Lycopene treatment improves intrahepatic fibrosis and attenuates pathological angiogenesis in biliary cirrhotic rats

BACKGROUND

Liver cirrhosis is characterized by liver fibrosis and pathological angiogenesis, which results in hyperdynamic circulation, portal-systemic collateral vascular formation, and abnormal angiogenesis. Lycopene is a nutrient mostly found in tomatoes. The beneficial effects of lycopene include anti-inflammation, anti-oxidation, anti-fibrosis, and anti-angiogenesis; however, the association between liver cirrhosis and pathological angiogenesis has yet to be studied. This study aimed to investigate the effects of lycopene on biliary cirrhotic rats.

METHODS

The efficacy of lycopene treatment in common bile duct ligation (BDL)-induced biliary cirrhotic rats was evaluated. Sham-operated rats served as surgical controls. Lycopene (20 mg/kg/day, oral gavage) or vehicle was administered to BDL or sham-operated rats for 4 weeks, after which the hemodynamics, liver biochemistry, portal-systemic shunting, liver and mesenteric angiogenesis, and hepatic angiogenesis-related protein expressions were examined.

RESULTS

Lycopene alleviated hyperdynamic circulation as evidenced by decreased cardiac index and increased peripheral vascular resistance (p < 0.05), but it did not affect portal pressure or liver biochemistry in the BDL rats (p > 0.05). Lycopene significantly diminished the shunting degree of portal-systemic collaterals (p = 0.04) and mesenteric vascular density (p = 0.01), and also ameliorated intrahepatic angiogenesis and liver fibrosis. In addition, lycopene upregulated endothelial nitric oxide synthase, protein kinase B (Akt) and phosphatidylinositol 3-kinases (PI3K), and downregulated vascular endothelial growth factor receptor 2 (VEGFR-2) protein expressions (p < 0.05) in the livers of the BDL rats.

CONCLUSION

Lycopene ameliorated liver fibrosis, hyperdynamic circulation, and pathological angiogenesis in biliary cirrhotic rats, possibly through the modulation of intrahepatic Akt/PI3K/eNOS and VEGFR-2 pathways.

Modulation of aromatase expression in human breast tissue

Aromatase plays an important role in breast cancer development through its role in the synthesis of estrogen. Aromatase expression in breast tissue can be regulated by several mechanisms. The major promoter usage for aromatase expression in breast tumors (i.e. cAMP-stimulated promoters I.3 and II) is different from that in normal breast tissue (i.e. glucocorticoid-stimulated promoter I.4). Recent characterization of transcription factors that interact with the two important regulatory elements near promoters I.3 and II, i.e. S1 and CREaro, helps us better understand the mechanism of the switch of promoter usage between normal breast tissue and cancer tissue. It is thought that in normal breast tissue, the function of promoters I.3 and II is suppressed through the binding of EAR-2, COUP-TFI, and EARgamma to S1, and through the binding of Snail/Slug proteins to their binding site that quenchs the CREaro activity. In cancer tissue, the expression levels of EAR-2, COUP-TFI, EARgamma, Snail, and Slug decrease, and aromatase expression is then up regulated through the binding of ERRalpha-1 to S1 and the binding of CREB or related factors to CREaro. Results from this and other laboratories reveal that aromatase activity in aromatase expressing cells can also be modified by treatment with aromatase inhibitors and the antiestrogen ICI 182, 780. While aromatase inhibitors are used to treat breast cancer, the treatment has been found to increase the level of aromatase in the breast tissue of some patients. The enhancement of aromatase activity by aromatase inhibitors is thought to be due to a decrease of aromatase protein degradation by enzyme-inhibitor complex formation, up-regulation of the aromatase gene transcription through a cAMP-mediated mechanism, and an induction of aromatase expression by gonadtropins that are released from the pituitary in response to a reduction of estrogen levels in circulation in premenopausal women. Antiestrogen ICI 182, 780 has been found to suppress aromatase expression, but the mechanism has not yet been determined. In addition, aromatase activity and expression can be affected by environmental chemicals. A detailed structure-function study has revealed that flavones, but not isoflavones, are inhibitors of aromatase. It was found that flavones bind to the active site of aromatase in an orientation in which their rings-A and -C mimic rings-D and -C of the androgen substrate. The modulation of aromatase expression by endocrine disrupting chemicals is exemplified by two organochlorine pesticides (i.e. toxaphene and chlordane) that have been found to be antagonists of ERRalpha-1 orphan receptor. These compounds reduce ERRalpha-1 activity, resulting in a suppression of aromatase expression.

White button mushroom phytochemicals inhibit aromatase activity and breast cancer cell proliferation

Estrogen is a major factor in the development of breast cancer. In situ estrogen production by aromatase/estrogen synthetase in breast cancer plays a dominant role in tumor proliferation. Because natural compounds such as flavones and isoflavones have been shown to be inhibitors of aromatase, it is thought that vegetables that contain these phytochemicals can inhibit aromatase activity and suppress breast cancer cell proliferation. Heat-stable extracts were prepared from vegetables and screened for their ability to inhibit aromatase activity in a human placental microsome assay. The white button mushroom (species Agaricus bisporus) suppressed aromatase activity dose dependently. Enzyme kinetics demonstrated mixed inhibition, suggesting the presence of multiple inhibitors or more than one inhibitory mechanism. "In cell" aromatase activity and cell proliferation were measured using MCF-7aro, an aromatase-transfected breast cancer cell line. Phytochemicals in the mushroom aqueous extract inhibited aromatase activity and proliferation of MCF-7aro cells. These results suggest that diets high in mushrooms may modulate the aromatase activity and function in chemoprevention in postmenopausal women by reducing the in situ production of estrogen.

Evaluation of the mechanism of aromatase cytochrome P450. A site-directed mutagenesis study

Aromatase (CYP19) catalyzes three consecutive hydroxylation reactions converting C19 androgens to aromatic C18 estrogenic steroids. In this study, five human aromatase mutants (E302D, S478A, S478T, H480K, and H480Q) were prepared using a mammalian cell expression system. These mutants were evaluated by enzyme kinetic analysis, inhibitory profile studies, and reaction intermediate measurements. Three steroidal inhibitors [4-hydroxyandrostenedione (4-OHA), 7alpha-(4'-amino)phenylthio-1,4-androstandiene-3,17-dione (7alpha-APTADD), and bridge (2,19-methyleneoxy) androstene-3,17-dione (MDL 101003)], and four nonsteroidal inhibitors [aminoglutethimide (AG), CGS 20267, ICI D1033, and vorozole (R83842)] were used in the inhibitory profile studies. Our computer model of aromatase suggests that Glu302 is situated in the conserved I-helix region and located near the C-19 position of the steroid substrate. The model was supported by significant changes in kinetic parameters and a sevenfold increase in the Ki value of MDL 101,003 for the mutant E302D. As S478A was found to have kinetic properties similar to the wild-type enzyme and a much higher activity than S478T, Ser478 is thought to be situated in a rather restricted environment. There was a 10-fold increase in the Ki value of 7alpha-APTADD for S478T over that for the wild-type enzyme, suggesting that Ser478 might be near the C-7 position of the substrate. The reaction intermediate analysis revealed that significantly more 19-ol intermediate was generated by both S478A and S478T than the wild-type enzyme. These results would support a hypothesis that Ser478 plays a role in the first and second hydroxylation reactions. A positive charged amino acid is preferred at position 480 as shown by the fact that H480K has a significantly higher activity than H480Q. The Ki value of 4-OHA for H480Q was found to be three times that of the wild-type enzyme. In addition, significantly more 19-ol and 19-al intermediates were detected for both mutants H480K and H480Q than for the wild-type enzyme. Evaluation of the two mutations at His480 allows us to propose that this residue may participate in the aromatization reaction (the third step) by acting as a hydrogen bond donor for the C-3 keto group of the substrate. Furthermore, new products were generated when the enzyme was mutated at Ser478 and His480. Thus, these two residues must play an important role in the catalysis and are likely closer to the substrate binding site than previously predicted.

Catalytic differences between porcine blastocyst and placental aromatase isozymes

Two isozymes of porcine aromatase, the placental and the blastocyst forms, were expressed in CHO cells using the mammalian cell transfection method. Using an 'in-cell' assay (a 3H-water release method), catalytic parameters of the porcine placental aromatase were found to be very similar to those of the human enzyme; however, the activity of the blastocyst isozyme was found to be one-thirtieth that of the placental isozyme. Product isolation assay (using testosterone as the substrate) revealed that the major steroid products were 17beta-estradiol and 19-nortestosterone. The product ratio of estradiol/19-nortestosterone was found to be 94 : 6 for the porcine placental form, 6 : 94 for the porcine blastocyst form, and 92 : 8 for the human wild-type aromatase. Therefore, the porcine blastocyst aromatase isozyme catalyzes mainly androgen 19-desmethylation rather than aromatization. In addition, inhibition profile analyses on the placental and blastocyst isozymes were performed using three steroidal inhibitors [4-hydroxyandro-stenedione (4-OHA), 7alpha-(4'-amino)phenylthio-1, 4-androstandiene-3,17-dione (7alpha-APTADD), and bridge (2, 19-methyleneoxy) androstene-3,17-dione (MDL 101,003)], and four nonsteroidal inhibitors [aminoglutethimide (AG), CGS 20267, ICI D1033, and vorozole (R83842)]. While the two isozymes of porcine aromatase share 93% amino-acid sequence identity, our results indicate that the two porcine aromatase isozymes have distinct responses to various aromatase inhibitors.

Prognosis in presumptive hypoxic-ischemic coma in nonneurologic trauma

BACKGROUND

The neurologic outcome of comatose patients has a wide variation from complete reawakening to death. Methods of predicting the outcome of coma caused by either head injury or cardiac arrest have been the subject of much discussion in the literature. However, prediction of neurologic prognosis in comatose trauma patients without head injury has rarely been discussed. We reviewed our experience in treating patients with presumptive hypoxic-ischemic coma after trauma and tried to identify factors relating to their neurologic outcomes.

METHODS

Thirty-six patients with normal brain computed tomographic scans, who remained comatose 10 minutes after stabilization of their hemodynamic status, were studied. Serial motor response, verbal response, pupillary light reflex, presence of spontaneous breathing and seizure, and blood glucose level were recorded to evaluate their roles in predicting neurologic outcomes.

RESULTS

There were five deaths (mortality rate, 14%) and 11 patients (31%) with neurologic deficits. An absence of spontaneous breathing, a blood glucose level greater than 300 mg/dL during resuscitation, and a presence of seizure signified a poor prognosis. Initial neurologic evaluation at 10 minutes after stabilization of hemodynamic status was not accurate in predicting outcome. A motor response worse than withdrawal from painful stimuli at 24 hours after injury and an absence of pupillary light reflex at 48 hours after injury predicted a poor neurologic outcome, with a 100% accuracy rate.

CONCLUSION

Hypoxic-ischemic coma in patients sustaining major trauma yielded a significantly better survival and neurologic outcome than that induced by cardiac arrest or head injury. Decision-making in the first 24 hours after injury should not be affected by the patient's neurologic status at that time. A motor response worse than withdrawal at 24 hours after injury and an absence of pupillary light reflex at 48 hours after injury predicted a poor neurologic outcome.

Small bowel perforation: is urgent surgery necessary?

BACKGROUND

Controversies regarding how urgent bowel perforation should be diagnosed and treated exist in recent reports. The approach for early diagnosis is also debatable. The purposes of this study were to evaluate the relationship between treatment delay and outcome of small bowel perforation after blunt abdominal trauma and to determine the best assessment plan for the diagnosis of this injury.

METHODS

One hundred eleven consecutive patients with small bowel perforations caused by blunt abdominal trauma were retrospectively reviewed. The patients were divided into four groups according to the time interval between injury and surgery. Hospital stay, time to resume oral intake, and mortality and morbidity rates were compared between groups. Physical signs, laboratory and computed tomographic findings, and the results of diagnostic peritoneal lavage were analyzed to find the most sensitive and specific test for early diagnosis of small bowel perforation.

RESULTS

Delay in surgery for more than 24 hours did not significantly increase the mortality with modern method of treatment; however, complications increased dramatically. Hospital stay and time to resume oral intake increased significantly when surgery was delayed for more than 24 hours. Abdominal tenderness was a common finding, but it was not specific for bowel perforation. Only 40% of the computed tomographic scans were diagnostic for bowel perforations: 50% of them showed suggestive signs, and 10% were considered as negative. Persistence of abdominal signs indicated peritoneal lavage. By using cell count ratio in diagnostic peritoneal lavage and/or increased lavage amylase activity, presence of particulate matter and/or bacteria in the lavage fluid, all patients with intraperitoneal bowel perforation were diagnosed accurately before operation.

CONCLUSION

Small bowel perforation has low mortality and complication rates if it is treated earlier than 24 hours after injury. The principle of "rushing to the operation suite" for a stable blunt abdominal trauma patients without detailed systemic examination is not justified. The priority of treatment for the small bowel perforation should be lower than the limb-threatening injuries. Diagnostic peritoneal lavage provides high sensitivity and specificity rates for the diagnosis of small bowel perforation if a specially designed positive criterion is applied.

Breast tumor aromatase: functional role and transcriptional regulation

Aromatase has been shown to be expressed at a higher level in human breast cancer tissue than in normal breast tissue, by means of enzyme activity measurement, immunocytochemistry, and RT-PCR analysis. Cell culture including MCF-7 breast cancer cells, animal experiments using aromatase-transfected breast cancer cells, and transgenic mouse studies have demonstrated that estrogen production in situ plays a more important role than circulating estrogens in breast tumor promotion. In addition, tumor aromatase is believed to be able to stimulate breast cancer growth through both autocrine and paracrine pathways, as demonstrated by a three-dimensional cell culture study. RT-PCR and gene transcriptional studies have revealed that the aromatase promoter is switched from a glucocorticoid-stimulated promoter, I.4, in normal tissue to cAMP-stimulated promoters, I.3 and II, in cancerous tissue. Recently, we identified and characterized a cAMP-responsive element (CREaro) upstream from promoter I.3 by DNA deletion and mutational analyses. Our results from promoter functional analysis also demonstrated an interaction between the CREaro and the silencer element (S1) that was identified previously in our laboratory. In the presence of cAMP, the positive regulatory CREaro can overcome the action of the silencer on the function of promoter I.3. On the basis of results generated from our own and other laboratories, we propose that, in normal breast adipose stromal cells and fibroblasts, aromatase expression is driven by promoter I.4 (glucocorticoid dependent), and that the action of promoters I.3 and II is suppressed by the silencer negative regulatory element. However, in cancer cells and surrounding adipose stromal cells, the cAMP level increases, and aromatase promoters are switched to cAMP-dependent promoters - I.3 and II. Furthermore, we applied the yeast one-hybrid screening method to search for proteins interacting with the silencer element, S1. The major protein identified was ERRalpha-1; however, SF-1, which is present in the ovary, is not detected in breast cancer tissue. Using a reporter plasmid with the aromatase genomic fragment containing promoter I.3 and S1, in breast cancer SK-BR-3 cells, ERRalpha-1 was found to have a positive regulatory function. It is believed that the silencer element in the human aromatase gene may function differently in different tissues, as a result of distinct expression patterns of transcription factors.

Functional characterization of 102-amino acid-deleted form of human aromatase (delta102-aromatase)

A truncate form of human aromatase cDNA that corresponds to the recently identified rat cortical type aromatase mRNA variant (Yamada-Mouri et al., J. Steroid Biochem. Molec. Biol., 60: 325-329, 1997) has been generated, and the amino-terminus deleted form of the enzyme has been expressed in CHO cells. The resulting product lacking 102 residues from the N-terminus of aromatase (i.e. 102-aromatase) showed an extremely low enzyme activity using an 'In-cell' assay. A strong aromatase activity, however, was observed for the delta102-aromatase using an in vitro method on the solublized preparations. The in vitro activity was dependent on both incubation time and NADPH concentration as well as inclusion of NADPH-cytochrome P450 reductase in the assay mixture. The average turnover rate of aromatization of the reconstituted delta102-aromatase was 6.8 min(-1). The results of the immunosuppression assay suggested that delta102-aromatase still holds the epitope interactive to MAb3-2C2, a monoclonal antibody raised agaist human placental aromatase P450. Furthermore, the IC50 values of MAb3-2C2 were determined to be 24 and 23 microg/ml for the whole homogenate and the 105,000 x g precipitate fractions prepared from the truncated aromatase expressing cells, respectively, whereas an IC50 of 1.3 microg/ml was shown for the full-length human aromatase. These results indicate that the delta102-aromatase P450 can be expressed and is catalytically competent as the full-length enzyme, but the epitope structure for the monoclonal antibody MAb3-2C2 is altered from that of the native enzyme. In addition, the intracellular distribution of delta102-aromatase may be different from that of the wild-type enzyme, explaining why very low activity was measured using an 'In-cell' assay.

Induction of aromatase expression by aminoglutethimide, an aromatase inhibitor that is used to treat breast cancer in postmenopausal women

Aromatase, a cytochrome P450, catalyzes three consecutive hydroxylation reactions converting C19 androgens to aromatic C18 estrogenic steroids. Aminoglutethimide (AG) is an aromatase inhibitor used to treat estrogen-dependent breast cancer. While AG is effective in inhibiting aromatase, it was found that aromatase activity in tumors of some breast cancer patients elevated after AG treatment (Miller and O'Neill, Steroids, 50: 245-252, 1987). These results may explain why some patients failed therapy after extensive AG treatment. Recently, we found that AG treatment increased aromatase activity in SK-BR-3, JAR, and HepG2 cell lines in a dose- and incubation time-dependent manner. AG induction is thought to occur at the transcriptional level because the aromatase mRNA level elevated after AG treatment in SK-BR-3 and HepG2 cells, as demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) analysis, and AG treatment did not increase aromatase activity in aromatase cDNA transfected cell lines (driven by the beta-actin promoter). Our primer-specific RT-PCR analysis revealed that in SK-BR-3 cells, AG enhanced the action of a promoter which is different from promoter I.1, I.3, or II. Furthermore, since the AG induction was found to be suppressed by SQ 22536, an adenylate cyclase inhibitor, a cAMP-dependent mechanism might be involved. Our study provides an insight as to why some patients fail therapy after extensive AG treatment.

Retroperitoneal laparostomy: an effective treatment of extensive intractable retroperitoneal abscess after blunt duodenal trauma

BACKGROUND

Delay in surgical treatment and duodenal wound dehiscence are two major causes of extensive retroperitoneal abscess formation after blunt duodenal injury. This complication is traditionally treated with primary repair of the duodenal wound and drainage of the abscess through anterior laparotomy. Pyloric exclusion is sometimes added as an adjunctive procedure. The anterior approach, however, may result in inadequate drainage, and repeat surgery is sometimes needed. We reviewed our experiences and evaluated the effectiveness of retroperitoneal laparostomy for the treatment of retroperitoneal abscess with continuous soiling.

METHODS

There were 52 blunt duodenal injuries during a 7-year period. Eleven patients developed extensive retroperitoneal abscesses.

RESULTS

All 11 patients were treated with anterior laparotomy initially. Five patients recovered after this procedure. Six patients continued to have retroperitoneal abscesses and were under septic status. Two patients received another anterior drainage, and had recurrent abscesses later. Retroperitoneal laparostomy was performed for these six patients. After retroperitoneal laparostomy, daily wound care, and antibiotic treatment, all six patients recovered. Only two patients developed incisional hernia.

CONCLUSION

Retroperitoneal laparostomy is effective in treating extensive intractable retroperitoneal abscess after blunt duodenal injury. Patients with the complications of duodenal leak and extensive retroperitoneal abscess should be treated with pyloric exclusion and drainage through anterior laparotomy first. If the duodenal wound does not heal after pyloric exclusion and retroperitoneal abscess persists, retroperitoneal laparostomy should be performed without further attempt to repair the wound.

Pooling of contrast material on computed tomography mandates aggressive management of blunt hepatic injury

BACKGROUND

Nonoperative management of blunt hepatic injury is currently a widely accepted treatment modality. Computed tomography (CT) is an important imaging study both for diagnosis and follow-up of these patients. There is, however, no reliable predictor of failure of nonoperative treatment other than the ultimate development of hemodynamic instability. Previous reports mostly were based on the data obtained from low-speed dynamic incremental scanners. The purpose of this study is to evaluate the value of a high-speed helical scanner in predicting the outcome of patients managed nonoperatively.

METHODS

During a 30-month period, 194 patients with blunt hepatic injury were treated, 150 of them were hemodynamically stable after initial resuscitation and underwent abdominal CT examination. All CT scans were performed with the High Speed Advantage Scanner. The CT scans and medical records were reviewed.

RESULTS

Nonoperative management was successfully applied to all patients with grade I and II, 93% of grade III, 87% of grade IV, and 67% of grade V liver injuries. Twelve patients required liver-related celiotomy. Pooling of contrast material was detected on the CT scans of 8 patients. Six (75%) of these patients developed hemodynamic instability and required liver-related celiotomy later. Pooling of contrast material can be detected in 50% of the patients receiving liver-related celiotomy.

CONCLUSION

The presence of pooling of contrast material within the hepatic parenchyma indicates free extravasation of blood as a result of active bleeding. In patients with blunt hepatic injury, if this sign is detected, nonoperative treatment should be terminated and angiography or celiotomy undertaken promptly. With the increasing use of high-speed spiral CT scanner and improvement in scanning technique, pooling of contrast material may become a sensitive sign for active bleeding and may be used as a guide for the selection of treatment modality.

Selective application of laparoscopy and fibrin glue in the failure of nonoperative management of blunt hepatic trauma

BACKGROUND

Most blunt hepatic trauma patients can be managed nonoperatively. The current failure rate in adult blunt hepatic trauma is reportedly 0 to 19%. We wished to evaluate the applicability of laparoscopy and fibrin glue as a minimally invasive alternative to laparotomy in these unsuccessfully nonoperative cases.

METHODS

All adult patients with blunt hepatic trauma managed nonoperatively at Linkou, Chang Gung Memorial Hospital Medical Center, Taipei, Taiwan, over a 2-year period from July 1, 1994, to June 30, 1996, were eligible for the study. A laparoscopic examination was performed on those who failed conservative care before undertaking an exploratory laparotomy. Fibrin glue was sprayed over the wound surface if ongoing hemorrhage was evident from any liver laceration. The clinical data, operative and laparoscopic findings, operative methods, and outcomes of these patients were studied.

RESULTS

Of the 61 patients, 55 patients were successfully treated without operation. Of the six failures (10%) all were liver related. After the introduction of laparoscopy, the nontherapeutic laparotomy rate would have decreased from 100% (6 of 6) to 50% (3 of 6), and with the adjunctive use of fibrin glue, the laparotomy rate went down to 0% (0 of 6). There were no deaths among the six patients receiving laparoscopy and fibrin glues; and only one developed a liver abscess, for a morbidity rate of 17% (1 of 6).

CONCLUSIONS

The selective use of laparoscopy and fibrin glue can effectively reduce the nontherapeutic laparotomy rate among blunt hepatic trauma patients who fail nonoperative management.

Molecular basis of the inhibition of human aromatase (estrogen synthetase) by flavone and isoflavone phytoestrogens: A site-directed mutagenesis study

Flavone and isoflavone phytoestrogens are plant chemicals and are known to be competitive inhibitors of cytochrome P450 aromatase with respect to the androgen substrate. Aromatase is the enzyme that converts androgen to estrogen; therefore, these plant chemicals are thought to be capable of modifying the estrogen level in women. In this study, the inhibition profiles of four flavones [chrysin (5, 7-dihydroxyflavone), 7,8-dihydroxyflavone, baicalein (5,6,7-trihydroxyflavone), and galangin (3,5,7-trihydroxyflavone)], two isoflavones [genistein (4,5,7-trihydroxyisoflavone) and biochanin A (5,7-dihydroxy-4-methoxyisoflavone)], one flavanone [naringenin (4, 5,7-trihydroxyflavanone)], and one naphthoflavone (alpha-naphthoflavone) on the wild-type and six human aromatase mutants (I133Y, P308F, D309A, T310S, I395F, and I474Y) were determined. In combination with computer modeling, the binding characteristics and the structure requirement for flavone and isoflavone phytoestrogens to inhibit human aromatase were obtained. These compounds were found to bind to the active site of aromatase in an orientation in which rings A and C mimic rings D and C of the androgen substrate, respectively. This study also provides a molecular basis as to why isoflavones are significantly poorer inhibitors of aromatase than flavones.

Binding characteristics of aromatase inhibitors and phytoestrogens to human aromatase

We have evaluated the binding characteristics of three steroidal inhibitors [4-hydroxyandrostenedione (4-OHA), 7alpha-(4'-amino)phenylthio-1,4-androstadiene-3,17-dione (7alpha-APTADD), and bridge (2,19-methyleneoxy) androstene-3,17-dione (MDL 101,003)], four nonsteroidal inhibitors [aminoglutethimide (AG), CGS 20267, ICI D1033, and vorozole (R83842)], and two flavone phytoestrogens (chrysin, and 7,8-dihydroxyflavone) to aromatase through a combination of computer modeling and inhibitory profile studies on the wild-type and six aromatase mutants (I133Y, P308F, D309A, T310S, I395F, and I474Y). We have generated two aromatase models based on the x-ray structures of cytochrome P450-cam and cytochrome P450bm3, respectively. A major difference between the cytochrome P450cam-based and cytochrome P450bm3-based models is in the predicted lengths of helices F and G. In the cytochrome P450cam-based model, helices F and G lie antiparallel and extend across the active-site face of the molecule from one edge to the center, so that the carboxyl-terminal residues of helix F and the N-terminal residues of helix G make a major contribution to the structure of the active site. In the cytochrome P450bm3-based model, both helices are longer and so extend almost all the way across the active-site face of the molecule. Considering the size of the androgen substrate, we evaluated our results mainly based on the cytochrome P450cam model. The mutations involved in this study are thought to be at or near the proposed active site pocket. The inhibitory profile analysis has produced very interesting results and provided a molecular basis as to how seven aromatase inhibitors with different structures bind to the active site of aromatase. Furthermore, the investigation reveals that phytoestrogens bind to the active site of aromatase in a different orientation from that in the estrogen receptor.

Binding characteristics of seven inhibitors of human aromatase: a site-directed mutagenesis study

Aromatase, a cytochrome P450, catalyzes three consecutive hydroxylation reactions converting C19 androgens to aromatic C18 estrogenic steroids. In this study, eight human aromatase mutants (I133Y, I133W, F235L, I395F, I474Y, I474W, I474M, and I474N) were prepared to evaluate the active site and a proposed hydrophobic pocket of the enzyme that exists in an aromatase model based on the X-ray structure of cytochrome P450cam. In addition, the binding characteristics of three steroidal inhibitors [4-hydroxyandrostenedione, 7alpha-(4'-amino)phenylthio-1,4-androstandiene-3,17-dione, and bridge (2,19-methyleneoxy)androstene-3,17-dione (MDL 101,003)] and four nonsteroidal inhibitors [aminoglutethimide, CGS 20267, ICI D1033, and vorozole (R83842)] were investigated through inhibitory profile studies on the eight new and three previously generated mutants (P308F, D309A, and T310S). The latter analyses have provided a molecular basis regarding how seven aromatase inhibitors with different structures bind to the active site of aromatase.

Purification and structural characterization of porcine L-threonine dehydrogenase

L-Threonine dehydrogenase was purified 10,000-fold to a specific activity approximately 300 mumol.min-1.mg-1 protein from porcine liver mitochondria. Purification to apparent homogeneity was achieved by sequential chromatography on DEAE Sepharose FF, Affi-Gel Blue, Sephacryl S-200, Matrex Gel Red A, and Matrex Gel Green A. The subunit molecular mass was estimated as 37 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, while an apparent native molecular mass of 73 kDa was shown by gel filtration chromatography, suggesting a dimeric structure. The purified enzyme was subjected to proteolytic degradation and the resulting peptides were isolated exclusively by reverse-phase high-performance liquid chromatography. Approximately 70% of the total sequence was obtained and the N-terminal amino acid sequence of the intact polypeptide chain was thus tentatively extended to residue 40.

Effect of 16,16-dimethyl prostaglandin E2 on lipidic organelles of rat gastric surface mucous cells

BACKGROUND

We examined the effect of 16,16-dimethyl prostaglandin E2 (dmPGE2) on the subcellular distribution of phospholipids in rat gastric surface mucous cells (SMCs) using the cytochemical stain, iodoplatinate (IP).

METHODS

The volume of a number of subcellular organelles and the density of IP reactivity within these organelles was determined by modified vertical section stereology.

RESULTS

The volume occupied by most of the subcellular organelles was not affected by dmPGE2 treatment, with the exception that the volume fraction of two classes of large infranuclear inclusion bodies (LIIB1 and LIIB2, organelles we have previously shown to contain hydrophobic lipids), were significantly expanded by a factor of 3-4-fold. The distribution of IP reactivity among the various subcellular compartments appeared to undergo a shift in response to dmPGE2 treatment. Once again the major prostanoid effect was seen in the infranuclear inclusion bodies, as the volume density of IP reactivity was increased 2-24-fold in LIIB1 and 9-10-fold in LIIB2 in comparison to control values.

CONCLUSION

dmPGE2 administration to rats induces an increase in the volume and IP reactivity of a family of lipid-containing organelles, which may underlie its ability to increase the hydrophobic surface properties of the stomach.

Integration of a curved hybrid waveguide lens and photodetector array in a GaAs waveguide

For the first time, we believe, the integration of a waveguide lens and a photodetector array in GaAs for operation at a 1.3-microm wavelength is reported. The waveguide lens is a newly devised curved hybrid Fresnel/Bragg chirp grating lens fabricated by the ion-million technique. Desirable performance characteristics, including high throughput efficiency, freedom from coma (up to +/-4 deg off axis), and a near-diffraction-limited focal-spot size, have been demonstrated with this curved hybrid lens. The 10-element photodetector array of the InGaAs photoconducting type shows a measured gain-bandwidth product that is higher than 1 GHz at high frequency, while at a lower frequency the gain is in the range of several thousands. The curved-hybrid-lens-photodetector array combination realized in the GaAs 5 x 13 mm(2) in size has produced a well-resolved element spacing of 10 microm with cross talk that is lower than -14 dB. This lens-photodetector array combination constitutes a basc structure for the realization of monolit ic acousto-optic and electro-optic circuits such as integrated-optic rf spectrum analyzers and multiport switches.

Use of fluorescent hydrophobic dyes in establishing the presence of lipids in the gastric mucus gel layer

The hydrophobic property of crude samples of canine and porcine mucus was demonstrated by its binding and reactivity with two fluorescent dyes, 1-anilinonaphthalene-8-sulfonic acid (ANS) and 1,6-diphenyl-1,3,5-hexatriene (DPH). The contribution of lipids to these hydrophobic binding sites was indicated by our observations that the DPH-induced fluorescence of both porcine and canine gastric mucus was reduced greater than 75% after lipid extraction. Fluorescence microscopy revealed an extracellular band of intense reactivity in association with the mucus gel layer overlying the rat gastric mucosa that was abolished if the frozen sections were pretreated with lipid solvents. When rats pretreated with indomethacin were injected with a cytoprotective dose of 16,16-dimethyl-PGE2, there was an increase in fluorescence of the gastric perfusate treated with ANS, suggesting that hydrophobic factors, perhaps lipids, were being secreted in association with mucus. These extracellular lipids may play an important role in conferring protective barrier properties to the mucus gel layer.

Endothelin stimulates cardiac alpha- and beta- myosin heavy chain gene expression

The effect of endothelin-1 on cardiac myosin heavy chain gene expression was examined using an isolated neonatal rat myocardial cell culture system. The effects of endothelin-1 on the expression of alpha- and beta- myosin heavy chain genes in the primary rat myocardial cell culture system were examined by S1 nuclease protection analysis. Endothelin-1 was found to stimulate both alpha- and beta- myosin heavy chain gene expression. The 5' flanking regions of both the alpha- and beta- myosin heavy chain gene promoters ligated to a reporter gene, chloramphenicol acetyltransferase, were used to study the effect of endothelin-1 on transcription. Myocardial cells treated with endothelin-1 increased the transcription rate of alpha- and beta- myosin heavy chain genes in a dose-dependent manner. Thus, the hypertrophic effect of endothelin-1 on cardiac myocytes involves augmentation of alpha- and beta- myosin heavy chain gene expression by increasing gene transcription.

Phospholipid- and neutral lipid-containing organelles of rat gastroduodenal mucous cells. Possible origin of the hydrophobic mucosal lining

In this study, an attempt was made to localize the cell types and subcellular organelles that synthesize and secrete surface-active lipids from the rat gastroduodenal mucosa. Two fluorescent hydrophobic probes--Nile Red and 1-anilinonaphthalene-8-sulfonic acid--and a phospholipid-selective cytochemical stain--iodoplatinate--were used for fluorescence and electron microscopic studies, respectively. The results showed the presence of phospholipid and neutral lipid fluorescent hot spots in the mucous cells of both the gastric mucosa and the submucosal Brunner's glands of the duodenum. In contrast, other cell types of the stomach (parietal, chief, and endocrine cells) or the duodenum (goblet cells and villous and crypt enterocytes) were either unreactive or weakly stained with the dyes. Ultrastructurally, two classes of large infranuclear inclusion bodies were observed in these two types of mucous cells. The location and size of these inclusion bodies appeared to be in agreement with the position and size of the large hydrophobic fluorescent hot spots detected at the light microscopic level. The ultrastructural appearance, localization, and histochemical staining pattern of these lipid-containing organelles suggest that they are specific for these cell types and not a general feature of degenerative epithelium undergoing lysosome-induced autolysis. It was concluded that the mucous cells of both the stomach and the Brunner's glands contain a subcellular organelle that stores hydrophobic material constituting both neutral lipids and phospholipids. These lipidic substances may be secreted into the gastroduodenal mucous gel and provide its surface with a nonwettable lining to repel luminal acid.

Effects of 16,16-dimethyl prostaglandin E2 on glycoprotein and lipid synthesis of gastric epithelial cells grown in a primary culture

We investigated the biosynthesis of phospholipid, neutral lipids, glycoproteins, and DNA in primary cultures of rat oxyntic mucosal cells. In addition, responses of these biosynthetic pathways to the gastric protective agent 16,16-dimethyl prostaglandin E2 (dmPGE2) were studied. Cultured gastric cells under control conditions synthesized glycoprotein in a linear manner over time. The cells responded to dmPGE2 with an increase in glycoprotein synthesis without an effect on DNA synthesis. Investigations of lipid synthesis showed that phospholipid was produced in a linear fashion by these cells, however, no effect of exogenously administered dmPGE2 on its rate of formation was discernible. In contrast, the incorporation of labeled palmitate into neutral lipids revealed that triglyceride biosynthesis was significantly increased by the addition of dmPGE2 to the culture medium, which could be further enhanced by the administration of the phosphodiesterase inhibitor, isobutyl methyl xanthine. Cyclic nucleotide involvement was further suggested by our finding that triglyceride synthesis in cultured gastric mucous cells could be increased a comparable amount by the addition of both dbcAMP and dbcGMP to the medium. The possible relationship between these biochemical alterations and the gastric protective action of dmPGE2 is discussed.

Gastric protective activity of mixtures of saturated polar and neutral lipids in rats

It has been shown that intragastric treatment of rats with a suspension of dipalmitoylphosphatidylcholine and tripalmitin at a 1:4 ratio (5 mg lipid/mL per rat) provided rats with highly efficaceous and consistent protection against a variety of ulcerogenic agents and conditions. The gastric protective activity of this mixture was of long duration (t 1/2 approximately 9 hours. In an attempt to understand the mechanism of protection, it was determined that the ulcerogen-induced reduction in gastric surface hydrophobicity was reversed in rats pretreated with the mixture. However, the lipid mixture did not affect the gastric emptying rate and maintained its cytoprotective activity in indomethacin-treated rats. These results indicate that the mixture's protective effect was not mediated by alterations in either gastrointestinal motility or the gastric accumulation of lipids or "cytoprotective" metabolites (prostaglandins). The mixture also appreciably reduced gastric lesion score in response to acid if one or both the lipids was substituted for a metabolically inert ether analogue, suggesting that lipid metabolism makes a negligible contribution to the protective response. Electron microscopic observation indicated that the predominent structure in the mixture is a microemulsion in which a dipalmitoylphosphatidylcholine monolayer encapsulates a tripalmitin core. Last, the improved gastric protective activity of the mixture in comparison to dipalmitoylphosphatidylcholine liposomes is discussed regarding marked differences in the physical structure of the two suspensions and the rate at which lipids in these states adsorb to a surface to enhance its hydrophobic properties.

A method to preserve extracellular surfactant-like phospholipids on the luminal surface of rodent gastric mucosa

Previous results from our laboratory employing the phospholipid-selective cytochemical stain iodoplatinate (IP) suggest that surfactant-like phospholipids (SLPL) are intracellularly contained within rodent gastric mucous cells and are occasionally seen extracellularly within the mucous gel layer. This hydrophobic lipid coating may provide the stomach with a protective water-repellent lining against the corrosive gastric juice in the lumen. Extracellular SLPL are frequently removed during tissue processing for electron microscopy. In this study, we developed a simple method employing an agarose-embedding technique to retain these extracellular SLPL in gastric mucosa excised from rats pre-treated with prostaglandin (to stimulate gastric surfactant/mucus secretion). With the help of polypropylene supporting screens and cassette carriers, thin slices of agarose-embedded gastric mucosa were well preserved and uniformly stained with IP. Extracellular myelin figures were well retained over the interfoveolar surface as well as in the pit region. The IP-reactive substances were seen within or coating the surface of the mucous gel. Our results also indicate that agarose is useful not only for supporting soft tissue while preparing sections with a microslicer but also for preservation of extracellular lipoidal material for electron microscopic observation.

Morphological effects of aspirin and prostaglandin on the canine gastric mucosal surface. Analysis with a phospholipid-selective cytochemical stain

An iodoplatinate technique that selectively stains phospholipid was used to evaluate morphologically the effects of aspirin and 16,16-dimethyl prostaglandin E2 on canine gastric mucosa in an in vitro Ussing chamber system. The association between these morphological alterations and the changes in mucosal surface hydrophobicity as determined by contact angle analysis was also investigated. Prostaglandin (1 microgram/ml) did not alter aspirin-induced cell injury, although it reduced (45%) the detachment of damaged cells from the lamina propria. Mucus release appeared to be stimulated independently both by aspirin and prostaglandin treatment and by the blotting and drying procedure routinely performed before contact angle analysis. When an extracellular mucus gel coat was present, it contained numerous iodoplatinate-reactive vesicles and myelinated or lamellated structures. Iodoplatinate-reactive substances also appeared at the luminal surface of the mucus gel as a filamentous band. This band of reactivity was frequently seen after simultaneous treatment with prostaglandin and aspirin but only sporadically observed after aspirin treatment alone. The hydrophobic nature of the canine gastric mucosa under the above experimental conditions correlated well (r = 0.743, p less than 0.005) with the percentage of mucosal surface covered by this filamentous band, and less so with the density of iodoplatinate-reactive structures within the mucus gel. We conclude that phospholipid structures in the mucus gel may account for the hydrophobic nature of the gastric mucosal surface and the ability of damaging and "cytoprotective" agents to influence both surface wettability and barrier integrity.

Luminal surface hydrophobicity of canine gastric mucosa is dependent on a surface mucous gel

The contribution of the surface mucous gel to the stomach's hydrophobic luminal properties and how these properties are affected by both damaging and cytoprotective agents were studied. Canine gastric mucosa, determined to be hydrophobic in nature by contact angle analysis, had an adherent periodic acid-Schiff-reactive mucous gel layer over 85% of its luminal surface, as observed under light microscopy. Extracellular structures reactive with the phospholipid-selective stain, iodoplatinate, were observed ultrastructurally in these tissues, within and at the luminal interface of the surface mucous gel. Incubating the luminal surface of gastric mucosa mounted in Ussing chambers in acidified aspirin promoted the exfoliation of surface epithelium and markedly reduced surface hydrophobicity, surface periodic acid-Schiff reactivity, and transmucosal potential difference. Addition of 16,16-dimethyl prostaglandin E2 to the nutrient compartment of these chambers maintained surface hydrophobicity at control levels but did not prevent aspirin-induced reductions in potential difference or cellular damage to the surface epithelium. However, prostaglandin did attenuate exfoliation of aspirin-damaged surface mucous cells and preserved the surface mucous gel. These results indicate that the stomach's hydrophobic lining is closely associated with the presence of a surface mucous gel layer, is not an effective barrier to the penetration of lipid-soluble damaging agents such as acidified aspirin, and is maintained by exogenous prostaglandin as is the mucous gel layer, even in the presence of luminal aspirin. The ability of prostaglandin to maintain a hydrophobic mucous gel layer over compromised tissue may, in part, explain its ability to limit aspirin-induced injury and promote the recovery and restitution of the surface epithelium.

Volume and pressure during transient added resistance

Total respiratory resistance (Rrs) can be computed from measurements of flow before and during a brief period of added resistance. This "added resistance' method does not require measurement of total driving pressure (Pt). One of the assumptions of this method is that the change in Pt (delta Pt) is negligible during the time of increased resistance. To evaluate this assumption we measured both the volume exhaled during a brief imposition of an external resistor, and the total respiratory compliance (Crs) of 7 healthy volunteers. The mean volume exhaled was 18.6 ml, and the mean Crs was 88 ml/cm H2O. The volume exhaled divided by Crs gives the change in total static elastic recoil pressure (delta Pel, rs), which is one component of delta Pt. The mean delta Pel, rs was 0.22 cm H2O. Since the pressure exerted by contraction of inspiratory muscles (Pmus,I) opposes Pel, rs, we also estimated delta Pmus,I and subtracted it from delta Pel, rs to obtain delta Pt. The computed mean delta Pt during the time of added resistance was 0.045 cm H2O. This value is quite small in relation to Pt during a spontaneous expiration at rest. We also studied 13 subjects with Chronic Obstructive Pulmonary Disease and found no significant effect of transient added resistance on intraesophageal pressure. We conclude that the assumption of negligible delta Pt should not prevent the added resistance method from being very useful, particularly when simplicity of equipment and testing procedure are important.

Determination of total respiratory resistance in health and disease by added external resistance

Previous studies have indicated that total respiratory resistance (Rrs) can be measured by addition of an external resistor. In an earlier study, the apparatus used to accomplish this included a multiperforated steel plate. In this study, we sought to improve the device. Details of this are given in this article. With this device, resistance was found to be reproducible over five consecutive days, and was sensitive to the increase in airway resistance induced by head and neck flexion. We also report on a comparison between this method and a commercially available device that works on the "interruptor" principle. There was no significant difference in either mean or variance of resistance between the two methods. The instrumentation required for the newly designed method is minimal, and its operation is simple. Furthermore, the measurement can be performed without invasive procedures during tidal breathing.

Localization of phospholipid-rich zones in rat gastric mucosa: possible origin of a protective hydrophobic luminal lining

Mammalian gastric mucosa is unusually hydrophobic or nonwettable, which may be an essential biophysical characteristic of the gastric mucosal barrier. Since this property may be attributable to an adsorbed layer of surface-active phospholipids (SAPL), we investigated the distribution of SAPL in rat oxyntic mucosa. Ferric hematoxylin (FH) and iodoplatinate (IP), selective histochemical stains for phospholipids (as confirmed by spot tests), were used to detect SAPL in frozen sections and aldehyde-fixed tissue, respectively. Using FH staining in conjunction with extraction procedures that either solvate or preserve SAPL, we determined that positive reactivity was the greatest in the apical third of the oxyntic mucosa between the glandular neck region and the surface. IP reactivity appeared to parallel the FH staining pattern. Mucous cells, especially the surface epithelial cells, were heavily stained. Electron microscopic examination revealed that these cells contain inclusion bodies associated with various subcellular organelles, e.g., nuclear envelope, endoplasmic reticulum, Golgi apparatus and its vesicles, and mucous secretory granules. Vesicles and myelin figures, which resembled those found in lung surfactant, were observed extracellularly in close association with the surface mucous cells. Our findings suggest that mucous cells are actively involved in synthesis and storage of SAPL, which may be an essential component of the stomach's protective hydrophobic lining.