Control of seed coat thickness and permeability in soybean : a possible adaptation to stress

Although the seed coat, through its thickness and permeability, often regulates seed germination, very little is known about the control of its development. Using soybean (Glycine max [L.] Merrill) explants, podbearing cuttings in which defined solutions can be substituted for the roots, we have demonstrated that cytokinin and mineral nutrients moving through the xylem can control soybean seed coat development. Lack of cytokinin and minerals in the culture solution, causes a thicker, less permeable seed coat to develop. The seeds with thickened coats will imbibe water rapidly if scarified; furthermore, these scratched seeds also germinate and produce normal plants. Inasmuch as stress (e.g. drought) decreases mineral assimilation and cytokinin production by the roots, the resulting delay in germination could be an adaptive response to stress.     

Synthesis and antibody-mediated detection of oligonucleotides containing multiple 2,4-dinitrophenyl reporter groups.

A series of non-nucleoside-based 2,4-dinitrophenyl (DNP) phosphoramidites have been prepared and used in the multiple labelling of oligonucleotides during solid-phase synthesis. The length of spacer arm between the DNP label and the oligonucleotide phosphate backbone, and the number of attached DNP groups have both been varied in order to determine the optimum conditions for anti-DNP antibody binding. Detection using enzyme-linked colorimetric techniques showed sensitivity equivalent to that obtainable using biotinylated oligonucleotides.     

Sequence variation at the major histocompatibility complex locus DQ beta in beluga whales (Delphinapterus leucas) [published erratum appears in Mol Biol Evol 1995 Nov;12(6):1174]

Genetic variation at the Major Histocompatibility Complex locus DQ beta was analyzed in 233 beluga whales (Delphinapterus leucas) from seven populations: St. Lawrence Estuary, eastern Beaufort Sea, eastern Chukchi Sea, western Hudson Bay, eastern Hudson Bay, southeastern Baffin Island, and High Arctic and in 12 narwhals (Monodon monoceros) sympatric with the High Arctic beluga population. Variation was assessed by amplification of the exon coding for the peptide binding region via the polymerase chain reaction, followed by either cloning and DNA sequencing or single-stranded conformation polymorphism analysis. Five alleles were found across the beluga populations and one in the narwhal. Pairwise comparisons of these alleles showed a 5:1 ratio of nonsynonymous to synonymous substitutions per site leading to eight amino acid differences, five of which were nonconservative substitutions, centered around positions previously shown to be important for peptide binding. Although the amount of allelic variation is low when compared with terrestrial mammals, the nature of the substitutions in the peptide binding sites indicates an important role for the DQ beta locus in the cellular immune response of beluga whales. Comparisons of allele frequencies among populations show the High Arctic population to be different (P < or = .005) from the other beluga populations surveyed. In these other populations an allele, Dele-DQ beta*0101-2, was found in 98% of the animals, while in the High Arctic it was found in only 52% of the animals. Two other alleles were found at high frequencies in the High Arctic population, one being very similar to the single allele found in narwhal.      

Grain dust and the lungs.

Grain dust is composed of a large number of materials, including various types of grain and their disintegration products, silica, fungi, insects and mites. The clinical syndromes described in relation to exposure to grain dust are chronic bronchitis, grain dust asthma, extrinsic allergic alveolitis, grain fever and silo-filler''s lung. Rhinitis and conjunctivitis are also common in grain workers. While the concentration and the quality of dust influence the frequency and the type of clinical syndrome in grain workers, host factors are also important. Of the latter, smoking is the most important factor influencing the frequency of chronic bronchitis. The role of atopy and of bronchial hyperreactivity in grain dust asthma has yet to be assessed. Several well designed studies are currently being carried out in North America not only to delineate the frequency of the respiratory abnormalities, the pathogenetic mechanisms and the host factors, but also to establish a meaningful threshold limit concentration for grain dust.     

Meta-analysis identifies pleiotropic loci controlling phenotypic trade-offs in sorghum

Community association populations are composed of phenotypically and genetically diverse accessions. Once these populations are genotyped, the resulting marker data can be reused by different groups investigating the genetic basis of different traits. Because the same genotypes are observed and scored for a wide range of traits in different environments, these populations represent a unique resource to investigate pleiotropy. Here, we assembled a set of 234 separate trait datasets for the Sorghum Association Panel, a group of 406 sorghum genotypes widely employed by the sorghum genetics community. Comparison of genome-wide association studies (GWAS) conducted with two independently generated marker sets for this population demonstrate that existing genetic marker sets do not saturate the genome and likely capture only 35–43% of potentially detectable loci controlling variation for traits scored in this population. While limited evidence for pleiotropy was apparent in cross-GWAS comparisons, a multivariate adaptive shrinkage approach recovered both known pleiotropic effects of existing loci and new pleiotropic effects, particularly significant impacts of known dwarfing genes on root architecture. In addition, we identified new loci with pleiotropic effects consistent with known trade-offs in sorghum development. These results demonstrate the potential for mining existing trait datasets from widely used community association populations to enable new discoveries from existing trait datasets as new, denser genetic marker datasets are generated for existing community association populations.     

Analysis of microsatellite instability and loss of heterozygosity in breast cancer with the use of a well characterized multiplex system

Analysis of microsatellite instability (MI) and loss of heterozygosity (LOH) is recommended for screening patients with sporadic and hereditary malignancies. This study shows an application of a fluorescent hexaplex PCR system for microsatellite typing on A.L.F. DNA Sequencer (Pharmacia Biotech). This technique detects changes in microsatellites providing a time-efficient, reliable and accurate method for MI and LOH analyses. The Fragment Manager software was used for automated size calculation and quantitation of DNA fragments, enabling rapid and precise measurement of allelic ratios. We examined 70 breast cancer and 70 control DNA specimens, classified all the patterns of microsatellite alterations, and set up MI and LOH assessment criteria for the automated multiplex fluorescent method.     

Does delivery volume of family physicians predict maternal and newborn outcome?

Background

The number of births attended by individual family physicians who practice intrapartum care varies. We wanted to determine if the practice–volume relations that have been shown in other fields of medical practice also exist in maternity care practice by family doctors.

Methods

For the period April 1997 to August 1998, we analyzed all singleton births at a major maternity teaching hospital for which the family physician was the responsible physician. Physicians were grouped into 3 categories on the basis of the number of births they attended each year: fewer than 12, 12 to 24, and 25 or more. Physicians with a low volume of deliveries (72 physicians, 549 births), those with a medium volume of deliveries (34 physicians, 871 births) and those with a high volume of deliveries (46 physicians, 3024 births) were compared in terms of maternal and newborn outcomes. The main outcome measures were maternal morbidity, 5-minute Apgar score and admission of the baby to the neonatal intensive care unit or special care unit. Secondary outcomes were obstetric procedures and consultation patterns.

Results

There was no difference among the 3 volume cohorts in terms of rates of maternal complications of delivery, 5-minute Apgar scores of less than 7 or admissions to the neonatal intensive care unit or the special care unit, either before or after adjustment for parity, pregnancy-induced hypertension, diabetes, ethnicity, lone parent status, maternal age, gestational age, newborn birth weight and newborn head circumference at birth. High- and medium-volume family physicians consulted with obstetricians less often than low-volume family physicians (adjusted odds ratio [OR] 0.586 [95% confidence interval, CI, 0.479–0.718] and 0.739 [95% CI 0.583–0.935] respectively). High- and medium-volume family physicians transferred the delivery to an obstetrician less often than low-volume family physicians (adjusted OR 0.668 [95% CI 0.542–0.823] and 0.776 [95% CI 0.607–0.992] respectively). Inductions were performed by medium-volume family physicians more often than by low-volume family physicians (adjusted OR 1.437 [95% CI 1.036–1.992].

Interpretation

Family physicians'' delivery volumes were not associated with adverse outcomes for mothers or newborns. Low-volume family physicians referred patients and transferred deliveries to obstetricians more frequently than high- or medium-volume family physicians. Further research is needed to validate these findings in smaller facilities, both urban and rural.More than 20 years ago, Luft and associates¹ conducted one of the earliest volume–outcome studies. Since then, many studies addressing the relation between volume of procedures and patient outcomes have been published.^2,3 In some of these studies, either the hospital size or the physician procedural volume was used as a surrogate for physician expertise. Among studies analyzing hospital volumes and outcomes, better outcomes have been associated with higher patient volumes in some instances^4,5,6,7 but not others.^3,8,9 Some studies of individual provider volume have shown a positive relation between volume and outcomes,^10,11 whereas others have shown no relation or inconsistent results.^3,12 Finally, a few studies analyzing both hospital volume and provider volume have reported a positive volume–outcome relation.^13,14Criticism levelled at the methods used in volume–outcome studies have addressed the lack of adjustment for case mix, different cutoff points for volume categories and retrospective design.³ Other factors that have an effect on patient outcomes but that have not been included in previous volume analyses include health maintenance organization status, physician certification and years since graduation, and patient socioeconomic status, age and ethnicity. Furthermore, most of the studies on volume have covered surgical or oncology specialities.The few studies that have been done on volume and outcome in maternity care have shown variable effects. Rural health care is often associated with lower volumes of obstetric procedures. However, no differences in maternal or newborn outcomes have been shown in some comparisons of births in urban and rural locations.^15,16,17,18 Other studies have shown poorer maternal and newborn outcomes in low-volume hospitals, neonatal intensive care units (NICUs) and rural locations.^19,20,21,22 Conversely, higher volume (hospitals with more than 1000 deliveries per year) has been associated with more maternal lacerations or complications.²³When the health care provider has been the unit of analysis, a relation between volume and maternal or newborn outcome has been demonstrated in at least one study²⁴ but not in others.^25,26 Low volume has been defined as 20 to 24 deliveries per year.^24,26 Hass and colleagues²⁴ reported an adjusted odds ratio (OR) of 1.4 for low birth weight for infants delivered by low-volume non-board-certified physicians relative to high-volume non-board-certified physicians; the adjusted OR was 1.56 for low-volume board-certified physicians relative to high-volume board-certified physicians (98.7% of whom were obstetricians).Possible explanations for the differences among studies include differences in health care delivery systems, insurance coverage, experience and training of providers, maternal risk factors, triage or transfer of high-risk cases, choice of outcome measures, and changes over time in access to care, quality assurance and standard of living. Relations have been reported between maternal or newborn outcomes and smoking, maternal history of low birth weight (for previous pregnancies), pregnancy–induced hypertension, diabetes, prepregnancy weight, gestational weight gain, maternal height and age, multiple gestation, previous vaginal birth after cesarean section, history of previous delivery problems, parity, large-for-date fetus, ethnicity and fetal sex.^25,27,28,29 Few studies of the relation between volume of births and obstetric outcome have been able to control for these potentially confounding variables and adjust for maternal risk factors.Our database of detailed accounts of births in one hospital setting allowed us to examine this issue more rigorously. We posed 2 research questions: Is there a relation between the volume of deliveries attended by individual family physicians and maternal and newborn outcomes? If there are differences in outcomes, are they related to different physician practice styles and consultation patterns?     

Modeling the kinetics of acylation of insulin using a recursive method for solving the systems of coupled differential equations

This paper describes a theoretical method for solving systems of coupled differential equations that describe the kinetics of complicated reaction networks in which a molecule having multiple reaction sites reacts irreversibly with multiple equivalents of a ligand (reagent). The members of the network differ in the number of equivalents of reagent that have reacted, and in the patterns of sites of reaction. A recursive algorithm generates series, asymptotic, and average solutions describing this kinetic scheme. This method was validated by successfully simulating the experimental data for the kinetics of acylation of insulin.