The cellular metabolism and systemic toxicity of arsenic

Although it has been known for decades that humans and many other species convert inorganic arsenic to mono- and dimethylated metabolites, relatively little attention has been given to the biological effects of these methylated products. It has been widely held that inorganic arsenicals were the species that accounted for the toxic and carcinogenic effects of this metalloid and that methylation was properly regarded as a mechanism for detoxification of arsenic. Elucidation of the metabolic pathway for arsenic has changed our understanding of the significance of methylation. Both methylated and dimethylated arsenicals that contain arsenic in the trivalent oxidation state have been identified as intermediates in the metabolic pathway. These compounds have been detected in human cells cultured in the presence of inorganic arsenic and in urine of individuals who were chronically exposed to inorganic arsenic. Methylated and dimethylated arsenicals that contain arsenic in the trivalent oxidation state are more cytotoxic, more genotoxic, and more potent inhibitors of the activities of some enzymes than are inorganic arsenicals that contain arsenic in the trivalent oxidation state. Hence, it is reasonable to describe the methylation of arsenic as a pathway for its activation, not as a mode of detoxification. This review summarizes the current knowledge of the processes that control the formation and fate of the methylated metabolites of arsenic and of the biological effects of these compounds. Given the considerable interest in the dose-response relationships for arsenic as a toxin and a carcinogen, understanding the metabolism of arsenic may be critical to assessing the risk associated with chronic exposure to this element.

Early photocycle kinetic behavior of the E46A and Y42F mutants of photoactive yellow protein: femtosecond spectroscopy

In the photoactive yellow protein, PYP, both Glu46 and Tyr42 form hydrogen bonds to the phenolic OH group of the p-hydroxycinnamoyl chromophore. Previous work on replacement of the carboxyl group of Glu46 by an amide group (Glu46Gln) has shown that changing the nature of this hydrogen bond has a minimal effect on the rate constant for the formation of the first intermediate (I(0)) and on the excited state lifetime, whereas the rate constants for the formation of the second (I(0)( not equal)) and third (I(1)) intermediates were increased by factors of approximately 30 and 5, respectively. In the present experiments, two additional mutants (Glu46Ala and Tyr42Phe) have been studied. These two mutants are shown to behave kinetically very similarly to one another. In both cases, the rate constant for I(0) formation is decreased by a factor of approximately 2, with little or no effect on the photochemical yield as a consequence of a compensating increase in the excited state lifetime. Although we are unable to resolve the rate constant for the formation of the second intermediate from that of the first intermediate, the rate constant for the formation of the third intermediate is increased by a factor of approximately 100. The structural implications of these results are discussed.

[Clinicopathologic features and prognosis of lymphoepithelioma-like carcinoma of the lung]

OBJECTIVE

To analyze the clinicopathologic features and prognosis of lymphoepithelioma-like carcinoma (LELC) of the lung.

METHODS

26 cases of pulmonary LELC with available long-term follow-up information were compared with 84 cases of pulmonary non-LELC(33 cases of squamous cell carcinoma, 36 cases of adenocarcinoma, 6 cases of adeno-squamous carcinoma and 9 cases of large cell carcinoma) with available long-term follow-up information using Kaplan-Meier method and the generalized Wilcoxon test.

RESULTS

LELC of the lung had a better prognosis than non-LELC (P < 0.05). Further study showed that pulmonary LELC had a significantly better prognosis than adeno-squamous carcinoma and large cell carcinoma. However, there was no significant prognostic differences between pulmonary LELC and squamous cell carcinoma and adenocarcinoma. Tumor recurrence and necrosis (> or = 5% of tumor) were associated with poor prognosis.

CONCLUSION

Pulmonary LELC, which is a very rare and unique entity, has a better prognosis after therapy.

GL331 induces down-regulation of cyclin D1 expression via enhanced proteolysis and repressed transcription

GL331 is a novel podophyllotoxin-derived compound. In this study, GL331 induced human lung adenocarcinoma cell line CL1-5 growth arrest before death during the initial 24-h incubation period. We found that GL331 had no inhibitory effect on the expression of cyclins E, A, B1, CDK 4, and CDK 2; instead, its cell growth-inhibitory effect was partly attributable to an early down-regulation of cyclin D1 expression and in turn the reduction of retinoblastoma protein phosphorylation. GL331 enhanced the proteolysis of cyclin D1, and a proteasome inhibitor was able to block GL331-caused cyclin D1 reduction, suggesting that GL331-stimulated cyclin D1 degradation was through proteasomal processes. Additionally, GL331 reduced cellular cyclin D1 mRNA level down to 45% of control in 4 h and further to around 20% in 12 h. However, GL331 did not accelerate the disappearance of cyclin D1 mRNA under the condition of transcription blockage induced by actinomycin D. It was reported that a certain region in the 3'-untranslated region (UTR) of cyclin D1 mRNA mediated the mRNA degradation upon extracellular stresses. Herein, transient transfection studies demonstrated that the 3'-UTR insertion did not confer the susceptibility of luciferase reporter gene to the GL331 treatment. Together, these data suggested that GL331 did not decrease the stability of cyclin D1 mRNA. On the other hand, we found that GL331 specifically inhibited the cyclin D1 promoter-driven luciferase reporter activity. Western blot analyses showed that GL331 decreased the level of phosphorylated extracellular signal-regulated kinase (Erk), with no effect on p38 or c-Jun NH(2)-terminal kinase. Furthermore, GL331's inhibition of cyclin D1 promoter was attenuated by ectopic Erk-2 overexpression. These data suggested that GL331 inhibited cyclin D1 gene transcription via the Erk signaling pathway. In summary, we report that GL331 induced an early decline of cyclin D1 expression by dual mechanisms: 1) enhancement of protein turnover and 2) repression of Erk-mediated gene transcription.

Cytokeratin 20 as an immunocytochemical marker for detection of urothelial carcinoma in atypical cytology: preliminary retrospective study on archived urine slides

Previous studies have shown that expression of cytokeratin 20 (CK20), a constituent of intermediate filaments, is increased in malignant versus benign urine samples. To evaluate whether immunocytochemical staining of CK20 on archived urine slides could be used as a potential adjunct marker for triage of atypical urine cytology, we analyzed a total of 77 archived urine slides obtained from a spectrum of patients with various risks of developing urothelial carcinoma. These patients were divided into four groups on the basis of initial urine cytologic results and subsequent follow-up biopsy findings; group 1 had negative results in both evaluations, whereas the results in group 4 were positive for both cytology and biopsy. Groups 2 and 3 had a diagnosis of atypical urine cytology; however, patients in group 3 had a positive follow-up biopsy, and patients in group 2 did not. The Papanicolaou-stained archived urine slides were destained and then restained immunocytochemically with monoclonal antibody against CK20. With 5% positively stained nonumbrella cells as a threshold, CK20 was positive in 94.4% of group 3 or 4 patients. In contrast, CK20 was positive in 27.3% of group 2 patients and in 10.5% of group 1 patients. The overall sensitivity and specificity for CK20 for the detection of urothelial carcinoma in this population of patients were 94.4% and 80.5%, respectively. This study demonstrated that immunocytochemical analysis of CK20 on archived urine slides could be used to triage atypical urine cytology into low- and high-risk categories and that CK20 might be a simple and useful early detection marker for urothelial carcinoma.

In vitro and in vivo evaluations of biodegradable implants for hormone replacement therapy: effect of system design and PK-PD relationship

This investigation evaluated the feasibility of using subdermally implantable devices fabricated by nonconventional 3-dimensional printing technology for controlled delivery of ethinyl estradiol (EE2). In vitro release kinetics of EE2 and in vivo pharmacokinetics/pharmacodynamics in ovariectomized New Zealand White rabbits were carried out to study 3 implant prototypes: implant I (single-channel EE2 distribution in polycaprolactone polymer core), implant II (homogeneous EE2 distribution in polycaprolactone polymer matrix), and implant III (concentration-gradient EE2 distribution in polycaprolactone and poly(dl-lactide-co-glycolide) (50:50 matrix). EE2 was found to be released from all the implants in a nonlinear pattern with an order of implant III > implant II > implant I. The noncompartmental pharmacokinetic analysis of plasma EE2 profiles in rabbits indicated a significant difference (p < .05) in Cmax, tmax, and mean residence time between implant I and implants II and III, but no difference in the area under the plasma concentration time curves calculated by trapezoidal rule (AUC) among the implants. For pharmacodynamic studies, endogenous follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were observed to be suppressed following implantation of all implants, which demonstrated that a therapeutically effective dose of EE2 had been delivered. Furthermore, the noncompartmental analysis of plasma FSH and LH profiles in rabbits showed a significant difference (p < .05) in AUC and the mean residence time between implant III and implants I and II. A good in vivo/in vitro relationship was observed between daily amounts of EE2 released and plasma profiles of EE2 for all implants. This relationship suggests that plasma profiles of EE2 could be predicted from in vitro measurement of daily amount of EE2 released. Therefore, performing in vitro drug release studies may aid in the development of an EE2 implant with the desired in vivo release rate.

An agrin minigene rescues dystrophic symptoms in a mouse model for congenital muscular dystrophy

Congenital muscular dystrophy is a heterogeneous and severe, progressive muscle-wasting disease that frequently leads to death in early childhood. Most cases of congenital muscular dystrophy are caused by mutations in LAMA2, the gene encoding the alpha2 chain of the main laminin isoforms expressed by muscle fibres. Muscle fibre deterioration in this disease is thought to be caused by the failure to form the primary laminin scaffold, which is necessary for basement membrane structure, and the missing interaction between muscle basement membrane and the dystrophin-glycoprotein complex (DGC) or the integrins. With the aim to restore muscle function in a mouse model for this disease, we have designed a minigene of agrin, a protein known for its role in the formation of the neuromuscular junction. Here we show that this mini-agrin-which binds to basement membrane and to alpha-dystroglycan, a member of the DGC-amends muscle pathology by a mechanism that includes agrin-mediated stabilization of alpha-dystroglycan and the laminin alpha5 chain. Our data provides in vivo evidence that a non-homologous protein in combination with rational protein design can be used to devise therapeutic tools that may restore muscle function in human muscular dystrophies.

Reduced levels of amyloid beta-peptide antibody in Alzheimer disease

OBJECTIVE

To investigate whether it was possible to detect the presence and different levels of naturally occurring anti-beta-amyloid (Abeta) antibodies in the CSF of patients with AD and age-matched controls by employing a sensitive ELISA.

BACKGROUND

Immunization with preaggregated amyloid beta-peptide (Abeta(1-42)) and administration of antibodies against Abeta into amyloid precursor protein APP(V717F)- transgenic mice (an animal model of AD) have recently been reported to dramatically reduce amyloid plaque deposition, neuritic dystrophy, and astrogliosis, most likely by enhancing Abeta clearance from brain.

METHODS

A sensitive ELISA was performed to detect levels of naturally occurring anti-Abeta antibodies in the CSF of patients with AD and age-matched controls. Additionally, an immunoprecipitation assay was performed to confirm that naturally occurring anti-Abeta antibodies also exist in the human blood.

RESULT

- Naturally occurring antibodies directed against Abeta were found in the CSF and plasma of patients with AD and healthy control subjects. Moreover, CSF anti-Abeta antibody titers are significantly lower in patients with AD compared with healthy control subjects.

CONCLUSION

Naturally occurring antibodies directed against Abeta exist in human CSF and plasma. The CSF anti-Abeta antibody titers may be helpful in better understanding the effects of future immunologic therapies for AD.

Exciton dynamics in FMO bacteriochlorophyll protein at low temperatures

A time response over almost 5 decades (from 10(-13) to about 10(-8) s) to a (sub)picosecond laser pulse excitation has been observed in the Fenna, Matthews, and Olson (FMO) antenna protein trimer. The FMO protein is unique in having a fine-structured bacteriochiorophyll a Qy exciton absorption spectrum over the whole investigated temperature range between 6 and 160 K. As measured by a two-color pump-probe differential absorption, the population decay of the exciton states of seven strongly coupled bacteriochlorophyll a molecules in a protein monomer is the dominant dynamical process in the subpicosecond time domain. The through-band scattering takes a few picoseconds and depends only weakly on temperature, probably because of a low density of exciton states. At low temperatures, evidence for a slow pico-nanosecond relaxation process has also been obtained via time-dependent red-shift and broadening of the exciton emission spectrum. Two nonexclusive tentative interpretations to this effect have been provided. The phenomenon may be due to exciton solvation in the surrounding protein and water-glycerol matrix or/and due to slow scattering of closely spaced bacteriochlorophyll a exciton states in a protein trimer. The shape of the excited-state absorption spectrum (arising from transitions between singly and doubly excited exciton states) and its oscillator strength has been roughly estimated from the analysis of the pump-probe spectrum. The spectrum peaks at around 805 nm and is less featured compared to the ground-state absorption spectrum. Both spectra have comparable strength.

Limited acid hydrolysis as a means of fragmenting proteins isolated upon ProteinChip array surfaces

ProteinChip array technology enables protein purification, protein profiling, and biomarker discovery on a convenient biochip platform. Traditional proteomic approaches towards protein identification rely upon the generation of peptides through the use of specific proteases. However, for a variety of reasons, the digestion of proteins bound to planar arrays by specific proteases, such as trypsin, has proven to be difficult, at times providing little or no protein digestion at all. Additionally, should more than one protein be present on the array surface, the digestion product consists of peptides from different proteins, adding another dimension of complexity to database mining approaches. These factors have driven our group to explore alternative means of on-chip protein digestion. In this article, we describe an approach to generate peptide maps by limited acid hydrolysis. Depending upon the adsorbed protein, this method requires between 500 femtomole to 5 picomole of protein for on-chip hydrolysis. Besides generating several internal peptide fragments, limited acid hydrolysis also has the advantage of generating peptide ladders from the N- or C-terminus of the protein. From these ladders, partial primary sequence of the protein can be directly derived when analyzed by a simple laser desorption/ionization mass spectrometer. Furthermore, tandem mass spectrometry can be performed on several internal peptide fragments, thus facilitating the identification of several proteins within a mixture. Based upon the preliminary results of this work, we continue to explore the possibility of using limited acid hydrolysis to identify unknown proteins captured on ProteinChip array surfaces.

Epidemiology of thoracolumbar spine injury in blunt trauma

OBJECTIVE

To evaluate the prevalence, distribution, and demographics of thoracolumbar (TL) spine injuries following blunt trauma.

METHODS

Prospective, cross-sectional study of a consecutive sample of all blunt trauma patients presenting initially to the emergency department (ED) of a Level 1 trauma center and undergoing thoracic and/or lumbar spine radiography from August 1997 to November 1998. The age, sex, and mechanism of injury of each patient as well as location and type of spine injury were recorded for those patients with vertebral fractures, dislocations, or subluxations.

RESULTS

Two thousand four hundred four blunt trauma patients were enrolled. Vertebral injuries were identified in 152 individuals (6.3%, 95% CI = 5.4% to 7.4%). Two hundred sixty distinct anatomic levels of injury were identified in these 152 individuals. Of these 260 injuries, 42 (16.2%) occurred at L1, 38 (14.6%) at L2, 29 (11.1%) at L3, and 27 (10.4%) at T12, making these the most commonly injured vertebrae. Injuries were most common (34 patients) in those aged 30-39 years and were least common (12 patients) in those under 18 years. Compression fractures (52%) were the most common injury in the thoracic spine, while transverse process fractures (48%) were the most common injuries in the lumbar spine.

CONCLUSIONS

The prevalence of TL injuries in ED blunt trauma patients undergoing TL radiographs is 6.3%. The most commonly injured area of the TL spine is the thoracolumbar junction.

Piperazine-based CCR5 antagonists as HIV-1 inhibitors. I: 2(S)-methyl piperazine as a key pharmacophore element

Optimization of the piperidino-piperazines 1 and 2 provided early leads 3 and 4, which showed good activity in the CCR5-RANTES binding assay and in antiviral assays. A systematic study around these structures showed that the 2(S)-methyl piperazine is essential for CCR5 affinity, which is further enhanced by forming the 2,6-dimethyl benzamide of the piperidine.

Spectral inhomogeneity of photosystem I and its influence on excitation equilibration and trapping in the cyanobacterium Synechocystis sp. PCC6803 at 77 K

Ultrafast transient absorption spectroscopy was used to probe excitation energy transfer and trapping at 77 K in the photosystem I (PSI) core antenna from the cyanobacterium Synechocystis sp. PCC 6803. Excitation of the bulk antenna at 670 and 680 nm induces a subpicosecond energy transfer process that populates the Chl a spectral form at 685--687 nm within few transfer steps (300--400 fs). On a picosecond time scale equilibration with the longest-wavelength absorbing pigments occurs within 4-6 ps, slightly slower than at room temperature. At low temperatures in the absence of uphill energy transfer the energy equilibration processes involve low-energy shifted chlorophyll spectral forms of the bulk antenna participating in a 30--50-ps process of photochemical trapping of the excitation by P(700). These spectral forms might originate from clustered pigments in the core antenna and coupled chlorophylls of the reaction center. Part of the excitation is trapped on a pool of the longest-wavelength absorbing pigments serving as deep traps at 77 K. Transient hole burning of the ground-state absorption of the PSI with excitation at 710 and 720 nm indicates heterogeneity of the red pigment absorption band with two broad homogeneous transitions at 708 nm and 714 nm (full-width at half-maximum (fwhm) approximately 200--300 cm(-1)). The origin of these two bands is attributed to the presence of two chlorophyll dimers, while the appearance of the early time bleaching bands at 683 nm and 678 nm under excitation into the red side of the absorption spectrum (>690 nm) can be explained by borrowing of the dipole strength by the ground-state absorption of the chlorophyll a monomers from the excited-state absorption of the dimeric red pigments.

(R)-methanandamide and Delta 9-THC as discriminative stimuli in rats: tests with the cannabinoid antagonist SR-141716 and the endogenous ligand anandamide

RATIONALE AND OBJECTIVES

(R)-methanandamide (AM-356), a metabolically more stable chiral analog of the endocannabinoid ligand anandamide, was used as a representative of fatty acid ethanolamide CB1 receptor ligands to characterize the discriminative stimulus functions of anandamides.

METHODS

Rats discriminated between 10 mg/kg (R)-methanandamide and vehicle administered IP 15 min prior to session onset. Another group of rats was initially trained to discriminate between 3 mg/kg Delta9-THC and vehicle given IP 30 min prior to session onset; for anandamide testing, the animals were retrained with 1.8 and 5.6 mg/kg Delta9-THC. A two lever operant methodology (FR10) was used.

RESULTS

Delta9-THC was more potent than (R)-methanandamide at both 15 and 30 min post-injection, irrespective of the training drug used. Additional tests with 10 and 18 mg/kg (R)-methanandamide suggested that the effects were declining by 1 h. The cannabinoid antagonist SR 141716 (0.3 and 1 mg/kg) produced rightward shifts in the Delta9-THC dose-response curve for Delta9-THC-appropriate responding and for (R)-methanandamide-appropriate responding (surmountable antagonism). SR-141716 (0.3 and 1 mg/kg) antagonized the ability of (R)-methanandamide to occasion either Delta9-THC-appropriate responding or (R)-methanandamide-appropriate responding. This antagonism was surmountable only at a dose of 0.3 mg/kg SR-1421716 in the (R)-methanandamide-trained rats. SR-141716 did not antagonize the rate-decreasing effects of (R)-methanandamide in either the Delta9-THC or the (R)-methanandamide trained rats. Response suppression precluded testing doses higher than 30 mg/kg (R)-methanandamide. Tests with SR-141716 (1 and 10 mg/kg) alone resulted in <3% Delta9-THC-appropriate responding. With 10 mg/kg SR-141716, response rate was significantly lower as compared to the rate observed during a vehicle test. Tests with anandamide (10 and 18 mg/kg) resulted in 41% and 85% (R)-methanandamide-appropriate responding at a 3-min pre-treatment time, but in a maximum of 15% (R)-methanandamide-appropriate responding at a longer (15 min) pre-treatment time. In the Delta9-THC (1.8 and 5.6 mg/kg) trained rats, anandamide never produced more than about 20% Delta9-THC-appropriate responding.

CONCLUSION

The results add to a growing body of evidence indicating that there are both similarities and dissimilarities between classical cannabinoids such as THC and endogenous fatty acid ethanolamides.

[Mortality study of major non-communicable diseases in Shanghai, from 1951 to 1998]

OBJECTIVE

To study the transition of major non-communicable diseases (NCDs) in Shanghai.

METHODS

Demographic and mortality data since early 1950s in Shanghai was used. Linear regression model was employed to evaluate the mortality trends of diseases.

RESULTS

During the past five decades, age-adjusted mortality had been gradually decreasing, with leading cause of deaths shifting from infectious diseases to NCDs. In 1998, the average life expectancy reached 77.03, and the three leading causes of deaths, i.e. tumor, cardio-vascular diseases and respiratory diseases, accounted for 75% of all deaths. The crude mortality of major NCDs increased consistently. However, the age-adjusted mortality trends of major NCDs decreased during the past two decades after a 30-year's increase. Turnover took place in the late 1970s for tumors, for coronary heart in late 1980s diseases and in the early 1990s for strokes. For malignant tumors, the age-adjusted mortality of breast cancer, cancer of colon and rectum did not significantly decrease in the past two decades.

CONCLUSION

The increase of crude mortality of major NCDs was mainly due to the trend of aging in Shanghai. It is suggested that the risk factors of major NCDs had decreased to some extent but the behavior and dietary related risk factors remained serious.

Photoswitched singlet energy transfer in a porphyrin-spiropyran dyad

A photochromic nitrospiropyran moiety (Sp) has been covalently linked to a zinc (PZn) and to a free-base (P(H2)) porphyrin. In the resulting dyads (P(Zn)-Sp(c) and P(H2)-Sp(c)), the porphyrin first excited singlet states are unperturbed by the closed form of the attached spiropyran. Excitation of the spiropyran moiety of either dyad in the near-UV region results in ring opening to a merocyanine form (P-Sp(o)) that absorbs at 600 nm. The open form re-closes thermally in 2-methyltetrahydrofuran with a time constant of 20 s, or following irradiation into the 600 nm band. Excitation of the zinc porphyrin moiety in the merocyanine form of the dyad yields 1PZn-Sp(o). The lifetime of the zinc porphyrin excited state is reduced from its usual value of 1.8 ns to 130 ps by singlet-singlet energy transfer to the merocyanine moiety to give PZn-1Sp(o). The quantum yield of energy transfer is 0.93. Quenching is also observed in the free base dyad, where 1P(H2)-Sp(o) and P(H2)-1Sp(o) exchange singlet excitation energy. This photoswitchable quenching phenomenon provides light-activated control of the porphyrin excited states, and consequently control of any subsequent energy or electron-transfer processes that might be initiated by these excited states in more complex molecular photonic or optoelectronic devices.

Stereochemical selectivity of methanandamides for the CB1 and CB2 cannabinoid receptors and their metabolic stability

Several chiral, analogues of the endogenous cannabinoid receptor ligand, arachidonylethanolamide (anandamide), methylated at the 2,1' and 2' positions using asymmetric synthesis were evaluated in order to study (a) stereoselectivity of binding to CB1 and CB2 cannabinoid receptors; and (b) metabolic stability with regard to anandamide amidase. Enantiomerically pure 2-methyl arachidonic acids were synthesized through diastereoselective methylation of the respective chiral 2-oxazolidinone enolate derivatives and CB1 and CB2 receptor affinities of the resulting chiral anandamides were evaluated using a standard receptor binding assay. Introduction of a single 2-methyl group increased affinity for CB1, led to limited enantioselectivity and only modestly improved metabolic stability. However, a high degree of enantio- and diastereoselectivity was observed for the 2,1'-dimethyl analogues. (R)-N-(1-methyl-2-hydroxyethyl)-2-(R)-methyl-arachidonamide (4) exhibited the highest CB1 receptor affinity in this series with a K(i) of 7.42 nM, an at least 10-fold improvement on anandamide (K(i)=78.2 nM). The introduction of two methyl groups at the 2-position of anandamide led to no change in affinity for CB1 but somewhat enhanced metabolic stability. Conversely, chiral headgroup methylation in the 2-gem-dimethyl series led to chiral analogues possessing a wide range of CB1 affinities. Of these the (S)-2,2,2'-trimethyl analogue (12) had the highest affinity for CB1 almost equal to that of anandamide. In agreement with our previous anandamide structure-activity relationship work, the analogues in this study showed high selectivity for the CB1 receptor over CB2. The results are evaluated in terms of stereochemical factors affecting the ligand's affinity for CB1 using receptor-essential volume mapping as an aid. Based on the results, a partial CB1 receptor site model is proposed, that bears two hydrophobic pockets capable of accommodating 1'- and 2-methyl groups

Three-dimensional finite element analyses of four designs of a high-strength silicon nitride implant

The effects of implant shape and size on the stress distribution around high-strength silicon nitride implants under vertical and oblique forces were determined using a three-dimensional finite element analysis. Finite element models were designed using as a basis the serial sections of the mandible. Using Auto-CAD software, the model simulated the placement of implants in the molar region of the left mandible. Results of the analyses demonstrated that mainly the implant root shape and the directions of bite forces influence the stress distributions in the supporting bone around each implant. Implant size is a lesser factor. The serrated implants presented a larger surface area to the bone than either the cylindrical or tapered implants, which resulted in lower compressive stress around the serrated implants. With increasing implant diameter and length, compressive stress decreased. The mean compressive stress distribution on the serrated implants was more flat (platykurtic) than on either the cylindrical or tapered implants. Results of studies on two load directions (vertical and oblique) showed that, in either case, the compressive stress in the cortical bone around the neck of the implant was higher than in the cancellous bone along the length of the implant. The most extreme principal compressive stress was found with oblique force. This study provides the first information on the relationship between shape of the silicon nitride implant and stress on the supporting bone.

Roles of acyl-coenzyme A:cholesterol acyltransferase-1 and -2

Acyl-coenzyme A:cholesterol acyltransferase (ACAT) is an intracellular enzyme that produces cholesteryl esters in various tissues. In mammals, two ACAT genes (ACAT1 and ACAT2) have been identified. Together, these two enzymes are involved in storing cholesteryl esters as lipid droplets, in macrophage foam-cell formation, in absorbing dietary cholesterol, and in supplying cholesteryl esters as part of the core lipid for lipoprotein synthesis and assembly. The key difference in tissue distribution of ACAT1 and ACAT2 between humans, mice and monkeys is that, in adult human liver (including hepatocytes and bile duct cells), the major enzyme is ACAT1, rather than ACAT2. There is compelling evidence implicating a role for ACAT1 in macrophage foam-cell formation, and for ACAT2 in intestinal cholesterol absorption. However, further studies at the biochemical and cell biological levels are needed in order to clarify the functional roles of ACAT1 and ACAT2 in the VLDL or chylomicron synthesis/assembly process.

A Chlamydia trachomatis UDP-N-acetylglucosamine acyltransferase selective for myristoyl-acyl carrier protein. Expression in Escherichia coli and formation of hybrid lipid A species

Chlamydia trachomatis lipid A is unusual in that it is acylated with myristoyl chains at the glucosamine 3 and 3' positions. We have cloned and expressed the gene encoding UDP-N-acetylglucosamine 3-O-acyltransferase of C. trachomatis (CtlpxA), the first enzyme of lipid A biosynthesis. C. trachomatis LpxA displays approximately 20-fold selectivity for myristoyl-ACP over R/S-3-hydroxymyristoyl-ACP under standard assay conditions, consistent with the proposed structure of C. trachomatis lipid A. CtLpxA is the first reported UDP-N-acetylglucosamine acyltransferase that prefers a non-hydroxylated acyl-ACP to a hydroxyacyl-ACP. When CtlpxA was expressed in RO138, a temperature-sensitive lpxA mutant of Escherichia coli, five new hybrid lipid A species were made in vivo after 2 h at 42 degrees C, in place of Escherichia coli lipid A. These compounds were purified and analyzed by matrix-assisted laser desorption ionization/time of flight mass spectrometry. In each case, a myristoyl chain replaced one or both of the ester linked 3-hydroxymyristoyl residues of E. coli lipid A. With prolonged growth at 42 degrees C, all the ester-linked 3-hydroxymyristoyl residues were replaced with myristate chains. Re-engineering the structure of E. coli lipid A should facilitate the microbiological production of novel agonists or antagonists of the innate immunity receptor TLR-4, with possible uses as adjuvants or anti-inflammatory agents.

[The prognostic research of expression and relationship between Helicobacter pylori of c-met oncogene correlation with gastric mucosal proliferation]

OBJECTIVE

To determine whether there is a relationship between Helicobacter pylori (Hp) and expression of c-met oncogene and proliferating cell nuclear antigen (PCNA) in gastric mucosal lesions, and prognostic significance of gastric carcinomas(GC).

METHODS

Expression of c-met and PCNA were investigated in 145 gastric mucosal lesions by using immunohistochemistry. Hp was examined by Warthin-Starry method.

RESULTS

For chronic superficial gastritis (CSG), chronic atrophic gastritis and intestinal metaplasia (CAS + IM), dysplasia(DYS), early GC and advanced GC, the positive rates of c-met and PCNA were higher in IM, DYS and GC than in CSG (P < 0.05). Expressions of c-met and PCNA increased with the increasing proliferation of gastric mucosa, in rank correlation test, they had a close relationship (P < 0.01). Expressions of c-met and PCNA were correlated significantly with histologic type, serosal invasion and lymph node metastasis. In particular, the expression of c-met and PCNA were significantly higher in Borrmann type 4 GC, type 3 GC and type 1, 2 than in early GC(P < 0.05). By rank correlation test, c-met and PCNA have a close relationship (P < 0.001). Expressions of c-met of Hp positive were higher than Hp negative in intestinal GC (P < 0.05). Expressions of c-met were correlated significantly with Hp positive in CAG + IM, DYS and GC. The survival rate of patients with Hp infection was significantly poorer than that of patients with Hp non-infection.

CONCLUSIONS

The expression of c-met may be is associated with proliferation and malignant transformation of gastric mucosa. These results suggest that expression of c-met may be a new prognostic factor in gastric carcinoma. Hp infection and expression of c-met may be associated with in proliferation and malignant transformation of gastric mucosa. Hp infection is associated with prognosis of gastric carcinoma.

[Study of susceptibility loci located within Xp11 in attention deficit hyperactivity disorder]

OBJECTIVE

To detect the genetic relationship between monoamine oxidase(MAO) A type gene and attention deficit hyperactivity disorder(ADHD) in Chinese.

METHODS

The haplotype-based haplotype relative risk(HHRR) and the transmission disequilibrium test(TDT) methods were used to analyze the genetic association and linkage in 60 ADHD children and their parents.

RESULTS

In this sample were found significant association (chi(2)=4.90, P<0.05) and linkage (chi(2)=4.84, P<0.05) between the MAOCA 114bp allele and DSM-III-R-diagnosed ADHD in trios composed of father, mother and affected offspring.

CONCLUSION

The above results suggested that ADHD was associated and in linkage with MAO A gene, and the susceptibility loci might reside in chromosome Xp11 for ADHD.