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Biomedical subjects

C Mao

Publications and source records attributed to C Mao.

At least 109 records · Page 6Linked to original sources
PubMed1997

Crystal structure of a thermostable Bacillus DNA polymerase I large fragment at 2.1 A resolution.

BACKGROUND: The study of DNA polymerases in the Pol l family is central to the understanding of DNA replication and repair. DNA polymerases are used in many molecular biology techniques, including PCR, which require a thermostable polymerase. In order to learn about Pol I function and the basis of thermostability, we undertook structural studies of a new thermostable DNA polymerase. RESULTS: A DNA polymerase large, Klenow-like, fragment from a recently identified thermostable strain of Bacillus stearothermophilus (BF) was cloned, sequenced, overexpressed and characterized. Its crystal structure was determined to 2.1 A resolution by the method of multiple isomorphous replacement. CONCLUSIONS: This structure represents the highest resolution view of a Pol I enzyme obtained to date. Comparison of the three Pol I structures reveals no compelling evidence for many of the specific interactions that have been proposed to induce thermostability, but suggests that thermostability arises from innumerable small changes distributed throughout the protein structure. The polymerase domain is highly conserved in all three proteins. The N-terminal domains are highly divergent in sequence, but retain a common fold. When present, the 3'-5' proofreading exonuclease activity is associated with this domain. Its absence is associated with changes in catalytic residues that coordinate the divalent ions required for activity and in loops connecting homologous secondary structural elements. In BF, these changes result in a blockage of the DNA-binding cleft.

Amino Acid Sequence↗
PubMed1997

[Changes in airway space following mandibular setback using sagittal split ramus osteotomy with rigid internal fixation].

The changes in airway space following mandibular setback using sagittal split ramus osteotomy and rigid internal fixation were studied in 28 Japanese patients with mandibular prognathism. Lateral cephalometric radiographs were taken immediately before and shortly after surgery as well as 5 to 12 months postoperation. The mean setback of mandible was 8.3 mm in the right side, and 8.2 mm in the left side. The mean amount of relapse of pogonion point during the following-up period was 0.52 mm horizontally, and 0.92 mm vertically. A significant decrease in airway space width and area, espacially in the lower part of airway space was found following mandibular setback shortly after surgery. Although there was some increase both in airway space width and area during the following-up period, they did not increase to their original values. This suggests that the narrowing of airway space following mandibular setback using sagittal split osteotomy can be permanent. No significant correlation was found between the amount of mandibular setback and airway space changes, and no significant correlation was found between the amount of airway space changes and relapse of pogonion point during the following-up period.

Adolescent↗
PubMed1997

[Guided tissue regeneration around dental implants in immediate extraction sockets: comparison of resorbable and nonresorbable membranes].

OBJECTIVE: This study was performed to compare the efficacy of guided tissue regeneration (GTR) around dental implants immediately placed into extraction sockets by resorbable or nonresorbable membranes. METHODS: Mandibular P2, P3, and P4 of four adult beagle dogs were extracted bilaterally, and buccal standard defects were created and measured. Eighteen commercially pure titanium Steri-Oss implant fixtures were placed into the fresh extraction sockets. Four untreated implants were as controls, four implants received polytetrafluoroethylene (e-PTFE, Gore-Tex) membranes, five implants received collagen membranes, and five implants received polyglactin 910 mesh. After 14 weeks, clinical measurements were taken and the dogs were sacrificed and all specimens retrieved for histologic and histomophometric evaluation. RESULTS: The average gain in bone height was 2.1 mm for untreated control sites, 3.3 mm for Gore-Tex sites, 3.8 mm for collagen sites, and 1.3 mm for polyglactin 910 sites. CONCLUSION: The results of this study indicated that Gore-Tex and collagen membrane produced good results for GTR around implants. Collagen membrane can be a valid alternative to Gore-Tex membrane to improve bone regeneration around dental implants, while polyglactin 910 mesh seemed not suitable to be used as GTR membrane in immediate implantation for its high infection rate.

Animals↗
PubMed1997

Changes in airway space following mandibular setback using sagittal split osteotomy and rigid internal fixation.

The changes in airway space following mandibular setback using sagittal split osteotomy and rigid internal fixation were studied in 28 Japanese patients with mandibular prognathism. The correlation between the amount of mandibular setback and airway space changes, as well as the correlation between the amount of airway space changes and relapse of pognion point during the following-up period were also studied. Lateral cephalometric radiographs were taken immediately before and shortly after surgery as well as 5 to 12 months postoperation. The cephalometric evaluations of airway space width and area were based on stable craniofacial landmarks. The mean setback of mandible was 8.3 mm in the right side, and 8.2 mm in the left side. The mean amount of relapse of pogonion point during the following-up period was 0.52 mm horizontally, and 0.92 mm vertically. A significant decrease in airway space width and area, especially in the lower part of airway space was found following mandibular setback shortly after surgery. Although there was some increase both in airway space width and area during the following-up period, they did not increase to their original values. This suggests that the narrowing of airway space following mandibular setback using sagittal split osteotomy can be permanent. No significant correlation was found between the amount of mandibular setback and airway space changes. Since the relapse of pogonion point during the following-up period was too small, there is no significant correlation between it and the amount of airway space changes.

Adolescent↗
PubMed1997

Guided tissue regeneration around dental implants in immediate extraction sockets: comparison of resorbable and nonresorbable membranes.

This study was performed to compare the efficacy of guided tissue regeneration (GTR) around dental implants immediately placed into extraction sockets by resorbable of nonresorbable membranes. Mandibular P2, P3, and P4 of four adult beagle dogs were extracted bilaterally, and buccal standard defects were created and measured. Eighteen commercially pure titanium Steri-Oss implant fixtures were placed into the fresh extraction sockets. Four implants were untreated controls, four implants received polytetrafluoroethylene (e-PTFE, Gore-Tex) membranes, five implants received collagen membranes (ParaGuide), and five implants received polyglactin 910 mesh (Vicryl). After 14 weeks, clinical measurements were taken and the dogs were sacrificed and all specimens retrieved for histologic and histomorphometric evaluation. The average gain in bone height was 2.1 mm for untreated control sites, 3.3 mm for Gore-Tex sites, 3.8 mm for collagen sites, and 1.3 mm for polyglactin 910 sites. The greatest gain in bone height and volume was seen for two sites that received Gore-Tex membranes and remained covered for the entire evaluation interval. The results of this study indicate that Gore-Tex and collagen membrane produced good results for GTR around implants immediately placed into extraction sockets. Since collagen membrane does not cause obvious infection and does not need the surgical reentry for membrane removal, it can be a valid alternative to Gore-Tex membrane to improve bone regeneration around dental implants, while polyglactin 910 mesh seems not suitable to be used as GTR membrane in immediate implantation for its high infection rate.

Animals↗
PubMed1997

[The research on analgestic and anti-inflammatory action of different processed products of Achyranthes bidentata].

Analgestic effect of different processed products of Achyranthes bidentata in mice was observed in hot plate and acetic acid induced writhing test. The experiment results showed that water extract of Achyranthes bidentata and its processed products could inhibit the pain. The analgestic effect of its product processed with wine is the most powerful and lasting. The results showed that Achyranthes bidentata could obviously inhibit the ear inflammation of mice which was led by croton fruit oil. The anti-inflammatory effect of its product processed with wine is the most powerful.

Acetic Acid↗
PubMed1997

[A resonance Raman spectrometer with UV-visible continuously tunable excitation lines].

A set of resonance Raman spectrometer with excitation lines continuously tunable in 220-970nm, which is a first set in China, has been assembled. The factors influenced on the signal noise ratio (SNR) of spectra were analyzed in detail. The methods to improve the SNR were suggested and the parameters of the spectrometer were optimized. A satisfied Raman spectra can be obtained.

English Abstract↗
PubMed1996

Photo-cross-linking of rabbit skeletal troponin I deletion mutants with troponin C and its thiol mutants: the inhibitory region enhances binding of troponin I fragments to troponin C.

Contraction of vertebrate striated muscle is regulated by the strong Ca(2+)-dependent interaction between troponin I (TnI) and troponin C (TnC). To critically evaluate this interaction, we generated four recombinant deletion fragments of rabbit fast skeletal TnI: the NH2-terminal fragment (TnI1-94), the NH2 terminus and the inhibitory region (TnI1-120), the inhibitory region and the COOH terminus (TnI96-181), and the COOH-terminal fragment (TnI122-181) containing amino acid residues 1-94, 1-120, 96-181, and 122-181, respectively. Native TnC and seven thiol mutants, containing single cysteine residues in the two globular domains and in the central helix of TnC, e.g., Cys-12, Cys-21, Cys-57, Cys-89, Cys-122, Cys-133, and Cys-158, were labeled with 4-maleimidobenzophenone, and their interaction with the recombinant TnI fragments and the synthetic inhibitory peptide (TnI98-114, residues 98-114) was studied by photo-cross-linking. Extensive cross-linking occurred between various domains of TnC and TnI. The cross-linking patterns (a) showed that both NH2- and COOH-terminal fragments of TnI are accessible to both of the globular domains of TnC, (b) indicated that linkage of the NH2- and COOH-terminal sequences to the inhibitory region of TnI (TnIir) caused marked enhancement of cross-linking with native TnC and all seven thiol mutants, and (c) identified the region in TnC where TnIir binds as that containing residues 98, 133, 158, and 57. Thus, the results suggest that TnI and TnC may adopt flexible and dynamic conformations in which multiple interactions involving various domains of the two polypeptides occur and TnIir acting as a linker facilitates these interactions. The interaction of TnI and its fragments with actin, TnC, and TnT, considered together with the biological activity indicates that residues 96-120 represent a key structural and functional region of TnI. Whereas the NH2-terminal region of TnI stabilizes binding to TnC and TnT, the COOH-terminal region stabilizes TnC and actin binding.

Amino Acid Sequence↗
PubMed1996

Molecular cloning and characterization of SCaMPER, a sphingolipid Ca2+ release-mediating protein from endoplasmic reticulum.

Release of Ca2+ stored in endoplasmic reticulum is a ubiquitous mechanism involved in cellular signal transduction, proliferation, and apoptosis. Recently, sphingolipid metabolites have been recognized as mediators of intracellular Ca2+ release, through their action at a previously undescribed intracellular Ca2+ channel. Here we describe the molecular cloning and characterization of a protein that causes the expression of sphingosyl-phosphocholine-mediated Ca2+ release when its complementary RNA is injected into Xenopus oocytes. SCaMPER (for sphingolipid Ca2+ release-mediating protein of endoplasmic reticulum) is an 181 amino acid protein with two putative membrane-spanning domains. SCaMPER is incorporated into microsomes upon expression in SO cells or after translation in vitro. It mediates Ca2+ release at 4 degrees C as well as 22 degrees C, consistent with having ion channel function. The EC50 for Ca2+ release from Xenopus oocytes is 40 microM, similar to sphingosyl-phosphocholine-mediated Ca2+ release from permeabilized mammalian cells. Because Ca2+ release is not blocked by ryanodine or La3+, the activity described here is distinct from the Ca2+ release activity of the ryanodine receptor and the inositol 1,4,5-trisphosphate receptor. The properties of SCaMPER are identical to those of the sphingolipid-gated Ca2+ channel that we have previously described. These findings suggest that SCaMPER is a sphingolipid-gated Ca2+-permeable channel and support its role as a mediator of this pathway for intracellular Ca2+ signal transduction.

Amino Acid Sequence↗
PubMed1996

Differential phosphorylations of Spi-B and Spi-1 transcription factors.

Spi-1/PU-1 and Spi-B are hematopoietic transcription factors, which, in vitro, display similar affinities for DNA target sequences containing the consensus binding site 5'-GGAA-3'. While the role of Spi-1 in the transcriptional regulation of B cell and myeloid specific genes has been largely demonstrated, the biological function of Spi-B still remains to be elucidated. Since Spi-B and Spi-1 are very divergent in their transactivator domain, these domains might acquire functional specificity in vivo by interacting with different co-factors and/or by undergoing different phosphorylations. First, we observed that casein kinase II phosphorylates Spi-B as well as Spi-1, in vitro. Then, by affinity chromatographies and in vitro kinase assays with fusion proteins between glutathione-S-transferase and the transactivator domain of Spi-B, two kinases were identified on their ability to interact and phosphorylate this domain; the MAP kinase ERK1 and the stress activated protein kinase JNK1. The Threonine 56 was defined as the ERK1 phosphorylation site by using phosphoamino-acid analyses and a Spi-B mutant version with the substitution T56 to A56. Strikingly, ERK1 failed to phosphorylate Spi-1, in vitro, whereas JNK1, like CK II, phosphorylated Spi-B and Spi-1. In addition, other purified Spi-B-kinase activities, unidentified as yet, display similar specificity than ERK1 for Spi-B versus Spi-1. Furthermore, the evident interaction of pRb protein with the transactivator domain of Spi-B in an unphosphorylated state disappeared when this domain was first phosphorylated in vitro either by ERK1 or by the purified Spi-B-kinase activities. Our data revealed multiple phosphorylation sites within Spi-B whose some of them appeared specific for Spi-B versus Spi-1 and which may account for differential regulation of their activities.

Amino Acid Sequence↗
PubMed1996

Assignment of the human fast skeletal troponin T gene (TNNT3) to chromosome 11p15.5: evidence for the presence of 11pter in a monochromosome 9 somatic cell hybrid in NIGMS mapping panel 2.

Human fast skeletal troponin T (TnTf), the tropomyosin binding component of the multisubunit troponin complex, plays an important role in the Ca2+ regulation of striated muscle contraction. Specific primers designed from the 3' end of human TnTf cDNA were used to amplify an intronic region by polymerase chain reaction (PCR). This TnTf-specific PCR product was detected from two somatic cell hybrids containing human chromosomes 9 and 11, respectively, in NIGMS mapping panel 2. However, further studies with other somatic hybrid cell lines (Bios Laboratory) localized the TnTf gene (HGMW-approved symbol TNNT3) only to chromosome 11. This observation was further confirmed by fluorescence in situ hybridization with a 12-kb TnTf genomic probe generated by extended PCR, showing the sublocalization of the gene to band p15.5 on chromosome 11. This locus is of specific interest, as Beckwith-Wiedemann syndrome and various childhood and adult tumor-related abnormalities have been mapped to this region. The study also indicates the presence of an 11pter region in the NIGMS cell hybrid GM10611, which has previously been reported to contain only human chromosome 9.

Animals↗
PubMed1996

Pancreatitis associated with neuroendocrine (islet cell) tumors of the pancreas.

BACKGROUND: The association of pancreatitis with neuroendocrine tumors of the pancreas is uncommon, whereas its association with exocrine pancreatic cancer is well recognized. Since the latter, but not the islet cell tumor, is thought to originate within the ductal system, it is not surprising that pancreatitis is less likely to result from the islet cell tumor. The senior author has recently noted that the first recognizable indication of an islet cell carcinoma may be one or more discrete attacks of acute pancreatitis. METHODS AND RESULTS: Acute pancreatitis, resulting from an islet cell tumor, has been observed in five patients, in one of whom it had become chronic. In four of the patients, the tumor was malignant. A review of the English language literature reveals 14 such patients with pancreatitis, and 2 others have been noted in other languages (a total of 21 patients). The tumor was malignant in 15 of the 21 patients (71%). Although the development of pancreatitis was found to result from the obstruction of the duct in most patients, at least three seemed unrelated. In 12 of 21 cases (57%), an acute attack of pancreatitis, usually recurrent, was the initial syndrome, in contradistinction to pancreatitis resulting from exocrine tumors, which has usually been chronic in nature. CONCLUSION: Pancreatitis, particularly acute pancreatitis, may result from an islet cell tumor. Although unusual, its occurrence may be the first signal of the presence of the tumor. In our experience, obstruction of the pancreatic duct by the islet cell carcinoma appears to be the important etiologic factor.

Acute Disease↗
PubMed1996

Cytokine gene expression in the MRL/lpr model of lupus nephritis.

The murine MRL/lpr model of lupus nephritis is characterized by a systemic autoimmune syndrome closely resembling the human disease. The lpr mutation represents a defect in the expression of the apoptosis-signaling Fas antigen gene which causes accelerated autoimmune disease in MRL/ lpr mice and a milder, non-lethal autoimmune syndrome in C57BL6-lpr/lpr mice. The role of cytokines in autoimmune pathogenesis and its relationship with the lpr mutation remains poorly understood. In this study we utilized a RNase protection assay to quantitatively and simultaneously examine the expression of 10 different cytokine genes, namely IL-1 alpha, II-1 beta, IL-2, IL-3, IL-4, IL-5, IL-6, IFN-gamma, TNF-alpha, and TNF-beta in kidney, spleen, liver, and lymph nodes obtained from pre-diseased and diseased lupus-prone MRL/lpr, pre-diseased MRL/+2 and C57BL/6-lpr mice, as well as healthy non-autoimmune C57BL/6 and Balb/c mice. Diseased MRL/lpr mice demonstrated marked and predominant IL-1 beta gene upregulation in kidneys, liver, lymph nodes and spleen. Increased message for both TNF-alpha and IFN-gamma genes was also observed in lymph nodes, and less consistently, in the spleen, and kidneys derived from diseased MRL/lpr mice as compared to pre-diseased MRL/+2 or normal nonautoimmune control mice. Furthermore, a modest increase in the expression of both IL-1 beta and IFN-gamma message was observed in lymphoid organs of pre-diseased MRL/lpr and C57BL/6-lpr mice compared with MRL/+2 and C57BL/6 controls, respectively. Increased IL-1 beta gene expression was associated with the presence of the lpr mutation, was observed during the prediseased stage, and increased during active disease in both male and female mice. In summary, these results demonstrate that generalized up-regulation of IL-1 beta gene expression, in concert with a more limited up-regulation of both TNF-alpha and IFN-gamma expression, are prominent features of the autoimmune syndrome in the MRL/lpr model of SLE and may contribute to the disease-accelerating effect of the lpr mutation.

Animals↗
PubMed1996

Invasive pneumococcal infections in human immunodeficiency virus-infected children.

Invasive pneumococcal infection (IPI) is the most common serious bacterial infection in human immunodeficiency virus (HIV)-infected children. Data from a population-based pediatric HIV surveillance project were used to determine the incidence of IPI in HIV-infected children and to conduct a case-control study assessing potential risk factors for IPI in HIV-infected children. There were 50 episodes of IPI and a cumulative incidence of 6.1 cases/100 patient-years through age 7 years. Children with IPI were more likely to have a prior AIDS diagnosis (odds ratio, 4.2; 95% confidence interval, 1.2-15.1) and higher levels of IgG and IgM (P=.01) than were controls. In a separate case-control study, the manifestations of IPI in HIV-infected children were compared with those in HIV-negative controls. Focal complication rates in the 2 groups did not differ; however, HIV-infected children were less likely than controls to have leukocytosis (P<.001) and more likely to have isolates with penicillin resistance (P=.03).

Age Factors↗
PubMed1996

Glucagonoma associated with calculous pancreatitis.

A Patient with a glucagonoma associated with calculous pancreatitis is reported. The authors know of only one other such patient. Because the calculous pancreatitis developed both upstream and downstream from the tumor, it cannot be attributed to obstruction of the pancreatic duct by the tumor. Continued critical appraisal is needed to determine whether the association of the glucagonoma and pancreatitis is etiologically related or merely coincidental.

Acute Disease↗
PubMed1996

IL-1 beta gene expression in B cells derived from the murine MRL/lpr model of lupus.

The MRL/lpr model of SLE resembles human lupus in its various immunopathologic characteristics including the presence of high-level IgG and anti-DNA antibody production and multisystem organ involvement (nephritis, arthritis, and vasculitis). Our previous studies have shown that IL-1 overactivity in B cells plays a potentially important role in driving IgG and autoantibody production. However, the underlying mechanisms determining IL-1 overactivity are poorly understood. We studied IL-1 beta gene expression and transcriptional rates in B cells derived from old and young MRL/lpr, MRL/+ +, and non-autoimmune control mice using semi-quantitative RT-PCR and the nuclear run-on assay. RT-PCR demonstrated increased steady-state IL-1 beta gene expression in B cells derived from old MRL/lpr mice as compared to either young MRL/lpr or control mice. Furthermore, IL-1 beta gene expression in B cells was associated with the presence of the lpr mutation because heightened IL-1 beta message was observed in RNA obtained from MRL/lpr but not MRL/+ + B cells. IL-1 beta transcriptional rates measured by the nuclear run-on assay were very similar in B cells from old and young MRL/lpr and control mice. These observations suggest that IL-1 overactivity in B cells obtained from old diseased MRL/lpr results from heightened IL-1 beta message, is associated with the presence of the lpr mutation, and is likely to reflect post-transcriptional stabilization of IL-1 beta mRNA.

Aging↗
PubMed1996

The vascular wall as a target for association studies by the candidate gene approach.

The implication of polymorphisms of candidate genes in the variation of quantitative traits can be studied by using marker genotypes in association studies. The vascular wall properties, such as wall thickness and compliance, can be approached by such strategies. A rational choice of candidate genes can be based on an extensive knowledge of the cellular and biochemical processes occurring in the vascular wall. Molecular cloning and the availability of markers on several genes allow the investigation of a large number of candidate genes. This review summarizes the knowledge of some aspects of cell proliferation and differentiation in the vascular wall and the results already obtained by association studies on vascular wall phenotypes.

Animals↗