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J Parker

Publications and source records attributed to J Parker.

At least 19 recordsLinked to original sources
PubMed2006

Watershed nitrogen and mercury geochemical fluxes integrate landscape factors in long-term research watersheds at Acadia National Park, Maine, USA.

This paper is an overview of this special issue devoted to watershed research in Acadia National Park (Acadia NP). The papers address components of an integrated research program on two upland watersheds at Acadia NP, USA (44 degrees 20' N latitude; 68 degrees 15' E longitude). These watersheds were instrumented in 1998 to provide a long-term foundation for regional ecological and watershed research. The research was initiated as part of EPA/NPS PRIMENet (Park Research and Intensive Monitoring of Ecosystems Network), a system of UV-monitoring stations and long-term watershed research sites located in US national parks. The initial goals at Acadia NP were to address research questions about mercury, acid rain, and nitrogen saturation developed from prior research. The project design was based on natural differences in forests and soils induced by an intense wildfire in one watershed in 1947. There is no evidence of fire in the reference watershed for several hundred years. We are testing hypotheses about controls on surface water chemistry, and bioavailability of contaminants in the contrasting watersheds. The unburned 47-ha Hadlock Brook watershed is 70% spruce-fir mature conifer forest. In contrast, burned 32-ha Cadillac Brook watershed, 4 km northeast of the Hadlock watershed, is 20% regenerating mixed northern hardwoods and 60% shrub/rocky balds. Differences in atmospheric deposition are controlled primarily by forest stand composition and age. The watersheds are gauged and have water chemistry stations at 122 m (Cadillac) and 137 m (Hadlock); watershed maximum elevations are 468 and 380 m, respectively. The stream water chemistry patterns reflect, in part, the legacy of the intense fire, which, in turn, controls differences in forest vegetation and soil characteristics. These factors result in higher nitrogen and mercury flux from the unburned watershed, reflecting differences in atmospheric deposition, contrasting ecosystem pools of nitrogen and mercury, and inferred differences in internal cycling and bioavailabilty.

Acid Rain↗
PubMed2006

Critical pathways in heart function: bis(2-chloroethoxy)methane-induced heart gene transcript change in F344 rats.

Gene transcript changes after exposure to the heart toxin, bis(2-chloroethoxy)methane (CEM), were analyzed to elucidate mechanisms in cardiotoxicity and recovery. CEM was administered to 5-week-old male F344/N rats at 0, 200, 400, or 600 mg/kg by dermal exposure, 5 days per week, for a total of 12 doses by study day 16. Heart toxicity occurred after 2 days of dosing in all 3 regions of the heart (atrium, ventricle, interventricular septum) and was characterized by myofiber vacuolation, necrosis, mononuclear-cell infiltration, and atrial thrombosis. Ultrastructural analysis revealed that the primary site of damage was the mitochondrion. By day 5, even though dosing was continued, the toxic lesions in the heart began to resolve, and by study day 16, the heart appeared histologically normal. RNA was extracted from whole hearts after 2 or 5 days of CEM dosing. After a screen for transcript change by microarray analysis, dose-response trends for selected transcripts were analyzed by qRT-PCR. The selected transcripts code for proteins involved in energy production, control of calcium levels, and maintenance of heart function. The down-regulation of ATP subunit transcripts (Atp5j, ATP5k), which reside in the mitochondrial membranes, indicated a decrease in energy supply at day 2 and day 5. This was accompanied by down-regulation of transcripts involved in high-energy consumption processes such as membrane transport and ion channel transcripts (e.g., abc1a, kcnj12). The up-regulation of transcripts encoding for temperature regulation and calcium binding proteins (ucp1 and calb3) only at the 2 low exposure levels, suggest that these adaptive processes cannot occur in association with severe cardiotoxicity as seen in hearts at the high exposure level. Transcript expression changes occurred within 2 days of CEM exposure, and were dose-and time-dependent. The heart transcript changes suggest that CEM cardiotoxicity activates protective processes associated energy conservation and maintenance of heart function.

Animals↗
PubMed2005

A simulation-based approach to forecasting the next great San Francisco earthquake.

In 1906 the great San Francisco earthquake and fire destroyed much of the city. As we approach the 100-year anniversary of that event, a critical concern is the hazard posed by another such earthquake. In this article, we examine the assumptions presently used to compute the probability of occurrence of these earthquakes. We also present the results of a numerical simulation of interacting faults on the San Andreas system. Called Virtual California, this simulation can be used to compute the times, locations, and magnitudes of simulated earthquakes on the San Andreas fault in the vicinity of San Francisco. Of particular importance are results for the statistical distribution of recurrence times between great earthquakes, results that are difficult or impossible to obtain from a purely field-based approach.

Disasters↗
PubMed2003

Radiographic abnormalities among construction workers exposed to quartz containing dust.

BACKGROUND: Construction workers are exposed to quartz containing respirable dust, at levels that may cause fibrosis in the lungs. Studies so far have not established a dose-response relation for radiographic abnormalities for this occupational group. AIMS: To measure the extent of radiographic abnormalities among construction workers primarily exposed to quartz containing respirable dust. METHODS: A cross sectional study on radiographic abnormalities indicative of pneumoconiosis was conducted among 1339 construction workers mainly involved in grinding, (jack)-hammering, drilling, cutting, sawing, and polishing. Radiological abnormalities were determined by median results of the 1980 International Labour Organisation system of three certified "B" readers. Questionnaires were used for assessment of occupational history, presence of respiratory diseases, and symptoms and smoking habits. RESULTS: An abnormality of ILO profusion category 1/0 and greater was observed on 10.2% of the chest radiographs, and profusion category of 1/1 or greater on 2.9% of the radiographs. The average duration of exposure of this group was 19 years and the average age was 42. The predominant type of small opacities (irregularly shaped) is presumably indicative of mixed dust pneumoconiosis. The prevalence of early signs of nodular silicosis (small rounded opacities of category 1/0 or greater) was low (0.8%). CONCLUSIONS: The study suggests an elevated risk of radiographic abnormalities among these workers with expected high exposure. An association between radiographic abnormalities and cumulative exposure to quartz containing dust from construction sites was observed, after correction for potentially confounding variables.

Adult↗
PubMed2002

Studies of embryo transfer from cattle clinically affected by bovine spongiform encephalopathy (BSE).

Semen from 13 bulls, eight with clinical bovine spongiform encephalopathy (BSE), was used to artificially inseminate (AI) 167 cows with clinical BSE, and their resultant embryos were collected non-surgically seven days after AI. The viable and non-viable embryos with intact zonae pellucidae were washed 10 times (as recommended by the International Embryo Transfer Society) then frozen. Later, 587 of the viable embryos were transferred singly into 347 recipient heifers imported from New Zealand, and 266 live offspring were born of which 54.1 per cent had a BSE-positive sire and a BSE-positive dam. The recipients were monitored for clinical signs of BSE for seven years after the transfer, and the offspring were monitored for seven years after birth. Twenty-seven of the recipients and 20 offspring died while being monitored but none showed signs of BSE. Their brains, and the brains of the recipients and offspring killed after seven years, were examined for BSE by histopathology, PrP immunohistochemistry, and by electron microscopy for scrapie-associated fibrils. They were all negative. In addition, 1020 non-viable embryos were sonicated and injected intracerebrally into susceptible mice (20 embryos per mouse) which were monitored for up to 700 days, after which their brains were examined for spongiform lesions. They were all negative. It is concluded that embryos are unlikely to carry BSE infectivity even if they have been collected at the end-stage of the disease, when the risk of maternal transmission is believed to be highest.

Animals↗
PubMed2002

Does the opioid-sparing effect of rectal diclofenac following total abdominal hysterectomy benefit the patient?

BACKGROUND: The aim of this prospective, double-blind, randomized, placebo-controlled clinical trial was to investigate the opioid-sparing effects of rectal diclofenac following total abdominal hysterectomy. METHODS: Forty ASA I-II patients, aged 20-60 yr, were randomized to receive identical-looking suppositories of either diclofenac 75 mg or placebo, twice daily. All patients were given a standardized anaesthetic, with intravenous morphine via a patient-controlled analgesia device and either diclofenac or placebo for postoperative analgesia. RESULTS: The median 24 h morphine consumption (interquartile range) was significantly higher (P=0.02) in the placebo group [59 (45-85) mg] than in the diclofenac group [31 (14-65) mg]. In comparison with the placebo group, there were significant reductions in total pain score in the diclofenac group at rest (P=0.04) and on movement (P<0.01). Total (SD) sedation score was significantly lower (P=0.04) in the diclofenac group [90 (73) mm] than in the placebo group [148 (89) mm]. Total (interquartile range) nausea score was significantly lower (P<0.01) in the diclofenac group [14 (0-53) mm] than in the placebo group [64 (30-109) mm]. There was no significant difference between the two groups of patients in episodes of vomiting or number of rescue antiemetics. CONCLUSIONS: Rectal diclofenac reduces morphine consumption, improves postoperative analgesia, and reduces the incidence of adverse effects such as sedation and nausea.

Administration, Rectal↗
PubMed2001

Observation of a (6)(LambdaLambda)He double hypernucleus.

A double-hyperfragment event has been found in a hybrid-emulsion experiment. It is identified uniquely as the sequential decay of ( 6)(LambdaLambda)He emitted from a Xi(-) hyperon nuclear capture at rest. The mass of ( 6)(LambdaLambda)He and the Lambda-Lambda interaction energy DeltaB(LambdaLambda) have been measured for the first time devoid of the ambiguities due to the possibilities of excited states. The value of DeltaB(LambdaLambda) is 1.01+/-0.20(+0.18)(-0.11) MeV. This demonstrates that the Lambda-Lambda interaction is weakly attractive.

Journal Article↗
PubMed2001

The CGM1a (CEACAM3/CD66d)-mediated phagocytic pathway of Neisseria gonorrhoeae expressing opacity proteins is also the pathway to cell death.

Phagocytosis of Opa+ Neisseria gonorrhoeae (gonococcus, GC) by neutrophils is in part dependent on the interaction of Opa proteins with CGM1a (CEACAM3/CD66d) antigens, a neutrophil-specific receptor. However, the signaling pathways leading to phagocytosis have not been characterized. Here we show that interaction of OpaI bacteria with neutrophils or CGM1a-transfected DT40 cells induces calcium flux, which correlates with phagocytosis of bacteria. We identified an immunoreceptor tyrosine-based activation motif (ITAM) in CGM1a, and showed that the ability of CGM1a to transduce signals and mediate phagocytosis was abolished by mutation of the ITAM tyrosines. We also demonstrated that CGM1a-ITAM-mediated bacterial phagocytosis is dependent on Syk and phospholipase C activity in DT40 cells. Unexpectedly, the activation of the CGM1a-ITAM phagocytic pathway by Opa+ GC results in induction of cell death.

Amino Acid Sequence↗
PubMed2001

A new technique for esophagojejunostomy after total gastrectomy for gastric cancer.

BACKGROUND: The critical part of any operation involving a proximal gastric resection is the esophageal anastomosis. Leakage from this anastomosis is one of the main reasons for postoperative morbidity and death after gastrectomy. Application of the double-stapling technique affords many of the same advantages that it does for low rectal tumors, especially in obese patients with narrow costal margins. METHODS: A new technique for esophagojejunostomy after total gastrectomy for gastric cancer is described. RESULTS: This technique has been used in 3 patients. At a follow-up of 22 months, there have been no anastomotic leaks or evidence of clinical stenoses. CONCLUSIONS: This technique minimizes manipulation and dissection around the distal esophagus. Not only does this make the operation easier, but it also allows for a longer proximal resection margin. Possibly this will result in lower rates of esophageal breakdown.

Equipment Design↗
PubMed2001

Preparing for the end of life: preferences of patients, families, physicians, and other care providers.

To examine patients', families', and health care providers' preferences regarding preparation for the end of life, attributes of preparation were generated in qualitative focus group discussions and subsequently tested for generalizability in a quantitative national survey. Respondents from all groups showed consensus on the importance of naming someone to make decisions, knowing what to expect about one's physical condition, having financial affairs in order, having treatment preferences in writing, and knowing that one's physician is comfortable talking about death and dying. Patients were more likely than physicians to want to plan funerals and know the timing of death and less likely than all other groups to want to discuss personal fears. Participants in care of dying patients agree overwhelmingly with the importance of preparation. However, significant barriers to preparation impede it from being a common part of clinical encounters. Further research and training are needed to ensure that the desire for greater preparation is translated into improved action toward preparation in medical practice.

Adult↗
PubMed2001

Biolistic transformation of Arabidopsis root hairs: a novel technique to facilitate map-based cloning.

The final stage of map-based gene isolation is complementation of the mutant phenotype with wild-type DNA to determine the exact location of the gene of interest. This usually involves Agrobacterium tumefaciens-mediated transformation, which is reliable and produces stable transformants. However, the process of Agrobacterium transformation may take up to three months to complete. If the mutant phenotype can be seen in a single cell, and the wild-type copy of the gene can act cell autonomously, then complementation of the whole plant is not strictly necessary. We have developed a technique for the biolistic transformation of Arabidopsis thaliana root hairs, and used this to test large insert clones for complementation of two recessive mutant phenotypes, a procedure that takes less than a day. Our results show that biolistic transformation can be used with transient assays to conduct rapid tests for complementation by large insert clones.

Agrobacterium tumefaciens↗
PubMed2001

Defining radiographic criteria for flexion-extension studies of the cervical spine.

STUDY OBJECTIVE: We sought to describe and measure 3 radiographic variables in normal male volunteers and determine whether these variables could be useful in establishing more objective radiographic criteria for evaluation of flexion-extension studies of the cervical spine. In addition, we hypothesized that patients with a normal cervical spine should not have greater than 2 mm of subluxation present with flexion or extension. METHODS: A prospective, observational study of normal male volunteers between the ages of 18 and 40 years was performed. We obtained radiographs of all participants in neutral, flexion, and extension positions and measured the amount of subluxation and interspinous distance, as well as the degree of vertebral angulation between C3 and C7. RESULTS: One hundred male volunteers were included in the study. Subluxation during flexion (compared with neutral) was greater than 2 mm in none of the participants at each level from C3 to C7 (95% confidence interval [CI] 0 to 3.6); subluxation in extension was greater than 2 mm in one participant at one level from C3 to C4 (95% CI 0 to 5.5) and none of the participants at each of the remaining 3 levels from C4 to C7 (95% CI 0 to 3.6). Comparing flexion with the neutral position, the mean vertebral angulation and SD were 24.2 degrees and 13.3 degrees, and the 95% certainty interval (CEI) was -1.9 to 50.2. Comparing extension with the neutral position, the mean vertebral angulation was 14.1 degrees, with an SD of 13.3 degrees, and the 95% CEI was -4.6 to 32.8. The mean change in interspinous distance between the neutral position and flexion varied from 1.2 to 4.6 mm (SD 1.7 to 2.4 mm), depending on the level of cervical spine studied. When comparing the neutral position and extension, the mean change in interspinous distance varied from 1.2 to 2.2 mm (SD 1.7 to 1.9). CONCLUSION: Currently, there are no clinically validated criteria for evaluating flexion-extension studies of the cervical spine. Our study suggests that subluxation greater than 2 mm in men 18 to 40 years of age may be a useful variable for further study as an indicator of ligamentous injury. Interspinous distance and vertebral angulation appear less likely to have useful clinical application.

Adolescent↗
PubMed2001

The nucleus double array cochlear implant: a new concept for the obliterated cochlea.

OBJECTIVE: To increase the number of intracochlear electrodes that may be inserted into a totally obliterated cochlea, a special implant has been developed in collaboration with Cochlear Limited. This implant features two separate electrode carriers containing 11 and 10 active electrodes, respectively, as well as a reference electrode located on the receiver-stimulator package. The potential stimulation modes available with this device therefore include monopolar and bipolar stimulation, and stimulation between both arrays. SURGICAL TECHNIQUE: A cochleostomy anterior to the round window provides access to the basal turn (both the scala tympani and the scala vestibuli), and new built connective tissue and bone can be removed until the anterior wall of the basal turn is approached. A second cochleostomy is performed at the second turn caudal of the cochleariform process and 2 mm anterior of the oval window after removal of the incus. New tissue should also be removed if necessary. The two electrode carriers are then placed into the scala tympani of the basal and the scala vestibuli of the second turn, respectively. The remaining surgical procedure is identical with that used for cochlear implantation in patients without obliterated cochleas. PATIENTS: In this clinical study, 10 patients aged 32 to 66 years with an obliterated cochlea each received a double array cochlear implant. All patients had total obliteration of the basal turn either on preoperative imaging or during surgery. Intraoperatively, the second turn was not obliterated in only 4 of 10 patients. Postoperatively, a standard audiologic test battery was used to determine auditory improvement over time. POSTOPERATIVE RESULTS: All patients achieved significantly improved speech understanding when the additional apical electrode array was used, compared with the use of each electrode array independently. No complications occurred. CONCLUSION: In patients with a totally obliterated cochlea, the number of intracochlear electrodes can be increased by use of the Nucleus double array implant. As a result, patients achieve significantly better auditory results.

Adult↗
PubMed2001

The advantages of microlaparoscopic left upper quadrant entry in selected patients.

We describe a series of cases where microlaparoscopic left upper quadrant (LUQ) entry was used as the primary peritoneal entry site in patients considered unsuitable for initial port placement through the umbilicus. Microlaparoscopic LUQ entry is becoming a standard technique in gynaecological laparoscopic surgery and appears to provide a safe alternative entry site in selected patients.

Adult↗