IB Cells Research Articles

An immersed boundary method coupled non-hydrostatic model for free surface flow

An efficient numerical model has been developed for the study of three-dimensional free surface flow, which combines a non-hydrostatic model with the immersed boundary method (IBM). The model utilizes the transformed σ coordinate in the vertical direction, which has been found to be highly effective in accurately capturing the free surface and uneven bottom. In addition, IBM is implemented by introducing a virtual boundary force into the momentum equations to emulate the natural boundary conditions. This implementation enhances the ability of the model in simulating the interactions of wave and solid structures. A robust boundary recognition method is used to identify the location of IB cells neighboring the virtual boundary. Furthermore, a water elevation correction method has been proposed to handle the integral discontinuity in the vertical direction caused by the submerged solid bodies. By adding the virtual boundary forces to the IB cells, the no-slip velocity condition at the solid boundary is effectively enforced. To validate the performance of the model, the numerical results have been compared with experimental data. The benchmark tests focused on the free surface evolution, velocity distributions and the dynamic pressures verified the performance of the numerical model and the robust strategy of the IBM.

γδ Tcells license immature B cells to produce a broad range of polyreactive antibodies.

Immature autoreactive B cells are present in all healthy individuals, but it is unclear which signals are required for their maturation into antibody-producing cells. Inducible depletion of γδ Tcells show that direct interaction between γδ Tcells and immature B cells in the spleen support an "innate" transition to mature B cells with a broad range of antigen specificities. IL-4 production of γδ Tcells and cell-to-cell contact via CD30L support B cell maturation and induce genes of the unfolded protein response and mTORC1 signaling. Eight days after invivo depletion of γδ Tcells, increased numbers of B cells are already stuck in the transitional phase and express increased levels of IgD and CD21. Absence of γδ Tcells leads also to reduced levels of serum anti-nuclear autoantibodies, making γδ Tcells an attractive target to treat autoimmunity.

An immersed boundary method with y+‐adaptive wall function for smooth wall shear

AbstractImmersed boundary (IB) method with a wall function for high Reynolds number flows is attractive when the boundary is complex and evolving. However, when combined with IB method, existing wall functions cannot produce smooth wall shear stress, which is important for many processes such as erosion. The root cause is the discontinuity between the log‐law and laminar layers in most wall functions. A wall function in IB methods is typically enforced through IB cells. However, for complex and evolving boundaries, IB cells can be located in either the log‐law layer or the laminar layer, which follow different laws. To remedy this, a new method is introduced with a y+‐adaptive strategy. The idea is that when an IB cell is too close to an IB, it is replaced by a neighboring fluid cell further away from the boundary. Consequently, all IB cells are in the log‐law layer. The resulting wall shear stress is much smoother. This adaptive strategy is a compromise between how accurate the location of an IB wall is represented and the smoothness of simulated wall shear. Example cases in 1D, 2D, and 3D show the y+‐adaptive wall function produces results compared well with theory and experiments.

Loss of the cytostome-cytopharynx and endocytic ability are late events in Trypanosoma cruzi metacyclogenesis.

Trypanosoma cruzi epimastigotes uptake nutrients by endocytosis via the cytostome-cytopharynx complex - an anterior opening (cytostome) continuous with a funnel-shaped invagination (cytopharynx) that extends to the posterior of the cell, accompanied by microtubules. During metacyclogenesis - the transformation of epimastigotes into human-infective metacyclic trypomastigotes - the cytostome-cytopharynx complex disappears, as trypomastigotes lose endocytic ability. To date, no studies have examined cytostome-cytopharynx complex disappearance in detail, or determined if endocytic activity persists during metacyclogenesis. Here, we produced 3D reconstructions of metacyclogenesis intermediates (Ia, Ib, Ic) using electron microscopy tomography and focused ion beam-scanning electron microscopy (FIB-SEM), concentrating on the cytostome-cytopharynx complex and adjacent structures, including the preoral ridge (POR). Parasite endocytic potential was examined by incubation of intermediate forms with the endocytic tracer transferrin (Tf)-Au. Ia, Ib and Ic cells were capable of internalizing Tf-Au, and had a shorter cytopharynx than that of epimastigotes, with the cytostome/POR progressively displaced towards the posterior, following the movement of the kinetoplast/flagellar pocket. While some Ic cells had a short cytopharynx with an enlarged proximal end (∼300nm in diameter, larger than that of the cytostome), other Ic cells had no cytopharynx invagination, but retained the cytopharynx microtubules, which were also present in metacyclics. We conclude that cytostome-cytopharynx disappearance and loss of endocytic ability are late events in metacyclogenesis, during which the cytostome is displaced towards the posterior, probably due to a link to the kinetoplast/flagellar pocket. Retention of the cytopharynx microtubules by metacyclics may allow prompt cytostome-cytopharynx reassembly in amastigotes, upon host cell infection.

Hebbian and Homeostatic Plasticity Mechanisms in Regular Spiking and Intrinsic Bursting Cells of Cortical Layer 5

SummaryLayer 5 contains the major projection neurons of the neocortex and is composed of two major cell types: regular spiking (RS) cells, which have cortico-cortical projections, and intrinsic bursting cells (IB), which have subcortical projections. Little is known about the plasticity processes and specifically the molecular mechanisms by which these two cell classes develop and maintain their unique integrative properties. In this study, we find that RS and IB cells show fundementally different experience-dependent plasticity processes and integrate Hebbian and homeostatic components of plasticity differently. Both RS and IB cells showed TNFα-dependent homeostatic plasticity in response to sensory deprivation, but IB cells were capable of a much faster synaptic depression and homeostatic rebound than RS cells. Only IB cells showed input-specific potentiation that depended on CaMKII autophosphorylation. Our findings demonstrate that plasticity mechanisms are not uniform within the neocortex, even within a cortical layer, but are specialized within subcircuits.

피뿔고둥 Rapana venosa (Valencienes) 정소소엽 내에서의 생식세포 발달과 정자형성과정 중 출현하는 비정형 세포들의 미세구조적 연구 및 저정낭의 발달단계에 따른 상피세포들의 주기적 변화

피뿔고둥, Rapana venosa의 정소소엽 내에서 정자형성과정 중에 생성되는 정상적인 생식세포의 발달과 함께 섞이어 일정 시기에만 출현하는 비정형세포들을 미세구조적으로 관찰하였고, 또한 정소 발달단계에 따른 저정낭 내층 상피세포들의 주기적 변화를 조직학적 관찰에 의해 조사하였다. 생식세포의 발달단계는 정원세포기, 정모세포기, 정세포기, 정자기로 나누어지며, 정모세포기는 다시 제1 정모세포기와 제2 정모세포기로 세분할 수 있어, 총 5 단계로 구분할 수 있었다. 정상적인 웅성생식세포들의 분화와 발달과정은 다른 복족류 종들과 유사하였다. 정자는 길이가 대략 <TEX>$50{\mu}m$</TEX> 정도이었다. 정자의 미부 편모의 악소님 (axoneme) 은 주변에 9쌍의 미세소관들과 중앙에 1쌍의 미세소관들로 구성되어 있다. 즉, 9+2 구조를 이루고 있다. 특히, 대형 복족류 중 뿔소라과 피뿔고둥의 경우는 예외적으로 다른 이매패류나 두족류 등과 달리 정소소엽 내에서 정자형성과정 중에 정상적인 생식세포들 사이에서 총 4종 (Type IA, IB, Type IIA, IIB) 의 비정형세포들 (atypical cells) 이 함께 출현하는 특징을 보이고 있는데, 이러한 현상은 대형 복족류의 단지 소수의 종들에 한하여 출현하는 예외적인 특이한 현상이라 할 수 있다. 그러나 비정형세포들은 저정낭의 여러 단계 중 내층 상피세포들 내에서는 발견되지 않았다. 추측컨대 몇 가지 비정형세포들은 리소좀-모양의 공포들이나 리소좀-모양의 소체들을 가지는데, 이들은 정소소엽 내에서 붕괴나 그 자신들의 흡수에 관여하는 것으로 추정된다. 상당량의 정자들이 정소소엽 내에서 형성되어, 그들의 일부는 7월 말까지 정소에서 저정낭으로 이동된다. 교미 성기는 6-7 월 사이이었다. 피뿔고둥 저정낭 발달단계의 주기적 변화는 (1) S-1 단계 (휴지단계), (2) S-II 단계 (축적단계), 그리고 S-III 단계 (배정단계) 의 3 단계로 구분되었다. Germ cell development and cyclic changes in the epithelial cells of the seminal vesicle of the male rapa whelk, Rapana venosa, were investigated by cytological and histological observations. The process of germ cell development can be classified into five stages: (1) spermatogonial, (2) primary spermatocyte, (3) secodary spermatocyte, (4) spermatid, and (5) spermatozoon. In particular, four atypical cells (Type IA, IB, IIA and IIB cells) occur among normal germ cells in the acini during spermatogenesis. Presumably, the atypical cells, which have lysosome-like vacuoles or lysosome-like bodies in the cells, are involved in breakdown and absorption themselves in the acini. However, atypical cells were not found in the epithelial cells of the inner layer of the seminal vesicle. A considerable amount of spermatozoa are transported from the testis towards the the seminal vesicles until late July. The main coupulation period is between June and July. The process of the cyclical changes of the seminal vesicles can be classified into three phases: (1) resting, (2) accumulating, and (3) spent. Yellow granular bodies are involved in resorption or digestion of residual spermatozoa.

Wing (Ib) cells in frog taste discs detect dietary unsaturated fatty acids

The effects of unsaturated fatty acids on membrane properties were studied using conventional whole-cell patch-clamp recording of isolated wing (Ib) cells in bullfrog (Lithobates catesbeianus) taste discs. Applying arachidonic acid to the bath induced monophasic inward currents in 60% of wing cells and biphasic inward and outward currents in the other cells. The intracellular dialysis of arachidonic acid did not induce an inward current; however, it enhanced a slowly developing Ba2+-sensitive outward current. The effects of various unsaturated fatty acids were explored under the condition of Cs+ internal solution. Linoleic and α-linolenic acids induced large inward currents. Oleic, eicosapentaenoic and docosahexaenoic acids elicited the same inward currents as those of arachidonic acid. Wing cells, under the basal condition with Cs+ internal solution, displayed a small inward current of −1.1±0.1pA/pF at −50mV (n=40), in which the peak existed at a membrane potential of −49mV. Removing external Ca2+ further increased the inward current by −2.9±0.3pA/pF at −50mV (n=4) from the basal current and the peak was located at −55mV. External linoleic acid (50μM) also induced a similar inward current of −5.6±0.6pA/pF at −50mV (n=19) from the basal current and the peak was located at −61mV. External Ca2+-free saline and linoleic acid induced similar current/voltage (I/V) relationships elicited by a ramp voltage as well as voltage steps. Linoleic acid-induced currents were not influenced by replacing internal EGTA with BAPTA, whereas inward currents disappeared under the elimination of external Na+ and addition of flufenamic acid. These results suggest that dietary unsaturated fatty acids may depolarize wing (Ib) cells, which affects the excitability of these cells.

Evaluation of Feedforward and Feedback Contributions to Hand Stiffness and Variability in Multijoint Arm Control

The purpose of this study is to validate a neuromechanical model of the virtual arm (VA) by comparing emerging behaviors of the model to those of experimental observations. Hand stiffness of the VA model was obtained by either theoretical computation or simulated perturbations. Variability in hand position of the VA was generated by adding signal dependent noise (SDN) to the motoneuron pools of muscles. Reflex circuits of Ia, Ib and Renshaw cells were included to regulate the motoneuron pool outputs. Evaluation of hand stiffness and variability was conducted in simulations with and without afferent feedback under different patterns of muscle activations during postural maintenance. The simulated hand stiffness and variability ellipses captured the experimentally observed features in shape, magnitude and orientation. Steady state afferent feedback contributed significantly to the increase in hand stiffness by 35.75±16.99% in area, 18.37±7.80% and 16.15±7.15% in major and minor axes; and to the reduction of hand variability by 49.41±21.19% in area, 36.89±12.78% and 18.87±23.32% in major and minor axes. The VA model reproduced the neuromechanical behaviors that were consistent with experimental data, and it could be a useful tool for study of neural control of posture and movement, as well as for application to rehabilitation.

Clostridium perfringens Iota-Toxin b Induces Rapid Cell Necrosis

Clostridium perfringens iota-toxin is a binary toxin composed of an enzyme component (Ia) and a binding component (Ib). Each component alone lacks toxic activity, but together they produce cytotoxic effects. We examined the cytotoxicity of iota-toxin Ib in eight cell lines. A431 and A549 cells were susceptible to Ib, but MDCK, Vero, CHO, Caco-2, HT-29, and DLD-1 cells were not. Ib bound and formed oligomers in the membranes of A431 and MDCK cells. However, Ib entered MDCK cells but not A431 cells, suggesting that uptake is essential for cellular survival. Ib also induced cell swelling and the rapid depletion of cellular ATP in A431 and A549 cells but not the insensitive cell lines. In A431 cells, Ib binds and oligomerizes mainly in nonlipid rafts in the membranes. Disruption of lipid rafts by methyl-β-cyclodextrin did not impair ATP depletion or cell death caused by Ib. Ib induced permeabilization by propidium iodide without DNA fragmentation in A431 cells. Ultrastructural studies revealed that A431 cells undergo necrosis after treatment with Ib. Ib caused a disruption of mitochondrial permeability and the release of cytochrome c. Staining with active-form-specific antibodies showed that the proapoptotic Bcl-2-family proteins Bax and Bak were activated and colocalized with mitochondria in Ib-treated A431 cells. We demonstrate that Ib by itself produces cytotoxic activity through necrosis.

Electrical Properties and Gustatory Responses of Various Taste Disk Cells of Frog Fungiform Papillae

We compared the electrical properties and gustatory response profiles of types Ia cell (mucus cell), Ib cell (wing cell), and II/III cell (receptor cell) in the taste disks of the frog fungiform papillae. The large depolarizing responses of all types of cell induced by 1 M NaCl were accompanied by a large decrease in the membrane resistance and had the same reversal potential of approximately +5 mV. The large depolarizing responses of all cell types for 1 mM acetic acid were accompanied by a small decrease in the membrane resistance. The small depolarizing responses of all cell types for 10 mM quinine-HCl (Q-HCl) were accompanied by an increase in the membrane resistance, but those for 1 M sucrose were accompanied by a decrease in the membrane resistance. The reversal potential of sucrose responses in all cell types were approximately +12 mV. Taken together, depolarizing responses of Ia, Ib, and II/III cells for each taste stimulus are likely to be generated by the same mechanisms. Gustatory depolarizing response profiles indicated that 1) each of Ia, Ib, and II/III cells responded 100% to 1 M NaCl and 1 mM acetic acid with depolarizing responses, 2) approximately 50% of each cell type responded to 10 mM Q-HCl with depolarizations, and 3) each approximately 40% of Ia and Ib cells and approximately 90% of II/III cells responded to 1 M sucrose with depolarizations. These results suggest that the receptor molecules for NaCl, acid, and Q-HCl stimuli are equivalently distributed on all cell types, but the receptor molecules for sugar stimuli are richer on II/III cells than on Ia and Ib cells. Type III cells having afferent synapses may play a main role in gustatory transduction and transmission.

Electrophysiological Diversity of Layer 5 Pyramidal Cells in the Prefrontal Cortex of the Rhesus Monkey: In Vitro Slice Studies

Whole cell patch-clamp recordings were employed to characterize the electrophysiological properties of layer 5 pyramidal cells in slices of the prefrontal cortex (Area 46) of the rhesus monkey. Four electrophysiologically distinct cell types were discriminated based on distinctive repetitive action potential (AP) firing patterns and single AP characteristics: regular-spiking slowly adapting type-1 cells (RS1; 62%), regular-spiking slowly adapting type-2 cells (RS2; 18%), regular-spiking fast-adapting cells (FA; 15%), and intrinsically bursting cells (IB; 5%). These cells did not differ with regard to their location in layer 5 nor in their dendritic morphology. In RS1 cells, AP threshold and amplitude did not change significantly during a 2-s spike train, whereas in RS2 and FA cells, AP threshold increased significantly and AP amplitude decreased significantly during the train. In FA cells, complete adaptation of AP firing was observed within 600 ms. IB cells displayed an all-or-none burst of three to six APs, followed by RS1-type firing behavior. RS1 cells could be further subdivided into three subtypes. Low-threshold spiking (LTS) RS1 cells exhibited an initial doublet riding on a depolarizing potential at the onset of a spike train and a prominent depolarizing afterpotential (DAP); intermediate RS1 cells (IM) exhibited a DAP, but no initial doublet, and non-LTS RS1 cells exhibited neither a DAP nor an initial doublet. RS2 and FA cells did not exhibit a DAP or initial doublets. The distinctive firing patterns of these diverse layer 5 pyramidal cells may reflect different roles played by these cells in the mediation of subcortical neuronal activity by the dorsolateral PFC.

Dopamine -Hydroxylase-like Immunoreactive Cells in the Frog Taste Disc

We immunohistochemically examined the existence of dopamine beta-hydroxylase (DBH), a noradrenalin (NA)-synthesizing enzyme from dopamine, in the taste disc of frog, Rana catesbeiana. DBH-like immunoreactive cells were located in the intermediate layer in the taste disc; the cells showed an apical process reaching the surface of the disc and one or several basal processes. Cells with a thick apical process and those with a thin apical process were both immunoreactive: these cells corresponded to type II and III receptor cells of the frog taste disc. Immunoreactive granules were observed in the cytoplasm of those cells. In the frog taste disc, only type III cells are reported to have afferent synapses with the nerve via basal processes but those basal processes have not been reported in type II cells. In the present study, we found that type II-like cells possessed a long basal process extending toward the basal lamina. Mucous (type Ia) cells, wing (type Ib) cells, and glia-like sustentacular (type Ic) cells were all immunohistochemically unreactive. The present observations support the argument that NA (or adrenalin) may work as a chemical transmitter in the frog taste organ.

On the Responses of Zinkernagel and Hengartner: An Invitation to Join the Fray

On the Responses of Zinkernagel and Hengartner: An Invitation to Join the Fray

Voltage-gated inward currents of morphologically identified cells of the frog taste disc.

We used the patch clamp technique to record from taste cells in vertical slices of the bullfrog (Rana catesbeiana) taste disc. Cell types were identified by staining with Lucifer yellow in a pipette after recording their electrophysiological properties. Cells could be divided into the following three groups: type Ib (wing) cells with sheet-like apical processes, type II (rod) cells with single thick rod-like apical processes and type III (rod) cells with thin rod-like apical processes. No dye-coupling was seen either between cells of the same type or between cells of different types. We focused on the voltage-gated inward currents of the three types of cells. Type Ib and type II cells exhibited tetrodotoxin (TTX)-sensitive voltage-gated Na+ currents. Surprisingly, type III cells showed TTX-resistant voltage-gated Na+ currents and exhibited a lack of TTX-sensitive Na+ currents. TTX-resistant voltage-gated Na+ currents in taste cells are reported for the first time here. The time constant for the inactivating portion of the voltage-gated inward Na+ currents of type III cells was much larger than that of type Ib and type II cells. Therefore, slow inactivation of inward Na+ currents characterizes type III cells. Amplitudes of the maximum peak inward currents of type III cells were smaller than those of type Ib and type II cells. However, the density (pA/pF) of the maximum peak inward currents of type III cells was much higher than that of type Ib cells and close to that of type II cells. No evidence of the presence of voltage-gated Ca2+ channels in frog taste cells has been presented up to now. In this study, voltage-gated Ba2+ currents were observed in type III cells but not in type Ib and type II cells when the bath solution was a standard Ba2+ solution containing 25 mM Ba2+. Voltage-gated Ba2+ currents were blocked by addition of 2 mM CoCl2 to the standard Ba2+ solution, suggesting that type III cells possess the voltage-gated Ca2+ channels and they do classical (calcium-influx) synaptic transmission. It appears that type III cells are taste receptor cells.

Electrophysiological and morphological diversity of neurons from the rat subicular complex in vitro.

We combined whole-cell recordings with Neurobiotin labeling to examine the electrophysiological and morphological properties of neurons from the ventral subicular complex in vitro (including the subicular, presubicular, and parasubicular areas). No a priori morphological sampling criteria were used to select cells. Cells were classified as bursting (IB), regular-spiking (RS), and fast-spiking (FS) according to their firing patterns in response to depolarizing current pulses. A number of cells remained unclassified. We found 54% RS, 26% IB, 11% FS, and 9% unclassified cells out of a total of 131 neurons examined. We also found cells showing intrinsic membrane potential oscillations (MPO) (6%), which represented a subgroup of the unclassified cells. We analyzed several electrophysiological parameters and found that RS and IB cells can be subclassified into two separate subgroups. RS cells were subclassified as tonic and adapting, according to the degree of firing adaptation. Both responded with single spikes to orthodromic stimulation. IB cells were subclassified in two subgroups according to their capacity to fire more than one burst, and showed different responses to orthodromic stimulation. We observed that bursting in these two subgroups appeared to involve both Ca2+ and persistent Na+ components. Both IB and RS cells, as well as MPO neurons, were projecting cells. FS cells were morphologically identified as local circuit interneurons. We also analyzed the spatial distribution of these cell types from the vicinity of CA1 to the parasubicular areas. We conclude that, in contrast to the commonly accepted idea of the subicular complex as a bursting structure, there is a wide electrophysiological variability even within a given cellular group.

Electrophysiological properties of pyramidal neurons in the rat prefrontal cortex: an in vivo intracellular recording study.

In order to determine the electrophysiological properties of prefrontal cortex pyramidal neurons in vivo, intracellular recordings coupled with neurobiotin injection were performed in anesthetized rats. Three main classes of pyramidal cells were distinguished according to both their firing patterns in response to depolarizing current pulses and the characteristics of their action potentials: regular spiking (RS, n = 71); intrinsic (inactivating) bursting (IB, n = 8); and non-inactivating bursting (NIB, n = 26) cells. RS cells were further subdivided into slow-adapting and fast-adapting types, according to their firing frequency adaptation. IB and fast-adapting RS cells could exhibit different firing patterns depending on the intensity of the depolarizing current. In response to successive depolarizing pulses of a given intensity, NIB and some RS cells showed variations in their firing patterns, probably due to the impact of local synaptic activity. All the labeled neurons were pyramidal cells with an apical dendrite that formed a terminal tuft in layer I. As compared to RS cells, NIB cells had a smaller somatic size and their apical dendritic tuft was less extensive, while IB cells presented a larger somatic size, thicker dendrites and a wider extent of their basal and apical dendritic arborization. In conclusion, we found in the rat prefrontal cortex, in vivo, different electrophysiological classes of pyramidal cells whose output firing patterns depend on interactions between their intrinsic properties and the ongoing synaptic activity.

Physiology of morphologically identified cells of the bullfrog fungiform papilla.

Voltage-gated ionic current and the response to quinine were studied on the four types of morphologically identified taste cells of the bullfrog fungiform papilla by whole-cell patch clamp recording with a Lucifer yellow-filled pipette. Dye-coupled type Ia cells (mucous cells) did not show voltage-activated currents. Type Ib cells (wing cells) characterized by the fin-like processes, type II cells (rod cells) having a thick straight dendrite running to the surface and type III cells with a thin dendrite had voltage-gated sodium (INa) and potassium currents (IK) and generated action potentials. The amplitude of INa was significantly larger in type Ib and II cells than in type III cells. Type Ib and II cells responded to quinine but Type III cells did not.

Layer-Specific Intracolumnar and Transcolumnar Functional Connectivity of Layer V Pyramidal Cells in Rat Barrel Cortex

Layer V pyramidal cells in rat barrel cortex are considered to play an important role in intracolumnar and transcolumnar signal processing. However, the precise circuitry mediating this processing is still incompletely understood. Here we obtained detailed maps of excitatory and inhibitory synaptic inputs onto the two major layer V pyramidal cell subtypes, intrinsically burst spiking (IB) and regular spiking (RS) cells, using a combination of caged glutamate photolysis, whole-cell patch-clamp recording, and three-dimensional reconstruction of biocytin-labeled cells. To excite presynaptic neurons with laminar specificity, the release of caged glutamate was calibrated and restricted to small areas of 50 x 50 microm in all cortical layers and in at least two neighboring barrel-related columns. IB cells received intracolumnar excitatory input from all layers, with the largest EPSP amplitudes originating from neurons in layers IV and VI. Prominent transcolumnar excitatory inputs were provided by presynaptic neurons also located in layers IV, V, and VI of neighboring columns. Inhibitory inputs were rare. In contrast, RS cells received distinct intracolumnar inhibitory inputs, especially from layers II/III and V. Intracolumnar excitatory inputs to RS cells were prominent from layers II-V, but relatively weak from layer VI. Conspicuous transcolumnar excitatory inputs could be evoked solely in layers IV and V. Our results show that layer V pyramidal cells are synaptically driven by presynaptic neurons located in every layer of the barrel cortex. RS cells seem to be preferentially involved in intracolumnar signal processing, whereas IB cells effectively integrate excitatory inputs across several columns.

Alteration of mannose transport in fibroblasts from type I carbohydrate deficient glycoprotein syndrome patients

The aim of the present study was to explore how mannose enters fibroblasts derived from a panel of children suffering from different subtypes of type I carbohydrate deficient glycoprotein syndrome: seven carbohydrate deficient glycoprotein syndrome subtype Ia (phosphomannomutase deficiency), two carbohydrate deficient glycoprotein syndrome subtype Ib (phosphomannose isomerase deficiency) and two carbohydrate deficient glycoprotein syndrome subtype Ix (not identified deficiency). We showed that a specific mannose transport system exists in all the cells tested but has different characteristics with respect to carbohydrate deficient glycoprotein syndrome subtypes. Subtype Ia fibroblasts presented a mannose uptake equivalent or higher (maximum 1.6-fold) than control cells with a d-[2- 3H]-mannose incorporation in nascent N-glycoproteins decreased up to 7-fold. Compared to control cells, the mannose uptake was greatly stimulated in subtype Ib (4.0-fold), due to lower K uptake and higher V max values. Subtype Ib cells showed an increased incorporation of d-[2- 3H]-mannose into nascent N-glycoproteins. Subtype Ix fibroblasts presented an intermediary status with mannose uptake equivalent to the control but with an increased incorporation of d-[2- 3H]-mannose in nascent N-glycoproteins. All together, our results demonstrate quantitative and/or qualitative modifications in mannose transport of all carbohydrate deficient glycoprotein syndrome fibroblasts in comparison to control cells, with a relative homogeneity within a considered subtype of carbohydrate deficient glycoprotein syndrome. These results are consistent with the possible use of mannose as a therapeutic agent in carbohydrate deficient glycoprotein syndrome Ib and Ix.

Immunocytochemical localization of gamma-aminobutyric acid plasma membrane transporters in the tiger salamander retina.

Gamma-aminobutyric acid (GABA) plasma membrane transporters (GATs) play an important role in regulating GABA neurotransmission in the nervous system. The distribution of two GATs, GAT 1 and GAT 3, in salamander retina was investigated by using affinity-purified polyclonal antisera directed to the predicted C-terminals of rat GAT 1 and rat GAT 3. GAT 1-immunoreactivity (-IR) was found in type IB and IIB orthotopic bipolar cells (BCs) located in the distal and middle of the inner nuclear layer (INL), respectively; in type IIA and IA amacrine cells (ACs) located in the middle and proximal INL, respectively; and in interplexiform cells and cells in the ganglion cell layer (GCL). No detectable staining was found in horizontal cells (HCs) or in structures resembling Müller cells. GAT 1-immunoreactive fibers were present in the outer plexiform layer (OPL) and inner plexiform layer (IPL) in three bands corresponding to the three bands previously reported to be GABA-IR. GAT 3 antibodies labeled fewer cells and cell types than GAT 1 antibodies. GAT 3-IR was localized to type IIA and IA ACs and cells in the GCL, but not to BCs, HCs, or Müller cell-like structures. There was weak labeling of the OPL and stronger labeling of the IPL, with three distinct bands at the same depth as observed with GAT 1-IR. Double-labeling showed that the majority of GAT 1-IR BCs (88%), ACs (88%), and cells in the GCL (78%) colocalized with GABA-IR. The present study provides the first direct evidence of the expression of two GAT subtypes in neurons of nonmammalian retinas. These transporters could regulate GABA neurotransmission by reuptake and termination of GABA's action and, perhaps, by GABA release mechanisms. The presence of GAT 1-IR/GABA-IR bipolar cells further supports our earlier observations that a subgroup of orthotopic bipolar cells are likely to be GABAergic.