Search PubMed⌕ Search

Biomedical subjects

Y Kim

Publications and source records attributed to Y Kim.

At least 523 records · Page 29Linked to original sources
PubMed1996

Expression of the C terminus of the amyloid precursor protein alters growth factor responsiveness in stably transfected PC12 cells.

The amyloid precursor protein (APP) is a molecule centrally involved in Alzheimer disease pathology, but whose normal function is still poorly understood. To investigate the consequences of increased intracellular production of various regions of APP on cellular physiology, we stably transfected PC12 cells with the C-terminal 100 amino acids of the human APP. In eight transfected clones that express the APP(C100) protein, exposure to nerve growth factor (NGF) did not promote differentiation. Transfectants continued to divide and failed to elaborate extensive neurites, whereas control PC12 cells, mock-transfected PC12 cells, and a nonexpressing transfected cell line did develop neurites and stopped dividing after NGF stimulation. Unlike NGF treatment, treatment with basic fibroblast growth factor profoundly accelerated neurite outgrowth in transfected cells. Also, a dramatic increase in a tyrosine phosphatase activity was noted. Expression and accumulation of APP C100 protein in PC12 cells results in an abnormal response to growth factor stimulation.

Amyloid beta-Protein Precursor↗
PubMed1996

Small bowel preservation using a cavitary two-layer (University of Wisconsin solution/perfluorochemical) cold storage method.

Preservation of the small bowel by a cavitary two-layer (University of Wisconsin solution [UW]/perfluorochemical) cold storage method was evaluated in the heterotopic rat segmental small bowel transplant model. Simple cold storage UW was effective only for 24-hr preservation. However, the cavitary two-layer method using UW made it possible to prolong preservation time up to 48 hr. Furthermore, without oxygen bubbling, the cavitary two-layer method was not effective for 48-hr preservation. Histologic studies of grafts preserved by the cavitary two-layer method for 48 hr at 7 days after transplantation showed normal architecture of the intestinal mucosa. This study demonstrates that the oxygenation of the small bowel during preservation by the cavitary two-layer method using UW makes it possible to extend preservation time up to 48 hr in the heterotopic rat segmental small bowel transplant model.

Adenosine↗
PubMed1996

Nucleotide sequence of salicylate hydroxylase gene and its 5'-flanking region of Pseudomonas putida KF715.

The salicylate hydroxylase, a flavoprotein monooxygenase, catalyzes the decarboxylative hydroxylation of salicylate to form catechol. Nucleotide sequence of a salicylate hydroxylase gene and its 5'-flanking region in chromosomal DNA of Pseudomonas putida KF715 was analyzed. The salicylate hydroxylase was encoded in an open reading frame with 1308 base pairs which can encode a polypeptide of molecular weight 48 kDa with 435 amino acids. The open reading frame was preceded by a putative ribosome-binding sequence. A predicted amino acid sequence of the salicylate hydroxylase exhibited 84% identity with corresponding enzyme encoded in NAH7 plasmid, and 20 to 30% homologies with other similar flavoprotein monooxygenases. A 5'-flanking sequence of the salicylate hydroxylase gene exhibited extensive homology with promoter and nahR-binding site of sal operon in NAH7 plasmid.

Amino Acid Sequence↗
PubMed1996

Resuscitation of ischemically damaged pancreas during short-term preservation at 20 degrees C by the two-layer (University of Wisconsin solution/perfluorochemical) method.

We have shown that 24-hr preservation by a two-layer (University of Wisconsin solution [UW]/perfluorochemical [PFC]) cold storage method allows tissue ATP synthesis and makes it possible to resuscitate a canine pancreas subjected to 90 min of warm ischemia. The purpose of this study was to examine whether increasing preservation temperature to 20 degrees C makes it possible to shorten a preservation period for recovery of ischemically damaged pancreas grafts. After 90 min of warm ischemia, canine pancreas grafts were preserved using the two-layer (UW/PFC) method for 1 to 8 hr at 20 degrees C, and then autotransplanted. A K-value of intravenous glucose tolerance test more than 1.0 at 2 weeks after transplantation was considered graft survival. ATP tissue levels were measured by high performance liquid chromatography at the end of preservation. Pancreatic tissue perfusions were measured using an H2 clearance technique after 30 min to 4 hr of reperfusion. Pancreas grafts subjected to 90 min of warm ischemia were not viable (0/5, control group). However, 3- and 5-hr preservations made it possible to recover the ischemically damaged pancreas (3/5 and 5/5, respectively), although 1- and 8-hr preservations were not successful (0/3 and 0/3, respectively). ATP tissue levels in 1-hr-preserved grafts were 2.55 +/- 0.38 mumol/g dry weight and were significantly lower compared with the levels in 5- and 8-hr-preserved grafts, 9.40 +/- 2.09 (P < 0.01) and 7.37 +/- 1.06 (P < 0.01), respectively. On the other hand, pancreatic tissue perfusions in 8-hr-preserved grafts after 2 hr of reperfusion were 28.50 +/- 7.52 ml/100 g/min and were significantly lower than the values in 1- and 5-hr-preserved grafts, 66.0 +/- 11.22 (P < 0.01) and 57.10 +/- 4.40 (P < 0.01), respectively. It was suggested that 1-hr-preservation was not enough to synthesize ATP, which was essential to repair damaged cells, although vascular microcirculation at reperfusion was maintained and 8-hr preservation incurred microcirculatory disturbances, although ATP for repairing damaged cells was synthesized. We conclude that 3- to 5-hr preservation at 20 degrees C by the two-layer (UW/PFC) method accelerates ATP synthesis, which is essential for repairing damaged cells and protects vascular microcirculation. This makes it possible to resuscitate ischemically damaged pancreases faster. This method holds promise for pancreas-kidney transplantation from cardiac arrest donors.

Adenosine↗
PubMed1996

Gas-generating systems in acute renal allograft rejection in the rat. Co-induction of heme oxygenase and nitric oxide synthase.

Gases are now viewed as biologic messengers, and in this regard, carbon monoxide and nitric oxide are incriminated in signaling processes in neural tissue. Carbon monoxide is generated by heme oxygenase (HO), an enzyme inducible by heme, cytokines, and oxidative stress and considered an antioxidant response; nitric oxide is generated by nitric oxide synthase, an enzyme also inducible by cytokines. Since mononuclear cells infiltrate the acutely rejecting kidney, and foster within the kidney oxidative stress and a cytokine-enriched milieu, we examined the expression of these enzymes in acute renal allograft rejection (AR) (Brown Norway kidney to a Lewis rat; n = 17) and in control isografts (Lewis kidney to a Lewis rat; n = 17). No immunosuppressives were used. We found marked induction of HO mRNA and protein in renal allografts at day 5 after transplantation. Prominent expression of HO protein, as detected by immunofluorescence, was observed in the mononuclear cells infiltrating the renal allograft. More than 80% of these cells were macrophages, as identified by positive staining with ED1 antibody. ED1+ cells were rare in isografts and did not stain for HO. We also found co-expression of mRNA and protein for the inducible isoform of nitric oxide synthase (iNOS) in AR at day 5 after transplantation. Induction of HO and iNOS may reflect the cellular effect of diverse cytokines elaborated in the rejecting kidney. HO may enable the macrophage to degrade heme-containing proteins released from erythrocytes and other damaged cells; alternatively, induction of HO may defend the macrophage against oxidant injury. Increased nitric oxide, as a result of iNOS activity, may antagonize the vasoconstrictive effects of a number of mediators (i.e., thromboxane and endothelin) present in acute rejection; conversely, nitric oxide may prove cytotoxic through a number of recognized effects. Our studies provide the first demonstration of the induction of HO in the rejecting renal allograft as well as the first demonstration in vivo for the induction of HO in macrophages at the site of an inflammatory response. Such expression, linked as it is to the expression of iNOS, indicates that the macrophage mimics the behavior of neural cells by generating these gaseous messengers; thus, neural cells are not alone in deploying these mediators. Through a number of effects, these products of HO and iNOS may influence the nature and severity of tissue injury in AR.

Animals↗
PubMed1996

Cold shock induces a major ribosomal-associated protein that unwinds double-stranded RNA in Escherichia coli.

A 70-kDa protein was specifically induced in Escherichia coli when the culture temperature was shifted from 37 to 15 degrees C. The protein was identified to be the product of the deaD gene (reassigned csdA) encoding a DEAD-box protein. Furthermore, after the shift from 37 to 15 degrees C, CsdA was exclusively localized in the ribosomal fraction and became a major ribosomal-associated protein in cells grown at 15 degrees C. The csdA deletion significantly impaired cell growth and the synthesis of a number of proteins, specifically the derepression of heat-shock proteins, at low temperature. Purified CsdA was found to unwind double-stranded RNA in the absence of ATP. Therefore, the requirement for CsdA in derepression of heat-shock protein synthesis is a cold shock-induced function possibly mediated by destabilization of secondary structures previously identified in the rpoH mRNA.

Amino Acid Sequence↗
PubMed1996

Biliary-enteric anastomosis by means of a single layer of serosubmucosal sutures without T-tube drainage.

BACKGROUND: To lessen anastomotic stricture after biliary-enteric anastomosis, we developed a new biliary-enteric anastomosis that uses a single layer of interrupted serosubmucosal sutures without T-tube drainage. OBJECTIVE: To evaluate the safety and reliability of this new technique in a canine model of choledochoduodenostomy. METHODS: In 10 beagles, the common bile duct (2 to 3 mm in diameter) was ligated close to the duodenum with 3-0 polyglactin. On the fifth day after operation, the serum bilirubin level was elevated (137 to 205 mumol/L [8 to 12 mg/dL]) and the bile duct was dilated. The anastomosis between serosubmucosal layers of the dilated bile duct (8 to 10 mm in diameter) and duodenum was accomplished with interrupted sutures of 6-0 polyglactin with two needles. Stitches were inserted in the submucosal plane at the cut edge of the duct and duodenum to appose the mucosa accurately and to avoid accidental perforation of the entire thickness of the duct and duodenum. A T tube was not placed. RESULTS: There was no anastomotic leakage and the bilirubin level was normalized (14 to 17 mumol/L [0.8 to 1.0 mg/dL]) 7 days after operation for anastomosis. Histologic examination of specimens removed 6 or 12 months after operation showed good connective-tissue union and good mucosal continuity between the bile duct and the duodenum. There was no mucosal scarring and contracture or stricture formation. CONCLUSION: This new technique is simple and reliable and is recommended as an alternative method for restoring the continuity between the bile duct and intestinal tract after operation for obstructive jaundice caused by benign and malignant stricture of the bile duct.

Animals↗
PubMed1996

Ultrafast high resolution separation of large DNA fragments by pulsed-field capillary electrophoresis.

Pulsed-field capillary electrophoresis (PFCE) in buffers containing ultradilute polymer solutions is used to separate long chain dsDNA in less than 4 min. Separations are shown to work with chain lengths below 10 kbp and greater than 1.5 Mbp. Several pulse protocols have been examined. If running time is to be minimized, a field inversion with higher peak amplitude in the forward direction than in the reverse, but with equal pulse durations, provides the best resolution. Other protocols can provide higher resolution, but only with longer running times.

Cellulose↗
PubMed1996

Multifractionated high-dose-rate brachytherapy with concomitant daily teletherapy for cervical cancer.

BACKGROUND: High-dose-rate (HDR) brachytherapy has been the preferred treatment for cervical cancer at Wayne State University since 1987. The outcome of the first 105 patients treated is analyzed. PURPOSE: To determine clinical efficacy of the HDR modality. METHODS: We reviewed 105 patients and evaluated the 88 patients treated for cervical carcinoma with HDR and external beam radiotherapy (EBRT) from August 1987 to December 1992. Patients received initial external radiation to the pelvis (total dose of 19.8 to 39.6 Gy in 11 to 22 fractions), followed by outpatient HDR brachytherapy (3 fractions/week, 386 cGy/fraction to Point A, total of 8 to 12 fractions) and concurrent daily EBRT (1.8 to 2.0 Gy) to lateral parametria. During the HDR period of treatment, step wedge transmission blocks were used to shield central pelvic tissue while treating peripheral pelvic tissues with EBRT. Patient distributions were as follows: 25, IB/IIA; 35, IIB/IIIA; and 28, IIIB/IVA. There were 56 African American and 32 Caucasian patients with mean age of 55 (range 19-89). The median follow-up was 33 months (range 20 to 76 months). Kaplan-Meier analysis was performed. RESULTS: Three-year survival rates were 88%, IB/IIA; 69%, IIB/IIIA; 56%, IIIB/IVA; and 72% overall. Local control was achieved in 71/88 (80%) of patients. Failure site was cervix or within the pelvis in 12 patients, distant metastasis only 17 patients, and combined local and distant in 5 patients. Of the failures, 82% (28/34) died within 2 years. There were 3 grade III/complications (3.4%). CONCLUSION: Results compare favorably with previous LDR experience.

Adult↗
PubMed1996

Resuscitation of ischemically damaged pancreas by the two-layer (University of Wisconsin solution/perfluorochemical) mild hypothermic storage method.

We have shown that 24-hour preservation by a two-layer [University of Wisconsin solution (UW)/perfluorochemical (PFC)] cold storage method at 4 degrees C allowed tissue ATP synthesis and resuscitated canine pancreases subjected to 90 minutes of warm ischemia. The purpose of this study was to examine whether the two-layer (UW/PFC) mild hypothermic storage method at 20 degrees C could shorten a preservation period for recovery of ischemically damaged pancreas and clarify changes of tissue adenine nucleotide metabolism and tissue perfusions. After 90 minutes of warm ischemia, canine pancreas grafts were preserved by the two-layer method and then autotransplanted. Tissue adenine nucleotide levels at the end of preservation and tissue perfusions after reperfusion were measured. Pancreas grafts subjected to 90 minutes of warm ischemia did not survive (0 of 5), without preservation. During a 5-hour preservation by the two-layer cold storage method the grafts did not synthesize enough ATP to repair damaged cell, although tissue perfusions were maintained after reperfusion. Consequently, ischemically damaged pancreases were not resuscitated (0 of 3). However, during 5-hour preservation by the two-layer mild hypothermic storage method, the grafts supplied enough ATP for processes that repair damaged cells, and tissue perfusions were maintained after reperfusion. As a result, ischemically damaged grafts were resuscitated (5 of 5). We conclude that 5-hour preservation by the two-layer mild hypothermic storage method accelerates ATP synthesis, which is essential for repairing damaged cells and protects the vascular microcirculation. This method can resuscitate ischemically damaged pancreas faster and holds promise for pancreas-kidney transplantation from cardiac arrest donors.

Adenine Nucleotides↗
PubMed1996

Object-free adaptive meshing in highly heterogeneous 3-D domains.

Traditional approaches to the generation of finite element meshes are well suited for modeling the homogeneous or mildly heterogeneous domains presented by man-made objects, but are difficult to apply to the complex 3-D domains encountered in some biomedical applications. In this paper, we describe an adaptive algorithm that automates the modeling of these domains. The method differs from traditional approaches in that no explicit description is required of the boundaries between objects with dissimilar material properties. The algorithm uses images of the tissue class to build irregular meshes, and continuity is enforced by constraining the solution at irregular nodes. Local estimates of the error in the flux solution are used to refine the mesh. For an analytic problem with a rapid change along a spherical boundary, the adaptive method converges to a 1% voltage error using 25% of the degrees of freedom required by a uniform refinement, and to a 5% voltage gradient error using 11% of the degrees of freedom. For a defibrillation model in a pig thorax, the voltage gradient solution in the ventricles of the heart converges to within 5% of a uniform mesh solution using less than 8% of the memory and processing resources required by a uniform mesh, which has been the only practical alternative for subject-specific modeling.

Algorithms↗
PubMed1996

Three-dimensional ultrasonic angiography using power-mode Doppler.

To visualize the vascular anatomy of parenchymal organs, we have developed a system for producing three-dimensional ultrasonic angiograms (3D USA) from a series of two-dimensional power-mode Doppler ultrasound (PDU) scans. PDU scans were acquired using a commercial scanner and image-registration hardware. Two-dimensional images were digitized, and specially designed software reconstructed 3D volumes and displayed volume-rendered images. The geometric accuracy of our system was assessed by scanning a flow phantom constructed from tubing. The system was tested on patients by scanning native and transplanted kidneys, and placentas. Three-dimensional images of the phantoms depicted the spatial relationships between flow within the tubing segments and contained less than 1 mm of geometric distortion. Three-dimensional images of the kidney and placenta demonstrated that spatial relationships between vasculature structures could be visualized with 3D USA. Applications of this new technique include analysis of vascular anatomy and the potential assessment of organ perfusion.

Angiography↗
PubMed1996

Automatic fetal head measurements from sonographic images.

RATIONALE AND OBJECTIVES: We designed an image processing technique to automatically measure the biparietal diameter (BPD) and head circumference (HC) from prenatal sonograms. We evaluated the performance of the algorithm by comparing the resulting measurements with those made by experienced sonographers. METHODS: Thirty-five digitized sonograms of the fetal head were obtained during routine imaging. The BPD and HC were automatically computed by detecting the inner and outer boundaries of the fetal skull using the computer vision technique known as the "active contour model." Six experienced sonographers also measured the BPD and HC on these images. RESULTS: The algorithm failed to locate the boundaries in two of the 35 cases. For the remaining cases, the mean absolute difference between the automated measurements and the average of the six observers was 1.4% for BPD and 2.9% for HC. The correlations were .999 for the BPD and .994 for the HC. The computer's measurements were no different from the six observers' measurements than the observers' measurements were from one another. CONCLUSION: The tested algorithm effectively and accurately measures BPD and HC automatically. We are currently in the process of integrating this algorithm into an ultrasound machine.

Algorithms↗
PubMed1996

Cardiac parasympathetic nervous system activity does not increase in anticipation of sleep.

Parasympathetic Nervous System (PNS) activity increases while Sympathetic Nervous System (SNS) activity remains relatively stable from wakefulness to NREM sleep. However, it is not clear whether these changes are specifically associated with NREM sleep, or whether they anticipate sleep onset. The latter may occur if ANS activity was influenced by the circadian system. This issue was investigated by conducting spectral analysis of heart beat-to-beat intervals (Periodogram method), collected from 20 healthy male and female subjects at three different times across 24 h; in the morning, just prior to normal sleep onset time, and in slow-wave sleep (SWS). Subjects were supine in all conditions and awake in the first two conditions. The high- and low-frequency peaks, reflecting PNS and SNS activity, respectively, were expressed as proportions of the total power. PNS activity decreased significantly from the morning (0.22) to the presleep period (0.19), before it increased to its maximum during SWS (0.33). In contrast, SNS activity was similar in each of the three conditions (0.07, 0.06, and 0.05 for morning, presleep and SWS, respectively). Thus there do not appear to be changes in PNS activity in anticipation of sleep, as would be predicted on the basis of a circadian influence on the PNS. Instead the increased PNS activity appears to be sleep dependent.

Adolescent↗
PubMed1996

Improved recovery after cold crystalloid cardioplegia using low-dose glutamate enrichment during reperfusion after aortic unclamping: a study in isolated blood-perfused pig hearts.

Increased glutamate utilization is a part of the metabolic adaptation to oxygen deprivation by the heart. The effect of low-dose L-glutamate (2 mmol/L) during continuous reperfusion after aortic unclamping on postcardioplegic recovery was studied in pig hearts similar in size, anatomy, and function to the human adult heart. After cold crystalloid cardioplegic arrest (CCC) with Bretschneider solution no 3, hearts were excised from pigs weighing 70-80 kgs (heart weight, average +/- SEM: 308 +/- 4 grams), and reperfused in an isolated blood-perfused heart model for 120 minutes. Three groups of hearts were compared. One group of hearts was subjected to 30 minutes of CCC only (30 min group; n = 9), another group of hearts to 90 minutes of CCC and storage (Control group: n = 16), and a third group to 90 minutes of CCC and storage, but with L-glutamate added to the blood reperfusate (2 mmol/L) (Glutamate group: n = 18). In the Control group 14 of 16 hearts (88%) needed electrical defibrillation after start of reperfusion, significantly more (p < 0.05) than the 8 of 18 (44%) in the Glutamate group; the difference between the 30-min (2 of 9 [22%]) and the Glutamate group was not significant (p = 0.48). Developed left-ventricular pressure (DLVP) and positive dP/dtmax (+dP/dtmax) was significantly higher in the Glutamate group than in the Control group during early reperfusion (DLVP: p < 0.05: +dP/dtmax: p < 0.01) and the entire reperfusion (DLVP and +dP/dtmax: p < 0.05), while reperfusion responses in the Glutamate and 30-min groups were not significantly different. Furthermore, myocardial oxygen uptake was significantly higher in the Glutamate group than in the Control group (p < 0.001), but not higher than that in the 30-min group. Decreased lactate release was found in the Glutamate group compared to the Control group during early reperfusion (p < 0.01), and the entire reperfusion (p < 0.001). No differences were found between the Control and Glutamate groups in alanine exchange. Thus, L-glutamate has a beneficial effect in pig hearts on both functional and metabolic recovery after cold crystalloid cardioplegia and storage when present in a concentration even as low as 2 mmol/L during continuous reperfusion after aortic unclamping. A possible mechanism is a glutamate-induced stimulation of the malate-aspartate shuttle leading to increased intramyocardial lactate utilization.

Adult↗
PubMed1996

Suppression of TRH-stimulated TSH secretion by glucose-induced hypothalamic somatostatin release.

To determine whether the combined glucose-thyrotropin-releasing hormone (TRH) test can be a useful method for the evaluation of the hypothalamic somatostatinergic activity, we investigated whether TRH-induced thyroid stimulating hormone (TSH) secretion can be suppressed by the oral glucose administration that stimulates the hypothalamic somatostatin (SRIH) secretion. Six tests were performed in ten healthy young men. Test 1: 1 ml of normal saline was intravenously administered at 0 min. Test 2: TRH was administered intravenously at 0 min. Test 3: Glucose, 75 g, was administered orally at -60 min. Test 4: Glucose and TRH were administered as above. Test 5: Pyridostigmine (PST), 120 mg, was given orally at -90 min followed by the administration of GH and TRH as above. Basal TSH levels were suppressed slightly, but significantly. In Test 3 compared to those observed in Test 1. The oral glucose administration also significantly suppressed TRH-stimulated TSH response by 27-35% between 40 min and 80 min in Test 4. In contrast, the pretreatment with PST completely reverted the suppressive effect of glucose on TRH-stimulated TSH response in Test 5. These data suggest that the increased hypothalamic SRIH secretion induced by oral glucose administration can suppress TRH-stimulated TSH response in normal men, and the combined glucose-TRH test can be a useful method to evaluate the hypothalamic somatostatinergic activity.

Adult↗