Refrigeration Period Research Articles

Lavaged excised rat lungs as a model of surfactant deficiency.

These studies investigated the mechanical, biophysical and biochemical properties of multiply lavaged excised rat lungs at 37°C to define a surfactant-deficient lung model for the evaluation of surfactant replacement mixtures and methodologies. The volume-pressure (VP) and volume-surface tension characteristics of excised lungs were determined before and after extensive washing with physiologic saline. Following a series of 15 consecutive lavages, a highly reproducible, sigmoidal deflation VP curve was observed, and recoil pressures at lung volumes below 95% of total lung capacity (TLC) were increased over baseline. The volume of trapped gas (Vtg) at 0 cm H2O transpulmonary pressure was reduced from 10.6% TLC before lavage to 2.0% TLC after. Prior to lavage, calculated alveolar surface tension decayed exponentially during lung deflation from an assumed maximum of 46.0 dynes/cm at TLC to <5.0 dynes/cm at 75% TLC and to <1.0 dyne/cm at 35% TLC. Following lavage, calculated surface tension was higher at all lung volumes and had a value of 18.0 dynes/cm at 75% TLC and 13.5 dynes/cm at 35% TLC. To determine the stability of the surfactant-deficient lavaged lung, VP properties were measured after subsequent periods of ventilation and refrigeration (for 72 hours at 4°C); VP characteristics and Vtg of lavaged lungs were found to be unaffected by these maneuvers. In a subgroup of experiments, the surfactant-deficient lung model was used to evaluate the effect of tracheal instillations of various amounts of a natural lung surfactant extract. A progressive return of normal lung mechanics was observed as the amount of instilled surfactant was increased from 0 to 74.0 µmoles of dispersed phospholipid in 2.5 ml of 0.15 M NaCl. Our results show that lavage of excised rat lungs yields a reproducible and stable state of surfactant deficiency at 37°C which is suitable for the evaluation of surfactant replacement mixtures and techniques.

Survival and infestivity of Sarcoptes scabiei var. canis and var. hominis

Sarcoptes scabiei var. canis served as a suitable model for the study of S. scabiei var. hominis survival. S. scabiei var. canis and var. hominis mites were found to survive off the host for 24 to 36 hours at room conditions (21 degrees C and 40% to 80% relative humidity [RH]), and the canine variety survived 19 days at 10 degrees C and 97% RH. Female mites survived decidedly longer than male mites at comparable conditions. Generally, higher RH values and lower temperatures favored survival, whereas higher temperature and lower RH led to early death. Most canine scabies mites that were held off the host for 36 hours at 75% RH and 22 degrees to 24 degrees C remained infective and penetrated when returned to the host. Live mites of the human variety that were recovered from bed linen slept on by infested patients would also penetrate a host after being held off a host for 96 hours in alternating 12-hour periods of room conditions and refrigeration. Penetration required less than 30 minutes for all life stages of both varieties, and it was accomplished by a mite secretion that dissolved the host tissue. Dislodged mites, particularly those in close proximity to the source, can be a likely source of infestation.

Transient natural convection heat and mass transfer during refrigeration of air by horizontal tubes

Experiments were carried out on transient heat and mass transfer by natural convection during refrigeration of air by horizontal tubes in the range 10 3−10 6for Gr Pr and Gr Sc. The heat and mass transfer coefficients during the period of refrigeration were studied. The time required from the moment of starting refrigeration of air until approaching constant values of heat and mass transfer coefficients was obtained.

The terminal Miocene event

The Messinian salinity crisis in the Mediterranean Basin, which resulted in a paleontological and stratigraphical hiatus between the Lyellian Miocene and Pliocene faunal sequences, has a relatively brief history (∼1.5 m.y.) coincident with upper Zone N17 planktonic microfauna and within calcareous nannoplankton Zones NN11 and NN12. In the Andalusian Stage stratotype, located in the Atlantic-connected Guadalquivir Basin of southwestern Spain, paleobathymetric analysis of benthonic foraminifera indicates a marked reduction in water level, from ca. 70–100 m to ca. 30 m, in uppermost N17 levels, and a return to former water depths coincidentally with the beginning of the Pliocene (Zone N18 microfauna) which is calibrated to t = 5 Ma. An apparently simultaneous regression is evident in upper Zone N17 levels of the Neogene basins of southeastern Spain studied by C.Montenat, and alkaline volcanics at Barqueros (Murcia) within the N17 sequence have K-Ar ages indicating that the regression began less than 6.5 Ma. The Spanish regression is clearly linked with the Messinian salinity crisis, and it can also be biochronologically correlated to a period of marked eustatic lowering and refrigeration recorded in Kapitean strata of New Zealand and thereby to a great, perhaps maximum temporary expansion of grounded ice on the Antarctic continental shelf. It is clear nevertheless that no eustatic sea-level change of even this magnitude could have isolated the Mediterranean Basin unless it had already been nearly isolated by tectonism. Therefore two stages in Messinian history are envisioned following Ruggieri: (1) An initial deep-water phase marked by refluxive concentration controlled by a tectonically elevated sill, during which evaporites and associated sediments accumulated in marginal sea level areas and in great saline bodies in the depths of the basin; this event lasted about 1 m.y. and spanned the interval between 6.5 and 5.5 Ma. (2) A terminal phase of total isolation caused by eustatic lowering of the world sea level, during which erosion and desiccation features were developed which fit the “deep-basin, shallow-water” model of Hsu¨, Cita and Ryan. This second phase spanned the interval approximately between 5.5–5.0 Ma.

Hibernation Study with Lysiphlebus testaceipes , 1 Parasite of the Greenbug 23

A significant, although low, number of the hymenopterous parasites, Lysiphlebus testaceipes (Cresson), emerged from mummies of the parasitized greenbugs, Schizaphis graminum (Rondani) during refrigeration at 3.3°C. After refrigeration, high numbers of adult progeny emerged at 24°C from parasite mummies stored at –4.4, –1.1, and 3.3°C for 7 days. The difference in the emergence numbers between the temperatures was non-significant, as were the differences between adult progeny numbers from mummies produced by virgin parasites and female parasites placed with males for copulation. Low numbers of adult parasites emerged at 24.0°C from mummies stored for 30 days at all 3 temperature levels and for 60 days at –1.1 °C. Development and emergence required 2–5 days more for those few parasites which emerged from mummies stored at –1.1°C, excluding the refrigeration period, when compared to uninterrupted development at 24.0°C which required 9–11 days.

Trans-ovum transmission of a nuclear-polyhedrosis virus in the gypsy moth and the inducement of virus susceptibility

Eggs of the gypsy moth, Porthetria dispar, were collected from six sites differing in topography from wet to dry, in density of the gypsy-moth population, and in age or duration of the outbreak. Eggs collected from one site on March 23, 1968, responded differently than eggs of any of the other collections after as little as 7 days at 0–2°C. About 80% of the larvae hatching from these eggs died of nuclear polyhedrosis in the first instar. These virus-susceptible larvae made it possible to demonstrate, by surface disinfection, that trans-ovum transmission of the nuclear-polyhedrosis virus (NPHV) takes place via the surface of the egg. The hatching larva becomes infected by ingesting part of the egg shell. (An improved method of surface disinfection with 0.1% sodium hypochlorite is described. This reduced the incidence of polyhedrosis in the susceptible larvae from 80% to 0.1%.) Larvae from eggs collected at hatching time from the same site as the susceptible group of March 23 had less than 10% polyhedrosis. This was also true for larvae from eggs collected at the other sites both at hatching time and in the previous months of December and January. Larvae from eggs collected in the winter months and refrigerated at 0–2°C for up to 7 months suffered less than 10% polyhedrosis. Thus, long periods of refrigeration did not induce susceptibility to the NPHV. The data suggest that initial mortality of first-instar larvae in the field, exclusive of larva-to-larva transmission typically would be less than 10%. By comparison with the 80% polyhedrosis observed in the virus-susceptible larvae it appears that there is normally a high incidence of transmission of the virus and that most larvae become infected as they hatch. Since less than 10% die in early instars there appears to be some natural resistance to acute infection. Apparently by March 23 eggs in the field undergo some change as the weather begins to moderate. After this the unhatched larvae cannot tolerate prolonged chilling at 0–2°C without becoming susceptible to acute infection from NPHV.

Toxic effects of Microcystis aeruginosa Kg. extracts on Daphnia longispina O. F. Müller and Eucypris virens Jurine

From the above one can infer that: 1. Living cells of Microcystis aeruginosa in which the blue-violet pigment was not yet discharged, had during 21 days no toxic effects upon Daphnia longispina, increasing in some way their surviving ability with no checking influence upon their reproduction. 2. The blue-violet pigment yielded by Microcystis through refrigeration and defrosting processes, had a toxic influence upon Daphnia longispina and Eucypris virens, this influence being more intense after a longer period of refrigeration of Microcystis and growing with the degree of its concentration. 3. Individuals of Eucypris virens were especially sensible to toxic effects of blue-violet pigment of Microcystis aeruginosa, obtained through refrigeration.

The Ontogeny of Blister Beetles (Coleoptera, Meloidae) I. A Study of Three Species of the Genus Pyrota

Postembryonic ontogeny in the Meloidae is described briefly and a nomenclature of larval phases is proposed. Pyrota mutata Gemminger, P. niyrovittata (Haag-Rutenberg), and P. palpalis Champion were reared to the coarctate phase or beyond on a diet of honey bee provisions and larvae. First-instar Pyrota larvae can develop on pollen mixed with water or honey, but the duration of the instar is decreased by the addition of a bee larva to the diet. The first grub phase consists of 4 instars; larvae in this phase attack bee larvae readily but do not require them for growth. Larvae of P. nigrovittata and P. palpalis reached the coarctate phase in means of 38 and 32 days, respectively, at 27°C; those of P. mutata did so in a mean of 20 days, at a slightly higher temperature. All coarctate larvae of P. mutata and P. nigrovittata diapaused. The ontogeny of P. palpalis was extremely variable beyond the first grub phase. Five of 13 coarctates of this species failed to diapause; 1 larva developed directly to the pupal stage from the coarctate phase; 5 spent 2 instars in the coarctate phase; and 1 of those that reached the second grub phase subsequently reverted to the coarctate before continuing development. In addition, nearly all coarctate larvae of P. palpalis retained first grub anatomical characteristics to a greater or lesser extent. Larvae of P. palpalis (the only species reared to the adult stage) that diapaused in the coarctate phase required a mean of 212 days for complete development (excluding a period of refrigeration during diapause) ; a nondiapausing larva completed development in 57 days. Anatomical changes during ontogeny are extensive and in some cases profound. Interspecific differences in larval anatomy are relatively slight and vary in nature with the phases.

Factors affecting the cation transport of calf lens

It has been demonstrated that, upon incubation at 37° following a period of refrigeration, calf lens is capable of active extrusion of sodium and concentration of potassium. The net movement of cations occures against concentration gradients and is inhibited markedly by low levels of ouabain. In the presence of glucose, active transport occurs equally as well anaerobically as it does aerobically. This and other evidence presented indicate that lens is capable of maintaining its vital processes by energy supplied from the anaerobic pathway of metabolism. It was shown that aerobic metabolism also exists in this ocular tissue, but apparently plays a less prominent role. There seems to be a correlation between the high energy phosphate level and the effectivess of cation transport and amino acid incorporation.

Determining the Relative Economy of Home-Produced and Purchased Milk

W n. JHETHER to operate a oneor two-cow dairy to produce milk for family use or to buy dairy products is a farm and home management problem facing many farm families. They would like to have a basis for determining the circumstances in which money is saved by producing milk for family use rather than buying it, and the extent of the saving. In this paper a model has been developed which relates the cost of producing milk from one or two cows to varying levels of family consumption. For purposes of illustration data primarily for the North Central states have been used. Extension Service personnel or other agricultural consultants counseling with farm families would of course use production and cost data applicable to their state or region. While factors that determine the cost of producing milk are given especial emphasis here, it is understood that other points may be stressed in counseling with families. Most important of these is helping families determine the milk necessary to meet their nutritional needs.2 Consumption survey data repeatedly show that families that have homeproduced milk use more milk and milk products than those who do not.3 Due consideration, too, should be given to such nonmonetary factors as the inconvenience of daily caring for the cow and the milk and the extra effort that is necessary to produce products comparable in quality to those from good commercial dairies. On the other hand, weight should also be given the convenience of a milk supply that is close at hand and needs only short periods of refrigeration.

Probable Substages of Glaciation on Iztaccihuatl, Mexico

Five substages of glaciation, all probably Wisconsin, on the west side of Iztaccihuatl in Mexico are evidenced by series of great lateral moraines at altitudes of 3,100-3,500 m., by higher, relatively insignificant moraines, and by prominent moraines at 4,270-4,450 m. Small moraines above 4,400 m. within upper valley heads represent 3 and possibly 4 periods of refrigeration after the Thermal Maximum; three small separate hanging glaciers exist today on the west side.