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K Fisher

Publications and source records attributed to K Fisher.

At least 19 recordsLinked to original sources
PubMed1992

Evidence for a third transcript from the human factor VIII gene.

Intron 22 of the human factor VIII gene was recently found to contain a gene, associated with a CpG island, which is transcribed in the direction opposite to factor VIII. We now report that another transcript emanates from the island and is transcribed in the same direction as factor VIII. The divergent transcripts originate within 122 bases of each other. The newly identified 5' exon in intron 22 potentially codes for eight amino acids and is spliced to exons 23-26, with the factor VIII reading frame maintained. The protein encoded by this transcript would include the factor VIII C2 domain, responsible for phospholipid binding and essential for coagulant activity.

Amino Acid Sequence↗
PubMed1991

Klebsiella pneumoniae nitrogenase. The pre-steady-state kinetics of MoFe-protein reduction and hydrogen evolution under conditions of limiting electron flux show that the rates of association with the Fe-protein and electron transfer are independent of the oxidation level of the MoFe-protein.

The pre-steady-state kinetics of H2 evolution from Klebsiella pneumoniae nitrogenase functioning at 23 degrees C, pH 7.4, under conditions of extremely low electron flux through the MoFe-protein exhibited a lag phase of several minutes duration. The approach to a steady-state rate of H2 evolution was accompanied by a 50% decrease in the amplitude of the MoFe-protein e.p.r. signal. These kinetics have been simulated using our published kinetic model for nitrogenase [Lowe & Thorneley (1984) Biochem. J. 224, 877-886], which was developed using data obtained with nitrogenase functioning at high electron fluxes. The e.p.r. data showed that the rate of complex-formation between reduced Fe-protein and the MoFe-protein (k+1 = 5 x 10(7) M-1.s-1) is the same for the resting (E0) and one-electron-reduced (E1H) states of the MoFe-protein. Stopped-flow spectrophotometry also showed that electron transfer from the Fe-protein to the MoFe-protein in states E0 and E1H occurs at the same rate (kobs. = 140 s-1). These data support our previous assumption that the rate constants that define the 'Fe-protein cycle' are independent of the level of reduction of the MoFe-protein.

Computer Simulation↗
PubMed1991

Safe performance of difficult laparoscopic cholecystectomies.

Laparoscopic cholecystectomy has been advocated for the treatment of uncomplicated symptomatic gallstone disease, but has not been widely advocated for the management of more complicated gallbladder disease such as acute cholecystitis, previous surgery, or common duct stones. During the last 9 months, 360 patients underwent laparoscopic removal of their gallbladder. A total of 138 had a complicated presentation, making surgery more difficult. This article discusses the management of these patients with acute cholecystitis, previous surgery, or common duct disease. Using the described techniques, there were no complications or mortality. Laparoscopic management of difficult gallbladder problems is safe and effective.

Acute Disease↗
PubMed1991

Multiple carriers for dipeptide transport: carrier-mediated transport of glycyl-L-proline in renal BBMV.

To determine whether multiple carriers are responsible for luminal uptake of glycyl-L-proline (Gly-Pro) in the renal proximal tubule, transport of Gly-[3H]Pro was measured in brush-border membrane vesicles (BBMV). A Line-weaver-Burk analysis of Michaelis-Menten kinetics revealed the presence of two carriers: a lower affinity, higher capacity carrier (Km = 1.3 x 10(-2) M; Vmax = 4.6 x 10(-8) mol.mg-1.min-1) and a higher affinity, lower capacity carrier (Km = 2.7 x 10(-7) M; Vmax = 7.8 x 10(-13) mol.mg-1.min-1). The dipeptides Gly-Sar, beta Ala-His, and pyroGlu-His competitively inhibited the low-affinity carrier. No effect on the Km or Vmax of Gly-Pro transport in this range was seen in the presence of the dipeptides Gly-Gly or cycloHis-Pro. The high-affinity carrier exhibited a different inhibition spectrum. Competitive inhibition of Gly-Pro transport was demonstrated for the dipeptides Gly-Gly and Gly-Sar. However, none of the other peptides tested above altered Gly-Pro transport in the high-affinity range, including pyroGlu-His, which is transported by a high-affinity carrier. At both low (4 x 10(-8) M) and high (4 x 10(-3) M) concentrations, uptake of Gly-Pro was stimulated in the presence of an inwardly directed H+ gradient but was unaffected by the presence of an inward Na+ gradient. In addition, measurements in the presence of valinomycin and an outwardly directed K+ gradient strongly suggest that H(+)-stimulated uptake at both concentrations is electrogenic.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Klebsiella pneumoniae nitrogenase. Mechanism of acetylene reduction and its inhibition by carbon monoxide.

The electron flux through the MoFe-protein of nitrogenase from Klebsiella pneumoniae determines the absolute and relative rates of 2H+ reduction to H2 and acetylene (C2H2) reduction to ethylene (C2H4) at saturating levels of reductant (Na2S2O4) and MgATP. High electron flux, induced by a high Fe-protein (Kp2)/MoFe protein (Kp1) ratio, favours C2H2 reduction. These data can be explained if ethylene, the two-electron reduction product of C2H2, is not released until three electrons have been transferred from Kp2 to Kp1. This explanation is also consistent with a pre-steady-state lag phase for C2H4 formation of 250 ms observed when functioning enzyme is quenched with acid. Electron flux through nitrogenase is inhibited by C2H2 at high protein concentrations. This is because the association rate between Kp1 and oxidized Kp2 is enhanced by C2H2, leading to an increased steady-state concentration of the inhibitory complex Kp2oxKp1C2H2. This effect is not relieved by CO. Thus CO and C2H2 (or C2H4) must be bound at the same time to distinct sites, presumably at Mo or Fe centres, on the enzyme.

Acetylene↗
PubMed1990

A protocol for management of temporomandibular joint ankylosis.

A management protocol for temporomandibular joint (TMJ) ankylosis consisting of 1) aggressive resection, 2) ipsilateral coronoidectomy, 3) contralateral coronoidectomy when necessary, 4) lining of the TMJ with temporalis fascia or cartilage, 5) reconstruction of the ramus with a costochondral graft, 6) rigid fixation, and 7) early mobilization and aggressive physiotherapy is presented. The protocol was retrospectively evaluated in the first 14 patients (18 involved TMJs) treated and followed postoperatively for at least 1 year. The facial asymmetries present in all unilateral cases remained corrected. The mean maximum postoperative interincisal opening at 1 year was 37.5 mm (292.36% mean increase), lateral excursions were present in 16 of 18 joints (vs 0 of 18 joints preoperatively), and pain was present in 2 of 18 joints (vs 13 of 18 preoperatively). The results of this study indicate that this protocol is effective for treatment of TMJ ankylosis.

Adolescent↗
PubMed1990

Routine quality assurance and results of a diagnostic radiology quality assurance programme.

Routine testing of diagnostic radiology equipment performance has shown that more than 10% of equipment has not been properly setup. It also identifies equipment which is deteriorating in use as well as faults which need immediate correction. There is little doubt it is cost-effective and has also been shown to be effective in reducing the collective dose to the population from diagnostic radiology.

England↗
PubMed1989

Kinetics and mechanism of the reaction of cyanide with molybdenum nitrogenase from Azotobacter vinelandii.

The steady-state kinetic behavior of the six-electron reduction of N2 by nitrogenase is known to differ markedly from the six-electron reduction of cyanide in two ways. First, on extrapolation to infinite concentration of cyanide, the H2 evolution reaction is almost completely suppressed whereas at extrapolated infinite concentration of N2, H2 evolution continues. Second, as the ratio of the Fe protein to the MoFe protein increases, the reduction of N2 is favored over H2 evolution, whereas the reduction of cyanide becomes less favored relative to H2 evolution. We have extended these steady-state experiments with Azotobacter vinelandii nitrogenase to include a third observation, that the six-electron reduction of N2 is favored over H2 evolution at high total protein concentrations whereas cyanide reduction is less favored over H2 evolution at high total protein concentrations. All three steady-state observations can be explained by a model whereby cyanide is proposed to bind to a redox state of the MoFe protein more oxidized than that reactive toward H2 evolution and N2 reduction. To test this model, we have examined the pre-steady-state kinetic behavior of both cyanide reduction by A. vinelandii nitrogenase and cyanide inhibition of total electron flow through nitrogenase. The data show that in the presence or absence of cyanide there is a short lag of 100 ms before H2 is detected, followed by a linear phase of H2 evolution lasting for about 3 s, during which time no effects of cyanide are observable. After 3 s electron flow is finally inhibited by cyanide, and the cyanide reduction product CH4 is finally formed.(ABSTRACT TRUNCATED AT 250 WORDS)

Azotobacter↗
PubMed1989

Low-affinity transport of pyroglutamyl-histidine in renal brush-border membrane vesicles.

These studies were performed to determine if a low-affinity carrier is present in the luminal membrane of proximal tubular cells for the transport of the dipeptide, pyroglutamyl-histidine (pGlu-His). We have previously described the existence of a specific, high-affinity, low-capacity [transport constant (Kt) = 9.3 X 10(-8) M, Vmax = 6.1 X 10(-12) mol.mg-1.min-1] carrier for pGlu-His in renal brush-border membrane vesicles. In the present study, we sought to demonstrate that multiple carriers exist for the transport of a single dipeptide by determining whether a low-affinity carrier also exists for the uptake of pGlu-His. Transport of pGlu-His into brush-border membrane vesicles was saturable over the concentration range of 10(-5)-10(-3) M, yielding a Kt of 6.3 X 10(-5) M and a Vmax of 2.2 X 10(-10) mol.mg-1.min-1. Uptake was inhibited by the dipeptides glycyl-proline, glycyl-sarcosine, and carnosine but not by the tripeptide pyroglutamyl-histidyl-prolinamide. We conclude that 1) pGlu-His is transported across the luminal membrane of the proximal tubule by multiple carriers and 2) the lower affinity carrier, unlike the higher affinity carrier, is nonspecific with respect to other dipeptides.

Biological Transport↗
PubMed1988

Monolayer coupling in phosphatidylserine bilayers: distinct phase transitions induced by magnesium interacting with one or both monolayers.

We have investigated the thermotropic behavior of phospatidylserine bilayers interacting with Mg2+ either on one side or both sides, using differential scanning calorimetry. Large unilamellar vesicles (LUV) of phosphatidylserine exposed to Mg2+ on the external side only displayed an upward shift of the gel-liquid transition temperature (Tm) of about 6-8 degrees C relative to the Tm of LUV in Na+. Mg2+ was shown not to enter the vesicle interior, by means of fluorescence measurements on encapsulated 8-hydroxyquinoline-5-sulfonate. Multilamellar vesicles prepared in the presence of Mg2+, or vesicles prepared by Mg2+-induced fusion of small unilamellar vesicles, had Tm values that were shifted upward by about 16-17 C degrees. When the latter preparation was treated with EDTA to produce vesicles with Mg2+ inside and Na+ outside, the Tm was found to be shifted again by only 6-8 degrees C. These observations indicate that the monolayer interacting with Na+ fluidizes the monolayer interacting with Mg2+, and that the latter tends to solidify the former. The two monolayers thus appear to be coupled, possibly by hydrocarbon chain interdigitation.

Animals↗
PubMed1988

Regulation of reconstituted renal Na+/H+ exchanger by calcium-dependent protein kinases.

Studies were performed to determine the effect of protein phosphorylation mediated by calcium-calmodulin-dependent multifunctional protein kinase II and calcium-phospholipid-dependent protein kinase on Na+/H+ exchange activity. Proteins from the apical membrane of the proximal tubule of the rabbit kidney were solubilized in octyl glucoside and incubated in phosphorylating solutions containing the protein kinase. 22Na+ uptake was determined subsequently after reconstitution of the proteins into proteoliposomes. Calcium-calmodulin-dependent multifunction protein kinase II inhibited the amiloride-sensitive component of proton gradient-stimulated Na+ uptake in a dose-dependent manner. The inhibitory effect of this kinase had an absolute requirement for calmodulin, Ca2+, and ATP. Calcium-phospholipid-dependent protein kinase stimulated the amiloride-sensitive component of proton gradient-stimulated Na+ uptake in a dose-dependent manner. The stimulating effect of this kinase had an absolute requirement for ATP, Ca2+, and an active phorbol ester. These experiments indicate that Na+/H+ exchange activity of proteoliposomes reconstituted with proteins from renal brush-border membranes are inhibited by protein phosphorylation mediated by calcium-calmodulin-dependent multifunctional protein kinase II and stimulated by that mediated by calcium-calmodulin-dependent protein kinase.

Adenosine Triphosphate↗
PubMed1988

Comparison of propofol and thiopental for the induction of anesthesia.

We compared the safety, efficacy, and side effects of induction of anesthesia with propofol (2.5 mg/kg), a new intravenous agent, and thiopental (4.0 mg/kg) in 62 patients in American Society of Anesthesiologists class I or II. There was no significant difference between induction times for the propofol (40.0 +/- 2.0 sec) and thiopental (44.0 +/- 4.0 sec) groups. Propofol administration produced a significant fall (P less than .05) in systolic blood pressure (SBP), from 134.1 +/- 2.6 mm Hg before injection to 128.3 +/- 2.4, 118.2 +/- 2.7, and 114.4 +/- 2.8 mm Hg one, two, and three minutes after injection, respectively. Diastolic blood pressure (DBP) fell significantly (P less than .05) during the three postinjection periods. Heart rate (HR) rose significantly (P less than .05), from 78.6 +/- 3.1 beats per minute before injection to 89.4 +/- 3.4 beats per minute one minute after injection. In patients given thiopental, SBP fell significantly (P less than .05), from 131.7 +/- 2.7 mm Hg before induction to 126.4 +/- 3.4 and 126.9 +/- 4.0 mm Hg two and three minutes after injection, respectively. The DBP did not change significantly in the thiopental group, but the HR rose significantly (P less than .05), from 73.3 +/- 2.8 beats per minute before injection to 83.9 +/- 3.0, 90.1 +/- 2.3, and 84.2 +/- 2.4 beats per minute one, two, and three minutes after injection, respectively. In 94% of patients given propofol, there were apneic periods of more than 60 seconds, compared to 50% in the thiopental group (P less than .05). There was a significant difference (P less than .05) between groups for the incidence of pain on injection; 31% of the patients receiving propofol had pain, compared to 3% of those receiving thiopental.

Adolescent↗
PubMed1988

Ecological evaluation of a rehabilitative environment for spinal cord injured people: behavioural mapping and feedback.

A behavioural mapping procedure was used to describe the behavioural profile, pattern of interaction and location of patients and staff in a rehabilitation unit for traumatically spinal cord injured people. Naturalistic observations were randomly obtained by trained observers during two observational periods, using 10 behavioural categories drafted from the observational literature. Feedback of the results was given to staff between the observational periods. Results suggested that patients spent a considerable proportion of their time in solitary and disengaged behaviours. Analysis of the behavioural profile of patients revealed little difference between the therapeutic day and the evening. Patients were also observed to spend large amounts of time in the ward area during the day. These results are at variance with the concept of active rehabilitation, and also raise questions concerning institutionalization. The efficacy of feedback in initiating institutional change is also examined. Comparison is made with previous research and strategies for change are suggested.

Environment↗
PubMed1988

Carrier-mediated transport of pyroglutamyl-histidine in renal brush border membrane vesicles.

These studies were performed to determine if a transmembrane carrier for pyroglutamyl-histidine (pGlu-His) is present in the luminal membrane of renal proximal tubular cells. Previous studies have suggested the intact transepithelial transport of pGlu-His, a dipeptide formed by the hydrolysis of luteinizing hormone-releasing hormone by enzymes associated with the brush border in the proximal nephron. With the use of a renal brush border membrane vesicle preparation, pGlu-His showed H+-stimulated, Na-independent, saturable transport into an osmotically active space. High-pressure liquid chromatographic analysis of both the intravesicular and extravesicular fluids indicated intact uptake of the dipeptide. The transport constant (Kt) and Vmax for pGlu-His transport were 9.3 X 10(-8) M and 6.1 X 10(-12) mol.mg-1.min-1, respectively. Transport of pGlu-His was not inhibited by the dipeptides glycyl-proline, glycyl-sarcosine, and N-beta-alanyl-L-histidine, which have been previously shown to be transported into renal brush border vesicles via a single, low-affinity, high-capacity, Na-independent, and H+-stimulated peptide carrier. In addition, the gamma-glutamyl-containing peptides gamma-glutamyl-histidine and N(N-L-gamma-glutamyl-L-cysteinyl)glycine and the tripeptide pyroglutamyl-histidyl-prolinamide were without an inhibitory effect. In contrast, transport of pGlu-His was inhibited by the dipeptide pyroglutamyl-alanine. This study demonstrates the existence of a high-affinity, low-capacity H+ cotransport system for pGlu-His in the proximal tubular luminal plasmalemma, which appears to be specific for pyroglutamyl-containing dipeptides. The data indicate that multiple dipeptide carriers are present in the proximal nephron.

Animals↗