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Biomedical subjects

J J Chang

Publications and source records attributed to J J Chang.

At least 73 records · Page 4Linked to original sources
PubMed1990

[The relationship between early motor stage and hand function recovery six months after stroke].

The prognosis of hemiplegic hand function may reflect intrinsic recovery. Applying the variables of initial neurological loss in the hemiplegic upper extremity to predict the prognosis of hand function will enable therapists to establish the ultimate goals of rehabilitation and to select the appropriate treatment programs. Pinch and grip strength tests, Frenchay arm function test and the nine-hole peg test were used to determine the relationship between the initial Brunnstrom motor stage of the hemiplegic upper extremity and the prognosis of hand function after six months. Forty stroke patients were divided into three groups. Group I was subjects with a motor stage below the Brunnstrom motor stage III in both proximal and distal parts of the hemiplegic upper extremity. Group II was subjects with motor stage below Brunnstrom motor stage III in the proximal part and above stage III in the distal part or vice versa. Group III was subjects with a motor stage above Brunnstrom motor stage III both in the proximal and the distal parts. The results of this study indicated that the prognosis of the Brunnstrom motor stage of the hemiplegic upper extremity generally improved about one or two stages. According to the results of the grip and pinch strength tests, the Frenchay arm function test or the nine-hole peg test, group I patients could hardly use their affected hand functionally. The grip strength and the pinch strength deficits of group I were 93.8% and 91.4% respectively. The grip strength and the pinch strength deficits of group II were 72.1% and 68.5% respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Cytotoxicity of isoquinoline alkaloids and their N-oxides.

A series of 53 isoquinoline alkaloids and their N-oxides have been tested for their cytotoxicity against A-549, HCT-8, KB, P-388, and L-1210 cells. These alkaloids include two tetrahydroprotoberberines, two protoberberines, six aporphines, one morphinandienone, five oxoaporphines, seven phenanthrenes, one spirobenzylisoquinoline N-oxide, nine aporphine N-oxides, seven benzyltetrahydroisoquinoline N-oxides, one benzylisoquinoline N-oxide, one protopine N-oxide, three tetrahydroprotoberberine N-oxides, four pavine N-oxides, and four phenanthrene N-oxides. The results are discussed on the basis of structure-activity relationships.

Alkaloids↗
PubMed1986

Role of arginine residues in the coagulant activity of high molecular weight kininogen.

High molecular weight (HMW) kininogen, the cofactor for activation of the contact system of plasma proteolysis, transports and optimally positions prekallikrein and factor XI on a negatively charged surface, allowing those zymogens to be activated by surface-bound factor XIIa. HMW kininogen circulates in plasma as a procofactor that, after cleavage by kallikrein or factor XIIa, gains ability to bind to the surface. The mechanism responsible for this increased affinity for the surface is unknown. We hypothesized that modification of arginine residues may prevent cleavage of HMW kininogen, since the initial kallikrein-induced cleavage sites on the HMW kininogen molecule are at the NH2 terminal and the COOH terminal of the bradykinin-containing portion of the molecule, each of which contains arginine. We found that modification with butanedione of four arginine residues in the HMW kininogen molecule prevented bradykinin release, which results from cleavage of HMW kininogen. Furthermore, HMW kininogen coagulant activity was lost, in proportion to the degree of arginine modification, until 6.6 residues had been modified. Complex formation with prekallikrein, however, was found to be uneffected by the modification of modified HMW kininogen. To account for the loss of coagulant activity, we also examined the ability of modified HMWKa (active cofactor) to bind to an activating surface. The affinity of modified HMWKa for kaolin was tenfold less than the affinity of unmodified HMWKa. These data suggest that arginine residues play a critical role in the ability of HMW kininogen to function as an activation cofactor, both by preventing the cleavages that produce HMWKa as well as by decreasing the affinity of HMWKa for the surface.

Arginine↗
PubMed1985

Cooperative and non-cooperative processes of apparent movement of random-dot cinematograms.

In this study, we investigated the cooperative and non-cooperative models of stereopsis on apparent movement of the short-range process using spatial frequency filtered random-dot cinematograms. Our results showed that when spatial frequencies were below 4 cycles/degree, maximum displacement (dmax) was decreasing (linearly) with increasing mean frequencies, but at 4 cycles/degree and above dmax stayed constant. For low frequencies, non-cooperative models such as Marr and Poggio's could explain these findings, but not for frequencies above 4 cycles/degree. However, in a previous study we found that the average cooperative neighbourhood for apparent movement of the short-range process is 15 arc min. This fortuitous agreement on 4 cycles/degree could suggest that dmax being constant at frequencies above 4 cycles is related to a cooperative process.

Depth Perception↗
PubMed1984

Cooperative phenomena in apparent movement perception of random-dot cinematograms.

To determine if apparent movement perception of random-dot cinematograms (RDC) is a cooperative process, we examined the interaction between adjacent areas whose movement, when perceived independently, was in opposite directions. The stimulus contained alternating ambiguous and unambiguous horizontal random-dot stripes of equal width. The ambiguous areas were biased in a specific direction opposite to the movement of the unambiguous areas. The cooperative process was evaluated by noting that the unambiguous areas were able to reverse the perceived direction of the ambiguous areas. Thus all dots were seen to move uniformly in the unambiguous direction. This phenomenon was dependent on the amount of bias inserted in the ambiguous areas and the width of the stripes. A Cooperative Strength (CS) index was computed. We found that CS depended on the stripe width, and that the average cooperative neighborhood was about 15 min arc in visual angle, suggesting a relationship to the diameter of cortical hypercolumns.

Form Perception↗
PubMed1984

Biochemistry of renin.

Biochemical features of renin have been studied. Determination of the amino acid sequence and catalytically essential groups in the active sites of mouse submandibular gland revealed the similarity of renin with acid proteases. Yet stringent substrate specificity, neutral pH optimum of its enzyme activity and the unique structure of the activation peptide distinguish it from digestive enzymes. Inactive renin was identified as renin zymogen by complete purification and translation in vitro.

Amino Acid Sequence↗
PubMed1984

Regulation of the coagulant activity and surface binding of high molecular weight kininogen.

Cleavage of the procofactor, high molecular weight kininogen, by kallikrein, is required for expression of it cofactor activity. Coagulant activity associated with the light chain of high molecular weight kininogen is destroyed by proteolysis by factor XIa. The heavy chain of high molecular weight kininogen augments the binding of the light chain to activating surfaces without itself expressing coagulant activity.

Blood Coagulation Factors↗
PubMed1983

Displacement limits, directional anisotropy and direction versus form discrimination in random-dot cinematograms.

Apparent motion mediated by the short-range process was studied. Random-dot cinematograms were used to determine the maximum displacement (dmax) for motion-direction and pattern discrimination. dmax is the maximum spatial separation between a correlated region (target) in the two successively presented random-dot images, when observers can correctly identify the direction of motion or the shape of the target. We have found that: (1) dmax for motion-direction discrimination increases with the square root of the display area; (2) dmax is invariant with eccentricities of 4 deg arc; (3) For rectangular targets and brief presentations, dmax increases with increases of that target-dimension which is parallel to the orientation of the movement. These findings indicate that short-range movement perception is an orientation specific global process. Furthermore, motion-direction discrimination and pattern discrimination of random-dot cinematograms may be mediated by different levels of processes. However, even for pattern discrimination dmax in visual angle increases with increased target area.

Discrimination, Psychological↗
PubMed1983

Displacement limits for spatial frequency filtered random-dot cinematograms in apparent motion.

Two-dimensional band-pass filtered random-dot cinematograms were used to study apparent movement mediated by the short-range process. In the first experiment maximum displacement (dmax) for correct direction of movement was measured for symmetrically filtered low-pass, medium-pass, and high-pass images. dmax was found to be limited by the grain size in the image and increased with the target area. Since eccentric presentation had no effect on dmax, the increase of dmax with target area suggests that apparent movement perception is a global process. In the second experiment the stimulus was filtered differentially in the two orthogonal directions using cone filtering. dmax was found to be commensurate with the length of the clusters in the direction of the movement.

Form Perception↗
PubMed1983

Electron microscopy of frozen hydrated sections of vitreous ice and vitrified biological samples.

The preparation and high resolution observation of frozen hydrated thin sections has been studied by transmission electron microscopy (TEM and STEM) on model systems, including pure water, protein solutions, catalase crystals, myelin sheath and various tissues. The state of the ice is determined by electron diffraction. Mass measurement in the electron microscope is used to determine section thickness and control hydration. An adequate depth of vitrified material for sectioning can be obtained from many biological suspensions or untreated tissues. Frozen hydrated sections around 100 nm thick can be produced under optimal conditions from vitreous ice or from vitrified biological samples. Sectioning, transfer and observation in the electron microscope is feasible without alteration of the sample hydration or its initial vitrification. Biological structures can be preserved and observed down to 10 nm. Under favourable working conditions, specimen compression during sectioning and electron beam damage are the factors limiting high resolution observations.

Animals↗
PubMed1983

Structure of mouse submaxillary gland renin.

To determine the structural basis for the highly specific action of renin, structural features of the active site and the complete amino acid sequence of mouse submaxillary gland renin were determined. A rapid method was developed for a large scale purification of renin from mouse submaxillary gland. The active site of renin was shown to consist of 2 aspartyl residues, 2 tyrosyl residues and one arginyl residue, the structures analogous to the active site of pepsin and other acid proteases. Renin was found to consist of one heavy chain (Mr = 31,036) and one light chain (Mr = 5,458) connected by a disulfide bridge. Amino acid sequences of these chains were determined using overlapping peptides generated by cleavage with cyanogen bromide, trypsin, Staphylococcus aureus protease and Lysobacter enzymogenes endoproteinase Lys-C. Sequences involving 2 catalytically essential aspartyl residues 32 and 215, characteristic to acid proteases, were found identical with pepsin, penicillopepsin and chymosin. The sequence of L-chain was homologous with carboxyl terminal region of porcine pepsin in 46% of amino acid residues. H-chain showed 41% homology with 284 residues on the amino-terminal side of the porcine pepsin molecule. Residues identical in renin and acid proteases are distributed throughout the length of the molecules, suggesting a similarity in their overall structure.

Amino Acid Sequence↗