Synthesis, structure, thermal and non-linear optical properties of L-argininium hydrogen selenite

L-Argininium hydrogen selenite (C(6)H(15)N(4)O(2)HSeO(3)) is a new semiorganic compound of the hydrogen selenite family with non-linear optical properties. The crystal lattice is monoclinic with unit-cell parameters a = 22.493 (5), b = 5.1624 (13), c = 9.730 (4) A, beta = 95.68 (3) degrees, V = 1124.3 (6) A(3), Z = 4, space group C2. Second-harmonic generation measurements performed on powder samples, using a Q-switched Nd:Yag laser (lambda = 1064 nm), showed the second-harmonic power to be about twice that of urea. Differential scanning calorimetry measurements revealed the existence of a phase transition with onset at 289 K.

Neutralization of dermonecrotic and lethal activities and differences among 32-35 kDa toxins of medically important Loxosceles spider venoms in Brazil revealed by monoclonal antibodies

Neutralization of dermonecrotic and lethal activities and differences among the principal toxic proteins (32-35 kDa) of medically important Loxosceles spider venoms in Brazil (Loxosceles gaucho, Loxosceles laeta and Loxosceles intermedia) were studied using monoclonal antibodies (MAbs) produced against the dermonecrotic component (35 kDa) of L. gaucho venom. MAb titers were 512,000 to homologous venom, between 2000 and 64,000 for L. intermedia venom and between 1000 and 64,000 for L. laeta venom. By Western blotting, MAbs could recognize mainly the 35 kDa protein of L. gaucho venom and with less intensity the 35 kDa protein of L. intermedia venom. These MAbs also recognized weakly or did not recognize the 32 kDa component of L. laeta venom. Only MoALg1 showed high affinity for L. gaucho venom and neutralized in vivo 90-97% of the dermonecrotic activity, besides delaying the lethality induced by homologous venom. MoALg1 maintained its capacity to neutralize the dermonecrotic activity, even when administered (i.v.) 6h after envenoming (i.d.). All MAbs obtained failed to neutralize the toxic activities of the heterologous venoms.These results suggest that different epitopes are present in the protein responsible for the dermonecrotic activity of Loxosceles venoms, and confirm the participation of other venom components during the local reaction process. This study also confirms the importance of antibodies for neutralization of dermonecrotic activity, even when administered some hours after envenoming, and emphasizes the differences of composition and toxicity of medically important Loxosceles venoms. These findings must be considered in order to improve loxoscelism immunotherapy.

Tolerance to the antinociceptive effect of Crotalus durissus terrificus snake venom in mice is mediated by pharmacodynamic mechanisms

Crotalus durissus terrificus venom exerts central and peripheral antinociceptive effect mediated by opioid receptors. The present work investigated the tolerance to the antinociceptive effect of the venom and characterised the mechanisms involved in this phenomenon. The hot plate test, applied in mice, was used for pain threshold determination. The venom (200 microg/kg) was administered by oral route, daily, for 14 days, and the nociceptive test was applied before and on days 1, 7 and 14 of the treatment. Prolonged treatment with venom lead to the development of tolerance to the antinociceptive effect. Tolerant animals exhibited increased sodium pentobarbital-induced sleeping time, although total hepatic microsomal cytochrome P450 was not altered. The antinociceptive effect of a single dose of venom (200 microg/kg) is mediated by kappa opioid receptors. Mice long-term-treated with venom showed cross-tolerance to U-TRANS, an agonist of kappa-opioid receptor, but not to morphine or DAMGO, two mu-opioid receptor agonists. Prolonged administration of venom did not cause symptoms of abstinence syndrome. These data indicate that prolonged treatment with C. durissus terrificus venom induces tolerance to the antinociceptive effect and that pharmacodynamic mechanisms are involved in the genesis of this phenomenon.

P-glycoprotein inhibitors stimulate renal phosphate reabsorption in rats

BACKGROUND

Dipyridamole (Dip) was previously shown to increase renal phosphate (Pi) reabsorption in humans. However, the mechanism(s) underlying this renal tubular effect is not fully elucidated. It is known that Dip inhibits the activity of the P-glycoprotein (Pgp) multidrug resistance protein 1 (MDR1) expressed on the apical membrane of renal proximal tubular cells where the Na-Pi cotransporter (NPT2) is also expressed. We hypothesized that Dip could increase renal Pi reabsorption by inhibiting Pgp activity.

METHODS

To test this hypothesis, the effects of Dip, verapamil (Ver), and cyclosporine A (CsA), three unrelated Pgp inhibitors, were studied on the renal Pi reabsorption in rats.

RESULTS

All three drugs decreased the fractional excretion of Pi (FE(Pi)) in a dose-dependent manner within one hour after beginning the drug infusion, without altering the glomerular filtration rate or serum parathyroid hormone concentration. Sodium-dependent Pi uptake but not Na-glucose transport was increased in brush-border membrane vesicles (BBMVs) when comparing treated with untreated rats. Western blot analysis showed that NPT2 protein was increased in BBMVs from treated rats. Dip and Ver had no effect when applied directly to BBMVs prepared from untreated rats. Pretreatment of rats with colchicine prevented the effects of Dip on the FE(Pi) and NPT2 expression in brush-border membranes.

CONCLUSIONS

Our results suggest that inhibition of Pgp in the proximal tubule increases Pi uptake and NPT2 translocation to the apical membrane.

Production and characterization of a monoclonal antibody against an Ascaris suum allergenic component

Ascaris suum allergenic components (PIII) separated by gel filtration chromatography of an adult worm extract were used to immunize BALB/c mice. Popliteal lymph node cells taken from the immunized animals were fused with SP2/O myeloma cells using polyethylene glycol (MW 1450) as fusogen. The hybridomas were cultured in HAT-containing medium and cloned at limiting dilutions. Supernatants from the growing hybrids were screened by ELISA using plates coated with PIII or the A. suum crude extract. The monoclonal antibody obtained, named MAC-3 (mouse anti-A. suum allergenic component), is an IgG1 kappa mouse immunoglobulin that specifically recognizes a 29,000 molecular weight protein (called allergenic protein) with an affinity constant of 1.7 x 10(9) M-1. The A. suum components recognized by MAC-3 induce specific IgE antibody production in immunized BALB/c mice. Ascitic fluid induced in Swiss mice by injecting ip the hybridoma cells and incomplete Freund's adjuvant was purified by affinity chromatography using a protein A-Sepharose column. The purified monoclonal antibody was then coupled to activated Sepharose beads in order to isolate the A. suum allergenic component from the whole extract by affinity chromatography.

Lachesis muta muta venom: immunological differences compared with Bothrops atrox venom and importance of specific antivenom therapy

Lachesis muta muta and Bothrops atrox snakes are responsible for most accidents occurring in the Amazon. The clinical features of the accidents are similar; however, there are still controversies about the efficacy of Bothrops antivenoms for treating L. m. muta accidents. In this work, we evaluated the antigenic cross-reactivity between these venoms using polyclonal and monoclonal antibodies and the efficacy of B. atrox and L. m. muta experimental antivenoms in cross-neutralizing the main toxic activities of each venom. Electrophoretic patterns differed consistently between the species. However, antigenic cross-reactivity was extensive except for a few bands. Several species-specific monoclonal antibodies were obtained by immunization of Balb/c mice with L. m. muta whole venom or B. atrox and L. m. muta specific antigens. The monoclonal antibodies specific to L. m. muta recognized different bands of this venom and the antibodies specific to B. atrox recognized a complex pattern on whole venom by Western blotting. These antibodies are important tools for developing an immunoassay able to discriminate patients bitten by these snakes. The experiments involving cross-neutralization of the main activities of the venoms showed that hemorrhage and blood incoagulability induced by B. atrox venom were similarly neutralized by both B. atrox and L. m. muta antivenoms. However, B. atrox antivenom partially neutralized the hemorrhage and completely failed in neutralizing coagulopathy induced by L. m. muta venom. Therefore, antigenic variation between B. atrox and L. m. muta venoms does occur and the use of specific antivenom is suggested for patients bitten by Lachesis snakes.

Specific heterologous F(ab')2 antibodies revert blood incoagulability resulting from envenoming by Lonomia obliqua caterpillars

Contact with Lonomia obliqua caterpillars results in a bleeding syndrome characterized by hemorrhage and blood coagulation disturbances. Conventional therapy using antifibrinolytics or cryoprecipitates has been unable to treat pathophysiologic alterations. As antivenoms are effective therapy for treatment of victims of venomous animals, a process of manufacturing a specific antilonomic serum by immunizing horses with Lonomia caterpillar bristle extracts (LBE) was developed. Lonomia caterpillar bristle extracts exhibited several protein bands on SDS-PAGE, induced blood coagulation abnormalities and lethality in mice, and stimulated specific antibody production in horses. Sera obtained from immunized horses were rich in anti-LBE specific antibodies distributed among the horse IgG isotypes. These antibodies had the ability to recognize various LBE antigens as well as to neutralize their coagulopathy-inducing activity. The antivenom manufactured by the developed process was composed of purified and sterilized F(ab')2 with ED50 = 38.61 microl, potency = 0.29 mg/ml, and 95% confidence limit of potency 0.20-1.36.

Successful prevention of hiv transmission from mother to infant in Brazil using a multidisciplinary team approach

OBJECTIVES

To determine the HIV vertical transmission rate (VTR) and associated risk factors by use of zidovudine and infant care education in Brazil.

METHODS

Since 1995, a prospective cohort of HIV infected pregnant women has been followed at the Federal University of Rio de Janeiro. A multidisciplinary team was established to implement the best available strategy to prevent maternal-infant HIV transmission. Patients with AIDS or low CD(4) and high viral load received anti-retroviral drugs in addition to zidovudine. Children were considered infected if they had 2 positive PCR-RNA tests between 1 and 4 months of age, or were HIV antibody positive after 18 months. Education regarding infant treatment and use of formula instead of breast feeding was provided.

RESULTS

Between 1995 and August, 2000, HIV status was determined for 145 infants. Compliance with intra-partum treatment, infant treatment and use of formula was 88.2%. Intra-partum zidovudine treatment was completed in 134/145 (92.6%) of patients; 88.1% had rupture of membranes < 4 hours; 85.4% of mothers were asymptomatic. The mean CD(4) count was 428.4 cells and mean viral load 39,050 copies. HIV vertical transmission rate was 4/145 (2.75%; CI: 0.1%-5.4%). The only risk factor significantly associated with transmission was a failure to use zidovudine intra-partum in 2 of the 4 mothers (50% versus 6.4% in non-transmitting mothers). A trend toward low CD(4) and high viral load at entry, and rupture of membranes > 4 hours were associated with increased HIV transmission.

CONCLUSION

HIV vertical transmission in Brazil was reduced to a level similar to other countries with the most effective prevention programs using a multidisciplinary team approach. A high level of compliance for use of anti-retroviral drugs, the provision of health education to mothers, and use of formula for all exposed infants.

Effects of acute and chronic hypertension on the labyrinthine barriers in rat

Hearing loss, vertigo, and tinnitus have been related to arterial hypertension. The aim of the present work was to study the permeability of the blood-perilymph and of the labyrinthine barrier, between endolymph and perilymph, to small molecules during chronic and acute hypertension. Experiments were performed in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Acute hypertension was induced by phenylephrine. Perilymph was sampled from the first turn of the scala vestibuli and the Na, K, urea, and radioactive concentrations ((14)C-urea and (3)H-mannitol) were measured. In another experimental set, the endocochlear potential was recorded from the basal turn of scala media, before and after phenylephrine injection. The composition of the perilymph and the kinetic constants for (14)C-urea and (3)H-mannitol were similar in WKY and SHR, and not modified after acute hypertension. In endolymph, the endocochlear potential in SHR (+80+/-2.7 mV, n=24) was lower (P<0.001) than in WKY (+98+/-1.5 mV, n=29). The endocochlear potential was decreased by 40 mV during acute hypertensive peak in seven out of 19 WKY but not in SHR rats (n=13). In conclusion, chronic or acute hypertension did not severely alter the permeability to small molecules of the blood-perilymph barrier. The relationship between the low endocochlear potential and hypertension in SHR remains to be evaluated. After acute hypertensive peak, the presence of vascular protective mechanisms in the cochlea could account for the stable endocochlear potential recorded in SHR and 60% of normotensive rats.

Sulfate homeostasis, NaSi-1 cotransporter, and SAT-1 exchanger expression in chronic renal failure in rats

BACKGROUND

It is known that hypersulfatemia, like hyperphosphatemia, occurs in chronic renal failure (CRF). The aim of this study was to assess the effects of CRF on sulfate homeostasis and on sodium sulfate cotransport (NaSi-1) and sulfate/oxalate-bicarbonate exchanger (Sat-1) expression in the kidney. In addition, sulfate homeostasis was compared with phosphate homeostasis.

METHODS

Experimental studies were performed in adult male rats at three and six weeks after 80% subtotal nephrectomy (Nx) or sham-operation (S) (N = 9 per group). Transporter protein and mRNA expressions were measured by Western blot and RNase protection assay (RPA), respectively. Results were quantitated by densitometric scanning (Western) and electronic autoradiography (RPA), and were expressed in densitometric units (DUs; Western) and cpm (RPA).

RESULTS

Creatinine clearance was lower in Nx-3 compared with S-3 rats (0.23 vs. 0.51 mL/min/100 g body weight, P < 0.001) and was further impaired in Nx-6 rats (0.15 vs. 0.48, P < 0.001). Sulfatemia was significantly higher in Nx-3 rats (1.08 vs. 0.84 mmol/L, P < 0.05) and further increased in Nx-6 rats (1.42 vs. 0.90 mmol/L, P < 0.01). Fractional sulfate excretion (FESO4) was increased by twofold in Nx-3 and Nx-6 rats compared with corresponding S rats. Phosphatemia did not differ between Nx-3 rats and controls, but was increased in Nx-6 rats (P < 0.01). Total amounts of both NaSi-1 and Sat-1 proteins were significantly decreased in both Nx-3 and Nx-6 rats when compared with controls. However, NaSi-1 protein and mRNA densities did not significantly change in Nx-3 rats, but were significantly increased in Nx-6 rats when compared with controls (4.8 vs. 3.7 DU/microg protein, P < 0.05, and 7.1 vs. 2.8 cpm/microg RNA, P < 0.01, respectively, for protein and mRNA). In contrast to NaSi-1, Sat-1 protein density was significantly decreased both in Nx-3 (2.9 vs. 3.6 DU/microg protein, P < 0.05) and Nx-6 rats (2.4 vs. 3.4 DU/microg protein, P < 0.05), and Sat-1 mRNA density significantly decreased in Nx-6 rats (10.7 vs. 14.7 cpm/microg RNA, P < 0.05). Na-PO4 cotransporter (NaPi-2) protein total abundance and density were decreased at three and six weeks in Nx rats.

CONCLUSIONS

These results demonstrate that both NaSi-1 and Sat-1 total protein abundances are decreased in CRF, which may contribute to the increase in fractional sulfate excretion. Strikingly, NaSi-1 density was not decreased in CRF three weeks after Nx, and furthermore, increased six weeks after Nx, in contrast to NaPi-2 density, which was decreased at both times. The significance of this difference remains to be determined, but may explain why hypersulfatemia occurs earlier than hyperphosphatemia in CRF.

Efficacy of bothropic antivenom and its IgG(T) fraction in restoring fibrinogen levels of Bothrops jararaca envenomed mice

Bothropic antivenom and its IgG(T) fraction, administered 4 h after experimental envenoming by Bothrops jararaca in Swiss mice, were compared for their abilities to restore fibrinogen 24 or 48 h after treatment. IgG(T) was able to normalise fibrinogen levels as efficiently as conventional antivenom. As IgG(T) also neutralises most anti-toxic activities of Bothrops venom, our results suggest that IgG(T) could be a better alternative treatment for envenoming due to the reduced amount of extraneous proteins, which may facilitate the induction of early adverse reactions.

Horse IgG isotypes and cross-neutralization of two snake antivenoms produced in Brazil and Costa Rica

Horse IgG isotypes and cross-neutralization of two snake antivenoms produced in Brazil and Costa Rica. Toxicon 000-000. This work compared the specificity, ELISA titers and IgG subclass content of the polyvalent antivenom (anti-Bothrops asper, Crotalus durissus durissus and Lachesis muta stenophrys) of Instituto Clodomiro Picado (Costa Rica) and the bothropic antivenom (anti-Bothrops jararaca, B. jararacussu, B. moojeni, B. neuwiedi and B. alternatus) of Instituto Butantan (Brazil). The role of IgG(T) and IgGa subclasses in neutralization of some venom toxic activities and the cross neutralization of the antivenoms against B. jararaca and B. asper venoms were also evaluated. Both antivenoms were able to recognize B. asper and B. jararaca venoms by immunoblotting and presented similar antibody titers when assayed by ELISA. IgG(T) was highest, followed by IgGa, IgGb and IgGc. IgGa and IgG(T) isotypes isolated from both antivenoms by affinity chromatography were tested for neutralization of lethal, hemorrhagic, coagulant and phospholipase A2 activities of the homologous venoms. In both antivenoms, IgG(T) was the major isotype responsible for neutralization of all the tested activities, followed by IgGa. These results suggest that Instituto Butantan and Instituto Clodomiro Picado antivenoms have the same IgG profile and their neutralizing ability is due mostly to the IgG(T) isotype. Also, they neutralize lethality in mice induced by homologous and heterologous venoms, the bothropic antivenom of Instituto Butantan being more effective.

Hypoxia upregulates activity and expression of the glucose transporter GLUT1 in alveolar epithelial cells

Alveolar epithelial cells (AEC) are directly exposed to high alveolar O(2) tension. Many pulmonary disorders are associated with a decrease in alveolar O(2) tension and AEC need to develop adaptative mechanisms to cope with O(2) deprivation. Under hypoxia, because of inhibition of oxidative phosphorylation, adenosine triphosphate supply is dependent on the ability of cells to increase anaerobic glycolysis. In this study we show that under hypoxia, primary rat AEC maintained their energy status close to that of normoxic cells through increasing anaerobic glycolysis. We therefore examined the effect of hypoxia on glucose transport and evaluated the mechanisms of this regulation. Hypoxia induced a stimulation of Na-independent glucose transport, as shown by the increase in 2-deoxy-D-glucose (DG) uptake. This increase was dependent on time and O(2) concentration: maximal at 0% O(2) for 18 h, and reversible after hypoxic cells were allowed to recover in normoxia. Concomitantly, exposure of AEC to hypoxia (18 h 0% O(2)) induced a 3-fold increase of glucose transporter GLUT1 at both protein and messenger RNA (mRNA) levels. To determine whether the increase in GLUT1 mRNA level was dependent on O(2) deprivation per se or resulted from decrease of oxidative phosphorylation, we examined in normoxic cells the effects of cobalt chloride and Na azide, respectively. Cobalt chloride (100 microM) and Na azide (1 mM) increased both mRNA levels and DG uptake, mimicking the effect of hypoxia. Electrophoretic mobility shift assays revealed a hypoxic and a cobalt chloride induction of a hypoxia-inducible factor (HIF) that bound to the sequence of nucleotides, corresponding to a hypoxia-inducible element upstream of the GLUT1 gene. AEC also expressed this factor under nonhypoxic conditions. Together, our results demonstrate that AEC increased glucose transport in response to hypoxia by regulating GLUT1 gene-encoding protein. This regulation likely occurred at the transcriptional level through the activation of an HIF, the nature of which remains to be elucidated.

NaPO(4) cotransport type III (PiT1) expression in human embryonic kidney cells and regulation by PTH

The aim of the present study was to characterize the type(s) of NaPO(4) cotransporter expressed in the human renal cell line HEK-293 and its regulation by parathyroid hormone (PTH) in wild-type cells and in cells transfected by the PTH/PTH-related protein (PTHrP) receptor. The results showed that human embryonic kidney HEK-293 cells expressed NaPO(4) cotransporter type III (PiT1) mRNA and protein. In contrast, type I (NPT1) or II (NPT2) cotransporter mRNA were not expressed. Na(+)-dependent phosphate uptake followed a Michaelis-Menten model (apparent maximal transport rate and affinity constant: 23.32 +/- 0.69 nmol PO(4). mg protein(-1). 10 min(-1) and 0.147 +/- 0.014 mM KH(2)PO(4), respectively), was stimulated by phosphate deprivation (maximal increase 24.5 +/- 0.8%, P < 0.001, after 15 h of phosphate deprivation), and was inhibited by increasing pH (3.6 +/- 0.2-fold decrease at pH 8.5, P < 0.0001). It was inhibited in a time- and concentration-dependent fashion by PTH in HEK-293 cells stably transfected by PTH/PTHrP receptors but not in parental HEK-293 cells. Maximal inhibition of Na(+)-dependent phosphate transport was observed at 30 min after the addition of 72 nM PTH-(1-34) (31.5 +/- 2.4% inhibition, P < 0.01). PTH inhibition of phosphate transport was maintained in phosphate-deprived cells and reversed by both GF109203X (10(-6) M) or staurosporine (5.5 nM), two protein kinase C inhibitors. Na(+)-dependent phosphate uptake was also significantly inhibited by phorbol 12-myristate 13-acetate (20.9 +/- 3.9% inhibition, P < 0.001) but not by dibutyril-cAMP (10(-4) M) or forskolin (50 microM). The physiological role played by type III NaPO(4) cotransport expression in the overall renal regulation of phosphate homeostasis remains to be established.

Abnormal sulfate metabolism in vitamin D-deficient rats

To explore the possibility that vitamin D status regulates sulfate homeostasis, plasma sulfate levels, renal sulfate excretion, and the expression of the renal Na-SO4 cotransporter were evaluated in vitamin D-deficient (D-D-) rats and in D-D- rats rendered normocalcemic by either vitamin D or calcium/lactose supplementation. D-D- rats had significantly lower plasma sulfate levels than control animals (0.93+/-0.01 and 1.15+/-0.05 mM, respectively, P < 0.05), and fractional sulfate renal excretion was approximately threefold higher comparing D-D- and control rats. A decrease in renal cortical brush border membrane Na-SO4 cotransport activity, associated with a parallel decrease in both renal Na-SO4 cotransport protein and mRNA content (78+/-3 and 73+/-3% decreases, respectively, compared with control values), was also observed in D-D- rats. Vitamin D supplementation resulted in a return to normal of plasma sulfate, fractional sulfate excretion, and both renal Na-SO4 cotransport mRNA and protein. In contrast, renal sulfate excretion and renal Na-SO4 cotransport activity, protein abundance, and mRNA remained decreased in vitamin D-depleted rats fed a diet supplemented with lactose and calcium, despite that these rats were normocalcemic, and had significantly lower levels of parathyroid hormone and 25(OH)- and 1,25(OH)2-vitamin D levels than the vitamin D-supplemented groups. These results demonstrate that vitamin D modulates renal Na-SO4 sulfate cotransport and sulfate homeostasis. The ability of vitamin D status to regulate Na-SO4 cotransport appears to be a direct effect, and is not mediated by the effects of vitamin D on plasma calcium or parathyroid hormone levels. Because sulfate is required for synthesis of essential matrix components, abnormal sulfate metabolism in vitamin D-deficient animals may contribute to producing some of the abnormalities observed in rickets and osteomalacia.

Synthetic lipopeptides incorporated in liposomes: in vitro stimulation of the proliferation of murine splenocytes and in vivo induction of an immune response against a peptide antigen

Amphiphilic lipopeptides, such as Pam3CysAlaGly and Pam3CysSerSer, were synthesized and incorporated into liposomes, and their ability to induce the proliferation of BALB/c mouse splenocyte was tested in vitro. When compared to monophosphoryl lipid A (MPL) the following potency order was found: liposomal lipopeptides > liposomal MPL > free (emulsified) lipopeptides. These results strongly depend on the size of the vesicles used: a mitogenic effect was observed only with lipopeptides incorporated within vesicles of diameter < or = 100 nm while lipopeptides in larger vesicles (diameter approximately 300 nm) gave no response. This may be related to the necessity for the liposome-associated lipopeptides to be endocytosed to reach putative intracellular targets. As immunoadjuvanticity seems to be linked to B-lymphocyte activation, the lipopeptides represent attractive alternatives to MPL for the realization of completely synthetic liposome-based peptide vaccine formulations. This was borne out by showing that Pam3CysAlaGly and Pam3CysSerSer, when incorporated in small unilamellar vesicles carrying a covalently conjugated synthetic peptide of sequence IRGERA, corresponding to an epitope of the C-terminal region of histone H3, were able to induce a potent and long-lasting immune response.

Neutralization of bothropic and crotalic venom toxic activities by IgG(T) and IgGa subclasses isolated from immune horse serum

IgG(T) and IgGa isotypes were isolated from horse hyperimmune anti-bothropic and anti-crotalic sera using a combination of two affinity chromatographic processes. IgG(T) and IgGa isotypes were isolated from these sera by chromatography on protein A-Sepharose followed by separation of the two isotypes by chromatography on a column of anti-IgG(T)-Sepharose. LO-HoGT-1, a rat anti-horse IgG(T) monoclonal antibody, was used. A comparative study of the efficiency of these isotypes in neutralizing the main toxic activities of the homologous venoms was carried out. It was found that IgG(T) was about three-fold and seven-fold more protective than IgGa for neutralization of the lethal activity of B. jararaca and C. d. terrificus venoms, respectively. IgG(T) was also more effective than IgGa for the neutralization of the haemorrhagic activity induced by B. jararaca venom, while both isotypes neutralized equally well the blood incoagulability induced by this venom. The results suggest that IgG(T) is the most protective isotype present in both anti-bothropic and anti-crotalic sera, followed by IgGa. Owing to their very low concentration in the serum, other IgG isotypes are not likely to be important in neutralizing the venoms' toxic activities.

[Evaluation of the Cell-DYN 35))]

The Cell-Dyn 3500 is an automated haematology analyzer which quantitatively measures and computes haematological quantities including a full "five-part" white cell differential. It measures 22 parameters for erythrocytes, white blood cells and platelets, also giving the respective histograms. Evaluation of the Cell-Dyn 3500 was performed according to the International Committee for Standardization in Haematology (ICSH) norms, for a period of 5 weeks. A total of 1,235 samples were studied by comparison with the Coulter MaxM. The five-part white cell differential and the flagging system were estimated and compared with the smear examination of 506 samples, by four clinical pathologists trained in cytology. Good correlation was obtained within, between batches, and day-to-day, for the following parameters: red blood cells (RBC), haemoglobin (HGB), mean cell volume (MCV), white blood cells (WBC) and platelets (PLT). The accuracy was estimated (RBC, HGB, VGM, WBC and PLT) each day with three different levels of titrated controls with good results. The linearity was established for RBC, HGB, WBC and PLT. The results obtained were good. Carry-over studies were performed according to the Broughton method for the same parameters and the results were also good. Stability studies for the automatic parameters including the differential white blood cell count showed that these parameters were stable at 4 degrees C for 48 hours. At room temperature the stability was reduced to 7 hours. Agreement was good between the Cell-Dyn 3500 and the Coulter MaxM, for the automatic haemocytometric values. The comparative studies between the five-part white cell differential of the haematologic analyzer and the manual differential showed excellent results for neutrophils and lymphocytes, very good for monocytes and eosinophils. For the flag estimation two criteria were established, one based on the clinical significance and the other based on the alarm detection described in the analyzer manual. The specificity was good for both criteria. In general the sensibility was better for the second criteria. The Cell-Dyn 3500 has thus shown to be a good haematology analyser which greatly reduces the morphological examination of smears.

Expression of alternatively spliced isoforms of the parathyroid hormone (PTH)/PTH-related peptide receptor messenger RNA in human kidney and bone cells

Using a PCR-based strategy, two variants of the PTH/PTH-related peptide (PTH-rp) receptor mRNA were identified in human kidney, SaOS-2 human osteoblast cells, and rat bone that are produced by alternative splicing of exons coding for the N-terminal portion of the receptor. In the S-N3-E2 isoform, the exon coding the signal peptide (S) is spliced to an alternative 3'-acceptor site, producing a product respecting the reading frame, but in which the E1 exon is replaced by 12 amino acids derived from the N3 intron. In the S-E2 isoform, in which the E1 exon is deleted by cassette exclusion, the reading frame is changed, but a truncated receptor may be produced by reinitiation of translation at an overlapping stop/start codon. After transfection of COS and Chinese hamster ovary cells with the originally described S-E1-E2 isoform and the two splice variants, active transcription of PTH/PTH-rp receptor mRNA was detected by RT-PCR in all cases. Cell lines transfected with the S-E1-E2 and S-N3-E2 isoforms displayed a 15- to 25-fold and 2- to 3-fold increase, respectively, in cAMP content after stimulation with 2.4 x 10(-7) M human PTH(1-34), whereas cells transfected with the S-E2 isoform did not respond. PTH elicited an increase in intracellular calcium only in cells transfected with the S-E1-E2 isoform. Studies evaluating the surface expression of receptors using anti-human PTH/PTH-rp receptor antibodies and the ability of transfected cells to bind [125I]PTH-rp indicated that the low or absent responses to PTH stimulation resulted, at least in part, from low surface expression of the S-N3-E2 and S-E2 isoforms. These studies support the conclusion that exon E1 is extremely important in promoting surface expression of the PTH/PTH-rp receptor but indicate that isoforms lacking this exon can retain the ability to recognize PTH. The possible intracellular expression of these splice variants, which account for 15-20% of total PTH/PTH-rp receptor mRNA, needs to be evaluated.

Antigenic cross-reactivity among components of Brazilian Elapidae snake venoms

Snake venoms from M. corallinus (LD50 = 7.1 +/- 0.83 micrograms), M. frontalis (LD50 = 19.3 +/- 3.13 micrograms), M. ibiboboca (LD50 = 19.8 +/- 2.07 micrograms) and M. spiixi (LD50 = 6.7 +/- 1.25 micrograms) (family Elapidae, genus Micrurus) injected into horses alone or in combination (M. corallinus with M. frontalis) elicit antibody production, as indicated in vivo by neutralization of venom lethality and in vitro by enzyme-linked immunosorbent assay (ELISA), immunoelectrophoresis (IE) and Western blotting (WB). Venom lethality was efficiently neutralized by the antisera, with the monovalent antivenoms being more efficient than the bivalent antivenom. Antibodies against venom components were detected by all antisera at different titers by ELISA. Upon IE, antisera against M. spiixi and M. frontalis venoms cross-reacted with the four types of venoms studied and recognized several molecular components, the precipitin lines obtained had distinct intensities and electrophoretic motilities, whereas the antivenom against M. corallinus only recognized components of its venom but not of the others. All antivenoms cross-reacted with all the elapid venoms in WB revealing several bands with distinct MWs in M. corallinus and M. spiixi venoms, two very sharp and separate bands in M. corallinus venom and a very sharp band of high MW together with several other smaller and faint bands in M. frontalis venom. The data indicate that snake venoms of the genus Micrurus are good immunogens that contain many cross-reactive molecules, and that their toxic components are neutralized more effectively by monovalent rather than by bivalent antivenom.

A rapid and efficient purification method for horse IgG(T) using a rat monoclonal antibody

1. Louvain rats (IgK-1a) were immunized with horse IgG(T). To generate mAb to IgG(T), popliteal lymph node cells taken from the immunized animals were fused to a non-secreting LOU/C immunocytoma (IR983F). The hybridomas were cultured in HAT-containing medium and cloned under limiting dilution conditions. Supernatants from the growing hybrids were screened by ELISA using plates coated with horse IgG(T) or IgGa+b+c. 2. The anti-IgG(T) mAb obtained was named LO-HoGT-1 (LOU anti-horse IgG(T)). It is an IgG2a rat antibody whose light chain allotype is IgK-1a, and with an affinity constant of 2.9 x 10(10) M-1. 3. Ascites was induced in LOU (IgK-1b) rats by injecting the hybridoma cells and incomplete Freund's adjuvant ip. To obtain purified mAb, ascitic fluid was applied to a Sepharose anti-rat LOU IgK-1a chain column. 4. The purified mAb was then coupled to Sepharose. Immunoelectrophoretically pure IgG(T) was obtained by passage of horse serum through this column. The entire procedure took less than 30 min and resulted in a highly purified IgG(T).

Selective induction of protection against influenza virus infection in mice by a lipid-peptide conjugate delivered in liposomes

We have previously reported (Muller et al. Vaccine 1990, 8, 308) that two cyclic peptide analogues called D loop and K loop, corresponding to residues 139-147 in site A of the haemagglutinin (HA) of influenza A virus (strain X31), were both able to provide protective immunity to infected OF1 mice when administered in the form of peptide-ovalbumin conjugates. The predicted conformation of the D loop is nearly identical to that of the native loop known from the X-ray structure of HA, while the predicted conformation of the K loop differs significantly from the native one. In this study, the two peptides were conjugated to small unilamellar liposomes, thus creating a chemically defined immunogen, and OF1 mice were immunized with these liposomes containing monophosphoryl lipid A as adjuvant. Compared with protein carrier systems, the liposomal preparations are completely synthetic and avoid the use of Freund's adjuvant. By using liposomes associated with the D loop, we were able to achieve 70% protection of the mice against intranasal challenge with the influenza virus while no protection was obtained with the liposome-associated K loop. The difference in effect between the two liposome and ovalbumin carrier systems may result from the induction of different structures in the peptides when coupled to lipid anchors than when coupled to proteins.

Isolation of IgGT from hyperimmune horse anti-snake venom serum: its protective ability

Hyperimmune horse anti-bothropic serum, used in serum therapy, was analyzed for its IgGT content and protective ability. IgGT was isolated through a combination of salt-mediated hydrophobic chromatography and protein A affinity chromatography. The chromatographic fractions obtained were analyzed with regard to their isotype content and protective ability. The results suggest that the protective ability of hyperimmune anti-venom serum is located mainly in the IgGT subclass.

Kinetics of class II MHC expression on cytotoxic T cells generated by skin allograft

In the present work the kinetics of class II MHC expression on OX8+ lymphocytes generated by skin allograft and its relationship to the lytic activity were studied. Mononuclear cells from the spleen of LEW (RT1(1) rats bearing BN (RT1n) skin graft for 3, 5 or 7 days were sorted out by sequential immune affinity using columns of Degalan-V26 beads treated with anti-rat or anti-mouse Ig. After depletion of B cells, T cells were precoated with W3/25 MoAb (anti-CD4 equivalent) and sorted out using an anti-mouse Ig column. The W3/25-/OX8+ cells (CD8 equivalent) were then coated with OX4 MoAb (anti-RT1.B) or murine A.TH anti-A.TL alloantiserum (anti I-E, cross-reacts with RT1.D) and were passed through a new anti-mouse Ig column in order to obtain the four subpopulations, RT1.B+, .B-, .D+ and .D-. Their specific lytic activity against BN Con A-stimulated cells increased from the 3rd to the 7th d after the skin graft. The lytic activity observed on the 3rd and 5th d was associated with all four subpopulations analyzed. In contrast, on the 7th d, the lytic activity was concentrated in the RT1.B+ subpopulation. These results, associated with the increase in the number of OX8+/RT1.B+ cells along with days after graft, suggest that RT1.B expression is not essential but is associated with the effectiveness of the cytotoxic activity. It is also possible that RT1.B expression is a marker of cytotoxic T-cell differentiation.

[Effects of barbexaclone in Lennox-Gastaut syndrome]

The Lennox-Gastaut syndrome has been a source of interest for many workers both from a clinical and electroencephalographic view point. Treatment has always posed problems. Without suggesting an ideal medication for this syndrome, the authors have obtained good results with barbexaclone. Taking into consideration the convulsive manifestations, psychic changes and electroencephalographic details as parameters the therapeutic efficacy of this drug was studied in seven cases.

[Re-evaluation of barbexaclone in 20 epileptic patients]

The clinically observed results in 20 patients treated with barbexaclone for a period of 2 1/2 years are reported. Therapeutic efficiency as well as side effects are discussed. The authors draw attention to the fact that there was a concomitant improvement in the behaviour of some patients and a diminution of maintainence dosage in relation to a previously published trial.

[Clinical trial with barbexaclone in epilepsies]

A open clinic assay with barbexaclone which is an association of phenobarvital with light stimulant of the central nervous system (tau-l-ciclohexil-2-methil-aminopropane) for the treatment of epileptic disorders is reported. The authors have studied 40 patients aged between 0-12 years of age, of both sexes, all of them having convulsive seizures of the Grand Mal type associated or not to other epileptic manifestations. After analysing the different aspects of the group they consider satisfactory the results obtained: very good or good in 82,5% of the cases.