Skin blood flow in the Wistar-Kyoto rat and the spontaneously hypertensive rat

• 1.1. Using laser Doppler techniques in man, we have previously demonstrated differences in skin blood flow properties at sites with primarily nutritive (NUTR) perfusion, such as the elbow or knee, as compared to sites such as the finger pulp, with predominantly arteriovenous anastomotic (AVA) perfusion.
• 2.2. Basal and heat stimulated flow is greater at AVA sites. In man, blood pressure changes are reflected primarily by changes at AVA rather than NUTR sites.
• 3.3. These blood pressure induced changes affect the red blood cell velocity (VEL) component at AVA sites more than microvascular volume (VOL).
• 4.4. Given these findings in man, we decided to compare skin blood flow properties in a suitable animal model.
• 5.5. We chose the Wistar-Kyoto (WKY) and Spontaneously Hypertensive Rat (SHR) strains, in view of the marked difference in systemic blood pressure in these two related strains.
• 6.6. Skin blood flow varied considerably at different skin sites in the rats. Skin sites with hair covering, on the back and at the base of the tail, showed low basal and heat stimulated blood flow.
• 7.7. In contrast, the plantar surface of the paw behaved similarly to the finger or toe pulps in man, with 3–4-fold higher basal flow than the hair covered areas and a 7–8-fold rise with local heating to 44°C.
• 8.8. Furthermore, there was a 25% greater blood flow at the plantar paw surface in the SHR rats as compared to the WKY rats, corresponding to the 25% higher systemic blood pressure in these animals.
• 9.9. The heat induced increase in flow at the plantar surface of the paw was primarily a result of a marked increase in VEL rather than VOL.
• 10.10. The higher flow at this site in SHR as compared to WKY rats was likewise ascribable to an increase in VEL, VOL being equivalent in the two strains.

     

Metacognition in the rat

The ability to reflect on one's own mental processes, termed metacognition, is a defining feature of human existence [1, 2]. Consequently, a fundamental question in comparative cognition is whether nonhuman animals have knowledge of their own cognitive states [3]. Recent evidence suggests that people and nonhuman primates [4-8] but not less "cognitively sophisticated" species [3, 9, 10] are capable of metacognition. Here, we demonstrate for the first time that rats are capable of metacognition--i.e., they know when they do not know the answer in a duration-discrimination test. Before taking the duration test, rats were given the opportunity to decline the test. On other trials, they were not given the option to decline the test. Accurate performance on the duration test yielded a large reward, whereas inaccurate performance resulted in no reward. Declining a test yielded a small but guaranteed reward. If rats possess knowledge regarding whether they know the answer to the test, they would be expected to decline most frequently on difficult tests and show lowest accuracy on difficult tests that cannot be declined [4]. Our data provide evidence for both predictions and suggest that a nonprimate has knowledge of its own cognitive state.     

Effects of rat cytomegalovirus on the nervous system of the early rat embryo

The purpose of the study was to investigate the impact of rat cytomegalovirus (RCMV) infection on the development of the nervous system in rat embryos, and to evaluate the involvement of Wnt signaling pathway key molecules and the downstream gene neurogenin 1 (Ngn1) in RCMV infected neural stem cells (NSCs). Infection and control groups were established, each containing 20 pregnant Wistar rats. Rats in the infection group were inoculated with RCMV by intraperitoneal injection on the first day of pregnancy. Rat E20 embryos were taken to evaluate the teratogenic rate. NSCs were isolated from E13 embryos, and maintained in vitro. We found: 1) Poor fetal development was found in the infection group with low survival and high malformation rates. 2) The proliferation and differentiation of NSCs were affected. In the infection group, NSCs proliferated more slowly and had a lower neurosphere formation rate than the control. The differentiation ratio from NSCs to neurons and glial cells was significantly different from that of the control, showed by immunofluorescence staining. 3) Ngn1 mRNA expression and the nuclear β-catenin protein level were significantly lower than the control on day 2 when NSCs differentiated. 4) The Morris water maze test was performed on 4-week pups, and the infected rats were found worse in learning and memory ability. In a summary, RCMV infection caused abnormalities in the rat embryonic nervous system, significantly inhibited NSC proliferation and differentiation, and inhibited the expression of key molecules in the Wnt/β-catenin signaling pathway so as to affect NSCs differentiation. This may be an important mechanism by which RCMV causes embryonic nervous system abnormalities.     

Transfer of the heritable nonhemolytic jaundice trait from the Gunn rat to the Sprague-Dawley rat

Congenital nonhemolytic jaundice as observed in the Gunn rat was transferred successfully to the Sprague-Dawley rat. This jaundice trait occurs as the result of a deficiency of bilirubin glucuronyltransferase and appeared to transfer by simple Mendelian inheritance. A comparison of jaundiced Gunn with jaundiced Gunn-Sprague-Dawley cross rats for plasma bilirubin level, bilirubin glucuronyltransferase activity and female reproductive performance showed no significant difference between the two jaundiced rat groups. The phenotypic expression of the jaundice trait as viewed by the parameters used in this study appeared to be the same for both the Gunn and Gunn-Sprague-Dawley cross rats. The transfer of the jaundice trait to another rat strain enhances the opportunity to characterize this animal model and to determine the possible influence of a long-term closed mating system.     

Depot iron in the rat liver after hypertransfusion with rat erythrocytes

In the rat liver the deposition of iron was measured after hypertransfusion with rat erythrocytes. The liver iron fractions were studied during four weeks after the hypertransfusions. In the first week the haemosiderin iron fraction increased together with the ferritin iron fraction. Most iron was deposited as ferritin iron. In the last week of the experiments, while the ferritin iron fraction still increased, the haemosiderin iron fraction decreased. At the same time plasma iron was utilized when erythropoiesis, which had been suppressed by the hypertransfusion, recommenced. It is suggest that, under these experimental conditions, liver haemosiderin iron is used in haemoglobin synthesis.     

Metabolic fate of rat and human lipoprotein apoproteins in the rat

The fate of (125)I-labeled apolipoproteins was studied in vivo in rats that had received intravenous injections of (125)I-labeled rat HDL and (125)I-labeled human HDL, LDL, and VLDL. Plasma decay curves of rat and human HDL were exponential with similar half-lives in the circulation (11-12 hr). After injection, low molecular weight apolipoproteins (apoLP-alanine of human HDL and fraction HS-3 of rat HDL) were found to redistribute to other lipoproteins, predominantly VLDL. Decay curves of individual HDL proteins were constructed after lipoprotein fractionation, delipidation, and polyacrylamide gel electrophoresis. It was found that the half-lives of the different HDL apoproteins were not identical. A major rat HDL protein (52% of total counts) had a circulating half-life (t((1/2))) of 12.5 hr. Two others had a t((1/2)) of 8-9 hr while the t((1/2)) of several others was 11-12 hr. The t((1/2)) of three well-characterized human HDL apoproteins, apoLP-glutamine I, apoLP-glutamine II, and apoLP-alanine, were 13.5, 9.0, and 15.0 hr, respectively. The fate of (125)I-labeled human VLDL and LDL apoproteins in rats was similar to that described previously in humans. After injection of (125)I-labeled human VLDL into rats, apoLP-glutamic acid and apoLP-alanine rapidly transferred to rat HDL and were lost thereafter from the circulation from both VLDL and HDL. The apoLDL moiety of human VLDL moved metabolically to the LDL density range (d = 1.019-1.063) through a lipoprotein of intermediate density (d = 1.006-1.019).     

Episodic-like memory in the rat

A fundamental question in comparative cognition is whether animals remember unique, personal past experiences. It has long been argued that memories for specific events (referred to as episodic memory) are unique to humans. Recently, considerable evidence has accumulated to show that food-storing birds possess critical behavioral elements of episodic memory, referred to as episodic-like memory in acknowledgment of the fact that behavioral criteria do not assess subjective experiences. Here we show that rats have a detailed representation of remembered events and meet behavioral criteria for episodic-like memory. We provided rats with access to locations baited with distinctive (e.g., grape and raspberry) or nondistinctive (regular chow) flavors. Locations with a distinctive flavor replenished after a long but not a short delay, and locations with the nondistinctive flavor never replenished. One distinctive flavor was devalued after encoding its location by prefeeding that flavor (satiation) or by pairing it with lithium chloride (acquired taste aversion), while the other distinctive flavor was not devalued. The rats selectively decreased revisits to the devalued distinctive flavor but not to the nondevalued distinctive flavor. The present studies demonstrate that rats selectively encode the content of episodic-like memories.     

Inosine metabolism in the rat

1. Uptake and subsequent metabolism of purine and ribose moieties was monitored after intravenous administration of doubly labelled inosine. 2. More than 95% was cleared from the plasma within 5 min, and 99% within 20 min. 3. Approx. 50% of the 160 mumol total was rapidly incorporated into liver and kidney. Kidney removed the greatest amount (21 mumol/g wet wt.), about 10-fold more than heart, lung or liver. Lung and heart accounted for only 3%. These tissues then lost radioactivity during the remainder of the experiment. Radioactivity in the skeletal muscle, in contrast, increased from 8% of the injected dose at 5 min to 40% at 60 min. 4. In liver, kidney, heart and lung there was a significant difference in the fate of inosine. After initial incorporation of inosine, kidney predominantly lost inosine; heart preferentially lost purines; lung preferentially lost ribose radioactivity; and in liver the ribose radioactivity was rapidly lost, whereas purine was retained. Some of the ribose moiety was metabolized to glucose, presumably in the liver, and then released into the blood. Ribose radioactivity (probably as glucose) and radioactive hypoxanthine accumulated in skeletal muscle throughout the experiment. 5. Inosine caused a rapid and prolonged increase in the blood glucose content, from 6 to 15 mM in 60 min. This was accompanied by a small increase in plasma insulin. 6. It is concluded that the purine and ribose radioactivity lost from the kidney, liver and other tissues becomes incorporated into skeletal muscle.