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Biomedical subjects

H M Lee

Publications and source records attributed to H M Lee.

At least 109 records · Page 6Linked to original sources
PubMed1999

Noninvasive evaluation of coronary artery bypass graft patency using three-dimensional angiography obtained with contrast-enhanced electron beam CT.

OBJECTIVE: The purpose of this study was to determine the accuracy of three-dimensional coronary angiography obtained with electron beam CT in the assessment of the patency of coronary artery bypass grafts. SUBJECTS AND METHODS: Twenty-five patients who had undergone coronary artery bypass graft surgery were included. All patients underwent electron beam CT and conventional coronary angiography for the evaluation of the status of their bypass grafts. Three-dimensional reconstructions of the heart and bypass grafts were compared with selective angiographic images of the bypass grafts. RESULTS: Fifty-seven saphenous vein grafts and 22 left internal mammary artery grafts were evaluated for occlusion or patency. Sensitivity and specificity of electron beam CT in revealing left internal mammary artery patency were 80% and 82.4%, respectively. Sensitivity and specificity of electron beam CT in revealing saphenous vein graft patency were 91.7% and 91.1%, respectively. Sensitivity and specificity of electron beam CT for evaluating saphenous vein grafts according to coronary area were as follows: saphenous vein grafts to left anterior descending artery, 100% and 100%, respectively; to diagonal branch, 100% and 100%; to left circumflex artery, 100% and 88.9%; and to right coronary artery, 75% and 85.7%. CONCLUSION: Three-dimensional coronary angiography obtained with electron beam CT is a promising, useful, and relatively accurate diagnostic imaging technique for the evaluation of graft patency in patients who have undergone coronary artery bypass graft surgery.

Coronary Angiography↗
PubMed1999

Adenosine rinse in human orthotopic liver transplantation: results of a randomized, double-blind trial.

OBJECTIVE: The study was aimed at determining whether the vasodilator, adenosine, shown to produce dramatic improvement in liver graft and animal acute and long-term survival, would be beneficial in human liver transplantation. METHODS: A prospective, randomized, double-blind trial of an adenosine rinse preservation solution in human orthotopic liver transplantation (OLTX) was conducted in 43 consecutive transplants. Intraoperative and postoperative care was performed by a single transplant team utilizing a quadruple drug immunosuppressive protocol, with complete 5-year patient follow-up. At implantation all allografts were flushed with a 4 degrees C (pH 7.4) Normosol solution, with 0.12 mM adenosine or without adenosine. RESULTS: Recipient characteristics were similar in the treated and control groups including age, pre-OLTX diagnosis, and United Network for Organ Sharing (UNOS) status. Donor variables were equivalent in the two groups including age, weight, prothrombin time, and serum chemistries. Operative variables showed no differences except a significant (p = 0.006) reduction of veno-venous bypass time in the adenosine treated group. Liver allograft function improved in the adenosine rinse groups as measured by both postoperative bile production (218 +/- 156cc/24h adenosine vs. 116 +/- 78 cc/24 h without adenosine, p = 0.03) and Factor 7 production at day 3 (64 +/- 26% adenosine vs. 51 +/- 20% without adenosine, p = 0.08). The adenosine treated group had an insignificant 10% patient and graft improvement in survival at 6 months to 60 months compared to the control group. CONCLUSIONS: These results suggest that adenosine added to the intraoperative flush solution during human liver transplantation is safe, does not reduce cardiac stability at reperfusion, improves early liver allograft function, but has an insignificant short- and long-term affect on allograft survival.

Adenosine↗
PubMed1999

Sacroiliac joint tuberculosis. Classification and treatment.

The authors treated 16 patients with tuberculosis of the sacroiliac joint. Twelve were treated surgically and four were treated conservatively. The clinical symptoms were buttock and low back pain in all patients, and most had difficulty walking (68.6%) and had radicular pain in their lower limbs (50%). Of the 16 patients, four (15%) had associated tuberculous spondylitis, six (37.5%) had an abscess in the gluteal region, and two (12.5%) had an abscess in the inguinal region. The diagnosis was proven by pathologic specimen in 12 patients and by clinical symptoms, laboratory data, and radiologic findings in the remaining four patients. The authors classified tuberculous sacroiliitis into four types based on the clinical and radiologic findings. Types 1 and 2 were treated conservatively with chemotherapy alone, whereas Types 3 and 4 were treated with surgery and chemotherapy. Healing occurred and was evident in patients who had curettage and arthrodesis (Types 3 and 4) at a mean of 20.8 months, which was comparable with healing in the patients who had chemotherapy alone that occurred at a mean of 23.5 months (Types 1 and 2). The authors suggest that the new classification will be helpful in determining the therapeutic plan of tuberculous sacroiliitis.

Adolescent↗
PubMed1998

The propeptide domain of membrane type 1 matrix metalloproteinase is required for binding of tissue inhibitor of metalloproteinases and for activation of pro-gelatinase A.

Activation of secreted latent matrix metalloproteinases (MMPs) is accompanied by cleavage of the N-terminal propeptide, thereby liberating the active zinc from binding to the conserved cysteine in the pro-domain. It has been assumed that an analogous mechanism is responsible for the activation of membrane type 1 MMP (MT1-MMP). Using recombinant wild-type MT1-MMP cDNA and mutant cDNAs transfected into COS-1 cells lacking endogenous MT1-MMP, we have examined the function of the propeptide domain of MT1-MMP. MT1-MMP was characterized by immunoblotting, surface biotinylation, gelatin substrate zymography, and 125I-tissue inhibitor of metalloproteinases 2 (TIMP-2) binding. In contrast to wild-type MT1-MMP-transfected COS-1 cells, transfected COS-1 cells containing a deletion of the N-terminal propeptide domain of MT1-MMP or a chimeric construction (substitution of the pro-domain of MT1-MMP with that of collagenase 3) were functionally inactive in terms of binding of 125I-labeled TIMP-2 to the cell surface and initiating the activation of pro-gelatinase A. These results support the concept that in its native plasma membrane-inserted form, the pro-domain of MT1-MMP plays an essential role in TIMP-2 binding and subsequent activation of pro-gelatinase A.

Enzyme Activation↗
PubMed1998

The role of steroids and their effects on phospholipase A2. An animal model of radiculopathy.

STUDY DESIGN: The possible role of phospholipase A2 in an animal model for lumbar radiculopathy and mechanisms of epidural steroid injections were studied. OBJECTIVES: To clarify the pathophysiologic mechanism of the recently proved animal model for lumbar radiculopathy and to characterize further the mechanisms of action of steroids. SUMMARY OF BACKGROUND DATA: There have been several reported animal models of peripheral neuropathy. Recently an animal model that shows reliable behavioral and neurochemical changes was proposed, and epidural steroid injections in this model were effective in the reduction of thermal hyperalgesia and allodynia. METHOD: In a behavioral study, 24 rats were divided into 4 groups: Group I, loose ligature of the left L4 and L5 nerve roots with 4-0 chromic gut sutures and an epidural injection of 0.1 mL of saline at 3 days after surgery; Group II, same as Group I but with an epidural injection of 0.1 mL of betamethasone on the day before the operation; Group II, same as Group II except injection at 1 day after surgery; Group IV, same as Group II except injection at 3 days after surgery. To test the phospholipase A2 activity in the nerve roots and dorsal root ganglia after the operation, eight rats were killed at given intervals. Analysis of variance techniques were used to test behavioral pattern changes and phospholipase A2 activity across time in each group. RESULTS: Thermal hyperalgesia reached its maximal point at 3 weeks after surgery in Group I, but in steroid injection groups, the recovery from hyperalgesia was faster than in Group I. However, there was no significant difference in recovery time among steroid injection groups. The level of phospholipase A2 activity was at its maximum at 1 week after surgery in Groups I and IV. It showed a steady reduction in the steroid group, whereas it remained relatively high and dropped rapidly after 3 weeks in the saline-treated group, and returned to the level of a normal nerve root at 6 weeks after surgery. CONCLUSION: These results suggest that the behavioral pattern changes observed in the irritated nerve root model are caused in part by a high level of phospholipase A2 activity initiated by inflammation, and that the mechanism of action of epidural steroid injection in this model is inhibition of phospholipase A2 activity.

Animals↗
PubMed1998

A role for the signal transduction protein PII in the control of nitrate/nitrite uptake in a cyanobacterium.

In the cyanobacterium Synechococcus sp. strain PCC 7942, ammonium exerts a rapid and reversible inhibition of the nitrate and nitrite uptake, and the PII protein (GlnB) is differentially phosphorylated depending on the intracellular N/C balance. RNA/DNA hybridizations, as well as nitrate and nitrite uptake experiments, were carried out with the wild-type strain and a PII-null mutant. The transcriptional control by ammonium of the expression of the nir-nrt ABCD-narB operon remained operative in the mutant but, in contrast to the wild-type strain, the mutant took up nitrate and nitrite even in the presence of ammonium. Moreover, the wild-type phenotype was restored by insertion of a copy of the wild-type glnB gene in the genome of the PII-null mutant. These results indicate that the unphosphorylated form of PII is involved in the short-term inhibition by ammonium of the nitrate and nitrite uptake in Synechococcus sp. strain PCC 7942.

Ammonium Chloride↗
PubMed1998

The effect of epidural injection of betamethasone or bupivacaine in a rat model of lumbar radiculopathy.

STUDY DESIGN: The effect of epidural injection of betamethasone or bupivacaine was investigated in an animal model of lumbar radiculopathy. OBJECTIVE: To investigate the effects of an epidural steroid (betamethasone) or a local anesthetic (bupivacaine) in an animal model of radiculopathy produced by nerve root irritation. SUMMARY OF BACKGROUND DATA: Epidural injections are commonly used for the treatment of low back pain and sciatica. However, efficacy remains controversial, and there is a paucity of basic information to support clinical use or the injections. METHODS: Fifty-one rats were used. The left L4 and L5 nerve roots were loosely ligated with chromic gut, and either betamethasone, bupivacaine, betamethasone in combination with bupivacaine, or saline was injected using an epidurally placed catheter. The effects of epidural injection were evaluated using response to noxious stimuli and immunohistochemical methods. RESULTS: In betamethasone-treated rats (either alone or in combination with bupivacaine), thermal hyperalgesia was significantly less (P < 0.010 after surgery than that in saline- or bupivacaine-treated groups, in which the hyperalgesia was maximum at 2-3 postoperative weeks before resolving 5 weeks after surgery. Immunohistochemical analysis did not correlate with these results. CONCLUSIONS: Epidural steroid injection has a significant effect on the thermal hyperalgesia produced in a model of radiculopathy, which may provide clinical support for advocates of epidural steroids.

Anesthetics, Local↗
PubMed1998

Timing algorithm for bolus chase MR digital subtraction angiography.

To acquire multiple longitudinal locations in the lower extremity after a single contrast injection, appropriate table translation and contrast injection are required. An approximate model based on constant bolus velocity was developed to describe the space-time course of a contrast bolus in the lower extremity. This model was verified in dynamic MR angiograms acquired in a group of patients using time-resolved 2D MR digital subtraction angiography (MRDSA). From this contrast bolus passage model, a timing algorithm for table translation and contrast injection was developed for bolus chase MRDSA, subsequently validated in bolus chase 2D MRDSA experiments. All targeted major peripheral arteries were well depicted in bolus chase 2D MRDSA using this timing algorithm and a single 15-ml contrast dose.

Adult↗
PubMed1998

Dynamic k-space filling for bolus chase 3D MR digital subtraction angiography.

A bolus chase three-dimensional (3D) MR digital subtraction angiography (MRDSA) technique was implemented using dynamic k-space filling. This technique permits rapid 3D arterial imaging of the entire lower extremity at multiple stations using a single intravenous injection. Image acquisition at the first (most proximal) station starts from the edge of k-space and ends in the center of k-space (edge-center order). Image acquisition for middle stations starts from the edge of k-space, arrives at the center of k-space at the middle of data acquisition, and ends at the edge of k-space (edge-center-edge order). Image acquisition for the last station starts from the center of k-space and ends at the edge of k-space (center-edge order). This dynamic k-space filling minimizes contrast dose and motion artifacts. Bolus chase 3D MRDSA was performed on four normal volunteers and three patients using a multiple-phase 3D fast gradient-echo sequence, 25-ml gadolinium dose, and a prototype stepping table. Total bolus chase 3D acquisition time was 46 s. Mask subtraction using both complex and magnitude subtraction was performed. Complex subtraction was found to be necessary for proper delineation of arteries below the aortic bifurcation. Diagnostic results were consistently obtained for all subjects.

Adult↗
PubMed1998

Should vein be saved for future operations? A 15-year review of infrainguinal bypasses and the subsequent need for autogenous vein.

The decision to use prosthetic or autogenous vein as the initial conduit for first-time vascular bypass of the lower extremity depends in part on the likelihood of subsequent need for autogenous conduit for another leg or heart bypass. The true frequency of these later events is not known. To answer this question, we analyzed a database of infrainguinal and coronary artery bypasses (CABG) performed at one institution between January 1980 and July 1995, to determine how many patients required subsequent infrainguinal bypass or CABG after their initial leg bypass. Five hundred and seventy-two infrainguinal bypasses were performed on 440 patients (mean age 63.9); average follow-up was 5.6 years. The clinical philosophy favored autogenous vein for first bypass, which was used in 84% of first operations performed during the study period while prosthetic material was used in 16%. For patients in which vein was used for the first operation, and who went on to have a second operation, the use of prosthetic conduit rose from 16% of operations to 27% (p < 0.05). The rate of subsequent CABG after leg bypass was very low, 2% at 5 years, 3% at 10 years. The cumulative probability of requiring a subsequent infrainguinal bypass was 27% at 5 years, 32% at 10 years. Of these, 46% were ipsilateral and 54% were contralateral. Considering only subsequent tibial bypasses (where vein might be considered obligatory), the cumulative 5-year rate of subsequent leg bypass was only 13%. Another bypass was most likely to occur within the first 3 years, rarely thereafter. In summary, after primary infrainguinal bypass, additional procedures using vein may arise in 1/4 to 1/3 of patients, mostly in the first 3 years. However, only 13% will definitely need vein for tibial bypass in 5 years, and subsequent CABG is uncommon.

Aged↗
PubMed1998

Arecoline desensitizes carbachol-stimulated phosphatidylinositol breakdown in rat brain cortices.

To understand the effects of arecoline administration on the muscarinic cholinergic signaling pathway, rats were injected with arecoline, 10 mg/kg i.p., and the carbachol-stimulated phosphoinositide breakdown in rat brain cortical slices was examined. In vivo administration of arecoline resulted in inhibition of carbachol-stimulated phosphoinositide turnover in rat brain cortical slices. Arecoline was a partial agonist with peak effects of 30% of the maximum as obtained with carbachol. Coaddition of arecoline inhibited the carbachol-stimulated phosphoinositide breakdown. Pretreatment of rat brain cortical slices with arecoline in vitro resulted in a dose-dependent inhibition of carbachol-stimulated [3H]inositol monophosphate accumulation. The inhibition occurred rapidly, with half-maximal inhibition occurring at 15 min and maximal inhibition achieved within 60 min. The inhibition of phosphoinositide breakdown was recovered 1 h after arecoline was removed. When synaptoneurosomes were used for the ligand binding studies, arecoline pretreatment was found to have decreased the maximal ligand binding (Bmax) without inducing any marked change in binding affinity (K(D)). The influence could be recovered by incubating the synaptoneurosomes in the absence of arecoline for 2 h. Taken together, these data suggest that the underlying mechanism by which phosphoinositide turnover is inhibited is arecoline-induced receptor sequestration.

Animals↗
PubMed1998

Prevalence of unilateral hearing loss in children: the National Health and Nutrition Examination Survey II and the Hispanic Health and Nutrition Examination Survey.

We compared population-based prevalence rates of unilateral hearing loss among African-American, Cuban-American, Mexican-American, Puerto Rican, and non-Hispanic White children 6 to 19 yr of age. The prevalence (per thousand) of overall hearing loss (average decibel HTL >30) ranged from 6.4 in Mexican-Americans to 12.3 in Cuban-Americans. The prevalence of moderate to profound unilateral hearing loss (average decibel HTL >50) ranged from 0.0 in Cuban-Americans to 5.2 in Puerto Ricans. No statistically significant age or gender differences were found within any of the ethnic groups. Among these five ethnic groups, it is estimated that approximately 391,000 school-aged children in the United States have unilateral hearing loss.

Adolescent↗
PubMed1998

Bolus-chase MR digital subtraction angiography in the lower extremity.

A bolus-chase magnetic resonance (MR) angiographic technique performed with a prototypic stepping table and coil holder and a 15-20-mL injection of contrast material was developed to depict the entire lower extremity. Image acquisition was synchronized with passage of the contrast medium bolus through the lower extremity. Ten subjects underwent the examination, which was performed in less than 1 minute. All major arteries were well demonstrated in all cases.

Adult↗
PubMed1998

Distal lower extremity arteries: evaluation with two-dimensional MR digital subtraction angiography.

PURPOSE: To test the hypothesis that magnetic resonance (MR) digital subtraction angiography is superior to two-dimensional time-of-flight (TOF) MR angiography for demonstration of patent arteries in the distal lower extremity. MATERIALS AND METHODS: Thirty-seven lower extremities in 23 consecutive patients were imaged with two-dimensional TOF MR angiography and two-dimensional MR digital subtraction angiography. Images were interpreted in a randomized and blinded manner. Each lower extremity was subdivided into seven potential arterial segments. The number of digital arteries visualized was also determined. Overall image quality of MR digital subtraction and TOF angiograms was compared. The relative ability of MR digital subtraction angiography and TOF MR angiography to demonstrate patent arterial segments was assessed. RESULTS: MR digital subtraction angiography was significantly superior to TOF MR angiography for demonstration of patent arterial segments and digital arteries (P < .001). MR digital subtraction angiographic images were qualitatively superior to TOF images (P < .001). CONCLUSION: Two-dimensional MR digital subtraction angiography is superior to two-dimensional TOF MR angiography for help in identifying patent segments in the distal lower extremity.

Adult↗
PubMed1998

Tetracyclines inhibit connective tissue breakdown by multiple non-antimicrobial mechanisms.

A seminal experiment involving a germ-free rat model of connective tissue breakdown (followed soon thereafter by a series of in vitro studies) identified an unexpected non-antimicrobial property of tetracyclines (TCs). This ability of TCs to inhibit matrix metalloproteinases (MMPs) such as collagenase was found to reflect multiple direct and indirect mechanisms of action, and to be therapeutically useful in a variety of dental (e.g., adult periodontitis) and medical (e.g., arthritis, osteoporosis, cancer) diseases. The site on the TC molecule responsible for its MMP-inhibitory activity was identified which led to the development of a series of chemically modified non-antimicrobial analogs, called CMTs, which also have therapeutic potential but do not appear to induce antibiotic side-effects. Longitudinal double-blind studies on humans with adult periodontitis have demonstrated that a sub-antimicrobial dose of doxycycline (previously reported to suppress collagenase activity in the periodontal pocket) is safe and effective and has recently been approved by the FDA as an adjunct to scaling and root planing.

Animals↗