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Biomedical subjects

K Liu

Publications and source records attributed to K Liu.

At least 271 records · Page 15Linked to original sources
PubMed1997

Homopurine and homopyrimidine strands complementary in parallel orientation form an antiparallel duplex at neutral pH with A-C, G-T, and T-C mismatched base pairs.

DNA sequences d-TGAGGAAAGAAGGT (a 14-mer) and d-CTCCTTTCTTCC (a 12-mer) are complementary in parallel orientation forming either Donohue (reverse Watson-Crick) base pairing at neutral pH or Hoogsteen base pairing at slightly acidic pH. The structure of the complex formed by dissolving the two strands in equimolar ratio in water has been investigated by nmr. At neutral pH, the system forms an ordered antiparallel duplex with five A : T and four G : C Watson-Crick base pairs and three mismatches, namely G-T, A-C, and T-C. The nuclear Overhauser effect cross-peak pattern suggests an overall B-DNA conformation with major structural perturbations near the mismatches. The duplex has a low melting point and dissociates directly into single strands with a broad melting profile. The hydrogen-bonding schemes in the mismatched base pairs have been investigated. It has been shown earlier that in acidic pH, the system prefers a triple-stranded structure with two pyrimidine strands and one purine strand. One of the pyrimidine strands has protonated cytosines, forms Hoogsteen base pairing, and is aligned parallel to the purine strand; the other has nonprotonated cytosines and has base-pairing scheme similar to the one discussed in this paper. The parallel duplex is therefore less stable than either the antiparallel duplex or the triplex, in spite of its perfect complementarity.

Base Composition↗
PubMed1997

Hyaline matrix material in high-grade endometrial stromal sarcoma diagnosed by fine-needle aspiration: case report.

We present a case of a high-grade endometrial stromal sarcoma metastatic to the abdomen with an unusual extracellular hyaline matrix material seen on fine needle aspiration biopsy. The patient was initially diagnosed with a stage IIIA high-grade endometrial stromal sarcoma and had received four cycles of chemotherapy over the past year. She subsequently developed an abdominal mass that consisted of discohesive small cells with scanty cytoplasm on fine needle aspiration. On the Diff-Quik-stained smears, metachromatic, extracellular hyaline material was identified. This appeared on the Papanicolaou-stained smear as cyanophilic material and did not react with reticulin stain. This case emphasizes the importance to the cytopathologist of including endometrial stromal sarcoma in the differential diagnosis of hyaline matrix material.

Abdominal Neoplasms↗
PubMed1997

Cytologic features of pulmonary metastasis from a granulosa cell tumor diagnosed by fine-needle aspiration: a case report.

We report on a case of a granulosa cell tumor of the ovary metastatic to the lung and diagnosed by fine-needle aspiration. The patient was a 70-yr-old woman who was diagnosed with a granulosa cell tumor of the ovary 17 yr previously. She subsequently developed abdominal metastases and received several cycles of chemotherapy. A 0.5-cm right upper lobe pulmonary nodule was found on a routine chest radiograph and subsequent computerized tomography scan. Aspiration cytology of this pulmonary nodule demonstrated small, relatively uniform neoplastic cells with nuclear grooves and indentations consistent with a granulosa cell tumor. The differential diagnosis of granulosa cell tumors from other metastatic and pulmonary lesions is reviewed.

Aged↗
PubMed1997

Differential expression of CD44s and CD44v10 proteins and syndecan in normal and irradiated mouse epidermis.

The role of the CD44s adhesion molecule, its epithelial isoforms and its relationship to epidermal proteoglycans such as syndecan was studied in normal and irradiated mouse skin. In normal mouse skin, only 10% of basal cells are strongly CD44s-immunopositive, with a cytoplasmic expression pattern. Double-label experiments with the basal cell marker keratin 14 confirmed the epithelial nature of the strongly CD44s-positive cell type in the basal layer. Some spinous keratinocytes and the majority of the remaining basal cells exhibited a weak membranous staining pattern. In contrast, the epithelial isoform, CD44v10, was strongly present in all basal and suprabasal epithelial cells of the epidermis, with a membranous staining pattern. Syndecan was found in the granular layer of the normal epidermis only. After 1 week of daily irradiation, the entire basal cell layer of the epidermis expressed CD44s in the membrane, but with a varying degree of staining intensity. This reactivity spread to the upper spinous layer after 3 weeks of treatment. In hyperproliferative epidermis, there was no difference in the staining patterns between CD44s and CD44v10. The expression of syndecan switched from the granular layer to the basal and lower spinous layers after 2 weeks of daily irradiation. Immunoreactivity for syndecan was also strongly enhanced in the dermis of irradiated samples. The results suggest an important role for syndecan and CD44 in proliferative processes during radiation-induced accelerated repopulation.

Animals↗
PubMed1997

Arterial oxygen desaturation during emergent nonsedated upper gastrointestinal endoscopy in the emergency department.

A prospective study was conducted to see whether emergent esophagogastroduodenoscopy (EGD) in patients with active upper gastrointestinal (GI) bleeding is associated with more oxygen desaturation than nonemergent EGD. Emergent EGD was performed in the study patients with active upper GI bleeding. Nonemergent EGD was performed in the control patients. Determination of oxygen saturation (Sao2) was measured by pulse oximeter. A decrease in Sao2 of > 4% was more frequent in the study patients (26%, 13 of 50) than in controls (6%, 3 of 50) (P < .01). During EGD, mean oxygen saturation decreased significantly in both groups of patients. After EGD, mean oxygen saturation did not recover toward the pre-endoscopy insertion level in the study group (P < .01). A linear association was found that oxygen desaturation = 5.46 + 0.15 (status) -0.06 (baseline oxygen saturation). Emergent EGD for active upper GI bleeding in the emergency department tends to be associated with more frequent significant oxygen desaturation than nonemergent EGD. Continuous oxygen supplementation and oxygen saturation monitoring may be used during emergent nonsedated EGD in the emergency department.

Acute Disease↗
PubMed1997

Identification of two types of autoreactive T lymphocyte clones cultured from cardiac allograft-infiltrating cells incubated with recombinant mycobacterial heat shock protein 71.

Recent studies in several laboratories have advanced the concept that during cellular rejection, the allograft undergoes a stress response which regulates the expression of stress proteins (or heat shock proteins, hsp) and triggers the recruitment and activation of hsp-reactive lymphocytes. In a rat model of heterotopic heart transplants we have found that allograft-infiltrating lymphocytes respond to recombinant mycobacterial hsp and irradiated syngeneic spleen cells as a source of self-APC (antigen-presenting cells). This report describes T cell clones generated by culturing ACI into Lewis rat cardiac allograft-derived lymphocytes with mycobacterial hsp71, syngeneic spleen cells and IL-2 (interleukin-2). Two groups of self-APC-reactive T cell clones have been distinguished, all of them are CD3+, CD4+, CD8-. One group is referred to as hsp71-dependent, autoreactive T cells because these clones respond to self-APC but only in the presence of hsp71. No reactivity is seen with mycobacterial hsp65 or when hsp71 is tested with allo-PC from ACI donors or third-party APC from Brown Norway (BN) rats. Treatment of hsp71 with trypsin, polymyxin B or ATP-agarose chromatography abrogates the hsp71 effect thus indicating that structurally intact hsp71 must interact with self-APC which then activate hsp71-dependent, autoreactive T cells. The second group of clones reacts to self-APC and while their response does not require the presence of hsp71, their proliferation is often augmented by hsp71 but not by hsp65. These hsp71-independent, autoreactive clones do not respond to allo-APC from ACI donors or third-party APC from BN rats. Polymyxin or trypsin treatment had no significant effect on their proliferative responses. The data with the anti-TCR-alpha beta monoclonal antibody R73 offer additional evidence for two functionally different types of self-APC reactive CD4 cells infiltrating the allograft. R73 inhibits the proliferation of self-APC induced responses of hsp-71-independent clones as well as the allo-APC induced responses of alloreactive T cell clones. In contrast, this antibody augments the responses of hsp71-dependent T cells. Moreover, these clones can also proliferate in response to self-APC when hsp71 is substituted by R73. The hsp71-dependency of self-APC reactive T cell reactivity represents a previously unrecognized mechanism of cellular immunity to allografts. This mechanism might be related to the peptide binding properties of hsp71 and the ability of stress proteins to function as molecular chaperones in antigen processing.

Animals↗
PubMed1997

Determination of aluminium-26 in biological materials by accelerator mass spectrometry.

Studies of the biological chemistry of aluminium can gain significantly from the use of the long-lived isotope 26Al as a tracer, although the cost of the isotope often precludes its determination by radiochemical counting techniques. Accelerator mass spectrometry (AMS) provides an ultra-sensitive method of determination, free from isobaric interference from atomic (26Mg) or molecular species. The source materials for AMS can be aluminium oxide or phosphate, both of which can be readily prepared at a sufficient level of purity from biological substrates. Natural aluminium (27Al, 100%) is added to the preparations as a chemical yield monitor and to provide the reference for the isotope ratio measurement. 26Al/27Al ratios can be determined over the range 10(-14)-10(-7), implying a limit of detection for 26Al of around 10(-18) g. The precision of measurement and long-term reproducibility are < 5% and < 7% (RSD), respectively. Chemical methodologies for routine measurements on blood and urine samples have been developed.

Aluminum↗
PubMed1997

Functional expression of Drosophila para sodium channels. Modulation by the membrane protein TipE and toxin pharmacology.

The Drosophila para sodium channel alpha subunit was expressed in Xenopus oocytes alone and in combination with tipE, a putative Drosophila sodium channel accessory subunit. Coexpression of tipE with para results in elevated levels of sodium currents and accelerated current decay. Para/TipE sodium channels have biophysical and pharmacological properties similar to those of native channels. However, the pharmacology of these channels differs from that of vertebrate sodium channels: (a) toxin II from Anemonia sulcata, which slows inactivation, binds to Para and some mammalian sodium channels with similar affinity (Kd congruent with 10 nM), but this toxin causes a 100-fold greater decrease in the rate of inactivation of Para/TipE than of mammalian channels; (b) Para sodium channels are >10-fold more sensitive to block by tetrodotoxin; and (c) modification by the pyrethroid insecticide permethrin is >100-fold more potent for Para than for rat brain type IIA sodium channels. Our results suggest that the selective toxicity of pyrethroid insecticides is due at least in part to the greater affinity of pyrethroids for insect sodium channels than for mammalian sodium channels.

Animals↗
PubMed1997

Compartmentalization of human chorionic gonadotrophin sensitivity and luteinizing hormone receptor mRNA in different subtypes of the human corpus luteum.

The relationship was investigated between different ultrasonographically defined subtypes of the human corpus luteum and progesterone production. Twenty-one women in the mid-luteal phase who underwent laparotomy for benign uterine conditions volunteered for this study. The corpus luteum was identified by preoperative ultrasound and classified into four types according to earlier established criteria, where types a and c were centrally hypoechoic, types b and d were centrally echogenic, types a and b had thin surrounding 'walls' (<3 mm) and types c and d had thick walls (<3 mm). After luteectomy, the theca externa capsule was removed and tissue from directly beneath the surface ('peripheral region') and the layer immediately beneath ('inner region') minced into 4-6 mg pieces. Following preincubation, pieces were incubated for 3 h at 37 degrees C in HEPES-minimal essential medium buffer with or without human chorionic gonadotrophin (HCG; 10 IU/ml), and subsequently progesterone accumulation in the medium was determined by radioimmunoassay. The highest progesterone production was consistently seen in the peripheral region. Type a had a significantly (P > 0.01) lower progesterone production (3.2 +/- 1.5 nmol/g tissue wet weight, mean +/- SEM, n = 4) than that of types b, c and d (17.7 +/- 3.5 nmol/g tissue wet weight, n = 9). All types responded to HCG with an almost two-fold increase in progesterone production. However, the maximal progesterone produced following stimulation by HCG in the type a corpus luteum was <50% of the basal (unstimulated) progesterone synthesis of any other type of corpus luteum. Using in-situ hybridization, with a primate RNA probe complementary to the region coding the extracellular part of the luteinizing hormone (LH) receptor, a highly localized expression of LH receptor mRNA to the peripheral region was found. Negligible or low levels of expression were found in the theca externa capsule and the inner region. No obvious correlations between the different subtypes of corpora lutea and LH receptor mRNA expression were seen. Thus, the ultrasonographic detection of a thin-walled and centrally hypoechoic corpus luteum correlates well with reduced progesterone secretion. The underlying cellular mechanism does not appear to involve a diminished sensitivity to the gonadotrophic stimulation by LH or HCG.

Adult↗
PubMed1997

Lidocaine suppresses the anoxic depolarization and reduces the increase in the intracellular Ca2+ concentration in gerbil hippocampal neurons.

BACKGROUND: The movement of ions, particularly Ca2+, across the plasma membrane of neurons is regarded as an initial element of the development of ischemic neuronal damage. Because the mechanism by which lidocaine protects neurons against ischemia is unclear, the effects of lidocaine on the ischemia-induced membrane depolarization, histologic outcome, and the change in the intracellular Ca2+ concentration in the gerbil hippocampus were studied. METHODS: The changes in the direct-current potential shift in the hippocampal CA1 area produced by transient forebrain ischemia for 4 min were compared in animals given lidocaine (0.8 micromol administered intracerebroventricularly) 10 min before ischemia and those given saline. The histologic outcome was evaluated 7 days after ischemia by assessing delayed neuronal death in hippocampal CA1 pyramidal cells in these animals. In a second study, hypoxia-induced intracellular Ca2+ increases were evaluated by in vitro microfluorometry in gerbil hippocampal slices, and the effects of lidocaine (10, 50, and 100 microM) on the Ca2+ accumulation were examined. In addition, the effect of lidocaine (100 microM) drug perfusion with a Ca2+-free ischemia-like medium was investigated. RESULTS: The preischemic administration of lidocaine delayed the onset of the ischemia-induced membrane depolarization (anoxic depolarization) and reduced its maximal amplitude. The histologic outcome was improved by the preischemic treatment with lidocaine. The in vitro hypoxia-induced increase in the intracellular concentration of Ca2+ was suppressed by the perfusion with lidocaine-containing mediums (50 and 100 microM), regarding the initiation and the extent of the increase. The hypoxia-induced intracellular Ca2+ elevation in the Ca2+-free condition was similar to that in the Ca2+-containing condition. Perfusion with lidocaine (100 microM) inhibited this elevation in the Ca2+-free condition. CONCLUSIONS: Lidocaine helps protect neurons from ischemia by suppressing the direct-current potential shift, by inhibiting the release of Ca2+ from the intracellular Ca2+ stores, and by inhibiting the influx from the extracellular space.

Anesthetics, Local↗
PubMed1997

Dietary vitamin C, beta-carotene and 30-year risk of stroke: results from the Western Electric Study.

The relations of dietary antioxidants vitamin C and beta-carotene to 30-year risk of stroke incidence and mortality were investigated prospectively in the Chicago Western Electric Study among 1,843 middle-aged men who remained free of cardiovascular disease through their second examination. Stroke mortality was ascertained from death certificates, and nonfatal stroke from records of the Health Care Financing Administration. During 46, 102 person-years of follow-up, 222 strokes occurred; 76 of them were fatal. After adjustment for age, systolic blood pressure, cigarette smoking, body mass index, serum cholesterol, total energy intake, alcohol consumption, and diabetes, relative risks (and 95% confidence intervals) for nonfatal and fatal strokes (n = 222) in highest versus lowest quartiles of dietary beta-carotene and vitamin C intake were 0.84 (0.57-1.24) and 0.71 (0.47-1.05), respectively. Generally similar results were observed for fatal strokes (n = 76). Although there was a modest decrease in risk of stroke with higher intake of beta-carotene and vitamin-C intake, these data do not provide definitive evidence that high intake of antioxidant vitamins decreases risk of stroke.

Adult↗
PubMed1997

Factor VII, cholesterol, and triglycerides. The CARDIA Study. Coronary Artery Risk Development in Young Adults Study.

Cross-sectional studies have shown that factor VII coagulant activity (VIIc) is positively associated with plasma total cholesterol (TC), LDL cholesterol, and triglycerides (TG) as well as body mass index (BMI) and diastolic blood pressure. To determine whether changes in VIIc parallel changes in coronary risk factors over a period of 2 years, we examined data from 1514 participants in the Coronary Artery Risk Development in Young Adults Study (CARDIA), an ongoing investigation of lifestyles and evolution of cardiovascular risk factors. Subjects were 23 to 35 years old at the year 5 examination. Cross-sectional analyses at these examinations showed that VIIc was positively correlated (P < .001) with TC and TG in all race/sex groups except for TC in black women at the year 5 examination. Changes in VIIc over the 2-year period were correlated positively with changes in TC in all except black men and TG in all groups; the association of VIIc change with change in TC and TG was reduced only slightly with adjustment for age and BMI at year 5 and 2-year change in BMI. To determine whether the higher levels of VIIc in subjects with higher lipid values were due to activation of the factor or to an increase in the concentration of the factor VII clotting protein, we measured factor VII antigen (VIIag) in a randomly selected subsample of 223 subjects at the year 7 examination. In all sex/race groups, VIIag correlated with VIIc (r = .69 to 0.81). After adjustment for sex and race, the partial correlation coefficient between TG and VIIc was .28 (P = .0001); between TG and VIIag, .35 (P = .0001); between TC and VIIc, .39 (P = .0001); and between TC and VIIag, 0.43 (P = .0001). No associations were observed between lipid levels and the ratio of VIIc to VIIag. We conclude that the raised VIIc with higher lipid levels occurs in blacks as well as whites, in men and women, persists over time, and represents a true increase in the plasma concentration of this clotting factor.

Adult↗
PubMed1997

Diabetes, asymptomatic hyperglycemia, and 22-year mortality in black and white men. The Chicago Heart Association Detection Project in Industry Study.

OBJECTIVE: To assess relationships of diabetes and asymptomatic hyperglycemia at baseline to the risk of cardiovascular disease (CVD) and all-cause (ALL) mortality in employed, white and black middle-aged men. RESEARCH DESIGN AND METHODS: A prospective cohort study of 11,554 white men and 666 black men between the ages 35 and 64 from 1967 to 1973 was conducted using data from the Chicago Heart Association (CHA) Detection Project in Industry 22-year mortality follow-up. cox proportional hazards models, adjusted fro age and other CVD risk factors, were used to estimate the relative risk (RR) and the 95% CI of mortality associated with baseline glycemic status. RESULTS: Age-adjusted baseline prevalence of clinical diabetes was similar in white (3.7%) and black (4.3%) men; asymptomatic hyperglycemia (glucose post-50-g load > or = 11.1 mmol/l) was present in 11.1% of whites and 7.8% of blacks. After controlling for age, lifestyle, and other CVD risk factors, mortality risk was increased among white men with clinical diabetes (CVD: RR 2.51, CI 2.08-3.02; ALL: RR 1.88, CI 1.63-2.17) and asymptomatic hyperglycemia (CVD: RR 1.18, CI 1.01-1.37; ALL: RR 1.24, CI 1.11-1.37), compared with men with postload glucose < 8.9 mmol/l. Risks were similarly, though nonsignificantly (owing to low statistical power), increased among black men with clinical diabetes (CVD: RR 1.60, CI 0.60-4.29; ALL: RR 1.78, CI 0.97-3.25) and asymptomatic hyperglycemia (CVD: RR 1.29, CI 0.61-2.72; ALL: RR 1.37, CI 0.85-2.20). CONCLUSIONS: Asymptomatic hyperglycemia and clinical diabetes appear to confer increased mortality risk in both white and black men. In addition, mortality risk is increased with increased severity of glycemia. These findings indicate the importance of applying efforts to reduce risk factors and prevent diabetes in both blacks and whites.

Administration, Oral↗
PubMed1997

[Characteristics of diagnosis and treatment of traumatic intracerebellar hemorrhage].

We treated 10 cases of traumatic intracerebellar hamorrhage, which accounted for 3.7% of intracranial hemnatomas patients in the same period. Two cases had an initial GCS score less than 8. and 8 patients had GCS score of 11-15. Hematomas averaged 6.39 ml. It's a major method for analysis of traumatic mechanism and CT scan. Under normal conditions surgical operation is necessary. The hemispheric hematomas of limited size (less than 3 cm) may be treated conservatively when consciousness is stable.

Adolescent↗
PubMed1997

[Spinal segment distribution of neural innervation related houhai acupoint--studied by CB-HRP tracing method focused on observation of the dendrites of spinal motor neurons].

The spinal segment distribution of neural innervation related Houhai acupoint in rats has been investigted by using horseradish peroxidase conjugated cholera toxin B subunit (CB-HRP) tracing technique. Spinal motoneurons (Mn) in L6-S1 were labeled retrogradely by CB-HRP, and their features have been characterized: 1) their marginal plexus of the dendrites radially projected to the lateral and/or anterior funiculus and their distal portions forming subpial dendritic plexus; 2) the medial dendrites ran along the ventral margin of the gray commissure and their distal portions surrounded the central canal' forming a subependymal dendritic plexus. Both of them are Golgi-phobic. Some distal branches of dendrites penetrated to the contralateral gray matter. The dendritic arbors of the labeled motoneurons in the group of electro-acupuncture or group of acupoint-inoculation with sheep red blood cells contracted in comparison with that in the normal control group. The primary sensory transganglionic labeled fibers and preterminal fibers revealed by CB-HRP in the dorsal horn and dorsal commissural nucleus of the spinal cord (L5-S2) converged and overlaped with the dendrites of retrogradely labeled motoneurons. The results indicated there is a reflect circuit of afferent-integration-efferent neuro-network in the spinal cord related Houhai acupoint. The Mns retrogradely labeled by CB-HRP in the L6-S1 segments might be involved in Houhai acupuncture.

Acupuncture Points↗