existence of pseudohypacusis, to determine its type, and to quantify the auditory thresholds.

Characterization of acoustic reflex latency in normal-hearing subjects

Acoustic reflex latency (ARL) has been suggested as an indicator in otoneurological diagnosis. However, limited normative data are available. Conflicting evidence exists regarding the effect of stimulus parameters such as frequency on ARL. In addition, there has been little research investigating the effects of ipsilateral and contralateral stimulation on ARL. In view of these problems, ARL was measured in 30 normal-hearing subjects using 500, 1000, 2000, 4000 Hz tones, low-pass noise, high-pass noise, broadband noise and clicks as activating stimuli. Six parameters of ARL: 10%-on latency, 90%-on latency, 10%-off latency, 90%-off latency, rise time and fall time, were recorded using computerized equipment and analyzed in correlation to the activating frequency and intensity. This study indicated that 500 Hz, 1000 Hz tones, and band noise were more effective in eliciting measurable ARL, whereas 4000 Hz tone and click produced a low percentage of measurable ARL. ARL was shown to increase as the stimulus frequency increased and stimulus intensity decreased. No statistically significant differences were found between the ipsilateral ARL and contralateral ARL.

Audiologic manifestations of Noonan syndrome

A comprehensive audiologic study of a family with Noonan syndrome is reported together with a review of 20 cases of this syndrome with regard to hearing sensitivity and middle ear status. An incidence of progressive sensorineural hearing loss at the high frequencies is found for 50% of the ears. It is emphasized that early audiologic management may improve the quality of life for patients with Noonan syndrome.

Audiologic Manifestations of Noonan Syndrome

A comprehensive audiologic study of a family with Noonan syndrome is reported together with a review of 20 cases of this syndrome with regard to hearing sensitivity and middle ear status. An incidence of progressive sensorineural hearing loss at the high frequencies is found for 50% of the ears. It is emphasized that early audiologic management may improve the quality of life for patients with Noonan syndrome.

Laryngeal evoked brainstem responses in humans: a preliminary study

Laryngeal evoked brainstem responses (LBRs) were recorded in normal human subjects in an attempt to develop a central laryngeal function test and enhance our understanding of neurolaryngologic disorders. The results showed that the human LBR consists of five positive peaks and five negative peaks reproducible within 10 ms after a vibratory stimulation to the superior laryngeal nerve (SLN). The waveform reproducibility was verified by blocking the SLN and topically anesthetizing the hypopharyngeal cavity. The morphology and latency of peak 5 were similar to results obtained in animal LBR experiments. It was concluded that a vibratory stimulation to the SLN was a noninvasive method to elicit far-field potentials from the central laryngeal pathway. These findings encourage further effort to establish normative data and explore clinical correlations.