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Biomedical subjects

C Ma

Publications and source records attributed to C Ma.

At least 19 recordsLinked to original sources
PubMed2006

Optimization of medium and cultivation conditions for alkaline protease production by the marine yeast Aureobasidium pullulans.

A yeast strain, Aureobasidium pullulans, which could produce the high yield of protease was isolated from sediment of saltern in Qingdao, China. Maximum production of enzyme (623.1 U/mg protein; 7.2 U/ml) was obtained in a medium containing 2.5 g soluble starch and 2.0 g NaNO(3), 100ml seawater, initial pH 6.0, after fermentation at 24.5 degrees C for 30 h. The protease had the highest activity at pH 9.0 and 45 degrees C.

Ascomycota↗
PubMed2006

Alcohol-inducible gene expression in transgenic Populus.

We tested the efficiency and optimized the conditions for controlled alcohol-inducible transgene expression in Populus using gus as a reporter gene. Specificity of induction, efficiency in different organs, effect of three chemical inducers, and induction methods were tested using up to 10 independent transgenic events generated in two different Populus genotypes. The optimal inducer concentration and the duration of induction period were determined in dose-response and in time-course experiments. Under in vitro conditions, beta-glucuronidase (GUS) induction was efficient both in the aerial parts and in the roots of regenerated plantlets. Among the chemical inducers tested, ethanol was the most effective activator with no apparent phytotoxicity when concentrations were at or below 2%. After 5 days of treatment, fluorometrically-determined the GUS activity could be detected when inducing with ethanol at concentrations as low as 0.5%. Prolonged induction by ethanol vapors significantly increased the GUS activity in leaves from both the tissue culture plants and greenhouse-grown plants.

Acetaldehyde↗
PubMed2005

Inflammatory mediators enhance the excitability of chronically compressed dorsal root ganglion neurons.

A laterally herniated disk, spinal stenosis, and various degenerative or traumatic diseases of the spine can sometimes lead to a chronic compression and inflammation of the dorsal root ganglion and chronic abnormal sensations including pain. After a chronic compression of the dorsal root ganglion (CCD) in rats, the somata in the dorsal root ganglion (DRG) become hyperexcitable, and some exhibit ectopic, spontaneous activity (SA). Inflammatory mediators have a potential role in modulating the excitability of DRG neurons and therefore may contribute to the neuronal hyperexcitability after CCD. In this study, an inflammatory soup (IS) consisting of bradykinin, serotonin, prostaglandin E2, and histamine (each 10(-6) M) was applied topically to the DRG. The responses of DRG neurons were electrophysiologically recorded extracellularly from teased dorsal root fibers or intracellularly from the somata in the intact DRG or from dissociated neurons within 30 h of culture. In all three preparations, IS remarkably increased the discharge rates of SA CCD neurons and evoked discharges in more silent-CCD than control neurons. IS slightly depolarized the resting membrane potential and decreased the current and voltage thresholds of action potential in both intact and dissociated neurons, although the magnitude of depolarization or decrease in action potential threshold was not significantly different between CCD and control. IS-evoked responses were found in a proportion of neurons in each size category including those with and without nociceptive properties. Inflammatory mediators, by increasing the excitability of DRG somata, may contribute to CCD-induced neuronal hyperexcitability and to hyperalgesia and tactile allodynia.

Action Potentials↗
PubMed2005

A method for repositioning of stereotactic brain patients with the aid of real-time CT image guidance.

This note presents a method that recalculates the coordinates of the isocentre for patients undergoing stereotactic radiotherapy to the brain with a relocatable head frame based on a pre-treatment CT scan. The method was evaluated by comparing initial stereotactic coordinates of the isocentre with the recalculated coordinates for eight single-fraction patients. These patients had the Brown-Roberts-Wells (BRW) frame fixed to the outer table of the skull, and therefore the coordinates of any anatomical point should be identical between the initial scan and the pre-treatment scan. The differences between the two sets of coordinates were attributed to errors in the method. The results showed that the systematic errors in the recalculated coordinates were less than 0.05 mm, and they were not statistically significant. The random errors (one standard deviation) were from 0.35 mm (lateral) to 0.58 mm (vertical). The average value of the combined 3D difference was 0.75 mm.

Algorithms↗
PubMed2005

Biosynthesis and purification of a hydrophobic peptide from transmembrane domains of G-protein-coupled CB2 receptor.

A major challenge for the structural study of the seven-transmembrane G-protein-coupled receptors is to obtain a sufficient amount of purified protein at the milligram level, which is required for either nuclear magnetic resonance (NMR) spectroscopy or X-ray crystallography. In order to develop a high-yield and cost-effective method, and also to obtain preliminary structural information for the computer modeling of the three-dimensional receptor structural model, a highly hydrophobic peptide from human cannabinoid subtype 2 receptor CB2(65-101), was chosen to develop high-yield membrane protein expression and purification methods. The peptide included the second transmembrane helix with the associated loop regions of the CB2 receptor. It was over-expressed in Escherichia coli, with a modified TrpDelta LE1413 (TrpLE) leading fusion sequence and a nine-histidine tag, and was then separated and purified from the tag in a preparative scale. An experimental protocol for the chemical cleavage of membrane protein fragment was developed using cyanogen bromide to remove the TrpLE tag from the hydrophobic fusion protein. In addition, protein uniformly labeled with isotopic 15N was obtained by expression in 15N-enriched minimum media. The developed and optimized preparation scheme of expression, cleavage, and purification provided a sufficient amount of peptide for NMR structure analysis and other biophysical studies that will be reported elsewhere. The process of fusion protein cleavage following purification was monitored by high-performance liquid chromatography (HPLC) and mass spectrometry (MS), and the final sample was validated by MS and circular dichroism experiments.

Base Sequence↗
PubMed2004

Stereotactic IMRT for prostate cancer: dosimetric impact of multileaf collimator leaf width in the treatment of prostate cancer with IMRT.

The focus of this work is the dosimetric impact of multileaf collimator (MLC) leaf width on the treatment of prostate cancer with intensity-modulated radiation therapy (IMRT). Ten patients with prostate cancer were planned for IMRT delivery using two different MLC leaf widths--4mm and 10mm--representing the Radionics micro-multileaf collimator (mMLC) and Siemens MLC, respectively. Treatment planning was performed on the XKnifeRT2 treatment-planning system (Radionics, Burlington, MA). All beams and optimization parameters were identical for the mMLC and MLC plans. All the plans were normalized to ensure that 95% of the planning target volume (PTV) received 100% of the prescribed dose. The differences in dose distribution between the two different plans were assessed by dose-volume histogram (DVH) analysis of the target and critical organs. We specifically compared the volume of rectum receiving 40 Gy (V40), 50 Gy (V50), 60 Gy (V60), the dose received by 17% and 35% of rectum (D17 and D35), and the maximum dose to 1 cm3 of the rectum for a prescription dose of 74 Gy. For the urinary bladder, the dose received by 25% of bladder (D25), V40, and the maximum dose to 1 cm3 of the organ were recorded. For PTV we compared the maximum dose to the "hottest" 1 cm3 (Dmax1 cm3) and the dose to 99% of the PTV (D99). The dose inhomogeneity in the target, defined as the ratio of the difference in Dmax1 cm3 and D99 to the prescribed dose, was also compared between the two plans. In all cases studied, significant reductions in the volume of rectum receiving doses less than 65 Gy were seen using the mMLC. The average decrease in the volume of the rectum receiving 40 Gy, 50 Gy, and 60 Gy using the mMLC plans was 40.2%, 33.4%, and 17.7%, respectively, with p < 0.0001 for V40 and V50 and p < 0.012 for V60. The mean dose reductions for D17 and D35 for the rectum using the mMLC were 20.4% (p < 0.0001) and 18.3% (p < 0.0002), respectively. There were consistent reductions in all dose indices studied for the bladder. The target dose inhomogeneity was improved in the mMLC plans by an average of 29%. In the high-dose range, there was no significant difference in the dose deposited in the "hottest" 1 cm3 of the rectum between the two plans for all cases (p > 0.78). In conclusion, the use of the mMLC for IMRT of the prostate resulted in significant improvement in the DVH parameters of the prostate and critical organs, which may improve the therapeutic ratio.

Equipment Design↗
PubMed2004

Association between apolipoprotein CI HpaI polymorphism and sporadic Alzheimer's disease in Chinese.

OBJECTIVE: To investigate into the relationship of apolipoprotein CI (ApoCI) polymorphism with sporadic Alzheimer's disease (AD) in Chinese. SUBJECTS AND METHODS: A total of 257 AD patients and 242 age-matched elderly individuals were genotyped for the ApoCI HpaI and apolipoprotein E (ApoE) HhaI polymorphisms. RESULTS: The ApoCI A allele was associated with AD of moderate to severe dementia when patients were divided into two subgroups according to Clinical Dementia Rating scale, and the AA genotype was strongly associated with moderate to severe AD in ApoE epsilon4 allele carriers [odds ratio (OR) = 8.19, 95% confidential interval: 1.28-52.30, after adjusting for age and gender by logistic regression analysis], although in total no significant differences of allele or genotype frequency between patients and controls were found. CONCLUSION: The present study partially confirmed the previous findings, suggesting that the ApoCI A allele might contribute to the susceptibility to moderate to severe sporadic AD in Chinese.

Aged↗
PubMed2004

Collagen type I prevents glyoxal-induced apoptosis in osteoblastic cells cultured on titanium alloy.

Advanced glycation end products (AGEs) irreversibly cross-link proteins with sugars and accumulate at a higher age and in diabetes, processes which can interfere with the integration of implants into the tissue. Glyoxal is a highly reactive glycating agent involved in the formation of AGEs and is known to induce apoptosis, as revealed by the upregulation of caspase-3 and fractin (caspase-3 being a key enzyme activated during the late stage of apoptosis and fractin being a caspase-cleaved actin fragment). In this study, we investigated the influence of collagen type I coating on the cytotoxic effect of glyoxal on rat calvarial osteoblastic cells and on human osteosarcoma cells (Saos-2) grown on titanium alloy, Ti6Al4V. Activation of caspase-3 and fractin was measured by counting immunohistochemically stained cells and by flow cytometry with propidium iodide (detection of the apoptosis indicating a sub-G1 peak). Our results showed an increased number of apoptotic osteoblasts after incubation with glyoxal on Ti6Al4V discs. However, the number of apoptotic cells on collagen-coated titanium was significantly smaller than on uncoated titanium after the same treatment. The present findings demonstrate that osteoblasts treated with glyoxal undergo apoptosis, whereas collagen type I coating of titanium alloys (used for implants) has an antiapoptotic function.

Alloys↗
PubMed2003

p16INK4a expression in actinic keratosis and Bowen's disease.

BACKGROUND: Progression of cutaneous squamous neoplasms from actinic keratosis (AK) to Bowen's disease (BD; squamous cell carcinoma in situ) has important implications for clinical management and treatment, thus requiring accurate diagnosis. p16INK4a is a cell cycle regulatory tumour suppressor protein that negatively regulates D-type cyclins in the G1 cell cycle phase via intimate interplay with the retinoblastoma gene. Expression of a paraffin-reactive p16INK4a marker has recently been shown to increase in cervical squamous neoplasms as lesions progress from low-grade dysplasia to squamous cell carcinoma in situ. p16INK4a expression in the progression of squamous cutaneous neoplasia, however, has not been evaluated. OBJECTIVES: To evaluate p16INK4a expression in the progression of squamous cutaneous neoplasia. METHODS: Biopsies of 203 squamous cutaneous neoplasms with unequivocal features of AK (n = 87) and BD (n = 116) as well as a benign squamous control group (verruca vulgaris: n = 10; seborrhoeic keratosis: n = 11; scar tissue: n = 8) obtained between January and December 2001 at Henry Ford Hospital (Detroit, MI, U.S.A.) were immunostained for p16INK4a (Dako; clone E6H4; dilution 1 : 50) using large core (1.5 mm) tissue microarray analysis. Nuclear/cytoplasmic immunoreactivity in > 10% of neoplastic cells was considered positive. RESULTS: Of 203 cases, 166 (81.8%) were interpretable (AK 59; BD 107). Mean patient age was 71.0 years (range 33-93); 57% were male. Sites of involvement were: head and extremities 75.9%, trunk/buttocks 21.7%, genital region 2.4%. p16INK4a immunostaining was positive in 90 of 107 (84.1%) BD cases, four of 59 (6.8%) AK cases and none of 29 benign squamous controls. The sensitivity and specificity of p16INK4a for a diagnosis of BD (vs. benign squamous controls/AK) was 84.1% and 95.5%, respectively (P < 0.0001, Fisher's exact test, two-sided). CONCLUSIONS: p16INK4a is a sensitive and specific marker for distinguishing BD from AK/benign squamous cutaneous lesions and may be helpful as an adjunct to histomorphology in the diagnosis and appropriate clinical management of these lesions.

Adult↗
PubMed2002

Variation of nanomechanical properties of bone by gene mutation in the zebrafish.

Significant variations of nanomechanical properties and fracture morphology between gene-mutated liliput(dtc232) (lil/lil) zebrafish skeletal bone and wild-type bone have been observed. Nanoindentation measurement disclosed that lil/lil bone has 36% lower nanohardness and 32% lower elastic modulus. The standard deviations of hardness and elastic modulus of lil/lil bone were both much higher than those of wild-type bone. SEM morphology of fracture surfaces further revealed that in bones after gene mutation, formative microcracks make the performance reduction and the increasing of brittleness. What is more, the plywood-like structure of the normal bone does not exist in the lil/lil bone.

Animals↗
PubMed2002

Pattern recognition proteins in Manduca sexta plasma.

Recognition of nonself is the first step in mounting immune responses. In the innate immune systems of both vertebrates and arthropods, such recognition, termed pattern recognition, is mediated by a group of proteins, known as pattern recognition proteins or receptors. Different pattern recognition proteins recognize and bind to molecules (molecular patterns) present on the surface of microorganisms but absent from animals. These molecular patterns include microbial cell wall components such as bacterial lipopolysaccharide, lipoteichoic acid and peptidoglycan, and fungal beta-1,3-glucans. Binding of pattern recognition proteins to these molecular patterns triggers responses such as phagocytosis, nodule formation, encapsulation, activation of proteinase cascades, and synthesis of antimicrobial peptides. In this article, we describe four classes of pattern recognition proteins, hemolin, peptidoglycan recognition protein, beta-1,3-glucan recognition proteins, and immulectins (C-type lectins) involved in immune responses of the tobacco hornworm, Manduca sexta.

Amino Acid Sequence↗
PubMed2002

Effects of GnRH analogues, 'add-back' steroid therapy, antiestrogen and antiprogestins on leiomyoma and myometrial smooth muscle cell growth and transforming growth factor-beta expression.

The objective of this study was to elucidate the biological significance of GnRH and antiprogestins and antiestrogen in leiomyoma and their interactions with ovarian steroid 'add-back' therapy. Leiomyoma and myometrial smooth muscle cells (LSMC and MSMC) were isolated and exposed to GnRH agonist (leuprolide acetate, LA), 17beta-estradiol (E2), medroxyprogesterone acetate (MPA), GnRH antagonist (Antide), estrogen antagonist, ICI182780 (Fulvestrant) and progesterone antagonists RU486 (Mifepristone) and ZK98299 (Onapristone) and combinations thereof. The rate of DNA synthesis, cell proliferation and transforming growth factor-beta (TGF-beta) expression were then determined. In both cell types, we found that in a dose-dependent manner, LA inhibited, whereas E2, MPA and the combination of E2 + MPA stimulated, the rate of DNA synthesis in these cells. Antide reversed the inhibitory effect of LA, while LA partly inhibited the stimulatory effect of the steroids. In addition, RU486, ICI182780 and ZK98299 at 0.1 micro mol/l or higher doses inhibited the rate of DNA synthesis and partly reversed the effects of E2 and/or MPA. We also found that LSMC expressed elevated levels of TGF-beta1 compared with MSMC. In both cell types, the effects of LA, E2, MPA, RU, ZK and ICI and combinations thereof on TGF-beta1 production were reflective of their effects on DNA synthesis. In line with this, TGF-beta1 was found to stimulate DNA synthesis and the E2-, TGF-beta1- or E2 + TGF-beta1-induced DNA synthesis was found to be inhibited by TGF-beta1 neutralizing antibodies and/or LA. In conclusion, the results provide further evidence that GnRH agonist- and RU486-induced leiomyoma regression is mediated in part through an interactive mechanism that results in altered cell growth and suppression of TGF-beta production.

Estradiol↗
PubMed2001

Bryostatin-1 specifically inhibits in vitro IgE synthesis.

Bryostatin-1, a macrocyclic lactone, is an antineoplastic agent that potently activates protein kinase C. Bryostatin-1 (Bryo) had an immunomodulatory effect on murine B cells in that it specifically inhibited IgE production. IgE levels were inhibited in a B cell dose-response curve, whereas IgM and IgG1 were induced by Bryo treatment. Taken together, ELISPOT and surface Ig staining data suggested that Bryo inhibition occurred at the level of class switching. RT-PCR and real time PCR data showed that this inhibition was achieved at an early step in switch recombination, namely, the appearance of Iepsilon germline transcripts. Although Bryo caused a delay in the proliferative response of IL-4/CD40 ligand trimer-stimulated B cells, CFSE studies revealed that the Bryo-mediated inhibition of class switching to IgE occurred independently of the number of division cycles. Notably, Bryo showed the same specific IgE inhibition in human B cells. This study provides evidence for a unique mechanism regulating IgE production possibly downstream of PKC by specifically modulating Iepsilon germline transcription.

Animals↗
PubMed2001

Efficient asymmetric synthesis of biologically important tryptophan analogues via a palladium-mediated heteroannulation reaction.

A novel and concise synthesis of optically active tryptophan derivatives was developed via a palladium-catalyzed heteroannulation reaction of substituted o-iodoanilines with an internal alkyne. The required internal alkyne 14a or 25 was prepared in greater than 96% de via alkylation of the Schöllkopf chiral auxiliary 19 employing diphenyl phosphate as the leaving group. The Schöllkopf chiral auxiliary was chosen here for the preparation of L-tryptophans would be available from D-valine while the D-isomers required for natural product total synthesis would originate from the inexpensive L-valine (300-g scale). Applications of the palladium-catalyzed heteroannulation reaction were extended to the first asymmetric synthesis of L-isotryptophan 38 and L-benz[f]tryptophan 39. More importantly, the optically pure 6-methoxy-D-tryptophan 62 was prepared by this protocol on a large scale (>300 g). This should permit entry into many ring-A oxygenated indole alkaloids when coupled with the asymmetric Pictet-Spengler reaction. In addition, an improved total synthesis of tryprostatin A (9a) was accomplished in 43% overall yield employing this palladium-mediated process.

Alkylation↗
PubMed2001

Matrix immobilization enhances the tissue repair activity of growth factor gene therapy vectors.

Although growth factor proteins display potent tissue repair activities, difficulty in sustaining localized therapeutic concentrations limits their therapeutic activity. We reasoned that enhanced histogenesis might be achieved by combining growth factor genes with biocompatible matrices capable of immobilizing vectors at delivery sites. When delivered to subcutaneously implanted sponges, a platelet-derived growth factor B-encoding adenovirus (AdPDGF-B) formulated in a collagen matrix enhanced granulation tissue deposition 3- to 4-fold (p < or = 0.0002), whereas vectors encoding fibroblast growth factor 2 or vascular endothelial growth factor promoted primarily angiogenic responses. By day 8 posttreatment of ischemic excisional wounds, collagen-formulated AdPDGF-B enhanced granulation tissue and epithelial areas up to 13- and 6-fold (p < 0.009), respectively, and wound closure up to 2-fold (p < 0.05). At longer times, complete healing without excessive scar formation was achieved. Collagen matrices were shown to retain both vector and transgene products within delivery sites, enabling the transduction and stimulation of infiltrating repair cells. Quantitative PCR and RT-PCR demonstrated both vector DNA and transgene mRNA within wound beds as late as 28 days posttreatment. By contrast, aqueous formulations allowed vector seepage from application sites, leading to PDGF-induced hyperplasia in surrounding tissues but not wound beds. Finally, repeated applications of PDGF-BB protein were required for neotissue induction approaching equivalence to a single application of collagen-immobilized AdPDGF-B, confirming the utility of this gene transfer approach. Overall, these studies demonstrate that immobilizing matrices enable the controlled delivery and activity of tissue promoting genes for the effective regeneration of injured tissues.

Adenoviridae↗
PubMed2001

[The antagonistic effects of adrenomedullin on biological events governed by transforming growth factor beta in HK-2 cell line].

OBJECTIVE: To investigate the influence of adrenomedullin (AM) on the biological events governed by transforming growth factorbeta (TGF-beta) in human tubular epithelial cell line (HK-2). METHODS: Cell proliferation was determined by (3)H-TdR incorporation; ELISA method was used to detect the level of secreted fibronectin (FN); total collagen synthesis and secretion were reflected by (3)H-proline incorporation and the radioactivity of (3)H-hydroproline in the culture medium; the expression of FN mRNA, collagen IV mRNA and TIMP-1mRNA was determined by RT-PCR; plasma AM was measured by radioimmunoassay. RESULTS: (1) AM had no effect on cell growth inhibition of TGF-beta(1) (P > 0.05); (2) AM dose-dependently inhibited collagen synthesis and secretion stimulated by TGF-beta(1). As compared with those in TGF-beta group, collagen synthesis and secretion in AM (10(-8) mol/L group were inhibited by 8% (P > 0.05) and 30% (P < 0.05), respectively; and the collagen synthesis and secretion in AM (10(-7) mol/L) group were inhibited by 57% (P < 0.05) and 64% (P < 0.01), respectively in AM (10(-7) mol/L) group. Similarly, AM (10(-8) mol/L) inhibited the FN secretion (20 ng/microliter +/- 5 ng/microliter) stimulated by TGF-beta(1) (28 ng/microliter +/- 6 ng/microliter) (P < 0.05). RT-PCR showed that AM significantly down-regulated the expression of collagen IV, FN and TIMP-1 mRNA stimulated by TGF-beta(1). (3) The plasma AM in patients with mild tubulointerstitial lesion was 1. 2 times higher than that in normal controls. the plasma AM in patients with severe tubulointerstitial lesion was 2.2 times higher than that in normal controls. The plasma AM in patients with severe tubulointerstitial lesion was 50% higher than that in patients with mild tubulointerstitial lesion (P < 0.01). CONCLUSIONS: AM antagonizes the biological action of TGF-beta(1) on extracellular matrix accumulation; plasma AM increases in glomerulonephritis patients and correlates with the degree of tubulointerstitial lesion.

Adolescent↗