Protection of A/He mice by a Friend virus pseudotype against challenge with Friend virus.

Prior inoculation of 7-wk-old A/He mice with the Graffi pseudotype of Friend virus protected the animals against subsequent challenge with Friend virus. Graffi leukemia virus itself did not induce protection, probably because it failed to replicate in these mice.     

Thermoregulation and heterothermy in some of the smaller flying foxes (Megachiroptera) of New Guinea

Summary Body temperature, heterothermy, oxygen consumption, heart rate, and evaporative water loss were studied in four species of flying foxes (Megachiroptera), Dobsonia minor, Nyctimene major, Nyctimene albiventer, and Paranyctimene raptor, from the vicinity of Madang on the north coast of New Guinea.The thermoregulatory response of D. minor resembled that of most other placental mammals weighing 80 to 100 g. Body temperatures were relatively stable at ambient temperatures between 5 and 34°. The mean oxygen consumption at rest between 30 and 35° was 1.26 cc O₂ (g·hr)^–1. At ambient temperatures between 5 and 35° evaporative water loss averaged 4.5 mg (g·hr)^–1 and increased sharply at higher temperatures. When subjected to heat stress the animals panted, salivated, and licked the wings, belly, and uropatagium. At temperatures above 38° the ratio of heat lost through evaporation to heat production exceeded 1. Minimal heart rates in resting animals near thermal neutrality were approximately 275/min.In those parameters measured, N. major which weighed about 80 g resembled D. minor. Nyctimene albiventer and P. raptor weigh less than 30 g and are among the smallest of the flying foxes. Each shows both homeothermic and heterothermic patterns of response. At an ambient temperature of 35° the minimal oxygen consumption of homeothermic N. albiventer and P. raptor were 1.43 and 1.38 cc O₂ (g·hr)^–1, respectively. Oxygen consumption of homeothermic N. albiventer at 25°, 2.59 cc O₂ (g.hr)^–1, was almost quadruple that of torpid animals at the same temperature. During the daytime both N. albiventer and P. raptor characteristically allowed their body temperatures to fall to near 25°. Both readily aroused from the hypothermic state through physiological means. Heart rates of homeothermic N. albiventer resting at 35° ranged from 312 to 326/min while those of animals torpid at 25° were 88 to 96/min.The capacity for heterothermy has not previously been demonstrated in any members of the Megachiroptera, but our data indicate that it can occur on a daily basis in N. albiventer and P. raptor. This capacity appears to be related to size since it occurs in none of the larger flying foxes so far studied.The data presently available indicate that the relation of body weight to standard metabolism in the Megachiroptera is similar to that of the other placental mammals. In the species we studied, thermal conductances were higher, and heart rates, lower than predicted for mammals of their sizes.These studies were carried out during the 1969 Alpha Helix Expedition to New Guinea and were supported in part by grants GB-5139, GB-3656, and GB-8445 from the U. S. National Science Foundation.     

A bivariate radioimmunoassay for arginine vasopressin and the synthetic antidiuretic agent 1-deamino-8-D-arginine vasopressin (desmopressin)

Pairs of radioimmunoassays, each of which include a two-dimensional matrix of standards, have been previously employed to resolve specificity problems in steroid immunoassay. In this study the bivariate radioimmunoassay principle has been applied to simultaneous measurement of plasma antidiuretic hormone, arginine vasopressin, and the synthetic antidiuretic agent 1-deamino-8-D-arginine vasopressin (desmopressin), by utilizing two arginine vasopressin antisera which show significantly different cross-reactivities with the synthetic analog. Data processing consists of mathematical representation of two curved dose-response surfaces followed by solution of this pair of nonlinear simultaneous equations for the unknown arginine vasopressin and desmopressin concentrations. Details of numerical procedures are given in the Appendix. The assay appears entirely adequate in terms of sensitivity, accuracy, and precision for measurement of these antidiuretic agents in clinical samples. No evidence of significant covariance in estimated concentrations could be detected but precision of estimation is (not unexpectedly) a function of the concentration of both agents. The plasma disappearance half-time of desmopressin (probably the second of a biphasic disappearance) was estimated as 37 min in one normal subject, which is in good agreement with a previously reported value of 30 min.     

Seasonal changes in moult,body mass and reproductive condition in siskins Carduelis spinus exposed to daylength regimes simulating different latitudes

Birds use change in daylength during the year to time events during their annual cycles. Individual Eurasian siskins Carduelis spinus can breed and winter in widely separated areas in different years. Birds at different latitudes will experience different changes in photoperiod. So how does latitude affect photoperiodic control? Our aim in this study was to find whether Siskins caught from the wild in Britain and exposed to different photoperiodic regimes, typical of widely separated latitudes, would differ in the subsequent timing and duration of their moults and associated processes. Siskins were caught in late February and early March, and initially kept outside on natural photoperiods. From the spring equinox (21 March), they were divided into three groups kept under photoperiodic regimes that simulated latitudes 40°, 55° and 70°N respectively. All three groups showed highly significant subsequent changes in body mass, fat scores and cloacal protuberance size. Moult of the primary feathers started during June – August (mean 9 July), and lasted 61–99 days (mean 75 days). Birds that started to moult late in the season had shorter moult durations. All individuals showed lower mass and fat levels during moult than before or after moult. Crucially, there were no significant differences in the timing of these events between the three photoperiodic groups. Apparently these birds did not use prevailing absolute photoperiod or the prevailing rate of change in photoperiod to time moult‐related seasonal events, but used instead some other feature of the annual photoperiod cycle or some form of interval timer linked to photoperiod.