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Biomedical subjects

H Ma

Publications and source records attributed to H Ma.

At least 217 records · Page 12Linked to original sources
PubMed1996

The repetitive histologic pattern of vascular cardiac allograft rejection. Increased incidence associated with longer exposure to prophylactic murine monoclonal anti-CD3 antibody (OKT3).

While vascular cardiac allograft rejection increases morbidity and mortality following transplantation, factors predisposing to its development have not been completely elucidated. To evaluate the influence of the duration of early rejection prophylaxis with the murine monoclonal anti-CD3 antibody (OKT3) on the development of a repetitive histologic pattern of vascular cardiac allograft rejection, endomyocardial biopsies from 344 heart transplant recipients were prospectively evaluated. The influence of clinical characteristics was assessed. Eighty-three patients (24%) developed and 261 patients (76%) did not develop a repetitive histologic pattern of vascular cardiac allograft rejection. The vascular rejection pattern was more common in patients with a positive crossmatch (89% versus 11%, P<0.0001) and OKT3 sensitization (73% versus 27%, P<0.0001), and was positively correlated with the duration of OKT3 treatment (P<0.0001). The correlation persists even after excluding patients with a positive crossmatch or OKT3 sensitization. Patients developing a repetitive histologic pattern of vascular cardiac allograft rejection early after transplantation had decreased allograft survival (P=0.0008). The development of a repetitive histologic pattern of vascular cardiac allograft rejection is positively correlated with the duration of OKT3 treatment. Judicious use of OKT3 in early rejection prophylaxis in cardiac transplantation is warranted.

Adult↗
PubMed1996

Ca2+ channel activation by platelet-derived growth factor-induced tyrosine phosphorylation and Ras guanine triphosphate-binding proteins in rat glomerular mesangial cells.

We investigated the signaling pathways mediating 1-pS Ca2+ channel activation by PDGF in cultured rat mesangial cells. In cell-attached patches, intrapipette PDGF-BB (PDGF B chain homodimer isoform) (50 ng/ml) dramatically stimulates channel activity (P < 0.003, n = 6). Tyrosine kinase inhibition (100 microM genistein or 10 microM tryphostin 9) abolished PDGF-induced channel activation (P < 0.02, n = 6). In excised patches, the effect of tyrosine kinase inhibition could be reversed by 200 microM GTPgammaS (P < 0.02, n = 4). In contrast, 200 microM GDPbetaS inhibited PDGF-induced channel activity (P < 0.04, n = 6). Pertussis toxin (250 ng/ml) had no effect on PDGF-induced channel activity (P = 0.45, n = 6). When excised patches were exposed to anti-Ras antibody (5 microg/ml), PDGF-induced channel activity was abolished (P < 0.002, n = 11). Western immunoblots revealed that PDGF-BB binding stimulates the formation of a membrane-bound complex consisting of growth factor receptor-binding protein 2, son of sevenless, and the PDGF-beta receptor. Complex formation was abolished by genistein. In mesangial cells, the intrinsic tyrosine kinase activity of the PDGF-beta receptor stimulates the formation of a membrane-bound growth factor receptor-binding protein 2/son of sevenless/PDGF-beta receptor complex and activation of the pertussis toxin-insensitive GTP-binding protein, p21-Ras, which leads to the opening of 1-pS Ca2+ channels.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Identification and analysis of an Autographa californica nuclear polyhedrosis virus structural protein of the occlusion-derived virus envelope: ODV-E56.

An Autographa californica nuclear polyhedrosis virus gene encoding an occlusion-derived virus (ODV) envelope protein of 56 kDa was identified and sequenced. Transcription initiates from a conserved baculovirus late motif (ATAAG) with transcripts detected from 16 through 72 hr p.i. The protein is detected in infected cell extracts from 36 hr p.i. Western blot assay of ODV, BV, viral envelope, and nucleocapsid preparations coupled with immunoelectron microscopy reveal that this protein localizes to the ODV envelope. This protein is named ODV-E56 to identify its viral origin, envelope location, and apparent molecular weight. ODV-E56 is enriched in viral induced intranuclear microvesicles as determined by immunogold labeling. A mutant was constructed with the C-terminal portion of the protein replaced with beta-galactosidase. The fusion protein, E56-beta-gal, locates to the viral nucleocapsids and not to the ODV envelope or intranuclear microvesicles. This suggests that the signals necessary for transport and/or retention into these structures lies within the C-terminal portion of ODV-E56. Additionally, both ODV-E56 and E56-beta-gal are enriched in electron dense regions that cluster around the inner nuclear membrane and within the nucleoplasm.

Amino Acid Sequence↗
PubMed1996

A light and electron microscopic radioautographic study on RNA synthesis in the retina of chick embryo.

The incorporation of 3H-uridine into RNA of chick embryo retina was studied by light and electron microscopic radioautography. The numbers of silver grains were counted over the nucleus, nucleolus and cytoplasm of the cells in three different regions of the same retina of 2, 3, 4, and 7 day chick embryos. The results showed an increase of 3H-uridine incorporation from embryonic day 2 to 7. In every stage of development of the chick embryo retina, the number of silver grains was higher in the anterior than in the other two regions of the retina. In the three cell compartments of every embryo group, the number of silver grains was higher in the nucleus than in the nucleolus and cytoplasm. The results show further that the grains were less in the cytoplasm of the retinal cells of the day 2 embryo group and higher in the other groups especially in the day 7 embryos. Ultrastructural changes were also observed during the studied period of retina development.

Animals↗
PubMed1996

Cloning, expression and characterization of an unusual guanine phosphoribosyltransferase from Giardia lamblia.

Giardia lamblia is one of the most ancient eukaryotes identified to date. It lacks de novo purine biosynthesis and is thought to rely solely on the functions of two salvage enzymes, adenine and guanine phosphoribosyltransferases (APRTase and GPRTase). We have cloned the gene encoding the G. lamblia GPRTase by complementation of the E. coli strain Sø609 (delta gpt-pro-lac, thi, hpt, pup, purH,J, strA) with a genomic library consisting of Sau3AI-digested G. lamblia DNA inserted into the Bluescript vector. Transformed Sø609 colonies grew on minimal medium supplemented with guanine at a frequency of 3.3 x 10(-5) ampicillin-resistant colonies, but were unable to salvage hypoxanthine or xanthine, as predicted from previous studies of the native G. lamblia GPRTase. The sequence analysis of cloned DNA fragments reveals an open reading frame of 690 bp, encoding a protein of 26.3 kDa with an estimated pI of 6.83, in agreement with the reported subunit molecular weight of the native G. lamblia GPRTase. The deduced protein has less than 20% sequence identity to the human and other known HGPRTases, and features several significant changes in the primary sequence of the putative active sites of the enzyme, which may reflect the stringent substrate specificity of GPRTase. The recombinant GPRTase was expressed in E. coli and purified to > 95% homogeneity. Kinetic studies of the recombinant enzyme showed an apparent K(m) of 74 microM for guanine. Hypoxanthine as an alternate purine substrate was used only when present in millimolar amounts, and xanthine was not utilized at all. This Giardia enzyme is thus a highly unique purine PRTase without a known parallel in any other living organisms.

Amino Acid Sequence↗
PubMed1996

Specific expression of the AGL1 MADS-box gene suggests regulatory functions in Arabidopsis gynoecium and ovule development.

Several members of the MADS-box gene family have been shown to be important regulators of flower development, controlling such well-studied early events as the formation of the floral meristem and the specification of floral organ identity. Other floral-specific MADS-box genes, of as yet unknown function, have been isolated by homology and are proposed to be part of a regulatory hierarchy controlling flower development. Some of these genes might regulate later aspects of flower development, such as development of individual floral organs, which is less well studied at the molecular level. This paper presents a detailed analysis of the expression pattern of one such gene from Arabidopsis, AGL1, using RNA in situ hybridization. It is found that AGL1 is specifically expressed in particular regions of the gynoecium and ovule, only during and after floral development stage 7. AGL1 expression at the tip of the growing carpel primordia, along the margins of the ovary valves in developing and mature gynoecia and in specific regions of developing and mature ovules provides important insights into the possible roles of AGL1. It is proposed that AGL1 may have regulatory functions in the structural definition and/or function of the valve margins, in axis maintenance during ovule development, in nutritional supply to the growing ovule and embryo sac, and in pollen tube guidance. In the floral homeotic mutants ag-1, ap3-3 and ap2-2, AGL1 mRNA is expressed in an organ-dependent manner, suggesting that AGL1 is a carpel-specific gene and as such ultimately depends upon the carpel identity gene AG for proper gene expression.

Arabidopsis↗
PubMed1996

DNA binding properties of two Arabidopsis MADS domain proteins: binding consensus and dimer formation.

MADS domain proteins are members of a highly conserved family found in all eukaryotes. Genetic studies clearly indicate that many plant MADS domain proteins have different regulatory functions in flower development, yet they share a highly conserved DNA binding domain and can bind to very similar sequences. How, then, can these MADS box genes confer their specific functions? Here, we describe results from DNA binding studies of AGL1 and AGL2 (for AGAMOUS-like), two Arabidopsis MADS domain proteins that are preferentially expressed in flowers. We demonstrate that both proteins are sequence-specific DNA binding proteins and show that each binding consensus has distinct features, suggestion a mechanism for specificity. In addition, we show that the proteins with more similar amino acid sequences have more similar binding sequences. We also found that AGL2 binds to DNA in vitro as a dimer and determined the region of AGL2 that is sufficient for DNA binding and dimerization. Finally, we show that several plant MADS domain proteins can bind to DNA either as homodimers or as heterodimers, suggesting that the number of different regulators could be much greater than the number of MADS box genes.

Amino Acid Sequence↗
PubMed1996

Functional domains of the floral regulator AGAMOUS: characterization of the DNA binding domain and analysis of dominant negative mutations.

The Arabidopsis MADS box gene AGAMOUS (AG) controls reproductive organ identity and floral meristem determinacy. The AG protein binds in vitro to DNA sequences similar to the targets of known MADS domain transcription factors. Whereas most plant MADS domain proteins begin with the MADS domain, AG and its orthologs contain a region N-terminal to the MADS domain. All plant MADS domain proteins share another region with moderate sequence similarity called the K domain. Neither the region (I region) that lies between the MADS and K domains nor the C-terminal region is conserved. We show here that the AG MADS domain and the I region are necessary and sufficient for DNA binding in vitro and that AG binds to DNA as a dimer. To investigate the in vivo function of the regions of AG not required for in vitro DNA binding, we introduced several AG constructs into wild-type plants and characterized their floral phenotypes. We show that transgenic Arabidopsis plants with a 35S-AG construct encoding an AG protein lacking the N-terminal region produced apetala 2 (ap2)-like flowers similar to those ectopically expressing AG proteins retaining the N-terminal region. This result suggests that the N-terminal region is not required to produce the ap2-like phenotype. In addition, transformants with a 35S-AG construct encoding an AG protein lacking the C-terminal region produced ag-like flowers, indicating that this truncated AG protein inhibits normal AG function. Finally, transformants with a 35S-AG construct encoding an AG protein lacking both K and C regions produced flowers with more stamens and carpels. The phenotypes of the AG transformants demonstrate that both the K domain and the C-terminal region have important and distinct in vivo functions. We discuss possible mechanisms through which AG may regulate downstream genes.

Arabidopsis↗
PubMed1996

ANG II-induced tyrosine phosphorylation stimulates phospholipase C-gamma 1 and Cl-channels in mesangial cells.

Angiotensin II (ANG II)-induced, activation of phospholipase C (PLC) and Ca(2+)-dependent Cl-channels is an important signal transduction pathway for mesangial cell contraction and growth. Although ANG II receptors are traditionally though to be G protein coupled, recent evidence suggests that they may also mediate protein tyrosine phosphorylation. In cultured rat mesangial cells, 10(-7) MANG II stimulated the tyrosine phosphorylation of PLC-gamma 1 and elevation of intracellular inositol 1,4,5-trisphosphate (IP3) and Ca2+ levels; peak response occurred within 0.5 min. In cell-attached patches, ANG II stimulated the activity of Ca(2+)-dependent, 3- to 4-pS Cl-channels (number of channels x open probability) from 0.063 +/- 0.022 to 0.77 +/- 0.20. Tyrosine kinase inhibition with genistein or herbimycin A blocked all four ANG II-induced responses. We conclude the following. 1) Stimulation of inositol phosphate hydrolysis by PLC, release of IP3-dependent intracellular Ca2+ stores, and activation of Ca(2+)-dependent C1-channels by ANG II are dependent on the tyrosine phosphorylation of PLC-gamma 1.2) This ANG II-induced signal transduction cascade provides a possible mechanism for both the contractile and growth-stimulating effects of ANG II on glomerular mesangial cells.

Angiotensin II↗
PubMed1996

Luminal adenosine receptors regulate amiloride-sensitive Na+ channels in A6 distal nephron cells.

To investigate the effects of luminal adenosine on amiloride-sensitive Na+ channels, we applied the cell-attached patch-clamp technique to A6 distal nephron cells. Exposure to luminal 30 nM adenosine increased number of channels x open probability (NP0) from 0.38 +/- 0.08 to 0.77 +/- 0.09 (means +/- SE; P < 0.01, n = 17). Luminal exposure to an A1-receptor antagonist (30 nM 8-cyclopentyl-1,3-dipropylxanthine) abolished (P = 0.17, n = 11), whereas an A1 agonist (30 nM N6-cyclohexyladenosine) reproduced (P < 0.02, n = 6) the stimulatory effect of 30 nM adenosine. In contrast, higher concentrations of luminal adenosine (1 or 10 microM) decreased NP0 from 0.65 +/- 0.09 to 0.24 +/- 0.10 (P < 0.02, n = 11) and from 0.80 +/- 0.11 to 0.19 +/- 0.03 (P < 0.01, n = 8), respectively. Channel inhibition by high-dose luminal adenosine was abolished by an A2 antagonist (30 microM 3,7-dimethyl-1-propargylxanthine; P = 0.2, n = 10) and mimicked by an A2 agonist (100 nM CGS-21680 hydrochloride; P < 0.0005, n = 8). We conclude that 1) purinergic regulation of distal nephron Na+ channels is mediated by stimulatory apical A1 receptors and inhibitory apical A2 receptors; 2) basal urinary adenosine concentrations (in nM) would stimulate Na+ reabsorption, whereas higher urinary concentrations (in microM), e.g., renal ischemia and elevations in filtered NaCl load, would increase Na+ excretion; and 3) urinary adenosine may be involved in feedback regulation of distal nephron Na+ transport.

Adenosine↗
PubMed1996

Regulation of PDGF-beta receptor-operated Ca2+ channels by phospholipase C-gamma 1 in glomerular mesangial cells.

Platelet-derived growth factor (PDGF)-induced Ca2+ signaling mechanisms were examined in cultured rat glomerular mesangial cells. PDGF-BB stimulated the tyrosine phosphorylation of phospholipase C (PLC)-gamma 1, the formation of a PLC-gamma 1/PDGF-beta receptor membrane complex, and the generation of intracellular inositol 1,4,5-trisphosphate (IP3). Preincubation with a tyrosine kinase inhibitor (genistein) abolished these PDGF-induced responses. Activation of 1-pS Ca2+ channels in cell-attached patches by intrapipette PDGF-BB was also abolished by tyrosine kinase inhibition. In the absence of PDGF-BB, channels were activated in cell-attached patches exposed to intrapipette thapsigargin (IP3-independent releaser of intracellular Ca2+ stores) and in excised inside-out patches exposed to increasing "cytoplasmic" Ca2+ (10(-8) to 10(-6) M). In cell-attached patches, channel activation by PDGF-BB was abolished when extracellular Ca2+ was < 1 mM. In glomerular mesangial cells 1) PDGF-BB stimulates tyrosine phosphorylation of PLC-gamma 1, PDGF-beta receptor/PLC-gamma 1 membrane complex formation, IP3 production, and 1-pS Ca2+ channel activity; 2) all four PDGF-induced responses are abolished by tyrosine kinase inhibition; 3) PDGF receptor-operated Ca2+ channels are sensitive to both intra- and extracellular Ca2+.

Animals↗
PubMed1996

Exercise capacity after heart transplantation: influence of donor and recipient characteristics.

BACKGROUND: For incompletely understood reasons, cardiac transplant recipients achieve only 60% to 70% of predicted values for maximal exercise capacity. The objective was to determine the characteristics of cardiac transplant recipients that are predictive of exercise capacity. METHODS: One hundred ten patients underwent maximal exercise testing using a modified Naughton protocol 26 +/- 1 months after transplantation. Recipient characteristics, resting hemodynamic variables and exercise parameters were compared using univariate and multivariate analyses. RESULTS: The average maximum heart rate was 85% of predicted, and the average peak oxygen consumption (Vo2) was 17.7 +/- 0.3 ml/kg/min (64% of predicted). Pretransplant status, etiology of heart failure, ischemic time, degree of HLA disparity, cumulative corticosteroid exposure, and number of rejection episodes failed to correlate with any exercise parameter. Older recipient age and female gender were associated with greater values for the proportion of the predicted peak Vo2 (p < 0.001 for age; p = 0.001 for gender). Older donor age was the strongest independent predictor of a decreased chronotropic response (p < 0.001) and was a weak predictor of decreased peak Vo2 (p = 0.014). Even in the multivariate analysis, maintenance prednisone dose negatively impacts exercise duration (p = 0.05), peak Vo2 (p = 0.035) and percent of predicted peak Vo2 (p = 0.032). Of all characteristics tested, pulmonary vascular resistance within 24 hours of exercise most powerfully predicts exercise duration (p = 0.002) and peak Vo2 (p = 0.001). CONCLUSIONS: Female recipients and older recipients have a lower absolute exercise capacity, but achieve a greater proportion of their predicted capacity. Recipients of older donor hearts and those receiving chronic corticosteroids have decreased exercise capacity. Pulmonary vascular resistance is inversely correlated with exercise capacity.

Adolescent↗
PubMed1996

[Micronucleus effect induced by Helicobacter pylori on human gastric mucous epithelial membrane].

A large number of data from epidemiologic and statistical studies showed there was a relationship between infection of Helicobacter pylori (Hp) and gastric carcinogenesis, but its mechanism was unclear. Micronucleus test in vitro, one of cytogenotoxic studies, was carried out to study mutagenicity of Hp. Results showed micronucleus formation in gastric mucous epithelial membrane cell GES-1 treated with ultra-sonicated Hp for 72 hours was significantly greater than in the negative controls. There existed a dose-response relationship between them when concentration of Hp reached a range of 0.3-1.7 mg/L. As concentration of Hp reached 1.7 mg/L, percentage of micronucleus formation was five times higher than that of controls. When concentration of Hp increased to 4.3 to 10.7 mg/L, micronucleus formation did not increase but it was still over two times higher than that in controls. It suggests that there exists a direct cytogenotoxic effect of Hp on human gastric mucous epithelial membrane.

Epithelium↗
PubMed1996

[Loss of alveolar attachments in smoker's lungs and its relation to small airway abnormalities].

The alveolar attachments and small airway abnormalities in the lungs of smokers were measured by computerized imaging to study the relationship between loss of alveolar attachments and small airway abnormalities, the smoker's lungs were divided into three groups: no emphysema (NE), centrilobular emphysema (CLE) and panlobular emphysema (PLE). The distance between normal alveolar attachments (Distance) and percent abnormal alveolar attachments (% Abnormal) in CLE were significantly higher than in NE (P < 0.05 and P < 0.01), and no significant difference in the number of normal alveolar attachments in the 3 groups. The small airway wall area (WA) and deformity index (DI) in CLE differed significantly from MA and DI in NE (P < 0.05 for all). There were no differences between PLE and NE in these indices. Distance and % Abnormal correlated significantly with WA and DI, but the correlations were shown only in CLE. We concluded that alveolar attachment destruction in smoker's lungs was closely associated with small airway abnormalities, which indicated the different patterns of emphysema, CLE and PLE, probably have different pathogenesis respectively.

Adult↗
PubMed1996

[A clinical and pathological study of gliosarcoma].

In order to study the clinicopathological features, histogenesis and prognosis, 12 cases of gliosarcoma were reported representing 0.4% of a series of 2743 patients undergoing biopsy for CNS tumors. All the tumors originated from the cerebral hemispheres with a predilection for the temporal lobes. Half of the cases show more firm consistency and are rather well demarcated from brain tissue. Clinically, they are sometimes mistaken for meningiomas. Of the 10 patients with follow-up, 9 have died. The mean survival period after operation was 8 months, 1 cases is still alive and well for 3.2 years. There were some cases in which the origin of spindle cell populations could not be determined by H & E staining. Glioblastoma and malignant fibrous histiocytoma (MFH) element of the tumor was confirmed by electron microscopical examination and immunohistochemical stains for GFAP, Mac 387, VIM, FV III RA, etc. Osteosarcoma component in the tumor was detected in one case. It was accepted that MFH arose from the primitive uncommited mesenchyme.

Adult↗
PubMed1996

[Difference of the discharges from the postganglionic fibers of the celiac ganglion induced by electroacupuncture at zusanli and yanglingquan].

The changes of the discharge from postganglionic fibers of the celiac ganglion induced by electroacupuncture (EA) at Zusanli and Yanglingquan were measured on 25 healthy rabbits. The result shows that the sympathetic activity can be inhibited by EA at both acupoints above. The depression of the sympathetic activity resulted from EA at Zusanli was significant stronger than that at Yanglingquan (P < 0.05). This result indicates that there is the relative individuality in the function of the different acupoints on the different channels.

Acupuncture Points↗
PubMed1996

[Extended SMAS dissection as a modified approach to rhytidectomy].

A variation of the SMAS technique is introduced. During the operation, the SMAS was treated in two parts. The fixed part that is closely attached to the preparotid fascia is on the pre-auricle area. The movable part of the SMAS is from the lower part of the parotid gland to the platysma. The movable part of the SMAS was mobilized, elevated and fixed upwards to the fixed area. From January to November of 1995 at Chirurgie Esthetique Europeenne in Strasbourg, the authors did rhytidectomy on 31 cases using this technique with impressive results and minimal complications.

Adult↗