Loss of G(1)/S checkpoint in human immunodeficiency virus type 1-infected cells is associated with a lack of cyclin-dependent kinase inhibitor p21/Waf1.

Productive high-titer infection by human immunodeficiency virus type 1 (HIV-1) requires the activation of target cells. Infection of quiescent peripheral CD4 lymphocytes by HIV-1 results in incomplete, labile reverse transcripts and lack of viral progeny formation. An interplay between Tat and p53 has previously been reported, where Tat inhibited the transcription of the p53 gene, which may aid in the development of AIDS-related malignancies, and p53 expression inhibited HIV-1 long terminal repeat transcription.

Transcriptional up-regulation of the cyclin D2 gene and acquisition of new cyclin-dependent kinase partners in human T-cell leukemia virus type 1-infected cells.

Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent for adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis. Tax(1) is a 40-kDa phosphoprotein, predominantly localized in the nucleus of the host cell, which functions to transactivate both viral and cellular promoters. It seems likely that HTLV-1, through expression of the viral regulatory protein Tax(1), provides some initial alteration in cell metabolism predisposing the development of ATL.

New DNA enzyme targeting Egr-1 mRNA inhibits vascular smooth muscle proliferation and regrowth after injury.

Early growth response factor-1 (Egr-1) binds to the promoters of many genes whose products influence cell movement and replication in the artery wall. Here we targeted Egr-1 using a new class of DNA-based enzyme that specifically cleaved Egr-1 mRNA, blocked induction of Egr-1 protein, and inhibited cell proliferation and wound repair in culture. The DNA enzyme also inhibited Egr-1 induction and neointima formation after balloon injury to the rat carotid artery wall.

Vascular smooth muscle cells express the transcriptional corepressor NAB2 in response to injury.

The early growth response 1 (Egr-1 or NGFI-A) gene product is a zinc finger protein transcription factor which has been implicated in the regulation of genes differentially expressed during the development of vascular disease. Egr-1 activity is regulated by alterations in the amount of protein, as well as protein-protein interactions with positive and negative transcriptional cofactors. NGFI-A-binding protein 2 (NAB2) is an example of a negative transcriptional cofactor capable of binding directly to Egr-1 and repressing Egr-1-mediated transcription.

Vascular smooth muscle cell proliferation and regrowth after mechanical injury in vitro are Egr-1/NGFI-A-dependent.

Smooth muscle cell (SMC) proliferation is a key event in renarrowing of blood vessels after balloon angioplasty. Mechanical injury imparted to the arterial wall in experimental models induces the expression of the immediate-early gene, egr-1. Egr-1 binds to and activates expression from the proximal promoters of multiple genes whose products can, in turn, influence the vascular response to injury.

GC factor 2 represses platelet-derived growth factor A-chain gene transcription and is itself induced by arterial injury.

Platelet-derived growth factor (PDGF) is a mitogen and chemoattractant for a wide variety of cell types. The genes encoding PDGF A chain (PDGF-A) and PDGF B chain (PDGF-B) reside on separate chromosomes and are independently regulated at the level of transcription. Regulatory events underlying inducible PDGF-A expression have been the focus of much investigation.

Early growth response factor-1 induction by injury is triggered by release and paracrine activation by fibroblast growth factor-2.

Cell migration and proliferation that follows injury to the artery wall is preceded by signaling and transcriptional events that converge at the promoters of multiple genes whose products can influence formation of the neointima. Transcription factors, such as early growth response factor-1 (Egr-1), with nucleotide recognition elements in the promoters of many pathophysiologically relevant genes, are expressed at the endothelial wound edge within minutes of injury. The mechanisms underlying the inducible expression of Egr-1 in this setting are not clear.

Activation of the K-ras oncogene in colorectal neoplasms is associated with decreased apoptosis.

Background: Recent in vitro data indicate that the oncogenic effects of activated ras genes may be mediated, at least in part, through inhibition of apoptotic cell death. To examine this proposition in vivo, the relationship between mutations of the K-ras gene and the frequency of apoptosis was studied in a series of 69 sporadic colorectal neoplasms (11 adenomas and 58 carcinomas).

Methods: Mutations in codon 12 of K-ras were determined by a single tube, enriched polymerase chain reaction.

Detection of K-ras point mutation by enriched PCR-colorimetric plate assay.

Point mutations in the K-ras gene are frequently observed in a variety of human malignancies, including colorectal and pancreatic cancers. In this paper, we describe a sensitive procedure for the detection of point mutations of codon 12 of the K-ras gene. The assay employs a single-tube enriched PCR procedure, coupled to colorimetric detection.

In vitro activity of minimised hammerhead ribozymes.

A number of minimised hammerhead ribozymes (minizymes) which lack stem II have been kinetically characterised. These minizymes display optimal cleavage activity at temperatures around 37 degrees C. The cleavage reactions of the minizymes are first order in hydroxide ion concentration up to around pH 9.

A rapid PCR ELISA for the detection of activated K-ras in colorectal cancer.

Aims-To develop a rapid PCR ELISA procedure for the detection of mutations in K-ras in a microtitre plate format, and to evaluate the assay for the detection of these mutations in human colorectal cancer.Methods-An enriched PCR method was used with labelled primers, and PCR product was captured on GCN4 coated immunoassay plates. Detection of biotinylated mutant product was performed by colorimetric assay with streptavidin-horseradish peroxidase.

Sodium channel mutations in acetazolamide-responsive myotonia congenita, paramyotonia congenita, and hyperkalemic periodic paralysis.

Hyperkalemic periodic paralysis (hyperKPP) and paramyotonia congenita (PC) are genetic muscle disorders sharing the common features of myotonia and episodic weakness. In hyperKPP, patient symptoms and signs are worsened by elevated serum potassium, whereas in PC, muscle cooling exacerbates the condition. There are patients in whom features of both hyperKPP and PC are present.

Modified therapy with 5-fluorouracil, doxorubicin, and methotrexate in advanced gastric cancer.

Background: In an attempt to decrease the toxic effects of fluorouracil, doxorubicin, and methotrexate (FAMTX) by reducing the dose of methotrexate from 1500 mg/m2, according to the original regimen, to 1000 mg/m2, the authors designed the modified FAMTX treatment that was evaluated in a prospective Phase II-III randomized trial.

Methods: Patients with advanced gastric cancer were randomized to receive modified FAMTX treatment or supportive measures only (control group). In the middle of the study, the randomization was interrupted because of strong evidence of benefit in terms of tumor reduction and projected survival in the treatment arm receiving chemotherapy.

A ribozyme with DNA in the hybridising arms displays enhanced cleavage ability.

Hammerhead ribozymes cleave RNA substrates containing the UX sequence, where X = U, C or A, embedded within sequences which are complementary to the hybridising 'arms' of the ribozyme. In this study we have replaced the RNA in the hybridising arms of the ribozyme with DNA, and the resulting ribozyme is many times more active than its precursor. In turnover-kinetics experiments with a 13-mer RNA substrate, the kcat/Km ratios are 10 and 150 microM-1min-1 for the RNA- and DNA-armed ribozymes, respectively.

Structure and sequence of the rfb (O antigen) gene cluster of Salmonella serovar typhimurium (strain LT2).

The rfb gene cluster of Salmonella LT2 has been cloned and sequenced. The genes rfbA, rfbB, rfbD, rfbF, rfbG, rfbK, rfbM and rfbP were located individually and the gene rfbL was located outside the cluster. Approximately 16 open reading frames were found in the region which is essential for the expression of O antigen.

High level expression and purification of dthymidine diphospho-D-glucose 4,6-dehydratase (rfbB) from Salmonella serovar typhimurium LT2.

The rfbB gene (dThymidine-diphospho-D-glucose-4,6-dehydratase) from Salmonella serovar typhimurium LT2 was cloned and over-expressed using the T7 RNA polymerase/promoter system. The expressed protein, which represents almost 10% of the total cellular protein was purified 14-fold. dTDP-D-glucose 4,6-dehydratase is a homodimer of 43 kDa subunits, is highly specific for dTDP-D-glucose and shows a Km of 427 microM and Vmax of 0.

Lobular carcinoma in situ of the breast.

Lobular carcinoma in situ of the breast is a well defined pathologic entity which is found in about 2.5 per cent of all specimens of the breast taken for biopsy and most commonly occurs in premenopausal females. Its diagnosis is virtually always incidental due to the absence of any clinical indication of its presence.