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Biomedical subjects

E Hall

Publications and source records attributed to E Hall.

At least 109 records · Page 6Linked to original sources
PubMed1984

An implementation of dual energy CT scanning.

We have described a prereconstruction method for dual energy (PREDECT) analysis of CT scans. In theory, this method can (a) eliminate beam hardening and produce an accuracy comparable with monoenergetic scans and (b) provide the effective atomic number and electron density of any voxel scanned. Our implementation proves these statements and eliminates some of the objectionable noise. We constructed a phantom with a cylindrical sleeve-like compartment containing known amounts of high atomic number material simulating a removable skull. Conventional scans, with and without this beam hardener, were done of a water bath containing tubes of high electron and high atomic number material. Dual energy scans were then done for PREDECT. To increase the effective separation of the low and high energy beams by using more appropriate tube filtration, we fabricated a beam filter changer containing erbium, tungsten, aluminum, and steel. We used erbium, tungsten, and steel at high energy and aluminum, steel, and erbium at low energy for data acquisition. The reconstructions were compared visually and numerically for noise levels with the original steel only filtration. We found a decrease in noise down to approximately one-half the prior level when erbium/aluminum or tungsten/aluminum replaced the steel/steel filter. Erbium and tungsten were equally effective. Steel/erbium and steel/aluminum also significantly reduced image noise. The noise in the photoelectric (P) and Compton (C) images is negatively correlated. At any pixel, if the noise is positive in the P image, it is most probably negative in the C. Using this fact, the noise was reduced by postreconstruction processing.

Humans↗
PubMed1984

The development of IgE-suppressive immunocompetence in young animals: influence of exposure to antigen in the presence or absence of maternal immunity.

Previous studies recognized a prolonged suppression of egg-albumin (EA)-specific IgE responsiveness in the progeny of immunized female rats, and showed that an identical effect was produced by the administration of small amounts of specific IgG during the first few days of life. Both manipulations also elevated the primary IgG response to a subsequent immunization but with less consistency. We have now investigated the effects on the progeny of varying the type of maternal response by immunizing with antigen given with or without adjuvant. Mothers immunized with EA without adjuvant (by mouth or parenterally) in whom both IgE and IgG responses are thereby suppressed do not influence the antibody-responsiveness of their progeny. By contrast, mothers immunized with EA in adjuvant, a procedure which suppresses IgE but enhances IgG responsiveness to the antigen, transfer both effects to their offspring. In this way, both IgE-suppression and IgG-enhancement are seen to correlate with the transmission of maternal IgG. EA administered either by mouth or parenterally in the period up to 6 weeks after birth, suppresses both IgE and IgG responses to subsequent specific challenges in a dose-dependent manner. The results of feeding antigen to the progeny of (IgG-transmitting) immune mothers indicated that passive and active immunity in the young rat, although both suppressing IgE-responsiveness, do not have additive depressive effects.

Adjuvants, Immunologic↗
PubMed1983

IgE production in rat fascioliasis.

F. hepatica infection of rats caused a prolonged elevation of serum total IgE reflecting the continued presence of live worms in the host. Infection with 40 metacercariae stimulated higher total IgE levels than infection with 20 metacercariae. The parasite specific IgE response was biphasic, the first peak coinciding with the migratory phase in the liver parenchyma and the second with the establishment of flukes in the bile ducts.

Animals↗
PubMed1983

IgE suppression by maternal IgG.

Rats born of egg albumin immunized mothers have a diminished capacity to produce IgE antibody to egg albumin persisting for at least 13-14 weeks after birth. At the same time the primary IgG response to the antigen is usually enhanced. Previous studies indicated that these effects were mediated by factors transferred in maternal milk. The phenomenon can be duplicated by the administration of small quantities of immune serum to rats during the first 3 weeks of life. The active component of immune serum is shown to be specific antibody. Suckling rats acquire egg-albumin-specific IgG from the immune mother via the milk. Their serum level approaches that of the mother by 20 days but declines rapidly after weaning to become undetectable by 6-8 weeks. As maternal influence on the immune responsiveness of the offspring persists for several weeks beyond this time, it is unlikely that the mechanism involves a simple blocking by circulating antibody of the access of antigen to cellular receptors. Alternative mechanisms are briefly discussed. Attention is drawn to the possibility that the suppression of IgE antibody responsiveness by maternal IgG may represent a physiological regulatory process with a role in inhibiting the development of infantile allergies.

Animals↗
PubMed1982

Boosterable IgE antibody response in mice without the use of adjuvant.

A mouse model is presented giving boosterable IgE antibody responses preceding the IgG antibody responses without using adjuvants. Groups of CBA mice were injected subcutaneously with minute doses of penicilloyl bovine gammaglobulin, 3.8-94 ng daily for one or two 10-day periods. Some groups of animals were simultaneously given Bordetella pertussis bacteria intraperitoneally. The IgE antibody responses were recorded with passive cutaneous anaphylaxis (PCA) in rats as well with RAST. IgG antibody responses were determined with a double antibody assay. An overall good agreement between the antibody activity in the PCA and RAST was seen, both tests showing boosterable IgE antibody responses. Some discrepancies between the two tests are discussed.

Adjuvants, Immunologic↗
PubMed1981

Regulation of ongoing IgE antibody responses with minute doses antigen.

Repeated challenge of egg albumin-immunized Hooded Lister rats with a tiny amount of antigen presents a stimulus not only to effector cells for an IgE response but also to a related class-selective suppressive mechanism which eventually becomes predominant. The results obtained suggest that IgE responsiveness is abrogated by exposure to an antigen dose which is several orders of magnitude lower than required for the regulation of antibody of other classes.

Animals↗
PubMed1981

Adoptive transfer of total and parasite-specific IgE responses in rats infected with Nippostrongylus brasiliensis.

Infection of rats with Nippostrongylus brasiliensis has both a parasite-specific and non-specific IgE stimulating effect. Both these responses can be adoptively transferred with thoracic duct lymphocytes (TDL) from infected rats. The character of the IgE response in the recipient rats was related to the stage after infection of the cell donors. TDL from hyperimmune rats adoptively transferred high serum titres of parasite-specific IgE to infected recipient rats and substantially increased the levels of total IgE. However, adoptive immunization with TDL from donors infected 10 days previously did not stimulate parasite-specific IgE and only slightly increased total IgE levels. After cell fractionation the sIg- cells from day 10 TDL increased the level of total IgE but not parasite-specific IgE whereas sIg- cells from hyperimmune TDL did not induce any IgE response unless given with sIg+ cells. The possible reasons for this are discussed.

Animals↗
PubMed1980

Antigens in penicillin allergy. V. On the relative allergenic potency of antigens carrying penicilloyl determinants derived from azidocillin, ampicillin and benzylpenicillin.

The effects of the different acyl side chains of azidocillin, ampicillin and benzylpenicillin on the immunogenic potency of penicilloylated antigens as well as on the specificity of the developed antibodies were investigated in CBA mice. The antigens used were penicilloylated bovine gammaglobulin (BGG), bovine serum albumin (BSA) and human serum albumin (HSA). Immunization was performed with injection of high doses of antigens together with adjuvant or by injection of minute amounts of antigen over periods of 10 days. IgE antibodies were recorded with PCA in rats and IgG antibodies were measured with a double antibody assay. The nature of the carrier as well as the number of epitopes was found to influence the development of antibodies irrespective of the immunization schedule used. The immunogenic activity of the PO-BSA antigens was related to the epitope density. The PO-BSA antigens were, in contrast to the PO-BGG antigens, weak immunogens in the CBA mice. The acyl side chains of the different penicillins influenced the induction and specificity of the IgE antibody responses obtained after daily treatment.

Ampicillin↗
PubMed1980

Adjuvants in the induction and enhancement of rat IgE responses.

In Hooded Lister rats the primary IgE antibody response induced by immunization with antigen and adjuvant may be enhanced either specifically by a further dose of antigen (booster response) or non-specifically by infection with helminth parasites (potentiated response). The initial immunizing technique can influence the occurrence and level of these enhanced responses and here we describe the effect of using different adjuvants in the priming event. Although the level of the primary response was broadly similar following immunization with egg-albumin and the adjuvants Bordetella pertussis aluminium hydroxide or Freund's complete adjuvant, the booster response was inhibited and the potentiated response intensified in animals immunized with the latter two adjuvants. A significant IgE booster response could only be obtained if B. pertussis had been used in the initial immunization. When aluminium hydroxide was adsorbed to B. pertussis it was found to have the same inhibitory effect on subsequent booster responses as when it was adsorbed to antigen. These results are discussed in relation to the intricacies of IgE production in the present model and to more general mechanisms of adjuvant action.

Adjuvants, Immunologic↗
PubMed1977

Reduced dose of Rho(D) immune globulin following induced first-trimester abortion.

A double-blind study of women after first-trimester abortion supports the efficacy of low-dose Rho(D) immune globulin (human) in the prevention of Rh sensitization. Twenty-seven per cent of patients demonstrated a fetomaternal blood leak based on Kleihauer-Betke stains. In follow-up testing, the percentage of positive titers and the absolute titer of detectable antibody at various intervals were related to the dose of administered immune globulin. This study confirmed the possible risk of sensitization in Rh-negative postabortal women and suggests the practical use of single low-dose immune globulin preparations in prevention.

Abortion, Induced↗