Retention and separation of adenosine and analogues by affinity chromatography with an aptamer stationary phase

A biotinylated-DNA aptamer (molecular weight 16,600) that binds adenosine and related compounds in solution was immobilized by reaction with streptavidin, which had been covalently attached to porous chromatographic supports. The aptamer medium was packed into fused-silica capillaries (50-150-microm i.d.) to form affinity chromatography columns. Frontal chromatography analysis indicated that the dissociation constants (Kd) of cyclic-AMP, AMP, ATP, ADP, and adenosine were 138 +/- 18, 58 +/- 2, 38 +/- 2, 28 +/- 6 and 3 +/- 1 microM, respectively, for aptamer immobilized on a controlled pore glass support. Similar values were obtained for aptamer immobilized on a polystyrene support except for a slightly higher Kd for adenosine. The Kd for adenosine is similar to the previously reported value of 6 +/- 3 microM for adenosine-aptamer in solution indicating that immobilized aptamers can have affinity similar to that of the solution forms. Columns had 20 nmol of binding sites/100 microL of support media, which is 3.3-fold higher than that previously reported for immobilization of IgG on similar media, indicating that the aptamer can be immobilized with higher density than antibodies. Variation of mobile-phase conditions revealed that ionic strength and Mg2+ level had strong effects on retention of analytes while pH and buffer composition had less of an effect. It was demonstrated that the column could selectively retain and separate cyclic-AMP, NAD+, AMP, ADP, ATP, and adenosine, even in complex mixtures such as tissue extracts.

[Automatic analysis and research on the trend of ST-T segment based on KL transform]

In view of the limitation of monitoring the trend of ST segment with the traditional method(ST level), we introduce a new monitor method based on KL transform. This method has overcome many disadvantages of ST level, e.g. the susceptibility to interference, a large variation of performance and the reflection of isolated characteristic. This method can characterize the signals stably and adequately. We have made experiment and analyzed the property of this method by using the standard database. The results indicate that the KL transform is of great clinical significance in detecting and monitoring the abnormality of the ST-T segment waveform over a long period of time, and the effect of monitor is also laid on the selection of KL series.

Relationship between plasma D(-)-lactate and intestinal damage after severe injuries in rats

AIM: To explore the kinetic changes in plasma D(-)-lactate and lipopolysaccharide (LPS) levels, and investigate whether D(-)-lactate could be used as a marker of intestinal injury in rats following gut ischemia/reperfusion, burn, and acute necrotizing pancreatitis (ANP).

METHODS: Three models were developed in rats: ① gut ischemia/reperfusion obtained by one hour of superior mesenteric artery occlusion followed by reperfusion; ② severe burn injury created by 30% of total body surface area (TBSA) full-thickness scald burn; and ③ ANP induced by continuous inverse infusion of sodium taurocholate and trypsin into main pancreatic duct. Plasma levels of D(-)-lactate in systemic circulation and LPS in portal circulation were measured by enzymatic-spectrophotometric method and limulus amebocyte lysate (LAL) test kit, respectively. Tissue samples of intestine were taken for histological analysis.

RESULTS: One hour gut ischemia followed by reperfusion injuries resulted in a significant elevation in plasma D(-)-lactate and LPS levels, and there was a significant correlation between the plasma D(-)-lactate and LPS (r = 0.719, P < 0.05). The plasma concentrations of D(-)-lactate and LPS increased significantly at 6 h postburn, and there was also a remarkable correlation between them (r = 0.877, P < 0.01). D(-)-lactate and LPS levels elevated significantly at 2 h after ANP, with a similar significant correlation between the two levels (r = 0.798, P < 0.01). The desquamation of intestine villi and infiltration of inflammatory cells in the lamina propria were observed in all groups.

CONCLUSION: The changes of plasma D(-)-lactate levels in systemic blood paralleled with LPS levels in the portal vein blood. The measurement of plasma D(-)-lactate level may be a useful marker to assess the intestinal injury and to monitor an increase of intestinal permeability and endotoxemia following severe injuries in early stage.

[Research of drug resistance and detection of methicillin-resistant Staphylococcus aureus in chronic maxillary sinusitis]

OBJECTIVE

To investigate the detection method of methicillin-resistant staphylococcus aureus (MRSA) in chronic maxillary sinusitis and the situation of drug resistance to some common antibiotics.

METHOD

Using multiplex polymerase chain reaction technique to detect the drug resistant gene (mecA) of MRSA and specific gene (femA) of staphylococcus aureus at the same time. Drug resistant tests were performed with disk diffusion (K-B) method.

RESULT

femA is a specific gene of staphylococcus aureus, the detective ratio of mecA in MRSA is 96.2% (51/53). Vancomycin is the only antibiotic which is sensitive to MRSA, while others are not.

CONCLUSION

MRSA can be rapidly and specifically identified with multiplex PCR. There are drug resistance to many antibiotic drugs for MRSA.

[The study of intrapleural urokinase in the prevention of pleural thickening and loculated effusions by tuberculous pleurisy]

OBJECTIVE

To investigate the effects of intrapleural urokinase in the prevention of pleural thickening and loculated pleural effusions by tuberculous pleural effusion.

METHOD

Eighty-one patients with tuberculous pleural effusion were randomized into 2 groups, intrapleural urokinase group (group I) and conventional group (group C). The patients in group I were injected with urokinase 100 000 IU intrapleurally after each thoracocentesis on twice a week basis, other therapies were similar to group C.

RESULTS

The mean volume of fluid drained in group I was (3 981 +/- 573) ml, while it was (3 045 +/- 498) ml in group C (P < 0.01). The mean thickness of pleura in group I was (1.10 +/- 0.20) mm, but it was (1.40 +/- 0.30) mm in group C (P < 0.01), the incidence of pleural adhesion and location in group I was 10%, while it was 36% in group C (P < 0.01). The mean number of injection was (4.6 +/- 1.4) (ranged 3 approximately 8). The resolution time of pleural effusion was prolonged slightly, but there was no significant difference between two groups.

CONCLUSION

Intrapleural urokinase can evidently increase the volume of pleural effusion drained and prevent pleural thickening and adhesion.

Shape complementarity, binding-site dynamics, and transition state stabilization: a theoretical study of Diels-Alder catalysis by antibody 1E9

Antibody 1E9 is a protein catalyst for the Diels-Alder reaction between tetrachlorothiophene dioxide and N-ethylmaleimide. Quantum mechanical calculations have been employed to study the 1E9-catalyzed Diels-Alder reaction in the gas phase. The transition states and intermediates were all determined at the B3LYP/6-31G*//HF/6-31G* level. The cycloaddition step is predicted to be rate-determining, and the endo reaction pathway is strongly favored. Binding of the reactants and the transition states to antibody 1E9 was investigated by docking and molecular dynamics simulations. The linear interaction energy (LIE) method was adopted to estimate the free energy barrier of the 1E9-catalyzed Diels-Alder reaction. The catalytic efficiency of antibody 1E9 is achieved by enthalpic stabilization of the transition state, near-perfect shape complementarity of the hydrophobic binding site for the transition state, and a strategically placed hydrogen-bonding interaction.

[The prevention of infection complicating acute necrotizing pancreatitis:an experimental study]

OBJECTIVE

To observe the effects of 5 intervention measures on infection complicating acute necrotizing pancreatitis (ANP) in dogs and rats.

METHODS

A lethal model of ANP was reproduced by infusion of artificial bile into the biliopancreatic duct. Animals were divided randomly into: ANP group (no treatment); Chinese medicine group ("Qing Yi Tang"); Bifidobacterium mixture group; purgation group (MgSO(4)); selective decontamination of the digestive tract (SDD) group; and somatostatin group. The pancreas and intestine were observed morphologically and tight junction on ileum epithelia was assessed on cryofracture replicas. Blood and/or tissue levels of DAO and D-lactic acid and uric contents of lactulose/mannitol (L/M), served as indicators of gut barrier function, were measured at various time points. Intestinal flora and incidence of bacterial translocation (BT) to organs were examined.

RESULTS

In early stage of ANP, mucosal and epithelial tight junction damage and flora disturbance occurred in the gut. In addition, the gut barrier function indicators deteriorated. The BT rates were as high as 78.6% (canine) and 59.5% (rat). Treatment with Chinese medicine markedly improved gut barrier function and reduced BT rate (32.1% - 37.0%). Having similar purgative response as Chinese medicine, MgSO4 did not show any beneficial effect on gut barrier protection and the incidence of BT was not reduced. In bifidobacterium mixture and SDD group, flora balance was preserved well and similar results as Chinese medicine were obtained. The BT rates of these two groups decreased to 33.9% and 33.3%, respectively. Somatostatin markedly blunted pancreatic tissue injury and ameliorated gut barrier damage during early phase of ANP. All intervention measures except for purgation also decreased mortalities (14.3% - 35.3%, compared with 58.8% of the no treatment group).

CONCLUSIONS

Treatment with Chinese medicine, bifidobacterium mixture, SDD and somatostatin attenuated gut barrier damage and BT after ANP, and could be used to prevent secondary infection after ANP, but purgation alone is not effective.

[Effects of glibenclamide on mRNA level of ATP-sensitive potassium channels of heart in normal and streptozotocin-induced diabetic rats]

OBJECTIVE

To estimate if any difference exists in mRNA expression levels of KATP (SUR1, SUR2, Kir6.2) in heart tissues between streptozotocin-induced diabetic and normal rats, and to examine if any changes of heart KATP in mRNA level occurred after long-term Glibenclamide administration among the diabetic and control rats.

METHODS

Part 1: Adult male Sprague-Dawley (SD) rats were allocated into three groups: one group (n = 13) was taken as normal control, and the other two groups were diabetic models induced by a single intraperitoneal injection of streptozotocin (60 mg/kg). One of the diabetic groups (n = 10) was treated with premixed insulin (30%RI, 70%NPH) 4 - 8 units/day by subcutaneous injection at 4 - 5 pm everyday for two weeks. Part 2: Four groups of adult male SD rats were enrolled into the study. Group one (D1) was diabetes control induced by streptozotocin (n = 9), group two (DG2) was the diabetes treated with Glibenclamide (n = 14). Group three (N3) was normal control (n = 10), and group four (NG4) received Glibenclamide administration without diabetes (n = 14). DG2 and NG4 were given 10 mg/kg Glibenclamide intraperitonealy at 4 - 5 pm everyday for 14 days. Single-stranded digoxigenin-labeled probes were generated with RT-PCR. A total of 30 microgram of unfractionated RNA was transferred onto nylon membranes by dot-blot. Hybridization was performed at 50 degrees C for 16 hours with high SDS concentration hybridization buffer.

RESULTS

Study one: There was no significant difference in mRNA expression levels of SUR1, SUR2, and Kir6.2 in heart between diabetic, insulin-treated diabetic and control groups (P > 0.05). Study two: Glibenclamide-treated non-diabetic rats had higher mRNA expression levels of SUR1 and SUR2 in heart than normal control. The SUR1 were 43.0 +/- 16.6 vs 30.8 +/- 7.8 (P < 0.05), SUR2 161.9 +/- 51.0 vs 118.9 +/- 40.9 (P < 0.05), respectively. No difference in heart Kir6.2 mRNA level was found between the two groups (P > 0.05). Comparison between Glibenclamide-treated diabetic and non-treated diabetic rats showed that there was no change in mRNA levels of SUR1, SUR2 and Kir6.2 in heart (P > 0.05).

CONCLUSION

Chronic Glibenclamide-treatment up-regulates KATP gene transcriptional expression of heart in non-diabetic rats. The Streptozotocin-inducing diabetes itself does not affect the mRNA expression of KATP (SUR1, SUR2, and Kir6.2) in extra-pancreas tissues, but decreases the response of KATP to chronic Glibenclamide-treatment at transcriptional level.

[Effect of xanthone from Canscora lucidissima on cultured myocytes anoxia-reoxygenation injuries]

The anoxia/reoxygenation model of cultured neonatal rats myocardial cells were developed, according to Laarse's method: anoxia and glucose deficiency for 60 min followed by reoxygenation and re-exposure to glucose for 30 min. The results showed that the survival rate of myocardial cells in the anoxia group was significantly decreased, release of lactate dehydrogenase (LDH) from myocytes was increased and membrane fluidity was decreased, all the changes were much more severe in the reoxygenation group. 30 min before anoxia, addition of xanthones: 1,8-dihydroxy-3, 5-dimethoxyxanthone, 1-hydroxy-3,5-dimethoxyanthone and 1-hydroxy-3,7,8-trithoxyxanthone, isolated from Canscora lucidissima increased the rate of myocardial cells and membrane fluidity, decreased the release of LDH. These results suggested that xanthone may provide some protective effects on the anoxia/reoxygenation damages on myocardium.

Molecular cloning, sequencing and expression of obese gene in the Chinese

OBJECTIVE

To construct the human obese (ob) cDNA clone in the Chinese, and analyze the expression of the ob gene in adipose tissue of obese, non-obese subjects and nooinsulin-dependent diabetes mellitus (NIDDM) Chinese patients.

METHODS

A ob cDNA clone was isolated by reverse transcription polymerase chain reaction (RT-PCR). Four groups of Chinese subjects participated in the study: 1) 12 obese subjects [body mass index (BMI): 28.5 +/- 2.3 kg/m2]; 2) 11 non-obese subjects (BMI: 21.0 +/- 1.5 kg/m2); 3) 8 obese NIDDM patients (BMI: 27.0 +/- 1.4 kg/m2); 4) 11 non-obese NIDDM patients (BMI: 21.2 +/- 1.4 kg/m2). The expression of ob gene mRNA in abdominal subcutaneous adipose tissue was examined using RNA dot blot hybridization with a digoxigenin-labeled human ob cDNA probe. The hybridized signals were quantitated by densitometry.

RESULTS

A full human ob cDNA fragment which included a glutamine codon at +49 was obtained. A base substitution (A to G) in the coding region at position 287 was found, resulting in a glutamine being replaced by an arginine. Expression of the ob gene was significantly higher in Chinese obese subjects compared to non-obese ones (P < 0.05), and positively correlated with the BMI. No significant difference in the amount of ob mRNA was detected between non-diabetic and diabetic groups at the same BMI level.

CONCLUSIONS

We constructed a full length human ob cDNA clone. The expression of the ob gene was significantly higher in Chinese obese subjects than in non-obese ones. The metabolic and hormonal changes associated with NIDDM are not the main factors regulating the expression of the ob gene.

Evolution of shape complementarity and catalytic efficiency from a primordial antibody template

The crystal structure of an efficient Diels-Alder antibody catalyst at 1.9 angstrom resolution reveals almost perfect shape complementarity with its transition state analog. Comparison with highly related progesterone and Diels-Alderase antibodies that arose from the same primordial germ line template shows the relatively subtle mutational steps that were able to evolve both structural complementarity and catalytic efficiency.

[Study on measuring method of pulse oxygen saturation in clinical monitor]

In this paper, a measuring system of pulse oxygen saturation is presented, which is based on the Lambert-beer Principle, using the relative intensities at two wavelengths in the red and infrared ranges. In order to meet the special demand of continuous clinical physiological monitoring, two circuits and appropriate algorithms are designed, one circuit, a feedback circuit controlled by micro-controller, automatically regulates the base line of signal, another circuit is a controlled integral circuit which automatically regulates the amplitude of waveforms. As the result, the drift of base line in this system, especially the effects caused by the physiological differences of human bodies, which will deteriorate the system, have been reduced. The system is satisfactory to clinical monitoring.

[The study of architecture of portable multiparameter physiological monitor]

The portable multiparameter physiological monitor now becomes a hot point of competition of international manufactures. The paper uses the UPM-2001 patient monitor as an example, studies the key points of design of portable-type monitor which breaks through the traditional architecture of desk-type monitor.

[Hepatitis B virus replication status and its response to surgery for tumor in hepatocellular carcinoma patients with positive markers of HBV]

OBJECTIVE

To investigate the status of hepatitis B virus (HBV) activity in patients with hepatocellular carcinoma (HCC) and its response to surgical interventions for tumor in HBV positive HCC patients.

METHOD

We analyzed HBV marker results and detected HBV DNA in sera of 97 HCC patients (pre-operation 66 cases, post-operation 31 cases) with polymerase chain reaction (PCR) assay. We also investigated the HBV DNA titer in sera before and one week after operation in 20 HCC patients with positive HBV markers by quantitative polymerase chain reaction (Q-PCR).

RESULT

HBV DNA positive rate in sera was 40.9% and 64.52% in the two subgroup respectively (P < 0.05). HBV DNA titer in sera increased after operation (P < 0.01).

CONCLUSION

The infection rate of HBV in Chinese HCC patients is very high. The replication of hepatitis B virus is strong in partial HBV marker positive HCC patients and surgical interventions may promote the virus replication.

Self-gelatinizable copolymer immobilized glucose biosensor based on prussian blue modified graphite electrode

A novel poly(vinyl alcohol) grafting 4-vinylpyridine self-gelatinizable copolymer was adapted to immobilize glucose oxidase. The reduction of hydrogen peroxide (H2O2) was detected at a Prussian Blue (PB) modified graphite electrode. A stable and sensitive glucose amperometric biosensor is described. The copolymer is a good biocompatible polymer in which the glucose oxidase retains high activity. Moreover, the copolymer can adhere firmly to the inorganic PB membrane. The sensor showed an apparent Michaelis-Menten constant of 18 +/- 0.2 mM and a maximum current density of 1.14 microA cm-2 mM-1. The linear range is from 5 microM to 4.5 mM glucose and the detection limit is 0.5 microM glucose. The catalytic efficiency of PB for the reduction of H2O2 is higher than that for the oxidation of H2O2. Glucose concentrations in serum samples from healthy persons and diabetic patients were determined using the sensor. The results compared well with those provided by the hospital using a spectroscopy method.

Amperometric glucose biosensor based on sol-gel organic-inorganic hybrid material

A new type of sol-gel organic-inorganic hybrid material was developed and used for the production of biosensors. This material is composed of silica sol and a grafting copolymer of poly(vinyl alcohol) with 4-vinylpyridine. It prevents the cracking of conventional sol-gel-derived glasses and eliminates the swelling of the hydrogel. The optimum composition of the hybrid material was first examined, and then glucose oxidase was immobilized in this matrix to demonstrate its application. The characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The biosensor exhibited a series of good properties: high sensitivity (600 nA mmol-1 L-1), short response time (11 s) and remarkable long-term stability in storage (at least 5 months). In addition, the characteristics of the second-generation biosensor with the use of tetrathiafulvalene as a mediator were discussed.

An antibody exo Diels-Alderase inhibitor complex at 1.95 angstrom resolution

A highly specific Diels-Alder protein catalyst was made by manipulating the antibody repertoire of the immune system. The catalytic antibody 13G5 catalyzes a disfavored exo Diels-Alder transformation in a reaction for which there is no natural enzyme counterpart and that yields a single regioisomer in high enantiomeric excess. The crystal structure of the antibody Fab in complex with a ferrocenyl inhibitor containing the essential haptenic core that elicited 13G5 was determined at 1.95 angstrom resolution. Three key antibody residues appear to be responsible for the observed catalysis and product control. Tyrosine-L36 acts as a Lewis acid activating the dienophile for nucleophilic attack, and asparagine-L91 and aspartic acid-H50 form hydrogen bonds to the carboxylate side chain that substitutes for the carbamate diene substrate. This hydrogen-bonding scheme leads to rate acceleration and also pronounced stereoselectivity. Docking experiments with the four possible ortho transition states of the reaction explain the specific exo effect and suggest that the (3R,4R)-exo stereoisomer is the preferred product.

Spontaneous lifetime in a dielectrically-apertured Fabry-Perot microcavity

We present calculations of the modification of the spontaneous emission rate from a point source dipole in a Fabry-Perot microcavity containing an optically thin dielectric aperture. The dielectric aperture is described as a passive current source which is driven by the spontaneous point source. The spontaneous emission rate is shown to depend on the details of the aperture design, and shows a strong enhancement on resonance due to 3-dimensional optical confinement by the dielectric aperture.

Radiation fields from whispering-gallery modes of oxide-confined vertical-cavity surface-emitting lasers

Near- and far-field radiation patterns are analyzed for whispering-gallery-mode lasing in native-oxide-confined vertical-cavity surface-emitting lasers. Calculations from classical antenna theory based on the higher-order Bessel functions are compared with experiment and shown to be a useful predictor of the measured radiation fields. The most interesting features of the lasing modes are the multiple and uniformly distributed intensity spots in the near and far fields.

AmpliTaq DNA polymerase, FS dye-terminator sequencing: analysis of peak height patterns

Taq DNA polymerases in which the phenylalanine is substituted by a tyrosine at position 667 (Taq F667Y) are members of a new class of DNA polymerases that incorporate chain-terminating dideoxyribonucleoside triphosphates (ddNTPs) much more efficiently than the wild-type Taq DNA polymerase. Improved incorporation of ddNTPs into DNA during cycle sequencing using AmpliTaq DNA polymerase, FS (Taq-FS, a member of the Taq F667Y family), and dye-labeled primers results in nearly uniform peak heights in the sequencing trace. This is not the case when dye-labeled ddNTPs are used in Taq-FS cycle sequencing reactions. While the rate of dye-terminator incorporation is more efficient with Taq-FS, the peak pattern is still highly variable and different from that produced by the wild-type enzyme. We have systematically examined pairs of sequence-tagged sites that vary at only a single nucleotide to determine how base changes influence the peak heights of neighboring bases in sequencing traces generated by the Taq-FS dye-terminator chemistry. In 31 of 64 possible 3-base windows (48%), we find that the peak height of a particular base can be predicted by knowing just one or two bases 5' to the base in question. We have also compared and contrasted the peak patterns produced by the Taq-FS enzyme with those previously identified for the wild-type enzyme. Establishing the patterns in peak heights within local sequence contexts can improve the accuracy of base-calling and the identification of polymorphisms/mutations when using the Taq-FS dye-terminator cycle-sequencing chemistry.

Testing the feasibility of DNA typing for human identification by PCR and an oligonucleotide ligation assay

The use of DNA typing in human genome analysis is increasing and finding widespread application in the area of forensic and paternity testing. In this report, we explore the feasibility of typing single nucleotide polymorphisms (SNPs) by using a semiautomated method for analyzing human DNA samples. In this approach, PCR is used to amplify segments of human DNA containing a common SNP. Allelic nucleotides in the amplified product are then typed by a colorimetric implementation of the oligonucleotide ligation assay (OLA). The results of the combined assay, PCR/OLA, are read directly by a spectrophotometer; the absorbances are compiled; and the genotypes are automatically determined. A panel of 20 markers has been developed for DNA typing and has been tested using a sample panel from the CEPH pedigrees (CEPH parents). The results of this typing, as well as the potential to apply this method to larger populations, are discussed.

Increasing the information content of STS-based genome maps: identifying polymorphisms in mapped STSs

Physical maps of the human genome are being constructed by many groups using a mapping strategy that relies on the development of sequence-tagged sites (STSs). Thousands of physically mapped STSs, representing hundreds of kilobases (kb) of unique human DNA sequence, have been generated by these efforts. Since sequence variations are found every 1-2 kb in the genome, it is possible to extract additional information from mapped STSs by scanning them for variations. By screening 154 of the STSs published by the Whitehead Institute/MIT Genome Center, we have identified 47 new DNA sequence polymorphisms among the 37.2 kb of unique DNA sequence contained in these STSs. Using a sequence-based approach to estimate allele frequencies for these variations, 29 of the substitution polymorphisms (1 in 1.3 kb) were found to have heterozygosities exceeding 32%. Our study shows that the information content of STS-based genome maps can be increased with minimal additional effort by scanning for DNA polymorphisms, and that ambiguities and errors in the initial STS sequence can be resolved and corrected in the process.

Endothelial function following ischemia

The consequences of ischemia and reperfusion on endothelial dependent and independent coronary flow patterns following a variety of ischemic insults in isolated perfused rabbit hearts were studied. A blood perfused ex vivo model was developed that provided reliable and stable systolic performance comparable to crystalloid perfused hearts, but with a four to sevenfold decrease in resting coronary flow and a three to six fold increase in coronary flow reserve compared to Krebs' perfusion. Following incremental graded 37 degrees C ischemia of 10 to 45 minutes, blood perfused hearts had compromised systolic performance, but unaffected response to exogenous endothelial dependent and independent agonists whereas in crystalloid perfused hearts, the response to these same agonists was blunted prior to noting a decrement in systolic function. Further studies assessed the consequences of 30 and 45 minutes of ischemia on the regulatory role of basal nitric oxide released by the coronary endothelium. In both blood and crystalloid perfused hearts, basal nitric oxide secretion had a significant and persistent regulatory role on coronary vascular tonus over a tenfold range of coronary flow despite ischemic injury that severely depressed systolic performance. Finally, hearts were preserved in University of Wisconsin (UW) or St. Thomas' (ST) solutions for 4 hours at 4 degrees C. With crystalloid perfusion, ST results in impaired postischemic response to both endothelial dependent and independent agonists. After UW preservation and with all blood perfused hearts, postischemic flow patterns were unchanged. Using physiological blood perfusion protocols, the endothelium and arterial smooth muscle were found more resistant to ischemia-reperfusion injury than the myocyte.

Peak height variations in automated sequencing of PCR products using Taq dye-terminator chemistry

Direct sequencing of PCR products using Taq DNA polymerase with dye-labeled dideoxy chain terminators results in traces with uneven peaks. The peak height variations reflect the disproportionate rate of incorporation of deoxynucleotides vs. their analogs, a phenomenon that is highly dependent on the neighboring DNA sequence. Such peak height variations make it difficult to call bases correctly or to interpret whether or not a polymorphism is present. We have systematically examined pairs of sequence-tagged sites that vary at only one nucleotide to determine how a single base change will affect the peak heights of neighboring bases. We have found that the peak height of a particular base can often be predicted from the knowledge of just one or two nucleotides 5'- to the base in question. We have also observed several artifacts that occur consistently in the sequencing traces. These artifacts can be misinterpreted as polymorphisms or can obscure the real peak at that site. The empirically derived trends presented in this report can be utilized profitably when one is editing sequence data or examining them for polymorphisms and mutations.

Coronary flow reserve after ischemia and reperfusion of the isolated heart. Divergent results with crystalloid versus blood perfusion

Mechanical function and coronary hemodynamics were assessed in 73 isolated rabbit hearts randomly subjected to 0, 10, 20, 30, or 45 minutes of 37 degrees C global ischemia and 45 minutes of reperfusion in either a modified Krebs buffer or homologous blood-perfused Langendorff mode (n = 7 to 9 hearts per group). Isovolumic developed pressure, resting coronary flow, and response to endothelium-dependent (bradykinin) and -independent (nitroglycerin) agonists were quantitated at defined preload and heart rate. Perfusate did not influence systolic performance, which was impaired after 30 minutes of ischemia and fell to 64% to 72% of preischemic values after 45 minutes of ischemia (p < 0.05). However, basal coronary flow was at least sixfold greater in crystalloid-perfused hearts. Moreover, coronary hyperemia (p < 0.05) persisted for Krebs-perfused hearts subjected to all but the longest ischemic interval. After equilibration, all postischemic blood-perfused hearts had basal flow unchanged from before ischemia. Bradykinin and nitroglycerin induced similar increases in coronary flow for each group before and after each ischemia interval. However, the magnitude of this increase was greater in blood-perfused hearts (p < 0.01) and was not attenuated by the ischemic times encompassed in this protocol. In contrast, endothelium-dependent and -independent coronary flow reserve was abolished after 20 minutes of ischemia or longer in Krebs-perfused hearts. These data suggest that the unphysiologic resting flow patterns of crystalloid-perfused isolated hearts obfuscate interpretation of the interaction between coronary flow reserve and ischemic injury.

Recency, duration, and progestin content of oral contraceptives in relation to the incidence of endometrial cancer (Washington, USA)

Women who have used combined oral contraceptives (COC) have a reduced risk of endometrial cancer relative to that of women who have never used oral contraceptives, but it is unclear whether the size of the reduction is influenced by the progestin content of the preparation. We analyzed data from two population-based case-control studies of endometrial cancer to investigate this question. Among women aged 40 to 59 years who were residents of King or Pierce Counties, Washington (United States), incident cases who were diagnosed during 1975-77 or 1985-87 were identified. Personal interviews were conducted with 316 such women and their responses compared with those of 501 controls who were selected by household surveys or random-digit dialing. A reduced risk of endometrial cancer associated with COC use was present only among users of five or more years' duration, and even then only in women who were not long-term users of unopposed postmenopausal estrogens. Among these women, the relative risk (RR) of endometrial cancer did not differ according to the progestin potency of the COC used: it was equally low for women who had used a COC with low progestin content (RR = 0.2, 95 percent confidence interval [CI] = 0.1-0.8) as for women who had used a COC with high progestin content (RR = 0.3, CI = 0.1-0.9). Our results argue that, if the reduced risk of endometrial cancer in long-term users of COCs is due to the progestins contained in these preparations, that amount of progestin in most COCs exceeds the threshold amount needed to produce this beneficial effect.