The increase in testicular vascular permeability induced by human chorionic gonadotrophin involves 5-hydroxytryptamine and possibly oestrogens, but not testosterone, prostaglandins, histamine or bradykinin.

Possible intermediates in the response of the rat testicular vasculature to human chorionic gonadotrophin (hCG) have been investigated. Ketanserin, an antagonist of 5-hydroxytryptamine, significantly reduced the increase in 1-h albumin space seen 20 h after hCG, as did one aromatase inhibitor (1,4,6-androstatriene-3,17-dione), but the effect of another (testolactone) did not reach significance. Aminoglutethimide, which inhibits overall steroid synthesis as well as aromatase, reduced the albumin space in both control and hCG-injected rats but the hCG response, as judged by the ratio between treated and control rats, was unaffected. Inhibitors of overall steroid synthesis (WIN 32,729), prostaglandin synthesis (meclofenamic acid or indomethacin) and angiotensin converting enzyme (captopril) and blockers of H1 and H2 histamine receptors (mepyramine, cimetidine or ranitidine) were without effect. The time course of the vascular response to hCG is quite different from the response in testosterone secretion by the testis. Considerable numbers of mast cells were found in the vicinity of the testicular artery in the testicular capsule, and these may be a source of 5-hydroxytryptamine.

Cell proliferation in follicle-associated epithelium of mouse Peyer's patch.

Follicle-associated epithelium (FAE) from the mouse Peyer's patch consists of a dome part containing goblet as well as columnar epithelial cells and a crypt part, containing Paneth as well as goblet and undifferentiated epithelial cells. The proportions of columnar epithelial, goblet and Paneth cells in the FAE are similar to those found in normal crypt/villus complexes. Mitosis is confined to the crypts of the FAE. The cell-renewal time for FAE columnar epithelial cells, estimated from experiments using tritiated thymidine, is approximately 60 hours. Large numbers of lymphoid cells are also present in the FAE, particularly in regions distal to the crypts. The similarity between follicle-associated and villus epithelial structure is discussed, together with its possible relevance to "M" cell formation within the FAE.

Use of differential interference contrast microscopy to determine cell renewal times in mouse intestine.

Pieces of mouse mid jejunum have been cleared in glycerin and examined by differential interference contrast microscopy at low powers of magnification. The position and number of crypts and villi can be determined in the same specimen using this technique. The calculated value for crypt/villus ratio 4.53 +/- 0.99 (mean +/- SD) is less than a previously published value obtained using indirect techniques. A revised estimate of cell renewal time, based on this newly determined value for crypt/villus ratio, is 45 h. This agrees with earlier estimates derived from entirely different methods of analysis. The general usefulness of this form of light microscopy in helping one appreciate some three-dimensional problems in mucosal architecture is emphasized.

Observations on pituitary and cerebral catecholamines in Brattleboro rats.

The combined neural and intermediate lobes (N.I.L.) of the pituitary glands of Brattleboro rats contained significantly more noradrenaline (NA) than those of normal controls of the same age. In addition, in 4 and 6 months old rats the N.I.L. of the homozygotes (Di-rats) contained about twice as much NA as those of the heterozygotes (non-Di-rats). In the enlarged and hyperaemic neural lobes of the Di-rats enlarged blood vessels could be seen. They were surrounded by a rich network of nerve fibres which displayed catecholamine fluorescence. The NA concentrations in the medial basal hypothalamus (M.B.H.) of 4, 6, and 9 months old Di-rats were significantly higher than those of the non-Di-rats and of controls of the same age. This may contribute to the diminished ACTH secretion in Brattleboro rats. The total amount of DA contained in the N.I.L. of 9 months old Di-rats was 20% lower than in the non-Di-rats of the same age. The concentrations of homovanillic acid (HVA) in the corpora striata of 4 months old Di- and non-Di-rats was significantly higher than in older Brattleboro rats and in control rats of various strains and ages. At 9 months it was nearly twice as high in the Di-rats as in the non-Di-rats. The concentrations of dihydroxyphenylacetic acid in the striata of 4--6 months old Di- and non-Di-rats were higher than those of Long Evans rats of the same age.

Villus growth and cell replacement in the small intestine of the neonatal pig.

Cells produced in the crypts of newborn pig ileum migrate onto villi during development. There is little or no corresponding loss of cells from villus tips during the first week of postnatal life. Villus growth during this period is largely responsible for the slow rate of cellular renewal seen to take place.

Cell replacement and changing transport function in the neonatal pig colon.

1. Measurements of intracellular methionine concentration in pig colon, following in vitro incubation in methionine containine medium, have been carried out during the first 10 days of post-natal life. 2. The new-born pig colon concentrates methionine within its mucosa. Autoradiography of 3H-labelled phenylalanine shows it to be accumulated to greatest extent in cells located in the surface epithelium. 3. The ability of the colonic mucosa to concentrate methionine disappears during the first few days of post-natal life. 4. Radioactive thymidine, injected at birth, shows cell mitosis to be confined to the lower third of each colonic crypt. Labelled cells later migrate out of the crypts on to the surface epithelium. The cell replacement time is 105 h. 5. The time course for the fall in the ability of the pig colon to actively accumulate methionine corresponds to that predicted if cells synthesized from birth were unable to transport this amino acid. 6. The ability of the new-born pig colon to transport amino acids, though transient, may be physiologically important. The nature of the signal which changes the physiological function of cells synthesized post-natally remains to be determined.