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G Webb

Publications and source records attributed to G Webb.

85 records · Page 5Linked to original sources
PubMed1978

Partial purification and some properties of a cholinesterase from bush bean (Phaseolus vulgaris L.) roots.

A cholinesterase was partially purified from bush bean (Phaseolus vulgaris L.) roots by using acridinium-based ligand affinity chromatography. The procedure gave a 78-fold increase in specific activity, although at least three inactive contaminants remained. The enzyme activity was maximal against acetyl esters of choline and was inhibited by neostigmine. Di-isopropyl phosphorofluoridate completely inhibited activity at concentrations greater than 0.1 mM. The catalytic centre activity was 2 X 10(-4) times that of electric eel acetylcholinesterase. Cholinesterase activity appeared as a peak (s = 4.2 +/- 0.1 S) after isokinetic sedimentation. The Stokes radius was 4.00 nm and the apparent molecular weight was 72700 +/- 1900. The smallest active and native form of the enzyme appeared to be a monomer. This contrasts with animal acetylcholinesterases, in which the smallest active and native forms are multimeric.

Binding Sites↗
PubMed1978

Acetylcholinesterase: characterization of native and proteolytically derived forms and identification of structural protein components.

The assymmetric 18S and 14S forms of acetylcholinesterase (EC 3.1.1.7) from Electrophorus electricus purified by affinity chromatography on N-methylacridinium Sepharose 2B were subjected to trypsin or collagenase proteolysis and changes in the enzyme composition and structure were monitored by sucrose gradient sedimentation, gel chromatography, and sodium dodecyl sulphate - polyacrylamide gel electrophoresis. A distinction between autolytic and tryptic degradation products is described and the generation of two new forms of acetylcholinesterase from the 18S and 14S enzyme by collagenase proteolysis is reported. The species derived from the 18S form of acetylcholinesterase has a sedimentation coefficient of 21.1S and a Stokes radius of 12.9 nm while the 14S form gives rise to a 17.3S species with a Stokes radius of 11.1 nm. The proteolytically sensitive component ('tail') of the asymmetric forms of acetylcholinesterase is identified with a subunit of 45 000 daltons on sodium dodecyl sulphate - polyacrylamide electrophoresis gels.

Acetylcholinesterase↗
PubMed1977

Subxiphoid pericardial window in patients with suspected traumatic pericardial tamponade.

The technique, indications, and results of subxiphoid pericardial window in penetrating chest wounds with suspected traumatic pericardial tamponade are reported. The classic signs of pericardial tamponade (elevated central venous pressure, muffled heart sounds, and paradoxical pulse) are unreliable in an emergency situation. Chest roentgenograms and electrocardiograms are of little diagnostic value. Pericardicentesis was either falsely positive or negative in 50% of our patients. Therefore, unexplained high central venous pressure and hypotension were considered to be pericardial tamponade until disproved by the results of a subxiphoid pericardial window. There were 4 negative and 46 positive findings of tamponade in 50 consecutive patients with suspected traumatic pericardial tamponade who underwent creation of a subxiphoid pericardial window. There were no deaths or complications from the procedures. The early use of subxiphoid pericardial window has been a major factor in reducing our mortality rate from penetrating heart wounds to 12% overall, and 8% in the past three years.

Blood Pressure↗
PubMedDate not supplied

Chromosomal localization of the human urokinase plasminogen activator receptor and plasminogen activator inhibitor type-2 genes: implications in colorectal cancer.

Activation of the proenzyme of urokinase (uPA) on the surface of cancer cells has been implicated in the initiation of focal proteolytic mechanisms that permit invasion and metastasis by colon cancers. The activity of uPA on the cell surface appears to be a function of the number of uPA-specific receptors (uPAR) and the extent of inhibition of uPA by plasminogen activator inhibitors (PAI). The mapping of the genes coding for uPAR, and for PAI-2, was performed to determine whether their chromosomal localization suggested their involvement in the genetic alterations associated with cancer cell DNA. This study confirms the localization of the human urokinase plasminogen activator receptor gene to chromosome 19q and, using in situ hybridization, provides a precise localization to chromosome 19q13.2. In addition, our results confirm the previous allocation of the human plasminogen activator inhibitor-2 gene to a location 18q21.3-->18q22.1, a location that corresponds to the commonest (> 70%) somatic deletions found in colorectal carcinomas. The mapping of the uPAR and PAI-2 genes enables the elucidation of their possible involvement in the genetic alterations that determine the invasive and metastatic phenotypes in colorectal cancer.

Chromosome Mapping↗