Evaluation of testing capabilities for the determination of melamine in milk through an interlaboratory proficiency test programme during the melamine crisis

An interlaboratory proficiency testing programme for melamine in milk was organized for field laboratories in Hong Kong, China, during the melamine crisis in late September 2008. One blank test sample and three homogenous samples prepared by gravimetric spiking of melamine at the concentration range of zero to 4.5 mg kg(-1) were given to participants in this programme. A total of 13 participants returned the results to the organizer and they used either liquid chromatography-tandem mass spectrometry (LC-MS/MS) or gas chromatography-mass spectrometry (GC-MS) for their determinations. The performance of the participants was assessed by determining z-scores, calculated from the bias from the assigned reference values and Horwitz standard deviation. The median values of pooled data were found to be in good agreement with the reference values and the majority of the participants demonstrated their capabilities in the quantitative measurement of melamine in milk samples. However, four participants gave false-positive results for the blank test sample, probably due to cross-contamination from other samples, and they were requested to investigate the actual causes. In summary, eight participants (or 62%) demonstrated their competence for all the four test samples.

DNA Damage Induced by Hypocrellin-A Photosensitization

Hypocrellin-A (HC-A) isolated from Hypocrellia bambusae Sacc., is a new and effective photosensitizer. Illumination of sarcoma 180 cells with visible light in the presence of HC-A leads to a decrease in cell viability and 3H-TdR incorporation, causes DNA strand breakage, and results in the selective destruction of guanine moieties in DNA. HC-A photosensitization causes an increase in the theta 260/theta 280 ratio in the circular dichroism spectra of DNA in vitro. Of the four usual 2'-deoxynucleotides illuminated in the presence of HC-A only 2'-deoxyguanylic acid was destroyed.

Cyclooxygenase inhibitors differentially modulate p73 isoforms in neuroblastoma

p73 encodes multiple functionally distinct isoforms. Proapoptotic TAp73 isoforms contain a transactivation (TA) domain, and like p53, have tumor suppressor properties and are activated by chemotherapies to induce cell death. In contrast, antiapoptotic DeltaNp73 isoforms lack the TA domain and are dominant-negative inhibitors of p53 and TAp73. DeltaNp73 proteins are overexpressed in a variety of tumors including neuroblastoma. Thus, identification of drugs that upregulate TAp73 and/or downregulate DeltaNp73 represents a potential therapeutic strategy. Here, we report that cyclooxygenase (COX) inhibitors induce apoptosis independent of p53, and differentially modulate endogenous p73 isoforms in neuroblastoma and other tumors. COX inhibitor-mediated apoptosis is associated with the induction of TAp73beta and its target genes. COX inhibitors also downregulate the alternative-spliced DeltaNp73(AS) isoforms, Deltaexon2 and Deltaexon2/3. Furthermore, forced expression of DeltaNp73(AS) results in diminished apoptosis in response to the selective COX-2 inhibitor celecoxib. Celecoxib-mediated downregulation of DeltaNp73(AS) is associated with decreased E2F1 levels and diminished E2F1 activation of the p73 promoter. These results provide the first evidence that COX inhibitors differentially modulate p73 isoforms leading to enhanced apoptosis, and support the potential use of COX inhibitors as novel regulators of p73 to enhance chemosensitivity in tumors with deregulated E2F1 and in those with wild-type (wt) or mutant p53.

Cyclooxygenase inhibitors modulate the p53/HDM2 pathway and enhance chemotherapy-induced apoptosis in neuroblastoma

Cyclooxygenase-2 (COX-2) is upregulated in many tumors including neuroblastoma, and its overexpression has been implicated in resistance to p53-dependent apoptosis. Although p53 is rarely mutated in neuroblastoma, the p53 protein is rendered inactive via several mechanisms including sequestration in the cytoplasm. Here, we show that COX inhibitors inhibit the growth of neuroblastoma and when combined with low doses of chemotherapy, exert synergistic effects on neuroblastoma cells. Following COX inhibitor treatment, HDM2, which targets p53 for ubiquitin-mediated degradation, is downregulated, resulting in an attenuation of p53 ubiquitination and an increase in p53 half-life. The level of HDM2 phosphorylation at ser166, which influences both HDM2 and p53 subcellular distribution, is markedly diminished in response to COX inhibitors and is associated with increased p53 nuclear localization. Combining COX inhibitors with low-dose chemotherapy potentiates apoptosis and p53 stability, nuclear localization, and activity. p53 knockdown by siRNA resulted in the rescue of COX-inhibitor-treated cells, indicating that COX inhibitor-induced apoptosis is, at least in part, p53-dependent. Taken together, these results provide the first evidence that COX inhibitors enhance chemosensitivity in neuroblastoma via downregulating HDM2 and augmenting p53 stability and nuclear accumulation.

Adaptations of linkage and association methods for the study of asthma, a complex trait

Early studies that found significant linkage between markers on 5q and asthma and IgE have not been reproduced. In an attempt to improve the power of these studies we performed a variance components linkage analysis and transmission-disequilibrium tests (TDT) with haplotypes using markers on 5q, using the Southampton and Perth data sets supplied by GAW. The linkage analysis with covariates revealed a maximum lod of 1.57 in the Perth families. The addition of age and RAST significantly improved the fit of the null models but did not improve the lod scores. The TDT tests showed a marginally significant association with D5S393 and D5S399 and with three markers together (IL9, IL4, D5S393). We conclude that further studies are needed to delineate the environmental contribution to this disease so that the genetic factors can be more easily identified. In addition, haplotype analysis may help to identify specific genetic effects.

Assessing the effect of sampling strategies on the power of linkage analysis to identify pathway-specific loci underlying a complex disease

Using the simulated general population data sets, we first examined the effect of sampling strategies on the power of identifying linkage by selecting samples with (A) two affected sibs in a nuclear family and (B) one affected sib and one sib with an intermediate trait value in the upper quantiles. Second, we evaluated the improvement in power when analyzing correlated traits simultaneously. Under each selection criteria, 100 replicates of 300 nuclear families were sampled and analyzed with two-point linkage analysis for ten markers (1 cM apart) from each of the candidate regions. Different genes were identified under different sampling strategies. When a gene has a pleitropic effect, it is more powerful to analyze correlated traits simultaneously, either by using a linear combination or the larger value of standardized traits, than to analyze each trait separately.

Genome scan for blood pressure in Dutch dyslipidemic families reveals linkage to a locus on chromosome 4p

Genes contributing to common forms of hypertension are largely unknown. A number of studies in humans and in animal models have revealed associations between insulin resistance, dyslipidemia, and elevated hypertension. To identify genes contributing to blood pressure (BP) variation associated with insulin-resistant dyslipidemia, we conducted a genome-wide scan for BP in a set of 18 Dutch families exhibiting the common lipid disorder familial combined hyperlipidemia. Our results reveal a locus on chromosome 4 that exhibits a significant lod score of 3.9 with systolic BP. In addition, this locus also appears to influence plasma free fatty acid levels (lod=2.4). After adjustment for age and gender, the lod score for systolic BP increased to 4.6, whereas the lod score for free fatty acid levels did not change. The chromosome 4 locus contains an attractive candidate gene, alpha-adducin, which has been associated with altered BP in animal studies and in some human populations. However, we found no evidence for an association between 2 intragenic alpha-adducin polymorphisms and systolic BP in this sample. We also observed suggestive evidence for linkage (lod=1.8) of diastolic BP to the lipoprotein lipase gene locus on chromosome 8p, supporting a finding previously observed in a separate insulin-resistant population. In addition, we also obtained suggestive evidence for linkage of systolic BP (lod=2.4) and plasma apolipoprotein B levels (lod=2.0) to a locus on proximal chromosome 19p. In conclusion, our genome scan results support the existence of multiple genetic factors that can influence both BP and plasma lipid parameters.

Coincident linkage of fasting plasma insulin and blood pressure to chromosome 7q in hypertensive hispanic families

BACKGROUND

Insulin resistance (IR) and hyperinsulinemia are phenotypically associated with hypertension. We have previously provided evidence that blood pressure (BP) and IR cosegregate in Hispanic families, suggesting that this association has a genetic component. In the present study, we provide further support for the hypothesis of a genetic basis for the BP-IR relationship from a genetic linkage study.

METHODS AND RESULTS

A 10-cM genome scan was conducted in 390 Hispanic family members of 77 hypertensive probands. Detailed measurements of BP, glucose, insulin levels, and insulin sensitivity (euglycemic clamp) were performed in adult offspring of probands. Multipoint variance component linkage analysis was used. A region on chromosome 7q seemed to influence both IR and BP. The greatest evidence for linkage was found for fasting insulin (lod score=3.36 at 128 cM), followed by systolic BP (lod score=2.06 at 120 cM). Fine mapping with greater marker density in this region increased the maximum lod score for fasting insulin to 3.94 at 125 cM (P=0.00002); lod score for systolic BP was 2.51 at 112 cM. Coincident mapping at this locus also included insulin sensitivity measured by the homeostasis assessment model (HOMA) and serum leptin concentrations. Insulin sensitivity by euglycemic clamp did not map to the same locus.

CONCLUSIONS

Our results demonstrate that a major gene determining fasting insulin is located on chromosome 7q. Linkage of BP, HOMA, and leptin levels to the same region suggests this locus may broadly influence traits associated with IR and supports a genetic basis for phenotypic associations in IR syndrome.

The heterogeneity in risk factors of lung cancer and the difference of histologic distribution between genders in Taiwan

OBJECTIVE

The difference in histologic patterns of lung cancer between men and women in Taiwan may be associated with the heterogeneity in causal factors of lung cancer between the sexes. A sex- and age-matched case-control study was designed to investigate such a relationship.

METHODS

Cases consisted of 236 male and 291 female incident cases with newly diagnosed and histologically confirmed primary carcinoma of the lung, and were compared to one or two individually matched controls.

RESULTS

Cigarette smoking, occupations, and previous tuberculosis history were found to independently correlate with an elevated risk of squamous/small cell carcinoma and adenocarcinoma for male patients. However, there was little difference in the effect of these risk factors except smoking. The use of fume extractors in the kitchen, and the habit of waiting to fry after the fumes were emitted, separately explained the majority of the attributable fraction of female squamous/small cell carcinoma (28.2%) and adenocarcinoma (47.7%). With the exception of a kitchen with fume extractors and a clinical history of tuberculosis, the environmental causal factors of lung cancer were heterogeneous between these two histologic cell groups.

CONCLUSIONS

Our results suggested that the causal factors of lung cancer might be specific for the type of tumor concerned. The gender-specific risk factors of lung cancer could partly explain the difference in cell-type distribution between men and women.

Evidence for joint genetic control of insulin sensitivity and systolic blood pressure in hispanic families with a hypertensive proband

BACKGROUND

The clustering of hypertension, insulin resistance, and obesity remains unexplained. We tested for genetic and nongenetic influences on the association among these traits in Hispanic families with hypertension.

METHODS AND RESULTS

Blood pressure and body mass index (BMI) were measured in 331 members of 73 Hispanic families in which an index case (proband) had hypertension. Insulin sensitivity (S(I)) was measured by euglycemic clamp in 287 probands and their spouses (parents' generation) or their adult offspring. Correlation analysis examined relationships among traits within and between generations. Path analysis estimated genetic and nongenetic contributions to variability in systolic blood pressure (SBP), S(I), and the correlation between them. In the offspring, there was a significant correlation between individuals for each trait, as well as significant correlations within and between individuals for all possible pairs of traits. Between generations, SBP, S(I), and BMI in parents correlated with the same traits in their offspring; BMI in parents correlated with S(I) and SBP in offspring; and S(I) in parents correlated with SBP in offspring. Path analysis estimated that among offspring, genetic effects unrelated to BMI accounted for 60.8% of the variation in SBP, 36.8% of the variation in S(I), and 31.5% of the correlation between SBP and S(I) after adjustment for age and sex. Heritable effects related to BMI accounted for an additional 14.0% of variation in SBP, 26.8% of variation in S(I), and 56.3% of variation in their correlation.

CONCLUSIONS

Clustering of hypertension and insulin resistance in Hispanic Americans is accounted for in part by heritable factors both associated with and independent of BMI.

Segregation analysis of asthma: recessive major gene component for asthma in relation to history of atopic diseases

Although asthma has a significant heritable component, the mode of inheritance remains controversial because of the complexity of the disease and the influence of environmental factors. Segregation analysis for asthma are performed with and without a history of atopic diseases (dermatitis and rhinitis) after adjusting for environmental factors. To investigate whether asthma may be inherited through a major gene with two alleles, the REGD program of the Statistical Analysis for Genetic Epidemiology (SAGE) package was conducted in 1,990 individuals from 227 families with at least one asthmatic child in a cross-sectional study of respiratory diseases in Southern Taiwan. Other covariates adjusted for included age, sex, current smoking, and environmental tobacco smoking. The hypothesis of Mendelian model and no parent-offspring transmission was rejected. However, when the variables of atopic disease and environmental factors were included in the model as covariates, the models for a two-allele gene with a recessive or codominant inheritance could not be rejected, and Akaike's Information Criterion was smaller (1,377. 13) for the recessive model than all of the other models tested, assuming a major gene with a population frequency of 0.56 +/- 0.04. However, Mendelian model without family effect was rejected. In conclusion, a history of asthma in parents is a strong risk factor for asthma in offspring. Under the assumptions of the applied segregation, at least one major gene exists that could be a gene involved also in allergy. However, the data suggest that a single locus gene explains a portion of asthma that is related to the history of atopic diseases. In addition, a polygenic/multifactorial (genetic and environmental factors) influence with a recessive component inheritance may be involved in the pathogenesis of asthma.

Segregation analysis of drinking problem in elderly men and their first-degree relatives from the Western Collaborative Group Study

PURPOSE

The purpose of this study is to determine the mode of inheritance of alcohol-related drinking problems.

METHODS

Family history was collected by interview from 493 elderly male participants (probands) in a follow-up cardiovascular exam of healthy white men living in the San Francisco Bay Area and Los Angeles. Segregation analysis was used to test for the presence of a major gene effect underlying the liability to develop an alcohol-related drinking problem.

RESULTS

The results showed that the liability to drinking problem is due, in part, to a single major gene with no residual effects from shared familial influences.

CONCLUSIONS

These results suggest that at least one major gene is involved in the genetic predisposition to develop drinking problem in late adulthood.

Segregation analysis of cardiovascular reactivity to laboratory stressors

To better understand the contribution of major gene influences to individual differences in cardiovascular reactivity, we performed a segregation analysis on blood pressure responses to two laboratory tasks, mental arithmetic and bicycle exercise. The study population consisted of 1,451 adults (age > or = 18 years) who were members of 81 Utah pedigrees. Only 864 members performed the bicycle task because persons age 60 years or older or with heart disease were excluded. Blood pressure reactivity to mental arithmetic was defined as change from resting values, and reactivity to the bicycle task was defined as the difference between maximum blood pressure during exercise and resting values adjusted for the individual's workload. Complex segregation analysis and likelihood procedures were used to test for a major gene effect controlling blood pressure reactivity to each task. Two modifiers of the penetrance, age and sex, were considered parameters in these models. We found that diastolic blood pressure (DBP) but not systolic blood pressure reactivities to the mental arithmetic and bicycle exercise tasks were controlled by major gene effects. The best-fitting model, however, differed for the two tasks. For DBP reactivity to mental arithmetic, a major codominant model with gene frequency 0.10 was the best-fitting model; for the bicycle task, the best-fitting model was a mixed recessive model with gene frequency 0.21. Sex differences in DBP reactivity were significant in both tasks: the effect of age was significant only for the mental arithmetic task. These results suggest a significant genetic component for DBP reactivity to laboratory stressors.

A genetic analysis of smoking behavior in family members of older adult males

AIMS

To conduct a genetic study of smoking behavior in 493 three-generation families.

DESIGN

Complex segregation analysis and maximum likelihood statistics were used to describe the familial clustering of ever-smoking under several transmission models.

SETTING

The Western Collaborative Group Study, an ageing and health study currently in its 39th year of follow-up.

PARTICIPANTS

Probands were male participants who were of mean age 71.6 years at the time of the family history interview in 1986-88.

MEASUREMENTS

Data were collected via an interview that focused on the family smoking history of participants. Smoking histories of all first-degree relatives were obtained from probands.

FINDINGS

Evidence for genetic transmission was indicated by rejection of both the environmental and sporadic models in favor of a Mendelian genetic model with residual familial effects from spouses and both parents.

CONCLUSIONS

The best-fitting model was that of a dominant major gene with low estimated frequency and residual familial correlations. This is the first study to date to model the familial transmission of ever-smoking in three-generation families.

Chinese food cooking and lung cancer in women nonsmokers

Cigarette smoking cannot fully explain the epidemiologic characteristics of lung cancer in Taiwanese women, who smoke rarely but have lung cancer relatively often. In a previous study, the authors suspected that exposure to fumes from cooking oils was an important risk factor for lung cancer in Taiwanese women nonsmokers in the Republic of China. In a new case-control study conducted in 1993-1996, they further explored the association of oil fumes with lung cancer in women. Two sets of controls were used concurrently. The subjects were 131 nonsmoking incident cases with newly diagnosed and histologically confirmed primary carcinoma of the lung, 252 hospital controls hospitalized for causes unrelated to diseases of smoking, and 262 community controls; all controls were women nonsmokers matched by age and date of interview. Details on cooking conditions and habits were collected, in addition to other epidemiologic data. Lung cancer risk increased with the number of meals per day to about threefold for women who cooked these meals each day. The risk was also greater if women usually waited until fumes were emitted from the cooking oil before they began cooking (adjusted odds ratios = 2.0-2.6) and if they did not use a fume extractor (adjusted odds ratios = 3.2-12.2). These results suggest that a proportion of lung cancer may be attributable to the habit of waiting until the cooking oil has been heated to a high temperature before cooking the food.

Segregation analysis reveals a major gene effect controlling systolic blood pressure and BMI in an Israeli population

It has been suggested that genetic factors control blood pressure level at all ages. However, the evidence is limited because of the composite nature of blood pressure and the heterogeneity of the studied samples. The purpose of the present study is to test for genetic influences on systolic blood pressure (SBP) level in a community-based Israeli family study. Segregation analysis was performed on 622 adults from 208 pedigrees. Age, sex, and body mass index (BMI) were significant covariates of SBP. Segregation analysis rejected the environmental transmission model but not the mixed Mendelian transmission model. The best-fitting genetic model was the mixed codominant model, with a heritability of 0.32 and an allele frequency of 0.18 for high SBP level. We further tested whether SBP and BMI shared a common major gene effect. Using bivariate segregation analysis involving two traits and a single locus, we found evidence for a single-locus pleiotropic effect on SBP and BMI. The allele frequency of this major locus was 0.24. The residual genetic correlation resulting from additive polygenes and the environmental correlation between these two traits were not different from zero after taking into account the shared major gene effect. The proportion of phenotypic variation attributable to this major gene effect increased with age for SBP but decreased with age for BMI.

The value of ultrasound in the assessment of incompetent perforating veins

To determine the value of ultrasound in identifying significant perforator disease we assessed 121 perforators in 90 legs of 61 consecutive patients referred for assessment of varicose veins over a 6 month period. Perforators greater than 4mm in diameter demonstrated reflux in approximately 60% of cases, perforators 3-4 mm in diameter demonstrated reflux in approximately 45% and perforators less than 3 mm in diameter demonstrated reflux in approximately 25% of cases. From correlation with previous published data we recommend that all perforators greater than 4 mm in diameter be considered incompetent regardless of whether reflux is demonstrated.

Evidence for a major gene influencing 7-year increases in diastolic blood pressure with age

The contribution of genetic factors to blood pressure levels is well established. The contribution of genes to the longitudinal change in blood pressure has been less well studied, because of the lack of longitudinal family data. The present study investigated a possible major-gene effect on the observed increase with age in diastolic blood pressure (DBP) levels. Subjects included 965 unmedicated adults (age > or = 18 years) in 73 pedigrees collected in Utah as part of a longitudinal cardiovascular family study. Segregation analysis of DBP change over 7.2 years of follow-up identified a recessive major-gene effect with a gene frequency of p = .23. There was also a significant age effect on the genotypic means, which decreased expression of the major gene at older ages. For those inferred to have the genotype responsible for large DBP increases, DBP increased 32.3%, compared with a 1.5% increase in the nonsusceptible group (P < .0001). The relative risk of developing hypertension between the susceptible and nonsusceptible groups after 7.2 years was 2.4 (P = .006). Baseline DBP reactivities to mental arithmetic (P < .0001), and isometric handgrip (P < .0001) stress tests were greatest in those assigned to the susceptible genotype. We conclude that age-related changes in DBP are influenced by a major gene. Characteristics of this major-gene effect for greater age-related blood pressure increases include greater reactivity to mental and physical stressors. The present study thus provides evidence for genetic control of changes in blood pressure, in addition to the previously suggested genetic control of absolute blood pressure level.

Binding of etiopurpurin to human plasma proteins. Delivery in cremophor EL and dimethyl sulphoxide. III

Binding of the photosensitizer etiopurpurin (ET2) to human plasma was assessed, using conditions that would yield a high percentage of ET2 in the form of LDL-bound monomers which may favor photosensitizer tumor localization. Two delivery systems, Cremophor EL (CRM) and dimethyl sulphoxide (DMSO), were used. The binding of ET2 to CRM-modified lipoproteins was compared to the binding of the dye to the native proteins using delivery in DMSO. Plasma-bound monomers and unbound high density aggregates were shown to coexist. The density and rate of formation of the dye aggregates were correlated. The aggregates formed by delivery in DMSO could be partially converted into plasma-bound monomeric ET2. There was no mode-delivery-effect upon the distribution of monomeric ET2 among the plasma proteins. 70% of monomeric ET2 was bound to LDL and most of the remainder to HDL. In delivery in DMSO the yield of LDL-bound dye monomers (up to 30% of added ET2) increased with decreasing concentration of ET2 in the delivery solution and with increasing time of incubation (< or = 48 hr). Long incubation also induced changes in the densities of LDL and HDL. The yields of LDL-bound monomers (up to 40%) increased with increasing concentration of CRM-bound ET2. High yields of LDL-bound monomers were obtained using both modes of delivery. Although the aggregates associated with the two modes of delivery had different properties. The change in lipoprotein composition might be involved in the conversion of aggregates into plasma-bound monomers.

[The effects of management difficulty and family functions on metabolic control of insulin-dependent diabetes mellitus]

This study was designed as a quantitative study. Subjects ranging from the fourth grade of primary school to the third year of senior high school were drawn from the survey project of Taipei IDDM Registry and from the Kang-Tai IDDM Association. The mothers of these diabetic children were asked to complete questionnaires. The purpose of this paper was to explore the influences of maternal stress, management difficulties and family function on self-management of diabetes and HbA1c. Results indicated that family function was positively and significantly related with self-management. There was a significant correlation between the difficulty of diet control and self-management. The total self-management, blood glucose monitoring and preventive measures for hypoglycemia were negatively correlated with HbA1c. Forty-six point six percent of the variance of self-management could be explained by the family role function, paternal education, patient's school grade, religion and difficulty of diet control. Forty-two point six percent of the variance of HbA1c could be accounted for by total self-management, payment method, difficulty of blood glucose monitoring and frequency of hospitalization due to hypoglycemia.

Binding of etiopurpurin and tin-coordinated etiopurpurin to human plasma proteins. Delivery in cremophore EL and dimethyl sulfoxide (paper II)

Purpurins are potent hydrophobic photosensitizers in vivo. Cremopfore EL is an important vehicle for the administration of hydrophobic drugs. Mode-delivery-effects on the binding of etiopurpurin (ET2) to human plasma (LDL, HDL, and high density proteins, HDP) is studied for delivery in CRMaq and in DMSO by ultracentrifugation. A similar study of SnET2 is available (Kongshaug et al., 1993) and has been extended. In the absence of plasma, only nonfluorescent ET2 entities (aggregates) were present, a portion of which moved unaffected by gravity (small aggregates), the remainder according to their densities (high density aggregates). Aggregated ET2 showed, at high salt density, similar positions and halfwidths in the gradient, and similar adsorption properties as the aggregates in plasma-containing samples. In CRMaq (1 mg CRM/ml) the adsorptive loss of the dye affected only marginally the binding of fluorescent monomeric ET2. In this mode (i) 20% of ET2 was bound as monomers, about 70% of which to CRM-modified LDL, most of the remainder to CRM-modified HDL; (ii) such HDL also marginally bound small aggregates; (iii) only monomeric ET2 was bound to CRM-modified LDL. In delivery in DMSO, aggregated ET2 (98% of ET2 in the gradient) converted, post centrifugally, into minor amounts of HDL-bound monomeric ET2; LDL-bound ET2 included monomers (about 50%) and small aggregates, mainly dimers. The percentage binding of SnET2 to HDP was independent of the concentrations of CRMaq and HDL. Plasma-bound small aggregates (such as dimers) and plasma-unbound high density aggregates (mean densities of 1.13-1.19 g/ml) were substantially present in the plasma-containing samples. There were mode-delivery-effects upon the yields and properties of aggregated ET2, and upon the yields of plasma-bound monomeric ET2. Monomeric ET2 showed a remarkably high percentage binding to LDL and was similarly distributed among the lipoproteins as is total cholesterol. There was little or no real mode-delivery-effect upon the distribution of monomeric ET2 among the plasma proteins. The affinity of CRM-modified LDL for SnET2 was similar to that of HDL plus HDP in native plasma.

Binding of drugs to human plasma proteins, exemplified by Sn(IV)-etiopurpurin dichloride delivered in cremophor and DMSO

1. The mode-delivery-effect upon the binding of Sn(IV)-etiopurpurin dichloride (SnET2) in human plasma has been studied by ultracentrifugation, combined with absorption and fluorescence spectroscopy. SnET2 was delivered to plasma either in Cremophore EL (CRM) or in dimethyl sulfoxide (DMSO). To facilitate interpretation, optical, conductivity and aggregation properties of SnET2 were obtained for various solutions. 2. The second order rate constant for the aggregation of SnET2 monomers seemed to be remarkably small, of the order of 10(3) M-1 min-1. 3. SnET2 was bound as monomeric entities. Such entities had environmental-sensitive fluorescent properties dependent on the type of protein or solvent (DMSO, CRM, H2O) with which they interacted. 4. SnET2 showed saturable binding with high density subfraction(s) of high density lipoproteins and with one or more high density proteins. Complete or substantial saturation was achieved at the SnET2 level of 3.5 micrograms/ml. Such binding might be mediated by apolipoprotein D and alpha 1-acid glycoprotein. 5. There was little effect of SnET2 concentrations (3.5-35 micrograms SnET2/ml) upon the plasma binding of SnET2, irrespective of the mode of delivery. 6. The percentages of SnET2 bound to low density lipoproteins (LDL), high density lipoproteins (HDL), and high density proteins (HDP) were 10, 70 and 20%, respectively, for delivery in DMSO. The value for LDL also includes binding with very low density lipoproteins (VLDL). For delivery in CRM the corresponding values were 20, 50 and 30%. Apparently, CRM interacted with HDL entities and reduced their affinity for SnET2. 7. The distribution pattern of SnET2 among lipoproteins reflects interactions with apoproteins and/or with surface phospholipids rather than with core lipid constituents of lipoproteins. 8. Conductivity measurements showed that SnET2 was partly an ionic entity in water. 9. The plasma binding of SnET2 is compared with the corresponding binding of other drugs, both tetrapyrroles and nontetrapyrroles.

The effect of glucose administration on the uptake of photofrin II in a human tumor xenograft

Athymic BALB/c nude mice, bearing a human melanoma LOX, were given the photosensitizing drug Photofrin II (10 mg/kg body wt.) intraperitoneally. The mice were also given one of the following chemicals intraperitoneally: glucose, galactose and glucose plus nordihydroguaiaretic acid (NDGA) which is an inhibitor of glycolysis. Multiple injections of glucose (3 g/kg body wt. given at -1, 0, +1 and +3 h relative to the injection of 10 mg/kg of Photofrin II at time 0) resulted in a significant increase in the uptake of Photofrin II in the tumor 4 h after a Photofrin II injection, while the uptake of Photofrin II in the other tissues remained unchanged. Administration of galactose had no significant effect on the uptake of Photofrin II in the tissues studied (tumor, muscle, skin and liver). NDGA seemed to abolish the effect of glucose injection.

Interaction of cremophor EL with human plasma

1. Interaction of cremophor EL (CRM) with human plasma lipoproteins and nonlipoproteins has been investigated by ultracentrifugation. 2. VLDL has only a low or negligible capacity to bind CRM, i.e. there is little or no change in the optical absorption at 280 nm of VLDL when CRM is added. 3. A low density subfraction of low density lipoproteins seems to associate substantially with CRM at relatively low CRM concentrations (1-3 mg/ml), but such association is not evident for CRM concentrations in the region 12-116 mg/ml. 4. Low density lipoproteins (LDL) may act as a carrier for CRM-emulsions, yet there seems to be no concomitant change in the 280 nm optical absorption of the proteins of LDL. 5. The position in the gradient (i.e. in the centrifugation tube after centrifugation) of high density lipoproteins (HDL) is shifted towards lower density in the presence of 1-4 mg CRM/ml. For higher concentrations of CRM, a destruction of HDL can be observed: the HDL distribution is converted into a bimodal distribution of respectively lighter and heavier "HDL"-particles than the normal ones; the densities at the peaks of these distributions are approximately 1.07 g/ml (light), 1.20 g/ml (heavy) and 1.11 g/ml (normal HDL). The optical extinction coefficient is apparently the same for the proteins of normal--and modified HDL. 6. Even high CRM concentrations (less than or equal to 116 mg/ml) have no perceptible effect on the gradient positions and profile of human serum albumin (HSA) and/or other heavy proteins. 7. The possible biological significance of these findings is briefly touched upon.

Tin etiopurpurin dichloride-sensitized lipid photooxidation of erythrocyte membranes

Tin(IV) etiopurpurin dichloride (SnET2 x 2Cl) is a photosensitizer which has been shown to be an effective photodynamic agent for the treatment of transplantable animal tumors in vivo. The purpose of this study was to understand the effect of SnET2 x 2Cl on membrane lipid peroxidation. When erythrocyte membranes were exposed to visible light in the presence of SnET2 x 2Cl, lipid peroxidation was observed. An accumulation of lipid hydroperoxides and an increase in lipid fluorescence were also observed. Thin layer chromatography of lipid extracts from photooxidized membrane revealed photoperoxide products derived from phospholipid. Investigations into the mechanism(s) of lipid peroxidation by SnET2 x 2Cl and light-sensitized membranes were also performed. Results indicate that singlet oxygen (1O2) plays a major role in lipid peroxidation.

[Hypocrellin A-sensitized photodamage on erythrocyte membrane protein and phospholipid]

In this paper, using human erythrocyte membrane, the photodamage of Hypocrellin A to membrane protein and phospholipid was studied by measuring the lipid peroxidation, the damage of phospholipid, the change of protein secondary structure, the endogenous fluorescence change and SDS-polyacrylamide gel electrophoresis analysis. These results showed that illumination of erythrocyte membrane in presence of Hypocrellin A can cause lipid peroxidation producing fluorescence adduct and MDA, decomposing in phospholipid composition in which PE and PS were more sensitive than others. Meanwhile, the secondary structure of membrane protein was destroyed and endogenous fluorescence decreased. The photodamage on phospholipid and spectrin occurred more seriously in the case they were embedded in membrane than they were in isolated form. So we suggest that they are interactions existing between proteins and phospholipids to enhance the damage on protein and phospholipid during the HA-sensitized photodamage on membrane.

[The study on hypocrellin A-sensitized photoinactivation of enzymes of human erythrocyte membranes]

Hypocrellin A (HA)-sensitized photoinactivation of enzymes in human erythrocyte membrane, including AchE, GPDH, Na(+)-K+ ATPase, Ca2(+)-Mg2+ ATPase were studied in this paper. The sensitivity of these four enzymes inactivated by HA and light are as following order: Ca2(+)-Mg2+ ATPase greater than Na(+)-K+ ATPase greater than GPDH greater than AchE. The relationship among ATPase inactivation, sulfhydryl photoinactivation and lipid peroxidation was also investigated. Results show that SH group photooxidation probably is one of the major reasons of enzyme inactivation whereas lipid peroxidation has little effect. The isolated GPDH was less sensitive than that membrane-bound, GSH, NAD acted protectively on GPDH and ATPase respectively. The evidence of electrophoresis and protein intrinsic fluorescence showed that protein structure did not change significantly even though most activity had lost in case of GPDH.