High-precision lattice QCD confronts experiment

The recently developed Symanzik-improved staggered-quark discretization allows unquenched lattice-QCD simulations with much smaller (and more realistic) quark masses than previously possible. To test this formalism, we compare experiment with a variety of nonperturbative calculations in QCD drawn from a restricted set of "gold-plated" quantities. We find agreement to within statistical and systematic errors of 3% or less. We discuss the implications for phenomenology and, in particular, for heavy-quark physics.

Transgenic mice overexpressing the neurotrophic factor S-100 beta show neuronal cytoskeletal and behavioral signs of altered aging processes: implications for Alzheimer's disease and Down's syndrome

S-100 beta is a neurotrophic factor released by astroglial cells and localized to chromosome 21, within the region which is considered obligate for Down's syndrome (DS). S-100 beta is increased in the postmortem brains of both DS and Alzheimer's disease. Transgenic mice, produced by insertion of the human gene for S-100 beta, were examined for dendritic development at two ages, using an antibody against microtubule associated protein-2 (MAP-2). At the earliest stages, the density of dendrites within the hippocampus of transgenic animals exceeded that of controls. Also, MAP-2 immunostaining was evident in the region of the cell body. By 1 year of age, the transgenic animals had significant loss of dendrites compared to controls and the number of cells showing cell body staining was further increased. These pathological changes could be indicative of the presence of neurofibrillary tangles and cytoskeletal collapse. Behaviorally, younger transgenic animals could not perform in a learning task as well as controls. Together, these findings suggest that increased S-100 beta in brain may lead to accelerated development, followed by increased aging. The pathological changes may prove useful as an animal model of Down's syndrome and Alzheimer's disease.

Midtrimester uterine rupture. A case report

BACKGROUND

Uterine rupture during the second trimester is a rare obstetric emergency. There have been 31 reported cases since 1968, with 25 occurring during elective termination of pregnancy. Four cases occurred in patients with transverse lower uterine segment cesarean scars.

CASE

In this case, uterine rupture of a classical cesarean scar occurred during second-trimester termination.

CONCLUSION

This is the first reported case of rupture of a classical cesarean scar during second-trimester pregnancy termination.

Early intrauterine development: II. The rate of growth in Black and Central American populations between 10 and 20 weeks' gestation

The application of the growth-rate standards, extablished for Caucasian embryos and fetuses in a previous report, to Black and Central American racial groups has been investigated. Comparison between menstrual age and crown-to-rump length indicated differences in the 10 to 15 weeks' gestation range. However, growth rates for the same groups were practically identical between the 15th and 20th weeks of pregnancy. This finding suggests that the actual rate of growth is closely similar in the respective ethnic groups and that apparent discrepancies reflect erroneous, or purposefully false, menstrual histories rather than dissimilar growth patterns. Largely identical rates of development were suggested by the crown-rump length to foot length to body weight interrelations among the various racial groups. A moderate, but rather predictable, deviation from the earlier established standards was noted in the crown-rump length versus foot length ratios of Black American fetuses, providing the only exception to what appears to be a practically identical rate of growth for the investigated ethnic groups in the first half of gestation. The evaluation of the results was extended to involve the effect of educational and social factors on currently available data of embryonic and fetal growth. It is suggested that heretofore unconsidered factors may affect the validity of widely quoted standards of intrauterine growth.

Early intrauterine development: I. The rate of growth of Caucasian embryos and fetuses between the 6th and 20th weeks of gestation

Liberalization of abortion laws in various countries and states of Europe and America has offered an opportunity for the study of the correlations between menstrual age and the rate of bodily development of human embryos and fetuses. In several institutions where local bylaws mandated the consent of the patients requesting therapeutic abortion to pathological investigation of the products of conception, various parameters of growth were measured systematically. These included crown-rump and foot lengths and body weight. The analysis of the data indicated that in the embryosic stages of development the rate of growth is substantially slower than it had been assumed previously. In the more advanced fetal stages of development the findings supported the validity of the long-established standard of Streeter. Since the current study has been based on apparently normal gestations of healthy women, whereas earlier data had rested, to a great extent, on spontaneously aborted and extopic embryon and fetuses, it seems evident that pathological specimens are not suitable for the purpose of establishing reliable standards of normal intrauterine growth rate. The present data support the suggestion, based on various experimental and clinical observations, that pathological gestations often result from abnormal ovulations that occur at times other than the mid-cycle and that such conceptions are frequently followed by a bleeding episode that simulates menstruation. It is likely that the inclusion of a high number of such cases biased the results of earlier investigations concerning embryonic growth rate on account of the frequent incidence of erroneous menstrual histories. The material available did not permit the extension of the investigation beyond the 20th week of gestation. It appears, however, that the average growth rate in the mid-trimester may be slower than the data adopted by the American Academy of Pediatrics would indicate. The possible causes of some phenomena observed in the course of the investigation, such as unexplained scatter of growth-rate patterns at all developmental stages and discrepancies among various literary data, have been discussed in some detail. While a tentative attempt has been made to correlate the investigated parameters of fetal growth with biparietal diameters of the head, a measurement accessible to direct assessment by sonography during pregnancy, the necessity of improving these standards through a prospective study has been emphasized.