Altered cocaine potency in the nucleus accumbens following 7-day withdrawal from intermittent but not continuous treatment: voltammetric assessment of dopamine uptake in the rat

Using in vitro fast scan cyclic voltammetry, we measured cocaine potency for inhibiting dopamine uptake/clearance in accumbens slices 7 days after withdrawal from chronic cocaine pretreatments. Rats were pretreated with 40 mg/kg per day for 14 days, either via continuous osmotic minipumps or by once-daily injections. The cocaine potency was subsequently assessed for endogenous and exogenous dopamine applied via single-pulse electrical stimulation and caged-dopamine photolysis, respectively. Under baseline conditions, no differences in either endogenous or exogenous dopamine kinetics were observed in the two cocaine pretreatment groups. In contrast, the potency of bath-applied cocaine for inhibiting endogenous dopamine uptake was enhanced in the intermittent injection group with no change in the continuous infusion group. The selective increase in the cocaine potency following injections was also demonstrable for clearance of photo-applied DA. The enhanced cocaine potency in the accumbens slices following 7 days of withdrawal is consistent with the residual sensitization to cocaine-induced locomotion following daily cocaine injections. Behavioral tolerance following continuous infusion, on the other hand, may be mediated via a mechanism distinct from altered dopamine uptake.

Distribution of HIV type 1 (HIV-1) in blood components: detection and significance of high levels of HIV-1 associated with platelets

BACKGROUND

Although inactivation of enveloped viruses transmitted by plasma derivatives has been successful, no methods for virus inactivation or removal have been established for platelet concentrates or red cell (RBC) components. Relatively little is known regarding the extent or significance of virus interactions with the cellular constituents in these components.

STUDY DESIGN AND METHODS

Units of whole blood were collected from six HIV type 1 (HIV-1)-positive, asymptomatic individuals and separated into peripheral blood mononuclear cells (PBMNCs), cell-free plasma, white cell-reduced platelet concentrate, and white cell-reduced RBCs. DNA and RNA polymerase chain reaction and virus culture methods were used to study the compartmentalization of HIV-1 immediately after component preparation and after storage.

RESULTS

As expected, HIV DNA and infectious virus were detected in fresh blood and in PBMNCs, and virion-associated RNA was detected in fresh plasma from all six donors. The levels of viral nucleic acids in these preparations remained relatively stable with 4 degrees C storage, whereas infectivity of PBMNCs was rapidly lost. Washed RBCs tested negative for HIV in all assays at all time points. Platelets retained high levels of HIV RNA (but not infectivity) after extensive washing, as well as after storage at 4 and 22 degrees C. High-level platelet-associated HIV-1 was also demonstrated in samples collected during early seroconversion. Periseroconversion and postseroconversion levels of platelet-associated HIV-1 correlated with the level of plasma viremia and with the rate of progression to AIDS. Cell-free virus from donor plasma and tissue culture fluid rapidly and firmly attached to platelets from noninfected donors. Infectivity of tissue culture virus bound to platelets was demonstrated in vitro.

CONCLUSION

Significant levels of HIV-1 are associated with platelets during all stages of infection. Platelet-associated HIV could either mediate virus clearance or facilitate virus dissemination and expanded tropism. Finally, virus inactivation research must address virus associations with platelets.

CCR5 coreceptor utilization involves a highly conserved arginine residue of HIV type 1 gp120

The seven-transmembrane CCR5 was recently found to double as a coreceptor for a genetically diverse family of human and nonhuman primate lentiviruses. Paradoxically, the main region of the envelope protein believed to be involved in CCR5 utilization was mapped to hypervariable region 3, or V3, of the envelope glycoprotein gp120. In this study, we addressed the question of whether functional convergence in CCR5 utilization is mediated by certain V3 residues that are highly conserved among HIV type 1 (HIV-1), HIV type 2, and simian immunodeficiency virus. Site-directed mutagenesis carried out on three such V3 residues revealed that the Arg-298 of HIV-1 gp120 has an important role in CCR5 utilization. In contrast, no effect was observed for the other residues we tested. The inability of Arg-298 mutants to use CCR5 was not attributed to global alteration of gp120 conformation. Neither the expression, processing, and incorporation of mutant envelope proteins into virions, nor CD4 binding were significantly affected by the mutations. This interpretation is further supported by the finding that alanine substitutions of five residues immediately adjacent to the arginine residue had no effect on CCR5 utilization. Taken together, our data strongly suggests that the highly conserved Arg-298 residue identified in the V3 of HIV-1 has a significant role in CCR5 utilization, and may represent an unusually conserved target for future anti-viral designs.

Predictive value of creatine kinase (CK)-MB for diagnosis of acute myocardial infarction after major noncardiac surgery

BACKGROUND

The aim of this study was to provide insight into the interpretation of CK-MB data after major noncardiac surgery.

METHODS

Some 3,321 patients who underwent major non-emergent noncardiac procedures (orthopedic 31%, intrathoracic 12%, vascular 22%, other 35%) were studied. All patients had at least two CK samples measured postoperatively.

RESULTS

Acute myocardial infarction was diagnosed in 43 (1.3%) patients using study criteria including CK-MB and electrocardiographic data. All of the various threshold values of peak CK-MB values and peak CK-MB as a percentage of total CK had poor positive predictive values because of high false positive rates and the low rate of acute myocardial infarction.

CONCLUSION

These data demonstrate the need for markers of myocardial injury with greater cardiac specificity after noncardiac surgery.

Purification and characterization of a novel levanoctaose-producing levanase from Pseudomonas strain K-52

Levan-assimilating micro-organisms from soil samples were screened for levanoligosaccharide-generating enzyme production. The isolated strain K-52 produced an extracellular levanoctaose-generating enzyme and was identified as belonging to genus Pseudomonas. The levanase was purified to homogeneity by (NH4)2SO4 fractionation and successive column chromatography on DEAE-cellulose, phenyl-Toyopearl 650 M, Sephadex G-100 and hydroxyapatite. The molecular mass of the enzyme was estimated as approx. 38 kDa by both SDS/PAGE and gel filtration, and its isoelectric point was approx. pH 4.8. The optimum temperature and pH for the enzyme reaction were 35 and 7.0 respectively. The enzyme was stable at a pH range of 6.0-9.0 at 4 degrees C and up to 40 degrees C at pH 6.8. The enzyme activity was inhibited by Fe2+, Cu2+, Hg2+ and Ag2+. The levanase was specific toward 2,6-beta-D-fructosidic linkages of levan and did not hydrolyse other polysaccharides such as inulin and dextran. Chemical modification on the levanase suggested that cysteine and histidine residues are essential for enzyme activity. The levanoctaose liberated by levanase reaction was used selectively only by the intestinal beneficial micro-organisms, such as Bifidobacterium and Lactobacillus spp.

Effects of blood flow and venous network on the survival of the arterialized venous flap

The purpose of this study was to evaluate further factors that could explain the survival mechanism in the arterialized venous flap. The authors used 16 canines to investigate the survival rate and pattern of the arterialized venous flap and compared the results with those of the conventional saphenous flap. The number and distribution of draining veins in the arterialized venous flap group were varied to observe their impact on the survival rate and pattern. Gross examination of venous network, blood gas, venogram, blood pressure, and histologic study were also carried out. Although there was no significant difference in final survival rate between conventional flap and arterialized venous flap with two efferent veins (p > 0.01), that of the arterialized venous flap increased significantly as the number of draining veins increased. Blood gas analysis showed that more effective oxygen consumption took place when the number of draining veins increased. By measuring the blood flow and volume at 8 hours after the operation with a laser Doppler flowmeter, it was possible to predict the necrosis of the arterialized venous flap. Attachment to a high pressure arterial blood flow system induced smooth muscle proliferation and neogrowth of elastic fibers in the veins. Furthermore, progressive narrowing of the lumen hastened the development of a collateral circulation, demonstrated on a venogram by the tortuous vessels and neovascularization up to the flap margin. To make it possible to predict and achieve complete survival of the arterialized venous flap, the following criteria must be considered: (a) an arterialized venous flap should be designed to contain most of the venous network in the center, (b) the arterial inflow has to be anastomosed to one afferent vein, (c) two or more efferent veins should drain the arterialized venous flap.

The effect of prior dural puncture on cerebrospinal fluid sufentanil concentrations in sheep after the administration of epidural sufentanil

Sufentanil is a highly lipid soluble opioid that provides potent analgesia when administered in the subarachnoid space. Unfortunately, the penetration of sufentanil into the cerebrospinal fluid (CSF) after epidural administration is poor, and limits its effectiveness for epidural analgesia. Dural puncture may enhance the movement of epidural sufentanil into the subarachnoid space and increase its effectiveness. To determine whether the administration of epidural sufentanil adjacent to a dural puncture results in significantly greater CSF concentrations, 18 adult ewes were studied. Animals in the control group had an epidural catheter placed at the superior border of the pelvis without dural puncture. Animals in the study group had an epidural catheter placed, followed by a dural puncture performed using an 18-gauge Touhy needle. The dural puncture was performed one interspace cephalad to the epidural catheter. One hour after dural puncture, each animal received a loading dose of 0.35 microg/kg of sufentanil (5 microg/mL) through the epidural catheter, followed by an infusion of epidural sufentanil 0.15 microg x kg(-1) x h(-1) for a period of 4 h. After 4 h, CSF was sampled from a site one interspace caudad to the epidural catheter as well as at the cisterna magna. The mean CSF concentration of sufentanil at the level of the pelvis for animals with a dural puncture was 12.1 +/- 3.0 ng/mL compared with 1.8 ng/mL in controls with intact dura. Sufentanil concentrations at the cisterna magna were below the level of detection (0.08 ng/mL) for all animals in both groups. We conclude that an 18-gauge dural puncture significantly increases movement of sufentanil from the epidural to the intrathecal space. This increase in sufentanil concentration at the level of the pelvis was not associated with detectable levels of sufentanil at the brainstem.

IMPLICATIONS

This study addresses the effect of dural puncture on spinal fluid concentrations of sufentanil after epidural administration. A sheep model was used to measure drug concentrations in the spinal fluid at the levels of the pelvis and brainstem after epidural administration. Dural puncture significantly enhanced movement of sufentanil into the spinal fluid at the level of the pelvis, but brainstem concentrations were below the level of detection. Analgesic concentrations of spinal sufentanil in the clinical setting, as well as brainstem concentrations associated with respiratory depression, have yet to be defined.

Purification and cloning of glyoxalase II from rat liver

Glyoxalase (GLO) II, which is a component of GLO system and catalyze the conversion of S-lactoyl-glutathione to D-lactate, was purified 1488 fold from rat liver by two steps of Affigel blue and carbobenzoxyglutathione-Sepharose 4B affinity chromatography. The molecular weight of the enzyme was estimated to be 29 kDa which is similar to those from other species. The sequence of N-terminal 9 amino acid residues was determined to be MGIRLLPAT. This was then used to synthesize degenerative primers. cDNA clone was isolated by first synthesizing cDNA from RNA and then PCR amplification. The sequence of cDNA clone was determined by serial sequencing analysis.

Early indicators of prognosis in upper gastrointestinal hemorrhage

OBJECTIVE

Endoscopy allows accurate risk stratification of patients presenting with gastrointestinal bleeding; frequently, however, it is not immediately available. Initial management and triage of patients thus depends on nonendoscopic information. We sought to risk stratify patients with upper gastrointestinal bleeding using variables available on initial presentation (ie., before endoscopy).

METHODS

A retrospective observational study was performed using data from 335 admissions with an initial diagnosis of upper gastrointestinal hemorrhage. All patients underwent endoscopy and were evaluated for an adverse outcome during their hospitalization. An adverse outcome was defined as death, the need for any operation, recurrent hematemesis, recurrent melena after initial clearing, or a hematocrit falling despite transfusion.

RESULTS

Univariate analysis identified 17 distinct variables associated (p < 0.05) with an adverse outcome. A stepwise logistic regression identified five variables as independent predictors (p < 0.05) of an adverse outcome: an initial hematocrit <30%, initial systolic blood pressure < 100 mm Hg, red blood in the nasogastric lavage, history of cirrhosis or ascites on exam, and a history of vomiting red blood. We derived a decision rule based on patients having 0-5 of these independent predictors. This decision rule allowed identification of a large patient population with a <10% chance of an adverse outcome.

CONCLUSION

Risk stratification is possible from information available at the time of initial presentation. If confirmed in other populations, these predictors can be used to identify patients who require a less intensive level of care.

Alterations in baseline activity and quinpirole sensitivity in putative dopamine neurons in the substantia nigra and ventral tegmental area after withdrawal from cocaine pretreatment

Using in vivo single-unit recording, we compared in rats the-effects of continuous infusion and once-a-day injections of cocaine on the activity of single putative dopamine neurons in the substantia nigra and ventral tegmental area. After a 7-day withdrawal, we determined: (1) the number of spontaneously active neurons and their bursting patterns and (2) sensitivity of these neurons to intravenous quinpirole. In the substantia nigra, continuous cocaine infusion reduced the number of neurons without affecting the bursting patterns; daily injections were without effects. In the ventral tegmental area, continuous infusion reduced the bursting activity without affecting the number of neurons, whereas injections increased number of neurons without changes in the bursting pattern. Acute sulpiride normalized all the changes in both cell body areas. The quinpirole sensitivity was selectively increased in the nigral neurons following withdrawal from continuous infusion. Possible role of D2/autoreceptor mechanisms in these changes is discussed.

Quantitation of white cell subpopulations by polymerase chain reaction using frozen whole-blood samples. Viral Activation Transfusion Study

BACKGROUND

Previous methods for processing whole blood (WB) for nucleic acid analyses of white cells (WBCs) required fresh blood samples. A simple protocol that involves the freezing of WB for quantitative polymerase chain reaction (PCR) analyses was evaluated.

STUDY DESIGN AND METHODS

Controlled studies were conducted in which paired fresh and frozen WB preparations were analyzed. The integrity of WBCs in the frozen WB samples was first assessed by flow cytometry using CD45 fluorescence, and calibration beads to quantitate recovery of WBC subsets. PCR of an HLA-DQ-A sequence was used to quantitate residual WBCs in a double-filtered red cell (RBC) component spiked with serial dilutions of WBCs, as well as in 51 filtered RBCs and 19 filtered platelet concentrates. Y-chromosome-specific PCR was used to quantitate male WBCs in five female WB samples spiked with serial dilutions of male WBCs and in serially collected frozen WB samples from four females transfused with male blood components.

RESULTS

By flow cytometry, all major WBC subpopulations in frozen-thawed WB were quantitatively recovered and immunologically intact, although they were nonviable. HLA-DQ-A PCR quantitation of a dilution series from 8 to 16,700 per mL of WBCs spiked into double-filtered RBCs showed linear correlation of the results with both fresh and frozen preparations of the expected WBC concentrations (r2 = 0.98, p<0.0001 for both), without significant difference between observed and expected values (p>0.05). Y-chromosome-specific PCR results in female WB samples spiked with male WBCs were not significantly different in fresh and frozen preparations over a 3 log10 range of male cells. The results of WBC survival studies on frozen WB samples were consistent with previous observations in fresh blood samples.

CONCLUSION

Direct freezing of WB enables subsequent recovery of WBCs for quantitative PCR analyses, with results comparable to those of fresh preparations.This protocol should facilitate wider implementation of nucleic acid-based analyses for quality control of WBC-reduced components, as well as for prospective clinical studies of microchimerism in transfusion and transplant recipients.

Localization of nerve growth factor, trkA and P75 immunoreactivity in the hippocampal formation and basal forebrain of adult rats

In the immunohistochemical staining of nerve growth factor, it has been reported that fixation-dependent lability of nerve growth factor hampers its localization. In the present study, we used two different polyclonal antibodies to immunostain nerve growth factor in rat brain tissue. We found that in paraformaldehyde-fixed (immersion- or perfusion-fixed) brains, nerve growth factor-like immunoreactivity was located primarily in the cytoplasmic membrane and fiber tract of hippocampal neurons and was sparse in cortical neurons. When fresh frozen brain sections were fixed in paraformaldehyde solution, nerve-growth factor-like immunoreactivity was distributed evenly in the cell body. However, when fresh frozen brain sections were fixed in acetone, immunoreactivity to nerve growth factor was present as discrete or confluent dense particles in the cell body, especially in the nuclear region. Also, when paraformaldehyde-perfusion-fixed brain sections were heat treated in salt solution before immunostaining, nerve growth factor-like immunoreactivity could be retrieved in the cytoplasmic and nuclear regions. The hippocampal formation, cerebral cortex and basal forebrain expressed nerve growth factor-like immunoreactivity. Double immunostaining in fresh frozen brains showed that the low-affinity nerve growth factor receptor (p75) co-expressed with nerve growth factor and trkA proto-oncogene in basal forebrain neurons. Our study shows that formaldehyde fixation can mask nerve growth factor antigen, and special treatment, such as heating, is needed to retrieve nerve growth factor antigen to permit immunohistochemical detection. For immunohistochemical study of nerve growth factor in rat brain tissue, successful immunostaining can be obtained by using fresh frozen brains to prevent the masking effect of fixatives or by using paraformaldehyde-fixed brains with heat treatment. It is likely that nerve growth factor is synthesized and accumulated mainly in the cell body but not in the fiber tracts, which is similar to the distribution of its messenger RNA. The co-existence of p75 with nerve growth factor and trkA in basal forebrain neurons suggests the role of low- and high-affinity receptors in regulating the trophic effect of nerve growth factor.

Analysis of the envelope region of hepatitis G virus isolated from Korean patients

The genetic diversity of hepatitis G virus (HGV) was investigated. By using a RT-PCR procedure, 14% of either HBV (hepatitis B virus)- or HCV (hepatitis C virus)-positive Korean hepatitis patients were proved to be HGV positives. Nucleotide sequences in the E1 region of the eight isolates from Korean patients and the six previously reported isolates were compared. Nucleotide substitutions spread uniformly throughout the E1 region. Sequence homology among the Korean isolates was 84-99% and 88-99% at the nucleotide and amino acid sequences, respectively, whereas those from different geographic areas was slightly lower at both levels. At least two genotypes might exist among the Korean HGV isolates. Compared to the corresponding region of HCV, the E1 sequence from HGV is moderately conserved. In addition, as frameshift mutations were observed in most of the Korean isolates compared to the prototype HGV sequence, the Korean isolates might not use the translational initiation site of the prototype HGV for polyprotein translation. Because a putative signal sequence of E1 for entry into endoplasmic reticulum starts from the N-terminus of the polyprotein, and capsid-like peptides composed of basic amino acids could not be detected from the upstream region of E1, the core protein of HGV is absent, or at least not present, at the region next to 5'-UTR. Therefore, HGV could be clearly distinguished from other genera of Flaviviridae.

Purification and characterization of lipopolysaccharide induced TNF-like factor from rabbit serum

A TNF-like factor was purified from lipopolysaccharide (LPS) induced New Zealand white rabbit serum. The TNF-like factor was purified by DEAE-Sephacel, Sephacryl S-200, Mono-Q, CM-affi gel Blue, Superose 12 H/R preparative columns to the specific activity of 4 x 10(6) U/mg protein. The purified protein was 45 kDa in its oligomeric form and 22 kDa in its monomeric form. Rabbit TNF-like factor had a pI value of 5.0 and was resistant to trypsin digestion. The TNF-like factor reacted with polyclonal-Ab against human TNFalpha on immunoblot and immunoprecipitation analysis and interacted with human TNF receptors. Taken together, rabbit TNF-like factor might be a high molecular weight form of rabbit TNFalpha.

A prediction rule for the use of postdischarge medical services

OBJECTIVE

To develop and validate a prediction rule screening instrument, easily incorporated into the routine hospital admission assessment, that could facilitate discharge planning by identifying patients at the time of admission who are most likely to need postdischarge medical services.

DESIGN

Prospective cohort study with separate phases for prediction rule development and validation.

SETTING

Urban teaching hospital.

PATIENTS/PARTICIPANTS

General medical service patients, 381 in the derivation phase and 323 in the validation phase, who provided self-reported medical history, health status, and demographic data as a part of their admission nursing assessment, and were subsequently discharged alive.

MEASUREMENTS AND MAIN RESULTS

Use of postdischarge medical services such as visiting nurse or physical therapy, medical equipment, or placement in a rehabilitation or long-term care facility was determined. A prediction rule based on a patient's age and Medical Outcomes Study 36-Item Short Form Health Survey (SF-36) physical function and social function scores stratified patients with regard to their risk of using postdischarge medical services. In the validation set, the rate of actual postdischarge medical service use was 15% (15 of 97), 36% (39 of 107), and 58% (57 of 98) among patients characterized by the prediction rule as being at "low", "intermediate," and "high" risk of using postdischarge medical services, respectively.

CONCLUSIONS

This prediction rule stratified general medical patients with regard to their likelihood of needing discharge planning to arrange for postdischarge medical services. Further research is necessary to determine whether prospective identification of patients likely to need discharge planning will make the hospital discharge planning process more efficient.

Hirayama disease: MR diagnosis

We report the MR findings in two cases of Hirayama disease, a kind of cervical myelopathy related to flexion movements of the neck. In flexion MR studies, we can see the striking and pathognomonic picture of anterior shifting of posterior dura at the lower cervical spinal canal. In nonflexion studies, we find that asymmetric cord atrophy, especially at the lower cervical cord, though subtle, is highly suggestive of Hirayama disease. When it is seen, a flexion MR study is warranted to prove this diagnosis.

Ultrastructure of neuromuscular junction in vacor-induced diabetic rats

OBJECTIVES

Rodenticide Vacor causes a severe peripheral neuropathy in humans. Electrophysiologic studies on a peripheral motor nerve-skeletal system of Vacor-treated rat showed decreased amplitude of muscle action potential without conduction velocity abnormalities. The ultrastructural studies of the neuromuscular junction were performed to clarify the anatomic site of the Vacor-induced peripheral neuropathy in male Wistar rats.

METHODS

After oral administration of a single dose of Vacor, 80 mg/kg of body weight, to the experimental animals, neuromuscular junctions within the interosseous muscles of the hind foot were observed in time.

RESULTS

No axon terminal change was noted until 24 hours after the administration of Vacor. Remarkable loss of presynaptic vesicles and swollen endoplasmic reticulum in the axon terminal were developed at 3 days after Vacor treatment. Progressive degenerative changes consisting of marked loss of presynaptic vesicles, focal disruption of membrane in the axon terminal with disappearance of the number of the damaged axon terminal appeared, and flattening of postsynaptic folds was also seen.

CONCLUSIONS

These results suggest that degenerative changes in axon terminal at neuromuscular junction may contribute to the peripheral neuropathy developed in the early phase of Vacor poisoning.

First report of microcystins in Taiwan

This is the first report on microcystins from Microcystis aeruginosa Kützing in Taiwan. A total of nine strains of cyanobacteria have been isolated from eutrophic aquaculture ponds and water reservoirs. By mouse toxicity assay, six of the nine strains had LD100 in the range of 25-100 mg per kg mouse for dried bacterial mass. Microcystin-LR and -RR were found in all toxic strains and their contents ranged from 0.11-10.06 microg and 0.08 2.21 microg per mg of dried bacteria, respectively. Microcystin-RA, a minor component found only in M. TN-2 and M. CY-1 strains, was identified as a new microcystin. All three toxins were isolated by a serial separation on an LH-20 column, Si-flash column chromatography and reverse phase HPLC. Toxins were further identified by comparing their FABMS, 1H and 1H-1H COSY NMR spectra with the authentic microcystin-LR. Several other microcystin-like compounds were also found in the cultured strains and their structures are being determined.

Clinical correlates and prognostic significance of early negative exercise tolerance test in patients with acute chest pain seen in the hospital emergency department

An exercise tolerance test (ETT) is often performed to identify patients for early discharge after observation for acute chest pain, but the safety of this strategy is unproven. We prospectively studied 276 low-risk patients who underwent an ETT within 48 hours after presentation to the emergency department with acute chest pain. The ETT was considered negative if subjects achieved at least stage I of the Bruce protocol and the electrocardiogram showed no evidence of ischemia. There were no complications associated with ETT performance. The ETT was negative in 195 patients (71%); there was no identifiable subsets of patients at very low probability of an abnormal test. During the 6-month follow-up, patients with a negative ETT had fewer additional visits to the emergency department (17% vs 21%, respectively; p < 0.05) and fewer readmissions to the hospital (12% vs 17%; p < 0.01) than those with positive or inconclusive ETTs. No patient with a negative ETT died and only 4 patients with a negative ETT experienced a major cardiac event (myocardial infarction, coronary angioplasty, or bypass) within 6 months. Among these 4 patients, only 1 had an event within 4 months. In conclusion, our results suggest that ETT can be safely used to identify patients at low risk of subsequent events. Patients without a clearly negative test are at increased risk for readmission and cardiac events, and should be reevaluated either during the same admission or shortly after discharge.

Hepatitis B virus X protein interferes with cellular DNA repair

The hepatitis B virus X protein (HBx) is a broadly acting transactivator implicated in the development of liver cancer. Recently, HBx has been reported to interact with several different cellular proteins, including our report of its binding to XAP-1, the human homolog of the simian repair protein UVDDB. In the present study, several HBx mutants were used to localize the minimal domain of HBx required for binding to XAP-1/UVDDB to amino acids 55 to 101. The normal function of XAP-1/UVDDB is thought to involve binding to damaged DNA, the first step in nucleotide excision repair (NER); therefore, we hypothesized that this interaction may affect the cell's capacity to correct lesions in the genome. When tested in two independent assays that measure NER (unscheduled DNA synthesis and host cell reactivation), the expression of HBx significantly inhibited the ability of cells to repair damaged DNA. Under the assay conditions, HBx was expressed at a level similar to that previously observed during natural viral infection and was able to transactivate several target reporter genes. These results are consistent with a model in which HBx acts as a cofactor in hepatocarcinogenesis by preventing the cell from efficiently repairing damaged DNA, thus leading to an accumulation of DNA mutations and, eventually, cancer. An adverse effect on cellular DNA repair processes suggests a new mechanism by which a tumor-associated virus might contribute to carcinogenesis.

Cytokine networks in the pathogenesis of bronchial asthma: implications for therapy

Bronchial asthma is characterised by a multicellular inflammatory process in the airways. The bronchial inflammation is orchestrated by a network of cytokines and growth factors which includes those encoded by the GM-CSF/IL-4/IL-5 gene cluster on chromosome 5. Their cellular origins are diverse and include both inflammatory and structural cells in the airways. The efficacy of glucocorticoids in the therapy of bronchial asthma may include the ability to disrupt these cytokine networks. The failure of glucocorticoids to provide benefit in some asthmatic patients may be caused by an excess of pro-inflammatory transcription factors which sequester the glucocorticoid receptor (GR), thereby preventing it from exerting its anti-inflammatory effects. Progress is being made in the elucidation of the molecular regulation of the transcription of TH2 cytokine genes. These novel insights may provide future strategies for therapeutic intervention in asthma.

Synthesis and anti-inflammatory effect of chalcones and related compounds

PURPOSE

Mast cell and neutrophil degranulations are the important players in inflammatory disorders. Combined with potent inhibition of chemical mediators released from mast cells and neutrophil degranulations, it could be a promising anti-inflammatory agent. 2',5'-Dihydroxychalcone has been reported as a potent chemical mediator and cyclooxygenase inhibitor. In an effort to continually develop potent anti-inflammatory agents, a novel series of chalcone, 2'- and 3'-hydroxychalcones, 2',5'-dihydroxychalcones and flavanones were continually synthesized to evaluate their inhibitory effects on the activation of mast cells and neutrophils and the inhibitory effect on phlogist-induced hind-paw edema in mice.

METHODS

A series of chalcones and related compounds were prepared by Claisen-Schmidt condensation of appropriate acetophenones with appropriate aromatic aldehyde and the anti-inflammatory activities of these synthetic compounds were studied on inhibitory effects on the activation of mast cells and neutrophils.

RESULTS

Some chalcones showed strong inhibitory effects on the release of beta-glucuronidase and histamine from rat peritoneal mast cells stimulated with compound 48/80. Almost all chalcones and 4'-hydroxyflavanone exhibited potent inhibitory effects on the release of beta-glucuronidase and lysozyme from rat neutrophils stimulated with formyl-Met-Leu-Phe (fMLP). Some chalcones showed potent inhibitory effects on superoxide formation of rat neutrophils stimulated with fMLP/cytochalasin B (CB) or phorbol myristate acetate (PMA). 2',3-Dihydroxy-, 2',5'-dihydroxy-4-chloro-, and 2',5'-dihydroxychalcone showed remarkable inhibitory effects on hind-paw edema induced by polymyxin B in normal as well as in adrenalectomized mice.

CONCLUSIONS

These results indicated that the anti-inflammatory effects of these compounds were mediated, at least partly, through the suppression of chemical mediators released from mast cells and neutrophils.