Acyclovir and transmission of HIV-1 from persons infected with HIV-1 and HSV-2.

BACKGROUND: Most persons who are infected with human immunodeficiency virus type 1 (HIV-1) are also infected with herpes simplex virus type 2 (HSV-2), which is frequently reactivated and is associated with increased plasma and genital levels of HIV-1. Therapy to suppress HSV-2 reduces the frequency of reactivation of HSV-2 as well as HIV-1 levels, suggesting that suppression of HSV-2 may reduce the risk of transmission of HIV-1. METHODS: We conducted a randomized, placebo-controlled trial of suppressive therapy for HSV-2 (acyclovir at a dose of 400 mg orally twice daily) in couples in which only one of the partners was seropositive for HIV-1 (CD4 count, > or = 250 cells per cubic millimeter) and that partner was also infected with HSV-2 and was not taking antiretroviral therapy at the time of enrollment. The primary end point was transmission of HIV-1 to the partner who was not initially infected with HIV-1; linkage of transmissions was assessed by means of genetic sequencing of viruses. RESULTS: A total of 3408 couples were enrolled at 14 sites in Africa. Of the partners who were infected with HIV-1, 68% were women, and the baseline median CD4 count was 462 cells per cubic millimeter. Of 132 HIV-1 seroconversions that occurred after randomization (an incidence of 2.7 per 100 person-years), 84 were linked within couples by viral sequencing: 41 in the acyclovir group and 43 in the placebo group (hazard ratio with acyclovir, 0.92, 95% confidence interval [CI], 0.60 to 1.41; P=0.69). Suppression with acyclovir reduced the mean plasma concentration of HIV-1 by 0.25 log(10) copies per milliliter (95% CI, 0.22 to 0.29; P<0.001) and the occurrence of HSV-2-positive genital ulcers by 73% (risk ratio, 0.27; 95% CI, 0.20 to 0.36; P<0.001). A total of 92% of the partners infected with HIV-1 and 84% of the partners not infected with HIV-1 remained in the study for 24 months. The level of adherence to the dispensed study drug was 96%. No serious adverse events related to acyclovir were observed. CONCLUSIONS: Daily acyclovir therapy did not reduce the risk of transmission of HIV-1, despite a reduction in plasma HIV-1 RNA of 0.25 log(10) copies per milliliter and a 73% reduction in the occurrence of genital ulcers due to HSV-2. (ClinicalTrials.gov number, NCT00194519.)

Dynamic regulation of spinal pro-inflammatory cytokine release in the rat in vivo following peripheral nerve injury.

Spinal release of cytokines may play a critical role in the maladapted nociceptive signaling underlying chronic pain states. In order to investigate this biology, we have developed a novel 'high flux' intrathecal microdialysis approach in combination with multiplex bead-based immunoassay technology to concurrently monitor the spinal release of interleukin (IL)-1beta, IL-6 and tumour necrosis factor (TNF)alpha in rats with unilateral sciatic nerve chronic constriction injury (CCI). Intrathecal microdialysis was performed under isoflurane/N(2)O anaesthesia in rats with confirmed mechanical hypersensitivity. In a first study, C-fiber strength electrical stimulation of the operated nerve in neuropathic rats was found to evoke a dramatic increase in IL-1beta efflux ( approximately 15-fold) that was significantly greater than that observed in the sham-operated group. Spinal IL-6 efflux was also responsive to primary afferent stimulation, whereas TNFalpha was not. In a second study, treatment with the glial inhibitor propentofylline for 7days normalized CCI-induced mechanical hypersensitivity. In the same animals, this treatment also significantly reduced intrathecal IL-1beta, IL-6 and TNFalpha and prevented afferent stimulation-evoked cytokine release of both IL-1beta and IL-6. These results provide support for glia as the source of the majority of intrathecal IL-1beta, IL-6 and TNFalpha that accompanies mechanical hypersensitivity in the CCI rat. Moreover, our studies demonstrate the ability of a neurone-glia signaling mechanism to dynamically modulate this release and support a role of spinal IL-1beta in the phasic transmission of abnormal pain signals.

Safety implications of the Boyle-Davis mouth gag and tracheal tube position in tonsillectomy.

BACKGROUND: The risk of death after tonsillectomy is extremely small, and is mostly caused by the direct or indirect effects of haemorrhage or anaesthetic complications. These complications include aspiration, accidental dislodgement of the tracheal tube (TT), and pneumothorax or pneumomediastinum. The Boyle-Davis mouth gag (BDG) is a device used to visualize the oropharynx and stabilize the TT during tonsillectomy. We postulate that a deployed BDG may influence the position of the TT, and potentially result in silent aspiration, accidental extubation, and unilateral pulmonary ventilation. This has not, to our knowledge, been evaluated before. The aim of this prospective, pilot study was to evaluate the displacement of the TT upon opening and closing the BDG, in an objective manner. METHODS: Patients undergoing tonsillectomy with/without adenoidectomy at a regional department underwent flexible bronchoscopy to evaluate the changes in position of the TT tip with the BDG in an open and closed position, relative to the position of the carina. RESULTS: Twenty-three patients were enrolled into the study. Deploying the BDG resulted in TT displacement in 96% of patients. The mean displacement was 9.5 mm (range -10 to +27 mm). CONCLUSIONS: We believe that this study raises concerns not previously highlighted, on how manipulating a BDG may influence the TT position. It may serve to explain additional mechanisms of potentially fatal anaesthetic complications such as TT dislodgement, unilateral ventilation, and pneumothorax, particularly in paediatric patients, after tonsillectomy.

The effect of head protection on the hearing of rugby players.

OBJECTIVE: Professional rugby players utilise various methods of head protection to prevent against the development of a pinna haematoma. This study tests the hypothesis that these measures, whilst preventing injury, decrease the wearers' hearing threshold and therefore their performance. DESIGN AND PARTICIPANTS: Eight patients had free field audiometry performed in a soundproof room, with warble tones. All patients were young men (mean 24.75 years (range 22-34)). No participant had ear symptomatology or a past history of ear surgery. Three separate audiological assessments were performed on each patient: normal free field audiometry in a sound field room, following application of adhesive tape and whilst wearing a scrum cap. All measurements were performed by a single audiological scientist. A significant clinical drop in hearing threshold was defined as an increase of 10 dB. RESULTS: No patient demonstrated a significant drop in hearing threshold following the application of either tape or a scrum cap, nor was there a significant difference in the mean (SD) warble tone average: air 7.03 (5.47); tape 7.19 (6.40); scrum cap 6.56 (5.58). CONCLUSION: Theoretical concerns that "ear taping" and scrum caps affect hearing of rugby players are unfounded and should not discourage their use.

On the redshift distribution and physical properties of ACT-selected DSFGs.

We present multi-wavelength detections of nine candidate gravitationally-lensed dusty star-forming galaxies (DSFGs) selected at 218GHz (1.4mm) from the ACT equatorial survey. Among the brightest ACT sources, these represent the subset of the total ACT sample lying in Herschel SPIRE fields, and all nine of the 218GHz detections were found to have bright Herschel counterparts. By fitting their spectral energy distributions (SEDs) with a modified blackbody model with power-law temperature distribution, we find the sample has a median redshift of z = 4.1 - 1.0 + 1.1 (68 per cent confidence interval), as expected for 218GHz selection, and an apparent total infrared luminosity of log 10 ( µ L IR / L ⊙ ) = 13.86 - 0.30 + 0.33 , which suggests that they are either strongly lensed sources or unresolved collections of unlensed DSFGs. The effective apparent diameter of the sample is µ d = 4.2 - 1.0 + 1.7 kpc , further evidence of strong lensing or multiplicity, since the typical diameter of dusty star-forming galaxies is 1.0-2.5 kpc. We emphasize that the effective apparent diameter derives from SED modelling without the assumption of optically thin dust (as opposed to image morphology). We find that the sources have substantial optical depth. ( τ = 4.2 - 1.9 + 3.7 ) to dust around the peak in the modified blackbody spectrum (λ obs ⩽ 500µm), a result that is robust to model choice.

Genomic variation of human papillomavirus type 16 and risk for high grade cervical intraepithelial neoplasia.

BACKGROUND: Epidemiologic studies have demonstrated strong and consistent associations between the detection of human papillomavirus (HPV) type 16 DNA and the risk of cervical intraepithelial neoplasia (CIN) and cervical cancer. However, HPV16 is also the most common type of HPV in the normal population, and only a minority of women with HPV16 infection develop cervical cancer. Studies of genomic heterogeneity in HPV16 have demonstrated the presence of multiple variant forms in all human populations examined to date. It is conceivable that the natural variants of HPV16 in a given population may not have the same biologic behavior. PURPOSE: This study was designed to determine the association between natural variants of HPV16 and the risk of biopsy-confirmed CIN 2 or 3, the most important precancerous lesions of the uterine cervix. METHODS: Prospective studies were conducted among 1) women attending a university and 2) women presenting to a sexually transmitted disease clinic. Subjects were eligible for inclusion in this investigation if the initial cytologic findings did not reveal CIN 2-3 and HPV16 DNA was detected by means of a polymerase chain reaction (PCR)-based method in one or more cervical or vulvovaginal samples. Eligible subjects were followed every 4 months with cervical Pap smears and colposcopic examinations. Women were referred for biopsy if cytology or colposcopy suggested CIN 2-3. Two groups of HPV16 variants, prototype-like and nonprototype-like, were determined by means of single-strand conformation polymorphism (SSCP) analysis of PCR products from the noncoding region of the viral genome. Representative SSCP patterns from HPV16 variants were further characterized by direct DNA sequencing of the PCR products. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated by Cox regression analysis. RESULTS: Prototype-like variants accounted for 79% of the HPV16 detected in university students and 86% of the virus detected in patients presenting to the sexually transmitted disease clinic. CIN 2-3 was confirmed by biopsy in nine of 57 HPV16-positive women attending the university and in 10 of 66 HPV16-positive women presenting to the sexually transmitted disease clinic. Among university students, those with HPV16 nonprototype-like variants were 6.5 (95% CI = 1.6-27.2) times more likely to develop CIN 2-3 than those with prototype-like variants. A similar association was observed among women presenting to the sexually transmitted disease clinic (RR = 4.5; 95% CI = 0.9-23.8). CONCLUSIONS: This study suggests that the risk of developing CIN 2-3 is not the same with all variants of HPV16 and that nonprototype-like variants confer a greater risk compared with prototype-like variants. The important genomic differences underlying this increased risk of CIN 2-3 remain to be determined.

Risk of anal carcinoma in situ in relation to human papillomavirus type 16 variants.

Infection with human papillomavirus (HPV), especially HPV16, is central to the development of squamous anogenital cancers and their precursor lesions, termed "squamous intraepithelial neoplasias." Men who have sex with men, particularly those who are infected with HIV, are at a high risk for anal infection with HPV16 and for low-grade anal neoplasia; however, only a subset of these men develop anal invasive cancer or its immediate precursor lesion, anal carcinoma in situ (CIS). To examine the hypothesis that certain variants of HPV16 are most strongly associated with development of anal CIS, we followed 589 men who have sex with men whose initial anal cytological smears did not show anal CIS. Anoscopy, anal cytology, and PCR-based assays for detection and classification of HPV types were performed every 4-6 months, with HPV16 further classified by single-stranded conformation polymorphism analysis as being a prototype-like (PL) or non-prototype-like (NPL) variant. Anal CIS was histologically confirmed in 6 of 384 (1.6%) consistently HPV16-negative men, in 12 of 183 (6.6%) men with HPV16 PL variants, and in 4 of 22 (18.2%) men with HPV16 NPL variants. After adjustment for anal cytological diagnoses at study entry, HIV status and CD4 count, and detection of HPV types other than type 16, men with HPV16 NPL variants were 3.2 times (95% confidence interval, 1.0-10.3) more likely to develop anal CIS than were those with PL variants. Neither detection of HPV16 DNA at high levels nor detection of HPV16 DNA for a prolonged period, factors that we previously demonstrated to be associated with risk of high-grade anal squamous intraepithelial neoplasia, was significantly associated with HPV16 NPL variants. The biological mechanism relating to Ihis excess risk remains undetermined.

Auditory canal exostoses in Irish surfers.

AIM: Surfing is increasing in popularity in Ireland. Exostoses of the external auditory canal are a common finding in those who surf in cold water. The aim of this study was to examine the prevalence of external canal exostoses in a population of Irish surfers. METHODS: A cross-sectional study of Irish surfers was carried out. Patients were examined and questioned on their knowledge of exostoses, surfing routine, use of barrier protection and symptoms experienced. RESULTS: 119 surfers were analysed. 66 % of the surfers examined exhibited exostoses and 88 % were unaware of their diagnosis. Those that developed exostoses had surfed for a mean of 5,028 h, those that did not had surfed for a significantly shorter mean of 1,909 h (p = 0.0002). CONCLUSIONS: This is first study of this nature in the UK or Ireland. With a 5- to 6-year lag phase for exostoses to develop, these patients are likely to become an increasing part of Otolaryngologist's workload.

Interactions among Janus kinases and the prolactin (PRL) receptor in the regulation of a PRL response element.

PRL regulates milk gene expression, at least in part, by activating JAK2 kinase and STAT5 (signal transducer and activator of transcription 5), initially termed mammary gland factor (MGF). These experiments were initiated to gain a better understanding of the mechanisms of transcriptional activation via PRL receptor (PRL-R) signaling. Binding of PRL to the recombinant pigeon PRL-R-activated transcription driven by a 2.8 kbp 5'-fragment of the rat beta-casein gene. PRL enhanced the expression of chimeric reporters containing the beta-casein PRL response element (PRE), but not the c-fos sis-inducible element, when the reporters were transfected into Chinese hamster ovary cells with the PRL-R. Wild type receptor, which contains a duplication of the entire extracellular ligand-binding domain, was only slightly more effective than a truncation mutant with a single extracellular domain. Transfection with either JAK1, JAK2, or JAK3 increased basal transcription through both the PRE and sis-inducible element. Coexpression of JAK2 with PRL-R resulted in amplification of the induction of the PRE by PRL, whereas JAKs 1 and 3 did not amplify the PRL effect. Overexpression of JAK2 mutants blocked PRE activation by PRL. Mutant JAK2 also interfered with PRE activation by JAK3 but did not affect JAK1's stimulatory effect.

Estrogen replacement and coronary artery disease. Effect on survival in postmenopausal women.

The relationship among postmenopausal estrogen use, coronary stenosis, and survival was examined retrospectively in 2268 women undergoing coronary angiography. The patients were selected for study if their age was 55 years or older at the time of angiography or if they had previously undergone bilateral oophorectomy. Postmenopausal estrogen use in 1178 patients with coronary artery disease (greater than 70% stenosis) and 644 patients with mild to moderate coronary artery disease (5% to 69% stenosis) was compared with 446 control subjects (0% stenosis) using life-table analysis. Over 10 years of follow-up, there was no significant difference in survival among patients initially free of coronary lesions on arteriography who had either never used (377) or ever used (69) estrogens. Among patients with mild to moderate coronary stenosis, 10-year survival of those who had never used estrogens was 85.0% and it was 95.6% among 99 "ever users." Survival was 60.0% among those with more than 70% coronary stenosis who had never used estrogen and it was 97.0% among 70 ever users. The "never users" group were older (65 vs 59 years), had a lower proportion of cigarette smokers (40% vs 57.1%), a higher proportion of subjects with diabetes (21.7% vs 12.9%) and hyperlipidemia (58% vs 44%), and approximately equal numbers of hypertensives (56.0% vs 54.3%). Cox's proportional hazards model was used to estimate survival as a function of multiple covariables. Estrogen use was found to have a significant, independent effect on survival in women. We conclude that estrogen replacement after menopause prolongs survival when coronary artery disease is present, but it has less effect in the absence of coronary artery disease.

Tophaceous gout presenting as a dorsal nasal lump.

A literature review reveals that gout has been described as affecting many sites in the head and neck region, both in the arthritic and tophaceous form. Gout can often mimic malignancy or infection, and has been described as causing acute airway problems requiring emergency tracheotomy. Here we describe the first published case of tophaceous gout affecting the soft tissues overlying the nasal bones. The patient presented with a bony, hard, dorsal hump and requested aesthetic rhinoplasty. We also describe an endoscopic technique for removal of tophi using a powered microdebrider system with a protected burr head. Endoscopic powered microdebrider blade excision of tophi affecting the limbs has already been described, with reduced complications when compared with conventional curettage and debridement techniques. This is the first such application to the nose.

Viral gene therapy for head and neck cancer.

BACKGROUND: Viral gene therapy is a promising new treatment modality for head and neck cancer. This paper provides the reader with a review of the relevant literature in this field. RESULTS: There are government licensed viral gene therapy products currently in use for head and neck cancer, utilised in conjunction with established treatment modalities. The viruses target tumour-associated genes, with the first licensed virus replacing p53 gene function, which is frequently lost in tumourigenesis. Oncolytic viruses selectively destroy cancer cells through viral replication and can be armed with therapeutic transgenes. CONCLUSION: Despite considerable advances in this field over the last 40 years, further research is needed to improve the overall efficacy of the viruses and allow their widespread utilisation in the management of head and neck cancer.

Interlaboratory comparison of neuropathology assessments in Alzheimer's disease: a study of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD)

Concerns about intercenter variation in methods and interpretation prompted CERAD investigators to examine standardization of the neuropathological assessment of Alzheimer's disease (AD). Contiguous frontal lobe sections derived from autopsy brains of eight patients clinically diagnosed as having probable AD and two cognitively normal individuals were distributed to 24 neuropathologists from 18 medical centers in the United States and Canada. Using their routine staining method(s), neuropathologists determined the rank order of severity of AD neuropathology in these cases, as well as semiquantitative and quantitative senile plaque and neurofibrillary tangle frequencies. Ranking of the ten cases revealed 75% inter-rater reliability among the 24 raters. Semiquantitative analyses showed reasonable inter-rater agreement, whereas quantitative measures yielded significant differences between raters for plaque and tangle counts (p < 0.0001). These differences reflected variation in stain sensitivity, staining technique (even when the same stain was used), and interpretation of the histological findings. Ratings on the cases with the highest proportions of diffuse plaques showed the greatest dependence upon stain sensitivity and variability in interpretation. This study indicates that greater attention to quality improvement is needed for the neuropathological evaluation of AD, particularly when pooling data in multicenter studies such as CERAD.

Prolactin-induced proliferation of the Nb2 T-lymphoma is associated with protein kinase-C-independent phosphorylation of stathmin.

Phosphorylation of stathmin, a 19-kDa protein found in many tissues, has been linked to cell differentiation and proliferation. This protein is present in lymphocytes, and both phosphorylation and expression of stathmin are regulated by lymphotropic agents. In this study an antibody specific for stathmin was used to examine phosphorylation in response to PRL. The results suggest that PRL stimulates stathmin phosphorylation in the Nb2 lymphoma and that phosphorylation correlates with PRL-induced cell proliferation. Stathmin expression does not change substantially as PRL-stimulated Nb2 cells move through the cell cycle and enter into the S-phase. Thus, stathmin phosphorylation, but not expression, is regulated by PRL. Activation of protein kinase-C (PKC) in Nb2 cells also induces phosphorylation of stathmin, but PKC does not appear to mediate phosphorylation in response to PRL. The pattern of phosphorylation in response to 12-O-tetradecanoylphorbol-13-acetate differs from that in response to PRL, and down-regulation of PKC does not inhibit PRL-induced phosphorylation or proliferation. In addition to stathmin, PRL increases phosphorylation of a group of stathmin-like proteins. Phosphorylation of these proteins also correlates well with PRL-induced proliferation. Taken together, the results suggest that phosphorylation of stathmin and stathmin-like proteins may mediate some actions of PRL in Nb2 cells. The results further suggest that activation of PKC is not an important early event in PRL-stimulated mitogenesis in Nb2 cells.

20K is bound with high affinity by one rat and one of two rabbit growth hormone receptors.

A naturally occurring variant of human (h)GH, designated 20K, is equipotent with hGH(22K) in stimulating growth in hypophysectomized rats. However, despite high growth-promoting activity in vivo, 20K is a poor inhibitor of 125I-hGH(22K) binding to GH receptors in radioreceptor assays. In order to resolve the differences between bioassay and radioreceptor assay data, we have examined the binding of 20K to rat and rabbit liver GH receptors. Our data indicate that the GH receptor in rat liver binds 20K with an affinity only slightly lower than that for hGH(22K), in accordance with bioassay data. In the rabbit, however, 20K is bound with high affinity by only a small subset of the GH receptors which bind hGH(22K) with high affinity. The GH receptors which bind 20K appear to belong to the same of subset of receptors which bind rat and rabbit GH with high affinity.

Analysis of growth hormone and lactogenic binding sites cross-linked to iodinated human growth hormone.

GH (GHR) and lactogenic receptors were analyzed after use of the cross-linking reagent ethylene glycol bis-(succinimidyl succinate) to attach covalently iodinated human GH (hGH) to binding proteins 1) on intact IM-9 lymphocytes, 2) in a partially purified GHR preparation from rabbit liver, and 3) in crude microsomal fractions from rabbit liver, rabbit mammary gland, and rat liver. The latter two microsomal preparations contain primarily lactogenic receptors, whereas in IM-9 lymphocytes and the rabbit liver preparations, GHR predominate. Cross-linked [125I]hGH-receptor complexes were solubilized, reduced, and separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Analysis of proteins cross-linked to [125I]hGH in the microsomal fraction from rabbit liver showed a specifically labeled complex with an estimated molecular weight (mol wt) of 75K. A slightly lower mol wt (71K) was determined for the complex labeled in the purified GHR preparation. In contrast to the relatively low mol wt complexes in rabbit liver, a complex that migrated with an apparent mol wt of 130K was identified in IM-9 lymphocytes. Labeled complexes were identified at 66K from rat liver and 61K from rabbit mammary gland. If it is assumed that hGH contributes 21K to the mol wt of the radiolabeled complexes, then the approximate mol wts of hGH-binding sites are 50-54K from rabbit liver, 109K from IM-9 lymphocytes, 45K from rat liver, and 40K from rabbit mammary gland.

A monoclonal antibody to the growth hormone receptor of rabbit liver membranes.

A monoclonal antibody which recognizes the [125I]human GH ([125I]hGH)-binding proteins of rabbit liver has been produced using hybridoma technology. A CB6F1/J mouse was immunized over a period of 82 days with a partially purified GH receptor (GHr) preparation. On the 83rd day, spleen cells from the mouse were fused with P3x20 mouse myeloma cells using polyethylene glycol 1540. Hydridomas were produced by selection in hypoxanthine, aminopterin, and thymidine in RPMI/1640 medium and screened for antibody production using a binding inhibition assay. Four antibody-secreting clones were isolated from the same primary well, and one of these was injected ip into mice to generate ascitic fluid. At a concentration of 1:10,000, the ascitic fluid inhibited 50% of the specific binding of [125I]hGH to rabbit liver GHr, and at higher concentrations, the ascitic fluid was capable of inhibiting 95% of the specific binding. The ascitic fluid does not bind [125I]hGH nor does it inhibit [125I]hGH binding to rat liver membranes, rabbit mammary gland, or IM9 lymphocytes. More than 90% of the antibody activity was abolished by goat antimouse immunoglobulin G antiserum. An immunoglobulin fraction from the ascitic fluid, precipitated by ammonium sulfate and coupled to activated CH Sepharose, specifically adsorbed an [125I]hGH binding moiety from Triton X-100-solubilized rabbit liver membranes. After dissociation by brief exposure to 0.1 M glycine (pH 2.0), the moiety retained hGH-binding activity. Preliminary experiments indicate that the antibody will be helpful in purification of the rabbit liver GH receptor.

UP-regulation of lactogenic receptors -- an immunological artifact?

We examined whether injection of heterologous hormones for more than one week might evoke a humoral immune response which would simulate receptor induction. Male rats were injected daily for ten days with human growth hormone (hGH) or ovine prolactin (oPRL), and binding of 125I-hGH and 125I-oPRL was examined in serum and in membranes from liver and lung. Specific binding of 125I-hGH and 125I-oPRL increased in the sera of hGH- and oPRL-injected animals, respectively. A marked increase in hGH but not oPRL binding also occurred in crude membrane-preparations of tissues from hGH-injected rats. Similarly oPRL but not hGH binding increased in tissues of PRL-injected animals. Furthermore, binding activity solubilized from liver membranes of hormone-injected rats was precipitated with Staphylococcus aureus (protein A) indicating that the induced binding sites were immunoglobulin-like. Hence apparent up-regulation of lactogenic receptors following long-term treatment with heterologous hormones may be due to generation of anti-hormone antibodies.

Circulating antagonist of luteinizing hormone in association with infertility in stallions.

Using a LH radioligand receptor assay (RRA) previously validated for use in serum and an equine monoclonal RIA, we have distinguished a subset of subfertile stallions with an elevated RRA/RIA ratio. After purification of the active moiety by anion exchange chromatography and immunoprecipitation with the equine LH (eLH) monoclonal antibody, RRA activity remained in the supernatant. This activity was also recognized by a polyclonal LH antibody (GDN 15) with wide cross-species recognition. This active fraction was further purified by gel filtration chromatography and shown to displace labeled eLH in a dose-dependent fashion in the RRA with an inhibition slope of 2.8 compared with a slope of 1.1 for native eLH. This fraction also inhibited the LH-stimulated steroidogenesis of Leydig cells in vitro in a dose-dependent fashion, but had no effect on basal (minus LH) steroid production. Polyacrylamide gel electrophoresis and electroelution of this material demonstrated RRA activity in a fraction with a mol wt between 45-66 kDa. We conclude that this substance 1) competitively inhibited binding of eLH and hCG to the LH receptor, 2) antagonized LH-stimulated steroidogenesis in vitro, and 3) may represent a LH isoform found in association with infertility in these animals.