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Cytophotometric determinations on gallocyanine-chromalum stained preparations reveal the presence in the bursa of Fabricius of a characteristic lymphoid cell type within the medulla of bursal follicles. In comparison with the cortical lymphocytes the nuclei of these cells show lower volume and nucleic acid content. Such differences are not detectable at hatching but are quite clear in the fully grown organ.

1. 1. Ischemic changes were produced in twelve dogs by embolization with lycopodium spores. Nine dogs were operated upon in a similar manner but were not embolized. Two dogs were anesthetized with pentobarbital, while in two other dogs the femoral artery was occluded for 1 to 3 hours by the application of a hemostat. 2. 2. Fibrinolytic and antifibrinolytic activity were studied in these animals by means of undiluted and diluted plasma lysis times, euglobulin lysis times, antithrombolysin lysis times and plasma fibrinogen concentrations for 72 hour periods. 3. 3. Antifibrinolytic activity progressively rose in the animals embolized with lycopodium spores. In those who were operated upon but not embolized antifibrinolytic activity rose slightly during the first 24 hours but then failed to rise significantly. No appreciable changes were noted in the animals merely anesthetized with pentobarbital. 4. 4. Increased fibrinolytic activity appeared in the plasma of dogs whose femoral arteries were clamped with hemostats for 1 to 3 hours. This activity was greatly enhanced by the subsequent administration of Thrombolysin.

The effect of intravenously administered nicotine (20 µg ./Kg./min.) on the coronary blood flow and related hemodynamic parameters was studied in the normal intact dog and in the dog with chronic coronary insufficiency as produced either by coronary artery ligation or gradual coronary artery narrowing. Nicotine increases cardiac work markedly by an increase in the mean arterial blood pressure and cardiac output. The degree of this increase is similar in normal dogs arid dogs with chronic coronary insufficiency. The mean control coronary blood flow was moderately decreased in dogs with coronary artery ligation and markedly decreased in dogs with narrowing of the two main branches of the left coronaryatery. Nicotine produced an increase in coronary blood flow which in normal dogs was observed to be as high as 125 per cent on an average over the control value. The average increase was consider ably less in dogs with ligation of one coronary artery branch (82.5 per cent) and in dogs with narrowing of two main branches (83.3 per cent). The degree of coronary narrowing and/or occlusion was directly related to the response of the coronary flow; the greater the coronary impairment, the smaller was the increment in corollary blood flow frequently dropped below the control value in the postinfusion period, Coronary vascular resistance and myocardial oxygen utilization declined during the event of nicotine administration. The response of the coronary blood flow to nicotine resembled that of anoxemia in the presence of coronary insufficiency. These findings would appear to have a bearing on the clinical problem relative to the effect of nicotine in the human subject with coronary artery disease.

The effect of a new coronary vasodilator (Persantin), which produces a marked increase in coronary blood flow (up to 159 per cent in normal animals) without increasing cardiac contractility or cardiac work, has been studied in the experimental animal. This is associated with a marked decrease in coronary resistance. There is an increase in the coronary venous oxygen content and a decrease in the coronary A-V oxygen difference; the cardiac output is only slightly affected. Increase in the coronary blood flow has also been observed in dogs in which coronary in sufficiency has been produced by coronary ligation and by narrowing of the lumen of the coronary artery by the application of casein rings. This was accompanied by no significant increase in cardiac work.

By means of immunochemical techniques, the protein components of the water-soluble fraction (WSF) of the egg yolk have been examined in the unincubated egg and during incubation. Anti-ovalbumin and anti-total adult chicken serum antisera have been employed. Ovalbumin can be detected in the unincubated WSF as well as during incubation; its concentration seems to increase during incubation. In the WSF of the unincubated egg, six proteins immunologically related to adult serum proteins can be detected. They correspond to α-livetin, α1-globulin, β-livetin, ovotransferrin (conalbumin) and γ-livetin (two components). β-Livetin disappears after the 14th day of incubation while the other components can be demonstrated till hatching. The findings are discussed in relation to the data available in the literature.

At low concentration sphingomyelin stabilizes the DNA helix, whereas at high concentrations it labilizes the DNA helix. The nature of bonds between DNA and sphingomyelin has been examined and the probable existence of a DNA-sphingomyelin complex in vivo is suggested.

In birds albumen represents a substantial part of the reserve material for their embryological development (Romanoff & Romanoff, 1949). In Gallus gallus albumen proteins form 50 % of non-incubated egg protein content (Romanoff & Romanoff, 1949). During incubation such material is absorbed and utilized, to a great extent, for the synthesis of embryonal proteins (Fiske & Boyden, 1926; Rupe & Farmer, 1955). It is not yet well understood how these processes (albumen absorption and utilization for the energetic and nutritional needs of the embryo) take place. The present available data indicate that the amount of albumen solids begins to diminish starting from 11 to 12 days of incubation (Romanoff & Romanoff, 1933; Rupe & Farmer, 1955). From 13 to 14 days, after the sero-amniotic connexion perforates, the protein content of the amniotic fluid shows a marked increase because of the passage of albumen (Needham, 1931 ; Romanoff, 1960). During the same development period albumen proteins can be recovered, in large amounts, in the yolk (Saito, Martin & Cook, 1965; Carinci, Wegelin & Manzoli-Guidotti, 1966).

Water-soluble proteins, mainly livetins (α-, β-, γ-), are present in hen egg yolk (Martin, Vandegaer & Cook, 1957). They represent 5% of fresh yolk solids (Saito, Martin & Cook, 1965). During the later stages of incubation the watersoluble proteins (water-soluble fraction, WSF) undergo a marked increase in relative proportion; after 15 days of incubation they form over 15% and at 18 days over 40% of yolk-residual solids (Saito et al . 1965). This proportional increase of the WSF is tentatively explained by the passage of egg-white proteins into yolk (Mclndoe, 1960; Saito et al . 1965). Indeed some egg-white proteins (ovalbumin, conalbumin and lysozyme) have been found in the yolk from 14 to 15 days of incubation (Saito & Martin, 1966; Carinci, Wegelin & Manzoli-Guidotti, 1966). At these stages ovalbumin is present in the yolk in such a great quantity that it is difficult to detect qualitative and quantitative changes of other proteins without resorting to further fractionations.

Cortical and medullary lymphocytes from the chicken bursa of Fabricius were examined for their DNA content and [3H]thymidine incorporation. The kinetics of the latter is different for both cell types, while chemical and cytophotometric tests showed cortical lymphocytes to contain more DNA. In addition, immunofluorescent detection of membrane-bound immunoglobulins demonstrated that most medullary cells are B lymphocytes. Therefore, the cortex and the medulla appear to be distinct compartments of the bursal follicle, the cortex being a zone of continuous lymphocyte proliferation, while the medulla contains an homogeneous population with fully developed immunological competence.

High concentrations of lecithin, phosphatidylethanolamine, phosphatidylserine, cholesterol and lauric acid have a destabilizing effect on the DNA helix. On the contrary, lower concentrations of the same lipids produce stabilization on DNA. The stabilizing and destabilizing effects with sphingomyelin components can be mainly attributed to sphingosine and lignoceric acid components, whereas glycerophosphorylcholine probably has a minimal effect. The saturated long-chain fatty acids (C 18:0 , C 24:0 ) were capable of having a moderate destabilizing effect on DNA; however, the unsaturated fatty acids were found to be generally more stabilizing in nature. The type of bonding within the lipid-DNA interaction has been investigated and the existence of a lipid-DNA complex in vivo has been considered.

Histones and ribosomal proteins of the chicken thymus, bursa of Fabricius and spleen show, from hatching up to the 100th day, significant similarities on acrylamide gel electrophoresis. On the contrary, the sedimentation profiles of crude ribosomal preparations of the same organs, exhibit peculiar characters on ultracentrifugal analysis. Polysomes are detectable in the thymus and the bursa at hatching, while they only appear in the spleen 30 days later. The latter findings could be related to early immunoglobulin synthesis in the bursa and, respectively, to the later establishment of lymphocyte-plasma cell clones in the spleen.