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Biomedical subjects

J Nielsen

Publications and source records attributed to J Nielsen.

At least 181 records · Page 10Linked to original sources
PubMed1998

Pharmacologically evoked fictive motor patterns in the acutely spinalized marmoset monkey (Callithrix jacchus).

The existence of a spinal network capable of generating rhythmic alternating activity resembling locomotion still has not been firmly established in primates, including man, although evidence for one is accumulating. The present study investigated whether it is possible to activate such a network by administration of a variety of pharmacological agents to acutely spinalized marmoset monkeys (Callithrix jacchus) in the absence of phasic afferent input to the spinal cord. Fourteen marmoset monkeys were decerebrated, spinalized, and paralyzed. The nerves supplying both hindlimbs were cut and recorded from. In 5 monkeys the effect of electrical stimulation of the brainstem was investigated before spinalization. In 3 of these monkeys, rhythmic activity alternating between extensors and flexor nerves was seen. In the 2 other monkeys only synchronized activity was elicited. In acutely spinalized monkeys, administration of L-3,4-dihydroxyphenylalanine (L-dopa; 3-4 h after treatment with nialamide) failed to evoke any rhythmic alternating activity. In contrast, administration of clonidine elicited alternating activity in all of 8 monkeys tested. In 4 of these monkeys, the activity was restricted to alternation between ipsilateral and contralateral flexor nerves, whereas alternating activity between ipsilateral flexors and extensors was also seen in the other 4 monkeys. Administration of excitatory amino acids (NMDA or NMA) also elicited rhythmic alternating activity in 7 of 10 spinalized monkeys. In 4, rhythmic alternating activity was seen between extensors and flexors on one limb as well as between ipsilateral and contralateral flexors. In 3 monkeys NMDA/NMA produced alternation between extensors and flexors of one limb without alternation between the ipsilateral and contralateral sides. Administration of noradrenaline failed to elicit any rhythmic activity, but rather completely depressed already existing activity. Administration of serotonin (5-HT) was ineffective in facilitating alternating activity in 6 of 8 monkeys and was facilitatory to rhythmic activity in the other 2. We suggest that these data provide further evidence of a network capable of eliciting rhythmic alternating activity resembling locomotion in the primate spinal cord. The network, however, seems to be more difficult to activate pharmacologically in those conditions than in other mammals. This may especially be the case in higher primates, including man.

Animals↗
PubMed1998

Carbon catabolite repression of invertase during batch cultivations of Saccharomyces cerevisiae: the role of glucose, fructose, and mannose.

When Saccharomyces cerevisiae are grown on a mixture of glucose and another fermentable sugar such as sucrose, maltose or galactose, the metabolism is diauxic, i.e. glucose is metabolized first, whereas the other sugars are metabolized when glucose is exhausted. This phenomenon is a consequence of glucose repression, or more generally, catabolite repression. Besides glucose, the hexoses fructose and mannose are generally also believed to trigger catabolite repression. In this study, batch fermentations of S. cerevisiae in mixtures of sucrose and either glucose, fructose or mannose were performed. It was found that the utilization of sucrose is inhibited by concentrations of either glucose or fructose higher than 5 g/l, and thus that glucose and fructose are equally capable of exerting catabolite repression. However, sucrose was found to be hydrolyzed to glucose and fructose, even when the mannose concentration was as high as 17 g/l, indicating, that mannose is not a repressing sugar. It is suggested that the capability to trigger catabolite repression is connected to hexokinase PII, which is involved in the in vivo phosphorylation of glucose and fructose.

Biomass↗
PubMed1998

Mapping the antigenic structure of porcine parvovirus at the level of peptides.

The antigenic structure of the capsid proteins of porcine parvovirus (PPV) was investigated. A total of nine linear epitopes were identified by Pepscan using porcine or rabbit anti-PPV antisera. No sites were identified with a panel of neutralising monoclonal antibodies (MAbs). All epitopes were located in the region corresponding to the major capsid protein VP2. Based on this information, and on analogy to other autonomous parvoviruses, 24 different peptides were synthesised, coupled to keyhole limpet haemocyanin (KLH) and used to immunise rabbits. Most antisera were able to bind viral protein. Only peptides from the N-terminal part of VP2 were able to induce virus-neutralising antibodies, although at low levels. A similar neutralising activity could be obtained in pigs. The exposure of the N-terminus was shown in full virions, both by immunoelectron microscopy and absorption experiments. It is concluded that in PPV, the VP2 N-terminus is involved in virus neutralisation (VN) and peptides from this region are therefore primary targets for developing peptide-based vaccines against this virus.

Amino Acid Sequence↗
PubMed1998

The relationship between sensory thresholds and mechanical hyperalgesia in nerve injury.

The paradoxical combination of sensory loss within the area where pain is felt together with pain evoked by non-noxious stimuli (allodynia) is a characteristic feature of neuropathic pain. This study examined the relationship between (mechanical and thermal) pain thresholds and dynamic and static hyperalgesia in 15 patients with traumatic nerve injury and brush-evoked pain. Sensory tests were carried out both in the allodynic skin area and in the unaffected contralateral mirror image skin. The sensory characteristics included: visual analogue scale (VAS) score of ongoing pain, detection and pain threshold to thermal and mechanical stimuli, and temporal summation to repetitive heat and pinprick stimuli. Temporal summation was evoked by pinprick stimuli at 2.0 Hz but not at 0.2 Hz in allodynic skin. No difference was observed in temporal summation to heat stimuli. There was a significant and inverse relation between heat and cold pain difference and mechanically evoked pain. Patients with heat hyperalgesia had a significantly higher VAS score of mechanical hyperalgesia than patients with heat hypoalgesia. There was no relationship between dynamic and static evoked hyperalgesia. These findings suggest a differential processing of repetitive thermal and mechanical stimuli in the central nervous system. Both dynamic and static mechanical hyperalgesia are maintained by activity in heat-sensitive nociceptors, but they are probably mediated by distinct mechanisms.

Adult↗
PubMed1998

Cerebral blood-flow changes evoked by two levels of painful heat stimulation: a positron emission tomography study in humans.

Positron emission tomography (PET) and accumulation of H(2)(15)O as a marker of neuronal activity were used to create maps of cerebral blood-flow changes evoked by painful heat stimulation in 10 subjects. Two levels of painful tonic and phasic heat stimuli were applied with use of a newly developed contact heat thermode on the volar surface of the dominant (right) arm. The subjects participated in two separate PET sessions. Maps reflecting low and high levels of painful tonic heat were obtained in the first session, and low and high levels of painful phasic heat in the second session. The subjects scored their peak pain intensity and unpleasantness on 10-cm visual analogue scales. For each subject, PET images were aligned to nuclear magnetic resonance (NMR) images and remapped into the standardized co-ordinate system of Talairach. After normalization of the PET volumes, subtraction images were formed voxel-by-voxel and converted to a t-statistic volume. The perceived pain intensity and unpleasantness were identical with painful tonic and phasic heat stimulation. Directed searches revealed significant blood-flow increases in the contralateral primary sensorimotor cortex (MI/SI), SII, insular cortex and cingulate cortex when the low tonic heat map was subtracted from the high. A similar, but not identical, pain-processing network was observed for the maps representing the subtraction of low and high phasic heat. In this subtraction, the blood-flow increases in MSI/SI did not reach statistical significance, and significant blood flow decreases were found in the contralateral middle temporal gyrus. Finally, the location of the activation site in the cingulate cortex was different from that observed during tonic heat pain. This study has provided more evidence for the existence of a common pain-processing network engaged during the perception of different levels of toxic and phasic heat pain. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.

Journal Article↗
PubMed1998

The importance of stimulus configuration for temporal summation of first and second pain to repeated heat stimuli.

Temporal summation of pain is suggested to be an important factor during various clinical conditions. Controversies exist as to whether temporal summation exists for Adeltafibre-mediated first pain. The aim of the present human experimental study was to investigate the importance of stimulus configuration (intensity, inter-pulse interval, location) for temporal summation of radiant (laser)- and contact-heat-induced pain. Consecutive stimuli were applied to the same or to adjacent skin locations. Both stimulation techniques evoked rapid temperature changes, which is an important parameter for recruitment of specific cutaneous nociceptors (Adelta and C fibres). Psychophysical thresholds and intensity ratings were used to assess the pain evoked by repeated stimuli applied to the hairy skin of nine volunteers. Inter-pulse interval (IPI) and stimulus intensity were important and interrelated parameters for temporal summation of pain. An increase in IPI resulted in a decreased summation, whereas increased stimulus intensity resulted in increased summation. Brief heat pulses evoked both first and second pain, and summation of the different pain qualities was investigated. Taking the latency from stimulation to perception into consideration, we were able to differentiate and find summation of first (Adeltafibre-mediated) and second pain (C fibre-mediated). Summation of first pain was more pronounced for high (38 degrees C) than for low (30-32 degrees C) baseline temperature. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.

Journal Article↗
PubMed1998

The role of metabolic engineering in the production of secondary metabolites.

In the production of secondary metabolites yield and productivity are the most important design parameters. The focus is therefore to direct the carbon fluxes towards the product of interest, and this can be obtained through metabolic engineering whereby directed genetic changes are introduced into the production strain. In this process it is, however, important to analyze the metabolic network through measurement of the intracellular metabolites and the flux distributions. Besides playing an important role in the optimization of existing processes, metabolic engineering also offers the possibility to construct strains that produce novel metabolites, either through the recruitment of heterologous enzyme activities or through introduction of specific mutations in catalytic activities.

Anti-Bacterial Agents↗
PubMed1998

Global spatial sampling with isotropic virtual planes: estimators of length density and total length in thick, arbitrarily orientated sections.

Existing design-based direct length estimators require random rotation around at least one axis of the tissue specimen prior to sectioning to ensure isotropy of test probes. In some tissue it is, however, difficult or even impossible to define the region of interest, unless the tissue is sectioned in a specific, nonrandom orientation. Spatial uniform sampling with isotropic virtual planes circumvents the use of physically isotropic or vertical sections. The structure that is contained in a thick physical section is investigated with software-randomized isotropic virtual planes in volume probes in systematically sampled microscope fields using computer-assisted stereological analysis. A fixed volume of 3D space in each uniformly sampled field is probed with systematic random, isotropic virtual planes by a line that moves across the computer screen showing live video images of the microscope field when the test volume is scanned with a focal plane. The intersections between the linear structure and the virtual probes are counted with columns of two dimensional disectors. Global spatial sampling with sets of isotropic uniform random virtual planes provides a basis for length density estimates from a set of parallel physical sections of any orientation preferred by the investigator, i.e. the simplest sampling scheme in stereology. Additional virtues include optimal conditions for reducing the estimator variance, the possibility to estimate total length directly using a fractionator design and the potential to estimate efficiently the distribution of directions from a set of parallel physical sections with arbitrary orientation. Other implementations of the basic idea, systematic uniform sampling using probes that have total 3D x 4pi freedom inside the section, and therefore independent of the position and the orientation of the physical section, are briefly discussed.

Journal Article↗
PubMed1998

Poor value of surveillance cultures for prediction of septicaemia caused by coagulase-negative staphylococci in patients undergoing haemodialysis with central venous catheters.

Surveillance cultures for the demonstration of coagulase-negative staphylococci in patients on catheter haemodialysis were performed in an attempt to predict dialysis catheter-related septicaemia. In all, 43 patients with 67 haemodialysis catheters were followed for a 1-y period. Once a week, swab specimens were obtained from the skin at the insertion site and the hub, and blood cultures were obtained from the catheter. Among coagulase-negative staphylococci, S. epidermidis was the most frequently (80%) isolated species, and two biotypes accounted for 55.7% of the 41 biotypes isolated. 11 septicaemia cases due to coagulase-negative staphylococci occurred, all caused by S. epidermidis, and the incidence of S. epidermidis septicaemia was 21% among patients and 16% among catheter periods. S. epidermidis septicaemia occurred in 17%, 31% and 33% of all catheter periods in which S. epidermidis was cultured from the skin, hub and catheter blood, respectively. In two-thirds of all catheter periods, S. epidermidis was cultured from catheter blood despite lack of clinical signs of septicaemia. In conclusion, cultures from the skin, hub or catheter blood are not useful for prediction of dialysis catheter-related septicaemia due to coagulase-negative staphylococci. When septicaemia is suspected, peripheral blood cultures are mandatory to reach a correct diagnosis and aetiology.

Adult↗
PubMed1998

The influence of rate of temperature change and peak stimulus duration on pain intensity and quality.

An important aspect of experimental pain research is that the assessment methods can investigate the different aspects of pain perception. The aim of the present study was to investigate the influence of rate of temperature change and peak stimulus duration on heat evoked pain intensity and quality. All stimuli were applied within the medial aspect of the anterior forearm. The rate of temperature change was varied from 1 to 16 degrees C/s without any effect on the pain threshold. The pain threshold decreased with an increasing peak stimulus duration from 0.1 to 2 s, but not from 2 to 3 s. The pain intensity for suprathreshold stimuli (46 degrees C, 48 degrees C, 50 degrees C) increased for decreasing rates and increasing duration. The pain intensity was highly correlated with the energy of the stimulus. When the rates of temperature change (1-16 degrees C/s) are varied, no differences between pricking and burning pain were present at either low stimulus intensity (46 degrees C) or high stimulus intensity (50 degrees C). At low stimulus intensity (46 degrees C), the pricking pain was not influenced by the duration (0.1-3 s), but the burning pain was intensified when the duration was increased from 1.5 to 3 s. At high intensity stimuli (50 degrees C), the pricking pain intensified with an increased duration, whereas burning pain did not. The heat pain threshold is influenced by the peak stimulus duration, and not by the rate of temperature change. If suprathreshold stimuli are used, both the rate of temperature change and the peak stimulus duration can strongly affect the pain intensity and the pain quality. Therefore, the same stimulus modality can be used to assess the modulation of different pain intensities and of the pricking and burning pain qualities simply by varying the stimulus configuration.

Adult↗
PubMed1998

Staphylococcus aureus bacteraemia among patients undergoing dialysis--focus on dialysis catheter-related cases.

BACKGROUND: Central venous catheter-related infections are the most common cause of nosocomial S. aureus bacteraemia in Denmark. Central venous catheters are often used for dialysis, and patients on dialysis often run into staphylococcal infections. The purpose of this study was to investigate S. aureus bacteraemia among dialysis patients, especially those related to dialysis catheters. METHODS: This was a retrospective study of 14,387 consecutive S. aureus bacteraemia cases during the period 1976-93, of which 793 cases occurred among dialysis patients. By reviewing the case records, 65 dialysis catheter-related cases were described more thoroughly. RESULTS: The number of S. aureus bacteraemia cases among dialysis patients as a proportion of all cases in Denmark has increased from 5.2 to 14.7% during the study period, but the annual incidence among these patients has been almost stable during the period (median 5.7% (3.2-9.0%)). Patients on dialysis had a lower mortality than other patients with S. aureus bacteraemia (18.9 vs 29.0%), but a four times higher mortality from central venous catheter-related S. aureus bacteraemia (5.3 vs 1.3%, P < 0.001). The mortality from dialysis catheter-related S. aureus bacteraemia was correlated with greater age (median 71 years (57-73) vs median 56.5 years (15-76), P < 0.01) and with septic shock (55.5 vs 7.1%, P < 0.05). Patients on dialysis had a lower frequency of S. aureus endocarditis (3.3 vs 5.4%, P < 0.01) and of S. aureus bone and joint infections (3.3 vs 8.2%, P < 0.001) than other patients. Patients undergoing dialysis had a later onset of catheter-related S. aureus bacteraemia than other patients (median 15 days (1-145) vs 5 days (1-134), P < 0.05). CONCLUSIONS: Patients on dialysis are at a high risk of S. aureus bacteraemia and they have a four times higher mortality from central venous catheter-related S. aureus bacteraemia than other patients. There is need for prospective studies in which patients as well as catheters are followed more thoroughly to study the pathogenesis of dialysis catheter-related infections.

Adult↗
PubMed1998

Dialysis catheter-related septicaemia--focus on Staphylococcus aureus septicaemia.

BACKGROUND: Dialysis catheters are a common cause of nosocomial septicaemia in haemodialysis units usually due to staphylococci, of which Staphylococcus aureus is the most pathogenic. In this study, the epidemiology and pathogenesis of dialysis catheter-related infections were studied, and methods to identify patients with these infections were evaluated. METHODS: A one-year prospective study of 67 catheters in 43 haemodialysis patients was performed. Details about patients and catheters were obtained successively during the catheter period, and biochemical parameters expected to be related to infection were measured. After catheter insertion, all patients were screened for nasal carriage of S. aureus, and a culture was taken from the skin overlying the catheter insertion site. Once a week, cultures were taken from the insertion site and from the hub, and aerobic and anaerobic blood cultures were drawn from the catheter. If clinical signs of septicaemia occurred, peripheral blood cultures were also performed, when it was possible. RESULTS: The incidence of septicaemia was 49% (21/43) in patients, and 56% of all cases were caused by S. aureus. The mortality was 14% (3/21) and the incidence of severe secondary complications to septicaemia was 24% (5/31). In all, 80% of all severe complications and 75% of all deaths from septicaemia were due to S. aureus. With respect to S. aureus septicaemia, the predictive values of positive (P) and negative (N) S. aureus cultures were as follows: nasal culture, P=36% (10/28), N=90% (35/39); culture from the insertion site, P=72% (13/18), N=98% (48/49); and culture from the hub, P=75% (3/4), N=83% (52/63). The risk ratio for S. aureus septicaemia was 26.2 (6.1-113), P=0.0001, according to the presence of S. aureus at the insertion site, and 3.3 (0.74-15.1), P=0.12 according to nasal carriage of S. aureus. The frequency of S. aureus phage-type Group 2 (43%) was much higher than the general frequency of this phage-type in Denmark, which is about 23%. Catheter blood cultures were positive although there were no clinical signs of septicaemia in 34% (23/67) of all catheter periods--84% of these were due to coagulase-negative staphylococci. CONCLUSIONS: Dialysis catheter-related S. aureus septicaemia was highly unlikely if the patient had not been carrying S. aureus in the nose or at the insertion site during the time the catheter was in place. The best predictor of dialysis catheter-related S. aureus septicaemia was a positive S. aureus culture from the insertion site. Positive catheter blood cultures unrelated to any clinical signs of septicaemia occurred in one-third of all catheter periods, and 84% of these were due to coagulase-negative staphylococci.

Adult↗
PubMed1998

Religious coping and health status in medically ill hospitalized older adults.

Associations between specific religious coping (RC) behaviors and health status in medically ill hospitalized older patients were examined and compared with associations between nonreligious coping (NRC) behaviors and health status. The sample consisted of 577 patients age 55 or over consecutively admitted to the general medical inpatient services of Duke University Medical Center (78%) or the Durham VA Medical Center (22%). Information was gathered on 21 types of RC, 11 types of NRC, and 3 global indicators of religious activity (GIRA). Health measures included multiple domains of physical health, depressive symptoms, quality of life, stress-related growth, cooperativeness, and spiritual growth. Demographic factors, education, and admitting hospital were control variables. "Negative" and "positive" types of religious coping were identified. Negative RC behaviors related to poorer physical health, worse quality of life, and greater depression were reappraisals of God as punishing, reappraisals involving demonic forces, pleading for direct intercession, and expression of spiritual discontent. Coping that was self-directed (excluding God's help) or involved expressions reflecting negative attitudes toward God, clergy, or church members were also related to greater depression and poorer quality of life. Positive RC behaviors related to better mental health were reappraisal of God as benevolent, collaboration with God, seeking a connection with God, seeking support from clergy/church members, and giving religious help to others. Of 21 RC behaviors, 16 were positively related to stress-related growth, 15 were related to greater cooperativeness, and 16 were related to greater spiritual growth. These relationships were both more frequent and stronger than those found for NRC behaviors. Certain types of RC are more strongly related to better health status than other RC types. Associations between RC behaviors and mental health status are at least as strong, if not stronger, than those observed with NRC behaviors.

Adaptation, Psychological↗
PubMed1998

Exteroceptive suppression of masseter muscle: assessment of two methods for quantitating suppression periods.

OBJECTIVES: The late exteroceptive suppression period (ES2) of the masseter muscle is conventionally quantified by a combination of measures of duration, amplitude, or mean activity. The combination of measures makes it difficult to compare ES2s obtained from different set-ups. An unbiased method for quantitating ES2 is introduced allowing ranking of ES2s. The introduced method is utilized to evaluate stimulus and recording conditions under which ES2 is maximal. MATERIAL AND METHODS: Fifteen male volunteers participated in 3 experiments designed to determine the effect of level of teeth clenching, stimulus intensity, and perceived pain intensity on the ES2. RESULTS: Coefficients of variance (1 h/1 month) were: duration: 11%/43%, latency: 9%/12%, and magnitude of suppression: 11%/12%. A level of teeth clenching of 66% of maximal voluntary bite force, and a stimulus intensity below pain detection threshold was associated with maximal magnitude of suppression of ES2. CONCLUSION: The introduced method is reproducible and allows ranking and stimulus-response estimations of ES2. It is suggested that ES2 does not reflect activity along the nociceptive pathways in the trigeminal region.

Adult↗
PubMed1998

Sensitivity of H-reflexes and stretch reflexes to presynaptic inhibition in humans.

The sensitivity of soleus H-reflexes, T-reflexes, and short-latency stretch reflexes (M1) to presynaptic inhibition evoked by a weak tap applied to the biceps femoris tendon or stimulation of the common peroneal nerve (CPN) was compared in 17 healthy human subjects. The H-reflex was strongly depressed for a period lasting up to 300-400 ms (depression to 48 +/- 23%, mean +/- SD, of control at a conditioning test interval of 70 ms) by the biceps femoris tendon tap. In contrast, the short-latency soleus stretch reflex elicited by a quick passive dorsiflexion of the ankle joint was not depressed. The soleus T-reflex elicited by an Achilles tendon tap was only weakly depressed (92 +/- 8%). The H-reflex was also significantly more depressed than the T-reflex at long intervals (>15 ms) after stimulation of CPN (H-reflex 63 +/- 14%, T-reflex 91 +/- 13%; P < 0. 01). However, the short-latency (2 ms) disynaptic reciprocal Ia inhibition evoked by stimulation of CPN was equally strong for H- and T-reflexes (H-reflex 72 +/- 10%, T-reflex 67 +/- 13%; P = 0.07). Peaks in the poststimulus time histogram (PSTH) of the discharge probability of single soleus motor units (n = 53) elicited by an Achilles tendon tap had a longer duration than peaks evoked by electrical stimulation of the tibial nerve (on average 5.0 ms as compared with 2.7 ms). All parts of the electrically evoked peaks were depressed by the conditioning biceps femoris tendon tap (average depression to 55 +/- 27% of control; P < 0.001). A similar depression was observed for the initial 2 ms of the peaks evoked by the Achilles tendon tap (69 +/- 48%; P < 0.001), but the last 2 ms were not depressed. Conditioning stimulation of the CPN at long intervals (>15 ms) also depressed all parts of the electrically evoked PSTH peaks (n = 34; average 65%; P < 0.001) but had only a significant effect on the initial 2 ms of the peaks evoked by the Achilles tendon tap (85%; P < 0.001). We suggest that the different sensitivity of mechanically and electrically evoked reflexes to presynaptic inhibition is caused by a difference in the shape and composition of the excitatory postsynaptic potentials underlying the two reflexes. This difference may be explained by a different composition and/or temporal dispersion of the afferent volleys evoked by electrical and mechanical stimuli. We conclude that it is not straightforward to predict the modulation of stretch reflexes based on observations of H-reflex modulation.

Adult↗
PubMed1998

Screening of an inhibitor of the tetracycline efflux pump in a tetracycline-resistant clinical-isolate of Staphylococcus aureus 743.

Clinically-isolated methicillin-resistant Staphylococcus aureus (MRSA) strain 743 exhibited resistance to tetracycline as judged from the active efflux of the drug. The efflux of tetracycline was inhibited by an uncoupler, carbonyl cyanide m-chlorophenylhydrazone (CCCP), and minocycline. Inhibitors of the efflux pump were examined in this strain to determine the cellular accumulation of tetracycline. Out of seven compounds examined, three caused a significant increase in the cellular concentration of tetracycline by inhibiting the efflux pump. Two of them seem to be energy inhibitors. Ro 07-3149 inhibited the efflux pump without affecting the energy state, and exhibited very low antibacterial activity but showed weak synergy with tetracycline.

Anti-Bacterial Agents↗
PubMed1998

Thawed cod fillets spoil less rapidly than unfrozen fillets when stored under modified atmosphere at 2 degrees C.

The effect of two months of frozen storage at -20 degrees C on the spoilage characteristics and shelf life of thawed and modified atmosphere packed (MAP) cod fillets stored at 2 degrees C was studied. Thawed MAP cod fillets were compared with fresh cod fillets stored in CO2-containing modified atmospheres with and without added oxygen. The shelf life of 11 to 12 days in the fresh MAP cod was extended to more than 20 days in the thawed MAP cod at 2 degrees C. This shelf life extension was most likely due to the inactivation of the spoilage bacterium Photobacterium phosphoreum during frozen storage as reflected both in chemical analyses and sensory evaluation. In contrast to fresh MAP cod fillets no significant production of trimethylamine occurred and almost no amine odor and taste were detected during 20 days of chill storage of thawed MAP cod fillets. The use of frozen fillets as raw material not only provides a more stable product in MAP but also allows much greater flexibility for production and distribution. However, a slightly increased concentration of dimethylamine, a larger drip loss, and detection of weak frozen storage flavor were observed in the thawed MAP cod fillets.

Amines↗