A study has been ~n a d e of the time variations of T-A isother~ns of stearic acid films a t air/water interfaces using all automatic recording surface balance of the vertical pull type.The existence of coherent lilms below molecular areas of 22 scl. A/mo~ecu~e has been found t o be dependent on the temperature, rate of co~npression, and the history of compressio~l of a given film. The behavior a t or near collapse, the decrease in T with time after sudden compression (relaxation), and the increase in T with time after sudden expansion (recovery) have been studied.The results have been interpreted on the basis of structural changes in the monolayer. INTRODUCTIOSAlthough extensive studies have been made on the pressure-area (T-A) isotherms of simple long-chain fatty acids spread as uilimolecular films a t the air/water interface, little attention has been given to the possible time-dependency of these mechanical properties. By analogy with three-dimensional viscoelastic systems, it is not surprising that the T-A isotherms of two-dimensional systems should be time-dependent. This dependency has been observed experimentally under conditions of slow manual compression for stearic and other fatty acid films (1, 2, 3) and with automatic compression and surface pressure recording techniques for films of palmitic (4) and stearic (5, 6) acids.The collapse of stearic acid films may occur with compression to 19 sq. A/molecule surface area (5, 6, 7) or before this area is attained (1). In more definitive studies of collapse Muller (8) has suggested that a stearic acid film collapses by a stepwise wrinkling leading to the formation of numerous strata. Kirnball and Ries (9) have reported the appearance of long wrinkles two molecules deep (100 A) in electron micrographs of collapsed hexatricontanoic acid monolayers.In the present study the T-A -time relations of stearic acid films have been investigated up to and beyond the collapse region in an attempt to elucidate the molecular processes associated with the formation and collapse of unimolecular films. Studies have been made of: (a) the effect of conlpression rate on the T-A isotherin, ( b ) the "variation of T with time after repeated compressions and expansions of the film a t molecular areas between 19 and 24 sq. A, and (c) the effect of repeated compressions on the a-A isotherin of the same film. EXPEIIIMENTAL P A R TThe Film Balance Description T h e surface pressure measurements were made with an automatically recording film balance of the Wilhelmy type. T h e balance incorporated a null-balance feature activated by the electronic servo-mechanism of Mauer (10) applied to a chainomatic balance. This surface balance was found to be capable of rapid and precise response to increasing or decreasing surface pressure.'iVfanuscript

Background: Mutations in the slow skeletal muscle troponin T (TNNT1) gene cause a congenital nemaline myopathy resulting in death from respiratory insufficiency in early infancy. We report on four French Canadians with a novel congenital TNNT1 myopathy. Methods: Patients underwent lower extremity and paraspinal MRI, quadriceps biopsy and genetic testing. TNNT1 expression in muscle was assessed by quantitative PCR and immunoblotting. Wild type or mutated TNNT1 mRNAs were co-injected with morpholinos in a zebrafish knockdown model to assess for rescue of the morphant phenotype. Results: Four patients shared a novel missense homozygous mutation in TNNT1. They developed from childhood slowly progressive limb-girdle weakness with spinal rigidity and contractures. They suffered from restrictive lung disease and recurrent episodes of rhabdomyolysis. Older patients remained ambulatory into their sixties. Lower extremity MRI showed symmetrical myopathic changes. Paraspinal MRI showed diffuse fibro-fatty involution. Biopsies showed multi-minicores. Nemaline rods were seen in half the patients. TNNT1 mRNA expression was similar in controls and patients, while levels of TNNT1 protein were reduced in patients. Wild type TNNT1 mRNA rescued the zebrafish morphants but mutant transcripts failed to do so. Conclusions: This study expands the spectrum of TNNT1-related myopathy to include a milder clinical phenotype caused by a functionally-confirmed novel mutation.

Objective Recessive null variants of the slow skeletal muscle troponin T1 (TNNT1) gene are a rare cause of nemaline myopathy that is fatal in infancy due to respiratory insufficiency. Muscle biopsy shows rods and fiber type disproportion. We report on 4 French Canadians with a novel form of recessive congenital TNNT1 core‐rod myopathy. Methods Patients underwent full clinical characterization, lower limb magnetic resonance imaging (MRI), muscle biopsy, and genetic testing. A zebrafish loss‐of‐function model using morpholinos was created to assess the pathogenicity of the identified variant. Wild‐type or mutated human TNNT1 mRNAs were coinjected with morpholinos to assess their abilities to rescue the morphant phenotype. Results Three adults and 1 child shared a novel missense homozygous variant in the TNNT1 gene (NM_003283.6: c.287T > C; p.Leu96Pro). They developed from childhood very slowly progressive limb‐girdle weakness with rigid spine and disabling contractures. They suffered from restrictive lung disease requiring noninvasive mechanical ventilation in 3 patients, as well as recurrent episodes of rhabdomyolysis triggered by infections, which were relieved by dantrolene in 1 patient. Older patients remained ambulatory into their 60s. MRI of the leg muscles showed fibrofatty infiltration predominating in the posterior thigh and the deep posterior leg compartments. Muscle biopsies showed multiminicores and lobulated fibers, rods in half the patients, and no fiber type disproportion. Wild‐type TNNT1 mRNA rescued the zebrafish morphants, but mutant transcripts failed to do so. Interpretation This study expands the phenotypic spectrum of TNNT1 myopathy and provides functional evidence for the pathogenicity of the newly identified missense mutation. ANN NEUROL 2020;87:568–583

Ultrace~ltrifugal seditnentation of alkali lignin fractions revealed marked boundary spreading a t low and high centrifugal fields. An analysis of the gradient diagrams indicated a wide distribution of sedimentation coefficients ranging from 0.5 to over 400X10-13 second. There was only a small decrease in the polydispersity on subfractionation. The distributions were continuous with a single peak and positive skewness. A linear relationship was found between the intrinsic viscosity and the standard deviation of the weight-average sedimentation coefficient. The sedimentation coefficient based on the movement of the maximum ordinate a t a field of 11.5X103 g was several times greater than the corresponding coefficient for the same fraction a t 200X103g. A qualitative interpretation of this phenomenon is given in terms of the Fasen and the Archibald solution to the Lamm equation.