Biomedical subjects

K Chin

Publications and source records attributed to K Chin.

At least 73 records · Page 4Linked to original sources

PubMed1997

Maturation of tympanic membrane layers and collagen in the embryonic and post-hatch chick (Gallus domesticus).

The surface area of the chick (Gallus domesticus) tympanic membrane (TM) increases by as much as 400% from hatching to 70 days of age (Cohen et al. [1992] J. Morphol. 212:187-193). The present study is concerned with the processes that contribute to this remarkable size increase. Middle-ear specimens were harvested in embryos aged between E10 and E18, and in post-hatch animals between days P1 and P57. Specimens were embedded in paraffin, cut in serial sections, stained for collagen fibers, and examined with light microscopy. Four locations were examined in each specimen: the anterior and posterior perimeter of the TM, the TM, over the extra-stapedius, and the TM at the tip of the extra-columella. The thickness of the epithelial, respiratory, and lamina propria layers was measured at each location. The radial collagen fibers in the lamina propria were also counted at each location, and fiber density per square micrometer was determined at each age. Thickness of the epithelial and respiratory layers remains relatively constant throughout development in all areas of the TM, whereas the lamina propria at the extra-columella and extra-stapedius continues to thicken with increasing age. Collagen density also increases during development, and this is attributed to an increase in fiber number and a reduction in the space between fibers. The results suggest that collagen may be synthesized first in the central regions of the TM and then later in more peripheral areas of the TM.

Aging↗

PubMed1997

Differences in hip axis and femoral neck length in premenopausal women of Polynesian, Asian and European origin.

There are substantial inter-racial differences in hip fracture incidence. Studies in several different ethnic groups have suggested that differences in the length of the femoral neck may contribute to these. The present study assesses femoral neck and hip axis lengths in three ethnic groups in which it has not been documented previously (Chinese, Indians and Polynesians) and compares these values with those in Europeans. Lengths were measured from dual-energy X-ray absorptiometry scans of the proximal femur in normal premenopausal women (n = 225). The Polynesian (1.65 m) and European (1.64 m) women were significantly taller than the two Asian groups (mean height in each, 1.58 m). There were also differences in mean body weight, the Polynesians being the heaviest (76 kg) and the Chinese the lightest (53 kg). Femoral neck lengths were (mean +/- SD) Chinese 61.5 +/- 4.4 mm, Indian 61.5 +/- 5.1 mm, Polynesian 68.2 +/- 4.3 mm and Europeans 66.0 +/- 4.8 mm. Hip axis lengths were Chinese 98.0 +/- 5.6 mm, Indian 94.5 +/- 5.2 mm, Polynesian 106.4 +/- 5.3 mm and European 102.3 +/- 5.3 mm. Each of the other groups were significantly different from the Europeans for both variables and, in general, this remained so after height adjustment. These data suggest that shorter femoral necks are common to the major Asian racial groups. However, in contrast to all other ethnic groups studied, Polynesians have longer femoral necks than Europeans and their low incidence of hip fracture is not explicable, therefore, in terms of their femoral neck length. This suggests that either higher bone density or other more subtle differences in proximal femoral geometry must account for the low hip fracture incidence in Polynesians.

Absorptiometry, Photon↗

PubMed1997

The effect of the level of ventilatory assist on the level of respiratory drive in decerebrate cats.

The present study was undertaken to investigate whether, independent of changes in PaCO2, ventilatory assist influences not only the pattern but also the level of the respiratory drive. The experiments were performed on decerebrate and paralyzed cats ventilated by a phrenic-driven servo respirator at three different FICO2 levels (0, 0.30, 0.05). The level of ventilatory assist was altered within the range where PaCO2 did not exceed 80 Torr. A higher FICO2 accompanied a higher level of ventilatory assist. The relationship between the minute phrenic activity and log10 PaCO2 at a given FICO2 was linear. No significant difference was found in the regression lines at different levels of FICO2. We conclude that ventilatory assist has little effect on the respiratory drive at a constant level of chemical feedback during hypercapnia.

Animals↗

PubMed1997

Hypoxaemia in patients with hyperventilation syndrome.

We assessed 12 patients with hyperventilation syndrome (HVS) who had experienced hypoxaemia (PaO2 < 60 Torr or SaO2 < 90%) despite the lack of any other organic disease and variability in their blood gas data. Hypoxic and hypercapnic ventilatory responses were measured in nine. Eight of the 12 patients had been referred from other hospitals to our institution for hypoxaemia of unknown origin. Mean PaO2 (n = 12) at rest (non-attack stage) was 87.3 +/- 7.5 Torr (mean +/- SD). Their (n = 9) hypoxic (-0.53 +/- 0.32 l/min/%; range 0.12-0.99) and hypercapnic (2.01 +/- 0.76 l/min/Torr; range 0.69-3.17) ventilatory responses were both within the normal range in our laboratory. The patients with HVS had variable blood gas data, and some of them also exhibited hypercapnia (PaCO2 > 45 Torr). Clinicians who treat patients with HVS should be aware of the possibility of hypoxaemia, even when ventilatory responses are normal. Physicians should also consider HVS as a diagnosis when treating patients with hypoxaemia of unknown origin.

Adult↗

PubMed1997

Asian-American adolescent immigrants: the New York City schools experience.

This article describes development and implementation of a school-based vaccination program that targeted Asian-American adolescents. The program was implemented by the Chinatown Health Clinic in New York City in two high schools and a junior high school in Lower Manhattan. The article examines strategies effective in vaccinating this varied group of adolescents. Rates of completion for the three-dose hepatitis B vaccine are compared between schools. Optional serology testing for hepatitis B infection was conducted as part of the school program and rates of infection in this population are presented. The article discusses the importance and effectiveness of school-based programs in providing essential health services to this group of adolescents.

Adolescent↗

PubMed1997

Heat shock protein 72 level decreases during sleep in patients with obstructive sleep apnea syndrome.

Patients with obstructive sleep apnea syndrome (OSAS) suffer from stresses related to repetitive apneas during sleep. To examine whether the level of 72 kDa heat shock protein (HSP72) increases during sleep, 11 OSAS patients (apnea-hypopnea index: 63.5 +/- 36.1, mean +/- SD) underwent polysomnography and their peripheral blood mononuclear cells (PBMC) were isolated before, during, and after sleep. HSP72 level was determined by Western blotting and hsp72 mRNA level was quantified by Northern blotting. Nine normal subjects without OSAS were examined as normal controls. HSP72 level decreased progressively during sleep and its level at 8:00 A.M. was 78.0 +/- 17.5% of that at 8:00 P.M. (p < 0.01). No such decrease was seen in normal subjects. When OSAS patients received nasal continuous positive airway pressure (NCPAP) therapy, HSP72 level did not decrease significantly. In untreated OSAS patients, hsp72 mRNA level decreased during sleep (p < 0.01). When OSAS patients were treated with NCPAP therapy, the decrease in hsp72 mRNA level was not observed. HSP72 level before sleep in OSAS patients was higher than that in normal subjects (p < 0.01). We concluded that repetitive apneas caused high HSP72 level before sleep in OSAS patients and that NCPAP therapy had significant effect on HSP72 levels during sleep.

Blotting, Northern↗

PubMed1997

Hypoxic ventilatory response and breathlessness following hypocapnic and isocapnic hyperventilation.

STUDY OBJECTIVES: To investigate the etiology of posthyperventilation (post-HV) hypoxemia following voluntary hyperventilation (VHV), we examined the effects of hypocapnic (hypo-CO2) and isocapnic (iso-CO2) VHV on the hypoxic ventilatory response (O2-response) and on the sensation of breathlessness during the O2-response. METHODS: O2-responses and visual analog scale (VAS) scores for estimating breathlessness in 10 normal subjects during the O2-response under iso-CO2 conditions and under hypo-CO2 conditions immediately following voluntary maximal HV of 3 min duration were examined. RESULTS: Although there was no significant difference in the post-HV ventilation levels following hypo-CO2 vs iso-CO2 VHV, the VAS scores at the start of the O2-response following hypo-CO2 VHV (30.2+/-24.2 mm) were significantly higher (p<0.05) than the VAS scores at the start of the O2-response following iso-CO2 VHV (13.7+/-8.4 mm). However, VHV did not have a significant effect on the O2-response at 2 min after the VHV when the arterial O2 saturation (SaO2) was below 90%. The nonsteady-state hypo-CO2 induced by VHV greatly attenuated the O2-response below 90% SaO2 and VAS scores at 70% SaO2. CONCLUSIONS: Elevated VAS scores immediately following the hypo-CO2 VHV, which might be independent of actual breathing levels, and the attenuation of the O2-response following the hypo-CO2 VHV were not due to input from lung and chest wall mechanoreceptors induced by the hyperpnea itself, but rather to the hypo-CO2 induced by hyperpnea.

Adult↗

PubMed1997

Ventilatory support during exercise in patients with pulmonary tuberculosis sequelae.

STUDY OBJECTIVE: The aim of this study was to determine whether intermittent positive pressure ventilation through a nasal mask (NIPPV) applied during exercise in patients with pulmonary tuberculosis sequelae (PTS) could improve arterial blood gas measurements, ameliorate breathlessness, and increase exercise endurance. PATIENTS: Seven PTS patients with a severe restrictive ventilatory defect (mean [SD] vital capacity, 1.02 [0.25] I) enrolled in this study had experienced NIPPV previously, and were familiar with the procedure. DESIGN: The patients underwent four constant-load cycle ergometer tests in the supine position to tolerance. The tests were performed with and without NIPPV, while breathing normoxic air (Air) or supplemental oxygen (O2; 35%). NIPPV was delivered during exercise in a controlled, volume-cycled mechanical ventilation mode, and the ventilator settings were modulated manually to meet patients' respiratory demands as estimated from the airway pressure waveform and the patient's breathlessness. RESULTS: All patients matched their breathing to the ventilator cycle during most of the exercise while receiving NIPPV. NIPPV significantly prolonged their exercise endurance time, from a mean (SD) of 180 (58) s to 310 (96) s in Air, and from 227 (64) s to 465 (201) s in O2. During exercise, NIPPV effectively decreased their breathlessness and significantly improved arterial blood gas measurements. CONCLUSIONS: NIPPV applied during exercise can effectively support ventilation, significantly ameliorate breathlessness, and consequently improve exercise endurance in patients with PTS.

Aged↗

PubMed1997

Changes in the arterial PCO2 during a single night's sleep in patients with obstructive sleep apnea.

To investigate the relationship between hypercapnia during sleep and its influence on the PaCO2 during the morning after sleep in patients with obstructive sleep apnea syndrome (OSAS), the transcutaneous PCO2 (PtcCO2) was measured throughout the night, and the arterial blood gases (ABG) were also measured while awake before and after polysomnography in 30 OSAS patients with (n=13, hypercapnic group: HC) and without (n=17, normocapnic group: NC) hypercapnia. Significant differences were observed in the body mass index (p=0.03), the difference between the highest PtcCO2 during sleep and the PtcCO2 during awake before sleep (D-PtcCO2), (HC: 11.l+/-1.7 mmHg; NC: 6.3+/-0.5 mmHg; p=0.0057) and the lowest SaO2 during sleep (p=0.0007). In the HC, the PaCO2 on the morning after sleep (50.0+/-0.14 mmHg) was significantly increased (p=0.0029) compared with the PaCO2 on the night before sleep (47.4+/-1.1 mmHg). In the NC, this phenomenon was not observed. Severe hypercapnia (high D-PtcCO2) during a single night's sleep has a significant effect on the waking PaCO2 immediately following sleep in the HC.

Body Mass Index↗

PubMed1997

Ventilatory responses and subjective sensations during arm exercise and hypercapnia in patients with lower-cervical and upper-thoracic spinal cord injuries.

We measured the ventilatory responses and subjective sensations during arm exercise in patients with lower cervical and upper thoracic spinal cord injuries in order to evaluate the effects of chest wall deafferentation on these responses. Visual analog scales with verbal descriptors were used to quantify respiratory sensations of different affectional qualities. Patients as well as normal subjects reported stronger respiratory sensations upon CO2 rebreathing as compared to during arm exercise with an equivalent minute ventilation (p<0.05). There were no qualitative nor quantitative differences in the respiratory sensations during CO2 rebreathing between the patients and normal subjects. However, patients with spinal cord injuries showed a higher minute ventilation and a lower end-tidal PCO2 during incremental arm exercises (p<0.01), and thus tended to hyperventilate. We conclude that chest wall afferent denervation does not contribute significantly to the perception of breathlessness in patients with spinal cord injuries.

Adult↗

PubMed1997

Effects of resistive load on the phase difference between chest and mouth flow in patients with chronic obstructive pulmonary disease.

The influence of the resistive load on the phase difference (PD) between chest wall and mouth flow in patients with chronic obstructive pulmonary disease (COPD) was investigated, and the factors that induce an enlargement of the PD were assessed. After a resistance tube (R = 2.8 hPa/l/s) was applied to the mouth of the subjects, the PDs increased significantly both in normal (pre: 2.20 +/- 0.89, post: 5.60 +/- 2.04, P < 0.01) and in COPD (pre: 10.86 +/- 3.81; post: 13.12 +/- 3.64, P < 0.01). A significant correlation between the airway resistance and PD was noted (r = 0.730, P < 0.001). These results suggest that airway resistance is an important determinant for the PD. The predicted phase difference (PD') was then calculated by the Runge-Kutta method, using the measured chest flow, the time domain functions of airway resistance and the thoracic gas volume during a respiratory cycle, assuming that the respiratory system was a single compartment. The PD/PD' at pre-resistive load was significantly larger in COPD than in normal subjects (normal: 1.03 +/- 0.11; COPD, 1.45 +/- 0.19, P < 0.01), whereas the PD/PD' at a post-resistive load was significantly smaller than at the pre-resistive load in COPD patients. These results agree well with the two parallel or serial compartment model with inhomogeneous airway resistance, where the mechanical property of the partitioning tissue between the two compartments was taken into account. The pattern of the increase in the work energy consumed within the airway lumen calculated from this model was almost the same as for PD. Thus, we conclude that the PD may be a good index of the overload of the respiratory movement and available to predict muscle fatigue in COPD patients.

Adult↗

PubMed1997

Quantitative assessment of the spatial distribution of low attenuation areas on X-ray CT using texture analysis in patients with chronic pulmonary emphysema.

An automated and quantitative assessment of the spatial distribution of low attenuation areas (LAA) on X-ray CT was performed using texture analysis in chronic pulmonary emphysema (CPE) patients. LAA was defined as those areas having a density less than the mean minus one SD of the control (-960 HU). The probability of change from non-LAA to LAA between a given pair of pixels with horizontal intervals of i pixels (RNi) was evaluated, because this reflects the interaction between LAA and non-LAA regions with different resolutions. The relationship between the percentage area of the LAA over the total area of the entire lung field (LAA%) was subsequently estimated. The RNi increased sharply as the i value increased from 1 to 5, but then almost became a plateau for i values larger than 5. This suggests that the fundamental structures in the LAA areas ranged from 1 x 1 to 5 x 5 pixels in size. RN1-LAA% and RN5-LAA% plots produced curves which were convex, with peak values at approximately 50 LAA% of 0.09 and 0.18, respectively. In the RN5/RN1-LAA% plot, the RN5/RN1 ratio remained constant at 2.0 regardless of the LAA%. A random process simulation was performed to determine the patterns of LAA proliferation if the spatial distribution of the LAA units was random. When the unit size was kept constant, the results of the simulation did not fit the empirical relationship between the LAA% and the three parameters (RN1, RN5 and RN5/RN1). The simulation provided the best-fitting curves when the unit size of the LAA increased in proportion with the LAA%, starting from a 1 x 1 pixel size increasing at a ratio 1 x 1/(5 LAA%). This suggested that the LAA units do not proliferate randomly in spatial orientation at a fixed unit size, but rather spread throughout the whole lung field in a congregated form whilst increasing their unit size. Thus, it may be concluded that healthy lung tissues near emphysematous lesions have a high probability of suffering from emphysema in the future. This may be due to a direct effect of the neighboring emphysematous lesion or due to a pathologic change in the larger bronchii which dominate both the healthy tissues and the emphysematous lesions.

Aged↗

PubMed1997

Assessment of cardiac sympathetic function with iodine-123-MIBG imaging in obstructive sleep apnea syndrome.

UNLABELLED: Iodine-123-MIBG imaging has been used to evaluate myocardial sympathetic function in various cardiac diseases. In patients with obstructive sleep apnea syndrome (OSAS), increased sympathetic activity has been widely recognized, as assessed by measuring the plasma concentration and urinary excretion of catecholamines and by measuring muscle sympathetic nerve activity. However, these measurements are not specific indices of cardiac sympathetic function. Therefore, this study was undertaken to assess cardiac sympathetic function in patients with OSAS using MIBG cardiac scintigraphy. METHODS: This study consisted of 11 patients (10 men, 1 woman; mean age 43 +/- 16 yr) with a diagnosis of OSAS established by polysomnography, and 8 age-matched normal control subjects (7 men, 1 woman; mean age 45 +/- 18 yr). Early (15 min) and delayed (3 hr) planar images were taken after the injection of 111 MBq of [123I]MIBG. The mean counts of the whole heart and the mediastinum were obtained to calculate heart-to-mediastinum count ratios from the early images (H/Me) and from the delayed images (H/Md) and the myocardial washout rate (WR). Eight patients were restudied after 1 mo of nasal continuous positive airway pressure treatment. RESULTS: The H/Me and H/Md ratios were significantly lower in the patients than in the control subjects (H/Me, 2.49 +/- 0.32 versus 2.84 +/- 0.34, p = 0.0207; and H/Md, 2.33 +/- 0.30 versus 3.02 +/- 0.36, p = 0.0013). The WR was higher in the patients than in the control subjects (36.2 +/- 9.0% versus 23.6 +/- 4.9%, p = 0.0022). The H/Me and H/Md ratios in the patients were significantly correlated with the apnea-hypopnea index and the degree of hypoxemia during sleep. After treatment, H/Me and H/Md remained unchanged, but WR significantly recovered (from 34.9 +/- 10.4% to 26.3 +/- 7.7%, p = 0.0357). CONCLUSION: Cardiac sympathetic function and integrity are impaired in subjects with OSAS when compared with age-matched control subjects. MIBG cardiac imaging can be helpful in evaluating cardiac involvement and efficacy of therapy in OSAS.

3-Iodobenzylguanidine↗

PubMed1997

Standardization of low attenuation area versus total lung area in chest X-ray CT as an indicator of chronic pulmonary emphysema.

We examined the methods for measuring the LAA% (100 x low attenuation area/total lung area) on thoracic X-ray CT scans in order to develop a useful indicator of chronic pulmonary emphysema (CPE). First, we modified the method for calculating the LAA% to be applicable by the programming tool installed in a commercially available CT machine in order to minimize manual procedures. This new method proved to be applicable in all CT machines produced after 1987. Second, we examined the difference in the Hounsfield Unit (HU) between different CT machines using two kinds of phantoms. One phantom was composed of Styrofoam, which has a density similar to the low attenuation areas. The other phantom was composed of Styrofoam and water, which has a density similar to the lung. We proved that the difference of LAA% with the correct value was 5% at maximum among four different CT machines. Thus, the phantom developed in the present study may play an important role in the standardization of HU. Finally, the possibility of decreasing the X-ray levels was examined. Twenty-five percent of the standard electrical current provided the same LAA% in cases where the subject was an established CPE patient, whereas the LAA% was overestimated in subjects with a normal LAA% value. However, a correction using a linear regression equation may be possible in the latter cases. It may be concluded that LAA% analysis can easily be performed in many city hospital, without much investment of manual procedures or any corrections to the HU levels between different CT machines. This method may be useful as a routine follow up for CPE patients because of the smaller irradiated dose given when using a CT machine.

Algorithms↗

PubMed1996

Longer femoral necks in the young: a predictor of further increases in hip fracture incidence?

AIMS: To determine whether femoral neck length, a risk factor for hip fracture, is likely to increase in the coming decades in normal elderly New Zealand women. METHODS: Femoral neck length was measured from dual-energy x-ray absorptiometry scans of the proximal femur in white women aged 19-88 years (n = 211). Since this length remains constant throughout adult life, it is possible to predict future trends in this index in the elderly, from its measurement at the present time in younger adults. RESULTS: Femoral neck length was inversely related to age (p = 0.018) such that a 3.7 mm (5.7%) difference occurred over the age-range of this sample. CONCLUSIONS: Femoral neck length in elderly New Zealand women is likely to increase in the coming decades. As a result of the dependence of hip fracture risk on femoral neck length, future age-adjusted hip fracture incidence will increase by about 50% over the next 50 years unless significant public health initiatives are taken, either to increase bone density or to reduce fall frequency.

Absorptiometry, Photon↗

PubMed1996

Association of p53 protein expression with responses and survival of patients with locally advanced esophageal carcinoma treated with chemoradiotherapy.

Immunohistochemical analysis was performed to determine the clinical role of p53 mutations in patients with locally advanced esophageal carcinomas treated with concurrent chemoradiotherapy. The subjects of this study were 20 patients with previously untreated esophageal carcinomas with evidence of T4 disease and/or distant node metastases. Treatment comprised protracted 5-fluorouracil and 2-h cisplatinum infusions along with radiation treatment with a total radiation dose of 60 Gy. Tumor specimens from 18 of the 20 patients were analyzed immunohistochemically. Mutant p53 protein expression in the biopsy materials from the primary tumors was analyzed by immunohistochemical staining using a polyclonal antibody, RSP53. Expression of p53 was detected immunohistochemically in 10 (56%) of the 18 esophageal tumors, the cancer cell nuclei of which were diffusely stained. There were no significant differences between the patient backgrounds of the p53-"positive" and "negative" groups. Four (40%) of the 10 patients with p53 expression achieved overall complete remissions (CRSs) and 7 (70%) of these 10 achieved CRs of their primary tumors. In contrast, none of the 8 p53-negative patients achieved overall CRs and two (25%) achieved CRs of their primary tumors. The CR rates overall and of primary tumors tended to be higher in the p53-positive than negative group, but the differences were not significant. The survival rate for the 10 patients with p53 expression was better than that for the 8 negative ones (P>0.01): their median survival times were 12 and 4.5 months, respectively. Expression of p53 protein may be an indicator of a favorable prognosis in patients with locally advanced esophageal carcinomas treated with concurrent chemoradiotherapy.

Aged↗

PubMed1996

Continuous infusion of DL-alpha-difluoromethylornithine and improved efficacy against a rat model of Pneumocystis carinii pneumonia.

The rapid depletion of Pneumocystis carinii polyamines caused by in vitro exposure to DL-alpha-difluoromethylornithine (DFMO; also called eflornithine or Ornidyl) and the rapid repletion following removal of this drug suggested that the in vivo efficacy of DFMO against P. carinii pneumonia (PCP) may be limited by troughs in drug concentration resulting from the schedule of administration. This led to the prediction that, compared with the response to the standard animal protocol of administering DFMO in drinking water, the response of a rat model of PCP to DFMO would be lessened by bolus administration and improved by continuous infusion. These predictions were confirmed. Intraperitoneal bolus administration of up to 3 g of DFMO kg of body weight-1 was completely ineffective, although this dose has been shown to be effective when given in the drinking water. Conversely, continuous infusion improved the response against PCP seven- to ninefold over the response to drinking water administration. These findings suggest that, compared with the standard clinical investigational protocol for treatment of PCP with DFMO given in four divided daily doses, continuous infusion combined with monitoring of drug concentrations in plasma may improve efficacy and/or reduce the already low rate of adverse effects.

Administration, Oral↗

PubMed1996

Trophozoite elimination in a rat model of Pneumocystis carinii pneumonia by clinically achievable plasma deferoxamine concentrations.

In a rat model of Pneumocystis carinii pneumonia, a 3-week infusion of deferoxamine producing concentrations in plasma of > or = 1.5 micrograms m-1 eliminated the trophozoite life cycle stage. Since this concentration is well below that routinely achieved in patients treated for iron overload, deferoxamine has promise as a therapy for AIDS-associated P.carinii pneumonia.

Animals↗