Conditioned changes in ultrasonic vocalizations to an aversive olfactory stimulus are lateralized in 6-day-old rats

Using a soft rubber plug to block airflow in one naris, Kucharski, Johanson, and Hall (1986) found that some forms of olfactory memory (e.g., odor preferences) were lateralized in young rats while other forms (e.g., conditioned activation and mouthing) were not. The present experiments extended that research by showing that conditioned increases in ultrasonic vocalizations were also lateralized. That is, when exposed to an odor that was previously paired with footshock, 6-day-old rats significantly increased their rate of vocalizing. This response only occurred, however, when the naris open at training was also open at test. The use of the developing rat as a natural split-brain preparation appears to be an effective procedure with which to broaden current approaches to the analysis of learning, memory, and emotion.

Effects of multisensory environmental stimulation on contextual conditioning in the developing rat

The effect of increased exposure to multisensory stimulation during development on conditioned freezing to contextual cues in preweanling Sprague-Dawley rats was examined. Rats given increased environmental stimulation exhibited long-term contextual conditioning at a younger age than rats that did not receive such stimulation when there was either low or moderate levels of conditioning (Experiments 1 and 2). These differences in contextual conditioning were not a result of the stimulated rats reacting differently to shock (Experiment 4) or merely freezing more than the nonstimulated rats in all situations (Experiment 3). The role of the glucocorticoid system in the enhanced contextual learning of stimulated preweanling rats and the advantages of the contextual conditioning procedure for studying the effects of environmental stimulation are discussed.

Shock sensitization of startle: learned or unlearned fear?

Following shock, rats exhibit a potentiated startle response to a sudden, loud noise. It has been suggested that this shock sensitization of the startle response can be used as a model preparation for studying unlearned fear. After reviewing the theoretical and empirical bases for this claim, the results of several recent studies that show that the shock sensitization of startle effect is actually mediated by contextually conditioned fear are presented. From this, it is concluded that the shock sensitization of startle procedure is an appropriate model preparation for studying contextual conditioning but is not an appropriate procedure for studying unlearned fear. Several other procedures that have potential as model preparations for studying unlearned fear are discussed briefly.

Shock sensitization of startle in the developing rat

Rats given a series of shocks exhibit a potentiated startle response to a loud acoustic stimulus compared to nonshocked animals. Experiment 1 showed that this shock sensitization of startle, like conditioned fear potentiation of startle to discrete cues, emerges relatively late in development (i.e., 23 days of age). Although different testing procedures were used in Experiment 2, preweanling rats still failed to exhibit the shock sensitization of startle effect. The failure to observe the shock sensitization of startle effect in preweanling rats was not due to age differences in contextual conditioning produced by the shock treatment (Experiment 3). The results of this study are discussed in terms of (a) the emergence of fear potentiation of startle during development, and (b) the relation between conditioned freezing and startle potentiation.

Energy expenditure in acetaminophen-induced fulminant hepatic failure

OBJECTIVE

To determine energy expenditure in critically ill patients suffering from acetaminophen-induced fulminant hepatic failure and compare it with values obtained in matched, healthy control subjects and in patients studied during the anhepatic period of elective liver transplantation.

DESIGN

Prospective, controlled, observational study.

SETTING

A ten-bed intensive therapy unit and a liver transplant unit at a University teaching hospital.

PATIENTS AND SUBJECTS

Sixteen patients suffering from acetaminophen-induced fulminant hepatic failure who were sedated, paralyzed, and mechanically ventilated; 16 age-, gender-, and weight-matched, awake, healthy control subjects; and 16 patients with chronic liver disease, undergoing elective liver transplantation, who were studied during the anhepatic period of surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The mean energy expenditure was calculated in each case for a 30-min period, using indirect calorimetry. In the patients undergoing liver transplantation, measurements were performed after clamping the hepatic veins and recipient hepatectomy. Energy expenditure was markedly increased in the fulminant hepatic failure group (mean energy expenditure, 4.05 [SD 0.52] kJ x kg(-1) x hr(-1)), in comparison with healthy control subjects (mean, 3.44 [0.27] kJ x kg(-1) x hr(-1); mean difference, 18%; p < .001) and in comparison with patients during the anhepatic period of liver transplantation (mean, 3.15 [0.61] kJ x kg(-1) x hr(-1); mean difference, 29%; p < .001). These differences were even more pronounced when a correction factor for differences in core temperature was included in the calculation. Harris-Benedict predictions of energy expenditure were unreliable in the patients with acute liver failure. No correlations were found among energy expenditure and hemodynamic variables, the requirement for vasoconstrictors, or the presence of renal failure.

CONCLUSIONS

Despite the loss of functioning liver cell mass, the metabolic rate is substantially increased in patients with acetaminophen-induced fulminant hepatic failure. This finding is consistent with the marked systemic inflammatory response, which accompanies acute hepatic failure. The Harris-Benedict equation is unreliable when an estimation of energy expenditure is required in patients with this condition.

Effects of environmental enrichment on rate of contextual processing and discriminative ability in adult rats

The effect of environmental enrichment on conditioned freezing to contextual cues in adult Sprague-Dawley rats was examined. The freezing of both enriched-and standard-reared rats increased with the time spent in the chamber prior to shock. Both groups of rats showed equally low levels of contextual conditioning following a preshock period of 4 s and equally high levels following a 120-s preshock period. However, following a preshock period of 16 s enriched rats displayed more contextual conditioning than standard rats. That is, enriched rats appeared to process contextual information faster than their standard-reared counterparts. Enriched- reared rats also showed a greater ability to discriminate between the conditioning context and a similar but distinctive context. Hence, in addition to forming a representation of the context in memory more rapidly than standard-reared rats, enriched-reared rats also appear to form a more complex representation.

Conditioned odor potentiation of startle in rats

An odor previously paired with shock was shown to be an effective stimulus for potentiating the startle response in rats (Experiments 1 and 2). This effect required more than 1 odor-shock pairing (Experiment 3), was relatively long lasting (Experiment 4), and was specific to the odor previously paired with shock (Experiment 5). The implications of these findings for the startle probe procedure and for neural models of learning and memory based on results obtained with that procedure are discussed.

Implementing evidence-based practice

Traditional methods of disseminating research findings through publication has had only a limited impact on clinical practice. Issues of time and professional territorialism may be barriers to change. More active interventions are needed to ensure that findings are implemented.

A practical approach to vascular access for hemodialysis and predictors of success

PURPOSE

The long-term results and predictors of success for vascular access at The Toronto Hospital were studied. This report describes the access program and emphasizes the role of the vascular access coordinator.

METHODS

A total of 384 consecutive patients underwent 466 vascular access procedures. The access program is centered around a dedicated, full-time vascular access coordinator, who is a registered nurse and is responsible for all aspects of access care, including follow-up. Outcome variables were collected prospectively. Primary, primary-assisted, and secondary success was determined by means of Kaplan-Meier analysis, and the stepwise Cox proportional hazards model was used for multivariate analysis of the factors that were independently predictive of primary success.

RESULTS

There were 235 autogenous arteriovenous fistulae (AVFs) and 231 arteriovenous grafts (AVGs). The cumulative primary, assisted-primary, and secondary success (patent and functional for effective dialysis) at 24 months for all 466 cases combined was 36% +/- 3%, 54% +/- 3%, and 66% +/- 3%, respectively. The primary success for AVFs and AVGs at 2 years was 54% +/- 4% and 18% +/- 4%, respectively (P <.001; log-rank test); the primary-assisted success for AVFs and AVGs at 2 years was 62% +/- 4% and 44% +/- 6%, respectively (P <.001; log-rank test); and the secondary success for AVFs and AVGs at 2 years was 70% +/- 4% and 60% +/- 5%, respectively (P =.331; log-rank test). Stratification of variables revealed significant benefit for AVFs (P =.001), the female sex (P =.014), and the absence of diabetes mellitus (P =.001). Multivariate analysis with Cox regression determined that access type (AVF vs AVG; P =.001) and diabetes mellitus (P =.024) were independently predictive of primary success. The improved clinical coordination of access patients with the initiation of the vascular access program resulted in a significant reduction in length of hospital stay before and after the program was organized (2.5 +/- 0.06 vs 1.1 +/- 0.03 days; P =.001).

CONCLUSION

The organization of a vascular access program in a practical and cost-effective way for reduced length of hospital stay is streamlined through a dedicated access coordinator, who ensures an integrated, multidisciplinary approach. The results for the Cox model is useful when discussing the anticipated results of access procedures with individual patients.

Suppressors of cytokine signaling (SOCS): negative regulators of signal transduction

SOCS-1 was originally identified as an inhibitor of interleukin-6 signal transduction and is a member of a family of proteins (SOCS-1 to SOCS-7 and CIS) that contain an SH2 domain and a conserved carboxyl-terminal SOCS box motif. Mutation studies have established that critical contributions from both the amino-terminal and SH2 domains are essential for SOCS-1 and SOCS-3 to inhibit cytokine signaling. Inhibition of cytokine-dependent activation of STAT3 occurred in cells expressing either SOCS-1 or SOCS-3, but unlike SOCS-1, SOCS-3 did not directly interact with or inhibit the activity of JAK kinases. Although the conserved SOCS box motif appeared to be dispensable for SOCS-1 and SOCS-3 action when overexpressed, this domain interacts with elongin proteins and may be important in regulating protein turnover. In gene knockout studies, SOCS-1(-/-) mice were born but failed to thrive and died within 3 weeks of age with fatty degeneration of the liver and hemopoietic infiltration of several organs. The thymus in SOCS-1(-/-) mice was small, the animals were lymphopenic, and deficiencies in B lymphocytes were evident within hemopoietic organs. We propose that the absence of SOCS-1 in these mice prevents lymphocytes and liver cells from appropriately controlling signals from cytokines with cytotoxic side effects.

Conditioned odor potentiation of startle in rats

An odor previously paired with shock was shown to be an effective stimulus for potentiating the startle response in rats (Experiments 1 and 2). This effect required more than 1 odor-shock pairing (Experiment 3), was relatively long lasting (Experiment 4), and was specific to the odor previously paired with shock (Experiment 5). The implications of these findings for the startle probe procedure and for neural models of learning and memory based on results obtained with that procedure are discussed.

A mutation at codon 279 (N279K) in exon 10 of the Tau gene causes a tauopathy with dementia and supranuclear palsy

Recently intronic and exonic mutations in the Tau gene have been found to be associated with familial neurodegenerative syndromes characterized not only by a predominantly frontotemporal dementia but also by the presence of neurological signs consistent with the dysfunction of multiple subcortical neuronal circuitries. Among families, the symptomatology appears to vary in quality and severity in relation to the specific Tau gene mutation and often may include parkinsonism, supranuclear palsies, and/or myoclonus, in addition to dementia. We carried out molecular genetic and neuropathological studies on two patients from a French family presenting, early in their fifth decade, a cognitive impairment and supranuclear palsy followed by an akinetic rigid syndrome and dementia. The proband died severely demented 7 years after the onset of the symptoms; currently, his brother is still alive although his disease is progressing. In both patients, we found a Tau gene mutation in exon 10 at codon 279, resulting in an asparagine to lysine substitution (N279K). Neuropathologically, widespread neuronal and glial tau accumulation in the cortex, basal ganglia, brain stem nuclei as well as in the white matter were the hallmark of the disease. These deposits were shown by immunohistochemistry and immunoelectron microscopy, using a battery of antibodies to phosphorylation-dependent and phosphorylation-independent epitopes present in multiple tau regions. In the neocortex, tau-immunopositive glial cells were more numerous than immunopositive neurons; the deeper cortical layers as well as the white matter adjacent to the cortex contained the largest amount of immunolabeled glial cells. In contrast, some brain stem nuclei contained more neurons with tau deposits than immunolabeled glial cells. The correlation of clinical, neuropathological and molecular genetic findings emphasize the phenotypic heterogeneity of diseases caused by Tau gene mutations. Furthermore, to test the effect of the N279K mutation and compare it with the effect of the P301L exon 10 mutation on alternative splicing of Tau exon 10, we used an exon amplification assay. Our results suggest that the N279K mutation affects splicing similar to the intronic mutations, allowing exon 10 to be incorporated more frequently in the Tau transcript.

Macronutrient preference, dietary intake, and substrate oxidation among stable cirrhotic patients

Anorexia in liver disease is common; however, its association with aberrant metabolism and the type of cirrhosis has not been considered. Dietary intake, nutritional status, fasting substrate oxidation, and macronutrient preference were examined in controls (n = 18) and 65 patients with hepatocellular (n = 31) or biliary cirrhosis (n = 34). Energy intakes were lowest in hepatocellular patients (controls: 9.0 +/- 0.48 megajoules/day compared with biliary: 7.0 +/- 0.40 MJ/day, P <.05; controls compared with hepatocellular 6.5 +/- 0.39 megajoules/day, P <.01). Triceps skinfold was lower only in hepatocellular patients (controls: 109 +/- 9.2% compared with hepatocellular 79 +/- 5.6%, P <.05). The fasting rate of lipid oxidation was elevated in hepatocellular patients when compared with controls and biliary patients (controls: 40.9 +/- 15.1 mg/min compared with hepatocellular 62.8 +/- 16.8 mg/min, P <.001, and biliary : 45.5 +/- 17.0 mg/min compared with hepatocellular, P <.001). Control subjects exhibited a greater preference for the high fat, moderate carbohydrate food (controls: median 7.0 IQR 2.0 compared with biliary: median 5.0 interquartile range [IQR] 4.7, P <.01) (controls compared with hepatocellular: median 6.0 IQR 4.0, P <.01). Cirrhotic patients' spontaneous dietary intake is lower than that of controls and recommended intakes. Although macronutrient preference ratings were different within cirrhotic patient groups it remains unclear whether associated nutrient deficits are metabolically driven and dictated by primary cause.

Developmental changes in seizure susceptibility during ethanol withdrawal

It has recently been established that adolescence may represent a developmentally sensitive period with respect to the effects of ethanol, particularly within the NMDA neurotransmitter system. However, the same may also be true of the GABA system. There is evidence to suggest that the number of GABA receptors and their kinetics may change across development. The purpose of this study was to determine if GABA-mediated seizure susceptibility during ethanol withdrawal differed between adolescent and adult animals. Results indicate that adult animals pretreated with ethanol were more likely to achieve maximal tonic-clonic seizure activity and spent more time in stage 3 (or higher) seizure activity than all other groups. These data lend additional support to the contention that adolescent and adult animals differ in their susceptibility to the effects of ethanol and that this susceptibility is transmitter dependent.