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Biomedical subjects

G Lang

Publications and source records attributed to G Lang.

At least 19 recordsLinked to original sources
PubMed1992

Characterization of a novel T lymphocyte protein which binds to a site related to steroid/thyroid hormone receptor response elements in the negative regulatory sequence of the human immunodeficiency virus long terminal repeat.

We have previously identified a T lymphocyte protein which binds to a site within the LTR of the human immunodeficiency virus type 1 (HIV-1) and exerts an inhibitory effect on virus gene expression. The palindromic site (site B) recognized by this protein is related to the palindromic binding sites of members of the steroid/thyroid hormone receptor family. Here we characterize the T cell protein binding to this site as a 100 kD protein which is most abundant in T cells and which binds to site B as a 200 kD complex. This protein is distinct from other members of the steroid/thyroid hormone receptor family including the COUP protein which has a closely related DNA binding specificity.

Base Sequence↗
PubMed1992

X-ray crystallographic characterisation of type-2-depleted ascorbate oxidase from zucchini.

The type-2 depleted form of ascorbate oxidase from zucchini has been prepared in crystals and characterised by X-ray crystallography and EPR spectroscopy. The X-ray structure analysis by difference-Fourier techniques and refinement shows that, on average, about 1.3 Cu atoms/ascorbate oxidase monomer are removed. The copper is lost from the trinuclear site whereby the EPR-active type-2 copper is depleted most; type-1 copper is not affected. This observation indicates preferential formation of a 1 Cu-depleted form with the hole equally distributed over all three copper sites. Each of these 1 Cu-depleted species may represent an anti-ferromagnetically coupled copper pair which is EPR-silent and could explain the disappearance of the type-2 EPR signal.

Ascorbate Oxidase↗
PubMed1992

Stable growth transformation of human T lymphocytes by herpesvirus saimiri.

Herpesvirus saimiri induces T-cell lymphomas in various species of New World monkeys and in rabbits, and it is able to immortalize monkey T lymphocytes in vitro. Sequences responsible for these effects have been localized to a region of the genome that varies significantly among the virus subgroups A, B, and C. We now report that infection of human blood lymphocytes and thymocytes with strains of subgroup C, in contrast to viruses of the other subgroups, yields continuously proliferating T-cell lines with the phenotype of mature CD4- or CD8-positive cells. Infection with strains of Herpes-virus saimiri subgroup C can thus be used to generate human T-cell lines for a variety of immunological and developmental studies.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1992

Incidence and phenotype restriction of lymphoid BLT-serine protease granules in spontaneously diabetes prone BB rats compared with a normal rat strain.

In diabetes prone BB rats a relative increase of serine protease (SP)-positive lymphocytes (39.8 +/- 10%) was observed in peripheral blood at the time of diabetes manifestation (DM) compared with non-diabetic healthy Sprague Dawley control rats (Co: 10.3 +/- 4%), with BB rats at age of premanifestation (PM: 14.7 +/- 4%) and beyond age of expected manifestation (non-diabetic animals, ND: 25.2 +/- 4%). Similar absolute numbers were found in diabetic BB rats in comparison with Sprague Dawley rats. In PM, absolute numbers were lower in comparison with diabetic BB rats. SP granular positivity was found restricted to OX8+ lymphocytes. SP granule-bearing OX8+ lymphocytes were more frequently seen in the BB rat strain (PM: 74.3 +/- 8%; DM: 79.4 +/- 8%; ND: 78 +/- 10%) compared with normal rats (Co: 32.5 +/- 8%). Absolute numbers were lower in PM animals in comparison with DM rats. OX8+ cells were found in a higher relative number in DM animals (49.1 +/- 7%) compared with controls (28.2 +/- 3%), PM (26.3 +/- 5%) and ND (34 +/- 2%) animals. T lymphocytes expressing the W3/25+ marker, invariably negative for SP granules, were present in a higher relative number in ND (49.8 +/- 7%) and the control group (52.3 +/- 10%) compared with PM (31 +/- 8%) and DM (38 +/- 11%) animals. Absolute numbers of the OX39+ lymphocyte subpopulation were decreased in PM and DM-BB rats in comparison with the control group.

Animals↗
PubMed1991

Deletion analysis of the human CD2 gene locus control region in transgenic mice.

Genomic sequences located at the 3' flanking region of the human CD2 gene confer high level tissue-specific, position-independent expression of the gene when introduced in the germ line of mice. In order to further characterize these sequences a range of deletions, from the 3' end were produced and transgenic mice were generated with the human CD2 (hCD2) gene linked to these deleted fragments. This allowed us to establish the minimum sequences necessary for the copy-dependent transgene expression. 2.1 kb or 1.5 kb of 3' flanking sequences linked to a hCD2 mini-gene is sufficient to allow T-cell specific, copy-dependent, integration-independent expression in transgenic mice. 1.1 kb of 3' sequences results in the gene being expressed in a T-cell specific manner, but copy-dependent, integration-independent expression was not observed in a small number of transgenic animals. 0.2 or 0.5 kb of 3' flanking sequences were insufficient to allow expression above the level previously found with a human CD2 gene which lacked 3' flanking sequences. We conclude that the Locus Control Region (LCR) effect is caused by 1.5 kb of flanking sequences immediately 3' to the polyadenylation signal of the gene.

Animals↗
PubMed1991

6'-substituted naphthalene-2-carboxylic acid analogs, a new class of retinoic acid receptor subtype-specific ligands.

The biological response to retinoic acid (RA) and synthetic derivatives (retinoids) is mediated by three nuclear retinoic acid receptors, RAR alpha, beta and gamma. To explore the potential of retinoids as receptor subtype selective activators, we employed a transcriptional activation assay. Hybrid receptors that recognize an estrogen response element were used to avoid measuring activities of endogenous retinoic acid receptors. In response to retinoic acid, the three hybrid receptors ER-RAR alpha, ER-RAR beta and ER-RAR gamma exhibited the same induction profile as the corresponding wild type receptors RAR alpha, RAR beta, and RAR gamma. Three different retinoids, analogs of 6'-substituted naphthalene-2-carboxylic acid, elicited strong transcriptional activation of gamma receptor while no activation of alpha receptor was observed. Conversely, two retinobenzoic acid analogs showed a limited alpha selectivity. We conclude that retinoids with unique profiles of retinoic acid receptor subtype selectivity can be defined and tested for their impact on cellular differentiation and for therapeutical applications.

Animals↗
PubMed1991

Reconstitution of an active surface CD2 by DNA transfer in CD2-CD3+ Jurkat cells facilitates CD3-T cell receptor-mediated IL-2 production.

To investigate the requirements for CD2 expression in the activation of T lymphocytes via the CD3-TCR complex, we produced and characterized a series of CD2-variants of the IL-2 producing Jurkat leukemia cell line, J32 (surface phenotype, CD2+, CD3+, CD28+). These mutants were derived by radiation and immunoselection, and were cloned under limiting dilution conditions. A total of 3 out of 30 of these mutants selectively lost the expression of both CD2 surface molecules and CD2 mRNA, and retained the expression of the CD3-TCR complex and the CD28 molecule. A mitogenic combination of anti-CD2 antibodies (9.6 + 9-1) failed to stimulate activation of these variants as measured by mobilization of intracellular Ca2+ and by IL-2 production. The CD2- mutants stimulated with anti-CD3 or anti-TCR mAb revealed an 8- to 32-fold decrease in IL-2 production and IL-2 mRNA accumulation as compared with the parental cells. No alteration of CD3-TCR-induced mobilization of intracellular Ca2+ was observed in the CD2- mutants. Reconstitution of CD2 expression by gene transfer in two J32 CD2- mutants restored IL-2 production and IL-2 mRNA accumulation in responses to both anti-CD2 and anti-CD3-TCR mAb. These results are the first direct demonstration of the requirement for CD2 molecules in optimizing IL-2 response in human T cells stimulated via CD3-TCR complex.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1991

Mössbauer spectroscopy of iron-ovotransferrin: a crystal field interpretation.

Mössbauer spectra from frozen solutions of ovotransferrin were recorded in a variety of applied external magnetic fields and at various temperatures in a small applied field. The results were fitted to a simple model for the electronic structure at the iron site. This model requires admixtures of the free ion 6S and 4P states, indicating a weak cubic crystal field. Possible implications of this model regarding the binding site are discussed.

Binding Sites↗
PubMed1991

Immunohistochemical studies on uterine tumors. I. Invasive squamous cell carcinomas of the cervix and their precursors.

40 invasive carcinomas and 80 preinvasive lesions of the uterine cervix were studied immunohistochemically; 40 benign lesions served as controls. On histological and immunohistochemical examination, invasive and preinvasive carcinomas were subdivided in the squamous (large cell, ectocervical) type and the reserve cell (small, large or clear cell, endocervical) type. Immunohistochemically, 100% of the invasive and preinvasive squamous cell carcinomas were positive with anticytokeratins 13, 14, 16 and negative with anticytokeratin 8 and anti-CEA. Most of the invasive and preinvasive reserve cell carcinomas showed a coexpression of cytokeratins 13, 14, 16, 8 and CEA. The subdivision of invasive carcinomas of the ecto- and endocervix into squamous cell and reserve cell types made by means of their structural differences is substantiated and re-evaluated by their immunohistochemical reactions. Both types of carcinomas retain the complex pattern of cytokeratins shown by their cells of origin. The reserve cell carcinomas, in addition, acquire a coexpression for CEA that indicates malignant transformation. The subdivision is of clinical importance because both types of carcinomas vary in their mode and speed of invasion and spread and in their association with HPV infection.

Carcinoembryonic Antigen↗
PubMed1991

Relationship between allozymes, heterozygosity and morphological characters in red deer (Cervus elaphus), and the influence of selective hunting on allele frequency distribution.

Morphological characters in red deer (Cervus elaphus), which serve as criteria for selective hunting, were examined in relation to electrophoretic variation in three populations from the Vosges in eastern France. From the polymorphic loci examined, certain alleles at Idh-2, Me-1 and Acp-1 showed significant associations with a special development of body and antler characters selected for by hunters. Idh-2(125) was associated with larger hind foot length in females and a higher number of antler points in males. Me-1(90) and Acp-1(100) were associated with small spikes. The populations studied differed from one another in the duration and intensity of selective hunting and the increase or decrease in the respective allele frequencies could be explained by selection for large body size, a high number of antler points and against small spikes in yearlings, rather than by genetic drift. Among other morphological characters examined, the length of the main beam was significantly associated with the allele Acp-2(100). In contrast, no associations could be detected between overall heterozygosity and the development or the degree of asymmetry (in paired structures) of any of the morphological traits in question. Although no obvious differences in the overall values of polymorphism or heterozygosity were found between the populations, selective hunting leads towards a change in allele frequencies and eventually to the loss of one or the other rare allele.

Alleles↗
PubMed1991

Human CD2 is functional in CD2 transgenic mice.

We aimed to study the biochemical consequences of T-cell activation via the CD2 antigen in mouse T cells. The lack of stimulatory monoclonal antibodies against the mouse CD2 antigen led us to analyse this problem in transgenic mice carrying and expressing the human CD2 gene. Monoclonal antibodies to the human CD2 antigen that were mitogenic for human T cells induced proliferation of mouse T cells from the CD2 transgenic mice. Stimulation was accompanied by rapid phosphorylation of the murine CD3 gamma chain and T-cell receptor zeta chain. These results demonstrate that the human CD2 antigen is functional in the CD2 transgenic mice and indicate a considerable conservation of the signal transducing processes and also the activation mechanisms between mouse and man.

Animals↗
PubMed1991

The seroprevalence of coxiellosis (Q fever) in Ontario sheep flocks.

A serological survey for Coxiella burnetii was undertaken on a randomly selected population of 103 Ontario sheep flocks. Twenty-two flocks had at least one positive ewe; seven flocks had two or more reactors. The positive flocks were geographically clustered northwest of Guelph. Crutch-clipping of the ewe's wool prior to lambing, and total confinement housing at lambing in winter and spring seemed to lower the probability of seroreactivity of the flock (p less than 0.05). The study suggests that sheep are not a major reservoir for Coxiella burnetii in Ontario.

Analysis of Variance↗
PubMed1990

Electronic and stereochemical characterizations of the photoinduced intermediates of nitrosyl complexes of metal (S = 5/2)-substituted hemoproteins trapped at low temperature.

Low temperature photolysis of nitric oxide from the nitrosyl complexes of ferric myoglobin (NO-Fe(III)Mb) and manganese(II)-porphyrin-substituted myoglobin (NO-Mn(II)Mb) was examined by electron paramagnetic resonance (EPR) spectroscopy in order to elucidate the electronic and structural natures of the photoinduced intermediates of these hemoprotein-ligand complexes trapped at low temperature. The photoproduct of NO-Fe(III)Mb at 5 K exhibited entirely new X-band EPR absorptions in the magnetic field strength from 0 to 0.4 tesla. The widespread absorption together with distinct, sharp zero-field absorption was consistently observed in the photoproduct of the isoelectronic NO-Mn(II)Mb. These novel ERP signals indicate a spin-coupled pair with an effective spin of S = 2 between the high spin metal center (S = 5/2) and the photodissociated NO (S = 1/2) trapped adjacent to the metal center. On the other hand, the photolyzed form of nitrosyl complexes of Fe(III)- and Mn(II)-Glycera hemoglobins, in which the distal histidine of Mb is replaced by a leucyl residue, exhibited somewhat broader EPR absorptions similar to those of the corresponding native Fe(III)- or unliganded Mn(II)-Glycera hemoglobins, respectively, indicating that the photodissociated NO molecule moved farther away from the metal center in the heme pocket. These observations show the importance of the interaction of the distal residue with the ligand in determining the nature of the photolyzed states.

Animals↗
PubMed1990

Measurement of ATP synthesis rates by 31P-NMR spectroscopy in the intact myocardium in vivo.

The ability to measure ATP synthesis rates using 31P-NMR spectroscopy is demonstrated in the normal, ischemic, and postischemic myocardium in vivo. Cardiopulmonary bypass (CBP) was employed to induce 20 min of global myocardial ischemia, and to conduct magnetization transfer measurements during the ischemic episode and following reperfusion and return to normal circulation. For the first few minutes of ischemia, transfer of magnetization from ATP gamma to Pi was extensive and the resultant fractional reduction (delta M/M0) in the Pi resonance intensity reached approximately 100%. Subsequent to reperfusion and stabilization off CPB and on normal circulation, both the fractional reduction and the spin-lattice relaxation time, T1*, of the Pi resonance were determined when ATP gamma spins were saturated. Under these conditions, the unidirectional ATP synthesis rate was 0.41 +/- 0.09 (SEM, N = 4) mumol/s/g wet wt. The data suggest that in the canine myocardium in vivo, glycolytic enzymes mediate a very rapid exchange between Pi and ATP gamma-phosphates during early phases of ischemia; in the postischemic reperfused myocardium, however, the glycolytic contribution to the unidirectional Pi----ATP rate measured by NMR in vivo is relatively small compared to that observed in glucose-perfused, postischemic rat hearts.

Adenosine Triphosphate↗
PubMed1990

Monoamine oxidase inhibition by moclobemide and 2-amino-ethyl carboxamide derivatives: mode of action and kinetic characteristics.

The selective, reversible inhibitors of monoamine oxidase (MAO) moclobemide and Ro 41-1049 (selective for MAO-A), as well as of Ro 16-6491 and Ro 19-6327 (selective for MAO-B) inhibited the enzyme with an initial competitive phase, followed by a time-dependent inhibition of MAO. Ro 41-1049, Ro 16-6491 and Ro 19-6327, being activated by MAO into reversible adducts, fit into the classification as mechanism-based inhibitors. Conversely, since no product formation was observed after incubation of tissue homogenates with moclobemide, this drug probably belongs to the class of the "slow-binding" MAO inhibitors.

Animals↗
PubMed1990

The histogenetic origin of cervical mesonephric hyperplasia and mesonephric adenocarcinoma of the uterine cervix studied with immunohistochemical methods.

Forty-four cases of mesonephric hyperplasia (MH) and two adenocarcinomas arising from mesonephric remnants (MA) in the cervix were compared immunohistochemically with 10 embryonic and fetal mesonephric tissues. The mesonephric cells retained their pattern for intermediate filaments during ontogenesis, as well as in the mature, hyperplastic, and neoplastic states: they expressed cytokeratin 8, cytokeratin 13, and vimentin, the two latter in variable amounts. In embryonic mesonephric tissues, cytokeratin was absent, whereas the staining for vimentin was intense. Fetal mesonephric cells stained for cytokeratin 13 and vimentin, but that staining diminished as maturation progressed. All MH and MA expressed cytokeratin 8, whereas only 20-30% of the cells in MH and 10-20% of carcinomatous mesonephric cells showed positive reactions with anti-cytokeratin 13 and anti-vimentin. CEA was always negative in cells of mesonephric origin. We regard these results to be important, since the reactions with anti-CEA and anti-vimentin enable one to distinguish cervical adenocarcinomas of mesonephric origin from those of endocervical origin, the latter being CEA-positive and vimentin-negative. Clinical studies revealed that approximately 75% of the patients with MH had used oral contraceptives for several years, 46% had precancerous lesions of the cervix, and in 62% the cervical mucosa showed adenomatous microglandular hyperplasia. We believe that hyperplasia of mesonephric remnants in the cervix may occur more often in patients with disturbed hormonal balance. However, the lack of a control population does not enable us to advance this hypothesis with assurance.

Adult↗
PubMed1990

trans activation of the thymidylate synthase promoter of herpesvirus saimiri.

Herpesvirus saimiri has been shown to possess a thymidylate synthase (TS) gene that is unusual in its transcriptional regulation. Although TS is believed to be required for viral DNA synthesis, the TS-specific 2.5-kb mRNA was found most abundantly during the late phases of asynchronous virus replication in permissive cultures. To study the kinetics of gene activation, the TS promoter and regulatory sequences were cloned upstream of the chloramphenicol acetyltransferase (CAT) gene. No CAT expression or transcripts were found after transfection of fusion genes into permissive owl monkey kidney (OMK) cells. However, the promoter was strongly activated when CAT plasmids were cotransfected with intact herpesvirus saimiri virion DNA or were transferred to OMK cells that were lytically infected with herpesvirus saimiri or a related herpesvirus, herpesvirus ateles. CAT was expressed at reduced levels in cultures when viral DNA replication was inhibited by phosphonoacetic acid; this indicates that the gene is activated during the delayed-early phase. However, the highest amounts of mRNA were present in the late period of replication. Deletion analyses localized essential response elements for trans activation in the promoter upstream region between nucleotides -311 and -56; they consisted of related tandem repeats and perfect palindromes. A sequence with two overlapping palindromes of 16 and 18 bp was found to be a major target for activation of the herpesvirus saimiri TS promoter. These palindromes did not have any significant homologies with known sequences of herpesviruses or cellular DNA; the 18-bp palindrome had, however, a certain structural similarity with a conserved sequence of the E2-responsive cis sequence that is required for transcription regulation of early papillomavirus genes.

Animals↗