[The PCR amplification, cloning, sequencing, expression in E. coli of gene encoding endoflagella subunit protein (fla B) from Leptospira interrogans serovar lai]

A pair of oligonucleotide primers were designed by ourselves to amplify the endoflagella gene of L. interrogans serovar lai. A fragment about 840 bp was generated with PCR and inserted into plasmid pUC8 after the fragment and pUC8 were digested respectively with Bam HI and Pst I. A recombinant plasmid (designated as pLF1) was obtained. SDS-PAGE analysis indicated that a 33 kd was expressed in E. coli JM103 harboring pLF1 and the expression level of the protein was 11% of total bacterial soluble proteins. Western blot analysis showed that the protein band could be recognized by the antiserum against the endoflagella (Axiall filament) of Leptospira interrogans serovar lai. Nucleotide seguence data showed an open reading frame encoding 282 aminoacids residues, corresponding to a protein of molecular weight 33.6 kd. The G + C content of endoflagella subunit protein gene was 48 mol%. Therefore, the G + C content of the leptospiral fla B Gene is significantly higher than the reported 39 mol% G + C content of leptospiral genome of L.interrogans serovar lai but similar to the G + C of the Treponema pallidum genome. Comparison of the deduced endoflagellar subunit protein (fla B) amino acid sequence with flagellins from other bacteria revealed a high level of identity with the Treponema pallidum fla B proteins. Immunization/protection experiment was performed on the model of BALB/c mice and showed that the survival rate in the group JM103-pLF1 was higher than that in the group JM103-pUC8, but statistically the difference between them was significant (P < 0.05) and pLF1 did not induce significant levels of agglutinating antibodies against L.interrogans serovar lai.

In vivo studies of cadmium-induced apoptosis in testicular tissue of the rat and its modulation by a chelating agent

In vivo CdCl2-induced apoptotic DNA fragmentation in the testes of the male Wistar rat has been demonstrated on agarose gel. Characteristic DNA migration patterns (laddering) provide evidence of apoptosis (programmed cell death) in testicular tissue of rats administered CdCl2 at a level of 0.03 mmol/kg 48 h previously. Evidence that administration of an appropriate cadmium chelating agent within the first 24 h can suppress some or all of the apoptotic changes in testicular DNA has also been obtained for the first time. A greater reduction in apoptosis is observed as the interval between the administration of the cadmium and that of the chelating agent is shortened. Administration of monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) to male Wistar rats given CdCl2 is effective in the modulation of the typically apoptotic DNA fragmentation and associated histopathologic injury when the antagonist is given within approximately 1 h after the CdCl2 exposure. When the antagonist is given at later times there is a progressively more pronounced degradation of the DNA into oligonucleotides as seen in the typical electrophoretic DNA ladder pattern found with apoptosis. There is also a progressive increase in histopathological tissue changes as the antagonist is administered at progressively greater intervals after the cadmium.

Comparison of multilayer neural network and Nearest Neighbor Classifiers for handwritten digit recognition

The basic Nearest Neighbor Classifier (NNC) is often inefficient for classification in terms of memory space and computing time needed if all training samples are used as prototypes. These problems can be solved by reducing the number of prototypes using clustering algorithms and optimizing the prototypes using a special neural network model. In this paper, we compare the performance of the multilayer neural network and an Optimized Nearest Neighbor Classifier (ONNC) for handwritten digit recognition applications. We show that an ONNC can have the same recognition performance as an equivalent neural network classifier. The ONNC can be efficiently implemented using prototype and variable ranking, partial summation and distance triangular inequality based strategies. It requires the same memory space as, but less, training time and classification time than the neural network.

Homodimerization and intermolecular tyrosine phosphorylation of the Tyk-2 tyrosine kinase

The Jak kinases and Stat transcription factors play a major role in signaling of various cytokines including IFN alpha. In this report we show a ligand-independent interaction between Tyk-2 and Jak-1 kinases. We also demonstrate that the Tyk-2 kinase forms a homodimer that has the ability to undergo intermolecular tyrosine phosphorylation. The formation of the Tyk-2 homodimer is independent of both tyrosine phosphorylation and the presence of the tyrosine kinase domain.

Structural and electronic similarity but functional difference in methylmalonyl-CoA mutase between coenzyme B12 and the analog 2',5'-dideoxyadenosylcobalamin

The cofactor analog 2',5'-dideoxyadenosylcobalamin (ddAdoCbl) differs from the natural cofactor coenzyme B12 [5'-deoxyadenosylcobalamin (dAdoCbl)] by lacking only one oxygen atom. The 1H and 13C NMR spectra of ddAdoCbl have been assigned unambiguously by homonuclear and heteronuclear 2D NMR techniques. The 1H, 13C, and 31P chemical shift values for ddAdoCbl were compared with those of another organocobalamin, namely dAdoCbl. This assessment shows that the analog is very similar both electronically and structurally to the natural cofactor. The effectiveness of ddAdoCbl as a cofactor for both the human and Propionibacterium shermanii methylmalonyl-CoA mutases was compared with that of the natural cofactor. ddAdoCbl was found to be a competitive inhibitor with respect to dAdoCbl. Similar binding affinities to both enzymes were found for both the ddAdoCbl analog and the natural cofactor. However, in the presence of ddAdoCbl, the rate of conversion of methylmalonyl-CoA to succinyl-CoA was only 1-2% of that seen with the natural cofactor. There were no changes with time in the visible absorption spectrum of the bound cofactor analog in the presence of substrate, suggesting that the Co-C bond was not cleaved. The CD (circular dichroism) spectra of dAdoCbl and ddAdoCbl are very similar, consistent with the NMR results. The CD spectral changes upon binding to P. shermanii methylmalonyl-CoA mutase are large compared to those reported on the binding of dAdoCbl to ethanolamine ammonia lyase. Furthermore, the CD spectra of both enzyme-bound cobalamins are very similar, suggesting that similar changes in the conformation or structure in these cobalamins occur on binding to the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

FFA-1, a protein that promotes the formation of replication centers within nuclei

In the nuclei of eukaryotic cells, initiation of DNA replication occurs at a discrete number of foci. One component of these foci is the DNA replication factor RP-A. Here, the process leading to the association of RP-A with foci was reconstituted with cytosolic fractions derived from Xenopus eggs. With the use of this fractionated system, a 170-kilodalton protein required for the assembly of RP-A into foci was identified and purified. The protein appears to be an integral component of the foci at which replication of DNA is initiated in eukaryotic nuclei.

Cooperativity between non-polar and ionic forces in the binding of bacterial cell wall analogues by vancomycin in aqueous solution

The clinically important glycopeptide antibiotic vancomycin binds to bacterial cell wall peptides of Gram-positive bacteria which terminate in -Lys-D-Ala-D-Ala, thereby inhibiting cell wall synthesis resulting in cell death. We have removed the N-terminal leucine residue of vancomycin by an Edman degradation and acylated the exposed amino group of residue 2 with N-Me-Gly, N-Me-D-Ala, acetyl, butyl, and isohexyl groups to generate novel vancomycin analogues. The binding of vancomycin and these vancomycin analogues to the bacterial cell wall analogue di-N-Ac-L-Lys-D-Ala-D-Ala (DALAA) was studied by NMR techniques and UV spectroscopy. The effects that these structural modifications of the carboxylate binding pocket of vancomycin have on the antibiotic-DALAA recognition process show that a cooperative effect between non-polar and ionic forces appears to be partly responsible for the highly efficient sequestering of the DALAA C-terminal carboxylate from aqueous solution.

Alcohol and aldehyde dehydrogenase genotypes and drinking behavior of Chinese living in Shanghai

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), the principal enzymes responsible for oxidative metabolism of ethanol, exist in multiple, genetically determined molecular forms. Widely different kinetic properties in some of these isozymes account for the individual differences in alcohol sensitivity. In this study we used the polymerase chain reaction/restriction fragment length polymorphism method to determine the genotypes of the ADH2 and ALDH2 loci of alcoholic and nonalcoholic Chinese living in Shanghai. We also investigated the subjects' drinking patterns by means of semistructured interviews. The alcoholics had significantly lower frequencies of the ADH2(2) and ALDH2(2) alleles than did the nonalcoholics, suggesting the inhibitory effects of these alleles for the development of alcoholism. In the nonalcoholic subjects, ADH2(2) had little, if any, effect, despite the significant effect of the ALDH2(2) allele in decreasing the alcohol consumption of the individual. Taken together, these results fit the proposed hypothesis for the development of alcoholism, i.e., drinking behavior is greatly influenced by the individual's genotypes of alcohol-metabolizing enzymes, and the risk of becoming alcoholic is proportionate with the ethanol consumption of the individual.

Proteoglycan biosynthesis is required in BC3H1 myogenic cells for modulation of vascular smooth muscle alpha-actin gene expression in response to microenvironmental signals

Induction of vascular smooth muscle (VSM) alpha-actin mRNA expression during cytodifferentiation of mouse BC3H1 myogenic cells coincides with the accumulation of cell surface- and extracellular matrix-associated sulfated proteoglycans. Inhibition of proteoglycan biosynthesis in myogenic cells using an artificial beta-D-xyloside glycosaminoglycan acceptor was accompanied by a reduction in cell surface/extracellular matrix proteoglycans and VSM alpha-actin mRNA expression while enhancing the secretion of free chondroitin sulfate/dermatan sulfate and heparan sulfate glycosaminoglycans into the culture medium. Maximum inhibition of VSM alpha-actin mRNA expression required that proteoglycan biosynthesis be blocked during the early phase of cytodifferentiation when myoblasts were fully confluent and quiescent. The inhibitory effect of beta-D-xyloside on alpha-actin mRNA expression resulted from attenuation at both the transcriptional and post-transcriptional control points. Sustained proteoglycan biosynthesis was required for induction of VSM alpha-actin mRNA in quiescent myoblasts in response to cytodifferentiation-permissive, substrate-associated macromolecules (SAM) or upon exposure to soluble serum factors capable of transiently stimulating VSM alpha-actin gene transcription. The results suggested that efficient myoblast cytodifferentiation and modulation of VSM alpha-actin mRNA levels depended on intact cell surface proteoglycans to convey signals generated as a consequence of cellular interaction with substrate components and serum factors.

Expression of receptor protein tyrosine phosphatase-sigma (RPTP-sigma) in the nervous system of the developing and adult rat

The expression of receptor protein tyrosine phosphatase-sigma (RPTP-sigma) mRNA during rat development was examined by Northern blot and in situ hybridization analyses. Northern blot analysis revealed that the two transcripts (5.7 kb and 6.9 kb) had different spatial and temporal patterns of expression. The 6.9-kb transcript was more abundant during embryonic development, whereas the 5.7-kb transcript was more abundant during postnatal development and in the adult. In situ hybridization revealed that RPTP-sigma mRNA was widely expressed throughout the central and peripheral nervous system during embryonic development. Very high levels were seen in the ventricular zone, subventricular zone, cortex, dorsal root ganglia, cranial nerve ganglia, olfactory epithelium, and retina. During postnatal development the level of expression decreased in most brain regions. However, high levels continued to be seen in the hippocampus. Emulsion autoradiography revealed that the majority of RPTP-sigma mRNA is expressed in neurons. Northern analysis showed that cultured glial cells expressed the 6.9-kb transcript, but not the 5.7-kb. RPTP-sigma mRNA expression profiles were clearly distinct from those of leukocyte antigen-related protein (LAR), a closely related RPTP. The spatiotemporal pattern of RPTP-sigma mRNA expression indicates that RPTP-sigma may play a role in the development of the nervous system.

Stat recruitment by tyrosine-phosphorylated cytokine receptors: an ordered reversible affinity-driven process

Herein, we demonstrate that purified Stat1 binds to its tyrosine-phosphorylated docking site on the IFN gamma receptor alpha chain in a direct, specific, and reversible manner. Using surface plasmon resonance, we determine the affinity (KD = 137 nM) and specificity of the interaction and define the minimum affinity needed for receptor-mediated Stat1 activation. In addition, we quantitate the relative ability of purified Stat1 to interact with tyrosine-phosphorylated binding sites on other Stat proteins. Finally, we describe experiments that imply that the unidirectional release of activated Stat1 from the IFN gamma receptor reflects the preference of free tyrosine-phosphorylated Stat1 monomers to form high avidity reciprocal homodimers rather than reassociating with the receptor binding site. Our results demonstrate that IFN gamma-induced Stat1 activation is an ordered and affinity-driven process and we propose that this process may serve as a paradigm for Stat activation by other cytokine receptors.

An analysis of the regulation of DNA synthesis by cdk2, Cip1, and licensing factor

The activation of DNA replication appears to involve at least four steps. These include origin recognition, origin unwinding, primer synthesis, and a switching step to a continuous elongation mode. Moreover, in higher eukaryotes a number of studies have shown that much of the DNA replication which occurs is restricted to specific sites within the nuclei. It has been proposed that these replication foci are composed of a large number of origin sites which are clustered together into an aggregate. The molecular basis for this aggregation is currently not well understood. Regulation of the activation of DNA replication is a complicated process. The G1-S kinase cdk2 is a positive regulator of replication. The p21 protein is a negative regulator of replication both by inhibiting cdk2 kinase and the replication protein PCNA. Moreover, it has been proposed that origin usage is restricted to a single firing per cell cycle by a "licensing factor." Using a cell-free replication system derived from Xenopus eggs we have investigated at what step in the replication process these regulators participate. We present evidence that the clustered organization of DNA into foci is not a transient arrangement, but rather, it persists following DNA replication. We also find that foci form on both sperm chromatin and bacteriophage lambda DNA incubated in extracts depleted of cdk2 kinase. Therefore, our data support the conclusion that organization of chromatin into foci is an early event in the replication pathway preceding activation of cdk2 kinase. With respect to the role of cdk2 during activation of DNA replication we find that in cdk2-depleted extracts primer synthesis does not occur and RP-A remains tightly associated with foci. This strongly suggests that cdk2 kinase is required for activating the origin unwinding step of the replication process. Consistent with this interpretation we find that addition of rate limiting quantities of the cdk2 inhibitor p21 protein to an extract delays primer synthesis. Interestingly, in the presence of p21 primer synthesis does occur after a delay and then replication arrests. This is consistent with the published demonstration that p21 can inhibit PCNA, a protein required for replication beyond the priming step. Therefore, our results provide additional support to the proposal that the post-priming switching step is a key regulatory step in replication. With respect to the role of licensing factor during DNA replication it has recently been shown that treatment of mitotic extracts with kinase inhibitor DMAP inactivates "licensing factor."(ABSTRACT TRUNCATED AT 400 WORDS)

Susceptibility artifact reduction in fat suppression

Strong fat signal in regions where a large susceptibility difference exists, for instance at the interface between air and tissue near the maxillary sinus, may not be eliminated by currently available fat suppression techniques without sacrificing the overall quality of the images. In this article, we show that this fat signal, which appears as a susceptibility artifact, can be significantly reduced by using an optimized presaturation pulse with sharp edges and a broad bandwidth, while causing minimal disturbance of the water signal. Several optimized presaturation pulses can be reproduced by the Fourier coefficients provided in the Appendix.

Clinical observation on 80 children with peptic ulcer treated primarily by traditional Chinese medicine

Using the empirical recipe of Wang Pengfei (a very experienced TCM doctor) as the main treatment, the authors treated 80 children with peptic ulcer by means of promoting blood circulation, removing blood stasis as well as regulating the flow of qi, alleviating pain, tonifying the stomach and reinforcing the spleen. Measures for hemostasis, correction of anemia and other general treatment were also taken. After 8 weeks of treatment, a total effective rate of 92.5% was obtained.

Handwritten digit recognition using two-layer self-organizing maps

In this paper, we present a two-layer self-organizing neural network based method for handwritten digit recognition. The network consists of a base layer self-organizing map and a set of corresponding maps in the second layer. The input patterns are partitioned into subspace in the first layer. Patterns in a subspace are led to the second layer and a corresponding map is built according to the first layer performance. In the classification process, each pattern searches for several closest nodes from the base map and then it is classified into a specified class by determining the nearest model of the corresponding maps in the second layer. The new method yielded higher accuracy and faster performance than the ordinary self-organizing neural network.

Direct binding to and tyrosine phosphorylation of the alpha subunit of the type I interferon receptor by p135tyk2 tyrosine kinase

Binding of type I interferons (IFNs) to their receptors induces rapid tyrosine phosphorylation of multiple proteins, including the alpha and beta subunits of the receptor, the polypeptides that form the transcriptional activator ISGF3 alpha (Stat113, Stat84, and Stat91), and the p135tyk2 and Jak-1 tyrosine kinases. In this report, we demonstrate that the alpha subunit of the type I IFN receptor (IFN-R) corresponds to the product of a previously cloned receptor subunit cDNA and, further, that the p135tyk2 tyrosine kinase directly binds and tyrosine phosphorylates this receptor subunit. Glutathione S-transferase (GST) fusion proteins encoding the different regions of the cytoplasmic domain of the alpha subunit can bind the p135tyk2 contained in human cell lysates. The association between the alpha subunit and Tyk2 was demonstrated by immunoblotting with anti-Tyk2 and antiphosphotyrosine antibodies and by using an in vitro kinase assay. Analogous experiments were then performed with recombinant baculoviruses encoding constitutively active Jak family tyrosine kinases. In this case, p135tyk2, but not Jak-1 or Jak-2 protein, binds to the GST-IFN-R proteins, suggesting that the interaction between these two proteins is both direct and specific. We also demonstrate that Tyk2, from extracts of either IFN alpha-treated human cells or insect cells infected with the recombinant baculoviruses, can catalyze in vitro phosphorylation of GST-IFN-R protein in a specific manner. Deletion mutants of the GST-IFN-R protein were used to localize both the binding and tyrosine phosphorylation site(s) to a 46-amino-acid juxtamembrane region of the alpha subunit, which shows sequence homology to functionally similar regions of other cytokine receptor proteins. These data support the hypothesis that the Tyk2 protein functions as part of a receptor complex to initiate intracellular signaling in response to type I IFNs.

[The clinicopathologic study of histiocytic necrotizing lymphadenitis and the differentiated diagnosis with malignant lymphoma--report of 31 cases]

Histiocytic necrotizing lymphadenitis (HNL) is a kind of rare benign disease, predilection to involve the neck of young women, causing enlargement of the lymph nodes and usually accompanying by fever and other constitutional symptoms, and a unique clinicopathologic course are characteristic of this disease. Because its histomorphology has a given spectrum changing, it may lead to misdiagnosis for someone who is unfamiliar with it. According to the document records, misdiagnostis of HNL could be up to 30%-40%, especially in its early proliferative stage. In this 31 cases analysis, the authors systematically summarize the clinicopathologic characteristics of this lesion, and focus to elucidate the different features between HNL and lymphoma. Although presently it is thought that the disease is self-limited, there are two cases with clinical manifestations of systemic lupus erythematosus in our series. Possibly, the two diseases may have some intrinsic relationships. Long term follow-up of its final outcome in these patients is necessary to clarify whether or not HNL is a self-limiting or progressive disease.

A computer simulation study on the input function sampling schedules in tracer kinetic modeling with positron emission tomography (PET)

Tracer kinetic modeling with positron emission tomography (PET) requires measurements of the time-activity curves in both plasma (PTAC) and tissue (TTAC) to estimate physiological parameters, i.e. to fit the parameters of certain compartmental models using PTAC and TTAC as the model input and output functions, respectively. In this paper, we first explored the optimal blood sampling schedule (OBSS) for the input function, based on the tracer [18F]2-fluoro-2-deoxy-D-glucose (FDG) blood sample experimental data. Then using a 5-parameter FDG model we investigated the effects of the plasma sampling schedule, as well as PTAC measurement noise, on the estimation accuracy and reliability of FDG model macro- and micro-parameters and the physiological parameter local cerebral metabolic rates of glucose (LCMRGlc), using computer simulation. Three different methods were used: (a) estimation of the FDG model parameters ignoring PTAC noise using the traditional PTAC schedule (non-OBSS); (b) estimation of the PTAC model parameters and FDG model parameters simultaneously using both non-OBSS and OBSS; (c) estimation of the PTAC model parameters first, then the FDG model parameters using both non-OBSS and OBSS. The results show that OBSS can provide more reliable estimates and largely simplifies the experiment operations.

Community-based psychiatric rehabilitation in Shanghai. Facilities, services, outcome, and culture-specific characteristics

This paper describes the community mental health services in Shanghai, analyses the effectiveness of these services, and discusses their culture-specific characteristics. It reports on a prospective, matched-control study of the three most important types of service: a community follow-up programme in psychiatric out-patient clinics at primary-level general hospitals, 'guardianship networks' operated by non-professional volunteers, and work therapy stations. In total 308 pairs of subjects completed the study. Using Chinese versions of the Disability Assessment Schedule to assess impairment in psychosocial functioning and the Present State Examination to assess the levels of positive and negative symptoms, ten blind evaluators who had excellent inter-rater reliability assessed the functioning of subjects at enrollment and every six months for the next two years. Over the two years, symptoms and social functioning improved in the treatment groups and deteriorated in the control groups. Thus these community psychiatric services have the dual benefit of promoting rehabilitation and preventing psychosocial deterioration.

[Pathological and ultrastructural changes in conjunctival malignant melanoma treated by cryotherapy]

The liquid nitrogen cryotherapy was used to treat conjunctival malignant melanoma. Light and transmission electron microscopic examinations were carried out before, during and after the treatment. It was discovered that the tumor cells died within a few minutes after the cryoapplication. Under transmission electron microscope, marked necrosis of tumor cells was seen 10-14 days after the treatment and a large amount of collagenous fibers and fibroblast hyperplasia were seen in the tumor in 3-4 weeks following the application, while the tumor cells were seldom found. Under light microscope, as significant necrosis of the malignant melanoma occurred, the surface conjunctival epithelium gradually grew and covered the defect of the conjunctiva, showing that the malignant melanoma cells are much more sensitive to the cryoapplication than the normal conjunctival epithelial cells.

Constrained learning vector quantization

Kohonen's learning vector quantization (LVQ) is an efficient neural network based technique for pattern recognition. The performance of the method depends on proper selection of the learning parameters. Over-training may cause a degradation in recognition rate of the final classifier. In this paper we introduce constrained learning vector quantization (CLVQ). In this method the updated coefficients in each iteration are accepted only if the recognition performance of the classifier after updating is not decreased for the training samples compared with that before updating, a constraint widely used in many prototype editing procedures to simplify and optimize a nearest neighbor classifier (NNC). An efficient computer algorithm is developed to implement this constraint. The method is verified with experimental results. It is shown that CLVQ outperforms and may even require much less training time than LVQ.

Relationship of the celiac and superior mesenteric arteries to the vertebral bodies and its clinical relevance

To determine the relationship of the origins of the celiac artery (CA) and superior mesenteric artery (SMA) to the vertebral bodies, and their distribution in males and females, we examined them quantitatively on the angiograms of 1,591 patients (male 1,003, female 588). Our results showed that the origins of the CA and SMA were highly variable: 14.0% of the CA originated beyond the extent of the lower half of T12 to the upper part of L1, and 24.7% of the SMA originated beyond the level of L1. The origin of the SMA was more variable than that of the CA (p < 0.01). The variation in the origin of the CA was not significantly different (p > 0.05) between males (13.4%) and females (15.1%), but a statistically significant difference (p < 0.01) between males (22.3%) and females (28.7%) was shown for the SMA. The distance between the origin of the two arteries was over 3 cm in six patients (0.4%). Our results provide a valuable reference for clinical practice.

Functional consequences of iron supplementation in iron-deficient female cotton mill workers in Beijing, China

Eighty iron-deficient, nonpregnant female workers were randomly assigned to ferrous sulphate (60 or 120 mg Fe/d) or placebo treatment for 12 wk. Energy expenditure was estimated during 3 d by heart rate (HR) recording. Production efficiency (PE) was calculated as the ratio of productivity to energy expenditure. In the iron-treated group mean hemoglobin (Hb) increased from 114 to 127 g/L (P < 0.001), mean serum ferritin increased from 9.7 to 30.0 micrograms/L (P < 0.001), and mean free erythrocyte protoporphyrin decreased from 1.01 to 0.49 mumol/L (P < 0.001). Mean HR at work decreased from 95.5 to 91.1 beats/min (P < 0.001), which was inversely correlated with the change in Hb (r = -0.60, P < 0.001). PE increased significantly in the iron-treated group (P < 0.001) and its change paralleled the change in Hb (r = 0.58, P < 0.001). The results show that iron supplementation enabled these women to do the same work at a lower energy cost.

p135tyk2, an interferon-alpha-activated tyrosine kinase, is physically associated with an interferon-alpha receptor

Recent genetic studies have linked the tyk2 gene, which encodes a novel type of non-receptor tyrosine kinase, to the interferon-alpha intracellular signaling pathway. In this report, biochemical evidence is presented which supports this proposed function for the tyk2 tyrosine kinase and further defines its role in the interferon-alpha signaling cascade. Specifically, the tyk2 gene is shown to encode a 135-kDa protein which is rapidly phosphorylated on tyrosine in response to interferon-alpha treatment. Indirect evidence suggests that the tyrosine phosphorylation of p135tyk2 is the result of autokinase activity, implying that the Tyk2 tyrosine kinase is activated by interferon-alpha treatment. Two complementary methods demonstrate a physical association between p135tyk2 and the alpha-subunit of the interferon-alpha receptor. First, immunoblots show that monoclonal antibodies against the alpha-subunit of the interferon-alpha receptor can co-immunoprecipitate p135tyk2. Second, interferon-alpha receptor proteins which have been labeled by affinity cross-linking with 125I-interferon-alpha 2 can be co-immunoprecipitated using anti-tyk2 antisera. Taken together, these data suggest that an interferon-alpha receptor-p135tyk2 complex functions, in a manner analogous to the CD4-lck tyrosine kinase complex, to initiate the interferon-alpha signaling cascade.

Interaction of calmodulin with synthetic deletion peptides of melittin

The 26-residue peptide melittin present in bee venom has been shown to bind calmodulin tightly. In this study we synthesized the following series of deletion peptides of melittin by the solid-phase method: Mel12, Mel13, Mel14, Mel15, Mel15F. The results of this study show that the deletion peptides Mel14 and Mel15 have almost the same binding activity as the intact native peptide. Each deletion peptide forms a 1:1 complex with calmodulin according to electrophoresis analysis. When the tryptophanyl residue of Mel15 was replaced by the phenylalaninyl residue, the dissociation constant of the peptide-calmodulin complex increased. This shows the importance of the tryptophanyl residue for binding to calmodulin.

A novel receptor tyrosine phosphatase-sigma that is highly expressed in the nervous system

A novel transmembrane receptor protein tyrosine phosphatase-sigma (RPTP-sigma) was cloned from a rat brain stem cDNA library. The extracellular segment of one form of RPTP-sigma contains 824 amino acids and is composed of three immunoglobulin-like and five fibronectin type III (FNIII)-like repeats. The 627-amino acid cytoplasmic region of RPTP-sigma consists of two catalytic domains oriented in tandem. Northern blot analyses indicate that RPTP-sigma is highly expressed in the brain as two major transcripts of 5.7 and 6.9 kilobases (kb). The 5.7-kb transcript is expressed exclusively in the brain while the 6.9-kb species can be detected in the lung and heart, but at significantly lower levels. In situ hybridization studies confirm that RPTP-sigma is localized predominantly in the nervous system and can be detected in the rat as early as embryonic day 12. During embryonic development, RPTP-sigma is expressed extensively in the central and peripheral nervous systems, including the trigeminal and dorsal root ganglia as well as the retina. In adult rat brain, expression is restricted primarily to the olfactory tubercule, cerebellum, and hippocampus. Within the latter structure, RPTP-sigma is present in the pyramidal cell layer and granular layer of the dentate gyrus. Transfection of RPTP-sigma cDNA into human embryonic kidney 293 cells results in the synthesis of a protein with an apparent molecular mass of 200 kDa as detected by immunoprecipitation and immunoblot analyses using polyclonal antibodies against the FNIII-like repeats present in the extracellular domain of RPTP-sigma. The gene for RPTP-sigma has been mapped to distal chromosome 17 in the mouse.

Mechanism of adenylate kinase. 1H, 13C, and 15N NMR assignments, secondary structures, and substrate binding sites

Backbone 1H, 13C, and 15N NMR assignments were obtained for the complex of chicken muscle adenylate kinase (AK) with its bisubstrate analog, MgAP5A [magnesium P1,P5-bis(5'-adenosyl)-pentaphosphate]. The assignments were used to elucidate the secondary structures and the enzyme-MgAP5A interactions. The work involves two unusual features: the molecular weight of AK (21.6 kDa) is one of the largest, on a monomeric basis, for which nearly complete assignment has been reported to date, and the assignment was performed at pH 7.1 instead of the acidic pH used for most other proteins. The results are summarized as follows. Firstly, unambiguous sequential assignments of backbone resonances have been achieved effectively by the combined use of two sequential assignment methods: NOE-directed assignments and the recently developed 1J-coupling-directed assignments. The starting points of the assignments were provided by several specifically labeled enzyme samples. Over 90% of the backbone 1H, 13C, and 15N resonances have been assigned. Secondly, spin system information was obtained from the HCCH-TOCSY and HCCH-COSY experiments as well as from 2D homonuclear NMR data. Overall, the side-chain resonances of ca. 40% of the residues, including most of the those displaying NOEs with the adenosine moieties of MgAP5A, have been assigned. Thirdly, secondary structural elements in the AK-MgAP5A complex were identified by extensive analyses of 1H-15N 2D HMQC-NOESY and 3D NOESY-HMQC spectra. Overall, the enzyme consists of ca. 60% alpha-helices and a five-stranded parallel beta-sheet. The results are compared with the secondary structure of the free AK from porcine muscle in crystals [Dreusicke, D., Karplus, P. A., & Schulz, G. E. (1988) J. Mol. Biol. 199, 359-371]. Lastly, most of the intermolecular NOEs between AK and the adenosine moieties of MgAP5A have been identified: Thr39, Leu43, Gly64, Leu66, Val67, Val72, and Gln101 are in proximity to the adenosine moiety of the adenosine 5'-monophosphate site, whereas Thr23 is in proximity to that of the adenosine 5'-triphosphate site. These data are discussed in relation to previous results from site-directed mutagenesis, NMR, and X-ray studies and in relation to the mechanism of catalysis.

Cell cycle-regulated nuclear localization of MCM2 and MCM3, which are required for the initiation of DNA synthesis at chromosomal replication origins in yeast

MCM2 and MCM3 are two genetically interacting and structurally related proteins essential for growth in Saccharomyces cerevisiae. Mutants defective in these proteins affect the stability of minichromosomes in general, but the severity of the defect is dependent on the autonomously replicating sequence (ARS) that drives the replication of that plasmid. In this paper we show by two-dimensional gel electrophoresis that the initiation of DNA synthesis at chromosomal replication origins is also reduced in frequency in these mutants. We show further that the nuclear and subnuclear localizations of the MCM2 and MCM3 proteins are temporally regulated with respect to the cell cycle. These proteins enter the nucleus at the end of mitosis, persist there throughout G1 phase, and disappear from it at the beginning of S phase. Once inside the nucleus, a fraction of the MCM2 and MCM3 proteins becomes tightly associated with DNA. The association of MCM2 and MCM3 with chromatin presumably leads to the initiation of DNA synthesis, and their subsequent disappearance from the nucleus presumably prevents reinitiation of DNA synthesis at replication origins. This temporally and spatially restricted localization of MCM2 and MCM3 in the nucleus may serve to ensure that DNA replication occurs once and only once per cell cycle.

DNA fingerprinting in relation to male dominance and paternity in a captive colony of tammar wallabies (Macropus eugenii)

The tammar wallaby has a polygynous mating system in which the dominant male usually controls initial access to oestrous females by mating first and then guarding the female from the advances of other subordinate males. In this study we used DNA fingerprinting with a human 3' hypervariable region (HVR) alpha globin probe to examine the paternity of pouch young progeny from 13 female tammars that were given continual access during the breeding season to a group of four sexually mature males. Constant individual-specific DNA profiles were observed for each animal. Paternity for 22 pouch young was successfully assigned using visual and computer-based analyses. However, no statistical difference was observed between the number of young sired by any of the four males (chi 2 = 2, d.f. = 3, P > 0.1). Mate guarding by the dominant male in our captive breeding group was not, therefore, sufficient to prevent successful subsequent matings by subordinates nor to enhance the genetic contribution of this male to the next generation. In each analysis, visual and computer assignments of paternity coincided, and these concurred with the results of a relatedness test which found that a large number of DNA bands were shared by sires and their progeny. The results from this paternity study show that first mating and subsequent mate guarding by the dominant male tammar wallaby in our captive group do not significantly skew the outcome of paternity towards this male and away from other males that subsequently mate with each female.

Fat tissue and fat suppression

Fat tissues consist of fat cells, capillaries, and collagen fibers. In order to completely suppress the signals from fat tissues in clinical magnetic resonance imaging, the signal from capillaries and collagen fibers as well as from fat cells should all be suppressed. We have previously reported that fat signal can be uniformly suppressed by applying an optimized presaturation pulse. The inhomogeneously broadened fat peak of tissue spectrum is excited by the optimized pulse and dephased by a subsequent field gradient. The broadened water peak is not affected. In this paper we discuss a technique that suppresses signals from fat tissues completely as well as uniformly. This technique is based on the cancellation of fat and water signals in the same image voxel by combining the optimized selective excitation with the opposite phase imaging technique. Experimental and clinical images demonstrate that the new technique improves the delineation and depiction of anatomy in clinical fat suppression imaging.

Data truncation artifact reduction in MR imaging using a multilayer neural network

A magnetic resonance image (MRI) may contain truncation artifacts if there are not enough high-frequency data when the conventional Fourier transform method is used for reconstruction. A method for reducing the artifacts using a multilayer neural network is presented. The network consists of one linear output layer and at least one nonlinear hidden layer. The missing high-frequency components are predicted based on known low-frequency components and are used to reduce the truncation artifacts of the image. Results from a series of simulation experiments are discussed.

MR image compression using iterated function systems

This paper presents a method for MR image compression using iterated function systems based on fractal models. The method makes use of self-similarities of an image and achieves compression by matching similar image blocks. A fast matching procedure is proposed in this paper for efficient image encoding. The method is tested with real MR images.

Beneficial effects of berberine on hemodynamics during acute ischemic left ventricular failure in dogs

In 18 dogs ischemic left ventricular failure characterized by a 30 percent reduction in peak rate of rise of left ventricular pressure (+dp/dt) and elevation of left ventricular end-diastolic pressure (LVEDP) to 15 mmHg or more was produced by ligation of the proximal left anterior descending coronary artery followed by serial occlusions of the distal left circumflex coronary artery. In 10 days, administration of berberine in an intravenous bolus injection (1 mg/kg, within 3 minutes) followed by a constant infusion (0.2 mg/kg/min, 30 minutes) increased the cardiac output (CO) from 1.25 +/- 0.12 to 1.61 +/- 0.17 L/min (P < 0.05), and +dp/dt from 810 +/- 85 to 1021 +/- 130 mmHg/s (P < 0.01), and decreased LVEDP from 16.5 +/- 1.3 to 12.0 +/- 1.0 mmHg (P < 0.05), diastolic blood pressure from 94 +/- 6 to 84 +/- 5 mmHg (P < 0.01), systemic vascular resistance from 7303 +/- 278 to 5442 +/- 231 dynes.x/cm5 (P < 0.01), but did not affect the heart rate. Injection of 5% glucose with the same volume did not improve CO and dp/dt (P > 0.05) but increased the LVEDP from 17.1 +/- 1.4 to 17.8 +/- 1.6 mmHg (P < 0.01) in 8 dogs. The levels of plasma concentration of berberine was determined with high-performance liquid chromatography. The changes in plasma drug level were found parallel to hemodynamic effects of berberine. The results of this study showed that berberine was able to improve the impaired left ventricular function by its positive inotropic effect and mild systemic vasodilatation.

Density-dependent modulation of vascular smooth muscle alpha-actin biosynthetic processing in differentiated BC3H1 myogenic cells

The expression of vascular smooth muscle (VSM) alpha-actin mRNA during BC3H1 myogenic cell differentiation is specifically stimulated by conditions of high cell density. Non-proteolytic dissociation of cell-cell and cell-matrix contacts in post-confluent cultures of BC3H1 myocytes using EDTA promotes loss of the differentiated morphological phenotype. EDTA-dispersed myocytes exhibit an undifferentiated fibroblastoid appearance and contained reduced levels of both VSM and skeletal alpha-actin mRNA. Muscle alpha-actin mRNA levels in EDTA-dispersed myocytes were not restored to that observed in confluent myocyte preparations by experimental manipulation of cell density conditions. Pulse-labeling techniques using L-[35S]cysteine to identify muscle actin biosynthetic intermediates revealed that EDTA-dispersed myocytes expressed nascent forms of both the VSM and skeletal muscle alpha-actin polypeptide chains. However EDTA-dispersed myocytes were less efficient in the post-translational processing of immature VSM alpha-actin compared to non-dispersed myocytes. Simple cell-to-cell contact may mediate VSM alpha-actin processing efficiency since high-density preparations of EDTA-dispersed myocytes processed more VSM alpha-actin intermediate than myocytes plated at low density. The actin isoform selectivity of the response to modulation of intercellular contacts suggests that actin biosynthesis in BC3H1 myogenic cells involves mechanisms capable of discriminating between different isoform classes of nascent actin polypeptide chains.

An efficient algorithm for MR image reconstruction and compression

In magnetic resonance imaging (MRI), the original data are sampled in the spatial frequency domain. The sampled data thus constitute a set of discrete Fourier transform (DFT) coefficients. The image is usually reconstructed by taking inverse DFT. The image data may then be efficiently compressed using the discrete cosine transform (DCT). We present here a method of using DCT to treat the sampled data, which combines two procedures, image reconstruction and data compression. This method may be particularly useful in medical picture archiving and communication systems (PACS) where both image reconstruction and compression are important issues.

Mechanism of adenylate kinase. Structural and functional roles of the conserved arginine-97 and arginine-132

The structural and functional roles of two conserved active site residues, Arg-97 and Arg-132, in chicken muscle adenylate kinase (AK) were evaluated by site-directed mutagenesis in conjunction with one- and two-dimensional proton nuclear magnetic resonance (NMR), kinetics, and guanidine hydrochloride-induced denaturation. In addition, 31P NMR analysis was used to evaluate the contribution of Arg-97 to the phosphorus stereospecificity of AK. The results and conclusions are summarized as follows: (i) Kinetic analysis of R97M reveals 6- and 28-fold increases in the dissociation constant Ki and Michaelis constant K of AMP, respectively, and a moderate 30-fold decrease in kcat. The Ki and K values of MgATP are relatively unperturbed. The localized effect of AMP stabilization was independently confirmed by proton NMR titration, which showed a ca. 20-fold increase in the dissociation constant of AMP but not of MgATP. (ii) R132M affords a dramatic decrease in kcat by a factor of 8.0 x 10(3), with unchanged dissociation and Michaelis constants for either substrate. The lack of perturbation in the affinities toward substrates was confirmed by proton NMR titration. (iii) Although small chemical shift changes were observed for the free mutants and their complexes with substrates, further analyses by nuclear Overhauser enhanced spectroscopy with the bisubstrate analogue inhibitor, P1,P5-bis(5'-adenosyl)pentaphosphate (AP5A), indicated little perturbation in the global conformation. (iv) Contributions to conformational stability by Arg-97 and Arg-132 are negligible on the basis of the free energy of unfolding, delta GdH2O. (v) R97M was predicted and demonstrated to exhibit enhanced stereospecificity at the AMP site by at least 10-fold relative to WT in the conversion of adenosine 5'-monothiophosphate to adenosine 5'-(1-thiodiphosphate). This result for R97M was predicted on the basis of the orientation of Arg-97 relative to Arg-44 and AMP in the active site as observed in available crystal structures and the stereospecificity results of R44M [Jiang, R.-T., Dahnke, T., & Tsai, M.-D. (1991) J. Am. Chem. Soc. 113, 5485-5486]. (vi) The above structural and functional analyses led us to conclude that Arg-97 interacts with the phosphoryl group of AMP, beginning at the binary complex (1-2 kcal/mol), continuing through the transition state (3.5 kcal/mol), and that Arg-132 stabilizes the transition state by greater than 5 kcal/mol. (vii) The functional importance of Arg-97 appears to be similar to that of Arg-44 [Yan, H., Dahnke, T., Zhou, B., Nakazawa, A., & Tsai, M.-D. (1990) Biochemistry 29, 10956-10964].(ABSTRACT TRUNCATED AT 400 WORDS)

[Effect of hypoxia on vasodilation induced by substance P (SP) and calcitonin gene-related peptide (CGRP)]

In this paper, isolated rabbit arteries (renal artery, RA; femoral artery, FA; basilar artery, BA) were used to study the effect of hypoxia on vasodilation induced by substance P (SP) and calcitonin gene-related peptide (CGRP). The results showed that hypoxia caused a marked decrease of the arteries, response to SP (10(-7) mol/L) and CGRP (2.8 x 10(-9) mol/L). Repeated hypoxia even resulted in a complete disappearance of response. On the second hypoxia, CGRP (2.8 x 10(-9) mol/L) induced vasodilation on BA was vanished. On the third hypoxia, vasodilation induced by CGRP (2.8 x 10(-9) mol/L) on FA and that induced by SP (2 x 10(-7) mol/L) on BA were vanished, and CGRP (2.8 x 10(-9) mol/L) induced a lesser extent of vasodilation on RA. At the fourth time, SP (10(-7) mol/L) -induced vasodilation of FA disappeared, and that on RA was small. At the fifth time, the effect of SP (10(-7) mol/L) on RA was nearly vanished. It is concluded that the effect of hypoxia on CGRP-induced vasodilation is stronger than that on SP-induced vasodilation, and the effect is most pronounced on the BA.

Fat suppression with an improved selective presaturation pulse

Chemical shift selective (CHESS) imaging is an efficient and easily implemented technique for suppression of the fat component in clinical images. A Gaussian pulse is widely used as the selective presaturation pulse in the CHESS technique. However, a Gaussian pulse hardly performs well even if the magnetic field is very carefully shimmed. In clinical applications, the fat and water peaks are always inhomogeneously broadened. We have analyzed the performance of the Gaussian pulse in the presence of magnetic field inhomogeneities and present a more efficient selective presaturation pulse developed by applying the conjugate gradient method. The resulting pulse performs well without any requirement for magnetic field homogeneity greater than needed for routine diagnostic MR imaging.

Motion artifact suppression: a review of post-processing techniques

Patient motion during data acquisition in magnetic resonance imaging causes artifacts in the reconstructed image, which for two-dimensional Fourier transform imaging techniques appear as blurring and ghost repetitions of the moving structures. While the problem with intra-view effects has been effectively addressed using gradient moment nulling techniques, there is no corresponding technique for inter-view effects with equal effectiveness and general applicability. A number of techniques have been proposed for correcting the inter-view effects, and these may be divided into those that minimise the corruption of the data, and those that post-process the data to restore the image. The techniques in the former category are briefly reviewed, then those in the latter category are examined in detail. These are analysed in terms of motion model, model parameter estimation, and data correction.