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Biomedical subjects

G Peters

Publications and source records attributed to G Peters.

At least 145 records · Page 8Linked to original sources

Evidence for different modes of action of cyclin-dependent kinase inhibitors: p15 and p16 bind to kinases, p21 and p27 bind to cyclins.

A number of low molecular weight proteins have recently been identified that specifically inhibit the function of cyclin-dependent protein kinases in mammalian cells. These fall into two distinct families based on primary sequence comparisons and probable modes of action. Using a simple in vitro binding assay, we show that p21CDKN1 and the related p27KIP1 can efficiently interact with cyclins D1, D2, D3, E and A, and to a lesser extent with cyclin B. By generating a deleted form of cyclin D1 that binds to p21 and p27 but not to Cdks, we confirm that these interaction do not depend on stoichiometric amounts of the relevant kinase subunit. Moreover, p21 and p27 do not detectably associated with kinase subunits unless a cyclin is present. This is in sharp contrast to the properties of p16CDKN2 and p15MTS2/INK4b which bind to Cdk4 and Cdk6 in the absence of any cyclin. These data suggest that p21 and p27 act as broad spectrum regulators of cyclin dependent kinase function by participating in ternary complexes whereas the p16 family specifically interfere with the formation of cyclin D-dependent kinase complexes.

Carrier Proteins↗

Cyclin D1 protein analysis in the diagnosis of mantle cell lymphoma.

Mantle cell lymphoma (MCL) is a clinicopathologic entity that is difficult to diagnose on histopathologic criteria. Approximately 50% to 70% of MCL contain a t(11;14)(q13;q32) translocation involving the cyclin D1 gene. Irrespective of this rearrangement, almost all MCL show overexpression of the cyclin D1 gene at the mRNA level. Other B-cell non-Hodgkin's lymphomas (NHL) do not show this rearrangement or overexpression of cyclin D1. We developed an immunohistochemical assay to detect overexpression of the cyclin D1 protein on conventional formalin-fixed, paraffin-embedded biopsies using the well-defined monoclonal antibody DCS-6. Expression in tumor cells was compared with expression of cyclin D1 in endothelial cells and fibroblasts. An exclusively nuclear staining pattern was observed. Moreover, expression was directly compared with the expression observed by immunoblot analysis with the same antibody, as well as with mRNA expression and with the occurrence of genomic rearrangements within the BCL-1 locus. Of 13 MCL that were analyzed by immunohistochemistry and immunoblot, 12 showed overexpression with both techniques, whereas no overexpression was observed in 39 other NHL. Of 13 additional MCL studied either by immunohistochemistry or immunoblot, 11 also showed overexpression. Two lymphomas morphologically indistinguishable from MCL but with an aberrant immunophenotype (CD5 negative, CD10 positive) both lacked overexpression of cyclin D1. These results underscore the significance of overexpression of the cyclin D1 protein as a specific marker for MCL. Detection of cyclin D1 overexpression on formalin-fixed, paraffin-embedded tissues using the DCS-6 monoclonal antibody can be applied for routine diagnostic purposes.

Antibodies, Monoclonal↗

Complex structure and regulation of the P16 (MTS1) locus.

The p16 gene (P16, MTS1, CDKN2) encodes a negative regulator of the cell cycle. Molecular genetic techniques have been used to explore the role of p16 in normal development and cancer. Two transcripts derived from the p16 gene with distinct protein coding potentials are described. The previously undescribed transcript form has the same exons 2 and 3 as the p16-encoding mRNA but contains a different exon 1. The human p16 transcripts are detected in various tissues, and the ratio of the transcripts is regulated in both a tissue-specific and cell cycle-specific manner. The P16-derived mRNAs are probably generated from separate promoters, and transcription from one of the promoters appears to be regulated, at least in part, by the retinoblastoma gene product.

Base Sequence↗

Retinoblastoma-protein-dependent cell-cycle inhibition by the tumour suppressor p16.

D-type cyclins, in association with the cyclin-dependent kinases Cdk4 or Cdk6, promote progression through the G1 phase of the cell cycle by phosphorylating the retinoblastoma protein (RB). The activities of Cdk4 and Cdk6 are constrained by inhibitors such as p16, the product of the CDKN2 gene on human chromosome 9p21 (refs 12-14). The frequent deletion or mutation of CDKN2 in tumour cells suggests that p16 acts as a tumour suppressor. We show that wild-type p16 arrests normal diploid cells in late G1, whereas a tumour-associated mutant of p16 does not. Significantly, the ability of p16 to induce cell-cycle arrest is lost in cells lacking functional RB, including primary fibroblasts from Rb-/- mouse embryos. Thus, loss of p16, overexpression of D-cyclins and loss of RB have similar effects on G1 progression, and may represent a common pathway to tumorigenesis.

Animals↗

Cyclin D2 is a moderately oscillating nucleoprotein required for G1 phase progression in specific cell types.

To explore regulation and function of cyclin D2, a candidate cell cycle-regulatory proto-oncogene, we examined subcellular localisation, cell type- and cell cycle-dependent expression, and requirement of cyclin D2 protein for G1 progression, in a panel of 40 human normal and cancer cell types. Except for lymphoid cells and sarcoma cell lines, expression of cyclin D2 was considerably more restricted than that of cyclin D1, whereas both D-type cyclin proteins were low or undetectable in cells lacking functional retinoblastoma gene product. In G1 cells, the cyclin D2 protein was more resistant to extraction and localised predominantly to nuclei, whereas it became more soluble and distributed in both nuclei and cytoplasm from G1/S transition onwards. Centrifugal elutriation and multiparameter flow cytometry analyses of several cell types showed moderate cell cycle oscillation with maximum levels of the cyclin D2 protein reached in late G1. Microinjection and/or electroporation of antibodies to cyclin D2 during G1 arrested the cyclin D2-expressing lymphocytes, breast myoepithelium, and U-2-OS sarcoma cells in G1 phase, whereas cyclin D2-negative cell types were unaffected by such treatment. Consistent with the putative proto-oncogenic role of cyclin D2 in specific cell types, our data show that this G1 cyclin has properties closely resembling those of cyclin D1, including the essential positive role in regulation of G1.

Animals↗

Amplification of chromosome band 11q13 and a role for cyclin D1 in human breast cancer.

In this paper we describe how research on the mouse mammary tumor virus model of breast cancer resulted in the identification of an amplified region of DNA on human chromosome 11 band q13. This amplification occurs in approximately 15% of primary breast cancers. Several candidate oncogenes map within the amplicon but by analysing expression of these genes a strong case can be made for a role for cyclin D1 in tumorigenesis. Immunohistochemical staining indicates that cyclin D1 is expressed at elevated levels in around 40% of breast cancers, including those with the 11q13 amplification. The potential function of cyclin D1 as a regulator of early cell division cycle events would be consistent with a role in neoplasia.

Blotting, Southern↗

Lack of cyclin D-Cdk complexes in Rb-negative cells correlates with high levels of p16INK4/MTS1 tumour suppressor gene product.

D-type cyclins, in association with the cyclin-dependent kinases Cdk4 or Cdk6, regulate events in the G1 phase of the cell cycle and may contribute to the phosphorylation of the retinoblastoma gene product (Rb). However, in cells in which the function of Rb has been compromised, either by naturally arising mutations or through binding to proteins encoded by DNA tumour viruses, Cdk4 and Cdk6 are not associated with D cyclins. Instead, both kinases form binary complexes with a stable 16 kDa protein (p16) encoded by the putative tumour suppressor gene INK4/MTS1 on human chromosome 9p21. Here we show an inverse correlation between Rb status and the expression of p16. Since Rb-negative cells express high levels of p16, we suggest that in these cells p16 competes with D cyclins for binding to Cdk4 and Cdk6 and prevents formation of active complexes. In line with these predictions, DNA tumour virus oncoproteins do not disrupt cyclin D1-Cdk4 complexes in cells lacking p16.

Carrier Proteins↗

Genomic organization of the mouse cyclin D1 gene (Cyl-1).

To determine the genomic organization of the mouse cyclin D1 locus (Cyl-1), a series of cosmids and cDNAs were recovered by hybridization with a genomic probe representing the 5' end of the homologous human gene, CCND1. Primer extension indicated that transcripts originate from one of three adjacent nucleotides at a single start site. Two overlapping cDNA clones that essentially accounted for the complete sequence of the larger 4.0-kb Cyl-1 transcript were characterized. A combination of RNase protection and sequencing across intron-exon boundaries established that the gene is organized into five coding exons with a long 3' untranslated region. Repeated attempts to isolate clones corresponding to the minor 3.5-kb RNA were compromised by the presence of an internal poly(A) domain. However, hybridization with specific probes revealed that the minor transcript lacks approximately 800 nucleotides from the 3' end of the major transcript and may be generated by a novel mechanism or by RNA processing.

Amino Acid Sequence↗

Measurement of tissue viability using intravital microscopy and fluorescent nuclear dyes.

Intravital microscopy used with fluorescent vital stains provides the opportunity to measure the temporal and spatial extent of tissue injury following disease processes. However, this assumes that prolonged exposure to such dyes does not alter microvascular perfusion or cellular viability. To test this hypothesis, the extensor digitorum longus (EDL) muscle in 24 male Wistar rats, anesthetized with sodium pentobarbital (Somnotal, 65 mg/kg, ip), were prepared for microscopy. The EDL was either bathed continuously (n = 6) in Krebs solution containing bisbenzimide (5 micrograms/ml; labels nuclei of all cells) and ethidium bromide (5 micrograms/ml; labels nuclei of injured cells) or had dyes topically applied 1 hr (n = 4) and 4 hr (n = 4) following dissection of the muscle. Noxious stimuli (i.e., hypoxia:FiO2 of 8-10% (n = 3), 95% ethanol (n = 3), and 2 hr ischemia followed by 90 min reperfusion (n = 4) were used to test the ability of ethidium bromide, when used in conjunction with intravital microscopy, to differentiate injured tissue. Video recordings at the surface of the EDL muscle were made every 30 min for 5 hr from which the number of perfused capillaries was counted (NCper). The numbers of bisbenzimide- and ethidium bromide-labeled nuclei were counted at the surface of the muscle and at two to three additional locations within the muscle (to a maximum depth of approximately 120-160 microns). The average NCper (19.05 +/- 1.7) remained constant over 5 hr, while the number of nuclei stained by bisbenzimide increased linearly with time from an initial value of 1218 +/- 125.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Cyclin D1 as a cellular proto-oncogene.

Deregulated expression of cyclin D1 occurs in several types of human cancer. Since it often results from a specific chromosomal abnormality, this over-expression is likely to be significant in the development of the disease. Cyclin D1 is also implicated in virally induced tumors in mice and transgenic models based on ectopic expression if cyclin D1 recapitulate features of the naturally occurring tumors. By these criteria, as well as its effects in transfected rodent cells, cyclin D1 has the hallmarks of a cellular proto-oncogene. Although the normal role of cyclin D1 is not well understood, its oncogenic properties appear to involve functional interactions with cyclin-dependent kinases, the retinoblastoma gene product and the MTS1/p16 tumor suppressor gene.

Amino Acid Sequence↗

Chromosome 11q13 markers and D-type cyclins in breast cancer.

One in six primary human breast cancers has DNA amplification centered on the cyclin D1 gene (CCND1) on chromosome 11q13. This genetic abnormality is preferentially associated with estrogen-receptor positive tumors and may define a sub-class of patients with an adverse prognosis. Although CCND1 has the credentials of a cellular oncogene, being a target for chromosomal translocation and retroviral integration, the 11q13 amplicon encompasses several other markers and CCND1 is not the only candidate for the key gene on the amplified DNA. To assess their relative importance, we have constructed a physical map of the amplified DNA and compared the extent and frequency of amplification across the region. Since it is likely that the gene providing the selective force for amplification will be expressed at elevated levels, we have also examined expression of both RNA and protein. By these criteria, cyclin D1 remains the strongest candidate for the key oncogene on the amplicon and we are currently investigating the functional consequences of its over-expression.

Breast Neoplasms↗

[Lethal, non-menstrual toxic shock syndrome associated with Staphylococcus aureus sepsis].

We report a rare case of non-menstrual toxic shock syndrome (TSS) in the course of Staphylococcus aureus sepsis in a 31-year-old primigravida who developed high fever and severe pulmonary and cardiovascular failure within a few hours at the end of the 29th week of a twin pregnancy. Mechanical ventilation was necessary due to signs of adult respiratory distress syndrome (ARDS) and catecholamines were needed to maintain a somewhat adequate blood pressure. A forceps delivery was performed immediately. Postoperatively, the patient was brought to the intensive care unit (ICU) due to the suspicion of severe septic shock. In addition to the extreme cardiovascular instability and massive disturbance of pulmonary gas exchange, the clinical picture was characterised by a disseminated intravascular coagulopathy (DIC) with marked petechial bleeding and ecchymoses on all extremities. Moreover, a confluent, spotty exanthem of the trunk and extremities could be seen. Despite all therapeutic efforts, the patient died within a few hours after admission to the ICU with signs of multiorgan failure. Post-mortem, multiple staphylococcal abscesses were found in the kidneys, liver, and uterus. Moreover, acute ulcerous endocarditis of the mitral valve and septic myocardial foci with myocarditis were seen. The Staph. aureus strain isolated from the blood cultures was shown to produce TSS toxin 1 (TSST-1) and enterotoxin B. In summary, the clinical picture can be interpreted as severe staphylococcal sepsis complicated by TSS. TSS is a specific type of infectious disease, occurring mainly in young women during the menstrual period (80%-90%), but it has also been reported in non-menstrual cases (10%-20%). It is characterised by sudden-onset high fever, hypotension, rash, mucosal hyperaemia, and various additional symptoms such as myalgia, vomiting, and diarrhoea. The clinical course depends on the extent of the organ failure due to decreased tissue perfusion during hypotension. Severe cases are accompanied by multiple organ-system failure including impaired renal function, which is reversible in nearly all cases. Respiratory failure ranges from interstitial and alveolar aedema to ARDS in 10% of cases; severe DIC is seen in 10%-15%. Another severe clinical complication is cardiac insufficiency. The etiology of TSS is based on a localized or, rarely, systemic infection with certain Staph. aureus strains that are capable of producing toxins, the most important one being TSST-1. Staph. aureus strains can also produce various other enterotoxins that may be involved in the pathogenesis of TSS. The pathogenetic importance of the toxins is supported by the antibody titers in TSS patients: more than 80% of healthy adults show high levels of antibody titers, whereas 90% of TSS patients exhibit low levels in the acute phase followed by a significant increase during convalescence. It is not clear whether the toxins cause TSS by a direct effect or by release of mediators due to their function as superantigens. The clinical characteristics of non-menstrual TSS are identical to those of menstrual TSS, but it can occur in many clinical settings in both sexes at any age. Severe clinical courses are more frequent in non-menstrual TSS: the mortality is about 8%-11% in non-menstrual TSS compared to 2%-5% in menstrual TSS. The diagnosis is based mainly on clinical signs and the isolation of toxin-producing Staph. aureus strains. Besides antibiotic therapy, treatment is primarily directed to the correction of hypotension and additional organ-system failure. Other therapeutic measures such as the elimination of toxins by plasma separation or the administration of antibodies or gamma-globulins are subjects of investigation with no general recommendations at this time.

Adult↗

Methicillin-resistant Staphylococcus haemolyticus on the hands of health care workers: a route of transmission or a source?

We undertook a cross-sectional study of hand carriage and environmental contamination of methicillin-resistant coagulase-negative staphylococci on three wards of a single subspeciality surgical service. Sixteen hand cultures from 15 health care workers and 32 environmental cultures were obtained. Of 49 isolates, 35 (72%) were Staphylococcus haemolyticus. This species comprised 14 of the 16 (87%) hand isolates and 21 of the 32 (66%) environmental isolates. Using restriction length polymorphism of total DNA, we identified a single clone of S. haemolyticus on the hands of four health care workers and in the environment at seven locations on two wards. The widespread dissemination of a single clone suggests transmission of S. haemolyticus on the wards and prompts further prospective studies.

Carrier State↗

In-vitro activity of three fluoroquinolones, cefotaxime and clindamycin against staphylococci.

The in-vitro activity of three fluoroquinolones (ciprofloxacin, ofloxacin, temafloxacin) against 200 well-defined clinical isolates of staphylococci was investigated. The in-vitro activity of the fluoroquinolones tested was equal, with a strong indication of cross resistance. A clear distribution over two populations of different quinolone susceptibility--"naturally susceptible" and "naturally resistant" strains--could be found in penicillin-resistant, methicillin-susceptible Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus haemolyticus.

Aminoglycosides↗

Cytotoxic T-lymphocyte induction in asymptomatic HIV-1-infected patients immunized with Retrovector-transduced autologous fibroblasts expressing HIV-1IIIB Env/Rev proteins.

OBJECTIVE: To demonstrate the safety and enhancement of HIV-1-specific immune responses in HIV-infected asymptomatic patients following treatment with retroviral vector (Retrovector)-transduced autologous fibroblasts (VTAF) expressing HIV-1IIIB Env/Rev proteins. DESIGN: A non-placebo-controlled, single arm Phase I study. PARTICIPANTS: Four HIV-1-seropositive asymptomatic volunteers were selected based on age (18-50 years), CD4/CD3 lymphocyte counts (> 600 x 10(6)/l or > 40%), and positive delayed-type hypersensitivity test to at least one recall antigen. INTERVENTIONS: Patients were treated at 2-week intervals with a total of three intramuscular injections of irradiated autologous fibroblasts transduced with a molecularly engineered, non-replicating amphotropic murine retrovector encoding the HIV-1IIIB Env/Rev proteins. MAIN OUTCOME MEASURES: The clinical status of patients was assessed by history, physical examination, serum chemistry and hematology, CD4/CD3 lymphocyte counts, HIV viral burden, and monitored throughout the study to detect potentially treatment-induced toxic or unwanted side-effects. In addition, HIV-1-specific cytotoxic T-lymphocyte (CTL) activity was measured to determine the biological activity of VTAF. RESULTS: No acute local or systemic adverse events occurred following three injections with VTAF. Furthermore, a statistically significant increase of CD8+ CTL activity against HIV-1IIIB Env/Rev-expressing targets was observed in peripheral blood mononuclear cells from two out of four patients. CONCLUSIONS: This is the first report of the administration of a gene transfer treatment to HIV-1-infected patients and provides initial support for the safety and activity of retrovector-transduced fibroblasts administered to asymptomatic patients. This treatment resulted in the detection of increased HIV-1IIIB Env/Rev-specific CTL activity in two HIV-seropositive patients and could provide a better understanding of the role of CTL activity in HIV disease progression.

AIDS Vaccines↗

Antimicrobial susceptibilities of Stomatococcus mucilaginosus and of Micrococcus spp.

The in vitro susceptibilities of 63 isolates of Stomatococcus mucilaginosus and of 188 isolates of Micrococcus spp. to 18 antimicrobial agents were determined by the agar dilution method. Many beta-lactams, imipenem, rifampin, and the glycopeptides were shown to be active in vitro against Stomatococcus and Micrococcus isolates, whereas the activities of antibiotics such as some aminoglycosides, erythromycin, and fosfomycin against an important number of these microorganisms are limited.

Anti-Bacterial Agents↗

Expression of cyclin D2 in Epstein-Barr virus-positive Burkitt's lymphoma cell lines is related to methylation status of the gene.

The cyclin D2 gene is not expressed in resting primary B lymphocytes or in group I Burkitt's lymphoma (BL) cell lines that retain the characteristics of authentic BL cells. Expression of cyclin D2 is induced in primary B lymphocytes following infection with Epstein-Barr virus (EBV) or transfection of the EBV genes EBNA-LP and EBNA-2. However, attempts to induce cyclin D2 expression in BL cell lines by the enforced expression of EBV genes were unsuccessful. Since the demethylation agent 5-azacytidine has been shown to modulate viral gene expression in BL cells, we explored the possibility that methylation plays a significant role in the control of cyclin D2 expression. We show that 5-azacytidine treatment of the Mutu CI 179 BL cell line led to expression of cyclin D2 RNA and that expression correlated with differences in the methylation status of a CCGG restriction enzyme site near the transcription initiation region of the cyclin D2 gene. Thus, methylation appears to play a direct role in the regulation of the cyclin D2 locus in BL.

Antigens, Viral↗

Prevention of intraoperative contamination from large ulcerative cutaneous lesions.

A method for managing head and neck malignancies with cutaneous ulceration prior to excision is described. At our institution all lesions with cutaneous extension and erosion have been treated in this manner prior to excision. The exact number of treated cases, however, is unknown, since this number is not placed in the medical record. Although the risk of tumor "take" resulting from the spillage or implantation of tumor cells from an ulcerated lesion is probably small, the previously described technique is simple and inexpensive and should be employed as a precautionary measure to further minimize this risk.

Cellulose, Oxidized↗