DETECTION OF SPECIFIC ANTIGEN IN SV40-TRANSFORMED CELLS BY IMMUNOFLUORESCENCE

With an immunofluorescent technique involving the use of serum of hamsters with SV40 tumors, nuclear fluorescence was detected in each of five cell lines, derived from four mammalian species, transformed by SV40 virus. Essentially all nuclei, including those of multinuclear cells, were fluorescent-stainable. Serum of hamsters bearing SV40 tumors was also found to give nuclear fluorescence in susceptible cells (AGMK or BSC-1) acutely infected with SV40 virus. These findings provide further evidence that cellular incorporation of the SV40 viral genome, with partial expression of the genome by synthesis of at least one virus-specific antigen, is an integral property of all SV40 transformed cells.

THE RELATIONSHIP OF A TYPE OF MYCOPLASMA ISOLATED FROM TISSUE CULTURES TO A NEW HUMAN ORAL MYCOPLASMA

A previously unidentified type of Mycoplasma found as a contaminant in tissue cultures and in a culture of Eaton agent, is identical with a newly recognized human oral type.

I am indebted to Drs Herdersheê and Chanock for sending me their cultures and relevant information.

VISUAL PIGMENTS OF SINGLE PRIMATE CONES

Single parafoveal cones from human and monkey retinas were examined in a recording microspectrophotometer. Three types of receptors with maximum absorption in the yellow, green, and violet regions of the spectruin were found. Thus the commonly held belief, for which there has previously been no direct and unequivocal evidence, that color vision is mediated by several kinds of receptors (possibly three), each containing photopigments absorbing in diflerent regions of the spectrum, is confirmed.

A COMPARATIVE STUDY OF SUSCEPTIBILITY OF PRIMARY MONKEY KIDNEY CELLS, HEP 2 CELLS AND HELA CELLS TO A VARIETY OF FAECAL VIRUSES

A comparative study of the susceptibility of monkey kidney, Hep 2 and HeLa cells to enteroviruses and adenoviruses is made. It seems that this Hep 2 cell line is as effective as the monkey kidney cells in their susceptibility to vaccine strains of polioviruses and far better than monkey kidney cells in their susceptibility to strains of ECHO 6 and ECHO 11 from clinical material. It is as effective as, or slightly better than, HeLa cells for the isolation of adenoviruses. It also compares favourably with monkey kidney cells for the isolation of other enteroviruses.

We are most grateful to Glaxo Laboratories Ltd. for the supplies of monkey kidney cells used in this investigation.

ELICITATION OF AGGRESSION BY A PHYSICAL BLOW

Squirrel monkeys were exposed to brief tail-pinches in the presence of a cloth-covered ball. Attack was elicited against the ball as a direct function of the force of the tail-pinch. This finding in conjunction with previous findings regarding electric shock and intense heat demonstrates that several types of aversive stimulation can elicit aggression.

FOVEAL RECEPTORS OF THE MONKEY RETINA: FINE STRUCTURE

The outer segments of the foveal cones of the rhesus monkey are about 40 microns long and 0.9 microns wide. They consist of stacks of membrane-limited, transverse discs about 140 A thick, surrounded by a plasma membrane. The inner segments are about 30 microns long and 2.5 to 3 microns wide at the base, and they taper gradually to a tip diameter of about 1.5 microns. They contain many long mitochondria which are oriented length-wise and are concentrated in the distal portion of the segment. The terminal pedicles show many synaptic contacts, probably as many as 36 per pedicle.

RESPONSES OF SINGLE CELLS IN VISUAL SYSTEM TO SHIFTS IN THE WAVELENGTH OF LIGHT

Spectrally opponent cells of the macaque lateral geniculate are very sensitive to shifts from one wavelength to another, independent of the relative intensities of the different wavelengths. Shifts in opposite spectral directions from the adaptation wavelength produce opposite changes in firing rate, regardless of the particular wavelengths involved; however, any given cell is more sensitive to shifts in some spectral regions than in others.

PRIMATE RETINA: DUPLEX FUNCTION OF DARK-ADAPTED GANGLION CELLS

Certain ganglion cells from the central region of dark-adapted retina of the rhesus monkey respond to stimulation of both rod and cone receptors. With dim stimuli the function of these ganglion cells is determined entirely by the rods; with brighter stimuli that affect both dark-adapted rods and cones, little evidence of rod function is detectable because a cone mechanism appears to determine both the latency and frequency of ganglion-cell firing.

DIFFERENTIATION OF A PRECISE TIMING RESPONSE

Humans, monkeys, and rats were trained by a process of successive differentiations to press a bar for at least 1.00 sec but for no longer than 1.27 sec. Initially, animals were reinforced for all responses, then a minimum duration of response was gradually differentiated, below which no responses were reinforced. Finally, a maximum duration of response was differentiated above which no responses were reinforced. The duration of response in all three species approximated the minimum duration of response necessary for reinforcement. As the duration of response necessary for reinforcement increased, so did the mean duration of response in the three species. As the maximum allowable duration decreased, further compression of the mean occurred. The fact that the acquisition of the differentiation was approximately the same in all three species is a further indication of the control reinforcement exerts on operant responding.

VARIABLES DETERMINING THE EFFECTS OF DELAY IN REINFORCEMENT

Procedures were discovered for maintaining a small fixed-ratio performance under 24-hr delay in reinforcement, by appropriate manipulation of the length of delay, amount of food delivered, and size of the fixed ratio. Other experiments showed that (1) the parameters discovered in the first experiment could produce the same result without the complex history of the first procedures; (2) the same parameters of the delayed-reinforcement procedure could maintain an explicit chain of responses; (3) gradual increase in the delay in reinforcement from small to large values was not a necessary condition for achieving the major result, if large amounts of food were delivered as reinforcement and all of the behaviors were first under good control of the relevant stimuli with short delays.