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Biomedical subjects

A T Ricker

Publications and source records attributed to A T Ricker.

11 recordsLinked to original sources
PubMed1995

Adrenocorticotropin receptor gene mutations in familial glucocorticoid deficiency: relationships with clinical features in four families.

Familial glucocorticoid deficiency is an autosomal recessive syndrome of adrenal unresponsiveness to ACTH characterized by glucocorticoid deficiency, high plasma ACTH levels, and a normal renin-aldosterone axis. Defects of the ACTH receptor have been suggested as a possible cause, and we have previously reported a number of novel mutations of the ACTH receptor gene in some, but not all, cases, suggesting that familial glucocorticoid deficiency may have a heterogeneous molecular etiology. Here we report the clinical features and ACTH receptor gene analysis in four patients from different families. We found that two patients were compound heterozygotes for the S74I and R128C mutations (patient A) and I44M and L192fs frame shift mutations (patient B). The other two patients (C and D) were of different ethnic ancestry, but were both homozygous for a R146H mutation. Segregation studies within families revealed heterozygosity in the parents and several other family members. Human CRH tests in the parents of patients A and B showed normal cortisol and ACTH responses in the S74I, R128C, and I44M heterozygotes and exaggerated cortisol and ACTH responses in the L192fs heterozygote, suggesting that the physiological ACTH increment induced in this test did not reveal evidence of subclinical ACTH resistance, and that this test may not be of value in ascertaining heterozygosity.

Adrenocorticotropic Hormone↗
PubMed1989

Radioassay determination of insulin autoantibodies in NOD mice. Correlation with increased risk of progression to overt diabetes.

In an initial cross-sectional study, 29 female and 25 male nondiabetic weaned nonobese diabetic (NOD) mice of various ages (age range 30-300 days, mean 108 +/- 10 days) and 11 unweaned NOD pups were evaluated for competitive insulin autoantibodies (CIAAs) with a fluid-phase radioassay. Eleven of 54 (20%) weaned NOD mice had CIAA levels above the range (greater than 39 nU/ml) of 81 control mice. The group of NOD mice that progressed to diabetes had a significantly higher level of CIAAs than NOD mice that did not progress to diabetes (NOD mice progressing to diabetes: CIAA 63 +/- 12 nU/ml; NOD mice not progressing to diabetes: CIAA 8 +/- 4 nU/ml; P less than .02). Seven of 11 (64%) NOD mice having CIAA concentrations exceeding the normal range progressed to diabetes, whereas only 4 of 43 (9%) NOD mice progressed to diabetes without detection of elevated CIAAs (Fisher's exact test, P less than .0005). The relative risk of progressing to overt diabetes with CIAA levels greater than 39 nU/ml was therefore 17 (P less than .005), giving a positive predictive value of 64%, a negative predictive value of 91%, and an overall accuracy of 85%. None of 11 unweaned NOD pups had CIAA levels above the normal range (mean -9.4 +/- 4.9 nU/ml). At 6 wk of age, 37% of female NOD mice were CIAA+, whereas none of the male animals exceeded the normal range at this age (38 +/- 13 vs. 5 +/- 6 nU/ml, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

A novel neuroendocrine cell surface glycoprotein: identification, isolation, and initial characterization.

Murine monoclonal antibodies (MAbs) HISL-5, -9, and -14, generated after immunization of mice with human pancreatic islet cell preparations, recognize a differentiation antigen expressed by the pancreatic islet cells. These MAbs react strongly with all endocrine cell subtypes of human pancreatic islets, but minimally if at all with the exocrine acinar cells, vascular cells, and stromal connective tissue cells of the pancreas. The antigen is located on the cell surface (plasma membranes), as indicated by immunofluorescence staining of viable cell preparations. Besides the pancreatic islets, HISL-5, -9, and -14 antigenic determinants are also expressed by thyroid follicular cells, parathyroid chief cells, and anterior pituitary cells, other commonly involved targets in organ-specific autoimmune disorders. Preliminary biochemical findings indicated that the MAb-defined epitope(s) is trypsin sensitive and resistant to periodate oxidation and exposure to chloroform-methanol. Further biochemical studies, including single step MAb immunoaffinity chromatographic purification, indicate that the antigen recognized by the MAbs HISL-5, -9, and -14 is a 100 K glycoprotein.

Animals↗
PubMed1988

Transient hyperglycemia in childhood: identification of a subgroup with imminent diabetes mellitus.

Transient hyperglycemia may represent the earliest manifestation of IDDM. In a series of 30 children referred for transient hyperglycemia, 8/30 (27%) developed IDDM within 10 months of their initial evaluation. Three children with detectable cytoplasmic islet cell antibodies (ICA) and/or positive insulin autoantibodies (CIAA) all developed IDDM, compared to 21% of ICA negative children and 13% who were CIAA negative. Of those with impaired glucose tolerance, 6/11 (55%) developed IDDM, as did 1/14 with normal OGTT. Of the children with a low "K rate" on IVGTT, 75% developed IDDM, compared to 1/13 with a normal "K rate". All four children (100%) whose first phase (1' + 3') insulin secretion never exceeded the first percentile developed IDDM within nine months, while no child with first phase insulin secretion above the first percentile (0/16) developed IDDM during 19 +/- 9 months (mean +/- SD) of follow-up. Thus, in our experience the oral glucose tolerance test is a less accurate predictor of impending IDDM; immunological abnormalities have the highest positive predictive value, while the first phase insulin secretion during an intravenous glucose tolerance test has the highest negative predictive value and the greatest overall accuracy of prediction.

Adolescent↗
PubMed1986

Use of Y chromosome specific probes to detect low level sex chromosome mosaicism.

An individual found to be a true hermaphrodite at laparotomy, is presented. Cytogenetic studies which initially disclosed a 46,XX karyotype, conflicted with the anatomic presence of a testis. More extensive analysis of peripheral lymphocytes and skin fibroblasts revealed low level 46,XX/69,XXY mosaicism. DNA hybridization studies, using highly repeated Y chromosome specific probes, confirmed the rare presence of Y chromosome bearing cells. Such combined clinical and molecular studies can have an important impact on diagnosis and management of cases in which sex chromosome mosaicism is suspected.

Child, Preschool↗
PubMed1986

Autoimmunity to insulin, beta cell dysfunction, and development of insulin-dependent diabetes mellitus.

Circulating insulin autoantibodies (INSAAb) were measured in discordant monozygotic twins, first-degree relatives, and other groups at "high risk" for the development of insulin-dependent diabetes mellitus (IDDM), and these results correlated with both islet cell antibody (ICAb) status and beta cell function. INSAAb were positive in 31.6% (12 of 38) ICAb-positive subjects but in only 3.1% (3 of 97) ICAb-negative subjects (X2 = 22.4; P less than 0.001). Elevated levels of INSAAb tended to correlate with younger age and were observed in individuals irrespective of the prevailing degree of their beta cell function. Eight of 15 subjects detected to be INSAAb positive have thus far progressed to clinical IDDM (X2 = 18.3; P less than 0.001). Thus, autoantibodies reactive with the insulin molecule (1) appear to constitute an additional serologic marker of ongoing autoimmunity and development of IDDM, and (2) may reflect heterogeneity in the pathogenesis of IDDM.

Adolescent↗
PubMed1982

Isolation of cDNA clones for the human complement protein factor B, a class III major histocompatibility complex gene product.

cDNA clones corresponding to a major histocompatibility class III antigen, the complement protein factor B, have been isolated from a human adult liver cDNA library. The clones, ranging in size from 1.0 to 2.3 kilobases, were identified by direct hybridization with two synthetic oligonucleotide mixtures. Two regions of the factor B amino acid sequence, each with minimal ambiguity in codon assignment, were chosen for synthesis of the oligonucleotides. The sequences of two clones have been partially determined. They contain coding information for the amino acid sequence of the Bb fragment of factor B and the entire 3' -untranslated region.

Adult↗
PubMedDate not supplied

Sequence of cDNA encoding human insulin-like growth factor I precursor.

Somatomedins (SM) or insulin-like growth factors (IGF) constitute a heterogeneous group of peptides with important growth-promoting effects in vitro as well as in vivo. Amino acid sequences have been determined for only two of them, IGF-I and IGF-II, which are highly homologous. IGF-I, which is identical with SM-C, is composed of 70 amino acid residues and IGF-II contains 73 amino acids and may be identical with SM-A. Other peptides with different charge properties but with similar SM-like or insulin-like behaviour in biological and receptor assays, have been described but have not yet been fully characterized. The liver is known to be a major site of production of these peptides, but many other tissues--especially in the fetus--may synthesize them as well. We report here the nucleotide sequence of a human liver cDNA encoding the complete amino acid sequence of IGF-I. The IGF-I coding region is flanked by sequences encoding an amino-terminal peptide of at least 25 amino acid residues and a carboxyl-terminal peptide of 35 amino acids. This provides evidence that IGF-I is synthesized as a precursor protein and that formation of IGF-I from this precursor requires proteolytic processing at both ends.

Base Sequence↗