Long temporal gradient of retrograde amnesia for a well-discriminated stimulus

This experiment tested the general validity of recent findings that retrograde amnesia can be produced by electroconvulsive shock only if the shock is administered within 10 to 30 seconds after the learning trial. Precautions were taken to avoid confusion of other shock effects with retrograde amnesia. A temporal gradient of elec- troconvulsive shock-produced retrograde amnesia, extending up to at least 1 hour, for a well-discriminated stimulus, was demonstrated in mice in a one-trial learning passive avoidance situation.     

A long-snouted predatory dinosaur from africa and the evolution of spinosaurids

Fossils discovered in Lower Cretaceous (Aptian) rocks in the Tenere Desert of central Niger provide new information about spinosaurids, a peculiar group of piscivorous theropod dinosaurs. The remains, which represent a new genus and species, reveal the extreme elongation and transverse compression of the spinosaurid snout. The postcranial bones include blade-shaped vertebral spines that form a low sail over the hips. Phylogenetic analysis suggests that the enlarged thumb claw and robust forelimb evolved during the Jurassic, before the elongated snout and other fish-eating adaptations in the skull. The close phylogenetic relationship between the new African spinosaurid and Baryonyx from Europe provides evidence of dispersal across the Tethys seaway during the Early Cretaceous.     

Deficits in passive avoidance and fear conditioning in mice with septal lesions

By means of a simple activity measure, mice with lesions of the septal forebrain were tested for passive avoidance (response inhibition) and fear conditioning. In two separate experiments animals with septal lesions showed little or no conditioning, as evidenced by lack of suppression of activity during and following activitycontingent foot shock. Results support and extend thehypothesis that these deficits in passive avoidance derive from the removal of normal inhibitory influences mediated by the septal area.     

Corpus Luteum Development and Function after Supplementation of Long‐Acting Progesterone During the Early Luteal Phase in Beef Cattle

Strategic supplementation of P4 may be used to increase conception rates in cattle, but timing of supplementation in relation to ovulation, mass of supplementary P4 and formulation of the P4‐containing supplement has not been determined for beef cattle. Effects of supplementation of long‐acting progesterone (P4) on Days 2 or 3 post‐ovulation on development, function and regression of corpus luteum (CL) were studied in beef cattle. Cows were synchronized with an oestradiol/P4‐based protocol and treated with 150 or 300 mg of long‐acting P4 on Day 2 or 3 post‐ovulation (6–7 cows/group). Colour‐doppler ultrasound scanning and blood sample collection were performed from Day 2–21.5. Plasma P4 concentrations were greater (p < 0.05) from Day 2.5–5.5 in the Day 2‐treated groups and from Day 3.5–5.5 in the Day 3‐treated cows than in the control group. CL area and blood flow during Day 2–8.5 did not differ (p > 0.05) among groups, suggesting no effect of P4 treatment on luteal development. The frequency of cows that began luteolysis before Day 15 was greater (p < 0.04) in cows treated with 300 mg than in the controls, but there were no differences between non‐treated and 150 mg‐treated cows. The interval from pre‐treatment ovulation to functional and structural luteolysis was shorter (p < 0.01) in the combined P4‐treated groups than in the control cows. In conclusion, was showed for the first time that long‐acting P4 supplementation on Day 2 or 3 post‐ovulation increases P4 concentrations for ≥3 day, has no effect on luteal development, but anticipates the beginning of luteolysis in beef cattle.     

Amnesic effects of small bilateral brain puncture in the mouse

A small acute brain puncture produced retrograde amnesia in a passive avoidance learning situation in mice. If injury to the hippocampus was inflicted either immediately, 1 hour after the learning, or 1 hour before the learning, the animals showed a retention deficit; the degree of this deficit was related to the time interval. No effect of this injury was observed on retest performance when the animals were treated as long as 6 hours before or after the learning trial.