Experimental infection of Mouflon-domestic sheep hybrids with caprine arthritis-encephalitis virus

OBJECTIVE

To determine whether monocyte-derived macrophages from Mouflon-domestic sheep hybrids (Ovis musimon X Ovis spp) were susceptible to productive infection with caprine arthritis-encephalitis virus (CAEV) in vitro and whether experimental inoculation of Mouflon-domestic sheep hybrids with a molecularly cloned CAEV would result in persistent infection.

ANIMALS

5 Mouflon hybrids.

PROCEDURE

Macrophage monolayers were inoculated with virus in vitro. Three animals were inoculated with virus intratracheally.

RESULTS

Productive replication of CAEV was demonstrated in monocyte-derived macrophages following in vitro and in vivo inoculation. Titer of infectious cytopathic CAEV produced by macrophages from the Mouflon hybrids was similar to titers produced by macrophages from an infected goat or by synovial membrane cells. Isolation of virus from monocyte-derived macrophages and use of a semiquantitative polymerase chain reaction assay to amplify a portion of the viral genome demonstrated persistent virus replication in all 3 inoculated animals. Two weeks after inoculation of sheep, approximately 1 of 5,000 monocytes was harboring the virus.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that Mouflon-domestic sheep hybrids are susceptible to infection with isolates of CAEV that cause infection in domestic small ruminants.

2-Tetradecylglycidic acid, an inhibitor of carnitine palmitoyltransferase-1, induces myocardial hypertrophy via the AT1 receptor

Activation of the antiogensin II, type 1 (AT1) receptor mediates the myocardial response to numerous hypertrophic stimuli. This study tested the hypothesis that 2-tetradecylglycidic acid (TDGA), an oxirane carboxylate inhibitor of mitochondrial carnitine plamitoyltransferase-1, induces myocardial hypertrophy via the AT1 receptor system. Male Sprague-Dawley rats treated with 10 mg TDGA/kg/day for 7 days had a heart wet weight:body weight ratio of 3. 58+/-0.16 mg/g compared with a ratio of 2.79+/-0.07 for rats treated with vehicle (P<0.05). The plasma level of antiogensin II was 117. 75+/-17.39 pg/ml in rats treated with 10 mg TDGA/kg/day compared with 54.0+/-11.38 pg/ml for rats treated with vehicle (P<0.05). The plasma level of angiotensin I in these two groups of rats was not different statistically. Rats treated with TDGA and given drinking water containing 1 mg losartan/ml had a heart wet weight:body weight ratio of 2.84+/-0.05 mg/g. This value was not statistically different from the value measured in rats given drinking water containing 1 mg losartan/ml and treated with vehicle alone. No significant difference in the heart wet weight:dry weight ratio occurred among these groups of rats. Finally, treating rats with TDGA or giving rats drinking water that contained 1 mg losartan/ml altered neither their heart rate nor their mean arterial blood pressure when compared with untreated rats. This data, therefore, suggests that oxirane carboxylates induce myocardial hypertrophy by activating the AT1 receptor independent of changes in systemic hemodynamics.

Goat milk epithelial cells are highly permissive to CAEV infection in vitro

The main route of small ruminant lentivirus dissemination is the ingestion of infected cells present in colostrum and milk from infected animals. However, whether only macrophages or other cell subtypes are involved in this transmission is unknown. We derived epithelial cell cultures, 100% cytokeratin positive, from milk of naturally infected and noninfected goats. One such culture, derived from a naturally infected goat, constitutively produced a high titer of virus in the absence of any cytopathic effect. The other cultures, negative for natural lentivirus infection, were tested for their susceptibility to infection with the CAEV-CO strain and a French field isolate CAEV-3112. We showed that milk epithelial cells are easily infected by either virus and produce viruses at titers as high as those obtained in permissive goat synovial membrane cells. The CAEV-CO strain replicated in milk epithelial cells in absence of any cytopathic effect, whereas the CAEV-3112 field isolate induced both cell fusion and cell lysis. Our results suggest that CAEV-infected milk epithelial cells of small ruminants may play an important role in virus transmission and pathogenesis.

Evidence for angiotensin-converting enzyme- and chymase-mediated angiotensin II formation in the interstitial fluid space of the dog heart in vivo

BACKGROUND

We have previously demonstrated that angiotensin II (Ang II) levels in the interstitial fluid (ISF) space of the heart are higher than in the blood plasma and do not change after systemic infusion of Ang I. In this study, we assess the enzymatic mechanisms (chymase versus ACE) by which Ang II is generated in the ISF space of the dog heart in vivo.

METHODS AND RESULTS

Cardiac microdialysis probes were implanted in the left ventricular (LV) myocardium (3 to 4 probes per dog) of 12 anesthetized open-chest normal dogs. ISF Ang I and II levels were measured at baseline and during ISF infusion of Ang I (15 micromol/L, n=12), Ang I+the ACE inhibitor captopril (cap) (2.5 mmol/L, n=4), Ang I+the chymase inhibitor chymostatin (chy) (1 mmol/L, n=4), and Ang I+cap+chy (n=4). ISF infusion of Ang I increased ISF Ang II levels 100-fold (P<0.01), whereas aortic and coronary sinus plasma Ang I and II levels were unaffected and were 100-fold lower than ISF levels. Compared with ISF infusion of Ang I alone, Ang I+cap (n=4) produced a greater reduction in ISF Ang II levels than did Ang I+chy (n=4) (71% versus 43%, P<0.01), whereas Ang I+cap+chy produced a 100% decrease in ISF Ang II levels.

CONCLUSIONS

This study demonstrates for the first time a very high capacity for conversion of Ang I to Ang II mediated by both ACE and chymase in the ISF space of the dog heart in vivo.

Modulation of kainate-induced responses by pentobarbitone and GYKI-53784 in rat abducens motoneurons in vivo

The modulation of kainate-induced responses by pentobarbitone and the 2,3-benzodiazepine GYKI-53784 (LY303070), a potent non-competitive AMPA antagonist, was studied in vivo using both extracellular recordings of antidromic field potentials and intracellular recordings from abducens motoneurons in ketamine/diazepam-anesthetized rats. In previous studies on pentobarbitone-anesthetized rats [M. Ouardouz, J. Durand, GYKI-52466 antagonizes glutamate responses but not NMDA and kainate responses in rat abducens motoneurons, Neurosci. Lett. 125 (1991) 5-8; M. Ouardouz, J. Durand, Involvement of AMPA receptors in trigeminal postsynaptic potentials recorded in rat abducens motoneurons in vivo, Eur. J. Neurosci. 6 (1994) 1662-1668; A. Ruiz, J. Durand, Blocking the trigeminal EPSPs in rat abducens motoneurons in vivo with the AMPA antagonists, NBQX and GYKI-53655, J. Neurophysiol. (1998) submitted], we showed that 2,3-benzodiazepines do not affect kainate-induced depolarizations in abducens motoneurons. Here, we tested whether pentobarbitone is involved in the pharmacological discrimination by 2,3-benzodiazepines between AMPA- and kainate-induced responses. Kainate-induced depolarizations were reversibly depressed after application of either GYKI-53784 and pentobarbitone. However, kainate-induced depolarizations were not inhibited by GYKI-53784 with pentobarbitone; they were even potentiated sometimes. Using extracellular recordings, we confirmed that in the presence of pentobarbitone, GYKI-53784 counteracts the effects of AMPA but not of kainate on antidromic field potentials in the abducens nucleus. Blockade of kainate-induced responses by GYKI-53784 was reversed with pentobarbitone, which appears relevant to the discrimination between AMPA- and kainate receptor-mediated responses in vivo. In the presence of pentobarbitone, kainate would depolarize motoneurons mainly via kainate receptors since kainate-induced responses were not depressed by 2,3-benzodiazepines. This finding strongly favors the existence of kainate receptors in adult motoneurons but their role is still unknown.

Degradation of polychlorinated biphenyl metabolites by naphthalene-catabolizing enzymes

The ability of the dehydrogenase and ring cleavage dioxygenase of the naphthalene degradation pathway to transform 3,4-dihydroxylated biphenyl metabolites was investigated. 1,2-Dihydro-1, 2-dihydroxynaphthalene dehydrogenase was expressed as a histidine-tagged protein. The purified enzyme transformed 2, 3-dihydro-2,3-dihydroxybiphenyl, 3,4-dihydro-3,4-dihydroxybiphenyl, and 3,4-dihydro-3,4-dihydroxy-2,2',5,5'-tetrachlorobiphenyl to 2, 3-dihydroxybiphenyl, 3,4-dihydroxybiphenyl (3,4-DHB), and 3, 4-dihydroxy-2,2',5,5'-tetrachlorobiphenyl (3,4-DH-2,2',5,5'-TCB), respectively. Our data also suggested that purified 1, 2-dihydroxynaphthalene dioxygenase catalyzed the meta cleavage of 3, 4-DHB in both the 2,3 and 4,5 positions. This enzyme cleaved 3, 4-DH-2,2',5,5'-TCB and 3,4-DHB at similar rates. These results demonstrate the utility of the naphthalene catabolic enzymes in expanding the ability of the bph pathway to degrade polychlorinated biphenyls.

Toxicity of Xylocaine to rabbit corneal endothelium

PURPOSE

To assess the toxicity of lidocaine hydrochloride (Xylocaine) to the corneal endothelium.

SETTING

Department of Ophthalmology, Hôtel-Dieu Hospital, Paris, France.

METHODS

Rabbit corneas were excised and the endothelium was exposed to balanced salt solution (BSS), Xylocaine 1%, or Xylocaine 5% (5 corneas/group) for 20 minutes. The endothelium was then stained with trypan blue and alizarin red, and 5 photomicrographs were taken of each cornea at a standard magnification and analyzed with a digital imaging system (Biocom 200).

RESULTS

Xylocaine solutions produced changes in endothelial cell morphology, but there was no cell staining with trypan blue. Corneas exposed to Xylocaine 5% had more marked cell alterations. Small areas of cells were lost from all 15 corneas, mainly at the periphery, but the differences among the 3 groups of corneas were not significant.

CONCLUSION

Exposure of rabbit corneal endothelium to Xylocaine solutions in vitro was not associated with trypan blue staining of endothelial cells.

Clinical comparison of acoustic and electronic stethoscopes and design of a new electronic stethoscope

This clinical study was performed to evaluate the advantages and limitations of 3 acoustic stethoscopes and 3 electronic stethoscopes. It shows that it is possible to design a new electronic stethoscope by considering the advantages of both the acoustic and electronic stethoscopes.

Endothelial damage caused by uncoated and fluorocarbon-coated poly(methyl methacrylate) intraocular lenses

PURPOSE

To assess endothelial damage induced by poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) coated with a fluorocarbon polymer, Teflon AF, to make them highly hydrophobic.

SETTING

Department of Ophthalmology. Hôtel-Dieu Hospital, Paris, France.

METHODS

Ten Teflon-coated and 10 uncoated PMMA IOLs were used in an in vitro static touch model. The corneal endothelium was placed in direct contact with the IOL for 15 seconds and then stained with trypan blue and alizarin red. The endothelial damage produced by each IOL in the area of contact was assessed semiquantitatively and quantitatively.

RESULTS

Teflon-coated IOLs produced significantly less endothelial damage than uncoated PMMA IOLs (P < .0001). Endothelial cells in contact with Teflon-coated IOLs did not usually adhere to the IOL surface. In contrast, the uncoated IOLs produced large areas of endothelial cell loss.

CONCLUSION

Teflon-coated PMMA IOLs have an antiadhesive effect that reduced endothelial damage after IOL insertion in an in vitro model.

Compartmentalization of angiotensin II generation in the dog heart. Evidence for independent mechanisms in intravascular and interstitial spaces

Angiotensin-converting enzyme inhibitors have beneficial effects that are presumably mediated by decreased angiotensin II (ANG II) production. In this study, we measure for the first time ANG I and ANG II levels in the interstitial fluid (ISF) space of the heart. ISF and aortic plasma ANG I and II levels were obtained at baseline, during intravenous infusion of ANG I (5 microM, 0.1 ml/min, 60 min), and during ANG I + the angiotensin-converting enzyme inhibitor captopril (cap) (2.5 mM, 0.1 ml/min, 60 min) in six anesthetized open-chested dogs. ISF samples were obtained using microdialysis probes inserted into the left ventricular myocardium (3-4 probes/dog). ANG I increased mean arterial pressure from 102+/-3 (SEM) to 124+/-3 mmHg (P < 0.01); addition of cap decreased MAP to 95+/-3 mmHg (P < 0.01). ANG I infusion increased aortic plasma ANG I and ANG II (pg/ml) (ANG I = 101+/-129 to 370+/-158 pg/ml, P < 0.01; and ANG II = 22+/-40 to 466+/-49, P < 0.01); addition of cap further increased ANG I (1,790+/-158, P < 0.01) and decreased ANG II (33+/-49, P < 0.01). ISF ANG I and ANG II levels (pg/ml) were > 100-fold higher than plasma levels, and did not change from baseline (8,122+/-528 and 6,333+/-677), during ANG I (8,269+/-502 and 6, 139+/-695) or ANG I + cap (8,753+/-502 and 5,884+/-695). The finding of very high ANG I and ANG II levels in the ISF vs. intravascular space that are not affected by IV ANG I or cap suggests that ANG II production and/or degradation in the heart is compartmentalized and mediated by different enzymatic mechanisms in the interstitial and intravascular spaces.

The orally active nonpeptide endothelin A-receptor antagonist A-127722 prevents and reverses hypoxia-induced pulmonary hypertension and pulmonary vascular remodeling in Sprague-Dawley rats

Exposure to hypoxia is associated with increased pulmonary artery pressure and plasma endothelin (ET-1) levels and with selective enhancement of ET-1 peptide and messenger RNA (mRNA) and endothelin-A (ET-A) receptor mRNA in rat lung. Our study tested the hypothesis that A-127722, an orally active antagonist of the ET-A receptor, can prevent hypoxia-induced pulmonary hypertension and vascular remodeling in the rat. Pretreatment with A-127722 (3, 10, and 30 mg/kg/day in drinking water for 2 days) caused dose-dependent inhibition of the pulmonary vasoconstrictor response to short-term hypoxia (10% O2, 90 min). Long-term A-127722 treatment (10 mg/kg/day in drinking water for 2 weeks) instituted 48 h before hypoxic exposure attenuated the subsequent development of pulmonary hypertension, the associated right atrial hypertrophy, and pulmonary vascular remodeling. Institution of A-127722 treatment (10 mg/kg/day in drinking water for 4 weeks) after 2 weeks of hypoxia retarded the progression of established hypoxia-induced pulmonary hypertension and right atrial hypertrophy and reversed the pulmonary vascular remodeling despite continuing hypoxic exposure. These findings support the hypothesis that endogenous ET-1 plays a major role in hypoxic pulmonary vasoconstriction/hypertension, right heart hypertrophy, and pulmonary vascular remodeling and suggest that ET-A receptor blockers may be useful in the treatment and prevention of hypoxic pulmonary hypertension in humans.

Sexually dimorphic response of the balloon-injured rat carotid artery to hormone treatment

BACKGROUND

Estrogen blunts the neointimal response to vascular injury in gonadectomized rats of both sexes; addition of a progestin blocks the estrogen effect. This study tested, in intact rats of both sexes, whether (1) exogenous estrogen has a vasoprotective effect in injured carotid arteries, (2) progestin (medroxyprogesterone acetate, MPA) blocks the vasoprotective effect of estrogen, and (3) any observed sexual dimorphism in the responses to estrogen and/or MPA can be accounted for by differences in serum 17 beta-estradiol levels.

METHODS AND RESULTS

Intact male and female Sprague-Dawley rats were randomly divided into four subgroups treated with either (1) 17 beta-estradiol, (2) MPA, (3) 17 beta-estradiol + MPA, or (4) vehicle and were subjected to balloon injury of the right common carotid artery. Two weeks later, rats were killed by an overdose of pentobarbital, and the carotid arteries were evaluated for myointimal thickening. Neither estradiol nor MPA altered the neointimal response in males. In females, estradiol reduced and MPA enhanced the response, whereas addition of MPA to estradiol blocked the vasoprotective effects of estrogen.

CONCLUSIONS

Intact male rats but not intact females are resistant to the vasoprotective effects of exogenous estrogen, despite attainment of physiological (for females) serum 17 beta-estradiol levels. MPA enhances the neointimal response in intact females, presumably by blocking the production and thus the vasoprotective effect of endogenous estrogen.

Arachidonic acid-induced calcium signalling in human airway smooth muscle cells

The spatiotemporal distribution of Ca2+ signals evoked by arachidonic acid (AA) was investigated in human bronchial smooth muscle cells (SMC), using the single cell video imaging technique and Fura-2 as a fluorescent dye. Baseline Ca2+ levels were markedly heterogeneous in one and the same cell; the local Ca2 concentration laid between 90 +/- 11 and 215 +/- 18 nM (n = 15). AA (2 mM) induced propagating Ca2+ waves, travelling at a mean velocity of 18 +/- 3 microns/sec (n = 7). Ca2+ signals originated at discrete trigger zones, whose kinetic properties differed from those of neighbouring regions. Ca2+ in the trigger zones rose in two phases, with rates of 9.5 +/- 0.8 and 88 +/- 6 nM/sec (n = 17). A single cell frequently exhibited more than one trigger zones. In some cells, the wave did not reach all regions; such inert zones separated functionally the cell in independently active regions. Some regions presented Ca2+ signals that did not spread to the rest of the cell, forming isolated foci. The spatiotemporal variability of Ca2+ signals evoked by AA could result from the heterogeneity of Ca2+ homeostatic processes.

Hypoxia stimulates atrial natriuretic peptide gene expression in cultured atrial cardiocytes

The current study tested the hypothesis that hypoxia stimulates atrial natriuretic peptide (ANP) gene expression and secretion in cultured atrial myocytes (AT-1 cells). AT-1 cells were obtained from a transplantable mouse atrial cardiomyocyte tumor lineage. Confluent AT-1 cells were exposed to hypoxia (1% oxygen) or normoxia (21% oxygen) as controls for 6 hours to 7 days. Medium ANP levels were measured by radioimmunoassay, and intracellular ANP gene transcripts were quantified by Northern and slot blot analyses. Exposure to hypoxia resulted in a significant increase in cellular ANP mRNA levels within 36 hours, which peaked (3.6-fold increase) at 2 days after hypoxic exposure, and produced a time-dependent increase in the release of ANP from AT-1 cells for 2 to 7 days. Transfection studies with recombinant DNA constructs that contained fragments of the -3003/+62 sequence of the ANP promoter and the luciferase reporter gene revealed that the regulatory sequences that mediate the hypoxia-induced increase in transcription are located within a region that extends from -638 to -518 bp to the transcriptional start site of the ANP gene. Gel mobility shift assays demonstrated that hypoxia-inducible nuclear proteins that bound to the 120-bp putative hypoxia-responsive elements of the ANP gene were produced during hypoxic exposure. We have thus defined a 120-bp region within the ANP gene promoter that contains hypoxia-responsive elements that might be responsible for the enhancement of ANP gene expression in atrial myocytes during hypoxic exposure.

Medroxyprogesterone attenuates estrogen-mediated inhibition of neointima formation after balloon injury of the rat carotid artery

BACKGROUND

Estrogen blunts the neointimal proliferative response to balloon injury of the carotid artery in intact female rats and gonadectomized rats of both sexes. This study tested whether, in gonadectomized rats of both sexes. (1) progestin (medroxyprogesterone acetate, MPA) alters neointima formation in injured carotid arteries, (2) addition of MPA alters the antiproliferative effects of estrogen, and (3) an interaction between MPA and estrogen can be accounted for by MPA-induced alterations in serum 17 beta-estradiol levels.

METHODS AND RESULTS

Male and female Sprague-Dawley rats were subjected to gonadectomy, then were randomly divided into four subgroups and treated with either (1) 17 beta-estradiol, (2) MPA, (3) 17 beta-estradiol + MPA, or (4) vehicle, and balloon injury of the right common carotid artery was carried out. Two weeks later, rats were killed by overdose of pentobarbital, and the carotid arteries were subjected to morphometric analysis for evaluation of myointimal thickening. Estradiol inhibited myointimal proliferation after vascular injury in gonadectomized rats of both sexes (P < .05). MPA alone did not alter neointima formation, but addition of MPA to estradiol completely blocked the antiproliferative effects of estrogen without altering serum 17 beta-estradiol levels.

CONCLUSIONS

These data indicate that exogenous progestin given alone does not alter the vascular injury response in the rat carotid injury model but that addition of a progestin blocks the antiproliferative effects of estrogen in this model. These effects are seen in gonadectomized rats of both sexes. These findings have direct implications for postmenopausal hormone replacement therapy in humans.

Local mechanisms of phase-dependent postsynaptic modifications of NMDA-induced oscillations in the abducens motoneurons: a simulation study

1. In vivo experiments have shown that extracellular microelectrophoretic application of N-methyl-D-aspartate (NMDA) induced oscillatory plateau potentials with bursts of action potentials in rat abducens motoneurons. The period of these slow NMDA oscillations could be altered by single trigeminal non-NMDA excitatory input delivered at low frequency during the NMDA oscillations. 2. A resetting of the oscillations was observed depending on the phase of slow oscillatory cycle during which the trigeminal excitation occurred. 3. We investigated local mechanisms responsible for the phase-dependent modifications of NMDA oscillations, including contributions of voltage and concentration transients, in the mathematical model of the isopotential membrane compartment equipped with voltage-gated Na+, K+, and Ca2+ channels, with Ca2+-dependent K+ channels, and with ligand-gated NMDA and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor channels. The faithful model was constructed with the use of models described earlier, which were modified by increasing time constants of kinetic variables of all voltage-gated conductances and by including coupled dynamics of voltages and ion concentrations. The changes in ion concentrations were produced near the membrane by transmembrane currents and removal mechanisms (pumps, diffusion). 4. This work focuses on local arrangement of voltage- and ligand-gated conductances and on local ion concentration changes in two separate pools: the postsynaptic pool of AMPA receptors and the extrasynaptic pool. In terms of the electrotonic and diffusional length constants, these pools were electrotonically close but diffusionally remote. 5. It was found that the effect of resetting can be produced by a local interaction between plateau and spike-generating conductances and glutamate receptors. 6. In vivo phase-dependent interactions between NMDA oscillations and AMPA synaptic input were reproduced by the local model only when changes in intracellular sodium and extracellular potassium concentrations were taken into account and the mechanisms of ion removal from postsynaptic pools had slower kinetics than the fast pump system operating in the extracellular pool. 7. Postsynaptic changes in ion concentrations of Na+ and K+ in intra- and extracellular layers near the membrane shift of Nernst equilibrium potentials for these ions depending on the phase of activation of synaptic input. Thus Na+ and k+ components of all transmembrane currents involved in the pattern generation are differently affected by synaptic action during the oscillations. We conclude that slow postsynaptic changes in ion concentrations near the membrane play a key role in the resetting of the NMDA oscillations.

Incorporation of a fluorocarbon polymer implanted at the posterior surface of the rabbit cornea

An implant of porous expanded polytetrafluoroethylene (PTFE) in the corneal stroma allows fast cell colonization and can become translucent. We studied the behavior of the same polymer implanted in the anterior chamber of the rabbit eye and sutured to the posterior surface of the cornea. The expanded tetrafluoroethylene was provided as 200-micron thick sheets in 3 pore diameters (20, 50 and 80 microns). Disks (5 mm) were implanted in the anterior chambers of 20 rabbits and sutured to the posterior surface of the cornea. Histological and ultrastructural studies were performed after 3 and 4 months. Quantimetry was done on TEM images to analyze the fibrillar structure of the intercellular matrix inside and around the implanted polymer. The material was well tolerated. In all cases there was mild central corneal edema, which disappeared after 1 month. Mild neovascularization occurred in five cases, decreasing after 1 month. The polymer became translucent after 8 days. Keratocytes from the corneal stroma colonized the implant via breaks in the Descemet's membrane along the sutures. Quantimetry showed three types of fibrils inside and beside the polymer. Corneal endothelial cells regenerated over the fibroblasts and the polymer. This fluorocarbon polymer implanted in the anterior chamber and sutured to the posterior surface of the cornea was well tolerated, and there was real incorporation, with keratocytes producing collagen fibrils inside the polymer and endothelial cells forming a posterior cell monolayer. This is promising for the development of a keratoprothesis with posterior fixation.

International migration and development in Mexican communities

The theoretical and empirical literature generally regards international migration as producing a cycle of dependency and stunted development in sending communities. Most migrants' earnings are spent on consumption; few funds are channeled into productive investment. We argue that this view is misleading because it ignores the conditions under which productive investment is likely to be possible and profitable. We analyze the determinants of migrants' savings and remittance decisions, using variables defined at the individual, household, community, and macroeconomic levels. We identify the conditions under which U.S. earnings are repatriated to Mexico as remittances and savings, and indicate the factors leading to their productive investment.

Inositol phosphate turnover in human airways: effect of arachidonic acid metabolism

The aim of this study was to examine the role of the phospholipase A2-arachidonic acid (PLA2-AA) pathway in response to histamine and the possible effect of AA metabolites on the generation of inositol-phosphates (IPs) in airway smooth muscle cells (SMC). Radiolabelled IPs-were analyzed by high-performance liquid chromatography (HPLC). Indomethacin, a cyclooxygenase inhibitor, potentiated the IP production evoked by a 5-sec application of histamine, while it decreased the effect of a 5-min incubation with the agonist, suggesting a time-dependent modulation of phospholipase C (PLC) activity by prostaglandins (PGs). Exogenous AA elicited the generation of IPs; this effect was suppressed by cyclooxygenase inhibition. Therefore, several steps in the AA metabolic pathways appear to modulate the production of IPs in human airway SMC.

Estrogen reduces myointimal proliferation after balloon injury of rat carotid artery

BACKGROUND

Vascular disease progresses more slowly in females with functional ovaries than in males. The mechanisms of this vasoprotective effect of female sex are incompletely understood. This study tested (1) whether there is a sex difference in the development of myointimal proliferation after balloon injury of the rat carotid artery in vivo, (2) whether this response is estrogen or androgen dependent, and (3) whether there is a sexual dimorphism in expression of the c-myc proto-oncogene in intact and/or damaged rat carotid arteries.

METHODS AND RESULTS

Ten-week-old male and female Sprague-Dawley rats were either gonadectomized or studied intact. Gonadectomized rats of both sexes were implanted with estradiol, testosterone, or nothing (control) 3 days before vascular injury. Two weeks later, the rats were killed by overdose of pentobarbital, and the injured right and uninjured control left carotid arteries were fixed and subjected to morphometric analysis for evaluation of the degree of myointimal thickening. Separate groups of intact male and female rats were killed at 1 and 2 hours after vascular injury, and total RNA from injured and uninjured vessels was subjected to Northern blot analysis for assessment of steady state c-myc mRNA levels. Neointimal area and the ratio of neointimal to medial area were significantly less in intact female rats than in intact male rats (P < .05). Gonadectomy of female rats was associated with a greater increase in neointima formation after balloon injury than that observed in intact females (P < .05), but testosterone replacement did not further enhance this response. Estradiol treatment significantly inhibited myointimal proliferation after vascular injury in gonadectomized rats of both sexes (P < .05). Neither gonadectomy nor gonadectomy plus testosterone replacement altered the myointimal proliferative response to balloon injury in male rats. Steady state c-myc mRNA levels were detectable in undamaged carotid arteries in intact rats of both sexes and were significantly greater in males than in females; c-myc mRNA levels were increased in both sexes after carotid injury, but the response was significantly larger in magnitude and more rapid in males than in females.

CONCLUSIONS

These data indicate that the sex difference in myointimal proliferation after vascular injury is estrogen dependent. C-myc gene expression is greater in the undamaged carotid artery of the male than in that of the female, and the responsiveness of this gene to balloon injury of the artery is more rapid and more robust in the male than in the female rat. These findings have direct implications for the prevention and treatment of vascular disease in humans.