A study on visual evoked potential to show the relationship between the eyes and the twelve regular channels

The visual electrophysiologic method was used to investigate the relationship between the eyes and the 12 regular channels. The values of the latent period and the amplitude of P100 wave were calculated and compared statistically. The results show that: 1) The eyes and the 12 regular channels are closely related, no matter whether the channels are classically associated with the eyes or not, while the control (non-channel)/ point has no such relationship; 2) the degrees of relationship between the eyes and the 12 regular channels vary significantly; and 3) acupuncture at the 12 regular channels induces different effects on the visual evoked potential that the Urinary Bladder Channel presents a facilitation effect whereas all the other channels chiefly show an inhibitory effect.

Quasi-bandlimited properties of radon transforms and their implications for increasing angular sampling densities

The n-dimensional (n-D) radon transform, which forms the mathematical basis for a broad variety of tomographic imaging applications, can be viewed as an n-D function in n-D sinogram space. Accurate reconstruction of continuous or discrete tomographic images requires full knowledge of the radon transform in the corresponding n-D sinogram space. In practice, however, one can have only a finite set of discrete samples of the radon transform in the sinogram space. One often derives the desired full knowledge of the radon transform from its discrete samples by invoking various interpolation algorithms. According to the Wittaker-Shannon sampling theorem, a necessary condition for a full and unique recovery of the radon transform from its discrete samples is that the radon transform itself be bandlimited. Therefore, it is necessary to analyze the bandlimited properties of the radon transform. In this work, we analyze explicitly the bandlimited properties of the radon transform and show that the radon transform is mathematically quasi-bandlimited [or essentially bandlimited] in two quantitative senses and can essentially be treated as bandlimited in practice. The quasi-bandlimited properties can be used for increasing the angular sampling density of the radon transform.

Image restoration and reconstruction with a Bayesian approach

We have extended Johnson's Bayesian method for image restoration and reconstruction by introducing diagonal line sites, using symmetric neighborhood configurations, and employing an additional hyperparameter for estimation of line sites. A general formulation for arbitrary neighborhood configurations was derived. The major part of this paper deals with the conduct of computer simulations intended to examine the effect of the hyperparameters, the diagonal line sites, and the size of the neighborhood configuration on the performance of the proposed Bayesian method. We show that, for optimal performance, distinct hyperparameters should be used for the intensity sites and line sites. The results also suggest that a large neighborhood configuration should be used. By comparing the near-optimal restored images, we demonstrated that the use of diagonal line sites, along with the symmetric configurations thus made possible, can effectively remove the blocky edge artifacts and produce images of better quality. When the method was applied to positron emission tomography (PET) image reconstruction, our results showed that the quality of the reconstructed images was improved for both computer-simulated and real patient PET data.

NO decreases phosphorylation of focal adhesion proteins via reduction of Ca in rat aortic smooth muscle cells

Our laboratory has previously reported that the antimitogenic effect of nitric oxide (NO) in primary cultures of rat aortic smooth muscle cells may be attributed to activation of protein tyrosine phosphatase and dephosphorylation of protein phosphotyrosine [G.S. Dhaunsi, C. Matthews, K. Kaur, and A. Hassid, Am, J. Physiol. 272 (Heart Circ. Physiol. 41): H1342-H1349, 1997]. The goal of the current study was to investigate the role of cytoplasmic Ca in this process and to identify protein substrates that are dephosphorylated by treatment with NO. Treatment of primary rat aortic smooth muscle cell cultures with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) decreased cytoplasmic Ca levels and elicited phosphotyrosine dephosphorylation. Both effects were mimicked by the extracellular and intracellular Ca chelators ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) and 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), respectively, and by the Ca channel blocker nifedipine. Conversely, elevation of cytoplasmic Ca via the use of the Ca ionophore A-23187 or high extracellular K+ prevented or attenuated SNAP-induced dephosphorylation. Both BAPTA and nifedipine also decreased DNA synthesis, providing further evidence to link dephosphorylation to antimitogenesis. Two of the proteins dephosphorylated by treatment of cells with NO or EGTA were identified as the focal adhesion proteins, cortactin and paxillin. These results indicate that NO-induced dephosphorylation of protein phosphotyrosine is mediated by reduction of cytoplasmic Ca and suggest that dephosphorylation of focal adhesion proteins may be of relevance to the antimitogenic effect of NO.

[Detection of hemophilia A carriers by PCR analysis of hind III polymorphism in the factor VIII gene]

OBJECTIVE

To explore a scheme of using PCR analysis in the detection of carriers of Hind III polymorphism of factor VIII gene of hemophilia A.

METHODS

Implicating intron 19 of the factor VIII gene of 6 patients with the hemophilia A and 207 unrelated X-chromosomes were amplified by PCR and were analysed by means of Amp-RFLPs of Hind III.

RESULTS

The incidence of the polymorphic Hind III sites in the given population was found to be 0.29. The frequence of the Hind III heterozygotes in women calculated according to Hardy-Weinberg equation was 0.41, which proved to be informative enough for carrier detection and prenatal diagnosis of hemophilia A. 2 out of 6 families (33%)examined in this study were informative.

CONCLUSION

The new scheme proved to be effective for hemophilia A carrier detection and prenatal diagnosis.

A general approach for multidimensional smoothing

Smoothing is closely related to regression in statistics. It is frequently applied to data that contain statistical noise in attempts to discern and highlight patterns concealed in the data. In medical imaging applications, the acquired data are often N dimensional (where N > or = 2) and thus multidimensional smoothing approaches would best exploit the multidimensional correlations inherent in the data. Unfortunately, extensions of advanced (especially adaptive) one-dimensional smoothing approaches to multidimensional data are, in general, theoretically challenging and computationally prohibitive. In this work, we propose a novel approach that accomplishes effectively higher-dimensional smoothing by exploiting the Fourier transform properties of the data to reduce data dimensions, allowing for lower-dimensional smoothing. We present the theoretical basis for this approach and verify this approach by applying it to computer-simulated data as well as real data acquired in medical imaging studies.

Hypervariability generated by natural selection in an extracellular complement-inhibiting protein of serotype M1 strains of group A Streptococcus

In many countries, M1 strains of the human pathogenic bacterium group A Streptococcus are the most common serotype recovered from patients with invasive disease episodes. Strains of this serotype express an extracellular protein that inhibits complement [streptococcal inhibitor of complement (Sic)] and is therefore believed to be a virulence factor. Comparative sequence analysis of the 915-bp sic gene in 165 M1 organisms recovered from diverse localities and infection types identified 62 alleles. Inasmuch as multilocus enzyme electrophoresis and pulsed-field gel electrophoresis previously showed that most M1 organisms represent a distinct streptococcal clone, the extent of sic gene polymorphism was unexpected. The level of polymorphism greatly exceeds that recorded for all other genes examined in serotype M1 strains. All insertions and deletions are in frame, and virtually all nucleotide substitutions alter the amino acid sequence of the Sic protein. These molecular features indicate that structural change in Sic is mediated by natural selection. Study of 70 strains recovered from two temporally distinct epidemics of streptococcal infections in the former East Germany found little sharing of Sic variants among strains recovered in the different time periods. Taken together, the data indicate that sic is a uniquely variable gene and provide insight into a potential molecular mechanism contributing to fluctuations in streptococcal disease frequency and severity.

[Isolation of antibacterial polypeptides of human cervical mucus]

The acid-soluble extract of human cervical mucus was obtained by solving mucus with 5% acetic acid in the presence of protease inhibitor. The antibacterial activity of the acid-soluble extract was analyzed by gel overlay technique. The result showed that two protein bands which were designated human cervical protein-1 (Hcp-1), human cervical protein-2(Hcp-2) were potently antibacterial against E. coli 25922 and S. aureus 25923. Tricine-SDS-PAGE analysis indicated that Hcp-1, Hcp-2 actually contained three and four protein bands respectively. The molecular weights of Hcp-1 were 6.7 kd, 10 kd, 15.4 kd; these of Hcp-2 were 4.4 kd, 6.7 kd, 9 kd, 15.4 kd. Our studies suggested that human cervical mucosa might secrete some currently-unknown antibacterial polypeptides which play an important role in the cervical defense against infection.

[The study of radioresistance of BHRF1 gene]

In order to learn relationship between the expression of BHRF1 gene and radiative sensitivity of cells of nasopharyngeal carcinoma. High BHRF1 expressive vector was set up and transfected in the cell line of nasopharyngeal carcinoma, CNE2. Then the cells were radiated to test its ability of clone formation in nude mice. The results showed that the tumors formed by BHRF1-CNE2 cells were lighter before radiation and weighter after radiation (P < 0.01), and apoptotic index of BHRF1-CHE2 was less than control groups (P < 0.01). So, it suggests that the BHRF1 expression could prevent apoptosis by enhancing the resistibility of the tumor cells to radiation.

The prognostic role of p53, metallothionein, P-glycoprotein, and MIB-1 in muscle-invasive urothelial transitional cell carcinoma

Tissue from primary tumors was analyzed for 118 patients with urothelial cancer who subsequently received cisplatin-based chemotherapy. Immunohistochemical staining was performed for nuclear p53 reactivity; for two proposed mediators of drug resistance, metallothionein (MT) and P-glycoprotein; and for the cell proliferation marker MIB-1. For each marker, immunoreactivity was expressed as a percentage of positively staining cells, and overall intensity of staining was graded on a scale from 0 to 3. The product of these two measurements was calculated to generate a percentage-intensity index. Clinical data were obtained independently via retrospective chart review. Chemotherapy regimens containing cisplatin (cisplatin, methotrexate, and vinblastine or methotrexate, vinblastine, doxorubicin, and cisplatin) were administered for metastatic disease (n = 64), for locally advanced disease (n = 45), or as an adjuvant treatment (n = 9). The overall response rate was 56% among 99 evaluable patients, and median survival was 12.7 months. By univariate analysis, Eastern Cooperative Oncology Group performance status (P = 0.0025), tumor grade (P = 0.03), percentage of MT staining (P = 0.01), and percentage-intensity index of MT staining (P = 0.04) were significant predictors of response to chemotherapy. The first three of these were significant in a multivariate model (P = 0.05, 0.04, and 0.04, respectively). By subgroup analysis, the percentage of MT staining predicted for response in metastatic disease (P = 0.03), but not in locally advanced disease (P = 0.28). Only performance status was significantly related to overall survival (P = 0.0001, log-rank test) in the whole cohort. Overexpression of MT in the 64 patients with metastatic disease was associated with a shorter survival (P = 0.04). Expression of p53, P-glycoprotein, and MIB-1 did not predict for survival. In conclusion, overexpression of MT is associated with a poorer outcome from chemotherapy, possibly due to cisplatin resistance.

[Cytochrome P450*2D6 gene polymorphism in Chinese population]

OBJECTIVE

To demonstrate the cytochrome P450*2D6(CYP*2D6) gene polymorphism distribution in Chinese.

METHODS

The polymorphisms of CYP*2D6 gene in 100 Chinese people were studied with polymerase chain reaction and Xba I restriction fragment length polymorphic (RFLP) techniques.

RESULTS

The frequencies of CYP*2D6 gene A, B, D and E mutations were 1%, 6.5%, 0.5% and 1%, respectively; the genotypes of 29kb/29kb,44kb/29kb and 44kb/44kb Xba I RFLP were 38%, 46% and 13%, respectively. It was found that 12% of B mutations were linked with even though A and B mutations were mainly associated with 29kb/29kb genotype.

CONCLUSION

The frequencies of the four kinds of CYP*2D6 gene mutation in Chinese were lower than those of the European, but the frequency of Xba I 44kb allele was a little higher.

Characterization of group A Streptococcus strains recovered from Mexican children with pharyngitis by automated DNA sequencing of virulence-related genes: unexpectedly large variation in the gene (sic) encoding a complement-inhibiting protein

Sequence variation was studied in several target genes in 54 strains of group A Streptococcus (GAS) cultured from children with pharyngitis in Mexico City. Although 16 distinct emm alleles were identified, only 4 had not been previously described. Virtually all bacteria (31 of 33 [94%] with the streptococcal pyrogenic exotoxin gene (speA) had emm1-related, emm3, or emm6 alleles. The gene (sic) encoding an extracellular GAS protein that inhibits complement function was unusually variable among isolates with the emm1 family of alleles, with a total of seven variants identified. The data suggest that many GAS strains infecting Mexican children are genetically similar to organisms commonly encountered in the United States and western Europe. Sequence variation in the sic gene is useful for rapid differentiation among GAS isolates with the emm1 family of alleles.

[Immunohistochemical study of type IV collagen chain distribution within basement membrane in patients with Alport syndrome]

To observe the distribution of type IV collagen chains within basement membrane in patients with Alport syndrome (AS), discuss the pathogenesis of AS and assess the diagnostic value of indirect immunofluorescent study of type IV collagen chains. By using indirect immunofluorescence technique, the distribution of different chains of type IV collagen in specimen of renal (6 specimens) and skin (5 specimens) basement membrane of 8 AS patients belonging to 7 kindreds were investigated. In 4 male patients with X-linked dominant (XD) AS, the specific monoclonal antibodies against NC1 domains of the alpha 3, alpha 4 and alpha 5 chains of type IV collagen failed to localize on glomerular basement membrane (GBM) and the alpha 5 chain of type IV collagen were also absent in the epidermal basement membrane (EBM). The results of immunofluorescent study were positive in 3 autosomal dominant and 1 autosomal recessive AS patients as same as that in control. AS presents a biochemical abnormality of type IV collagen. The pathogenesis of XD-AS may associate with the abnormal products of alpha 5 chain. The immunofluorescent study of type IV collagen chains distribution within GBM and EBM by using monoclonal antibodies is useful in confirming the diagnosis of AS, especially XD-AS.

[Pharmacognostical identification of Anoectochilus roxburghii]

This paper reported the pharmacognostical identification on characters, microscopic characteristics and TLC of the Anoectochilus roxburghii (Wall.) Lindl., and compared with different resouce samples. The results may provide reference for its identification.

[Molecular evolution of MHC DQA genes. II. Phylogenetic analysis based on nucleotide substitution and SCU bias]

Phylogenetics of 23 alleles at MHC DQA loci in 7 mammalian species was studied based on their nucleotide (NT) substitution and synonymous codon usage (SCU) bias. (1) It was demonstrated that the NT substitution rates are 1.0 x 10(-9) NT/site/yr for exon2 and 1.3 x 10(-9) NT/site/yr for exon2-4 in a large time scale, which is similar to other nuclear genes, while for mouse and rat the rates are nearly twice as high as above mentioned. (2) The DQA locus diversity and their interallelic diversity developed long after the radiation of mammalian 80Mya (million years ago). The bovine counterpart, of, and with the same recent ancestor of ovine DQA2, remains to be discovered. HLA-DQA2 locus split from HLA-DQA1 ancestor at the time between 12 approximately 20 Mya while allele diversity of HLA-DQA1 emerged and developed from 24 Mya to less than 1 Mya. (3) The phylogenetic trees based on SCU divergence reflect the phylogenetics of MHC DQA genes quite well generally in a new respect and reveal that HLA-DQA2 has a distinctive SCU bias different from all other MHC DQA locianalyzed. It indicates that SCU statistics plays an important and unique role in phylogenetic analysis of orthologous genes. The method to estimate the SCU divergence and SCU similarity was improved in this research.

Synthesis and DNA-binding ability of Sp1 protein zinc finger domain and its peptidomimetics

The second zinc finger fragment of Sp1 (Sp1-ZF2), its mutant (Sp1-ZF2/HT. E(20) --> H, R(23) --> T), and two mimic analogues (ZF20 and ZF15) were synthesized by stepwise solid phase technique. The CD spectra and UV-visible spectrum with CoC1(2) indicated that the formation of zinc finger structure was affected not only by the hydrophobic amino acids but also by the change of the distance between Cys and His. Gel-retardat ion electrophoresis assays indicated that the Glu and Arg residues are very important for recognition. A single zinc finger like Sp1-ZF2 is able to bind DNA sequence specifically.

[The effect of the expression of BHRF1 gene of EB virus on the proliferation of the cells of nasopharyngeal carcinoma]

In order to learn the effect of the expression of BHRF1 of Epstein-Barr virus on the growth of the cell of nasopharyngeal carcinoma, high BHRF1 expressive vector was set up and transfected in low grade cell line of nasopharyngeal carcinoma, CNE2. Then the cells were cultivated under the condition of insufficient nutrition. The results show that the BHRF1 expression can prohibit the expression of PCNA, and enhance the survival of tumor cells under conditions of nutrition deprivation. So, it suggests that BHRF1 of EB virus could be involved in the development of nasopharyngeal carcinoma.

[Study on prethrombotic state in patients with paroxysmal nocturnal hemoglobinuria]

OBJECTIVE

To explore the mechanism of thrombogenesis in patients with paroxysmal nocturnal hemoglobinuria (PNH).

METHODS

Thirteen parameters concerning endotheliocytes, platelets, blood coagulation, and fibrinolysis were measured in 21 PNH patients.

RESULTS

As compared with normal controls, plasma fibrin peptide A (FPA) levels were significantly higher, but antithrombin-III (AT-III) and protein C (PC) antigen levels lower in the PNH patients. Plasma tissue plasminogen activator (t-PA) activities were significantly lower while plasminogen activator inhibitor (PAI) activities markedly higher in the patients than those in the controls. The levels of the blood coagulation and fibrinolysis parameters changed more notably during the occurrence of thrombosis and hemoglobinuria episodes in the PNH patients. Platelet adhesion rates, platelet aggregation rates, beta-thromboglobulin (beta-TG), and granule membrane protein-140 (GMP-140) were within the normal ranges. Plasma vWF:Ag and endothelin-1 (ET-1) concentrations were normal in the patients as well.

CONCLUSION

Prethrombotic state is present in PNH patients, which may be caused by hypercoagulability and low fibrinolytic activity.

Restricted structural gene polymorphism in the Mycobacterium tuberculosis complex indicates evolutionarily recent global dissemination

One-third of humans are infected with Mycobacterium tuberculosis, the causative agent of tuberculosis. Sequence analysis of two megabases in 26 structural genes or loci in strains recovered globally discovered a striking reduction of silent nucleotide substitutions compared with other human bacterial pathogens. The lack of neutral mutations in structural genes indicates that M. tuberculosis is evolutionarily young and has recently spread globally. Species diversity is largely caused by rapidly evolving insertion sequences, which means that mobile element movement is a fundamental process generating genomic variation in this pathogen. Three genetic groups of M. tuberculosis were identified based on two polymorphisms that occur at high frequency in the genes encoding catalase-peroxidase and the A subunit of gyrase. Group 1 organisms are evolutionarily old and allied with M. bovis, the cause of bovine tuberculosis. A subset of several distinct insertion sequence IS6110 subtypes of this genetic group have IS6110 integrated at the identical chromosomal insertion site, located between dnaA and dnaN in the region containing the origin of replication. Remarkably, study of approximately 6,000 isolates from patients in Houston and the New York City area discovered that 47 of 48 relatively large case clusters were caused by genotypic group 1 and 2 but not group 3 organisms. The observation that the newly emergent group 3 organisms are associated with sporadic rather than clustered cases suggests that the pathogen is evolving toward a state of reduced transmissability or virulence.

Routine rapid Mycobacterium species assignment based on species-specific allelic variation in the 65-kilodalton heat shock protein gene (hsp65)

OBJECTIVE

To assess the utility of automated DNA sequencing strategies for Mycobacterium species assignment and surrogate rifampin susceptibility testing of Mycobacterium tuberculosis complex isolates in a hospital-based clinical microbiology laboratory.

DESIGN

Consecutive patient specimens (n = 161) cultured in BACTEC 12B medium (growth index of 50 or greater) or on solid media (Löwenstein-Jensen) were analyzed. A 360-bp segment of a gene (hsp65) encoding a 65-kd heat shock protein was sequenced to identify species-specific allelic polymorphism. Identification of sequence variation in the rpoB gene encoding the beta subunit of RNA polymerase was used as a surrogate method to assess rifampin susceptibility in M tuberculosis complex isolates.

RESULTS

The automated DNA sequencing strategies rapidly identified virtually all mycobacteria (158 [98%] of 161) to the species level and unambiguously characterized the region of rpoB that contains mutations responsible for rifampin resistance in M tuberculosis strains. With few exceptions, DNA sequence-based species assignment data agreed with diagnostic information obtained by conventional methods. All discrepancies were due to ambiguous biochemical test data or interpretation. The rifampin susceptibility phenotype was correctly predicted for all strains by rpoB sequencing.

CONCLUSIONS

Rapid mycobacterial species assignment based on hsp65 sequencing can be routinely performed in a hospital diagnostic microbiology laboratory setting. The method is especially useful for identification of fastidious organisms, such as Mycobacterium genavense. Sequencing of the rifampin-resistance-determining region of rpoB provides a convenient surrogate strategy for predicting rifampin susceptibility in M tuberculosis complex isolates.

Ethambutol resistance in Mycobacterium tuberculosis: critical role of embB mutations

Ethambutol [(S,S')-2,2'-(ethylenediimino)di-1-butanol; EMB], is a first-line drug used to treat tuberculosis. To gain insight into the molecular basis of EMB resistance, we characterized the 10-kb embCAB locus in 16 EMB-resistant and 3 EMB-susceptible genetically distinct Mycobacterium tuberculosis strains from diverse localities by automated DNA sequencing and single-stranded conformation polymorphism analysis. All 19 organisms had virtually identical sequences for the entire 10-kb region. Eight EMB-resistant organisms had mutations located in codon 306 of embB that resulted in the replacement of the wild-type Met residue with Ile or Val. Automated sequence analysis of the 5' region (1,892 bp) of embB in an additional 69 EMB-resistant and 30 EMB-susceptible M. tuberculosis isolates from diverse geographic localities and representing 70 distinct IS6110 fingerprints confirmed the unique association of substitutions in amino acid residue 306 of EmbB with EMB resistance. Six other embB nucleotide substitutions resulting in four amino acid replacements were uniquely found in resistant strains. Sixty-nine percent of epidemiologically unassociated EMB-resistant organisms had an amino acid substitution not found in susceptible strains, and most (89%) replacements occurred at amino acid residue 306 of EmbB. For strains with the Met306Leu or Met306Val replacements EMB MICs were generally higher (40 microg/ml) than those for organisms with Met306Ile substitutions (20 microg/ml). The data are consistent with the idea that amino acid substitutions in EmbB alter the drug-protein interaction and thereby cause EMB resistance.

[Prevalence of diabetes and its risk factors in China 1994. National Diabetes Prevention and Control Cooperative Group]

We studied the prevalence of diabetes and impaired glucose tolerance (IGT) and their risk factors in the population of China. It was a population-based, cross-sectional study of 224,251 residents aged 25 years and over in 19 provinces and areas, including cities and rural areas of the North, South, East, West and central China. Using 1985 WHO criteria, We found the prevalence of diabetes and IGT were 2.51% and 3.20% respectively in 213,515 subjects aged 25 to 64 years. 70.33% of the subjects had newly recognised diabetes. The prevalence of diabetes in China is about 3 times higher than it was ten years ago, and the rate is increasing faster in the countryside than in cities. On average, subjects with diabetes are older, have higher personal annual incomes, and have more frequently a family history of diabetes. They also have higher mean body mass index (BMI), ratio of circumference of the waist to hip, systolic blood pressure, diastolic blood pressure and a greater prevalence of hypertension. They perform less physical activity and receive less education than persons with normal OGTT. Multiple logistic, stepwise regression analysis shows that age, BMI (or WHR), family history of diabetes, hypertension, less physical activity and higher annual income are independent risk factors of NIDDM, and that low education is also an independent risk factor of NIDDM in people with higher personal annual income.

[The changes and relation among platelet function, plasma heparin and anti-coagulation-III: activity in patients with hemorrhagic fever with renal syndrome]

Blood platelet count (BPC), platelet adhesive rate (PAdT), platelet aggregate rate (PAgT), plasma heparin and anti-coagulation-III: activity (AT-III: alpha) were determined in 55 cases with hemorrhagic fever with renal syndrome (HFRS). In these patients, decreased BPC, defect PAdT, PAgT, increased plasma heparin as well as decreased AT-III: a were found, moreover, these changes were much notable in patients with severe type. A positive correlation existed between plasma heparin and BPC, PAdT, PAgT in cases with 80% AT-III: alpha or above (r values were -0.4344, -.7157 and -0.5547 respectly, p<0.01). The results suggested that plasma heparin may be one of factors resulting in decreased BPC and defect platelet function in HFRS patients with 80% AT-III: alpha or above.

[The genetical effects of degUS gene in Bacillus subtilis Ki-2-132]

Using the methods of recombination and gene disruption, the effects of degUS gene in Bacillus subtilis Ki-2-132 were studied. The results showed that the gene could affect all protease-producing, competence formation, cell mobility and repression effects of glucose on protease-production. This implies that it is a pleitropic gene in Bacillus subtilis Ki-2-132. The disruption of the gene caused morphological changes and repressed the expression of aprE in vectors.

[Molecular evolution of MHC DQA genes. I. The maintenance of interallelic divergence and the influence of GC content on gene structure]

The analyses of the proportion of synonymous and missense nucleotide substitution (PS and PN) in different exons, antigen recognition sites (ARS) and non-ARS of EN2 (NAEN2) of 23 alleles at MHC DQA loci in 7 mammal species gave rise to the following findings. (1) PN was about twice as much as PS in ARS among the alleles at DQA1 of any given species, i.e. 7 alleles at HLA-DQA1 or 8 alleles at IaAa this accords with overdominant selection; (2) PS showed more or less the same as PN in ARS among different loci (DQA1 or DQA2 in different species, or DQA1 and DQA2 in one species) or NAEN2 of all comparative pairs, this conforms the expectation of neutral selection; (3) In exon4 and exon3, not only was the substitution proportion extremely low, but also PS was much higher than PN (the ratio PS over PN is 19.5 in alleles at IaAa of mouse and 4 among alleles at different loci), this coincides obviously with purification selection. The analysis of GC content of MHC DQA showed that its peaks were in the regions corresponding to the middle bulks of some domains, that the highest and constant level was in exon4 and that GC content in the third codon position (GC III content) associates inversely with PS. These results indicate that the specified maintenance mechanisms of interallelic diversity relevant to their functions exist in given exons corresponding to some domains of the same MHC DQA locus and GC III content is an important factor in keeping the structure and function of gene under selection constraint. The method for estimating nucleotide substitution proportion was modified.

The "proper" binormal model: parametric receiver operating characteristic curve estimation with degenerate data

RATIONALE AND OBJECTIVES

The authors assessed the use of a "proper" binormal model and a new algorithm for maximum-likelihood estimation of receiver operating characteristic (ROC) curves from degenerate data.

METHODS

The proper binormal ROC model uses as its decision variable a monotonic transformation of the likelihood ratio that is associated with a pair of normal distributions, thereby ensuring fitted ROC curves with monotonic slope but maintaining a relationship with the conventional binormal model. A computer program entitled PROPROC was used to fit proper ROC curves to data obtained from computer-simulated and real observer studies.

RESULTS

ROC indexes such as total area were estimated with PROPROC and compared with the corresponding values obtained from the conventional procedures.

CONCLUSION

The proper binormal ROC model overcomes the problem of degeneracy in ROC curve fitting. PROPROC is highly robust and yields ROC estimates with less bias and greater precision than those obtained with the conventional binormal model.

Subspecific differentiation of Mycobacterium avium complex strains by automated sequencing of a region of the gene (hsp65) encoding a 65-kilodalton heat shock protein

To develop a strategy for rapid species assignment and strain differentiation of Mycobacterium avium complex (MAC) organisms, the sequence of a 360-bp region of the gene (hsp65) encoding a 65-kDa heat shock protein was determined for 56 isolates, including 21 patient isolates and 35 reference strains. Eleven hsp65 alleles were identified, and there was no sharing of alleles between strains classified as M. avium and Mycobacterium intracellulare based on serovar and species-specific DNA hybridization probes. Phylogenetic analysis showed that 30 strains had one of two hsp65 alleles which were found in known M. avium organisms, 23 strains had one of six alleles allied with known M. intracellulare organisms, and three MAC isolates had one of three hsp65 alleles that differed substantially from the consensus M. avium and M. intracellulare hsp65 sequences. Estimates of strain relationships based on the sequences of hsp65 and the 16S-23S ribosomal DNA internal transcribed spacer were similar. Automated DNA sequencing of a 360-bp region of the hsp65 gene from MAC organisms provides a rapid and unambiguous marker system for strain differentiation and permits specific assignment of these acid-fast organisms for diagnostic purposes.

[Clinical characteristics and main diagnostic points of latent autoimmune diabetes mellitus in adults]

To understand latent autoimmune diabetes mellitus in adults (LADA), we compared the clinical characteristics, fasting plasma glucose and C-peptide level, genetic frequency of HLA-DQA1, -DQB1 chain in 25 patients with LADA, 57 patients with insulin-dependent diabetes mellitus (IDDM, 21 patients with children-onset IDDM, 36 patients with adult-onset IDDM with ketosis), 38 patients with NIDDM (mild and moderate 30 patients and severe 8) and 42 normal persons. The onset of age was 20-48 years old associated with obvious polyphagia, and weight loss. Body mass index (BMI) was < or = 25 and fasting plasma glucose was > or = 16.5 mmol/L (297 mg/dl). Fasting and 1, 2 hour post prandial C-peptide level showed low and flatter curve (0.4, 0.8 and 0.8 nmol/L respectively). Glutamate decarboxylase (GAD) antibody was positive. HLA-DQ beta chain substitution of aspartate molecule was at position 57 (susceptic gene). LADA could be diagnosed if a patient has the first point and any point of the second to the fourth point. Patients with LADA should take diet, exercises, especially insulin as early as possible in order to control fasting and post prandial plasma glucose, and prevent from further destroy of residue islet B cells and reduce diabetic complications of eye, kidney and nerve.

Mutations associated with pyrazinamide resistance in pncA of Mycobacterium tuberculosis complex organisms

A gene (pncA) with mutations associated with pyrazinamide resistance in Mycobacterium tuberculosis complex members was characterized in 67 pyrazinamide-resistant and 51 pyrazinamide-susceptible isolates recovered from diverse geographic localities and anatomic sites and typed by IS6110 profiling. All pyrazinamide-susceptible organisms had identical pncA alleles. In striking contrast, 72% of the 67 resistant organisms had pncA mutations that altered the primary amino acid sequence of pyrazinamidase. A total of 17 previously undescribed mutations were found, including upstream mutations, missense changes, nucleotide insertions and deletions, and termination mutations. The mutations were arrayed along virtually the entire length of the gene. These data are further evidence that most drug resistance in M. tuberculosis is due to simple mutations occurring in chromosomally encoded genes rather than to acquisition of resistance genes by horizontal transfer events.

Analysis of the oxyR-ahpC region in isoniazid-resistant and -susceptible Mycobacterium tuberculosis complex organisms recovered from diseased humans and animals in diverse localities

Automated DNA sequencing was used to analyze the oxyR-ahpC region in 229 Mycobacterium tuberculosis complex isolates recently recovered from diseased humans and animals. The entire 1,221-bp region was studied in 118 isolates, and 111 other isolates were sequenced for oxyR, ahpC, or the 105-bp oxyR-ahpC intergenic region. The sample included isoniazid (INH)-susceptible and -resistant organisms in which the katG gene and inhA locus had previously been sequenced in their entirety to identify polymorphisms. A total of 16 polymorphic sites was identified, including 5 located in oxyR, 2 in ahpC, and 9 in the 105-bp intergenic region. All polymorphic sites located in the intergenic region, and the two missense substitutions identified in ahpC, occurred in INH-resistant organisms. In contrast, there was no preferential association of polymorphisms in oxyR, a pseudogene, with INH-resistant organisms. Surprisingly, most INH-resistant strains with KatG codon 315 substitutions that substantially reduce catalase-peroxidase activity and confer high MICs of INH lacked alterations in the ahpC gene or oxyR-ahpC intervening region. Taken together, the data are consistent with the hypothesis that some polymorphisms located in the ahpC-oxyR intergenic region are selected for after reduction in catalase or peroxidase activity attributable to katG alterations arising with INH therapy. These mutations are uncommon in recently recovered clinically significant organisms, and hence, there is no strict association with INH-resistant patient isolates. The ahpC compensatory mutations are apparently uncommon because strains with a KatG null phenotype are relatively rare among epidemiologically independent INH-resistant organisms.

Identification and subspecific differentiation of Mycobacterium scrofulaceum by automated sequencing of a region of the gene (hsp65) encoding a 65-kilodalton heat shock protein

Mycobacterium scrofulaceum is most commonly recovered from children with cervical lymphadenitis, although it also accounts for approximately 2% of the mycobacterial infections in AIDS patients. Species assignment of M. scrofulaceum isolated by conventional techniques can be difficult and time-consuming. To develop a strategy for rapid species assignment of these organisms, a 360-bp region of the gene (hsp65) encoding a 65-kDa heat shock protein in 37 isolates from diverse sources was sequenced. Eight hsp65 alleles were identified, and these sequences formed phylogenetic clusters and lineages largely distinct from other Mycobacterium species. There was incomplete correlation between serovar designation and hsp65 allele assignment. The hsp65 data correlated strongly with the results of sequence analysis of the gene coding for 16S rRNA. Automated DNA sequencing of a 360-bp region of the hsp65 gene provides a rapid and unambiguous method for species assignment of these acid-fast organisms for diagnostic purposes.

Long-term blood pressure control in older Chinese patients with isolated systolic hypertension: a progress report on the Syst-China trial

This report on the ongoing double-blind placebo-controlled Syst-China trial investigated whether antihypertensive drug treatment based mainly on a calcium entry blocker and a converting enzyme inhibitor, would be suitable for maintaining long-term blood pressure (BP) control in older Chinese patients (average age: 67 years) with isolated systolic hypertension (systolic pressure 160-219 mm Hg and diastolic pressure < 95 mm Hg). Active treatment consisted of nitrendipine (10- 40 mg/day) with the possible addition of captopril (12.5- 50 mg/day) and hydrochlorothiazide (12.5-50 mg/day), as necessary to reduce systolic pressure to a level of 150 mm Hg or lower and by at least 20 mm Hg. Matching placebos were used in the control group. This progress analysis was restricted to BP control up to 3 years of follow-up. The placebo (n = 1134) and active treatment n = 1245) groups had similar characteristics at enrolment. The sitting BP averaged 170/86 mm Hg. Systolic pressure fell (P < 0.001) on average 8 mm Hg more on active treatment than on placebo and diastolic pressure 3 mm Hg more. Fewer patients remained on monotherapy in the placebo than in the active treatment group (P < 0.001); on placebo the second and third line medications were started more frequently (P < 0.001). This progress report showed that significant BP reduction can be achieved and maintained in older Chinese patients treated with a calcium antagonist, associated with a converting-enzyme inhibitor and a thiazide, as necessary. Whether this BP reduction would result in a clinically meaningful decrease of cardiovascular complications is still under investigation.

Comparative antimycobacterial activities of rifampin, rifapentine, and KRM-1648 against a collection of rifampin-resistant Mycobacterium tuberculosis isolates with known rpoB mutations

A collection of 24 rifampin-resistant clinical isolates of Mycobacterium tuberculosis with characterized RNA polymerase beta-subunit (rpoB) gene mutations was tested against the antimycobacterial agents rifampin, rifapentine, and KRM-1648 to correlate levels of resistance with specific rpoB genotypes. The results indicate that KRM-1648 is more active in vitro than rifampin and rifapentine, and its ability to overcome rifampin resistance in strains with four different genetic alterations may prove to be useful in understanding structure-function relationships.

[Chemical constituents of Aster albscens Hand.-Mazz]

Four compounds, stigmasterol, D-hurulon-14-en-3-ol, stigma-delta7.22-dien-3beta-palmitate and friedelin were isolated from the root of Aster albscens for the first time. Their structures were elucidated by spectral methods.

Identification of a polymorphic nucleotide in oxyR specific for Mycobacterium bovis

Automated sequence analysis of a 410-bp region of the axyR gene in 105 Mycobacterium tuberculosis complex isolates identified a polymorphic nucleotide that differentiated Mycobacterium bovis isolates from other complex members. All 29 M. bovis isolates sequenced had an adenine residue at nucleotide 285, whereas all 76 other complex isolates had a guanine residue. PCR-restriction fragment length polymorphism analysis of oxyR with restriction endonuclease AluI in an additional 255 complex isolates from widespread intercontinental sources confirmed and extended the unique association of adenine at position 285 with M. bovis isolates.

Prevalence and incidence of NIDDM in Daqing City

OBJECTIVE

To investigate the prevalence and incidence of non-insulin dependent diabetes (NIDDM) in China by WHO criteria.

METHODS

In the prevalence survey of NIDDM all 110660 participants (55391 men, 53269 women) were inhabitants of Daqing City, the largest oil center in northeast China, accounting for 87.3% of the 25 to 74 aged population in this city. They were screened by measuring two-hour plasma glucose concentrations (PG2 h) after a breakfast containing at least 80 g of carbohydrate, then a standard oral glucose tolerance test (OGTT, 75 g glucose load) was performed in 4209 subjects with PG2 h more than 6.67 mmol/L in this screen. NIDDM and impaired glucose tolerance (IGT) were diagnosed using WHO criteria. Incidence survey was made in 36471 non-diabetics identified in the prevalence survey. Two-hour urine-glucose after breakfast was determined during first screen. The urine-glucose trace or positive subjects were then followed by OGTT. Glucose was measured by glucose oxidation method.

RESULTS AND CONCLUSIONS

In prevalence survey, 630 newly diagnosed NIDDM (296 males, 334 females) and 596 IGT (318 males, 278 females) were found in 110660 (male:female = 55391/53269) studied subjects in addition to 190 previously diagnosed NIDDM. Thus the total prevalence of NIDDM was 7.7/1000, and IGT was 5.5/1000. Standardized to the Chinese population in 1982, the prevalences are 12.6/1000 (95% CI = 12.0/1000-13.3/1000) and 7.7/1000 (95% CI = 7.16/1000-8.19/1000) respectively. In the incidence survey, 191 NIDDM (103 males, 88 females) were diagnosed in the 36471 (male:female = 18801/17670) non-diabetics from 1986 to 1990, thus the annual incidence of NIDDM was 131/100000 (137 males, 125 females). Standardized incidence is 131/100000 (95% CI = 94/100000-168/ 100000). It is estimated that there would be more than 700 thousand new diabetics per year in 24-74 years old Chinese if Chinese population were 1.3 billion in the early 21st century.

Hyperattenuating rim on noncontrast CT of the liver: probable peritumoral sparing of fatty infiltration

CT scans showing a hyperattenuating rim within the liver were retrospectively evaluated in 10 patients to clarify the character, aetiology and clinical significance. All patients had hepatic tumours (7 cavernous haemangiomas in 6 patients, 3 metastatic tumours and 1 hepatocellular carcinoma) as well as fatty infiltration of the liver. Typical features of the hyperattenuating rim on noncontrast CT of the liver included (1) attenuation similar to that of the spleen, (2) a circular or semicircular shape, (3) a width of a few millimeters, (4) peritumoral localization and (5) loss of visualization with contrast enhancement. No such rims were noted around hepatic tumours unassociated with fatty infiltration. Peritumoral sparing of fatty infiltration was inferred. A hyperattenuating rim on noncontrast liver CT, although rare, suggests the presence of a hepatic tumour in fatty liver.

Rat brain cannabinoid receptor modulates N-type Ca2+ channels in a neuronal expression system

Modulation of neuronal ion channels by the cloned rat brain CB1 cannabinoid receptor was investigated with the use of a heterologous neuronal expression system. Transient expression of the rat brain CB1 cannabinoid receptor was accomplished through microinjection of in vitro transcribed cRNA into the cytoplasm of enzymatically dissociated adult rat superior cervical ganglion neurons. The cannabimimetic aminoalkylindole WIN 55,212-2 inhibited whole-cell Ca2+ currents in neurons injected 16-25 hr previously with rat brain CB1 cannabinoid receptor cRNA. Inhibition of the Ca2+ current was voltage and concentration dependent, with a maximal inhibition of 73% and an IC50 value of 47 nM. The synthetic cannabinoid analogue CP55,940 also inhibited Ca2+ currents, with a maximal inhibition of 38% and an IC50 value of 7 nM. Ca2+ current inhibition was blocked by inclusion of guanosine-5'-O-(2-thiodiphosphate) in the intracellular patch pipette solution or by pretreatment with pertussis toxin. Pretreatment with the N-type Ca2+ channel antagonist omega-conotoxin GVIA reduced the inhibition by 100 nM WIN 55,212-2 from 44% to 6%, indicating that N-type Ca2+ channels are a target of cannabinoid action. On washout of WIN 55,212-2, the Ca2+ current amplitude "overrecovered" in 47% of the neurons tested. Anandamide, the endogenous cannabimimetic compound, had an inconsistent effect on the voltage-dependent Ca2+ currents in the majority of neurons microinjected with cannabinoid receptor cRNA. Ca2+ channels were a specific effector target of the cannabinoid receptor, as two different K+ currents, the M current and the A current, were not modulated by the cannabimimetic WIN 55,212-2.

Characterization of rpsL and rrs mutations in streptomycin-resistant Mycobacterium tuberculosis isolates from diverse geographic localities

Two genes (rpsL and rrs) with mutations associated with streptomycin resistance in Mycobacterium tuberculosis were characterized in 78 streptomycin-resistant and 61 streptomycin-susceptible isolates recovered from patients living in the United States, South America, Europe, Africa, and Asia. Fifty-four percent of the 78 resistant organisms had missense mutations in codon 43 of rpsL resulting in a K-43-->R substitution. Mutations in codon 88 of rpsL were also identified in four Asian isolates.

Origin and interstate spread of a New York City multidrug-resistant Mycobacterium tuberculosis clone family

OBJECTIVE

To determine whether isolates of Mycobacterium tuberculosis from New York and elsewhere that are resistant to four or more primary antimicrobial agents and responsible for widespread disease in the 1990s represent a newly emerged clone or a heterogeneous array of unrelated organisms.

SETTING

New York City area and selected locations in the United States.

PATIENTS

M tuberculosis isolates from 1953 patients in New York and multidrug-resistant isolates from six patients from other US communities.

DESIGN

Convenience sample of all M tuberculosis strains (M tuberculosis isolates resistant to rifampin, streptomycin, isoniazid, and ethambutol, and sometimes ethionamide, kanamycin, capreomycin, or ciprofloxacin) submitted to the Public Health Research Institute Tuberculosis Center since 1991 and samples submitted to the Centers for Disease Control and Prevention from throughout the United States. The samples submitted were representative of the New York City strains of M tuberculosis.

MAIN OUTCOME MEASURE

Characterization of resistant M tuberculosis strains studied by IS6110 and polymorphic GC-rich repetitive sequence (PGRS) hybridization patterns, multiplex polymerase chain reaction (PCR) analysis, and automated DNA sequencing of genes containing mutations associated with resistance to rifampin (rpoB), isoniazid (katG and inhA locus), and streptomycin (strA and rrs).

RESULTS

Multidrug-resistant M tuberculosis isolates were recovered from 253 New York City patients and had the same or closely allied IS6110 and PGRS patterns, multiplex PCR type, and gene mutations associated with resistance to rifampin, isoniazid, and streptomycin. Isolates with these same molecular characteristics were recovered from patients in Florida and Nevada, health care workers in Atlanta, Ga, and Miami, Fla, and an individual who recently moved from New York City to Denver, Colo, and caused disease or skin test conversion in at least 12 people in a nursing home environment.

CONCLUSIONS

The results document the molecular origin and spread of progeny of a closely related family of multidrug-resistant M tuberculosis strains that have recently shared a common ancestor and undergone clonal expansion. The multidrug-resistant phenotype in these organisms arose by sequential acquisition of resistance-conferring mutations in several genes, most likely as a consequence of antibiotic selection of randomly occurring mutants in concert with inadequately treated infections. Dissemination of these difficult-to-treat bacteria throughout New York City and to at least four additional US cities has adverse implications for tuberculosis control in the 21st century.

Fatty mass in the inferior vena cava at CT: lipoma or normal variant?

Fatty mass in the intrahepatic portion of the inferior vena cava (IVC) is an unusual lesion. We describe two cases of fatty mass appearing in the lumen of the IVC on CT and MRI study. We assume that this can be regarded as a benign process, and is mostly a normal variant.

Detection of human papillomavirus types 16, 18 DNA related sequences in bronchogenic carcinoma by polymerase chain reaction

In studying the relationship between human papillomavirus (HPV) and bronchogenic carcinoma, "high-risk" HPV 16, 18 DNA sequences were detected in samples from 50 lung cancer patients, 18 patients with benign pulmonary diseases and 4 fetal lung tissues by polymerase chain reaction (PCR) and dot-blot hybridization with biotin-labelled probes. The results showed that HPV 16, 18 DNA related sequences were found in 32% of lung cancer specimens, with 10 cases of HPV 16, 5 cases of HPV 18 and 1 case of both types. 48.15% (13/27) of squamous cell carcinomas were shown to be positive for HPV 16, 18 DNA. In addition, two adenocarcinomas and one small cell carcinoma were positive for HPV 16 DNA. No specimens from benign diseases tissues and fetal lung tissues showed positive results. These results suggest that primary bronchogenic carcinoma is related to HPV infection.

A lectin-like peptide isolated from the venom of the Chinese bird spider Selenocosmia huwena

A peptide with haemagglutination activity was isolated from the venom of the Chinese bird spider Selenocosmia huwena by means of ion-exchange and reverse-phase high-performance liquid chromatography. This peptide, named SHLP-I, agglutinates human and mice erythrocytes at a minimum concentration of 125 micrograms/ml and 31 micrograms/ml, respectively. It consists of 32 amino acid residues including 3 Trp and 6 Cys residues, the latter of which form three disulfide bounds. The complete amino acid sequence was determined. The N-terminal and C-terminal residues were Gly and Trp, respectively. SHLP-I shows homology with a fragment of great nettle lectin and with huwentoxin-I from the venom of the same spider.

Genetic diversity and relationships among Streptococcus pyogenes strains expressing serotype M1 protein: recent intercontinental spread of a subclone causing episodes of invasive disease

Chromosomal diversity and relationships among 126 Streptococcus pyogenes strains expressing M1 protein from 13 countries on five continents were analyzed by multilocus enzyme electrophoresis and restriction fragment profiling by pulsed-field gel electrophoresis. All isolates were studied for the presence of the gene encoding streptococcal pyrogenic exotoxin A by PCR. Strain subsets were also examined by automated DNA sequencing for allelic polymorphism in genes encoding M protein (emm), streptococcal pyrogenic exotoxin A (speA), streptokinase (ska), pyrogenic exotoxin B (interleukin-1 beta convertase) (speB), and C5a peptidase (scp). Seven distinct emm1 alleles that encode M proteins differing at one or more amino acids in the N-terminal variable region were identified. Although substantial levels of genetic diversity exist among M1-expressing organisms, most invasive disease episodes are caused by two subclones marked by distinctive multilocus enzyme electrophoretic profiles and pulsed-field gel electrophoresis restriction fragment length polymorphism (RFLP) types. One of these subclones (ET 1/RFLP pattern 1a) has the speA gene and was recovered worldwide. Identity of speA, emm1, speB, and ska alleles in virtually all isolates of ET 1/RFLP type 1a means that these organisms share a common ancestor and that global dispersion of this M1-expressing subclone has occurred very recently. The occurrence of the same emm and ska alleles in strains that are well differentiated in overall chromosomal character demonstrates that horizontal transfer and recombination play a fundamental role in diversifying natural populations of S. pyogenes.

[Effect of dietary and/or exercise intervention on incidence of diabetes in 530 subjects with impaired glucose tolerance from 1986-1992]

577 subjects with impaired glucose tolerance (IGT) aged from 25 to 74 were identified in Daqing in 1986. They were stratified according to BMI > or = 25 (352 cases) and BMI < 25 (225 cases) and subjects in each BMI group were randomly assigned to four groups: control, diet, exercise and diet plus exercise intervention groups (each group had similar age, BMI, fasting and 2-hour plasma glucose level). A six-year follow up study indicated that incidence of diabetes per 100-person-year was 15.7, 10.0, 8.3 and 9.6 in control, diet, exercise and diet plus exercise groups respectively. Proportional hazards regression analysis controlling for differences in baseline factors (age, sex, BMI and plasma glucose) showed that diet and/or exercise intervention were inversely related to the incidence of diabetes. The better the actual intervention, the less the incidence of diabetes. Therefore, the results strongly indicate that diet and/or exercise intervention treatment are effective methods to reduce the incidence of diabetes.

Analysis of noise properties of a class of exact methods of inverting the 2-D exponential radon transform [SPECT application]

A general approach that the authors proposed elsewhere reveals the intrinsic relationship among methods for inversion of the 2-D exponential Radon transform described by Bellini et al. (1979), by Tretiak and Metz (1980), by Hawkins et al. (1988), and by Inouye et al. (1989). Moreover, the authors' approach provides an infinite class of linear methods for inverting the 2-D exponential Radon transform. In the work reported here, the authors systematically investigated the noise characteristics of the methods in this class, obtaining analytical forms for the autocovariance and the variance of the images reconstructed by use of various methods. The noise properties of a new "quasi-optimal" method were then compared theoretically to those of other methods of the class. The authors' analysis demonstrates that the quasi-optimal method achieves smaller global variance in the reconstructed images than do the other methods of the class. Extensive numerical simulation studies confirm this prediction.