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Biomedical subjects

M M Lee

Publications and source records attributed to M M Lee.

At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

Effects of pressure on vesicle size, density, and distribution in the canine carotid arterial endothelium.

The purpose of the present experiment was to study the effects of internal hydrostatic pressure on vesicle size, density, and distribution in the canine carotid arterial endothelium by transmission electron microscopy. The pressures applied in this study were 0 (control), 40, 60, 80, 100, and 150 mm Hg. The results of transmission electron microscopy and computer analysis on the plasmalemmal vesicles of aortic endothelium showed that luminal, abluminal, and junctional vesicles all increased their diameter as the pressure was raised from 0 mm Hg, reaching a maximum at 80 mm Hg, and then decreased in size with further increases in pressure to 150 mm Hg. There was a significant difference in diameter among vesicles in different regions of the endothelium, with the diameter of luminal vesicles larger than those of abluminal and junctional vesicles. The densities of vesicles showed very little change from 0 to 80 mm Hg; but they increased markedly as the pressure was further raised from 80 to 150 mm Hg. These results indicate that pressure is an important mechanical factor governing the size and density of plasmalemmal vesicles in aortic endothelium.

Animals↗
PubMedDate not supplied

Sulfuric acid aerosol induces changes in alveolar surface tension in the guinea pig but not in the rat.

The purpose of this study was to investigate the effects of an acid aerosol, at high concentration, on the surface properties of the extracellular fluid lining the airways and alveolae. Guinea pigs and rats were exposed to 43 mg/m3 and 94 mg/m3 of sulfuric acid aerosol mass median aerodynamic diameter (MMAD) 0.9 micron or water aerosol (control), respectively, for 4 hours in an exposure chamber. Surfactant material was extracted from bronchoalveolar lavage fluid (BAL) by centrifugation, and phospholipid, protein, and cell concentrations measured. The extract was reconstituted to 300 micrograms/mL of phospholipid, and its surface properties assessed with a captive bubble surfactometer. The minimum surface tension for the acid-exposed guinea pig BAL was 12.1 +/- 8.48 (mean +/- SD) mN/m, which was significantly higher than the control group, 2.0 +/- 0.43 (mean +/- SD) or the acid-exposed rats, 1.29 +/- 0.11 (mean +/- SD). The change in film area obtained by compressing the film from equilibrium surface tension (25 mN/m) to its minimum value (gamma min) was 62.9 +/- 13.83 (mean +/- SD)% for acid-exposed guinea pigs, compared to 16.3 +/- 5.77 (mean +/- SD)% for the control guinea pigs. The most sensitive index of surfactant inhibition was found to be the maximum film compressibility (Cmax) of the compression isotherm. This index was 119 times greater for the acid-exposed guinea pigs compared to control animals. These abnormalities were associated with an elevation of total protein (0.95 +/- 0.33 [mean +/- SD] mg/mL compared to 0.13 +/- 0.03 [mean +/- SD] mg/mL in controls) and polymorphonuclear leucocytes in the BAL. There was no change in total phospholipids. By contrast BAL retrieved from rats exposed to approximately twice the concentration of acid aerosol showed no cellular nor biochemical abnormalities and its surface tension properties were normal. We conclude that the abnormalities of surfactant activity in the acid-exposed guinea pigs result from the cellular and humoral responses of acute lung injury rather than a direct effect of acid.

Administration, Inhalation↗
PubMedDate not supplied

The mammography controversy: a case for breast self-examination.

More and more nurses are held legally accountable for their practice. The mammography controversy and the directives in the NIH guidelines must be taken into account by nurses because of their implications for preventive health care and early detection of breast cancer. Mortality rates from breast cancer are high enough that the importance of regular, competent BSE by women cannot be overestimated. Nursing is in an ideal position within the health care delivery system to promote BSE. In the meantime, the answer to the question of whether to use mammography as a routine screening device for asymptomatic women under age 50 can only come from research that is designed to demonstrate the relative risks and benefits of the procedure for this age group.

Adult↗
PubMedDate not supplied

In vitro and in vivo growth inhibition of SC-M1 gastric cancer cells by retinoic acid.

Retinoids are differentiating agents that have been used successfully for the treatment of acute promyelocytic leukemia. When combined with interferons, they are active in preventing second malignancies in patients with head and neck cancer. Our previous studies have demonstrated cytostatic effects of alltrans-retinoic acid (tRA) on SC-M1 gastric cancer cells in vitro. The activity of tRA and 13-cis-retinoic acid (cRA) on SC-M1 cells was compared both in vitro and in vivo in this study. Measurement of total cellular DNA was used to determine cell growth in vitro. The effect of retinoic acid on tumor growth was evaluated by implanting sustained release tRA or cRA pellets into athymic nude mice. The results showed that tRA was more potent than cRA in suppressing the growth of SC-M1 gastric cancer cells in vitro. Both tRA and cRA were effective in suppressing the growth of SC-M1 tumors in athymic nude mice. No change in the differentiation status and cell cycle phase distribution in excised tumors was observed. Side effects such as bone fractures and weight loss were observed in mice of both treatment groups. The results suggest that retinoic acid may provide therapeutic advantages for the treatment of gastric cancer.

Animals↗
PubMedDate not supplied

Effects of oscillatory mechanical disturbance on macromolecular uptake by arterial wall.

Transport of 125I-albumin by isolated segments of canine common carotid arteries was studied in vitro at zero transmural pressure. Sinusoidal oscillatory variations in length (peak change 4%) for 15 minutes at frequencies of 5 and 10 Hz caused 40% increase in 125I-albumin uptake, and also a 30% increase in the apparent luminal surface area. Changes in the duration and frequency of oscillation indicate that the total number of oscillations (= frequency X duration) was the critical parameter in causing these effects. The increase in apparent luminal surface area was correlated with regional flattening of the internal elastic lamina and the overlying endothelial cells, as demonstrated by transmission and scanning electron microscopy. Endothelial vesicles were counted with the aid of ruthenium red as a postfixation extracellular marker. The ratio of unstained free vesicles to total vesicles averaged 0.083 in the control state and decreased slightly to 0.070 after oscillation. Although the decrease in free vesicle population indicated an acceleration of vesicle diffusion, our theoretical computations showed that the resulting increase in vesicle flux was negligible. The increase in 125I-albumin uptake by the artery following mechanical oscillation is mainly attributable to the increase in apparent luminal surface area.

Animals↗
PubMedDate not supplied

Macromolecular transport across arterial and venous endothelium in rats. Studies with Evans blue-albumin and horseradish peroxidase.

Atherosclerotic lesions are characterized by lipid infiltration in regions with high rates of endothelial cell turnover. The present investigation was designed to elucidate the route of macromolecular transport across vascular endothelium. The aorta and vena cava of male Sprague-Dawley rats were perfusion-fixed after the intravenous injection of Evans-blue albumin (EBA) or horseradish peroxidase (HRP). Fluorescence microscopic examination of en face preparation of the aorta stained with hematoxylin allowed the identification of endothelial cells that underwent mitosis, together with the localization and quantification of fluorescent spots for EBA leakage. The HRP specimens were subjected to histochemical treatment, and HRP leakage was seen as brown spots under the light microscope. Silver nitrate stain was added in both EBA and HRP studies to outline cell boundaries and to visualize stigmata, stomata, and dead cells. In the aorta, almost every dividing cell showed junctional leakage to albumin and HRP, with clustering of leaky spots around the branch orifices. Time-dependent studies showed gradual increases in the diameter and number of these heterogeneously sized leaky spots, which finally fused to sizes corresponding to the "blue areas" for EBA or "brown areas" for HRP. Compared with arteries, veins had fewer mitotic cells, but more dead cells and diffuse dye-staining areas, indicating a more rapid transport of macromolecules. The leaky spots in the artery were associated mainly with mitotic cells, dead cells, and stigmata, whereas those in the vein occurred primarily at regions with dead cells. These results suggest that the preferential association of the enhanced transport of macromolecules with mitosis in the arterial as compared to venous endothelium and the differential behavior in transmural transport between arteries and veins may form the basis for the predilection of atherosclerosis in arteries.

Animals↗
PubMedDate not supplied

Effects of acid aerosol exposure on the surface properties of airway mucus.

It was hypothesized that the mucous layer lining the tracheas of rats and guinea pigs contains surfactant material capable of lowering the air/mucus surface tension, gamma, and that exposure to an irritant aerosol would raise the gamma. The gamma of the surface film was measured directly by a spreading droplet technique and indirectly by displacement of polymethyl methacrylate particles into the aqueous layer. The morphology of the mucous film was examined by electron microscopy after nonaqueous fixation. gamma was 33.3 +/- 0.70 (SE) mN/m and 32.3 +/- 0.68 (SE) mN/m for the normal rat and guinea pig trachea, respectively. Exposure for 4 h to aerosols of sulfuric acid (94.1 +/- 18.68 (SD) and 43.3 +/- 4.57 (SD) mg/m3) caused a several-fold increase in thickness of the mucous layer with exudation of protein-like material. The osmiophilic surfactant film at the air/mucus interface became irregularly thickened and multilayered. Despite these morphological changes gamma remained low, 33.2 +/- 0.43 (SE) mN/m and 32.6 +/- 0.60 (SE) mN/m for rats and guinea pigs, respectively, and displacement of particles into the subphase was not compromised. The results indicate that rodent tracheas are able to maintain a low surface tension in the presence of injury.

Aerosols↗
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Red cell membrane elasticity as determined by flow channel technique.

The elasticity of red cell membrane was determined in a rectangular flow channel under controlled shear flow. The relation between shear stress and cell extension ratio (lambda) has been analyzed with the use of Evans' two-dimensional model. The deformed cell shapes observed experimentally agreed well with the model with lambda up to 1.4. The best correlation was found at lambda = 1.2. The analysis suggests a nonlinear extensional membrane modulus in the low stress range encountered in the flow channel. In terms of an appropriate strain parameter, the elastic modulus is shown to rise toward the level encountered in micropipette aspiration experiments. The implications of the present findings in modeling of cell mechanics and in cell hemolysis are discussed.

Elasticity↗
PubMedDate not supplied

Bowen's disease.

Explore the source record for details and available documents.

Bowen's Disease↗
PubMedDate not supplied

Multimodality therapy in advanced paranasal sinus carcinoma: superior long-term results.

PURPOSE: This study was conducted to determine the efficacy of multimodality treatment for stage III and IV, locoregionally advanced paranasal sinus carcinoma. PATIENTS AND METHODS: A subgroup analysis of 19 consecutive patients with stage III or IV paranasal sinus carcinoma treated with multimodality therapy from head and neck cancer protocols between 1984 and 1996 were analyzed for outcome. Sixteen patients received induction chemotherapy consisting of three cycles of cisplatin and 5-fluorouracil, followed by traditional resection (14 patients) or surgical debulking (two patients). Surgery was followed by concomitant chemoradiotherapy with hydroxyurea and 5-fluorouracil in a week-on, week-off sequence in 15 patients. One patient received standard radiation therapy. An additional three patients were treated with a sequence of surgical resection followed by concomitant chemoradiotherapy. The median total dose to the primary tumor was 60 Gy (range, 45-74 Gy). RESULTS: The overall survival at 5 and 10 years by lifetable analysis was 72.7% and 53.9%, respectively, and the disease-free survival at both 5 and 10 years was 66.6%. Local control was 76.1% at both 5 and 10 years. In the subgroup of patients treated with induction chemotherapy, 87% (14/16) achieved a clinical response. A complete response was confirmed at the time of surgery in five patients, whereas 11 patients had residual disease in the surgical specimen. Regional and distant failures were unusual (one patient each), with a 10-year regional control rate of 93% and a distant control rate of 95.5%. Serious, nonreversible long-term complications included two cases of unilateral blindness, one cataract, and one case of ototoxicity. DISCUSSION: An excellent long-term outcome with respect to local control, overall survival, and disease-free survival is achieved in locoregionally advanced paranasal sinus cancer treated with induction chemotherapy, surgery, and concomitant chemoradiotherapy. The 15 patients treated with this regimen had 10-year overall survival, disease-free survival, and local control rates of 56%, 73%, and 79%, respectively. These results are encouraging and are superior to the 40% survival achieved with surgery and radiation therapy. Further investigation of this regimen is warranted.

Adult↗
PubMedDate not supplied

Müllerian inhibiting substance inhibits testosterone synthesis in adult rats.

Müllerian inhibiting substance (MIS) is a gonadal hormone that causes regression of the Müllerian ducts during male sexual differentiation. Postnatally, MIS inhibits the proliferation and differentiation of immature Leydig cells, and transgenic mice that overexpress MIS have decreased serum testosterone concentrations. To elucidate the effects of MIS on androgen regulation in the postnatal testis, we examined testosterone synthesis in adult Sprague-Dawley rats following intratesticular and intraperitoneal injections of MIS. Intratesticular MIS injection achieved high local concentrations of MIS (574.0 +/- 60.0 ng/mL) at 4 hours, with a corresponding decline in serum testosterone concentrations to 0.7 +/- 0.1 ng/mL, compared to 1.1 +/- 0.2 ng/mL with intraperitoneal MIS and 1.6 +/- 0.1 ng/mL with intratesticular vehicle (IT-Veh) (P < .001). Intratesticular administration of MIS (IT-MIS) resulted in much higher serum and testicular interstitial fluid MIS concentrations than the intraperitoneal route. To directly examine the testosterone production rate in MIS-treated animals, we isolated Leydig cells from MIS and vehicle-injected testes. Primary Leydig cells exposed to MIS had a lower testosterone production rate and decreased expression of p450c17 (hydroxylase/lyase) and luteinizing hormone (LH) receptor mRNAs than that of vehicle-injected controls or the noninjected contralateral testis. In conclusion, intratesticular administration of MIS caused a decline in serum testosterone concentrations by decreasing the rate of testosterone biosynthesis, confirming that MIS can regulate adult Leydig cell androgen production. The ability of MIS to down-regulate mRNA expression of the p450c17 and LH receptor genes suggests that this effect is mediated transcriptionally. These data indicate that, in addition to its role in embryonic differentiation of the male reproductive tract, MIS has a regulatory function in the postnatal testis. We conclude that one such function is for MIS to directly inhibit adult Leydig cell steroidogenesis.

Animals↗
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The association of dietary fat with ability to obtain breast fluid by nipple aspiration.

The ability to obtain breast fluid by nipple aspiration was examined in relation to self-reported dietary fat intake in 1347 white and 153 black women. Study participants were between 20 and 59 years of age, were not pregnant or breastfeeding, and had no history of breast cancer. The proportion of women from whom nipple aspirate fluid was obtained increased with increasing dietary fat consumption; the odds ratio for obtaining breast fluid was 1.4 (95% confidence interval, 1.0-1.8) in white women who consumed over 90 g of fat/day compared with those who consumed less than 50 g of fat/day, adjusting for age, smoking, and parity. Among black women, the association was much stronger; the odds ratio for obtaining nipple aspirate fluid in those who consumed over 90 g of fat/day was 3.6 (95% confidence interval, 1.3-10.1) compared with those who consumed less than 50 g of fat/day. In both blacks and whites, the associations were most pronounced in women aged 30-44 years. These findings suggest a relationship between dietary fat consumption and breast secretion.

Adult↗
PubMedDate not supplied

Charcot arthropathy of the first metatarsophalangeal joint.

The authors present an unusual case study of a Charcot joint of the first metatarsophalangeal articulation as well as a successful tibial sesamoidectomy for an associated chronic ulceration. Serial radiographs document the destructive disease process. The authors also address the etiologies of peripheral neuropathy, diagnostic tests to differentiate between Charcot joint and osteomyelitis, and both conservative and surgical management of Charcot joints.

Aged↗
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Topical Bactroban (mupirocin): efficacy in treating burn wounds infected with methicillin-resistant staphylococci.

Bacterial antimicrobial susceptibility predictors such as the minimal inhibitory concentration (MIC) assay and Nathans Agar Well Diffusion (NAWD) assay provide essential information relevant to the therapeutic approach in burn-wound sepsis. The susceptibilities of 68 gram-positive burn-wound isolates were tested against topical Bactroban (mupirocin) (Beecham Laboratories, Bristol, Tenn.) and compared with other topical antimicrobials such as mafenide acetate, silver sulfadiazine, and bacitracin/neomycin/polymyxin (BNP). Topical susceptibility data were obtained with a modification of NAWD assay. Bactroban's antimicrobial activity was greater than that of mafenide acetate (100% vs 97%), and significantly greater than that of silver sulfadiazine and that of BNP (p less than 0.001). Of the 68 isolates that were susceptible to Bactroban, 51 were predominately methicillin-resistant staphylococci (MRSA). Bactroban showed in vitro activity against 71% of the 85 gram-negative isolates tested. Mafenide acetate showed activity against 89% of these isolates, a significant difference compared with Bactroban (p less than 0.02). In general, no significant difference was found between the activities of Bactroban and silver sulfadiazine against the gram-negative isolates. The activities of mafenide acetate and silver sulfadiazine against isolates of Pseudomonas aeruginosa were significantly greater than that of Bactroban (p less than 0.05). Bactroban may be used in the treatment of documented staphylococcal burn-wound infections. On the basis of the in vitro data, 13 patients with MRSA burn-wound infections susceptible to Bactroban were evaluated. Quantitative wound biopsies were employed to determine the efficacy of this therapeutic approach. The outcome of these infections was correctly predicted by the NAWD assay in 92.3% of the patients treated (p less than 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗