Chondritic meteorites and the lunar surface.

The landing dynamics of and soil penetration by Surveyor I indicated that the lunar soil has a porosity in the range 0.35 to 0.45. Experiments with Surveyor III's surface sampler for soil mechanics show that the lunar soil is approximately incompressible (as the word is used in soil mechanics) and that it has an angle of internal friction of 35 to 37 degrees; these results likewise point to a porosity of 0.35 to 0.45 for the lunar soil. Combination of these porosity measurements with the already-determined radar reflectivity fixes limits to the dielectric constant of the grains of the lunar soil. The highest possible value is about 5.9, relative to vacuum; a more plausible value is near 4.3. Either figure is inconsistent with the idea that the lunar surface is covered by chondritic meteorites or other ultrabasic rocks. The data point to acid rocks, or possibly vesicular basalts; carbonaceous chondrites are not excluded.

Lunar surface strength: implications of luna 9 landing.

The ability of the lunar surface to support statically the Luna 9 copsule indicates that the surface can bear at least 5 x 10(3) dyne per square centimeter (10(-1) lb/in.(2)). Analysis of the landing dynamics, using available data, gives a lower bound of about 1 to 2 x 10(5) dyne/cm(2), but this estimate may not be conservative because of uncertainties regarding the shock-absorbing system used and the direction of the velocity vector at impact.

Apollo 11 soil mechanics investigation.

The fine-grained surface material at the Apollo 11 landing site is a brownish, medium-gray, slightly cohesive granular soil, with bulky grains in the silt-to-fine-sand range, having a specific gravity of 3.1 and exhibiting adhesive characteristics. Within the upper few centimeters, the lunar soil has an average density of about 1.6 grams per cubic centimeter and is similar in appearance and behavior to the soils studied at the Surveyor equatorial landing sites. Althouglh considerably different in composition and in range of particle shapes, it is similar in its mechanical behavior to terrestrial soils of the same grain size distribution.

Physical properties of the martian surface from the viking 1 lander: preliminary results.

The purpose of the physical properties experiment is to determine the characteristics of the martian "soil" based on the use of the Viking lander imaging system, the surface sampler, and engineering sensors. Viking 1 lander made physical contact with the surface of Mars at 11:53:07.1 hours on 20 July 1976 G.M.T. Twenty-five seconds later a high-resolution image sequence of the area around a footpad was started which contained the first information about surface conditions on Mars. The next image is a survey of the martian landscape in front of the lander, including a view of the top support of two of the landing legs. Each leg has a stroke gauge which extends from the top of the leg support an amount equal to the crushing experienced by the shock absorbers during touchdown. Subsequent images provided views of all three stroke gauges which, together with the knowledge of the impact velocity, allow determination of "soil" properties. In the images there is evidence of surface erosion from the engines. Several laboratory tests were carried out prior to the mission with a descent engine to determine what surface alterations might occur during a Mars landing. On sol 2 the shroud, which protected the surface sampler collector head from biological contamination, was ejected onto the surface. Later a cylindrical pin which dropped from the boom housing of the surface sampler during the modified unlatching sequence produced a crater (the second Mars penetrometer experiment). These two experiments provided further insight into the physical properties of the martian surface.

The "soil" of Mars (viking 1).

The location of the Viking 1 lander is most ideal for the study of soil properties because it has one footpad in soft material and one on hard material. As each soil sample was acquired, information on soil properties was obtained. Although analysis is still under way, early results on bulk density, particle size, angle of internal friction, cohesion, adhesion, and penetration resistance of the soil of Mars are presented.

The environs of viking 2 lander.

Forty-six days after Viking 1 landed, Viking 2 landed in Utopia Planitia, about 6500 kilometers away from the landing site of Viking 1. Images show that in the immediate vicinity of the Viking 2 landing site the surface is covered with rocks, some of which are partially buried, and fine-grained materials. The surface sampler, the lander cameras, engineering sensors, and some data from the other lander experiments were used to investigate the properties of the surface. Lander 2 has a more homogeneous surface, more coarse-grained material, an extensive crust, small rocks or clods which seem to be difficult to collect, and more extensive erosion by the retro-engine exhaust gases than lander 1. A report on the physical properties of the martian surface based on data obtained through sol 58 on Viking 2 and a brief description of activities on Viking 1 after sol 36 are given.

Surveyor v: lunar surface mechanical properties.

The mechanical properties of the lunar soil at the Surveyor V landing site seem to be generally consistent with values determined for soils at the landing sites of Surveyor I and III. These three maria sites are hundreds of kilometers apart. However, the static bearing capability may be somewhat lower than that at the previous landing sites (2 x 10(5) to 6 x 10(5) dynes per square centimeter or 3 to 8 pounds per square inch). The results of the erosion experiment, the spacecraft landing effects, and other observations indicate that the soil has significant amounts of fine-grained material and a measurable cohesion.

Oxidative phosphorylation and aspects of calcium metabolism in myocardia of hypercholesterolaemic swine with moderate coronary atherosclerosis.

Aspects of myocardial oxidative phosphorylation and Ca2+ metabolism were studied in a swine model in which coronary atherosclerosis was induced by a combination of denudation of the endothelium of the coronary arteries plus 7--11 months of feeding a high fat--high cholesterol diet. By microscopy, a moderate amount of coronary atherosclerosis was present at the time of sacrifice, and 2 of the 14 swine hearts had old myocardial infarcts. Myocardial mitochondria from grossly normal areas showed partial uncoupling and decreased state 3 O2 uptake with 3 of 4 substrates tested. In addition, Ca2+ stimulated mitochondrial respiration was decreased in the atherosclerotic swine. In the sarcoplasmic reticulum Ca2+ uptake under conditions of heavy loading was greater in the atherosclerotic swine than in control animals. The degree of atherosclerosis was not great enough to suggest that persistent myocardial ischaemia was present. Possibly coronary artery spasm induced an intermittent ischaemia resulting in the metabolic abnormalities observed, or the changes may have been brought about by the effects of the high fat--high cholesterol diet on subcellular membranes.

Endothelial cell denudation, labelling indices and monocyte attachment in advanced swine coronary artery lesions.

This study shows that frank endothelial denudation, as measured by scanning electron microscopy, is associated with coronary artery atherosclerotic lesions in swine fed hyperlipidemic diets for 9 or 18 months. The largest areas of endothelial cell denudation were found to be associated with the most advanced atherosclerotic lesions, and lesser areas of denudation were present in less severely atherosclerotic arteries. Overall, the study suggests that frank endothelial denudation in swine coronaries occurs secondarily to advanced lesion development, and is proportionate to the amount of lesion present. In contrast attachment of monocytes to the endothelial surface was not proportionate to the amount of lesion present. While the number of attached monocytes after 9 or 18 months of a hyperlipidemic diet was much greater than in the mash-fed swine, there was no difference between the two hyperlipidemic groups. In both hyperlipidemic groups, the attached monocytes were concentrated over lesion areas. By scanning electron microscopy, most attached monocytes in these perfused coronary arteries showed a slender foot process extending into a gap between endothelial cells. Endothelial cell turnover, as measured by tritiated thymidine labelling indices, increased with the amount of coronary artery atherosclerosis. However, it did not become significantly greater than in mash-fed swine until advanced lesions developed.

Endothelial cell labeling indices in swine aortas in relation to intimal cell mass-derived atherosclerotic lesions.

In the swine abdominal aorta, most atherosclerotic lesions arise from naturally occurring collections of intimal cells called intimal cell masses. The main objective of this study was to determine if the tritiated thymidine labeling index of endothelial cells lying over intimal cell masses was greater than that of endothelial cells not over intimal cell masses. A higher endothelial cell labeling index over intimal cell masses would indicate possibly a greater turnover in the area. Such a finding would suggest possible transient but repeated breaks in the endothelial cell barrier that might contribute to the initiation of the atherosclerotic lesion in intimal cell masses. In 2 groups of mash-fed swine, 2 and 11 months old, no differences were found in labeling indices of endothelial cells lying over or not over intimal cell masses. It appears that the initiation of atherosclerosis in swine abdominal aorta is not dependent upon pre-existing altered endothelial cell kinetics as measured by tritiated thymidine labeling indices. The labeling index of cells within the intimal cell mass was significantly higher than in the media; this also is obviously not dependent upon an increased labeling index of the covering endothelial cells. Another group of swine were killed at 11 months of age after receiving a hyperlipidemic diet for 270 days. The labeling index of endothelial cells over atherosclerotic lesions was significantly higher than the labeling index of endothelial cells not over lesions in these swine, and also significantly higher than that of endothelial cells over intimal cell masses in the 11-month old mash-fed group.(ABSTRACT TRUNCATED AT 250 WORDS)

Atherosclerotic lesions in coronary arteries of hyperlipidemic swine. Part 2. Endothelial cell kinetics and leukocyte adherence associated with early lesions.

The role of endothelial cells (EC) in the development and progression of early swine intimal cell mass (ICM)-derived coronary artery lesions in 55 swine fed either a mash or hyperlipidemic diet for 14, 49 or 90 days was investigated. Characteristics studied were endothelial cell turnover (using tritiated thymidine autoradiography), adhesion of leukocytes (presumably chiefly monocytes) to endothelium, and the presence or absence of endothelial cell denudation. The major findings were: An increased adherence of leucocytes to endothelial cells over ICM-lesions in the HL-90 day group compared to the corresponding mash value at 90 days as well as to that of each of the other HL and mash groups. Significant positive correlation between the labeling indices (LI) of endothelial cells lying over coronary artery lesion cells and the labeling indices of the underlying ICM-lesion cells; also, a significant positive correlation between the labeling indices of endothelial cells over lesions of the abdominal aorta and those of the coronary arteries. At 90 days the endothelial cell LI over lesions in the HL group was significantly higher than the corresponding values in the mash group. Since the EC increase rates by growth in the two groups are also significantly different, the differences in LIs reflect at least in part EC growth differences and no strong conclusion can be made regarding possible cell turnover differences. No frank endothelial denudation was found. The findings suggest that in swine coronary arteries participation by monocytes from circulating blood is a factor in the early progression of the lesion as well as smooth muscle cell proliferation.

Intimal cell mass-derived atherosclerotic lesions in the abdominal aorta of hyperlipidemic swine. Part 2. Investigation of endothelial cell changes and leukocyte adherence associated with early smooth muscle cell proliferative activity.

We have investigated several aspects of endothelial cell (EC) behavior during the initiation and early development of intimal cell mass (ICM)-derived atherosclerotic lesions in the distal abdominal aortas of young swine fed hyperlipidemic (HL) diets for 0, 14, 49, or 90 days. By scanning electron microscopy no breaks in endothelial integrity or other abnormalities were observed even at 90 days on diet after lesions were well established. Also, counts of leukocytes adherent to the endothelium by both scanning and light microscopy revealed no greater numbers in HL than in mash control swine. Estimates of individual EC losses over ICM-lesions in the HL swine (based on calculations from tritiated thymidine labeling indices and EC growth rates determined by counts) suggested a loss of approximately one per 100 EC/day. This loss over ICM lesion was not significantly greater than that over ICM in mash controls, but was significantly greater than that of EC not over ICM lesions in the same HL animal. In any event, the estimated loss seems to be too trivial for the endothelial barrier to be compromised even transiently in a biologically significant fashion. A significant correlation was observed between tritiated thymidine labeling indices of cells within the ICM lesions and of those of the overlying EC that was not observed with the ICM in the controls. Possibly the positive correlation may be a result of the abluminal surface of the overlying EC being exposed to the abnormal milieu of the ICM lesion. It is emphasized that results reported here apply only to ICM-derived lesions at an early stage of development and that they do not contradict results obtained by others with other lesion types such as those derived from monocytes. Furthermore, in later stages of development of ICM-derived lesions in the same model we know that extensive endothelial cell damage can be demonstrated. Also, functional changes in endothelial permeability may have been present in early stages that would not have been detected with the methods used in this study.

Distribution of intimal smooth muscle cell masses and their relationship to early atherosclerosis in the abdominal aortas of young swine.

In the abdominal aortas of young mash-fed swine, intimal cell masses (pads, cushions) are located predominantly away from blood vessel orifices. They are found scattered throughout the aorta but nevertheless have a definite pattern of distribution. In the distal one half of the abdominal aorta, they are more frequent in the ventral quandrant than in the dorsal or either lateral quadrant. In the proximal half, intimal cell masses are more frequent in the dorsal quadrant. When experimental atherosclerosis is induced in the abdominal aortas of young swine by either a hypercholesterolemic diet or by aortic ballooning followed by a hypercholesterolemic diet, the distribution of early lesions is similar. The lesions are found predominantly in quadrants where intimal cell masses were found to be most frequent in the control group of swine. The results suggest that most of the lesions, though not necessarily all, arose from pre-existing intimal cell masses beneath the aortic surface.

Effects of methyl prednisolone and colchicine on the development of aortic atherosclerosis in swine.

The effect of methyl prednisolone and colchicine on the development of both the early proliferative and advanced atherosclerotic lesion in swine aorta was studied. In order to accelerate the development of atherosclerosis, the abdominal aortic endothelium was partially denuded by a balloon before the animals were placed on either a moderate or severe hypercholesterolemic diet. Neither drug in either dietary group inhibited the development of atherosclerosis. Swine receiving methyl prednisolone and severe hypercholesterolemic diet actually had a significantly greater number of the advanced necrotic lesions and more arterial calcification than the group receiving the atherogenic diet alone. In addition, the thoracic aorta of swine receiving the moderate hypercholesterolemic diet and methyl prednisolone showed larger amounts of lipid than did the non-drug fed control group. In swine receiving the moderate hypercholesterolemic diet, methyl prednisolone significantly raised serum cholesterol levels. Colchicine only slightly worsened the atherosclerosis in swine aorta and had no effect on serum cholesterol levels.

Epizootiology and distribution of transmissible sarcoma in Maryland softshell clams, Mya arenaria, 1984-1988.

Seasonal and geographic studies of transmissible sarcoma in Maryland softshell clams, Mya arenaria, were carried out from 1984 to 1988. Three major epizootics occurred in our sampling location during this time, resulting in prevalences as high as 90%, with comparable mortalities in other high prevalence areas. The disease invaded populations of large adult clams first, later spreading to the small juvenile clam populations. An apparent 2-year cycle was noted with varying seasonal effects. Affected sites tended to be in the main stem of Chesapeake Bay north of Tangier Sound, primarily in the areas where the major harvesting occurs. Several sites, mostly in upstream locations, were consistently free of disease. The epizootiological study supports the interpretation that the disease is infectious exclusively to this species. Regression analysis between sarcoma prevalence and contaminant levels in clam tissues showed a significant correlation (p = 0.0001) between chlordane levels and this disease. No correlations were found with other contaminants that were analyzed.

Restoration of myocardial bioenergetic metabolism in swine after periods of ischemic ventricular fibrillation.

Myocardial mitochondrial function and high energy phosphate levels were measured in normal swine, in swine after either 5 or 10 minutes of ischemic ventricular fibrillation (IVF) while on cardiopulmonary bypass, and in swine defibrillated after either 5 or 10 minutes of IVE. The damage to myocardial mitochondria induced by IVF, such as partial uncoupling, decreased oxygen uptake, and loss of cytochrome oxidase activity, was completely reversed almost instantly by coronary artery perfusion and the restoration of sinus rhythm. After either 5 or 10 minutes of IVF followed by coronary artery reperfusion and defibrillation, myocardial creatine phosphate (CP), adenosine monophosphate (AMP) and adenosine diphosphate (ADP) return to normal levels very rapidly. However, adenosine triphosphate (ATP) levels remain significantly lower than control levels. If the bioenergetic mechanisms of swine and human myocardium are similar, it appears that IVF at least for a 10 minute period produces no damage to myocardial mitochondria that is not corrected by perfusion of the coronary arteries and re-establishment of sinus rhythm. Furthermore, sinus rhythm can be re-established and maintained despite signficantly lower levels of myocardial ATP.

Optical and digital image processing in high-resolution electron microscopy.

A comparison is made of the deblurring by digital and optical processing of a single conventional bright field electron image of ferritin particles distributed on a carbon supporting film. The deblurring functions include the effects of the partial temporal and partial spatial coherence of the electron beam, the phase contrast transfer function of the objective lens and Weiner signal to noise optimisation. Practical aspects of the similar results achieved by the two methods are discussed. The relative advantages and disadvantages of the batch and interactive computer modes for picture processing are considered in an Appendix.

Endothelial and lesion cell growth patterns of early smooth-muscle cell atherosclerotic lesions in swine.

This study shows that the endothelial cell turnover over the early porcine atherosclerotic lesion is more or less uniform in distribution. This is contrary to the findings in White Carneau pigeons where the increased endothelial cell turnover has a zonal pattern, being much greater at the lesion edge. The difference in the endothelial cell pattern of turnover in the two lesions probably is a reflection of their different manner of development. The porcine abdominal aortic lesion is derived from naturally occurring preexisting collections of intimal smooth-muscle cells called intimal cell masses. After 90 days of a hyperlipidemic diet these lesions are composed predominantly of smooth-muscle cells, with very few monocytes. The White Carneau pigeon lesion develops from circulating monocytes that have been shown to adhere to the edge of the lesion.

Evans blue dye: its accumulation in extracellular space in relation to endothelial cell basement membrane in normal an atherosclerotic areas of abdominal aorta.

Intravenously (IV) injected Evans blue dye consistently accumulates at particular areas in aortas of normal swine. Theses areas are also where IV injected tracer cholesterol accumulates. We studied the ultrastructural characteristics of blue vs nonblue areas in the abdominal aortas of both control and atherosclerotic swine. In blue areas, the basement membrane was largely missing beneath the endothelial cells in both normal swine and swine with raised atherosclerotic lesions; the basement membrane that was present was often discontinuous. If the basement membrane helps regulate the transport of Evans blue dye across the arterial wall, its absence may play a part in the accumulation of the dye. In raised atherosclerotic lesions, those portions that accumulated Evans blue dye had a larger amount of amorphous extracellular matrix than did nonblue areas. No consistent difference between blue and nonblue areas were seen in the endothelial cell junctions of abdominal aortas in either control or atherosclerotic swine. Similarly, no differences were demonstrable in the number of Golgi complexes, mitochondria, or profiles of smooth or rough endoplasmic reticulum per cell.

Evans blue dye. Accumulation in swine aortic intimal cell collections and atherosclerotic lesions.

A two-part study concerned the accumulation of intravenously injected Evans blue dye in the abdominal aorta of swine. In normolipidemic swine weighing up to 90 kg each, Evans blue accumulated predominantly in areas of the aorta that were the site of intimal smooth muscle cell collections. The second part of the study dealt with Evans blue accumulation in swine with advanced atherosclerosis. The extent of blue staining in these animals was not significantly different than in normolipidemic, nonatherosclerotic swine of the same size. The dye showed a predilection for raised atherosclerotic lesions, but only one quarter of the surface of these lesions was stained. Histologic studies of the uppermost portion of blue and nonblue lesion areas showed that the dye preferentially accumulated in regions with lower concentrations of foam cells. Injected isotopic cholesterol tended to accumulate in the blue rather than the nonblue areas.