Biomedical subjects

S Grinstein

Publications and source records attributed to S Grinstein.

At least 181 records · Page 10Linked to original sources

PubMed1992

Phorbol ester-induced actin assembly in neutrophils: role of protein kinase C.

The shape changes and membrane ruffling that accompany neutrophil activation are dependent on the assembly and reorganization of the actin cytoskeleton, the molecular basis of which remains to be clarified. A role of protein kinase C (PKC) has been postulated because neutrophil activation, with the attendant shape and membrane ruffling changes, can be initiated by phorbol esters, known activators of PKC. It has become apparent, however, that multiple isoforms of PKC with differing substrate specificities exist. To reassess the role of PKC in cytoskeletal reorganization, we compared the effects of diacylglycerol analogs and of PKC antagonists on kinase activity and on actin assembly in human neutrophils. Ruffling of the plasma membrane was assessed by scanning EM, and spatial redistribution of filamentous (F)-actin was assessed by scanning confocal microscopy. Staining with NBD-phallacidin and incorporation of actin into the Triton X-100-insoluble ("cytoskeletal") fraction were used to quantify the formation of (F)-actin. [32P]ATP was used to detect protein phosphorylation in electroporated cells. Exposure of neutrophils to 4 beta-PMA (an activator of PKC) induced protein phosphorylation, membrane ruffling, and assembly and reorganization of the actin cytoskeleton, whereas the 4a-isomer, which is inactive towards PKC, failed to produce any of these changes. Moreover, 1,2-dioctanoylglycerol, mezerein, and 3-(N-acetylamino)-5-(N-decyl-N-methylamino)-benzyl alcohol, which are nonphorbol activators of PKC, also promoted actin assembly. Although these effects were consistent with a role of PKC, the following observations suggested that stimulation of conventional isoforms of the kinase were not directly responsible for actin assembly: (a) Okadaic acid, an inhibitor of phosphatases 1 and 2A, potentiated PMA-induced protein phosphorylation, but not actin assembly; and (b) PMA-induced actin assembly and membrane ruffling were not prevented by the conventional PKC inhibitors 1-(5-isoquinolinesulfonyl)-2-methylpiperazine, staurosporine, calphostin C, or sphingosine at concentrations that precluded PMA-induced protein phosphorylation and superoxide production. On the other hand, PMA-induced actin assembly was inhibited by long-chain fatty acid coenzyme A esters, known inhibitors of nuclear PKC (nPKC). We conclude that PMA-induced actin assembly is unlikely to be mediated by the conventional isoforms of PKC, but may be mediated by novel isoforms of the kinase such as nPKC.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1992

Participation of immune complexes in adenovirus infection.

To determine the participation of immune complexes during adenovirus infection, we evaluated serum and necropsy specimens of patients with confirmed adenovirus infection of the lower respiratory tract. In lung and kidney from seven dead patients, immunofluorescence revealed the presence of hexon, immunoglobulins and complement. These patients had clinical manifestations of kidney dysfunction. In dead patients (3/3 in whom serum was available) neither anti-adenovirus antibodies nor adenovirus-specific immune complexes could be found in the final stage of the infection. However, two of these patients had anti-adenovirus antibodies and immune complexes in samples obtained early in the infection. Most patients (16/19) who survived the infection had circulating anti-adenovirus antibodies. Half also had immune complexes specific for adenovirus in some moment of the illness. This suggests that immune complexes arise during respiratory infection by adenovirus, probably contributing to its clinical picture.

Adenovirus Infections, Human↗

PubMed1992

Modulation of neutrophil activation by okadaic acid, a protein phosphatase inhibitor.

We determined the effects of okadaic acid (OA), a specific inhibitor of protein phosphatases 1 (PP1) and 2A (PP2A), on protein phosphorylation and on the activation of the NADPH oxidase in human neutrophils. In otherwise unstimulated cells, OA induced phosphoprotein accumulation, revealing the presence of constitutively active protein kinases. Pulse-chase experiments in electropermeabilized cells confirmed that this effect was due, at least in part, to inhibition of dephosphorylation. OA potentiated phosphoprotein accumulation induced by phorbol esters and by the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP). In phorbol ester-stimulated cells, OA prolonged the respiratory response after inhibition of protein kinase C (PKC) with staurosporine, consistent with a reduced rate of dephosphorylation of active phosphorylated components. Similarly, OA delayed the inactivation of the burst after displacement of FMLP from its receptor by a competitive antagonist. This suggests that the substrates of the protein kinases activated by FMLP are dephosphorylated by PP1 and/or PP2A. That phosphatases control the intensity and duration of the respiratory response is suggested by the finding that OA magnified and prolonged the oxidative burst elicited by FMLP. In contrast, pretreatment with OA produced a time-dependent inhibition of the phorbol ester-induced respiratory burst. Under conditions where inhibition of the phorbol ester response was nearly complete, activation by the chemoattractant peptide not only persisted but was in fact accentuated. These findings provide strong evidence that receptor-mediated stimulation of the NADPH oxidase can occur by pathways not involving PKC.

Cell Membrane Permeability↗

PubMed1992

Activation of permeabilized neutrophils: role of anions.

Activation of neutrophils was recently reported to be accompanied by large changes in their Cl- content [J. B. Myers, H. F. Cantiello, J. H. Schwartz, and A. I. Tauber. Am. J. Physiol. 259 (Cell Physiol. 28): C531-C540, 1990]. The significance of these ionic changes to the immune response has not been studied. To evaluate the role of intracellular [Cl-], the anionic composition of the cytosol was varied in human neutrophils permeabilized by electroporation or by treatment with streptolysin O. In Cl(-)-rich media, permeabilized but otherwise untreated cells remained quiescent, resembling unstimulated intact cells. In contrast, suspension of permeabilized cells in Cl(-)-depleted media elicited protein phosphorylation, actin polymerization, secretion of lysozyme, and a respiratory burst. The latter was demonstrated by several criteria to be mediated by the NADPH oxidase. The responses observed in Cl(-)-depleted media were insensitive to pretreatment of the cells with pertussis toxin but were inhibited by addition of GDP or by omission of ATP. The data suggest that an early event in signal transduction, common to several effectors, is sensitive to the ionic composition of the cytosol. This component, possibly a GTP-binding protein, may be affected by the anion concentration changes reported to occur during physiological stimulation of neutrophils.

Anions↗

PubMed1992

V-ATPases in phagocytic cells.

V-ATPases in phagocytic cells are known to mediate the acidification of most intracellular organelles. Proton-pump-mediated acidification of these organellar compartments is vital to numerous cell processes, including receptor recycling, protein processing and sorting and microbial degradation. Recent studies have suggested a role for V-ATPases in cytoplasmic pH homeostasis. The present discussion will review the current knowledge regarding the presence of V-ATPases in both the plasmalemmal and organellar membranes of phagocytic cells, the regulation of proton pump activity in these locations and the functional significance of pump-mediated proton translocation.

Adenosine Triphosphatases↗

PubMed1992

Detection of soluble exoantigens of Trypanosoma cruzi by a dot-immunobinding assay.

A simple and highly sensitive assay for the detection of Trypanosoma cruzi antigens by spotting samples on nitrocellulose membrane filters is described. The immobilized antigens are analyzed by subsequent binding of specific anti-T. cruzi immunoglobulins and secondary enzyme-labeled antibodies. Trypomastigote exoantigens were determined by this technique in the supernatant from cell cultures two days after infection. The T. cruzi circulating antigens present in serum specimens collected from mice infected with the parasite were demonstrable by day 3 of infection, when the parasitemia was still low. Antigenemia was also demonstrable by the dot-immunobinding assay in 14 of 16 congenitally infected patients. No cross-reactivity was observed using sera from healthy individuals, as well as from patients with other related parasitoses. The assay proved to be easy to perform and requires only small volumes of samples.

Animals↗

PubMed1992

Effect of DNA concentration on recombinant plasmid recovery after blunt-end ligation.

We describe conditions for optimal recovery of recombinant plasmids after blunt-end ligation. It was found that one of the most critical parameters of the blunt-end ligation reaction is total DNA concentration (vector plus incoming DNA). This concentration was optimal in the range of 1-5 micrograms/ml of reaction mixture. Concentrations larger than 10 micrograms/ml result in strong inhibition. The optimal molar relationship between incoming DNA and vector was found to be 1 or less. Under these conditions, using dephosphorylated vector, recombinants are generated at a frequency of 10(6) colonies per microgram of insert, provided that transforming efficiency is about 5 x 10(7) colonies per microgram of plasmid DNA.

Chemical Phenomena↗

PubMed1991

Determinants of the phagosomal pH in macrophages. In situ assessment of vacuolar H(+)-ATPase activity, counterion conductance, and H+ "leak".

We studied the factors that determine the intraphagosomal pH (pHp) in elicited murine peritoneal macrophages. pHp was measured in situ by recording the fluorescence of covalently fluoresceinated Staphylococcus aureus ingested by the macrophages. Following spontaneous acidification of the phagosomes, passive (leak) H+ permeability was determined measuring the rate of change of pHp upon complete inhibition of the H+ pump with bafilomycin A1. A significant, but comparatively low passive H+ permeability was detected. The existence of a passive H+ leak implies that continuous energy expenditure is required for the maintenance of an acidic pHp. In combination with ionophores, bafilomycin was also used to estimate the counterion permeability. The counterion conductance was found to be severalfold higher than the H+ leak. Ion substitution experiments in electropermeabilized cells and the inhibitory effects of quinine and 5-nitro-2-(3-phenylpropylamino)benzoic acid suggest that both monovalent anions and cations permeate the phagosomal membrane. The activity of the H+ pump was measured at various pHp levels. In the steady state, the rate of H+ pumping was considerably lower than counterion permeation. These findings suggest that the phagosomal membrane potential is insignificant. Consistent with this notion, increasing phagosomal conductance with ionophores failed to accelerate the rate of H+ pumping. Thus, the transmembrane delta pH is the predominant component of the proton-motive force across the phagosomal membrane in the steady state. The rate of H+ pumping was found to decrease steeply as the phagosomal lumen became acidified. Therefore, the pH sensitivity of the H+ pump, which possibly reflects a kinetic or allosteric effect, is the primary determinant of pHp.

Animals↗

PubMed1991

Protein kinase C activates an H+ (equivalent) conductance in the plasma membrane of human neutrophils.

The rate of metabolic acid generation by neutrophils increases greatly when they are activated. Intracellular acidification is prevented in part by Na+/H+ exchange, but a sizable component of H+ extrusion persists in the nominal absence of Na+ and HCO3-. In this report we determined the contribution to H+ extrusion of a putative H+ conductive pathway and its mode of activation. In unstimulated cells, H+ conductance was found to be low and unaffected by depolarization. An experimental system was designed to minimize the metabolic acid generation and membrane potential changes associated with neutrophil activation. By using this system, beta-phorbol esters were shown to increase the H+ (equivalent) permeability of the plasma membrane. The direction of the phorbol ester-induced fluxes was dictated by the electrochemical H+ gradient. Moreover, the parallel migration of a counterion through a rheogenic pathway was necessary for the displacement of measurable amounts of H+ equivalents across the membrane. These findings suggest that the H+ flux is conductive. The effect of beta-phorbol esters was mimicked by diacylglycerol and mezerein and was blocked by staurosporine, whereas alpha-phorbol esters were ineffective. Together, these findings indicate that stimulation of protein kinase C induces the activation of an H+ conductance in the plasma membrane of human neutrophils. Preliminary evidence for activation of a separate, bafilomycin A1-sensitive H+ extrusion mechanism, likely a vacuolar type H(+)-ATPase, is also presented.

Alkaloids↗

PubMed1991

Coupling between intracellular Ca2+ stores and the Ca2+ permeability of the plasma membrane. Comparison of the effects of thapsigargin, 2,5-di-(tert-butyl)-1,4-hydroquinone, and cyclopiazonic acid in rat thymic lymphocytes.

The regulation of Ca2+ uptake by receptors is incompletely understood. It has been proposed that the Ca2+ permeability of the plasma membrane increases in response to depletion of a critical intracellular Ca2+ storage compartment (Takemura, H., Hughes, A. R., Thastrup, O., and Putney, J. W. (1989) J. Biol. Chem. 264, 12266-12271). This hypothesis is based largely on the effect of thapsigargin, an inhibitor of endomembrane CA(2+)-ATPases. Due to the existence of an endogenous leak, inhibition of Ca2+ uptake by thapsigargin induces depletion of the stores. This is accompanied by increased plasmalemmal Ca2+ permeability, without change in the level of inositol phosphates. On the other hand, depletion of the intracellular stores by 2,5-di(tert-butyl)-1,4-hydroquinone (BHQ), a chemically unrelated inhibitor of the Ca(2+)-ATPases, fails to induce Ca2+ influx (Kass, G. E., Duddy, S. K., Moore, G. A., and Orrenius, S. (1989) J. Biol. Chem. 264, 15192-15198). In an attempt to reconcile these observations, we analyzed in lymphocytes the mode of action of thapsigargin and BHQ. In addition, we tested the effects of cyclopiazonic acid (CPA), a blocker of the skeletal muscle sarcoplasmic reticulum Ca(2+)-ATPase. All three compounds released Ca2+ from a common intracellular compartment. Thapsigargin and low concentrations of BHQ and CPA concomitantly elevated the plasmalemmal Ca2+ permeability. Higher concentrations of BHQ and CPA produced a secondary inhibition of the Ca2+ entry pathway, by a mechanism seemingly unrelated to their effects on the internal stores. This inhibitory side effect can account for the reported discrepancies between the effects of thapsigargin and BHQ. The data provide further support for the notion that endomembrane Ca2+ stores are functionally coupled to the plasma membrane Ca2+ permeability pathway.

Animals↗

PubMed1991

Nitric oxide derived from L-arginine impairs cytoplasmic pH regulation by vacuolar-type H+ ATPases in peritoneal macrophages.

The ability of macrophages (Møs) to function within an acidic environment has been shown to depend on cytoplasmic pH (pHi) regulation by vacuolar-type H+ ATPases. Møs metabolize L-arginine via an oxidative pathway that generates nitric oxide, nitrate, and nitrite. Since each of these products could potentially inhibit vacuolar-type H+ ATPases, we investigated the effect of L-arginine metabolism on Mø pHi regulation in thioglycolate-elicited murine peritoneal Møs. H+ ATPase-mediated pHi recovery from an imposed cytoplasmic acid load was measured fluorometrically. When Møs were incubated with L-arginine (0.25-2.0 mM), their rate of pHi recovery declined progressively from 2 to 6 h of incubation. By contrast, the recovery rate of cells incubated in arginine-free medium remained stable over the same period. The impairment of pHi recovery was specific for L-arginine, and was blocked competitively by NG-monomethyl-L-arginine, demonstrating its dependence on L-arginine metabolism. In addition, the inhibition of pHi recovery was enhanced by lipopolysaccharide, an agent known to stimulate L-arginine metabolism by Møs. Scavenging the L-arginine metabolite nitric oxide with either ferrous sulphate or ferrous myoglobin prevented the inhibition of pHi recovery, implying that L-arginine-derived nitric oxide was the species responsible for the inhibition. This concept was supported by the finding of elevated nitrite levels in the supernatant of cells incubated in L-arginine. Furthermore, incubation of Møs with sodium nitroprusside mimicked the L-arginine-dependent inhibition of H+ ATPase activity. Treatment with the cyclic GMP analogue, 8-bromoguanosine 3':5'-cyclic monophosphate, similarly impaired Mø pHi recovery, suggesting that a nitric oxide-stimulated elevation of cyclic GMP may contribute to the L-arginine-dependent inhibition of pHi regulation.

Acid-Base Equilibrium↗

PubMed1991

The chloride channel blocker 5-nitro-2-(3-phenylpropyl-amino) benzoic acid (NPPB) uncouples mitochondria and increases the proton permeability of the plasma membrane in phagocytic cells.

We present evidence that the potent chloride channel blocker NPPB has protonophoric activity in the mitochondria and across the plasma membrane of phagocytic cells. The resting O2 consumption of murine peritoneal macrophages was stimulated up to 2.5-fold in the presence of NPPB, with a K0.5 of 15 microM. The stimulatory effect of NPPB on O2 consumption, like that of the classical protonophore CCCP, was prevented by the mitochondrial respiratory chain inhibitors antimycin A, rotenone or cyanide. NPPB also mediated rheogenic proton transport across the plasma membrane of human neutrophils and macrophages in the direction dictated by the electrochemical proton gradient. As a consequence of its protonophoric activity, NPPB uncoupled mitochondrial ATP synthesis, resulting in partial depletion of cellular ATP. These observations indicate that, at the concentrations frequently used for blockade of anion channels, NPPB acts as an effective protonophore, potentially disturbing cytosolic pH and mitochondrial ATP synthesis.

Adenosine Triphosphate↗

PubMed1991

Okadaic acid, a phosphatase inhibitor, induces activation and phosphorylation of the Na+/H+ antiport.

We determined the effect of okadaic acid (OA), a potent phosphoprotein phosphatase inhibitor, on the intracellular pH (pHi) of rat thymic lymphocytes and human bladder carcinoma cells. OA induced a rapid and sustained cytosolic alkalinization. This pHi increase was Na(+)-dependent and was inhibited by 5,N-disubstituted analogs of amiloride, indicating mediation by the Na+/H+ antiport. As described for other stimulants, such as mitogens and hypertonic challenge, activation of the antiport by OA is attributable to an upward shift in its pHi dependence. Accordingly, the alkalinization produced by the phosphatase inhibitor was not additive with that induced osmotically. Activation of the antiport by OA was accompanied by a marked increase in phosphoprotein accumulation, revealing the presence of active protein kinases in otherwise unstimulated cells. We considered the possibility that phosphorylation of the antiport itself or of an ancillary protein is responsible for activation of Na+/H+ exchange. Consistent with this notion, the alkalinization induced by OA was absent in ATP depleted cells. More importantly, immunoprecipitation experiments demonstrated increased phosphorylation of the antiport following treatment with OA. We conclude that, upon inhibition of phosphoprotein phosphatase activity, constitutively active kinases induce the activation of Na+/H+ exchange, possibly by direct phosphorylation of the antiport.

Adenosine Triphosphate↗

PubMed1991

Mechanism of vanadate-induced activation of tyrosine phosphorylation and of the respiratory burst in HL60 cells. Role of reduced oxygen metabolites.

Vanadate induces phosphotyrosine accumulation and activates O2 consumption in permeabilized differentiated HL60 cells. NADPH, the substrate of the respiratory burst oxidase, was found to be necessary not only for the increased O2 consumption, but also for tyrosine phosphorylation. The effect of NADPH was not due to reduction of vanadate to vanadyl. Instead, NADPH was required for the synthesis of superoxide, which triggered the formation of peroxovanadyl [V(4+)-OO] and vanadyl hydroperoxide [V(4+)-OOH]. One or both of these species, rather than vanadate itself, appears to be responsible for phosphotyrosine accumulation and activation of the respiratory burst. Accordingly, the stimulatory effects of vanadate and NADPH were abrogated by superoxide dismutase. Moreover, phosphorylation was activated in the absence of NADPH by treatment with V(4+)-OO and/or V(4+)-OOH, generated by treatment of orthovanadate with KO2 or H2O2 respectively. The main source of the superoxide involved in the formation of V(4+)-OO and V(4+)-OOH is the NADPH oxidase. This was shown by the inhibitory effects of diphenylene iodonium and by the failure of undifferentiated cells, which lack oxidase activity, to undergo tyrosine phosphorylation when treated with vanadate and NADPH. By contrast, exogenously generated V(4+)-OO induced marked phosphorylation in the undifferentiated cells, demonstrating the presence of the appropriate tyrosine kinases and phosphatases. A good correlation was found to exist between induction of tyrosine phosphorylation and activation of the respiratory burst, suggesting a causal relationship. Therefore an amplification cycle appears to exist in cells treated with vanadate, whereby trace amounts of superoxide initiate the formation of V(4+)-OO and/or V(4+)-OOH. These peroxides promote phosphotyrosine formation, most likely by inhibition of tyrosine phosphatases. Accumulation of critical tyrosine-phosphorylated proteins then initiates a respiratory burst, with abundant production of superoxide. The newly formed superoxide catalyses the formation of additional V(4+)-OO and/or V(4+)-OOH, thereby magnifying the response. Since vanadium derivatives are ubiquitous in animal tissues, V(4+)-OO and/or V(4+)-OOH could be formed in vivo by reduced O2 metabolites, becoming potential endogenous tyrosine phosphatase inhibitors. Because of their potency, peroxides of vanadate may be useful as probes for the study of protein phosphotyrosine turnover.

Granulocytes↗

PubMed1991

The role of intracellular Ca2+ in the regulation of the plasma membrane Ca2+ permeability of unstimulated rat lymphocytes.

The mechanism responsible for the increase in cytosolic free Ca2+ concentration ([Ca2+]i) during mitogenic stimulation of lymphocytes has been widely investigated. By contrast, little is known about the processes underlying Ca2+i homeostasis in resting (unstimulated) cells. It has been suggested that [Ca2+]i is an important determinant of the rate of Ca2+ influx following mitogenic activation. Using rat thymic lymphocytes, we investigated whether the resting influx pathway is similarly controlled by [Ca2+]i. Otherwise untreated cells were Ca(2+)-depleted by loading with Ca2+ chelators while suspended in Ca(2+)-free solution. Ca2+ depletion induced an 8-fold increase in the rate of unidirectional Ca2+ uptake. The depletion-activated flux was voltage-sensitive and was blocked by La3+ and by compound SK&F 96365, a receptor-operated Ca2+ channel blocker. Upon reintroduction to Ca(2+)-containing solution, the increased influx brought about a rapid recovery of [Ca2+]i. Detailed analysis of the magnitude of the 45Ca2+ flux during this recovery indicated that [Ca2+]i is not the primary determinant of the plasmalemmal Ca2+ permeability. Instead, depletion of an internal thapsigargin-sensitive store correlates with and appears to be responsible for the increased permeability of the plasma membrane. Accordingly, the Ca2+ fluxes induced by intracellular Ca2+ depletion and by thapsigargin were pharmacologically indistinguishable. Mitogenic lectins also released Ca2+ from a thapsigargin-sensitive store and activated a plasmalemmal Ca2+ permeability displaying identical pharmacology. The data support the existence of a coupling process whereby the degree of filling of an internal Ca2+ store dictates the Ca2+ permeability of the plasma membrane. This coupling mechanism is important not only in mediating the effects of mitogens and other agonists, as suggested before, but seemingly also in the control of resting Ca2+i homeostasis in unstimulated cells.

Aminoquinolines↗

PubMed1991

Regulation of cytoplasmic pH in phagocytic cell function and dysfunction.

To ensure effective antimicrobial or tumouricidal function, phagocytic cells must maintain their cytoplasmic pH (pHi) at a level conductive to optimal intracellular enzyme activity. The mechanisms by which neutrophils and macrophages regulate their cytoplasmic pH include bicarbonate-independent ion transport systems, most notably the Na+/H+ exchanger, and bicarbonate-dependent ion transport systems, which can be subdivided into the cation-independent and Na(+)-dependent forms of chloride/bicarbonate exchange. In addition, macrophages have been shown to recover from intracellular acid loading by means of an ATP-dependent proton extrusion mechanism, which has the characteristics of a vacuolar-type H+ ATPase. In the microenvironment typically associated with abscesses, the low extracellular pH and the presence of short chain fatty acid by-products of bacterial metabolism tend to induce cytoplasmic acid loading. In this setting, the ability of the various pHi regulatory mechanisms to protect pHi may be overcome, leading to cytoplasmic acidification. Several investigators have shown that cytoplasmic acidification impairs the ability of neutrophils to migrate in response to chemotactic stimuli, and also impairs their ability to generate a respiratory burst, thus inhibiting the release of toxic oxygen radicals. This may result in the inability of phagocytes to effect complete abscess resolution.

Abscess↗

PubMed1991

Evidence of infection with organisms producing Shiga-like toxins in household contacts of children with the hemolytic uremic syndrome.

We conducted a prospective study in 87 household contacts of 51 children with hemolytic uremic syndrome to determine the frequency of infection with Shiga-like toxin-producing bacteria. Gastrointestinal tract symptoms occurred in only 1 of 87 contacts. Free fecal toxin was detected in 25 of 64 (39%) of the household members. Neutralization with specific antisera to Shiga-like toxins I and II (SLT-I, SLT-II) revealed that in 6 of these household contacts only SLT-I was present in stool, in 10 only SLT-II was present and in 9 both toxins were found. Thirty-three percent of the hemolytic uremic syndrome families in which 2 or more members were studied had more than 1 household member with free fecal toxin in stool. None of the household contacts was found to have E. coli O157:H7 in feces. Serum samples were available in 77 household contacts; 75% (58 of 77) had serum neutralizing titers of greater than or equal to 1:4 to 1 or both toxins. In those contacts for whom paired sera were available, seroconversion was found in 10 of 24 (42%). These data show that household contacts of children with hemolytic uremic syndrome are commonly colonized with Shiga-like toxin-producing E. coli and seroconversion to Shiga-like toxins occurs frequently in family members of children with hemolytic uremic syndrome.

Adult↗

PubMed1991

Presence and integration of human papillomavirus type 6 in a tonsillar carcinoma.

Human papillomavirus type 6 subtype a (HPV-6a) was detected in a human invasive tonsillar carcinoma. Southern blot hybridization analysis showed the presence of additional bands when using non-cutting and single-cut restriction enzymes. Molecular cloning yielded two recombinant clones of 8.0 and 1.4 kb in size. The first represents the complete HPV-6a genome. Sequence analysis of the second clone showed a 0.6 kb DNA sequence corresponding to the L2 region of HPV-6a, whereas the rest belongs to cellular sequences. These data show the presence of a usually low risk HPV type in an invasive carcinoma, at an unusual infection site, with viral DNA integrated into the host genome. These findings add evidence in support of the hypothesis of a relationship between HPV infection and at least some ororespiratory cancers.

Base Sequence↗