The stability of duplexes involving AT and/or G4EtC base pairs is not dependent on their AT/G4EtC ratio content. Implication for DNA sequencing by hybridization.

Sequencing by the recently reported hybridization technique requires the formation of DNA duplexes with similar stabilities. In this paper we describe a new strategy to obtain DNA duplexes with a thermal stability independent of their AT/GC ratio content. Melting data were acquired on 35 natural and 27 modified duplexes of a given length and of varying base compositions. Duplexes built with AT and/or G4EtC base pairs exhibit a thermal stability restrained to a lower range of temperature than that of the corresponding natural compounds (16 instead of 51 degrees C). The 16 degrees C difference in thermal stability observed between the least stable and the most stable duplex built with AT and/or G4EtC base pairs is mainly due to the sequence effect and not to their AT/G4EtC ratio content. Thus N -4-ethyl-2'-deoxycytidine (d4EtC) hybridizes specifically with natural deoxyguanosine leading to a G4EtC base pair whose stability is very close to that of the natural AT base pair. Oligonucleotide probes involving d4EtC can be easily prepared by chemical synthesis with phosphoramidite chemistry. Modified DNA targets were successfully amplified by random priming or PCR techniques using d4EtCTP, dATP, dGTP and dTTP in the presence of DNA polymerase. This new system might be very useful for DNA sequencing by hybridization.

Distribution of IgA subclass response to Coxiella burnetii in patients with acute and chronic Q fever.

The progression of Coxiella burnetii infection to acute or chronic Q fever has been attributed to biological characteristics of the bacterium and to the host immune response. We measured whether serum levels of total and specific subclasses IgA1 and IgA2 could be correlated with the course of disease in acute and chronic Q fever infections, and with the occurrence of endocarditis. In patients with chronic infection, total IgA2 levels were significantly increased. Q-fever-specific IgA1 antibodies were detectable in both acute and chronic infections, but only patients with endocarditis had IgA2 antibodies to C. burnetii phase II antigens. These findings indicate that the measurement of IgA subclasses may be a useful aid in the serological diagnosis of Q fever. Our results reinforce the idea that immunologically mediated host factors are important in the pathogenesis of Q fever and in the disease outcome of this infection.

Modification of DNA duplexes to smooth their thermal stability independently of their base content for DNA sequencing by hybridization.

The possibility of equalizing DNA duplex stability is essential for the application of sequencing by hybridization. In this paper we describe a new strategy to obtain DNA duplexes with a thermal stability independent of their base content. Modified *C bases have been developed and incorporated into oligonucleotides. The influence of these modifications on duplex stability has been studied by absorption spectroscopy, thus allowing selection of N -4-ethyl-2'-deoxycytidine (d4EtC), which hybridizes specifically with natural dG to give a G4EtC base pair whose stability is very close to that of natural AT base pairs. Duplexes built with AT and/or G4EtC base pairs exhibit thermal stabilities independent of their base content in a classical buffer solution, thus enabling control of the stability of DNA hybrids as a function of their length only.

Effects of V.M.H. lesions on plasma insulin in the goose.

The effects of bilateral electrolytic lesions of the ventromedial hypothalamus (V.M.H.) were examined in male geese. In addition to the known effects (hyperphagia, obesity and liver steatosis), V.M.H. lesions slightly increased plasma insulin level in the fasting and the fed state and largely enhanced insulin levels observed during an oral glucose and amino acid load. Therefore, V.M.H. lesions potentiate insulin release which may in turn participate in the development of hyperphagia and fattening in the goose as in mammals.

[An analysis of feeding patterns in the adult pig]. / Etude de la séquence alimentaire du porc adulte.

Feeding behavior has been analyzed in Large-White and Chinese pig breeds. Maximally automatized apparatuses, especially adapted to animal size, were used. Besides the usual parameters measured such as food intake, meal size, meal duration, meal frequency, intermeal intervals and postprandial correlation, these apparatuses also permitted us to measure the rate of intake during the meal. This rate was constant throughout the meal in ad libitum conditions and after 24-hour deprivation. A positive correlation between meal size and length of the postmeal interval was found in only half of the animals. During this work, we began to study the mechanisms initiating food intake.

[Role of the ventromedial nucleus of the hypothalamus in regulating feeding behavior in Landes geese]. / Importance du noyau ventro-médian de l'hypothalamus dans la régulation du comportement alimentaire de l'oie de race landaise.

This study shows the apparent role of the ventromedial nucleus of the hypothalamus (VMH) in regulating food intake in the goose. The feeding pattern of normal animals has been compared with that of animals made hyperphagic by destruction of the VMH. Lesioning of the VMH modified the circadian pattern of intake. All the geese tended to equalize their intakes between the light and dark periods. The overall effect of lesioning was considerable hyperphagia resulting from an increase in the number of meals and of their amplitude and duration, as well as in the rate of ingestion. We have emphasized the importance of defining the meal when interpreting changes in the correlations between the amount of food ingested during the meal and the length of pre or postprandial intervals after destruction of the VMH. Although it is important, the fatty liver syndrome induced after hyperphagia is not sufficient to produce fatty livers which can compete with those obtained by traditional cramming.

[Feeding pattern of the landes goose]. / Détermination du profil alimentaire de l'oie de race Landaise.

This is a study of the comparative physiology of the feeding sequence in 24 Landes geese fed ad libitum. The relative parameters of feeding behavior and the apparatuses used have been described. We found that the 24-hour light/dark cycle, corresponding to maximal ingestion, was not the same in all the animals studied. Two groups were distinguished: those tending to be diurnal and those tending to be nocturnal. The feeding pattern of the animals in each group and from day to day was constant. The correlation between the amount ingested during the meal and the length of pre or post-prandial intervals showed great variation, and the choice of meal definition considerably affected the results.

Effect of induced hypothalamic hyperphagia and forced-feeding on organ weight and tissular development in Landes geese.

The effects of induced hypothalamic hyperphagia and forced-feeding were studied in 30 geese of the Landes breed. They were housed in individual cages under a dark-light cycle of 12 hrs light-12 hrs darkness. Eleven geese with ventromedian hypothalamic (VMH) lesions and 8 controls were fed ad libitum. A third lot of 11 force-fed animals was pair-fed with the operated geese. The study lasted 4 weeks after an adaptation period to the new environmental conditions. The daily food intake of the geese and their weekly liveweight gain were monitored. After VMH lesions, the mean food intake of the geese increased by 169 p. 100 so that after each treatment their liveweight increased and they became obese (P less than 0.001). The tissue distribution of the group with lesions showed a higher amount of subcutaneous fat (P less than 0.05), while the mesenteric fat (P less than 0.05) was more abundant after forced-feeding. The liver weight was much higher in all cases; its increment reached 311 p. 100 in geese with VMH lesions and 193 p. 100 in the force-fed. However, those values were too low when compared to the means obtained by traditional forced-feeding. Hyperphagia in the geese was very marked as compared to that in rats, but it was insufficient to produce a considerable hepatic steatosis.

[Analysis of porcine feeding patterns from weaning to adulthood]. / Analyse de la séquence alimentaire du porc, du sevrage à l'état adulte.

This study describes the instruments used in recording the feeding patterns of 21 pigs of three different breeds fed ad libitum from weaning to adulthood. The feeding behavior of the pigs was characterized by 1) the presence of well individualized meals, and 2) the circadian distribution of food intake: whatever the breed, the animals preferred to eat in the daytime. This diurnal character of food intake was accentuated gradually with age. The frequency of the daily food intake decreased progressively from a mean of 9.5 meals after weaning to usually 3 at adulthood when growth was finished (2 meals in the daytime and 1 at night).