[Development and prospect of plant mutation breeding induced by aviation and spaceflight in China]

Since 1987, about fifty species, three hundred varieties of crops have been sent in recoverable satellites or high altitude balloon (HAB). The selected lines include a high-yield, disease-resist, and hybrid-vigorous rice line, a recovered line of Japonica rice restoring sterility of Indica rice, a new green pepper strain which grows fruits over 500 g, a disease-resist, high-quality tomato line, a big-pod rape line, a big-fruit white lotus line and a big-bulb lily. The special conditions in the outer space can induce a variety of mutations in the plants and their progeny, which provides a new way for the plant breeding.

[Studies on hereditary variations of millet seed after high altitude balloon flight]

OBJECTIVE

To select high yield, high protein and fatty acid millet.

METHOD

Air-dried seeds of millet were carried by high altitude balloon (HAB) for 8 h. Botany characteristics of these seeds were analyzed and studied after recovery.

RESULT

Germinating potential rose 21.1%, germinating percentage reduced 5.2% as compared with the control; plant height was 6.8 cm lower than that of the control in SP1; while flag-leaf area and spike weight were 25% and 15.9% higher than those of the control respectively. Large-spike strains were stable in SP3 pregeny. In SP3(-2), the contents of seed protein and fatty acid were more than those of control; in SP3(-5), the average spike length was 5.8 cm, and the content of Fe element in seed was 61.5 mg/kg more than these of control; in SP4 superspike strains, spike character, chlorophyll content and photosynthetic rate were significantly higher than the control during growing phase and growing anaphase, photosynthetic rate in flag-leaf was over 27.9% higher than those in the control.

CONCLUSION

New strains with high protein and fatty acid and high yield could be selected by HAB. The characteristics of these variations in the new strain is hereditable.

[Chromosome aberration of pollen mother cell of broccoli (Brassica oleralea var. Italica) induced by space flight]

OBJECTIVE

To study the cytogenetic effect of space flight on broccoli seeds and the mechanism of mutations of the plant.

METHOD

Dry seeds of broccoli were sent to the space on board a recoverable satellite for 8 days. After recovery the seeds were planted in the field. Chromosome behaviour of pollen mother cell (PMC) samples were observed following the method of ZHU Cheng, 1982. Pollen samples were stained and embeded in lacto-phenol fuchsin for fertility determination.

RESULT

Unequal chromosome numbers of broccoli's PMC were found in the diakinesis stage, such as reducing n = 6, 7 or increasing n = 11 (earth-control number is n = 9); inversion or translocation of chromosomes occurred, and lagging chromosome were found in the anaphase and telophase of PMC meiosis growing rate and growing potential of the seeds were observed after recovery.

CONCLUSION

Leaves cexaceous decrease and aberrations in the chromosome of PMC are found in broccoli after space flight.

Remodeling of HDL by CETP in vivo and by CETP and hepatic lipase in vitro results in enhanced uptake of HDL CE by cells expressing scavenger receptor B-I

The transport of HDL cholesteryl esters (CE) from plasma to the liver involves a direct uptake pathway, mediated by hepatic scavenger receptor B-I (SR-BI), and an indirect pathway, involving the exchange of HDL CE for triglycerides (TG) of TG-rich lipoproteins by cholesteryl ester transfer protein (CETP). We carried out HDL CE turnover studies in mice expressing human CETP and/or human lecithin:cholesterol acyltransferase (LCAT) transgenes on a background of human apoA-I expression. The fractional clearance of HDL CE by the liver was delayed by LCAT transgene, while the CETP transgene increased it. However, there was no incremental transfer of HDL CE radioactivity to the TG-rich lipoprotein fraction in mice expressing CETP, suggesting increased direct removal of HDL CE in the liver. To evaluate the possibility that this might be mediated by SR-BI, HDL isolated from plasma of the different groups of transgenic mice was incubated with SR-BI transfected or control CHO cells. HDL isolated from mice expressing CETP showed a 2- to 4-fold increase in SR-BI-mediated HDL CE uptake, compared to HDL from mice lacking CETP. The addition of pure CETP to HDL in cell culture did not lead to increased selective uptake of HDL CE by cells. However, when human HDL was enriched with TG by incubation with TG-rich lipoproteins in the presence of CETP, then treated with hepatic lipase, there was a significant enhancement of HDL CE uptake. Thus, the remodeling of human HDL by CETP, involving CE;-TG interchange, followed by the action of hepatic lipase (HL), leads to the enhanced uptake of HDL CE by cellular SR-BI. These observations suggest that in animals such as humans in which both the selective uptake and CETP pathways are active, the two pathways could operate in a synergistic fashion to enhance reverse cholesterol transport.

ApoA-II maintains HDL levels in part by inhibition of hepatic lipase. Studies In apoA-II and hepatic lipase double knockout mice

High density lipoprotein (HDL) cholesterol levels are inversely related to the risk of developing coronary heart disease. Apolipoprotein (apo) A-II is the second most abundant HDL apolipoprotein and apoA-II knockout mice show a 70% reduction in HDL cholesterol levels. There is also evidence, using human apoA-II transgenic mice, that apoA-II can prevent hepatic lipase-mediated HDL triglyceride hydrolysis and reduction in HDL size. These observations suggest the hypothesis that apoA-II maintains HDL levels, at least in part, by inhibiting hepatic lipase. To evaluate this, apoA-II knockout mice were crossbred with hepatic lipase knockout mice. Compared to apoA-II-deficient mice, in double knockout mice there were increased HDL cholesterol levels (57% in males and 60% in females), increased HDL size, and decreased HDL cholesteryl ester fractional catabolic rate. In vitro incubation studies of plasma from apoA-II knockout mice, which contains largely apoA-I HDL particles, showed active lipolysis of HDL triglyceride, whereas similar studies of plasma from apoA-I knockout mice, which contains largely apoA-II particles, did not. In summary, these results strongly suggest that apoA-II is a physiological inhibitor of hepatic lipase and that this is at least part of the mechanism whereby apoA-II maintains HDL cholesterol levels.

Probucol enhances selective uptake of HDL-associated cholesteryl esters in vitro by a scavenger receptor B-I-dependent mechanism

Recently, the class B, type I scavenger receptor (SR-BI) has been shown to mediate the selective uptake of high density lipoprotein (HDL) cholesteryl esters (CEs), ie, lipid uptake independent of HDL holoparticle uptake. In vivo, this selective uptake delivers CEs to the liver for excretion and to steroidogenic tissues for hormone synthesis. Probucol, a hydrophobic antioxidant drug, lowers plasma cholesterol in humans and rodents and may inhibit progression of atherosclerosis and postangioplasty restenosis. In this study, the effect of probucol on HDL selective CE uptake was investigated in mice and in cells expressing SR-BI. Probucol feeding lowered plasma HDL cholesterol and markedly increased selective CE uptake from HDL in the liver and adrenal glands. However, probucol did not alter SR-BI protein levels in membranes from these organs. When incubated with control Chinese hamster ovary (CHO) cells, HDL isolated from probucol-treated mice (P-HDL) and HDL from control mice (C-HDL) showed similar low selective uptake of CEs. However, when incubated with SR-BI-transfected CHO cells, P-HDL showed a 2-fold increase in selective uptake compared with C-HDL. In an adrenal cell line (Y1-BS1), which expresses SR-BI in an adrenocorticotropic hormone-inducible manner, P-HDL showed significantly greater selective CE uptake than did C-HDL, and the differential response was amplified by adrenocorticotropic hormone treatment. In contrast to P-HDL, incorporation of this compound into HDL in vitro did not result in stimulation of selective CE uptake by SR-BI-transfected CHO cells, even though a significant mass of probucol could be detected in the HDL preparation. The specific interaction of P-HDL with SR-BI in cell culture could be observed after only 24 hours of probucol feeding, when there were minimal changes in HDL size and composition. Thus, probucol or one of its metabolites increases selective CE uptake in vivo by modifying HDL in a way that causes enhanced interaction with SR-BI. The increased interaction of P-HDL with SR-BI in the liver and arterial wall may be partly responsible for the effects of probucol on atherosclerosis and restenosis.

Targeted mutation of plasma phospholipid transfer protein gene markedly reduces high-density lipoprotein levels

It has been proposed that the plasma phospholipid transfer protein (PLTP) facilitates the transfer of phospholipids and cholesterol from triglyceride-rich lipoproteins (TRL) into high-density lipoproteins (HDL). To evaluate the in vivo role of PLTP in lipoprotein metabolism, we used homologous recombination in embryonic stem cells and produced mice with no PLTP gene expression. Analysis of plasma of F2 homozygous PLTP-/- mice showed complete loss of phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, sphingomyelin, and partial loss of free cholesterol transfer activities. Moreover, the in vivo transfer of [3H]phosphatidylcholine ether from very-low-density proteins (VLDL) to HDL was abolished in PLTP-/- mice. On a chow diet, PLTP-/- mice showed marked decreases in HDL phospholipid (60%), cholesterol (65%), and apo AI (85%), but no significant change in non-HDL lipid or apo B levels, compared with wild-type littermates. On a high-fat diet, HDL levels were similarly decreased, but there was also an increase in VLDL and LDL phospholipids (210%), free cholesterol (60%), and cholesteryl ester (40%) without change in apo B levels, suggesting accumulation of surface components of TRL. Vesicular lipoproteins were shown by negative-stain electron microscopy of the free cholesterol- and phospholipid-enriched IDL/LDL fraction. Thus, PLTP is the major factor facilitating transfer of VLDL phospholipid into HDL. Reduced plasma PLTP activity causes markedly decreased HDL lipid and apoprotein, demonstrating the importance of transfer of surface components of TRL in the maintenance of HDL levels. Vesicular lipoproteins accumulating in PLTP-/- mice on a high-fat diet could influence the development of atherosclerosis.

Preoperative transcatheter arterial chemoembolization and prognosis of patients with hepatocellular carcinomas: retrospective analysis of 120 cases

To clarify whether preoperative transcatheter arterial chemoembolization (TAE) improves the prognosis of patients with hepatocellular carcinoma (HCC) after surgery, 120 patients who had undergone hepatectomy for HCC from 1988 to 1994 and satisfied the criteria of stages II and III were enrolled in this study. Forty-four patients underwent preoperative TAE (group A) and 76 patients did not (group B). No significant differences in the outcomes were observed between these two groups. To rectify the comparison, patients with tumors 2 to 8 cm were assigned to groups A1 (n = 24) and B1 (n = 57), and those with tumors > 8 cm were assigned to groups A2 (n = 20) and B2 (n = 19), respectively. Although no significant differences in survival between groups A1 and B1 were found, group A2 presented superior 1-, 2-, and 3-year tumor-free survival rates of 80%, 55%, and 32% and 1-, 3-, and 5-year cumulative survival rates of 90%, 53%, and 42%. These figures are in comparison with the tumor-free survival rates of 50%, 22%, and 11% (p = 0.06), and the cumulative survival rates of 72%, 33%, and 11% (p = 0.01) during the same periods for group B2, respectively. The Cox regression model revealed that for patients with tumors > 8 cm, the relative risk of preoperative TAE for overall survival was 0.38 (p = 0.017), indicating that preoperative TAE might benefit patients with tumors > 8 cm but not those with tumors 2 to 8 cm.

Increased high density lipoprotein (HDL), defective hepatic catabolism of ApoA-I and ApoA-II, and decreased ApoA-I mRNA in ob/ob mice. Possible role of leptin in stimulation of HDL turnover

Abnormalities of plasma high density lipoprotein (HDL) levels commonly reflect altered metabolism of the major HDL apolipoproteins, apoA-I and apoA-II, but the regulation of apolipoprotein metabolism is poorly understood. Two mouse models of obesity, ob/ob and db/db, have markedly increased plasma HDL cholesterol levels. The purpose of this study was to evaluate mechanisms responsible for increased HDL in ob/ob mice and to assess potential reversibility by leptin administration. ob/ob mice were found to have increased HDL cholesterol (2-fold), apoA-I (1.3-fold), and apoA-II (4-fold). ApoA-I mRNA was markedly decreased (to 25% of wild-type) and apoA-II mRNA was unchanged, suggesting a defect in HDL catabolism. HDL apoprotein turnover studies using nondegradable radiolabels confirmed a decrease in catabolism of apoA-I and apoA-II and a 4-fold decrease in hepatic uptake in ob/ob mice compared with wild-type, but similar renal uptake. Low dose leptin treatment markedly lowered HDL cholesterol and apoA-II levels in both ob/ob mice and in lean wild-type mice, and it restored apoA-I mRNA to normal levels in ob/ob mice. These changes occurred without significant alteration in body weight. Moreover, ob/ob neuropeptide Y-/- mice, despite marked attenuation of diabetes and obesity phenotypes, showed no change in HDL cholesterol levels relative to ob/ob mice. Thus, increased HDL levels in ob/ob mice reflect a marked hepatic catabolic defect for apoA-I and apoA-II. In the case of apoA-I, this is offset by decreased apoA-I mRNA, resulting in apoA-II-rich HDL particles. The studies reveal a specific HDL particle catabolic pathway that is down-regulated in ob/ob mice and suggest that HDL apolipoprotein turnover may be regulated by obesity and/or leptin signaling.

Expression of plasma phospholipid transfer protein mRNA in normal and emphysematous lungs and regulation by hypoxia

The lung is the major site expressing plasma phospholipid transfer protein (PLTP) mRNA in humans and mice, suggesting that this protein might have an important role in maintaining normal function of this organ. In the lung of human collagenase transgenic mice, an emphysematous animal model, PLTP mRNA was 3-fold higher than in control mice. However, the mRNA in other tissues was not changed. To further assess the expression and function of PLTP, we measured PLTP mRNA level in lung tissue of two emphysematous patients and found that the mRNA was 4-fold higher than in control subjects. In situ hybridization on mouse lung suggested positive staining in alveolar type II epithelial cells. In addition, immortalized rat alveolar pre-type II epithelial cells and freshly isolated mature rat alveolar type II epithelial cells both highly expressed PLTP mRNA, and the former cells actively secreted PLTP activity into the medium. To examine the possible mechanisms leading to high levels of PLTP expression in vivo, we exposed the pre-type II cells to hypoxia and demonstrated induction of PLTP mRNA and a coordinate increase in secreted PLTP activity. Thus, the PLTP gene is highly expressed in alveolar type II epithelial cells and is induced during hypoxia and in emphysema. These observations suggest that a hypoxic stimulus occurring in emphysema may be a novel mechanism that contributes to enhanced expression of PLTP.

L-arginine prevents xanthoma development and inhibits atherosclerosis in LDL receptor knockout mice

BACKGROUND

The potential antiatherosclerotic actions of NO were investigated in four groups of mice (n = 10 per group) lacking functional LDL receptor genes, an animal model of familial hypercholesterolemia. Group 1 was fed a regular chow diet. Groups 2 through 4 were fed a 1.25% high-cholesterol diet. In addition, group 3 received supplemental L-arginine and group 4 received L-arginine and N omega-nitro-L-arginine (L-NA), an inhibitor of NO synthase (NOS).

METHODS AND RESULTS

Animals were killed at 6 months; aortas were stained with oil red O for planimetry and with antibodies against constitutive and inducible NOSs. Plasma cholesterol was markedly increased in the animals receiving the high-cholesterol diet. Xanthomas appeared in all mice fed the high-cholesterol diet alone but not in those receiving L-arginine. Aortic atherosclerosis was present in all mice on the high-cholesterol diet. The mean atherosclerotic lesion area was reduced significantly (P < .01) in the cholesterol-fed mice given L-arginine compared with those receiving the high-cholesterol diet alone. The mean atherosclerotic lesion area was significantly larger (P < .01) in cholesterol-fed mice receiving L-arginine + L-NA than in those on the high-cholesterol diet alone. Within the atherosclerotic plaques, endothelial cells immunoreacted for endothelial cell NOS; macrophages, foam cells, and smooth muscle cells immunostained strongly for inducible NOS and nitrotyrosine residues.

CONCLUSIONS

The data indicate that L-arginine prevents xanthoma formation and reduces atherosclerosis in LDL receptor knockout mice fed a high-cholesterol diet. The abrogation of the beneficial effects of L-arginine by L-NA suggests that the antiatherosclerotic actions of L-arginine are mediated by NOS. The data suggest that L-arginine may be beneficial in familial hypercholesterolemia.

Structure-function relationships of human cholesteryl ester transfer protein: analysis using monoclonal antibodies

Cholesteryl ester transfer protein (CETP), a 476 amino acid glycoprotein, mediates cholesteryl ester (CE), triglyceride, and phospholipid transfer among plasma lipoproteins. A monoclonal antibody (mAb), TP2, specific for an epitope within the last 26 amino acids of CETP has been shown to block all CETP-mediated lipid transfer, apparently by limiting access to lipid-binding sites in the carboxy terminal of CETP. A new panel of 16 anti-human CETP mAbs has now been used to further probe the structure-function relationships of CETP. Of the new mAbs, 9 partially inhibit CETP-mediated CE transfer (24-43%) from HDL to LDL. The corresponding epitopes were mapped within the CETP primary structure by the reactivity of the mAbs with CETP variants having deletions or amino acid substitutions. Of the 9 new, neutralizing mAbs, 6 are specific for epitopes situated between residues 410-450 and two others for epitopes between residues 184-260 and 332-366, respectively. The epitope of one neutralizing mAbs could not be mapped. Therefore, binding of mAbs to epitopes situated in four non-overlapping regions within CETP primary structure that are separated by as many as 280 residues can neutralize CETP-mediated CE transfer. Epitopes of mAbs that do not influence CE transfer activity map to the regions 184-260, 261-331, and 367-409, respectively. When pairs of mAbs were tested for their abilities to mutually compete for binding to immobilized CETP, competition was observed for mAbs specific for epitopes that are distant in CETP primary structure. The cross-competition patterns demonstrate that the carboxy terminal 60% of CETP adopts a compact structure. Together with previous mutagenesis studies, the data suggests that a carboxy terminal neutral lipid binding domain may be in close proximity to a lipoprotein binding region within native CETP.

Profound induction of hepatic cholesteryl ester transfer protein transgene expression in apolipoprotein E and low density lipoprotein receptor gene knockout mice. A novel mechanism signals changes in plasma cholesterol levels

The plasma cholesteryl ester transfer protein (CETP) mediates the transfer of cholesteryl esters from HDL to other lipoproteins and is a key regulated component of reverse cholesterol transport. Dietary hypercholesterolemia results in increased hepatic CETP gene transcription and higher plasma CETP levels. To investigate the mechanisms by which the liver senses hypercholesterolemia, mice containing a natural flanking region CETP transgene (NFR-CETP transgene) were bred with apo E or LDL receptor gene knockout mice (E0 or LDLr0 mice). Compared to NFR-CETP transgenic (Tg) mice with intact apo E genes, in NFR-CETP Tg/E0 mice there was an eightfold induction of plasma CETP levels and a parallel increase in hepatic CETP mRNA levels. Other sterol-responsive genes (LDL receptor and hydroxymethyl glutaryl CoA reductase) also showed evidence of altered regulation with decreased abundance of their mRNAs in the E0 background. A similar induction of plasma CETP and hepatic CETP mRNA levels resulted from breeding the NFR-CETP transgene into the LDL receptor gene knockout background. When placed on a high cholesterol diet, there was a further increase in CETP levels in both E0 and LDLr0 backgrounds. In CETP Tg, CETP Tg/E0, and CETP Tg/LDLr0 mice on different diets, plasma CETP and CETP mRNA levels were highly correlated with plasma cholesterol levels. The results indicate that hepatic CETP gene expression is driven by a mechanism which senses changes in plasma cholesterol levels independent of apo E and LDL receptors. Hepatic sterol-sensitive genes have mechanisms to sense hypercholesterolemia that do not require classical receptor-mediated lipoprotein uptake.

Regulation of murine plasma phospholipid transfer protein activity and mRNA levels by lipopolysaccharide and high cholesterol diet

Plasma phospholipid transfer protein mediates the net movement of phospholipids between lipoproteins and between lipid bilayers and high density lipoprotein. In this study, the mouse phospholipid transfer protein cDNA was cloned by reverse transcription polymerase chain reactions based on the cDNA sequence of human phospholipid transfer protein. The predicted amino acid sequence of mouse phospholipid transfer protein shows the protein to be 476 amino acids long and to have a sequence identity of 83% with that of human phospholipid transfer protein. Mouse plasma phospholipid transfer protein activity is 1.5-2 times that of human plasma phospholipid transfer protein activity. As in humans, mouse peripheral tissues displayed a higher abundance of phospholipid transfer protein mRNA than observed in central organs. The order of phospholipid transfer protein mRNA expression was as follows: lung > adipose tissue, placenta, testis > brain > muscle, heart, liver. We examined the regulation of phospholipid transfer protein expression by dietary cholesterol and by bacterial lipopolysaccharide. A high fat, high cholesterol diet caused a significant increase (35%) in plasma phospholipid transfer protein activity and a significant increase (18%) in high density lipoprotein phospholipids. This increased activity was accompanied by approximately 100% increase in phospholipid transfer protein mRNA in lung. After lipopolysaccharide injection, plasma phospholipid transfer protein activity was decreased by approximately 66%. This decrease in activity was associated with a similar decrease in phospholipid transfer protein mRNA in lung, adipose tissue, and liver. The decrease in plasma phospholipid transfer protein activity was also associated with a significant increase (17%) in high density lipoprotein phospholipid concentration. The opposite changes in phospholipids levels with lipopolysaccharide treatment and dietary cholesterol despite similarly increased high density lipoprotein phospholipids levels indicate that high density lipoprotein phospholipids levels are likely determined both by phospholipid transfer protein levels and by gradients of phospholipids concentration between high density lipoprotein and other phospholipids sources.

Point mutagenesis of positively charged amino acids of cholesteryl ester transfer protein: conserved residues within the lipid transfer/lipopolysaccharide binding protein gene family essential for function

The cholesteryl ester transfer protein (CETP) binds to plasma lipoproteins and transfers neutral lipids between them. Previous studies showed that lipoprotein binding involves ionic interactions between CETP and lipoproteins, with increased binding of CETP to lipoproteins carrying increased negative charge. In order to understand the molecular determinants of lipoprotein binding in CETP, site-directed mutagenesis was carried out on positively charged amino acids within and outside regions of conserved sequence in the putative family of lipid transfer/lipopolysaccharide (LPS) binding proteins (LT/LBP). Within the conserved regions, two mutant proteins, K233A and R259D, were well secreted by the transfected cells but showed markedly reduced cholesteryl ester transfer activity. Separating the bound from free CETP by gel filtration after incubation with HDL, HDL binding by K233A was found to be impaired, suggesting that the binding deficiency of the mutant may be responsible for decreased transfer activity. Kinetic analysis showed a marked increase in the apparent Km but no change in Vmax, consistent with a lipoprotein binding defect. Thus, within CETP, K233 and R259 play an essential role in cholesteryl ester transfer activity probably by mediating binding of CETP to lipoproteins. Sequence alignment of CETP, phospholipid transfer protein, LPS binding protein, and bactericidal permeability-inducing protein showed that K223 and R259 were strictly conserved as positively charged amino acids, suggesting a common function within the LT/LBP gene family.

Decreased cholesteryl ester transfer protein (CETP) mRNA and protein and increased high density lipoprotein following lipopolysaccharide administration in human CETP transgenic mice

The plasma cholesteryl ester transfer protein (CETP) mediates the exchange of HDL cholesteryl esters (CE) and VLDL triglycerides leading to catabolism of HDL. There is some evidence that HDL ameliorates the toxicity of LPS, and LPS is known to influence several enzymes affecting HDL metabolism. Therefore, the effects of LPS on CETP and plasma lipoproteins were examined in human CETP transgenic mice. Administration of LPS to mice expressing a CETP transgene linked to its natural flanking sequences (NFR-CETP Tg) resulted in a rapid marked decrease in hepatic CETP mRNA and plasma CETP concentration. Corticosteroid injection produced a similar decrease in hepatic CETP mRNA and adrenalectomy abolished this response to LPS. LPS caused disproportionate reductions in plasma CETP activity compared to mass, and was found to be a potent inhibitor of CETP activity when added directly to plasma. LPS was injected into mice expressing (A) a human apoA-I transgene, (B) apoA-I and NFR-CETP transgenes, or (C) apoA-I and LPS-inducible metallothionein promoter-driven CETP transgenes, producing (A) minimal changes in HDL cholesterol, (B) decreased plasma CETP and increased HDL cholesterol, and (C) increased plasma CETP and decreased HDL cholesterol. Thus, LPS administration produces a profound decrease in hepatic CETP mRNA, primarily as a result of adrenal corticosteroid release. The decrease in plasma CETP activity after LPS administration may reflect both this effect as well as a direct interaction between CETP and LPS. The decrease of CETP in response to LPS has major effects on HDL levels, and may represent an adaptive response to preserve or increase HDL and thereby modify the response to LPS.

Genetic cholesteryl ester transfer protein deficiency caused by two prevalent mutations as a major determinant of increased levels of high density lipoprotein cholesterol

Genetic determinants of HDL cholesterol (HDL-C) levels in the general population are poorly understood. We previously described plasma cholesteryl ester transfer protein (CETP) deficiency due to an intron 14 G(+1)-to-A mutation(Int14 A) in several families with very high HDL-C levels in Japan. Subjects with HDL-C > or = 100 mg/dl (n = 130) were screened by PCR single strand conformational polymorphism analysis of the CETP gene. Two other mutations were identified by DNA sequencing or primer-mediated restriction map modification of PCR products: a novel intron 14 splice donor site mutation caused by a T insertion at position +3 from the exon14/intron14 boundary (Int14 T) and a missense mutation (Asp442 to Gly) within exon 15 (D442G). The Int14 T mutation was only found in one family. However, the D442G and Int14 A mutations were highly prevalent in subjects with HDL-C > or = 60 mg/dl, with combined allele frequencies of 9%, 12%, 21% and 43% for HDL-C 60-79, 80-99, 100-119, and > or = 120 mg/dl, respectively. Furthermore, prevalences of the D442G and Int14 A mutations were extremely high in a general sample of Japanese men (n = 236), with heterozygote frequencies of 7% and 2%, respectively. These two mutations accounted for about 10% of the total variance of HDL-C in this population. The phenotype in a genetic compound heterozygote (Int14 T and Int14 A) was similar to that of Int14 A homozygotes (no detectable CETP and markedly increased HDL-C), indicating that the Int14 T produces a null allele. In four D442G homozygotes, mean HDL-C levels (86 +/- 26 mg/dl) were lower than in Int14 A homozygotes (158 +/- 35 mg/dl), reflecting residual CETP activity in plasma. In 47 D442G heterozygotes, mean HDL-C levels were 91 +/- 23 mg/dl, similar to the level in D442G homozygotes, and significantly greater than mean HDL-C levels in Int14 A heterozygotes (69 +/- 15 mg/dl). Thus, the D442G mutation acts differently to the null mutations with weaker effects on HDL in the homozygous state and stronger effects in the heterozygotes, suggesting dominant expression of a partially defective allele. CETP deficiency, reflecting two prevalent mutations (D442G and Int14 A), is the first example of a genetic deficiency state which is sufficiently common to explain a significant fraction of the variation in HDL-C in the general population.

Down-regulation of mRNA for the low density lipoprotein receptor in transgenic mice containing the gene for human cholesteryl ester transfer protein. Mechanism to explain accumulation of lipoprotein B particles

To evaluate the effects of cholesteryl ester transfer protein (CETP) on apoB-containing lipoproteins, we analyzed plasma lipoproteins from three different lines of human CETP transgenic mice, with plasma CETP concentration ranging from low (1.5 microgram/ml) to high levels (8.5 micrograms/ml). With increasing CETP concentration, very low density lipoprotein and low density lipoprotein (LDL) cholesteryl ester (CE) and apoB were progressively increased, and high density lipoprotein CE was decreased. To investigate the mechanism of accumulation of lipoproteins containing apoB (lipoprotein B), the abundance of hepatic LDL receptor mRNA was determined. LDL receptor mRNA was reduced as a result of CETP expression, with maximum repression to about 48% of the level of non-transgenic mice. Among the different lines of CETP transgenic mice there was an inverse relationship between plasma CETP concentration and hepatic LDL receptor mRNA abundance (r = -0.94, p < 0.01). CETP expression also led to increased cholesterol and cholesteryl ester content in liver and to decreased abundance of mRNAs encoding 3-hydroxy-3-methylglutaryl-coenzyme A reductase and 7-alpha-hydroxylase. Thus, CETP expression results in increased cholesteryl ester concentration in very low density lipoprotein and LDL, probably reflecting both CE transfer from high density lipoprotein and accumulation of lipoprotein B particles. The accumulation of lipoprotein B particles results from CETP-mediated down-regulation of liver LDL receptors, possibly due to enhanced return of cholesterol to the liver.

A missense mutation in the cholesteryl ester transfer protein gene with possible dominant effects on plasma high density lipoproteins

Plasma HDL are a negative risk factor for atherosclerosis. Cholesteryl ester transfer protein (CETP; 476 amino acids) transfers cholesteryl ester from HDL to other lipoproteins. Subjects with homozygous CETP deficiency caused by a gene splicing defect have markedly elevated HDL; however, heterozygotes have only mild increases in HDL. We describe two probands with a CETP missense mutation (442 D:G). Although heterozygous, they have threefold increases in HDL concentration and markedly decreased plasma CETP mass and activity, suggesting that the mutation has dominant effects on CETP and HDL in vivo. Cellular expression of mutant cDNA results in secretion of only 30% of wild type CETP activity. Moreover, coexpression of wild type and mutant cDNAs leads to inhibition of wild type secretion and activity. The dominant effects of the CETP missense mutation during cellular expression probably explains why the probands have markedly increased HDL in the heterozygous state, and suggests that the active molecular species of CETP may be multimeric.

Electrophysiological analysis of the nasal chemical senses in garter snakes

Electroolfactogram and electrovomeronasogram recordings were made from garter snakes stimulated with vapor of amyl acetate, butanol and of earthworm wash. The olfactory epithelium was more sensitive than the vomeronasal epithelium to all three stimuli. Volatiles from prey washes were capable of stimulating the olfactory epithelium when delivered as airstreams. The vomeronasal epithelium was sensitive only to the air delivery of vapor of amyl acetate. Single unit recordings from the mitral cell layer of the accessory olfactory bulb of garter snakes were made in response to liquid delivery of a variety of chemical stimuli including classical odorants, amino acids and proteins derived from prey. All three classes of stimuli altered unit firing in the accessory olfactory bulb. Amyl acetate, earthworm wash, goldfish wash and non-volatile amino acids delivered as liquid stimuli to the vomeronasal epithelium produced responses in the accessory olfactory bulb that were more distinct and reliable than the electrovomeronasogram responses to airborne odorants recorded at the periphery. Both excitatory and inhibitory responses were observed in the accessory olfactory bulb of garter snakes. The direction of the response to a given stimulus differed for different neurons. Responses were frequently biphasic and could last longer than 50 seconds. Individual neurons responded to different classes of stimuli suggesting that they are broadly tuned.

Chemical and immunological analysis of prey-derived vomeronasal stimulants

We have isolated seven proteins from earthworm preparations that are chemoattractive to garter snakes. Three of these proteins have been purified to homogeneity: two from aqueous earthworm wash (EWW) and one from electric shock-induced earthworm secretion (ESS). One of the two highly purified proteins from EWW has a relative molecular mass of 20 kDa and contains free sulfhydryl groups that appear to play a functional role in its chemoattractivity. The other purified protein from EWW has a molecular mass of 3 kDa (low molecular weight protein, LMW). The highly purified chemoattractive protein (ES20) from ESS is a glycoprotein having a minimum molecular mass of 15.4 kDa calculated from its amino acid and carbohydrate contents. It consists of a single polypeptide chain. The sequence of terminal 15 amino acid residues from its amino (NH2-) terminal has been determined. It binds specifically to the membranes of vomeronasal sensory epithelium in a saturable and reversible fashion with a Kd value of about 0.3 microM and Bmax value of 0.4 nmol/mg of protein. This protein causes an increase in firing rate of individual neurons in the accessory olfactory bulb of garter snakes, the projection site for vomeronasal neurons. All the isolated chemoattractive proteins from both earthworm preparations can be divided immunologically into three groups: (i) those closely related to the ES20 snake-attractive protein, (ii) those closely related to the LMW snake-attractive protein, and (iii) those unrelated to either ES20 or the LMW protein.

The CCAAT/enhancer-binding protein trans-activates the human cholesteryl ester transfer protein gene promoter

The plasma cholesteryl ester transfer protein (CETP), primarily synthesized in the liver of several species, is expressed at very low levels in a number of transformed human liver cell lines. The human CETP gene promoter contains a sequence that closely resembles the binding site for the transcription factor CCAAT/enhancer-binding protein (C/EBP). This site is capable of binding C/EBP, as shown by electrophoretic mobility shift and DNase I footprint analyses. Transient expression of the bacterial chloramphenicol acetyltransferase gene under the control of the human CETP gene promotor gave low activities in the human hepatoma cell line, HepG2. However, in the presence of C/EBP, CAT activity was markedly elevated indicating that CETP gene promoter activity was enhanced. In primary cultures of isolated hepatocytes, CETP mRNA was lost rapidly and in parallel with the C/EBP mRNA. C/EBP may play an important role in the proper maintenance of CETP gene promoter activity, and its low levels in proliferating or cultured cells may account for the low level of the CETP gene expression in immortalized human liver cell lines or cultured hepatocytes.

[Histopathological and immunopathological studies on experimental pulmonary candidiasis]

Experimental pulmonary candidiasis was produced by intratracheal inoculation of candida albicans in mice. The pathological changes could be divided into two stages, dominated by polymorphonuclear leukocyte infiltration and granuloma formation respectively. Preincubation of C. albicans with mouse anti-C. albicans antibody showed no obvious effect on pathological changes of the lungs as compared with the changes in the control mice, indicating that specific antibody did not play a crucial role in the defence mechanism of the lungs against C. albicans infection in normal mice. In the mice injected with antineoplastic drugs and hormones, abundant pseudohyphae were found in the lungs. Tissue necrosis and hemorrhage were obvious.

Dietary cholesterol increases transcription of the human cholesteryl ester transfer protein gene in transgenic mice. Dependence on natural flanking sequences

To investigate the regulation of expression of the human cholesteryl ester transfer protein (CETP) gene, transgenic mice were prepared using a CETP minigene linked to the natural flanking sequences of the human CETP gene. By using a transgene containing 3.2 kb of upstream and 2.0 kb of downstream flanking sequence, five different lines of transgenic mice were generated. The abundance of CETP mRNA in various tissues was determined on standard laboratory diet or high fat, high cholesterol diets. In three lines of transgenic mice the tissues expressing the human CETP mRNA were similar to those in humans (liver, spleen, small intestine, kidney, and adipose tissue); in two lines expression was more restricted. There was a marked (4-10-fold) induction of liver CETP mRNA in response to a high fat, high cholesterol diet. The increase in hepatic CETP mRNA was accompanied by a fivefold increase in transcription rate of the CETP transgene, and a 2.5-fold increase in plasma CETP mass and activity. In contrast, CETP transgenic mice, in which the CETP minigene was linked to a metallothionein promoter rather than to its own flanking sequences, showed no change in liver CETP mRNA in response to a high cholesterol diet. Thus (a) the CETP minigene or natural flanking sequences contain elements directing authentic tissue-specific expression; (b) a high cholesterol diet induces CETP transgene transcription, causing increased hepatic CETP mRNA and plasma CETP; (c) this cholesterol response requires DNA sequences contained in the natural flanking regions of the human CETP gene.