Small-scale turbulence and plankton contact rates

Theoretical and empirical studies of plankton trophodynamicsare usually based on some function of the relative density ofpredator-and-prey plankton. Such approaches based only on therelative density of predator and prey generally underestimatepredator-prey contact rates because contact depends on boththe relative density and the relative velocity of predator andprey. We estimate the components of predator-and-prey contactthat are due to small-scale turbulence. The small-scale turbulenceeffect suggests reconsidering estimates of plankton food requirements,energy gain-and-loss from foraging and mechanisms associatedwith patch formation and dissipation.     

Electrical stability of erythrocytes in the presence of divalent cations

Erythrocytes suspended in a medium of low ionic strength lyse under the effect of an exponential electrical pulse. The percentage of haemolysed cells decreases several-fold in the presence of divalent cations. The protective action of the ions studied increases in the following order: Ca⁺⁺, Mg⁺⁺, Zn⁺⁺. It is assumed that divalent ions bind to the negative charges of the lipid and protein molecules and reduce their electrostatic repulsion, which results in stabilization of the membranes.     

The determination of the kinetics of polysaccharide thermal degradation using high temperature viscosity measurements

Information about the thermal degradation of the polysaccharides sodium alginate, carrageenan and carboxymethyl cellulose has been obtained from the time dependence of the viscosity at high temperatures measured using a slit viscometer. The viscosity is related to the molecular weight using previously-published relations between the zero shear specific viscosity and the coil overlap parameter in conjunction with the appropriate Mark-Houwink equation. It is found that alginate is much less stable than carboxymethyl cellulose and carrageenan. Activation energies for depolymerisation obtained from Arrhenius plots in the presence of oxygen ranged from 50 kJ/mol for alginate to 105 kJ/mol for κ-carrageenan.     

Parallel bioassay of 27 bombesin-like peptides on 9 smooth muscle preparations. Structure-activity relationships and bombesin receptor subtypes

Thirteen natural bombesin-like peptides and 14 synthetic analogues were submitted to parallel bioassay on 9 smooth muscle preparations in order to determine their relative potency, in comparison to bombesin and litorin. The natural peptides of the bombesin subfamily showed a uniformly high or moderate potency on all preparations. However, synthetic bombesins of shorter chain length (hepta- and octapeptides) manifested a good potency only on the rat uterus preparation. Among the peptides of the litorin and phyllolitorin subfamilies, only litorin and ranatensin presented a full spectrum of potency, equalling or even surpassing that of bombesin. All other natural and synthetic members of the two subfamilies showed a sharply dissociated spectrum of potency on the different smooth muscle preparations. The only exception was the rat urinary bladder and, in part, the chicken intestine, on which the peptides displayed a uniformly high potency, comparable to, or even greater than that of bombesin. The present results help to explain structure/activity relationships and suggest the probable existence, in the periphery, of multiple bombesin receptor subtypes.     

Hormonal imprinting and damages caused by fetal steroid treatment. Influence of fetal treatment with pregnancy-protecting steroids (allylestrenol, diethylstilbestrol) on the effect of gonadotropin administered to cockerels perinatally and at the age of six weeks

Single fetal (9th day) treatment with either diethylstilbestrol (DES) or allylestrenol (AE) caused a considerable decrease, both at the age of five days and six weeks, in the weight of the testicles and the diameter of the seminiferous cords, while the ratio of spermatogonia to primary spermatocytes increased. When measured either at the age of five days or six weeks, gonadotropin treatment [a combination of follicle stimulating hormone (FSH) and luteinizing hormone (LH)], administered twice daily for three days after the hatching, led to an increase in the above-mentioned parameter and to a shift in the cell ratio towards the control value. However, the absolute value of the controls treated with FSH-LH was by far not reached. The effect of perinatal treatment could be detected even in adulthood, namely, at the age of five days the response capability was relatively weak in the cockerels treated with DES and AE, while high responsiveness was observed at the age of six weeks. In some cases the relative value of the increment exceeded even that of the control; however in absolute term it was well below the control. On the basis of these experiments it might be concluded that hormonal imprinting evoked by FSH-LH treatment also occurs in the gonad damaged by DES and AE. The setting in of imprinting ameliorates the damages caused by DES and AE and increases the response capability of the cells.     

Sex-steroid-sensitive stromal cells and oviduct differentiation

The chick oviduct differentiates during sexual maturation before the age of 20 weeks. In the present work we used immunohistochemistry to study sexual maturation associated progesterone receptor (PR) expression in the chick oviduct as an indication of progesterone sensitivity. Since the PR is estrogen inducible protein, its expression also reflects the effects of endogenous estrogens. Thus PR expression can be used as a marker for action and sensitivity of cells to these sex steroids. In the luminal epithelium and mesothelium (peritoneal epithelium) the PR was expressed in high concentrations from the time before hatching (the constitutive PR). The PR was not detectable in stromal cells of immature chicks. At the age of 7-10 weeks the PR was detected in submucosal but not in mucosal stromal cells (the inductive PR). The appearance of these PR-expressing cells was associated with an increase in luminal epithelial cell proliferation. At the age of 14-16 weeks the mucosal plicae increased in height and the PR-expressing stromal cells were seen in the center of these mucosal plicae. There were also areas in the mucosal plicae where a large number of stromal cells expressing the PR were seen in the mucosal layer. Thereafter the size of the oviduct increased rapidly and the gland formation commenced. In the fully matured oviduct (over 18 weeks of age) virtually all stromal cells both in mucosa and submucosa expressed the PR. It is concluded that the PR expression in the luminal epithelium and mesothelium was constitutive (independent of sexual maturation). In stromal cells this was expressed during sexual maturation (probably induced by endogenous estrogen) and was associated with histological changes in the oviduct. We propose that direct effects of estrogen and progesterone in the oviduct growth and glandular formation are mediated through these stromal cells.     

Commercial blast-freezing of third-stage Anisakis simplex larvae encapsulated in salmon and rockfish

Sixty-four fish were blast-frozen to -35 C for 15 hr to determine the effects of commercial blast-freezing on the viability of third-stage larvae of Anisakis simplex encapsulated in the muscle and viscera of sockeye salmon (Oncorhynchus nerka) and canary rockfish (Sebastes pinniger). Parallel tests were conducted on larval nematodes in 16 whole (round) salmon, 16 dressed salmon (heads and viscera removed), and 32 whole (round) rockfish. After blast-freezing, 4 in-the-round salmon, 4 dressed salmon, and 8 in-the-round rockfish were examined at 1, 24, 48, and 72 hr. A total of 3,539 dead and 6 live larvae were collected from the fish tissues after standard enzymatic digestion. Salmon were infected with 1,245 of these larvae, and rockfish with 2,300. The 6 live worms, 2 from salmon and 4 from rockfish rounds, were recovered from muscle 1 hr after freezing; they were slightly motile and showed severe internal damage. No viable worms were found at or after 24 hr. The commercial blast-freezing process effectively killed larval nematodes in whole or dressed fish. Market-ready samples of previously blast-frozen silver salmon (O. kisutch) and chum salmon (O. keta) fillets and chum salmon steaks yielded no live worms, thereby confirming the efficacy of this process.     

Serodiagnosis of Streptococcus pneumoniae infection in guinea pigs by an enzyme-linked immunosorbent assay

Guineapig antibodies to Streptococcus pneumoniae (SPN) serotype 19F were detected by an enzyme-linked immunosorbent assay using a simple procedure. In experimentally infected hosts, antibody was detectable as early as 2 to 3 weeks after infection, and high titres were maintained for a long period. Antibodies higher than 1:64 were regarded as specific. In a field study, high antibody titres were shown in SPN enzootic colonies in contrast to negative or low antibody titres in a majority of the animals from non-enzootic and SPF colonies.     

Antibodies to pollen exines

A polyclonal antiserum and monoclonal antibodies have been prepared to purified pollen exines of Calocedrus decurrens Florin. The location of the antigen is in the exine, as shown by light-and electron-microscopic immunocytochemistry. The greatest reduction in antibody binding follows treatment of the exine with chemicals known to alter sporopollenin. These results provide evidence that sporopollenin is antigenic. Exines of ten species of gymnosperms and angiosperms also bound the polyclonal antiserum, indicating similarity of sporopollenin structure.