Tumour susceptibility and spontaneous mutation in mice deficient in Mlh1, Pms1 and Pms2 DNA mismatch repair

Germline mutations in the human MSH2, MLH1, PMS2 and PMS1 DNA mismatch repair (MMR) gene homologues appear to be responsible for most cases of hereditary non-polyposis colorectal cancer (HNPCC; refs 1-5). An important role for DNA replication errors in colorectal tumorigenesis has been suggested by the finding of frequent alterations in the length of specific mononucleotide tracts within genes controlling cell growth, including TGF-beta receptor type II (ref. 6), BAX (ref. 7) and APC (ref. 8). A broader role for MMR deficiency in human tumorigenesis is implicated by microsatellite instability in a fraction of sporadic tumours, including gastric, endometrial and colorectal malignancies. To better define the role of individual MMR genes in cancer susceptibility and MMR functions, we have generated mice deficient for the murine homologues of the human genes MLH1, PMS1 and PMS2. Surprisingly, we find that these mice show different tumour susceptibilities, most notably, to intestinal adenomas and adenocarcinomas, and different mutational spectra. Our results suggest that a general increase in replication errors may not be sufficient for intestinal tumour formation and that these genes share overlapping, but not identical functions.

[Studies on mutagenicity of humic acid samples collected from arsenosis-affected areas in China]

OBJECTIVE

To explore whether there is mutagenicity of humic acid samples collected from arsenosis affected areas in China.

METHODS

Ames' test was used for natural humic acid samples extracted from the coal containing high arsenic in Guizhou Province, and the well water in the areas with blackfoot disease in Taiwan and with arsenosis in Inner Mongolia of China.

RESULTS

Coefficients of revertant mutation were 1.02-0.82 net revertant per microgram (rev/microgram) of humic acid extracted from the coal containing high arsenic in Guizhou without rat liver homogenate (-S9), and 1.53-1.12 rev/microgram of that with rat liver homogenate (+S9), with an obvious dose-response relationship.

CONCLUSION

Humic acid extracted from the coal containing high arsenic produced in Guizhou could cause stronger direct mutation in Salmonella typhimurium TA98 (frameshift mutation) and that extracted from the well water in the areas with blackfoot disease in Taiwan could cause weaker direct mutation in Salmonella typhimurium (-S9), but that extracted from the well water with arsenosis in Inner Mongolia could not cause mutation. Mutagenicity of commercial humic acid, purchased from Aldrich Co. in the United States, arsenic and iron was also studied, and no mutagenicity was found for them independently, but arsenic combined with humic acid, at certain concentrations, could cause weak mutation in TA98 (-S9), with or without iron. No mutagenicity in TA100 (+/- S9, base pair substitution mutation) was found in all the samples mentioned above.

Incorporation of a set enumeration trees-based classifier into a hybrid computer-assisted diagnosis scheme for mass detection

RATIONALE AND OBJECTIVES

The authors evaluated whether a hybrid classifier of two independent computer-aided diagnosis (CAD) schemes, the set enumeration (SE) trees approach and an artificial neural network (ANN), could improve the detection of masses on digitized mammograms. The potential benefits resulting from the interpretability of the SE trees model was also explored.

MATERIALS AND METHODS

Two hundred thirty verified mass regions and 230 negative but suspicious regions were randomly selected from 618 digitized mammograms. Each region was represented by a 24-parameter feature vector. These features were used as input data for the SE trees and ANN-based schemes. After the positive and negative regions were randomly segmented into five exclusive partitions, a fivefold cross-validation method was applied to evaluate and compare the performance of the SE trees, ANN, and hybrid system in the identification of masses.

RESULTS

The performance of the SE trees approach was comparable to that of the ANN. The average area under the receiver operating characteristic (ROC) curves for all five partitions was 0.88 (standard deviation, 0.04). Owing to the relatively low correlation between the region-based results of the SE trees and ANN methods, the hybrid classifier yielded a significantly improved performance, with an area under the ROC curve of 0.94 (standard deviation, 0.02; P < .05).

CONCLUSION

The hybrid CAD scheme significantly improved performance. The amenability of the SE trees models to interpretation may aid in the assessment of the importance of specific features.

Using targeted large deletions and high-efficiency N-ethyl-N-nitrosourea mutagenesis for functional analyses of the mammalian genome

The Human Genome Project has generated nucleotide sequences from an estimated 80,000 to 100,000 genes, only a small fraction of which have a known role. Nucleotide sequence information alone is insufficient to predict gene function. One of the most powerful ways of revealing gene function, as demonstrated in bacteria, worms, yeast, and flies, is to generate mutations and characterize them at both the phenotypic and the molecular levels. Given the physiological and anatomical parallels between mouse and human, genotype-phenotype relationships established in mice can be extrapolated to human syndromes. A new method is described for functional genetic analyses in the mouse that uses loxP/Cre engineering to generate coat color-tagged large deletions. The haploid regions can then be dissected by mutagenesis with N-ethyl-N-nitrosourea in phenotype-driven screens to obtain functional information on genes in any desired region of the mouse genome.

Immunosenescence and germinal center reaction

Dysfunction of the immune system in aged individuals includes at least two important factors: accumulation of immunocytes with reduced function and accumulation of lymphocyte clones with self-reactive potential. Coincidently, there is a profound reduction of the germinal center reaction in the aged. While this reduction is likely the result of age-associated impairment in lymphocyte function (e.g. diminished response to costimulus, altered lymphokine production etc.), the reduction of germinal centers may itself make an important contribution to further immunological dysfunction.

V(D)J recombinase activity in a subset of germinal center B lymphocytes

Reexpression of the V(D)J recombinase-activating genes RAG1 and RAG2 in germinal center B cells creates the potential for immunoglobulin gene rearrangement and the generation of new antigen receptor specificities. Intermediate products of V(D)J recombination are abundant in a subset of germinal center B cells, demonstrating that the kappa immunoglobulin light-chain locus becomes a substrate for renewed V(D)J recombinase activity. This recombinationally active cell compartment contains many heavy-chain VDJ rearrangements that encode low-affinity or nonfunctional antibody. In germinal centers, secondary V(D)J recombination may be induced by diminished binding to antigen ligands, thereby limiting abrupt changes in receptor specificity to B cells that are usually eliminated from the germinal center reaction. This restriction preserves efficient antigen-driven selection in germinal centers while allowing for saltations in the somatic evolution of B cells.

Color Doppler imaging diagnosis of intra-ocular tumor

OBJECTIVE

To demonstrate the color Doppler imaging (CDI) of intra-ocular tumors and its importance in the diagnosis of these tumors.

METHODS

Ninety-two patients with intra-ocular tumors (105 eyes) were examined by using CDI to observe the vasculature of these tumors, and using SAS soft ware to analyze the results.

RESULTS

Blood flow signal was found in retinoblastoma, melanoma of choroid, angioma of choroid, angioma of optic disc, Coats' disease, persistent hyperplastic primary vitreous (PHPV) and metastatic tumors of choroid, but not found in choroid osteoma and melanocytoma of optic disc. The blood flow decreases in central retinal artery in choroidal melanoma and also in ophthalmic artery, central retinal artery and posterior ciliary artery in angioma of choroid (P < 0.01). It was found that blood velocity is much faster in choroidal melanoma than in choroidal angioma (P < 0.05).

CONCLUSIONS

CDI is very important and helpful in the diagnosis of intra-ocular tumors.

Distinctive characteristics of germinal center B cells

A cardinal property of the immune system is its ability to respond to an antigen that was encountered years before with an accelerated and enhanced secondary response. The property of anamnestic reactions depends upon the formation of long-lived compartments of specialized T and B lymphocytes called memory cells. While the origin of the memory T-cell compartment is not known, germinal centers are the specialized sites for memory B-cell generation and the immunoglobulin V-region hypermutation necessary for the affinity maturation of serum antibody. Interestingly, the peripheral differentiation pathway that leads to this most mature B-cell state begins with the recapitulation of many characters of immature B lymphocytes in bone marrow. This review describes the distinctive cellular basis of germinal center reaction and the characteristics of B cells in germinal centers that later enter the memory pool.

Adequacy testing of training set sample sizes in the development of a computer-assisted diagnosis scheme

RATIONALE AND OBJECTIVES

The authors assessed the performance changes of a computer-assisted diagnosis (CAD) scheme as a function of the number of regions used for training (rule-setting).

MATERIALS AND METHODS

One hundred twenty regions depicting actual masses and 400 suspicious but actually negative regions were selected as a testing data set from a database of 2,146 regions identified as suspicious on 618 mammograms. An artificial neural network using 24 and 16 region-based features as input neurons was applied to classify the regions as positive or negative for the presence of a mass. CAD scheme performance was evaluated on the testing data set as the number of regions used for training increased from 60 to 496.

RESULTS

As the number of regions in the training sets increased, the results decreased and plateaued beyond a sample size of approximately 200 regions. Performance with the testing data set continued to improve as the training data set increased in size.

CONCLUSION

A trend in a system's performance as a function of training set size can be used to assess adequacy of the training data set in the development of a CAD scheme.

Increment of hFIX expression with endogenous intron 1 in vitro

This paper probes into the feasibility of increasing expression level of hFIX gene with endogenous intron 1 sequence. hFIX minigene was obtained with middle sequence truncated intron 1 inserted into the relative site of hFIX cDNA, and plasmid vector pKG5i'IX, retroviral vector GINaCi'IX were constructed. These vectors were transduced into target cells of PA317, C2C12, primary rabbit skin fibroblasts (RSF) and primary human skin fibroblasts (HSF). The expression level of mixed colonies are PA317/pKGoi'IX, 151 ng/10(6) cells/24h; PA317/G1NaCi'IX, 308 ng/10(6) cells/24 h; C2C12/G1 NaCi'IX, 188 ng/10(5) cells/24 h; RSF/G1NaCi'IX, 1929 ng/10(5) cells/24 h; HSF/G1NaCi'IX, 1646 ng/10(6) cells/24 h. These results indicated that hFIX minigene with intron 1 is able to increase the expression level to about 3 times of that of hFIX cDNA. Meanwhile, in order to study the application of hFIX minigene in the retroviral-mediated gene transfer system and refrain from intron splicing during viral production, a retroviral vector G1NaCi'IXR with reversely inserted hFIX minigene expression cassette was constructed. The expression level of reverse constructor in PA317 cells was 390 ng/10(6) cells/24 h with 79% of bioactivity. PCR detection of HT/G1NaCi'IXR cells infected with PA317/G1NaCi'IXR supernatant confirmed the existence of intron 1 sequence. These results suggested that expression vector with forward-inserted intron1-carrying hFIX expression cassette can be used in directed gene transfer, but when using the retroviral-mediated gene transfer system, reversely-inserted intronl-carrying hFIX expression cassette should be considered.

Computer-aided detection of clustered microcalcifications on digitized mammograms: a robustness experiment

RATIONALE AND OBJECTIVES

The authors assessed the performance of an existing computer-aided diagnosis (CAD) scheme for the detection of clustered microcalcifications in a large image database.

METHODS

A previously developed, rule-based system was used to assess detectability of microcalcification clusters in a set of 386 digitized mammograms with 239 verified clusters visible on 191 images. The test was performed without any reoptimization of the scheme. None of the 386 images had been used in any previous scheme development or testing procedures.

RESULTS

The CAD scheme achieved 89.5% sensitivity at an average false-positive detection rate of 0.39 per image. In 75% of all images, no false-positive findings occurred. Twenty-three of 25 false-negative findings (misses) occurred during the last two stages in the detection process.

CONCLUSION

This scheme produced reasonable results in a large data set of images with a large variety of cluster characteristics.

Detection of neuroblastoma cells in blood by reverse transcriptase-polymerase chain reaction

OBJECTIVE

To determine whether circulating tumor cells are present in patients with localized or disseminated neuroblastoma (NB).

METHODS

Sixteen pediatric malignant tumor cell lines, including 10 NB, 4 primitive neuroectodermal tumor (PENT), 2 Wilms' tumor and 39 samples (tumor tissue, bone marrow and peripheral blood) from 8 patients with NB, were evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR) using two markers: neuroendocrine protein gene products 9.5 (PGP 9.5) and tyrosine hydroxylase (TH).

RESULTS

Analysis of RT-PCR products by agarose electrophoresis demonstrated that in culture cell lines the specificity for NB was highest in TH (9/10 with NB, 3/4 with PNET, 0/2 with Wilms' tumor) and the sensitivity was highest in PGP 9.5 10(-7). PGP 9.5 and TH mRNA were undetectable in the peripheral blood mononuclear cells (PBMNC) from normal children. Expression of these markers in 8 patients with NB at diagnosis and during treatment was found positive in 5 out of 8, all had been proved paralleling with their disease status. Two of the 5 became negative after further treatment.

CONCLUSIONS

These systems allow the detection of circulating NB cells with higher sensitivity and specificity. When RT-PCR is clinically used for the detection of NB cells in blood, that both PGP 9.5 and TH should be selected is recommended. The assessment of bone marrow alone might not be used as a single index of tumor dissemination.

Severe life stress as a predictor of early disease progression in HIV infection

OBJECTIVE

Although there is evidence that stress is associated with alterations in immunity, the role of emotional factors in the onset and course of immune-based diseases such as cancer and AIDS has not been established. This prospective study was designed to test the hypothesis that stressful life events accelerate the course of HIV disease.

METHOD

Ninety-three HIV-positive homosexual men who were without clinical symptoms at the time of entry into the study were studied for up to 42 months. Subjects received comprehensive medical, neurological, neuropsychological, and psychiatric assessments every 6 months, including assessment of stressful life events during the preceding 6-month interval. Several statistical approaches were used to assess the relation between stress and disease progression.

RESULTS

The time of the first disease progression was analyzed with a proportional hazard survival method, which demonstrated that the more severe the life stress experienced, the greater the risk of early HIV disease progression. Specifically, for every one severe stress per 6-month study interval, the risk of early disease progression was doubled. Among a subset of 66 subjects who had been in the study for at least 24 months, logistic regression analyses showed that higher severe life stress increased the odds of developing HIV disease progression nearly fourfold. the degree of disease progression was also predicted by severe life stress when a proportional odds logistic regression model was used for analysis.

CONCLUSIONS

This report presents the first evidence from a prospective research study that severe life event stress is associated with an increased rate of early HIV disease progression.

Characterization of a novel mammalian RGS protein that binds to Galpha proteins and inhibits pheromone signaling in yeast

Genetic studies of molecules that negatively regulate G-coupled receptor functions have led to the identification of a large gene family with an evolutionarily conserved domain, termed the RGS domain. It is now understood that RGS proteins serve as GTPase-activating proteins for subfamilies of the heterotrimeric G-proteins. We have isolated from mouse pituitary a full-length cDNA clone encoding a novel member of the RGS protein family, termed RGS16, as well as the full-length cDNA of mRGS5 and mRGS2. Tissue distribution analysis shows that the novel RGS16 is predominantly expressed in liver and pituitary, and that RGS5 is preferentially expressed in heart and skeletal muscle. In contrast, RGS2 is widely expressed. Genetic analysis using the pheromone response halo assay and FUS1 gene induction assay show that overexpression of the RGS16 gene dramatically inhibits yeast response to alpha-factor, whereas neither RGS2 nor RGS5 has any discernible effect on pheromone sensitivity, pointing to a possible functional diversity among RGS proteins. In vitro binding assays reveal that RGS5 and RGS16 bind to Galphai and Galphao subunits of heterotrimeric G-proteins, but not to Galphas. Based on mutational analysis of the conserved residues in the RGS domain, we suggest that the G-protein binding and GTPase-activating protein activity may involve distinct functional structures of the RGS proteins, indicating that RGS proteins may exert a dual function in the attenuation of signaling via G-coupled receptors.

[The experimental pathology and clinical treatment of microwave tissue coagulation for ocular superficial lesions]

OBJECTIVE

To investigate the therapeutic effect of a new therapy, microwave tissue coagulation (MTC), for treatment of ocular diseases.

METHODS

HSE-5M Mircotaze (manufactured by HEIWA Electronic Industrial Co. Osaka, Japan) was used for the treatment of sixty-four cases with ocular superficial lesions. Animal experiment was performed with this technique before application in patients. Twelve rabbit monocular eyeballs were coagulated just posterior to the corneoscleral limbus in order to find a dose which is effective and safe for the human eye ball. The models of microwave coagulative lesions were made in the contralateral eyes of the twelve rabbit eyeballs.

RESULTS

The coagulation-induced "ulcers" were exfoliated gradually and healed finally from three to seven days. Histopathology of the coagulative areas showed coagulative necrosis with infiltration of lymphocytes and plasma cells. The results of sixty-four cases treated with MTC technique show that the damaging effect of coagulation on tissues is very mild, so that it heals very soon and the clinical process is consistent with the experimental pathological process.

CONCLUSIONS

If the dosage of the technique is controlled in the range of safety and effectiveness, the MTC therapy is effective for the treatment of superficial ocular disease. The clinical and pathological examinations demonstrate that the therapy does not damage the ocular structure.

Neoteny in lymphocytes: Rag1 and Rag2 expression in germinal center B cells

The products of the Rag1 and Rag2 genes drive genomic V(D)J rearrangements that assemble functional immunoglobulin and T cell antigen receptor genes. Expression of the Rag genes has been thought to be limited to developmentally immature lymphocyte populations that in normal adult animals are primarily restricted to the bone marrow and thymus. Abundant RAG1 and RAG2 protein and messenger RNA was detected in the activated B cells that populate murine splenic and Peyer's patch germinal centers. Germinal center B cells thus share fundamental characteristics of immature lymphocytes, raising the possibility that antigen-dependent secondary V(D)J rearrangements modify the peripheral antibody repertoire.

Mass detection in digitized mammograms using two independent computer-assisted diagnosis schemes

OBJECTIVE

Using two independent computer-assisted diagnosis (CAD) schemes, we investigated the potential to improve the sensitivity of mass detection by applying a logical "or" operation and to improve the specificity using a logical "and" operation.

MATERIALS AND METHODS

Two independent mass detectors, one with Gaussian bandpass filtering and multilayer topographic feature analysis and the other with a five-stage search for a single suspicious region, were applied to a large image database that included 428 digitized mammograms with 220 verified masses. The performance of the two schemes and a combination of them in the form of either logical "or" or logical "and" operations were compared.

RESULTS

In this preliminary study, a multilayer topographic feature analysis CAD scheme (CAD-1) achieved a sensitivity of 96% and had a false-positive detection rate of 0.79 per image. A five-stage search method scheme (CAD-2) achieved a sensitivity of 94% and had a false-positive detection rate of 1.69 per image. With an "or" operation, the combined results yielded 100% sensitivity with a false-positive detection rate of 2.07 per image. A logical "and" operation produced a reduction of the false-positive detection rate to 0.4 per image, but sensitivity also decreased to 90%.

CONCLUSION

Similar to an independent double-reading approach and depending upon the relevant clinical question, sensitivity or specificity can be improved by combining the results of several independent CAD schemes.

On the reporting of mass contrast in CAD research

As research efforts for developing computer-aided diagnosis (CAD) schemes of digitized mammograms increase and interscheme results are compared, the desire to establish an acceptable consistent reporting protocol of the distribution of abnormal characteristic is becoming an issue. "Mass contrast" is very important and frequently reported in current CAD studies. In this report, 100 verified mass regions were analyzed systemically using 6 different definitions of "mass contrast." Measured variability in mass contrast was demonstrated by the distribution shift in this group masses. The need for universally accepted and largely standardized descriptors of objects of interest is clearly demonstrated.

Alternative pathways for the selection of antigen-specific peripheral T cells

In the thymus, maturing lymphocytes receive activation signals mediated by the T-cell antigen receptor (TCR) that either promote clonal survival (positive selection) or induce apoptosis (negative selection). This balance between life and death is mirrored by the sensitivity of cortical thymocytes to apoptotic death induced by antibodies against the CD3 component of the TCR signal-transduction complex, bacterial superantigens that bind to the TCR beta-chain, and corticosteroids. In contrast, mature peripheral T cells are positively activated by anti-CD3 antibody or superantigens and are resistant to steroid-induced death. Here we show that in splenic germinal centres, T cells regain thymocyte-like sensitivity to TCR- and steroid-induced apoptosis and undergo antigen-driven positive and negative selection. T-cell responses elsewhere in the spleen are unaccompanied by programmed cell death. Our observations define a new differentiation pathway for peripheral T cells and suggest that germinal centres induce a lymphocyte phenotype necessary for the maintenance of self-tolerance.

Adaptive computer-aided diagnosis scheme of digitized mammograms

RATIONALE AND OBJECTIVES

We investigated an adaptive rule-based computer-aided diagnosis (CAD) scheme for digitized mammograms that can be optimized by using an image difficulty index as determined from global measures of image characteristics.

METHODS

First, we defined an image "difficulty" index based on image feature measurements in both the spatial and frequency domains. The CAD scheme then segmented the database into three groups. An image database of 428 digitized mammograms with 220 verified masses was randomly divided into two subsets, one for training (rule-setting) and the other for testing the adaptive CAD scheme. Each of the image difficulty groups in the training set was optimized independently to achieve a low false-positive detection rate while maintaining high detection sensitivity. Scheme performance was then evaluated with the test set, and the results were compared with a global rule-based system that was optimized without the adaptive method.

RESULTS

In this preliminary study, a relatively simple adaptive scheme reduced false-positive mass detections compared with the nonadaptive scheme from 0.85 to 0.53 per image. At the same time sensitivity was not significantly changed.

CONCLUSION

This adaptive CAD scheme has distinct advantages in improving CAD scheme performance as long as the training database includes a large number of cases in each image difficulty group with a variety of true-positive abnormalities.

Gamma delta T cell help of B cells is induced by repeated parasitic infection, in the absence of other T cells

BACKGROUND

gamma delta T cells, like alpha beta T cells, are components of all well-studied vertebrate immune systems. Yet, the contribution of gamma delta T cells to immune responses is poorly characterized. In particular, it has not been resolved whether gamma delta cells, independent of any other T cells, can help B cells produce immunoglobulin and form germinal centers, anatomical foci of specialized T cell-B cell collaboration.

RESULTS

TCR beta-/- mice, which lack all T cells except gamma delta T cells, routinely displayed higher levels of antibody than fully T cell-deficient mice. Repeated parasitic infection of TCR beta-/- mice, but not of T cell-deficient mice, increased antibody levels and induced germinal centers that contained B cells and monoclonal gamma delta cells in close juxtaposition. However, antibody specificities were more commonly against self than against the challenging pathogen. gamma delta T cell-B cell help was not induced by repeated inoculation of TCR beta-/- mice with mycobacterial antigens.

CONCLUSIONS

In the absence of any other T cells, gamma delta T cell-B cell collaboration can be significantly enhanced by repeated infection. However, the lack of obvious enrichment for antibodies against the challenging pathogen distinguishes gamma delta T cell help from alpha beta T cell help induced under analogous circumstances. The increased production of generalized antibodies may be particularly relevant to the development of autoimmunity, which commonly occurs in patients suffering from alpha beta T cell deficiencies, such as AIDS.

Long-term survival of solid organ allografts by brief anti-lymphocyte function-associated antigen-1 monoclonal antibody monotherapy

Strategies targeting lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18) and intercellular adhesion molecule-1 (ICAM-1) have previously been shown to produce long-term survival of solid organ allografts in animals only when both CD11a and ICAM-1 are targeted for a brief (6-7 days) time or when extended (14 weeks) treatment with anti-CD11a monoclonal antibody (mAb) is administered. We show that recipient pretreatment followed by a brief (13 days) treatment course with high-dose anti-CD11a mAb alone produces long-term survival of cardiac allografts in the rigorous, nonprimarily vascularized heart allograft model in mice. This treatment regimen induces specific unresponsiveness in our model. In recipients bearing long-term beating cardiac grafts after treatment with anti-CD11a mAb, there still exists a high frequency of potentially antigen-reactive T cells in isolated peripheral blood lymphocyte fractions. Therefore, clonal deletion does not appear to explain the induction of specific unresponsiveness by treatment with anti-CD11a mAb in this model. These findings support the further investigation of the use of high-dose anti-LFA-1 mAb monotherapy in the pre- and early postoperative period to promote solid organ allograft survival.

Robustness of computerized identification of masses in digitized mammograms. A preliminary assessment

RATIONALE AND OBJECTIVES

The authors assess the robustness of a computer-aided diagnosis (CAD) scheme with five rule-based stages to identify regions suspicious for mass in digitized mammograms.

METHODS

With a database of 428 mammograms, 234 of which had not been analyzed by this scheme before, the authors evaluated the performance robustness of their CAD scheme. The following four issues were investigated to assess the variability of the scheme's performance due to: (1) the maximum permissible number of "masses" detected at each stage; (2) exclusion of selected individual rule-based stages; (3) added image noise; and (4) repeated digitizations of the same image.

RESULTS

Enabling the CAD scheme to select a maximum of two suspicious mass regions at any one stage increased sensitivity by as much as 4% (from 93% to 97%), but it increased the false-positive detection rate by as much as 1.2 per image (from 1.7 to 2.9). Eliminating any individual stage decreased sensitivity by as much as 6%, but this reduced the false-positive detection rate by as much as 0.4 per image (from 1.7 to 1.3). The addition of reasonable noise levels decreased sensitivity by as much as 4% without substantially affecting the false-positive detections. Repeated digitizations of selected images demonstrated a scheme sensitivity of 93% +/- 1.8% with more than a 90% overlap of the false-positive regions.

CONCLUSIONS

The results of this preliminary study clearly indicate that this scheme is reasonably robust to the variables investigated here.

T helper cells in murine germinal centers are antigen-specific emigrants that downregulate Thy-1

After immunization, activated splenic T cells proliferate in periarteriolar lymphoid sheaths (PALS) and subsequently migrate to the lymphoid follicle where they enter nascent germinal centers. Analysis of TCR V(D)J gene rearrangements indicates extensive emigration, frequently involving more than a single white pulp region. These migrants constitute a unique set of T helper cells that express antigen-specific alpha beta TCR, CD3, and CD4, but little or no Thy-1, a differentiation antigen present on the great majority of peripheral murine T lymphocytes. The origin of CD4+ Thy-1 follicular T cells appears to be the Thy+ population in the PALS, as both sets commonly share identical V(D)J rearrangements.

[Extraction of humic acid from drinking water in area with arsenosis in inner Mongolia and Taiwan and comparison of its spectrometry]

In order to study etiology of blackfoot disease in Taiwan and to explore whether it can occur in the area with arsenosis in Inner Mongolia in the future, chemical components of specimens of drinking water from Taiwan and Inner Mongolia were determined and compared with infrared (IR), ultra-violet (UV) spectrometry and fluorescence spectrometry. Humic acid was extracted from the water samples by XAD-7 ion-exchange resin and Sephadex G-25 gel filtration chromatography, respectively, yielding the same results. Studies showed arsenic and humic acid levels in water samples both from Taiwan and Inner Mongolia all were higher, and their fluorescence and UV-spectra were similar, except a small difference in their IR spectra. Their effects on environment are under further studies.

Germinal center formation, immunoglobulin class switching, and autoantibody production driven by "non alpha/beta" T cells

The production of class-switched antibodies, particularly immunoglobulin (Ig) G1 and IgE, occurs efficiently in T cell receptor (TCR) alpha-/- mice that are congenitally devoid of alpha/beta T cells. This finding runs counter to a wealth of data indicating that IgG1 and IgE synthesis are largely dependent on the collaboration between B and alpha/beta T cells. Furthermore, many of the antibodies synthesized in TCR alpha-/- mice are reactive to a similar spectrum of self-antigens as that targeted by autoantibodies characterizing human systemic lupus erythematosus (SLE). SLE, too, is most commonly regarded as an alpha/beta T cell-mediated condition. To distinguish whether the development of autoantibodies in TCR alpha-/- mice is due to an intrinsic de-regulation of B cells, or to a heretofore poorly characterized collaboration between B and "non-alpha/beta T" cells, the phenotype has been reconstituted by transfer of various populations of B and non-alpha/beta T cells including cloned gamma/delta T cells derived from TCR alpha-/- mice, to severe combined immunodeficient (SCID) mice. The results establish that the reproducible production of IgG1 (including autoantibodies) is a product of non-alpha/beta T cell help that can be provided by gamma/delta T cells. This type of B-T collaboration sustains the production of germinal centers, lymphoid follicles that ordinarily are anatomical signatures of alpha/beta T-B cell collaboration. Thus, non-alpha/beta T cell help may drive Ig synthesis and autoreactivity under various circumstances, especially in cases of alpha/beta T cell immunodeficiency.

Computerized identification of suspicious regions for masses in digitized mammograms

RATIONALE AND OBJECTIVES

A simple and effective computerized detection scheme was developed to identify suspicious mass regions in digitized mammograms.

METHODS

This method identifies a maximum of five suspicious mass regions per image and was tested with a database of 510 images, including 162 verified masses. It includes a series of five rule-based processes that select one region with each of the following characteristics: 1) a global minimum of optical density in a smoothed image; 2) a local minimum of optical density in the original image; 3) a local minimum of optical density in a filtered image; 4) a small "mass" of low contrast; and 5) a small "mass" of high contrast.

RESULTS

This multi-stage process achieved a sensitivity of 95% while limiting false-positive detection rates to below an average of two per image.

CONCLUSION

Because this method limits the initial number of suspicious mass regions while retaining high sensitivity, it may be applicable to clinically usable computer-aided diagnosis schemes.

Digital mammography: mixed feature neural network with spectral entropy decision for detection of microcalcifications

A computationally efficient mixed feature based neural network (MFNN) is proposed for the detection of microcalcification clusters (MCCs) in digitized mammograms. The MFNN employs features computed in both the spatial and spectral domain and uses spectral entropy as a decision parameter. Backpropagation with Kalman filtering (KF) is employed to allow more efficient network training as required for evaluation of different features, input images, and related error analysis. A previously reported, wavelet-based image-enhancement method is also employed to enhance microcalcification clusters for improved detection. The relative performance of the MFNN for both the raw and enhanced images is evaluated using a common image database of 30 digitized mammograms, with 20 images containing 21 biopsy proven MCCs and ten normal cases. The computed sensitivity (true positive (TP) detection rate) was 90.1% with an average low false positive (FP) detection of 0.71 MCCs/image for the enhanced images using a modified k-fold validation error estimation technique. The corresponding computed sensitivity for the raw images was reduced to 81.4% and with 0.59 FP's MCCs/image. A relative comparison to an earlier neural network (NN) design, using only spatially related features, suggests the importance of the addition of spectral domain features when the raw image data is analyzed.

[Effects of SL-probiotic preparation on the body weight and phagocytosis of white mice]

Effects of SL-probiotic preparation on the body weight and the phagocytic functions in white mice were studied. Bioassay of its toxicity showed SL-P was non-toxic. Body weight of the treated mice increased significantly as compared with that of controls 10 days after treatment with SL-probiotic preparation. Phagocytic activity, acid phosphatase activity, lysozyme activity of the peritoneal macrophages of the tested mice were enhanced significantly as compared with those of normal controls. The same results were obtained with respect to serum lysozyme activity. These observations showed that SL-probiotic preparation could activate macrophage function in mice and hence enhancement of non-specific immunity.

Computerized detection of masses from digitized mammograms: comparison of single-image segmentation and bilateral-image subtraction

RATIONALE AND OBJECTIVES

Two methods--single-image segmentation and bilateral-image subtraction--have been used commonly as the first stage in computer-aided detection (CAD) schemes to detect masses on digitized mammograms. In the current study, we investigated and compared the advantages and disadvantages of the two methods in achieving a high sensitivity for mass detection.

METHODS

Two CAD schemes were tested. One used Gaussian filtering based on single-image segmentation, and the other used bilateral-image subtraction based on left-right image pairs to identify suspicious mass regions. A clinical database that contained 152 verified mass cases was used to compare the two approaches.

RESULTS

The single-image segmentation method yielded 100% sensitivity and had a somewhat higher number of initial suspicious regions. The bilateral-image subtraction method missed several true-positive regions at the initial phase. Each approach achieved more than 90% sensitivity at a false-positive rate of approximately 0.8 per image.

CONCLUSION

Optimal initial image segmentation schemes may depend on the complete detection and classification method used. Single-image segmentation methods may perform comparably with bilateral-image segmentation schemes, and these techniques appear to be more versatile and easily adaptable to future clinical CAD applications.

In situ studies of the primary immune response to (4-hydroxy-3-nitrophenyl)acetyl. IV. Affinity-dependent, antigen-driven B cell apoptosis in germinal centers as a mechanism for maintaining self-tolerance

Germinal centers (GCs) are the sites of antigen-driven V(D)J gene hypermutation and selection necessary for the generation of high affinity memory B lymphocytes. Despite the antigen dependence of this reaction, injection of soluble antigen during an established primary immune response induces massive apoptotic death in GC B cells, but not in clonally related populations of nonfollicular B lymphoblasts and plasmacytes. Cell death in GCs occurs predominantly among light zone centrocytes, is antigen specific, and peaks within 4-8 h after injection. Antigen-induced programmed death does not involve cellular interactions mediated by CD40 ligand (CD40L) or Fas; disruption of GCs by antibody specific for CD40L was not driven by apoptosis and C57BL/6.lpr mice, though unable to express the Fas death trigger, remained fully susceptible to soluble antigen. Single injections of antigen did not significantly decrease GC numbers or average size, but repeated injections during an 18-h period resulted in fewer and substantially smaller GCs. As cell loss appeared most extensive in the light zone, decreased GC cellularity after prolonged exposure to soluble antigen implies that the Ig- centroblasts of the dark zone may require replenishment from light zone cells that have survived antigenic selection. GC cell death is avidity-dependent; oligovalent antigen induced relatively little apoptosis and GC B cells that survived long exposures to multivalent antigen expressed atypical VDJ rearrangements unlikely to encode high affinity antibody. Antigen-induced apoptotic death in GCs may represent a mechanism for the peripheral deletion of autoreactive B cell mutants much as the combinatorial repertoire of immature B lymphocytes is censored in the bone marrow.

Computerized detection of masses in digitized mammograms using single-image segmentation and a multilayer topographic feature analysis

RATIONALE AND OBJECTIVES

We developed and evaluated a computer-aided detection (CAD) scheme for masses in digitized mammograms.

METHODS

A multistep CAD scheme was developed and tested. The method uses a technique of single-image segmentation with Gaussian bandpass filtering to yield a high sensitivity for mass detection. A rule-based multilayer topographic feature analysis method is then used to classify suspected regions. A set of 260 cases, including 162 verified masses, was divided into two subsets; one set was used to set the rule-based classification and one was used to test the performance of the scheme.

RESULTS

In a preliminary clinical study, the implemented detection scheme yielded 98% sensitivity with a false-positive detection rate of less than one false-positive region per image.

CONCLUSION

Single-image segmentation methods seem to have high sensitivity in selecting true-positive mass regions in the first stage of a CAD scheme. A multilayer topographic image feature analysis method in the second stage of a CAD scheme has the potential to significantly reduce the false-positive detection rate.

Therapeutic potentiation of the immune system by costimulatory Schiff-base-forming drugs

Immune responses are orchestrated by CD4 T lymphocytes, which receive a cognitive signal when clonally distributed receptors are occupied by major histocompatibility complex (MHC) class II-bound peptides on antigen-presenting cells (APCs). The APCs provide costimulatory signals, through macromolecules such as CD80, that regulate outcomes in terms of T-cell activation or anergy. We have studied essential complementary chemical events in the form of Schiff base formation between carbonyls and amines that are constitutively expressed on presenting cell and T-cell surfaces and provide a new target for manipulation of immune responses. Here we show that small Schiff base-forming molecules can substitute for the physiological donor of carbonyl groups and provide a costimulatory signal to CD4 Th-cells through a mechanism that activates clofilium-sensitive K+ and Na+ transport. One such molecule, tucaresol, enhances CD4 Th-cell responses, selectively favouring a Th1-type profile of cytokine production. In vivo tucaresol potently enhances CD4 Th-cell priming and CD8 cytotoxic T-cell priming to viral antigens, and has substantial therapeutic activity in murine models of disease.

Computer-aided detection of clustered microcalcifications in digitized mammograms

RATIONALE AND OBJECTIVES

We investigated a computer-aided detection (CAD) scheme for clustered microcalcifications in digitized mammograms.

METHODS

A multistage CAD scheme was developed and tested. To increase sensitivity, the scheme uses a Gaussian band-pass filter and nonlinear threshold. A multistage local minimum searching routine and a multilayer topographic feature analysis are used to reduce the false-positive detection rate. One hundred ten digitized mammograms were used in this preliminary test, with 55 images containing one or two verified microcalcification clusters.

RESULTS

The CAD scheme achieved 100% sensitivity and had an average false-positive detection rate of 0.18 per image.

CONCLUSION

The CAD scheme performs as well as many published schemes and has some unique advantages to further improve detection sensitivity and specificity of future CAD schemes.

Cellular interaction in germinal centers. Roles of CD40 ligand and B7-2 in established germinal centers

Costimulatory interactions between T and B lymphocytes are crucial for T cell activation and B cell proliferation and differentiation. We have compared the roles of CD40L and B7-2 in the initiation and maturation of humoral immunity by administering anti-CD40 ligand (L) or anti-B7-2 Ab during the early (days -1 to 3) or late (days 6-10) phases of primary responses to thymus-dependent (Td) and -independent (Ti) Ags. Germinal center (GC) formation in response to a Td Ag was inhibited completely by the early administration of anti-CD40L or anti-B7-2 Abs. Later in the response, established GCs remained sensitive to anti-CD40L but were resistant to treatment with anti-B7-2. However, Ig hypermutation was reduced dramatically in GCs of anti-B7-2-treated mice and humoral memory was impaired. Early administration of anti-CD40L reduced serum Ab levels to approximately 10% of controls, whereas early treatment with anti-B7-2 reduced Ab production by only 50%. Later treatments with either Ab had no effect on Ab production. Response to a type II Ti Ag was more resistant than Td responses to interruption of costimulatory interactions. Our findings suggest that the costimulatory roles of CD40:CD40L and B7-2:CD28/CTLA-4 differ in the GC; administration of anti-CD40L abrogates an established GC reaction, whereas Ab to B7-2 suppresses Ig hypermutation and entry into the B cell memory compartment. Once B cells have entered the differentiation pathway to Ab production, neither CD40L nor B7-2 is necessary for their continued differentiation and persistence.

Cellular interaction in germinal centers. Roles of CD40 ligand and B7-2 in established germinal centers

Costimulatory interactions between T and B lymphocytes are crucial for T cell activation and B cell proliferation and differentiation. We have compared the roles of CD40L and B7-2 in the initiation and maturation of humoral immunity by administering anti-CD40 ligand (L) or anti-B7-2 Ab during the early (days -1 to 3) or late (days 6-10) phases of primary responses to thymus-dependent (Td) and -independent (Ti) Ags. Germinal center (GC) formation in response to a Td Ag was inhibited completely by the early administration of anti-CD40L or anti-B7-2 Abs. Later in the response, established GCs remained sensitive to anti-CD40L but were resistant to treatment with anti-B7-2. However, Ig hypermutation was reduced dramatically in GCs of anti-B7-2-treated mice and humoral memory was impaired. Early administration of anti-CD40L reduced serum Ab levels to approximately 10% of controls, whereas early treatment with anti-B7-2 reduced Ab production by only 50%. Later treatments with either Ab had no effect on Ab production. Response to a type II Ti Ag was more resistant than Td responses to interruption of costimulatory interactions. Our findings suggest that the costimulatory roles of CD40:CD40L and B7-2:CD28/CTLA-4 differ in the GC; administration of anti-CD40L abrogates an established GC reaction, whereas Ab to B7-2 suppresses Ig hypermutation and entry into the B cell memory compartment. Once B cells have entered the differentiation pathway to Ab production, neither CD40L nor B7-2 is necessary for their continued differentiation and persistence.

Construction and high expression of retroviral vector with human clotting factor IX cDNA in vitro

The construction of the high titer and highly expressed safety retroviral vector carrying human clotting factor IX cDNA is reported. Retroviral vectors LNCIX, LIXSN and LCIXSN, driven by hCMV, LTR and hCMV combined with LTR promoter respectively, were constructed, based on the retroviral vector LNL6, and transferred into packaging cell line PA317 with electroporation. Human clotting factor IX was detected in the cultured cells transduced with LNCIX and LIXSN but not in the cells transduced with LCIXSN. The viral titer of PA317/LNCIX was 800,000 CFU per mL. With ELISA detection, it was found that the cells transduced with this vector can express human clotting factor IX at the level of 3.3 micrograms per 10(6) cells in 24 h in human fibrosarcoma cells HT-1080 and 2.5 micrograms per 10(6) cells in 24 h in hemophilia B patients' skin fibroblast HSF cells, and more than 80% of them were biologically active. The viral titer and expression of human FIX were increased, and the construction of retroviral vector backbone was improved and the safety was guaranteed as compared to those vectors used previously. These vectors may produce a sufficient quantity of factor IX proteins to cause the phenotypic modification for hemophilia B patients.

Galactose oxidation as a potent vaccine adjuvant strategy. Efficacy in murine models and in protection against a bovine parasitic infection

Potent immunological adjuvants are urgently required to complement subunit protein and peptide vaccines in prophylactic and therapeutic vaccination. Carbonyl-amino condensations, which are essential to the inductive interaction between antigen-presenting cells and T-helper cells, were tested as a target for the enhancement or immune responses to vaccine antigens. Enzymic oxidation of cell surface galactose by the novel adjuvant NAGO, to increase amine-reactive carbonyl groups on lymphocytes and antigen-presenting cells, provided a potent noninflammatory method of enhancing the immunogenicity of viral, bacterial, and protozoal subunit vaccines in mice. In pilot protection studies with a glutathione-S-transferase vaccine against bovine Fasciola hepatica, a formulation containing NAGO as sole adjuvant agent proved very effective in inducing protection. In terms of protection in individual animals, NAGO alone was better than Quil A emulsified in squalene Montanide (five of eight animals were protected better than 80% by NAGO; four of eight animals were protected better than 93% by NAGO; two of eight animals were protected better than 80% by QA/SM). QA/SM (69% mean protection) was, however, more consistent overall than NAGO (65% mean protection). NAGO proved more effective in murine models when combined with muramyl dipeptide, but this combination has yet to be tested in protection studies.

Effect of cortisol on energy expenditure and amino acid metabolism in humans

Hydrocortisone was infused overnight into nine normal healthy adults on three occasions at 0, 80, and 200 micrograms.kg-1.h-1, producing plasma cortisol concentrations of 10.6 +/- 1.2, 34.0 +/- 2.0, and 64.9 +/- 4.3 micrograms/dl, respectively. L-[1-13C]leucine, L-[phenyl-2H5]phenylalanine, and L-[2-15N]glutamine were infused during the last 7 h of hypercortisolemia to measure amino acid kinetics. During the last 3.5 h, somatostatin, glucagon, and insulin were infused to reduce the cortisol-induced elevation in plasma insulin to basal. Hypercortisolemia increased plasma glucose, free fatty acid (FFA), and insulin concentrations. Institution of the somatostatin clamp returned insulin to basal but increased glucose and FFA. Acute hypercortisolemia increased protein breakdown 5-20%, as measured by increases in leucine and phenylalanine appearance rates. Normalizing insulin during hypercortisolemia did not alter phenylalanine flux but enhanced leucine appearance rate, the latter result indicating that insulin was affecting leucine metabolism during hypercortisolemia. The fraction of the leucine flux that was oxidized was not significantly increased with hypercortisolemia, but disposal by the nonoxidative route of leucine uptake for protein synthesis was increased. Hypercortisolemia increased cycling of amino acids by increasing protein breakdown and synthesis, but the increase in this process could have increased resting energy expenditure (REE) only 1-2%. Hypercortisolemia increased glutamine flux in a dose-dependent fashion through an increase in de novo synthesis, which presumably reflects increased release from skeletal muscle. Hypercortisolemia increased REE 9-15% at the 80 and 200 micrograms.kg-1.h-1 infusion rates. Respiratory quotient did not rise with cortisol infusion but tended to decrease, suggesting that the increase in REE was fueled by increased oxidation of fat. These data demonstrate that hypercortisolemia increases metabolic rate and may be in part responsible for the hypermetabolic state in injury.

Structurally related but functionally distinct yeast Sm D core small nuclear ribonucleoprotein particle proteins

Spliceosome assembly during pre-mRNA splicing requires the correct positioning of the U1, U2, U4/U6, and U5 small nuclear ribonucleoprotein particles (snRNPs) on the precursor mRNA. The structure and integrity of these snRNPs are maintained in part by the association of the snRNAs with core snRNP (Sm) proteins. The Sm proteins also play a pivotal role in metazoan snRNP biogenesis. We have characterized a Saccharomyces cerevisiae gene, SMD3, that encodes the core snRNP protein Smd3. The Smd3 protein is required for pre-mRNA splicing in vivo. Depletion of this protein from yeast cells affects the levels of U snRNAs and their cap modification, indicating that Smd3 is required for snRNP biogenesis. Smd3 is structurally and functionally distinct from the previously described yeast core polypeptide Smd1. Although Smd3 and Smd1 are both associated with the spliceosomal snRNPs, overexpression of one cannot compensate for the loss of the other. Thus, these two proteins have distinct functions. A pool of Smd3 exists in the yeast cytoplasm. This is consistent with the possibility that snRNP assembly in S. cerevisiae, as in metazoans, is initiated in the cytoplasm from a pool of RNA-free core snRNP protein complexes.

Locus-specific somatic hypermutation in germinal centre T cells

Somatic hypermutation and affinity-driven selection of active immunoglobulin genes occur in germinal centres (GCs), resulting in the generation of high-affinity memory B cells. In contrast, T lymphocytes do not require the germinal centre microenvironment to establish memory and the T-cell antigen receptor (TCR) genes, though homologous to immunoglobulin genes, are believed to be incapable of hypermutation. Here we present direct evidence that the small population of antigen-specific T cells that are recruited into splenic GCs acquire mutations in the variable region of genes encoding TCR alpha-chains (V alpha) but not those of beta-chains. These locus-specific mutations reach frequencies comparable to mutated immunoglobulin VH exons recovered from the same site and exhibit similar substitution biases and DNA strand polarity. T cells bearing identical mutations appear in multiple GCs, raising the possibility that some cells bearing mutant TCRs may re-enter the peripheral lymphocyte pool.

Fractal analysis of trabecular patterns in projection radiographs. An assessment

RATIONALE AND OBJECTIVES

Fractal analysis of digitized images has been investigated in recent years as a potential measure of structural bone strength. Several technical issues associated with such measurements are assessed.

METHODS

In a series of experiments using a hand phantom, the effects of system noise and modulation transfer function on fractal dimension were explored. The authors evaluated a method for correcting the estimated power spectrum using a step-wedge image exposed and digitized under identical conditions as a reference.

RESULTS

System noise and modulation transfer function significantly affect estimated fractal dimension in bony regions computed from conventional radiographs.

CONCLUSIONS

Before conventional radiographs are used for fractal analysis in the clinical environment, many of the technical problems associated with this methodology must be addressed.