3D topography of noncompact zone Golgi tubules in rat spermatids: A computer-assisted serial section reconstruction study

In the golgi apparatus, the 3d topography of saccules in the compact zones (czs) is better understood than that of tubules in the noncompact zones (nczs). The positioning of ncz tubules relative to each other and to cz saccules was studied in rat spermatids by computer-assisted serial section microscopy. Methods twenty-four (semi) serials (3-6 consecutive sections each) in total were collected from untreated tissues and from tissues treated for glucose-6-phosphatase (g6p) cytochemistry as an alignment tool. The serials proceeded along either the cis-trans or the medial-lateral axes of the golgi and collectively sampled all portions of this organelle. Selected serials were computer reconstructed and the final models displayed in red-green/red-blue stereo. Results in single thin sections, ncz tubules typically appeared randomly oriented; however, in serial sections a high degree of organization was evident. Most tubules were traceable to the type of tubular networks (tns) that interconnect equivalent cz saccules (see review rambourg and clermont, 1990) such tns were present at consecutive saccular levels through each ncz, were stacked like the saccules from which they originate, and in many regions were aligned from cis-trans. The cis-most of the tns projected above the cis-pole of the stacked saccules and were penetrated by coated and uncoated er buds. Conclusions the function of the extensive ncz tubular domain, consisting of the stacked and aligned tns, will have to be addressed in future studies. However, the specific topography of the cis-most tns make them candidates to serve as acceptor membranes in er-golgi transport. Anat. Rec. 250:381–396, 1998

3D topography of noncompact zone Golgi tubules in rat spermatids: A computer-assisted serial section reconstruction study

In the golgi apparatus, the 3d topography of saccules in the compact zones (czs) is better understood than that of tubules in the noncompact zones (nczs). The positioning of ncz tubules relative to each other and to cz saccules was studied in rat spermatids by computer-assisted serial section microscopy. Methods twenty-four (semi) serials (3-6 consecutive sections each) in total were collected from untreated tissues and from tissues treated for glucose-6-phosphatase (g6p) cytochemistry as an alignment tool. The serials proceeded along either the cis-trans or the medial-lateral axes of the golgi and collectively sampled all portions of this organelle. Selected serials were computer reconstructed and the final models displayed in red-green/red-blue stereo. Results in single thin sections, ncz tubules typically appeared randomly oriented; however, in serial sections a high degree of organization was evident. Most tubules were traceable to the type of tubular networks (tns) that interconnect equivalent cz saccules (see review rambourg and clermont, 1990) such tns were present at consecutive saccular levels through each ncz, were stacked like the saccules from which they originate, and in many regions were aligned from cis-trans. The cis-most of the tns projected above the cis-pole of the stacked saccules and were penetrated by coated and uncoated er buds. Conclusions the function of the extensive ncz tubular domain, consisting of the stacked and aligned tns, will have to be addressed in future studies. However, the specific topography of the cis-most tns make them candidates to serve as acceptor membranes in er-golgi transport. Anat. Rec. 250:381–396, 1998

Structure of the Golgi and Distribution of Reporter Molecules at 20°C Reveals the Complexity of the Exit Compartments

Incubating cells at 20°C blocks transport out of the Golgi complex and amplifies the exit compartments. We have used the 20°C block, followed by EM tomography and serial section reconstruction, to study the structure of Golgi exit sites in NRK cells. The dominant feature of Golgi structure in temperature-blocked cells is the presence of large bulging domains on the three trans-most cisternae. These domains extend laterally from the stack and are continuous with “cisternal” domains that maintain normal thickness and alignment with the other stacked Golgi cisternae. The bulging domains do not resemble the perpendicularly extending tubules associated with the trans-cisternae of control cells. Such tubules are completely absent in temperature-blocked cells. The three cisternae with bulging domains can be identified as trans by their association with specialized ER and the presence of clathrin-coated buds on the trans-most cisterna only. Immunogold labeling and immunoblots show a significant degradation of a medial- and a trans-Golgi marker with no evidence for their redistribution within the Golgi or to other organelles. These data suggest that exit from the Golgi occurs directly from three trans-cisternae and that specialized ER plays a significant role in trans-Golgi function

Marked variation in the definition and diagnosis of delayed graft function: a systematic review

Background. The term delayed graft function (DGF) is commonly used to describe the need for dialysis after receiving a kidney transplant. DGF increases morbidity after transplantation, prolongs hospitalization and may lead to premature graft failure. Various definitions of DGF are used in the literature without a uniformly accepted technique to identify DGF

Distinct Functions for Arf Guanine Nucleotide Exchange Factors at the Golgi Complex: GBF1 and BIGs Are Required for Assembly and Maintenance of the Golgi Stack and trans-Golgi Network, Respectively

We examined the relative function of the two classes of guanine nucleotide exchange factors (GEFs) for ADP-ribosylation factors that regulate recruitment of coat proteins on the Golgi complex. Complementary overexpression and RNA-based knockdown approaches established that GBF1 regulates COPI recruitment on cis-Golgi compartments, whereas BIGs appear specialized for adaptor proteins on the trans-Golgi. Knockdown of GBF1 and/or COPI did not prevent export of VSVGtsO45 from the endoplasmic reticulum (ER), but caused its accumulation into peripheral vesiculotubular clusters. In contrast, knockdown of BIG1 and BIG2 caused loss of clathrin adaptor proteins and redistribution of several TGN markers, but had no impact on COPI and several Golgi markers. Surprisingly, brefeldin A–inhibited guanine nucleotide exchange factors (BIGs) knockdown prevented neither traffic of VSVGtsO45 to the plasma membrane nor assembly of a polarized Golgi stack. Our observations indicate that COPII is the only coat required for sorting and export from the ER exit sites, whereas GBF1 but not BIGs, is required for COPI recruitment, Golgi subcompartmentalization, and cargo progression to the cell surface