Biomedical subjects

Stephen C Jones

Publications and source records attributed to Stephen C Jones.

18 recordsLinked to original sources

PubMed2006

Differences between arterial occlusive and cortical photothrombosis stroke models with magnetic resonance imaging and microtubule-associated protein-2 immunoreactivity.

The differences between two models of cerebral ischemia [middle cerebral arterial transection (MCAT) and cortical photothrombosis (PT)] were explored with multiparametric MRI of apparent diffusion coefficient trace (ADCtr), cerebral blood flow (CBF) and T1. Microtubule-associated protein-2 (MAP2) immunoreactivity sections aligned with the MR images in the same coronal plane were used to map the infarct and to guide region-of-interest selection. In ischemic cortex, the larger T1 increase in PT versus MCAT (42+/-7% vs. 16+/-5%) is related to the different character of edema between these models; yet, neither CBF nor ADCtr discriminated between them at 3.5 h, suggesting that different mechanisms of ischemic damage to the brain cells resulted in the same ADCtr value. CBF and ADCtr were depressed in immediately adjacent ischemic border by 27+/-7% and 47+/-10%, respectively, in MCAT but not in PT, suggesting marginal perfusion in MCAT. CBF in homotopic normal cortex in the opposite hemisphere was higher for PT compared with MCAT (199+/-20 and 134+/-10 ml/100 g/min, respectively). Different pathological processes in the two models affect CBF, ADCtr and T1 in a unique, regionally specific manner. The PT model differs substantially from the MCAT and is not a model of cortical ischemia with an appreciable border zone.

Animals↗

PubMed2006

Stroke onset time using sodium MRI in rat focal cerebral ischemia.

BACKGROUND AND PURPOSE: Thrombolytic therapy with intravenous tPA must be administered within 3 hours after stroke onset. However, stroke onset time cannot be established in 20% to 45% of potential patients. We propose that the rate of increase of the brain concentration of sodium ([Na+]br) after stroke, monitored using sodium MRI in a rat model of cortical ischemia, is linear in each individual animal, can locate the ischemic region, and can be used to estimate onset time. METHODS: After induction of focal cortical ischemia in rats under isoflurane anesthesia, [Na+]br time course maps were acquired continuously on a 3 T whole body scanner from 2 to 7 hours after occlusion followed by T2-weighted proton images. Microtubule-associated protein-2 immunostained brain sections were used to verify the location of the infarct. RESULTS: The ischemic region identified with microtubule-associated protein-2 corresponded to the region of maximum [Na+]br increase (P<0.001; n=5), and all of the animals demonstrated high linearity. [Na+]br increased at a mean rate of 25+/-4.7%/h in ischemic tissue (P=0.013) but not in normal cortex (1.0+/-1.1%/h; P=0.42). The mean onset time error was 1+/-4 minutes (n=4). CONCLUSIONS: These results of sodium MRI show that the region of maximum [Na+]br increase corresponds to the ischemic region. Although [Na+]br increases at a different rate in each animal, the increase is linear, and, therefore, onset time can be estimated. These findings suggest that this method can be used as a ticking clock to estimate time elapsed after vascular occlusion.

Animals↗

PubMed2006

T-cell receptor Valpha spectratype analysis of a CD4-mediated T-cell response against minor histocompatibility antigens involved in severe graft-versus-host disease.

Although CD4(+) T cells can have an important role in mediating lethal graft-versus-host disease (GVHD) directed to multiple minor histocompatibility antigens (miHA) after bone marrow transplantation, their precise characterization and effector function remains elusive. In this regard, T cell receptor (TCR) Vbeta spectratype analysis has been a powerful tool for identifying donor CD4(+) T cell populations expanding to host miHA after bone marrow transplantation in the major histocompatibility complex-matched C57BL/6 (B6) --> C.B10-H2(b) (BALB.B) model of lethal GVHD. Removal of all of the Vbeta(+) T cell families containing these responding cells from the donor inoculum has proven to be an effective means of preventing the development of GVHD. Previous studies have also found that of the 11 miHA-responsive B6 CD4(+) Vbeta(+) T cell families, transplantation of Vbeta2(+) and Vbeta11(+) T cells together into lethally irradiated BALB.B mice appeared to be primarily responsible for the severity of resultant GVHD. Further focusing on these critical CD4 responses, in this study we demonstrate that B6 CD4(+)Vbeta11(+) T cells alone can induce lethal GVHD in BALB.B recipients. In addition, immunohistochemical staining of host lingual and intestinal epithelial tissues supported the capacity of Vbeta11(+) T cells to infiltrate typical GVHD-associated target areas. To further characterize the specific CD4(+)Vbeta11(+) T cells involved in this anti-miHA response, TCR Valpha spectratype analysis was performed and indicated that 6 Valpha chains were used by this reactive population. These results provide further evidence that a restricted repertoire of T cell specificities, presumably recognizing a correspondingly low number of miHA, is sufficient for the induction of severe GVHD.

Animals↗

PubMed2006

CD4+ T-cell memory: generation and multi-faceted roles for CD4+ T cells in protective immunity to influenza.

We have outlined the carefully orchestrated process of CD4+ T-cell differentiation from naïve to effector and from effector to memory cells with a focus on how these processes can be studied in vivo in responses to pathogen infection. We emphasize that the regulatory factors that determine the quality and quantity of the effector and memory cells generated include (i) the antigen dose during the initial T-cell interaction with antigen-presenting cells; (ii) the dose and duration of repeated interactions; and (iii) the milieu of inflammatory and growth cytokines that responding CD4+ T cells encounter. We suggest that heterogeneity in these regulatory factors leads to the generation of a spectrum of effectors with different functional attributes. Furthermore, we suggest that it is the presence of effectors at different stages along a pathway of progressive linear differentiation that leads to a related spectrum of memory cells. Our studies particularly highlight the multifaceted roles of CD4+ effector and memory T cells in protective responses to influenza infection and support the concept that efficient priming of CD4+ T cells that react to shared influenza proteins could contribute greatly to vaccine strategies for influenza.

Animals↗

PubMed2004

Heterogeneous response of cerebral blood flow to hypotension demonstrated by laser speckle imaging flowmetry in rats.

The response of cerebral blood flow (CBF) to mild hypotension shows great variability. CBF changes in different cortical regions at a mean arterial blood pressure (MABP) of 70 mmHg (near the lower limit of CBF-pressure autoregulation) were analyzed using laser speckle imaging flowmetry (LSIF). We hypothesize that variations in CBF autoregulation might be due to differences between regions within the cortex of each animal, regional heterogeneity, as opposed to differences between animals. Different responses of local CBF to hypotension in each rat were demonstrated as %CBF(70), the ratio of CBF at a MABP of 70 mmHg to CBF at a MABP of 100 mmHg. Regional heterogeneity ranged from 12 to 51%, expressed as the coefficient of variation of %CBF(70). At the same time LSIF revealed distinctly different patterns of CBF-pressure autoregulation between animals. Between-animal heterogeneity represents a continuous distribution, spread between animals with predominantly decreased CBF (%CBF(70) < 85%, rat #3) and animals with a high proportion of increased flow responses (%CBF(70) > 115%, rat #2). There are approximately equal contributions to the heterogeneity of %CBF(70) from within-animal (57 +/- 5%, percent variance +/- standard error) and between-animal (43 +/- 26%) variations. Within-animal variations could be due to heterogeneity of vascular anatomy, while the diversity of vascular control mechanisms might contribute to between-animal variations.

Animals↗

PubMed2004

Specific donor Vbeta-associated CD4 T-cell responses correlate with severe acute graft-versus-host disease directed to multiple minor histocompatibility antigens.

CXB-2/By (CXB-2) recombinant inbred mice express a subset of the minor histocompatibility antigen (miHA) repertoire expressed by C.B10-H2(b)/LiMcdJ (BALB.B) mice. On lethal irradiation and the transplantation of H2(b)-matched C57BL/6 (B6) T cell-depleted bone marrow cells, along with naive unfractionated T cells, both strains succumb to acute graft-versus-host disease (GVHD). Although alloreactive B6 CD4(+) T cells are a necessary source of T-cell help for the B6 CD8(+) component of the GVHD response in both recipient strains, they are capable of mediating severe GVHD by themselves only in BALB.B mice. Previous CD4(+) T-cell receptor repertoire analysis demonstrated overlapping oligoclonal Vbeta use between the CD4(+) B6 anti-BALB.B and B6 anti-CXB-2 responses, with indications of additional BALB.B unique T-cell responses (Vbeta2 and Vbeta11). We report here that the more severe B6 anti-BALB.B response is not due to a quantitative difference in the responding cells, because the frequency of alloreactive donor CD4(+) T cells over time was equivalent in the spleens of BALB.B versus CXB-2 recipients. The responses were also similar in the number of infiltrating B6 CD4(+) T cells in the lingual epithelium of the 2 recipients. In contrast, a significantly greater degree of infiltration and injury of BALB.B intestinal epithelium correlated with the increased level of clinical GVHD severity. Of most significance, despite the involvement of at least 11 Vbeta-associated CD4(+) T-cell families in the overall B6 anti-BALB.B response, the development of severe GVHD correlated with the presence of Vbeta2- and Vbeta11-positive donor T cells. Transplantation of donor CD4(+) T cells from Vbeta-associated families that were shared between the B6 anti-BALB.B and anti-CXB-2 responses resulted in minimal GVHD potential. These data suggest that severe GVHD across miHA barriers depends on the involvement of a restricted number of potent T-cell specificities and implies that there are only a limited number of corresponding responsible miHAs.

Acute Disease↗

PubMed2004

Evolution of responding CD4+ and CD8+ T-cell repertoires during the development of graft-versus-host disease directed to minor histocompatibility antigens.

Graft-versus-host disease (GVHD) can be induced in lethally irradiated mice after allogeneic bone marrow transplantation between major histocompatibility complex-matched strains expressing multiple minor histocompatibility antigen differences. In the B6 --> BALB.B irradiation model, both CD4(+) and CD8(+) donor T cells have the capacity to mediate lethal GVHD. Previously, CDR3-size spectratyping was used to analyze these T-cell responses at a single early time point (day 5) after transplantation and revealed clonal or oligoclonal expansions of the V beta 2, 4, and 6 to 14 families for the CD4(+) response and of the V beta 4, 6, 8 to 11, and 14 families for the B6 CD8(+) response. Appropriate positive selection of these T-cell receptor V beta-skewed CD4(+) and CD8(+) T-cell subsets and their subsequent transfer into lethally irradiated BALB.B recipients resulted in fatal GVHD induction. In contrast, BALB.B mice transplanted with nonskewed V beta CD4(+) T cells survived, with minimal symptoms of GVHD. This study was undertaken to investigate the evolution of the donor/antihost minor histocompatibility antigen T-cell repertoire responses throughout the course of GVHD development. The results indicated that a number of V beta families were consistently involved throughout the course of GVHD, whereas some V beta families exhibited skewed expansions only in either the early or late stages of disease. In addition, sequence analysis of relevant representative skewed CDR3 bands from the CD4(+) V beta 11(+) and the CD8(+) V beta 14(+) families, both of which exhibited strong consistent responses, demonstrated increased use of the J beta 2.5 and J beta 2.4 segments, respectively, thus identifying the T-cell receptor specificities involved.

Animals↗

PubMed2004

Validation of the OSCAR 2 oscillometric 24-hour ambulatory blood pressure monitor according to the International Protocol for the validation of blood pressure measuring devices.

OBJECTIVES: The accuracy of blood pressure measuring devices is of prime importance and should be validated before devices are used clinically. We carried out an independent evaluation of the OSCAR 2 oscillometric ambulatory blood pressure monitor (SunTech Medical model 222) according to the European Society of Hypertension International Protocol. METHODS: Adult subjects were recruited from patients and staff at The James Cook University Hospital, Middlesbrough, UK. Nine sequential same-arm blood pressure measurements were taken alternating between simultaneous readings by two independent, trained observers using mercury sphygmomanometers and the device operated by a third observer. In phase one, 15 subjects participated (five in each of the low, medium and high blood pressure ranges) with 18 subjects participating in phase two. Data from 33 subjects (11 in each of the three blood pressure ranges) were analysed for systolic (19 male, 14 female, mean age 56.0 years) and for diastolic (17 male, 16 female, mean age 51.1 years) blood pressure. RESULTS: The OSCAR 2 passed the first phase of the validation process. In phase 2.1, the OSCAR 2 monitor had 71 readings within 5 mmHg, 86 within 10 mmHg and 94 within 15 mmHg for systolic blood pressure (SBP) and 72 readings within 5 mmHg, 88 within 10 mmHg and 96 within 15 mmHg for diastolic blood pressure (DBP). Mean (+/-SD) differences between observers and device were 0.9+/-2.3 mmHg for SBP and -0.5+/-2.3 mmHg for DBP. In phase 2, 24 subjects had at least two of the differences within 5 mmHg and three subjects had no differences within 5 mmHg for SBP while for DBP 25 subjects had at least two of the differences within 5 mmHg and two subjects had no differences within 5 mmHg. CONCLUSIONS: The OSCAR 2 passes all requirements for validation by the International Protocol and can be recommended for clinical use in an adult population.

Adult↗

PubMed2004

Subcutaneous estrogen replacement therapy.

Subcutaneous estrogen replacement involves placement of estradiol pellets in the subcutaneous area of the lower abdomen or buttocks. Physiologic levels of estradiol are obtained, and follicle stimulating hormone levels are suppressed, similar to values found during premenopause. Insertion is a minor office procedure, with the usual starting dose of 25 mg of estradiol placed; it provides climacteric symptom relief and osteoporosis protection as well as the many other benefits of estrogen replacement. Supplementation with testosterone pellets can be performed, if indicated, at the same time. Patients with an intact uterus require progesterone therapy to protect the endometrium, as do patients using other forms of estrogen replacement. Return of climacteric symptoms, combined with serum levels, can be used to determine the timing of redosing, which is about every 6 months for most patients.

Absorbable Implants↗

PubMed2003

12E2: a cloned murine dermal cell with features of dermal dendrocytes and capacity to produce pathologic changes resembling early Kaposi's sarcoma.

Factor XIIIa-positive dendrocytes are abundant within the dermis and have been implicated in the pathogenesis of various disorders, including AIDS-related Kaposi's sarcoma. Purified cultures of factor XIIIa-positive normal dermal dendrocytes have not as yet been achieved. 12E2 is a cloned cell line derived from superficial murine dermis where factor XIIIa-positive dendrocytes are abundant. Subconfluent cultures of 12E2 demonstrate polydendritic cell contours with thin, elongated membranous projections. These cells express Factor XIIIa and VCAM-1 by immunohistochemistry and by Western blot analysis of 12E2 cell lysates. 12E2 cells also constitutively express the Langerhans-cell-related epitope DEC-205, detected by NLDC-145 antibody and the CD80 co-stimulatory molecule, as well as Ia antigen on exposure to interferon-gamma. Cells so treated exhibit significant ability to present alloantigens in vitro. 12E2 cells are shown to express mRNA for numerous cytokines, including interleukin (IL)-1alpha, IL-1beta, IL-5, IL-6, IL-7, tumor necrosis factor-alpha and granulocyte macrophage-colony stimulating factor, by reverse-transcriptase polymerase chain reaction followed by Southern blot hybridization. Microinjection of 12E2 cells, but not 3T3control fibroblasts, into footpads of syngeneic and SCID mice results in lesions that mimic the histology and immunohistochemistry of human Kaposi's sarcoma. In aggregate, these data indicate that 12E2 cells 1) share lineage characteristics with factor XIIIa-positive dermal dendrocytes, 2) produce mRNA for numerous cytokines and are cytokine responsive to interferon-gamma, and 3) behave in vivo in a manner that resembles Kaposi's sarcoma, a condition known to involve proliferation of human dermal dendrocytes.

3T3 Cells↗

PubMed2003

An epithelial target site in experimental graft-versus-host disease and cytokine-mediated cytotoxicity is defined by cytokeratin 15 expression.

The identity of cells within squamous epithelia that represent primary targets in acute graft-versus-host disease (GVHD) has been an enigma. Murine effector T cells implicated in the alloresponse by Vbeta complementarity-determining region-3 spectratype analysis were detected with a Vbeta-specific monoclonal antibody within discrete microdomains of tongue (lingual) squamous epithelium. These microdomains, termed rete-like prominences (RLPs), are similar to the rete ridges of human skin. Cells forming the basal layer of RLPs and of human skin rete ridges were shown to express a distinctive pattern of keratin expression defined by antibodies to cytokeratin 15 (K15). In experimental murine GVHD elicited across minor histocompatibility antigen barriers (miHA), early lesions involved selective apoptosis and loss of K15(+) staining within lingual RLPs. An in vitro organ culture model designed to investigate target cell injury by short-term exposure to tumor necrosis factor-alpha and interleukin-1beta, mediators relevant to GVHD, showed a similar pattern of apoptosis and loss of K15(+) reactivity within RLPs. In aggregate, these findings establish a novel cytoskeletal marker for target epithelial subpopulations that should facilitate evaluation of mechanisms of host cell injury in GVHD. These data may also enable the development of therapeutic approaches to abrogate disease at the level of target cell blockade.

Animals↗

PubMed2003

Cardiotrophin-1: expression in experimental myocardial infarction and potential role in post-MI wound healing.

Cardiotrophin-1 (CT-1), a member of the IL-6 family of cytokines, has been shown to be elevated in the serum of patients with ischemic heart disease and valvular heart disease, and induces cardiomyocyte hypertrophy in vitro. We investigated expression of CT-1 in post-MI rat heart and the effect of CT-1 on cultured primary adult rat cardiac fibroblasts. Elevated CT-1 expression was observed in the infarct zone at 24 h and continued through 2, 4 and 8 weeks post-MI, compared to sham-operated animals. CT-1 induced rapid phosphorylation of Jak, Jak2, STAT1, STAT3, p42/44 MAPK and Akt in cultured adult cardiac fibroblasts. CT-1 induced cardiac fibroblast protein synthesis and proliferation. Protein and DNA synthesis were dependent on activation of Jak/STAT, MEK1/2, PI3K and Src pathways as evidenced by decreased 3H-leucine and 3H-thymidine incorporation after pretreatment with AG490, PD98059, LY294002 and genistein respectively. Furthermore, CT-1 treatment increased procollagen-1-carboxypropeptide (PICP) synthesis, a marker of mature collagen synthesis. CT-1 induced cell migration of rat cardiac fibroblasts. Our results suggest that CT-1, as expressed in post-MI heart, may play an important role in infarct scar formation and ongoing remodeling of the scar. CT-1 was able to initiate each of the processes considered important in the formation of infarct scar including cardiac fibroblast migration as well as fibroblast proliferation and collagen synthesis. Further work is required to determine factors that induce CT-1 expression and interplay with other mediators of cardiac infarct wound healing in the setting of acute cardiac ischemia and chronic post-MI heart failure.

Animals↗

PubMed2003

Post-hematopoietic cell transplantation control of graft-versus-host disease by donor CD425 T cells to allow an effective graft-versus-leukemia response.

After allogeneic hematopoietic cell transplantation (HCT), the high inverse correlation between graft-versus-host disease (GVHD) and leukemic relapse requires that calculated measures be taken to reduce GVHD pathology while retaining the graft-versus-leukemia (GVL) effect. We sought to determine whether donor CD4(+)CD25(+) regulatory T cells could control ongoing GVHD, thereby providing an initial window of time in which the alloreactive anti-host response is permitted to begin, with the intent of most effectively eliminating residual leukemia cells. Prevention of lethal GVHD by infusion of donor CD4(+)CD25(+) cells early after HCT (day 2) was achieved across a major histocompatibility complex barrier in the haploidentical C3H-->(B6xC3H)F(1) model. However, in vitro expansion of donor CD4(+)CD25(+) T cells, stimulated by recipient cells in the presence of high-dose interleukin-2, was required for successful regulation. In contrast, in the major histocompatibility complex-matched, minor histocompatibility antigen-disparate, CD8-mediated B10.BR-->CBA GVHD model, lethal disease could be completely prevented by a single infusion of freshly isolated donor CD4(+)CD25(+) cells administered as late as 10 days after HCT. Of importance, this late regulatory effect required only a 3:1 ratio of effector CD8:CD4(+)CD25(+) T cells, indicating a strong potential for the delayed infusion of CD4(+)CD25(+) cells to control GVHD across minor histocompatibility antigen barriers. Furthermore, this regulation did not interfere with complete and lasting donor engraftment of the hematopoietic compartment. Of most significance, the day 10 infusion of donor CD4(+)CD25(+) cells into CBA HCT recipients that had been challenged with the MMCBA6 myeloid leukemia cell line did not block an effective GVL response, despite reducing lethal GVHD. These results suggest that donor CD4(+)CD25(+) T cells infused soon after transplantation can ameliorate the development of GVHD without sacrificing a sufficient GVL effect.

Animals↗

PubMed2003

Nitric oxide synthase inhibition depresses the height of the cerebral blood flow-pressure autoregulation curve during moderate hypotension.

Variations in the height of the CBF response to hypotension have been described recently in normal animals. The authors evaluated the effects of nitric oxide synthase (NOS) inhibition on these variations in height using laser Doppler flowmetry in 42 anesthetized (halothane and N2O) male Sprague-Dawley rats prepared with a superfused closed cranial window. In four groups (time control, enantiomer control, NOS inhibition, and reinfusion control) exsanguination to MABPs from 100 to 40 mm Hg was used to produce autoregulatory curves. For each curve the lower limit of autoregulation (the MABP at the first decrease in CBF) was identified; the pattern of autoregulation was classified as "peak" (15% increase in %CBF), "classic" (plateau with a decrease at the lower limit of autoregulation), or "none" (15% decrease in %CBF); and the autoregulatory height as the %CBF at 70 mm Hg (%CBF(70)) was determined. NOS inhibition decreased %CBF(70) in the NOS inhibition group (P = 0.014), in the control (combined time and enantiomer control) group (P = 0.015), and in the reinfusion control group (P = 0.025). NOS inhibition via superfusion depressed the autoregulatory pattern (P = 0.02, McNemar test on changes in autoregulatory pattern) compared with control (P = 0.375). Analysis of covariance showed that changes induced by NOS inhibition in the parameters of autoregulatory height are not related to changes in the lower limit, but are strongly (P < 0.001) related to each other. NOS inhibition depressed the autoregulatory pattern, decreasing the seemingly paradoxical increase in CBF as blood pressure decreases. These results suggest that nitric oxide increases CBF near the lower limit and augments the hypotensive portion of the autoregulatory curve.

Animals↗

PubMed2003

Importance of minor histocompatibility antigen expression by nonhematopoietic tissues in a CD4+ T cell-mediated graft-versus-host disease model.

Minor histocompatibility antigens with expression restricted to the recipient hematopoietic compartment represent prospective immunological targets for graft-versus-leukemia therapy. It remains unclear, however, whether donor T cell recognition of these hematopoietically derived minor histocompatibility antigens will induce significant graft-versus-host disease (GVHD). Using established bone marrow irradiation chimeras across the multiple minor histocompatibility antigen-disparate, C57BL/6-->BALB.B combination, we studied the occurrence of lethal GVHD mediated by CD4+ T cells in recipient mice expressing only hematopoietically derived alloantigens. Even substantial dosages of donor C57BL/6 CD4+ T cells were unable to elicit lethal GVHD when transplanted into [BALB.B-->C57BL/6] chimeras. Instead, chimeric mice displayed transient cachexia with reduced target-tissue injury over time, reflecting an early, limited, graft-versus-host response. On the other hand, the importance of minor histocompatibility antigens derived from nonhematopoietic tissues was demonstrated by the finding that [C57BL/6-->BALB.B] chimeric mice succumbed to C57BL/6 CD4+ T cell-mediated GVHD. These data suggest that severe acute CD4+ T cell-mediated GVHD across this minor histocompatibility antigen barrier depends on the expression of nonhematopoietically rather than hematopoietically derived alloantigens for maximal target-tissue infiltration and injury.

Animals↗

PubMed2002

Suramin reduces infarct volume in a model of focal brain ischemia in rats.

Extracellular adenosine 5'-triphosphate (ATP) provides excitatory transmission in the central nervous system. Stimulation by ATP of ionotropic ligand-gated ion channel purinoceptors (P(2X)) leads to increased intracellular calcium levels, and activation of P(2X) receptors may be involved in the process of excitotoxic neuronal injury caused by stroke. Suramin, as an agent that is known to block P(2X) receptors at a specific concentration, was assessed for its neuroprotective potential in a model of experimental stroke in the rat. We propose that the effectiveness of suramin is limited to those concentrations where it is an effective P(2X) receptor antagonist. Focal brain ischemia was produced by unilateral occlusion and transection of the middle cerebral artery (MCAT) and bilateral occlusion of the common carotid arteries (CCA). Thirty-four male Sprague-Dawley rats were randomly separated into five groups. Changes in regional cerebral blood flow in the ischemic region were verified by laser Doppler flowmetry. All rats received, over a period of 30 min before MCAT, a dose of suramin at 0 (saline), 25, 50, 100, or 250 mg/kg intravenously in a volume of 1 ml using an infusion pump. Six hours after ischemia onset, evaluation of the neurologic status and cerebral blood flow was followed by morphometric analysis of infarct volume. During the surgical procedure mean arterial pressure, blood gases (PaCO(2), PaO(2)), and pH were monitored. A dose-dependent decrease in infarct volume (slope -0.049, SE 0.009, P<0.001) was observed in groups treated over the dose range of 0 to 100 mg/kg (r(2)=0.55). Suramin at a dose of 100 mg/kg significantly decreased infarct volume (n=9, P<0.001) and edema volume (P=0.003). The neuroprotective effect of suramin at a dose of 100 mg/kg was supported by an improved neurologic score in this group (median 0) compared with a median of 3 in control animals (P=0.02). These findings indicate that suramin at 100 mg/kg is an effective pre-treatment neuroprotective agent. As the estimated brain concentration of 10 microM (from McNally et al., 2000, Life Sci 67:1847-1857) is the IC(50) for suramin-mediated P(2X) antagonism, these results suggest that interference with the ATP excitatory system could provide neuroprotection from brain ischemia.

Animals↗

PubMed2002

Variability in the magnitude of the cerebral blood flow response and the shape of the cerebral blood flow-pressure autoregulation curve during hypotension in normal rats [corrected].

BACKGROUND: The maintenance of constant cerebral blood flow (CBF) as mean cerebral perfusion pressure (CPP) varies is commonly referred to as CBF-pressure autoregulation. The lower limit of autoregulation is the CPP at which the vasodilatory capacity is exhausted and flow falls with pressure. We evaluated variability in the magnitude of percent change in CBF during the hypotensive portion of the autoregulatory curve. We hypothesize that this variability, in normal animals, obeys a Gaussian distribution and characterizes a vasodilatory mechanism that is inherently different from that described by the lower limit. METHODS: Sixty-five male Sprague-Dawley rats were anesthetized with 0.5-1% halothane and 70% nitrous oxide in oxygen. Body temperature was maintained at 37 degrees C. Using a closed, superfused cranial window, CBF (as % of control) was determined using laser Doppler flowmetry (LDF) through the window with the intracranial pressure set at 10 mmHg. Animals with low vascular reactivity to inhaled carbon dioxide and superfused adenosine diphosphate (ADP) or acetylcholine were excluded. MABP was sequentially lowered by exsanguination to 100, 85, 70, 55, and 40 mmHg. Using the %CBF versus CPP plots for each curve (1) the lower limit of autoregulation was identified; (2) the pattern of autoregulation was classified as "peak" (a rise in LDF flow of at least 15% as arterial pressure was dropped), "classic" (plateau with a fall), or "none" (a fall in LDF flow of greater than 15%); (3) the area under the autoregulatory curve between CPPs of 30 and 90 mmHg was calculated; and (4) the magnitude of the %CBF response to hypotension was assessed by determining the %CBF at a CPP of 60 mmHg (%CBFCPP60). RESULTS: Of the 65 curves, 21 had the peak pattern, 33 the classic pattern, and 11 the none pattern. The %CBFCPP60 and autoregulatory area displayed Gaussian distributions, consistent with normal variability. Although %CBFCPP60, autoregulatory area, and pattern were significantly correlated (r or rho > 0.84, P < 0.001), the lower limit correlated weakly with autoregulatory area (r = 0.34, P = 0.012), and not at all with autoregulatory pattern or %CBFCPP60. CONCLUSIONS: The %CBFCPP60 measures an aspect of the autoregulatory curve that is distinct from the lower limit. The peak autoregulatory pattern indicates that vessels are dilating more than is necessary to maintain a plateau in response to the pressure decrease, whereas the none pattern existed in spite of acceptable vascular responses to inhaled carbon dioxide and superfused ADP or ACh and the lack of surgical trauma. These results provide a different view of autoregulation during hypotension, are most likely dependent on the highly regional CBF method used, and could have implications concerning potential cerebral ischemia and hypotension during anesthesia.

Anesthesia, Inhalation↗

PubMed2002

Decreased Smad 7 expression contributes to cardiac fibrosis in the infarcted rat heart.

We examined the role of the transforming growth factor (TGF)-beta(1) signaling inhibitor Smad 7 in cardiac fibrosis. TGF-beta(1) (10 ng/ml) was found to increase cytosolic Smad 7 expression in primary adult rat fibroblasts and induce rapid nuclear export of exogenous Smad 7 in COS-7 cells. Furthermore, overexpression of Smad 7 in primary adult fibroblasts was associated with suppressed collagen type I and III expression. We detected Smad 7, phosphorylated Smad 2, TGF-beta type I receptor (TbetaRI), and TGF-beta(1) proteins in postmyocardial infarct (MI) rat hearts. In 2 and 4 wk post-MI hearts, Smad 7 and TbetaRI expression were decreased in scar tissue, whereas TGF-beta(1) expression was increased in scar and viable tissue. In the 8 wk post-MI heart, Smad 7 expression was decreased in both scar tissue and myocardium remote to the infarct scar. Finally, we confirmed that these changes are paralleled by decreased expression of cytosolic phosphorylated receptor-regulated Smad 2 in 4-wk viable myocardium and in 2- and 4-wk infarct scar tissues. Taken together, our data imply that decreased inhibitory Smad 7 signal in cardiac fibroblasts may play a role in the pathogenesis of cardiac fibrosis in the post-MI heart.

Animals↗