Acute ethanol and selected growth suppressor transcripts in regenerating rat liver

To study the effects of acute ethanol on regenerating rat liver, the mRNA transcript levels of growth suppressor genes (prohibitin, TGF beta-1 and p53) were measured by Northern blot analysis during the G0, G1, and early S phases of compensatory growth after 70% partial hepatectomy (PH) in adult male rats. Selected animals were gavaged with either ethanol (3 g/kg) or glucose and underwent PH 1 h later. Other animals were either sham operated or underwent PH without gavage. Prohibitin and p53 transcripts were increased in relative abundance (as measured by an increase in band intensity) near the G1/S boundary (8-12 h post-PH) following both glucose and ethanol gavage. A transient increase in prohibitin transcripts at 0.5-1 h post-PH was found to be characteristic of glucose and nongavaged rats. Ethanol gavage significantly increased the relative abundance of prohibitin transcripts at 0.5-2 h post-PH. An increase in the TGF beta-1 transcripts at 4 h post-PH was found in the glucose and nongavaged rats. Ethanol gavage resulted in variable TGF beta-1 transcript expression near hepatectomy (0 h); however, mean differences were not statistically significant. Sham operation had no effect on the mRNA transcripts of the selected genes during the time periods sampled. These results and previous work suggest that the mitoinhibitory effects of acute ethanol exposure may occur via modulation of growth suppressor and proto-oncogene expression.

Inference for smooth curves in longitudinal data with application to an AIDS clinical trial

We discuss a longitudinal study where data for many subjects are collected at irregular intervals. The study is a randomized trial of HIV infected subjects and the response variable of interest is serum neopterin. The mean of the outcome variable, taken over patients in each treatment group, is assumed to follow a smooth curve. Piecewise cubic polynomials with a moderate number of knots are used to model the curves. A general parametric form is assumed for the covariance structure. Maximum penalized likelihood estimation is used to smooth the over-parameterized curves. Statistical inference for the mean curves, including confidence bands and hypothesis tests, is discussed. Two approaches, one using a Bayesian interpretation of the penalized likelihood and the other based on the asymptotic distribution of the maximum penalized likelihood estimates, are discussed and contrasted. The properties of the confidence bands obtained from these two approaches are evaluated by examining their coverage rates in a simulation study.

Characterization of an upstream regulatory sequence and its binding protein in the mouse apolipoprotein E gene

The mouse apolipoprotein (apo) E gene from strain C57BL/6 was isolated from a genomic DNA library and its complete nucleotide sequence, together with 1.3 kilobase of 5' flanking DNA and 300 base pairs of the 3' flanking DNA, was determined. Regulatory sequences in the proximal 5' flanking region of the gene were identified. Using a chloramphenicol acetyltransferase transient assay system, positive and negative cis-acting sequences were mapped within 380 base pairs of the 5' flanking region of the mouse apoE gene. Two nuclear protein binding sites were identified within this region by DNase I footprinting. We have characterized one of these regions, termed mouse apoE regulatory sequence (MARS-2), which spans nucleotides -151 to -133. Gel mobility shift assays using oligonucleotides of the MARS-2 sequence having specific deletions or substitutions as probes or competitors showed that the essential sequence of MARS-2 required for nuclear protein binding consists of 16 nucleotides encompassing -151 to -136. When nuclear extracts from different cells were examined, L cells and mouse liver nuclear protein contained the highest levels of binding protein for the MARS-2 probe. This protein, termed MARS-2 binding protein, was purified from mouse liver nuclear extracts to homogeneity using gel filtration and MARS-2 oligonucleotide-specific column chromatographic procedures. The Mr = 66,000 binding protein showed a gel mobility shift band that was identical to that of crude nuclear extracts.

Annexin I concentration, phospholipase activity and thromboxane synthesis in irradiated rat lung

Annexin I, a member of a family of Ca(2+)-dependent phospholipid-binding proteins (PLBP), has been suggested as a regulator of prostaglandin metabolism as a result of its inhibitory effect on phospholipase A2. Synthesis of prostaglandin is increased in irradiated tissue, but the mechanism underlying this increase has not been delineated. It is conceivable that a decrease in the level of annexin I resulting in increased phospholipase activity may be responsible for the enhanced synthesis of prostaglandin. Accordingly, we measured the level of a lung 36 kDa PLBP, which possesses characteristics of annexin I, as well as the activity of phospholipase and the synthesis of thromboxane A2 (TXA2) in irradiated rat lung. The right lung of rats was irradiated with 0, 15 or 30 Gy of X rays and the animals were sacrificed after 3 months. Phospholipid binding protein was assayed by its ability to transfer unilamellar liposomes to multilamellar liposomes and by immunoblotting against anti-36 kDa rabbit PLBP antisera. Production of TXA2 by minced lung tissue was determined by radioimmunoassay of its stable metabolite TXB2. Phospholipase activity was assayed by hydrolysis of [14C]dioleoylphosphatidylcholine. Our results showed that PLBP activity in the lungs irradiated with 30 Gy was lower than that in the lungs irradiated with 0 and 15 Gy (8.82 +/- 0.47 compared to 9.73 +/- 0.49 and 9.95 +/- 0.78 nmol phospholipid transferred/mg protein, respectively). Western blotting demonstrated a near total depletion of annexin I in the lungs irradiated with 30 Gy. Phospholipase activity was also lower in the lungs irradiated with 30 Gy compared to that in the lungs irradiated with 0 Gy (0.23 +/- 0.01 vs 0.32 +/- 0.01 nmol phosphatidylcholine liberated/mg protein/min, P < 0.001). Reduced phospholipase activity was observed not only in the cytosolic or soluble fraction of lung homogenate, but also in precipitates obtained after 21,000g and 100,000g centrifugation. Despite this decline in phospholipase activity, there was a 2.8-fold increase in the synthesis of thromboxane (367 +/- 65 compared to 1076 +/- 143 pg TXB2/mg tissue/10 min for lungs irradiated with 0 and 30 Gy, respectively). These results are not consistent with the hypothesis that increased synthesis of thromboxane A2 in irradiated rat lung is a direct result of elevated phospholipase activity. In fact, phospholipase activity is decreased in the irradiated lung, despite a decline in the concentration of annexin I, its putative inhibitor.

Characterization of an upstream regulatory element of the human apolipoprotein E gene, and purification of its binding protein from the human placenta

We have previously demonstrated that expression of the human apolipoprotein (apo) E gene is controlled by multiple regulatory elements in the promoter [Paik et al. (1988) J. Biol. Chem. 263, 13340-13349; Chang et al. (1990) J. Biol. Chem. 265, 9496-9504]. To extend these studies, we have characterized an element in the apoE gene promoter that spans nucleotides -101 to -89, upstream regulatory element 3 (URE3). Transcription of promoter/marker gene constructs in vitro showed that URE3 modulates gene expression. Gel mobility shift assays of URE3 using human placental nuclear extracts detected a specific binding protein whose activity can be modulated by micromolar amounts of divalent copper and zinc. Competitive binding and gel shift assays with mutant oligonucleotides revealed critical nucleotides within URE3 required for its specific nuclear protein-binding activity. Gel filtration and oligonucleotide affinity chromatography were employed to isolate a URE3-binding protein (URE3BP) from human placental nuclear extracts. Purified URE3BP appears to be a M(r) = 300,000 protein that is composed of four equally-sized basic subunits of M(r) = 67,000. These studies indicate that URE3 is an active regulatory component of the apoE gene.

CD4+ T-cell number at the time of acquired immunodeficiency syndrome

In this article, the authors adapt and extend the methodology of Phillips (Phillips et al. J Acquir Immune Defic Syndr 1992;5:148-52) to estimate the distribution of CD4+ T-cell number at the time of acquired immunodeficiency syndrome (AIDS) and to estimate the correlation between CD4+ T-cell number at AIDS and CD4+ T-cell number prior to human immunodeficiency virus infection. Using data from the Los Angeles portion of the Multicenter AIDS Cohort Study, the authors find that the median CD4+ T-cell count at the time of AIDS is 67 cells/mm3 with a 95% confidence interval of 58-84. The 5th and 95th percentiles of the distribution are 8 and 284, respectively. The authors estimate the correlation between the CD4+ T-cell number at the time of AIDS and the CD4+ T-cell number prior to human immunodeficiency virus infection to be 0.71 with a 95% confidence interval of 0.21-0.94. This very high correlation is suggestive of biologic hypotheses concerning possible control of the circulating CD4+ T-cell number. The high correlation can also be useful in determining when to start prophylactic treatment.

The subcellular localization of defensins and myeloperoxidase in human neutrophils: immunocytochemical evidence for azurophil granule heterogeneity

We used immunogold electron microscopy to examine the distribution of human defensins 1-3 (HNP1-3) and myeloperoxidase (MPO) in the cytoplasmic granules of thin-sectioned, normal human neutrophils. The presence of MPO, defensins, or both was noted in 388 (62.3%) of 623 granule profiles. Whereas MPO and defensins colocalized in 32.5% of such granules, 32.7% demonstrated only MPO and 34.8% demonstrated only defensins. The staining densities of MPO and HNP1-3 showed a low correlation, even when both molecules were present in the same granules (r = 0.09), indicating that they were not present in fixed relative proportions even when colocalized. The low partial correlation coefficient (r = -0.23) between MPO and HNP1-3 for the 388 labeled granules controlling for granule area suggested that the deposition of MPO and defensins might even be negatively correlated. The distribution of MPO and defensins within the cytoplasmic granules of human neutrophils followed a "non-colocalization and multi-compartmental" model that conflicts with the classical notion of azurophil granules as a homogeneous population of organelles marked by the presence of MPO.

Nucleotide sequence stability of the genome of hepatitis delta virus

Cultured cells were cotransfected with a fully sequenced 1,679-base cDNA clone of human hepatitis delta virus (HDV) RNA genome and a cDNA for the genome of woodchuck hepatitis virus (WHV). The HDV particles released were able to infect a woodchuck that was chronically infected with WHV. The HDV so produced was passaged a total of six times in woodchucks in order to determine the stability of the HDV nucleotide sequence. During a final chronic infection with such virus, liver RNA was extracted, and the HDV nucleotide sequence for the 352-base region, positions 905 to 1256, was obtained. By means of PCR, we obtained double-stranded cDNA both for direct sequencing and also for molecular cloning followed by sequencing. By direct sequencing, we found that a consensus sequence existed and was identical to the original sequence. From the sequences of 31 clones, we found 32% (10 of 31) to be identical to the original single nucleotide sequence. For the remainder, there were neither insertions nor deletions but there was a small number of single-nucleotide changes. These changes were predominantly transitions rather than transversions. Furthermore, the transitions were largely of just two types, uridine to cytidine and adenosine to guanosine. Of the 40 changes detected on HDV, 35% (14 of 40) occurred within an eight-nucleotide region that included position 1012, previously shown to be a site of RNA editing. These findings may have significant implications regarding both the stability of the HDV RNA genome and the mechanism of RNA editing.

Regulation of the myoblast-specific expression of the human beta-enolase gene

The muscle-specific beta-enolase gene is expressed in proliferating adult myoblasts as well as in differentiated myotubes. Through deletion-transfection analysis, we identified a 79-base pair enhancer from the beta-enolase gene that leads to high level expression of a reporter gene in myoblasts, but not in fibroblasts. Following myoblast differentiation into myotubes, the activity of the enhancer declined, indicating that beta-enolase gene expression in myotubes is mediated by other regulators, possibly the myogenic helix-loop-helix family of transcription factors. Electrophoretic mobility shift assays indicated that proteins present in myoblast nuclear extracts specifically bind to the 3' half of the 79-base pair enhancer. This region contains an ets DNA-binding motif which is required not only for high level activity in myoblasts, but also for repressing activity in fibroblasts. Furthermore, the beta-enolase myoblast-specific enhancer shows limited similarity to the myoblast-specific enhancer associated with the human desmin gene, suggesting that gene expression in adult myoblasts may be coordinately regulated.

Intracellular cleavage and ligation of hepatitis delta virus genomic RNA: regulation of ribozyme activity by cis-acting sequences and host factors

During replication, a ribozyme within the genomic RNA of hepatitis delta virus cleaves multimeric precursors to release a unit-length linear intermediate. Intramolecular ligation of this intermediate produces the circular genomic RNA. Although one copy of the ribozyme is reconstituted by such ligation, it does not subsequently cleave and destroy the circular conformation. We have identified cis-acting attenuator sequences that prevent self-cleavage of the circular product by base pairing with and inactivating the ribozyme. Furthermore, we have shown that during the initial processing of the multimeric precursor RNA, host-specific factors activate the ribozyme by preventing its association with the attenuator sequences. Thus, we demonstrate a novel switching mechanism that regulates ribozyme activity inside the cell.

Dose-response relationship for radiation therapy of subclinical disease

PURPOSE

To determine the dose-response relationship for elective treatment of subclinical metastatic deposits and validate a model for metastatic tumor cell burden.

METHODS AND MATERIALS

The incidence of overt metastases in electively irradiated potential sites of spread from carcinomas of the head and neck, breast, cervix, ovary, lung, and testis, and from melanomas and osteosarcomas, was compared with the incidence in patients not receiving elective irradiation. The reduction in incidence of metastases was analyzed as a function of radiation dose.

RESULTS

The dose-response curve for control of subclinical metastases is linear and shallow, and extrapolates to a dose intercept not demonstrably different from zero. A small threshold may reflect growth of residual micrometastases between treatment for the primary and elective irradiation. The shallow linear dose response reflects interpatient heterogeneity in metastatic tumor cell burden, ranging from 1 to M cells, where M is the upper limit of clinical undetectability. While a dose of 50 Gy in 2 Gy fractions is necessary to achieve an overall 90% reduction in the incidence of metastases, the metastatic cell burden in a proportion of patients can be eliminated by low doses. Thus, worthwhile rates of control can still be achieved when "tolerance" dictates lower than optimal doses, evidenced by the linearity and lack of significant threshold in the dose-response curve. This is an important difference from treatment of gross disease. The biological effectiveness of elective treatment is measured directly by the percent reduction in failure rate. Although it depends upon the log cell kill, it relates only to that proportion of patients harboring subclinical disease, and, therefore, is not well described by the increase in the cure rate for the total patient population. The linear dose-response relationship for reduction in failure rate is independent of the "natural" (untreated) incidence of subclinical metastasis, and, therefore, of site, histology, growth rate, stage, or other characteristics of the tumor. Conversely, the clinical effectiveness of elective treatment is measured by increase in tumor control rate and depends upon the "natural" incidence of metastasis: the higher it is, the greater the absolute increase in cure rate from a constant biological effect (log cell kill).

CONCLUSIONS

(a) High control rates for subclinical metastases require doses of about 50 Gy in 2 Gy fractions, but worthwhile benefits can be achieved by lower doses if necessitated by reduced tolerance; (b) elective treatment of subclinical metastases should be instituted close to the time of treatment of the primary; (c) the biological effectiveness of elective radiation (or chemotherapy) should be measured by the percentage decrease in metastasis, not by improvements in the rate of control; and (d) demonstration of success in clinical trials of adjuvant therapy is more likely the higher the incidence of metastases in untreated controls.

Resistance to HIV-1 infection. Multicenter AIDS Cohort Study

Men from the Multicenter AIDS Cohort Study were classified as "susceptible" and "resistant" to HIV infection. Resistant men were still HIV antibody negative in 1993 and were estimated to have had > 45 different anal intercourse partners (median, 92; range, 46-504) in the 2.5 years before visit 2 (1985). Susceptible men were seroconverters who were estimated to have had < 13 different anal partners (median, 4; range, 0-12). Leukocyte groups were compared between the two groups of men. Values were excluded for 12 months before the first antibody-positive visit in the susceptible men. White blood cells, polymorphonuclear neutrophils, total lymphocyte count, CD8+ percentage and number, and CD3+ and CD4+ number were higher in the resistant men. Logistic regression analyses were used to develop 50 bivariate models. Higher levels of neutrophils and CD8+ cells were included in four of the six best-fitting bivariate models, suggesting that each is associated with resistance to HIV-1 infection. These results support the hypothesis that CD8+ cells may modulate the outcome of HIV-1 exposure.

Binding of an alpha 2 adrenergic receptor third intracellular loop peptide to G beta and the amino terminus of G alpha

The structural basis of receptor-G protein interactions was examined using a photoaffinity derivative of a G protein-activating receptor-derived peptide (Q peptide) from the carboxyl-terminal region of the third intracellular loop of alpha 2 adrenergic receptor. A diazopyruvoyl photoaffinity derivative of this peptide (DAP-Q) was cross-linked to purified bovine brain Go. Specific, competable cross-linking of 750 nM DAP-Q to sites on both the alpha o and beta subunits was observed. No specific cross-linking was seen with non-target proteins or heat-denatured G protein subunits. 125I-DAP-Q labeled the 2-kDa amino-terminal fragment of alpha o as determined by protease digestion of the cross-linked G protein followed by gel electrophoresis or h igh pressure liquid chromatography purification and mass spectroscopy of the radiolabeled proteolysis fragment. The functional significance of incorporation into beta gamma subunit is supported by the absolute requirement of beta gamma subunit for DAP-Q stimulation of Go/Gi GTPase. Thus, specific interactions of G protein-coupled receptors with the beta subunit of G protein, in addition to those with the alpha subunit, appear to be important for receptor-G protein coupling.

Color technology in video endoscopy

The psychophysical aspects of the color experience and the clinical significance of color during video endoscopy are introduced in this paper. This introduction includes a description of how colors are rendered in video endoscope systems along with basic colorimetry, the science of color. Together these provide the clinical engineer with an understanding of color and a method of effectively communicating color information. The ability to standardize color rendition in video endoscopy systems is not yet available. Nonetheless, an argument is presented in favor of the clinical engineer normalizing color rendition in video endoscope systems in the hospital and educating the clinicians on managing endoscopic system color performance in the clinical setting.

Peptides as probes for G protein signal transduction

Triggered by agonist binding to cell surface receptors, the heterotrimeric G proteins dissociate into alpha and beta gamma subunits, each activating distinct second messenger pathways. Peptides from the primary sequences of receptors, G proteins, and effectors have been used to study the molecular interactions between these proteins. Receptor-derived peptides from the second, third and fourth intracellular loops and certain naturally occurring peptides antagonize G protein interactions and can directly activate G protein. These peptides bind to G protein sites that include the N and C terminal regions of the alpha subunit and a yet to be identified region of the beta subunit. Peptides have also been useful in characterizing G protein-effector interactions. The identification of the contact sites between proteins involved in G protein signal transduction should aid in the development of non-peptide mimetic therapeutics which could specifically modify G protein-mediated cellular responses.

The extent, time course, and fraction size dependence of mouse spinal cord recovery from radiation injury

PURPOSE

This experiment was designed to assess: (a) the influence of fraction size and time interval between fractions on the tolerance of the spinal cord to high cumulative doses of radiation; and (b) the influence of the long-term recovery process on the tolerance of the spinal cord to reirradiation.

METHODS AND MATERIALS

The T10-L2 level of the spinal cord of C3Hf mice was irradiated using a conventionally fractionated regimen of 2.0 Gy once daily, a prolonged fractionated regimen of 1.2 Gy once daily, a hyperfractionated regimen of 1.2 Gy twice daily, or a single dose of 12 Gy followed 0-190 days later by a second dose of 5-20 Gy. Mice in the multifractionated regimen groups were given a single 15 Gy top-up dose 24 h after reaching a cumulative fractionated dose of 24-70 Gy. Hind limb strength was measured weekly for 2 years after the completion of irradiation.

RESULTS

Paralysis occurred in a bimodal time distribution, with peaks at 5-10 months and 15-23 months after the completion of irradiation. The cumulative radiation dose was directly associated with the incidence of paralysis in each radiation schedule (p < 0.0001) and inversely associated with the time to onset of paralysis in the 1.2 Gy b.i.d. (p = 0.0001) and 2.0 Gy q.d. schedules (p = 0.03). The median latency of paralysis in each group was inversely associated with the incidence of paralysis in that group (p < 0.001). Decreasing the fraction size from 2.0 to 1.2 Gy once daily markedly increased the radiation tolerance of the spinal cord (p < 0.0001), consistent with a very small alpha-beta value of -0.30 Gy (approximately 95% confidence interval -0.72, +0.18) in the linear-quadratic model. Decreasing the time interval from 24 h to alternating 8 and 16 h periods produced an offsetting diminuation in cord tolerance (p < 0.0001). The 1.2 Gy once daily schedule resulted in ED20 and ED50 values that were approximately double those of the 2.0 Gy once daily and the 1.2 Gy twice daily schedules and a relative risk of paralysis from a given dose that was 0.03 times the risk associated with the other two regimens (p < 0.0001). There was no significant difference between the 2.0 Gy once daily and the 1.2 Gy twice daily dose-paralysis curves (p = 0.86). The residual from a single 12 Gy radiation dose was 17% after 190 days, leaving the retreatment ED50 only 10% below the ED50 of previously unirradiated spinal cord. The relative risk of paralysis after 12 Gy plus a second radiation dose decreased from 1.00 with no time interval between doses to 0.51-0.73 with a 0.25, 1 or 3 day interval, 0.32 with a 7 day interval, 0.11 with a 30 day interval, and 0.06 with a 190 day interval.

CONCLUSION

The increased radiation tolerance of the murine spinal cord produced by decreasing the fraction size from 2.0 to 1.2 Gy was offset by the diminished tolerance produced by decreasing the time interval between fractions from 24 to 8-16 h, resulting in no significant difference in the dose-paralysis curves of conventional and hyperfractionated radiation schedules. The rodent spinal cord eliminates the majority of the occult radiation injury produced by a radiation dose equal to half the ED50 during the months following irradiation. This permits retreatment of previously irradiated spinal cord to high doses without the induction of myelopathy.

The effectiveness of interventions on incubation of AIDS as measured by secular increases within a population

Methods are developed to estimate and test for the impact of intervention use on a population's survival function (time to AIDS). Each participant's history is divided into J + 1 components: omega 0 occurring before the intervention is available and omega 1 to omega J occurring later, as the intervention becomes successively more available. Distribution free truncated Kaplan-Meier models based on time since exposure fit separately to the risk sets/outcomes in omega 0 to omega J directly show the changing patterns of survival. Multivariate proportional hazards models can be used to adjust for covariates. Application of these methods indicates that availability of proven anti-AIDS interventions may have delayed time to AIDS by 8 months in an educated HIV-1 infected homosexual cohort with good access to medical care.

Marker values at the time of an AIDS diagnosis

In this paper statistical methods are proposed to estimate the distribution of a CD4 T-cell number at the time of a clinical AIDS endpoint from serial measurements of CD4 T-cell values in a cohort study. The statistical formulation of the problem is that of survival analysis with interval censored data, but in which the endpoints are obtained with measurement error. A measurement error likelihood is developed, assuming normality of the CD4 distribution at AIDS. A maximum likelihood estimation procedure and a Gibbs sampling approach are implemented.

Apparent helper-independent infection of woodchucks by hepatitis delta virus and subsequent rescue with woodchuck hepatitis virus

Hepatitis delta virus (HDV) is a subviral agent of humans which is dependent upon hepatitis B virus as a helper for transmission. HDV can be experimentally transmitted to woodchucks by using woodchuck hepatitis virus (WHV) as the helper. We used this model system to study two types of HDV infections: those of animals already chronically infected with WHV and those of animals without any evidence of prior exposure to WHV. At 5 to 10 days after infection with HDV, liver biopsies of these two groups of animals indicated that around 1% of the hepatocytes were infected (HDV antigen positive). Moreover, similar amounts of replicative forms of HDV RNA were detected. In contrast, by 20 days postinfection, the two groups of animals were quite different in the extent of the HDV infection. The animals chronically infected with WHV showed spread of the infection within the liver and the release of high titers of HDV into the serum. In contrast, the animals not previously exposed to WHV showed a progressive reduction in liver involvement, and at no time up to 165 days postinfection could we detect HDV particles in the serum. However, if these animals were inoculated with a relatively high titer of WHV at either 7 or even 33 days after the HDV infection, HDV viremia was observed. Our data support the interpretation that in these animals, hepatocytes were initially infected in the absence of helper virus, HDV genome replication took place, and ultimately these replicating genomes were rescued by the secondary WHV infection. The observation that HDV can survive in the liver for at least 33 days in the absence of coinfecting helper virus may be relevant to the reemergence of HDV infection following liver transplantation.

Overexpression of hepatic lipase in transgenic rabbits leads to a marked reduction of plasma high density lipoproteins and intermediate density lipoproteins

To elucidate the precise metabolic roles of hepatic lipase (HL), a human HL cDNA in a liver-specific expression vector was used to generate transgenic lines in the rabbit, an animal that normally expresses low levels of this enzyme. HL was detected in the plasma of all rabbits only after the administration of heparin; HL activity in transgenic rabbits was found at levels up to 80-fold greater than that in nontransgenic littermates. This increase in enzyme activity was associated with as much as a 5-fold decrease in total plasma cholesterol levels. Expression of the transgene resulted in a dramatic reduction in the level of large high density lipoproteins (HDL1 and HDL2) as well as dense HDL3. A reduction in the quantity of intermediate density lipoproteins (IDL) was also observed. These results demonstrate that HL functions in the metabolism of HDL and IDL, thereby playing a key role in plasma cholesterol homeostasis.

Identification of apolipoprotein B-100 low density lipoproteins, apolipoprotein B-48 remnants, and apolipoprotein E-rich high density lipoproteins in the mouse

Plasma lipoprotein fractions from inbred C57BL/6J mice and outbred ICR mice were prepared by sequential density ultracentrifugation using density ranges that were optimized for separating mouse lipoproteins, or by Superose 6 HR10/30 fast performance liquid chromatography (FPLC). The lipoproteins were characterized by migration behavior in agarose, apolipoprotein (apo) composition, lipid composition, and particle size distribution. Both sequential density ultracentrifugation and Superose 6 FPLC were adapted for the separation of lipoproteins from a single mouse. In the plasma of ICR and C57BL/6J mice, in contrast to human plasma, alpha-migrating high density lipoproteins (HDL) and beta-migrating low density lipoproteins (LDL) had overlapping density ranges. For example, beta-migrating apoB-100 LDL, slow pre-beta-migrating apoB-48 remnants, and alpha-migrating HDL1 were found together in the d 1.02-1.04 g/ml fraction. The d 1.04-1.06 g/ml fraction contained beta-migrating apoB-100 LDL and alpha-migrating HDL1. Large HDL1 that were found at d 1.02-1.06 g/ml were apoE-rich HDL1, characteristic of cholesteryl ester transfer protein-deficient mammals. The d 1.10-1.21 g/ml fraction, in addition to alpha-migrating HDL, included unique slow beta-migrating particles that contained apoE and apoA-I but was deficient in neutral lipids. These slow beta-HDL eluted in the same FPLC fractions as dense alpha-migrating HDL. Compared to ICR mouse plasma, C57BL/6J mouse plasma contained more LDL and less HDL1, which might contribute to the susceptibility of C57BL/6J and the resistance of ICR mice to the development of aortic fatty streak lesions when challenged with an atherogenic diet.

Smoothing grouped bivariate data to obtain the incubation period distribution of AIDS

We use a penalized likelihood approach to obtain a smooth estimate of a bivariate distribution from grouped data where each observation consists of a region in a plane. The purpose of the analysis is to estimate the incubation period distribution of AIDS from the Multicenter AIDS Cohort Study, a prevalent cohort of homosexual men. In this article we illustrate the usefulness of the penalized likelihood approach. We also discuss the use of a cross-validation and a Bayesian scheme to choose the smoothing parameters and bootstrap samples to assess uncertainty.