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The primary in vitro plaque forming cell (PFC) response of mouse (C57BL/6J) spleen cells to sheep red blood cells (SRBC) was inhibited by two sources of crude and two sources of partially purified mouse interferon. The substance(s) in the interferon preparations which induced PFC and antiviral inhibitory activity have the following common characteristics: a) The interferon preparations were of different potencies and specific activities, but they inhibited the PFC response in proportion to their activities; 20 to 60 units were the minimal amounts required for greater than 90% inhibition of the PFC response. b) Both the antiviral activity and the PFC inhibitory activity of the interferons were neutralized by antibody specific for mouse interferon. c) Both activities were partially or completely inactivated by heating at 60 degrees C for 1 h. d) Human interferons had neither antiviral activity nor PFC inhibitory activity in mouse cells. e) Limited exposure (4 h) of cells to interferon significantly inhibits both viral infection and the PFC response. f) Both the antiviral activity and the PFC inhibitory activity of the interferon preparations are acid stable. It is concluded, therefore, that the inhibition of the primary in vitro PFC response is due to interferon in the preparations. Maximum inhibition of the PFC response occurred when interferon was added to cultured at the same time as SRBC. Significant inhibition was also observed when interferon was added 1 day later, and slight enhancement was observed when added at days 2 and 3 of SRBC addition. Kinetic data showed that the greater the concentration of interferon added to the cultures, the earlier the effect on the PFC response. The presence of interferon in cultures for the first 4 h is sufficient to inhibit the PFC response. Interferon, then, appears to affect some early event(s), which leads to inhibition of the PFC response. Since mature T cells can be one of the sources of interferon, we have demonstrated a suppressor effect of a T cell lymphokine. The precise relationship of interferon to various expressions of suppressor T cell effects remains to be determined.

During the first 24 h of in vitro incubation of excised potato tuber (Solanum tuberosum L.) discs, the appearance of phenylalanine ammonia-lyase (PAL; EC 3.4.1.5) and the accumulation of chlorogenic acid are both stimulated by infection with Phytophthora infestans (Mont.) de Bary. Whereas in control tissue the level of PAL reached a stable plateau value after 40 h, in infected tissue it subsequently rose again, in one experiment, as the fungal mycelium developed. In the infected but not the control tissue, the level of chlorogenic acid subsequently fell to about to about 20% of its maximum after 50 h. The time courses of increases in cinnamic acid 4-hydroxylase (CA4H; EC 1.14.13.11; 0–60 h) and of caffeic acid acid o-methyltransferase (COMT; EC 2.1.1.42; 0–160 h) are not altered by fungal infection. If the discs are restored to the tuber environment immediately after excision, by placing them inside a “host tuber”, the activity of PAL as well as those of CA4H and COMT remained at the constant low endogenous level for at least 60 h, irrespective of whether the discs had first been inoculated with P. infestans. The increase in PAL may not be an obligatory feature of the P. infestans/potato compatible interaction but dependent on an underlying wound response. The experiments provide further evidence that PAL is the rate limiting step of chlorogenic acid biosynthesis in potato tuber discs.

The ultimate goal of the cone method of colostomy irrigation is to return patients with colostomies to their former role in society with confidence in themselves to the extent that having a colostomy is not considered a handicap. The results have generally been excellent. We believe all patients with stomas should be afforded the opportunity to attempt colostomy irrigation.

Selective depletion of T1 and T2 lymphocyte subpopulations of mouse spleens was accomplished by injecting mice subcutaneously with 5 mg cortisone acetate (CA) or 0.1 ml antithymocyte serum (ATS), respectively. Selectively depleted and control spleen cells were cultured in vitro and were tested for their ability to produce the lymphokine immune interferon (IIF) in response to the following mitogens: staphylococcal enterotoxin A (SEA), concanavalin A (ConA), and phytohaemagglutinin-P (PHA). The data indicate that SEA and PHA induce IIF from T1 and T2 cells respectively; ConA induces IIF from both T1 and T2 cells. Mice were also injected subcutaneously with 10 mg gallic acid (GA) and the pattern of mitogen-induction of IIF from GA-treated spleen cells was compared with that of CA- and ATS-treated spleen cells. GA pretreatment of mice, like CA pretreatment, resulted in a significant decrease in SEA-induced IIF; GA probably exerts its effect on T1 suppressor cells.

Staphylococcal enterotoxins, like several plant lectins, have been shown to stimulate mitogenic activity and lymphokine production in lymphocytes. The effect of enterotoxins A and B on the primary in vitro plaque-forming cell (PFC) response of mouse (C57BL/6) spleen cells to sheep red blood cells (SRBC) was examined. PFC responses in 4- or 5-day cultures were inhibited greater than 90% by 0.1 mug enterotoxin A and by 3- to 6-mug enterotoxin B when the toxins were added to the cultures either at the time of SRBC addition or 24 hr before. Both enterotoxins A and B were shown to be T lymphocyte mitogens. Kinetic data indicated that the enterotoxins (10 mug) inhibited the PFC response as early as day 3, but were relatively more inhibitory at days 4 and 5. The PFC response was inhibited when enterotoxins were added to cultures at the same time as antigen or a day later; it was enhanced when added at day 2; and it was unaffected when added at day 3 of 4-day cultures. Further, the presence of enterotoxin A during the first 24 hr of culture and subsequent removal was still as effective in inhibiting the PFC response as when it was present throughout the culture period. The PFC inhibitory properties of enterotoxins appear, then, to affect some early event(s) in the in vitro immune response. Alpha-methyl-D-mannopyranoside blocked the PFC inhibitory effect of concanavalin A (con A), but it had no effect on enterotoxin A. The two mitogens appear, then, to react with different receptors on the lymphocytes or to differ in the dynamics of their reactivity. The effects of staphylococcal enterotoxins on the PFC response of spleen cells were remarkably similar to those reported for lectins such as con A. Enterotoxins are structurally simpler than con A and should therefore be quite useful in studying various biologic activities of lymphocytes.

The move towards restoring teeth with materials which more closely match the properties of the lost dental tissues is gathering momentum. Of the materials currently available, glass ionomer cements are adhesive to dentine and enamel, leach fluoride, have negligible contraction on setting and are tooth-coloured; but their abrasion resistance is poor. Composite materials can be bonded to enamel and dentine and are made in a range of tooth-coloured shades. Their polymerisation contraction is a problem and, although they are more abrasion resistant than glass ionomer cements, there is still some anxiety about this. Porcelain has good abrasion resistance but does not bond directly to dental tissues and the need to manufacture porcelain restorations in the laboratory adds to their cost and increases the number of clinical appointments necessary. The CEREC machine produces porcelain inlays at the chairside which are used in combination with composite and glass ionomer materials to produce a restoration which optimises the advantageous properties of all three materials. The restoration can be completed in a single appointment.

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Values of PAH and Radio-Hippuran clearances, obtained simultaneously in 96 individual renal clearances for 16 patients, were plotted against each other and a regression line calculated which shows a linear relationship between the two substances. Knowing the value of the Radio-Hippuran clearance, by use of the regression line, the effective renal plasma flow in terms of PAH clearance can be estimated. This method of determination gives an accurate and less laborious measure of renal plasma flow than chemical determinations of PAH. Submitted on July 21, 1961