A MAP kinase-dependent spindle assembly checkpoint in Xenopus egg extracts

Like early Xenopus embryos, extracts made from Xenopus eggs lack the cell cycle checkpoint that keeps anaphase from occurring before spindle assembly is complete. At very high densities of sperm nuclei, however, microtubule depolymerization arrests the extracts in mitosis. The arrested extracts have high levels of maturation-promoting factor activity, fail to degrade cyclin B, and contain activated ERK2/mitogen-activated protein (MAP) kinase. The addition of the purified MAP kinase-specific phosphatase MKP-1 demonstrates that MAP kinase activity is required for both the establishment and maintenance of the mitotic arrest induced by spindle depolymerization. Increased calcium concentrations, which release unfertilized frog eggs from their natural arrest in metaphase of meiosis II, have no effect on the mitotic arrest.

Epicardial strains in embryonic chick ventricle at stages 16 through 24

Embryonic cardiac development depends, in part, on the local biomechanical environment. Tracking the motions of microspheres attached to the embryonic chick ventricle, we computed two-dimensional epicardial strains at Hamburger-Hamilton stages 16, 18, 21, and 24 (2.5, 3.5, 4.0, and 4.5 days, respectively, of a 21-day incubation period). First, in a cross-sectional study, strains were measured in separate embryos at each stage (n > or = 19 per stage). Then, in a longitudinal study, strains were measured serially on the same heart, with the eggs resealed and reincubated between successive stages (n > or = 4 per stage). Although the heart undergoes major changes in mass, morphology, and loading during the studied stages, both studies showed that peak circumferential and longitudinal strains relative to end diastole were similar in magnitude (0.13 to 0.16) and did not change significantly across the stage range. The peak principal strains also showed no significant changes, with magnitudes of approximately 0.11 and 0.18. The shear strains were small, and their signs varied from one heart to another. These results suggest that wall strain is maintained within a relatively narrow range during primary cardiac morphogenesis.

The coordinated action of protein tyrosine phosphatases and kinases in cell signaling

The levels of tyrosine phosphorylation required for cell growth and differentiation are achieved through the coordinated action of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Depending upon the cellular context, these two types of enzymes may either antagonize or cooperate with each other during the signal transmission process. An imbalance between these enzymes may impair normal cell growth, leading to cellular transformation. Both PTKs and PTPs have evolved to a level of structural diversity that allows them to regulate many cellular processes. This review will focus on several specific examples that highlight the interplay between PTPs and PTKs in cell signaling.

[Quantitative analysis of 6,7-dimethylesculetin and capillarisine in Artemisia capillaris Thunb. and prescriptions containing the crude drug]

In this report, an accurate method for quantitatively analysing the 6,7-dimethylesculetin and capillarisine in Artemisia capillaris and the prescriptions containing the crude drug has been established by three dimension gradient HPLC, by which the trace amount of these compounds in the samples can be determined. 6,7-Dimethylesculetin is calculated by the regression equation Y = 84.15X-0.023 (r = 1.000), and capillarisine is calculated by Y = 62.17X - 0.149 (r = 1.000). In the formula, Y represents concentration of compounds and X represents area of the peak.

Inhibition of Ras-induced DNA synthesis by expression of the phosphatase MKP-1

Mitogen-activated protein kinases (MAP kinases) are common components of signaling pathways induced by diverse growth stimuli. Although the guanidine nucleotide-binding Ras proteins are known to be upstream activators of MAP kinases, the extent to which MAP kinases directly contribute to the mitogenic effect of Ras is as yet undefined. In this study, inhibition of MAP kinases by the MAP kinase phosphatase MKP-1 blocked the induction of DNA synthesis in quiescent rat embryonic fibroblast REF-52 cells by an activated mutant of Ras, V12Ras. These results suggest an essential role for activation of MAP kinases in the transition from the quiescent to the DNA replication phase of the eukaryotic cell cycle.

Calculation of spectral linewidth reduction of external-cavity strong-feedback semiconductor lasers

It is shown that, to calculate the spectral linewidth reduction of an external-cavity semiconductor laser with strong external feedback, the complex laser field equation and the general linewidth-reduction equations must be modified to avoid inconsistencies. The resulting set of consistent equations and the consequent consistent linewidth reductions are discussed.

Split tolerance induced by orthotopic liver transplantation in mice

Spontaneous orthotopic liver allograft acceptance associated with microchimerism in mice induces tolerance to subsequent skin or heart transplants from the donor but not third-party animals. Despite in vivo hyporesponsiveness, in vitro MLC and CTL assays showed continuing antidonor reactivity. Cells isolated from recipients' spleens and grafted livers, when tested in MLC and CTL assays, were antidonor reactive out to 3 months to the same degree as splenocytes obtained from either naive or presensitized (with skin or heart) mice. Nevertheless, passive transfer of splenocytes or liver lymphocytes from liver tolerant mice, but not naive or sensitized donor strain mice, were able to prolong skin graft survival significantly in naive irradiated recipients. By using a strain combination in which the donor but not the recipient expressed the stimulatory endogenous super-Ag (Mlsf), it was possible to determine whether super-Ag-reactive T cells bearing V beta 5 and V beta 11 were deleted or anergic. Phenotypic analysis of cells isolated from recipients' spleens and grafted livers (up to 90 days after transplant), when compared with naive animals, showed no significant difference in V beta 5 and V beta 11 TCR expression. Additionally, when these isolated spleen cells were tested for antibody-mediated stimulation, both anti-V beta 5 and V beta 11 TCR mAb led to marked proliferation of cells obtained from naive and liver-transplanted recipients, but as expected, proliferation was very low in cells from naive donors. These results suggest that liver transplantation induces donor-specific tolerance in vivo, which may not be reflected in in vitro proliferative and cytotoxicity assays (split tolerance). Furthermore, this tolerance does not seem to be induced by clonal deletion or anergy of minor-lymphocyte-stimulating-antigen-reactive T cells in the recipients.

Characteristics of two-dimensional and color Doppler ultrasonography in Graves' disease

Color Doppler flow imaging (CDFI) was performed in 24 patients with Graves' disease and the results were compared with those from 8 patients with Hashimoto's disease, 6 patients with simple diffuse goiter, and 15 normal volunteers. All cases were confirmed by clinical, laboratory tests or pathology. CDFI of Graves' disease showed diffuse or localized hypoechoes within the thyroid glands, rich flow signals in the hypoechoes, accelerated flow velocity, and decreased resistance in the superior thyroid arteries (STA) and arteries within the glands. These appearances were characteristic as compared with the controls. The rate of flow in STA of Graves' disease patients was 8 to 10 times higher than that in the normal volunteers. This study demonstrates that CDFI is convenient and efficient as compared with isotope scan and some other laboratory tests, and can be widely used in the diagnosis of Graves' disease.

Measurement of the geometric parameters of the aortic bifurcation from magnetic resonance images

This paper presents a method for measuring arterial geometry in vivo using MRI. The approach was validated using MR images of three perfused compliant casts of human aortic bifurcations whose geometry was known. Preliminary human studies demonstrated the reproducibility of the technique. The approach was applied to 20 normal individuals to study the effects of age, race, and gender on the geometry of the aortic bifurcation. The results show that older people tend to have a smaller bifurcation angle, lower planarity, and larger angular asymmetry than younger people. Asians have larger bifurcation angles than whites. The bifurcation of males is more asymmetric than that of females. These results may have implications regarding the heritability of arterial geometry, the similarities of cardiovascular risk within families, and differences in risk among groups.

Body segment growth during infancy

In order to better understand relationships between physical growth and motor development during infancy, changes in segment inertias were examined. A rationale based on dynamic systems theory and intersegmental moments was used to select the variables: the segment mass and principal moments of nine segments. The hypothesis was that there are differences in growth velocity between segments and these are consistent with the principles of cephalocaudal development and distal to proximal growth. A mathematical model of the segments was used to examine changes of the inertia parameters. Twenty-seven normal infants carried to full term and aged between 2 and 9 months at the beginning of the study were photographed once a month for 6 months. Outlines of segments from front and side 35 mm images were digitized and mass and principal moments of inertia estimates obtained. Polynomial regression was used to give the development curves regression coefficients for the 155 data points. Also, linear regressions were fitted to the six growth data points of each subject. Most of the relationships between chronological age and segment mass and principal moments were significant and linear. The differences in growth velocity between segments were significant and partially consistent with the growth principles. However, there were considerable differences, in particular for the lower trunk and the shank, where it appears that growth may be irregular until after the age of 15 months.

Free radical mechanism in enhancement of radiosensitization by SRSBR

The free radical mechanism of enhancing radiosensibility by the Synergic Recipe to Strengthen Body Resistance (SRSBR) consisting of 10 Chinese drugs was studied by electron spin resonance (ESR) with spin trapping reagent--Nitroso-tert-butane (NtB) following irradiation of the Deoxy thymidine (dT) solution system by 60Co 3.7 PBq. The results showed SRSBR cannot only enhance the generation of e- aq but also enhance the production of . OH and H . after irradiation with gamma ray in dT-NtB-SRSBR aqueous solution system. These result in damage to biological molecules, attacking and killing tumor cells radiosensitized by SRSBR. The characteristics of SRSBR for radiosensitization are concluded to be increasing production of . OH and H. in comparison with the well-known radiosensitizer-Misonidazole (Miso).

MKP-1 (3CH134), an immediate early gene product, is a dual specificity phosphatase that dephosphorylates MAP kinase in vivo

Mitogenic stimulation of cells induces rapid and transient activation of MAP kinases. Here we report that a growth factor-inducible gene, 3CH134, encodes a dual specificity phosphatase that dephosphorylates and inactivates p42MAPK both in vitro and in vivo. In vitro, 3CH134 protein dephosphorylates both T183 and Y185 in p42MAPK. In serum-stimulated normal fibroblasts, the kinetics of inactivation of p42MAPK coincides with the appearance of newly synthesized 3CH134 protein, and the protein synthesis inhibitor cycloheximide leads to persistent activation of MAP kinase. Expression of 3CH134 in COS cells leads to selective dephosphorylation of p42MAPK from the spectrum of phosphotyrosyl proteins. 3CH134 blocks phosphorylation and activation of p42MAPK mediated by serum, oncogenic Ras, or activated Raf, whereas the catalytically inactive mutant of the phosphatase, Cys-258-->Ser, augments MAP kinase phosphorylation under similar conditions. The mutant 3CH134 protein also forms a physical complex with the phosphorylated form of p42MAPK. These findings suggest that 3CH134 is a physiological MAP kinase phosphatase; we propose the name MKP-1 for this phosphatase.

The growth factor-inducible immediate-early gene 3CH134 encodes a protein-tyrosine-phosphatase

Stimulation of fibroblasts with serum growth factors results in the rapid activation of a set of immediate-early genes, among them 3CH134. We have purified a bacterially expressed form of the 3CH134-encoded polypeptide and demonstrated that it has intrinsic protein-tyrosine-phosphatase (PTPase; protein-tyrosine-phosphate phosphohydrolase, EC 3.1.3.48) activity in vitro. This activity is optimal at pH 7.5, is sensitive to vanadate and cysteinyl modifying agents, and is insensitive to a panel of serine/threonine phosphatase inhibitors. Purified 3CH134 protein displays a high degree of selectivity among the tyrosine-phosphorylated polypeptide substrates tested. Under our assay conditions, the rates of dephosphorylation are in the order EDNDYINASL peptide < myelin basic protein < reduced, carboxyamidomethylated, and maleylated lysozyme (RCML) < p42mapk. There is a 200-fold range in rates for these substrates, with p42mapk dephosphorylated 15-fold more rapidly than RCML. Although 3CH134 is most closely related to the tyrosine/serine dual-specificity phosphatase VH1, we failed to detect any 3CH134-directed activity on casein or RCML phosphorylated on serine/threonine residues by cAMP-dependent protein kinase. Since 3CH134 expression is controlled transcriptionally and posttranscriptionally, it may represent a class of PTPases whose activity is regulated at the level of protein synthesis and degradation.

Serum protein-binding characteristics of vancomycin

A synthesis of studies of serum protein binding of vancomycin and its reported abnormal binding in serum with very high concentrations of immunoglobulin A (IgA) suggests that this antibiotic may be bound to more than one serum protein. Using an ultrafiltration method for separating free from bound drug and high-performance liquid chromatography to measure drug concentration, we studied the binding characteristics of vancomycin for alpha-1 acid glycoprotein, IgG, IgM, IgA, and albumin. The results showed that vancomycin does not bind to alpha-1 acid glycoprotein, IgG, or IgM. Major binding to albumin and IgA occurs, and total drug binding to serum proteins can be fully explained by binding to these two proteins. We calculated an N (number of binding sites per molecule) of 1.3 +/- 0.4 and a K (association constant) of 3.3 x 10(5) +/- 6.3 x 10(4) M-1 (NK = 4.3 x 10(5) M-1) for binding to IgA, whereas the corresponding NK value for albumin was only 527.5 M-1, indicating that vancomycin preferentially binds to IgA. Very high concentrations of IgA in serum (i.e., grams per deciliter), such as in patients with IgA myeloma, may result in the paradox of high (total) concentrations of vancomycin in serum that may be clinically ineffective.

A protein-tyrosine/serine phosphatase encoded by the genome of the cyanobacterium Nostoc commune UTEX 584

Protein-tyrosine phosphorylation has long been regarded as an exclusively eukaryotic phenomenon. Although some non-eukaryotes, mainly viruses, possess genes encoding protein-tyrosine kinases or protein-tyrosine phosphatases, these were probably appropriated from the eukaryotic hosts that constitute the sites of action of these enzymes. Herein we identify a gene, iphP, from the chromosome of the cyanobacterium Nostoc commune UTEX 584 that contains the His-Cys-Xaa-Ala-Gly-Xaa-Xaa-Arg sequence characteristic of known protein-tyrosine phosphatases. The expressed gene product, IphP, displayed protein-tyrosine phosphatase activity toward phosphotyrosine residues on reduced, carboxyamidomethylated, and maleylated lysozyme with optimum activity at pH 5.0. In addition, IphP dephosphorylated the phosphoseryl groups on casein that had been phosphorylated by the cAMP-dependent protein kinase. Cell lysates of N. commune probed with antibodies to phosphotyrosine indicated the presence of a tyrosine-phosphorylated protein of M(r) approximately 85 kDa. This tyrosine-phosphorylated protein was detected in cells grown in the presence of combined nitrogen but not in nitrogen-deficient media that induces the formation of differentiated N2-fixing cells (heterocysts). Together, these data suggest a role for protein-tyrosine phosphorylation in regulating cellular functions in this cyanobacterium. IphP is the first protein-tyrosine phosphatase to be discovered that is encoded by the chromosomal DNA of any prokaryote. Given the free-living nature of N. commune and the phylogenetic antiquity of the cyanobacteria, these findings suggest for the first time the existence of a protein-tyrosine phosphatase of genuine, unambiguous prokaryotic ancestry, thus raising fundamental questions as to the origin and role of tyrosine phosphorylation.

[Ureaplasma urealyticum and intrauterine infection of fetus]

Ureaplasma urealyticum (Uu) infection in pregnancy can lead to a poor outcome. To confirm the relation between Uu and intrauterine infection, 65 placentas were taken for isolation and identification of Uu from pregnant women with positive antibody to Uu. Uu was isolated from 13 (20%) of the 65 placentas. The pathologic examination of 6 placentas showed that there were acute or chronic inflammatory cell infiltration. Cord blood IgM antibody was examined by ELISA from 5 cases in which Uu was isolated from placentas and 3 of them was positive to Uu. The 5 cord blood specimens were assayed by the metabolic inhibition test for serotypes of Uu, and one of them was serotype 8. Since the isolation of Uu from some pregnant women, the pathologic changes of placentas, and the detection of specific IgM from cord blood showed a good consistency, we conclude that the Uu infection may occur in utero.

Atrial natriuretic peptide inhibits growth of hepatoblastoma (HEP G2) cells by means of activation of clearance receptors

To investigate whether atrial natriuretic factor regulates the growth of hepatocytes and to determine the receptor subtype involved in such modulation, we studied the effect of atrial natriuretic factor 103-126 and clearance receptor binding analogs of atrial natriuretic factor, (des-(Q116, S117, G118, L119, G120) atrial natriuretic factor 102-121 and des-(C105,121) atrial natriuretic factor 104-126) on growth of human hepatoblastoma cells. Atrial natriuretic factor 103-126 and des-(Q116, S117, G118, L119, G120) atrial natriuretic factor 102-121 inhibited thymidine incorporation into human hepatoblastoma cells cultured in the presence of bovine serum albumin and epidermal growth factor but not in cells cultured in bovine serum albumin alone. Moreover, atrial natriuretic factor 103-126, des-(Q116, S117, G118, L119, G120) atrial natriuretic factor 102-121 and des-(C105,121) atrial natriuretic factor 104-126, in a concentration-dependent manner, inhibited thymidine incorporation and cell proliferation. As monitored by the ability of des-(Q116, S117, G118, L119, G120) atrial natriuretic factor 102-121 to displace 125I-labeled atrial natriuretic factor, epidermal growth factor increased the expression of cell surface clearance receptors. Epidermal growth factor also transiently increased the cellular content of atrial natriuretic factor clearance receptor messenger RNA without altering the levels of guanylyl cyclase-linked atrial natriuretic factor receptor messenger RNA levels. Maximal increase in atrial natriuretic factor clearance receptor messenger RNA coincided with the maximal increase in des-(Q116, S117, G118, L119, G120) atrial natriuretic factor 102-121-displaceable 125I-atrial natriuretic factor binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of poor control of film processors on mammographic image quality

With the increasingly stringent standards of image quality in mammography, film processor quality control is especially important. Current methods are not sufficient for ensuring good processing. The authors used a sensitometer and densitometer system to evaluate the performance of 22 processors at 16 mammographic facilities. Standard sensitometric values of two films were established, and processor performance was assessed for variations from these standards. Developer chemistry of each processor was analyzed and correlated with its sensitometric values. Ten processors were retested, and nine were found to be out of calibration. The developer components of hydroquinone, sulfites, bromide, and alkalinity varied the most, and low concentrations of hydroquinone were associated with lower average gradients at two facilities. Use of the sensitometer and densitometer system helps identify out-of-calibration processors, but further study is needed to correlate sensitometric values with developer component values. The authors believe that present quality control would be improved if sensitometric or other tests could be used to identify developer components that are out of calibration.

Simplification of antibiotic dose adjustments in renal insufficiency: the DREM system

Many clinicians, unassisted by reference books, are unable to make the required dose adjustment of antibiotics needed when a patient has renal insufficiency. We describe the DREM (dosing in renopathy by easy-to-use multipliers) system, which simplifies the understanding and the process of dose adjustment. DREM is a two-step process: Cockcroft and Gault estimation of creatinine clearance (CLcr) from age, sex, and serum creatinine and calculation of the adjusted dose or dosing interval by multipliers. If the normal dose is multiplied by the dose multiplier (CLcr/100) and the dosing interval by the interval multiplier (100/CLcr), the adjusted dose and interval, respectively, are obtained. Theoretical trough concentrations calculated with the DREM system correlated closely (r = 0.9) with actual concentrations obtained from doses calculated by the Hull and Sarubbi method in 23 patients. With DREM, gentamicin or tobramycin trough concentrations above 2 micrograms/ml were less likely to occur. The DREM system is a simple and easily remembered method for dose adjustments of certain anti-infective agents in renal insufficiency. Dose estimates with this method are reasonably accurate and compare favourably with other standard methods of correction.

Stability analysis for grating-tuned strong-external-feedback semiconductor lasers

We give a simple stability analysis within the scope of steady-state solution for the grating-tuned strong-external-feedback semiconductor lasers. In our model, a fluctuation in the refractive index of an active medium through the coupling of carrier density will cause another fluctuation in the refractive index. If the latter is always smaller than the former, the fluctuation will be damped, and therefore the corresponding operating point of the laser is stable. Our analysis indicates that there are various stable and unstable operating-frequency ranges for various reflectivities of the internal facet of the laser diode. In addition, it agrees well with the experimental results and explains the bistability of threshold gain versus operating frequency.

Analysis of polarization dynamics by singularity decomposition method

The driving point immittance (impedance or admittance) function is commonly used in electrical characterization of polarized materials and interfaces. The immittance function typically attenuates following a power function dependence on frequency. This fact has been recognized as a macroscopic dynamical property manifested by strongly interacting dielectric, viscoelastic and magnetic materials and interfaces between different conducting substances. Linear interfacial polarization processes which occur at metal electrode-electrolyte interfaces have been represented by the Fractional Power Pole [FPP] function in single or multiple stages. The FPP function is referred to as the Davidson-Cole function in the dielectrics literature. A related function widely used in mathematical modeling of dielectric and viscoelastic polarization dynamics is the Cole-Cole function. The fractional power factor which parametrizes the FPP or the Davidson-Cole function has been shown earlier to equal the logarithmic ratio of the locations of the pole-zero singularities. In this paper we first review a modified form of the singularity decomposition of the FPP function accomplished within a prescribed error range. The distribution spectrum and the corresponding simulation by a cascade R-C network, as opposed to the synthesis by a ladder R-C network, are readily obtained as the next step in the simulation. The method is then applied to decompose the Cole-Cole function; the pole-zero placement of the singularity function is determined and the equivalent cascade R-C network is synthesized.

[Effects of McAbs HIP2, APT4 and HI117 on the human platelet cytoskeleton]

The effects of monoclonal antibodies HIP2, APT4 and HI117 on the platelet cytoskeleton were investigated. The results showed that HIP2, APT4 and HI117 could induce an increase of platelet cytoskeleton materials in PRP. The action of HIP2 and APT4 could be obviously inhibited by the calmodulin inhibitor EBB. The inhibition rates of EBB were 76.3% and 48.95%, respectively. But EBB couldn't inhibit the HI117-induced an increase of platelet cytoskeleton materials. EBB could completely inhibit APT4-induced platelet aggregation(100%) and partially inhibit HIP2-induced platelet aggregation (14.26%). It couldn't inhibit HI117-induced platelet aggregation. These McAbs couldn't induce aggregation and actin mobilization in washed platelets in the presence of EDTA. The results indicate that platelet aggregation and the increase of actin induced by these McAbs, in addition to Ca2+, could be related to a factor or factors in the plasma. The Ca(2+)-CM system might play an important role in platelet aggregation and actin mobilization induced by HIP2 and APT4.

Genetic and physical analyses of sister chromatid exchange in yeast meiosis

We have used nonessential circular minichromosomes to monitor sister chromatid exchange during yeast meiosis. Genetic analysis shows that a 64-kb circular minichromosome undergoes sister chromatid exchange during 40% of meioses. This frequency is not reduced by the presence of a homologous linear minichromosome. Furthermore, sister chromatid exchange can be stimulated by the presence of a 12-kb ARG4 DNA fragment, which contains initiation sites for meiotic gene conversion. Using physical analysis, we have directly identified a product of sister chromatid exchange: a head-to-tail dimer form of a circular minichromosome. This dimer form is absent in a rad50S mutant strain, which is deficient in processing of the ends of meiosis-specific double-stranded breaks into single-stranded DNA tails. Our studies suggest that meiotic sister chromatid exchange is stimulated by the same mechanism as meiotic homolog exchange.