Ultrastructure of ultraviolet radiation-induced hairless mouse skin carcinogenesis, with special reference to the epidermal-dermal junction

The ultrastructure of ultraviolet (UV)-induced skin pathology was studied in mice to complement previously reported gross and light microscopic findings, and to assess further the usefulness of the animal model for study of sunlight associated epidermal tumours in man. Hairless albino (HRA/Skh-1) mice were exposed to a minimal erythemal dose from a filtered light source emitting both UVA and UVB, approximating solar emission. Samples of normal and hyperplastic skin, pedunculated papillomas, carcinomas in situ and invasive squamous cell carcinomas were processed for transmission electron microscopy once their identity was confirmed by light microscopic examination. Keratinocyte pleomorphism became more marked and cell to cell contact diminished as malignancy developed. For papillomas, carcinomas in situ and invasive squamous cell carcinomas, there was a progressive disruption of the epidermal junction which became marked upon frank invasion. Most of the differences between the various categories of pathological change, therefore, were not absolute but rather of degree, supporting the notion that invasive squamous cell carcinoma represents an end stage for malignancy which may arise de novo, directly from hyperplastic skin, or proceed from other tumour types. The similarity in structure of the mouse tumours to comparable tumours in man supports the usefulness of the animal model and suggests that the results have implications for sunlight associated tumours in man.

Some effects of early monocular deprivation in the Mongolian gerbil

The effects of short- and long-term early monocular deprivation were investigated in 4 Mongolian gerbils using interocular differences in grating acuity as a measure of deprivation-induced impairment. All gerbils showed acuity deficits in the initially deprived eye, ranging in magnitude from 0.24-1.40 octaves. One month of monocular deprivation from eye opening proved sufficient to induce a permanent acuity impairment.

Intrazeolite photochemistry. IV. Studies of carbonyl photochemistry on the hydrophobic zeolite Silicalite using time-resolved diffuse reflectance techniques

Transient absorption and luminescence from aromatic ketone triplets (xanthone, acetophenone, butyrophenone, valerophenone, p-methoxyacetophenone, β-phenyl-p-methoxypropiophenone and benzil) supported on the hydrophobic zeolite Silicalite have been obtained by time-resolved diffuse reflectance laser flash photolysis. These experiments were aimed at establishing the usefulness of this technique for studies of zeolite supported photoreactions. While the transient spectral properties can be used to examine the properties of the supporting media, the decays of the signals frequently follow complex kinetic behaviour. The decays for such heterogeneous systems cannot be easily fit to clean first or second order kinetics and are thought to be a mixture of several first order decays arising from triplets in different inclusion and adsorption sites. Evidence is presented for close-packing of the aromatic substrates and for triplet lifetime enhancement. Although the triplet spectrum of included benzil shows evidence for considerable axial freedom, the results for β-phenylpropiophenones indicate that other types of motion are restricted for included ketones. It is also found that the rate of the Norrish Type II reactions of valerophenone and butyrophenone supported on Silicalite are decreased with respect to the rates in solution.

Visual texture segmentation in cats

The segmentation of visual images on the basis of textural discontinuity was studied in cats using two behavioural paradigms. The first task (Experiment 1) required the animals to detect the presence of a target square of one texture embedded in a background of a second texture. The second task (Experiment 2) required the cats to discriminate between two forms (square and triangle) both of which were defined by texture-texture boundaries. Both detection and discrimination tasks were presented in a transfer paradigm in which the animals first learned a luminance-based form of the same problem. The results indicate that cats are able to segment a visual array on the basis of textural discontinuity in the absence of global luminance differences between figure and ground, and that they are able to use the contour information provided by texture-texture boundaries as a basis for form discrimination.

Eye and brain growth in the Mongolian gerbil (Meriones unguiculatus)

Eye and brain growth were evaluated by measures of weight and surface dimensions at 11 ages spanning the period from birth to 150 days of age in the Mongolian gerbil (Meriones unguiculatus). Brain weight was found to increase very rapidly until day 18, followed by a more gradual increase to asymptote by 70 days of age. Eye growth follows overall body growth more closely than brain growth. Eye shape was found to change from ovoid to spherical over the first 70 days of life. The possible relationship between eye growth and retinal specialization is considered, and brain growth is compared across several rodent species.

Vernier acuity in the cat: its relation to hyperacuity

Vernier thresholds were measured behaviourally in five cats using offsets in gratings of two spatial frequencies and in single lines. Thresholds ranged from 2.2 to 6.7', and no threshold differences were found across stimuli. These results are discussed in relationships with published spatial resolution data and are related to the optical and neural characteristics of the cat's visual system. It is concluded that if vernier acuity is a hyperacuity in cats, the improvement in grain is not of the same magnitude as it is in humans.

The development of visual acuity in the Mongolian gerbil (Meriones unguiculatus)

The development of visual acuity for vertically oriented gratings was followed in gerbil pups from 34 days of age until adulthood using a jumping stand procedure. Acuity was found to improve gradually from an initial level of about 0.7 cycles/degree to asymptotic values of 1.2-1.6 cycles/degree by 70 days of age. Acuity did not vary as a function of viewing distance over the range tested (17.5-46 cm). Practice was found to play some role in the acuity changes seen but cannot alone explain the results. The contributions of other performance variables and of neural development are considered.

The long-term effects of removal of sensorimotor cortex in infant and adult rhesus monkeys

A comparison is made between the long-term effects of the unilateral removal of sensorimotor cortex in infant and adult rhesus monkeys. Both infants and adults recovered to a remarkable extent. They walked, climbed and jumped with ease. However, neither infant nor adult monkeys could grip food by using thumb and forefinger independently of the other fingers. It was demonstrated in the adults that there was a permanent impairment in the use not only of the fingers but also the wrist and forearm. The results do not support the claim made by Kennard (1942) that infants recover more completely than adults from the effects of brain lesions. An analysis of the relevant evidence suggests that compensation occurs only when the animal is very immature at the time of operation. The brain is much more mature in a neonatal monkey than a rat or hamster. True compensation can probably only occur in monkeys if the lesion is made well before birth.

A pulse radiolysis study of zinc(II)-insulin

Reactions of eaq with zinc(II)-insulin at pH 6.6 and 9.0 yielded relatively low disulphide anion absorptions, suggesting eaq reacts at other sites than S-S. A similar conclusion was reached for the reation of CO2 where an even lower yield of disulphide anion was found. However, here the disulphide anion yield increased with 'prepulsing'. Simultaneously the rate constant decreased, implying that a more reactive site was 'cleaned up'. While no reaction of Br2 with insulin was observed, both OH and Cl2 reacted rapidly and predominantly at the tyrosine residues. The second order rate constants, calculated in terms of insulin monomer concentrations, are reported for eaq, CO2 and Cl2. The transient spectra qualitatively support evidence regarding the accessibility of S-S bonds and tryosine residues in the various forms of insulin as predicted from earlier studies.

Young kittens can learn complex visual pattern discriminations

Kittens begin to display visually elicited responses shortly after eye opening. The pupillary reflex, optokinetic response, visual placing and avoidance of the deep side of the visual cliff all appear between the second and fifth weeks of life, and evidence of visual learning in homing behaviour has been described at the same early age. However, an attempt to elicit pattern preferences in kittens of this age (usually considered the easiest way to demonstrate discriminatory behaviour in immature organisms) was unsuccessful, evidently because such kittens show little spontaneous visual interest. This is surprising in view of electrophysiological findings which emphasise the importance of the fourth to sixth weeks in the development of cortical feature-analysing mechanisms; perhaps the stimulus-seeking methodology of Dodwell et al. is anappropriate for the visual modality at such an early age. Recently, visual acuity measurements have been reported for kittens as young as 30 d of age using a contour versus no-contour discrimination on a modified Lashley jumping stand. With this technique we have now trained kittens of under 50 d of age to perform more complex pattern discriminations.