Release of cotyledonary shoots of pea (<Emphasis Type="Italic">Pisum sativum</Emphasis>) seedlings from inhibition as related to endogenous zeatin and ethylene and exogenous IAA and benzyladenine

This paper deals with apical dominance using a dicotylar model obtained after decapitation of pea seedlings with two shoots — one dominant and the other inhibited. When the dominant shoot was decapitated the inhibited one is released from inhibition and after 24 to 72 h begins to grow. However, the levels of trans-zeatin and production of ethylene increase within 4 and 6 hours respectively after release from inhibition, and within an interval of 72 h the levels of both phytohormones begin gradually to decrease. This indicates that also in this model, the release from apical dominance is associated with an increase in the level of cytokinin zeatin and, thereafter, also with an increased production of ethylene. If indolyl-3-acetic acid (IAA) is applied on the decapitated main stem after decapitation of the dominant shoot, the growth of the initially inhibited one is very strongly retarded; if, however, IAA is applied on the decapitated dominant shoot, this inhibition is significantly weaker. This means that the inhibiting effect of IAA on the inhibited shoot originates to a greater degree from the main stem rather than from the dominant shoot. The effect of benzyladenine (BA) is transferred equally from the decapitated main stem and from the decapitated dominant shoot because the initially inhibited shoot begins to grow as well as also other shoots from serial cotyledonary buds.     

Trichome micromorphology in <Emphasis Type="Italic">Teucrium</Emphasis> (Lamiaceae) species growing in Croatia

Micromorphological investigation of the types, dimensions and distribution of characteristic trichomes in leaves and stems in Teucrium L. species (T. arduini L., T. chamaedrys L., T. flavum L., T. montanum L., T. polium L., and T. scordium L. subsp. scordioides Schreb.) distributed in Croatia was carried out as part of the taxonomical study of the genus Teucrium. Secretory types of hairs, peltate and capitate hairs were observed on the epidermis of stems and leaves of all investigated species. Non-secretory, acicular hairs were almost completely lacking on stems of T. scordium subsp. scordioides. Flagelliform hairs were not found in T. flavum and T. polium. Cladose hairs were present only in T. polium. The largest micromorphological variability was established between wild and cultivated samples of T. arduini and T. scordium subsp. scordioides, while cultivated and wild specimens of T. polium were almost identical. Differences were primarily observed in trichome dimensions and much less in micromorphological features.     

Effect of selenium supplementation in asthmatic subjects on the expression of endothelial cell adhesion molecules in culture

Endothelial cells play a major role in immunologic reactions, in which cellular adhesion molecules P-selectin, ICAM-1, VCAM-1, and ELAM-1 are important mediators in the recruitment of leukocytes in pulmonary inflammation. Selenium (Se) is known to modulate immunological mechanisms of asthma. The aim of our investigation was to examine whether Se supplementation in cortico-dependent asthmatic patients may modulate adhesion molecule expression in cultured endothelium. Our findings indicated that P-selectin, VCAM-1, and ELAM-1 expression on human umbilical vein endothelial cells stimulated with peripheral blood mononuclear cells obtained from asthmatics before supplementation with Se was significantly higher than from healthy donors (p < 0.05). The production of ICAM-1 showed only slight augmentation. The levels of VCAM-1 and ELAM-1 expression were significantly decreased after 3 mo of Se supplementation (p < 0.05). After 6 mo of intervention period the intensity of P-selectin and ICAM-1 expression was also significantly reduced (p < 0.05 andp < 0.01, respectively). The inhibitory effect of Se on the adhesion molecule expression was studied in cultured endothelial cells after interferon-γ stimulation. Our data suggest that Se affects the expression of P-selectin, ICAM-1, VCAM-1, and ELAM-1 in a dosedependent manner and the half-maximal inhibitory concentrations were 3.4, 0.5, 4, and 3.8 μg/mL, respectively. The maximal inhibitions (greater than 80%) were observed in vitro with 10 μg/mL Se (p < 0.01). Regulation of adhesion molecule expression may be an important mechanism through which the inflammation may be controlled.     

Effects of plant density and nutrient levels on fruit polymorphism in Atriplex sagittata

Atriplex sagittata is a heterocarpic species producing three types of fruits which differ in morphology and ecological properties. This study focused on variation in biomass allocation into particular fruit types under different density and fertilization levels. The reduction in total weight under stressful conditions was accompanied by a reduction of reproductive structures in terms of both total fruit production and mean fruit weight. Allocation of biomass to particular fruit types under different density-fertilization treatments showed considerable variation. The non-dormant, bracteolate fruit type (termed C) contributed 80–90% to the total fecundity and its production was not affected by density-fertilization treatments. The production of this fruit type is higher in the upper part of the maternal plant stem. Production of the very dormant ebracteate fruit type (termed A) increased under favourable conditions and was greater on the lower part of the stem, whereas more of the so-called type B fruit (covered by bracteoles and exhibiting dispersal and dormancy characteristics intermediate between types A and C) was produced under suboptimal conditions and was concentrated in the middle part of the plant body. This pattern contradicts to some extent the theory that deeply dormant and less dispersible fruits will be produced under stressful conditions and may be considered a new model for the behaviour of plants with more than two heterocarpic fruits. The type B fruit, intermediate in both morphology and ecological behaviour, provides a continuum between extreme strategies. Received: 8 February 1998 / Accepted: 19 November 1998     

Properties of pupil mechanisms in owl-fly Ascalaphus macaronius (Neuroptera)

Regulation of light flux by pupil mechanisms in the UV-sensitive superposition eye of owl-fly Ascalaphus macaronius (Neuroptera) was studied with a fast reflection microspectrophotometric technique. The spectral sensitivity of pupil reaction, which was calculated on the basis of changes of transient amplitude reflection, was almost identical with the one of Deilephila eye. This indicates that in spite of different life styles and spectral sensitivities of photoreceptors, pupil closing is triggered by the same photosensitive structure in both eyes. By measuring the spectra of reflected light from the Ascalaphus eye between 400 and 700 nm after different dark periods following light stimulation, it was established that the restoration of reflection was much faster in the red than in the blue spectral range. Based on this, we propose that two different pupil mechanisms with different spectral absorption characteristics are involved in light-flux regulation. Fast-reacting pupil is probably represented by screening pigment migration in the secondary pigment cells and a slow blue-absorbing system by the activity in primary pigment cells. The importance of two different pupils for the photoregeneration of visual pigment is discussed. Accepted: 1 October 1998     

Revealing human impact on natural ecosystems through soil bacterial DNA sampled from an archaeological site

Human activities have affected the surrounding natural ecosystems, including belowground microorganisms, for millennia. Their short- and medium-term effects on the diversity and the composition of soil microbial communities are well-documented, but their lasting effects remain unknown. When unoccupied for centuries, archaeological sites are appropriate for studying the long-term effects of past human occupancy on natural ecosystems, including the soil compartment. In this work, the soil chemical and bacterial compositions were compared between the Roman fort of Hegra (Saudi Arabia) abandoned for 1500 years, and a preserved area located at 120 m of the southern wall of the Roman fort where no human occupancy was detected. We show that the four centuries of human occupancy have deeply and lastingly modified both the soil chemical and bacterial compositions inside the Roman fort. We also highlight different bacterial putative functions between the two areas, notably associated with human occupancy. Finally, this work shows that the use of soils from archaeological sites causes little disruption and can bring relevant information, at a large scale, during the initial surveys of archaeological sites.     

Gazing into the abyss: A glimpse into the diversity,distribution, and behaviour of heterotrophic protists from the deep-sea floor

The benthic biome of the deep-sea floor, one of the largest biomes on Earth, is dominated by diverse and highly productive heterotrophic protists, second only to prokaryotes in terms of biomass. Recent evidence suggests that these protists play a significant role in ocean biogeochemistry, representing an untapped source of knowledge. DNA metabarcoding and environmental sample sequencing have revealed that deep-sea abyssal protists exhibit high levels of specificity and diversity across local regions. This review aims to provide a comprehensive summary of the known heterotrophic protists from the deep-sea floor, their geographic distribution, and their interactions in terms of parasitism and predation. We offer an overview of the most abundant groups and discuss their potential ecological roles. We argue that the exploration of the biodiversity and species-specific features of these protists should be integrated into broader deep-sea research and assessments of how benthic biomes may respond to future environmental changes.     

Transplants of Human Mesenchymal Stem Cells Improve Functional Recovery After Spinal Cord Injury in the Rat

Human mesenchymal stem cells (hMSCs) derived from adult bone marrow represent a potentially useful source of cells for cell replacement therapy after nervous tissue damage. They can be expanded in culture and reintroduced into patients as autografts or allografts with unique immunologic properties. The aim of the present study was to investigate (i) survival, migration, differentiation properties of hMSCs transplanted into non-immunosuppressed rats after spinal cord injury (SCI) and (ii) impact of hMSC transplantation on functional recovery. Seven days after SCI, rats received i.v. injection of hMSCs (2×10⁶ in 0.5 mL DMEM) isolated from adult healthy donors. Functional recovery was assessed by Basso–Beattie–Bresnahan (BBB) score weekly for 28 days. Our results showed gradual improvement of locomotor function in transplanted rats with statistically significant differences at 21 and 28 days. Immunocytochemical analysis using human nuclei (NUMA) and BrdU antibodies confirmed survival and migration of hMSCs into the injury site. Transplanted cells were found to infiltrate mainly into the ventrolateral white matter tracts, spreading also to adjacent segments located rostro-caudaly to the injury epicenter. In double-stained preparations, hMSCs were found to differentiate into oligodendrocytes (APC), but not into cells expressing neuronal markers (NeuN). Accumulation of GAP-43 regrowing axons within damaged white matter tracts after transplantation was observed. Our findings indicate that hMSCs may facilitate recovery from spinal cord injury by remyelinating spared white matter tracts and/or by enhancing axonal growth. In addition, low immunogenicity of hMSCs was confirmed by survival of donor cells without immunosuppressive treatment.