Lectin binding sites on head structures of the spermatid and spermatozoon of the mosquito Culex quinquefasciatus (Diptera, Culicidae)

Sperm structure of Limoniidae and their phylogenetic relationship with Tipulidae (Diptera, Nematocera)

The sperm ultrastructure of a few species of Limoniidae (Limonia nigropunctata; L. nubeculosa; Chionea n. sp.; C. alpina; C. lutescens) was studied. The two species of Limonia have a monolayered acrosome with crystallized material, a three-lobed nucleus in cross section, a ring of centriole adjunct material and a flagellum which consists of a 9+9+1 axoneme and a single mitochondrial derivative. The central axonemal tubule is provided with 15 protofilaments in its tubular wall, while the accessory tubules have 13 protofilaments and are flanked by the electron-dense intertubular material. The three species of Chionea share a monolayered acrosome, a nucleus with two longitudinal grooves, a centriole adjunct material which surrounds the centriole and the initial part of the axoneme. The axoneme is of conventional type, with 9+9+2 microtubular pattern, with accessory tubules provided with 13 protofilaments and intertubular material. However, in C. lutescens the accessory tubules start with 15 protofilaments and transform into a tubule with 13 protofilaments. These data are discussed in the light of the phylogenetic relationship between Limoniidae and Tipulidae. For this purpose, the sperm ultrastructure of Nephrotoma appendiculata was also considered comparatively.

Nuclear changes and acrosome formation during spermiogenesis in Euchistus heros (Hemiptera: Pentatomidae)

Ultrastructural and cytochemical studies were carried out on nuclear changes and acrosome formation during the spermiogenesis of the phytophagous bug Euchistus heros. The development of the nucleus involves changes in the shape and in degree of chromatin condensation: initially it is dispersed and with a low-electron density, then assumes a fibrillar arrangement and finally compacts in an electron-dense material. The acrosome is formed by the Golgi complex and presents unusual morphological features during its development. The reaction product of acid phosphatase, glucose-6-phosphatase and thiamine pyrophosphatase activities were detected during various stages of acrosome development. In contrast, residues of alpha-N-acetylgalactosamine and basic proteins were only reported in the intermediate and late stages of the differentiation process, respectively.

Glycoconjugates of the surface of the spermatozoa of Drosophila melanogaster: a qualitative and quantitative study

The important roles played by glycoconjugates in the recognition of gametes and in fertilization are well documented. In the present study, the nature and distribution of carbohydrate residues of the plasma membrane of spermatozoa of Drosophila melanogaster were characterized by use of FITC-conjugated lectins as probes. The plasma membrane bound agglutinins from Concanavalia ensiformis (Con A) and Pisum sativum (PSA), native and succinylated agglutinins from wheat germ (WGA and s-WGA), the A4 isoform of agglutinin-I from Griffonia simplicifolia (GSA-I A4), and, to a lesser extent, the lectins from Dolichus biflorus (DBA), lotus tetragonolobus (LTA), and Glycine maximus (SBA). Each lectin gave a specific pattern of binding. The extent of binding of Con A, WGA, s-WGA, and GSA-I A4 over the acrosomal region was greater than over nonacrosomal regions, indicating the concentration of alpha-mannose/alpha-glucose, beta-N-acetylglucosamine, and alpha-N-acetylgalactosamine residues in this area of the plasma membrane. The surface of the sperm failed to react with lectins from Ricinus communis (RCA-I), Limulus polyphemus (LPA), and Limax flavus (LFA) and with the B4 isoform of agglutinin-I from Griffonia simplicifolia-I (GSA-I B4). The plasma membrane over the nucleus did not react with any of the lectins tested. Quantitative analysis of binding of Con A, s-WGA, and GSA-I A4 to spermatozoa showed that only Con A bound consistently to the sperm surface, showing high affinity for the acrosomal area of the plasma membrane. The other lectins tested bound only to limited and variably sized fractions of the total population of sperm.(ABSTRACT TRUNCATED AT 250 WORDS)

ConA-binding proteins of the sperm surface are conserved through evolution and in sperm maturation

Lectin-binding glycoconjugates present on the surface of spermatozoa are believed to play a crucial role in sperm maturation, capacitation, acrosome reaction, or sperm-egg interaction. We have studied ConA-binding surface proteins on spermatozoa from different mammalian species. First, ConA-binding proteins were isolated from boar spermatozoa by affinity chromatography. ConA-binding ability was confirmed by Enzyme-linked Lectin assay (ELLA). Monoclonal (MAb436/10) and polyclonal antibodies were raised against chromatography fractions containing purified ConA-binding proteins of boar spermatozoa. MAb436/10 (IgG2a) recognizes a 40 kD ConA-binding antigen. Indirect immunofluorescence on fixed and unfixed boar spermatozoa with MAb436/10 indicated a plasma membrane localization of antigen 436/10 in the acrosomal macrodomain. Interspecies cross-reactivity with MAb436/10 was found by whole cell ELISA and immunocytochemistry. MAb436/10 cross-reacted with human, horse, guinea-pig, bull, and ram spermatozoa in both assays. Expression of ConA-binding antigen 436/10 on guinea pig sperm surface was detectable during spermiogenesis and in early stages of sperm maturation. Change of regionalization of the antigen did not occur during the epididymal passage. ConA-binding antigen 436/10 was also detectable in testis and caudal segments of the epididymis. These findings suggest that ConA-binding proteins located in the acrosomal region are highly conserved through evolution as well as in sperm maturation indicating an important role for the physiology of spermatozoa.