SUMMARY By varying the time of hydrolysis for the Feulgen reaction, done under conditions that protect the backbone of the DNA, it is possible to distinguish three species of DNA that are characterised by their lability to acid hydrolysis. The most labile DNA was found, in greatest proportions, in malignant cells; this may be helpful in diagnostic cytology. The fact that the cytologically normal cells, in grade V smears, also show this labile DNA may well facilitate cytological screening even in those smears that contain very few neoplastic cells.In the search for functional tests to complement the conventional cytological screening for cervical and endometrial cancers1 2 our interest has turned to the nature of chromatin in the "malignant" cell nucleus.

The plasma of normal man and the rat, and an acetone extract of hypothalamus from the rat, have an ability to inhibit Na-K-ATPase which is related directly to salt intake. The ability of the plasma to inhibit Na-K-ATPase is raised in essential hypertension. The ability of plasma and of an acetone extract of hypothalamus from six spontaneously hypertensive (SHR) rats and six normotensive control (WKY) rats to inhibit Na-K-ATPase of fresh guinea-pig kidney was studied using cytochemical bioassay techniques. With a validated assay, which measures the capacity of biological samples to stimulate glucose-6-phosphate dehydrogenase (G6PD) as an index of their capacity to inhibit Na-K-ATPase, the mean G6PD-stimulating ability of the plasma from the SHR and the WKY rat was 772.3 +/- 48.1 units/ml and 12.5 +/- 2.6 units/ml respectively (P less than 0.01) and of the hypothalamic extracts it was 2.2 +/- 1.7 X 10(8) and 4.5 +/- 1.8 X 10(4) units/hypothalamus (P less than 0.01). With a semi-quantitative cytochemical assay, which measures Na-K-ATPase activity directly, plasma and an acetone extract of hypothalamus from the spontaneously hypertensive rat had much greater capacities to inhibit Na-K-ATPase than plasma and extract from the WKY rat. These raised levels of Na-K-ATPase inhibitory activity in the plasma of the SHR rat are similar to the highest values found in the plasma of patients with essential hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute volume expansion, increased sodium intake, and restraint on sodium excretion endow the plasma with an increased capacity to inhibit sodium transport. Cytochemical techniques can detect the presence of Na+K+-adenosine triphosphatase (ATPase) inhibitor in the plasma of normal humans and rats, the concentration of which is controlled by salt intake. The substance responsible appears to originate in the hypothalamus, where the concentration is also controlled by salt intake. The plasma concentration of the cytochemically detectable Na+,K+-ATPase inhibitor is substantially raised in the plasma of patients with essential hypertension, spontaneously hypertensive rats (SHR) and of Milan hypertensive rats. The concentration of activity in the hypothalamus of SHR is also considerably raised. These findings demonstrate that these forms of hypertension are associated with a rise in the concentration of a cytochemically detectable circulating Na+,K+-ATPase inhibitor that under normal circumstances is controlled by salt intake.

After some years of seeking a simple but effective method to lay cells on slides in an evenly dispersed monolayer for automated cell scanners we managed to utilise what we believe to be the electrical charges on the cell and slide surface to achieve this end. The machine scanners required additional techniques to disrupt cell clusters and prevent reaggregation of cells, and these are detailed in our previous publication.' These are not necessary for visual screening.It is well known that cells acquire a negative charge in solution, and we sought to increase this on the one hand and, on the other, to induce a positive charge on the slide surface. After much experimentation we achieved some success with the latter by the use of the cationic polymerised amino acid polylysine, which attaches as a monolayer to the negatively charged glass surface, leaving excess positive charge available for the attraction of cells.2 The latter, moreover, appear to remain discrete, if not to repel each other under gentle sedimentation forces of 1 g, to result in a fairly well-dispersed monolayer. Whatever the form of attachment achieved, it appears strong enough to withstand the gentle 'wash-off' of the fluid after 2-5 minutes' sedimentation and the rigours of the subsequent staining schedule.We thought that such a technique would be useful in a number of different ways in routine cytology practice where cells are in solution to start off with, as in the case of urine, or where, to produce better results, cells could be put into suspension-not necessarily dispersed-and then laid down more evenly and flat with less curling or overlap of the cytoplasm or even nucleus. We have found that cyst fluids lend themselves readily to such techniques, which result in more even cell spreads without the accompanying debris, and this aspect has been

This is related to the nature of the cytochemical lysosomal reaction: provided that a partially hydrophilic substrate such as leucine naphthylamide (for lysosomal arylamidase activity) is used as the chromogenic substrate, the full activity of the intralysosomal enzyme in relatively normal cells will not be expressed because the lysosomal membrane will retard entry of the hydrophilic substrate to the enzyme. The activity