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J G Wood

Publications and source records attributed to J G Wood.

At least 19 recordsLinked to original sources
PubMed2001

The effect of nitric oxide inhibition on blood pressure depends on rat strain.

BACKGROUND: Nitric oxide is a continuously released endothelium-derived vasodilator and plays an important role in the maintenance of blood pressure (BP). Rat strains appear to differ in their resting BP and their response to the intravenous administration of N(omega)-nitro-l-arginine methyl ester (l-NAME), a nitric oxide synthase inhibitor. The presence of diabetes and hypertension also leads to differences in BP responses to l-NAME. We postulated that the contribution of NO to resting BP varies between rat strains and certain strains may be more sensitive to the effects of NO blockade. METHODS: Blood pressure was continuously measured using a carotid arterial catheter and the responses to l-NAME were compared in anesthetized Lewis and Sprague-Dawley rats during a 2-h control period and a 2-h experimental period. l-NAME was given by a 50 mg/kg bolus followed by a 10 mg/kg/h infusion via a mesenteric vein. RESULTS: During the control period, the Lewis animals had lower systolic and diastolic BPs of 103 +/- 1 and 80 +/- 1 mm Hg compared with 127 +/- 1 and 105 +/- 1 mm Hg measured in Sprague-Dawley rats (P < 0.01). Although l-NAME infusion increased systolic BP in both strains compared with control values (P < 0.00005), the magnitude was significantly greater in Sprague-Dawley than Lewis animals (P = 0.0142); additionally, the BP was unstable in the Lewis animals. Furthermore, pulse pressure decreased during l-NAME in Lewis animals but increased in Sprague-Dawley animals (P < 0.00005). There were no significant changes in serum concentrations of aspartate transaminase nor of nitrite plus nitrate after l-NAME in either group. CONCLUSION: These results indicate that the effect of l-NAME on systemic BP differs markedly in Sprague-Dawley and Lewis rats, suggesting that the role of nitric oxide in regulation of resting vascular resistance may differ significantly between these rat strains. Rat strain is an important consideration for valid comparisons between studies.

Animals↗
PubMed2001

Leukocyte-endothelial interactions in environmental hypoxia.

Hypoxia induced by reducing inspired PO2 (PIO2) to 70 Torr, promotes a rapid microvascular response characterized by increased leukocyte rolling and adherence to the venular endothelium, leukocyte emigration to the perivascular space and increased vascular permeability. This appears to be a generalized response since it is observed in venules of the mesentery, cremaster muscle and pial microcirculations. After three weeks of acclimatization to hypoxia (barometric pressure 380 Torr, PIO2 70 Torr), the initial microvascular response resolves and exposure to even lower PIO2 (50 Torr) fails to elicit a microvascular response. The initial response is accompanied by a reversible increase in the generation of reactive oxygen species (ROS) and is blocked by antioxidants and by interventions that increase the tissue levels of nitric oxide (NO). In contrast to ischemia/reperfusion, ROS levels increase during hypoxia and return towards pre-hypoxic values after return to normoxia. Acclimatization involves upregulation of inducible NO synthase (iNOS): inhibition of iNOS using two different antagonists results in increased leukocyte-endothelial interactions and increased ROS generation. The results suggest that hypoxia initially leads to an alteration of the ROS/NO balance which is eventually restored during the acclimatization process. This phenomenon may have relevance to the microcirculatory alterations associated with hypoxic exposure, including acute mountain sickness and high altitude pulmonary and cerebral edema.

Altitude Sickness↗
PubMed2001

Leukotriene B(4) promotes reactive oxidant generation and leukocyte adherence during acute hypoxia.

Acute systemic hypoxia produces rapid leukocyte adherence in the rat mesenteric microcirculation, although the underlying mechanisms are not fully known. Hypoxia is known to increase reactive oxygen species (ROS) generation, which could result in formation of the lipid inflammatory mediator leukotriene B(4) (LTB(4)). The goal of this study was to examine the role of LTB(4) in hypoxia-induced microvascular alterations. Using intravital microscopy, we determined the effect of the LTB(4) antagonist, LTB(4)-dimethyl amide (LTB(4)-DMA), on ROS generation and leukocyte adherence in mesenteric venules during hypoxia. Exogenous LTB(4) increased ROS generation to 144 +/- 8% compared with control values and also promoted leukocyte adherence. These responses to LTB(4) were blocked by pretreating the mesentery with LTB(4)-DMA. Leukopenia did not significantly attenuate the LTB(4)-induced increase in ROS generation (142 +/- 12.1%). LTB(4)-DMA substantially, though not completely, reduced hypoxia-induced ROS generation from 66 +/- 18% to 11 +/- 4% above control values. Hypoxia-induced leukocyte adherence was significantly attenuated by LTB(4)-DMA. Our results support a role for LTB(4) in the mechanism of hypoxia-induced ROS generation and leukocyte adherence in the rat mesenteric microcirculation.

Acute Disease↗
PubMed2000

Phosphorylation of human tau protein by microtubule-associated kinases: GSK3beta and cdk5 are key participants.

Microtubules (MTs), primarily composed of alpha and beta tubulin polymers, must often work in concert with microtubule-associated proteins (MAPs) in order to modulate their functional demands. In a mature brain neuron, one of the key MAPs that resides primarily in the axonal compartment is the tau protein. Tau, in the adult human brain, is a set of six protein isoforms, whose binding affinity to MTs can be modulated by phosphorylation. In addition to the role that phosphorylation of tau plays in the "normal" physiology of neurons, hyperphosphorylated tau is the primary component of the fibrillary pathology in Alzheimer's disease (AD). Although many protein kinases are known to phosphorylate tau in vitro, the in vivo players contributing to the hyperphosphorylation of tau remain elusive. The experiments in this study attempt to define which protein kinases and protein phosphatases reside in the associated network of microtubules, thereby being strategically positioned to influence the phosphorylation of tau. Microtubule fractions are utilized to determine which of the microtubule-associated kinases most readily impacts the phosphorylation of tau at "AD-like" sites. Results from this study indicate that PKA, CK1, GSK3beta, and cdk5 associate with microtubules. Among the MT-associated kinases, GSK3beta and cdk5 most readily contribute to the ATP-induced "AD-like" phosphorylation of tau.

Adenosine Triphosphate↗
PubMed2000

Regulation of microglial tyrosine phosphorylation in response to neuronal injury.

The regulation and substrate specificity of microglial phosphotyrosine (ptyr) increases accompanying motor neuron degeneration in the rat spinal cord induced by injection of the cytotoxic lectin, ricin, into sciatic nerve were examined using specific enzyme inhibitors, immunohistochemistry, and Western blot analyses. Optical density measurements of immunostained sections show that microglial ptyr levels are elevated at 3 days postinjection. This period coincides with initial stages of neuronal degeneration, and ptyr levels are maximal at 7 days. We next asked whether this increase is due to increased tyrosine kinase or decreased tyrosine phosphatase activities by assaying ptyr immunostaining in animals that received osmotic pump infusion of the nonreceptor tyrosine kinase inhibitor, herbimycin A, for the 7-day survival period. When compared to the control ventral horn, microglial ptyr on the experimental side was attenuated by at least 45% in the presence of herbimycin A. In order to identify microglial substrates undergoing increased tyrosine phosphorylation, Western blot analysis was performed on hemicord and punch biopsy samples from control and experimental sides following ricin injection. A subset of two proteins was identified whose increased ptyr was almost completely attenuated in the herbimycin-A-treated animals. We conclude that the data support earlier indications that upregulation of microglial tyrosine phosphorylation is a key early event in response to neuronal injury. Further, this upregulation is due to turning on tyrosine kinase activities, particularly nonreceptor kinases, and the end product is phosphorylation of a very limited number of substrates. This suggests the activation of specific tyrosine phosphorylation pathways, which may represent critical therapeutic intervention points, rather than a global response. The results are discussed in terms of recent cell culture models of microglial activation and earlier data demonstrating elevated microglial ptyr in neurodegenerative disease.

Animals↗
PubMed2000

Differential host inflammatory responses to viable versus antibiotic-killed bacteria in experimental microbial sepsis.

Staphylococcus aureus killed during imipenem or ceftazidime chemotherapy in mice elicited an early release of tumor necrosis factor alpha (TNF-alpha) into the systemic circulation. This response was coincident in time with an increase in leukocyte-endothelium adhesive interactions in the microvasculature. Equivalent responses were not observed without the antibiotic treatment (imipenem or ceftazidime). Protective efficacy of the same antibiotic treatment was markedly diminished in D-galactosamine-treated mice compared to controls; e.g., it dropped from 2,000-fold to 70-fold with 4 mg of imipenem per kg given at the time of challenge. Nevertheless, protection was quantitatively restored upon concurrent administration of neutralizing anti-TNF-alpha antibody or 4 mg of dexamethasone per kg to these TNF-alpha-hypersensitive mice. Importantly, protection afforded by dexamethasone was not seen when the animals were challenged with viable organisms but without the concurrent administration of antibiotic. An early TNF-alpha response could also be demonstrated upon challenge with Escherichia coli, but in this instance, neither the timing nor the magnitude of that response was influenced by treatment with these antibiotics. We conclude from these studies that the inflammatory response to viable versus killed bacteria may differ markedly depending on the particular bacterium, host sensitivity to TNF-alpha, and possibly the Gram stain classification.

Animals↗
PubMed2000

Systemic hypoxia increases leukocyte emigration and vascular permeability in conscious rats.

We recently observed that acute systemic hypoxia produces rapid increases in leukocyte adherence in the mesenteric microcirculation of the anesthetized rat Wood JG, Johnson JS, Mattioli LF, and Gonzalez NC. J Appl Physiol 87: 1734-1740, 1999; Wood JG, Mattioli LF, and Gonzalez NC. J Appl Physiol 87: 873-881, 1999. Hypoxia-induced leukocyte adherence is associated with an increase in reactive oxygen species (ROS) generation and is attenuated by antioxidants or interventions that increase tissue levels of nitric oxide (NO). These results suggest that the acute effects of hypoxia on leukocyte-endothelial interactions are caused by a change in the ROS-NO balance. The present experiments were designed to extend our observations of the initial microcirculatory response to hypoxia; specifically, we wanted to determine whether the response to systemic hypoxia involves increased microvascular permeability and leukocyte emigration and whether ROS generation and decreased NO levels contribute to these responses. At this time, there is conflicting evidence, from in vitro studies, regarding the effect of hypoxia on these indexes of vascular function. Our studies were carried out in the physiological setting of the conscious animal, in which a prolonged hypoxic exposure is possible without the adverse effects that may develop under anesthesia. The central observation of these studies is that conscious animals exposed for 4 h to environmental hypoxia show increased microvascular permeability and emigration of leukocytes into the extravascular space of the mesenteric circulation. Furthermore, these events are dependent on increased ROS generation and, possibly, a subsequent decrease in tissue NO levels during systemic hypoxia. Our results show that systemic hypoxia profoundly affects vascular endothelial function through changes in the ROS-NO balance in the conscious animal.

Animals↗
PubMed2000

Computerized system for outcomes-based antiemetic therapy in children.

OBJECTIVE: To introduce a computerized data collection system used for an outcomes-based approach to antiemetic therapy in children, and to present data collected with this system in support of a new antiemetic dosing regimen. METHODS: A validated nausea/vomiting survey was used to collect data on nausea severity (NSEV), vomiting severity (VSEV), daily activity interference (DAI), and the number of vomiting episodes. NSEV, VSEV, and DAI were rated as 0 = none to 3 = severe. All children and/or their parents were surveyed following the completion of each highly emetogenic chemotherapy regimen. This survey was computerized and transferred to a handheld data entry unit. Time and motion studies were performed to compare the time required to collect nausea/vomiting data and transfer the data to a computerized database with the hand-held system versus traditional paper (manual) surveys. The hand-held technology was used to collect survey data for children receiving a new antiemetic regimen (daily ondansetron and dexamethasone [OD]), which was then compared with data obtained with a previously employed regimen (thrice-daily ondansetron and daily methylprednisolone [OM]). Statistical analysis and a cost-effectiveness analysis (CEA) were performed to compare the two antiemetic regimens. RESULTS: The mean time required for total data entry with the manual system was 5.2 minutes per survey versus 2.4 minutes with the hand-held technology (p = 0.0026). A total of 376 nausea/vomiting surveys in 78 children receiving the OM antiemetic regimen were compared with 153 surveys in 38 children treated with the OD regimen. The mean survey scores were as follows: NSEV (1.2 vs. 0.8), VSEV (1.0 vs. 0.7), DAI (1.0 vs. 0.7), and number of vomiting episodes (4.3 vs. 2.1) for OM and OD, respectively; all were significantly lower with the OD regimen (p < 0.05). The percentage of patients with complete control of nausea and vomiting (19.2% vs. 39.2%) and good control (55.6% vs. 65.4%) were significantly greater with the OD regimen (p < 0.05). The CEA revealed that the OD resulted in a reduction of approximately $31 per patient for good protection and a $258 reduction for complete protection from nausea and vomiting. CONCLUSIONS: A computerized outcomes-based system aided by handheld technology allowed for more prompt and efficient collection of nausea/vomiting data. The OD antiemetic regimen was shown to be a more cost-effective alternative for children receiving severely emetogenic chemotherapy.

Antiemetics↗
PubMed1999

Regulation of tau phosphorylation in microtubule fractions by apolipoprotein E.

In Alzheimer's disease (AD), a family of proteins collectively named tau are displaced from their normal association with microtubules and are found in in a hyperphosphorylated state deposited into paired helical filaments (PHFs). PHFs are the hallmark cytoskeletal pathology of the disease, and the degree of PHF pathology correlates with the clinical severity of AD. Certain apolipoprotein E (apoE) isoforms have been identified as either risk or protective factors for AD, and one of the proposed mechanisms involves an interaction and potentially modulatory effects on tau hyperphosphorylation by the different apoE isoforms. In these studies, we directly tested the effects of apoE, E2, E3, and E4 on AD-like phosphorylation of tau in brain microtubule fractions. We found that apoE attenuates tau hyperphosphorylation in the fractions, but the pattern was indistinguishable for the different isoforms.

Adenosine Triphosphate↗
PubMed1999

Characterization of microtubule-associated proteins in teleosts.

Although microtubules are known to play an important role in many cellular processes, they have been virtually neglected in fish. In this report, microtubule-associated proteins (MAPs) in fish (teleost) were characterized using antibodies (Abs) directed against the mammalian MAPs tau, MAP1A and B, and MAP 2. Two different populations of tau-like proteins (TLPs) were found in fish brain using the anti-tau Abs Tau-1, Tau-2, tau5', and tau3'. The TLPs that were recognized by Tau-1, Tau-2, and tau5' were (1) heat-stable; (2) the same molecular weight as mammalian TLPs: 59-62 kDa; (3) not enriched in microtubules prepared from catfish brain; and (4) localized to the cell body of neurons in fish brains. While the TLPs recognized by tau3' Abs were (1) heat-stable; (2) lower molecular weight than mammalian TLPs: 32-55 vs. 50-65 kDa; (3) enriched in microtubule fractions prepared from catfish brain, and (4) localized to the axons of neurons. These results are consistent with two different populations of TLPs being present in fish brains. While MAP2 was found to be approximately the same molecular weight, 250 kDa, in zebrafish and goldfish as in mammals and to be distributed to dendrites in the fish brain, both MAP1A and MAP1B were found to be about 25% the mass of their mammalian homologs. These results suggest that MAPS in fish have some characteristics similar to their mammalian counterparts, but also possess some unique properties that require further study to elucidate their function.

Animals↗
PubMed1999

Leukocyte adherence and sequestration following hemorrhagic shock and total ischemia in rats.

The pathogenesis of generalized microvascular injury following hemorrhagic shock and total ischemia appears to be dependent on leukocytes interacting with the venular endothelium. The purpose of this study was to compare leukocyte adherence and sequestration following hemorrhagic shock with that of total ischemia in the small bowel mesentery of rats. Leukocyte adherence and sequestration was measured by direct visualization in vivo using intravital microscopy. In addition, sequestration was also quantitated by measuring tissue levels of myeloperoxidase, a marker of leukocyte infiltration. Mean arterial blood pressure was decreased to 40 mm Hg for 30 min (hemorrhagic shock group). In the total ischemia group, both the superior and inferior mesenteric arteries were clamped for 30 min followed by reperfusion. Hemorrhagic shock (9.4+/-1.5 cell/100 microm) and total ischemia (8.3+/-3 cell/100 microm) caused a statistically significant increases in leukocyte adherence 60 min postinsult as compared with controls (.9+/-1.5 cell/100 microm). However, the increase in leukocyte adherence appeared earlier and to a greater degree initially following total ischemia. Leukocyte sequestration as measured by intravital microscopy was significant only after total ischemia [(24.6+/-1.7 cell/(100 microm)2; p<.01] and not hemorrhagic shock [3.4+/-.6 cell/(100 microm)2] versus controls [2.2+/-.2 cell/(100 microm)2]. This difference in sequestration was also confirmed by tissue levels of myeloperoxidase. The results of this study suggest that the microvascular response following hemorrhagic shock is different than that of total ischemia, and caution is warranted when extrapolating the experimental results of one to the other.

Animals↗
PubMed1999

Hypoxia causes leukocyte adherence to mesenteric venules in nonacclimatized, but not in acclimatized, rats.

Although the effects of ischemia-reperfusion have received considerable attention, few studies have directly evaluated the microcirculatory response to systemic hypoxia. The overall objective of this study was to assess the effect of environmental hypoxia on adhesive interactions of circulating leukocytes with rat mesenteric venules by using intravital microscopy. Experiments were designed to 1) characterize the adhesive interactions of circulating leukocytes to venules during acute hypoxia produced by a reduction in inspired PO(2), 2) evaluate the role of nitric oxide in these adhesive interactions, 3) determine whether the effect of hypoxia on leukocyte adhesive interactions differs between acclimatized and nonacclimatized rats, and 4) assess whether compensatory changes in nitric oxide formation contribute to this difference. The results showed that acute hypoxia promotes leukocyte-endothelial adherence in mesenteric venules of nonacclimatized rats. The mechanism of this response is consistent with depletion of nitric oxide within the microcirculation. In contrast, no leukocyte-endothelial adherence occurred during hypoxia in rats acclimatized to hypobaric hypoxia. The results are consistent with increased nitric oxide formation due to expression of inducible nitric oxide synthase during the acclimatization period. Further studies are needed to establish the cause of nitric oxide depletion during acute hypoxia as well as to define the compensatory responses that attenuate hypoxia-induced leukocyte-endothelial adherence in the microvasculature of acclimatized rats.

Acclimatization↗
PubMed1999

Systemic hypoxia promotes leukocyte-endothelial adherence via reactive oxidant generation.

We recently demonstrated that systemic hypoxia during reduced inspired PO(2) produces a rapid increase in leukocyte adherence to rat mesenteric venules. Evidence suggests that the mechanism of this response involves decreased nitric oxide (NO) levels. One possible pathway for NO depletion could involve increased reactive oxygen species (ROS) generation resulting in inactivation of NO. The overall goal of the present study was to examine the role of ROS in promoting leukocyte-endothelial adherence during systemic hypoxia. Experiments were designed to 1) evaluate changes in ROS generation in the mesenteric microcirculation during systemic hypoxia, 2) determine how the ROS signal changes when PO(2) levels return to normal after a period of systemic hypoxia, 3) assess the effect of antioxidants on ROS generation during hypoxia, and 4) utilize antioxidants to examine the functional relationship between ROS generation and leukocyte adherence during hypoxia. The major findings from this study are that systemic hypoxia increases ROS generation within the mesenteric microcirculation and that antioxidants prevent the increase in leukocyte-endothelial adhesive interactions observed in hypoxia.

Animals↗
PubMed1998

Unusual proliferation arrest and transcriptional control properties of a newly discovered E2F family member, E2F-6.

E2F transcription factors play an important role in the regulation of cell cycle progression. We report here the cloning and characterization of an additional member of this family, E2F-6. E2F-6 lacks pocket protein binding and transactivation domains, and it is a potent transcriptional repressor that contains a modular repression domain at its carboxyl terminus. Overproduction of E2F-6 had no specific effect on cell cycle progression in asynchronously growing Saos2 and NIH 3T3 cells, but it inhibited entry into S phase of NIH 3T3 cells stimulated to exit G0. Taken together, these data suggest that E2F-6 can regulate a subset of E2F-dependent genes whose products are required for entry into the cell cycle but not for normal cell cycle progression.

3T3 Cells↗
PubMed1998

PAF and CD18 mediate neutrophil infiltration in upper gastrointestinal tract during intra-abdominal sepsis.

Neutrophil infiltration is a critical event in the development of multiple organ failure during sepsis. We hypothesized that platelet-activating factor (PAF) release contributes to neutrophil infiltration in the gastrointestinal tract during sepsis. In the first experiments we administered exogenous PAF (1.56, 6.25, 25, and 100 ng . kg-1 . min-1 for 30 min) to urethan-anesthetized Sprague-Dawley rats. PAF was administered alone or in combination with either the PAF antagonist WEB-2086 (250 microg . kg-1 . min-1), a monoclonal antibody (MAb) to CD18, or a MAb to intercellular adhesion molecule 1 (ICAM-1). In separate groups of rats, cecal ligation and incision (CLI) was performed to create intra-abdominal sepsis, which we hypothesized would stimulate the release of endogenous PAF. CLI was performed in rats given either saline, WEB-2086, anti-CD18, or anti-ICAM-1 MAb. After these experiments, tissue myeloperoxidase (MPO) levels were determined as a marker of neutrophil infiltration. Both exogenous PAF and CLI induced significant increases in MPO activity in the stomach and duodenum. These increases were significantly attenuated by WEB-2086, anti-CD18 MAb, and anti-ICAM-1 MAb in both PAF- and CLI-treated rats. These results suggest that both the inflammatory mediator PAF and the CD18 integrins play a major role in neutrophil infiltration in the upper gastrointestinal tract during sepsis.

Abdomen↗
PubMed1997

A human-specific polymorphism in the coding region of the aggrecan gene. Variable number of tandem repeats produce a range of core protein sizes in the general population.

Aggrecan, one of the major structural genes of cartilage, encodes a proteoglycan core protein composed of an extended central glycosaminoglycan-bearing domain, flanked by globular domains at each end. The central region consists of long stretches of repeating amino acids that serve as attachment sites for glycosaminoglycans such as chondroitin and keratan sulfate; the terminal globular domains interact with other cartilage components. The glycosaminoglycan attachment region is encoded in several species by a single large exon, within which are several different types of repeating sequences. Several species show within this exon a similar block of conserved repeats for attachment of chondroitin sulfate, but in humans this group of repeats is particularly well conserved. Examination of genomic DNA from a population of unrelated individuals by polymerase chain reaction or Southern blot assays shows this block of repeat sequences exists in multiple allelic forms, which differ by the number of repeats at this site in each allele. Thirteen different alleles have been identified, with repeat numbers ranging from 13 to 33. This is an unusual example of an expressed variable number of tandem repeat polymorphism. This polymorphism is apparently restricted to humans, of several species examined. This polymorphism results in individuals with differing length aggrecan core proteins, bearing different numbers of potential attachment sites for chondroitin sulfate. The possibility exists for a molecular understanding of biological variation in cartilage functional properties.

Aggrecans↗