Cyclical parthenogenetic reproduction in the Russian wheat aphid (Hemiptera: Aphididae) in the United States: sexual reproduction and its outcome on biotypic diversity.

In 1986, the Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae), became an invasive species of United States. Nearly 20 yr later, new biotypes appeared that were capable of overcoming most sources of resistance and became a renewed threat to wheat, Triticum aestivum L., production. Cyclical (CP) and obligate (OP) parthenogenesis enables aphids to both adapt to changing environments and exploit host resources. We documented these forms of reproduction for Russian wheat aphid in wheat and wild grasses in the Central Great Plains and Rocky Mountain regions during falls 2004-2009. Colonies from sample sites also were held under unheated greenhouse conditions and observed for the presence of sexual morphs and eggs through the winter. Russian wheat aphid populations were mainly OP and attempted to overwinter as adults, regardless of region sampled. A few populations contained oviparae but no males (gynocyclic) and were not specific to any particular region. Observation of the Russian wheat aphid colonies under greenhouse conditions failed to produce males or eggs. In spring 2007, CP was confirmed in a small population of Russian wheat aphid that eclosed from eggs (fundatricies) on wild grasses and wheat near Dove Creek, CO, in the Colorado Plateau region where other aphid species undergo CP. Lineages from ninety-three fundatricies were screened against 16 resistant and susceptible cereal entries to determine their biotypic classification. A high degree of biotypic diversity (41.4%) was detected in this population. Although CP was a rare in Russian wheat aphid populations, genetic recombination during the sexual cycle creates new biotypes and can have significant effects on population genetics.

Biology and biotype determination of greenbug, Schizaphis graminum (Hemiptera: Aphididae), on seashore paspalum turfgrass (Paspalum vaginatum).

Greenbug, Schizaphis graminum (Rondani) (Hemiptera: Aphididae), was first discovered damaging seashore paspalum (Paspalum vaginatum Swartz) turfgrass in November 2003 at Belle Glade, FL. Inquiries to several golf courses with seashore paspalum turf across southern Florida indicated infestation was wide spread by April 2004. Damage symptoms progress from water soaked lesions surrounding feeding sites within 24 h to chlorosis and necrosis of leaf tips within 96 h. Problems caused by greenbug feeding were initially misdiagnosed as fertilizer, disease, other insects, or water management problems because aphids were not previously found on warm season turfgrasses. Greenbug development and fecundity studies were conducted on six seashore paspalum varieties: 'Aloha,' 'SeaDwarf,' 'SeaGreen,' 'SeaIsle,' 'SeaWay,' and 'SeaWolf.' Greenbug did not survive on 'SeaWolf.' Development rates (mean +/- SEM) ranged from 7.6 +/- 0.2 to 8.2 +/- 0.2 d on the remaining varieties. Greenbug longevity and fecundity on 'Aloha' were significantly less than on the other varieties. The estimated intrinsic rate of natural increase (r(m)) for greenbug ranged from 0.24 to 0.26 across tested varieties. Values for net reproductive rate (R(o)) ranged from 12.3 on 'Aloha' to 40.4 on 'SeaWay.' In feeding trials on indicator plants, the Florida isolate of greenbug exhibited a unique biotypic profile most commonly found on noncultivated grass hosts. It was virulent on the wheat variety GRS1201 that is resistant to the principal agricultural biotypes attacking small grains and to all currently available resistant sorghum varieties.

Response of resistant and susceptible barley to infestations of five Diuraphis noxia (Homoptera: Aphididae) biotypes.

Since 2003, four new biotypes of the Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Homoptera: Aphididae), RWA2-RWA5, have been discovered that have the ability to damage most of the wheat germplasm resistant to the original Russian wheat aphid population (RWA1). Barley germplasm lines with resistance to RWA1 have not yet been evaluated against the newest biotypes. Our study compared how biotypes RWA1-RWA5 affected the growth and leaf damage of RWA1-resistant germplasm (STARS 9301B, STARS 9577B), moderately resistant germplasm (MR-015), and susceptible varieties (Schuyler, Harrington, and Morex) under greenhouse conditions. Russian wheat aphid population levels also were determined 14 d after plant infestation. STARS 9301B exhibited strong resistance by showing only small differences in leaf damage and growth parameters from the feeding by the biotypes. STARS 9577B showed greater differences in damage by the Russian wheat aphid biotypes than STARS 9301B, yet, the ratings were still within the resistant category (e.g., chlorosis rating 2.3-4.9). Leaf chlorosis ratings for MR-015 ranged from 5.0 to 6.9 and fell within the moderately resistant to susceptible categories for all the biotypes. The greatest difference in leaf chlorosis occurred in Morex where RWA2 showed less virulence than the other biotypes. Feeding by the Russian wheat aphid biotypes produced only small differences in leaf rolling and plant growth within plant entries. Population levels of the Russian wheat aphid biotypes did not differ within barley entries (n = 610-971) at the termination of the study (14 d). From our research, we conclude that the new Russian wheat aphid biotypes pose no serious threat to the key sources of resistance in barley (STARS 9301B and 9577B).

Mitochondrial DNA sequence divergence among Schizaphis graminum (Hemiptera: Aphididae) clones from cultivated and non-cultivated hosts: haplotype and host associations.

A 1.0 kb region of the mitochondrial cytochrome oxidase subunit I gene from the greenbug aphid, Schizaphis graminum (Rondani), was sequenced for 24 field collected clones from non-cultivated and cultivated hosts. Maximum likelihood, maximum parsimony and neighbour-joining phylogenies were estimated for these clones, plus 12 previously sequenced clones. All three tests produced trees with identical topologies and confirmed the presence of three clades within S. graminum. Clones showed no relationship between biotype and mtDNA haplotype. At least one biotype was found in all three clades, suggesting exchange among clades of genetic material conditioning for crop virulence, or the sharing of a common ancestor. However, there was a relationship between host and haplotype. Clade 1 was the most homogeneous and contained 12 of 16 clones collected from cultivated hosts and five of the six collected from johnsongrass, Sorghum halepense, a congener of cultivated sorghum, S. bicolor. Four of the six clones collected from Agropyron spp. were found in clade 2. Clade 3 contained two clones from wheat, Triticum aestivum, and four from non-cultivated hosts other than Agropyron spp. A partitioning of populations by mtDNA haplotype and host suggests the occurrence of host adapted races in Schizaphis graminum.

Efficacy of pyramiding greenbug (Homoptera: Aphididae) resistance genes in wheat.

Durable resistance to greenbug, Schizaphis graminum (Rondani), in wheat is a goal of wheat improvement teams, and one that has been complicated by the regular occurrence of damaging biotypes. Simulation modeling studies suggest that pyramiding resistance genes, i.e., combining more than one resistance gene in a single cultivar or hybrid, may provide more durable resistance than sequential releases of single genes. We examined this theory by pyramiding resistance genes in wheat and testing a series of greenbug biotypes. Resistance genes Gb2, Gb3, and Gb6, and pyramided genes Gb2/Gb3, Gb2/Gb6, and Gb3/Gb6 were tested for effectiveness against biotypes E, F, G, H, and I. By comparing reactions of plants with pyramided genes to those with single resistance genes, we found that pyramiding provided no additional protection over that conferred by the single resistance genes. Based on the results of this test, we concluded that the sequential release of single resistance genes, combined with careful monitoring of greenbug population biotypes, is the most effective gene deployment strategy for greenbug resistance in wheat.

Relative suitability of crested wheatgrass and other perennial grass hosts for the Russian wheat aphid (Homoptera: Aphididae).

The Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera: Aphididae), reproduces parthenogenetically in North America and must survive year-round on host plants, including in late summer when small grains are not in cultivation. During this time, cool-season perennial wheatgrasses (Poaceae: Triticeae) contribute substantially to aphid survival, crested wheatgrass (Agropyron spp.) particularly. In greenhouse studies, the number of aphids per plant was measured after four infestation periods on unvernalized and vernalized wheatgrasses. Before placement on these test plant species, aphids were reared either on winter wheat or on the grass host species on which aphid progeny were counted. On vernalized plants, aphids reared on wheat resulted in more aphids per test plant than when the aphids were reared on wheatgrasses, but on unvernalized plants the number of aphids per test plant did not differ significantly regardless of rearing host. Aphids on crested wheatgrass were similar in number to the other grasses when plants were unvernalized. However, when plants were vernalized, crested wheatgrass supported significantly more aphids than some of the other hosts. Aphid numbers increased on all test species as infestation period lengthened, and plant growth was largely unaffected by aphid feeding. These results suggest if sufficient moisture is available during summer when small grains are not in cultivation, all host species observed are capable of sustaining aphids. Crested wheatgrass is an abundant and important host of the Russian wheat aphid in its northern range of the western United States, but other less prevalent wheatgrasses also may contribute to aphid survival during late summer when small grains are not in cultivation.

Mitochondrial DNA sequence divergence among greenbug (Homoptera: aphididae) biotypes: evidence for host-adapted races.

The full complement of known greenbug, Schizaphis graminum (Rondani), biotypes found in the USA were subjected to a molecular phylogenetic analysis based on a 1.2-kb portion of the cytochrome oxidase I mitochondrial gene. In addition to these nine biotypes (B, C, E, F, G, H, I, J and K), a probable isolate of the enigmatic biotype A (NY), a 'new biotype' collected from Elymus canadensis (L.) (CWR), and an isolate from Germany (EUR) were included. Schizaphis rotundiventris (Signoret) was included as an outgroup. Genetic distances among S. graminum biotypes ranged from 0.08% to 6.17% difference in nucleotide substitutions. Neighbour-joining, maximum parsimony and maximum likelihood analyses all produced dendrograms revealing three clades within S. graminum. Clade 1 contained the 'agricultural' biotypes commonly found on sorghum and wheat (C, E, K, I, plus J) and there were few substitutions among these biotypes. Clade 2 contained F, G and NY, and Clade 3 contained B, CWR and EUR, all of which are rarely found on crops. The rarest biotype, H, fell outside the above clades and may represent another Schizaphis species. S. graminum biotypes are a mixture of genotypes belonging to three clades and may have diverged as host-adapted races on wild grasses.

Incidence of asystole in electroconvulsive therapy in elderly patients.

The authors prospectively investigated the incidence of asystole (absence of heartbeat for 5 seconds) in elderly patients receiving electroconvulsive therapy (ECT) at a university-based geriatric psychiatry unit. In all, 65.8% of patients experienced asystole at some time during their course of ECT. Those who experienced asystole were significantly younger (average age, 72.2) than those without asystole (average age, 77.0; P = 0.026) and were also less likely to have cardiac rhythm disturbances on electrocardiogram (P = 0.024). Medical history, history of cardiac disease, electrode placement, energy level, and number of ECT treatments did not predict asystole. Asystole is a common side effect of ECT in elderly patients. It was not associated with any untoward outcome. The fact that "old-old" patients and those with cardiac disease are less likely to experience asystole than younger, healthier patients is reassuring to practitioners of ECT.

Intersection of the complement and immune systems: a signal transduction complex of the B lymphocyte-containing complement receptor type 2 and CD19.

The complement system augments the humoral immune response, possibly by a mechanism that involves the B lymphocyte membrane receptor, CR2, which binds the C3dg fragment of C3 and triggers several B cell responses in vitro. The present study demonstrates that CR2 associates with a complex of membrane proteins that may mediate signal transduction by ligated CR2. Monoclonal antibodies to CR2 immunoprecipitated from digitonin lysates of Raji B lymphoblastoid cells a membrane complex containing CR2, approximately equimolar amounts of CD19, which is a member of the immunoglobulin superfamily, and three unidentified components: p130, p50, and p20. The complex, which was immunoprecipitated also with anti-CD19, could be dissociated by Nonidet P-40, accounting for its absence in previous studies of CR2. Expression of recombinant CR2 and CD19 in K562 erythroleukemia cells led to formation of a complex that contained not only these two proteins but also p130, p50, and p20, and another component, p14. These unidentified components of the CR2/CD19 complex coimmunoprecipitated with CD19 and not with CR2 from singly transfected cells, indicating primary association with the former. CD19 replicated the capacity of CR2 to interact synergistically with mIgM for increasing free intracellular Ca2+, suggesting that the complex mediates this function of CR2. Therefore, CR2 associates directly with CD19 to become a ligand-binding subunit of a pre-existing signal transduction complex of the B cell that may be representative of a family of membrane protein complexes. This interaction between the complement and immune systems differs from that between immunoglobulin and Clq by involving membrane rather than plasma proteins, and by having complement involved in the afferent phase of the immune response.

Characterization of human synovial mast cells.

Human synovium obtained at arthroplasty from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) were characterized by assessing mast cell morphology, content and function. Histological studies confirmed significant numbers of mast cells in both RA and OA synovium. Electron microscopic data support the morphologic similarity between human synovial mast cells and human mast cells in lung and intestine. Likewise, synovial mast cells do not appear to be functionally different from pulmonary or intestinal mucosal mast cells. Mast cell suspensions with a cellular histamine content of 4.3 +/- 0.5 pg/cell (mean +/- SEM) released histamine following provocation with anti-IgE and calcium ionophore but not compound 48/80, f-met peptide or bradykinin. Prostaglandin D2 (PGD2) and leukotriene C4 (LTC4) were also released in response to anti-IgE. Auranofin inhibited anti-IgE provoked histamine, PGD2 and LTC4 release while gold sodium thiomalate, cromolyn and indomethacin had no effect on histamine release. Theophylline inhibited anti-IgE induced histamine release only at concentrations greater than or equal to 10(-3) M. Our study argues against functional or morphologic mast cell heterogeneity of human intestinal, lung and synovial origin and suggests that mast cells may have a pathogenic role in both RA and OA.

Osmoregulation of vasopressin secretion and thirst in cyclical oedema.

Osmoregulation of vasopressin release and thirst was studied in the mid-follicular and mid-luteal phases of the menstrual cycle of five patients with cyclical oedema defined by peripheral oedema and weight gain (greater than 3.0 kg) manifest in two consecutive luteal phases. Results are compared to those already obtained in eight healthy women. In the patients, basal plasma osmolality in the mid-luteal phase was significantly lower than in the mid-follicular periods (patients, 283 +/- 1, 287 +/- 1 mOsmol/kg, respectively, mean +/- SEM, P less than 0.05; controls, 282 +/- 1, 286 +/- 1 mOsmol/kg, respectively, P less than 0.05). Plasma osmolality (pOsm) and plasma arginine vasopressin (pAVP) were measured during hypertonic (850 mmol/l) saline infusion in both phases of the cycle; linear regression analyses of these data gave the following mean regression equations, (i) mid-follicular, pAVP = 0.55 (pOsm - 285), r = 0.94 and (ii) mid-luteal, pAVP = 0.42 (pOsm - 281), r = 0.93. The abscissal intercept was significantly different (P less than 0.025). Osmotic threshold for severe thirst onset was lower in the mid-luteal phase compared to the mid-follicular value (296 +/- 1, 299 +/- 1 mOsmol/kg, respectively, P less than 0.01). Basal data and results of thirst onset and theoretical threshold for vasopressin release in response to osmotic stimulation obtained in the patients were similar to healthy control women. We conclude that osmoregulation in cyclical oedema is normal.

Acute suppression of plasma vasopressin and thirst after drinking in hypernatremic humans.

Drinking rapidly abolishes thirst and vasopressin secretion in dehydrated humans before major changes in plasma osmolality are observed. We studied the effects of drinking on plasma vasopressin and thirst in seven healthy volunteers rendered hypernatremic by the infusion of hypertonic (855 mmol/l) sodium chloride solution. Thirst was measured on a visual analogue scale (0-10 cm). Infusion of hypertonic saline caused linear increases in plasma osmolality (289 +/- 1 to 306 +/- 1 mosmol/kg, mean +/- SE, P less than 0.001), plasma vasopressin (0.6 +/- 0.2 to 6.4 +/- 1.9 pmol/l, P less than 0.001), and thirst (1.4 +/- 0.4 to 7.4 +/- 0.5 cm, P less than 0.001). Water was allowed 15 min after cessation of the infusion, and within 5 min of drinking both plasma vasopressin and thirst were significantly lower than postinfusion. After 20 min of drinking, plasma vasopressin had fallen from 6.5 +/- 0.9 to 1.3 +/- 0.3 pmol/l (P less than 0.001) and thirst from 7.7 +/- 0.5 to 1.0 +/- 0.2 cm (P less than 0.001) despite no significant change in plasma osmolality (306 +/- 0.9 to 304 +/- 0.8 mosmol/kg, P = 0.17), and the drinking of 1,200 +/- 60 ml of water, over 85% of the mean cumulative water intake in the 30-min drinking period. Control studies in the same subjects showed comparable rises in plasma vasopressin, plasma osmolality, and thirst during hypertonic saline infusion but no fall in any of these parameters during an equivalent 30-min period after the infusions, during which water was withheld.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of enzyme inhibitors of pregnancy associated oxytocinase: application to the measurement of plasma immunoreactive oxytocin during human labour.

The presence of the human placental enzyme, oxytocinase, in blood samples taken during pregnancy causes major methological problems in the radioimmunoassay for plasma oxytocin. Inadequate inhibition of the enzyme activity may lead to spuriously high or low values of plasma oxytocin. This study systematically investigates a variety of enzyme inhibitors. The optimum inhibitory system was obtained by the addition of 10 microliters of cold 125 mmol/l 1.10 phenanthrolene and 1 mol/l EDTA per ml of whole blood into the syringe. Complete enzyme inhibition was maintained for up to 60 min, during which time the lithium heparinized plasma samples were extracted by the Florisil method. Following extraction there was no enzyme activity in the extract residue. Concentrations of phenanthrolene and EDTA necessary to eliminate enzyme activity were 50- and 10-fold greater, respectively, than in any previously reported method. Recovery of synthetic oxytocin added to pregnancy plasma with inhibitors was 80% or higher, over the concentration range 1-100 pmol/l. Extract residue could be stored at -20 degrees C for up to 7 weeks. Dilutions of pregnancy plasma extracts ran parallel to the oxytocin standard curve. Studies on plasma concentrations of oxytocin (OT) during the first stage of labour in 6 patients showed that 3 had pulsatile plasma OT, peak values ranging from 4-10 pmol/l in phase with uterine concentrations, but 2 who had regular uterine activity had no episodic changes in plasma OT. One patient with hypocontractile labour had low non-fluctuating plasma OT.

The osmotic thresholds for thirst and vasopressin release are similar in healthy man.

The relationship between thirst perception and plasma osmolality was studied during hypertonic and physiological saline infusion in ten healthy volunteers. Thirst perception was quantified using a linear visual analogue scale which volunteers marked at intervals during the infusion periods. Infusion of hypertonic saline caused a steady rise in plasma osmolality together with a progressive linear increase in thirst perception and also plasma arginine vasopressin. No significant changes in thirst, plasma osmolality or plasma arginine vasopressin occurred during infusion of physiological saline. Linear regression analysis of the results defined the functions. Thirst (cm) = 0.3 (plasma osmolality-281) (r = +0.92, P less than 0.001) and plasma arginine vasopressin (pmol/l) = 0.4 (plasma osmolality-285) (r = +0.96, P less than 0.001). The osmolar threshold for thirst onset thus defined (281 mosmol/kg) was much lower than in previous studies and similar to the theoretical osmolar threshold for vasopressin release (285 mosmol/kg). We conclude that thirst perception rises in a progressive fashion throughout a wide range of plasma osmolality and that the osmolar threshold for thirst onset is similar to the theoretical osmolar threshold for vasopressin release. The results are compatible with the concept of either a single osmoreceptor subserving both thirst and vasopressin release, or two osmoreceptors sharing similar functional characteristics.

Interference in the cytochemical assay of plasma vasopressin by a circulating factor induced by salt-loading in man.

Infusion of hypertonic saline into six normal volunteers caused an increase in plasma osmolality from 286.8 +/- 1.7 (mean +/- S.E.M.) to 307.6 +/- 2.6 mosmol/kg (P less than 0.001), a 7.1% increase in estimated blood volume, a rise in plasma immunoreactive arginine vasopressin (AVP) concentrations from 1.3 +/- 0.2 to 12.7 +/- 3.6 pmol/l (P less than 0.001) but no change in plasma AVP concentrations (2.1 +/- 0.9 and 1.9 +/- 1.3 pmol/l) as measured by a cytochemical technique based on the ability of AVP to stimulate rat renal medullary Na+/K+-ATPase activity. Addition of synthetic AVP to plasma obtained before, during and after hypertonic saline infusion also failed to stimulate Na+/K+-ATPase activity. The results suggest that infusion of hypertonic saline interfered with the cytochemical assay for AVP by inhibiting AVP-stimulated medullary Na+/K+-ATPase activity. We conclude that the use of this cytochemical method to detect plasma AVP has severe limitations under these experimental conditions.

Development of a cytochemical assay for plasma vasopressin: application to studies on water loading normal man.

A cytochemical assay has been developed to measure human plasma arginine vasopressin. It is based on the stimulation of Na+-K+, ATPase activity located in the outer medulla of the rat kidney, and is capable of detecting very low plasma arginine vasopressin concentrations, limit of detection 0.01 pmol/l. Specificity for vasopressin stimulation of the enzyme is conferred on the assay by the use of specific vasopressin antiserum. Index of precision of the assay is 0.21. Degradation of arginine vasopressin in plasma in inhibited by phenanthroline. Samples may be stored up to 8 weeks at -70 degrees C. Intra- and inter-assay coefficients of variation were 22% (n = 8) and 104% (n = 12), respectively. A sustained water load in eight healthy male adults caused a fall in plasma osmolality from a basal of 286.5 +/- 2.0 (mean +/- SEM) to 279.2 +/- 2.4 mmol/kg after the load (P less than 0.001), which was associated with a reduction in urine osmolality from 867 +/- 54 to 69 +/- 3 mmol/kg. Plasma immunoreactive arginine vasopressin fell from 1.3 +/- 0.3 pmol/l to become undetectable (less than 0.3 pmol/l), but plasma cytochemical arginine vasopressin decreased from 0.96 +/- 0.14 to 0.07 +/- 0.02 pmol/l. There was a curvilinear relationship between plasma osmolality and plasma cytochemical arginine vasopressin, which militated against the concept of an osmotic threshold for vasopressin release.

Recurrent pregnancy-induced polyuria and thirst due to hypothalamic diabetes insipidus: an investigation into possible mechanisms responsible for polyuria.

A young patient developed hypothalamic diabetes insipidus due to histiocytosis in infancy and was satisfactorily treated with Pitressin. As a teenager she no longer had thirst or polyuria after treatment was stopped. These symptoms only returned during her two pregnancies. When non-pregnant her urine output was 1.7-2.0 1/24 h, basal plasma osmolality 288-290 mOsm/kg, and during pregnancy 24 h urine volume was 4.5-5.21, plasma osmolality 278-280 mOsm/kg. Studies on osmoregulation of thirst and AVP release, and on renal sensitivity to the V2 agonist desmopressin and endogenous vasopressin were performed in pregnant and non-pregnant states. She had no circulating antibodies to AVP, and the effect of pregnancy-associated vasopressinase was eliminated. Results showed lowered basal plasma osmolality and osmolar thirst threshold in pregnancy but no failure of the renal concentrating mechanism. Plasma AVP concentrations after osmotic stimulation were lower in pregnancy. We propose that she developed thirst and polyuria during pregnancy because of lowering of her osmolar thirst threshold to plasma osmolalities which caused her to drink sufficient quantities of fluid to further reduce AVP secretion. We cannot exclude, however, the possibility that there was increased clearance of circulating AVP.

Simultaneous determination of total IgE and allergen-specific IgE in serum by the MAST chemiluminescent assay system.

We have developed a chemiluminescent immunoenzymometric system. The first commercial application of this chemiluminescent assay (CLA) is the measurement of total IgE and allergen-specific IgE in human serum. The CLA system is a second-generation adaptation of the MAST RIA allergy profiling system. The MAST CLA system assay protocol consists of three steps: overnight incubation of serum, a 4-h incubation with enzyme-labeled antibody, and a 30-min chemiluminescent reaction, which produces a visible image (immunograph) on high-speed Polaroid instant film. The densities of the bands produced on the film are quantified with an inexpensive microprocessor-controlled infrared transmittance densitometer. The novel luminogenic substrates used yield a constant light output for over 2 h with an intensity at least 10-fold greater than that of commercial chemiluminescent reagents. The MAST CLA system exhibits sensitivity, specificity, and precision equal to that of the MAST RIA system (r = 0.96 for 40 serum samples analyzed with 25 allergens). As many as 35 different allergens per sample can be quantified in a single assay. The MAST CLA system requires no standard curve or volume-dependent pipetting steps, incorporates both positive and negative controls for each sample, and quantifies allergen-specific IgE at picomolar concentrations.

The effect of vasopressin infusion on glucose metabolism in man.

Studies on intact animals and isolated rat hepatocytes have shown that arginine vasopression (AVP) stimulates glycogen phosphorylase to break down glycogen and raise plasma glucose concentrations. Since no similar work has been performed on healthy human adults, the effect of moderate (25 pmol/min) and high (75 pmol/min) dose AVP infusion on plasma glucose, intermediary metabolites, glucose kinetics, and circulating glucagon and insulin concentrations was investigated. After AVP infusion, plasma glucose rose from 4.9 +/- 0.1 to a peak of 5.7 +/- 0.2 mmol/l (P less than 0.001), but no changes in blood lactate, pyruvate, alanine, glycerol or 3-hydroxybutyrate concentrations were observed. The glucose rise was accounted for entirely by an increase in the rate of appearance of glucose from 11.19 +/- 0.43 to 13.38 +/- 0.63 mu mol/kg/min (P less than 0.001). Infusion of AVP also increased plasma glucagon concentrations from 38 +/- 8 to 79 +/- 20 pg/l (P less than 0.01). The hyperglycaemic effect of AVP may be mediated solely by stimulation of glucagon release, but we cannot exclude direct stimulation of glycogen phosphorylase activity.