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Biomedical subjects

B B Lee

Publications and source records attributed to B B Lee.

At least 55 records · Page 3Linked to original sources
PubMed2001

Comparison of metaraminol and ephedrine infusions for maintaining arterial pressure during spinal anesthesia for elective cesarean section.

BACKGROUND: Although ephedrine is usually recommended as the first-line vasopressor in obstetrics, its superiority over other vasopressors has not been proven in humans. METHODS: In a double-blind study, the authors randomized women having elective cesarean section with spinal anesthesia to receive an intravenous infusion of ephedrine, starting at 5 mg/min (n = 25), or metaraminol, starting at 0.25 mg/min (n = 25), titrated to maintain systolic arterial pressure in the target range 90-100% of baseline. Umbilical cord gases, maternal hemodynamics, uterine artery puLsatility index, and Apgar scores were compared. RESULTS: Systolic arterial pressure was maintained more closely in the target range in the metaraminol group compared with the ephedrine group. In the metaraminol group, umbilical arterial pH was greater (median and interquartile range, 7.31 and 7.31-7.33 vs. 7.24 and 7.14-7.29; P < 0.0001), and umbilical venous pH was greater (7.36 and 7.35-7.38 vs. 7.33 and 7.26-7.34; P < 0.0001) compared with the ephedrine group. No patient in the metaraminol group had umbilical arterial pH less than 7.2, compared with nine patients (39%) in the ephedrine group (P = 0.0005). Apgar scores were similar between groups. Changes in uterine artery pulsatility index were similar between groups. CONCLUSIONS: When used by infusion to maintain arterial pressure during spinal anesthesia for cesarean section, metaraminol was associated with less neonatal acidosis and more closely controlled titration of arterial pressure compared with ephedrine.

Adult↗
PubMed2001

Primate horizontal cell dynamics: an analysis of sensitivity regulation in the outer retina.

The human cone visual system maintains sensitivity over a broad range of illumination, from below 1 troland to 1,000,000 trolands. While the cone photoreceptors themselves are an important locus for sensitivity regulation-or light adaptation-the degree to which they contribute in primates remains unclear. To determine the range of sensitivity regulation in the outer retina, the temporal dynamics, neural gain control, and response range compression were measured in second-order neurons, the H1 horizontal cells, of the macaque retina. Situated at the first synapse in the retina, H1 cells receive input from a large population of cones. Lee et al. have previously shown that sensitivity regulation in H1 cells is both cone type-specific and spatially restricted. The sensitivity regulation seen in H1 cells at moderate illuminances thus takes place before the summation of cone signals in these cells, and the data establish the H1 cell as a convenient locus for analyzing cone signals. In the present study, cone-driven responses of primate H1 cells to temporally modulated sine-wave stimuli and to increment pulses were measured at steady levels of 1-1,000 trolands. The H1 cell gave a modulated response to sine-wave stimuli and hyperpolarized to increment pulses with overshoots at stimulus onset and offset. The temporal amplitude sensitivity function was primarily low-pass in shape, with a small degree of low-frequency roll off and a resonance shoulder near 40 Hz. A model incorporating a cascade of first-order filters together with an underdamped second-order filter could describe both temporal sinusoidal and pulse hyperpolarizations. Amplitude sensitivity was estimated from both pulse and sine-wave data as a function of the steady adaptation level. Sensitivity at low light levels (1 troland) showed a slowing in temporal dynamics, indicating time-dependent sensitivity regulation. Sensitivity was reduced at light levels above approximately 10 trolands, reflecting both response range compression and neural gain control. Thus the outer retina is a major locus for sensitivity regulation in primates.

Animals↗
PubMed2001

Tumor necrosis factor receptor superfamily 14 is involved in atherogenesis by inducing proinflammatory cytokines and matrix metalloproteinases.

Tumor necrosis factor (TNF) receptor superfamily 14 (TNFRSF14) is the cellular receptor for TNF superfamily 14 (LIGHT). Immunohistochemical staining of human carotid atherosclerotic plaques revealed a high level of expression of the TNFRSF14 in regions rich in macrophages/foam cells. To investigate the role of TNFRSF14 in the functioning of monocytes in relation to atherogenesis, we have analyzed TNFRSF14 expression levels and cellular events after stimulation of TNFRSF14 in peripheral blood monocytes or the human macrophage-like cell line, THP-1. A high level of expression of TNFRSF14 was detected in activated monocytes, in macrophages derived from monocytes, and in THP-1 cells. Concomitant activation of THP-1 cells with interferon-gamma and immobilized anti-TNFRSF14 monoclonal antibody resulted in synergistic induction of proatherogenic cytokines, such as TNF-alpha and interleukin-8. Activation of THP-1 cells with immobilized anti-TNFRSF14 monoclonal antibody induced expression of matrix metalloproteinase (MMP)-1, MMP-9, MMP-13, and tissue inhibitors of metalloproteinase-1 and -2. Furthermore, immunohistochemical staining of atherosclerotic plaques with severe infiltration of foam cells revealed that the expression patterns of TNFRSF14 and MMP-1, -9, and -13 overlapped. Treatment of THP-1 cells with soluble LIGHT also caused induction of MMP-9 and interleukin-8. These data suggest that TNFRSF14 is involved in atherosclerosis via the induction of proatherogenic cytokines and decreasing plaque stability by inducing extracellular matrix-degrading enzymes.

Aged↗
PubMed2001

The palatal island flap for reconstruction of palatal and retromolar trigone defects revisited.

BACKGROUND: Although a host of local soft tissue flaps have been described for the reconstruction of postoperative palatal defects, tissue-borne palatal obturators remain the most common form of rehabilitation of these defects. The palatal island flap, first applied to the reconstruction of the retromolar trigone and palatal defects, was first described by Gullane and Arena in 1977. This single-staged mucoperiosteal flap offers a reliable source of regional vascularized soft tissue that obviates the need for prosthetic palatal rehabilitation. OBJECTIVE: To describe a series of 5 cases in which the palatal island flap was used as a primary palatal or retromolar reconstruction. METHODS: We have retrospectively reviewed 5 consecutive cases between March 1998 and August 1999 wherein palatal island flaps were used for the primary reconstruction of postablative palatal defects. Each case was reviewed for primary pathologic findings, postoperative wound complications, postoperative speech and swallowing, and donor site morbidity. Selection of this reconstructive technique was based on the size and location of the defect and the assessment by the surgeon that the arc of rotation and amount of residual palatal mucosa were appropriate. RESULTS: Six local palatal island flaps were performed on 5 patients who had not undergone irradiation (1 patient underwent bilateral flaps). The primary pathologic findings included T1 N0 squamous cell carcinoma, T4 N0 squamous cell carcinoma, T2 N0 low-grade mucoepidermoid carcinoma, pigmented neurofibroma, and T2 N0 low-grade clear cell carcinoma. All of the lesions were located on the hard or soft palate or the retromolar trigone, and the average defect size was 7.2 cm(2). All 5 patients began an oral diet between postoperative days 1 and 5 (mean, 2 days), and all patients were discharged home without postoperative donor site or recipient site complications between days 1 and 6 (mean, 3 days). Donor site reepithelialization was complete by 4 weeks in all 5 patients. CONCLUSIONS: The palatal island flap offers a reliable method of primary reconstruction for limited lesions of the retromolar trigone and hard and soft palate. The mucoperiosteal tissue associated with this flap is ideal for partitioning the oral and nasal cavities and obviates the need for prosthetic palatal obturation.

Aged↗
PubMed2000

Visual responses of ganglion cells of a New-World primate, the capuchin monkey, Cebus apella.

1. The genetic basis of colour vision in New-World primates differs from that in humans and other Old-World primates. Most New-World primate species show a polymorphism; all males are dichromats and most females trichromats. 2. In the retina of Old-World primates such as the macaque, the physiological correlates of trichromacy are well established. Comparison of the retinae in New- and Old-World species may help constrain hypotheses as to the evolution of colour vision and the pathways associated with it. 3. Ganglion cell behaviour was recorded from trichromatic and dichromatic members of a New-World species (the capuchin monkey, Cebus apella) and compared with macaque data. Despite some differences in quantitative detail (such as a temporal response extended to higher frequencies), results from trichromatic animals strongly resembled those from the macaque. 4. In particular, cells of the parvocellular (PC) pathway showed characteristic frequency-dependent changes in responsivity to luminance and chromatic modulation, cells of the magnocellular (MC) pathway showed frequency-doubled responses to chromatic modulation, and the surround of MC cells received a chromatic input revealed on changing the phase of heterochromatically modulated lights. 5. Ganglion cells of dichromats were colour-blind versions of those of trichromats. 6. This strong physiological homology is consistent with a common origin of trichromacy in New- and Old-World monkeys; in the New-World primate the presence of two pigments in the middle-to-long wavelength range permits full expression of the retinal mechanisms of trichromatic vision.

Animals↗
PubMed2000

The relationship between the angiographic findings and the clinical features of carotid artery plaque.

The purpose of this study was to investigate the histological characteristics of atheromatous carotid plaque, and to analyze the relationship between the angiographic findings and the clinical features. We retrospectively reviewed 55 cases of carotid endarterectomy for extracranial internal carotid artery stenosis, who were treated at our institute from January 1995 to December 1997. The histological examination included hematoxylin-eosin staining, Masson-trichrome staining, and immunostaining for antismooth muscle antibody and anti-CD68 antibody. The main compositions of the carotid plaque included synthetic type vascular smooth muscle cells and extracellular matrix. The histological findings showed ulceration in 49 (89.1%) cases, calcium deposits in 42 (76.4%) cases, and an inflammatory reaction in 44 (80.0%) cases. Neurological abnormalities were strongly associated with plaque ulceration (P = 0.045) and an inflammatory reaction (P = 0.013), whereas no correlation existed regarding calcium deposits (P = 0.173). The angiographic findings showed ulceration in 46 (83.6%) cases. Plaque ulceration in the angiography findings showed no statistically significant correlation with the histologic findings (P = 0.410) and preoperative neurologic abnormalities (P = 0.059). All of the atherosclerotic risk factors such as hypertension, smoking, diabetes mellitus, hyperlipidemia, and myocardial infarction had no statistically significant correlation with the histological features of the carotid plaque. In conclusion, the main compositions of carotid plaque were synthetic-type vascular smooth muscle cells and extracellular matrix. The histological ulceration and inflammatory reaction of the plaque showed a statistically significant correlation with the preoperative neurologic symptoms, whereas no correlation was seen in the calcium deposits. Angiographic ulceration showed no correlation with the histological findings or preoperative neurologic abnormalities. In addition, the histological findings showed no correlation with the atherosclerotic risk factors.

Aged↗
PubMed2000

Chromatic and luminance contributions to a hyperacuity task.

Displacement thresholds with incremental chromatic and luminance edges were measured on different backgrounds. Above 3% luminance contrast, thresholds were always similar. At luminance contrasts below 3%, luminance edges could not be detected, but chromatic edges were still visible. At these low contrasts displacement thresholds for chromatic edges increased to a high level. We interpret these data in terms of multiple mechanisms; above 3% contrast a luminance mechanism determines thresholds, but when, at lower contrasts, chromatic mechanisms support detection, they also support the spatial task. Physiological data were consistent with the different mechanisms originating at the retinal ganglion cell level.

Animals↗
PubMed2000

Closed loop control of anaesthesia: an assessment of the bispectral index as the target of control.

We investigated the performance of a closed-loop system for administration of general anaesthesia, using the bispectral index as a target for control. One hundred patients undergoing gynaecological or general surgery were studied. In 60 patients, anaesthesia was maintained by intravenous infusion of a propofol/alfentanil mixture. In 40, an isoflurane/nitrous oxide based technique was used. For each technique, patients were randomly allocated to receive either closed-loop or manually controlled administration of the relevant agents (propofol/alfentanil or isoflurane), with an intra-operative target bispectral index of 50 in all cases. Closed-loop and manually controlled administration of anaesthesia resulted in similar intra-operative conditions and initial recovery characteristics. During maintenance of anaesthesia, cardiovascular and electro-encephalographic variables did not differ between closed-loop and manual control groups and deviation of bispectral index from the target value was similar. Intra-operative concentrations of propofol, alfentanil and isoflurane were within normal clinical ranges. Episodes of light anaesthesia were more common in the closed-loop group for patients receiving propofol/alfentanil anaesthesia and in the manual group for patients receiving isoflurane/nitrous oxide anaesthesia. Convenience aside, the closed-loop system showed no clinical advantage over conventional, manually adjusted techniques of anaesthetic administration.

Adult↗
PubMed2000

A dose-response study of prophylactic intravenous ephedrine for the prevention of hypotension during spinal anesthesia for cesarean delivery.

UNLABELLED: We performed a randomized, double-blinded dose-finding study of IV ephedrine for prophylaxis for hypotension in 80 women who received an IV crystalloid preload and spinal anesthesia for elective cesarean delivery. One minute after the intrathecal injection, patients were given saline control or ephedrine 10, 20, or 30 mg IV for 30 s. Systolic arterial pressure (SAP) in the first 12 min after the spinal injection was greater in the 30-mg group compared with other groups (P < 0.05). Hypotension occurred in 7 patients (35%) in the 30-mg group compared with 19 (95%), 17 (85%), and 16 (80%) patients in the control and 10- and 20-mg groups, respectively (P < 0.0001). Maximum decrease in SAP was smaller in the 30-mg group (mean lowest SAP 87% of baseline, range 58%-105%) compared with other groups (P < 0.01). Reactive hypertension occurred in 9 patients (45%) in the 30-mg group (mean highest SAP 120% of baseline, range 104%-143%) compared with 2 (10%), 1 (5%), and 5 (25%) patients in the other groups (P = 0.009). Heart rate changes, total ephedrine requirement, incidence of nausea and vomiting, and neonatal outcome were similar among groups. The proportion of patients with umbilical arterial pH < 7.2 was 10.5%, 25%, 42%, and 22% in the control, 10-, 20-, and 30-mg groups, respectively (P = 0. 12). We conclude that the smallest effective dose of ephedrine to reduce the incidence of hypotension was 30 mg. However, this dose did not completely eliminate hypotension, nausea and vomiting, and fetal acidosis, and it caused reactive hypertension in some patients. IMPLICATIONS: We investigated different doses of IV ephedrine as prophylaxis for hypotension during spinal anesthesia for cesarean delivery and found that the smallest effective dose was 30 mg. However, this dose did not completely eliminate hypotension, caused reactive hypertension in some patients, and did not improve neonatal outcome.

Acidosis↗
PubMed2000

Prevalence of foam cells and helper-T cells in atherosclerotic plaques of Korean patients with carotid atheroma.

BACKGROUND: Inflammation and activation of immune cells have important roles in the pathogenesis of atherosclerosis. We analyzed the involvement of various immune cells in the pathogenesis of atherosclerosis. METHODS: We investigated the presence of foam cells, lymphocytes and killer cells in 11 atherosclerotic plaque specimens removed from Korean patients who underwent carotid endoarterectomy. Atherosclerotic plaques were analyzed by immunohistochemistry using monoclonal antibody specific to foam cells (anti-CD68), pan-T cells (anti-CD3), helper-T cells (anti-CD4), cytotoxic T cells (anti-CD8), granular component of killer cells (anti-TIA-1) and pan-B cells (anti-CD20). RESULTS: Analysis revealed a general infiltration of immune cells not only in atherosclerotic plaques but also in the vascular wall adjacent to the plaque. Heavy infiltration of CD68+ macrophage was observed in all cases. In addition, significant infiltration of CD3+ T-lymphocytes was observed in all cases, while CD20+ B-cells were observed in only a few cases. Majority of the CD3+ cells was found to be CD4+ helper-T cells. CD8+ cytotoxic T cells and TIA-1+ cells were less prominent. CONCLUSION: Analysis of the human atherosclerotic plaques suggested that helper-T cells and foam cells had a major role in the plaque development.

Aged↗
PubMed2000

Preservation of renal function in reimplantation of renal artery of abdominal aortic aneurysm.

Intraoperative administration of diuretics and renal hypothermia with cold (4 degrees C) heparinized Ringer's lactate were useful methods for preserving renal function during warm ischemia time. 54-year and 74-year-old men were diagnosed as abdominal aortic aneurysm. Their left renal and accessory left renal arteries originated from the border zone of the aneurysm. We reported two cases of reimplantation of the renal artery in abdominal aortic aneurysm without deterioration of renal function.

Aged↗
PubMed1999

Horizontal cells reveal cone type-specific adaptation in primate retina.

The human cone visual system maintains contrast sensitivity over a wide range of ambient illumination, a property known as light adaptation. The first stage in light adaptation is believed to take place at the first neural step in vision, within the long, middle, and short wavelength sensitive cone photoreceptors. To determine the properties of adaptation in primate outer retina, we measured cone signals in second-order interneurons, the horizontal cells, of the macaque monkey. Horizontal cells provide a unique site for studying early adaptational mechanisms; they are but one synapse away from the photoreceptors, and each horizontal cell receives excitatory inputs from many cones. Light adaptation occurred over the entire range of light levels evaluated, a luminance range of 15-1,850 trolands. Adaptation was demonstrated to be independent in each cone type and to be spatially restricted. Thus, in primates, a major source of sensitivity regulation occurs before summation of cone signals in the horizontal cell.

Adaptation, Physiological↗