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Biomedical subjects

C C Kao

Publications and source records attributed to C C Kao.

108 records · Page 6Linked to original sources
PubMed1977

The mechanism of spinal cord cavitation follwing spinal cord transection. Part 2. Electron microscopic observations.

The authors report their findings by electron microscopy after microsurgical subpial spinal cord transection in dogs. After cord transection, conspicuous myelin microcysts are formed in a background of otherwise intact cord tisue at a distance of 1 to 2 mm from the cut end of the cord, both proximal and distal to the transection, Seen through the electron microscope, the microcysts iss a myelin sac distended by fluid under pressure, containing a swollen axon filled with excessive axoplasmic organelles; that is, a terminal club. Later the microcysts and terminal clubs rupture. The large spaces within the microcysts are opened to heretofore small extracellular spaces and the spinal cord tissues are destroyed. Thus, microcysts are precursors of large cavitites seen at the ends of transcreted cord stumps. The formation of microcysts and their subsequent rupture, which leads to cord cavitation, is interpreted as an inherent response of cord tissue to injury, and the result of an abortive attempt at cord regeneration.

Animals↗
PubMed1977

The mechanism of spinal cord cavitation following spinal cord transection. Part 3: Delayed grafting with and without spinal cord retransection.

Cavitation adjacent to transection of spinal cords can be successfully eliminated by a second operation 1 week after the initial spinal cord transection. The second operation consists of removal of the necrotic spinal cord tissue, thus producing a gap. Segments of autogenous sciatic nerve are inserted into the gap between the spinal cord stumps. If the spinal cord is injured by retransection at the second operation, cavitation again occurs in the spinal cord stumps resulting in separation of the nerve grafts from the spinal cord. The results of the present experiments support the concept that lysosomal spinal cord autotomy, which causes spinal cord cavitation, is a self-limiting process and that once the spinal cord has completed the autotomy, the process will not occur again unless the spinal cord is agiain traumatized.

Animals↗
PubMedDate not supplied

Characterization of a negative regulator of exopolysaccharide production by the plant-pathogenic bacterium Pseudomonas solanacearum.

Wild-type strains of the bacterial wilt pathogen Pseudomonas solanacearum exhibit reduced exopolysaccharide production and virulence when transformed with plasmids carrying the epsR locus. To understand the function of epsR, we used mutagenesis and DNA sequencing to identify the gene responsible for the shutoff of exopolysaccharide production. The epsR gene encodes a 236-amino-acid polypeptide that, based on polypeptide sequence homology, has significant similarity to other proteins of the luxR family of environmentally responsive, two-component regulatory systems. When a mutated copy of the epsR gene was marker-exchanged into the wild-type P. solanacearum chromosome, however, we observed no effect on growth in culture or on exopolysaccharide production. This suggests that the EpsR phenotype becomes apparent only via overproduction of the EpsR protein. By means of an antiserum directed against the EpsR protein, we detected the overproduction of EpsR in cell lysates of a strain of P. solanacearum harboring a multicopy plasmid with an active epsR gene but not in one harboring the same plasmid with a mutated epsR gene.

Amino Acid Sequence↗
PubMedDate not supplied

Complementation analyses of Pseudomonas solanacearum extracellular polysaccharide mutants and identification of genes responsive to EpsR.

Many plant-pathogenic bacteria require extracellular polysaccharides (EPS) for successful infection. For example, mutations tht prevent EPS production in the bacterial wilt pathogen, Pseudomonas solanacearum, will reduce the ability to wilt plants. While several P. solanacearum EPS genes have been identified and characterized, a systematic analysis of EPS mutants has not previously been performed. We have screened over 12,000 transposon-tagged mutants and categorized 66EPS::lacZ mutants into nine complementation sets. Five of these are composed of previously characterized EPS structural and regulatory loci; four contain newly described EPS loci. One of the four novel complementation sets has been determined to be defective for both EPS and lipopolysaccharide production. We also used the EPS::lacZ mutants to examine the interaction between P. solanacearum EPS genes. Overexpression of the previously described regulator EpsR was found to down-regulate the expression of genes encoding production of the major acidic form EPS.

Bacterial Proteins↗
PubMedDate not supplied

Quantitative measurement of improvement in sitting balance in children with spastic cerebral palsy after selective posterior rhizotomy.

Severe muscular spasticity encountered frequently in patients with spastic cerebral palsy not only affects patient locomotor function but also causes musculoskeletal complications. Significant reduction of spasticity over pelvis and lower limbs after selective posterior rhizotomy (SPR) results in improvement of trunk stability, locomotor function, and function of upper limbs also. The purpose of this study was to investigate the difference of sitting balance before and after SPR using a quantitative measurement in sitting stability represented as dispersion index provided by the Chattecx Balance System. Seventeen children with spastic cerebral palsy, ten boys and seven girls, with a mean age of 5.06 yr, underwent SPR. Their sitting stability under static and dynamic, visual and nonvisual testing conditions was assessed before SPR and three mo after SPR. Their sitting balance showed significant improvement at postoperative evaluation except for the static-nonvisual testing condition. Dispersion index under the dynamic testing condition was significantly higher than under the static testing condition, which implies that dynamic sitting balance was worse than static sitting balance in these patients. There was no statistical difference of sitting performance between visual and nonvisual condition both preoperatively and postoperatively. Quantitative measurement of dispersion index provided by the Chattecx Balance System offers an objective evidence of improvement in sitting balance for children after SPR.

Cerebral Palsy↗
PubMedDate not supplied

Xeromammographic image quality.

Xeroradiography is a diagnostic modality whose image-forming properties are fundamentally different from those of the conventional silver halide process. In this work, the xeromammographic process, representing the low-constrast limit of xeroradiography, is analyzed in detail. A step by step approach is taken, whereby th eimiting factors in the exposure and development stages are identified and quantified. The sensitivity of the Se layer is also computed and the concept of optimal exposure introduced. The paper concludes by considering a simple model for xeroradiographic noise.

Mammography↗
PubMedDate not supplied

Epstein-Barr virus pneumonia associated with hemophagocytic syndrome: report of one case.

An 8-year-old girl was admitted because of high fever and cough for seven days. The physical examination on admission revealed diffuse moist rales over the left lung field. Her high fever persisted, and she subsequently developed hepatosplenomegaly, lymphadenopathy, skin rashes, subconjunctival hemorrhage, diffuse pulmonary infiltrates, abnormal liver function, anemia, thrombocytopenia, leukocytosis, and hypoalbuminemia. A bone marrow study revealed increased numbers of macrophages with apparent hemophagocytosis. She developed respiratory failure and required artificial ventilation, but finally died despite resuscitative efforts. Serology for EB virus initially revealed negative findings, but on the 24th day after admission, showed IgG antibody to viral capsid antigen 320x (+), and IgM antibody to viral capsid antigen (+). This is a very unusual case of fatal EB virus pneumonia associated with hemophagocytic syndrome.

Child↗