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Biomedical subjects

K R Williams

Publications and source records attributed to K R Williams.

At least 163 records · Page 9Linked to original sources
PubMed1984

Care of the patient critically ill with inflammatory bowel disease.

The nurse is instrumental in providing and coordinating the complex care of the patient critically ill with inflammatory bowel disease. Knowledge of the disease process and its complications provides the nurse a foundation for understanding the clinical course of the disease and for planning patient care. Management of alterations in nutritional status, wound healing, and fluid and electrolyte balance ensure an optimal recovery trajectory.

Colitis, Ulcerative↗
PubMed1983

Limited proteolysis studies on the Escherichia coli single-stranded DNA binding protein. Evidence for a functionally homologous domain in both the Escherichia coli and T4 DNA binding proteins.

Limited proteolysis can be used to remove either 42 or 62 amino acids at the COOH terminus of the 18,873-dalton Escherichia coli single-stranded DNA binding protein (SSB). Since poly(dT), but not d(pT)16, increases the rate of this reaction, it appears that cooperative SSB binding to single-stranded DNA (ssDNA) is associated with a conformational change that increases the exposure of the COOH terminus to proteolysis. As a result of this DNA-induced conformational change, we presume that the COOH-terminal region of SSB will become more accessible for interacting with other proteins that utilize the SSB:ssDNA complex as a substrate and that are involved in E. coli DNA replication, repair, and recombination. Removal of this COOH-terminal domain from SSB results in a stronger helix-destabilizing protein which suggests this region may be important for controlling the ability of SSB to denature double-stranded DNA. Since similar results have previously been reported for the bacteriophage T4 gene 32 protein (Williams, K.R., and Konigsberg, W. (1978) J. Biol. Chem. 253, 2463-2470; Hosoda, J., and Moise, H. (1978) J. Biol. Chem. 253, 7547-7555), the acidic, COOH-terminal domains of these two single-stranded DNA binding proteins may be functionally homologous. Preliminary evidence is cited that suggests other prokaryotic and eukaryotic DNA binding proteins may contain similar functional domains essential for controlling their ability to invade double helical DNA.

Amino Acid Sequence↗
PubMed1983

A model for the calculation of mechanical power during distance running.

Because widely varying estimates of mechanical power have been calculated for a given speed of running by previous investigators, the effects of various assumptions necessary for mechanical power calculations were evaluated via a segmental energy analysis using 3-D cine data from 31 well-trained subjects running overground at 3.57 ms-1. The magnitude of power calculated was very dependent upon assumptions involving the amount of between segment energy transfer occurring, the relative metabolic cost of positive vs negative work, the amount of the total negative work attributed to muscular work, the effects of elastic storage of energy and on the choice of cutoff frequency in filtering the coordinate data. Mechanical power values ranged from 273 to 1775 W depending on the particular assumptions made and computational methods employed giving efficiency ratios from 0.31 to 1.97. These results point to a need for more definitive research into the role played by energy transfer, negative work, and elastic storage of energy before confidence in measured mechanical power can be established.

Biomechanical Phenomena↗
PubMed1983

A scanning transmission electron microscopy study of two dental amalgams.

Two fully aged amalgam alloys were examined using a scanning transmission electron microscope both in the transmission and scanning mode. The dispersed type amalgam containing a distribution of silver-copper spheres in addition to the Ag3Sn powder showed a markedly reduced gamma 1 grain size compared to a conventional Ag3Sn type amalgam. It is suggested that the increased compressive creep strength of the dispersed type material is a direct result of the reduced gamma 1 grain size and not due to a dispersion hardening effect from the cores of the remaining Ag-Cu spheres. Similarly, the formation of complex Cu-Sn intermediate phases at the Ag-Cu sphere surfaces are unlikely to lead to a dispersion strengthening effect. It is postulated that the reduced grain size in high copper amalgams is a consequence of the enhanced nucleating effect of a copper based phase on gamma 1.

Biomechanical Phenomena↗
PubMed1983

Cyclic creep and fracture of dental amalgam.

The creep strain rate and fracture of several dental amalgams has been shown to be markedly dependent on the type of loading applied. Cyclic loading typical of the in vivo situation increases creep rates and reduces times to fracture when analysis is based on a Mechanical Equation of State. The cyclic strain rate enhancement over static loading is highest for conventional amalgam while the modern ternary alloys show the smallest increases.

Biomechanical Phenomena↗
PubMed1983

F sex factor encodes a single-stranded DNA binding protein (SSB) with extensive sequence homology to Escherichia coli SSB.

We have determined the sequence of the gene encoding a single-stranded DNA (ss DNA) binding protein (SSB) from the Escherichia coli F sex factor and the amino acid sequence of the protein it encodes. The protein has extensive homology with E. coli SSB, particularly within its NH2-terminal region, where 87 of the first 115 amino acid residues are identical to those of the E. coli protein. We have previously shown that this portion of E. coli SSB contains the DNA binding region. The sequences diverge extensively in their COOH-terminal regions, although small areas of homology exist in several places. Six of the last seven amino acid residues of the two proteins are identical, which may have implications in terms of the direct interactions of these proteins with other proteins required for DNA replication, recombination, and repair. The coding region of the F plasmid ssf gene is 537 base pairs. The protein encoded by the gene contains 178 amino acids (one more than E. coli SSB) and has a calculated molecular weight of 19,505. Other than the presumptive Shine-Dalgarno sequence, the promoter and terminator regions of both genes are not similar. The most significant feature in this regard may be the lack of a region of dyad symmetry within the presumptive promoter of the F plasmid ssf gene as is found in the region of the presumptive E. coli ssb promoter. In this report the predicted secondary structures of both the F plasmid and E. coli SSB proteins are compared and the evolutionary significance of their sequence and structural similarities to the functional domains of the proteins are discussed.

Amino Acid Sequence↗
PubMed1982

Bacteriophage T4 gene 45. Sequences of the structural gene and its protein product.

Bacteriophage T4 gene 45 codes for a protein whose functions are required for both T4 DNA replication and T4 late gene transcription. To facilitate studies of the interactions of 45 protein with the T4 DNA replication complex and with RNA polymerase, we have determined the primary structure of 45 protein. The amino acid sequence of 45 protein has been determined by correlating nucleotide sequence analysis of gene 45 with protein chemistry studies of 45 protein. Our studies indicate that gene 45 codes for a polypeptide containing 227 amino acids, with a calculated Mr = 24,710. The coding region of gene 46 is preceded by a putative promoter containing sequences which are homologous to Escherichia coli RNA polymerase recognition and binding regions. In addition, there are sequence similarities in the translation initiation regions of gene 45 and the rIIB gene, which may relate to their common regulation by regA protein.

Base Sequence↗
PubMed1982

Structure of dihydrofolate reductase: primary sequence of the bovine liver enzyme.

The primary structure of dihydrofolate reductase from bovine liver has been established by Edman degradation of the intact carboxymethylated protein and of peptides obtained from the protein by the action of cyanogen bromide, trypsin, and the protease from Staphylococcus aureus, respectively. Since separation of some of the peptide mixtures by classical methods proved impossible, new systems were developed for the use of high-performance liquid chromatography to separate such mixtures. Some of the cleavage procedures used to obtain peptides gave atypical results at certain peptide bonds. The results are discussed in terms of the residues involved in these unexpectedly resistant or sensitive bonds. The sequence of the bovine liver enzyme is compared with those published for the enzyme from other sources, and known or probable functions of invariant residues are described. Sequences of vertebrate and bacterial reductases are compared and contrasted, and a possible role is considered for the residues which are invariant in bacterial reductases, but different in vertebrate reductases, in determining the selective inhibitory action of trimethoprim on bacterial reductases.

Amino Acid Sequence↗
PubMed1982

The effect of stride length variation on oxygen uptake during distance running.

Ten recreational runners (mean VO2max 64.7 ml . kg-1 . min-1) underwent a 5-d acclimation period to treadmill running at a 7 min . mile-1 pace (3.83 m . s-1) for 30 min each day. During these runs their freely chosen stride lengths were determined and expressed as a percentage of leg length (%LL). On two subsequent testing days stride length was systematically varied over a range of +/- 20% LL about the freely chosen value. O2 uptake was determined by the Douglas Bag method. All subjects exhibited a stride length of which O2 uptake was minimized, although the individual profiles varied considerably. The mean increases in VO2 were 2.6 and 3.4 ml . kg-1 . min-1 at the short- and long-stride length extremes, respectively. During unrestricted running deviations from optimal stride length caused a mean increase in VO2 of 0.2 ml . kg-1 . min-1. The relatively efficient running patterns used by the subjects during unrestricted running indicate either an adaption to the chosen stride length through training or a successful process of energy optimization.

Adaptation, Physiological↗
PubMed1982

Clonotypes of anti-phosphocholine antibodies induced with Proteus morganii (Potter). II. Heterogeneity, class, and idiotypic analyses of the repertoires in BALB/c and A/HeJ mice.

The heterogeneity of the PC-specific IgG response of Proteus morganii (Potter) was systematically analyzed. Serum samples from individual mice were focused in paired adjacent tracks, PC-specific antibodies were detected with 125I-PC-RNase, and the resulting autoradiographs were examined for co-focusing bands. Both the number of different antibody band groups and their frequency of expression were determined. Varying qualitatively from simple to complex, the spectrotypes of 38 BALB/c and 19 A/HeJ each appeared unique. However, after thorough analysis for co-focusing bands. It was evident that each spectrotype reflected a unique combination of shared band groups rather than numerous uniquely focusing band groups. The responses of A/HeJ and BALB/c showed striking similarities qualitatively in the appearance of individual spectrotypes. The heterogeneity of the two strains was also similar quantitatively. The basis for this finite though complex heterogeneity was examined by in situ subclass analysis after IEF and idiotype analysis of IEF bands by using antibodies purified from individual BALB/c and A/HeJ. Each mouse primarily expressed IgG3, and antibody bands of this subclass ranged from pI of 6.75 to 8.2. IgG1-positive bands ranged from pI of 6 to 7. Minimal amounts of IgG2 and IgM were detected. In comparisons of individual mice, there was more heterogeneity apparent in the IgG3 subclass than in the IgG1. The idiotype, IdX-M603, was found in both subclasses and also in multiple band groups focusing at different positions within each subgroup. Possible explanations for this heterogeneity among these idiotypically related antibodies are discussed.

Animals↗
PubMed1981

Primary structure of the bacteriophage T4 DNA helix-destabilizing protein.

The amino acid sequence of the single-stranded DNA-binding protein encoded by gene 32 of bacteriophage T4 has been determined by manual and automated sequencing of peptides derived from cyanogen bromide cleavage and digestion with trypsin, chymotrypsin, and staphylococcal protease. Tryptic digestion of citraconylated or succinylated gene 32 protein yields five peptides containing 4, 27, 42, 65, and 163 residues, respectively, which can be separated by Sephadex chromatography. Each of these tryptic peptides was subjected to automated sequencing and, if necessary, more extensive cleavage. The gene 32 protein contains 301 amino acids and has a molecular weight of 33,487. Based on its primary structure, the gene 32 protein is predicted to contain 36% alpha helix, 18% beta sheet, and 46% random coil. The native protein can be specifically cleaved at lysine 21 and 253 by limited trypsin digestion. Previous studies have shown that the "B" region (residues 1 to 21) is essential for cooperative binding to single-stranded DNA. The "A" region (residues 254 to 301) has been implicated in controlling the helix-destabilizing "activity" of gene 32 protein and in interacting with other T4 DNA replication proteins. The "A" region has a net charge of -10 and, in addition, contains two unusual stretches of 4 serine residues separated by glycine 284. The region between positions 72 and 116 contains 6 of the 8 tyrosine residues in the protein and may be important for DNA binding.

Amino Acid Sequence↗
PubMed1981

Sequences of the ssb gene and protein.

We have determined the sequences of the ssb gene and protein of Escherichia coli. The coding region of ssb is 534 base pairs and is preceeded and followed by dyad symmetries of 39 base pairs and 27 base pairs, respectively. The promoter for ssb is close to that for uvrA and these two genes are transcribed in opposite directions: ssb clockwise and uvrA counterclockwise on the standard E. coli genetic map. The DNA helix-destabilizing protein encoded by the ssb gene (single-strand binding protein) contains 177 amino acids and has a calculated molecular weight of 18,873. Although there is no extensive sequence homology among the three helix-destabilizing proteins whose sequences are now known, both the E. coli and bacteriophage T4 DNA helix-destabilizing proteins do contain an acidic, alpha-helical region at their carboxy termini that may be functionally homologous. The remainder of the E. coli helix-destabilizing protein can be divided into two apparent domains on the basis of its amino acid sequence. The amino-terminal region (residues 1-105) contains 79% of the charged residues (27 out of 34 total) in the protein and is predicted to have a high degree of secondary structure (alpha helix and beta pleated sheet). In contrast, the region including residues 106-165 contains only two charged amino acids and is devoid of alpha helix or beta pleated sheet.

Amino Acid Sequence↗