Cellular functions of diabetic cardiomyocytes: contractility, rapid-cooling contracture, and ryanodine binding

To study the mechanisms of cardiac dysfunction in experimental diabetes, adult rat cardiomyocyte shortening (measured with a video edge-detector system), the sarcoplasmic reticulum (SR) Ca2+ content [assessed by rapid-cooling contracture (RCC) and caffeine contracture (CC)] was examined. Ryanodine binding to the SR Ca(2+)-release channel of myocardium homogenate was also studied. Myocytes from diabetic rats showed depressed shortening (44% decrease compared with controls), reduced maximum rates of shortening and relengthening (58 and 56% decrease, respectively), and prolonged time to peak shortening (47% increase). RCCs and CCs from diabetic cells were 68 and 75% of the control values, respectively. Most of these cardiomyocyte abnormalities were corrected by daily insulin treatment in the diabetic rats. Ryanodine binding parameters indicated that the number of high-affinity binding sites was decreased in diabetic hearts. These data suggest that changes in contractile parameters as measured in diabetic myocytes are in good agreement with data obtained from intact heart or cardiac tissue preparations. Decreased SR Ca2+ content and reduced ryanodine binding sites indicate that the SR functions of storage and release of Ca2+ were depressed. This consequently may cause depressed contraction in diabetic hearts.

Pharmacokinetics of SDZ 64-412, a novel antiasthmatic agent, following intravenous, oral, and inhalation dosing in the rat

The pharmacokinetics of SDZ 64-412, an antiasthmatic agent, were investigated following intravenous, oral, and inhalation dosing in rats. 14C-SDZ 64-412 was administered intravenously (2.75 mg kg-1) and orally (5.5 mg kg-1, 110 mg kg-1), whereas non-radiolabeled drug (5.04 mg kg-1) was administered using nose-only inhalation chambers. Radioactivity and parent drug concentrations in blood, lung, and excreta were determined at designated times post-dose. SDZ 64-412 was rapidly and extensively (approximately 80%) absorbed following both oral doses, although absorption appeared to be prolonged with increasing dose. The absorbed drug was shown to undergo extensive and saturable first-pass metabolism. The bioavailability of the parent drug, calculated by dose-normalized AUC and deconvolution methods, was only 10-15% from the low dose, but increased to approximately 40% following the high dose. Following inhalation dosing, SDZ 64-412 concentrations in blood and lungs increased rapidly, and did not decline immediately after termination of dosing. The inhalation dose yielded a bioavailability of approximately 40%, and AUC of the drug in lungs was approximately 25 times greater than in blood. In general, SDZ 64-412 was extensively distributed and rapidly eliminated from the systemic circulation. Biliary excretion was the predominant route of radioactivity excretion. The present findings suggest that inhalation administration provides a viable means of delivery of SDZ 64-412.

In vitro characterization of nonpeptide irreversible inhibitors of HIV proteases

The irreversible inhibition of human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) proteases by 1,2-epoxy-3-(p-nitrophenoxy)propane (EPNP) and eight haloperidol derivatives has been studied. EPNP specifically inhibits HIV-1 and HIV-2 proteases with a stoichiometry of one EPNP molecule/dimeric enzyme. The site of modification of HIV-2 protease by EPNP has been unambiguously identified as Asp-25 using high performance tandem mass spectrometry. The haloperidol derivatives assayed consist of epoxides, ynones, and alpha,beta-unsaturated ketones. The Kinact values for these haloperidol derivatives range from 10.7 to 521 microM for HIV-1 protease and from 8.6 to 283 microM for the HIV-2 enzyme, being in some cases approximately 1000-fold more potent irreverisble inhibitors of HIV proteases than EPNP. This potency results from the haloperidol character of the compounds and the chemical reactivity of the groups capable of forming a covalent bond with the enzyme. Covalent modification of HIV-2 protease by a radiolabeled epoxide derivative of haloperidol, UCSF 84, is prevented by EPNP and the peptidomimetic transition state analog U-85548. In similar experiments, incorporation of UCSF 84 into HIV-1 protease is partially prevented by these active-site inhibitors. In contrast, a mutant HIV-1 protease, HIV-1 PR C95M, in which Cys-95 has been replaced by Met, is labeled 50% less than HIV-1 protease and is fully protected by EPNP and U-85548. These results indicate the presence of 2 reactive residues in HIV-1 protease: Cys-95 and another located in the active site of the enzyme. The alpha,beta-unsaturated ketone derivative of haloperidol, UCSF 191, which is stable over a broad pH range, was used to study the pH profile of inactivation of HIV-1 and HIV-2 proteases. Comparison of the profiles of inactivation of wild-type HIV-1 protease, HIV-1 PR C95M, and HIV-1 PR C67L as well as HIV-2 protease (which has no cysteine residues) reveals the contribution of Cys-95 to the reactivity of these irreversible inhibitors. The inhibitors UCSF 70, UCSF 84, UCSF 115, UCSF 142, and UCSF 191 reduce p55gag polyprotein processing when assayed in a mammalian cell line that produces HIV-1 viral particles lacking the envelope.

Impact of acid and pepsin on human esophageal prostaglandins

OBJECTIVES

Although the prostaglandin-mediated mucosal protection within the gastric compartment has been well established, its potential role in the maintenance of integrity of the esophageal mucosa in humans has not been explored due to the lack of appropriate methodology.

METHODS

We have recently developed an esophageal perfusion catheter, equipped with two balloons, compartmentalizing a 7.5-cm segment of the esophageal lumen. Using this catheter, we studied the impact of the luminal perfusion with saline, HCl (0.01 M, pH 2.1), and HCl/pepsin solutions (0.5 mg/ml) on esophageal luminal release of PGE2 in 21 asymptomatic, presumably healthy volunteers (12 M, 9F; mean age 40 yr). The content of PGE2 in its methyl oximated form was measured by RIA (Amersham, IL), using a novel iodinated label. Results are expressed as mean +/- SEM. Student's t test was used for statistical analysis.

RESULTS

Perfusion of the esophageal lumen resulted in continuous release of PGE2 into the perfusate at the rate of 1880 +/- 393 pg/min during the first 8-min perfusion period. During continuation of perfusion with saline, the luminal release of PGE2 was maintained at the rate of 1820 +/- 640 pg/min during the second 8-min perfusion period. This rate declined (although in nonsignificant fashion; p < 0.2) during the third perfusion period, reaching a plateau of 1220 +/- 473 pg/min and maintained during the last (period IV) perfusion period with saline. Introduction of acid during the perfusion period II in the second group of investigated subjects resulted in a rapid and statistically significant decline of the luminal release of PGE2 to the value of 1020 +/- 167 ng/min (p < 0.01). Continuation of esophageal perfusion with acid during the next 8-min perfusion period further diminished the luminal release of PGE2 to the value of 520 +/- 73; p < 0.001. The significant decline in the rate of luminal PGE2 release was still maintained despite the replacement of acid with saline during the ending 8-min perfusion (period IV; 560 +/- 80 ng/min; p < 0.001). Esophageal perfusion with HCl/pepsin solution, in group III subjects, potentiated luminal release of PGE2, reaching the value of 1553 +/- 340 pg/min, which is 3 times higher than the value of PGE2 observed during corresponding perfusion with HCl (period III; p < 0.03). This significant impact of HCl/pepsin solution was still maintained despite the substitution of HCl/pepsin with NaCl during the last perfusion period, and was still significantly higher (1260 +/- 220 pg/min; p < 0.02) than the corresponding value during the ending perfusion with NaCl after HCl (group II). This study for the first time demonstrates that luminal release of PGE2 in humans remains under a significant impact of luminal chemical factors such as acid and pepsin.

CONCLUSION

The modulatory effect of acid and pepsin on esophageal mucosal prostaglandin release may play a role in the development of reflux-related mucosal pathology.

In vivo microleakage of luting cements for cast crowns

Standardized tooth preparations were completed on previously intact human molars in vivo, and castings were made with a precious metal ceramic alloy by conventional techniques. The castings were randomly assigned to the following luting agents: zinc phosphate, composite resin-glass ionomer hybrid, and a composite resin-glass ionomer hybrid with a dentinal bonding agent and were cemented in a standardized manner to periodontally compromised molars. After 6 months the teeth were carefully extracted, stained, embedded, and sectioned, and the in vivo microleakage was measured. ANOVA disclosed significant differences between groups, and a multiple comparisons test revealed that the zinc phosphate group leaked significantly more than other cement groups.

Determination of amide-type local anaesthetics by direct injection of plasma in a column-switching high-performance liquid chromatographic system using a pre-column with a semipermeable surface

A high-performance liquid chromatographic method using column switching was applied to the direct determination of two local anaesthetics, ropivacaine and bupivacaine, in human plasma. The method is intended to be used in a combined LC-GC system; here only the LC-part is described. After addition of internal standard, the samples were filtered and directly injected into a semipermeable surface (SPS) pre-column where the analytes were strongly retained and separated from many endogenous compounds by a short washing step. The retained analytes were transferred by a buffered methanol phase from the pre-column into a carbonaceous HPLC column and they were detected by UV detection at 254 nm. The SPS pre-column could withstand numerous (> 200) direct injections of plasma samples (10 microliters). The method has a detection limit of 8.2 ng and requires a total assay time of 15 min per plasma sample. Quantitative recoveries were obtained over the range 3.3-114 micrograms/ml with inter-day precisions of 1.6-5.2% (C.V.).

Impairment of salivary epidermal growth factor secretory response to esophageal mechanical and chemical stimulation in patients with reflux esophagitis

OBJECTIVES

It has been demonstrated recently that salivary epidermal growth factor (sEGF) output in healthy individuals is strongly and significantly influenced by esophageal intraluminal mechanical and chemical stimuli. Therefore, we have studied the impact of intraesophageal mechanical and chemical stressors on the rate of secretion of sEGF in 14 patients with reflux esophagitis (RE), and compared these results with corresponding parameters measured in 14 sex- and age-matched controls.

METHODS

EGF was assessed in saliva collected during basal conditions, chewing of parafilm, placement of esophageal tubing, inflation of intraesophageal balloons, and perfusion with NaCl, HCl, and HCl/pepsin solutions. The concentration of sEGF was measured with an RIA kit from Amersham (Arlington Heights, IL).

RESULTS

The concentrations of sEGF were (mean +/- SEM) 2.50 +/- 0.32 ng/ml and 2.00 +/- 0.37 ng/ml in basal saliva and during stimulation by chewing the parafilm, respectively. Basal sEGF value appeared to be significantly higher than in controls (2.50 +/- 0.32 vs. 1.90 +/- 0.22 ng/ml, p < 0.05, in one-tailed t test). Placement of intraesophageal tubing resulted in a significant decline of sEGF concentration, compared with parafilm-stimulated conditions (1.25 +/- 0.12 vs. 2.00 +/- 0.37 ng/ml, p < 0.0001) and corresponding tubing-stimulated sEGF value in controls (1.25 +/- 0.12 vs. 1.52 +/- 0.16 ng/ml, p < 0.05). sEGF concentrations after inflation of intraesophageal balloons and subsequent perfusion with initial saline, HCl, HCl/pepsin, and ending saline were also highly significantly lower (1.05 +/- 0.18 ng/ml, p < 0.001; 1.10 +/- 0.20 ng/ml, p < 0.001; 1.10 +/- 0.18 ng/ml, p < 0.001; 1.10 +/- 0.19 ng/ml, p < 0.001; and 1.05 +/- 0.18 ng/ml, p < 0.001, respectively) than sEGF concentration recorded during stimulation with parafilm. Concentrations of sEGF during esophageal perfusion with HCl, HCl/pepsin, and ending saline were also significantly lower than corresponding values in controls (1.10 +/- 0.18 vs. 1.49 +/- 0.11 ng/ml, p < 0.05; 1.10 +/- 0.19 vs. 1.59 +/- 0.11 ng/ml, p < 0.05; and 1.05 +/- 0.18 vs. 1.65 +/- 0.13 ng/ml, p < 0.01, respectively). The rate of sEGF output, which was 1.30 +/- 0.24 ng/min during basal conditions, increased significantly during stimulation with parafilm (2.30 +/- 0.38 ng/min, p < 0.05). Both basal and parafilm-stimulated sEGF outputs were somewhat higher, although nonsignificantly, than corresponding values recorded in healthy individuals. Mechanical and chemical stimulation (initial NaCl, HCl, and ending NaCl) failed to evoke a significant increase in sEGF output over the value observed during parafilm stimulation in patients with RE, although such a significant increase was clearly demonstrated in healthy individuals. Therefore, sEGF output in patients with RE remained significantly lower than corresponding values recorded in controls during an entire mechanical stimulation (2.65 +/- 0.35 vs. 4.60 +/- 0.85 ng/min, p < 0.001, after placement of intraesophageal tubing and 2.80 +/- 0.54 vs. 5.15 +/- 0.70 ng/min, p < 0.001, after inflation of balloons). sEGF output in patients with RE remained also significantly lower than adequate control values during chemical stimulation (3.65 +/- 0.64 vs. 5.20 +/- 0.60 ng/min, p < 0.05, during perfusion with initial saline; 3.70 +/- 0.70 vs. 5.20 +/- 0.60 ng/min, p < 0.05, during perfusion with HCl; 3.70 +/- 0.52 vs. 5.55 +/- 0.72 ng/min, p < 0.01, during perfusion with HCl/pepsin, and 3.30 +/- 0.56 vs. 5.80 +/- 0.86 ng/min, p < 0.001, during ending saline).

CONCLUSION

Impairment in sEGF secretion during mechanical and chemical intraesophageal stimulation, mimicking the natural scenario occurring during gastroesophageal reflux, may facilitate the development of esophageal mucosal pathology and delay the healing of already developed mucosal injury.

[Serological investigation on intrafamilial transmission of HCV infection]

To clarify the intrafamilial transmission of HCV infection, the antibody to HCV was assayed in 124 serum samples from the family members of 60 HCV-Ab (+) index cases (group C), and compared with that from 83 family members of 40 HCV-Ab (-) index patients with hepatitis B (group B), Nine of 124, including 2 parents, 6 spouse and 1 granddaughter, were positive for anti-HCV. The prevalence of anti-HCV was 7.3% (9/124) in total, and 1.85% (2/108) in the subjects who had no history of blood donation. None of 83 was positive for anti-HCV in group B. On the other hand, the prevalence of HBV infection was 25.33% in the group of HCV infection only, and 40.91% in the group with HBV/HCV double-infection or HBV infection. It indicates that the risk of HBV intrafamilial transmission is higher than that of HCV, and the risk of transmission of HCV from mother to infant may be lower than that of sexual transmission.

[Atrial specific granules are an intracellular calcium store]

In order to elucidate whether the secretion of atrial natriuretic peptide (ANP) is correlated to the release of calcium (Ca) from the atrial specific granules (ASG), it is necessary to explore whether the ASG contain highly concentrated Ca and how the high Ca is maintained in the ASG. The present study was designed to determine Ca in the ASG with the quantitative electron microscope X-ray microanalysis and Ca(2+)-ATPase with electron microscopic (EM) cytochemical technique. The ultrathin cryosections of rapid frozen fresh rat auricles were used for measuring Ca concentration with a JEM-1200EX electron microscope equipped with a Link AN 10,000 energy dispersive X-ray spectroscope. The measurement showed that the Ca concentration in the ASG was quite high, being 81 +/- 15 mmol/kg (n = 10), comparable with that found in the sarcoplasmic reticulum. With the Ca(2+)-ATPase EM cytochemical technique, the reaction products proved to be deposited on the membrane of the ASG. It was postulated that the Ca(2+)-ATPase on the membrane of ASG pumped Ca2+ out of the cytosol into the ASG and thus maintained a high Ca concentration inside the ASG. Therefore, the ASG might be considered to be a Ca store in atrial cardiocytes.

Peptide-antibody conjugates for tumour therapy: a MHC-class-II-restricted tetanus toxin peptide coupled to an anti-Ig light chain antibody can induce cytotoxic lysis of a human B-cell lymphoma by specific CD4 T cells

Anti-idiotype antibody therapy of B-cell lymphomas, despite numerous promising experimental and clinical studies, has so far met with limited success. Tailor-made monoclonal anti-idiotype antibodies have been injected into a large series of lymphoma patients, with a few impressive complete tumour remissions but a large majority of negative responses. The results presented here suggest that, by coupling to antilymphoma idiotype antibodies a few molecules of the tetanus toxin universal epitope peptide P2 (830-843), one could markedly increase the efficiency of this therapy. We show that after 2-hr incubation with conjugates consisting of the tetanus toxin peptide P2 coupled by an S-S bridge to monoclonal antibodies directed to the lambda light chain of human immunoglobulin, human B-lymphoma cells can be specifically lysed by a CD4 T-lymphocyte clone specific for the P2 peptide. Antibody without peptide did not induce B-cell killing by the CD4 T-lymphocyte clone. The free cysteine-peptide was also able to induce lysis of the B-lymphoma target by the T-lymphocyte clone, but at a molar concentration 500 to 1000 times higher than that of the coupled peptide. Proliferation assays confirmed that the antibody-peptide conjugate was antigenically active at a much lower concentration than the free peptide. They also showed that antibody-peptide conjugates required an intact processing function of the B cell for peptide presentation, which could be selectively inhibited by leupeptin and chloroquine.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemically-modified tetracycline normalizes collagen metabolism in diabetic rats: a dose-response study

An earlier study indicated that a chemically-modified non-antimicrobial tetracycline (4-de-dimethylaminotetracycline; CMT-1) can inhibit excess collagenase activity in the connective tissues of diabetic rats, however, the optimum oral dose and resulting serum concentration were not determined. In the current study, adult male Sprague-Dawley rats (body weight approx. 350 g) were made diabetic by streptozotocin injection and administered by oral gavage either 0, 1, 2, 5, or 10 mg CMT-1 per day. After 3 weeks of drug therapy, the rats were killed and gingiva, skin, and serum collected. The tissues were 1) extracted, partially purified and analyzed for collagenase activity using [3H-methyl] collagen as substrate and SDS-PAGE/fluorography; 2) extracted in neutral salt and dilute acid solutions (4 degrees C) to assess collagen solubility; and 3) analyzed for hydroxyproline to determine tissue (skin) collagen mass. Serum was analyzed for glucose and CMT-1 concentration, the latter by HPLC. Inducing diabetes dramatically increased both gingival and skin collagenase activity and reduced skin collagen mass by 69.8%. Increasing the oral dose of CMT-1 progressively increased the serum concentration of the drug from 0.6-6.5 micrograms/ml and progressively decreased the excessive collagenase activity in gingiva and skin (p < 0.01 vs untreated diabetics). Although skin collagen mass tended to be increased at all oral doses of CMT-1, only the 5 mg dose effect was statistically significant (p < 0.01). The diabetes-induced reduction in collagen solubility, a classic abnormality (reflecting excessive collagen crosslinking) of this disease, was also normalized by CMT-1 therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Atomic-nitrogen production in a radio-frequency plasma source

The first high-resolution study, to our knowledge, of the optical emission from an Oxford Applied Research MPD21 nitrogen-plasma source is reported. The spectroscopic results clearly show that the MPD21 nitrogen-plasma source generates an appreciable flux of nitrogen atoms. This suggests that nitrogen atoms are the plasma species responsible for the successful p-type doping of ZnSe:N and related alloys.

Effect of esophageal intraluminal mechanical and chemical stressors on salivary epidermal growth factor in humans

Although various animal and clinical studies have demonstrated the significant effect of salivary epidermal growth factor (sEGF) on esophageal morphology and function, its secretory patterns still remain inadequately explored. Therefore, we have studied the impact of esophageal mechanical and chemical stimuli on sEGF in humans. sEGF was measured in saliva collected during basal conditions, chewing of parafilm, placement of esophageal tubing, inflation of intraesophageal balloons, and perfusion with NaCl, HCl, and HCl/pepsin solutions. The concentration of sEGF was measured with a radioimmunoassay kit from Amersham (Arlington Heights, IL). The concentration of sEGF in basal saliva was (mean +/- SEM) 2.08 +/- 0.22 ng/ml. Chewing the parafilm resulted in a significant decline of sEGF concentration to the value of 1.39 +/- 0.16 ng/ml (p < 0.0005). Similar decline in sEGF concentration also prevailed after placement of intraesophageal tubing (p < 0.03), and inflation of intraesophageal balloons (p < 0.01). This decline intensified significantly when prolonged esophageal perfusion with saline was implemented (p < 0.03 vs. tubing). Substitution of NaCl with HCl in the second and third perfusion periods prevented the decline in sEGF concentration, whereas HCl accompanied by pepsin enhanced sEGF concentration. The rate of sEGF output was 0.90 +/- 0.13 ng/min during basal conditions and increased significantly during parafilm chewing (1.53 +/- 0.25 ng/min; p < 0.05). However, sEGF secretion during both placement of esophageal tubing and inflation of balloons increased 4.1- and 4.9-fold, respectively (p < 0.002 and < 0.00005), over the basal value, and 2.4- and 2.9-fold, respectively, over the parafilm stimulated secretion. Subsequently, we observed a further significant decline of sEGF output (p < 0.05) which was sustained during perfusion of the esophagus with saline. Interestingly, esophageal perfusion with HCl prevented the decline of sEGF secretion observed during perfusion with saline. sEGF output during esophageal perfusion with HCl/pepsin exhibited a strong increase, reaching the value of 5.86 +/- 0.70 ng/ml. This value corresponds to a 58% increase over the secretory rate observed during mechanical stimulation by placement of esophageal tubing (3.71 +/- 0.47; p < 0.05). HCl/pepsin-induced potentiation of sEGF secretion was also highly significantly increased over both the value recorded during basal (p < 0.0005) and parafilm-stimulated (p < 0.002) conditions. Subsequent substitution of HCl/pepsin solution with a final saline perfusate still maintained enhanced sEGF output, compared with both basal (p < 0.02) and parafilm-stimulated conditions (p < 0.02).(ABSTRACT TRUNCATED AT 400 WORDS)

Circadian rhythm in aspirin (ASA)-induced injury to the stomach of the fasted rat

Circadian rhythms exist in several gastric parameters affecting ulcerogenesis. This study investigated possible circadian rhythmicity in observed aspirin (ASA)-induced gastric lesions in the rat. In five experiments 183 rats were studied at 14 time points over a 24-hr period. Rats were adapted for three weeks on a 12-hr light schedule, fasted 18 hr, then given oral acidified ASA. One hour later, the rats were sacrificed, the stomachs were removed, stretched flat, photographed, scanned, and measured for percent area of gross lesions in the gastric corpus by computer planimetry. Cosinor rhythmometric analysis showed a significant (P < 0.001) rhythm. Mean of rhythm (MESOR) was 5.60 +/- 0.25% of total corpus. Amplitude was 25.89 +/- 6.07% of MESOR. Peak time (acrophase) was 1909 +/- 0101 hr after lights on. Thus, gastric vulnerability to ASA injury exhibited circadian rhythmicity with peak injury during the dark period in this species.

Evidence on secretion of epidermal growth factor by the esophageal mucosa in humans

Luminal release of esophageal epidermal growth factor (EGF) into the perfusing solutions (saline, HCl, and HCl/pepsin), aspirated with the newly developed esophageal perfusion catheter, was measured in 20 healthy volunteers (12 male, 8 female; mean age 40 yr; range 30-56 yr). A potential salivary contamination was excluded by a complete seal (with two balloons) of perfused esophageal segment and by a simultaneous, carefully monitored, collection of saliva. The concentration of EGF in each of 16 fully recovered 2-min perfusion samples was measured by RIA kit (Amersham, IL). The concentration of EGF in recovered NaCl perfusate varied between (mean +/- SEM) 1.78 +/- 0.19 and 2.14 +/- 0.14 ng/ml, whereas output varied between 9.25 +/- 0.98 and 11.14 +/- 0.82 ng/min. During perfusion with HCl, both the concentration of EGF within the esophageal perfusate and its secretion declined significantly to a value of 0.68 +/- 0.17 ng/ml (p < 0.0001) and 3.56 +/- 0.90 ng/min (p < 0.0001), respectively. Introduction of pepsin into an acidic perfusion solution (0.5 mg/ml of HCl) resulted in a significant increase in EGF concentration (1.99 +/- 0.36 ng/ml; p < 0.001) and output (10.24 +/- 1.84; p < 0.01), compared with EGF values recorded during perfusion with HCl. EGF output, calculated from a sealed 7.5-cm segment of the esophagus, was 10.39 +/- 0.89 ng/min, and was maintained at a steady state throughout an entire saline perfusion procedure. We present evidence that human esophageal mucosa has an enormous EGF secretory potential. The rapid esophageal EGF secretory response to intraluminal challenge with aggressive factors implies its role in the maintenance of the mucosal integrity.

Physical properties of fixed prosthodontic, resin composite luting agents

This study determined and compared physical properties of six fixed prosthodontic resin composite luting agents and one control. Inorganic filler content, compressive strength, diametral tensile strength, film thickness, and Knoop hardness were determined. The amounts of filler and the physical properties varied widely among materials. One material, which contained a minimal amount of filler, underwent so much plastic deformation that its strengths could not be measured. All other materials demonstrated high strengths. The materials with the least filler demonstrated the least resistance to indentation. The material with the lowest film thickness had not set at the time of measurement, 10 minutes after mixing. Most materials had unacceptable film thicknesses. Only one material demonstrated acceptable physical properties throughout the study.

Elevated endometrial natural killer cell activity during early porcine pregnancy is conceptus-mediated

This study investigated an extended time course of endometrial NK cell activity during gestation and the mechanisms underlying changes in uterine NK cell activity in pigs. Endometrial tissues were collected from cyclic, pseudopregnant and pregnant nulliparous pigs on various days post-estrus, and from pigs 10 days after insemination with seminal plasma or killed spermatozoa. NK effector cells were isolated from each endometrial sample, size fractionated and tested for cytolytic activity against NK target cells (K562) using chromium release assays and immunocytochemically for the frequency of perforin-positive cells. Various cell fractions showed different levels of NK activity and had different proportions of cells expressing perforin. Morphologically, cells in the fraction with maximal NK activity almost all showed typical lymphocyte size and shape. Substantially elevated NK cell activity was recorded in pregnant pigs on days 10 and 20 of gestation. By day 30, the cytolytic activity declined dramatically to an almost undetectable level. Very little activity was found in uterine cells isolated from cyclic, pseudopregnant, and seminal plasma or killed spermatozoa inseminated animals, and no differences were detected either between follicular and luteal phases of the estrous cycle or between different days of pseudopregnancy. These results indicate that elevated NK cell activity during early porcine pregnancy cannot be attributed to contributions from either the maternal systemic endocrine status or from components of boar semen. The changes in NK cell activity observed in porcine endometrial tissues during early pregnancy must therefore be associated with the actual presence of conceptuses.

Compressive and diametral tensile strengths of current adhesive luting agents

Strength parameters greatly influence the selection of luting agents. This study compared the compressive and diametral tensile strengths of six classes of new adhesive luting agents (ALAs) with zinc phosphate as the controls. The 11 materials tested were prepared according to the manufacturers' instructions for use as luting agents. Mean compressive and diametral strengths and standard errors were calculated for each luting agent (n = 10). Analysis of variance was computed (p < 0.0011) and multiple comparisons tests were performed. Compressive strengths varied from 41.5 MPa for a hydroxyapatite ALA to 178.5 MPa for a composite resin ALA. Diametral tensile strengths ranged from 8.1 MPa for a hydroxyapatite ALA to 45.1 MPa for a composite resin ALA. Conventional powder-liquid glass ionomer ALAs, an encapsulated glass ionomer ALA, a composite resin-glass ionomer hybrid ALA, and the composite resin ALAs demonstrated significantly greater compressive and diametral strengths than the zinc phosphate cements.