Prognostic value of dobutamine stress test in patients with septic shock

AIM

To evaluate the prognostic effect of dobutamine stress test in patients with septic shock.

METHODS

Patients with septic shock received intravenous infusion of dobutamine at 10 microg . kg-1 . min-1 for 1 h. Hemodynamics and oxygen metabolism was observed. A patient who was able to increase oxygen consumption index (VO2) by >15 % was designated as a responder to the test.

RESULTS

In 47 patients with septic shock, twenty one responders and twenty six nonresponders were identified, and mortality was 33.3 % and 76.9 % respectively. After the dobutamine infusion, the responders showed increases in cardiac index (18.1 %), oxygen delivery index (12.7 %), VO2 (38.6 %), and oxygen extraction ratio (18.0 %), and reductions in systemic vascular resistance index (18.5 %). The nonresponders demonstrated increases in cardiac index (11.5 %), but no change in oxygen delivery, VO2, and oxygen extraction ratio.

CONCLUSION

Dobutamine stress test might be a good predictor of outcome in patients with septic shock.

Induction of experimental autoimmune keratitis by adoptive transfer of human corneal antigen-specific T-cell line

PURPOSE

To establish a permanent human corneal antigen (HuCOAg)-specific T-cell line and to determine whether line cells are capable of inducing inflammatory keratitis by adoptive transfer.

METHODS

Lymphoid cells harvested from HuCOAg-immunized Lewis rats were expanded to a permanent T-cell line by repetitive cycles of restimulation with HuCOAg and irradiated antigen-presenting cells and propagation in interleukin 2-containing medium. The phenotype and epitope specificity of the line cells were determined. Adoptive transfer was performed after seven cycles by intraperitoneal injection of activated T cells into irradiated recipient rats.

RESULTS

A panel of 11 overlapping synthetic HuCOAg peptides to identify T-cell epitopes recognized by the line cells was used. The cells responded selectively to a synthetic peptide containing an immunodominant epitope of HuCOAg (peptides 69-83). Line cells bore the surface phenotype of the T-helper/inducer marker (W 3/25(+) or CD4(+)). Intraperitoneal inoculation of naive rats with 5 x 10(7) activated line cells led to maximal clinical signs of stromal keratitis 7 to 9 days after transfer, characterized by corneal haze, conjunctival and episcleral injection, corneal infiltrates, and neovascularization. Histopathologic examination of the tissues revealed numerous lymphocytes and macrophages and some polymorphonuclear leukocytes along with neovascularization. The pathologic lesions were confined to the peripheral corneal stroma. Immunohistochemical studies demonstrated that the overwhelming majority of the inflammatory cells were CD4(+) T lymphocytes and macrophages; an upregulation of major histocompatibility complex class II antigen expression was also noted.

CONCLUSIONS

A long-term, rat T-cell line of CD4(+) phenotype specific for HuCOAg that can induce autoimmune keratitis by adoptive transfer of the line cells to naive syngeneic recipients is described. With the development of this cell line, the mechanisms by which T cells exert their immunopathologic effects in experimental autoimmune keratitis models can be studied.

Protein kinase c regulates purinergic component of neurogenic contractions in mouse bladder

PURPOSE

We evaluate the role of protein kinase C in excitatory purinergic neurotransmission in the mouse bladder.

MATERIALS AND METHODS

In isolated mouse detrusor strips contractile responses to electrical field stimulation were mostly mediated by neural released acetylcholine and adenosine triphosphate (ATP). The changes in neurotransmission were measured indirectly by recording the contraction of detrusor strips in response to repetitive electrical field stimulation by trains of electrical pulses at 8 Hz. 1 second in duration.

RESULTS

A protein kinase C activator, 1 to 2.5 nM. (beta-phorbol-12,13-dibutyrate (beta-PDBu), but not the inactive form alpha-phorbol-12,13-dibutyrate, significantly enhanced neurogenic detrusor contractions. The purinergic component of the evoked detrusor contractions in the presence of atropine was specifically sensitive to this enhancing effect by beta-PDBu but the cholinergic component in the alpha,beta-methylene ATP treated detrusors remained unaffected. This enhancing effect of beta-PDBu was dependent on the extracellular calcium (Ca2+) concentration. A P and/or Q type Ca2+ channel blocker, 0.1 and 0.3 microM. omega-conotoxin-MVIIC, and protein kinase C inhibitors, 0.3 and 1 microM. staurosporine and 0.3 and 1 microM. bisindolylmaleimide I but not 0.1 and 0.3 microM. omega-conotoxin-GVIA, an N type Ca2+ channel blocker, abolished the effect of beta-PDBu. Moreover, beta-PDBu did not affect the muscle responses induced by the exogenous agonists carbachol or alpha,beta-methylene ATP and potassium chloride.

CONCLUSIONS

These results suggest that the activation of Ca2+ channel, especially the P and/or Q type, may be involved in the enhancing effect of protein kinase C activator beta-PDBu on muscle contractions elicited by excitatory purinergic neurotransmission in the mouse detrusor strips.

An increase in free radical production by means of an anion channel blocker DIDS in mouse peritoneal neutrophils

DIDS (4, 4'-diisothiocyanostilbene-2, 2'-disulfonic acid) has been recognized as an anion channel blocker. In this study, we demonstrated that DIDS significantly enhanced the production of free radicals in mouse peritoneal neutrophils. By means of a luminol-chemiluminescence (LCL) monitoring system, DIDS markedly increased LCL which could be suppressed by SOD, sodium azide (NaN3), EGTA and BAPTA-AM and only slightly inhibited by staurosporine (STP). Depletion of the endoplasmic reticulum (ER)-Ca2+ store by means of thapsigargin (TG) had no effects on DIDS-enhanced LCL, but DIDS significantly increased the amount of intracellular free calcium as monitored by means of fura-2 staining. These results indicate that DIDS may enhance free radical production mediated by Ca2+ release from the mitochondria. Both phorbol-12-myristate-13-acetate (PMA) and DIDS can induce increased translocation of p47-phox of the neutrophil to the membrane fraction, which is inhibited by STP pretreatment. Since free radical generation could reduce the cytoplasmic pH (pHi), we further examined whether DIDS was capable of inducing intracellular acidification. The result indicated that DIDS certainly lowered the pHi which was also suppressed by pretreatment with either NaN3 or NaCN, but not by diphenyleneiodonium (DPI). These findings lead us to propose a working hypothesis that DIDS mainly induces superoxide production accompanied by decreasing pHi mediated through a Ca2+ -dependent effect on the mitochondria rather than on NADPH oxidase. Using the lipophilic fluorescent dye DiOC6(3), we showed that DIDS decreased the transitional mitochondrial membrane potential. NaN3, but not STP or pyrrolidine dithiocarbamate (PDTC), antagonized DIDS in the course of decreasing the mitochondrial membrane potential. Taken together, all of these findings imply a possible role of anion channels of the mitochondria in modulating free radical production and intracellular acidification of neutrophils through alteration of the mitochondrial transition membrane potential and Ca2+ -release.

Characteristics of Vibrio parahaemolyticus O3:K6 from Asia

A variety of serovars of the food-borne pathogen Vibrio parahaemolyticus normally cause infection. Since 1996, the O3:K6 strains of this pathogen have caused pandemics in many Asian countries, including Taiwan. For a better understanding of these pandemic strains, the recently isolated clinical O3:K6 strains from India, Japan, Korea, and Taiwan were examined in terms of pulsed-field gel electrophoresis (PFGE) typing and other biological characteristics. After PFGE and cluster analysis, all the O3:K6 strains were grouped into two unrelated groups. The recently isolated O3:K6 strains were all in one group, consisting of eight closely related patterns, with I1(81%) and I5(13%) being the most frequent patterns. Pattern I1 was the major one for strains from Japan, Korea, and Taiwan. All recently isolated O3:K6 strains carried the thermostable direct hemolysin (tdh) gene. No significant difference was observed between recently isolated O3:K6 strains and either non-O3:K6 reference strains or old O3:K6 strains isolated before 1996 with respect to antibiotic susceptibility, the level of thermostable direct hemolysin, and the susceptibility to environmental stresses. Results in this study confirmed that the recently isolated O3:K6 strains of V. parahaemolyticus are genetically close to each other, while the other biological traits examined were usually strain dependent, and no unique trait was found in the recently isolated O3:K6 strains.

Death signaling pathway induced by pyrrolidine dithiocarbamate-Cu(2+) complex in the cultured rat cortical astrocytes

The chelating and antioxidant effects of pyrrolidine dithiocarbamate (PDTC) have been investigated extensively for preventing cell death induced by different insults. However, the toxic effects of PDTC have been studied only recently and fewer studies on the toxic effects on astrocytes have been reported. In our study, we demonstrated that both PDTC and Cu(2+) alone were rated as only weakly toxic in inducing cell death in cortical astrocytes with IC(50) of 300 microM and 180 microM, respectively. However, PDTC and Cu(2+) in the complex form markedly potentiated with each other by about 1,000-fold with IC(50) of 0.3 microM PDTC plus 10 microM Cu(2+). Other metals at concentrations of 3-10 microM (VO(4)(5+), Cr(6+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Zn(2+), Pb(2+), Bi(2+), Ba(2+), UO(2+), Cs(+), SeO(4)(2-), La(3+)) had no such potentiating effects on PDTC. Changes in morphology (nuclear condensation), apoptotic body formation, and hypodiploidity of DNA suggested that the PDTC-Cu(2+) complex induced cell death through an apoptotic process. Further studies showed that the PDTC-Cu(2+) complex decreased mitochondrial membrane potential, increased hydrogen peroxide production, and depleted GSH contents. After the increased oxidative stress, PDTC-Cu(2+) complex differentially activated JNKs, ERK, p38 and caspase 3, which caused PARP degradation in a time-dependent manner. All these effects were consistent with the increased cellular Cu contents. The nonpermeable copper-specific chelator bathocuproine disulfonate (BCPS), but not the permeable Cu(2+) chelator neocuproine, abolished all the observed effects. Antioxidants (N-acetylcysteine [NAC], vitamin C), catalase, and Cu(2+)-binding proteins (albumin, hemoglobin, and higher serum) reduced the cytotoxic effects of PDTC-Cu(2+) complex. We concluded that the death signaling pathway of PDTC-Cu(2+) complex was mediated by oxidative stress and subsequent JNK activation. These findings imply that PDTC, a widely used pesticide and medicine that is capable of penetrating the blood-brain barrier, may cause neurotoxicity through astrocyte dysfunction.

Characterization of Vibrio parahaemolyticus isolates obtained from foodborne illness outbreaks during 1992 through 1995 in Taiwan

Vibrio parahaemolyticus is an important foodborne pathogen in Taiwan and many other Asian countries. A total of 371 isolates of V. parahaemolyticus collected from patients involved in foodborne illness outbreaks in Taiwan from 1992 to 1995 were characterized. These isolates had typical biochemical characteristics and only 4% were urease positive. The most frequently isolated serovars were O5:K15 (18.5%), O4:K8 (16.2%), O3:K29 (12.5%), O1:K56 (8.3%), O2:K3 (6.5%), and O4:K12 (6.0%). Most of the isolates were susceptible to nalidixic acid, tetracycline, tobramycin, cephalothin, and gentamicin. About 10% of the isolates were resistant to seven or more antibiotics. Approximately 92.4% of these V. parahaemolyticus showed beta-hemolysis on Wagatsuma blood agar plate and approximately 62.1% of these isolates exhibited detectable amounts of thermostable direct hemolysin. Most of the isolates examined exhibited two copies of tdh genes on the 1.3- and 2.5-kb HindIII-digested chromosome fragments with several variations on other fragments. A pulsed-field gel electrophoresis (PFGE) subspecies typing scheme was used to analyze these domestic isolates and the O3:K6 strains from Japan, Korea, and Taiwan. Fifty seven patterns were differentiated with A, B, C, E, and H being the major domestic types (cumulatively 76% of isolates), while O3:K6 strains (PFGE type I), abruptly occurring since 1996, were genetically distant from the major domestic types.

Diversity of Helicobacter pylori among Chinese persons with H. pylori infection

To determine whether there is diversity among clinical isolates of Helicobacter pylori in Chinese patients with peptic ulcer disease, 40 strains of H. pylori were isolated from antral biopsy specimens obtained at the gastroenterology clinic of Xiangya Hospital from January 1996 to June 1998. Total protein profile by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and DNA diversity by polymerase chain reaction-random amplified polymorphic DNA (PCR-RAPD) fingerprinting were performed with these isolates. All the isolates from peptic ulcer disease were relatively homogeneous in protein profiles, but they showed a great DNA sequence diversity by PCR-RAPD fingerprinting. In Chinese patients H. pylori demonstrated an enormous diversity. The diversity among clinical isolates of H. pylori could be distinctly demonstrated and this observation will be helpful in the management of intrafamilial and recurrent H. pylori infection. PCR-RAPD fingerprinting is an efficient method of distinguishing between clinical isolates of H. pylori.

High glucose-induced apoptosis in human endothelial cells is mediated by sequential activations of c-Jun NH(2)-terminal kinase and caspase-3

BACKGROUND

Diabetes mellitus causes multiple cardiovascular complications. High glucose can induce reactive oxygen species and apoptosis in endothelial cells. Little is known about the molecular mechanisms in high glucose-induced endothelial cell apoptosis.

METHODS AND RESULTS

We elucidated the signaling pathway of high glucose-induced apoptosis in human umbilical vein endothelial cells (HUVECs). HUVECs were treated with media containing 5.5, 19, or 33 mmol/L of glucose in the presence or absence of an antioxidant, ascorbic acid. The level of intracellular H(2)O(2) was measured by flow cytometry. For detection of apoptosis, the cell death detection ELISA assay and the morphological Hoechst staining were used. High glucose was capable of inducing the activity of c-Jun NH(2)-terminal kinase (JNK) but not extracellular signal-regulated kinase 1/2 or p38 mitogen-activated protein kinase during the treatment periods, as evidenced by immunocomplex kinase assay. Moreover, we found that the interleukin 1beta-converting enzyme (ICE)/CED-3 family protease (caspase-3) became activated in high glucose-induced apoptosis. Caspase-3/CPP32-specific inhibitor, Ac-DEVD-CHO, could inhibit high glucose-induced apoptosis. Furthermore, we found that JNK1 specific antisense oligonucleotide could suppress caspase-3 activity but not affect H(2)O(2) generation and could block apoptosis induced by high glucose. Also, H(2)O(2) generation, JNK activity, caspase-3 activity, and the subsequent apoptosis induced by high glucose could be suppressed by ascorbic acid.

CONCLUSIONS

The present study indicates that reactive oxygen species induced by high glucose may be involved in JNK activation, which in turn triggers the caspase-3 that facilitates the apoptosis in HUVECs.

Effects of cartap on isolated mouse phrenic nerve diaphragm and its related mechanism

Cartap, a nereistoxin analogue pesticide, is reported to have no irritation to eyes in rabbits. However, we have demonstrated recently that cartap could actually cause acute death in rabbits via ocular exposure. Our preliminary study with isolated mouse phrenic nerve diaphragms has shown that instead of neuromuscular blockade, cartap caused muscular contracture. The objective of the study was to examine the effect of cartap on the neuromuscular junction in more detail and to investigate its possible underlying mechanism with isolated mouse phrenic nerve diaphragms and sarcoplasmic reticulum (SR) vesicles. Cartap or nereistoxin at various concentrations was added in the organ bath with isolated mouse phrenic nerve diaphragm and both nerve- and muscle-evoked twitches were recorded. Instead of blocking the neuromuscular transmission as nereistoxin did, cartap caused contracture in stimulated or quiescent isolated mouse phrenic nerve diaphragm. Both the cartap-induced muscular contracture force and the time interval to initiate the contracture were dose-dependent. The contracture induced by cartap was not affected by the pretreatment of the diaphragm with the acetylcholine receptor blocker alpha-bungarotoxin; the Na(+) channel blocker tetrodotoxin; or various Ca(2+) channel blockers, NiCl(2), verapamil, and nifedipine. On the contrary, the contracture was significantly inhibited when the diaphragm was pretreated with ryanodine or EGTA containing Ca(2+)-free Krebs solution or in combination. This suggested that both internal and extracellular Ca(2+) might participate in cartap-induced skeletal muscle contracture. Moreover, cartap inhibited the [(3)H]-ryanodine binding to the Ca(2+) release channel of SR in a dose-dependent manner. Additionally, cartap could induce a significant reduction in Ca(2+)-ATPase activity of SR vesicles at a relatively high dose. The results suggested that cartap might cause the influx of extracellular Ca(2+) and the release of internal Ca(2+), with subsequent induction of muscular contracture in the isolated mouse phrenic nerve diaphragm. Based on these findings, we propose that the acute death of rabbits following ocular exposure to cartap might have resulted from respiratory failure secondary to diaphragm contracture.

A simple modified arthroscopic procedure for fixation of displaced tibial eminence fractures

SUMMARY

Avulsion fractures of the tibial eminence have been well described in children and adults with an increased in incidence resulting from road traffic and athletic accidents. According to the literature, only surgical treatment is advocated because of the high incidence of the nonunion and instability following conservative treatment. Open reduction can cause some morbidity and, therefore, arthroscopic techniques have been developed. The limitations of the techniques are related to technical difficulty and unstable fixation. We report a simple and effective method of fixation with the following advantages: (1) use of metallic suture for stable fixation, (2) the fixation device is easily removed in the office, (3) there is no need of additional instruments, and (4) the minimal size of the fixation device avoids damage to the anterior cruciate ligament insertion. This technique has been used in a series of 10 consecutive patients treated for avulsion fractures of the tibial spine since 1991, resulting in a high rate of excellent and good results without any case of nonunion fracture or related complication.

Alterations in the properties and isoforms of sciatic nerve Na(+), K(+)-ATPase in methylcyclopentadienyl manganese tricarbonyl-treated mice

The in vivo effect of methylcyclopentadienyl manganese tricarbonyl (MMT), an organic manganese-containing compound, on the mouse motor nerve was studied. The motor nerve conduction velocity was markedly decreased in MMT-treated mice. The Na(+),K(+)-ATPase activity of sciatic nerve isolated from MMT-treated mice was decreased; however, the sciatic nerve Na(+),K(+)-ATPase activity was not affected by the in vitro treatment of MMT. Moreover, [(3)H]ouabain binding of sciatic nerve isolated from MMT-treated mice was decreased. Using Western blot analysis, the amount of Na(+),K(+)-ATPase catalytic alpha1 subunit polypeptide in sciatic nerve of MMT-treated mice was also decreased. These results indicate that a causal relationship may exist between reduced nerve Na(+),K(+)-ATPase activity and motor nerve conduction velocity in MMT-treated mice and that a measurable decrease in alpha1 catalytic subunit isoform of Na(+),K(+)-ATPase may be necessary for the development of peripheral neuropathy by MMT.

Complete reconstitution of clathrin basket formation with recombinant protein fragments: adaptor control of clathrin self-assembly

Clathrin polymerization into a polyhedral basket, surrounding budding membrane vesicles, mediates protein sorting during endocytosis and organelle biogenesis. Adaptor proteins target clathrin assembly to specific membrane sites and sequester receptors into the clathrin coat. We have reconstituted complete clathrin basket formation from recombinantly expressed fragments of clathrin and adaptors. This reconstitution reveals a hierarchy of clathrin self-assembly interactions and demonstrates that adaptors control basket formation by alignment of the distal domains of the clathrin triskelion leg through their binding to the terminal domain.

Calgranulin C has filariacidal and filariastatic activity

The calgranulins are a family of calcium- and zinc-binding proteins produced by neutrophils, monocytes, and other cells. Calgranulins are released during inflammatory responses and have antimicrobial activity. Recently, one of the calgranulins, human calgranulin C (CaGC), has been implicated as an important component of the host responses that limit the parasite burden during filarial nematode infections. The goal of this work was to test the hypothesis that human CaGC has biologic activity against filarial parasites. Brugia malayi microfilariae and adults were exposed in vitro to 0.75 to 100 nM recombinant human CaGC. Recombinant CaGC affected adult and larval parasites in a dose-dependent fashion. Microfilariae were more sensitive to the action of CaGC than were adult parasites. At high levels, CaGC was both macrofilariacidal and microfilariacidal. At lower levels, the percentage of parasites killed was dependent on the level of CaGC in the culture system. The larvae not killed had limited motility. The filariastatic effect of low-level CaGC was reversed when the CaGC was removed from the culture system. Immunohistochemical analysis demonstrated that human CaGC accumulated in the cells of the hypodermis-lateral chord of adult and larval parasites. The antifilarial activity of CaGC was not due to the sequestration of zinc. Thus, the cellular and molecular mechanisms that result in the production and release of CaGC in humans may play a key role in the regulation of filarial parasite numbers.

Apoptosis induced by a corneal-endothelium-derived cytokine

PURPOSE

The purpose of this study was to isolate and characterize cDNA clones encoding target proteins for autoantibodies in patients at high risk for transplant rejection.

METHODS

A pool of 10 sera from patients at high risk for rejection who had undergone corneal transplantation was used for immunoscreening of an endothelial cDNA library, and the cDNA fragments were subcloned into prokaryotic expression vectors to generate recombinant fusion proteins. Cytotoxicity of recombinant protein was determined by a modified 51Cr-release assay. Apoptosis induced by recombinant protein was determined by fluorescent dye-chromatin fragmentation assay and by TdT-dUTP terminal nick-end labeling (TUNEL) assay. An enzyme-linked immunosorbent assay was used to detect the presence of antibodies to recombinant protein in the sera of high-risk patients undergoing corneal transplantation and of control subjects.

RESULTS

Screening of 500,000 plaques identified six positive clones, one of which demonstrated extensive homology with a novel tumor-derived cytokine termed endothelial monocyte-activating polypeptide (EMAP). EMAP was synthesized as a 39-kDa precursor that was proteolytically cleaved to generate an active 22-kDa cytokine. The mature peptide of EMAP alone was capable of inducing the death of cultured endothelial cells, whereas the propeptide was inactive. The protein synthesis inhibitor cycloheximide potentiated EMAP-induced apoptosis in endothelial cells. Cell death by apoptosis was evidenced by DNA fragmentation, extensive surface bleb formation, and chromatin condensation. A statistically significant difference was found in the level of antibodies specific to EMAP between patients at high risk for corneal transplant rejection and control subjects (P<0.001). The antibody levels were elevated in patients with severe graft reaction when compared with patients with no graft reaction (P<0.001).

CONCLUSIONS

These studies demonstrated that EMAP is a novel protein in corneal endothelial cells that is capable of inducing programmed cell death. Overexpression of this cytokine could initiate endothelial cell damage leading to stromal edema and corneal decompensation.

Incidence of highly genetically diversified Vibrio parahaemolyticus in seafood imported from Asian countries

Vibrio parahaemolyticus is an important pathogen of humans and aquacultured animals, especially in Asian countries. In this study, we examined 686 samples of seafood imported from Hong Kong, Indonesia, Thailand and Vietnam for V. parahaemolyticus. V. parahaemolyticus was recovered from 315 (45.9%) samples. The incidence of V. parahaemolyticus in products from Hong Kong and Thailand was markedly higher than the incidence in products from Indonesia and Vietnam. The incidence rates in shrimp, crab, snail, lobster, sand crab, fish and crawfish were 75.8, 73.3, 44.3, 44.1, 32.5, 29.3 and 21.1%, respectively. None of the isolates possessed the hemolysin genes (tdh, trh). The chromosomal DNA of 121 randomly selected imported isolates and three local environmental strains was digested with SfiI and analyzed by pulsed-field gel electrophoresis (PFGE). These isolates were then grouped into 96 different but mostly unique PFGE patterns. After hierarchical cluster analysis, these patterns could be arbitrarily grouped into twenty-two PFGE types (type A to V). A wide range of PFGE types were identified in isolates from different origin. Moreover, the PFGE types were not specifically associated with the origin or kind of seafood. These results reveal the high genetic diversity in V. parahaemolyticus isolated from seafood.

Nitric oxide prevents apoptosis of human endothelial cells from high glucose exposure during early stage

Hyperglycemia is a major cause of diabetic vascular disease. High glucose can induce reactive oxygen species (ROS) and nitric oxide (NO) generation, which can subsequently induce endothelial dysfunction. High glucose is also capable of triggering endothelial cell apoptosis. Little is known about the molecular mechanisms and the role of ROS and NO in high glucose-induced endothelial cell apoptosis. This study was designed to determine the involvement of ROS and NO in high glucose-induced endothelial cell apoptosis. Expression of endothelial nitric oxide synthase (eNOS) protein and apoptosis were studied in cultured human umbilical vein endothelial cells (HUVECs) exposed to control-level (5.5 mM) and high-level (33 mM) glucose at various periods (e.g., 2, 12, 24, 48 h). We also examined the effect of high glucose on H(2)O(2) production using flow cytometry. The results showed that eNOS protein expression was up-regulated by high glucose exposure for 2-6 h and gradually reduced after longer exposure in HUVECs. H(2)O(2) production and apoptosis, which can be reversed by vitamin C and NO donor (sodium nitroprusside), but enhanced by NOS inhibitor (N(G)-nitro-L-arginine methyl ether), were collated to a different time course (24-48 h) to HUVECs. These results provide the molecular basis for understanding that NO plays a protective role from apoptosis of HUVECs during the early stage (<24 h) of high glucose exposure, but in the late stage (>24 h), high glucose exposure leads to the imbalance of NO and ROS, resulting to the observed apoptosis. This may explain, at least in part, the impaired endothelial function and vascular complication of diabetic mellitus that would occur at late stages.

Effect of estrogen on cellular metabolism of the human anterior cruciate ligament

Previous studies from this laboratory have established the presence of estrogen receptors in the human anterior cruciate ligament. The purpose of this study was to investigate the effects of 17 beta-estradiol on cell proliferation and procollagen levels, as an indicator of collagen synthesis, in the human anterior cruciate ligament fibroblasts. Fibroblast proliferation and procollagen synthesis in response to near log concentrations of 17 beta-estradiol (at 0.0029 ng/mL, 0.025 ng/mL, 0.25 ng/mL, 2.5 ng/mL, and 25 ng/mL) were assessed with the measurement of 3H-thymidine incorporation and Types 1 and 3 procollagen specific equilibrium radioimmunoassays. On Days 1 and 3, there was a dose dependent decrease in the proliferation of anterior cruciate ligament fibroblasts with increasing estradiol concentrations. This dose dependent effect of decreased fibroblast proliferation with increasing estradiol concentrations became less apparent at 7, 10, and 14 days. On Days 1 and 3, procollagen synthesis decreased in a dose dependent manner with increasing estradiol concentrations. On Days 7, 10, and 14, this dose dependent effect was attenuated. No significant differences in Type 3 procollagen synthesis by anterior cruciate ligament fibroblasts were observed with varying estradiol concentrations at any of the designated points. These early physiologic changes in fibroblast proliferation and Type I procollagen synthesis may provide a biologic explanation for the increased anterior cruciate ligament injury rate observed in female athletes, suggesting that it is the acute cyclic variations in the female athlete who is menstruating that predisposes her to ligamentous injury.

Sensitivity of L-(-)2,3-dideoxythiacytidine resistant hepatitis B virus to other antiviral nucleoside analogues

L-(-)2',3'-Dideoxythiacytidine (L(-)SddC, Lamivudine) resistant hepatitis B virus (HBV) develops in patients after prolonged treatment. Point mutations detected in the viral genome from these patients have been shown to be responsible for L(-)SddC resistance. Therefore, new drugs active against L(-)SddC resistant HBV are needed. Using a transient transfection system, we studied the sensitivity of L(-)SddC resistant HBV to other anti-HBV nucleoside analogues. It was found that the L526M mutation alone caused greater resistance to penciclovir (PCV) than did the V553I mutation alone. Both mutations also caused the virus to be less sensitive to L(-)SddC and 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil (L-FMAU), although the degree of resistance was much less than that to PCV. The A546V mutation had no impact on the sensitivity to L(-)SddC, L-FMAU, and PCV. When these single mutations were coupled with the M550V/I mutation, all the double mutants were resistant to those drugs. Although 2',3'-dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine (L(-)Fd4C) was also less active, the IC50 of L(-)Fd4C against the L(-)SddC resistant mutant was at least fifty times lower than that against cell growth in culture. DNA polymerase associated with L(-)SddC resistant virions was also found to be less sensitive than that with wild-type HBV to those L-nucleoside triphosphates. All the L(-)SddC resistant mutants were still sensitive to 9-(2-phosphonylmethoxyethyl)-adenine (PMEA). These results suggest that different mutations in the HBV genome have a different impact on its sensitivity to those compounds, and L(-)SddC resistant HBV may also be resistant to PCV, L-FMAU, and L(-)Fd4C. A nucleoside analogue less toxic than PMEA could be developed against L(-)SddC resistant HBV.

Clathrin self-assembly is mediated by a tandemly repeated superhelix

Clathrin is a triskelion-shaped cytoplasmic protein that polymerizes into a polyhedral lattice on intracellular membranes to form protein-coated membrane vesicles. Lattice formation induces the sorting of membrane proteins during endocytosis and organelle biogenesis by interacting with membrane-associated adaptor molecules. The clathrin triskelion is a trimer of heavy-chain subunits (1,675 residues), each binding a single light-chain subunit, in the hub domain (residues 1,074-1,675). Light chains negatively modulate polymerization so that intracellular clathrin assembly is adaptor-dependent. Here we report the atomic structure, to 2.6 A resolution, of hub residues 1,210-1,516 involved in mediating spontaneous clathrin heavy-chain polymerization and light-chain association. The hub fragment folds into an elongated coil of alpha-helices, and alignment analyses reveal a 145-residue motif that is repeated seven times along the filamentous leg and appears in other proteins involved in vacuolar protein sorting. The resulting model provides a three-dimensional framework for understanding clathrin heavy-chain self-assembly, light-chain binding and trimerization.

Cytokine-induced calgranulin C expression in keratocytes

The authors have identified a corneal stromal protein (CO-Ag) that may be involved in the pathogenesis of Mooren's ulcer. The CO-Ag cDNA sequence is identical to that of human neutrophil calgranulin C (CaGC). This study sought to demonstrate expression of the CaGC gene in the human cornea and in corneal keratocytes after cytokine stimulation. In situ hybridization and immunohistochemistry were used to localize CaGC mRNA and protein in normal and diseased human corneas, including a specimen with Mooren's ulcer. Cultured bovine keratocytes were stimulated with IL-1 alpha or TNF-alpha, and reverse transcription polymerase chain reaction (RT-PCR) was performed to amplify CaGC cDNA from cytokine-stimulated keratocytes and unstimulated controls. Southern blotting verified the specificity of the RT-PCR amplification products. In situ hybridization detected human CaGC mRNA in the stroma of corneas with Fuchs' dystrophy, postinfection corneas, and a cornea with Mooren's ulcer. In cultured bovine keratocytes, peak levels of CaGC mRNA were reached 6 h after cytokine stimulation. Southern blots with an oligonucleotide probe specific for CaGC detected the RT-PCR products of expected sizes (273 bp) and confirmed that the amplified CO-Ag sequence was identical to that of CaGC. These studies are the first to demonstrate the presence of CaGC in the human cornea and the ability of stromal keratocytes to produce CaGC (CO-Ag). The up-regulation of CaGC gene expression by corneal keratocytes due to proinflammatory cytokines from trauma or inflammation may induce autoimmunity that ultimately results in Mooren's ulceration.

EGF receptor signaling stimulates SRC kinase phosphorylation of clathrin, influencing clathrin redistribution and EGF uptake

Epidermal growth factor (EGF) binding to its receptor causes rapid phosphorylation of the clathrin heavy chain at tyrosine 1477, which lies in a domain controlling clathrin assembly. EGF-mediated clathrin phosphorylation is followed by clathrin redistribution to the cell periphery and is the product of downstream activation of SRC kinase by EGF receptor (EGFR) signaling. In cells lacking SRC kinase, or cells treated with a specific SRC family kinase inhibitor, EGF stimulation of clathrin phosphorylation and redistribution does not occur, and EGF endocytosis is delayed. These observations demonstrate a role for SRC kinase in modification and recruitment of clathrin during ligand-induced EGFR endocytosis and thereby define a novel effector mechanism for regulation of endocytosis by receptor signaling.

Ankle sprains and other soft tissue injuries

Lateral ankle sprains are the most frequently encountered injuries in sports. In the evaluation of lateral ankle injury, one should consider all soft tissue structures (i.e., peroneal tendons, ligaments of the ankle, subtalar joints, around the lateral ankle). The treatment of most ankle sprains has evolved from immobilization to functional rehabilitation. Many patients with ankle sprains return to their previous activities. A few patients are left with pain and residual instability after conservative treatment; thus, the question of when to operate on acute severe ankle sprain remains controversial. The other challenge physicians face is the problem of persistent lateral ankle pain after sprain. This condition may be due to intra-articular or extra-articular pathology (i.e., soft tissue lateral ankle impingement, osteochondral lesion, or partial peroneal tendon tear). Diagnosis can be made with careful history, physical examination, and appropriate ancillary studies. Only proper diagnosis can lead to uncompromised, undelayed patient care.