Expression of IAP family proteins and its clinical importance in breast cancer patients

Inhibitor of apoptosis (IAP) family proteins is involved in mechanisms of resistance to apoptosis in various cancer cells. The aim of this study was to assess the expression of selected IAP proteins such as XIAP, cIAP-1, cIAP-2 and survivin in breast cancer patients and evaluates their relationship with the prognostic and predictive factors and their impact to overall survival (OS) and progression free survival (PFS). The study was conducted with the use of tissue samples prospectively collected from 92 previously untreated female breast cancer patients. The control encompassed 10 fibroadenoma patients. The expression of XIAP, cIAP-1, cIAP-2 and survivin was assessed using flow multicolor cytometry. XIAP expression was present in 99 % of the breast cancer patients (91/92) with the median expression 13.65% (range 1-66.8%). Expression of XIAP in breast cancer was significantly higher compared to the control group (p=0.006). Median expression of cIAP-1, cIAP-2 and survivin in the study group was 25.95% (range 0.8-83.7%), 16.7% (range 1-53.2%) and 4.6% (range 0-43%) respectively. In the rank Spearman test, strong correlations (p<0.001) were seen among the expressions of XIAP, cIAP-2 and survivin, in all combination. Additionally, week correlation between XIAP and cIAP-1 was observed (p=0.02). The median expression of XIAP and survivin was significantly higher in more advanced tumors (stages pT2/pT3 vs. pT1). The median PFS and OS in breast cancer group were 46.15 and 47.1 months respectively. No significant correlations were observed among expressions of IAP family proteins and survival. However, low expression of XIAP in breast cancer showed trend to longer PFS (p=0.08). XIAP, cIAP-1 cIAP-2 and survivin participate in antiapoptotic mechanisms in breast cancer and XIAP and survivin seem to have the most significant prognostic importance. Further studies are needed to establish more complete prognostic and predictive values of IAP family proteins in breast cancer patients.

Membrane expression of the death ligand trail receptors DR4 and DR5 in the normal endometrium, endometrial atypical hyperplasia and endometrioid endometrial cancer

To assess membrane expression of DR4 and DR5 in the normal endometrium (NE), endometrial atypical hyperplasia (EAH) and endometrioid endometrial cancer (EEC), the study examined 101 patients: 20 NE, 14 EAH and 67 EEC. The expression of DR4 and DR5 was examined and presented as the total score (TS). DR4 expression was seen in 18 NE, 11 EAH and 10 EEC. DR5 expression was seen in 20 NE, 13 EAH and 21 EEC. A strong correlation between type of endometrial tissue and TS of both receptors was identified. In EEC TS of DR4 and DR5 was not related to grading, staging or survival. Malignant transformation in the endometrium is related to reduction of membrane DR4 and DR5 expression. The level of membrane staining of the receptors in EEC is not dependent on grading and staging, and is not sufficient to predict survival in EEC patients.

Construction of a tissue microarray with two millimeters cores of endometrioid endometrial cancer: factors affecting the quality of the recipient block

The tissue microarray (TMA) method currently is not used to render a primary diagnosis of cancer, but its scientific value has been proved in studies of various cancer types. TMA technology still is not used often for uterine tumors, however. We investigated the repeatability of histological diagnosis of endometrioid endometrial cancer (EEC) using conventional histology and TMA using 2 mm cores. We examined EEC tissues from 171 patients. Formalin fixed, paraffin embedded tissue donor blocks from EEC specimens were selected and examined histologically. Duplicate 2 mm tissue cores were inserted into a TMA recipient block. EEC tissues were examined as hematoxylin-eosin stained sections from the TMAs. EEC tissue was identified in the TMAs in 158 cases (92.4%) and not found in 13 cases (7.6%). On the TMA slides, both EEC positive cores were identified in 129 cases (75.4%), but only one core in 29 cases (17.0%). Among 342 biopsies of the donor blocks (each case in duplicate), EEC was found in 287 cases (83.9%) using the TMA: 124/146 (84.9%) with superficial infiltration, 153/178 (86.0%) with deep myometrial infiltration, and 10/18 (55.6%) without myometrial infiltration. We concluded that two 2 mm tissue cores from a biopsy of a donor block inserted into a TMA recipient block were sufficient to diagnose EEC in more than 90% of cases. EEC was identified in the TMAs with similar frequency with respect to superficial and deep myometrial infiltration. Cases without myometrial infiltration were identified less often.

Bone metastases from gynaecological epithelial cancers

The aim of this study was to investigate the clinical features and prognosis in patients with gynaecological epithelial cancers metastasised to bones. A total of 26 patients were studied retrospectively. Clinical and pathological data were analysed along with a follow-up. It was found that the interval from primary diagnosis of cancer until bony relapse varied between 0 and 163 months (31.4 ± 36.8). Bone metastases were solitary in 11 cases and multifocal in 15 cases. A total of 14 patients demonstrated only bony metastases while 12 had both bony and non-bony metastases. The time to follow-up from the diagnosis of osseous relapse varied between 1 and 43 months (10.0 ± 10.4). During follow-ups, 13 patients died and 13 patients survived. In both univariate and multivariate analyses, synchronous non-bony metastases and symptomatic treatment without oncological therapy impaired prognosis. It was concluded that even in the presence of multiple bone metastases, some patients may benefit from radiotherapy, chemotherapy or a combination of both, rather than palliative care alone, providing they do not have additional soft tissue metastases.

Correlation of Smac/DIABLO protein expression with the clinico-pathological features of breast cancer patients

Smac/DIABLO protein promotes caspase-dependent apoptosis by inhibition of inhibitor of apoptosis protein (IAP) family members. The role of Smac/DIABLO in breast cancer has not been yet established. Therefore, the aim of the study was to assess the expression of this protein in tumor cells from breast cancer patients. The expression of Smac/DIABLO was analyzed in 62 breast cancer patients by flow cytometry. The obtained results were compared with expression of this protein in benign breast tumor tissue, which served as the control (11 patients with fibroadenoma). Expression of caspase-3 proteins in breast cancer was also evaluated. Smac/DIABLO expression in breast cancer was correlated with clinical and pathological data. Although the expression of Smac/DIABLO protein was found in all examined samples of both the breast cancer and fibroadenoma patients, the median expression of Smac/Diablo in breast cancer was significantly lower than in the control (39.1% vs. 48.1%; p=0.0047). Smac/DIABLO expression correlated with expression of caspase-3 (p=0.000008). In pT1 breast cancer patients, expression of Smac/DIABLO protein was higher than in those with pT2-3 (p=0.02). Diffuse cancer infiltration significantly correlated with lower expression of Smac/DIABLO protein (p=0.02). Moreover, there was a loose correlation between low expression of Smac/DIABLO protein and cancer embolus in minor blood and lymphatic vessels (p=0.08). Our results indicate that expression of Smac/DIABLO inversely correlates with the tumor stage, which may suggest that this protein may play an important role in the breast cancer development.

Studies on antioxidant properties of polyphenol-rich extract from berries of Aronia melanocarpa in blood platelets

The antioxidant properties of extract from berries of Aronia melanocarpa (chokeberry) containing: anthocyanidines, phenolic acids and quercetine glycosides on oxidative/nitrative stress induced by peroxynitrite (ONOO(-), a powerful physiological oxidant, nitrating species and inflammatory mediator) in human blood platelets were studied in vitro. The extract from A. melanocarpa (5 - 50 microg/mL) significantly inhibited platelet protein carbonylation (measured by ELISA method) and thiol oxidation estimated with 5,5'-dithio-bis(2-nitro-benzoic acid) (DTNB) induced by peroxynitrite (0.1 mM) (IC(50)--35 microg/mL for protein carbonylation, and IC(50)--33 microg/mL for protein thiol oxidation). The tested extract only slightly reduced platelet protein nitration (measured by C- ELISA method). The extract also caused a distinct reduction of platelet lipid peroxidation induced by peroxynitrite. Moreover, in our preliminary experiments we observed that the extract (50 microg/mL) reduced oxidative/nitrative stress in blood platelets from patients with breast cancer. The obtained results indicate that in vitro the extract from A. melanocarpa has the protective effects against peroxynitrite-induced oxidative/nitrative damage to the human platelet proteins and lipids. The extract from A. melanocarpa seems to be also useful as an antioxidant in patients with breast cancer.

Expression of tumour necrosis factor-related apoptosis-inducing ligand and caspase-3 in relation to grade of inflammation and stage of fibrosis in chronic hepatitis C

AIM

To assess whether the distribution of the recently described proapoptotic ligand, tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), and the apoptosis effector, caspase-3 alters with the degree of inflammation and fibrosis present in liver biopsy specimens from patients with chronic hepatitis C virus infection.

METHODS AND RESULTS

Expression of TRAIL and caspase-3 was assessed immunohistochemically in liver biopsy specimens obtained from 89 adults with chronic hepatitis C. Expression of TRAIL in hepatocytes correlated inversely with stage of fibrosis (P = 0.001), classified according to the Scheuer score; expression of caspase-3 in hepatocytes correlated with grade of inflammation (P = 0.012). Expression of TRAIL in hepatocytes was not correlated with grade of inflammation (P > 0.05); expression of caspase-3 was not correlated with stage of fibrosis (P > 0.05). Maximum expression of proapoptotic TRAIL protein was observed in cases with low grade inflammation (G0) and low stage fibrosis (S1). Maximum expression of caspase-3 in hepatocytes was observed in cases with high grade inflammation (G3-4) and high stage fibrosis (S3), but not with liver cirrhosis (S4).

CONCLUSIONS

There is a significant decrease in TRAIL expression with increasing grade of inflammation, whereas caspase-3 expression is significantly increased with advanced fibrosis, short of cirrhosis.

Astonishingly rapid growth of malignant cystosarcoma phyllodes tumor in a pregnant woman--a case report

There are very few reports concerning the presence of malignant cystosarcoma phyllodes (CSP) in breasts of pregnant women. In the hereby described case, a 28-year-old woman presented in our department with huge (18 x 11 x 8 cm) tumor of left breast, 2 weeks after labor. The patient discovered a tumor in 34th week of pregnancy, 6 weeks before labor. Histopatholgic examination of excised tumor revealed the presence of malignant CSP tumor. Simple mastectomy was proposed to patient as a best treatment modality. However, the patient refused. She underwent excision of tumor bed (2-cm tumor-free margin was achieved). Despite insufficient treatment, she remains free of disease 20 months after the wide excision of breast malignancy. It is not known how pregnancy influences prognosis of patients with malignant CSP. Lack of such information prompted us to describe the clinical course of our patient.

Expression of Bax, Bcl-xL and Bcl-2 proteins in relation to grade of inflammation and stage of fibrosis in chronic hepatitis C

AIMS

To determine the expression of regulators of apoptosis in chronic hepatitis C.

METHODS AND RESULTS

Expression of Bax, Bcl-xL and Bcl-2 proteins was assessed immunohistochemically in liver biopsy specimens obtained from 89 adults with chronic hepatitis C. Expression of Bax in hepatocytes correlated inversely with grade of inflammation (P < 0.001) and stage of fibrosis (P = 0.011), classified according to the Scheuer score; expression of Bcl-xL in hepatocytes did not correlate with grade of inflammation (P = 0.106) or stage of fibrosis (P = 0.078); maximum Bcl-xL expression was observed in grade 3 inflammation and stage 4 fibrosis. Expression of Bcl-2 protein in hepatocytes was present in only two cases (both with advanced disease); the expression of Bcl-2 protein in interlobular bile duct epithelial cells correlated with the grade of inflammation (P = 0.018), but not with stage of fibrosis (P = 0.154). The expression of Bcl-2 protein in lymphoid cells infiltrating portal zones and lobules did not correlate with grade of inflammation (P = 0.113) or stage of fibrosis (P = 0.815).

CONCLUSION

Major differences in expression of studied proteins were observed in relation to grade of inflammation and stage of fibrosis in chronic hepatitis C.

Sentinel node biopsy in patients with breast cancer—evaluation of exposureto radiation of medical staff

AIM

To measure the absorbed doses of radiation to hands of medical staff performing sentinel node biopsy in breast cancer patients.

METHODS

The study was conducted in 2004, during sentinel node biopsies in 13 breast cancer patients (T1/T2N0). Sentinel nodes were identified with the use of combined radiotracer/blue dye technique (lymphoscintigraphy--99mTc on albumin carrier, surgery after 24 h; blue dye; intraoperative detection of gamma radiation). Highly sensitive thermoluminescent dosimeters (TLD) made of LiF were used to assess the absorbed doses of radiation during the procedure. During lymphoscintigraphy and during surgical procedure a total of 57 TLDs was placed on different parts of hands of medical staff.

RESULTS

Maximal dose recorded during lymphoscintigraphy by TLDs placed on the hands of the physician injecting the radiotracer was 164 microSv. Mean recorded doses were higher for non-dominant hand, especially for distal parts of the index finger, third finger and thumb. During the surgical procedure, TLDs placed on the hands of medical staff recorded much lower doses of radiation than during lymphoscintigraphy. The highest dose was recorded by TLD placed on the pulp of the dominant hand index finger (22 microSv) of the operating surgeon. Mean doses recorded by TLDs placed on the hands of the operating surgeon ranged from 2 to 8 microSv. The absorbed dose of radiation to hands of the scrub nurse was similar to that absorbed to hands of the operating surgeon.

CONCLUSION

The maximum recorded dose during sentinel node biopsy in this study was 2200 times smaller than current 1-year dose limit.

Patients with Paget disease of nipple and with palpable mass in breast have unfavorable prognosis

Recent data indicate that in breast cancer patients the presence of Paget disease of the nipple may be related to poor prognosis. Therefore, we decided to assess long-term results of the treatment of such patients, and to assess the relationship between the physical and pathological findings and prognosis. The files of 60 patients with Paget disease of the nipple who were treated between 1977 and 2000 were analyzed retrospectively with respect to the results of physical and pathologic examinations, disease recurrence and survival. In 38/60 patients, the cancer was invasive. In 26/60 patients, palpable masses in the breast were diagnosed. The 5-year overall survival probability was 0.68; the probability was 0.82 for patients without palpable masses, 0.51 for those with palpable masses, 0.91 for patients without invasive cancer and 0.58 for patients with associated invasive cancer. In conclusions, patients with Paget disease of the nipple and with palpable mass in the breast had unfavorable diagnosis. The nature of all nipple changes should be explained as early as possible in order to diagnose the disease when no mass is palpable in the breast.

Clinically silent Paget disease of male nipple

Male breast cancer constitutes less than 1% of all breast cancer cases. Special types, such as Paget disease of the breast, are extremely rare. To our knowledge there are less than 50 cases of Paget disease of male breast described in world medical literature. Authors present pathologically proven but clinically silent case of Paget disease of the nipple in an 86-year old male with breast cancer. Literature data suggest that the prognosis of male Paget cancer is worse than in "ordinary" male breast cancer. Therefore, the histologic diagnosis of Paget disease, even in an asymptomatic male patient, may have negative prognostic value.

Surgical and combined treatment of gastric cancer--own experience

PURPOSE

In Poland, as well as all over the world, gastric cancer is still among the leading causes of mortality and morbidity from malignant diseases. Many attempts were made to improve the results of the treatment. In this paper we present our 25-year experience in this field.

MATERIAL AND METHODS

From 1977 to 2000 in the Clinical Department of Surgical Oncology, Medical University of Łódź, we treated 353 patients (males 63%; females 37%) with the diagnosis of gastric cancer, confirmed histologically. We analysed the age of patients, location of primary tumor, histologic type, stage of the disease, type of surgery, type of reconstruction of GI tract, type of adjuvant therapy and survival.

RESULTS

In patients with the disease in stage I and II according to UICC Fielding classification, the best results were achieved. Five year survival reached 76% which means that early recognised gastric cancer may be cured. However, patients from this group constituted only 6.7% of all the treated population. In patients with stage III disease, 5 year survival was 34.5%. In patients with IVA stage of the disease (72 cases), in whom only cytoreductive-palliative surgery was performed, 5-year survival was 16.7%. No patient with IVB stage of the disease (purely palliative procedures performed) survived 5 years. Significant improvement of distant results was, observed in patients receiving EAP as an adjuvant therapy (25.1% of 5-year survivors) in comparison to control group patients treated solely with surgery (18.2% of 5 year survivors). In 97 patients after total gastrectomy, significantly lower complication rate was observed in patients in whom intestinal pouch was created (Hunt-Lawrence) than in patients in whom the pouch was not created (Roux-Y, Engel-Graham).

CONCLUSION

In our opinion, we should consequently implement guidelines known as the "Polish Consensus of Gastric Cancer Treatment", like extensive radical stomach resection (whenever possible) with regional lymphadenectomy and adjuvant therapy.

Difference between liver and spleen CT numbers in the normal adult: its usefulness in predicting the presence of diffuse liver disease

A constant relationship was found between the mean CT numbers of the liver and spleen in 100 normal adults. This relationship was characterized by a mean CT number consistently higher for the liver (24.9 +/- 4.6) than for the spleen (21.1 +/- 4.1). The range for liver CT numbers was 16.7-37.2, and for the spleen it was 14.9-34.3. The mean liver-spleen CT number difference for all subjects was 3.8 +/- 2.1 (p < 0.001); in every instance, the livers exhibiting the high mean CT numbers were in subjects with high mean spleen CT numbers, with the same concordance for low mean CT numbers. This relationship between liver and spleen may be useful in the clinical setting in which a normal liver with low CT numbers must be differentiated from one in which the CT number is low because of fatty infiltration; the fatty liver will exhibit a lower mean CT number than the spleen.

Computed tomography of the spleen

Computed tomography (CT) has proved to be valuable in the diagnosis of a wide variety of congenital, inflammatory, traumatic, and neoplastic lesions of the spleen, in addition to identifying certain normal variants which may present problems. A comprehensive review of the CT characteristics of splenic lesions and variants is provided, and CT is compared with other imaging modalities, principally radionuclide imaging.

Relative suitability of 1-palmitoyl and 1-stearoyl homologues of 1-acyl-sn-glycerylphosphorylcholine and different acyl donors for phosphatidylcholine synthesis via acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase in rat lung microsomes

The relative suitability of the 1-palmitoyl and 1-stearoyl homologues of 1-acyl-sn-glyceryl-phosphorylcholine and different acyl donors were tested as substrates for phosphatidylcholine synthesis via the acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase in rat lung microsomes. The acyl acceptor was an almost equi-molar mixture of the [3H]palmitoyl plus [14C]stearoyl species of 1-acyl-sn-glycero-3-phosphorylcholine with palmitoyl-, stearoyl-, oleoyl-, linoleoyl-, or arachidonoyl-CoA serving as the acyl donor. At all concentrations of acyl acceptor, reaction velocities with 20:4-CoA greater than or equal to 18:2-CoA > 18:1-CoA > 16:0-CoA >18:0-CoA. Furthermore, the acyltransferase selectively utilized the 1-palmitoyl over the 1-stearoyl species of 1-acylglycerylphosphorylcholine by 4.2- to 5.7-fold under optimal assay conditions with the various acyl-CoA thiolesters. However, the degree of preference exhibited for the 1-palmitoyl-sn-glycero-3-phosphorylcholine, as acyl acceptor, versus the 1-stearoyl homologue with palmitoyl-CoA as the acyl donor was not significantly different from that obtained with the other acyl-CoA derivatives. Thus, the specificity of the acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase indicates an ability of this enzyme to produce dipalmitoyl phosphatidylcholine but it cannot independently explain the predominance of dipalmitoyl phosphatidylcholine in lung or the tendency of stearate at the 1-position to associate with fatty acids of increasing unsaturation at the 2-position.

The formation of phosphatidylinositol by acylation of 2-acyl-sn-glycero-3-phosphorylinositol in rat liver microsomes

The conversion of 2-acyl-sn-glycero-3-phosphorylinositol into phosphatidylinositol via acyl-CoA: 2-acyl-sn-glycero-3-phosphorylinositol acyltransferase activity was found to occur in rat liver microsomes. Over a wide range of conditions, stearic acid was preferred over palmitate by the acyltransferase when these acids were presented in mixtures as acyl-CoA derivatives. The potential importance of this enzyme activity for the entry of stearic acid into the 1-position of hepatic phosphatidylinositol is further supported by its greater preference for stearate relative to the acyl-CoA:2-acyl-sn-glycero-3-phosphorylcholine acyltransferase under certain assay conditions.

Synthesis of 1-palmitoyl and 1-stearoyl phosphatidylcholines from mixtures of acyl acceptors via acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase in liver microsomes

The fatty acid selectivity of the acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase in rat liver microsomes was studied using a mixture of the [1-(3)H]palmitoyl plus [1-(14C)stearoyl molecular species of 1-acylglyceryl-phosphorylcholine. At a 1-acyl-sn-glycero-3-phosphorylcholine concentration of 0.16 mM, the enzyme exhibited a selectivity of 3.5-fold for the 1-palmitoyl over the 1-stearoyl species of the acyl acceptor and reaction velocities with linoleoyl- and arachidonoyl-CoA were 38--47% greater than with oleoyl-CoA. Lowering the acceptor concentration to 0.016 mM gave reaction rates with the polyenoic thiolesters which were 174--187% greater than with oleoyl-CoA and the 1-palmitoyl-sn-glycero-3-phosphorylcholine was preferred by 2.2, 1.6, and 1.6-fold with oleoyl-, linoleoyl- and arachidonoyl-CoA, respectively. The results support the potential importance of the fatty acid selectivities of the acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase towards both acyl acceptor and donor in regulating the phosphatidylcholine species formed by the reaction in vivo.

Substrate selectivity of diacylglycerol kinase in guinea pig brain

The present study was conducted to test the selectivity of the microsomal diaclyglycerol kinase (ATP:1,2-diacyl-sn-glycerol-phosphotransferase) from guinea pig brain towards different, 1,2-diacyl-sn-glycerols. The molecular species added to the incubation medium as substrates were a mixture of the 1-[3H]palmitoyl plus 1-[14C]stearoyl homologs of either the monoenoic (2-oleoyl), dienoic (2-linoleoyl), tetraenoic (2-arachidonoyl), or hexaenoic (2-docosahexaenoyl) diacylglycerols. Rates of phosphatidic acid synthesis (1-palmitoy plus 1-stearoyl homologs) with each of the four classes of unsaturated diacylglycerols were not greatly different, although they were moderately higher in the case of the monoenes. No marked enzyme selectivity for either the 1-palmitoyl or 1-stearoyl homolog of the various 1-saturated 2-unsaturated diacylglycerols was apparent. Generally similar results were obtained with the diacylglycerol kinase in rat brain microsomes.

The relative utilization of different molecular species of unsaturated 1,2-diacyglycerols by the acyl-CoA:1,2-diacyl-sn-glycerol acyltransferase in rat liver microsomes

The possible selectivity of the acyl-CaA:1,2-diacyl-sn-glycerol acyltransferase in rat liver microsomes towards different molecular species of 1,2-diacyl-sn-glycerols was studied. Triacylglycerol synthesis was determined by monitoring the entry of radioactive palmitate from [1-14C]palmitoyl-CoA into triacylglycerol in the presence of various diacylglycerols. The diacylglycerol acyltransferase did not exhibit any selectivity against hexaenoic precursors under the assay conditions used (0.25 mM diacylglycerol in medium) and the rates of triacylglycerol synthesis observed with various diacylglycerols were not significantly different when the data were analyzed statistically. The results that the extremely low level of docosahexaenoic acid in triacylglycerols cannot be attributed to a discrimination of the diacylglycerol acyltransferase against 1-saturated 2-docosahexaenoyl precursors.

Differential biosynthesis of molecular species of 1,2-diacyl-sn-glycerols and phosphatidylcholines in cold and warm acclimated goldfish (Carassius auratus L.)

The initial incorporation of glycerol-3H into the molecular species of liver 1,2-diacyl-sn-glycerols and phosphatidylcholines was studied in vivo using goldfish acclimated to 10 C and 30 C. A 1.5- and 2.2-fold higher proportion of the total radioactivity in the diacylglycerols from cold acclimated fish was found to be associated with the trienoic and pentaenoic species, respectively, when compared to warm acclimated fish. In the phosphatidylcholines, 1.9- and 1.3-fold greater percentages of the newly-incorporated radioactivity were found in tetraenoic and pentaenoic molecules, respectively, from cold relative to warm acclimated fish which suggests a preferential synthesis of these molecules relative to other molecular species in response to a lowering of environmental temperature. The present results indicate, therefore, that environmental temperature influences the complement of molecular species of diacylglycerols an phosphatidylcholines which fish produce by way of de novo biosynthesis in vivo.

Activity of phospholipid-synthesizing enzymes in rat liver plasma membranes and the source of biliary lecithin

The potential for the synthesis of phosphatidylcholine by the bile canalicular membrane of the liver cell was assessed by measuring the activity of a number of phospholipid synthesizing enzymes in isolated bile canalicular membrane fractions from rat liver. The activity of these various enzymes was compared to that present in noncanalicular liver cell plasma membranes and in microsomes. The CDP-choline:1,2-diacyl-sn-glycerol-cholinephosphotransferase was virtually absent from the bile canalicular membranes but the specific activities of S-adenosyl-L-methionine:phosphatidyl-ethanolamine N-methyltransferase and acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase were 11-15% of those found in the microsomes. The bile canalicular membranes also contained detectable acyl-CoA:sn-glycero-3-phosphate acyltransferase activity and the ability to potentiate the Ca++-stimulated exchange of bases between different phospholipids. These findings indicate that the bile canalicular membranes have a very limited capacity for the formation of phosphatidylcholine under the assay conditions employed.

Incorporation of Fatty Acids into Phosphatidylcholine by Acyl-CoA: l-acyl-sn-glycero-3-phosphorylcholine Acyltransferase in Liver of Rainbow trout, Salmo gairdneri

The formation of phosphatidylcholine by acylation of 1-acyl-sn-glycero-3-phosphorylcholine with fatty acids was demonstrated in microsomal preparations from the livers of rainbow trout (Salmo gairdneri). Maximum incorporation of fatty acids into phosphatidylcholine was highly dependent upon the addition of 1-acyl-sn-glycero-3-phosphorylcholine to the incubation medium when activated acids in the form of [14C]acyl-CoA esters were provided. The acyl-CoA: 1-acyl-sn-glycero-3-phosphorylcholine acyltransferase showed a selectivity for unsaturated (oleate) over saturated (palmitate) fatty acids when microsomes were prepared from rainbow trout acclimated to 7 or 15 C and assays conducted at both temperatures. The presence of an acyl-CoA hydrolase in the microsomal preparations is also reported. The possible function of the acyltransferase in rearranging the fatty acid composition of cellular phospholipid when fish are exposed to a change in environmental temperature is discussed.

Biosynthesis of molecular species of CDP-diglyceride from endogenously-labeled phosphatidate in rat liver microsomes

The biosynthesis of [14C] CDP-diglyceride was studied using rat liver microsomes which were endogenously labeled with [14C] phosphatidic acid by preincubation of unlabeled microsomes with sn-[14C] glycerol-3-phosphate and appropriate cofactors. The formation of CDP-diglyceride from radioactive phosphatidate showed an absolute requirement for CTP and MgCl2. The newly formed [14C] CDP-diglyceride was characterized by thin layer chromatography (TLC), isotopic labeling from radioactive CTP, and its ability to serve as substrate for the microsomal enzyme, CDP-diglyceride: inositol phosphatidyltransferase. The distributions of radioactive glycerol-3-phosphate among the various chemical classes of microsomal [14C] phosphatidate and [14C] CDP-diglyceride were determined following argentation TLC of their 1,2-diglyceride acetate derivatives. Most of the radioactivity among the phosphatidic acids was present in the monoenoic (36%) and dienoic (33%) molecular species, whereas 10, 8, 4, and 8% were associated with the saturates, trienes, tetraenes, and polyenes, respectively. Similar distributions of radioactivity were found among the corresponding classes of newly formed CDP-diglyceride. Only a slight enrichment of radioactivity in the tetraenoic CDP-diglyceride was found relative to the corresponding phosphatidates. Therefore, under the conditions of study, the microsomal CTP: phosphatidate cytidylyltransferase produces mainly monoenoic and dienoic species of CDP-diglyceride and shows little specificity towards different molecular species of phosphatidic acids. The present results suggest also that the arachidonoyl phosphatidate derived from the microsomal acylation of sn-glycerol-3-phosphate is not likely the major source of arachidonic acid in liver phosphatidylinositol.

Biosynthesis of Lecithin by the CDP-Choline Pathway in Liver Microsomes of Rainbow Trout, Salmo gairdneri

The enzymatic synthesis of lecithin from CDP-choline (14C) was characterized in microsomal preparations from the livers of rainbow trout (Salmo gairdneri). Optimal activity was obtained with the addition of 1,2-digylceride and Mg++ to the incubation medium. There was a 290% stimulation in cholinephosphotransferase activity when the incubation temperature was raised from 15 to 37 C. The results indicate that the CDP-choline pathway is operative in the formation of lecithin in the liver of rainbow trout. The possible function of this reaction in the acclimation offish to environmental temperature is discussed.