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In 13 wallabies (Macropus eugenii, the tammar), microelectrode recordings of the activity of units in the superficial layers of the superior colliculus in response to a flashing light spot were used to make a map of the spatial location of their receptive fields. This article describes the projection of a normal eye to the contralateral colliculus. Ten of the 13 animals had one rotated eye and these projections are analysed in the accompanying paper (James et al., this issue). Units responded briskly to the stimulus at light on and off and had receptive fields about 5 degrees across. The centres of receptive fields from a regular array of recording points on the colliculus were plotted with a perimeter and fitted to a flattened representation of the colliculus according to a spline technique. The visual field of each colliculus extends from 25 degrees ipsilateral to the vertical meridian to 120 degrees temporal contralaterally. The lines of isoazimuth are regularly spaced and parallel and run mediolaterally on the colliculus. The horizon is represented by a line running rostrocaudally and the parallels are more widely spaced near the horizon and become compressed in the superior and inferior fields. The variation of areal magnification factor fits the distribution of density of retinal ganglion cells very well. Anisotropy of the projection means that the increased ganglion cell density of the retinal visual streak is entirely accommodated by magnification in the vertical direction, while the magnification of the azimuthal projection is equal over the whole field. No responses were recorded from the ipsilateral eye even though anatomically there is a direct retinal ipsilateral projection.

CR-39 plastic was attached to household glass objects to learn whether residual radioactivity from radon decay products could be measured and correlated with cumulative radon exposures over defined time periods. Such an approach could be used to increase the completeness of exposure data collected in epidemiologic studies of residential radon. Inability to estimate radon concentrations for all residences adversely effects statistical power and thus the ability to detect an effect of radon exposure on lung cancer risk. A feasibility study was performed to determine if affixing CR-39 surface monitors to selected glass, ceramic, or enameled objects provided comparable estimates of past residential radon exposure to those obtained from year-long ambient alpha track-etch measurements. The CR-39 measurements of alpha activity in the surface of selected objects correlated with ambient radon measurements (R2 = 0.48) provided that reliable information was obtained on the history and age of the objects. This technique has now been incorporated into an epidemiologic study of radon and lung cancer to more fully estimate past exposure to indoor radon.

The development of an automated system for activity-weighted size distribution measurements now permits more complete exposure and dose assessment for indoor radon decay products. Exposures characterized by the semi-continuous measurement of activity-weighted size distributions of radon decay products were obtained over four test periods in three normally occupied houses, two of which were occupied by cigarette smokers. These measured activity size distributions were used to calculate exposure-dose conversion coefficients and the annual effective doses. These doses were found to be approximately two-fold higher than the values derived conventionally from the measured radon concentration, on the assumption that indoor exposure to 20 Bq m-3 radon gas concentration corresponds to an annual effective dose 1 mSv y-1. The degree to which aerosol-measurement-based dose estimates were higher than radon-gas-based estimates was found to be influenced if the study house occupant was a cigarette smoker. Reassessment of the measured PAEC-weighted radon progeny particle size distribution in terms of the classical "unattached" and "attached" modes yielded lower estimates of the exposure-effective dose conversion coefficient that were similar to the reference values derived from a recent study by the National Research Council. Thus, by not resolving the measured radon progeny PAEC that is associated with particles intermediate in size between the two classical radon progeny modes, the estimated annual effective doses were also found to be similar to the values derived conventionally from the measured radon gas concentration. It is concluded that the observed presence of 4 to 13% of the radon progeny PAEC in the size-range 1.5 to 15 nm diameter is a dosimetrically significant factor that appears to be commonplace in various home environments.

The distribution of thorium in the liver of a patient 36 y after injection with Thorotrast was examined with autoradiographic and scanning electron microscope backscatter image techniques. Autoradiographic examination of randomly selected histologic sections of the liver showed a total alpha activity calculated at 33.7 Bq g-1, with the highest concentration of alpha activity sequestered in subcapsular scare tissue. Subcapsular scare tissue received 4.8 cGy d-1 of alpha radiation, periportal areas were accumulating 1.4 cGy d-1, and the hepatic cord areas 0.09 cGy d-1 of alpha radiation at the time of death. The concentration of dose in periportal areas correlates with higher incidence of bile duct tumors (than hepatocellular carcinomas) found in patients exposed to Thorotrast. The backscatter technique was demonstrated as useful for identifying thorium in liver specimens.

Particle transport by oscillating flow in a tapered channel or in a tapered tube was computed from the complete equations of motion. These geometries represent a simplified model of the divergent flow field of the mammalian bronchial tree. The computed deformation profile of a line of particles, transported by the oscillatory motion, was compared with prior experimental results and analytical calculations. All three methods agree that there is transport in the divergent direction of the tube by an axial stream of steady drift in the core for moderately high frequency of oscillation (Womersley parameter in the range of 1 to 10). Bidirectional flow is established by an annular stream in the convergent direction, with no net flow on integral cycles of the oscillating fluid. At higher frequency, however, the steady stream transforms to a different shape in the tapered tube, with transport in the divergent direction nearer the walls of the tube, rather than in the core. Transport by the continuing streams with oscillatory ventilation of the respiratory tract should deliver medicinal aerosols of low intrinsic particle mobility to the peripheral regions of the lungs.

We have developed a model to calculate the dose to the cell nucleus in cells exposed in suspension to radon and/or radon progeny. The model addresses the influence of (1) different radiation qualities and energies in the irradiation milieu; (2) the contribution to dose from radioactivity in the medium surrounding the cell after exposure to the radon gas as well as that from excess radon progeny associated with the cell; (3) the geometry of the cell and of the radiosensitive target, the cell nucleus; (4) the intracellular localization of the radionuclides; (5) attenuation of the alpha particles by the cytoplasm; (6) the radionuclide concentrations in the medium; and (7) the length of exposure. Investigation of the influence of these various parameters was made using an irradiation system in which cells were exposed to 212Bi, which decays to stability with the emission of an alpha particle (either 6.05 or 8.78 MeV). The information from these studies was then used to develop the system further for more complex systems in which 222Rn and its progeny are present. The model takes into account the contribution of dose from different radiation sources using scintillation counts of the medium and the cells, and it is useful for calculations of dose in situations where cells are exposed in suspension culture.

We document the occurrence of "sex ratio" meiotic drive in natural populations of Drosophila testacea. "Sex ratio" males sire greater than 95% female offspring. Genetic analysis reveals that this effect is due to a meiotically driven X chromosome, as in other species of Drosophila in which "sex ratio" has been found. In contrast to other drosophilids, the "sex ratio" and standard chromosomes of D. testacea do not differ in gene arrangement, implying that the effect may be due to a single genetic factor in this species. In all likelihood, the "sex ratio" condition has evolved independently in D. testacea and in the Drosophila obscura species group, as the loci responsible for the effect occur on different chromosomal elements. An important ecological consequence of "sex ratio" is that natural populations of D. testacea exhibit a strong female bias. Because D. testacea mates, oviposits, and feeds as adults and larvae on mushrooms, this species provides an excellent opportunity to study the selective factors in nature that prevent "sex ratio" chromosomes from increasing to fixation and causing the extinction of the species.

Direct measurements of bronchial deposition in ventilated pig lungs are reported for radon daughter ions and condensation nuclei. Comparisons are made with deposition calculated from the theory of particle diffusion in steady, laminar air-flow. In segmental bronchi, the observed deposition of condensation nuclei was within about 25% of that calculated. Deposition was greater by up to a factor 2 in main stem and lobar bronchi. Deposition in the trachea depended upon the entrance conditions set by vocal cords. For thorium-B ions, deposition in segmental bronchi was a factor 4 less than calculated, apparently due to rapid hygroscopic growth. Clearance rates by dissolution from bronchial epithelium in vivo for lead and bismuth ions are also reported. Approximately 10% of 212Pb ions diffused into blood with a half-time of about 70 min and 30% of 212Bi ions with a much shorter half-time of about 7 min. The implications of these data in the calculation of radiation dose from inhaled radon daughters are discussed.

Serum samples from 894 wild animals (representing 31 species) from Trinidad and Grenada were examined by the microscopic agglutination test for leptospiral antibodies; 198 were positive. These included 39 bats, 88 mongooses, six opossums, 10 peridomestic rodents, 15 forest rodents, 10 lizards, and 30 toads. Thirteen pathogenic serogroups were involved. Thirty-nine Leptospira isolates were reported from mongooses, opossums, rodents and toads.

For radiation protection purposes, the International Commission on Radiological Protection (ICRP) Task Group proposes to apportion radiation risk within the respiratory tract according to the tumor mortality rates observed in the different anatomical regions. This approach requires that doses absorbed by extrathoracic tissues must be considered, in addition to those in the lung. For the extrathoracic region, the tissues at highest potential risk are the pharyngeal parts of the nasopharynx and oropharynx and a part of the larynx. In the lung, all tissues are potentially at risk, and it is necessary to consider doses absorbed by bronchial tissues, the lung parenchyma, and lymph nodes. This paper outlines the methods proposed by the Task Group to evaluate the heterogeneous doses absorbed by sensitive cells in these tissues from radioactive decays of alpha-emitters. The objective is to evaluate doses to broad regions of the respiratory tract, where the regions are defined to reflect substantial differences in potential risk when taking into account deposition and clearance behavior. The Task Group proposes to represent the respiratory tract by three generic regions: an extrathoracic region and two thoracic regions, one clearing fast and one slowly. The models of aerosol deposition and clearance applied for each region are outlined. To illustrate the use of the model, doses are evaluated for the key cases of short-lived radionuclides and long-lived insoluble alpha-emitters and are discussed with regard to current ICRP recommendations.

The time course of retention of 212Pb ions in ciliated nasal epithelium and of tagged insoluble particles, which served both as a deposition vector and marker for mucus, was measured in 13 rats by counting the head externally at 2 min intervals up to 100 min after deposition. On average, 70-75% of insoluble particles introduced onto ciliated epithelium in 3 microliters of distilled water were cleared to the gut with a half-time of approximately 15 min (range 6-35 min). A smaller fraction of lead ions (averaging about 60%) introduced in the same water sample was cleared to the gut with a half-time in each rat similar to that of particle clearance. Rapid uptake of about 8% of deposited 212Pb into blood was also observed. A compartment model consistent with the observed nasal retention and appearance of 212Pb in blood showed that, on average, 8% of deposited lead ions were transferred to the blood with a half-time of 15 min. For about 35% of the deposited lead ions and 25% of the particles, no clearance was detected up to 60-100 min after deposition. It is probable that a fraction of the lead ions are retained by epithelial tissue.

The absorption of 212Pb ions from bronchial epithelium to blood has been investigated in anaesthetized rabbits. The 212Pb ions were introduced by intubation either into the trachea or into smaller, more distal bronchi. Removal from lung was followed by external gamma-counting. Mucociliary clearance to the GI tract was blocked by tracheostomy. Two distinct phases of clearance from bronchial epithelium to blood were observed. Approximately 20% of deposited 212Pb is rapidly absorbed with a half-time of about 4 min, the remainder with a biological half-time of about 9 h, irrespective of the site of instillation in the bronchial tree. Two hours after deposition, the 212Pb remaining in lung was found to be partitioned between mucus and the bronchial epithelium, with a substantial but minor fraction in the epithelium. Uptake of 212Pb in the skeleton was estimated to be about 20% of the 212Pb entering the blood circulation. Removal by the kidneys, at 25%, was comparable with skeletal uptake. These results are compared with previously published work using rodents, dogs and man which demonstrated either rapid or slow absorption but not both phases occuring together.

All known isolates of Leptospira interrogans obtained in Trinidad, Grenada and St. Vincent up to the end of 1979 are listed. There were 80 from Trinidad, 20 from Grenada and 2 from St. Vincent, representing at least 20 serotypes from 11 or more serogroups. Six of the serotypes were first reported from Trinidad. The leptospires were isolated from man, domestic animals and wildlife species.

A general algorithm for solving first-order compartmental models including recycling systems has been developed and its implementation on a microcomputer is described. Matrix algebra is used to obtain for any compartmental model an analytical solution, which is expressed as the exponential of a matrix of rate constants. A special technique is used in the algorithm to enable this exponential to be evaluated with a rapidly converging series. Truncation errors incurred in this process are estimated automatically. Thus, in an extreme case, where these errors may be significant, the appropriate action can be taken. Given a particular model, the user enters the model parameters into a rate matrix according to a simple rule. The algorithm then uses this matrix to solve the model, and thus no specialized mathematical knowledge is needed. The algorithm is given in a short BASIC program (60 lines) listed in an appendix. No additional software is required. By running this program on a standard microcomputer, the user can solve models of any complexity: those up to 15 compartments in seconds and those up to 30 compartments within a minute. The algorithm is thus ideally suited to solve kinetic models describing the transport of radionuclides in the environment or the translocation of elements in biological systems such as the metabolic models recommended by the International Commission on Radiological Protection (ICRP). Given the initial amount of material in each compartment at time t = 0, together with its radioactive decay constant, the algorithm gives both the amount in each compartment at any future time t and the number of disintegrations that will have occurred in each compartment up to time t. The computer program, shown in an appendix, could easily be used to calculate disintegrations over any time interval of interest, or to predict the quantities or fractions of an intake expected to be present in any in vivo or excretion compartments of interest. Thus, the algorithm can be useful in both the design and conduct of bioassay and internal dose assessment procedures.

Sera from 1,206 livestock animals and chickens on Grenada and Trinidad were tested for leptospiral antibodies by the microscopic agglutination test. 376 of the sera were positive (25% of those tested on Grenada and 44% on Trinidad). The positive sera were obtained from 25% of 324 cattle, 35% of 130 pigs, 35% of 146 sheep, 25% of 44 goats and 11% of 175 chickens on Grenada; and 92% of 26 cattle, 53% of 122 pigs, 76% of 87 horses and donkeys and 11% of 144 chickens on Trinidad. Eight sera from ducks and geese on Trinidad were tested and found to be negative. The serogroups most commonly found to react with the sera of the Grenadian animals were Autumnalis, Icterohaemorrhagiae, Hebdomadis and the related serogroups Sejroe and Mini, and Pyrogenes; in the Trinidadian animals they were Icterohaemorrhagiae, Autumnalis, Hebdomadis and its related serogroups, and Panama. Strains of serogroup Pomona do not appear to have become established as livestock pathogens on the islands.