Socioeconomic correlates of infant mortality in Hong Kong, 1979-93

Although Hong Kong's infant mortality is among the lowest in the world, there may still be subgroups in the population with unusually high and possibly avoidable mortality rates. We conducted an ecological study on the relationship between socioeconomic deprivation and infant mortality in Hong Kong by using government data from three periods: 1979-83, 1984-88 and 1989-93. The study population comprised all infant births in 65 modified districts in Hong Kong in the period 1979-93. Infant, neonatal and post-neonatal mortality rates (IMRs, NMRs and PNMRs) were used as the health indicators. An F score was derived from highly correlated socioeconomic variables by factor analysis and used as a summary index of socioeconomic status. In 1979-83, socioeconomic deprivation was found to be significantly associated with high IMRs and high NMRs in both sexes, while in 1984-88 this association was observed only in baby girls. None of the observed associations were significant in 1989-93. Overall, the territory's infant mortality rates fell from 10.2 per thousand live births in 1979-83 to 5.6 per thousand live births in 1989-93. Individual-based studies are needed to ascertain whether this apparent disappearance of the socioeconomic relationship with infant and neonatal mortality is real.

Influence of chronic fluorosis on membrane lipids in rat brain

Brain membrane lipid in rats were analyzed after being fed either 30 or 100 ppm fluoride for 3, 5, and 7 months. The protein content of brain with fluorosis decreased, whereas the DNA content remained stable during the entire period of investigation. After 7 months of fluoride treatment, the total brain phospholipid content decreased by 10% and 20% in the 30 and 100 ppm fluoride groups, respectively. The main species of phospholipid influenced by fluorosis were phosphatidylethanolamine, phosphatidylcholine, and phosphatidylserine. The fatty acid and aldehyde compositions of individual phospholipid classes were unchanged. No modifications could be detected in the amounts of cholesterol and dolichol. After 3 months of fluoride treatment, ubiquinone contents in brain were lower; however, at 7 months they were obviously increased in both groups of fluoride treatment. The results demonstrate that the contents of phospholipid and ubiquinone are modified in brains affected by chronic fluorosis and these changes of membrane lipids could be involved in the pathogenesis of this disease.

Insulin-like growth factor-I affects perinatal lethality and postnatal development in a gene dosage-dependent manner: manipulation using the Cre/loxP system in transgenic mice

Insulin-like growth factor-I (IGF-I) is essential for cell growth, differentiation and postnatal development. A null mutation in igf-1 causes intrauterine growth retardation and perinatal lethality. The present study was designed to test the lower limit of igf-1 gene dosage that ensures survival and postnatal growth by using the Cre/loxP system. Mice with variable reductions in IGF-I levels were generated by crossing EIIa-cre transgenic mice and mice with loxP-flanked igf-1 locus (igf-1/flox). EIIa-cre mice express bacteriophage P1 Cre (causes recombination) recombinase under the adenovirus promoter EIIa, during early embryonic development before implantation, and cause genomic recombination of the igf-1/flox locus. Mice with the most extensive recombination die immediately after birth, while the survivors have significant growth retardation in proportion to the reduction in their igf-1 gene. Interestingly, this gene dosage effect on body weight was not very significant before weaning. However, when the young animals were weaned at 3 weeks, the igf-1 gene dosage was the only independent predictor of the weight gain between 3 and 6 weeks among the parameters tested. Although growth retarded, mice with Cre-induced partial igf-1 deficiency were fertile and gave birth to null mice. Thus Cre-induced genomic recombination using the EIIa promoter occurs during development and creates distinct phenotypes compared with the conventional null mutation. This variability allows for postnatal survival and will enable one to begin to explore the role of the endocrine vs. paracrine effects of IGF-I.

An ISDN-based telemedicine system

Our preliminary results show the telemedicine system is successful. It does fulfill the 3 goals we set earlier. However, for such a system to be cost effective, the communication cost need to be cut further. In fact, video is not required at all time. We are hoping to establish criteria and operational procedure for use of video. Also some sort of standard should be set up for evaluation of the quality of telemedicine.

In vitro methionine oxidation of recombinant human leptin

PURPOSE

To investigate the role and importance of the four methionines in recombinant human leptin, and the effect of methionine oxidation in leptin structural stability and biological activity.

METHODS

Oxidized leptin derivatives were prepared in the presence of H2O2 and t-butylhydroperoxide, separated by RP-HPLC, and characterized by peptide mapping and LC/MS. Their biophysical and biological properties were studied.

RESULTS

Six major species of oxidized leptins were detected: two mono-oxidized, one di-oxidized, two tri-oxidized, and one tetra-oxidized. Further oxidation at cystine disulfide was also detected. Kinetic analysis indicated that oxidation at Met1 and Met69 proceeded first and independently. In 48 mM t-butylhydroperoxide, the pseudo first-order rate constants, k1 and k69, were 1.5 x 10(-3) and 2.3 x 10(-4) min-1. No change in the secondary or tertiary structure was detected for Met1 mono-oxidized and Met1, Met69 di-oxidized leptins. The Met1 mono-oxidized leptin retained full potency as compared to native leptin. A slight decrease of thermostability and a significant loss of the in vitro bioactivity were observed for Met1, Met69 di-oxidized leptin. Both Met55 and Met137 were not oxidized in t-butylhydroperoxide but only in H2O2. They appeared to be much less accessible to oxidation and might interact with the hydrophobic core structure of the leptin molecule.

CONCLUSIONS

The oxidation of leptin occurred in the order of Met1 > Met69 >> Met55 approximately Met137, and the importance for maintaining leptin structural integrity was Met55 approximately Met137 >> Met69 approximately Met1. Met69, but not Met1, plays a critical role in the protein stability and activity.

Agreement on responses to respiratory illnesses questionnaire

The prevalence of respiratory symptoms and illnesses among 2225 schoolchildren in Hong Kong was studied by questionnaires administered independently to them and their parents. The agreement was generally poor for respiratory symptoms. The disparity shows the need for cross validation of clinical information in history taking.

Angiotensin II-nitric oxide interaction on sympathetic outflow in conscious rabbits

Increasing evidence suggests that endogenous NO inhibits sympathetic outflow in anesthetized animals. However, in a recent study from this laboratory, we were unable to find any evidence of increased renal sympathetic nerve activity (RSNA) in response to blockade of NO synthesis in conscious rabbits. Because angiotensin II (Ang II) increases sympathetic outflow, one factor for this discrepancy may be the difference in the resting level of Ang II, which may be lower in well-trained conscious animals. In the present study, the effects of blockade of NO synthesis with Nomega-nitro-L-arginine methyl ester (L-NAME, 30 mg/kg IV) on resting RSNA with and without a background intravenous infusion of Ang II (10 ng.kg(-1).min(-1)) was investigated in conscious rabbits. Intravenous administration of L-NAME (30 mg/kg) caused an increase in mean arterial blood pressure (MAP, from 80.4+/-2.9 to 92.8+/-2.5; P=.0001) and a decrease in RSNA (from 100+/-0% to 53.4+/-8.6%, P=.0016). When the elevated blood pressure was returned to control by infusion of hydralazine (0.01 to 0.06 mg.kg(-1).min(-1)), RSNA returned to the level before L-NAME administration. During a sustained infusion of Ang II (10 ng.kg(-1).min(-1)), L-NAME increased MAP from 89.2+/-2.9 to 109.0+/-4.3 mm Hg (P=.0101) and decreased RSNA from 100.0+/-0% to 53.7+/-7.5% (P=.0013). Under this circumstance, however, when the MAP was returned to the level that existed before the administration of L-NAME, RSNA increased significantly above the level that existed before the administration of L-NAME (164.5+/-17.7% versus 100+/-0%, P=.0151). The enhancement of the sympathetic response by Ang II was completely blocked by the AT1 receptor antagonist, losartan. In contrast, during a background infusion of phenylephrine, which increased MAP to the same level as produced by Ang II, L-NAME had no effect on RSNA when MAP was returned to the control level. Nomega-Nitro-D-arginine methyl ester had no effect on MAP and RSNA. Intravenous infusion of Ang II alone for 75 minutes had no effect on RSNA when MAP was returned to control levels. These data suggest that an elevated level of Ang II is critical for the inhibitory effect of NO on sympathetic outflow in conscious rabbits and imply that these two substances have a major impact on the regulation of sympathetic outflow.

Blockade of neuronal nitric oxide synthase alters the baroreflex control of heart rate in the rabbit

In previous studies we used NG-nitro-L-arginine (L-NNA) to investigate the role of nitric oxide (NO) in baroreflex control of heart rate (HR) and renal sympathetic nerve activity (RSNA). L-NNA increased resting mean arterial pressure (MAP), decreased HR, and did not change or slightly decreased RSNA. These changes complicated the assessment of the central effects of NO on the baroreflex control of HR and RSNA. Therefore, in the present study the effects of the relatively selective neuronal NO synthase inhibitor 7-nitroindazole (7-NI) on the baroreflex control of HR and RSNA were investigated in rabbits. Intraperitoneal injection of 7-NI (50 mg/kg) had no effect on resting HR, MAP, or RSNA. 7-NI significantly reduced the lower plateau of the HR-MAP baroreflex curve from 140 +/- 4 to 125 +/- 4 and from 177 +/- 10 to 120 +/- 9 beats/min in conscious and anesthetized preparations, respectively (P < 0.05). In contrast, there was no significant difference in the RSNA-MAP curves before and after 7-NI administration in conscious or anesthetized preparations. These data suggest that blockade of neuronal NO synthase influences baroreflex control of HR but not of RSNA in rabbits.

Transforming potential of the herpesvirus oncoprotein MEQ: morphological transformation, serum-independent growth, and inhibition of apoptosis

Marek's disease virus (MDV) induces the rapid development of overwhelming T-cell lymphomas in chickens. One of its candidate oncogenes, meq (MDV Eco Q) which encodes a bZIP protein, has been biochemically characterized as a transcription factor. Interestingly, MEQ proteins are expressed not only in the nucleoplasm but also in the coiled bodies and the nucleolus. Its novel subcellular localization suggests that MEQ may be involved in other functions beyond its transcriptional potential. In this report we show that MEQ proteins are expressed ubiquitously and abundantly in MDV tumor cell lines. Overexpression of MEQ results in transformation of a rodent fibroblast cell line, Rat-2. The criteria of transformation are based on morphological transfiguration, anchorage-independent growth, and serum-independent growth. Furthermore, MEQ is able to distend the transforming capacity of MEQ-transformed Rat-2 cells through inhibition of apoptosis. Specifically, MEQ can efficiently protect Rat-2 cells from cell death induced by multiple modes including tumor necrosis factor alpha, C2-ceramide, UV irradiation, and serum deprivation. Its antiapoptotic function requires new protein synthesis, as treatment with a protein synthesis inhibitor, cycloheximide, partially reversed MEQ's antiapoptotic effect. Coincidentally, transcriptional induction of bcl-2 and suppression of bax are also observed in MEQ-transformed Rat-2 cells. Taken together, our results suggest that MEQ antagonizes apoptosis through regulation of its downstream target genes involved in apoptotic and/or antiapoptotic pathways.

Determination of tumor necrosis factor binding protein disulfide structure: deviation of the fourth domain structure from the TNFR/NGFR family cysteine-rich region signature

Tumor necrosis factor binding protein is a soluble molecule derived from the extracellular domain of the 55 kDa human tumor necrosis factor receptor, which can block the biological function of tumor necrosis factor by binding to the growth factor. This cysteine-rich molecule is subdivided into four domains, each containing six conserved cysteines that form three intrachain disulfide linkages known as the tumor necrosis factor receptor/nerve growth factor receptor family cysteine-rich region signature structure. In an effort to elucidate the molecular integrity of the molecule, we performed detailed analysis and searched for strategies to elucidate the complete disulfide structure of the E. coli-derived tumor necrosis factor binding protein and to determine the disulfide arrangement in the fourth domain of Chinese hamster ovary cell-derived molecule. The methods employed included various proteolytic digestions, peptide mapping, partial reduction, and assignment of disulfides by N-terminal sequencing and matrix-assisted laser desorption ionization mass spectrometry with post-source decay. The first three domains of the molecule were confirmed to have disulfide structures identical to the cysteine-rich region signature structure found in the above-mentioned receptor superfamily. The fourth domain has a different structure from the first three domains where the last four cysteines form two disulfide bonds in opposite positions.

The constitutively active mutant Galpha13 transforms mouse fibroblast cells deficient in insulin-like growth factor-I receptor

Insulin-like growth factor-I (IGF-I) receptor plays an important role in normal cell cycle progression and tumor growth, and it is thought to be essential for cellular transformation. To test this hypothesis, we stably transfected a GTPase-deficient mutant human Galpha13, which is highly oncogenic when overexpressed in vitro, into R- fibroblasts derived from IGF-I receptor-deficient mice. Northern blots of multiple clones revealed the expression of a 1.8-kilobase pair mutant Galpha13 transcript in transfected cells, in addition to the 6-kilobase pair endogenous mRNA. The transfection resulted in a doubling of the expression of Galpha13 protein in these cells as assessed by Western blot analysis. The transforming ability of the mutant Galpha13 was tested using the soft agar assay. Nontransfected R- cells cultured with 10% fetal bovine serum failed to form colonies after 3 weeks. Most of the mutant Galpha13-expressing clones formed significant numbers of colonies (11-50 colonies/1000 cells plated). Overexpression of the IGF-I receptor enabled R- cells to form colonies (27 colonies), and co-transfection of the mutant Galpha13 caused a further increase in colony formation (117-153 colonies) in three of five clones analyzed. Apparently Galpha13 works through pathways other than mitogen-activated protein kinase and c-Jun N-terminal kinase in transforming R- cells, because their activities were not significantly altered by the mutant Galpha13 expression. These results demonstrate that Galpha13 can induce cellular transformation through pathways apparently independent of the IGF-I receptor and that activation of the IGF-I receptor signaling pathways, although not essential for the transforming phenotype, enhances the effect of other pathways.

Factors associated with the utilization of traditional Chinese medicine in a small town in Hong Kong

The practice of Traditional Chinese Medicine (TCM) is largely unregulated in Hong Kong. Yet, as previous studies have shown, a sizable segment of the population consults TCM practitioners for health problems. This paper uses health care utilization data from a telephone health survey of 847 adult subjects in Tai Po District who had suffered from acute illness in the past month, to examine the profile of TCM users in the District. Women, older residents, unemployed workers, low skill laborers, current smokers and subjects dissatisfied with the quality of private sector clinics were significantly more likely to consult TCM practitioners.

Somatostatin-14, somatostatin-28, and prosomatostatin[1-10] are independently and efficiently processed from prosomatostatin in the constitutive secretory pathway in islet somatostatin tumor cells (1027B2)

We have characterized the biosynthetic origin of somatostatin-14 (SS-14), SS-28, and pro-SS[1-10] from pro-SS (PSS) in 1027B2 rat islet tumor cells. Because these cells lack regulated secretion and show unresponsiveness of the SS gene to cAMP, we have additionally carried out morphological and functional studies to elucidate the molecular defect in cAMP signalling and to localize the sites of PSS maturation along the secretory pathway. Cell extracts and secretion media were analysed by high performance liquid chromatography and specific C- and N-terminal radioimmunoassays. Electron microscopic sampling of 1027B2 cell cultures showed that most cells had very few dense core secretory granules for heterogeneous sizes. The cells expressed the endoproteases furin, PC1, and PC2 and contained large quantities of fully processed SS-14 and SS-28 with very little unprocessed PSS (ratio SS-14:SS-28:PSS = 39:51:10%). They secreted high concentrations of SS-14, SS-28, and PSS[1-10] constitutively along with PC1 and PC2. Pulse-chase studies demonstrated that PSS is rapidly (within 15 min), and efficiently processed to SS-14, SS-28, and PSS[1-10] via separate biosynthetic pathways: PSS --> SS-14 + 8 kDa; PSS --> SS-28 + 7 kDa; PSS --> PSS[1-10]. Monensin reduced intracellular SS-like immunoreactivity without altering processing efficiency. Transfection with the catalytic subunit of protein kinase A (PKA-C) activated SS promoter-CAT activating indicating that the defect in cAMP-dependent signaling in 1027B2 cells lies at the level of PKA-C. PKA-C overexpression failed to alter the ratio of processed SS-14 and SS-28. These results demonstrate that SS-14, SS-28, and PSS[1-10] are independently synthesized from PSS and that efficient precursor processing can occur within the constitutive secretory pathway in the relative absence of dense core secretory vesicles.

Lysophosphatidic acid stimulates proliferation of human retinal pigment epithelial cells

PURPOSE

Proliferative vitreoretinopathy (PVR) can arise from an exaggerated wound-healing response by retinal pigment epithelial (RPE) cells. Lysophosphatidic acid (LPA) is a simple phospholipid, which is secreted by cells, activates G protein-coupled receptors, and appears to contribute to wound healing in other tissues. The present study examined the effects of LPA on three aspects of the behavior of cultured human RPE cells that are important in the pathogenesis of PVR: proliferation, chemotaxis, and contraction.

METHODS

Human RPE cells were harvested from donor eyes and cultured using standard culture techniques. Proliferation was assessed by counting cells, cell migration with a modified Boyden chamber, and contraction by seeding RPE cells in a collagen cell.

RESULTS

LPA (10 microM) induced RPE cell proliferation and weak chemotaxis, but no gel contraction. RPE cell proliferation increased in a dose-dependent manner from 0.1-100 microM LPA. Consistent with LPA actions at a receptor, an LPA analogue, lysophosphatidylcholine (LPC), was much less effective than LPA in stimulating proliferation and the proliferative response was blocked by pertussis or cholera toxin. Phosphatidic acid (PA) induced a similar proliferative response as LPA.

CONCLUSION

These suggest that LPA can potently stimulate RPE cell proliferation via activation of a G-protein coupled receptor. LPA, which can be released by thrombin-activated platelets and growth factor-activated fibroblasts, might, therefore, play a role in the development of PVR.

Nucleolar and nuclear localization properties of a herpesvirus bZIP oncoprotein, MEQ

Marek's disease virus (MDV) is one of the most oncogenic herpesviruses and induces T lymphomas in chickens within weeks after infection. Only a limited number of viral transcripts are detected in MDV tumor samples and cell lines. One of the major transcripts encodes MEQ, a 339-amino-acid bZIP protein which is homologous to the Jun/Fos family of transcription factors. The C-terminal half of MEQ contains proline-rich repeats and, when fused to the DNA-binding domain of a yeast transcription factor, Gal4 (residues 1 to 147), exhibits transactivation function. MEQ can dimerize with itself and with c-Jun. The MEQ-c-Jun heterodimers bind to an AP-1-like enhancer within the MEQ promoter region with greater affinity than do homodimers of either protein, and they transactivate MEQ expression. Here we show that MEQ is expressed in the nucleus but, interestingly, with a predominant fraction in the nucleoli and coiled bodies. This makes MEQ the first bZIP protein to be identified in the nucleoli. MEQ contains two stretches of basic residues, designated basic region 1 (BR1) and basic region 2 (BR2). Using a series of deletion mutants, we have mapped the primary nuclear localization signal (NLS) and the sole nucleolar localization signal (NoLS) to the BR2 region. BR1 was shown to provide an auxiliary signal in nuclear translocation. To demonstrate that BR2 is an authentic NoLS, BR2 was fused to cytoplasmic v-Raf (delta gag) kinase. The BR2-Raf fusion protein was observed to migrate into the nucleoplasm and the nucleolus. The BR2 region can be further divided into two long arginine-lysine stretches, BR2N and BR2C, which are separated by the five amino acids Asn-Arg-Asp-Ala-Ala (NRDAA). We provide evidence that the requirement for nuclear translocation is less stringent than that for nucleolar translocation, as either BR2N or BR2C alone is sufficient to translocate the cytoplasmic v-Raf (delta gag) into the nucleus, but only in combination can they translocate v-Raf (delta gag) into the nucleolus. Our studies demonstrate that MEQ is both a nuclear and nucleolar protein, adding MEQ to the growing list of transactivators which localize to the nucleolus.

Avian leukemias and lymphomas: interplay between retroviruses and herpesviruses

Avian leukemias and lymphomas are caused primarily by retroviruses and herpesviruses. The protooncogenes activated by avian retroviral insertions in B & T-cell lymphomas will be summarized, with discussion on a new common insertion site, bravo, associated with RAV-O LTR insertion. Two novel interactions between avian retroviruses and Marek's disease herpesvirus (MDV) will be described: one involves direct interactions between putative viral oncoproteins and the other integrative recombination between these two viruses.

Angiotensin II blockade [corrected] enhances baroreflex control of sympathetic outflow in heart failure

Enhanced sympathetic outflow is seen in both patients with congestive heart failure and animals with experimental heart failure. In a previous study, we demonstrated that the baroreflex control of heart rate was impaired in conscious rabbits with pacing-induced heart failure and that this impairment was partially restored by blockade of angiotensin II type 1 (AT1) receptors. In the present study, we determined the interaction between the renin-angiotensin system and baroreflex control of renal sympathetic nerve activity in normal conscious rabbits and conscious rabbits with pacing-induced heart failure before and after AT1 receptor blockade. Heart failure was induced by rapid ventricular pacing at a rate of 360 to 380 beats per minute for an average of 16.7 +/- 0.6 days. To generate baroreflex curves, we altered arterial pressure by administering phenylephrine and sodium nitroprusside. A sigmoidal logistic function was fit to renal sympathetic nerve activity-mean arterial pressure relationships for analysis of several components of baroreflex function. AT1 receptors were blocked by intravenous administration of the specific antagonist L-158,809. In normal rabbits, there was no significant difference in any parameter of baroreflex function before and after blockade of AT1 receptors. In contrast, blockade of AT1 receptors enhanced baroreflex sensitivity in heart failure rabbits. The maximal gain increased to 5.0 +/- 0.7% renal sympathetic nerve activity/mm Hg from 2.6 +/- 0.3 (P < .05). Although L-158,809 had no effect on baseline renal sympathetic nerve activity in normal rabbits, analysis of the data in the heart failure rabbits indicated that baseline renal sympathetic nerve activity was reduced from 33 +/- 5% to 17 +/- 4% after L-158,809 administration after adjustment for changes in arterial pressure. These data suggest that angiotensin II plays a role in baroreflex impairment in this model of heart failure and may be in part responsible for the depressed baroreflex sensitivity observed in heart failure.

Schistosoma mansoni elastase: an immune target regulated during the parasite life-cycle

Recombinant Schistosoma mansoni elastase was expressed in Escherichia coli and an antiserum raised against the recombinant protein was used to investigate stage-specific control of elastase in the parasite, and to determine whether the enzyme could form the basis of a strategy to prevent larval invasion of the host. Results showed that the expression of elastase is developmentally regulated, even if the basal promoter activity does not seem to be stage specific. The analysis of mRNA expression showed the presence of elastase transcript in adult worms although we could not detect the protein at this stage, suggesting that S. mansoni employs a form of translational control. The measurement of elastase levels in supernatants of culture schistosomula combined with the localization of elastase in cercarieae invading mouse skin showed that the enzyme is heavily released during penetration. Finally, we studied the cytotoxic activity of rat anti-elastase sera, and the analysis of the isotypic profile suggested that IgG2a anti-elastase may be responsible for the cytotoxic effect.

Expression of NF-Y nuclear factor in Schistosoma mansoni

The A subunit of NF-Y nuclear factor from Schistosoma mansoni was expressed in E. coli fused to a histidine tag and purified by affinity chromatography using a Ni(2+)-Agarose matrix. Antibodies against the recombinant protein were prepared and used for Western blot and immunolocalization. The presence of SMNF-YA in all stages of the parasite life-cycle was determined by RT-PCR and Western blot analysis. The immunolocalization of SMNF-YA showed the presence of this factor in a parenchymal cell population of cercariae and adult worms and in embryos within eggs. The expression of SMNF-YA was demonstrated to decrease in maturating spermatozoites whereas an accumulation of this factor was observed in the nucleus from oocytes during their maturation processes.

Sex differences in the determination of abdominal leak point pressure in patients with intrinsic sphincter deficiency

PURPOSE

We determined the effect of a urethral catheter on abdominal leak point pressure in men and women with intrinsic sphincter deficiency.

MATERIALS AND METHODS

A total of 21 consecutive men treated with prostatectomy and 19 women with intrinsic sphincter deficiency underwent abdominal leak point pressure measurements with a rectal catheter before and after removal of a 10F urethral catheter.

RESULTS

Of the 19 women 2 had leakage only when the urethral catheter was removed, while 17 had excellent correlation between abdominal leak point pressures before and after catheter removal (r = 0.83). In contrast, 10 of 21 men had leakage only when the urethral catheter was removed and 11 had weak correlation between abdominal leak point pressures before and after catheter removal (r = 0.46).

CONCLUSIONS

An indwelling 10F urethral catheter is much more likely to invalidate abdominal leak point pressure measurement in men than in women with intrinsic sphincter deficiency.

Ultrastructural localization of Sm28 GST protective antigen in Schistosoma mansoni adult worms

The localization of the 28 kDa Schistosoma mansoni glutathione S-transferase (Sm28 GST) has been investigated using immunohistochemistry and electron microscopy and the results compared with previously published data. This study confirms the wide distribution of this antigen in the parasite. In male and female worms, Sm28 GST is localized in the tegument, the parenchyma, the oesophageal epithelium and in genital organs. Sm28 GST was clearly detected in germinal and sustentacular cells. The decrease of staining intensity during the differentiation of germinal cells suggests a down-regulated expression of the molecule. At the ultrastructural level, this antigen was abundant in nuclei and less present in the cytoplasm. The marked heterogeneity observed in the staining of individual worms indicates that Sm28 GST seems to be closely associated with the parasite's metabolism. The results are discussed in relation to the biological and protective functions of the protein.

Blockade of AT1 receptors enhances baroreflex control of heart rate in conscious rabbits with heart failure

Because the renin-angiotensin system is activated in heart failure, we hypothesized that angiotensin II (ANG II) plays a role in altering baroreflex sensitivity in the setting of heart failure. Accordingly, we evaluated the baroreflex control of heart rate (HR) in conscious, chronically instrumented rabbits in the normal state and after the establishment of heart failure. Heart failure was induced by rapid ventricular pacing at a rate of 360-380 beats/min for an average of 14.5 +/- 1.4 days. The data were compared with normal rabbits instrumented in a similar fashion. Baroreflex curves were generated by inflation of implanted hydraulic occluders on the vena cava and aortic arch or by administration of phenylephrine and sodium nitroprusside. Experiments were carried out before and after intravenous administration of the AT1 antagonist L-158,809. Rabbits with heart failure exhibited significantly lower arterial pressure (81 +/- 3 vs. 69 +/- 4 mmHg, P < 0.05), elevated resting HR (230 +/- 5 vs. 260 +/- 10 beats/min, P < 0.05), and elevated left atrial pressure (3.6 +/- 0.7 vs. 13.1 +/- 0.7 mmHg, P < 0.05). ANG II blockade had little effect on resting or baroreflex parameters in normal rabbits. However, in rabbits with heart failure, L-158,809 enhanced baroreflex sensitivity (2.7 +/- 0.5 vs. 4.7 +/- 0.8 beats.min-1.mmHg-1; P < 0.05), primarily by increasing the minimum HR evoked during baroreceptor activation. beta 1-Blockade had no effect on any baroreflex parameter after L-158,809 in rabbits with heart failure. However, L-158,809 significantly reduced the minimum HR after pretreatment with atropine in rabbits with heart failure. These data suggest that ANG II plays a role in modulation of cardiac sympathetic tone in this model of heart failure and may be responsible for the depressed baroreflex sensitivity observed in heart failure.

Effects of NO on baroreflex control of heart rate and renal nerve activity in conscious rabbits

Recent data suggest that nitric oxide (NO) plays a role in the modulation of sympathetic nerve activity and baroreflex sensitivity. Most of these studies have been carried out in anesthetized preparations, and little if any comparison has been made on the relative role of NO on the baroreflex control of heart rate and sympathetic nerve activity. In the present studies, the effect of the NO synthase inhibitor NG-nitro-L-arginine (L-NNA) on the baroreflex control of heart rate (HR) and renal sympathetic nerve activity (RSNA) were investigated in conscious, instrumented rabbits. Intravenous bolus injections of 13 mg/kg of L-NNA decreased baseline HR (from 205.0 +/- 6.0 to 145.5 +/- 8.2 beats/min; P < 0.05) without significant changes in mean arterial pressure (MAP) and RSNA. L-NNA significantly reduced the lower plateau of the HR-MAP curves and increased the sensitivities of baroreflex control of HR and RSNA. L-Arginine (600 mg/kg i.v.) but not D-arginine reversed the above effects. The effects of L-NNA on baseline HR were not completely blocked by metoprolol (2 mg/kg) or by atropine (0.2 mg/kg). After pretreatment with metoprolol, baroreflex sensitivity was reduced and L-NNA increased baroreflex sensitivity back to the control level. After pretreatment with atropine, L-NNA still reduced the lower plateau but did not significantly affect baroreflex sensitivity. L-NNA increased the HR responses but not the RSNA response to electrical stimulation of the aortic nerve in chloralose-anesthetized, sinoaortic-denervated (SAD) rabbits. L-NNA had no effect on the HR response to right vagal stimulation. In both conscious intact and SAD rabbits, L-NNA did not increase baseline RSNA. These results suggest that endogenous NO decreases baroreflex control of HR and RSNA. Both sympathetic and parasympathetic components play a role in the effects of NO on the baroreflex control of HR. The effects of NO in the central nervous system play a more important role in the baroreflex control of HR than of RSNA.