Methodologies, findings, and implications of chemical carcinogenesis studies: their significance for hazard assessment (review)

The experimental techniques, methods of evaluation, and environmental implications of the findings of chemical carcinogenesis studies and related subject areas are herein critically reviewed. It is concluded that firstly, certain presently used procedures provide the best possibilities for the study of the hazardous nature of chemicals. Secondly, other matters, including the dosage of chemicals, animal species, meaning of the term "tumor induction", values of short-term tests, evaluation of tumor incidences, relation of the responses of humans and animals to carcinogenic stimuli, require new attitudes, innovative approaches, and meaningful changes. Thirdly, some of the issues are and will remain controversial until our basic knowledge substantially improves. Finally, it appears advisable to abandon some of the dogmatic attitudes for a more flexible approach.     

Model identification and estimation of organ-function parameters using radioactive tracers and the impulse-response function

Examination of the input-output events in functioning organs by the use of the impulse-response function (IRF) for a radioactive tracer is gaining more and more ground in nuclear medicine. This study summarizes the development of deconvolution analysis, laying special stress on the model-free approach. System linearity and time invariance are discussed, and means of eliminating noise in IRFs originating from the input and organ-time-activity curves are outlined. Typical IRFs are illustrated by flow diagrams, time-domain curves, and their representation by Laplace transforms. The cases of nondiffusible and diffusible tracers as well as parenchymally extracted and transported substances are discussed. Methods for the derivation of models and for the calculation of physiologically important parameters from theIRFs are suggested.At present, a guest scientist at the Institute for Medicine, Nuclear Research Center Jülich, Jülich, Federal Republic of Germany     

Postinjury Primary Abdominal Compartment Syndrome

Postinjury abdominal compartment syndrome (ACS) has evolved during the 1980s together with the introduction of damage control surgery (DCS) principles. DCS made it possible to salvage severely injured trauma patients who previously would have exsanguinated due to uncontrollable coagulopathic bleeding. These patients had severe hemorrhagic shock; their abdomens were tightly packed and had ongoing massive resuscitation. ACS is a lethal complication of the damage control patients. For today the pathophysiological characteristics of ACS are described, the intra-abdominal pressure is measured on many intensive care units. Postinjury ACS (primary and secondary) is one of the better characterized etiological types of ACS: risk factors, diagnostic criteria, independent predictors and preventive strategies are all well documented. Since the mortality of full-blown postinjury ACS is still unacceptably high and does not seem to improve with earlier decompression, prevention is the recommended strategy to decrease the morbidity and mortality. Open abdomen is one of the important preventive strategies but it is not free from morbidity and mortality. With aggressive open abdomen management in postinjury ACS these complications can be minimized. More importantly, timely hemorrhage control and hemostatic resuscitation are the likely solutions for more efficient prevention of the postinjury ACS.     

The interpretation of intra-abdominal pressures from animal models: the rabbit to human example

IntroductionThe importance of the abdominal wall characteristics in intraabdominal pressure (IAP), intraabdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are poorly understood. The applicability of laboratory research findings to human scenarios is unknown due to the potential differences in abdominal wall elastance (AWE) amongst species. The aims of the study are to describe the AWE curve in rabbits and to compare it to the available human data.Materials and methodsProspective experimental animal study in the setting of research laboratory. Male New Zealand White rabbits weighting 2.7 kg ± 0.1 kg, were anesthetized and the AWE was determined by infusion of lactated Ringer's solution into the peritoneal cavity whilst the IAP was measured. A meta-analysis of peer-reviewed studies was conducted to define human AWE.ResultsThe described AWE was lower in the rabbit than in humans. The function comparing human and rabbit was: log_e human IAP = (0.58 log_e rabbit IAP + 1.6).ConclusionsThe AWE can vary amongst species. This study determined the relationship to allow the comparison of rabbit and human IAP. The proposed mathematical function is important for the advancement of interpretation and understanding of animal research into IAH and ACS. We recommend developing model-specific functions comparing individual animal models’ IAP and that of humans.     

The representation of the visual field in three extrastriate areas of the ferret (Mustela putorius) and the relationship of retinotopy and field boundaries to callosal connectivity

We describe representations of the visual field in areas 18, 19 and 21 of the ferret using standard microelectrode mapping techniques. In all areas the azimuths are represented as islands of peripheral visual field surrounded by central visual field representation. The zero meridian was found at the 17/18 and 19/21 borders; at the 18/19 and anterior border of 21 the relative periphery of the visual field was found. In areas 18 and 19, elevations are represented in a smooth medio-lateral progression from lower to upper visual field. In several cases the elevations in area 21 evidenced a similar medio-lateral progression; however, in others the elevations exhibited a split representation of the horizontal meridian. Anatomically determined callosal connections coincided with the representation of azimuths near the zero meridian. Medio-lateral bands of callosal connectivity that straddle the 17/18 and 19/21 borders are connected by bridges of callosally projecting cells. Acallosal cortical islands corresponded to the peripheral visual field and were found straddling the 18/19 border and the anterior border of area 21. The results are discussed in relation to callosal connectivity and retinotopy in extrastriate visual cortex and to proposed homologies of carnivore and primate visual cortex.