PubMed Health⌕ Search

Biomedical subjects

M Coughlin

Publications and source records attributed to M Coughlin.

13 recordsLinked to original sources
PubMed1998

The relation between identification and discrimination of vowels in young and elderly listeners.

This study examined both the identification and discrimination of vowels by three listener groups: elderly hearing-impaired, elderly normal-hearing, and young normal-hearing. Each hearing-impaired listener had a longstanding symmetrical, sloping, mild-to-moderate sensorineural hearing loss. Two signal levels [70 and 95 dB sound-pressure level (SPL)] were selected to assess the effects of audibility on both tasks. The stimuli were four vowels, /I,e, epsilon, ae/, synthesized for a female talker. Difference limens (DLs) were estimated for both F1 and F2 formants using adaptive tracking. Discrimination DLs for F1 formants were the same across groups and levels. Discrimination DLs for F2 showed that the best formant resolution was for the young normal-hearing group, the poorest was for the elderly normal-hearing group, and resolution for the elderly hearing-impaired group fell in between the other two at both signal levels. Only the elderly hearing-impaired group had DLs that were significantly poorer than those of the young listeners at the lower, 70 dB, level. In the identification task at both levels, young normal-hearing listeners demonstrated near-perfect performance (M = 95%), while both elderly groups were similar to one another and demonstrated lower performance (M = 71%). The results were examined using correlational analysis of the performance of the hearing-impaired subjects relative to that of the normal-hearing groups. The results suggest that both age and hearing impairment contribute to decreased vowel perception performance in elderly hearing-impaired persons.

Adult↗
PubMed1997

Differences in performance between Oticon MultiFocus Compact and ReSound BT2-E hearing aids.

Differences in performance were evaluated between binaural fittings of the Oticon MultiFocus (MF) and ReSound BT2-E on 25 hearing-impaired subjects across two sites. Subjects were initially fit using each manufacturer's algorithm and adjustments were made at 1 week based on subjects' responses to diary questions. Performance was assessed after a 4- to 6-week trial period with each hearing aid set using the Speech Perception in Noise (SPIN) test administered at 50, 65, and 80 dB SPL, the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire, loudness judgments of female connected discourse at 65 and 80 dB SPL, and an overall preference selection. The MF yielded significantly better SPIN scores at 50 and 65 dB SPL, while the BT2-E yielded a significantly better score at 80 dB SPL. No statistically significant differences were found in the APHAB benefit scores between the hearing aid sets, but both sets were significantly better than the subjects' own hearing aids on three of the four subscales. The MF produced slightly higher mean loudness judgments at both input levels than the BT2-E. Finally, 12 subjects preferred the BT2-E, 10 subjects preferred the MF, and three subjects stated no preference. The results are discussed in terms of audiogram effects on preference and effects of differences in signal processing approaches between the devices.

Audiometry↗
PubMed1996

Reliability and stability of various hearing-aid outcome measures in a group of elderly hearing-aid wearers.

Twenty elderly persons with hearing impairment were fit with binaural in-the-ear hearing aids and followed for a 6-month period post-fit. Several hearing-aid outcome measures were obtained at 0, 7, 15, 30, 60, 90, and 180 days post-fit. Outcome measures included (a) objective measures of benefit obtained with nonsense-syllable materials in quiet (CUNY Nonsense Syllable Test, NST) and sentences in multitalker babble (Hearing in Noise Test, HINT); (b) two subjective measures of benefit, one derived from pre-fit/post-fit comparisons on a general scale of hearing handicap (Hearing Handicap Inventory for the Elderly, HHIE) and the other based on a subjective scale of post-fit hearing-aid benefit (Hearing Aid Performance Inventory, HAPI); (c) a questionnaire on hearing-aid satisfaction; (d) an objective measure of hearing-aid use; and (e) a subjective measure of hearing-aid use. Reliability and stability of each measure were examined through repeated-measures analyses of variance, a series of test-retest correlations, and, where possible, scatterplots of the scores against their corresponding 95% critical differences. Many of the measures were found to be both reliable and stable indicators of hearing-aid outcome.

Aged↗
PubMed1996

Evaluation of the use of a new compact disc for auditory perceptual assessment in the elderly.

The present study examined the performance of 40 normal-hearing young adults and 38 elderly adults, some normal hearing and some hearing impaired, on the Department of Veterans Affairs' new compact disc (VA-CD) for auditory perceptual assessment. Principal-components factor analyses were performed on the test scores from each group of subjects with very similar results obtained from each group in terms of the number of factors identified (3), the percentage of variance explained by these factors individually and collectively (about 72%), and the association of various test scores with each factor. The 10 tests examined here were found to be associated with three underlying factors identified as a general speech-understanding ability (about 42% of variance), temporal sequencing capacity (about 18% of variance), and processing ability under conditions of dichotic competition (about 12% of variance). Among the elderly, hearing loss was strongly and negatively associated with general speech-recognition ability, whereas age was moderately associated with the other two factors. Test scores for several measures of auditory perceptual processing were negatively affected by the presence of peripheral hearing loss in the elderly even when administered at the highest recommended presentation level (90 dB SPL). In addition, some tests among those examined were found to have inadequate test-retest reliability for clinical use with the elderly.

Adolescent↗
PubMed1992

The effect of neonatal treatment of rats with nerve growth factor on the blood pressure and structure of the mesenteric arteries.

Newborn male Wistar rats were treated with nerve growth factor daily by subcutaneous injection for 2 weeks, and control rats were treated with either cytochrome c or buffered saline. Average body weight of the treated animals was lower than that of the controls during the 2 weeks of treatment, but became similar to that of the controls thereafter. Tissue levels of norepinephrine were elevated in the brain, adrenal glands, mesenteric arteries, and vas deferens of the treated animals immediately after the treatment, but became similar in the three groups 2 weeks after the termination of the treatment. Blood pressure and heart rate were measured beginning at 4 weeks of age until 28 weeks, when the rats were sacrificed and the mesenteric arteries sampled for morphometric measurements of vessel wall dimensions. Pretreatment with nerve growth factor did not affect blood pressure, nor heart rate. Structural alteration of the three types of mesenteric arteries was also absent in the treated animals. We conclude that even though neonatal treatment of normal Wistar rats with nerve growth factor for 2 weeks induced an elevation of the norepinephrine levels in several tissues at the end of the treatment period, it was not sufficient to produce hypertension and structural alterations in the blood vessels.

Aging↗
PubMed1992

Sensory nerves in adult rats regenerate and restore sensory function to the skin independently of endogenous NGF.

We have investigated the possible roles of NGF, and of impulse activity, in the regeneration of sensory nerves. Unexpectedly, the ability of crushed axons to regrow and to restore functional recovery of three sensory modalities in adult rat skin (A alpha-mediated touch, A delta-mediated mechanonociception, and C-fiber-mediated heat nociception) was totally unaffected by anti-NGF treatment. This finding applied even when the anti-NGF dosage was almost eight times that which entirely blocked collateral sprouting of the undamaged axons of both classes of nociceptive nerves (the A alpha-axons do not sprout in adult animals). In the same anti-NGF-treated animal, regeneration would proceed normally on the one side, while collateral sprouting was prevented on the other. Light microscopic and EM examination revealed that in the denervated skin the regenerating axons utilized the same dermal perineurial pathways followed by collaterally sprouting axons. Regeneration within these antibody-accessible pathways progressed normally during anti-NGF treatment, extending 1-2 cm beyond the former field borders, that is, into territory whose invasion by collaterally sprouting axons was totally blocked. The blood-nerve barrier is absent within the degenerating peripheral nerve trunk, a putative NGF source for regenerating fibers but not for sprouting ones. The NGF-independent regeneration was also found to be unaffected when putative spinal cord sources of NGF were eliminated by dorsal root excision. Anti-NGF treatment also failed to block regeneration across 4 mm excision gaps in the nerve trunk. The daily anti-NGF regime continued to be effective for at least 8 weeks, at which time newly evoked collateral sprouting could still be blocked. Exogenous NGF, in doses that evoke collateral sprouting de novo in normal skin, failed to influence regeneration. Finally, an electrical stimulus regime, which markedly reduces the latency of collateral sprouting, failed to affect the time to arrival of regenerating axons at the skin, or the rate of their arborization in it. We conclude that, in striking contrast to their collateral sprouting, the regeneration of nociceptive axons occurs independently of endogenous NGF and is unaffected by impulse activity. These findings further support the proposal that these two growth behaviors have basically different biological functions in the organism.

Animals↗
PubMed1992

Endogenous NGF and nerve impulses regulate the collateral sprouting of sensory axons in the skin of the adult rat.

We have investigated the co-involvement of endogenous NGF and impulses in the collateral sprouting of cutaneous sensory nerves in adult rats, specifically the A delta-axons involved in mechanonociception and the C-fibers that mediate heat nociception. Their collateral sprouting was measured by the progressive expansion, respectively, of the behaviorally defined "pinch" and "heat" fields into surrounding denervated skin (the light-touch A alpha-fibers do not sprout in adult mammals). The expansions of such "isolated" fields were totally prevented in animals injected daily with anti-NGF serum, but developed normally after treatment was discontinued. Light microscopic and EM examination of the skin confirmed that the effect of the anti-NGF treatment was attributable to its prevention of collateral sprouting. Initiation of treatment would also rapidly halt sprouting already in progress. Finally, intradermal injections of purified NGF protein would not only increase the rate of nociceptive fiber sprouting, but also evoke sprouting de novo within normally innervated skin (again, A alpha-axons were unaffected). We conclude that the collateral sprouting of intact nociceptive nerves following partial denervation of skin is entirely dependent on endogenous NGF. The observed latency of this sprouting was 10-12 d; we estimate, however, that at least 2 d of field expansion is required for its reliable detection. Thus, about 8-10 d are required for NGF levels in the skin to rise to effective levels, and for the neurons to respond and initiate sprouting. From indirect findings, the NGF component of this sprouting latency appears to be about 2 d. In accord with earlier findings, the remaining "initiation time" was reduced by 5-6 d if the neurons were briefly excited, even 2 d prior to the isolation of their fields. Unexpectedly, this phenomenon of "precocious sprouting" requires that endogenous NGF be available; the sprouting latency reverted to normal values when the conditioning impulses were evoked during a 2 d anti-NGF "umbrella." In contrast to the impulse-sensitive neuronal mechanisms involved in the initiation of sprouting, those underlying the sprouting rate were unaffected by nerve activity and were entirely dependent on the level of endogenous NGF. We suggest that interactions like that revealed in these studies between a sprouting agent and impulses that seem to prime the neuron's response to it contribute to plasticity within the nervous system.

Animals↗
PubMed1991

Interaction between sympathetic nervous system and adrenal medulla in the control of cardiovascular changes in hypertension.

The role of the sympathetic nervous system and adrenal medulla in the development of cardiovascular changes and hypertension was studied in spontaneously hypertensive rats (SHRs), and the results compared with age-matched normotensive Wistar-Kyoto (WKY) rats. Sympathectomy was initiated in newborn rats through daily injection with antiserum to nerve growth factor for 1 week, followed by daily injection with guanethidine for 3 weeks. Removal of the adrenal medulla was carried out in 4-week-old rats after the last guanethidine injection. Such a combination treatment was effective in permanently preventing the development of hypertension in the SHRs, and the blood pressure was maintained at the level of WKY rats. The heart rate of the SHRs and WKY rats was not affected by such treatment. Hypertrophy of the heart and of the vessel wall in the mesenteric arteries was also prevented by such treatment. We conclude that in the SHR, the sympathetic nervous system and the adrenal medulla are essential for the development of cardiovascular changes and hypertension.

Adrenal Medulla↗
PubMed1991

Combined effect of neonatal sympathectomy and adrenal demedullation on blood pressure and vascular changes in spontaneously hypertensive rats.

Neonatal sympathectomy using a combined treatment with antiserum to nerve growth factor and guanethidine during the first 4 weeks after birth was carried out in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. Bilateral adrenal demedullation was performed in 4-week-old sympathectomized SHR and WKY rats. The development of hypertension in SHR was prevented by sympathectomy, but the blood pressure (BP) was still higher than in age-matched WKY rats. Demedullation reduced the BP of sympathectomized SHR to the same level as that of WKY rats. Heart rates of SHR and WKY rats were not affected by the treatments. Morphometric measurements of the mesenteric arteries showed that sympathectomy significantly reduced the medial mass in the mesenteric arteries of SHR, mainly through a reduction in the number of smooth muscle cell layers. In sympathectomized SHR, demedullation increased the lumen size of muscular arteries under maximally relaxed conditions, which might explain the further reduction in BP in these animals. Demedullation in sympathectomized SHR and WKY rats caused a decrease in smooth muscle cell layers in the superior mesenteric artery, but the same treatment resulted in a slight increase in the number of smooth muscle cell layers in the large and small mesenteric arteries of SHR and WKY rats. Adventitial area was increased in some mesenteric arteries of SHR and WKY rats by sympathectomy, and demedullation caused a further increase in the size of adventitia in WKY rats. Heart weight in SHR was normalized to the level found in WKY rats by sympathectomy and demedullation. We conclude that in sympathectomized SHR, the elevated BP was maintained by the adrenal medulla.

Adrenal Medulla↗
PubMed1987

Evidence that endogenous beta nerve growth factor is responsible for the collateral sprouting, but not the regeneration, of nociceptive axons in adult rats.

A key role has not yet been identified for beta nerve growth factor (NGF) in the growth responses that continue to be expressed in the sensory neurons of adult animals. We have now examined the effects of daily administration to adult rats (and in a few experiments, mice) of antiserum to NGF on (i) the collateral sprouting of undamaged nociceptive nerves that occurs into denervated adjacent skin and (ii) the regeneration of cutaneous sensory axons that occurs after they are damaged. The results were unexpected. All collateral sprouting was prevented and that already in progress was halted; sprouting resumed when treatment was discontinued. In contrast, the reestablishment, and even enlargement, of cutaneous nerve fields by regenerating axons was unaffected by anti-NGF treatment, even after dorsal rhizotomy was done to eliminate any central trophic support. In denervated skin, regenerating and collaterally sprouting axons utilized the same cellular pathways to establish functionally identical fields, thus displaying apparently identical growth behaviors, yet anti-NGF treatment clearly distinguished between them. We suggest that endogenous NGF is responsible for the collateral sprouting of nociceptive axons, probably reflecting an ongoing function of NGF in the regulation of their fields. This demonstration in the adult sensory system of a defined role for NGF in nerve growth could apply to nerve growth factors generally in the adult nervous system. The regeneration, however, of nociceptive axons (and nonnociceptive one) is not dependent on NGF.

Animals↗
PubMed1985

Role of mediastinoscopy in pretreatment staging of patients with primary lung cancer.

Since the introduction of mediastinoscopy, there has been a great deal of discussion regarding indications for this technique and the significance of positive findings. We undertook this study to determine the role of clinical staging and the value of routine mediastinoscopy in the treatment selection of patients with primary lung cancer. From 1975 to 1983, 1,259 consecutive patients with proven and operable lung cancer underwent preresection mediastinoscopy. Nodes were sampled at three levels, and findings were recorded by location, invasiveness, and histology. There were no operative deaths, but 3 patients had a major complication. Mediastinoscopy was positive in 339 (27%) patients and negative in 920 (73%). In the group with positive findings, 303 patients had no operation because a curative resection was not possible (extranodal metastases, 180; location, 76; histology, 47). No patient survived 5 years, and only 4% survived 2 years. Of the 36 patients considered to have operable disease, 28 underwent resection with a projected 5-year survival of 18%. In the group with negative findings, 89% had a curative resection with a hospital mortality of 3.2% and 5-year survival of 53%. When results of mediastinoscopy were correlated with findings at thoracotomy, the sensitivity of the test was 93% on nodes in the superior mediastinum and the specificity, 100%. This study shows that mediastinoscopy is safe and is an accurate indicator of the presence or absence of tumor in superior mediastinal nodes. If positive nodes are found, a curative resection is generally not possible, thoracotomy is avoided, and the overall survival is low.

Adult↗
PubMed1984

Inspiratory muscle strength and body composition in patients receiving total parenteral nutrition therapy.

We examined the relationship between inspiratory muscle strength and body composition in 59 patients receiving total parenteral nutrition (TPN). Inspiratory muscle strength was assessed by measuring maximal inspiratory pressure (Pm) after a tidal expiration, with the patient supine and the nose occluded. Body composition was determined by multiple isotope dilution. Body cell mass (BCM) and extracellular mass were estimated by measuring total exchangeable potassium (Ke) and total exchangeable sodium (Nae), respectively; Nae/Ke, an index of the nutritional state, was calculated from these values. The effect of changes in muscle mass was evaluated in 29 of the patients by simultaneous determination of Pm and body composition, prior to and at 2-wk intervals during TPN therapy. The Pm was lower (mean +/- 1 SE:33.5 +/- 2.8 cm H2O) in malnourished patients than in those who were in the normal Nae/Ke range (45.3 +/- 4.8 cm H2O, p less than 0.05). Loss of strength was related to reduction in muscle mass because BCM was also reduced in malnourished patients (15.6 +/- 0.8 kg) when compared to those with normal Nae/Ke (19.3 +/- 0.9 kg), (p less than 0.05), and Pm was positively correlated with BCM (r = 0.27, p less than 0.01). Changes in BCM were accompanied by appropriate changes in Pm during the study period (r = 0.44, p less than 0.01); the majority (21 patients) showed improvement in both BCM and Pm.(ABSTRACT TRUNCATED AT 250 WORDS)

Body Composition↗