An ultrastructural study of spermatogenesis and sperm morula breakdown inArenicola marina (L.) (Annelida: Polychaeta)

Spermatogenesis in the lugwormArenicola marina, in common with other members of Arenicolidae, occurs in the coelomic fluid and results in the formation of discs of mature spermatozoa known as a morulae. Within a morula, individual spermatozoa are connected by a common mass of cytoplasm called the cytophore and therefore make up a syncitium. Immediately prior to spawning, and in response to an endocrine substance known as “Sperm Maturation Factor” (SMF), the structure of the sperm morulae breaks down and free spermatozoa are liberated. These are subsequently spawned from the body cavity. The investigation described here uses transmission electron microscopy to investigate the ultrastructural changes, which accompany spermatogenesis and the breakdown of sperm morulae in response to SMF in vitro. The study demonstrates that the cytophore appears to have a key role both during spermatogenesis and during sperm morula breakdown. The ultrastructure of sperm morulae and of mature spermatozoa is described. The structure of spermatozoa is shown to be primitive with a single flagellum which appears to be coiled at its distal end. The phagocytosis of free spermatozoa by coelomocytes is also described and it is suggested that these may play a role in the resorption of unspawned gametes in vivo.     

The phylogenetic relationships of the bilby, Macrotis lagotis (Peramelimorphia: Thylacomyidae), to the bandicoots- DNA sequence evidence

Partial sequencing of the 12S ribosomal RNA gene was used to test two competing hypotheses concerning the phylogenetic relationship of the bilby (Macrotis lagotis) to the Australian and New Guinean species of bandicoot. The first hypothesis proposes that the Australian and New Guinean bandicoots are in a monophyletic clade to the exclusion of the bilbies, whereas the second hypothesis proposes that the bilby is monophyletic with the Australian bandicoots to the exclusion of the New Guinean bandicoots. Phylogenies determined by both maximum-likelihood and neighbour-joining approaches supported the first hypothesis in which the bilby is excluded from the clade represented by the Australian and New Guinean bandicoots. Monophyly of the Australian and New Guinean bandicoots is consistent with the biogeographical scenario in which Australia and Papua New Guinea have undergone repeated connection and disconnection over the last 20 million years.     

Fine needle aspiration cytology of granulomatous mastitis. Report of a case and review of the literature

A case of granulomatous mastitis diagnosed by fine needle aspiration (FNA) cytology alone is reported. A 24-year-old pregnant woman presented with a six-week history of a rapidly enlarging breast mass, considered clinically to be malignant. The FNA smears contained numerous aggregates of epithelioid histiocytes admixed with Langhans' and foreign-body giant cells, lymphocytes, neutrophilic leukocytes and apoptotic debris, leading to a diagnosis of granulomatous mastitis. The features of granulomatous mastitis and its differential diagnoses are discussed.     

基于PBL模式的生物化学教学探索

目的:评价PBL教学模式在生物化学中应用的教学效果,对生物化学理论教学的方式进行探讨。方法:用PBL模式进行教学,采用理论考试的形式对教学效果进行评价。结果:PBL教学组的学生在学习态度和积极性等方面好于传统教学组;在考试成绩方面PBL教学组病例分析考试成绩好于传统教学组,而基础知识考试成绩没有差别。结论:PBL模式能提高学生的分析问题和解决问题的综合应用能力,而基础知识的掌握程度与传统教学相比没有区别。     

Relationship between the fertile period and sperm transport in the bitch

Following ejaculation into the vagina, dog sperm remain functionally competent for many days, acquire the ability to fertilize, and are delivered to an appropriate site within the uterine tube synchronously with the appearance of fertile oocytes. The mechanisms involved in regulating this system are complex, and allow for sperm storage within the female reproductive tract. The aim of this paper is to review current knowledge of the transportation of sperm and their biology within the reproductive tract of the bitch.     

The cytologic diagnosis of adenocarcinoma in situ of the cervix uteri and related lesions. III. Pitfalls in diagnosis

Potential pitfalls in the cytologic diagnosis of adenocarcinoma in situ (AIS) of the cervix are illustrated by the presentation of three cases of benign cervical lesions initially diagnosed as AIS: cervical endometriosis, tubal metaplasia of the endocervix and changes due to a previous biopsy. The differential diagnosis of endocervical glandular abnormalities is discussed.     

Nuclear division in the cyst,and white spot nuclei preceding cyst formation,inAcetabularia wettsteinii

Summary Electron microscopy of nuclear division in young cysts ofAcetabularia wettsteinii shows that the dividing nucleus hat two additional cisternae of endoplasmic reticulum immediately outside the nuclear envelope. These additional cisternae are attached to, and apparently formed from a membrane body which develops outside the nucleus in early prophase. The interphase nucleus does not have the additional cisternae. The nucleoli are extruded from the nucleus at anaphase, the nucleolar bodies remaining in the peri-nuclear cytoplasm. The chromosomes have localized centromeres; the stratified ultrastructure characteristic of some chlorophycean and animal kinetochores has not been found inAcetabularia, although the kinetochore appears distinct, projecting from the chromatid, and has attached microtubules. The condensed bodies of the white spot nucleus are discussed.     

The evolutionary ecology of pre- and post-meiotic sperm senescence

Male reproductive success is an extremely variable fitness component. Understanding the maintenance of this variation is a key challenge in evolutionary biology. An often neglected source of variation in male reproductive success is determined by age-dependent patterns of decline in sperm fitness. Two pathways mediate sperm senescence: pre-meiotic senescence of somatic and germ cells of the ageing male, and post-meiotic ageing of the spermatozoon. Recently, theoretical and empirical studies have highlighted wide-ranging implications of both pathways. We clarify different mechanisms of sperm senescence, outlining their distinct evolutionary implications for the male, the female and the zygote, and their influence on fundamental evolutionary processes, including the evolution of anisogamy, sexual conflict, sexual selection, and applied issues such as assisted conception.     

Contact of dog spermatozoa with homologous uterine tube epithelium prolongs flagellar activity in relation to the stage of the estrous cycle

There is scant information about the storage of spermatozoa within the reproductive tract of the bitch. In several species the uterine tube plays a significant role in sperm storage. The present study was performed to investigate the interaction between spermatozoa and the epithelium of the uterine tube, in particular how this interaction might influence the flagellar activity of spermatozoa in relation to the stage of the estrous cycle. Epithelium was harvested from uterine tubes of 24 bitches at various stages of the estrous cycle (estrus, luteal phase or anestrus), and cultured with pooled spermatozoa collected from 6 dogs. Spermatozoa rapidly bound to the epithelial surface by their heads and the majority of attached spermatozoa were motile. The intimate association between spermatozoa and the uterine tube epithelium maintained motility in a manner that was related to the stage of the estrous cycle. Flagellar activity was significantly greater for spermatozoa bound to estrous epithelium than epithelium from the luteal phase or anestrus. On average, approximately 10% of spermatozoa that were attached to the uterine tube epithelium of estrous bitches retained their flagellar activity for 48 h after innoculation. There was no apparent influence of the region of the uterine tube on this effect. These findings suggest that the uterine tube may form a functional spermatozoal reservoir in the bitch.     

Avermectins and flea control: structure-activity relationships and the selection of selamectin for development as an endectocide for companion animals

Evaluation of a wide range of avermectin derivatives for flea activity in an in vitro feeding screen using the cat flea, Ctenocephalides felis, revealed a narrow structure-activity relationship (SAR) with activity surprisingly associated with monosaccharides and especially their C-5-oximes. We discovered commercially exploitable flea activity in a single compound, selamectin 33, which also possessed the necessary antiparasitic spectrum and margin of safety for development as a broad-spectrum companion animal endectocide.