Compliance with needle-use declarations at two Olympic Winter Games: Sochi (2014) and PyeongChang (2018)

Objectives

We describe compliance with the ‘IOC Needle Policy’ at two Winter Olympic Games (Sochi and PyeongChang) and compare these findings to those of the Summer Olympic Games of Rio de Janeiro.

Method

All needle-use declaration(s) (NUD) received during the course of the 2014 and 2018 Olympic Games were reviewed. We recorded socio-demographic data, the nature and purpose of needle use, product(s) injected, and route of administration. Data were analysed descriptively.

Results

In total, doctors from 22 National Olympic Committees (NOCs) submitted 122 NUD involving 82 athletes in Sochi; in PyeongChang, doctors from 19 NOCs submitted 82 NUD involving 61 athletes. This represented approximately 2% of all athletes at both Games, and 25% and 20% of all NOCs participating in Sochi and PyeongChang, respectively. No marked differences in the NUD distribution patterns were apparent when comparing the two Winter Olympic Games. The most commonly administered substances were as follows: local anaesthetics, non-steroidal anti-inflammatory drug and glucocorticoids. Physicians submitted multiple NUD for 24% of all athletes who required a NUD.

Conclusion

A limited number of NOCs submitted NUD suggesting a low incidence of needle use or limited compliance (approximately 2%). A key challenge for the future is to increase the rate of compliance in submitting NUD. More effective education of NOCs, team physicians and athletes regarding the NUD policy, its purpose, and the necessity for NUD submissions, in association with the enforcement of the appropriate sanctions following non-compliance are needed.

Needle-use declarations at the Olympic Games Rio 2016

AIM

We report on the results of the 'IOC Needle Policy' applied during the course of the Games of the XXXI Summer Olympiad in Rio de Janeiro, Brazil. The policy was intended to empower physicians to ensure appropriate clinical use of needles within team medical environments, enhance the safety of those responsible for housekeeping services and others in the Olympic environment, and permit documentation of such procedures as an adjunct to the doping control programme. Any needle use required the submission of an 'Injection Declaration Form' to IOC medical officials.

METHOD

All 'Injection Declaration Forms' were reviewed and archived. The declarations provided basic information regarding the nature of the needle use and the product(s) involved, the physician, athlete and respective National Olympic Committee (NOC). The details of the declarations were subsequently categorised.

RESULTS

A total of 367 declarations were received from physicians representing 49 NOCs. Needle-use declarations were more common in athletics, gymnastics, football and aquatics. A single product was administered in 60% of the cases, and more than one product was administered in 40%. The majority of declarations indicated the use of local anaesthetics, glucocorticoids, non-steroidal anti-inflammatory drugs and analgesics.

CONCLUSION

The introduction of a 'Needle Policy' in the Olympic Games setting was intended to minimise the use of needles by non-physicians, promote evidence-based practice and to deter needle-based doping practices. Declarations were received from 49 of 209 NOCs suggesting either that needle use is minimal among certain teams or opportunities remain to enhance compliance with such policies at future games.

Molecular shape of the cationic lipid controls the structure of cationic lipid/dioleylphosphatidylethanolamine-DNA complexes and the efficiency of gene delivery

Pyridinium amphiphiles, abbreviated as SAINT, are highly efficient vectors for delivery of DNA into cells. Within a group of structurally related compounds that differ in transfection capacity, we have investigated the role of the shape and structure of the pyridinium molecule on the stability of bilayers formed from a given SAINT and dioleoylphosphatidylethanolamine (DOPE) and on the polymorphism of SAINT/DOPE-DNA complexes. Using electron microscopy and small angle x-ray scattering, a relationship was established between the structure, stability, and morphology of the lipoplexes and their transfection efficiency. The structure with the lowest ratio of the cross-sectional area occupied by polar over hydrophobic domains (SAINT-2) formed the most unstable bilayers when mixed with DOPE and tended to convert into the hexagonal structure. In SAINT-2-containing lipoplexes, a hexagonal topology was apparent, provided that DOPE was present and complex assembly occurred in 150 mm NaCl. If not, a lamellar phase was obtained, as for lipoplexes prepared from geometrically more balanced SAINT structures. The hexagonal topology strongly promotes transfection efficiency, whereas a strongly reduced activity is seen for complexes displaying the lamellar topology. We conclude that in the DOPE-containing complexes the molecular shape and the nonbilayer preferences of the cationic lipid control the topology of the lipoplex and thereby the transfection efficiency.

Analysis of allergens in rat fur and saliva

BACKGROUND

The fur is an important source of allergens in many mammal species, but this source has not been extensively studied in rats. Rat room dust contains high-molecular-weight allergens that have been found to cross-react with fur and its presumed salivary contaminants. The role of rat fur and saliva as a source of respiratory allergens merits further investigation. The objective was to describe the allergens present in the fur and saliva of male rats.

METHODS

Allergen extracts were prepared from the saliva and fur of the pelts from adult male rats. Immunoblotting was used to describe the allergens present in rat fur and saliva with serum from 76 and 25 individuals, respectively.

RESULTS

There was considerable variation between the individuals in the binding of IgE to the separated fur and saliva allergens. Immunoblot analysis identified 23 allergens in rat fur. "Major" allergens were found at the "origin", and at 55, 51, 19, and 17 kDa, and "intermediate" allergens at 74, 67 (probably albumin), and 21.5 (diffuse) kDa. Seventeen salivary allergens were described with "major" allergens at 21.5, 19.5, 19, 18, and 17.5 kDa. Many subjects had IgE to the 67 kDa (56%) and 43 kDa (64%) allergens but the density of staining was weak.

CONCLUSION

Rat fur and saliva are the sources of many allergens. Fur contained five "major" allergens and was a complex source of allergens of relatively high molecular weight (>22 kDa). The most important salivary allergens have molecular weights of less than 22 kDa. Fur is the most probable source of the high-molecular-weight allergens found in rat room dust.

Sugar-based tertiary amino gemini surfactants with a vesicle-to-micelle transition in the endosomal pH range mediate efficient transfection in vitro

Novel reduced sugar gemini amphiphiles linked through their tertiary amino head groups via alkyl spacers of 4 or 6 carbons, and with varying (unsaturated) alkyl tail lengths of 12--18, have been synthesized and tested for transfection in vitro in an adherent Chinese hamster ovary cell line (CHO-K1). Transfection efficiencies peaked at 2.7 times that of the commercial standard Lipofectamine Plus/2000 for pure solutions of the compound bearing unsaturated (oleyl) alkyl tails. For those compounds bearing saturated alkyl tails, transfection efficiency peaked at a tail length of 16, at a level similar to Lipofectamine Plus/2000. All of the amphiphiles formed bilayer vesicles at physiological pH. Some of the amino groups at the surface were protonated, and vesicles therefore bore a positive charge. Increased protonation with reduced pH resulted in greatly increased monomer solubility and a morphology change from vesicle to micelle at characteristic pH values, dependent on the tail length. For the compounds promoting high transfection efficiency, this characteristic pH was within the range found in the endosomal compartment (7.4--4.0). Formation of mixed micelles between gemini surfactant and membrane phospholipids at reduced pH may therefore provide a method of endosome rupture and subsequent escape of entrapped DNA, thus discarding the need for extra fusogenic or endosomolytic agents. The positive charge on the vesicles at physiological pH drives the colloidal association with DNA. Small angle X-ray scattering measurements indicate that lamellar aggregates are formed, which have a d spacing of 48--54 A. Preliminary differential scanning calorimetric measurements suggest that reduction of pH causes a disordering of the hydrocarbon region of the DNA-surfactant complex.

Identification of some rabbit allergens as lipocalins

Rabbits are frequently used as laboratory animals or kept as domestic pets. Rabbit serum albumin and a 17-kDa protein referred to as Ory c 1 have previously been reported as allergens. Several other allergenic proteins have been recognized by crossed immuno-electrophoresis but have not been characterized. The aim of this study was to characterize the allergenic proteins present in rabbit saliva, urine and fur on the basis of molecular size and, where possible, to determine their amino acid sequences. Extracts from the male New Zealand white rabbit were used for developing specific direct RAST and RAST inhibition assays. Proteins in the extracts were separated by SDS-PAGE and the individual allergens identified by immunoblotting with serum from rabbit-allergic individuals. The N-termini of four allergens were sequenced. Saliva was the most potent extract. In total, 26 protein bands were recognized as allergens in the three extracts: 12 in saliva, seven in urine and seven in fur. Their molecular weights ranged from an 8-kDa species in saliva to an 80-kDa protein in urine. The N terminal sequences of an 18 kDa and a 21-kDa species in saliva, were identified as lipocalins with sequence similarity to a recently described odourant binding protein. This is the first evidence that allergens from the rabbit are members of the lipocalin superfamily of proteins, suggesting that similar mechanisms may be involved in eliciting the allergic response to rabbits. The 18 kDa allergen from saliva may be the previously named rabbit allergen, Ory c 1.

Electron microscopic investigation of the morphology and calcium-induced fusion of lipid vesicles with an oligomerised inner leaflet

The lipid head groups in the inner leaflet of unilamellar bilayer vesicles of the synthetic lipids DHPBNS and DDPBNS can be selectively oligomerised. Earlier studies have established that these vesicles fuse much slower and less extensively upon oligomerisation of the lipid head groups. The morphology and calcium-induced fusion of vesicles of DHPBNS and DDPBNS were investigated using cryo-electron microscopy. DHPBNS vesicles are not spherical but flattened, ellipsoidal structures. Upon addition of CaCl(2), DHPBNS vesicles with an oligomerised inner leaflet were occasionally observed in an arrested hemifused state. However, the evidence for hemifusion is not equivocal due to potential artefacts of sample preparation. DDPBNS vesicles show the expected spherical morphology. Upon addition of excess CaCl(2), DDPBNS vesicles fuse into dense aggregates that show a regular spacing corresponding to the bilayer width. Upon addition of EDTA, the aggregates readily disperse into large unilamellar vesicles. At low concentration of calcium ion, DDPBNS vesicles with an oligomerised inner leaflet form small multilamellar aggregates, in which a spacing corresponding to the bilayer width appears. Addition of excess EDTA results in slow dispersal of the Ca2+-lipid aggregates into a heterogeneous mixture of bilamellar, spherical vesicles and networks of thread-like vesicles. These lipid bilayer rearrangements are discussed within the context of shape transformations and fusion of lipid membranes.

Preparation and properties of arsonolipid containing liposomes

Arsonolipids are analogs of phosphonolipids which have a chemically versatile head group. In preliminary cell culture studies, liposomes composed solely of arsonolipids or of phosholipid-arsonolipid mixtures, demonstrate a specific toxicity against cancer cells (Gortzi et al., unpublished results). The possibility of using such formulations as an alternative of arsenic trioxide with or without combination of other cytostatic agents (encapsulated in their aqueous interior) prompted the investigation of their physicochemical characteristics. Herein we compared the characteristics of arsonolipid containing vesicles with different lipid compositions. Experimental results and morphological observations reveal that non-sonicated formulations have different structures and stability (when both membrane integrity and aggregation are taken into account) depending on the acyl chain length of the arsonolipid. When phospholipids and especially cholesterol are included in their membranes almost all arsonolipids studied produce more stable vesicles. An interesting aspect of these arsonolipid containing vesicles is also their negative surface charge, which may be modulated by mixing phospholipids with arsonolipids. Sonicated vesicles have smaller sizes and profoundly higher stability, especially when containing cholesterol and phosphatidylcholine mixed with arsonolipids. The only exception is that of the arsonolipid with the C(12) acyl chain which was observed to produce long tubes which break down to cubes by sonication. In conclusion, these initial studies demonstrate that sonicated vesicles composed of arsonolipid and phospholipid mixtures mixed with cholesterol posses the stability required to be used as an arsonolipid delivery system. In addition, although cryo-electron microscopy demonstrated that the sonicated vesicles are elliptical in shape, their encapsulation efficiency is not significantly lower than sonicated phospholipid liposomes. Thereby, these vesicles may be also used for the delivery of other drug molecules which can be sufficiently retained in their aqueous interior.

An indirect perfluorosulfonated ionomer-coated electrochemical immunosensor for the detection of the protein human chorionic gonadotrophin

The development of an amperometric immunosensor for the detection of human chorionic gonadotrophin (hCG) is described. In this immunosensor, Nafion was used to immobilize an anti-hCG monoclonal antibody onto a glassy carbon electrode. A systematic study on the effects of experimental parameters such as the quantity of ethanol present in the Nafion solution, the percentage composition of Nafion, the pH of the immobilization buffer, and the concentration of antibody used for entrapment experiments on the binding between the immobilized antibody and 125I-labeled hCG has been carried out. Two immobilization methods, coimmobilization and adsorption immobilization, have then been attempted. A binding of approximately 3% was obtained in the former method, while 5.5% binding was achieved in the latter. On the basis of these results, adsorption immobilization was employed to entrap antibody on the electrode surface. A sandwich assay was then developed for hCG in which the enzyme horseradish peroxidase was conjugated to a second anti-hCG monoclonal antibody. The activity of the enzyme was determined electrochemically by the reduction of benzoquinone to hydroquinone. Binding of hCG to immobilized antibody determines the quantity of enzyme-conjugated antibody at the electrode surface, permitting the quantification of hCG. By a standard additions calibration method of hCG performed in blank human serum samples, the immunosensor exhibits a limit of linearity at 200 mIU mL-1 and a detection limit of 11.2 mIU mL-1 (based on twice the standard deviation of the blank solution).

Binding of annexin V to bilayers with various phospholipid compositions using glass beads in a flow cytometer

Annexin V belongs to the family of calcium-dependent phospholipid binding proteins and binds almost solely to phosphatidylserine (PS). When annexin V is used to detect loss of membrane asymmetry in cellular systems, the binding properties under physiological conditions are of importance. Most biochemical studies use optimized binding conditions, conditions that are often far from physiological. For the interpretation of flow cytometric studies that use fluorescent annexin V to probe PS exposure, it is important to know what mixture of lipid species exposed in the outer leaflet of a membrane can evoke a positive annexin V signal. The lipid species is important in this respect as well as the concentration that just evokes a positive signal (detection level). Furthermore, the influence of the composition of the lipid matrix (cholesterol content, other phospholipid species) was investigated, as well as the influence of the calcium concentration on annexin V binding. In this study, we report on the binding of annexin V to phospholipid bilayers (adsorbed to glass beads) as measured by flow cytometry at physiological conditions. Annexin V binding was found to increase rapidly, with increasing PS concentrations up to a certain level (attained at 6 mol% PS). Further increase of the PS concentration resulted only in a slight increase of annexin V binding. Calcium concentrations below 3 mM were found to reduce the sensitivity of the binding assay. Phosphatidylethanolamine incorporated in the phospholipid bilayer resulted in a lower threshold for the binding assay, whereas sphingomyelin had no influence on the binding of annexin V and cholesterol reduces binding of annexin V to lipid bilayers. These data may help in the interpretation of results obtained from binding of annexin V to cell membranes (e.g., involved in apoptosis).

Surface exposure of phosphatidylserine during apoptosis of rat thymocytes precedes nuclear changes

Cell surface exposure of phosphatidylserine (PS) during apoptosis serves recognition and removal of the dying cell by phagocytes. Loss of phospholipid asymmetry and PS exposure is investigated by immunocytochemistry and related to morphological changes. Loss of membrane asymmetry was determined on dexamethasone-treated rat thymocytes using the PS specific probe annexin V. Thymocytes incubated in the presence of dexamethasone were studied in time series during the execution of the apoptotic program. Thymocytes first start to expose PS at their cell surface. At this initial stage the barrier function of the plasma membrane remains intact. At a later stage the plasma membrane becomes leaky for compounds like propidium iodide and subsequently the cell disintegrates into apoptotic bodies. Microscopical evaluation of dexamethasone-treated thymocytes showed that the cells with an apoptotic morphology all bound annexin V. The cells with a normal viable morphology lacked annexin V binding except for those cells that started to shed small vesicles. These vesicles were positive for annexin V, indicating a local disturbance of the phospholipid asymmetry. The local exposure of PS is considered to be a very early event of apoptosis, preceding the full sequence of morphological changes at the ultrastructural level.

Reevaluation of the effect of lysoyzme on Escherichia coli employing ultrarapid freezing followed by cryoelectronmicroscopy or freeze substitution

Lysozyme is able to lyse Gram-positive bacteria acting as muramidase on the peptidoglycan polymer. Gram-negative bacteria in vitro are not lysed by lysozyme. It was assumed that the peptido-glycan is protected by the outer membrane and thus that Gram-negative bacteria are not affected by lysozyme without the aid of other factors such as EDTA or complement which enable lysozyme to penetrate the outer membrane. Accidentally, Pellegrini et al. [(1992) J. Appl. Bacteriol., 72:180-187] found that lysozyme per se is able to kill some Gram-negative bacteria. On the basis of morphological and immunocytochemical findings obtained from chemically fixed bacteria, it was concluded that lysozyme does not lyse Gram-negative bacteria but affects the cytoplasm of for example, Escherichia coli, leading to its disintegration, whilst the membranes do not break down. In an attempt to clarify the action of lysozyme on E. coli, we employed cryotechniques including ultrarapid freezing, cryomicroscopy and freeze substitution, and immunolabeling. Bacteria that were immediately frozen after exposure to lysozyme remained morphologically intact. Individual bacteria plated on agar after exposure to lysozyme were mostly intact when frozen within a few seconds. However, inner and outer membranes of 80% of the bacteria were disrupted, whereas the cytoplasm of only a few bacteria showed signs of disintegration when bacteria were frozen with a delay of only 5 min of plating onto pure agar or agar containing growth medium. After a period of time of 15 min between plating onto agar and freezing, about 97% of the bacteria showed changes of disintegration of various extent. Immunolabeling showed that lysozyme binds to the outer cell membrane and may penetrate the membrane, reaching the periplasmic space and possibly the inner cell membrane. The ultrastructural findings and the results of antibacterial assays suggest that lysozyme is bactericidal for E. coli but is not able to induce disintegration. Disintegration is accomplished by changes of the environment starting at the cell membranes. The mechanism by which lysozyme penetrates the membrane, the way it acts to be bactericidal, and the way disintegration is initiated remain to be clarified.

Distribution of Heterodera glycines in Ohio

A 4-year systematic survey for the presence of soybean cyst nematode Heterodera glycines in Ohio soybean fields was initiated in 1992. A total of 667 soybean fields in 63 counties was sampled. Heterodera glycines was present in 91 fields in 40 counties based on soil samples collected, and in one field in each of three additional counties based on soil samples submitted to the Plant and Pest Diagnostic Clinic or through a preliminary survey conducted in 1991. Soybean hectarage in the 43 counties with at least one field known to be infested with H. glycines accounts for 79% of the total Ohio soybean production area. Eight races of H. glycines were identified in 33 samples from 18 counties. The most common was race 3, identified in 15 samples; others were races 1, 2, 4, 5, 6, 10, and 14.

Transmembrane gradient driven phase transitions within vesicles: lessons for drug delivery

Phase transitions in closed vesicles, i.e., microenvironments defined by the size of the vesicle, its contents, and permeability of its membrane are becoming increasingly important in several scientific disciplines including catalysis, growth of small crystals, cell function studies, and drug delivery. The membrane composed from lipid bilayer is in general impermeable to ions and larger hydrophilic ions. Ion transport can be regulated by ionophores while permeation of neutral and weakly hydrophobic molecules can be controlled by concentration gradients. Some weak acids or bases, however, can be transported through the membrane due to various gradients, such as electrical, ionic (pH) or specific salt (chemical potential) gradients. Upon permeation of appropriate species and reaction with the encapsulated species precipitation may occur in the vesicle interior. Alternatively, these molecules can also associate with the leaflets of the bilayer according to the transmembrane potential. Efficient liposomal therapeutics require high drug to lipid ratios and drug molecules should have, especially when associated with long circulating liposomes, low leakage rates. In this article we present very efficient encapsulation of two drugs via their intraliposomal precipitation, characterize the state of encapsulated drug within the liposome and try to fit the experimental data with a recently developed theoretical model. Nice agreement between a model which is based on chemical potential equilibration of membrane permeable species with experimental data was observed. The high loading efficiencies, however are only necessary but not sufficient condition for effective therapies. If adequate drug retention within liposomes, especially in the case of long-circulating ones, is not achieved, the therapeutic index decreases substantially. Anticancer drug doxorubicin precipitates in the liposome interior in a form of gel with low solubility product and practically does not leak out in blood circulation in the scale of days. With an antibiotic, ciprofloxacin, the high loading efficacy and test tube stability is not reproduced in in vitro plasma leakage assays and in vivo. We believe that the reasons are higher solubility product of precipitated drug in the liposome, larger fraction of neutral molecules due closer pK values of the drug with the pH conditions in the solutions and high membrane permeability of this molecule. High resolution cryoEM shows that encapsulated anticancer agent doxorubicin is precipitated in the form of bundles of parallel fibers while antibiotic ciprofloxacin shows globular precipitate. Doxorubicin gelatin also causes the change of vesicle shape.

Allergy to laboratory animals among animal handlers

OBJECTIVE

To determine the prevalence among laboratory animal handlers of allergy to laboratory animals and of asthma and the factors associated with their development.

DESIGN

A cross-sectional survey.

SETTING

Teaching and research institutions in Sydney, between January 1989 and December 1992.

PARTICIPANTS

Laboratory animal handlers (teaching and research staff, animal house workers and animal husbandry students and teachers).

MAIN OUTCOME MEASURES

Duration of exposure to laboratory animals, allergic symptoms on contact, skin reactivity to laboratory and domestic animal allergens and evidence of current asthma.

RESULTS

228 subjects were surveyed. Allergy symptoms occurred in 73 (56%) of the subjects exposed to laboratory animals for three months or more. This group also had significantly higher prevalences of skin reactivity to laboratory animal allergens (62%) and bronchial hyperresponsiveness (21%) than those with shorter exposure (14% and 8%, respectively). Atopic subjects exposed to laboratory animals (particularly those sensitised to domestic animals) and animal attendants (with a high intensity of exposure to laboratory animals) had significantly higher frequencies of skin reactivity to laboratory animals and asthma than other subjects (77% and 30%, respectively, among exposed atopic subjects and 84% and 33%, respectively, among animal attendants).

CONCLUSIONS

Allergy to laboratory animals is an occupational hazard among laboratory animal handlers, especially for those who are atopic and sensitised to domestic animals, and may lead to the development of asthma. Screening for atopy and skin reactivity to laboratory animals before and during employment would enable those at risk to take precautions.

Ultrastructural detection of surface exposed phosphatidylserine on activated blood platelets

Phosphatidylserine (PS) is normally restricted to the inner leaflet of the plasma membrane of cells (including blood platelets). Upon cell activation PS may become exposed to the outer surface of the cell. Cell membranes with surface exposed PS at the outside form a catalytic surface for coagulation reactions. When platelets are activated with ionophore or with thrombin in combination with thapsigargin, calcium induced scrambling of phospholipids takes place, resulting in PS exposure. Concomitant with PS exposition structural changes take place. On resting and activated platelets we combined the immunocytochemical detection of surface exposed PS with (ultra)structural information. Blood platelets were activated in the presence of annexin V, a protein which binds to PS in the presence of Ca2+. Annexin V was found to bind to lipid bilayers containing more than 5 mole % PS as estimated by binding of fluorescent-labelled annexin V to liposomes with varying PS concentrations. After vitrification, freeze-substitution and embedding of the platelets, annexin V was located on ultra thin sections, as detected by an anti-annexin V antibody and gold labelled protein A. Upon activation, the platelets show two different forms; irregular platelets with unchanged cytoplasm and round cells with apparently diluted cytoplasm. Activation with ionophore initially resulted in both forms, but after ten minutes only round platelets with diluted cytoplasm were observed. Both forms of these platelets as well as the microvesicles were found to be annexin V positive. However upon activation with thrombin in combination with thapsigargin, only the round cells with diluted cytoplasm and microvesicles were annexin V positive, whereas platelets with unchanged cytoplasm, even when microvesicles are present, are negative for annexin V.

Aggregation of phospholipid vesicles by a chimeric protein with the N-terminus of annexin I and the core of annexin V

A chimeric protein was produced with the N-terminal domain (amino acids 1-45) of annexin I and the core of annexin V (amino acids 19-320). This protein, annexin IN-VC, has a similar Ca2+ requirement for binding to phospholipid bilayers of 20% phosphatidylserine (PS)/80% phosphatidylcholine (PC) as annexin V. In contrast to annexin V, this protein has a strong potency to aggregate phospholipid vesicles as is shown by turbidimetric measurements and cryo-electron microscopy. Ellipsometry was employed to study quantitatively the phenomenon of phospholipid vesicle adhesion to annexin IN-VC bound to a planar phospholipid bilayer. The amount of phospholipid vesicles bound by annexin IN-VC on the planar bilayer is proportional to its surface coverage and can be inhibited by coadsorption of annexin V on the planar bilayer or by shielding the phospholipid surface of the vesicles with blood coagulation factor Va. Annexin IN-VC, like annexin V, does not bind to pure PC bilayers, but its adsorption on anionic phospholipid bilayers brings about the capacity to bind pure PC vesicles. This suggests that annexin IN-VC generates or exposes after binding to anionic phospholipids another phospholipid binding site, that differs from the annexin V phospholipid binding site. Collectively, the data suggest that two-dimensional cluster formation of annexin IN-VC on a bilayer with anionic phospholipids is involved in vesicle adherence.

Monitoring of unbound protein in vesicle suspensions with off-null ellipsometry

In studies on the binding of proteins to small unilamellar phospholipid vesicles (SUV), the concentration of unbound protein usually remains unknown, because the vesicles cannot be separated from the bulk solution. In the present study, this limitation was overcome by addition of a supported planar phospholipid bilayer to the cuvette containing a vesicle suspension. Ellipsometric measurement of the protein adsorption velocities on this bilayer allowed determination of the concentrations of unbound protein. At high protein concentrations the adsorption is rapidly completed and the usual null-ellipsometry is too slow to obtain well-defined initial adsorption rates. Therefore, an off-null technique was developed, allowing measurement of the adsorbed protein mass at time intervals of 20 ms. Binding of prothrombin and coagulation factor Xa was measured in SUV suspensions prepared from a 20% dioleoylphosphatidylserine (DOPS) and 80% dioleoylphosphatidylcholine (DOPC) phospholipid mixture. For prothrombin, a dissociation constant Kd = 140 +/- 27 nM (mean +/- S.E.) and maximal surface concentration gamma max = (8.9 +/- 0.8) x 10(-3) mole of protein per mole of lipid, were obtained. For factor Xa, these values were Kd = 49.6 +/- 6.3 nM and gamma max = (23.0 +/- 1.4) x 10(-3) mole of protein per mole of lipid. These binding parameters are similar to those obtained earlier for planar bilayers. Apparently, the binding of factor Xa and prothrombin is not dependent on surface curvature.

Isoelectric charge of recombinant human follicle-stimulating hormone isoforms determines receptor affinity and in vitro bioactivity

Recombinant human FSH (rhFSH) was obtained by expressing the human FSH alpha- and beta-subunit complementary DNAs in the chinese hamster ovary cell line. Isoforms of rhFSH were resolved into specific isoelectric (pI) fractions by chromatofocusing. rhFSH isoforms ranged from pI 3.0-5.5 with a modal value of pI 4.2. Analysis of the biological activity of specific pI isoforms of rhFSH was undertaken using both the rat granulosa cell aromatase (in vitro) bioassay and a RRA. More acidic isoforms (e.g. pI 3.5) showed significantly lower affinity (P < 0.05) for rat testicular FSH receptors than did the less acidic isoforms (e.g. pI 4.8). Consistent with the receptor binding affinity data, the more acidic fractions resulted in significantly less activation (P < 0.05) of rat granulosa cell aromatase activity, as measured by estrogen production, than did the less acidic isoforms. The observed bioactivities and their correlation with the pI values of the rhFSH isoforms are consistent with observations of differing bioactivities seen in both pituitary and urinary FSH isoforms. These results demonstrate that rhFSH, made in the chinese hamster ovary cell line, is both biologically active and has isoform profiles, and presumably carbohydrate structures, that closely resemble those seen in natural hFSH.

Gelation of liposome interior. A novel method for drug encapsulation

Liposomes can be loaded with weak acids and bases, which exist in solutions in equilibrium with membrane permeable uncharged form, using various gradients across their membranes. Because in some cases the estimated drug concentration in the loaded liposomes exceeds their aqueous solubility we investigated the physical state of the liposome encapsulated anticancer drug Doxorubicin. X-Ray diffraction, electron microscopy, and test tube solubility experiments have shown that upon encapsulation the drug molecules form a gel-like phase.

Clustering of lipid-bound annexin V may explain its anticoagulant effect

In 1985 we isolated a new vascular anticoagulant protein VAC alpha, now called annexin V, with a high binding affinity (Kd less than 10(-10) M) for phospholipids. Its anticoagulant effect was attributed to displacement of coagulation factors from the phospholipid membrane. The present study demonstrates that the inhibition of prothrombinase activity by annexin V strongly depends on the curvature of the membrane surface and on the calcium concentration. Half-maximal inhibition of prothrombinase on and binding of annexin V to small vesicles, composed of 20% phosphatidylserine and 80% phosphatidylcholine, requires 2-3 mM calcium. With large vesicles and planar bilayers considerably less calcium is required for inhibition of prothrombinase and for lipid binding. Half-maximal binding of annexin V to large vesicles and to planar bilayers occurs at 0.7 and 0.2 mM calcium, respectively. This seemingly confirms the displacement model. The displacement of coagulation factors, however, proved to be incomplete, with residual surface concentrations of factors Xa, Va, and prothrombin sufficient for effective production of thrombin. Cryoelectron microscopy revealed that annexin V binding to large vesicles caused planar facets, indicating the formation of large sheets of clustered annexin V. Apparently, the formation of these two-dimensional arrays is promoted by calcium and hampered by high surface curvature. It is speculated that the complete inhibition (greater than 99%) of prothrombinase activity by annexin V is caused by the reduced lateral mobility of prothrombin and factor Xa in rigid sheets of annexin V covering the membrane.

Influence of nutritional status on growth hormone-dependent circulating somatomedin-C activity in mature sheep

The effect of daily administration of ovine GH for a period of 4 weeks on somatomedin-C biological activity in plasma was investigated in mature Merino sheep fed a maintenance energy intake (low plane; LP) or 1.6 times this amount (high plane; HP). The GH treatment resulted in a significant (P less than 0.05) increase in plasma GH levels in blood samples collected 23.5 h after each daily injection in both LP and HP groups. Plasma concentrations of somatomedin-C activity and insulin were significantly stimulated to a maximum level by the third GH injection and remained at this level for 7 days. Subsequently, circulating levels of both hormones fell to 40-50% of the peak response to GH and returned to basal levels within 48 h of the cessation of GH injections. In the HP group the response of plasma insulin and somatomedin-C activity to GH injection was greater than in the LP group.

Lipid polymorphism as observed by cryo-electron microscopy

Lipid polymorphism was studied with the aim to gain more insight in bilayer to non-bilayer phase transitions, with particular emphasis on the development of cubic structures on one hand and inverted hexagonal structures on the other hand. Thin vitrified films prepared from aqueous lipid suspensions were used in this study. The entire hydrated contents of these films can be visualized in their two-dimensional projection by cryo-electron microscopy. As the starting material, unilamellar vesicles were prepared from mixtures of dioleoylphosphatidylethanolamine, dioleoylphosphatidylcholine and cholesterol. By heating of the suspension, vesicle fusion (Frederik et al. (1989) Biochim. Biophys. Acta 979, 275-278) and lipid polymorphism was induced. From these suspensions thin films were prepared at various temperatures, and vitrified for low temperature observation. In a parallel series of experiments samples were fast-frozen for freeze-fracture analysis. In vitrified thin films bilayer structures were often observed in coexistence with an inverted hexagonal structure. The bilayer areas were frequently of a complex structure because multiple contacts between stacked membranes were found. These contact points were variable in size and shape and usually had the form of a diabolo (when viewed side-on) giving the impression of a bilayer contact with an aqueous channel. This structure is compatible with the interlamellar attachment site (ILA) proposed by Siegel ((1986) Biophys. J. 49, 1155-1170). In some specimens ILA's seemed to merge into arrays. After thermal cycling of the suspension, arrays of packed globules were observed, which are likely the result of close packing of ILA's. The arrays probably represent a cubic structure. A comparison of freeze-fracture replicas and vitrified thin films indicated that both techniques may provide valuable structural information on lipid polymorphism. Most of the lipidic particles observed by freeze-fracturing probably correspond to the ILA's (fractured around their waist region) as observed in vitrified thin films. The results obtained with vitrified thin films were interpreted in relation to the principles of thin-film formation. Finally, we speculate that lipid structures occurring close to each other in space may represent a developmental series of structures occurring successively in time.

Perspective and limitations of cryo-electron microscopy. From model systems to biological specimens

We investigated the possibility of vitrifying temperature-sensitive lipid phases as well as (small) biological specimens. From a suspension of unilamellar vesicles, prepared from dipalmitoyl-phosphatidylcholine (DPPC), thin aqueous films were formed at various temperatures. With cryo-electron microscopy vesicles were found to be smooth, rippled and faceted or faceted only, depending on the temperature of thin-film formation (318, 312 and 296 K respectively). The morphology and the electron diffraction patterns indicate that membranes can by physically fixed by vitrification in their high-temperature configuration and studied at low temperature by cryo-electron microscopy. This finding suggests that it may also be possible to preserve, in their original state, the more complex membrane systems found in living organisms by initiating rapid-cooling at a physiological temperature. This was explored by vitrification of thin films formed on specimen grids with (human) blood platelets adhering to collagen fibres. Low-temperature observation with an acceleration voltage of 120 kV revealed subcellular details, More details were observed when using higher accelerating voltages (200 and 300 kV) of the electron beam. The results presented in this paper illustrate the great potential of cryo-electron microscopy in the study of membrane dynamics, both in relatively simple model membrane systems and in more complex biological membrane systems.

Somatomedin-C, physical fitness, and bone density

Somatomedin-C (Sm-C) or insulin-like growth factor-I, GH and physical fitness decline with age. Physical fitness and muscle strength are important determinants of bone density, and the age-related decline in bone density may be related in part to a decline in fitness and muscle strength. Also, Sm-C has been shown to stimulate osteoblasts in vitro and may effect skeletal muscle mass. We postulated that the age-related decline in GH and Sm-C levels may be related to an age-related decline in physical fitness and/or muscle strength, and the effect of physical fitness and muscle strength on bone may be mediated by Sm-C. We, therefore, examined the relationship between circulating GH and Sm-C levels and physical fitness, as determined by predicted maximal oxygen uptake (VO2max) in 134 normal women, 34 of whom were postmenopausal. In a subgroup of 62 women overall muscle strength was estimated as the sum of the Z-sores for biceps, quadriceps, and grip strength. Overall muscle strength correlated with GH levels (r = 0.28; P less than 0.02), but not with Sm-C levels. There was a significant positive relationship between plasma Sm-C levels and VO2max in all women (r = 0.47; P less than 0.001) and in the postmenopausal group alone (r = 0.05; P less than 0.01). Although there was a significant negative relationship between Sm-C and age (r = -0.36; P = 0.001), VO2max was a better independent predictor than age (r = 0.47; P = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of biosynthetic human growth hormone on insulin action in individual tissues of the rat in vivo

Excessive endogenous production or exogenous administration of human growth hormone (hGH) causes insulin resistance at both the hepatic and extrahepatic levels. However, which extrahepatic tissues are involved have not been defined. We have examined the diabetogenic action of authentic biosynthetic hGH on whole body glucose disposal, hepatic glucose output, and glucose metabolism in individual peripheral tissues. The use of a highly purified preparation of the hormone allowed us to examine the isolated effects of 22K hGH. The euglycemic hyperinsulinemic (approximately 100 mU/L) clamp plus 3H-2-deoxyglucose technique was used to quantitate the effects of hGH on insulin action in vivo. Administration of biosynthetic hGH at a dose of 10 IU/kg/24 h for 48 hours in male Wistar rats (approximately 340 g) produced a highly significant decrease in the steady state clamp glucose infusion rate (GIR) when compared with controls (8.1 +/- 0.6 v 18.7 +/- 0.7 mg/kg/min, P less than .001), reduced insulin-mediated suppression of hepatic glucose output (Ra) (3.9 +/- 0.6 v 0.7 +/- 0.3 mg/kg/min, P less than .05) and a decreased clamp glucose disposal rate (Rd) (12.0 +/- 0.4 v 18.10 +/- 1.1 mg/kg/min, P less than .001). There was a significant decrease in insulin-mediated glucose uptake as indicated by tissue accumulation of [3H]-2-deoxyglucose phosphorylation in diaphragm and hindlimb muscles. Insulin action was more substantially reduced in muscles (approximately 50%) than in adipose tissues (approximately 20%). These studies confirm that the diabetogenic action of hGH in the rat is due to a combination of inhibition of insulin suppression of hepatic glucose output and inhibition of the uptake and subsequent utilization of glucose in skeletal muscles.

Formation of multilamellar vesicles by addition of tannic acid to phosphatidylcholine-containing small unilamellar vesicles

Tannic acid induces aggregation and formation of multilamellar vesicles when added to preparations of small unilamellar vesicles, specifically those containing phosphatidylcholine. Aggregation and clustering of vesicles was demonstrated by cryo-electron microscopy of thin films and by freeze-fracture technique. Turbidity measurements revealed an approximately one-to-one molar ratio between tannic acid and phosphatidylcholine necessary for a fast and massive aggregation of the small unilamellar vesicles. When tannic acid-induced aggregates were dehydrated and embedded for conventional thin-section electron microscopy, multilamellar vesicles were retrieved in thin sections. It is concluded from morphological studies, as well as previous tracer studies, that tannic acid, at least to a great extent, prevents the extraction of phosphatidylcholine. Multilamellar vesicles were also observed in tannic acid-treated vesicles prepared from total lipid extracts from either rabbit or rat hearts. Substantially more multilamellar vesicles were retrieved in the rabbit vesicle preparation. This difference can probably be explained by the difference in the proportion of the plasmalogen phosphatidylcholine, and possibly the content of sphingomyelin, in lipid extracts of rabbit and rat hearts. It is concluded that the dual effect (reduced extraction and aggregation) of tannic acid on phosphatidylcholines should be taken into consideration when tannic acid is used in tissue preparation.

Dual effect of tannic acid on the preservation and ultrastructure of phosphatidyl choline vesicles

The use of tannic acid has been proposed to improve the preservation of phospholipids in tissues. We investigated the effects of tannic acid on the preservation of small unilamellar vesicles, prepared from sonicated aqueous suspensions of phospholipids. With cryo-electron microscopy it is demonstrated that small unilamellar vesicles are formed after sonication of the phospholipid suspensions. Fixation of vesicles without tannic acid results in extraction of the phospholipids during dehydration and embedding. Fixation of vesicles containing phosphatidyl choline with tannic acid, with or without glutaraldehyde, results in a fast (within a second) aggregation of the vesicles and the resulting sediment can be dehydrated and embedded when a postfixation in osmium tetroxide is carried out. Small unilamellar vesicles fixed in this way are retrieved in thin sections as multilamellar vesicles with a periodicity of about 5 nm for dimyristoylphosphatidyl choline and about 6 nm for dioleoylphosphatidyl choline. By using 14C-phosphatidyl choline it was also demonstrated that tannic acid prevents to a large extent the extraction of phosphatidyl choline during fixation, dehydration and embedding. This dual effect of tannic acid on phosphatidyl choline, aggregation and fixation, should be considered when using tannic acid in tissue preparation.

Quantification of urinary growth hormone (GH) excretion by centrifugal ultrafiltration and radioimmunoassay: appraisal of the relationship between 24 h urinary GH and mean 24 h serum GH levels in normal and abnormal states of GH secretion

We have applied a simple method for the quantification of 24 h urinary GH excretion (24 h UGH), combining centrifugal ultrafiltration and radio-immunoassay (RIA), to an appraisal of the relationship between 24 h UGH and mean 24 h serum GH levels in normal and abnormal states of GH secretion. Forty-four subjects, comprising 13 normal adults, 12 short-statured subjects and 19 subjects with active acromegaly, underwent blood sampling at 20-min intervals and concurrent urine collection for 24 h. Mean 24 h serum GH and 24 h UGH were also determined in four post-menopausal women before and during cyclical oestrogen replacement therapy, and 24 h UGH was measured in six normal men prior to and following the subcutaneous administration of biosynthetic GH (0.2 IU/kg). Each subject's mean 24 h serum GH level was determined by assaying a 'pooled' sample, derived from equal aliquots of the 73 serum samples obtained during the 24 h study. The method for quantification of 24 h UGH employs centrifugal microconcentrators, and involves a 50-fold concentration of urine, followed by dialysis and RIA. Surface adsorptive hormone loss during sample collection and ultrafiltration is minimized by the prior addition of bovine serum albumin to the urine collection container. Immunoreactive GH in ultrafiltered urine dilutes in parallel with the RIA standard curve. GH is stable in urine stored at - 20 degrees C for at least 12 months. There was a highly significant correlation between 24 h UGH and mean 24 h serum GH values obtained from the combined population of normal adults (including the post-menopausal women during oestrogen therapy) and short-statured subjects (r = 0.69, P less than 0.0001). A significant correlation was also found in short-statured subjects alone (r = 0.63, P less than 0.05). In contrast, there was no significant correlation between 24 h UGH and mean 24 h serum GH in subjects with active acromegaly, and their 24 h UGH values were not distinguishable from those of the 'non-acromegalic' subjects. A significant increase in 24 h UGH occurred in the post-menopausal women given cyclical oestrogen replacement therapy (9.7 +/- 2.6 (mean +/- SE) to 24.6 +/- 1.0 muIU/mmol creatinine, P less than 0.02), reflecting the increase in their mean 24 h serum GH levels (0.8 +/- 0.3 to 5.3 +/- 0.7 mIU/l, P less than 0.01). Twenty-four hour UGH increased from 4.6 +/- 0.6 to 17.1 +/- 2.1 muIU/mmol creatinine (P less than 0.002) in the men given biosynthetic GH. Twenty-four hour UGH measurements reflect mean 24 h serum GH levels in normal adults and short-statured subjects. While the measurement of 24 h UGH shows promise as an investigative tool, our results cast doubt on its use in the diagnosis of acromegaly.

The pharmacokinetics, safety and endocrine effects of authentic biosynthetic human growth hormone in normal subjects

The pharmacokinetics, safety and endocrine effects of an authentic human growth hormone (bio-hGH), produced by the expression of genomic hGH in a mammalian cell line, were studied in six healthy young men who were administered 0.2 U/kg/day subcutaneously for five consecutive days. Changes in sodium balance and in thyroid function were studied during the week of bio-hGH administration and safety parameters were monitored over a 3-week period. Growth hormone levels reached a mean (+/- SD) peak of 106 +/- 10 mIU/l at 3.3 +/- 0.5 h following the first dose and resulted in a significant rise of somatomedin C. free fatty acids, fasting blood glucose and insulin concentrations. Bio-hGH administration resulted in a significant increase in body weight (80.0 +/- 4.5 to 81.1 +/- 4.3 kg; P less than 0.01) which was associated with a marked reduction in urinary sodium excretion (196 +/- 38 to 45 +/- 20 mmol/day; P less than 0.025). Serum T3 increased during bio-hGH administration and was associated with reciprocal changes in free thyroxine and TSH concentrations. Cardiac, hepatic, renal, biochemical, haematological, endocrinological and immunological functions remained normal throughout the study. No antibodies to hGH or to host cell protein developed during the study. The results show that bio-hGH is safe in the short term, well tolerated, possesses pharmacokinetic and biological properties similar to pituitary hGH, and has distinct effects on sodium balance and on thyroid function. This study stresses the need to monitor patients for effects on sodium retention, carbohydrate metabolism and thyroid function when using hGH doses of 1.0 U/kg/week (40 U/m2/week) or more in patients with GH responsive short stature.

Intermediary structures during membrane fusion as observed by cryo-electron microscopy

Lipidic phases, containing 'lipidic particles' (dioleoylphosphatidylethanolamine/cholesterol/dioleoylphosphatidylcho lin e and cardiolipin/dimyristoylphosphatidylcholine in the presence of Ca2+) have been investigated by preparing thin films from a suspension of sonicated vesicles. These thin films were vitrified and observed 'directly' by cryo-electron microscopy in their hydrated form. The thin films show various fusion products and fusion intermediates such as lipidic particles.

Specificity of two-site immunoassays

When cross-reaction in two-site immunoassays was investigated both theoretically and experimentally it was found that such systems do not always result in enhanced specificity. Computer simulation studies indicated that substances which display negligible cross-reaction in a radioimmunoassay could produce an assay response identical to that of the analyte in a two-site immunoassay using excess antibody. Cross-reactivity in two differing two-site immunoassays was compared to that obtained in radioimmunoassays using the same monoclonal antibodies for human chorionic gonadotrophin. In addition to the effects of excess antibody, cross-reactivity was observed in one of the two-site immunoassays which could not have been predicted from the specificity of the antibodies or cross-reactivity in the radioimmunoassays. The unexpected cross-reaction of the beta subunit of human chorionic gonadotrophin in the assay resulted from an apparent alteration in the specificity of one of the antibodies following binding of the beta subunit to the second antibody. These studies emphasise the complexity of binding reactions in two-site immunoassays.

Phospholipid, nature's own slide and cover slip for cryo-electron microscopy

Thin films of surface-active compounds, with or without particulate material, can be obtained by immersing and withdrawing a bare specimen grid from a solution/suspension of the compound. Immediately after withdrawing the grid, thinning of the film starts. Thinning is initially powered by gravity and capillary forces and will proceed in thin films (less than 100 nm) driven by intermolecular forces until the London-van der Waals attractive forces come to an equilibrium with electrostatic repulsion of similarly charged surfaces of the film. With small unilamellar vesicles prepared from the phospholipid dimyristoyl phosphatidyl choline (DMPC) the draining behaviour of these films was studied by cryo-electron microscopy. Small unilamellar vesicles were observed within the film as well as the coalescence of these vesicles into sheets ('leaky' membrane fusion). Sheets dominate the images when films are allowed to drain for longer periods (greater than 3 min). Thin films were formed on grids from catalase crystals suspended in a DMPC suspension and vitrified by cooling. High-resolution information was obtained by electron diffraction at low temperature and under low-dose conditions from catalase crystals surrounded by small vesicles as well as from catalase crystals surrounded by sheets of DMPC. In the latter case the water content drops from 99% (DMPC in small vesicles) to less than 30% (DMPC in sheets) during draining. Ferritin was added to a DMPC suspension and thin films were prepared and vitrified. After prolonged draining ferritin molecules were deposited in layers with a stepwise increase in thickness. Draining of thin films has thus a dehydrating effect as well as a sorting and ordering effect. These effects must be considered when using surface-active compounds at air-water interfaces as a slide and cover slip for electron microscopy.

Heterophilic antibodies: a problem for all immunoassays

We verified that antibody-binding substances in serum that interfere in two-site immunoassays involving murine antibodies are heterophilic antibodies. Incubation of serum containing heterophilic antibodies and a murine monoclonal antibody to human choriogonadotropin (hCG) leads to formation of a series of soluble immune complexes. We investigated the recognition of hCG by reagent antibody in the presence of heterophilic antibodies and found this recognition to be diminished. Consequently, about 30% of serum samples containing heterophilic antibodies falsely appear to contain increased concentrations of hCG. The effect on analyte recognition probably results from steric inhibition of hCG binding to complexed antibody. Heterophilic antibodies detected with a murine antibody also bound immunoglobulin from several other species but did not bind all of those tested.

Heterophilic antibodies: a problem for all immunoassays

We verified that antibody-binding substances in serum that interfere in two-site immunoassays involving murine antibodies are heterophilic antibodies. Incubation of serum containing heterophilic antibodies and a murine monoclonal antibody to human choriogonadotropin (hCG) leads to formation of a series of soluble immune complexes. We investigated the recognition of hCG by reagent antibody in the presence of heterophilic antibodies and found this recognition to be diminished. Consequently, about 30% of serum samples containing heterophilic antibodies falsely appear to contain increased concentrations of hCG. The effect on analyte recognition probably results from steric inhibition of hCG binding to complexed antibody. Heterophilic antibodies detected with a murine antibody also bound immunoglobulin from several other species but did not bind all of those tested.

Incidence and specificity of interference in two-site immunoassays

Using a modified "two-site" immunoradiometric assay, termed an "interference assay," we have demonstrated the occurrence of non-analyte antibody-binding substances in approximately 40% of serum samples. These substances multivalently bind antibodies from any of several species at a site other than the antigen-binding site. Using a two-site immunoradiometric assay for human choriogonadotropin, we have investigated their effect on analyte quantification. In this system these antibody-binding substances mimic the presence of analyte; when analyte is actually present, they can also cause over- or underestimates. Addition of excess nonspecific immunoglobulin from an appropriate species eliminates this interference. However, the amount of nonspecific immunoglobulin added to an assay system may not always be enough to block interference in all samples.

Incidence and specificity of interference in two-site immunoassays

Using a modified "two-site" immunoradiometric assay, termed an "interference assay," we have demonstrated the occurrence of non-analyte antibody-binding substances in approximately 40% of serum samples. These substances multivalently bind antibodies from any of several species at a site other than the antigen-binding site. Using a two-site immunoradiometric assay for human choriogonadotropin, we have investigated their effect on analyte quantification. In this system these antibody-binding substances mimic the presence of analyte; when analyte is actually present, they can also cause over- or underestimates. Addition of excess nonspecific immunoglobulin from an appropriate species eliminates this interference. However, the amount of nonspecific immunoglobulin added to an assay system may not always be enough to block interference in all samples.

Error in laboratory reference limits as shown in a collaborative quality-assurance program

Laboratories participate in collaborative quality-assurance programs to maintain and improve the quality of their diagnostic assays, but little attention has been paid to diagnostic quality in these programs. We used a national quality-assurance program to assess the quality of laboratory reference intervals as exemplified by triiodothyronine, thyroxin, and thyrotropin immunoassays. The limits of the reference intervals used by laboratories bear virtually no relationship to laboratory bias, i.e., whether assays read "high" or "low." Further, correcting assay results from different laboratories for the reference limits used increases rather than decreases interlaboratory scatter. We conclude that the analytical quality of immunoassays now exceeds the quality of the reference limits supplied to clinicians to assist diagnosis, and that nationally or internationally defined reference limits would therefore provide more information at less cost than do individual laboratory reference limits.

Error in laboratory reference limits as shown in a collaborative quality-assurance program

Laboratories participate in collaborative quality-assurance programs to maintain and improve the quality of their diagnostic assays, but little attention has been paid to diagnostic quality in these programs. We used a national quality-assurance program to assess the quality of laboratory reference intervals as exemplified by triiodothyronine, thyroxin, and thyrotropin immunoassays. The limits of the reference intervals used by laboratories bear virtually no relationship to laboratory bias, i.e., whether assays read "high" or "low." Further, correcting assay results from different laboratories for the reference limits used increases rather than decreases interlaboratory scatter. We conclude that the analytical quality of immunoassays now exceeds the quality of the reference limits supplied to clinicians to assist diagnosis, and that nationally or internationally defined reference limits would therefore provide more information at less cost than do individual laboratory reference limits.

Localization of human pituitary hormones by multiple immunoenzyme staining procedures using monoclonal and polyclonal antibodies

Mouse monoclonal and rabbit polyclonal antibodies to human pituitary hormones were applied together to sections of normal and neoplastic human pituitary tissue. Binding sites were revealed with species-specific immune reagents combined with various enzymes (peroxidase, alkaline phosphatase, and beta-D-galactosidase). The enzymes were developed separately to give differently colored end-products. Where two hormones were present in the same cell, a mixed color was produced. Up to four hormones could be immunostained in a single section. Multiple immunoenzymatic staining has great potential for the analysis of plural antigen production by single cells and relationships between cells producing different antigens.

Circulating insulin-like growth factor I levels in newborn premature and full-term infants followed longitudinally

Longitudinal circulating levels of insulin-like growth factor I (IGF-I) were measured by radioimmunoassay after acid/ethanol extraction of serum or plasma in 44 appropriate-for-gestational age (AGA) premature infants, 7 small-for-gestational age (SGA) premature infants and 9 AGA full-term infants. The subjects were divided into cohorts with gestational age at birth 26-29 weeks, 30-33 weeks, 34-37 weeks and 38-42 weeks (full-term). The premature infants in this study exhibited diminished growth as compared with normal intrauterine growth. In all but the earliest premature infant cohort there was an immediate fall from the mean fetal IGF-I level, as reflected by the cord value, to a basal postnatal circulating level of IGF-I. The basal level of circulating IGF-I in premature infants was related only to gestational age. It increased slowly from 25 weeks gestation until four weeks after full-term equivalent and was independent of time of birth. Full-term infants were distinguished from early premature infants by the occurrence of a prominent postnatal surge in circulating IGF-I levels that was characterised by a significant (P less than 0.02) increase between day 1 and days 10-15. The SGA and AGA infants in the 34-37 week cohort showed similar profiles of circulating IGF-I with no significant difference in cord values between the two groups.

Covert cross reactants in a two-site immunoassay studied with monoclonal antibodies

A one-step two-site immunoradiometric assay for the measurement of free beta subunit of human chorionic gonadotrophin (beta-hCG) was developed using monoclonal antibodies. The immobilized antibody was specific for free beta subunit and the radiolabeled antibody recognized both intact human chorionic gonadotrophin (hCG) and free beta subunit. Although the level of hCG "cross-reaction" was low when studied using conventional techniques, the apparent beta-hCG content of samples was found to be inversely proportional to the hCG level. From both experimental evidence and computer simulation studies this was found to be due to the binding of hCG to the limited amount of 125I-labeled antibody present. The term covert cross reactants has been introduced to describe substances which bind to only one of the antibodies in a two-site immunoassay. When establishing such an assay the effect of covert cross reactants on the response of an analyte should be investigated.

The production of monoclonal antibodies to human chorionic gonadotrophin and its subunits

The difficulties encountered in producing highly specific antisera to human chorionic gonadotrophin (hCG) were overcome by the use of hybridoma technology. A panel of monoclonal antibodies directed toward hCG and its subunits was produced. Of the four antibodies which were fully characterized, one recognized the intact hCG molecule only, a second recognized only the free beta-subunit, a third recognized only the free alpha-subunit and the fourth bound to the beta-subunit of hCG both when it was in the free form and when it was associated with the alpha-subunit forming the intact hCG molecule. There was no significant cross-reaction of any of these antibodies with the pituitary glycoprotein hormones. The four antibodies had high binding affinities which should permit their use in immunoassays for measurement of circulating levels of hCG and its subunits.

The production of high affinity monoclonal antibodies to human growth hormone

The primary aim of this work was to produce specific monoclonal antibodies to human growth hormone (hGH) for use in a diagnostic RIA of hGH levels in serum. Three different schedules were used for immunization of BALB/c mice and the splenocytes from each mouse were fused with myeloma cells Sp 2/0 Ag 14. Each fusion resulted in the production of hundreds of hybridomas secreting hGH-directed antibodies. Six antibodies have been fully characterized and have been grouped into pairs which recognize 3 different epitopes on the hGH molecule. One pair exhibits no cross reaction with the structurally related placental hormone, human placental lactogen (hPL), a second pair has low cross reaction with hPL (1.6-3%) and a third pair reacts equally well with hGH and hPL indicating binding to a common epitope in the 2 molecules. The highest affinity antibody, 74/6, which has an affinity constant of 4.4 X 10(10) l/mol and 3% cross-reactivity with hPL, has been used to establish a RIA for serum hGH measurements. Evidence is provided that hGH levels measured in this assay correlate well with those obtained in a conventional rabbit antiserum assay.

Use of immunoaffinity chromatography for purification of 125I-labeled human prolactin

We assessed a simple method for purifying 125I-labeled human prolactin, taking advantage of the abundant supplies of monoclonal antibodies available. 125I-Labeled human prolactin purified by immunoaffinity chromatography is compared with that purified by gel filtration on Sephadex G-100. We used monoclonal antibodies to prolactin to prepare the affinity chromatography columns. Prolactin was radiolabeled by the Chloramine T method, purified by each of the above procedures, and the binding and displacement characteristics were studied in radioimmunoassays in which either monoclonal antibodies or a rabbit anti-prolactin serum was the first antibody. A nonimmune fraction of 125I-labeled prolactin that co-eluted with the immunoreactive hormone from Sephadex G-100 was removed by affinity chromatography, which increased the antibody binding of 125I-labeled prolactin in the radioimmunoassay in the absence of unlabeled antigen (B/T0, in percent) twofold or more, increased the assay sensitivity, and increased the slope of antigen displacement measured by the 50% intercept. Several advantages make this the purification method of choice.

Use of immunoaffinity chromatography for purification of 125I-labeled human prolactin

We assessed a simple method for purifying 125I-labeled human prolactin, taking advantage of the abundant supplies of monoclonal antibodies available. 125I-Labeled human prolactin purified by immunoaffinity chromatography is compared with that purified by gel filtration on Sephadex G-100. We used monoclonal antibodies to prolactin to prepare the affinity chromatography columns. Prolactin was radiolabeled by the Chloramine T method, purified by each of the above procedures, and the binding and displacement characteristics were studied in radioimmunoassays in which either monoclonal antibodies or a rabbit anti-prolactin serum was the first antibody. A nonimmune fraction of 125I-labeled prolactin that co-eluted with the immunoreactive hormone from Sephadex G-100 was removed by affinity chromatography, which increased the antibody binding of 125I-labeled prolactin in the radioimmunoassay in the absence of unlabeled antigen (B/T0, in percent) twofold or more, increased the assay sensitivity, and increased the slope of antigen displacement measured by the 50% intercept. Several advantages make this the purification method of choice.

A monoclonal antibody suitable for the radioimmunoassay of prolactin in human serum

Monoclonal antibodies directed toward human PRL (hPRL) have been produced by fusion of mouse myeloma cells (Sp2/0-Ag 14) with spleen cells from mice immunized with hPRL. Total immunizing doses of 20 microgram and 64 microgram hPRL resulted in the production of three highly specific hPRL antibodies. The high affinity antibody, with a Ka value of 0.23 X 10(10) M-1, was used to establish a RIA highly suitable for the measurement of hPRL levels in human serum. The correlation of serum hPRL levels measured using the antibody and those in a conventional rabbit anti-hPRL assay was 0.99 (y = 1.16 - 7.2). These results demonstrate that using the mouse hybridoma technique, it is possible to produce high affinity monospecific monoclonal antibody suitable for the measurement of hPRL in human serum.

Lectins used to prepare serum free of glycoprotein hormones for use as a matrix in radioimmunoassay

Hormone-free serum is required for use as a matrix for standards in the radioimmunoassay of hormones. The glycoprotein hormones are difficult to remove from serum by conventional techniques. We exploited the specific binding of carbohydrates by lectins to extract glycoprotein hormones from human serum. Passing serum over Concanavalin A Sepharose efficiently removed lutropin and the beta subunit of choriogonadotropin. Wheat-Germ Lectin Sepharose completely removed these, and also follitropin and thyrotropin. The latter treatment is shown to provide a suitable matrix for standards in radioimmunoassays of the four hormones.