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Biomedical subjects

Q Y Kong

Publications and source records attributed to Q Y Kong.

14 recordsLinked to original sources
PubMed2006

Impulsive solvent heating probed by picosecond x-ray diffraction.

The time-resolved diffraction signal from a laser-excited solution has three principal components: the solute-only term, the solute-solvent cross term, and the solvent-only term. The last term is very sensitive to the thermodynamic state of the bulk solvent, which may change during a chemical reaction due to energy transfer from light-absorbing solute molecules to the surrounding solvent molecules and the following relaxation to equilibrium with the environment around the scattering volume. The volume expansion coefficient alpha for a liquid is typically approximately 1 x 10(-3) K(-1), which is about 1000 times greater than for a solid. Hence solvent scattering is a very sensitive on-line thermometer. The decomposition of the scattered x-ray signal has so far been aided by molecular dynamics (MD) simulations, a method capable of simulating the solvent response as well as the solute term and solute/solvent cross terms for the data analysis. Here we present an experimental procedure, applicable to most hydrogen containing solvents, that directly measures the solvent response to a transient temperature rise. The overtone modes of OH stretching and CH3 asymmetric stretching in liquid methanol were excited by near-infrared femtosecond laser pulses at 1.5 and 1.7 microm and the ensuing hydrodynamics, induced by the transfer of heat from a subset of excited CH3OH* to the bulk and the subsequent thermal expansion, were probed by 100 ps x-ray pulses from a synchrotron. The time-resolved data allowed us to extract two key differentials: the change in the solvent diffraction from a temperature change at constant density, seen at a very short time delay approximately 100 ps, and a term from a change in density at constant temperature. The latter term becomes relevant at later times approximately 1 mus when the bulk of liquid expands to accommodate its new temperature at ambient pressure. These two terms are the principal building blocks in the hydrodynamic equation of state, and they are needed in a self-consistent reconstruction of the solvent response during a chemical reaction. We compare the experimental solvent terms with those from MD simulations. The use of experimentally determined solvent differentials greatly improved the quality of global fits when applied to the time-resolved data for C2H4I2 dissolved in methanol.

Chemistry, Physical↗
PubMed2005

Ultrafast x-ray diffraction of transient molecular structures in solution.

We report direct structural evidence of the bridged radical (CH2ICH2.) in a polar solution, obtained using time-resolved liquid-phase x-ray diffraction. This transient intermediate has long been hypothesized to explain stereo-chemical control in many association and/or dissociation reactions involving haloalkanes. Ultrashort optical pulses were used to dissociate an iodine atom from the haloethane molecule (C2H4I2) dissolved in methanol, and the diffraction of picosecond x-ray pulses from a synchrotron supports the following structural dynamics, with approximately 0.01 angstrom spatial resolution and approximately 100 picosecond time resolution: The loss of one iodine atom from C2H4I2 leads to the C-I-C triangular geometry of CH2ICH2.. This transient C2H4I then binds to an iodine atom to form a new species, the C2H4I-I isomer, which eventually decays into C2H4 + I2. Solvent dynamics were also extracted from the data, revealing a change in the solvent cage geometry, heating, and thermal expansion.

Computer Simulation↗
PubMed2001

Loss of phospholipids asymmetry in red blood cells contributes to anemia in uremic patients.

Anemia is common in dialysis patients. Change in phospholipids asymmetry in red blood cells (RBCs) may affect the removal of RBCs from the circulation and thus shorten the lifespan of RBCs. In the present study, we investigated phospholipids asymmetry in RBCs in uremic patients and its relationship with anemia. We studied 34 continuous ambulatory peritoneal dialysis (CAPD) patients (age: 51 +/- 15 years), 73 hemodialysis (HD) patients (age: 48 +/- 12 years), 8 pre-dialysis renal-failure patients (age: 42 +/- 21 years), and 16 healthy controls (age: 32 +/- 9 years). All patients were clinically stable. Phospholipids asymmetry as measured by phosphatidylserine exposure was determined by a flow-cytometric annexin V-binding assay. Hemoglobin levels were 93 +/- 20 g/L, 83 +/- 17 g/L, 78 +/- 21 g/L, and 145.8 +/- 12.5 g/L for CAPD patients, pre-dialysis patients, HD patients, and healthy controls respectively. Phosphatidylserine exposure in RBCs was significantly higher in uremic patients as compared with healthy controls, especially in HD patients--whose values were significantly higher than values seen in CAPD patients and pre-dialysis patients. No significant difference was seen in RBC phosphatidylserine exposure between pre-dialysis patients and CAPD patients. Cells positive for annexin V binding were 1.58%, 1.40%, 2.11%, and 0.71% for CAPD patients, pre-dialysis patients, HD patients, and healthy controls respectively. Significant reverse correlations were seen between annexin V and hemoglobin (r = -0.381, p < 0.001), and between annexin V and hematocrit (r = -0.355, p < 0.001). Our results suggest that (1) anemia is common in our uremic patients, especially in HD patients; and (2) anemia in uremic patients may be partly related to the loss of phospholipids asymmetry in RBCs.

Adult↗
PubMed2000

CD40 ligand expression on macrophages during peritonitis in continuous ambulatory peritoneal dialysis patients.

CD40-CD40 ligand (CD40L) interaction plays an important role in macrophage/monocyte-mediated inflammatory processes by up-regulating cytokine production by macrophages/monocytes and by preventing macrophage apoptosis at the inflammation sites. The present study investigated the possible regulation of CD40L expression in peritonitis during continuous ambulatory peritoneal dialysis (CAPD). We used fluorescence-activated cell sorter (FACS) analysis to detect CD40L expression on macrophages obtained from peritoneal dialysate. Our results showed that CD40L expression on macrophages was significantly increased in a peritonitis group (4.62 +/- 6.54) as compared to a control group (0.76 +/- 0.30, p < 0.01). The CD40L-positive cells were also significantly increased during peritonitis (97.86% +/- 1.67% in the peritonitis group as compared to 73.10% +/- 26.94% in the control group, p < 0.05). After successful treatment, the expression of CD40L was significantly reduced (3.66 +/- 1.12 vs 1.05 +/- 0.02, p < 0.05). We conclude that functionally expressed CD40L on macrophages may take part in acute inflammatory response during peritonitis in CAPD and may play an important role in the local defense against infection in the peritoneal cavity.

Acute Disease↗
PubMed1992

[Fetal umbilical arterial blood flow velocity waveforms as measured in the uterus by pulsed Doppler and B-mode ultrasound].

3.0 MHz Doppler ultrasound was used to measure the umbilical arterial blood flow velocity waveforms (FVW) in 174 fetuses between 22-42 weeks of gestation. The A/B ratio (systolic/diastolic), resistance index (RI), pulsatility index (PI) and impedance index (ImI) were used as indexes of placental flow resistance. In normal pregnancy (n = 152), 460 measurements were performed. Analysis of these waveforms demonstrated that the placental is an organ of low vascular resistance and that placental resistance to blood flow gradually declines with advancing gestational age. Our results indicated a significant negative correlation between each of the four indexes and gestational age. There was a small but significant decrease in all four indexes, from 22-42 weeks. 56 scans were performed on 22 fetuses with intrauterine growth retardation (IUGR). The sonograms from these IUGR fetuses showed different characteristics which implied a high distal impedance to the blood flow. 16 of these (72.7%) presented an abnormal increase in all four indexes.

Adult↗
PubMed1991

[Ultrasonographic study of trophoblastic neoplasms. A report of 185 cases].

B-scan ultrasonography was used in 94 cases of hydatidiform mole (benign group), 62 cases of invasive mole and 29 cases of choriocarcinoma (malignant group). A correct diagnosis was made in 91.5% of cases of the benign group and 91.3% of the malignant group. Chemotherapy was given to all patients with invasive mole or choriocarcinoma, and hysterectomy was done in 47 cases after chemotherapy. During chemotherapy a gradual regression of the intramural lesions was demonstrated by ultrasonography with fall of hCG titer. The authors suggest that the B-scan ultrasonography is a safe and useful method in monitoring the response of the trophoblastic tumors to chemotherapy.

Antineoplastic Agents↗
PubMed1991

Lymphonodovenous anastomosis in the treatment of chyluria.

Thirty cases of chyluria were treated by means of lymphonodovenous anastomoses according to the principles of lymphovenous shunt. A conical tissue of lymph node close to the greater saphenous vein in the inguinal region was removed and the remaining tunnel-shaped node was anastomosed to the vein to drain the lymph into the venous system. Twenty-one cases were followed up for six months after the operation. Among them, 16 (76.2%) showed disappearance of chyluria, and 2 (9.5%) were improved, giving an effective rate of 85.7%. This operation avoids damage to both the afferent and efferent lymphatic vessels, and affords a large anastomotic stoma for free passage of the lymph into the vein.

Adult↗
PubMed1984

Observations of Langerhans' cells in leprosy using monoclonal antibody OKT6.

Changes in the Langerhans' cells (LC) in seven cases of leprosy were observed using the monoclonal antibody OKT6. In the epidermis of the lesions of most of the leprosy cases, the processes of LC were reduced or diminished. Some LC were disintegrated. In two BT cases in the upgrading (type 1) reactional stage, either increased numbers and aggregation of OKT6-positive cells in clusters or their disintegration was seen in different areas of the epidermis.

Adult↗
PubMed1982

Preliminary observation on Langerhan's cells in leprosy.

Langerhans' cells were enumerated in the skin of eight borderline and tuberculoid leprosy patients by the enzymatic histochemical demonstration of ATPase in these cells in epidermal sheets. The number of Langerhans' cells was significantly reduced in the skin lesions of these patients compared with normal appearing skin from the same patients. The morphological details of these cells were not clear under light microscopy; further study with electron microscopy is desirable.

Adolescent↗