NifB and NifEN protein levels are regulated by ClpX2 under nitrogen fixation conditions in Azotobacter vinelandii

The major part of biological nitrogen fixation is catalysed by the molybdenum nitrogenase that carries at its active site the iron and molybdenum cofactor (FeMo-co). The nitrogen fixation (nif) genes required for the biosynthesis of FeMo-co are derepressed in the absence of a source of fixed nitrogen. The nifB gene product is remarkable because it assembles NifB-co, a complex cluster proposed to comprise a [6Fe-9S-X] cluster, from simpler [Fe-S] clusters common to other metabolic pathways. NifB-co is a common intermediate of the biosyntheses of the cofactors present in the molybdenum, vanadium and iron nitrogenases. In this work, the expression of the Azotobacter vinelandii nifB gene was uncoupled from its natural nif regulation to show that NifB protein levels are lower in cells growing diazotrophically than in cells growing at the expense of ammonium. A. vinelandii carries a duplicated copy of the ATPase component of the ubiquitous ClpXP protease (ClpX2), which is induced under nitrogen fixing conditions. Inactivation of clpX2 resulted in the accumulation of NifB and NifEN and a defect in diazotrophic growth, especially when iron was in short supply. Mutations in nifE, nifN and nifX or in nifA also affected NifB accumulation, suggesting that NifB susceptibility to degradation might vary during its catalytic cycle.

A sterile alpha-motif domain in NafY targets apo-NifDK for iron-molybdenum cofactor delivery via a tethered domain

NafY participates in the final steps of nitrogenase maturation, having a dual role as iron-molybdenum cofactor (FeMo-co) carrier and as chaperone to the FeMo-co-deficient apo-NifDK (apo-dinitrogenase). NafY contains an N-terminal domain of unknown function (n-NafY) and a C-terminal domain (core-NafY) necessary for FeMo-co binding. We show here that n-NafY and core-NafY have very weak interactions in intact NafY. The NMR structure of n-NafY reveals that it belongs to the sterile α-motif (SAM) family of domains, which are frequently involved in protein-protein interactions. The presence of a SAM domain in NafY was unexpected and could not be inferred from its amino acid sequence. Although SAM domains are very commonly found in eukaryotic proteins, they have rarely been identified in prokaryotes. The n-NafY SAM domain binds apo-NifDK. As opposed to full-length NafY, n-NafY impaired FeMo-co insertion when present in molar excess relative to FeMo-co and apo-NifDK. The implications of these observations are discussed to offer a plausible mechanism of FeMo-co insertion. NafY domain structure, molecular tumbling, and interdomain motion, as well as NafY interaction with apo-NifDK are consistent with the function of NafY in FeMo-co delivery to apo-NifDK.

Molybdenum trafficking for nitrogen fixation

The molybdenum nitrogenase is responsible for most biological nitrogen fixation, a prokaryotic metabolic process that determines the global biogeochemical cycles of nitrogen and carbon. Here we describe the trafficking of molybdenum for nitrogen fixation in the model diazotrophic bacterium Azotobacter vinelandii. The genes and proteins involved in molybdenum uptake, homeostasis, storage, regulation, and nitrogenase cofactor biosynthesis are reviewed. Molybdenum biochemistry in A. vinelandii reveals unexpected mechanisms and a new role for iron-sulfur clusters in the sequestration and delivery of molybdenum.

Extended X-ray absorption fine structure and nuclear resonance vibrational spectroscopy reveal that NifB-co, a FeMo-co precursor, comprises a 6Fe core with an interstitial light atom

NifB-co, an Fe-S cluster produced by the enzyme NifB, is an intermediate on the biosynthetic pathway to the iron molybdenum cofactor (FeMo-co) of nitrogenase. We have used Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy together with (57)Fe nuclear resonance vibrational spectroscopy (NRVS) to probe the structure of NifB-co while bound to the NifX protein from Azotobacter vinelandii. The spectra have been interpreted in part by comparison with data for the completed FeMo-co attached to the NafY carrier protein: the NafY:FeMo-co complex. EXAFS analysis of the NifX:NifB-co complex yields an average Fe-S distance of 2.26 A and average Fe-Fe distances of 2.66 and 3.74 A. Search profile analyses reveal the presence of a single Fe-X (X = C, N, or O) interaction at 2.04 A, compared to a 2.00 A Fe-X interaction found in the NafY:FeMo-co EXAFS. This suggests that the interstitial light atom (X) proposed to be present in FeMo-co has already inserted at the NifB-co stage of biosynthesis. The NRVS exhibits strong bands from Fe-S stretching modes peaking around 270, 315, 385, and 408 cm(-1). Additional intensity at approximately 185-200 cm(-1) is interpreted as a set of cluster "breathing" modes similar to those seen for the FeMo-cofactor. The strength and location of these modes also suggest that the FeMo-co interstitial light atom seen in the crystal structure is already in place in NifB-co. Both the EXAFS and NRVS data for NifX:NifB-co are best simulated using a Fe 6S 9X trigonal prism structure analogous to the 6Fe core of FeMo-co, although a 7Fe structure made by capping one trigonal 3S terminus with Fe cannot be ruled out. The results are consistent with the conclusion that the interstitial light atom is already present at an early stage in FeMo-co biosynthesis prior to the incorporation of Mo and R-homocitrate.

Structural motifs of syringyl peroxidases are conserved during angiosperm evolution

The most distinctive variation in the monomer composition of lignins in vascular land plants is that between the two main groups of seed plants. Thus, whereas gymnosperm (softwood) lignins are typically composed of guaiacyl (G) units, angiosperm (hardwood) lignins are largely composed of similar levels of G and syringyl (S) units. However, there are some studies that suggest that certain angiosperm peroxidases are unable to oxidize sinapyl alcohol, and a coniferyl alcohol shuttle has been proposed for oxidizing S units during the biosynthesis of lignins. With this in mind, a screening of the presence of S peroxidases in angiosperms (including woody species and forages) was performed. Contrarily to what might be expected, the intercellular washing fluids from lignifying tissues of 25 woody, herbaceous, and shrub species, belonging to both monocots and dicotyledons, all showed both S peroxidase activities and basic peroxidase isoenzymes analogous, with regard the isoelectric point, to the Zinnia elegans basic peroxidase isoenzyme, the only S peroxidase that has been fully characterized. These results led to the protein database in the search for homologies between angiosperm peroxidases and a true eudicot S peroxidase, the Z. elegans peroxidase. The findings showed that certain structural motifs of S peroxidases are conserved within the first 15 million years of angiosperm history, because they are found in peroxidases from the two major lineages of flowering plants, eumagnoliids and eudicotyledons, of note being the presence of these peroxidases in Amborella and Nymphaeales, which represent the first stages of angiosperm evolution. These phylogenetic studies also suggest that guaiacyl peroxidases apparently constitute the most "evolved state" of the plant peroxidase family evolution.

Web-PACS for Multicenter Clinical Trials

Medical information systems are not designed for clinical trials using clinical imaging. This paper presents a conceptual model for clinical trials based on medical imaging from two complementary points of view: a technical model and a business model. A Web information system (WIS) for supporting multicenter clinical trials has been designed to implement the proposed model. We show that our approach overcomes the actual limitations by facilitating medical image management in the context of clinical trials or cooperative research.

NifX and NifEN exchange NifB cofactor and the VK-cluster, a newly isolated intermediate of the iron-molybdenum cofactor biosynthetic pathway

The iron-molybdenum cofactor of nitrogenase (FeMo-co) is synthesized in a multistep process catalysed by several Nif proteins and is finally inserted into a pre-synthesized apo-dinitrogenase to generate mature dinitrogenase protein. The NifEN complex serves as scaffold for some steps of this synthesis, while NifX belongs to a family of small proteins that bind either FeMo-co precursors or FeMo-co during cofactor synthesis. In this work, the binding of FeMo-co precursors and their transfer between purified Azotobacter vinelandii NifX and NifEN proteins was studied to shed light on the role of NifX on FeMo-co synthesis. Purified NifX binds NifB cofactor (NifB-co), a precursor to FeMo-co, with high affinity and is able to transfer it to the NifEN complex. In addition, NifEN and NifX exchange another [Fe-S] cluster that serves as a FeMo-co precursor, and we have designated it as the VK-cluster. In contrast to NifB-co, the VK-cluster is electronic paramagnetic resonance (EPR)-active in the reduced and the oxidized states. The NifX/VK-cluster complex is unable to support in vitro FeMo-co synthesis in the absence of NifEN because further processing of the VK-cluster into FeMo-co requires the simultaneous activities of NifEN and NifH. Our in vitro studies suggest that the role of NifX in vivo is to serve as transient reservoir of FeMo-co precursors and thus help control their flux during FeMo-co synthesis.

Purification of a NifEN protein complex that contains bound molybdenum and a FeMo-Co precursor from an Azotobacter vinelandii DeltanifHDK strain

The NifEN protein complex serves as a molecular scaffold where some of the steps for the assembly of the iron-molybdenum cofactor (FeMo-co) of nitrogenase take place. A His-tagged version of the NifEN complex has been previously purified and shown to carry two identical [4Fe-4S] clusters of unknown function and a [Fe-S]-containing FeMo-co precursor. We have improved the purification of the his-NifEN protein from a DeltanifHDK strain of Azotobacter vinelandii and have found that the amounts of iron and molybdenum within NifEN were significantly higher than those reported previously. In an in vitro FeMo-co synthesis system with purified components, the NifEN protein served as a source of both molybdenum and a [Fe-S]-containing FeMo-co precursor, showing significant FeMo-co synthesis activity in the absence of externally added molybdate. Thus, the NifEN scaffold protein, purified from DeltanifHDK background, contained the Nif-Bco-derived Fe-S cluster and molybdenum, although these FeMo-co constituents were present at different levels within the protein complex.

Identification of a Ferric uptake regulator from Microcystis aeruginosa PCC7806

Ferric uptake regulator (Fur) proteins are widely recognized as repressors that in many prokaryotes regulate a large number of genes involved in iron homeostasis and oxidative stress response. In our study, we were able to identify the complete sequence of the fur gene from Microcystis aeruginosa using inverse-polymerase chain reaction. DNA sequence analysis confirmed the presence of a 183 amino-acid open reading frame that showed high identity with Fur proteins reported for cyanobacteria. The recombinant Fur protein has been purified and electrophoretical mobility shift assays shown to be active. Mn2+ and dithiothreitol enable Fur to bind to its promoter, with dithiothreitol being more potent. The expression of Fur in Microcystis was induced about twofold in iron-deficient conditions.

Reproductive characteristics of grass-fed, luteinizing hormone-releasing hormone-immunocastrated Bos indicus bulls1

Two field trials were conducted in Brazil to evaluate LHRH immunocastration of Bos indicus bulls (d 0 = 2 yr of age). In Study I, 72 bulls were assigned randomly to one of three treatment groups: LHRH0-immunized, castrated, and intact. Immunized animals (n = 25) received a primary and two booster injections of ovalbumin-LHRH-7 and thioredoxin-LHRH-7 fusion proteins on d 0, 141, and 287. Twenty-three bulls were surgically castrated on d 141, and 24 served as intact controls. All animals were slaughtered on d 385, at approximately 3 yr of age. In Study II, 216 bulls were assigned randomly to the same three treatments as in Study I; however, because of a drought in the area, bulls were kept on pasture an additional year, and a fourth treatment was added, in which one-half the LHRH-immunized bulls received an additional booster on d 639 (fourth immunization). All animals in Study II were slaughtered on d 741 (4 yr of age). Luteinizing hormone-releasing hormone antibodies increased following each immunization for immunized bulls, but they were not detectable in castrate or intact animals in either study. Consequently, scrotal circumference was suppressed in immunized bulls compared with intact controls in both studies. By d 287, serum concentrations of testosterone in LHRH-immunized bulls were decreased compared with intact controls (P < 0.01). In both studies, testes and epididymal weights at slaughter were greater (P < 0.01) for intact (500 +/- 17 and 60 +/- 2 g, respectively) than for immunized bulls (173 +/- 22 and 26 +/- 2 g, respectively) and fourth immunization bulls (78 +/- 23 and 20 +/- 2 g, respectively; Study II). At the end of each study, BW was greater (P < 0.01) for intact bulls than for castrated and LHRH-immunized animals. In these two studies, the efficacy of the LHRH fusion proteins to induce an effect similar to that of surgical castration was considered 92 and 93%, respectively. These data support the concept that immunocastration of bulls at 2 yr of age was successful and that it has practical application as a tool for producing grass-fattened bulls in Brazil.

Effects of locoweed on serum swainsonine and selected serum constituents in sheep during acute and subacute oral/intraruminal exposure1

A study was conducted to evaluate the effects of acute and subacute locoweed exposure on serum swainsonine concentrations and selected serum constituents in sheep. Thirteen mixed-breed wethers (BW = 47.5 +/- 9.3 kg) were assigned randomly to 0.2, 0.4, or 0.8 mg of swainsonine x kg BW(-1) x d(-1) treatments. During acute (24 h) and subacute (19 d) exposure, serum swainsonine was detected in all treatments and was greatest (P < 0.03) in the 0.8 mg treatment. Serum alkaline phosphate (ALK-P) activity was increased (P < 0.01) for the 0.8 mg treatment compared with baseline (0 h) by 7 h and continued to increase throughout the initial 22 h following acute exposure to locoweed. A linear increase (P < 0.01) in serum ALK-P activity was noted, with the rate being 3.00 +/- 0.56 U x L(-1) x h(-1). Serum ALK-P activity was increased (P < 0.05) across treatments on d 7 over d -19, -12, 0, 1, 21, and 26; on d 14 over d -19, -12, 0, and 26; and on d 19 over d -19, -12, 0, 1, 21, and 26. By d 20, approximately 48 h after last exposure to swainsonine, serum ALK-P activities were no longer different (P = 0.13) than baseline (d -19, -12, and 0), and by d 26 values had generally returned to baseline. No linear (P = 0.98), quadratic (P = 0.63), or cubic effects of swainsonine with time from exposure were noted for serum aspartate aminotransferase. Similar to serum ALK-P activities, serum aspartate aminotransferase activities were increased (P < 0.05) across treatment levels on d 7, 14, 19, 20, 21, and 26 over those on d -19, -12, 0, and 1. Total serum Fe was decreased (P < 0.05) within the initial 22 h following the swainsonine exposure. On d 21 (48 h after swainsonine feeding ended), serum Fe increased to 472 mg/L. Concentrations of ceruloplasmin were lower (P < 0.10) on d 14 and 19 following exposure to locoweed. Recovery of ceruloplasmin levels coincided with similar changes in serum Fe. There was a linear (slope = 0.33 mg x dL(-1) x d(-1); P < 0.01) effect with time of exposure to locoweed (i.e., swainsonine) on serum triglyceride concentrations. Rapid changes in serum ALK-P and Fe concentrations without parallel changes in other damage markers indicate that acute exposure to swainsonine induces metabolic changes that may impair animal production and health before events of cytotoxicity thought to induce clinical manifestation of locoism.

Effect of Lameness on Ovarian Activity in Postpartum Holstein Cows

A longitudinal study was conducted to examine the relationship between lameness and delayed ovarian cyclicity during the first 60 d postpartum and days to first luteal activity during the first 300 d postpartum in Holstein cows. Two hundred thirty-eight cows from a 600-cow dairy that calved during a 12-mo period were used. Cows were classified into 1 of 6 categories of lameness during the first 35 d postpartum using a locomotion scoring system. Cows were blood-sampled weekly for detection of plasma progesterone concentrations during the first 300 d postpartum. Cows with delayed resumption of ovarian cyclicity were defined as those with progesterone concentrations consistently <1 ng/mL during the first 60 d postpartum. The null hypothesis that risk of delayed cyclicity is the same in cows classified as nonlame, moderately lame, or lame (after adjusting for potential modifying or confounding effects of loss of body condition and other variables related with delayed cyclicity) was tested using logistic regression. Analysis of results of the study reported here support the hypothesis that lameness is associated with delayed ovarian activity in Holstein cows during the early postpartum period. Cows classified as lame had 3.5 times greater odds of delayed cyclicity, compared with cows classified as nonlame. Attributable proportion analysis indicated that delayed ovarian cyclicity in lame cows would be reduced by 71%, if lameness had been prevented.

Adrenal oncocytoma: US and CT findings

We describe a case of an oncocytoma occurring in the adrenal gland, a rare location, and describe US and CT findings of this tumor in our patient. The mass was well marginated but heterogeneous on both CT and US and unfortunately the imaging findings of the tumor are non-specific.

Adult intussuception as a cause of abdominal symptoms: a case report and review of literature

Intussusceptions are frequently encountered in children. In adults, they are uncommon and have a different etiology. Our case is one such example of a rare, pathologically proven, recto-rectal intussusception due to an adenocarcinoma with characteristic CT findings.

Serum thyroid hormones and reproductive characteristics of Rambouillet ewe lambs treated with propylthiouracil before puberty

Twenty-four Rambouillet ewe lambs (average weight=43.7+/-1.2 kg, approximately 6 months of age) were used to examine the effect of thyroid suppression before the onset of puberty on serum thyroid hormones, body weights (BW), and reproductive performance. Beginning in early September, ewe lambs were randomly assigned to three treatments (n=8 lambs/treatment). All animals remained in a single pen (4 x 12 m) with access to salt, water, shade and alfalfa hay (2.5 kg per animal per day) throughout the experiment. Beginning on Day 0 (first day of treatment), all ewe lambs received daily treatments (gavage) for 15 days consisting of 0, 20, or 40 mg 6-N-propyl-2-thiouracil(PTU)/kg BW per day. Beginning on Day 15, the 20 and 40 mg treatments were lowered to 10 and 20 mg PTU/kg BW, respectively. All animals were treated for 28 days. Ovarian cyclicity was determined by twice weekly progesterone (P(4)) analysis. Thyroxine (T(4)) concentrations were similar on Day 0 (61.6, 54.8 and 56.9+/-2.5 ng/ml, P=0.17) in ewe lambs receiving 0, 20 and 40 mg PTU/kg BW, respectively. By Day 7, both PTU-treated groups had T(4) values less than 20 ng/ml (9.0 and 15.4+/-2.5 ng/ml) compared with 78.5 ng/ml in controls (P<0.01). By 7 days after termination of PTU treatment, serum T(4) had risen to 29.1 and 26.9 (+/-2.9)ng/ml in the 20/10 and 40/20 PTU groups, respectively. On Day 66, control ewes had 55.0 ng T(4)/ml compared with 43.1 and 39.0 (+/-2.6 ng/ml) for ewes in the 20/10 and 40/20 groups, respectively (linear, P<0.01). Serum triiodothyronine (T(3)) followed a similar pattern to that observed for T(4). Ewe lamb BW were similar (P>0.50) among groups throughout the treatment period. However, following the treatment, PTU-treated ewes tended (P<0.10) to weigh less than controls. Average Julian day of puberty was also similar (P>0.50) among treatments (286, 288 and 288+/-5 days; control, 20/10 and 40/20, respectively). Control ewes had a pregnancy rate of 75%, while both PTU-treated groups had pregnancy rates of 88% (P>0.20). The administration of PTU resulted in a rapid decline in serum T(4) and T(3) but neither time of puberty nor pregnancy rates were affected by lowered thyroid hormones.

Ovarian cyclicity in thyroid-suppressed ewes treated with propylthiouracil immediately before onset of seasonal anestrus

Two experiments were conducted to determine if propylthiouracil (PTU)-induced thyroid suppression immediately before onset of anestrus would extend the breeding season in mature ewes. In Exp. 1, twice-weekly serum concentrations of progesterone indicated that all ewes were cyclic before initiation of treatment. Beginning on d 0 (January 17), ewes received 0 (n = 4), 20 (n = 5), or 40 (n = 5) mg of PTU x kg(-1) of body weight (BW) x (-1) for 35 d. Blood samples were collected regularly throughout the trial and serum thyroxine and progesterone were quantified. Ewe BW were similar (P > 0.90) among treatments before the experiment began (mean = 78.2 +/- 4.5 kg). Likewise, serum concentrations of thyroxine averaged 86.5 +/- 8.0 ng/mL on d 0. After 11 d of PTU treatment, serum thyroxine was 90.2,75.2, and 44.2 +/- 14.0 ng/mL in ewes receiving 0, 20, and 40 mg of PTU/kg BW, respectively (linear effect, P = 0.04). On d 20, thyroxine values in the three respective groups were 73.0, 51.1, and 16.1 +/- 12.9 ng/mL (linear effect, P < 0.01). Fourteen days after PTU treatment ended, serum thyroxine did not differ (P = 0.53) among the three respective groups (71.4,73.3, and 57.5 +/- 11.8 ng/mL). Ewes receiving PTU tended to weigh less on d 42 (84.2, 78.2, and 71.8 +/- 5.1 kg for ewes treated with 0, 20, and 40 mg PTU/kg, respectively; linear effect, P = 0.10). Day of onset of anestrus was designated as the day on which serum progesterone decreased and remained below 1 ng/mL. Ewes treated with 0, 20, or 40 mg of PTU/kg BW became anestrous on d 16,40, and 81 (+/- 12) of the experiment, respectively (linear effect, P < 0.01). At the time the 35-d treatment period ended, 25, 60, and 100% of ewes receiving 0, 20, or 40 mg of PTU/kg exhibited normal estrous cycles. In Exp. 2, ewes received 0, 20, or 40 mg of PTU/kg BW for 14 d. The dose was then decreased to 0, 10, and 20 mg of PTU/kg BW for the remaining 21 d. Serum thyroxine decreased to concentrations below 20 ng/mL by d 9 after initiation of PTU treatment. Ewe weights did not differ throughout the trial and no BW loss was observed. The average day that each group entered anestrus was similar to those in Exp 1. Large doses of PTU dramatically lower serum thyroxine and this effect appears to inhibit onset of anestrus in ewes.

Relationships of metabolic hormones and serum glucose to growth and reproductive development in performance-tested Angus, Brangus, and Brahman bulls

Understanding mechanisms that regulate growth and reproduction are important for improving selection strategies in cattle. In this study, Angus, Brangus, and Brahman bulls (n = 7 per breed) of similar age were selected from a group of 65 weanlings. Bulls were evaluated after weaning (i.e., approximately 6 mo of age) for 112 d for serum concentrations of metabolic hormones and glucose, growth, and reproductive traits. Performance data and blood sera were collected on d 0, 28, 56, 84, and 112. Sera were also collected in periods from d 50 to 59 (56D) and 103 to 112 (112D). Angus bulls were heavier (P < 0.05) throughout the study than Brahman bulls and were heavier than Brangus bulls on d 56, 84, and 112. Initial and final BW for Angus, Brangus, and Brahman bulls were 292.7, 260.6, and 230.4 and 468.3, 435.6, and 350.7 +/- 12 kg, respectively. Conversely, Brahman bulls had greater hip height (P < 0.05) than Brangus, and Brangus were taller (P < 0.05) than Angus. Angus bulls had the greatest (P < 0.05) scrotal circumference (SC) and Brahman bulls the least. Mean SC across days was 31.5, 29.7, and 25.0 +/- 0.6 cm for the three respective breeds. Serum testosterone was greater (P < 0.01) in Angus and Brangus bulls (10.0 and 8.9 +/- 1.4 ng/mL) than in Brahman bulls (4.0 +/- 1.4 ng/mL) throughout the study. After d 112, 100, 86, and 57% of the Angus, Brangus, and Brahman bulls passed a breeding soundness exam (P = 0.51). Serum concentrations of IGF-I and leptin were greater (P < or = 0.06) in Angus bulls on d 56, 84, and 112 than in Brangus and Brahman bulls. Serum concentrations of GH (P < 0.08) and glucose (P < 0.03) were greater in Brangus bulls than in Angus or Brahman bulls throughout the study. Prediction analyses suggested that serum concentrations of leptin could be used to predict (P < or = 0.08) BW and SC (R2 > 0.82) in the 56D and 112D periods among these breeds. Leptin was also useful in predicting (P < or = 0.09) serum concentrations of GH and testosterone in the 112D period (R2 > 0.32). Residual correlation analyses with the effect of breed removed suggested that leptin was correlated (r > or => 0.53, P < 0.05) with both SC and serum testosterone. Angus and Brahman cattle differ in phenotype, level of adiposity, and rate of sexual development. Data herein suggest that these characteristics could be due to varying mechanisms by which metabolic hormones such as leptin, GH, and(or) IGF-I are regulated.

Serum luteinizing hormone, growth hormone and insulin-like growth factor-I after releasing hormone challenge in prepubertal ewe lambs selected for twinning

Two studies evaluated hormonal markers as indicators of the onset of puberty in Debouillet sheep selected for twinning. In Trial 1, 29 ewe lambs (50 +/- 0.5 kg, 159 to 187 d of age) were given 10 microg GnRH (i.v.) on September 15 and blood was collected at 30 min intervals after the injection for 2 h. Additional samples were taken twice weekly and progesterone (P4) was measured. The day that serum P4 was greater than 1 ng/mL for 2 consecutive sampling days was classified as the day of puberty. Average day of puberty was October 12 (average age at puberty was 199 d) and ewes with values less or greater than the average were classified as early or late, respectively. Average weight at GnRH challenge was 50 kg and ewes weighing less or more were classified as light or heavy, respectively. Early ewes weighed more (P = 0.01) and reached puberty sooner (P = 0.01) than late ewes. Heavy lambs reached puberty earlier, weighed more at GnRH challenge, and had more LH area under the curve (AUC, P < 0.05) than light ewes. In Trial 2, we gave 27 ewe lambs (54 +/- 0.9 kg, 173 to 189 d of age) a single i.v. injection of 10 microg GnRH and 10 microg GHRH on September 17. Average day of puberty was October 13, average weight was 54 kg, and average age at puberty was 208 d. Categories were designated as described for Trial 1. Early lambs reached puberty sooner (P = 0.01) and weighed more (P = 0.01) than late lambs, but the puberty groups had similar LH AUC (P = 0.64) and GH AUC (P = 0.75), whereas IGF-I was greater (P = 0.01) in early puberty ewes than in late puberty ewes. Heavy lambs reached puberty earlier (P = 0.06), weighed more (P = 0.01), and tended (P = 0.11) to have more GH AUC than light ewes. No difference was observed in LH AUC or IGF-I between weight groups (P > 0.15). Results suggest that serum LH after GnRH is not a reliable indicator of the onset of puberty in ewe lambs selected for twinning, but heavier ewes tended to produce more GH after a GHRH challenge and reach puberty earlier than lighter ewe lambs.

Multiresolution analysis in fMRI: sensitivity and specificity in the detection of brain activation

Multiresolution analysis of fMRI studies using wavelets is a new approach, previously reported to yield higher sensitivity in the detection of activation areas. No data are available, however, in the literature on the analytic approach and wavelet bases that produce optimum results. The present study was undertaken to assess the performance of different wavelet decomposition schemes by making use of a "gold standard," a realistic computer-simulated phantom. As activation areas are then known "a priori," accurate assessments of sensitivity, specificity, ROC curve area and spatial resolution can be obtained. This approach has allowed us to study the effect of different factors: the size of the activation area, activity level, signal-to-noise ratio (SNR), use of pre-smoothing, wavelet base function and order and resolution level depth. Activations were detected by performing t-tests in the wavelet domain and constructing the final image from those coefficients that passed the significance test at a given P-value threshold. In contrast to previously reported data, our simulation study shows that lower wavelet orders and resolution depths should be used to obtain optimum results (in terms of ROC curve area). The Gabor decomposition offers the maximum fidelity in preserving activation area shapes. No major differences were found between other wavelet bases functions. Data pre-smoothing increases ROC area for all but very small activation region sizes.

Unusual bone marrow manifestations of parvovirus B19 infection in immunocompromised patients

Parvovirus B19 is responsible for a spectrum of disease in humans. The usual bone marrow findings in acute parvovirus infections are marked erythroid hypoplasia and occasional giant erythroblasts. Intranuclear inclusions in developing erythroid precursors are rarely described in children or adults with parvovirus infection, although abundant intranuclear inclusions are commonly observed in the placenta and other tissues in infected fetuses. In this study, 8 patients are reported in whom the first evidence of parvovirus infection was the recognition of numerous intranuclear inclusions in erythroid precursors on bone marrow biopsy sections. Six of the 8 patients had documented immunodeficiencies; 4 had acquired immune deficiency syndrome (AIDS), and 2 were on chemotherapy. Five of 7 patients were negative for immunoglobulin G (IgG) antiparvovirus antibodies, including all 4 with AIDS. Unlike the typical pattern in parvovirus infection, the bone marrow was hypercellular in most of the patients, and erythroid precursors were usually increased with the entire spectrum of normoblast maturation represented; abundant intranuclear inclusions were observed similar to the finding in fetuses. The inclusions were variably eosinophilic and compressed the chromatin against the nuclear membrane. In situ hybridization showed parvovirus B19 DNA in numerous erythroid precursors in all cases. The findings of erythroid maturation and abundant viral inclusions in these immunocompromised patients is consistent with the hypothesis that failure to produce effective IgG parvovirus neutralizing antibodies may lead to persistent infection through viral tolerance that allows erythroid development of infected cells past the pronormoblast stage. Identification of parvovirus inclusions in marrow biopsies and subsequent confirmation of infection by in situ hybridization can be important in the assessment of anemia in immunodeficient patients because serological studies for parvovirus B19 are frequently negative.

Secondary prevention of venous thromboembolism: A role for low-molecular-weight heparin

BACKGROUND

After a short initial course of heparin therapy, patients with venous thrombo-embolism (VTE) require continuing anticoagulant therapy for several months after hospital discharge. At present, two small-scale studies have compared the efficacy and safety of low-molecular-weight heparin (LMWH) with warfarin in the secondary prevention of VTE.

PATIENTS AND METHODS

We studied 654 consecutive patients, 202 with pulmonary embolism (PE) and 452 patients with deep vein thrombosis (DVT) of the lower limbs. 220/654 patients (34%) were considered to have some contraindications to coumarin, and were discharged on LMWH (dalteparin, Fragmin((R)), 10, 000 IU s.c. once daily). The remaining 434/654 patients were asked to choose between either coumarin or LMWH: 190 patients preferred LMWH and 244 coumarin. Patients were followed up for a 3-month (DVT patients) or 6-month (PE patients) period.

RESULTS

14/654 patients (2%) developed recurrent VTE while on anticoagulant therapy. One in every three recurrent episodes was PE (which was fatal in 2/5 patients), and half of the recurrent DVT were located in the contralateral leg. We failed to find any differences between patients receiving LMWH and those on coumarin therapy, but recurrences were more common in patients with cancer (hazard ratio: 17.15; 95% CI: 4.0-73.5; p < 0.001). 21 patients (3.3%) bled (major bleeding 5 patients; minor bleeding 16). Bleeding was more common in patients on coumarin therapy (hazard ratio: 3.14; 95% CI: 1.20-8.22; p = 0.02).

CONCLUSIONS

Long-term LMWH therapy proved to be both effective and safe in the long-term treatment of VTE. Thus, we suggest long-term LMWH therapy should be considered for patients with contraindications to coumarin, or those with difficulties in coming to laboratory control.