p53 in cutaneous melanoma: immunoreactivity and correlation with prognosis

p53 protein immunoreactivity was investigated in cutaneous Spitz naevi (n = 7), superficial spreading (n = 21) and nodular (n = 6) melanomas using the monoclonal antibody DO-7. Nuclear immunostaining for p53 protein was observed in 41% of all the melanomas but not in any of the Spitz naevi studied. This difference in p53 immunoreactivity appeared statistically significant (P = 0.0001; chi 2 test). There were also differences in p53 immunoreactivity between superficial spreading and nodular melanomas (P = 0.001, chi 2 test), where up to 38% of superficial spreading melanomas and 50% of nodular melanomas had demonstrated p53 nuclear immunostaining. An apparently significant correlation was observed between melanomas with poor prognostic histological indices and p53 immunoreactivity (P = 0.0016; chi 2 test). In conclusion, increased p53 protein immunoreactivity is found in melanomas and is associated with poorer prognosis. The differences in p53 immunohistological expression between cutaneous melanomas and Spitz naevi suggest that alterations of the protein may be important in the pathogenesis of the tumour.

Quantitative analysis of intraepithelial large granular lymphocyte distribution and maternofetal cellular interactions in the synepitheliochorial placenta of the deer

Intraepithelial lymphocytes are a constant feature of ruminant uterine epithelium in nonpregnant animals. Quantitation in 6 species of deer shows that the proportion of large granular lymphocytes (LGL) in this population increases markedly and continuously from the earliest implantation to the latest (midpregnant) stage examined. The size of individual granules also increases. Fetal trophectodermal binucleate cells are also present from the earliest stage in all deer examined and follow a usual ruminant life cycle: migrating and fusing with uterine epithelial cells to form trinucleate cells before releasing their granules to the maternal compartment and finally degenerating and being reabsorbed by the trophectodermal uninucleate cells. Deer LGLs were usually closely associated with the degranulating fetomaternal hybrid trinucleate cells but showed no ultrastructural changes themselves. This association indicates a dynamic interaction between deer LGL and trinucleate cells which could serve as one of the factors restricting the extent of trinucleate cell progression to a continuous syncytium as found in sheep and goats.

Core antigen mutations of human hepatitis B virus in hepatomas accumulate in MHC class II-restricted T cell epitopes

Despite the extensive molecular information on serum-derived human hepatitis B viruses (HBV), liver-derived replicative HBV genomes have remained largely uninvestigated. We have examined the sequences of the entire core antigen (nucleocapsid) of liver-derived HBVs in 15 different hepatoma patients. Bona fide mutations, rather than subtype polymorphism, have been identified based on the high-frequency occurrence of structural differences from wild type at the highly evolutionarily conserved positions, instead of at the positions known to contain genetic heterogeneity among different isolates from different geographic locations. The distribution of these naturally occurring mutations of HBV core gene appears to be nonrandom and is found predominantly within three major (I, IV, and V) and four minor domains (II, III, VI, and VII). In general, domain IV mutations correlate with domain V mutations. The replicative HBV DNAs tend to accumulate a higher number of mutated core domains than the integrated HBV DNAs. At the domain level, there is no significant difference in HBV core mutation frequencies between the liver tumors and the adjacent nontumorous livers. Strikingly, domains I, III, and V coincide with three major known T cell epitopes within the core protein in acute and chronic hepatitis B patients. Furthermore, these domains coincide with HLA class II-restricted T cell epitopes, rather than with the conventional HLA class I-restricted epitopes of cytotoxic T lymphocytes. Our results support the hypothesis that HBV core antigen variants can accomplish immunoevasion via accumulated escape mutations. In addition, they also provide a potential molecular explanation for the maintenance of persistent infection of human hepatitis B virus in chronic carriers.

Emphysematous gastritis secondary to acute gastric dilatation

Emphysematous gastritis is a life-threatening disease. Although rare in incidence, it has a fulminating course with a high mortality rate. A case of a 58 year old male with emphysematous gastritis is reported. Initially, he presented with acute gastric dilatation secondary to anorexia/bulimia-like behaviour. Later, emphysematous gastritis developed. The abdominal sonographic findings, which have not been previously described in the literature, showed intramural gas and gastric wall thickening. After receiving a total gastrectomy, he had a satisfactory outcome. The present report discusses the possible aetiologic relationship between acute gastric dilatation and emphysematous gastritis, and suggests abdominal sonography to be the first choice of diagnostic measure for patients and the intramural gas in the gastric wall. This is the first case of emphysematous gastritis diagnosed by abdominal sonography.

Primary cutaneous Ewing's sarcoma/peripheral primitive neuroectodermal tumors in childhood. A molecular, cytogenetic, and immunohistochemical study

Childhood cutaneous and subcutaneous malignancies are rare and include metastatic tumors of diverse histogenesis as well as primary lesions, such as sweat gland carcinomas. Some cutaneous malignancies exhibit a small round cell tumor morphology with few definitive differentiating features; they can thus pose a significant diagnostic problem. We describe two primary malignancies of the skin and superficial subcutis, which were originally diagnosed as sweat gland carcinomas on the basis of their morphological features. A cytogenetic analysis performed on one of these lesions showed the t(11;22)(q24;q12) rearrangement, believed to be unique to the Ewing's sarcoma/peripheral primitive neuroectodermal tumor (ES/pPNET) group of neoplasms. In view of this unexpected result, reverse transcriptase-polymerase chain reaction analysis was performed on both lesions and showed that they expressed EWS/FLI-1 fusion gene mRNA transcripts, the molecular equivalent of t(11;22)(q24;q12). The two tumors also had an immunohistochemical profile suggesting ES/pPNET, including strong expression of the MIC2 antigen. Both patients were treated with wide local excision, and one was given a course of chemotherapy. Neither patient showed evidence of tumor elsewhere after follow-up periods of 2 years and 16 years. These findings suggest that these tumors are indeed a form of primary ES/pPNET arising in the skin or superficial subcutis, which may be of low-grade malignancy and curable by local surgery.

In vitro assembly of infectious virions of double-stranded DNA phage phi 29 from cloned gene products and synthetic nucleic acids

Up to 6 x 10(7) PFU of infectious virions of the double-stranded DNA bacteriophage phi 29 per ml were assembled in vitro, with 11 proteins derived from cloned genes and nucleic acids synthesized separately. The genomic DNA-gp3 protein conjugate was efficiently packaged into a purified recombinant procapsid with the aid of a small viral RNA (pRNA) transcript, a DNA-packaging ATPase (gp16), and ATP. The DNA-filled capsids were subsequently converted into infectious virions after the addition of four more recombinant proteins for neck and tail assembly. Electron microscopy and genome restriction mapping confirmed the identity of the infectious phi 29 virions synthesized in this system. A nonstructural protein, gp13, was indispensable for the assembly of infectious virions. The overproduced tail protein gp9 was present in solution in mostly dimeric form and was purified to homogeneity. The purified gp9 was biologically active for in vitro phi 29 assembly. Higher-order concentration dependence of in vitro phi 29 assembly on gp9 suggests that a complete tail did not form before attaching to the DNA-filled capsid, a result contrary to earlier findings for phages T4 and lambda. The work described here constitutes an extremely sensitive assay system for the analysis of components in phi 29 assembly and dissection of functional domains of structural components, enzymes, and pRNA (C.-S. Lee and P. Guo, Virology 202:1039-1042, 1995). Efficient packaging of foreign DNA in vitro and synthesis of viral particles from recombinant proteins facilitate the development of phi 29 as an in vivo gene delivery system. The finding that purified tail protein was able to incorporate into infectious virions might allow the construction of chimeric phi 29 carrying a tail fused to ligands for specific receptor of human cells.

Sequential interactions of structural proteins in phage phi 29 procapsid assembly

The mechanism of viral capsid assembly is an intriguing problem because of its fundamental importance to research on synthetic viral particle vaccines, gene delivery systems, antiviral drugs, chimeric viruses displaying antigens or ligands, and the study of macromolecular interactions. The genes coding for the scaffolding (gp7), capsid (gp8), and portal vertex (gp10) proteins of the procapsid of bacteriophage phi 29 of Bacillus subtilis were expressed in Escherichia coli individually or in combination to study the mechanism of phi 29 procapsid assembly. When expressed alone, gp7 existed as a soluble monomer, gp8 aggregated into inclusion bodies, and gp10 formed the portal vertex. Circular dichroisin spectrum analysis indicated that gp7 is mainly composed of alpha helices. When two of the proteins were coexpressed, gp7 and gp8 assembled into procapsid-like particles with variable sizes and shapes, gp7 and gp10 formed unstable complexes, and gp8 and gp10 did not interact. These results suggested that gp7 served as a bridge for gp8 and gp10. When gp7, gp8, and gp10 were coexpressed, active procapsids were produced. Complementation of extracts containing one or two structural components could not produce active procapsids, indicating that no stable intermediates were formed. A dimeric gp7 concatemer promoted the solubility of gp8 but was inactive in the assembly of procapsid or procapsid-like particles. Mutation at the C terminus of gp7 prevented it from interacting with gp8, indicating that this part of gp7 may be important for interaction with gp8. Coexpression of the portal protein (gp20) of phage T4 with phi 29 gp7 and gp8 revealed the lack of interaction between T4 gp20 and phi 29 gp7 and/or gp8. Perturbing the ratio of the three structural proteins by duplicating one or another gene did not reduce the yield of potentially infectious particles. Changing of the order of gene arrangement in plasmids did not affect the formation of active procapsids significantly. These results indicate that phi 29 procapsid assembly deviated from the single-assembly pathway and that coexistence of all three components with a threshold concentration was required for procapsid assembly. The trimolecular interaction was so rapid that no true intermediates could be isolated. This finding is in accord with the result of capsid assembly obtained by the equilibrium model proposed by A. Zlotnick (J. Mol. Biol. 241:59-67, 1994).

Audiological profiles and Menière's disease

Pure-tone audiograms of 501 patients with preoperative Menière's disease were analyzed. Age of onset and incidence of bilaterality were studied. The most common audiogram was the peak-type (50.26%), next the falling-type (26.26%), and then the dip-type (9.24%). Although few papers mention this peak audiogram, we suggest it is a diagnostic feature of Menière's disease. Average age of onset was 42.59 years; this did not differ from males to females. Prevalence in females exceeded that in males by about 4:3. The disease was bilateral in 31.13%. Generally, those with better hearing thresholds at the first examination had less tendency to develop bilaterality. Age of onset was not significantly correlated with bilaterality.

Evaluation of biomarkers for occupational exposure to benzene

OBJECTIVE

To evaluate the relations between environmental benzene concentrations and various biomarkers of exposure to benzene.

METHODS

Analyses were carried out on environmental air, unmetabolised benzene in urine, trans, trans-muconic acid (ttMA), and three major phenolic metabolites of benzene; catechol, hydroquinone, and phenol, in two field studies on 64 workers exposed to benzene concentrations from 0.12 to 68 ppm, the time weighted average (TWA). Forty nonexposed subjects were also investigated.

RESULTS

Among the five urinary biomarkers studied, ttMA correlated best with environmental benzene concentration (correlation coefficient, r = 0.87). When urinary phenolic metabolites were compared with environmental benzene, hydroquinone correlated best with benzene in air. No correlation was found between unmetabolised benzene in urine and environmental benzene concentrations. The correlation coefficients for environmental benzene and end of shift catechol, hydroquinone, and phenol were 0.30, 0.70, and 0.66, respectively. Detailed analysis, however, suggests that urinary phenol was not a specific biomarker for exposure below 5 ppm. In contrast, ttMA and hydroquinone seemed to be specific and sensitive even at concentrations of below 1 ppm. Although unmetabolised benzene in urine showed good correlation with atmospheric benzene (r = 0.50, P < 0.05), data were insufficient to suggest that it is a useful biomarker for exposure to low concentrations of benzene. The results from the present study also showed that both ttMA and hydroquinone were able to differentiate the background level found in subjects not occupationally exposed and those exposed to less than 1 ppm of benzene. This suggests that these two biomarkers are useful indices for monitoring low concentrations of benzene. Furthermore, these two metabolites are known to be involved in bone marrow leukaemogenesis, their applications in biological monitoring could thus be important in risk assessment.

CONCLUSION

The good correlations between ttMA, hydroquinone, and atmospheric benzene, even at concentrations of less than 1 ppm, suggest that they are sensitive and specific biomarkers for benzene exposure.

Electrophysiological manifestations of the excitable gap of slow-fast AV nodal reentrant tachycardia demonstrated by single extrastimulation

BACKGROUND

Although AV nodal reentrant tachycardia (AVNRT) is a well-known rhythm disorder, its anatomic substrate and electrophysiological mechanism remain to be defined. Previously, the description of the excitable gap (EG) of AVNRT was based on electrical stimulation performed from sites remote from the reentrant circuit. In the present study, we characterized the EG of AVNRT by atrial extrastimulation close to the putative reentrant circuit in the AV junction.

METHODS AND RESULTS

In 16 patients (3 men, 13 women; mean age, 45 +/- 13 years) with inducible slow-fast AVNRT (mean cycle length, 353 +/- 52 ms), single extrastimuli with a 10-ms decrement in the premature coupling interval were delivered from the anterosuperior interatrial septum (fast pathway area) and the posteroinferior interatrial septum (slow pathway area) from late diastole until atrial refractoriness. An EG was considered present when resetting or termination of AVNRT was induced by single atrial extrastimulation. The study showed that the duration of the EG of AVNRT was wide, measuring 121 +/- 56 and 123 +/- 47 ms and occupying 33 +/- 11% and 34 +/- 9% of the tachycardia cycle length during single extrastimulation from the slow pathway area and the fast pathway area, respectively. The resetting pattern most commonly manifested as the sum of the coupling interval and the return cycle being less than a fully compensatory pause (two times the basic tachycardia cycle length). However, patterns equal to and greater than a fully compensatory pause were also observed. Of note, in 2 of the 16 patients, atrial extrastimulation from either the fast or slow pathway area also affected the preceding tachycardia cycle length (HH interval), indicating alteration of the anterograde input. In all patients, the curve derived from plotting the coupling interval of extrastimuli against the return cycle during resetting exhibited an "increasing" pattern. The mode of tachycardia termination usually occurred when the premature atrial impulse was orthodromically blocked in the anterograde slow pathway.

CONCLUSIONS

The EG of slow-fast AVNRT is relatively wide, as demonstrated by single atrial extrastimulation from the interatrial septum near the AV junction. Overall, the electrophysiological manifestations of the EG of AVNRT are very similar to those described in AV reciprocating tachycardia incorporating an accessory connection. These findings lend further support to the notion that, in humans, AVNRT involves a reentrant mechanism with a wide excitable gap.

Cellular immune responses in the pig uterus during pregnancy

In pigs, little is known about the role of the uterine immune system during pregnancy. Immunohistochemical studies were conducted using a panel of monoclonal antibodies to pig leukocytes on uterine tissues taken from gilts after fertile mating and at different stages of pregnancy. Acute inflammation in the endometrium in response to fertile mating which included marked changes in the tissue and immune cell components of the endometrium was observed. Throughout pregnancy the pig uterus contained a substantial population of leukocytes. MHC class II staining was prominent in the endometrium at all stages examined and included macrophages, dendritic and fibroblast-like cells, lymphocytes and the endothelial lining of many uterine blood vessels. The majority of lymphoid cells were CD2+, indicating the prevalence of T cells. In early pregnancy specific changes were seen in the tissue distribution of uterine immune cells. Following placentation distinct cellular changes in the local immune cell environment of the uterus were also observed despite the non-invasive nature of the pig placenta. There appears to be suppression and activation of various immune cell components in the uteri of pregnant pigs. This phenomenon is presumably in response to foetal or trophoblast antigens, suggesting that the local immune system is involved in the uterine response to pregnancy.

Localization of uridine 5'-diphosphate-glucuronosyltransferase in human liver injury

BACKGROUND/AIMS

Pharmacokinetic studies in patients with cirrhosis have shown a decreased clearance of drugs metabolized by cytochrome P450, whereas drugs metabolized by glucuronidation frequently have a normal elimination. The mechanism for the apparent preservation of glucuronidation has not been elucidated. The aim of this study was to examine the expression of uridine 5'-diphosphate-glucuronosyltransferase (UGT) in human liver injuries.

METHODS

UGT was measured by immunohistochemistry using a UGT polyclonal antibody, which was then compared with a representative isoform of cytochrome P450. Normal liver biopsy specimens (n = 8) and a spectrum of liver injury biopsy specimens (n = 47) were examined.

RESULTS

Compared with normal liver, increased staining for UGT in remaining hepatocytes was seen in liver damaged by chronic alcohol abuse, but the most intense immunoreactivity was observed in remaining and regenerative hepatocytes in specimens with cirrhosis. Primary biliary cirrhosis showed diffusely increased immunoreactivity. Other nonmalignant groups showed an increased staining relative to chronicity of liver disease. In contrast, in all liver injuries, cytochrome P450 staining was reduced as compared with controls.

CONCLUSIONS

Chronic liver damage results in increased UGT in remaining viable hepatocytes. Mechanisms may operate in liver injury to preserve expression of UGT in functional hepatocytes, and this may explain the preservation of glucuronidation in cirrhosis.

Numerical simulation of instantaneous backflow through central clearance of bileaflet mechanical heart valves at closure: shear stress and pressure fields within clearance

Instantaneous backflow through central clearance of bileaflet heart valves at the instant of closure is investigated. An Edwards-Duromedics valve in the mitral position is employed to measure the transient pressures near the entrance and exit region in an in vitro flow chamber. A region surrounding the clearance is modelled, and two-dimensional quasi-steady-state numerical simulations are performed, with the measured transient pressure difference across the clearance as a driving force for the flow. The results show that pressure difference several times larger than the driving pressure used to close the valve is established across the clearance for about 0.5 ms at the moment of closure. The resulting average wall shear stress is an order of magnitude larger than the turbulent Reynolds stresses reported distal to the valve during opening. A local jump in the shear stress distribution and fall in the pressure distribution are observed at the entrance region. Rounding of the corners in the channel entrance attenuates these spikes. The results of the study indicate that backflow through clearance at closure may be one reason for the haemolysis and thrombosis associated with mechanical heart valves, despite the short duration of the flow field.

Risk factors and predictors of outcome in an Australian cohort with hepatitis C virus infection

OBJECTIVES

To define demographic and epidemiological features of an Australian population with chronic hepatitis C virus (HCV) infection and determine predictors of histological and clinical outcome.

DESIGN

Cohort study.

PATIENTS AND SETTING

342 consecutive HCV antibody-positive patients referred to the liver clinic of a major metropolitan general hospital.

OUTCOME MEASURES

Demographic data, serial alanine aminotransferase (ALT) levels, full blood count for all patients. Percutaneous liver biopsy in 152 patients (44%).

RESULTS

51% of patients had previously used injecting drugs, 15% had received a blood transfusion and 27% had no definite percutaneous risk factor (sporadic group). The injecting drug users (IDUs) were younger and more likely to have been born in Australia. The sporadic group were older and frequently were born in Mediterranean or Asian countries. A history of excessive alcohol use was common, particularly among IDUs (60%). Of 152 patients who had a liver biopsy, 49 had cirrhosis and 103 had chronic hepatitis. Some patients with a normal ALT level had marked necro-inflammatory activity. On univariate analysis, the presence of cirrhosis correlated with older age (P < 0.0001), lack of an identifiable risk factor (P < 0.001) and birth in a Mediterranean or Asian country (P < 0.0001). On multivariate analysis, the only significant predictor of cirrhosis was age (P < 0.001). Among patients with an identifiable percutaneous risk factor, cirrhosis was seen at a median time of 18 years after first exposure to risk, compared with 13 years in patients with chronic hepatitis (P < 0.01). Patients with clinical evidence of portal hypertension were, on average, 15 years older than those with histological cirrhosis only (P < 0.01).

CONCLUSIONS

Injecting drug use is the major risk factor for chronic HCV infection in Australia. In patients with an identifiable risk factor, the most significant factor associated with a biopsy finding of cirrhosis is the time since first exposure to HCV.

p53 protein immunoreactivity in cancers of the gallbladder, extrahepatic bile ducts and ampulla of Vater

Immunohistochemical expression of the p53 protein was investigated in carcinoma of the gallbladder (n = 13), common bile duct (n = 7) and ampulla of Vater (n = 9) using the polyclonal, CM1, and monoclonal, DO7, antibodies (Novocastra). This was compared with cases of chronic cholecystitis (n = 11) and preneoplastic lesions of the gallbladder (n = 4) and ampulla (n = 3). Nuclear immunostaining for p53 protein was found only in the poorly differentiated adenocarcinomas of the gallbladder (n = 9) and were associated with a shorter patient survival period (median: 18.6 mths). The moderately differentiated adenocarcinomas (n = 4) did not show p53 immunostaining and were associated with a longer median survival period (26 mths). The gallbladder dysplasias and adenoma also had no p53 protein immunoreactivity. The common bile duct carcinomas did not stain for p53. Focal p53 immunoreactivity was present in only one (11%) of the cases of ampullary carcinoma and in one (9%) of chronic cholecystitis. In summary, increased p53 immunostaining was associated with reduced patient survival and found more frequently in poorly differentiated adenocarcinoma of the gallbladder but not in the better differentiated carcinoma, chronic cholecystitis or preneoplastic lesions of the gallbladder. The differences in p53 immunohistological expression between gallbladder, common bile duct and ampullary carcinomas justify further investigation into the molecular mechanisms responsible for their development.

Patterns of asymmetry do not change over the course of idiopathic parkinsonism: implications for pathogenesis

We investigated the asymmetry of focal deficits of bradykinesia in a cross-sectional study of 198 patients with idiopathic parkinsonism. We have analyzed the difference in Unified Parkinson's Disease Rating Scale (UPDRS) scores between the more and less affected sides in these patients, whose duration of symptoms ranged from 1 to 15 years. There was no significant change in the asymmetry or focality over this period; the deficit for each side progressed faster initially and then approached the normal age-related linear rate of decline. Previous studies indicate that there is an inverse linear relation between the UPDRS bradykinesia score and the nigral dopaminergic cell count. We infer that the rate of death of nigral dopaminergic neurons is predetermined from the time of onset of pathogenesis. The simplest explanation is that a causal event kills some cells and damages others so that they undergo premature death. This sequence of changes could be implemented through environmental (toxic or viral) damage to the genome. Several diverse sources of evidence support this concept.

[Complications of massive blood transfusion after intrathoracic hemorrhage--a case report]

Acute hemorrhage leading to acute hypovolomic shock is a medical emergency carrying high mortality. It therefore requires prompt and effective treatment. We reported a case of lung tumor receiving lobectomy at our hospital. Repeated internal bleeding due to subclavian artery perforation occurred three times within three weeks after the surgery. During the period of resuscitation, the patient received emergently massive blood transfusion. Some complications of massive blood transfusion. Some complications of massive blood transfusion were noted later. A total of 89 units of whole blood, 34 units of fresh frozen plasma and 28 units of platelet was given.

Identification of 'molten globule'-like state in all beta-sheet protein

The cardiotoxin analogue III (CTX III), isolated from the Taiwan Cobra venom (Naja naja atra), is a sixty amino acid, all beta-sheet protein. The 2,2,2-trifluoro ethanol (TFE) induced unfolding of CTX III is studied under acidic conditions (pH 2.5). Using circular dichroism, 1-anilino-8-napthalene sulphonic acid binding and NMR experiments, it is shown that stable, partially structured state(s) ['molten globule'-like state] is formed between 50 and 80% TFE concentrations. The protein was found to exist in an unfolded state in 80% TFE containing 2M urea. The TFE induced unfolding process is shown to be completely reversible. In the 'molten globule' state of CTX III in 80% TFE, though portion(s) of the backbone of the protein assume helical conformation, most of the original beta-sheet secondary structural elements in the protein are intact. In our opinion, this is the first report of the identification of a 'molten globule'-like state in the unfolding pathway of an all beta-sheet monomeric protein.

Molecular dynamics simulations of chlorambucil/DNA adducts. A structural basis for the 5'-GNC interstrand DNA crosslink formed by nitrogen mustards

The alkylation of DNA by chlorambucil has been studied using a computational approach. Molecular dynamics simulations were performed on the fully solvated non-covalent complex, two monoadducts and a crosslinked diadduct of chlorambucil with the d(CGG3G2CGC).-d(GCG1CCCG) duplex, in which the N7 atoms of G1, G2 and G3 are potential alkylation sites. The results provide a structural basis for the preference of nitrogen mustards to crosslink DNA duplexes at a 5'-GNC site (a 1,3 crosslink, G1-G3) rather than at a 5'-GC sites (a 1,2 crosslink, G1-G2). In the non-covalent complex simulation the drug reoriented from a non-interstrand crosslinking location to a position favorable for G1-G3 diadduct formation. It proved possible to construct a G1-G3 diadduct from a structure from the non-covalent simulation, and continue the molecular dynamics calculation without further disruption of the DNA structure. A crosslinked diadduct developed with four BII conformations on the 3' side of each alkylated guanine and of their respective complementary cytosine. In the first monoadduct simulation the starting point was the same DNA conformation used in the crosslinked diadduct simulation with alkylation at G1. In this simulation the DNA deformation was reduced, with the helix returning to a more canonical form. A second monoadduct simulation was started from a canonical DNA conformation alkylated at G3. Here, no significant motion towards a potential crosslinking conformation occurred. Collectively, the results suggest that crosslink formation is dependent upon the drug orientation prior to alkylation and the required deformation of the DNA to permit 1,3 crosslinking can largely be achieved in the non-covalent complex.

A model to study cytokine profiles in primary and heterologously secondary Dengue-2 virus infections

Roles of cytokines in primary and secondary Dengue virus (DV) infections are not completely understood. In this study, we challenged mononuclear leukocytes (MNLs) obtained from non-immune and DV-1-infected donors with DV-2 in vitro to mimic primary and heterologously secondary DV-2 infections, respectively. We found that MNLs in response to DV-2 could release a large amount of interleukin-1 (IL-1 beta) and tumor necrosis factor alpha (TNF alpha). However, IL-1 beta and TNF alpha released by MNLs with primary or heterologously secondary exposure to DV-2 were not significantly different. In contrast, MNLs with heterologously secondary DV-2 infections produced significantly higher amount of interferon gamma (IFN gamma) than those with primary DV-2 infections. These results suggest that IFN gamma, but not TNF alpha or IL-1 beta, may in part participate in the pathogenesis of Dengue shock syndrome (DSS) frequently found in heterologously secondary DV-2 infections.

Properties of uracil phosphoribosyltransferase from Giardia intestinalis

Incorporation of pyrimidine ribonucleotides in Giardia intestinalis occurs via uracil phosphoribosyltransferase (UPRTase). The enzyme was purified over 1000-fold to apparent homogeneity from parasite extracts, using Fast Protein Liquid Chromatography, namely Mono Q anion exchange, Mono P chromatofocusing and Superose 12 chromatography. The specific activity of the purified enzyme was 3100 nmol min-1 mg protein-1. The enzyme was found to be a dimer of mol. wt. 76,000. Kinetic analysis, including initial velocity and product inhibition studies, indicated that it obeyed a rapid-random equilibrium mechanism. GTP and dGTP caused a dramatic increase in the activity of the enzyme, though there was no effect on the Michaelis constants. All other nucleotides tested were without effect or were inhibitory. The effect of GTP is similar to that observed for UPRTase from E. coli but not from other eukaryotes.

Neurophysin stimulates prolactin release from primary cultured rat pituitary cells

The neurohypophysial hormones, oxytocin and vasopressin, are present as non-covalently bound complexes with their designated neurophysin in the secretory granules of the posterior pituitary. The neurophysins are generally considered to be biologically inert carrier proteins for oxytocin and vasopressin. We have examined the actions of bovine neurophysin-I (bNP-I), bovine neurophysin-II (bNP-II), rat neurophysin (rat NP) and oxytocin on prolactin release using primary cultured rat pituitary cells. A dynamic perifusion system was chosen to test their stimulatory actions. The rat NP and bNP-II stimulated prolactin release. It is a new observation that rat NP and bNP-II stimulate prolactin release from primary cultured rat pituitary cells. The maximum sensitivities, the lowest concentration which stimulate prolactin release, of rat NP, bNP-II, bNP-I and oxytocin in primary cultured cells were 1 nmol/1, 1 nmol/l, 1000 nmol/1 and 1 nmol/1 respectively. The maximum sensitivities of rat NP and bNP-II were within the physiologically relevant concentrations.

Gas chromatographic determination of triclopyr in fruits and vegetables

This research was comprised of two parts: quantitative analyses, and confirmatory test. In the quantitative analyses, five classes of fruits and vegetables comprising 10 individual commodities were fortified with triclopyr herbicide at 0.4 and 0.8 ppm level. Triclopyr was extracted from the matrices and derivatized separately to 2-chloroethylene ester with 2-chloroethanol-BCl3 and methyl ester with diazomethane. The esters were then quantitated by GC-ECD and GC-NPD. The GC-ECD recoveries for 2-chloroethylene ester were 100.0% and 100.7% at 0.4 ppm and 0.8 ppm fortification levels, respectively, whereas methyl ester recovery was 103.9% at 0.4 ppm fortification level. Similarly, the GC-NPD recoveries for 2-chloroethylene ester were 99.0% and 97.9% at 0.4 ppm and 0.8 ppm fortification levels respectively, whereas methyl ester recovery was 102.0% at 0.4 ppm fortification level. In the confirmatory test, the 2-chloroethylene ester was introduced into a GC-ion trap. The EI mass spectrum was then interpreted based on the criteria of molecular ion, isotopes, base ion, characteristic ions and the nitrogen rule. Compared to existing methods, this method has reduced partition solvents to nearly one-tenth. In addition, this method proved to be simple, fast, safe and accurate.