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Biomedical subjects

C Park

Publications and source records attributed to C Park.

At least 271 records · Page 15Linked to original sources
PubMed1987

Spontaneous osteonecrosis of the knee. Scintigraphic findings.

Three cases of spontaneous osteonecrosis (SON) of the knee, comprised of two cases involving the medial tibial plateau and one involving the medial femoral condyle, are reported. Because of the relatively normal x-rays early in the course of the disease, the differential diagnosis of a painful knee is markedly shortened with the typical scintigraphic findings in SON. The scintigraphic findings represent a focal area of increased activity at the affected site on a three-phase bone scan.

Aged↗
PubMed1986

Transfer of chromosomal mutations to plasmids via Hfr-mediated conduction.

Nonconjugative plasmids can be transferred from an Hfr donor to a recipient by Hfr-mediated conduction. We found that this phenomenon can be employed to obtain a plasmid in which a mutation in a chromosomal gene has been transferred to the copy of that gene contained in the hybrid plasmid.

Bacterial Proteins↗
PubMed1986

Mutations specifically affecting ligand interaction of the Trg chemosensory transducer.

The Trg transducer mediates chemotactic response to galactose and ribose by interacting, respectively, with sugar-occupied galactose- and ribose-binding proteins. Adaptation is linked to methylation of specific glutamyl residues of the Trg protein. This study characterized two trg mutations that affect interaction with binding protein ligands but do not affect methylation or adaptation. The mutant phenotypes indicated that the steady-state activity of methyl-accepting sites is independent of ligand-binding activity. The mutation trg-8 changed arginine 85 to histidine, and trg-19 changed glycine 151 to aspartate. The locations of the mutational changes provided direct evidence for functioning of the amino-terminal domain of Trg in ligand recognition. Cross-inhibition of tactic sensitivity by the two Trg-linked attractants implies competition for a common site on Trg. However, the single amino acid substitution caused by trg-19 greatly reduced the response to galactose but left unperturbed the response to ribose. Thus Trg must recognize the two sugar-binding proteins at nonidentical sites, and the complementary sites on the respective binding proteins should differ. trg-8 mutants were substantially defective in the response to both galactose and ribose. An increase in cellular content of Trg-8 protein improved the response to galactose but not to ribose. It appears that Trg-8 protein is defective in the generation of the putative conformational change induced by ligand interaction. The asymmetry of the mutational defect implies that functional separation of interaction sites could persist beyond the initial stage of ligand binding.

Bacterial Proteins↗
PubMed1986

Mutation plus amplification of a transducer gene disrupts general chemotactic behavior in Escherichia coli.

Transducers are transmembrane receptor proteins that generate intracellular signals on stimulation and participate in adaptation by appropriate changes in the level of methylation. The transducer mutation trg-21 conferred a Trg- phenotype and defective taxis to galactose and ribose but a normal response to other attractants when present in a single chromosomal copy. Amplification of trg-21 by a multicopy plasmid made host cells generally nonchemotactic. The dominant phenotype resulted from a strong counterclockwise rotational bias of flagellar motors in Che- cells. Apparently, the Trg21 transducer sends a continuous counterclockwise signal to flagella independent of tactic stimulation. It appears that the cell has a homeostatic capacity that is sufficient to compensate for the effect of mutant transducers produced from a single chromosomal copy of trg-21, but the capacity is exceeded in cells that have multiple copies of the gene. The Trg21 protein did not have a significant effect on methylesterase activity, indicating that the two global effects of a stimulated transducer, that is, on flagellar rotation and on modification enzymes, can occur independently. The mutant protein exhibited essentially normal turnover of methyl groups but had a drastic defect in deamidation which thus reduced the number of methyl-accepting sites. The trg-21 mutation substitutes a threonine for Ala-419. This alanine is a conserved residue in all sequenced transducers and is in a region of the carboxy-terminal domain in which homology among the transducers is very high. The Trg21 phenotype implicates this conserved region in the generation of the excitatory signal which is directed at the flagella.

Bacterial Proteins↗
PubMed1984

Structure of the Trg protein: Homologies with and differences from other sensory transducers of Escherichia coli.

Transducer proteins are central to chemotaxis in Escherichia coli. Three transducer genes comprise a homologous gene family, while a fourth gene, trg, is more distantly related. We have determined the nucleotide sequence of trg. The deduced sequence of the Trg protein has features in common with other transducers as well as regions of significant divergence. The protein sequence suggests the same transmembrane structure postulated for other transducers: an extra cytoplasmic NH2-terminal domain connected by a membrane-spanning region to an intracellular COOH-terminal domain. The COOH-terminal domain of Trg exhibits substantial sequence identity with the corresponding domains of the other transducers, particularly near the sites of covalent modification. Trg appears to have the same five methyl-accepting sites identified in the Tsr protein. Two of those sites are glutamines that are deamidated to yield methyl-accepting glutamates, while the remainder are synthesized as glutamates. Conservation in number but not in position of modified glutamines in Trg compared to the other transducers is consistent with the notion that uncharged glutamines at a specific number of modification sites serve to balance the signaling state of newly synthesized transducers. The NH2-terminal domain of Trg exhibits no significant homology with other transducers, implying that trg may be a fusion of the common COOH-terminal transducer sequence with an unrelated NH2-terminal sequence. The location of specific mutations within trg provides support for the suggestion that ligand-binding sites are in the NH2-terminal domains.

Amino Acid Sequence↗
PubMed1984

Plantar pressures and gait parameters: a study of foot shape and limb rotations in children.

The most frequent referral diagnosis of childhood to an orthopaedic department is a limb rotational anomaly which manifests itself as either an abnormality of gait or flatfeet. The child is usually asymptomatic, the anxiety being generated in the minds of the parents. One hundred normal children were studied using a Pedobarograph to assess underfoot pressures, and a simple walkway to measure dynamic gait parameters. The results have been correlated with age, and the trends suggest that the pedobarograms may be of use in the prognostication of lower limb rotations. The methods, which are totally noninvasive and can be carried out in the clinic, have the added advantage of reassuring parents that "something is being done."

Adolescent↗
PubMed1983

Effect of the extracellular matrix on plasminogen activator isozyme activities of human mammary epithelial cells in culture.

Multiple molecular forms of plasminogen activator were detected in normal human mammary epithelial cells in culture. Cells derived from (normal) breast mammoplasty specimens and grown on the surface of collagen gels exhibited three major classes of plasminogen activator isozymes (Mr = 100,000 [100K], 75,000 [75K], and 55,000 [55K]). The activity of the 100K and 75K isozymes was greatly reduced when the cells were grown on conventional tissue-culture-grade plastic surfaces. MCF-7, a human mammary carcinoma cell line, exhibited predominantly or exclusively the 55K isozyme, irrespective of the cell growth substratum. The activity of the 55K isozyme was more than twofold higher for MCF-7 cells grown on collagen gels than for cells grown on plastic. Progesterone, diethylstilbestrol, and estrogen stimulated the activity of the 55K isozyme of MCF-7 cells, but only when the cells were grown on a plastic surface. The plasminogen activator activities of the normal human mammary epithelial cells were not stimulated by these hormones, irrespective of the growth substratum. These results show that the expression of plasminogen activator isozymes by human mammary epithelial cells is subject to modulation by the extracellular matrix. Normal and malignant cells may differ in their responsiveness to these effects.

Breast↗
PubMed1982

Management of the deformed rheumatoid forefoot. A comparison of conservative and surgical methods.

In a retrospective survey of 65 patients who had rheumatoid arthritis, the late results of excision arthroplasty of the forefoot were investigated and compared with nonoperative management. Subjective assessment of foot shape and severity of pain as well as objective changes in gait and deformity were considered. Surgery relieved pain initially, but the recurrence rate of metatarsalgia was high. In those who wore surgical shoes, lack of cosmesis was the most important factor in determining poor compliance. The operation was recommended at random, and there was little difference in the outcomes of nonoperative and surgical treatments. A long-term randomized prospective trial is required to establish the criteria for selection of a management regime.

Adult↗
PubMed1981

Systemic Haemophilus influenzae infections in a community hospital: prevalence of ampicillin resistance.

Ampicillin-resistant strains are presently known to account for 10% to 20% of type b Haemophilus influenzae infections in the United States. To determine whether the incidence in a community hospital parallels that of several university hospitals, we reviewed medical records of the 99 children with type b Haemophilus systemic infections for the period 1976 to 1979. These cass represented 1.8% of all pediatric medical admissions. In 1976-1977, 5% of those infections were caused by resistant strains; the incidence increased to 19% for the period 1978-1979. This increase on a community hospital level parallels the increase in ampicillin resistance in Haemophilus noted in university hospitals and underscores the need for chloramphenicol (alone or in combination with ampicillin) as initial treatment for systemic Haemophilus infections.

Ampicillin↗
PubMed1981

Stereophotogrammetry and relief photography in the assessment of foot disorders.

Expanded polyethylene foam (Plastazote) is used in the treatment of rheumatoid, diabetic, and leprotic foot disorders. This paper describes a diagnostic use for this material. Two photographic techniques combine to give vivid and quantitative representations of foot deformities which are easily applicable to clinical use. Relief photography uses illumination to create an illusion of solidity in a 2-dimensional photography. Stereophotogrammetry produces contour plots from stereopairs of photographs of the Plastazote footprint. After use the impressions are trimmed and slipped into the patient's shoes in the same way as any other foam insole.

Dermatoglyphics↗