Effect on cooking time on mutagen formation in smoke, crust and pan residue from pan-broiled pork

The effect of cooking time on mutagenic activity in crust, pan residue and smoke from pan-broiled pork patties was studied in the Ames Salmonella mutagenicity test system. The effect on mutagenicity of reheating the cooked patties and of keeping them warm was also studied. The meat was broiled at 200 degrees C for various times between 2 and 10 min. Broiled meat was reheated up to 5 times at 200 degrees C, each time to a centre temperature of 70 degrees C. Reheating was also performed in a microwave oven for 2 min and in an electric oven at 200 degrees C for 10 min. In addition, broiled patties were kept warm at 60 degrees C in an incubator for up to 9 hr. The mutagenic activity increased rapidly in all fractions except the volatile phase over the first 6 min of cooking, after which time only a slight increase was seen. At cooking times below 4 min no mutagenic activity was detected in the smoke. Reheating or keeping the meat warm for up to 9 hr had very little effect on the mutagenic activity of the meat. Reversed-phase high-performance liquid chromatography mutagenicity profiles of the aerosol, crust and pan-residue extracts showed no major qualitative differences in samples cooked at different times. It is concluded that during pan broiling at 200 degrees C the major part of the mutagenic activity is formed during the first 6 min of cooking. Reheating the meat or keeping it warm does not significantly affect the mutagenic activity. No major additional mutagens are formed during continued heating for up to 25 min.     

The use of tracheal implants in toxicology and carcinogenesis research

Tracheal implants have served as an important experimental pathology tool with which to study the toxic and/or carcinogenic effects of chemicals upon upper respiratory tract epithelium. Initial studies with this method utilized heterotopic rat tracheal transplants which were exposed to compounds of interest, and assessed for toxic and/or carcinogenic endpoints. Grafts containing rodent tissue have proved useful for studying the cellular and biochemical features of neoplastic progression at different time intervals following in vivo exposure to carcinogens. More recent studies have utilized epithelial denuded tracheal implants inoculated with respiratory cell populations, and xenografted into immunodeficient nu/nu mice. This technique permits the study of airway epithelium from a variety of species, including man. The advent of molecular pathology techniques such as in situ hybridization will further expand the uses of tracheal implant technology for studies with xenografted human tissues. Such implants should prove useful for the examination of species- and tissue-specific characteristics of growth and differentiation by providing a bridge between cell culture and whole animal studies.     

Tachykinin receptors of the NK2 type involved in the acetylcholine release by nicotine in guinea-pig bladder.

1. The effects of guanethidine and tachykinins on nicotine- and electrical stimulation-induced cholinoceptor responses were studied in isolated urinary bladder from the guinea-pig. 2. Acetylcholine release and the contractile response stimulated by nicotine were partially reduced by a sympathetic nerve blocker, guanethidine. Neurokinin A (but not substance P methyl ester or senktide) enhanced both acetylcholine release and contraction by nicotine in the presence of guanethidine. 3. Frequency-contraction curves (1 to 50 Hz) for electrical field stimulation (EFS) were partially reduced by atropine (1 microM), and after desensitization to alpha,beta-methylene adenosine 5'-triphosphate, the atropine-resistant contraction to EFS was completely abolished. Guanethidine, the tachykinin antagonist [D-Arg1, D-Pro2, Trp7,9, Leu11]-substance P and application of neurokinin A or substance P did not change the contractile response to EFS. Preganglionic nerve stimulation (5 Hz and 20 Hz) also evoked a similar response to EFS and was not influenced at all by guanethidine or neurokinin A. 4. We conclude that the ability of nicotine to release acetylcholine is enhanced both by endogenous tachykinins (probably released from sympathetic nerves) and by exogenously applied tachykinins as a result of interaction with NK2 receptors in the urinary bladder.     

Movement-related potential measures of different modes of movement selection in Parkinson's disease

Movement-related potentials were recorded preceding self-paced voluntary movements in patients with Parkinson's disease and in healthy subjects of the same age group. We compared the Readiness Potential preceding joystick movements in a fixed direction and preceding joystick movements in freely selected directions. In normal subjects the Readiness Potential amplitude was higher preceding freely selected movements than preceding movements in a fixed direction. The Readiness Potential in Parkinson patients failed to be modified by the different modes of movement selection. The modulation of the Readiness Potential by different ways of preparing for movement might be due to the supplementary motor area (SMA) being more strongly engaged by tasks requiring internal control of movements than by tasks that are externally structured. The results suggest that this task-dependent variation of SMA activity is reduced in Parkinson's disease. A failing capacity to adapt SMA activity to different task demands has previously been suggested by evidence from positron emission tomography studies using similar tasks.     

Intraoperative coronary artery endarterectomy with excimer laser

Compared with continuous-wave lasers, excimer lasers exhibit several in vitro advantages: nonthermal ablation process and linear relation between the number of pulses and the depth of the crater. A 308 nm, 20 nsec pulse duration, 1 to 5 repetition rate laser was specifically designed for clinical application. At the time of cardiopulmonary bypass in 10 symptomatic patients, before bypass grafting, a 1 mm diameter core specifically ultraviolet-tipped fiberoptic scope was introduced via the coronary arteriotomy and placed upstream (seven patients) and downstream (three patients) in contact with the stenosis. Laser power was increasingly delivered up to the clearing of the stenosis or occlusion. Quality of angioplasty was controlled by calibration of the neolumen, cardioplegic solution output through the laser-treated segment, and an eighth day or sixth month coronary arteriogram. In the first three patients studied on the eighth day, all laser-treated coronary artery segments showed an early parallel-linked patent neolumen despite competitive bypass graft flow. In the patients studied after 6 months, all recanalized segments were patent except one; in one patient the venous graft was occluded, but the upstream laser angioplasty was patent. The main limitation of the method lies in the fact that laser coronary recanalization is confined to the fiber core diameter. We conclude that (1) excimer laser angioplasty may be safe and efficient during surgical procedure and (2) as catheter flexibility remains the most critical problem, we are now assuming an appropriate tool with a multifiber system that is suitable for intraoperative as well as percutaneous routes.     

A case of pheochromocytoma with severe paralytic ileus

We report herein a rare case of a 26 year old woman with pheochromocytoma complicated by paralytic ileus. She presented with remarkable abdominal distension and respiratory difficulty but was effectively treated by surgical removal of the tumor with preoperative and operative management using alpha and beta adrenergic blocking agents. An excessive and persistent catecholamine production from large tumors or massive metastases characterizes this rare complication, and a review of the English and Japanese literature is given following this report.     

Theoretical calculation of the longitudinal spherical aberration of rigid and soft contact lenses

Although previous investigators have attempted to calculate the longitudinal spherical aberration inherent in soft and rigid contact lenses both on and off the eye, the use of inappropriate assumptions on which to base their calculations has left the problem unresolved. In this study, the longitudinal spherical aberration of both soft and rigid contact lenses was calculated surface by surface both in air and on the eye using a two-dimensional, exact ray tracing program. The erroneous assumptions made by previous investigators were avoided by using an elliptical model for the anterior corneal surface and assuming that the posterior surfaces of soft lenses aligned exactly with the anterior corneal surface after flexure onto the eye. The results demonstrated that, with a 6-mm pupil, contact lenses induce significant levels of spherical aberration in the ocular system for soft lenses of back vertex power greater than +3.00 D or -6.00 D and for rigid lenses of powers more positive than -3.00 D. It is suggested that visual disturbance due to induced spherical aberration has not been a major clinical problem in the past because these conditions fall outside those experienced by a large proportion of the contact lens-wearing public.