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Biomedical subjects

G King

Publications and source records attributed to G King.

At least 109 records · Page 6Linked to original sources
PubMed1995

An evaluation of the staining of lymphomas and normal tissues by the rabbit polyclonal antibody to protein gene product 9.5 following non-enzymatic retrieval of antigen.

We have previously described the staining of normal follicle centre lymphoid cells by the rabbit polyclonal antibody to protein gene product 9.5 (PGP9.5), following an antigen unmasking step employing heat pretreatment. Applying this finding to a range of lymphomas to determine whether this phenomenon could have a role in identifying lymphomas of follicle centre origin revealed no relationship between type or grade of lymphoma and staining of neoplastic cells. Testing a range of normal tissues following antigen retrieval displayed increased sensitivity and a greater range of tissue positivity. Immunoblots of gel electrophoresed tonsil and brain extract were performed. Although subjecting these blots to antigen unmasking increased sensitivity, no novel epitopes, in terms of additional bands, appeared. This suggested that antibody specificity remained unaltered.

Blotting, Western↗
PubMed1995

Restriction alleviation and modification enhancement by the Rac prophage of Escherichia coli K-12.

Bacteriophage lambda encodes an antirestriction function, RaI, which is able to modulate the activity of the Escherichia coli K-12 restriction and modification system, EcoKI. Here we report the characterization of an analogous function, Lar, expressed by E. coli sbcA mutants and the hybrid phage lambda reverse. E. coli sbcA mutants and lambda reverse both express genes of the Rac prophage, and we have located the lar gene immediately downstream of recT in this element. The lar gene has been cloned in an expression plasmid, and a combination of site-directed mutagenesis and labelling of plasmid-encoded proteins has enabled us to identify a number of translational products of lar, the smallest of which is sufficient for restriction alleviation. Lar, like RaI, is able both to alleviate restriction and to enhance modification by EcoKI. Lar, therefore, is functionally similar to RaI and the nucleotide sequences of their genes share 47% identity, indicating a common origin. A comparison of the predicted amino acid sequences of Lar and RaI shows only a 25% identity, but a few short regions do align and may indicate residues important for structure and/or function.

Amino Acid Sequence↗
PubMed1995

Immunocytochemical study of the ontogeny of the marsupial Didelphis albiventris immune system.

Marsupials have considerable merits as models for studying the developmental dynamics of the mammalian immune system, but until recently there has been a conspicuous lack of specific immune probes to facilitate such studies. To begin a precise study of the ontogeny of the marsupial Didelphis albiventris we have used cross-reactive polyclonal antibodies raised against evolutionarily highly conserved peptides which form part of the antigen specific receptor complexes of human differentiated lymphocytes. Moreover, because of antigen receptor conservation, the antibodies also recognise specifically the immunocompetent T and B lymphocytes of other species including those in the organs of the opossum. Use of the antipeptide antibodies together with other cross-reacting antibodies has allowed us to study the cellular immunology of T and B cells and antigen presenting cells (APC) during the development of thymus, skin, lymph nodes and spleen in the Brazilian white-belly opossum. The molecular nature and identity of the T cell antigens detected in opossum tissues were confirmed by immunoblotting. These findings indicate that it is now possible to exploit these antibody probes for comparative mammalian studies, and indeed to investigate interesting features of the opossum, such as reaction of the immature immune system of the pouch young to antigenic stimulation.

Animals↗
PubMed1995

A statistical model estimating the number of African-American physicians in the United States.

Using mark-recaptured methodology and network sampling procedures, a statistical model was developed to estimate the number of African-American physicians in the United States. A sample (stratified by geographic region, medical specialty and an age surrogate) was selected from the National Medical Association's Masterfile of Black Physicians (NMAMBP). Respondents were asked to list the names of five black physicians who resided or practiced in their immediate geographic area. Data also were collected about citizenry as well as other demographic and professional information. The NMAMBP was used mathematically as a "marked" group that could then be "recaptured," allowing mark-recapture methodology to be used as the nucleus of the statistical estimation procedure. The results revealed that in 1991, the total number of US African-American physicians (black US citizens) was estimated to be 16,282 with a conservative standard error of 764 and an approximate 95% confidence interval, yielding a range of 14,754 to 17,810 physicians. This estimate is from 17% to about 32% lower than the 21,538 black doctors reported by the 1990 Bureau of the Census and has important implications for attempts to reform the health-care system and policies designed to produce more African-American physicians.

Black or African American↗
PubMed1994

CD62/P-selectin binding sites for myeloid cells and sulfatides are overlapping.

P-Selectin (CD62/GMP140/PADGEM) is an inducible cell-surface glycoprotein expressed by endothelial cells and platelets following stimulation by inflammatory mediators such as thrombin, histamine, or peroxides. P-Selectin mediates the binding of leukocytes to activated vascular endothelium at sites of inflammation and plays a role in mediating the binding of activated platelets to leukocytes and the vascular cell wall. The adhesive function of P-selectin is mediated by its calcium-dependent (or C-type) lectin domain, which is known to bind to carbohydrate ligands including fucosyl-N-acetyllactosamine (Lex, CD15), sialyl-Lex, and 3-sulfated galactosylceramides (sulfatides). Sulfatides can efficiently block P-selectin/myeloid cell binding in vitro and are excreted at high levels by activated granulocytes. These observations led to the hypothesis that sulfatide may play a role in facilitating the disengagement of CD62, allowing the efficient exit of granulocytes from the blood stream at sites of inflammation. In this report, we extend our previous mutagenesis analysis of the P-selectin binding site [Hollenbaugh, D., Bajorath, J., Stenkamp, R., & Aruffo, A. (1993) Biochemistry 32, 2960] and show that replacement of Tyr48 with Ser or Lys113 with Arg results in P-selectin mutants that, although correctly folded, do not bind to HL60 cells. These results suggest that the conservation of charged and hydrogen-bonding site chains is not sufficient to maintain the P-selectin function and that the exact stereochemistry provided by the side chains of residues lining the P-selectin binding pocket is critical for P-selectin binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1994

Non-enzymatic retrieval of antigen permits staining of follicle centre cells by the rabbit polyclonal antibody to protein gene product 9.5.

The rabbit polyclonal antibody to protein gene product 9.5 (PGP9.5) will detect the L1 isoenzyme of ubiquitin carboxy-terminal hydrolase (UCH), which is a marker for neurones and neuroendocrine tissue. We re-evaluated this antibody using the technique of non-enzymatic antigen retrieval (boiling sections in citrate buffer, heated by microwave oven) followed by streptavidin-biotin-peroxidase staining. Due to the fortuitous choice of appendix as positive control material containing small nerves, we found strong, repeatable cytoplasmic and nuclear staining of lymphoid follicle centre cells in addition to neural tissue. This effect could be repeated on other lymphoid tissues and was not dependent on microwave heating, but did require boiling in an ionic buffer solution. Staining was also observed with a fresh batch of antibody and with four of the five different batches of antibody which were supplied to us. This pattern was not obtained in fresh tissue, in fixed material following trypsinization, or by increasing the primary antibody concentration. We suggest that the boiling of sections in citrate buffer is exposing an epitope for the anti-PGP9.5 antibody which is inaccessible in the native or fixed state and therefore we would recommend retesting of antibody specificity following non-enzymatic retrieval of antigen.

Animals↗
PubMed1994

Atypical alveolar hyperplasia: relationship with pulmonary adenocarcinoma, p53, and c-erbB-2 expression.

Atypical alveolar hyperplasia (AAH) has recently been described in human lungs in association with primary lung cancer, particularly adenocarcinoma. Unlike proximal bronchogenic carcinoma, peripheral (parenchymal) adenocarcinoma of the lung does not have a well-recognized progenitor lesion. Epidemiological morphometric, and cytofluorometric data in the literature suggest that AAH is a candidate premalignant entity. In this study, 97 AAH lesions were found in lungs resected from 29 patients (1-13 lesions per case, mean 3.5) being treated for presumed carcinoma (25/29 had adenocarcinoma). From a study case-load of 285 adenocarcinoma-bearing lungs, the AAH incidence was 8.8 per cent. Sections of 67 AAH lesions from 19 patients were stained using monoclonal antibodies against Ki67 (MIB1), p53 (DO7), and c-erbB-2 (NCL-CB11). Ki67 was expressed in up to 10 per cent of AAH nuclei. Thirty-nine lesions (58 per cent) showed stainable p53 protein, while five (7 per cent) expressed membrane c-erbB-2 oncoprotein. These latter five lesions were all strongly positive for p53, and both p53 and c-erbB staining was associated with increased cellular crowding and pleomorphism in AAH. These data demonstrate that AAH exhibits some genetic changes associated with malignancy and thereby support the hypothesis that AAH is premalignant.

Adenocarcinoma↗
PubMed1994

An energy-minimized casein submicelle working model.

To develop a molecular basis for structure-function relationships of the complex milk protein system, an energy-minimized, three-dimensional model of a casein submicelle was constructed consisting of kappa-casein, four alpha s1-casein, and four beta-casein molecules. The models for the individual caseins were from previously reported energy-minimized, three-dimensional structures. Docking of one kappa-casein and four alpha s1-casein molecules produced a framework structure through the interaction of two hydrophobic antiparallel sheets of kappa-casein with two small hydrophobic antiparallel sheets (residue 163-174) of two preformed alpha s1-casein dimers. The resulting structure is approximately spherically symmetric, with a loose packing density; its external portion is composed of the hydrophilic domains of the four alpha s1-caseins, while the central portion contains two hydrophbic cavities on either side of the kappa-casein central structure. Symmetric and asymmetric preformed dimers of beta-casein formed from the interactions of C-terminal beta-spiral regions as a hinge point could easily be docked into each of the two central cavities of the alpha-kappa framework. This yielded two plausible energy-minimized, three-dimensional structures for submicellar casein, one with two symmetric beta-casein dimers and one with two asymmetric dimers. These refined submicellar structures are in good agreement with biochemical, chemical, and solution structural information available for submicellar casein.

Animals↗
PubMed1994

Comparison of the three-dimensional molecular models of bovine submicellar caseins with small-angle X-ray scattering. Influence of protein hydration.

To test the applicability of two energy-minimized, three-dimensional structures of the bovine casein submicelle, theoretical small-angle X-ray scattering curves in the presence and absence of water were compared to experimental data. The published method simulates molecular dynamics of proteins in solution by employing adjustable Debye-Waller temperature factors (B factors) for the protein, for the solvent, and for protein-bound water. The programs were first tested upon bovine pancreatic trypsin inhibitor beginning with its known X-ray crystal structure. To approximate the degree of protein hydration previously determined by NMR relaxation experiments (0.01 g water/g protein), 120 water molecules were docked into the large void of the kappa-casein portion of the structure for both the symmetric and asymmetric casein submicelle models. To approximate hydrodynamic hydration (0.244 g water/g protein), 2703 water molecules were added to each of the above structures using the "droplet" algorithm in the Sybyl molecular modeling package. All structures were then energy-minimized and their solvation energies calculated. Theoretical small-angle X-ray scattering curves were calculated for all unhydrated and hydrated structures and compared with experimentally determined scattering profiles for submicellar casein. Best results were achieved with the 120-bound-water structure for both the symmetric and asymmetric submicelle models. Comparison of results for the protein submicelle models with those for the theoretical and literature values of bovine pancreatic trypsin inhibitor demonstrates the applicability of the methodology.

Animals↗
PubMed1994

Restriction enzymes in cells, not eppendorfs.

Restriction enzymes are essential reagents to molecular biologists, but their relevance to bacterial populations is less obvious. Most bacteria encode restriction and modification systems and these are commonly considered to be a barrier to phage infection. Current evidence also supports a more general role for them in genetic recombination.

Bacteria↗
PubMed1994

Effects of sialoadenectomy and exogenous EGF on molar drift and orthodontic tooth movement in rats.

Effects on bone remodeling have been attributed to epidermal growth factor (EGF). Sialoadenectomy (SX) removes the major source of EGF in rodents and decreases both salivary and serum EGF levels. EGF effects on rat alveolar bone remodeling manifested by molar drift (MD) and orthodontic tooth movement (OTM) were examined using the following two approaches: 1) EGF depletion by SX and replacement by orally administered EGF (50 micrograms.animal-1.day-1); 2) sham rats supplemented with matching amounts of EGF. MD and OTM were measured using cephalometric radiographs; bone formation was measured histomorphometrically using tetracycline labeling. Normal MD was not detected after SX, and alveolar bone formation was significantly reduced both around the tooth and in nondental sites. Replacement EGF given to SX rats and supplemental EGF administered to sham rats changed the direction and enhanced the rate of MD. A mesially directed orthodontic force applied to the molars of SX animals increased bone formation on the distal aspect of the tooth roots. Supplemental EGF did not significantly affect OTM. EGF affects alveolar bone remodeling, as manifested clinically by alterations in normal maxillary MD.

Administration, Oral↗
PubMed1994

Health care reform and the Medicare program.

None of the health care reform bills introduced during the last session of Congress would have ended the deepening Medicare fiscal crisis. Delays in resolving Medicare's fiscal problems will increase generational inequities and cause disruptions in health care delivery. Because of the pressures of increasing health care costs on government, business, and individuals, comprehensive health care reform will be deliberated in future sessions of Congress. It remains to be seen, though, whether policymakers will be able to develop reforms that address the basic problem of rising health care costs.

Costs and Cost Analysis↗
PubMed1994

The effect of variable delays on self-control.

Five pigeons served as subjects in an experiment that examined the effects of variable as opposed to fixed delays on preference in a self-control paradigm (choice between larger, more delayed and smaller, less delayed reinforcers). Nonindependent concurrent variable-interval schedules were used to measure choice. When delays to the larger, more delayed reinforcers were variable as opposed to fixed, the subjects showed an increased preference for that alternative (the self-control alternative). A series of regressions revealed that the hyperbolic decay model and incentive theory provided poor fits to the data, but a modified version of the generalized matching law provided an adequate fit. Together, consistent with a general prediction made by discounting models, the data supported the conclusion that variable delays can increase self-control. However, specific discounting models were not able to explain the present data well.

Journal Article↗
PubMed1994

Abnormality of the contralateral ligament after injuries of the medial collateral ligament. An experimental study in rabbits.

The right medial collateral ligament of ninety-four adult, female rabbits was transected operatively. At three, six, fourteen, or forty weeks after the operation, the uninjured, contralateral (left) medial collateral ligaments of seventy-eight of the animals were tested biomechanically and compared with the left medial collateral ligaments of thirty-three normal female rabbits. The diameters of the mid-substance collagen fibrils in the medial collateral ligaments were also measured in the uninjured, contralateral hindlimbs of four animals at each interval and compared with the fibril diameters in three normal animals at each of three corresponding intervals. Subtle but significant differences between the uninjured, contralateral and the normal medial collateral ligaments with regard to biomechanical properties of collagen fibril diameters were found at all time-intervals. These results support the notion of a significant effect on the contralateral ligament after an injury to the medial collateral ligament and suggest that contralateral ligaments cannot be considered as a normal control group even in this relatively benign model of knee injury.

Analysis of Variance↗