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Biomedical subjects

D A Miller

Publications and source records attributed to D A Miller.

At least 19 recordsLinked to original sources
PubMed1992

Characterization of a bifunctional peptidylglycine alpha-amidating enzyme expressed in Chinese hamster ovary cells.

Peptidylglycine alpha-amidating enzyme (alpha-AE) catalyzes the conversion of glycine-extended prohormones to their biologically active alpha-amidated forms. We have derived a clonal Chinese hamster ovary cell line that secretes significant quantities of active alpha-AE. Enzyme production was increased by selection for methotrexate-resistant cells expressing a dicistronic message. Amplification of the alpha-AE gene was monitored by Southern blot analysis, enzyme activity, and immunoreactive protein throughout the selection process. The soluble enzyme is bifunctional as determined by the ability to convert either the glycine-extended substrate, dansyl-Tyr--Val--Gly, or the intermediate, dansyl-Tyr--Val--alpha-hydroxyglycine, to the dansyl-Tyr--Val--NH2 product. The recombinant alpha-AE was purified by a simple two-step chromatographic process. The purified enzyme is partially glycosylated and the glycosylated and nonglycosylated forms of the enzyme were separated on a Con A-Sepharose column. The kinetic constants for dansyl-Tyr--Val--Gly, dansyl-Tyr--Val--alpha-hydroxyglycine, ascorbate, and catechol were the same for both forms of alpha-AE. In addition, mimosine is competitive vs ascorbate with K(is) = 3.5 microM for the nonglycosylated alpha-AE and K(is) = 4.2 microM for the glycosylated alpha-AE. Therefore, the presence or absence of asparagine-linked oligosaccharide does not affect the catalytic efficiency of the enzyme. Overexpression of the recombinant enzyme in CHO cells greatly enhances expression of the endogenous gene, implicating a feedback mechanism on the alpha-AE gene.

Amino Acid Sequence↗
PubMed1992

Ullrich-Turner syndrome with a small ring X chromosome and presence of mental retardation.

Since some patients with Ullrich-Turner syndrome (UTS) have mental retardation, we reviewed our experience to look for a high-risk subgroup. Among 190 UTS and gonadal dysgenesis patients with X chromosome abnormalities, 12 had mental retardation. All of the six (100%) with a small ring X were educable (EMI) or trainable mentally impaired (TMI) with more severe delay than expected in UTS. Among the 184 with other X abnormalities, only 6 had similar delays (2 from postnatal catastrophes), for a frequency of 3.3% mental retardation among those without a small ring X; only 2.2% of these had unexplained mental retardation. Polymerase chain reaction studies showed no Y-derived material in the 2 patients who were evaluated, and in situ hybridization confirmed X origin of the ring in the 6 subjects who were evaluated. We describe the phenotype of the 6 individuals with a small ring X, and an additional 2 patients with a small ring X who were identified outside the survey. The subjects with a small ring X comprised a clinically distinct subgroup which had EMI/TMI and shorter stature than expected in UTS. Seizures and a head circumference less than 10th centile were observed in half of the patients with a small ring X, and strabismus, epicanthus, and single palmar creases were present in more than half. A "triangular" face in childhood, pigmentary dysplasia, sacral dimple, and heart defects were also common. Neck webbing appeared to be less frequent than in 45,X. We hypothesize that the high risk of mental retardation in this form of the UTS results from lack of lyonization of the ring X due to loss of the X inactivation center. Excluding those with a small ring X, mental retardation is not significantly increased in patients with UTS.

Adolescent↗
PubMed1992

Leptospira serology in small ruminants on St. Croix, U.S. Virgin Islands.

A serological survey of 16 serovars of Leptospira interrogans, previously reported in tropical small ruminants, was undertaken to determine the serovars involved and the prevalence of these antibodies in sheep and goats on St. Croix, U. S. Virgin Islands (USVI). Seven of eight goat herds (108 animals) had at least two seropositive animals in each herd with an individual animal seroprevalence of 26%. The 53 sheep tested (one flock only) showed a 32% seroprevalence. Antibodies against seven serovars were detected in goats (autumnalis, ballum, bataviae, bratislava, canicola, icterohemorrhagiae, and pyrogenes). In addition, hardjo antibodies were detected in sheep. Serovar autumnalis accounted for about 30% of seropositive animals in each species. Many animals showed titers against more than one serovar. The number of seropositive animals suggests Leptospira may be a factor in the health of small ruminants on St. Croix.

Agglutination Tests↗
PubMed1992

Methylation of the 5' flanking sequences of the ribosomal DNA in human cell lines and in a human-hamster hybrid cell line.

In a human lymphoblastoid cell line (Z83) in which rDNA genes on chromosome 22 are amplified but transcribed at a low level, immunocytological studies with antibodies to 5 methylcytidine provided evidence for hypermethylation of the rDNA. The extent of methylation of the 5' flanking sequences of the ribosomal DNA was examined by comparing the size of restriction fragments obtained by digestion of genomic DNA with EcoRI and HpaII or EcoRI and MspI. Southern blots indicated hypermethylation of the 5' flanking sequences of many copies of rRNA genes in these cells, but not in a control lymphoblastoid cell line without rDNA amplification. Results obtained with a somatic hybrid human-hamster cell line, in which the rRNA genes on the single human chromosome 22 are inactive, showed that only a small fraction of the CCGG sites in the 5' flanking sequences of the transcriptionally silent rRNA genes in this hybrid were methylated. Since inactive rRNA genes can show such a minimal level of methylation, it is likely that the extreme hypermethylation of the amplified rRNA genes in Z83 occurred in association with their inactivation rather than following it.

Animals↗
PubMed1992

Isolation and characterization of a mouse subtelomeric sequence.

A mouse subtelomeric sequence, ST1, was generated from genomic DNA of the mouse HR9 (129/Sv origin) cell line by the polymerase chain reaction (PCR) using a single telomeric primer. ST1 was cloned and characterized: it is composed of 670 bp of novel DNA sequence flanked on each end by inverted telomeric hexanucleotide repeats (TTAGGG)n. PCR amplification from BALB/c mouse DNA using this single primer gave the same major product. Southern analysis and PCR using internal ST1 primers confirmed that the ST1 sequence is present in mouse genomic DNA. In situ hybridization to metaphase chromosomes of SJL origin mapped ST1 to many, if not every, mouse telomere. PCR experiments using different combinations of the telomeric, minor satellite, and ST1 primers indicated that some ST1 copies are adjacent to minor satellite sequences, that telomeric and ST1 sequences are not generally interspersed with minor satellite sequences, and that ST1 and the minor satellite have a consistent and specific orientation relative to each other and to the telomere.

Animals↗
PubMed1992

Cross sections of natSb(p,x) reactions for 30-46 MeV protons.

In order to optimize the production of 118Te in thick targets for use in a 118Te/118Sb radionuclide generator, the excitation function for the 121Sb(p,4n)118Te reaction has been measured for 30-46 MeV protons. The excitation functions for the competing reactions natSb(p,xn)119mTe, natSb(p,xn)119Te, natSb(p,xn)121mTe, natSb(p,pxn)120mSb and 123Sb(p,pn)122Sb have also been determined using stacked foil techniques. The 121Sb(p,4n)118Te reaction cross section maximum was found to be 480 mbarn at 44 MeV. In order to minimize the 119m + 119Te interference a minimum proton beam energy of 40 MeV is required. The cross section results are compared with published data and with calculated excitation functions.

Antimony↗
PubMed1992

Isolation and comparative mapping of a human chromosome 20-specific alpha-satellite DNA clone.

We have isolated and characterized a human genomic DNA clone (PZ20, locus D20Z2) that identifies, under high-stringency hybridization conditions, an alphoid DNA subset specific for chromosome 20. The specificity was determined using fluorescence in situ hybridization. Sequence analysis confirmed our previously reported data on the great similarity between the chromosome 20 and chromosome 2 alphoid subsets. Comparative mapping of pZ20 on chimpanzee and gorilla chromosomes, also performed under high-stringency conditions, indicates that the alphoid subset has ancestral sequences on chimpanzee chromosome 11 and gorilla chromosome 19. However, no hybridization was observed to chromosomes 21 in the great apes, the homolog of human chromosome 20.

Animals↗
PubMed1992

Phenotypic alterations in fibroblasts and fibrosarcoma cells that overexpress latent transforming growth factor-beta 1.

Mouse embryo-derived AKR-2B fibroblasts and murine fibrosarcoma cells (the 1591 cell line) were transfected with a murine transforming growth factor-beta 1 (TGF beta 1) cDNA under the transcriptional control of either the simian virus-40 early promoter or the cytomegalovirus promoter/enhancer. Selected clones secreted 2- to 4-fold more TGF beta-competing activity into their media than the parental cell line or neomycin-transfected controls. The TGF beta 1 released into the cell-conditioned medium was latent. Despite the latency of the overexpressed TGF beta 1, TGF beta 1-transfected cells exhibited phenotypic features of TGF beta 1-treated cells. When confluent, the TGF beta 1-transfected cells had the morphological characteristics of the parental cells that have been treated with active TGF beta 1. AKR-2B cells that expressed higher levels of TGF beta 1 also expressed high levels of c-sis and c-myc mRNAs and decreased TGF beta 2 and TGF beta 3 mRNAs in the same manner as parental AKR-2B cells that had been treated with active TGF beta 1. The transfected 1591 cells that overexpressed TGF beta 1 bound less [125I]TGF beta 1 than did parental 1591 cells, but after a mild acid wash demonstrated an increase in [125I]TGF beta 1 binding. Our results suggest that these TGF beta 1-transfected fibroblast and fibrosarcoma cells have the capacity to activate TGF beta; however, as very little activated TGF beta is detected in the medium, it is hypothesized that these cells activate latent TGF beta 1 and bind the activated TGF beta 1, thus acquiring a phenotype consistent with TGF beta 1-treated cells.

Animals↗
PubMed1992

[Chronic gastritis from the aspect of a thrombohemorrhagic syndrome].

As many as 148 patients were examined to demonstrate that chronic gastritis (CG) runs its course in the presence of marked changes in microcirculation and hemostasis which go into the framework of the chronic recurrent thrombohemorrhagic syndrome. The manifestations of the latter one were more appreciable in a dramatic exacerbation of the disease, erosive gastritis, diffuse atrophy of the mucous membrane and secretory insufficiency of the stomach, and disease standing over 10 years. The disorders indicated are involved into the pathogenesis of CG and promote the development of morphofunctional alterations in the gastric mucosa.

Adult↗
PubMed1991

Telomeric associations and consistent growth factor overexpression detected in giant cell tumor of bone.

Tumor specimens from 15 patients with giant cell tumor (GCT) of bone were cytogenetically analyzed. A subset of five individuals had tumor cells harvested and polyadenylated RNA isolated. Multiple Northern blots were performed utilizing radiolabeled probes for the growth factors TGF beta 1, TGF beta 2, TGF beta 3, and TGF alpha (TGF, transforming growth factor). RNAs from other types of neoplasms and nonneoplastic cells were examined as controls. The most consistent cytogenetic abnormality detected involved multiple telomeric associations (TAs), most frequently involving the terminus of the long arm of chromosome 19 (19q). Northern blot analysis revealed a consistent expression of TGF beta 1 and TGF beta 2 with an inconsistent mRNA expression for the other TGFs. There was a relative overexpression of mRNA for TGF beta 2. The gene location for TGF beta 1 is near the 19q terminus and thus it is speculated that TGF beta may play a role in the neoplastic transformation of GCT.

Adult↗
PubMed1991

Inheritance of ribosomal gene activity and level of DNA methylation of individual gene clusters in a three generation family.

Ribosomal gene activity and levels of DNA methylation were investigated by cytochemical and immunological methods in the nucleolar organizer regions (NORs) of individually recognised acrocentric chromosomes. Mendelian inheritance of ribosomal gene activity in a three generation family was demonstrated, together with consistent behaviour of individual gene clusters in different carriers, even when environmental conditions were changed. For most chromosomes, an inverse relationship between gene activity and the level of DNA methylation was observed. Exceptions were the two chromosomes 15 and chromosomes 13cp and 22p, all being strongly chromomycin-A3-positive in their short arms. These chromosomes bound to anti-5-MeC antibodies with differential frequencies in the different carriers. The possibility of involvement of repetitive GC-rich DNA in this behaviour is discussed.

Azacitidine↗
PubMed1991

A chimpanzee-derived chromosome-specific alpha satellite DNA sequence conserved between chimpanzee and human.

We describe a cloned 2.7 kb alpha satellite sequence, Pan-3, from the pygmy chimpanzee (Pan paniscus) that specifically hybridizes in situ to chromosome 19 in the pygmy chimpanzee and to the homeologous human chromosome, no. 17. Using high stringency conditions of hybridization on Southern blots, this sequence hybridized to DNA from both species of chimpanzee (P. paniscus and P. troglodytes) and from human but not to DNA from gorilla (Gorilla gorilla) or orangutan (Pongo pygmaeus). Partial sequence analysis showed that Pan-3 and a previously described human chromosome 17-specific clone have up to 91% sequence identity. To our knowledge this is the highest sequence similarity reported between alphoid subsets from human and any other primate.

Animals↗
PubMed1991

Comparative mapping of a gorilla-derived alpha satellite DNA clone on great ape and human chromosomes.

We have isolated an alpha satellite DNA clone, pG3.9, from gorilla DNA. Fluorescence in situ hybridization on banded chromosomes under high stringency conditions revealed that pG3.9 identifies homologous sequences at the centromeric region of ten gorilla chromosomes, and, with few exceptions, also recognizes the homologous chromosomes in human. A pG3.9-like alphoid DNA is present on a larger number of orangutan chromosomes, but, in contrast, is present on only two chromosomes in the chimpanzee. These results show that the chromosomal subsets of related alpha satellite DNA sequences may undergo different patterns of evolution.

Animals↗
PubMed1991

Isolation of a variant family of mouse minor satellite DNA that hybridizes preferentially to chromosome 4.

Two cosmids (HRS-1 and HRS-2) containing mouse minor satellite DNA sequences have been isolated from a mouse genomic library. In situ hybridization under moderate stringency conditions to metaphase chromosomes from RCS-5, a tumor cell line derived from the SJL strain, mapped both HRS-1 and HRS-2 to the centromeric region of chromosome 4. Sequence data indicate that these cloned minor satellite DNA sequences have a basic higher order repeat of 180 bp, composed of three diverged 60-bp monomers. Digestion of mouse genomic DNA with several restriction enzymes produces a ladder of minor satellite fragments based on a 120-bp repeat. The restriction enzyme NlaIII (CATG) digests all the minor satellite DNA into three prominent bands of 120, 240, and 360 bp and a weak band of 180 bp. Thus, the majority of minor satellite sequences in the genome are arranged in repeats based on a 120-bp dimer, while the family of minor satellite sequences described here represents a rare variant of these sequences. Our results raise the possibility that there may be other variant families of minor satellites analogous to those of alphoid DNA present in humans.

Animals↗
PubMed1991

Urokinase treatment of neonatal aortoiliac thrombosis caused by umbilical artery catheterization: a case report.

Umbilical artery catheterization is known to be associated with aortoiliac thrombosis in approximately 1% of newborns in whom catheters are placed. We describe a case of catheter-associated aortoiliac thrombosis in a newborn who was successfully treated by urokinase infusion. The infant was monitored by imaging studies followed by ultrasonography. The use of real-time ultrasonography enabled us to image this infant's aortoiliac thrombosis in an accurate, noninvasive manner and monitor the effectiveness of thrombolytic therapy. The fibrinolytic state was achieved with a combination of intravenous and intraarterial infusions of urokinase. Frequent measurement of prothrombin time, activated partial thromboplastin time, fibrinogen, and thrombin time was used to guide fibrinolytic therapy. We reviewed the literature for similar cases of aortoiliac thrombosis in newborns; some were managed by medical means, others by operation. The success rate of the two approaches appeared to be approximately equal. Therefore we recommend the less invasive approach first--urokinase therapy--to be followed by surgical intervention if thrombolysis is unsuccessful.

Aorta, Thoracic↗
PubMed1991

Establishing a family practice: a model to determine economic feasibility.

The availability of adequate health care is a major concern of urban and rural citizens. Community leaders and hospital administrators attempting to recruit family physicians and health care providers considering a specific community need a method by which they can evaluate a community's potential for supporting a first or additional primary care physician. To develop this method, a detailed survey of family practices geographically dispersed throughout Oklahoma was conducted in 1989. Data collected from family physicians and their administrative staff reflected the volume of ambulatory and hospital visits and the direct and indirect costs of the practice over the previous 12 months. Using the fixed and operating cost data, as well as number of patient visits and patient care revenue, we designed a model to project the economic feasibility of establishing a family practice in a specific community. This model can be used to project the number of visits a community can generate for a prospective family physician, as well as the direct and indirect costs, gross revenue, and net income of the practice.

Adolescent↗
PubMed1991

The cognitive context of examinations in psychiatry using Bloom's taxonomy.

Psychiatric practice involves complex thinking patterns. In addition to commanding a huge number of facts, the student must learn to manipulate factual knowledge to solve diagnostic problems, develop treatment plans, and critically evaluate those plans. This study demonstrates an empirical method for evaluating the level of cognitive processes tested in multiple choice examinations. Use of Bloom's taxonomy in evaluating test items demonstrated the majority of test items on a psychiatry clerkship examination and a resident in-training examination fell into the most basic cognitive level, that of simple recall. The utility of Bloom's taxonomy is discussed along with implications for medical education.

Cognition↗