Effects of plant size on photosynthesis and water relations in the desert shrub Prosopis glandulosa (Fabaceae)

The Jornada del Muerto basin of the Chihuahuan Desert of southern New Mexico, USA, has undergone a marked transition of plant communities. Shrubs such as mesquite (Prosopis glandulosa) have greatly increased or now dominate in areas that were previously dominated by perennial grasses. The replacement of grasses by shrubs requires an establishment phase where small shrubs must compete directly with similar-sized grass plants. This is followed by a phase in which large, established shrubs sequester nutrients and water within their biomass and alter soil resources directly under their canopy, creating “islands” of fertility. We hypothesized that these two phases were associated with shrubs having different physiological response capacities related to their age or size and the resource structure of the environment. As a corollary, we hypothesized that responses of small shrubs would be more tightly coupled to variation in soil moisture availability compared to large shrubs. To test these hypotheses, we studied gas exchange and water relations of small (establishing) and large (established) shrubs growing in the Jornada del Muerto as a function of varying soil moisture during the season. The small shrubs had greater net assimilation, stomatal conductance, transpiration, and xylem water potential than large shrubs following high summer rainfall in July, and highest seasonal soil moisture at 0.3 m. High rates of carbon assimilation and water use would be an advantage for small shrubs competing with grasses when shallow soil moisture was plentiful. Large shrubs had greater net assimilation and water-use efficiency, and lower xylem water potential than small shrubs following a dry period in September, when soil moisture at 0.3 m was lowest. Low xylem water potentials and high water-use efficiency would allow large shrubs to continue acquiring and conserving water as soil moisture is depleted. Although the study provides evidence of differences in physiological responses of different-sized shrubs, there was not support for the hypothesis that small shrubs are more closely coupled to variation in soil moisture availability than large shrubs. Small shrubs may actually be less coupled to soil moisture than large shrubs, and thus avoid conditions when continued transpiration could not be matched by equivalent water uptake.     

PATTERNS IN LEAF MORPHOLOGY AND PHOTOSYNTHESIS IN SHOOTS OF SASSAFRAS ALBIDUM (LAURACEAE)

Trees of Sassafras albidum (Nuttall) Nees. display leaves that fall into discrete categories of form. Unlobed leaves, with undissected margins, predominate at proximal and distal nodes of shoots, while lobed leaves are most common at intermediate nodes. In this study we investigated the hypothesis that shoots of sassafras respond to environmental changes over the growing season by generating predictable nodal patterns for leaf morphology and physiology. We recorded leaf shape category and measured leaf surface area, node number, chlorophyll content, nitrogen content, and photosynthesis in four trees. Over 1,000 measurements of photosynthesis were made in situ, using the LI-Cor LI 6200 portable photosynthesis system. The two trees growing under heavy shade had few lobed leaves (2.0% and 18.8%) and often had negative carbon balance, with positive net photosynthesis occurring during sun flecks. The two trees growing in more open conditions had many more lobed leaves (56.3% and 61.0%) and higher, less variable net photosynthetic rates. As indicated by chlorophyll and nitrogen contents, the highest leaf photosynthetic rates occurred at intermediate nodes (nodes six to nine), and this was shifted distally along the shoot during the growing season. Leaves at intermediate nodes also had the largest surface areas and the greatest frequency of lobing. In comparative experiments with models, lobing was shown to enhance free-convectional heat loss relative to unlobed leaves of the same surface area. Due to their large surface area, these leaves also have the highest rates of whole leaf photosynthesis. Under conditions of equivalent photosynthetically active radiation, lobed leaves had higher rates of net photosynthesis than did unlobed leaves. We conclude that shoots of sassafras produce groups of leaves with predictably different morphological and physiological specializations.     

Use of agricultural surpluses for production of biomass by marine microalgae

The marine microalga Phaeodactylum tricornutum was cultivated in semi-continuous culture under mixotrophic conditions with the soluble fractions of potato, rye and wheat flours that had been naturally fermented, at 2% or 4% (w/v). The rye flour produced the highest microalgal cellular density of 90×10⁶ cells.ml^-1 when supplemented with NaNO₃ and NaH₂PO₄. The autotrophic control only gave 57×10⁶ cells.ml^-1. The value of agricultural surpluses, such as rye flour, can therefore be increased by its use in the production of valuable, microalgal biomass which is rich in protein, pigments and fatty acids.     

Late afternoon administration of melatonin is prosomatotrophic and exerts androgen independent effects on erythropoiesis in male house sparrow Passer domesticus.

In the third week of September 1989, birds were purchased locally and acclimated to their housing conditions in a room fully exposed to natural day length (average: 11.96 hr) and temperature (26 degrees +/- 2 degrees C) for 2 weeks. Birds were in the regressive phase of their annual gonadal cycle. In the first experiment 24 birds were selected randomly and were divided into 3 groups of 8 birds each. Initial body weight and bill color score were recorded. The birds of group-I and group-II were injected daily with 5 and 10 micrograms of melatonin in 0.1 ml of vehicle, respectively. The birds of group-III were injected with vehicle only and treated as control. Injections were given daily between 1700 and 1730 hrs over a period of 10 days. At the termination of the experiment, the birds were weighed, sacrificed, bill color scored, blood collected and immediately processed to determine the number of erythrocytes and hemoglobin concentration. The mean body weight loss amounted to 9.6% in vehicle-treated house sparrow. Birds receiving low and high doses of melatonin maintained their initial body weight. Melatonin significantly accelerated the rate of bleaching of bill color. Results clearly indicate that in house sparrow, melatonin produces prosomatotrophic and antigonadotrophic effects. The low dose of melatonin stimulated erythropoiesis significantly. In the second experiment, melatonin nullified the castration-induced decline in the number of circulating red cells. This clearly suggests that the influence of melatonin on erythropoietic machinery appears to be independent of testicular hormone(s).     

Apoptotic mechanisms of myricitrin isolated from Madhuca longifolia leaves in HL-60 leukemia cells

Molecular Biology Reports - Myricitrin, a naturally occurring flavonoid in Madhuca longifolia, possesses several medicinal properties. Even though our earlier work revealed its role against the...     

Hydroxychloroquine-mediated inhibition of SARS-CoV-2 entry is attenuated by TMPRSS2

Hydroxychloroquine, used to treat malaria and some autoimmune disorders, potently inhibits viral infection of SARS coronavirus (SARS-CoV-1) and SARS-CoV-2 in cell-culture studies. However, human clinical trials of hydroxychloroquine failed to establish its usefulness as treatment for COVID-19. This compound is known to interfere with endosomal acidification necessary to the proteolytic activity of cathepsins. Following receptor binding and endocytosis, cathepsin L can cleave the SARS-CoV-1 and SARS-CoV-2 spike (S) proteins, thereby activating membrane fusion for cell entry. The plasma membrane-associated protease TMPRSS2 can similarly cleave these S proteins and activate viral entry at the cell surface. Here we show that the SARS-CoV-2 entry process is more dependent than that of SARS-CoV-1 on TMPRSS2 expression. This difference can be reversed when the furin-cleavage site of the SARS-CoV-2 S protein is ablated or when it is introduced into the SARS-CoV-1 S protein. We also show that hydroxychloroquine efficiently blocks viral entry mediated by cathepsin L, but not by TMPRSS2, and that a combination of hydroxychloroquine and a clinically-tested TMPRSS2 inhibitor prevents SARS-CoV-2 infection more potently than either drug alone. These studies identify functional differences between SARS-CoV-1 and -2 entry processes, and provide a mechanistic explanation for the limited in vivo utility of hydroxychloroquine as a treatment for COVID-19.     

Characterization and Cytotoxic Evaluation of Bacteriocins Possessing Antibiofilm Activity Produced by Lactobacillus plantarum SJ33

International Journal of Peptide Research and Therapeutics - Biofilm forming pathogens are among the major causes of hospital-acquired infections and are not much affected by antibiotic treatment....     

Associations of methyl donor and methylation inhibitor levels during anti-oxidant therapy in heart failure

Journal of Physiology and Biochemistry - Redox balance and methylation are crucial to homeostasis and are linked by the methionine-homocysteine cycle. We examined whether differences in methylation...     

Synthesis of functionalized amino acid derivatives as new pharmacophores for designing anticancer agents

A new series of functionalized amino acid derivatives N-substituted 1-N-(tert-butoxycarbonyl)-2,2-dimethyl-4-phenyl-5-oxazolidine carboxamide (1-17) and 1-N-substituted-3-amino-2-hydroxy-3-phenylpropane-1-carboxamide (18-34) were synthesized and evaluated for their in vitro cytotoxicity against human cancer cell lines. Compound 6 has shown interesting cytotoxicity (IC₅₀ = 5.67 μm) in ovarian cancer, while compound 10 exhibited promising cytotoxicity in ovarian (IC₅₀ = 6.1 μm) and oral (IC₅₀ = 4.17 μm) cancers. These compounds could be of use in designing new anti-cancer agents.     

Synthesis of azatricyclodiones & octahydro-benzo[f]isoindoles and their antimicrobial evaluation

A series of azatricyclodiones and octahydro-benzo[f]isoindoles have been synthesized by (4+2) Diels-Alder cycloaddition of maleimides with furfuryl amine. Reaction of azatricyclodiones with isocyanates led to the respective ureides. All of the compounds were screened against a number of bacteria and fungi. One of the compounds (2) displayed moderate antitubercular activity while two compounds (2) and (4) inhibited the fungal growth at 25 μg/mL.