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Biomedical subjects

J F Smith

Publications and source records attributed to J F Smith.

At least 19 recordsLinked to original sources
PubMed1995

Attenuated mutants of Venezuelan equine encephalitis virus containing lethal mutations in the PE2 cleavage signal combined with a second-site suppressor mutation in E1.

The PE2 cleavage signal in a full-length cDNA clone of the alphavirus Venezuelan equine encephalitis virus (VEE) was ablated by site-directed mutagenesis. RNA transcripts derived from the resulting plasmids programmed the production of nonviable particles upon transfection of baby hamster kidney (BHK) cells. However, the mutant RNAs also gave rise to a small proportion of viable revertants. Analysis of these biological revertants and their molecularly cloned homologs demonstrated that second-site suppressor mutations at either E2 position 243 or E1 position 253 were able to restore viability to PE2 cleavage signal mutants. The viable revertants incorporated unprocessed PE2 into particles which showed normal infectivity for BHK cells, but reduced ability to grow in C6/36 mosquito cells. A mutant carrying a lethal PE2 cleavage signal mutation in combination with a suppressor at E1 253 was either avirulent or highly attenuated in adult mice when inoculated by the subcutaneous, intracerebral, or intranasal route and conferred complete protection against both intraperitoneal and intranasal challenge with virulent VEE. These results indicate the close functional association of the E2 and E1 proteins in the alphavirus spike. They also have implications for the design of recombinant live virus vaccines for VEE, for other alphaviruses, and for other viruses that use a similar mechanism for glycoprotein maturation.

Amino Acid Sequence↗
PubMed1995

Second trimester uterine atony imitating ectopic pregnancy: magnetic resonance diagnosis.

When an obstetrical patient was referred for inability to auscultate fetal heart tones at 18 weeks' gestation, ultrasound identified a single living fetus in the maternal right upper quadrant. Magnetic resonance imaging (MRI) ruled out a suspected uterine ectopic pregnancy and avoided laparotomy. The patient experienced an uncomplicated term delivery. MRI is a useful adjunct to ultrasound for mid-trimester pregnancy localization when the differential diagnosis includes uterine eccyesis.

Adult↗
PubMed1995

Transvaginal sonographic measurement of cervical length. Evaluation of twin pregnancies.

Twin gestations continue to contribute significantly to perinatal morbidity and mortality. The increased perinatal risks associated with twin gestations are directly related to prematurity. Thus, further characterization of the risks of prematurity may yield useful information in managing these patients. We investigated transvaginal ultrasound measurement of the cervix throughout twin gestations and compared these findings to those in singleton pregnancies. Twenty-five patients with twin gestations underwent 53 cervical length measurements. As compared to cervical length in singleton pregnancies, that in twins was significantly shorter for matched gestational age groups.

Adolescent↗
PubMed1995

Doppler velocimetry and fetal heart rate pattern observations in acute cocaine intoxication. A case report.

While the use of cocaine in pregnancy continues to be a significant contributor to adverse maternal and perinatal outcomes, systematic study of the physiologic effects of cocaine in human gestation remains difficult. In a case of acute cocaine intoxication in the third trimester, Doppler velocimetry suggested a physiologic response from the uterine artery but not the umbilical artery. Furthermore, the abnormal uterine artery velocimetry was associated with a positive nonreactive contraction stress test, which became negative and reactive as the effects of the cocaine wore off and the velocimetry returned to normal. These observations suggest that the uterine arteries are more sensitive to cocaine than are the umbilical arteries and that abnormal fetal heart rate patterns during acute cocaine intoxication may be transitory.

Adult↗
PubMed1995

Percutaneous interventions for ischemic heart disease.

In the United States, when necessary due to symptoms or prognosis, percutaneous coronary interventions are performed on patients with ischemic heart disease more frequently than is coronary artery bypass surgery. A wide array of options are available to the interventional cardiologist. Improvements over the 17 years that coronary balloon angioplasty has been performed have kept it the primary therapy. It is currently used safely and effectively in the majority of patients. The problems of abrupt closure, restenosis, and inadequate results in some complex lesions have spurred the development of intracoronary stents, coronary atherectomy and ablation devices, and coronary excimer lasers. Metallic stents perform well in large vessels to treat abrupt closures and to reduce restenosis, but confer a risk of hemorrhage. Specific complexities of lesion characteristics determine the effective use of atherectomy/ablation devices and lasers. Future technologic improvements anticipate even better treatments for patients with coronary artery disease.

Angioplasty, Balloon, Coronary↗
PubMed1994

A molecular genetic approach to the study of Venezuelan equine encephalitis virus pathogenesis.

Viral pathogenesis can be described as a series of steps, analogous to a biochemical pathway, whose endpoint is disease of the infected host. Distinct viral functions may be critical at each required step. Our genetic approach is to use Venezuelan equine encephalitis virus (VEE) mutants blocked at different steps to delineate the process of pathogenesis. A full-length cDNA clone of a virulent strain of VEE was used as a template for in vitro mutagenesis to produce attenuated single-site mutants. The spread of molecularly cloned parent or mutant viruses in the mouse was monitored by infectivity, immunocytochemistry, in situ hybridization and histopathology. Virulent VEE spread through the lymphatic system, produced viremia and replicated in several visceral organs. As virus was being cleared from these sites, it began to appear in the brain, frequently beginning in the olfactory tracts. A single-site mutant in the E2 glycoprotein appeared to block pathogenesis at a very early step, and required a reversion mutation to spread beyond the site of inoculation. The feasibility of combining attenuating mutations to produce a stable VEE vaccine strain has been demonstrated using three E2 mutations.

Amino Acid Sequence↗
PubMed1994

A contextual-behavioral model of empowerment: case studies involving people with physical disabilities.

When people with disabilities, ethnic minorities, older adults, women, and others lack power, they usually experience adverse conditions disproportionate to other members of society. Empowerment--the process by which people gain some control over valued events, outcomes, and resources--is an important construct for understanding and improving the lives of people of marginal status. This manuscript presents a contextual-behavioral model of empowerment and its application in collaborative research with people with physical disabilities. The eight case studies illustrate 18 tactics for promoting empowerment that flow from the model. The case studies show the use of different combinations of empowerment tactics in a variety of contexts: (a) setting improvement agendas from the perspective of people with disabilities, (b) enforcing ordinances that preserve access to parking spaces designated for people with disabilities, (c) enabling access to homes through housing modifications, (d) enhancing support available through mutual-aid groups, (e) developing skills for recruiting mentors, (f) promoting self-directed behavior change with personal and health concerns, (g) enhancing skills for personal self-advocacy, and (h) building the capacities of groups of people with disabilities for systems advocacy. Finally, we discuss issues that may contribute to research and action related to empowerment.

Activities of Daily Living↗
PubMed1994

Surfactant protein A and saturated phosphatidylcholine in respiratory distress syndrome.

We measured surfactant protein A (SP-A) by ELISA using a rabbit antihuman SP-A polyclonal antibody and saturated phosphatidylcholine (SPC) by thin-layer chromatography in sequential tracheal fluid samples obtained from 16 preterm neonates without lung disease and 37 with respiratory distress syndrome (RDS). SP-A and SPC were lower in neonates with RDS than in control infants (1.0 +/- 0.1 versus 8.9 +/- 2.2 ng SP-A/microgram protein [p < 0.0001] and 0.20 +/- 0.05 versus 0.70 +/- 0.19 mumol SPC/mg protein [p < 0.01], respectively). Initial SP-A concentrations correlated inversely with severity of RDS (r = 0.45, p < 0.01) but did not correlate with initial SPC levels. Significant increases in SP-A were detectable within 12 to 24 h after birth in neonates with RDS. Further increases occurred subsequently and were similar for neonates treated with either a synthetic (Exosurf) or a modified natural (Survanta) surfactant. Using two-dimensional gel electrophoresis, SP-A in tracheal fluid obtained during the early and recovery phases of RDS exhibited lesser degrees of posttranslational modification than SP-A forms from control neonates. Administration of Exosurf or Survanta resulted in comparable increases in SPC in tracheal fluid. Preterm neonates with RDS seem to have an immature SP-A metabolism that persists for several days after birth. The type of surfactant used does not modify the recovery of SP-A or SPC in tracheal fluid from infants with RDS.

Analysis of Variance↗
PubMed1994

Cranio-orbital reconstruction: safety and image quality of metallic implants on CT and MRI scanning.

A study was undertaken to evaluate the safety of magnetic resonance imaging (MRI) of metallic implants used in cranio-orbital reconstruction (stainless steel wire and titanium and Vitallium plates) and also to compare the degree of artifact created on computed tomographic (CT) scanning and MRI by each material. Samples of each material were tested for deflection (movement) in a 1.5-T MRI field and for temperature change under conditions simulating a clinical MRI scan. None of the materials exhibited any deflection, and none exhibited any significant temperature change compared with water. Standardized bars of each material and commonly used, commercially available titanium and Vitallium implants (plates, mesh) were evaluated for artifact. On blinded evaluation by three radiologists and on quantitative computer analysis of the CT images, the stainless steel produced the most artifact on both CT scan and MRI, followed by the Vitallium, with the least artifact caused by titanium. All the titanium images were felt to be acceptable to detect orbital pathology, while only the images with the thinnest Vitallium (micromesh) implant were acceptable.

Animals↗
PubMed1992

Comparison of the sequence and structure of transcription factor IIIA from Bufo americanus and Rana pipiens.

Amino acid (aa) sequences of transcription factor IIIA (TFIIIA) from the toad, Bufo americanus, and the grass frog, Rana pipiens, were determined by cDNA cloning and DNA sequencing. The 3'-untranslated regions of the cDNAs reveal that the TFIIIA gene polyadenylation signal is ATTAAA, rather than the conventional AATAAA. The B. americanus and R. pipiens proteins share about 60% aa sequence homology with each other and with Xenopus laevis TFIIIA. Although these results indicate that TFIIIA has more sequence variation than other DNA-binding proteins, a number of conserved features are evident and of likely functional significance. These include potential guanine nucleotide-binding sites at arginines in zinc fingers (ZnF) II, V, and IX, acidic residues between metal-coordinating cysteines, and a basic region in the C-terminal tail possibly involved in transcription promotion. Sequence similarity also exists in an aa stretch bridging the ninth ZnF and C-terminal tail of both TFIIIA and the 5S RNA-binding protein, p43. DNase I protection analyses demonstrate that B. americanus and R. pipiens TFIIIA interact with the internal control region (ICR) of the Xenopus borealis 5S RNA-encoding gene (5S) in different manners: the B. americanus interaction is similar to X. laevis TFIIIA, protecting the entire 5S gene ICR (nt +96 to +43) from DNase I digestion, whereas the R. pipiens TFIIIA strongly protects the ICR from nt +96 up to +78 and less strongly from +78 to +43. Possibly accounting for the binding differences observed, R. pipiens and R. catesbeiana oocyte 5S RNAs (and by inference 5S genes) were found to contain a G or U at nt position 50 while B. americanus, X. laevis, and other eukaryotic 5S RNAs have an A in the analogous position (nt 53 in generalized eukaryotic structure).

Amino Acid Sequence↗