Search PubMed⌕ Search

Biomedical subjects

J Pohl

Publications and source records attributed to J Pohl.

At least 127 records · Page 7Linked to original sources
PubMed1990

Disulfide bridges of bovine spleen cathepsin B.

Bovine spleen cathepsin B contains 7 disulfide bridges. Cleavage of the enzyme with cyanogen bromide gives rise to a large and a small fragment. The former contains all disulfide bridges. Their arrangement was determined by analysis of amino-acid sequences and compositions of subfragments prepared by cleavage of the large cyanogen-bromide fragment with trypsin, chymotrypsin and the staphylococcal proteinase using specific methods for the detection of S-S-bonds. Disulfide bridges link together Cys14-Cys43, Cys26-Cys71, Cys62-Cys128, Cys63-Cys67, Cys100-Cys132, Cys108-Cys119 and Cys148-Cys252.

Amino Acid Sequence↗
PubMed1989

The neuron-specific protein PGP 9.5 is a ubiquitin carboxyl-terminal hydrolase.

A complementary DNA (cDNA) for ubiquitin carboxyl-terminal hydrolase isozyme L3 was cloned from human B cells. The cDNA encodes a protein of 230 amino acids with a molecular mass of 26.182 daltons. The human protein is very similar to the bovine homolog, with only three amino acids differing in over 100 residues compared. The amino acid sequence deduced from the cDNA was 54% identical to that of the neuron-specific protein PGP 9.5. Purification of bovine PGP 9.5 confirmed that it is also a ubiquitin carboxyl-terminal hydrolase. These results suggest that a family of such related proteins exists and that their expression is tissue-specific.

Amino Acid Sequence↗
PubMed1989

Augmentation of host antitumor immunity by low doses of cyclophosphamide and mafosfamide in two animal tumor models.

By cloning in vitro we have obtained two sublines of the L5222 rat leukemia, one with high (L5222-S) and the other with low (L5222-R) in vivo sensitivities to non-toxic doses of mafosfamide, a stabilized derivative of 4-hydroxy-cyclophosphamide. This sensitivity in vivo was not related to the cytotoxic activity of the drug in vitro. Treatment of rats bearing the L5222-S and of mice transplanted with the MOPC-315 plasmocytoma with low doses of mafosfamide or cyclophosphamide resulted in a high percentage of surviving animals, which were resistant to a subsequent tumor challenge. Viable leukemic cells were needed to establish antitumor immunity, since it was not possible to induce resistance by injection of mitomycin-C-treated, non-viable L5222 cells. The adoptive transfer of spleen cells from animals immune against the L5222-S and the MOPC-315 resulted in resistance of the syngeneic recipients against a rechallenge with tumor cells, provided that the animals were treated with an immunosuppressive dose (100 mg/kg) of cyclophosphamide prior to the spleen cell implantation. In nude mice treatment of the L5222 with low doses of mafosfamide also resulted in surviving animals, however resistance to a second tumor challenge occurred only sporadically. The data presented confirm that therapy with cyclophosphamide or mafosfamide enhances host antitumor immunity but, contrary to previous reports, it could be demonstrated that successful tumor rejection was independent of T cells.

Adjuvants, Immunologic↗
PubMed1989

Induction of urokinase activity and malignant phenotype in bladder carcinoma cells after transfection of the activated Ha-ras oncogene.

In order to characterize further the previously observed induction of a highly metastatic phenotype in mouse bladder carcinoma cells by Ha-ras transfection, we studied production of plasminogen activator, in vitro invasiveness, and the potential for lung colonization of these cells. The parent carcinoma cells produced predominantly tissue-type plasminogen activator. Out of 13 clones of ras-transfected cells tested, 8 secreted quantitatively elevated levels of plasminogen activator (up to 3.5-fold) as compared to the control transfectants. The plasminogen activator activity in cell lysates was maximally increased 3-fold, the surface-associated activity increased 2.5-fold. The secreted plasminogen activator of cloned ras-transfected cells was characterized to be predominantly of the urokinase type (71.3% compared to 20.5% with the parental BL cells). Thus, in addition to the quantitative augmentation of plasminogen activator production and secretion in a large fraction of the ras-transfected cell population, a significant qualitative shift from tissue-type to urokinase-type has been observed. In addition, ras-transfection augmented the capacity of the cells for invasion into Matrigel in a double-filter in vitro assay as well as their ability to colonize the lungs of syngeneic animals. These malignant properties of the transfected cells might be responsible for their highly metastatic behaviour induced by ras transfection.

Animals↗
PubMed1989

Induction of the metastatic phenotype by transfection of the nuclear oncogene p53: increases in cytoplasmic diacylglycerol levels and reduction in class I major histocompatibility antigen expression are not sufficient to explain the changes in metastatic capacities.

Transfection of the oncogene encoding the nuclear protein p53 into a low-metastatic mouse carcinoma cell line resulted in enhanced metastatic capabilities in clones that showed increased p53 protein expression [Pohl J, Goldfinger N, Radler-Pohl A, Rotter V, Schirrmacher V (1988) Mol Cell Biol 8:2078-2081]. This effect seemed neither to be due to increase in cytoplasmic diacylglycerol levels nor to reduced cell-surface expression of class I major histocompatibility antigens.

Animals↗
PubMed1989

Experimental investigations into the carcinogenic effect of antitumor and immunosuppressive agents.

In a comprehensive experimental study on rats, the carcinogenicity of various therapeutically important antitumor drugs was investigated. The influences of strain, sex, dose and time of administration were systematically varied. The tested compounds showed remarkable differences in their carcinogenic potential. These differences were particularly obvious, not only when the total tumor rate was analyzed, but also when the distribution of tumor rates to the various localizations was considered (tumor spectrum). Three classes of carcinogenic substances were identified: (1) Substances showing a specific carcinogenicity: they lead to tumorogenesis primarily in organs or organ systems that, in the untreated control animals, remain virtually tumor-free for life. One example of such a substance is chlormethine. (2) Substances with non-specific carcinogenicity: they lead to an increase in tumors in organs that are also stricken in the control animals, however, to a clearly reduced extent. Oxazaphosphorine carcinogenicity is typical for this class. (3) Substances of mixed-type carcinogenicity: this group shows non-specific carcinogenicity, as well as a carcinogenic action with marked organ specificity. One example of this class is procarbazine. The antimetabolites tested were shown to be practically non-carcinogenic. Characteristic differences occurred between the two rat strains used in the investigation, Sprague-Dawley and BD II, with regard to the spontaneous tumor spectrum and the organ-related extent of carcinogenicity under the influence of the substances tested. In an experiment involving short-term application (up to 17% LD50, five times i.v. at 14-day intervals), the carcinogenic effects were substantially lower than in an experiment involving long-term application (up to 7% LD50, once a week for 52 weeks, i.v.), although the strain- and substance-specific characteristics in both experiments were rather similar.

Animals↗
PubMed1989

[Assessing the extent of gynecologic tumors by a sonographic tumor score with special reference to ovarian cancer].

Ultrasonic findings in 1317 operatively confirmed gynecological tumors were classified according to five degrees of homogeneity: I, clearly outlined solitary cysts; II, clearly outlined homogeneous tumors; III, poorly defined or slightly heterogeneous tumors; IV, marked heterogeneous tumors; V, completely heterogeneous tumors. In the different groups, the rates of malignancy were: I, 0.9%, II, 1.9%; III, 17%; IV, 58%; and V, 75%. In a further study 1082 patients with a negative or doubtful result of the physical examination were investigated using ultrasound. Abnormal findings in 126 cases were able to detect 8 carcinomas, 25 kystomas, and 63 other tumors.

Female↗
PubMed1989

Chloroacetaldehyde and its contribution to urotoxicity during treatment with cyclophosphamide or ifosfamide. An experimental study/short communication.

Based on clinical data, indicating that chloroacetaldehyde (CAA) is an important metabolite of oxazaphosphorine cytostatics, an experimental study was carried out in order to elucidate the role of CAA in the development of hemorrhagic cystitis. The data demonstrate that CAA after i.v. administration does not contribute to bladder damage. When instilled directly into the bladder, CAA exerts urotoxic effects, it is, however, susceptible to detoxification with mesna.

Acetaldehyde↗
PubMed1988

Amino acid sequence of bovine spleen cathepsin B.

The complete amino acid sequence of bovine spleen cathepsin B was determined by manual and automatic Edman degradation of fragments prepared by proteolytic or chemical digestion of the enzyme. The single-chain form of the enzyme consists of 253 amino acid residues and its Mr is 27,468 (carbohydrate moiety not included). The light chain (residues 1-47) and the heavy chain (residues 50-253) of the enzyme are linked by the sequence -Gly-Arg (residues 48 and 49) in the single-chain form. Bovine spleen cathepsin B shows 80% sequence homology with cathepsins B from other species. An outstanding feature of bovine spleen cathepsin B not observed with the other cathepsins B is the presence of two additional half-cystine residues.

Amino Acid Sequence↗
PubMed1988

Secondary enzyme-substrate interactions: kinetic evidence for ionic interactions between substrate side chains and the pepsin active site.

The possibility that pig pepsin has a cation binding specificity in its secondary binding subsites has been examined by the pepsin-catalyzed hydrolysis of a series of synthetic octa- to undecapeptide substrates. These chromophoric substrates are cleaved by pepsin in the phenylalanyl-p-nitrophenylalanyl (Phe-Nph) bond. Lys and Arg residues were placed into seven different positions in the substrates, and their effect on kcat and Km was examined between pH 2.8 and pH 5.8 (I = 0.1 M, 37 degrees C). Kinetic evidence indicates the existence in the enzyme binding subsites S4, S3, S2, S3', S4', and S5' of a group(s) which become(s) negatively charged at higher pH. For most substrates, the magnitude as well as the pH dependence of kcat was unaffected by the presence of Lys or Arg in these peptides. In contrast, changes up to 5 orders of magnitude were observed for Km, depending on the number of basic residues and on their positions in the sequence. Km for a group of substrates at pH greater than 5.5 was lower than 50 nM. Values for kcat/Km for some substrates exceed the level of 10(8) M-1 s-1. Therefore, the free energy derived from ionic interactions in secondary binding sites influences mostly the binding step on the reaction pathway. This result is in contrast to the previous observations that the length and the hydrophobic character of the substrate residues in some positions influence kcat with little effect on Km toward shorter substrates of pepsin [Fruton, J. (1976) Adv. Enzymol. Relat. Areas Mol. Biol. 44, 1-36].

Amino Acid Sequence↗
PubMed1988

Selective enhancement of metastatic capacity in mouse bladder carcinoma cells after transfection with DNA from liver metastases of human colon carcinoma.

To identify sequences associated with a metastatic phenotype, DNA fragments isolated from 2 separate human colon carcinoma metastases were transfected into a mouse bladder carcinoma cell line together with the neoR gene as selectable marker. It was found that bulk populations of neomycin resistant cells carrying these human sequences caused more metastases in syngeneic mice than did control cells transfected with calf thymus DNA. Cells isolated from metastases retained the highly metastatic phenotype when transferred to secondary hosts.

Animals↗
PubMed1988

A model to account for the effects of oncogenes, TPA, and retinoic acid on the regulation of genes involved in metastasis.

We have postulated that signals from the microenvironment can induce shifts in tumor cell phenotypes and that microenvironmental factors are therefore important for cancer metastasis. In this article we expand on this hypothesis and propose a model to explain (a) how extracellular signals can lead to changes in tumor phenotypes, and (b) how cytoplasmic oncogenes, which influence signal transducing pathways as well as nuclear oncogenes regulating gene expression via DNA binding transacting factors, might affect metastatic competence.

Animals↗
PubMed1988

Analysis of metastatic competence of mouse bladder carcinoma cells after transfection with activated Ha-ras or N-ras oncogenes.

Transfection of the Ha-ras oncogene into a low metastatic epithelial cell line resulted in the acquirement of significantly increased metastatic capacity. This alteration in metastatic competence of a carcinoma line in a syngeneic system seemed to be a selective change and was not affected by parameters such as tumor latency period or local tumor growth. Transfection of the selection marker vectors with normal cellular DNA or with the N-ras gene did not lead to significantly increased metastatic capacity. Analysis of metastatic variants after oncogene transfection and in vivo selection showed integration of N-ras, but not of Ha-ras oncogenes. A possible role for the Ha-ras oncogene in the initial steps of metastasis will be discussed.

Animals↗
PubMed1988

Child sexual abuse prevention: evaluation of a teacher training model.

Teachers are potentially helpful resource persons for large numbers of sexually abused children who may have difficulty disclosing abuse, particularly to family members. In the present study, the effectiveness of a 6-hour teacher training workshop on child sexual abuse prevention was evaluated. Responses of 26 female elementary teachers who participated in the workshop were compared to responses of 19 control teachers on several pre-, post-, and follow-up measures. Relative to controls, trained teachers demonstrated significant increases from pre- to post-testing in knowledge about child sexual abuse and pro-prevention opinions. On a post-only vignettes measure, trained teachers were better able than control teachers to identify behavioral indicators of abuse and suggest appropriate interventions for hypothetical sexually abused children. Over a 6-week follow-up period, trained teachers read more about child abuse than control teachers but did not differ on other behavioral dimensions such as reporting suspected abuse cases. Further research will examine the effects of additional teacher training over an extended follow-up period.

Adult↗
PubMed1988

p53 increases experimental metastatic capacity of murine carcinoma cells.

Transfection of a cloned p53 gene into a murine bladder carcinoma cell with a low metastatic capacity led to elevated levels of p53 protein in clonal transfectants. After intravenous inoculation into syngeneic mice, p53-transfected clones showed significantly increased metastatic potential in comparison with control transfectants. The observed change did not seem to be due to a change in growth potential per se since the cell lines showed similar growth properties in vitro.

Animals↗
PubMed1988

[Detection of liver metastases in gynecologic neoplasms by sonography, scintigraphy, computerized tomography and liver enzymes].

In a retrospective study the diagnostic validity of sonography (US), computer-tomography (CT), scintigraphy (SC) and serum alkaline phosphatase (AP) in the detection of liver metastases was evaluated in 929 patients with malignant tumors: ovary (n = 367), mamma (n = 189), endometrium (n = 181), cervix (n = 162), fallopian tube (n = 10), vulva (n = 20). Definitive diagnosis was confirmed by autopsy (n = 51), surgical intervention (n = 297) or follow-up (n = 581). Specificity, sensitivity and overall accuracy of the different methods in the indication of liver metastasis were as follows: CT (n = 58) 81%, 98%, 93%, US (n = 929) 70%, 94%, 90%, SC (n = 512) 66%, 85%, 81%, AP (n = 325) 68%, 93%, 87%. In the last examination period, US and CT reached comparable results. In view of efficiency, AP and US would appear suitable for routine control in gynecological malignancies.

Alanine Transaminase↗