Nonlinear wave mixing in a multilongitudinal-mode erbium-doped fiber laser

The emission spectrum of an erbium-doped fiber ring laser is shown to result from the nonlinear wave mixing taking place between the multiple oscillating longitudinal modes. The dependence of the resultant spectral broadening upon the signal power circulating in the laser cavity is investigated both theoretically and experimentally. In the case considered here, the extent of this spectral broadening is shown to be restrained only by the spectrally discriminating element inserted in the laser cavity. Predictions of the numerical simulations for the signal buildup and propagation in the laser cavity are found to be in good agreement with the experiment.

Pulse collisions in the stretched-pulse fiber laser

We report the observation of a new regime of operation in the stretched-pulse fiber laser in which two groups of bound pulses travel in the cavity at different velocities. The pulse groups collide periodically and remain apparently unaltered after the collisions. The observed group-velocity difference is shown to exhibit a strong dependence on the time interval between the pulses in each bound state.

Alpha linolenic acid in cholesterol esters: a marker of alphalinolenic acid intake in newborns

OBJECTIVE

To evaluate alpha-linolenic acid (ALA) (18∶3 n-3) and linolenic acid (LA) (18∶2 n-6) in cholesterol esters (CE) as markers of ALA and LA dietary intakes in preterm infants.

SUBJECTS

Forty-five preterm infants: two groups fed different formulas, the third fed human milk.

DESIGN

ALA and LA dietary intakes were precisely recorded in each infant to accurately determine the cumulative amount of ingested ALA and LA during two intervals: (i) between the second day after the first significant formula intake (D0) and the fifteenth day (D15); and (ii) between D0 and the first day of the 37th week of post-conception age (W37). The corresponding amounts of ingested ALA and LA were related to ALA and LA levels determined by capillary column gas-liquid chromatography in plasma cholesterol esters at D15 and W37, respectively.

RESULTS

ALA in CE was very significantly correlated to D0-D15 and D0-W37 ALA intakes (0.66; P=0.0001 and 0.70; P=0.0001), respectively. LA in CE was weakly correlated to D0-D15 LA intakes (0.03; P=0.01) and whatever the group (human milk or enriched formula) the correlation was lost at W37.

CONCLUSION

In preterm infants, ALA in CE can be considered as representative of ALA dietary intakes, whereas LA in CE appears as a poor marker of LA intakes.

Fatty acid composition of four microsporidian species compared to that of their host fishes

The fatty acid composition of four microsporidian species (Glugea atherinae, Spraguea lophii, Glugea americanus, and Pleistophora mirandellae) and their host fishes has been determined using gas chromatography. Twenty-four fatty acids were identified with differences in relative abundance of fatty acids among the four parasites. Certain even-saturated fatty acids were found in a very high proportion: palmitic acid (16:0) represented one-third of total fatty acids in Pleistophora mirandellae. The level of docosahexaenoic acid (22:6omega3) attained 26-28% in Glugea atherinae, Spraguea lophii, and Glugea americanus, but only 8-9% in P. mirandellae. With respect to fatty acid compositions of host organs, some significant differences were evident between marine and freshwater fishes. Palmitic acid was prevalent in the marine fishes, Atherinae boyeri and Lophius piscatorius, and oleic acid (18:1omega9) in the freshwater fish Leuciscus cephalus. The proportion of docosahexaenoic acid in marine fishes was two or three times as great as in freshwater fish Leuciscus. The high polyunsaturated fatty acid content in both parasites and host fishes may be related to the scavenging of these fatty acids by the parasites rather than a microsporidia-specific fatty acid biosynthesis pathway.

Differences between polyunsaturated fatty acid status of non-institutionalised elderly women and younger controls: a bioconversion defect can be suspected

OBJECTIVE

To evaluate the polyunsaturated fatty acid (PUFA) status in non-institutionalised elderly women and to detect a possible essential fatty acid bioconversion defect.

DESIGN AND SUBJECTS

The fatty acid composition of total plasma lipids, plasma triglycerides (TG), cholesterol esters (CE), phospholipids (PL), and erythrocytes was determined by capillary column gas-liquid chromatography in a sample of 200 non-institutionalised healthy elderly women over 75 years of age. The data were compared with those of a control group of 50 young female volunteers aged 20-48 y.

RESULTS

In elderly women, the n-6 series precursor, linoleic acid (18:2 n-6), was lower in TG and CE (P = 0.029 and 0.014, respectively). In CE, this fatty acid was highly correlated with vegetable and vegetal fat intakes (P < 0.0001), suggesting a lower dietary supply than in controls. Higher percentages of 16:1 n-7 were found in all the plasma lipid fractions in elderly women, especially in CE (P < 0.0001). The ratios 20:4 n-6/20:3 n-6 and 22:6 n-3/20:5 n-3 were significantly lower in PL from elderly women (P < 0.005 and P < 0.002, respectively), raising the question of the efficiency of the terminal steps of 20:4 n-6 and 22:6 n-3 biosynthesis. Dietary investigations in elderly women indicated that a high dietary protein intake via meat probably contributed to the supply of 20:4 n-6 and thus maintained the status of this fatty acid, despite the suspected altered biosynthesis.

CONCLUSION

The PUFA status in the elderly women group could be more fragile and dependent on exogenous supply of long-chain PUFAs than previously suspected.

Longitudinal multicentric study of plasma and red blood cell fatty acids and lipids in preterm newborns fed human milk

The present multicentric study (three centers) deals with the values of plasma and red blood cell fatty acids obtained in a group of 18 preterm newborns after 2 days (D2), 15 days (D15) and 5 weeks (37th week postconception: 37th wk) of human milk feeding. Analytical methods were randomized between the three centers and quality control was evaluated by repeated analysis of reference samples. 20:4 n-6 varied from 10.71 +/- 1.58% to 9.51 +/- 1.65 and 10.10 +/- 1.42% in plasma phospholipids and from 16.59 +/- 3.30% to 14.68 +/- 3.14 and 18.24 +/- 4.09% in red blood cell phosphatidylethanolamine (RBC-PE) at D2, D15 and 37th wk, respectively, contrasting with the important rise of the precursor (18:2 n-6) in all the fractions studied. In RBC-PE, 22:6 n-3 significantly declined from 3.52 +/- 1. 03% at D2 to 2.56 +/- 0.83% at D15 (p < 0.02) and recovered its initial level at 37th wk (4.08 +/- 1.94%). The recovery of long chain polyunsaturated fatty acid homeostasis at that time was also confirmed by the decline of 16:1 n-7 in cholesterol esters (10.69 +/- 3.92 to 4.32 +/- 2.38%).

Effects of preterm infant formula supplementation with alpha-linolenic acid with a linoleate/alpha-linolenate ratio of 6: a multicentric study

OBJECTIVE

To investigate the effects of a milk formula supplemented with a alpha-linolenic acid (ALA) (18:2 n-6/18:3 n-3 ratio near 6/1) on plasma and red blood cell (RBC) fatty acids (FAs) in premature infants and compare with a non supplemented formula (18:2 n-6/18:3 n-3 = 22/1).

DESIGN AND SUBJECTS

Infants of mothers who elected not to breast-feed were randomly assigned to either a high alpha linolenic formula (HLF: n = 31) group or a low alpha-linolenic formula (LLF: n = 32) control group. Infants fed human milk (HM: n = 25) were enrolled concurrently as a reference group. Anthropometric and biological measurements were made after two days (D2) and 15 d (D15) of enteral feeding and at the 37th week (W37) of postconceptual age. In HLF, the 18:3 n-3 content was 1.95% of total FAs (0.77% of total energy) and the 18:2 n-6/18:3 n-3 ratio was near 6/1. In LLF, the 18:3 n-3 content was 0.55% of total FAs (0.22% of total energy) and the 18:2 n-6/18:3 n-3 ratio was 22/1.

RESULTS

ALA supplementation had minimal effect on the n-6 series, did not alter the anthropometric data and confirmed the conversion of ALA into docosahexaenoic acid (DHA). Throughout the study, it maintained, the RBC membrane DHA values within the confidence interval of those obtained in the HM group. Such was not the case with LLF CONCLUSION: alpha-linolenic acid supplementation (from Rapeseed oil and in a 18:2 n-6/18:3 n-3 ratio = 6) in premature infant formula can contribute efficiently to the maintenance of the n-3 status in the premature newborns.

[Biological effects on premature neonates of a milk formula enriched with alpha-linolenic acid: a multicenter study]

Nervous tissues and the retina are rich in docosahexaenoic acid [DHA, C22: 6(n-3)], an essential fatty acid which is the product of the elongation and desaturation of alpha-linolenic acid [alpha-LnA, C18:3(n-3)]. Lower plasma and membrane DHA levels as well as impaired nervous function (psychomotor development, visual disturbances) have been observed in premature babies receiving standard milk products compared to breast-fed babies and have been related to the lack of long-chain (> C20) fatty acids in these products. In the present study, we have investigated whether it is possible to increase the plasma and erythrocyte DHA level in premature infants by giving them a milk formula enriched in alpha-LnA (1.95% vs 0.55%). Results showed that, after 15 days of feeding, alpha-LnA supplementation significantly increased plasma DHA availability [2.20 vs 1.54% (p < 0.0001) in the plasma phospholipids] and increased DHA level in erythrocyte membranes [3.02 vs 2.54% (n.s.) in the red blood cell phosphatidylethanolamines]. At the LA/alpha-LnA ratio used (6/1), there was only a limited impact on the n-6 pathway which was reflected in a slight decrease in the arachidonic acid (AA) of the plasma phospholipids [6.88 vs 7.53% (p < 0.05) after 15 days]. Furthermore, the AA content of the red blood cell phosphatidylethanolamines was perfectly preserved even after a mean period of 4-5 weeks of feeding [(15.70 vs 14.86% (n.s)]. The observed enhancement in fatty acids of the n-3 series calls for a prospective study investigating whether these improvements are associated with changes in the kinetics of psychomotor development and in the visual function of enriched-formula-fed versus breast-fed babies.

Nervonic acid in red blood cell sphingomyelin in premature infants: an index of myelin maturation?

The present study addresses the question whether nervonic acid (24:1n-9) accumulation in sphingomyelin (SM) of red blood cells (RBC) could yield information on cerebrum maturation in premature infants. The study included 28 premature eutrophic infants of 31.5 wk gestational age. Eleven were fed with human milk, nine with a regular formula and eight with an alpha-linolenate-enriched formula. The fatty acid composition of the SM fraction was determined by gas-liquid chromatography on a 50-m fused silica capillary column. At 32 wk gestational age, the main fatty acids in SM were 16:0, 18:0, 20:0, 22:0, 24:0 and 24:1n-9. After five weeks of feeding, at week 37 of postconceptional age, the most striking variation was a rise in 24:1n-9, from 9.9 +/- 0.7 to 12.8 +/- 0.9 (P < 0.02), regardless of regimen in all three feeding groups. The rise in 24:1n-9 after birth in premature eutrophic infants is the beginning of a trend toward the higher levels in 24:1n-9 observed in mature newborns and older infants. The 24:1n-9 level in SM of RBC from premature infants may reflect 24:1n-9 levels in SM of brain and could thus reflect brain maturity.

[Jails and AIDS. Risk factors for HIV infection in the prisons of Madrid]

The spread and risk factors for HIV infection were studied in 288 men and 95 women at the prisons of Carabanchel and Yeserias, Madrid. These men and women requested care at the AIDS prevention program in the jails of Madrid, from April to December 1987. Among the men studied at Carabanchel, 55% were positive to HIV (77% seropositivity among intravenous drug users, IVDU). Tattooing (OR = 2.8), and number of times in prison (OR = 4.5 comparing those who had been 8 or more times in prison with those who had been in prison only once) were independent risk factors for infection, after controlling for IVDU. No association was found between seropositive status to HIV and reported anal intercourse. Among the women studied at Yeserias, the proportion of HIV seropositive women was 26% (70% of the IVDUs were seropositive). Tattooing, number of times in prison, history of prostitution and history of syphilis were associated with HIV infection. When controlling for IVDU, number of times in prison and history of prostitution were not independent risk factors for infection. These data indicate that there is a need for control measures to avoid further spread of the HIV infection among the inmate population, in particular through the use of contaminated needles while in prison.

Proton and phosphorus NMR study of RNA self-complementary hexamers: influence of the 5-methylcytidine on the conformational transitions and the molecular motions

We present proton and phosphorus NMR data, which contribute to explain why the 5-methylcytidine (m5C) differently affects the conformational transitions of CGUAm5CG (Bloch et al., FEBS Letters 219, 464 (1987)) and CGm5CGCG (Ceolin et al., J. Am. Chem. Soc. 109, 2539 (1987)). The atypical intermediate form observed in the random coil to A-like duplex transition of CGm5CGCG is determined: this original duplex structure exhibits a frame-shift pairing of the two strands, with a partial conservation of the A-type structure. In the case of CGUAm5CG such a pairing process would lead to a complete mismatch pairing. This feature probably explains that the NMR data of CGUACG and CGUAm5CG are similar and consistent with a random coil to A-type helix transition. Nevertheless a significant difference between the correlation times observed for the molecular motions of the two duplexes is detected. Another example of unusual conformational transition of methylated RNA oligomers is given by CAm5CGUG.

Plasma fatty acid composition and lipid peroxide levels in children with paucity of interlobular bile ducts

The total and free fatty acid composition of plasma and lipid peroxide concentrations was studied in 32 cholestatic children with syndromatic paucity of interlobular bile ducts (Alagille's syndrome). The mean lipid peroxide value in these patients was 8.80 +/- 3.70 nmol/ml, nearly 4 times higher than the mean control value. Compared to the control group, the patients exhibited significant variations in total fatty acids, and in particular a relative decrease in linoleic acid (from 29.5 +/- 6.1% in the controls to 19.1 +/- 8.03% in the patients) compensated by an increase in saturated and monounsaturated fatty acids. The plasma lipid peroxide levels were inversely correlated with the unsaturated/saturated fatty acids ratio in total fatty acids, and with the vitamin E status (vitamin E/total lipids). Most of the total and free fatty acid variations observed were largest in patients with severe jaundice. Dietary fat malabsorption and the increase in lipid peroxidation partly explain these results. Furthermore, in free fatty acids, we observed a marked increase in arachidonic acid (from 1.43 +/- 0.85% in the controls to 4.27 +/- 2.24% in the patients), suggesting abnormal eicosanoid synthesis.

Sequence-dependence of the conformational changes induced by the 5-methyl cytosine in synthetic RNA oligomers

The RNA hexamer containing a 5-methyl cytosine (m5C) r(CGUAm5CG) was studied by 1H and 31P NMR at 500 MHz and 121 MHz, respectively. In contrast to r(CGm5CGCG) which exhibits an atypic duplex structure [(1987) J. Am. Chem. Soc. 109, 2539-2541], r(CGUAm5CG) adopts a classical A-type conformation. This result demonstrates that the influence of the m5C on the conformation of RNA hexamers is sequence-dependent.

Ultraviolet optogalvanic laser spectroscopy of iron for reference wavelengths

We present a preliminary study of a UV optogalvanic spectrum obtained by using a see-through iron hollow cathode and a tunable pulsed laser in the 240-260-nm range. The hollow cathode used and described is a homemade device that can be run in static- or dynamic-flow gas regimes. Spectra have been recorded with argon and neon buffer gases, and many classified Fe I lines have been identified. The accuracy of the measured wave numbers is limited at present to 0.05 cm(-1) by the spectral width of the UV laser. This iron optogalvanic spectrum is proposed for reference-wavelength calibration in UV laser spectroscopy, and an application to the study of Ba(+) Rydberg levels is reported. Possibilities for future developments of such a device are analyzed.

Chemical and enzymatic oxidative coupling of 5-hydroxy-N,N-dimethyltryptamine with amines

As part of a program aiming to obtain a covalent labeling of serotoninergic receptors we have studied the oxidative coupling of serotonin derivatives with amino compounds. The oxidation of bufotenine (2) by MnO2 and human ceruloplasmin followed by the Michael type addition with dansylcadaverine and dansyllysine gave a fluorescent adduct identified as fused oxazole structure 4.

Thrombectomy: surgical treatment of the thrombosed Björk-Shiley prosthesis. Report of seven cases and review of the literature

Among 1,000 patients with 1,225 Björk-Shiley prostheses, we have detected 12 cases (0.98%) of late thrombosis of the Prosthesis, seven of which were successfully managed by thrombectomy. A review of other authors' experience with this procedure shows no deaths directly attributable to thrombectomy, although two patients had cerebral embolization during the procedure. For prevention of this complication, we propose that both the aorta and the left atrium be explored during thrombectomy of either the mitral or the aortic prosthesis so as to achieve complete exposure of the left ventricular outflow tract and complete removal of any thrombus located in the ventricle. We consider this the procedure of tract and complete removal of any thrombus located in the ventricle. We consider this the procedure of choice in thrombosis of the Björk-Shiley prosthesis. Replacement of the prosthesis would then be restricted to cases of prosthesis damage or those in which adequate anticoagulation cannot be maintained.