Hypersensitivity responses and repeated infections with Lucilia cuprina, the sheep blowfly.

, , and 1992. Hypersensitivity responses and repeated infections with Lucilia cuprina, the sheep blowfly. International Journal for Parasitology 22: 1175–1177. Sheep repeatedly infected with L. cuprina at 2- but not 4-week intervals developed partial resistance to infection after five infections, as measured by larval recovery. However, resistance did not persist for more than three infections. Skin weal responses were measured after injection of larval products simultaneously with each infection. The only correlation between weal size and larval recoveries occurred at infection 1 and indicated a relationship between skin sensitivity and innate rather than acquired resistance. The results suggest that resistance to L. cuprina can develop after repeated infections but that it is short lived and requires frequent larval exposure. A role for hypersensitivity responses was not confirmed by the weal responses but was suggested by the size of wound developed per larva recovered.     

Influence of root diameter on the penetration of seminal roots into a compacted subsoil

A field experiment was conducted to evaluate the influence of root diameter on the ability of roots of eight plant species to penetrate a compacted subsoil below a tilled layer. The soil was a fine sandy loam red-brown earth with a soil strength of about 3.0 MPa (at water content of 0.13 kg kg^-1, corresponding to 0.81 plastic limit) at the base of a tilled layer. Relative root diameter (RRD), which was calculated as the ratio of the mean diameters of roots of plants grown in compacted soil to the mean diameters of those from uncompacted soil, was used to compare the sensitivity of roots to thicken under mechanical stress.Diameters of root tips of plants grown in soil with a compacted layer were consistently larger than those from uncompacted soil. Tap-rooted species generally had bigger diameters and RRDs than fibrous-rooted species. A higher proportion of thicker roots penetrated the strong layer at the interface than thinner roots. There were differences between plant species in the extent to which root diameter increased in response to the compaction. The roots which had larger RRD also tended to have higher penetration percentage.The results suggest that the size of a root has a significant influence on its ability to penetrate strong soil layers. It is suggested that this could be related to the effects which root diameter may have on root growth pressure and on the mode of soil deformation during penetration.     

Determination of the time of ovulation in chimpanzees by measurement of LH, estrone sulfate, and pregnanediol 3 alpha-glucuronide in urine: comparison with serum hormone patterns.

The concentrations of LH, total estrogens, and pregnanediol 3 alpha-glucuronide (PdG) were determined by specific radioimmunoassays on daily overnight urine samples obtained in 13 menstrual cycles of six adult female chimpanzees during the periods of increasing, maximal, and decreasing tumescence of the perineal sex skin. The peaks of estrogens and LH and the rise in PdG in urine accurately reflected the peaks of estradiol-17 beta and LH and the subsequent rise in progesterone in the serum of the same animals during the same menstrual cycles, and can be used to predict and verify the occurrence of ovulation, thus avoiding the repeated tranquilizations necessary to obtain daily blood samples.     

Cone penetrometer testing,hydropunch®, and borehole geophysics applications for environmental investigations

An effective groundwater monitoring system can be implemented by the combined utilization of cone penetrometer (CPT), HydroPunch^® sampling, and borehole geophysical methods. The combined techniques provide a cost‐effective method for the design of a groundwater monitoring system for geologists or hydrogeologists assessing a site. With the relatively high costs associated with determining groundwater quality for site assessments, coupled with regulatory agency compliance, these combined methods can provide an effective edge in an increasingly competitive environmental industry. CPT combined with HydroPunch sampling can delineate the horizontal and vertical extent and concentration of a contaminant plume, define the extent and thickness of a free product plume, define soil and aquifer characteristics, and aid in the proper selection of well location and screen placement. The use of borehole geophysics further enhances the interpretation provided from the CPT. The interpretation of borehole geophysics provides additional information about the deposition regime of the area of investigation and a more detailed investigation of the stratigraphy. The CPT and HydroPunch can be used in unconsolidated sediments, and HydroPunch sampling can be combined with a hollow‐stem auger system. Borehole geophysics can be run in almost any environment. CPT and borehole geophysics provide information on specific lithologic characteristics necessary to obtain a groundwater sample from vertically separated aquifers. The HydroPunch can obtain a discrete, chemically representative groundwater sample from the targeted aquifer. CPT and borehole geophysics can also be used to determine lithology and for correlation of equivalent stratas from one borehole or well to the next. Borehole geophysical interpretation also provides a means of determining not only the stratigraphy and lithology but also the aquifer parameters and the type of fluids in the aquifer. Hydrogeologic and geologic data obtained from using these three methods can be employed to maximize the cost‐effectiveness and design efficiency of a groundwater monitoring system. Proper location of wells and screened interval placements are determined by a coherent design process rather than by random chance. Two studies demonstrating the combined applications of CPT, HydroPunch, and borehole geophysics for the design and placement of groundwater monitoring wells are presented in the following discussion.     

Temperature effects on bioenergetics of growth, assimilaton efficiency and thyroid activity in juvenile varand lizards

When varanid lizards, Varanus niloticus, were allowed to select their preferred body temperature (c. 34°C) they exhibited swifter growth, larger food intake and superior efficiency of conversion when compared with animals restricted to a maximum body temperature of 24°C. At the higher temperature the animals also exhibited a higher metabolic rate and increased thyroid activity, while those at the lower temperature lostproportionately more energy via respiration. A complete energy budget over a period of 6 weeks is presented.     

Intracellular ionic activities in frog skin

Summary Asymmetrical displacement currents are measured in the absence and in the presence of the lipophilic anion dipicrylamine (DPA) in the extracellular solution of nerve fibres of the frogRana esculenta. DPA (30nM-3 M) enhances the current by a component that has the properties expected for a translocation current of DPA ion across the lipid membrane. Analysis in terms of a single-barrier model yields the translocation rate constant (k), the total surface density of DPA absorbed to the membrane (N _t ), and the equidistribution voltage (). The value ofk of about 10⁴ s^–1 is similar to that for a solvent-free artificial bilayer formed by the Montal-Mueller method. The surface densityN _t varies with the DPA concentration as it does in the artificial bilayer, but is about tenfold smaller at all concentrations. The DPA ions sense an intrinsic electric field that is offset by a transmembrane voltage between 0 and 30 mV (inside positive). The part of the axolemma probed by the DPA ion appears as a thin (<2.5 nm), fluid bilayer of lipids. DPA ions seem, however, to be excluded from the major part of the axolemma as if this area is occupied by integral proteins or negative charges.     

Interrelationship of Meloidogyne hapla and Ditylenchus dipsaci on Resistant and Susceptible Alfalfa

Simultaneous inoculations of alfalfa with Meloidogyne hapla larvae and Ditylenchus dipsaci at 16, 20, 24, and 28 C did not depress penetration of either nematode in ''Nev Syn XX'' -a selection resistant to M. hapla and D. dipsaci, ''Vernal 298'' -a selection resistant to M. hapla and susceptible to D. dipsaci, ''Lahontan'' -a cultivar resistant to D. dipsaci and susceptible to M. hapla, and ''Ranger'' -a cultivar susceptible to both M. hapla and D, dipsaci. Infection with D. dipsaci depressed growth of susceptible ''Vernal 298'' and ''Ranger'' at all soil temperatures, except for ''Vernal 298'' at 16 C. Infection with M. hapla alone did not depress growth of any of the alfalfas. A combination of M. hapla and D. dipsaci resulted in a synergistic weight depression on ''Ranger'' at all soil temperatures. Inoculation of the four alfalfas with D. dipsaci 2, 4, 6, and 8 wk before inoculation with M. hapla at 16, 20, 24, and 28 C did not influence the resistance or susceptibility of ''Nev Syn XX,'' ''Lahontan,'' or ''Ranger.'' However, galling of ''Vernal 298'' by M. hapla was affected by soil temperature, plant age, and inoculation with D. dipsaci.     

Kinetics of ionic transport across frog skin: Two concentration-dependent processes

Summary Sodium and chloride influxes across the nonshort-circuited isolated skin ofRana esculenta were measured at widely varying external ionic concentrations.The curve describing sodium transport has two Michaelis-Menten components linked at an inflection point occurring at an external sodium concentration of about 7 meq. Chloride transport can also be represented by two saturating components. A possible explanation of these kinetics is discussed.At sodium concentrations lower than 4 meq it is possible to define a component of the sodium transport mechanism as having a high affinity for sodium and which is independent of the nature of the external anion. A high affinity for chloride of the chloride transport system functioning at low external concentrations is also found but is significantly different from that of sodium. These systems show the physiological characteristics of the countertransports (Na _ext ⁺ /H _int ⁺ ; Cl _ext ^– /HCO _3int ^– ) functioning at low external concentrations.At external concentrations higher than 4 meq a low affinity transporting system in which chloride and sodium are linked superimpose on the high affinity components.The physiological significance of these results is discussed.     

Time and process of sperm penetration into cumulus-free mouse eggs fertilized in vitro

Sperm penetration through the zona pellucida and fusion of the sperm head with the vitellus were observed continuously and filmed under phase optics in cumulus-free living mouse eggs inseminated in vitro with capacitated epididymal sperm. Most spermatozoa penetrated the zona pellucida, traversed the perivitelline space, and fused with the vitellus at an angle nearly perpendicular to the surface. The mean duration required for sperm to penetrate the zona pellucida was 20 minutes with a range of 15–26 minutes. Sperm traversed the perivitelline space in less than one second. The initial contact of sperm with the vitellus generally took place at the tip of the sperm head. When the tip of the sperm head contacted the vitellus there was an immediate reduction in the rate of flagellation, followed by the gradual sinking of the sperm head into the vitellus.     

Antimetabolic activities of 2-fluoro-L-histidine.

2-Fluoro-L-Histidine inhibits protein synthesis in various cell cultures, as measured by ³H-leucine incorporation. This histidine analog also inhibits the cytopathogenicity of a number of RNA and DNA viruses in primary and continuous cell cultures; it blocks the transformation of normal mouse (MO) cells by murine sarcoma virus, and partially suppresses the release of murine leukemia virus by a continuously infected mouse cell line (JLSV5). In human skin fibroblasts, it reduces the interferon-inducing capacity of poly(I)·poly(C). Inhibition of cell protein synthesis may be the common cause of the various effects. 4-Fluoro-L-histidine is essentially inert in all of the test systems examined.