General principles of radioimmunoassay

Molecular Modeling Methods in the Development of Affine and Specific Protein-Binding Agents

High-affinity and specific agents are widely applied in various areas, including diagnostics, scientific research, and disease therapy (as drugs and drug delivery systems). It takes significant time to develop them. For this reason, development of high-affinity agents extensively utilizes computer methods at various stages for the analysis and modeling of these molecules. The review describes the main affinity and specific agents, such as monoclonal antibodies and their fragments, antibody mimetics, aptamers, and molecularly imprinted polymers. The methods of their obtaining as well as their main advantages and disadvantages are briefly described, with special attention focused on the molecular modeling methods used for their analysis and development.

Mpox: a review of laboratory detection techniques

Mpox (formerly monkeypox) is a zoonotic disease caused by monkeypox virus (MPXV), which, like smallpox, is characterised by skin rashes. While the world is currently grappling with the coronavirus disease 2019 pandemic, the appearance of MPXV has presented a global threat and raised concerns worldwide. Since May 2022, MPXV has spread rapidly in non-endemic mpox areas. As of 27 June 2023, the virus has spread to more than 112 countries and regions, with over 88,060 laboratory-confirmed cases and 147 deaths. Thus, measures to control the mpox epidemic are urgently needed. As the principal methods for identifying and monitoring mpox, laboratory detection techniques play an important role in mpox diagnosis. This review summarises the currently-used laboratory techniques for MPXV detection, discusses progress in improving these methods, and compares the benefits and limitations of various diagnostic detection methods. Currently, nucleic acid amplification tests, such as the polymerase chain reaction, are the most commonly used. Immunological methods have also been applied to diagnose the disease, which can help us discover new features of MPXV, improve diagnostic accuracy, track epidemic trends, and guide future prevention and control strategies, which are also vital for controlling mpox epidemics. This review provides a resource for the scientific community and should stimulate more research and development in alternative diagnostics to be applied to this and future public health crises.

Application of Enzyme-Linked Fluorescence Assay (ELFA) to Obtain In Vivo Matured Dog Oocytes through the Assessment of Progesterone Level

Successful dog cloning requires a sufficient number of in vivo matured oocytes as recipient oocytes for reconstructing embryos. The accurate prediction of the ovulation day in estrus bitches is critical for collecting mature oocytes. Traditionally, a specific serum progesterone (P4) range in the radioimmunoassay (RIA) system has been used for the prediction of ovulation. In this study, we investigated the use of an enzyme-linked fluorescence assay (ELFA) system for the measurement of P4. Serum samples of estrus bitches were analyzed using both RIA and ELFA, and the measured P4 values of ELFA were sorted into 11 groups based on the standard concentration measured in RIA and compared. In addition, to examine the tendency of changes in the P4 values in each system, the P4 values on ovulation day (from D - 6 to D + 1) in both systems were compared. The ELFA range of 5.0-12.0 ng/mL was derived from the RIA standard range of 4.0-8.0 ng/mL. The rates of acquired matured oocytes in RIA and ELFA were 55.47% and 65.19%, respectively. The ELFA system successfully produced cloned puppies after the transfer of the reconstructed cloned oocytes. Our findings suggest that the ELFA system is suitable for obtaining in vivo matured oocytes for dog cloning.

Jasmonate perception: Ligand-receptor interaction, regulation, and evolution

Phytohormones integrate external environmental and developmental signals with internal cellular responses for plant survival and multiplication in changing surroundings. Jasmonate (JA), which might originate from prokaryotes and benefit plant terrestrial adaptation, is a vital phytohormone that regulates diverse developmental processes and defense responses against various environmental stresses. In this review, we first provide an overview of ligand-receptor binding techniques used for the characterization of phytohormone-receptor interactions, then introduce the identification of the receptor COI1 and active JA molecules, and finally summarize recent advances on the regulation of JA perception and its evolution.

Animal Models in Pharmacology: A Brief History Awarding the Nobel Prizes for Physiology or Medicine

BACKGROUND

The Nobel Prize of Physiology or Medicine (NPPM) has recognized the work of 222 scientists from different nationalities, from 1901 until 2020. From the total, 186 award researchers used animal models in their projects, and 21 were attributed to scientists and projects directly related to Pharmacology. In the most recent years, genetics is a dominant scientific area, while at the beginning of the 20th century, most of the studies were more related to anatomy, cytology, and physiology.

SUMMARY

Mammalian models were used in 144 NPPM projects, being rodents the most used group of species. Moreover, 92 researchers included domestic species in their work. The criteria used to choose the species, the number of animals used and the experimental protocol is always debatable and dependent on the scientific area of the study; however, the 3R's principle can be applied to most scientific fields. Independently of the species, the animal model can be classified in different types and criteria, depending on their ecology, genetics, and mode of action. Key-Messages: The use of animal models in NPPM awarded projects, namely in Pharmacology, illustrates their importance, need and benefit to improve scientific knowledge and create solutions. In the future, with the contribute of technology, it might be possible to refine the use of animal models in pharmacology studies.

Radiolabeled hormones in insulin research, a minireview

Preparation of both 125 I-labeled insulin and insulin-like growth factor 1 (IGF-1) was critical because it enabled a detailed characterization of binding properties of these important hormones towards their cognate transmembrane receptors. Binding modes of hundreds of hormone derivatives were analyzed using competition radioligand binding assays. This effort has resulted in development of six insulin analogs that are today clinically used for the treatment of diabetes. Here, we will briefly summarize a history of insulin research employing iodinated hormones.

Whey protein sweetened with Stevia rebaudiana Bertoni (Bert.) increases mitochondrial biogenesis markers in the skeletal muscle of resistance-trained rats

Background

A combination of resistance training and whey protein supplementation is a common practice among athletes and recreational exercisers to enhance muscle growth and strength. Although their safety as food additives is controversial, artificial sweeteners are present in whey protein supplements. Thus, natural sweeteners extracted from the leaves of Stevia rebaudiana are a potential alternative, due to their safety and health benefits. Here, we investigated the effects of whey protein sweetened with S. rebaudiana on physical performance and mitochondrial biogenesis markers in the skeletal muscle of resistance-trained rats.

Methods

Forty male Wistar rats were distributed into four groups: sedentary rats, trained rats, trained rats receiving whey protein and trained rats receiving whey protein sweetened with S. rebaudiana leaf extracts. Resistance training was performed by climbing a ladder 5 days per week, during 8-weeks. The training sessions consisted of four climbs carrying a load of 50, 75, 90, and 100% of the maximum load-carrying capacity which we determined before by performing a maximum load-carrying test for each animal. After this period, we collected plasma and tissues samples to evaluate biochemical, histological and molecular (western blot) parameters in these rats.

Results

Dietary supplementation with whey protein sweetened with S. rebaudiana significantly enhanced the maximum load-carrying capacity of resistance-trained rats, compared with non-sweetened whey protein supplementation. This enhanced physical performance was accompanied by an increase in the weight of the gastrocnemius and soleus muscle pads. Although the muscle pad of the biceps brachii was not altered, we observed a significant increase in PGC-1α expression, which was followed by a similar pattern in TFAM protein expression, two important mitochondrial biogenesis markers. In addition, a higher level of AMPK phosphorylation was observed in these resistance-trained rats. Finally, supplementation with whey protein sweetened with S. rebaudiana also induced a significant decrease in retroperitoneal adipocyte diameter and an increase in the weight of brown adipose tissue pads in resistance-trained rats.

Conclusion

The addition of Stevia rebaudiana leaf extracts to whey protein appears to be a potential strategy for those who want to increase muscular mass and strength and also improve mitochondrial function. This strategy may be useful for both athletes and patients with metabolic disorders, such as obesity and type 2 diabetes.

Cascading Amplification of Immunoassay Signal by Cell-Free Expression of Firefly Luciferase from Detection Antibody-Conjugated DNA in an Escherichia coli Extract

An expression immunoassay is a powerful technique that combines unique features of immunosorbent assays and cell-free protein synthesis. The main advantage of the expression immunoassay is a greatly amplified signal, whereas a conventional enzyme-linked immunosorbent assay (ELISA) employs a single enzyme molecule conjugated to a detection antibody to produce a measurable signal. Expression immunoassays utilize a DNA molecule conjugated to a target-bound antibody to generate multiple enzyme molecules that then produce the signal. To date, expression immunoassays have not been widely adopted due to the limited availability of efficient methods for translating antibody-conjugated DNA. We developed a highly efficient translation module for expression immunoassays using an Escherichia coli extract-based cell-free protein synthesis system. When we used our immunoassay technique to detect α-fetoprotein, we achieved a limit of detection of 7 fM. Given the outstanding sensitivity that can be obtained with only minimal modifications to the procedure of standard ELISA, we believe that this method will open up new possibilities for widespread application of expression immunoassays to ultrasensitive detection and diagnostics.

Metabolic biomarkers for chronic kidney disease

Chronic kidney disease (CKD) is an increasingly recognized burden for patients and health care systems with high (and growing) global incidence and prevalence, significant mortality, and disproportionately high treatment costs. Yet, the available diagnostic tools are either impractical in clinical routine or have serious shortcomings impeding a well-informed disease management although optimized treatment strategies with proven benefits for the patients have become available. Advances in bioanalytical technologies have facilitated studies that identified genomic, proteomic, and metabolic biomarker candidates, and confirmed some of them in independent cohorts. This review summarizes the CKD-related markers discovered so far, and focuses on compounds and pathways, for which there is quantitative data, substantiating evidence from translational research, and a mechanistic understanding of the processes involved. Also, multiparametric marker panels have been suggested that showed promising diagnostic and prognostic performance in initial analyses although the data basis from prospective trials is very limited. Large-scale studies, however, are underway and will provide the information for validating a set of parameters and discarding others. Finally, the path from clinical research to a routine application is discussed, focusing on potential obstacles such as the use of mass spectrometry, and the feasibility of obtaining regulatory approval for targeted metabolomics assays.

Methods for Detection of Aflatoxins in Agricultural Food Crops

Aflatoxins are toxic carcinogenic secondary metabolites produced predominantly by two fungal species: Aspergillus flavus and Aspergillus parasiticus. These fungal species are contaminants of foodstuff as well as feeds and are responsible for aflatoxin contamination of these agro products. The toxicity and potency of aflatoxins make them the primary health hazard as well as responsible for losses associated with contaminations of processed foods and feeds. Determination of aflatoxins concentration in food stuff and feeds is thus very important. However, due to their low concentration in foods and feedstuff, analytical methods for detection and quantification of aflatoxins have to be specific, sensitive, and simple to carry out. Several methods including thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), mass spectroscopy, enzyme-linked immune-sorbent assay (ELISA), and electrochemical immunosensor, among others, have been described for detecting and quantifying aflatoxins in foods. Each of these methods has advantages and limitations in aflatoxins analysis. This review critically examines each of the methods used for detection of aflatoxins in foodstuff, highlighting the advantages and limitations of each method. Finally, a way forward for overcoming such obstacles is suggested.

Decoding the substrate supply to human neuronal nitric oxide synthase

Nitric oxide, produced by the neuronal nitric oxide synthase (nNOS) from L-arginine is an important second messenger molecule in the central nervous system: It influences the synthesis and release of neurotransmitters and plays an important role in long-term potentiation, long-term depression and neuroendocrine secretion. However, under certain pathological conditions such as Alzheimer’s or Parkinson’s disease, stroke and multiple sclerosis, excessive NO production can lead to tissue damage. It is thus desirable to control NO production in these situations. So far, little is known about the substrate supply to human nNOS as a determinant of its activity. Measuring bioactive NO via cGMP formation in reporter cells, we demonstrate here that nNOS in both, human A673 neuroepithelioma and TGW-nu-I neuroblastoma cells can be fast and efficiently nourished by extracellular arginine that enters the cells via membrane transporters (pool I that is freely exchangeable with the extracellular space). When this pool was depleted, NO synthesis was partially sustained by intracellular arginine sources not freely exchangeable with the extracellular space (pool II). Protein breakdown made up by far the largest part of pool II in both cell types. In contrast, citrulline to arginine conversion maintained NO synthesis only in TGW-nu-I neuroblastoma, but not A673 neuroepithelioma cells. Histidine mimicked the effect of protease inhibitors causing an almost complete nNOS inhibition in cells incubated additionally in lysine that depletes the exchangeable arginine pool. Our results identify new ways to modulate nNOS activity by modifying its substrate supply.

Visualization and analysis of vascular receptors using confocal laser scanning microscopy and fluorescent ligands

The use of fluorescent ligands to analyze receptor distribution is increasing in popularity. This is due to the ever growing number of fluorescent ligands and the increased sensitivity of microscope-based technologies. Image-analysis methods have advanced to a stage where quantification of fluorescent signals is relatively simple (if used appropriately). In this chapter we describe a method of analyzing the 2D and 3D distribution of fluorescent ligands in segments of blood vessels. In addition, we introduce the issues surrounding the accurate analysis of colocalization of two different fluorescent ligands.

Development and analytical validation of a radioimmunoassay for the measurement of alpha1-proteinase inhibitor concentrations in feces from healthy puppies and adult dogs

Canine α1-proteinase inhibitor (cα1-PI), a proteolysis-resistant protein with a molecular weight similar to albumin, has been shown to be clinically useful as a marker for gastrointestinal protein loss in dogs. A competitive, liquid-phase radioimmunoassay was developed and analytically validated. Fecal samples were collected from 101 healthy pet dogs of various breeds and ages, and fecal cα1-PI (Fcα1-PI) concentrations were compared between dogs of different age groups. A reference interval for Fcα1-PI concentration was calculated using the central 95th percentile. Analytical sensitivity of the assay was 2.2 µg Fcα1-PI/g feces. Observed-to-expected ratios for the serial dilution and spiking recovery of 9 and 6 fecal extracts ranged from 90.4 to 152.0% and from 71.3 to 112.3%, respectively. Coefficients of variation for intra- and interassay variability for 6 fecal extracts were ≤10.8% and ≤12.5%, respectively. The reference intervals for the mean and maximum Fcα1-PI from fecal samples collected on 3 consecutive days were 2.2–13.9 µg/g and 2.2–21.0 µg/g, respectively. Fcα1-PI was significantly higher in dogs <1 year of age ( P < 0.0001 for both mean and maximum Fcα1-PI for the 3 samples). The radioimmunoassay described is sensitive, linear, precise, reproducible, and accurate for clinical use, thus allowing reliable quantification of Fcα1-PI in clinical patients. Using this assay, a mean or a maximum Fcα1-PI for 3 sampling days of >13.9 µg/g or >21.0 µg/g, respectively, should be considered abnormal in dogs >1 year of age. Fecal cα1-PI concentrations in dogs <1 year of age were significantly higher and should be carefully interpreted in this age group.

The RAPID method for blood processing yields new insight in plasma concentrations and molecular forms of circulating gut peptides

The correct identification of circulating molecular forms and measurement of peptide levels in blood entails that the endocrine peptide being studied is stable and recovered in good yields during blood processing. However, it is not clear whether this is achieved in studies using standard blood processing. Therefore, we compared peptide concentration and form of 12 (125)I-labeled peptides using the standard procedure (EDTA-blood on ice) and a new method employing Reduced temperatures, Acidification, Protease inhibition, Isotopic exogenous controls, and Dilution (RAPID). During standard processing there was at least 80% loss for calcitonin-gene-related peptide and cholecystokinin-58 (CCK-58) and more than 35% loss for amylin, insulin, peptide YY forms (PYY((1-36)) and PYY((3-36))), and somatostatin-28. In contrast, the RAPID method significantly improved the recovery for 11 of 12 peptides (P < 0.05) and eliminated the breakdown of endocrine peptides occurring after standard processing as reflected in radically changed molecular forms for CCK-58, gastrin-releasing peptide, somatostatin-28, and ghrelin. For endogenous ghrelin, this led to an acyl/total ghrelin ratio of 1:5 instead of 1:19 by the standard method. These results show that the RAPID method enables accurate assessment of circulating gut peptide concentrations and forms such as CCK-58, acylated ghrelin, and somatostatin-28. Therefore, the RAPID method represents an efficacious means to detect circulating variations in peptide concentrations and form relevant to the understanding of physiological function of endocrine peptides.

A selected history and future of immunoassay development and applications in clinical chemistry

BACKGROUND

The first immunoassay was described by Berson and Yalow in 1959. Their work resulted in their receipt of the Nobel Prize in Medicine in 1977. Since this introduction, immunoassays have evolved considerably.

METHODS

There have been several milestones that have led to the proliferation of modern immunoassays. The development of monoclonal antibodies from mouse hydridoma cells by Millstein and Kohler (Nobel Prize in 1984) enabled the production of high quantities of antibodies with well characterized epitope specificity. The first homogenous immunoassay (no separation step required) was the Enzyme Multiplied Immunoassay Technique (EMIT), which enabled adaptation of this assay onto automated chemistry platforms. EMIT was also one of the first immunoassay that made use of non-isotopic labels. Other non-isotopic labels became available such as chemiluminescence to improve the analytical sensitivity of immunoassays. The advantages of high-sensitivity immunoassays have created expanded diagnostic roles for some existing assays such as thyroid stimulating hormone for hyperthyroidism, C-reactive protein for cardiovascular risk assessment, and other applications. The development of instrumentation capable of automated heterogeneous immunoassays (separation step to improve sensitivity) has enabled movement of this technology from the "special chemistry" sections of a clinical laboratory into the "core" laboratory with other high-volume testing.

CONCLUSION

Today, immunoassays play a prominent role in the analysis of many clinical laboratory analytes such as proteins, hormones, drugs, and nucleic acids. The future involves development of assays with higher sensitivities which will enable the discovery of new biomarkers for disease diagnosis, and technology that will enable simultaneous multimarker analysis of tests whose needs are naturally grouped together (e.g., cytokines and allergens).

Insulin-like effects of Bauhinia forficata aqueous extract upon Tityus serrulatus scorpion envenoming

Scorpion envenoming causes an intense autonomic discharge, leading to a massive release of neurotransmitters, giving rise to several pathophysiological effects. In this work we report the effects of a Bauhinia forficata aqueous extract (BfAE) upon hyperglycemia, glycogenolysis, increase of plasma catecholamines, lethality and changes in serum insulin and plasma electrolytes induced by Tityus serrulatus scorpion venom (TSV). We compare them with the effects of the regular insulin therapy. The following treatments were performed: TSV (500 microg/kg, i.p.); BfAE (1g/kg, p.o.), 24, 12 and 1 h before and immediately after TSV or saline and insulin in a single dose (1.5 IU/kg, s.c.) after TSV. BfAE reduces the fast hyperglycemia induced by TSV, but it is deprived of hypoglycemic activity. The extract also did not reduce either the intense glycogenolysis or the release of catecholamines and did not stimulate the release of endogenous insulin, although causing changes in the electrolyte plasma levels similarly to insulin. Although BfAE and insulin antagonize some effects of TSV, they should be avoided in the treatment of Tityus serrulatus envenoming, since they enhance the lethality of the venom.

Development and validation of a radioimmunoassay for the measurement of canine pancreatic lipase immunoreactivity in serum of dogs

OBJECTIVE

To develop and validate a radioimmunoassay (RIA) for measuring canine pancreatic lipase immunoreactivity (cPLI) in serum obtained from dogs.

SAMPLE POPULATION

Serum samples from 47 healthy dogs.

PROCEDURES

Canine pancreatic lipase (cPL) was purified from pancreatic specimens of dogs. Antibodies against cPL were raised in rabbits and purified by use of affinity chromatography. A tracer was produced by iodination of cPL with 125I. An RIA was established and validated by determination of sensitivity, working range, dilutional parallelism, spiking recovery, and intra- and interassay variability. A reference range for cPLI in serum was established by use of the central 95th percentile for samples obtained from 47 healthy dogs.

RESULTS

Sensitivity and upper limit of the working range were 0.88 and 863 microg/L, respectively. Observed-to-expected ratios for serial dilutions ranged from 84.9 to 116.5% for 4 samples. Observed-to-expected ratios for spiking recovery ranged from 82.8 to 128.6% for 4 samples. Coefficients of variation for intra-assay variability for 4 serum samples were 18.3, 4.2, 3.5, and 8.9%, whereas interassay coefficients of variation were 29.2, 6.2, 3.9, and 4.4%, respectively. The reference range was 4.4 to 276.1 microg/L.

CONCLUSIONS AND CLINICAL RELEVANCE

We conclude that the RIA described is sensitive, linear, accurate, precise, and reproducible, with limited accuracy in the high end of the working range and limited precision and reproducibility in the low end of the working range. Additional studies are needed to evaluate whether this degree of accuracy, precision, and reproducibility will negatively impact clinical use of this assay.

Mini-RIA: adaptation of conventional 125I-labeled radioimmunoassay to a 96-tube format

Radioimmunoassay (RIA) employing iodinated ligands represents a popular measurement method for small molecules due to its excellent sensitivity and specificity. Yet performing RIAs of large numbers of tubes remains a tedious laboratory chore due to the need to individually handle tubes multiple times. We here present a method in which conventional 125I-labeled RIA ([125I] RIA) is adapted to a microtiter plate format, termed mini-RIA. Tubes are handled in batch for centrifugation or during the separation of antibody-bound ligand from free ligand. A simple draining device for batch decantation of free ligand from 96 minitubes is used. Optimal conditions for the mini-RIA were established using two workup methods-double-antibody immunoprecipitation and direct polyethylene glycol precipitation. Use of the mini-RIA method was found to result in a considerable savings in assay times; in addition, the sensitivity of the mini-RIA was improved over conventional RIA. The mini-RIA is particularly useful for assay of large numbers of samples derived from chromatographic methods, since aliquots can be transferred directly from the fraction collector into the minitubes using multiple channel pipettors. Because the method is flexible with regard to assay workup, we predict that most conventional [125I] RIAs can be adapted to the mini-RIA format.

Optimization of the cost and sensitivity of receptor- and enzyme-based assays

In detecting receptor antagonists or enzyme inhibitors, there are three parameters that often affect the outcome in a predictable quantitative manner: concentrations of the receptors (enzyme), labeled ligand (substrate), and antagonist (inhibitor). The usual goal of assay optimization is to maximize the ability of the assay to detect low concentrations of the analyte. Another question of practical importance, especially in screening of large numbers of samples, would be minimization of the reagent cost. Although the mathematical theory of optimization of the receptor binding assay was developed a long time ago, the resulting formulas (in the general case of unequal affinities of ligand and competitor) were not well suited for practical use. The current availability of computational programs, such as Mathematica, makes possible an efficient solution, both for receptor- and enzyme-based assays. We use a graphical approach to assay optimization and apply it to the following problems: (1) optimization of assay sensitivity, (2) optimization of the reagent cost, and (3) analysis of the entire range of the parameter values since the mathematically optimal values may sometimes be impractical. The computation is extremely simple and the problem can sometimes be solved in several minutes.

Measuring H type 1 and H type 2 antigens in human saliva by immunoassay using artificial antigens as standard substances

A time-resolved fluorometric immunoassay for water-soluble H antigens of ABH blood group substances has been developed. Introducing artificial antigens (trisaccharide-albumin complexes for H type 1 and H type 2) as reference substances, H blood group substances in human saliva were measured. The monoclonal antibody, anti-H 1E3, reacted with both H type 1 and type 2 chains, and the commercially available anti-H reacted with H type 2 chain. Using these two antibodies we found 10-20-fold higher concentration of H type 1 compared with that of H type 2 in human saliva. The H type 2 was not found in the saliva samples from nonsecretors, irrespective of ABO phenotypes. The results suggest that approximately 90% of A and B blood group substances in human saliva are built on type 1 chains.

Quantitative analysis of Le(a) and Le(b) antigens in human saliva

We have measured the H type 1, Le(a) and Le(b) antigens in the saliva from 129 Japanese individuals by a time-resolved europium ion fluorometric immunoassay using artificial antigen-albumin complexes as the reference substances. We confirmed that the amount of Le(b) was larger than that of Le(a) in the saliva from secretors (Le(a-b+)) and vice versa in the saliva from nonsecretors (Le(a+b-)). Unexpectedly, we discovered appreciable amounts of Le(b) with small amounts of H type 1 in the saliva from the nonsecretors. The concentration of Le(b) was about 10, 6 and 35% of the concentration of the Le(a) in the saliva from the nonsecretors of the A, B and O groups, respectively. The possible formation of Le(b) from Le(a), in addition to the formation of Le(b) from H type 1, in the salivary glands is discussed.

Oral absorption of biologically active insulin in common carp (Cyprinus carpio L.)

1. Bovine insulin dissolved in 0.05 M deoxycholic acid was absorbed through oral intubation in fish weighing 200-300 g. 2. The peak of absorption appeared in all fish, 30-45 min after intubation and was followed by a gradual decrease. The extent of absorption was extremely variable, with up to a 20-fold difference between individuals. No detectable insulin was found in fish intubated with vehicle. 3. The absorbed hormone retained 17-88% of its lipogenic bioactivity in vitro. The absorbed insulin lowered the levels of several amino acids in the intubated fish, indirectly indicating that its bioactivity was also retained in vivo.

Radioligand purification prior to routine receptor assays

The need to repurify the commercially available radioligands [3H]estradiol and [3H]testosterone before use in routine assays was investigated. Storage of these products for 2 months after delivery led to appreciable degradation of [3H]estradiol compared to [3H]testosterone. Unexpectedly, TLC and even HPLC procedures were ineffective in completely restoring the purity of [3H]-estradiol and the unremoved polar products induced important variations in our estrogen receptor assays. An increase in non-specific binding and a comcomitant decrease in total binding were observed resulting in an underestimation of specific binding sites and of the affinity constant. In some cases Scatchard analysis was not possible. We therefore strongly recommend the repurification of low-stability radioligands and propose an economic time-saving procedure for the purification of [3H]estradiol by solvent differential partition which requires no high-cost investment in apparatus.

Immunocytochemical localization of angiotensinogen in the rat brain

The distribution of angiotensinogen-like immunoreactivity in the rat brain was investigated using specific antisera against pure rat plasma angiotensinogen in conjunction with the sensitive streptavidin-biotin peroxidase method. Angiotensinogen antisera were shown by radioimmunoassay and Western blotting to recognize angiotensinogen from both rat plasma and cerebrospinal fluid, and to cross-react with des-AI-angiotensinogen (100%) but not with angiotensin I and II, tetradecapeptide, luteinizing hormone-releasing hormone, rat albumin and angiotensinogen from eight other species. Angiotensinogen-like immunoreactivity was detected throughout the rat brain in both neuroglia and neurons. The highest concentration of neuroglial angiotensinogen-like immunoreactivity was in the hypothalamus and preoptic areas, with moderate to heavy concentrations in the mesencephalon and myelencephalon. The cerebellum demonstrated neuroglial staining in the granular layer and fibre tracts. Very little neuroglial staining was noted in the cerebral cortex or olfactory bulbs. Neuronal immunostaining was observed throughout the globus pallidus and the caudate putamen, in various parts of the thalamus and the supraoptic nucleus of the hypothalamus. In the midbrain moderate immunostaining was observed in periaquaductal central gray, the deep mesencephalic nucleus, the inferior colliculus and in scattered cells in the anterior mesencephalon. In the medulla, neuronal staining was localized to the vestibular nuclei and to other cell bodies mainly in the dorsolateral regions. In the cerebellum, staining was noted mainly in the deeper cerebellar nuclei and in the Purkinje cells. Immunostaining in the cerebral cortex was localized to the cingulate cortex and the primary olfactory cortex. Light staining was present in the endopiriform cortex and in scattered neurons adjacent to the external capsule. In the olfactory bulbs light neuronal staining was mainly associated with the mitral cell layer. The widespread distribution of angiotensinogen-like immunoreactivity supports the view that it is synthesized in the central nervous system and forms part of a brain renin-angiotensin system. In addition, its presence at sites other than those normally associated with the control of blood pressure and fluid and electrolyte homeostasis suggests that its involvement may not be limited to these regulatory functions.

Serum immunoreactive insulin levels in intact and regenerating postmetamorphic Xenopus laevis

In order to confirm the presence of immunoreactive insulin (IRI) in the serum of postmetamorphic Xenopus laevis, radioimmunoassay (RIA) methods were used. The concentration of hormone found in samples of blood serum taken from nonanaesthetized intact male and female animals by the guillotine method was 10.46 +/- 0.76 microU/ml. Significantly higher IRI concentrations were found in our intact animals anaesthetized in MS 222 at pH 3.5 (21.9 microU/ml) compared with intact controls anaesthetized in MS 222 adjusted to pH 7.0 (14.4 microU/ml). During the wound-healing stage subsequent to forelimb amputation in the experimental cases (0 hours to 3 days) anaesthetized in MS 222 pH 7.0, there were intervals of significantly elevated serum IRI followed by a period of decreased IRI concentration compared with the levels in anaesthetized (MS 222 pH 7.0) and nonanaesthetized intact controls. These fluctuations were due, presumably, to stress caused by amputational injury and/or anaesthetic. Serum IRI increased steadily from 3 to 14 days postamputation then remained stable for the balance of the regeneration period (28 days) compared with nonanesthetized intact controls. A positive correlation was found between immunoreactive insulin and glucose levels in the serum of our animals. However, no correlation exists between serum IRI levels and serum osmolality in the data.

Characterization of murine monoclonal antibodies directed against basic fibroblast growth factor

Monoclonal antibodies (McAbs) were developed that identify the complete (1-146 aa) and the NH2-terminal truncated (des 1-15) form of bovine basic fibroblast growth factor (bFGF). Four McAbs, designated McAbs 6, 8, 38, and 42, bind the complete form of bFGF found in bovine pituitary, brain, and adrenal gland. One of these McAbs, McAbs 42, also binds to the des 1-15 aa form of bFGF found in bovine adrenal gland, kidney, and corpus luteum. None of the McAbs binds bovine-brain-derived acidic FGF (aFGF). McAbs 6, 8, and 38 recognized the same epitope located within the first ten residues of the NH2-terminal of complete bFGF. McAb 42 recognizes a "core" epitope found on both the complete and des 1-15 aa bFGFs. The McAbs are murine IgGs with affinity constants of 10(7)-10(8) liter/M for bovine-pituitary-derived bFGF. McAbs 8 and 42 have been used in a two-site ELISA to detect the complete form of bFGF. The ELISA is sensitive to 38.5 fmole/well of bFGF and is not affected by the presence of calf serum or bovine-brain-derived aFGF. These McAbs should be useful in distinguishing the native and des 1-15 aa forms of bFGF from each other, and from aFGF and other growth factors.

Scintillation proximity assay: a sensitive and continuous isotopic method for monitoring ligand/receptor and antigen/antibody interactions

Scintillation proximity assay (SPA) makes it possible to use radioisotopes for monitoring binding reactions continuously without the need to separate free from bound components. As a result SPA can be carried out more rapidly than most other methods used to monitor binding reactions. The methodology also lends itself to automation. The sensitivities already achieved with SPA procedures are comparable to the sensitivities of other procedures in use today. Another feature of SPA is that the key reagents (beads, 125I labeling) are relatively inexpensive. The principles of SPA, utilizing 125I-labeled molecules, are discussed and some applications to immunology, receptor binding, and measurement of potential across membranes are presented. SPA should also be applicable to monitoring interactions involving nucleic acids, lipids, and carbohydrates. Characteristics of some radionuclides, other than tritium and 125I, that may be used in SPA are presented.

Scintillation proximity radioimmunoassay utilizing 125I-labeled ligands

A unique type of radioimmunoassay is described that does not require centrifugation or separation. Microbeads containing a fluorophor are covalently linked to antibody. When an 125I-labeled antigen is added it binds to the beads and, by its proximity, the emitted short-range electrons of the 125I excite the fluorophor in the beads. The light emitted can be measured in a standard scintillation counter. Addition of unlabeled antigen from tissue extracts displaces the labeled ligand and diminishes the fluorescent signal. Application of scintillation proximity immunoassay to tissue enkephalins, serum thyroxin, and urinary morphine is described. Applications of the principle to study the kinetics of interaction between receptors and ligands are discussed.

Separation of radioiodinated angiotensins by chromatofocusing in minicolumns

Angiotensins I, II, and III (AI, AII, AIII) and Saralasin (Sar1-Ala8-AII) were labeled with 125I and separated from the nonlabeled forms on minicolumns (a Pasteur pipet ) of chromatofocusing medium. At low ionic strength, 125I-labeled angiotensins could be eluted with Polybuffer or a piperazine-histidine buffer at their approximate isoelectric points, while nonlabeled angiotensins remained adsorbed to the column and required 1 mol X liter-1 NaCl for elution. The 125I-labeled angiotensins prepared by this method were bound by antibodies (AI) and adrenal receptors (AII, Saralasin) to an extent similar to angiotensins prepared by DEAE-Sephadex A-25 chromatography. This new method of preparing radioiodinated angiotensins is rapid (15 min), inexpensive, and requires no fraction-collecting equipment.

Preparation of 125I-(Tyr 3)- and 125I-(Tyr 11)- neurotensin for radioimmunoassay

The chloramine-T method for radioiodination of neurotensin for radioimmunoassay was studied. As conventional procedures produced heterogeneous preparations, labelling was performed with a low amount of chloramine-T (1.8 nmol) in the presence of excess of peptide (6 nmol). Purification and complete separation of labelled from unlabelled peptide was obtained by ion-exchange chromatography on SP Sephadex C-25. Four labelled components were identified by isoelectric focusing, enzymatic cleavage and studies of immunoreactivity. The two components representing monoiodinated preparations labelled at Tyr 3 or Tyr 11 could be isolated. Depending on the binding site of the particular antiserum the appropriate tracer could be selected for use in the radioimmunoassay. The specific radioactivities were high (2303 (2137-2407) microCi/nmol and 1927 (1608-2307) microCi/nmol (median and range] and the stability of the label and the reproducibility of the procedure was good.

Double-antibody solid-phase radioimmunoassay for blood bradykinin

A solid phase radioimmunoassay for the determination of blood bradykinin has been developed. Highly specific antibodies against bradykinin were raised in rabbits after coupling the peptide to thyroglobulin. Iodination of [Tyr8]-bradykinin was carried out with a chloramine-T procedure resulting in a tracer with high specific activity. Bradykinin was isolated in the following way: blood was sampled directly into acetone, and lipids were removed by extraction with petroleum either (40-60 degrees C). The final purification was made on QAE-Sephadex A-25 at pH 7.4. The mean recovery of added [125I-Tyr8]-bradykinin was 28% with a sample volume of 6 ml whole blood. The sensitivity of the radioimmunoassay was 1.25 pg/tube or 3 pg/ml blood. The reproducibility of the method is satisfactory with a between-assay coefficient of variation below 16%. Levels found in venous blood were below 3 pg bradykinin/ml in normal persons.

Solid-phase double-antibody radioimmunoassay of pepsinogen I in serum

A solid-phase radioimmunoassay for the determination of pepsinogen I in serum has been developed. The antibody was raised in rabbits with pepsinogen I isolated from urine as previously described. Radioiodination was carried out with a chloramine-T procedure resulting in a tracer with excellent shelf life. In the standard procedure with a 24-h incubation time, followed by 2-h incubation with a second antibody coupled to a solid phase, 50 microliter serum was analyzed, standard range 1.88-60 ng PG I. An eight times more sensitive method was also developed using sequential saturation techniques. Specificity studies demonstrated 0.6% crossreactivity with PG II. The immunoreactivity of PG I purified from urine was nearly identical with the immunoreactivity of PG I purified from gastric mucosa. The levels of PG I in serum from 121 control subjects were similar to those obtained with conventional phase separation methods. It is concluded that the method is simple, precise and free from non-specific serum interference.

Direct radioimmunoassays of renin and renin substrate during converting-enzyme inhibition

In 10 severely hypertensive patients, on a low sodium diet, converting enzyme inhibition increased plasma renin activity and decreased plasma renin substrate. The use of direct radioimmunoassays for both the enzyme and its substrate showed that the number of immunoreactive renin molecules increased from 11.3 +/- 4.9 to 31.7 +/- 25.3 pmol 1(-1) whereas the number of immunoreactive renin substrate molecules decreased from 1.04 +/- 0.35 to 0.74 +/- 0.16 mumol 1(-1). The direct radioimmunoassay for angiotensinogen gave higher values than the direct enzymatic assay, and during converting enzyme inhibition, the difference between both methods increased in proportion to the rise in circulating renin. It is concluded that the difference between the renin substrate radioimmunoassay, which measures angiotensinogen and des-angio I-angiotensinogen, and the renin substrate enzymatic assay which only measures "active" substrate, is an index of the increased consumption of renin substrate, in a situation where the fall in angiotensin II enhances renin release and decreases renin substrate release.

[Study of the valuations of serum muscular enzymes and myoglobin after maximal exercise test and during the next 24 hours (author's transl)]

Twenty-eight male subjects underwent a maximal exercise test on an ergometric bicycle, 13 untrained and 15 trained subjects. At rest and after this maximal exercise, indicated by the increase of the serum lactate and pyruvate acids, venous blood samples were taken to study the release of muscular enzymes (SGOT, SGPT, LDH, alpha HBDH, CPK, CPK MB) and myoglobin in the next 24 h (3 min, 30 min, 8 h and 24 h after the end of this test). The statistic analysis of the results shows significant increases in comparison with the values at rest, according to the enzymes and the groups of subjects, especially for CPK, SGOT, SGPT for which the results are homogeneous with a peak at the 3rd min and the 8th h in the three groups and for HBD and LDH in the groups of trained subjects. However these values remain most often within the normal limits. These results are compared with those of previous works on the same subjects.