Biomedical subjects
Publications and source records attributed to M Zhang.
The studies on the chemical constituents of soft coral Lemnalia bournei led to the isolation of 2-deoxy-12-oxo-lemnacarnol, 22,23-dihydrobrassicasterol, gorgosterol and batyl alcohol. Their structures were deduced on the comprehensive spectral analysis. The four compounds were first obtained from the soft coral.
In order to increase yield, the cultivation of Pinellia ternata in artificial soil was studied, and its growth habits was investigated. At same time, the measures of dominating soil thickness, using nutrient solution as fertillizer and complete illumination were taken. The research results can supply a reference for the industrial production of P. ternata.
Three active components were isolated from treated dry-fruits of Brucea javanica (L.) Merr by chromatographic methods, and they were identified as Brusatol (I), Bruceine D (II), Bruceosidae A (III) by means of UV, IR, 1H-NMR, 13C-NMR spectroscopic analysis methods.
PURPOSE: To investigate the condition and change of corneal blindness (CB) in the past 30 years. METHODS: 1,001 blinding patients of corneal disease were clinically analysed from 1960 to 1989, including etiology, sex, age, occupation, difference between the urban and rural areas etc. RESULTS: The male predominated. Infection stood the first cause of blinding corneal diseases, followed by trauma, malnutrition and the others. HSV-1 keratitis was the most frequent infection in 1980s. The highest incidence of CB was 20-40 year-old. The number of CB caused by occupational trauma was more than that by ordinary trauma in 1960s, but from 1970s, the latter was more than the former. The number of CB in rural area was more than that in the urban in 1960s, but from 1970s, there was no significant difference between the two areas. The percentage of bilateral CB was gradually decreased. CONCLUSION: We should try to find more effective strategies to prevent and treat CB caused by HSV-1 keratitis, pay special attention to preschool blindness caused by perforation injuries and avoid infection after corneal injuries of foreign bodies.
The absorption spectra of VK3 in aqueous solution were studied by pulse radiolysis and laser photolysis technique, and the formation mechanism of intermediates of transient species was suggested, which gave the examples for studying the mechanism of blood-clotting of VK3 and provided the theoretic evidence for further understanding the reasons of VK3 as a radiosensitizer.
In this paper, we have studied all kinds of static absorption spectra and transient absorption spectra of podophyllotoxin and its derivatives. We have located the site of absorption spectra and their forming mechanism with spectrofluorometry, Ultraviolet, pulse radiolysis and laser photolysis, and suggested the connection of their structrue with their anti-tumour and toxicity.
The fluorescence-disappearing phenomenon (FDP) was used due to the nonlinear interaction between the laser and the matter, a universal phenomenon. It was often neglected during the research of surface-harmonic generation (SHG). Many experiments showed that there was a interior relation between FDP and SHG. In this paper, the mechanism of surface-harmonic generation has been discussed in detail, according to the fluorescence-disappear viewpoint and the fluorescence-disappear model (FDM) proposed also. The new mechanism was summarized by following three points: (a) The multiphoton absorption generated visible fluorescence spot, (b) Laser-heating effect and other effects promoted the conversion from spontaneous emission into quasi-stimulated emission, (c) Being accompanied by the fluorescence disappear, the part of laser energy which was initially used to cause fluorescence was now converted into developing the harmonic signal.
UNLABELLED: Inefficient intratumoral penetration of pharmaceuticals is one of the major limiting factors against effective tumor-targeting therapy. This study investigated the effect of the distribution pattern of the binding site in tumors on the penetration of target material. METHODS: In the first experiment, radiolabeled biotinylated monoclonal antibody, MLS128, was injected intraperitoneally or intravenously into nude mice bearing intraperitoneal human colon cancer xenografts. In the second experiment, radiolabeled streptavidin was injected intraperitoneally in the tumor-bearing mice after the pretargeting with the unlabeled biotinylated antibody. Intratumoral distribution of radioactivity was examined with quantitative autoradiography. RESULTS: There was no difference in the biodistribution of biotinylated antibody between intraperitoneal and intravenous administrations, but autoradiography showed a higher uptake in the margin and a lower uptake in the center of radioactivity in tumor nodules with intraperitoneal injection and a more uniform intratumoral radioactivity distribution with intravenous injection. In the two-step method, radioactivity in a low dose of streptavidin with intraperitoneal pretargeting primarily localized at the tumor margin. By increasing the dose, streptavidin penetrated more deeply. In tumors with intravenous pretargeting, a more uniform intratumoral distribution of streptavidin was obtained. The biodistribution of radiolabeled streptavidin was the same between different pretargeting routes. CONCLUSION: The better intratumoral penetration of radiolabeled streptavidin after intravenous pretargeting than intraperitoneal pretargeting with biotinylated antibody may be the result of different intratumoral distribution of the binding site for the radiolabel.
Photocrosslinking has identified the joiner between domains 2 and 3 [J(23)] as folding near domain 5 (D5), a highly conserved helical substructure of group II introns required for both splicing reactions. D5 RNAs labeled with the photocrosslinker 4-thiouridine (4sU) reacted with highly conserved nucleotides G588 and A589 in J(23) of various intron acceptor transcripts. These conjugates retained some ribozyme function with the lower helix of D5 crosslinked to J(23), so they represent active complexes. One partner of the gamma x gamma' tertiary interaction (A587 x U887) is also in J(23); even though gamma x gamma' is involved in step 2 of the splicing reaction, D5 has not previously been found to approach gamma x gamma'. Similar crosslinking patterns between D5 and J(23) were detected both before and after step 1 of the reaction, indicating that the lower helix of D5 is positioned similarly in both conformations of the active center. Our results suggest that the purine-rich J(23) strand is antiparallel to the D5 strand containing U32 and U33. Possibly, the interaction with J(23) helps position D5 correctly in the ribozyme active site; alternatively, J(23) itself might participate in the catalytic center.
The present study was designed to further investigate the nature of feeding induced by opioid stimulation of the nucleus accumbens through an examination of the effects of intra-accumbens (ACB) opioids on macronutrient selection. In 3-hr tests of free-feeding (satiated) rats, intra-ACB administration of the mu receptor agonist D-Ala2,N,Me-Phe4, Gly-ol5-enkephalin (DAMGO; 0, 0.025, 0.25 and 2.5 micrograms bilaterally) markedly enhanced the intake of fat or carbohydrate when the diets were presented individually (although the effect on fat intake was much greater in magnitude). Intra-ACB injections of DAMGO, however, produced potent preferential stimulatory effects on fat ingestion with no effect on carbohydrate ingestion when both fat and carbohydrate diets were present simultaneously. Moreover, this selective stimulation of fat intake was independent of base-line diet preference and could be blocked by systemic injection of naltrexone (5 mg/kg). We also examined the effect of 24-hr food deprivation on the pattern of macronutrient intake in rats with access to both carbohydrate and fat. In contrast to the DAMGO-induced selective enhancement of fat intake, food deprivation significantly increased the intake of both diets to the same extent; however, in this case, only the stimulated fat intake was blocked by systemic naltrexone. Intra-ACB administration of DAMGO in hungry rats produced an effect similar to that observed in free-feeding rats; preference was strongly shifted to fat intake. Similarly, the opioid antagonist naltrexone (20 micrograms) infused directly into ACB preferentially decreased fat intake in hungry rats. These findings suggest that endogenous opioids within the ventral striatum may participate in the mechanisms governing preferences for highly palatable foods, especially those rich in fat.
BACKGROUND: Bone resorption was elevated in ovariectomized rats during a 14-d orbital spaceflight over and above that caused by gonadal hormone deficiency. Locally produced cytokines are believed to have an important role in normal as well as abnormal bone resorption. METHODS: The purpose of the present study in the same rats was to determine whether spaceflight results in altered expression of cytokines in cancellous bone. The mRNA levels for selected cytokines were determined in proximal tibial metaphysis using ribonuclease (RNase) protection assays. RESULTS: The message for interleukin 1 receptor antagonist, interleukins 1alpha, 10, and 12, macrophage migration inhibitory factor, and tumor necrosis factor-alpha was below the limit of detection for all groups. Interleukin 6 and transforming growth factor-beta2 were expressed in bone but the mRNA levels for these cytokines were not altered by either ovariectomy or spaceflight. There was a tendency for interleukin-1beta message to be increased following ovariectomy (OVX) and this tendency achieved statistical significance following spaceflight. Finally, spaceflight resulted in an increase in the message level for interferon gamma in OVX rats. In summary, spaceflight results in increases in mRNA levels of two cytokines in OVX rats which have been shown to increase bone resorption.
P-glycoprotein (Pgp) is a membrane protein that transports chemotherapeutic drugs, causing multidrug resistance in human cancer cells. Pgp is a member of the ATP-binding cassette superfamily and functions as a transport ATPase. It has been suggested that the conformation of Pgp changes in the catalytic cycle. In this study, we tested this hypothesis by using limited proteolysis as a tool to detect different conformational states trapped by binding of nucleotide ligands and inhibitors. Pgp has high basal ATPase activity; that is, ATP hydrolysis by Pgp is not rigidly associated with drug transport. This activity provides a convenient method for studying the conformational change of Pgp induced by nucleotide ligands, in the absence of drug substrates which may generate complications due to their own binding. Inside-out membrane vesicles containing human Pgp were isolated from multidrug-resistant SKOV/VLB cells and treated with trypsin in the absence or presence of MgATP, Mg-adenosine 5'-[beta,gamma-imido]triphosphate (Mg-p[NH]ppA) and MgADP. Changes in the proteolysis profile of Pgp owing to binding of nucleotides were used to indicate the conformational changes in Pgp. We found that generation of tryptic fragments, including the loop linking transmembrane (TM) regions TM8 and TM9 of Pgp, were stimulated by the binding of Mg-p[NH]ppA, MgATP and MgADP, indicating that the Pgp conformation was changed by the binding of these nucleotides. The effects of nucleotides on Pgp conformation are directly associated with the binding and/or hydrolysis of these ligands. Four conformational states of Pgp were stabilized under different conditions with various ligands and inhibitors. We propose that cycling through these four states couples the Pgp-mediated MgATP hydrolysis to drug transport.
Human peripheral blood polymorphonuclear leukocytes were preincubated with N-acetylcystathionine and N-acetyl-S-(3-oxo-3-carboxy-n-propyl)cysteine (NAc-OCPC) found in the urine of a patient with cystathioninuria. NAc-OCPC significantly enhanced the N-formyl-methionyl-leucyl-phenylalanine-induced superoxide generation, whereas N-acetylcystathionine did not enhance the superoxide generation. When the cells were incubated with NAc-OCPC, the tyrosyl phosphorylation of 45 kDa protein of the cell was markedly increased with time. The phosphorylation process was dependent on the concentration of NAc-OCPC. Both the superoxide generation and the tyrosyl phosphorylation of 45 kDa protein increased by NAc-OCPC were inhibited by genistein and herbimycin A, the inhibitors of protein tyrosine kinase, but were rather enhanced by staurosporine, an inhibitor of protein kinase C.
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elafin is a unique elastase inhibitor. It is differentially expressed at the transcriptional level in human normal mammary epithelial cells and carcinomas. The elafin gene is induced by PMA in 21MT2 breast tumor cells. By deletion analysis and mutagenesis, we have identified the Ap1 site in the promoter as the cis element mediating transcriptional activation of elafin in 70N normal breast cells and its induction by phorbol 12-myristate 13-acetate (PMA) in 21MT2 breast tumors. PMA treatment induces AP1 factor expression, which binds to the Ap1 site of the elafin promoter. Mutation of this Ap1 abolishes the capability of induction by PMA. Furthermore, our data provide a basis for therapeutic manipulation of proteinase inhibitors such as elafin.
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1. To investigate synaptic mechanisms mediating chemosensory signalling in the carotid body, we developed co-cultures of chemoreceptor type 1 cell clusters and dissociated petrosal neurones (PNs) from 7- to 14-day-old rat pups and tested for functional connectivity in CO2-HCO3(-)-or Hepes-buffered medium at approximately 35 degrees C. 2. When cultured without type 1 cells, PNs were almost always quiescent (n = 104) and unresponsive to hypoxia (Po2 = 5-25 mmHg) during perforated patch, whole-cell recordings of membrane potential or voltage-activated currents; in contrast, many PNs (77 out of 170) that were juxtaposed to type 1 cell clusters in co-culture displayed spontaneous activity, comprising spikes and subthreshold potentials (SSPs) that resembled synaptic potentials. 3. Additional tests suggested that de novo chemical synapses developed between PNs and type 1 cell clusters in vitro. For example: (i) the spontaneous activity was reversibly suppressed by substituting low calcium-high magnesium in the bath; (ii) SSPs had variable amplitudes and persisted following action potential blockade with TTX (1 microM); (iii) the interval distribution between successive spontaneous events appeared random; and (iv) the frequency of spontaneous potentials was diminished (reversibly) by the nicotinic antagonist hexamethonium (100 microM), suggesting contributions from the spontaneous release of ACh. 4. Many complexes of 'juxtaposed' PNs and type 1 clusters were physiologically functional, since exposure to hypoxia caused a reversible depolarization and/or increased spike discharge in approximately 30% of such neurones (n = 140). The hypoxia-induced spike discharge persisted in the presence of the dopamine D2 receptor blocker spiperone (10-50 microM; n = 5); however, this discharge was reversibly inhibited by 100-200 microM hexamethonium, suggesting that it was mediated, at least in part, by ACh acting through nicotinic receptors. 5. The hypoxia-induced spike discharge and frequency of spontaneous potentials in co-cultured PNs were reversibly suppressed when the buffer was switched from CO2-HCO3- to Hepes (10 mM) at pH 7.4; further, 'functional' PNs that displayed spontaneous activity and/or hypoxia-induced responses in co-culture were encountered more frequently in CO2-HCO3- (> or = 40%) than in Hepes (< or = 26%) buffer. 6. We conclude that functional chemical synapses can develop de novo in cultures of carotid body type 1 cells and PNs and that ACh is probably an important excitatory neurotransmitter secreted from type 1 cells during hypoxic chemotransduction in the rat carotid body.
Differences in gene expression between benign and malignant human prostate specimens were investigated using the differential display technique. RNA samples from paired benign and malignant areas microdissected from opposite sides of the same prostate gland were used for reverse transcription PCR. A 477-bp band was identified that was consistently present in benign prostate but absent or diminished in intensity in malignant tissue. This band was cloned, and the sequence demonstrated 99% identity with a region in the fourth exon of the human neurofilament heavy chain gene (NF-H). Northern blotting with a cDNA probe derived from this band confirmed the presence of a similarly sized message of approximately 3.9 kb in both prostate and brain, and reverse transcription PCR using primers specific to an upstream region of exon 4 confirmed NF-H-like mRNA expression in benign prostatic tissue. Immunostaining with a monoclonal antibody to NF-H showed a positive reaction in benign prostatic epithelial cells but complete absence of staining in prostatic cancer cells. These data demonstrate the presence of a NF-H-like gene product in normal prostatic epithelial cells that is down-regulated or absent in prostatic carcinomas.