Random positions of dendritic spines in human cerebral cortex.

Dendritic spines establish most excitatory synapses in the brain and are located in Purkinje cell's dendrites along helical paths, perhaps maximizing the probability to contact different axons. To test whether spine helixes also occur in neocortex, we reconstructed >500 dendritic segments from adult human cortex obtained from autopsies. With Fourier analysis and spatial statistics, we analyzed spine position along apical and basal dendrites of layer 3 pyramidal neurons from frontal, temporal, and cingulate cortex. Although we occasionally detected helical positioning, for the great majority of dendrites we could not reject the null hypothesis of spatial randomness in spine locations, either in apical or basal dendrites, in neurons of different cortical areas or among spines of different volumes and lengths. We conclude that in adult human neocortex spine positions are mostly random. We discuss the relevance of these results for spine formation and plasticity and their functional impact for cortical circuits.

Hyperhomocysteinemia in pediatric and young adult renal transplant recipients.

Hyperhomocysteinemia (HHcy) has been recently identified as an important and reversible cardiovascular risk factor in adult and pediatric renal transplant recipients. A retrospective cross-sectional analysis of 70 pediatric and young adult renal transplant recipients was performed to determine the prevalence, and important clinical and laboratory correlates of HHcy. Total homocysteine concentration, free and protein bound, was determined by fluorescence polarization immunoassay using an IMX analyzer. Hyperhomocysteinemia was defined as a serum homocysteine (Hcy) level above the 95th percentile for age. Fifty-four of 70 patients (77%) had HHcy. Comparison of patients with HHcy with patients without HHcy demonstrated no statistical difference in age (p = 0.35), gender (p = 0.76) or donor type (p = 0.20). Patients with HHcy had significantly lower calculated creatinine clearance values (Ccr) (p = 0.02), 67.3 +/- 21.2 mL/min/1.73 m(2) vs. 90.7 +/- 32.3 mL/min/1.73 m(2) for patients without HHcy. Immunosuppression did not correlate with the diagnosis of HHcy. Stepwise logistic regression identified patient age (0.18, p = 0.013) and Ccr (-0.04, p = 0.011) as significant variables. In conclusion, HHcy is more common than expected in pediatric renal transplant recipients. Patients with Ccr <80 mL/min/1.73 m(2) were statistically more likely to have a diagnosis of HHcy. We recommend that Hcy levels should be evaluated in this high risk population.

Colonic hydrogen elimination and methane production in infants with and without infantile colic syndrome.

Our objective was to investigate the relationship between demographic factors, nutrition, stool gas production, and the existence of infantile colic (IC) syndrome. Hydrogen and methane production from stool specimens of infants with and without infantile colic was quantified at two separate time points, the age at presentation of colic (<12 weeks) and at >6 months of age. The relationship between demographic variables and IC was also studied. A total of 59 infants with ages ranging from 2 to 12 weeks were enrolled in the study. Of these, 30 infants developed symptoms of colic. No correlation was found between IC and birth weight, gestational age, sex, type of feeding, mean time of feeding, stool frequency, and consistency. There was also no correlation between IC and the parents' age or education or the infant's number of siblings. Analysis of the stool samples revealed that methane was produced at concentrations >2 ppm by 15.3% of the infants at age <3 months and by 46.4% of infants at age >6 months. The mean methane concentrations produced by stool increased with age (0.95 +/- 0.58 ppm at 3 months of age vs 1.29 +/- 0.65 ppm at 6 months of age. There was no difference in stool hydrogen concentration between infants with and without IC. In contrast, the mean methane level at 3 and 6 months of age was higher in infants without IC than with IC, but reached statistical significance only at 6 months of age (0.97 +/- 0.68 vs 0.93 +/- 0.46) (NS) at 3 months of age, and 1.56 +/- 0.55 vs 0.93 +/- 0.62 (P < 0.05) at 6 months of age respectively. Furthermore, infants that produced higher methane levels at 3 and 6 months of age had significantly (p < 0.05) less colic in the first months of life. In conclusions, methane production may play a role in the alleviation of IC. Future studies are needed to confirm our findings.