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R C Williams

Publications and source records attributed to R C Williams.

At least 343 records · Page 19Linked to original sources
PubMed1981

Molecular architecture of a light-harvesting antenna. In vitro assembly of the rod substructures of Synechococcus 6301 phycobilisomes.

The 75-, 33-, 30-, and 27-kilodalton polypeptide components ("linker polypeptides") of the phycobilisome of the unicellular cyanobacterium Synechococcus 6301 have been purified and characterized. In 0.6 M NaK phosphate buffer at pH 8, the 33-, 30-, and 27-kilodalton polypeptides assemble phycocyanin into ordered aggregates, whereas the 75-kilodalton polypeptide does not interact with phycocyanin. In the presence of the 33- and 30-kilodalton polypeptides, phycocyanin is assembled into hexameric discs and rods of stacked discs with the ultrastructural characteristics of the rod elements of intact phycobilisomes. Interaction of phycocyanin with only the 27-kilodalton polypeptide leads solely to the formation of discs that do not assemble into rods. Rods formed by interaction of phycocyanin with the 30- and 33-kilodalton polypeptides in the presence of the 27-kilodalton polypeptide are much shorter than those formed in its absence. This suggests that addition to growing rods of discs formed from phycocyanin and the 27-kilodalton polypeptide terminates rod assembly. Ordered structures formed upon interaction of phycocyanin with individual linker polypeptides contain at least 1 eq of linker polypeptide/(alpha beta)6 hexamer of phycocyanin. Complexes of phycocyanin with different linker polypeptides have distinctive spectroscopic properties that suggest a polar energy transfer along rod substructures toward the core. The linker polypeptides show no absorbance in the visible region of the spectrum. Peptide mapping shows that they are not related to each other by proteolytic processing.

Amino Acids↗
PubMed1981

The HLA loci of th Hopi and Navajo.

The purpose of this paper is to present the genetic distribution at the HLA-A, B, C, and DR loci in the Hopi and the Navajo. A sample of 100 out-patients from each tribe was selected at the Public Health Service Indian Hospital in Keam's Canyon, Arizona, and was typed for the antigens at the four loci. The distributions of the alleles and the haplotypes are similar in each tribe. A distance measure, f, confirms the genetic similarity of the two populations. It is concluded that the great cultural diversity of the Hopi and the Navajo is the result of a cultural evolution and diversification that has greatly outstripped the genetic evolution at the major histocompatibility loci over the past 20,000 years.

Arizona↗
PubMed1981

Flow cytometry and cytoadherence studies of sera from children with juvenile rheumatoid arthritis and normal controls.

Recently, antibodies reactive with T cell subpopulations have been reported to exist in children with active juvenile arthritis (JRA). In an attempt to verify and extend these observations, we have studied children with JRA for the presence of anti-T cell antibodies by flow cytometry and cytoadherence rosette techniques. T cells were isolated from peripheral blood mononuclear cells (PBL) by two methods: 1) Differential sedimentation of PBL rosetted with neuraminidase-treated sheep erythrocytes, and 2) removal of immunoglobulin positive PBL by rosetting with rabbit anti-human F(ab')2 coated bovine erythrocytes and differential sedimentation. Utilizing these methods to detect lymphoreactivity of JRA sera to either population of T cell isolates, we observed the binding of ultracentrifuged normal human sera (NHS) to be comparable to JRA sera (active and quiescent). NHS reacted with 15-25% of T cells. Further studies demonstrate that monomeric IgG was chiefly responsible for lymphoreactivity. The results of these studies are discussed in the context of previous observations.

Adolescent↗
PubMed1981

T gamma subset specificity of lymphocyte reactive factors in juvenile rheumatoid arthritis and systemic lupus erythematosus sera.

Sera from 34 patients with juvenile rheumatoid arthritis (JRA), 31 patients with systemic lupus erythematosus (SLE), and 22 normal controls were studied for microcytotoxicity before and after clearing in the ultracentrifuge. Normal T cells as well as T gamma and non-T gamma subpopulations were used. Before ultracentrifugation all test sera showed apparent T gamma cell specificity in the microcytotoxicity assay where rabbit complement was added. JRA and SLE sera produced much higher proportions of cell killing than normal controls. Ultracentrifugal clearing resulted in marked diminution in microcytotoxicity of JRA and some SLE sera. However, a considerable proportion of lupus sera continued to show T cell subset cytotoxicity after ultracentrifugal clearing. No evidence for significant alteration of T gamma rosetting capacity was recorded when ultracentrifuge-cleared test sera were preincubated with T cells prior to T gamma EA rosette formation. Apparent T gamma cytotoxic specificity in some uncleared JRA and SLE sera may relate to high molecular weight materials (IgM and immune complexes) present in such samples, whereas in others it relates to lymphocyte reactive antibody with subset reactivity.

Adult↗
PubMed1981

HLA-A2 and type 2 (insulin independent) diabetes mellitus in Pima Indians: an association of allele frequency with age.

In Pima Indians with Type 2 (insulin independent) diabetes mellitus, HLA-A2 allele frequencies were inversely associated with age, (0.72, 0.59, and 0.52 in those less than 35, 35 to 54, and 55 years old and over, respectively). This suggests that there may be a gene closely linked with the HLA-A locus which plays a role in the expression of diabetes in the Pimas by contributing to an earlier age of onset. HLA-A2 was found in 65% non-diabetic and 81% of 191 diabetic subjects (relative risk = 2.2).

Adult↗
PubMed1981

Characterization of renal tissue lymphocytes in patients with interstitial nephritis.

Five patients with interstitial nephritis who presented with a variety of clinical profiles were studied with particular emphasis on documentation of the cellular types of potentially immunocompetent lymphocytes and mononuclear cells present within interstitial renal infiltrates. Immunohistologic studies coupled with conventional light and electron microscopic observations indicated that most mononuclear cells making up renal interstitial infiltrates were T cells. Some chronic inflammatory cell foci within renal interstitium were characterized by clusters of Ia antigen-positive T cells considered to be markers for activated lymphocytes. B cells were present in very small proportions (5 percent or less). The profile of immunocompetent cells present in lesions of interstitial nephritis suggests a major role for cell-mediated immunity in this disorder. Increase in tissue lymphocytes of the T gamma subclass with receptors for the Fc portion of immunoglobulin G (IgG) also suggests local activation of intrinsic suppressor cell mechanisms.

Adolescent↗
PubMed1981

ATP-induced formation of an associated complex between microtubules and neurofilaments.

Neurofilaments (also called 10-nm filaments or intermediate filaments) from bovine brain were incubated with microtubule protein at 37 degrees C in the presence or absence of 1 mM ATP and in a buffer that allowed microtubule assembly. Falling-ball viscometry revealed that the (non-Newtonian) apparent viscosity of the ATP-containing mixtures is 5-20 times greater than that of the mixtures prepared without ATP. A larger ATP-dependent increase in viscosity (approximately 100-fold) was seen when purified tubulin replaced microtubule protein. The magnitude of the increase depended on the concentrations of both neurofilaments and tubulin. The presence of both neurofilaments and assembled microtubules was necessary for the increase to occur. The viscosity was drastically reduced by stirring or by cooling of the mixtures to 0 degrees C. Sedimentation velocity experiments, conducted at 35 degrees C on mixtures previously incubated at 35 degrees C, revealed the presence of a fraction of very rapidly sedimenting material (sedimentation coefficient greater than 1000 S) in the ATP-containing solutions but not in those prepared without ATP. It is concluded that an ATP-induced complex is formed between microtubules and neurofilaments. The observed complex may reflect interactions between microtubules and neurofilaments that are significant in vivo.

Adenosine Triphosphate↗
PubMed1981

Radiographic measurement of alveolar bone loss: a perspective in vitro.

In the present study, radiographs of a model simulating several degrees of alveolar bone height were taken at different vertical projection angles. Bone height was measured by three examiners utilizing a projection technique similar to that originally employed by Björn et al. (1966, 1969). Correlation coefficients of inter- and intra-examiner readings were found to be statistically significant. The 95% confidence interval of the mean deviation between the observed bone height and the true bone height was less than 5.5%. Further investigations are planned to determine whether this method of quantitating the information on radiographs exposed under various conditions is applicable in clinical practice.

Alveolar Process↗
PubMed1981

Characterization of the suppressor cell activity in human cord blood lymphocytes.

Newborn mononuclear cells are known to have increased suppressor activity when compared with adult cells. However, the precise phenotypic description of the suppressor cell subpopulation has not yet been reported. This study was designed to examine the surface markers on human cord blood cells as defined by monoclonal antibodies and to characterize cord blood mononuclear cells that suppress in vitro pokeweed mitogen-driven immunoglobulin production. The pattern of fluorescence with the 9,6-monoclonal antibody suggested either a decreased density or a partial blocking of E-receptors on cord blood lymphocytes. Otherwise, human cord and adult cells had similar proportions of T cell subpopulations. Different subsets of newborn cells isolated by a monoclonal antibody rosetting technique were tested for suppressor activity. Cord blood lymphocytes recognized by the OKT8 monoclonal antibody constituted the major functional suppressor cell subpopulation. These cells were present in both E-rosetting and non-E-rosetting populations. Removal of OKT8+ mononuclear cord blood cells abrogated most of the suppressor activity. Thus the major suppressor cell present in cord blood is an OKT8 positive lymphocyte.

Adult↗