Reduced oxidative susceptibility of LDL from patients participating in an intensive atherosclerosis treatment program

The goal of this investigation was to determine whether participation in an atherosclerosis treatment program would reduce the oxidative susceptibility of LDL from patients with coronary artery disease. The treatment program included intensive exercise therapy, stress management, and consumption of a diet containing 10% fat. The size and antioxidant and lipid contents of LDL particles from 25 patients were analyzed at baseline and after 3 mo of therapy. The susceptibility of LDL to copper-mediated oxidation was measured by a conjugated diene assay and headspace gas chromatography (HSGC). Atherosclerosis treatment significantly reduced plasma total cholesterol and apolipoprotein B concentrations and the molar ratio of LDL cholesterol ester to apolipoprotein B (P < 0.01). The LDL content of alpha-tocopherol and beta-carotene was increased (27% and 17%, respectively, P < 0.04) and the molar ratio of LDL cholesterol ester the sum of LDL alpha-tocopherol and LDL beta-carotene decreased from 159 at baseline to 122 at 3 mo (P < 0.01). The lag phase of LDL conjugated diene formation increased 24%, whereas the maximum rate of oxidation slowed 29% (P < 0.01). As assessed by HSGC, copper-catalyzed formation of volatile lipid oxidation products was reduced 15% (P < 0.007); the reduction in volatiles was correlated with an increase in the alpha-tocopherol content of LDL (r=-0.48, P < 0.01). The principal determinants of reduced LDL oxidative susceptibility were the particle contents of alpha-tocopherol and beta-carotene. To our knowledge, this is the first report to document a reduction in LDL oxidation in coronary artery disease patients undergoing atherosclerosis-reversal therapy.

Parvovirus B19-induced anemia as the presenting manifestation of X-linked hyper-IgM syndrome

Parvovirus B19 (B19) can cause chronic anemia due to persistent infection in immunocompromised hosts who cannot produce neutralizing antibody necessary for clearing B19. Three patients with X-linked hyper-IgM syndrome (XHIM), who were all asymptomatic until they developed B19-induced chronic anemia at the ages of 8, 14, and 17 years, respectively, were found to have mutations of the CD40L gene, including a missense mutation (T254M), a nonsense mutation resulting in a new initiation codon and loss of the intracellular domain (R11X), and a splice site mutation (nt 309+2t-->a). Antibody responses to the T cell-dependent antigen, bacteriophage phiX174, were impaired, but neutralizing antibody titers were higher than in XHIM patients with classic phenotype. All 3 patients responded to intravenous immune globulin (IVIG) treatment. Certain mutations of the CD40L gene result in a mild XHIM phenotype that may become apparent following B19 infection in patients not on IVIG therapy and therefore not protected from B19 infection.

Brachydactyly type A1 with abnormal menisci and scoliosis in three generations

We report a three-generation family in which four members had brachydactyly type A1, degenerative arthritis of the knee as a complication of abnormal menisci, and variable scoliosis. Nine of the 15 individuals in the two generations preceding the proband had brachydactyly. Three of these nine had degenerative arthritis of the knee including the proband's father who had meniscal degeneration with tears. One other had radiologically confirmed discoid menisci. Of those with brachydactyly, five also had scoliosis. Although autosomal dominant inheritance of brachydactyly A1 and discoid menisci have been reported separately, cosegregation of these features in one family has not previously been described and seems to comprise a unique autosomal dominant condition. The combination of brachydactyly, meniscal abnormalities including discoid meniscus, and scoliosis suggests that this disorder represents a new osteochondrodysplasia syndrome.

Developmental toxicity induced during early stages of mammalian embryogenesis

Both a conceptual and a practical borderland between teratology and mutagenesis is early embryogenesis, the period between fertilization and gastrulation. Radiation and a variety of chemicals adversely affect the early conceptus leading to in utero mortality and malformations. The post-fertilization period of susceptibility differs from exposures of gametes, the later producing excessive pre- and peri-implantational death and low rates of fetal anomalies predominated by growth retardation. In contrast mutagen exposure of the zygote induces peri-implantational death, pan-gestational death and fetal anomalies predominated by hydrops, abdominal wall defects, and eye aberrations. The mechanism for this pathology remains unclear. These same agents produce a broader range of phenotypic anomalies during the remainder of pre-gastrulation development with anomalies overlapping those induced during organogenesis. Retinoic acid and 5-azacytidine administered prior to gastrulation produce novel malformation syndromes indicative of gene expression modification. The rates and types of defects from mutagen treatment of both gametes and the early conceptus contrast with those resulting from embryonic treatment during organogenesis, and the mechanisms are likely to differ. The pre-gastrulation period has not been explored to the extent reported during gametogenesis or organogenesis. Pre-gastrulation teratology is a new area of investigation with relevance both to reproductive toxicology and to mammalian developmental biology.

Regression of severe atherosclerotic plaque in patients with mild elevation of LDL cholesterol

BACKGROUND

Intensive risk factor reduction in patients with dyslipidemias and coronary atherosclerosis has been shown to result in alterations in coronary artery morphology and reduced clinical events. However, the impact of such interventions in populations with relatively normal levels of low-density lipoproteins (LDL) is unclear.

METHODS

To test the hypothesis that intensive risk factor reduction results in angiographic regression in patients with only mildly elevated levels of LDL, 14 patients with angiographically proven coronary atherosclerosis were entered into the University of California Davis Coronary Artery Disease Regression Program and intensively treated with pharmacologic and nonpharmacologic interventions for 2 years. Quantitative angiography was performed prior to and after 2 years of therapy to determine changes in coronary artery diameter.

RESULTS

As a result of this program, dietary fat intake was reduced by 58% and LDL fell from 120 +/- 7 mg/dL to 104 +/- 6 mg/dL (p = 0.05). The average diameter of the measured arterial locations (including all 53 stenoses and 292 nondiscrete regions) on study entry was 2.74 +/- 0.05 mm. After 24 months, there was a net increase in arterial diameter (regression) of +0.05 +/- 0.04 mm to 2.81 +/- 0.05 mm (p = 0.01). While there was no significant change in the average diameter of discrete stenoses, all 8 lesions > or = 50% initial diameter narrowing regressed, with a mean diameter change of + 0.2 mm. Conversely, only 1 of 8 mild lesions < or = 20% regressed, while 4 progressed. Intermediate lesions (20% to 50%, n = 37) had balanced progression and regression.

CONCLUSIONS

When examined as a continuous variable, there was a significant linear correlation between initial lesion severity (% stenosis) and the extent of regression (mm). Therefore, risk factor reduction (dietary therapy, exercise, psycho-social counseling, and lipid lowering therapy) in patients with only mild dyslipidemia results in angiographic regression of more severe lesions (> 50% initial stenosis), but does not prevent progression of mild lesions (< 20%). These findings demonstrate that intensive risk factor reduction in patients with only mild elevation of lipids beneficially influences the morphology of the most severe lesions.

Human mucopolysaccharidosis IIID: clinical, biochemical, morphological and immunohistochemical characteristics

Mucopolysaccharidosis IIID (MPS IIID) is one of the rarest of the MPS-III syndromes. To date, the clinical manifestations of 10 patients have been reported, the deficient N-acetylglucosamine 6-sulfatase (G6S) enzyme has been purified, and the G6S gene has been cloned, sequenced and localized. However, morphological manifestations of this condition have not been reported and the pathogenesis of the severe neurological deficits remains an enigma. In this paper we describe and correlate the clinical, biochemical and pathological observations for 2 cases of MPS IIID. We used monoclonal antibodies against heparan sulfate (HS) and GM2-ganglioside, thin layer chromatography, mass spectrometry, and morphological techniques to demonstrate the nature and the distribution of the uncatabolized substrates. The majority of the cells in various tissues showed morphological changes expected with lysosomal storage of HS. The central nervous system (CNS) was most severely affected because of the secondary storage of GM2 and GM3 gangliosides in addition to the primary accumulation of HS. The extent as well as the distribution of the diverse storage materials varied within and among different neurons as observed in MPS-III A, B, and C syndromes. This study supports the hypothesis that the neurological dysfunction and neurodegeneration common to the Sanfilippo syndromes is, in part, due to the secondary metabolic perturbations induced by HS accumulation.

Nitric oxide mediates LDL uptake in the artery wall in response to high concentrations of 17 beta-estradiol

Female sex hormones are known to affect lipoprotein flux in the artery wall and atherosclerosis. However, the mechanisms of these artery wall effects are unclear. To examine the effect of 17 beta-estradiol (estradiol) on LDL uptake in the artery wall, we developed an isolated perfused rat carotid artery model from ovariectomized rats. LDL flux in the artery wall was measured by quantitative fluorescence microscopy before and after treatment with estradiol (0.001 to 10,000 nmol/L). Dose-response experiments showed no significant difference in the rate of LDL uptake when arteries were perfused with estradiol at physiological concentrations (0.001 to 1 nmol/L) compared with control perfusions. However, higher concentrations of estradiol (10 to 10,000 nmol/L) significantly increased the rate of LDL uptake in isolated arteries. Artery lumen volume significantly increased with perfusion of estradiol (1 to 100 nmol/L) but decreased after perfusions of higher concentrations of estradiol (1000 to 10,000 nmol/L). Additional studies were performed to examine mechanisms of estradiol-mediated increases in LDL uptake. The effect of estradiol (10 nmol/L) on the rate of LDL uptake was blocked by nitric oxide synthase inhibitors. However, the estrogen receptor antagonist tamoxifen did not block the effects of estradiol on the rate of LDL uptake. Our study indicates that modulation of LDL uptake in the artery wall by estradiol is concentration dependent. High concentrations of estradiol increase LDL uptake by production of endothelium-derived nitric oxide. These observations suggest that increased nitric oxide production compromises endothelial layer barrier function to increase LDL uptake in the artery wall.

Lipoprotein lipase increases lipoprotein binding to the artery wall and increases endothelial layer permeability by formation of lipolysis products

Mechanisms responsible for the accumulation of low-density lipoprotein (LDL) were investigated in a new model, the perfused hamster aorta. To do this, we developed a method to study LDL flux in real time in individually perfused arteries; each artery served as its own control. Using quantitative fluorescence microscopy, the rates of LDL accumulation and efflux were separately determined. Perfusion of arteries with buffer plus lipoprotein lipase (LpL) increased LDL accumulation 5-fold (0.1 +/- 0.03 mV/min [control] versus 0.5 +/- 0.05 mV/min [LpL]) by increasing LDL retention in the artery wall. This effect was blocked by heparin and monoclonal antibodies directed against the amino-terminal region of apolipoprotein B (apo B). This suggests that specific regions of apo B are involved in LDL accumulation within arteries. Also, the effect of hydrolysis of triglyceride-rich lipoproteins on endothelial barrier function was studied. We compared endothelial layer permeability using a water-soluble reference molecule, fluorescently labeled dextran. When LpL was added to hypertriglyceridemic plasma, dextran accumulation within the artery wall increased > 4-fold (0.024 +/- 0.01 mV/min [control] versus 0.098 +/- 0.05 mV/min [LpL]). Under the same conditions, LpL increased LDL accumulation approximately 3-fold (0.016 +/- 0.003 mV/min [control] versus 0.047 +/- 0.013 mV/min [LpL]). Rapid efflux of LDL from the artery wall indicated that increased endothelial layer permeability was the primary mechanism during periods of increased lipolysis. Our data demonstrate two LpL-mediated effects that may increase the amount of LDL in the artery wall. These findings may pertain to the observed relationship between increased postprandial lipemia and atherosclerosis.

Ras oncogene mutations in childhood brain tumors

Although N-nitroso compounds (NNC) are ubiquitous in the human environment and are known neurocarcinogens in animal models, results of epidemiological studies have not yet convincingly associated NNCs with brain tumor occurrence in humans. Animal studies have suggested that specific codons (12, 13, and 61) in the ras family are mutable by exposure to NNCs. The purpose of this study was to measure the presence of mutations in the ras family of oncogenes in tissue from childhood brain (CB) tumors as a preliminary step toward investigating their potential use as biomarkers of chemical exposure. DNA was extracted from paraffin-embedded formalin-fixed CB tumors from tissues resected during neurosurgical operations. Using the PCR, designed RFLP-screening methods, and sequencing, we attempted to screen brain tumors from 46 children for the presence of H, K, and N-ras mutations at codons 12, 13, and 61. Screening for oncogene mutations using PCR, RFLP methods, and DNA sequencing was successfully completed for a high proportion of the available specimens. Astrocytoma specimens from three children for whom screening with PCR was successfully completed were found to contain CAA-->GAA point mutations in K-ras at codon 61. None of the specimens contained mutations at any of the other locations. These results, although preliminary, provide a potential clue for future mechanistic studies of CB tumors. The possible roles of NNCs in inducing this mutation, or of this mutation as an early or late event in tumor progression, however, remain unclear.

The ultrastructure of skin from a patient with mucopolysaccharidosis IIID

Mucopolysaccharidosis IIID (MPS-IIID) is the rarest of the MPS-III syndromes. It is caused by deficient activity of lysosomal N-acetylglucosamine-6-sulfatase (G6S). To date, the clinical and biochemical features of seven patients with MPS-IIID have been reported, but no biopsy or autopsy findings have been described. The purpose of this report is to define the ultrastructure of affected cells seen in a skin biopsy from a 14-year-old boy. The child presented with progressive mental deterioration, hyperactivity and mild to moderate dysmorphism. The diagnosis of a mucopolysaccharidosis was suggested, but the initial urine analyses were negative for elevated mucopolysaccharides, and only the third analysis showed abnormal excretion of heparan sulfate. Because of the diagnostic difficulties posed by this case, a skin biopsy was performed for morphological and biochemical studies. Numerous vacuoles were noted in Schwann cells, fibroblasts, smooth muscle cells, eccrine gland and ductal epithelium in resin-embedded sections stained with toluidine blue. Ultrastructurally, many lysosomes were distended with abundant, fibrillar material. Occasionally, lamellated membranous structures were present within the same lysosomes. These findings are consistent with those seen in other forms of MPS, in which the lysosomal storage occurs predominantly, but not exclusively, in mesenchymal cells. Furthermore, deficient activity of G6S was confirmed in cultured skin fibroblasts. This study demonstrates that electron microscopy of skin biopsies is a useful method for identification of patients with clinical features of MPS-IIID whether or not heparan sulfaturia is present.

Effect of environmental tobacco smoke on LDL accumulation in the artery wall

BACKGROUND

Previous research has shown that exposure to environmental tobacco smoke (ETS) increases the risk of atherosclerosis. To test the hypothesis that exposure to ETS increases LDL accumulation in the artery wall, we developed a model to measure the rate of LDL accumulation in individually perfused rat carotid arteries after the artery had been perfused with plasma taken from rats exposed to ETS (ETS-plasma).

METHODS AND RESULTS

Rats were exposed to ETS in a chamber in which steady-state sidestream smoke was continuously circulating. After exposure, blood from the animals was collected. Carotid arteries from unexposed rats were perfused first with normal plasma containing fluorescently labeled LDL. Then the same arteries (10 arteries from five rats) were perfused with ETS-plasma plus fluorescently labeled LDL. Photometric measurements were made during perfusion of the arteries with fluorescently labeled LDL, and rate of LDL accumulation (mV/min) and lumen volume (mV) (volume of fluorescently labeled LDL solution) were determined. Perfusion with ETS-plasma increased the rate of LDL accumulation (mean +/- SEM, 6.9 +/- 1.8 mV/min) compared with control (1.6 +/- 0.40 mV/min, P < or = .02). LDL accumulation was primarily dependent on LDL interaction with ETS-plasma rather than the interaction of ETS-plasma with the artery wall. Also, ETS-plasma significantly increased lumen volume (43.3 +/- 5.1 mV) compared with control (35.1 +/- 4.4 mV, P < or = .005).

CONCLUSIONS

Exposure to ETS acutely increased LDL accumulation in perfused arteries. Repeated exposure to ETS may represent important early events in atherogenesis.

Bone marrow transplantation in Hunter syndrome

Hunter syndrome (mucopolysaccharidosis II) is a rare X-linked disorder of mucopolysaccharide metabolism that typically progresses to severe mental retardation and death by 18 years of age. A child with Hunter syndrome received an allogeneic bone marrow transplantation from an unaffected human leukocyte antigen-identical sibling at the age of 29 months without complications. Despite full and sustained engraftment now at 70 months after transplantation, the patient's neurocognitive abilities have continued to deteriorate. In this case, replacement of defective marrow-derived macrophages by bone marrow transplantation was not effective in preventing the neurologic progression of the disease in a child with the severe phenotype of Hunter syndrome.

Exposure to ethylene oxide during the early zygotic period induces skeletal anomalies in mouse fetuses

Exposure of mouse zygotes to ethylene oxide (EtO) has been shown to increase the incidence of external malformations among late fetuses [Generoso et al. (1987) Mutat. Res., 176:267-274; Rutledge and Generoso, (1989) Teratology, 39:563-572]. The present study was designed to determine whether EtO also affects the skeletal system. We report here the effects of varying times of exposure during the zygotic period on skeletal development. Female hybrid mice were injected intraperitoneally (IP) with 125 mg/kg EtO at 1, 3, 5, or 7 hr postmating. A positive control group consisted of female mice that were injected IP with 150 mg/kg EtO once daily between the 6th to 8th days of gestation. Day 17 fetuses were double-stained for "blind" examination of skeletal deviations and degree of ossification. Zygotic exposure to EtO significantly increased loss of conceptuses as well as the incidence of external defects, skeletal anomalies, and retarded ossification in live day 17 fetuses. An increase in the number of exposed fetuses with cleft sternum was observed with the highest rate (58.5%) occurring in fetuses whose mothers were exposed to EtO 3 hours postmating. Cleft sternum was seen in only 5% of fetuses exposed during the period of organogenesis and less than 1% of control fetuses. It is concluded that zygotic exposure to EtO produces a pattern of skeletal defects that differs from those observed following treatment with EtO during organogenesis.

Expression of myogenic regulatory proteins (myogenin and MyoD1) in small blue round cell tumors of childhood

The distinction of rhabdomyosarcoma (RMS) from other small blue round cell tumors of childhood, such as Ewing's sarcoma/peripheral primitive neuroectodermal tumor (pPNET) and neuroblastoma, continues to present a diagnostic challenge to pathologists. The recent recognition of the master role of myogenic regulatory proteins in skeletal muscle commitment and differentiation, and the availability of monoclonal antibodies to two of them (myogenin and MyoD1), has prompted us to test their diagnostic utility in routinely processed, formalin-fixed, and deparaffinized tissue. Preliminary studies had demonstrated that, with the use of heat-induced epitope retrieval techniques, expression of myogenin and MyoD1 could be documented specifically in nuclei of fetal skeletal muscle by the respective antibodies. We performed a retrospective immunohistochemical analysis on 72 cases of small blue round cell tumors, including 33 RMSs, 1 metastatic myogenous Wilms' tumor, 26 Ewing's sarcomas/pPNETs, and 12 neuroblastomas. Nuclear expression of myogenin and MyoD1 were both found in 30/33 non-overlapping cases of RMS, with no significant differences in the sensitivity with respect to histological subtypes, and in 1/1 case of myogenous Wilms' tumor. None of the neuroblastomas or Ewing's sarcomas/pPNETs demonstrated positive nuclear staining with either antibody. However, most of the neuroblastomas, and occasional Ewing's sarcomas/pPNETs, showed variable fibrillary, cytoplasmic immunoreactivity with antibody to MyoD1. We conclude that, with the use of microwave-based epitope retrieval, antibodies to myogenin and MyoD1 are both useful markers for the identification of RMS among other small blue round cell tumors of childhood, but antibodies to myogenin have technical advantages over those to MyoD1, as the latter may cross-react with an unknown cytoplasmic antigen in non-muscle cells and tumors.

Quality assurance in pediatric anatomic pathology: the Society for Pediatric Pathology slide survey program

The Society for Pediatric Pathology initiated an external slide survey program in 1989 and has produced yearly challenges of 12 autopsy and surgical pathology glass slides. The history and operational difficulties are reviewed. As the program matures, it presents new challenges in the area of proficiency testing and case acquisition.

Platelet-derived growth factor A-chain expression in developing and mature human kidneys and in Wilms' tumor

Regulated expression of PDGF A-chain may be important in kidney development. We employed two polyclonal antisera to detect expression of PDGF A-chain in fetal and normal adult kidneys by immunohistochemistry. Specificity of the antisera was demonstrated by Western blots of fetal and adult kidneys, demonstrating monospecific bands at 10 to 15 kD, and by absorption studies with PDGF-A peptide. PDGF A-chain is uniformly expressed by visceral glomerular epithelial cells and the epithelial cells of the distal nephron, including collecting ducts and contiguous urothelium lining the renal pelvis, in both fetal and adult kidneys. Fetal kidneys also demonstrate expression of PDGF A-chain at the earliest stages of vesicle formation from the metanephric blastema; this expression is then only intermittently detectable in developing glomeruli until differentiation of visceral epithelial cells occurs. Fetal and mature arterial smooth muscle cells, and some express PDGF A-chain. In situ hybridization with a riboprobe made from PDGF A-chain cDNA showed close correlation of mRNA expression with protein immunohistochemistry. PDGF A-chain expression was also identified in epithelial elements of 5/6 Wilms' tumors studied. These are the first studies to localize PDGF A-chain expression in human kidney and suggest sites of activity for PDGF A-chain in development, neoplasia, and in the renal arterial sclerosis of aging.

Biliary epithelial cells from mice with congenital polycystic kidney disease are hyperresponsive to epidermal growth factor

Epithelial hyperplasia is an early feature of the renal and biliary lesions in autosomal recessive polycystic kidney disease (ARPKD). To explore the cellular basis of this hyperplasia we isolated, cultured, and characterized biliary tract epithelium from common bile duct explants of mice with ARPKD (the BPK mouse) and controls. Primary cultures resulted in dense colonies of contact-inhibited epithelial cells with a homogenous growth pattern. Colony growth in serum-free basal medium (BM) of BPK-derived cells was not different from controls. Supplementation of BM with epidermal growth factor (EGF) induced a proliferative response in BPK-derived cells that was significantly increased over controls as assessed by [3H]thymidine uptake and expressed as percent change over growth in BM (BPK 239% and controls 131% of BM growth). In contrast, no differences between BPK- and control-derived cells were found with regard to the effects of BM supplementation with IGF-I, IGF-II, acidic fibroblast growth factor, keratinocyte growth factor, hepatocyte growth factor, or transforming growth factor-beta. Primary culture of biliary epithelium may provide a useful in vitro model for the study of the cellular pathophysiology of ARPKD. Our data demonstrate that increased epithelial sensitivity to EGF-like proteins may play a role in biliary epithelial proliferative changes which parallel renal tubular epithelial proliferation in ARPKD.

Solvent drag of LDL across mammalian endothelial barriers with increased permeability

We investigated the mechanisms of hamster low-density lipoprotein (LDL) transport across the endothelial barrier in individually perfused venular microvessels in hamster mesentery. These experiments are the first to use microperfusion techniques and quantitative fluorescence microscopy to investigate LDL transport across mammalian microvessel endothelium. The apparent permeability coefficient for hamster LDL, PsLDL, rose from 2.7 x 10(-7) cm/s at control to 23.2 x 10(-7) cm/s at the peak of the biphasic increase in microvessel permeability after exposure of the vessels to 100 microM histamine. Close to the peak, PsLDL rose 1.85 x 10(-7) cm/s for every centimeter of H2O increase in hydrostatic pressure. Thus, at a mean pressure of 11.3 cmH2O, 90% of the LDL flux was coupled to transendothelial water flow by a solvent drag mechanism. The corresponding solvent drag reflection coefficient for hamster LDL was estimated to be approximately 0.8. These results are consistent with sieving hamster LDL (effective radius 14.9 nm) through equivalent pores of approximately 22 nm radius. Similar results were found with human LDL (effective radius 13.2 nm) in hamster microvessels. The results provide a bridge between studies of LDL transport across cultured endothelial barriers, where high diffusive permeability coefficients to LDL may obscure the contributions of solvent drag, and studies in whole animals, where the consequences of sieving of LDL at the vessel wall, even in the high permeability state, have not received much attention.

Substance P increases microvascular permeability via nitric oxide-mediated convective pathways

The goal of these studies was to examine the effects of substance P, a tachykinin neuropeptide, on pathways of microvascular permeability. Individual frog mesenteric venular capillaries were cannulated, and albumin apparent permeability coefficients (Ps) were determined by quantitative fluorescence microscopy. Ps of albumin (PsAlb) rose from 6.8 +/- 1.8 (SE) cm.s-1.10(7) at control to 22.3 +/- 2.3 cm.s-1.10(7) when substance P (10(-11) M) was perfused. The effect of increased microvessel permeability induced by substance P (10(-11) M) was blocked with the nonpeptide substance P receptor antagonist CP-96,345 and NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase. PsAlb increased 0.99 cm.s-1.10(7) for every cmH2O increase in microvessel pressure after treatment of the vessel with substance P, demonstrating coupling of albumin flux to transvascular water flow. In conclusion, the mechanism of increased microvessel permeability in response to substance P appears to be the result of receptor-mediated increase in nitric oxide production and formation of water-filled convective pathways presumably located between adjacent endothelial cells.

Lipoprotein lipase (LpL) affects low density lipoprotein (LDL) flux through vascular tissue: evidence that LpL increases LDL accumulation in vascular tissue

A cardinal feature of the atherosclerotic lesion is increased low density lipoprotein (LDL) content of the arterial wall. Such increases in vascular wall LDL could result from either increased flux of circulating LDL across the arterial endothelial barrier or decreased efflux of LDL that has entered the vascular tissue. A number of studies have focused on factors that alter permeability of endothelial cell monolayers and intact blood vessels causing increased LDL influx. In contrast, the current studies were designed to test the hypothesis that lipoprotein lipase (LpL), increases LDL accumulation and decreases LDL efflux from vascular tissue. Frog mesenteric venular microvessels were cannulated and the rates of fluorescently labeled LDL accumulation (N/t) and efflux (T1/2) were measured by quantitative fluorescence microscopy. When the vessels were perfused with a solution containing bovine milk LpL (10(-5) g/ml) and human LDL (protein = 0.68 mg/ml), N/t was > 15x greater than that of control vessels which were perfused with LDL alone. LpL addition did not change albumin permeability, suggesting that increased N/t was not related to changes in vessel permeability. Increased LDL accumulation within the vessel could have resulted from either an increase in LDL influx from the vessel lumen into the vascular tissue or a decrease in efflux of LDL. Therefore, LDL efflux from vascular tissue was determined by measuring the rate of decline in fluorescence intensity of control and LpL-treated vessels after washout of the vessel lumen with a clear, nonfluorescent solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Limb and lower-body duplications induced by retinoic acid in mice

The zygote and subsequent preimplantation stages of early mammalian development are susceptible to certain chemical perturbations that cause abnormal development of the conceptus. In certain cases, disruption in patterns of gene expression could be a primary event leading to abnormal development. To investigate this hypothesis, we treated pregnant mice with trans-retinoic acid, a known modulator of gene expression. Treatments were administered at various times during pregastrulation stages and the presumed onset of gastrulation. trans-Retinoic acid induced a distinctive set of malformations, as manifest by supernumerary and ectopic limbs and duplication of portions of the lower body, but only when administered during the period of 4.5-5.5 days after mating. (Other malformations were induced at different stages.) The limb and lower-body duplications suggest that exogenous trans-retinoic acid may influence not only the pattern for the hindlimbs but also that for the entire lower body. Since it appears likely that the embryos were affected in the late blastocyst and proamniotic-embryo stages, the provocative possibility arises that aspects of pattern formation of limbs and lower body actually occur prior to gastrulation.

Quality improvement approaches. Survey of pathologists serving the pediatric patient

A questionnaire was circulated in 1990 by the Practice Committee of the Society for Pediatric Pathology to its membership to assess the involvement of pediatric pathology departments (PPDs) in quality improvement (QI) activities. Twenty-nine PPDs responded. Analysis of responses disclosed a wide variation in plans, although the majority (22 of 29) had developed or were in the process of developing (three of 29) a specific plan. The plans varied in sophistication and complexity. Pediatric pathologists (directors or designates) were heavily involved in assuming leadership roles for the QI activities in 25 of 28 PPDs. The PPDs with plans (25) had identified the QI indicators monitored either sporadically or on an ongoing basis. The respondents had several indicators in common, such as volume, technical, and clinical indicators, as well as indicators related to turnaround times, meetings, and internal and external consultations. The plurality of the monitors reported are related to indicators in the discipline of anatomic pathology. This review is therefore limited to QI issues in anatomic pediatric pathology. In conclusion, this survey functions to shed some light on the extent of involvement of PPDs in the management of QI. In addition, it provides a model for starting or improving the existing QI plans for PPDs.