The soluble pool of HLA-G produced by human trophoblasts does not include detectable levels of the intron 4-containing HLA-G5 and HLA-G6 isoforms

In the context of implantation and pregnancy, several immunomodulating functions have been attributed to the different HLA-G isoforms. Increasing attention is now being addressed to the actively secreted soluble forms, because they might have a systemic function or could be useful as diagnostic tools. However, the cellular source of secretion, even during pregnancy, where HLA-G expression level is known to be highest, is still under debate. To elucidate the conflicting results, we investigated the isoform distribution in human first trimester and term placentas in situ and in vitro. Results obtained by applying immunohistochemistry, western blot, enzyme-linked immunosorbent assay (ELISA) and RT-PCR show that (1) all of the alpha1 domain-containing HLA-G isoforms are restrictedly expressed in the extravillous cytotrophoblasts (EVCTs) and very few first-trimester syncytiotrophoblasts, which directly cover cell columns, whereas mesenchymal cells of the villous chorion do not express HLA-G; (2) as demonstrated in western blots, trophoblasts express only the HLA-G1 isoform; (3) HLA-G5 and -G6 transcripts could be detected in human term placenta and isolated first-trimester trophoblasts but levels are extremely low; and (4) conditioned media of primary first-trimester trophoblasts, and the chorion laeve-derived trophoblastic cell line AC1-M59 do contain HLA-G1 fragments shed from the cell surface. Our data provide substantial evidence that none of the intron 4-containing isoforms, the so-called actively secreted, soluble HLA-G5 or -G6, are produced by human trophoblasts in situ or in vitro.

The effects of saline gas composition and pH on haemodynamic stability in the perfused trout head preparation

The effects of saline gas composition and pH on various haemodynamic properties of the perfused trout head preparation were evaluated. Increasing the concentration of saline CO2 from a "normal" level of 0.3 ([Formula: see text]; 1 Torr = 133.322 Pa) to 5.0% [Formula: see text] resulted in a significant elevation of input pressure (Pi) and a reduction in the ratio of dorsal aortic [Formula: see text] to anterior-venous flow [Formula: see text], whereas a reduction of pH, at constant [Formula: see text], had only a slight effect on [Formula: see text]. Altering the [Formula: see text] of the saline from 5 to 350 Torr while maintaining water normoxic (140 Torr) was without effect on input pressure or flow distribution in the gills.

Effects of temperature change on acid-base regulation in skipjack tuna (Katsuwonus pelamis) blood

The effects of temperature change (in vitro) on acid-base balance of skipjack tuna blood were investigated. By examining the relationship between blood pH and temperature (in vitro) under conditions of constant CO2 tension (open system), it was observed that dpH/dT = -0.013 U/degrees C. This value falls well within the range of in vivo values reported for other ectothermic vertebrates, and is only slightly different than results obtained in vitro under conditions of constant CO2 content (closed system; dpH/dT = -0.0165 U/degrees C). It is concluded that changes in pH following temperature changes can be accounted for solely by the passive, in vitro behaviour of the chemical buffer system found in the blood, so that active regulatory mechanisms of pH adjustment need not be postulated for skipjack tuna.

Cardiovascular changes in the rainbow trout (Salmo gairdneri Richardson) during exercise

The effects of steady-state, aerobic swimming exercise upon the cardiovascular system of rainbow trout (Salmo gairdneri) are discussed. When these fish are forced to swim at 80% of their critical velocity, blood flow is redistributed in the systemic circulation to favour working muscles, at the expense of decreased flow to nonmuscle structures. Given oxygen uptake and cardiac output data, combined with blood flow distribution patterns during exercise, it is calculated that the working muscles can account for nearly all the measured increase in total oxygen uptake at this level of exercise. The possible underlying mechanisms for systemic blood flow control and the increase in gas exchange efficiency across the gills of exercising rainbow trout also are examined.

Oxygen uptake in the lingcod, Ophiodon elongatus, during progressive hypoxia

Oxygen uptake [Formula: see text] in the resting lingcod was 22.8 ± 0.6 mL O2∙h−1∙kg−1. During progressive environmental hypoxia lingcod maintained or elevated their [Formula: see text] provided the water oxygen tension was greater than 45 mmHg. Increased [Formula: see text] (up to fourfold) during moderate hypoxia was associated with activity.

Functional morphology of the gills of the bowfin, Amia calva L., with special reference to their significance during air exposure

The bowfin, Amia calva is a facultative air breathing fish restricted to North America and is reported to estivate. The relative and functional gill surface areas of A. calva are not reduced, as in many amphibious fish, but have areas comparable to many completely aquatic species. The secondary lamellae are fused to form a lattice-work of rectangular pores, a gill arrangement unique among fresh-water fishes. This highly modified gill structure imparts considerable rigidity such that these do not collapse upon air exposure. In vivo blood gas measurements from air exposed Amia reveal that these gills must be free of water, since there is both O2 uptake and CO2 excretion across them. The observed ventilatory motions therefore pass air over the secondary lamellae for diffusive gas exchange during air exposure. In the artificial conditions of our experiments, however, air exposure was associated with a marked acidosis and the fish died within 2 hours of being returned to normoxic water.

Aspects of bimodal gas exchange in the bowfin, Amia calva L. (actinopterygii: amiiformes)

The bowfin, Amia calva is a facultative air breathing fish which uses its respiratory swimbladder to augment oxygen uptake in normoxia at 30 degrees C. It does not die however, when denied access to the surface at this temperature. The bladder RQ is 0.21 while the gill RQ is 1.61 and thus most of the CO2 is excreted into the water across the gills. In aquatic hypoxia some of the oxygen taken up via the swimbladder is lost to the water across the gills. However CO2 excretion across the gills is maintained at the same rate as that found in normoxia.

Oxygen receptors in the rainbow trout, Salmo gairdneri

A new technique for the detection in situ of oxygen-sensitive chemoreceptors in fish is described. By studying the hypoxic responses of the rainbow trout, Salmo gairdneri, at least two loci of respiratory control were found to be operating. One component initiated the hypoxic bradycardia and its rapid release, a second was responsible for ventilatory responses. The anterodorsal region of the first branchial arches has been established as a peripheral oxygen-sensitive chemoreceptor site, mediating bradycardia, without affecting either the amplitude or frequency of breathing. The study does not preclude the existence of oxygen receptors in other areas of the fish.