Activation of V kappa gene rearrangement in pre-B cells follows the expression of membrane-bound immunoglobulin heavy chains.

During B cell development V kappa gene rearrangement seems to occur only in mu-positive pre-B cells. To study the role of the mu chain in the activation of the Ig kappa locus, we introduced expression vectors carrying different forms of the mu gene into null pre-B cells. The activation of the Ig kappa locus followed the expression of the membrane form (micron) of the mu chain. The expression of the secreted form (microS) did not result in the activation of the Ig kappa locus. We further show that both forms of the mu chain differ in their intracellular transport in pre-B cells.     

Sounds produced by spawning fishes

Synopsis Low frequency sounds are shown to be associated with the spawning of two Caribbean coral reef fishes: the hamlet, Hypoplectrus unicolor (Serranidae) and the striped parrotfish, Scarus iserti (Scaridae). Both fishes produce distinctive sounds while broadcasting gametes in midwater. H. unicolor produces sounds via muscle stimulation of the swimbladder. Fin movements among group spawning S. iserti produce hydrodynamic noise. Although reproductive behaviors of these two species have been previously studied in detail, the association of sounds with mating is new. The mating sounds cannot be easily detected by human hearing underwater but are recordable using a hydrophone. The sounds are distinct and recognizable enough to allow counting and acoustic mapping of mating events in these species.     

Molecular analysis confirms food source and simultaneous involvement of two distinct but related subgroups of Salmonella typhimurium bacteriophage type 10 in major interprovincial Salmonella outbreak.

More than 2,000 confirmed cases of food poisoning occurred in the four Atlantic provinces of Canada and in Ontario during the second and third quarters of 1984. Salmonella typhimurium phage type 10 was identified as the etiologic agent, and cheddar cheese was implicated as the source of infection. Strains isolated from infected humans and from cheese were indistinguishable by biotyping, antibiotic resistance typing, and phage typing. Plasmid analysis confirmed cheese as the source of infection and revealed the presence of two molecular subgroups of bacteriophage type 10. Group I strains carried 57-, 22.3-, and 3.4-kilobase (kb) plasmids; group II strains carried 57-, 4.6-, and 3.4-kb plasmids. Digestion with endonucleases HaeIII, HpaII, and AvaIII indicated that the 3.4-kb plasmids were identical. This outbreak was, therefore, caused by a mixed infection with two distinct but related bacteria. Group I strains are fairly common among Canadian S. typhimurium phage type 10 isolates, whereas group II strains appeared to be unique to this outbreak.     

Ocean current variability and the spawning season of Hawaiian reef fishes

Synopsis The spawning patterns of four Hawaiian reef fishes with similar reproductive habits, but different biogeographic distributions were studied from September 1980 to October 1981. Two species are Hawaiian endemics [Centropyge potteri (Pomacanthidae) and Chaetodon multicinctus (Chaetodontidae)] and the other two have pan-tropical Pacific distributions [Ctenochaetus strigosus and Zebrasoma flavescens (Acanthuridae)]. All showed increased spawning activity from January to July, the prevalent pattern among a majority of coastal marine fishes in Hawaii. Environmental correlatives to the period of peak reproduction include cycles of (a) daylight length and temperature which probably function as proximate cues and (b) seasonal variations in ocean current patterns which may ultimately affect survival of larvae and dispersal. Peak reproduction takes place during months when (1) mesoscale eddies most likely occur, and (2) the probability is greatest of drifting objects remaining near the islands.     

Spawning behavior ofChaetodon multicinctus (Chaetodontidae); pairs and intruders

Synopsis Spawning by the banded butterflyfish,Chaetodon multicinctus (Chaetodontidae) was observed on coral reefs off Kona, Hawaii. These fish occurred in male-female pairs during normal daytime activities, a behavior which is typical for the family. Courtship is also a paired male-female activity. During spawning, however, other individuals (males?) may intrude on the spawning pair. Spawning typically takes place at least a meter or two above the bottom. The spawning position consists of the male below and behind the female with his snout against the female's ventral flank or anal fin area. Intruding individuals may join in when the pair is in position and about to spawn. Intruders line-up against the male in the same position as he is against his female. Underwater photographs are included to illustrate these behaviors.     

Evidence for ram suspension feeding by the piscivore, Seriola dumerili (Carangidae)

Synopsis We have quantitatively analyzed a videotape of Seriola dumerili (Carangidae) displaying ram suspension-feeding behavior and ram ventilation in the field. This is the first report of facultative suspension feeding by a piscivorous carangid. The intraoral morphology of S. dumerili is not typical of ram suspension-feeding fishes in that closely-spaced, long gill rakers are lacking. While the mechanism of particle retention is not known for any ram suspension-feeding fish species, scanning electron microscopy revealed denticles on the branchial surfaces of S. dumerili that could play a role in particle entrapment.     

Preparation of spermatogenic cell populations at specific stages of differentiation in the human.

Studying biochemical events in human spermatogenesis requires separated populations of spermatogenic cells. Dissociation of these cells was performed by a Trypsin-DNAse method adapted from the technique used for rodents. Cell separation was performed by centrifugal elutriation. Seven populations were collected, one further purified by Percoll gradient centrifugation, giving nine different cell populations. The efficiency of the cell separation was evaluated by phase contrast microscopy, flow cytometric DNA analysis, and electron microscopy. Five populations were enriched in spermatids: two in round spermatids (87% and 73%), another in round (52%) and elongating (44%) spermatids, another constituted by 80% elongating spermatids, and the last by 90% elongated spermatids. Two of the four remaining populations were enriched in primary spermatocytes (74% and 54%); another population was the upper part of the Percoll gradient and constituted cytoplasmic lobes and residual bodies (89%); the last population was made up of various cells, with no specific enrichment. Electron microscopic observations revealed good preservation of the separated cells; only the flagella from elongated spermatids were lost. Furthermore, an unusual pattern of nucleoplasm distribution during stages 2-4 of spermatid differentiation was observed and its signification is discussed with regard to the shape of the human spermatozoon.     

Nesting,eggs and larvae of triggerfishes (Balistidae)

Synopsis Triggerfishes construct nests by excavating depressions in sand. Eggs are laid in an adhesive mass and anchored with rubble. A photograph of a newly-hatched embryo is included.     

Isolation of bacteriophage 14-lysogenized Salmonella from the freshwater aquarium snail Apullaria.

A naturally occurring Salmonella mikawasima serologically converted by phage 14 (6,7,14:y:e,n,z15) has been isolated for the first time. An S. tennessee variant seroconverted by phage 14 (6,7,14:z29:-) was also isolated. The source of these salmonellae was the common freshwater aquarium snail Ampullaria. Phage 14 prepared from these serovariants was lytic for S. bovis-morbificans (6,8:r:1,5) and for S. hadar (6,8:z10:e,n,x).