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G Ma

Publications and source records attributed to G Ma.

101 records · Page 6Linked to original sources
PubMed1986

Diagnostic value of thyrotropin concentrations in serum as measured by a sensitive immunoradiometric assay.

A new, highly sensitive immunoradiometric thyrotropin (TSH) assay involving solid-phase-coupled monoclonal antibodies (Boots-Celltech Sucrosep IRMA-TSH) has been evaluated in a wide variety of patients with thyroidal and nonthyroidal illnesses and the results compared with those obtained by conventional diagnostic TSH RIAs. The sensitivity of the present assay ranged from 0.036 to 0.1 milli-int. unit/L (mean 0.056). TSH, measurable in serum of each of 128 euthyroid patients, ranged from 0.1 to 6.3 milli-int. units/L (mean 1.7, SD 1.1). Similar concentrations were found in 15 healthy pregnant women. TSH was undetectable in 27 hyperthyroid patients, of whom six were tested with thyroliberin stimulation and failed to respond. The mean TSH concentration measured in 62 seriously ill hospital patients of 2.7 (SD 2.5) milli-int. units/L was significantly higher (p less than 0.05) than in the euthyroid patients. Basal values and peak TSH responses to thyroliberin testing correlated well (r = 0.63, n = 48), irrespective of clinical diagnosis. We conclude that the present assay readily discriminates between euthyroid and hyperthyroid patients and should replace conventional TSH RIAs in diagnostic laboratories.

Adolescent↗
PubMed1986

Binding characteristics of thyroxin binding globulin in serum of normal, pregnant, and severely ill euthyroid patients.

Serum from normal, pregnant, and severely ill patients was stripped of endogenous thyroid hormones and diluted 1100-fold in barbital buffer. We then used it to study the binding characteristics of thyroxin binding globulin (TBG), noting significant differences in binding capacities among the groups. The mean (+/- SD) triiodothyronine/thyroxin ratio for binding capacity was 18 +/- 4 for normal subjects. The ratio was significantly increased in pregnant patients, 21 +/- 4 (p less than 0.05), and significantly lower in severely ill patients, 12 +/- 4 (p less than 0.05). When serum was diluted before assay, to give a uniform TBG concentration among groups, these apparent differences in binding characteristics were eliminated. It therefore is unlikely that different molecular species of TBG account for the variations in binding characteristics in these clinical states. Apparently, the distribution of thyroxin and triiodothyronine among the binding sites on TBG changes with variations in TBG concentration. This may explain the discrepancies observed in the concentrations of free thyroid hormones as estimated by various methodologies.

Binding, Competitive↗
PubMed1986

Immunoradiometric assay with use of magnetizable particles: measurement of thyrotropin in blood spots, to screen for neonatal hypothyroidism.

We adapted a commercial immunoradiometric assay (IRMA) to measure thyrotropin in filter-paper blood spots. Two 3-mm blood spots are used for each standard and sample. These are incubated for 2 h with radiolabeled antibody and for 30 min with magnetic antibody, followed by a 10-min separation procedure. Assay sensitivity is 6 milli-int. units/L. Coefficients of variation (precision profile of the standard curve) ranged from 4.3 to 9.6%. The coefficient of correlation (r) between thyrotropin concentrations in the blood spots and in serum was 0.93. Pre-elution of the blood spots is necessary for short incubation time. Short incubation time, little need for specialized equipment, the high precision and sensitivity characteristic of IRMA, and ease of collection, transport, and storage of the blood-spot samples make this assay suitable for neonatal hypothyroid screening.

Humans↗
PubMedDate not supplied

Inheritance and allelism tests of Raiden soybean for resistance to soybean mosaic virus.

The gene symbol Rsv2 was previously assigned to the gene in the soybean [Glycine max (L.) Merr.] line OX670 for resistance to soybean mosaic virus (SMV). The Rsv2 gene was reported to be derived from the Raiden soybean (PI 360844) and to be independent of Rsv1. Accumulated data from our genetic experiments were in disagreement with this conclusion. In this study, Raiden and L88-8431, a Williams BC5 isoline with SMV resistance derived from Raiden, were crossed with two SMV-susceptible cultivars to investigate the mode of inheritance of SMV resistance in Raiden. They were also crossed with five resistant cultivars to examine the allelomorphic relationships of the Raiden gene with other reported genes at the Rsv1 locus. F1 plants, F2 populations, and F2-derived F3 (F2:3) lines were tested with SMV strains G1 or G7 in the greenhouse or in the field. The individual plant reactions were classified as resistant (R, symptomless), necrotic (N, systemic necrosis), or susceptible (S, mosaic). The F2 populations from R x S crosses segregated in a ratio of 3 (R + N):1 S and the F2:3 lines from Lee 68 (S) x Raiden (R) exhibited a segregation pattern of 1 (all R):2 segregating:1 (all S). The F2 populations and F2:3 progenies from all R x R crosses did not show any segregation for susceptibility. These results demonstrate that the resistance to SMV in Raiden and L88-8431 is controlled by a single dominant gene and the gene is allelic to Rsv1. The heterozygous plants from R x S and R x N crosses exhibited systemic necrosis when inoculated with SMV G7, indicating a partial dominance nature of the resistance gene. Raiden and L88-8431 are both resistant to SMV G1-G4 and G7, but necrotic to G5, G6, and G7A. Since the resistance gene in Raiden is clearly an allele at the Rsv1 locus and it exhibits a unique reaction to the SMV strain groups, assignment of a new gene symbol, Rsv1-r, to replace Rsv2 would seem appropriate. Further research is ongoing to investigate the possible existence of the Rsv2 locus in OX670 and its relatives.

Crosses, Genetic↗
PubMedDate not supplied

Complementary action of two independent dominant genes in Columbia soybean for resistance to Soybean mosaic virus.

A stem-tip necrosis disease was observed in the soybean [Glycine max (L.) Merr.] cultivar Columbia and its derivative OX686 when infected with a necrosis-causing strain of Soybean mosaic virus (SMV) in Canada. A dominant gene named Rsv3 was found in OX686 for the necrotic reaction. In the present research we have found that Columbia is resistant to all known SMV strains G1-G7, except G4. Genetic studies were conducted to investigate the inheritance of resistance in Columbia and interactions of resistance gene(s) with SMV strains. Columbia was crossed with a susceptible cultivar, Lee 68, and with resistant lines PI96983, Ogden, and LR1, each possessing a resistance gene at the Rsv1 locus. F(1) individuals, F(2) populations, and F(2:3) lines from these crosses were inoculated with G7 or G1 in the greenhouse. Our inheritance data confirmed the presence of two independent dominant genes for SMV resistance in Columbia. Results from allelism tests further demonstrate that the two genes (referred to as R3 and R4 in this article) in Columbia were independent of the Rsv1 locus. R3 appears to be the same gene previously reported as Rsv3 in OX686, which was derived from Columbia. The R3 gene confers resistance to G7, but necrosis to G1. The other gene, R4, conditions resistance to G1 and G7 at the early seedling stage and then a delayed mild mosaic reaction (late susceptible) 3 weeks later. Plants carrying both the R3 and R4 genes were completely resistant to both G1 and G7, indicating that the two genes interact in a complementary fashion. Plants heterozygous for R3 or R4 exhibited systemic necrosis or late susceptibility, suggesting that the resistance is allele dosage dependent. The R4 gene appeared epistatic to R3 since it masked expression of necrosis associated with the response of R3. The complementary interaction of two resistance genes, as exhibited in Columbia, can be useful in development of soybean cultivars with multiple and durable resistance to SMV.

Colombia↗
PubMedDate not supplied

Genetic study of a lethal necrosis to soybean mosaic virus in PI 507389 soybean.

PI 507389 soybean [Glycine max (L.) Merr.], a large-seeded line from Japan, exhibits a rapid, lethal, necrotic response to strains G1, G2, G5, and G6 of soybean mosaic virus (SMV). Unlike the hypersensitive necrotic reaction, this stem-tip necrosis can be a serious threat to soybean production. To investigate the genetic basis of lethal necrosis (LN), PI 507389 was crossed with the susceptible (S) cv. Lee 68 and with resistant (R) lines PI 96983, cv. York, and cv. Marshall, which carry single dominant genes for SMV resistance at the Rsv1 locus. F(1) plants, F(2) populations, and F(2:3) lines were inoculated with G1 and G6 in the greenhouse or in the field. Results indicated that LN is controlled by a single gene allelic to Rsv1, and this allele in PI 507389 is recessive to R alleles in PI 96983, York, and Marshall. The LN allele is codominant with the allele for S, for the heterozygotes showed a mixed phenotype of both necrosis (N) and mosaic (M) symptoms (NM). The LN allele becomes recessive to the S allele as the mixed NM shifts to S at a later stage in response to more virulent strains. The gene symbol Rsv1-n is assigned for the allele conferring LN in PI 507389. Rsv1-n is the only allele at the Rsv1 locus conditioning N to G1 and no R to any other SMV strains, and thus a unique genotype for SMV strain differentiation. The phenotypic expression of heterozygotes and the dominance relationships among R, N, and S depend on the virulence of SMV strains, source of alleles, and developmental stage.

Alleles↗
PubMedDate not supplied

Genetics of resistance to two strains of soybean mosaic virus in differential soybean genotypes.

There are seven pathotypes of soybean mosaic virus (SMV) representing seven strain groups (G1-G7) in the United States. Soybean genotypes [Glycine max (L.) Merr.] may exhibit resistant (R), susceptible (S), or necrotic (N) reactions upon interacting with different SMV strains. This research was conducted to investigate whether reactions to two SMV strains are controlled by the same gene or by separate genes. Two SMV-resistant soybean lines, LR1 and LR2, were crossed with the susceptible cultivar Lee 68. LR1 contains a resistance gene Rsv1-s and is resistant to strains G1-G4 and G7. LR2 contains the Rsv4 gene and is resistant to strains G1-G7. Two hundred F(2:3) lines from LR1 x Lee 68 and 262 F(2:3) lines from LR2 x Lee 68 were screened for SMV reaction. Seeds from each F2 plant were randomly divided into two subsamples. A minimum of 20 seeds from each subsample were planted in the greenhouse and plants were inoculated with either G1 or G7. G1 is the least virulent, whereas G7 is the most virulent strain of SMV. The results showed that all the F(2:3) lines from both crosses exhibited the same reaction to G1 and G7. No recombinants were found in all the progenies for reactions to G1 and G7 in either cross. The results indicate that reactions to both G1 and G7 are controlled by either the same gene or very closely linked genes. This research finding is valuable for studying the resistance mechanism and interactions of soybean genotypes and SMV strains and for breeding SMV resistance to multiple strains.

Crosses, Genetic↗
PubMedDate not supplied

Confidence bands for receiver operating characteristic curves.

Receiver operating characteristic (ROC) curves are mapped out by the two types of errors that are generated by varying the decision threshold used to determine which subjects will be considered abnormal. Under the conventional binormal model for the ROC curve, two-sided and one-sided simultaneous confidence bands for an entire ROC curve, or for a portion of an ROC curve, are constructed by employing Working-Hotelling-type confidence bands for simple linear regression. Pointwise confidence bands are presented for comparison. The cases in which one has only asymptotically normally distributed estimates of the parameters of the ROC curve and consistent estimates of their variance-covariance matrix are emphasized. The methods extend beyond binormal models.

Confidence Intervals↗