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Biomedical subjects

M Yoon

Publications and source records attributed to M Yoon.

34 records · Page 2Linked to original sources
PubMed1992

Localized carcinoma of the external ear is an unrecognized aggressive disease with a high propensity for local regional recurrence.

Management problems in patients with recurrent squamous cell carcinoma (SCC) of the external ear (pinna) have prompted a review of the management and treatment outcomes of patients who present with localized disease. Forty patients were seen over a 15-year period (1972 to 1991). Thirty-six were men, and 4 were women, with an age range from 43 to 93 years (average age: 71 years). Presenting TNM status was stage 0 in 2 patients, stage I in 15 patients, stage II in 13 patients, stage III in 2 patients, stage IV in 4 patients, and unknown stage in 4 patients. Thirty-six patients had clinically negative nodes at presentation (N0), and 4 had palpable nodes (N+). The primary treatment was local excision in 13 patients, Mohs' micrographic surgery in 16 patients, local excision plus external beam radiotherapy in 4 patients, and radical resection (parotidectomy/neck dissection/mastoidectomy) with or without radiotherapy in 5 patients. Two patients with stage IV disease died after diagnosis and prior to treatment, and two other patients with stage IV disease received palliative chemotherapy. Twenty patients developed recurrence from 2 months to 8 years. It included nine local recurrences, eight regional recurrences (parotid/neck/mastoid), and three distant metastases (lung or brain). After treatment of the recurrences in 20 patients, 8 are alive 15 months to 16 years later, 2 patients died of other diseases, and 10 patients died of SCC. The recurrences were managed by reoperation, radiotherapy, or chemotherapy. From the results of this study, we conclude that localized carcinoma of the external ear has a high propensity for local and regional failure and merits more aggressive treatment of the primary lesion and elective treatment of the regional lymph nodes and parotid gland in high-risk patients.

Adult↗
PubMed1990

Effects of early parent touch on preterm infants' heart rates and arterial oxygen saturation levels.

A descriptive exploratory design was used in this study to evaluate the effects of early parent touch on the heart rates and arterial oxygen (O2) saturation levels of 36 preterm infants. The infants were between 27-33 weeks gestational age at birth, and were free of congenital defects. Infants were videotaped during parent visits on up to three separate occasions during the first month of life. Parents were encouraged to interact with their infants as they usually would, and data on the infants' heart rates and O2 saturation levels were recorded every 6 seconds on a portable computer that was interfaced with the infants' monitors. Mean O2 saturation levels were significantly lower during parent touch than during baseline periods on 45% of the visits, and significantly higher during parent touch periods on 19% of the visits. O2 saturation variability was greater during periods of parent touch, and there were more abnormal O2 saturation values during parent touch than during baseline periods. Mean heart rates during parent touch were significantly lower compared to baseline on 17% of the visits, and were higher during parent touch on 43% of the visits. There were no overall differences in mean heart rates between baseline, parent touch and post-visit classifications, although heart rate variability was greater during periods of parent touch. The results indicate that preterm infants' responses to early parent touch are variable, and suggest that blanket policies that limit parent touch during the early weeks of life may not be appropriate.(ABSTRACT TRUNCATED AT 250 WORDS)

Cues↗
PubMed1990

Photochemical and photophysical properties of piroxicam and benoxaprofen in various solvents.

Laser flash spectroscopy was used to examine the title compounds. Piroxicam has a triplet transient with a maximum near 450 and a lifetime of 3-21 microseconds depending on the solvent. The relative quantum yield is highly solvent dependent being maximum in toluene and greater than or equal to 14 fold lower in hydrogen bonding solvents. There is another transient which is assigned as a proton transferred ground state transient. Some permanent photoproduct also appears to be produced. Benoxaprofen also has a triplet transient with a maximum near 420 nm with a lifetime of 65 microseconds to greater than or equal to 250 microseconds depending on the solvent. In this case, the relative quantum yield only slightly varies among polar and hydrogen bonding solvents. This is in marked contrast to published data on the fluorescence yield. Some permanent photoproduct appears to be produced.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1990

The Uniform Status of Children of Assisted Conception Act: does it protect the best interests of the child in a surrogate arrangement?

Medical technology is easing the plight of many infertile couples by offering such reproductive alternatives as in vitro fertilization, artificial insemination and surrogacy. In response to the changes in our society's definition of family, wrought by scientific advances, the National Conference of Commissioners on Uniform States Laws promulgated the Uniform Status of Children of Assisted Conception Act. The purpose of this Act is to protect the interests of children born through extraordinary medical procedures. This Note analyzes the Act's provisions regarding surrogacy and focuses on how the Commission's regulatory scheme fails to protect the child's interests. The Act's alternative of voiding the surrogacy contract also does not protect the child's interests. A more complete regulatory scheme which protects the adult parties' interests, as well as the child's, should be devised, as the adequacy of the adult parties' protection ultimately affects the child's well-being.

Abortion, Legal↗
PubMed1982

Redistribution of proteins of fast axonal transport following administration of beta,beta'-iminodipropionitrile: a quantitative autoradiographic study.

Beta,beta'-iminodipropionitrile (IDPN) produces a rearrangement of axoplasmic organelles with displacement of microtubules, smooth endoplasmic reticulum, and mitochondria toward the center and of neurofilaments toward the periphery of the axon, whereas the rate of the fast component of axonal transport is unchanged. Separation of microtubules and neurofilaments makes the IDPN axons an excellent model for study of the role of these two organelles in axonal transport. The cross-sectional distribution of [3H]-labeled proteins moving with the front of the fast transport was analyzed by quantitative electron microscopic autoradiography in sciatic nerves of IDPN-treated and control rats, 6 h after injection of a 1:1 mixture of [3H]-proline and [3H]-lysine into lumbar ventral horns. In IDPN axons most of the transported [3H] proteins were located in the central region with microtubules, smooth endoplasmic reticulum and mitochondria, whereas few or none were in the periphery with neurofilaments. In control axons the [3H]-labeled proteins were uniformly distributed within the axoplasm. It is concluded that in fast axonal transport: (a) neurofilaments play no primary role; (b) the normal architecture of the axonal cytoskeleton and the normal cross-sectional distribution of transported materials are not indispensable for the maintenance of a normal rate of transport. The present findings are consistent with the models of fast transport that envision microtubules as the key organelles in providing directionality and propulsive force to the fast component of axonal transport.

Animals↗
PubMed1981

The pH dependence of photosensory responses in Stentor coeruleus and model system.

1. Live Stentor coeruleus exhibits a substantially red-shifted fluorescence maximum, corresponding to the anionic species of the photoreceptor chromophore. No change was observed in either the absorption or fluorescence excitation spectrum, indicating an efficient deprotonation of the photoreceptor pigment upon excitation by light. 2 Changes in external pH exhibit a dramatic effect on the pulmonary response of Stentor. Phototaxis is specifically inhibited at pH less than 6, with loss of photosensory perception which is restored when the pH is returned to pH greater than 6. 3. Fluorescence changes of 9-aminoacridine in suspensions of live Stentor indicate the generation of a pH gradient upon irradiation with light. Both pH gradient and phototaxis were inhibited by the addition of nigericin and p-tri-fluoromethoxy carbonyl cyanide phenylhydrazone (FCCP). 4. Incorporation of the Stentor photoreceptor protein in to artificial liposomes demonstrates the ability of the system to generate pH gradients across model membranes as monitored by the quenching of 9-aminoacridine fluorescence. The effect of external pH on net proton movement in the model system is strikingly similar to the pH dependent of the liver Stentor, thus lending support for transient proton flux being an important mode of light signal processing for photosensory transduction.

Animals↗
PubMed1980

Calcium regulatory action of endogenous rat calcitonin demonstrated by passive immunization with calcitonin antibodies.

The calcium regulatory role of calcitonin (CT) in murine physiology was evaluated with a combination of immunological techniques, bioassays, and gland ablation. Passive immunization of rats with neutralizing CT antibodies caused an immediate but transient increase in plasma calcium with a time course similar to that observed in thyroparathyroidectomized animals. In animals fasted during the day and fed at night (1700-0700 h), acutely decreasing endogenous CT (< 100 pg/ml) by thyroparathyroidectomy or by passive immunization with CT antibodies resulted in a greater increase in plasma calcium in the preprandial (1600 h) than in the postprandial inverse correlation between immunoreactive CT and plasma calcium, a known secretagogue for CT. In these animals on a restricted feeding schedule, a sharp preprandial (1600 h) rise in immunoreactive and bioactive CT and a circadian rhythm in plasma calcium were also observed. The onset of the increase in circulating CT preceded the onset of feeding and coincided with or shortly preceded the daily nadir of plasma calcium. These findngs establish that CT has a primary calcium regulatory role in murine physiology. More specifically, they demonstrate that 1) the postthyroparathyroidectomy increase in plasma calcium is due specifically to the loss of CT, 2) passive immunization is a feasible technique for evaluating the actions of endogenous CT, 3) the role of CT in calcium regulation cannot be restricted to that of preventing prandial and postprandial increase in blood calcium, and 4) factors other than calcium must be involved in the control of CT secretion in the nonfed state.

Animals↗
PubMed1972

Influence of adaptation level on response pattern and sensitivity of ganglion cells in the cat's retina.

1. The effect of background illumination on response pattern is correlated with its effect on visual sensitivity by analysing post-stimulus time-histograms obtained from single ganglion cells in the cat's retina at various levels of background illumination between zero and 2 x 10(6) photons (wave-length 523 nm).sec(-1).deg(-2) (via 5.7 mm(2) pupil).2. If background illumination did not exceed a critical value, about 10(3) photons (523 nm).sec(-1).deg(-2) (via 5.7 mm(2) pupil), stimulation of the centre of a receptive field resulted in either sustained excitation (i.e. increase in discharge rate) during ;on' and cessation of the excitation at ;off' (on-centre unit), or sustained inhibition (i.e. decrease in discharge rate) during ;on' and cessation of the inhibition at ;off' (off-centre unit). Within this low adaptational level, a ganglion cell maintained its maximum sensitivity regardless of whether the weak background light was presented or not.3. When background level exceeded the critical value up to 2 x 10(6) photons (523 nm).sec(-1).deg(-2), however, the simple, sustained responses changed into compound responses with two transient components of opposite polarities, either excitation at ;on' and inhibition at ;off' (on-centre unit), or inhibition at ;on' and excitation at ;off' (off-centre unit), and also the sensitivity began to decrease as the background increased, approximately obeying Weber's law.4. It is suggested that a ganglion cell gives simple-sustained response when its gain control mechanism remains inactive at a low background illumination below a critical level, whereas it gives compound-transient response when its gain control mechanism becomes active as background illumination exceeds the critical value.

Adaptation, Ocular↗