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Biomedical subjects

C Ince

Publications and source records attributed to C Ince.

At least 55 records · Page 3Linked to original sources
PubMed1994

A novel two-compartment culture dish allows microscopic evaluation of two different treatments in one cell culture simultaneously. Influence of external pH on Na+/Ca2+ exchanger activity in cultured rat cardiomyocytes.

A new type of culture dish containing two separate compartments is described, that can be used in high-magnification microscopy. Using the dish, two halves of a single-cell culture, grown on a standard coverslip, can be exposed to different treatments simultaneously, allowing the effect of one treatment to be compared with that of the other treatment in the same culture. This way, the natural variability that might exist between different individual cultures is circumvented. In addition, by simultaneously conducting two experiments per dish, the number of experiments needed can be decreased. This both reduces the time to complete a series of experiments and allows the optimal use of specimens that are difficult to obtain, such as human material. We found there is an excellent barrier between the two compartments for lipophilic and hydrophilic compounds, and for low-molecular-mass cations. To illustrate the use of the dish we describe the influence of external pH on the activity of the Na+/Ca2+ exchanger in intact cultured neonatal rat ventricular cardiomyocytes. The intracellular free calcium concentration ([Ca2+]i) in the cardiomyocytes, measured using fura-2 and imaging fluorescence microscopy, was studied during sodium-free incubation. The resulting rise in [Ca2+]i at pH 7.4 in one compartment was compared with that in the other compartment in which the pH was either 6.0, 7.0, 7.4 or 8.0. It was found that below pH 7.4, Na+/Ca2+ exchanger activity was diminished, whereas at pH higher than 7.4 the Na+/Ca2+ exchanger activity was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Tonometry to assess the adequacy of splanchnic oxygenation in the critically ill patient.

Tonometry, a relatively non-invasive technique for indirectly measuring the intramucosal pH (pHi) of the gastrointestinal tract, has recently been developed for use in critically ill patients. Reports in the literature suggest that the technique is of greatest benefit to patients at risk of developing reductions in splanchnic oxygenation (decreased O2 delivery) in whom early detection of the ischemic episode could possibly guide treatment. Tonometry, although still at a relatively early stage in its clinical development, could be of value for selected patient groups although further evaluation of the technique is necessary.

Clinical Trials as Topic↗
PubMed1993

Imminent ischemia in normal and hypertrophic Langendorff rat hearts; effects of fatty acids and superoxide dismutase monitored by NADH surface fluorescence.

Hypertrophic hearts contain areas of hypoperfusion which can be visualized by increased NADH surface fluorescence during in vitro perfusion without oxygen-carrying particles under constant pressure and pacing. By contrast, fluorescence remained low when non-hypertrophic hearts were used instead. When during perfusion of normal hearts the pH of the medium was lowered from 7.5 to 7.0, areas of high fluorescence appeared in a few minutes. The high fluorescent areas under conditions of cardiac hypertrophy or pH 7.0 perfusion could be reduced by addition of superoxide dismutase. It indicates that oxygen free radicals interfere with proper flow regulation in areas of low pH. Fluorescence in hypertrophic hearts also diminished during addition of albumin-bound oleate to the standard, glucose-containing, medium. This is in agreement with our earlier finding of fatty acid protection from acidosis-initiated loss of capillary flow (Biochim. Biophys. Acta, 1033 (1990) 214-218). In contrast to low concentrations of free fatty acids, high concentrations interfere with tissue oxygenation. This has been illustrated by the use of 1 mM octanoate, which after a few min caused the appearance of high fluorescent areas. We conclude that decompensation of flow in hypoperfused areas of heart, as occurs in hypertrophy, may be stimulated by acidosis and oxygen free radicals.

Acidosis↗
PubMed1993

A new ventilation inhomogeneity index from multiple breath indicator gas washout tests in mechanically ventilated patients.

OBJECTIVES: a) To determine the validity of a new method to analyze indicator gas washout tests on mechanically ventilated patients. This method takes into account the difference between the end-expiratory gas fraction and the mean gas fraction in the lung and provides the end-expiratory lung volume and a new index of ventilation inhomogeneity called volumes regression index. b) To determine the validity of this index as a predictor of chronic obstructive pulmonary disease. c) To compare this index with the moment ratio index and Becklake index. DESIGN: Prospective study of diagnostic test. Criterium standards: Closed-circuit indicator gas dilution technique and Tiffeneau index. SETTING: Surgical intensive care unit of a university hospital. PATIENTS: A total of 38 mechanically ventilated postoperative patients, divided into two groups: the obstructive group (n = 21) and the nonobstructive group (n = 17), based on their preoperative lung function. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: a) The mean coefficient of variation of all lung volume measurements in a group of nine healthy volunteers was 5%, and the difference between this technique and the closed-circuit helium dilution measurements was -2 +/- 5%. In patients, the mean coefficient of variation of the lung volume measurements was 3.5%. The volumes regression index was measured as 0.02 +/- 0.04 in a dummy lung, 0.37 +/- 0.08 in the healthy volunteers, 0.64 +/- 0.23 in the nonobstructive patients, and 1.1 +/- 0.3 in the obstructive patients. The volumes regression index provided a better correlation (r2 = .46) with preoperatively determined Tiffeneau index than the Becklake index (r2 = .11) or the moment ratio index (r2 = .18). CONCLUSION: The proposed technique provides a means for accurate measurement of the end-expiratory lung volume and the amount of ventilation inhomogeneity in mechanically ventilated intensive care unit patients.

Adult↗
PubMed1993

Decreased mortality rate and length of hospital stay in surgical intensive care unit patients with successful selective decontamination of the gut.

OBJECTIVE: Current studies concerning selective decontamination of the digestive tract have failed to demonstrate a decrease in the length of hospital stay and mortality rate, despite the finding of a significantly lower number of infections. To evaluate this issue in more detail, the relationship between the mortality rate and length of stay with respect to colonization and infections was studied within a group of patients receiving selective decontamination. Special attention was given to the efficacy of decontamination within each patient. The main question addressed was whether an effect on mortality rate was present, and if so, why this effect was not apparent until now. DESIGN: Prospective observational cohort study. SETTING: Surgical intensive care unit (ICU) in a university hospital. PATIENTS: Ninety-seven patients primarily admitted into the surgical ICU who received selective decontamination. Transferred patients were excluded. The majority of the surgeries were elective, and all patients completed the follow-up. INTERVENTIONS: All patients received polymyxin E, amphotericin B, and norfloxacin four times a day in a 2% solution of Orabase orally and enterally as suspensions of 200, 500, and 50 mg, respectively. Assessment of the efficacy of selective decontamination was done by identification of Gram-negative microorganisms in surveillance cultures from the oropharynx and rectum. Predicted mortality rates for each patient were calculated with a logistic regression formula. MEASUREMENTS AND MAIN RESULTS: A possible benefit of selective decontamination of the digestive tract would be expressed by lower actual mortality rates compared to predicted mortality rates. Since we expected the efficacy of decontamination to have an influence on infection and mortality rates, we evaluated these rates in terms of successful or unsuccessful decontamination. Most patients (n = 72) were successfully decontaminated. Actual death rates in these patients were significantly lower than the expected rates (as calculated by the Acute Physiology and Chronic Health Evaluation [APACHE] II scoring system) (18% vs. 40%, p = .006), whereas no difference was found in those patients with failed decontamination (n = 25, death rate 44%). The patients with unsuccessful selective decontamination had significantly longer hospital (52 vs. 34 days) and ICU lengths of stays (23 vs. 9 days; p = .002) and higher mortality rates (44% vs. 18%, p = .020) when compared with those patients who were successfully decontaminated. CONCLUSIONS: These results indicate that selective decontamination is beneficial in terms of mortality rate and length of stay in surgical patients only when successful decontamination has been achieved. The subgroup of patients for whom decontamination is not successful might be responsible for the obscurity in mortality effects of selective decontamination in studies until now. It is expected that identification and subsequent elimination of possible risk factors that cause a failure of selective decontamination can result in lower morbidity and mortality rates in critically ill, surgical patients admitted to the ICU.

Anti-Bacterial Agents↗
PubMed1993

Heterogeneity of the hypoxic state in rat heart is determined at capillary level.

Heterogeneity in the hypoxic state of Tyrode-perfused rat hearts was studied using NADH and Pd-porphine videofluorometry. Ischemic as well as high-flow anoxia resulted in a homogeneous rise of tissue NADH fluorescence, whereas normoxic recovery from both types of anoxia caused transiently persisting patchy fluorescent areas. Patterns were always the same for a given heart. PO2 distribution in the vasculature measured by Pd-porphine phosphorescence showed patterns similar to the NADH fluorescence patterns. Microsphere embolization of the capillaries, but not of arterioles, elicited identical NADH fluorescence patterns as seen during recovery from anoxia without microspheres. High heartbeat rates also caused patchy fluorescent areas but not in the presence of adenosine. Patterns corresponded to those seen during normoxic recovery from anoxia under low beat rates. It is concluded that there are circulatory units in the rat heart at the capillary level that result in the temporary persistence of anoxic areas during recovery from anoxia. These vulnerable areas are the first to be compromised during high heartbeat rates.

Animals↗
PubMed1992

A simple device to inject indicator gas for wash-out tests during mechanical ventilation.

OBJECTIVE: To evaluate a simple device which injects a constant fraction of indicator gas to the inspiratory mixture for performing multi-breath wash-out tests during controlled ventilation. DESIGN: the technique in which the indicator gas is injected at the mouth of the patient (post-mix) is compared with the technique where the indicator gas is administered in the bellows of the ventilator (pre-mix). SETTING: Surgical Intensive Care Unit of a University Hospital. PATIENTS: 10 post-operative mechanically ventilated patients. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: 3 wash-out tests with the post-mix and 3 wash-out tests with the pre-mix method were performed within an hour on every patient. The calculated mean end expiratory lung volume (EEV) was 1.91 +/- 0.871 with the post-mix technique and 1.89 +/- 0.881 with the pre-mix technique. There was a good agreement with a mean difference of -1.9 +/- 6.5% in the calculated EEV values by the two different techniques. CONCLUSION: The described injector is an affordable device, is easy to assemble and can be incorporated in most electronically regulated ventilators to perform multi-breath indicator gas wash-out tests for pulmonary monitoring at the bed side of ICU patients.

Aged↗
PubMed1992

ATP-sensitive potassium channel is essential to maintain basal coronary vascular tone in vivo.

Glibenclamide, a known selective inhibitor of ATP-sensitive potassium channels, was infused into the coronary vasculature of anesthetized dogs and of isolated perfused rabbit hearts to assess the role of this channel in the maintenance of basal coronary resistance. Infusion of glibenclamide at a concentration of 55-80 microM in the dogs resulted in a twofold steady-state increase in coronary resistance with resultant tissue ischemia. Infusion of 1 microM glibenclamide in the isolated hearts resulted in a 67% increase in coronary resistance with resultant tissue ischemia. The ischemic changes were reversible upon removal of the drug. These findings indicate that the ATP-sensitive K+ channel plays a significant role in the maintenance of basal coronary resistance in vivo. Higher concentrations of glibenclamide (80-100 microM) in the in vivo dog heart consistently gave rise to an oscillating pattern of coronary flow. These oscillations were either eliminated or decreased in amplitude and frequency by the infusion of 8-phenyltheophylline, a specific competitive inhibitor of adenosine receptors. 31P-nuclear magnetic resonance spectroscopy performed at the peaks and troughs of these oscillations revealed oscillation of the phosphorylation potential at the same frequency. Thus adenosine release caused by tissue ischemia appears to play a major role in creating the oscillating pattern of coronary blood flow, that occurs during the inhibition of ATP-sensitive K+ channels by glibenclamide.

Adenosine Triphosphate↗
PubMed1992

Optical spectroscopic imaging for non-invasive evaluation of tissue oxygenation.

Altered rates of oxygen delivery and uptake between and possibly within different organs occur during critical illness. The mechanisms governing this heterogeneity are as yet not fully understood and techniques directed at being able to map the course of oxygen to the mitochondria to produce ATP, the main molecule needed to drive energy requiring processes in the cell, would give valuable information about the mechanisms underlying organ dysfunction during disease. Oxidative phosphorylation occurring in the mitochondria is the main site for the production of ATP in mammalian cells. Metabolic substrates, ADP and Pi, and O2 are the ingredients needed to produce ATP. Due to the central role of oxidative phosphorylation in the metabolism of the cell, much attention has been directed at developing non-invasive techniques to measure intermediates of the oxidative phosphorylation in tissue as an indication of the metabolic state of tissue. One such method enables mapping the distribution of tissue hypoxia by use of a fluorescence technique based on the measurements reduced nicotine amide dinucleotide (NADH). NADH is situated at the high-energy side of the respiratory chain and during tissue hypoxia accumulates in concentration because less NADH is oxidized to NAD+. Excitation of NADH by 366 nm light produces, unlike NAD+, fluorescence at 460 nm light. Previously, however, producing images of NADH fluorescence distribution in tissue has been limited to saline perfused in vitro models. We recently undertook to develop an NADH videoflurometer sensitive enough to NADH fluorescence in vivo (Ince C, Bruining HA (1991) Optical Spectroscopy for the measurement of tissue hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Fluorometry↗
PubMed1991

A phase I study of a combination of allopurinol, 5-fluorouracil and leucovorin followed by hydroxyurea in patients with advanced gastrointestinal and breast cancer.

Twenty patients with advanced carcinomas of the colorectum, pancreas, stomach, and breast were enrolled in a Phase I study of a sequential administration of 5-fluorouracil-leucovorin (FU-LV) combination followed by hydroxyurea (HU) with allopurinol protection (HALF regimen). As a weekly regimen for 6 weeks, followed by a rest period of 2 weeks, FU was administered intravenously (i.v.) during infusion of a 2-hour i.v. infusion of LV at a dose of 500 mg/m2. Six hours following the FU-LV combination, HU (1 gm/m2) was administered orally. Allopurinol (300 mg every 8 hours, orally) was given the day before and on the day of the administration of the FU-LV combination. The starting dose of FU was 300 mg/m2, with escalations to 900 mg/m2. Mucositis, diarrhea, and hematologic toxicities were mild and sporadic with FU doses up to 750 mg/m2 and occurred in patients who had received prior treatment with FU and/or radiotherapy. Dose-limiting neurocerebellar toxicity was observed in 2 out of 6 patients who received a FU dose of 900 mg/m2. Three additional patients experienced moderate neuromotor toxicity at this dose level. Among 17 patients evaluable for response, partial responses were seen in 3 of the 9 patients with colorectal cancer, 1 of the 3 patients each with carcinoma of breast and pancreas. Three of the 5 responses occurred in patients who had received prior treatment with FU and/or radiation therapy. An FU dose of 750 mg/m2 is recommended for a Phase II trial of the HALF regimen.

Aged↗
PubMed1990

A micro-perfusion chamber for single-cell fluorescence measurements.

A versatile closed micro-perfusion chamber designed for single-cell fluorescence measurements under maximum microscopic magnification is described. Glass coverslips with adherent cells can be attached to the top or bottom of the chamber, depending on whether an inverted or an upright microscope is used. Eight conical holes drilled in the side of the chamber serve for the insertion of plugs with attachments for perfusion, rapid injection of small amounts of reagents, temperature measurements or for heating the interior of the chamber. Materials used in the construction of the chamber are non-toxic and resistant to standard sterilization procedures. Perfusion and temperature properties of the chamber are described. Single cell fluorescence measurements are presented in human monocyte-derived macrophages in which NAD(P)H and intracellular calcium are measured.

Calcium↗
PubMed1990

Selective decontamination to reduce gram-negative colonisation and infections after oesophageal resection.

181 patients undergoing resection of the oesophagus for carcinoma were randomised to receive selective decontamination (test group) or conventional perioperative antibiotic prophylaxis (controls). 114 patients were finally included in the study: 12 of 56 test patients had 18 infections, whereas 32 of 58 controls acquired 51 infections. Colonisation with aerobic gram-negative microorganisms, and the number of postoperative respiratory tract infections were significantly lower in the test patients. The postoperative therapeutic use of antibiotics was significantly lower in the test group. No endogenous infections were caused by gram-negative bacilli in the test group. Selective decontamination reduces colonisation with gram-negative bacilli and postoperative infections after resection of the oesophagus.

Adult↗
PubMed1990

Heterogeneous NADH fluorescence during post-anoxic reactive hyperemia in saline perfused rat heart.

In the present study epicardial NADH fluorescence photographs were taken of rat hearts during dynamic transitions of oxygen content of the myocardium. Hearts were perfused in a Langendorff set-up where it was possible to switch between low and high-pO2 perfusates. NADH fluorescence photographs were taken with a suitable fluorescence set-up and photo negatives digitized and analyzed by use of a computer. Restoration of perfusion with a high-pO2 solution resulted in a reactive hyperemic flow being established. Prior to the occlusion being lifted high NADH fluorescence was observed. Reactive hyperemic flow was associated with heterogenic NADH fluorescence patterns which diminished as control flow was restored. The patterns observed during reactive hyperemia were identical to those observed when tissue oxygen was restored by high-pO2 perfusion following high flow hypoxia achieved by low-pO2 perfusion. This study shows that heterogenic epicardial flow patterns are associated with reactive hyperemia.

Animals↗
PubMed1990

Effects of selective decontamination on gram-negative colonisation, infections and development of bacterial resistance in esophageal resection.

Patients undergoing an esophageal resection because of carcinoma are at risk of developing postoperative respiratory tract infections. These patients were studied with respect to preceding colonisation with gram-negative bacilli and the effect of selective decontamination (SD) in decreasing this phenomenon, thereby reducing gram-negative infections. We randomised prospectively 114 patients into a test group receiving SD-medication (n = 56) and a control group receiving conventional prophylaxis. Postoperatively, all patients were admitted to the intensive care unit and mechanically ventilated. The preoperative administration of SD-medication resulted in adequate decontamination within 3-4 days in most patients, and SD could prevent gram-negative colonisation and infections effectively. Discontinuation of SD showed gram-negative (re-)colonisation, and resulted in 12 infections in 4 patients having late complications. This indicates that prolonged use in these patients might be beneficial. This new antibiotic prophylaxis proved effective, without causing an increase in bacterial resistance.

Anti-Bacterial Agents↗
PubMed1990

Design and validation of an indicator gas injector for multiple gas washout tests in mechanically ventilated patients.

A device to produce a stepwise indicator gas fraction variation to initiate a washout test in mechanically ventilated patients is described. The device, which can be used in conjunction with the commonly used Siemens-Elema series 900 ventilators, is based on simple, off-the-shelf technology. It features the simultaneous use of two indicator gases (so that the influence of diffusion processes in the gas exchange to the patient can be measured) and maintains a nearly constant FIO2 during a washout procedure. With this indicator gas injector, the transition time of the indicator gas fraction at the beginning of a washout proved to be short enough to detect ventilation inhomogeneity by visual inspection of the washout curves. Functional residual capacity measurements using this device are presented on a test lung with known volume, on healthy volunteers, and on critically ill patients.

Adolescent↗
PubMed1989

Early events in the antiproliferative action of tumor necrosis factor are similar to the early events in epidermal growth factor growth stimulation.

The process of TNF-induced cytotoxicity is complex but appears to be mediated through a TNF-specific cell surface receptor. Recent evidence suggests that TNF action on tumor cells may be antagonized by epidermal growth factor (EGF) and other EGF-receptor modulatory peptides implicating a role for EGF-R in the process of TNF-induced cytotoxicity. In the present report, we investigated the biochemical actions of TNF on several biochemical events known to occur in the process of EGF signal transduction in intact cells. The actions of TNF were compared directly to those of EGF in both TNF-sensitive and -resistant tumor cell lines. In TNF-sensitive ME-180 cervical carcinoma cells, TNF (20 ng/ml) stimulated the tyrosine protein kinase activity of the EGF-receptor (EGF-R) fivefold when measured by receptor autophosphorylation in an immune complex kinase assay. TNF activation of EGF-R kinase activity in ME-180 was measurable 10 min after TNF incubation and enzymatic activity remained elevated 20 min after TNF addition. Activation of the receptor by TNF correlated with increased 32P incorporation into EGF-R protein when receptor was immunoprecipitated from 32P-equilibrated cells following a 20 min incubation with TNF. Acid hydrolysis of EGF-R protein isolated from TNF-treated ME-180 cells demonstrates an increase in the phosphotyrosine content of EGF-R when compared to receptor isolated from untreated cells. The results suggest that TNF increased EGF-R tyrosine protein kinase activity and the state of EGF-receptor tyrosine phosphorylation in a manner similar to that reported for EGF. However, TNF does not appear to be structurally related to EGF since TNF was unable to directly activate EGF-R when incubated with extensively washed immunoprecipitates of EGF-R. In TNF-resistant T24 bladder carcinoma cells, TNF failed to alter EGF-R tyrosine protein kinase activity although both EGF and phorbol ester were shown to modulate the enzymatic activity of the receptor in these cells. These results indicate that the ability of TNF to modulate EGF-R kinase in target cells may correlate with its cytotoxic actions on TNF-sensitive tumor cells. Other biochemical activities associated with the induction or regulation of cellular growth were examined in TNF- or EGF-treated tumor cells. EGF stimulated a rapid 8-16-fold increase in the expression of the proto-oncogene c-myc when analyzed by dot-blot analysis of total cellular RNA or Northern blot hybridization of polyadenylated RNA. TNF treatment failed to alter c-myc expression in ME-180 cells when analyzed by either technique.(ABSTRACT TRUNCATED AT 400 WORDS)

Cell Division↗