Hypoxia induces the expression of a 43-kDa protein (PROXY-1) in normal and malignant cells

This study was designed to determine the expression of cellular factors that may participate in phenotypic changes that occur under conditions of hypoxia. Using the RT-PCR differential display method, we isolated a cDNA fragment corresponding to a gene whose expression was induced in trophoblast and breast carcinoma cells cultured under 1 or 2% oxygen vs 4% oxygen or higher. This gene encodes a 43-kDa protein initially identified in homocysteine-treated endothelial cells and later shown to be upregulated in various human and mouse cell types (termed RTP, Drg1, Cap43, rit42, Ndr1). Herein we refer to this gene product as PROXY-1, for Protein Regulated by OXYgen-1. Elevated mRNA and protein levels were first observed in cells cultured in 1% oxygen for 8 h. Although PROXY-1 mRNA levels returned to near-control values within 2 h of reexposure to 20% oxygen, protein levels remained high 72 h after reexposure to 20% oxygen. Treatment of cells with hypoxia mimics such as cobalt or iron chelators also increased PROXY-1 expression. Moreover, presence of 30% carbon monoxide in the hypoxic atmosphere abrogated the upregulation of PROXY-1 expression. These findings suggest that hypoxia upregulates PROXY-1 levels through a heme protein-dependent pathway and that assessment of PROXY-1 expression may be of potential use in evaluating tissue hypoxia.

Expression of phosphodiesterase 4D (PDE4D) is regulated by both the cyclic AMP-dependent protein kinase and mitogen-activated protein kinase signaling pathways. A potential mechanism allowing for the coordinated regulation of PDE4D activity and expression in cells

Multiple families of cyclic nucleotide phosphodiesterases (PDE) have been described, and the regulated expression of these genes in cells is complex. Although cAMP is known to control the expression of certain PDE in cells, presumably reflecting a system of feedback on cAMP signaling, relatively little is known about the influence of non-cAMP signaling systems on PDE expression. In this study, we describe a novel mechanism by which activators of the protein kinase C (PKC)-Raf-MEK-ERK cascade regulate phosphodiesterase 4D (PDE4D) expression in vascular smooth muscle cells (VSMC) and assess the functional consequences of this effect. Whereas a prolonged elevation of cAMP in VSMC resulted in a protein kinase A (PKA)-dependent induction of expression of two PDE4D variants (PDE4D1 and PDE4D2), simultaneous activation of both the cAMP-PKA and PKC-Raf-MEK-ERK signaling cascades blunted this cAMP-mediated increase in PDE4D expression. By using biochemical, molecular biological, and pharmacological approaches, we demonstrate that this PDE4D-selective effect of activators of the PKC-Raf-MEK-ERK cascade was mediated through a mechanism involving altered PDE4D mRNA stability and markedly attenuated the cAMP-mediated desensitization that results from prolonged activation of the cAMP signaling system in cells. The data are presented in the context of activators of the PKC-Raf-MEK-ERK cascade having both short and long term effects on PDE4D activity and expression in cells that may influence cAMP signaling.

ANP in regulation of arterial pressure and fluid-electrolyte balance: lessons from genetic mouse models

The recent development of genetic mouse models presenting life-long alterations in expression of the genes for atrial natriuretic peptide (ANP) or its receptors (NPR-A, NPR-C) has uncovered a physiological role of this hormone in chronic blood pressure homeostasis. Transgenic mice overexpressing a transthyretin-ANP fusion gene are hypotensive relative to the nontransgenic littermates, whereas mice harboring functional disruptions of the ANP or NPR-A genes are hypertensive compared with their respective wild-type counterparts. The chronic hypotensive action of ANP is determined by vasodilation of the resistance vasculature, which is probably mediated by attenuation of vascular sympathetic tone at one or several prejunctional sites. Under conditions of normal dietary salt consumption, the hypotensive action of ANP is dissociated from the natriuretic activity of the hormone. However, during elevated dietary salt intake, ANP-mediated antagonism of the renin-angiotensin system is essential for maintenance of blood pressure constancy, inasmuch as the ANP gene "knockout" mice (ANP -/-) develop a salt-sensitive component of hypertension in association with failure to adequately downregulate plasma renin activity. These findings imply that genetic deficiencies in ANP or natriuretic receptor activity may be underlying causative factors in the etiology of salt-sensitive variants of hypertensive disease and other sodium-retaining disorders, such as congestive heart failure and cirrhosis.

Altered expression of natriuretic peptide receptors in proANP gene disrupted mice

BACKGROUND

The atrial natriuretic peptide (ANP) family is a complex system consisting of at least three polypeptides and at least three types of receptor. Each peptide interacts with different types of receptor at varying degrees of affinity. To determine if natriuretic peptide levels influence natriuretic peptide receptor expression and regulation, we examined the expression of guanylyl cyclase linked GC-A, GC-B and C-receptor in the lungs of mice with a mutation that inactivates the ANP gene (Nppa).

METHODS

The mRNA level of GC-A, GC-B and C-receptor in the lung were studied by ribonuclease protection assays (RPA).

RESULTS

Results of RPA showed that although the mRNA level of GC-A and GC-B of heterozygous ANP+/- was not different from wild type ANP+/+ mice, they were significantly higher in the homozygous mutant ANP-/- mice. In addition, C-receptor mRNA level in ANP+/- and ANP-/- was significantly lower than ANP+/+ mice. The C-receptor results were confirmed by receptor binding assays and affinity cross-linking studies.

CONCLUSIONS

Taken together these data suggest that permanent removal of ANP from the natriuretic peptide system results in an up-regulation of GC-A and GC-B, and a corresponding down-regulation of C-receptor in the lung of proANP gene disrupted mice. We postulated that changes in the natriuretic peptide receptor population may result in chronic hypertension and cardiac hypertrophy in the ANP-/- mice.

Tuberculosis surveillance in immigrants through health undertakings in Western Australia

SETTING

Tuberculosis Control Program, Western Australia.

OBJECTIVE

To assess the effectiveness and efficiency of tuberculosis (TB) surveillance in immigrants.

DESIGN

Retrospective descriptive analysis of records of immigrants who first registered with the Tuberculosis Program from January 1994 to December 1995, having entered Western Australia on health undertakings (nonlegal contracts signed by those determined during premigration screening to require post-arrival evaluation).

RESULTS

Of 1,344 immigrants on health undertakings for TB in the period, 587 (44%) had findings directly related to TB through pre-migration screening, 69 of whom required treatment for active disease. Another 443 (33%) had chest X-ray changes for which TB could not be excluded. Of the remaining 314 (23%), 172 had poor quality X-rays. Post-arrival assessment and follow-up of the whole group detected four of seven additional cases of active TB, 373 persons (28%) requiring on-going surveillance, 667 (50%) with non-TB conditions and 280 (21%) with normal chest X-rays.

CONCLUSIONS

Migrant surveillance for TB in Australia is effective in detecting active disease and identifying a high-risk subgroup requiring further evaluation. Efficiency can be improved and high compliance achieved with simple administrative changes. Routine pre-migration Mantoux testing is inappropriate, and its inclusion in post-arrival assessments should be a national policy decision.

Developmental regulation of the translational repressor NAT1 during cardiac development

The process of translation initiation has been postulated to play an important role in the regulation of cellular growth and proliferation. Here, we report the identification and differential expression of a fundamental translational repressor NAT1, during early postnatal cardiac development. Differential display analysis of RNA obtained from 3-day and 4-week-old rat hearts resulted in the cloning and identification of a 396 bp cDNA fragment (DRCF-6) which corresponded to the 3' terminal portion of NAT1. Northern blot analysis revealed that the mRNA expression of NAT1 was markedly elevated during the first 2 weeks of postnatal life, with an apparent peak level of expression occurring at 1 week. NAT1 mRNA levels then steadily decreased to 4 weeks of age. The NAT1 transcript has previously been shown to be extensively edited by the enzyme APOBEC-1, which deaminates specific cytidine bases to uridine; cytidine deamination at a glutamine codon (CAA) results in the formation of a stop codon (UAA) and consequently, premature termination of translation. Accordingly, Western blot analysis detected the presence of several smaller proteins in addition to the full length NAT1 protein (97 kDa), each exhibiting a distinct pattern of expression during cardiac development. APOBEC-1 editing of NAT1 during cardiac development was further supported by primer extension analysis of cytidine 1699, which was found to be predominantly edited to uridine. Immunohistochemical staining showed that NAT1 is expressed predominantly in atrial and ventricular myocytes, although staining was also detected in vascular smooth muscle cells and in the endocardium. These results suggest that NAT1 may play a role in the postnatal development of the heart and demonstrate that APOBEC-1 editing may possibly be a novel mechanism by which translation is regulated during cardiac development.

Chronic regulation of arterial blood pressure in ANP transgenic and knockout mice: role of cardiovascular sympathetic tone

OBJECTIVE

Atrial natriuretic peptide (ANP) lowers arterial blood pressure (ABP) chronically, in association with vasodilation of the resistance vasculature. The mechanism mediating the chronic relaxant effect of ANP is likely indirectly mediated by interactions with tonic vasoeffector mechanisms, inasmuch as the resistance vasculature is relatively insensitive to direct cGMP-mediated relaxation by ANP. On the basis of evidence that ANP has widespread sympatholytic activity, the current study investigated whether the chronic hypotensive effect of ANP is mediated by attenuation of tonic cardiovascular sympathetic tone.

METHODS

Total plasma catecholamine concentration and changes in basal ABP and heart rate (HR) following autonomic ganglionic blockade were measured as indices of underlying sympathetic nerve activity in hypotensive ANP-overexpressing transgenic mice (TTR-ANP), hypertensive ANP knockout mice (-/-) and the genetically-matched wild type (NT and +/+, respectively) control mice. Pressor and chronotropic responses to norepinephrine infusion were measured in ganglion-blocked mice of all genotypes, and norepinephrine receptor binding was assessed in representative tissues of -/- and +/+ mice, in order to determine whether peripheral adrenergic receptor responsiveness is altered by ANP-genotype.

RESULTS

Basal ABP was significantly lower in TTR-ANP and higher in -/- compared to their wild-type controls. Basal HR did not differ significantly between mutant and control mice. Autonomic ganglionic blockade reduced ABP and HR in all genotypes, however, the relative decrease in ABP was significantly smaller in TTR-ANP and greater in -/- mice than in their respective controls. Total plasma catecholamine was significantly higher in -/- than in +/+ mice but did not differ significantly between TTR-ANP and NT mice. Norepinephrine infusion during ganglionic blockade elicited quantitatively similar pressor and chronotropic responses in mutant and control mice. Tissue norepinephrine binding did not differ significantly between -/- and +/+ mice.

CONCLUSIONS

The present study shows that differences in endogenous ANP activity in mice, resulting in chronic alterations in ABP are accompanied by directional changes in underlying cardiovascular sympathetic tone, and suggests that the chronic vasodilator effect of ANP is, at least partially, dependent on attenuation of vascular sympathetic tone, possibly at a prejunctional site(s).

Molecular cloning and developmental expression of rat glycogenin in cardiac tissue

Glycogenin is a self-glycosylating protein required to initiate glycogen biosynthesis. Utilizing the differential display technique to analyze changes in gene expression during early postnatal cardiac development, we have isolated and cloned a 484 bp cDNA fragment that corresponds to the 3' end of rat glycogenin. Northern blot analysis on neonatal cardiac tissues demonstrated hybridization to a 1.7-1.8 kb transcript, which was highly expressed at 3 days and at progressively reduced levels at 1, 2, 3 and 4 weeks of age. A 1624 bp fragment of rat glycogenin was cloned by RT-PCR that includes a 1002 bp open reading frame encoding a 333 amino acid protein. At the nucleotide level, rat glycogenin exhibited 87.2 and 83.6% identity with human and rabbit glycogenin over the open reading frame. The deduced amino acid sequence showed 86.7 and 83.4% identity with human and rabbit sequences, respectively. Given the significance of glycogenin in glycogen biosynthesis, the results of this study suggest a possible molecular basis for the regulation of glycogen during early postnatal cardiac development. In addition, the nucleotide and amino acid sequences of rat glycogenin may be used to investigate the physiological and pathophysiological roles of glycogenin in rat tissues.

Chronic hypertension in ANP knockout mice: contribution of peripheral resistance

Atrial Natriuretic Peptide (ANP) exerts a chronic hypotensive effect which is mediated by a reduction in total peripheral resistance (TPR). Mice with a homozygous disruption of the pro-ANP gene (-/-) fail to synthesize ANP and develop chronic hypertension in comparison to their normotensive wild-type (+/+) siblings. In order to determine whether alterations in basal hemodynamics underlie the hypertension associated with lack of endogenous ANP activity, we used anesthetized mice to measure arterial blood pressure (ABP) and heart rate (HR), as well as cardiac output (CO) by thermodilution technique. -/- (n = 7) and +/+ (n = 10) mice of comparable weight and age were used. Stroke volume (SV) and TPR were derived from CO, HR, and ABP by a standard formula. ABP (mm Hg) was significantly higher in -/- (132+/-4) (P < 0.0001) than in +/+ mice (95+/-2). CO (ml min(-1)), HR(beats min(-1))and SV (microl beat(-1)) did not differ significantly between -/- and +/+ mice (CO -/- = 7.3+/-0.5, +/+ = 8.3+/-0.6; HR -/- = 407+/-22, +/+ = 462+/-21; SV -/- = 17.6+/-1.1, +/+ = 17.6+/-1.7). However, TPR (mm Hg ml(-1) min(-1)) was significantly elevated in -/- mice (18.4+/-0.7) compared to +/+ mice (12.3+/-1) (P = 0.0003). Autonomic ganglion blockade with a mixture of hexamethonium and pentolinium was followed by comparable percent reductions in CO (-/- = 28+/-4, +/+ = 29+/-3), HR (-/- = 9+/-4, +/+ = 16+/-4) and SV(-/- = 21+/-4, +/+ = 15+/-6) in both genotypes. However, the concomitant decrease in ABP (%) in -/- (41+/-2) was significantly greater than in +/+ (23+/-4) mice (P = 0.0009) and was accompanied by a significant reduction in TPR. We conclude that the hypertension associated with lack of endogenous ANP is due to elevated TPR, which is determined by an increase in cardiovascular autonomic tone.

Preventive therapy for tuberculosis in Western Australia

SETTING

State Tuberculosis Control Programme, Western Australia.

OBJECTIVE

To ascertain baseline information, applicability and efficacy of preventive therapy for tuberculosis (TB) under indirectly supervised treatment in Western Australia.

DESIGN

Retrospective analyses of records of persons with TB infection who were prescribed preventive therapy for the period 1993-1996 inclusive, using simple descriptive statistics.

RESULTS

Preventive therapy was given to 411 persons after screening for TB due to on-arrival migrant surveillance (269), contact tracing (59), tuberculin surveys (59) and other reasons (24). Six-month isoniazid monotherapy (HMT) was prescribed for 403 and multidrug regimens for the remaining eight. Excepting 34 whose compliance was unknown, varying degrees of treatment non-adherence were found in 90 (24%) of the remaining 369 persons given HMT, including 36 (10%) with under five months of total medication. Minor adverse drug effects occurred in 32 (9%) subjects and contributed to the non-adherence in 23 of these. One person has since developed active TB.

CONCLUSIONS

Preventive therapy in Western Australia conformed to generally accepted guidelines. Varying degrees of non-adherence to HMT occurred in 24% of persons, but 90% completed adequate therapy under indirect supervision. Non-adherence is significantly related to adverse drug effects.

Differential display analysis of oxygen-mediated changes in gene expression in first trimester human trophoblast cells

Physiologic or pathologically induced periods of exposure to relatively low levels of oxygen during pregnancy affect the expression and function of certain genes in the placenta. In this study, the differential display technique was utilized to identify genes that are regulated in cultured cytotrophoblast cells by exposure to low levels of oxygen. Using this approach, four genes, which have been designated HRF-1, HRF-2, HRF-6, and HRF-8, were cloned and partially characterized. Northern blot analysis showed that clones HRF-1 and HRF-2 were downregulated in response to exposure to low levels of oxygen, whereas expression of HRF-6 and HRF-8 was increased. DNA sequencing and sequence analysis revealed that HRF-1 may represent an alternatively spliced or tissue-specific form of the Kruppel family zinc finger protein znfp104 gene. Clone HRF-2 showed a high degree of identity with exons 9, 10 and 11 of N33, a gene that is located within a homozygously deleted region of metastatic prostate cancer. Clones HRF-6 and HRF-8 did not exhibit significant sequence identity with known sequences in GenBank and may represent novel genes. None of these genes have previously been shown to be present in trophoblast cells, nor have their expressions been shown to be regulated by oxygen. This study demonstrates that the differential display technique is a novel and effective method to analyse oxygen-mediated changes in gene expression in trophoblast cells.

Chest radiography and tuberculosis case-finding in Western Australia

A retrospective study to assess the role of chest radiography (CR) in the control of tuberculosis (TB) in Western Australia (WA) was carried out by reviewing the annual reports from 1948 to 1983 and analysing the records at the Perth Chest Clinic (PCC) for a 12-month period in 1992-93. Mass miniature radiography in WA was introduced in 1948 and was selective up to 1951, yielding 3.3 cases of active TB per 10(3) films and accounting for 18.3% of the total notifications. It became a compulsory statewide screening procedure from 1952 to 1972. During this period the average yield was 0.7 cases/10(3) films and they accounted for 19.6% of the notifications. Thereafter the examination was again selective, detecting 0.2 cases/10(3) films and accounting for 2.7% of the notifications for 1977-79. From 1 July 1992 to 30 June 1993, a total of 2456 asymptomatic persons had chest X-ray records at the PCC relating to contact tracing (456), positive Mantoux reaction (330), pre-employment clearance as child-care workers (616) and application for permanent residence (1054). Overall, their X-rays were reported as normal in 95.4%, abnormal and of clinical significance in 2.7% and abnormal but of no significance in 1.9%. Active TB was detected in 0.2%, giving a yield of 2.4 cases/10(3) films and accounting for 10% of the notifications for the 12-month period. This study shows that mass CR, when judiciously applied, can contribute significantly to TB case-finding even in low-prevalence countries where the goal is the elimination of the disease.

Vitamin A and cancer prevention I: observations in workers previously exposed to asbestos at Wittenoom, Western Australia

Our aim was to describe a vitamin A-based cancer prevention program for former asbestos workers and to check for possible harmful effects by comparing rates of disease and death in study subjects with subjects who chose not to join. All subjects had been occupationally exposed to crocidolite at Wittenoom Gorge between 1943 and 1966; 1,677 subjects indicated interest in the program and 1,203 joined between June 1990 and May 1995. Comparison subjects consisted of 996 former workers known to be alive in Western Australia in 1990 who did not join the program. Program subjects were provided with annual supplies of vitamin A (either synthetic beta-carotene or retinol), help in quitting smoking and dietary advice. The comparison group received only mail contact. Both groups were followed up to December 1994 for vital status and cancer information, and rates of cancer and death from various causes were compared. Mortality in both groups was higher than expected (standardised mortality ratio 1.23 in program subjects and 1.67 in comparison subjects). After adjustment for age, smoking and asbestos exposure, the relative rates in participants compared with non-participants was below I for all examined cancers and causes of death. For mesothelioma and lung cancer, group differences increased with time from entry, whereas other differences dissipated with time. No significant side effects were reported. In conclusion, program participants had significantly lower mortality than non-participants, but the rates of the 2 groups converged with time.

Vitamin A and cancer prevention II: comparison of the effects of retinol and beta-carotene

Former blue asbestos workers known to be at high risk of asbestos-related diseases, particularly malignant mesothelioma and lung cancer, were enrolled in a chemo-prevention program using vitamin A. Our aims were to compare rates of disease and death in subjects randomly assigned to beta-carotene or retinol. Subjects were assigned randomly to take 30 mg/day beta-carotene (512 subjects) or 25,000 IU/day retinol (512 subjects) and followed up through death and cancer registries from the start of the study in June 1990 till May 1995. Comparison between groups was by Cox regression in both intention-to-treat analyses and efficacy analyses based on treatment actually taken. Median follow-up time was 232 weeks. Four cases of lung cancer and 3 cases of mesothelioma were observed in subjects randomised to retinol and 6 cases of lung cancer and 12 cases of mesothelioma in subjects randomised to beta-carotene. The relative rate of mesothelioma (the most common single cause of death in our study) for those on retinol compared with those on beta-carotene was 0.24 (95% CI 0.07-0.86). In the retinol group, there was also a significantly lower rate for death from all causes but a higher rate of ischaemic heart disease mortality. Similar results were found with efficacy analyses. Our results confirm other findings of a lack of any benefit from administration of large doses of synthetic beta-carotene. The finding of significantly lower rates of mesothelioma among subjects assigned to retinol requires further investigation.

Salt-sensitive hypertension in ANP knockout mice: potential role of abnormal plasma renin activity

Atrial natriuretic peptide (ANP), a peptide hormone produced by the heart, exerts a chronic hypotensive effect. Knockout mice with a homozygous disruption of the pro-ANP gene (-/-) are incapable of producing ANP and are hypertensive relative to their wild-type (+/+) siblings. Previous studies showed that arterial blood pressure (ABP) was further increased in conscious -/- mice kept for 2 wk on 2% salt, but not in anesthetized -/- mice after 1 wk on 8% salt. To determine whether inconsistencies in observed effects of salt on ABP of -/- mice are due to duration of increased salt intake and/or the state of consciousness of the animals, we measured ABP from an exteriorized carotid catheter during and after recovery from anesthesia with ketamine-xylazine in adult +/+ and -/- mice kept on low (LS; 0.008% NaCl)- or high (HS; 8% NaCl)-salt diets for 3-4 wk. Conscious ABP +/- SE (mmHg) of +/+ mice did not differ significantly on either diet (HS, 113 +/- 3; LS, 110 +/- 5). However, on HS diet -/- mice had significantly higher ABP (135 +/- 3; P < 0.001) than both -/- (115 +/- 2) and +/+ (110 +/- 5) mice on LS diet. Anesthesia decreased ABP in all groups, but the the genotype- and diet-related differences were preserved. Plasma renin activity (PRA, ng ANG I.ml-1.h-1) in blood collected at termination of experiment was appropriately different on the 2 diets in +/+ mice (HS, 4.9 +/- 1.9; LS, 21 +/- 2.8). However, PRA failed to decrease in -/- mice on HS diet (HS, 18 +/- 2.9; LS, 19 +/- 3.7). Independent of genotype, concentration of endothelin-1 (ET-1, pg/mg protein) and endothelial constitutive NOS (ecNOS, density/100 micrograms protein) was significantly elevated in kidneys of mice fed on HS diet (ET-1 -/-, 31 +/- 4.7 and +/+, 32 +/- 4.1; ecNOS -/-, 160 +/- 19 and +/+, 156 +/- 19) compared with mice fed on LS diet (ET-1 -/-, 19 +/- 1.9 and +/+, 21 +/- 1.8; ecNOS -/-, 109 +/- 13 and +/+, 112 +/- 18). We conclude that, regardless of the state of alertness, -/- mice develop salt-sensitive hypertension after prolonged feeding on HS, in part due to their inability to reduce PRA, whereas the specific renal upregulation of ecNOS and ET-1 in response to HS intake may be an ANP-independent adaptive adjustment aimed at improving kidney function and counteracting the pressor effect of salt.

Dopamine D2 receptor mediates both inhibitory and stimulatory actions on prolactin release

Dopamine is considered to be the major physiological tonic inhibitor of prolactin release, yet there is increasing evidence showing that it can also stimulate prolactin release from lactotrophs. In primary cultured lactotrophs, the major dopamine receptors responsible for inhibiting prolactin release are dopamine D2 receptors. A dopamine receptor subtype may be responsible for the stimulatory action, yet one cannot exclude the possibility that a dopamine D2 receptor can play dual roles. This study was therefore undertaken to investigate if dopamine both stimulates and inhibits prolactin secretion through activation of the same dopamine D2 receptor. GH4ZR7 cells, which have only one type of dopamine receptors--D2s, were perifused with different concentrations of dopamine, and the perifusate was assayed for prolactin; 10(-7) mol/L dopamine stimulated prolactin release (p < 0.05; n = 5), whereas 5 x 10(-4) mol/L dopamine inhibited prolactin secretion (p < 0.05; n = 5). In the pertussis toxin-treated cells, 10(-7) mol/L dopamine stimulated prolactin release (p < 0.05; n = 5), and 5 x 10(-4) mol/L dopamine did not significantly change the rate of prolactin release. These results indicate that both the stimulatory and inhibitory actions of dopamine are likely mediated by the same D2 receptor subtype, since GH4ZR7 cells express only D2s receptors. They also confirm that the inhibitory action of dopamine is mediated through a Gi protein; and the stimulatory action of dopamine is mediated through a PTX-insensitive pathway. These findings suggest that D2 receptors are coupled to both Gi and Gs proteins.

Cellular localization of gp46 at the human fetal-maternal interface

gp46 is a collagen-binding heat-shock glycoprotein with a possible role in the biosynthesis of collagen as well as in cell differentiation and fusion. In this study, the relative levels of gp46 protein and its mRNA transcript were examined, as well as the mRNA levels of collagen types I and IV in first trimester and term human placental tissues. Western blot analysis revealed substantially higher levels of gp46 in first trimester placentae than in term placentae. Similarly, elevated levels of type IV collagen transcript were detected in first trimester relative to term issues. Interestingly, the levels of gp46 and type I collagen mRNA remained unchanged. Immunohistochemical analysis of first trimester tissues demonstrated intense gp46 staining in mononucleated villous and extravillous cytotrophoblasts, decidual cells and in the villous connective tissue stroma. Syncytiotrophoblast in the same tissues also exhibited gp46 staining but at a reduced intensity. In chronic villi of term placentae, faint gp46 staining was only observed in the syncytiotrophoblast layer. However, as in the first trimester placentae, intense labelling was evident in the extravillous cytotrophoblasts and decidual cells of these tissues. These results suggest a developmental regulation of gp46 expression at the fetal-maternal interface during pregnancy and suggest a possible functional link between gp46 and collagen type IV. during gestation.

Heme oxygenase activity and immunohistochemical localization in bovine pulmonary artery and vein

Recent studies suggest that carbon monoxide (CO) derived from heme oxygenase (HO)-catalyzed metabolism of heme plays a role in the regulation of cell function and communication. In blood vessels, CO may regulate vascular smooth-muscle tone through the activation of soluble guanylyl cyclase, in a manner similar to that of nitric oxide. The objective of this study was to determine the relation between HO enzymatic activity and localization of HO protein in bovine pulmonary blood vessels. HO enzymatic activity was determined by quantitating the rate of CO formation in the microsomal fraction of homogenates of bovine pulmonary artery (BPA) and vein (BPV). HO protein was localized by immunohistochemical analysis of paraformaldehyde-fixed tissue by using polyclonal antibodies to inducible HO (HO-1) and noninducible HO (HO-2). HO enzymatic activity was measured in BPA and BPV, which correlated with the presence of HO protein. In BPA, HO enzymatic activity was found in the adventitia and medial layer; HO protein was localized in the nerves and vasa vasorum of the adventitia and was found throughout the smooth-muscle cells in the medial layer. The data clearly demonstrate the presence of HO enzymatic activity for the formation of CO in blood vessels that contain HO protein.

Successful pregnancies with the use of laminaria tents before embryo transfer for refractory cervical stenosis

OBJECTIVE

To determine whether laminaria tents are a safe and effective method of cervical dilatation in patients with a history of cervical stenosis and difficult ET.

DESIGN

Case reports describing two patients.

SETTING

Tertiary care, assisted reproduction practice.

PATIENT(S)

Two patients with cervical stenosis and a history of multiple failed cycles of IVF.

INTERVENTION(S)

Laminaria tents were placed intracervically before ET.

MAIN OUTCOME MEASURE(S)

Presence of a gestational sac and fetal heartbeat on ultrasound.

RESULT(S)

Successful clinical pregnancies occurred in both patients after laminaria placement and ET.

CONCLUSION(S)

Laminaria tent cervical dilatation appears to be a safe and effective option to assist ET in patients with a history of cervical stenosis.

Cloning, sequencing, and enzymatic activity of an inducible aldo-keto reductase from Chinese hamster ovary cells

Treatment of Chinese hamster ovary (CHO) cells by the aldehyde containing calpain inhibitor I resulted in the induction of a 35-kDa protein that was partially sequenced and shown to be a member of the aldo-keto reductase superfamily (Inoue, S., Sharma, R. C., Schimke, R. T., and Simoni, R. D. (1993) J. Biol. Chem. 268, 5894-5898). Using rapid amplification of cDNA ends polymerase chain reaction, we have sequenced the cDNA for this protein (CHO reductase). This enzyme is a new member of the aldo-keto reductase superfamily and shows greatest amino acid sequence identity to mouse fibroblast growth factor-regulated protein and mouse vas deferens protein (92 and 80% sequence identity, respectively). The enzyme exhibits about 70% sequence identity with the aldose reductases (ALR2; EC 1.1.1.21) and about 47% with the aldehyde reductases (ALR1; EC 1.1.1.2). Northern analysis showed that it is induced in preference to either ALR1 or ALR2 and RNase protection assays showed gene expression in bladder, testis, jejunum, and ovary in descending order of expression. The cDNA for this inducible reductase was cloned into the pET16b vector and expressed in BL21(DE3) cells. Expressed CHO reductase showed kinetic properties distinct from either ALR1 or ALR2 including the ability to metabolize ketones. This protein joins a growing number of inducible aldo-keto reductases that may play a role in cellular regulation and protection.

Dopamine causes ultrastructural changes in prolactin cells of tilapia (Oreochromis niloticus)

This study was undertaken to examine ultrastructural changes induced by dopamine in fish prolactin cells. Tilapia adenohypophyses were incubated with dopamine and evaluated by electron microscopy. The quantities of rough endoplasmic reticulum (RER) in prolactin cells increased and the number of secretory granules were decreased by dopamine (10(-6) mol/l) treatment. Another set of adenohypophysial tissues was placed back into control medium for 10 min following a 3 h incubation period with dopamine (10(-6) mol/l) (RE10 min group). This group had significantly less RER than the 3 h dopamine-treated tissue, and the shape of many granules in the RE10 min group changed from spherical to rod-like. In addition, some of the granule content appeared to diffuse out of granules since some were not fully surrounded by membrane. It was therefore hypothesized that the rod-shaped granules might be the result of prolactin secretion by diffusion.

Tissue distribution and immunohistochemical localization of the collagen-binding heat-shock protein gp46 in neonatal rats

Collagen-binding heat-shock proteins of M(r) 46-47 kDa have been postulated to function as putative molecular chaperones in the biosynthesis of collagen in several species. The rat homologue of this family of heat-shock proteins is called gp46. In the present study, we employed Western blotting and immunohistochemical methods to determine the tissue distribution and cellular localization of gp46 in the thoracic aorta, heart, kidney, liver and lung of eight-day-old Wistar rats. Highest levels of gp46 were detected in the thoracic aorta and lung, followed by the kidney and heart. Gp46 levels were low to undetectable by Western blot analysis in the liver. Immunohistochemistry revealed that gp46 labelling was observed almost exclusively in three distinct cell types: fibroblasts, muscle cells, and some epithelial cells. Gp46 was detected in the fibroblasts of the hepatic triad, in the interstitium of the alveolar wall and in the tunica adventitia of blood vessels in the majority of tissues examined, in atrial and ventricular cardiomyocytes, in vascular smooth muscle cells of the abluminal portion of the tunica media, in parietal epithelial cells and mesangial cells of the glomerulus, in epithelial cells of the distal tubules and collecting ducts in the kidney and clusters of immature renal tubules, in epithelial cells of the bile duct, and in mesodermal cells surrounding the liver. These results demonstrate that gp46 is present in collagen producing cells and cells undergoing rapid growth and development, suggesting that gp46 may play a significant role in these processes.

Mucinous biliary cystadenoma with mesenchymal stroma: expressions of CA 19-9 and carcinoembryonic antigen in serum and cystic fluid

A case of mucinous biliary cystadenoma with mesenchymal stroma (CMS tumor) in a 64-year-old woman is reported. The patient presented with acute abdominal pain and a palpable mass in the upper abdomen. Computed tomography and abdominal sonography showed characteristic multilocular cysts in the left lobe of the liver. Serum CA 19-9 was elevated to 108 U/ml with normal carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) levels. The levels of CA 19-9 and CEA in the cystic fluid were high at 7430 U/ml and 576 ng/ml, respectively. The serum CA 19-9 returned to 35 U/ml 4 weeks after tumor resection. These corresponding findings of both tumor markers in the serum and cystic fluid imply that (1) CA 19-9 and CEA both exist in the epithelial component of CMS tumors as evidenced by immunohistochemical stain, (2) serum CA 19-9 is a valuable marker in the diagnosis and monitoring of CMS, and (3) in cystic fluid, there are more significantly high levels of CA 19-9 in CMS compared with levels in simple cyst and polycystic liver disease. Therefore, measurement of CA 19-9 in cystic fluid and serum may be helpful in the differential diagnosis of hepatic cystic lesions.

Expression of atrial natriuretic peptide by third-trimester placental cytotrophoblasts in women

Atrial natriuretic peptide (ANP) is a vasoactive molecule with a potential role in modulating uteroplacental blood flow. We examined the expression of ANP in the third-trimester fetomaternal interface by immunohistochemistry performed on sections of placental tissue as well as by reverse transcriptase-polymerase chain reaction (RT-PCR) and RIA performed on isolated, purified term trophoblasts. Results from immunohistochemical studies on ten normal term placental samples revealed labeling of extravillous interstitial and cytotrophoblastic shell trophoblasts. The trophoblastic identity of the cells was determined by labeling of adjacent serial sections with anti-cytokeratin antibody. Labeling of decidual tissue was also observed in some samples (3 of 10 samples), whereas villous trophoblastic tissue showed no labeling. RT-PCR analysis of RNA extracted from isolated third-trimester trophoblasts revealed the presence of a 0.45-kb and band corresponding to ANP mRNA. Sequencing of the amplified cDNA confirmed its identity. RIA on lysates of isolated trophoblasts revealed the presence of ANP at a level of 41 pg +/- 8 pg/10(7) cells (n = 4; range = 16.8-50.4 pg/10(7) cells). These results indicate that placental cytotrophoblastic tissue is a source of ANP. This molecule might play a role in the regulation of uteroplacental and/or fetoplacental blood flow.