DIFFERENT ANESTHESIA IN RAT INDUCES DISTINCT INTER-STRUCTURE BRAIN DYNAMIC DETECTED BY HIGUCHI FRACTAL DIMENSION

The complexity, entropy and other non-linear measures of the electroencephalogram (EEG), such as Higuchi fractal dimension (FD), have been recently proposed as the measures of anesthesia depth and sedation. We hypothesized that during unconciousness in rats induced by the general anesthetics with opposite mechanism of action, behaviorally and poligraphically controlled as appropriately achieved stable anesthesia, we can detect distinct inter-structure brain dynamic using mean FDs. We used the surrogate data test for nonlinearity in order to establish the existence of nonlinear dynamics, and to justify the use of FD as a nonlinear measure in the time series analysis. The surrogate data of predefined probability distribution and autocorrelation properties have been generated using the algorithm of statically transformed autoregressive process (STAP). FD then is applied to quantify EEG signal complexity at the cortical, hippocampal and pontine level during stable general anesthesia (ketamine/xylazine or nembutal anesthesia). Our study showed for the first time that global neuronal inhibition caused by different mechanisms of anesthetic action induced distinct brain inter-structure complexity gradient in Sprague Dawley rats. EEG signal complexities were higher at cortical and hippocampal level in ketamine/xylazine vs. nembutal anesthesia, with the dominance of hippocampal complexity. In nembutal anesthesia the complexity dominance moved to pontine level, and ponto-hippocampo-cortical decreasing complexity gradient was established. This study has proved the Higuchi fractal dimension as a valuable tool for measuring the anesthesia induced inter-structure EEG complexity.

Diaphragm reinnervation by laryngeal motoneurons

Inspiratory activity of the paralyzed diaphragm was restored by reinnervation with brain stem laryngeal motoneurons. In 10 anesthetized cats, the right recurrent laryngeal nerve (RLN) was cut and anastomosed to the distal stump of either one or both roots (C5-C6) of the ipsilateral phrenic nerve. Three to four months later, reinnervation was assessed under deep anesthesia by the reappearance in the paralyzed diaphragm of 1) direct electromyographic (EMG) responses after electrical stimulation of the RLN and 2) spontaneous inspiratory bursts. Serial radiography, performed on five animals, revealed diaphragmatic excursions of comparable amplitude on the normal and reinnervated sides. Six to twelve months after anastomosis, laparotomy (performed under Nembutal anesthesia) allowed inspection and EMG recording of the spontaneous inspiratory contractions of the reinnervated areas and their sustained responses to tetanic RLN stimulation. Inspiratory discharges showed a ramplike recruitment similar to that of the normal diaphragm. Although the RLN contains a number of expiratory axons, multiple-site recordings disclosed expiratory EMG discharges only once. Histological analysis confirmed the substitution of phrenic axons by regenerating RLN fibers.

Mechanical properties of primate gallbladder: description by a dynamic method

Biomechanical theory was applied to devise a dynamic method for describing gallbladder tone in an in situ baboon model. Under pentobarbital sodium (Nembutal) anesthesia, cyclical infusion of bile into and withdrawal of bile from the gallbladder with continuous pressure monitoring allow instantaneous measurement of the pressure-volume ratio and thus of mean gallbladder compliance. This paper describes the method and details the manner of data analysis. Pharmacologic and hormonal agents with known gallbladder effects are used in order to demonstrate the sensitivity of the method. Pilocarpine, histamine, and cholecystokinin cause contraction of the primate gallbladder smooth muscle; this contraction is reflected in decreased compliance by continuous monitoring. Atropine administration results in increased ability to accommodate volume infusions; this effect has not been demonstrated by static monitoring in previous experiments. This new method allows continuous monitoring of compliance and offers both simplicity and sensitivity when compared with previous methods.

Effects of luminal nutrition and metabolic status on in vivo glucose absorption

Luminal nutrients, but not metabolic status, maintain active glucose transport by the rat intestine in vitro. The present study was designed to examine the effects of these factors on the in vivo absorption of glucose and 3-O-methylglucose. Rats were fed either intraluminally or by total parenteral nutrition (TPN) for 7 days or fasted for 72 h. Sugar absorption was measured under pentobarbital sodium (Nembutal) anesthesia at concentrations from 7 to 28 mM. Luminally fed rats had a significantly greater mucosal mass and absorption rates per centimeter of both sugars than either TPN or fasted animals. However, TPN rats had significantly greater absorption per milligram protein (i.e., specific activity) for both glucose and 3-O-methylglucose than luminally fed rats. In addition, TPN rats absorbed significantly more glucose per milligram protein, but not 3-O-methylglucose, than fasted animals. These data indicate: 1) luminal nutrients maintain glucose absorption by their trophic effects on mucosal mass; 2) the increase in specific activity for sugar absorption after TPN is unrelated to caloric balance; and 3) intestinal glucose metabolism affects its rate of absorption of glucose, but not 3-O-methylglucose.

Hematological alterations and response to acute hypobaric stress

Exposure of rats to simulated altitude (15,000 ft) for 1 day and 3 and 9 wk produced progressive polycythemia, elevated 2,3-diphosphoglycerate levels and raised P50 values; the latter two parameters decreased toward control values after 9 wk. Carbon monoxide (38–43% HbCO) exposure produced polycythemia after 3- and 9-wk exposure, no change in 2,3-DPG and a fall in P50 value. Ten days' treatment with sodium cyanate produced a large decrease in 2,3-DPG and P50. Survival during 90 min of acute hypobaria (0.3 atm) under Nembutal anesthesia was highest with NaOCN (75%), intermediate with 3- and 9-wk exposure to altitude and CO (56–58%) lower in 1-day altitude exposure (44%) and lowest in controls (5%). Heart and ventilation rate was monitored during this hypobaric test and response patterns established for each exposure/treatment. In states of extreme oxygen deprivation the results suggest, in order of importance, the survival value of 1) increased oxygen-hemoglobin affinity, and 2) polycythemia.

Adrenocorticotropin Secretion Rates Following Histamine Injection in Adult and Newborn Dogs

The metabolic clearance rate (MCR) for ACTH in adult dogs was previously shown not to vary significantly with varying plasma ACTH concentrations or among dogs. This is confirmed here for pups aged 1–7 days. Hence, ACTH secretion rates can be continuously calculated from a continuous function of plasma ACTH vs. time. Each of seven adult dogs under Nembutal anesthesia received two or three intravenous (i.v.) injections of histamine with increasing doses. The first injections in each dog ranged from 7 to 50 μg/kg, while the last dose was 62–108 μg/kg. A total of 16 injections were given. Twelve pups (two litters of six) aged 1–7 days each received one injection of histamine of 76–116 μg/kg (i.v.). ACTH concentrations in plasma were determined by an adrenal cell suspension bioassay before, and 6 times after each injection. Nine pups also underwent determinations of their MCR for ACTH, with plateau concentrations determined at three times during an ACTH infusion. Continuous curves of ACTH secretion rates were calculated for all 28 histamine injections, showing that all except the 1-day-old pups secrete considerable ACTH when stressed. Compared to adult dogs, the pups show lower secretion rate peaks and shorter periods of rapid secretion. Changes in plasma glucocorticoids also suggest that the adrenal cortex of newborn dogs can respond to ACTH by increased glucocorticoid secretion.