Plasma Membrane Lipid Research Articles

Exploring the Molecular Basis of Anticancer Activity in Various Moss Species Against Colorectal Cancer Cells

Background: Mushrooms are shown to protect against the side effects of cancer. Therefore, mushrooms with proven anticancer properties and active ingredients are fascinating in the search for new cancer drugs. Objective: In this study, the effects of extracts from Hericium coralloides (M1), Lactarius deliciosus (M2), Lepista nuda (M3), Pleurotus ostreatus (M4), and Suillus collitinus (M5) together on HCT116 were investigated. Mesenchymal stem cells (MSCs) were used to study the effect on healthy cells. Methods: MTT was used to determine cell viability. Dose-response curves were generated, the IC50 values of the compounds were calculated, and the effect of the extracts was compared using it. The FTIR was used to analyze the quantitative changes of the cellular components. Results and Discussion: The evaluation of the IC50 values of all fungal species showed that they reduced the cell viability of HCT116 cells. In contrast, no significant reduction in cell viability was observed in MSCs. Changes in the ratio of cell membrane lipids, proteins, and cell nucleic acids between control and fungal-treated HCT116 cells were detected by FTIR. Many of the chemotherapeutic agents are of plant origin, and many resources should still be explored to inhibit the side effects of cancer therapy. Conclusion: The data obtained through this experiment will serve as a reference for studies to be a new source of anticancer drugs in modern pharmacology.

Exploring the interplay between yeast cell membrane lipid adaptation and physiological response to acetic acid stress.

In the present study, we successfully engineered a yeast strain that could grow under high acetic acid stress by regulating its diacylglycerol metabolism. We compared how the plasma membrane and total cell membranes responded to acetic acid by adjusting their lipid content. By combining physiological and lipidomics analyses in cells cultivated in the absence or presence of acetic acid, we found that the capacity of the membrane to adapt lipid composition together with sufficient energy supply influenced membrane properties in response to stress. We suggest that potentiating the intracellular energy system or enhancing lipid transport to destination membranes should be taken into account when designing membrane engineering strategies. The findings highlight new directions for future yeast cell factory engineering.

Chorein deficiency promotes ferroptosis.

Ferroptosis is a type of programmed cell death owed to an intracellular accumulation of iron resulting in the generation reactive oxygen species, which in turn can cause peroxidation of plasma membrane lipids and ultimately result in cell death. We investigated the potential involvement of VPS13A deficiency in ferroptosis. The VPS13A gene encodes for chorein, and its deficiency is a molecular cause of chorea-acanthocytosis (ChAc), a Huntington-like disease with neurodegeneration in the striatum. In our previous study, we found male infertility characterized by increased malondialdehyde staining of the spermatozoa in the testes of the ChAc model mice. Thus, in this study we performed metabolome analysis of sperm extracted from the epididymis of the ChAc model mice, which revealed decreased cystine levels, suggesting an association between chorein deficiency and ferroptosis. We then investigated the role of chorein in ferroptosis using VPS13A knockdown (VPS13A-KD) HEK293 cells. We found that VPS13A-KD cells displayed a significantly diminished resistance to tert-Butyl hydroperoxide (tBHP)-induced lipid peroxidation and cell death compared to control cells, which could be rescued by treatment with ferrostatin-1. Moreover, VPS13A-KD cells showed Fe(II) accumulation, suggesting an impaired capacity for divalent iron removal. In the cytosolic fraction of VPS13A-KD cells, the protein level of glutathione peroxidase 4 (GPX4) was significantly reduced, suggesting that dysfunction of chorein impairs GPX4 transport, thereby facilitating ferroptosis. These results suggest that ferroptosis may contribute to neurodegeneration in ChAc caused by loss of chorein function.

Metabolomic profiling reveals new insights into human adenovirus type 7 infection

Human adenovirus type 7 (HAdV-7) is a prominent pathogen that causes severe pneumonia in children in China. However, the interaction between HAdV-7 infection and host metabolism is still poorly understood. To gain a comprehensive understanding of the metabolic interplay between host cells and the virus, we analysed the energy and lipid metabolism profiles of the HAdV-7-infected lung cancer cell line A549 by ultrahigh-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (ESI-QTRAP-MS/MS). Our study revealed significant alterations in various metabolic processes, including the tricarboxylic acid cycle, purine and pyrimidine metabolism, amino acid metabolism, nucleotide metabolism, and lipid metabolism, in A549 cells after HAdV-7 infection. Moreover, HAdV-7 infection stimulated enhanced synthesis of membrane lipids in A549 cells. These findings emphasize the crucial role of metabolism in viral infection and suggest that modulating host cell metabolism could be a promising approach for targeted drug development and infection control.

Celastrol-Loaded Hyaluronic Acid/Cancer Cell Membrane Lipid Nanoparticles for Targeted Hepatocellular Carcinoma Prevention.

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide, and its prevention and treatment face severe challenges. It is crucial to improve the targeting of drugs on tumor cells and tissues. Celastrol (CeT), as an active ingredient of traditional Chinese medicine, possesses strong antitumor effects, especially in triggering apoptosis of HCC. However, due to its toxicity and lack of targeting, its application is greatly limited. HMCLPs, a nano-biomimetic platform carrying CeT with controllable drug release, enhanced targeting, and immunocompatibility, were developed for the first time, which can be used for the treatment of HCC. By utilizing homologous cell membranes and hyaluronic acid (HA), HMCLPs can precisely target tumor regions and release CeT in a controlled manner. Both in vitro and in vivo studies have demonstrated that HMCLPs loaded with CeT significantly increased the accumulation of reactive oxygen species (ROS), induced mitochondrial damage, and triggered apoptosis of HCC cells, resulting in effective treatment with minimal adverse reaction. The development of HMCLPs as a nanocarrier system for CeT delivery offers a promising therapeutic strategy for HCC. This innovative approach improves the targeted delivery and bioavailability of CeT, dramatically induces apoptosis in HCC cells, and exerts its powerful antitumor effects while minimizing systemic toxicity. The present study highlights the potential of combining innovative nanocarriers with powerful natural compounds such as CeT to enhance efficacy and reduce toxicity.

A Lipid-Raft Theory of Alzheimer's Disease.

I present a theory of Alzheimer's disease (AD) that explains its symptoms, pathology, and risk factors. To do this, I introduce a new theory of brain plasticity that elucidates the physiological roles of AD-related agents. New events generate synaptic and branching candidates competing for long-term enhancement. Competition resolution crucially depends on the formation of membrane lipid rafts, which requires astrocyte-produced cholesterol. Sporadic AD is caused by impaired formation of plasma-membrane lipid rafts, preventing the conversion of short- to long-term memory and yielding excessive tau phosphorylation, intracellular cholesterol accumulation, synaptic dysfunction, and neurodegeneration. Amyloid β (Aβ) production is promoted by cholesterol during the switch to competition resolution, and cholesterol accumulation stimulates chronic Aβ production, secretion, and aggregation. The theory addresses all of the major established facts known about the disease and is supported by strong evidence.

A fungal phospholipase C involved in the degradation of plant glycosylinositol phosphorylceramides during Arabidopsis/Botrytis interaction

This study investigates the presence and significance of phosphorylated oligosaccharides that accumulate during the interaction between Arabidopsis thaliana and Botrytis cinerea, a necrotrophic fungus that poses a major threat to crops worldwide. While previous research has extensively characterized cell wall-derived molecules during fungal infection, the role of plasma membrane-derived ones remains unclear. Here, we reveal the discovery of inositol phosphate glycans (IPGs) released during infection, originating from plant sphingolipids, specifically glycosylinositol phosphorylceramides (GIPC). Advanced chromatography, mass spectrometry techniques and molecular biology were employed to identify these IPGs, and determine their origins. In addition to the well-characterized role of B. cinerea in releasing cell wall-degrading enzymes, this research suggests that B. cinerea’s enzymatic machinery may also target the degradation of the plant plasma membrane. As a consequence of this, IPGs identical to those generated by the host plant are released, most likely due to activity of a putative phospholipase C that acts on GIPC plasma membrane lipids. These insights could pave the way for developing new strategies to enhance crop resistance by focusing on membrane integrity in addition to cell wall fortification.

Membrane structure-responsive lipid scrambling by TMEM63B to control plasma membrane lipid distribution.

Phospholipids are asymmetrically distributed in the plasma membrane (PM), with phosphatidylcholine and sphingomyelin abundant in the outer leaflet. However, the mechanisms by which their distribution is regulated remain unclear. Here, we show that transmembrane protein 63B (TMEM63B) functions as a membrane structure-responsive lipid scramblase localized at the PM and lysosomes, activating bidirectional lipid translocation upon changes in membrane curvature and thickness. TMEM63B contains two intracellular loops with palmitoylated cysteine residue clusters essential for its scrambling function. TMEM63B deficiency alters phosphatidylcholine and sphingomyelin distributions in the PM. Persons with heterozygous mutations in TMEM63B are known to develop neurodevelopmental disorders. We show that V44M, the most frequent substitution, confers constitutive scramblase activity on TMEM63B, disrupting PM phospholipid asymmetry. We determined the cryo-electron microscopy structures of TMEM63B in its open and closed conformations, uncovering a lipid translocation pathway formed in response to changes in the membrane environment. Together, our results identify TMEM63B as a membrane structure-responsive scramblase that controls PM lipid distribution and we reveal the molecular basis for lipid scrambling and its biological importance.

Molecular mechanism of GIRK2 channel gating modulated by cholesteryl hemisuccinate.

Cholesterol, an essential lipid of cell membranes, regulates G protein-gated inwardly rectifying potassium (GIRK) channel activity. Previous studies have shown that cholesterol activates GIRK2 homotetrameric channels, which are expressed in dopaminergic neurons of the brain. Deletion of GIRK2 channels affects both GIRK2 homo- and heterotetrames and can lead to abnormal neuronal excitability, including conditions such as epilepsy and addiction. A 3.5Å cryo-EM structure of GIRK2 in complex with CHS (cholesteryl hemisuccinate) and PIP2 (phosphatidylinositol 4,5-bisphosphate) has been solved. This structure provides the opportunity to study GIRK2 channel gating dynamics regulated by cholesterol using gating molecular dynamics (GMD) simulations. In the present study, we conducted microsecond-long GMD simulations on the GIRK2 channel in its APO, PIP2, and PIP2/CHS bound states, followed by systematic analysis to gain molecular insights into how CHS modulates GIRK2 channel gating. We found that CHS binding facilitates GIRK2 channel opening, with 43 K+ ion permeation events observed, compared to 0 and 2 K+ ion permeation events for GIRK2-APO and GIRK2/PIP2, respectively. Binding of CHS to the GIRK2 channel enhances PIP2 and channel interactions, which is consistent with previous experimental results. The negatively charged PIP2 alters the internal electrostatic potential field in the channel and lowers the negative free energy barrier for K+ ion permeation.

Glucose-dependent glycosphingolipid biosynthesis fuels CD8+ T cell function and tumor control.

Glucose is essential for T cell proliferation and function, yet its specific metabolic roles in vivo remain poorly defined. Here, we identify glycosphingolipid (GSL) biosynthesis as a key pathway fueled by glucose that enables CD8+ T cell expansion and cytotoxic function in vivo. Using 13C-based stable isotope tracing, we demonstrate that CD8+ effector T cells use glucose to synthesize uridine diphosphate-glucose (UDP-Glc), a precursor for glycogen, glycan, and GSL biosynthesis. Inhibiting GSL production by targeting the enzymes UGP2 or UGCG impairs CD8+ T cell expansion and cytolytic activity without affecting glucose-dependent energy production. Mechanistically, we show that glucose-dependent GSL biosynthesis is required for plasma membrane lipid raft integrity and aggregation following TCR stimulation. Moreover, UGCG-deficient CD8+ T cells display reduced granzyme expression and tumor control in vivo. Together, our data establish GSL biosynthesis as a critical metabolic fate of glucose-independent of energy production-required for CD8+ T cell responses in vivo.

Radioprotective potential of pomegranate peel extract against gamma irradiation-induced hazards

BackgroundWhile gamma irradiation’s damaging biological effects are well-established, the natural radioprotective agents from agricultural waste remain an underexplored area of significant potential.Aim of studyThis study was to investigate the novel use of pomegranate peel ethanol extract (PE) as a radioprotective agent against gamma radiation damage.MethodsWe pretreated Wistar rats with PE (100 mg/kg) for 14 days prior to 6 Gy gamma irradiation. We analyzed blood biochemicals, oxidative stress, and inflammatory markers. These included tests of red cell membrane integrity, lipid and protein oxidation, antioxidant enzyme levels, and cytokine profiles.ResultsThe study showed that PE demonstrated remarkable radioprotective effects across multiple parameters. Antioxidants were significantly enhanced, as evidenced by increased glutathione peroxidase activity (87.00 ± 6.11 mg/ml in PE-treated irradiated rats compared to 26.40 ± 1.21 mg/ml in irradiated controls). Oxidative damage was markedly reduced, with MDA levels dropping from 9.59 ± 0.24 nmol/ml in irradiated controls to near-control levels in PE-treated rats. Notably, PE treatment resulted in unprecedented maintenance of red blood cell membrane integrity post-irradiation. Furthermore, PE exhibited novel modulation of inflammatory cytokines, effectively reducing pro-inflammatory markers IL-6 and TNF-α while simultaneously boosting anti-inflammatory IL-4 and IL-10 levels. These multifaceted protective effects highlight PE’s potential as a comprehensive radioprotective agent.ConclusionThis study presents PE as an effective new natural radioprotective agent. Its protective effect is due to its high polyphenol content, which enhances antioxidant defenses, reduces oxidative damage, and prevents inflammation. The findings open new avenues for sustainable, cost-effective radioprotection strategies and demonstrate the potential for repurposing agricultural byproducts for critical health applications.

An Overview of Multifaceted Applications and the Future Prospects of Glyceroglycolipids in Plants.

Glyceroglycolipids (GGLs) are a class of lipid molecules that contain a glycerol backbone and one or more carbohydrate moieties, giving them amphipathic properties with both hydrophilic and hydrophobic regions. This amphipathic nature is fundamental for composing cell membrane lipid bilayers. These compounds are primarily distributed on the inner chloroplast membranes of plants and exhibit a unique structure with numerous biological activities. Moreover, GGLs play a pivotal role in photosynthesis and energy conversion in plants and effectively respond to environmental stressors. This Review discusses the distribution, synthesis pathways, and functions of GGLs in plants and describes the recent updates on various methods for extracting, isolating, and identifying GGLs. Finally, this Review discusses the biological activities of plant GGLs, including their anti-inflammatory, antiviral, and anticancer properties, and highlights their potential applications in the fields of pharmaceuticals, food, and cosmetics. This Review provides insights into GGLs, offering research support for the application of these natural molecules in the realm of holistic health.

Potency of Red Guava Fruitghurt as an Antioxidant

Antioxidants are compounds needed by the body to protect body cells from damage caused by free radicals. Free radicals can damage macromolecules such as cell membrane lipids, DNA, and proteins, and cause cell oxidative stress. Red Guava Fruitghurt is a probiotic with the basic ingredients of fruit. The purpose of this study is to determine the effect of fruitghurt on the MDA levels in the blood of mice induced by CCl4. This was an experimental study conducted using mice (Mus musculus) which were divided into three treatment groups – the negative control group (that were not induced and were not given fruitghurt), the positive control group (that were induced with CCl4 but not given fruitghurt), and the treatment group (that were induced with CCl4 and given fruitghurt). The data obtained in the study were analyzed using the one-way ANOVA test, and the results showed significant differences between the treatment groups. Giving fruitghurt to the P1 group had a significant effect on reducing malondialdehyde levels compared to the positive control group, with a P-value of 0.03. Lactobacillus acidophilus bacteria found in this fruitghurt can reduce oxidative stress by inhibiting ascorbic acid oxidation, reducing activity and capturing radial superoxide anions, hydrogen peroxide, and free radicals, and inhibiting lipid oxidation. So this fruitghurt has antioxidant properties. This is also strengthened by the content of red guava which is rich in phenolics, flavonoids, and vitamin C that have good free radical scavenging activity, so guava fruit is a natural source of antioxidants. Keywords: antioxidants, fruitghurt, malon dialdehyde, probiotics, red guava

A fatty acid-ordered plasma membrane environment is critical for Ebola virus matrix protein assembly and budding

Plasma membrane (PM) domains and order phases have been shown to play a key role in the assembly, release, and entry of several lipid-enveloped viruses. In the present study, we provide a mechanistic understanding of the Ebola virus (EBOV) matrix protein VP40 interaction with PM lipids and their effect on VP40 oligomerization, a crucial step for viral assembly and budding. VP40 matrix formation is sufficient to induce changes in the PM fluidity. We demonstrate that the distance between the lipid headgroups, the fatty acid tail saturation, and the PM order are important factors for the stability of VP40 binding and oligomerization at the PM. The use of FDA-approved drugs to fluidize the PM destabilizes the viral matrix assembly leading to a reduction in budding efficiency. Overall, these findings support an EBOV assembly mechanism that reaches beyond lipid headgroup specificity by using ordered PM lipid regions independent of cholesterol.

High-Resolution Magic-Angle Spinning Nuclear Magnetic Resonance Identifies Impairment of Metabolism by T-2 Toxin, in Relation to Toxicity, in Zebrafish Embryo Model.

Among the widespread trichothecene mycotoxins, T-2 toxin is considered the most toxic congener. In the present study, we utilized high-resolution magic-angle spinning nuclear magnetic resonance (HRMAS NMR), coupled to the zebrafish (Danio rerio) embryo model, as a toxicometabolomics approach to elucidate the cellular, molecular and biochemical pathways associated with T-2 toxicity. Aligned with previous studies in the zebrafish embryo model, exposure to T-2 toxin was lethal in the high parts-per-billion (ppb) range, with a median lethal concentration (LC50) of 105 ppb. Exposure to the toxins was, furthermore, associated with system-specific alterations in the production of reactive oxygen species (ROS), including decreased ROS production in the liver and increased ROS in the brain region, in the exposed embryos. Moreover, metabolic profiling based on HRMAS NMR revealed the modulation of numerous, interrelated metabolites, specifically including those associated with (1) phase I and II detoxification, and antioxidant pathways; (2) disruption of the phosphocholine lipids of cell membranes; (3) mitochondrial energy metabolism, including apparent disruption of the tricarboxylic acid (TCA) cycle, and the electron transport chain of oxidative phosphorylation, as well as "upstream" effects on carbohydrate, i.e., glucose metabolism; and (4) several compensatory catabolic pathways. Taken together, these observations enabled development of an integrated, system-level model of T-2 toxicity in relation to human and animal health.

Impact of semen cryopreservation season on invitro embryo production of prepubertal goat oocytes.

Goat production is affected by reproductive seasonality. Invitro embryo production (IVEP) could overcome this effect. This study aimed to evaluate the impact of the season of semen collection/freezing on IVEP of prepubertal goat oocytes and on sperm quality and functionality concerning capacitation. Semen from six fertile bucks was collected, pooled and cryopreserved in spring and autumn and used for IVEP of oocytes recovered during the breeding season. Oocytes were IVM in TCM-199 with hormones, EGF and cysteamine; fertilized and cultured in BO-IVF and BO-IVC media (IVF Bioscience, UK). Semen samples were assessed at 0 and 3 h after culture in capacitating (BO-IVF, CAP) and non-capacitating conditions for sperm plasma membrane and acrosome integrity, mitochondrial membrane potential (MMP), intracellular calcium and plasma membrane lipid disorder. Blastocyst production was higher with spring sperm compared to autumn (12.0% vs. 2.1%, respectively; p < .05). After CAP, acrosome reaction and intracellular calcium were higher (p < .05) in spring than autumn sperm. No differences were found in other sperm parameters. In conclusion, seasonal variations in the IVEP of prepubertal goats could be linked to differences in sperm ability to undergo invitro capacitation.

A phosphorylation-controlled switch confers cell cycle-dependent protein relocalization.

Tools for acute manipulation of protein localization enable elucidation of spatiotemporally defined functions, but their reliance on exogenous triggers can interfere with cell physiology. This limitation is particularly apparent for studying mitosis, whose highly choreographed events are sensitive to perturbations. Here we exploit the serendipitous discovery of a phosphorylation-controlled, cell cycle-dependent localization change of the adaptor protein PLEKHA5 to develop a system for mitosis-specific protein recruitment to the plasma membrane that requires no exogenous stimulus. Mitosis-enabled anchor-away/recruiter system comprises an engineered, 15 kDa module derived from PLEKHA5 capable of recruiting functional protein cargoes to the plasma membrane during mitosis, either through direct fusion or via GFP-GFP nanobody interaction. Applications of the mitosis-enabled anchor-away/recruiter system include both knock sideways to rapidly extract proteins from their native localizations during mitosis and conditional recruitment of lipid-metabolizing enzymes for mitosis-selective editing of plasma membrane lipid content, without the need for exogenous triggers or perturbative synchronization methods.

HIV-1 assembly - when virology meets biophysics.

Cells naturally produce vesicles that bud from different lipid membranes using dedicated molecular machineries. Enveloped RNA viruses, including human immunodeficiency virus type 1 (HIV-1), also generate particles that bud from host cell membranes by hijacking cellular factors and signaling pathways similar to those involved in the budding of extracellular vesicles. HIV-1 buds from the host cell plasma membrane mainly via the self-assembly of Gag, a structural protein. Gag is a polyprotein that forms assembly complexes containing viral genomic RNA (gRNA), host cell lipids and proteins. HIV-1 Gag binds and segregates host cell plasma membrane lipids while self-assembling simultaneously on the gRNA and the plasma membrane. This self-assembly causes membrane bending and formation of a new viral particle with the help of host cell proteins, likely including cortical actin-associated factors. However, it is unclear whether the energy of Gag self-assembly is sufficient to generate new HIV-1 particles. In this Review, we discuss these processes in the light of the past and recent virology literature, incorporating lessons from studies on the quantitative biophysics of viral self-assembly, and explore how Gag might reorganize the plasma membrane and divert host cell membrane curving proteins and cortical actin-related factors to achieve particle assembly and budding.

Photodynamic antibacterial activity of CoTiO3/ZnIn2S4 Z-type heterojunction and its efficient enhancement mechanism by reactive oxygen species

The Solar-powered photocatalytic antibacterial technology has received widespread attention as a safe and efficient environmental self-cleaning technology, but its application remains a challenging task. Taking inspiration from the design of heterojunction structures in photocatalytic materials, this study employed a precipitation in-situ synthesis method to successfully construct a CoTiO3/ZnIn2S4 (CTZIS) Z-scheme heterojunction with excellent photocatalytic performance by depositing layered ZnIn2S4 nanosheets in situ on a rod-shaped CoTiO3 support. After visible-light irradiation for 20 min, the CTZIS antimicrobial agent (100 μg/mL) exhibited an ultra-high bacterial inactivation rate of 99.9 %, which was 10 and 11 times higher than that of ZnIn2S4 and CoTiO3 under the same conditions, using E. coli as the study object. Meanwhile, bacteria treated with CTZIS exhibited the highest degree of cell membrane lipid peroxidation and the lowest activity of intracellular respiratory chain dehydrogenase, demonstrating excellent antibacterial performance. After testing and calculation, it was found that the excellent antibacterial activity comes from the solid gap electric field between heterojunctions, which enhances the effective spatial separation of photo-generated carriers and effectively increases the quantum yield of reactive oxygen species (ROS). The synergistic antibacterial mechanism of CTZIS from bacterial surface to bacterial interior co-damage was revealed, in which the production of • O2‐ and •OH are a key active substance in the process of bacterial oxidative stress inactivation.

Exogenous Methyl Jasmonate Alleviates Mechanical Damage in Banana Fruit by Regulating Membrane Lipid Metabolism

Bananas are economically important fruits, but they are vulnerable to mechanical damage during harvesting and transport. This study examined the effects of methyl jasmonate (MeJA) on the cell membrane integrity and membrane lipid metabolism of wounded banana fruits after harvest. The results showed that 10 and 50 μM MeJA treatments on mechanically wounded bananas significantly delayed ripening and senescence in comparison with the control. At the end of storage, MeJA-treated groups showed a significant reduction in electrolyte leakage and malondialdehyde content, indicating that MeJA protected cell membrane integrity. MeJA also led to a significant decrease in the activity of antioxidant enzymes, including lipoxygenase, diacylglycerol kinase, and lipid phosphate phosphatase. Furthermore, MeJA reduced phospholipase (C and D), phosphatidic acid, and diacylglycerol levels, as well as slowed down the decrease in phosphatidylcholine and phosphatidylinositol contents. Compared to the control, MeJA significantly downregulated the expression of MaPLDγ, MaPLDα, and MaPLDζ. Therefore, MeJA treatment could be a reliable method to delay the senescence of harvested banana fruits subjected to mechanical wounding.