Putative Evidence Research Articles

Current perspectives on the Pleistocene archaeology of eastern Beringia

Most recent summaries of eastern Beringian (Alaska and Yukon) archaeology present the Nenana complex, beginning 11,500–12,000 14C yr B.P., as the beginning of the regional archaeological record. Either explicitly or tacitly, these summaries dismiss or ignore a body of older putative evidence of human occupation that may span the late Wisconsin stade and even extend into part of the mid-Wisconsin interstade. This paper summarizes the interpretive problems surrounding the older findings, bringing together data that have accumulated over a period of two decades, in the hope that a coherent presentation will encourage more careful appraisals of the materials. The paper concludes with a family of testable hypotheses concerning the beginnings of human occupation in eastern Beringia. The hypothesis that people were present during the mid-Wisconsin interstade has not yet been falsified.

A genome-wide scan in families with maturity-onset diabetes of the young: evidence for further genetic heterogeneity.

Maturity-onset diabetes of the young (MODY) is a heterogeneous single gene disorder characterized by non-insulin-dependent diabetes, an early onset and autosomal dominant inheritance. Mutations in six genes have been shown to cause MODY. Approximately 15-20% of families fitting MODY criteria do not have mutations in any of the known genes. These families provide a rich resource for the identification of new MODY genes. This will potentially enable further dissection of clinical heterogeneity and bring new insights into mechanisms of beta-cell dysfunction. To facilitate the identification of novel MODY loci, we combined the results from three genome-wide scans on a total of 23 families fitting MODY criteria. We used both a strict parametric model of inheritance with heterogeneity and a model-free analysis. We did not identify any single novel locus but provided putative evidence for linkage to chromosomes 6 (nonparametric linkage [NPL]score 2.12 at 71 cM) and 10 (NPL score 1.88 at 169-175 cM), and to chromosomes 3 (heterogeneity LOD [HLOD] score 1.27 at 124 cM) and 5 (HLOD score 1.22 at 175 cM) in 14 more strictly defined families. Our results provide evidence for further heterogeneity in MODY.

Biological invasion of the Indo-Pacific lionfish Pterois volitans along the Atlantic coast of North America

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 235:289-297 (2002) - doi:10.3354/meps235289 Biological invasion of the Indo-Pacific lionfish Pterois volitans along the Atlantic coast of North America Paula E. Whitfield1,*, Todd Gardner2, Stephen P. Vives3, Matthew R. Gilligan4, Walter R. Courtenay Jr.5, G. Carleton Ray6, Jonathan A. Hare1 1NOAA Beaufort Laboratory, 101 Pivers Island Road, Beaufort, North Carolina 28516, USA 2Biology Department, 130 Gittleson Hall, Hofstra University, Hempstead, New York 11549-1140, USA 3Department of Biology, Georgia Southern University, PO Box 8042, Statesboro, Georgia 30460-8042, USA 4Marine Science Programs, Savannah State University, PO Box 20467, Savannah, Georgia 31404, USA 5Florida Caribbean Science Center, US Geological Survey, 7920 NW 71st Street, Gainesville, Florida 32653, USA 6Department of Environmental Sciences, University of Virginia, 291 McCormick Rd, Charlottesville, Virginia 22904, USA *E-mail: paula.whitfield@noaa.gov ABSTRACT: The occurrence of lionfish Pterois volitans is reported from the western Atlantic Ocean. Adults were collected off the coasts of North Carolina, Georgia and Florida, and juveniles were collected along the shore of Long Island, New York. They have also been found around Bermuda. Lionfish are indigenous to tropical waters of the western Pacific and their occurrence along the east coast of the United States represents a human-induced introduction. Distribution of adults suggests lionfish are surviving in the western Atlantic and capture of juveniles provides putative evidence of reproduction. The most likely pathway of introduction is aquarium releases, but introduction via ballast water cannot be ruled out. The ecosystem of the southeastern United States continental shelf is already undergoing change: reef fish communities are becoming more tropical and many fish species are overfished. These ongoing changes, along with limited information regarding the biology of P. volitans, make predictions of long-term effects of the introduction difficult. This discovery represents the first, apparently successful introduction, of a marine fish from the western Pacific to Atlantic coastal waters of the United States. KEY WORDS: Biological invasions · Nonindigenous species · Marine fish · Scorpaenidae · Marine introductions · Lionfish · Pterois volitans · Invasive species · Pteroinae Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 235. Online publication date: June 19, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Hospital hairdresser as a potential source of cross-infection with MRSA

Following medical staff concerns about patients screening positive for methicillin-resistantStaphylococcus aureus (MRSA) from the hairline site only, it was suggested that the hospital hairdresser could be a possible source for cross-contamination. Analysis of her procedures and decontamination practices confirmed her to be a potential source. Swabbing of her equipment after a day's session with her normal cleansing practice revealed the presence of MRSA, confirmed by phage typing as an epidemic strain within the hospital. This provided putative evidence for a vehicle of transmission. A review of advice for hairdressers in hospitals was obtained from the literature and via a telephone survey of infection control nurses in London. A composite policy was produced for hairdressers attending MRSA-positive patients in hospital to minimize this potential risk.

Molecular analyses of a putative CTXphi precursor and evidence for independent acquisition of distinct CTX(phi)s by toxigenic Vibrio cholerae.

The genes encoding cholera toxin (ctxA and ctxB) are encoded in the genome of CTXphi, a filamentous phage that infects Vibrio cholerae. To study the evolutionary history of CTXphi, we examined genome diversity in CTX(phi)s derived from a variety of epidemic and nonepidemic Vibrio sp. natural isolates. Among these were three V. cholerae strains that contained CTX prophage sequences but not the ctxA and ctxB genes. These prophages each gave rise to a plasmid form whose genomic organization was very similar to that of the CTXphi replicative form, with the exception of missing ctxAB. Sequence analysis of these three plasmids revealed that they lacked the upstream control region normally found 5' of ctxA, as well as the ctxAB promoter region and coding sequences. These findings are consistent with the hypothesis that a CTXphi precursor that lacked ctxAB simultaneously acquired the toxin genes and their regulatory sequences. To assess the evolutionary relationships among additional CTX(phi)s, two CTXphi-encoded genes, orfU and zot, were sequenced from 13 V. cholerae and 4 V. mimicus isolates. Comparative nucleotide sequence analyses revealed that the CTX(phi)s derived from classical and El Tor V. cholerae isolates comprise two distinct lineages within otherwise nearly identical chromosomal backgrounds (based on mdh sequences). These findings suggest that nontoxigenic precursors of the two V. cholerae O1 biotypes independently acquired distinct CTX(phi)s.

Inhibition of nitric oxide synthase ameliorates cellular injury in sickle cell mouse kidneys

In previous studies of transgenic sickle cell mice, increased renal expression of inducible nitric oxide synthase (iNOS) and endothelial cell isoform of NOS (EcNOS) was found by Western blot and immunohistochemistry. In addition, putative evidence of peroxynitrite (ONOO-) formation was found in the form of positive immunostaining and immunoblot for nitrotyrosine. Apoptosis was also detected by DNA strand breakage and TUNEL assay. The present study was carried out to examine the role of NO/ONOO- in mediating renal tubular cell apoptosis in sickle cell mouse kidneys. Mercaptoethylguanidine (MEG), a compound that selectively inhibits iNOS and also is a scavenger of ONOO-, was administered intraperitoneally over a five-day period to control and betas mice. Immunohistochemistry of iNOS and nitrotyrosine, DNA electrophoresis, ApoTACS assay for apoptosis, and Western blot of poly(ADP-ribose) polymerase (PARP) were carried out. MEG administration virtually eliminated renal immunostaining of iNOS and nitrotyrosine and prevented DNA strand breakage. In addition, Western blot analysis of PARP, a nuclear DNA-reparative enzyme activated in response to DNA strand breakage, was found to be cleavaged in hypoxic betas mice, but was partially protected in MEG-treated betas hypoxic mice. Finally, apoptosis was markedly reduced by MEG in betas hypoxic mice. These observations provide evidence that NO and/or ONOO- are responsible for initiating cell damage, which leads to apoptosis in sickle cell mouse kidneys.

Mitogen-activated protein kinase phosphorylation in kidneys of beta(s) sickle cell mice.

Previous studies in beta(s) sickle cell mice demonstrated renal immunostaining for nitrotyrosine, which is putative evidence of peroxynitrite (ONOO(-)) formation. ONOO(-) is known to nitrate tyrosine residues of various enzymes, thereby interfering with phosphorylation and inactivating them. The present study examined the state of phosphorylation of mitogen-activated protein (MAP) kinase signal transduction enzymes, i.e., p38, c-Jun NH(2)-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK). Western blot performed with antibodies directed against specific phosphorylated threonine/tyrosine residues of these enzymes demonstrated reduced phosphorylation of renal p38 and a trend toward reduced phosphorylation of ERK. In contrast, phosphorylation of renal JNK was markedly increased compared with normal mice. The abundance of MAP kinase phosphatase-1 (MKP-1), a key upstream enzyme that modulates phosphorylation of MAP kinases, was not different in beta(s) versus normal mice. To determine whether nitration of tyrosine by ONOO(-) was responsible for reduced phosphorylation of p38 and ERK, mercaptoethylguanidine (MEG), a compound known to reduce inducible isoform of nitric oxide synthase activity and to scavenge ONOO(-), was administered to beta(s) mice for 5 d. MEG was found to restore phosphorylation of p38 and ERK toward normal levels. These observations provide evidence that ONOO(-) (or closely related reaction products of NO) contributes to dephosphorylation of p38 and ERK, and presumably reduces activity of these enzymes. The increased phosphorylation of JNK, which suggests activation of this signaling pathway by extracellular stress signals, may play a role in apoptosis in the kidneys of these mice. The changes in phosphorylation of MAP kinase pathways found in this study could have important consequences for regulation of nuclear transcription factors, and thus renal function and pathology in sickle cell kidneys.

13C and 15N depletion in components of a foodweb from an ephemeral boreal wetland compared to boreal lakes : putative evidence for microbial processes

Stable carbon and nitrogen isotope ratios were used to posit the relative importance of microbial processes on energy pathways in an ephemeral, humic boreal wetland compared to four clearwater lakes in northwestern Ontario, Canada. In addition to algae and dipteran larvae, odonate larvae were sampled as these latter organisms are known to predate indiscriminately on smaller invertebrates and are thus likely to have average isotope ratios reflective of their habitats. Similarities in δ13C and δ15N values between lake insect larvae and emerged adults suggested that littoral foodwebs in these oligotrophic lakes may rely to a considerable degree upon terrestrial carbon. Wetland insect larvae and algae were depleted in both 13C and 15N compared to biota in lakes. Carbon isotope analysis implied a substantial presence of microbial respiration from decomposition in the humic wetland, whereas nitrogen isotope analysis suggested the prevalence of microbially modified nitrogen dynamics, including the possibilty of N-fixation.

DNA Measurement and Immunohistochemical characterization of Epithelial and Mesenchymal Cells in Canine Mixed Mammary Tumours: Putative Evidence for a Common Histogenesis

DNA measurement by image cytometry, and a detailed immunohistochemical study using monoclonal antibodies directed against different human cytokeratin types, muscle-specific actin, vimentin and S100 protein were carried out on normal canine mammary tissue (n=4), benign canine mammary mixed tumours (n=20) and malignant canine mammary mixed tumours (n=13). The results showed that ductal and alveolar luminal cells in normal and neoplastic tissue were immunoreactive with CAM5.2 and AE1/AE3 antibodies recognizing human keratins.Basal/myoepithelial cells were clearly differentiated from ductal and alveolar epithelial cells, since the latter only expressed cytokeratins, whereas the former also expressed vimentin and muscle-specific actin. This immunohistochemical study showed that there is loss of expression of muscle-specific actin and cytokeratins in areas of myoepithelial proliferation, and enhanced expression of vimentin and S100 protein in proliferative areas with osseous and/or chondroid metaplasia. The ploidy studies revealed that 20% (4/20) of benign and 54% (7/13) of malignant mixed tumours of canine mammary gland were aneuploid and that the epithelial and myoepithelial components of the mixed tumours had identical DNA content.Our results reinforce the role of myoepithelial cells in mesenchymal metaplasia in mixed mammary tumours and suggest the possibility of a common origin of both components from a totipotential stem cell with capacity for divergent differentiation.

Apoptosis In Esophageal Cancer Following Induction Chemoradiotherapy

Background.The poor survival of patients with esophageal cancer following esophagectomy has led to intense investigation into combined modality therapy. Based on results from clinical trials examining chemoradiotherapy alone without surgery, resection has come under increased scrutiny and its necessity as a component of a multimodal approach has been questioned. In this study, we examined whether residual tumor cells in esophagectomy specimens following induction chemoradiotherapy are viable and, therefore, provide putative evidence for the appropriateness of esophagectomy.Materials and methods.Between August 1991 and January 1995, 46 patients were entered into an induction chemoradiotherapy trial consisting of 5-fluorouracil, cisplatin, α-interferon, and concurrent external beam radiotherapy followed by esophagectomy. Response was determined histologically and apoptosis assessed with a terminal deoxytransferase assay system. p53 status was determined by immunohistochemistry and mutational analysis.Results.Thirty-eight patients underwent esophagectomy, 33 of whom had either a complete (n= 10) or partial (n= 23) response. None of the 28 patients with residual tumor in the resected specimen had 100% apoptotic cells and the vast majority of specimens had less than a 10% apoptotic rate. The percentage of apoptotic cells did correlate with tumor differentiation but not with histologic type nor presence of p53 mutations.Conclusions.These data suggest that resection following upfront chemoradiotherapy is a necessary component of a multimodality approach to esophageal cancer and will ultimately provide superior local-regional control to a nonsurgical approach.

Neonereites uniserialis from c. 600 Ma year old rocks in western Scotland and the emergence of animals

A chain of pellets (Neonereites uniserialis) , usually attributed to a coelomate or pseudocoelomate metazoan, is described from the middle Dalradian Bonahaven Formation of western Scotland, in sandstones not far above the Port Askaig Tillite. This trail lies more than 8 km below U-Pb zircon-dated Tayvallich lavas (595 ± 4 Ma) and predates early deformation plus intrusion by granites at Ben Vuirich dated at 597 ±11 and 590 ± 2 Ma. U-Pb zircon chronology for early metazoan evolution suggests that this is the earliest putative evidence for coelomates or pseudocoelomate discovered so far, with a minimum ‘interglacial’ age of c. 600 Ma bp . It is from about this time that a fall takes place in the maximum δ 13 C of carbonates, suggestive of a decline in the long term rate of carbon burial. One explanation for this decline is the increasing impact of metazoan bioturbation through the late Neoproterozoic to Cambrian interval.

Diversity and plasticity of self recognition during the development of multiple sclerosis.

Recent studies using murine animal model systems indicate that clinical progression of autoimmune disease may be due to the sequential accumulation of neoautoreactivity characterized by extensive plasticity of self recognition. In the present study, we addressed the question of whether a similar paradigm of self recognition is implicated in the development of multiple sclerosis (MS), a demyelinating disease with a presumed autoimmune etiology. Our approach was to determine serial changes over a 12-18-mo period in response to an epitope-mapping series of 265 12-mer peptides of myelin proteolipid protein (PLP) by patients with isolated monosymptomatic demyelinating syndromes (IMDS), a group of distinct clinical disorders with variable rates of progression to MS. Our data showed that an extensive array of proteolipid protein peptides could elicit autoreactivity. Moreover, differential autoreactive patterns were evident within IMDS patient subpopulations. Monocentric monophasic IMDS patients with no evidence of prior subclinical disease typically showed fully sustained autoreactivity characterized by extensive plasticity, epitope focusing, shifting, and spreading of responses to new self determinants. In contrast, multicentric monophasic IMDS patients with putative evidence of prior asymptomatic lesion formation typically showed partially sustained autoreactivity characterized by abrupt abrogation of responses to an extensive array of self determinants. No sustained autoreactivity was observed in normal control subjects or in patients with other neurologic diseases. Our results indicate that self recognition associated with the development of MS is a developmental process characterized by autoreactive diversity, plasticity, and instability.

The role of the 'central' cholecystokinin-B receptor in panic disorder.

Research investigating the neurobiological underpinnings of anxiety disorder have mainly been focused on dysfunction of the GABA, noradrenergic and serotonergic (5-HT) neuronal systems. Just recently, in both animal and human studies, evidence has been found for a possible role of the cholecystokinin (CCK) neuronal system in the pathogenesis of anxiety disorder. Behaviorally, animal studies revealed anxiogenic-like properties for the 'central' CCKB receptor agonists, while CCKB receptor antagonists displayed intrinsic anxiolytic properties. Similarly, in man, CCKB receptor agonists, like pentagastrin and CCK4, were found to be able to elicited panic attacks in both panic disorder (PD) patients and healthy volunteers. These effects appear due to stimulation of the CCKB receptor. In addition, clinically effective panicolytic agents reduce the sensitivity to CCK4 in PD patients. Taken together, these findings may suggest a role for CCK in the neurobiology of PD. On the other hand, there is circumstantial evidence for involvement of several other neuronal systems, such as the serotonergic, noradrenergic and GABA-ergic system, in the regulation of anxiety. Interestingly, evidence has been found for an interaction between CCK and 5-HT and that this interaction plays a role in the mediation of anxiety. This presentation will critically discuss the evidence for the role of the CCKB receptor in anxiety and in addition, will focus on the putative evidence that the role of CCK in anxiety is mediated by its interaction with the serotonergic neuronal system.

Coelenterazine distribution and luciferase characteristics in oceanic decapod crustaceans

Coelenterazine biosynthesis has recently been demonstrated in the developing eggs of the decapod Systellaspis debilis. The cellular source of coelenterazine and the potential for biosynthesis in adult decapods, however, have not been fully investigated. We have conducted a systematic study of coelenterazine content in >230 individual decapods representing 19 species of Oplophoridae and 22 species from other families. We show for the first time that coelenterazine is responsible for both secretory and photophore luminescence in the same decapod. Tissues associated with secretory luminescence (hepatopancreas and stomach) in the Oplophoridae contained almost 3 orders of magnitude more coelenterazine (mean value=2154 pmol per specimen) than cuticular photophores (mean value=8 pmol per specimen). Coelenterazine content increases by 2 to 4 orders of magnitude during the development of three species of Oplophoridae. Species of Oplophoridae contain an order of magnitude more coelenterazine than those of other families (mean value=154 pmol per specimen). Coelenterazine was also detected in 11 apparently nonluminous decapod species (mean value=200 pmol per specimen). S. debilis luciferase characterisation enabled a luciferase assay to be developed to facilitate studies of the environmental control of bioluminescence. We hypothesise that the coelenterazine requirement in secretory bioluminescence exceeds that which could be assimilated from the food-chain. The significant increase of coelenterazine during the life cycle of secretory decapods supports this hypothesis. Putative evidence for environmental control of coelenterazine luminescence is also reported.

THE NEAR‐SPINELESS TRACHELOMONAS GRANDIS (EUGLENOPHYCEAE) SUPERFICIALLY APPEARS SPINY BY ATTRACTING BACTERIA TO ITS SURFACE1,2

ABSTRACT Trachelomonas grandis Singh has a mucilaginous, highly porous mineralized lorica (envelope) generally without ornamentation except occasionally for a few short, tapered, anterior or posterior spines. However, as our first cultures of this species aged, rod‐shaped structures appeared on the loricas. That these surface projections were bacteria was determined by scanning and transmission electron microscopy. The bacteria, 2‐6 μm long with rounded apices, were oriented perpendicular to the exterior lorica surface and were attached on one end by apically produced tie‐down fibers. The bacteria also secreted fibers over their entire surface, forming a network between them that collapsed during specimen preparation for scanning electron microscopy. The density of the surface bacteria increased with time until the lorica took on a “spiny” appearance superficially similar to lorica extensions of algal origin. In mature algal specimens, an estimated 1200‐1800 bacteria per lorica occurred as a monolayer, the maximum number related to the surface area of the lorica available for bacterial colonization. The bacteria, always motionless while attached, showed putative evidence of budding. Fission formed short chains of up to three cells on the lorica. Our cultures maintained this association for 8 years (1972‐1979). However, cultures ordered for further study in the past year have failed to develop loricas with more than just a few bacterial cells, and most have none.

Effect of oxygen tension and cardiovascular operations on the myocardial antioxidant enzyme activities in patients with tetralogy of Fallot and aorta-coronary bypass

Since the chronically cyanotic myocardium appears to be more susceptible to reperfusion injury after cardiac operations than the noncyanotic myocardium, we studied the association between the preoperative arterial oxygen tension and the myocardial superoxide dismutase, catalase, and glutathione peroxidase activities. Fourteen patients with tetralogy of Fallot scheduled for elective operations had baseline arterial blood gas measurements done before operation. During the operation right ventricular biopsy specimens were taken for enzyme analysis immediately before cold blood cardioplegic arrest and 20 minutes after crossclamp removal. The tissue antioxidant enzyme activities of the patients with tetralogy of Fallot were compared with the myocardial results in 15 adults with stable angina pectoris having elective aorta-coronary artery bypass graft operations. Myocardial tissues removed from two patients with hypertrophic obstructive cardiomyopathy who had corrective operations were analyzed for antioxidant activities. There were no changes in myocardial antioxidant enzyme activities during the operation in the patients with tetralogy of Fallot and coronary artery bypass graft. The myocardial superoxide dismutase, catalase, and glutathione peroxidase activities correlated (0.82, 0.68, and 0.89, respectively) significantly (p values were less than 0.01, 0.05, and 0.01, respectively) with the preoperative arterial oxygen tensions in the patients with tetralogy of Fallot. The myocardial glutathione peroxidase activities were at least four times higher in the myocardium of patients with coronary artery bypass graft and hypertrophic obstructive cardiomyopathy than in that of those with tetralogy of Fallot. This study provides putative evidence that the myocardium of patients with tetralogy of Fallot is a risk of oxygen-derived free radical injury during and immediately after corrective cardiovascular operations.

Ammonium-stimulated potassium release from Lemna minor L. grown on a medium containing nitrate as N-source

Net K-efflux from duckweed ( Lemna minor L.) was initiated by the addition of NH 4Cl to nutrient medium with NO 3 as the only nitrogen source. Other NH 4-salts (sulfate or nitrate) were also effective, while LiCl, NaCl, RbCl or CsCl caused no major K-release under the same conditions. Sodium, Rb and Cs ions lowered the net K-uptake observed in controls with no effector added, while in presence of Li ions the absorption of K was stimulated. These results provide putative evidence that K-release into the medium is specific for NH 4 addition and not a general effect of monovalent cations. The level and the time course for K-efflux depended on the NH 4 concentration added (1–30 mM), but the pH in the medium (3.7, 6.8 or 7.9) caused only minor effects. These findings suggest that the K-release was initiated by NH 4 ions rather than by NH 3 passing through the plasmalemma. Magnesium ions were released in a similar manner after NH 4 additions, but only to about 10% of the rate observed for K. No clear NH 4-stimulated net efflux was observed for Na and Ca ions. Potassium-release was not detectable after the addition of high NH 4 concentrations to duckweed grown on NH 4-medium. The release of K was apparently associated with the transition from NO 3 to NH 4 utilization and might be linked directly or indirectly to the high initial absorption rate for NH 4.

Effect of oxygen tension on the anti-oxidant enzyme activities of tetralogy of Fallot ventricular myocytes

Since the chronically cyanotic tetralogy of Fallot (TOF) myocardium is more sensitive to reperfusion injury after cardiac surgery than the adult myocardium, we decided to study the regulation of myocardial superoxide dismutase (SOD), catalase and glutathione peroxidase by oxygen tension. TOF myocytes were cultured at a P o 2 of 150 mmHg for 30 days to establish the culture. The cells were then cultured at P o 2 of 150 and 40 mmHg and the myocyte antioxidant enzymes measured at days 3, 7, 14 and 21. On day 21 the myocytes cultured at P o 2 of 40 mmHg were then cultured at 150 mmHg and SOD and catalase activities measured on days 28 and 35. Although there were no differences in the rates of incorporation of 35S-methionine into the myocytes at either P o 2 on these days, the myocytes scavenger enzyme levels were significantly higher by day 14 when cultured at a P o 2 of 150 mmHg than at a P o 2 of 40 mmHg. With the increase in oxygen tension from 40 to 150 mmHg, SOD and catalase activities increased significantly by day 35. The myocytes cultured at P o 2 40 mmHg were more sensitive by day 7 to an hypoxanthine-xanthine oxidase generated free radical injury than the P o 2 150 mmHg cultured cells. The regulation of these enzyme activities by oxygen tension and the increased sensitivity to free radical injury of the myocytes cultured at an oxygen tension of 40 mmHg provide putative evidence that the chronically cyanotic myocardium may be less well protected than the normally perfused myocardium against oxygen-mediated free radical injury and be at higher risk for cardiovascular surgery.

The impact on archaeology of radiocarbon dating by accelerator mass spectrometry

Radiocarbon dating by accelerator mass spectrometry (AMS) differs fundamentally from conventional 14 C dating because it is based on direct determination of the ratio of 14 C : 12 C atoms rather than on counting the radioactivity of 14 C. It is therefore possible to measure much lower levels of 14 C in a sample much more rapidly than the conventional technique allows. Consequently, minimum sample size is reduced approximately 1000-fold (from ca . 1 g to ca . 1 mg) and the datable time span of the method can, theoretically, be doubled (from ca . 40 ka to ca . 80 ka). As yet, extension of the time span has not been achieved, because of the effects of sample contamination, but the great reduction in sample size is already having a major impact on archaeology by extending the range of organic remains that can be dated, and, especially, by allowing the archaeologist and the radiocarbon chemist to adopt more selective sampling strategies. This greater selectivity, in the field and the laboratory, is the most important archaeological attribute of AMS 14 C dating. It allows on-site chronological consistency to be tested by multiple sampling; archaeological materials to be dated that contain too little C, or are too rare or valuable, to be dated by the conventional method; and the validity of a date to be tested by isolating and independently dating particular fractions in chemically complex samples. AMS laboratories have only been processing archaeological samples since 1982, but already several, notably those at Oxford, Toronto, and Tucson, Arizona, have made substantial contributions to archaeological dating. The Oxford laboratory has, since 1983, processed ca. 1200 samples and published over 500 archaeological dates. Particular attention is therefore paid in this paper to the archaeological significance of the dates obtained at Oxford. The ams 14C technique can contribute to archaeological dating in two complementary ways: (i) by testing prevailing assumptions about the antiquity of indirectly dated objects and materials, i.e. verification or falsification dating; and (ii) by dating new or existing archaeological sequences in greater detail than can be achieved by the conventional 14 C technique, i.e. the building of new and more detailed chronologies. In this paper, recent archaeological applications of the new technique are reviewed under these two headings: verification dating applied to the origin and spread of anatomically modern humans in Europe and the Americas, to putative evidence for early (pre-Neolithic) agriculture in Israel and Egypt, and to the dating of rare Palaeolithic and later artefacts; and the building of new and more-detailed chronologies illustrated by reference to Upper Palaeolithic sequences in Europe, Mesolithic—Neolithic sequences in Southwest Asia, and Neolithic-Bronze Age chronologies in Britain. It is concluded that the development and application of the ams technique represents a revolution in 14 C dating that will have a profound impact on many aspects of archaeological research.

Avocado cellulase: nucleotide sequence of a putative full-length cDNA clone and evidence for a small gene family

A cDNA library was prepared from ripe avocado fruit (Persea americana Mill. cv. Hass) and screened for clones hybridizing to a 600 bp cDNA clone (pAV5) coding for avocado fruit cellulase. This screening led to the isolation of a clone (pAV363) containing a 2021 nucleotide transcribed sequence and an approximately 150 nucleotide poly(A) tail. Hybridization of pAV363 to a northern blot shows that the length of the homologous message is approximately 2.2 kb. The nucleotide sequence of this putative full-length mRNA clone contains an open reading frame of 1482 nucleotides which codes for a polypeptide of 54.1 kD. The deduced amino acid composition compares favorably with the amino acid composition of native avocado cellulase determined by amino acid analysis. Southern blot analysis of Hind III and Eco RI endonuclease digested genomic DNA indicates a small family of cellulase genes.