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L K Ernst

Publications and source records attributed to L K Ernst.

At least 19 recordsLinked to original sources
PubMed2006

[Retroviral-mediated gene transfer as an effective tool for the in vitro genetic transformation of chicken embryonic cells and production of transgenic chickens].

The data on the in vitro and in vivo (into embryonic disk) retroviral-mediated transfer of genetic information into chicken embryonic cells are presented. The estimated transformation frequency of the cultured target cells constituted 8 x 10(-4) to 5 x 10(-3). A transgenic rooster, carrying recombinant DNA in blood, heart, liver, and intestine cells, was obtained.

Animals↗
PubMed2005

[Dynamics of spermatogenesis in rabbits Oryctolagus cuniculus].

The rabbit spermatogenesis was investigated in dynamics with morphology of testicular tissues being analysed. Allocation characteristic of spermatogenous epithelium cells in spermatic ductules was examined for 19 age groups of rabbit males aged from 10 days to 12 months. The availability of three types of spermatogonia A, intermediate and B was analysed. In has been determined that the age from 10 days to 4 weeks is optimal for isolation of testis stem cells, when rabbit spermatogonia are represented by spermatogonia of A-type only.

Animal Husbandry↗
PubMed1999

Receptor-mediated transport of foreign DNA into preimplantation mammalian embryos.

Mouse and rabbit preimplantation embryos with intact zona pellucida were incubated for 3 hr with DNA-carrying constructs containing insulin as an internalizable ligand: (insulin-polylysine)-DNA and (insulin-polylysine)-DNA-(streptavidin-polylysine)-(biotinylated adenovirus). Video-intensified microscopy demonstrated that the constructs penetrated the zona pellucida and accumulated in the blastomere perinuclear space. The percentage of blastocysts formed was about 70% after incubation of zygotes and two-cell embryos with the constructs. Foreign DNA was detected after 51 hr in 80% of rabbit embryos and after 96 hr in 73% of mouse embryos. Inclusion of various adenoviruses into the construct improved foreign DNA preservation in early embryos. Blot hybridization revealed genome-integrated foreign DNA in 12- and 15-day mouse embryos and in a newborn. Thus, the ligand-mediated mechanism can be employed for introducing foreign genetic material into early mammalian embryos; insulin provides for delivery inside the cell and to the nucleus, while adenoviruses ensure release from endosomes.

Adenoviridae↗
PubMed1999

Ligand binding specificities and signal transduction pathways of Fc gamma receptor IIc isoforms: the CD32 isoforms expressed by human NK cells.

We recently reported that human NK cells express, in addition to CD16 [Fcgamma receptor (FcgammaR) IIIA], a second type of FcgammaR, namely CD32 (FcgammaRII). Molecular characterization of CD32 transcripts expressed by highly purified NK cells revealed that they predominantly express products of the FcgammaRIIC gene. Using stable Jurkat transfectants we have analyzed the functional properties of two FcgammaRIIc-specific isoforms isolated from NK cells, namely FcgammaRIIc1 and FcgammaRIIc3, which differ in their cytoplasmic tails. The ligand binding specificity for both murine and human IgG isotypes was found to be similar to that observed for FcgammaRIIb isoforms. Immunoprecipitation studies of FcgammaRIIc isoforms expressed in Jurkat cells revealed a protein of around 40 kDa for FcgammaRIIc1, and a protein of around 32 kDa for FcgammaRIIc3. Signal transduction studies performed on FcgammaRIIc1-expressing Jurkat cells indicated that this molecule is functional, i. e. capable of Ca2+ mobilization and activation of Lck, Zap-70 and Syk protein tyrosine kinases, although the CD3 zeta chain was not found to functionally associate with FcgammaRIIc1. In contrast, FcgammaRIIc3 transfectants showed an impaired ability of this molecule to mobilize Ca2+, but activation of Lck was detected following activation via FcgammaRIIc3. These studies demonstrate the functional activity of FcgammaRIIc isoforms and suggest that the presence of CD32, in addition to CD16, on NK cells may have functional relevance.

Antigens, CD↗
PubMed1999

Functional CD32 molecules on human NK cells.

Human NK cells are large granular lymphocytes that kill neoplastic or virally infected targets using perforin-dependent mechanisms. CD16 or FcgammaRIII is one of the cell surface molecules that can trigger the killing machinery following binding of the Fc portion of IgG to the receptor: a mechanism known as antibody dependent cell-mediated cytotoxicity (ADCC). We have recently shown that some individuals express an additional FcgammaR on their NK cells, CD32 or FcgammaRII. This receptor has now been characterized at the molecular, biochemical and functional level. The present review outlines our findings to date on the features of this novel receptor. These findings suggest that the presence of a functional FcgammaRII on the surface of NK cells could have important clinical consequences in both tumor immunotherapy and autoimmune disease.

Alleles↗
PubMed1998

Receptor-mediated transfection of murine and ovine mammary glands in vivo.

Transfection of HC-11 murine epithelial mammary cells as well as murine and sheep mammary glands were carried out using insulin-containing constructs that deliver DNA by receptor-mediated endocytosis to receptor-expressing cells. In vivo transfection of mammary gland tissue with the luciferase gene was carried out by introducing the DNA constructs into the mammary ducts of both mice and sheep. The successful transfection of ewe mammary glands was demonstrated by the detection of luciferase activity in mammary gland biopsy material up to a month after a single administration of the construct. To test whether products of expression of transfected genes could be secreted into the milk in this system, the N-terminal secretory signal sequences of bovine beta-lactoglobulin or the entire coding sequence of human alpha-lactalbumin were fused to the N terminus of the luciferase gene. After transfection with the modified luciferases, both murine and sheep milk could be shown to contain luciferase activity, whereas mice, which had been transfected with the nonmodified luciferase gene, did not secrete any activity in the milk. This approach demonstrates for the first time the possibility of gene transfer in vivo into mammary gland epithelial cells using constructs delivering DNA via receptor-mediated endocytosis.

Animals↗
PubMed1998

Expression of functional CD32 molecules on human NK cells is determined by an allelic polymorphism of the FcgammaRIIC gene.

Human natural killer (NK) cells were thought to express only FcgammaRIIIA (CD16), but recent reports have indicated that NK cells also express a second type of FcgammaR, ie, FcgammaRII (CD32). We have isolated, cloned, and sequenced full-length cDNAs of FcgammaRII from NK cells derived from several normal individuals that may represent four different products of the FcgammaRIIC gene. One transcript (IIc1) is identical with the already described FcgammaRIIc form. The other three (IIc2-IIc4) appear to represent unique, alternatively spliced products of the same gene, and include a possible soluble form. Analyses of the full-length clones have revealed an allelic polymorphism in the first extracellular exon, resulting in either a functional open reading frame isoform or a null allele. Stable transfection experiments enabled us to determine a unique binding pattern of anti-CD32 monoclonal antibodies to FcgammaRIIc. Further analyses of NK-cell preparations revealed heterogeneity in CD32 expression, ranging from donors lacking CD32 expression to donors expressing high levels of CD32 that were capable of triggering cytotoxicity. Differences in expression were correlated with the presence or absence of null alleles. These data show that certain individuals express high levels of functional FcgammaRIIc isoforms on their NK cells.

Alleles↗
PubMed1998

Laparoscopic recovery of pronuclear-stage goat embryos.

The oviducts of 16 Saanen does, superovulated with follicle-stimulating hormone (FSH) and synchronised with prostaglandin F2 alpha were flushed 75 to 86 hours after the injection of prostaglandin. The mean (sd) ovulation rate was 13.7 (3.9). The flushings were directed orthograde through a flexible intravenous catheter, which was introduced into the oviduct via the infundibulum. The flushing medium was recovered by a balloon-catheter, which was placed in the uterine lumen near the uterotubal junction. Five does were flushed unilaterally either because they had one blocked oviduct or because they had ovulated on only one ovary. The overall embryo recovery rate was 72 per cent. Nine weeks later 11 of the donor ewes were examined laparoscopically and no adhesions of the reproductive organs were observed. Eight of these does were synchronised with progestagen-vaginal sponges, superovulated with FSH and their oviducts were flushed again. Their mean ovulation rate was 16.0 (4.3) and 86 per cent of the embryos were recovered. The optimal time to obtain pronuclear stage embryos was 75 to 78 hours after the injection of prostaglandin. All the embryos recovered within this period were at the pronuclear stage whereas 28 per cent of those recovered one to six hours later were at the two- or four-cell stage.

Animals↗
PubMed1998

Molecular characterization of six variant Fcgamma receptor class I (CD64) transcripts.

In humans, three distinct but closely related classes of receptors that bind the Fc portion of IgG (FcgammaRI, II and III) have been identified. FcgammaRI can bind monomeric IgG with high affinity and has a unique third extracellular domain (EC3). Three very similar genes have been characterized for FcgammaRI (A, B, C). Although the sequences are remarkably similar, a number of coding-region differences discriminate between the genes and amongst their transcripts. Six distinct FcgammaRI transcripts were analysed. Three transcripts, one from each gene, contain all six exons. Only the gene A transcript appears to encode a bona fide high affinity receptor, a three Ig-domain membrane spanning receptor that can bind monomeric IgG. Stop codons in the EC3 domains of the gene B and gene C isoforms would be predicted to generate secreted receptors. Three transcripts are alternatively spliced isoforms, one from gene A and two from gene B. One gene B transcript encodes a two Ig-domain transmembrane receptor which has structural characteristics of a low affinity FcgammaR.

Animals↗
PubMed1998

[Comparative analysis of Ayrshire and Black Pied cattle breeds by histocompatibility markers].

Distribution of BoLA-A antigens and BoLA-DRB3 alleles was studied by means of the microlymphocytotoxic test (BoLA-A) and the PCR-RFLP method (BoLA-DRB3) using restriction endonucleases RSAI, HaeIII, and XhoII in Ayrshire (n = 127) and Black Pied (n = 129) cattle breeds. Comparative analysis of profiles for class I antigens revealed significant differences in the frequencies of antigens W2, W6, W10, W31, W44, W15, and W19 (P > 99%). The studied breeds also differ in the spectrum of BoLA-DRB3 alleles and distribution of their frequencies. Heterogeneous allele frequency profile was detected in Ayrshire cattle: five of 18 detected alleles (DRB3.2*7, *8, *10, *24, and *28) accounted for 77%. Allele DRB3.2*7 (37.6%), which is classed with rare alleles in Black Pied cattle is the most common in Ayrshire cattle. The observed heterozygosity level in the combined sample of Black Pied breed (0.836) is higher than in Ayrshire breed (0.070). In both breeds, the heterozygosity level was studied in the groups of healthy and ill with persistent lymphocytosis (caused by bovine leukemia virus) animals and in the group of virus carriers in Ayrshire breed. In ill animals, a decrease in the observed heterozygosity level was detected, as compared to healthy animals and the expected heterozygosity level. The observed heterozygosity level exceeds the expected one in virus carriers. The detected features of the heterozygosity level in the studied groups allow the heterozygosity level for locus BoLA-DRB3 to be considered a nonspecific factor of resistance to leukemia and are heterozygous animals to have higher resistance to bovine leukemia. The presence of a larger proportion of highly productive animals (the annual productivity of more than 7000 kg) in the group of ill Ayrshire cattle animals, as compared to healthy animals to established. To increase resistance to bovine leukemia, the obtained data indicate the importance of the control of heterozygosity level and genetic diversity for gene BoLA-DRB3 in cattle herds.

Alleles↗
PubMed1998

[Genetics of ketosis resistance in cattle].

The frequency of ketosis among the Black-pied cattle in western Siberia have been determined. The genotype of sires and genetic composition of lines were shown to affect resistance and susceptibility to ketosis. The heritability of resistance to the disease was 0.186. Variation in biochemical parameters and natural resistance in cows with ketosis and in healthy cows was studied.

Animals↗
PubMed1997

[Features of the distribution of BoLA-A antigens and alleles of the BoLA-DRB3 gene in Black Pied cattle in relation to association with leukemia].

The character of distribution of BoLA class-I antigens was studied in Black Pied cattle populations differing in status in relation to leukemia. Associative relationships of distinct antigens with resistance and susceptibility to leukemia were revealed. Using the statusmetria method, an integral estimate of predisposition to leukemia (Z) was calculated taking into consideration the contribution of each antigen in the immunogenetic status of the animal. The interval of Z values was determined, which allowed animals to be divided into groups according to resistance or susceptibility to leukemia. Alleles of the BoLA-DRB3 gene were typed in subsamples of animals with leukemia and healthy animals by the PCR-RFLP method. Twenty alleles of the gene were detected, and their frequencies were determined in both subsamples. Alleles mediating resistance of animals to leukemia (BoLA-DRB3.2*11, *23, and *28) were distributed in the group of healthy animals with frequencies of 0.079, 0.132, and 0.053, respectively; they were completely absent in animals with leukemia. The data on the estimate of animal status in relation to leukemia, which were obtained by the method of statusmetria taking in consideration the real contribution of the each class-I antigen in the detection of the disease risk (value Z), and data of allele typing by the PCR-RFLP method were shown to be in good agreement. The possibility of using BoLA class-I antigen typing in herds to determine the number of animals with leukemia was demonstrated.

Alleles↗
PubMed1995

Molecular basis for a familial defect in phagocyte expression of IgG receptor I (CD64).

Four individuals have been identified, within a single family, who lack phagocyte expression of the high affinity type I IgG receptor (CD64). As a result, their monocytes are unable to support mouse IgG2a anti-CD3-induced T cell mitogenesis (nonresponder individuals). Southern blotting proved all three human Fc gamma receptor I (hFc gamma RI) genes to be present in nonresponders without major structural changes. Nucleotide sequencing showed identical hFc gamma RIA promoter regions in all individuals. At the message level, a distinct difference was noted between monocytes from control (responder) donors and from nonresponders. Both a 1.7- and 1.6-kb message were found in responders, whereas in nonresponders only the 1.6-kb species was detectable. Reverse transcriptase-PCR analyses showed the hFc gamma RIa transcript (encoding a receptor with three extracellular Ig-like domains) to be present at a approximately 15- to 20-fold lower level in nonresponder monocytes. Importantly, we found a single nucleotide difference (C --> T) within the extracellular domain exon 1-encoding region of hFc gamma RIA in nonresponders, resulting in the change of codon 92 (encoding an arginine) into a termination codon. This change likely affects mRNA stability and, thereby, leads to undetectable expression of phagocyte-hFc gamma RIa. Despite this defect, these individuals are apparently healthy, suggesting that hFc gamma RIa is dispensable for phagocyte functioning.

Adult↗
PubMed1995

Gene therapeutic approaches to primary and metastatic brain tumors: II. ribozyme-mediated suppression of CD44 expression.

Glioblastomas are highly invasive intracerebral tumors that are known to express the CD44 cell adhesion molecule. Human glioma cell adhesion and invasion in vitro may in part be mediated by the interaction of CD44 with extracellular matrix proteins. To suppress the growth and invasive effects of CD44 expression on primary brain tumors we have designed two hammerhead ribozymes as potential gene therapeutic agents. Both ribozymes designed to target exon 2 of CD44 exhibited in vitro cleavage of in vitro transcribed CD44s and CD44R1 RNAs. The anti-CD44 effect of these ribozymes results from directed RNA cleavage, requiring both a target sequence and an appropriate catalytic center. Further, following transient transfection of one of these ribozymes into the SNB-19 glioma cell line, significant in vivo cleavage activity against cellular CD44 transcripts was demonstrated by flow cytometrical analysis. These preliminary results suggest that CD44-directed hammerhead ribozymes may be useful as gene therapeutic agents.

Base Sequence↗
PubMed1994

Molecular basis for H blood group deficiency in Bombay (Oh) and para-Bombay individuals.

The penultimate step in the biosynthesis of the human ABO blood group oligosaccharide antigens is catalyzed by alpha-(1,2)-fucosyltransferase(s) (GDP-L-fucose: beta-D-galactoside 2-alpha-L-fucosyltransferase, EC 2.4.1.69), whose expression is determined by the H and Secretor (SE) blood group loci (also known as FUT1 and FUT2, respectively). These enzymes construct Fuc alpha 1-->2Gal beta-linkages, known as H determinants, which are essential precursors to the A and B antigens. Erythrocytes from individuals with the rare Bombay and para-Bombay blood group phenotypes are deficient in H determinants, and thus A and B determinants, as a consequence of apparent homozygosity for null alleles at the H locus. We report a molecular analysis of a human alpha-(1,2)-fucosyltransferase gene, thought to correspond to the H blood group locus, in a Bombay pedigree and a para-Bombay pedigree. We find inactivating point mutations in the coding regions of both alleles of this gene in each H-deficient individual. These results define the molecular basis for H blood group antigen deficiency in Bombay and para-Bombay phenotypes, provide compelling evidence that this gene represents the human H blood group locus, and strongly support a hypothesis that the H and SE loci represent distinct alpha-(1,2)-fucosyltransferase genes. Candidate sequences for the human SE locus are identified by low-stringency Southern blot hybridization analyses, using a probe derived from the H alpha-(1,2)-fucosyltransferase gene.

ABO Blood-Group System↗
PubMed1994

Clustering of the high affinity Fc receptor for immunoglobulin G (Fc gamma RI) results in phosphorylation of its associated gamma-chain.

We are investigating the role of gamma-chain in functions mediated by the high affinity Fc receptor for IgG (Fc gamma RI). In a previous study, we found that gamma-chain, which is a member of the family of zeta-chain proteins, associates with Fc gamma RI. Here we show that clustering of Fc gamma RI leads to a rapid and transient tyrosine phosphorylation of gamma-chain in U937 cells. The response was limited to Fc gamma RI activation, and no phosphorylation of gamma-chain was observed after cross-linking of monoclonal antibodies to other surface receptors on these cells. The gamma-chain phosphorylated after Fc gamma RI clustering was the gamma-chain associated with the receptor. We also identified Syk as one of the kinases associated with the receptor complex. Upon Fc gamma RI activation, Syk, but not ZAP-70, was phosphorylated, and reimmunoadsorption experiments of phosphoproteins from immune complex in vitro kinase assays indicated that Syk is part of the activated gamma-chain-Fc gamma RI complex. These results suggest that gamma-chain links Fc gamma RI to intracellular transduction pathways.

Adenosine Triphosphate↗
PubMed1993

Association of the high-affinity receptor for IgG (Fc gamma RI) with the gamma subunit of the IgE receptor.

How receptors for the Fc portion of IgG antibodies (Fc gamma R) trigger a variety of immune functions by clustering upon engagement of ligand is largely unknown. Of the three distinct classes of human Fc gamma R, only Fc gamma RIIIA has been shown to associate with a potential signal-generating subunit, either the gamma chain or the zeta chain. With these studies we show that Fc gamma RI, the high-affinity receptor for IgG, also is found in association with gamma chain. This association can be demonstrated by using anti-Fc gamma RI antibodies, Fc gamma RI ligand, and anti-gamma-chain antibodies that coadsorb the proteins from detergent lysates of Fc gamma RI-expressing cells. The association of Fc gamma RI and gamma chain can be reconstituted by cotransfection of cDNAs for both proteins into COS cells.

Animals↗