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Biomedical subjects

S F Sun

Publications and source records attributed to S F Sun.

At least 19 recordsLinked to original sources
PubMed1997

Ventilation and hypoxic ventilatory responsiveness in Chinese-Tibetan residents at 3,658 m.

When breathing ambient air at rest at 3,658 m altitude, Tibetan lifelong residents of 3,658 m ventilate as much as newcomers acclimatized to high altitude; they also ventilate more and have greater hypoxic ventilatory responses (HVRs) than do Han ("Chinese") long-term residents at 3,658 m. This suggests that Tibetan ancestry is advantageous in protecting resting ventilation levels during years of hypoxic exposure and is of interest in light of the permissive role of hypoventilation in the development of chronic mountain sickness, which is nearly absent among Tibetans. The existence of individuals with mixed Tibetan-Chinese ancestry (Han-Tibetans) residing at 3,658 m affords an opportunity to test this hypothesis. Eighteen men born in Lhasa, Tibet, China (3,658 m) to Tibetan mothers and Han fathers were compared with 27 Tibetan men and 30 Han men residing at 3,658 m who were previously studied. We used the same study procedures (minute ventilation was measured with a dry-gas flowmeter during room air breathing and hyperoxia and with a 13-liter spirometer-rebreathing system during the hypoxic and hypercapnic tests). During room air breathing at 3,658 m (inspired O2 pressure = 93 Torr), Han-Tibetans resembled Tibetans in ventilation (12.1 +/- 0.6 vs. 11.5+/- 0.5 l/min BTPS, respectively) but had HVR that were blunted (63 +/- 16 vs. 121 +/- 13, respectively, for HVR shape parameter A) and declined with increasing duration of high-altitude residence. During administered hyperoxia (inspired O2 pressure = 310 Torr) at 3,658 m, the paradoxical hyperventilation previously seen in Tibetan but not Han residents at 3,658 m (11.8 +/- 0.5 vs. 10.1 +/- 0.5 l/min BTPS) was absent in these Han-Tibetans (9.8 +/- 0.6 l/min BTPS). Thus, although longer duration of high-altitude residence appears to progressively blunt HVR among Han-Tibetans born and residing at 3, 658 m, their Tibetan ancestry appears protective in their maintenance of high resting ventilation levels despite diminished chemosensitivity.

Adult↗
PubMed1992

Are Tibetans better adapted?

Evidence is reviewed from our recent (1987-1991) investigations which demonstrate better high-altitude adaptation among Tibetans than in acclimatized newcomers or other lifelong high-altitude residents. Characteristics of oxygen transport contributing to the Tibetans' remarkable exercise performance are described.

Acclimatization↗
PubMed1991

Increased vital and total lung capacities in Tibetan compared to Han residents of Lhasa (3,658 m).

Larger chest dimensions and lung volumes have been reported for Andean high-altitude natives compared with sea-level residents and implicated in raising lung diffusing capacity. Studies conducted in Nepal suggested that lifelong Himalayan residents did not have enlarged chest dimensions. To determine if high-altitude Himalayans (Tibetans) had larger lung volumes than acclimatized newcomers (Han "Chinese"), we studied 38 Tibetan and 43 Han residents of Lhasa, Tibet Autonomous Region, China (elevation 3,658 m) matched for age, height, weight, and smoking history. The Tibetan compared with the Han subjects had a larger total lung capacity [6.80 +/- 0.19 (mean +/- SEM) vs 6.24 +/- 0.18 l BTPS, P less than 0.05], vital capacity (5.00 +/- 0.08 vs 4.51 +/- 0.10 1 BTPS, P less than 0.05), and tended to have a greater residual volume (1.86 +/- 0.12 vs 1.56 +/- 0.09 1 BTPS, P less than 0.06). Chest circumference was greater in the Tibetan than the Han subjects (85 +/- 1 vs 82 +/- 1 cm, P less than 0.05) and correlated with vital capacity in each group as well as in the two groups combined (r = 0.69, P less than 0.05). Han who had migrated to high altitude as children (less than or equal to 5 years old, n = 6) compared to Han adult migrants (greater than or equal to 18 years old, n = 26) were shorter but had similar lung volumes and capacities when normalized for body size. The Tibetans' vital capacity and total lung capacity in relation to body size were similar to values reported previously for lifelong residents of high altitude in South and North America. Thus, Tibetans, like North and South American high-altitude residents, have larger lung volumes. This may be important for raising lung diffusing capacity and preserving arterial oxygen saturation during exercise.

Adult↗
PubMed1990

Greater maximal O2 uptakes and vital capacities in Tibetan than Han residents of Lhasa.

Maximal O2 uptake provides an index of the integrated functioning of the O2 transport system. Whether lifelong high altitude residents have greater maximal exercise capacities than acclimatized newcomers is of interest for determining whether years to generations of high altitude exposure influence maximal O2 uptake and, if so, what components of O2 transport are involved. We studied 16 Tibetan lifelong residents of Lhasa, Tibet, China (3658 m) and 20 Han ("Chinese") 8 +/- 1 year residents of the same altitude who were matched for age, height, weight and lack of exercise training. At maximal effort, the Tibetans compared to the Hans had greater O2 uptakes (51 +/- 1 vs 46 +/- 1 ml STPD.min-1.(kg bw)-1, P less than 0.05), exercise workloads (177 +/- 5 vs 155 +/- 6 watts, P less than 0.05), minute ventilations (149 +/- 6 vs 126 +/- 4 IBTPS/min, P less than 0.01) and O2 pulse (15.2 +/- 0.4 vs 13.3 +/- 0.5 ml O2 consumption/heart beat, P less than 0.05). Equally high heart rates were present at maximal effort (191 +/- 3 vs 187 +/- 3 beats/min, P = NS), supporting the likelihood that true maxima were achieved in both groups. The greater minute ventilation in the Tibetans resulted from greater tidal volume and the greater maximal tidal volume correlated positively with the resting vital capacity. We concluded that the Tibetans achieved a higher maximal O2 uptake than the Hans, implying an increased capacity for O2 transport to the working muscle.

Acclimatization↗
PubMed1990

Decreased ventilation and hypoxic ventilatory responsiveness are not reversed by naloxone in Lhasa residents with chronic mountain sickness.

Persons with chronic mountain sickness (CMS) hypoventilate and are more hypoxemic than normal individuals, but the cause of the hypoventilation is unclear. Studies of 14 patients with CMS and 11 healthy age-matched control subjects residing in Lhasa, Tibet, China (3,658 m) were conducted to test the hypothesis that hypoventilation, blunted hypoxic ventilatory responsiveness (HVR), and hypoxic ventilatory depression of CMS were due to increased endogenous opioid production. Patients with CMS compared with control subjects exhibited hypoventilation (end-tidal carbon dioxide pressure [PETCO2] = 36.6 +/- 1.0 versus 31.5 +/- 0.5 mm Hg, p less than 0.05), lower tidal volume (VT = 0.54 +/- 0.02 versus 0.61 +/- 0.02 ml BTPS, p less than 0.05), blunted HVR (shape parameter A = 17 +/- 8 versus 114 +/- 22 mm Hg/L BTPS/min, p less than 0.05), and a depressant effect of ambient hypoxia on ventilation (delta PETCO2 with acute hyperoxia = -3.5 +/- 0.5 versus -1.0 +/- 0.6 mm Hg, p less than 0.05). Reduced forced expiratory volume in 1 s to vital capacity ratios (FEV1/VC) and a higher proportion of cigarette smokers in the group of patients with CMS compared with control subjects suggested that at least some patients with CMS had mild airway obstructive lung disease. Naloxone infusion (0.14 mg/kg) to six patients with CMS did not change resting VT, PETCO2, HVR, or SaO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Altitude Sickness↗
PubMed1990

Relationship between dietary factors and blood pressure in China. The Sino-Japan CARDIAC Cooperative Research Group.

As part of the international cooperative Cardiovascular Diseases and Alimentary Comparison (CARDIAC) Study, we carried out surveys for the relationship of dietary factors to blood pressure (BP) in 10 areas in China, (Altai, Beijing, Guangzhou, Guiyang, Hetian, Lhasa, Shanghai, Shijiazhuang, Tulufan, and Urumqi). Systolic BP and diastolic BP were significantly positively associated with salt excretion and body mass index. However, 3-methylhistidine divided by creatinine, and taurine divided by urea nitrogen in 24-h urine were significantly negatively associated with both BPs. These results suggest that meat protein intake may beneficially influence BP, whereas salt may adversely affect BP.

Blood Pressure↗
PubMed1989

Circular dichroism of bovine serum albumin in divalent salt solutions.

The circular dichroism of bovine serum albumin in divalent salt solutions was investigated. The salts selected were magnesium chloride and calcium chloride. Their effects on the secondary and tertiary structures of the protein were compared with that of lithium chloride. It is well known that the elements Ca, Mg, and Li have many properties in common. The results show the similarity of their ions in the capacity of deforming protein, in spite of their characteristic pharmacological functions.

Calcium Chloride↗
PubMed1989

Prevention of myocardial reperfusion injury with free radical scavengers. An experimental study.

The changes in endogenous superoxide dismutase (ESOD) during myocardial ischemia and reperfusion and the efficacy of oxygen free radical scavengers in myocardial protection were investigated in an isolated heart model connected with the recirculating nonpulsatile perfusion circuit. Subjected to a 2-hour period of global ischemia (27 C), the heart was reperfused with 37 C oxygen diluted auto-blood for 60 minutes. Superoxide dismutase plus catalase was added into the cardioplegic solution and reperfusates. ESOD activity was measured by pyrogallol method. The results of the experiment showed that ESOD activity after ischemia and reperfusion was decreased and the addition of oxygen free radical scavengers (SOD and CAT) to the cardioplegic solution and the reperfusates greatly reduced the leakage of myocardial enzymes, coronary vascular resistance, and the ultrastructural damages of the myocardium. These results suggest that the use of SOD and CAT may inhibit myocardial reperfusion injury by scavenging oxygen-derived free radicals.

Animals↗
PubMed1985

Mitral valve prolapse in myotonic dystrophy.

Forty-three patients with myotonic dystrophy (MyD) and 43 age- and sex-matched controls were prospectively evaluated for mitral valve prolapse (MVP) using both cardiac auscultation and echocardiography (ECHO). Prevalence of MVP was significantly increased in MyD patients when using either abnormal auscultation plus abnormal ECHO (23.3%, P less than 0.02) or abnormal ECHO alone (30%, P less than 0.01) as diagnostic criteria for MVP. Frequency of MVP was even more increased in patients with a thin, flat chest compared with patients with normal physical appearance (P less than 0.007). These findings are in support of the concept that the increased frequency of MVP in neuromuscular disorders is likely due to geometrical changes of the heart caused by thorax deformities, rather than structural changes of the mitral valve. For this reason, MVP in MyD probably belongs to the entity of so-called benign, secondary MVP. This is further supported by the absence of symptoms of "systemic" complications of MVP in our patient population.

Adolescent↗
PubMed1985

Distal ulnar neuropathy. Clinical and electrophysiologic aspects.

Nine patients with distal ulnar neuropathy were studied. Weakness of the hand muscles was the only abnormality in six patients; abnormal sensation was present in two patients. The cause was known in seven patients: chronic "occupational" nerve compression occurred in three meat packers and two long-distance bicyclists--acute blunt trauma to the palm of the hand in two patients. Our study indicates that electromyographic abnormalities in distal ulnar neuropathy are more variable than reported. The electromyographic findings indicated predominant axonal degeneration of motor nerve fibers, contrasting also to electromyographic abnormalities seen in entrapment neuropathies. The reasons for these differences are discussed.

Adult↗
PubMed1985

Myotonic dystrophy: obstetric and neonatal complications.

Myotonic dystrophy is a relatively common disorder. Since the clinical expression is highly variable, diagnosis is often made only after the birth of an infant with severe congenital myotonic dystrophy. Seven such cases are described. A history of obstetric complications was present in the six multiparous mothers. Neither the neonatal features nor the pregnancy complications are specific, but their combinations should suggest the diagnosis, which can be confirmed by neurologic evaluation of the infant's mother.

Adult↗
PubMed1984

Study of binding of warfarin to serum albumins by high-performance liquid chromatography.

The binding of warfarin to human serum albumin and bovine serum albumin, respectively, was studied by high-performance liquid chromatography (HPLC). Based upon the Hummel - Dreyer method, two techniques were developed: the internal calibration and the external calibration. The results obtained by the HPLC method and those obtained by the classical method (equilibrium dialysis) were compared. The external calibration method seems to be superior to others for its simplicity, speed and convenience.

Animals↗
PubMed1984

Hypertrophic form of peroneal muscular atrophy (PMA): unusual nerve conduction results.

A family with a hypertrophic form of peroneal muscular atrophy (PMA) was studied with typical clinical and electrophysiological abnormalities in the propositus and her child. The propositus' father was asymptomatic and slowing of nerve conduction velocities was limited to the peroneal nerves. Actual parentage was confirmed by 22 different serologic and electrophoretic marker systems.

Adolescent↗
PubMed1984

Distal ulnar neuropathy in meat packers. An occupational disease?

Distal ulnar neuropathy at the wrist level was observed in three meat packers. The diagnosis was confirmed electromyographically, by follow-up, and with surgical exploration. Compression neuropathy of the distal ulnar nerve has been a well-recognized occupational hazard and is cause by chronic and repeated compression of the ulnar nerve at the level of Guyon's canal; pathogenetic mechanisms differ from those observed in the more common carpal tunnel syndrome.

Adult↗