Inhibitory learning and memory in newborn rats influenced by nitric oxide.

The impact of nitric oxide on learning, memory processing and retrieval was studied in the neonatal rats. For comparison, spontaneous motor activity and changes of brain temperature were also studied after nitric oxide manipulations in identical age groups. The nitric oxide availability was either increased by a systemic or intracerebroventricular application of L-arginine, a substrate of nitric-oxide synthase, or decreased by nitro-L-arginine, its inhibitor. L-arginine, 20 mM or nitro-L-arginine, 10 or 5 mM were given intraperitoneally, 1 ml/100 g weight, or in the amounts of 11 into both lateral cerebral ventricles. Intact and saline injected pups were used as controls. Spontaneous motor behavior of newborn pups were not unambiguously affected by nitric oxide, and the same applies to changes of brain and body temperature or heart rate. In no case any correlation with changes of learning and/or memory could be established. Learning was dose dependently impaired relative to controls by intraperitoneal application of nitroarginine. L-arginine only slightly decreased numbers of trials to both criteria and partially abolished the blocking effect of nitroarginine on nitric oxide synthase. With the use of intracerebroventricular injections the positive impact of L-arginine on learning became highly significant. In 24-h memory, intraperitoneal injections of L-arginine enhanced the retention indexes. The impairing effect of nitro-L-arginine significantly increased with delaying after-learning application intervals, being more pronounced at the 3-h than at 0-h interval. Here also, its effect was partially abolished by L-arginine. Effects of nitric-oxide availability in brain after intracerebroventricular application of these substances at 16 various post-learning intervals were assessed on memory processing and retrieval. A general enhancing effect of increased nitric-oxide supply on 24-h retention indexes was found through all studied intervals, which was not, however, monotonous, but several peaks appeared with application at 3, 6, 18 and 23.5 h after learning. On the other hand, the suppressive effect of NArg was not evident relative to saline before the 6-h post-learning injection delay. These results show that nitric oxide exerts a considerable central modulatory effect on learning, memory processing and retrieval at the very early postnatal period of the rat. The efficiency of nitric-oxide manipulations depends on its actual bioavailability in the brain and the stage of memory processing.

High functioning fragile X males: demonstration of an unmethylated fully expanded FMR-1 mutation associated with protein expression.

Fragile X (fra(X)) males with a standardized IQ score of 70 or higher represent a high functioning (HF) or nonretarded fra(X) male group. This group, which does not include nonpenetrant males, has received little research attention to date. Of 221 fra(X) males who had been evaluated through The Children's Hospital in Denver since 1981 and had completed cognitive or developmental testing, 29 (13%) were high functioning by the above definition. We found that HF males on the whole had a lower cytogenetic score and were younger than retarded fra(X) males, but there was no difference between these two groups in the number of typical fra(X) physical manifestations present. FMR-1 DNA testing was performed on 134 fra(X) males and methylation status was determined for 51 of these. A greater percentage of HF males had a mosaic pattern or an incompletely methylated full mutation than did retarded males. A unique DNA pattern, an unmethylated fully expanded mutation, was discovered in 3 of the highest functioning fra(X) males. Protein studies performed on 2 of these males demonstrated the presence of FMR-1 protein, albeit at lower levels than normal. FMR-1 protein was not present in retarded fra(X) males. Significant FMR-1 protein expression may be responsible for higher cognitive functioning in the 2 males with unmethylated fully expanded mutations compared to retarded fra(X) males.

Histochemical and biochemical observations of the spleen in atypical Niemann-Pick disease and in idiopathic thrombocytopenic purpura.

In a case of adolescent Niemann-Pick disease (NP) and in a case of idiopathic thrombocytopenic purpura (ITP), the histologic picture of the spleen showed appreciable similarity in localization of sparing cells and in a number of histochemical tests. The sphingomyelin, which was the main organ phospholipid in both conditions, contained substantially elevated content of C24 fatty acids. Detailed analysis of spleen lipids showed great relative increase of lysobisphosphatidic acid and of cholesterol which was in NP mainly in free form but in ITP surprisingly mainly esterified, mostly to oleic and palmitic acid. Possible molecular mechanism of sphingomyelin storage was enzymologically followed in model conditions using separated lipid fractions from NP's spleen. The activity of sphingomyelinase (Cl. perfringens exotoxin) was in comparison to phospholipase C relatively specifically inhibited by lysobisphosphatidic acid.

Effects of postnatal influences on conditioning and some functional and structural brain parameters in rats.

Early postnatal influences were studied in rats in three different ways: (i) different litter size, (ii) feeding with restricted amount of protein, (iii) different level of afferent stimulation. A complex evaluation of spontaneous activity, conditioning, electrophysiological and biochemical analyses was used in these experiments. Medium sized litters showed the greater electrophysiological reactivity (cortical evoked potentials) and the most stable performance in different kinds of conditioning (avoidance) experiments. Animals reared on a low protein diet were subnormal in electrophysiological indices, and had a lower level of biochemical activity for materials Involved in neural excitability, electrogenesis, and cellular and subcellular energetic metabolism (phospholipids, proteins, DNA, RNA). In all respects (behavioral, electrophysiological and biochemical tests) animals with partial sensory deprivation in the postnatal period had the lowest indices. The "stimulated" animals on the other hand were superior to both other groups in the tests used for the analysis of higher nervous activity, but electrophysiological and biochemical analyses did not show clear differences between the "stimulated" and control animals. Optimal development of brain functions requires adequate conditions in the early postnatal period. However, the "adequacy" of them conditions has dill to be determined more precisely.

Liver cell cytoplasmic inclusions in experimental porphyrias: their demonstration with the ferric ferricyanide reduction reaction.

In the present paper we describe needle-shaped and granular cytoplasmic inclusions in the liver cells of mice and rats with experimental porphyria biochemically resembling human porphyria cutanea tarda. The inclusions were inconspicuous in routine histological slides. The ferric ferricyanide reduction reaction, however, enabled us to demonstrate their shape and location within the hepatic lobule. Needle-shaped inclusions are considered to represent a structure specifically seen in experimental porphyrias resembling porphyria cutanea tarda. These structures are similar to the inclusions seen in human porphyria cutanea tarda.

The influence of 3-aminopropansulphonic acid (3-APS) on thalamic neurons.

The possible pathways conducting pain are still being discussed. One of the possible pathways may pass through the centrum medianum (CM). In the present study the activity of neurones of CM in cats was recorded using glass-micropipettes. 3-aminopropansulphonic acid (3-APS), which is a GABA analogue was administered intravenously in a dose of 0.1, 0.2, 0.5 and 1.0 mmol/kg. The depressive effect starts at the dose of 0.2 mmol/kg. The duration of the effect depends on the dose of 3-APS. Hence 3-APS has a very strong effect on other thalamic neurones so that it may be used for influencing their activity.

Functional and structural effects of GM-1 ganglioside treatment on peripheral nerve grafting in the rat.

Peripheral nerve regeneration after traumatic injury and standard repair with a nerve autograft is usually incomplete. This study tested the influence of graft vascularity and pharmacological intervention with GM-1 ganglioside on nerve regeneration in a rat sciatic nerve model. Controls included an unoperated contralateral side and sham-operated groups either with or without the GM-1. During the 5 months of recovery, locomotion was tested by the sciatic function index (SFI). At killing, anesthetized animals were prepared for nerve conduction velocity (NCV) studies, followed by the wet weight of the gastrocnemius muscle (expression of atrophy), toe-chewing (expression of lesion severity and sensory loss), and histological examination of the nerve segments. The SFI showed a slight but significant recovery for both the vascular and avascular groups (34% at 20 weeks), but when GM-1 ganglioside treatment was included, the SFI was poor throughout (20-33%). The average NCV of the graft groups without GM-1 was 46% to 57% of the normal nerve (52.7 m/s), whereas for the groups treated with GM-1, it was 63% to 64% of normal; treatment of the non-vascular graft group significantly improved recovery. A uniformly poor recovery from muscle atrophy was seen for all nerve graft groups (62-67%) compared with normal controls. The mean number of toes per foot chewed was 1.9 and 2.4 in graft groups without GM-1 treatment and 0.9 and 1.3 in graft groups treated with GM-1. This treatment significantly reduced both the extent and the number of animals exhibiting autotomy. The qualitative microscopic appearance of the distal nerve segment in all surgical groups was similar. We conclude that the systemic addition of GM-1 ganglioside enhances only some aspects of regeneration in grafted nerves, possibly with a preferential effect on sensory nerve regeneration and functional recovery.

Molecular predictors of cognitive involvement in female carriers of fragile X syndrome.

OBJECTIVE: Fragile X syndrome is caused by a mutation involving expansion of a CGG trinucleotide repeat segment in the fragile X mental retardation-1 (FMR1) gene on the long arm of the X chromosome. This study was undertaken to determine the relative impact of three molecular characteristics of the FMR1 mutation--number of CGG repeats, methylation status, and X inactivation ratio--on the cognitive involvement of female carriers of fragile X syndrome. DESIGN: Retrospective study with new DNA analysis of known female carriers of fragile X syndrome. SETTING: Molecular studies were conducted in a university-based DNA diagnostic laboratory. Patients were originally ascertained through a regional fragile X clinic in a university-affiliated pediatric hospital. PATIENTS: Forty-eight female carriers of fragile X syndrome were studied, including 22 with a premutation (a small expansion to approximately 50 to 200 CGG repeats), 23 with a full mutation (a full expansion to > 200 CGG repeats), and three with both types of mutations (mosaics). RESULTS: Median IQ score was significantly lower for females with a full mutation than for females with a premutation. No significant relationship was found between IQ score and number of CGG repeats or percentage methylation of the mutant allele within each mutation category. In addition, no significant relationship was found between IQ score and the proportion of normal FMR1 alleles on the active X chromosome in the carrier female group as a whole or in either mutation subgroup. Comparisons of leukocytes and saliva-borne epithelial cells in certain full-mutation carriers revealed striking differences in FMR1 mutation sizes. CONCLUSIONS: Mutation category remains the most important predictor of affectedness in female carriers of fragile X syndrome. Our data do not support use of the proportion of normal FMR1 alleles on the active X chromosome as a predictor of cognitive involvement in female carriers with full mutations. Individual tissue-specific differences exist in the heterogeneous sizes of full mutations and in the presence of premutation/full-mutation mosaicism.