Optimal state filtering and parameter identification for linear systems

This paper presents the optimal filtering and parameter identification problem for linear stochastic systems with unknown multiplicative and additive parameters over linear observations, where unknown parameters are considered Wiener processes. The original problem is reduced to the filtering problem for an extended state vector that incorporates parameters as additional states. The obtained optimal filter for the extended state vector also serves as the optimal identifier for the unknown parameters. Performance of the designed optimal state filter and parameter identifier is verified for both stable and unstable linear uncertain systems. Copyright © 2007 John Wiley & Sons, Ltd.     

Peroxisome proliferator-activated receptor beta/delta exerts a strong protection from ischemic acute renal failure

Ischemic acute renal failure is characterized by damages to the proximal straight tubule in the outer medulla. Lesions include loss of polarity, shedding into the tubule lumen, and eventually necrotic or apoptotic death of epithelial cells. It was recently shown that peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) increases keratinocyte survival after an inflammatory reaction. Therefore, whether PPARbeta/delta could contribute also to the control of tubular epithelium death after renal ischemia/reperfusion was tested. It was found that PPARbeta/delta+/- and PPARbeta/delta-/- mutant mice exhibited much greater kidney dysfunction and injury than wild-type counterparts after a 30-min renal ischemia followed by a 36-h reperfusion. Conversely, wild-type mice that were given the specific PPARbeta/delta ligand L-165041 before renal ischemia were completely protected against renal dysfunction, as indicated by the lack of rise in serum creatinine and fractional excretion of Na+. This protective effect was accompanied by a significant reduction in medullary necrosis, apoptosis, and inflammation. On the basis of in vitro studies, PPARbeta/delta ligands seem to exert their role by activating the antiapoptotic Akt signaling pathway and, unexpectedly, by increasing the spreading of tubular epithelial cells, thus limiting potentially their shedding and anoikis. These results point to PPARbeta/delta as a remarkable new target for preconditioning strategies.     

A randomized, double-blind, placebo-controlled trial to determine effectiveness of antibiotic prophylaxis for tension-free mesh herniorrhaphy

BACKGROUND: In recent years, use of prosthetic material for inguinal hernia repair has increased dramatically. Tension-free repairs have gained popularity not only for recurrent or complicated hernias, but for primary hernia repairs as well. Although routine use of prophylactic antibiotics is not recommended in the Philippines for open nonimplant herniorrhaphy, there is little direct clinical evidence on which to base recommendations when implantable mesh is used. STUDY DESIGN: We conducted a prospective, randomized, double-blind, placebo-controlled trial comparing wound infection rates in 360 patients (180 received prophylactic antibiotics, 180 received a placebo) undergoing primary inguinal hernia repair electively using polypropylene mesh. Age, gender, American Society of Anesthesiologists class, type of hernia, type of anesthesia, and duration of operation were recorded. Infections were evaluated 1 week, 2 weeks, and 1 month after operation by an independent surgeon. All complications were recorded. Results were assessed using chi-square, Fisher's exact test, and Student's t-tests as appropriate. RESULTS: Groups were well matched for all preoperative variables studied, including comorbid conditions. Six patients from the antibiotic group and four from the placebo group failed to followup after the second week. Superficial surgical site infection developed in 3 patients (1.7%) from the antibiotic group and 6 (3.3%) from the placebo group (p = 0.50). One from each group developed deep surgical site infection. Both patients were readmitted and underwent repeated debridement, which eventually resulted in graft loss. CONCLUSIONS: Preoperative administration of single-dose antibiotic for tension-free inguinal mesh herniorrhaphy did not markedly decrease risk of wound infection in this patient population. Our results do not support use of antibiotic prophylaxis for tension-free mesh herniorrhaphy.     

Laparoscopic versus standard appendectomy outcomes and cost comparisons in the private sector

Minimally invasive surgery has been proposed as the preferred treatment strategy for various gastrointestinal disorders due to shorter hospital stay, less pain, quicker return to normal activities, and improved cosmesis. However, these advantages may not be straightforward for laparoscopic appendectomy, and optimal management of remains controversial. One hundred forty-eight patients with clinical and radiologic diagnoses of acute appendicitis treated in two different hospitals were retrospectively reviewed. Seventy-eight patients underwent laparoscopic appendectomy in hospital A and 70 patients underwent standard appendectomy in hospital B. Patients treated by either type of surgery were compared in terms of clinical and pathologic features, operation characteristics, complications, and costs. There were no significant differences between both groups in terms of clinical features, radiologic studies, complications, and final pathology findings (P > .05). Hospital stay was significantly shorter and bowel movements recovered quicker in the laparoscopy group. However, overall and operating room costs were significantly higher in patients treated by laparoscopy (P < .01). Our series show a subtle difference in terms of hospital stay and bowel movement recovery, favoring patients treated by laparoscopy. However, these results have to be carefully examined and weighed, because overall costs and operating room costs were significantly higher in the laparoscopy group. Presented at the Forty-Sixth Annual Meeting of The Society for Surgery of the Alimentary Tract, Chicago, Illinois, May 14–18, 2005 (oral presentation).     

Absorption rates and free radical scavenging values of vitamin C-lipid metabolites in human lymphoblastic cells.

BACKGROUND: In this study we investigated the cellular absorption rates, antioxidant and free radical scavenging activity of vitamin C-lipid metabolites. The absorption was measured in a human lymphoblastic cell line using a spectrophotometric technique. MATERIAL/METHODS: Cellular vitamin C levels in the human lymphoblastic H9 cell line were measured using the 2,4-dinitrophenylhydrazine spectrophotometric technique. Free radical scavenging activity of vitamin C-lipid metabolites was measured by the reduction of 1,1-diphenyl-2-picryl hydrazyl (DPPH) to 1,1-diphenyl-2-picryl hydrazine. Vitamin C-lipid metabolite scavenging of peroxyl radical oxygen reactive species (ORAC) was determined by fluorescence spectrophotometry. RESULTS: Compared to ascorbic acid (AA), calcium ascorbate (CaA), and calcium ascorbate-calcium threonate-dehydroascorbate (Ester-C), vitamin C-lipid metabolites (PureWay-C) were more rapidly absorbed by the H9 human T-lymphocytes. The vitamin C-lipid metabolites (PureWay-C) also reduced pesticide-induced T-lymphocyte aggregation by 84%, while calcium ascorbate-calcium threonate-dehydroascorbate (Ester-C) reduced aggregation by only 34%. The vitamin C-lipid metabolites (PureWay-C) demonstrated free radical scavenging activity of nearly 100% reduction of DPPH at 20 microg/ml and oxygen radical scavenging of over 1200 micro Trolox equivalents per gram. CONCLUSIONS: These data demonstrate that the vitamin C-lipid metabolites (PureWay-C) are more rapidly taken-up and absorbed by cells than other forms of vitamin C, including Ester-C. This increased rate of absorption correlates with an increased protection of the T-lymphocytes from pesticide toxicities. Further, vitamin C-lipid metabolites (PureWay-C) are a potent antioxidant and have significant free radical scavenging capabilities.     

Acute epidural hematoma: an analysis of factors influencing the outcome of patients undergoing surgery in coma

Mortality due to epidural hematoma is virtually restricted to patients who undergo surgery for that condition while in coma. The authors have analyzed the factors influencing the outcome of 64 patients who underwent epidural hematoma evacuation while in coma. These patients represented 41% of the 156 patients operated on for epidural hematoma at their centers after the introduction of computerized tomography (CT). Eighteen patients (28.1%) died, two (3.1%) became severely disabled, and 44 (68.8%) made a functional recovery. The mortality rate for the entire series was 12%, significantly lower than the 30% rate observed when only angiographic studies were available. A significant correlation was found between the final result and the mechanism of injury, the interval between trauma and surgery, the motor score at operation, the hematoma CT density (homogeneous vs. heterogeneous), and the hematoma volume. The patient's age, the course of consciousness before operation (whether there was a lucid interval), and the clot location did not correlate with the final outcome. The mortality rate was significantly higher in patients operated on within 6 hours or between 6 and 12 hours after injury than in those undergoing surgery 12 to 48 hours after injury. Compared with the patients operated on later, the patients undergoing surgery in the early period were, on the average, older and had more rapidly developing symptoms, more pupillary changes, lower motor scores at surgery, larger hematomas, a higher incidence of mixed CT density clots, more severe associated intracranial lesions, and higher postoperative intracranial pressure (ICP). The mechanism of trauma seems to influence the course of consciousness before and after surgery. Passengers injured in traffic accidents had a lower incidence of a lucid interval and longer postoperative coma than patients with low-speed trauma, suggesting more frequent association of diffuse white matter-shearing injury. The duration of postoperative coma correlated with the morbidity rate in survivors. Forty-eight patients (75%) had one or more associated intracranial lesions, and 70% of these required treatment for elevation of ICP after hematoma evacuation. An ICP of over 35 mm Hg strongly correlated with poor outcome; administration of high-dose barbiturates was the only effective means for lowering ICP in nine of 15 patients who developed severe intracranial hypertension after surgery. This study attempts to identify patients at greater risk for presenting postoperative complications and to define a strategy for control CT scanning and ICP monitoring.     

Effect of high-dose methylprednisolone infusion on polymorphonuclear leukocyte function in patients with systemic lupus erythematosus

We have studied the effect of high-dose (1 gm) methylprednisolone infusion on polymorphonuclear leukocyte (PMN) function in 11 patients with active systemic lupus erythematosus (SLE). The only alteration of polymorphonuclear leukocyte function produced consistently by methylprednisolone was decreased adherence to plastic surfaces when tested 2 hours after infusion. This steroid-induced abnormality, however, was transient. Cells obtained from patients 24 hours after a single dose of drug exhibited normal adhesiveness. These results indicate that single, large doses of methylprednisolone do not produce long-lasting abnormalities of PMN function in patients with lupus.     

Pregnancy outcome in congenital dyserythropoietic anemia type I

Objectives: Congenital dyserythropoietic anemia type I (CDA I) is a rare inherited disease characterized by moderate to severe macrocytic anemia and abnormal erythroid precursors with nuclear chromatin bridges and spongy heterochromatin. Moderate to severe maternal anemia is a recognized independent risk factor for low birth weight (LBW) and complicated delivery. The aim of the study was to review the outcome of pregnancies in women with CDA I. Methods: The clinical and laboratory records of 28 spontaneous pregnancies in six Bedouin women with CDA I were reviewed. The results were compared with findings from a retrospective review of a large population‐based registry including all pregnancies in Bedouin women during the same 15‐yr period. Results: Eighteen pregnancies in women with CDA I (64%) were complicated. One pregnancy was aborted spontaneously in the first trimester and one resulted in a non‐viable fetus (stillborn at 26 wk). Cesarean section (CS) was performed in 10 pregnancies (36%). Eleven of the 26 newborns (42%) had a LBW: six were born prematurely and five were small for gestational age. The odds ratio for CS in women with CDA I compared with healthy Bedouin women was 4.5 [95% confidence interval (CI) 1.2–10.3], and for a LBW infant, 5.5 (95% CI 2.4–12.3). Careful follow‐up was associated with significantly better fetal outcome (P = 0.05). Conclusions: Pregnancies in women with CDA I are at high risk for delivery‐related and outcome complications. To improve fetal outcome, women with CDA I should be carefully monitored during pregnancy.