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Biomedical subjects

H Cai

Publications and source records attributed to H Cai.

At least 145 records · Page 8Linked to original sources
PubMed1996

A new single-fibre laser Doppler flowmeter based on digital signal processing.

A new laser Doppler flowmeter, based on a personal computer with a digital signal processor for detecting the blood perfusion in skeletal muscle, was designed and evaluated. An infrared laser diode (750 nm) fed a single optical fibre, 400 microns in diameter, which was introduced into the muscle. A PC equipped with a digital processing unit was used for emulation of the laser Doppler algorithm and for presentation of the measurement results. The Doppler signal power spectral density and corresponding flow values were visualized on the computer screen continuously in real-time, and could also be saved on the hard disk for off-line analyses. The graphic-user interface supported by Labwindows software made the system easy to use. It is possible to alter in the software the signal processing and the ways in which the signals and results are presented. The new system was evaluated by using a flow model as well as a mechanical model. The model studies showed linear relationships between particle velocity and flow in the range of 0-5 mm s-1. The system was also tested in measurements of the blood flow in the brachioradial muscle, and was found to have advantages over our previously used systems.

Algorithms↗
PubMed1996

Study on ultrastructural cytochemistry and pathogenic mechanism of Trichomonas vaginalis.

OBJECTIVE: To study the relation among enzymic ultrastructural localizations, cell organelles and functions of Trichomonas vaginalis (T. vaginalis) as well as its pathogenic mechanism. MATERIAL AND METHODS: The specimens were Trichomonas vaginalis cultured purely for several generations. After prefixation, several electron microscopic cytochemical reactions for marker enzymes of lysosome, Golgi body, mitochondrion and microbody as well as Ur-Pb-Cu impregnation were undertaken. Then the specimens were post-fixed and embedded, and the unstained ultrathin sections were observed under a transmission electron microscope. RESULTS: The activities of acid phosphatase and cytidine monophosphatase appeared in the primary and secondary lysosomes of the parasite, and the reaction product of peroxidase was found in the secondary lysosomes. It was found that lysosomes could release hydrolytic enzymes out of the cell. The reaction products of thiamine pyrophosphatase and nicotinamide adenine dinucleotide phosphatase were located within the mature-surface and intermediate saccules of Golgi body respectively. The reactions for succinate dehydrogenase, cytochrome oxidase and catalase were negative. The hydrogenosomes, endoplasmic reticulum and Golgi bodies of the parasite were densely stained by Ur-Pb-Cu impregnation method. CONCLUSIONS: T.vaginalis has lysosomal system which can release hydrolases out of the parasite, causing damage to the vaginal and urethral epithelial cells. This may be an important pathogenic mechanism of vaginitis and urethritis caused by T.vaginalis. This protozoon has well-developed Golgi bodies and rich endoplasmic reticulum. It lacks mitochondrion and microbody, but has abundant hydrogenosomes which are energy producing organelles of anaerobic metabolism and resemble microbody in morphology and mitochondrion in some functions.

Animals↗
PubMed1996

[Using ligustrazini and angelica sinensis treat the bleomycin-induced pulmonary fibrosis in rats].

OBJECTIVE: To seek a kind of Chinese traditional medicine to treat the bleomycin-induced pulmonary fibrosis. METHODS: SD rats with bleomycin A(s) induced pulmonary fibrosis, were divided into 4 groups. Normal control group (10 rats), untreated model group (35 rats), ligustrazini group (10 rats), Angelica sinensis group (10 rats). Both ligustrazini and angelica sinensis were given intraperitoneally by injection daily for 28 days. Then all rats were put to death and took out the lungs for examination. Using histopathological examination and image processing computer assisted to evaluate the result of treatments. RESULTS: Ligustrazini could obviously reduced alveolitis and fibrosis and Angelica sinensis had the similar but lesser result. CONCLUSION: Ligustrazini and angelica sinensis have successful result of treatment for pulmonary fibrosis.

Animals↗
PubMed1996

[The effect of electro-acupuncture on the adrenal gland of endotoxic shocked rats].

The quantitative histochemical changes of glycogen SDH in the adrenal gland of endotoxic-shocked rat induced by electro-acupuncture were observed in this paper. The result indicates that electro-acupuncture at "Ren Zhong" or "Zusali" of endotoxic shocked animal might improve the function of adrenal cortex and achieve recovery in certain extent.

Adrenal Glands↗
PubMed1996

[Mechanism of inhibitory action of sodium ferulate on liver lipid peroxidation in mice].

The study has shown that sodium ferulate (SF) significantly inhibits the rise of liver lipid peroxides MDA content, alleviates the depletion of hepatic GSH pond, and reverses the decline of GST, GSH-Px levels in ethanol treated mice. The results indicate this inhibitory action of SF is related to diminishing the generation of oxygen free radicals by stabilizing GSH and related enzyme levels.

Animals↗
PubMed1995

The alpha 1-adrenoceptor antagonist, doxazosin, modulates the lower limit of autoregulation of cerebral blood flow during hemorrhagic hypotension in anesthetized hypertensive rats.

The objective of the present study was to examine the effects of administration of an alpha 1-adrenoceptor antagonist, doxazosin, for 7 days on cerebral blood flow and the autoregulatory response to hypotension in anesthetized spontaneously hypertensive rats. We determined the cerebral blood flow at rest and during hemorrhagic hypotension in 14 rats of each group using laser-Doppler flowmetry, and at the same time, the absolute baseline cerebral blood flow values at the parietal cortex were also quantified in some of the rats with the hydrogen clearance method. Baseline mean arterial pressure was significantly lowered, by 41 mm Hg, in the doxazosin-treated group, while the baseline cerebral blood flow was 31 +/- 4 ml/100 g/min(mean +/- S.D.) which was almost the same as the 32 +/- 5 ml/100 G/min in the control group. The lower limits of cerebral blood flow autoregulation were 139 +/- 9 mm Hg in the control group and 96 +/- 12 mm Hg in the treated group; the difference was significant (P < 0.001). The present results demonstrated that the lower limit of cerebral blood flow autoregulation shifts to a lower level after chronic treatment with doxazosin, an effect which is favorable for the maintenance of cerebral blood flow under hypotensive conditions.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1995

Transcriptional repression in the Drosophila embryo.

Transcriptional repression is essential for the conversion of crude maternal gradients into sharp territories of tissue differentiation in the Drosophila embryo. Evidence will be presented suggesting that some of the embryonic repressors function through a short-range 'quenching' mechanism, whereby a repressor works over short distances (ca. 50 b.p.) to block neighbouring activators within a target enhancer. This type of repression can explain how different enhancers work autonomously within complex modular promoters. However, at least one of the repressors operating in the early embryo works through a long-range, or silencing, mechanism. The binding of a silencer to a given enhancer leads to the inactivation of all enhancers within a complex promoter. The analysis of chromatin boundary elements suggest that silencers and enhancers might work through distinct mechanisms. We speculate that silencers constrain the evolution of complex promoters.

Animals↗
PubMed1995

Functional glycosylation sites of the rat luteinizing hormone receptor required for ligand binding.

The contribution of N-linked glycosylation to the ligand binding activity of the rat luteinizing hormone receptor (LHR) was studied in wild-type and mutant LHR expressed in mammalian (COS1) cells and overexpressed in insect (Sf9) cells. The binding affinities of the holoreceptor and its truncated splice variant (form B) lacking the transmembrane domain were equivalent in both cell lines. Tunicamycin-treated transfected Sf9 cells expressed a carbohydrate-free LH receptor that lacked hormone binding activity. Functional carbohydrate chains essential for binding activity were localized to glycosylation sites at Asn-173 and Asn-152. Glycosidase treatment of the double mutant N173Q/N152Q revealed the presence of at least one additional carbohydrate chain at Asn-269, Asn-277, or Asn-291 that does not contribute to hormone binding. Asn-77 was not glycosylated, but its mutation to Gln reduced hormone binding. LHR expressed in insect cells contained only high mannose carbohydrate chains, and those located at Asn-173 and Asn-152 were sufficient for high-affinity hormone binding. Enzymatic cleavage of glycosyl chains indicated that only the proximal N-acetylglucosamine residue, which is common to high mannose and complex carbohydrate forms, is necessary for acquisition of the high affinity conformation of the receptor. The carbohydrate chains of the LHR appear to be involved in intramolecular folding of the nascent receptor rather than in its interaction with the hormone.

Alternative Splicing↗
PubMed1995

Proofreading-defective DNA polymerase II increases adaptive mutation in Escherichia coli.

The role of Escherichia coli DNA polymerase (Pol) II in producing or avoiding mutations was investigated by replacing the chromosomal Pol II gene (polB+) by a gene encoding an exonuclease-deficient mutant Pol II (polBex1). The polBex1 allele increased adaptive mutations on an episome in nondividing cells under lactose selection. The presence of a Pol III antimutator allele (dnaE915) reduced adaptive mutations in both polB+ cells and cells deleted for polB (polB delta 1) to below the wild-type level, suggesting that both Pol II and Pol III are synthesizing episomal DNA in nondividing cells but that in wild-type cells Pol III generates the adaptive mutations. The adaptive mutations were mainly -1 frame-shifts occurring in short homopolymeric runs and were similar in wild-type, polB delta 1, and polBex1 strains. Mutations produced by both Pol III and Pol II ex1 were corrected by the mutHLS mismatch repair system.

Acclimatization↗
PubMed1995

Modulation of enhancer-promoter interactions by insulators in the Drosophila embryo.

Insulator DNAs, or boundary elements, functionally isolate neighbouring genes by blocking interactions between distal enhancers and inappropriate target promoters. The best-characterized insulators in Drosophila correspond to a 340-base-pair (bp) fragment from the gypsy retrotransposon, and the scs and scs' sequences flanking the 87A1 hsp70 locus. Here we demonstrate that both insulators block the interaction of defined even-skipped (eve) stripe enhancers when positioned between the enhancer and the target promoter. The simultaneous use of two stripe enhancers (eve stripes 2 and 3) provides evidence that enhancers lying distal to the insulator are selectively blocked. The insertion of stripe-insulator-stripe sequences between two divergently transcribed promoters indicates that enhancers barred from acting on one basal promoter are fully accessible to appropriate regulatory factors for activating the other promoter. These results suggest that insulators do not propagate changes in chromatin structure. Finally, we present evidence that the gypsy insulator does not block interactions between a silencer element and a basal promoter. Taken together, these results suggest that insulators might not be restricted to the functional isolation of neighbouring genetic loci. Rather, they might function as flexible regulatory elements that modulate enhancer-promoter interactions within complex promoters and complex genetic loci.

Animals↗
PubMed1995

Absorption, tissue distribution and in vivo stability in rats of a hybrid antisense oligonucleotide following oral administration.

In vivo stability and oral bioavailability of an oligodeoxynucleotide phosphorothioate containing segments of 2'-O-methyloligoribonucleotide phosphorothioates at both the 3'- and 5'-ends (hybrid oligonucleotide) were studied. A 25-mer 35S-labeled hybrid oligonucleotide was administered to rats by gavage at a dose of 50 mg/kg body weight. HPLC analysis revealed that this hybrid oligonucleotide was stable in the gastrointestinal tract for up to 6 hr following oral administration. Radioactivity associated with the hybrid oligonucleotide was detectable in portal venous plasma, systemic plasma, various tissues, and urine. Intact hybrid oligonucleotide was detected, by HPLC analysis, in portal venous plasma, systemic plasma, and various tissues. The majority of the radioactivity in urine was associated with degradative products with lower molecular weights, but the intact form was also detected. In summary, the hybrid oligonucleotide was absorbed intact through the gastrointestinal tract, indicating the possibility of oral administration of oligonucleotides, a finding that may be important in the development of antisense oligonucleotides as therapeutic agents.

Administration, Oral↗
PubMed1995

Purification and properties of wild-type and exonuclease-deficient DNA polymerase II from Escherichia coli.

Wild-type DNA polymerase II (pol II) and an exonuclease-deficient pol II mutant (D155A/E157A) have been overexpressed and purified in high yield from Escherichia coli. Wild-type pol II exhibits a high proofreading 3'-exonuclease to polymerase ratio, similar in magnitude to that observed for bacteriophage T4 DNA polymerase. While copying a 250-nucleotide region of the lacZ alpha gene, the fidelity of wild-type pol II is high, with error rates for single-base substitution and frameshift errors being < or = 10(-6). In contrast, the pol II exonuclease-deficient mutant generated a variety of base substitution and single base frameshift errors, as well as deletions between both perfect and imperfect directly repeated sequences separated by a few to hundreds of nucleotides. Error rates for the pol II exonuclease-deficient mutant were from > or = 13- to > or = 240-fold higher than for wild-type pol II, depending on the type of error considered. These data suggest that from 90 to > 99% of base substitutions, frameshifts, and large deletions are efficiently proofread by the enzyme. The results of these experiments together with recent in vivo studies suggest an important role for pol II in the fidelity of DNA synthesis in cells.

Base Sequence↗
PubMed1995

Effects of psychophysiological stress on trapezius muscles blood flow and electromyography during static load.

Mental stress was induced by the Stroop colour word task (CW task) and the effects on the microcirculation and electromyography (EMG) in the upper portion of the trapezius muscle were studied during a series of fatiguing, standardized static contractions. A lowered blood flow of the skin recorded continuously by laser-Doppler flowmetry (LDF) was used as a stress indicator in addition to an elevated heart rate. Muscle blood flow was recorded continuously by LDF using a single optical fibre placed inside the muscle, and related to surface EMG. A group of 20 healthy women of different ages was examined. Recordings were made during a 50-min period in the following sequence: a 10-min series of alternating 1-min periods of rest and stepwise increased contraction induced by keeping the arms straight and elevated at 30, 60, 90 and 135 degrees with a 1-kg load carried in each hand; a 10-min recovery period without load; a repeated contraction series with simultaneous performance of the CW task; a second 10-min recovery period, and a second contraction series without CW task. Signal processing was done on line by computer. The LDF and root mean square (rms)-EMG values were calculated, as well as the EMG mean power frequency (MPF) for fatigue. The CW-task added to the contraction series caused an increase in the heart rate accompanied by a decrease in the blood flow to the skin and a 30% increase in the blood flow in the exercising muscle. Both returned to normal during the subsequent recovery period and showed normal levels during the final contraction series without CW. The rms-EMG showed a 20% increase that persisted during the final contraction series performed without CW. There was no influence on MPF. This CW has previously been shown to evoke an increased secretion of adrenaline from the adrenal medullae to the blood. The increased blood flow in the exercising muscle would therefore appear to have been caused by beta-adrenoceptor vasodilatation, and the fall in the blood flow in the skin by alpha-adrenoceptor vasoconstriction. The findings may have implications for work situations characterized by repetitive static loads to the shoulder muscles and psychological stress.

Adult↗
PubMed1995

Microcirculation in the upper trapezius muscle during sustained shoulder load in healthy women--an endurance study using percutaneous laser-Doppler flowmetry and surface electromyography.

Microcirculation in the upper portion of the trapezius muscle was measured percutaneously in a group of 16 healthy women of different ages by continuous laser-Doppler flowmetry (LDF) in relation to electromyography (EMG) during an endurance test. During the measurements the subject kept her arms straight and elevated at 45 degrees in the scapular plane and held a 1-kg load in each hand as long as possible. This was followed by rest with the arms hanging and carrying no load. The 10-min recording period comprised 1-min initial rest followed by the endurance test and then recovery. Signal processing was done by computer on line. The LDF and root-mean-square (rms) EMG signals were normalized. Spectrum analyses of EMG mean power frequency (MPF) were performed. The amount of load produced was on average 2,267 (SD 939) N.m.s, i.e. shoulder torque x time expressed as Newton meter seconds, and the endurance time was 4.3 (SD 1.20) min. The rms-EMG as well as the LDF increased significantly during endurance, both when related to endurance time and to amount of load. The MPF showed no significant changes. The mean total increase in muscle blood flow was 175% of that recorded in the initial rest period. The average increase per each 10 s of contraction was 2.9%. Maximum was reached during the 1st min of recovery followed by a fall to the base level that was reached within 77 s on average. The amount of load produced and the blood flow increase was smaller than that found in a separate study of men, indicating a lower functional capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Measurement by laser-Doppler flowmetry of microcirculation in lower leg muscle at different blood fluxes in relation to electromyographically determined contraction and accumulated fatigue.

Single-fibre percutaneous laser-Doppler flowmetry (LDF) of the tibialis anterior muscle was performed continuously for measurement of the microcirculation during different blood fluxes, as well as in relation to different muscle activities and fatigue determined electromyographically (EMG). The laser-Doppler power spectrum density function was studied in a frequency range of 0-8.2 Hz as representing the blood flow most selectively. Reduced blood flow from tourniquet inflation caused a decrease in signal power density, compared to that of intact blood flow at rest. During postocclusion reactive hyperaemia an increased signal power was recorded. This reached its maximum within 4.4 (SD 1.88) s after deflation of the tourniquet. The different fluxes were recorded at high sensitivity and disturbances were small. Periods of 1-min static dorsi-flexion of the foot at 10, 20, 30, 40, and 50% MVC (maximal voluntary contraction) with 1-min rest between were associated with a significant increase in LDF, the recordings obtained during the rest periods showing a tendency towards an increase. A decrease in the EMG mean power frequency (MPF) indicated accumulated fatigue. The LDF for the rest periods that followed upon continuous contractions up to the same MVC levels showed a tendency towards an increase but variability was large. With further development, these techniques may be useful in the evaluation of insufficiency of the peripheral circulation.

Adult↗