PubMed Health⌕ Search

Biomedical subjects

L de Leij

Publications and source records attributed to L de Leij.

At least 73 records · Page 4Linked to original sources
PubMed1988

Monoclonal Antibodies to the Cell-Wall-Associated Proteinase of Lactococcus lactis subsp. cremoris Wg2.

Twelve monoclonal antibodies directed to the cell-wall-associated proteinase of Lactococcus lactis subsp. cremoris Wg2 were isolated after immunization of BALB/c mice with a partially purified preparation of the proteinase. The monoclonal antibodies reacted with the 126-kilodalton proteinase band in a Western immunoblot. All but one of the monoclonal antibodies reacted with protein bands with a molecular weight below 126,000, possibly degradation products of the proteinase. The monoclonal antibodies could be divided into six groups according to their different reactions with the proteinase degradation products in the Western blot. Different groups of monoclonal antibodies reacted with different components of the L. lactis subsp. cremoris Wg2 proteinase. Crossed immunoelectrophoresis showed that monoclonal antibody groups I, II, and III react with proteinase component A and that groups IV, V, and VI react with proteinase component B. The isolated monoclonal antibodies cross-reacted with the proteinases of other L. lactis subspecies. Monoclonal antibodies of group IV cross-reacted with proteinase component C of other L. lactis subsp. cremoris strains. The molecular weight of the proteinase attached to the cells of L. lactis subsp. cremoris Wg2 was 200,000, which is different from the previously reported values. This could be analyzed by immunodetection of the proteinase on a Western blot. This value corresponds to the molecular weight calculated from the amino acid sequence of the cloned L. lactis subsp. cremoris Wg2 proteinase gene.

Journal Article↗
PubMed1988

Detection of small cell lung cancer metastases in bone marrow aspirates using monoclonal antibody directed against neuroendocrine differentiation antigen.

To detect metastases in the bone marrow of patients with small cell lung cancer, immunofluorescence with a monoclonal antibody detecting a membrane antigen (MOC-1) associated with small cell lung cancer was performed on 53 bone marrow aspirates from 30 patients. In 19 (63%) patients MOC-1 reactive cells were detected. Simultaneous histopathological examination of the bone marrow biopsy specimens detected tumour cells in only six (20%). The method is more sensitive than conventional histochemical staining of bone marrow aspirate and may eventually be able to show additional subgroups, such as patients with limited disease who might benefit from adjuvant radiotherapy or surgery.

Antibodies, Monoclonal↗
PubMed1987

Monoclonal antibodies in lung cancer pathology.

Monoclonal antibody based immunohistochemistry is a very powerful tool for the establishment of a pathological diagnosis of lung cancer. Applying a panel of intermediate filament antisera and an antibody recognizing neuroendocrine differentiation we have tested about 240 human lung tumors and 15 human lung tumor cell lines. Our results can be summarized as follows: a differential diagnosis between neuroendocrine and non-neuroendocrine lung tumors can be obtained by the application of the monoclonal antibody MOC-1 directed against neuroendocrine antigens. Immunohistochemistry can lead to a better recognition of lung tumor heterogeneity within the established histologies. Examples of this phenomenon are: the presence of neuroendocrine and/or neural components within non-neuroendocrine tumors. The presence of squamous cell or adenocarcinomatous differentiation in non-SCLC can be detected by chain specific anti-cytokeratin antibodies. The degree of differentiation towards the variant type within SCLC can be detected by the monoclonal antibody directed against neurofilaments. lung cancer cell lines can serve as an in vitro model for immunohistochemical studies on different lung cancer subtypes.

Adenocarcinoma↗
PubMed1987

Small cell lung cancer.

It can be stated that, depending on the type of lung cancer, the best opportunity for curative treatment is in the early stage of disease, when cancer is limited to the lung and surgical intervention can be indicated. Especially in the case of SCLC, the number of patients presenting with such a limited disease is very low. In SCLC, chemo- and/or radiotherapy can induce initial good responses, which, although not curative in most cases, can elongate life for an average of 10 months. Although changes and refinements in treatment are continuously introduced, further progresses in the outcome have not achieved for the last decennium. Therefore, more fundamental research is needed to indicate new treatment avenues. A number of findings appear promising in this field. Firstly, the development of tissue culture techniques has enabled a better study of the biological properties of both SCLC and non-SCLC. Secondly, the development of monoclonal antibodies has refined the possibilities to type lung cancer. Particularly if monoclonal antibodies could be identified which occurrence turns out to be relevant to prognosis, immunohistopathology could become an important additional tool for the assessment of a pathological diagnosis in lung cancer. In addition, monoclonal antibodies which are specific for lung cancer could be used for an immunotherapeutical approach in the near future. Such a treatment might complement currently available treatment modalities.

Carcinoma, Small Cell↗
PubMed1987

Genome analysis of small cell lung cancer (SCLC) and clinical significance.

A chromosome analysis of three cell lines derived from SCLC showed deletions of the short arm of chromosome 3 with bands p21-p23 as the shortest region of overlap. Hybridization of a polymorphic 3p21 probe to DNA from leukocytes of seven SCLC patients revealed heterozygosity for two of them. In the tumours of both these patients the probe detected homozygosity. This suggests the presence of a mutant cancer gene in the short arm of chromosome 3 which might express itself and/or activate some oncogene(s) after deletion of a suppressing normal allele. Amplification of the oncogene C-MYC was found in four cell lines including the ones cytogenetically analyzed. Amplification of C-MYC, though to a lesser degree, was also found in an available pleural effusate from which one of these lines had been established. As shown by in situ hybridization, the amplified oncogene was present in double minutes in three of the cell lines. In the remaining line it was in a homogeneously staining chromosome region. All patients from whom cell lines with C-MYC amplification were obtained had a negative response to chemotherapy. The observed correlation between amplification of C-MYC, occurrence of so-called variant type SCLC-derived cell lines, and negative response to chemotherapy indicates that a genome analysis of SCLC might provide further criteria for the characterization and subdivision of this highly malignant cancer and thereby a base for an optimal selection of therapy for distinct cases of SCLC.

Carcinoma, Small Cell↗
PubMed1986

Inhibition of mitochondrial protein synthesis leads to proliferation arrest in the G1-phase of the cell cycle.

Mitochondrial protein synthesis is specifically inhibited by low concentrations of tetracyclines. Prolonged inhibition of mitochondrial protein synthesis leads to a lack of oxidative ATP generating capacity, which results in proliferation arrest of normal and malignant cells of epithelial origin, as has been shown previously. The present study indicates that this holds true also for fibroblasts and sarcoma cells. It is shown that this proliferation arrest leads to accumulation of the growth-arrested cells in the G1-phase of the cell cycle. This offers several interesting possibilities to use tetracyclines in anticancer combination therapies.

Animals↗
PubMed1985

Identical chromosome translocations involving the region of the c-myb oncogene in four metastases of a mediastinal teratocarcinoma.

A 39-year-old white male presented with a disseminated mediastinal teratocarcinoma. Karyotyping was performed on two mature residual metastatic lesions in the lungs immediately following chemotherapy, on a recurring lung lesion after 5 months, and on a metastasis in the right thigh 5 months after salvage chemotherapy. All four lesions were pseudoeuploid and showed identical chromosomal abnormalities: a translocation with the two chromosomes #6 and one chromosome #11 involved, resulting in 46, XY, t (6;6;11) (q21;q23;q13). The breakpoint in chromosome #6 is in the region to which the oncogene c-myb has been localized, and the breakpoint in chromosome #11 is at a known fragile and possibly oncogenic site, suggesting that the translocations in this case may have played a crucial role in the development of the malignancy.

Adult↗
PubMed1985

Neuroendocrine differentiation antigen on human lung carcinoma and Kulchitski cells.

In the normal lung, a subset of cells with a histological appearance consistent with that of Kulchitski cells are the only lung cells reacting with a monoclonal antibody (MOC-1) raised against a human small cell lung carcinoma-derived cell line. Outside the lung, a subset of normal endocrine cells (in the adrenal, thyroid, ovary, and pancreas) as well as neural cells (brain and peripheral Schwann cells) also express the antigen detected by MOC-1 (named MOC-1-related antigen). Some of these positively reacting cells are ectodermally derived, whereas others are of proven endodermal origin, indicating that the MOC-1-related antigen is not a cell lineage-specific antigen. Instead, the common expression of the antigen by cells with a neural, endocrine, or neuroendocrine function suggests that the antigen related to a neuroendocrine differentiation state of these cells. The presence of the MOC-1-related antigen on several non-lung tumors mostly paralleled its normal tissue distribution, indicating that the antigen is generally retained upon malignant transformation. In lung carcinoma, the antigen proves to be present on almost all small cell carcinomas tested. In addition, adenocarcinoma and mixed adenosquamous carcinoma could also express the antigen, whereas pure squamous cell carcinoma generally did not. This finding will be discussed in relation to a proposed "common stem cell" histogenesis of lung carcinoma.

APUD Cells↗
PubMed1985

Characterization of three new variant type cell lines derived from small cell carcinoma of the lung.

Three new, well growing cell lines (GLC-1, GLC-2, and GLC-3) have been established from small cell lung carcinoma (SCLC) and characterized. A subclone (GLC-1-M13) markedly different from its parent line GLC-1 was also isolated and characterized. Cytogenetic analysis of the cell lines revealed deletions in the short arm of chromosome 3 as a most consistent chromosomal aberration. The deleted region was not identical in all metaphases, 3p(21-23) being the shortest region of overlap. Despite their SCLC origin GLC-1, GLC-2, and GLC-3 do not show pronounced SCLC differentiation features. Neurosecretory granula were very rare (GLC-1) or completely absent (GLC-2 and GLC-3), whereas the SCLC-related enzyme and hormone markers L-3,4-dihydroxyphenylalanine decarboxylase, neuron-specific enolase, creatine kinase BB, and bombesin-like immunoreactivity were variably expressed. Although the subclone GLC-1-M13 was derived from the poorly differentiated GLC-1, it behaved according to the above criteria as a differentiated "classic" SCLC cell line. When assessed with specific monoclonal antibodies the different cell lines appeared to express different subsets of intermediate filament proteins, indicative for different stages and directions of differentiation: "undifferentiated" (GLC-1 and GLC-2); "neural tissue related" (GLC-2); "simple epithelium" related (GLC-1-M13); and a combination of simple and squamous epithelium related (GLC-3). We conclude that GLC-1, GLC-2, and GLC-3 represent dedifferentiated forms of SCLC, related to the recently described "variant" type of SCLC, whereas the clonal derivate GLC-1-M13 behaves like a differentiated "classic" SCLC cell line.

Carcinoma, Small Cell↗
PubMed1984

Immunoperoxidase staining on frozen tissue sections as a first screening assay in the preparation of monoclonal antibodies directed against small cell carcinoma of the lung.

To prepare monoclonal antibodies against small cell carcinoma of the lung (SCCL), we have used an SCCL-derived cell line as immunogen. A first screening of hybridoma supernatants was performed on frozen tissue sections of a biopsy with histologically proven SCCL involvement. Screening on tissue sections is a valuable technique, especially for the isolation of monoclonal antibodies directed against tumor antigens. A drawback of this procedure is that it is laborious. To circumvent this, we have reduced the number of supernatants to be screened by increasing the number of seeded hybridomas per well. Although this resulted in the growth of 5-20 hybridomas per well, among which there was always at least one that secreted antibodies against 'common antigens', clones that secreted specific antibodies could still be revealed by testing supernatants which were preabsorbed with thrombocytes. This has resulted in the isolation of 7 monoclonal antibodies directed against SCCL associated antigens.

Antibodies, Monoclonal↗
PubMed1983

In situ analysis of the mononuclear cell infiltrate in primary malignant melanoma of the skin.

Monoclonal antibodies, directed against functionally different lymphocyte subsets, were applied on frozen sections of primary malignant melanomas and benign nevi. Positive reaction was identified by means of an immunoperoxidase method. It was found that lymphocytic infiltrate underneath and in between malignant melanoma is composed of approximately equal numbers of OKT4 positive helper and OKT8 positive suppressor/cytotoxic T cells. The majority of these lymphocytes also expressed HLA-Dr antigen, indicating an activated state. In addition HLA-Dr, OKT6 positive dendritic cells were present in the infiltrate and between the melanoma cells. Finally, melanoma cells expressed demonstrable amounts of HLA A, B, C antigens, whereas benign nevi did not. It is concluded that all ingredients for a successful immune reaction against primary malignant melanoma are on hand. This finding is in agreement with the relatively frequent occurrence of partial or even complete regression of primary malignant melanoma of the skin.

Antibodies, Monoclonal↗
PubMed1979

Nature of the regions involved in the insertion of newly synthesized protein into the outer membrane of Escherichia coli.

Outer membrane proteins are synthesized by cytoplasmic membrane-bound polysomes, and inserted at insertion sites which cover about 10% of the total outer membrane when cells grow with a generation time of 1 h. A membrane fraction enriched in outer membrane insertion regions was isolated and partly characterized. The rat at which newly inserted proteins are transferred from such insertion regions into the rest of the outer membrane was found to be very fast; the new protein content of insertion regions and that of the remaining outer membrane equilibrate completely within about 20 s at 25 degrees C. Given the rather rigid structure of the outer membrane and the multiple interactions between outer membrane components and the murein layer, lateral diffusion of newly inserted proteins from insertion sites to the remaining outer membrane is not likely to explain this rapid equilibration. Instead, the data support a model in which insertion regions move along the cell surface, leaving behind stationary, newly inserted outer membrane proteins.

Bacterial Proteins↗
PubMed1978

Insertion of newly synthesized proteins into the outer membrane of Escherichia coli.

The insertion of newly synthesized proteins into the outer membrane of Escherichia coli has been examined. The results show that there is no precurser pool of outer membrane proteins in the cytoplasmic membrane because first, the incorporation of a [35S]methionine pulse into outer membrane proteins completely parallels its incorporation into cytoplasmic membrane proteins, and second, under optimal isolation conditions, no outer membrane proteins are found in the cytoplasmic membrane, even when the membranes are analysed after being labeled for only 15 s. The [35S]methionine present in the outer membrane after a pulse of 15 s was found in protein fragments of varying sizes rather than in specific outer membrane proteins. This label could however be chased into specific proteins within 30--120 s, depending on the size of the protein, indicating that although unfinished protein fragments were present in the outer membrane, they were completed by subsequent chain elongation. Thus, outer membrane proteins are inserted into the outer membrane while still attached to ribosomes. Since ribosomes which are linked to the cell envelope by nascent polypeptide chains are stationary, the mRNA which is being translated by these ribosomes moves along the inner cell surface.

Bacterial Proteins↗
PubMed1976

Release of outer membrane fragments from normally growing Escherichia coli.

A complex containing lipopolysaccharides, phospholipids and proteine separated from the medium by gelfiltration on Sephadex G-200 or by centrifugation. Electron microscopy revealed that this material is released as vesicles and membrane fragements. To determine the origin of these fragments, they were compared to outer and cytoplasmic membranes with respect to keto-deoxyoctulosonic acid, phospholipid, and protein content, phospholipid composition, fatty acid composition, protein distribution on sodium dodecyl sulfate-polyacrylamide gels, buoyant density, and content of several membrane marker enzymes. The results of this comparison indicate that the membrane fragments found in the culture supernatant of normally growing Escherichia coli consist of practically unmodified outer membrane. Possible mechanisms as to the cause of the release of outer membrane fragments, and its relationship to cell-division, are discussed.

Bacterial Proteins↗
PubMedDate not supplied

Serum as a modulator of lipoplex-mediated gene transfection: dependence of amphiphile, cell type and complex stability.

BACKGROUND: Cationic liposomes belong to the family of non-viral vectors for gene delivery. Despite several drawbacks, such as low efficiency compared to viruses and inactivation by serum, cationic liposomes remain a promising tool for gene therapy. Therefore further investigation of the mechanism of transfection and improvement of formulations are warranted. METHOD: In a comparative study, we investigated the effect of serum on the ability of SAINT, a novel synthetic amphiphile, and Lipofectin to mediate transfection in vitro, employing a variety of cell lines. RESULTS: In all cell types, SAINT-mediated transfection was not significantly affected by the presence of serum, in contrast to Lipofectin-mediated transfection. Intriguingly, the extent of complex association was enhanced in the presence of serum, while cell association of the Lipofectin complex was approximately two-fold higher than that of SAINT. These data imply that transfection efficiency and the amount of cell-associated complex are not related. However, when the helper lipid dioleoylphosphatidylethanolamine (DOPE) was substituted for cholesterol, SAINT-mediated transfection was reduced in the presence of serum. This indicates that lipoplex composition rather than the cationic lipid per se codetermines the effect of serum. Also, the presence of serum decreased cytotoxicity, while no correlation could be demonstrated between toxicity and transfection efficiency. The binding of serum proteins to either complex was identical, both in terms of protein identity and relative amounts. CONCLUSION: We propose that serum, in conjunction with cell-specific factors and lipoplex composition, determines complex (in)stability, which is crucial for effective gene delivery and expression.

Animals↗