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K T Yang

Publications and source records attributed to K T Yang.

15 recordsLinked to original sources
PubMed2001

Arachidonic acid-induced H+ and Ca2+ increases in both the cytoplasm and nucleoplasm of rat cerebellar granule cells.

1. Arachidonic acid (AA) exerts multiple physiological and pathophysiological effects in the brain. By continuously measuring the intracellular pH (pH(i)) and Ca2+ levels ([Ca2+]i) in primary cultured rat cerebellar granule cells, we have found, for the first time, that 20 min treatment with 10 microM AA resulted in marked increases in Ca2+ and H+ levels in both the cytosol and nucleus. 2. A much higher concentration (40 mM) of another weak acid, propionic acid, was needed to induce a similar change in pH(i). The [Ca2+]i increase was probably caused by AA-induced activation of Ni2+-sensitive cationic channels, but did not involve NMDA channels or the Na+-Ca2+ exchanger. 3. AA-induced acidosis occurs by a different mechanism involving predominantly the passive diffusion of the un-ionized form of AA, rather than a protein carrier, as proposed by Kamp & Hamilton for fatty acids (FAs) in artificial phospholipid bilayers (the 'flip-flop' model). The following results, which are similar to those observed in lipid bilayers, support this conclusion: (1) FAs containing a -COOH group (AA, linoleic acid, alpha-linolenic acid, and docosahexaenoic acid) induced intracellular acidosis, whereas a FA with a -COOCH3 group (AA methyl ester) had little effect on pH(i), (2) a FA amine, tetradecylamine, induced intracellular alkalosis, and (3) the AA-/FA-induced pH(i) changes were reversed by bovine serum albumin. 4. Further evidence in support of a passive diffusion model, rather than a membrane protein carrier, is that: (1) there was a linear relationship between the initial rate of acid flux and the concentration of AA (2-100 microM), (2) acidosis was not inhibited by 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid, a potent inhibitor of the plasma membrane FA carrier protein, and (3) the involvement of most known H+-related membrane carriers and H+ conductance has been ruled out. 5. Since AA can be released under both physiological and pathophysiological conditions, the possible significance of the AA-evoked increases in H+ and Ca2+ in both the cytoplasm and nucleoplasm is discussed.

Acidosis↗
PubMed1999

Correlation of vasomotor- and respiratory-controlling mechanisms around the caudal ventrolateral medulla in cats.

We examined the involvement of caudal ventrolateral medulla (CVLM) in respiratory control. Microinjection of glutamate (Glu) into CVLM decreased systemic arterial blood pressure (SAP) and altered phrenic nerve activities (PNA). Among 143 depressor sites, 55% (78/143) increased respiratory frequency (Rf), while 72% altered PNA amplitude (36% increased and 36% decreased). A small but significant positive correlation was observed between the magnitudes of depressor responses and inhibition of PNA amplitude (r = 0.1718, n = 143), indicating a substantial cross-talk between depressor and PNA inhibitory neurons. Furthermore, microinjections of acetylcholine (ACh) mimicked the Glu-induced depressor responses. However, ACh did not alter Rf, but still reduced PNA amplitude. Our findings suggest that Rf-regulating and depressor neurons are two separate neuronal populations, coexisting in CVLM. The PNA inhibitory and depressor neurons, in contrast, could have stronger correlation.

Acetylcholine↗
PubMed1999

Fragile X premutation is a significant risk factor for premature ovarian failure: the International Collaborative POF in Fragile X study--preliminary data.

The preliminary results of an international collaborative study examining premature menopause in fragile X carriers are presented. A total of 760 women from fragile X families was surveyed about their fragile X carrier status and their menstrual and reproductive histories. Among the subjects, 395 carried a premutation, 128 carried a full mutation, and 237 were noncarriers. Sixty-three (16%) of the premutation carriers had experienced menopause prior to the age of 40 compared with none of the full mutation carriers and one (0.4%) of the controls. Based on these preliminary data, there is a significant association between fragile X premutation carrier status and premature menopause.

Adolescent↗
PubMed1998

Evaluation of global and regional left ventricular function using technetium-99m sestamibi ECG-gated single-photon emission tomography.

We evaluated a method for the assessment of left ventricular (LV) function with technetium-99m sestamibi ECG-gated single-photon emission tomography (GSPET). GSPET was performed at rest in 21 patients. Images were reconstructed to obtain end-diastolic (ED) and end-systolic (ES) images. Endocardial and epicardial edges of the left ventricle for the ED and ES images were defined using the gradient images and the algorithm developed. LV wall thickness was measured for the mid-ventricular slices of ED and ES images at 10 degrees intervals. The systolic thickening (ST) and the LV ejection fraction [LVEF(GSPECT)] could be determined. These values were compared with the LV ejection fraction (LVEF) estimated using the gated blood pool method. There was a linear correlation between LVEF and ST (r=0.79), and LVEF and LVEF(GSPET) (r=0.87). Histograms of LV thicknesses were generated. Agreement for evaluation of regional wall motion between the method using histograms of LV thicknesses and the gated blood pool study was 92.8% (kappa=0.75). It is concluded that with an appropriate method for LV edge detection, GSPET with 99mTc-labelled perfusion agents is of use for simultaneous evaluation of myocardial perfusion and assessment of LV function.

Electrocardiography↗
PubMed1994

A semi-automated method for edge detection in the evaluation of left ventricular function using ECG-gated single-photon emission tomography.

Thallium-201 gated single-photon emission tomography (GSPET) of myocardium was performed at rest in 18 patients. Images were reconstructed to obtain end-diastolic (ED) and end-systolic (ES) images. The endocardial and epicardial edges of the left ventricle (LV) for the ED and ES images were defined for the mid-ventricular images of the short-axis slices, using a semi-automated method. LV wall thickness was measured for ED and ES images at 10 degrees intervals. Mean LV thickness was derived as the mean of the LV thickness for the three mid-ventricular slices. The systolic thickening (ST) was derived as: mean LV thickness (ES)--mean LV thickness (ED). The systolic thickening ratio (STR) was defined as: ST/mean LV thickness (ED). LV cavity area was measured. The dilation ratio (DR) was defined as: [mean cavity area (ED)--mean cavity area (ES)]/mean cavity area (ED). LV ejection fraction (LVEF) was estimated using technetium-99m gated blood pool study. There was a linear correlation between LVEF and ST (r = 0.85), LVEF and STR (r = 0.77) and LVEF and DR (r = 0.81). There was a strong correlation (r = 0.85) between regional STR and regional percent count increase in 52 segments which did not have perfusion defects. As well as for the evaluation of myocardial perfusion, GSPET images can be of use for the assessment of LV function using an appropriate method for LV edge detection.

Algorithms↗
PubMed1992

Radionuclide hysterosalpingography with technetium-99m-pertechnetate: application and radiation dose to the ovaries.

Although radionuclide hysterosalpingography (RNHSG) has been suggested as an efficient procedure for assessing function of fallopian tubes, the radiation dose to the ovaries was addressed as an important issue to be taken into consideration. We describe a modified method of RNHSG, calculating the radiation dose to the ovaries. A small dose of approximately 18.5 MBq (0.5 mCi) of [99mTc]pertechnetate was administered directly into the uterine cavity without overpressure. The accuracy of the method was 84.5% as compared with the contrast hysterosalpingography. The estimated average dose to the ovaries was 0.057 mGy/MBq (0.21 rad/mCi) or 1.08 mGy (108 mrad) per study. RNHSG is an accurate method for functional study of fallopian tube patency with low radiation dose.

Adult↗
PubMed1991

Usefulness of Tl-201 SPECT imaging in evaluation of left ventricular hypertrophy and dilation in patients with previous myocardial infarction.

Using short axis slices of Tl-201 myocardial SPECT images, total left ventricular (LV) mass, perfused LV mass, defect size, defect mass, ratio of total LV area to cavity area (T/C), ratio of radius of total LV area to radius of cavity area (TR/CR), and ratio of wall thickness to radius of cavity area (W/R) were obtained. The left ventricular ejection fraction (LVEF) was calculated using blood pool imaging studies. A total of 33 patients with old myocardial infarctions were studied. The patients were divided into group 1 (n = 16) with no history of heart failure, and group 2 (n = 17) with a history of heart failure. The LVEF (P less than 0.001), T/C (P less than 0.005), TR/CR (P less than 0.005) and W/R (P less than 0.001) were significantly lower, while the total LV mass (P less than 0.001) and perfused LV mass (P less than 0.01) were significantly higher in group 2. In the whole group of 33 patients, there was inverse linear correlation between the total LV mass and LVEF (r = -0.82), perfused LV mass and LVEF (r = -0.67), and defect mass and LVEF (r = -0.59). There was linear correlation between W/R and LVEF (r = 0.64). Nonlinear correlations were found between T/C and LVEF (r = 0.81) and TR/CR and LVEF (r = 0.80). Tl-201 myocardial SPECT imaging is useful for the evaluation of LV hypertrophy and cavity dilation in patients with previous myocardial infarction.

Adult↗
PubMed1989

Quality control of 99mTc-labeled dextran for lymphoscintigraphy.

99mTc-labeled dextran has been suggested as a lymphoscintigraphic agent. However, quality-control results from previous studies have been controversial. In this study, the optimal concentration of stannous ion and pH value were determined to obtain maximal labeling. Paper and thin-layer chromatography showed total labeling efficiency as high as 98.4%. Anthrone test of the supernatant of the segments from thin-layer chromatographic strip was performed. Colorimetric determinations verified that dextran was found in the same locations as the peak radioactivity.

Chromatography, Paper↗
PubMedDate not supplied

Automatic ventricular edge detection for determination of left ventricular volumes, ejection fraction and regional ejection fractions from first pass radioisotope angiography.

An automated method for detection of left ventricular (LV) outline (including the aortic and mitral valve planes) was developed for measurements of end-diastolic volume (EDV), end-systolic volume (ESV), global ejection fraction (EF), and regional EFs from first pass radioisotope ventriculography. The procedure includes: (1) interpolative background subtraction, (2) construction of gradient images, (3) automatic detection of valve planes, and (4) automatic radial search of LV outlines. The correlation between contrast angiography and Tc-99m first pass study was r = 0.84 (SEE = 23.4) for EDV, r = 0.93 (SEE = 12.8) for ESV, r = 0.84 (SEE = 6.91) for EF (via counts) and r = 0.80 (SEE = 8.56) for EF (via area-length method). Tests of intra-observer, inter-observer and inter-study variability revealed low level of variability. The results showed the potential of the automation of data processing for first pass radioisotope ventriculography.

Cardiac Volume↗