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Biomedical subjects

S Strobel

Publications and source records attributed to S Strobel.

At least 55 records · Page 3Linked to original sources
PubMed1995

Interaction of SecB with intermediates along the folding pathway of maltose-binding protein.

SecB, a molecular chaperone involved in protein export in Escherichia coli, displays the remarkable ability to selectively bind many different polypeptide ligands whose only common feature is that of being nonnative. The selectivity is explained in part by a kinetic partitioning between the folding of a polypeptide and its association with SecB. SecB has no affinity for native, stably folded polypeptides but interacts tightly with polypeptides that are nonnative. In order to better understand the nature of the binding, we have examined the interaction of SecB with intermediates along the folding pathway of maltose-binding protein. Taking advantage of forms of maltose-binding protein that are altered in their folding properties, we show that the first intermediate in folding, represented by the collapsed state, binds to SecB, and that the polypeptide remains active as a ligand until it crosses the final energy barrier to attain the native state.

ATP-Binding Cassette Transporters↗
PubMed1995

Effect of heparin anticoagulation on neutrophil adhesion molecules and release of IL8: C3 is not essential.

OBJECTIVE: To examine the role of heparin in modulating neutrophil activation and release of cytokine. BACKGROUND: Up-regulation of CD11b, down-regulation of L-selectin on neutrophil cell surface and release of IL8 occur in response to extracorporeal circulation (ECC) and were proposed to cause leakage of the capillaries in patients. DESIGN: In a series of experiments, we examined the effect of heparin (4 U/ml) comparing it with ethylenediamine tetra-acetate (EDTA, 1.5 mg/ml) and citrate mixture (100 microliters/ml), heparin dose-response, IL8 (human recombinant IL8) dose-response and protamine (80 micrograms/ml) neutralisation of heparin (4 U/ml) using donor blood (total of 38). The role of complement component type 3 (C3) was tested. Neutrophils from a patient with complete C3 deficiency were stimulated by using heparin and cobra venom factor (10 micrograms/ml) and compared with controls (n = 5). CD11b and L-selectin expressions were assayed immediately and serially up to 120 min using immune fluorescence and flow cytometry. Serum concentrations of IL8 were determined by using enzyme-linked immunosorbent assay. RESULTS: The medians of up-regulation of CD11b were 540.2 (range 235.2-653.3) for heparin vs. 186.5 (55.7-207.1) for EDTA and 192.5 (69.2-263.8) for citrate mixture, P < 0.01. The medians of down-regulation of L-selectin were 79 (32-192) for heparin vs. 18.4 (0-188) for EDTA and 36.2 (7.4-135) for citrate mixture, P < 0.05. Up-regulation of CD11b, down-regulation of L-s and release of IL8 were inversely related to heparin concentration (r = 0.87, P < 0.05). Serum concentration of IL8 had a direct relationship to the changes in CD11b and L-selectin expression (r = 0.92). Heparin-protamine complex was less stimulant to expression of CD11b and L-selectin than heparin or protamine (P < 0.05). In blood samples from C3-deficient patients, heparin and cobra venom factor caused up-regulation of CD11b and down-regulation of L-selectin similar to that of controls (P > 0.05). CONCLUSIONS: Heparin stimulates up-regulation of neutrophil adhesion molecules CD11b, down-regulation of L-selectin and release of IL8. These effects are inversely related to heparin concentration and are independent of C3 activation. IL8 has a direct relationship to activation of neutrophil adhesion molecules. Increasing heparin dosage reduces neutrophil activation and may reduce the morbidity of patients.

Adolescent↗
PubMed1995

Experimental intestinal hypersensitivity. Effect of four anti-allergic drugs on protein uptake, permeability to sugars and mucosal mast-cell activation.

The ability of four drugs with anti-allergic action to modulate the uptake of bystander protein, lactulose/rhamnose permeability ratios and mast cell activation was studied in rats presensitized with egg albumin in alum and challenged intraduodenally with the same antigen. Beclomethasone dipropionate (BDP) and nedocromil both significantly reduced the uptake of the bystander protein, bovine serum albumin (P < 0.002 and P > 0.02 respectively). BDP also significantly reduced sugar permeability (P < 0.01). In animals with elevated lactulose/rhamnose permeability ratios we confirmed our earlier observation of a significant correlation between levels of the specific mucosal mast cell protease Rat Chymase II (RChyII-previously known as RMCPII) and the sugar ratios. None of the drugs had any influence on the levels of mast cell protease II released following challenge and there was no correlation between the histological light microscopic appearance of the mast cells and the experimental treatment administered. Our results suggest that in the gut the pharmacological effect of anti-allergic drugs may be complex. Some, such as nedocromil, appear to act only on the mechanisms underlying increased protein uptake whereas others, such as BDP, appear to abrogate both increased protein uptake and increased sugar permeability.

Animals↗
PubMed1995

A prospective study of CD45 isoform expression in haemophagocytic lymphohistiocytosis; an abnormal inherited immunophenotype in one family.

In a prospective study, CD45 isoform expression on T lymphocytes was analysed in seven patients with haemophagocytic lymphohistiocytosis (HLH) and their family members. Six patients, their parents and seven healthy age-matched controls showed the normal pattern of three subpopulations of CD45R expression. In one patient, his mother and one of his healthy brothers only two subpopulations could be identified, which might indicate that the maturation from a CD45RA/RO double-positive to a CD45RO single-positive phenotype does not occur in these individuals. It is not clear if this finding had any impact on the development of HLH in this patient and if the pattern of CD45RA and RO expression observed in this family might represent a predisposition to HLH. In another patient a marked increase of the CD45RO single-positive T cell population was observed during a period of increased disease activity. The clinical relevance of this observation and whether CD45RO expression could serve as a marker for disease activity, or in selected individuals as a susceptibility marker for HLH, remain unknown.

Child↗
PubMed1995

Mechanisms in adverse reactions to food. Mechanisms of tolerance and sensitization in the intestine and other organs of the body.

The intestinal tract is the major immunological organ of the human body. The gut associated lymphoid tissues (GALT) play an important role in the suppression of adverse reactions to foods and in the induction of "Oral Tolerance". Immunologically mediated clinical reactions to foods exist outside the gut environment and can affect virtually all organ systems.

Food Hypersensitivity↗
PubMed1995

Neutrophil activation in paediatric extracorporeal circuits: effect of circulation and temperature variation.

OBJECTIVE: Upregulation of neutrophil adhesion molecules (CD11b and L-selectin) and release of a modulating cytokine (IL8) have been reported in vivo and in vitro in adult cardiopulmonary bypass. The aim of this study was to determine whether paediatric bypass preparations have similar influences and whether neutrophil-endothelium interactions are required for IL8 release. METHODS: In vitro paediatric cardiopulmonary bypass circuits (n = 15) were constructed (identical to those used clinically), as well as static loops (n = 15) using donor blood. The effects of circulation and temperature (17 degrees C, 25 degrees C, 37 degrees C) on the initiation of acute inflammation were examined. Cellular expressions of neutrophil adhesion molecules CD11b and L-selectin were assayed by immunofluorescence technique, and serum IL8, IL6, TNF-alpha, leucocyte elastase, and terminal complement complex were measured by ELISA. RESULTS: In all experiments, an immediate increase in CD11b expression occurred [median values, in relative fluorescence units: 64.9 (range 45.3-212.9) at rest; 365.2 (205-835.4) at 10 min; P < 0.001], along with a decrease in L-selectin expression [153.5 (115.5-220.7) at rest; 42 (12-134) at 10 min; P < 0.01]. Serum concentrations of the following increased gradually and were higher in circulation than in static loops: IL8 [1500 (500-2500) pg.ml-1 in circuit v 600 (180-1500) pg.ml-1 in loop, P < 0.001]; TNF-alpha P < 0.05]; and terminal complement complex [25.9 (6.8-120) v 4.7 (0-21.6) AU.ml-1, P < 0.01]. Cooling decreased and rewarming increased upregulation of CD11b and downregulation of L-selectin and release of IL8. IL6 was undetectable. CONCLUSIONS: In the absence of endothelium, in vitro paediatric cardiopulmonary bypass causes profound acute inflammatory changes in donor blood with release of IL8. These changes were greater than in adult cardiopulmonary bypass. Temperature variation and circulation modulate the responses.

Adult↗
PubMed1995

Partial characterization of a circulating tolerogenic moiety which, after a feed of ovalbumin, suppresses delayed-type hypersensitivity in recipient mice.

Serum collected 60 min after feeding ovalbumin (OVA) to BALB/c mice transfers specific tolerance to naive recipients via an unknown mechanism. We have now identified a large fragment of the OVA molecule as the putative active moiety. Specific absorption of immunoreactive OVA from tolerogenic serum by immunoaffinity chromatography removed the tolerogenic activity; following elution of the bound OVA and subsequent injection into naive recipients it was possible to demonstrate tolerogenic activity equivalent to that seen with unmanipulated serum. Passage of OVA tolerogenic serum through a bovine serum albumin (BSA)-specific affinity column had no effect on in vivo OVA tolerogenic activity. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting using anti-OVA antibodies demonstrated the presence of two bands with apparent molecular weights (MW) of 21,000 and 24,000 in the OVA-related material absorbed from the tolerogenic serum. The 24,000 MW moiety was also visualized by silver staining. These moieties are putative candidate tolerogens as they were absent from normal BALB/c mouse serum analysed 5 min after feeding OVA and from severe combined immunodeficiency (SCID) mouse serum--without tolerising activity--analysed 60 min after a similar feed.

Animals↗
PubMed1994

Endotoxin-induced neutrophil adherence to endothelium: relationship to CD11b/CD18 and L-selectin expression and matrix disruption.

The injury to vascular endothelium seen in severe bacterial infection may be mediated by neutrophil-derived enzymes. Neutrophil adhesion to endothelium, a prerequisite for this process, is mediated sequentially by the leukocyte adhesion molecules L-selectin and the beta 2 integrins, including CD11b/CD18. We have explored the relationship between expression of these molecules, neutrophil adherence, endothelial activation, and consequent endothelial injury, as assessed in vitro by changes to HS and FN matrices that colocalize. Endothelial prestimulation with LPS (endotoxin) caused an increase in adherence and an inversely proportional disruption in the HS matrix; disruption of the FN matrix only occurred on the further addition of fMLP. Although maximal changes in these matrices were associated with elevation of neutrophil CD11b/CD18 and reduction in L-selectin expression, these changes did not determine either the nature or extent of endothelial damage. CD11b/CD18 expression was similar in both adherent and nonadherent neutrophils, while L-selectin was shed in association with adherence in the absence of other stimuli. These changes in expression were thus independently regulated. This model may provide further insights into the interrelationship between neutrophil adhesion and activation and endothelial damage in infection with gram-negative bacteria.

Antigens, CD↗
PubMed1994

Haemophagocytic lymphohistiocytosis: experience at two U.K. centres.

Haemophagocytic lymphohistiocytosis (HLH) is a rare disorder of inappropriate macrophage activation. Both familial and sporadic forms, which may be infection-associated, are recognized. Between 1985 and 1991 we treated 23 cases of HLH (12 male, 11 female). There were eight familial cases, defined by a previously affected sibling and/or history of consanguinity, age 3 d to 15 months at presentation. The age of the remaining 15 cases varied from 1 month to 9.5 years. A potential viral trigger was identified in four cases (EBV, two; parvovirus B19, one; echovirus II, one) including one familial case. Six of eight (75%) patients who received supportive care alone, including all four familial cases, died within 6 months of presentation. Both long-term survivors in this group presented at an older age (7.5 and 8 years) and had proven or suspected virus-associated HLH. 15 patients were treated with etoposide (150-250 mg/m2 days 1-3 every 21 d) and methylprednisolone; 10 patients received intrathecal methotrexate in addition. In nine (60%) of these cases a complete (six) or partial (three) response was achieved, though one child suffered a fatal 'tumour lysis' syndrome. Overall mortality in the treated group was 66.6%, being highest (75%) in patients under 2 years at presentation compared to 33% in those over 2 years. Two of three familial and one of five sporadic cases relapsed and died 3 d to 20 months from diagnosis. Only one familial case survives at follow-up of 11 months. Of the five remaining survivors, two received allogeneic bone marrow transplantation (one matched related, one haploidentical) and are alive at 11 and 29 months. Three cases aged 2.5, 7.5 and 9.5 years remain in remission at 11, 20 and 25 months respectively. The high mortality of HLH supports a role for allogeneic BMT in selected cases, particularly those with a familial basis or under 2 years at presentation.

Bone Marrow↗
PubMed1994

Laryngo-onycho-cutaneous syndrome: an inherited epithelial defect.

Three children with an unusual but clearly defined combination of clinical findings that appear to have been inherited in an autosomal recessive manner are described. All had developed laryngeal abnormalities, chronic skin ulceration, nail dystrophy, and conjunctival disease in infancy. In every case, dental enamel was hypoplastic and both skin and mucosal surfaces demonstrated increased susceptibility to trauma. Progression of disease occurred, to life threatening respiratory obstruction in two cases and to effective blindness and fatal respiratory obstruction in the third child. All of these children came from the Pakistani ethnic group. No medical treatment has halted progression of this disease but laser therapy has been partially successful in alleviating laryngeal manifestations. Ultrastructural and immunohistological examination of unaffected skin was undertaken in each child. No abnormality was found in the child with the mildest clinical disease. Both of the other children showed abnormal hemidesmosomes on ultrastructural examination. The most severely affected child also had abnormally weak immunoreactivity with antibodies G71 and GB3 directed against basal cell alpha 6 beta 4 integrin and the basement membrane glycoprotein nicein respectively. These abnormal findings are also seen in skin from patients with junctional epidermolysis bullosa. These three children have the laryngo-onycho-cutaneous syndrome, which may not be rare in their ethnic group. The available clinical and pathological evidence is consistent with this syndrome being caused by an inherited defect affecting the lamina lucida of the skin basement membrane zone. The laryngo-onycho-cutaneous syndrome may therefore represent a new and distinctive type of junctional epidermolysis bullosa.

Child, Preschool↗
PubMed1994

Hypogammaglobulinaemia associated with normal or increased IgM (the hyper IgM syndrome): a case series review.

The clinical and immunological aspects of 16 children with the syndrome of hypogammaglobulinaemia associated with normal or increased IgM (the hyper IgM syndrome) and their responses to treatment are reviewed. Increased concentrations of IgM, neutropenia, and recurrent infections could usually be controlled by antimicrobial and intravenous immunoglobulin treatment. Together with the bacterial infections characteristic of hypogammaglobulinaemia, these patients often developed opportunistic infections, including Pneumocystis carinii pneumonia, often presenting in the first year of life. The occurrence of sclerosing cholangitis, neurological complications, and neutropenia may be a result of an underlying cell mediated immune deficiency, autoimmunity, or infection. Despite a high incidence of opportunistic infections, immunological investigations did not show any abnormality of T cell function. These findings are discussed in the light of the recent demonstration that the lack of expression of a T lymphocyte activation antigen is the molecular basis of the X linked form of the disorder.

Agammaglobulinemia↗
PubMed1994

Failure of SCID mice to generate an oral tolerogen after a feed of ovalbumin: a role for a functioning gut-associated lymphoid system.

The role of the mucosal immune system in the generation of circulating tolerogenic ovalbumin (OVA) moieties has been investigated after a single feed of the protein. Serum collected from SCID mice 1 hr after a 25-mg feed of OVA was unable to transfer tolerance of delayed-type hypersensitivity (DTH) into naive BALB/c recipients. This is in contrast to serum collected from BALB/c mice which was able to transfer DTH tolerance to naive BALB/c recipients. The levels of circulating OVA detected in the serum of SCID mice 60 min after feeding OVA were approximately half those detected in the serum of BALB/c mice at the same time-point. However even dose adjustment of SCID mouse serum to a level of immunoreactive OVA equivalent to that found in BALB/c serum was unable to induce DTH tolerance in BALB/c recipients. This failure of SCID serum to transfer tolerance was shown to be unrelated to the germ-free conditions under which SCID mice are kept. Serum from OVA-fed germ-free BALB/c mice transferred DTH tolerance at equivalent levels to serum from conventionally reared BALB/c mice. When the intestinal morphology and intraepithelial lymphocyte (IEL) numbers in the duodenum of SCID mice were compared to conventionally reared and germ-free BALB/c controls, SCID mice were characterized by a lower number of IEL with a different morphology from the majority of IEL found in BALB/c mice.

Administration, Oral↗
PubMed1993

Folding of maltose-binding protein. Evidence for the identity of the rate-determining step in vivo and in vitro.

The folding of maltose-binding protein, a periplasmic protein in Escherichia coli, was shown to proceed through the same rate-limiting step whether folding occurred in the cell under physiological conditions or in vitro in the absence of other proteins. Four species of maltose-binding protein containing aminoacyl substitutions identified as decreasing the rate of folding of the protein in vivo were purified, and their denaturant-induced folding transitions were analyzed by monitoring the intrinsic fluorescence of tryptophan. In all four cases the rate of folding in vitro was slower than that of the wild-type maltose-binding protein; thus the same step determines the rate of folding in vivo and in vitro. Furthermore, examination of the three-dimensional structure of maltose-binding protein as determined by x-ray crystallography (F. Quiocho, personal communication; Spurlino, J. C., Lu, G.-Y., and Quiocho, F. A. (1991) J. Biol. Chem. 266, 5202-5219) indicates that all 4 of the residues identified as crucial to folding lie in one structural element of the native protein. We conclude that the rate-limiting step both in vivo and in vitro involves formation of this element of structure.

ATP-Binding Cassette Transporters↗
PubMed1993

Changes in neutrophil CD11b/CD18 and L-selectin expression and release of interleukin 8 and elastase in paediatric cardiopulmonary bypass.

Children undergoing cardiopulmonary bypass (CPB) surgery for congenital heart defects develop an acute post-operative capillary leak which may be due to endothelial injury inflicted by adherent neutrophils (PMN). Direct immunofluorescence and flow cytometry were used to measure CD11a/CD18, CD11b/CD18 and L-selectin (L-s) expression on circulating PMN in CPB circuits containing human blood and in children undergoing CPB. In vitro, a general rise in CD11b/CD18 expression over 2 h contrasted with complete loss of L-s in a small but progressively increasing proportion of PMN. Marked but inconsistent changes in CD11b/CD18 and L-s were observed in vivo, in conjunction with fluctuations in circulating PMN count. Circulating IL-8 was detected starting at rewarming from hypothermia and reperfusion of the heart and lungs with a simultaneous, closely correlated rise in both PMN count and circulating elastase. IL-1 and TNF were not detected. These studies demonstrate changes in the pathways of PMN-endothelial interaction during and after CPB.

Antigens, CD↗