Omasal flow of nonstructural carbohydrates and nitrogenous compounds in lactating dairy cows fed diets containing timothy cut in the afternoon or morning.

Shifting the cutting of grass from morning to afternoon has been shown to increase the concentration of nonstructural carbohydrates (NSC) in forages. We compared the effects of diets (66:34, forage:concentrate ratio) containing a mix (% of the diet dry matter) of baleages (46.5%) and silages (19.3%) harvested from timothy cut in the afternoon (p.m.-cut TIM diet) or morning (a.m.-cut TIM diet) on omasal flows of NSC and nitrogenous fractions, ruminal and total-tract digestibilities of nutrients, plasma concentration of AA, and milk yield and composition. Eight ruminally cannulated Holstein cows averaging (mean ± standard deviation) 31.4 ± 6.13 kg/d of milk, 136 ± 17.0 d in milk, and 611 ± 66.4 kg of body weight in the beginning of the experiment were used in a crossover design with 21-d periods (14 d for diet adaptation and 7 d for data and sample collection). Intake of total ethanol-soluble carbohydrates (TESC; +150 g/d), starch (+129 g/d), and total NSC (TESC plus starch = +278 g/d) was greater with feeding the p.m.- than the a.m.-cut TIM diet. Likewise, the apparent ruminal digestibilities of TESC (+149 g/d), starch (+167 g/d), and total NSC (+316 g/d) increased in the p.m.-cut TIM diet. Diets, however, had no effect on the omasal flows and apparent ruminal and total-tract digestibilities of dry matter and organic matter. Intake of N increased in cows fed the p.m.- versus the a.m.-cut TIM diet (562 and 528 g/d, respectively) despite no effect of diets on dry matter intake. Diets did not affect the omasal flows of total nonammonia N, total bacterial nonammonia N, nonammonia and nonbacterial N, and individual AA, and the efficiency of microbial protein synthesis in the rumen. Contrarily, supply of rumen-degradable protein increased (+9.2%) in cows fed the p.m.-cut TIM diet, with this response driven by the 6.4% increase in N intake. Plasma concentrations of essential and nonessential AA followed the omasal flow of AA and were not changed by diets. Feeding the p.m.- versus the a.m.-cut diet significantly increased yields of 4% fat-corrected milk and milk fat, and tended to increase energy-corrected milk, milk true protein, and milk lactose yields. Overall, feeding the p.m.-cut TIM diet to mid-lactation dairy cows did not improve microbial protein synthesis and omasal flow of AA, and these responses were in line with the lack of a treatment effect on dry matter intake.

Performance and nitrogen use efficiency in mid-lactation dairy cows fed timothy cut in the afternoon or morning.

Shifting cutting from morning to afternoon has been shown to increase the concentration of nonstructural carbohydrates in forages. We hypothesized that, compared with a total mixed ration containing timothy baleage and silage cut in the morning (a.m.-cut TIM), a total mixed ration containing timothy baleage and silage cut in the afternoon (p.m.-cut TIM) would improve animal performance and N use efficiency in mid-lactation Holstein cows due to enhanced supply of ruminal fermentable energy. The objective of this study was to compare the effects of p.m.- versus a.m.-cut TIM on milk yield, concentrations and yields of milk components, ruminal metabolism, and plasma concentrations of AA in mid-lactation Holstein cows. Ten (6 ruminally cannulated) primiparous cows averaging 139±13 d in milk and 550±56 kg of body weight, and 6 (2 ruminally cannulated) multiparous cows averaging 128±11 d in milk and 632±57 kg of body weight at the beginning of the experiment, were used in a crossover design. Each period lasted 21 d with 14 d for diet adaptation and 7 d for data and sample collection. The concentration of nonstructural carbohydrates (water-soluble carbohydrates plus starch) was numerically greater in the p.m.- versus the a.m.-cut TIM and averaged 13.2±1.06% and 12.2±1.13%, respectively. Treatment × parity effects were observed for milk urea N, feed efficiency, and milk N efficiency, whereas parity effects were observed for nutrient intake, milk yield, and plasma concentration of several essential and nonessential AA. Intakes of dry matter (19.3 versus 18.6 kg/d) and nonstructural carbohydrates (2.56 versus 2.31 kg/d), and yields of 4% fat-corrected milk (23.1 versus 22.2 kg/d), energy-corrected milk (25.0 versus 24.1 kg/d), milk fat (0.91 versus 0.88 kg/d), and milk protein (0.77 versus 0.73 kg/d) were all greatest with feeding p.m.-cut TIM. Milk yield (23.5 versus 22.7 kg/d) tended to increase in cows fed p.m.-cut TIM. The ruminal fermentation profiles and plasma concentrations of AA were mostly unaffected by treatments. However, ruminal valerate (1.01 versus 1.17 mol/100 mol) and plasma Gly (172 versus 188 µM) were lowest with feeding p.m.-cut TIM. Overall, feeding mid-lactation dairy cows a total mixed ration that consisted of p.m.-cut timothy baleage and silage significantly increased dry matter intake and yields of milk, milk fat, and milk protein.

Alfalfa baleage with increased concentration of nonstructural carbohydrates supplemented with a corn-based concentrate did not improve production and nitrogen utilization in early lactation dairy cows.

The objective of this study was to investigate the effects of feeding alfalfa baleage with different concentrations of nonstructural carbohydrates (NSC) supplemented with a common corn-based concentrate on performance, ruminal fermentation profile, N utilization, and omasal flow of nutrients in dairy cows during early lactation. Ten multiparous (8 ruminally cannulated) and 8 primiparous Holstein cows were randomly assigned to treatments (high- or low-NSC diet) in a crossover design. The difference in NSC concentration between the 2 alfalfa baleages fed from d14 to 21 averaged 14 g of NSC/kg of dry matter (DM). Forages and concentrate were offered in separate meals with forages fed once and concentrate offered 3 times daily. Except for the molar proportion of valerate, which was lowest in cows fed the high-NSC diet, no other changes in ruminal fermentation were observed. Omasal flows of most nitrogenous fractions, including bacterial nonammonia N and AA, were not affected by treatments. Apparent ruminal digestibilities of neutral and acid detergent fiber and N were lowest, whereas that of total ethanol-soluble carbohydrates was highest when feeding the high-NSC diet. Postruminal digestibilities of DM, organic matter, fiber, and N were highest in cows fed the high-NSC diet, resulting in no difference in total-tract digestibilities. Total-tract digestibility of total ethanol-soluble carbohydrates was highest in cows fed the high-NSC diet, but that of starch did not differ across treatments. Although milk yield and total DM intake did not differ between treatments, yields of milk fat and 4% fat-corrected milk decreased significantly in cows fed the high-NSC diet. Milk concentration of urea N was lowest, and that of ruminal NH3-N highest, in cows fed the high-NSC diet. Plasma urea N concentration tended to be decreased in cows fed the high-NSC diet, but concentrations of AA were not affected by treatments, with the exception of Asp and Cys, both of which were lowest in cows fed the low-NSC diet. Feeding diets with contrasting NSC concentrations did not improve milk production, N utilization, or bacterial protein synthesis, possibly because intakes of NSC and DM were similar between treatments. Overall, results from the current study should be interpreted cautiously because of the lack of difference in dietary NSC intake between treatments and reduced N and fiber intakes when feeding the high-NSC diet.

Effects of nonstructural carbohydrate concentration in alfalfa on fermentation and microbial protein synthesis in continuous culture.

Insufficient readily fermentable energy combined with extensive degradation of proteins in alfalfa (Medicago sativa L.) may result in poor forage N utilization by ruminants. Using the inherent genetic variability and differences between harvests, our objective was to compare the effect of contrasting concentrations of nonstructural carbohydrates (NSC) in alfalfa on rumen fermentation and microbial protein synthesis. Individual genotypes of the alfalfa cultivar AC Caribou grown near Québec City, Québec, Canada, were harvested at the vegetative and early flowering stages, dried at 55 degrees C, ground, and analyzed for soluble carbohydrates (fructose + sucrose + glucose + pinitol) and starch. Approximately 20 genotypes having, respectively, the highest and lowest NSC concentrations were pooled to constitute 2 contrasted 1-kg forage samples. Samples of high- (17.9% DM) and low- (7.4% DM) NSC alfalfa were respectively allocated to separate dual-flow fermenters in a completely randomized design with 3 replications. Rumen inoculum was obtained from 4 ruminally fistulated cows in early lactation that were fed a TMR with a 50:50 forage to concentrate ratio. A 10-d incubation period was used, with the first 6 d serving as an adaptation period followed by 4 d of sampling with solid and liquid dilution rates in the fermenters set at approximately 2.0 and 4.3%/h, respectively. High versus low NSC concentration in alfalfa significantly enhanced the apparent digestibility of OM (59.1% for high-NSC alfalfa vs. 54.4% for low-NSC alfalfa) and DM (60.0 vs. 54.3%) and the true digestibility of DM (74.1 vs. 64.7%). Increasing NSC concentration in alfalfa (high vs. low) significantly decreased ruminal pH (6.85 vs. 7.08) and NH(3)-N concentration (26.0 vs. 33.6 mg/dL) and increased total VFA concentration (94.9 vs. 83.0mM). Molar proportions of acetate, isobutyrate, and isovalerate significantly decreased, whereas molar proportions of propionate and butyrate significantly increased with high-NSC alfalfa, resulting in a more glucogenic fermentation. More importantly, microbial N flow (263 vs. 230 mg/d) and bacterial N efficiency (41.1 vs. 29.6% of available N), measured using (15)N as a microbial marker, both significantly increased with the high-NSC alfalfa. These results indicate that increasing the concentration of NSC in alfalfa promotes a glucogenic fermentation and enhances microbial N synthesis in the rumen.

Near-infrared reflectance spectroscopy prediction of neutral detergent-soluble carbohydrates in timothy and alfalfa.

Carbohydrates in forage crops can be divided into neutral detergent-insoluble fiber and neutral detergent-soluble carbohydrates (NDSC); the latter includes organic acids (OA), total ethanol:water-soluble carbohydrates (TESC), starch, and neutral detergent-soluble fiber (NDSF). The accurate and efficient estimation of NDSC in forage crops is essential for improving the performance of dairy cattle. In the present study, visible and near-infrared reflectance spectroscopy (NIRS) were applied to evaluate the feasibility of predicting OA, TESC, starch, NDSF, NDSC, and all related constituents used to calculate these 5 carbohydrate fractions in timothy and alfalfa. Forage samples (n = 1,008) of timothy and alfalfa were taken at the first and second harvests at 2 sites in 2007; samples were dried, ground, and then scanned (400 to 2,500 nm) using an NIRSystems 6500 monochromator. A calibration (n = 60) and a validation (n = 15) set of samples were selected for each species and then chemically analyzed. Concentrations of TESC and NDSC in timothy, as well as starch in alfalfa, were successfully predicted, but many other carbohydrate fractions were not predicted accurately when calibrations were performed using single-species sample sets. Both sets of samples were combined to form new calibration (n = 120) and validation (n = 30) sets of alfalfa and timothy samples. Calibration and validation statistics for the combined sets of alfalfa and timothy samples indicated that TESC, starch, and NDSC were predicted successfully, with coefficients of determination of prediction of 0.92, 0.89, and 0.93, and a ratio of prediction to deviation (RPD) of 3.3, 3.1, and 3.6, respectively. The NDSF prediction was classified as moderately successful The NIRS prediction of OA was unsuccessful All related constituents were predicted successfully by NIRS except ethanol-insoluble residual OM, with Our results confirm the feasibility of using NIRS to predict NDSC, its fractions, and other related constituents, except for OA and ethanol-insoluble residual OM, in timothy and alfalfa forage samples.

Alfalfa cut at sundown and harvested as baleage increases bacterial protein synthesis in late-lactation dairy cows.

Alfalfa (Medicago sativa L.) cut at sundown (p.m.) has been shown to have a greater concentration of total nonstructural carbohydrates (TNC) than when cut at sunup (a.m.). Eight ruminally cannulated Holstein cows that were part of a larger lactation trial were used in a crossover design (24-d periods) to investigate the effects of alfalfa cutting time on digestibility and omasal flow of nutrients. Alfalfa was cut at sundown or sunup, field-wilted, and harvested as baleage (530 +/- 15.0 g of dry matter/kg of fresh matter). The difference in TNC concentration between p.m. and a.m. alfalfa within each pair of bales fed daily during the 10 d of data and sample collection varied from -10 to 50 g/ kg of dry matter. Each pair of bales was fed for ad libitum intake to cows once daily with no concentrate. During the 3 d of omasal sampling, intake (+0.8 kg/d) and omasal flow of organic matter (OM; +0.42 kg/d) tended to be greater when cows were fed p.m. vs. a.m. alfalfa, but no differences were found for ruminal and postruminal digestion of this nutrient. Similarly, N apparently digested ruminally and postruminally did not differ when feeding p.m. vs. a.m. alfalfa. However, N truly digested in the rumen, as a proportion of N intake, was significantly greater in cows fed p.m. (79%) vs. a.m. alfalfa (74%), thus suggesting that longer wilting time of alfalfa cut at sundown increased forage proteolysis. Supply of rumen-degradable protein did not change (2,716 g/d) when averaged across treatments, whereas omasal flow of non-NH(3) nonbacterial N was significantly decreased (-29 g/d) when feeding p.m. vs. a.m. alfalfa. Omasal flow of total bacterial non-NH(3)-N (NAN) increased (+21 g/d) significantly when cows were fed p.m. vs. a.m. alfalfa possibly because bacteria from cows fed p.m. alfalfa captured significantly more NH(3) than those from cows fed a.m. alfalfa. Therefore, greater availability of fermentable energy as TNC appears to increase the capacity of microbes to uptake NH(3)-N and convert it to microbial protein. Enhanced OM intake can also explain the observed increase in bacterial protein synthesis with p.m. alfalfa. Efficiency of bacterial protein synthesis, expressed on a fermented OM basis or as grams of bacterial NAN per gram of rumen-degradable N, did not differ between p.m. and a.m. alfalfa. Conversely, bacterial efficiency, as grams of bacterial NAN per gram of N intake, was significantly increased when cows were fed p.m. baleage. No significant difference between forage treatments was found for the omasal flow of total AA from omasal true digesta, suggesting no benefit of daytime cutting management on the passage of total AA to the lower gastrointestinal tract. Enhancing energy intake and TNC concentration of alfalfa by shifting forage cutting from sunup to sundown increased protein synthesis and NH(3) uptake by ruminal bacteria indicating an improvement in N utilization.

Alfalfa cut at sundown and harvested as baleage improves milk yield of late-lactation dairy cows.

Alfalfa (Medicago sativa L.) cut at sundown has been shown to contain greater concentration of total nonstructural carbohydrates (TNC) than that cut at sunup. Fourteen multiparous (8 ruminally cannulated) and 2 primiparous lactating dairy cows were randomly assigned to 2 treatments in a crossover design (2 periods of 24 d) to investigate the effects of alfalfa daytime cutting management on ruminal metabolism, nutrient digestibility, N balance, and milk yield. Half of each alfalfa field (total of 3 fields) was cut at sundown (PM) after a sunny day, whereas the second half was cut at sunup (AM) on the following day. Both PM and AM cuts were field-wilted and harvested as baleage (531 +/- 15.0 g of dry matter/kg of fresh matter). Bales (PM and AM) were ranked according to their concentrations of TNC, paired, and each pair of PM and AM baleages was then assigned to each experimental day (total of 48 d). The difference in TNC concentration between PM and AM baleages fed during the 10 d of data and sample collection varied from -10 to 50 g/kg of dry matter. Each pair of baleage was fed ad libitum to cows once daily with no concentrate. Ruminal molar proportion of acetate and total volatile fatty acid concentration were greater in animals fed the AM baleage, whereas the proportion of valerate was greater with PM baleage; no other significant changes in ruminal molar proportions of volatile fatty acids were observed between forage treatments. Digestible organic matter intake, organic matter digestibility, and plasma Lys concentration were significantly greater in cows fed PM alfalfa, suggesting that more nutrients were available for milk synthesis. Significantly lower body weight gain and retained N as a proportion of N intake were observed in cows fed PM alfalfa, thus suggesting that nutrients were channeled to milk synthesis rather than to body reserves. Intake of dry matter (+1.0 kg/d), and yields of milk (+1.0 kg/d), milk fat (+70 g/d), and milk protein (+40 g/d) were significantly greater in cows fed PM vs. AM alfalfa. Concentration of milk urea N and excretion of urea N as a proportion of total urinary N were significantly reduced, and milk N efficiency was increased when feeding PM vs. AM alfalfa, indicating an improvement in N utilization. Increasing the TNC concentration of alfalfa by shifting forage cutting from sunup to sundown improved N utilization and milk production in late-lactation dairy cows.

Production of a diagnostic monoclonal antibody in perennial alfalfa plants.

The increasing use of monoclonal antibodies (mAbs) in diagnostic reagents necessitates efficient and cost-effective mAb production methods. In blood banks, one of the most routinely used reagents is the anti-human IgG reagent used for the detection of non-agglutinating antibodies. Here we report the production of a functional, purified anti-human IgG, through the expression of its encoding genes in perennial transgenic alfalfa. Transgenic plants expressing the light- and heavy-chain encoding mRNAs were obtained, and plants from crosses were found to express fully assembled C5-1. The purification procedure yielded mainly the H2L2 form with specificity and affinity identical to those of hybridoma-derived C5-1. The ability to accumulate the antibody was maintained both in parental F1 lines during repeated harvesting and in clonal material; the antibody was stable in the drying hay as in extracts made in pure water. Also, plant and hybridoma-derived C5-1 had similar in vivo half-lives in mice. These results indicate that plant C5-1 could be used in a diagnostic reagent as effectively as hybridoma-derived C5-1, and demonstrates the usefulness of perennial systems for the cost-effective, stable, and reliable production of large amounts of mAbs.

An alfalfa rubisco small subunit homologue shares cis-acting elements with the regulatory sequences of the RbcS-3A gene from pea.

A genomic clone of RbcS was isolated from an alfalfa (Medicago sativa L. cv. Apica) genomic library and characterized. Although this clone has structural features similar to a functional gene, the second exon is interrupted by a stop codon and thus is not fully translatable in the plant. Sequence analysis of the 5' and 3' noncoding regions of RbcSK-1A showed a high sequence homology to the flanking sequences of the RbcS-3A gene from pea. The regions of homology contain many important cis-regulatory elements shown to be essential for regulation of the RbcS-3A gene in pea. The promoter of this alfalfa rubisco clone was used in a translational fusion to test its ability to control the expression of the GUS reporter gene in an homologous nuclear background. High levels of GUS enzyme activity were recorded. These strong levels are comparable to some exceptionally high levels produced in other studies following the use of photosynthesis gene promoters in fusions with the GUS reporter gene.

Differential accumulation of two glycine-rich proteins during cold-acclimation alfalfa.

Two mRNAs, MsaCiA and MsaCiB, encoding for proteins harboring glycine-rich motifs, accumulate in alfalfa during cold acclimation. Fusion polypeptides containing the amino acid sequences deduced from these mRNAs were produced in Escherichia coli and used to raise antibodies. Each antibody cross-reacted specifically with soluble polypeptides, MSACIA-32 and MSACIB, respectively. These polypeptides were detectable only in crowns of cold-acclimated plants, even though MsaCiA mRNA accumulated in both crows and leaves during cold acclimation. The analysis of parietal proteins showed that several MSACIA-related proteins, with a molecular mass of 32, 41 and 68 kDa, did accumulate in leaf cell walls and one of 59 kDa crown cell walls. This diversity is most probably due to a tissue-specific maturation of MSACIA. A discrepancy was found between the time-course of accumulation of MSACIB and the one of the corresponding transcript. These results indicate that timing and localization of MSACIA and MSACIB expression are different, and suggest that this differential expression involves both transcriptional and post-transcriptional events. Comparisons made among six cultivars of contrasting freezing tolerance suggest that low tolerance could be explained by failure to accumulate proteins like MSACIA and MSACIB at a sufficient level.

Changes in ABA and gene expression in cold-acclimated sugar maple.

To determine if cold acclimation of sugar maple (Acer saccharum Marsh.) is associated with specific changes in gene expression under natural hardening conditions, we compared bud and root translatable mRNAs of potted maple seedlings after cold acclimation under natural conditions and following spring dehardening. Cold-hardened roots and buds were sampled in January when tissues reached their maximum hardiness. Freezing tolerance, expressed as the lethal temperature for 50% of the tissues (LT(50)), was estimated at -17 degrees C for roots, and at lower than -36 degrees C for buds. Approximately ten transcripts were specifically synthesized in cold-acclimated buds, or were more abundant in cold-acclimated buds than in unhardened buds. Cold hardening was also associated with changes in translation. At least five translation products were more abundant in cold-acclimated buds and roots compared with unhardened tissues. Abscisic acid (ABA) concentration increased approximately tenfold in the xylem sap following winter acclimation, and the maximum concentration was reached just before maximal acclimation. We discuss the potential involvement of ABA in the observed modification of gene expression during cold hardening.

Characterization and mutational analysis of nodHPQ genes of Rhizobium sp. strain N33.

We have shown, by sequencing the nodulation gene region of Rhizobium sp. strain N33 previously isolated from the Canadian high arctic, that the nodHPQ genes are located in a 4.8-kb region downstream of nodBCIJ. The open reading frames of nodHPQ are 747, 906, and 1941 nucleotides long, respectively. The strain N33 genome contains one copy of nodH and two copies of nodPQ that are homologous to those genes in Rhizobium meliloti. Tn5 insertions in the nodHPQ genes of strain N33 did not affect the formation of nodules on the two homologous hosts, Astragalus cicer and Onobrychis viciifolia. Since strain N33 contains the nodBCIJHPQ genes and the recently sequenced nodAFEG genes, we looked for similar host range with R. meliloti. Strain N33 and R. meliloti strains A2 and RCR2011 were shown to induce the formation of root nodules on plants of O. viciifolia. However, strain N33, compared with R. meliloti strains, was able to elicit a few, white, empty, root nodules on Medicago sativa. R. meliloti strains, compared with strain N33, were shown to induce only few nodules containing bacteria on A. cicer. Induction of nod genes transcription in strain N33 was shown to be induced by a variety of flavonoid compounds that are different from those inducing nod genes from R. meliloti.

A cold-induced gene from Medicago sativa encodes a bimodular protein similar to developmentally regulated proteins.

A new cold-regulated (COR) gene, msa CIC, was isolated by differential screening of a cDNA library from cold-acclimated crowns of alfalfa (Medicago sativa L. cv. Apica). Transcripts of msa CIC were not detectable in unacclimated alfalfa and accumulated to higher levels in cold-acclimated plants of the cold-tolerant cv. Apica than in those of the cold-sensitive cv. CUF-101. The DNA sequence analysis of a full-length cDNA clone revealed that msa CIC encodes for a putative protein (MSACIC) of 166 amino acids with distinct proline-rich and hydrophobic domains. Protein sequence comparisons indicated that MSACIC is similar to a group of bimodular proteins that are developmentally regulated in other plant species.

Pseudoaneurysm after Bentall repair: magnetic resonance imaging assessment.

The prevalence and natural history of pseudoaneurysms (PA) following Bentall procedure has not been established. To determine the follow-up of PA in patients, the authors report their experience with magnetic resonance imaging (MRI) since 1988. Spin-echo technique suspected PA in 19 of the 27 patients who underwent aortic valve and ascending aortic replacement between 1980 and 1991. Mean PA diameter was less than 4 cm in 13 patients (group 1) and at least 4 cm in six patients (group 2). Two patients in group 1 were lost at follow-up while two others in this group died after first spin-echo examination (one death was related to PA formation). Repeated MRIs were thus possible in nine patients in group 1 and in all patients in group 2, averaging 2.2 +/- 1.1 examinations per patient for group 1 and 1.8 +/- 1.1 for group 2. PA assessed in six group 1 patients and one group 2 patient suggested thrombosed PA or postoperative hematoma. PA remained stable in two group 1 patients and one group 2 patient. One patient from group 1, in whom PA increased at follow-up, died suddenly. Four patients in group 2 required correction of PA, which had increased in diameter. Recently, addition of cine MRI has allowed visualization of turbulent flow within PA, thus increasing MRI specificity for PA diagnosis. In conclusion, MRI constitutes a reliable noninvasive imaging technique for diagnosis and follow-up of PA after Bentall repair.

Right ventricular rupture. A complication of postoperative mediastinitis.

Mediastinitis-related right ventricular rupture is an unusual but potentially life-threatening complication of cardiac operations. Between January 1981 and December 1990, a total of 10,182 patients underwent heart operations for ischemic, valvular, and congenital heart disease at the Montreal Heart Institute. Forty-eight patients (0.5%) had postoperative mediastinitis necessitating surgical exploration and sternal debridement. The mediastinum was left open for daily irrigation with povidone-iodine and chest reconstruction was postponed. During treatment, seven patients (0.07%) had right ventricular rupture necessitating immediate surgical repair. All had ischemic heart disease before the operation. There were five women and two men, ages ranging from 52 to 65 years (mean 58 +/- 5 years). Surgical repair consisted of autologous patch covered with omentoplasty assisted with cardiopulmonary bypass. Two patients died, one during the operation of massive hemorrhage and the other 10 days after the operation of uncontrolled sepsis. Five patients survived 2 to 29 months (mean 23 +/- 10 months) after right ventricular rupture, with an overall survival of 71%. Obesity was more frequent in the patients with right ventricular rupture and was found to be a significant risk factor (multivariate analysis, p < 0.05, relative risk 3.22). Histologic examination of the right ventricle in the patient who died after a successful repair revealed fatty infiltration of the right ventricular wall. This may have predisposed the patient toward ventricular rupture. In conclusion, right ventricular rupture, an unusual event in heart surgery, is related to open sternal debridement. Favorable outcome of this complication depends on immediate surgical management, autologous repair, and the use of omentoplasty.

A new cold-induced alfalfa gene is associated with enhanced hardening at subzero temperature.

When alfalfa (Medicago sativa L. cv Apica) plants grown at room temperature are transferred to 2 degrees C, the temperature at which 50% of the plants fail to survive (LT50) decreases from -6 to -14 degrees C during the first 2 weeks but then increases to -9 degrees C during the subsequent 2 weeks. However, when plants are kept for 2 weeks at 2 degrees C and then transferred to -2 degrees C for another two weeks, the LT50 declines to -16 degrees C. These changes in freezing tolerance are paralleled by changes in transcript levels of cas15 (cold acclimation-specific gene encoding a 14.5-kD protein), a cold-induced gene. Cold-activation of cas15 occurs even when protein synthesis is inhibited by more than 90%, suggesting that cold-initiated events up to and including the accumulation of cas15 transcripts depend on preexisting gene products. cas15 shows little homology to any known gene at the nucleotide or amino acid level. The deduced polypeptide (CAS15) of 14.5 kD contains four repeats of a decapeptide motif and possesses a bipartite sequence domain at the carboxy terminus with homology to the reported nuclear-targeting signal sequences. Although the relative amount of cas15 DNA as a fraction of the total genomic DNA is similar in cultivars with different degrees of freezing tolerance, its organization in the genome is different. The possible role of cas15 in the development of cold-induced freezing tolerance is discussed.

[Magnetic resonance imaging in the diagnosis and follow-up of false aneurysms after Bentall's operation]. / La résonance magnétique pour le diagnostic et le suivi des pseudoanévrismes après intervention de type Bentall.

The prevalence and natural history of pseudo-aneurysm (PA) following Bentall procedure has not been established. To determine the follow-up of such patients, we report our experience with magnetic resonance imaging (MRI) used since 1988. At first, spin-echo exam, PA was suspected in 19 patients among 27 patients who underwent aortic valve and ascending aortic replacement between 1980 and 1991. Mean PA diameter was < 4 cm in 13 patients (group 1) and > or = 4 cm in six patients (group 2). Two patients of group 1 were lost at follow-up while two others died after the first spin-echo exam, one death being related to PA formation. Repeated MRIs were done in nine patients of group 1 and all patients of group 2 averaging respectively 2.2 +/- 1.1 exams per patient for group 1 and 1.8 +/- 1.1 for group 2. PA regressed in six patients of group 1 and one patient of group 2 thus suggesting thrombosed PA or postoperative haematoma. PA remained stable in two patients of group 1 and one patient of group 2. One patient of group 1 in whom PA increased at follow-up died suddenly. Four patients of group 2 required surgical correction of their PA. One of these patients died of massive hemoptysis 2 months following reintervention. Recently, addition of cine MRI allows visualization of turbulent flow within the PA thus increasing MRI specificity for PA diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortopulmonary fistula detected by echocardiography 12 years after aortoplasty for correction of ascending aorta aneurysm.

We describe a case of aortopulmonary fistula in which the correct diagnosis was made by transthoracic echocardiography. The transesophageal approach, because of severe aortic dilatation, failed to provide the correct diagnosis, underlining the importance of complete transthoracic and transesophageal studies in the evaluation of aortic aneurysms.

Echocardiographic diagnosis of left ventricular outflow tract obstruction after mitral valvuloplasty with a flexible Duran ring.

We report on a patient in whom left ventricular outflow obstruction developed after mitral valve repair with a flexible Duran ring. This complication has been reported in 4.5% to 21% of patients when a rigid Carpentier ring was used but was thought to be eliminated with the use of flexible rings.