Weitere Untersuchungen zur phytochrominduzierten Akkumulation von Ascorbinsäure beim Senfkeimling (Sinapis alba L.)

Summary The accumulation of ascorbic acid (AS) in the young mustard seedling is greatly increased by the action of the active form of phytochrome (P₇₃₀) (see Schopfer, 1966). There is no photosynthesis in continuous far-red light, which was used throughout the experiments. The phytochrome-mediated increase in AS approximately parallels the synthesis of anthocyanin in the seedling, although the onset of AS-accumulation precedes the anthocyanin synthesis by 2–3 hours (Fig. 4 and 5).—The action of P₇₃₀ increases the amount of AS in every part of the seedling (cotyledons, hypocotyl, radicula) (Fig. 1–3). This increase in AS parallels the formation of P₇₃₀ rather than the different growth responses of these organs (enlargement of the cotyledons, inhibition of hypocotyl and radicula lengthening). The lag in AS-accumulation after onset of far-red irradiation is the same in all 3 parts of the seedling (about 1 hour under the experimental conditions; Fig. 4).—Actinomycin D (10 g/ml), which strongly inhibits anthocyanin synthesis (Fig. 9 and 10), has no corresponding effect on P₇₃₀-dependent increase in AS-accumulation (Fig. 7 and 8). This result support the hypothesis that already active genes are only slightly influenced by actinomycin D (see Lange and Mohr, 1965). It also shows that, in contrast to its role in anthocyanin synthesis, P₇₃₀ probably does not act by initiating potentially active genes in the case of AS-accumulation. — A dark synthesis of anthocyanin in the cotyledons can be obtained by application of AS to the seedlings (Fig. 11). Glucose and sucrose are ineffective in this respect (Table 2). The effect of AS-feeding on anthocyanin synthesis can be inhibited by actinomycin D in very much the same way as light induced anthocyanin synthesis is inhibited (Table 3). — Also the RNA content of the cotyledons is increased by feeding AS in the dark (Table 4).These results are in line with the earlier suggested hypothesis (see Schopfer, 1966) that increase in AS-accumulation is a very early event in the mediation of some positive photoresponses, e.g. anthocyanin synthesis. According to the hypothesis of Mohr (1966 a, b) it has been concluded that AS functions as a part of the signal chain of phytochrome-mediated photomorphogenesis. This signal chain is thought to start differential gene activation to bring about positive photoresponses.     

Die Hemmung der Phytochrominduzierten Photomorphogenese („Positive” Photomorphosen) des Senfkeimlings (Sinapis alba L.) Durch Actinomycin D und Puromycin

Zusammenfassung Die positiven Photomorphosen Öffnung des Hypokotylhakens und Entfaltung der Kotyledonen können ganz ähnlich wie die phytochrominduzierte Anthocyansynthese und andere positive Photomorphosen durch Actinomycin D und Puromycin gehemmt werden. Man kann daraus schließen, daß diese beiden photomorphogenetischen Reaktionen des Senfkeimlings ebenfalls durch eine von P₇₃₀ über eine Signalkette ausgelöste Aktivierung von potentiell aktiven Genen veranlaßt werden.

---

The inhibition of phytochrome-mediated photomorphogenesis (positive photoresponses) by actinomycin D and puromycin in the mustard seedling (Sinapis alba L.)

Summary The many photochrome-mediated photoresponses of a seedling (Sinapis alba L., white seeded mustard) can be divided into 3 categories: positive, negative, and complex photoresponses. Positive photoresponses are those which are characterized by an initiation or a promotion of biosynthetic or growth processes (Mohr, 1966b). Phytochrome-mediated anthocyanin synthesis is the prototype of a positive photoresponse. It has been shown in previous papers (e.g. Lange and Mohr, 1965; Mohr et al., 1965) that positive photoresponses can be specifically inhibited by actinomycin D and puromycin. It has been concluded that in the case of positive photoresponses P₇₃₀ (the active phytochrome) exerts its function through differential gene activation.—In the present paper it has been demonstrated that phytochrome-mediated positive photoresponses of the mustard seedling like opening of the hypocotylar hook and unfolding of the cotyledons can be inhibited by relatively low doses of actinomycin D and puromycin in very much the same way as anthocyanin synthesis or cotyledon enlargement is inhibited. It has been concluded that in these cases too the action of P₇₃₀ must be attributed to an activation of potentially active genes in the manner postulated on the basis of the data on anthocyanin synthesis.

---

---

Die Arbeit wurde durch Sachbeihilfen der Deutschen Forschungsgemeinschaft und der Stiftung Volkswagenwerk (an Prof. Mohr) ermöglicht.     

The basic flow equations of electrophysiology in the presence of chemical reactions: I. Development of the equations

Starting from the basic flux equation, it is possible to obtain an integral form relating the current componentsI _i at an arbitrary pointr ₂ to the distribution of mobilities and concentrationsc _i, potential forces\(\bar \mu \), and chemical productivityp _i without any restrictive assumptions such as constant mobilities, constant field, steady state, or electrical neutrality. The equation is

$$\begin{gathered} I_i (r_2 ) = G_i (r_2 )\left[ {\Delta \bar \mu _i - \int_{r_1 }^{r_2 } {z_i } FA\left( {p_i - dc_i /dt} \right)\left( {\frac{1}{{G_i (r)}}} \right)dr} \right]; \hfill \\ G_i (r) = 1/\int_{r_1 }^r {\frac{{dr}}{{z_i^2 F^2 c_i u_i }}.} \hfill \\ \end{gathered} $$     

Influence of protein structure on selection of nitrous acid induced mutants of TMV

Summary Calculated values for amino acid replacements in nitrous acid induced mutants of TMV are compared with experimentally found data. 60 of 68 analysed mutants (Wittmann, 1962, 1964; Tsugita and Fraenkel-Conrat, 1962) may be explained by transitions CU and A(H)G (Schuster, Schramm, 1958; Mundry, Gierer, 1958). Replacements of non-polar amino acids are less frequent than replacements of polar amino acids. Threonine is the most frequently replaced amino acid. Since substitutions are predominantly by leucine it is assumed that the non-polar character of threonine is predominant. 66% of all replacements are found in the tryptic peptides I, IV, and XI, indicating that these peptides or at least part of them are of less importance for the structure than the others. Based on the results on hemoglobins and myoglobin (Perutz, Kendrew, and H. C. Watson, 1965), and the amino acid replacements of TMV, one may predict helical parts of the TMV protein chain. A correlation of amino acid replacements and symptoms on host plants is evident. It is concluded that special types of replacements were selected preferentially because symptoms were used as the selection system.     

Clinical Use of a New Mitral Disc Valve

A disc valve of new design was used successfully for the replacement of the mitral valve in patients with rheumatic mitral valve disease. This valve would appear to have the following advantages over the mitral ball valve prosthesis:• Lower left atrial pressure after replacement.• Elimination of the hazard of left ventricular outflow tract obstruction with mitral valve replacement.• Decreased incidence of thromboembolization.• Abolition of possibility of ventricular septal irritation.Despite the better outlook for this valve compared with the ball valve for mitral valve substitution, the mitral valve should always be repaired whenever feasible. Repair is possible in the majority of patients.     

Dermatopathic Lymphadenopathy—A Clinicopathologic Analysis of Lymph Node Biopsy Over a 15-Year Period

Forty cases of dermatopathic lymphadenopathy were found in a series of 906 consecutive lymph node biopsies (4.8 per cent).The histologic development and progression of the disease was correlated with the clinical state of the patient.In 35 of 40 cases the patients had active skin disease at the time of the biopsy; one of the remaining five patients had Hodgkin''s disease, one had multiple myeloma and one had secondary syphilis. In the other two, no organic cause was found.In nine cases (22.5 per cent), the histological pattern typical of dermatopathic lymphadenopathy was associated with malignant lymphoma. Except for two biopsies, which showed coexisting malignant lymphoma and dermatopathic lymphadenopathy, no histologic features were found which distinguished patients with malignant lymphoma from the remainder.While the pathogenesis of the lymph node changes remains obscure, the histologic features suggest that it is at least in part an immune response, although the nature of the responsible antigen is unknown.     

Effect of Osmotic Shock and Low Salt Concentration on Survival and Density of Bacteriophages T4B and T4Bo1

Measurements of survival and buoyant densities of bacteriophages T4B, T4Bo(1), and T4D have demonstrated the following: (a) After suspension in a concentrated salt solution, T4B and T4D are sensitive both to osmotic shock and to subsequent exposure to low monovalent salt concentrations. (b) Sensitivity of T4B to dilution from a concentrated salt solution is dependent on dilution rate, that of T4D is less dependent, and that of T4Bo(1) is independent. (c) Sensitivity of all three phages to low salt concentrations depends on initial salt concentrations to a variable extent. (d) Density gradient profiles indicate that nearly half of osmotically shocked T4B retain their DNA. Similar analysis demonstrates that few, if any, T4Bo(1) lose DNA when subjected to a treatment causing 90% loss of infectivity. (e) The effective buoyant densities of T4B and T4Bo(1) depend significantly on the dilution treatments to which the phages are subjected prior to centrifugation in CsCl gradients. These data are explicable in terms of the different relative permeabilities of the phages to water and solutes, and of alterations in the counterion distribution surrounding the DNA within the phage heads.     

Ventricular septal defect with bidirectional shunting: Mathematical considerations

Previously proposed formulae for the quantitative estimation of bidirectional shunts across ventricular septal defects require determination of the oxygen contents of mixed venous, pulmonary artery, pulmonary venous, and aortic blood. Because these formulae do not take into account the mixing of oxygenated with unoxygenated blood within the ventricles, their use must result in underestimation of shunt flows in each direction. A mathematical model for a ventricular defect is examined, in which it is assumed that mixing of blood occurs in each of six sites in the venae cavae or right atrium, right ventricle, pulmonary artery, left atrium, left ventricle, and aorta. A total of fourteen streams of blood can flow from one to another of these mixing sites. As long as complete mixing occurs in the six specified mixing sites, any degree of mixing or non-mixing of the various streams is permitted. From the equations characterizing the model, formulae are derived in which the shunt flow in each direction is expressed in terms of the oxygen contents in the six mixing sites and the fractions of blood which enter the shunt from either side without prior mixing in a ventricular mixing site. The previously reported formulae, which apply when no ventricular mixing is allowed to occur, lead to theoretical minimum values for the shunt flows in each direction. At the opposite extreme where all the shunting blood is required to mix in a ventricle before entering the shunt, formulae for maximum possible shunt flows are also obtained. The absolute values for the left-to-right and right-to-left shunt flows, which must lie somewhere between the theoretical maximum and minimum values, cannot be computed from blood gas data alone. This work was supported in part by grant HE-07563 from the National Heart Institute of the National Institutes of Health and grants-in-aid from the American and North Carolina Heart Associations and the Life Insurance Medical Research Fund. Work completed during tenure as U.S.P.H.S. post-doctoral fellow.