The effects of portacaval shunt upon hepatic cholesterol synthesis and cyclic AMP in dogs and baboons

Hepatic cholesterol synthesis, hepatic cyclic AMP, and portal and peripheral insulin and glucagon levels were investigated in nine dogs and three baboons after complete portacaval shunt. Cholesterol synthesis as measured with acetate incorporation was reduced in both species. Hepatic cyclic AMP increased in dogs. Changes in portal and systemic insulin were inconsistent, but hyper-glucagonemia occurred regularly. Diminished hepatic cholesterol synthesis is apparently one factor, although probably not the only one, in the antilipidemic effect of portacaval shunt. This altered cholesterol metabolism may be due to a change in the hormonal environment of the liver caused by portal diversion

The effect of splanchnic viscera removal upon canine liver regeneration

The influence of portal blood factors on canine liver regeneration was studied with graded nonhepatic splanchnic evisceration, coupled with 44 and 72 per cent hepatectomies. In one type of experiment, the pancreas was retained while the rest of the intra-abdominal gastrointestinal tract was removed. In a second variety, total pancreatectomy was performed with preservation of the intra-abdominal organs. In a third kind of experiment, total nonhepatic splanchnic evisceration was performed. Liver regeneration after hepatectomy was decreased by all three kinds of viscera removed as judged by deoxyribonucleic acid synthesis, autoradiography and mitotic index. Pancreatectomy and nonpancreatic splanchnic evisceration caused almost equal decreases in the regenerative response. Total nonhepatic splanchnic evisceration essentially halted regeneration during the first three postoperative days and intraportal infusions of insulin or glucagon, or both together, did not reverse this effect. The decrease in liver membrane bound adenyl cyclase activity and biphasic change in liver cyclic 3',5'-adenosine monophosphate concentrations normally seen partial hepatectomy was disrupted after the various eviscerations. Adenyl cyclase activity and cyclic monophosphate concentrations tended to be higher than normal in the eviscerated dogs. These observations provide more support for our previously proposed hypothesis that control of liver regeneration is by multiple factors. Pancreatic hormones are important modifiers of this response but by no means exercise exclusive control. Other substances of gastrointestinal origin, presumably including hormones and nutrient supply apparently play important specific roles. The volume of portal flow is a secondary and nonspecific, but possibly significant, factor

Impaired clearance of ceftizoxime and cefotaxime after orthotopic liver transplantation.

The pharmacokinetics of ceftizoxime (CZX) and of cefotaxime (CTX) were studied in five children and five adults after orthotopic liver transplantation (OLT). Delayed clearance of CZX (clearance of 0.21 to 1.26 ml/min per kg [body weight]) and CTX (clearance of 0.40 to 1.49 ml/min per kg) occurred in 7 of the 10 OLT patients. We conclude that abnormal CZX and CTX clearance is common after OLT and may be associated with minimal change in serum creatinine

Planning for cycling in the dispersed city: Establishing a hierarchy of effectiveness of municipal cycling policies

Urban utility cycling is being promoted widely due to various health, social, economic and environmental benefits. This study seeks to identify and rank which municipal-level policies and other factors are most influential in increasing cycling as a means of everyday transport and improving the real and perceived cycling safety in car-oriented urban centres. This is achieved by identifying the key factors thought to influence cycle use and by establishing a hierarchy of effectiveness of municipal cycling policies. Data was collected through interviews with a panel of experts who also completed a Delphi study, a technique rarely used in cycling policy research, to collect and compare expert opinions to predict the outcomes of policies and external factors. Policies and external factors were scored in a theoretical policy framework according to their perceived relative influence on cycling levels and cycling safety. The results reinforce previous findings in the literature but allow for generalisation in car-oriented urban centres due to the breadth of factors evaluated. It was found that providing cycling infrastructure is perceived to be a prerequisite for inducing utility cycling mode share. External factors such as urban form, the relative attractiveness of cycling to travel by car and wider governmental policy were perceived to have a strong influence. The generation and maintenance of political and public support is also suggested to be critical success factor

Designing the Optimal Bit: Balancing Energetic Cost, Speed and Reliability

We consider the technologically relevant costs of operating a reliable bit that can be erased rapidly. We find that both erasing and reliability times are non-monotonic in the underlying friction, leading to a trade-off between erasing speed and bit reliability. Fast erasure is possible at the expense of low reliability at moderate friction, and high reliability comes at the expense of slow erasure in the underdamped and overdamped limits. Within a given class of bit parameters and control strategies, we define "optimal" designs of bits that meet the desired reliability and erasing time requirements with the lowest operational work cost. We find that optimal designs always saturate the bound on the erasing time requirement, but can exceed the required reliability time if critically damped. The non-trivial geometry of the reliability and erasing time-scales allows us to exclude large regions of parameter space as sub-optimal. We find that optimal designs are either critically damped or close to critical damping under the erasing procedure

Environmental Clutter Elicits Behavioral Adaptations During Natural Behaviors in Echolocating Bats

The natural environment is filled with clutter that creates challenges for animals participating in routine tasks like orientation, foraging, and communication. For echolocating bats that primarily rely on an active sensory system, the effects of acoustic and physical clutter become more prominent with the potential to completely degrade the individuals’ ability effectively navigate their environment or engage in prey capture. From sonar jamming moths and competitive conspecifics to rapid prey pursuit in dense forests, bats must quickly adapt their sensory-guided flight behaviors in real-time to remain effective aerial predators. To explore the sources of acoustic clutter and their effects on natural bat behaviors, a literature review is presented on the historical and current perspectives on sonar jamming and the underlying mechanisms of the jamming avoidance response. This is followed by experimental evidence of bats making use of a jamming avoidance response when presented with playback of heterospecific bat calls thought to decrease foraging efficacy. Bats were found to significantly alter their individual echolocation call features in a manner that is thought to improve the signal-to-noise ratio, which would aid in the increased detection of their own echoes. The remaining chapters explore how bats might make use of multisensory cues when environmental conditions are unfavorable for echolocation alone and how bats adjust their flight strategies when navigating in a novel environment filled with physical clutter. These chapters respectively report that multimodal cues comprised of visual and acoustic information lead to enhancement of responses during an obstacle avoidance task and that significant changes in flight kinematics can be observed in cluttered vs. open environments