PubMed Health⌕ Search

Biomedical subjects

G Jacobson

Publications and source records attributed to G Jacobson.

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↗
PubMed2001

Synthesizing spatially complex sound in virtual space: an accurate offline algorithm.

The study of spatial processing in the auditory system usually requires complex experimental setups, using arrays of speakers or speakers mounted on moving arms. These devices, while allowing precision in the presentation of the spatial attributes of sound, are complex, expensive and limited. Alternative approaches rely on virtual space sound delivery. In this paper, we describe a virtual space algorithm that enables accurate reconstruction of eardrum waveforms for arbitrary sound sources moving along arbitrary trajectories in space. A physical validation of the synthesis algorithm is performed by comparing waveforms recorded during real motion with waveforms synthesized by the algorithm. As a demonstration of possible applications of the algorithm, virtual motion stimuli are used to reproduce psychophysical results in humans and for studying responses of barn owls to auditory motion stimuli.

Acoustic Stimulation↗
PubMed1999

Medical management of non-viable early first trimester pregnancy.

OBJECTIVE: To compare the efficacy of intramuscular methotrexate plus vaginal misoprostol to vaginal misoprostol alone in completing abortion in women with non-viable early first trimester pregnancy. METHOD: Twenty-one women with non-viable pregnancy up to 49 days gestation were randomized to receive intramuscular methotrexate, followed 2 days later by vaginal misoprostol or misoprostol alone. We also collected patient satisfaction information. RESULT: Complete abortion occurred in all 12 (100%) women in the combined group and eight of nine (89%, RR = 1.13, CI 0.89-1.42) women in the misoprostol only group. Of the women, 75% rated their experience as good and would choose medical management again. CONCLUSION: Either methotrexate plus misoprostol or misoprostol alone effectively completed abortion in women with non-viable early pregnancy and represent acceptable medical alternatives to surgery or expectant management.

Abortifacient Agents, Nonsteroidal↗
PubMed1999

Renal effects of low to moderate doses of dopamine in newborn piglets.

PURPOSE: Administration of dopamine to adult animal and human subjects results in increased renal blood flow, and it may also enhance the glomerular filtration rate. However, renal hemodynamic effects of exogenous dopamine in the neonate are unclear. In this study, we examined the renal actions of low to moderate doses of exogenous dopamine in newborn piglets. METHODS: The animals were anesthetized, catheterized for vascular access and urine collection, and assigned randomly to a control group or treatment groups receiving dopamine infusion at 2, 5, or 10 microg/kg/min. Data were collected at baseline, during dopamine infusion, and 1 hour after cessation of infusion. Mean arterial blood pressure (MAP) and heart rate (HR) were monitored. Glomerular filtration rate (GFR), cardiac index (CI), and renal blood flow (RBF) were determined. Fractional excretion of sodium (FENa) was calculated. RESULTS: Dopamine did not alter renal blood flow nor did it significantly alter CI in spite of a modest increase in heart rate and mean arterial blood pressure. There was a statistically significant increase in GFR at 10 microg/kg/min and in FENa at all doses. CONCLUSIONS: Low doses of dopamine produce significant natriuresis probably by direct action on renal tubules and at moderate doses via, both, increase in GFR and a direct tubular effect. Low and moderate doses of dopamine do not increase RBF as seen in adult animals, possibly because of immaturity of dopaminergic receptors in newborn piglets.

Animals↗
PubMed1999

Single-strand conformational polymorphism (SSCP)-detected p53 gene mutations are a less sensitive marker of malignancy in pleural fluids than p53 immunostaining.

p53 immunostaining has been advocated as a marker of malignancy in pleural biopsies and serous fluids. The object of this study was to compare the sensitivity and specificity of p53 immunostaining for the detection of malignant cells in pleural fluids with a technique designed to detect p53 gene mutations in exons 5, 6, 7 and 8 by SSCP and nucleotide sequencing. Five out of eight pleural fluids containing adenocarcinoma showed p53 immunostaining and two of these also showed polymorphisms on SSCP and a mutation on sequencing. None of the 10 benign pleural fluids showed immunostaining for p53 or polymorphisms on SSCP. We believe that the poor sensitivity of p53 gene mutation by SSCP is mainly due to DNA from the background reactive cells 'swamping' the mutant DNA. We do not advocate its use as a diagnostic aid.

Adenocarcinoma↗
PubMed1999

Mutations of p53 gene and SV40 sequences in asbestos associated and non-asbestos-associated mesotheliomas.

AIM: To examine mesotheliomas for a possible relation between p53 immunostaining, p53 gene mutation, simian virus 40 (SV40), and asbestos exposure. METHODS: Paraffin sections from 11 mesotheliomas were used for p53 immunostaining and also to extract DNA. This was analysed for the presence of mutations in exons 5 to 8 of the p53 gene using a "cold" single strand conformational polymorphism method, together with sequencing. The DNA from the paraffin sections was also used to search for SV40 sequences. A 105 base pair segment at the 3' of the SV40 large T antigen (Tag) was targeted and any PCR amplification products were sequenced to confirm that they were of SV40 origin. EDAX electron microscopic differential mineral fibre counts were performed on dried lung tissue at a specialist referral centre. RESULTS: The fibre counts showed that seven of the mesotheliomas were associated with abnormally high asbestos exposure. Of these, two showed p53 immunostaining, none showed p53 gene mutation, and five showed SV40. Of the four other mesotheliomas, three showed p53 immunostaining, one showed a (silent) p53 mutation, and none showed SV40. The difference in frequency of SV40 detection was significant at the p < 0.05 level. CONCLUSIONS: Immunostaining for the p53 gene was relatively common but p53 mutations were rare in this series. SV40 virus sequence was detected in five of seven asbestos associated mesotheliomas but in none of the non-asbestos-associated mesotheliomas. This suggests there may be a synergistic interaction between asbestos and SV40 in human mesotheliomas. A study with a larger number of cases is needed to investigate these observations further.

Asbestos↗
PubMed1999

Intraarterial chemoembolisation with lipiodol and epirubicin in hepatocellular cancer--improved survival in some patients?

BACKGROUND AND AIMS: Arterial chemoembolisation with lipiodol and a cytotoxic drug is reported to give equivocal results in irresectable primary hepatocellular cancer (HCC). In order to further elucidate the possible response to this treatment, we analysed the results of all patients with irresectable HCC treated with chemoembolisation at our hospital. MATERIAL AND METHODS: 58 consecutive patients with HCC were treated with lipiodolepirubicin chemoembolisation between February 1988 - October 1994 and followed until death or October 1998. RESULTS: The average survival was 11.7 months and median survival was 6 months. 17 patients had only one treatment mostly due to death within 6 weeks after the first treatment. Patients with an open portal system at inclusion (50% of all) were found to have significantly increased survival after 6 and 12 months compared to those with portal obstruction. The subgroup of patients displaying a decrease in tumour size as judged by repeated CT scan 6 months after inclusion had significantly increased survival; all survived more than 12 months (median survival 30 months). CONCLUSIONS: Chemoembolisation with lipiodol-epirubicin may have an impact on survival on selected patients with irresectable hepatocellular cancer. The treatment may justifiably be offered patients with an open portal venous system and without liver failure.

Adult↗
PubMed1998

Mutations of p53 gene can be detected in the plasma of patients with large bowel carcinoma.

AIMS: To attempt to detect p53 gene mutations in the plasma of patients with large bowel carcinoma. METHODS: Plasma was collected from 20 control patients with no history of cancer and from 17 patients with large bowel carcinoma. Corresponding tumour and benign lymph node (control) samples for each of the carcinoma patients were obtained from paraffin blocks. A Dukes' stage was determined for each tumour. DNA was extracted from the plasma samples and the paraffin embedded tissue using previously described methods. A nested primer polymerase chain reaction protocol was used for the amplification of exons 5 to 8 of the p53 gene. "Cold" single strand conformational polymorphism (SSCP) was performed on mini gels and silver stained. Abnormal bands were excised, the DNA eluted, and reamplified for automated dye termination sequencing. Any sample showing an apparent mutation was rechecked from the original extracted DNA sample at least three times. RESULTS: p53 gene mutations were not found in the control specimens. They were found in both the primary tumour and the plasma in three cases, in the primary tumour alone in one case, and in the plasma alone in two cases. One of the latter two cases also had metastatic transitional cell carcinoma of the bladder and the other had widespread metastatic deposits. One of the cases with mutant DNA in both the plasma and the primary was a Dukes' stage B tumour. The others were Dukes' C and Dukes' D. CONCLUSIONS: p53 gene mutations can be detected in the plasma of some patients with large bowel carcinoma and these are concordant with those in the primary carcinomas.

Adult↗
PubMed1997

Magnetic resonance angiography in the resectability assessment of suspected pancreatic tumours.

The aim of this prospective study was to evaluate MRI, including MR angiography (MRA), in the preoperative assessment of the resectability of suspected malignancy of the pancreas. A total of 17 patients with suspected pancreatic carcinoma and planned surgery were investigated with conventional angiography, ultrasonography with Doppler technique, MRI and MRA. The MRA protocol included both 2D inflow angiography and 3D phase-contrast angiography. Surgery was carried out in 13 patients. The image quality of MRA was judged satisfactory in all cases. The findings with respect to vascular involvement agreed between the radiological methods in all but 3 cases. When the findings were correlated with the final diagnosis, one false-negative case was found for each of the three methods. The results suggest that MRI with MRA, including both the phase-contrast and inflow techniques, has a similar diagnostic value to that of conventional angiography and ultrasonography in the preoperative assessment of the portal venous system in patients with pancreatic carcinoma. Further studies are needed to establish the optimal diagnostic procedure.

Biopsy↗
PubMed1996

Efficiency of percutaneous core biopsy in pancreatic tumor diagnosis.

BACKGROUND: Radiologic diagnosis of pancreatic tumors exhibits limited precision. The aim of this study was to investigate the outcome and complications of pancreatic core biopsy in patients with suspected pancreatic neoplasms. METHODS: One hundred patients underwent ultrasonography-guided core biopsy of 1.2 mm external diameter. Medical charts were examined for biochemical and clinical signs of complications. Final diagnosis was settled by operation, autopsy, and clinical signs of the disease including survival with at least 2.3 years of follow-up. RESULTS: Histopathologic biopsy evaluation showed correct discrimination between exocrine and endocrine tumors and nonneoplastic conditions in 89 patients. No false-positive cancer diagnosis was found, and guidance on nature of primary tumors was obtained for eight of eight metastases. The sensitivity was 91% for exocrine and 87% for endocrine pancreatic tumors, and negative predictive values of these diagnoses were 83% and 97%, respectively. No clinically significant complications were noted. CONCLUSIONS: Core biopsy is an attractive alternative to diagnostic laparotomy in unresectable pancreatic cancer and efficiently provides diagnosis of endocrine tumors and pancreatic metastases in conjunction with rare complications. Benign biopsy findings cannot be used to exclude presence of primary or metastatic pancreatic neoplasms.

Biopsy↗
PubMed1996

Lack of correlation between flow cytometric and immunohistologic proliferation measurements of tumors.

We compared different means of assaying tumor proliferative activity by either flow cytometric or immunohistologic methods in formalin-fixed, paraffin-embedded blocks. A series of 84 Dukes' stage B colorectal carcinomas were examined to identify high-risk patients who may potentially benefit from adjuvant therapy. Flow cytometric analysis was performed by a modified Hedley method with a combined S+G2/M phase proliferative fraction calculated by means of a rectangular model after debris subtraction. Immunohistologic tumor proliferative activity was analyzed by means of serial step sections from the same blocks used for flow cytometric examination with antibodies to proliferating cell nuclear antigen (PCNA) and Ki-67 (MIB-1). Mean with standard deviation and (range) tumor proliferative activity measurements were: flow cytometric analysis: proliferative fraction = 14.8% +/- 5.3 (5-27%), PCNA = 43.2% +/- 21.2 (4-90%), and MIB-1 = 16.2% +/- 10.8 (2-47%). No correlation was found between flow cytometric proliferative fraction and immunohistologic tumor proliferation measurement or between PCNA and MIB-1 staining indices. Lack of correlation between flow cytometric and immunohistologic findings may be related to the use of archival formalin-fixed paraffin-embedded tissue for flow cytometric evaluation, with resultant increased debris and decreased accuracy of cell cycle calculations. Discordance between PCNA and MIB-1 may reflect inherent problems with anti-PCNA antibody staining of formalin-fixed tissues whereby anti-PCNA clone PC-10 detects non-replicon associated PCNA in formalin-fixed tissues. Prospective studies using fresh tissue with two-color multiparameter flow cytometric analysis and histogram-dependent background fitting may help to clarify the relationship between findings of tumor proliferation as analyzed by flow cytometric and by immunohistologic techniques.

Adenocarcinoma↗
PubMed1991

Treatment planning optimization using constrained simulated annealing.

A variation of simulated annealing optimization called 'constrained simulated annealing' is used with a simple annealing schedule to optimize beam weights and angles in radiation therapy treatment planning. Constrained simulated annealing is demonstrated using two contrasting objective functions which incorporate both biological response and dose-volume considerations. The first objective function maximizes the probability of a complication-free treatment (PCFT) by minimizing the normal tissue complications subject to the constraint that the entire target volume receives a prescribed minimum turmourcidal dose with a specified dose homogeneity. Probabilities of normal tissue complication are based on published normal tissue complication probability functions and computed from dose-volume histograms. The second objective function maximizes the isocentre dose subject to a set of customized normal tissue dose-volume and target volume dose homogeneity constraints (MVDL). Although the PCFT objective function gives consistently lower estimates of normal tissue complication probabilities, the ability to specify individualized dose-volume limits, and therefore the individualized probability of complication, for an individual organ makes the MDVL objective function more useful for treatment planning.

Esophageal Neoplasms↗
PubMed1990

Important parameters in semi-dry electrophoretic transfer.

The efficiency of semi-dry electrophoretic transfer after sodium dodecyl sulfate (SDS)-electrophoresis using PhastGel media was investigated in a model system using three isotope labelled proteins. To give a full picture of the blotting process the amount of protein present in the gel, membranes, and filter papers was determined after different transfer times. The influence of the transfer buffer, commonly used additives such as methanol and SDS, and several different immobilizing matrices was investigated. Soybean trypsin inhibitor, bovine serum albumin, and ferritin were used as model proteins to study the effect of size on transfer efficiency. Basically, all three stages of the blotting process decide the result; the elution of protein from the gel, the immobilization of protein to the membrane, and the loss of material from the membrane during transfer. A theoretical explanation for the observed poor binding to a second membrane is discussed. Our results show that the buffer composition has little influence on the efficiency of transfer from the gel, but can be significant to the binding capacity of the membrane. In all experiments performed, there was never one moment during the transfer when all protein was eluted from the gel and simultaneously still bound to the membrane. The highest recovery in the membrane was obtained at different time intervals for different proteins. This indicates that quantitative transfer procedures cannot be generalized. However, obtaining an optimal method for reliable quantification of a specific protein or group of proteins is possible. For general protein staining of nitrocellulose and polyvinylidene difluoride membranes, a highly sensitive silver staining method requiring only 15 min has been used.

Buffers↗
PubMed1988

Fast horizontal electrophoresis. II. Development of fast automated staining procedures using PhastSystem.

The development of equipment for fast automated staining is described. It is possible to handle staining procedures with up to 20 steps and nine different solutions. To increase the reaction rate in the reaction chamber, the gels are rotated and high temperatures are used. The temperature in the reaction chamber is controlled between room temperature and 50 degrees C. Increased temperature, above 20 degrees C, generally results in faster staining and destaining. However, some reactions proceed better at a low temperature, including fixation of proteins with TCA, and the development step in silver staining, where increased temperatures cause a high background stain. Silver staining using acidic silver nitrate solution is preferred, due to easy preparation and good storage stability of the reagents. This method also causes little precipitation of silver on the walls of the reaction chamber. Silver staining is accomplished within one hour. Staining with PhastGel Blue is accomplished within 30 min.

Automation↗