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Biomedical subjects

J B Fisher

Publications and source records attributed to J B Fisher.

At least 19 recordsLinked to original sources
PubMed2004

Leaf photosynthetic traits scale with hydraulic conductivity and wood density in Panamanian forest canopy trees.

We investigated how water transport capacity, wood density and wood anatomy were related to leaf photosynthetic traits in two lowland forests in Panama. Leaf-specific hydraulic conductivity ( k(L)) of upper branches was positively correlated with maximum rates of net CO(2) assimilation per unit leaf area ( A(area)) and stomatal conductance ( g(s)) across 20 species of canopy trees. Maximum k(L) showed stronger correlation with A(area) than initial k(L) suggesting that allocation to photosynthetic potential is proportional to maximum water transport capacity. Terminal branch k(L) was negatively correlated with A(area)/ g(s) and positively correlated with photosynthesis per unit N, indicating a trade-off of efficient use of water against efficient use of N in photosynthesis as water transport efficiency varied. Specific hydraulic conductivity calculated from xylem anatomical characteristics ( k(theoretical)) was positively related to A(area) and k(L), consistent with relationships among physiological measurements. Branch wood density was negatively correlated with wood water storage at saturation, k(L), A(area), net CO(2) assimilation per unit leaf mass ( A(mass)), and minimum leaf water potential measured on covered leaves, suggesting that wood density constrains physiological function to specific operating ranges. Kinetic and static indices of branch water transport capacity thus exhibit considerable co-ordination with allocation to potential carbon gain. Our results indicate that understanding tree hydraulic architecture provides added insights to comparisons of leaf level measurements among species, and links photosynthetic allocation patterns with branch hydraulic processes.

Carbon Dioxide↗
PubMed2001

The internal jugular vein maintains its regional anatomy and patency after carotid endarterectomy: a prospective study.

OBJECTIVE: To validate the authors' published surface landmarks for gaining percutaneous access to the internal jugular vein (IJV), and to determine whether these surface landmarks were altered after neck surgery. SUMMARY BACKGROUND DATA: Carotid puncture and pneumothorax continue to be the most frequent mechanical complications of percutaneous IJV venipuncture, particularly when the anterior or posterior approaches are used. The authors' modified technique of IJV venipuncture was associated with a 0.6% complication rate; notably, there were no instances of carotid artery puncture. Determining the accuracy of this method using duplex ultrasound would enhance the technique's applicability and safety. The authors also hypothesized that previous neck surgery would alter the regional anatomy in relation to these surface landmarks for IJV venipuncture. METHODS: The authors prospectively evaluated 417 IJVs in 209 consecutive patients undergoing carotid duplex imaging before and after carotid endarterectomy (CEA). Patients who had undergone CEA were enrolled to investigate the effect of neck surgery on IJV anatomy. The opposite, nonoperated side of the neck served as a control for each patient. The position of the IJV in relation to the surface landmarks, the mobility of the IJV on neck rotation, and the size, patency, and relation of the IJV to the carotid artery were evaluated. RESULTS: Overall accuracy of the surface landmarks for locating the IJV percutaneously was 99% for the control group and 95% for the CEA group. With neck rotation, the IJV was located in a more lateral position in relation to the landmarks that would significantly reduce its accessibility. After neck rotation, it was also noted that the carotid artery moved behind the jugular vein in 85% of the patients in both groups. The mean size of the vein and its patency were similar in both groups. CONCLUSIONS: Duplex imaging validated the accuracy of the surface landmarks for IJV cannulation and documented the adverse effects of neck rotation. IJV anatomy is not altered after CEA.

Aged↗
PubMed2001

Stem vascular architecture in the rattan palm Calamus (Arecaceae-Calamoideae-Calaminae).

Climbing stems in the rattan genus Calamus can reach lengths of well over 100 m, are long-lived, and yet their vascular tissue is entirely primary. Such a combination suggests that stem vasculature is efficient and resistant to hydraulic disruption. By means of an optical shuttle and video recording of sequential images we analyzed the stem of a cultivated species. The stem has vascular features that are unusual compared with those in arborescent palms and seemingly inefficient in terms of long-distance water transport. Axial bundles are discontinuous basally because leaf traces, when followed downwards, always end blindly below. Furthermore, there is no regular distal branching of each leaf trace at its level of departure into a leaf, so that neither a continuing axial bundle nor bridges to adjacent axial bundles are produced as in the standard palm construction. Instead, the axial bundles in the stem periphery are connected to leaf traces and to each other by narrow and irregular transverse or oblique commissures that are not the developmental homologues of bridges. As in other palms, metaxylem within a leaf trace is not continuous into the leaf so that the only connection to a leaf is via protoxylem. Within the stem, protoxylem (tracheids) and metaxylem (vessels) are never contiguous, unlike in other palms, which suggests that water can only move from metaxylem to protoxylem, and hence into the leaf, across a hydraulic resistance. We suggest that this minimizes cavitation of vessels and/or may be associated with an unknown mechanism that refills embolized vessels. Also, the metaxylem can be significant in stem water storage in the absence of abundant ground parenchyma.

Journal Article↗
PubMed2000

Thorn and hook ontogeny in Artabotrys hexapetalus (Annonaceae).

Artabotrys hexapetalus is widely planted in the tropics and is known as "climbing ylang-ylang," an ornamental liana or woody climber. New natural sprouts, or water shoots, and those induced by the damage of Hurricane Andrew (24 August 1992) were collected and fixed in formalin/acidic acid/alcohol. Seeds from these plants were planted and grown in a greenhouse where seedling morphology was observed and young material collected and fixed. The development of lateral plagiotropic and orthotropic shoots was studied using both epi-illumination light microscopy and scanning electron microscopy. A series of buds develops in the axils of leaves on the orthotropic shoot. At the lateral margins of the axillary shelf, plagiotropic shoots form that will develop into either vegetative shoots, or thorns, or sympodial shoots that bear hooks and flowers. In between the two marginal buds, a series of median vertical buds develop that either remain dormant or grow out as renewal orthotropic shoots. Previous work that suggested that the plagiotropic shoot buds were displaced out of the median vertical series of supernumerary buds is not supported. The sympodial development of plagiotropic branches as inflorescence hooks is documented.

Journal Article↗
PubMed1999

Tandem duplication polymorphism upstream of the dopamine D4 receptor gene (DRD4).

The dopamine D4 receptor (DRD4) is a member of the D2-like dopamine receptor family. Polymorphisms at the DRD4 gene have been examined for association with a wide range of neuropsychiatric disorders and normal behavioral variation. The DRD4 gene is unusual in its high amount of expressed polymorphism in humans. Here we study the identification of a polymorphic tandem duplication of 120 bp located 1.2 kb upstream of the initiation codon. The duplicated region contains consensus sequences of binding sites for several known transcription factors, suggesting that different alleles may differ in their transcriptional activity. Because chimpanzees, gorillas, and orangutans lack the duplication, the duplicated allele is inferred to be derived. The frequency of this derived duplication allele ranges from 0.40-0.81 in the 11 populations from around the world typed for this polymorphism. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:705-709, 1999.

Alleles↗
PubMed1997

Branch geometry in Cornus kousa (Cornaceae): computer simulations.

Computer simulations similar to actual trees were constructed using simple branching rules. Branch orientation with respect to the direction of gravity was a fundamental consideration. In Cornus kousa BUERG. ex HANCE, several types of branches develop from winter buds, varying from orthotropic shoots to plagiotropic ones. Based on actual observations and measurements of branching structures with a wide range of orientations, we made a flexible geometrical model consisting of five forking branches that varied in outgrowth depending on the direction of the shoot with respect to gravity. Repetition of the branching by computer generated a realistic tree pattern, which was close to the shape of a young C. kousa tree. Reproductive shoots seem to be under a branching rule that was a modification of vegetative branching, although the reproductive branch size was considerably smaller than the vegetative one, and reproductive branching was bifurcated instead of five-forked. We conclude that all branchings in orthotropic and plagiotropic shoots in the vegetative phase and shoots in the reproductive phase are formed under the same branching rule, but each has different parameter values.

Computer Simulation↗
PubMed1996

A case study of the natural attenuation of gas condensate hydrocarbons in soil and groundwater.

Condensate liquids have been found to contaminate soil and groundwater at two gas production sites in the Denver Basin operated by Amoco Production Co. These sites have been closely monitored since July 1993 to determine whether intrinsic aerobic or anaerobic bioremediation of hydrocarbons occurs at a sufficient rate and to an adequate end point to support a no-intervention decision. Groundwater monitoring and analysis of soil cores suggest that intrinsic bioremediation is occurring at these sites by multiple pathways, including aerobic oxidation, Fe(III) reduction, and sulfate reduction.

Environmental Monitoring↗
PubMed1995

Spontaneous arterial thrombosis associated with nephrotic syndrome: case report and review of the literature.

Hypercoagulability is a recognized complication of the nephrotic syndrome which commonly affects the venous system. Arterial thrombosis is very rare. Multiple factors contribute to the predisposition to thromboembolism in this condition. This report deals with a case of femoral artery thrombosis which responded well to thrombectomy and a short course of anticoagulant therapy. In spite of several exacerbations of his disease, our patients had no recurrence of thrombosis. Review of the literature reveals high rates of limb loss and recurrence of thrombosis. We, therefore, feel that it is important to emphasize this rare entity in view of the associated morbidity.

Adult↗
PubMed1993

The effects of bedside pulmonary mechanics testing during infant mechanical ventilation: a retrospective analysis.

We examined the effects of regular bedside testing of pulmonary mechanics (PM) on the outcome of 468 acutely ill, mechanically ventilated neonates. During the first of two 18-month study periods, 217 infants were mechanically ventilated without the assistance of PM measurements. During the second 18-month period, 251 infants were ventilated with the assistance of at least daily PM measurements. Using data obtained from the PM tests, we adjusted the infants' ventilators to maintain tidal volume, inspiratory time, and pressure-volume loops within predetermined limits. With the exception of the PM measurements, given the limitations of retrospective analyses, both groups of infants received identical medical and nursing care. The infants ventilated with the assistance of PM testing developed fewer pneumothoraces (4.0%; 10/251) vs. no PM testing, 10.1% (22/217); P < 0.05 by Chi-square analysis]. Infants weighing less than 1,500 g ventilated with the assistance of PM measurements had less intraventricular hemorrhage (IVH) overall, most notably, less grades I and II IVH (total IVH-PM testing, 39.1% vs. no PM testing, 65.7%; P < 0.01; Grades I-II IVH-PM testing, 30.4% vs. no PM testing, 54.9%; P < 0.01). IVH incidence was decreased independent of pneumothorax occurrence. Survival rates, incidences of bronchopulmonary dysplasia, and durations of mechanical ventilation and hospitalization were similar. This retrospective analysis suggests that PM testing during infant mechanical ventilation reduces common acute ventilator-associated complications.

Bronchopulmonary Dysplasia↗
PubMed1993

The Ohio Cancer Information Service: technology transfer on clinical trials and other measures of cancer control.

We examined trends in caller queries on tobacco, mammography, Pap tests, and clinical trials to the NCI-sponsored Cancer Information Service (CIS) of Ohio via its toll free telephone number (1-800-4-CANCER) during 1986-1991. Calls on NCI-approved clinical trials and treatment protocols tripled during the study period (from 6% in 1986 to 20% in 1991, p < 0.01) primarily due to counselor-initiated (proactive) recommendations and actions. Calls on breast cancer showed a significant increase whereas calls on respiratory system cancers showed a decline over the time period. There was also a dramatic increase in calls on mammography, reflecting the impact of national and local promotion of breast screening. Queries on tobacco use and Pap tests declined, perhaps due to a perceived saturation effect of public education on these two topics. Our results support the use of CIS as a technology transfer system.

Breast Neoplasms↗
PubMed1992

Radial artery collateral aneurysm: a rare entity resulting from an unusual etiology.

Atherosclerotic occlusive disease of the upper extremity can be a challenging and complex problem for the vascular surgeon. Due to the variety of pathologies that can affect the upper extremity, an accurate diagnosis may be difficult to obtain. We describe the case of a 52-year-old white man who presents with a pulsatile mass on the volar aspect of the right wrist. Arteriography of the aortic arch and right upper extremity revealed an 80% atherosclerotic stenosis at the origin of the right subclavian artery, as well as occlusion of the superficial radial artery. The occlusion resulted in the formation of an aneurysmal collateral, which communicated with the superficial palmar arch. A right carotid-subclavian bypass was necessary to prevent further embolic phenomena. The radial artery aneurysm was treated by resection and primary repair.

Aneurysm↗
PubMed1992

Aortic laceration: a rare complication of laparoscopy.

Aortic laceration during laparoscopic procedures is a rare but well-known complication with a high mortality rate. Thus far, few cases which were recognized and treated successfully have been reported in the literature; the exact incidence is not known. Such a complication occurred after an elective laparoscopic sterilization in a 35-year-old woman. The situation was recognized early and successfully treated. The common complications of laparoscopy are usually of a minor nature but a few are life threatening. This case illustrates the need for emphasis on the prevention of complications and the appropriate course of action in the event of their occurrence.

Adult↗
PubMed1992

Poor predictive value of hematocrit and hemodynamic parameters for erythrocyte deficits after extensive elective vascular operations.

Fluid resuscitation and transfusion therapy are particularly critical in patients undergoing extensive vascular operations because of diffuse atherosclerosis and the risk of perioperative myocardial infarction. Sophisticated perioperative monitoring has reduced the mortality rate substantially, but indications for transfusion remain controversial. We determined erythrocyte volume, (EV), total blood volume (TBV) and plasma volume (PV) preoperatively and 18 to 24 hours postoperatively in 41 elderly patients (68.8 +/- 1.3 years) undergoing elective vascular operations (30 abdominal aortic aneurysmorrhaphy, ten aortofemoral bypass and one carotid endarterectomy). EV was measured using 51chromium-labeled autologous erythrocytes; TBV and PV were calculated from EV and total body hematocrit (peripheral venous hematocrit [HCT] x 0.89). Ideal blood volumes were calculated from nomograms based on body surface area and gender. Relationships between body volumes (percentage of ideal), simultaneously measured peripheral venous HCT and hemodynamic parameters heart rate, mean arterial pressure, central venous pressure, pulmonary capillary wedge pressure, cardiac index and systemic vascular resistance index were studied by stepwise regression. In 24 patients, blood volumes and hemodynamic parameters were also measured in the recovery room. HCT significantly correlated with EV at all three time periods (p less than 0.001), but the ability of HCT to predict EV in an individual patient was relatively poor (r = 0.50 preoperatively; r = 0.54 in recovery room and r = 0.66 24 hour postoperatively). By 24 hours postoperatively, EV had decreased to 78.3 +/- 2.4 percent of ideal EV (range of 47 to 112 percent). However, only two patients had HCT less than 30 despite the fact that 13 of 41 patients had an EV deficit of greater than 30 percent. No patient had a HCT of less than 25 percent. Hemodynamic parameters did not contribute to the prediction of EV, PV or TBV at any time. Two patients had myocardial infarctions postoperatively associated with 24 hour EV deficits of 18.5 and 29.6 percent. One patient died of a pulmonary embolus. Because of these findings, the concept of a "transfusion trigger" must be viewed with caution, since many patients undergoing vascular operations will have considerable EV deficits despite an "acceptable" HCT.

Age Factors↗
PubMed1991

Effect of graft material on loss of erythrocytes after aortic operations.

It has been suggested that loss of erythrocytes after abdominal aortic grafting is influenced by the type of synthetic graft used. A prospective randomized study was done to compare loss of erythrocytes in patients receiving Dacron (polyester fiber, Meadox woven double velour) and Gore-Tex (polytetrafluoroethylene [PTFE]) grafts during the perioperative period. A total of 25 patients (13 Dacron and 12 PTFE) was studied, including 21 with abdominal aortic aneurysms and four with aortoiliac occlusive disease. Erythrocyte volume (EV) was measured using 51Cr-labeled autologous erythrocytes on the day prior to the operation, one to two hours after the operation when the patients were hemodynamically stable and 24 hours postoperatively. In addition to measurements of 51Cr EV and the volume of intraoperatively salvaged washed erythrocytes, the length of storage of the units of homologous liquid preserved erythrocytes at 4 degrees C. prior to transfusion were recorded. The mean intraoperative erythrocyte loss (+/- S.D.) for the Dacron group was 892 +/- 543 milliliters and for the PTFE group, 842 +/- 403 milliliters (p = NS). Patients in the Dacron group received intraoperatively 2.2 +/- 1.6 (units +/- S.D.) milliliters with a range of zero to 4 units of homologous liquid preserved erythrocytes and patients in the PTFE group received 1.2 +/- 1.2 milliliters with a range of zero to 3 units of homologous liquid preserved erythrocytes (p = NS). The mean total loss of erythrocytes (+/- S.D.) was 1,055 +/- 649 milliliters for the Dacron group and 978 +/- 503 milliliters for the PTFE group (p = NS). Despite inherent differences in graft material, there were no significant differences in intraoperative or post-operative loss of erythrocytes or in the number of homologous units of liquid preserved erythrocytes transfused with a p value of less than 0.05 considered significant.

Aged↗
PubMed1990

Effect of spontaneous and mechanical breathing on dynamic lung mechanics in hyaline membrane disease.

We measured then compared the dynamic lung mechanics of spontaneous breaths and mechanical breaths in 9 mechanically ventilated neonates with hyaline membrane disease. All were receiving intermittent mandatory ventilation. All breathed spontaneously between ventilator breaths. Tidal volume, transpulmonary pressure, dynamic lung compliance, airways resistance, and peak inspiratory and peak expiratory gas flows were determined for both the mechanical and the spontaneous breaths. The mechanical breaths consistently had larger tidal volumes, higher transpulmonary pressures, higher airway resistance, and lower lung compliance values (P less than 0.05). Peak inspiratory and expiratory gas flows were also higher (P less than 0.01) during mechanical breathing. The spontaneous breaths generated by patients and the mechanical breaths generated by mechanical ventilators are different. The lung mechanics measurements of these two different types of breathing should be collected, analyzed, and reported separately.

Humans↗
PubMed1990

Use of a beta-agonist in ventilated, very-low-birth-weight babies: a longitudinal evaluation.

To determine if there is a specific postnatal (PNA) or postconceptional age (PCA) at which ventilated preterm infants respond to beta-agonists, we evaluated 15 infants with a mean gestational age of 26.5 +/- 1.5 weeks and mean birth weight of 0.89 +/- 0.23 kg who required mechanical ventilation at 10 days of age. Weekly pulmonary function testing (PFT) was performed before and 1 h after administration of albuterol. Taking the group as a whole, as well as individual babies, regression analysis showed no relationship between positive response and either PNA or PCA. Evaluation of individual infants, however, showed that some consistently responded to beta-agonists whereas others did not. We recommend individual PFT to identify those infants who will benefit from use of beta-agonists.

Albuterol↗