Lipedema: The Use of Cultured Adipocytes for Identification of Diagnostic Markers.

BACKGROUND: Lipedema, diagnosed most often in women, is a progressive disease characterized by the disproportionate and symmetrical distribution of adipose tissue, primarily in the extremities. Although numerous results from in vitro and in vivo studies have been published, many questions regarding the pathology and genetic background of lipedema remain unanswered. METHODS: In this study, adipose tissue-derived stromal/stem cells were isolated from lipoaspirates derived from nonobese and obese donors with or without lipedema. Growth and morphology, metabolic activity, differentiation potential, and gene expression were evaluated using quantification of lipid accumulation, metabolic activity assay, live-cell imaging, reverse transcription polymerase chain reaction, quantitative polymerase chain reaction, and immunocytochemical staining. RESULTS: The adipogenic potential of lipedema and nonlipedema adipose tissue-derived stromal/stem cells did not rise in parallel with the donors' body mass index and did not differ significantly between groups. However, in vitro differentiated adipocytes from nonobese lipedema donors showed significant upregulation of adipogenic gene expression compared with nonobese controls. All other genes tested were expressed equally in lipedema and nonlipedema adipocytes. The adiponectin/leptin ratio was significantly reduced in adipocytes from obese lipedema donors compared with their nonobese lipedema counterparts. Increased stress fiber-integrated smooth muscle actin was visible in lipedema adipocytes compared with nonlipedema controls and appeared enhanced in adipocytes from obese lipedema donors. CONCLUSIONS: Not only lipedema per se but also body mass index of donors affect adipogenic gene expression substantially in vitro. The significantly reduced adiponectin/leptin ratio and the increased occurrence of myofibroblast-like cells in obese lipedema adipocyte cultures underscores the importance of attention to the co-occurrence of lipedema and obesity. These are important findings toward accurate diagnosis of lipedema. CLINICAL RELEVANCE STATEMENT: Our study highlights not only the difficulty in lipedema diagnostics but also the tremendous need for further studies on lipedema tissue. Although lipedema might seem to be an underestimated field in plastic and reconstructive surgery, the power it holds to provide better treatment to future patients can not be promoted enough.

Lipedema Research-Quo Vadis?

When studying the current literature, one might get the impression that lipedema is a "modern" disease, with increasing incidence and augmenting prevalence throughout Western countries during the last decade. However, a quick look into older textbooks shows that disproportionate accumulation of fat in female bodies has long been known without being recognized as an independent disease. Nevertheless, it was not until 1940 that Allen and Hines described a "syndrome characterized by fat legs and orthostatic edema" in a seminal publication. The mere awareness that people who have lipedema are not just overweight but suffer from a yet poorly defined pathological condition, may be considered a decisive leap forward in the understanding of lipedema. A number of comprehensive publications have since dealt with the clinical presentation of lipedema and have provided the first clues towards the potential pathological mechanisms underlying its initiation and progression. Nevertheless, despite all effort that has been undertaken to unravel lipedema pathology, many questions have remained unanswered. What can be deduced with certainty from all experimental and medical evidence available so far is that lipedema is neither a cosmetic problem nor is it a problem of lifestyle but should be accepted as a serious disease with yet undetermined genetic background, which makes women's lives unbearable from both a physical and psychological point of view. To date, results from clinical inspections have led to the categorization of various types and stages of lipedema, describing how the extremities are affected and evaluating its progression, as demonstrated by skin alterations, adipose tissue volume increase and physical and everyday-behavioral impediments. There is accumulating evidence showing that advanced stages of lipedema are usually accompanied by excessive weight or obesity. Thus, it is not unreasonable to assume that the progression of lipedema is largely driven by weight gain and the pathological alterations associated with it. Similarly, secondary lymphedema is frequently found in lipedema patients at advanced stages. Needless to say, both conditions considerably blur the clinical presentation of lipedema, making diagnosis difficult and scientific research challenging. The present literature review will focus on lipedema research, based on evidence fromex vivo and in vitro data, which has accumulated throughout the last few decades. We will also open the discussion as to whether the currently used categorization of lipedema stages is still sufficient and up-to-date for the accurate description of this enigmatic disease, whose name, strangely enough, does not match its pathologic correlate.

Histone deacetylase 1 expression is inversely correlated with age in the short-lived fish Nothobranchius furzeri.

Aging is associated with profound changes in the epigenome, resulting in alterations of gene expression, epigenetic landscape, and genome architecture. Class I Histone deacetylases (HDACs), consisting of HDAC1, HDAC2, HDAC3, and HDAC8, play a major role in epigenetic regulation of chromatin structure and transcriptional control, and have been implicated as key players in the pathogenesis of age-dependent diseases and disorders affecting health and longevity. Here, we report the identification of class I Hdac orthologs and their detailed spatio-temporal expression profile in the short-lived fish Nothobranchius furzeri from the onset of embryogenesis until old age covering the entire lifespan of the organism. Database search of the recently annotated N. furzeri genomes retrieved four distinct genes: two copies of hdac1 and one copy of each hdac3 and hdac8. However, no hdac2 ortholog could be identified. Phylogenetic analysis grouped the individual killifish class I Hdacs within the well-defined terminal clades. We find that upon aging, Hdac1 is significantly down-regulated in muscle, liver, and brain, and this age-dependent down-regulation in brain clearly correlates with increased mRNA levels of the cyclin-dependent kinase inhibitor cdkn1a (p21). Furthermore, this apparent reduction of class I HDACs in transcript and protein levels is mirrored in the mouse brain, highlighting an evolutionarily conserved role of class I HDACs during normal development and in the aging process.

Effects of a forgiveness intervention for older adults.

The authors' aim in the present study was to examine the effects of a brief forgiveness intervention for older adults. The psychoeducational group intervention consists of (a) established core components of previous forgiveness interventions and (b) additional components considering specific needs of older adults. Seventy-eight older adults (mean age 70.1 years) were randomized to a treatment condition or a waiting-list control condition. The intervention reduced the levels of perceived actual transgression painfulness, transgression-related emotions and cognitions, and negative affect. These findings suggest the promise of forgiveness interventions for older adults that help participants clarify and deal with past, present, and future interpersonal transgressions.

Histone deacetylase inhibitor Trichostatin A induces neural tube defects and promotes neural crest specification in the chicken neural tube.

Epigenetic mechanisms serve as key regulatory elements during vertebrate embryogenesis. Histone acetylation levels, controlled by the opposing action of histone acetyl transferases (HATs) and histone deacetylases (HDACs), influence the accessibility of DNA to transcription factors and thereby dynamically regulate transcriptional programs. HDACs execute important functions in the control of proliferation, differentiation, and the establishment of cell identities during embryonic development. To investigate the global role of the HDAC family during neural tube development, we employed Trichostatin A (TSA) to locally block enzymatic HDAC activity in chick embryos in ovo. We found that TSA treatment induces neural tube defects at the level of the posterior neuropore, ranging from slight undulations to a complete failure of neural tube closure. This phenotype is accompanied by morphological changes in neuroepithelial cells and induction of apoptosis. As a molecular consequence of HDAC inhibition, we observed a timely deregulated cadherin switching in the dorsal neural tube, illustrated by induction of Cadherin 6B as well as reciprocal downregulation of N-Cadherin expression. Concomitantly, several neural crest specific markers, including Bmp4, Pax3, Sox9 and Sox10 are induced, causing a premature loss of epithelial characteristics. Our findings provide evidence that HDAC function is crucial to control the regulatory circuits operating during trunk neural crest development and neural tube closure.

The interferon stimulated gene 12 inactivates vasculoprotective functions of NR4A nuclear receptors.

RATIONALE: Innate and adaptive immune responses alter numerous homeostatic processes that are controlled by nuclear hormone receptors. NR4A1 is a nuclear receptor that is induced in vascular pathologies, where it mediates protection. OBJECTIVE: The underlying mechanisms that regulate the activity of NR4A1 during vascular injury are not clear. We therefore searched for modulators of NR4A1 function that are present during vascular inflammation. METHODS AND RESULTS: We report that the protein encoded by interferon stimulated gene 12 (ISG12), is a novel interaction partner of NR4A1 that inhibits the transcriptional activities of NR4A1 by mediating its Crm1-dependent nuclear export. Using 2 models of vascular injury, we show that ISG12-deficient mice are protected from neointima formation. This effect is dependent on the presence of NR4A1, as mice deficient for both ISG12 and NR4A1 exhibit neointima formation similar to wild-type mice. CONCLUSIONS: These findings identify a previously unrecognized feedback loop activated by interferons that inhibits the vasculoprotective functions of NR4A nuclear receptors, providing a potential new therapeutic target for interferon-driven pathologies.

Do agreeableness and neuroticism explain age differences in the tendency to forgive others?

Previous research has shown that age is positively related to a dispositional tendency to forgive others. The present investigation tested the hypothesis that agreeableness and neuroticism partially mediate the association between age and forgivingness. Data from two representative cross-sectional samples of adults were used to test this hypothesis. Results from Study 1 (N = 962, age range: 19-84 years) support the hypothesis, indicating that agreeableness and neuroticism explained, in part, age differences in tendencies to forgive. Study 2 (N = 451, age range: 20-83 years) replicated and extended the results by including transgression occurrences as a third mediator. The results showed that agreeableness and neuroticism explain the association between age and the tendency to forgive others over and above the effect of transgression occurrences.

Thyroid hormone controls cone opsin expression in the retina of adult rodents.

Mammalian retinas display an astonishing diversity in the spatial arrangement of their spectral cone photoreceptors, probably in adaptation to different visual environments. Opsin expression patterns like the dorsoventral gradients of short-wave-sensitive (S) and middle- to long-wave-sensitive (M) cone opsin found in many species are established early in development and thought to be stable thereafter throughout life. In mouse early development, thyroid hormone (TH), through its receptor TRß2, is an important regulator of cone spectral identity. However, the role of TH in the maintenance of the mature cone photoreceptor pattern is unclear. We here show that TH also controls adult cone opsin expression. Methimazole-induced suppression of serum TH in adult mice and rats yielded no changes in cone numbers but reversibly altered cone patterns by activating the expression of S-cone opsin and repressing the expression of M-cone opsin. Furthermore, treatment of athyroid Pax8(-/-) mice with TH restored a wild-type pattern of cone opsin expression that reverted back to the mutant S-opsin-dominated pattern after termination of treatment. No evidence for cone death or the generation of new cones from retinal progenitors was found in retinas that shifted opsin expression patterns. Together, this suggests that opsin expression in terminally differentiated mammalian cones remains subject to control by TH, a finding that is in contradiction to previous work and challenges the current view that opsin identity in mature mammalian cones is fixed by permanent gene silencing.

Proteomic characterization of human early pro-angiogenic cells.

Early pro-angiogenic cells (EPCs) have been shown to be involved in neovascularization, angiogenesis and re-endothelialization and cathepsin L inhibition blunted their pro-angiogenic effect. In the present study, we have analysed and mapped the proteome and secretome of human EPCs, utilizing a combination of difference in-gel electrophoresis (DIGE) and shotgun proteomics. A population of 206 protein spots were analysed, with 171 being identified in the cellular proteome of EPCs. 82 proteins were identified in their conditioned medium, including the alternative macrophage markers C-C motif chemokine 18 (CCL18) and the hemoglobin scavenger receptor CD163 as well as platelet factor 4 (CXCL4) and platelet basic protein (CXCL7) with "platelet alpha granule" being returned as the top category according to the Gene Ontology Annotation. Apart from cathepsin L, the cathepsin L inhibitor also attenuated the release of a wide range of other cathepsins and lysosomal proteins such as legumain, but stimulated the secretion of members of the S100 protein family. The data presented here are the most comprehensive characterization of protein expression and secretion in human EPCs to date and highlight the potential importance of cysteine proteases in the processing of platelet factors for their pro-angiogenic potential. This article is part of a special issue entitled, "Cardiovascular Stem Cells Revisited".

Immunohistochemical expression analysis of Cx43, Cx26, c-KIT and PlAP in contralateral testis biopsies of patients with non-seminomatous testicular germ cell tumor.

Non seminomatous testicular germ cell tumors (NSTGCTs) express fetal stem cell markers and display dysregulation of connexin 43 expression. Persistence of fetal spermatogonial characteristics was implicated in the emergence of testicular germ cell tumors. The objective of this study was to analyze the tubular architecture in contralateral testes of patients with NSTGCT. We studied morphologic alterations, expression patterns of markers for the integrity of the germinal epithelium (gap junction proteins connexin 43 and 26), as well as of the embryonic markers c-KIT and placental alkaline phosphatase (PlAP), both established markers to detect carcinoma in situ (CIS). In all samples, tubules showing maturation of germ cells up to spermatozoa were observed. In addition, tubules with alterations in tubular architecture and with impaired spermatogenesis occurred. In tubules showing aberrant spermatogenesis, connexin 43 (Cx43) signal was down-regulated and a shift of signal from gap junctions to the cytoplasm occurred. Concomitantly, Cx26 was found highly up-regulated in tubules with incomplete and aberrant germ cell maturation. All testes exhibited single spermatogonia with positive reaction for c-KIT and a significant positive correlation was found between the mean number of c-KIT positive spermatogonia per tubule and the percentage of tubules presenting severely impaired spermatogenesis. Our data show alterations of the normal architecture of the germinal epithelium and disturbances of spermatogenesis in the contralateral testes of patients with NSTGCT in all cases evaluated. The concomitant occurrence of c-KIT positive spermatogonia and defects in tubular architecture is in line with the hypothesis that patients with NSTGCT suffer from disturbed germ cell development.

Expression of class I histone deacetylases during chick and mouse development.

Histone deacetylases (HDACs) are a family of enzymes which regulate the acetylation state of nucleosomal histones, as well as non-histone proteins. By altering local chromatin architecture, HDACs play important roles in shaping cell differentiation and morphogenesis. Expression of class I HDACs during early chick development has so far not been analyzed. Here, we report the expression profile of chick class I HDACs from the onset of gastrulation (HH2) to day 4 of development and compare it to relevant stages during mouse development. Visualized by in situ hybridization to whole mount embryos and tissue sections, we found tissue-specific overlapping temporal and spatial expression domains for all four class I HDACs in chick and mouse, although species-specific differences could be identified. All class I HDACs in both species are highly expressed in the developing brain. In particular, HDAC1 is expressed at sites of anterior and posterior neural tube closure most obvious in the hot spot-like expression of HDAC1 in HH12 chicken embryos. A significant species-specific spatio-temporal expression pattern was observed for HDAC8. Whereas HDAC8 is exclusively found in fore- and midbrain regions during early mouse embryogenesis, the chick ortholog shows an expanded expression pattern, suggesting a more diversified role of HDAC8 in the chick system. Our results present a basis for further functional analysis of class I HDACs in chick development.

Stomatin-like protein-1 interacts with stomatin and is targeted to late endosomes.

The human stomatin-like protein-1 (SLP-1) is a membrane protein with a characteristic bipartite structure containing a stomatin domain and a sterol carrier protein-2 (SCP-2) domain. This structure suggests a role for SLP-1 in sterol/lipid transfer and transport. Because SLP-1 has not been investigated, we first studied the molecular and cell biological characteristics of the expressed protein. We show here that SLP-1 localizes to the late endosomal compartment, like stomatin. Unlike stomatin, SLP-1 does not localize to the plasma membrane. Overexpression of SLP-1 leads to the redistribution of stomatin from the plasma membrane to late endosomes suggesting a complex formation between these proteins. We found that the targeting of SLP-1 to late endosomes is caused by a GYXXPhi (Phi being a bulky, hydrophobic amino acid) sorting signal at the N terminus. Mutation of this signal results in plasma membrane localization. SLP-1 and stomatin co-localize in the late endosomal compartment, they co-immunoprecipitate, thus showing a direct interaction, and they associate with detergent-resistant membranes. In accordance with the proposed lipid transfer function, we show that, under conditions of blocked cholesterol efflux from late endosomes, SLP-1 induces the formation of enlarged, cholesterol-filled, weakly LAMP-2-positive, acidic vesicles in the perinuclear region. This massive cholesterol accumulation clearly depends on the SCP-2 domain of SLP-1, suggesting a role for this domain in cholesterol transfer to late endosomes.

Proteomic analysis reveals presence of platelet microparticles in endothelial progenitor cell cultures.

The concept of endothelial progenitor cells (EPCs) has attracted considerable interest in cardiovascular research, but despite a decade of research there are still no specific markers for EPCs and results from clinical trials remain controversial. Using liquid chromatography-tandem mass spectrometry, we analyzed the protein composition of microparticles (MPs) originating from the cell surface of EPC cultures. Our data revealed that the conventional methods for isolating mononuclear cells lead to a contamination with platelet proteins. Notably, platelets readily disintegrate into platelet MPs. These platelet MPs are taken up by the mononuclear cell population, which acquires "endothelial" characteristics (CD31, von Willebrand factor [VWF], lectin-binding), and angiogenic properties. In a large population-based study (n = 526), platelets emerged as a positive predictor for the number of colony-forming units and early outgrowth EPCs. Our study provides the first evidence that the cell type consistent with current definitions of an EPC phenotype may arise from an uptake of platelet MPs by mononuclear cells resulting in a gross misinterpretation of their cellular progeny. These findings demonstrate the advantage of using an unbiased proteomic approach to assess cellular phenotypes and advise caution in attributing the benefits in clinical trials using unselected bone marrow mononuclear cells (BMCs) to stem cell-mediated repair.

Cone photoreceptors and potential UV vision in a subterranean insectivore, the European mole.

We have examined the presence, the distribution, and the opsin identity of photoreceptor types in the retina of the European mole, Talpa europaea, a subterranean insectivore with regressed morphology of the visual system. Cones and rods were identified using opsin antisera, and their topographies determined from flat-mounted retinas. The retina (total area 0.75 mm(2)) contains about 100,000 photoreceptors, 10-12% of which are cones. Rod density is low (theoretical maximum 127,000 mm(-2)). Cone density peaks in central retina (17,750 mm(-2)). Similar to most mammals, two cone opsins, shortwave-sensitive (S) and middle-to-long-wave-sensitive (M), are present. Cone distribution shows a dorsoventral gradient with higher S cone numbers in ventral retina. Coexpression of S and M opsin occurs in more than 30% of the cones. Partial sequencing of the S opsin gene strongly supports UV sensitivity of the mole S cone photopigment. Amino acids that spectrally tune the S opsin are identical in T. europaea and in mammals with known UV cone photosensitivity. The lens transmits light down to 300 nm. Together, our data suggest that photopic vision and UV sensitivity of a cone pigment play a functional role in the European mole.

Establishment of vessel-like structures in long-term three-dimensional tissue culture of myocardium: an electron microscopy study.

To assess whether long-term three-dimensional (3D) tissue culture of myocardium enables the in vitro establishment of vessel-like structures, myocardial tissue from newborn mice was incubated under conditions of 3D culture for at least 3 weeks, and studied by phase-contrast microscopy, conventional histology, immunohistochemistry, and electron microscopy. During 3 weeks of culture, a mean 24.35 +/- 3.74% of all aggregates contracted spontaneously. The contracting aggregates displayed a tissue-like architecture with small basal and apical zones, and a large central zone. The basal and apical zone consisted of immature mesenchymal cells. The underlying shell of the aggregate contained many cardiomyocytes. Vessel-like structures were found concentrated within the aggregates. Immunohistochemistry showed that up to 15% of the cells in the central zone of the aggregate were positive for the endothelial-specific BS-I lectin. Vessel-like structures were formed by cells, which often showed intracytoplasmatic lumena. Surrounding the neocapillaries, structures of a rudimentary basal membrane could be detected. A 3D culture of myocardial tissue permits the establishment of a rudimentary capillary network within the tissue aggregates, which presumably guarantees a sufficient tissue perfusion up to a maximum aggregate diameter of approximately 900 microm.

Induction of apoptosis in the human mast cell leukemia cell line HMC-1 by various antineoplastic drugs.

Mast cell leukemia (MCL) is a rare disorder characterized by rapid disease progression, resistance against conventional cytoreductive drugs, and short survival. In an attempt to identify drugs that show significant antiproliferative effects on neoplastic mast cells (MC), we exposed the MCL-derived cell line HMC-1 to various cytotoxic drugs including 2-chlorodeoxyadenosine [2CdA], fludarabine and cytosine arabinoside [ARA-C]. The effects of these drugs on 3H-thymidine incorporation, electron microscopic signs of apoptosis, and DNA fragmentation in HMC-1 cells, were analyzed. As assessed by 3H-thymidine incorporation, all drugs produced inhibition of proliferation in HMC-1 cells with the following rank order of potency: ARA-C > doxorubicine > 2-CdA > etoposide > vincristine > fludarabine > cisplatin. Fludarabin, cisplatin, etoposide and 2-CdA also induced ladder-type fragmentation of DNA, endonuclease activity in a Tunel assay, and electron microscopic signs of apoptosis in HMC-1 cells. Together, our data show that various cytostatic drugs can induce apoptosis and inhibition of proliferation in the human MCL cell line HMC-1. Whether these drugs, alone or in combination, are also effective in patients with MCL, remains to be determined.

The presence of stomatin in detergent-insoluble domains of neutrophil granule membranes.

Neutrophil azurophil granules, traditionally regarded as the neutrophil counterpart to lysosomes, lack the lysosomal marker lysosome-associated membrane glycoprotein and have recently been suggested to be nonlysosomal secretory organelles. The membrane of the azurophil granules is poorly characterized-CD63 and CD68 are the only membrane proteins identified so far. Here, azurophil granule membranes were isolated by Percoll gradient subcellular fractionation. Using matrix-assisted laser desorption ionization time of flight mass spectrometry of tryptic peptides from an isolated protein, stomatin was identified in these membranes. Using immunoelectron microscopy and immunoblot analysis of isolated organelles, stomatin was found to be subcellularly localized, not only to the azurophil granules but also by a major part to the specific granules and by a minor part to the secretory vesicles/plasma membrane. We also show the presence of detergent-insoluble, low-density membrane domains in the plasma membrane and the granule membranes and found stomatin to be localized to these domains.

Chemoimmunohormonal therapy with carmustine, dacarbazine, cisplatin, tamoxifen, and interferon for metastatic melanoma: a prospective phase II study.

The objective of this study was to investigate the efficacy of our treatment regimen in metastatic melanoma. Thirty patients entered the study after undergoing a thorough metastatic workup. Treatment protocol included carmustine (BCNU) (150 mg/m(2) IV, day 1) every 6 weeks, dacarbazine (DTIC) (220 mg/m(2) IV, days 1-3), and cisplatin (25 mg/m(2) IV, days 1-3) every 3 weeks, interferon A-2B (6 x 10(6) U/m daily s.c. on days 4-8 and 16-20) and tamoxifen 20 mg/day for 6 weeks. Among 29 evaluable patients, overall response was seen in 15 (52%) and complete response in 5 (17%) patients. Median duration of partial response was 4 months (range, 1-12 months); of complete response was 8 months (range, 2-14 months). Complete response continues in two patients with lung metastases. Median survival time was 8.7 months. Side effects were tolerable. Four (13%) patients developed neutropenic fever, and platelet transfusions were required in five (17%) patients. One patient died of neutropenic sepsis. Thrombocytopenia caused prolongation of the median interval between the first and second courses, and drug doses were reduced in the second course in 8 of 26 (31%) patients. Our chemoimmunohormonal regimen is efficient in metastatic malignant melanoma and can induce durable remission. Severe thrombocytopenia leads to a reduction of carmustine dose in a new protocol.

Stomatin is a major lipid-raft component of platelet alpha granules.

Lipid rafts are detergent-resistant, cholesterol- and sphingolipid-rich membrane domains that are involved in important cellular processes such as signal transduction and intracellular trafficking. Stomatin, a major lipid-raft component of erythrocytes and epithelial cells, is also an abundant platelet protein. Microscopical methods and subcellular fractionation showed that stomatin is located mainly at the alpha-granular membrane. The lipid-raft marker proteins flotillin-1 and flotillin-2 were also present in platelets but excluded from alpha granules. Stomatin and the flotillins were associated with Triton X-100-insoluble lipid rafts. Whereas stomatin was partly soluble in Triton X-100, it was insoluble in the detergents Lubrol and 3-[(3-cholamidopropyl)dimethylamonio]-1-propyl sulfonate (CHAPS). Flotation experiments after CHAPS lysis of platelets revealed a distinct set of lipid-raft-associated proteins, which were identified by matrix-assisted laser desorption/ionization mass spectrometry as stomatin, flotillin-1, flotillin-2, CD36, CD9, integrin alpha(IIb)beta(3), and the glucose transporter GLUT-3. Stomatin, the flotillins, and CD36 were exclusively present in this lipid-raft fraction. Activation of platelets by calcium ionophore A23187 or thrombin led to translocation of stomatin to the plasma membrane, cleavage by calpain, and specific sorting into released microvesicles. In conclusion, this study demonstrated the existence of alpha-granular lipid rafts and suggests an important role for stomatin in the organization and function of alpha granules.