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Biomedical subjects

N Jensen

Publications and source records attributed to N Jensen.

At least 19 recordsLinked to original sources
PubMed2006

Salt, alone or in combination with sucrose, can improve the survival of Escherichia coli O157 (SERL 2) in model acidic sauces.

The commercial production of microbiologically safe and stable sauces containing acetic acid is guided by the Comité des Industries des Mayonnaises et Sauces Condimentaires de la Communauté Economique Européenne's (CIMSCEE) code. The CIMSCEE safety value is calculated using a linear regression equation combining weighted contributions of pH and aqueous-phase concentrations of undissociated acetic acid, NaCl, and sugars. By implication, the CIMSCEE safety equation predicts that increasing concentrations of hurdles will always increase inactivation of the target pathogen. In this study, the time to achieve a 3-log10 reduction of an acid-resistant, acid-adapted, Shiga toxin-producing Escherichia coli (STEC) O157 isolate was determined experimentally for 81 formulations at various pHs and acetic acid, NaCl, and sucrose concentrations in a broth model. The combinations were intended to simulate the aqueous phase of acidic sauces and dressings. Experimental data were fitted to the log logistic model to estimate the time to 3-log10 reduction (t3D). Comparison of fitted t3D estimates with CIMSCEE values showed agreement in predicting safety (as defined by CIMSCEE) for the majority of formulations. However, CIMSCEE safety predictions were "fail dangerous" for 13 of 81 formulations. Among these formulations and others, the observed E. coli t3D initially increased and then decreased with increasing osmolalities (NaCl and sucrose). Relative protection increased with exposure time where the protective effect of NaCl predominated. While commercial acidic sauces are not considered high-risk vehicles for STEC, interactions among hurdles that decrease their combined effectiveness are deserving of further investigation because they may reveal mechanisms of broader relevance in the inactivation of pathogens in foods.

Acetic Acid↗
PubMed2005

Effects of three months of low molecular weight heparin (dalteparin) treatment after bypass surgery for lower limb ischemia--a randomised placebo-controlled double blind multicentre trial.

OBJECTIVES: To test the hypothesis that long-term postoperative dalteparin (Fragmin), Pharmacia Corp) treatment improves primary patency of peripheral arterial bypass grafts (PABG) in lower limb ischemia patients on acetylsalicylic acid (ASA) treatment. DESIGN: Prospective randomised double blind multicenter study. MATERIALS AND METHODS: Using a computer algorithm 284 patients with lower limb ischemia, most with pre-operative ischemic ulceration or partial gangrene, from 12 hospitals were randomised, after PABG, to 5000 IU dalteparin or placebo injections once daily for 3 months. All patients received 75 mg of ASA daily for 12 months. Graft patency was assessed at 1, 3 and 12 months. RESULTS: At 1 year, 42 patients had died or were lost to follow-up. Compliance with the injection schedule was 80%. Primary patency rate, in the dalteparin versus the control group, respectively, was 83 versus 80% (n.s.) at 3 months and 59% for both groups at 12 months. Major complication rates and cardiovascular morbidity were not different between the two groups. CONCLUSIONS: In patients on ASA treatment, long-term postoperative dalteparin treatment did not improve patency after peripheral artery bypass grafting. Therefore, low molecular weight heparin treatment cannot be recommended for routine use after bypass surgery for critical lower limb ischemia.

Aged↗
PubMed2003

Role of Alicyclobacillus acidoterrestris in the development of a disinfectant taint in shelf-stable fruit juice.

AIMS: This study was undertaken to identify the bacterium and metabolic products contributing to a disinfectant taint in shelf-stable fruit juice and to determine some of the growth conditions for the organism. METHODS AND RESULTS: Microbiological examination of tainted and untainted fruit juice drinks detected low numbers of acid-dependent, thermotolerant, spore-forming bacteria in the tainted juices only. The presence of omega-cyclohexyl fatty acids was confirmed in two of the isolates by cell membrane fatty acid analysis. The isolates were subsequently identified as Alicyclobacillus acidoterrestris by partial 16S rDNA sequencing. Studies on the isolates showed growth at pH 2.5-6.0 and 19.5-58 degrees C. Gas chromatography/mass spectrometry (GC/MS) was used to identify and quantify 2,6-dibromophenol (2,6-DBP) and 2,6-dichlorophenol (2,6-DCP) in the tainted juice. Challenge studies in a mixed fruit drink inoculated with the two isolates and the type strain of A. acidoterrestris, incubated at 44-46 degrees C for 4 d, showed the production of both metabolites, which were confirmed and quantified by GC/MS. CONCLUSIONS: The results show that A. acidoterrestris can produce 2,6-DBP and 2,6-DCP in shelf-stable juices. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report detailing experimental methodology showing that A. acidoterrestris can produce 2,6-DCP in foods. Control of storage temperatures (to < 20 degrees C) immediately after processing may provide an effective control measure for the fruit juice industry to prevent spoilage by A. acidoterrestris.

Chlorophenols↗
PubMed2001

Cobalt(II), nickel(II), copper(II), and zinc(II) complexes with [3(5)]adamanzane, 1,5,9,13-tetraazabicyclo[7.7.3]nonadecane, and [(2.3)(2).2(1)] adamanzane, 1,5,9,12-tetraazabicyclo[7.5.2]hexadecane.

Isolation of the free bicyclic tetraamine, [3(5)]adamanzane.H(2)O (1,5,9,13-tetraazabicyclo[7.7.3]nonadecane.H(2)O), is reported along with the synthesis and characterization of a copper(II) complex of the smaller macrocycle [(2.3)(2).2(1)]adamanzane (1,5,9,12-tetraazabicyclo[7.5.2]hexadecane) and of three cobalt(II), four nickel(II), one copper(II), and two zinc(II) complexes with [3(5)]adamanzane. For nine of these compounds (2-8, 10b, and 12) the single-crystal X-ray structures were determined. The coordination geometry around the metal ion is square pyramidal in [Cu([(2.3)(2).2(1)]adz)Br]ClO(4) (2) and trigonal bipyramidal in the isostructural structures [Cu([3(5)]adz)Br]Br (3), [Ni([3(5)]adz)Cl]Cl (5), [Ni([3(5)]adz)Br]Br (6), and [Co([3(5)]adz)Cl]Cl (8). In [Ni([3(5)]adz)(NO(3))]NO(3) (4) and [Ni([3(5)]adz)(ClO(4))]ClO(4) (7) the coordination geometry around nickel(II) is a distorted octahedron with the inorganic ligands at cis positions. The coordination polyhedron around the metal ion in [Co([3(5)]adz)][ZnCl(4)] (10b) and [Zn([3(5)]adz)][ZnCl(4)] (12) is a slightly distorted tetrahedron. Anation equilibrium constants were determined spectrophotometrically for complexes 2-6 at 25 and 40 degrees C and fall in the region 2-10 M(-1) for the halide complexes and 30-65 M(-1) for the nickel(II) nitrate complex (4). Rate constants for the dissociation of the macrocyclic ligand from the metal ions in 5 M HCl were determined for complexes 2, 3, 5, 8, 10, and 12. The reaction rates vary from half-lives at 40 degrees C of 14 min for the dissociation of the Zn([3(5)]adz)(2+) complex (12) to 14-15 months for the Ni([3(5)]adz)Cl(+) ion (5).

Journal Article↗
PubMed2001

Blood gases and oximetry: calibration-free new dry-chemistry and optical technology for near-patient testing.

The first calibration-free Near-Patient-Testing instrument (NPT7) for blood gases, pH and oximetry has been developed. With cartridges of 30 single-use cuvettes, the NPT7 needs no preparation prior to sample aspiration, no manual calibration, and no maintenance apart from paper and cartridge changes and regulatory quality control. Each cuvette measures pCO2, pO2, pH, total hemoglobin (ctHb), oxygen saturation (sO2), fractions of carboxyhemoglobin (FCOHb) and methemoglobin (FMetHb) on 95 microl whole blood with a 110-s measuring cycle. The measurement principles are as follows: pCO2-three-wavelength infrared spectroscopy of dissolved CO2; pO2-measurement of O2-induced changes in the decay time of phosphorescence; pH-the absorbance spectra change of an azo-dye color indicator; and oximetry is performed with a 128-wavelength spectrophotometer. We determined the within and between instrument variations with tonometered whole blood on seven prototype instruments, using between one and five control levels per analyte. The 95% analytical performance limits: +/-(/Bias/ +2 xS(T)) in the NPT7 instrument matched the analytical performance criteria for the measured quantities as defined by AACC guidelines. The application of these optical measuring methods for blood gases, pH and oximetry in single-use devices introduces a new concept into point-of-care testing (POCT), where preanalytical activities otherwise associated with instrument preparation are eliminated.

Blood Gas Analysis↗
PubMed2001

Formation of guaiacol in chocolate milk by the psychrotrophic bacterium Rahnella aquatilis.

AIMS: The aim of this study was to identify the causative agent of a smoky/phenolic taint in refrigerated full cream chocolate milk. METHODS AND RESULTS: Microbiological examination of spoiled and unspoiled milk samples from the same processor showed high numbers of the psychrotrophic coliform Rahnella aquatilis in the spoiled samples only. Gas chromatography/mass spectrometry (GC/MS) was used to identify and quantify the taint compound as guaiacol (2-methoxyphenol) in the spoiled milk. Challenge studies in UHT chocolate and white milks inoculated with the isolate and incubated at 4-5 degrees C and 8-9 degrees C for 6 d showed the production of guaiacol in chocolate milk only, which was confirmed and quantified by GC/MS. CONCLUSIONS: The results indicate that if present in refrigerated chocolate milk, Rah. aquatilis can produce guaiacol within the expected shelf-life of the product, even without temperature abuse. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report that the coliform Rah. aquatilis can produce guaiacol in refrigerated chocolate milk products.

Animals↗
PubMed2001

Frequency of nightly wetting and the efficiency of alarm treatment of nocturnal enuresis.

OBJECTIVE: This study aimed to investigate the efficiency of alarm treatment in patients suffering from nocturnal enuresis (NE). MATERIAL AND METHODS: The weekly frequency of nightly wetting was used as an indicator of the patient's predisposition for alarm treatment and thus of the efficiency of the alarm. RESULTS: The pattern of relapse is shown in connection with a status I year after treatment ended for those who volunteered successful treatment. CONCLUSIONS: Patients with the highest pretreatment frequencies of NE achieved better results from treatment with an alarm and ended up in a better situation than those with lower frequencies of NE receiving the same treatment.

Adolescent↗
PubMed2000

Role of Yersinia intermedia and Pseudomonas putida in the development of a fruity off-flavour in pasteurized milk.

Analysis by gas chromatography-mass spectrometry of pasteurized milk with a fruity (pineapple like) off odour and a sour, rancid and soapy taste indicated the presence of concentrations at microg/ml levels of ethyl butanoate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, octanoic acid, decanoic acid and dodecanoic acid. The off-odour and taste were attributed to the presence of these compounds in the milk. Microbiological examination confirmed that the milk was also contaminated with a series of psychrotrophic bacteria including Yersinia intermedia, Pseudomonas putida and Rahnella aquatilis. Growth of isolates of these bacteria in UHT milk at 23 degrees C for 7 d showed that Yer. intermedia produced significant quantities of the C4-C12 alkanoic acids; Ps. putida produced only small quantities of these acids and Rah. aquatilis produced none. In addition, Yer. intermedia and Ps. putida also produced small but significant quantities of the corresponding ethyl esters. In milk inoculated with both Yer. intermedia and Ps. patida, the quantity of ethyl esters produced was greater than that found in cultures containing only one of the isolates. These studies indicated that Yer. intermedia was the principal source of the alkanoic acids in the tainted milk and that the major producer of the corresponding ethyl esters was Ps. patida. This is the first report that Yer. intermedia and Ps. putida can cause an off-odour or taste in dairy products.

Animals↗
PubMed1998

ETA and ETB receptor antagonists synergistically increase extracellular endothelin-1 levels in primary rat astrocyte cultures.

Astrocytes produce and bind endothelins (ETs), suggesting that these cells have ET autoregulatory and eliminatory functions. To further investigate these functions in primary rat astrocytes, ET-1 levels in the cell culture media (RIA/HPLC) and intracellular content of ET-1 mRNA (RT PCR) were measured under basal and stimulated (thrombin, 2.2 U/ml) conditions in the presence and absence of ETA and ETB selective antagonists (BQ123 or LU135252, and BQ788, respectively). Neither basal nor stimulated ET-1 levels in astrocyte media were influenced by ETA or ETB antagonists alone, but were significantly increased by a combination of both. ir ET-3 levels were not affected by antagonist treatment. Exogenous ET-1, added to the cultures, was rapidly cleared from the supernatant; this clearance was markedly inhibited by a combination of BQ123 and BQ788. ET-1 mRNA levels were not altered by any treatment. To conclude, in primary rat astrocyte cultures, extracellular ET-1 is cleared by binding to ET-receptors, apparently involving both, ETA and ETB sites. Thus, a blockade of the astrocytic ET eliminatory function as a consequence of the in vivo application of non-selective ET receptor antagonists may lead to increased extracellular ET levels in the brain.

Animals↗
PubMed1998

ET(A) and ET(B) specific ligands synergistically antagonize endothelin-1 binding to an atypical endothelin receptor in primary rat astrocytes.

Using a whole-cell binding procedure with long incubations at low temperature and subsequent acid stripping, we have characterized an atypical endothelin (ET) receptor in primary rat cortical astrocyte cultures. We found the following: (a) no competition for 125I-ET-1 binding by the ET(A) antagonists BQ-123 and LU 135252 or the ET(B) agonist IRL 1620; (b) weak competition by the ET(B) antagonist BQ-788 and by the predominant ET(B) ligand ET-3; (c) potent synergistic competition of ET(A) and ET(B) ligands in combination for 125I-ET-1 binding; (d) potent competition of ET-1 with any of the radioligands used, 125I-ET-1, 125I-IRL 1620, and [3H]BQ-123; (e) lack of competition of IRL 1620 and BQ-123 with the respective other radioligand; (f) shifting of the amount of acid-strippable 125I-ET-1 binding from 20 to 80% by ET(B) ligands and to 4% by ET(A) ligands; and (g) as a control, typical ET(A) and ET(B) binding characteristics of the RAT-1 fibroblast and the U373MG astrocytoma cell line, respectively, under our assay conditions. The unusual binding properties of astrocytic ET receptors described in this study appear to be the result of several binding sites in the receptor for different ET ligands or ligand epitopes.

Animals↗
PubMed1997

Early attachment of leucocytes, platelets and fibrinogen in endothelial cell-seeded Dacron venous conduits.

BACKGROUND: There is a need for prosthetic venous conduits in surgery for trauma, cancer and thrombotic disease. Such conduits in use today have a low patency rate, leaving room for much improvement. METHODS: This experimental study investigated the dynamics of the early attachment of radiolabelled platelets, leucocytes and fibrinogen to endothelial cell-seeded Dacron venous conduits in sheep. Grafts were placed as jugular vein interposition grafts, seeded on one side, not seeded on the other, and followed for 4 h. RESULTS: No difference could be demonstrated between the two graft types. Platelets showed an increasing attachment during the whole period, leucocytes an immediate attachment followed by an undulating pattern, and fibrinogen an immediate attachment with a tendency to decrease. Measurements on the vein itself showed a high attachment and, for platelets, an extremely high attachment when measured after the graft in the direction of flow. CONCLUSION: The seeding process did not seem to affect early thrombogenicity. The carefully dissected vein wall showed highly thrombogenic properties, in many ways as high as in the prosthetic graft.

Animals↗
PubMed1996

Early attachment of platelets, leukocytes, and fibrinogen in endothelial cell seeded Dacron grafts.

Endothelial cell seeding has been advocated as a method for reducing the thrombogenicity of prosthetic grafts. Principally two different techniques for endothelial cell seeding can be used: immediate seeding of grafts followed by implantation or initial growth and establishment of an endothelial cell-covered surface before subsequent late implantation. This study was designed to determine whether the immediate seeding technique altered thrombogenicity directly after graft implantation. Carotid arteries from 19 sheep were replaced with Dacron interposition grafts; one side was seeded with endothelial cells and the other side was left unseeded. The dynamics of thrombus formation involving radiolabeled platelets, leukocytes, and fibrinogen were studied for 4 hours with flow reduced to 35 ml/min. No difference in platelet uptake (approximately 6-fold increase compared to baseline values) was found between endothelial cell seeded and unseeded grafts. Likewise, there were no differences in leukocyte uptake (approximately 4-fold increase) or fibrinogen uptake (approximately 10- to 15-fold increase) between the two groups. No differences were demonstrated with regard to patency or thrombus weight. In this experimental investigation we were unable to verify any change in the uptake of platelets, white blood cells, or fibrinogen between endothelial cell seeded and unseeded Dacron grafts during the first 4 hours after graft placement. Immediate seeding does not affect the initial thrombogenicity of grafts.

Animals↗
PubMed1996

Recovery of endothelial cells and prostanoid production in endothelial cell-seeded grafts.

OBJECTIVE: To investigate the function and morphology of endothelial cell (EC) seeded grafts. DESIGN: Experimental, open study. CHIEF OUTCOME MEASURES: Endoluminal release of prostacyclin (6-Keto-PGF1 alpha) and thromboxane B2 (TxB2), patency, EC coverage and cell identity. MATERIALS: In 12 sheep, segments of both carotid arteries were excised. On one side a seeded and on the other an unseeded dacron graft were inserted. After 3 months the grafts were excised. In grafts and arteries, the endoluminal release of 6-keto-PGF1 alpha and TxB2 was determined in a perfusion system. Scanning electron microscopy (SEM) and light microscopy were used to determine the EC coverage and cell identity. RESULTS: Eight animals survived. Three seeded and two unseeded grafts were occluded. Prostacyclin release did not differ significantly between seeded and unseeded grafts and arteries, when the arteries were looked upon as one group. When the graft was compared with its corresponding artery, i.e. the artery it replaced, a significantly lower release was found in the unseeded group. Thromboxane release was undetectable in arteries but significantly higher in both graft groups. SEM revealed a cellular coverage of 75% in the seeded grafts and 50% in the unseeded (not significant). Light microscopy showed a patchy staining for Factor VIII-related antigen in some grafts in both groups. CONCLUSION: Prostacyclin release in unseeded and seeded dacron grafts did not differ 3 months after implantation in sheep, except when the graft was compared with its corresponding artery. The significance of this remains to be settled. Seeded grafts did not have a higher proportion of endothelial coverage than unseeded grafts.

6-Ketoprostaglandin F1 alpha↗
PubMed1996

In vitro attachment of endothelial cells to different graft materials.

The purpose of this study was to compare the degree of endothelial cell attachment to different synthetic vascular graft materials. Human microvessel endothelial cells were labelled with indium-111-oxine, injected into 9 different vascular grafts and left to adhere for 40 min. Unattached cells were removed and radioactivity of the grafts measured. Grafts were flushed with 20 ml phosphate-buffered saline during 5 s to remove cells with poor attachment and radioactivity was measured again. Attachment differed between the grafts. In order of decreasing attachment the grafts were albumin-coated Dacron (47%), preclotted Dacron (35-44%), gelatin-coated Dacron (20%), gelatin-coated polyurethane (17%), collagen-coated Dacron (12%), preclotted expanded polytetrafluoroethylene (ePTFE; 3%). Albumin-coated Dacron showed the highest degree of cell attachment of ePTFE the lowest. Statistically significant differences exist between ePTFE and all other grafts and between albumin-coated and collagen-coated Dacron, gelatin-coated polyurethane and gelatin-coated Dacron.

Blood Vessel Prosthesis↗
PubMed1995

Use of advance directives: a survey in three clinics.

Advance directives (ADs) are instructions from patients to their physician and family regarding their wishes for medical care in the event they become incapable of communicating those wishes. This study sought to describe the characteristics of adults who have completed advance directives and those who have expressed interest in them, and to determine what distinguishes these groups from the group with no interest in ADs. A further objective was to survey the study population on the barriers to completion of ADs. A random sample of 160 outpatients visiting one of three clinics (General Internal Medicine Clinic (GIM), HIV Clinic, and Oncology Clinic) were selected for the study. A 10-item questionnaire was administered which included questions on familiarity with, sources of information on, and interest in ADs. Demographic information was collected as well as information on subject experiences with illness and death. Twenty-six of the 160 participants (16%) had completed ADs. The prevalence of completion differed among the three clinics: HIV Clinic 25%, Oncology Clinic 18%, and GIM Clinic 8%. Nearly all patients (95%) expressed interest in ADs. Those not interested in ADs were more likely than those who were interested or those who had already completed ADs to have been in an intensive care unit themselves. Multiple barriers to completing ADs were identified. Advance directives are still used by relatively few people despite a general openness and interest in them. Few characteristics, demographic and otherwise, were identified to distinguish those who completed ADs from those who did not.

Adult↗
PubMed1994

Loss of seeded endothelial cells in vivo. A study of Dacron grafts under different flow conditions.

OBJECTIVES: To assess, in vivo, the loss of endothelial cells seeded in a Dacron graft at low, restricted arterial flow and at normal unrestricted flow. DESIGN AND SETTING: Laboratory animal study. MATERIALS: Indium-111-oxine labelled endothelial cells were seeded in externally supported, preclotted Dacron grafts, inserted as interposition grafts in the carotid arteries of nine sheep. Activity (radioactivity) was measured, flow established, on one side unrestricted 120-180 ml/minute, and on the other restricted to 50 ml/minute by a distal clamp. OUTCOME MEASURES: The reduction in activity over the grafts was measured for 2 hours. RESULTS: There was an immediate loss of activity to around 80% and thereafter a lower rate of cell loss to around 50%. No difference could be demonstrated in the loss from low flow compared to high flow grafts. All grafts were patent. There was no difference in thrombus weights. CONCLUSION: No difference could be demonstrated in seeded endothelial cell loss from a Dacron graft in vivo at low flow (50 ml/minute) compared with unrestricted flow (120-180 ml/minute).

Animals↗
PubMed1994

Short AV interval VDD pacing does not prevent tilt induced vasovagal syncope in patients with cardioinhibitory vasovagal syndrome.

Eleven subjects (mean age 50 years, range 33-71 years), who had previously received permanent dual chamber pacemakers for cardioinhibitory vasovagal syncope, underwent paired Westminster protocol tilt tests, one with short AV delay VDD pacing and one without pacing, to test the hypothesis that continuous ventricular pacing would prevent the cardiac initiation of vasovagal syncope. Nine (82%) of the paced tilts produced positive vasovagal outcomes compared with seven (64%) of the unpaced tilts. No important differences in the heart rate or blood pressure behavior during tilt or the time to positive vasovagal outcomes were observed between the paired tilts. There was more accelerated syncope/presyncope once symptoms had developed during the paced tilts of subjects in whom both study tilts were positive, although this did not reach statistical significance (P = 0.054). This study shows that atrial synchronous ventricular pacing does not prevent the initiation, or progression, of tilt induced vasovagal syncope in predisposed subjects.

Adult↗