Improving the mismatch between light and nanoscale objects with gold bowtie nanoantennas.

Metallic bowtie nanoantennas should provide optical fields that are confined to spatial scales far below the diffraction limit. To improve the mismatch between optical wavelengths and nanoscale objects, we have lithographically fabricated Au bowties with lengths approximately 75 nm and gaps of tens of nm. Using two-photon-excited photoluminescence of Au, the local intensity enhancement factor relative to that for the incident diffraction-limited beam has been experimentally determined for the first time. Enhancements >10(3) occur for 20 nm gap bowties, in good agreement with theoretical simulations.

Photodynamic treatment of neoplastic lesions of the gastrointestinal tract. Recent advances in techniques and results.

Photodynamic therapy (PDT) is a form of cancer treatment based on the selective accumulation of a photosensitizer (by exogenous or endogenous means) in neoplastic tissue. Subsequent activation of the photosensitizer by a specific wavelength of light results in tumor cell death. Activation of a photosensitizer to the appropriate energy state results in the production of singlet oxygen, a powerful oxidizing agent. PDT can kill cells by three mechanisms: direct cell death by photooxidation, apoptosis, or as a consequence of vascular shutdown. The toxicity of PDT is site specific and dependent on the organ being irradiated and the selectivity of the photosensitizer for target tissue over normal tissue. However, there are also reactions related to the sensitizer per se that are independent of those related to the treatment site. Such reactions include cutaneous photosensitization, nausea, vomiting, hypotension, and altered liver 'function' tests. Excitation of photosensitizer by an incident photon produces reemission of a fluorescent photon, which can be used to detect a tumor that is not ordinarily evident. The major limiting factor in using PDT is the depth of tumor kill. The majority of clinical experience involving PDT of the gastrointestinal tract involves patients who are considered to be poor operative risks, and reported follow-ups after treatment are not only limited but also variable.

Current concepts in gastrointestinal photodynamic therapy.

OBJECTIVE: To review current concepts of photodynamic therapy (PDT) applied to the treatment of tumors of the gastrointestinal tract. SUMMARY BACKGROUND DATA: PDT initially involves the uptake or production of a photosensitive compound by tumor cells. Subsequent activation of the photoreactive compound by a specific wavelength of light results in cell death, either directly or as a result of vascular compromise and/or apoptosis. METHODS: The authors selectively review current concepts relating to photosensitization, photoactivation, time of PDT application, tissue selectivity, sites of photodynamic action, PDT effects on normal tissue, limitations of PDT, toxicity of photosensitizers, application of principles of PDT to tumor detection, and current applications of PDT to tumors of the gastrointestinal tract. RESULTS: PDT is clearly effective for small cancers, but it is not yet clear in which cases such treatment is more effective than other currently acceptable approaches. The major side effect of PDT is cutaneous photosensitization. The major limitation of PDT is depth of tumor kill. As data from current and future clinical trials become available, a clearer perspective of where PDT fits in the treatment of cancers will be gained. Many issues regarding pharmacokinetic data of photosensitizers, newer technology involved in light sources, optimal treatment regimens that take advantage of the pharmacophysiology of photoablation, and light dosimetry still require solution. One can foresee application of differing sensitizers and light sources depending on the specific clinical situation. As technologic advances occur, interstitial PDT may have significant application. CONCLUSIONS: PDT has a potentially important role either as a primary or adjuvant mode of treatment of tumors of the gastrointestinal tract.

Tumor blood-flow changes following protoporphyrin IX-based photodynamic therapy in mice and humans.

The effects of aminolevulinic acid (ALA)-based photodynamic therapy (PDT) on tumor blood flow are controversial. This study examines the effects of ALA and Photofrin-based PDT on blood flow of Colon-26 tumors implanted in mice as well as the effects of ALA-based PDT on blood flow of human colorectal carcinomas and a carcinoid tumor in situ. Tumors are implanted in both flanks of mice. One tumor of each animal serves as a control. Blood flow is measured using a laser Doppler method. Tumor blood flow in mice not receiving a photosensitizer but treated with three different light fluences (50, 100 and 150 J/cm2) does not differ significantly from blood flow in the untreated tumor in the opposite flank. PDT after ALA administration using the three different light fluences does not significantly affect blood flow. In contrast, PDT after Photofrin administration causes a significant decrease in tumor blood flow with each light fluence, but this change is not as dramatic as reported in other studies. In contrast to mice, six patients who receive ALA prior to surgery all show a decrease in blood flow (mean = 51.8%, p < 0.001) after PDT using 100 J/cm2. Comparison with other published results suggests that it is likely that flow measurement by the laser Doppler method underestimates the effects of PDT on tumor blood flow due to the depth of laser penetration. Nevertheless, the present observations on blood flow suggest that the effects of ALA-based PDT on adenocarcinomas of the colon and rectum as well as an intra-abdominal carcinoid tumor in humans are more pronounced than would be predicated by some animal studies.

Hemodynamic effects of 5-aminolevulinic acid in humans.

Endogenous protoporphyrin IX (PpIX), which results from the oral administration of 5-aminolevulinic acid (ALA), is being investigated for its efficacy as a photosensitizing agent for photodynamic therapy (PDT). Clinical use of ALA has been associated with only mild gastrointestinal side effects. The hemodynamic effects of orally administered ALA in doses used for PDT are unknown. Six patients with a significant history of cardiac disease underwent Swan-Ganz catheterization prior to ALA administration and abdominal operation for PDT. Hemodynamic data collection began at least 1 h prior to ALA, and continued for at least 4 h subsequently, during which time no other medications were administered. When compared to measurements made prior to ALA administration, all patients displayed a significant decrease in systolic and diastolic blood pressures, pulmonary artery systolic and diastolic pressures as well as pulmonary vascular resistance. Five of the six patients also developed a decrease in systemic vascular resistance. No significant changes in pulmonary capillary wedge pressure, cardiac output or cardiac index was observed, but the mean pulse rate rose significantly. These findings cannot be explained on the basis of other cardiovascular depressants or to poor central volume status. Although no adverse sequela were appreciated as a result of the observed hemodynamic changes, this potential should be recognized in patients undergoing PDT using ALA.

Effects of fractionated 5-aminolevulinic acid administration on tissue levels of protoporphyrin in vivo.

The photodynamic therapy (PDT) of malignant tissues can be achieved via the administration of 5-aminolevulinic acid (ALA), which is naturally converted to the photoreactive substance protoporphyrin IX (PP). This study compares bolus with fractionated ALA dosing in order to determine whether one of these methods results in a higher tissue concentration of PP. Mice bearing a subcutaneously implanted colon-26 tumor were treated with ALA (200 mg kg-1), given intravenously either as a single bolus or as three equally divided doses at 50 min intervals. Tissue samples of tumor, kidney, skin, liver, skeletal muscle, colon and plasma were obtained 2, 3, 4 and 6 h later for the analysis of PP concentrations. Fractionated dosing results in significantly higher concentrations of PP at 4 and 6 h for kidney, 3 and 6 h for skin, 3 h for colon and 6 h for liver. In contrast, fractionated dosing has no significant effect on the PP concentrations of muscle and plasma. Fractionated dosing results in a significantly greater PP concentration in the tumor at 3 h relative to that observed for the bolus dose. However, from a consideration of the time of PP measurement, it is concluded that fractionated dosing may not cause a significant increase in the PP concentration in colon-26 tumors relative to that observed for the bolus dose.

On-line fluorescence of human tissues after oral administration of 5-aminolevulinic acid.

It is important to have a frame of reference for the timing of photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA) so that PDT can occur when the tissue levels of protoporphyrin IX (PP) are at a maximum. This study describes a non-invasive fluorescence technique for detecting tissue PP levels after systemic ALA administration in patients with gastrointestinal cancer. The data suggest that the intensity of tumor surface fluorescence correlates with the tumor PP concentration. Spectrophotofluorometric measurements of skin and buccal mucosa also offer an easily acquired and rapid means for determining changes in plasma concentrations of PP. A number of potential variables, including blood flow, affect the intensity of fluorescence. We report that fluorescence measurements in situ are best adapted to the measurement of changes in the porphyrin levels in tissues rather than the absolute concentrations.

Side effects and photosensitization of human tissues after aminolevulinic acid.

Aminolevulinic acid (ALA) is being used as a "prodrug" for photodynamic therapy. The side effects of ALA have been only anecdotally reported and these effects as well as pharmacokinetics of the photosensitizing end product of ALA, protoporphyrin IX (PpIX), in patients undergoing operation are unknown. This study systematically determines the side effects of ALA and pharmacokinetics of PpIX in patients undergoing abdominal surgery. Patients were given 30 or 60 mg/kg ALA preoperatively, kept in subdued light for 48 hr, and monitored clinically and with laboratory tests for 5 to 7 days and for at least 2 months thereafter. Periodic plasma samples and tissue biopsies were analyzed for PpIX concentrations using a photodiode array system. No patient developed symptoms of porphyria other than nausea and vomiting, which occurred in 20%. Nearly one-quarter of patients developed transient abnormal liver functions. No patient developed cutaneous phototoxicity, abnormal neurologic function, or unexpected postoperative laboratory tests. The times of peak plasma, skin, skeletal muscle, omental, mucosal, muscularis mucosal, and tumor concentrations of PpIX varied among patients. In general, PpIX concentrations were significantly greater with the higher dose of ALA. Tumor PpIX concentrations were significantly greater than in other tissues except liver. In conclusion, ALA, up to 60 mg/kg, is associated with minimal side effects in patients undergoing operation. Actual tissue concentrations of PpIX suggest that endogenous photosensitization using systemically administered ALA is a mode of PDT feasible for treatment of adenocarcinomas of the gastrointestinal tract in humans.

Plasma levels of protoporphyrin IX in humans after oral administration of 5-aminolevulinic acid.

We report on the pharmacokinetics of PP formation and elimination in 4 patients after the administration of oral ALA (60 mg kg-1). After a brief distribution phase, plasma PP levels decline (half life = 8 h) and was almost undetectable by 48 h post-administration. This confirms pharmacokinetic clinical data which show that ALA in a shortened interval of skin photosensitization compared with other sensitizers such as Photofrin and 'HPD'. A brief summary of other clinical-toxicity findings is reported.

Treatment efficacy: aphasia.

This article presents a brief overview of aphasia, followed by a summary of research studies and program evaluation data addressed to answering the question of the efficacy of treatment for aphasia. Selected studies are reviewed in terms of the quality of evidence they present. In addition, a number of questions that remain unanswered are also presented. Several tables, designed to provide clarifying information concerning several aspects of research design (number and types of patients studied, examples of well-designed small-group or single-subject studies, clinical techniques for which efficacy data are available), are included. The conclusion of this review is that, generally, treatment for aphasia is efficacious.

An apoptotic response to photodynamic therapy with endogenous protoporphyrin in vivo.

CDF1 mice bearing the colon-26 tumor were treated with aminolevulinic acid (200 mg kg-1) by tail-vein injection, with tumor sites irradiated 4 h later at 633 nm (75-120 J cm-2). 10 h after irradiation, samples of tumors were removed for histology studies and analysis of DNA fragmentation by static gel electrophoresis. The resulting patterns indicate an apoptotic response to photodynamic therapy with endogenously formed protoporphyrin.

Feasibility of photodynamic therapy using endogenous photosensitization for colon cancer.

A novel approach to photodynamic therapy (PDT) involves endogenous photosensitization by the oral administration of delta-aminolevulinic acid (ALA), a naturally occurring substance that is the precursor of protoporphyrin IX (PpIX). A 60-year-old man with adenocarcinoma of the sigmoid colon received ALA, 60 mg/kg by mouth. Six hours later, when the plasma level of PpIX had peaked, the tumor was exposed locally to red light at 633 nm to activate PpIX. Endoscopy and biopsy findings subsequent to this treatment showed unequivocal visible changes and necrosis. Six months later, the patient again underwent successful treatment without adverse effects. This report suggests a role for PDT using endogenous photosensitization in certain circumstances involving adenocarcinoma of the large intestine.

The effects of dietary ellagic acid on rat hepatic and esophageal mucosal cytochromes P450 and phase II enzymes.

Ellagic acid (EA), a naturally occurring plant polyphenol possesses broad chemoprotective properties. Dietary EA has been shown to reduce the incidence of N-2-fluorenylacetamide-induced hepatocarcinogenesis in rats and N-nitrosomethylbenzylamine (NMBA)-induced rat esophageal tumors. In this study changes in the expression and activities of specific rat hepatic and esophageal mucosal cytochromes P450 (P450) and phase II enzymes following dietary EA treatment were investigated. Liver and esophageal mucosal microsomes and cytosol were prepared from three groups of Fisher 344 rats which were fed an AIN-76 diet containing no EA or 0.4 or 4.0 g/kg EA for 23 days. In the liver total P450 content decreased by up to 25% and P450 2E1-catalyzed p-nitrophenol hydroxylation decreased by 15%. No changes were observed in P450 1A1, 2B1 or 3A1/2 expression or activities or cytochrome b5 activity. P450 reductase activity decreased by up to 28%. Microsomal epoxide hydrolase (mEH) expression decreased by up to 85% after EA treatment, but mEH activities did not change. The hepatic phase II enzymes glutathione S-transferase (GST), NAD(P)H:quinone reductase [NAD-(P)H:QR] and UDP glucuronosyltransferase (UDPGT) activities increased by up to 26, 17 and 75% respectively. Assays for specific forms of GST indicated marked increases in the activities of isozymes 2-2 (190%), 4-4 (150%) and 5-5 (82%). In the rat esophageal mucosa only P450 1A1 could be detected by Western blot analysis and androstendione was the only P450 metabolite of testosterone detectable. However, there were no differences in the expression of P450 1A1, the formation of androstendione or NAD(P)H:QR activities between control and EA-fed rats in the esophagus. Although there was no significant decrease in overall GST activity, as measured with 1-chloro-2,4-dinitrobenzene (CDNB), there was a significant decrease in the activity of the 2-2 isozyme (66% of control). In vitro incubations showed that EA at a concentration of 100 microM inhibited P450 2E1, 1A1 and 2B1 activities by 87, 55 and 18% respectively, but did not affect 3A1/2 activity. Using standard steady-state kinetic analyses, EA was shown to be a potent non-competitive inhibitor of both liver microsomal ethoxyresorufin O-deethylase and p-nitrophenol hydroxylase activities, with apparent Ki values of approximately 55 and 14 microM respectively. In conclusion, these results demonstrate that EA causes a decrease in total hepatic P450 with a significant effect on hepatic P450 2E1, increases some hepatic phase II enzyme activities [GST, NAD-(P)H:QR and UDPGT] and decreases hepatic mEH expression. It also inhibits the catalytic activity of some P450 isozymes in vitro. Thus the chemoprotective effect of EA against various chemically induced cancers may involve decreases in the rates of metabolism of these carcinogens by phase I enzymes, due to both direct inhibition of catalytic activity and modulation of gene expression, in addition to effects on the expression of phase II enzymes, thereby enhancing the ability of the target tissues to detoxify the reactive intermediates.

An introduction to logistic regression with an application to the analysis of language recovery following a stroke.

The aim of a statistical model is to present a simplified representation of the underlying structure in a data set by separating systematic features from random variation. Sometimes the purpose of a statistical model is to provide a simple descriptive summary of the data and sometimes it is to use the data for comparative or inferential purposes. In practice, the specification of a statistical model requires a thorough understanding of the substantive area of application, an assessment of the validity of the assumptions of the model, and an evaluation of the fit of the model to the data. In this paper, as an illustration of these aspects of the statistical modeling of data, we consider the specification, application, and interpretation of a logistic regression model for the investigation of relationships between binary response data and a collection of explanatory variables. We illustrate applications of the methodology using data from a prospective study of spontaneous language recovery following a stroke (Holland, Greenhouse, Fromm, & Swindell, 1989).

Do isolated gastric mucosal surface cells from rabbits secrete HCO3-?

Only indirect observations suggest that gastric surface cells secrete HCOH3-, which, if the case, should result in an alteration of intracellular pH. This study attempts to determine if HCO3- transport is notable in intracellular pH regulation by isolated surface cells. Maintenance of cellular pH during perfusion with HCO3(-)-free Ringer's solution is unaffected by either the absence of Cl- or the presence of an inhibitor of HCO3- transport, 4,4'-diisothiocyanostilbene-2-2'-disulfonate (DIDS). This implies the absence of Cl-/HCO3- exchange and HCO3- transport related to Na+. Addition of HCO3-/CO2 to the perfusate results in acidification due to CO2. The pH then drifts upward, which is prevented by amiloride, an inhibitor of Na+/H+ exchange. Calculated H+ efflux is not significantly affected by HCO3-/CO2. Removal of HCO3-/CO2 results in alkalinization, which is unaffected by the absence of Cl-. Alkalinization following HCO3-/CO2 removal is significantly impaired by acetazolamide. Once alkalinization occurs, the pH declines slowly and is unaffected by a Cl(-)-free perfusate or amiloride or conductance but is markedly accelerated by a Na(+)-free perfusate. The latter is prevented by amiloride but not by DIDS. Thus, under isolated conditions, gastric mucosal surface cells do not appear to be a major source of HCO3- secretion. Alkalinization of the cells can occur as a result of carbonic anhydrase activity, but the alkalinization is maintained by an extracellular Na+ gradient that prevents exchange of intracellular Na+ with extracellular H+.

Infected retroperitoneal fat necrosis associated with acute pancreatitis.

Treatment of necrosis associated with acute pancreatitis is controversial. Forty consecutive patients (63.4 +/- 1.4 years of age) with necrotic retroperitoneal fat associated with nonalcoholic pancreatitis were treated by débridement and closed drainage. None of the patients had overt pancreatic necrosis. Eight percent of the patients were operated upon 48.4 +/- 2.9 days (late referrals) and 20 percent on 4.3 +/- 0.6 days after the onset of pancreatitis. The main indication for operation was clinical deterioration. All patients had bacterial infection of the necrosis and none had a preoperative invasive procedure. Twenty-five percent of the patients had colonic necrosis at initial operation; this did not progress thereafter. No patient had histologically identifiable pancreas, which remained grossly intact at the conclusion of operation. Morbidity included postoperative "septic shock" in 97.5 percent of the patients, renal failure in 40.0 percent and enterocutaneous fistula in 47.5 percent. Reoperation for a persistent septic focus was required for 25 percent of the patients. The mortality rate was only 2.5 percent. No patient operated upon early had colonic necrosis or postoperative worsening of renal function or a fistula or required reoperation. The outcome suggests that most patients with infected retroperitoneal fat necrosis do not require pancreatic resection. Open drainage or use of continuous lavage, or both, are not necessary to achieve a low mortality rate. Retroperitoneal necrosis can harbor infection much earlier than commonly believed. While mortality has not been clearly shown to be related to early or late débridement, early operation upon patients with infected necrosis may decrease the morbidity rate.

Pancreaticoduodenectomy for recurrent alcoholic pancreatitis associated with microabscesses.

While pancreaticoduodenectomy is reported to be successful in certain patients with symptomatic recurrent or chronic pancreatitis, there are few criteria indicating who will benefit from such an extensive operation. This report consists of a small group of well-defined patients with recurrent episodes of alcoholic pancreatitis who benefited from pancreaticoduodenectomy. The courses of each patient were remarkably similar--recurrent episodes of pancreatitis, weight loss, epigastric pain, intermittent fevers, persistently elevated serum amylase and leukocyte counts, negative blood cultures, intermittent jaundice, failure of endoscopic retrograde cholangiopancreatography and scans showing a persistent mass in the head of the pancreas and biliary obstruction. While no patient had evidence of abscess at elective operation, all had multiple microscopic abscesses, apparently localized to the enlarged pancreatic head. Such localized microabscesses are not necessarily associated with acute clinical deterioration, positive blood cultures, cannulation of the pancreatic duct or pancreatic ductal dilatation. All patients benefited from operation. The presentation of recurrent episodes of pancreatitis associated with persistent enlargement of the pancreatic head and biliary obstruction without relentless progression of jaundice suggests that the patient will benefit from pancreaticoduodenectomy.

Na+ effects on intracellular pH of isolated, perfused rabbit gastric mucosal surface cells.

The effects of extracellular Na+ on intracellular pH were studied by perfusing BCECF loaded gastric mucosal surface cells adherent to glass coverslips held in a spectrophotofluorometer. Removal of Na+ from a NaCl Ringer perfusate (pH 7.4) resulted in progressive intracellular acidification, which was partially blocked by amiloride. An H+ conductance did not appear to be present. Acidification induced either by Na+ removal or by a NH4 prepulse was reversed by extracellular Na+, but this effect was not completely prevented by amiloride. Amiloride significantly, but not completely, inhibited Na22 uptake by gastric mucosal surface cells. The data suggest that extracellular Na+ maintains intracellular pH of gastric mucosal surface cells through amiloride-sensitive and -insensitive pathways. In the absence of extracellular Na+, cellular acidification seemed to be partially due to Na+/H+ exchange.

Is preoperative parenteral nutrition necessary for patients with predominantly ileal Crohn's disease?

We reviewed 46 consecutive patients with Crohn's disease predominantly affecting the ileum who specifically underwent right-sided ileocolectomy with primary anastomosis. All had a primary ileocolic anastomosis done by suture in a single-layer closed fashion. Of these 46 patients, 19.6% had overt intra-abdominal sepsis, 30.4% had prior surgery, and 95.7% were taking corticosteroid drugs just before their operation. The mean (+/- SE) age was 31.5 +/- 2.0 years. The serum albumin level was less than 35 g/L in 93.5% of patients; all had a hematocrit value less than 0.36, and 80.4% lost more than 15% of their normal body weight. No patient received parenteral nutrition either preoperatively or postoperatively. No change in the preoperative, intraoperative, or postoperative approach to treating patients with predominantly ileal Crohn's disease occurred during the 10-year period of review. There was a 2.2% incidence of perioperative complications (one superficial wound infection) and a 6.5% incidence of late (>1.49 months) complications (two suture sinuses and one wound abscess unassociated with a fistula). Our findings suggest that preoperative parenteral nutrition is unnecessary in the majority of patients with predominantly ileal Crohn's disease specifically undergoing right-sided ileocolectomy and primary ileocolic anastomosis.