Endogenous gibberellins and amylase activity in tall and dwarf strains of rice (Oryza sativa)

Summary 2 tall and 7 dwarf strains of rice were sprayed with 0 or 40 g ml^–1 GA₃, 4 dwarf strains responded to exogenous GA₃, and showed a markedly lower endogenous gibberellin content than the tall strains, while 2 dwarf strains did not respond to GA₃ application and had considerably higher endogenous gibberellin levels than the tall ones. Amylase activity in germinating seeds showed a significant negative correlation with the endogenous gibberellin content.     

Level of marker enzymes in spermatogenesis on administration of PGF2a in rats

Summary Intrapertioneal administration of PGF_2a in rats significantly increased testicular acid phosphatase (p<0.05), decreased hyaluronidase (p<0.05), whereas the activities of 5-nucleotidase, N-acetyl-B-glucosaminidase, B-galactosidase and uridine diphosphatase remained unaffected.Acknowledgment. We are grateful to Dr D. Sundaresan, for his interest in the study and to Mr B. M. Sharma for technical assistance.     

Serum iron level of the common Indian frogRana tigrina Daud.

Summary A study extending over a period of 2 years has been made on serum iron level of common Indian frogR. tigrina. Serum iron averages 99.4 g/100 ml in female and 92.60 g/100 ml in males. The serum iron concentration is relatively high from May to October. Starvation has been found to decrease the serum iron level from the 16th day onwards.Acknowledgment. Thanks are due to Professor Dr M. M. Goil, Head of the Zoology Department for guidance and help in various ways and to Professor Dr R. K. Sharma for valuable suggestions.     

Electronic structure of the iron-based superconductor LaOFeP

The recent discovery of superconductivity in the iron oxypnictide family of compounds has generated intense interest. The layered crystal structure with transition-metal ions in planar square-lattice form and the discovery of spin-density-wave order near 130 K (refs 10, 11) seem to hint at a strong similarity with the copper oxide superconductors. An important current issue is the nature of the ground state of the parent compounds. Two distinct classes of theories, distinguished by the underlying band structure, have been put forward: a local-moment antiferromagnetic ground state in the strong-coupling approach, and an itinerant ground state in the weak-coupling approach. The first approach stresses on-site correlations, proximity to a Mott-insulating state and, thus, the resemblance to the high-transition-temperature copper oxides, whereas the second approach emphasizes the itinerant-electron physics and the interplay between the competing ferromagnetic and antiferromagnetic fluctuations. The debate over the two approaches is partly due to the lack of conclusive experimental information on the electronic structures. Here we report angle-resolved photoemission spectroscopy (ARPES) of LaOFeP (superconducting transition temperature, T(c) = 5.9 K), the first-reported iron-based superconductor. Our results favour the itinerant ground state, albeit with band renormalization. In addition, our data reveal important differences between these and copper-based superconductors.     

Alzheimer’s disease: the impact of age-related changes in reproductive hormones

Two classes of ovarian steroids, estrogens and progestins, are potent in protecting neurons against acute toxic events as well as chronic neurodegeneration. Herein we review the evidence for neuroprotection by both classes of steroids, provide plausible mechanisms for these potent neuroprotective activities and indicate the need for further clinical trials of both estrogens and progestins in protection against acute and chronic conditions that cause neuronal death. Estrogens at concentrations ranging from physiological to pharmacological are neuroprotective in a variety of in vitro and in vivo models of cerebral ischemia and brain trauma as well as in reducing key neuropathologies of Alzheimers disease. While the mechanisms of this potent neuroprotection are currently unresolved, a mitochondrial mechanism is involved. Progestins have been recently shown to activate many of the signaling pathways used by estrogens to neuroprotect, and progestins have been shown to protect against neuronal loss in vitro and in vivo in a variety of models of acute insult. Collectively, results of these animal and tissue culture models suggest that the loss of both estrogens and progestins at the menopause makes the brain more vulnerable to acute insults and chronic neurodegenerative diseases. Further clinical assessment of appropriate regimens of estrogens, progestins and their combination are supported by these data.     

A human ortholog of archaeal DNA repair protein Hef is defective in Fanconi anemia complementation group M

Fanconi anemia is a genetic disease characterized by genomic instability and cancer predisposition. Nine genes involved in Fanconi anemia have been identified; their products participate in a DNA damage-response network involving BRCA1 and BRCA2 (refs. 2,3). We previously purified a Fanconi anemia core complex containing the FANCL ubiquitin ligase and six other Fanconi anemia-associated proteins. Each protein in this complex is essential for monoubiquitination of FANCD2, a key reaction in the Fanconi anemia DNA damage-response pathway. Here we show that another component of this complex, FAAP250, is mutant in individuals with Fanconi anemia of a new complementation group (FA-M). FAAP250 or FANCM has sequence similarity to known DNA-repair proteins, including archaeal Hef, yeast MPH1 and human ERCC4 or XPF. FANCM can dissociate DNA triplex, possibly owing to its ability to translocate on duplex DNA. FANCM is essential for monoubiquitination of FANCD2 and becomes hyperphosphorylated in response to DNA damage. Our data suggest an evolutionary link between Fanconi anemia-associated proteins and DNA repair; FANCM may act as an engine that translocates the Fanconi anemia core complex along DNA.     

Thyroid activity in response to some gonadal steroids in methallibure-treatedHeteropneustes fossilis (Bloch)

Summary Methallibure treatment is as effective as hypophysectomy in reducing thyroid activity inH. fossilis. Sex steroids (TP and EB) administration restored thyroid activity in methallibure-treated females to normal level, but failed to elicit any response in males. This drug seems to block TSH secretion and thyroid hormone synthesis inH. fossilis.Financial assistance in the form of SRF from ICAR, New Delhi to one of us (R.B.R.), gift of methallibure from ICI Ltd., UK and TSH from NIH, USA, to T.P.S. are gratefully acknowledged.