Influence of culture medium pH on charasome development and chloride transport inChara corallina

Summary Internodal cells ofChara, grown in culture either at pH 5.7, 6.5 or 7.5, were studied to determine their chloride influx capability, the quantitative aspects of charasome morphology and the degree to which these two parameters could be correlated. In cells grown at pH 5.7 the charasomes were relatively small, were widely spaced on the plasma membrane, and contributed only a 0.6% increase to the surface area of the plasma membrane in the acid region of the cell. In contrast, the charasome membrane surface area of cells grown at pH 7.5 had increased × 19, the density of charasomes on the cell surface increased × 42, thus producing a × 3.57 increase in the acid region plasma membrane surface area. Chloride influx in cells grown at pH 7.5 was × 8.7–12.7 greater than in cells grown at pH 5.7. Cells that had been starved of chloride exhibited a × 2.4 average increase in the rate of chloride influx. Our observations establish the existence of a positive correlation between the rate of chloride influx and the increase in membrane surface area due to charasomes, although other factors, such as the effect of pH on transport-related enzymes, and the effect of charasome structure on chemical equilibria, may also be of importance.     

Growth in vitro of arrested embryos from lethal mutants ofArabidopsis thaliana

Summary Seventeen embryo-lethal mutants ofArabidopsis thaliana with lethal phases ranging from the globular to mature cotyledon stages of development were analyzed by culturing arrested embryos on nutrient media designed to promote either callus formation or the completion of embryo development and the recovery of homozygous mutant plants. Enriched media supplemented with vitamins, amino acids, and nucleosides were used to identify potential auxotrophic mutants. Wild-type embryos produced extensive callus on basal and enriched media supplemented with 2,4-D and kinetin. Numerous roots developed when wildtype callus was grown in the presence of NAA and kinetin. Mutant embryos arrested prior to the heart stage of development formed only a slight amount of callus on basal and enriched media. Arrested embryos from mutants 122G-E and 112A-2A reached a later stage of development and gave the most interesting responses in culture. 122G-E mutant embryos failed to grow on basal media but produced extensive callus and homozygous mutant plants on enriched media. The specific nutrient required for growth of this mutant remains to be determined. Arrested embryos from mutant 112A-2A developed into abnormal plants without roots when placed in culture. Mutant callus also failed to form roots on a variety of root-inducing media. Expression of this mutant gene therefore disrupts development of the root apical meristem during both embryogenesis in vivo and organogenesis in vitro.     

Breeding vervet monkeys in a closed environment

A breeding group of vervet monkeys produced 95 offspring over five years. Fetal wastage for 114 pregnancies was 16.7%. Uterine sizes were recorded for 103 pregnancies in various stages of gestation. This enabled diagnosis of pregnancy, estimation of stage of gestation, and prediction of parturition to within two weeks. Detailed observations were made on dental eruption, pelage development, and growth of 57 infants.     

Photosynthetic electron transport and establishment of an associated trans-thylakoid proton electrochemical gradient during development of the wheat leaf

Abstract Photosynthetic electron transport activities and the ability to generate and maintain a trans-thylakoid proton electrochemical gradient were examined during chloroplast development in 4-day-old wheat leaves grown under a diurnal light regime. Polarographic and spectropholometric studies on leaf tissue demonstrated that poorly developed chloroplasls at the leaf base could photo-oxidize water and transfer electrons from photosystem 2 to photosystem 1. The capacity for non-cyclic whole-chain electron transport increased during chloroplast development. Thylakoids isolated from the leaf base, although capable of pumping protons into the inlrathylakoid space, could not maintain a trans-membrane proton electrochemical gradient; this ability developed at later stages of chloroplast biogenesis in the leaf. The implications of these results for the energetics of the developing leaf are discussed.     

Possible metabolic basis for the developmental anomaly observed in in vitro culture,called ‘vitreous plants’

Previous studies have shown that the development anomaly encountered in meristem culture, known as vitreous plants, is due to deficient lignin synthesis. This anomaly can be cured by addition of phloridzin to the culture medium. This study examines the activities of some enzymes involved in the synthesis of lignins and of flavonoids in normal and in vitreous plants of two apple cultivars. The results showed that all enzymes were consistently less active in the vitreous plants. This agrees with previous studies made on the hydroxycinnamate: CoA ligase activity in Prunus avium (L.) meristem-derived plants. The study on the substrate specificity of the enzyme demonstrates that while its activity is lower in the vitreous plant, its conformation is identical with that of the normal plant; the substrate that is specific to enzyme extracts of both sources is para-coumaric acid.     

The hypothalamo-hypophysial system of the frog Rana temporaria

Summary The median eminence (ME) of the adult frog, Rana temporaria, was studied by means of electron microscopy including quantitative electron-microscopic autoradiography. In frogs captured in May and June numerous peptidergic neurosecretory fibres extending via the internal zone to the pars nervosa display large swellings containing few granules, mitochondria, neurotubules and cisternae of the smooth endoplasmic reticulum. In addition, few secretory globules up to 1.5 m in diameter occur in these varicosities. In animals collected during the autumn period many of these neurosecretory swellings filled with neurosecretory granules and polymorphic inclusions resemble Herring bodies. Three types of granule-containing neurosecretory fibres were observed in the external zone (EZ) of the ME of adult R. temporaria. Peptidergic A₁- and A₂-type fibres are characterized by granules 150–220 nm and 100–160 nm in diameter, respectively. Monoaminergic fibres of type B with granules approximately 100 nm in diameter represent 50% of all neurosecretory elements in the EZ of the frog ME; 12% of the total number of granule-bearing axons in the EZ actively taking up radiolabelled 5-hydroxytryptophan are thought to be serotoninergic terminals. Neurosecretory terminals of all types and glial vascular endfeet establish direct contacts with the perivascular space of the primary portal capillaries. Some neurosecretory terminals are separated from the lumen of the third ventricle by a thin cytoplasmic lamella of tanycytes. The possible physiological significance of this structural pattern is discussed.     

Biosynthesis and distribution of ecdysone and 20-OH-ecdysone in Aedes aegypti

The distribution and biosynthesis of ecdysone and 20-hydroxyecdysone (20-OH-ecdysone) was followed in sugar- and blood-fed female Aedes aegypti. In both sugar- and early blood-fed animals most of the ecdysteroid determined by radioimmunoassay was found outside the ovary. Twenty-four to 40 h after blood feeding, however, ecdysteroid was distributed between ovary and carcass in the ratio of 1:1.5. Ecdysteroid titer reached a plateau between 18 to 40 h after the blood meal and decreased thereafter. Analysis of the ecdysteroid titer using thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) revealed that both 20-OH-ecdysone and ecdysone were synthesized after the blood meal. The ratio of 20-OH-ecdysone to ecdysone remained essentially constant and fluctuated in parallel throughout egg development. Chromatography of the early ecdysteroid peak (8 h after feeding) using TLC and HPLC indicated that although it cross-reacted with ecdysteroid antibodies, it did not have the same elution times as ecdysone and 20-OH-ecdysone and is, therefore, probably a precursor of these ecdysteroids. Injections of egg development neurosecretory hormone (EDNH) preparation purified to near homogeneity, into ligated abdomens, induced ecdysteroid synthesis only if the abdomens were first treated with methoprene (12.5 pg). Methoprene at this concentration did not stimulate ecdysteroid synthesis in these abdomens. When blood-fed females were treated with [4-¹⁴C] cholesterol and analyzed using TLC and HPLC procedures, both [¹⁴C]labeled ecdysone and [¹⁴C]labeled 20-OH-ecdysone were synthesized in the ratio of 1:1.5. This report is the first to show that both ecdysone and 20-OH-ecdysone are synthesized in vivo in female A. aegypti.     

Photosynthetic characteristics of detached barley leaves during greening in the presence of SAN 9785

The effects of the pyridazinone compound SAN 9785 on the photosynthetic competence of leaves, on the photochemical activity of isolated thylakoids and on the formation and spectral properties of chlorophyll-protein complexes were studied during a 72-h greening period of detached etiolated leaves of barley (Hordeum vulgare L. cv. Horpácsi kétsoros). It was established that i) the photosynthetic capacity of the leaves decreased considerably (by 80 and 90%, as determined by¹⁴CO₂ fixation and fast fluorescence induction measurements, respectively); ii) the photochemical activity of isolated thylakoids from water to potassium ferricyanide and from dichlorophenol indophenol/ascorbate to methylviologen exhibited only slight reductions when expressed on a chlorophyll basis compared with the control; iii) the slow fluorescence induction curves of the treated leaves demonstrated the presence of a peculiar fluorescence component interrupting the quenching of fluorescence at around 1 min illumination; iv) a shortage of the chlorophyll-protein complex of photosystem I (CPI) occurred with a higher content of the monomer of the light harvesting complex in the thylakoids of treated leaves; and v) the fluorescence spectrum of the CPI band present in treated leaves indicates the destruction of the structural integrity of this complex during isolation from the membrane.Abbreviations Chl chlorophyll - CPI, CPII chlorophyll-protein complexes of the reaction centres of PSI and PSII - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DPIP 2,6-dichlorophenol indophenol - DPIPH₂ chemically reduced form of DPIP - F _o fluorescence of constant yield - F _v fluorescence of variable yield - F _i ,F _m mitial and maximum yield of fluorescence - LHCP³ monomer of the light-harvesting complex - LHCP² and LHCP¹ oligomers of the light-harvesting complex LHCP³ - PSI, PSII photosystems I, II - SAN 9785 4-chloro-5-(dimethylamino)-2-phenyl-3(2H)-pyridazinone, also known as BASF 13-338 - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis     

The carotenoid and abscisic acid content of viviparous kernels and seedlings ofZea mays L.

Carotenoid and abscisic acid (ABA) levels were determined in endosperm, embryos and seedlings of wild-type and viviparous (vp) mutants ofZea mays L. Carotenoid concentrations were determined by absorption spectrometry following purification by high-performance liquid chromatography and ABA concentrations by combined gas chromatography-mass spectrometry. Lutein and zeaxanthin were the terminal carotenoids in wild-type tissue. The carotenoid profiles ofvp-1 andvp-8 tissue were similar to that of the wild type; invp-2, vp-5, vp-7 andvp-9 carotenogenesis was blocked at early stages so that xanthophylls were absent. Except forvp-1, where the ABA content was similar to the wild type, the ABA content ofvp embryos was substantially reduced, to 6–16% of the corresponding wild type. Thus, the absence of xanthophylls was associated with reduced ABA content, which was in turn correlated with vivipary. Kernels ofvp-8 had a reduced ABA content although xanthophylls were present. Seedlings of carotenoid-deficient mutants rescued from viviparous kernels contained less ABA than did wild-type seedlings grown in the same way. Furthermore, the ABA concentration of such seedlings did not increase in response to water deficit. Conversely,vp-1 seedlings contained normal levels of carotenoids and ABA. Carotenoid-deficient seedlings did not contain appreciable amounts of chlorophyll so that chloroplast development was not normal. Thus ABA-deficiency could be associated with abnormal plastid development rather than the absence of carotenoids per se.Abbreviations ABA abscisic acid - DAP days after pollination - i.d. internal diameter - FW fresh weight - GC-MS combined gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - MS mass spectrometry - vp viviparous