Etiology of preoperative anemia in patients undergoing scheduled cardiac surgery

PURPOSE

Ten percent of our cardiac surgical patients have preoperative anemia. Anemia diagnosed before scheduled cardiac surgery is a strong predictor of the need for homologous blood transfusion (RBC) perioperatively but the cause of this preoperative anemia is not known. The purpose of this study was to evaluate the etiology of preoperative anemia.

METHODS

Seventy-five consecutive anemic cardiosurgical patients (Hb = < 120 g x L(-1) the day before surgery) were studied prospectively. All had multiple diagnostic blood tests done in the preoperative period to diagnose the cause of the anemia and subsequently underwent non-emergency cardiac surgery. Anesthesia and RBC transfusion were standardized according to the protocol. Data in respect to operation, RBC and other blood product transfusion during operation and hospital stay were recorded.

RESULTS

Hospital-acquired anemia was present in 37.3% of anemic patients (hemoglobin decrease during hospitalization before surgery > or =9 g x l(-1)). The second most common diagnosis was iron deficiency anemia (29.3% patients) followed by anemia of chronic renal disease (10.7% patients). When coronary angiography was performed close to operation time, patients had a higher decrease in hemoglobin concentration during hospitalization --suggesting that blood loss during angiography was, in part, responsible for anemia. Seventy-five percent of anemic patients were transfused with RBC perioperatively compared with our overall transfusion rate of 30% of cardiac surgery patients.

CONCLUSIONS

In the majority of patients, preoperative anemia is potentially preventable. Investigation and treatment of anemia before cardiac surgery should be a priority in preparing the patient for surgery.

Expression and translocation of Rac2 in eosinophils during superoxide generation

Eosinophils induce tissue injury by releasing granule-associated cytotoxic proteins, lipid mediators and superoxide anions in response to appropriate stimuli. Superoxide generation associated with respiratory burst is largely dependent on the assembly of the NADPH oxidase complex in the membrane, consisting of membrane-bound cytochrome b558 and translocated p47phox and p67phox. The activation of this complex is critically dependent on the translocation of GTP-bound Rac1, or its homologue Rac2, from the cytosol to the membrane in neutrophils. Rac expression has not yet been fully characterized in eosinophils. We proposed that eosinophils translate and express Rac2 and its GDP-dissociation inhibitor, RhoGDI. Furthermore, we hypothesized that Rac2 translocates along with p47phox and p67phox proteins from the cytosol to the plasma membrane during respiratory burst. By reverse transcription-polymerase chain reaction analysis and sequencing of the amplified product, guinea-pig eosinophils were found to express Rac2 mRNA, exhibiting 93% homology with the human Rac2 sequence. Rac1 mRNA was also detected in eosinophils but not its translated product. In contrast, Rac2 protein expression was detected using a specific antibody. In subcellular fractions, Rac2 was found to translocate, along with p47phox and p67phox, from cytosol to plasma membrane-associated fractions following phorbol myristate acetate stimulation, while RhoGDI remained within cytosolic fractions. These findings suggest that Rac2 is preferentially expressed and activated in eosinophils, and is likely to be a crucial regulator of the release of reactive oxygen species from these cells during inflammatory reactions.

[The diagnostic and therapeutic value of flexible bronchoscopy in foreign-body aspiration misdiagnosed as other respiratory diseases]

To explore the causes of missed diagnosis of foreign-body aspiration and summarize the experiences on the diagnostic and therapeutic use of flexible bronchoscopy (FB) in these patients. Twelve cases of foreign-body aspiration misdiagnosed as other respiratory diseases, confirmed by FB examination were analyzed. All of these patients had no histories of foreign-body aspiration, and no foreign-body shadows were found on their chest films. But there were atelectasis, hilar enlargement and obstructive pneumonia found on the films. Among the patients in this group, 7 cases were misdiagnosed as lung cancer, 2 cases of pneumonia and asthma each, and 1 case as tuberculosis. The diagnoses of all the 12 cases were confirmed by FB examinations. The foreign-bodies of the 11 cases were successfully grasped and taken out through the FB. This suggests that FB should be of great diagnostic and therapeutic value in patients with foreign-body aspiration misdiagnosed as other respiratory diseases.

Vascular endothelial growth factor in pleural fluid

STUDY OBJECTIVES

The purpose of this study was to analyze the relationship of the pleural fluid vascular endothelial growth factor (VEGF) level with the diagnostic category and with the pleural fluid characteristics in a group of 70 patients.

DESIGN

The VEGF levels of consecutive patients undergoing therapeutic thoracentesis were determined with an enzyme-linked immunosorbent assay.

SETTING

University-affiliated tertiary care center.

RESULTS

The median level of pleural fluid VEGF in the patients with congestive heart failure (150 pg/mL) was significantly (p < 0.05) lower than the median level in the patients with coronary artery bypass grafting (357 pg/mL), which in turn was significantly lower (p < 0.05) than the median levels in the patients with malignancy (1,097 pg/mL). The overlap between groups, however, limits the diagnostic usefulness of pleural fluid VEGF levels. The VEGF level was most closely correlated with the lactate dehydrogenase level (r = 0.42, p < 0.001) and was also significantly correlated with the total pleural fluid protein level. The median VEGF levels in the pleural fluid of patients with breast cancer were significantly lower (p = 0.017) than in those with lung cancer. The VEGF level was very high (3,294 pg/mL) in the one patient with pulmonary embolism.

CONCLUSIONS

We conclude that the VEGF levels in pleural fluid differ significantly from one diagnostic category to another with the highest median levels occurring in patients with malignant pleural effusions. We speculate that VEGF may be responsible for the pleural fluid accumulation in at least some situations.

Human acyl-CoA:cholesterol acyltransferase-1 in the endoplasmic reticulum contains seven transmembrane domains

Acyl-CoA:cholesterol acyltransferase (ACAT) plays important roles in cellular cholesterol homeostasis and is involved in atherosclerosis. ACAT-1 protein is located mainly in the ER. The hydropathy plot suggests that ACAT-1 protein contains multiple transmembrane segments. We inserted either the hemagglutinin tag or the HisT7 tag at various hydrophilic regions within the human ACAT-1 protein and used immunofluorescence microscopy to determine the topography of the tagged proteins expressed in mutant Chinese hamster ovary cells lacking endogenous ACAT. All of the tagged proteins are located mainly in the ER and retain full or partial enzyme activities. None of the tagged proteins produces detectable intracellular degradation intermediates. Treating cells with digitonin at 5 micrograms/ml permeabilizes the plasma membranes while leaving the ER membranes sealed; in contrast, treating cells with 0.25% Triton X-100 or with cold methanol permeabilizes both the plasma membranes and the ER membranes. After appropriate permeabilization, double immunostaining using antibodies against the N-terminal region and against the inserted tag were used to visualize various regions of the tagged protein. The results show that human ACAT-1 in the ER contains seven transmembrane domains.

Autocatalytic processing of site-1 protease removes propeptide and permits cleavage of sterol regulatory element-binding proteins

Site-1 protease (S1P) is a subtilisin-related protease that cleaves sterol regulatory element-binding proteins (SREBPs) in the endoplasmic reticulum lumen, thereby initiating a process by which the transcriptionally active NH(2)-terminal fragments of SREBPs are released from membranes. In the current experiments, we transfected cDNAs encoding epitope-tagged hamster S1P into HEK-293 cells or mutant hamster cells that lack S1P. Protease protection assays showed that the bulk of S1P is in the endoplasmic reticulum lumen, anchored by a COOH-terminal membrane-spanning segment. Cleavage of the NH(2)-terminal signal sequence of S1P generates S1P-A (amino acids 23-1052), which is inactive. The protein is self-activated by an intramolecular cleavage at Site-B, generating S1P-B (amino acids 138-1052) and liberating a 115-amino acid propeptide that is secreted intact into the medium. The sequence at Site-B is RSLK, which differs from the RSVL sequence at the cleavage site in SREBP-2. S1P-B is further cleaved at an internal RRLL sequence to yield S1P-C (amino acids 187-1052). Mutational analysis suggests that S1P-B and S1P-C are both active in cleaving SREBP-2 in a fashion that requires SREBP cleavage-activating protein. The activity of S1P-C may be short-lived because it appears to be transported to the Golgi, a site at which SREBP-2 cleavage may not normally occur. These data provide the initial description of the processing of a subtilisin-related protease that controls the level of cholesterol in blood and cells. In an accompanying paper (Cheng, D., Espenshade, P. J., Slaughter, C. A., Jaen, J. C., Brown, M. S., and Goldstein, J. L. (1999), J. Biol. Chem., 274, 22805-22812), we develop an in vitro assay to characterize the activity of purified recombinant S1P.

Secreted site-1 protease cleaves peptides corresponding to luminal loop of sterol regulatory element-binding proteins

We describe a permanent line of Chinese hamster ovary cells transfected with a cDNA encoding a truncated form of Site-1 protease (S1P) that is secreted into the culture medium in an enzymatically active form. S1P, a subtilisin-like protease, normally cleaves the luminal loop of sterol regulatory element-binding proteins (SREBPs). This cleavage initiates the two-step proteolytic process by which the NH(2)-terminal domains of SREBPs are released from cell membranes for translocation to the nucleus, where they activate transcription of genes involved in the biosynthesis and uptake of cholesterol and fatty acids. Truncated S1P (amino acids 1-983), produced by the transfected Chinese hamster ovary cells, lacks the COOH-terminal membrane anchor. Like native S1P, this truncated protein undergoes normal autocatalytic processing after residue 137 to release an NH(2)-terminal propeptide, thereby generating an active form, designated S1P-B. Prior to secretion, truncated S1P-B, like native S1P-B, is cleaved further after residue 186 to generate S1P-C, which is the only form that appears in the culture medium. The secreted enzyme, designated S1P(983)-C, cleaves a synthetic peptide that terminates in a 7-amino-4-methyl-coumarin fluorochrome. This peptide, RSLK-MCA, corresponds to the internal propeptide cleavage site that generates S1P-B as described in the accompanying paper (Espenshade, P. J., Cheng, D., Goldstein, J. L., and Brown, M. S. (1999), J. Biol. Chem. 274, 22795-22804). The secreted enzyme does not cleave RSVL-MCA, a peptide corresponding to the physiologic cleavage site in SREBP-2. However, S1P(983)-C does cleave after this leucine when the RSVL sequence is contained within a 16-residue peptide corresponding to the central portion of the SREBP-2 luminal loop. The catalytic activity of S1P(983)-C differs from that of furin/prohormone convertases, two related proteases, in its more alkaline pH optimum (pH 7-8), its relative resistance to calcium chelating agents, and its ability to cleave after lysine or leucine rather than arginine. These data provide direct biochemical evidence that S1P is the protease that cleaves SREBPs and thereby functions to control lipid biosynthesis and uptake in animal cells.

Wide local excision (WLE) for vaginal intraepithelial neoplasia (VAIN)

BACKGROUND

To assess the use of wide local excision in the treatment of VAIN.

METHODS

A retrospective review on 40 WLE procedures for VAIN.

RESULTS

The mean age was 60 years. Thirty-six (90%) patients had previous treatment for genital tract cancer or pre-cancer. The median duration and blood loss during operation was 45 minutes and 50 mls respectively. Fifteen complications affected 11 patients. Only one of five patients with 'vaginal cancer' was diagnosed prior to WLE. Of the 35 patients treated for VAIN 3, 12 (34%) developed abnormal cytology during follow up three had residual VAIN 3, five had recurrent VAIN 3 and four had invasive cancer diagnosed. The remaining 23 (66%) patients were disease free at a median follow up of 44 months.

CONCLUSIONS

Ablative therapy for VAIN 3 is unsafe as occult invasive foci can be missed by biopsy. WLE is efficacious in treating high grade VAIN 3. Long term surveillance of the lower genital tract is needed to diagnose metachronous lesions.

[Demonstration for periodicity of leptospirosis in Yichang City of Hubei Province during 1960-1997]

OBJECTIVE

To study the periodicity of leptospirosis incidence.

METHODS

Data of leptospirosis epidemics in Yichang City collected during the past 38 years from 1960 to 1997 were analyzed with periodic graphics method.

RESULTS

Cause-specific incidence rate of leptospirosis was 15.43 per 100,000 in average, with an epidemic interval of 10 years, with statistical significance in periodic vibration (J = 4.179, P < 0.05).

CONCLUSION

The results mentioned above provided scientific basis for the effective control and prevention of the disease.

[The identification of banding chromosomes by computer image analysis]

The analysis system for banding chromosomes (SYSTEM), an image analysis software, was programmed. By the SYSTEM the photos of Chinese G banding chromosomes were analyzed. It showed that the karyotype of the chromosomes of persons was recorded in high speed and efficiency, and that the chromosomes of alike ordinal number from different persons could be compared directly. That would presage, by this kind of the high effective operation, a favorable condition was created for the application of the polymorphism of the chromosomes to the parentage diagnosis.

Large pleural effusions occurring after coronary artery bypass grafting. Cardiovascular Surgery Associates, PC

BACKGROUND

Large pleural effusions sometimes occur after coronary artery bypass grafting (CABG), but their characteristics and clinical course are largely unknown.

OBJECTIVE

To describe the clinical course and pleural fluid findings in patients with large pleural effusions occurring after CABG.

DESIGN

Retrospective case series.

SETTING

Tertiary care, university-affiliated, nonprofit teaching hospital.

PATIENTS

3707 patients who had CABG between 1 February 1996 and 1 August 1997.

MEASUREMENTS

Chest radiographs were reviewed, and information on pleural fluid findings, pleural effusion treatment, and cardiac surgery was obtained from medical records and a cardiac surgery database.

RESULTS

Pleural effusions that occupied more than 25% of the hemithorax were found in 29 patients (0.78%). Seven of the effusions were attributed to congestive heart failure, 2 were attributed to pericarditis, and 1 was attributed to pulmonary embolism. The explanation for the remaining 19 effusions was unclear. All but 2 effusions were predominantly left-sided. Of these 19 effusions, 8 were bloody and 11 were nonbloody. Bloody effusions usually occurred earlier, contained higher lactic acid dehydrogenase levels, and were frequently eosinophilic. Nonbloody effusions tended to be more difficult to manage.

CONCLUSIONS

Large pleural effusions may develop in a small proportion of patients after CABG. The cause of many of these effusions is unclear. Most bloody effusions can be managed with one to three therapeutic thoracenteses. Resolution of nonbloody effusions may require anti-inflammatory agents, tube thoracostomy, or intrapleural injection of sclerosing agents.

[The change of plasma level of endothelin-1 in patients with cor pulmonale and the effects of Captopril]

The purpose of this study was to investigate the role of endothelin(ET) in the development of cor pulmonale and the mechanism of captopril in treatment. The plasma ET-1 levels of 36 patients with cor pulmonale and 20 normal subjects were measured by radioimmunoassay. Twenty patients were treated with antibiotics and oxygen, and the other 16 patients were treated with antibiotics, oxygen and captopril for 14 days. The results showed that the ET-1 level of patients with cor pulmonale (88.9 +/- 8.9 ng/L) was significantly higher than that of normal control (53.5 +/- 5.1 ng/L). After treatment, the ET-1 level declined significantly in both groups of patients (P < 0.01); the ET-1 level in patients treated with captopril was lower than that in patients not treated with captopril (P < 0.05), but the level of ET-1 in patients was still higher than that of normal control (P < 0.05). These suggest that ET-1 may play an important role in the onset of cor pulmonale and captopril can reduce the ET-1 level.

Mitomycin chemotherapeutic pleurodesis to palliate malignant pleural effusions secondary to gynecological cancer

BACKGROUND

To assess the efficacy of mitomycin pleurodesis in women with end stage malignant effusion.

METHODS

Retrospective analysis.

RESULTS

Of the 13 patients treated six had ovarian, six had endometrial and one had cervical adenocarcinoma. The median time of onset of effusion from diagnosis of primary disease was 12 months (range 1-75). Ten patients were evaluable for response. The median age of the patients was 59 years (range 42 to 74). Ten (77%) of them had repeated thoracocentesis prior to mitomycin pleurodesis. The median duration and volume of drainage was 4 days (range 2-11) and 3.1 liters (range 1.2-10.2) respectively. One of two patients developed a pneumothorax and required the insertion of an additional chest drain. Overall, seven patients (70%) responded - one completely (CR) and six partially (PR), while three did not respond. Four of five patients with ovarian cancer had a partial response, two of four patients with endometrial cancer (one CR and one PR) responded. The only patient with cervical cancer had a partial response. Nine patients (69%) had enough symptomatic improvement to be discharged home. The drug cost of bleomycin 60 units (US$191), another commonly used agent, was more than twice as expensive as mitomycin 30 mg (US$84).

CONCLUSIONS

Mitomycin pleurodesis can palliate 70% of patients for at least 1 month. It offers cheap and effective palliation. There is a suggestion that patients' quality of life is improved.

SNARE complex proteins, including the cognate pair VAMP-2 and syntaxin-4, are expressed in cultured oligodendrocytes

Myelin membrane synthesis in the CNS by oligodendrocytes (OLs) involves directed intracellular transport and targeting of copious amounts of specialized lipids and proteins over a relatively short time span. As in other plasma membrane-directed fusion, this process is expected to use specific trafficking and vesicle fusion proteins characteristic of the SNARE model. We have investigated the developmental expression of SNARE proteins in highly enriched primary cultures of OLs at discrete stages of differentiation. VAMP-2/synaptobrevin-2, syntaxin-2 and -4, nsec-1/munc-18-1, Rab3a, synaptophysin, and synapsin were expressed. During differentiation, expression of the vesicular SNARE VAMP-2, the small GTP-binding protein Rab3a, and the target SNARE syntaxin-4 were up-regulated. VAMP-2 and Rab3 proteins detected immunocytochemically in cultured OLs were localized within the developing process network; in situ anti-VAMP-2 antibody stained the perikarya of rows of cells with the distribution and appearance of OLs. We discuss the potential involvement of SNARE complex proteins in a plasma membrane-directed transport mechanism targeting nascent myelin vesicles to the forming myelin sheath.

Activation of acyl-CoA cholesterol acyltransferase: redistribution in microsomal fragments of cholesterol and its facilitated movement by methyl-beta-cyclodextrin

Acyl-CoA cholesterol acyltransferase (ACAT) (EC 2.3.1.26) in the yolk sac membrane of chicken eggs plays an important role in the transport of lipids, which serve as both structural components and as an energy source during embryogenesis. ACAT from the yolk sac membrane of chicken eggs 16 d after fertilization has higher activity and better stability than its mammalian liver counterpart. During our study of the avian enzyme, ACAT was found to be activated up to twofold during storage at 4 degrees C. The activation was investigated, and data suggest that redistribution of cholesterol within microsomal vesicles leads to the increase. Methyl-beta-cyclodextrin (MbetaCD) increases activation an additional twofold, possibly by facilitating the movement of cholesterol within microsomal fragments and allowing redistribution of cholesterol in lipid bilayers to a greater extent. Treatment of microsomes with MbetaCD removes cholesterol from the membranes. Controlled amounts of cholesterol can be restored to the membranes by mixing them with cholesterol-phosphatidylcholine liposomes in the presence of MbetaCD. Under these conditions, the plot of ACAT vs. cholesterol mole fraction in the liposomes is sigmoidal. The finding that MbetaCD can enhance cholesterol transfer between liposomes and microsomes and reduce the limitation of slow movement of nonpolar molecules in aqueous media should make cyclodextrins more useful in in vitro studies of apolar molecule transport between membrane vesicles.

[The change of plasma level of endothelin in patients with acute attack of asthma]

In order to assess the interaction of endothelin (ET) and acute attack of asthma, the plasma levels of ET in 23 patients with acute attack of asthma and 12 normal controls were measured by radioimmunoassay. The partial pressure of oxygen in arterial blood (PaO2) and peak flow (PEF) were measured synchronously. The results showed that the plasma ET level in asthmatic patients (89.2 +/- 8.4 ng/L) was much higher than that in normal controls (52.2 +/- 6.5 ng/L), P < 0.001. There was a significant negative correlation between the plasma level of ET and the PaO2 (r = -0.7893, P < 0.01) or PEF (r = -0.7124, P < 0.01). The results suggest that ET may play a role in acute attack of asthma, and its level may stand for the degree of the disease.

In vitro resistance to thrombin-induced platelet microbicidal protein among clinical bacteremic isolates of Staphylococcus aureus correlates with an endovascular infectious source

Platelet microbicidal proteins (PMPs), small cationic peptides released at sites of endovascular damage, kill common bloodstream pathogens in vitro. Our group previously showed that in vitro resistance of clinical staphylococcal and viridans group streptococcal bacteremic strains to PMPs correlated with the diagnosis of infective endocarditis (IE) (Wu et al., Antimicrob. Agents Chemother. 38:729-732, 1994). However, that study was limited by (i) the small number of Staphylococcus aureus isolates from IE patients, (ii) the retrospective nature of the case definitions, and (iii) the diverse geographic sources of strains. The present study evaluated the in vitro PMP susceptibility phenotype of a large number of staphylococcemic isolates (n = 60), collected at a single medical center and categorized by defined and validated clinical criteria. A significantly higher proportion of staphylococcemic strains from patients with IE was PMP resistant in vitro than the proportion of strains from patients with soft tissue sepsis (83% and 33%, respectively; P < 0.01). Moreover, the levels of PMP resistance (mean percent survival of strains after 2-h exposure to PMP in vitro) were significantly higher for isolates from patients with IE and with vascular catheter sepsis than for strains from patients with abscess sepsis (P < 0.005 and P < 0.01, respectively). These data further support the concept that bloodstream pathogens that exhibit innate or acquired PMP resistance have a survival advantage with respect to either the induction or progression of endovascular infections.

[Inhibition of potassium channel by chronic hypoxia on pulmonary artery smooth muscle cells in rats]

OBJECTIVE

To explore the possible effect of potassium channel in chronic hypoxic pulmonary hypertension.

METHOD

Male Wistar rats were placed in the identical normobaric or hypoxic environmental chamber. In one chamber, rats were maintained in 10% +/- 0.5% O2(by displacement with N2) for 3 weeks, whereas in the other, rats were maintained in air. The single smooth muscle cell was isolated from pulmonary artery (phi 200-700 microns) of Wistar rats with acute enzymatic digestion method. Using patch-clamp technique, we recorded the outward K+ currents in pulmonary artery smooth muscle cells and identified a Ca2+.ATP activated K+ channel (K+Ca-ATP) and a delayed rectifier K+ channel among the outward K+ currents. We compared the activities of Ca2+.ATP activated K+ channel (K+Ca-ATP) or delayed rectifier K+ channel in smooth muscle cells isolated from pulmonary artery of chronic hypoxic and normoxic rats.

RESULT

The activities of Ca2+.ATP activated K+ channel (K+Ca-ATP) and delayed rectifier K+ channel in chronic hypoxic group are much lower than that in normal group (T test, P < 0.01). Cromakalim (10 mmol) caused a marked enhancement of activity of the reduced K+Ca-ATP but not the delayed rectifier K+ channel in rats of hypoxic group.

CONCLUSION

The persistent decrease of potassium channel activity may contribute to setting the development of chronic hypoxic pulmonary hypertension. Cromakalim, one of potassium channel openers, can decrease the pulmonary hypertension induced by chronic hypoxia and may be a new effective drug for treatment of hypoxic pulmonary hypertension.

Isolation of cholesterol-requiring mutant Chinese hamster ovary cells with defects in cleavage of sterol regulatory element-binding proteins at site 1

The synthesis and uptake of cholesterol requires transcription factors designated sterol regulatory element-binding proteins (SREBPs). SREBPs are bound to membranes in a hairpin orientation with their transcriptionally active NH2-terminal segments facing the cytosol. The NH2-terminal segments are released from membranes by two-step proteolysis initiated by site 1 protease (S1P), which cleaves in the luminal loop between two membrane-spanning segments. Next, site 2 protease (S2P) releases the NH2-terminal fragment of SREBP. The S2P gene was recently isolated by complementation cloning using Chinese hamster ovary cells that require cholesterol for growth, due to a mutation in the S2P gene. A similar approach cannot be used for S1P because all previous cholesterol auxotrophs manifest defects in S2P, which is encoded by a single copy gene. To circumvent this problem, in the current studies we transfected Chinese hamster ovary cells with the S2P cDNA, assuring multiple copies. We mutagenized the cells, selected for cholesterol auxotrophy, and identified two mutant cell lines (SRD-12A and -12B) that fail to cleave SREBPs at site 1. Complementation analysis demonstrated that the defects in both cell lines are recessive and noncomplementing, indicating a mutation in the same gene. These cells should now be useful for expression cloning of the sterol-regulated S1P gene.

Molecular identification of the sterol-regulated luminal protease that cleaves SREBPs and controls lipid composition of animal cells

The lipid composition of animal cells is controlled by SREBPs, transcription factors released from membranes by sterol-regulated proteolysis. Release is initiated by Site-1 protease (S1P), which cleaves SREBPs in the ER luminal loop between two membrane-spanning regions. To clone S1P, we prepared pCMV-PLAP-BP2, which encodes a fusion protein that contains placental alkaline phosphatase (PLAP) in the ER lumen flanked by cleavage sites for signal peptidase and S1P. In sterol-deprived cells, cleavage by both proteases leads to PLAP secretion. PLAP is not secreted by SRD-12B cells, cholesterol auxotrophs that lack S1P. We transfected SRD-12B cells with pCMV-PLAP-BP2 plus pools of CHO cDNAs and identified a cDNA that restores Site-1 cleavage and PLAP secretion. The cDNA encodes S1P, an intraluminal 1052-amino-acid membrane-bound subtilisin-like protease. We propose that S1P is the sterol-regulated protease that controls lipid metabolism in animal cells.

[Effect of tetrandrine on the collagen contents of lungs in rats with chronic hypoxia]

OBJECTIVE

To investigate the effect of tetrandrine (Tet) on the collagen contents of lung tissues in rats with chronic hypoxic pulmonary hypertension.

METHOD

Using colorimetric method after oxidized by chloramine T to determine hydroxyproline contents of lung tissues and extrapulmonary arteries, using Masson method, image pattern analysis technique and gray scale scanning to observe the changes of collagen distribution in extrapulmonary arteries and lung tissues in rats with hypoxia and the effect of treatment with Tet.

RESULT

Tet could remarkably reduce the mean pulmonary arterial pressure and pulmonary vascular resistance in rats with hypoxic pulmonary hypertension and could inhibit the increase of collagen contents in lung tissues and extrapulmonary arterial wall.

CONCLUSION

Tet may be used as one of the main drugs in the treatment of chronic hypoxic pulmonary hypertension due to its action of reducing mPAP and collagen contents.

[Changes of the gene expression of vascular endothelial growth factor in the lung of rats with chronic hypoxic pulmonary hypertension]

To observe the effect of chronic hypoxia on the gene expression of vascular endothelial growth factor (VEGF) in rat's lung, and the role of VEGF in the pathogenesis of hypoxic pulmonary hypertension, thirteen male Wistar rats were exposed to isobaric hypoxia for 3 weeks. The pulmonary artery pressure was measured by right cardiac catheterization. The serum level of VEGF was measured by Elisa. The VEGF cRNA was labeled with digoxigenin-UTP by in vitro transcription. The expression of VEGF mRNA in the lung was examined by hybridization in situ. The pulmonary artery pressure was significantly increased after hypoxic exposure. The serum level of VEGF in rats treated with hypoxia (420.3 +/- 73.1 pg/ml) was significantly increased in comparison with that of normal rats (322.2 +/- 58.1 pg/ml). The VEGF hybridization signals on the wall of pulmonary arteriole were significantly increased in rats with pulmonary hypertension. Chronic hypoxia can markedly increase expression of VEGF mRNA in the pulmonary arteriole and hence stimulate VEGF synthesis and secretion. The increase of VEGF may play a role in the developing process of hypoxic pulmonary hypertension.