mechanisms largely yet uncharacterized. We investigated the role of Rab27b in the terminal release of these secretory vesicles. Confocal fluorescence microscopy analysis of primary cultured rabbit lacrimal gland acinar cells revealed that Rab27b was enriched on the membrane of large subapical vesicles that were significantly colocalized with Rab3D and Myosin 5C. Stimulation of cultured acinar cells with the secretagogue carbachol resulted in apical fusion of these secretory vesicles with the plasma membrane. Evaluation of morphological changes by transmission electron microscopy of lacrimal glands from Rab27b Ϫ/Ϫ and Rab27 ash/ash /Rab27b Ϫ/Ϫ mice, but not ashen mice deficient in Rab27a, showed changes in abundance and organization of secretory vesicles, further confirming a role for this protein in secretory vesicle exocytosis. Glands lacking Rab27b also showed increased lysosomes, damaged mitochondria, and autophagosomelike organelles. In vitro, expression of constitutively active Rab27b increased the average size but retained the subapical distribution of Rab27b-enriched secretory vesicles, whereas dominant-negative Rab27b redistributed this protein from membrane to the cytoplasm. Functional studies measuring release of a cotransduced secretory protein, syncollin-GFP, showed that constitutively active Rab27b enhanced, whereas dominant-negative Rab27b suppressed, stimulated release. Disruption of actin filaments inhibited vesicle fusion to the apical membrane but did not disrupt homotypic fusion. These data show that Rab27b participates in aspects of lacrimal gland acinar cell secretory vesicle formation and release. actin; Rab3d; exocrine secretion; syncollin; mouse models A FUNCTIONING LACRIMAL GLAND (LG) is critical for a healthy ocular surface. This exocrine gland is the primary source of tear proteins and fluid, which, released up on the gland's exposure to sympathetic or parasympathetic agonists provided by innervating nerves, contribute to the middle aqueous layer of the precorneal film. Much of the LG's secretions originate from acinar cells, which constitute over 80% of the mass of the LG (13). These LG acinar cells produce a diverse array of secretory proteins that are internally sorted into large pools of serous and mucous secretory vesicles (SV) sized ϳ1 m in diameter and stored beneath the apical plasma membrane (APM) in preparation for regulated exocytosis. SV contents include nutrients and growth factors (lacritin and EGF), antibacterial and antiviral factors (secretory IgA and lactoferrin), and an array of proteases and lysosomal hydrolases (10, 39, 47). Despite its physiological importance, however, few studies have focused on the mechanisms of secretory membrane trafficking in LG acinar cells, in part due to the fragility and heterogeneity of these LG acinar SV relative to those in other acinar secretory cells, e.g., pancreatic acini (7).The current schematic of exocytosis in the LG acinar cell suggests multiple participants. Mature LG acinar cell SV localize beneath an actin-rich network und...
Oxytocin (OT) elicits weight loss in diet-induced obese (DIO) rodents, nonhuman primates, and humans, in part, by reducing food intake. Chronic OT administration produces more sustained weight loss in high-fat diet (HFD)-fed DIO rodents relative to chow-fed controls, but the reasons for this effect remain unclear. We hypothesized that HFD-induced obesity is associated with elevated OT receptor (OXTR) binding in brain regions where OT is known to cause decreased food intake and that this sensitized neural system is one mechanism by which OT preferentially elicits weight loss in DIO rodents. We therefore determined the impact of diet (HFD vs chow) and drug treatment (chronic OT infusion vs vehicle) on (1) OXTR binding in hindbrain and forebrain sites where OT suppresses food intake relative to control sites that express OXTR and (2) forebrain vasopressin 1a receptor (AVPR1a) density to evaluate the specificity of any OT effects. Using quantitative receptor autoradiography, we found that (1) diet composition failed to alter OXTR or AVPR1a binding; (2) chronic OT treatment produced largely global reductions in forebrain OXTR and AVPR1a binding without significantly altering hindbrain OXTR binding. These findings suggest that forebrain OXTR and AVPR1a are down-regulated in response to chronic OT treatment. Given that chronic intranasal OT may be used as a therapeutic strategy to treat obesity, future studies should consider the potential downregulatory effect that chronic treatment can have across forebrain and hindbrain nonapeptide receptors and assess the potential contribution of both receptor subtypes to the outcome measures.
Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is a progressive disorder associated with deficiency of mitochondrial aspartyl-tRNA synthetase, a homodimer encoded by the gene DARS2. There is a wide range in age of onset of symptoms, typically from childhood to adulthood, with very few cases of infantile onset disease reported. We report a child at age 10 years with perinatal onset of symptoms evidenced by congenital microcephaly with progression to severe but non-lethal epileptic encephalopathy and spastic quadriplegia. A comprehensive epilepsy focused gene panel performed as a trio with parents detected a novel homozygous DARS2 variant. This variant is located at the dimer interface in a critical catalytic domain and is expected to result in markedly reduced enzyme activity which likely explains the severe and early onset symptoms in this case.
We triangulated quantitative and qualitative assessments to evaluate participants’ acceptability of 0.05% dapivirine rectal microbicide (RM) gel administered via two separate modalities (a rectal applicator and an artificial phallus for use as a coital simulation device) as part of a Phase I trial (N = 14) among men who have sex with men (MSM) randomized using a 1:1 ratio. Overall, participants reported favorable acceptability of the gel (n = 11; 78.6%), the same or more at the end of the study compared to when they started the study. Additionally, when discussing their preferred administration modality, they noted that both methods had positive qualities but also potential areas of improvement. Our findings underscore the need to create multiple delivery methods for a future microbicide gel (i.e., with and without the need for an applicator) and highlight the importance of offering MSM choices in how biomedical HIV prevention strategies are delivered.
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