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Biomedical subjects

L T Kim

Publications and source records attributed to L T Kim.

At least 19 recordsLinked to original sources
PubMed2001

FAK induction in keratinocytes in an in vitro model of reepithelialization.

During reepithelialization, keratinocytes must become activated in order to migrate over the provisional extracellular matrix of the wound. Previously we have shown that focal adhesion kinase (FAK) is induced in activated keratinocytes. The mechanisms responsible for keratinocyte activation are unknown. Here we use an organ culture system to investigate FAK up-regulation and regulation of keratinocyte activation. Normal human skin was cultured on type I collagen. Keratinocytes migrated out of the explant onto the supporting collagen. Immunostaining for FAK showed induction in the migrating epithelium and also in the center of the explant some distance from the cut edge. Cells from the center of the explant expressed FAK and showed the activated phenotype as defined by their ability to spread on collagen. Since FAK is a tyrosine kinase, the tyrosine kinase inhibitors genistein or herbimycin A were added to the explant medium for 24 h. Inhibition of tyrosine kinase activity delayed epithelial migration, but keratinocytes were able to begin migrating after removal of the inhibitors. We conclude that FAK is up-regulated in keratinocytes in this whole skin explant model. Furthermore FAK up-regulation and keratinocyte activation are not confined to the migrating cells but are found in cells some distance from the skin margin. These data suggest that (1) cell migration, contact with wound matrix molecules, loss of cell-cell contact, or loss of basement membrane contact is not necessary for FAK up-regulation or keratinocyte activation; and (2) tyrosine kinase signaling pathways are important for reepithelialization.

Cell Movement↗
PubMed2001

Radiologic characterization of adrenal masses: the role of computed tomography--derived attenuation values.

BACKGROUND: Recent studies suggest that low computed tomography (CT) attenuation values can be used to differentiate benign adrenal adenomas from non-adenomas. We examined the utility of non-enhanced CT attenuation values of <or=10 Hounsfield units (HU) in differentiating adrenal adenomas from non-adenomas. METHODS: During a 25-month period, patients who underwent adrenalectomy for adrenal masses visualized on abdominal CT were evaluated. Histopathologic examination of the excised adrenal mass was the gold standard for diagnosis. Patients who have undergone contrast-enhanced CT and those with bilateral adrenal masses were excluded. Statistical analysis was performed with the Student t test. RESULTS: Fourteen patients met study criteria. Seven adenomas and 7 non-adenomas were identified. Mean CT attenuation values were 29 +/- 18 HU. There were no differences in age or tumor weight and size between groups. Adrenal adenomas had significantly lower attenuation values compared with non-adenomas, 17 +/- 14 HU versus 43 +/- 11 HU, (P < .05). The sensitivity-to-specificity ratio for diagnosing an adrenal adenoma was 43%:100%, whereas the positive and negative predictive values were 100% and 64%, respectively. All adrenal masses with attenuation values of <or=10 HU were adenomas. CONCLUSIONS: The attenuation value of <or=10 HU on non-enhanced CT correctly identifies adrenal adenomas and is highly predictive of the diagnosis of adenoma.

Adenoma↗
PubMed2000

Focal adhesion kinase up-regulation and signaling in activated keratinocytes.

BACKGROUND: During wound healing keratinocytes undergo a process called "activation" that enables the cells to spread and migrate on wound matrix molecules. Focal adhesion kinase (FAK) is a key component of integrin-mediated intracellular signaling. We investigated the induction of FAK and its signaling activity during keratinocyte activation. MATERIALS AND METHODS: Keratinocytes were harvested from normal human skin. Previous work has shown that culture of keratinocytes causes activation in a manner similar to reepithelialization. Freshly isolated, unactivated cells were compared with cultured, activated cells. Activated cells were further examined either as growing colonies or after replating on type I collagen. FAK content was assessed by Western blotting. FAK distribution was shown using indirect immunofluorescence. FAK signaling activity was assessed using an antiphosphotyrosine antibody. RESULTS: FAK was not detectable by Western blotting in freshly isolated cells. In contrast FAK was detected in activated cells. FAK was up-regulated between Days 2 and 4 after cell isolation from skin. Immunostaining of activated, growing keratinocyte colonies in vitro showed a diffuse, cytoplasmic pattern. When these cells were replated on collagen, FAK became concentrated in focal adhesions. Lysates from replated cells showed increased tyrosine phosphorylation of FAK. CONCLUSIONS: In summary FAK is induced in keratinocytes in a time course comparable to that of activation. FAK is phosphorylated and undergoes redistribution to focal adhesions when cells are plated on the beta(1) integrin ligand collagen. These data suggest that induction of FAK and subsequent FAK-induced signaling may be responsible for changes in integrin-mediated behavior of activated keratinocytes during reepithelialization.

Cells, Cultured↗
PubMed2000

A clinical pathway for inguinal hernia repair reduces hospital admissions.

BACKGROUND: Clinical pathways have been advocated as a means to improve and standardize patient care while reducing costs through improved efficiency. This study examines the hypothesis that development of a clinical pathway reduces hospital admissions in a Veterans Affairs (VA) medical center. MATERIALS AND METHODS: For the year prior to June 1997, 168 elective inguinal herniorrhaphies were performed. This constituted the prepathway (pre-P) group. One hundred ninety-six elective inguinal herniorrhaphies were performed during the year following institution of the clinical pathway-the postpathway (post-P) group. RESULTS: Hospital admissions were compared between the two groups. In the pre-P group 61 of the 168 patients (36%) were admitted while 29 of the 196 patients (15%) in the post-P group were admitted (P < 0.001). In the pre-P group 27 of the 53 patients reviewed (51%) had either no justification or inadequate justification for admission. In the post-P group 8 of the 29 patients admitted (28%) had inadequate justification (pre-P vs post-P, P = 0.124). Common reasons for admission included pain, perioperative complications, and concurrent medical problems or surgical procedures. The most common single cause other than pain was urinary retention. The average age of patients requiring admission was greater both pre-P and post-P. CONCLUSIONS: We conclude that institution of a clinical pathway for inguinal herniorrhaphy decreased hospital admissions. The reasons for this decrease are probably multifactorial and include improvements in physician and staff awareness. The decrease in unnecessary admissions should result in more efficient use of hospital resources.

Age Factors↗
PubMed2000

Identification of high-risk residents.

BACKGROUND: Identification of high-risk residents allows remediation and support for administrative action when necessary. This study characterizes differences in documentation of marginally performing residents in a general surgery residency. METHODS: High-risk residents were identified by the former program director. Twenty-four of one hundred fifteen residents over a 10-year period had one to four problematic areas: cognitive, synthetic, family/health, and interpersonal skills. Outcomes included finished (18), voluntary withdrawal (1), and involuntary withdrawal (5). A case-control study matching controls to cases by date of entry into the training program was used. Records were reviewed for demographics, preentry qualifications, American Board of Surgery In-Training Exam (ABSITE) scores, letters of complaint or praise, events of counseling, and monthly ratings. The records of 48 residents were reviewed. Ward evaluations were on eight categories with a 5-point Leikert scale (3-unacceptable to 7-outstanding). The evaluation score assigns points only to low ratings. High scores represent progressively poorer performance. A Wilcoxon signed ranks test was used to compare the cases and controls for continuous variables. The McNemar test was used in comparisons of categorical data with binary outcomes. Exact P values are reported. RESULTS: Objective data were similar for both groups. Study residents tended to score higher on monthly evaluations at Year 2 and by Year 3 this achieved significance (0.026). Study residents were more likely to have negative faculty letters (0.016) and events of counseling by a faculty member (0.017) and the program director (0.005). CONCLUSIONS: Identification of residents at risk should begin as early as possible during training. A combination of faculty evaluations and evidence of letters of counseling can detect high-risk residents. Programs may use such indicators to support decisions regarding remedial work or administrative action.

Documentation↗
PubMed2000

Factors affecting recurrence following incisional herniorrhaphy.

The purpose of this study was to determine the influence of chronic illness, obesity, and type of repair on the likelihood of recurrence following incisional herniorrhaphy. The medical records of 77 patients who underwent elective repair of a midline incisional hernia at the Dallas Veterans Affairs Medical Center between 1991 and 1995 were reviewed. Demographic data, presence of chronic illnesses, type of repair, and presence of recurrence were noted. Ninety-six percent of the patients were men, with an average age of 59 years. More than 50% of the patients had chronic lung or cardiac diseases and more than 40% weighed > or = 120% of their ideal body weight and had a body mass index (BMI) > or = 30. Sixty-two percent of the patients underwent primary reapproximation of the fascia (tissue repair), whereas 38% underwent repair with prosthetic material (prosthetic repair). The overall recurrence rate was 45%, with a median follow-up of 45 months (range 6-73). Seventy-four percent of the recurrences presented within 3 years of repair. The recurrence rate for those patients undergoing a tissue repair was 54%, whereas the recurrence rate following prosthetic repair was 29%. The incidence of recurrence for patients with pulmonary or cardiac disease or diabetes mellitus was similar to that of patients without these illnesses. The percent ideal body weight and BMI of patients who developed a recurrent hernia, particularly following a prosthetic repair, were significantly greater than those of patients whose repairs remained intact. These data strongly support the use of prosthetic repairs for incisional hernias, particularly in patients who are overweight.

Aged↗
PubMed2000

Prostaglandins potentiate U-46619-induced pulmonary microvascular dysfunction.

The induction of cyclooxygenase is an important event in the pathophysiology of acute lung injury. The purpose of this study was to examine the synergistic effects of various cyclooxygenase products (PGE(2), PGI(2), PGF(2alpha)) on thromboxane A(2) (TxA(2))-mediated pulmonary microvascular dysfunction. The lungs of Sprague-Dawley rats were perfused ex vivo with Krebs-Henseleit buffer containing indomethacin and PGE(2) (5 x 10(-8) to 1 x 10(-7) M), PGF(2alpha) (7 x 10(-9) to 5 x 10(-6) M), or PGI(2) (5 x 10(-8) to 2 x 10(-5) M). The TxA(2)-receptor agonist U-46619 (7 x 10(-8) M) was then added to the perfusate, and then the capillary filtration coefficient (K(f)), pulmonary arterial pressure (Ppa), and total pulmonary vascular resistance (RT) were determined. The K(f) of lungs perfused with U-46619 was twice that of lungs perfused with buffer alone (P = 0.05). The presence of PGE(2), PGF(2alpha), and PGI(2) within the perfusate of lungs exposed to U-46619 caused 118, 65, and 68% increases in K(f), respectively, over that of lungs perfused with U-46619 alone (P < 0.03). The RT of lungs perfused with PGE(2) + U-46619 was approximately 30% greater than that of lungs exposed to either U-46619 (P < 0.02) or PGE(2) (P < 0.01) alone. When paired measurements of RT taken before and then 15 min after the addition of U-46619 were compared, PGI(2) was found to attenuate U-46619-induced increases in RT (P < 0.01). These data suggest that PGE(2), PGI(2), and PGF(2alpha) potentiate the effects of TxA(2)-receptor activation on pulmonary microvascular permeability.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1999

Nitric oxide and thromboxane A2-mediated pulmonary microvascular dysfunction.

OBJECTIVES: To examine whether the lung releases nitric oxide (NO) in response to thromboxane A2 and to examine the local release of NO as a protective compensatory mechanism by which the lung responds to the proinflammatory and vasoactive effects of thromboxane A2. DESIGN: The lungs of anesthetized Sprague-Dawley rats were perfused in vitro with Krebs-Henseleit buffer that contained an inhibitor of NO synthase (nitroglycerinenitro-L-arginine methyl ester [L-NAME]) (10(-4) mol/L), an NO donor (sodium nitroprusside) (10(-8) mol/L), or perfusate alone. Following equilibration, the thromboxane A2 receptor agonist 9,11-dideoxy-11alpha, 9alpha-epoxymethanoprostaglandin F2alpha(U-46619) (7.1 X 10(-8) mol/L) was added to the perfusate. Fifteen minutes later, the capillary filtration coefficient, pulmonary arterial pressure, and vascular resistance were measured. Pulmonary NO release was assessed by quantitating the release of cyclic guanosine monophosphate into the perfusate. RESULTS: The capillary filtration coefficient of lungs exposed to U-46619 was 3.5 times greater than that of lungs perfused with buffer alone (P<.05). The addition of sodium nitroprusside reduced the increase in capillary filtration coefficient associated with U-46619 by 50% (P<.05) whereas L-NAME had no effect. The addition of U-46619 to the perfused lung caused a 3.0+/-0.4 mm Hg increase in pulmonary artery pressure (P<.01) with a corresponding rise in total vascular resistance (P<.05). This effect was exacerbated by L-NAME (P<.05) and inhibited by sodium nitroprusside (P<.05). Exposure of the isolated lungs to U-46619 caused a 4-fold increase in cyclic guanosine monophosphate levels within the perfusate. CONCLUSION: These data are consistent with the hypothesis that NO release may be an important protective mechanism by which the lung responds to thromboxane A2.

Animals↗
PubMed1999

The validity of quick intraoperative parathyroid hormone assay: an evaluation in seventy-two patients based on gross morphologic criteria.

BACKGROUND: Parathyroidectomy for primary hyperparathyroidism has conventionally required identification of all parathyroid glands with excision of grossly abnormal glands. Using this approach, cure rates exceed 95%. Directed cervical exploration has been advocated using quick intraoperative parathyroid hormone (QPTH) assay with preoperative localization. Adoption of this approach requires validation of the accuracy of QPTH assay. METHODS: Patients with primary hyperparathyroidism undergoing bilateral neck exploration during a 31-month period were reviewed. Uniglandular (UGD) or multiglandular (MGD) disease was determined by gross morphologic criteria. QPTH assays were performed before skin incision and at 5, 10, and 20 minutes after excision of each abnormal gland. A 10-minute QPTH decrease of 50% from baseline levels indicated curative excision. These data were not used to guide extent of exploration or tissue resection. RESULTS: Of 72 patients, 55 (76%) had UGD and 17 (24%) had MGD. QPTH assay accurately predicted the disease state in 89%. Four (7%) UGD patients did not have an appropriate QPTH decline at 10 minutes. Four (24%) MGD patients had an inappropriate QPTH decline at 10 minutes. CONCLUSIONS: Using QPTH guided exploration, 6% (4 of 72) of patients would undergo unnecessary extended exploration and 6% (4 of 72) (95% CI, 1% to 13%) may require reoperation for unidentified MGD. These results validate the accuracy of QPTH assay.

Calcium↗
PubMed1998

Integrin alpha v promoter activity in keratinocytes.

BACKGROUND: During reepithelialization keratinocytes show increased expression of the integrin subunit alpha-v. We have investigated the promoter region of the alpha-v integrin subunit to learn more about its regulation. METHODS: The promoter region of the human integrin alpha-v gene was cloned into a luciferase reporter vector. Deletional mutants were created using PCR. Computerized sequence analysis was performed using the Wisconsin Package. Gel-shift analysis was performed using keratinocyte nuclear extracts and oligonucleotides spanning th regions of interest. RESULTS: Deletion from -522 bp to -235 resulted in no discernible effect on promoter activity. In contrast deletion of the next 22 bp, which included a putative ets binding site, reduced activity by approximately half. Further deletion to -139 bp essentially abolished promoter activity. Computer searching of this region of the integrin alpha-v promoter revealed two tandemly repeated motifs, TCCTCCTCC, that had previously been implicated in the function of the epidermal growth factor receptor (EGFR) promoter. Comparison of the alpha-v integrin promoter to the EGFR promoter revealed an area of high homology in this region. Gel-shift analysis revealed binding of a single-strand specific DNA binding protein to single stranded oligos comprising these motifs, but no binding of factors to the double- stranded oligo containing the ets binding site. CONCLUSIONS: In keratinocytes alpha-v integrin expression is controlled by a region of the promoter with high homology to the epidermal growth factor receptor promoter This region binds single-strand specific DNA binding proteins that are likely to be important in controlling transcription.

Antigens, CD↗
PubMed1998

Alveolar macrophage response to remote organ injury.

Intestinal reperfusion (IR)-induced pulmonary edema has been related to endogenous pulmonary thromboxane A2 (TxA2) release. This study examines the hypothesis that alveolar macrophages (aMphis) activated during IR are an important cellular source of TxA2 in this model. Anesthetized Sprague Dawley rats underwent 120 min of intestinal ischemia and 60 min of reperfusion (IR) or sham operation (Sham). aMphis were isolated by bronchoalveolar lavage and incubated in Krebs buffer for 30 min, after which the supernatant was analyzed for TxB2 (metabolite of TxA2) and prostaglandin E2. Other parameters of aMphi activation measured included lysosomal enzyme release (beta-glucuronidase), superoxide (O2-) release, and procoagulant activity. aMphis from animals sustaining IR generated more than twice as much TxA2 and prostaglandin E2 as did those isolated from controls (p < .05). Other evidence of aMphi activation included a nearly 100-fold increase in procoagulant activity, a 7-fold increase in beta-glucuronidase release, and a 2.5-fold increase in O2- release over that of controls (p < .05). These data suggest that TxA2 is a major eicosanoid product of aMphis during IR and that aMphis may be an important cellular participant in IR-induced pulmonary microvascular injury, either directly by releasing O2-, lysosomal enzymes, and pro-coagulant factors, or indirectly by generating TxA2.

Animals↗
PubMed1997

Evidence that beta1 integrins in keratinocyte cell-cell junctions are not in the ligand-occupied conformation.

Integrins are a family of heterodimeric cell surface molecules that function as adhesion receptors in cell-cell and cell-extracellular matrix contact. Integrins of the beta1 family are found on keratinocytes clustered at sites of cell-cell junctions both in culture and in normal skin. The possibility that these integrins function in cell-cell adhesion has been both supported and refuted in recent conflicting publications. Rather than testing further for the presence or absence of an interaction, we present evidence to show that beta1 integrins in keratinocyte cell-cell junctions are in the non-ligand-occupied conformation. We transfected keratinocytes with a construct that expresses a chimeric cell surface molecule containing the integrin beta1 cytoplasmic tail. This chimera is thought to mimic the ligand-occupied receptor and has previously been shown to be actively localized to focal adhesions in fibroblasts. We find that keratinocytes are also able to localize this chimera in focal adhesions but do not localize it to areas of cell-cell junctions. A monoclonal anti-beta1 antibody that has been previously shown to preferentially recognize ligand-occupied beta1 receptors was used to stain keratinocytes. This antibody showed staining of focal adhesions, with little or no staining of cell-cell junctions. In contrast, four other anti-beta1 antibodies showed strong, preferential staining at cell-celljunctions. Double staining confirmed that both the conformation-specific monoclonal antibody and a pan-beta1 antibody were capable of recognizing the same focal adhesions. Taken together, these data indicate that integrins in cell- cell junctions of keratinocytes are in the non-ligand-occupied conformation. Although we do not directly prove the absence of an integrin-integrin interaction at this site, we show that any such interaction does not induce the ligand-occupied conformation and, therefore, is less likely to play a major role in cytoskeletal re-organization or signal transduction.

Antibodies, Monoclonal↗
PubMed1997

The regulation of expression of integrin receptors.

The integrins are a family of cell surface receptors that mediate cell-extracellular matrix and cell-cell interactions. The quantities and activities of these receptors are modulated during a wide variety of biological processes. A variety of agents have been found to affect expression of integrins and their function. These include cytokines, hormones, and pharmacologic agents. Mechanisms regulating integrin expression and function include regulation of protein levels by transcriptional or posttranscriptional mechanisms, alteration of protein structure by alternative splicing of mRNA, mobilization to the cell surface of preexisting intracellular stores of integrins, and modulation of receptor activity (inside-out signaling). We review studies that assess the effects of external agents on integrin levels using the cytokine TGFbeta as an example. We also review studies that analyze integrin regulation with an emphasis on the control of integrin gene transcription. This review shows that the strategies for integrin modulation are quite complex. This regulatory sophistication is likely necessary, given the critical role that integrins play in the myriad social interactions of cells.

Animals↗
PubMed1992

Altered glycosylation and cell surface expression of beta 1 integrin receptors during keratinocyte activation.

We studied the mechanism by which cell adhesiveness becomes activated when keratinocytes are removed from skin and placed into cell culture. Our results suggest that activation involves altered beta 1 integrin subunit glycosylation accompanied by an increase in cell surface beta 1 integrin receptors. Activated keratinocytes contained two forms of the beta 1 integrin subunit, approximately 93 kDa and approximately 113 kDa. As shown by pulse-chase experiments, the smaller represented the cytoplasmic precursor of the larger, and only the 113 kDa mature form was detected in integrin receptors expressed at the cell surface. Pre-activated keratinocytes contained beta 1 integrin subunits ranging from approximately 97 to 110 kDa. These beta 1 subunits had been processed through the Golgi, based on resistance to endoglycosidase-H treatment, and were not converted to 113 kDa subunits during subsequent cell culture. Experiments with endoglycosidase-F showed that differences in the apparent sizes of beta 1 integrin subunits observed in pre-activated and activated keratinocytes could be attributed to differences in subunit glycosylation. Smaller beta 1 subunits found in pre-activated keratinocytes, like the precursor beta 1 subunits of activated cells, appeared to be less efficient in reaching the cell surface. Overall, a approximately 10-fold increase in the level of cell surface integrin receptors occurred concomitant with the increased proportion of 113 kDa beta 1 subunits found in activated cells. Endoglycosidase-F experiments also indicated that there were changes in keratinocyte alpha subunits associated with beta 1. In related experiments, keratinocytes cultured in low Ca2+, serum-free MCDB medium for 4 days proliferated but their adhesiveness did not become activated. Therefore, keratinocyte proliferation and activation of adhesion are regulated separately. Finally, substantial activation of keratinocytes was observed when serum was added to cells cultured in MCDB with serum, indicating a role for serum factors in the activation process.

Animals↗
PubMed1991

Altered processing of integrin receptors during keratinocyte activation.

We used monoclonal antibodies against specific integrin subunits to examine the role of integrin receptors in keratinocyte activation. We found that before activation, beta 1 subunits in keratinocytes showed a diffuse distribution, whereas after activation, keratinocytes organized beta 1 receptors into marginal adhesion plaques. In immunoprecipitation experiments with antibodies against beta 1 integrin subunits, we found mostly immature subunits synthesized in keratinocytes freshly harvested from skin. Moreover, integrin receptor complexes immunoprecipitated from these cells by monoclonal antibodies against alpha 2, alpha 3, or alpha 5 subunits contained only immature beta 1 subunits. With keratinocytes cultured 4-7 days, anti-beta 1 antibodies immunoprecipitated mostly mature beta 1 subunits, and integrin complexes immunoprecipitated from cultured cells by anti-alpha subunit antibodies contained mostly mature beta 1 subunits. Antibodies directed against beta 1 subunits also inhibited keratinocyte migration. Based on these results, we suggest that up-regulation of migration by activated keratinocytes depends on changes in processing of pre-beta 1 subunits to mature beta 1 subunits. We also studied the distribution of integrin subunits in skin and on keratinocytes migrating out of skin explants. Whereas beta 1, alpha 2, and alpha 3 subunits were detected in keratinocytes in skin and migrating out of explants, alpha 5 subunits were observed only in migrating cells.

Cell Differentiation↗
PubMed1989

Cervical adenocarcinoma in women with nasopharyngeal carcinoma (NPC).

Multiple primary cancers account for only 0.38% of all cases in the Singapore Cancer Registry. The close temporal association of nasopharyngeal carcinoma (NPC) in three Chinese women with uterine cervical adenocarcinoma was observed in our department within a 3-month period; one other case was extracted from the local literature. Although NPC is a common neoplasm in local Chinese women, uterine cervical adenocarcinomas comprise only 8% of cervical cancers locally. The close occurrence of these cancers does not seem to be related to the therapy used for cervical cancer and suggests that an association of the Epstein-Barr virus (EBV) with uterine cervical adenocarcinoma should be further investigated.

Adenocarcinoma↗
PubMed1985

Stroke volume in-vivo using multiple 2D echo views from one echo window.

We recently validated in-vitro a new mathematical approach to echocardiographic volume calculation. With this method all echo views are acquired from one point as the transducer is tilted. The angle of tilt of the transducer must be measured. A tilt frame was designed for use in-vivo that does not interfere with imaging. The method was then tested in-vivo by comparing echocardiographic stroke volume with stroke volume determined by the acetylene rebreathing technique. Normal subjects were studied with either lower body negative pressure or continuous isoproterenol infusion. The regression line was Echo SV=-19.7 + 1.2*Acet SV, with R=0.80, SEE=17.1, MPE=17%. We conclude that this is an accurate, non-geometric method for ventricular volume calculation.

Acetylene↗