Magnocellular neurons of the supraoptic nucleus receive glutamatergic excitatory inputs that regulate the firing activity and hormone release from these neurons. A strong, brief activation of these ...excitatory inputs induces a lingering barrage of tetrodotoxin-resistant miniature EPSCs (mEPSCs) that lasts for tens of minutes. This is known to accompany an immediate increase in large amplitude mEPSCs. However, it remains unknown how long this amplitude increase can last and whether it is simply a byproduct of greater release probability. Using in vitro patch clamp recording on acute rat brain slices, we found that a brief, high frequency stimulation (HFS) of afferents induced a potentiation of mEPSC amplitude lasting up to 20 min. This amplitude potentiation did not correlate with changes in mEPSC frequency, suggesting that it does not reflect changes in presynaptic release probability. Nonetheless, neither postsynaptic calcium chelator nor the NMDA receptor antagonist blocked the potentiation. Together with the known calcium dependency of HFS-induced potentiation of mEPSCs, our results imply that mEPSC amplitude increase requires presynaptic calcium. Further analysis showed multimodal distribution of mEPSC amplitude, suggesting that large mEPSCs were due to multivesicular glutamate release, even at late post-HFS when the frequency is no longer elevated. In conclusion, high frequency activation of excitatory synapses induces lasting multivesicular release in the SON, which is independent of changes in release probability. This represents a novel form of synaptic plasticity that may contribute to prolonged excitatory tone necessary for generation of burst firing of magnocellular neurons.
Orexin neurons in the lateral hypothalamus (LH)/perifornical area (PFA) are known to promote food intake as well as provide excitatory influence on the dopaminergic reward pathway. Dopamine (DA), in ...turn, inhibits the reward pathway and food intake through its action in the LH/PFA. However, the cellular mechanism by which DA modulates orexin neurons remains largely unknown. Therefore, we examined the effect of DA on the excitatory neurotransmission to orexin neurons. Whole-cell patch-clamp recordings were performed using acute rat hypothalamic slices, and orexin neurons were identified by their electrophysiological and immunohistochemical characteristics. Pharmacologically isolated action potential-independent miniature EPSCs (mEPSCs) were monitored. Bath application of DA induced a bidirectional effect on the excitatory synaptic transmission dose dependently. A low dose of DA (1 microM) increased mEPSC frequency, which was blocked by the D1-like receptor antagonist SCH 23390, and mimicked by the D1-like receptor agonist SKF 81297. In contrast, higher doses of DA (10-100 microM) decreased mEPSC frequency, which could be blocked with the D2-like receptor antagonist, sulpiride. Quinpirole, the D2-like receptor agonist, also reduced mEPSC frequency. None of these compounds affected the mEPSCs amplitude, suggesting the locus of action was presynaptic. Furthermore, DA (1 microM) induced an increase in the action potential firing, whereas DA (100 microM) hyperpolarized and ceased the firing of orexin neurons, indicating the effect of DA on excitatory synaptic transmission may influence the activity of the postsynaptic cell. In conclusion, our results suggest that D1- and D2-like receptors have opposing effects on the excitatory presynaptic terminals impinging onto orexin neurons.
The glutamatergic synapses of the supraoptic nucleus display a unique activity-dependent plasticity characterized by a barrage
of tetrodotoxin-resistant miniature EPSCs (mEPSCs) persisting for 5â20 ...min, causing postsynaptic excitation. We investigated
how this short-term synaptic potentiation (STP) induced by a brief high-frequency stimulation (HFS) of afferents was initiated
and maintained without lingering presynaptic firing, using in vitro patch-clamp recording on rat brain slices. We found that following the immediate rise in mEPSC frequency, STP decayed with
two-exponential functions indicative of two discrete phases. STP depends entirely on extracellular Ca 2+ which enters the presynaptic terminals through voltage-gated Ca 2+ channels but also, to a much lesser degree, through a pathway independent of these channels or reverse mode of the plasma
membrane Na + âCa 2+ exchanger. Initiation of STP is largely mediated by any of the N-, P/Q- or L-type channels, and only a simultaneous application
of specific blockers for all these channels attenuates STP. Furthermore, the second phase of STP is curtailed by the inhibition
of mitochondrial Ca 2+ uptake or mitochondrial Na + âCa 2+ exchanger. mEPSCs amplitude is also potentiated by HFS which requires extracellular Ca 2+ . In conclusion, induction of mEPSC-STP is redundantly mediated by presynaptic N-, P/Q- and L-type Ca 2+ channels while the second phase depends on mitochondrial Ca 2+ sequestration and release. Since glutamate influences unique firing patterns that optimize hormone release by supraoptic
magnocellular neurons, a prolonged barrage of spontaneous excitatory transmission may aid in the induction of respective firing
activities.
The glutamatergic synapses of the supraoptic nucleus display a unique activity‐dependent plasticity characterized by a barrage of tetrodotoxin‐resistant miniature EPSCs (mEPSCs) persisting for 5–20 ...min, causing postsynaptic excitation. We investigated how this short‐term synaptic potentiation (STP) induced by a brief high‐frequency stimulation (HFS) of afferents was initiated and maintained without lingering presynaptic firing, using
in vitro
patch‐clamp recording on rat brain slices. We found that following the immediate rise in mEPSC frequency, STP decayed with two‐exponential functions indicative of two discrete phases. STP depends entirely on extracellular Ca
2+
which enters the presynaptic terminals through voltage‐gated Ca
2+
channels but also, to a much lesser degree, through a pathway independent of these channels or reverse mode of the plasma membrane Na
+
–Ca
2+
exchanger. Initiation of STP is largely mediated by any of the N‐, P/Q‐ or L‐type channels, and only a simultaneous application of specific blockers for all these channels attenuates STP. Furthermore, the second phase of STP is curtailed by the inhibition of mitochondrial Ca
2+
uptake or mitochondrial Na
+
–Ca
2+
exchanger. mEPSCs amplitude is also potentiated by HFS which requires extracellular Ca
2+
. In conclusion, induction of mEPSC‐STP is redundantly mediated by presynaptic N‐, P/Q‐ and L‐type Ca
2+
channels while the second phase depends on mitochondrial Ca
2+
sequestration and release. Since glutamate influences unique firing patterns that optimize hormone release by supraoptic magnocellular neurons, a prolonged barrage of spontaneous excitatory transmission may aid in the induction of respective firing activities.
Short tandem repeats (STRs) are hotspots of genomic variability in the human germline because of their high mutation rates, which have long been attributed largely to polymerase slippage during DNA ...replication. This model suggests that STR mutation rates should scale linearly with a father's age, as progenitor cells continually divide after puberty. In contrast, it suggests that STR mutation rates should not scale with a mother's age at her child's conception, since oocytes spend a mother's reproductive years arrested in meiosis II and undergo a fixed number of cell divisions that are independent of the age at ovulation. Yet, mirroring recent findings, we find that STR mutation rates covary with paternal and maternal age, implying that some STR mutations are caused by DNA damage in quiescent cells rather than polymerase slippage in replicating progenitor cells. These results echo the recent finding that DNA damage in oocytes is a significant source of de novo single nucleotide variants and corroborate evidence of STR expansion in postmitotic cells. However, we find that the maternal age effect is not confined to known hotspots of oocyte mutagenesis, nor are postzygotic mutations likely to contribute significantly. STR nucleotide composition demonstrates divergent effects on de novo mutation (DNM) rates between sexes. Unlike the paternal lineage, maternally derived DNMs at A/T STRs display a significantly greater association with maternal age than DNMs at G/C-containing STRs. These observations may suggest the mechanism and developmental timing of certain STR mutations and contradict prior attribution of replication slippage as the primary mechanism of STR mutagenesis.
Although alterations in myeloid cells have been observed in COVID-19, the specific underlying mechanisms are not completely understood. Here, we examine the function of classical CD14
monocytes in ...patients with mild and moderate COVID-19 during the acute phase of infection and in healthy individuals. Monocytes from COVID-19 patients display altered expression of cell surface receptors and a dysfunctional metabolic profile that distinguish them from healthy monocytes. Secondary pathogen sensing ex vivo leads to defects in pro-inflammatory cytokine and type-I IFN production in moderate COVID-19 cases, together with defects in glycolysis. COVID-19 monocytes switch their gene expression profile from canonical innate immune to pro-thrombotic signatures and are functionally pro-thrombotic, both at baseline and following ex vivo stimulation with SARS-CoV-2. Transcriptionally, COVID-19 monocytes are characterized by enrichment of pathways involved in hemostasis, immunothrombosis, platelet aggregation and other accessory pathways to platelet activation and clot formation. These results identify a potential mechanism by which monocyte dysfunction may contribute to COVID-19 pathology.
DNA methylation, which is modulated by both genetic factors and environmental exposures, may offer a unique opportunity to discover novel biomarkers of disease-related brain phenotypes, even when ...measured in other tissues than brain, such as blood. A few studies of small sample sizes have revealed associations between blood DNA methylation and neuropsychopathology, however, large-scale epigenome-wide association studies (EWAS) are needed to investigate the utility of DNA methylation profiling as a peripheral marker for the brain. Here, in an analysis of eleven international cohorts, totalling 3337 individuals, we report epigenome-wide meta-analyses of blood DNA methylation with volumes of the hippocampus, thalamus and nucleus accumbens (NAcc)-three subcortical regions selected for their associations with disease and heritability and volumetric variability. Analyses of individual CpGs revealed genome-wide significant associations with hippocampal volume at two loci. No significant associations were found for analyses of thalamus and nucleus accumbens volumes. Cluster-based analyses revealed additional differentially methylated regions (DMRs) associated with hippocampal volume. DNA methylation at these loci affected expression of proximal genes involved in learning and memory, stem cell maintenance and differentiation, fatty acid metabolism and type-2 diabetes. These DNA methylation marks, their interaction with genetic variants and their impact on gene expression offer new insights into the relationship between epigenetic variation and brain structure and may provide the basis for biomarker discovery in neurodegeneration and neuropsychiatric conditions.
This Research Letter summarizes all updates to the 2019 Guidelines through September 2023, including: endorsement of the 2021 Opportunistic Infections guidelines for HIV+ or immunosuppressed ...patients; clarification of use of human papillomavirus testing alone for patients undergoing observation for cervical intraepithelial neoplasia 2; revision of unsatisfactory cytology management; clarification that 2012 guidelines should be followed for patients aged 25 years and older screened with cytology only; management of patients for whom colposcopy was recommended but not completed; clarification that after treatment for cervical intraepithelial neoplasia 2+, 3 negative human papillomavirus tests or cotests at 6, 18, and 30 months are recommended before the patient can return to a 3-year testing interval; and clarification of postcolposcopy management of minimally abnormal results.
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