Two-site enzyme immunometric assays for determination of native and denatured beta-lactoglobulin

Two enzyme immunometric assays suitable for measuring native and denatured beta-lactoglobulin (BLg) have been developed. The assays were performed in 96-well microtitre plates and were based on the use of pairs of monoclonal antibodies specific to either the native form or the reduced and carboxymethylated form of BLg (RCM-BLg). Detection limits of 30 and 200 pg/ml were obtained for the native BLg and the RCM-BLg assay, respectively, with very low or negligible cross-reactivity of the other milk proteins and tryptic fragments of BLg. The validity of the assays in different media such as cow's milk and cow's milk products, saline buffer or serum was supported by recovery experiments. The assays were first applied to the determination of BLg and RCM-BLg in PBS and in raw skimmed milk. The ability of the RCM-BLg assay to detect heat-denatured BLg was confirmed by a kinetic study of BLg heat-denaturation in the two media. During heat treatment, the decrease in the concentration of native BLg was associated with an increase in denatured BLg specifically detected by the RCM-BLg assay. By selecting an appropriate monoclonal antibody which failed to recognize caprine BLg, we were able to establish a modified sandwich immunoassay permitting very sensitive detection of cow's milk in goat's milk.     

Urine but not plasma nitric oxide metabolites are decreased in women with preeclampsia

OBJECTIVE: Nitric oxide is a potent vasorelaxant produced by endothelial cells. We tested the hypothesis that urinary and perhaps plasma nitric oxide metabolites would be reduced in women with preeclampsia. STUDY DESIGN: Plasma and urine from 14 women meeting strict clinical criteria for the diagnosis of preeclampsia and 20 normal nulliparous women were assayed for the stable metabolites of nitric oxide, nitrate and nitrite. RESULT: There was no significant difference of plasma concentrations of nitrate and nitrite between women with preeclampsia and women with normal pregnancies (32.7 +/- 3.1 vs 25.8 +/- 2.4 micromol/L). Plasma creatinine levels were elevated in women with preeclampsia (0.85 +/- 0.09 vs 0.66 +/- 0.02 mg/dl, p<0.01), indicating a reduced glomerular filtration rate. Urine concentrations of nitrate and nitrite normalized by creatinine excretion were significantly lower in women with preeclampsia compared with normal pregnant women (0.37 +/- 0.06 vs 0.69 +/- 0.11 micromol of nitrite per milligram creatinine, p. <0.05). CONCLUSIONS: Our study using concomitant measurement of plasma and urine nitrate and nitrite suggests a reduced production of nitric oxide in women with preeclampsia compared with normal pregnant women.     

Retinal changes mimicking diabetic retinopathy in two nondiabetic, growth hormone-treated patients

A role for GH in the pathogenesis of diabetic retinopathy has long been postulated. Previous clinical studies, however, have been confounded by hyperglycemia. We have identified 2 cases of retinopathy associated with exogenous GH therapy in nondiabetic patients. Cases were identified through the MedWatch drug surveillance system of the U.S. Food and Drug Administration. Causality by concomitant medications was excluded by a search of the literature and the FDA data base. The first patient, an obese, 31-yr-old male with traumatic hypothalamic injury, presented with nonproliferative retinopathy and macular edema, resulting in decreased visual acuity (OD 20/40-1; OS count fingers), which required laser surgery. Human GH had been initiated at 0.009 mg/ kg.day, 14 months earlier, and titrated to 0.017 mg/kg.day. The second patient, a nonobese, 11-yr-old girl receiving GH for the management of short stature in Turner's Syndrome, presented with neovascularization. GH doses were 0.033 mg/kg.day for the first 17 months and 0.043 mg/ kg.day for the following 5 months. Cumulative laboratory and clinical observations suggest that GH and related peptides have a role in retinal pathology independent of the degree of glucose tolerance.     

Takayasu's arteritis as a cause of renovascular hypertension in a non-Asian population

Takayasu's disease (TD) is a chronic inflammatory arteritis which affects the aorta and its main branches and occasionally the pulmonary artery. Its cause is not known. Clinical manifestations are due to the intensity and location of arterial inflammation in the acute phase, as well as chronic arterial stenosis over time; 50% of patients have hypertension. Although TD appears to be more common in Asia, increasing numbers of patients of different races are observed in Western countries. The most important pathogenetic mechanism of hypertension seems to be through renal artery stenosis. We show here seven Caucasian hypertensive patients with TD and renovascular stenosis and arterial hypertension. One case was diagnosed in the acute phase of the disease, while in the others diagnosis was established in an advanced occlusive phase. Basic diagnosis was established by angiographic study, with biopsy confirmation in two cases. All patients had at least three of the six criteria listed as diagnostic of TD (by the American College of Reumatology). All patients had the following criteria: age of disease onset before 40 years (symptoms or findings related to TD), vascular bruits in different areas and all patients also had aortic and renal arterial stenosis with some lesions of the main aortic branches. Six of them had claudication of the extremities. We describe their clinical, analytical and angiographic features and also the therapeutic approach. We discuss the aetiopathogenic mechanisms of hypertension in this disease and suggest that TD is not an unusual cause of vasculorenal hypertension.     

Melatonin receptors mediate contraction of a rat cerebral artery

Melatonin receptors are expressed in the cerebral arteries of the rat which form the circle of Willis. We report here that melatonin induces contraction of in vitro preparations of pressurized rat posterior communicating artery, in a concentration-dependent manner. This action of melatonin is inhibited by S-20928, a specific melatonin receptor antagonist. Our results demonstrate that the contractile action of melatonin is mediated by its receptors in the cerebral artery, and suggest a role for melatonin in the regulation of cerebral circulation.     

Molecular typing shows a high level of HLA class I incompatibility in serologically well matched donor/patient pairs: implications for unrelated bone marrow donor selection

In comparison with HLA-matched sibling bone marrow transplants, unrelated donor transplants are associated with increased graft-versus-host disease and graft failure. This is likely in part due to HLA incompatibilities not identified by current matching strategies. High resolution DNA-based typing methods for HLA class II loci have improved donor selection and treatment outcome in unrelated donor bone marrow transplantation. By using DNA-based typing methods for HLA-A and -B on a cohort of 100 potential bone marrow donor/patient pairs, we find that serological typing for HLA class I is limited in its ability to identify incompatibilities in unrelated pairs. Furthermore, the incompatibilities identified are associated with the presence at high frequency of alloreactive cytotoxic T-lymphocyte precursors. DNA typing also indicates that HLA-C mismatches are common in HLA-A and -B serologically matched pairs. Such mismatches appear to be significantly less immunogenic with respect to cytotoxic T-lymphocyte recognition, but are expected to influence natural killer cell activity. Thus, improved resolution of HLA class I shows many previously undisclosed mismatches that appear to be immunologically functional. Use of high resolution typing methods in routine matching is expected to improve unrelated donor selection and transplant outcome.     

Littoral cell angioma of the spleen: US and MR imaging findings

In this article, we describe the ultrasound and magnetic resonance imaging findings of a littoral cell angioma of the spleen. This benign vascular neoplasm of the spleen has been described, but to our knowledge there has been no case published in the literature that describes its imaging features.