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Biomedical subjects

K Li

Publications and source records attributed to K Li.

At least 397 records · Page 22Linked to original sources
PubMed1990

[Ultrasonic pulsed Doppler duplex system determination of portal hemodynamic changes in portal hypertension].

Ultrasonic pulsed Doppler duplex system was used to observe the portal hemodynamic changes before and after shunting or nonshunting operations. The results of preoperative measurements revealed significant increases of blood flow volumes of portal and splenic veins in portal hypertension subjects, and a positive correlation was obtained in the subjects with portal hypertension. Postoperative results showed significant reduction of portal blood flow volume more after shunting than the nonshunting operations. The etiology of portal hypertension and the causes of portal hemodynamic changes due to operations were discussed.

Azygos Vein↗
PubMed1989

A human muscle adenine nucleotide translocator gene has four exons, is located on chromosome 4, and is differentially expressed.

The human heart-skeletal muscle adenine nucleotide translocator (ANT1) gene was isolated and sequenced. It spans 5.8 kilobases and contains four exons. The 5'-nontranscribed region contains typical CCAAT and TATA sequences, a 22-nucleotide pair inverted repeat and a 13-nucleotide pair sequence homologous to a similar region in the ATP synthase beta subunit gene. The region surrounding the first exon and intron is G+C-region surrounding the first exon and intron is G+C-rich, and the intron contains three Sp1 binding motifs. ANT1 was assigned to chromosome 4 using both flow-sorted chromosomes and segregating human-mouse hybrid cells. Additional ANT sequences were found on at least two other chromosomes. ANT1 transcripts were present at high levels in human heart and skeletal muscle but were almost undetectable in liver, kidney, and brain. By contrast, fibroblast ANT (ANT2) mRNAs were present in all five tissues. The unique nature and arrangement of the ANT1 transcriptional control elements may account for this differential expression.

Adult↗
PubMed1989

Regulation of the inducible heat shock 71 genes in early neural development of cultured rat embryos.

Activation of the inducible heat shock 71 genes and their role in the heat shock response was studied in vitro in 9.5 day-old rat embryos at neural tube closure. The transcriptional response of a 71 kilodalton (kD) heat shock gene induced after various regimes of heat shock and acquired thermotolerance was investigated. Expression and accumulation of the heat shock (hs) 71 mRNA in the neuroectoderm was studied by Northern and dot blot analysis. Specific expression in various cell types and regions of the neuroectoderm were examined by in situ hybridization. Exposure of embryos to a heat shock at 43 degrees C for 7.5 min caused high levels of hs mRNA 71 accumulation in the neuroectoderm, pronounced protein synthesis inhibition, and regulated recovery. Specific neuroectoderm cell death followed, resulting in major developmental defects of the eye and forebrain region. A mild heat shock of 42 degrees C for 10 min induced the heat shock response, hsp synthesis, and cell recovery, but produced no cell death or deformities. Preheating the embryo at 42 degrees C resulted in acquired thermotolerance to an otherwise teratogenic 43 degrees C heat shock. Thermotolerance was associated with a rapid recovery of protein synthesis associated with hs 71 mRNA expression. Dot blot analysis showed that after a 42 degrees C heat shock, 71 mRNA was rapidly transcribed and transported into the cytoplasm where it was degraded within 2 hr of the initial response. The results suggest that the heat shock protein (hsp) 71 gene may have a protective rather than a rescuing function.

Animals↗
PubMed1989

Testing some attribution-emotion relations in the People's Republic of China.

We conducted a questionnaire study to test the generality of attribution-emotion relations to individuals in the People's Republic of China. Replications of prior findings of studies conducted with American subjects were reported: (a) High effort and success enhanced interpersonal evaluations when ability, effort, and outcome information were provided; (b) affective communications of pity, anger, and guilt were respectively used to infer low ability, lack of effort, and teacher as causes of failure; (c) effort and ability levels were inferred from the presence or absence of anger reactions; and (d) controllable causes of a broken social contract were expected to result in anger from others. Chinese and American respondents also indicated what situations would arouse the affects of anger, guilt, pity, pride, and shame. We found no evidence for the characterization of Chinese as (a) emphasizing effort over ability as a cause of achievement outcomes or (b) de-emphasizing the importance of personal achievement and stressing group goals and accomplishments.

Achievement↗
PubMed1989

Stenotic amplification of vasoconstriction responses.

Based on simple hemodynamic principles, arterial stenoses could accentuate the effects of arterial vasoconstriction by reducing intraluminal pressure. To examine this mechanism we employed an in vitro stenotic carotid artery preparation. Eight carotid arteries, obtained from anesthetized heartworm-positive dogs, were isolated and perfused with a physiological salt solution under constant pressure (100 mmHg) and with a fixed distal resistance. After creating an intraluminal stenosis, proximal pressure, distal pressure, and flow were continuously recorded as norepinephrine was incrementally added to the perfusion reservoir. At each norepinephrine concentration, arterial dimensions were recorded on 35-mm film and measured by quantitative dimensional analysis. These data were approximated by a four-parameter logistic equation. The proximal diameter data were considered to represent solely the effects of arterial vasoconstriction, while the stenotic diameter data were considered to be affected both by arterial vasoconstriction and by stenotic pressures. The stenotic diameters shortened significantly more than the proximal diameter (1.2 +/- 2 vs. 0.5 +/- 0.1 mm, P less than 0.01). The shape of the stenotic diameter dose-response curve was similar to the distal pressure curve and was significantly (P less than 0.05; - 3.4 +/- 0.7) steeper than the proximal diameter curve (-0.7 +/- 0.1). Furthermore, the half maximum effective doses (ED50) were significantly interrelated for distal pressure and stenotic diameter data and unrelated for proximal diameter data. In five additional experiments, to eliminate the stenotic pressure changes, the flow was maintained constant. Maintaining stenotic vasoconstriction response (0.6 +/- 2 mm). The results of the present study show exaggerated stenotic vasoconstriction caused by a stenotic pressure decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Viral etiology of cervical carcinoma. Human papilloma virus and herpes simplex virus type 2.

The possible role of human papilloma virus (HPV) and herpes simplex virus type 2 (HSV-2) in the viral etiology of cervical carcinoma was investigated a series of cervical lesions were studied for the presence of HPV and HSV-2 DNA sequences as well as HPV and HSV-2 antigens by DNA dot blot hybridization technique and high-specificity PAP staining method. The results obtained were correlated with the histologic diagnosis. HPV 16 DNA sequences detected in cervical carcinoma biopsies were 43%, whereas HSV-2 DNA sequences were only 8%. HPV antigens detected in cervical dysplasia were 31%, whereas those detected in cervical carcinoma and cervicitis were the least. HSV-2 antigens were detected in chronic cervicitis, dysplasia and cervical carcinoma. The difference in positive rate between the cervical carcinoma and cervicitis groups was statistically significant, (chi-square test, P less than 0.01). No HPV DNA and HSV-2 DNA sequences were found in the same specimen, although both HPV DNA sequences and HSV-2 antigens were found in the same sample in some cases. The results indicate that the viral etiology of cervical carcinoma may be multifactorial. Both HSV-2 and HPV may be associated with cervical carcinoma, but the mechanisms involved are different. HSV-2 and HPV may act synergistically in the development of cervical carcinoma.

Antigens, Viral, Tumor↗
PubMed1988

Elevated environmental temperature alters the responses of the reproductive and thyroid axes of female Syrian hamsters to afternoon melatonin injections.

Female Syrian hamsters were kept in a light (14:10 h light:dark cycle, lights on 0600 h)- and temperature (22 or 30 degrees C)-controlled room; some groups were treated with an afternoon s.c. injection of melatonin (6.25, 12.5, or 25 micrograms/day) for 11 or 14 weeks. The melatonin-induced suppression of the reproductive system in hamsters maintained at 22 degrees C (as measured by vaginal cycles, uterine weights, ovarian histology, and plasma and pituitary prolactin levels) was delayed if hamsters were kept at 30 degrees C. The dose-related depression of thyroxine (T4) after melatonin injections for 14 weeks in 22 degrees C was not seen at 30 degrees C. Rather, the depression of plasma T4 and triiodothyronine (T3) seen at the end of 11 or 14 weeks of exposure to 30 degrees C without melatonin injections (vs. control levels at 22 degrees C) was offset by melatonin injections, raising T4 and T3 particularly at the lower doses. In contrast, there was no consistent effect of higher temperature alone on reproductive variables. The interactive effects of temperature and melatonin on the reproductive and thyroidal systems in female hamsters are apparently complex and probably provide a fine-tuning mechanism for the environmental control of endocrine physiology.

Animals↗
PubMed1988

Influence of melatonin on the testicular regression induced by subcutaneous testosterone pellets in male rats kept in long or short photoperiod.

Daily afternoon injections of 25 micrograms melatonin for 12 weeks had no effect on testicular weights of male rats kept in long photoperiod (14L:10D); similarly, exposure of rats to short photoperiod (2L:22D) had no effect on gonadal weight. However, rats maintained in a long or short photoperiod and implanted every 2 weeks with a 15 mm Silastic pellet containing testosterone showed a significant reduction in testicular weight; this effect was more pronounced in rats exposed to a short photoperiod. Melatonin injections in testosterone-treated rats in a long photoperiod exacerbated the inhibitory effects of testosterone alone. Subcutaneous 2-weekly implants of a beeswax pellet containing 1 mg melatonin reversed the effects of the melatonin injections on relative testicular weights but not those due to short photoperiod exposure. Testosterone implants significantly reduced pituitary LH values in long and short photoperiod-exposed animals, more particularly in those exposed to short photoperiod. Melatonin injections alone or in combination with melatonin pellets did not further exaggerate the depression in pituitary LH due to testosterone alone in long photoperiod-exposed animals; similarly melatonin pellets did not reverse the depression in pituitary LH observed. No significant differences in plasma prolactin concentrations or in thyroxine concentrations or free thyroxine index were observed after any combination of treatments. We therefore suggest that the effects observed with short photoperiod may be due to melatonin.

Animals↗
PubMed1988

MR diagnosis of pancreatic transplant rejection.

To determine the role of MR imaging in the assessment of pancreatic transplant rejection, we prospectively obtained 13 MR scans in nine transplant patients. The presence of rejection was verified pathologically by pancreatic transplant biopsies in five patients. In two additional patients, rejection was proved by concordant renal transplant biopsy as well as by compatible clinical and laboratory data. In the remaining two patients, in whom no biopsy was done, clinical and laboratory data showed no evidence of rejection. The mean T2 of the seven pancreata undergoing rejection was significantly elevated (86 msec) compared with the mean T2 of the two transplants not undergoing rejection (59 msec) (p less than .002). These preliminary results suggest that MR may be useful in the noninvasive diagnosis of pancreatic rejection.

Biopsy↗
PubMed1987

Protective effects of captopril and enalapril on myocardial ischemia and reperfusion damage of rat.

The protective effect of angiotensin-converting enzyme inhibitors (ACEI) on myocardial ischemia and reperfusion damage was estimated in rat hearts, both in vivo and in vitro. Enalapril 2.5 mg/kg ip pretreatment at 24 and 5 h before coronary occlusion, significantly blunted the rise of CPK (445 +/- 151 vs 649 +/- 244 mu/ml, P less than 0.05) and improved electrocardiogram (ECG) 8 h after coronary occlusion. In global ischemia and reperfusion ex vivo, enalapril improved contractility (0.9 +/- 0.2 vs 0.3 +/- 0.3 g, P less than 0.05) and coronary flow (15.6 +/- 3.3 vs 11.9 +/- 3.1 ml/min/g, P less than 0.05), shortened significantly the duration of reperfusion arrhythmia (3.1 +/- 2.7 vs 9.7 +/- 8.1 min, P less than 0.05). In Langendorffs heart, captopril remarkably preserved force of contraction (2.1 +/- 0.4 vs 1.4 +/- 0.4 g, P less than 0.01) and coronary flow (2.7 +/- 0.5 vs 3.6 +/- 0.9 ml/min/g, P less than 0.05) in segmental infarction deteriorated by angiotensin I. Captopril 10(-5) M infusion reduced the release of CPK (435 +/- 112 vs 640 +/- 123 mu/min coronary flow, P less than 0.05). This action was almost completely abolished by pretreating and infusing with indomethacin. As a positive control, prostacyclin 5 X 10(-7) M infusion further reduced the release of CPK to 330 +/- 77 mu/min. It is concluded that angiotensin-converting enzyme inhibitor can protect both myocardial ischemia and reperfusion damage in rat hearts. The mechanism of protection was ascribed to reduced production of angiotensin II by ACE inhibition and increased prostacyclin release in the myocardium.

Angiotensin I↗
PubMed1987

cDNA sequence of a human skeletal muscle ADP/ATP translocator: lack of a leader peptide, divergence from a fibroblast translocator cDNA, and coevolution with mitochondrial DNA genes.

We have characterized a 1400-nucleotide cDNA for the human skeletal muscle ADP/ATP translocator. The deduced amino acid sequence is 94% homologous to the beef heart ADP/ATP translocator protein and contains only a single additional amino-terminal methionine. This implies that the human translocator lacks an amino-terminal targeting peptide, a conclusion substantiated by measuring the molecular weight of the protein synthesized in vitro. A 1400-nucleotide transcript encoding the skeletal muscle translocator was detected on blots of total RNA from human heart, kidney, skeletal muscle, and HeLa cells by hybridization with oligonucleotide probes homologous to the coding region and 3' noncoding region of the cDNA. However, the level of this mRNA varied substantially among tissues. Comparison of our skeletal muscle translocator sequence with that of a recently published human fibroblast translocator cognate revealed that the two proteins are 88% identical and diverged about 275 million years ago. Hence, tissues vary both in the level of expression of individual translocator genes and in differential expression of cognate translocator genes. Comparison of the base substitution rates of the ADP/ATP translocator and the oxidative phosphorylation genes encoded by mitochondrial DNA revealed that the mitochondrial DNA genes fix 10 times more synonymous substitutions and 12 times more replacement substitutions; yet, these nuclear and cytoplasmic respiration genes experience comparable evolutionary constraints. This suggests that the mitochondrial DNA genes are highly prone to deleterious mutations.

Base Sequence↗
PubMed1987

Influence of psoralen on NAT activity and melatonin levels in rat pineal gland during the daily period of darkness.

A single injection of either 5 or 10 mg/kg 8-methoxypsoralen (8-MOP) was given intraperitoneally to male rats at the end of the 14 h light phase (at 2000 h). Two h later (at 2200 h), when the normal nocturnal surge of N-acetyltransferase (NAT) activity and melatonin content in the pineal gland had begun in vehicle-injected controls, mean pineal NAT after the 10 mg/kg 8-MOP was 1.8-fold higher than that after vehicle, though pineal melatonin content did not differ between vehicle- and drug-injected rats. By 4 h into the dark period (at 2400 h), the NAT activity in both 8-MOP injected groups of rats was greater than that in vehicle treated animals; again, however, 8-MOP treatment did not influence the pineal melatonin content. At 0200 h (6 h into the dark period), the difference between the NAT activity in pineals of rats treated with 5 mg/kg 8-MOP and the vehicle was not statistically significant, but the animals that received 10 mg/kg drug still had statistically elevated levels of the serotonin acetylating enzyme. At 0200 h the pineal melatonin levels were equivalent among the three treatment groups. Rats given 5mg/kg 8-MOP always had NAT values intermediate between those of rats injected with vehicle and those that received 10 mg/kg 8-MOP suggesting that the NAT response to the drug was dose related. These results show that the pineal response to psoralen involves an elevation of NAT activity without a commensurate change in the melatonin content of the gland.

Acetyltransferases↗
PubMed1987

Norepinephrine or isoproterenol stimulation of pineal N-acetyltransferase activity and melatonin content in the Syrian hamster is restricted to the second half of the daily dark phase.

Seven experiments were performed to investigate the sensitivity of the hamster pineal gland to exogenously administered norepinephrine (NE). In these studies NE (1 mg/kg) administration was preceded (10 min earlier) by the injection of the catecholamine uptake inhibitor desmethylimipramine (DMI; 5 mg/kg). When DMI and NE were given at night, the hamsters were exposed to light to depress pineal N-acetyltransferase activity and melatonin values to low levels; the drugs were then given 20 (DMI) and 30 (NE) min later, and the subsequent changes in pineal N-acetyltransferase and melatonin were monitored. The combination of DMI and NE administration anytime during the normal light period or during the first 4 h of the normal dark period failed to stimulate either pineal N-acetyltransferase activity or melatonin levels. Conversely, DMI followed by NE (injected either intraperitoneally or subcutaneously) in the second half of the dark phase typically stimulated pineal melatonin production. Likewise, the NE agonist isoproterenol promoted pineal melatonin production only in the latter half of the dark phase. If hamsters were exposed to continual light at night or if they were superior cervical ganglionectomized, a procedure which sympathetically denervates the pineal gland, the stimulatory effect of NE on melatonin production was significantly suppressed. Thus, the hamster pineal gland is sensitive to NE only during the latter half of the normal dark period and both darkness and an intact sympathetic innervation to the pineal gland are required for the gland to develop maximal sensitivity to the catecholamine. Also, the hamster pineal seems not to exhibit a supersensitivity response to NE following a period of reduced exposure to the catecholamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetyltransferases↗
PubMed1987

Elevated ambient temperature retards the atrophic response of the neuroendocrine-reproductive axis of male Syrian hamsters to either daily afternoon melatonin injections or to short photoperiod exposure.

Adult male Syrian (golden) hamsters, maintained under either 22 +/- 2 or 32 +/- 2 degrees C, were treated with 8 or 11 weeks of exposure to either long photoperiod (14:10), short photoperiod (8:16), or to long photoperiod with a daily afternoon melatonin injection. By 8 weeks, the animals kept at 22 degrees C and treated with daily afternoon melatonin injection exhibited a dramatic reduction in testicular and accessory sex organ weight, but the animals kept at 32 degrees C and treated in the same way exhibited only slight decreases in testicular and accessory organ weights. Short photoperiod caused a slight decrease in testicular and accessory organ weights of hamster kept at 22 degrees C, while it had no significant effects on reproductive organ weights of the animals maintained under 32 degrees C. By 11 weeks, the daily afternoon melatonin injection elicited further reduction in testicular and accessory organ weights of the animals maintained under both 22 and 32 degrees C. However, the reduction in animals kept at 32 degrees C was not as great as that in animals kept at 22 degrees C. Although short photoperiod caused an obvious decline in reproductive organ weights of the animals at 22 degrees C, only a slight decrease was seen in hamsters at 32 degrees C. As with reproductive organ weights, testosterone levels were depressed more rapidly and completely in animals maintained at 22 degrees C. These results indicate that elevated ambient temperature changes the rate at which the gonads of hamsters regress in response to daily afternoon melatonin injections or short photoperiod.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗