Problems with entropy in biology

Entropy has been widely referred to as a measure of biological order. The validity of this notion is discussed in conjunction with it's relation to the spontaneous creation of order. Information theory offers a quantitative method for characterization of order, however, it is not fundamentally connected to formalisms of irreversible thermodynamics, and it is severely limited because the meaning and value of the information is neglected. A completely general notation is proposed for including measures of order of a biological system in the entropy balance equation of irreversible thermodynamics. Problems of assigning energetic equivalents to measures of order are indicated, with a final focus on the problem of meaning and value.

An improved system for preparative starch block electrophoresis

A starch block electrophoresis system is described which includes (a) a single-unit Lucite electrophoresis chamber, (b) temperature control with a circulating water bath and casting resin-coated brass cooling plate, (c) continuous monitoring of block surface temperature and (d) an easily-assembled apparatus for rapid elution of protein from the starch segments.

Oral manifestations of Crohn's disease without demonstrable gastrointestinal lesions

The literature relating to oral manifestations of Crohn's disease is reviewed and a case is reported in which clinical and histopathologic features of oral Crohn's disease are present without demonstrable gastrointestinal lesions. It is suggested that it is reasonable to make a firm diagnosis of the condition on this evidence alone and to monitor the patient for subsequent gastrointestinal symptoms, so that treatment can be instituted at an early stage.

Binocular interaction fields of single units in the cat striate cortex

1. Based on average response histograms to an optimal stimulus, binocular interaction field plots were obtained from twenty-five simple neurones in the striate cortex of the cat. Each binocularly activated cell has two interaction fields, one for each eye. The binocular interaction field for one eye plots the changes in the amplitude of the response from the other eye as the two receptive fields of the binocularly activated cell are moved across one another, first into and then out of alignment in the plane of the optimal stimulus (tangent screen).2. The binocular interaction field provides an important clue to the nature of the spatial organization of the excitatory and inhibitory regions of the monocular receptive field. The commonest type of receptive field organization has regions of inhibition (inhibitory side bands) to either side of the discharge centre in the direction at right angles to the optimal stimulus orientation. As well as inhibition, there are subliminal excitatory effects.3. Binocular interaction fields differ with the various cell types, i.e. cells that are discharged only from the one eye, cells binocularly discharged with very weak or absent monocular responses and cells showing binocularly opposite direction selectivity.4. Marked facilitation to an optimal stimulus occurs when the two receptive fields of a binocularly activated neurone are in accurate alignment. Facilitation switches to depression for very small degrees of receptive field misalignment in a direction at right angles to the optimal stimulus orientation. These observations are of importance in relation to mechanisms for binocular single vision and depth discrimination.

The limitations of exfoliative cytology for the detection of epithelial atypia in oral leukoplakias

Two hundred and ninety-nine oral leukoplakias were examined by exfoliative cytology; 83 of these lesions were biopsied because of clinical or previous histological features. Epithelial atypia was found in 16 of these biopsies, exfoliative cytology detecting epithelial atypia in only 6 of these cases. Thus exfoliative cytology used alone would have led to a false negative diagnosis in 10 out of 16 (62%) of the cases with epithelial atypia verified by histology. In addition, in no instance was exfoliative cytology responsible for the detection of an epithelial atypia that had been overlooked by consideration of clinical or previous histological features. Exfoliative cytology was successful in the detection of atypia only in those cases in which the surface of the lesion was either ulcerated or not keratinized; all keratinized lesions with atypia yielded negative cytology. The results of this study lead to the conclusion that exfoliative cytology is not to be recommended as a routine diagnostic or screening procedure for the detection of possibly pre-malignant features in oral leukoplakias.

Reverse smoking in Andhra Pradesh, India: a study of palatal lesions among 10,169 villagers

In the district of Srikakulam in Andhra Pradesh in South India the habit of reverse smoking is widespread. In a house to house survey of oral cancer and precancerous conditions, comprising 10,169 villagers, 43·8% were reverse smokers; the female: male ratio being 1·7: 1. Ten previously undiagnosed cases of oral cancer, 9 located to palate, were found. The prevalences for leukoplakia, preleukoplakia and leukokeratosis nicotina palati were 4·9%, 2·9% and 9·5%. Of 497 leukoplakias, 422 were located to the palate and 413 of these patients had the habit of reverse smoking. Histologically, 80% of 381 palatal biopsies had a hyperorthokeratosis. Epithelial atypia was found in 15·3% of leukoplakias, in 3·6% of the preleukoplakias, and in 9·1% of leukokeratosis nicotina palati. Various explanations for the habit of reverse smoking are suggested and discussed. In addition to reverse smoking, other tobacco habits were also recorded; all habits and oral lesions were compared and have been discussed according to their apparent interrelationships and distribution by sex and age.

A teratoma of the lung containing teeth

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