Morphological correlates of pyramidal cell axonal myelination in mouse and human neocortex

The axons of neocortical pyramidal neurons are frequently myelinated. Heterogeneity in the topography of axonal myelination in the cerebral cortex has been attributed to a combination of electrophysiological activity, axonal morphology, and neuronal-glial interactions. Previously, we showed that axonal segment length and caliber are critical local determinants of fast-spiking interneuron myelination. However, the factors that determine the myelination of individual axonal segments along neocortical pyramidal neurons remain largely unexplored. Here, we used structured illumination microscopy to examine the extent to which axonal morphology is predictive of the topography of myelination along neocortical pyramidal neurons. We identified critical thresholds for axonal caliber and interbranch distance that are necessary, but not sufficient, for myelination of pyramidal cell axons in mouse primary somatosensory cortex (S1). Specifically, we found that pyramidal neuron axonal segments with a caliber < 0.24 μm or interbranch distance < 18.10 μm are rarely myelinated. Moreover, we further confirmed that these findings in mice are similar for human neocortical pyramidal cell myelination (caliber < 0.25 μm, interbranch distance < 19.00 μm), suggesting that this mechanism is evolutionarily conserved. Taken together, our findings suggest that axonal morphology is a critical correlate of the topography and cell-type specificity of neocortical myelination.

Fast-spiking parvalbumin-positive interneurons in brain physiology and Alzheimer's disease

Fast-spiking parvalbumin (PV) interneurons are inhibitory interneurons with unique morphological and functional properties that allow them to precisely control local circuitry, brain networks and memory processing. Since the discovery in 1987 that PV is expressed in a subset of fast-spiking GABAergic inhibitory neurons, our knowledge of the complex molecular and physiological properties of these cells has been expanding. In this review, we highlight the specific properties of PV neurons that allow them to fire at high frequency and with high reliability, enabling them to control network oscillations and shape the encoding, consolidation and retrieval of memories. We next discuss multiple studies reporting PV neuron impairment as a critical step in neuronal network dysfunction and cognitive decline in mouse models of Alzheimer's disease (AD). Finally, we propose potential mechanisms underlying PV neuron dysfunction in AD and we argue that early changes in PV neuron activity could be a causal step in AD-associated network and memory impairment and a significant contributor to disease pathogenesis.

Pelvic lymph node dissection for nodal oligometastatic prostate cancer detected by 68Ga-PSMA-positron emission tomography/computerized tomography

BACKGROUND

The first evaluation of pelvic extended lymph node dissection (pLND) in oligometastatic prostate cancer (PCa) detected by (68)Ga-PSMA PET/CT.

METHODS

Retrospective analysis of 35 PCa patients underwent (68)Ga-PSMA PET/CT affected by biochemical recurrence (BCR) after curative treatment (n = 23) or before primary therapy of high-risk PCa (n = 12). We performed pLND associated with pathologic imaging in 17 men with nodal oligometastatic PCa.

RESULTS

Indicative lesions for PCa in PET/CT were detected in 91.4% (32 of 35) of patients. Nodal, bone, visceral (pulmonary), and within the prostate suspected disease were detected in 72% (23 of 32), 16% (5 of 32), 6% (2 of 32), and 47% (15 of 32) of patients, respectively. Median serum PSA in patients with pathological radiotracer uptake in recurrent and high-risk PCa patients was 2.9 ng/ml (range 0.18-30) and 19.5 ng/ml (range 6-90), respectively. The median number of removed lymph nodes with pLND in recurrent and high-risk PCa was 10 (range 4-17) and 12 (range 8-29) per patient and the median number of positive lymph nodes was 1 (range 1-2) and 3 (2-3) per patient, respectively. In total, two false positive and one false-negative lymph node were found. Diagnostic accuracies per nodal lesion in total of 213 removed nodes: sensitivity, 94%; specificity, 99%; positive predictive value (PPV), 89%, and negative predictive value (NPV), 99.5%. After pLND, 53% (9 of 17) of patients received androgen deprivation therapy and/or radiation therapy and hormonal therapy, while 47% (8 of 17) of patients remained free of any post-surgery therapy. Follow-up PSA remained less than 0.2 ng/ml in 82% (14 of 17) of patients. After pLND, immediate BCR (PSA never measured less than 0.2 ng/ml) in 18% (3 of 17) of patients was recorded.

CONCLUSIONS

This represents the first study of pLND in the setting of nodal oligometastatic PCa detected by (68)Ga-PSMA PET/CT. The use of (68)Ga-PSMA PET/CT could be to improve the accuracy for the detection of nodal micrometastases. These promising findings need validation in larger studies.

Reducing hippocampal extracellular matrix reverses early memory deficits in a mouse model of Alzheimer's disease

Alzheimer’s disease is caused by increased production or reduced clearance of amyloid-β, which results in the formation amyloid-β plaques and triggers a cascade of downstream events leading to progressive neurodegeneration. The earliest clinical symptoms of Alzheimer’s disease, i.e., memory loss, are however poorly understood from a molecular and cellular perspective. Here we used APPswe/PS1dE9 (APP/PS1) transgenic mice to study the early pre-pathological effects of increased amyloid-β levels on hippocampal synaptic plasticity and memory. Using an unbiased proteomics approach we show that the early increase in amyloid-β levels in APP/PS1 mice at three months of age coincides with a robust and significant upregulation of several protein components of the extracellular matrix in hippocampal synaptosome preparations. This increase in extracellular matrix levels occurred well before the onset of plaque formation and was paralleled by impairments in hippocampal long-term potentiation and contextual memory. Direct injection into the hippocampus of the extracellular matrix inactivating enzyme chondroitinase ABC restored both long-term potentiation and contextual memory performance. These findings indicate an important role for the extracellular matrix in causing early memory loss in Alzheimer’s disease.

Effectiveness of iron therapy on breath-holding spells

OBJECTIVE

The objective of this study is to investigate the effect of iron therapy on breath-holding spells (BHS).

METHODOLOGY

Sixty-seven children with BHS were enrolled in a clinical trial to evaluate the effect of iron therapy on BHS. At the beginning of therapy, the clinical, laboratory, and demographic characteristics of the patients in the treatment group (n = 33) and placebo group (n = 34) were comparable. Patients were assessed weekly for the first 8 weeks and then every 2 weeks for the next 8 weeks. Response to therapy was assessed by the change in the frequency of BHS.

RESULTS

Children treated with iron showed significant reduction in the frequency of BHS (88%) compared with the frequency (6%) in the placebo group. As expected, the treated group showed a significant improvement of a number of blood indexes compared with the placebo group. Baseline mean levels of hemoglobin and total iron binding capacity were predictive of a favorable response to iron treatment.

CONCLUSION

Results of this study indicate that iron therapy is effective in the treatment of BHS and that iron-deficient children seem to be more likely to benefit from such therapy. Response to iron therapy was strongly correlated with improvement in blood indexes.

Rotavirus-associated diarrhoea in children in a refugee camp in Jordan

Studies on the rotavirus-associated acute diarrhoeal illness in Jordanian children are non-existent. The present case-control study was conducted to investigate the prevalence of rotavirus diarrhoea among children aged less than 5 years, attending the United Nations Refugee World Aid Clinic in northern Jordan. The potential environmental and behavioural risk factors contributing to the infection were also studied. Using the ELISA technique rotavirus antigens were detected in the stool samples of 35% of the 220 cases of gastroenteritis and in 3% of the control group. The control subjects were matched for age and sex with the cases. The overall prevalence was significantly higher (62%) in children aged less than 24 months [OR = 2.4, 95% CI (1.1-5.1)] than those in the older age groups. Severe cases of diarrhoea were rare. Diarrhoea due to rotavirus was more prevalent during the summer months (June-August). Risk factors for acute diarrhoea in these children are related to the infant feeding practices of using unboiled tap water to prepare the formula milk, and the low educational level of the mothers.

Serum ferritin in evaluation of iron status in children

The value of serum ferritin in assessing iron status was studied in 192 preschool age children between the ages of 3 and 60 months. Children were considered to have iron deficiency if the transferrin saturation was less than 16% and the peripheral smear revealed microcytosis and hypochromia. Anemia was present when hemoglobin level was 10.5 g/dl. According to this criteria, 46% of children screened had either iron deficiency (11.5%) or iron deficiency anemia (34.4%). Mean serum ferritin for the iron deficiency anemia group was 39.1 ng/mg as compared to 41.7 ng/ml for the iron deficiency group and 84.7 ng/ml for the normal group. Even though the serum ferritin level was lower in the iron deficiency group, the difference in the means did not reach statistical significance. Furthermore, only 30% of children who had either iron deficiency or iron deficiency anemia had serum ferritin level of less than 12 ng/ml, the level considered diagnostic for iron deficiency. It can be concluded that serum ferritin cannot be used alone for iron status determination. Multiple parameters will make the assessment more reliable.