Geometry and the Organizational Principle of Spine Synapses along a Dendrite.

Precise information on synapse organization in a dendrite is crucial to understanding the mechanisms underlying voltage integration and the variability in the strength of synaptic inputs across dendrites of different complex morphologies. Here, we used focused ion beam/scanning electron microscope (FIB/SEM) to image the dendritic spines of mice in the hippocampal CA1 region, CA3 region, somatosensory cortex, striatum, and cerebellum (CB). Our results show that the spine geometry and dimensions differ across neuronal cell types. Despite this difference, dendritic spines were organized in an orchestrated manner such that the postsynaptic density (PSD) area per unit length of dendrite scaled positively with the dendritic diameter in CA1 proximal stratum radiatum (PSR), cortex, and CB. The ratio of the PSD area to neck length was kept relatively uniform across dendrites of different diameters in CA1 PSR. Computer simulation suggests that a similar level of synaptic strength across different dendrites in CA1 PSR enables the effective transfer of synaptic inputs from the dendrites toward soma. Excitatory postsynaptic potentials (EPSPs), evoked at single spines by glutamate uncaging and recorded at the soma, show that the neck length is more influential than head width in regulating the EPSP magnitude at the soma. Our study describes thorough morphologic features and the organizational principles of dendritic spines in different brain regions.

Ultrastructural Observation of Glutamatergic Synapses by Focused Ion Beam Scanning Electron Microscopy (FIB/SEM).

A thorough understanding of the synaptic ultrastructure is necessary to bridge our current knowledge gap about the relationship between neuronal structure and function. Recent development of focused ion beam scanning electron microscopy (FIB/SEM) has made it possible to image neuronal structures with high speed and efficiency. Here, we present our routine protocol for correlative two-photon microscopy and FIB/SEM imaging of glutamatergic synapses. Femtosecond-pulsed near-infrared laser was used to create fiducial marks around the dendrite of interest in aldehyde-fixed tissues. Thereafter, samples were subjected to en bloc staining with rOTO (reduced osmium tetroxide-thiocarbohydrazide-osmium tetroxide), followed by lead aspartate and uranyl acetate to enhance tissue contrast. Reliable detection of postsynaptic density (PSD) and plasma membrane contours by the sample preparation protocol optimized for FIB/SEM allows us to precisely evaluate morphological features that shape glutamatergic synaptic transmission.

Comparison of two screening tests for HIV-Associated Neurocognitive Disorder suspected Japanese patients with respect to cART usage.

In this study, we demonstrated the pervasiveness of HIV-associated neurocognitive disorders (HAND) among a selection of Japanese patients as well as evaluated and compared the Mini Mental State Examination (MMSE) and the International HIV Dementia Scale (IHDS) for use as a screening tool among combination anti-retroviral therapy (cART)-naïve and cART experienced patients. The MMSE and the IHDS have both been used as HAND screening tests around the world with variable success. It has been reported the increased usage of cART the utility of these screening tests may have been diminished due to the decreased severity of impairment and the altered pattern of neurocognitive impairments in cART era HAND patients. It is therefore possible the MMSE and the IHDS may still be useful among cART-naïve patients even in the cART era. However, only one study has investigated and compared the screening results of the IHDS among cART-naïve and cART experienced patients. All HIV positive patients who visited, or were admitted, to the Ryukyu University Hospital between January 2009 and March 2014 were evaluated for inclusion. Selected patients (n = 49) had data without omission for all tests. The overall prevalence of HAND in our cohort was 44%. The area under the curve (AUC), for all subjects using the MMSE and the IHDS, were 0.60 and 0.69, respectively. However, the AUC among cART-naïve patients were 0.58 and 0.76 for the MMSE and the IHDS, respectively. Whereas, cART experienced patients had an AUC of 0.60 and 0.61, respectively. Overall, the MMSE demonstrated a poor screening ability for HAND, regardless of cART usage (the cut-off value of 27 had a Youden's J-Index of 0.1, in all groups). Alternatively, the IHDS was moderately useful for HAND screening among cART-naïve patients (the cut-off value of 11 had a Youden's J-Index of 0.4), but performed poorly as a screening test among cART experienced patients (the cut-off value of 11 had a Youden's J-Index of 0.1).

Association of age and time of disease with HIV-associated neurocognitive disorders: a Japanese nationwide multicenter study.

There is no detailed information on the association between age, time of disease, and HIV-associated neurocognitive disorders (HAND). In this prospective study involving 17 medical facilities across Japan, we recruited HIV-infected patients to complete a 14-test neuropsychological battery that assess eight neurocognitive domains. HAND were diagnosed by the Frascati criteria. Of 1399 recruited patients, 728 were enrolled. The prevalence of HAND was 25.3% [13.5% asymptomatic neurocognitive impairment, 10.6% mild neurocognitive disorder (MND), and 1.2% HIV-associated dementia (HAD)]. Tests that assess executive and visuospatial functions showed better diagnostic accuracy than other tests for HAND. Multivariate analysis identified age (≥ 50 years) and incomplete virological suppression as risk factors for MND and HAD and current ART as a protective factor. The prevalence of MND and HAD was low in the early stage of infection (6.3% in ≥ 2 to < 6 years), then increased in the later stage [17.3% in ≥ 11 years, p = 0.001 (vs. ≥ 2 to < 6 years)], independent of age or treatment. Older patients were more likely to show MND or HAD in the early stage of HIV infection (26.7 vs. 8.7% for < 2 years and 17.4 vs. 3.1% for ≥ 2 to < 6 years, p = 0.040 and 0.004, respectively) compared to younger ones. In conclusion, MND and HAD were more commonly found in later years since diagnosis of HIV infection and older patients are at risk of neurocognitive impairment at the early stage of HIV infection. Tests for executive and visuospatial functions seem more sensitive than other tests for diagnosing HAND.

Lifelong Prophylaxis With Trimethoprim-Sulfamethoxazole for Prevention of Outbreak of Pneumocystis jirovecii Pneumonia in Kidney Transplant Recipients.

BACKGROUND: Outbreaks of Pneumocystis jirovecii pneumonia (PCP) in kidney transplant recipients are frequently reported worldwide. However, the general guidelines propose only short-term prophylaxis with trimethoprim-sulfamethoxazole after kidney transplantation. We experienced 3 PCP outbreaks in the last 10 years despite providing the recommended prophylaxis. The purpose of this study was to find a prophylaxis regimen that could successfully prevent future PCP outbreaks in immunosuppressed kidney transplant recipients. METHODS: Occurrence of PCP at our hospital since 2004 was reviewed. A total of 48 cases were diagnosed from July 2004 through December 2014. Genotypes of P. jirovecii were determined in these cases. RESULTS: Three PCP outbreaks by 3 different genotypes of P. jirovecii in each outbreak occurred with 2-year intervals in last 10 years. Molecular analysis showed that each intraoutbreak was caused by identical P. jirovecii, whereas interoutbreaks were caused by different genotypes. Although short-term prophylaxis was provided to all kidney recipients after each outbreak after identification of a single PCP case, additional outbreaks were not prevented because the universal prophylaxis had already been completed when new case of PCP emerged. CONCLUSIONS: The contagious nature of P. jirovecii allows easy development of outbreaks of PCP in immunosuppressed kidney transplant recipients. Although the universal short-term prophylaxis is effective in controlling ongoing outbreak, lifelong prophylaxis of kidney transplant recipients should be considered to prevent new outbreaks.