Exploring the relationship between physiological measures of cochlear and brainstem function

OBJECTIVE

Otoacoustic emissions and the speech-evoked auditory brainstem response are objective indices of peripheral auditory physiology that are used clinically for assessing hearing function. While each measure has been extensively explored, their interdependence and the relationships between them remain relatively unexplored.

METHODS

Distortion product otoacoustic emissions (DPOAEs) and speech-evoked auditory brainstem responses (sABRs) were recorded from 28 normal-hearing adults. Through correlational analyses, DPOAE characteristics were compared to measures of sABR timing and frequency encoding. Data were organized into two DPOAE (Strength and Structure) and five brainstem (Onset, Spectrotemporal, Harmonics, Envelope Boundary, and Pitch) composite measures.

RESULTS

DPOAE Strength shows significant relationships with sABR Spectrotemporal and Harmonics measures. DPOAE Structure shows significant relationships with sABR Envelope Boundary. Neither DPOAE Strength nor Structure is related to sABR Pitch.

CONCLUSIONS

The results of the present study show that certain aspects of the speech-evoked auditory brainstem responses are related to, or covary with, cochlear function as measured by distortion product otoacoustic emissions.

SIGNIFICANCE

These results form a foundation for future work in clinical populations. Analyzing cochlear and brainstem function in parallel in different clinical populations will provide a more sensitive clinical battery for identifying the locus of different disorders (e.g., language based learning impairments, hearing impairment).

Deficient brainstem encoding of pitch in children with Autism Spectrum Disorders

OBJECTIVE

Deficient prosody is a hallmark of the pragmatic (socially contextualized) language impairment in Autism Spectrum Disorders (ASD). Prosody communicates emotion and intention and is conveyed through acoustic cues such as pitch contour. Thus, the objective of this study was to examine the subcortical representations of prosodic speech in children with ASD.

METHODS

Using passively evoked brainstem responses to speech syllables with descending and ascending pitch contours, we examined sensory encoding of pitch in children with ASD who had normal intelligence and hearing and were age-matched with typically developing (TD) control children.

RESULTS

We found that some children on the autism spectrum show deficient pitch tracking (evidenced by increased Frequency and Slope Errors and reduced phase locking) compared with TD children.

CONCLUSIONS

This is the first demonstration of subcortical involvement in prosody encoding deficits in this population of children.

SIGNIFICANCE

Our findings may have implications for diagnostic and remediation strategies in a subset of children with ASD and open up an avenue for future investigations.

A Molecular Classification of Papillary Renal Cell Carcinoma

Despite the moderate incidence of papillary renal cell carcinoma (PRCC), there is a disproportionately limited understanding of its underlying genetic programs. There is no effective therapy for metastatic PRCC, and patients are often excluded from kidney cancer trials. A morphologic classification of PRCC into type 1 and 2 tumors has been recently proposed, but its biological relevance remains uncertain. We studied the gene expression profiles of 34 cases of PRCC using Affymetrix HGU133 Plus 2.0 arrays (54,675 probe sets) using both unsupervised and supervised analyses. Comparative genomic microarray analysis was used to infer cytogenetic aberrations, and pathways were ranked with a curated database. Expression of selected genes was validated by immunohistochemistry in 34 samples with 15 independent tumors. We identified two highly distinct molecular PRCC subclasses with morphologic correlation. The first class, with excellent survival, corresponded to three histologic subtypes: type 1, low-grade type 2, and mixed type 1/low-grade type 2 tumors. The second class, with poor survival, corresponded to high-grade type 2 tumors (n = 11). Dysregulation of G1-S and G2-M checkpoint genes were found in class 1 and 2 tumors, respectively, alongside characteristic chromosomal aberrations. We identified a seven-transcript predictor that classified samples on cross-validation with 97% accuracy. Immunohistochemistry confirmed high expression of cytokeratin 7 in class 1 tumors and of topoisomerase IIalpha in class 2 tumors. We report two molecular subclasses of PRCC, which are biologically and clinically distinct and may be readily distinguished in a clinical setting.

Nonrandom distribution of aberrant promoter methylation of cancer-related genes in sporadic breast tumors

PURPOSE

In an effort to additionally determine the global patterns of CpG island hypermethylation in sporadic breast cancer, we searched for aberrant promoter methylation at 10 gene loci in 54 primary breast cancer and 10 breast benign lesions.

EXPERIMENTAL DESIGN

Genomic DNA sodium bisulfate converted from benign and malignant tissues was used as template in methyl-specific PCR for BRCA1, p16, ESR1, GSTP1, TRbeta1, RARbeta2, HIC1, APC, CCND2, and CDH1 genes.

RESULTS

The majority of the breast cancer (85%) showed aberrant methylation in at least 1 of the loci tested with half of them displaying 3 or more methylated genes. The highest frequency of aberrant promoter methylation was found for HIC1 (48%) followed by ESR1 (46%), and CDH1 (39%). Similar methylation frequencies were detected for breast benign lesions with the exception of the CDH1 gene (P = 0.02). The analysis of methylation distribution indicates a statistically significant association between methylation of the ESR1 promoter, and methylation at CDH1, TRbeta1, GSTP1, and CCND2 loci (P < 0.03). Methylated status of the BRCA1 promoter was inversely correlated with methylation at the RARbeta2 locus (P < 0.03).

CONCLUSIONS

Our results suggest a nonrandom distribution for promoter hypermethylation in sporadic breast cancer, with tumor subsets characterized by aberrant methylation of specific cancer-related genes. These breast cancer subgroups may represent separate biological entities with potential differences in sensitivity to therapy, occurrence of metastasis, and overall prognosis.

Bipolar needle electrocautery for laparoscopic partial nephrectomy without renal vascular occlusion in a porcine model

OBJECTIVES

To report a novel method of accomplishing laparoscopic lower pole partial nephrectomy in an acute porcine model using a bipolar needle electrode without the need for renal arterial occlusion.

METHODS

Six animals (12 renal units) underwent laparoscopic polar nephrectomy using the bipolar needle electrode. After complete laparoscopic mobilization of the lower pole of the kidney, the bipolar needle electrode was repeatedly inserted full-thickness into the renal parenchyma and applied transversely, creating regional ischemia to the entire lower pole without renal vascular occlusion. The specimen was then amputated using laparoscopic scissors.

RESULTS

For the 12 laparoscopic partial nephrectomies, the mean operative time was 39 +/- 30 minutes, and the mean blood loss was 90 +/- 112 mL. Of the 12 cases, 10 (83%) were performed successfully with the bipolar needle electrocautery as the only source of hemostasis and without the need for ancillary hemostatic measures. Two of the procedures (17%) required temporary arterial control for hemostasis. For the successful procedures, the mean operative time was 29 +/- 4 minutes, and the mean blood loss was 48 +/- 11 mL. Histologic analysis of the specimens demonstrated coagulative necrosis between 2 and 4 mm from the line of the surgical incision.

CONCLUSIONS

Bipolar needle electrocautery is a promising device that can be used to facilitate laparoscopic partial nephrectomy with minimal blood loss and without the need for renal arterial occlusion and warm ischemia. Additional studies are required to optimize the delivery parameters of this device.

Molecular analysis of peritoneal fluid in ovarian cancer patients

To determine whether genetic abnormalities present in primary ovarian tumors can be used to detect cancer cells in peritoneal fluid, we tested 14 ovarian cancers and 1 benign tumor of the ovary for loss of heterozygosity (LOH) at chromosomal arms 13q, 17p, 17q, and 22q and for mutations in the p53 and K-ras genes. In each case, matched primary tumor, normal tissue, and peritoneal fluid were analyzed. The highest frequency of LOH was found on chromosomal arm 17p (42%), followed by chromosomal arm 17q (36%), 22q (30%), and 13q (21%). Identical alterations were detected in matched peritoneal fluid (either peritoneal wash or ascitic fluid) in 3 of the 8 patients with LOH in the tumor (38%). Direct sequence analysis detected p53 mutations in 3 of the 14 malignant tumors (21%) and no (0) K-ras mutations. Identical mutations were detected in matched peritoneal fluid from all 3 patients with p53 mutations. All 8 of the 14 (57%) malignant tumors that showed at least one genetic abnormality were serous adenocarcinoma and identical alterations were detected in 5 of the 8 (62%) matched peritoneal fluid samples. Our findings indicate that molecular abnormalities can be detected in peritoneal fluid from patients with ovarian cancer and may be used to complement current conventional diagnostic procedures for detection of primary ovarian cancer.

High-intensity focused ultrasound ablation of the epididymis in a canine model: a potential alternative to vasectomy

BACKGROUND AND PURPOSE

High-intensity focused ultrasound (HIFU) is a noninvasive technology capable of inducing thermal coagulative necrosis of subsurface structures without injuring intervening tissues. We have previously reported on the feasibility of HIFU vasectomy in a canine model. In this study, we evaluated the feasibility of HIFU ablation of the canine epididymis as an alternative to vasectomy. The epididymis may be a better target than the vas deferens because it is larger, more easily positioned in the HIFU focal zone, and more susceptible to occlusive injury at lower energy levels, thus reducing collateral damage.

MATERIALS AND METHODS

A hand-held HIFU clamp was used to grasp the epididymides of anesthetized dogs (eight surgically exposed and six grasped transcutaneously). An ultrasound transducer in the clamp focused energy on a 1 x 3 x 8-mm target zone centered between the clamp jaws. Ultrasonic energy (6-19 W) was delivered to this target zone for various times (16-150 seconds). The vas, epididymis, and testis were harvested for histologic examination 2 weeks after ablation.

RESULTS

Seven of the eight epididymides ablated after surgical exposure demonstrated histologic findings associated with occlusion (fibrosis, hemorrhage, and proximal duct dilatation). Five of the six epididymides ablated transcutaneously also demonstrated histologic evidence of occlusion. Skin burns were evident overlying three epididymides, and one testicular injury was noted adjacent to an ablated region of the epididymis.

CONCLUSION

High-intensity focused ultrasound ablation of the epididymis causes injury and histologic changes associated with epididymal occlusion. Further investigations are under way to optimize ablation parameters and to confirm azoospermia with ejaculate studies. Refinement of this technology may provide a rapid noninvasive alternative to conventional vasectomy.

High intensity focused ultrasound ablation of the vas deferens in a canine model

PURPOSE

High intensity focused ultrasound is an ablative technology capable of producing thermal coagulative necrosis of sub-surface structures without injuring intervening tissues. We assessed the feasibility of using high intensity focused ultrasound to produce occlusion of the canine vas deferens.

MATERIALS AND METHODS

A high intensity focused ultrasound transducer was incorporated into a hand held clip specially designed to grasp the vas deferens transcutaneously. Slots within the jaws of the clip ensured that the vas deferens and high intensity focused ultrasound target zone were properly co-located. We ablated 10 vasa using a range of power and time parameters. At 2 weeks after ablation each vas, epididymis and testis was surgically harvested en bloc. Retrograde vasography was performed to assess vasal occlusion, followed by pathological analysis.

RESULTS

High intensity focused ultrasound occlusion of the vas deferens was confirmed in 4 specimens ablated with parameters at the upper end of the parameter range, 2 of the 2 ablated with 7 W. for 60 seconds and 2 of the 4 ablated with 7 W. for 30 seconds. Histological injury was noted in 8 of the 10 ablated specimens. Skin burns that developed over 4 of the targeted vasa were conservatively managed. Bilateral sham procedures in a control dog resulted in patent vasa and no associated skin burns.

CONCLUSIONS

We demonstrated the feasibility of noninvasive, transcutaneous high intensity focused ultrasound occlusion of the vas deferens with ablation powers at the upper end of the tested range, that is 7 W. Modifications of the hand held clip and optimization of ablation parameters would likely improve the success rate of this procedure. Refinement of this technology may provide a rapid noninvasive alternative to conventional vasectomy.

Interdigitating dendritic cell sarcoma: a rare malignancy responsive to ABVD chemotherapy

Interdigitating dendritic cell sarcoma (IDCS) is an aggressive neoplasm of which fewer than 25 cases have been reported in the world literature. This malignancy is difficult to diagnose because of its rarity, and because of the subtle histopathologic features that distinguish IDCS from similar tumors arising from reticular cells. To date, there exists no consensus on a standard chemotherapeutic regimen for IDCS. Patients with this malignancy have been treated with chemotherapy regimens used against non-Hodgkin's lymphomas. Responses to these regimens have been variable, but mostly unsuccessful. In this article we describe a case of IDCS occurring in a 44 year old female who presented with abdominal pain and inguinal adenopathy. Staging of the tumor with CT scan, PET scan, and bone marrow biopsy demonstrated inguinal and abdominal lymphadenopathies, a large mass encasing the small bowel, and extensive liver infiltration. Morphologic and cytochemical analysis of biopsies from the abdominal mass and inguinal node were consistent with a diagnosis of IDCS, and immunohistochemical stains of the lymph node were positive for CLA, Kp-1, S-100, while negative for CD1a, CD3, CD20, CKER, and HMB45. Treatment of this patient with ABVD chemotherapy resulted in rapid clinical improvement with a marked decrease in tumor burden after two cycles of ABVD, and a complete response after six cycles of therapy.

Abnormal neural encoding of repeated speech stimuli in noise in children with learning problems

OBJECTIVES

This study investigated whether neurophysiologic responses to repeated speech stimuli, presented in quiet and noise, differed between normal children (NL) and children with learning problems (LP).

METHODS

Subjects were normal-hearing, school-age children. NL subjects scored significantly better than LP subjects on measures of reading, spelling and speech sound discrimination. Stimuli (40 ms /da/) were presented to the right ear at 80 dB SPL. Stimuli were presented in trains of four, separated within trains by 360 ms. The interval between trains was 1060 ms. Stimuli were presented in quiet and in white noise (S/N+15). Cortical responses were recorded from an electrode placed along the midline at Cz.

RESULTS

Correlations between the first and 4th responses were lower in noise than in quiet for LP subjects only. Response correlations in quiet were no different between groups. There were no root-mean-square (RMS) amplitude differences between groups.

CONCLUSIONS

Response correlation in noise suggested that the LP population consisted of two subgroups, one whose responses appeared relatively normal, and another whose responses were severely degraded by repetition in noise. Response correlations in noise were related to behavioral measures of auditory processing and spelling. These findings suggest that abnormal, asynchronous, auditory cortical encoding may underlie some language-based learning problems.

Detection of mitochondrial DNA mutations in primary breast cancer and fine-needle aspirates

To determine the frequency and distribution of mitochondrial DNA mutations in breast cancer, 18 primary breast tumors were analyzed by direct sequencing. Twelve somatic mutations not present in matched lymphocytes and normal breast tissues were detected in 11 of the tumors screened (61%). Of these mutations, five (42%) were deletions or insertions in a homopolymeric C-stretch between nucleotides 303-315 (D310) within the D-loop. The remaining seven mutations (58%) were single-base substitutions in the coding (ND1, ND4, ND5, and cytochrome b genes) or noncoding regions (D-loop) of the mitochondrial genome. In three cases (25%), the mutations detected in coding regions led to amino acid substitutions in the protein sequence. We then screened an additional 46 primary breast tumors with a rapid PCR-based assay to identify poly-C alterations in D310, and we found seven more cancers with alterations. Using D310 mutations as clonal marker, we detected identical changes in five of five matched fine-needle aspirates and in four of four metastases-positive lymph nodes. The high frequency of D310 alterations in primary breast cancer combined with the high sensitivity of the PCR-based assays provides a new molecular tool for cancer detection.

Identification of a mononucleotide repeat as a major target for mitochondrial DNA alterations in human tumors

Mitochondrial DNA (mtDNA) mutations scattered through coding and noncoding regions have been reported in cancer. The mechanisms that generate such mutations and the importance of mtDNA mutations in tumor development are still not clear. Here we present the identification of a specific and highly polymorphic homopolymeric C stretch (D310), located within the displacement (D) loop, as a mutational hotspot in primary tumors. Twenty-two % of the 247 primary tumors analyzed harbored somatic deletions/insertions at this mononucleotide repeat. Moreover, these alterations were also present in head and neck preneoplastic lesions. We further characterized the D310 variants that appeared in the lung and head and neck tumors. Most of the somatic alterations found in tumors showed deletion/insertions of 1- or 2-bp generating D310 variants identical to constitutive polymorphisms described previously. Sequencing analysis of individual clones from lymphocytes revealed that patients with D310 mutations in the tumors had statistically significant higher levels of D310 heteroplasmy (more than one length variant) in the lymphocyte mtDNA as compared with the patients without D310 mutations in the tumor mtDNA. On the basis of our observations, we propose a model in which D310 alterations are already present in normal cells and achieve homoplasmy in the tumor through a restriction/amplification event attributable to random genetic drift and clonal expansion.

Molecular detection of cervical intraepithelial neoplasia and cervical carcinoma by microsatellite analysis of Papanicolaou smears

Carcinoma of the uterine cervix is one of the most common malignancies worldwide, yet it is clearly preventable by population screening. The Papanicolaou (Pap) smear has proved to be the most successful test for the detection of precancerous lesions and is largely responsible for the reduction of cervical cancer mortality and morbidity rates. However, the Pap smear is not perfect; false-negative results of various rates are reported. To improve the diagnostic efficacy of cervical cytology, we performed microsatellite analysis on paired Pap smear samples from cervical lesions. Nine microsatellite markers were chosen from chromosomal regions commonly displaying loss of heterozygostity (LOH) in cervical cancer and those displaying microsatellite instability (MI) in other squamous cell cancer. Microsatellite alterations were detected in 16/21 (76%) Pap smear DNA samples including 11 of 13 (85%) smears from invasive squamous cell carcinomas (SCCs) and 5 of 8 (63%) from squamous intraepithelial lesions (SILs). Microsatellite alterations detected in the Pap smear DNA were identical to those identified in seven paired primary tumors available for analysis. Moreover, this molecular approach detected genetic alterations in two cases apparently negative by cytologic examination. None (0/25) of the control patients displayed microsatellite alterations in paired Pap smears. Microsatellite analysis of cervical cytologic samples may provide a complementary method to analyze suspicious but not diagnostic cytologic samples further.

Neurobiologic responses to speech in noise in children with learning problems: deficits and strategies for improvement

OBJECTIVES

Some children with learning problems (LP) experience speech-sound perception deficits that worsen in background noise. The first goal was to determine whether these impairments are associated with abnormal neurophysiologic representation of speech features in noise reflected at brain-stem and cortical levels. The second goal was to examine the perceptual and neurophysiological benefits provided to an impaired system by acoustic cue enhancements.

METHODS

Behavioral speech perception measures (just noticeable difference scores), auditory brain-stem responses, frequency-following responses and cortical-evoked potentials (P1, N1, P1', N1') were studied in a group of LP children and compared to responses in normal children.

RESULTS

We report abnormalities in the fundamental sensory representation of sound at brain-stem and cortical levels in the LP children when speech sounds were presented in noise, but not in quiet. Specifically, the neurophysiologic responses from these LP children displayed a different spectral pattern and lacked precision in the neural representation of key stimulus features. Cue enhancement benefited both behavioral and neurophysiological responses.

CONCLUSIONS

Overall, these findings contribute to our understanding of the preconscious biological processes underlying perception deficits and may assist in the design of effective intervention strategies.

Gas chromatography/combustion/isotope ratio mass spectrometry to control the misuse of androgens in breeding animals: new derivatisation method applied to testosterone metabolites and precursors in urine samples

A new derivatisation reaction applied to the analysis of steroids by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) was studied. The trimethylsilylated steroids were characterised by well-resolved chromatographic signals, no peak tailing, reproducible 13C/12C measurements (0.32 per thousand, n = 28), good signal-to-noise ratio and absolute intensity (5 x 10(-9) A, 20 ng), and a slow degradation of copper oxide pellets in the combustion furnace. In addition, two new metabolites and one precursor of testosterone in bovine have been brought into consideration and used for GC/C/IRMS measurements, namely, 3beta-hydroxy-5alpha-androstan-17-one (epiandrosterone), 3beta,17alpha-dihydroxy-5alpha-androstane, and 3beta,17alpha-dihydroxy-5-androstene. The new findings have been applied to an elimination study in bovine of testosterone metabolites after an intramuscular injection of testosterone enanthate. Significant differences (up to 4 per thousand) between testosterone metabolites and precursor were detectable at least three weeks after administration.

Speech-evoked neurophysiologic responses in children with learning problems: development and behavioral correlates of perception

OBJECTIVES

To evaluate the maturational progression of speech-evoked P1/N1/N2 cortical responses over the life span, determine whether responses are distinctive in clinical populations experiencing learning problems and elucidate the functional significance of these responses.

DESIGN

The P1/N1/N2 complex was measured in 150 normal subjects (5 to 78 yr) and 86 subjects with learning problems (LP) (8 to 15 yr) to a synthetic CV syllable. Analyses included description and comparison of the developmental time course in both groups and evaluation of the relationship between P1/N1/N2 and children's performance on speech discrimination tasks and standardized learning measures.

RESULTS

Findings revealed significant changes in waveform morphology, latency and amplitude as a function of age. Maturational patterns in the group of children with learning problems did not differ from the normal group. P1/N1/N2 parameters were significantly correlated with standardized tests of Spelling, Auditory Processing and Listening Comprehension in the LP group. Moreover, there was a predictive relationship between Auditory Processing and N2 latency.

CONCLUSIONS

The P1/N1/N2 complex changes throughout life from school-age to old age. The developmental sequence throughout the school-age years is similar in normal and LP children. Thus, differences in the rate of P1/Nl/N2 latency and amplitude development do not appear to be distinctive in these two populations. The relationship between P1/N1/N2 parameters and standardized measures of learning (particularly between Auditory Processing and N2 latency) provides new information about the role of these responses in hearing and highlights the potential value in characterizing auditory processing deficits.

Reconstruction of complex cranial wounds with demineralized bone matrix and bilayer artificial skin

Complex wounds involving loss of both cranium and scalp are difficult to reconstruct. Current solutions include both autogenous and alloplastic materials. Tissue engineering provides interesting alternatives for reconstruction of missing bone and soft tissue. Demineralized bone matrix and Integra, artificial bilayer skin substitute, have been used successfully to reconstruct bone and skin as isolated defects, but never in combination. This study investigates the possibility of using demineralized bone matrix in a gel carrier and Integra for combined cranial and scalp defects. The study was divided into two parts. In the first, demineralized bone matrix in the forms of Grafton Flex (n = 12) and Grafton putty (n = 12) was used to reconstruct 15-mm critical size cranial defects in female adult New Zealand White rabbits. In the control group (n = 6), the defect was left empty. The second part of the study investigated the use of Integra and Grafton Flex to reconstruct a 15-mm cranial defect with an overlying full-thickness scalp defect (n = 6). The first study revealed bony healing of the critical-size cranial defect with demineralized bone matrix. The second study demonstrated successful reconstitution of scalp and cranium with both demineralized bone matrix and Integra. We conclude that complex cranial defects involving bone and soft tissue may be successfully reconstructed with their tissue-engineered substrates, demineralized bone matrix (Grafton) and Integra artificial skin.

Aging affects hemispheric asymmetry in the neural representation of speech sounds

Hemispheric asymmetries in the processing of elemental speech sounds appear to be critical for normal speech perception. This study investigated the effects of age on hemispheric asymmetry observed in the neurophysiological responses to speech stimuli in three groups of normal hearing, right-handed subjects: children (ages, 8-11 years), young adults (ages, 20-25 years), and older adults (ages > 55 years). Peak-to-peak response amplitudes of the auditory cortical P1-N1 complex obtained over right and left temporal lobes were examined to determine the degree of left/right asymmetry in the neurophysiological responses elicited by synthetic speech syllables in each of the three subject groups. In addition, mismatch negativity (MMN) responses, which are elicited by acoustic change, were obtained. Whereas children and young adults demonstrated larger P1-N1-evoked response amplitudes over the left temporal lobe than over the right, responses from elderly subjects were symmetrical. In contrast, MMN responses, which reflect an echoic memory process, were symmetrical in all subject groups. The differences observed in the neurophysiological responses were accompanied by a finding of significantly poorer ability to discriminate speech syllables involving rapid spectrotemporal changes in the older adult group. This study demonstrates a biological, age-related change in the neural representation of basic speech sounds and suggests one possible underlying mechanism for the speech perception difficulties exhibited by aging adults. Furthermore, results of this study support previous findings suggesting a dissociation between neural mechanisms underlying those processes that reflect the basic representation of sound structure and those that represent auditory echoic memory and stimulus change.

Comparative microsatellite analysis in discerning origin of disseminated tumor: the case of a patient with malignant ascites and a history of multiple tumors

The origin of metastatic carcinoma is now always easily resolved on the basis of conventional dinical and pathological parameters, particularly in patients with more than 1 primary tumor. When 1 of the tumors is a renal cell carcinoma, the clinical picture is further confounded by the tendency of these tumors to be locally silent, to metastasize to unusual sites, and to disseminate long after removal of the primary tumor. We compared tumors for loss (ie, deletion) of loci on chromosomal arms 3p, 5q, 11q, and 18q in a patient with a malignant ascites fluid, a remote history of renal and colonic neoplasms, and a strong clinical suspicion of disseminated gastrointestinal adenocarcinoma. DNA from microdissected tumors and normal tissues was subjected to polymerase chain reaction-based microsatellite analysis. Even though the clinical picture suggested a gastrointestinal origin, comparison of genetic alterations clearly showed that the malignant ascites represented recurrence of the renal cell carcinoma. The malignant ascites and the primary renal cell carcinoma showed identical patterns of allelic loss at all loci tested. In contrast, the malignant ascites and colonic adenoma showed discordant patterns of allelic loss. Comparative microsatellite analysis provides a rapid genetic approach for discerning the origin of metastatic tumor spread. This may be a useful diagnostic adjunct when tumor origin is not clear on clinical or morphological grounds. In some instances, it may even provide a reasonable alternative to an extensive and costly conventional work-up.

Thalamic asymmetry is related to acoustic signal complexity

Hemispheric asymmetries in response to speech sounds are well documented. However, it is not known if these asymmetries reflect only cortical hemispheric specialization to language or whether they also reflect pre-conscious encoding of signals at lower levels of the auditory pathway. This study examined differences in neural representations of signals with acoustic properties inherent to speech in the left versus right side of the thalamus. Specifically, 2000 Hz tone bursts, clicks and synthesized forms of the phoneme /da/ were presented to anesthetized guinea pigs. Evoked responses were recorded simultaneously from aggregate cell groups in the left and right medial geniculate bodies. Results showed an asymmetric response to complex auditory stimuli between the left versus right auditory thalamus, but not to the simple tonal signal. Moreover, asymmetries differed in male versus female animals.

Is it really a mismatch negativity? An assessment of methods for determining response validity in individual subjects

Mismatch negativity (MMN) responses were collected from 86 normal school-age children in response to synthesized speech syllables, /wa/and two variants of /ba/. Waveform characteristics and statistical properties of the responses were analyzed across stimulus conditions in order to assess methods for determining response validity in individuals. Methods were compared using signal detection theory techniques. Criteria based on measurements of response area, onset latency, and duration were the best indicators of response validity. Also a promising indicator of validity was the interval of significance based on Z transformations determined by considering the variance of the underlying noise distribution. Correlations of individual responses with the grand average and integral calculations of the response negativity showed somewhat lower d' values. Statistical methods which utilized response subaverages were the poorest indicators of response validity. Likely the methods are limited primarily by the signal to noise ratio of the MMN compared to the underlying physiologic noise. Improvement of the signal to noise ratio remains a significant factor in the interpretation of MMN for individual subjects.

Acoustic elements of speechlike stimuli are reflected in surface recorded responses over the guinea pig temporal lobe

Auditory evoked potentials measured from the guinea pig temporal lobe surface reflect acoustic elements of synthesized speech syllables. Eliciting stimuli included a four formant anchor stimulus /ba/, with a 40-ms formant transition duration. The other stimuli differed from /ba/ along simple acoustic dimensions. The /pa/ stimuli differed on a VOT continuum; /da/ stimuli had a higher frequency F2 onset; /wa/ had a longer (80 ms) formant transition duration; and /bi/ differed in three vowel formant frequencies. The /ba/ and /da/ onset response latencies decreased systematically with increasing F2 onset frequency. The response to the /pa/ voicing increased in latency with increasing VOT and showed a physiologic discontinuity at VOT of 15-20 ms. Responses to /ba/ and /wa/ showed similar onset morphology but significant amplitude differences at latencies corresponding to vowel onset. Significant amplitude differences in /ba/ and /bi/ responses corresponded in latency to both consonant and vowel portions of the syllables. Similar to previous reports in the awake monkey for VOT, these results demonstrate in the anesthetized guinea pig that acoustic elements essential to speech perception are reflected in aggregate response of ensembles of cortical neurons.

Speech-evoked cognitive P300 potentials in cochlear implant recipients

The cognitive P300 evoked potential was elicited by speech stimuli in successful cochlear implant recipients, and the resulting P300 morphology was remarkably similar to that of normal-hearing individuals. The P300 was elicited by the synthesized speech pair/da/and/di/ presented using an oddball paradigm to nine "good" Nucleus cochlear implant users and nine age-matched normal-hearing subjects (34-81 yr old). There were no significant differences in P300 amplitude and latency between the two groups. Moreover, the N1 and P2 potentials occurred at similar latencies in the two groups, although the N1 amplitude was significantly smaller in the cochlear implant users. The P300 was absent in one "poor" cochlear implant user. The results suggest that the P300 may serve as a useful tool for evaluating the cognitive aspects of auditory processing in cochlear implant recipients, and that it may aid in assessing the success of cochlear implantation.

Acoustic features and acoustic changes are represented by different central pathways

The central processing of acoustic stimulus changes can be observed neurophysiologically in the mismatch negativity auditory evoked potential (MMN). Stimuli differing in interaural phase were used to investigate the contributions of the primary and non-primary auditory pathways to the encoding of binaural stimuli and to investigate passively elicited measures of binaural processing in experimental animals. In guinea pigs, the MMN was obtained in response to 1000 Hz tones embedded in white noise (S:N = 2 dB). Using a modified oddball paradigm (that is, two stimuli presented in a series, each with a different probability of occurrence), stimuli were presented binaurally with both the tone and noise in-phase to the two ears (S0N0) as the standard stimulus ans the tone 180 degrees out-of-phase (S(PI)N0) as the deviant stimulus. The MMN, by definition, should occur only in response to a change, or 'mismatch,' between the standard and deviant stimuli. The response to the deviant stimulus in the oddball paradigm was compared to the response to the same stimulus when presented in a series alone. The responses to S0N0 and S(PI)N0 collected in a series alone, termed the intrinsic responses, were also compared. Responses were recorded from two surface epidural electrodes - one at the posterior midline and one over the left temporal lobe. AEPs from these locations have been shown to reflect the activity of primary and non-primary thalamo-cortical pathways respectively. A significant MMN was observed at the midline electrode, but no MMN was observed over the temporal lobe.(ABSTRACT TRUNCATED AT 250 WORDS)

Discrimination of speech-like contrasts in the auditory thalamus and cortex

The neurophysiologic discrimination of acoustic contrasts was investigated as reflected by the mismatch negativity (MMN) response. Evoked responses were recorded from guinea pig thalamus (medial geniculate nucleus) and epidural surface in response to synthesized speech contrasts /ga/-/da/ and /ba/-/wa/. From the caudomedial portion of the medial geniculate nucleus, /ba/-/wa/ elicited a strong mismatch response, whereas /ga/-/da/ did not. Neither stimulus contrast elicited an MMN from the ventral, or primary, portion of medial geniculate. Both stimulus contrasts elicited an MMN from the midline surface. Neither contrast elicited an MMN from the surface over the temporal lobe. Results indicate a hierarchy of processing of the spectrotemporal changes which characterize formant transitions. Also, results indicate that the nonprimary portions of the auditory pathway contribute substantially to the MMN.

Nonprimary auditory thalamic representation of acoustic change

1. The mismatch response, or mismatch negativity (MMN), is a neurophysiologic response to stimulus change. In humans and other animals, the MMN may underlie the ability to discriminate acoustic differences, a fundamental aspect of auditory perception. 2. This study investigated the role of the thalamus in the generation of a tone-evoked MMN in guinea pigs. Electrodes were placed in the caudomedial (nonprimary) and ventral (primary) subdivisions of the auditory thalamus (medial geniculate nucleus). Surface epidural electrodes were placed at the midline and over the temporal lobe. The MMN was elicited by a deviant stimulus (2,450-Hz tone burst) embedded in a sequence of standard stimuli (2,300-Hz tone bursts). 3. A tone-evoked MMN was present in nonprimary thalamus but was absent in the primary thalamus. Surface-recorded MMNs were measured at the midline but not over the temporal lobe. The correspondence between nonprimary thalamic responses and midline surface potentials, and between primary thalamic responses and temporal surface potentials, is consistent with data reported for the auditory middle latency responses in guinea pigs. 4. The results demonstrate that the nonprimary auditory thalamus contributes to the generation of a tone-evoked MMN in the guinea pig. Furthermore, the data indicate that the guinea pig is a feasible model for investigating central auditory processes underlying acoustic discrimination.

Binaural response patterns in subdivisions of the medial geniculate body

Auditory evoked potentials (AEPs) to binaural click stimulation were examined in the ventral (MGv) and caudomedial (MGcm) subdivisions of the medial geniculate body (MG) in guinea pigs. Binaural stimulation caused a decrease in amplitude for the response component recorded from the MGv, but an increase in amplitude for the AEP component recorded from the MGcm. Findings suggest that the evoked responses recorded from MGv and MGcm are functionally distinct. The inhibitory binaural response (BR) pattern seen in MGv was similar to that of the middle latency response (MLR) component recorded over the temporal cortex, while the additive BR pattern typical of the MGcm was similar to that of the surface midline MLR component. Furthermore, these data imply that the binaural response patterns seen in the primary and non-primary auditory cortex may be processed and encoded at the thalamic level. It is concluded that the distinct BR patterns noted for the two MG subdivisions reflect the predominant type of binaurally responsive neurons within the respective pathways.

Mismatch negativity in the neurophysiologic/behavioral evaluation of auditory processing deficits: a case study

The subject of this case report is an 18-year-old woman with grossly abnormal auditory brain stem response (ABR), normal peripheral hearing, and specific behavioral auditory processing deficits. Auditory middle latency responses (MLRs) and cortical potentials N1, P2, and P300 were intact. The mismatch negativity (MMN) was normal in response to certain synthesized speech stimuli and impaired to others--consistent with her behavioral discrimination of these stimuli. Behavioral tests of auditory processing were consistent with auditory brain stem dysfunction. A neuropsychological evaluation revealed normal intellectual and academic performance. The subject was in her first year of college at the time of the evaluation. This case study is important because: (1) Although there have been several reports of absent/abnormal ABR with preserved peripheral hearing and deficits in auditory processing, little is known about the specific nature of the auditory deficits experienced by these individuals. Such information may be valuable to the clinical management of patients with this constellation of findings. (2) Of interest is the information that the mismatch negativity (MMN) cortical event-related potential can bring to the evaluation of patients with auditory processing deficits. The MMN reflects central auditory processing of small acoustic differences and may provide an objective measure of auditory discrimination. (3) From a theorectical standpoint, a patient with neural deficits affecting specific components of the auditory pathway provides insight into the relationship between evoked potentials and physiological mechanisms of auditory processing. How do various components of the auditory pathway contribute to speech discrimination? How might evoked potentials reflect the processes underlying the neural coding of specific features of speech stimuli such as timing and spectral cues?

Speech-evoked cortical potentials in children

Event-related potentials (ERPs) were obtained to synthesized speech stimuli in 16 school-aged children (7-11 years) and compared to responses in 10 adults. P1, N1, and P2 event-related potentials were elicited by the phoneme /ga/. The mismatch negativity (MMN) was elicited by variants of /da/ and /ga/, which differ in the onset frequency of the second and third formant transitions. In general, the well-defined N1/P2 complex characteristic of the adult response, was not found in children. Waves P1 and N1 had longer peak latencies in children than in adults. Wave P2 amplitude was smaller in children than in adults. In contrast to the often poorly delineated earlier cortical potentials, the MMN was well defined in children. Significant MMNs were obtained in all subjects tested. MMN magnitude (peak amplitude and area) was significantly larger in the children. No significant differences were found in peak latency and duration of the MMN in children compared to the adult response. Another negative wave occurring at 400 msec was also observed in response to the deviant stimuli. This negative wave occurred at a similar latency in adults and children and was significantly larger and more robust in children. Results support the view that development of ERPs does not involve a hierarchical process with respect to latency. That is, earlier occurring waves do not necessarily mature before later occurring waves. The latencies of P1, N1, and P2 and overall morphology of these waves may provide a measure of maturation of central pathways. The early development of the MMN, its apparent robustness in school-aged children, and its reflection of the processing of acoustic differences in speech stimuli suggest its possible use in the assessment of central auditory function.

Hearing loss in children with Down syndrome

Conventional behavioral testing of hearing shows that children with Down syndrome have a high prevalence of hearing deficits. However, most young (< 3.5 years of age) children with Down syndrome are unable to cooperate in this type of testing. We evaluated auditory brain-stem responses of 47 unselected patients 2 months to 3 1/2 years of age. Thirty-four percent had normal hearing, 28% had unilateral loss, and 38% had bilateral loss. Type of loss was conductive in 19 ears, mixed in 14, and sensorineural in 16. Degree of loss was mild in 33 ears, moderate in 13, and severe to profound in 3. Language quotients and degree of hearing loss were compared and an association was not found. Because of the high prevalence of hearing loss in children with Down syndrome, we recommend evaluation of auditory brain-stem responses in the first 6 months of life.

Mismatch negativity in school-age children to speech stimuli that are just perceptibly different

The mismatch negativity event-related potential (MMN) was elicited in normal school-age children in response to just perceptibly different variants of the speech phoneme /da/. A significant MMN was measured in each subject tested. Child and adult MMNs were similar with respect to peak latency and duration. Measures of MMN magnitude (peak-to-peak amplitude and area) were significantly larger in children than in adults. The results of the present study indicate that the MMN can be elicited in response to minimal acoustic stimulus differences in complex speech signals in school-age children. The results support the feasibility of using the MMN as a tool in the study of deficient auditory perception in children.

Acoustic versus phonetic representation of speech as reflected by the mismatch negativity event-related potential

The concept of categorical perception of speech and speech-like sounds has been central to models of speech perception for decades. Event-related potentials (ERPs) provide a neurophysiologic perspective of this important phenomenon. In the present experiment the mismatch negativity (MMN) event-related potential, which is sensitive to fine acoustic differences, was recorded in adults. Of interest was whether the MMN reflects the acoustic or categorical perception of speech. The MMN was elicited by stimulus pairs (along a continuum varying in place of articulation from /da/ to /ga/) which had been identified as the same phoneme /da/ (within category condition) and as different phonemes /da/ and /ga/ (across categories condition). The acoustic differences between these two pairs of stimuli were equivalent. The MMN was observed in all subjects both in the within and across category conditions. Furthermore, the MMN did not differ in latency, amplitude or area within and across categories. That is, the MMN indicated equal discrimination both across and within categories. These results suggest that the MMN appears to reflect the processing of acoustic aspects of the speech stimulus, but not phonetic processing into categories. The MMN appears to be an extremely sensitive electrophysiologic index of minimal acoustic differences in speech stimuli.

Reticular formation influences on primary and non-primary auditory pathways as reflected by the middle latency response

Ongoing studies are aimed at identifying the neural pathways responsible for the middle latency response (MLR). These studies involve the analysis of surface and intracranial potentials following pharmacologic inactivation (with lidocaine) of discrete regions of the guinea pig brain. Previous investigations have shown that MLR surface waves recorded over the temporal lobe originate from pathways anatomically and functionally distinct from those that generate MLR waves recorded over the midline, and that both primary and non-primary auditory thalamo-cortical pathways contribute to the guinea pig MLR. The present investigation examines the role of the mesencephalic reticular formation (mRF) in the MLR generating system. Inactivation of the mRF was associated with disruption of the midline response. These waves have been shown to reflect activity from non-primary subdivisions of the thalamo-cortical pathway. Components recorded over the temporal lobe were also affected, consisting of amplitude reduction and latency prolongation without changes in response morphology. Changes in temporal MLR components with mRF inactivation were smaller than those associated with direct inactivation of primary and non-primary subdivisions of the medial geniculate body. These findings indicate that mRF input is essential for normal generation of those components of the MLR thought to reflect both primary and non-primary auditory pathway activity.

Contributions of medial geniculate body subdivisions to the middle latency response

Ongoing studies in our laboratory, concerned with identifying the neural pathways responsible for the auditory middle latency response (MLR), have involved analysis of surface and intracranial potentials following pharmacologic inactivation (with lidocaine) of small regions in the guinea pig brain. Previous studies indicate that MLR surface waves recorded over the temporal lobe originate from pathways anatomically distinct from those that generate MLR waves recorded over the midline. The medial geniculate body (MG) contributes to both MLR responses. At issue here are the relative contributions of ventral and caudomedial subdivisions, which have been linked to primary and non-primary auditory pathways, respectively. Ventral and caudomedial subdivisions contributed to the surface-recorded MLR in a distinctive manner. Lidocaine injections to both areas reduced the amplitude of the surface temporal response. Caudomedial injections had a much greater effect on the surface midline responses than did injections in the ventral portion. Thus, the ventral division, a part of the primary auditory pathway, contributes chiefly to the temporal response. The caudomedial portion, which may be linked to non-primary auditory pathways, contributes to both responses.

Binaural stimulation reveals functional differences between midline and temporal components of the middle latency response in guinea pigs

Two morphologically distinct auditory middle latency response (MLR) wave forms can be recorded from the surface of the guinea pig brain. The temporal response is recorded from the temporal lobe contralateral to the stimulus ear, and the midline response is recorded over the posterior midline. Experimental evidence suggests that different neural generators contribute to the two responses. Furthermore, it appears that the temporal response principally reflects activity of the primary auditory pathway while the midline response reflects non-primary pathways. Although it is known that neurons throughout the auditory pathway exhibit distinct binaural interaction (BI) properties, thus far there have been no systematic attempts to differentiate the MLR wave forms in response to binaural stimulation. The purpose of this study was to determine if binaural click stimulation could functionally differentiate the midline and temporal MLR responses in the guinea pig. Binaural click stimulation caused a significant decrease in temporal MLR peak amplitudes, and a significant increase in midline MLR amplitudes. The fact that different BI patterns were observed suggests that the two MLR components are functionally distinct. The data further support the hypothesis that the midline and temporal MLR in guinea pigs reflect different neural generators and pathways.

Mismatch negativity event-related potential elicited by speech stimuli

The mismatch negativity (MMN) is a passively elicited event-related potential that is extremely sensitive to acoustic stimulus properties. The MMN was characterized in normal adults and school-age children in response to speech stimuli differing minimally in the onset frequency of the second and third formant transitions. The speech-evoked MMN consists of a negative waveform at about 230 msec that occurs in response to the deviant stimulus when it is presented in an oddball paradigm. It is absent in response to that same stimulus when presented alone. The MMN was clearly present in all adults and children tested. Using the procedures developed in this study, this event-related potential was found to be robust enough in individual subjects to be considered a potential clinical measure for assessing central auditory function in school-age children and adults.

Subcortical and cortical components of the MLR generating system

The contributions of the auditory thalamo-cortical pathway, mesencephalic reticular formation, and inferior colliculus to the surface recorded auditory middle latency response (MLR) were assessed by selective inactivation of these areas with lidocaine. Evoked responses were recorded simultaneously from these areas and from the cortical surface. Lidocaine-induced changes were compared across recording sites. In the guinea pig, surface components measured from over the temporal lobe (waves A, B and C) and the midline (waves M- and M+) have been previously shown to reflect the activity of two distinct generating mechanisms. Effects of lidocaine injections corresponded to selective changes in components from these two systems. Injections in the medial geniculate body (MGB) were associated with total disruption of surface potentials measured over the temporal lobe, auditory cortex (AC) responses, and local activity in MGB. Thus the thalamo-cortical pathway appears to be important for the generation of MLRs recorded from the surface of the temporal lobe. These injections generally did not alter the surface midline responses or activity obtained from either the mesencephalic reticular formation (mRF) or the inferior colliculus (IC). Lidocaine injections within AC did not alter the basic response morphology of surface potentials, nor were significant changes measured within AC. Lidocaine injections into the mRF produced changes in all surface temporal potentials, the M+ midline surface potential, and in local potentials recorded from MGB and mRF. Injections into the IC changed surface and subcortical responses at all sites. This was the only injection to affect activity at the latency of surface midline wave, M-1. This wave may be the animal analogue for human wave Na. Control experiments indicated that the effects observed were specific to the neural inactivation of target areas. The MLR generating system appears to consist of contributions and interactions from multiple areas including the auditory thalamo-cortical pathway, mRF and IC. The animal model and experimental strategy described appear promising for linking the contributions from specific brain areas to surface MLR waves.

Vasoactive intestinal peptide: a neurotrophic releasing agent and an astroglial mitogen

Vasoactive intestinal peptide (VIP) increases neuronal survival in dissociated spinal cord cultures during a critical period of development. In the present study, two mechanisms contributing to this action of VIP have been observed: 1) VIP was shown to be a secretagogue for neuron survival-promoting activity; and 2) VIP was found to be an astroglial mitogen. A high molecular weight substance (greater than 30 kDa), which increased neuronal survival in tetrodotoxin (TTX)-treated spinal cord cultures, was detected in the medium from nonneuronal cells incubated for 1 hr with 0.1 nM VIP. In addition, 3H-thymidine autoradiography and glial fibrillary acid protein (GFAP) immunocytochemistry were used to show that a 5 day treatment with (VIP) increased astroglial mitosis. This effect was specific for astroglia, as silver grain-positive cells not exhibiting GFAP immunoreactivity did not increase in number after VIP treatment. The dual action of VIP may regulate glial-derived trophic substances that are important for neuronal survival during the course of development.

N-methyl-D-aspartate receptors influence neuronal survival in developing spinal cord cultures

Neuronal cell death, which exhibits precise spatial and temporal regulation, serves to remodel and optimize function in the developing nervous system. The mechanisms underlying neuronal cell death are poorly understood, but electrical activity and trophic substances appear to be among the important determinants of survival. We find that N-methyl-D-aspartate (NMDA) receptor antagonists induce neuronal cell death in developing spinal cord cultures. The magnitude of cell death is similar in amount to that produced by blocking action potentials with tetrodotoxin (TTX). The NMDA antagonists and TTX accelerate neuronal death in 2-week-old cultures but not in those that are 1 month old. Low concentrations of NMDA increased neuronal survival under conditions of electrical blockade with TTX. In addition, treatment with low levels of a calcium ionophore also decreased cell death associated with TTX. These results suggest that the NMDA receptor is an important determinant of neuronal survival and that this influence is stage-dependent and likely to be calcium-mediated.

The effect of testosterone and progesterone on the response of the reticulo-endothelial system and reproductive tract to oestrogen in the male mouse

In intact and orchidectomized animals testosterone had no effect on the reticulo-endothelial system (RES) when administered alone; it potentiated the stimulant effect of 17β-oestradiol on the RES, but had no effect on the RE stimulation produced by diethylstilboestrol. Progesterone was a mild RE stimulant; it had no effect on the RE stimulation produced by 17β-oestradiol or diethylstilboestrol.

Both testosterone and oestrogen caused weight increase in the levator ani of orchidectomized animals; progesterone had no effect. Testosterone and progesterone had no effect on the myotrophic action of 17β-oestradiol, but both compounds inhibited the myotrophic effect of diethylstilboestrol.

The results show that in the male, as in the female, the action of oestrogen on the RES is independent of its action on the reproductive tract, although these two biological activities are contained in the same molecule.

The effect of various anti-oestrogenic compounds on the reticulo-endothelial system and reproductive tract in the ovariectomized mouse

(1) Testosterone, progesterone, oestriol, 17α-ethynyl-19-nortestosterone and MER-25 were shown to inhibit the vaginal smear response and the uterine growth response to 17β-oestradiol and diethylstilboestrol.

(2) Testosterone potentiated the stimulant effect of 17β-oestradiol on the reticulo-endothelial system (RES); but had no effect on the RE stimulation produced by diethylstilboestrol.

(3) Progesterone had no effect on RE stimulation produced by 17β-oestradiol or diethylstilboestrol.

(4) Oestriol and 17α-ethynyl-19-nortestosterone had no effect on RE stimulation produced by 17β-oestradiol; but both compounds inhibited the stimulant effect of diethylstilboestrol on the RES.

(5) MER-25 inhibited RE stimulation produced by both 17β-oestradiol and diethylstilboestrol.

(6) The effect of anti-oestrogens on oestrogen-produced RE stimulation was shown to depend on the nature of the stimulating oestrogen used.