Showing papers by "Andrew J. Watson published in 1993"

Evidence for slow mixing across the pycnocline from an open-ocean tracer-release experiment

Abstract: THE distributions of heat, salt and trace substances in the ocean thermocline depend on mixing along and across surfaces of equal density (isopycnal and diapycnal mixing, respectively). Measurements of the invasion of anthropogenic tracers, such as bomb tritium and 3He (see, for example, refs 1 and 2), have indicated that isopycnal processes dominate diapycnal mixing, and turbulence measurements have suggested that diapycnal mixing is small3,4, but it has not been possible to measure accurately the diapycnal diffusivity. Here we report such a measurement, obtained from the vertical dispersal of a patch of the inert compound SF6 released in the open ocean. The diapycnal diffusivity, averaged over hundreds of kilometres and five months, was 0.11 ± 0.02 cm2 s−1, confirming previous estimates1–4. Such a low diffusivity can support only a rather small diapycnal flux of nitrate into the euphotic zone; it justifies the neglect of diapycnal mixing in dynamic models of the thermocline25–27, and implies that heat, salt and tracers must penetrate the thermocline mostly by transport along, rather than across, density surfaces.

Patterns of expression of metalloproteinases and their inhibitors in human malignant lymphomas.

Abstract: Forty-two cases of malignant lymphomas were studied for the expression of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) by Northern blot and in situ hybridization. The lymphomas were classified according to Working Formulation classification (25 high grade, 15 low grade, and 2 intermediate grade). The MMPs studied included: 72-kDa and 92-kDa gelatinases (type IV collagenases), interstitial collagenase, PUMP-1 (MMP-7), and stromelysins 1 and 3. TIMPs included TIMP-1 and TIMP-2. All but one case expressed TIMP-1, and TIMP-2 transcripts were detected in 35 cases. Among the MMPs, 92-kDa gelatinase was expressed most consistently (35 cases), whereas mRNA transcripts of 72-kDa gelatinase, interstitial collagenase, and PUMP-1 were detected in only a few cases. Stromelysins 1 and 3 mRNAs were not detected in any of the tumors studied. However, marked differences in the level of expression of certain MMPs and TIMPs were found among different grades of malignant lymphomas. The low grade tumors expressed low and relatively constant levels of TIMP-1, TIMP-2, and 92-kDa gelatinase transcripts, whereas high grade lymphomas displayed variable amounts of mRNAs for TIMPs and MMPs, with a trend toward elevated TIMP-1 and 92-kDa gelatinase mRNA levels. In situ hybridization localized TIMP-1 transcripts to stromal cells, while 92-kDa gelatinase transcripts were most abundant in "starry sky" macrophages and large lymphoma cells. Zymography showed that active 92-kDa gelatinase is present in tumor protein extracts and differences in the level of the enzymatic activity were seen between low and high grade lymphomas. Our data indicate that 92-kDa gelatinase and TIMP-1 expression by human malignant lymphomas may play an important role in controlling their biologic aggressiveness.

Diurnal variation in surface pCO2 and O2 at 60°N, 20°W in the North Atlantic

Abstract: A method for rapid determination of the partial pressure of carbon dioxide at the sea-surface is described. The method was employed along with a pulsed oxygen electrode to monitor daily changes in surface pCO 2 and O 2 close to a drifting buoy deployed at approximately 59°N, 20°W. During a 4 day period a gradual rise in oxygen saturation and corresponding fall in pCO 2 was observed in the surface layer. Corrections are made for gas exchange of O 2 using wind speed data, the correction being an important fraction of the supersaturation observed in the water. Estimates of net community production and photosynthetic quotients are derived, giving a range of PQs from 0.9 to 1.5. Though variations in the local hydrography reduce the accuracy of these estimates, the potential of this approach to estimate productivity appears promising.

Expression of IGF ligand and receptor genes during preimplantation mammalian development

Abstract: The temporal patterns of expression of genes encoding insulin-like growth factor (IGF) ligands and receptors during very early development have been investigated in several laboratories in several different mammalian species. Both reverse transcription-polymerase chain reaction (RT-PCR) and immunocytochemical techniques have been used to identify the time of appearance of gene transcripts or end-products. In preimplantation mouse embryos, IGF-II ligand and receptor gene activity is detectable as early as at the two-cell stage, the time when transcription from the embryonic genome is activated, but receptors for insulin and IGF-I are not detectable until the compacted eight-cell stage. Transcripts for insulin or IGF-I are not detectable in preimplantation mouse embryos, although the ligands are present in the reproductive tract. The pattern of IGF gene expression is not, however, identical in all mammalian species. In cow embryos, for example, transcripts for IGF-I and IGF-II ligands and receptors and insulin receptors have been detected at all stages of preimplantation development from mature oocyte to blastocyst (Watson et al., 1992). Attempts to quantitate transcript abundance in these early embryos are in progress in our laboratory. In the preimplantation mouse embryo, transcripts for several different IGF-binding proteins (IGFBP-2, -3, -4, and -6) have been detected by RTPCR procedures. In addition, transcripts for IGFBPs have been identified in RNA derived from cumulus cells, the ovary, the oviduct, the uterus, and the decidua. These findings suggest that the interactions of IGF ligands and receptors in preimplantation development might, indeed, be modulated by IGFBPs. Approaches to function of IGFs in preimplantation embryos have involved analysis of the stimulatory effects on metabolism and cell division when IGFs are added exogenously to embryos in culture in simple defined medium (for example, see Harvey and Kaye, 1991) or observations in the reduction in rate of development following interference with IGF expression (see Rappolee et al., 1992). In general, members of the insulin and IGF gene family of polypeptides have been shown to lead to an enhahancement of development in vitro in both laboratory and domestic mammalian species. © 1993 Wiley-Liss, Inc.

Trace Gases and Air-Sea Exchanges

Abstract: The most widely used approach for calculating the flux of gases across the sea surface is from the product of the concentration difference across the interface and a kinetic parameter, often called the transfer velocity. During the NERC North Sea Community Research Project (CRP) a considerable effort was made to improve our knowledge of both of these terms.

The Caenorhabditis elegans genome sequencing project: First steps in automation

Abstract: Novel biochemical processes using magnetic particles have been automated to provide a robotic system to perform processes for large-scale shotgun sequencing.

Air-Sea Gas Exchange and Carbon Dioxide

Abstract: An understanding of air-sea exchange, and the ability to calculate fluxes of interesting atmospheric gases into and out of the oceans, is an important tool in global biogeochemistry. For some gases, (dimethylsulphide for example) the process of gas exchange is itself a limiting factor controlling the flux: this gas is generated in excess in surface water, and the amount getting into the atmosphere is limited by the rate of air-sea exchange.

Activation of the Embryonic Genome: Comparisons Between Mouse and Bovine Development

Abstract: Eutherian mammalian preimplantation development includes an essential transitional period during which the embryo proceeds from an initial interval of maternal control (established during oogenesis) to embryonic control resulting from the activation of transcriptional activity from the embryonic genome (1–3). As for most aspects of early mammalian development, the events surrounding the activation of the embryonic genome are most readily examined in the mouse. There is, however, evidence to suggest that the mouse may display a pattern of preimplantation development (certainly in the timing of the major events) that is unique. It is, therefore, essential to broaden the analysis of preimplantation development to include other mammalian species. A comparison of several species in Table 9.1 shows that there is considerable variation in the timing, cell number, and developmental stage at which the early embryos of these groups undergo the major morphogenetic events of preimplantation development (4, 5). As shown in Table 9.2, these variations also reflect contrasts in the timing of the molecular and biochemical events of preimplantation development.

Air-Sea Exchange of CO2 and Its Relation to Primary Production

Abstract: The natural processes which determine how much CO2 is in the atmosphere have never been more intensely and urgently studied than at present. The urgency stems from our realization that we are changing the global climate fundamentally and rapidly by the addition of radiatively active “greenhouse” gases to the atmosphere, CO2 foremost among them. The rate of rise of CO2 concentrations is considerably mitigated, however, by the existence of a net sink for atmospheric CO2 which is about half as large as the total anthropogenic input, (fossil fuel burning and deforestation). Figure 1, based on data in the IPCC scientific assessment (IPCC, 1990) gives estimated net sources and sinks of atmospheric CO2. All of the fluxes shown are, it should be stressed, net. In particular, the ocean uptake of about 2 Gt C yr−1 is the difference between two nearly equal fluxes of order 100 Gt C yr−1 into and out of the ocean.

The gas transfer velocity — wind speed relationship at Siblyback Lake: A reply to comments by Kwan and Taylor

Abstract: In their reassessment of our windspeed results from Siblyback Lake (Upstill-Goddard et al., 1990), Kwan and Taylor (1993) critically re-evaluate our graphical extrapolation of the 10-m wind ( U 10 ) made from simultaneous measurements at 1.5 m and 3 m. DOI: 10.1034/j.1600-0889.1993.t01-2-00007.x