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Topic:Immunology

The equine immune system is a complex network of cells, tissues, and organs that work collaboratively to defend against pathogens and maintain homeostasis. It consists of innate and adaptive components, each with distinct functions and mechanisms. The innate immune system provides the first line of defense through physical barriers, phagocytic cells, and the complement system. The adaptive immune system involves lymphocytes, such as B cells and T cells, which generate specific responses to antigens and provide immunological memory. Research in equine immunology explores the interactions between these components, the impact of genetic and environmental factors on immune function, and the development of vaccines and therapeutics. This page gathers peer-reviewed studies and scholarly articles focusing on the mechanisms, regulation, and clinical applications of the equine immune system in health and disease.
Cloning and sequence analysis of a protective M-like protein gene from Streptococcus equi subsp. zooepidemicus.
Infection and immunity    April 1, 1995   Volume 63, Issue 4 1440-1445 doi: 10.1128/iai.63.4.1440-1445.1995
Timoney JF, Walker J, Zhou M, Ding J.Streptococcus equi subsp. zooepidemicus, a Lancefield group C streptococcus, is a frequently isolated opportunist pathogen from a variety of animal hosts, including the horse. Previous studies have indicated that equine strains carry antigens with characteristics of the antiphagocytic M proteins on the Lancefield groups A and G streptococci. We have cloned a protective M-like protein gene (SzPW60) of an equine strain of S. equi subsp. zooepidemicus W60 and determined its sequence. This gene encodes a protein with a molecular weight of 40,123 which protects mice against subsp. zooepidemicus but...
Delineating minimal protein domains and promoter elements for transcriptional activation by lentivirus Tat proteins.
Journal of virology    April 1, 1995   Volume 69, Issue 4 2605-2610 doi: 10.1128/JVI.69.4.2605-2610.1995
Southgate CD, Green MR.Lentivirus Tat proteins comprise a novel class of RNA-binding transcriptional activators that are essential for viral replication. In this study, we performed a series of protein fusion experiments to delineate the minimal protein domains and promoter elements required for Tat action. We show that a 15-amino-acid region of equine infectious anemia virus (EIAV) Tat protein, when fused to the GAL4 or LexA DNA binding domain, can activate transcription in appropriate promoter contexts. In the natural human immunodeficiency virus type 1 long terminal repeat, activation by Tat is dependent on multi...
Cellular and antibody responses to equine herpesviruses 1 and 4 following vaccination of horses with modified-live and inactivated viruses.
Journal of the American Veterinary Medical Association    March 15, 1995   Volume 206, Issue 6 823-832 
Ellis JA, Bogdan JR, Kanara EW, Morley PS, Haines DM.The ability of monovalent and bivalent equine herpesvirus (EHV) vaccines to stimulate cellular and antibody responses to EHV-1 and EHV-4 was compared in healthy horses. Comparison of data from lymphocyte blastogenesis tests in which live viruses were used as antigens and that were conducted prior to vaccination and after 2 vaccinations revealed that horses given modified-live EHV-1 had significant increases in proliferative responses to EHV-1 (P = 0.03) and EHV-4 (P = 0.04). Responses to EHV-1 and EHV-4 in horses given the inactivated-virus bivalent vaccine were less; however, significant diff...
Abnormal patterns of equine leucocyte differentiation antigen expression in severe combined immunodeficiency foals suggests the phenotype of normal equine natural killer cells.
Immunology    March 1, 1995   Volume 84, Issue 3 495-499 
Lunn DP, McClure JT, Schobert CS, Holmes MA.Severe combined immunodeficiency (SCID) is a fatal autosommal disease of Arabian horses that leads to failure of maturation of T- and B-lymphocyte populations, although natural killer (NK) cells are unaffected. Thymic and lymph node tissues from two foals suffering from SCID were examined in an immunohistological study using a panel of monoclonal antibodies recognising equine leucocyte differentiation antigens. In both foals, the majority of cells in lymphoid tissues had an EqCD3-EqCD4-EqCD8+ phenotype, although rare EqCD3+ cells were also detected. The EqCD3-EqCD4-EqCD8+ cells may represent a...
Immunohistochemical localisation of met-enkephalin in the adrenal gland of the fetal and newborn horse.
Equine veterinary journal    March 1, 1995   Volume 27, Issue 2 147-149 doi: 10.1111/j.2042-3306.1995.tb03052.x
Challis JR, Han X, Matthews SG, Fowden AL, Silver M, Holdstock N, McGladdery A, Ousey JC, Allen WR, Rossdale PD.No abstract available
Antiphagocytic properties of uterine isolates of Streptococcus zooepidemicus and mechanisms of killing in freshly obtained blood of horses.
American journal of veterinary research    March 1, 1995   Volume 56, Issue 3 321-328 
Causey RC, Paccamonti DL, Todd WJ.A total of 22 clinical streptococcal isolates, predominantly Streptococcus zooepidemicus, associated with endometritis in horses were tested for their ability to withstand the natural bactericidal properties of freshly obtained blood. During a 3-hour incubation in blood from a single horse, 8 of these isolates survived and grew, the remainder were killed. To determine whether this ability to grow extended to blood of other horses, 5 of these growing isolates were tested for their ability to grow in the blood of 5 additional horses. The same 5 horses were used for each isolate. The isolates gre...
Accumulation of chromotrope 2R positive cells in equine endometrium during early pregnancy and expression of transforming growth factor-beta 2 (TGF-beta 2).
Journal of reproduction and fertility    March 1, 1995   Volume 103, Issue 2 339-347 doi: 10.1530/jrf.0.1030339
Lea RG, Stewart F, Allen WR, Ohno I, Clark DA.Endometrial tissue from the gravid uterine horn of pregnant mares was examined by northern analysis and in situ hybridization for mRNA that hybridized to cDNA and RNA probes generated from a mouse TGF-beta 2 1.2 kb cDNA clone. The mouse cDNA probe hybridized to characteristic TGF-beta 2 mRNA transcripts on a northern blot of total RNA isolated from horse endometrium collected at day 45 of gestation. Two major 4.0 and 3.5 kb transcripts and possibly a minor 1.6 kb transcript were observed, consistent with specific hybridization to equine TGF-beta 2 mRNA. By in situ hybridization, riboprobes tra...
Spontaneous equine pulmonary granular cell tumors: morphologic, histochemical, and immunohistochemical characterization.
Veterinary pathology    March 1, 1995   Volume 32, Issue 2 101-106 doi: 10.1177/030098589503200201
Kelley LC, Hill JE, Hafner S, Wortham KJ.Spontaneous equine pulmonary granular cell tumors were diagnosed in six mature horses at slaughter. These tumors were grossly recognized as multiple (5/6) or single (1/6) creamy white, firm nodules. The tumors, located adjacent to bronchi and bronchioles, often invaded airways, resulting in partial to complete occlusion of the lumina. Neoplastic cells were rounded to polyhedral with numerous eosinophilic cytoplasmic granules that reacted uniformly positive with S-100 and neuron-specific enolase antibodies and multifocally with glial fibrillary acidic protein antibodies. These cells were negati...
Evaluation of Directigen Flu A assay for detection of influenza antigen in nasal secretions of horses.
Equine veterinary journal    March 1, 1995   Volume 27, Issue 2 131-134 doi: 10.1111/j.2042-3306.1995.tb03049.x
Morley PS, Bogdan JR, Townsend HG, Haines DM.The Directigen Flu A assay (Becton Dickinson, Microbiology Systems, Mississauga, Ontario, Canada) is a commercially available immunoassay designed for rapid in vitro recognition of influenza A nucleoprotein. The purpose of this study was to evaluate this assay for detection of influenza virus in nasal secretions of naturally infected horses. The assay was shown to react with representative strains of influenza virus which cause disease in horses and did not react with nasal secretions from uninfected horses kept in isolation. Between 33% and 45% of nasal secretions specimens obtained from clin...
Anti-collagen antibodies and immune complexes in equine joint diseases.
Veterinary immunology and immunopathology    March 1, 1995   Volume 45, Issue 1-2 19-30 doi: 10.1016/0165-2427(94)05325-m
Osborne AC, Carter SD, May SA, Bennett D.An investigation was made into the possible contribution of autoimmune mechanisms to equine arthropathies. Serum and synovial fluid (SF) immune complexes and anti-collagen Type II antibodies were measured, by ELISA, in groups of horses with naturally occurring osteoarthritis (OA), osteochondritis dissecans (OCD), bone fracture, traumatised joints, synovitis, infected joints and non-diseased (control) joints. Significantly raised anti-collagen Type II antibodies were found in osteoarthritic (P < 0.02) and traumatised joint synovial fluids (P < 0.01) compared with the control, where ten of...
Immunohistochemical localisation of steroidogenic enzymes and phenylethanolamine-N-methyl-transferase (PNMT) in the adrenal gland of the fetal and newborn foal.
Equine veterinary journal    March 1, 1995   Volume 27, Issue 2 140-146 doi: 10.1111/j.2042-3306.1995.tb03051.x
Han X, Fowden AL, Silver M, Holdstock N, McGladdery AJ, Ousey JC, Allen WR, Rossdale PD, Challis JR.An increase in fetal adrenal cortisol output signals the onset of parturition in many animal species but, in the fetal horse, plasma concentrations of cortisol remain low for much of late pregnancy, with a rise occurring only very close to the time of birth (term 320-360 days). Immunohistochemistry was used to determine the localisation and changes in distribution of key steroidogenic enzymes for cortisol production; P450scc, P450C17 and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in adrenal tissue from fetal and newborn horses and these findings were correlated with the appearance of imm...
Enhanced sensitivity to neutralizing antibodies in a variant of equine infectious anemia virus is linked to amino acid substitutions in the surface unit envelope glycoprotein.
Journal of virology    March 1, 1995   Volume 69, Issue 3 1493-1499 doi: 10.1128/JVI.69.3.1493-1499.1995
Cook RF, Berger SL, Rushlow KE, McManus JM, Cook SJ, Harrold S, Raabe ML, Montelaro RC, Issel CJ.Serial passage of the prototype (PR) cell-adapted Wyoming strain of equine infectious anemia virus (EIAV) in fetal donkey dermal (FDD) rather than fetal horse (designated fetal equine kidney [FEK]) cell cultures resulted in the generation of a variant virus strain which produced accelerated cytopathic effects in FDD cells and was 100- to 1,000-fold more sensitive to neutralizing antibodies than its parent. This neutralization-sensitive variant was designated the FDD strain. Although there were differences in glycosylation between the PR and FDD strains, passage of the FDD virus in FEK cells di...
The equine endometrial cup reaction: a review.
The veterinary quarterly    March 1, 1995   Volume 17, Issue 1 21-29 doi: 10.1080/01652176.1995.9694525
Koets AP.The function of eCG in equine pregnancy is far from clear but it has become evident that eCG has little or no FSH activity in the horse and is therefore probably not responsible for the secondary ovulations. eCG does have luteotrophic activity and it could play a role in the resurgence of the primary corpus luteum (1,7,44). Some evidence exists that the receptor population on the equine gonads is heterogenous in a way that makes it possible to distinguish eCG from eLH, resulting in different post-receptor effects (7). There is also evidence that eCG itself is heterogenous, both in glycosylatio...
An 80-kDa syncytiotrophoblast alloantigen bound to maternal alloantibody in term placenta.
American journal of reproductive immunology (New York, N.Y. : 1989)    March 1, 1995   Volume 33, Issue 3 213-220 doi: 10.1111/j.1600-0897.1995.tb00887.x
Jalali GR, Rezai A, Underwood JL, Mowbray JF, Surridge SH, Allen WR, Matthias S.We have shown that most of the IgG present on term syncytiotrophoblast, membrane, microvesicles is bound to an 80 kDa protein antigen (R80K). Methods: Microvesicles were prepared from term human placenta, and the IgG eluted at pH3. Results: When IgG antibody was eluted at pH3 and reacted with acid-treated vesicles of other placentae, the alloantibody always bound to the preparation from which it was obtained, but only to about 10% of acid-treated preparations from other placentae. A similar polymorphic protein found in association with IgG antibody was found in term horse placentae. Cross-reac...
Regulation of granule size in human and horse eosinophils by number of fusion events among unit granules.
The Journal of physiology    February 15, 1995   Volume 483 ( Pt 1), Issue Pt 1 201-209 doi: 10.1113/jphysiol.1995.sp020578
Hartmann J, Scepek S, Lindau M.1. We have investigated the granule size distributions in human and horse eosinophils by time-resolved patch-clamp capacitance measurements. 2. During exocytosis of single granules the electrical capacitance of the plasma membrane increases in discrete steps. The steps in horse cells are about six times larger than those in human cells in accordance with the difference in granule size. 3. In both species a multimodal capacitance step size distribution is observed with a first peak at 6-7 fF corresponding to granules with a diameter of about 450-500 nm and a surface area of about 0.7 microns2, ...
Polyclonal antibody-based antigen-detection immunoassay for diagnosis of Trypanosoma evansi in buffaloes and horses.
Veterinary parasitology    February 1, 1995   Volume 56, Issue 4 261-267 doi: 10.1016/0304-4017(94)00689-a
Singh V, Chaudhari SS, Kumar S, Chhabra MB.An enzyme-linked immunosorbent assay (ELISA) was employed for the detection of Trypanosoma evansi antigens in serum samples of field cases of buffaloes and horses in northern India. In 323 naturally infected/suspected buffaloes, circulating antigenaemia was detected in 180 (55.72%), whereas parasitaemia by wet blood smear examination was found in 62 (19.19%) only. The antigen-ELISA was positive in 47 of the 62 parasitologically proven cases and in 86 of the 116 cases with anti-trypanosome antibodies detected by ELISA. Of the 80 horses examined antigen-ELISA was positive in 45 (56.75%) sera. Th...
Characterisation of a membrane receptor on ruminants and equine platelets and peripheral blood leukocytes similar to the human integrin receptor glycoprotein IIb/IIIa (CD41/61).
Veterinary immunology and immunopathology    February 1, 1995   Volume 44, Issue 3-4 359-368 doi: 10.1016/0165-2427(94)05310-o
Pintado CO, Friend M, Llanes D.This paper describes two anti-glycoprotein IIb/IIIa or CD41/61 murine monoclonal antibodies (Co.35E4 and Co.2oA1). The cellular distribution and apparent molecular weight of the antigen detected by these antibodies is consistent with their reaction with ruminant and equine glycoprotein IIb/IIIa. Biochemical analysis of the equine molecule using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) revealed bands of 24, 100 and 110 kDa under reducing conditions and 115 and 80 kDa under nonreducing conditions. Biochemical analysis of ruminant antigen revealed that the 24 kDa band...
Production of monoclonal antibodies in horses.
Methods in molecular biology (Clifton, N.J.)    January 1, 1995   Volume 45 55-60 doi: 10.1385/0-89603-308-2:55
Perryman LE, Mason PH.Monoclonal antibodies (MAbs) have been successfully used to evaluate immune responses in horses, and to target important antigens of equine infectious agents to which protective immune responses may be directed (1–5). Most of these studies are performed with murine MAb produced by fusing spleen cells from immunized mice with an appropriate myeloma cell line, as described in Chapter 3. However, there are experimental questions for which murine MAb are not adequate. These include: 1.Definition of microbial epitopes recognized by the infected host; 2.Identification of immunodominant epito...
The complete cDNA and deduced amino acid sequence of equine IgE.
Molecular immunology    January 1, 1995   Volume 32, Issue 1 1-8 doi: 10.1016/0161-5890(94)00143-o
Navarro P, Barbis DP, Antczak D, Butler JE.The cDNA from a transcript encoding the complete heavy chain of the equine immunoglobulin IgE has been cloned and sequenced. A fragment of the equine epsilon gene was amplified from cDNA using PCR and this fragment was then used to probe a horse cDNA library prepared from peripheral blood lymphocytes. A recombinant clone containing the cDNA encoding the complete horse epsilon chain and its associated V-D-J and leader, was subsequently isolated and sequenced. Comparison of the deduced amino acid sequence of equine IgE with the C epsilon heavy chains of other species indicates it to be most simi...
Platelet activating factor mimics antigen-induced cutaneous inflammatory responses in sweet itch horses.
Veterinary immunology and immunopathology    January 1, 1995   Volume 44, Issue 2 115-128 doi: 10.1016/0165-2427(94)05299-8
Foster AP, Lees P, Cunningham FM.Hypersensitivity responses to biting flies such as Culicoides are believed to be the cause of sweet itch, a seasonal intensely pruritic skin condition of horses. Little is known about the mediators released by antigen in the skin of affected horses. In the present study the cutaneous vascular and cellular responses to intradermally injected platelet activating factor (PAF) have been characterised in sweet itch cases during the active phase of the disease and compared with those of Culicoides antigen extract. Histamine was used as a positive control in vascular permeability studies. Responses w...
Seroanalysis of Tyzzer’s disease in horses: implications that multiple strains can infect Equidae.
Equine veterinary journal    January 1, 1995   Volume 27, Issue 1 8-12 doi: 10.1111/j.2042-3306.1995.tb03025.x
Hook RR, Riley LK, Franklin CL, Besch-Williford CL.A monoclonal antibody based competitive inhibition assay was used to detect antibodies in horse sera to purified flagellar antigens from distinct Clostridium piliforme isolates. Sequential absorption of hyperimmune rat serum to C. piliforme isolate E (horse-origin isolate), a positive C. piliforme-immune horse serum, and other suspected immune horse sera with unrelated bacteria or C. piliforme isolates E or isolate R1 (rat-origin isolate) alone demonstrated the specificity of this assay for C. piliforme. This specificity was associated with the inhibition of monoclonal antibody binding to C. p...
The nucleotide sequence of asinine herpesvirus 3 glycoprotein G indicates that the donkey virus is closely related to equine herpesvirus 1.
Archives of virology    January 1, 1995   Volume 140, Issue 9 1653-1662 doi: 10.1007/BF01322539
Ficorilli N, Studdert MJ, Crabb BS.The nucleotide sequence of the glycoprotein G (gG) homologue of asinine herpesvirus 3 (AHV3), a respiratory alphaherpesvirus of donkeys, was determined. The AHV3 gG gene consists of 1233 base pairs (bp) and codes for a predicted protein of 411 amino acids. This is identical in size to the equine herpesvirus 1 (EHV1) gG gene and 6 amino acids longer than the equine herpesvirus 4 (EHV4) gG gene. The predicted amino acid sequence of AHV3 gG has characteristics of a class 1 membrane protein. The amino acid sequence of AHV3 gG shows 92% and 60% identity to EHV1 gG and EHV4 gG respectively. Two regi...
Enzyme-linked immunosorbent assay for myosin heavy chains in the horse.
Reproduction, nutrition, development    January 1, 1995   Volume 35, Issue 6 619-628 doi: 10.1051/rnd:19950602
Barrey E, Valette JP, Jouglin M, Picard B, Geay Y, Robelin J.The content in slow and fast myosin heavy chains (MHC 1 and MHC 2) of 5 equine muscles was determined using an enzyme-linked immunosorbent assay. The results obtained with this immunoenzymatic method were compared with complementary techniques: electrophoresis and immunohistochemistry. Slices of masseter, diaphragm, tensor faciae latae, semitendinosus and cutaneus trunci were obtained from a 12-year-old saddle horse after slaughter. Muscular proteins were specifically extracted to be analysed by ELISA. The technique used 2 complimentary monoclonal antibodies (MAb). MAb 1 was prepared from a hu...
A type-specific serological test to distinguish antibodies to equine herpesviruses 4 and 1.
Archives of virology    January 1, 1995   Volume 140, Issue 2 245-258 doi: 10.1007/BF01309860
Crabb BS, MacPherson CM, Reubel GH, Browning GF, Studdert MJ, Drummer HE.We describe a type-specific ELISA, which distinguishes antibody to equine herpesvirus 4 (EHV4; equine rhinopneumonitis) and EHV1 (equine abortion virus) thereby identifying horses that have been infected with either or both of these antigenically related viruses. The antigens used are parts of the EHV4 and EHV1 glycoprotein G (gG) homologues expressed in E. coli as fusion proteins [Crabb and Studdert, 1993: J Virol 67: 6332-6338). The expressed proteins comprise corresponding regions of the gG molecules that are highly divergent and encompass strong, typespecific epitopes. Plasma samples from ...
Horse (Equus caballus) T-cell receptor alpha, gamma, and delta chain genes: nucleotide sequences and tissue-specific gene expression.
Immunogenetics    January 1, 1995   Volume 42, Issue 2 112-122 doi: 10.1007/BF00178585
Schrenzel MD, Ferrick DA.Horse (Equus caballus) T-cell receptor alpha (TCRA), gamma (TCRG), and delta (TCRD) chain genes were isolated from a cDNA library and characterized. Five unique TCRAV families, including four full-length sequences, five distinct TCRAJ genes, and a single TCRAC gene were identified. TCRAV genes had closest homology with human sequences and least similarity to rat genes. Among eight horse TCRG genes, two distinct constant region genes with considerable variation in the connecting region were identified, but no variable or joining genes were present. Southern blot hybridization confirmed the pres...
In vitro assessment of two species of nematophagous fungi (Arthrobotrys oligospora and Arthrobotrys flagrans) to control the development of infective cyathostome larvae from naturally infected horses.
Veterinary parasitology    January 1, 1995   Volume 56, Issue 1-3 181-187 doi: 10.1016/0304-4017(94)00663-w
Bird J, Herd RP.The ability of two species of nematophagous fungi, Arthrobotrys oligospora and Arthrobotrys flagrans (syn. Trichothecium flagrans, Duddingtonia flagrans), to control the development of infective larvae in feces from naturally infected horses was assessed in vitro. The horses were from a farm where it had been previously established that cyathostomes accounted for 100% of the strongyle egg output. The feces from these naturally infected horses were mixed with spores of each fungal species at four concentrations: 0 (control), 1, 10, and 100 spores per egg. Five replicates for each group were inc...
Major histocompatibility complex class I-restricted cytotoxic T-lymphocyte responses in horses infected with equine herpesvirus 1.
Journal of virology    January 1, 1995   Volume 69, Issue 1 606-612 doi: 10.1128/JVI.69.1.606-612.1995
Allen G, Yeargan M, Costa LR, Cross R.An experimental system that permits sensitive and reproducible detection of equine herpesvirus 1 (EHV-1)-specific cytotoxic T-lymphocyte (CTL) activity in the horse was developed. Peripheral blood mononuclear cells (PBMC) collected from immune horses were restimulated in vitro by culture with live EHV-1. Cytotoxic activity against virus-infected, pokeweed mitogen-stimulated lymphoblast targets was assessed in a 4-h 51Cr release assay. The optimal conditions for in vitro stimulation of equine memory CTLs and for preparation of EHV-1-infected target cells expressing viral antigens were systemati...
Flow-cytometric studies of the phagocytic capacities of equine neutrophils.
Acta veterinaria Scandinavica    January 1, 1995   Volume 36, Issue 4 553-562 doi: 10.1186/BF03547669
Johannisson A, Gröndahl G, Demmers S, Jensen-Waern M.Methodological aspects of flow-cytometric evaluation of the phagocytic properties of equine neutrophils were elucidated. The kinetics of attachment and ingestion were studied, and the phagocytic process was more rapidly completed when serum-opsonized yeast cells were used than with use of IgG-opsonized yeast cells. Trypan blue was successfully used to quench fluorescence of non-ingested yeast cells. There were only minor differences in the kinetics of phagocytosis between quenched and unquenched samples, indicating that attachment is rapidly followed by ingestion. Trypan blue quenching caused ...
Response of ponies to adjuvanted EHV-1 whole virus vaccine and challenge with virus of the homologous strain.
The British veterinary journal    January 1, 1995   Volume 151, Issue 1 27-37 doi: 10.1016/s0007-1935(05)80061-2
Dolby CA, Hannant D, Mumford JA.Five yearling ponies were vaccinated with inactivated Equid herpesvirus type 1 (EHV-1) in Freund's complete adjuvant as a double emulsion and revaccinated 6 weeks later with EHV-1 in Freund's incomplete adjuvant. These ponies and three age-matched controls were challenged intra-nasally after a further 6 weeks with homologous live virus and monitored clinically, biologically and serologically. After challenge, clinical signs were mild in both groups. No cell-associated viraemias were detected in vaccinated ponies. Vaccination induced high levels of complement-fixing (CF) and virus-neutralizing ...
Horse plasma corticotrophin-releasing hormone (CRH): characterisation and lack of a late gestational rise or a plasma CRH-binding protein.
The Journal of endocrinology    December 1, 1994   Volume 143, Issue 3 455-460 doi: 10.1677/joe.0.1430455
Ellis MJ, Livesey JH, Donald RA.Immunoreactive corticotrophin-releasing hormone (irCRH) was present in methanolic extracts of equine peripheral blood and showed no elevation in maternal peripheral serum in late gestation (0.54 +/- 0.25 pmol/l; mean +/- S.D.) compared with control horses (0.41 +/- 0.15 pmol/l). The irCRH of methanolic extracts of pituitary venous plasma had a similar elution position following reverse-phase HPLC to synthetic human CRH(1-41) and to irCRH released from horse stalk-median eminence tissue incubated in vitro. Gel chromatographic studies showed no evidence for a plasma CRH-binding protein (CRHBP) a...