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Biomedical subjects

K Pak

Publications and source records attributed to K Pak.

At least 19 recordsLinked to original sources
PubMed2004

Identification of a novel Pseudomonas syringae Psy61 effector with virulence and avirulence functions by a HrpL-dependent promoter-trap assay.

The hrp pathogenicity island of Pseudomonas syringae encodes a type III secretion system (TTSS) that translocates effectors into plant cells. Most genes encoding effectors are dispersed in the P. syringae genome. Regardless of location, all are regulated coordinately by the alternative sigma factor HrpL. An HrpL-dependent promoter-trap assay was developed to screen genomic libraries of P. syringae strains for promoters whose activity in Escherichia coli is dependent on an inducible hrpL construct. Twenty-two HrpL-dependent promoter fragments were isolated from P. syringae Psy61 that included promoters for known HrpL-dependent genes. One fragment also was isolated that shared no similarity with known genes but retained a near consensus HrpL-dependent promoter. The sequence of the region revealed a 375-amino acid open reading frame encoding a 40.5-kDa product that was designated HopPsyL. HopPsyL was structurally similar to other secreted effectors and carried a putative chloroplast-targeting signal and two predicted transmembrane domains. HopPsyL':'AvrRpt2 fusions were translocated into host cells via the P. syringae pv. tomato DC3000 hrp TTSS. A hopPsyL::kan mutant of Psy61 exhibited strongly reduced virulence in Phaseolus vulgaris cv. Kentucky Wonder, but did not appear to act as a defense response suppressor. The ectopically expressed gene reduced the virulence of Pseudomonas syringae DC3000 transformants in Arabidopsis thaliana Col-0. The gene was shown to be conserved in 6 of 10 P. syringae pv. syringae strains but was not detected in 35 strains of other pathovars. HopPsyL appears to be a novel TTSS-dependent effector that functions as a host-species-specific virulence factor in Psy61.

Arabidopsis↗
PubMed2003

Involvement of ras activation in toxic hair cell damage of the mammalian cochlea.

To identify possible intracellular mediators of hair cell (HC) death due to ototoxins, we treated basal-turn, neonatal, rat HCs in vitro with several intracellular signaling inhibitors, prior to and during gentamicin exposure. The general guanine nucleotide-binding protein (G-protein) inhibitor, GDP-betaS (1 mM), provided potent HC protection, suggesting involvement of G-proteins in the intracellular pathway linking gentamicin exposure to HC death. ADP-betaS had minimal effect, indicating that the protection is specific to guanosine diphosphate (GDP)-binding, rather than a general reaction to nucleotides. Azido-GTP(32) photolabeling and gel electrophoresis indicated activation of an approximately 21 kDa G-protein in HCs after exposure to gentamicin. Spectroscopic analysis of peptide fragments from this band matched its sequence with H-Ras. The Ras inhibitors B581 (50 microM) and FTI-277 (10 microM) provided potent protection against damage and reduced c-Jun activation in HC nuclei, suggesting that activation of Ras is functionally involved in damage to these cells due to gentamicin.

Animals↗
PubMed2001

Ras/MEK but not p38 signaling mediates NT-3-induced neurite extension from spiral ganglion neurons.

Neurotrophin (NT)-3 is expressed in the neuronal target tissue of the developing rat cochlea and has been shown to promote the survival and neurite outgrowth of spiral ganglion (SG) neurons, suggesting a role for this protein during the innervation of the organ of Corti. In other neurons, NT-3 can mediate neuritogenesis and survival via a number of intracellular signal pathways. To date, the intracellular transduction pathways involved in the mediation of NT-3 effects have not been investigated in SG neurons. To determine whether the activities of NT-3 on SG neurons are dependent on the activation of mitogen-activated protein kinase kinases (MEK)/extracellular-signal-regulated kinases (ERK), Ras, and/or p38, SG explants from postnatal-day 4 rats were cultured with NT-3 and increasing concentrations of the MEK inhibitor U0126, the Ras farnesyl-transferase inhibitor (FTI)-277, and the p38 inhibitor SB203580. After fixation and immunocytochemical labeling, neurite growth was evaluated. A dose-dependent decrease of the effects of NT-3 on length and number of processes was observed in the U0126- and FTI-277-treated SG neurons. In contrast, SB203580 had no significant effect on NT-3-mediated stimulation of neurite growth, in terms of either number or length. The results suggest that NT-3 effects on SG neurons are mediated primarily by the Ras/MEK/ERK signaling pathway.

Animals↗
PubMed2001

Growth factors influence growth and differentiation of the middle ear mucosa.

OBJECTIVE: Otitis media is a major cause of morbidity in pediatric and adult patients. This inflammatory condition is characterized by mucosal hyperplasia that is thought to be mediated by the complex actions of growth factors and their respective receptors. It was the purpose of this study to determine which growth factors might be responsible for the growth and differentiation of the middle ear epithelium during otitis media. STUDY DESIGN: The effect of several growth factors on the expansion and differentiation of normal middle ear mucosa was evaluated in tissue culture. MATERIALS AND METHODS: Explants of normal rat middle ear mucosa were exposed in vitro to six different growth factors known to influence epithelial cells in other tissues: epidermal growth factor, amphiregulin, betacellulin, heregulin-alpha, keratinocyte growth factor, and hepatocyte growth factor. RESULTS: After 12 days, the growth and level of cytokeratin expression were analyzed for each of the explant outgrowths. Each factor appeared to have a significant, concentration-dependent effect on either the growth or differentiation of the cultured middle ear epithelial cells. CONCLUSION: The results suggest that several of the tested growth factors may play a significant role in controlling hyperplasia of the middle ear mucosa during otitis media.

Amphiregulin↗
PubMed2001

Enhancer-binding proteins HrpR and HrpS interact to regulate hrp-encoded type III protein secretion in Pseudomonas syringae strains.

In Pseudomonas syringae strains, the hrp-hrc pathogenicity island consists of an HrpL-dependent regulon that encodes a type III protein translocation complex and translocated effector proteins required for pathogenesis. HrpR and HrpS function as positive regulatory factors for the hrpL promoter, but their mechanism of action has not been established. Both HrpR and HrpS are structurally related to enhancer-binding proteins, but they lack receiver domains and do not appear to require a cognate protein kinase for activity. hrpR and hrpS were shown to be expressed as an operon: a promoter was identified 5' to hrpR, and reverse transcriptase PCR detected the presence of an hrpRS transcript. The hrpR promoter and coding sequence were conserved among P. syringae strains. The coding sequences for hrpR and hrpS were cloned into compatible expression vectors, and their activities were monitored in Escherichia coli transformants carrying an hrpL'-lacZ fusion. HrpS could function as a weak activator of the hrpL promoter, but the activity was only 2.5% of the activity detected when both HrpR and HrpS were expressed in the reporter strain. This finding is consistent with a requirement for both HrpR and HrpS in the activation of the hrpL promoter. By using a yeast two-hybrid assay, an interaction between HrpR and HrpS was detected, suggestive of the formation of a heteromeric complex. Physical interaction of HrpR and HrpS was confirmed by column-binding experiments. The results show that HrpR and HrpS physically interact to regulate the sigma(54)-dependent hrpL promoter in P. syringae strains.

Bacterial Proteins↗
PubMed2000

The predictive value of indium-111 leukocyte scans in the diagnosis of infected total hip, knee, or resection arthroplasties.

To evaluate the usefulness of the indium-111 scan in detecting actually or potentially infected total hip, knee, and resection arthroplasties, 153 scans were performed on 143 patients who underwent reoperation for a loose or painful total joint arthroplasty or a resection arthroplasty between 1990 and 1996. Scans were interpreted as infected, not infected, or equivocal by an experienced nuclear medicine radiologist. Patients were considered to be infected if they met any 2 of the following criteria: i) positive intraoperative cultures, ii) final permanent histologic section indicating acute inflammation, and iii) intraoperative findings of gross purulence within the joint. Twenty-six patients (17%) met the infection criteria at the time of reoperation. Indium scans were found to have a 77% sensitivity, 86% specificity, 54% and 95% positive and negative predictive values, and 84% accuracy for the prediction of infection. Of 6 equivocal scans, none were infected. The results of this study suggest limited indications for the use of the indium-111 scan in the evaluation of painful hip, knee, or resection arthroplasties. A negative indium scan may be helpful in suggesting the absence of infection in cases in which the diagnosis is not otherwise evident.

Adult↗
PubMed1998

Mercury methylation by interspecies hydrogen and acetate transfer between sulfidogens and methanogens.

Cocultures of Desulfovibrio desulfuricans and Methanococcus maripaludis grew on sulfate-free lactate medium while vigorously methylating Hg2+. Individually, neither bacterium could grow or methylate mercury in this medium. Similar synergistic growth of sulfidogens and methanogens may create favorable conditions for Hg2+ methylation in low-sulfate anoxic freshwater sediments.

Acetic Acid↗
PubMed1996

[Dynamic Gd-DTPA-enhanced MR imaging in evaluation of the function of transplanted kidneys].

The purpose of the study was to evaluate the potential of dynamic Gd-DTPA-enhanced MR imaging in assessing of the function of transplanted kidneys. Dynamic MR imaging was performed using the GRASS pulse sequence in 21 subjects (56 examinations), and in each examination 30 images were obtained after a bolus injection of Gd-DTPA. Imaging findings including signal increase and/or signal drop in cortex, signal drop in medulla, and signal drop in calyces were utilized for the evaluation of renal function. Renal function was also evaluated using the following parameters: Ta, time between the initial observation of signal increase in cortex and signal drop in medulla. Tb, time between the initial observation of signal drop in medulla and in calyces; Tc, Ta + Tb, and Max. C/M, maximum ratio of signal intensity between cortex and medulla among 30 images. In the group of patients with normal graft function (Ccr > or = 60ml/min), all imaging findings were observed. In the group of patients with mild graft dysfunction (30ml/min < or = Ccr < 60ml/min), all imaging findings but signal drop in cortex were observed. The time parameters of Ta, Tb, and Tc were significantly larger, and Max. C/M was significantly smaller than those observed in the group with normal graft function. In the group of patients with severe graft dysfunction (Ccr < 30ml/min), almost none of the findings were observed. The investigation in patients in the postoperative state revealed a close correlation of the imaging findings and the values of parameters with changes in graft function over time. The results indicated the usefulness of the method in semiquantitative evaluation of graft function, including that of patients in postoperative state. This study suggests that dynamic Gd-DTPA-enhanced MR imaging could be a valuable method for the management of transplanted kidneys.

Adolescent↗
PubMed1993

Primary malignant melanoma of the female urethra.

BACKGROUND: Malignant melanoma is one of the rarest tumors of the female urethra. The prognosis of urethral melanoma is poor. METHODS: A 59-year-old woman underwent total urethrectomy, bilateral inguinal lymph node dissection, and vesicostomy for Stage A primary malignant melanoma of the urethra. She received adjuvant therapy consisting of dacarbazine, vincristine, cyclophosphamide, and alpha-interferon. Two years later, repair of the parastomal hernia and interposition of an isoperistaltically ileum intussusception between the bladder and the abdominal wall were done. RESULTS: Complete continence was achieved, and the patient catheterizes herself every 3-5 hours during the day and once at night without difficulty. She has survived 5 years without any evidence of tumor recurrence. CONCLUSIONS: There have been only six case reports of women with primary malignant melanoma of the urethra surviving more than 5 years, including this case. Total urethrectomy with bilateral inguinal lymph node dissection should be done as the initial form of the treatment in patients with this disease who have no evidence of distant metastasis. The postoperative adjuvant therapy, consisting of alpha-interferon and chemotherapy, should be administered immediately; therefore, vesicostomy was done because it is a simple procedure. However, this type of urinary diversion requires an external appliance. Clinicians should consider the patient's quality of life, prognosis, and general condition and attempt to solve the problems of patients 2-3 years after the operation.

Combined Modality Therapy↗
PubMed1991

[Experimental study on intraoperative autotransfusion during urological operation].

The value of autotransfusion is widely recognized in the surgical community and may be of increasing importance in prevention of acquired immunodeficiency syndrome and hepatitis. The concern of possible contamination of the blood with urine, bacteria in urine or viable tumor cells has limited the wide use of intraoperative autotransfusion (IAT) in urological operation. There have been no experimental reports about protection of the blood from such contamination. To investigate separation of the blood from a contaminated mixture by using an autotransfusion machine, Haemonetic Cell Saver, a study composed of three experiments was performed. First, 200 ml of blood was mixed 200 ml of urine, and thereafter, the mixture was processed by the machine and the concentration erythrocytes were collected in a bag. Biochemical analysis of the collected erythrocyte solution (CES) was performed. Second, 200 ml of blood was mixed with 200 ml of urine that was adjusted to contain each 10(7)/ml of four bacterial strains. The bacteriological study of the CES was performed. Third, 200 ml of blood was mixed with 200 ml of urine that was adjusted to contain 10(7) cancer cells. Two cell lines, KK47 originated from human bladder cancer and ACHN originated from human renal cell carcinoma was used. The cytological study of the CES was performed. The results of these experiments were: Urine constituents were completely removed from the mixture. However, all strains of bacteria could not be separated, although the number of bacteria decreased. Cancer cells were found in the CES. In conclusion IAT should be done at urological operation in selected patients that have sterile urine and do not have tumor cells in the operation field.

Blood↗
PubMed1991

Emphysematous cystitis: report of a case.

Emphysematous cystitis is characterized by gas collection within the bladder wall and lumen. A case of emphysematous cystitis in a 74-year-old diabetic male is reported. Radiogram demonstrated an enlarged bladder with intraluminal gas.

Aged↗
PubMed1991

[Multilocular cystic renal cell carcinoma: report of a case].

We report a case of multilocular cystic renal cell carcinoma seen in a 54-year-old man. At the annual health check he was found to have numerous cysts of various sizes in the lower pole of the left kidney. Plain CT scan disclosed a mass in the lower pole of the left kidney. On enhanced CT scan septa were visible, suggesting a multilocular cyst. Left renal arteriography disclosed a hypervascular mass in the lower pole of the left kidney. Radical nephrectomy was performed. The gross appearance of the cut surface showed a feature of multilocular cyst. The histopathological diagnosis was clear cell carcinoma. We describe the clinical features of multilocular cystic renal cell carcinoma and discuss the differential diagnosis.

Carcinoma, Renal Cell↗
PubMed1990

[Cyclosporin levels in semen of renal transplant patients].

Cyclosporin (CsA) has powerful immunosuppressive properties, and its recent application to organ transplantation has resulted in markedly improved graft survival. However, CsA has certain adverse side effects, the most notable being nephrotoxicity and hepatotoxicity. Among other untoward effects, little is known about the effects of CsA on the reproductive organs. Since good graft survival is now expected with CsA, the long term effect of the drug on the gonads should be monitored carefully, particularly for young recipients. Prior to investigation of the effect of CsA on the testis, the level of CsA in semen of the adult renal transplant patients were measured. Twelve samples of semen from eight recipients, mean age 35 (SD 9), were collected by masturbation in the morning just before taking CsA after more than 5 day abstinence, and it was frozen at -80 degrees C. They had been taking immunosuppressants that were a combination of either CsA and prednisolone, or CsA, azathioprine and prednisolone for 5 to 63 months. The dose of CsA was 3.7 mg/kg to 5.0 mg/kg. The range of the level of serum creatinine was 1.1 mg/dl to 2.9 mg/dl. CsA in whole blood was measured by high performance liquid chromatography (HPLC), and CsA in semen was also measured by HPLC after extracting CsA with diethylether. The level of CsA in semen was 27 ng/ml to 165 ng/ml and that in whole blood was 51 ng/ml to 133 ng/ml. The relation between both levels was linear (r = 0.68, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[A study on the hemodialysis period following cadaveric kidney transplantation--a comparison between two centers sharing cadaver donor kidney pairs].

To study the hemodialysis period following cadaveric renal transplantation, we reviewed 18 consecutive cadaver donor kidney pairs of which one kidney was transplanted at Shiga University of Medical Science (SUMS) while the contralateral kidney was transplanted at Kyoto Prefectural Medical University (KPMU) between January 1983 and September 1988. Of these 18 pairs, graft function was satisfactory and the recipient was free from hemodialysis in 13 pairs. However, the postoperative hemodialysis periods were different between the two centers. To clarify the factors causing this difference, recipient factors, such as age, HLA matching, total ischemic time of the graft (TIT), immunosuppression, onset of diuresis and postoperative complications were studied. There were no significant differences in age, HLA matching, or immunosuppression. TIT of cases at SUMS was significantly longer than that of cases at KPMU. The postoperative hemodialysis period at SUMS was 25.8 days and that at KPMU was 17.8 days, however, the difference was not statistically significant. The results of this study indicate that TIT seems to be a major factor relating to delayed graft function in cadaveric renal transplantation.

Adolescent↗
PubMed1990

[Cavernous hemangioma of the penis: report of a case immunohistochemically studied].

An 18-month-old boy was admitted in April, 1988 because of a penile mass which had been first noted at the age of one month. From nine months after birth, transient bleeding from the mass accompanied by pain had been occasionally noted. At the age of 14 months, the mass seemed to grow markedly. On physical examination, there was an irregularly shaped mass on the right side of the prepuce. It was palpated subcutaneously, soft in consistency and was 10 mm in diameter. It had a light-purple color. Upon surgery, the mass was found not to have originated from the cavernous body of the penis, so that it could be excised without difficulty. Histopathological diagnosis was cavernous hemangioma. Electron microscopic examination revealed findings suggestive of newly formed blood vessels such as abnormal cuboidal shape of endothelial cells and a high nucleocytoplasmic ratio. Immunohistochemical examination of factor VIII-related antigen was in homogeneously positive in vascular endothelial cells. To our knowledge, this is the twenty-eighth case reported in Japan.

Hemangioma, Cavernous↗
PubMed1989

A giant stone in the müllerian duct cyst.

Cystic diseases in the male pelvis are uncommon, and stones found in male pelvic cysts are very rare. We report a case of a giant stone found in the male pelvis. Computed tomography was helpful in locating the stone, and surgery revealed it to be a Müllerian duct cyst.

Calculi↗