Organically preserved microbial endoliths from the late Proterozoic of East Greenland

Diverse microorganisms ranging from cyanobacteria to eukaryotic algae and fungi live endolithically within ooids, hardgrounds and invertebrate shells on the present-day sea floor. These organisms are involved in the mechanical destruction of carbonates, and are useful ecological indicators of water depth and pollution. The Phanerozoic history of microbial endoliths has been elucidated through the study of microborings (the trace fossils of endolithic microorganisms) and rare cellularly preserved individuals, but nothing was known of the possible Precambrian evolution of comparable microorganisms until Campbell documented the occurrence of microborings in late Proterozoic ooids from central East Greenland. We now report the discovery of large populations of organically preserved endolithic microorganisms in silicified pisolites from 700-800-Myr-old Limestone-Dolomite Series of East Greenland. This fossil assemblage is significant for three reasons: (1) It confirms the prediction that oolites, pisolites and hardgrounds--the substrates for pre-Phanerozoic endoliths--provide a hitherto poorly explored but rewarding set of environments into which the search for early microfossils must be broadened; (2) the assemblage is diverse, containing about 12 taxa of morphologically distinct and previously unknown endolithic cyanobacteria, plus associated epilithic and interstitial populations; and (3) at least six of the fossil populations are indistinguishable in morphology, pattern of development, reproductive biology and inferred ecology from distinctive cyanobacterial species that bore ooids today in the Bahama Banks.     

Internalization of polypeptide hormones and receptor recycling

Conclusion The insulin receptor is an integral protein of the plasma membrane of the cell. It is composed of two subunits: an subunit, which binds the hormone, and a subunit which is a tyrosine specific protein kinase capable of undergoing autophosphorylation. These independent subunits are synthesized by way of a higher molecular weight single chain precursor and thus are the product of a single gene^{29, 49, 85} localized to chromosome 19^{29, 91}. Assuming that the insulin receptor is synthesized in the same fashion as other integral membrane glycoproteins, then the nucleus, the rough endoplasmic reticulum, and the Golgi apparatus are involved in its biosynthesis. Further, there must be some form of transport of the mature receptor subunits to the plasma membrane where they are inserted.By contrast, the endocytotic route involves coated pits, coated vesicles, large clear vesicles or endosomes, multivesicular bodies and other lysosomal forms. In addition, it is possible that some other as yet unidentified organelle is involved in recycling (fig. 8). At the present time, with respect to the insulin receptor, the biosynthetic pathway and the endocytotic pathway appear to be separate. Further, it does not appear that either pathway, i. e. synthesis or endocytosis, exerts a regulatory function over the other.     

New phytotoxic butenolides produced bySeiridium cardinale,the pathogen of cypress canker disease

Summary Two new butenolides, seiridin andiso-seiridin, were isolated from culture filtrates ofSeiridium cardinale, the pathogen of cypress canker, a destructive disease ofCupressus and relatedConiferae These metabolites were characterized as 3-methyl-4-(2-hydroxyheptyl)-2(5H)-furanone and its 4-(3-hydroxyheptyl) isomer, respectively. Chlorotic, and necrotic symptoms were produced on leaves of either host or non-host test plants by absorption of 0.3 mg/ml solutions of either compound. These also showed antibacterial activity.This study was supported in part by the National Research Council, Rome (special ad hoc project Chimica fine e secondaria) and in part by the Ministry of Education, Rome.     

Position of the Y-chromosome at somatic metaphase in patients with chronic myelogenous leukemia (CML)

Summary A random distribution of the Y-chromosome at somatic metaphase was found in 50 patients with Ph' positive chronic myelogenous leukemia (CML). Thus, it is concluded that the positive of the Y-chromosome at somatic metaphase does not appear to influence the loss from bone marrow cells.     

Hormonal induction of steroid sulphatase in the mouse

Summary By comparing steroid sulphatase levels per se, and also ratios to -galactosidase, in 6 sets of mice — normal females, entire and castrated males both with and without exogenous testosterone administration — we obtained support for the contention that induction of this enzyme is in part controlled by male hormones.     

Studies on some enzymes of the toad (Bufo melanostictus) testis and their probable role at the time of fertilization

Summary Glycosidases like sialidase,-galactosidase, -L-fucosidase, N-acetyl hexosaminidase and proteases were detected in toad testis. Neuraminic acid aldolase activity was also detected. The enzyme activities were found to vary as production of spermatozoa varied. All enzymes, except N-acetyl glucosaminidase, were shown to decrease after injection of toad pituitary extract and they were also found to be absent from testis containing no spermatozoa. The glycosidases were found to act on toad oviduct jelly and they may therefore be involved in the degradation of the jelly after fertilization, into smaller bits, which may be utilized as nutrients by the fertilized zygote.Acknowledgment. We thank Prof. T.R. Ramaiah, Head of the Department of Biochemistry, University of Mysore, for his help. We also acknowledge the financial assistance of University Grants Commission to one of us (MS) and CSIR through a grant No. 9 (165)83/EMR-II to HSS. Please address all correspondence to H.S. Seshadri.     

Loss of antibody production accompanied by chromosome loss in a cloned hybrid line secreting antibodies to sheep red blood cells

Summary Somatic cell hybrids between Sp2/O-Ag14 mouse myeloma cells and lymphocytes derived from BALB/c mice hyperimmunized with sheep red blood cells (SRBC) were produced. One hybrid producing IgG₁ antibody to SRBC was selected, cloned twice and subsequently transferred to BALB/c mice. After a number of transfers it was found that the antibody titer in ascitec fluid gradually decreased. Cytogenetic analysis revealed gradual chromosome loss in the hybrid clone, which produced progressively less antibody.     

Selective protection of cells against X-irradiation. Isoproterenol protects only those cells that possesβ-adrenoreceptors

Summary In mixed culture of Chinese hamster fibroblatst, clone 431, and transformed murine L fibroblasts, clone B-82, isoproterenol was found to protect only 431 cells against ionizing radiation. It was shown that 431 cells, in contrast to B-82 cells, possess-adrenoreceptors, and the radioprotective effect of isoproterenol can be realized only if this agent interacts with-adrenoreceptors coupled with the cAMP system. Since malignization often causes the disappearance of-adrenergic and other hormone receptors, the combined culturing and irradiation of the cells studied can be regarded as a model of the growth of malignant cells (B-82) among normal tissue cells (431 cells) under conditions of radiation therapy. A possibility of selective protection against radiation damage of normal tissue cells, with retention of the former radiosensitivity of tumor cells, is discussed.     

Patterns of dye coupling in the imaginal wing disk of Drosophila melanogaster

Responses of developing tissues to experimental disruption demonstrate that cell interaction is important both in generating positional information and in controlling growth. However, the mechanism by which cells interact and the range over which the interactions are effective are not known. In the imaginal disks of Drosophila melanogaster, experiments on pattern regulation following surgical ablation suggest that the cell interactions are very local in nature; in fact, most of the data can be explained by assuming that cells interact only with their immediate neighbours. In contrast, studies of cell division patterns in the same tissue indicate that the "local' proliferative response to an ablation extends over a distance of up to about eight cell diameters. Still longer-range interactions have been proposed on the basis of theoretical considerations. It is possible that the interactions are mediated by the transfer of small molecules through gap junctions, as gap junctions are abundant in imaginal disks at the appropriate developmental stages. We have explored the range, timing and directionality of dye coupling between the cells of the wing disk as a test of the possible role of gap junctions in imaginal disk patterning. Our results indicate that interactions over different ranges are possible depending on the nature of the molecule being transferred.