Human rhinovirus mutants resistant to low pH.

Mutants of human rhinovirus serotype 14 (HRV14) with increased resistance to treatment at low pH were obtained by repeated cycles of exposure to pH 4.5 and propagation in HeLa cells. Whereas wild-type virus lost more than 5 logs of infectivity upon incubation at pH 4.3, the three isolates examined were essentially unaffected. Conformational change of the viral capsid upon exposure to low pH was assessed as an increase of hydrophobicity by partition between an aqueous phase and a Triton X-114 phase; the mutants required exposure to a much lower pH to accumulate in the Triton phase than wild-type HRV14. The sequence of the capsid region was determined for three isolates; two isolates were found to have the changes Thr17 to lie in VP2 and Asn 100 to lie in VP1. The third isolate also had the change Thr17 to Ile in VP2; however, in VP1, Asp101 was replaced by Glu. Separate introduction of the mutations into full length cDNA clones of the wild-type sequence of HRV14 showed that only the changes in VP1 were necessary for the increased stability at pH 4.5. The implications of the mutations for the three-dimensional structure of the viral capsid are discussed.     

Reduced StartReact effect and freezing of gait in Parkinson’s disease: two of a kind?

Freezing of gait (FOG) is a disabling feature of Parkinson’s disease. Emerging evidence suggests that dysfunction of the pedunculopontine nucleus (PPN) and pontomedullary reticular formation (pmRF) plays a role in the causation of FOG. These brainstem structures can be examined by the StartReact paradigm, which utilizes a startling stimulus to accelerate reaction times (StartReact). Here, we examined gait initiation in PD patients with and without FOG using this paradigm. Twenty-six patients with Parkinson’s disease (12 freezers and 14 non-freezers) and 15 controls performed two tasks: rapid gait initiation in response to an imperative ‘go’ signal; and a control condition, involving a simple reaction-time task involving ankle dorsiflexion. During both tasks, a startling acoustic stimulus was combined with the imperative signal in 25 % of trials. In controls, the startle accelerated gait initiation and shortened the onset latency of tibialis anterior responses during ankle dorsiflexion. This acceleration was intact in non-freezers, but was significantly attenuated in the freezers. Independent of the occurrence of a startle, freezers showed a reduced length of the first step compared to non-freezers and controls. The diminished StartReact effect in freezers probably reflects deficient representation or release of motor programs at the brainstem reticular level due to dysfunction of the PPN, the pmRF, or both. These brainstem structures are presumably involved in integrating anticipatory postural adjustments with subsequent stepping movements. We suggest that with time-varying demands, these structures may no longer be able to coordinate the integration of anticipatory postural adjustments with steps, leading to FOG episodes.     

A comparison of cesarean section frequencies in two Norwegian hospitals

The two largest Norwegian obstetrical departments, in the cities of Bergen and Stavanger, differ markedly with regard to the frequency of Cesarean section. During the 1970's the proportions rose in both departments, but the Stavanger rate remained about half of that in Bergen, the latter following the national average. These differences were not reflected in the perinatal mortality, which had the same rates and fell equally in both hospitals. To search for explanations, all records of Cesarean section cases from the years 1974 and 1979 were studied in both hospitals. We found that mechanical indications, meaning disproportion and prolonged labor, accounted for most of the difference, whereas there was no significant rise in the frequencies for the indication fetal asphyxia in either of the hospitals, these being numerically the most important indications. In fact, there was no significant rise for mechanical indications in Stavanger between 1974 and 1979, whereas in Bergen the increased frequency for this indication gave the highest significance level for any of the seven subgroups of indications. It is suggested that the chain of command may be an important cause of the observed differences between the two departments, although this is not reflected in any stated or conscious policy in either place.     

Comparison of prenatal ultrasound and postmortem findings in fetuses and infants with congenital heart defects.

OBJECTIVE: Detection of congenital heart defects by prenatal ultrasound examination has been one of the great challenges since the investigation for fetal anomalies became part of the routine fetal examination. This prospective study was designed to evaluate the concordance of prenatal ultrasound findings with autopsy examination in a population consisting of both referred women and non-selected pregnant women. DESIGN: Criteria for inclusion were an ultrasound examination at the National Center for Fetal Medicine and an autopsy performed during the years 1985-94. Results from the ultrasound and autopsy examinations were systematized into categories depending on the degree of concordance. RESULTS: Of 408 infants and fetuses with developmental anomalies, 106 (26%) had congenital heart defects. In 63 (59%) of these 106 cases, the heart defect was the principal reason for the termination of pregnancy or the cause of death. Excluding five cases with a secundum atrial septal defect, there was complete agreement between the ultrasound examination and the autopsy findings in 74 (73%) of 101 cases. In 18 cases, there were minor discrepancies between ultrasound and autopsy findings. The main diagnosis was thus correct in 92 cases (91%). From the first time period (1985-89) to the second (1990-94), the detection rate of all heart defects increased from 48% to 82%. CONCLUSION: This study confirms a good correlation between ultrasound and autopsy diagnoses in fetuses and infants with congenital heart defects. A significant improvement in the detection of heart defects occurred from the first time period to the second and was probably due to increased experience and technical advances.     

Ductus venosus blood velocity and the umbilical circulation in the seriously growth-retarded fetus.

Based on the assumption that the ductus venosus is regulator of oxygenated blood in the fetus, the present study investigated the blood flow velocity of the ductus venosus in relation to the umbilical circulation in the that seriously growth-retarded fetus. The study group of 38 fetuses (gestational week 17-39) had no chromosomal aberrations or structural malformations and had an ultrasonographic biometry of < 2.5th centile and birth weight of 相似文献