Increasing atmospheric dryness reduces boreal forest tree growth

Rising atmospheric vapour pressure deficit (VPD) associated with climate change affects boreal forest growth via stomatal closure and soil dryness. However, the relationship between VPD and forest growth depends on the climatic context. Here we assess Canadian boreal forest responses to VPD changes from 1951-2018 using a well-replicated tree-growth increment network with approximately 5,000 species-site combinations. Of the 3,559 successful growth models, we observed a relationship between growth and concurrent summer VPD in one-third of the species-site combinations, and between growth and prior summer VPD in almost half of those combinations. The relationship between previous year VPD and current year growth was almost exclusively negative, while current year VPD also tended to reduce growth. Tree species, age, annual temperature, and soil moisture primarily determined tree VPD responses. Younger trees and species like white spruce and Douglas fir exhibited higher VPD sensitivity, as did areas with high annual temperature and low soil moisture. Since 1951, summer VPD increases in Canada have paralleled tree growth decreases, particularly in spruce species. Accelerating atmospheric dryness in the decades ahead will impair carbon storage and societal-economic services.

New tree-ring data from Canadian boreal and hemi-boreal forests provide insight for improving the climate sensitivity of terrestrial biosphere models

Understanding boreal/hemi-boreal forest growth sensitivity to seasonal variations in temperature and water availability provides important basis for projecting the potential impacts of climate change on the productivity of these ecosystems. Our best available information currently comes from a limited number of field experiments and terrestrial biosphere model (TBM) simulations of varying predictive accuracy. Here, we assessed the sensitivity of annual boreal/hemi-boreal forest growth in Canada to yearly fluctuations in seasonal climate variables using a large tree-ring dataset and compared this to the climate sensitivity of annual net primary productivity (NPP) estimates obtained from fourteen TBMs. We found that boreal/hemi-boreal forest growth sensitivity to fluctuations in seasonal temperature and precipitation variables changed along a southwestern to northeastern gradient, with growth limited almost entirely by temperature in the northeast and west and by water availability in the southwest. We also found a lag in growth climate sensitivity, with growth largely determined by the climate during the summer prior to ring formation. Analyses of NPP sensitivity to the same climate variables produced a similar southwest to northeast gradient in growth climate sensitivity for NPP estimates from all but three TBMs. However, analyses of growth from tree-ring data and analyses of NPP from TBMs produced contrasting evidence concerning the key climate variables limiting growth. While analyses of NPP primarily indicated a positive relationship between growth and seasonal temperature, tree-ring analyses indicated negative growth relationships to temperature. Also, the positive effect of precipitation on NPP derived from most TBMs was weaker than the positive effect of precipitation on tree-ring based growth: temperature had a more important limiting effect on NPP than tree-ring data indicated. These mismatches regarding the key climate variables limiting growth suggested that characterization of tree growth in TBMs might need revision, particularly regarding the effects of stomatal conductance and carbohydrate reserve dynamics.

Is the Kok effect a respiratory phenomenon? Metabolic insight using 13 C labeling in Helianthus annuus leaves

The Kok effect is a well-known phenomenon in which the quantum yield of photosynthesis changes abruptly at low light. This effect has often been interpreted as a shift in leaf respiratory metabolism and thus used widely to measure day respiration. However, there is still no formal evidence that the Kok effect has a respiratory origin. Here, both gas exchange and isotopic labeling were carried out on sunflower leaves, using glucose that was ¹³ C-enriched at specific C-atom positions. Position-specific decarboxylation measurements and NMR analysis of metabolites were used to trace the fate of C-atoms in metabolism. Decarboxylation rates were significant at low light (including above the Kok break point) and increased with decreasing irradiance below 100 µmol photons m^-2  s^-1 . The variation in several metabolite pools such as malate, fumarate or citrate, and flux calculations suggest the involvement of several decarboxylating pathways in the Kok effect, including the malic enzyme. Our results show that day respiratory CO₂ evolution plays an important role in the Kok effect. However, the increase in the apparent quantum yield of photosynthesis below the Kok break point is also probably related to malate metabolism, which participates in maintaining photosynthetic linear electron flow.

Seed quality and carbon primary metabolism

Improving seed quality is amongst the most important challenges of contemporary agriculture. In fact, using plant varieties with better germination rates that are more tolerant to stress during seedling establishment may improve crop yield considerably. Therefore, intense efforts are currently being devoted to improve seed quality in many species, mostly using genomics tools. However, despite its considerable importance during seed imbibition and germination processes, primary carbon metabolism in seeds is less studied. Our knowledge of the physiology of seed respiration and energy generation and the impact of these processes on seed performance have made limited progress over the past three decades. In particular, (isotope-assisted) metabolomics of seeds has only been assessed occasionally, and there is limited information on possible quantitative relationships between metabolic fluxes and seed quality. Here, we review the recent literature and provide an overview of potential links between metabolic efficiency, metabolic biomarkers, and seed quality and discuss implications for future research, including a climate change context.

Contrasting acclimation abilities of two dominant boreal conifers to elevated CO2 and temperature

High latitude forests will experience large changes in temperature and CO₂ concentrations this century. We evaluated the effects of future climate conditions on 2 dominant boreal tree species, Pinus sylvestris L. and Picea abies (L.) H. Karst, exposing seedlings to 3 seasons of ambient (430 ppm) or elevated CO₂ (750 ppm) and ambient temperatures, a + 4 °C warming or a + 8 °C warming. Pinus sylvestris responded positively to warming: seedlings developed a larger canopy, maintained high net CO₂ assimilation rates (A_net ), and acclimated dark respiration (R_dark ). In contrast, carbon fluxes in Picea abies were negatively impacted by warming: maximum rates of A_net decreased, electron transport was redirected to alternative electron acceptors, and thermal acclimation of R_dark was weak. Elevated CO₂ tended to exacerbate these effects in warm-grown Picea abies, and by the end of the experiment Picea abies from the +8 °C, high CO₂ treatment produced fewer buds than they had 3 years earlier. Treatments had little effect on leaf and wood anatomy. Our results highlight that species within the same plant functional type may show opposite responses to warming and imply that Picea abies may be particularly vulnerable to warming due to low plasticity in photosynthetic and respiratory metabolism.

Physiological acclimation dampens initial effects of elevated temperature and atmospheric CO2 concentration in mature boreal Norway spruce

Physiological processes of terrestrial plants regulate the land-atmosphere exchange of carbon, water, and energy, yet few studies have explored the acclimation responses of mature boreal conifer trees to climate change. Here we explored the acclimation responses of photosynthesis, respiration, and stomatal conductance to elevated temperature and/or CO₂ concentration ([CO₂ ]) in a 3-year field experiment with mature boreal Norway spruce. We found that elevated [CO₂ ] decreased photosynthetic carboxylation capacity (-23% at 25 °C) and increased shoot respiration (+64% at 15 °C), while warming had no significant effects. Shoot respiration, but not photosynthetic capacity, exhibited seasonal acclimation. Stomatal conductance at light saturation and a vapour pressure deficit of 1 kPa was unaffected by elevated [CO₂ ] but significantly decreased (-27%) by warming, and the ratio of intercellular to ambient [CO₂ ] was enhanced (+17%) by elevated [CO₂ ] and decreased (-12%) by warming. Many of these responses differ from those typically observed in temperate tree species. Our results show that long-term physiological acclimation dampens the initial stimulation of plant net carbon assimilation to elevated [CO₂ ], and of plant water use to warming. Models that do not account for these responses may thus overestimate the impacts of climate change on future boreal vegetation-atmosphere interactions.

Leaf day respiration: low CO2 flux but high significance for metabolism and carbon balance

Contents 986 I. 987 II. 987 III. 988 IV. 991 V. 992 VI. 995 VII. 997 VIII. 998 References 998 SUMMARY: It has been 75 yr since leaf respiratory metabolism in the light (day respiration) was identified as a low-flux metabolic pathway that accompanies photosynthesis. In principle, it provides carbon backbones for nitrogen assimilation and evolves CO₂ and thus impacts on plant carbon and nitrogen balances. However, for a long time, uncertainties have remained as to whether techniques used to measure day respiratory efflux were valid and whether day respiration responded to environmental gaseous conditions. In the past few years, significant advances have been made using carbon isotopes, 'omics' analyses and surveys of respiration rates in mesocosms or ecosystems. There is substantial evidence that day respiration should be viewed as a highly dynamic metabolic pathway that interacts with photosynthesis and photorespiration and responds to atmospheric CO₂ mole fraction. The view of leaf day respiration as a constant and/or negligible parameter of net carbon exchange is now outdated and it should now be regarded as a central actor of plant carbon-use efficiency.

Plant hydraulics as a central hub integrating plant and ecosystem function: meeting report for 'Emerging Frontiers in Plant Hydraulics' (Washington, DC, May 2015)

Water plays a central role in plant biology and the efficiency of water transport throughout the plant affects both photosynthetic rate and growth, an influence that scales up deterministically to the productivity of terrestrial ecosystems. Moreover, hydraulic traits mediate the ways in which plants interact with their abiotic and biotic environment. At landscape to global scale, plant hydraulic traits are important in describing the function of ecological communities and ecosystems. Plant hydraulics is increasingly recognized as a central hub within a network by which plant biology is connected to palaeobiology, agronomy, climatology, forestry, community and ecosystem ecology and earth-system science. Such grand challenges as anticipating and mitigating the impacts of climate change, and improving the security and sustainability of our food supply rely on our fundamental knowledge of how water behaves in the cells, tissues, organs, bodies and diverse communities of plants. A workshop, 'Emerging Frontiers in Plant Hydraulics' supported by the National Science Foundation, was held in Washington DC, 2015 to promote open discussion of new ideas, controversies regarding measurements and analyses, and especially, the potential for expansion of up-scaled and down-scaled inter-disciplinary research, and the strengthening of connections between plant hydraulic research, allied fields and global modelling efforts.

Primary health care services provided by nurse practitioners and family physicians in shared practice

BACKGROUND

Collaborative practice involving nurse practitioners (NPs) and family physicians (FPs) is undergoing a renaissance in Canada. However, it is not understood what services are delivered by FPs and NPs working collaboratively. One objective of this study was to determine what primary health care services are provided to patients by NPs and FPs working in the same rural practice setting.

METHODS

Baseline data from 2 rural Ontario primary care practices that participated in a pilot study of an outreach intervention to improve structured collaborative practice between NPs and FPs were analyzed to compare service provision by NPs and FPs. A total of 2 NPs and 4 FPs participated in data collection for 400 unique patient encounters over a 2-month period; the data included reasons for the visit, services provided during the visit and recommendations for further care. Indices of service delivery and descriptive statistics were generated to compare service provision by NPs and FPs.

RESULTS

We analzyed data from a total of 122 encounters involving NPs and 278 involving FPs. The most frequent reason for visiting an NP was to undergo a periodic health examination (27% of reasons for visit), whereas the most frequent reason for visiting an FP was cardiovascular disease other than hypertension (8%). Delivery of health promotion services was similar for NPs and FPs (11.3 v. 10.0 instances per full-time equivalent [FTE]). Delivery of curative services was lower for NPs than for FPs (18.8 v. 29.3 instances per FTE), as was provision of rehabilitative services (15.0 v. 63.7 instances per FTE). In contrast, NPs provided more services related to disease prevention (78.8 v. 55.7 instances per FTE) and more supportive services (43.8 v. 33.7 instances per FTE) than FPs. Of the 173 referrals made during encounters with FPs, follow-up with an FP was recommended in 132 (76%) cases and with an NP in 3 (2%). Of the 79 referrals made during encounters with NPs, follow-up with an NP was recommended in 47 (59%) cases and with an FP in 13 (16%) (p < 0.001).

INTERPRETATION

For the practices in this study NPs were underutilized with regard to curative and rehabilitative care. Referral patterns indicate little evidence of bidirectional referral (a measure of shared care). Explanations for the findings include medicolegal issues related to shared responsibility, lack of interdisciplinary education and lack of familiarity with the scope of NP practice.

Glutathione-S-Transferase as a selective inhibitor of oncogenic ras-p21-induced mitogenic signaling through blockade of activation of jun by jun-N-terminal kinase

We have identified the intracellular detoxification enzyme, glutathione-S-transferase (GST), as a potent inhibitor of the activation of jun by its kinase, jun-N-terminal kinase (JNK), in vitro. All three major isozymes (alpha, mu, and pi) bind to JNK-jun complexes and inhibit activation of jun by JNK. We now find that GST inhibits JNK-induced oocyte maturation in vivo and strongly inhibits oocyte maturation induced by oncogenic ras-p21 protein, but not by insulin-activated normal cellular p21 protein. These results correlate with the finding that oncogenic, but not insulin-activated normal, p21 induces high levels of activated JNK. GST also strongly blocks induction of oocyte maturation by protein kinase C (PKC) which is a critical downstream target of oncogenic but not normal ras-p21. Thus, we have established a new function for GST as a potent physiological inhibitor of the ras-JNK-jun pathway.

CXC and CC chemokine receptors on coronary and brain endothelia

BACKGROUND

Chemokine receptors on leukocytes play a key role in inflammation and HIV-1 infection. Chemokine receptors on endothelia may serve an important role in HIV-1 tissue invasion and angiogenesis.

MATERIALS AND METHODS

The expression of chemokine receptors in human brain microvascular endothelial cells (BMVEC) and coronary artery endothelial cells (CAEC) in vitro and cryostat sections of the heart tissue was determined by light and confocal microscopy and flow cytometry with monoclonal antibodies. Chemotaxis of endothelia by CC chemokines was evaluated in a transmigration assay.

RESULTS

In BMVEC, the chemokine receptors CCR3 and CXCR4 showed the strongest expression. CXCR4 was localized by confocal microscopy to both the cytoplasm and the plasma membrane of BMVEC. In CAEC, CXCR4 demonstrated a strong expression with predominantly periplasmic localization. CCR5 expression was detected both in BMVEC and CAEC but at a lower level. Human umbilical cord endothelial cells (HUVEC) expressed strongly CXCR4 but only weakly CCR3 and CCR5. Two additional CC chemokines, CCR2A and CCR4, were detected in BMVEC and CAEC by immunostaining. Immunocytochemistry of the heart tissues with monoclonal antibodies revealed a high expression of CXCR4 and CCR2A and a low expression of CCR3 and CCR5 on coronary vessel endothelia. Coronary endothelia showed in vitro a strong chemotactic response to the CC chemokines RANTES, MIP-1alpha, and MIP-1beta.

CONCLUSIONS

The endothelia isolated from the brain display strongly both the CCR3 and CXCR4 HIV-1 coreceptors, whereas the coronary endothelia express strongly only the CXCR4 coreceptor. CCR5 is expressed at a lower level in both endothelia. The differential display of CCR3 on the brain and coronary endothelia could be significant with respect to the differential susceptibility of the heart and the brain to HIV-1 invasion. In addition, CCR2A is strongly expressed in the heart endothelium. All of the above chemokine receptors could play a role in endothelial migration and repair.

Refinement of a rodent model of peripheral lymphedema

A reliable, inexpensive experimental counterpart of peripheral lymphedema has been notoriously difficult to reproduce thereby stifling basic and clinical research into this frustrating clinical condition. Accordingly, in 45 adult Wistar-Fuzzy rats, we attempted to produce sustained hindlimb lymphedema by either groin nodal/lymphatic microsurgical ablation (S) (guided by visual blue dye lymphography) or limited field-groin irradiation (R) alone (4500 rads) or combined S followed by R or R followed by S with an additional non-manipulated group serving as controls. Observations were made for 30-100 days thereafter. Hindlimb volumes were determined serially using the truncated cone formula based on multiple circumferential measurements at standardized intervals along the affected hindlimb and the findings compared with similar measurements in the contralateral non-manipulated hindlimb. In randomly selected rats from each group, lymphatic drainage was assessed by lymphangioscintigraphy (LAS), soft tissue swelling by magnetic resonance imaging (MRI), and edema fluid total protein content by refractometry. Whereas S or R alone produced only transient or mild hindlimb edema without associated morbidity or mortality, S-R or R-S induced moderate to severe sustained protein-rich hindlimb lymphedema associated with 9-13% early mortality and notable late local limb morbidity. Lymphatic obstruction was documented by sustained maintenance of increased hindlimb volume, subcutaneous fluid accumulation (MRI), and impaired lymphatic drainage (LAS). This reproducible rodent model of secondary lymphedema reliably simulates a stable clinical condition for a window of up to 100 days and should thereby facilitate standardized testing of therapeutic/preventive protocols and basic research into lymphatic dynamics in secondary lymphedema.

Expression of multiple matrix metalloproteinases and urokinase type plasminogen activator in cultured Kaposi sarcoma cells

Kaposi's sarcoma (KS) cells are considered to be of endothelial origin. KS lesions are characterized by hyperproliferation and an invasive phenotype. We have determined that KS cell cultures constitutively secrete multiple forms of several matrix metalloproteinases (MMPs) and an altered form of urokinase plasminogen activator (uPA) by zymogram and Western analysis of the culture media. MMPs are a family of secreted endoproteinases which degrade components of the extracellular matrix. Their enhanced expression and activity are strongly correlated with cellular processes involving tissue remodeling and invasion. The KS cells secrete increased levels of gelatinase A and B and a high molecular weight uPA in vitro when compared with non-KS endothelial or epithelial cells. Multiple forms of gelatinases A and B were observed on gelatin zymograms. Caseinolytic bands observed were confirmed by Western blot analysis to be due to stromelysin activity, whereas matrilysin was not detected by casein zymography. Western blot analysis also detected secretion of interstitial collagenase and high molecular weight uPA. Gelatinolytic activity with the mobility of gelatinase B was detected on gelatin zymograms, but not by Western analysis. This unusual constitutive expression pattern of MMPs and uPA by KS cells in vitro is characterized by elevated levels of gelatinase A, gelatinase B, interstitial collagenase, stromelysin and a high molecular weight form of uPA, and the lack of expression of matrilysin. These secreted MMPs, taken together, are capable of digesting a broad range of components of the extracellular matrix. This unusual pattern is likely to contribute to the characteristic hyperproliferative and invasive phenotype of KS lesions.

Cocaine enhances brain endothelial adhesion molecules and leukocyte migration

Leukocyte infiltration of cerebral vessels in cocaine-associated vasculopathy suggests that cocaine may enhance leukocyte migration. We have investigated cocaine's effects on leukocyte adhesion in human brain microvascular endothelial cell (BMVEC) cultures and monocyte migration in an in vitro blood-brain barrier (BBB) model constructed with BMVEC and astrocytes. Cocaine (10(-5) to 10(-9) M) enhanced adhesion of monocytes and neutrophils to BMVEC. In the BBB model, cocaine (10(-4) to 10(-8) M) enhanced monocyte transmigration. Cocaine increased expression of endothelial adhesion molecules, intercellular adhesion molecule-1 (ICAM-1, CD54), vascular cell adhesion molecule-1 (VCAM-1), and endothelial leukocyte adhesion molecule-1 (ELAM-1) on BMVEC. The peak effect on ICAM-1 expression was between 6 and 18 h after treatment. ICAM-1 was increased by cocaine in BMVEC, but not in human umbilical vein endothelial cells, and the enhancement was greater in a coculture of BMVEC with monocytes. ICAM-1 expression was enhanced by a transcriptional mechanism. Polymyxin B inhibited up-regulation of adhesion molecules by LPS but not by cocaine. In LPS-activated BMVEC/monocyte coculture, cocaine increased secretion of tumor necrosis factor-alpha and interleukin-6. Taken together, these findings indicate that cocaine enhances leukocyte migration across the cerebral vessel wall, in particular under inflammatory conditions, but the effects are variable in different individuals. Cocaine's effects are exerted through a cascade of augmented expression of inflammatory cytokines and endothelial adhesion molecules. These could underlie the cerebrovascular complications of cocaine abuse.

Cocaine opens the blood-brain barrier to HIV-1 invasion

Cocaine abuse has been associated with vasculitis and stroke, and is suspected to influence the progression of AIDS dementia. Cocaine may enhance HIV-1 neuroinvasion by actions directed at the blood-brain barrier. HIV-1 appears to penetrate the human brain microvascular endothelial cell barrier by a paracellular route breached by tumor necrosis factor-alpha (TNF-alpha). Cocaine's effects on the blood-brain barrier were investigated using human brain microvascular endothelial cells and peripheral blood monocytes. Cocaine (10(-5) M and 10(-6) M) increased molecular permeability of the barrier and viral invasion by the macrophage-tropic HIV-1(JR-FL) into the brain chamber. Cocaine also augmented apoptosis of brain endothelial cells and monocytes, increased secretion of four chemokines (interleukin-8, interferon-inducible protein-10, macrophage inflammatory protein-1alpha, and monocyte chemoattractant protein-1) and the cytokine, TNF-alpha, by human monocytes. TNF-alpha enhanced invasion of the brain compartment by macrophage-tropic, lymphotropic, and bitropic HIV-1 strains. These data indicate that HIV-1 neuroinvasion can be increased by (a) cocaine's direct effects on brain microvascular endothelial cells and (b) paracrine effects of cocaine-induced pro-inflammatory cytokines and chemokines on the blood-brain barrier.

Inhibition of normal and experimental angiotumor endothelial cell proliferation and cell cycle progression by 2-methoxyestradiol

With rapid growth and metabolism, aggressive cancers require an extensive vascular network, termed tumor angiogenesis. The body produces a variety of natural angiogenic inhibitors, among which is the mammalian estrogen metabolite, 2-methoxyestradiol (2-MeOE2). In this study, we compared the effects of 2-MeOE2 on a human umbilical vein cell line (HUVEC-C) and on an immortal, angiotumor-producing rat sinusoidal endothelial cell line (RSE-1). In vitro, the effects of varying concentrations of 2-MeOE2 from 0.01-100.0 microM were measured with cell counts and compared to control cells. HUVEC-C had an ED50 approximately 3.5 microM with approximately 27% inhibition of cell growth whereas RSE-1 had an ED50 approximately 2.2 microM with approximately 50% inhibition of cell growth compared with controls. The lowest concentration with maximal effect was 10.0 microM 2-MeOE2 for both cell lines. Using this concentration, flow cytometric analysis of cell cycles was performed with propidium iodide stained DNA of HUVEC-C and RSE-1 at 24 and 48 hr. Both demonstrated a significant (P < 0.0001) block at G2M of the cell cycle. At 48 hr, HUVEC-C had 32% of cells in G2M (control = 9% G2M), and RSE-1 had 36% of cells in G2M (control = 18% G2M). These findings demonstrate a strong in vitro antiproliferative effect of 2-MeOE2 on normal dividing endothelial as well as angiotumor cells mediated through a cell cycle-specific block at G2M. The antiendothelial, antiangiotumor effect of 2-MeOE2 supports its potential as a therapeutic agent against solid organ cancers, benign or malignant vascular growths, and other pathologic states dependent on angiogenesis.

Amyloid-beta induces chemokine secretion and monocyte migration across a human blood--brain barrier model

BACKGROUND

Aside from numerous parenchymal and vascular deposits of amyloid beta (A beta) peptide, neurofibrillary tangles, and neuronal and synaptic loss, the neuropathology of Alzheimer's disease is accompanied by a subtle and chronic inflammatory reaction that manifests itself as microglial activation. However, in Alzheimer's disease, alterations in the permeability of the blood-brain barrier and chemotaxis, in part mediated by chemokines and cytokines, may permit the recruitment and transendothelial passage of peripheral cells into the brain parenchyma.

MATERIALS AND METHODS

Human monocytes from different donors were tested for their capacity to differentiate into macrophages and their ability to secrete cytokines and chemokines in the presence of A beta 1-42. A paradigm of the blood-brain barrier was constructed utilizing human brain endothelial and astroglial cells with the anatomical and physiological characteristics observed in vivo. This model was used to test the ability of monocytes/macrophages to transmigrate when challenged by A beta 1-42 on the brain side of the blood-brain barrier model.

RESULTS

In cultures of peripheral monocytes, A beta 1-42 induced the secretion of proinflammatory cytokines TNF-alpha, IL-6, IL-1 beta, and IL-12, as well as CC chemokines MCP-1, MIP-1 alpha, and MIP-1 beta, and CXC chemokine IL-8 in a dose-related fashion. In the blood-brain barrier model, A beta 1-42 and monocytes on the brain side potentiated monocyte transmigration from the blood side to the brain side. A beta 1-42 stimulated differentiation of monocytes into adherent macrophages in a dose-related fashion. The magnitude of these proinflammatory effects of A beta 1-42 varied dramatically with monocytes from different donors.

CONCLUSION

In some individuals, circulating monocytes/macrophages, when recruited by chemokines produced by activated microglia and macrophages, could add to the inflammatory destruction of the brain in Alzheimer's disease.

Scatter factor promotes motility of human glioma and neuromicrovascular endothelial cells

Malignant gliomas are characterized by rapid growth, infiltration of normal brain tissue, and high levels of tumor-associated angiogenesis. The genetic and local environmental tissue factors responsible for the malignant progression from low to high grade gliomas and the highly malignant behavior of glioblastomas are not well understood. In a study of 77 human brain tissue extracts, high grade (III-IV) tumors had significantly greater scatter factor (SF) content than did low grade tumors or non-neoplastic tissue. To investigate the potential significance of SF accumulation in gliomas, we measured the effects of SF on DNA synthesis and motility of cultured human glioma cell lines. SF stimulated DNA synthesis in 7/10 glioma cell lines and in 3/3 neuromicrovascular endothelial cell (NMVEC) lines, consistent with our previous report that SF stimulated cell proliferation of a few human glioma cell lines. SF markedly stimulated the chemotactic migration of 10/10 glioma cell lines as well as 3/3 NMVEC lines. In addition, SF stimulated the 2-dimensional migration of glioma cells on culture surfaces coated with specific extracellular matrix molecules (collagen i.v., laminin, and fibronection). As expected based on these biologic responses to SF, 10/10 glioma lines and 4/4 NMVEC lines expressed mRNA for c-met, the SF receptor. To assess the possible in vivo significance of these migration assays, we compared the chemotactic response of a glioma cell line to human brain cyst fluids and tumor extracts that contained high or low SF concentrations. Fluids and extracts with high SF content tended to induce higher levels of chemotactic migration than did fluids and extracts with low SF content. Addition of anti-SF monoclonal antibody (MAb) inhibited migration induced by fluids and extracts with high SF content by about 30-50%.

Angiotensin converting enzyme inhibition improves baroreflex-induced noradrenaline spillover responses in rabbits with heart failure

Impaired baroreflex function is a characteristic feature of congestive heart failure (CHF), although the mechanism is obscure. This study examined the hypothesis that activation of the renin-angiotensin system contributes to baroreflex dysfunction in CHF. The acute effects of an angiotensin converting enzyme inhibitor, enalaprilat, on baroreflex-mediated changes in heart rate (HR), total and renal noradrenaline (NA) spillover rates were examined in conscious rabbits with doxorubicin-induced cardiomyopathic CHF. Studies were performed under resting conditions and in response to changes in mean arterial pressure (MAP) induced by sodium nitroprusside and phenylephrine infusions. Seven saline-treated (normal group) and 11 doxorubicin-treated rabbits (1 mg/kg administered intravenously twice weekly) were studied after 4 and 6 weeks' treatment. Five CHF rabbits received saline (C group) and 6 enalaprilat infusion (ACEI group) during each study period. After 4 weeks of doxorubicin, baroreflex-HR responses were normal, whereas baroreflex-NA spillover responses were enhanced. Enalaprilat infusion shifted the HR-MAP curve downwards to the left but had no effect on the NA spillover-MAP curves. After 6 weeks of doxorubicin, when CHF was established, baroreflex-HR and NA spillover curves were depressed. At this stage, enalaprilat had little effect on the HR-MAP curve but restored towards normal the NA spillover-MAP curves. The results suggest that the endogenous renin-angiotensin system contributes to attenuated baroreflex responses when CHF is established.

A model for monocyte migration through the blood-brain barrier during HIV-1 encephalitis

HIV-1 invades the central nervous system early during viral infection, but neurologic impairment usually occurs years later. The strongest predictor for clinical dementia is the absolute numbers of immunocompetent brain macrophages. Thus, how monocytes penetrate the brain during disease remains critical for understanding the neuropathogenic mechanisms of HIV-1 encephalitis. To these ends, we constructed an artificial blood-brain barrier (BBB) consisting of a matrix-coated membrane with brain microvascular endothelial cells (BMVEC) on one side and astrocytes on the other. Astrocyte endfeet contacted the monolayer of BMVEC that formed tight junctions. To determine the role of viral and immune factors in monocyte penetration across the BBB, HIV-infected or uninfected monocytes with or without immune stimulation were placed onto the upper chamber of the BBB model system. Placement of immune-stimulated (LPS-treated) cells onto the BBB construct elicited gaps between BMVEC, with bulging of nuclear zones and increased numbers of vesicular Golgi complexes and endoplasmic reticulum. This correlated with a profound increase (up to 20-fold) in the number of migrating cells. Viral infection did not enhance monocyte migration. The activated monocytes showed increased numbers of philopodia, lysosomes, and vesicular Golgi complexes and expressed large levels of proinflammatory cytokines (TNF-alpha, IL-6, and IL-10). These data suggest that a major mechanism for the transendothelial migration of monocytes during HIV encephalitis is the immune activation that accompanies viral infection of the central nervous system.

A model for monocyte migration through the blood-brain barrier during HIV-1 encephalitis

HIV-1 invades the central nervous system early during viral infection, but neurologic impairment usually occurs years later. The strongest predictor for clinical dementia is the absolute numbers of immunocompetent brain macrophages. Thus, how monocytes penetrate the brain during disease remains critical for understanding the neuropathogenic mechanisms of HIV-1 encephalitis. To these ends, we constructed an artificial blood-brain barrier (BBB) consisting of a matrix-coated membrane with brain microvascular endothelial cells (BMVEC) on one side and astrocytes on the other. Astrocyte endfeet contacted the monolayer of BMVEC that formed tight junctions. To determine the role of viral and immune factors in monocyte penetration across the BBB, HIV-infected or uninfected monocytes with or without immune stimulation were placed onto the upper chamber of the BBB model system. Placement of immune-stimulated (LPS-treated) cells onto the BBB construct elicited gaps between BMVEC, with bulging of nuclear zones and increased numbers of vesicular Golgi complexes and endoplasmic reticulum. This correlated with a profound increase (up to 20-fold) in the number of migrating cells. Viral infection did not enhance monocyte migration. The activated monocytes showed increased numbers of philopodia, lysosomes, and vesicular Golgi complexes and expressed large levels of proinflammatory cytokines (TNF-alpha, IL-6, and IL-10). These data suggest that a major mechanism for the transendothelial migration of monocytes during HIV encephalitis is the immune activation that accompanies viral infection of the central nervous system.

Scatter factor expression and regulation in human glial tumors

Scatter factor (SF) (also known as hepatocyte growth factor [HGF]) is a cytokine that induces cell motility in vitro and angiogenesis in vivo. SF appears to be a determinant of the malignant phenotype in certain systemic cancers. We detected SF in extracts prepared from human gliomas, with the highest levels found in malignant tumors. Human glioblastoma cells expressed both SF and its receptor (c-met protein) in vivo, as demonstrated by immunohistochemistry. Consistent with these observations, we found moderate to high levels of production of immunoreactive and biologically active SF by cultured human glioblastoma cells (3 of 8 lines) and by neural microvascular endothelial cells (NMVEC) (3 of 3 lines). SF stimulated the proliferation of glioblastoma and NMVEC cell lines by paracrine or autocrine mechanisms. Conditioned medium (CM) from both glioblastoma and NMVEC cells contained SF-inducing factor (SF-IF) activity, defined by its ability to stimulate SF production in an indicator cell line (MRC5 human fibroblasts). This activity consisted of a high-molecular-weight (> 30 kDa), heat-sensitive component and a low-molecular weight (< 30 kDa), heat-stable component. Furthermore, glioblastoma CM stimulated NMVEC SF production, and NMVEC CM stimulated glioblastoma cell SF production, by 3- to 6-fold in each case. Our findings demonstrate that SF-dependent interactions between glioma cells, and between glioma cells and endothelium, can contribute to the heterogeneous proliferative and angiogenic phenotypes of malignant gliomas in vivo.

Human herpesvirus 8 (Kaposi's sarcoma-associated herpesvirus) DNA in Kaposi's sarcoma lesions, AIDS Kaposi's sarcoma cell lines, endothelial Kaposi's sarcoma simulators, and the skin of immunosuppressed patients

We used the polymerase chain reaction on 63 tissue specimens of histologically staged classic Kaposi's sarcoma (KS) from 40 patients, 14 specimens from 14 acquired immune deficiency syndrome (AIDS)-KS cases (all from the same geographic area over a 10-year period), and peripheral blood mononuclear cells from 1 of the non-AIDS KS patients to amplify a specific 210-bp genomic sequence of the newly discovered KS-associated herpesvirus (KSHV). Also tested were 86 benign and malignant endothelial lesions, which potentially simulated each KS histological stage and were further matched by age approximation and by sex with a classical KS specimen. The lesions included hemangioma, lymphangioma, pyogenic granuloma, and angiosarcoma. KSHV was also sought in multiple well characterized vascular endothelial cell lines from AIDS-KS lesions and in 20 mainly cutaneous benign and malignant lesions from 15 immunosuppressed transplant patients. Overall, 92% of KS tissue specimens, representing 88% of classical KS and 100% of AIDS-KS patients, and in addition the sample of peripheral blood mononuclear cell DNA, were positive as visualized on ethidium bromide gels and confirmed by Southern blot hybridization (only 1 case was negative on gell visualization but positive on Southern blot), thus confirming the close association of KSHV with KS of different clinical forms. None of the various other endothelial lesion, skin lesions in immunosuppressed patients, or AIDS-KS endothelial cell lines contained amplifiable KSHV DNA, which indicates that reactivation of KSHV is not present in the skin lesions of immunosuppressed patients and probably is not a ubiquitous agent that secondarily infects proliferative endothelium. The absence of amplifiable virus DNA in the cultured endothelium of KS suggests that the stimulus for angioproliferation originates in another host cell or under conditions not reproduced in culture. The polymerase chain reaction is a specific and sensitive means of verifying KS in the differential diagnosis of angioproliferative lessons.

Suppression of noradrenaline spillover by the dopamine prodrug gamma-L-glutamyl-L-dopa: a central effect?

The DA prodrug gamma-L-glutamyl-L-dopa (gludopa) has a high degree of renal selectivity with 2-step conversion to DA in the kidney. The effects of gludopa, with and without DA-2 receptor blockade, on renal and total noradrenaline (NA) spillover, were studied in two groups of rabbits. Eight rabbits received gludopa infusion (25 and 100 micrograms/kg/min and 8 received an infusion of gludopa and DA-2 receptor antagonist, YM-09151 (50 micrograms/kg i.v.). Renal and total NA spillover rates were measured by 3H-NA tracer method before and after gludopa infusion. Brain NA, DA, gludopa and L-dopa content were measured after gludopa infusion in 5 rabbits; control values for tissue catecholamine and drug levels were obtained in 5 untreated rabbits. Gludopa infusion markedly increased kidney DA content (300-fold) and DA excretion (6000-fold) but had little effect on plasma DA. It produced a dose-related fall in mean (+/- SEM) renal NA spillover (21.6 +/- 3.7 to 10.6 +/- 2.7, 7.2 +/- 2.7 ng/min, p < 0.01). Even greater falls were observed in total NA spillover after gludopa (43.1 +/- 10.2 to 19.7 +/- 3.4, 9.4 +/- 1.8 ng/min, p < 0.01). DA-2 receptor antagonism had no influence on the effects of gludopa on either renal or total NA spillover. Significant amounts of gludopa were detected in the brain after drug infusion (0.28 +/- 13 nmol/g brain tissue). Gludopa, a putative renal selective dopamine prodrug with effects mediated via DA-1 receptors also significantly inhibits both renal and extra-renal NA spillover. This effect is not a DA-2 effect but may be mediated centrally.

Sympatho-inhibitory effects of gamma-l-glutamyl-l-dopa are not mediated by activation of dopamine-2 receptors in conscious rabbits

AIM

To define the role of dopamine-2 receptors in the sympatho-inhibitory effects of gamma-l-glutamyl-l-dopa in conscious rabbits.

METHOD

gamma-l-glutamyl-l-dopa (gludopa) was infused iv at 25 and 100 micrograms.kg-1.min-1 with and without prior dopamine-2 receptor blockade by YM-09151-2 (50 micrograms.kg-1 iv) in conscious rabbits.

RESULTS

Mean arterial pressure and heart rate remained unchanged while renal plasma flow increased. Arterial norepinephrine (NE) concentration, total and renal NE spillover rate were markedly decreased in a dose-related manner, which were not affected by prior dopamine-2 receptor blockade. Gludopa was detected in the whole brain (92 +/- 112 ng/g wet brain tissue) at the end of experiment although brain tissue levodopa, NE, and dopamine contents were not much different from those in the control group.

CONCLUSION

Gludopa decreased dose-dependently plasma NE concentration, and total and renal NE overflow to plasma, which were not mediated by activation of dopamine D2 receptors.

Angiotensin II enhances norepinephrine spillover during sympathetic activation in conscious rabbits

To investigate the potential modulating influence of angiotensin II (ANG II) on sympathetic activity in response to changes in baroreflex activity, renal and total norepinephrine (NE) spillover rates were examined during sodium nitroprusside (SNP) and phenylephrine (PE) infusions in four groups of conscious rabbits: 1) saline (control); 2) subpressor ANG II (ANG II, 2 ng.kg-1.min-1); 3) enalaprilat (MK-422, 200 micrograms/kg and 3.3 micrograms.kg-1.min-1); and 4) MK plus ANG II (MK+ANG II). Upper plateaus of baroreflex-NE spillover curves for renal and total NE spillover were reduced in the MK group (25 and 81 ng/min) compared with control (38 and 125 ng/min) and MK+ANG II (37 and 155 ng/min). To investigate the interaction of ANG II and sympathetic activity during treadmill exercise, hindlimb NE spillover rate was examined in three groups of rabbits: 1) control, 2) MK, and 3) MK+ANG II. Exercise at 6 and 12 m/min produced similar effort-related hemodynamic responses in the three groups. At maximal exercise, hindlimb NE spillover was reduced in the MK group (29 +/- 3 ng/min) compared with control (62 +/- 17 ng/min, P < 0.05) and MK+ANG II group (51 +/- 10 ng/min). It is concluded that endogenous ANG II enhances sympathetic activity during pharmacological (baroreflex) and physiological stimulation.

Regional blood flow effects of dopexamine versus enalaprilat during propofol anaesthesia in rabbits with experimental chronic heart failure

OBJECTIVE

Chronic congestive heart failure (CHF) was induced in rabbits with doxorubicin in order to evaluate: (1) haemodynamic and regional blood flow responses to propofol anaesthesia; (2) modification of these cardiovascular responses with background intravenous infusions of enalaprilat or dopexamine.

METHODS

Rabbits received either doxorubicin, 2 mg.kg-1 weekly intravenously for seven weeks (CHF, n = 6), or saline (controls, n = 6). Doppler flow probes were implanted on the ascending aorta, left renal artery, and lower abdominal aorta. In three separate studies propofol was infused for 40 min periods at 0.6 and then 1.2 mg.kg-1.min-1 after background infusions of either saline, enalaprilat (0.2 mg.kg-1 + 0.003 mg.kg-1.min-1), or dopexamine (0.008 mg.kg-1.min-1).

RESULTS

In normal rabbits propofol (1.2 mg.kg-1.min-1) reduced mean arterial pressure from awake control by 33(SEM 3)%, cardiac output by 24(4)%, and hindlimb blood flow (HBF) by 10(2)%, but did not change renal blood flow. In rabbits with CHF, although resting mean blood pressure was lower, propofol did not alter blood pressure or hindlimb blood flow, but renal blood flow was reduced by 37(6)%.

CONCLUSIONS

Both enalaprilat and dopexamine increased renal blood flow in the control and CHF groups. Enalaprilat caused marked hypotension during anaesthesia in the CHF group. Dopexamine increased mean arterial pressure, heart rate, and hindlimb blood flow during anaesthesia in controls, but not in CHF.

Sympatho-inhibitory effects of r-l-glutamyl-l-dopa in conscious rabbits

Renal and total norepinephrine (NE) spillover rates were studied with [3H] NE kinetic method during graded r-l-glutamyl-l-dopa (gludopa) i.v. infusion in conscious rabbits. Mean arterial pressure (MAP) and heart rate (HR) remained constant during the experiment. Gludopa i.v. infusion at 25 and 100 micrograms.kg-1.min-1 produced marked increases in urinary dopamine (DA) excretion and renal DA content. Although renal venous DA rose after gludopa infusion, the arterial DA was not significantly altered. Arterial plasma gludopa and levodopa levels reached 0.9 +/- 0.5, 3.2 +/- 0.8 micrograms.ml-1 and 3.0 +/- 1.8, 10.1 +/- 5.1 ng.ml-1 at the lower and higher gludopa doses, respectively. Gludopa elicited a pronounced dose-related fall in renal NE spillover, which only accounted for about one half of the reduction in overall NE spillover rate. Renal NE content was doubled. These results indicated that gludopa decreased the renal and extrarenal NE spillover to plasma. This reduction may be mediated by intrarenally synthesized DA via presynaptic DA-2 and alpha-2 receptors, but could also be explained by some central sympatho-inhibitory mechanism.

Beneficial acute effects of selective modulation of renal dopamine system by gamma-L-glutamyl-L-dopa in rabbits with congestive heart failure

gamma-L-Glutamyl-L-dopa (gludopa) is a dopamine (DA) prodrug with a high degree of renal selectivity. We compared the acute renal effects of gludopa in conscious control rabbits (n = 6) and rabbits with doxorubicin-induced congestive heart failure (CHF, n = 5). Normal saline and gludopa 25 and 100 micrograms/kg/min were infused intravenously (i.v.), each for 60 min. One week later, the same protocol was followed except that the DA-1 antagonist SCH 23390 was given i.v. in a dose of 0.3 mg/kg 10 min before gludopa infusion. An additional control group (n = 6) received the DA-1 antagonist alone and saline vehicle infusion throughout the study period. In both control and CHF groups, gludopa elicited significant and similar increases in urine flow (70, 62%), sodium excretion (127, 98%), and renal blood flow (RBF) (33, 27%), and decreased renal vascular resistance (RVR) (-23, -38%). All these changes were abolished by previous DA-1 antagonism with SCH 23390. Blood pressure (BP), heart rate (HR), and hindlimb blood flow (HBF) remained unchanged during gludopa infusion in both groups. In the control group, but not in the CHF group, plasma renin activity (PRA) increased during gludopa infusion; this was not influenced by DA-1 antagonism. In normal rabbits (n = 6), treatment with SCH 23390 alone had no significant effect on renal excretory function or haemodynamics. During gludopa administration, plasma DA concentration was not significantly altered, whereas urine DA excretion and renal DA content were markedly increased. Intrarenal conversion of gludopa to DA was significantly less in CHF rabbits as compared with the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Diet and ethanol modulate immune responses in young C57BL/6 mice

Chronic ethanol (ETOH) ingestion adversely affects the immunocompetence of alcohol abusers. ETOH directly impairs host defense mechanisms and indirectly modulates immunocompetence by interfering with the nutritional status of the alcoholic. It is not clear from the current literature, however, to what extent ETOH, nutritional status, or the combination of the two factors modulates immune mechanisms in chronic alcoholics. To date, most animal studies investigating the immunotoxicity of ETOH have neglected the dietary factors, which may have masked additional immunotoxic effects of ETOH. To examine these dietary factors, we fed mice three liquid ETOH diets with different dietary sufficiencies for 7 weeks and investigated various immune responses. Spleen cell number and secretions of immunoreactive interleukin-2 and tumor necrosis factor were totally independent of the diet, being affected only by ETOH. Body, spleen, and thymus weights, interferon-gamma secretion, and natural killer cell and phagocytic activities were modulated by ETOH as well as by diet. Natural killer cell and phagocytic activities were also directly affected by the nutritional quality of the diet. These results suggest that animal diets used in experimental studies of ETOH-induced immunomodulation must be planned and controlled carefully in order to single out the direct effects that ETOH has on the host defense system.

The dopamine prodrug, gludopa, decreases both renal and extrarenal noradrenaline spillover in conscious rabbits

1. Renal and total noradrenaline (NA) spillover rates were examined under control conditions and during graded infusions of gludopa (gamma-L-glutamyl-L-dopa) in conscious rabbits. 2. Gludopa infusion at 25 and 100 micrograms/kg per min did not alter mean arterial pressure (MAP) and heart rate (HR), but had significant dose-related effects on the renal dopamine (DA) system. At the high dose there were pronounced increases in urinary DA excretion (> 6000-fold) and renal DA content (> 100-fold); renal NA content doubled. 3. Renal venous DA increased after gludopa infusion, but arterial plasma DA concentrations were not significantly changed. Mean arterial plasma gludopa and L-dopa concentrations reached 890, 3190 ng/mL and 3, 10 ng/mL at low and high doses, respectively. 4. Gludopa resulted in a pronounced dose-dependent fall in renal NA spillover, which at 100 micrograms/kg per min accounted for almost half of the reduction in overall NA spillover rate. 5. The significant falls in renal and extrarenal NA spillover rate during gludopa infusion are consistent with suppression of renal and overall sympathetic activity. Gludopa-induced inhibition of renal NA spillover is likely to be due to the actions of DA generated in the kidney on presynaptic DA-2 and alpha-2 receptors. A central sympathoinhibitory mechanism may explain the reduced total NA spillover.

Enalaprilat restores sensitivity of baroreflex control of renal and total noradrenaline spillover in heart failure rabbit

1. The acute effect of an angiotensin converting enzyme inhibitor (ACEI), enalaprilat, on baroreflex-mediated changes in renal and total NA spillover rate in conscious rabbits with doxorubicin-induced cardiomyopathic congestive heart failure (CHF) were investigated under resting conditions and in response to changes in arterial pressure induced by sodium nitroprusside and phenylephrine infusions. 2. Six saline-treated (N group) and 11 doxorubicin-treated rabbits (1 mg/kg administered i.v. twice weekly) were studied after 4 and 6 weeks treatment. Five CHF rabbits received saline (C group) and six enalaprilat infusion (ACEI group). 3. After 4 weeks of doxorubicin, mean arterial pressure (MAP)-renal noradrenaline (NA) spillover and MAP-total NA spillover curves did not change during enalaprilat infusion. 4. After 6 weeks, the C group showed blunted MAP-renal NA spillover and MAP-total NA spillover curves. In the ACEI group, however, both curves returned toward those seen in the N group (slope of MAP-renal NA curve: from 0.27 to 1.80 ng/min per mmHg, MAP-total NA curve: from 1.61 to 3.59 ng/min per mmHg). 5. Results of this study indicate that enalaprilat enhances baroreflex control of renal and total NA spillover in rabbits with CHF and further support the view that activation of the renin-angiotensin system contributes significantly to the attenuated baroreflex responses in CHF.

Absence of monoclonal antibody detectable Kaposi sarcoma-specific antigens on lesion-derived cultured cells

To define the histogenesis and cell origin of Kaposi sarcoma (KS), we cultured KS cells without retrovirally conditioned media from three HIV seropositive AIDS patients and then attempted to raise mouse hybrid monoclonal antibodies (Mabs) specific to these AIDS-KS cells. After both in vivo and in vitro immunization trials, all putative Mabs reacted positively to KS cells but also non-specifically with other human (CH5 and OM) and non-human (RSE-1) control endothelial cell lines. To overcome this crossreactivity, we further "absorbed" previously cloned hybrids and pre-hybrid splenocytes by incubating them with the control endothelial cell lines to eliminate splenocytes and/or hybridomas reactive to normal endothelium. Whereas absorption successfully eliminated immunoreactivity to control endothelium, it also excluded reactivity to KS cells. These findings (lack of specific antigenicity and immunoresponsiveness of KS similar to non-KS control endothelium) suggest that AIDS-KS cells are neither antigenically transformed nor neoplastic, but instead represent dedifferentiated or transdifferentiated endothelium which retains immunogenicity of its original endothelial cell prototype.

Hypersensitivity pneumonitis: sensitivity of high-resolution CT in a population-based study

OBJECTIVE

Hypersensitivity pneumonitis refers to a group of pulmonary disorders caused by inhalation of organic or inorganic particulates by sensitized persons. The diagnosis relies on a constellation of findings: exposure to an offending antigen, characteristic signs and symptoms, abnormal chest findings on physical examination, and abnormalities on pulmonary function tests and radiographic evaluation. In population-based studies, the sensitivity of chest radiography for detection of this disease is relatively low. The aim of this study was to determine the sensitivity of high-resolution CT (HRCT) for detection of hypersensitivity pneumonitis diagnosed in a population of swimming-pool employees.

SUBJECTS AND METHODS

Thirty-one symptomatic employees of a recreation center who were referred because of possible hypersensitivity pneumonitis were examined by using chest radiography, HRCT, and fiberoptic bronchoscopy with bronchoalveolar lavage and transbronchial biopsy. Hypersensitivity pneumonitis was diagnosed in subjects who had two or more work-related signs or symptoms, abnormal results on transbronchial biopsies, and abnormal lymphocytosis as shown by examination of bronchoalveolar lavage fluid. The chest radiographs and HRCT scans were interpreted by consensus by two observers who were unaware of the clinical diagnosis.

RESULTS

Only one of 11 subjects with a diagnosis of hypersensitivity pneumonitis had abnormal findings on a chest radiograph. Five had abnormal HRCT findings. The abnormality in each case consisted of small, poorly defined centrilobular nodules with variable profusion. No subject without the disease had abnormal HRCT findings. Those who had granulomas shown by lung biopsy were more likely to have abnormal HRCT findings than were those who had more subtle histologic abnormalities.

CONCLUSION

The sensitivity of HRCT for the detection of hypersensitivity pneumonitis in a population-based study is greater than that of chest radiography. The finding of poorly defined centrilobular nodules on HRCT scans should prompt consideration of this disease.

DA-1 receptors mediate renal effects of the dopamine prodrug, gludopa, in conscious rabbits

1. Eight male rabbits were implanted with Doppler flow probes around the lower abdominal aorta and left renal artery. A 2 week recovery period was allowed prior to the experiment. 2. Normal saline, gludopa at 25 micrograms/kg per min and at 100 micrograms/kg per min were each infused i.v. for 60 min. One week later the same protocol was administered to four of these animals in addition to DA-1 antagonist SCH 23390 (0.3 mg/kg i.v.) before gludopa infusion. 3. Gludopa elicited significant increases in urine flow, urinary sodium excretion and renal blood flow, and decreased renal vascular resistance. These changes were abolished by the DA-1 antagonist. Blood pressure, heart rate and hindlimb blood flow remained unchanged. 4. Urine dopamine excretion was increased 1200-fold and 7800-fold after gludopa administration at 25 micrograms/kg per min and 100 micrograms/kg per min, respectively, while plasma dopamine concentration and plasma renin activity (PRA) were not significantly altered. However, PRA was elevated by gludopa with DA-1 antagonism. 5. The renal vasodilation, natriuresis and diuresis produced by gludopa in conscious rabbits appears to be mediated by locally generated dopamine via DA-1 receptors.

Vascular abnormalities in experimental and human lymphatic filariasis

Whereas clinical descriptions of grotesque lymphedema and standard light microscopy in human filariasis have elucidated the natural progression of this disease, the link between the nematode and vascular abnormalities including elephantiasis remains poorly understood. Accordingly, we examined the nature and distribution of lymphatic and blood vascular derangements in a variety of tissues and organs from 37 ferrets acutely and chronically infected with Brugia malayi and in 15 patients with Wuchereria bancrofti or Brugia malayi infestation (resected skin, subcutaneous tissue, and lymph nodes) using light and transmission electron microscopy, immunohistochemistry, and in vivo microscopy. In ferrets, eosinophilic abscesses and epithelioid and giant cell granulomas with fragmented worms in various stages of disintegration were found in multiple organs. Blood microvasculopathy consisted of endothelial hyperplasia, focal thickening and stenosis, vessel obliteration with marked perivascular infiltration of lymphocytes, plasma cells, eosinophils, and numerous large macrophages laden with a coarse golden-brown pigment. Endothelial ballooning and swelling, pavementing, denuding, scarring, and sludge formation were seen along with high endothelium in atypical locations. Dilated lymphatics were most prominent near adult worms and showed plump endothelium, thickened walls and valves, thrombus formation, and often perilymphangitis and adjacent tissue fibrosis. In vivo microscopy showed wriggling live adult worms in dilated incompetent sludge-filled groin lymphatics even when microfilaremia and peripheral edema were absent. In human tissues, in addition to "pachyderm" skin changes (keratosis, papillomatosis, acanthosis and collagen deposition), there was blood vessel and lymphatic vasculopathy similar to ferrets (angiocentric inflammation, congestion, vasculitis, thrombosis, thickened vessel walls, dilated lymphatics, lymphangitis, reactive lymph nodal hyperplasia and nodal fibrosis). These changes reflect generalized endothelial damage due to worm products, physical injury to valves and vessel walls from lymphatic-dwelling live worms, and host immune reactivity. Whereas adult worms target the lymphatic apparatus, their offspring and the host immune response primarily affects the blood microvasculature.

Cardiovascular effects of volatile anesthesia in rabbits: influence of chronic heart failure and enalaprilat treatment

Circulatory responses to isoflurane and halothane anesthesia were studied in eight rabbits with biventricular cardiomyopathy induced by doxorubicin (Adriamycin, 14 mg/kg IV over 7 wk) and in eight controls (saline injections). In preliminary operations pulsed-Doppler flow probes were placed on the ascending aorta, left renal artery, and lower abdominal aorta. Each group was studied after 4, 6, and 7 wk of treatment. The development of congestive heart failure (CHF) was associated with decreases in mean arterial pressure and cardiac output (CO) of 14% and 16%, respectively, (P less than 0.05) and an increase in heart rate. In controls, each anesthetic agent produced dose-related decreases in mean arterial pressure and increases in heart rate, but not significant changes in CO. Renal blood flow was reduced to a similar degree by 1.3 MAC halothane (24% decrease) and 1.3 MAC isoflurane (21% decrease); hindlimb blood flow was reduced only by halothane. As CHF developed there was an attenuation of the heart rate response to anesthesia. Halothane, but not isoflurane, significantly reduced CO in more advanced stages of CHF. The changes in renal blood flow and hindlimb blood flow with each anesthetic in the CHF group were similar to those observed in controls and did not vary with week of treatment. Administration of the angiotensin-converting enzyme inhibitor enalaprilat (0.2 mg/kg IV) reversed the CO and renal blood flow effects of halothane except after 7 wk of treatment in the CHF group, when the combination of halothane and enalaprilat resulted in severe circulatory depression.

Influence of cardiac failure on atrial natriuretic peptide responses in patients undergoing vascular surgery

Sixteen patients presenting for abdominal aortic surgery were divided into two groups according to whether or not there was a history and clinical evidence of chronic heart failure (CHF). Atrial natriuretic peptide (ANP) and catecholamines were measured during a preoperative exercise test and then with induction of anaesthesia and surgery. Patients in the CHF group (n = 8) had a much-reduced cardiac output (CO) rise in response to exercise compared to the control group (13% vs. 75%, P less than 0.05). This difference was due to the absence of a stroke volume increase in the CHF group. Induction of anaesthesia resulted in a greater fall in mean arterial pressure in the CHF group prior to the start of surgery, due to a greater fall in CO. Plasma ANP levels were higher in the CHF group at rest and at each exercise stage (P less than 0.05). ANP levels were not altered by induction of anaesthesia or intubation, but increased with the start of surgery in the CHF group (P less than 0.05). Increases in plasma catecholamine levels in response to exercise and to surgery were similar in the two groups. Changes in endogenous ANP may be important in counteracting the undesirable effects of vasoconstrictor hormones during physical exercise or surgical stress.

Norepinephrine spillover faithfully reflects renal sympathetic nerve activity in conscious rabbits

The relationship between directly recorded renal sympathetic nerve activity (RSNA) and simultaneous renal norepinephrine (NE) spillover rate across the kidney at rest and in response to changes in mean arterial pressure (MAP) was examined in six conscious rabbits. Integrated RSNA and renal NE spillover rate at rest were 5.1 +/- 1.1 microV/s and 20.8 +/- 3.0 ng/min, respectively. Sodium nitroprusside infusions at 10 and 20 microgram.kg-1.min-1 significantly increased RSNA by 42 +/- 14 and 84 +/- 14% and renal NE spillover rate 39 +/- 22 and 107 +/- 22% in response to falls in MAP of 15 +/- 2 and 21 +/- 2 mmHg (19 and 27%), respectively. During phenylephrine infusion at 8 micrograms.kg-1.min-1, RSNA and renal NE spillover rate significantly decreased by 65 +/- 14 and 67 +/- 16%, respectively, in response to a 15 +/- 2 mmHg (19%) rise in MAP. There was a highly significant positive correlation between changes in directly recorded RSNA and changes in renal NE spillover rate (r = 0.81, P less than 0.01). The ratio of renal to total NE spillover rate at rest was 0.44 +/- 0.06. This ratio was decreased during both sympathetic stimulation (0.30 +/- 0.04) and inhibition (0.26 +/- 0.06). This study indicates that the measurement of renal NE spillover rate is a useful reliable method for detecting the changes in RSNA and its relative contribution to overall sympathetic nerve activity in response to physiological stimuli in conscious rabbits.

Effect of angiotensin-converting enzyme inhibition on renal norepinephrine spillover rate and baroreflex responses in conscious rabbits

1. To evaluate the effects of angiotensin-converting enzyme (ACE) inhibition on sympathetic nerve activity, renal and total norepinephrine (NE) spillover rates were examined under control conditions and during enalaprilat infusion at rest and in response to sodium nitroprusside (SNP)-induced hypotension. 2. Resting renal and total NE spillover rate during enalaprilat infusion were similar to control values. 3. During SNP infusion at 10 micrograms/kg per min, renal NE spillover rate increased by 26% in enalaprilat-treated group and by 39% in controls, in response to falls in mean arterial pressure (MAP) of 25 and 19% respectively. 4. During sympathetic stimulation induced by SNP, total NE spillover rate was significantly increased in both groups, but the 50% (s.e.m. = 12) increase in the enalaprilat-treated group was less (P less than 0.05) than the 97% (s.e.m. = 16) change observed in controls. 5. Enalaprilat treatment resulted in a higher renal to total NE spillover ratio (P less than 0.05). The ratio fell in parallel in both groups during SNP-induced hypotension. 6. This study indicates that the sympathetic nervous system interacts dynamically with the renin-angiotensin system during hypotensive stimulation but this occurs predominantly at sites other than the kidney.

Renal norepinephrine spillover and baroreflex responses in evolving heart failure

Renal sympathetic nerve activity (RSNA), as assessed by norepinephrine (NE) spillover, was examined in conscious rabbits with adriamycin-induced cardiomyopathic heart failure (n = 5) and in control rabbits (n = 5). Each rabbit was studied after 4 and 6 wk of adriamycin (2 mg.kg-1.wk-1) or vehicle under resting conditions and in response to changes in mean arterial pressure (MAP) produced by infusions of sodium nitroprusside and phenylephrine. Basal renal NE spillover rate was significantly increased after 4 wk of adriamycin treatment compared with controls (24.2 +/- 2.5 vs. 15.2 +/- 2.4 ng/min, P less than 0.05). At this stage the two groups had similar systemic hemodynamics and renal blood flows. The baroreflex-renal NE spillover response to hypotension in the adriamycin-treated group showed a significant upward shift. After 6 wk of adriamycin treatment, there were significant falls in resting MAP (74 +/- 3 vs. 86 +/- 2 mmHg, P less than 0.01) and renal blood flow (78 +/- 6 vs. 109 +/- 8 ml/min, P less than 0.05). At this stage of established heart failure, resting renal NE spillover rate remained elevated but there was significant blunting of the baroreflex-renal NE spillover response. These results suggest that, in this model of low-output heart failure, there is an early increase in resting renal sympathetic activity that is sustained. The baroreflex-renal NE spillover curve changes during the course of development of heart failure.