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Biomedical subjects

A C Ho

Publications and source records attributed to A C Ho.

46 records · Page 3Linked to original sources
PubMed1994

Analysis of vascularized pigment epithelial detachments using indocyanine green videoangiography.

BACKGROUND: Occult choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) is known to occur with and without an associated serous pigment epithelial detachment (PED). Digital indocyanine green (ICG) videoangiography has been reported to provide enhanced definition of occult CNV. METHODS: A total of 244 of 657 (37%) consecutive patients with AMD, with occult CNV and an associated serous PED evident on fluorescein angiographic examination, were further studied with ICG videoangiography. RESULTS: On ICG videoangiographic examination, 9 of the 244 (4%) eyes had no evidence of underlying CNV, or essentially a pure serous PED. Each of the remaining 235 eyes (96%) had evidence of neovascularization and were defined as having a vascularized PED. These eyes were further divided into two groups, depending on the size and delineation of the neovascularization seen. Of the 235 eyes with vascularized PEDs, 89 (38%) had a solitary area of neovascularization that was well delineated, no more than one disc area in size, and defined as focal CNV. The other 146 (62%) eyes had a larger area of neovascularization, with variable delineation, defined as plaque CNV. Based on conventional guidelines, some patients were considered to be potentially eligible for laser photocoagulation treatment. CONCLUSION: The results of this study suggest that ICG videoangiography may be an important adjunct to the diagnosis, classification, and potential treatment of patients with AMD and occult CNV associated with a serous PED (vascularized PED).

Aged↗
PubMed1994

Decreased intracellular compartmentalization of doxorubicin in cell lines expressing P-glycoprotein.

After initial rapid [14C]doxorubicin distribution into drug-sensitive HL-60 and SU-4 cells, slow uptake continues for more than 4 hr, accounting for up to 80% of the total intracellular drug. In contrast, in P-glycoprotein-expressing drug-resistant HL-60R and SU-4R cells, doxorubicin distribution rapidly approaches equilibrium. The simplest kinetic model of this behavior consists of rapid diffusion from extracellular fluid into the cell, followed by uptake into a nonexchangeable intracellular pool. At 3.4 microM doxorubicin, transmembrane diffusion clearance was similar for all cell lines (0.78-0.98 microliter sec-1). There was no decrease in the normalized apparent volume of distribution in the P-glycoprotein-expressing cell lines, as would be expected if an active, unidirectional efflux were present. However, in resistant cells, doxorubicin accumulation in the nonexchangeable pool was up to 15-fold slower than in sensitive cells (0.004 vs. 0.050 microliter sec-1 in HL-60R vs. HL-60; 0.004 vs. 0.058 microliter sec-1 in SU-4R vs. SU-4). No pool inflow could be detected in either SU-4 or SU-4R cells exposed to doxorubicin at 0 degrees C, indicating that the nonexchangeable accumulation requires energy. The process preventing accumulation began to saturate in SU-4R cells at 20 microM doxorubicin, whereas no evidence of saturation was seen with HL-60R, which is more highly resistant than SU4R. We propose that alteration in compartmentalization is primarily responsible for the doxorubicin resistance observed in these cell lines.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Hemodynamic alterations in the acute retinal necrosis syndrome.

BACKGROUND: Clinical and histopathologic observations suggest a role for ischemia in the pathogenesis of the acute retinal necrosis (ARN) syndrome. Disruption of blood flow appears to occur at some level in the retina or choroid and may account for some of the major features of the syndrome. METHODS: To investigate these potential circulatory changes, color Doppler imaging (CDI) was used to quantitate blood flow velocities and vascular resistance in the central retinal, ophthalmic, and short posterior ciliary arteries in ten consecutive patients with unilateral ARN syndrome. Data were analyzed with a paired Student's t test. The unaffected fellow eyes served as controls. RESULTS: Blood flow velocities within the central retinal artery were significantly reduced in eyes with ARN syndrome compared with control eyes. In affected eyes, there was a mean reduction of 55%, 60%, and 72% in peak systolic, average, and end-diastolic velocities, respectively (P < 0.01). The calculated vascular resistance of the central retinal artery showed an upward trend, but the data fell short of statistical significance. Blood flow velocities from the ophthalmic and short posterior ciliary arteries were not significantly different compared with controls. CONCLUSIONS: This study demonstrates marked circulatory changes in the central retinal artery of eyes involved with the ARN syndrome. Although the exact mechanism and clinical significance are yet to be determined, the data support the presence of retinal arterial hemodynamic compromise in this condition.

Adult↗
PubMed1993

Pasteurella multocida keratitis and corneal laceration from a cat scratch.

A 24-year-old woman was evaluated 12 hours after she sustained a cat scratch to her left eye. Slit-lamp examination revealed a Seidel-positive corneal laceration with a surrounding dense full-thickness corneal ulcer and severe inflammatory reaction. Since the anterior chamber was well formed, it was decided not to repair the laceration on an emergency basis. She was initially treated with intensive topical fortified tobramycin and vancomycin, and intravenous gentamicin and clindamycin. Cultures of the corneal ulcer revealed Pasteurella multocida and the antibiotic regimen was adjusted appropriately. The laceration healed without surgery, and the infection resolved well, with excellent visual acuity.

Adult↗
PubMed1992

Color Doppler imaging of the ocular ischemic syndrome.

PURPOSE: This study describes hemodynamic characteristics of the ophthalmic, central retinal, and posterior ciliary arteries in 16 eyes of 11 patients with the ocular ischemic syndrome. Understanding the hemodynamic characteristics of the retrobulbar circulation may elucidate the natural history and pathophysiology of the ocular ischemic syndrome and perhaps form the basis for rational treatment of this condition. METHODS: Color Doppler imaging, a procedure that permits rapid noninvasive imaging of the ophthalmic, central retinal, and posterior ciliary arteries, was used to quantitate peak systolic blood flow velocities and vascular resistance (pulsatility index) within these vessels in study group eyes and in an age-matched control population. RESULTS: We demonstrated markedly reduced ocular ischemic syndrome central retinal and posterior ciliary artery peak systolic velocities compared with control group eyes. Central retinal and posterior ciliary artery vascular resistance (pulsatility index) was greater in ocular ischemic eyes versus control group eyes. Reversal of ophthalmic artery blood flow was detected in 12 of 16 ocular ischemic syndrome eyes. Study group eyes with poor vision had no detectable posterior ciliary arterial blood flow. CONCLUSION: Color Doppler imaging quantitates hemodynamic characteristics of the retrobulbar circulation in the ocular ischemic syndrome. There is markedly reduced peak systolic velocity and increased vascular resistance in ocular end arteries such as the central retinal and posterior ciliary arteries. Ophthalmic artery reversal of flow seems to represent collateral blood flow to lower resistance vascular beds. Posterior ciliary artery hypoperfusion may correlate with poor vision in the ocular ischemic syndrome.

Aged↗
PubMed1980

High performance liquid chromatographic determination of phenothiazine residues in sheep tissues.

A high performance liquid chromatographic (HPLC) technique is described for the determination of residue levels of the anthelmintic drug phenothiazine in sheep tissues. Phenothiazine was administered to sheep which were slaughtered after withholding periods of 24, 48, and 72 h. Residues of phenothiazine were then extracted from tissue samples by homogenization in methanol. The HPLC analysis of the extracts involved separation on a 10 micrometer silica column using a mobile phase of 0.3% n-propanol in cyclohexane. The lower limit of detection by ultraviolet absorption at 254 nm was 0.05 ppm.

Animals↗
PubMedDate not supplied

Macular hole.

A macular hole is a full-thickness defect of retinal tissue involving the anatomic fovea, thereby affecting central visual acuity. Macular holes have been associated with myriad ocular conditions and originally were described in the setting of trauma. The pathogenesis of idiopathic, age-related macular holes remains unclear despite a litany of theories. Recently, Gass has described an updated biomicroscopic classification of macular holes and postulated that tangential vitreous traction may play a role. Cellular components surrounding the rim of macular holes may also contribute tangential traction forces and elevate the rim. Pseudomacular holes may be mistaken for macular hole lesions, despite careful clinical examination. Careful biomicroscopic examination with a contact lens and use of the Watzke and laser aiming beam tests help to ensure accurate diagnosis. Newer imaging technology, such as optical coherence tomography, helps distinguish true macular holes from pseudoholes and may provide additional insight into the pathogenesis of this condition. Surgical management with or without pharmacosurgical adjuncts can improve vision in select cases. The most common surgical complication is progressive lens opacification in phakic patients.

Aged↗
PubMedDate not supplied

Perforation of the small bowel as a complication of laparoscopic cholecystectomy: CT findings.

Despite the widespread use of laparoscopic cholecystectomy, technical complications unique to the laparoscopic approach may lead to significant postoperative morbidity and mortality. We report a rare case of small bowel perforation due to trocar injury that led to extensive pneumoperitoneum and pneumomediastinum in a patient who underwent laparoscopic cholecystectomy. Small bowel injuries should be suspected when a large or an increasing amount of free air is detected following this procedure.

Adult↗