[Initial experiences with multi-slice detector spiral CT in diagnosis of arteriosclerosis of coronary vessels]

PURPOSE

Multi-row-detector-spiral-CT (MSCT) allows for 250 ms effective exposure time. The purpose of this study was to demonstrate the possibilities and limitations of this CT technology for non enhanced and contrast enhanced investigation of the coronary arteries.

METHODS

Investigation of the coronary arteries without contrast medium for quantification of coronary calcifications was performed in an obese patient (140 kg) with MSCT and electron beam CT (EBCT). In 56 patients contrast enhanced CT angiography of the coronary arteries was performed to determine image quality depending on the heart rate.

RESULTS

In the obese patient superior image quality could be achieved with MSCT allowing for reliable quantification of coronary calcifications. With MSCT angiography of the coronary arteries good image quality was achieved in patients with a heart rate of 59 +/- 8 beats per minute.

CONCLUSION

Even if there are limitations in patients with higher heart rates with an effective exposure time of 250 ms MSCT has clear advantage of image quality in the assessment of non enhanced and contrast enhanced coronary arteries.

The alteration of mitochondria is an early event of arsenic trioxide induced apoptosis in esophageal carcinoma cells

It is accepted that inorganic arsenic trioxide is an inducer of apoptosis for many types of cancer. Our previous studies have demonstrated that arsenic trioxide induces apoptosis of esophageal carcinoma cells. Administration of arsenic trioxide results in the inhibition of growth and survival of tumor cells. Esophageal carcinoma cells treated with arsenic trioxide for 3 days demonstrated a typical morphological appearance of apoptosis. To further examine molecular mechanism of arsenic trioxide induced apoptosis of esophageal carcinoma cells, we have investigated the early changes of the apoptotic cell induced by arsenic trioxide. Our results indicated that arsenic trioxide induced apoptosis of esophageal carcinoma cells occurs as early as 2 h after treatment. Annexin-v staining has further proved that the phosphatidylserine is exposed at 2 h. The early morphological change of arsenic trioxide treated cells was in the mitochondria. Arsenic trioxide treated cells displayed aggregated mitochondria. It induces accumulation of high electron-density amorphous substances, swollen and disruption of mitochondria in oesophageal carcinoma cells after 2 h treatment. The alteration of mitochondria induced by arsenic trioxide seems to occur before the condensation of chromatin. Thus, our data demonstrated that the primary target of arsenic trioxide induced apoptosis of esophageal carcinoma cells may be the mitochondria. It is possible that arsenic trioxide is a mitochondriotoxic agent.

[Catalysis kinetics-fluorescence analysis studies on Fe(III)-H2O2-furfural-7-amino-8-hydroxy-5-sulfo-quinoline system]

This paper reports that hydrogen peroxide oxidized furfural-7-amino-8-hydroxy-5-sulfo-quinoline(F7A8Q5S) under the catalysis of Fe(III). Results indicated that the fluorescence of F7A8Q5S was weak, but that of the oxidation product was strong. The peak was at lambda ex/lambda em = 330/405 (nm). The calibration curve of Fe(III) is linear between 0.0-40.0 micrograms.L-1, and the determination limit is 4.68 ng.L-1. So a new catalysis fluorescence analysis method was set up for the determination of trace amounts of Fe(III), based on its catalytic effect on F7A8Q5S oxidized by H2O2. This proposed method has been successful applied to the determination of Fe(III) in alloy samples.

[The diagnosis of stages T1 and T2 in laryngeal carcinoma with multislice spiral CT]

The purpose of the study was to preoperatively investigate small laryngeal carcinomas using multi-slice spiral CT (MSCT) and subsequent multiplanar reconstructions (MPR) and to compare the results to the detailed spread found at surgery and histology. Nine patients with small (T1, T2) laryngeal cancer were investigated on a MSCT scanner (Siemens plus 4 Volume Zoom, Siemens). A 4 x 1 mm collimation, 120 kV, 200 mAs and a 0.5 seconds rotation time were used, allowing a coverage of the entire larynx in approximately 10 seconds within a single breathhold. Multiplanar reconstruction's (MPR) in sagittal and coronal plane were reconstructed in all patients and rated in consensus reading. In 8 of nine patients, the glottic spread was detected by MSCT, in one cause of a supraglottic tumor a glottic invasion was excluded. The infiltration of the anterior commissure, the infiltration into the subglottic space and the extension into the hypopharynx was correctly assessed in all patients. MSCT was not able to predict infiltration of the arythnoids in two patients. The use of multi-slice spiral CT for the preoperative assessment of small laryngeal tumors shows great promise. The detection or exclusion of subtle spread of these tumors into the supra- or subglottic space and along the glottic level was possible with high accuracy. As the examination time is short, artifacts are rare and multiplanar reconstructions gain in clinical importance.

[Imaging of the thorax with multislice spiral CT]

With multislice spiral computed tomography (MSCT), existing indications for performing CT of the chest are strengthened and new applications are emerging. The high speed of MSCT improves efficiency, image quality and patient comfort of "routine" imaging of the chest. The ability to cover large volumes with thin slices improves the evaluation of mediastinal lymph nodes and pulmonary nodules and allows for high-quality secondary reconstruction. If a comprehensive diagnosis of the mediastinal structures and the pulmonary parenchyma is desired, MSCT for the first time allows reconstruction of contiguous and high-resolution (HRCT) sections from the same set of thin-collimation raw data. This way, contiguous chest images of superior and HRCT sections of equal image quality compared to conventional CT scanning can be obtained. Vascular protocols greatly benefit from the high speed of MSCT: For imaging the thoracic aorta or pulmonary emboli (PE), the amount of contrast material can be substantially reduced. Owing to thin collimation, the detection rate of small peripheral emboli can be significantly increased. If indicated, the entire subphrenic venous system can be evaluated during the same session, without additional contrast material.

[Computed tomography of the abdomen with multidetector-array CT]

BACKGROUND

The advent of multidetector CT (MDCT) constitutes a quantum leap creating a wealth of new opportunities in medical imaging. However, while the basic principles of spiral CT still apply, we are now challenged to rethink our strategies in planning a CT study to take full advantage of the increased capabilities of MDCT.

MATERIALS AND METHODS

We report here our preliminary experiences with MDCT for abdominal CT imaging within a 5-month period. During this time, suitable protocols for investigation of the abdomen using MDCT were developed. The capabilities of MDCT allow for tailoring dedicated CT protocols for routine applications as well as for biphasic liver studies and CT angiography of the aorta and abdominal vessels.

RESULTS

The speed of MDCT can either be used to reduce the time needed to cover a given volume, or to use narrower beam collimations to increase the resolution of detail along the z-axis and reduce volume averaging. Higher scan speed allows reduction of the amount of contrast material in vascular applications and suppression of motion artifacts. Higher spatial resolution with thinner collimations reduces volume averaging and improves the detection of small hepatic and pancreatic lesions. Detailed analysis of vascular structures and high-quality three-dimensional reformations become feasible. New problems arise from the large amount of data generated by MDCT.

CONCLUSIONS

MDCT offers a wealth of new opportunities that help us to come to a fast and accurate diagnosis in suspected abdominal disease. Traditional indications for performing CT are reemphasized and new clinical applications can be exploited.

Preoperative cooling and warming of the donor site increase survival of skin flaps by the mechanism of ischaemic preconditioning: an experimental study in rats

Recent studies show that survival of skin flaps can be increased by ischaemic preconditioning with repeated cycles of ischaemia and reperfusion before prolonged ischaemia or raising of the flap. In this study three cycles of cooling and warming of rat dorsal skin were used to regulate skin blood flow and to induce three cycles of ischaemia and reperfusion. In 10 Sprague-Dawley rats three cycles of cooling (-18 degrees C ice pack) and warming (45 degrees C running water) were used to regulate skin blood flow before the flaps were raised. Caudally-based skin flaps 11 x 2 cm were then raised to the left of the dorsal midline and sutured back. In the control group (n = 9) the flap was raised and sutured back without any treatment. Viability was assessed after seven days and the survival area calculated with planimetry. Viability increased from a mean (SD) of 61 (6)% in the control group to 77 (7)% in the experimental group (p < 0.0001). This study shows that preoperative cooling and warming of the donor site can be used to increase survival of skin flaps. The probable explanation is ischaemic preconditioning although the biochemical mechanism is unclear.

Cyclosporine attenuates pressure-overload hypertrophy in mice while enhancing susceptibility to decompensation and heart failure

Left ventricular hypertrophy (LVH) is a compensatory mechanism to cope with pressure overload. Recently, a calcineurin pathway mediating LVH and its prevention by cyclosporine was reported. We examined whether calcineurin mediates LVH due to pressure overload in mice. Pressure overload was induced by aortic banding in 53 mice (32 treated with cyclosporine [25 mg. kg-1. d-1], 21 treated with vehicle). There were 17 sham-operated mice (9 treated with vehicle, 8 treated with cyclosporine). At 3 weeks after surgery, LV weight to body weight was greater in the nontreatment banded group (4.39+/-0. 16 mg/g) than in the cyclosporine-treated banded group (3.95+/-0.14 mg/g, P<0.05), with both groups being greater compared with the entire group of sham-operated mice (3.02+/-0.04 mg/g). The pressure gradient between the ascending and abdominal aorta was not different between the cyclosporine-treated (49.6+/-6.1 mm Hg) and nontreatment groups (48.7+/-4.6 mm Hg). Although LV systolic pressure was lower in the cyclosporine-treated banded animals, LV systolic wall stress was similar in the nontreatment banded group and in the cyclosporine-treated group. However, LV dP/dt was lower (P=0.05) in the cyclosporine-treated banded group (4774+/-656 mm Hg/s) than in the nontreatment banded group (6604+/-516 mm Hg/s). During the protocol, 23 of 32 mice in the cyclosporine-treated group and 9 of 21 mice in the nontreatment group died. All deaths occurred within 10 days after surgery. Deaths caused by heart failure were 7.2-fold higher (P<0.05) in the cyclosporine-treated group, whereas deaths due to other causes were not different between the 2 groups. In addition, LV function of mice was assessed at 48 hours after banding; LV ejection fraction measured with echocardiography was lower (P<0.05) in the cyclosporine-treated banded group (66+/-3.0%) than in the nontreatment banded group (79+/-1.5%), whereas LV systolic wall stresses were similar. Calcineurin phosphatase activity was depressed similarly in both cyclosporine-treated groups compared with both nontreatment groups. Thus, cyclosporine could attenuate, but not prevent, LVH at the expense of inhibiting an important compensatory mechanism in response to pressure overload, resulting in reduced LV wall stress and function and increased susceptibility to decompensation and heart failure.

A prospective analysis of cognitive function and anticardiolipin antibodies in systemic lupus erythematosus

OBJECTIVE

To prospectively analyze the association between changes in cognitive function and circulating anticardiolipin antibodies (aCL) over a period of 5 years in patients with systemic lupus erythematosus (SLE).

METHODS

Cognitive function was assessed in 51 unselected female SLE patients at baseline and after a mean followup of 64.5 months (range 52-71 months), using standardized tests of cognitive function, i.e., the Wechsler Adult Intelligence Scale-Revised, the Wechsler Memory Scale-Revised, and the California Verbal Learning Test. Circulating IgG, IgA, and IgM aCL and anti-double-stranded DNA (anti-dsDNA) antibody levels were determined by enzyme-linked immunosorbent assay on 4-7 occasions over the same time period. Persistent antibody reactivity was defined as levels more than 2 standard deviations (moderately positive) and more than 5 standard deviations (highly positive) above the mean for normal controls over the duration of the study. Changes in overall cognitive performance and in raw scores on individual cognitive tests were compared in patients who were persistently positive or negative for aCL.

RESULTS

At baseline 11 patients (22%) were cognitively impaired, compared with 7 (14%) at followup. Between 16% and 37% of patients had persistently elevated aCL levels of different isotypes. There was no significant difference in the prevalence of overall cognitive impairment in patients who were persistently positive for aCL compared with those who were not. In contrast, over the period of study, patients who had persistent IgG aCL positivity had a reduction in psychomotor speed, and patients who had persistent IgA aCL positivity had a reduction in conceptual reasoning and executive ability. Similar associations with anti-dsDNA antibodies were not found.

CONCLUSION

These results suggest that IgG and IgA aCL may be responsible for long-term subtle deterioration in cognitive function in patients with SLE.

Indole-3-carbinol and tamoxifen cooperate to arrest the cell cycle of MCF-7 human breast cancer cells

The current options for treating breast cancer are limited to excision surgery, general chemotherapy, radiation therapy, and, in a minority of breast cancers that rely on estrogen for their growth, antiestrogen therapy. The naturally occurring chemical indole-3-carbinol (I3C), found in vegetables of the Brassica genus, is a promising anticancer agent that we have shown previously to induce a G1 cell cycle arrest of human breast cancer cell lines, independent of estrogen receptor signaling. Combinations of I3C and the antiestrogen tamoxifen cooperate to inhibit the growth of the estrogen-dependent human MCF-7 breast cancer cell line more effectively than either agent alone. This more stringent growth arrest was demonstrated by a decrease in adherent and anchorage-independent growth, reduced DNA synthesis, and a shift into the G1 phase of the cell cycle. A combination of I3C and tamoxifen also caused a more pronounced decrease in cyclin-dependent kinase (CDK) 2-specific enzymatic activity than either compound alone but had no effect on CDK2 protein expression. Importantly, treatment with I3C and tamoxifen ablated expression of the phosphorylated retinoblastoma protein (Rb), an endogenous substrate for the G1 CDKs, whereas either agent alone only partially inhibited endogenous Rb phosphorylation. Several lines of evidence suggest that I3C works through a mechanism distinct from tamoxifen. I3C failed to compete with estrogen for estrogen receptor binding, and it specifically down-regulated the expression of CDK6. These results demonstrate that I3C and tamoxifen work through different signal transduction pathways to suppress the growth of human breast cancer cells and may, therefore, represent a potential combinatorial therapy for estrogen-responsive breast cancer.

Suicidal behavior among young people in Singapore

The purpose of this study was to investigate suicidal behavior among young people in an Asian community. Tracing records of all patients below 21 years of age who attempted suicide and were managed in a teaching hospital, the authors found the incidence increased sixfold between 1991 and 1995. Young females of Indian origin were found to be a risk group. Differences in suicidal behavior among the three main ethnic communities appear to be influenced by various sociocultural factors. The most common diagnosis was adjustment disorder stemming from interpersonal losses and conflicts. Schizophrenia, alcohol, and other substance abuse were rarely reported.

Quantitative PCR for Listeria monocytogenes with colorimetric detection

An enzyme-linked immunosorbent assay (ELISA)-mediated polymerase chain reaction (PCR) technique was developed to detect and quantify Listeria monocytogenes in food products. The bacterial DNA was extracted from artificially contaminated food and co-amplified with a synthetic internal standard (IS) using primers specific for the target gene coding for the invasive-associated protein (i.a.p.), a virulence factor of L. monocytogenes (i.a.p.) or IS in the presence of fluorescein-dUTP PCR products were hybridized with biotinylated probes designed for the i.a.p. or IS, and then the hybrids were bound to a streptavidin-coated ELISA plate. An alkaline phosphatase-conjugated antibody to fluorescein was added to the plate and in the presence of substrate, PCR products were quantitated based on an optical density reading. The detection limit for L. monocytogenes experimentally inoculated into milk samples and channel catfish fillets was 20 CFU/ml and 1-2 CFU/g, respectively. Little or no cross reaction was detected in the presence of other spoilage and pathogenic organisms such as Pseudomonas aeruginosa, Aeromonas hydrophila, Escherichia coli, and Staphylococcus aureus. The ELISA-mediated PCR technique, when compared to traditional methods, is more rapid (2 working days) for detecting and quantifying L. monocytogenes.

Effect of trilinolein on strophanthidin-induced ventricular tachycardia in guinea pigs

Trilinolein, a triacylglycerol with linoleic acid, was found to inhibit Ca2+ influx in cardiomyocytes. The purpose of this study was to evaluate the effects of trilinolein on ventricular arrhythmia induced by intravenous strophanthidin in guinea pigs anesthetized with intraperitoneal urethane. After strophanthidin- induced ventricular tachycardia, treatment with trilinolein (0.1, 1, 10 and 100 microg/kg) or control (0.04% propylene glycol) did not terminate ventricular tachycardia. However, 1, 10 and 100 microg/kg trilinolein could narrow the width of the QRS complex during ventricular tachycardia. Pretreatment with trilinolein before strophanthidin administration did not prevent the occurrence of ventricular tachycardia; the doses of strophanthidin required to induce arrhythmias (ventricular extrasystole and ventricular tachycardia) were similar in guinea pigs pretreated with trilinolein or control. However, there were fewer ventricular extrasystoles in guinea pigs pretreated with trilinolein than in the control group (ANOVA, p < 0.01). Moreover, the ventricular extrasystoles were fewer in guinea pigs pretreated with higher doses of trilinolein (100 microg/kg, 103 +/- 60; 10 microg/kg, 188 +/- 86) than lower doses of trilinolein (1 microg/kg, 366 +/- 102; 0.1 microg/kg, 436 +/- 145). This study demonstrated that trilinolein was not effective in terminating or preventing strophanthidin-induced ventricular tachycardia. However, trilinolein could improve ventricular depolarization and suppress ventricular extrasystoles.

Reversal of optic disc topography in patients with glaucomatocyclitic crisis after remission of attack

PURPOSE

The authors investigate change in optic disc topography after reduction of intraocular pressure (IOP) in patients with glaucomatocyclitic crisis.

METHODS

During the attack of elevated IOP and after remission six eyes of six consecutive patients (46.3 +/- 12.7 years of age, 6 men) underwent optic disc imaging using confocal scanning laser tomography. For each imaging of one eye, a mean topograph was acquired after triple measurements with 15 degrees of field. Topical 0.5% timolol maleate and 1% prednisolone acetate with or without oral carbonic anhydrase inhibitor were administered after optic disc topography during the attack. The average time interval between the imaging during attack and after remission was 38.5 days (range, 21-87 days).

RESULTS

Mean IOP during the attack and after remission, and percent decrease in IOP were: 43.3 +/- 10.4 mmHg, 13.5 +/- 6.5 mmHg, and 69.4 +/- 10.2%, respectively. Significant decreases in cup area, cup volume, cup/disc area ratio, and mean cup depth and significant increases in rim area and rim volume were observed after IOP reduction (Wilcoxon signed rank test). Significant associations were found between percent decrease in IOP and percent decrease in cup volume and percent increase in rim area and rim volume.

CONCLUSION

In patients experiencing glaucomatocyclitic crisis, reversal of optic disc topography were associated with reduction of IOP.

Temporal variation in parasuicide among Singaporean Chinese

OBJECTIVE

The aim of this study was to determine whether there is any temporal variation in the incidence of parasuicide within the Chinese community and, if possible, to correlate the findings with prevailing cultural and social influences.

METHOD

All patients of Chinese origin referred to a teaching hospital in Singapore between 1990 and 1994 were included in the study. The cases were divided by sex and aggregated for the month and day of the week in which the parasuicides occurred.

RESULTS

Cases of parasuicide peaked on Mondays, while the lowest incidences occurred on Saturdays. The peak months were June, August and September with a trough in December and January.

CONCLUSIONS

The findings may not be amenable to any single explanation but the peak months coincided with the month of the Hungry Ghosts, which is believed to be a particularly inauspicious period, while the trough occurred during a festive period. Similarly, looking at the student population, the peaks coincided with the examination period. It appears that social and cultural factors play a significant role in the temporal variation in parasuicide in Singapore.

Peripapillary atrophy in normal and primary open-angle glaucoma

This study was undertaken in order to determine the value of measuring peripapillary atrophy for the diagnosis and follow-up of patients with glaucoma, and to evaluate how closely peripapillary atrophy is related to structural and functional optic nerve damage in glaucoma. Magnification-corrected morphometry of photographs using a computer graphic program and automated static threshold perimetry were performed in 234 eyes of 141 patients with primary open-angle glaucoma and 139 eyes of 86 normal subjects. The groups were not significantly different in age, refractive error or disc area. Zones alpha and beta were significantly larger, total peripapillary atrophy was significantly more extensive, and zone beta occurred more often in the glaucoma group than in the normal group. The frequency of zone beta increased with advancing glaucoma stage. The areas of zones alpha and beta and total peripapillary atrophy increased significantly with decreasing rim/disc area ratio, rim area, and mean deviation, and with increasing vertical and horizontal cup-to-disc ratios and cup area. Correlation coefficients were generally higher for zone beta than for zone alpha. Peripapillary atrophy was greater in a sector in which the neuroretinal rim loss was more marked. These findings suggest that increases in the extent of peripapillary atrophy are related to the severity of glaucomatous optic nerve damage and visual field defects, and that peripapillary atrophy is useful for the diagnosis and progression of glaucomatous nerve damage.

Retinal vessel diameter in normal and primary open-angle glaucoma

The purpose of this study was to determine how closely peripapillary retinal vessel diameter is related to functional and structural optic nerve damage in primary open-angle glaucoma. Using optic disc photographs of 234 eyes of 141 patients with primary open-angle glaucoma and 139 eyes of 86 normal subjects, the diameters of the superior and inferior temporal retinal arteries and veins were measured at the optic disc border. On the basis of rim/disc area ratio, the glaucoma group was divided into four stages: early, more than 0.61; medium, 0.60-0.41; advanced, 0.40-0.21; far advanced, less than 0.20. In the normal group the diameter of the inferior temporal vein was the largest, followed by that of the superior temporal vein, the inferior temporal artery, and the superior temporal artery. The diameters of the inferior and superior temporal retinal artery were significantly smaller at the early and medium stage, respectively, whereas both inferior and superior temporal retinal vein diameters were significantly smaller at the far advanced stage. The diameters of the inferior and superior temporal retinal arteries correlated significantly with neuroretinal rim area (r > or = 0.48, P = 0.0001), mean deviation (r > or = 0.42, P = 0.0001), vertical cup-to-disc ratio (r < or = -0.33, P = 0.0001), and peripapillary atrophy data (r < or = -0.14, P < 0.04). The results indicate that in primary open-angle glaucoma, vessel diameter becomes less as neuroretinal rim area decreases and visual field defects and peripapillary atrophy increase. Its evaluation can be helpful for the diagnosis of glaucoma and possibly also during follow-up.

Prognostic factors for adenocarcinoma of the gallbladder: an analysis of 162 cases

Carcinoma of the gallbladder is a rare neoplasm and is associated with a dismal prognosis. To analyze the natural history of this disease and prognostic factors, a large tumor registry database was accessed. During the period 1972 to 1995, 214 patients were entered. Adequate follow-up was available on 162 patients, and this group forms the basis of this review. There were 54 males and 108 females with a median age of 62 years. Median follow-up was 7 months. Right upper quadrant abdominal pain was the most frequent presenting symptom. Fifteen patients had an incidental finding of carcinoma after cholecystectomy. Overall, 5-year survival was 25 per cent, with a median survival time of 9.7 months. Survival was improved for patients with local disease compared with those with regional or metastatic disease. One hundred nine patients underwent surgical therapy. Complete resection was possible in 36 patients, whereas 44 patients had residual disease. Median survival time for patients with no residual disease was 67.2 months, whereas those for patients with microscopic residual tumor and gross residual tumor were 8.9 and 3.8 months, respectively (P < 0.000001). Gallbladder cancer is often diagnosed at an advanced stage and is associated with a poor prognosis. In patients with localized disease, surgical treatment provides the opportunity for long-term survival only when a complete resection can be performed. Prognosis for patients with microscopic residual and gross residual disease is similar.

Geographic and demographic differences in the frequency of human cytomegalovirus gB genotypes 1-4 in immunocompromised patients

To test the hypothesis that human cytomegalovirus (CMV) gB genotype may differ with geographic origin or patient demographics, CMV DNA was amplified for gB typing from immunocompromised patients in Italy and Africa and compared with previously reported frequencies in California. Increased gB2 frequency occurred in Italian homosexual AIDS patients, as compared with both Italian heterosexual injection drug users with AIDS and heterosexual Zimbabwe AIDS patients. Occurrence of gB3 in Italy was higher in injection drug users than in homosexual AIDS patients. The incidence of gB4 was higher overall in the Italian as compared with the California patients. Therefore geographic and demographic differences in patients affect gB distribution and should be considered before associations of gB genotypes and virulence are made.

The role of internal urease in acid resistance of Helicobacter pylori

BACKGROUND & AIMS

The relative role of internal urease for acid protection of Helicobacter pylori is unknown. The aim of this study was to determine the comparative importance of internal and external urease under acidic conditions.

METHODS

The pH optimum and measured Michaelis constant for urea of external urease and urease in intact bacteria at different medium pH (pHout) were measured using 14CO2 release from 14C-urea. The effect of urea on membrane potential and bacterial cytoplasmic pH was measured at different fixed pHout. 35S-methionine labeling and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of labeled proteins in the organism and medium measured protein synthesis at different pHout and mechanisms of urease externalization.

RESULTS

External urease had activity between pH 5.0 and 8.5 and internal urease between pHout 2.5 and 6.5, and its Michaelis constant at pHout 7.5 was 300 mmol/L but at pHout 4.5 was 0.5 mmol/L, similar to free urease. The addition of 5 mmol/L urea to bacteria at fixed pHout from 3.0 to 6.0 elevated potential to about -105 mV and periplasmic pH to about pH 6.2. Protein synthesis occurred mainly between pH 6.5 and 8.0, and urease activity resulted in increased protein synthesis at acidic pH. The labeling pattern of intrabacterial and released protein was similar.

CONCLUSIONS

Intracellular urease activity is regulated by external pH, defends against gastric acidity by increasing periplasmic pH and membrane potential, and stimulates protein synthesis at acidic pH. External urease is produced mostly by cell lysis.

Application of thrombin based fibrin glue and non-thrombin based batroxobin glue on intact human blood vessels: evidence for transmural thrombin activity

An alternative method of uniting small diameter vessels to obtain tissue union while limiting the thrombogenic effect of suture placement at a vessel anastomosis involves the use of a thrombin based fibrin glue as a surgical sealant. This investigation addresses whether the in vitro application of a thrombin based glue (TG), or batroxobin glue (BG), a non-thrombin based glue made with the snake venom enzyme batroxobin, alters intravascular platelet deposition (PD) or cleaves blood fibrinogen, as measured by fibrinopeptide A (FPA) production, when the respective glue is applied to the external surface of an intact human placental artery or an artery with an anastomosis. When TG was applied to the adventitial surface of an intact vessel or an anastomosis (n = 7) of control and experimental vessels, there was a significant increase in intraluminal platelet deposition, an effect not realized with BG (n = 12, intact vessel TG p = 0.01, BG p = 0.66, anastomosis TG p <0.01, BG p <0.01). Both TG and BG significantly increased FPA levels when human whole blood was perfused through both intact vessels or vessels containing an anastomosis when compared to control vessels (intact vessel TG and BG p <0.01, anastomosis TG and BG p <0.01). Labelled thrombin studies document the rapid passage of thrombin through an intact vessel wall or vessels with an anastomosis when TG was applied to the adventitial surface of the vessel. The data suggest that TG and BG are drug delivery systems for their respective enzymes that either pass through or transfer a message across not only a surgically created anastomosis, but also an intact vessel wall.

Roles of rDNA spacer and transcription unit-sequences in X-Y meiotic chromosome pairing in Drosophila melanogaster males

Meiotic pairing of the X and Y chromosomes in Drosophila melanogaster males is mediated by the rDNA repeats, which are present in two tandem clusters, one in the centric X heterochromatin and the other near the base of the short arm of the Y chromosome. Deletion of the X chromosomal rDNA cluster disrupts X-Y pairing and causes high frequences of X-Y nondisjunction. Pairing can be partly restored by insertions of cloned complete rRNA genes or by rDNA fragments that include the intergenic spacer (IGS) region. A 240 bp repeated sequence in the IGS was shown to be effective in promoting pairing when present at copy numbers above five. This study further defines the rDNA sequences involved in mediating pairing. Germline insertions of a P element construct containing most of the rDNA transcription unit but no promoter or IGS region were obtained. Two single-copy insertions and four two-copy insertions proved unable to stimulate X-Y disjunction when located on an rDNA-deficient X chromosome. In addition, three insertions of a P element construct consisting of the IGS and promoter regions of the rDNA were characterized molecularly. These three insertions had previously been shown to range in pairing ability from very weak to quite strong. Molecular analysis revealed that the three insertions also vary in copy number of the 240 bp IGS repeat and that these structural differences correlate with the differences in pairing ability. These data indicate that 240 bp repeats are considerably more effective than other regions of the rDNA in stimulating chromosome pairing.

Serotonin levels as a function of age in Aplysia californica

The neurotransmitter serotonin (5-HT) plays an important role in a number of behaviors in Aplysia californica some of which have been shown to vary with age. We were thus interested in examining the age-dependence of 5-HT in A. californica. Because animals of the same age can have very different weights, and weight alone is reliably known for wild-caught animals, we also examined the variation of 5-HT with weight. Serotonin was measured in the ring and abdominal ganglia combined, in lab-reared animals from 3 to 12 months post-hatch across a wide weight range. Serotonin increased rapidly from 4 to 6 months, and more slowly from 6 to 13 months. Serotonin scaled by soluble ganglion protein increased from 3 to 6-7 months, reached a maximum, and then decreased again. Serotonin, but not scaled 5-HT, increased significantly with weight across the whole weight range. Animals of the same weight, but different ages, had different 5-HT levels, as did young animals of the same age but different weight. Serotonin varied significantly with both age and weight, with the age-dependence being the more significant.

Identification and differentiation of mycobacteria using the PAN promoter sequence from Mycobacterium paratuberculosis as a DNA probe

A 165 bp DNA fragment containing the PAN promoter from Mycobacterium paratuberculosis was used as a probe in Southern blots to detect the presence of related sequences in other species of mycobacteria. Among the species tested homologous sequences appeared to be present in representative pathogens belonging to the Mycobacterium tuberculosis complex, the MAIS complex, Mycobacterium kansasii and also the non-pathogenic vaccine strain Mycobacterium bovis BCG. In addition, the probe could differentiate between these species on the basis of a restriction fragment length polymorphism (RFLP). No hybridization was observed with DNA extracted from a selected group of other slow-growing and fast-growing mycobacteria nor from a selection of other bacterial pathogens. It appears that the PAN sequence is identifying genomic regions common to the major pathogenic groups of mycobacteria.