Photoperiodic control of tetrasporangium formation in the red alga Rhodochorton purpureum

Six geographical isolates of Rhodochorton purpureum (Lightfoot) Rosenvinge (Rhodophyta, Nemalionales) formed tetrasporangia only in short days at 10°C. For most isolates, the critical day-length increased with latitude of origin from 9.5 h for an isolate from California to 14.5 h for one from Antarctica. Tetrasporangium production could be induced by 9–15 short-day cycles followed by a further 22–28 cycles in long days. A night-break consisting of 1 h of white light in the middle of a 16-h dark period inhibited the short-day response of isolates from low latitudes, but not those from higher latitudes. When a similar night-break was given in the middle of a 14-h dark period, however, the response of all isolates was at least partially inhibited. Night-breaks given at any time in the central 7 h of a 14-h dark period were equally inhibitory. Broad-band red light (0.3–0.4 mmol m^-2), given as a night-break, caused 50% inhibition of the short-day response. At a slightly higher photon exposure (0.6 mmol m^-2, given as 1 μmol m^-2 s^-1 for 10 min), narrow-band red (662 nm) and blue (448 nm) light caused similar inhibition, but green (547 nm) and far-red (731 nm) were ineffective as night-breaks. The inhibitory effect of a 10-min night-break with red light could not be reversed by subsequent exposure to an equal photon exposure of far-red light. These results add to the existing evidence that the pigments mediating photoperiodic responses among algae are more varied than those among flowering plants.     

Unique acceptors for poly(ADP-ribose) in resting,proliferating and DNA-damaged human lymphocytes

Acceptor proteins for poly(adenosine diphosphoribosyl)ation were determined in resting human lymphocytes, in lymphocytes with N-methyl-N′-nitro-N-nitrosoguanidine-induced DNA damage and in lymphocytes stimulated to proliferate by phytohemagglutinin. Kinetic studies showed that the increase in ADP-ribosylation which occurred in response to N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) treatment was greater in magnitude but more transient in duration than that which occurred in phytohemagglutinin-stimulated cells. Gel electrophoretic analyses revealed that MNNG treatment and phytohemagglutinin stimulation both caused an increase in ADP-ribosylation of poly(ADP-ribose) polymerase and core histones. In MNNG-treated cells, an increase in ADP-ribosylation of histone H1 was also observed. In contrast, phytohemagglutinin-stimulated cells showed no increase in ADP-ribosylation of histone H1. In MNNG-treated cells there was also ADP-ribosylation of a protein of molecular weight 62 000, while in phytohemagglutinin-stimulated cells there was a marked increase in ADP-ribosylation of a protein of molecular weight 96000. MNNG treatment of phytohemagglutinin-stimulated cells produced a pattern of ADP-ribosylation that appeared to be due to the combined effects of the individual treatments. 3-Aminobenzamide effectively inhibited ADP-ribosylation under all treatment conditions.     

Growth in the area of the inferior dental foramen of rats

The object of the present investigation was to see if the bone around the inferior dental nerve remodelled during mandibular growth and development. The investigation was carried out by injecting 27 albino Lewis rats with three fluorescent bone seeking dyes--oxytetracycline HCl (OTC), alizarin red S (ARS), and 2,4 bis-[N,N'-di' (carbomethyl-aminomethyl)] fluorescein (DCAF)--and then studying the bone around the inferior dental foramen. The mandibles of the animals were studied both macroscopically and microscopically under ultraviolet light to investigate the growth processes occurring and to see if the inferior dental foramen was relocated during growth. A quantitative analysis utilizing two specimens was also carried out for the same purpose. The results of both the qualitative and the quantitative analyses showed that the bone around the inferior dental nerve remodeled during mandibular growth. The mandible grew in an upward and backward direction, and the inferior dental foramen was correspondingly relocated in an upward and backward direction to maintain exactly the same position relative to the condyle and the posterior border of the ramus. This study, then, supports Moss's concept of the "unloaded" nerve, and is in keeping with his view of mandibular growth based on the functional matrix theory.     

Leaf microbodies (peroxisomes) and catalase localization in plants differing in their photosynthetic carbon pathways

Summary Kinetic studies of the uptake of hydroquinone--D-glucoside (arbutin) by excised roots of barley demonstrated that this compound is actively transported. Similar studies on the uptake of hydroquinone indicated that the latter compound enters the root tissues by diffusion. A concentration gradient favouring diffusion is maintained for at least three hours by the conversion of the aglucone to its correspondings glucoside. Hydroquinone, at a concentration of 5 mM, reduced uptake of ⁸⁶rubidium ion by approximately 30%.This work was supported by a grant from the National Research. Council of Canada     

Freeze-thaw-refreeze cycle to prepare lymphocytes for HLA antibody detection or tissue typing

Human lymphocytes stored in the frozen state may be thawed, placed on cytotoxicity plates, refrozen, rethawed and used for screening sera or tissue-typing of the cells. The simple procedure described uses only a ?90 °C refrigerator for both freezing and storage of the cells. The technique permits a laboratory to collect a variety of cells over a long period, so that a set of test plates with cells from 10 to 20 donors can be prepared when a convenient number of donor cells are available. Also, the refrozen cells in cytotoxicity test plates may be warmed to the temperature of dry ice for 24 hr, returned to the refrigerator set at a slightly lower temperature, and at a later time, these cells may be thawed and used for serum screening. In view of these results, it appears possible to ship the refrozen cells from one laboratory to another using simple dry ice storage during the transfer. Negative reactions due to soluble antigens in the suspending sera can be obviated by washing out these sera and replacing them with medium 199 or alternatively, fetal calf serum can be used to replace the human serum in the suspending media.     

Radioimmunoassay of human plasma corticosterone: method, measurement of episodic secretion and adrenal suppression and stimulation

A radioimmunoassay for human plasma corticosterone has been developed. Antisera were obtained by immunizing rabbits with corticosterone-21-hemisuccinate-BSA. An antiserum titer of 1:4000 was used for standard curves ranging from 0–1000 pg. Interfering steroids were removed from plasma extracts by paper chromatography. Plasma blanks obtained from adrenalectomized or Addisonian patients ranged from 29 to 42 ng/dl. Recovery of radioactive corticosterone through the entire method was 67.6 ± 5.2%. The coefficient of variation within assays was 19% and between assays 13%. The average 8 a.m. value in males was 396 ± 228 ng/dl and in females it was 655 ± 271 ng/dl. Corticosterone was found to be secreted episodically, in parallel with cortisol. Secretion of this steroid was suppressed by dexamethasone and stimulated by ACTH infusion.     

Inhibitors from Carob (Ceratonia siliqua L.) I. Nature of the Interaction With Gibberellic Acid on Shoot Growth

Concentrated whole extracts of the immature fruit of carob and 3 fractions derived from this extract have been shown to inhibit the gibberellic acid induced growth of pea seedlings. The inhibition can be completely reversed by increasing the amount of gibberellic acid. The inhibitors do not reduce the endogenous growth of seedlings but only that induced by gibberellic acid. One of the fractions is a newly separated one not previously reported.