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Biomedical subjects

A C Chen

Publications and source records attributed to A C Chen.

124 records · Page 7Linked to original sources
PubMed1977

Effects of intrasegmental electrical acupuncture on dental pain: evaluation by threshold estimation and sensory decision theory.

The effect of 80 min of low frequency (2 Hz) electric acupunctural stimulation at facial sites on the perception of induced dental pain was evaluated using both pain threshold and sensory decision theory (SDT) procedures. The demonstration of a 187% increase in threshold over a 20 min period of acupunctural stimulation replicated earlier work by Swedish investigators. SDT analyses indicated that the threshold increase reflected a relatively pure sensory change with no significant modification of response bias. However, subjects were able to perceive some of the stimuli presented below threshold level following acupuncture, thus indicating that the threshold concept has been an inadequate description of the phenomenon. This study demonstrated that intrasegmental analgesic stimulation is more efficacious than the extrasegmental meridian point stimulation used in our earlier studies. Possible mechanisms for the observed effect were discussed.

Acupuncture Therapy↗
PubMed1977

Hormonal regulation of trehalose metabolism in the blowfly Phormia Regina Meig.: effects of cardiacectomy and allatectomy at the subcellular level.

1. Kinetic properties of adult Phormia fat body glycogen synthetase were studied and compared to other animals. The KM for UDPG is 2.82 mM, decreasing to 0.58 mM in the presence of G-6-P. 2. The specific activity of fat body glycogen synthetase shows a reduction of 30% within 2 days after allatectomy. 3. Fat body T-6-P synthetase activity decreases to 70% of the control value after cardiacectomy. 4. Corpus cardiacum homogenate fails to induce higher T-6-P synthetase activity in cell-free preparations from cardiacectomized flies. 5. Interactions between corpus cardiacum and corpus allatum in regulating carbohydrate metabolism are discussed.

Animals↗
PubMedDate not supplied

Streaming potentials during the confined compression creep test of normal and proteoglycan-depleted cartilage.

The streaming potential response of cartilage in the confined compression creep configuration was assessed theoretically and measured experimentally in normal and proteoglycan-depleted tissue. The analytical solution, using the linear biphasic continuum model including electrokinetics and assuming homogeneous material properties, predicted that: (i) the peak streaming potential is delta V = ke x delta sigma, where ke is the electrokinetic coefficient and delta sigma is the change in compressive stress; (ii) the potential is maintained at 95 to 100% of the peak value for 0 < t < 0.10 tau, where tau is the gel diffusion time constant; and (iii) during short times, 0 < t < 0.01 tau, 90% of the peak streaming potential occurs over a region extending 23% into the tissue sample. Experimentally, adult bovine cartilage disks, 0.5 mm thick, were subjected to step changes of compressive stress. The measured changes in potential indicated a linear response for changes in stress up to 0.10 MPa. The ke of normal cartilage, estimated from the short time (0 < t < 2 sec) change in potential, was -1.65 +/- 1.25 mV/MPa. Digestion of cartilage by chondroitinase ABC resulted in an increased (less negative) ke of -0.75 +/- 0.70 mV/MPa and a 33 +/- 29% depletion of anionic glycosaminoglycan, whereas digestion with trypsin resulted in a further increase in ke to +1.74 +/- 0.95 mV/MPa and a 98 +/- 1 % depletion of glycosaminoglycan. The streaming potential measurement may be a useful addition to the widely used confined compression creep test to assess cartilage material properties.

Analysis of Variance↗
PubMedDate not supplied

Microcomputer analysis of cortical power spectrum: calibration and correlates of behavioral artifacts.

Cortical power spectrum (CPS) is a quantitative estimate of EEG spectral power density. The CPS provides suitably precise data for quantification and statistical inference compared to the qualitative evaluation of EGG when interpreted by clinicians or researchers. In the past decade, the CPS has been applied to the studies of cognitive functions, memory, psi phenomena, speech laterality, and states of consciousness including coma, sleep, anesthesia, pathophysiology and pain state. However, few systematic evaluations of CPS methodology have been reported, rendering cross-laboratory comparisons difficult and external validity of experimental results uncertain. This report first describes a calibration procedure employing a microcomputer system for measuring the functional relationship between input signals and output cortical powers. Second, we examine controlled behavioral artifact effects on the CPS. The behavioral artifacts observed in the CPS can provide a measurement anchor for less ambiguous interpretation of CPS experiments conducted in clinical or laboratory settings.

Cerebral Cortex↗
PubMedDate not supplied

Formulation of PEG-based hydrogels affects tissue-engineered cartilage construct characteristics.

The limited supply of cartilage tissue with appropriate sizes and shapes needed for reconstruction and repair has stimulated research in the area of hydrogels as scaffolds for cartilage tissue engineering. In this study we demonstrate that poly(ethylene glycol) (PEG)-based semi-interpenetrating (sIPN) network hydrogels, made with a crosslinkable poly(ethylene glycol)-dimethacrylate (PEGDM) component and a non-crosslinkable interpenetration poly(ethylene oxide) (PEO) component, and seeded with chondrocytes support cartilage construct growth having nominal thicknesses of 6 mm and relatively uniform safranin-O stained matrix when cultured statically, unlike constructs grown with prefabricated macroporous scaffolds. Even though changing the molecular weight of the PEO from 100 to 20 kDa reduces the viscosity of the precursor polymer solution, we have demonstrated that it does not appear to affect the histological or biochemical characteristics of cartilaginous constructs. Extracellular matrix (ECM) accumulation and the spatial uniformity of the ECM deposited by the embedded chondrocytes decreased, and hydrogel compressive properties increased, as the ratio of the PEGDM:PEO in the hydrogel formulation increased (from 30:70 to 100:0 PEGDM:PEO). Total collagen and glycosaminoglycan contents per dry weight were highest using the 30:70 PEGDM:PEO formulation (24.4+/-3.5% and 7.1+/-0.9%, respectively). The highest equilibrium compressive modulus was obtained using the 100:0 PEGDM:PEO formulation (0.32+/-0.07 MPa), which is similar to the compressive modulus of native articular cartilage. These results suggest that the versatility of PEG-based sIPN hydrogels makes them an attractive scaffold for tissue engineering of cartilage.

Journal Article↗
PubMedDate not supplied

Physical growth of Chinese school children 7-18 years, in 1985.

Physical development in Chinese school children was analysed based on a national survey in 1985. Close to half a million children and adolescents, aged 7-18, from Han ethnic group and 27 minority ethnic groups were assessed for height, weight, sitting-height, chest circumference, biacromial and biiliac diameters. Growth in Han children was greater than that in minority ethnic group children. The growth differences among minority ethnic groups were large. Growth in urban children was greater than that in rural children except in a few age groups of girls. A significant difference in children's growth was found between northern and southern divisions of China, it being greater in the north. The growth curves of physical characteristics demonstrated systematic regularity. Finally, the results of this study were compared with research reports from other world literature.

Adolescent↗
PubMedDate not supplied

Secular change in the growth and development of Han children in China.

This paper reports the secular change in physical growth and development of Han children in 12 Chinese metropolitan cities including Beijing, Tianjing, Shanghai, Jinan, Harbin, Shenyang, Changchun, Nanjing, Hangzhou, Wuhan, Guangzhou, and Chengdu. Based on a recent national survey of 14,688 healthy schoolchildren, aged 7-18 years, and together using the historical records of healthy schoolchildren as secondary data source, this study found a secular change in the growth and development of Chinese children and youth. In every decade between the 1950s and 1985 the average height increased by 2.66 cm (range 1.78-3.77) for boys and 2.40 cm (range 1.72-3.76) for girls, and the average weight increased by 1.64 kg (range 1.28-2.63) for boys and 1.14 kg (range 0.63-2.01) for girls in the 12 cities. In the last decade from the 1970s to 1985, the height and weight increments were highest in Beijing, Jinan, Shenyang and Shanghai. In addition, the increments were higher during the peak growth years than during other periods of growth. In the 30 years studied, the ages of maximum growth velocity were advanced, and they were 1 or 2 years earlier in 1985 than in the 1950s in most cities. When compared with the data from the 1930s the results indicate that, during the last half-century, height increased by 1.12-2.66 cm per decade for boys and 1.42-2.67 cm/decade for girls, while weight increased by 0.56-1.27 for boys and 0.65-1.18 kg for girls in Beijing, Shanghai, Nanjing, Hanzhou and Guangzhou.

Adolescent↗
PubMedDate not supplied

Developmental perspective of pulse rate, blood pressures and vital capacity in Chinese children.

Physiological development in Chinese children was analysed based on a national survey sample. Close to half a million children and adolescents, aged 7-18 years, from Han and 27 minority nationalities were assessed for pulse rate, systolic and diastolic blood pressure, and forced vital capacity in these 12 age groups. The factors of age, sex, race, and region (urban/rural, north/south) were analysed. P95 hypertension screening standard was established for each age group. These results were compared with research reports from world literature.

Adolescent↗
PubMedDate not supplied

The menarcheal age of Chinese girls.

The menarcheal age of Chinese girls was analysed based on a national survey in 1985. A total of 162,902 girls, aged 7-22 years, of Han nationality and 34,232 girls, aged 7-18, of 27 minority nationalities were sampled. Data were further subdivided into urban and rural areas. It was found that the curves of menstruating percentage in each of the subgroup were in long sigmoid shapes. The menstruating rate (MR) of Han girls was higher than that of the minority girls in almost every age group. The median menarcheal age (MMA) of Han girls was significantly lower than that of the minority girls. In Han nationality the urban girls showed higher MR and lower MMA than the rural girls. The influence of hereditary, cultural and economical factors on menarcheal age in Chinese girls is discussed. The data of this study were also compared with research reports from other world literature.

Adolescent↗
PubMedDate not supplied

Immunological study in three families of juvenile ankylosing spondylitis.

Three patients, all exhibiting symptoms before 15 years of age, were diagnosed as juvenile ankylosing spondylitis (JAS) by stigma of JAS. The families of these three patients--a total of fifteen first-degree relatives--had clinical, radiologic and laboratory examinations. All three patients and four family members (26%) had positive HLA-B27 and ankylosing spondylitis (AS). Five (33%) of these three family members had positive HLA-B27 but were asymptomatic; six members(40%) were HLA-B27 negative and symptom-free. A high positive rate of HLA-B27 was found among the patients (100%) and the family members (60%). The rheumatoid factor, antinuclear antibody, and anti-native DNA antibody were negative for all patients and family members. Significant elevation of IgG, IgA, and C3 were noted in the AS group. The CD3 cell was lower, and the ratio of CD4/CD8 was decreased in the AS group. Lympho-proliferative responses to phytomitogens (Con A, LPS and PHA) were also done in our study. There was no significant difference in Con A and LPS stimulation index among the AS group, symptom-free family members and normal controls.

Adolescent↗
PubMedDate not supplied

Analgesic action of intravenous diazepam.

Intravenous diazepam is commonly used in clinical dentistry to produce sedation for dental procedures. Its chief benefit seems to derive from its sedative and amnesic properties. The literature contains conflicting reports about the direct analgesic effects of the drug. In the present study, we observed significant increases for conventional pain threshold measures in response to electric tooth pulp stimulation and decreased sensitivity to a fixed painful stimulus when diazepam was administered intravenously using clinical criteria for conscious sedative dosages. The data support the possibility that intravenously administered diazepam in conscious sedative doses may have some analgesic action in addition to its better documented sedative and amnesic properties.

Adult↗