Biomedical subjects

R H Miller

Publications and source records attributed to R H Miller.

At least 145 records · Page 8Linked to original sources

PubMed1993

Heterogeneity of the woodchuck hepatitis virus genome in a chronically infected woodchuck.

The nucleotide sequence of an isolate of woodchuck hepatitis virus (WHV) from the serum of a woodchuck trapped in New York state (WHVNY) was compared with the sequences of previously published isolates. The nucleotide sequence of WHVNY was closest to that of an isolate originating from New Jersey: the two genomes shared a 15 nucleotide in-frame deletion in the region where the presurface and polymerase genes overlap (nucleotides 3260-3274) and differed by 54 point mutations (1.6% of genome). Amino acid differences ranged from 0.4% in the surface gene to 5.7% in the X gene. Three isolates from woodchucks that originated in Pennsylvania and Maryland did not contain the deletion and differed from WHVNY by 102 to 106 point mutations (3.0% to 3.2% of nucleotides). Amino acid changes ranged from 0.5% in the core gene to 5.7% in the X-gene. Thus, WHVNY differed little from previous isolates. Next, the genomes from 102 independent clones of WHVNY were compared to ascertain the extent of sequence variation among WHV genomes in a chronically infected animal. A total of 98 clones had genomes of unit length while 2 clones had genomes shorter than unit length and 2 clones had genomes longer than unit length. The clones not of unit length possessed deletions or inverted duplications of sequence. The rate of mutation in the viral genes was 2.65 mutations per 10,000 nucleotides in the precore domain, 1.27 per 10,000 in the X-gene, 0.98 per 10,000 in the presurface gene, and 3.77 per 10,000 at the 5' end of the core gene.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1993

Antigenic and differentiative heterogeneity among human glioblastomas.

Increasing evidence suggests that in mammals, astrocytes are a heterogenous family of cells all of which share certain properties, but differ in lineage, biochemical and functional aspects. It seems likely that glioblastomas, arising from glial precursors, may also represent a family of related but distinct cell types. We have examined the antigenic characteristics and differentiative potential of 7 different human glioblastoma cell lines in vitro. All the cell lines were labeled with a monoclonal antibody 7B11 which labels all classes of astrocytes and their precursors in the rat CNS. U138MG and Tm3 cells expressed antigens on their surfaces recognized by the monoclonal antibodies A2B5 and HNK-1. When grown in serum-free medium in the presence of cAMP and theophylline, U138MG cells assumed a process-bearing morphology and some cells expressed the Gal-C antigen specific for oligodendrocytes. Under identical conditions, Tm3 cells converted to process-bearing cells, some of which expressed glial fibrillary acidic protein (GFAP) specific for astrocytes. Other cell lines with similar antigenic characteristics did not respond similarly to cAMP and theophylline. Finally, A2781 cells were GFAP immunoreactive and unlabeled by either A2B5 or HNK-1 antibodies. These observations suggest that individual glioblastoma cell lines may be derived from distinct glial precursor cells in the vertebrate CNS.

Antibodies, Monoclonal↗

PubMed1993

High prevalence of hepatitis C virus (HCV) RNA in dialysis patients: failure of commercially available antibody tests to identify a significant number of patients with HCV infection. Copenhagen Dialysis HCV Study Group.

Results of serologic tests were correlated with hepatitis C virus (HCV) viremia, determined by a cDNA polymerase chain reaction assay to detect HCV RNA, in 340 Danish dialysis patients; of these, 28 (8.2%) were positive for antibodies to HCV (anti-HCV) with second-generation ELI-SAs. HCV RNA was found in sera from 27 of these 28 anti-HCV-positive patients. However, 8 dialysis patients had detectable levels of HCV RNA but were anti-HCV-negative with second-generation ELISAs. Among the 35 HCV-infected dialysis patients 16 were positive, 7 indeterminate, and 12 negative with the second-generation RIBA. More than 60% of patients with evidence of ongoing liver disease had HCV infection. Thus, current commercially available antibody tests did not accurately reflect the HCV status in dialysis patients. A relatively high prevalence (> 10%) of HCV RNA, closely associated with liver disease, was found among dialysis patients in a low-prevalence area of the world.

Base Sequence↗

PubMed1993

Modulation of adhesion molecule expression on rat cortical astrocytes during maturation.

During development of the vertebrate CNS the functional properties of astrocytes change significantly. Many of these functional changes result from modifications in the expression of cell surface adhesion molecules on astrocytes that mediate the interactions of astrocytes with other astrocytes, neurons, and growing axons. In this study we have compared the cell surface expression of HNK-1, NCAM, and laminin on rat cortical type-I-like astrocytes during maturation in vitro and in vivo. Both the proportion of immunoreactive cells and the relative levels of expression of these antigens on different aged astrocyte populations were assayed by flow cytometry. At birth, most cortical type-I astrocytes express high levels of HNK-1 and NCAM, while approximately 50% of the cells express laminin. During maturation in vitro, the proportion of cortical astrocytes that expressed these surface molecules decreased over a period of 28 days, even though cell size and glial fibrillary acidic protein content increased. During maturation in vivo, a qualitatively and temporally similar decrease in antigen expression on astrocytes was observed. This reduction in the expression of specific cell surface molecules on maturing astrocytes results from maturation of a single population of astrocytes and not differential proliferation of a nonexpressing subpopulation of astrocytes, as shown by cell cycle analysis of both immunoreactive and nonimmunoreactive cell populations. These data indicate that during maturation of rat cortical type-I-like astrocytes, the expression of cell surface adhesion molecules is regulated. Furthermore, this regulation appears to be cell autonomous and not dependent on environmental factors. Such regulation of adhesion molecule expression may have profound consequences for the functional properties of astrocytes during CNS maturation.

Aging↗

PubMed1993

The woodchuck hepatitis virus X gene is important for establishment of virus infection in woodchucks.

All mammalian hepadnaviruses possess a gene, termed X, that encodes a protein capable of transactivating virus gene expression. The X gene overlaps the polymerase and precore genes as well as two newly identified open reading frames (ORFs) termed ORF5 and ORF6. In this investigation, we examined whether ORF5, ORF6, and the X gene were important for the replication of woodchuck hepatitis virus (WHV) in susceptible woodchucks. First, we investigated whether proteins were produced from ORF5 and ORF6 by in vitro translation of appropriate viral transcripts, searched for antibodies against the putative proteins in the sera of animals infected with wild-type virus, and looked for an antisense WHV transcript, necessary for expression of a protein from ORF6, in the livers of acutely or chronically infected woodchucks. All such experiments yielded negative results. Next, we used oligonucleotide-directed mutagenesis to introduce termination codons into ORF5 and ORF6 at two locations within each ORF. Adult woodchucks in groups of three were transfected with one of the four mutant genomes. All of these woodchucks developed WHV infections that were indistinguishable from those of animals transfected with the wild-type WHV recombinant. Polymerase chain reaction amplification and direct DNA sequencing confirmed that reversion of the mutants to a wild-type genotype did not occur. Taken together, these data indicate that ORF5 and ORF6 are not essential for virus replication and are unlikely to represent authentic genes. Finally, we generated five WHV X-gene mutants that either removed the initiation codon for protein synthesis or truncated the carboxyl terminus of the protein by 3, 16, 31, or 52 amino acids. Groups of three adult woodchucks were transfected with one of the five X-gene mutants. Only the mutant that possessed an X gene lacking 3 amino acids from the carboxyl terminus was capable of replication within the 6-month time frame of the experiment. In contrast, all seven woodchucks transfected with wild-type WHV DNA developed markers consistent with viral infection. Thus, it is likely (P < 0.01) that the WHV X gene is important for virus replication in the natural host.

Amino Acid Sequence↗

PubMed1993

Deletion analysis of dengue virus type 4 nonstructural protein NS2B: identification of a domain required for NS2B-NS3 protease activity.

Most proteolytic cleavages in the nonstructural protein (NS) region of the flavivirus polyprotein are effected by a virus-encoded protease composed of two viral proteins, NS2B and NS3. The N-terminal 180-amino-acid-region of NS3 includes sequences with homology to the active sites of serine proteases, and there is evidence that this portion of NS3 can mediate proteolytic cleavages. In contrast, nothing is known about required sequences in NS2B. We constructed a series of deletion mutations in the NS2B portion of plasmid pTM/NS2B-30% NS3, which expresses dengue virus type 4 (DEN4) cDNA encoding NS2B and the N-terminal 184 residues of NS3 from the T7 RNA polymerase promoter. Mutant or wild-type plasmids were transfected into cells that had been infected with a recombinant vaccinia virus expressing T7 RNA polymerase, and the protease activities of the expressed polyproteins were assayed by examining the extent of self-cleavage at the NS2B-NS3 junction. The results identify a 40-amino-acid segment of NS2B (DEN4 amino acids 1396 to 1435) essential for protease activity. A hydrophobicity profile of DEN4 NS2B predicts this segment constitutes a hydrophilic domain surrounded by hydrophobic regions. Hydrophobicity profiles of the NS2B proteins of other flaviviruses show similar patterns. Amino acid sequence alignment of this domain of DEN4 NS2B with comparable regions of other proteins of flaviviruses indicates significant sequence conservation, especially at the N-terminal end. These observations suggest that the central hydrophilic domain of NS2B of these other flaviviruses will also prove to be essential for protease activity.

Amino Acid Sequence↗

PubMed1993

Plasma fibrinogen level is not elevated in young adults from families with premature ischemic heart disease.

Several epidemiological studies have found that the plasma fibrinogen level is a risk factor for ischemic heart disease (IHD), similar in importance to the serum cholesterol level. A family history of IHD is also a significant risk factor for IHD, statistically independent of the serum cholesterol level. Whether the familial risk for IHD is related to genetic control of the fibrinogen level is unknown. Estimates of the genetic contribution to the variance in plasma fibrinogen levels vary markedly. We previously found elevated levels of cholesterol and factor VII in young subjects with a familial history of premature IHD. In the present study we chose to measure fibrinogen, factor VII antigen, and total cholesterol levels in 43 asymptomatic first-degree relatives (< 50 years old) of patients with premature IHD and in 43 age- and sex-matched asymptomatic young adults at low risk of IHD. No subjects in either group were smokers. The mean plasma fibrinogen level of the high-risk group (259 mg/dL) did not differ significantly from that of the low-risk group (250 mg/dL; p > 0.4). In contrast, the high-risk group had significantly higher mean factor VII antigen (p < 0.001) and mean serum cholesterol (p < 0.0001) than the low-risk group. These data argue against the hypothesis that genetic determination of the plasma fibrinogen level is a common pathophysiological mechanism responsible for familial risk of IHD.

Adult↗

PubMed1993

An animal model for pharyngocutaneous fistulas.

Postoperative pharyngocutaneous fistula is not an uncommon complication. Although the frequency of postoperative fistulae has decreased with the use of perioperative broad-spectrum antibiotics, it remains a complication with significant morbidity and expense. We present an animal model for postoperative pharyngocutaneous fistulae based on increasing wound tension. The New Zealand white rabbit was used to assess the rate of wound breakdown in the thyrohyoid membrane. The animals were assigned to one of seven groups according to the width of tissue resected. After tissue resection, the pharyngeal wounds were repaired, as were the overlying skin wounds. Animals were monitored postoperatively up to 14 days, at which time they were killed and underwent autopsy. Statistically significant results were achieved that demonstrate an increasing incidence of pharyngeal wound breakdown associated with increasing width of tissue resected and, therefore, closure tension. The procedure and results will be presented in detail. We propose that this model may be used to assess postoperative wounds as well as substances or methods touted as promoters of wound healing.

Animals↗

PubMed1993

Oligodendrocyte precursors originate at the ventral ventricular zone dorsal to the ventral midline region in the embryonic rat spinal cord.

The precursors for oligodendrocytes, the myelinating cells of the vertebrate CNS, appear to be initially restricted to ventral regions of the embryonic rat spinal cord. These cells subsequently populate dorsal spinal cord regions where they acquire the mature characteristics of oligodendrocytes. To determine the location and timing of proliferation of oligodendrocyte precursors in the ventral spinal cord, and to map their pathways of migration in vivo, an assay that identifies mitotic cells was used in conjunction with antibodies that distinguish astrocytes, oligodendrocytes and their precursors. Between E16.5 and E18.5, two hours after a maternal injection of BrdU, the majority of proliferating cells were located in a discrete cluster at the ventral ventricular zone dorsal to the ventral midline region of the developing spinal cord. By contrast, 12-24 hours following a BrdU injection at E16.5, increasing numbers of labeled cells were seen in the dorsal and more lateral locations of the spinal cord. These observations suggest that BrdU-labeled ventral ventricular cells, or their progeny migrate dorsally and laterally during subsequent spinal cord development. To determine the nature of these proliferating cells, cultures of dorsal and ventral spinal cord from BrdU-labeled animals were double-labeled with antibodies that identify oligodendrocytes or astrocytes and anti-BrdU. In dorsal spinal cord cultures derived from animals that had received a single injection of BrdU at E16.5, the majority of proliferating cells differentiated into astrocytes while, in ventrally derived cultures from the same animals, the majority of proliferating cells differentiated into oligodendrocytes. In dorsal cultures prepared from animals that received multiple injections of BrdU between E16.5 and E18.5, many more cells were labeled with BrdU and approximately half of these differentiated into oligodendrocytes. These observations suggest that during embryonic development proliferating oligodendrocyte precursors are initially located at the ventral ventricular zone dorsal to the ventral midline region of the spinal cord and during subsequent maturation these cells or their progeny migrated dorsally in the ventricular region of the spinal cord, and laterally to reside in the developing white matter.

Animals↗

PubMed1993

Otolaryngology manpower in the year 2010.

The number of otolaryngologists practicing in the future is particularly pertinent in light of the changes taking place in American medicine today. A mathematical model is presented which projects the growth of otolaryngology manpower in the year 2010, taking into consideration the age distribution of practicing otolaryngologists, death rates, and the current production of residents. This model suggests that there will be a 21% increase in the number of otolaryngologists from 1990 to 2010. The main reason for the increase is the uneven distribution of otolaryngologists by age at the present time, with 49% of otolaryngologists being less than 45 years of age. There is concern that the American medical community is populated with too many specialists and that more emphasis should be placed on training generalists. The manpower issue should be studied in more detail, and future societal needs should be determined so that a rational policy on the growth of otolaryngology can be developed.

Adult↗

PubMed1993

Managed care: past evidence and potential trends.

Enrollment in network-based managed care plans has grown rapidly, raising important questions about the actual impact of different types of managed care plans on health care use, expenditure, and quality of care. In this article, we analyze the literature on the performance of managed care plans relative to fee-for-service plans. We find strong evidence that staff- and group-model HMOs have lowered utilization and expenditure relative to fee-for-service while maintaining quality of care. The relatively sparse evidence is more mixed on the performance of newer forms of managed care organizations (MCOs). We also speculate on future trends in network-based managed care. It is likely that employers will increase their economic leverage with managed care firms, accelerating processes that are leading to greater concentration of marketshare among managed care firms. In turn, newer forms of MCOs will increase their economic leverage with providers, which will help MCOs contain costs and monitor quality. Some of the newer MCOs will adapt important features of staff- and group-model HMOs, including increased emphasis on provider selection and reselection.

Costs and Cost Analysis↗

PubMed1993

Containing use and expenditures in publicly insured long-term care programs.

British Columbia and Manitoba have the most developed and comprehensive publicly financed long-term care (LTC) programs in North America. For U.S. policymakers, these programs are large-scale natural experiments with public LTC insurance. During the 1980s, both provinces successfully contained the growth of public expenditures on nursing homes, and one province successfully contained the growth of public expenditures on home support services, adjusting for population growth. Because provincial cost-control methods are similar to those that some States already use, it is likely that managers could contain the growth of public expenditures once a publicly insured U.S. LTC program was implemented. The level of public expenditure would depend partly on the level of compensation for LTC sector personnel, which is relatively low in the United States.

Aged↗

PubMed1993

Flow cytometric analysis of neutrophils in cows' milk.

Procedures were developed to count neutrophils in milk, using a flow cytometer. Milk samples from 2 experiments were counted: 1 with 4 noninfected cows and a second with 5 noninfected cows that were injected with endotoxin in 2 mammary quarters. Thus, the procedures were evaluated on normal milk and on that with high somatic cell count. Flow cytometric procedures involved fluorescence detection (from the dye carboxydimethylfluorescein diacetate) to distinguish intact and viable from fragmented cells, forward light scatter to detect cell size differences, and right-angle side scatter to detect cellular granularity. High fluorescence, large size, and high degree of granularity identified viable neutrophils. For all samples, neutrophils were also counted manually, using the cytologic centrifugation approach to create the slides; manual counts were used as the standard for comparison. In experiment 1 (normal milk), mean values for percentage of viable neutrophils estimated by manual and flow cytometry procedures agreed closely (26% vs 25.8% for foremilk and 28.8% vs 26.6% for bucket milk). Sources of variation in manual and flow cytometric estimates of percentage of neutrophils were examined. Cow variation was significant (P < 0.01) for manual and flow cytometric counts, but was larger for flow cytometric counts. Day-to-day variation in counts on milk from the same cow was negligible for manual counts, but was significant (P < 0.01) for flow cytometric counts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Vitamin K-dependent clotting factors are elevated in young adults who have close relatives with ischemic heart disease.

An increase in factor VII was found to be a risk factor for ischemic heart disease. The present study was designed to test the hypothesis that this increase in factor VII is part of a general increase in vitamin K-dependent clotting factors. Initially, a prospective analysis of factor VII antigen and prothrombin activity was performed in two groups of young subjects without symptoms who differed in their risk of ischemic heart disease based on a history (or lack thereof) of premature heart disease in a first-degree relative. A statistically significant increase in prothrombin activity and factor VII antigen was found in the high-risk group of subjects when compared with the low-risk group. In a second series of subjects, factor IX and X activity assays were also performed, and all four of the vitamin K-dependent clotting factors were found to be significantly higher in high-risk subjects when compared with low-risk subjects. A second goal of the study was to explore whether correlations between factor VII and cholesterol and triglycerides might be due to binding of factor VII with apolipoprotein B. Although a significant correlation of factor VII antigen with apolipoprotein B (rho = 0.523, p < 0.025) was found in our high-risk group of subjects, the correlation between factor VII and triglycerides (rho = 0.641, p < 0.005) was even stronger statistically, suggesting a probable interaction of factor VII with very-low-density lipoproteins in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Thyroglossal duct cysts.

The thyroglossal duct cyst (TGDC) is the most common congenital neck mass and the second most common of all childhood cervical masses. An anterior midline neck mass presenting before the age of twenty and displaying vertical movement with tongue protrusion and swallowing is characteristic of this lesion. Though concomitant agenesis of the thyroid is extremely rare, documentation of a normal thyroid preoperatively has become a legally protective requirement. Carcinoma in a TGDC is unusual and is rarely detected preoperatively, but a fine needle aspiration is helpful if a malignancy is suspected. Regardless, the treatment is a Sistrunk procedure: excision of the cyst, the tract connecting it to the foramen cecum, and the central portion of the hyoid bone.

Adult↗

PubMed1993

Tracheobronchopathia osteochondroplastica: a case report and a review of the literature.

Tracheobronchopathia osteochondroplastica is characterized by osseocartilaginous submucosal nodules projecting into the lumen of the larynx, trachea, and bronchi. Its etiology is unknown. Most cases are asymptomatic and frequently diagnosed incidentally during intubation or endoscopy. The diagnosis is made on the basis of endoscopy, CT scan, and histopathology. Fragments of adipose tissue, deposits of calcification and ossification often with foci of bone marrow and active hemopoiesis are present in the submucosa. Surgical treatment is indicated for airway obstruction and recurrent infections.

Aged↗

PubMed1992

Lack of protective immunity against reinfection with hepatitis C virus.

Some individuals infected with hepatitis C virus (HCV) experience multiple episodes of acute hepatitis. It is unclear whether these episodes are due to reinfection with HCV or to reactivation of the original virus infection. Markers of viral replication and host immunity were studied in five chimpanzees sequentially inoculated over a period of 3 years with different HCV strains of proven infectivity. Each rechallenge of a convalescent chimpanzee with the same or a different HCV strain resulted in the reappearance of viremia, which was due to infection with the subsequent challenge virus. The evidence indicates that HCV infection does not elicit protective immunity against reinfection with homologous or heterologous strains, which raises concerns for the development of effective vaccines against HCV.

Acute Disease↗

PubMed1992

Sequence analysis of the 5' noncoding region of hepatitis C virus.

We have determined the nucleotide sequence of the 5' noncoding (NC) region of the hepatitis C virus (HCV) genome in 44 isolates from around the world. We have identified several HCV isolates with significantly greater sequence heterogeneity than reported previously within the 5' NC region. The most distantly related isolates were only 90.1% identical. Nucleotide insertions were seen in three isolates. Analysis of the nucleotide sequence from 44 HCV isolates in this study combined with that of 37 isolates reported in the literature reveals that the 5' NC region of HCV consists of highly conserved domains interspersed with variable domains. The consensus sequence was identical to the prototype HCV sequence. Nucleotide variations were found in 45 (16%) of the 282 nucleotide positions analyzed and were primarily located in three domains of significant heterogeneity (positions -239 to -222, -167 to -118, and -100 to -72). Conversely, there were three highly conserved domains consisting of 18, 22, and 63 completely invariant nucleotides (positions -263 to -246, -199 to -178, and -65 to -3, respectively). Two nucleotide domains within the 5' NC region, conserved among all HCV isolates studied to date, shared statistically significant similarity with pestivirus 5' NC sequences, providing further evidence for a close evolutionary relationship between these two groups of viruses. Additional analysis revealed the presence of short open reading frames in all HCV isolates. Our sequence analysis of the 5' NC region of the HCV genome provides additional information about conserved elements within this region and suggests a possible functional role for the region in viral replication or gene expression. These data also have implications for selection of optimal primer sequences for the detection of HCV RNA by the PCR assay.

Base Sequence↗