Biomedical subjects

M Chiu

Publications and source records attributed to M Chiu.

15 recordsLinked to original sources

PubMed1993

Femoral vessel depth and the implications for groin node radiation.

PURPOSE: To quantify, based on pretreatment computer tomographic measurements, potential groin node depths, which will aid in optimal treatment planning for patients requiring groin node radiation. METHODS AND MATERIALS: The pretreatment computer tomographic scans of 50 gynecologic cancer patients were reviewed to determine the distance of each femoral vessel beneath the overlying skin surface, as an indicator of potential groin node depth. Correlative data regarding height and weight were obtained from patient medical records, and were used to calculate the Quetelet index, defined as (weight in kg)/(height in m)2. Treatment parameters of 5 patients who failed prophylactic groin radiation in a recently published study were assessed to determine if underdosage represented a possible cause of failure. RESULTS: Individual femoral vessel depths ranged from 2.0 to 18.5 cm. When the depths of all four femoral vessels were averaged in each patient, the mean "4-vessel average" depth for this patient population was 6.1 cm. The median Quetelet index for the group was 25.6, and there was a strong correlation between femoral vessel depth and patient Quetelet index. Recalculation of doses provided to the 5 patients failing prophylactic groin radiation in the Gynecologic Oncology Group study showed that all had received potential tumor doses < 4700 cGy, with 3 patients being underdosed by > 30%. CONCLUSION: While surgery is often indicated in the management of patients with potential groin node metastases, the role of prophylactic groin radiation should not be rejected. Data from this study may aid in the optimal design and implementation of groin node radiotherapy.

Adult↗

PubMed1989

Cochlear hair cell stereocilia loss in LP/J mice with bone dysplasia of the middle ear.

LP/J inbred mice spontaneously develop bony lesions of the middle ear and otic capsule that are similar to those of human otosclerosis and tympanosclerosis. These mice also have progressive loss of hearing due to cochlear hair cell loss. The purpose of this study was to describe quantitatively the deterioration and loss of cochlear hair cells to serve as a basis for future experiments attempting to alter the course of this disorder. Cochleas from 37 LP/J inbred mice were examined by scanning electron microscopy. The stereocilia loss in the cochlea was evident as early as 15 weeks of age and progressed from the basal turn to the apex. Outer hair cells were affected more than inner hair cells. As outer hair cells deteriorated we observed fusion, bending, and breakage of stereocilia. There were no apparent differences in the mode of deterioration among the three rows of outer hair cells. Stereocilia fusion of inner hair cells occurred at an older age, and giant, elongated stereocilia were found in some of the animals.

Animals↗

PubMed1988

A dihydropyridine calcium channel blocker with phosphodiesterase inhibitory activity: effects on cultured vascular smooth muscle and cultured heart cells.

To define the cellular mechanism of action of a dihydropyridine Ca channel antagonist in an experimental model system devoid of neural influences and reflex effects, we studied the actions of RS93522 on cultured vascular smooth muscle cells and on cultured chick embryo ventricular cells. 45Ca uptake by monolayer cultures of vascular smooth muscle cells was inhibited in a concentration-dependent manner. The IC50 for this effect was 10 nM, similar to that for nifedipine (7 nM) in the same system. 10(-6) M RS93522 inhibited 45Ca uptake more fully than 10(-6) M nifedipine (P less than 0.05). Using an optical-video system, the effect of RS93522 on amplitude of contraction of spontaneously beating cultured ventricular cells was studied. Amplitude of contraction was inhibited with IC50 = 7.9 x 10(-8)M. 45Ca uptake in myocytes was depressed by 15% at 5 min. RS93522 had the additional property of inhibiting phosphodiesterase activity in myocardial homogenates with IC50 = 1.6 x 10(-5)M; the potency and efficacy of phosphodiesterase inhibition was similar to that for milrinone in the same system. As expected of Ca channel antagonists, it has a negative inotropic effect on cultured myocardial cells. The compound also has phosphodiesterase inhibitory activity that possibly may potentiate vasodilatation and ameliorate, in part, negative inotropic effects. Thus, RS93522 has two distinct pharmacodynamic effects in myocytes and is a potent calcium channel blocker.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1987

The effect of pre-enucleation radiotherapy on mitotic activity of choroidal and ciliary body melanomas.

The authors studied the mitotic activity of 21 choroidal and ciliary body melanomas treated by external beam radiotherapy (2000 rad in 5 fractions over 5-7 days) before enucleation and 21 case-by-case matched nonirradiated uveal melanomas. The Wilcoxon signed ranks test and McNemar's fourfold table test were used to compare the mitotic activity of the irradiated and nonirradiated tumors. The results of these analyses suggest that pre-enucleation external beam radiotherapy substantially reduces the mitotic activity of posterior uveal melanomas (P less than 0.005). This information supports current efforts to mount a successful randomized clinical trial of pre-enucleation radiotherapy in high-risk patients with choroidal and ciliary body melanomas.

Choroid Neoplasms↗

PubMed1987

Short stature, growth hormone, insulin-like growth factors, and serum proteins in the Mountain Ok people of Papua New Guinea.

Short stature in man may result from a deficiency of GH or insulin-like growth factors (IGFs). In African pygmies and other individuals with the pygmy trait, serum GH and IGF-II are similar to levels in taller subjects, but serum IGF-I levels are low. To determine whether another population with comparably short stature has similar or related defects, we studied the Mountain Ok population of Papua New Guinea. The mean height of adult men was 152 +/- 6.0 (+/- SD) cm (n = 141), and that of women was 146 +/- 5.7 cm (n = 150). Serum GH and IGF-II concentrations were in the normal (U.S.) range in the Mountain Ok subjects. In the men, serum IGF-I values were also normal, thereby distinguishing the endocrine profile associated with short stature in these subjects from that in African pygmies. Serum IGF-I was not measured in any Mountain Ok women. Since marginal dietary protein is characteristic of the traditional Papua New Guinea diet, we determined serum albumin and prealbumin concentrations in the Mountain Ok subjects. The serum proteins were in the normal (U.S.) range (30-50 g/L for albumin; 10-40 mg/dL for prealbumin), indicating that chronic or acute malnutrition was unlikely in these subjects. Taken together, these findings indicate that short stature in the Mountain Ok people of Papua New Guinea is associated with normal serum GH, IGF-I, IGF-II, and protein levels and indicate that other factors determine stature in some populations with short stature.

Adolescent↗

PubMed1986

Angiographic architecture of intracranial vascular malformations and fistulas--pretherapeutic aspects.

The authors describe the angio-architecture of intracranial vascular malformations. Several patterns can be identified thanks to the intracranial superselective angiograms that can now be performed. Schematically, the following features can be seen: direct arterial supply, indirect arterial supply, flow-related arterial ectasia (aneurysm), dysplastic aneurysm, direct arteriovenous fistula, intralesional arterial ectasia (aneurysm), intralesional venous ectasia (aneurysm), venous ectasia. Each of these elementary arrangements are illustrated and their clinical significance outlined whenever possible. Finally, the dural AVM drainage into the cortical venous system serves as an almost experimental model for the appreciation of the role played by the venous congestive phenomenon in brain AVM symptoms.

Arteriovenous Fistula↗

PubMed1986

Neurological manifestations of intracranial dural arteriovenous malformations.

The authors describe their experience with four cases of dural arteriovenous malformation (AVM) which led them to analyze the clinical aspects of these lesions in an attempt to understand their pathophysiology. An additional 191 previously reported cases of dural AVM's were reviewed with special attention to the mechanism of intradural, central, and peripheral nervous system manifestations. Apart from the peripheral cranial nerve symptoms, which are most likely due to arterial steal, the central nervous system (CNS) symptoms appear to be related to passive venous hypertension and/or congestion. Generalized CNS symptoms can be related to cerebrospinal fluid malabsorption due either to increased pressure in the superior sagittal sinus, to venous sinus thrombosis, or to meningeal reaction resulting from minimal subarachnoid hemorrhages. These phenomena are not related to the anatomical type of venous drainage. On the other hand, focal CNS symptoms are specifically indicative of cortical venous drainage. Seizures, transient ischemic attacks, motor weakness, and brain-stem and cerebellar symptoms can be encountered depending on the territory of the draining vein or veins. Therefore, the localizing value of focal CNS symptomatology relates to the venous territory and not to the nidus or to the arterial supply characteristics of dural AVM's. Furthermore, the venous patterns of various dural AVM's at the base of the skull are expressed by differences in their clinical presentation. Dural AVM's of the floor of the anterior cranial fossa and of the tentorium are almost always drained by the cortical veins and, therefore, have a high risk of intradural bleeding. The remarkable similarities in the manifestations of dural and brain AVM's and the differences in the manifestations of dural and spinal dural AMV's are pointed out. High-quality angiograms and a multidisciplinary approach to the study of dural AVM's will provide the best understanding of their symptoms and, therefore, the most appropriate treatment strategy.

Adult↗

PubMed1986

Pediatric surgical neuroangiography. A multicentre approach.

Adult patients who require sophisticated embolization procedures are usually referred to centres where such expertise is available. Because of the special circumstances in the pediatric age group, this type of referral is often not feasible. The authors describe a model in which multiple pediatric institutions have access to sophisticated interventional neuroradiologic procedures through the collaboration of a group of neuroradiologists. The preliminary results are encouraging and appear to indicate that embolization in the pediatric age group can be safe and reliable if performed by well trained teams.

Child↗

PubMed1985

Dural AVM.

Explore the source record for details and available documents.

Cerebral Hemorrhage↗

PubMed1985

The lateral spinal artery of the upper cervical spinal cord. Anatomy, normal variations, and angiographic aspects.

The lateral spinal artery corresponds to the most rostral extent of the posterolateral arterial axis of the spinal cord. It supplies the posterior and lateral aspects of the spinal cord, and courses anterior to the posterior roots of the upper cervical spinal nerves (C-1 to C-4), and posterior to the dentate ligament. The lateral spinal artery anastomoses rostrally with the branches of the posterior inferior cerebellar artery (PICA) at the restiform body and laterally with the extraspinal arteries at the emergence of each nerve. It may originate either from the vertebral artery or from the PICA lateral to the medulla. Certain variations will cause an unusual but normal enlargement of the vessel in a specific portion of its course; these variations include vertebral artery duplication, a C-1 or C-2 vertebral origin of the PICA, a C-1 or C-2 occipital origin of the PICA, and an intradural course of the vertebral artery at C-2. Knowledge of these variations in the arterial supply to the area allows for an understanding of the different anatomic peculiarities present and their angiographic importance.

Angiography↗

PubMed1981

Delayed encephalopathy following carbon monoxide intoxication.

The case history and CT scan of a patient with delayed encephalopathy following carbon monoxide intoxication are described. The patient recovered. The CT scan revealed symmetrical areas of decreased density at the level of the globus pallidus. This case differs in several ways from other cases of carbon monoxide intoxication in which abnormalities of the CT scan were found.

Brain↗

PubMed1979

Painful tonic seizures in multiple sclerosis: localization of a lesion.

The history of a patient with painful tonic seizures in association with multiple sclerosis is related. These seizures have been thought by most authors to be spinal in origin. This case is reported because of the localization of a supratentorial lesion, clinically and on CT scan.

Basal Ganglia↗

PubMedDate not supplied

Cochlear hair cell loss in ears with cholesteatomas. Scanning electron microscopy study.

Cochleas from 16 Mongolian gerbils with spontaneous aural cholesteatomas, and four of similar age without cholesteatomas, were examined by scanning electron microscopy to quantify cochlear hair cell loss. Loss of hair cell stereocilia was found in all ears with cholesteatomas and was significantly increased when compared with uninvolved ears from animals of similar age. The hair cell loss associated with gerbilline cholesteatomas appeared to be most marked in the middle turn of the cochlea and increased in severity with increasing size of the cholesteatomas. Outer hair cells were affected more than inner hair cells. Inner and outer hair cell loss was not significantly different in infected cholesteatomas versus sterile cholesteatomas. The greater damage to hair cells at the middle turn compared to the basal turn suggests that these losses may be the result of some agent acting through the cochlear wall rather than through the round window.

Animals↗

PubMedDate not supplied

Ultrastructure of middle ear mucosa in the Mongolian gerbil, Meriones unguiculatus.

The Mongolian gerbil is an easily maintained rodent which has been useful for investigations of the middle and inner ear. The gerbil may be used as an animal model for otitis media and cholesteatoma. The purpose of this study was to describe the ultrastructure of the epithelial and subepithelial lining of the gerbilline middle ear. The middle ear of the gerbil is lined by an epithelial membrane which is similar in cell type to human and guinea pig middle ear mucosa. The major part of the middle ear is lined with simple, non-keratinizing squamous cells with or without microvilli. Ciliated and secretory cells were concentrated around the Eustachian tube orifice; additionally, ciliated cells were seen in two distinct bands extending posteriorly below the cochlea in the hypotympanum and above the cochlea toward the tensor tympani muscle. The subepithelial region consists of fusiform cells (fibroblasts or 'surface osteocytes') and collagen adjacent to bone. These cell types and their distribution further supports the use of the gerbil as a model for human disease.

Animals↗

PubMedDate not supplied

The role of dural anomalies in vein of Galen aneurysms: report of six cases and review of the literature.

It is proposed that the vein of Galen aneurysm represents a venous ectasia secondary to an increased flow (usually caused by a deep-seated arteriovenous shunt draining either directly into the vein of Galen aneurysm or into a tributary of the vein of Galen) associated with obstruction of a dural sinus distal to the aneurysm. The closer the venous obstruction is to the vein of Galen, the better the chances are of developing obstructive (noncommunicating) hydrocephalus and the more likely it is that the venous drainage from the rest of the brain will be unaffected. The farther the venous obstruction is from the vein of Galen aneurysm, the better the chances are of developing a communicating type of hydrocephalus. The development of cardiac failure is related to the magnitude of the arteriovenous shunt. Brain damage, seizures, and hemorrhage may be related to the retrograde venous engorgement, causing impaired drainage of the healthy brain. Careful attention should be paid to the venous drainage characteristics of the lesion because the types of dural venous obstructions and anomalies vary from case to case. The term "vein of Galen aneurysm" should be abandoned in favor of the term "vein of Galen ectasia."

Adult↗