Properties of bilayer membranes in the phase transition or phase separation region

The increase in passive permeability of bilayer membranes near the phase transition temperature is usually explained as caused by either the increase in the amount of 'boundary lipid' present in the membrane, or by the increase in lateral compressibility of the membrane. Since both the amount of 'boundary lipid' and the lateral compressibility show a similar anomaly near the transition temperature, it is difficult to distinguish experimentally between the two proposed mechanisms. We have examined some details of both of the proposed pictures. The fluid-solid boundary energy, neglected in previous work, has been computed as a function of the domain size. For a single component uncharged lipid bilayer, the results rule out the existence of even loosely defined solid domains in a fluid phase, or vice versa. Thermodynamic fluctuations, which are responsible for anomalous behaviour near the phase transition temperature, are not intense enough to approximate the formation of a domain of the opposite phase. Turning next to lateral compressibility of bilayer membranes we have considered two-component mixtures in the phase separation region. We present the first calculation of lateral compressibility for such systems. The behaviour shows interesting anomalies, which should correlate with existing and future data on transport across membranes.

A preliminary report of mortality patterns among foundry workers

A proportional mortality study was conducted utilizing the death records maintained from 1971 to 1975 by the International Molders and Allied Workers Union as part of a death benefits program. Death certificates were obtained on 3,013 members of the study group and classified according to the 8th Revision of the ICA by a trained nosologist. The ate- and race-specific cause distribution of all deaths among males in the United States for 1973 were used as a standard from which expected deaths were calculated. The statistical significance of differences between observed and expected numbers of deaths was determined by a chi-square test. The most statistically significant finding in this study was an excess lung cancer mortality (208 observed vs. 142 expected) and an excess mortality due to pneumoconiosis (29 observed vs. 5 expected). A discussion is included of the potential agents found in the foundry environment that may be responsible for the increased lung cancer risk.

Initial Observations of the Pioneer Venus Orbiter Solar Wind Plasma Experiment

Initial results of observations of the solar wind interaction with Venus indicate that Venus has a well-defined, strong, standing bow shock wave. Downstream from the shock, an ionosheath is observed in which the compressed and heated postshock plasma evidently interacts directly with the Venus ionosphere. Plasma ion velocity deflections observed within the ionosheath are consistent with flow around the blunt shape of the ionopause. The ionopause boundary is observed and defined by this experiment as the location where the ionosheath ion flow is first excluded. The positions of the bow shock and ionopause are variable and appear to respond to changes in the external solar wind pressure. Near the terminator the bow shock was observed at altitudes of approximately 4600 to approximately 12,000 kilometers. The ionopause altitutde ranged fromn as low as approximately 450 to approximately 1950 kilometers. Within the Venus ionosphere low-energy ions (energy per untit charge < 30 volts) were detected and have been tentatively idtentified as nonflowing ionospheric ions incident from a direction along the spacecraft velocity vector.

Drosophila hemolymph proteins: purification, characterization, and genetic mapping of larval serum protein 2 in D. melanogaster

Three of the major protein species present in the hemolymph of Drosophila melanogaster larvae just prior to pupation are absent from second instar larvae but accumulate rapidly during the third instar. This article describes the purification and characterization of one of these, larval serum protein (LSP) 2, using an immunological assay. It is a homohexamer of molecular weight about 450,000, with a polypeptide molecular weight of 78,000--83,000. Fast and slow electrophoretic variants of this protein map between the markers vin and gs, at 36--37 on chromosome 3.

Biochemical and immunological studies on larval serum protein 1, the major haemolymph protein of Drosophila melanogaster third-instar larvae

Larval serum protein 1 is the major haemolymph protein just before puparium formation in Drosophila melanogaster. It has been purified and characterised as a family of hexamers (molecular weight 450000-480000) of three immunologically related polypeptides (molecular weight 75000-81000). Homologous proteins, present in other dipterans, are similar in structure, amino acid composition and developmental profile.

Induced alteration in uptake properties of Tetrahymena and its association with the development of mating competency

The rate of uridine uptake in Tetrahymena declines by an order of magnitude by two hours after shiftdown to a non-nutrient buffer. This alteration in uptake properties cannot be accounted for by an increase in the intracellular pool of uridine, an increase in apparent Km for uptake or a decline in the rate in which uridine is processed intracellularly. It is argued that the decrease in uridine uptake is due to a reduction in numbers of functional transport molecules exposed at the cell surface and is a reflection of a developmentally related cell surface transformation. In addition, the putative decline in functional transport molecules cannot be entirely explained by metabolic turnover of these molecules in the absence of replacement, nor does it require the synthesis of new protein. We discuss the possibility that a shift in equilibrium between accessible and inaccessible transporters is operating. Finally, a close correlation between conditions which elicit the transport alteration and those which allow the development of mating competency suggests that the two phenomena may be coordinately regulated.

A case of afferent loop obstruction secondary to recurrent carcinoma of the stomach with ultrasound and C.T. scan findings

A case of afferent loop obstruction secondary to recurrent carcinoma of the stomach is reported. The patient presented in the early recurrence period with the clinical picture similar to that of pancreatic pseudocyst. This was the first reported case of afferent loop obstruction demonstrated by abdominal ultrasound and C.T. scan. The radiological distinguishing features and similarities of pancreatic pseudocyst and afferent loop obstruction are discussed. This case also shows a rarely reported manifestation of recurrent carcinoma of the stomach.

A cytological study of micronuclear elongation during conjugation in Tetrahymena

Micronuclear elongation is the first major event in a series of nuclear changes occurring during the sexual stage of the life cycle of Tetrahymena. Beginning at about one hour after cells of complementary mating types have conjugated, the micronucleus leaves its recess in the macronucleus and swells slightly. This is accompanied by a reorganization of its chromatin from a reticular to a solid body. In the next stage the micronucleus assumes an egg shape, a development concomitant with the appearance of microtubules. While the chromatin "spins out" from the dense body, and microtubules increase in number, the nucleus assumes a spindle shape. During the elongation, which increases the length of the nucleus some fifty fold, microtubules are prominent in clusters just internal to the nuclear membrane, and parallel to the longitudinal axis of the nucleus. When elongation is completed the nucleus is curved around the macronucleus. Internally, partially condensed strands of chromatin are located off-center, towards the macronuclear side, and the density of the microtubules is diminished. At all the stages, DNA is located throughout the nucleus; neither discrete chromosomes nor synaptonemal complexes are seen. Occasionally cytoplasmic membrane systems are seen fused to the nuclear envelope which retains the typical appearance of a double membrane with pores.

Desquamative interstitial pneumonia following long-term nitrofurantoin therapy

Two patients with diffuse interstitial lung disease after long-term nitrofurantoin therapy were characterized clinically by exertional dyspnea and basilar rales, roentgenographically by diffuse interstitial infiltrate and physiologically by a restrictive lung defect. Pathologically, light microscopy revealed desquamative interstitial pneumonia. In one patient electron microscopy was characteristic of desquamative interstitial pneumonia. Immunofluorescent studies of one biopsy specimen showed specific fluorescence of interstitial cells with immunoglobulin E and third component of complement. In in vitro studies, nitrofurantoin therapy failed to induce lymphoblast transformation or histamine release. Treatment consisted of discontinuing the administration of nitro=furantoin and adding corticosteroids. Both patients felt better and showed clinical improvement. Our findings suggest that in some cases desquamative interstitial pneumonia may be drug related.

Uridine uptake in a unicellular eukaryote during the interdivision period and after growth arrest

The rate of uridine uptake was measured in Tetrahymena after shiftdown to non-nutrient physiological salt solution. Uptake follows Michaelis-Menten kinetics and an apparent Km of transport of 2 X 10-minus 6 M has been estimated. This value is in good agreement with those reported for tissue-derived cells in culture. Incorporation of uridine into RNA follows similar kinetics suggesting that uptake is rate limiting for incorporation. Within three hours after shiftdown the rate of uptake is decreased by an order of magnitude. Also at three hours after shiftdown pairing occurs between cells of complementary mating types. It seems likely that the change in uptake is a reflection of a surface change associated with differentiation. The rate of uptake was also measured during the interdivision period using cells synchronized by a physical selection procedure. A change in rate occurs at the time the cells begin replication of DNA and is essentially stable thereafter. These results indicate that there exists in Tetrahymena a relationship between surface properties as assayed by uridine uptake and properties of growth and differentiation.

WISC and Nebraska performance of deaf and hearing children

The purpose of this study was threefold: (1) to evaluate the visual-perceptual skills of deaf and of hearing children; (2) to compare the performances of the two groups on two tests frequently used to assess intellectual functioning; and (3) to compare the performance of deaf children in a day school with those in a residential school. Results indicate deaf children are not inferior to hearing children on visual-perceptual tasks and day-school deaf children performed better than residential deaf children. Differences between the deaf and hearing on the two tests were significant on 3 of the 10 subtests. In addition, normative scores on at least one subtest of the Nebraska appear too high, and correction may be in order. Correlations between the two tests, for both deaf and hearing children, were low.

Structural Analysis of Basal Bodies of The Isolated Oral Apparatus of Tetrahymena Pyriformis

The oral apparatus of Tetrahymena pyriformis was isolated using a non-ionic detergent to disrupt the cell membrane. The mouth consists largely of basal bodies and microfilaments. Each basal body is attached to the mouth by a basal plate which is integrated into the meshwork of microfilaments that confers upon the oral apparatus its structural integrity.

Each basal body is composed of 9 triplet microtubules. Two of the 3 tubules, subfibres ‘A’ and ‘B’ are composed of filamentous rows of globules with a spacing of 4.5nm. The third tubule, subfibre ‘C’, is only one-third the length of the basal body.