Biomedical subjects

Li Gan

Publications and source records attributed to Li Gan.

23 records · Page 2Linked to original sources

PubMed2003

Immunohistochemical visualization of histone H1 phosphorylation in squamous intraepithelial lesions of the gynecologic tract.

Immunohistochemical staining was performed on gynecologic tract squamous intraepithelial lesions using a novel phosphorylation-specific monoclonal antibody (designated 12D11) that detects histone H1 when phosphorylated at a cyclin-dependent kinase (CDK)-responsive epitope. Findings were compared to immunostaining by MIB-1, an extensively studied antibody probe of proliferation. Routinely fixed and processed archival sections were subjected to distinct antigen retrieval and staining protocols for each antibody and were processed for immunodetection of either Ki-67 (with MIB-1) or phosphohistone H1, using a streptavidin-biotin kit and diaminobenzidine as chromagen. For 12D11 staining, antigen retrieval was performed at pH 4.0, and the antibody incubation buffer was supplemented with 1.0 M NaCl. Both 12D11 and MIB-1 stained parabasal cells in normal squamous epithelium. Staining by 12D11 and MIB-1 of cells in progressively higher strata was found to correlate with the severity of lesions. The mean proportion of positively stained cells was higher in MIB-1-stained sections than in 12D11-stained sections in normal squamous epithelium and in all grades of squamous intraepithelial lesions. We conclude that the changes in expression patterns of CDK-phosphorylated histone H1 in the spectrum of gynecologic squamous intraepithelial lesions are similar to staining patterns obtained with the proliferation probe MIB-1. The differing proportion of cells stained by MIB-1 and 12D11 suggests that phosphohistone H1 may be a useful alternative proliferation marker that detects a different subpopulation of cycling cells in premalignant squamous lesions.

Antibodies, Monoclonal↗

PubMed2003

p63 and TTF-1 immunostaining. A useful marker panel for distinguishing small cell carcinoma of lung from poorly differentiated squamous cell carcinoma of lung.

We studied the usefulness of p63 and thyroid transcription factor-1 (TTF-1) immunostains for differentiating poorly differentiated squamous cell carcinoma (PDSCC) from small cell lung carcinoma (SCLC). We used monoclonal antibodies reactive to p63 or TTF-1 to stain 4-microns-thick sections from 30 formalin-fixed, paraffin-embedded lung biopsy and resection specimens and 7 alcohol-fixed, formalin-postfixed, paraffin-embedded cell blocks from lung fine-needle aspirations (FNAs). For p63, we used a streptavidin-biotin kit, diaminobenzidine as the chromogen, and a hematoxylin counterstain. We used automated immunostaining for TTF-1. The 37 cases included 23 SCLCs, 13 PDSCCs, and 1 carcinoma initially diagnosed as PDSCC. All 23 SCLCs were negative or, rarely, equivocal for p63; 20 (87%) of 23 were TTF-1+; nuclear staining ranged from strong and/or frequent to weak and/or uncommon. All 13 PDSCCs were TTF-1-/p63+ with intense staining of 50% to 100% of tumor cells. One case originally diagnosed as PDSCC was TTF-1+/p63-, suggestive of SCLC; after morphologic reexamination and immunostaining for neuroendocrine markers, it was reclassified as intermediate-type SCLC. TTF-1 immunostaining showed equal or increased sensitivity in alcohol-fixed cytologic cell block samples compared with formalin-fixed biopsy material; in 1 SCLC case, the biopsy specimen was TTF-1-; however, the FNA cell block stained positively. p63 and TTF-1 appear to be useful for differentiating SCLC from lung PDSCC in formalin-fixed and alcohol-fixed, formalin-postfixed material.

Antibodies, Monoclonal↗

PubMed2002

Localization of the Slack potassium channel in the rat central nervous system.

The Slack gene encodes a voltage-dependent K(+) channel that has a unitary conductance of approximately 60 pS. Evidence from heterologous expression studies suggests that Slack channel subunits can also combine with the Slo subunit to generate Ca(2+)-activated K(+) channels of larger conductances. Nonetheless, the function of Slack in the brain remains to be identified. We have now generated an affinity-purified antibody against the N-terminal of rat Slack, for biochemical and immunohistochemical studies. The antibody recognized Slack in transiently transfected CHO cells both by immunocytochemistry and by Western blot analysis. The antibody also detected a single band in rat brain membranes. The localization of Slack in rat brain slices was then determined using the antibody. Most prominent Slack immunoreactivity occurs in the brainstem, in particular the trigeminal system and reticular formation, where very intense staining was found in both cell bodies and axonal fibers of associated nuclei. Labeling was also very strong in the vestibular and oculomotor nuclei. Within the auditory system, the medial nucleus of the trapezoid had a robust signal consistent with staining of the giant presynaptic terminals. Strong Slack immunoreactivity was present in the olfactory bulb, red nucleus, and deep cerebellar nuclei. There was labeling also in the thalamus, substantia nigra, and amygdala. The only cortical region in which Slack immunoreactivity was detected was the frontal cortex. The subcellular and regional distribution of Slack differs from that previously reported for the Slo channel subunit and suggests that Slack may also have an autonomous role in regulating the firing properties of neurons.

Amino Acid Sequence↗

PubMed2002

P63 in pulmonary epithelium, pulmonary squamous neoplasms, and other pulmonary tumors.

p63 is a p53-homologous nuclear protein that appears to play a crucial role in regulation of stem cell commitment in squamous and other epithelia. In this study, p63 expression was examined in benign lung and in neoplasms of pulmonary origin. Eighty sections from routinely fixed and processed archival bronchoscopic biopsy or lobectomy specimens were pretreated with citric acid (pH 6.0) for antigen retrieval, then incubated overnight with anti-p63 monoclonal antibody 4A4. Slides were stained using a streptavidin-biotin kit and diaminobenzidine as chromagen, and were counterstained with hematoxylin. In normal lung, p63 intensely stained nuclei of bronchial reserve cells but did not stain ciliated cells, alveolar epithelial cells, or nonepithelial cells. The lower strata of squamous metaplastic bronchial epithelium stained positively. All squamous-cell carcinomas stained positively (n = 30). In some well-differentiated carcinomas, staining was found at the periphery of tumor nests but was negative in central zones showing squamous maturation. Poorly differentiated carcinomas showed very high proportions (80% to 100%) of p63-positive nuclei. All small-cell carcinomas were p63 negative (n = 9). Staining of bronchioloalveolar carcinomas (n = 7) and adenocarcinomas (n = 23) was variable: some tumors showed no detectable staining, others showed heterogeneously positive staining. Adenosquamous carcinomas (n = 5) displayed a unique basalar staining pattern. Carcinoid tumors were almost entirely negative (n = 5). We conclude that p63 is expressed in benign bronchial stem cells, in neoplastic cells with either squamous differentiation or squamous differentiating potential, and in a subpopulation of adenocarcinomas. p63 immunostaining may also aid in some histopathologic distinctions, such as in small biopsies where the differential diagnosis is poorly differentiated squamous carcinoma versus small-cell carcinoma. A stem cell biology-based classification system for squamous carcinomas is proposed.

Adenocarcinoma↗

PubMed2001

Coordinate effects of human immunodeficiency virus type 1 protein Tat and cellular protein Puralpha on DNA replication initiated at the JC virus origin.

JC virus (JCV) causes progressive multifocal leukoencephalopathy, a demyelinating disease in brains of individuals with AIDS. Previous work has shown that the Tat protein, encoded by human immunodeficiency virus type 1 (HIV-1), can interact with cellular protein Puralpha to enhance both TAR-dependent HIV-1 transcription and JCV late gene transcription. Tat has been shown to activate JCV transcription through interaction with Puralpha, which binds to promoter sequence elements near the JCV origin of replication. DNA footprinting has shown that Puralpha and large T-antigen cooperatively interact at several binding sites in the origin and transcriptional control region. Overexpression of Puralpha inhibits replication initiated at the JCV origin by T-antigen. In transfected glial cells Tat reversed this inhibition and enhanced DNA replication. In an in vitro replication system maximal activation by Tat, more than sixfold the levels achieved with T-antigen alone, was achieved in the presence of Puralpha. Effects of mutant Tat proteins on both activation of replication and binding to Puralpha have revealed that Cys22 exerts a conformational effect that affects both activities. The origin of an archetypal strain of JCV was less susceptible to activation of replication by Tat relative to the rearranged Mad-1 strain. These results have revealed a previously undocumented role for Tat in DNA replication and have indicated a regulatory role for JCV origin auxiliary sequences in replication and activation by Tat.

Antigens, Viral, Tumor↗