The fine structure of the fertilization membrane of the feather star Comanthus japonica (Echinodermata: Crinoidea)

Scanning electron microscopy reveals that the outer surface of the Comanthus fertilization membrane bears a network of 14 µ high ridges outlining rows of polygonal facets; however, no spines are present. The so-called spines reported previously by light microscopists were simply optical cross sections of the ridges. Transmission electron microscopy reveals that the fertilization membrane has (1) an outer component consisting mainly of dense, granular material, and (2) an inner component consisting mainly of an interlacing network of 50 Å fibers of moderate electron density. Associated with the fibers of the inner component are dense granular rods and dense lentoid discs.     

Clonal diversity in human B cell lymphoma. I. Idiotypic and genetic analysis of lymphoma heterohybrids

Secretory heterohybrid clones from seven pristine human B cell lymphomas of diverse histologic types were established to investigate the question of tumor clonal diversity. We found that in six tumors, heterohybrid-derived Ig showed similar band patterns in IEF; families of anti-Id prepared from tumor Ig reacted uniformly with individual heterohybrids and original tumor; and the V gene loci displayed little variation on Southern analysis. In one patient who was followed with serial multiple site biopsies over a 14-mo period, clonal Id was preserved until the final stage of his disease, in spite of cytotoxic treatment. In a single follicular tumor (J.M.), each of the anti-Id reacted uniformly with the parent tumor and the individual heterohybrids, except that three of six clones failed to react with a single anti-Id family member. A Southern analysis of the VH gene locus revealed an identical gene rearrangement that was shared by the parent tumor and each heterohybrid. However, there was considerable heterogeneity of J.M. heterohybrid Ig in IEF gels, and we demonstrated the production of variant lambda L chains by the heterohybrid clones. One type of lambda L chain had a normal mobility in SDS-PAGE gels but larger lambda variants were produced by four of six heterohybrids. A Southern analysis of the VL gene displayed considerable variation in the type of lambda rearrangement present in the various heterohybrids, suggesting extensive diversity at the VL gene locus. In a second tumor (S.C.) that exhibited uniform anti-Id tumor reactivity we were also able to demonstrate the presence of a second minor tumor cell population (a biclonal tumor). Our data suggest that intraclonal VH variation may vary considerably with lymphoma subtype and mutagenic exposure and that an additional mechanism for generating spontaneous intraclonal heterogeneity is genetic variation at the VL locus.     

Beware the curriculum-reform troops

Questions of resource allocation can pose practical and ethical dilemmas for clinicians. In the Aristotelian conception of distributive justice, the unequal allocation of a scarce resource may be justified by morally relevant factors such as need or likelihood of benefit. Even using these criteria, it can be difficult to reconcile completing claims to determine which patients should be given priority. To what extent the physician''s fiduciary duty toward a patient should supersede the interests of other patients and society as a whole is also a matter of controversy. Although the courts have been reluctant to become involved in allocation decisions in health care, they expect physicians to show allegiance to their patients regardless of budgetary concerns. The allocation of resources on the basis of clinically irrelevant factors such as religion or sexual orientation is prohibited. Clear, fair and publicly acceptable institutional and professional policies can help to ensure that resource allocation decisions are transparent and defensible.     

Ultrastructure of dimorphic sperm and seminal receptacle in the hermaphrodites Barrimysia siphonosomae and Pseudopythina ochetostomae (Bivalvia, Galeommatoidea)

The intertidal Bivalvia Barrimysia siphonosomae (Montacutidae) and Pseudopythina ochetostomae (Kelliidae) live commensally with Siphonosoma cumanense (Sipuncula) and Ochetostoma erythrogrammon (Echiura), respectively. Both bivalves are hermaphrodites although males and females may occur. Paired, pouch-shaped seminal receptacles are located in the suprabranchial chamber near the genital opening of both species. The interior of the receptacles of sexually mature individuals contains numerous non-epithelial cells separated by narrow spaces that serve as a depot for sperm cells. Specimens of both species produce two sperm morphotypes. Euspermatozoa are oblong with elongate conical acrosomes, and a middlepiece consisting of about eight long mitochondria spirally arranged to form a sheath surrounding the basis of the flagellum. The paraspermatozoa are vermiform, about 4 µm broad and longer (up to 240 µm) in B. siphonosomae than in P. ochetostomae (ca 150 µm). The anterior, bullet-shaped, 4.5- or 3.0-µm-long acrosome is located above an elongate, 4- to 6-µm-long subcylindrical nucleus. Adjacent to the nucleus occurs a bundle of approximately 25 (B. siphonosomae) or ca 10 (P. ochetostomae) flagella. The cytoplasm of the sperm body contains spherical lipid droplets, glycogen deposits and numerous membrane-bound spindle- to rod-shaped electron-dense granules. It is presumed that both sperm types aggregate to form spermatozeugmata. The presence of a combination of almost identical and highly specialised euspermatozoa and paraspermatozoa in species of the two genera qualifies these structures as strong synapomorphies. Pseudopythina, as presently defined, is considered paraphyletic.     

Thompsonia dofleini,a colonial akentrogonid rhizocephalan with dimorphic,ova- or sperm-producing,externae (Crustacea,Cirripedia)

Summary Specimens of the blue swimming crab,Portunus pelagicus, are often infected with many thousands of externae ofThompsonia dofleini, all of which are connected through a common root system within the host crab. The species is unique in that the production of sperm cells takes place within the visceral mass of a small minority of the population of the externae. Spermatogonia are probably introduced by male cyprids into these externae when they are young, and they multiply and develop at the expense of the oocytes which rapidly disintegrate and ultimately disappear. It is assumed that the sperm cells are transferred to the ovary of the ordinary, egg-producing externae through the root system. Shortly after the eggs have been fertilized within the ovary they are transferred to the mantle cavity where they develop into cyprid larvae. The larvae become liberated when the externae drop off and the mantle wall disintegrates.Abbreviations used in the figures a annulus - an antennule - bm basal membrane around ovary - ce compound eye - cg cerebral ganglion - cr connecting root - cy cyprid larva(e) - c1 cuticle 1 - c2 cuticle 2 - do degenerating oocytes - e eggs in early division - ec embryonic cells - em embryos - en endocuticle of host - ep epidermis of host - ex exocuticle of host - hc hemocoelic cavity - m mantle - mc mantle cavity - mcy male cyprid - o ovary - oo oocyte - r rupture in wall of visceral mass - rs root system - sc scar - se spawned eggs - so spent ovary - sp spermatogonia - ss sperm and spermatids - st stalk - tc thickened cuticle of mantle cavity - th thorax - vm visceral mass - y yolk granules     

On three species and two new genera (Montacutella and Brachiomya) of galeommatoid bivalves from the irregular Sea Urchin Brissus latecarinatus with emphasis on their reproduction

Three species of galeommatoidean bivalves live commensally with Brissus latecarinatus (Echinoidea, Spatangoidea) near Phuket Marine Biological Center, Thailand. Scintillona brissae Morton and Scott (family Galeommatidae) and Montacutella echinophila gen. et sp. n. (family Montacutidae), live on the periproct, have very similar shells, but differ with regard to the number of demibranchs, occurrence of seminal receptacles, and sperm structure. Brachiomya stigmatica (Pilsbry) gen. n. (family Montacutidae), occupies the host's ambulacra. The external morphology and internal anatomy are described. Reproduction involves formation of dimorphic sperm enclosed in syncytial sperm packages produced in the testis and transferred to the gills of a sexual partner. On account of the structure of the animal, the shell hinge, and the sperm, B. stigmatica is transferred from the Galeommatidae to the Montacutidae.     

Carbon-specific phytoplankton growth rates: a comparison of methods

Measurements of biomass and growth rate of two axenic algalcultures were carried out using three different methodologicalapproaches: the specific ¹⁴C-labelling of chlorophyll a, [³H]adenineincorporation into DNA and net organic carbon assimilation.Time-course experiments revealed that the specific activitiesof chlorophyll a were significantly higher than the specificactivity of total algal carbon in six of seven experiments.When the specific activity of chlorophyll a is used to calculatethe carbon biomass and growth rate, the carbon biomass of thealgae will thus be underestimated and the specific growth ratewill be too high. Determination of growth rates from incorporationof [³H]adenine gave lower values than those obtained from netorganic carbon assimilation and from ¹⁴C incorporation intochlorophyll a. Problems with adenine saturation are suggested.When [³H]adenine is used to measure growth rates in dense algalcultures, additions of >1 µM [³H]adenine are oftenrequired to maximally label the extracellular and intracellularadenine pools and hence DNA.     

Disseminated intravascular coagulation and the balance between blood coagulation and fibrinolysis

The dynamic haemostatic balance between blood coagulation and fibrinolysis and its influence on the development of disseminated intravascular coagulation are described. The effects of heparin and antithrombin-III are illustrated by clinical cases.     

Triloborhynchus psilastericola n. sp., a parasitic turbellarian (Fam. Pterastericolidae) from the starfish Psilaster andromeda (Müller and Troschel)

The turbellarian Triloborhynchus psilastericola n.sp. (family Pterastericolidae) occurs in the starfish Psilaster andromeda. On approaching maturation it moves from the host's coelom into the glandular pockets of the pyloric caeca with simultaneous loss of almost the entire ciliation. Mature turbellarians feed on the tissue of the pyloric caeca.