Rehabilitation in the Philippines

The international community has perspective and experience that will freshen our approaches to rehabilitation. Martin Grabois, MD^*, editor of this special section, has gathered articles written by experts from other countries. The intention is to stimulate thought, discussion, and action—and to broaden horizons.     

Excitation Energy Transfer between Pigments in Photosynthetic Cells

The excitation lifetimes of photosynthetic pigments and the times needed for energy transfer between pigments in various algae, were determined in vitro and in vivo. For this purpose, the time curves of fluorescence rise and decay were measured by means of Brody''s instrument (10), and compared with theoretical curves obtained by the method of “convolution of the first kind.”¹     

Photosynthetic and leaf morphological characteristics in Leucaena leucocephala as affected by growth under different neutral shade levels

Morphological and physiological measurements on individual leaves of Leucaena leucocephala seedlings were used to study acclimation to neutral shading. The light-saturated photosynthetic rate (P_{n max}) ranged from 19.6 to 6.5 mol CO₂ m^–2 s^–1 as photosynthetic photon flux density (PPFD) during growth decreased from 27 to 1.6 mol m^–2 s^–1. Stomatal density varied from 144 mm^–2 in plants grown in high PPFD to 84 mm^–2 in plants grown in low PPFD. Average maximal stomatal conductance for H₂O was 1.1 in plants grown in high PPFD and 0.3 for plants grown in low PPFD. Plants grown in low PPFD had a greater total chlorophyll content than plants grown in high PPFD (7.2 vs 2.9 mg g^–1 on a unit fresh weight basis, and 4.3 vs 3.7 mg dm^–2 on a unit leaf area basis). Leaf area was largest when plants were grown under the intermediate PPFDs. Leaf density thickness was largest when plants were grown under the largest PPFDs. It is concluded that L. leucocephala shows extensive ability to acclimate to neutral shade, and could be considered a facultative shade plant.Abbreviations the initial slope of the photosynthesis vs PPFD curve - P_{n max} the light-saturated photosynthetic rate - PPFD photosynthetic photon flux density     

Human ACAP2 is a homolog of C. elegans CNT-1 that promotes apoptosis in cancer cells

Activation of caspases is an integral part of the apoptotic cell death program. Collectively, these proteases target hundreds of substrates, leading to the hypothesis that apoptosis is “death by a thousand cuts”. Recent work, however, has demonstrated that caspase cleavage of only a subset of these substrates directs apoptosis in the cell. One such example is C. elegans CNT-1, which is cleaved by CED-3 to generate a truncated form, tCNT-1, that acquires a potent phosphoinositide-binding activity and translocates to the plasma membrane where it inactivates AKT survival signaling. We report here that ACAP2, a homolog of C. elegans CNT-1, has a pro-apoptotic function and an identical phosphoinositide-binding pattern to that of tCNT-1, despite not being an apparent target of caspase cleavage. We show that knockdown of ACAP2 blocks apoptosis in cancer cells in response to the chemotherapeutic antimetabolite 5-fluorouracil and that ACAP2 expression is down-regulated in some esophageal cancers, leukemias and lymphomas. These results suggest that ACAP2 is a functional homolog of C. elegans CNT-1 and its inactivation or downregulation in human cells may contribute to cancer development.The caspases (cysteine aspartic acid proteases) are a class of proteases with diverse roles in cellular physiology including differentiation, inflammation and cell death.^1–3 Caspases play a critical role in apoptosis, where they collectively target hundreds of proteins. One prevailing view is that caspases drive apoptosis through a mass action effect due to hundreds of proteolytic cleavage events that lead to cellular disassembly and cell death.⁴ Recent studies, however, suggest that proteolysis of most substrates may simply be a bystander effect and that caspase cleavage of key proteins controlling a few specific cellular processes is what functionally drives apoptosis.⁵ Although much of the work to date has focused on factors acting upstream of caspase activation, it is becoming increasingly clear that events downstream of this commitment step are also tightly regulated and critically important for apoptosis. Presently, there is evidence of requirements for caspase-mediated control of the BCL2 family of anti-apoptotic proteins, mitochondrial elimination, chromosome fragmentation, phosphatidylserine externalization, and, as we have recently reported, inactivation of the AKT survival signaling pathway in programmed cell death (6-10 Therefore, a more thorough understanding of physiologically relevant caspase targets will increase our understanding of apoptosis in the context of animal development and disease.

Table 1

Human homologues of functional caspase targets in C. elegans. A summary of identified caspase substrates and caspase downstream events important for cell death execution in C. elegans and humans

Island biology: looking towards the future

Oceanic islands are renowned for the profound scientific insights that their fascinating biotas have provided to biologists during the past two centuries. Research presented at Island Biology 2014—an international conference, held in Honolulu, Hawaii (7–11 July 2014), which attracted 253 presenters and 430 participants from at least 35 countries¹—demonstrated that islands are reclaiming a leading role in ecology and evolution, especially for synthetic studies at the intersections of macroecology, evolution, community ecology and applied ecology. New dynamics in island biology are stimulated by four major developments. We are experiencing the emergence of a truly global and comprehensive island research community incorporating previously neglected islands and taxa. Macroecology and big-data analyses yield a wealth of global-scale synthetic studies and detailed multi-island comparisons, while other modern research approaches such as genomics, phylogenetic and functional ecology, and palaeoecology, are also dispersing to islands. And, increasingly tight collaborations between basic research and conservation management make islands places where new conservation solutions for the twenty-first century are being tested. Islands are home to a disproportionate share of the world''s rare (and extinct) species, and there is an urgent need to develop increasingly collaborative and innovative research to address their conservation requirements.     

Umashtanchaeviella plethotricha,a new genus and species of the family Tetracondylidae (Acari,Oribatida)

A new genus of oribatid mites of the family Tetracondylidae, Umashtanchaeviella gen. n., with type species Umashtanchaeviella plethotricha sp. n., is proposed and described from forest litter, the Bu Gia Map National Park, southern Vietnam. The new genus is distinguishable from other otocepheoid genera by the presence of notogastral plethotrichy.¹     

Announcing the call for the Issue Focus on the 2nd Costa Rican Biophysics Symposium—virtual meeting,March 2021

This Commentary is a call for submissions for the upcoming Issue Focus that will highlight some of the scientific topics discussed during the 2^nd Costa Rica Biophysics Symposium.

The Second Costa Rican Biophysics Symposium¹ was organized on March 11^th and March 12^th of 2021. The first edition of this symposium was organized in 2019 at the National Academy of Sciences in Costa Rica (Solís et al. 2020). Due to the success of this event, the organizers decided to pursue a second edition of this scientific meeting. However, the global emergency of COVID-19 forced to keep social distancing as part of the sanitary measures and therefore, the second edition was held virtually. Nevertheless, the event was a great success as measured by the number of registrations near to 130, the quality of the presentations of the 15 speakers from 5 different countries (Costa Rica, Switzerland, USA, France, and Germany), and the level of participation during the Q & A sessions of each talk. As the highlight of the symposium, we had the pleasure to host Dr. Francisco Bezanilla as the keynote speaker and who highlighted some of his recent work on non-canonical mechanisms of voltage sensor domain coupling to pore domains in voltage-gated potassium channels (Carvalho-de-Souza and Bezanilla 2019).In commemoration of the 2^nd Costa Rica Biophysics Symposium, Biophysical Reviews will publish an Issue Focus in 2022 highlighting some of the scientific topics discussed during the event. Review articles from speakers and attendees who were part of the event are solicited. The format for the review articles is similar to those submitted for the special issue of the 20^th International Congress of the International Union of Pure and Applied Biophysics (IUPAB) (Itri et al. 2021). The Special Issue for the 20^th IUPAB International Congress will be prepared and edited by the current authors (Christopher Solís, Gustavo Chaves, and José Ángel Rodriguez-Corrales).     

Photoautotrophic micropropagation of Russet Burbank Potato

The photoautotrophic micropropagation of potato cv. Russet Burbank was investigated. Single node microcuttings were grown for four weeks on Murashige and Skoog (MS) medium with or without sucrose (30 g l^–1) in the growth room at 21/19 °C day/night temperature, with 16-h photoperiod at 150 mol m^–2 s^–1, with or without supplemental CO₂ at 1500 l l^–1. A 20% increase in the number of nodes per stem (from 7.5 to 9.4) and a 50% increase in stem dry weight were observed in cultures grown on media with sucrose and in CO₂ enriched atmosphere comparing to the conventionally micropropagated cultures or the cultures grown photoautotrophically on media without sucrose but in air supplemented with 1500 l l^–1CO₂. Stems of these cultures (from media with sucrose in CO₂ enriched air) almost doubled in length the stems of cultures from the other two treatments. No significant differences were observed between Control (MS medium supplemented with sucrose, 30 g l^–1) and photoautotrophic cultures coming from MS medium with no sucrose grown under 1500 l l^–1 of CO₂. Photoautotrophic cultures produced stems averaging 43.3 mm, with 7 nodes and weighing 9.2 mg (dry weight), similar to conventionally grown in vitro cultures (47.9 mm with 7.5 nodes, 9.7 mg dry weight). Growers may consider photoautotrophic culturing of potato in areas where the high sterility levels are difficult to maintain. Supplementing air in the growth room with 1500 l l^–1 of CO₂ could be beneficial for potato plantlet production even on media containing sucrose since it significantly improved quality, size and biomass of produced plantlets, speeding up the multiplication.     

Utilization of l-alanine by Rhodopseudomonas acidophila

Rhodopseudomonas acidophila strain 7050 can satisfy all its nitrogen and carbon requirements from l-alanine. Addition of 100 M methionine sulfoximine to alanine grown cultures had no effect on growth rate indicating that deamination of alanine via alanine dehydrogenase and re-assimilation of the released NH ₄ ⁺ by glutamine synthetase/glutamate synthase was an insignificant route of nitrogen transfer in this bacterium. Determination of aminotransferase activities in cell-free extracts failed to demonstrate the presence of direct routes from alanine to either aspartate or glutamate. The only active aminotransferase involving l-alanine was the alanine-glyoxylate enzyme (114–167 nmol·min^–1·mg^–1 protein) which produced glycine as end-product. The amino group of glycine was further transaminated to yield aspartate via a glycineoxaloacetate aminotransferase (117–136 nmol·min^–1 ·mg^–1 protein). No activity was observed when 2-oxoglutarate was substituted for oxaloacetate. The formation of glutamate from aspartate was catalysed by aspartate-2-oxoglutarate aminotransferase (85–107 nmol·min^–1·mg^–1 protein). Determinations of free intracellular amino acid pools in alanine and alanine+100 M methionine sulfoximine grown cells showed the predominance of glutamate, glycine and aspartate, providing further evidence that in alanine grown cultures R. acidophila satisfies its nitrogen requirements for balanced growth by transamination.Abbreviations ADH alanine dehydrogenase - GDH glutamate dehydrogenase - GS glutamine synthetase - GOGAT glutamate synthase - MSO methionine sulfoximine - GOT glutamate-oxaloacetate aminotransferase - GPT glutamate-pyruvate amino-transferase - AGAT alanine-glyoxylate aminotransferase - GOAT glycine-oxaloacetate aminotransferase - GOTAT glycine-2-oxoglutarate aminotransferase - AOAT alanine-oxaloacetate aminotransferase     

Adjustment of thylakoid plastoquinone content and Photosystem I electron donor pool size in response to growth temperature and growth irradiance in winter rye (Secale cereale L.)

Winter rye (Secale cereale L. cv Musketeer) grown at 5 °C/250 µmol photons m^–2 s^–1 exhibited a relative reduction state of PS II comparable to that of rye grown at 20 °C but high light (800 µmol photons m^–2 s^–1) (1-q_P = 0.32) whereas winter rye grown at 20 °C/250 µmol photons m^–2 s^–1 exhibited values of 1-q_P ( 0.15) comparable to plants grown at 5 °C but low light (50 µmol photons m^–2 s^–1). The apparent size of the electron donor pool to PS I, estimated either in vivo or in vitro in the presence of methylviologen by A₈₂₀ was positively correlated with the relative reduction state of PS II under the steady-state growth conditions. Immunoblotting of rye thylakoid polypeptides indicated that the relative contents of Lhcb1, Lhcb2, D1, Cyt f, PC, PsaA/PsaB heterodimer and the -subunit of ATPase complex exhibited minimal changes on a Chl basis. In contrast, a 2-fold increase in plastoquinone A content was associated with increasing growth irradiance at growth temperatures of either 5 or 20 °C. We suggest that the increases in the apparent size of the electron donor pool to PS I associated with rye grown at either 5 °C/250 µmol photons m^–2 s^–1or 20 °C/800 µmol photons m^–2 s^–1 may be explained by an increased thylakoid plastoquinone A content, coupled with possible enhanced PS I cyclic electron transport and/or increased capacity for electron donation from the stroma to the intersystem electron transport chain. The results are discussed with respect to photosynthetic adjustment to changes in PS II excitation pressure in winter rye.     

Niche science: The aging stem cell

Studies on stem cell aging are uncovering molecular mechanisms of regenerative decline, providing new insight into potential rejuvenating therapies.Studies on stem cell aging are uncovering molecular mechanisms of regenerative decline, providing new insight into potential rejuvenating therapies. Most human tissues retain an amazing ability to regenerate well into adulthood. Somatic stem cells are central to this ability, replacing damaged cells and thus keeping the body in a highly functional state. Yet this process does not continue unabated forever, as aging is accompanied by a loss of this regenerative capacity. Presently, studies in invertebrate and vertebrate model systems are advancing our understanding of regenerative decline and are identifying strategies for ‘rejuvenating’ therapies that have the potential to extend human health- and lifespan.The feasibility of rejuvenating interventions was demonstrated by classic studies in which exposure to a young systemic environment restored regenerative capacity of muscle stem cells in old mice.¹ Similar rejuvenation has now been demonstrated for the central nervous system, suggesting that such interventions have systemic potential² and raising the question of whether the lifespan of the organism could be extended by restoring the regenerative capacity of adult stem cells. This has already been demonstrated in flies, where improved intestinal stem cell function leads to enhanced longevity.³Such studies have inspired the burgeoning field of “stem cell aging.”^4,5 A recent symposium at the Buck Institute for Research on Aging in Novato, CA showcased the field, bringing together researchers interested in the biology of aging and experts in stem cell biology, and covering topics ranging from basic research in stem cell aging to the use of stem cells in clinical applications. Clear from the meeting is that new molecular insight into stem cell aging is emerging at a rapid pace, revealing both the promises and challenges of deploying stem cell therapies for age-related diseases. The key questions are starting to be answered.     

Enzyme-linked immunosorbent assays for the measurement of blood group A and B glycosyltransferase activities

ELISA assays have been developed for (1–3)N-acetylgalactosaminyltransferase (blood group A transferase) and (1–3)galactosyltransferase (blood group B transferase) activities. In these assays, microtitre plates coated with the bovine serum albumin conjugate of a synthetic Fuc1–2Gal-R acceptor substrate are incubated with the appropriate nucleotide donor (UDP-GalNAc or UDP-Gal) and human serum as the enzyme source. The resulting trisaccharide products Fuc1–2(GalNAc1–3)Gal-R-BSA or Fuc1–2(Gal1–3)Gal-R-BSA are detected and quantified with monoclonal antibodies selected not to cross-react with the substrate structure. With less than a microliter of human serum, product formation is proportional to enzyme concentration and to time of incubation of up to 90 min.     

Interactive effects of soil nitrogen and atmospheric carbon dioxide on root/rhizosphere carbon dioxide efflux from loblolly and ponderosa pine seedlings

We measured CO₂ efflux from intact root/rhizosphere systems of 155 day old loblolly (Pinus taeda L.) and ponderosa (Pinus ponderosa Dougl. ex Laws.) pine seedlings in order to study the effects of elevated atmospheric CO₂ on the below-ground carbon balance of coniferous tree seedlings. Seedlings were grown in sterilized sand culture, watered daily with either 1, 3.5 or 7 mt M NH ₄ ⁺ , and maintained in an atmosphere of either 35 or 70 Pa CO₂. Carbon dioxide efflux (mol CO₂ plant^–1 s^–1) from the root/rhizosphere system of both species significantly increased when seedlings were grown in elevated CO₂, primarily due to large increases in root mass. Specific CO₂ efflux (mol CO₂ g root^–1 s^–1) responded to CO₂ only under conditions of adequate soil nitrogen availability (3.5 mt M). Under these conditions, CO₂ efflux rates from loblolly pine increased 70% from 0.0089 to 0.0151 mol g^–1 s^–1 with elevated CO₂ while ponderosa pine responded with a 59% decrease, from 0.0187 to 0.0077 mol g^–1 s^–1. Although below ground CO₂ efflux from seedlings grown in either sub-optimal (1 mt M) or supra-optimal (7 mt M) nitrogen availability did not respond to CO₂, there was a significant nitrogen treatment effect. Seedlings grown in supra-optimal soil nitrogen had significantly increased specific CO₂ efflux rates, and significantly lower total biomass compared to either of the other two nitrogen treatments. These results indicate that carbon losses from the root/rhizosphere systems are responsive to environmental resource availability, that the magnitude and direction of these responses are species dependent, and may lead to significantly different effects on whole plant carbon balance of these two forest tree species.     

The role of chloroplast-encoded protein biosynthesis on the rate of D1 protein degradation in Dunaliella salina

Mechanistic aspects of the Photosystem II (PS II) damage and repair cycle in Dunaliella salina were investigated. The work addressed the role of chloroplast-encoded protein biosynthesis on the rate of the D1 protein (chloroplast psbA gene product) degradation, following photoinhibition of PS II under in vivo conditions. Cells were grown under different light-intensities and the rate of D1 photodamage and degradation was measured via pulse-chase measurements with (³⁵S)sulfate. It is shown that no detectable difference exists in the rate of D1 degradation in D. salina, measured in the presence or absence of lincomycin, a chloroplast protein biosynthesis inhibitor. The results suggest that de novo D1 biosynthesis does not play a role in the regulation of D1 degradation. In low-light (100 mol photons m^–2 s^–1) grown cells, the rate of photodamage to D1 did not exceed the rate of its degradation and replacement. In high-light (2200 mol photons m^–1 s^–1) grown cells, the rate of D1 photodamage was faster than the rate of its degradation, resulting in a significant accumulation of photoinactivated PS II centers in the chloroplast thylakoids (chronic photoinhibition). The latter was coincident with the appearance of a 160 kD complex that contained photodamaged D1. Electron micrographs of D. salina thylakoids revealed extensive grana stacks in the thylakoid membrane of low-light grown cells. Only rudimentary appressions consisting of simple membrane pairings were found in the high-light grown cells. The results are discussed in terms of the regulation of D1 degradation in chloroplasts under in vivo conditions.Abbreviations Chl chlorophyll - D1 the 32 kD reaction center protein of PS II, encoded by the chloroplast psbA gene - D2 the 34 kD reaction center protein of PS II, encoded by the chloroplast psbD gene - HL high light - LL low light - Linc lincomycin     

Effects of constitutive expression of nitrate reductase in transgenic Nicotiana plumbaginifolia L. in response to varying nitrogen supply

Transformed Nicotiana plumbaginifolia plants with constitutive expression of nitrate reductase (NR) activity were grown at different levels of nitrogen nutrition. The gradients in foliar NO ₃ ^– content and maximum extractable NR activity observed with leaf order on the shoot, from base to apex, were much decreased as a result of N-deficiency in both the transformed plants and wild type controls grown under identical conditions. Constitutive expression of NR did not influence the foliar protein and chlorophyll contents under any circumstances. A reciprocal relationship between the observed maximal extractable NR activity of the leaves and their NO ₃ ^– content was observed in plants grown in nitrogen replete conditions at low irradiance (170 mol photons·m^–2 ·s^–1). This relationship disappeared at higher irradiance (450 mol photons·m^–2·S^–1) because the maximal extractable NR activity in the leaves of the wild type plants in these conditions increased to a level that was similar to, or greater than that found in constitutive NR-expressors. Much more NO ₃ ^– accumulated in the leaves of plants grown at 450 mol photons·m^–2·s^–1 than in those grown at 170 mol photons·m^–2·s^–1 in N-replete conditions. The foliar NO ₃ ^– level and maximal NR activity decreased with the imposition of N-deficiency in all plant types such that after prolonged exposure to nitrogen depletion very little NO ₃ ^– was found in the leaves and NR activity had decreased to almost zero. The activity of NR decreased under conditions of nitrogen deficiency. This regulation is multifactoral since there is no regulation of NR gene expression by NO ₃ ^– in the constitutive NR-expressors. We conclude that the NR protein is specifically targetted for destruction under nitrogen deficiency. Consequently, constitutive expression of NR activity does not benefit the plant in terms of increased biomass production in conditions of limiting nitrogen.Abbreviations Chl chlorophyll - N nitrogen - NR NADH-nitrate reductase - WT wild type     

Enhancement of production of cloned α-amylase by lactic acid feeding from recombinant Saccharomyces cerevisiae using a SUC2 promoter

-Amylase production was higher (13 units ml^–1) when a recombinant Saccharomyces cerevisiae containing a SUC2 promoter was grown with 10 g lactic acid l^–1 than without addition (8 units ml^–1). With continuous lactic acid feeding in the inducing phase, -amylase increased to 79 units ml^–1 in a 1-l jar fermenter.     

Photosynthetic Response to Irradiance in Valeriana jatamansi Jones,a Threatened Understorey Medicinal Herb of Western Himalaya

Net photosynthetic rate (P _N) of Valeriana jatamansi plants, grown under nylon net shade or under different tree canopies, was saturated with photons at 1 000 mol m^–2 s^–1 photosynthetic photon-flux-density (PPFD), whereas open-grown plants were able to photosynthesise even at higher PPFD, e.g. of 2 000 mol m^–2 s^–1. Plants grown under net shade had higher total chlorophyll (Chl) content per unit area of leaf surface. However, Chl a/b ratio was maximal in open-grown plants, but remained unchanged in plants grown in nylon net shade and under different tree canopies. Sun-grown plants had thicker leaves (higher leaf mass per leaf area unit), higher wax content, and higher P _N than shade grown plants. Thus V. jatamansi is able to acclimate to high PPFD and therefore this Himalayan species may be cultivated in open habitat to meet the ever-increasing industrial demand.