Muhammad Imran Arshad

Ethylene in Plant Physiology

Ethylene (C2H4) is a plant hormone that is involved in the regulation of many physiological responses (Abeles et al., 1992; Mattoo and Suttle, 1991; Reid, 1995). Initially designated as a “ripening hormone”, C2H4 is involved in almost all growth and developmental processes ranging from germination of seeds to senescence of various organs and in many responses to environmental stress. Ethylene production occurs in all plant organs, including roots, stems, leaves, buds, tubers, bulbs, flowers, and seeds, but the magnitude of C2H4 production varies from organ to organ and is dependent on growth and developmental processes. Recent scientific progress has increased the understanding of biosynthetic pathways and enzymes involved in C2H4 production including genetic control, leading to the development of several ways to manipulate C2H4 production by genetic alteration of plants (Kende, 1993; Fluhr and Mattoo, 1996; Zarembinski and Theologis, 1994; Stella et al, 1996; Woltering and de Vrije, 1995).

Factors Affecting Microbial Production of Ethylene

Since the publications of Biale (1940) and Miller et al. (1940) on C2H4 production by Penicillium digitatum, several workers have screened numerous microorganisms for their ability to produce C2H4. These studies revealed that a diverse group of soil microbiota, including pathogens, are very active in producing C2H4. According to Primrose (1979), C2H4 is synthesized by many species of bacteria and fungi, but is oxidized by only a limited number of microorganisms. Out of 166 strains of fungi, yeast, bacteria, and actinomycetes, 49 produced C2H4 (Fukuda et al., 1984). Among them 62% were molds, 20% were yeasts, 21% were bacteria, and 6% were actinomycetes. Out of 228 soil fungi tested by Ilag and Curtis (1968), 58 (25%) produced C2H4 , whereas 20 unidentified actinomycetes also produced C2H4. El-Sharouny (1984) reported that 31% of 80 fungal species isolated from diseased roots were capable of producing C2H4. Arshad and Frankenberger (1989) found that corn rhizosphere is quite rich with microbiota capable of producing C2H4 derived from L-methionine (MET), and among these, fungi were the most preponderant. Babiker and Pepper (1984) isolated 14 soil fungi that produced C2H4 in the presence of MET. Recently, Arshad and Akhter (unpublished data) screened rhizosphere microflora of maize, wheat, tomato and potato and found that fungal isolates predominently produced C2H4 from exogenous supplied L-MET or 2-oxo-4-methylthiobutyric acid (KMBA).

Crosstalk of liver immune cells and cell death mechanisms in different murine models of liver injury and its clinical relevance

Background Liver inflammation or hepatitis is a result of pluripotent interactions of cell death molecules, cytokines, chemokines and the resident immune cells collectively called as microenvironment. The interplay of these inflammatory mediators and switching of immune responses during hepatotoxic, viral, drug-induced and immune cell-mediated hepatitis decide the fate of liver pathology. The present review aimed to describe the mechanisms of liver injury, its relevance to human liver pathology and insights for the future therapeutic interventions. Data sources The data of mouse hepatic models and relevant human liver diseases presented in this review are systematically collected from PubMed, ScienceDirect and the Web of Science databases published in English. Results The hepatotoxic liver injury in mice induced by the metabolites of CCl4, acetaminophen or alcohol represent necrotic cell death with activation of cytochrome pathway, formation of reactive oxygen species (ROS) and mitochondrial damage. The Fas or TNF-α induced apoptotic liver injury was dependent on activation of caspases, release of cytochrome c and apoptosome formation. The ConA-hepatitis demonstrated the involvement of TRAIL-dependent necrotic/necroptotic cell death with activation of RIPK1/3. The α-GalCer-induced liver injury was mediated by TNF-α. The LPS-induced hepatitis involved TNF-α, Fas/FasL, and perforin/granzyme cell death pathways. The MHV3 or Poly(I:C) induced liver injury was mediated by natural killer cells and TNF-α signaling. The necrotic ischemia-reperfusion liver injury was mediated by hypoxia, ROS, and pro-inflammatory cytokines; however, necroptotic cell death was found in partial hepatectomy. The crucial role of immune cells and cell death mediators in viral hepatitis (HBV, HCV), drug-induced liver injury, non-alcoholic fatty liver disease and alcoholic liver disease in human were discussed. Conclusions The mouse animal models of hepatitis provide a parallel approach for the study of human liver pathology. Blocking or stimulating the pathways associated with liver cell death could unveil the novel therapeutic strategies in the management of liver diseases.

Recapitulation of the anti-Idiotype antibodies as vaccine candidate

AbstractᅟThe foreign antigen that enters into the body is detected by the immune system through antigen presenting cells leading to the production of antibodies. The use of anti-idiotype antibodies is a new way to excite the immune response that identifies and eliminates the foreign antigens entered into the body. These Anti-idiotype antibodies have the ability to decrease the non-specific binding of the antigenic protein epitopes because of high specificity for the antigenic determinants. The anti-idiotype antibodies attach to the paratope of idiotype antibody and stimulate a precise immune reaction same as that of external antigen. The anti-idiotype antibodies are the peerless therapeutic candidate as they mimic the antigenic structure and potentiate antibody and cell-mediated immunity. Even in the absence of foreign antigen, these anti-idiotype antibodies have the potential to provide long-lasting immunity. The present review is about immune regulations by anti-idiotype antibodies with some success therapeutic stories.The previous research analysis is evidence of anti-idiotype antibodies as an excellent candidate for the development of both human and animal vaccines although it has some gaps that are needed to be addressed.

Ethylene in Agriculture: Synthetic and Natural Sources and Applications

Ethylene as well as other plant growth regulators (PGRs) are important chemicals in agricultural production. Plant growth regulators are now used worldwide on a diversity of crops each year (Thomas, 1982). The plant hormone, C2H4 strongly influences nearly every development stage in plant growth, from germination to fruit ripening and senescence. Moreover, its critical role in post-harvest physiology of agricultural products has also been well documented. Obviously, a compound with so many different effects may be useful in many ways to modify plant growth and development as required by growers. However, many factors including its gaseous nature and some negative effects on plant growth, restrict the extensive practical usefulness of C2H4. Furthermore, the consistency of results observed under controlled experimental conditions may not always be achieved under conditions of practical applications (i.e., under natural field conditions).

Psychosocial-Stress, Liver Regeneration and Weight Gain: a Conspicuous Pathophysiological Triad

Psychosocial stress alters several physiological parameters resulting in multiple disorders, particularly compromising the immune system thereby provoking various diseases including liver disorders. However, the plausible underlying mechanisms remain elusive. Recent literature provides mechanistic evidences of detrimental effects of psychosocial stress on physiology of different body organs including liver. The data of stress-induced pathophysiological changes in liver functions and obesity were systematically collected from PubMed, ScienceDirect and the Web of Science Databases published in English. Stress and glucocorticoids (GCs) control food intake and energy expenditure through appetite stimulators neuropeptide Y (NYP) and agouti-related protein (AgRP) in hypothalamus. Principle effectors of the activated hypothalamic-pituitary-adrenal (HPA) axis in response to psychosocial stress are proopiomelanocortin (POMC)-derived adrenocorticotropic hormone (ACTH) and GCs. Stress-induced GCs hyper-secretion triggers glucocorticoid receptor (GR)-dependent transcriptional factor, nuclear factor kappa B (NFκB), which interferes TNFα-IL6 and keap1-Nrf2 pathways in liver regeneration and obesity through fine-tuning of TNFα, IL6 and Nrf2 signaling. In this review, it is contrived upon existing evidence to put forward a model whereby exposure to life-stress has a prominent impact over weight gain and can alter the regenerative mode of a damaged liver through Keap1-Nrf2 and TNFa-IL6 pathways.

Emergence of Extended Spectrum Beta-Lactamases-Producing Strains Belonging to Cefotaxime-M-1 Class from Intensive Care Units Patients and Environmental Surfaces in Pakistan

Aim : The emergence of multidrug-resistant (MDR) bacteria is the most dangerous threat for the treatment of infectious diseases. The aim of this study was to detect and characterize extended spectrum beta-lactamases (ESBLs) and carbapenemaseproducing Klebsiella pneumoniae and Escherichia coli among patients and environment of intensive care units (ICUs) of three tertiary care hospitals in Pakistan. Materials and Methods : A total of 82 samples from ICUs patients and inanimate environment (injection trays, wash basins, door handles, hand swabs of professionals, and ICU fridges) were screened for ESBL by culturing on CHROMagar-ESBL. ESBL and carbapenemases production were confirmed by double disc synergy test and modified Hodges test, respectively. Polymerase chain reaction was used to detect ESBL encoding genes bla cefotaxime (CTX-M), bla CTX-M-1, bla CTX-M-2, bla CTX-M-9, bla TEM, blaSHV and carbapenemase genes bla KPC, bla New Delhi metallo-beta-lactamase-1, bla OXA-48 and bla VIM. Results : Overall, ESBL production was found high 30/82 (36.5%) among isolates of which 15.8% K. pneumoniae and 20.7% E. coli were identified. All the K. pneumoniae and majority of E. coli isolates were MDR, i.e., resistance to three or more antimicrobial categories. Molecular characterization showed the bla CTX-M-1 as the predominant genotype found in 17/21 (80%) of the isolates. None of the strains was found positive for carbapenemase-encoding genes. Conclusion : In conclusion, this study demonstrates the emergence of MDR ESBL producing strains among ICU patients and hospital environment, posing a serious threat for the control of nosocomial infections.

Ethylene in Symbiosis

The involvement of C2H4 in plant responses to a variety of biotic and abiotic stress is well known (Abeles et al., 1992). The biotic stress includes parasitic and non-parasitic plant-microbe interactions, which play an important role in plant growth and development (Arshad and Frankenberger, 1992, 1993, 1998; Frankenberger and Arshad, 1995; Boiler, 1991; Abeles et al., 1992; Beyrle, 1995; Hirsch et al., 1997; Hirsch and Yang, 1994). The role of C2H4 in symbiotic associations is the major focus of this chapter.

Biochemistry of Microbial Production of Ethylene

The ability of microorganisms to derive C2H4 from a variety of compounds has made the biochemistry of microbial production of C2H4 very complex. The literature indicates that C2H4 -producing microorganisms do not follow the same pathway operative in higher plants (MET → SAM → ACC → C2H4). This subject has been reviewed elsewhere (Fukuda and Ogawa, 1991; Fukuda et al., 1993; Arshad and Frankenberger, 1993, 1998; Frankenberger and Arshad, 1995). However, many microorganisms do synthesize C2H4 from methionine. This chapter is dedicated to the microbial biosynthesis pathways involving substrates, enzymes, inhibitors and intermediary metabolism.

Ethylene in Pathogenesis

Stress C2H4 represents collectively the accelerated C2H4 production in plants induced by various abiotic (wounding, physical load, chilling temperatures, waterlogging, and exposure to chemicals) and biotic (disease and insect damage) factors. Plant C2H4 synthesis is often significantly increased during infection by pathogens and can also be induced by treatment with pathogen-derived elicitors (Boiler, 1991; Pegg, 1976b; Frankenberger and Arshad, 1995). It has been proposed that C2H4 acts as a messenger during plant-microbe interactions. This accelerated stress C2H4 during pathogenesis may be a stimulus for defense responses that lead to resistance or conversely, it may play a role in disease symptom development and in the weakening of endogenous resistance (Ben-David et al., 1986; Boiler, 1991; Pegg, 1976b; Stall and Hall, 1984; Yang and Hoffman, 1984; Abeles et al., 1992; Lund et al., 1998). By using various mutants of soybean altered in C2H4 sensitivity and a number of pathogens (virulent and avirulent), Hoffman et al. (1999) concluded that the reduced C2H4 sensitivity could be beneficial against some pathogens but deletrious to resistance against other pathogens. This chapter deals mainly with infection-induced C2H4 production and its possible role in disease or resistance development in the infected hosts. Excellent reviews related to this subject are published elsewhere (Abeles et al., 1992; Boiler, 1982, 1991, 1990; Hislop et al., 1973b; Archer and Hislop, 1975; Pegg, 1976b; Frankenberger and Arshad, 1995).