Inhibition of IAA-induced elongation in Avena coleoptile segments by lead: a physiological and an electron microscopic study.

A high resolution growth measuring apparatus was used to demonstrate the inhibition of auxin-induced cell elongation in oat coleoptile segments (Avena sativa L. var Holden) by lead at concentrations ranging from 2 x 10-6 M to 2 x 10-3 M. The inhibition was immediate, having no measurable lag period. Electron micrographs of lead-treated and control segments revealed that in the treated material, lead became localized as electron-dense granules in the cell walls and in vesicles associated with dictyosomes. These granules were found to be lead hydroxide phosphate by electron diffraction techniques. The possible significance of this localization and identification with regard to phosphatase activity is discussed.     

The quantification of formazans in tissue sections by microdensitometry. I. The use of neotetrazolium chloride

Synopsis This article describes the use of a microdensitometer for the measurement of formazan deposits in tissue sections. Some examples are given to illustrate the various applications of this technique in the assessment of glucose-6-phosphate dehydrogenase activity. These are (1) the separate measurement of the red half-formazan intermediate and purple diformazan of neotetrazolium, and the effect of incubation time on their production, (2) the measurement of activities in different regions of the liver lobule, and the selective effect of phenobarbitone, and (3) the measurement of enzyme activity in individual cartilage cells in normal and osteoarthrosis-prone animals. All activities can be expressed in absolute units as nmol hydrogen/mm³/hr, and thus compared with standard biochemical data. The activities obtained all fall within the range of published values for biochemical systems.Paper given at the Royal Microscopical Society's European Histochemistry Meeting at Nottingham in September 1975.     

Cationic ferritin uptake by cultured anterior pituitary cells treated with the proteinase inhibitor, BOC-DPhe-Phe-Lys-H

Cultured cells from the anterior pituitary glands of adult rats were treated with the tripeptide aldehyde proteinase inhibitor, BOC-DPhe-Phe-Lys-H. The addition of this tripeptide aldehyde decreased the in vitro release of prolactin to 25% of the control value, while the release of growth hormone in the same cultures decreased to 33% of the control value. Prolactin immunostaining was stronger in semithin sections of proteinase-inhibitor-treated cultures than in control sections. After 2 h treatment with the inhibitor, prolactin- and growth hormone-containing secretory granules were numerous, and the number of crinophagic vacuoles had increased. In the presence of the inhibitor, the overall cytoarchitecture of parenchymal cells was well preserved, and the pathway of the uptake of cationic ferritin appeared to be unaffected.     

Schistosoma mansoni: nucleic acid synthesis in immature females from single-sex infections, paired in vitro with intact males and male segments

1. The object of this study was to see whether stimulation of nucleic acid synthesis in immature females by male Schistosoma mansoni is mediated locally by contact, or is propagated systemically in the female. 2. Immature females perfused from single-sex animal infections were paired for one week in vitro with segments of males cut transversely into thirds; others were paired with intact males, or maintained without males; all were then incubated with [3H]-thymidine or tyrosine. 3. Washed females were bisected transversely and isotope uptake counted separately in the anterior and posterior halves. 4. The halves in contact with cut male segments showed significantly higher uptake of [3H]-thymidine than the non-contact halves, indicating increased DNA synthesis and cell division, but non-contact halves had greater uptake of [3H]-tyrosine. 5. Dot-blot hybridization with a female specific single stranded cDNA failed to detect production of the corresponding mRNA in females paired with male segments.