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Biomedical subjects

M G Scott

Publications and source records attributed to M G Scott.

At least 73 records · Page 4Linked to original sources
PubMed1994

Endogenous serum antibodies that interfere with a common thyroid hormone uptake assay: characterization and prevalence.

We identified individuals whose serum contained a substance that produced falsely decreased thyroid hormone (T)-uptake values determined by the Emit (Syva) procedure. Investigation of this interference was prompted by identification of a patient with T-uptake values inconsistent with clinical assessment. IgG depletion and supplementation studies with this patient's serum suggested that the interference was due to endogenous antibodies with specificity for the thyroxine-glucose-6-phosphate dehydrogenase conjugate in the Emit T-uptake assay. The prevalence of the interference was examined by prospectively comparing routine Emit T-uptake values of 1710 patients' samples to T-uptake values obtained by another method. Discrepant samples were also assayed by a radioactive binding triiodothyronine-uptake assay. We identified eight samples that had falsely decreased T-uptake values by Emit, for an overall prevalence of 0.46%. Among 45 consecutive patients with a T-uptake value < 20%, five patients, or 11%, were falsely decreased by Emit and three of these were clearly due to an interfering IgG. We suggest that samples with abnormally low T-uptake values determined by the Emit method be confirmed by an alternative method.

Adult↗
PubMed1994

Interference in ionized calcium measurements by heparin salts.

We determined the suitability of various heparin salts used for anticoagulation of whole-blood specimens for measurement of ionized calcium (iCa), blood gases, and electrolytes. We were particularly interested in a new heparin product containing both zinc and lithium cations (CNLZ heparin), in which the binding sites with greatest affinity for divalent cations are bound with zinc and low-affinity sites with lithium. In initial experiments Li heparin decreased iCa concentrations 0.07 mmol/L at the lowest heparin concentration (3000 units/L) and progressively lowered them at higher concentrations. Zn heparin initially increased iCa concentrations 0.06 mmol/L but progressively lowered them as the heparin concentration was increased. Li heparin interfered even when present in amounts (9 units per 3-mL syringe) minimally effective in preventing coagulation. Use of CNLZ heparin (36 units per 3-mL syringe; Zn 63-78 g/kg of heparin) largely eliminated interference of heparin in iCa measurements. In studies that included the effects of concentration of heparin through partial filling of syringes, specimens anticoagulated with CNLZ heparin compared well with unheparinized controls in measurements of iCa, blood gases, and electrolytes. Blood gases and iCa results on CNLZ-heparinized specimens from intensive-care-unit patients also compared well with specimens anticoagulated with a preparation of heparin (EB heparin) in which calcium has been added to balance the calcium-binding capacity. However, the presence of calcium in EB heparin significantly increased measured total calcium concentrations, whereas the new CNLZ heparin did not interfere in total calcium determinations.

Arteries↗
PubMed1993

Clonal characterization of the human IgG antibody repertoire to Haemophilus influenzae type b polysaccharide. V. In vivo expression of individual antibody clones is dependent on Ig CH haplotypes and the categories of antigen.

Antibodies (Ab) to the polysaccharide capsule of Haemophilus influenzae type b (Hib-PS) provide protection against Haemophilus influenzae type b disease in children, and Hib-PS vaccines with different immunologic properties are widely used clinically. The repertoire of human anti-Hib-PS Ab induced by these vaccines is relatively restricted and can be divided into two types by the structure of the light chain V region. Ab using A2-V kappa II gene product, which account for the majority of anti-Hib-PS Ab response in most patients, show little somatic mutations. In contrast, non-Ab using A2-V kappa II gene product use VL genes from the V kappa I, V kappa II, V kappa III, V kappa IV, and V lambda subgroups, are variably expressed among patients, and contain somatic mutations. To further study the expression of these two types of anti-Hib-PS Ab, we have produced KB13, a mAb specific for V kappa II subgroup, and used mAb specific for various other VL subgroups to develop immunoassays specific for anti-Hib-PS Ab of each VL subgroup. When Ig allotypes were studied for the effect on the Ab repertoire, A2-V kappa II (A2) Ab were found to be expressed less in patients expressing fb or zag CH haplotypes (p < 0.05). When the T cell-independent Hib-PS carbohydrate vaccine was compared to two T cell-dependent Hib-PS protein conjugate vaccines for their effect on Ab repertoire, Ab using V kappa III VL were found to be more often elicited with the conjugate vaccines than with the Hib-PS carbohydrate vaccine (p < 0.01). Thus, individual members of the anti-Hib-PS Ab repertoire differ not only in their V region structure but also in the control of their expression.

Adult↗
PubMed1993

A comparison of Agiolax and lactulose in elderly patients with chronic constipation.

In a double-blind crossover study the efficacies of Agiolax, a combination of fibre and senna pod, and lactulose were compared in 77 long-stay elderly patients with chronic constipation. Mean daily bowel frequency, stool consistency and ease of evacuation were significantly greater with Agiolax than lactulose. The recommended dose was exceeded more frequently with lactulose than Agiolax (chi 2 = 8.38, p < 0.01). Adverse effects were not different for the 2 treatments. In long-stay elderly patients with chronic constipation Agiolax and lactulose were well tolerated, but Agiolax proved a more effective treatment.

Aged↗
PubMed1992

Characterization of the human IgG antibody VL repertoire to Haemophilus influenzae type b polysaccharide.

The human antibody response to the capsular polysaccharide of Haemophilus influenzae type b (Hib) is a good model for examining human V region repertoires. While the VL repertoire of human antibodies to Hib polysaccharide is relatively simple and dominated by the product of a germline V kappa II gene named A2, at least five other VL genes can be expressed by some individuals. These include at least two V kappa I products and at least one V kappa III, one V kappa IV, and one V lambda product. The epitope recognized by a monoclonal anti-idiotype antibody is on the A2 V kappa II product.

Adult↗
PubMed1992

A pharmacokinetic and pharmacodynamic comparison of plain and enteric-coated prednisolone tablets.

1. Eight healthy volunteers and eight patients suffering from chronic obstructive pulmonary disease (COPD) received 30 mg prednisolone as plain (P) and enteric-coated tablets (EP) in a randomised, cross-over manner. Plasma prednisolone and cortisol and blood glucose were measured over 24 h. 2. Although absorption of prednisolone was considerably slower when administered as the enteric-coated form, peak plasma drug concentrations and total AUC (0,24 h) were equivalent for the two formulations. Malabsorption of prednisolone was not observed. 3. The administration of EP was associated with significantly less adrenal suppression in volunteers than P as judged by measurement of AUC (0,24 h) values for endogenous cortisol. However, this difference did not reach statistical significance in the patient group. 4. Plasma cortisol concentrations declined more slowly following administration of the enteric-coated form to both groups. The difference in time taken (median and range) to maximum suppression of cortisol was statistically significant (P less than 0.05) between P (2.5 h; 2-4 h) and EP (4 h; 3-12 h) preparations administered to volunteers. There was a similar significant difference (P less than 0.05) between P (2.5 h; 1-4 h) and EP (7 h; 2-12 h) in the patients. 5. Plasma cortisol concentrations were significantly lower at 24 h in patients receiving the enteric-coated product in association with higher terminal prednisolone concentrations. 6. Blood glucose concentrations increased over an 8 h period in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The human antibody V region repertoire to the type B capsular polysaccharide of Haemophilus influenzae.

The V region repertoire of the human antibody response to the type b capsular polysaccharide of Haemophilus influenzae (Hib-PS) is being defined at the molecular level using antibodies purified from serum of immunized adults. The VH of this response is restricted to the VHIII subgroup while the VL can be divided into two categories. The most common VL, expressed in > 90% of adults and usually constituting the majority of a subjects anti-Hib-PS antibody response, is restricted to the product of a single V kappa II gene known as A2 that probably lacks somatic mutations. The product of the A2 gene is invariably joined to one of several J kappa products by an inserted arginine at the V kappa-J kappa junction. In contrast to the restricted nature of the dominant VL clonotype, the second category of VL constitutes a heterogeneous group of at least seven different VL gene products that often contain somatic mutations and generally exhibit crossreactivity with a related polysaccharide from E. coli. Elucidation of anti-Hib-PS V regions at the molecular level will permit examination of structure-function relationships among these clinically important antibodies and should make the V region repertoire to Hib-PS a useful model for studying human V gene responses.

Amino Acid Sequence↗
PubMed1991

Clonal characterization of the human IgG antibody repertoire to Haemophilus influenzae type b polysaccharide. IV. The less frequently expressed VL are heterogeneous.

We previously demonstrated that the human anti-Haemophilus influenzae type b polysaccharide (Hib-PS) VL repertoire is dominated by a product of the V kappa II gene, A2, and that V kappa II-A2 anti-Hib-PS antibodies have little or no somatic mutation in VL. To further study this VL repertoire, we studied non-A2 anti-Hib-PS antibodies that were identified either serologically or by amino-terminal amino acid sequence analysis. Of 15 non-A2 anti-Hib-PS antibodies from 12 vaccinated adults, we found four V lambda, five V kappa I, one non-A2 V kappa II, four V kappa III, and one V kappa IV antibodies. As expected, all but two of these subjects also produced V kappa II-A2 antibodies. Interestingly, one of these subjects lacks the A2 gene in the germ line. However, both subjects who did not produce detectable V kappa II antibody did produce normal amounts of total anti-Hib-PS antibody after vaccination. Candidate V kappa genes for the non-A2 antibodies were identified by comparison of up to 60 VL amino acid residues, including CDR1 and CDR2, with all sequenced V kappa genes. V kappa I antibodies appear to be products of three newly sequenced V kappa I genes, O8, O18, and L11, that are reported here. The O8 and O18 genes encode identical amino acid sequences. The non-A2 V kappa II antibody is a likely product of the A1 or A17 genes, the V kappa III antibodies are likely products of the A27 gene, and the V kappa IV antibody is a product of the single V kappa IV gene, B3. Unlike V kappa II-A2 antibodies, the V kappa I, V kappa III, and V kappa IV antibodies differed by one to five CDR residues from the germ line product of the candidate genes, suggesting the presence of somatic mutations. Thus, anti-Hib-PS antibodies can be divided into two types, the most frequently observed A2 antibodies with little or no somatic mutation and non-A2 antibodies that likely contain somatic mutations.

Amino Acid Sequence↗
PubMed1991

Sublingual captopril--a pharmacokinetic and pharmacodynamic evaluation.

In this study we compared the pharmacokinetics and pharmacodynamics of captopril after sublingual and peroral administration. Single 25 mg doses of captopril were administered sublingually and perorally on two different occasions in a randomised cross-over fashion to eight healthy volunteers aged 22-35 years. The kinetics of unchanged captopril, plasma renin activity (PRA). BP and heart rate were studied over three hours after both peroral and sublingual administration of captopril. Mean pharmacokinetic parameters for unchanged captopril after sublingual administration were: Cmax, 234 ng.ml-1; tmax, 45 min; AUC (0-3 h), 15.1 micrograms.ml-1.min. Mean pharmacokinetic parameters for unchanged captopril after peroral administration were; Cmax, 228 ng.ml-1; tmax, 75 min; AUC (0-3 h), 17.0 micrograms.ml-1.min.tmax was significantly shorter when captopril was administered sublingually; all other pharmacokinetic parameters were equivalent. The plasma captopril concentrations achieved post drug administration led to increases in PRA and reductions in BP.tmax for PRA was 86 min for sublingual captopril and 113 min for perorally administered drug. Peak PRA values were, however, not significantly different. BP, as expected, was not reduced dramatically in these healthy volunteer subjects, however, in systolic BP vs time profiles, BP was significantly lower after volunteers received sublingual captopril. Heart rate increased slightly after captopril administration; there were no differences between the two routes of administration. Administration of captopril sublingually, therefore led to a more rapid attainment of plasma captopril concentrations and had a more rapid onset of pharmacological effect when compared with peroral administration.

Administration, Oral↗
PubMed1991

An idiotypic marker associated with a germ-line encoded kappa light chain variable region that predominates the vaccine-induced human antibody response to the Haemophilus influenzae b polysaccharide.

Human antibodies specific for the Haemophilus influenzae b polysaccharide (Hib PS) frequently express a cross-reactive idiotype (CRI), and commonly utilize a VL region that is the product of the V kappa II gene A2. To examine further anti-Hib PS V region expression and to determine whether CRI expression is correlated with the V kappa IIA2 chain, we isolated a monoclonal antibody (MAb) reactive with an idiotypic determinant of anti-Hib PS antibodies. This MAb inhibited Hib PS binding but did not react with Ig isotypic determinants. The CRI recognized by this MAb, designated HibId-1, was associated with the Hib PS-combining site since the reactivity of the MAb with anti-Hib PS antibodies could be inhibited by Hib PS. HibId-1 was expressed by 17 of 17 clonally purified and sequence-defined anti-Hib PS antibodies having V kappa IIA2 L chains. In contrast, 0 of 10 anti-Hib PS antibodies having either V lambda, V kappa I, or V kappa III chains expressed HibId-1. Western blot analysis showed that the MAb anti-CRI reacted with isolated anti-Hib PS V kappa IIA2 L chains but not with H chains or other L chains, indicating that the HibId-1 determinant is localized to the V kappa IIA2 chain, and does not require pairing with H chain for expression. Anti-Hib PS antibodies bearing HibId-1 were present in at least 85% of subjects immunized with either free Hib PS or Hib PS coupled to diphtheria toxoid (Hib PS-DT), and comprised on the average 60% of the total vaccine-induced serum anti-Hib PS. HibId-1 expression was not related to age at vaccination inasmuch as infants, children, and adults had similar distributions of HibId-1-positive anti-Hib PS after vaccination with Hib PS-DT. HibId-1 was expressed at a lower frequency and comprised a smaller fraction of the total anti-Hib PS antibody in adult preimmunization sera as compared to post-Hib PS immunization sera, suggesting that immunization preferentially stimulates HibId-1-positive B cells. These data demonstrate that antibodies bearing HibId-1/V kappa IIA2 comprise a predominant component of the anti-Hib PS response induced by immunization, and that this pattern of VL expression is established early in ontogeny.

Adult↗
PubMed1990

In situ chemical cleavage of proteins immobilized to glass-fiber and polyvinylidenedifluoride membranes: cleavage at tryptophan residues with 2-(2'-nitrophenylsulfenyl)-3-methyl-3'-bromoindolenine to obtain internal amino acid sequence.

Proteins immobilized to glass-fiber supports and polyvinylidenedifluoride membranes are cleaved in situ with a tryptophan residue-specific reagent, 2-(2'-nitrophenylsulfenyl)-3-methyl-3'-bromoindolenine. Protein fragments can be eluted from polyvinylidenedifluoride membranes after in situ digestion and electrophoresed and electroblotted to new polyvinylidenedifluoride membranes for subsequent sequence determination of selected bands. Five proteins (bovine serum albumin, ovalbumin, beta-casein, beta-lactoglobulin, and myoglobin) of known sequence containing one to three tryptophan residues each were used as model substrates to evaluate the specificity and extent of cleavage. Under the conditions used, the reaction is rapid and exhibits a high degree of specificity for tryptophan residues since N-terminal sequence analysis of the digested, immobilized samples yields the expected, newly generated N-termini. No detectable cleavage occurred at nontryptophan residues nor at acid labile aspartic acid-proline peptide bonds. Solution cleavage reactions were also performed and the resulting digest was analyzed by gel electrophoresis. We found a positive correlation between the solution and in situ cleavage reactions, in that, proteins which show cleavage in the solution reaction also yield internal sequence data after in situ digestion. Since tryptophan occurs with low frequency in proteins, this cleavage reaction has the potential to generate a small number of fragments and in favorable circumstances allow sequence analysis of the unfractionated reaction mixture. In addition, the sequence obtainable after, but not before, in situ digestion can be used as an indication that the N-terminus of the protein is blocked.

Amino Acid Sequence↗