High strength 7xxx aluminum alloy series, used in transport industry, are commonly welded with 5x... more High strength 7xxx aluminum alloy series, used in transport industry, are commonly welded with 5xxx filler metal alloys to produce joins with acceptable chemical properties. It was studied the weldability of ER5087 and ER5356 filler metals welded on a high strength AA7020-T6 base metal aluminum alloy using Houldcroft and Battelle weldability tests in order to determine solidification cracking susceptibility. Tests were made using full penetration bead on plate welds with manual GTA welding process. The crack surfaces were observed using Scanning Electron Microscopy (SEM). The results show that solidification cracking susceptibility of both materials is very similar, but ER5356 filler metal exhibit less variability in crack length compared to ER5087 filler metal. Fracture surfaces in both materials revealed a dendritic morphology of the solidifying weld metal.
Aluminum alloys from 7xxx series are very important in transportation industry. In this work, a f... more Aluminum alloys from 7xxx series are very important in transportation industry. In this work, a fractographic analysis in a welded structure made from AA7020-T6 was performed. The samples were extracted from the fractured surface and the chemical composition was measured using optical emission and energy dispersive spectrometry. The results showed porosity and liquation hot-cracking in the welds and cracks growing through these zones. In base metal, the cracks propagated by stress corrosion cracking and fatigue.
In this work, two different tests were done to establish the effect of heating cycles by welding ... more In this work, two different tests were done to establish the effect of heating cycles by welding in an AA7020-T6 aluminum alloy welded with ER5087 and ER5356 electrodes. During 10 months, welds were done to simulate in the laboratory several welding repairs (up to six repairs). Tensile and hardness measurements were done to evaluate the evolution of the properties against time. It was found that a single pass is enough to generate a heat-affected zone (HAZ) of 30 mm, and after four repairs the width of the HAZ exceeds 210 mm. In the HAZ, two regions were observed: the dissolution zone, which recovers a percentage of hardness by natural aging, and the over-aging zone, showing no increase in hardness. The results indicate that there is a maximum number of welding repairs that can be performed in a heat-treatable aluminum superstructure before it fails on the HAZ of the base material, since the tensile strength is reduced around 40 pct compared to the base metal.
Advances in Experimental Medicine and Biology, 2012
Lipopolysaccharide (LPS) administered I.P. increases significantly the activation of c-Fos in neu... more Lipopolysaccharide (LPS) administered I.P. increases significantly the activation of c-Fos in neurons of the nucleus of the solitary tract (NTS), which in turn activates hypothalamus-pituitary-adrenal axis. The vagus nerve appears to play a role in conveying cytokines signals to the central nervous system (CNS), since -in rodent models of sepsis- bilateral vagotomy abolishes increases in plasmatic glucocorticoid levels, but does not suppress c-Fos NTS activation. Considering that NTS also receives sensory inputs from carotid body chemoreceptors, we evaluated c-Fos activation and plasmatic cortisol levels 90 min after I.P. administration of 15 mg/kg LPS. Experiments were performed in male Sprague-Dawley rats, in control conditions and after bilateral carotid neurotomy (BCN). LPS administration significantly increases the number of c-Fos positive NTS neurons and plasmatic cortisol levels in animals with intact carotid/sinus nerves. When LPS was injected after BCN, the number of c-Fos positive NTS neurons, and plasmatic cortisol levels were not significantly modified. Our data suggest that carotid body chemoreceptors might mediate CNS activation during sepsis.
In the last years, the aquaculture crops have experienced an explosive and intensive growth, beca... more In the last years, the aquaculture crops have experienced an explosive and intensive growth, because of the high demand for protein. This growth has increased fish susceptibility to diseases and subsequent death. The constant biotic and abiotic changes experienced by fish species in culture are challenges that induce physiological, endocrine and immunological responses. These changes mitigate stress effects at the cellular level to maintain homeostasis. The effects of stress on the immune system have been studied for many years. While acute stress can have beneficial effects, chronic stress inhibits the immune response in mammals and teleost fish. In response to stress, a signaling cascade is triggered by the activation of neural circuits in the central nervous system because the hypothalamus is the central modulator of stress. This leads to the production of catecholamines, corticosteroid-releasing hormone, adrenocorticotropic hormone and glucocorticoids, which are the essential neuroendocrine mediators for this activation. Because stress situations are energetically demanding, the neuroendocrine signals are involved in metabolic support and will suppress the "less important" immune function. Understanding the cellular mechanisms of the neuroendocrine regulation of immunity in fish will allow the development of new pharmaceutical strategies and therapeutics for the prevention and treatment of diseases triggered by stress at all stages of fish cultures for commercial production.
Sepsis progresses to multiple organ dysfunction (MOD) due to the uncontrolled release of inflamma... more Sepsis progresses to multiple organ dysfunction (MOD) due to the uncontrolled release of inflammatory mediators. Carotid chemo/baro-receptors could play a protective role during sepsis. In anesthetized male rats, we measured cardiorespiratory variables and plasma TNF-α, glucocorticoids, epinephrine, and MOD marker levels 90 min after lipopolysaccharide (LPS) administration in control (SHAM surgery) and bilateral carotid chemo/ baro-denervated (BCN) rats. BCN prior to LPS blunted the tachypneic response and enhanced tachycardia and hypotension. BCN-LPS rats also showed blunted plasma glucocorticoid responses, boosted epinephrine and TNF-α responses, and earlier MOD onset with a lower survival time compared with SHAM-LPS rats. Consequently, the complete absence of carotid chemo/baro-sensory function modified the neural, endocrine and inflammatory responses to sepsis. Thus, carotid chemo/baro-receptors play a protective role in sepsis.
In addition to their role in cardiorespiratory regulation, carotid body (CB) chemoreceptors serve... more In addition to their role in cardiorespiratory regulation, carotid body (CB) chemoreceptors serve as sensors for inflammatory status and as a protective factor during sepsis. However, lipopolysaccharide-induced sepsis (LPS) reduces CB responsiveness to excitatory or depressant stimuli. We tested whether LPS exerts a direct effect on the carotid chemoreceptor pathway, the CB and its sensory ganglion. We determined that the rat CB and nodose-petrosal-jugular ganglion complex (NPJgc) express TLR4, TNF-␣ and its receptors (TNF-R1 and TNF-R2). LPS administration (15 mg/kg intraperitoneally) evoked MyD88-mechanism pathway activation in CB and NPJgc, with NF-B p65, p38 MAPK, and ERK activation. Consistently, LPS increased TNF-␣ and TNF-R2. Double-labeling studies showed that the aforementioned pathway occurs in TH-containing glomus cells and NPJgc neurons, components of the chemosensitive neural pathway. Thus, our results suggest that LPS acting directly through TLR4/MyD88-mechanism pathways increases TNF-␣ and TNF-R2 expression in the carotid chemoreceptor pathway. These results show a novel afferent pathway to the central nervous system during endotoxemia, and could be relevant in understanding sepsis pathophysiology and therapy.
In the absence of information on functional manifestations of carotid body (CB) inflammation, we ... more In the absence of information on functional manifestations of carotid body (CB) inflammation, we studied an experimental model in which lipopolysaccharide (LPS) administration to pentobarbitone-anaesthetized cats was performed by topical application upon the CB surface or by intravenous infusion (endotoxaemia). The latter caused: (i) disorganization of CB glomoids, increased connective tissue, and rapid recruitment of polymorphonuclear cells into the vascular bed and parenchyma within 4 h; (ii) increased respiratory frequency and diminished ventilatory chemoreflex responses to brief hypoxia (breathing 100% N(2) for 10 s) and diminished ventilatory chemosensory drive (assessed by 100% O(2) tests) during normoxia and hypoxia; (iii) tachycardia, increased haematocrit and systemic hypotension in response to LPS i.v.; and (iv) increased basal frequency of carotid chemosensory discharges during normoxia, but no change in maximal chemoreceptor responses to brief hypoxic exposures. Lipopolysaccharide-induced tachypnoea was prevented by prior bilateral carotid neurotomy. Apoptosis was not observed in CBs from cats subjected to endotoxaemia. Searching for pro-inflammatory mediators, tumour necrosis factor-alpha (TNF-alpha) was localized by immunohistochemistry in glomus and endothelial cells; reverse transcriptase-polymerase chain reaction revealed that the CB expresses the mRNAs for both type-1 (TNF-R1) and type-2 TNF-alpha receptors (TNF-R2); Western blot confirmed a band of the size expected for TNF-R1; and histochemistry showed the presence of TNF-R1 in glomus cells and of TNF-R2 in endothelial cells. Experiments in vitro showed that the frequency of carotid nerve discharges recorded from CBs perfused and superfused under normoxic conditions was not significantly modified by TNF-alpha, but that the enhanced frequency of chemosensory discharges recorded along responses to hypoxic stimulation was transiently diminished in a dose-dependent manner by TNF-alpha injections. The results suggest that the CB may operate as a sensor for immune signals, that the CB exhibits histological features of acute inflammation induced by LPS, that TNF-alpha may participate in LPS-induced changes in chemosensory activity and that some pathophysiological reactions to high levels of LPS in the bloodstream may originate from changes in CB function.
This investigation examined the role of estrogen receptor (ER) on the stimulatory effect of estra... more This investigation examined the role of estrogen receptor (ER) on the stimulatory effect of estradiol (E 2) on protein phosphorylation in the oviduct as well as on E 2-induced acceleration of oviductal oocyte transport in cyclic rats. Estrous rats were injected with E 2 s.c. and with the ER antagonist ICI 182 780 intrabursally (i.b.), and 6 h later, oviducts were excised and protein phosphorylation was determined by Western blot analysis. ICI 182 780 inhibited the E 2-induced phosphorylation of some oviductal proteins. Other estrous rats were treated with E 2 s.c. and ICI 182 780 i.b. The number of eggs in the oviduct, assessed 24 h later, showed that ICI 182 780 blocked the E 2-induced egg transport acceleration. The possible involvement of adenylyl cyclase, protein kinase A (PK-A), protein kinase C (PK-C), or tyrosine kinases on egg transport acceleration induced by E 2 was then examined. Selective inhibitors of adenylyl cyclase or PK-A inhibited the E 2-induced egg transport acceleration, whereas PK-C or tyrosine kinase inhibitors had no effect. Furthermore, forskolin, an adenylyl cyclase activator, mimicked the effect of E 2 on ovum transport and E 2 increased the level of cAMP in the oviduct of cycling rats. Finally, we measured PK-A activity in vitro in the presence of E 2 or E 2-ER complex. Activity of PK-A in the presence of E 2 or E 2-ER was similar to PK-A alone, showing that E 2 or E 2-ER did not directly activate PK-A. We conclude that the nongenomic pathway by which E 2 accelerates oviductal egg transport in the rat requires absolute participation of ER and cAMP and partial participation of PK-A signaling pathways in the oviduct. cyclic adenosine monophosphate, estradiol, estradiol receptor, oviduct, ovum pick-up/transport 1 This work received financial support from grants FONDECYT 2990007 and 8980008, Rockefeller Foundation (RF 98024, 98), Cátedra Presidencial en Ciencias H Croxatto, and MIFAB (Millennium Institute for Fundamental and Applied Biology).
The aim of this study was to assess the participation of carbohydrate residues in the adhesion of... more The aim of this study was to assess the participation of carbohydrate residues in the adhesion of spermatozoa to the oviductal epithelium in the rat. We first examined, by lectin labeling, the distribution of glycoconjugates in rat oviducts obtained under various hormonal environments. Several classes of glycoconjugates were abundant in the epithelium, and the expression of some of these molecules varied differentially in ampulla and isthmus, along the estrous cycle and with estradiol and progesterone treatment. Proestrous rats were intraoviductally injected with lectins Dolichos biflorus, Erythrina cristagalli, Helix pomatia, Arachis hypogea, Ulex europaeus I, Triticum vulgaris, or Tritrichomonas mobilensis and were inseminated with 10-20 million epididymal spermatozoa in each uterine horn. Three hours later, the total number of spermatozoa present in the oviduct and the proportion adhering to the epithelium were determined. Intraoviductal administration of lectins did not affect the total number of spermatozoa recovered from the oviduct and only the sialic acid-binding lectin TML decreased the percentage of sperm cells adhering to the epithelium. The involvement of sialic acid in sperm-oviduct adhesion was further explored, inseminating spermatozoa preincubated with mannose, galactose, sialic acid, fucose, fetuin, or asialofetuin. Sialic acid and fetuin inhibited sperm-oviduct binding while other carbohydrates had no effect. Using TML lectin immunohistochemistry, we found that sialic acid-rich glycoconjugates are equally localized in the epithelium of ampulla and isthmus of proestrous rats. The electrophoretic pattern of sialic acid-rich glycoproteins of the epithelium showed 15 major protein bands, for which molecular mass ranged from 200 to 50 kDa with no difference between ampulla and isthmus or between estrous cycle stages. Binding sites for sialic acid-fluorescein isothiocyanate were demonstrated on the surface of rat spermatozoa, and biotinylated sialic acid recognized 11 plasma membrane proteins of sperm cells. These groups of sialic acid-rich glycoproteins in the oviductal epithelium and of sialic acid-binding proteins in the plasma membrane of sperm cells are good candidates for further studies to characterize the molecules responsible for sperm binding. We con-1
High strength 7xxx aluminum alloy series, used in transport industry, are commonly welded with 5x... more High strength 7xxx aluminum alloy series, used in transport industry, are commonly welded with 5xxx filler metal alloys to produce joins with acceptable chemical properties. It was studied the weldability of ER5087 and ER5356 filler metals welded on a high strength AA7020-T6 base metal aluminum alloy using Houldcroft and Battelle weldability tests in order to determine solidification cracking susceptibility. Tests were made using full penetration bead on plate welds with manual GTA welding process. The crack surfaces were observed using Scanning Electron Microscopy (SEM). The results show that solidification cracking susceptibility of both materials is very similar, but ER5356 filler metal exhibit less variability in crack length compared to ER5087 filler metal. Fracture surfaces in both materials revealed a dendritic morphology of the solidifying weld metal.
Aluminum alloys from 7xxx series are very important in transportation industry. In this work, a f... more Aluminum alloys from 7xxx series are very important in transportation industry. In this work, a fractographic analysis in a welded structure made from AA7020-T6 was performed. The samples were extracted from the fractured surface and the chemical composition was measured using optical emission and energy dispersive spectrometry. The results showed porosity and liquation hot-cracking in the welds and cracks growing through these zones. In base metal, the cracks propagated by stress corrosion cracking and fatigue.
In this work, two different tests were done to establish the effect of heating cycles by welding ... more In this work, two different tests were done to establish the effect of heating cycles by welding in an AA7020-T6 aluminum alloy welded with ER5087 and ER5356 electrodes. During 10 months, welds were done to simulate in the laboratory several welding repairs (up to six repairs). Tensile and hardness measurements were done to evaluate the evolution of the properties against time. It was found that a single pass is enough to generate a heat-affected zone (HAZ) of 30 mm, and after four repairs the width of the HAZ exceeds 210 mm. In the HAZ, two regions were observed: the dissolution zone, which recovers a percentage of hardness by natural aging, and the over-aging zone, showing no increase in hardness. The results indicate that there is a maximum number of welding repairs that can be performed in a heat-treatable aluminum superstructure before it fails on the HAZ of the base material, since the tensile strength is reduced around 40 pct compared to the base metal.
Advances in Experimental Medicine and Biology, 2012
Lipopolysaccharide (LPS) administered I.P. increases significantly the activation of c-Fos in neu... more Lipopolysaccharide (LPS) administered I.P. increases significantly the activation of c-Fos in neurons of the nucleus of the solitary tract (NTS), which in turn activates hypothalamus-pituitary-adrenal axis. The vagus nerve appears to play a role in conveying cytokines signals to the central nervous system (CNS), since -in rodent models of sepsis- bilateral vagotomy abolishes increases in plasmatic glucocorticoid levels, but does not suppress c-Fos NTS activation. Considering that NTS also receives sensory inputs from carotid body chemoreceptors, we evaluated c-Fos activation and plasmatic cortisol levels 90 min after I.P. administration of 15 mg/kg LPS. Experiments were performed in male Sprague-Dawley rats, in control conditions and after bilateral carotid neurotomy (BCN). LPS administration significantly increases the number of c-Fos positive NTS neurons and plasmatic cortisol levels in animals with intact carotid/sinus nerves. When LPS was injected after BCN, the number of c-Fos positive NTS neurons, and plasmatic cortisol levels were not significantly modified. Our data suggest that carotid body chemoreceptors might mediate CNS activation during sepsis.
In the last years, the aquaculture crops have experienced an explosive and intensive growth, beca... more In the last years, the aquaculture crops have experienced an explosive and intensive growth, because of the high demand for protein. This growth has increased fish susceptibility to diseases and subsequent death. The constant biotic and abiotic changes experienced by fish species in culture are challenges that induce physiological, endocrine and immunological responses. These changes mitigate stress effects at the cellular level to maintain homeostasis. The effects of stress on the immune system have been studied for many years. While acute stress can have beneficial effects, chronic stress inhibits the immune response in mammals and teleost fish. In response to stress, a signaling cascade is triggered by the activation of neural circuits in the central nervous system because the hypothalamus is the central modulator of stress. This leads to the production of catecholamines, corticosteroid-releasing hormone, adrenocorticotropic hormone and glucocorticoids, which are the essential neuroendocrine mediators for this activation. Because stress situations are energetically demanding, the neuroendocrine signals are involved in metabolic support and will suppress the "less important" immune function. Understanding the cellular mechanisms of the neuroendocrine regulation of immunity in fish will allow the development of new pharmaceutical strategies and therapeutics for the prevention and treatment of diseases triggered by stress at all stages of fish cultures for commercial production.
Sepsis progresses to multiple organ dysfunction (MOD) due to the uncontrolled release of inflamma... more Sepsis progresses to multiple organ dysfunction (MOD) due to the uncontrolled release of inflammatory mediators. Carotid chemo/baro-receptors could play a protective role during sepsis. In anesthetized male rats, we measured cardiorespiratory variables and plasma TNF-α, glucocorticoids, epinephrine, and MOD marker levels 90 min after lipopolysaccharide (LPS) administration in control (SHAM surgery) and bilateral carotid chemo/ baro-denervated (BCN) rats. BCN prior to LPS blunted the tachypneic response and enhanced tachycardia and hypotension. BCN-LPS rats also showed blunted plasma glucocorticoid responses, boosted epinephrine and TNF-α responses, and earlier MOD onset with a lower survival time compared with SHAM-LPS rats. Consequently, the complete absence of carotid chemo/baro-sensory function modified the neural, endocrine and inflammatory responses to sepsis. Thus, carotid chemo/baro-receptors play a protective role in sepsis.
In addition to their role in cardiorespiratory regulation, carotid body (CB) chemoreceptors serve... more In addition to their role in cardiorespiratory regulation, carotid body (CB) chemoreceptors serve as sensors for inflammatory status and as a protective factor during sepsis. However, lipopolysaccharide-induced sepsis (LPS) reduces CB responsiveness to excitatory or depressant stimuli. We tested whether LPS exerts a direct effect on the carotid chemoreceptor pathway, the CB and its sensory ganglion. We determined that the rat CB and nodose-petrosal-jugular ganglion complex (NPJgc) express TLR4, TNF-␣ and its receptors (TNF-R1 and TNF-R2). LPS administration (15 mg/kg intraperitoneally) evoked MyD88-mechanism pathway activation in CB and NPJgc, with NF-B p65, p38 MAPK, and ERK activation. Consistently, LPS increased TNF-␣ and TNF-R2. Double-labeling studies showed that the aforementioned pathway occurs in TH-containing glomus cells and NPJgc neurons, components of the chemosensitive neural pathway. Thus, our results suggest that LPS acting directly through TLR4/MyD88-mechanism pathways increases TNF-␣ and TNF-R2 expression in the carotid chemoreceptor pathway. These results show a novel afferent pathway to the central nervous system during endotoxemia, and could be relevant in understanding sepsis pathophysiology and therapy.
In the absence of information on functional manifestations of carotid body (CB) inflammation, we ... more In the absence of information on functional manifestations of carotid body (CB) inflammation, we studied an experimental model in which lipopolysaccharide (LPS) administration to pentobarbitone-anaesthetized cats was performed by topical application upon the CB surface or by intravenous infusion (endotoxaemia). The latter caused: (i) disorganization of CB glomoids, increased connective tissue, and rapid recruitment of polymorphonuclear cells into the vascular bed and parenchyma within 4 h; (ii) increased respiratory frequency and diminished ventilatory chemoreflex responses to brief hypoxia (breathing 100% N(2) for 10 s) and diminished ventilatory chemosensory drive (assessed by 100% O(2) tests) during normoxia and hypoxia; (iii) tachycardia, increased haematocrit and systemic hypotension in response to LPS i.v.; and (iv) increased basal frequency of carotid chemosensory discharges during normoxia, but no change in maximal chemoreceptor responses to brief hypoxic exposures. Lipopolysaccharide-induced tachypnoea was prevented by prior bilateral carotid neurotomy. Apoptosis was not observed in CBs from cats subjected to endotoxaemia. Searching for pro-inflammatory mediators, tumour necrosis factor-alpha (TNF-alpha) was localized by immunohistochemistry in glomus and endothelial cells; reverse transcriptase-polymerase chain reaction revealed that the CB expresses the mRNAs for both type-1 (TNF-R1) and type-2 TNF-alpha receptors (TNF-R2); Western blot confirmed a band of the size expected for TNF-R1; and histochemistry showed the presence of TNF-R1 in glomus cells and of TNF-R2 in endothelial cells. Experiments in vitro showed that the frequency of carotid nerve discharges recorded from CBs perfused and superfused under normoxic conditions was not significantly modified by TNF-alpha, but that the enhanced frequency of chemosensory discharges recorded along responses to hypoxic stimulation was transiently diminished in a dose-dependent manner by TNF-alpha injections. The results suggest that the CB may operate as a sensor for immune signals, that the CB exhibits histological features of acute inflammation induced by LPS, that TNF-alpha may participate in LPS-induced changes in chemosensory activity and that some pathophysiological reactions to high levels of LPS in the bloodstream may originate from changes in CB function.
This investigation examined the role of estrogen receptor (ER) on the stimulatory effect of estra... more This investigation examined the role of estrogen receptor (ER) on the stimulatory effect of estradiol (E 2) on protein phosphorylation in the oviduct as well as on E 2-induced acceleration of oviductal oocyte transport in cyclic rats. Estrous rats were injected with E 2 s.c. and with the ER antagonist ICI 182 780 intrabursally (i.b.), and 6 h later, oviducts were excised and protein phosphorylation was determined by Western blot analysis. ICI 182 780 inhibited the E 2-induced phosphorylation of some oviductal proteins. Other estrous rats were treated with E 2 s.c. and ICI 182 780 i.b. The number of eggs in the oviduct, assessed 24 h later, showed that ICI 182 780 blocked the E 2-induced egg transport acceleration. The possible involvement of adenylyl cyclase, protein kinase A (PK-A), protein kinase C (PK-C), or tyrosine kinases on egg transport acceleration induced by E 2 was then examined. Selective inhibitors of adenylyl cyclase or PK-A inhibited the E 2-induced egg transport acceleration, whereas PK-C or tyrosine kinase inhibitors had no effect. Furthermore, forskolin, an adenylyl cyclase activator, mimicked the effect of E 2 on ovum transport and E 2 increased the level of cAMP in the oviduct of cycling rats. Finally, we measured PK-A activity in vitro in the presence of E 2 or E 2-ER complex. Activity of PK-A in the presence of E 2 or E 2-ER was similar to PK-A alone, showing that E 2 or E 2-ER did not directly activate PK-A. We conclude that the nongenomic pathway by which E 2 accelerates oviductal egg transport in the rat requires absolute participation of ER and cAMP and partial participation of PK-A signaling pathways in the oviduct. cyclic adenosine monophosphate, estradiol, estradiol receptor, oviduct, ovum pick-up/transport 1 This work received financial support from grants FONDECYT 2990007 and 8980008, Rockefeller Foundation (RF 98024, 98), Cátedra Presidencial en Ciencias H Croxatto, and MIFAB (Millennium Institute for Fundamental and Applied Biology).
The aim of this study was to assess the participation of carbohydrate residues in the adhesion of... more The aim of this study was to assess the participation of carbohydrate residues in the adhesion of spermatozoa to the oviductal epithelium in the rat. We first examined, by lectin labeling, the distribution of glycoconjugates in rat oviducts obtained under various hormonal environments. Several classes of glycoconjugates were abundant in the epithelium, and the expression of some of these molecules varied differentially in ampulla and isthmus, along the estrous cycle and with estradiol and progesterone treatment. Proestrous rats were intraoviductally injected with lectins Dolichos biflorus, Erythrina cristagalli, Helix pomatia, Arachis hypogea, Ulex europaeus I, Triticum vulgaris, or Tritrichomonas mobilensis and were inseminated with 10-20 million epididymal spermatozoa in each uterine horn. Three hours later, the total number of spermatozoa present in the oviduct and the proportion adhering to the epithelium were determined. Intraoviductal administration of lectins did not affect the total number of spermatozoa recovered from the oviduct and only the sialic acid-binding lectin TML decreased the percentage of sperm cells adhering to the epithelium. The involvement of sialic acid in sperm-oviduct adhesion was further explored, inseminating spermatozoa preincubated with mannose, galactose, sialic acid, fucose, fetuin, or asialofetuin. Sialic acid and fetuin inhibited sperm-oviduct binding while other carbohydrates had no effect. Using TML lectin immunohistochemistry, we found that sialic acid-rich glycoconjugates are equally localized in the epithelium of ampulla and isthmus of proestrous rats. The electrophoretic pattern of sialic acid-rich glycoproteins of the epithelium showed 15 major protein bands, for which molecular mass ranged from 200 to 50 kDa with no difference between ampulla and isthmus or between estrous cycle stages. Binding sites for sialic acid-fluorescein isothiocyanate were demonstrated on the surface of rat spermatozoa, and biotinylated sialic acid recognized 11 plasma membrane proteins of sperm cells. These groups of sialic acid-rich glycoproteins in the oviductal epithelium and of sialic acid-binding proteins in the plasma membrane of sperm cells are good candidates for further studies to characterize the molecules responsible for sperm binding. We con-1
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