Pit-1 mutation and lipoedema in a family.

BACKGROUND: A 23-year-old male was referred to our clinic with diagnosis of idiopathic isolated growth hormone deficiency. A detailed family history revealed short stature and swelling of legs which only affected females in four generations of his family. METHODS: Combined pituitary function tests revealed growth hormone deficiency, secondary hypothyroidism and hypoprolactinemia in the proband. His mother had hypoprolactinemia and growth hormone deficiency. A diagnosis of inherited combined pituitary deficiency due to a PIT-1 mutation was suspected in view of the short stature with associated multiple pituitary hormone deficiencies. RESULTS: A mutation was identified in PIT-1 (POU1F1), 196C>T, which produces the amino acid change P24L in exon 1. The mutation was also found in the mother of the proband but not in his phenotypically normal half-sister. CONCLUSION: The case shows a novel association of two rare conditions Pit-1 mutation and lipoedema in a family that has not been described before. It also allows formulation of hypothesis on the interaction of growth hormone and sex steroids resulting in abnormal fat distribution in predisposed subjects at the time of puberty.

Latent autoimmune diabetes in the young.

This case represents latent autoimmune diabetes in the young (LADY), and demonstrates that autoimmune diabetes can be slowly progressive even in younger patients with insulin independency period lasting for more than two years.

Testosterone selectively increases primary follicles in ovarian cortex grafted onto embryonic chick membranes: relevance to polycystic ovaries.

Histological studies have demonstrated that polycystic ovaries (PCO) contain increased numbers of preantral follicles with a specific increase in primary follicles. Polycystic ovary syndrome is associated with hyperandrogenism and pre- and postnatal androgenization of primates increases the pool of growing follicles producing changes resembling PCO. In vitro studies could test the hypothesis that androgens alter early folliculogenesis, but conventional culture techniques for small follicles are generally unsuitable in non-rodent species. Our objective was to develop and use a method to investigate the effects of testosterone on early folliculogenesis. We adapted an in ovo technique in which lamb cortical ovarian fragments were grafted onto the chorioallantoic membrane of fertilised chick eggs. Optimal experimental conditions for vascularisation and survival of tissue were determined and the model then used to investigate the effects of testosterone on follicle growth. Eggs were inoculated with testosterone at the time of implantation of the ovarian tissue, which was retrieved 5 days later. Tissue was sectioned and follicles staged and counted. There was no wholesale initiation of primordial follicle growth over the 5-day in ovo culture. Importantly, the proportion of primordial, primary and secondary follicles remained similar to those in unimplanted tissue. Testosterone increased the number of primary follicles by 50% compared with controls, an effect that was largely due to a reduction in atresia. In conclusion, incubation of ovarian cortex with testosterone reproduces the changes in early folliculogenesis reported in histological studies of PCO.

Pouch dilatation following laparoscopic adjustable gastric banding: psychobehavioral factors (can psychiatrists predict pouch dilatation?).

BACKGROUND: Laparoscopic adjustable gastric banding is increasingly being performed in morbidly obese individuals for weight loss. Some patients develop pouch dilatation as a postoperative complication that limits the utility of the procedure. Surgical variables are poor predictors of this complication. 5 patients from a series of 157 who underwent LAGB at a single center developed the condition. METHODS: Psychiatric and surgical case-notes were analyzed retrospectively for the presence of operationally defined psychiatric disorders and compared to 10 controls from the same population. RESULTS: Cases were significantly more likely to have past or current binge eating, emotionally triggered eating with reduced awareness of the link, a history of affective disorder, reduced sexual functioning and successful preoperative weight loss. No difference between groups was observed for compliance with orlistat, childhood sexual abuse, relationships with parents, history of bulimia nervosa, rate of band inflation or preoperative BMI. CONCLUSIONS: Psychological factors may be better predictors of pouch dilatation than biomedical variables. Disordered eating can be an attempt to modulate negative emotions. Pouch dilatation may be a consequence of this eating behavior.

Insulin resistance and endothelial dysfunction in the brothers of Indian subcontinent Asian women with polycystic ovaries.

BACKGROUND: Ultrasonographic appearances of polycystic ovaries (PCO) are found in 50% of South London Indian subcontinent Asians, a population at high risk of coronary disease and type 2 diabetes (DM). PCO is a familial condition but the genetics remain to be clarified. At present, the only characteristic documented in male family members is premature male pattern balding before the age of 30 years. Our aim was to quantify insulin resistance and endothelial cell function in the brothers of Indian subcontinent Asian women with PCO and/or a family history of type 2 DM. METHODS: Indian subcontinent Asian women (n = 40, age 16-40 years) with a brother available for study were recruited from the local population. They were stratified into four groups according to the ultrasound appearances of PCO and/or a family history of type 2 DM. Control subjects had no PCO and no family history of DM. Insulin sensitivity (KITT) was measured using a short insulin tolerance test and endothelial function using brachial artery ultrasound to measure flow-mediated dilatation (FMD). FINDINGS: Groups were well matched for age, body mass index (BMI) and waist-hip circumference ratios. Asian women with PCO demonstrated insulin resistance independent of BMI or family history of diabetes. Women with PCO and a family history of DM have reduced FMD, though PCO alone was not a marker. The brothers of women with PCO also have insulin resistance, comparable to that associated with a family history of type 2 DM. This was associated with elevations of blood pressure, abnormalities in serum lipid concentrations and impaired endothelial cell function. Endothelial cell function was particularly impaired in those subjects with both a sister with PCO and a family history of DM. INTERPRETATION: In an ethnic minority population at higher risk of coronary heart disease, brothers of women with PCO have evidence of insulin resistance and endothelial cell dysfunction in early adult life. Further study is required to establish whether these findings are associated with an increased incidence of cardiovascular events in this population.

Automated detection of diabetic retinopathy in digital retinal images: a tool for diabetic retinopathy screening.

AIMS: To develop a system to detect automatically features of diabetic retinopathy in colour digital retinal images and to evaluate its potential in diabetic retinopathy screening. METHODS: Macular centred 45 degrees colour retinal images from 1273 patients in an inner city diabetic retinopathy screening programme. A system was used involving pre-processing to standardize colour and enhance contrast, segmentation to reveal possible lesions and classification of lesions using an artificial neural network. The system was trained using a subset of images from 500 patients and evaluated by comparing its performance with a human grader on a test set of images from 773 patients. RESULTS: Maximum sensitivity for detection of any retinopathy on a per patient basis was 95.1%, accompanied by specificity of 46.3%. Specificity could be increased as far as 78.9% but was accompanied by a fall in sensitivity to 70.8%. At a setting with 94.8% sensitivity and 52.8% specificity, no cases of sight-threatening retinopathy were missed (retinopathy warranting immediate ophthalmology referral or re-examination sooner than 1 year by National Institute for Clinical Excellence criteria). If the system was implemented at 94.8% sensitivity setting over half the images with no retinopathy would be correctly identified, reducing the need for a human grader to examine images in 1/3 of patients. CONCLUSION: This system could be used when screening for diabetic retinopathy. At 94.8% sensitivity setting the number of normal images requiring examination by a human grader could be halved.

Circulating IGF-I levels in monitoring and predicting efficacy during long-term GH treatment of GH-deficient adults.

OBJECTIVE: To investigate the effects of long-term GH in GH-deficient adults, as predicted by IGF-I levels. METHODS: Patients received GH, 5 microg/kg per day for 1 Month and 10 microg/kg per day for another 12-30 Months. Changes in body composition, cardiac structure/function, serum lipids and quality of life were measured. RESULTS: There was a significant increase in lean body mass (LBM) (2.21 kg; P<0.0001) after 6 Months, which was sustained throughout treatment. A larger increase occurred in males than females (2.97 vs 1.19 kg; P<0.0001). Total fat mass was reduced (2.56 kg; P<0.0001 (3.26 kg males, 1.63 kg females)). Responsiveness to GH varied greatly, but LBM changes correlated with IGF-I changes (P<0.004). Furthermore, thinner patients experienced greater and progressive LBM increases. There was an increase in ejection fraction (3.85+/-9.95%; P=0.0002) after 6 Months, sustained to 18 Months. These cardiac effects were equal for males and females, and did not correlate with IGF-I levels. Serum low-density lipoprotein/high-density lipoprotein ratios decreased within 6 Months, and were sustained thereafter. Quality of life improved significantly after 6 Months, an effect that was sustained/enhanced as treatment continued. No major adverse events were identified. CONCLUSIONS: Improved body composition is both reflected by IGF-I changes and predicted inversely by baseline adiposity. Other effects of GH replacement on cardiac function, dyslipidaemia and quality of life, however, do not correlate with circulating IGF-I concentrations. Our findings validate the importance of sustained GH therapy, but caution on the interpretation of IGF-I levels in monitoring the long-term effects of GH treatment.

Gender-specific responses of lean body composition and non-gender-specific cardiac function improvement after GH replacement in GH-deficient adults.

GH deficiency (GHD) in adulthood is accompanied by physical and psychological impairments. One hundred fifteen patients (67 male, 48 female) with pronounced GHD were enrolled in a randomized, double-blind, placebo-controlled study with objectives that included effects on body composition, cardiac structure, and function and safety of replacement therapy with recombinant human GH (Saizen). Sixty patients (31 male, 29 female) received GH at a dose of 0.005-0.010 mg/kg.d, and 55 patients (36 male, 19 female) received placebo for 6 months. Assessment of body composition by dual-energy x-ray absorptiometry demonstrated a treatment difference in lean body mass increase of 2.1 kg (between-group comparison, P < 0.0001), which was significantly greater among males than females (P < 0.0001) [males: GH, +3.13 kg (2.42, 3.84); placebo, +0.11 kg (-0.60, 0.82); and females: GH, +0.64 kg (-0.15, 1.44); placebo: -0.90 kg (-2.20, 0.39)] [mean change 0-6 months (95% confidence limits)] and was associated with IGF-I changes. The decrease in fat mass of 2.8 kg (between-group comparison, P < 0.0001) noted by DEXA was also evident from bioelectric impedance and anthropometric measurements. Echocardiography showed comparable improvement in left ventricular systolic function after GH treatment in both genders. End-systolic volume decreased by 4.3 +/- 10.5 ml (from 35.8 +/- 17.6 ml; between-group comparison, P = 0.035) and ejection fraction increased by 5.1 +/- 10.0% (from 55.0 +/- 11.2%; between-group comparison, P = 0.048), approaching normalcy. Diastolic function did not change as assessed by isovolumic relaxation time, early diastolic flow, diastolic flow secondary to atrial contraction, or ratio of peak mitral early diastolic and atrial contraction velocity. GH treatment was well tolerated, with adverse events primarily related to effects on fluid balance. No apparent relationship between IGF-I levels and the occurrence or severity of adverse events was identified. In conclusion, GH replacement therapy in adults with GHD demonstrated beneficial effects on lean body mass composition that was more pronounced in males than females. In contrast, cardiac function improvement appears to benefit both genders equally.

Is the defect in pro-hormone processing in Type 2 diabetes mellitus restricted to the beta cell?

AIMS: To investigate whether the defect in pro-hormone processing in people with Type 2 diabetes mellitus is restricted to the pancreatic beta cell or whether there is evidence of a more generalized abnormality. METHODS: Ten Indian subcontinent Asian women with diet-controlled Type 2 diabetes were compared with a control group of nine non-diabetic Asian women who were matched for body mass index. All subjects underwent a standard 75 g oral glucose tolerance test during which plasma glucose, insulin, proinsulin and 32,33 split proinsulin were measured. Subjects in both groups then underwent an intravenous corticotrophin-releasing hormone (CRH) test with 100 microg human CRH. Plasma cortisol, adrenocorticotrophic hormone (ACTH) and ACTH precursors were measured. RESULTS: Basal levels of insulin were lower in diabetic subjects (32.5 (12.5-52) pmol/l) than in the control group (42.2 (21.4-63.0) pmol/l); normalized geometric mean (95% confidence interval), P<0.05; as were the levels at 30 min (29.5 (3.7-55.3) pmol/l) and (34.4 (10.7-58.2) pmol/l), P<0.05. The levels at 60 min were (26.7 (6.4-47.0) pmol/l) in subjects with diabetes and (13.6 (-11.3-38.5) pmol/l) in controls, P<0.05 and at 90 min these were (43.4 (19.4-67.4) pmol/l) and (19.3 (-4.6-43.3) pmol/l), P<0.05, respectively, after the 75-g oral glucose load. The acute insulin response was markedly reduced in the subjects with diabetes (1.8 (0.60-3.1) pmol insulin/ mmol glucose), compared with the control group (31.4 (8.0-54) pmol/l insulin/mmol glucose), P<0.005. Intact proinsulin was much higher in the diabetic subjects (23.9 (10.1-37) pmol/1) than in the control group (7.2 (3.9-10) pmol/1), P<0.002, as was the percentage of proinsulin-like molecules (28 (14-42) and 12 (8-17)%), respectively, P<0.01. There were no differences between basal or stimulated levels of ACTH precursors, ACTH or cortisol between the diabetic subjects and the controls. CONCLUSIONS: The defect in insulin secretion in Indian subcontinent Asian women with Type 2 diabetes is similar to that described in other populations with an increased prevalence of Type 2 diabetes. The absence of any defect in the processing of cortisol precursors in the women with Type 2 diabetes suggests that they do not have a generalized defect of hormone processing.

Thyrocyte release of asymmetric dimethylarginine does not account for human thyrocyte inhibition of endothelial cell cyclic GMP.

BACKGROUND: The thyroid gland produces and responds to the signalling molecule nitric oxide (NO). The activity of NO synthase (NOS) may be regulated by endogenous NOS inhibitors such as asymmetric dimethylarginine (ADMA). OBJECTIVE: To investigate whether human thyrocytes are capable of regulating NOS activity via the production of ADMA. DESIGN: Human thyrocytes were incubated with human umbilical vein endothelial cells (HUVEC) in order to determine the effect on HUVEC NOS activity. HUVEC cGMP production over a 3-h period was measured as an indicator of NOS activity in the absence and presence of thyrocytes. To determine thyrocyte production of ADMA, samples of conditioned media were analysed by HPLC. RESULTS: The presence of primary human thyrocytes or immortalized human thyrocyte SGHTL-189 cells caused a significant inhibition of both basal (approximately 57% inhibition) and thrombin-stimulated (approximately 42% inhibition) HUVEC cGMP production. Both primary human thyrocytes and SGHTL-189 cells released ADMA (approximately 0. 28 microg per 10(6) thyrocytes over a 3-day period). However, excess L-arginine, the natural substrate for NOS, was unable to overcome thyrocyte inhibition of HUVEC cGMP production. CONCLUSION: These data indicate that human thyrocytes potently reduce endothelial cell cGMP concentrations, and that thyrocytes produce the endogenous NOS inhibitor, ADMA. However, the inhibition of endothelial cGMP is not mediated via thyrocyte production of a competitive NOS inhibitor.

Regulation of macrophage nitric oxide synthesis by endothelial cells: a role for NG,NG-dimethylarginine.

NG,NG-dimethylarginine is an endogenous inhibitor of nitric oxide synthesis produced by endothelial cells and found in the plasma and urine of normal adults. We have examined the ability of NG, NG-dimethylarginine, produced by endothelial cells (SGHEC-7), to regulate the production of nitric oxide by lipopolysaccharide-stimulated mouse macrophage cells (J774.2). Stimulation of SGHEC-7 or J774.2 cells with lipopolysaccharide had no effect on their release of NG,NG-dimethylarginine into the culture supernatant. Stimulation of J774.2 cells with lipopolysaccharide for 24 h significantly stimulated nitric oxide production by J774.2 but not SGHEC-7 cells. When lipopolysaccharide-stimulated J774.2 cells were co-cultured with endothelial cells for 24 h, there was a significant inhibition of nitrite accumulation. The inhibition observed was dependent on the endothelial cell number (12 +/- 5% [mean +/- SEM] following incubation with 0.6 x 105 cells, up to 47 +/- 8% with 4.8 x 105 cells). The inhibitory effect of endothelial cells was prevented by incubation with increasing concentrations of L-arginine; the IC50 was 2.9 +/- 0.6 mM arginine. Western blot analysis indicated that the expression of inducible nitric oxide synthase was not inhibited by co-culture with SGHEC-7 cells. The results presented here demonstrate that NG,NG-dimethylarginine synthesized by endothelial cells may inhibit nitric oxide synthase in adjacent cells and play a role in the regulation of nitric oxide synthesis by macrophages.

Sexually dimorphic and radiation dose dependent effect of cranial irradiation on body mass index.

OBJECTIVES: To investigate the relation between cranial irradiation received during treatment for childhood leukaemia and obesity at final height. DESIGN: Retrospective cross sectional study. SETTING: Paediatric oncology centres at Great Ormond Street Hospital for Children and the Royal Marsden Hospital. SUBJECTS: Survivors of childhood leukaemia who received cranial irradiation, were in continuous first remission, and had reached final height. An unirradiated group of patients from the United Kingdom acute lymphoblastic leukaemia XI trial was also included; these patients were in continuous first remission and had been followed for at least four years from diagnosis. MAIN OUTCOME MEASURES: Body mass index standard deviation score (BMI z score) at final height for irradiated patients and at most recent follow up for unirradiated patients. Regression analysis was used to examine the effect on BMI z score of sex, age at diagnosis, and the dose of radiation received. RESULTS: For cranially irradiated patients, an increase in the BMI z score at final height was associated with female sex and lower radiation dose, but not with age at diagnosis. Severe obesity, defined as a BMI z score of > 3 at final height, was only present in girls who received 18-20 Gy irradiation and had a prevalence of 8%. Both male and female unirradiated patients had raised BMI z scores at latest follow up and there was no association with age at diagnosis. CONCLUSIONS: These data are further evidence for a sexually dimorphic and dose dependent effect of radiation on the human brain.

Reduced bone mineral density after surgical treatment for obesity.

OBJECTIVE: To investigate whether osteoporosis occurs after surgical treatment for obesity. DESIGN: A cross-sectional study of five groups of subjects who had undergone surgical treatment for obesity: five pre-menopausal women; 13 post-menopausal women; seven post-menopausal women taking oestrogen replacement (HRT); five men; and six women who had undergone surgical reversal (mean time 7 y). SUBJECTS: Thirty-six Caucasian subjects who had undergone jejunoileal or pancreaticobiliary bypass surgery at St George's Hospital between 1971 and 1992. Their mean age was 50.8 y (range 32-69 y) and the median time since the operation was 14.8y (range 4-23 y). MEASUREMENTS: A clinical questionnaire was used to exclude possible factors, which might influence bone mineral density. A single blood sample was collected for measurement of calcium, phosphate, alkaline phosphatase, albumin, magnesium, zinc, creatinine, thyroxine, 25-hydroxy-vitamin D, sex steroids, gonadotrophins and IGF-1 and 24 h urine calcium excretion was measured. Bone mineral density (BMD) was measured in the lumbar (L2-L4) spine (LS) and femoral neck (FN) by dual energy X-ray absorptiometry (DEXA). RESULTS: There was no difference in serum calcium, alkaline phosphatase, IGF-1, 25-hydroxy-vitamin D (25-OH vitamin D), magnesium or zinc concentrations between the five groups. The LS-BMD T score was lower (P < 0.05) in male subjects ( -2.08 +/- 1.04 mean 1.0 +/- s.d) and post-menopausal women not taking HRT ( -1.21 +/- 1.33) compared to the surgically reversed group (0.87 +/- 2.36). The male group was most severely affected, despite normal serum testosterone concentrations. Two of the five men studied, had a LS-BMD T score < -2.5 and two had a LS-BMD T score between -1.0 and -2.5. In contrast, six of the seven post-menopausal women on HRT had an LS BMD T score > - 1.0. There was no difference in the FN-BMD between the five groups. The presence of low BMD was not related to age, duration of bypass, or degree of postoperative weight loss. Iliac crest bone biopsies in three subjects with low BMD, confirmed the presence of osteoporosis. CONCLUSIONS: Reduced bone mineral density is a complication of jejunoileal bypass surgery.

Withholding thrombolysis in patients with diabetes mellitus and acute myocardial infarction.

The benefits of thrombolytic therapy in a patient with diabetes having a myocardial infarction are now well accepted but this treatment may be withheld inappropriately because of concerns about retinal haemorrhage. We therefore examined whether junior doctors alter their use of thrombolysis for the treatment of acute myocardial infarctions according to the type of diabetic retinopathy present. A questionnaire asking whether thrombolysis would be given to a 50-year-old male smoker with insulin-treated diabetes and an acute anterior MI was shown, with four unlabelled retinal photographs, to all doctors prescribing thrombolytic therapy in a south London teaching hospital and an affiliated district general hospital. In all, 24 medical SHOs, 16 medical registrars/specialist registrars, 3 medical senior registrars, and 23 casualty SHOs were interviewed. Of these 89% would thrombolyse such a patient with normal fundi, 55% with background diabetic retinopathy, 54 % if this also involved the macula, and 26% if they saw proliferative retinopathy. The more senior grades were more aggressive in their approach. As we believe that all patients with an acute anterior myocardial infarction and diabetes should be considered for thrombolysis irrespective of their retinal appearance these results suggest thrombolytic therapy is being withheld inappropriately.

Polycystic ovaries and associated metabolic abnormalities in Indian subcontinent Asian women.

OBJECTIVES: To determine the prevalence of polycystic ovaries (PCO) in Asian women living in England who are of Indian subcontinent origin or ancestry and to investigate the relationship between the presence of PCO and/or non-insulin dependent diabetes mellitus (NIDDM) and insulin sensitivity and other metabolic parameters. DESIGN: A random sample of Indian subcontinent Asian women was obtained from the lists of local General Practitioners and a translating service. These women were invited to attend for a medical history questionnaire, examination, venous blood sample for hormonal assessment and transvaginal ovarian ultrasonography. Groups of women without PCO or NIDDM, with NIDDM but not PCO, with PCO but not NIDDM and with both NIDDM and PCO were drawn at random from this population and from Indian subcontinent Asian women attending the Diabetes Unit. They underwent further studies, including measurement of insulin sensitivity using a short intravenous insulin tolerance test. SUBJECTS: 212 Indian subcontinent Asian women aged 18-40 took part in the initial study. Insulin sensitivity was measured in 13 women without PCO or NIDDM, 13 women with NIDDM but not PCO, 15 women with PCO but not NIDDM and 12 women with both NIDDM and PCO. MEASUREMENTS: The main outcome measures were prevalence of polycystic ovaries, clinical features of hyperandrogenism, fertility, blood pressure, serum gonadotrophins, testosterone and sex hormone binding globulin, fasting blood lipids, glucose and insulin, and insulin sensitivity. RESULTS: The prevalence of PCO in Indian subcontinent Asian women was 52% (110/212). There were significant associations between PCO and menstrual irregularity; infertility; the Ferriman and Gallwey score for body hair distribution; the presence of acanthosis nigricans and the fasting blood glucose concentration. There were no differences between women with PCO and those with normal ovarian morphology with respect to systolic and diastolic blood pressure, fasting total, HDL and LDL cholesterol and triglyceride concentrations. The subgroup of women without PCO or NIDDM had the highest insulin sensitivity (189.1 +/- 46.4 mumol glucose/l/min, mean +/- SD) and the women with both PCO and NIDDM had the lowest insulin sensitivity (80.5 +/- 30.9 mumol glucose/l/min). There was no significant difference in insulin sensitivity between those with PCO but not NIDDM (125.0 +/- 59.5 mumol glucose/l/min) and those with NIDDM but not PCO (120.8 + 38.0 mumol glucose/l/min). The effects of NIDDM and PCO on insulin sensitivity were independent; the effect of PCO on insulin sensitivity was -60 mumol glucose/l/min (95% confidence interval -100 to -21, P = 0.004) and the effect of NIDDM was -68 mumol glucose/l/min (95% confidence interval -105 to -31, P < 0.001). There were no significant relationships between insulin sensitivity and fasting plasma insulin, systolic or diastolic blood pressure, fasting serum cholesterol or triglyceride. CONCLUSIONS: The prevalence of polycystic ovaries in Indian subcontinent Asian women is very high and it has significant clinical associations. Polycystic ovaries and non-insulin dependent diabetes mellitus are associated with similar degrees of reduced insulin sensitivity in this population. Their effects are independent suggesting that these changes in insulin sensitivity involve different mechanisms. Polycystic ovaries unlike non-insulin dependent diabetes mellitus, are not associated with a defect in the secretion of insulin.

Production of glutathione-coated microtitre plates for capturing recombinant glutathione S-transferase fusion proteins as antigens in immunoassays.

Glutathione S-transferase (GST) is commonly used as a fusion partner in producing recombinant proteins and this technology is increasingly being used to produce antigens for use in immunoassays to measure antibodies. To circumvent the requirement to purify such antigens before use, we developed a method for coupling glutathione to microtitre plates so that GST-containing recombinant proteins could be purified and immobilised in one step in a suitable state for immunoassays. This procedure involves covalent linkage (using the heterobifunctional cross-linker sulphosuccinimidyl 4-(p-maleimidophenyl)butyrate) of reduced glutathione through its sulphydryl group to lysine residues of haemoglobin previously immobilised on microtitre plates. Haemoglobin was superior over other proteins tested in giving the lowest non-specific binding; in this regard it was also important to limit the amount of cross-linker used to 0.1 mM. Using glutamic acid decarboxylase as a model antigen, the new affinity capture assay was at least as good as the two-step procedure involving direct adsorption to plates of previously purified antigen; it may have the additional advantage of preserving the antigen in a more native conformation than direct adsorption. The new assay also performed as well as an assay using anti-GST antibodies adsorbed onto plates; glutathione plates, unlike anti-GST plates, will only capture recombinant proteins containing functional GST--a significant point for some recombinant expression systems in which a large proportion of the protein product is insoluble because of incorrect folding.