Biomedical subjects

P Knudson

Publications and source records attributed to P Knudson.

6 recordsLinked to original sources

PubMed1988

Post-traumatic toxic shock syndrome.

Toxic shock syndrome (TSS) associated with Staphylococcus occurs most commonly in menstruating women, although cases in both sexes have been reported. This report describes a severe case of TSS after a relatively minor stab wound. The male patient exhibited all of the major characteristics of this multisystem disease including anuric renal failure. TSS, which can be fatal, may result from surgical and traumatic wound infections and demands prompt recognition and treatment.

Acute Kidney Injury↗

PubMed1988

Improving the field triage of major trauma victims.

The Trauma Scores, CRAMS scales, and mechanisms of injury of 500 trauma patients were evaluated for their ability to identify a seriously injured patient. Serious injury was defined as one of the following: Injury Severity Score (ISS) greater than 15, or emergency-room Trauma Score less than or equal to 14, or injuries requiring greater than 3 days hospitalization, or death. With the addition of specific mechanisms of injury (auto vs. pedestrian accident at greater than 5 m.p.h., motor vehicle accident at greater than 40 m.p.h., motorcycle accident at greater than 20 m.p.h., or a major assault), the sensitivity of a field Trauma Score of less than 14 could be improved from 45% to 75%, with a reasonable specificity of 40%. With these same mechanisms, the sensitivity of a CRAMS scale of less than or equal to 8 increased from 66% to 93%, with a specificity of 30%. The addition of these mechanisms of injury to standard field triage scoring appears to improve the identification of seriously injured patients while retaining an acceptable level of overtriage.

Accidental Falls↗

PubMed1985

Adenosine 5'-phosphosulfate kinase from Penicillium chrysogenum. Determining ligand dissociation constants of binary and ternary complexes from the kinetics of enzyme inactivation.

Adenosine 5-phosphosulfate (APS) kinase from Penicillium chrysogenum is irreversibly inactivated by trinitrobenzene sulfonate in a pseudo-first order process. Under standard assay conditions kapp was 1.9 X 10(-3) s-1. Saturating MgATP or MgADP decreased Kapp to a limit of 4.1 X 10(-4) s-1. There are several explanations for the partial protection, including the presence of two essential lysyl side chains, only one of which is at the active site. Analysis of the inactivation kinetics by means of linear plots derived for partial protection yielded dissociation constants for E X MgATP (Kia) and E X MgADP (Kiq) of 2.9 mM and 1.8 mM, respectively. Low concentrations of APS alone provided no protection against trinitrobenzene sulfonate inactivation, but in the presence of 1 mM MgADP, as little as 2 microM APS provided additional protection while 100 microM APS reduced kapp to the limit of 4.1 X 10(-4) s-1. The results confirm the formation of a dead end E X MgADP X APS proposed earlier as the cause of the potent substrate inhibition by APS. Linear plots of 1/delta k versus 1/[MgADP] at different fixed [APS] and of 1/delta k versus 1/[APS] at different fixed [MgADP] were characteristic of the ordered binding of MgADP before APS (or the highly synergistic random binding of the two ligands). The true APS dissociation constant of the dead end E X MgADP X APS complex (K'ib) was determined to be 1.9 microM. From the value of K'ib and the previously reported value of KIB (apparent inhibition constant of APS as a substrate inhibitor of the catalytic reaction at saturating MgATP), the ratio of the MgADP and PAPS release rate constants (k4/k3) was calculated to be 11. Inactivation kinetics was used to study the effects of Mg2+ and high salt on ADP and APS binding. The results indicated that free ADP binds to the enzyme more tightly than does MgADP at low ionic strength. High salt decreased free ADP binding, but had little effect on MgADP binding. APS binds more tightly to E X MgADP in the absence or presence of salt than to E X ADP.

Adenosine Diphosphate↗

PubMed1985

Adenosinetriphosphate sulfurylase from Penicillium chrysogenum: steady-state kinetics of the forward and reverse reactions, alternative substrate kinetics, and equilibrium binding studies.

The kinetics of the forward ATP sulfurylase-catalyzed reaction were examined using a new assay based on 32PPi released from [gamma-32P]MgATP in the presence of inorganic sulfate. Replots yielded Vmaxf = 6.6 units mg protein-1, KmA = 0.13 mM, Kia = 0.33 mM, and KmB = 0.55 mM, where A = MgATP and B = SO2-4. Thiosulfate, a dead-end inhibitor of the reaction, was competitive with sulfate and noncompetitive with respect to MgATP. The ratio kcat/KmA was determined for several alternative inorganic substrates, B, where A = MgATP and B = SO2-4, SeO2-4, MoO2-4, WO2-4, or CrO2-4. For SO2-4 and SeO2-4, the ratio was 5-6.5 X 10(4) M-1 S-1; for the others, the ratio was 5.8-7.3 X 10(5) M-1 S-1. The results support a random addition of MgATP and inorganic substrate. The kinetics of the reverse reaction were examined using a new assay based on 35SO2-4 release from [35S]APS (adenosine 5'-phosphosulfate) in the presence of MgPPi. Reciprocal plots were linear, intersecting below the horizontal axis. Replots yielded Vmaxr = 50 units mg protein-1, KmQ = 0.3 microM, Kiq = 0.04 microM, and KmP = 4 microM, where Q = APS and P = PPi (total of all species). MgATP and SO2-4 were both competitive with APS and noncompetitive with respect to MgPPi. Taken together with earlier results suggesting that APS is competitive with both MgATP and SO2-4 and that MgPPi is noncompetitive with respect to both substrates, the qualitative results point to a random A-B, ordered P-Q kinetic mechanism. The Scatchard plot for [35S]APS binding was curved, indicating either negative cooperativity or more than a single class of sites. [gamma-32P]MgATP displayed half-site saturation in the presence of saturating FSO-3.

Adenosine Triphosphate↗

PubMed1985

APS kinase from Penicillium chrysogenum. Dissociation and reassociation of subunits as the basis of the reversible heat inactivation.

Adenosine-5'-phosphosulfate (APS) kinase from Penicillium chrysogenum, loses catalytic activity at temperatures greater than approximately 40 degrees C. When the heat-inactivated enzyme is cooled to 30 degrees C or lower, activity is regained in a time-dependent process. At an intermediary temperature (e.g. 36 degrees C) an equilibrium between active and inactive forms can be demonstrated. APS kinase from P. chrysogenum is a dimer (Mr = 57,000-60,000) composed of two apparently identical subunits. Three lines of evidence suggest that the reversible inactivation is a result of subunit dissociation and reassociation. (a) Inactivation is a first-order process. The half-time for inactivation at a given temperature is independent of the original enzyme concentration. Reactivation follows second-order kinetics. The half-time for reactivation is inversely proportional to the original enzyme concentration. (b) The equilibrium active/inactive ratio at 36 degrees C increases as the total initial enzyme concentration is increased. However, Keq,app at 5 mM MgATP and 36 degrees C calculated as [inactive sites]2/0.5 [active sites] is near-constant at about 1.7 X 10(-8) M over a 10-fold concentration range of enzyme. (c) At 46 degrees C, the inactive P. chrysogenum enzyme (assayed after reactivation) elutes from a calibrated gel filtration column at a position corresponding to Mr = 33,000. Substrates and products of the APS kinase reaction had no detectable effect on the rate of inactivation. However, MgATP and MgADP markedly stimulated the reactivation process (kapp = 3 X 10(5) M-1 X s-1 at 30 degrees C and 10 mM MgATP). The kapp for reactivation was a nearly linear function of MgATP up to about 20 mM suggesting that the monomer has a very low affinity for the nucleotide compared to that of the native dimer. Keq,app at 36 degrees C increases as the MgATP concentration is increased. The inactivation rate constant increased as the pH was decreased but no pK alpha could be determined. The reactivation rate constant increased as the pH was increased. An apparent pK alpha of 6.4 was estimated.

Adenosine Triphosphate↗

PubMed1982

Splenomegaly without an apparent cause.

Twenty-eight patients undergoing splenectomy for splenomegaly of unclear causation are presented. The cause of splenomegaly was determined at splenectomy in seven patients, none of whom had lymphoma. In three additional patients, disease associated with splenomegaly developed in the follow-up period after splenectomy. During the entire follow-up period, only one instance of lymphoma has developed. Especially in young patients who have a history of recent infection, a delay in performing splenectomy for splenomegaly is indicated.

Adolescent↗