Monte Carlo-minimization approach to the multiple-minima problem in protein folding

A Monte Carlo-minimization method has been developed to overcome the multiple-minima problem. The Metropolis Monte Carlo sampling, assisted by energy minimization, surmounts intervening barriers in moving through successive discrete local minima in the multidimensional energy surface. The method has located the lowest-energy minimum thus far reported for the brain pentapeptide [Met5]enkephalin in the absence of water. Presumably it is the global minimum-energy structure. This supports the concept that protein folding may be a Markov process. In the presence of water, the molecules appear to exist as an ensemble of different conformations.

Neural tube defects in Beijing-Tianjin area of China. Urban-rural distribution and some other epidemiological characteristics

Records in the obstetric wards and nurseries of 18 hospitals were reviewed and studied epidemiologically, covering about 210,000 deliveries and 1000 cases of neural tube defects (NTD). All live and still births occurred in the period 1970-84. Following the NTD classification used by Koch (1984), our case series consisted of anencephalus 50.3%, spina bifida 44.2%, and NTD with other system defects 5.5%. Overall NTD prevalence rate at birth was 4 per thousand, obviously higher than those in most other countries. Marked urban-rural differences in NTD prevalence rate at birth were observed. The rate in rural areas after correction for selection bias was still as high as 7.25 per thousand. As compared with cities and suburbs, the relative risk of NTD born to mothers in rural regions was 2.4. The male-to-female ratios were much less than 1 for various kinds of NTD. Looking at the effect of maternal age and birth order simultaneously in 12 different settings, it can be seen that prevalence of NTD was moderately higher among second and third births to women aged less than or equal to 24 and those greater than or equal to 35 years of age.

Muscarinic action of acetylcholine in the pigeon optic tectum

Eighty visual units were extracellularly recorded from the pigeon optic tectum, and the effects of iontophoretically applied acetylcholine and its antagonists, atropine and tubocurarine, on these units were examined. The results showed that acetylcholine in the avian tectum functions as an excitatory transmitter or modulator and acts predominantly through a muscarinic mode of action.

Squamous cell carcinoma of the breast

Squamous cell carcinoma is a rare type of breast malignancy. Three patients are described. The clinical features, histologic findings, and postoperative course are described. All three patients had operation, and two received chemotherapy and radiotherapy. Two patients are well 2 and 6 years postoperatively, and the third patient died from extensive metastases within 34 months after radical mastectomy without postoperative chemotherapy and radiotherapy.

Properties of electrophoretic fractions of human embryonic kidney cells separated on Space Shuttle flight STS-8

Suspensions of cultured primary human embryonic kidney cells were subjected to continuous flow electrophoresis on Space Shuttle flight STS-8. The objectives of the experiments were to obtain electrophoretically separated fractions of the original cell populations and to test these fractions for the amount and kind of urokinase (a kidney plasminogen activator that is used medically for digesting blood clots), the morphologies of cells in the individual fractions, and their cellular electrophoretic mobilities after separation and subsequent proliferation. Individual fractions were successfully cultured after return from orbit, and they were found to differ substantially from one another and from the starting sample with respect to all of these properties.