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Biomedical subjects

R Hess

Publications and source records attributed to R Hess.

At least 91 records · Page 5Linked to original sources
PubMed1980

Effects of hydroxyurea on postnatal growth and behaviour of rats.

Hydroxyurea was administered intraperitoneally to pregnant albino rats in a single dose of 2000 mg/kg on day 14 of gestation. Both the perinatal and postnatal mortality rates of the progeny were increased and their weight gain reduced. Exploratory locomotion of 32-day-old rats, calculated by means of an 'activity index', was significantly reduced. The treatment had no effect on the brain weight. The fertility of the progeny was not impaired.

Animals↗
PubMed1980

The optimization test in the guinea pig in relation to other predictive sensitization methods.

The allergenicity of various compounds was tested by means of the optimization procedure in the guinea-pig. Results with antibiotics, preservatives, fragrance raw materials and miscellaneous contactants are reported. Their relevance is critically discussed in relation to other animal sensitization methods (Draize, Bühler, open epicutaneous and maximization tests). Predictive animal tests are compared with those used in human allergy (Shelanski & Shelanski; maximization test). The importance of animal methods entailing the use of adjuvants is underlined.

Allergens↗
PubMed1980

Test-retest reliability of the test for auditory comprehension of language when it is used with mentally retarded children.

The Carrow (1973) Test for Auditory Comprehension of Language (TACL) is used frequently as part of a test battery to assess the language skills of mentally retarded children. This study determined its reliability with this population using a test-retest paradigm. Forty-four retarded children were given the test and then retested after a five-week interval. A reliability coefficient of 0.91 was obtained between pre-test and posttest administrations of the TACL. Internal stability was highest for total scores, the subtests measuring form class and function words, and grammatical categories. The low coefficients obtained for the subtests of morphological construction and syntactic suggest that these should be viewed with considerable caution when considered separately from the total test results.

Adolescent↗
PubMed1980

Amblyopia cannot be explained by considering only detection thresholds.

Threshold function and suprathreshold performance for nonacuity stimuli are compared for an amblyope who exhibits a low as well as a high spatial frequency threshold abnormality. The results show that (i) a suprathreshold abnormality involving discrimination and localization of easily visible stimuli occurs in amblyopia and (ii) suprathreshold abnormalities occur in amblyopia independent of any threshold dysfunction.

Amblyopia↗
PubMed1980

Predictive animal testing for photocontact allergenicity.

The purpose of this investigation was to establish a standardized animal model to predict the photoallergenic potential of new chemical compounds. In a first series of experiments the main factors influencing the induction of photoallergenicity were evaluated (induction concentration, pH of the test solution, pretreatment of the irradiation site with sodium lauryl sulphate, additional use of adjuvant injections and routes of administration). Osram Ultravitalux lamps were utilized for these studies. In a second series of experiments a Xenon 6000 W radiation source was used. Positive results were obtained with well known photosensitizers, as, for instance, the halogenated salicylanilides, as well as with so-called weak photoallergens (e.g. bithionol, sulphanilamide) by stimulating the animals' immune system with Freund's complete adjuvant. The photoallergenic compounds were at the same time tested for their contact allergenic potential in the optimization test. A standard procedure for the predictive photoallergenicity assay in guinea-pigs is proposed.

Adjuvants, Immunologic↗
PubMed1979

[Recurring loss of conciousness with middle brain symptoms in migraine].

A 49-year-old woman subject to frequent migraine attacks since childhood was seen for repeated episodes of confusion followed by loss of consciousness lasting for several hours. EEG during the acute stages showed marked slowing with bifrontal monorhythmic delta waves. After each episode, both the clinical and EEG findings subsided within hours. A similar course is described in a man who died at the age of 69 after preterminal mental deterioration. Autopsy showed evidence of bilateral damage to the hippocampal regions, apparently due to frequent impairment of perfusion in the last years of life. Atherosclerotic changes were within the normal range for his age. In both cases, the ischemic episodes are interpreted as consequences of constriction of the basilar artery, and it is assumed that the underlying mechanism is at least akin to that of migraine.

Aged↗
PubMed1979

Responses of single cells in cat's lateral geniculate nucleus and area 17 to the velocity of moving visual stimuli.

Neuronal responses to moving visual stimuli were recorded in the lateral geniculate nucleus (LGN) and area 17 of cats. Response duration (DE), number of spikes (NT), and mean frequency (FM) were estimated from the response histograms and analysed for their dependence on stimulus velocity. In the LGN, for about 2/3 of cells these response parameters changed monotonically with velocity up to about 100 degrees/s. In 1/3 of the cells, the response frequency was tuned to velocity. The speed at which individual cells reached a peak or plateau firing rate was correlated with their receptive field size. In area 17, most neurones were tuned to velocity. Nine out of 59 cells were insensitive to stimulus speed in that they responded equally well at stimulus velocities up to about 10 degrees/s. The results suggest that at higher levels in the nervous system information about velocity is represented in discrete groups of neurones. It is pointed out that different response parameters may be relevant for different perceptual phenomena associated with movement. The significance of integrational properties and lateral inhibition of nerve cells for the development of complex response properties is discussed.

Animals↗
PubMed1979

Clioquinol and 2,5-hexanedione induce different types of distal axonopathy in the dog.

The central distal axonopathy induced in dogs by the administration of high doses of clioquinol is contrasted with the central-peripheral distal axonopathy precipitated by intoxication with 2,5-hexanedione. Mature, pure-bred Beagle dogs received a daily oral dose of 400 mg/kg of clioquinol for up to 7 months, or 1 ml per animal (approximately corresponding to 110 mg/kg) of 2,5-hexanedione for up to 5 months. Intoxicated and control animal were killed and perfused at monthly intervals, so that the spatial-temporal development of the lesion could be followed and correlated with clinical symptoms. During the treatment, dogs intoxicated with 2,5-hexanedione developed symptoms of peripheral neuropathy consisting of flaccid weakness, muscle atrophy, hind-limb foot-drop and areflexia. By contrast, the dogs surviving clioquinol intoxication exhibited a stiff-legged gait, hyperreflexia but no muscle atrophy. Light and electron microscope examination of central and peripheral nervous tissue from dogs intoxicated with 2,5-hexanedione revealed giant axonal swelling and distal axonal degeneration. By contrast, dogs receiving clioquinol showed a distal axonal degeneration confined to the optic tract and the long spinal cord tracts, without any visible involvement of peripheral nerves.

Animals↗
PubMed1979

Differential susceptibility of peripheral nerves of the hen to triorthocresyl phosphate and to trauma.

The nerve fibres of largest diameter and of greatest length are considered to be the most vulnerable to triorthocresyl phosphate (TOCP). In this study, the differential vulnerability of the particular sciatic nerve branches was determined in the course of TOCP neuropathy and of Wallerian degeneration. The branch innervating the lateral gastrocnemius muscle, made up predominantly of large-diameter fibres, proved most susceptible to TOCP. By contrast, after proximal sciatic-nerve transection, degeneration commenced in the lateral nerve of the third digit, containing long nerve fibres of small diameter.

Animals↗