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Biomedical subjects

P J Lin

Publications and source records attributed to P J Lin.

At least 127 records · Page 7Linked to original sources
PubMed1991

Intrapericardial pheochromocytoma.

In a 34-year-old man with hypertension and increased urinary catecholamine excretion for 12 years, an m-[131I]iodobenzylguanidine scan and chest computed tomography located an intrapericardial pheochromocytoma in the left atrium. The tumor was excised through a left thoracotomy with cardiopulmonary bypass and circulatory arrest. At 34-month follow-up, blood pressure and urine catecholamine levels were normal. In the 15 cases of intrapericardial pheochromocytoma treated by resection reported in the literature, all 11 survivors were symptom-free except 1 who had residual left atrial tumor and multiple skeletal metastatic lesions. Computed tomography directed by the m-[131I]iodobenzylguanidine scan can be used for detailed location of the tumor. Appropriate surgical approach and use of cardiopulmonary bypass are critical in the resection of these highly vascular tumors.

Adult↗
PubMed1991

Traumatic asphyxia.

During a 5-year period, we treated 14 cases of traumatic asphyxia. There were 12 male and 2 female patients ranging in age from 2 to 32 years. Most suffered crushing injuries at work or were run over by motor vehicles. Mild to severe cervicofacial cyanosis and petechiae developed in all patients. A fear response was reported by 12 of the patients. Subconjunctival hemorrhage was also found in 12 patients. Nine patients had tachypnea and 7 complained of dyspnea. Most of the patients suffered some associated injuries including 8 head injuries, 7 pulmonary contusions, and 6 cases of blunt abdominal trauma. Less-associated injuries were rib fractures, brachial and radial nerve injuries, hemothorax, and pneumothorax. The hospital stay ranged from 4 to 28 days (mean, 14 days) and follow-up from 10 to 60 months (mean, 32 months). Treatment for traumatic asphyxia included measurement of arterial blood gases, oxygen supplementation, and intubation with mechanical ventilation. The patients' recovery conditions were relative to the severity of injury and the associated injuries.

Adolescent↗
PubMed1991

Superoxide anion mediates the endothelium-dependent contractions to serotonin by regenerated endothelium.

The endothelium modulates vascular tone by releasing a variety of vasoactive compounds that relax or contract the underlying vascular smooth muscle. We have previously demonstrated that regenerated endothelium exhibits endothelium-dependent hypercontraction to the platelet-derived compound serotonin (or 5-HT). To determine if this hypercontraction is mediated by superoxide anion produced by the endothelium, we performed balloon catheter denudation on the thoracic and abdominal aorta of male Lewis rats. Eight weeks after arterial injury, endothelium-dependent responses to serotonin were examined in tissue bath experiments. Vascular rings (5 mm in length), with and without endothelium, were contracted with norepinephrine and then exposed to serotonin (10(-9) to 3 x 10(-5) mol/L). Vascular rings with regenerated endothelium exhibited hypercontraction to serotonin (251% +/- 25% of initial norepinephrine contraction; p less than 0.05 compared with control rings, 175% +/- 13%). Removal of the endothelium (133% +/- 6%) or treatment with superoxide dismutase (184% +/- 7%), with or without catalase, prevented the endothelium-dependent constrictor effect of the serotonin. Ketanserin suppressed the vasoconstrictor effect of serotonin on control (93% +/- 15%) and regenerated (105% +/- 9%) rings with endothelium, indicating that the serotonin effect is mediated through the 5-HT2-serotonergic receptor. Deferoxamine or heat-inactivated superoxide dismutase did not modify the response. These observations support the hypothesis that superoxide anion is an endothelium-derived contracting factor produced by regenerated endothelium after intimal injury.

Animals↗
PubMed1991

Endothelium-dependent production of prostacyclin in human internal mammary artery.

The internal mammary artery (IMA) has become the conduit of choice in coronary artery bypass surgery because of superior long-term patency. It had been shown that IMA graft could release prostacyclin. Prostacyclin is a potent vasodilator and also can inhibit platelet aggregation. To determine the role of human IMA endothelium in production of prostacyclin, we tested the reactivity of segments of human IMA to hypoxia in vitro. Human IMAs were harvested during coronary artery bypass surgery. Prostacyclin was measured from fluid in the organ baths by radioimmunoassay of its major hydrolytic product 6-keto-prostaglandin F1 alpha. Rings (4 mm in length) of IMA, with and without endothelium, were suspended in organ baths containing physiologic salt solution. Rings were contracted with norepinephrine, and exposed to hypoxia (pO2 35 +/- 5 mmHg) for 15 minutes then reoxygenated. In segments with endothelium, hypoxia induced a transient relaxation followed by contraction. The transient relaxation was associated with a significantly increased production of 6-keto-prostaglandin-F1 alpha (from 34.1 +/- 2.7 pg/ml prehypoxia to 51.6 +/- 6.7 pg/ml during hypoxia, mean +/- SEM, p less than 0.05). This transient relaxation was blocked by indomethacin but not by NG-monomethyl-L-arginine (L-NMMA) and free radical scavengers (superoxide dismutase, catalase and deferoxamine). However, in segments without endothelium, the prehypoxia (14.7 +/- 0.9) and during hypoxia (15.5 +/- 1.4) level of 6-keto-prostaglandin F1 alpha were not increased and were significantly lower than those with endothelium. This study demonstrated that endothelium of IMA grafts could release prostacyclin either in a basal condition or upon stimulation of hypoxia. This ability possibly contributes to its long-term patency.

Cell Hypoxia↗
PubMed1991

Experiences in the management of cerebellopontine angle tumour: an analysis of 64 cases.

The surgical aspects of 64 consecutive cases of cerebellopontine angle tumours treated from January 1983 to December 1988 are reviewed. Nearly all of the procedures were done through a small suboccipital craniectomy. Two patients underwent a combined subtemporal- suboccipital approach. A stage-operation was performed on three patients harbouring a large to giant-size acoustic neuroma. The most common sign was loss of corneal reflex (29%). Hearing loss was present in 33 patients (51%). Trigeminal neuralgia occurred in 13 patients (20%) on the affected side. Hemifacial spasm was present in one patient with a 2-cm meningioma. The tumour pathology comprised of 37 acoustic neuromas, 16 meningiomas, 5 epidermoid cysts, 3 trigeminal neuromas, 1 metastatic adenocarcinoma, 1 facial neuroma, and 1 tuberculoma. Anatomic continuity of the facial nerve was preserved in 40 patients (66%). Operative mortality rate in this series was three (4.7%). None of the patients has had other further significant neurological deficits postoperatively. Most of our patients were in good condition after the operative procedures.

Adolescent↗
PubMed1991

Endothelium-dependent contraction and relaxation of the human and canine internal mammary artery: studies on bypass graft vasospasm.

The internal mammary artery (IMA) is the preferred conduit for coronary artery bypass graft because of superior late patency. However, IMA vasospasm may contribute to myocardial ischemia and early postoperative morbidity. To investigate mechanisms of vasospasm, we compared the reactivity of human and canine IMA segments in vitro to agonists known to release endothelium-derived contracting factor and endothelium-derived relaxing factor. Rings (4 mm in length) of human and canine IMA were studied in organ chambers. Human and canine vascular smooth muscle exhibited comparable contraction to norepinephrine (maximum = 7.55 +/- 0.63 gm and 6.4 +/- 0.90 gm, respectively) and relaxation to sodium nitroprusside. Human and canine IMAs exhibited comparable endothelium-derived relaxing factor-mediated relaxations to acetylcholine (human) and methacholine (canine). Human and canine IMA also exhibited comparable endothelium-dependent contraction to hypoxia (to 173.3% +/- 8.1% and 178.9% +/- 16.0% of initial prehypoxic tension; means +/- SEM; n = 12). Endothelium-dependent contraction to hypoxia in human and canine IMA could be attenuated by NG-monomethyl-L-arginine (10(-6) mol/L), a competitive inhibitor of L-arginine metabolism (n = 9 and n = 10 for human and canine; p less than 0.05). These studies establish that the canine is an appropriate model for study of human IMA vascular reactivity and that hypoxia can induce the release of an L-arginine-dependent, endothelium-derived contracting factor in the human and canine IMA. In vivo, the release of endothelium-derived contracting factor in response to hypoxemia may be cause of IMA vasospasm.

Acetylcholine↗
PubMed1991

Time course and extent of recovery of endothelium-dependent contractions and relaxations after direct arterial injury.

To determine the time course of the return of endothelium-dependent relaxations and contractions during intimal regeneration, we performed balloon endothelial denudation of the thoracic and abdominal aorta of male Lewis rats and examined smooth muscle function and endothelium-dependent responses in vitro at 1, 2, 4, and 8 weeks after aortic injury. At each study interval during endothelial cell regeneration, vascular smooth muscle contracted and relaxed normally to direct stimulation with norepinephrine and sodium nitroprusside. Endothelium-dependent contractions to serotonin returned to normal at 1 week and developed into a hypercontractile response at 8 weeks. Endothelium-dependent relaxations to acetylcholine returned to normal at 8 weeks, but endothelium-dependent relaxations to adenosine diphosphate remained impaired. These experiments demonstrate that regenerating endothelium regains the ability to produce contracting factor before relaxing factor, and it even exhibits potentiated contractile activity 8 weeks after injury. Thus, after direct arterial injury, regenerating endothelium has abnormal endothelium-dependent function that predisposes the vessel to vasospasm and thrombosis.

Acetylcholine↗
PubMed1991

Vasoconstriction to hypoxia of the human internal mammary artery.

Experiments were designed to determine the role of the endothelium in response to hypoxia in the human internal mammary artery (IMA). Segments of IMA were harvested during coronary artery bypass surgery. Rings (4 mm in length) of IMA, with and without endothelium, were suspended to force transducers in organ baths containing a physiologic salt solution (37 degrees C, 95% O2/5% CO2, and pH = 7.4). The rings were contracted with norepinephrine (NE, 1 x 10(-7) M, initial tension), and then exposed to hypoxia (95% N2/5% CO2, PO2 = 35 +/- 5 mmHg). In IMA segments with endothelium, hypoxia caused an initial, transient relaxation (hypoxic inhibition) to 52 +/- 9% of the initial tension, followed by contraction of the blood vessel (hypoxic potentiation; 178 +/- 10% of initial tension). In vessels without endothelium, hypoxia only induced relaxation (to 10 +/- 2% of initial tension). In vessels with endothelium, reoxygenation induced transient rapid relaxation (to 31 +/- 12%; post-hypoxic inhibition) which then stabilized to 50 +/- 14% of the initial tension. However, segments without endothelium returned to their initial tension. Indomethacin (1 x 10(-5) M) reduced the endothelium-dependent hypoxic contraction and abolished the hypoxic and post-hypoxic inhibition. Free radical scavengers (superoxide dismutase plus catalase and deferoxamine) did not modify the responses to hypoxia and reoxygenation. These experiments indicate that hypoxia induces the release of an endothelium-derived constricting cyclooxygenase product from the human IMA endothelium, and that reoxygenation causes release of a cyclooxygenase-dependent endothelium-derived relaxing factor. The release of endothelium-derived constricting factor(s) could induce vasospasm and cause cardiovascular collapse if IMA grafts are exposed to hypoxia perioperatively.

Cell Hypoxia↗
PubMed1989

Effects of unilateral naris closure on the olfactory epithelia of adult mice.

This study demonstrates, for the first time, that prolonged unilateral breathing can be harmful to the adult olfactory epithelium. Mice at least 5 months old had one naris closed by cautery and suture. These were divided into 5 groups of 10 mice which had unilateral naris closure for 1, 3, 6, 8 or 12 weeks. A control group of 10 mice was untreated. Variables that were assessed included the thicknesses and numbers of cells spanning olfactory epithelia in hematoxylin and eosin stained paraffin sections. Olfactory marker protein (OMP) immunohistochemistry was used to further visualize the differential impact of naris closure on the two sides of the nose. Unilateral naris closure for 6 weeks or longer caused dramatic losses of olfactory receptor cells in the rostral third of the open-side olfactory epithelia, but did not affect numbers of cells in caudal regions or on the closed sides. The thicknesses of the open and closed-side olfactory epithelia were significantly different for only the 8-week closure group. In most mice with unilateral naris closure for longer than 6 weeks there was little or no staining of the olfactory receptor neurons or their axon bundles for OMP in the affected regions of the open side.

Animals↗
PubMed1989

Frequency and space representation in the primary auditory cortex of the frequency modulating bat Eptesicus fuscus.

1. Frequency and space representation in the auditory cortex of the big brown bat, Eptesicus fuscus, were studied by recording responses of 223 neurons to acoustic stimuli presented in the bat's frontal auditory space. 2. The majority of the auditory cortical neurons were recorded at a depth of less than 500 microns with a response latency between 8 and 20 ms. They generally discharged phasically and had nonmonotonic intensity-rate functions. The minimum threshold, (MT) of these neurons was between 8 and 82 dB sound pressure level (SPL). Half of the cortical neurons showed spontaneous activity. All 55 threshold curves are V-shaped and can be described as broad, intermediate, or narrow. 3. Auditory cortical neurons are tonotopically organized along the anteroposterior axis of the auditory cortex. High-frequency-sensitive neurons are located anteriorly and low-frequency-sensitive neurons posteriorly. An overwhelming majority of neurons were sensitive to a frequency range between 30 and 75 kHz. 4. When a sound was delivered from the response center of a neuron on the bat's frontal auditory space, the neuron had its lowest MT. When the stimulus amplitude was increased above the MT, the neuron responded to sound delivered within a defined spatial area. The response center was not always at the geometric center of the spatial response area. The latter also expanded with stimulus amplitude. High-frequency-sensitive neurons tended to have smaller spatial response areas than low-frequency-sensitive neurons. 5. Response centers of all 223 neurons were located between 0 degrees and 50 degrees in azimuth, 2 degrees up and 25 degrees down in elevation of the contralateral frontal auditory space. Response centers of auditory cortical neurons tended to move toward the midline and slightly downward with increasing best frequency. 6. Auditory space representation appears to be systematically arranged according to the tonotopic axis of the auditory cortex. Thus, the lateral space is represented posteriorly and the middle space anteriorly. Space representation, however, is less systematic in the vertical direction. 7. Auditory cortical neurons are columnarly organized. Thus, the BFs, MTs, threshold curves, azimuthal location of response centers, and auditory spatial response areas of neurons sequentially isolated from an orthogonal electrode penetration are similar.

Acoustic Stimulation↗
PubMed1989

Transatrial membranotomy for Budd-Chiari syndrome.

In a 7-year period, transatrial membranotomy was performed in 11 patients with membranous obstruction of the inferior vena cava. There were 5 men and 6 women, ranging in age from 23 to 53 years. Clinical symptoms included jaundice in 4 patients, hepatomegaly in 4, leg edema or varicose veins in 10, and venous collaterals over the abdominal and chest wall in all 11 patients. Transatrial membranotomy was performed through a median sternotomy in all patients. When inferior vena cava venography revealed that the obstruction was accompanied by long segmental thrombosis, additional dilation was performed with a Hegar dilator. There was no surgical mortality. Early operative complications included pulmonary embolism in 2 patients and bleeding requiring reoperation in 1. In a mean follow-up period of 30.6 months (range, 2 to 88 months), 9 patients had no symptoms, transient pericardial constriction developed in 1 patient and resolved 1 month later, and restenosis of the inferior vena cava developed in another patient 1 year after the first operation. This latter patient received a second transatrial membranotomy followed by percutaneous balloon angioplasty of the inferior vena cava, with a satisfactory result at 8 months follow-up. We conclude that transatrial membranotomy is an effective and safe procedure for patients with membranous obstruction of the inferior vena cava.

Adult↗
PubMed1989

Surgical management of congenital coronary artery fistula.

Over a period of 6 years, 8 patients underwent surgical treatment at our hospital for congenital coronary artery fistula (CAF). The ages of the patients ranged from 4 months to 50 years (mean 22.7 years). Continuous heart murmurs could be heard in all patients, except one. The diagnosis was made by retrograde aortography and/or selective coronary arteriography. Only one patients had associated cardiac disease. All the drainage sites of the CAF were on the right side of the heart (right atrium, right ventricle, pulmonary artery). Two patients had both right and left CAFs. Symptoms due to "coronary steal" by a coronary artery fistula were demonstrated by a nuclear medicine study in one of our patients. Four patients were operated on with the aid of cardiopulmonary bypass. The other 4 patients were treated with suture ligation directly. There was no surgical mortality or morbidity, and the longterm results have been good. Since surgical correction is safe and effective, it would appear desirable for all patients with CAF be operated on. However, surgical intervention is controversial in asymptomatic patients.

Adult↗
PubMed1989

Acute mitral regurgitation secondary to blunt chest trauma: report of a case.

A 24-year-old male patient who sustained blunt trauma to the chest resulting in a flail chest, myocardial contusion and injury to mitral valve is reported. An emergency surgical correction of the mitral lesion was performed. A high index of suspicion, prompt diagnosis and aggressive intervention of such injuries can lead to successful repair of such a potentially fatal cardiac trauma.

Acute Disease↗
PubMed1987

Patient exposure and radiation environment of an extracorporeal shock wave lithotriptor system.

Radiation exposures to the patient undergoing extracorporeal shock wave lithotripsy were assessed along with the scattered radiation levels around the lithotriptor systems. The data gathered from 2 Dornier lithotriptor systems suggest that the lead shieldings required for this particular make and model are minimal. Owing to the physical size of the lithotriptor system, the treatment room housing it may not require additional lead shielding when the walls are constructed with appropriate materials. Typical radiation exposures to the patient have been assessed from the experimental data. The total amount of radiation exposures a patient is likely to receive has been estimated to be approximately 26 roentgens, for example 21 roentgens from 3 to 4 minutes of fluoroscopic exposure and 5 roentgens from 8 frames of video spot filming. The scattered radiation has been found to be approximately 0.5 mR. per hour at 3 feet or 91 cm. from the center of the lithotriptor water tank.

Fluoroscopy↗