Effects of manganese glycine on eggshell quality, eggshell ultrastructure, and elemental deposition in aged laying hens

Poor eggshell quality of eggs laid by aged laying hens is the major problem affecting the length of the rearing period in the laying hen industry. Trace elements are required and play vital roles in the eggshell quality of laying hens. Appropriate dose of organic microelements is environmentally friendly and sufficient to satisfy the needs of hens because of their greater bioavailability and lower excretion than inorganic forms. The aim of this experiment was to investigate the effects of manganese (Mn) glycine (MG) on eggshell quality, elemental deposition, and eggshell ultrastructure in aged laying hens. A total of 720 Hy-Line Brown hens 70 weeks old were assigned equally to four groups with six replicates of 30 birds each. The hens were fed basal diets (without Mn supplementation) supplemented with 120 mg/kg of Mn from manganese sulfate monohydrate (MSM), or 40, 80, or 120 mg/kg Mn from MG for 12 weeks. Dietary supplementation with 80 mg/kg Mn from MG resulted in the greatest eggshell strength after 6 weeks of treatment (P = 0.047), and in greater eggshell strength than observed in the MSM control after 12 weeks of treatment (P = 0.025). After 12 weeks of treatment, the eggs of hens in the MG groups showed lower mammillary layer thickness in the blunt end, equator, and acute end than observed in the MSM control group (P < 0.001). With the exception of the blunt ends of eggs from hens in the 120 mg/kg MG group, the eggs of hens in the MG groups, compared with the MSM control group, exhibited a lower mammillary layer ratio, and greater palisade layer ratio and effective layer ratio in the blunt end, equator, and acute end (P < 0.001). Dietary supplementation with 80 mg/kg Mn from MG, compared with the MSM control and 40 and 120 mg/kg MG, resulted in the greatest palisade layer thickness and effective layer thickness, and the lowest mammillary layer thickness in the equator (P < 0.001, P = 0.001, P < 0.001, respectively). Furthermore, supplementation with 80 mg/kg Mn from MG exhibited the greatest ratio of the palisade layer and effective layer, and the lowest mammillary layer ratio in the blunt end and equator (all P < 0.001). The Mn content of eggshells in hens-fed diets supplemented with 80 and 120 mg/kg Mn from MG was greater than that in the MSM control and 40 mg/kg MG groups (P = 0.035). Dietary supplementation with 80 or 120 mg/kg Mn from MG resulted in greater tibia Mn content than observed in the 40 mg/kg MG group (P = 0.019), and greater yolk Mn content than observed in the 40 mg/kg MG and MSM control groups (P = 0.018). In conclusion, dietary supplementation with 80 mg/kg Mn from MG, compared with the MSM control (120 mg/kg Mn), may increase the deposition efficiency of Mn, alter eggshell elemental composition, improve eggshell ultrastructure, and enhance eggshell strength in aged laying hens.

Effects of exogenous energy on synthesis of steroid hormones and expression characteristics of the CREB/StAR signaling pathway in theca cells of laying hen

Energy and the cAMP-response element binding protein (CREB)/steroidogenic acute regulatory protein (StAR) signaling pathway play important roles in steroid hormone production and follicular development in hens. This present study aimed to investigate the effects of exogenous energy on the synthesis of steroid hormones and the expression characteristics of the CREB/StAR signaling pathway in theca cells of laying hen. The primary theca cells of small yellow follicles were randomly divided into 6 treatments and cultured in medium with glucose concentrations of 1, 1.5, 3, 4.5, 6, and 7.5 mg/mL for 48 h. It was found that growth was robust and cell outlines were clear when cells were cultured with 1, 1.5, 3, and 4.5 mg/mL glucose, but cell viability was diminished and cell density decreased after exposure to glucose at 6 and 7.5 mg/mL for 48 h. Cell viability showed an increasing and then decreasing quadratic response to increasing glucose concentration in culture (r2 = 0.688, P < 0.001). The cell viability of theca cells cultured with 4.5 mg/mL glucose was greater than those cultured with 1, 1.5, 6, and 7.5 mg/mL glucose (P < 0.05). The concentration of estradiol in the medium containing 3 mg/mL glucose was higher than in medium containing 1, 1.5, and 6 mg/mL glucose (P < 0.05). There was an increasing and then decreasing quadratic correlation between progesterone concentrations and glucose concentrations (r2 = 0.522, P = 0.002). The concentration of progesterone in medium with 4.5 mg/mL glucose was higher than in medium with 1 and 7.5 mg/mL glucose (P < 0.05). There was an increasing and then decreasing quadratic correlation between the relative expression of CREB1 (r2 = 0.752, P < 0.001), StAR (r2 = 0.456, P = 0.002), CYP1B1 (r2 = 0.568, P < 0.001), and 3β-HSD (r2 = 0.319, P = 0.018) in theca cells of laying hens and glucose concentrations after treatment with different glucose concentrations for 48 h. After treatment with 4.5 mg/mL glucose, the expression of StAR, CYP1B1, and 3β-HSD genes were increased compared to treatment with 1, 1.5, 3, 6, and 7.5 mg/mL glucose (P < 0.001). There was an increasing and then decreasing quadratic correlation between glucose concentrations and protein expression of CREB1 (r2 = 0.819, P < 0.001), StAR (r2 = 0.844, P < 0.001), 3β-HSD (r2 = 0.801, P < 0.001), and CYP11A1 (r2 = 0.800, P < 0.001) in theca cells of laying hens. The protein expression of CREB1, StAR, and 3β-HSD in theca cells cultured with 4.5 mg/mL glucose was higher than in other groups (P < 0.001). The results indicate that the appropriate glucose concentration (4.5 mg/mL) can improve the synthesis of steroid hormones in theca cells of laying hens through the upregulation of key genes and proteins in the CREB/StAR signaling pathway.

Open or Not Open the Retroperitoneum: A Pandora's Box for Blunt High-Grade Pancreatic Trauma?

INTRODUCTION

The optimal management strategy for pancreatic trauma remains unclear. We aimed to determine whether the initial nonoperative management (NOM) strategy based on percutaneous drainage combined with endoscopic retrograde cholangiopancreatography guided stent placement would improve outcomes for blunt high-grade pancreatic trauma.

METHODS

Patients with blunt abdominal trauma who were hemodynamically stable without signs of diffuse peritonitis were consecutively enrolled at a high-volume center. The primary outcome was the occurrence of severe complications (Clavien‒Dindo classification ≥ Ⅲb) for patients who underwent initial laparotomy (LAP) versus NOM. Modified Poisson regression was used to model the primary outcome. Propensity score matching and weighting models were included into a regression-based sensitivity analysis.

RESULTS

Of 119 patients with grade III/IV pancreatic trauma, 29 patients underwent initial NOM, and 90 underwent initial LAP. The incidence of severe complications in the LAP group was higher than that in the NOM group (65/90 [72.2%] versus 9/29 [31.0%], P < 0.001). In the multivariable modified Poisson regression model, the relative risk for severe complications was decreased in the NOM group (relative risk, 0.52; 95% confidence interval, 0.30-0.90; P = 0.020). The results of the sensitivity analysis were consistent with those of the multivariable analysis. The mean number of reinterventions per patient was 1.8 in the NOM group and 2.6 in the LAP group (P = 0.067).

CONCLUSIONS

For blunt high-grade pancreatic trauma patients with stable hemodynamics and no diffuse peritonitis, the NOM strategy was associated with a lower risk of severe complications (Clavien‒Dindo classification ≥ Ⅲb) and did not require more invasive reintervention procedures. In high-volume centers with sufficient expertise, percutaneous drainage combined with endoscopic retrograde cholangiopancreatography guided stent placement may serve as an initial reasonable option for selected patients.

Effects of energy restriction during growing phase on the productive performance of Hyline Brown laying hens aged 6 to 72 wk

The aim of this study was to assess the effects of energy-restricted feeding during growing phase on the productive performance of Hyline Brown laying hens aged 6 to 72 wk. A total of 720 six-week-old layer chicks were allocated equally to 3 groups with 6 replicates of 40 pullets each, and were fed 1 of 3 diets that were nutritionally similar except for the apparent metabolizable energy corrected for nitrogen (AMEn) content. At the age of 6 to 17 wk, the pullets in the control group were given diet with 2,850 kcal/kg AMEn, and were fed ad libitum. The levels of AMEn in diet of pullets in the experimental groups were 90% (2,565 [2,850 × 90%] kcal/kg) and 80% (2,280 [2,850 × 80%] kcal/kg) of that in control group, and the daily amount of feed was restricted to the absolute quantity of the diet consumed by pullets in control group. At the age of 18 to 72 wk, all the hens were fed with the same diets ad libitum. As energy restriction increased in the growing phase, body weight (BW) dropped at the ages of 12 and 15 to 23 wk (at 23 wk: P = 0.001; at other ages: P < 0.001), but it showed no significant difference at 24 wk (P = 0.071). At 20 wk, restricting energy induced a delay in the development of sexual organs, including the ovary stroma, oviduct, and small yellow follicle (P < 0.05), as well as a delay in sexual maturity (P < 0.05). Consequently, the laying rate in the first and second periods dropped linearly (P = 0.046, 0.030, and 0.038, P < 0.001, respectively). The coefficient of variation (CV) in the BW at 19, 20, and 21 wk (P = 0.040, 0.023, and 0.042, respectively), the CV of age at first egg (P < 0.001), and CV of individual egg number at age 18 to 72 wk (P < 0.001) decreased linearly. There was a linear increase in the laying rate of hens in the later periods (at age 32-72 wk, P < 0.05), as well as in the average total egg number per hen and average laying rate at the age of 18 to 72 wk (P = 0.006). The average egg mass also showed a linear increase with increasing levels of energy restriction (P < 0.001). In summary, although appropriate energy restriction during growing phase delayed sexual maturity and sexual organ development in early-laying Hyline Brown pullets, it improved uniformity of BW, age at first egg laying, and individual egg number, and increased egg number per hen, laying rate, average egg mass, and number of settable eggs from 18 to 72 wk of age.

Initial suction drainage decreases severe postoperative complications after pancreatic trauma: A cohort study

BACKGROUND

Few studies have addressed the question of which drain types are more beneficial for patients with pancreatic trauma (PT).

AIM

To investigate whether sustained low negative pressure irrigation (NPI) suction drainage is superior to closed passive gravity (PG) drainage in PT patients.

METHODS

PT patients who underwent pancreatic surgery were enrolled consecutively at a referral trauma center from January 2009 to October 2021. The primary outcome was defined as the occurrence of severe complications (Clavien-Dindo grade ≥ Ⅲb). Multivariable logistic regression was used to model the primary outcome, and propensity score matching (PSM) was included in the regression-based sensitivity analysis.

RESULTS

In this study, 146 patients underwent initial PG drainage, and 50 underwent initial NPI suction drainage. In the entire cohort, a multivariable logistic regression model showed that the adjusted risk for severe complications was decreased with NPI suction drainage [14/50 (28.0%) vs 66/146 (45.2%); odds ratio (OR), 0.437; 95% confidence interval (CI): 0.203-0.940]. After 1:1 PSM, 44 matched pairs were identified. The proportion of each operative procedure performed for pancreatic injury-related and other intra-abdominal organ injury-related cases was comparable in the matched cohort. NPI suction drainage still showed a lower risk for severe complications [11/44 (25.0%) vs 21/44 (47.7%); OR, 0.365; 95%CI: 0.148-0.901]. A forest plot revealed that NPI suction drainage was associated with a lower risk of Clavien-Dindo severity in most subgroups.

CONCLUSION

This study, based on one of the largest PT populations in a single high-volume center, revealed that initial NPI suction drainage could be recommended as a safe and effective alternative for managing complex PT patients.

Postoperative pulmonary complications in older patients undergoing elective surgery with a supraglottic airway device or tracheal intubation

The two most commonly used airway management techniques during general anaesthesia are supraglottic airway devices and tracheal tubes. In older patients undergoing elective non-cardiothoracic surgery under general anaesthesia with positive pressure ventilation, we hypothesised that a composite measure of in-hospital postoperative pulmonary complications would be less frequent when a supraglottic airway device was used compared with a tracheal tube. We studied patients aged ≥ 70 years in 17 clinical centres. Patients were allocated randomly to airway management with a supraglottic airway device or a tracheal tube. Between August 2016 and April 2020, 2900 patients were studied, of whom 2751 were included in the primary analysis (1387 with supraglottic airway device and 1364 with a tracheal tube). Pre-operatively, 2431 (88.4%) patients were estimated to have a postoperative pulmonary complication risk index of 1-2. Postoperative pulmonary complications, mostly coughing, occurred in 270 of 1387 patients (19.5%) allocated to a supraglottic airway device and 342 of 1364 patients (25.1%) assigned to a tracheal tube (absolute difference -5.6% (95%CI -8.7 to -2.5), risk ratio 0.78 (95%CI 0.67-0.89); p < 0.001). Among otherwise healthy older patients undergoing elective surgery under general anaesthesia with intra-operative positive pressure ventilation of their lungs, there were fewer postoperative pulmonary complications when the airway was managed with a supraglottic airway device compared with a tracheal tube.

[Response characteristics of tislelizumab combined with chemotherapy in first-line treatment of locally advanced or metastatic non-squamous non-small cell lung cancer]

Objective: To investigate the response characteristics of patients with locally advanced/metastatic non-squamous non-small cell lung cancer (nsq-NSCLC) treated with tislelizumab in combination with chemotherapy in the first line. Methods: Patients with nsq-NSCLC who achieved complete or partial remission after treatment with tislelizumab in combination with chemotherapy or chemotherapy alone in the RATIONALE 304 study, as assessed by an independent review board, were selected to analyze the response characteristics and safety profile of the responders. Time to response (TTR) was defined as the time from randomization to the achievement of first objective response. Depth of response (DpR) was defined as the maximum percentage of tumor shrinkage compared with the sum of the baseline target lesion length diameters. Results: As of January 23, 2020, 128 patients treated with tislelizumab in combination with chemotherapy achieved objective tumor response (responders), representing 57.4%(128/223) of the intention-to-treat population, with a TTR of 5.1 to 33.3 weeks and a median TTR of 7.9 weeks. Of the responders (128), 50.8%(65) achieved first remission at the first efficacy assessment (week 6), 31.3%(40) at the second efficacy assessment (week 12), and 18.0%(23) at the third and subsequent tumor assessments. The percentages of responders who achieved a depth of tumor response of 30% to <50%, 50% to <70% and 70% to 100% were 45.3%(58/128), 28.1%(36/128) and 26.6%(34/128), respectively, with median progression-free survival (PFS) of 9.0 months (95% CI: 7.7 to 9.9 months), 11.5 months (95% CI: 7.7 months to not reached) and not reached (95% CI: 11.8 months to not estimable), respectively. Tislelizumab plus chemotherapy were generally well tolerated in responders with similar safety profile to the overall safety population. Conclusion: Among responders to tislelizumab in combination with chemotherapy for nsq-NSCLC, 82.0%(105/128) achieves response within the first two tumor assessments (12 weeks) and 18.0%(23/128) achieves response at later (18 to 33 weeks) assessments, and there is a trend toward prolonged PFS in responders with deeper tumor response.

Progress in research of acute pancreatitis in pregnancy

Acute pancreatitis in pregnancy (APIP) is a rare and severe complication of pregnancy, which is characterized by rapid onset, rapid progression, many complications, and high mortality. According to previous studies, the incidence of APIP is about 1/10000-1/1000 and increases with gestational age. Due to the differences in genetic background and dietary habits between Asian and European populations, the incidence of APIP in China is as high as 1.14‰-2.27‰, significantly higher than that in Western countries. The lack of specific clinical symptoms of APIP often leads to misdiagnosis or missed diagnosis, which greatly increases the difficulty of diagnosis and treatment. Despite the deepening of the research on APIP, its pathogenesis is still unclear. This paper will give a systematical review of APIP.

Effects of energy-restricted feeding during rearing on sexual maturation and reproductive performance of Rugao layer breeders

The aim of this study was to assess the effects of energy-restricted feeding during rearing on the sexual maturation and reproductive performance of Rugao layer breeders. A total of 2,400 8-wk-old Rugao layer breeders were randomly assigned to one of 5 groups (480 pullets per group) with eight replicates and were fed one of 5 diets that were nutritionally similar with the exception of apparent metabolizable energy corrected for nitrogen (AME_n) content (2,850, 2,750, 2,650, 2,550, and 2,450 kcal AME_n/kg) from 8 to 18 wks of age. The daily amount of feed was restricted to the absolute quantity of the diet consumed by laying hens fed 2,850 kcal AME_n per kg diet ad libitum (control). From 18 to 52 wks of age, all hens were fed basal diets ad libitum. The body weight of layer breeders at 18 wks of age decreased linearly with increasing energy restriction (P < 0.001), but caught up within 3 wks of ad libitum feeding (P = 0.290). The coefficient of variation of the body weight of the hens at 18, 21, and 24 wks of age decreased linearly (P = 0.010, 0.025, and 0.041, respectively) with increasing energy restriction during rearing. Energy-restricted feeding delayed sexual organ development at 18, 20, and 22 wks of age, including the number of large yellow follicles, oviduct length, oviduct length index, oviduct index, and ovary stroma index (P < 0.05), and delayed sexual maturity, including the age at laying the first egg and the age at 5% and 50% egg production (P = 0.042, 0.004, and 0.029, respectively). Consequently, egg number from 5% to 50% egg production decreased linearly as the degree of energy restriction increased (P = 0.001) and egg production of hens in the energy-restricted feeding groups was lower than that of hens in the ad libitum feeding group (6.36, 6.43, 6.4, and 4.61% vs. 14.29%; P < 0.05) from 18 to 20 wks of age. Furthermore, egg weight increased linearly as energy restriction increased (P < 0.001) and laying hens in the most severe energy-restricted feeding group had more setting eggs (normal eggs weighing >40 g) than hens in the ad libitum feeding and lighter energy-restricted feeding groups (149.57 vs. 144.34, 142.66, 143.63, and 141.78; P < 0.05). No significant differences were observed in fertility, hatchability of fertile eggs, and hatchability of setting eggs (P = 0.381, 0.790, and 0.605, respectively). In conclusion, moderate energy restriction (85.97%, 2,450 vs. 2,850 kcal AME_n/kg) from 8 to 18 wks of age increased egg weight as well as the production of setting eggs in native layer breeders throughout the laying period, without adverse effects on productive performance from 18 to 52 wks of age, or fertility and hatchability at 52 wks of age.

Digenic Inheritance and Gene-Environment Interaction in a Patient With Hypertriglyceridemia and Acute Pancreatitis

The etiology of hypertriglyceridemia (HTG) and acute pancreatitis (AP) is complex. Herein, we dissected the underlying etiology in a patient with HTG and AP. The patient had a 20-year history of heavy alcohol consumption and an 8-year history of mild HTG. He was hospitalized for alcohol-triggered AP, with a plasma triglyceride (TG) level up to 21.4 mmol/L. A temporary rise in post-heparin LPL concentration (1.5–2.5 times of controls) was noted during the early days of AP whilst LPL activity was consistently low (50∼70% of controls). His TG level rapidly decreased to normal in response to treatment, and remained normal to borderline high during a ∼3-year follow-up period during which he had abstained completely from alcohol. Sequencing of the five primary HTG genes (i.e., LPL, APOC2, APOA5, GPIHBP1 and LMF1) identified two heterozygous variants. One was the common APOA5 c.553G > T (p.Gly185Cys) variant, which has been previously associated with altered TG levels as well as HTG-induced acute pancreatitis (HTG-AP). The other was a rare variant in the LPL gene, c.756T > G (p.Ile252Met), which was predicted to be likely pathogenic and found experimentally to cause a 40% loss of LPL activity without affecting either protein synthesis or secretion. We provide evidence that both a gene-gene interaction (between the common APOA5 variant and the rare LPL variant) and a gene-environment interaction (between alcohol and digenic inheritance) might have contributed to the development of mild HTG and alcohol-triggered AP in the patient, thereby improving our understanding of the complex etiology of HTG and HTG-AP.

Genome-wide association studies for mottled eggs in chickens using a high-density single-nucleotide polymorphism array

Mottled eggs in layer chickens are gaining increasing attention because of the economic impact on the egg industry caused by the reduced sale value of commodity eggs. However, the genetic architecture underlying mottled eggs is not well understood. The genetic architecture underlying the mottled egg trait was investigated using genome-wide association studies (GWAS) by high-density arrays, using a total of 407 pink eggs and 799 blue eggs from an F₂ resource population generated by crossing Dongxiang Blue-shelled and White Leghorn chickens. The mottled egg score in blue eggs was found to be higher than that in pink eggs. The single-nucleotide polymorphism heritability of mottled egg at laying day and storage for 7 days was 0.18 and 0.20, respectively. Bivariate GWAS provided 29 significant loci, mainly located on GGA2, GGA3, GGA8, GGA10, GGA15, GGA17, and GGA23, affecting mottled egg on laying day. Candidate genes RIMS2, SLC25A32, RIMBP2, VPS13B, and RGS3 were obtained for mottled eggshell by bivariate GWAS and gene annotation. Our findings provide new insights into the genetic architecture of mottled egg in hens, and demonstrate that a genomic selection method would be profitable for breeding out the mottled egg trait.

Dietary supplementation of total flavonoids from Rhizoma Drynariae improves bone health in older caged laying hens

Caged layer osteoporosis (CLO) is a common bone metabolism diseases and poses a great threat to the production of laying hens. So far, there is no effective nutrition intervention to prevent CLO. The objective of this study was to evaluate the effects of dietary total flavonoids from Rhizoma Drynariae (TFRD), a Chinese herbal, on bone health, egg quality, and serum antioxidant capacity of caged laying hens. A total of two hundred sixteen, 54-wk-old Lohmann Pink-shell laying hens at were allocated to 3 groups with 6 replicates of 12 hens per replicate. The control group was fed a basal diet (BD) and 2 treatment groups additionally supplied with 0.5 or 2.0 g/kg TFRD, respectively. Results showed that supplying 2.0 g/kg TFRD enhanced the activities of serum total antioxidant capacity (P < 0.01) and glutathione peroxidase (P < 0.05) and had higher femur and tibia bone mineral density (both P < 0.05) compared with the control group. Dietary 2.0 g/kg TFRD also reduced the activities of serum alkaline phosphatase (P < 0.01), tartrate resistant acid phosphatase (P < 0.01), and the contents of osteocalcin (P < 0.01). Furthermore, tibia histomorphology observation showed that the microstructure of bone tissue was improved after TFRD treatment. Egg quality was not affected by TFRD while the egg weight significantly increased (P < 0.01). These findings suggested that TFRD has beneficial effects on bone health in older caged laying hens.

A novel anti-ageing mechanism for retinol: induction of dermal elastin synthesis and elastin fibre formation

Dermal elastic fibres are extracellular matrix protein complexes produced by fibroblasts and involved in skin elasticity. Elastin fibres decrease with age as a result of reduced synthesis and increased degradation, resulting in skin sagging and reduced skin elasticity. In this study, we show that retinol (ROL), known to enhance dermal collagen production, is also enhancing elastin fibre formation. ROL induced elastin gene expression and elastin fibre formation in cultured human dermal fibroblasts. Topical treatment of cultured human skin explants with a low dose (0.04%) of ROL increased mRNA and protein levels of tropoelastin and of fibrillin-1, an elastin accessory protein, as documented by QPCR and immunohistochemistry staining. Luna staining confirmed the increased elastin fibre network in the ROL-treated skin explants, as compared with untreated controls. These data demonstrate that ROL exerts its anti-ageing benefits not only via enhanced epidermal proliferation and increased collagen production, but also through an increase in elastin production and assembly.

Subjective assessments of safety, exposure to chemicals and use of personal protection equipment in seafaring

BACKGROUND

Most of the scientific publications from the maritime area are studies about the mortality and morbidity, while studies about the present hazards of potentially dangerous exposures are relatively rare.

AIMS

To describe the seafarers' assessments of the occupational safety on board, their exposure to chemicals and the use of personal protection equipment and to identify the areas for further risk assessment and preventive measures.

METHODS

A questionnaire study was carried out in 11 countries among seafarers who attended a regular health examination.

RESULTS

The total number of seafarers who participated in the study was 6461 (response rate 93.7%). The occupational safety on board was assessed to be very good or good in 82%. Multivariate analyses showed that the safety was assessed as lowest among ratings, seafarers<30 years of age, work in the engine rooms and on dry cargo ships. It was highest on crude oil tankers and supply ships. Fifty-five per cent of seafarers were exposed to chemicals. Personal protection equipment to chemicals was used 'always/almost always' in 93% of the exposed. Multivariate analysis showed that the use of personal protection was highest on deck, on the largest ships, on roll-on roll-off ships and on crude oil tankers.

CONCLUSION

The occupational safety and the use of personal protective equipment was assessed to be significantly different in some strata of the population and in specific working areas and types and sizes of ships.

Incidence of self-reported occupational injuries in seafaring--an international study

AIMS

Seafaring is known as a high-risk industry. The aims were to describe the incidence of non-fatal injuries among seafarers, including testing the hypothesis that long working hours might result in higher injury rates.

METHODS

A questionnaire study of injury on the latest tour of duty was carried out among seafarers in 11 countries with 6461 participants. The seafarers were asked if they were injured during the latest tour of duty and what was the number of hours worked.

RESULTS

During the latest tour of duty, 9.1% of all seafarers were injured and 4.3% had an injury with at least 1 day of incapacity. The injury incidence rates for cargo ships and tankers: 39.5 per 1 million work hours and 37.6 per 100,000 days. Multivariate analyses: incidence rate ratios (IRR) for >70 working hours per week compared with <57 h: 0.90 [95% confidence interval (95% CI) = 0.61-1.32]; non-officers compared with officers: IRR = 1.57 (95% CI = 1.14-2.15); seafarers <35 years compared with > or =35 years of age: IRR = 2.11 (1.57-2.86); tour lengths > or =117 days compared with <117 days: IRR = 0.27 (0.19-0.39). Main work area on the deck and in the service area compared with work in the engine room: IRR = 0.37 (0.27-0.52) and IRR = 0.49 (0.26-0.91), respectively.

CONCLUSIONS

There was no evidence that long working hours alone resulted in higher injury rates. Low self-perceived health, lack of use of personal protection and lack of occupational safety on board were significantly related to an increase in the injury risk.

[The presentation of neo gene in chimeric mice obtained from ES cells]

To explore the potentiality of the mouse ES cell line which is employed in our laboratory were transfected with neo gene and selected with G418. Some ES cell clones expressing neo gene were obtained. After ES clones were picked up and expanded, the ES cells were mircoinjected into blastocysts and implanted miceuterus. 60 blastocysts were implanted into 5 mice. Finally, 3 chimeric mice with neo gene were born. PCR was carried out to analyze the presentation of neo gene in tissues of chimeric mice. The results showed that many tissues harbored the neo gene, including skin, liver and blood et al.

[Detection of Cre recombinase activity in Mx-Cre transgenic mice induced by INF in vitro]

The Cre recombinase and its activity in C57-TgN(Mx-Cre) transgenic mice is studied by polymerase chain reaction (PCR), Western blot, immunohistochemistry, immunogold electron microscopy and Southern blot. C57-TgN(Mx-Cre) transgenic mice harbouring cre gene in genomic DNA is demonstrated by PCR, and these mice which are induced by INF-alpha 1b could express Cre recombinase, which is confirmed by Western blot. With immunohistochemistry, we find that the Cre recombinase expresses in hepatocyte cytoplasm and nuclear of C57-TgN(Mx-Cre) transgenic mice. Cre recombinase expressed in hepatocyte cytoplasm and nuclear is further confirmed by immunogold electon microscopy. And it is supported that the Cre recombinase which is created from C57-TgN(Mx-Cre) transgenic mice induced by INF-alpha 1b can direct DNA recombination reaction in vitro. All evidence leads us supporting the view that the Cre recombinase expressed in C57-TgN(Mx-Cre) transgenic mice has activity. Thus we find a method to detect the activity of Cre recombinase in vitro.

The cytoskeletal/non-muscle isoform of alpha-actinin is phosphorylated on its actin-binding domain by the focal adhesion kinase

alpha-Actinin is tyrosine-phosphorylated in activated human platelets (Izaguirre, G., Aguirre, L., Ji, P., Aneskievich, B., and Haimovich, B. (1999) J. Biol. Chem. 274, 37012--37020). Analysis of platelet RNA by reverse transcription-polymerase chain reaction revealed that alpha-actinin expressed in platelets is identical to the cytoskeletal/non-muscle isoform. A construct of this isoform containing a His(6) tag at the amino terminus was generated. Robust tyrosine phosphorylation of the recombinant protein was detected in cells treated with the tyrosine phosphatase inhibitor vanadate. The tyrosine phosphorylation site was localized to the amino-terminal domain by proteolytic digestion. A recombinant alpha-actinin protein containing a Tyr --> Phe mutation at position 12 (Y12F) was no longer phosphorylated when expressed in vanadate-treated cells, indicating that tyrosine 12 is the site of phosphorylation. The wild type recombinant protein was not phosphorylated in cells lacking the focal adhesion kinase (FAK). Re-expression of FAK in these cells restored alpha-actinin phosphorylation. Purified wild type alpha-actinin, but not the Y12F mutant, was phosphorylated in vitro by wild type as well as a Phe-397 mutant of FAK. In contrast, no phosphorylation was detected in the presence of a kinase-dead FAK. Tyrosine phosphorylation reduced the amount of alpha-actinin that cosedimented with actin filaments. These results establish that alpha-actinin is a direct substrate for FAK and suggest that alpha-actinin mediates FAK-dependent signals that could impact the physical properties of the cytoskeleton.

[Generation of Mx-cre transgenic mice]

To generate the transgenic mice expressing cyclization recombination enzyme, the recombinant gene, in which the coding region of cre gene is derived by the promoter of mouse Mx gene, was microinjected into pronuclei of fertilized mouse eggs. Founders of transgenic mice harbouring the recombinant gene were screened by polymerase chain reaction (PCR) at genomic DNA level and confirmed by Southern blot. One line of Mx-cre transgenic mice was obtained. Then, the Mx-cre transgenic mouse line was cultured and propagated.

Hypersensitization of tumor cells to glycolytic inhibitors

The slow growth of cells in the inner core of solid tumors presents a form of multidrug resistance to most of the standard chemotherapeutic agents, which target the outer more rapidly dividing cells. However, the anaerobic environment of the more centrally located tumor cells also provides an opportunity to exploit their dependence on glycolysis for therapeutic gain. We have developed two in vitro models to investigate this possibility. Model A represents osteosarcoma wild-type (wt) cells treated with agents which inhibit mitochondrial oxidative phosphorylation (Oxphos) by interacting with complexes I, III, and V of the electron transport chain in different ways, i.e., rhodamine 123 (Rho 123), rotenone, antimycin A, and oligomycin. All of these agents were found to hypersensitize wt cells to the glycolytic inhibitor 2-deoxyglucose. Cells treated with Rho 123 also become hypersensitive to oxamate, an analogue of pyruvate, which blocks the step of glycolysis that converts pyruvate to lactic acid. Model B is rho(0) cells which have lost their mitochondrial DNA and therefore cannot undergo Oxphos. These cells are 10 and 4.9 times more sensitive to 2-deoxyglucose and oxamate, respectively, than wt cells. Lactic acid levels, which are a measure of anaerobic metabolism, were found to be > 3 times higher in rho(0) than in wt cells. Moreover, when wt cells were treated with Rho 123, lactic acid amounts increased as a function of increasing Rho 123 doses. Under similar Rho 123 treatment, rho(0) cells did not increase their lactic acid levels. These data confirm that cell models A and B are similarly sensitive to glycolytic inhibitors due to their dependence on anaerobic metabolism. Overall, our in vitro results suggest that glycolytic inhibitors could be used to specifically target the slow-growing cells of a tumor and thereby increase the efficacy of current chemotherapeutic and irradiation protocols designed to kill rapidly dividing cells. Moreover, glycolytic inhibitors could be particularly useful in combination with anti-angiogenic agents, which, a priori, should make tumors more anaerobic.

[Expression of Trial in mammalian cell and its apoptosis activation in culture cells]

To develop a system for expression of Trail in mammalian cell. PCR and sequencing were used to clone and to confirm Trail gene. Then, we constructed the vector for expression of Trail in mammalian cells. HeLa cells, one of sensitive cell lines to Trail, were transfected with the vector DNA. After 48 h, flow cytometry was used to screen HeLa transfected by Trail. 19% of total cells happened to apoptosis. This study conforms that the production of Trail expressing in mammal cell can induce apoptosis and exhibit high bio-active. The results indicate the potential application of Trail to tumor immunotherapy.

Differential expression and functional analysis of Pitx2 isoforms in regulation of heart looping in the chick

Pitx2, a bicoid-related homeobox gene, plays a crucial role in the left-right axis determination and dextral looping of the vertebrate developing heart. We have examined the differential expression and function of two Pitx2 isoforms (Pitx2a and Pitx2c) that differ in the region 5' to the homeodomain, in early chick embryogenesis. Northern blot and RT-PCR analyses indicated the existence of Pitx2a and Pitx2c but not Pitx2b in the developing chick embryos. In situ hybridization demonstrated a restricted expression of Pitx2c in the left lateral plate mesoderm (LPM), left half of heart tube and head mesoderm, but its absence in the extra-embryonic tissues where vasculogenesis occurs. RT-PCR experiments revealed that Pitx2a is absent in the left LPM, but is present in the head and extra-embryonic mesoderm. However, ectopic expression of either Pitx2c or Pitx2a via retroviral infection to the right LMP equally randomized heart looping direction. Mapping of the transcriptional activation function to the C terminus that is identical in both isoforms explained the similar results obtained by the gain-of-function approach. In contrast, elimination of Pitx2c expression from the left LMP by antisense oligonucleotide resulted in a randomization of heart looping, while treatment of embryos with antisense oligonucleotide specific to Pitx2a failed to generate similar effect. We further constructed RCAS retroviral vectors expressing dominant negative Pitx2 isoforms in which the C-terminal transcriptional activation domain was replaced by the repressor domain of the Drosophila Engrailed protein (En(r)). Ectopic expression of Pitx2c-En(r), but not Pitx2a-En(r), to the left LPM randomized the heart looping. The results thus demonstrate that Pitx2c plays a crucial role in the left-right axis determination and rightward heart looping during chick embryogenesis.

Inhibition of hepatitis B virus by oxymatrine in vivo

AIM: To investigate the anti-HBV effect of oxymatrine (oxy) in vivo.

METHODS: HBV transgenic mice were produced by micro-injection of a 4.2 kb fragment containing the complete HBV genomes. Expression level of HBsAg and HBcAg in the transgenic mice liver was determined by immunohistochemical assay.

RESULTS: Four groups (6 mice in each group) were injected intraperitoneally with oxy at the dosage of 100, 200, and 300 mg/kg or with saline once a day for 30 d. Both HBsAg and HBcAg were positive in livers of all the six mice in the control group (injected with saline), and were positive in livers of two mice in 100 mg/kg group and 300 mg/kg group. In 200 mg/kg group, HBsAg and HBcAg were negative in livers of all the six mice. Based on the results, 200 mg/kg is the ideal dosage to explore the effect of oxy at different time points. According to the oxy treatment time, mice were divided into four groups: 10 d, 20 d, 30 d and 60 d (4 mice in each group). Each mouse underwent liver biopsy two weeks before the treatment of oxy. Down-regulation of HBsAg and HBcAg appeared after treatment of oxymatrine for 10 d and 20 d, Dane-like particles disappeared after the treatment of oxy for 20 d under electron microscopy, however, the expression level of HBsAg and HBcAg returned to normal 60 d later after oxy treatment.

CONCLUSION: oxymatrine can reduce the contents of HBsAg and HBcAg in transgenic mice liver,longer treatment time and larger dosage do not yield better effects.

[Effects of simulated weightlessness on carbohydrate intake and serum lipids]

OBJECTIVE

To observe the effects of simulated weightlessness on the nutritional state and contents of serum lipids in human.

METHOD

Eighteen healthy men were exposed to 21 d bed rest with -6 degrees head down tilt (HDT -6 degrees). Nutrients intake was calculated and the lipids levels were determined on the first, eleventh and twenty-first day.

RESULT

Intake of the three main nutrients, carbohydrates, protein and fat met the physiological requirement essentially, but carbohydrates intake was significantly reduced in the second week. There were no significant differences among the lipid levels during different periods.

CONCLUSION

Simulated weightlessness may exert a short-term and reversible influence on human nutritional intake except for lipids.

Measurement of percutaneous uptake of 2-methoxy ethanol vapor in humans

Absorption of vapors through skin has been largely ignored in occupational health, although for ethylene glycol ethers this route of exposure could be more important than inhalation. We used an automated concentration and humidity controlled system to measure real-time percutaneous absorption of 2-methoxy ethanol (ME) vapor in seven volunteers. The exposure concentration (300 +/- 10 ppm or 25 +/- 0.5 ppm), humidity (80 +/- 2%), and temperature (27.5 +/- 0.5 degrees C) were controlled throughout the experiments. Uptakes during 4-hour single-arm exposure at 25 ppm and 300 ppm were 7.0 mg and 65.3 +/- 25.0 mg, respectively, with corresponding uptake rates of 1.36 micrograms/cm2/hr and 13.2 +/- 5.0 micrograms/cm2/hr. Percutaneous absorption was consistent and unsaturated during exposure. Because the permeability constant of ME vapor (14.0 +/- 5.3 cm/hr) was much higher than that of many widely used organic chemicals, we concluded that vapor absorption through skin is a significant contributor to overall ME exposure.

Synergistic effect of prochlorperazine and dipyridamole on the cellular retention and cytotoxicity of doxorubicin

Incubation of drug-resistant human tumor cells with a combination of prochlorperazine and dipyridamole has additive/synergistic effect on the cellular retention and cytotoxicity of doxorubicin. In patients administered a fixed dose of doxorubicin and prochlorperazine with escalating doses of dipyridamole, mean plasma levels of dipyridamole and prochlorperazine achieved were as high as 3.01 +/- 0.41 microm and 0.94 +/- 0.09 microm, respectively. Plasma samples from patients were analyzed in an in vitro assay to monitor the effect on the cellular retention of tritium-labeled daunorubicin in MDR1-transfected P388 cells. In 22 of 49 of the plasma samples analyzed, the daunorubicin in efflux blocking activity was one-half or greater than that of cells incubated with 12.5 microM verapamil, a well-known efflux blocker. These observations suggest that a combination of prochlorperazine and dipyridamole may enhance cellular doxorubicin retention by blocking efflux while reducing normal tissue toxicity and unwanted side effects in vivo.

[Expression of 3'-truncated preS/S gene in transgenic mice]

The 3'-truncated preS/S region from HBV genome, encoding a transcriptional transactivator, was cloned and a recombination expression vector for 3'-truncated HBV preS/S sequences under the control of the CMV promoter was constructed by recombination DNA techniques. Then, the expression vector DNA was microinjected into pronuclei of fertilized mouse oocytes. Founders of transgenic mice harbouring the recombination gene which can be expressed were screened by polymerase chain reaction (PCR) at genomic DNA level and confirmed by ELISA andlysis at protein level. Two of 15 mice in one series of microinjections showed the expression of 3'-truncated preS/S gene from HBV genome. The expression vector of 3'-truncated preS/S gene might be helpful for further studies of relationship between the expression production of 3'-truncated preS/S sequence and HBV-associated oncogenesis in vitro. The transgenic mice with expressing 3'-truncated preS/S gene will provide new insight into its roles in the development of human hepatocelluar carcinoma (HCC) in vivo.

Cellular pharmacology of lipophilic anthracyclines in human tumor cells in culture selected for resistance to doxorubicin

We have studied the cytotoxicity and intracellular accumulation of two lipophilic anthracyclines, pirarubicin and idarubicin, as compared to doxorubicin, in two human tumor cell lines, MCF7 and K562, and in their doxorubicin-resistant counterparts, presenting the multidrug-resistant (MDR) phenotype. The new lipophilic anthracyclines were found to present a higher cytotoxicity and accumulation than the reference anthracycline, doxorubicin, and there was a significant inverse correlation between drug accumulation and IC50 in both cell types. With the aim of identifying the reasons for the higher cytotoxicity and accumulation of lipophilic anthracyclines, we used and compared the efficiency of three MDR modulators, verapamil, quinine and S-9788. We showed that all three were able to sensitize the resistant cells to the three anthracyclines, but with different efficiencies, S-9788 being the most active reverter and quinine the least active at equimolar doses. We also observed that there was no correlation between the abilities of a modulator to reverse resistance and to restore drug accumulation. In view of the sustained activity of the modulators to increase pirarubicin and idarubicin cytotoxicity and accumulation, as they do for doxorubicin, we conclude that the better efficiency of lipophilic anthracyclines is likely to be due to their high uptake rate rather than to a decreased activity of P-glycoprotein on these drug substrates.

Murine hepatic beta-galactoside alpha 2,6-sialyltransferase gene expression involves usage of a novel upstream exon region

ST6Gal I (beta-galactoside alpha 2,6-sialyltransferase, SiaT-1, ST6N, EC 2.4.99.1) mediates the attachment of the alpha 2,6-sialyl linkage common on N-linked glycans. Previous work suggests substantial inter-species conservation in SIAT1, the gene encoding ST6Gal I. In human and in rat, hepatic-specific SIAT1 transcription is initiated at Exon I. Here we report a surprising departure in the structural organization of the murine ST6Gal I gene. By a combination of primer extension analysis, 5'-RACE analysis, and analysis of genomic sequences, we show that the murine hepatic ST6Gal I mRNA contains a novel region 5' of Exon I. This novel sequence is encoded on a discrete upstream exon, Exon H. In contrast to human and rat hepatic ST6Gal I, the murine mRNA is transcriptionally initiated at the start of Exon H. Differential mRNA blot analysis indicates that transcripts containing Exon H sequences are preferentially expressed in liver.

Inhibition of protein kinase C in multidrug-resistant cells by modulators of multidrug resistance

We have evaluated the protein kinase C (PKC) activity in two series of cultured cell lines presenting the multidrug-resistance (MDR) phenotype and in the corresponding wild-type cells: the human KB 3.1, KB A1 and KB 8.5 cell lines, and the rat C6, C6 0.5 and C6 1V cell lines. We have observed an increase in PKC activity in the MDR cell lines of the KB cell lineage, proportional to their degree of resistance to doxorubicin. In contrast, the MDR cell lines of the C6 cell lineage presented no change (C6 0.5) or even decrease (C6 1V) in PKC activity; the basal level of PKC activity in C6 cells was, however, 50-fold higher than in KB 3.1 cells. We have tested, in these lines, the effect of four modulators of MDR: verapamil, cyclosporin A, quinine and S-9788, on doxorubicin acytotoxicity and on PKC activity. We observed that cyclosporin A and S-9788, which were the most active on MDR reversal, were able to inhibit PKC activity in the KB resistant lines as well as in all C6 lines, whereas verapamil and quinine had only marginal effects on PKC activity. The distribution of PKC isoenzymes was studied by Western blots. The PKC alpha, gamma and delta isoforms were increased in the KB resistant lines as compared to wild-type cells, which could account for the increase PKC activity we observed. In contrast, PKC alpha and gamma were decreased in C6 1V cells, as expected from the results obtained for total PKC activity, but we also noticed an important decrease in PKC delta in the C6 0.5 line. Our results suggest that an increase in PKC activity is not an absolute requirement for expression of MDR, provided that the basal level be high enough; and that some modulators may act on MDR, not only through direct P-glycoprotein interaction, but also through P-glycoprotein phosphorylation or expression. The distribution of PKC isoenzymes revealed that the modifications encountered between sensitive and resistant cells mainly concerned alpha, gamma and delta isoenzymes of PKC.

Relationship between the inhibition of azidopine binding to P-glycoprotein by MDR modulators and their efficiency in restoring doxorubicin intracellular accumulation

Using three different cell lines exhibiting the MDR phenotype, we have studied the ability of eight different modulators to restore doxorubicin intracellular accumulation and to inhibit azidopine binding to membrane extracts. One cell line was of human origin (KB VI) and two of murine origin, overexpressing two different isoforms of the mdrl gene (C6 IV and C6 0.5). The modulators were distributed in different drug classes: cyclosporine A and PSC-833, quinine and quinidine, nifedipine and nicardipine, and verapamil and S-9788. We observed that there was no strict parallelism between restoration of doxorubicin intracellular accumulation and inhibition of azidopine binding. However, when considering separately each group of drugs, it appeared that the most potent drug in inhibiting azidopine labelling of P-glycoprotein (P-gp) was also the most potent in restoring doxorubicin accumulation. This indicates that azidopine binding cannot be used as a general screening test for the identification of new modulators, but rather at the level of the selection of potent analogues within a chemical family. The three cell lines behaved similarly, indicating that the structural diversity of P-pgs did not influence the efficiency and binding of modulators.

Effects of modulators of multidrug resistance on the expression of the MDR1 gene on human KB cells in culture

The effect of four modulators of multidrug resistance (MDR) on the expression of the MDR1 gene was studied in two resistant variants of the KB cell lines, KB V1 and KB A1. This was done using a semi-quantitative assay based on mRNA reverse transcription coupled with polymerase chain reaction of the cDNA obtained. An automatic DNA sequencer was used for the measurement of the fluorescent amplification products and the MDR1 signal was compared to that of the beta-actin gene of the cells. After 24 h incubation with 15 microM of the modulators, MDR1 gene expression was slightly but significantly decreased by two of them, quinine and cyclosporine A, whereas verapamil and S-9788 had very little effect on this parameter. The effect were more pronounced in the KB A1 line than in the KB V1 line. The effect of quinine was studied over a longer time period (4-48 h) and was shown to be maximum at 24 h. These results favor the existence of a direct effect of some MDR reverters, especially quinine, on the expression of the MDR1 gene and could partially explain their modulating effect of MDR.

Genetics of scnDNA polymorphisms in juvenile oysters (Crassostrea virginica). Part I: Characterizing the inheritance of polymorphisms in controlled crosses

The amplification of DNA by polymerase chain reaction followed by restriction enzyme digestion was used to examine five anonymous single-copy nuclear DNA polymorphisms in 11 pair crosses for juvenile oysters (Crassostrea virginica). There was an overall 7% frequency of aberrant (non-Mendelian) offspring genotypes among 174 total pair-cross progeny. Strict Mendelian inheritance of alleles was observed for two of the five loci. Possible explanations for the aberrant offspring genotypes include nonamplifiable alleles owing to priming site polymorphism or aneuploidy, or paralogous amplification. Analysis of more pair crosses is needed to test these explanations.

On the mechanism of action of doxorubicin encapsulation in nanospheres for the reversal of multidrug resistance

We had previously shown that doxorubicin encapsulation in polyisohexylcyanocrylate nanospheres could circumvent the P-glycoprotein-mediated multidrug resistance (MDR) exhibited by C6 rat glioblastoma in culture. We then investigated what could be the mechanism of such a circumvention. The cytotoxicity of free and encapsulated doxorubicin was evaluated in two MDR variants of the C6 cell line in a device allowing the separation of cells from drugs by a polycarbonate membrane of 0.2 micron pore size. We observed that the progressive disruption of the nanospheres allowed their doxorubicin content to reach the cell monolayer and exert its cytotoxicity in a fashion similar to that exhibited by free doxorubicin. However, no circumvention of MDR is obtained by doxorubicin encapsulation when drug-containing nanospheres are separated from the cells by the polycarbonate membrane. In addition, no effect on azidopine binding to P-glycoprotein-enriched membranes is exerted by unloaded nanospheres, even after their spontaneous degradation in cell-culture medium. Taken together, these results suggest that a physical contact between doxorubicin-containing nanospheres and the cells is required for the circumvention of MDR. The role of degradation products from the nanospheres as modulators of P-glycoprotein activity can be ruled out.

Azelastine and flezelastine as reversing agents of multidrug resistance: pharmacological and molecular studies

The effects of two new phthalazinone derivatives, azelastine (AZ) and flezelastine (FZ), on the reversal of resistance to doxorubicin (dox) were studied using two variants of the rat C6 glioblastoma cell line, selected with dox (C6 0.5) or with vincristine (C6 1V). Both lines presented a multidrug-resistant phenotype which was, in the case of C6 0.5 cells, likely to be accompanied by an additional mechanism leading to intracellular tolerance of the drug. Both AZ and FZ reversed dox resistance in a concentration-dependent manner, and FZ was shown to be at least three times more potent than AZ. FZ was able, at a relatively high concentration (30 microM), to completely restore dox sensitivity in both cell lines. Both drugs were able to virtually restore dox accumulation to the level reached in sensitive cells, and, interestingly, this complete restoration occurred at lower concentrations of modulator than required for complete reversal of resistance. FZ was able to reverse dox intracellular tolerance of C6 0.5 cells and to restore dox accumulation at the IC50 to the level observed in sensitive cells. AZ and FZ both inhibited azidopine binding to membrane preparations of C6 0.5 and C6 1V cells, although FZ was more potent. Both drugs more successfully inhibited azidopine binding to membranes prepared from C6 1V cells (which express the mdr1b gene product) than to membranes from C6 0.5 cells (which express the mdr1a gene product). In view of its potent activity on MDR, further preclinical evaluation of FZ is warranted.

Failure of liposomal encapsulation of doxorubicin to circumvent multidrug resistance in an in vitro model of rat glioblastoma cells

We studied the capacity of doxorubicin encapsulation in liposomes of various lipid compositions to circumvent multidrug resistance in several variants of the C6 rat glioblastoma cell line in culture, and to inhibit azidopine binding to membranes isolated from these cells. Three formulations of liposomes were prepared: (a) phosphatidylcholine (PC)/phosphatidylserine (PS)/cholesterol (cho) at a 9/24 ratio; (b) PC/cardiolipin (CL)/cho at 10/1/4 ratio; (c) dipalmitoylphosphatidylcholine (DPPC)/cho at 11/4 ratio. Unloaded liposomes presented no cytotoxicity against sensitive or resistant cells. Doxorubicin encapsulated in PC/PS/cho and PC/CL/cho liposomes had a cytotoxic activity close to that of free doxorubicin, whereas doxorubicin encapsulated in DPPC/cho liposomes was significantly less active than free doxorubicin in sensitive as well as in two of the three multidrug resistant cell lines, and as active as free doxorubicin in the third one. Free doxorubicin was able to decrease 50% of [3H]azidopine photolabelling to P-glycoprotein at a concentration of 40 microM; doxorubicin encapsulated in PC/CL/cho or PC/PS/cho liposomes was able to inhibit [3H]azidopine binding similarly as free drug, whereas doxorubicin encapsulated in DPPC/cho liposomes had no significant effect on this parameter. Unloaded liposomes of either lipid composition had no effect on [3H]azidopine binding. Together with physical studies performed in parallel on doxorubicin trapping in liposomes (J Liposome Res 1993, 3, 753-766), these results suggest that doxorubicin leaked out of fluid liposomes (PC/PS/cho or PC/CL/cho), whereas rigid liposomes (DPPC/cho) were able to sequester the drug more efficiently. In that case, however, no availability of the drug to the cells was possible and only a weak cytotoxicity was exhibited, especially without any favourable effect on multidrug resistance. In conclusion, no reversal of doxorubicin resistance was found to occur through liposomal encapsulation of the drug.