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Biomedical subjects

M H Taylor

Publications and source records attributed to M H Taylor.

At least 19 recordsLinked to original sources
PubMed2002

Weakfish sonic muscle: influence of size, temperature and season.

The influence of temperature, size and season on the sounds produced by the sonic muscles of the weakfish Cynoscion regalis are categorized and used to formulate a hypothesis about the mechanism of sound generation by the sonic muscle and swimbladder. Sounds produced by male weakfish occur at the time and location of spawning and have been observed in courtship in captivity. Each call includes a series of 6-10 sound pulses, and each pulse expresses a damped, 2-3 cycle acoustic waveform generated by single simultaneous twitches of the bilateral sonic muscles. The sonic muscles triple in mass during the spawning season, and this hypertrophy is initiated by rising testosterone levels that trigger increases in myofibrillar and sarcoplasmic cross-sectional area of sonic muscle fibers. In response to increasing temperature, sound pressure level (SPL), dominant frequency and repetition rate increase, and pulse duration decreases. Likewise, SPL and pulse duration increase and dominant frequency decreases with fish size. Changes in acoustic parameters with fish size suggest the possibility that drumming sounds act as an 'honest' signal of male fitness during courtship. These parameters also correlate with seasonally increasing sonic muscle mass. We hypothesize that sonic muscle twitch duration rather than the resonant frequency of the swimbladder determines dominant frequency. The brief (3.5 ms), rapidly decaying acoustic pulses reflect a low-Q, broadly tuned resonator, suggesting that dominant frequency is determined by the forced response of the swimbladder to sonic muscle contractions. The changing dominant frequency with temperature in fish of the same size further suggests that frequency is not determined by the natural frequency of the bladder because temperature is unlikely to affect resonance. Finally, dominant frequency correlates with pulse duration (reflecting muscle twitch duration), and the inverse of the period of the second cycle of acoustic energy approximates the recorded frequency. This paper demonstrates for the first time that the dominant frequency of a fish sound produced by a single muscle twitch is apparently determined by the velocity of the muscle twitch rather than the natural frequency of the swimbladder.

Acclimatization↗
PubMed2000

Preventive medicine 2000: changing contexts and opportunities.

The teaching of preventive medicine in the medical school curriculum occurs both in independent and in interdisciplinary courses and units. A survey was conducted to examine the changes in preventive medicine context, content, and allotted hours that have occurred in the transition from the traditional Flexnerian curriculum to the more interdisciplinary, centrally controlled curriculum. Data on medical school curricula for 1990-91, 1993-94, 1995-96, and 1998-99 were examined for the 126 U.S. and 16 Canadian medical schools. By 1998-99, 35 schools moving to the new interdisciplinary format had retained preventive medicine teaching as a separate course, although the courses usually had incorporated topics that went beyond the traditional ones. In another 35 schools, preventive medicine hours had been lost in the transition; but in 25 of these new courses it was clear that preventive medicine played a very significant role. It can be assumed that the lost hours were more than replaced as preventive medicine concepts permeated these courses. Of greatest importance were the hallmark courses of the six nontraditional curricula that had designated preventive medicine a major-theme course. However, at ten schools, preventive medicine listings disappeared in the move to nontraditional curricula. Preventive medicine educators must step forward to use curricular restructuring to expand the role of preventive medicine in the curricula of their institutions, whether in stand-alone or in interdisciplinary courses. The goal, as always, is to provide future physicians with the knowledge and skills they need to provide proper care to their patients.

Canada↗
PubMed2000

Effects of fish size and temperature on weakfish disturbance calls: implications for the mechanism of sound generation.

To categorize variation in disturbance calls of the weakfish Cynoscion regalis and to understand their generation, we recorded sounds produced by different-sized fish, and by similar-sized fish at different temperatures, as well as muscle electromyograms. Single, simultaneous twitches of the bilateral sonic muscles produce a single sound pulse consisting of a two- to three-cycle acoustic waveform. Typical disturbance calls at 18 degrees C consist of trains of 2-15 pulses with a sound pressure level (SPL) of 74 dB re 20 microPa at 10 cm, a peak frequency of 540 Hz, a repetition rate of 20 Hz and a pulse duration of 3.5 ms. The pulse duration suggests an incredibly short twitch time. Sound pressure level (SPL) and pulse duration increase and dominant frequency decreases in larger fish, whereas SPL, repetition rate and dominant frequency increase and pulse duration decreases with increasing temperature. The dominant frequency is inversely related to pulse duration and appears to be determined by the duration of muscle contraction. We suggest that the lower dominant frequency of larger fish is caused by a longer pulse (=longer muscle twitch) and not by the lower resonant frequency of a larger swimbladder.

Acoustic Stimulation↗
PubMed1997

Prophylactic chemoradiation of inguinofemoral lymph nodes in patients with locally extensive vulvar cancer.

OBJECTIVE: Primary surgical resection of locally advanced squamous cancer of the vulva may compromise the integrity of important midline structures such as the anus, clitoris, urethra, and vagina. Chemoradiation (synchronous radiation and cytotoxic chemotherapy) has been used as alternative initial treatment which may serve as definitive management for some patients, or may reduce the scope and functional sequelae of subsequent surgery in others. Inguinofemoral node dissection is associated with substantial risk of both acute and late morbidity, prompting consideration of elective inclusion of groin nodes within the irradiated volume and deletion of subsequent groin surgery. Concern that disease relapse in the groins is potentially fatal suggested the prudence of formal outcome assessment of our recent experience with prophylactic treatment of clinically uninvolved groin nodes in the context of concurrent chemoradiation for locally advanced primary vulvar cancer. METHODS: A review was conducted of 23 previously untreated patients with locally advanced squamous cancer of the vulva (2 T2, 20 T3, 1 T4) and clinically uninvolved groin nodes (1969 FIGO stages 14 N0, 4 N1, and 5 N2 with negative node biopsies) who were treated since 1987 with chemoradiation administered to a volume electively including bilateral inguinofemoral nodes. These patients did not undergo subsequent groin surgery. RESULTS: With follow-up from 6 to 98 months (mean, 45.3 months; median, 42 months), no patient has failed in the prophylactically irradiated inguinofemoral nodes. No patient has developed lymphedema, vascular insufficiency, or neurological injury in a lower extremity, and no patient has experienced aseptic necrosis of a femur. CONCLUSIONS: Elective irradiation of the groin nodes in the context of initial chemoradiation for locally advanced vulvar cancer is an effective therapy associated with acceptable acute toxicity and minimal late sequelae. It constitutes a sensible alternative to groin dissection in this patient population.

Adolescent↗
PubMed1997

The effects of seasonal hypertrophy and atrophy on fiber morphology, metabolic substrate concentration and sound characteristics of the weakfish sonic muscle.

Male weakfish Cynoscion regalis possess highly specialized, bilateral, striated sonic muscles used in sound production associated with courtship. Androgen-driven hypertrophy of the muscles during the late spring spawning period results in a tripling of sonic muscle mass followed by post-spawning atrophy. This study examined the morphological and biochemical changes underlying seasonal changes in sonic muscle mass and the functional effects of these on contraction as measured by sound production. Sonic muscle fiber cross-sectional area (CSA) increased significantly during the period of hypertrophy and then decreased by nearly 60%. Both the CSA of the contractile cylinder and that of the peripheral sarcoplasm decreased significantly by late summer, with the peripheral ring of sarcoplasm virtually disappearing. Muscle protein content followed a similar trend, suggesting a major loss of structural elements during atrophy. Muscle glycogen and lipid content decreased precipitously in early June during the period of maximal sound production. Sound pressure level increased and sound pulse duration decreased with increasing sonic muscle mass, indicating that sonic muscle fibers contract with greater force and shorter duration during the spawning season. Neither the pulse repetition rate nor the number of pulses varied seasonally or with muscle mass, suggesting that the effects of steroids on the acoustic variables are more pronounced peripherally than in the central nervous system. Seasonal sonic muscle hypertrophy, therefore, functions as a secondary sexual characteristic that maximizes vocalization amplitude during the spawning period.

Androgens↗
PubMed1995

Effects of exogenous testosterone on sonic muscle mass in the weakfish, Cynoscion regalis.

Three testosterone (T) implant experiments were carried out to investigate the hormonal control of seasonal hypertrophy in the sound producing, or sonic, muscles of the weakfish Cynoscion regalis. The first experiment examined the role of T in the seasonal increase in sonic muscle mass noted in adult male weakfish during the spring and summer spawning period. Specimens held over-winter were implanted with T or vehicle prior to the natural spawning season. The sonic muscle mass of the T-implanted group increased two and a half-fold over a period of 3 weeks, while that of the sham-implanted group did not change. At the end of the experiment, the cross-sectional area of the sonic muscle fibers in the T-implanted group averaged 500 microns 2, while that of the sham-implanted group averaged 300 microns 2. In a second experiment, the elevated sonic muscle mass of spawning male weakfish was sustained with pharmacological levels of plasma T for a period of 4 months following the spawning season. The sonic muscle mass of the sham-implanted group decreased to typical postseason values. In a third experiment, male and female age-0 weakfish were held over-winter and then implanted with T in advance of their first natural spawning season. The sonic muscles of the T-treated male specimens attained twice the mass of those of the sham-implanted male specimens in 3 weeks time. No sonic muscle development was noted in any of the female specimens.

Aging↗
PubMed1993

Treatment of childhood acute myeloid leukaemia using the BFM-83 protocol.

Thirty children presenting with acute nonlymphoblastic leukaemia from June 1984 to December 1989 were treated at one UK centre using a West German protocol, AML-BFM-83. This consisted of Induction, an intensive outpatient-based Consolidation regimen with seven different drugs and cranial irradiation, and Continuation therapy with thioguanine and cytosine arabinoside for 2 years with additional Adriamycin in the first year. Twenty-five children achieved complete remission (83%). There were two early deaths from haemorrhage and infection and three from Induction failure. After a median follow-up time of 60 months, nine relapses have occurred, all in the bone marrow. Life table analysis revealed a probability for survival at 5 years of 47%, event-free survival 43%, and event-free interval 50%. Median bed occupancy for chemotherapy and toxicity was 41 days, with median hospital stays of 29 days for Induction, 11 days for Consolidation and less than 1 day for Continuation. This data suggests that long-term remissions can be achieved in just under half of children with acute nonlymphoblastic leukaemia while creating only modest demands on inpatient resources.

Acute Disease↗
PubMed1992

Gamma probe location of 111indium-labeled B72.3: an extension of immunoscintigraphy.

Eight colorectal and 5 ovarian cancer patients were evaluated with preoperative immunoscintigraphy and intraoperative gamma probe detection of 111indium-labeled monoclonal antibody B72.3. Immunoscintigraphy detected the presence of tumor in every patient shown to have tumor at surgery. There was one false-positive scan. A total of 21 pathologically verified lesions were identified at surgery in the 11 patients with tumor. Immunoscintigraphy localized 12 (57%) and intraoperative gamma probe detection located 17 (81%) of the lesions. Intraoperative probe detection located 6 of 8 lesions smaller than 1 cm and 3 lesions that were not identified on initial surgical exploration. The gamma probe offers information that is complementary to immunoscintigraphy in that (1) it aids the surgeon in locating intra- and extra-abdominal lesions previously identified by immunoscintigraphy, (2) it locates lesions too small to be seen by immunoscintigraphy alone, (3) it locates lesions that otherwise might be missed at surgery, and (4) it provides objective evidence for adequacy of surgical resection of cancer in the abdominal cavity.

Aged↗
PubMed1992

Synchronous radiation and cytotoxic chemotherapy for locally advanced or recurrent squamous cancer of the vulva.

Between July 1987 and September 1991 a program of external beam radiation and synchronous, radiopotentiating chemotherapy was employed to treat 25 women with locoregionally advanced or locoregionally recurrent squamous cancer of the vulva. Of 18 previously untreated patients, 1 was Stage II, 10 were Stage III, 6 were Stage IVA, and 1 was Stage IVB. Reasons for patient referral for nonsurgical management included the presence of initially unresectable disease (5 patients), disease extent which would have necessitated partial or total exenteration if treated surgically (9 patients), disease extent predictive of inadequate surgical margins (less than 1 cm gross margin) if treated by less than exenterative surgery (8 patients), and severe comorbid illness precluding surgical management (3 patients). Complete clinical response was obtained in 16 of 18 previously untreated patients (89%) and in 4 of 7 patients with recurrent disease following vulvar surgery (57%). Of 20 patients achieving a complete clinical response, 3 patients have relapsed within the irradiated volume at 11, 38, and 48 months following completion of treatment. Fourteen patients remain alive and continuously cancer free from 2-52 months after completion of treatment (median follow-up 24 months). This experience suggests that initial management with radiation and chemotherapy may offer some patients with locally advanced squamous cancer of the vulva an alternative to exenterative surgery and may hold curative potential for some patients with surgically unresectable or medically inoperable disease.

Adolescent↗
PubMed1987

Semilunar changes in estradiol and cortisol coincident with gonadal maturation and spawning in the killifish Fundulus heteroclitus.

Radioimmunoassay techniques were used to measure estradiol-17 beta (E2) and cortisol in the serum and ovarian fluid of Fundulus heteroclitus throughout complete semilunar spawning cycles. The cyclic nature of spawning activity was confirmed by monitoring the gonadosomatic index and noting the times at which ovulated eggs were found within the ovarian lumen. Levels of serum E2, ovarian fluid E2, and serum cortisol all exhibited cycles which paralleled the semilunar cycle of gonadal maturity and spawning in this euryhaline killifish. Elevations of serum cortisol were temporally associated with ovulation, whereas ovarian fluid E2 levels peaked several days prior to ovulation. Serum E2 remained elevated after ovarian fluid E2 levels had returned to baseline. Cortisol concentrations in ovarian fluid did not cycle and no correlation was apparent between serum cortisol and glucose concentrations.

Animals↗
PubMed1986

Oocyte maturation in the mummichog (Fundulus heteroclitus): effects of steroids on germinal vesicle breakdown of intact follicles in vitro.

The effects of several steroids on the maturation of follicle-enclosed oocytes of the mummichog Fundulus heteroclitus in vitro were examined. At a relatively high concentration (1.0 microgram/ml), a number of different steroids, including pregnenolone, 17 alpha-hydroxypregnenolone, corticosterone, cortisol, 11-deoxycorticosterone, 11-deoxycortisol, androstenedione, testosterone, progesterone, 17 alpha-hydroxyprogesterone, 20 beta-dihydroprogesterone, and 17 alpha-hydroxy-20 beta-dihydroprogesterone, were able to induce germinal vesicle breakdown (GVBD) in prematuration oocytes. Cholesterol, 17 beta-estradiol, 11-ketotestosterone, and 11 beta-hydroxytestosterone were totally ineffective. In general, 11-oxysteroids tended to be less effective than their 11-deoxysteroid counterparts. Two 20 beta-dihydroprogestins--17 alpha-hydroxy-20 beta-dihydroprogesterone and 20 beta-dihydroprogesterone--were the most potent maturation-inducing steroids, initiating 50% GVBD at 1 ng/ml in follicles obtained from ovaries containing mature or maturing follicles in vivo, or at 2.5-4.0 ng/ml in follicles from ovaries lacking mature or maturing oocytes in vivo. These results are consistent with several previous studies involving salmonids and various other teleosts, and suggest a possible physiological role for a 20 beta-dihydroprogestin in the resumption of meiotic maturation in F. heteroclitus.

20-alpha-Dihydroprogesterone↗
PubMed1985

Vinblastine, bleomycin, and cisplatin in malignant germ cell tumors of the ovary.

Fourteen patients with malignant ovarian germ cell tumors were treated with vinblastine, bleomycin, and cisplatin. A complete clinical response was achieved in all 14 patients; however, 1 patient had small macroscopic disease present at second-look laparotomy. One patient died of bleomycin pulmonary toxicity. The remaining 13 patients are alive and free of disease from 20 months to 8 years and 8 months after initial diagnosis. Serum alpha-fetoprotein and beta-human chorionic gonadotropin levels were monitored in all patients and were found to be reliable indicators of response to treatment and disease status. The uninvolved ovary was preserved in seven patients without compromising the response to treatment, and one patient subsequently became pregnant. Vinblastine, bleomycin, and cisplatin chemotherapy appears to be a safe, effective combination and is recommended as the primary treatment of choice in the management of patients with malignant ovarian germ cell tumors.

Adolescent↗
PubMed1985

Calcific metamorphosis with internal resorption.

We have presented a case in which 3.7-year-old patient exhibited calcific metamorphosis of a maxillary primary central incisor at the initial visit, with subsequently internal resorption developing in the same tooth. This case underscores the need for careful monitoring of traumatized teeth that have undergone calcific metamorphosis.

Child, Preschool↗