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H Morton

Publications and source records attributed to H Morton.

At least 19 recordsLinked to original sources
PubMed1992

Effect of monoclonal antibodies to early pregnancy factor (EPF) on the in vivo growth of transplantable murine tumours.

Neutralisation studies with monoclonal antibodies (mAbs) specific for early pregnancy factor (EPF) have shown it to be essential for the continuation of pregnancy in mice and the growth of some tumour cells in vitro. These studies report that the mAbs are also able to limit the growth of two murine tumour lines transplanted s.c. The development of MCA-2 tumours in CBA mice was unaffected by the injection of 1 mg anti-EPF IgM at the time of tumour cell inoculation. However, four doses of 500 micrograms anti-EPF, injected one dose per day for 4 days after tumour cell inoculation, significantly retarded tumour development such that no tumours were palpable on day 13. A similar dose regimen of control IgM had no effect on tumour size. Dose/response studies revealed that lower doses of anti-EPF administered after tumour cell inoculation were effective in retarding the growth of the MCA-2 tumours. The effects of anti-EPF mAb administration on the growth rate of palpable B16 tumours established s.c. in C57BL/6 mice was also determined. Tumours injected with 6 mg anti-EPF 5/341 or anti-EPF 5/333 mAbs showed significant decrease in the uptake of [3H]thymidine into tumour tissue, measured 16 h after injection. Furthermore, titration of sera for active EPF showed that a significant reduction in the EPF titre was associated with a significant inhibition of tumour DNA synthesis. Thus it appears that neutralisation of EPF retards tumour growth both in vitro and in vivo. In vitro the effects must be due to anti-EPF mAb interfering with a direct mechanism that contributes to the maintenance of cells in the active growing phase. However, in vivo host immunological mechanism that are modified to allow tumour survival may also be affected. The presence of EPF-induced suppressor factor circulating in the serum of tumour-bearing mice has been confirmed and the contribution of such factors to tumour progression must now be investigated.

Animals↗
PubMed1992

Early pregnancy factor has immunosuppressive and growth factor properties.

Early pregnancy factor (EPF) was first described as a pregnancy-associated substance, although recent studies suggest a more general link with cell development. It is a product of actively dividing cells and its apparent functional importance to them suggests its potential as a regulator of cell proliferation. The recent discovery of EPF in platelets has provided a comparatively rich and readily available source of EPF. The purification procedures employed to isolate EPF from this source have also been applied to pregnancy serum and urine, medium conditioned by oestrous mouse ovaries (stimulated with prolactin and embryo-conditioned medium), medium conditioned by tumour cells, and serum from rats 24 h after partial hepatectomy (PH). In all instances, biological activity followed the same pattern throughout. Furthermore, the final active reversed-phase high-performance liquid chromatography fraction from all sources was bound specifically by immobilized anti-EPF monoclonal antibodies (MAbs), indicating that the active fractions produced from these diverse sources are very closely related, if not identical. Some differences have been observed in the behaviour of EPF in various conditions. EPF is produced by proliferating tumour cells and by liver cells post-PH, and passive immunization studies with anti-EPF MAbs have shown that these cells need EPF for survival. In contrast, EPF has not been detected as a product of the pre-embryo, and addition of anti-EPF MAbs to embryo cultures does not adversely affect development from the 2-cell to the blastocyst stage. Although the pre-embryo is not dependent on EPF for its development in vitro, neutralization of EPF in vivo by anti-EPF MAbs retards its development. Thus, EPF appears to play an indirect role in maintaining the pre-embryo. By virtue of its ability to suppress the delayed-type hypersensitivity reaction, it has been suggested that EPF might act as an immunological response modifier of the maternal immune system. Alternatively, the effect of EPF on lymphocytes may be to reduce the expression of all or some cytokines and this could inhibit development. Whether or not EPF acts more directly as an autocrine growth factor from around the time of implantation, when the embryo first begins synthesis of EPF, is not known and remains to be investigated.

Animals↗
PubMed1991

Identification of a putative inhibitor of early pregnancy factor in mice.

Previous studies have indicated that early pregnancy factor (EPF) produced in the pre- and peri-implantation stage of pregnancy appears to consist of inactive components which combine to produce the active species. This is in contrast with EPF produced later in gestation which appears to consist of a single active species. The original studies on ammonium sulphate fractionation of mouse serum and in-vitro culture of mouse ovaries and oviducts have been repeated but tested in the bioassay for EPF, the rosette inhibition test, over an extended range of dilutions. This revealed that the two components in early pregnancy can be understood as EPF and an inhibitor(s). Once this inhibitor is removed, the active fractions in both early and late pregnancy sera exhibit similar behaviour in the above assay. It was shown also that the ovary alone is the source of activity but that this is modulated by an inhibitory substance(s) from the oviduct. Reversed-phase HPLC studies on purified 'early' EPF confirm that active and inhibitory components are present and demonstrate that the active component exhibits an identical elution pattern to 'late' EPF. Thus as pregnancy proceeds, it is not EPF that alters but rather the inhibitor(s), which disappears from the circulation soon after implantation. This substance(s) is under hormonal control, being present during oestrus as well as the early stages of pregnancy; it may be an important biological regulator of EPF. Its action in the rosette inhibition test has profound implications for further study using this bioassay.

Ammonium Sulfate↗
PubMed1991

Antibodies to early pregnancy factor retard embryonic development in mice in vivo.

Previous work in this laboratory has shown that passive immunization of mice against early pregnancy factor (EPF) leads to failure to maintain pregnancy. The findings presented in this paper demonstrate that this treatment affects the development of the embryos very early in gestation. By Day 3, 54 and 25% of embryos in the 2 groups treated with anti-EPF immunoglobulin (Ig)G and IgM, respectively, had not developed to the 4-cell stage, compared with 12 and 1% in the control groups. None of the embryos in the mice treated with anti-EPF had developed beyond the 8-cell stage. A similar delay in development after treatment was observed on Day 4. The effect apparent during the early stages of cleavage is an indirect rather than a direct one, as 2-cell embryos (32-36 h post coitum), cultured in vitro in the presence of anti-EPF antibodies, developed uninterrupted to the morula and blastocyst stage. The delay in development did not appear to be caused by a disruption of the normal pattern of circulating progesterone, as progesterone concentrations on Day 4 were within the normal range for Quackenbush mice.

Animals↗
PubMed1991

Relationship between early pregnancy factor, mouse embryo-conditioned medium and platelet-activating factor.

The effects of synthetic platelet-activating factor (PAF-acether) and mouse embryo-conditioned medium (a source of embryo-derived PAF (EPAF)) on production of early pregnancy factor (EPF) were compared. Embryo-conditioned medium, itself inactive in the EPF bioassay, stimulated ovarian production of EPF in vitro but PAF-acether did not. In vivo, embryo-conditioned medium induced EPF activity in serum of oestrous female, but not in male, mice in contrast to PAF-acether, which induced activity in serum of both male and female mice. This PAF-induced activity was transitory, declining significantly by 2 h and disappearing by 3 h after injection. Activity induced by embryo-conditioned medium was first evident at 2 h after injection, serum concentrations increasing up to 6 h after injection. By discriminating between the behaviour of PAF-acether and EPAF, these studies reinforce the conclusions of other workers that the molecule produced by the embryo is not PAF. Further investigations into the mechanism of action of PAF-acether revealed that it is a potent inducer of activity in the EPF bioassay, with an absolute requirement for platelets in the spleen cell suspension used in the assay. This platelet-derived active species was bound specifically by an anti-EPF monoclonal antibody, indicating that it is EPF-like. This is consistent with parallel studies showing that platelets are not required for induction of activity by either pregnancy serum or purified EPF. These studies were applied to the PAF-induced leukotriene-like species, which had been found by others to be active in the EPF bioassay. Pregnancy serum induced the appearance of this substance from the spleen cell suspension used in the assay; thus the leukotriene-like substance may be regarded as an effector molecule in vitro or mediator of the initiating stimulus of EPF in the bioassay.

Animals↗
PubMed1990

Monoclonal antibodies to early pregnancy factor perturb tumour cell growth.

The pregnancy-associated substance early pregnancy factor (EPF) has previously been reported as a product of tumours of germ cell origin. More recently EPF (or an EPF-related substance, tEPF) has also been detected in the serum of patients bearing tumours of non-germ cell origin. We report here the production of tEPF by a variety of cultured transformed and tumour cell lines, of both germ and non-germ cell origin. Antibodies specific for EPF remove all tEPF activity from tumour cell conditioned medium. tEPF production is found to be associated with cell division; tEPF is no longer detected after growth arrest or differentiation. Co-culture of tumour cells with increasing doses of anti-EPF monoclonal antibodies resulted in a significant, dose-dependent decrease in rate of cell growth and viability. Similar anti-EPF concentrations had no effect on the concanavalin A induced proliferation of mouse spleen cells. These studies suggest, therefore, that tEPF is a growth-regulated product of cultured tumour and transformed cells. These cells are also dependent upon tEPF for continued growth, i.e. tEPF is acting in the autocrine mode.

Animals↗
PubMed1990

Thromboxane A2 and prostaglandin endoperoxide analogue effects on porcine renal blood flow.

Thromboxane A2 (TxA2) has been implicated as a mediator of renal and cardiovascular diseases. However, the direct effects of TxA2 on the renal system have been difficult to study because of the instability of the agonist. In the present study injection of synthetic TxA2 directly into the renal artery of anesthetized pigs produced dose-related decreases in renal blood flow (RBF) from 101 +/- 11 to 12 +/- 3 ml/min at the highest dose (20 ng/kg). The reductions in RBF were similar to those produced by the stable prostaglandin endoperoxide analogue, U-44069, although TxA2 was three times more potent. Under these conditions there were no effects on either mean (MAP) or pulmonary arterial pressures (PAP), or the heart rate (HR). The maximal effects produced by TxA2 and U-44069 on RBF were reproducible and the response remained unchanged after pretreatment with either heparin or indomethacin. Systemically administered TxA2 (200 ng/kg iv) increased PAP from 20 +/- 1 to 34 +/- 3 mmHg and this effect was associated with modest increases in MAP and HR. Intravenous administration of the thromboxane receptor antagonist, L-655,240, inhibited the reductions in RBF produced by intrarenal TxA2 and U-44069 and attenuated the cardiopulmonary effects of TxA2 administered intravenously. The results demonstrate directly that TxA2 is a potent agent for decreasing RBF through interaction with a thromboxane receptor.

Animals↗
PubMed1989

Fractional conversion of thromboxane A2 and B2 to urinary 2,3-dinor-thromboxane B2 and 11-dehydrothromboxane B2 in the cynomolgus monkey.

Following the intravenous administration of thromboxane (TX) B2, the stable hydration product of TXA2, to human and nonhuman primates the most abundant urinary metabolites are 2,3-dinor-TXB2 and 11-dehydro-TXB2. However, it is not known whether fractional conversion of TXB2 to its enzymatic metabolites is an accurate representation of TXA2 metabolism. Thus, we have compared the metabolic disposition of synthetic TXA2 and TXB2 via the beta-oxidation and 11-OH-dehydrogenase pathways in vivo in the monkey. TXA2 or TXB2 (20 ng/kg) was intravenously administered to four cynomolgus monkeys pretreated with aspirin in order to suppress endogenous TXA2 production. Urinary TXB2, 2,3-dinor-TXB2 and 11-dehydro-TXB2 were measured before, during and up to 24 h after thromboxane administration by means of reversed-phase high-performance liquid chromatography radioimmunoassay. Aspirin treatment suppressed urinary 2,3-dinor-TXB2 and 11-dehydro-TXB2 by approx. 75%. A similar fractional conversion of TXA2 and TXB2 into 2,3-dinor-TXB2 and 11-dehydro-TXB2 was found. These results suggest that TXA2 is hydrolyzed to TXB2 prior to enzymatic degradation and that metabolites of the latter represent reliable indices of TXA2 biosynthesis. Due to the variability in the conversion of thromboxanes into 2,3-dinor-TXB2 and 11-dehydro-TXB2, the measurement of both metabolites seems to represent a more reliable index of acute changes in TXA2 production.

Animals↗
PubMed1989

Genetically-restricted effector molecules released by human lymphocytes in response to early pregnancy factor.

The binding of early pregnancy factor (EPF) to lymphocytes stimulates the release of soluble effector molecules. Studies in mice have shown that it is these factors rather than EPF as such which are inhibitory in the T cell-dependent reactions, the adoptive transfer of contact sensitivity and the rosette inhibition test. Two factors have been identified: mEPF-S1 (Mr approximately 15,000) is major histocompatibility complex (MHC)-restricted while mEPF-S2 (Mr approximately 55,000) is restricted to a locus (or loci) outside the MHC. In the present paper, evidence is presented which shows that EPF also induces the release of soluble mediators from human lymphocytes. With the rosette inhibition test two factors have been detected, both of similar size and genetic restriction to those described previously in the mouse. One factor, designated hEPF-S1 (Mr 14-18,000), is human lymphocyte antigen (HLA)-restricted and the other, hEPF-S2 (Mr 50-60,000), appears to be restricted to a locus (or loci) outside the HLA complex.

Chaperonin 10↗
PubMed1989

L-663,536 (MK-886) (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2 - dimethylpropanoic acid), a novel, orally active leukotriene biosynthesis inhibitor.

L-663,536 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2, 2-dimethylpropanoic acid) is a potent inhibitor of leukotriene (LT) biosynthesis in intact human polymorphonuclear leukocytes (PMN) (IC50, 2.5 nM). Similarly, L-663,536 inhibited A23187-induced LTB4 formation by rat peripheral blood and elicited PMN. At concentrations where inhibition of leukotriene biosynthesis occurred in human whole blood (1.1 microM), no effect was seen on cyclooxygenase or 12-lipoxygenase, an effect also observed in washed human platelets. The compound had no effect on rat or porcine 5-lipoxygenase indicating that L-663,536 is not a direct 5-lipoxygenase inhibitor. When administered in vivo L-663,536 was a potent inhibitor of antigen-induced dyspnea in inbred rats pretreated with methysergide (ED50, 0.036 mg/kg p.o.) and of Ascaris-induced bronchoconstriction in squirrel monkeys (1 mg/kg p.o.). The compound inhibited leukotriene biosynthesis in vivo in a rat pleurisy model (ED50, 0.2 mg/kg p.o.), an inflamed rat paw model (ED50, 0.8 mg/kg), a model of leukotriene excretion in rat bile following antigen provocation, and a model in the guinea-pig ear where leukotriene synthesis was induced by topical challenge with ionophore A23187 (ED50, 2.5 mg/kg p.o. and 0.6 micrograms topically). The results indicate that L-663,536 is a potent inhibitor of leukotriene biosynthesis both in vitro and in vivo indicating that the compound is suitable for studying the role of leukotrienes in a variety of pathological situations.

Animals↗
PubMed1989

Passive immunization of pregnant mice against early pregnancy factor causes loss of embryonic viability.

Early pregnancy factor (EPF) is a monitor of the incidence of fertilization and the progress of the early embryo. To determine whether, as well as being a marker of embryonic viability, EPF is also necessary for embryonic survival, passive immunization studies with monoclonal and polyclonal antibodies to EPF were carried out on pregnant mice. In the preparation of monoclonal antibodies, it was noted that most anti-EPF producing hybridomas failed to grow in vitro, while those that did grow produced only low yields of specific IgM antibodies. Two stable hybridoma cell lines were established both producing low affinity anti-EPF IgM; polyclonal anti-EPF IgG was prepared in rabbits. Mice were passively immunized with 500 micrograms monoclonal anti-EPF IgM at 32 and 56 h post coitum (total dose 1 mg) or with 500 micrograms polyclonal anti-EPF IgG at 8, 16, 32 and 40 h post coitum (total dose 2 mg). At 10 days, only 6/18 and 3/6 mice receiving monoclonal antibodies and 2/7 and 1/6 mice receiving polyclonal antibodies had maintained their pregnancies. In contrast, all mice receiving control IgM (N = 14) or control IgG (N = 4) and 22/23 receiving saline were still pregnant at Day 10.

Animals↗
PubMed1988

Identification of two suppressor factors induced by early pregnancy factor.

The binding of EPF to lymphocytes stimulates the release of soluble mediators, active in T cell dependent reactions, namely the rosette inhibition test and the adoptive transfer of contact sensitivity. On the basis of their ability to inhibit the delayed type hypersensitivity reaction in this latter assay, they have been classified as suppressor factors. This paper describes the identification of two EPF-induced suppressor factors. Unlike EPF which is neither species-restricted nor strain-restricted, these factors are genetically restricted in their action in the rosette inhibition test. EPF-S1 (estimated Mr 14,000) is restricted to the 1 region of the mouse MHC, while EPF-S2 (estimated Mr 55,000) is restricted to a locus (or loci) outside the MHC. Like other antigen non-specific factors, release of these suppressor factors can be stimulated also by Con A.

Animals↗
PubMed1979

Detection of early pregnancy in sheep by the rosette inhibition test.

The rossette inhibition test, an established test for determining the immunosuppressive potential of antilymphocyte serum, has been applied to the serum of sheep after mating. The rosette inhibition titre was much higher (12--26) in 7 sheep which were fertilized and remained pregnant for up to 21 days than in 5 sterile ewes mated with intact rams (8--10). The difference was apparent by 24 h after mating. One ewe had high titres for 6 days after mating but these then dropped and she returned to oestrus; early embryonic loss was suspected. Another ewe which returned to oestrus had consistently low titres. The results indicate that the rosette inhibition test can be used to detect fertilization, early embryonic death and continued pregnancy in sheep.

Animals↗
PubMed1979

A test for early pregnancy in sheep.

The rosette inhibition test has been used to detect an early pregnancy factor (EPF) in the serum of ewes. EPF was shown to be to be present within 72 h of mating and was still detectable after one month of gestation and in some cases after four months' gestation. The detection of EPF could be of value in the diagnosis of pregnancy in the ewe during the first month of gestation.

Animals↗