SynopsisMonte Carlo studies of the unperturbed amylosic chain conformation have been carried out in the approximation of separable chain configuration energies. Sample chains of arbitrary chain length have been generated so as to be distributed consistent with refined estimates of the configuration energy and thus suitable for evaluation of averages of the desired configuration-dependent properties. Perspective drawings of representative chains from the Monte Carlo sample have been made for comparison with standard idealizations of amylosic chain conformation. The molecular model employed generates a randomly coiling chain possessing perceptible regions of left-handed pseudohelical backbone trajectory. Distribution functions for the end-to-end distance of short amylosic chains disclose some propensity for the chain to suffer self-intersections at short range in the chain sequence, which may vitiate the usual amylosic chain models based on the assumed independence of sets of glycosidic linkage torsion angles. The amylosic persistence vector and persistence length have been calculated as a function of chain length for the chain model employed.

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We investigated whether malignant hyperthermia (MH)‐related contractile abnormalities, such as lowered contractile threshold, were expressed in MH‐susceptible (MHS) immature muscles and myotubes. Muscles from neonatal piglets homozygous for Arg615 (normal) or for Cys615 (MHS) ryanodine receptor alleles, and heterozygotes were used. Intact cell bundles from piglet muscles generally were similar in contractile properties to adult muscles of the same genotype. Thresholds for K contractures in normal, heterozygous, and MHS piglet muscles (40 mmol/L, 25 mmol/L and 15 mmol/K+, respectively) differed significantly. Cultured myotubes were subjected to a series of square pulses of varying strengths (−50 to +50 mV) and durations (25–300 ms) using whole cell patch‐clamp techniques. Threshold for contraction differed significantly among the three genotypes, for example, with 300 msec pulses thresholds were −6.9 ± 0.9, −12.4 ± 1.6, and −22.6 ± 2.6 mV for normal, heterozygous, and MHS myotubes, respectively. Thus, a significantly lower‐ than‐ normal threshold for contraction was expressed in MHS and heterozygous piglet muscles and myotubes. Furthermore, these developmentally immature preparations are likely to express other differences characteristic of adult MHS muscles, and thus provide suitable preparations for clinically relevant studies of MH‐related cellular abnormalities. © 1996 John Wiley & Sons, Inc.

SynopsisLight-scattering measurements have been carried out on carefully clarified aqueous solutions of pectin and pectic acid. The strong dependence of the inverse excess scattering intensity on angle yields pectin chain dimensions that are inconsistent with the complete molecular dispersion of pectin molecules possessing the degrees of polymerization indicated by the measured osmotic molecular weights. Negligible or negative concentration dependences of the inverse scattering intensities coupled with the centrifugation, filtration, and gel permeation chromatography behavior of the samples likewise suggest nonequilibriuni aggregation of the pectin molecules in solution. It is shown that the measured mean polymer chain dimensions can be rationalized in terms of the presence of a very small proportion of aggregated material.

We investigated whether malignant hyperthermia (MH)-related contractile abnormalities, such as lowered contractile threshold, were expressed in MH-susceptible (MHS) immature muscles and myotubes. Muscles from neonatal piglets homozygous for Arg6I5 (normal) or for Cys6I5 (MHS) ryanodine receptor alleles, and heterozygotes were used. Intact cell bundles from piglet muscles generally were similar in contractile properties to adult muscles of the same genotype. Thresholds for K contractures in normal, heterozygous, and MHS piglet muscles (40 mmol/L, 25 mmol/L and 15 mmol/L K', respectively) differed significantly. Cultured myotubes were subjected to a series of square pulses of varying strengths (-50 to +50 mV) and durations (25-300 ms) using whole cell patch-clamp techniques. Threshold for contraction differed significantly among the three genotypes, for example, with 300 msec pulses thresholds were -6.9 5 0.9, -12.4 5 1.6, and -22.6 ? 2.6 mV for normal, heterozygous and MHS myotubes, respectively. Thus a significantly lower than normal threshold for contraction was expressed in MHS and heterozygous piglet muscles and myotubes. Further, these developmentally immature preparations are likely to express other differences characteristic of adult MHS muscles, and thus provide suitable preparations for clinically relevant studies of MHrelated cellular abnormalities.