CHARACTERIZATION OF AN EMBRYOGENIC CELL SUSPENSION CULTURE DERIVED FROM CULTURED INFLORESCENCES OF PENNISETUM AMERICANUM (PEARL MILLET,GRAMINEAE)

An embryogenic suspension culture was established from cultured inflorescence segments of Pennisetum americanum in Murashige and Skoog's medium supplemented with 2.5 mg/1 2,4-dichlorophenoxyacetic acid (2,4-D) and 5% coconut milk. The suspension was composed of two major cell types: 1) small, richly cytoplasmic and starch-containing cells, generally found in small, compact clumps, here termed embryogenic cells; and 2) elongated, thick-walled cells with large vacuoles. By manipulating the duration of culture and dilution ratios (cell suspension: fresh medium) at the time of subculture, suspensions consisting predominantly of embryogenic cells were obtained. Suspensions grown for 2-3 wks were transferred to agar media with reduced amounts of 2,4-D. This resulted in the production of hundreds of globular and early cotyledonary embryoids. Further development of the embryoids was promoted by their transfer to a medium containing abscisic acid. Many of the embryoids germinated and produced normal green plants. Atypical embryoids, some containing many shoot meristems and a leafy scutellum, were also observed. The relevance of such atypical embryoids in the interpretation of organogenesis and embryogenesis reported in tissue cultures of cereal species is discussed. It is also suggested that somatic embryogenesis occurs in tissue cultures of most, if not all, species of cereals and grasses.     

Erythrocyte enzyme polymorphisms in the Kamboh caste of Patiala, Punjab

Data are presented on six erythrocyte enzyme polymorphisms (ADA, GLO I, EsD, AK, AP, GPI) in the Kamboh, a scheduled caste inhabiting the Patiala district of the Indian state of Punjab. With their high ADA2 (18.5%), Pa (42.5%) and GPI3 (5.3%) and a rather low GLO1 (18.8%) frequencies, the Kamboh differ from all other populations of Punjab.     

H2-CO2 Recirculation and pH Control for Growth of Methanogens in Mass Culture

We modified a fermentor (10-liter liquid volume) for the growth of anaerobic, H₂-CO₂-catabolizing bacteria. Gas in the fermentor (ca. 10% CO₂, 50% H₂, 40% CH₄) was recirculated by a diaphragm pump. During growth, the gas composition was maintained by the addition of a mixture of 80% H₂ and 20% CO₂, and this addition was controlled by a pH auxostat. During gas addition, gas was discharged from the recirculating gas stream and was collected by the displacement of an acidified salt solution.     

A theoretical and scanning electron microscope study on the electrically mediated inactivation of spermatozoa

Spermatozoa are known to carry a net negative charge and have been shown to die in a dc electric field, but the cause of the lethal effect has not been explored. We present here an experimental and theoretical analysis of various factors likely to lead to the mortality of spermatozoa. Alterations in the spermatozoon surface complex induced by the applied current density has been identified to be the most likely cause.     

Prevalence of simian malaria parasites in macaques of Singapore

Plasmodium knowlesi is a simian malaria parasite currently recognized as the fifth causative agent of human malaria. Recently, naturally acquired P. cynomolgi infection in humans was also detected in Southeast Asia. The main reservoir of both parasites is the long-tailed and pig-tailed macaques, which are indigenous in this region. Due to increased urbanization and changes in land use, there has been greater proximity and interaction between the long-tailed macaques and the general population in Singapore. As such, this study aims to determine the prevalence of simian malaria parasites in local macaques to assess the risk of zoonosis to the general human population. Screening for the presence of malaria parasites was conducted on blood samples from 660 peridomestic macaques collected between Jan 2008 and Mar 2017, and 379 wild macaques collected between Mar 2009 and Mar 2017, using a Pan-Plasmodium-genus specific PCR. Positive samples were then screened using a simian Plasmodium species-specific nested PCR assay to identify the species of parasites (P. knowlesi, P. coatneyi, P. fieldi, P. cynomolgi, and P. inui) present. All the peridomestic macaques sampled were tested negative for malaria, while 80.5% of the 379 wild macaques were infected. All five simian Plasmodium species were detected; P. cynomolgi being the most prevalent (71.5%), followed by P. knowlesi (47.5%), P. inui (42.0%), P. fieldi (32.5%), and P. coatneyi (28.5%). Co-infection with multiple species of Plasmodium parasites was also observed. The study revealed that Singapore’s wild long-tailed macaques are natural hosts of the five simian malaria parasite species, while no malaria was detected in all peridomestic macaques tested. Therefore, the risk of simian malaria transmission to the general human population is concluded to be low. However, this can be better demonstrated with the incrimination of the vectors of simian malaria parasites in Singapore.     

The possible involvement of CHI sequences in adaptive mutagenesis: Evidence from sequence analysis

Recently we proposed that sequences in the immediate neighbourhood of cytosine residues whose sequence context permits their methylation by DNA cytosine methyltransferase (Dcm) experience hypermutagenesis in cells exposed to nonlethal stresses. This hypothesis could explain the peculiar spectrum of the late-arising Lac⁺ mutants seen in theE. coli strain FC40. Here we present results of computer analysis which show that Dcm substrate sequences are overrepresented in theE. coli genome. Interestingly, certain noncanonical Dcm sequences are more overrepresented than the canonical one. The most overabundant of these, DCM-III (5’ GCTGG3’), forms the 5’ end of the recombinogenic octamer CHI (5’ GCTGGTGG3’). CHI is even more overrepresented than DCM-III. We propose that the overabundance of the DCM and CHI sequences is due to their ability to enhance adaptive fitness of the host by inducing hypermutagenesis in cells exposed to nonlethal, growth-blocking stresses. The CHI context seems to stimulate the adaptive activity of DCM-III by a mechanism which may not directly involve its recombinogenic activity.     

Philip R. White (1901–1968)—a tribute

The groundbreaking research carried out by Philip R. White in the 1930s and 1940s played a critical early role in the development of modern plant biotechnology and the production of biotech crops. He gained instant fame and became a historical figure early in his career by becoming the first person to attain unlimited growth of cultured plant tissues. White was one of the best known and most influential figures of his generation in plant cell culture research. His tireless and lifelong efforts to promote the use of plant cell culture systems inspired a generation of scientists and stimulated much scientific activity. White was not only a brilliant and visionary scientist but also a highly principled man who spoke courageously about the great moral and political issues of his day. He was admired as much for his science as for his humanity. His belief that plant cell culture research was not well represented at national and international meetings, and his deeply held conviction that science had to be international and without borders in order to be of service to humankind led to the founding of the International Association for Plant Biotechnology in 1963, currently the largest forum for the international plant biotechnology community. This tribute honors and celebrates Philip R. White for his inspiring science, for his kind and generous mentoring of young scientists, for his advocacy of plant cell culture research and its applications, for his promotion of international scientific exchange and cooperation, and for his leadership in the founding of the International Association for Plant Biotechnology.