Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Insulin was modified with d-biotin-N-hydroxysuccinimide ester in dimethylformamide. Mono-, di-, and triacylated insulins were separated by preparative isoelectric focusing. Monoacylated derivatives (isoelectric point 5.1) were fractionated twice on DEAE-cellulose to yield pure N epsilonB29-biotinylinsulin. The structure of the product was established by amino acid analysis before and after deamination. N epsilonB29-biotinylinsulin had biological activity indistinguishable from insulin on glucose oxidation and lipid synthesis assays using isolated rat epididymal fat cells. Complexes of N epsilonB29-biotinylinsulin with avidin, having essentially all but one binding site filled with biotin, were prepared in order to obtain a 1:1 insulin:avidin ration. The elicited identical maximal biological responses, but showed a potency decreased to 5% of that of insulin. Such complexes conjugated with ferritin will provide a useful tool in the development of electron microscopic stains of insulin receptors.
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PMID:N epsilonB29-(+)-biotinylinsulin and its complexes with avidin. Synthesis and biological activity. 62 Nov 98

MODIFICATIONS IN RABBIT SPERM PLASMA MEMBRANES DURING EPIDIDYMAL PASSAGE AND AFTER EJACULATION WERE INVESTIGATED BY USED OF THREE LECTINS: concanavalin A (Con A); Ricinus communis I (RCA(I)); and wheat germ agglutinin (WGA). During sperm passage from caput to cauda epididymis, agglutination by WGA drastically decreased, and agglutination by RCA(I) slightly decreased, although agglutination by Con A remained approximately unchanged. After ejaculation, spermatozoa were agglutinated to a similar degree or slightly less by Con A, WGA, and RCA(I), compared to cauda epididymal spermatozoa. Ultrastructural examination of sperm lectin-binding sites with ferritin- lectin conjugates revealed differences in the densities of lectin receptors in various sperm regions, and changes in the same regions during epididymal passage and after ejaculation. Ferritin-RCA(I) showed abrupt changes in lectin site densities between acrosomal and postacrosomal regions of sperm heads. The relative amounts of ferritin-RCA(I) bound to heads of caput epididymal or ejaculated spermatozoa. Tail regions were labeled by ferritin RCA(I) almost equally on caput and cauda epididymal spermatozoa, but the middle-piece region of ejaculated spermatozoa was slightly more densely labeled than the principal-piece region, and these two regions on ejaculated spermatozoa were labeled less than on caput and cuada epididymal spermatozoa. Ferritin-WGA densely labeled the acrosomal region of caput epididymal spermatozoa, although labeling of cauda epidiymal spermatozoa was relatively sparse except in the apical area of the acrosomal region. Ejaculated spermatozoa bound only a few molecules of ferritin-WGA, even at the highest conjugate concentrations used. Caput epididymal, but not cauda epididymal or ejaculated spermatozoa, bound ferritin-WGA in the tail regions. Dramatic differences in labeling densities during epididymal passage and after ejaculation were not found with ferritin-Con A.
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PMID:Lectin-binding sites on the plasma membranes of rabbit spermatozoa. Changes in surface receptors during epididymal Maturation and after ejaculation. 90 74

Upon release from the seminiferous epithelium, spermatoza show a small droplet of cytoplasm attached to the neck region. During transit of spermatozoa in the caput epididymidis, this cytoplasmic droplet migrates along the middle piece of the flagellum. In the corpus epididymidis, the droplet shows a lateral displacement, while in the cauda epididymidis it detaches from the spermatozoon. In the electron microscope, cytoplasmic droplets attached to spermatozoa were seen to contain numerous, short, straight or C-shaped, flattened membranous elements referred to as lamellae, small vesicles, and small particles (35-nm diameter) with a diffuse wall showing no apparent unit membrane. The lamellae were stacked closely on one another or arranged in a loose array. Structurally as well as cytochemically, with different cytochemical markers, the lamellae and vesicular elements failed to show any evidence of being components of the Golgi apparatus or elements of the endoplasmic reticulum. The lamellae, vesicular elements, and 35-nm particles were also seen free in the lumen of the corpus epididymidis but were especially prominent in the cauda epididymidis at a time when droplets were being released from spermatozoa. The lumen of the epididymis, as spermatozoa passed from the caput to the cauda epididymidis, was also noted to acquire progressively a flocculent background material. The epididymal epithelium is composed predominantly of principal and clear cells. The endocytic activity of clear cells was examined in rats at different time intervals after a single injection of cationic ferritin into the lumen of the cauda epididymidis. At 2 min the tracer was bound to the microvilli of these cells and was also observed within large coated and uncoated pits, subsurface coated vesicles, and numerous subsurface small uncoated vesicular membranous elements (150-200-nm diameter). At 5 min, in addition to the above structures, the tracer was present in endosomes, while at 15 and 30 min, pale and dense multivesicular bodies appeared labeled, respectively. At 1 and 2 hr, but more so at 6 hr large dense membrane-bound bodies identified cytochemically as secondary lysosomes became labeled. All of the above endocytic structures were also seen to contain the 35-nm particles, flattened or vesicular membranous profiles, and a fine flocculent background material reminiscent of those seen free in the lumen or found in cytoplasmic droplets attached to spermatozoa. (ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Role of epithelial clear cells of the rat epididymis in the disposal of the contents of cytoplasmic droplets detached from spermatozoa. 284 96

The structure, relative density, and distribution of anionic sites on the surface of epididymal and ejaculated spermatozoa were studied using polycationic ferritin (CF), colloidal iron hydroxide (CIH), various enzymatic treatments, methylation, and de-acetylation. Macro-molecules containing sugar residues, probably sialic acid, are part of the sperm membrane and show a characteristic distribution and density that is dependent of the sperm region and of its origin. Unlike the spermatozoa of other eutheria examined, the exposure of the stallion spermatozoa to neuraminidase treatment did not produce significant changes in the density of the negative charge of the sperm surface. The ability of purified neuraminidase to act only after saponification suggests that sialic acid may be present in the acetylated form. When CIH was used it is seen that the density of the negative charge is rather uniform within a particular segment of the spermatozoa and abruptly changes at the junction of morphologically distinct segments (Between the acrosomal and post acrosomal region of the sperm head and between the post acrosomal region and middle piece of the flagellum). The acrosome presented more negative groups dissociated at pH 1.8 than the postacrosomal region. A greater concentration of anionic sites over the flagellum was also observed when CIH and CF were used. This asymmetry probably represents different domains that may be related to specific functions. The cytochemical observations and the cellular electrophoretic mobility measurements did not show striking differences on the negative charge of sperm obtained from different regions of epididymis and ejaculates in contrast to previous results in other species. The spermatozoa collected from caput epididymidis bind CIH but not all population present equal response. In corpus and cauda region of epididymis the population displaying the capacity to bind CIH or CF significantly over the head and tail surface was the majority. This study corroborates that the distribution and density of terminal oligosaccharide residues on the sperm plasma membrane has species specific characteristics. The surface charge of the spermatozoa obtained either during the breeding or nonbreeding season, determined by measurements of cellular electrophoretic mobility and by the binding pattern of CIH and CF, does not show significant differences.
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PMID:Cytochemical analysis of the anionic sites on the membrane of the stallion spermatozoa during the epididymal transit. 350 80

Capillary endothelium can actively regulate vascular permeability of various serum proteins. Hormones such as insulin must interact with this capillary barrier in order to reach their respective target tissues. We have studied the binding and subsequent internalization of 125I-insulin in both native (freshly isolated) and primary cultured capillary endothelium derived from rat epididymal fat pads. Insulin association with the endothelium, internalization and degradation differed between freshly isolated and primary cultured capillaries. Specific binding in freshly isolated and cultured capillaries was temperature dependent, and was competitively inhibited in the presence of unlabelled insulin. Primary cultures of capillaries grown to confluence did not exhibit specific binding of insulin. Despite the lack of specific receptors for insulin, cultured cells vesicularly internalized insulin. Greater than 50% of the total associated insulin was not degraded by cultured endothelium. Morphological examinations using ferritin labelled insulin localized insulin associated to the capillary endothelial cell membrane and sequestered within pinocytotic vesicles. Incubation of freshly isolated capillaries with insulin stimulated the fluid phase endocytosis of 14C-sucrose; however, insulin had no effect on fluid phase endocytosis in cultured capillaries. These results indicate that capillary endothelium, isolated from rat epididymal fat, exhibit specific receptors for insulin. Binding of insulin to the capillary membrane is followed by internalization into cytoplasmic vesicles and partial degradation.
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PMID:Insulin binding and vesicular ingestion in capillary endothelium. 390 93

Anionic sites of rat epididymal spermatozoa were measured at pH 7.4 using tritiated polycationized ferritin. The spermatozoa from the caput region had 1.25 +/- 0.06 X 10(6) anionic sites per cell and a binding constant of 1.26 +/- 0.01 X 10(6) M-1. Spermatozoa from the cauda region had 1.50 +/- 0.09 X 10(6) anionic sites per cell and a binding constant of 4.84 +/- 0.82 X 10(6) M-1. The values were mean +/- s.d. The anionic sites were partly sensitive to treatments with neuraminidase, trypsin and Triton X-100.
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PMID:Measurement of anionic sites of rat epididymal spermatozoa using tritiated polycationized ferritin. 688 40

Microvessels isolated from rat epididymal fat exhibit differential vesicular ingestion rates for unmodified and non-enzymatically glycosylated rat albumin. While unmodified rat albumin is excluded from ingestion by endothelial micropinocytic vesicles, glycosylated albumin is avidly taken up by endocytosis. Interaction of albumin and glycosylated albumin with endothelium was studied with a double-label fluorescence assay of micropinocytosis. When glycosylated albumin was present at a concentration of 6% with respect to total albumin (the level found in "non diabetic" serum), only glycosylated albumin was ingested. At higher concentrations of glycosylated albumin (those found in diabetic serum), both albumin and glycosylated albumin are ingested. Glycosylation of endothelial membrane components results in stimulated ingestion of glycosylated albumin, persistent exclusion of unmodified albumin, and unaltered micropinocytic ingestion of native ferritin. These results indicate that nonenzymatic glycosylation of serum albumin may result in rapid vesicle-mediated extravasation of albumin. Chronic microvascular leakage of glycosylated albumin could contribute to the pathogenesis of diabetic microangiopathy.
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PMID:Micropinocytic ingestion of glycosylated albumin by isolated microvessels: possible role in pathogenesis of diabetic microangiopathy. 694 Dec 99

The aim of the present study was to provide a comprehensive morphological analysis of the porcine epididymis in view of the specific functions being performed in different regions of this organ. Blood supply and microvasculature of efferent ductules and epididymal duct were investigated by means of corrosion casts which were analysed macroscopically and by scanning electron microscopy. This revealed blood supply to the testis and epididymis to be closely related. The capillary pattern was typical for the efferent ductules, the caput, corpus, and distal cauda epididymidis, respectively. Corrosion casts were also used to visualize the course of the efferent ductules themselves. Tissue samples from different regions of the efferent ductules and epididymal duct were examined by light microscopy and both scanning and transmission electron microscopy, with special attention being payed to transitional areas. Morphological criteria allowed the distinction of three segments within the efferent ductules and of the initial segment, proximal caput, distal caput, corpus, proximal cauda, and distal cauda regions of the epididymal duct. Components of the endocytic apparatus of efferent ductule principal cells were identified by ferritin uptake. Ultrastructural evidence of absorption in the epididymal duct was particularly prominent in proximal and distal caput. Extensive cisternae of rough endoplasmic reticulum and a well-developed Golgi apparatus were indicative of active protein synthesis and secretion especially in the distal caput and corpus regions. However, assignment of various organelles in principal cells of the epididymal duct to either absorptive or secretory pathways still remains tentative.
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PMID:Morphological characteristics of boar efferent ductules and epididymal duct. 787 92

The cytoplasmic droplet of epididymal spermatozoa is a small localized outpouching of cytoplasm of the tail of unknown significance. EM revealed flattened saccular elements as the near exclusive membranous component of the droplet. Light and electron microscopic immunolabeling for Golgi/TGN markers showed these saccules to be reactive for antibodies to TGN38, protein affinity-purified alpha 2,6 sialyltransferase, and anti-human beta 1,4 galactosyltransferase. The saccules were isolated by subcellular fractionation and antibodies raised against this fraction immunolabeled the saccules of the droplet in situ as well as the Golgi region of somatic epithelial cells lining the epididymis. The isolated droplet fraction was enriched in galactosyltransferase and sialyltransferase activities, and endogenous glycosylation assays identified the modification of several endogenous glycopeptides. EM lectin staining in situ demonstrated galactose and N-acetyl galactosamine constituents in the saccules. Endocytic studies with cationic and anionic ferritin as well as HRP failed to identify the saccules as components of the endocytic apparatus. Epididymal spermatozoa were devoid of markers for the ER as well as the Golgi-associated coatamer protein beta-COP. It is therefore unlikely that the saccular elements of the droplet participate in vesicular protein transport. However, the identification of Golgi/TGN glycosylating activities in the saccules may be related to plasma membrane modifications which occur during epididymal sperm maturation.
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PMID:The cytoplasmic droplet of rat epididymal spermatozoa contains saccular elements with Golgi characteristics. 822 42

Vascular endothelial cells are associated with a number of anionic molecules. These anions are important in endothelial function, particularly in regulating permeability, haemostasis and cellular traffic. To explore the nature and distribution of anions on the brain endothelial cell (BEC) surface, we have examined rat brain endothelium in culture, and in situ. The anionic sites were probed with cationic colloidal gold and cationised ferritin, and visualised by light microscopy. Additionally we compared the distribution of the anionic sites on BEC with that present on other endothelial cell types in culture. The predominant anion detected on BEC was heparan sulphate (HS). This was distributed throughout the cell membrane, but was most densely associated with intercellular junctions. This pattern was distinct from the anionic locations observed in endothelia from aorta and epididymal fat microvessels. The distribution of anions was dependent on the age of cultured cells, with only minimal levels of HS seen at the periphery of younger cells. The nature and distribution of negative charge was different in situ. Here, sialic acid was the major surface anion, with only a small contribution from HS. The significance of these findings are discussed in relation to endothelial function in normal tissue and in pathological conditions.
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PMID:Distribution and analysis of surface charge on brain endothelium in vitro and in situ. 852 5


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