A man with severe leg burns.

A 52-year-old Hispanic male was transported to the emergency department after sustaining severe bilateral lower extremity burns in an electroplating factory. His examination revealed circumferential burns to the lower extremities with spotting in the perineum. The epidermis was stained green and sloughed off with gentle pressure. The underlying dermis was white and non-blanching, consistent with a full thickness burn. His feet were partially protected by his work boots where he had small areas of pink, blanchable, partial thickness burns (Fig. 1). Pertinent initial studies included a lactic acid level of 3.1 mmol/L and a creatinine of 1.02 mg/dL.

The use of novel biochemical markers in predicting spontaneously resolving 'pregnancies of unknown location'.

BACKGROUND: 'Pregnancies of unknown location' (PULs) include viable and failing intrauterine and extrauterine pregnancies. The aim of this study was to evaluate the role of novel biochemical markers in the prediction of spontaneous resolution of PULs. METHODS: Serum samples were taken at the first visit to the pregnancy unit for measuring the traditional markers ß-hCG and progesterone, and for inhibin A, inhibin pro-αC-related immunoreactivity (inhibin pro-αC-RI) and insulin-like growth factor-binding protein 1 (IGFBP-1). Follow-up was continued until the pregnancy had resolved, the location of the pregnancy and viability was determined or treatment was required. Outcomes were dichotomized into 'spontaneous resolution' and 'other outcome' categories. RESULTS: One-hundred and nine cases of PUL were included in the data analysis. Spontaneous resolution occurred in 70% and a further scan was required in 30% to reach a diagnosis. Levels of progesterone and inhibin A were significantly lower (both P < 0.001) and levels of IGFBP-1 significantly higher (P = 0.02) in the pregnancies that spontaneously resolved than in those pregnancies that required further intervention. In decision tree analysis, the novel markers were less useful than progesterone and ß-hCG in predicting spontaneously resolving PULs. Inhibin pro-αC-RI and IGFBP-1 were not useful in the prediction of spontaneously resolving PULs. Inhibin A is more predictive than ß-hCG alone, but serum progesterone is the best single marker and progesterone and hCG together continues to be the best way of predicting spontaneously resolving PULs. CONCLUSIONS: These novel biochemical markers are not clinically useful in predicting spontaneously resolving PULs.

Lactogenic immunity following vaccination of cattle with bovine coronavirus.

In order to investigate the ability of an oil adjuvanted vaccine containing bovine coronavirus antigen to enhance lactogenic immunity in the calf, pregnant cows and heifers were vaccinated and specific virus neutralising antibody levels determined in serum, colostrum and milk. Pre-existing antibody titres (as a result of natural infection) in the serum of these animals were found to be significantly increased as a result of a single shot vaccination carried out between 2 and 12 weeks before calving. This was reflected in a similar increase in the titre and duration of specific antibody in milk and colostrum that was passed on to the calves. The overall response observed was highly dependent on an adequate antigen payload being incorporated within the single dose vaccine. No abnormal local or systemic reactions were observed as a result of vaccination. It is hoped that this approach will lead to the production of a superior commercial vaccine for the protection of neonatal calves against enteric coronavirus infection.

Wild isolates of murine cytomegalovirus induce myocarditis and antibodies that cross-react with virus and cardiac myosin.

The laboratory-adapted K181 strain of murine cytomegalovirus (MCMV) induces both acute and chronic myocarditis, associated with autoantibodies to cardiac myosin, in susceptible BALB/c mice. However, the K181 MCMV strain has been maintained in the laboratory for many years and may not resemble naturally occurring strains of MCMV in its ability to induce myocarditis. Accordingly, six different isolates of MCMV from wild Mus domesticus were compared with K181 MCMV for their ability to induce myocarditis and autoantibodies to cardiac myosin in BALB/c mice. These isolates were shown to induce acute myocarditis similar to K181 MCMV, with associated focal and diffuse myocardial inflammation. However, the levels of myocarditis induced by the wild isolates during the chronic phase of the disease (days 32-56 post-infection) were low in contrast to the K181 strain. Interestingly, 30% of wild-trapped mice showed histological evidence of myocarditis and all were sero-positive to MCMV. Sera from BALB/c mice infected with wild MCMV isolates and from wild-trapped mice contained antibodies that cross-reacted with MCMV and cardiac myosin (S2 region). The cross-reactive region of MCMV was found to be a 50,000-55,000 MW viral polypeptide. These findings suggest that molecular mimicry may be involved in the pathogenesis of autoimmune myocarditis following infection with both laboratory and wild MCMV strains.

Incorporation of fludarabine and 1-beta-D-arabinofuranosylcytosine 5'-triphosphates by DNA polymerase alpha: affinity, interaction, and consequences.

Fludarabine and 1-beta-D-arabinofuranosylcytosine (ara-C) are effective nucleoside analogues for the treatment of leukemias when used as single agents or together. Recent trials of the fludarabine and ara-C therapy with or without growth factors suggested an improved clinical response by combining fludarabine and ara-C. The activity of these antimetabolites depends on their phosphorylation to the respective triphosphates, F-ara-ATP and ara-CTP. The principal mechanism through which these triphosphates cause cytotoxicity is incorporation into DNA and inhibition of further DNA synthesis. A model system of DNA primer extension on a defined template sequence was used to quantitate the consequences of incorporation of one or two analogues by human DNA polymerase alpha (pol alpha). The template (31-mer) was designed so that DNA pol alpha incorporated six deoxynucleotides (alternately G and T) on the 17-mer primer, followed by insertion of an A and then a C. The primer was then elongated with G and T to the full-length product. The apparent Kms of DNA pol alpha to incorporate these analogues (0. 053 and 0.077 microM, respectively) were similar to the Km for dCTP (0.037 microM) and dATP (0.044 microM), suggesting that the enzyme recognized these analogues and incorporated them efficiently on the growing DNA primer. The velocity of extension (Vmax) of these primers ranged between 0.53 and 0.77%/min when normal nucleotides were present. Once inserted at the 3'-terminus, F-ara-AMP or ara-CMP were poor substrates for extension. However, in reactions lacking dCTP and dATP and with high concentrations of ara-CTP, ara-CMP was inserted by pol alpha after incorporation of the F-ara-AMP residue. This tandem incorporation of the two analogues resulted in almost complete inhibition (99.3%) of further extension of the primer. In the presence of competing deoxynucleotides, each analogue resulted in a dose-dependent inhibition of DNA synthesis. When present together, inhibition of the primer elongation was more than additive at low concentrations of analogue triphosphates. Based on these results and the intracellular pharmacokinetics of ara-CTP and F-ara-ATP in leukemia blasts, we propose a pharmacodynamic model to explain interactions between these analogues during combination chemotherapy.

Difluorodeoxyguanosine: cytotoxicity, metabolism, and actions on DNA synthesis in human leukemia cells.

The success of gemcitabine (2',2'-difluorodeoxycytidine; dFdC) resulted in new interest in its purine congeners. Based on the structure-activity relationship studies of catabolism and anabolism, 2',2'-difluorodeoxyguanosine (dFdG) emerged as a lead candidate among the difluoropurine analogs. The cytotoxicity, metabolism, and actions of dFdG on DNA synthesis were studied in the human leukemia lymphoblastoid line CCRF-CEM. The IC50 values of dFdG after a 72-hour continuous incubation were 0.01, 0.03, and 0.28 mumol/L for CCRF-CEM, K562, and HL-60 cells, respectively. A cell line deficient in dCyd kinase was equally sensitive to dFdG, suggesting that, in contrast to dFdC, dFdG may be activated by other deoxynucleoside kinase(s). Consistent with these data, coincubation with dGuo spared the dFdG-mediated toxicity; however, up to 500 mumol/L dCyd failed to reverse the toxicity of dFdG. These observations indicated that dGuo kinase, which phosphorylates arabinosylguanine, also appears to play a major role in activating dFdG. CCRF-CEM cells incubated with varying concentrations of [3H]dFdG accumulated dFdGTP in a dose-dependent manner; a 3-hour incubation with 1 mmol/L dFdG resulted in more than 600 mumol/L intracellular dFdGTP. This is in contrast to the gemcitabine triphosphate accumulation, which is saturated at 10 to 20 mumol/L of exogenous dFdC. dFdG metabolites affected ribonucleotide reductase, resulting in a lowering of the dCTP pool; this is in agreement with the effect of dFdC on dNTP pools in leukemia cell lines. The major effect of dFdG on macromolecular synthesis was inhibition of DNA synthesis. DNA primer extension over a defined template revealed that dFdGTP was a good substrate for DNA polymerase alpha and incorporated opposite C sites of the template. Unlike arabinosyl analogs, but similar to gemcitabine triphosphate, dFdGTP incorporation caused DNA polymerase to pause after one normal deoxynucleotide was incorporated beyond the analog. The unique activation requirements of dFdG, its novel mode of inhibition of DNA synthesis, and its potent toxicity to human leukemia cells make it a promising new antimetabolite.

Cytotoxicity, metabolism, and mechanisms of action of 2',2'-difluorodeoxyguanosine in Chinese hamster ovary cells.

The emerging clinical success of gemcitabine (2',2'-difluorodeoxycytidine) stimulated interest in the synthesis and evaluation of purine congeners. The cytotoxicity, metabolism, and mechanisms of action of the lead candidate, 2',2'-difluorodeoxyguanosine (dFdGuo), were studied in Chinese hamster ovary cells. Unlike the natural nucleoside deoxyguanosine (dGuo), dFdGuo was not a substrate for purine nucleoside phosphorylase. Wild-type Chinese hamster ovary cells and a mutant line deficient in deoxycytidine (dCyd) kinase were similarly affected by dFdGuo (50% inhibitory concentration, 7.5 and 6.5 microM, respectively), suggesting that unlike gemcitabine, dCyd kinase was not responsible for activation of dFdGuo. This was further confirmed by separation of nucleoside kinases (adenosine kinase, dGuo kinase, and dCyd kinase) of Chinese hamster ovary cells on DEAE-cellulose column chromatography. The kinase activity that phosphorylated dGuo also converted dFdGuo to its monophosphate, suggesting that dGuo kinase activated dFdGuo. Consistent with this result, coincubation with dGuo spared the dFdGuo-mediated toxicity; however, addition of up to 10 mM dCyd did not reverse the toxicity of dFdGuo. Intracellularly, dFdGuo was phosphorylated to its mono-, di-, and triphosphates; dFdGuo triphosphate (dFdGTP) was the major metabolite and accumulated to 45 microM after a 6-h incubation with 30 microM dFdGuo. The elimination of dFdGTP was monophasic with a t1/2 of about 6 h. Deoxynucleotides were decreased in cells incubated with dFdGuo, suggesting that ribonucleotide reductase was inhibited. dATP, which decreased 78% after a 4-h incubation with 30 microM dFdGuo, was most affected. dFdGuo was a potent inhibitor of DNA synthesis. Extension of a DNA primer over a defined template in the presence of dFdGTP revealed that dFdGTP was a good substrate for incorporation opposite C sites of the template by DNA polymerase alpha. dFdGTP incorporation caused DNA polymerase alpha to pause after the polymerization of one additional deoxynucleotide. This pattern of inhibition, which is shared by gemcitabine, distinguishes 2',2'-difluoronucleosides from arabinosylnucleosides which halt primer extension at the incorporation site. dGTP competed effectively with dFdGTP for incorporation by DNA polymerase alpha. The unique activation requirements and patterns of inhibition of DNA synthesis distinguish this promising new antimetabolite from other nucleoside analogues.

The physicochemical, immunological and biological properties of rat pituitary and plasma LH.

A comparison was made between the properties of LH derived from female rat pituitary glands and plasma. Samples were collected from adult intact rats 5 h before or at the time of the pro-oestrous preovulatory LH surge; 27-day-old rats untreated or given 5 IU pregnant mares' serum gonadotrophin (PMSG) s.c. on day 25, which induced LH release 54 h later and adult ovariectomized rats untreated or primed with either 5 micrograms oestradiol benzoate s.c. or 5 micrograms oestradiol benzoate followed 48 h later by 0.5 mg progesterone s.c., which induced LH release 4-6 h later. All pituitary LH samples were totally bound to an anionic ion-exchange resin (DE52), while only a small proportion of the plasma LH was bound. Only 0-10% plasma LH obtained from intact, ovariectomized (with and without steroids) and untreated immature rats was bound, while a greater proportion of bound LH (36%) was noted in rats treated with PMSG. Gel filtration indicated only slight differences between pituitary and plasma LH, the former eluting marginally earlier than whole plasma and the unbound and bound plasma forms derived after separation by DE52 resin. Affinity chromatography (Concanavalin A and Glycine maximus) showed that LH from both sources possesses high mannose oligosaccharides and that plasma LH does not bear terminal N-acetyl galactosamine residues, although 20% of the pituitary form does. Plasma obtained from pro-oestrous rats had greater bioactivity than had pituitary LH in stimulating testosterone from Leydig cells and progesterone from granulosa cells in vitro, and inducing ovulation in immature rats in vivo. Leydig cell bioassays for LH in fractions obtained from ion-exchange separation indicate that steroidogenic activity of unbound plasma LH is greater than bound pituitary LH when they were collected at times of enhanced release. When release was inhibited (oestrogen-primed ovariectomized rats or immature rats), the steroidogenic activity of plasma and pituitary LH were similar and an acidic steroidogenic component was present in the plasma that was not recognized immunogenically as LH. In summary, pituitary LH undergoes a conversion on release into the plasma that involves a change in binding characteristics on an ion-exchange resin. In conditions when LH release is enhanced there is an increase in bioactivity of plasma LH owing to modification either by steroids or some other plasma factor(s) that perhaps influence the structure of LH directly or by steroids acting indirectly to alter GnRH release, which then modifies LH structure. These structural changes are minor and probably involve alterations in the glycosyl attachments.

A murine cytomegalovirus-neutralizing monoclonal antibody exhibits autoreactivity and induces tissue damage in vivo.

The autoreactivity of murine cytomegalovirus (MCMV)-neutralizing monoclonal antibody (mAb) AC1 was examined in vitro and in vivo. Both mAb AC1 and a human antiserum reactive with U1-small nuclear ribonucleoprotein (U1-snRNP) stained uninfected mouse embryo fibroblasts (MEF) in a speckled nuclear pattern and reacted with 70,000 molecular weight (MW) MEF nuclear antigens by immunoblotting, suggesting that mAb AC1 cross-reacted with the 70,000 MW component of U1-snRNP. However, only mAb AC1 cross-reacted with an additional epithelial cytoplasmic autoantigen present in cultured HEp2 cells. On tissue sections from uninfected mice, mAb AC1 predominantly reacted with a component of central and peripheral nervous systems, although cross-reactivity with the stratum spinosum of the skin and the outer sheath of hair follicles was also observed. Immunoblotting revealed that mAb AC1 reacted with phosphorylated epitopes present on a 98,000 MW MCMV structural protein and the 200,000 MW mouse neurofilament protein (NFP). Treatment of uninfected mice with mAb AC1 resulted in a severe interstitial pneumonia with greatly thickened and congested alveolar septa. Severe oedema of the hypodermis and a mild mesangial proliferative glomerulonephritis were also observed. These results demonstrate that a mAb reacting with a MCMV structural phosphoprotein which can protect mice against the dissemination of MCMV, can also promote the development of autoimmune disease. Therefore, the production of such cross-reactive antibodies may be an important mechanism in the development of autoimmunity following viral infection.

Fatal hemothorax from mycotic celiac artery aneurysm.

We present two cases of ruptured mycotic aneurysms infected with Staphylococcus aureus. Each patient had hemoptysis and in each case there was hemothorax caused by a ruptured mycotic aneurysm of the celiac artery. In case 1, the pathogenesis was transient Staphylococcus aureus septicemia infecting an atherosclerotic plaque with subsequent aneurysm formation and rupture. In case 2, the septicemia arose from an infected knee. The presentation of a celiac artery aneurysm as hemoptysis and as the cause of hemothorax is rare.

A recombinant subunit vaccine that protects progeny chickens from infectious bursal disease.

The major protective immunogen of infectious bursal disease virus (IBDV), VP2, was produced in a highly immunogenic form by expression in the yeast Saccharomyces cerevisiae. The recombinant protein, formulated as an oil-emulsion vaccine, induced both virus neutralising and ELISA antibodies in specific pathogen free hens. These antibodies were passed, via the egg yolk, to progeny chickens and protected them against a challenge infection with virulent IBDV. The protective efficacy of maternal antibodies to the recombinant VP2, as assessed by ELISA, was comparable to that of antibodies to the whole virus. The recombinant subunit vaccine induced anamnestic serum antibody responses in hens primed previously with live virus, and hence can replace the conventional inactivated vaccines administered to breeding hens.

Antigens recognized by the human immune response to severe leptospirosis in Barbados.

Serum samples obtained from patients hospitalized in Barbados with severe leptospirosis were tested by the microscopic agglutination test (MAT), enzyme immunoassay (EIA) and immunoblotting with leptospires that had been isolated from these patients. While serum samples taken a few days after onset of symptoms often showed no apparent correlation between MAT and EIA, later sequential serum samples produced similar profiles in both tests during the course of infection. Immunoblotting sonicate from Leptospira interrogans serovars arborea, copenhageni and bim with patients' sera, revealed reactions with a number of bands that corresponded with outer envelope components. These components included lipopolysaccharide (LPS), flagella and other outer membrane proteins, in addition to a low-molecular-weight (MW) carbohydrate cross-reactive with members of the Leptospiraceae. IgM antibodies elicited in the first to second week after infection reacted mainly with LPS and the low-MW cross-reactive carbohydrate. Comparative analysis of isolates of the same serovar by sodium dodecyl sulphate polyacrylamide gel electrophoresis and immunoblotting showed that while two serovar arborea isolates were identical, serovar bim isolates differed significantly from each other. This difference was also observed in comparative MAT testing.

Stimulation of luteinizing hormone-Beta messenger ribonucleic Acid and post-translational modification of luteinizing hormone isoforms by second messengers mediating the action of gonadotrophin-releasing hormone.

Abstract Several second messenger systems have been implicated in mediating the action of gonadotrophin-releasing hormone on the pituitary gonadotrophs and numerous studies have shown that activation of these systems induces luteinizing hormone (LH) secretion. However, it is not known how gonadotrophin-releasing hormone or the second messenger systems induce de novo LH biosynthesis and post-translational modification of the hormone. In these experiments hemipituitary glands have been perifused with drugs which activate second messengers or stimulate protein kinase C directly. The LH secretory responses have been correlated with measurements of common a and LHbeta mRNA and the molecular species of LH which were present in the pituitary perifusate after exposure to the drugs. Gonadotrophin-releasing hormone (50 ng/ml, 42 nM), with and without the presence of extracellular Ca(2+), the Ca(2+) ionophore, A23187 (10 muM), and phorbol 12-myristate (1 muM) all stimulated an increase in LHbeta mRNA compared with controls and the appearance of a different isoform of LH to that found stored in and released from the unstimulated pituitary gland. Phospholipase C was without effect on LHbeta mRNA levels and showed minimal efficacy in inducing the appearance of the different LH isoform.

Passive protection against infectious bursal disease virus by viral VP2 expressed in yeast.

Infectious bursal disease virus (IBDV), a pathogen of major economic importance to the world's poultry industries, causes a severe immunodepressive disease in young chickens. Maternal antibodies are able to protect the progeny passively from IBDV infection. The gene encoding the IBDV host-protective antigen (VP2) has been cloned and expressed in yeast resulting in the production of an antigen that very closely resembles native VP2. When injected into specific pathogen free chickens a single dose of microgram quantities of the yeast derived antigen induces high titres of virus neutralizing antibodies that are capable of passively protecting young chickens from infection with IBDV.

Antigens recognized by the human immune response to vaccination with a bivalent hardjo/pomona leptospiral vaccine.

Serum from volunteer subjects vaccinated with a bivalent whole cell vaccine of Leptospira interrogans serovar hardjo/serovar pomona grown in protein-free medium, was tested by the microscopic agglutination test (MAT), enzyme-immunoassay (EIA) and immunoblotting. Specific IgM antibodies to either serovars hardjo or pomona were detected in some subjects as early as 6 days after vaccination with peak antibody levels occurring 13-68 days after vaccination. Whereas all subjects produced specific IgM to both serovars, not all produced specific IgG to both serovars. Immunoblotting with hardjo sonicate revealed that all subjects produced IgM antibodies reacting with the 15, 23 and 28 kDa components of hardjo lipopolysaccharide (LPS), and most produced IgM antibodies that reacted with the 34.5 kDa flagellar doublet. In contrast, not all sera immunoblotted against pomona sonicate reacted with the 29 and 35 kDa components of pomona LPS. However all subjects produced antibodies reacting with a diffuse 14.4-27 kDa band. These antibodies appeared early in the immune response. Serum from the one vaccinated subject tested protected hamsters from acute lethal infection with serovar pomona.

Gonadotrophin glycosylation and function.

This review emphasizes the heterogeneous structure of the gonadotrophin hormones and the influence of different oligosaccharide structures on the bioactivity of these hormones. A summary has been made of the changes in biopotency of the gonadotrophins throughout the life-cycle of the human and in different endocrine states in the rat. In general it appears that the charge of the gonadotrophin conferred by the acid radicals attached to the terminal groups on the oligosaccharide structures strongly influences biopotency. Basic structures have a greater potency in in-vitro assays, but a short half-life in the circulation, while acidic isoforms are less potent, but have a longer circulatory time and are thus more active in in-vivo estimations. More basic forms are secreted over the adult reproductive years compared with the prepubertal period and old age. The glycosyl structure of the carbohydrate groups also alters in different endocrine states and is probably also important for the bioactivity and potency of the hormone. Gonadotrophin-releasing hormone (GnRH) and gonadal steroids can influence the type of isoform synthesized and released, and therefore affect the function of gonadotrophins. GnRH enhances glycosylation, sulphation and biopotency. Oestradiol potentiates the glycosylation induced by GnRH and reduces sialylation, while testosterone increases sialylation.

Assessing the veracity of children's testimony.

This study examines the effects of method of recall on the accuracy of adults' and children's eyewitness accounts. A filmed staged accident was used as test material and subjects questioned immediately after watching the accident. Eight pre-structured questions were asked. Children's representations are often poorly articulated and lack cohesion. Established information-gathering techniques should be tailored to allow children to provide evidence.

Identification of leptospiral flagellar antigens by gel electrophoresis and immunoblotting.

Flagella extracted from five serovars, representative of the pathogenic and saprophytic species of the Leptospiraceae, were morphologically similar. Analysis of Leptospira interrogans flagellar preparations by polyacrylamide gel electrophoresis revealed three common major bands in the (30-40) x 10(3)-mol. wt region, and serovar-specific bands in the lower region of the gels. Although some differences were observed, flagella extracted from L. biflexa serovar patoc and Leptonema illini revealed similar electrophoretic profiles to those seen in L. interrogans flagella. Immunoblot analysis showed that while flagellar components in the (20-30) x 10(3)-mol. wt region were recognised only by homologous rabbit antisera, a major protein doublet of (33-34) X 10(3)-mol. wt, depending on the species, was also demonstrated by heterologous antisera. The serovar-specific bands in the (20-30) x 10(3)-mol. wt region were composed of lipopolysaccharide (LPS). These results show that leptospiral flagella are immunogenic and contain antigens which are conserved among the different genera of the family Leptospiraceae.

Antigens recognised by the human immune response to infection with Leptospira interrogans serovar hardjo.

Serum samples from patients infected with Leptospira interrogans serovar hardjo were tested by the microscopic agglutination test (MAT), enzyme immunoassay (EIA) and immunoblotting. There was no apparent correlation between MAT titre and EIA optical density (OD) for individual serum samples, but sequential serum samples produced similar profiles in both tests during the course of an infection. Immunoblotting of hardjo sonicate with patients' sera revealed reactions with a number of bands, in the mol. wt (10(3] range 14.4-95. However, all serum samples reacted with the major 28 x 10(3)-mol. wt sub-unit of hardjo lipopolysaccharide (LPS) and most reacted with a (34.5-35) x 10(3)-mol. wt flagella doublet. Examination of sequential serum samples obtained over a period of about 3 months after infection revealed little change in the antigens detected after the second to third week of infection. Absorption of patients' sera with whole viable leptospires revealed that antibodies to several exposed antigens, including LPS, were produced. Sera which reacted with hardjo flagella also reacted with bands of similar mol. wts in preparations from other serovars.

Effect of bromocriptine on LH pulsatility in the polycystic ovary syndrome.

The effects were studied of bromocriptine, 10 mg daily for 1 year, on luteinizing hormone (LH) pulse characteristics in patients with classical polycystic ovarian syndrome (PCOS). All patients were hirsute, had been oligomenorrhoeic since menarche, had LH: FSH ratios of greater than 3:1, and either elevated serum testosterone (T) or dehydroepiandrosterone sulphate (DHAS) concentrations. In 10 subjects who completed the study menstrual frequency increased from an average of 3.6 to 8 per year but few of the cycles were ovulatory. Mean (SE) serum testosterone fell from 4.4 (0.5) nmol/l pretreatment to 2.8 (0.3) nmol/l (P less than 0.01) and DHAS from 7.9 (1.1) mumol/l to 5.4 (1.1) mumol/l (P less than 0.05). Serum delta 4 androstenedione and oestradiol did not change with bromocriptine treatment. Mean serum LH fell from 17.4 (2.4) IU/l to 11.2 (1.8) IU/l (P less than 0.03) after 12 months of bromocriptine. No pattern of LH pulsatility specific to PCOS was detected during 10 min sampling for an 8 h period prior to dopamine agonist treatment. LH interpeak interval (58 (5.2) min) and peak amplitude (156 (7.2%) of mean nadir) in untreated PCOS were similar to that of the mid-follicular stage of ovulatory cycles, and bromocriptine for 1 year did not alter these variables. We conclude that while bromocriptine reduces serum androgen levels and increases menstrual frequency it has no effect centrally to modify hypothalamic GnRH secretion. The reduction in LH levels by bromocriptine may be the result of diminished gonadotroph sensitivity to GnRH or reduced pituitary stores of LH available for release. Despite the return towards normal of various hormonal characteristics of PCOS, bromocriptine has little place in the management of this condition.