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Biomedical subjects

D M Schwartz

Publications and source records attributed to D M Schwartz.

At least 19 recordsLinked to original sources
PubMed1990

Management of traumatic hemorrhagic retinal detachment with pars plana vitrectomy.

Traumatic hemorrhagic retinal detachment may prevent successful visual rehabilitation of eyes with severe posterior segment injury. We managed 19 consecutive cases of traumatic hemorrhagic retinal detachment with pars plana vitrectomy, scleral buckling, and fluid-gas exchange, with or without internal drainage of subretinal hemorrhage. We based our approach on the amount of subretinal hemorrhage present and the location of associated retinal breaks. Internal drainage of subretinal hemorrhage was performed in 16 eyes to allow adequate retinopexy to hemorrhagically elevated retinal breaks (9 eyes), to remove massive subretinal hemorrhage (4 eyes), and to allow intraoperative reattachment when the retina exhibited bullous retinal detachment (3 eyes). Overall, with a minimum of 6 months of follow-up, anatomic reattachment was achieved in 13 (68%) of 19 eyes, and functional success (visual acuity 5/200 or better) was achieved in 6 (32%) of 19 eyes. Anatomic failure resulted from proliferative vitreoretinopathy (4 eyes) and globe atrophy (2 eyes). Drainage of subretinal blood appeared to be beneficial for hemorrhagically elevated retinal tears to allow adequate retinopexy and may help to accomplish long-term anatomic attachment in eyes with massive subretinal hemorrhage or bullous retinal detachment.

Adolescent↗
PubMed1990

Delayed sensorineural hearing loss following uncomplicated neurovascular decompression of the trigeminal root entry zone.

Trigeminal neuralgia (tic douloureux) is a condition characterized by intense, unilateral paroxysmal facial pain caused by an abnormality of the root entry zone of the trigeminal nerve. For patients with intractable pain unrelated to a pathologic process who fail to respond to conventional medical management, the microvascular decompression (MVD) is the operation of choice. Conductive or sensorineural hearing loss due either to stretching of the eighth nerve or hemotympanum during the operation is among the possible sequelae of MVD. We report on a perplexing case of delayed sensorineural hearing loss following uneventful microvascular decompression for trigeminal neuralgia that included intraoperative evoked potential monitoring.

Adult↗
PubMed1989

Intraoperative monitoring of brainstem auditory evoked potentials following emergency evacuation of a cerebellar vascular malformation.

This case report highlights the use and value of monitoring the auditory brainstem response during emergency neurosurgery. The prompt on-line changes in the auditory brainstem response after evacuation of a cerebellar arteriovenous malformation provided objective evidence of improved brainstem function, which aided in the management of this patient's disorder.

Adult↗
PubMed1989

Auditory brain stem responses in preterm infants: evidence of peripheral maturity.

This study explored further the relationship between peripheral and central auditory maturation on the basis of the auditory brain stem response. Auditory brain stem responses were recorded in preterm infants and adults to rarefaction and condensation click stimuli transduced through insert Tubephones. Infant recordings presented a triphasic waveform preceding wave I similar to that of the cochlear receptor potentials seen with adults during electrocochleography. Wave I latency and amplitude were found to be equivalent to those of adult subjects. Moreover, neither latency nor amplitude variability among infant wave I responses was found to be any greater than adults. Latencies of waves III and V, however, exhibited the expected differences relative to the adult comparison group. When the indirect evidence of cochlear receptor potentials in the infant are viewed adjacent to the observations that their ABR wave I latency, amplitude, and variability were entirely consistent with those of young adults, the data lend strong support for peripheral auditory electromaturity. These data are discussed relative to previously published reports of prolonged wave I latency in the infant which was attributed either to middle ear effects or immaturity of the cochlea and first order VIIIth nerve neurons.

Adult↗
PubMed1988

Inter- and intraclonal variability of polypeptides synthesized in a rat hepatoma cell line. Quantitative two-dimensional gel analysis.

To examine the degree of clonal heterogeneity in the synthesis of polypeptides in neoplastic cells, single-cell subclones from the rat hepatoma cell line H4-II-E were isolated. Polypeptides from the clones were resolved on high resolution two-dimensional polyacrylamide gels (PAGE), and quantitatively analyzed with a computerized two-dimensional PAGE analysis system developed in this laboratory. Only four qualitatively different spots were found which were synthesized in one of the subclones in four out of five experiments. In contrast, 5-20% of the spots showed statistically significant quantitative differences when any one subclone was compared to any other. These differences were generally quite small, averaging about 1.5-fold in intensity, although variations of fourfold or more were observed. Different cultures of the same subclone showed quantitative differences of the same order as seen in different subclones, indicating that this variability was primarily intraclonal in nature, i.e. associated with the cultures rather than the subclones. The distribution of quantitatively variable spots indicates that 50% or more of the polypeptides in these cells may display intraclonal variability. Similar results were obtained with a second set of subclones derived from these primary ones. Time course studies were conducted where cells were maintained continuously for 12 weeks, with samples taken for two-dimensional PAGE analysis once a week. The fraction of polypeptides that vary significantly generally increased with time between sampling points. Experiments with independent cultures grown in parallel indicate that about 4% of this variability can be correlated to the age of the culture media, although the majority appears due to uncontrolled and/or random differences that arise between cultures. These results indicate that independent cultures quickly develop detectable quantitative differences in the expression of a large fraction of their polypeptides. These differences cannot, at present, be associated with the observable biology of the cells and probably reflect time-associated variations in the balance of cellular macromolecular synthesis which arise in tissue culture cells.

Animals↗
PubMed1988

Reference threshold sound-pressure levels for the TDH-50 and ER-3A earphones.

Reference threshold sound-pressure levels were established for a new insert earphone, the ER-3A tubephone, and for the TDH-50 earphone. In test-retest comparisons, the tubephone produced estimates of auditory threshold as reliable as the thresholds produced by the supraaural earphone. Reference thresholds were developed for the two earphones from data contributed by three laboratories. While the TDH-50 data are in good agreement with the provisional ANSI 6-cc coupler reference levels (ASHA, 1982), the ER-3A data are at variance with the manufacturer's provisional recommendation for 2-cc coupler reference thresholds for frequencies below 1 kHz. The differences are attributed to physiologic noise that masked the lower frequency thresholds.

Acoustic Stimulation↗
PubMed1987

Neurodiagnostic audiology: contemporary perspectives.

This paper reviews the principals of clinical epidemiology as they relate to diagnostic audiology including the problems associated with the test battery approach. The paper also presents a philosophical discussion as to the influence of disease prevalence on diagnostic testing protocols in different clinical environments.

Hearing Tests↗
PubMed1987

Validity of acoustic reflectometry in detecting middle ear effusion.

Pneumootoscopy, tympanometry, and acoustic reflectometry were performed in 256 middle-class children seen in a surburban pediatric office. The results demonstrated that relectometry, when validated by otoscopic findings, detected middle ear effusion with 88% sensitivity and 83% specificity when a cut-off of 5 linear units was used. Corresponding values for tympanometry were 87% and 77.5%. These results are in keeping with those of earlier studies on acoustic reflectometry and demonstrate the usefulness of this simple technique in detecting chronic and acute otitis media with effusion.

Acoustic Impedance Tests↗
PubMed1986

Induction by phenobarbital in McA-RH7777 rat hepatoma cells of a polycyclic hydrocarbon inducible cytochrome P450.

The metabolism of 2-acetylaminofluorene (AAF) to its six oxidative metabolites has been used to study cytochrome P450 monooxygenase activity in two rat hepatoma cell lines, McA-RH7777 and Reuber H4-II-E. McA-RH7777 cells exhibited considerably higher basal activities than H4-II-E cells for all metabolic pathways studied. Phenobarbital induced AAF metabolite formation in McA-RH7777 cells to a similar extent as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), but was only a weak inducer of these activities in H4-II-E cells. Northern blot analysis utilizing specific phenobarbital or 3-methylcholanthrene inducible cytochrome P450 cDNA probes indicated that there was at least a 10-fold increase in a 3-methylcholanthrene inducible cytochrome P450 transcript in phenobarbital treated McA-RH7777 cells. These data suggest that in this transformed cell line phenobarbital behaves as a polycyclic hydrocarbon-like inducer.

2-Acetylaminofluorene↗
PubMed1986

Sequential analysis of chemically induced hepatoma development in rats by two dimensional electrophoresis.

Using the Solt-Farber hepatocarcinogenesis model, a large population of preneoplastic and neoplastic nodules were induced in male Fischer 344 rats. Total cellular polypeptides from normal liver and individual preneoplastic and neoplastic nodules were analyzed for both qualitative and quantitative changes using computer assisted high resolution two-dimensional electrophoresis. Approximately 800-1000 cytosolic and 1200-1400 membrane associated polypeptides were readily separated and detected using an ultrasensitive silver stain. The polypeptide patterns were remarkably similar for each tissue and only four qualitative polypeptide differences were noted. One cytosolic polypeptide, 6.8/57 (designated pl/Mr X 10(-3), and three membrane associated polypeptides, 6.25/41, 6.75/24, and 6.05/21, were expressed in both preneoplastic and neoplastic nodules but not in normal liver. No qualitative polypeptide differences were detected among the individual preneoplastic or individual neoplastic nodules or between preneoplastic and neoplastic nodules. Numerous quantitative changes in both known markers for hepatocarcinogenesis and in as yet unidentified polypeptides were noted. In particular, the Ya subunit of glutathione S-transferase B, the Yb subunit of glutathione S-transferase A, as well as the three isoelectric point variants of the Yp subunit of glutathione S-transferase P were increased 2-, 4-, and 7-fold, respectively, in preneoplastic and neoplastic nodules. Whereas DT-diaphorase was increased 2-3-fold in hyperplastic nodules as compared to normal liver, no differences in the expression of albumin were noted. Although no differences were observed in the expression of aldehyde dehydrogenase in preneoplastic and neoplastic nodules, polypeptide b (6.9/54) was shifted slightly toward the basic region in normal liver. alpha-Fetoprotein was not detected in either preneoplastic or neoplastic nodules. In addition to these changes in known markers, comparison of 500-800 cytosolic and 750-1000 membrane associated polypeptides showed that roughly 4-10% of the polypeptides were undergoing quantitative changes of at least 4-fold during these stages of hepatocarcinogenesis. Thirty (10 cytosolic and 20 membrane) polypeptides were significantly down-regulated while 22 (7 cytosolic and 15 membrane) polypeptides were up-regulated in both preneoplastic and neoplastic nodules. In all cases the direction and magnitude of change were the same in both preneoplastic and neoplastic nodules with the exception of three polypeptides.(ABSTRACT TRUNCATED AT 400 WORDS)

Albumins↗
PubMed1985

Auditory and vestibular function in hyperbaric oxygen.

The therapeutic value of high partial pressures of oxygen is limited by the toxicity of oxygen. Pulmonary damage, visual impairment, and convulsions are known hazards during hyperoxic exposure, but dose-effect relationships have not been quantified for specific organs or functions. As part of an integrated study of organ oxygen tolerance in man (Predictive Study V of the Institute for Environmental Medicine), auditory and vestibular function was evaluated in man before, during, and after exposure to 100% oxygen at 3 atmospheres absolute pressure for 2 to 3.5 hours. No alterations in hearing or equilibrium were detected, suggesting that ototoxicity is not a factor that would limit exposure under these conditions.

Adult↗
PubMed1984

Relationship between oxidative metabolism of 2-acetylaminofluorene, debrisoquine, bufuralol, and aldrin in human liver microsomes.

The capacity of human liver microsomes from 28 individuals to metabolize debrisoquine and bufuralol, two drugs oxidized polymorphically in humans, as well as the carcinogen 2-acetylaminofluorene (AAF), was determined. In addition, the cytochrome P-450 content and the capacity of these microsomes to carry out the epoxidation of aldrin were measured. Interindividual differences in debrisoquine 4-hydroxylation, bufuralol 1-hydroxylation, and aldrin epoxidation were 12-, 20-, and 2.4-fold, respectively. The metabolism of debrisoquine was not correlated with cytochrome P-450 content (r = 0.26), whereas both the metabolism of bufuralol (r = 0.45; r2 = 0.20) and the epoxidation of aldrin (r = 0.72; r2 = 0.52) were correlated. Rates of debrisoquine and bufuralol metabolism were significantly correlated (r = 0.73), whereas only weak correlations existed between debrisoquine:aldrin (r = 0.49) and bufuralol:aldrin (r = 0.51). Because biphasic kinetics have been observed in human liver microsomes for the 7- and 5-hydroxylation of AAF, two concentrations of this substrate were used. The disappearance of AAF at either 0.37 or 50 microM was not correlated with debrisoquine, bufuralol, or aldrin metabolism. Similarly, at 0.37 microM AAF, no correlation existed between the formation of N-, 1-, 3-, 5-, 7-, and 9-hydroxylation products of AAF and debrisoquine, bufuralol, or aldrin metabolism. At 50 microM AAF, only the 7-hydroxylation of this substrate correlated with bufuralol metabolism (r = 0.47). This lack of, or weak correlation between pathways leading to metabolic activation (N-hydroxylation) or detoxication (C-hydroxylation) of the carcinogen AAF and debrisoquine, bufuralol, and aldrin metabolism strongly suggests that different forms of cytochrome P-450 are involved in these pathways. In contrast, exceptionally high correlations (r greater than 0.94) existed between N-OH-AAF:1-OH-AAF. N-OH-AAF:7-OH-AAF, and 7-OH-AAF:1-OH-AAF at the low concentration of AAF, and imply that similar forms of cytochrome P-450 produce these metabolites. However, at 50 microM AAF, these correlations are considerably weaker and explain less than 35% of the variance in the data. It is concluded, based on these multiple cross-correlations, that common cytochrome P-450 isoenzymes are involved in the formation of AAF metabolites, while the metabolism of debrisoquine, bufuralol, and aldrin is unrelated to the metabolism of this carcinogen in human liver microsomes.

2-Acetylaminofluorene↗
PubMed1983

Test of the assumptions underlying comparative hearing aid evaluations.

Comparative hearing aid evaluations using NU-6 monosyllabic word lists were administered to adults with predominately high-frequency sensorineural hearing impairments who were randomly assigned to one of two experiments. In the first, three instruments were used that were electroacoustically similar and appropriate to the patients' hearing losses. In the second, the three hearing aids employed were electroacoustically quite different. Following an initial comparative hearing aid evaluation, the patients used the instruments during a trial-use week after which they ranked the aids in terms of benefit provided in daily communication. Following the trial-use week, the comparative hearing aid evaluation was repeated. The results suggest that significant interaid performance differences on the hearing aid evaluation are not likely to occur very often when the aids being evaluated are relatively homogeneous electroacoustically. In contrast, when electroacoustically heterogeneous instruments are evaluated, significant performance differences may occur frequently. Under such circumstances, however, the same instrument(s) would likely provide the best performance to most patients. The results further suggest that the reliability of standard monosyllabic word lists may not be adequate to detect typical interaid differences that occur in a comparative hearing aid evaluation and that the performance hierarchy is likely to change as the patient adjusts to amplification. Finally, the comparative hearing aid evaluation will not be a good predictor of success in daily communication unless relatively large performance differences exist among the instruments.

Acoustics↗
PubMed1983

Early abnormalities of brainstem auditory evoked potentials in Friedreich's ataxia: evidence of primary brainstem dysfunction.

We studied five children with classic Friedreich's ataxia, using an audiologic test battery to determine the primary site of auditory dysfunction. None of the children had any hearing complaints, and all were tested soon after onset of symptoms. The audiologic test battery consisted of brainstem auditory evoked potential test, tympanometry, and acoustic reflex measurements. The results indicated that the brainstem was the primary site of auditory dysfunction.

Brain↗