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A Dayan

Publications and source records attributed to A Dayan.

16 recordsLinked to original sources
PubMed2001

Complete replacement of the mitochondrial genotype in a Bos indicus calf reconstructed by nuclear transfer to a Bos taurus oocyte.

Due to the exclusively maternal inheritance of mitochondria, mitochondrial genotypes can be coupled to a particular nuclear genotype by continuous mating of founder females and their female offspring to males of the desired nuclear genotype. However, backcrossing is a gradual procedure that, apart from being lengthy, cannot ascertain that genetic and epigenetic changes will modify the original nuclear genotype. Animal cloning by nuclear transfer using host ooplasm carrying polymorphic mitochondrial genomes allows, among other biotechnology applications, the coupling of nuclear and mitochondrial genotypes of diverse origin within a single generation. Previous attempts to use Bos taurus oocytes as hosts to transfer nuclei from unrelated species led to the development to the blastocyst stage but none supported gestation to term. Our aim in this study was to determine whether B. taurus oocytes support development of nuclei from the closely related B. indicus cattle and to examine the fate of their mitochondrial genotypes throughout development. We show that indicus:taurus reconstructed oocytes develop to the blastocyst stage and produce live offspring after transfer to surrogate cows. We also demonstrate that, in reconstructed embryos, donor cell-derived mitochondria undergo a stringent genetic drift during early development leading, in most cases, to a reduction or complete elimination of B. indicus mtDNA. These results demonstrate that cross-subspecies animal cloning is a viable approach both for matching diverse nuclear and cytoplasmic genes to create novel breeds of cattle and for rescuing closely related endangered cattle.

Animals↗
PubMed1996

Biochemical and molecular studies of human methenyltetrahydrofolate synthetase.

5-FormylH4folate is administered clinically under the name Leucovorin in association with the antineoplastic agent 5-fluorouracil (5-FU) to enhance the cytotoxic effects of 5-FU. The combination has been shown to be superior to 5-FU alone in the treatment of patients with metastatic colorectal carcinoma. Methenyltetrahydrofolate synthetase (MTHFS) catalyzes the transformation of 5-formyl-tetrahydrofolate to methenylH4folate, which is the obligatory initial metabolic step prior to the intracellular conversion of 5-formylH4folate to other reduced folates and the increase in intracellular folate pools required for 5-FU potentiation. In the following paper, we will summarize results of biochemical and molecular studies of human MTHFS.

Animals↗
PubMed1996

Biochemical and Molecular Studies of Human Methenyltetrahydrofolate Synthetase.

5-FormylH(4)folate is administered clinically under the name Leucovorintrade mark in association with the antineoplastic agent 5-fluorouracil (5-FU) to enhance the cytotoxic effects of 5-FU. The combination has been shown to be superior to 5-FU alone in the treatment of patients with metastatic colorectal carcinoma. Methenyltetrahydrofolate synthetase (MTHFS) catalyzes the transformation of 5-formyltetrahydrofolate to methenylH(4)folate, which is the obligatory initial metabolic step prior to the intracellular conversion of 5-formylH(4)folate to other reduced folates and the increase in intracellular folate pools required for 5-FU potentiation. In the following paper, we will summarize results of biochemical and molecular studies of human MTHFS.

Journal Article↗
PubMed1995

Cloning and characterization of the human 5,10-methenyltetrahydrofolate synthetase-encoding cDNA.

Methenyltetrahydrofolate synthetase (MTHFS) catalyses the obligatory initial metabolic step in the intracellular conversion of 5-formyltetrahydrofolate to other reduced folates. We have isolated and sequenced a human MTHFS cDNA which is 872-bp long and codes for a 203-amino-acid protein of 23,229 Da. Escherichia coli BL21(DE3), transfected with pET11c plasmids containing an open reading frame encoding MTHFS, showed a 100-fold increase in MTHFS activity in bacterial extracts after IPTG induction. Northern blot studies of human tissues determined that the MTHFS mRNA was expressed preferentially in the liver and Southern blot analysis of human genomic DNA suggested the presence of a single-copy gene.

Amino Acid Sequence↗
PubMed1995

Prolonged impairment of hematopoiesis after high-dose therapy followed by autologous bone marrow transplantation.

Hematopoietic reconstitution has been studied in 180 patients after autologous bone marrow transplantation based on peripheral blood cell (PBC) recovery time and marrow progenitor counts sequentially tested for up to 4 years. Several factors that could influence hematopoietic reconstitution have been analyzed including sex, age, diagnosis, disease status, conditioning regimen, graft progenitor content, graft in vitro purging, and postgrafting administration of growth factors. Before transplantation, marrow progenitor values were normal only for colony-forming unit granulocyte macrophage (CFU-GM) in contrast to colony-forming unit-erythroid (CFU-E), burst-forming unit-erythroid (BFU-E), and colony-forming unit-megakaryocyte (CFU-Meg). After transplantation, as described with allogenic grafts, these values remained low for several years, although PBC counts were nearly normalized within a few weeks. Pregraft values were reached after 2 years for CFU-GM and BFU-E, and after 4 years for CFU-E, while CFU-Meg failed to reach pregraft values after this time. Normal levels were reached after 4 years only by CFU-GM. On univariate and multivariate analysis, the following factors appeared to delay both PBC and marrow progenitor reconstitution: underlying disease (particularly acute myeloid leukemias), graft characteristics such as low stem cell content and in vitro purging, conditioning regimens with total body irradiation or busulfan, and lack of postgraft administration of growth factors. In conclusion, high-dose therapy followed by bone marrow transplantation induces a deep and prolonged impairment of hematopoiesis irrespective of any alloimmune reaction or postgraft immunosuppressive therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Identification and characterization of human mitochondrial methenyltetrahydrofolate synthetase activity.

We present evidence for the presence of the folate metabolism enzyme methenyltetrahydrofolate synthetase (MTHFS) in mitochondria. MTHFS activity was identified in the matrix of mitochondria purified from human liver biopsies. Mitochondrial and cytoplasmic MTHFS specific activities are similar, 85% of the total cellular MTHFS activity is in the cytoplasm and both native enzymes have similar molecular weights (approximately 25 kDa). Studies using purified mitochondrial MTHFS from CA46 human Burkitt lymphoma cells reveal that mitochondrial MTHFS behaves kinetically like the cytoplasmic enzyme with Km values of 4.7, 0.8 and 22 microM respectively for (6R,S)-5-formyltetrahydrofolate monoglutamate, (6S)-5-formyltetrahydrofolate pentaglutamate and ATP. This finding adds to previous observations that various folate-dependent enzymes reside in the mitochondria of eucaryotic cells. Intracellular tetrahydrofolate metabolism is highly compartmentalized and mitochondrial MTHFS activity is necessary for the entry of mitochondrial 5-formyltetrahydrofolate into the mitochondrial folate pool.

Burkitt Lymphoma↗
PubMed1995

Cytokine production in long-term marrow cultures after autologous bone marrow transplantation.

We compared the release of granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF) and tumor necrosis factor alpha (TNF alpha) in the supernatant of long-term bone marrow cultures (LTBMC) derived from 10 control patients and from 14 patients before and 3 months after autologous bone marrow transplantation (BMT). The three cytokines were spontaneously present in the supernatant of cultures established from patients before and after autologous BMT, while GM-CSF remained undetectable in the supernatants of control patients. The maximal levels of cytokines were produced after the first week and were not statistically different between control, patients before and after grafts although the granulocyte-macrophage colony-forming unit (CFU-GM) production in long-term culture (LTC) was lower in patients after graft compared with control patients (median values at LTC initiation: 32 and 158, respectively, P < 0.001 and median values of the total production: 510 and 12406, respectively, P < 0.002). However, GM-CSF was more frequently detected in patients after graft than in control patients. This study demonstrated that the production of GM-CSF, G-CSF and TNF alpha is not impaired in patients after graft (medians 0, 870.5, 173.5 pg/ml and ranges 0-31.2, 0-10 000 and 0-1426, respectively) compared with control patients (medians 0, 69, 66 pg/ml and ranges 0, 0-13 280 and 0-1318, respectively), although patients after graft were shown to have lower marrow CFU-GM counts. These results suggest that the ability of the accessory cells to produce these cytokines was not reduced after autologous BMT.

Adolescent↗
PubMed1994

Haemopoiesis of transplanted patients with autologous marrows assessed by long-term marrow culture.

We assessed the effect of antitumoural therapy at intensive doses on the haemopoietic system using long-term marrow cultures (LTMC) established from 33 patients (25 with haematological diseases and eight with solid tumours) after autologous bone marrow transplantation (ABMT). When compared to 42 pre-graft patients, a decreased CFU-GM production and a defect in stromal layer (SL) confluence were found after ABMT on day 90 but also on day 365. However, these abnormalities were observed only in patients with haematological diseases and no differences between pre-graft and post-graft results were found in patients with solid tumours. Among the patients with haematological diseases, on day 90 those with acute lymphoid leukaemias showed lower CFU-GM production whereas patients with non-Hodgkin's lymphomas developed more frequently subconfluent or confluent SL. Other factors studied such as sex, patient age, disease status, marrow purging and post-graft administration of growth factors did not appear to influence post-graft LTMC results. Multivariate analysis including all the patients has shown (a) that solid tumours were associated with higher CFU-GM production, and (b) that conditioning regimens with total body irradiation (TBI) or busulfan led more frequently to non-confluent SL. In conclusion, high-dose therapy followed by ABMT can induce a persistent impairment of the stem cell and stromal cell compartments, particularly in patients with haematological diseases conditioned with TBI, despite the absence of any alloimmune reaction and post-graft immunosuppressive therapy.

Adolescent↗
PubMed1993

Pseudomonas aeruginosa and cystic fibrosis: intrastrain variability in relation to intensity of immune response and clinical outcome.

Over periods exceeding two years, 63 Pseudomonas aeruginosa strains isolated from three children with cystic fibrosis were characterized using a 154 character auxanogram. Numerical analysis was carried out to establish intrastrain variability in relation to intensity of immune response and clinical outcome. For two patients, strains segregated in two distinct phenons. For the last patient, strains did not cluster. The degree of intrastrain variability during the infection was correlated with an increasing number of precipitins and with an unfavorable clinical outcome. This would suggest that strains which have a singular potential for antigenic variability are more likely to promote a host-bacteria conflict.

Bacterial Typing Techniques↗
PubMed1992

Factors that influence the therapeutic activity of 5-fluorouracil [6RS]leucovorin combinations in colon adenocarcinoma xenografts.

The therapeutic activity of FUra alone or combined with [6RS]LV doses ranging from 50 to 1,000 mg/m2 was examined in eight colon adenocarcinoma xenografts, of which five were established from adult neoplasms (HxELC2, HxGC3, HxVRC5, HxHC1, and HxGC3/c1TK-c3 selected for TK deficiency) and three were derived from adolescent tumors (HxSJC3A, HxSJC3B, and HxSJC2). The growth-inhibitory effects of FUra were potentiated by higher doses of [6RS]LV (500-1,000 mg/m2) in three lines (HxGC3/c1TK-c3, HxSJC3A, and HxSJC3B) and by a low dose of [6RS]LV in only one tumor (HxVRC5). Expansion of pools of CH2-H4PteGlun+H4PteGlun (greater than or equal to 2.4-fold) in response to higher doses of [6RS]LV was obtained in all lines except HxHC1. Metabolism of [6RS]LV was high in HxVRC5, with high levels of 5-CH3-H4PteGlu being detected, but not in HxHC1, in which levels of 5-CH3-H4PteGlu and CH = H4PteGlu+10-CHO-H4PteGlu remained relatively low. In the adolescent tumors, levels of CH = H4PteGlu+10-CHO-H4PteGlu were consistently higher than those of 5-CH3-H4PteGlu following [6RS]LV administration, and in HxSJC3A, in which pools of CH2-H4PteGlun+H4PteGlun were significantly expanded, 5-CH3-H4PteGlu concentrations were lower than those observed in the other two lines. The sensitivity of tumors to FUra +/- [6RS]LV and the characteristics of [6S]LV metabolism did not correlate with the activity of CH = H4PteGlu synthetase, the enzyme responsible for the initial cellular metabolism of [6S]LV to CH = H4PteGlu. Thus, no single metabolic phenotype correlated with the [6RS]LV-induced expansion of CH2-H4PteGlun+H4PteGlun pools. Potentiation of the therapeutic efficacy of FUra by [6RS]LV was observed in HxGC3/c1TK-c3 xenografts but not in parent HxGC3 tumors, demonstrating the influence of dThd salvage capability in the response to FUra-[6RS]LV combinations. Plasma dThd concentrations in CBA/CaJ mice were high (1.1 microM). The present data therefore demonstrate the importance of (1) higher doses of [6RS]LV, (2) expansion of pools of CH2-H4PteGlun+H4PteGlun, and (3) dThd salvage capability in potentiation of the therapeutic efficacy of FUra in colon adenocarcinoma xenografts. The plasma levels of FUra achieved in mice are presented.

Adenocarcinoma↗
PubMed1992

A preliminary investigation of promotion of brain tumours by hexachlorophane in Sprague-Dawley rats transplacentally exposed to N-ethylnitrosourea.

Two-stage carcinogenesis (initiation and promotion) has been demonstrated in various mammalian tissues, but there is no conclusive evidence that it occurs in the nervous system. The present work has investigated the possibility that it might occur in the brain of the rat. Pregnant Sprague-Dawley rats were given an initiating dose (10 mg/kg intravenously (i.v.)) of N-ethylnitrosourea (ENU), which resulted in a low but consistent yield of brain tumours in the offspring. The dose was determined in a prior dose-response investigation. The 'initiated' offspring were treated postnatally with the putative promoter, hexachlorophane, and its ability to increase tumour incidence was examined by standardized step sectioning of the brain from rats killed at 6 months. There was no evidence of promotion of ENU-induced brain neoplasms by hexachlorophane in the rat. The experimental procedure led to a reproducible incidence of glial tumours in the pups.

Animals↗
PubMed1983

Complete programme for acute toxicity testing - not only LD50 determination.

The objective of any experimenter should be to obtain the maximum amount of useful information in the most economical manner possible. In this context, 'useful' means study both of the principal or anticipated actions of the compound under examination, and also detection of additional responses to it. For efficient evaluation, including greater statistical rigour, a continuous or graded response and quantitative measurement is preferable, although much can be done by simply analysis of the presence or absence of responses, even if these are complex or dependent upon subjective criteria. Consistency of experimental conditions, and of diagnostic criteria are essential, whether in single, exploratory or comparative tests. Acute toxicity tests, like other experiments, should be designed pragmatically, therefore, confirming to the properties of the substance under examination, but also with general or holistic coverage, albeit less specific, to detect unanticipated actions. Greater or lesser weight may be given to these two classes of method, depending on whether the test is done as part of a general screen of a previously unknown substance, or as a specific control measure done to assay one particular property. Extrapolation of the results to man or other species is only possible with the caution proper to any experiment done under restricted and highly artificial conditions, but the value of acute toxicity data has often been shown by experience gained in man.

Animals↗
PubMed1980

[Gestalt therapy of complaints].

People can express their suffering voicing it, complaining with their body, with gestures, movements; for alerts eyes it is even more comprehensive and true than words. Complaints that human beings are capable of expressing are not so many, there are only a handful, and this work intends to be exhaustive in its exposition. It is possible to complain against third persons. It is also possible to do so against oneself assuming either the intransigent attitude of a father who judges a son who does not fulfill his expectancies, or as a son who resents the paternal demands which he feels he cannot comply. Other kind of complaints include physical symptoms, either isolated (cephalea, dysnea, urticaria) or constituting syndromes or illnesses. Losses suffered are also a source of complaints, whatever the lost object might be (person, situation, material things or a part of oneself). It can be mourned because of its absence, or else by feeling guilty of the real or imaginary damage inflicted or else by feeling indisolubly linked to it with a phantom tie. Other types of complaints are the feeling of dependancy towards something oppressive, be it a substance, such as alcohol, smoking, drugs or overeating, or it may be a person or a situation. In view of the compulsive addiction characteristics with which the subject lives, it is possible to assimilate this dependancy and the feeling of oppression and damage to the link with a toxic.

Female↗