Biomedical subjects

J W Pollard

Publications and source records attributed to J W Pollard.

At least 91 records · Page 5Linked to original sources

PubMed1991

Lymphohematopoietic cytokines in the female reproductive tract.

The past year has seen an avalanche in publications describing the synthesis of lymphohematopoietic cytokines by the uterus and placenta. Dissection of the particular contributions of these factors will require genetic as well as biochemical approaches. The major events of the year therefore, were the identification and creation of mouse mutants that have provided novel insights into the roles of various cells and cytokines during gestation.

Animals↗

PubMed1991

Fertilizing capacity of bovine sperm may be maintained by binding of oviductal epithelial cells.

The ability of the bovine oviduct to maintain the motility and fertilizing capacity of bovine sperm was investigated by incubating frozen-thawed sperm with endosalpingeal epithelial cells cultured on either tissue culture plastic (nonpolarizing) or Matrigel-coated Millicell (polarizing) substrata. Sperm were also incubated in medium alone or with cultured bovine tracheal epithelial cells. Motility was determined at 6-h intervals over a 48-h period. The fertilizing capacity of sperm was evaluated after 0, 24, and 30 h of incubation by adding oocytes to the culture and determining the incidences of fertilization and polyspermy. Motility was maintained for 48 h in sperm that bound to endosalpingeal epithelial cells, but to a greater extent with polarized cells (38.4% motile) than with nonpolarized cells (0.8%). Fertilizing capacity was maintained for 30 h in sperm incubated with endosalpingeal epithelial cells on Matrigel/Millicell, but not in sperm incubated in medium alone or with tracheal cells. Only sperm incubated with oviductal cells developed hyperactivated motility. Scanning electron micrographs revealed that sperm were bound by the rostral portion of the intact acrosome to the apical surface of polarized endosalpingeal cells. These results suggest that the oviduct may not only store sperm but may also maintain sperm viability and fertilizing capacity during the preovulatory period.

Animals↗

PubMed1991

Expression of colony-stimulating factor-1 (CSF-1) messenger RNA in human endometrial glands during the menstrual cycle: molecular cloning of a novel transcript that predicts a cell surface form of CSF-1.

Colony-stimulating factor-1 (CSF-1) has been primarily characterized as a hematopoietic growth factor required for the proliferation and differentiation of monocytic cells. Recent immunohistological observations have shown that this growth factor is also synthesized by the glandular epithelial cells of the pregnant human endometrium and by first trimester human trophoblasts. In the present study endometrial glands were purified from nonpregnant human endometria collected through the menstrual cycle and examined for CSF-1 mRNA expression. The two major mRNAs (4.0 and 3.0 kilobases in length) detected in midproliferative and midsecretory phases differed in the size of the exon 6 and coded, respectively, for a secreted and a cell surface form of CSF-1. The 3.0-kilobase transcript represented a novel CSF-1 mRNA species that was molecularly cloned and sequenced. These data raise the possibility that CSF-1 may be involved in both distant and cell to cell regulatory pathways of cell proliferation and differentiation in the human endometrium.

Base Sequence↗

PubMed1991

Alterations in CSF-1 receptor expression and protein tyrosine phosphorylation in autonomous mutants of a CSF-1 dependent macrophage cell line.

One approach to the problem of growth factor signal transduction is to identify alterations in growth factor-regulated events in mutants possessing an altered proliferative response. This approach was used in a study of the alterations in protein tyrosine phosphorylation in 22 independently-arising autonomous mutants of the CSF-1-dependent mouse macrophage cell line, BAC1.2F5. Only 4 of the mutants produced CSF-1 and/or factors that were capable of down-regulating the CSF-1 receptor (CSF-1R), suggesting that the majority were altered in the signal transduction pathway for proliferation. All of the mutants possessed lower numbers (13-89%) of cell surface CSF-1Rs than wild type cells. With two possible exceptions, the phosphorylation of the anti-phosphotyrosine-reactive cell surface CSF-1Rs from CSF-1 stimulated cells was directly proportional to cell surface CSF-1R number. In the absence of CSF-1, three of the 22 mutants exhibited tyrosine phosphorylation of proteins that was not observed in wild type cells under the same conditions. The results indicate that this approach will be useful in the analysis of the growth factor regulated pathway for cell proliferation.

Animals↗

PubMed1991

Correction by CSF-1 of defects in the osteopetrotic op/op mouse suggests local, developmental, and humoral requirements for this growth factor.

Mice that are mutant at the op locus have a severe deficiency of mononuclear phagocytes due to an inactivating mutation in the CSF-1 (macrophage colony-stimulating factor, M-CSF) gene. op/op mice are toothless, possessing skeletal abnormalities, a low body weight, and compromised fertility; they are osteopetrotic due to a deficiency of osteoclasts. The congenital osteopetrosis, toothless phenotype, osteoclast deficit, and the defects in splenic and femoral macrophages were corrected by routes of administration of human recombinant CSF-1 that maintained normal circulating CSF-1 concentrations. Early restoration of circulating CSF-1 was required for rescue of the toothless phenotype, but only partially restored body weight. In contrast, the deficiencies of pleural and peritoneal cavity macrophages and the reduced female fertility were not corrected by restoration of circulating CSF-1. These results suggest that although circulating CSF-1 is required for osteoclast and macrophage production, local synthesis and action of the growth factor are important for certain target cell populations.

Animals↗

PubMed1990

Purification of bovine trophoblast protein-1 complex and quantification of its microheterogeneous variants as affected by culture conditions.

The bovine trophoblast protein-1 complex (bTP-1) is a group of glycosylated interferon-alpha 11, molecules secreted by the bovine conceptus that plays a critical role in preventing luteolysis during early pregnancy. In the current studies, secretion of individual variant forms of bTP-1 was quantified under a variety of culture conditions that could affect yields of bTP-1 for preparative-scale production of bTP-1. Additionally, a purification scheme for bTP-1 was developed. Conceptuses from Day 17 produced 13 proteins in the molecular weight and pI range characteristic of bTP-1, with 4-5 isoforms (pI = 5.6-6.6) at each of three molecular weight classes (21, 23.2 and 25.8 kDa). The major forms of bTP-1 were two variants of 23.2 kDa having pIs of 6.2 and 6.6. The relative proportion of bTP-1 variants was generally unaffected by culture conditions. Cultured conceptuses secreted bTP-1 at a sustained rate for 3 days and gaseous environment was without major effect on bTP-1 secretion. Conceptuses from superovulated cows also produced bTP-1 at Day 17 of pregnancy, suggesting that superovulation might be a useful method for increasing total bTP-1 yield per cow. The purification scheme that was developed utilized ultrafiltration with Centricon devices to achieve rapid molecular weight fractionation, desalting and concentration of conceptus secretory proteins prior to purification of bTP-1 using anion-exchange and gel filtration HPLC. The resultant preparation of bTP-1 included 9 variant forms of bTP-1 as well as a slight amount of a 45-kDa contaminant. Purified bTP-1 possessed antiviral activity but the specific activity was apparently reduced when conceptus-conditioned medium used for purification was stored for prolonged periods.

Animals↗

PubMed1990

Total absence of colony-stimulating factor 1 in the macrophage-deficient osteopetrotic (op/op) mouse.

Osteopetrotic (op/op) mutant mice suffer from congenital osteopetrosis due to a severe deficiency of osteoclasts. Furthermore, the total number of mononuclear phagocytes is extremely low in affected mice. Serum, 11 tissues, and different cell and organ conditioned media from op/op mice were shown to be devoid of biologically active colony-stimulating factor 1 (CSF-1), whereas all of these preparations from littermate control +/+ and +/op mice contained the growth factor. The deficiency was specific for CSF-1 in that serum or conditioned media from op/op mice possessed elevated levels of at least three other macrophage growth factors. Partial correction of the op/op defect was observed following intraperitoneal implantation of diffusion chambers containing L929 cells, which in culture produce CSF-1 as their sole macrophage growth factor. No rearrangement of the CSF-1 gene in op/op mice was detected by Southern analysis. However, in contrast to control lung fibroblasts, which contained 4.6- and 2.3-kilobase CSF-1 mRNAs, only the 4.6-kilobase species was detected in op/op cells. An alteration in the CSF-1 gene is strongly implicated as the primary defect in op/op mice because they do not contain detectable CSF-1, their defect is correctable by administration of CSF-1, the op locus and the CSF-1 gene map within the same region of mouse chromosome 3, their CSF-1 mRNA biosynthesis is altered, and the op/op phenotype is consistent with the phenotype expected in a CSF-1 deficient mouse.

Animals↗

PubMed1990

Distribution of mutations around rearranged heavy-chain antibody variable-region genes.

The mechanism of somatic hypermutation in the variable region of immunoglobulin genes expressed in mammalian B cells is a major unexplained phenomenon in the generation of diversity in the immune system. To evaluate possible mechanisms, the distribution of somatic mutations was examined for a group of five cloned, rearranged, somatically mutated VH genes generated in C57BL/6j mice. These mutated VH genes were sequenced and compared with their germ line counterparts from a point approximately 550 base pairs upstream of the transcription start site to an EcoRI site some 1,200 base pairs downstream of JH-4. The location of the transcription start (cap) sites was also precisely determined. Most (greater than or equal to 94%) of the 118 mutations scored occurred between the transcription start site and the distal end of JH-4. However, seven mutations occurred upstream of the transcribed region, and at least four were found downstream of JH-4. The target region for the mutator mechanism therefore clearly extends into the 3' nontranslated and 5' nontranscribed regions. Thus, models which propose the transcribed region of the DNA as the sole substrate for the mutation process are not ruled out but are inadequate to explain the upstream distribution of somatic mutations.

Animals↗

PubMed1990

Regulation of polypeptide growth factor synthesis and growth factor-related gene expression in the rat and mouse uterus before and after implantation.

It is apparent that the uterus is a rich source of growth factors, the synthesis of which may be induced by female sex steroids. These growth factors appear to be involved in complex autocrine/paracrine regulatory circuits which in turn interact with steroid hormones. With the exception of CSF-1, however, detailed studies of the appearance of these growth factors and their receptors during pregnancy and under different hormonal regimens have yet to be performed. Furthermore, causative roles have not been established for any of these growth factors in uterine biology and pregnancy. In the near future we can expect that, by using in-situ techniques, the producing and responding cells will be identified. Cell culture models will also have to be established to investigate specific growth factor-induced functions. In the longer term, once more is known about the regulation of uterine growth factors, imaginative new experiments need to be designed, perhaps involving transgenic animals, to establish causative roles for growth factors in uterine biology.

Animals↗

PubMed1990

Characterization and expression of uterine and placental alkaline phosphatases in the mouse.

Alkaline phosphatase (ALP) is rapidly induced in the uterine subepithelial stroma after a natural or artificial decidual stimulus. During gestation ALP-specific activity peaked at Day 7 to 8 (Day 1 is day of detection of the copulation plug) followed by a rapid decline to control levels by Day 9. This elevation in enzyme activity was preceded by an 8-fold induction of a 2.6 kilobase (kb) mRNA. This mRNA was not preferentially localized to implantation sites. ALP activity was detected in the placenta at Day 9 and reached maximum specific activity at Day 19. The placental ALP was also encoded by a 2.6 kb mRNA. Uterine and placental ALPs were inhibited to the same extent by levamisole, L-tryptophan and homoarginine. The calculated Ki values for these inhibitors were not statistically different between the uterine and placental forms. Km values towards the substrate p-nitrophenylphosphate, however, were statistically different between the uterine and placental forms. Both uterine and placental ALPs were stimulated 3-4-fold by addition of 2 mM-Mg2+. Electrophoretic mobilities on SDS polyacrylamide gel, where the enzyme migrated as a single band, were the same. The uterine form, however, could be distinguished from the placental isoenzyme by separation on non-denaturing polyacrylamide gels; the uterine form had a single zone of activity which migrated with an intermediate mobility between the two zones of activity detected for the placental enzyme. These differences in mobility could be ascribed to the sialic acid content of the enzyme because treatment with neuraminidase resulted in the uterine and placental forms migrating with comparable but slower mobilities in non-denaturing gels.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗

PubMed1989

A novel role for aminoacyl-tRNA synthetases in the regulation of polypeptide chain initiation.

Exposure of the temperature-sensitive leucyl-tRNA synthetase mutant of Chinese hamster ovary cells, tsH1, to the non-permissive temperature of 39.5 degrees C results in a rapid inhibition of polypeptide chain initiation. This inhibition is caused by a reduced ability of the eukaryotic initiation factor eIF-2 to participate in the formation of eIF-2.GTP.Met-tRNAf ternary complexes and thus in the formation of 43S ribosomal pre-initiation complexes. Associated with this decreased eIF-2 activity is an increased phosphorylation of the eIF-2 alpha subunit. It has previously been shown in other systems that phosphorylation of eIF-2 alpha slows the rate of recycling of eIF-2.GDP to eIF-2.GTP catalysed by the guanine nucleotide exchange factor eIF-2B. We show here that phosphorylation of eIF-2 alpha by the reticulocyte haem-controlled repressor also inhibits eIF-2B activity in cell-free extracts derived from tsH1 cells. Thus the observed increased phosphorylation of eIF-2 alpha at the non-permissive temperature in this system is consistent with impaired recycling of eIF-2 in vivo. Using a single-step temperature revertant of tsH1 cells, TR-3 (which has normal leucyl-tRNA synthetase activity at 39.5 degrees C), we demonstrate here that all inhibition of eIF-2 function reverts together with the synthetase mutation. This establishes the close link between synthetase function and eIF-2 activity. In contrast, recharging tRNALeu in vivo in tsH1 cells at 39.5 degrees C by treatment with a low concentration of cycloheximide failed to reverse the inhibition of eIF-2 function. This indicates that tRNA charging per se is not involved in the regulatory mechanism. Our data indicate a novel role for aminoacyl-tRNA synthetases in the regulation of eIF-2 function mediated through phosphorylation of the alpha subunit of this factor. However, in spite of the fact that cell-free extracts from Chinese hamster ovary cells contain protein kinase and phosphatase activities active against either exogenous or endogenous eIF-2 alpha, we have been unable to show any activation of kinase or inactivation of phosphatase following incubation of the cells at 39.5 degrees C.

Amino Acyl-tRNA Synthetases↗

PubMed1989

Temporal expression and location of colony-stimulating factor 1 (CSF-1) and its receptor in the female reproductive tract are consistent with CSF-1-regulated placental development.

During pregnancy the mouse uterine epithelial synthesis of the mononuclear phagocyte growth factor designated colony-stimulating factor 1 (CSF-1) is regulated by female sex steroids. To study the role of CSF-1 in the pregnant female reproductive tract, the temporal expression and cellular sites of synthesis of CSF-1 and CSF-1 receptor (CSF-1R) mRNA were determined. CSF-1 mRNA, predominantly the 2.3-kilobase (kb) form, was first detected by in situ hybridization in uterine epithelium prior to implantation on day 3 and subsequently increased, reaching a peak at days 14-15. Its expression was restricted to the uterine epithelium at all stages of gestation and was not localized to areas of implantation. CSF-1R mRNA was first detected in maternal decidua at day 6. It was expressed in the decidua basalis during placentation, after which its expression declined. At day 7.5, trophectodermal cells also expressed CSF-1R mRNA; during placentation, it was found also in the diploid trophoblasts. The high level of CSF-1R mRNA expression by trophoblast giant cells was independent of their location around the conceptus. There was a differential distribution of CSF-1R mRNA expression in the mature placenta, with expression in the giant trophoblastic layer greater than spongiotrophoblastic layer greater than labyrinthine layer until term. Yolk sac cells also expressed low levels of CSF-1R mRNA. The coincidence of uterine CSF-1 mRNA expression and CSF-1 synthesis with both placental growth and CSF-1R mRNA expression in decidual cells and trophoblasts strongly implicates CSF-1 in the regulation of placental growth and differentiation.

Animals↗

PubMed1989

Colony-stimulating factor-1 induces rapid behavioural responses in the mouse macrophage cell line, BAC1.2F5.

The cloned, SV40-immortalized mouse macrophage cell line, BAC1.2F5, resembles primary macrophages in its dependence on colony-stimulating factor-1 (CSF-1) for both viability and proliferation. Re-addition of CSF-1 stimulates rapid, transient behavioural changes in starved cells, which are rounded, with diffusely organized F-actin and few intracellular vesicles. Within 1 min, cells begin to spread, forming prominent, F-actin-rich ruffles. Small vesicles (0.5-1.0 microns), formed throughout extending lamellar processes, move centripetally and, after 3-5 min, fuse to form larger vesicles (2.0-4.0 microns), clustered around the nucleus. Immunofluorescence demonstrates that CSF-1, bound to cell-surface receptors, is internalized via these vesicles. Cell spreading and ruffling peak about 5 min after restimulation. Interference reflection microscopy indicates no corresponding change in the mode of cell-substratum adhesion: a single area of close adhesion underlies most of the cell and simply broadens during spreading. Analysis of cell aggregation kinetics shows no effect of CSF-1 on intercellular adhesiveness. Measurement of cell areas after starvation and restimulation demonstrates quantitatively the time-course and concentration-dependence of cell spreading. Mean area doubles within 5 min and, after a transient peak, decreases within 30 min to the value measured before starvation. This time-course corresponds to that of CSF-1 internalization and of the phosphorylation and subsequent degradation of CSF-1 receptors. The concentration-dependence of the spreading response resembles that of CSF-1-dependent survival and proliferation. The minimum detectable stimulation of spreading occurs at the concentration (22 pM) that supports survival without proliferation. Increasing stimulation of spreading occurs over the range of concentrations that elicit increasing proliferation.

Actins↗

PubMed1989

Effect of intrauterine and intramuscular administration of recombinant bovine interferon alpha 1 on luteal lifespan in cattle.

Intrauterine and intramuscular administration of interferon was tested for effectiveness in extending luteal lifespan in cattle. Intrauterine infusion of 1 mg of recombinant bovine interferon-alpha I1, twice daily, to lactating dairy cows from d 14 to 21 after estrus extended interestrous interval (30.4 +/- 1.91 d versus 24.8 +/- .58 d) and functional lifespan of the corpus luteum (28.4 +/- 2.01 d versus 23.6 +/- .75 d). In another experiment, twice daily intramuscular injection of 20 mg interferon to Simmental heifers from d 15 to 19 extended interestrous intervals (24.6 +/- 1.36 d versus 20.6 +/- .49 d) and functional lifespan of the corpus luteum (23.2 +/- .37 d versus 20.2 +/- .73 d). In a third experiment, pubertal dairy heifers received twice daily intramuscular injections of 0, 2.5, 5.0, or 10.0 mg/injection of interferon from d 14 to 21 after estrus. The three interferon-treated groups had longer interestrous intervals and functional luteal lifespans than the control group. Interestrous intervals were 22.0 +/- .68, 24.0 +/- 1.14, 24.6 +/- 1.17, and 25.4 +/- .97 d, respectively. The present data strengthen the theory that an interferon-alpha-like molecule can regulate luteal function in cattle. Such a regulatory compound might prove useful in schemes to reduce embryonic mortality caused by aberrant secretion of embryonic interferon.

Animals↗

PubMed1988

Culture of rabbit embryos and isolated blastomeres in hydrogel chambers implanted in the peritoneal cavity of intermediate mouse recipients.

Chambers made from polymerized 2-hydroxyethyl methacrylate were used for the in vivo culture of rabbit embryos or isolated blastomeres. In Experiment 1, culture of 119, one-cell embryos for 72 hr in saline-filled chambers implanted in the peritoneal cavity of male mice resulted in 72 morulae and 25 blastocysts. Transfer of these 97 embryos to recipient does resulted in the birth of 3 live offspring (3%). Culture of 119, one-cell embryos for 72 hr in saline-filled chambers implanted in the peritoneal cavity of female mice resulted in 23 morulae and 68 blastocysts. Transfer of these 91 embryos to recipient does resulted in the birth of 20 live offspring (22%). All of the 119 control, one-cell embryos had degenerated after 72 hr of in vitro culture in saline-filled chambers. In Experiment 2, culture of 80 blastomeres isolated from four-cell embryos for 72 hr in compartmentalized, medium-filled chambers implanted in the peritoneal cavity of female mice resulted in 21 morulae and 43 blastocysts. For both experiments, the recovery rate for embryos or isolated blastomeres after in vivo culture was 100%.

Animals↗

PubMed1988

RU 486 completely inhibits the action of progesterone on cell proliferation in the mouse uterus.

The antiprogestagen RU 486 completely inhibited the progesterone-induced switch in cell proliferation from the luminal and glandular epithelia to the stroma in response to oestradiol-17 beta. It also inhibited the progesterone-induced differentiation of the uterine epithelium. Since the proliferative switch of the uterus and the differentiation of the epithelium are prerequisites for implantation, these inhibitory actions may, in part, explain the ability of RU 486 to prevent implantation. Furthermore, it also suggests that the proliferative response to oestradiol in the presence of progesterone may be a sensitive assay for compounds with anti-progestational activity.

Animals↗

PubMed1987

Regulation of polypeptide chain initiation in Chinese hamster ovary cells with a temperature-sensitive leucyl-tRNA synthetase. Changes in phosphorylation of initiation factor eIF-2 and in the activity of the guanine nucleotide exchange factor GEF.

When cultures of the temperature-sensitive Chinese hamster ovary cell mutant tsH1 are shifted from 34 degrees C (permissive temperature) to 39.5 degrees C (nonpermissive temperature), protein synthesis is inhibited by more than 80%. This is due principally to a block in activity of polypeptide chain initiation factor eIF-2. In this paper we show that there is impairment of the ability of the guanine nucleotide exchange factor (GEF) to displace GDP from eIF-2 X GDP complexes in extracts from cells incubated at the nonpermissive temperature. Addition of GEF or of high concentrations of eIF-2 stimulates protein synthesis to the level observed in control cell extracts, suggesting that GEF is rate-limiting for eIF-2 activity and overall protein synthesis at the nonpermissive temperature. Analysis of eIF-2 by two-dimensional gel electrophoresis and immunoblotting reveals an increase in the proportion of the alpha subunit in the phosphorylated form from 5.5 +/- 2.4% to 17.2 +/- 3.9% on shifting tsH1 cells from 34 to 39.5 degrees C. No such effect is seen in wild-type cells, which do not exhibit temperature-sensitive protein synthetic activity. Since the primary lesion in tsH1 cells is in their leucyl-tRNA synthetase, these results suggest a role for eIF-2 phosphorylation and GEF activity in coupling the rate of polypeptide chain initiation to the activity of the chain elongation machinery.

Animals↗

PubMed1987

Isolation and characterization of a cloned growth factor dependent macrophage cell line, BAC1.2F5.

The SV40 transformed murine macrophage cell line, BAC1, proliferates in response to the colony stimulating factor, CSF-1 (Schwarzbaum et al., J. Immunol., 132:1158, 1984). In order to obtain a cell line suitable for biochemical and genetic studies of CSF-1 signal transduction, clones of BAC1 were established. Clones ranged from being completely autonomous to being completely dependent on CSF-1 for growth. Cells of one clone (2F5), which proliferated in response to either CSF-1 or granulocyte-macrophage CSF (GM-CSF) were characterized in detail. The kinetics of receptor-mediated internalization and intracellular destruction of CSF-1 were comparable to the kinetics observed with peritoneal exudate macrophages. CSF-1 was shown to regulate cell spreading, cell survival, protein degradation, and the duration of the G1 and S phases of the cell cycle. The 2F5 clone therefore exhibits a number of CSF-1 stimulated responses and is being used for genetic and biochemical studies of CSF-1 action.

Animals↗