Biomedical subjects

A J McKinley

Publications and source records attributed to A J McKinley.

7 recordsLinked to original sources

PubMed2002

Use of polymer mats in series for sequential reactive barrier remediation of ammonium-contaminated groundwater: laboratory column evaluation.

Large-scale column experiments were undertaken to evaluate the potential of in situ polymer mats (installed in series) to be used as permeable reactive barriers for delivery of oxidants and reductants to induce sequential bioremediation of ammonium-contaminated groundwater (approximately 120mg L(-1) NH4+-N), without bioaugmentation. The strategy was for the first group of polymer mats to deliver oxygen to induce bacterial nitrification of the ammonium to nitrite/ nitrate as the groundwater moved past and for the second group of polymer mats to deliver hydrogen or ethanol, to induce bacterial denitrification of the nitrite/nitrate to produce nitrogen gas. Once purging of the first polymer mat commenced, ammonium concentrations decreased downgradient from the polymer mats. Nitrification rates increased and stabilized over the 6-month experiment, with stable nitrification half-lives in the range 0.07-0.25 days. Nitrification most likely occurred in a biologically active zone at the polymer wall/aqueous interface. With hydrogen delivery via the polymer mats, a denitrification half-life (nitrate plus nitrite removal) of 3.5 days was induced. Denitrification rates were significantly enhanced when ethanol was delivered via a polymer mat, with denitrification half-lives in the range of 0.12-0.34 days. Nitrification/ denitrification rates were maintained for groundwater flow rates up to 300 m yr(-1), suggesting oxygen and ethanol delivery rates via the polymer mats were sufficient not to limit nitrification or denitrification. In soil columns, the polymer mat delivery system provided an effective and reliable technique for delivery of oxygen and hydrogen or ethanol for sequential nitrification/denitrification of ammonium-contaminated groundwater. Scale-up of this concept to a field pilot-scale is currently underway.

Biodegradation, Environmental↗

PubMed2001

Laparoscopy in a case of pediatric blunt abdominal trauma.

The use of laparoscopy in the assessment and treatment of blunt abdominal trauma has been reported for both adults and children. With increasing surgical experience and improvements in equipment, an expanding range of therapeutic interventions is available. The management of a 7-year-old boy who sustained blunt abdominal trauma during a fall from a bicycle is described. He was hemodynamically stable, but his abdomen remained tender, with guarding in the right upper quadrant. Serial ultrasound scans showed a thick-walled gallbladder and increasing intraabdominal fluid. Laparoscopy was used both as a diagnostic tool, and then as a therapeutic method. Diagnostic laparoscopy showed a ruptured gallbladder treated by laparoscopic cholecystectomy. A 3-cm grade 1 liver laceration also was identified, which required no intervention. Free bile was aspirated and the peritoneal cavity thoroughly lavaged. The child made a rapid postoperative recovery. The ultimate aim in the management of blunt trauma is to avoid unnecessary laparotomy while preventing undue delay in the detection of significant intraabdominal pathology. Computed tomography scanning, ultrasound scanning, and diagnostic peritoneal lavage all have strengths for detecting different injury types, but they also have a low specificity in determining the need for laparotomy. The advantages and limitations of laparoscopy in hemodynamically stable children who have sustained injuries from blunt trauma are discussed. The authors recommend laparoscopy in experienced hands as an additional tool for the optimal management of selected trauma cases.

Abdominal Injuries↗

PubMed2001

Oxidized adrenodoxin acts as a competitive inhibitor of cytochrome P450scc in mitochondria from the human placenta.

The conversion of cholesterol to pregnenolone by cytochrome P450scc is the rate-determining step in placental progesterone synthesis. The limiting component for placental cytochrome P450scc activity is the concentration of adrenodoxin reductase in the mitochondria, where it permits cytochrome P450scc to work at only 16% of maximum velocity. Adrenodoxin reductase serves to reduce adrenodoxin as part of the electron transfer from NADPH to cytochrome P450scc. We therefore measured the proportion of adrenodoxin in the reduced form in intact mitochondria from the human placenta during active pregnenolone synthesis, using EPR. We found that the adrenodoxin pool was only 30% reduced, indicating that the adrenodoxin reductase concentration was insufficient to maintain the adrenodoxin in the fully reduced state. As both oxidized and reduced adrenodoxin can bind to cytochrome P450scc we tested the ability of oxidized adrenodoxin to act as a competitive inhibitor of pregnenolone synthesis. This was done in a fully reconstituted system comprising 0.3% Tween 20 and purified proteins, and in a partially reconstituted system comprising submitochondrial particles, purified adrenodoxin and adrenodoxin reductase. We found that oxidized adrenodoxin is an effective competitive inhibitor of placental cytochrome P450scc with a Ki value half that of the Km for reduced adrenodoxin. We conclude that the limiting concentration of adrenodoxin reductase present in placental mitochondria has a two-fold effect on cytochrome P450scc activity. It limits the amount of reduced adrenodoxin that is available to donate electrons to cytochrome P450scc and the oxidized adrenodoxin that remains, competitively inhibits the cytochrome.

Adrenodoxin↗

PubMed2001

Restorative proctocolectomy.

The development and refinement of pelvic pouch surgery now allows the excision of a diseased colon while maintaining transanal faecal continence. The success of restorative proctocolectomy is largely dependent on careful patient selection combined with meticulous surgical technique. The authors discuss the main indications for restorative proctocolectomy and describe the surgical procedure.

Humans↗

PubMed2000

Luminescent photoproducts in UV-irradiated ice.

This Account describes the near-UV and visible luminescences emitted from crystalline, polycrystalline, and amorphous ices as a result of excitation by UV light. Vibrationally resolved, short-lived luminescence around 340 nm arises from excited O(2) formed by the reaction of two O atoms. Long-lived luminescence around 420 nm is tentatively assigned to a spin-forbidden (4)sigma(-) --> X(2)Pi transition of OH. This Account gives a history of the research into this little-known phenomenon, places it in the context of other spectroscopic studies of gaseous and solid water, and proposes future directions for the work.

Ice↗

PubMed1998

Tailoring the management of nonparasitic liver cysts.

OBJECTIVE: To determine the optimal management of symptomatic non-parasitic liver cysts. SUMMARY BACKGROUND DATA: Management options for symptomatic nonparasitic liver cysts lack substantiation through comparative studies with respect to safety and long-term effectiveness. METHODS: A retrospective review of the surgical management of patients with hepatic cysts between October 1988 and August 1997 was undertaken to determine morbidity rates and to assess long-term recurrence. RESULTS: Thirty-eight patients (35 women, 3 men) underwent 48 operations for symptomatic hepatic cysts of mean diameter 12 cm, with a mean follow-up of 41 months. Twenty-three patients had simple cysts, and 15 patients had polycystic liver disease (PCLD). The symptomatic recurrence rates after laparoscopic or open deroofing for simple cysts were 8% and 29%, and for PCLD 71% and 20%, respectively. There were no symptomatic recurrences after 14 hepatic resections. There were no perisurgical deaths; however, morbidity rates were significant after laparoscopic deroofing, open deroofing, and hepatic resection (25%, 36%, and 50%, respectively). CONCLUSIONS: Selection of patients with truly symptomatic hepatic cysts is crucial before considering interventional techniques. For simple cysts, radical laparoscopic deroofing is usually curative; open deroofing should be reserved for cysts inaccessible by laparoscopy. The latter technique is well tolerated; however, long-term symptom control is unpredictable in patients with PCLD. Hepatic resection for PCLD provides satisfactory long-term symptom control but has an appreciable morbidity rate. Although laparoscopic and open deroofing procedures are less reliable in the long term for solitary cysts, they might be useful steps before embarking on this major procedure.

Adult↗

PubMed1996

APC mutations in colorectal tumors with mismatch repair deficiency.

We have investigated the influence of genetic instability [replication error (RER) phenotype] on APC (adenomatous polyposis coli), a gene thought to initiate colorectal tumorigenesis. The prevalence of APC mutations was similar in RER and non-RER tumors, indicating that both tumor types share this step in neoplastic transformation. However, in a total of 101 sequenced mutations, we noted a substantial excess of APC frameshift mutations in the RER cases (70% in RER tumors versus 47% in non-RER tumors, P < 0.04). These frameshifts were characteristic of mutations arising in cells deficient in DNA mismatch repair, with a predilection for mononucleotide repeats in the RER tumors (P < 0.0002), particularly (A)n tracts (P < 0.00007). These findings suggest that the genetic instability that is reflected by the RER phenotype precedes, and is responsible for, APC mutation in RER large bowel tumors and have important implications for understanding the very earliest stages of neoplasia in patients with tumors deficient in mismatch repair.

Adenomatous Polyposis Coli↗