Surface transformation and photoinduced recovery in CdSe nanocrystals

CdSe nanocrystals in solution and films can enter a metastable state in which the highly luminescent nanocrystals become dark. This change, which we attribute to a surface transformation, can be caused by heating or by changing the environment of the nanocrystals at room temperature. The metastable transformation is reversed upon illumination of above-band-gap light, at which point the nanocrystals are again highly luminescent.

Endoscopic retrograde cholangiopancreatography in pancreatic trauma

The sensitivity and specificity of ERCP for the diagnosis of suspected pancreatic ductal rupture was prospectively studied. Fourteen consecutive patients who were referred for abdominal pain and hyperamylasemia subsequent to abdominal trauma underwent ERCP, the majority within 24 hours of admission. Twelve of these also underwent abdominal CT, and 7 had peritoneal lavage. Four patients were found to have ductal rupture at ERCP. This was confirmed at laparotomy. Three additional patients who underwent laparotomy were found not to have a ductal rupture, although one had a pancreatic capsular laceration. The remaining 7 had clinical resolution. ERCP was 100% sensitive and specific in the diagnosis of pancreatic ductal rupture, whereas no combination of serum amylase, CT scan, and peritoneal lavage was equally effective.

A locus conferring resistance to diet-induced hypercholesterolemia and atherosclerosis on mouse chromosome 2

Dietary cholesterol is known to raise total and low density lipoprotein cholesterol concentrations in humans and experimental animals, but the response among individuals varies greatly. Here we describe a mouse strain, C57BL/6ByJ (B6By), that is resistant to diet-induced hypercholesterolemia, in contrast to the phenotype seen in other common strains of mice including the closely related C57BL/6J (B6J) strain. Compared to B6J, B6By mice exhibit somewhat lower basal cholesterol levels on a chow diet, and show a relatively modest increase in absolute levels of total and LDL/VLDL cholesterol in response to an atherogenic diet containing 15% fat, 1.25% cholesterol, and 0.5% cholate. Correspondingly, B6By mice are also resistant to diet-induced aortic lesions, with less than 15% as many lesions as B6J. Food intake and cholesterol absorption are similar between B6By and B6J mice. To investigate the gene(s) underlying the resistant B6By phenotype, we performed genetic crosses with the unrelated mouse strain, A/J. A genome-wide scan revealed a locus, designated Diet1, on chromosome 2 near marker D2Mit117 showing highly significant linkage (lod = 9.6) between B6By alleles and hypo-response to diet. Examination of known genes in this region suggested that this locus represents a novel gene affecting plasma lipids and atherogenesis in response to diet.

A genome scan for familial combined hyperlipidemia reveals evidence of linkage with a locus on chromosome 11

Familial combined hyperlipidemia (FCHL) is a common familial lipid disorder characterized by a variable pattern of elevated levels of plasma cholesterol and/or triglycerides. It is present in 10%-20% of patients with premature coronary heart disease. The genetic etiology of the disease, including the number of genes involved and the magnitude of their effects, is unknown. Using a subset of 35 Dutch families ascertained for FCHL, we screened the genome, with a panel of 399 genetic markers, for chromosomal regions linked to genes contributing to FCHL. The results were analyzed by use of parametric-linkage methods in a two-stage study design. Four loci, on chromosomes 2p, 11p, 16q, and 19q, exhibited suggestive evidence for linkage with FCHL (LOD scores of 1.3-2.6). Markers within each of these regions were then examined in the original sample and in additional Dutch families with FCHL. The locus on chromosome 2 failed to show evidence for linkage, and the loci on chromosome 16q and 19q yielded only equivocal or suggestive evidence for linkage. However, one locus, near marker D11S1324 on the short arm of human chromosome 11, continued to show evidence for linkage with FCHL, in the second stage of this design. This region does not contain any strong candidate genes. These results provide evidence for a candidate chromosomal region for FCHL and support the concept that FCHL is complex and heterogeneous.

Effects of olfactory bulbectomy on neuropeptide gene expression in the rat olfactory/limbic system

Bilateral olfactory bulbectomy in the rat produces a well-characterized syndrome that is independent of anosmia. This syndrome is reversed by chronic antidepressant administration, which provides the basis for the olfactory bulbectomy model of depression. The present experiments focused on neuropeptide plasticity in central olfactory/limbic structures following olfactory bulbectomy in rats. Male Sprague-Dawley rats received bilateral surgical ablation of the olfactory bulbs, sham surgery, or no surgery and were killed either three, seven, 14 or 28 days later. Relative levels of messenger RNA encoding neuropeptide Y, somatostatin, thyrotropin-releasing hormone, and corticotropin-releasing factor precursors in the forebrain were measured by quantitative in situ hybridization histochemistry using oligonucleotide probes. Prepro-neuropeptide Y messenger RNA levels in the piriform cortex and dentate gyrus were significantly elevated in bulbectomized rats 14 and 28 days after surgery compared to sham-operated and surgically naive rats. Prepro-somatostatin messenger RNA levels in the piriform cortex were marginally increased in bulbectomized rats at these time-points. Thyrotropin-releasing hormone and corticotropin-releasing factor precursor messenger RNA levels were not altered in the brain regions studied. The results indicate that olfactory bulbectomy causes long-term increases in the expression of the neuropeptide Y gene. These findings suggest that neuropeptide Y plasticity in the olfactory/limbic system may contribute to the olfactory bulbectomy syndrome in rats, and they provide further evidence of a role for neuropeptide Y in the pathophysiology of depression.

Genetic loci controlling body fat, lipoprotein metabolism, and insulin levels in a multifactorial mouse model

We analyzed the inheritance of body fat, leptin levels, plasma lipoprotein levels, insulin levels, and related traits in an intercross between inbred mouse strains CAST/Ei and C57BL/6J. CAST/Ei mice are unusually lean, with only approximately 8% of body weight as fat, whereas C57BL/6J mice have approximately 18% body fat. Quantitative trait locus analysis using > 200 F2 mice revealed highly significant loci (lod scores > 4.3) on chromosomes 2 (three separate loci) and 9 that contribute to mouse fat-pad mass for mice on a high-fat diet. Some loci also influenced plasma lipoprotein levels and insulin levels either on chow or high-fat diets. Two loci for body fat and lipoprotein levels (on central and distal chromosome 2) coincided with a locus having strong effects on hepatic lipase activity, an activity associated with visceral obesity and lipoprotein levels in humans. A locus contributing to plasma leptin levels (lod score 5.3) but not obesity was identified on chromosome 4, near the leptin receptor gene. These data identify candidate regions and candidate genes for studies of human obesity and diabetes, and suggest obesity is highly complex in terms of the number of genetic factors involved. Finally, they support the existence of specific genetic interactions between body fat, insulin metabolism, and lipoprotein metabolism.

Immigrants and the criminal justice system: an exploratory study

Experts have argued that there are significant barriers to recent immigrants' use of the criminal justice system. This exploratory study, using convenience samples, is among the first to look empirically at the experiences of recent immigrant victims with the criminal justice system in the United States. Contrary to expectations, we found that immigrants reported relatively few problems unique to foreign-born persons in dealing with the police and the courts, and that their satisfaction with the justice system was comparable to levels reported in studies of native-born victims. The results suggest that although recent immigrants' expectations of the criminal justice system may be different from those of native born, the experiences of immigrant victims and their satisfaction with the justice system are similar in many respects to those of native-born victims.

Lipase engineering: a window into structure-function relationships

Utilization of genetic engineering techniques to create novel functional lipases has increased knowledge of structure-function relationships in this important class of enzymes. The examples of engineered lipases presented in this chapter addressed the investigation of domain-specific properties, heparin binding, and subunit orientation. Conclusions reached are credible because the designed lipases retained catalytic activity, implying native, or near-native, conformation. This approach has demonstrated vigor by determining the domain location of several important enzyme functions and by providing the first evidence that LPL subunits are arranged in a head-to-tail orientation. In conjunction with physical techniques, such as crystallography and nuclear magnetic resonance spectroscopy, the engineered lipase approach could reveal new insights into the mechanism by which lipolysis is accomplished. The studies described here represent only the first attempts to explore that subject; more sophisticated lipase engineering will be used in future as a window into structure-function relationships.

A molecular biology-based approach to resolve the subunit orientation of lipoprotein lipase

The subunit orientation of a dimeric enzyme influences the mechanism of action and function. To determine the subunit arrangement of lipoprotein lipase (LPL), a molecular biology-based approach was initiated. An eight amino acid linker region was engineered between two LPL monomers and expressed in COS-7 cells. The resultant tandem-repeat molecule (LPLTR) was lipolytically active and had kinetic parameters, salt inhibition, cofactor-dependent activity, heparin-binding characteristics, and a functional unit size very similar to the expressed native human enzyme. By these criteria, LPLTR was the functional equivalent of native LPL. Considering the length of the linker peptide (no more than 24 A), monomers in the tethered molecule were restricted to a head-to-tail subunit arrangement. Since LPLTR demonstrated native enzyme-like properties while constrained to this subunit arrangement, these results provide the first compelling evidence that native LPL monomers are arranged in a head-to-tail subunit orientation within the active dimer. Thus, LPL function in physiology, lipolysis, and binding to cell-surface components must now be addressed with this subunit orientation in mind. The utility of the tandem-repeat approach to resolve the subunit arrangement of an obligate dimer has been demonstrated with LPL and could be generalized for use with other oligomeric enzymes.

Increases in serum unbound free fatty acid levels following coronary angioplasty

Serum unbound free fatty acid levels (FFAu) were measured in patients undergoing percutaneous transluminal coronary angioplasty (PTCA) using the fluorescent probe acrylodan intestinal fatty acid binding protein (ADIFAB). These are the first measurements of FFAu, under nonphysiologic conditions. In these studies, FFAu, levels were determined in 22 patients 5 minutes before and 30 minutes after the procedure. Post-PTCA FFAu, levels were higher than pre-PTCA levels in all patients. The average post-PTCA level for all patients was 103 nM, about 14-fold higher than the 7.5 nM value observed in healthy subjects. Although all patients exhibited elevated FFAu levels after PTCA, ischemic ST-segment changes were observed in only 11 of these patients. The average post-PTCA FFAu levels for patients with significant ST-segment changes (123 nM) were significantly higher than those in patients who did not exhibit such changes (47 nM). Average FFAu (22 nM) levels before the procedure were elevated in the patient population relative to healthy subjects and these values correlated positively with post-PTCA levels. These results suggest that increased serum FFAu levels reflect angioplasty-induced ischemia and that FFAu levels may provide a more sensitive measure of ischemia than electrocardiographic measurements. Moreover, because 30% of these patients had post-PTCA FFAu concentrations exceeding those found to alter in vitro cell function, the increased serum FFAu levels that accompany ischemia may be deleterious for myocardial function.

Translational regulation of lipoprotein lipase by thyroid hormone is via a cytoplasmic repressor that interacts with the 3' untranslated region

To better characterize the increase in lipoprotein lipase (LPL) translation by hypothyroidism, adipocytes were prepared from control and hypothyroid rats. Whereas LPL synthesis was higher in hypothyroid adipocytes, with no change in mRNA levels, there was no increase in hormone-sensitive lipase (HSL) synthesis. To determine whether a transacting translation regulatory factor was present, a cytoplasmic fraction was prepared from control and hypothyroid adipocytes, and added to an in vitro translation system containing the hLPL mRNA. The hypothyroid cell fraction from adipose and heart yielded an increase in LPL translation, when compared to control extracts. Further experiments determined that the control adipocyte extract contained a translation-inhibitory factor that was 8-fold lower in activity in the hypothyroid extract. Using different LPL mRNA constructs in the in vitro translation reaction, the region that controlled translation was localized to nucleotides 1599 to 1638 (proximal 3' untranslated region (UTR)). To confirm the presence of a transacting factor, a sense RNA strand corresponding to this region was added to the in vitro translation reaction. This sense strand competed for the transacting factor in the control cell extract, yet had no effect on the hypothyroid cell extract. Thus, there is a translation repressor factor in the cytoplasm of rat adipocytes, and this factor is greatly reduced in activity in hypothyroid rat adipocytes. Because a similar mechanism of LPL regulation occurs in response to epinephrine, the absence of the translation repressor may be a mechanism for the loss of sensitivity of hypothyroid cells for catecholamines.

Domain-structure analysis of recombinant rat hormone-sensitive lipase

Hormone-sensitive lipase (HSL) plays a key role in lipid metabolism and overall energy homoeostasis, by controlling the release of fatty acids from stored triglycerides in adipose tissue. Lipases and esterases form a protein superfamily with a common structural fold, called the alpha/beta-hydrolase fold, and a catalytic triad of serine, aspartic or glutamic acid and histidine. Previous alignments between HSL and lipase 2 of Moraxella TA144 have been extended to cover a much larger part of the HSL sequence. From these extended alignments, possible sites for the catalytic triad and alpha/beta-hydrolase fold are suggested. Furthermore, it is proposed that HSL contains a structural domain with catalytic capacity and a regulatory module attached, as well as a structural N-terminal domain unique to this enzyme. In order to test the proposed domain structure, rat HSL was overexpressed and purified to homogeneity using a baculovirus/insect-cell expression system. The purification, resulting in > 99% purity, involved detergent solubilization followed by anion-exchange chromatography and hydrophobic-interaction chromatography. The purified recombinant enzyme was identical to rat adipose-tissue HSL with regard to specific activity, substrate specificity and ability to serve as a substrate for cAMP-dependent protein kinase. The recombinant HSL was subjected to denaturation by guanidine hydrochloride and limited proteolysis. These treatments resulted in more extensive loss of activity against phospholipid-stabilized lipid substrates than against water-soluble substrates, suggesting that the hydrolytic activity can be separated from recognition of lipid substrates. These data support the concept that HSL has at least two major domains.

Human hepatic lipase subunit structure determination

Chinese hamster ovary cells were stably transfected with a human hepatic lipase (HL) cDNA. The recombinant enzyme was purified from culture medium in milligram quantities and shown to have a molecular weight, specific activity, and heparin affinity equivalent to HL present in human post-heparin plasma. The techniques of intensity light scattering, sedimentation equilibrium, and radiation inactivation were employed to assess the subunit structure of HL. For intensity light scattering, purified enzyme was subjected to size exclusion chromatography coupled to three detectors in series: an ultraviolet absorbance monitor, a differential refractometer, and a light scattering photometer. The polypeptide molecular weight (without carbohydrate contributions) was calculated using the measurements from the three detectors combined with the extinction coefficient of human HL. A single protein peak containing HL activity was identified and calculated to have a molecular mass of 107,000 in excellent agreement with the expected value for a dimer of HL (106.8 kDa). In addition, sedimentation equilibrium studies revealed that HL had a molecular mass (with carbohydrate contributions) of 121 kDa. Finally, to determine the smallest structural unit required for lipolytic activity, HL was subjected to radiation inactivation. Purified HL was exposed to various doses of high energy electrons at -135 degrees C; lipase activity decreased as a single exponential function of the radiation dose to less than 0.01% remaining activity. The target size of functional HL was calculated to be 109 kDa, whereas the size of the structural unit was determined to be 63 kDa. These data indicate that two HL monomer subunits are required for lipolytic activity, consistent with an HL homodimer. A model for active dimeric hepatic lipase is presented with implications for physiological function.

Optical intensity mapping on the nanometer scale by near-field photodetection optical microscopy

Near-field photodetection optical microscopy (NPOM) is a fundamentally new approach to near-field optical microscopy. This scanning-probe technique uses a nanometer-scale photodiode detector as a near-field optical probe. We have fabricated probes for NPOM that have optically sensitive areas as small as 100 nm x 100 nm. These new NPOM probes have been employed to image light transmitted through holes in an aluminum film. Near-surface optical interference is observed near defects and edges of the aluminum film. The optical edge response is shown to be of the order of 100 nm.

Physician practices regarding anticoagulation and cardioversion of atrial fibrillation

BACKGROUND

Stroke is one of the most significant potential complications in patients who are undergoing cardioversion for atrial fibrillation. To minimize the risk of stroke, the American College of Chest Physicians' (ACCP's) Third Consensus Conference on Antithrombotic Therapy developed specific recommendations regarding anticoagulation before and following elective cardioversion of patients with atrial fibrillation.

OBJECTIVE

To determine if patients undergoing cardioversion for atrial fibrillation are administered anticoagulants according to the ACCP's Third Consensus Conference on Antithrombotic Therapy recommendations.

DESIGN

A retrospective review of cases of atrial fibrillation at a tertiary care teaching hospital to determine if physicians are routinely following these recommendations.

METHODS

Data were collected for the year 1994 for all patients admitted to a tertiary care teaching hospital with a diagnosis of atrial fibrillation (n = 111). The ACCP's recommendations that were evaluated included the following: patients undergoing elective cardioversion for atrial fibrillation should receive anticoagulation for 3 weeks before and 4 weeks following cardioversion except in cases of new-onset atrial fibrillation, and warfarin and heparin should be administered jointly for several days before discontinuation of heparin therapy.

RESULTS

Of the 111 patients who presented with a diagnosis of atrial fibrillation, 51 underwent elective cardioversion. In 18 (35%) of 51 cases, physicians failed to follow at least one of ACCP's recommendations regarding anticoagulation. These included failing to (1) administer anticoagulants to patients for 3 weeks before elective cardioversion (n = 14); (2) administer anticoagulants to patients for 4 weeks following cardioversion (n = 6); and (3) overlap heparin and/or warfarin therapies for 72 hours (n = 4). Six cases failed to meet more than one of these recommendations.

CONCLUSION

Physicians are not routinely following the ACCP's Third Consensus Conference on Antithrombotic Therapy recommendations regarding anticoagulation in elective cardioversion of atrial fibrillation, thus increasing patients' risk of stroke.

Adjusting to criminal victimization: the correlates of postcrime distress

This article explores the correlates of immediate and short-term psychological distress among victims of burglary, robbery, and nonsexual assault. A panel design was employed. Crime victims were interviewed within 1 month following the incident and again 3 months later. Four sets of predictors were examined: demographics, previctimization adjustment and stress, features of the crime incident, and victims' perceptions. Measures of distress included a range of standard indices of adjustment and symptomatology. Demographic characteristics and victim perceptions accounted for the greatest proportions of variance in the outcome measures at Time 1 and Time 2. The strongest predictors of psychological adjustment at the end of 3 months included adjustment after 1 month, education, victim injury, victims' beliefs that their lives had been endangered during the crime episode, and victims' appraisals of the world as meaningful. Implications for treatment and directions for future studies are discussed.

Regulation of lipoprotein lipase translation by epinephrine in 3T3-L1 cells. Importance of the 3' untranslated region

Lipoprotein lipase (LPL) is a central enzyme in lipoprotein metabolism and is in part responsible for adipocyte lipid accumulation. Catecholamines are known to decrease the activity of LPL in adipocytes, and we have previously demonstrated that this inhibition occurs posttranscriptionally, with a prominent inhibition of LPL translation. To better characterize the inhibition of LPL translation, 3T3-L1 cells were differentiated into adipocytes, and exposed to epinephrine. Epinephrine induced a dose-dependent decrease in LPL synthesis using [35S]methionine incorporation, with no change in LPL mRNA levels, demonstrating translational regulation of LPL in this cell line. The poly A-enriched RNA from epinephrine-treated cells was translated well in vitro, and there was no difference in the polysome profiles from control and epinephrine-treated cells, suggesting that epinephrine did not affect mRNA editing, and did not induce an inhibition of translation initiation. To obtain evidence for the presence of an inhibitory factor, a cytoplasmic extract from control, and epinephrine-treated adipocytes was human. When compared to the control cell extract, the epinephrine-treated cell extract sharply inhibited LPL translation in vitro, yet had no effect on the translation of other mRNAs. Epinephrine-treated cells had fourfold more of this inhibitor activity than control cells, and this translation inhibition was partially reversed by heat treatment. To determine what region of the LPL mRNA was involved in the translation inhibition, different LPL constructs were synthesized. The inhibitory effect of the epinephrine-treated cell extract was dependent on the presence of the first 40 nucleotides of the 3' (untranslated region UTR) (nucleotides 1599-1638), whereas deletion of the 5' UTR and other areas of the 3' UTR had no effect on translation inhibition. When a sense RNA strand corresponding to this region was added to the in vitro translation reaction, it restored translation towards normal, suggesting that the sense strand was competing for a transacting binding protein. Thus, epinephrine-treated adipocytes produced a transacting factor, probably a protein, that interacted with a region on the LPL mRNA between nucleotides 1599 and 1638, resulting in an inhibition of translation. These studies add new insight into the hormonal regulation of LPL.

Clinical and angiographic correlates of normal creatine kinase with increased MB isoenzymes in possible acute myocardial infarction

A retrospective study of patients with possible acute myocardial infarction was conducted over a 2-year period to evaluate the clinical characteristics, angiographic findings, and in-hospital prognosis in patients with normal total creatine kinase (CK) activity and increased MB isoenzyme activity (CK-MB). Thirty-nine cases were identified (study group) and compared with cases of Q-wave (n = 77) and non-Q-wave (n = 60) infarctions. Compared with the Q-wave group, study group patients were older (67.5 +/- 9.0 vs 60.8 +/- 11.5 years; p < 0.01) and more often had previous diagnoses of coronary disease (52.6% vs 18.2%; p < 0.01) and peripheral vascular disease (28.9% vs 10.4%; p = 0.02). Angina (92.2% vs 65.8%; p < 0.01) and ST elevation (81.8% vs 13.2%; p < 0.01) were more common in the Q-wave group. Nearly identical clinical profiles and electrocardiographic findings were observed in the study and non-Q-wave groups. Angiographic analysis revealed a higher frequency of multivessel disease in the study group (89.6%) than in the Q-wave group (48.6%, p < 0.01) but no difference between the study group and the non-Q-wave group (79.6%; p not statistically significant). Left ventricular function and in-hospital complications were similar among groups. It is concluded that patients with normal total CK activity and increased CK-MB concentration represent a subgroup of patients with non-Q-wave infarction with a high prevalence of multivessel coronary disease.