Perennial N2 supersaturation in an Antarctic lake

The dry valleys of southern Victoria Land in Antarctica contain several closed basins in which perennially ice-covered lakes are found. One of the most unusual features of these lakes is the occurrence of high O2 concentrations in the water column; values ranging from slightly more than saturation to more than four times saturation have been reported. Recently, we considered a bulk O2 budget for Lake Hoare, Antarctica, which led us to suggest that biological processes alone were not sufficient to explain the observed elevated oxygen levels. Consequently, there must be a non-biological source of O2. We suggested that this source results from the exclusion of O2 during the freezing of aerated meltstream water at the bottom of the ice cover, and predicted that this physical mechanism should also enhance the other atmospheric gases. Here we report the results of a study which, for the first time, documents the supersaturation of N2 in a lake. Dissolved N2 levels of 145% and 163% were determined from samples taken just below the ice cover and at a depth of 12 m, respectively. The relatively importance of biological and abiological sources is reflected in the ratio of N2 concentration to O2 concentration. In Lake Hoare this ratio was 1.20 at ice/water interface and 1.05 at 12 m; considerably different from the ratio in equilibrium with air (approximately 1.8). Based on these results, we have determined that about half of the net O2 production in the lake is the result of biological processes.     

A glucagon-secretin-like peptide stimulates the intrinsic nervous plexus of guinea pig gallbladder

Summary The role of vasoactive intestinal peptide (VIP), as a possible neurotransmitter of the intrinsic nerve plexus in the guinea pig gallbladder, was investigated by monitoring spontaneous contractile activity. VIP receptor antagonist (4 Cl-D-Phe⁶, Leu¹⁷)-VIP did not produce any effect on muscular tone and spontaneous activity, whereas (N-Ac-Tyr¹, D-Phe²)-GRF-(1-29)-NH₂, (14-GRF analog), which is known to stimulate digestive enzyme secretion by interacting with the VIP-preferring receptors, greatly increased the amplitude and frequency of waves as well as the muscular tone. Since VIP receptor antagonist acts selectively as a competitive antagonist for the action of VIP, we conclude that the gallbladder inhibitory intrinsic plexus neurotransmitter is not VIP, but a member of the glucagon-secretin family of peptides.     

Experimental hydrocephalus following mechanical increment of intraventricular pulse pressure

Summary Experimental hydrocephalus has been induced in lambs by artificial increase of the amplitude of intraventricular cerebrospinal fluid (CSF) oscillations related to arterial pulsations, without concominant changes of the mean CSF-pressure. The characteristics of this hydrocephalus demonstrate that the intraventricular CSF-pulsations can play a role in the genesis of ventricular dilatation. Such a method may be used to produce an original model of hydrocephalus independent of changes of CSF-circulation or absorption.This work was supported by grant of CNR.     

Life in extreme environments

Each recent report of liquid water existing elsewhere in the Solar System has reverberated through the international press and excited the imagination of humankind. Why? Because in the past few decades we have come to realize that where there is liquid water on Earth, virtually no matter what the physical conditions, there is life. What we previously thought of as insurmountable physical and chemical barriers to life, we now see as yet another niche harbouring 'extremophiles'. This realization, coupled with new data on the survival of microbes in the space environment and modelling of the potential for transfer of life between celestial bodies, suggests that life could be more common than previously thought. Here we examine critically what it means to be an extremophile, and the implications of this for evolution, biotechnology and especially the search for life in the Universe.     

A follow-up electrophysiological study of rats with poor intrauterine fetal growth: the development of visual evoked responses (VERs)

Summary The development of some electrophysiological activities of the visual system (VERs) was compared in control rats and in young rats with poor intrauterine fetal growth caused by an electrolytic lesion of the placenta. Treated rats showed a delayed development of the electrophysiological functions considered, thus confirming the postnatal effect of poor intrauterine fetal growth.This research was supported by grants of CNR and Ministero Pubblica Istruzione.     

A pathogenic hypothesis of malformation caused by amniocentesis.

The role of amniocentesis in producing fetal malformations has been investigated in the rat. Relevant uterine contractions were observed after amniocentesis. The pathogenetic mechanism of fetal malformations is discussed on the basis of the present results.     

Model of carbon fixation in microbial mats from 3,500 Myr ago to the present

Biological carbon fixation is an important part of global carbon cycling and ecology. Fixation that took place 3,500 million years ago is recorded in the laminated sedimentary rock structures known as stromatolites, which are fossilized remains of microbial mat communities. Stromatolites are the most abundant type of fossil found in the Proterozoic (2,500 to 590 Myr ago), but they then declined, possibly because of predation and competition. Using modern microbial mats as analogues for ancient stromatolites, we show that the rate of carbon fixation is higher at the greater levels of atmospheric CO2 that were probably present in the past. We suggest that carbon fixation in microbial mats was not carbon-limited during the early Precambrian, but became carbon-limited as the supply of inorganic carbon decreased. Carbon limitation led to a lower rate of carbon fixation, especially towards the end of the Precambrian. Thus, another reason for the decline of the stromatolites could have been a decrease in available CO2.     

A glucagon-secretin-like peptide stimulates the intrinsic nervous plexus of guinea pig gallbladder

The role of vasoactive intestinal peptide (VIP), as a possible neurotransmitter of the intrinsic nerve plexus in the guinea pig gallbladder, was investigated by monitoring spontaneous contractile activity. VIP receptor antagonist (4 Cl-D-Phe6, Leu 17)-VIP did not produce any effect on muscular tone and spontaneous activity, whereas (N-Ac-Tyr1, D-Phe2)-GRF-(1-29)-NH2, (14-GRF analog), which is known to stimulate digestive enzyme secretion by interacting with the VIP-preferring receptors, greatly increased the amplitude and frequency of waves as well as the muscular tone. Since VIP receptor antagonist acts selectively as a competitive antagonist for the action of VIP, we conclude that the gallbladder inhibitory intrinsic plexus neurotransmitter is not VIP, but a member of the glucagon-secretin family of peptides.     

A pathogenic hypothesis of malformation caused by amniocentesis

Summary The role of amniocentesis in producing fetal malformations has been investigated in the rat. Relevant uterine contractions were observed after amniocentesis. The pathogenetic mechanism of fetal malformations is discussed on the basis of the present results.This research was supported by a grant of CNR.