Effects of different cooking methods on the formation of food mutagens in meat

Hamburgers and chicken fillets were cooked in convection ovens, deep‐fried or contact fried and analysed for mutagenic activity using the Ames test. For the three different convection ovens, the cooking parameters studied included the presence of steam, air velocity, air temperature and holding time. For deep‐frying and contact frying, the cooking parameters included cooking temperature and cooking time. In cooked hamburgers, mutagenic activity was only detected in those that had been deep‐fried. In chicken fillets, mutagenic activity was detected in samples prepared with all cooking methods, being highest in the deep‐fried samples. Factorial analysis indicated that heat transfer was the most important factor affecting mutagenic activity. High temperature and high air velocity in the convection ovens enhanced mutagenic activity. The presence of steam reduced the mutagenic activity, except when high temperature was used in combination with high air velocity. In chicken fillets, high mutagenic activity correlated to high weight loss during cooking. Pan‐fried chicken fillets were analysed using high performance liquid chromatography (HPLC) and the mutagenic/carcinogenic heterocyclic amines 2‐amino‐3,8‐dimethylimidazo[4,5‐f ]‐quinoxaline (MeIQx), 2‐amino‐1‐methyl‐6‐phenylimidazo‐[4,5‐b]‐pyridine (PhIP) and the co‐mutagenic heterocyclic amine Norharman (9H‐pyrido[3,4‐b]‐indole) were identified. The HPLC fractions were tested for mutagenic activity and, apart from the mutagenic fractions corresponding to MeIQx and PhIP, several mutagenic fractions were detected that did not correspond to known heterocyclic amines.     

Clinical aspects of salivary gland tumors

This paper reports on epithelial tumours arising primarily in the major and minor salivary glands. The purpose of this presentation is to summarize our experience of salivary gland tumours on the basis of a material comprising of approximately 3000 salivary gland tumours as well as a review of the literature to date. The tumours are classified according to the classification recommended by WHO 1972. The incidence, location, symptomatology, grade of malignancy and treatment of the different tumour types in this classification are reviewed. Diagnostic procedures are discussed and a scheme for surgical treatment and radiotherapy of the different types of salivary gland tumours is proposed.     

Contamination of pasteurized milk by Bacillus cereus in the filling machine

The contamination of pasteurized milk by Bacillus cereus during the filling process was studied in two dairy plants. Samples of pasteurized milk were taken at four different sites along the production line. The samples were stored at 7 degrees C for 7 d, or at 10 degrees C for 5 d, before plate counting and random selection of B. cereus isolates. Isolates of B. cereus were typed by the polymerase chain reaction (PCR)-based method randomly amplified polymorphic DNA (RAPD). Samples taken at three different sites between the pasteurizer and the filling machine were all holding similar low concentrations of B. cereus, while an increase of the B. cereus count was seen in the consumer packages. More B. cereus of different RAPD types was growing in the consumer packages than in samples taken just before the filling machine. Several RAPD types found in the consumer packages were not detected in the samples taken just before the filling machine.     

The diabetic foot. Optimal prevention and treatment can halve the risk of amputation

Almost half of all lower leg amputations are performed in patients with diabetes. In over 70 per cent of these cases, amputation is precipitated by progression of foot ulceration to deep gangrenous infection. Most foot ulcers are preceded by trauma, usually due to ill-fitting shoes, and are precipitated by sensory motor neuropathy with varying degrees of peripheral vascular disease. The Swedish Medical Research Council and the Swedish Institute for Health Services Development arranged a conference on diabetic foot problems in April 1998, the purpose of which was to arrive at a consensus regarding the prevention and management of diabetic foot. It was concluded that a satisfactory multidisciplinary approach should include regular control of feet and footwear, preventive foot care (education, footwear, chiropody), continuous follow-up of high-risk feet, and early recognition of revascularisation. Continuous registration of amputation, irrespective of type, cause and site, might substantially reduce the amputation rate among diabetics. Were such an approach to reduce the incidence of diabetes-related amputation by 50 per cent, annual costs for the management of diabetic foot in Sweden would be reduce by SEK 400 million (the value of improved quality of life not taken into consideration).     

Nitric oxide synthase pathway may mediate human natural killer cell cytotoxicity

The present study provides evidence that the human natural killer (NK) cell effector mechanism causing target cytolysis has a requirement for L-arginine. In a deficient medium (DM) containing only salts, buffer system and glucose, NK cell-mediated cytotoxicity was found to decrease by 70% as compared to that obtained in a complete medium (CM). However, adding L-arginine to such DM could restore the activity of NK cells to the normal level. Many other components of CM, such as serum, glutamine and vitamins did not improve NK cell-mediated killing in DM. When all amino acids except L-arginine were added to DM only a partial recovery of NK cell functional cytolysis was seen. L-arginine enhanced the NK cell activity in a dose-dependent manner. Additionally, the inhibitor of both inducible and constitutive nitric oxide synthase, N-monomethyl-L-arginine (L-NMMA) inhibited NK cytolytic activity in DM supplemented with L-arginine indicating participation of nitric oxide (NO). The results also show that the stimulatory effect of L-arginine on human NK cell-mediated cytotoxicity was accompanied by an increase in NO formation as determined by accumulation of nitrite and citrulline. L-NMMA gave a dose-dependent reduction in NO generation as well. The nitrite and citrulline production dose-dependently correlated with not only the concentration of L-arginine in the cultivation medium, but also the enhanced NK cell-mediated cytolysis. Taken together, these findings could define a L-arginine/NO-linked effector mechanism in human NK cells. Nitrite and citrulline were not formed when NK cell-mediated target cell killing took place in a L-arginine-free DM supplemented with additives. Thus, it appears as if human NK cells may cause target cell killing via both NO-dependent and -independent processes.     

Investigation of Bacillus cereus contamination sites in a dairy plant with RAPD-PCR

The usefulness of RAPD-PCR as a typing method for investigation of Bacillus cereus isolates from a dairy plant was evaluated. A 1-d in-depth sampling study along the entire production line was performed and long-term sampling of products was conducted over two years. In addition, farm bulk tank isolates were collected. Isolates from an individual sample during storage at 7°C were often identical. Large clusters of identical isolates were found in the silo tank in the 1-d study and in samples from the long-term study. In combination with analytical data, these results indicated a prolonged contamination problem caused by a mesophilic strain early in the production chain. Detailed and useful information on occurrence of psychrotrophic B. cereus was obtained along the production line and among products. RAPD-PCR appeared to be a useful typing method for B. cereus isolates. In combination with carefully planned sampling and microbiological analysis, RAPD could be helpful in solving dairy contamination problems in pasteurized milk.     

Applying ATM/AAL2 as a switching technology in third-generationmobile access networks

In this article we focus on the transport and switching part of third-generation mobile access networks and outline some important aspects of applying ATM in these networks. In particular, we argue that in order for the mobile access network to support low-bit-rate delay-sensitive traffic consisting of short packets, the standardization of a new ATM adaptation layer, AAL2, and associated signaling protocol has been necessary. The AAL2 protocol has been designed to support low-bit-rate delay-sensitive services (typically compressed voice) where other adaptation layers fail to deliver the required QoS and maintain efficient resource utilization at the same time. Furthermore, in order to provide mobility and soft handover support in W-CDMA-based mobile networks such as UMTS or IMT-2000, there is also a strong demand for fast connection establishment and release. Therefore, when designing ATM-based cellular access networks some specific architectural and traffic management issues need to be addressed