Primary liver abscess due to Klebsiella pneumoniae in Taiwan

Pyogenic liver abscess is an uncommon complication of intra-abdominal or biliary tract infection and is usually a polymicrobial infection associated with high mortality and high rates of relapse. However, over the past 15 years, we have observed a new clinical syndrome in Taiwan: liver abscesses caused by a single microorganism, Klebsiella pneumoniae. We reviewed 182 cases of pyogenic liver abscess during the period September 1990 to June 1996; 160 of these cases were caused by K. pneumoniae alone, and 22 were polymicrobial. When patients with K. pneumoniae liver abscess were compared with those who had polymicrobial liver abscess, we found higher incidences of diabetes or glucose intolerance (75% vs. 4.5%) and metastatic infections (11.9% vs. 0) and lower rates of intra-abdominal abnormalities (0.6% vs. 95.5%), mortality (11.3% vs. 41%), and relapse (4.4% vs. 41%) in the former group. Liver abscess caused by K. pneumoniae is a new clinical syndrome that has emerged as an important infectious complication in diabetic patients in Taiwan.

The colon cancer burden of genetically defined hereditary nonpolyposis colon cancer

BACKGROUND & AIMS

Estimates of the frequency of hereditary nonpolyposis colon cancer (HNPCC) based on clinical criteria have varied widely. Recent studies of germline mismatch repair gene mutations have suggested that HNPCC accounts for close to 3% of all colon cancer, but this estimate may have been inflated by inclusion of founder effects peculiar to Finland. We therefore determined by genetic criteria the colon cancer burden associated with HNPCC in a population-based study of 1066 individuals from Utah and California.

METHODS

The coding regions of mismatch repair genes hMSH2 and hMLH1 were sequenced from the germline of those individuals whose tumors exhibited microsatellite instability.

RESULTS

Microsatellite instability was present in 16% (171/1066) of tumors. Pathogenic germline mismatch repair gene mutations were identified in 7 individuals, and missense amino acid changes of uncertain significance were identified in another 6 individuals. After adjusting for the availability of sufficient germline DNA for sequencing, the 7 clearly pathogenic mutations accounted for 0.86% of colon cancer at the population level. Individuals with these mutations were significantly younger, more likely to have a family history of colon and endometrial cancer, and more likely to have first-degree relatives with a young-age onset of colon cancer than individuals with unstable tumors but without germline mutations (P < 0.01).

CONCLUSIONS

We conclude that genetically defined HNPCC accounts for a very small percentage of colon cancer at the population level, a percentage less than that estimated by most previous clinical studies.

LNB-TM7, a group of seven-transmembrane proteins related to family-B G-protein-coupled receptors

A number of unusual seven-transmembrane molecules have recently been characterized that have significant amino acid sequence similarity within the membrane-spanning hydrophobic regions and intervening loops to members of G-protein-coupled receptor family B. However, in contrast to the family-B G-protein-coupled receptors, these molecules have unusually large N-terminal extracellular domains that contain a number of well- characterized protein modules. The range of cell types expressing these complex molecules and their potential roles in cell adhesion and signalling have become a major focus of research in a number of biological systems.

Surface gene mutants of hepatitis B virus in infants who develop acute or chronic infections despite immunoprophylaxis

Serum hepatitis B virus (HBV) DNA from 4 infants with fulminant hepatitis B, 3 infants with acute self-limited hepatitis B, and 15 infants with chronic HBV infection were amplified by polymerase chain reaction followed by direct sequencing of the region of HBV genome encoding the major antigenic epitopes of hepatitis B surface antigen (HBsAg). All infants were born to carrier mothers and administered immunoprophylaxis from birth. Serum HBV DNA from 13 carrier children born to carrier mothers who did not receive immunoprophylaxis and had comparable length of infection were studied as controls. An S mutant (residue 126, Thr to Ala) initially found in an infant with fulminant hepatitis was replaced by another S mutant (residue 145, Gly to Arg) 4 days later. In a girl with chronic hepatitis B, Ala-126 variant and Arg-145 variant were found at 17 and 25 months of age, respectively. The Arg-145 variant persisted for 8 years in an asymptomatic male carrier and for 1 year in an infant with chronic hepatitis B. The Ala-126 variant persisted for 11 years in one child who had an early loss of hepatitis B e antigen. In the majority of the infants' mothers, corresponding mutations in HBsAg were not detected in serum by direct sequencing. The S mutants detected in three carrier infants were not found in their mothers' serum after cloning and sequencing of 10 DNA clones from each maternal sample. None of the 13 control patients had detectable S mutants. These results suggest that S variants emerge or are selected under the immune pressure generated by the host or by administration of hepatitis B immune globulin and hepatitis B vaccination. An S mutant (residue 129, Gln to Arg) found in one mother-infant pair suggested a direct maternal-infant transmission, resulting in immunoprophylaxis failure. None of the family members of children infected with Arg-145 variant had the same variant infection, implying this variant's low transmissability.

Eosinophilic meningitis caused by Angiostrongylus cantonensis: report of 17 cases

PURPOSE

To describe two outbreaks of Angiostrongylus cantonensis infection that occurred in Kaohsiung, Taiwan, during 1998 and 1999, and to characterize the source of the outbreaks and the clinical manifestations of the disease.

SUBJECTS AND METHODS

We performed a retrospective cohort study among Thai laborers with eosinophilic meningitis who ate raw snails (Ampullarium canaliculatus), as well as an environmental surveillance of larvae in snails.

RESULTS

We enrolled 17 Thai laborers in whom severe headache and eosinophilia developed within 4 to 23 days after eating raw snails. Twelve (71%) developed eosinophilic meningitis. Third-stage larvae were found in the cerebrospinal fluids of 2 patients and in all 12 tested snails. Specific antibodies to A. cantonensis were detected in serum from 16 of the patients and in cerebrospinal fluid from 5 of the patients. Central nervous system manifestations included headache (n = 17 [100%]), fever (n = 11 [65%]), Brudzinski's sign/stiff neck (n = 11 [65%]), hyperesthesia (n = 3 [18%]), cranial nerve palsy (n = 2 [12%]), diplopia (n = 2 [12%]), and ataxia (n = 1 [6%]). Laboratory findings included peripheral eosinophilia (n = 15 [88%]) and cerebrospinal fluid eosinophilia (n = 12 [71%]); elevated immunoglobulin (Ig) E levels (n = 13 [100%]); and transient increases in white blood cell count (n = 7 [41%]) and in serum levels of creatine kinase (n = 7 [41%]), transaminase (n = 3 [18%]), and lactate dehydrogenase (n = 2 [12%]). The severity of illness and eosinophilia were correlated with the number of ingested snails. Meningeal and basal ganglion enhancement was noted on magnetic resonance imaging in several patients. Treatment with mebendazole combined with glucocorticosteroids appeared to shorten the course of the infection, but not the number of relapses. The eosinophil count fell to normal within 3 months, but IgE levels remained elevated for as long as 6 months. All patients recovered with minimal neurologic sequelae.

CONCLUSION

Eosinophilic meningitis caused by A. cantonensis should be considered in patients who have headache or central nervous system manifestations after eating raw snails.

Absence of infection in breast-fed infants born to hepatitis C virus-infected mothers

The role of breast-feeding in perinatal transmission of hepatitis C virus (HCV) was explored in 15 HCV-infected mothers and their infants. The 15 carrier mothers had anti-HCV titers ranging from 1:80 to 1:40,000 and also had HCV-ribonucleic acid with concentrations ranging from 10(4) to 2.5 x 10(8) copies/ml. Both anti-HCV antibody and HCV-ribonucleic acid were present in colostral samples in much lower levels, but none of the 11 breast-fed infants had evidence of HCV infection for up to 1 year of age. Thus breast-feeding seems safe for these infants.

Transplacental leakage of HBeAg-positive maternal blood as the most likely route in causing intrauterine infection with hepatitis B virus

Thirty-two HBeAg-positive carrier mothers and their 32 babies were investigated to elucidate the mechanism involved in intrauterine infection with HBV. Five mothers had symptoms and signs of threatened abortion and/or threatened preterm labor. Three mothers gave birth more than 6 weeks after the episodes, and their babies were those infected in utero. The other two gave birth within 1 week after the episodes, and the two babies were treated with HBIG immediately after birth; HBV infection was successfully prevented. Therefore we suggest that transplacental leakage of HBeAg-positive maternal blood, which is induced by uterine contractions during pregnancy and the disruption of placental barriers, is the most likely route to cause HBV intrauterine infection.

Possible role of high-titer maternal viremia in perinatal transmission of hepatitis C virus

To study perinatal transmission of hepatitis C virus (HCV), 15 anti-HCV-positive carrier mothers without human immunodeficiency virus coinfection were recruited. At delivery, maternal blood was taken and anti-HCV titer was determined and HCV RNA measured in each serum sample by reverse transcription polymerase chain reaction (PCR). A competitive PCR was used in selected samples to quantitate HCV concentration. The 15 neonates were followed regularly for 1 year and their sera were also assayed for anti-HCV and for HCV RNA by reverse transcription PCR. All the mothers were positive for HCV RNA. Only one normal spontaneously delivered neonate of a mother with extremely high titer of anti-HCV (1:20,000) and HCV concentration (10(10) copies/mL) had both anti-HCV and HCV RNA in serum for up to 6 months of age. In contrast, none of the remaining 14 neonates born to mothers with low- to high-titer anti-HCV (1:4-1:1000) and moderate amounts of HCV RNA (10(5)-10(6) copies/mL) contracted HCV infection. The results imply that high-titer maternal viremia and normal spontaneous delivery may allow more HCV to infect the neonate intrapartum, therefore establishing perinatal transmission.

Comparison of endometrial changes among symptomatic tamoxifen-treated and nontreated premenopausal and postmenopausal breast cancer patients

Breast cancer patients who received tamoxifen as adjuvant therapy have been reported to have more endometrial lesions such as polyps, hyperplasia, or carcinoma. We conducted a prospective study to elucidate the endometrial changes of premenopausal and postmenopausal breast cancer patients with tamoxifen. Sixty-seven symptomatic breast cancer patients who had been on tamoxifen treatment, including 34 premenopausal and 33 postmenopausal patients, and another group of 48 patients who had not been on tamoxifen, including 25 premenopausal and 23 postmenopausal patients, were recruited. Symptomatic patients were defined as having hypermenorrhea or abnormal vaginal bleeding among premenopausal patients or postmenopausal bleeding among postmenopausal patients. Endometrial thickness and uterine size determined by vaginal ultrasonography, histologic findings, and risk factors for endometrial cancer were compared. The mean endometrial thickness and uterine size showed no statistically significant difference in premenopausal patients with (n = 34) or without (n = 25) tamoxifen treatment, whereas there was a significant difference in the postmenopausal patients with (n = 33) or without (n = 23) tamoxifen treatment (12.11 +/- 12.38 mm vs 5.41 +/- 2.70 mm, P = 0.025; 234.71 +/- 76.36 cm3 vs 108.81 +/- 81.27 cm3, P = 0.0018, respectively). The frequency of endometrial histopathologic findings was 23.5% (8/34) in tamoxifen-treated women compared with 12.0% (3/25) in nontreated women (P = 0.269) in the premenopausal groups. In contrast, it was remarkably high with 66.7% (22/33) in tamoxifen-treated women compared with 30.4% (7/23) in the nontreated women in the postmenopausal groups (P = 0.025). There were four postmenopausal patients with tamoxifen, including three with atypical endometrial hyperplasia and one endometrial carcinoma, in contrast to no postmenopausal nontreated patients, although this difference did not reach statistical significance in this study (P = 0.096). There was a remarkably high prevalence of endometrial histopathologic findings in symptomatic tamoxifen-treated breast cancer patients, especially postmenopausal women. Tamoxifen might be associated with premalignant or malignant changes in postmenopausal endometrium. Thus timely, aggressive histologic assessment such as curettage or hysteroscope should be performed to detect the endometrial lesions when symptoms occur. Vaginal ultrasonography could be a useful tool to detect the endometrial lesions.

Interferon-based therapy reduces risk of stroke in chronic hepatitis C patients: a population-based cohort study in Taiwan

BACKGROUND

Hepatitis C virus (HCV) infection has been linked to an increased risk of insulin resistance and carotid atherosclerosis.

AIM

To investigate the association between HCV infection and stroke, and the effect of interferon-based therapy (IBT) on stroke risk in chronic hepatitis C (CHC) patients.

METHODS

We conducted a retrospective cohort study that followed up 3113 subjects with a newly detected HCV infection and 12 452 age- and gender-matched subjects without HCV infection selected from a random sample of 10(6) beneficiaries from the Taiwan National Health Insurance Program up to 5 years. Use of IBT was defined as treatment with interferon alpha, pegylated interferon alpha-2a or pegylated interferon alpha-2b for at least 3 months. The hazard ratio (HR) for newly detected stroke was calculated for subjects with HCV compared to those without HCV, and for IBT-treated HCV patients compared to non-IBT-treated HCV patients while adjusting for possible confounding factors.

RESULTS

The overall person-years of follow-up were 8624.11 in patients with HCV, 54,533.69 in patients without HCV, 666.65 in IBT-treated patients, and 7886.49 in nontreated patients. The multivariable-adjusted hazard ratio (HR) for newly detected stroke was 1.23 for subjects with HCV compared to the age- and sex-matched subjects without HCV (adjusted HR = 1.23, 95% CI = 1.06-1.42, P = 0.008). Moreover, use of IBT significantly reduced the risk of stroke in HCV patients (adjusted HR = 0.39, 95% CI = 0.16-0.95, P = 0.039) after adjusting for known prognostic factors.

CONCLUSIONS

Interferon-based therapy may reduce the long-term risk of stroke in patients with chronic HCV infection.

Cellular immune response to HBcAg in mother-to-infant transmission of hepatitis B virus

Cellular immunity to HBcAg was studied in hepatitis B virus carrier children and neonates born to hepatitis B virus carrier mothers. A significant proliferative response of peripheral blood mononuclear cells to HBcAg was found in 5 of 10 children with elevated ALT levels but in none of the nine HBeAg-positive children with normal ALT levels. HBeAg but not HBsAg was detected in cord blood of 9 of 10 neonates born to HBeAg-positive carrier mothers, suggesting exposure of these neonates to HBeAg in utero. However, cord mononuclear cells from neonates born to HBeAg-positive carrier mothers did not show a significant change in the proportion of suppressor and helper T-cell subsets or proliferative response to HBcAg. Nor did they produce interleukin-2 receptor after being cocultured with HBcAg. The unresponsiveness of peripheral-blood mononuclear cells or cord mononuclear cells to HBcAg was not reversed by CD8+ cell depletion. Although cord blood mononuclear cells from neonates born to carrier mothers positive for antibody to HBeAg also did not respond to HBcAg, we encountered an infant, born to a carrier mother positive for antibody to HBeAg, who contracted acute hepatitis B at 2.5 mo of age. The baby's peripheral-blood mononuclear cells showed a significant proliferative response to HBcAg. These results support the view that transplacental maternal HBeAg probably induces a specific unresponsiveness of helper T cells to HBcAg and HBeAg in the neonates born to HBeAg-positive carrier mothers. This specific helper T cell tolerance could be maintained throughout the early replicative phase of carrier state but might break someday with the appearance of raised ALT level.

Molecular analysis of the epidermal growth factor-like short consensus repeat domain-mediated protein-protein interactions: dissection of the CD97-CD55 complex

Epidermal growth factor-like (EGF) and short consensus repeat (SCR) domains are commonly found in cell surface and soluble proteins that mediate specific protein-protein recognition events. Unlike the immunoglobulin (Ig) superfamily, very little is known about the general properties of intermolecular interactions encoded by these common modules, and in particular, how specificity of binding is achieved. We have dissected the binding of CD97 (a member of the EGF-TM7 family) to the complement regulator CD55, two cell surface modular proteins that contain EGF and SCR domains, respectively. We demonstrate that the interaction is mediated solely by these domains and is characterized by a low affinity (86 microm) and rapid off-rate (at least 0.6 s(-1)). The interaction is Ca(2+) -dependent but is unaffected by glycosylation of the EGF domains. Using biotinylated multimerized peptides in cell binding assays and surface plasmon resonance, we show that a CD97-related EGF-TM7 molecule (termed EMR2), differing by only three amino acids within the EGF domains, binds CD55 with a K(D) at least an order of magnitude weaker than that of CD97. These results suggest that low affinity cell-cell interactions may be a general feature of highly expressed cell surface proteins and that specificity of SCR-EGF binding can be finely tuned by a small number of amino acid changes on the EGF module surface.

Hepatitis B surface antigenemia at birth: a long-term follow-up study

OBJECTIVE

To investigate the prevalence and outcome of hepatitis B surface antigenemia in newborns of hepatitis B e antigen (HBeAg)-positive hepatitis B surface antigen (HBsAg) carrier mothers under the current immunoprophylaxis program.

STUDY DESIGN

From 1984 to 1993, 665 high-risk newborns born to HBeAg-positive HBsAg carrier mothers were prospectively recruited. The newborns were tested for HBsAg soon after birth, before hepatitis B immune globulin administration. All newborns received hepatitis B immune globulin within 24 hours after birth plus subsequent hepatitis B vaccination. Those who were seropositive for HBsAg at birth were regularly followed up for their hepatitis B virus (HBV) markers, liver function profiles, and alpha-fetoprotein levels from 1984 to 1996.

RESULTS

Sixteen (2.4%) of the 665 subjects were found to be seropositive for HBsAg at birth, and all remained HBsAg-positive at 6 months of age. Twelve of the 16 received long-term follow-up care, and all were confirmed to have chronic HBV infection. Of the 12, 2 had HBeAg seroconversion, and 1 had alanine aminotransferase flares without HBeAg seroconversion. Delayed appearance of hepatitis B core antibody (anti-HBc) occurred in 2 without alanine aminotransferase elevation.

CONCLUSIONS

Current immunoprophylaxis strategy does not protect newborns with surface antigenemia, apparently acquired in utero, from becoming HBV carriers. Immunologic attempts to eliminate HBV may occur in carrier children infected in utero, despite their profound immune tolerance to HBV.

Human epidermal growth factor (EGF) module-containing mucin-like hormone receptor 3 is a new member of the EGF-TM7 family that recognizes a ligand on human macrophages and activated neutrophils

The epidermal growth factor (EGF)-TM7 subgroup of G-protein-coupled receptors is composed predominantly of leukocyte-restricted glycoproteins defined by their unique hybrid structure, in which extracellular EGF-like domains are coupled to a seven-span transmembrane moiety via a mucin-like stalk. The EGF-TM7 group comprises mouse F4/80, human EGF module-containing mucin-like hormone receptor (EMR) 1, human EMR2, and human and mouse CD97, the genes for which map to human chromosome 19p13 and the syntenic regions of the mouse genome. In this study we describe the cloning and characterization of EMR3, a novel human EGF-TM7 molecule, and show the existence of its cellular ligand. The EMR3 gene maps closely to the existing members of the EGF-TM7 family on human chromosome 19p13.1 and, in common with other EGF-TM7 genes, is capable of generating different protein isoforms through alternative splicing. Two alternative splice forms have been isolated: one encoding a 652-amino acid cell surface protein consisting of two EGF-like domains, a mucin stalk, and a putative G-protein-coupled receptor domain and the other encoding a truncated soluble form containing only two EGF-like domains. As with other members of the EGF-TM7 family, EMR3 mRNA displays a predominantly leukocyte-restricted expression pattern, with highest levels in neutrophils, monocytes, and macrophages. Through the use of soluble EMR3 multivalent probes we have shown the presence of a ligand at the surface of monocyte-derived macrophages and activated human neutrophils. These interactions suggest a potential role for EMR3 in myeloid-myeloid interactions during immune and inflammatory responses.

Human EMR2, a novel EGF-TM7 molecule on chromosome 19p13.1, is closely related to CD97

The epidermal growth factor (EGF)-TM7 proteins [EMR1, (EGF-like molecule containing mucin-like hormone receptor 1) F4/80, and CD97] constitute a recently defined class B GPCR subfamily and are predominantly expressed on leukocytes. These molecules possess N-terminal EGF-like domains coupled to a seven-span transmembrane (7TM) moiety via a mucin-like spacer domain. Genomic mapping analysis has suggested a possible EGF-TM7 gene family on the human chromosome 19p13 region. In this study, a new member of the EGF-TM7 family, EMR2, which shares strikingly similar molecular characteristics with CD97, is described. In addition to mapping closely to CD97 on human chromosome 19p13.1, EMR2 contains a total of five tandem EGF-like domains and expresses similar protein isoforms consisting of various numbers of EGF-like domains as a result of alternative RNA splicing. Furthermore, EMR2 and CD97 exhibit highly homologous EGF-like domains and share identical gene organization, indicating that both genes are the products of a recent gene duplication event. The homologous EGF-like domains enable the identification of both EMR2 and CD97 by monoclonal antibodies (mAbs) raised against the first EGF-like domain of CD97, whereas mAbs directed against the extracellular spacer domain of CD97 are able to differentiate these two proteins. Both EMR2 and CD97 are highly expressed in immune tissues; however, unlike CD97, which is ubiquitously expressed in most cell types, EMR2 expression is restricted to monocytes/M&phi; and granulocytes. EMR2 fails to interact with CD55, the cellular ligand for CD97, suggesting the possibility of a different cellular ligand(s). EMR2 may therefore have a unique function in cells of monocyte/M&phi; and granulocyte lineages.

Oxygen- and growth rate-dependent regulation of Escherichia coli fumarase (FumA, FumB, and FumC) activity

Escherichia coli contains three biochemically distinct fumarases which catalyze the interconversion of fumarate to L-malate in the tricarboxylic acid cycle. Batch culture studies indicated that fumarase activities varied according to carbon substrate and cell doubling time. Growth rate control of fumarase activities in the wild type and mutants was demonstrated in continuous culture; FumA and FumC activities were induced four- to fivefold when the cell growth rate (k) was lowered from 1.2/h to 0.24/h at 1 and 21% O(2), respectively. There was a twofold induction of FumA and FumC activities when acetate was utilized instead of glucose as the sole carbon source. However, these fumarase activities were still shown to be under growth rate control. Thus, the activity of the fumarases is regulated by the cell growth rate and carbon source utilization independently. Further examination of FumA and FumC activities in a cya mutant suggested that growth rate control of FumA and FumC activities is cyclic AMP dependent. Although the total fumarase activity increased under aerobic conditions, the individual fumarase activities varied under different oxygen levels. While FumB activity was maximal during anaerobic growth (k = 0.6/h), FumA was the major enzyme under anaerobic cell growth, and the maximum activity was achieved when oxygen was elevated to 1 to 2%. Further increase in the oxygen level caused inactivation of FumA and FumB activities by the high oxidized state, but FumC activity increased simultaneously when the oxygen level was higher than 4%. The same regulation of the activities of fumarases in response to different oxygen levels was also found in mutants. Therefore, synthesis of the three fumarase enzymes is controlled in a hierarchical fashion depending on the environmental oxygen that the cell encounters.

Proximal interphalangeal joint silicone replacement arthroplasty: clinical results using an anterior approach

Sixty-nine proximal interphalangeal joint silicone arthroplasties in 36 patients inserted through an anterior approach were reviewed. Average followup time was 3.4 years. The average extension deficit was slightly improved from 17 degrees to 8 degrees, but the total active motion (active flexion minus active extension) did not significantly increase (44 degrees to 46 degrees). Coronal plane deformities were not successfully corrected. Pain relief was obtained in 67 of 69 digits. There were 12 digits with complications, and five implants fractured. The anterior approach allows preservation of the central slip insertion and initiation of immediate active and passive joint motion. With proper indications, careful surgical technique, and a supervised therapy protocol, proximal interphalangeal joint silicone arthroplasty is a useful operation for pain relief and functional gain.

Extremely high prevalence of nasopharyngeal carriage of penicillin-resistant Streptococcus pneumoniae among children in Kaohsiung, Taiwan

Resistance (intermediate and high) to penicillin among Streptococcus pneumoniae strains is an emerging problem worldwide. From 1995 to 1997, isolates of S. pneumoniae not susceptible to penicillin were seen with increasing frequency from blood, cerebrospinal fluid, pleural fluid, and middle ear fluid from pediatric patients at the Veterans General Hospital-Kaohsiung. To determine the prevalence of carriage of these penicillin-nonsusceptible S. pneumoniae isolates, we obtained nasopharyngeal swab specimens from 2,905 children (ages, 2 months to 7 years) attending day-care centers or kindergartens or seen in our outpatient clinic. S. pneumoniae was isolated from 611 children, and 584 strains were available for analysis. The oxacillin disc test was used as a screening test to evaluate penicillin susceptibility. The MICs of 11 antibiotics (penicillin, cefaclor, cefuroxime, ceftriaxone, cefotaxime, imipenem, chloramphenicol, clarithromycin, rifampin, vancomycin, and teicoplanin) were determined by the E-test. Only 169 (29%) of the strains were susceptible to penicillin; 175 (30%) strains were intermediately resistant and 240 (41%) were highly resistant. The isolates also demonstrated high rates of resistance to other beta-lactams (46% were resistant to cefaclor, 45% were resistant to cefuroxime, 45% were resistant to ceftriaxone, 31% were resistant to cefotaxime, and 46% were resistant to imipenem). The rate of resistance to macrolide antimicrobial agents was strikingly high; 95% of the isolates were not susceptible to clarithromycin. However, 97% were susceptible to rifampin and 100% were susceptible to the two glycopeptides (vancomycin and teicoplanin). While reports of penicillin-resistant S. pneumoniae increased worldwide through the 1980s, the high prevalence (71%) of resistance reported here is astonishing. Surveillance of nasopharyngeal swab specimen cultures may provide useful information on the prevalence of nonsusceptible strains causing invasive disease. Such information could be used to guide therapy of pneumococcal infections.

Bcl-2 overexpression prevents apoptosis-induced Madin-Darby canine kidney simple epithelial cyst formation

BACKGROUND

Madin-Darby canine kidney (MDCK) cells develop into simple epithelial cell cysts when cultured in type I collagen gel. We found that MDCK cells initially grow into multilayer cell aggregates and subsequently develop central lumen that contain apoptotic cells. We hypothesized that apoptosis might be essential for the formation of MDCK cysts.

METHODS

Using MDCK cells cultured in collagen gel as the experimental model, we investigated how renal cells organize to form cysts. To delineate the role of apoptosis in the process of cyst formation, MDCK cells were transfected with the bcl-2 gene. Characterization of apoptosis was studied by morphological and biochemical methods.

RESULTS

Bcl-2 overexpression conferred resistance to apoptosis. Cultured in collagen gel, Bcl-2 transfectants rarely formed a simple epithelial cyst, but instead remained as a multilayer cell aggregate containing central or multiple lumens, or even developing into branching structures.

CONCLUSIONS

Because Bcl-2 overexpression averts cyst cavitation, these data clearly indicate that apoptosis is an essential initial event for renal cyst formation.

A support vector machines approach for virtual screening of active compounds of single and multiple mechanisms from large libraries at an improved hit-rate and enrichment factor

Support vector machines (SVM) and other machine-learning (ML) methods have been explored as ligand-based virtual screening (VS) tools for facilitating lead discovery. While exhibiting good hit selection performance, in screening large compound libraries, these methods tend to produce lower hit-rate than those of the best performing VS tools, partly because their training-sets contain limited spectrum of inactive compounds. We tested whether the performance of SVM can be improved by using training-sets of diverse inactive compounds. In retrospective database screening of active compounds of single mechanism (HIV protease inhibitors, DHFR inhibitors, dopamine antagonists) and multiple mechanisms (CNS active agents) from large libraries of 2.986 million compounds, the yields, hit-rates, and enrichment factors of our SVM models are 52.4-78.0%, 4.7-73.8%, and 214-10,543, respectively, compared to those of 62-95%, 0.65-35%, and 20-1200 by structure-based VS and 55-81%, 0.2-0.7%, and 110-795 by other ligand-based VS tools in screening libraries of >or=1 million compounds. The hit-rates are comparable and the enrichment factors are substantially better than the best results of other VS tools. 24.3-87.6% of the predicted hits are outside the known hit families. SVM appears to be potentially useful for facilitating lead discovery in VS of large compound libraries.

Cyclic AMP modifies the cellular distribution of connexin43 and induces a persistent increase in the junctional permeability of mouse mammary tumor cells

Direct communication between cells via gap junctions is thought to be an important component of homeostasis and coordinated cellular responses to external signals. We investigated how the second messenger cAMP exerts its effects on junctional communication in a mouse mammary tumor cell line, MMT22. Junctional permeance was quantitatively assessed using dye microinjection and video microscopy. An increase of permeance was found after exposure to 8-bromo-cAMP, being detectable after 30 minutes of treatment and attaining a fourfold higher level of permeance by 24 hours. This elevated level was maintained with continuous exposure to 8-bromo-cAMP for seven days. The permeability change was accompanied by an increase in gap junctions as shown by freeze-fracture electron microscopy and by confocal microscopy using antibodies directed against the gap junction protein, connexin43. The amount of detergent-insoluble connexin43 also increased with 8-bromo-cAMP treatment, and most of the increase could be attributed to an increase of slower migrating (i.e. phosphorylated) species of connexin43. However, connexin43 mRNA and the total cellular content of connexin43 did not change over this period of exposure to 8-bromo-cAMP, as shown by densitometric analyses of northern and western blots. We conclude that 8-bromo-cAMP affects the distribution of connexin43 such that a greater proportion of the protein is utilized for channel formation. Since these changes were relatively slow to develop and persisted with prolonged exposure to 8-bromo-cAMP, it is possible that the junctional permeability of these mammary tumor cells is linked to the ‘basal’ level of cAMP, i.e. levels maintained by the cells in accordance with a particular cell state.

Transdermal iontophoretic delivery of diclofenac sodium from various polymer formulations: in vitro and in vivo studies

The objective of this study was to evaluate the in vitro and in vivo transdermal iontophoresis of various diclofenac sodium polymer formulations. The excised rat skin, human skin as well as cellulose membrane were used to examine the in vitro drug permeation whereas the microdialysis technique was used to monitor the drug concentration in vivo. Polymer solutions based on polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) binary system showed higher drug permeability than that of single polymer vehicle. The effect of formulations on drug permeation through cellulose membrane was quite different from those through rat skin and human skin, which can be explained by the different permeation pathways between them. It appeared to be a membrane-controlled mechanism but not the vehicle matrix-controlled mechanism for diclofenac hydrogels when using skin as the diffusion barrier. The recovery of diclofenac sodium in the in vivo microdialysis was approximately 80-90%, indicating this technique can be used in the intradermal drug monitoring. For all the polymer formulations tested, there was a good relationship between the in vitro and in vivo drug permeation. A synergistic effect on drug permeation was observed when transdermal iontophoresis combined with the pretreatment of cardamom oil as a permeation enhancer.

Kinase activation of the non-receptor tyrosine kinase Etk/BMX alone is sufficient to transactivate STAT-mediated gene expression in salivary and lung epithelial cells

Etk/BMX is a non-receptor protein tyrosine kinase that requires a functional phosphatidylinositol 3-kinase via the pleckstrin homology domain to be activated by cytokine. In the present study, a conditionally active form of Etk was constructed by fusing the hormone-binding domain of estrogen receptor (ER) to an amino terminus truncated form of Etk, PHDelta1-68Etk, to generate DeltaEtk:ER. In stably transfected Pa-4DeltaEtk:ER cells, the activity of DeltaEtk:ER was stimulated within minutes by the treatment of DeltaEtk:ER stimulant, estradiol, and sustained for greater than 24 h. A robust induction in the phosphorylation of signal transducers and activators of transcription (STAT) proteins, including STAT1, STAT3, and STAT5, was accompanied with DeltaEtk:ER activation. Moreover, the conditionally activated Etk stimulated STAT1- and STAT5-dependent reporter activities by approximately 160- and approximately 15-fold, respectively, however, elicited only a modest STAT3-mediated reporter activation. Qualitatively comparable results were obtained in lung A549 cells, indicating that DeltaEtk:ER inducible system could function in an analogous fashion in different epithelial cells. Furthermore, we demonstrated that Etk activation alone augmented cyclin D1 promoter/enhancer activity via its STAT5 response element in both Pa-4DeltaEtk:ER and A549 cells. Altogether, these findings support the notion that the activation of Etk kinase is sufficient to transactivate STAT-mediated gene expression. Hence, our inducible DeltaEtk:ER system represents a novel approach to investigate the biochemical events following Etk activation and to evaluate the contribution by kinase activation of Etk alone or in conjunction with other signaling pathway(s) to the ultimate biological responses.

A common precursor for a putative hemorrhagic protein and rhodostomin, a platelet aggregation inhibitor of the venom of Calloselasma rhodostoma: molecular cloning and sequence analysis

Rhodostomin is a platelet aggregation inhibitor secreted by the venom gland of Calloselasma rhodostoma. We report here the isolation of a 1.67-kilobase (kb) lambda gt11 cDNA clone using degenerate oligonucleotide probe based on a partial amino acid sequence of rhodostomin. The amino acid sequence deduced from an open reading frame of the cDNA indicates that (i) the 68-amino acid sequence of rhodostomin is located at the carboxyl terminus of the precursor polypeptide and (ii) a peroxisomal targeting sequence (ser.his.ala.) exists between the stop codon and the rhodostomin sequence of the precursor. Since the amino-terminal segment of the deduced sequence shows a high degree of identity with hemorrhagic proteins, which are zinc-metalloproteinases, found in the venom of some crotalid and viperid snakes, our results also predict the existence of at least one such hemorrhagic protein in the venom of Calloselasma rhodostoma. The derivation of a platelet aggregation inhibitor and a hemorrhagic protein from the same precursor protein is consistent with the fact that these proteins may be synergistic in function.