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Biomedical subjects

D Hou

Publications and source records attributed to D Hou.

33 records · Page 2Linked to original sources
PubMed1996

Vaginal birth after cesarean section in twin gestation.

OBJECTIVE: We report a 10-year experience with vaginal birth after cesarean section in women with twins. STUDY DESIGN: Data were gathered from labor and delivery records and maternal and neonatal hospital charts. Women with a vertical uterine scar, a previous uterine rupture, an unrepaired dehiscence, or obstetric contraindications to labor were excluded from a trial of labor. Full-thickness uterine defects requiring intervention were classified as ruptures; all others were classified as dehiscences. RESULTS: Between Jan. 1, 1985, and Dec. 31, 1994, at Los Angeles County/University of Southern California Women's Hospital, 210 women with previous cesarean births were delivered of twins. One hundred eighteen (56%) underwent repeat cesarean delivery without a trial of labor. Ninety-two (44%) undertook a trial of labor with no uterine ruptures and no increase in maternal or perinatal morbidity or mortality. CONCLUSIONS: In women with twins a trial of labor after a previous cesarean section is a safe and effective alternative to routine repeat cesarean delivery.

Adult↗
PubMed1995

Histomorphologic analysis of the soft palate musculature in prenatal cleft and noncleft A/Jax mice.

The two specific aims of this study were as follows: to evaluate the appropriateness of the A/Jax mouse model in the investigation of the key cellular stages in prenatal soft palate morphogenesis and myogenesis; and to describe structural differences in the histomorphology of the soft palate anatomy from cleft and noncleft mice prior to, during, and after palatogenesis. Cleft-induced and control groups of A/Jax mouse embryos from timed pregnancies were harvested sequentially on gestational days 15 to 19. Embryos were weighed and staged for external body morphology. The heads were removed and fixed for light microscopy, sectioned serially in the frontal plane at 10 microns and stained with hematoxylin-eosin to characterize and compare the soft palate musculature. All observations were made at the head depth of the trigeminal ganglion in both age- and stage-matched embryos. The following findings were made: (1) the A/Jax mouse is a suitable animal model for the study of soft palate myogenesis; (2) there were no discernible morphologic differences between the soft palate muscles in cleft and noncleft A/Jax mice when viewed under light microscopy; (3) the soft palate and related muscles were identifiable as muscle fields, in both the cleft and noncleft fetuses, as early as gestational day 15 and as specific muscles at gestational day 18; (4) in both the cleft and noncleft A/Jax fetuses, the soft palate muscles appeared in a sequential anatomic fashion (the palatine aponeurosis appeared first, next the tensor palatini, and then the levator palatini muscles); and (5) in the cleft palate fetuses, both pterygoid plates were angulated and displaced laterally.

Analysis of Variance↗
PubMed1994

Activation-dependent ubiquitination of a T cell antigen receptor subunit on multiple intracellular lysines.

The T cell antigen receptor zeta chain and other T cell antigen receptor components are ubiquitinated on receptor occupancy. A systematic mutagenesis of the zeta subunit was undertaken to determine the sites of ubiquitination. Ubiquitination was found to occur in the cytoplasmic domain of zeta with multiple lysines serving as sites for mono- and polyubiquitination. The mutation of all potential sites of ubiquitination did not inhibit receptor tyrosine phosphorylation or the ubiquitination of other T cell antigen receptor subunits. Lysines introduced into nonnative positions in the zeta molecule were also able to serve as sites for ubiquitination. These findings demonstrate that once a T cell antigen receptor is targeted for ubiquitination, there is little specificity with regard to the lysine residues that are modified.

Amino Acid Sequence↗
PubMed1994

CD45 tyrosine phosphatase activity and membrane anchoring are required for T-cell antigen receptor signaling.

T cells that lack the CD45 transmembrane tyrosine phosphatase have a variety of T-cell receptor (TCR) signaling defects that are corrected by reexpression of wild-type CD45 or its intracytoplasmic domains. In this study, a chimeric molecule containing the myristylation sequence of Src and the intracellular portion of CD45, previously shown to restore function in CD45- T cells, was mutagenized to determine if membrane-associated CD45 tyrosine phosphatase activity is required to restore TCR-mediated signaling in CD45- T cells. Abolition of enzymatic activity by substitution of a serine for a critical cysteine in the first catalytic domain resulted in failure of this molecule to restore TCR signaling. Another mutation, in which a single amino acid substitution destroyed the myristylation site, resulted in failure of the chimeric molecule to partition to the plasma membrane. Although expressed at high levels and enzymatically active, this form of intracellular CD45 also failed to restore normal signaling in CD45- T cells. These findings strongly suggest that CD45's function in TCR signaling requires its proximity to membrane-associated tyrosine phosphatase substrates.

Amino Acid Sequence↗
PubMed1994

[Causes of death of the host of no. 2 Chu Grave in Baoshan, Jingmen, Hubei Province: a preliminary study].

On the bamboo slips found in the No. 2 Chu Grave unearthed in Baoshan, Jingmen, Hubei Province in 1986, there were records about its host, Shao Tuo, consulting a sorcerer for his disease from March 4 (Chu Calendar) 317 B.C. to May 7th (Chu calendar), 316 B.C. As a result of textual research on the name of disease recorded as heart disease, lower heart disease and abdominal heart disease; the symptoms such as short breath, upper abdominal distension and dropsy; the characteristics of the disease such as sudden and intermittent onset, more and more severe condition, relatively rapid death and so on, it is considered that Shao Tuo died of cardiac disease. The two possible reasons why Shao Tuo suffered from cardiac disease are also discussed.

China↗
PubMed1994

Inhomogeneous and complementary antegrade and retrograde delivery of cardioplegic solution in the absence of coronary artery obstruction.

Inhomogeneous delivery of cardioplegic solution may result in postischemic myocardial injury. This study compares the distribution of warm blood antegrade and retrograde cardioplegia to multiple discrete left ventricular myocardial regions in pigs with unobstructed coronary arteries. Cardioplegic solution was delivered antegradely and retrogradely at 150 ml/min, and flows to 1152 individual myocardial regions were determined twice for each route with four different radiolabeled microspheres. The antegrade system delivered greater flow to each gram of myocardium than did the retrograde system (1.37 +/- 0.31 versus 0.39 +/- 0.09 ml/gm per minute, p < 0.001). Flow to individual myocardial regions was significantly inhomogeneous for both antegrade and retrograde cardioplegia, but much more so for retrograde cardioplegia (coefficient of variation was 48% +/- 17% for antegrade cardioplegia and 106% +/- 16% for retrograde cardioplegia; p < 0.001). The pattern of flow to individual myocardial regions was highly reproducible for a given route of delivery as confirmed by repeated measurements with different radioactive microsphere isotopes (correlation coefficients 0.88 +/- 0.12 for AC1-AC2 and 0.84 +/- 0.10 RC1-RC2), but antegrade cardioplegia and retrograde cardioplegia patterns were significantly different and therefore complementary (correlation coefficients 0.03 +/- 0.04, p < 0.001). These findings support the routine combined use of antegrade cardioplegia and retrograde cardioplegia to enhance delivery of cardioplegic solution to all regions of the heart and minimize the potential risk of postischemic myocardial dysfunction.

Animals↗
PubMed1993

T cell antigen receptor-eta subunit. Low levels of expression and limited cross-species conservation.

The eta-subunit of the TCR is derived from an alternative splice product of the TCR-zeta gene. The eta-subunit has been extensively characterized in murine T cells, where up to 10% of TCR bear zeta-eta heterodimers rather than zeta-homodimers. In contrast to the significant levels of eta found in murine T cells, in human PBL an eta-like region is expressed spliced to upstream exons of the zeta-gene at no more than 0.25% the level of zeta-mRNA. Analysis of genomic DNA from five additional mammalian species demonstrated that eta-like sequences are highly conserved at a nucleic acid level. The protein sequences encoded in the eta-regions from various species ranged from 28 to 92 amino acids in length, with the first seven deduced amino acids of eta-being common to all species. Within three to five amino acids of this region, all species have five consecutive charged amino acids. Beyond this point, due to translation in different reading frames, there is no significant amino acid homology. The findings of low level of expression of eta-RNA, limited cross-species conservation on a protein level, and the lack of an established functional role for this alternative splice product raise questions as to the potential roles that this subunit may play in TCR function.

Amino Acid Sequence↗
PubMed1992

Activation-induced ubiquitination of the T cell antigen receptor.

The zeta subunit of the T cell antigen receptor (TCR) exists primarily as a disulfide-linked homodimer. This receptor subunit is important in TCR-mediated signal transduction and is a substrate for a TCR-activated protein tyrosine kinase. The zeta chain was found to undergo ubiquitination in response to receptor engagement. This posttranslational modification occurred in normal T cells and tumor lines. Both nonphosphorylated and phosphorylated zeta molecules were modified, and at least one other TCR subunit, CD3 delta, was also ubiquitinated after activation of the receptor. These findings suggest an expanded role for ubiquitination in transmembrane receptor function.

Animals↗
PubMed1992

Organization of the human T cell receptor zeta/eta gene and its genetic linkage to the Fc gamma RII-Fc gamma RIII gene cluster.

The zeta-subunit is the most recently characterized stoichiometric human TCR component. In this study we describe the molecular organization of the human zeta-gene. The zeta transcript is generated as the spliced product of eight exons that are separated by distances of 0.7 kb to more than 8 kb. Ribonuclease protection studies revealed multiple transcription initiation sites distributed over a range of approximately 115 bases. A variable number tandem repeat restriction fragment polymorphism contained within the structural gene has allowed for the localization of zeta within the human genome. Additionally, a restriction fragment polymorphism within the Fc gamma RII-Fc gamma RIII gene cluster has allowed for its localization on the map of human chromosome 1q and for the establishment of its linkage to the zeta-gene locus. A region that is highly homologous on a nucleotide level with the eta-exon of the murine zeta-gene is localized to the 3' region of the human zeta-gene. Surprisingly, translation of this region into protein results in a structure that is markedly divergent from its murine counterpart. This finding has important implications regarding the potential role of eta in T cell function.

Amino Acid Sequence↗
PubMed1989

Synthesis and receptor affinities of some conformationally restricted analogues of the dopamine D1 selective ligand (5R)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl- 1H-3-benzazepin-7-ol.

The synthesis of a structurally novel series of 6,6a,7,8,9,13b-hexahydro-5H-benzo[d]naphtho[2,1-b]azepines (2), conformationally restricted analogues of the dopamine D1 antagonist (5R)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepin -7-ol (SCH 23390, 1c), is described. Affinity for D1 receptors was determined by competition for rat striatal binding sites labeled by [3H]SCH 23390; affinity for D2 receptors was similarly determined by competition experiments using [3H]spiperone. Compounds in this series having the B/C-trans ring junction (2b and related analogues), where the D ring is unequivocally fixed in an equatorial orientation, possess considerably more D1 receptor affinity and selectivity vs the D2 receptor than the conformationally mobile cis stereoisomers (2a), thus leading to the conclusion that axial substituents at the 4- or 5-positions of the benzazepine nucleus are detrimental to D1 receptor affinity. Resolution and X-ray analysis demonstrated that D1 receptor affinity was preferentially associated with the (-)-6aS,13bR enantiomer of 2b.

Animals↗
PubMed1989

Prevention of myocardial reperfusion injury with free radical scavengers. An experimental study.

The changes in endogenous superoxide dismutase (ESOD) during myocardial ischemia and reperfusion and the efficacy of oxygen free radical scavengers in myocardial protection were investigated in an isolated heart model connected with the recirculating nonpulsatile perfusion circuit. Subjected to a 2-hour period of global ischemia (27 C), the heart was reperfused with 37 C oxygen diluted auto-blood for 60 minutes. Superoxide dismutase plus catalase was added into the cardioplegic solution and reperfusates. ESOD activity was measured by pyrogallol method. The results of the experiment showed that ESOD activity after ischemia and reperfusion was decreased and the addition of oxygen free radical scavengers (SOD and CAT) to the cardioplegic solution and the reperfusates greatly reduced the leakage of myocardial enzymes, coronary vascular resistance, and the ultrastructural damages of the myocardium. These results suggest that the use of SOD and CAT may inhibit myocardial reperfusion injury by scavenging oxygen-derived free radicals.

Animals↗
PubMed1988

Molecular cloning of the zeta chain of the T cell antigen receptor.

The T cell antigen receptor is a multi-subunit receptor complex present on the surface of all mature and many developing T cells. It consists of clonotypic heterodimers noncovalently linked to five invariant chains that are encoded by four genes and referred to as the CD3 complex. The CD3 gamma, delta, and epsilon chains have been molecularly characterized. In this report the molecular cloning of a complementary DNA encoding the zeta chain of the murine T cell antigen receptor is described. The predicted protein sequence of the zeta chain suggests a structure distinct from those of any of the previously described receptor subunits.

Amino Acid Sequence↗
PubMed1988

Molecular cloning and chromosomal localization of the human T-cell receptor zeta chain: distinction from the molecular CD3 complex.

The T-cell antigen receptor (TCR) is a multisubunit receptor complex specific to T cells subserving both antigen recognition and signal transduction functions. The zeta chain of the TCR is a component of all surface receptor complexes. This chain was first identified in murine T cells by virtue of the fact that it coimmunoprecipitates with the TCR complex using antibodies directed against either the clone-specific subunits or invariant CD3 subunits of the receptor. Recently, we have isolated a cDNA encoding the murine zeta. Using this as a probe, we have now isolated cDNAs encoding the human zeta. Sequence analysis of cDNAs encoding human and murine zeta reveals that it is a highly conserved protein. In addition to amino acid homology, there is remarkable interspecies conservation in the nucleotide sequence of the 5' and 3' untranslated regions of the zeta mRNA. The previously characterized invariant delta, epsilon, and gamma chains of the TCR, referred to as the CD3 complex, share significant sequence and structural homology with each other and are all located within 300 kilobases of each other on human chromosome 11 (11q23). zeta has no sequence similarity to the CD3 chains and the localization of the human zeta gene to the centromeric region of chromosome 1 underscores the fact that it is a distinct genetic component of the TCR.

Amino Acid Sequence↗
PubMedDate not supplied

A biochemical, histochemical, and electron microscopic study on the effects of iron-loading on the hearts of mice.

Acute iron poisoning and chronic iron overload are well-known causes of myocardial failure. Although the exact mechanism is not known, excess iron-catalyzed free radical generation is conjectured to play a role in damaging the myocardium and altering cardiac function. We report here on the effects of acute and chronic iron-loading on the total iron concentration, glutathione peroxidase activity, and cytotoxic aldehyde production in the heart of a murine model (n = 35). Light microscopic examination for the presence of ferrous and ferric iron was undertaken following histochemical staining for these species. In addition, examination of representative samples by transmission electron microscopy was performed. Our findings show that iron-loading can result in significant increases in total iron concentrations, alterations to glutathione peroxidase activity, and increases in cytotoxic aldehyde concentrations in the hearts of mice. Furthermore, we observe that iron-loading can significantly alter and damage various cellular constituents (e.g., mitochondria, lysosomes, sarcoplasmic reticulum) and this may have bearing on the mechanism of iron-induced heart failure.

Animals↗