Altered gating of opiate receptor-modulated K+ channels on amygdala neurons of morphine-dependent rats

The molecular mechanism of tolerance to opiate drugs is poorly understood. We have used single-channel patch-clamp recordings to study opiate receptor effects on dissociated neurons from rat amygdala, a limbic region implicated in addiction processes. A 130-pS inwardly rectifying K(+)-preferring cation channel was activated by mu opioid receptors in a membrane-delimited manner. After chronic treatment of the rats with morphine, channel gating changed markedly, with an approximately 100-fold decrease in open probability at a given morphine concentration. The change in channel gating correlated both in time course and in dose of morphine treatment with the development of functional opiate dependence and appeared to arise at a step after G-protein activation and before channel permeation by K(+). This decreased receptor-channel coupling appears to be large enough to account quantitatively for opiate tolerance and may represent one of the mechanisms through which tolerance occurs.

HNCAN pulse sequences for sequential backbone resonance assignment across proline residues in perdeuterated proteins

A TROSY-based triple-resonance pulse scheme is described which correlates backbone 1H and 15N chemical shifts of an amino acid residue with the 15N chemical shifts of both the sequentially preceding and following residues. The sequence employs 1J(NC alpha) and 2J(NC alpha) couplings in two sequential magnetization transfer steps in an 'out-and-back' manner. As a result, N,N connectivities are obtained irrespective of whether the neighbouring amide nitrogens are protonated or not, which makes the experiment suitable for the assignment of proline resonances. Two different three-dimensional variants of the pulse sequence are presented which differ in sensitivity and resolution to be achieved in one of the nitrogen dimensions. The new method is demonstrated with two uniformly 2H/13C/15N-labelled proteins in the 30-kDa range.

Mortality, morbidity, length and cost of hospitalization in very-low-birth-weight infants in the era of National Health Insurance in Taiwan: a medical center's experience

The impact of implementation of the National Health Insurance on the outcome, cost, and length of hospitalization of very-low-birth-weight (VLBW) infants is not clear in Taiwan. These data are important for the planning of medical care and regionalization in this area. This study was an attempt to examine these questions. We retrospectively collected mortality, morbidity, and length and cost of hospitalization data of VLBW (BW < 1500 g) infants between March 1995 and February 1998. There were totally 162 patients enrolled. The overall mortality rate was 21.6%; the birth weight (BW)-specific mortality rate was 72%, 31%, 19%, and 3% for infants with BWs of < 750 g, 750-999 g, 1000-1249 g, and 1250-1499 g, respectively. The incidence of morbidities were: respiratory distress syndrome (74%), patent ductus arteriosus (36%), necrotizing enterocolitis (9%), sepsis (42%), intraventricular hemorrhage (15%), retinopathy of prematurity (31%), failure to pass auditory brainstem response (ABR) (34%), and chronic lung disease (17%). The average length of hospitalization was 67.2 days, and the cost per infant was 62 x 10(4) NT dollars; 108 +/- 38 days, 73 +/- 32 x 10(4) NT dollars if BW < 750 g; 94 +/- 15 days, 99 +/- 35 x 10(4) NT dollars if BW 750-999 g; 66 +/- 23 days, 64 +/- 36 x 10(4) NT dollars if BW 1000-1249 g; and 43 +/- 14 days, 39 +/- 37 x 10(4) NT dollars if BW 1250-1499 g. In conclusion, VLBW infants are associated with high mortality and morbidity rates. They have long lengths and high costs of hospitalization, and therefore deserve attention in the implementation of the National Health Insurance and regionalization.

Buccal absorption of triclosan following topical mouthrinse application

PURPOSE

To determine clinically the buccal absorption and plaque retention of triclosan from a mouthrinse containing 0.03% triclosan.

MATERIALS AND METHODS

15 ml of the triclosan oral rinse (N=9) or placebo mouthrinse (N=12) was used twice daily for 21 days in humans. Blood, dental plaque and the expectorated oral rinse were collected prior to, during the treatment period at given intervals, and 8 days after the treatment. Dental plaque and blood samples were collected 1 hr and 4 hr after the morning rinse, respectively. The oral retention of triclosan was calculated by subtracting the amount of triclosan recovered in the expectorate from the triclosan dose applied (4.50 mg) in the mouthrinse. Plasma samples were analyzed for free triclosan (the parent molecule) and its glucuronide and sulfate conjugates, whereas dental plaque was analyzed only for total triclosan.

RESULTS

No significant treatment-related adverse effects were observed during the clinical phase of the study. The average daily oral retention of triclosan was calculated to be 0.660 mg, which is 7.33% of the triclosan dose applied (2 x 4.50 mg). Plaque contained an average 20.5-46.4 microg of triclosan per g of plaque collected. At various sampling times, mean plasma concentrations were: no detectable triclosan, 63.8-86.3 microg/ml of triclosan glucuronide and 8.23-18.0 ng/ml of triclosan sulfate. The mean total triclosan plasma concentration ranged from 74.5 to 94.2 microg/ml with plateau concentrations reached after 2 days of dosing. Eight days after the last treatment the triclosan plasma concentration returned to baseline levels (< 2 ng/ml).

'Sloughing-off' of heterochromatin in Werner's syndrome cells during high-temperature phosphate incubation

Previous investigations of cells undergoing rapid division revealed the presence of heterochromatic 'dots' in chromosomes as well as numerous chromocentres in interphase nuclei. Such structures were seen in human embryonic cells, as well as cells from organisms capable of regeneration, and cells from various malignancies. Cells with a reduced capacity for reproduction were found to be virtually devoid of nuclear chromocentres and chromosome dots after incubation in phosphate buffer at high temperature. The lack of heterochromatin in such cells (Werner's syndrome) thereby explained their reduced capacity for cell division and the resultant rapid rate of aging in individuals afflicted. Re-examination of such slides containing these cells revealed that chromocentres and chromosome dots were present initially, but the incubation process resulted in a 'sloughing-off' of such structures. The incubation process left these heterochromatic structures intact in malignant and control cells, inferring a link between cell proliferation and stable intact heterochromatin. These findings implicate heterochromatin as the object of the purported chromosomal instability factor characteristic of Werner's syndrome. The loss of heterochromatin did not result in chromosome breakage, suggesting that heterochromatin may not be an integral part of chromosome structure, but rather a surface feature or covering.

Clinical evidence for the lack of triclosan accumulation from daily use in dentifrices

PURPOSE

To demonstrate through clinical pharmacokinetic studies that triclosan does not accumulate in blood or plasma in human subjects who regularly use triclosan-containing dentifrice.

MATERIALS AND METHODS

Three clinical pharmacokinetic studies were conducted to assess the blood or plasma levels of triclosan following toothbrushing with dentifrice formulations containing triclosan. In Study 1, both a single-dose and a multiple-dose phase were conducted. In the single-dose phase, subjects brushed one time with 1.25 g dentifrice containing 0.3% triclosan (3.75 mg triclosan dose) and ingested all of the dentifrice. Blood samples were collected at multiple time points from pre-dose to 72 hrs post-dose and analyzed for total triclosan levels. In the multiple-dose phase, these same subjects brushed three times daily as in the single-dose phase. This pattern was followed for 12 consecutive days. Blood samples were taken for triclosan analysis at multiple time points up to 48 hrs after the first dose of day 12. Study 2 was a parallel, open-labeled clinical study to compare triclosan blood levels from twice daily brushing with 1 gm of dentifrice containing 0.2% triclosan to twice daily ingestion of 20 ml of a 0.01% triclosan aqueous solution over a period of 21 days. Blood samples were taken for triclosan analysis at baseline and at 4 hrs after the morning dose on days 7, 14, and 21. Study 3 was a parallel, double-blind, 12-wk brushing study with dentifrice containing 0.2% triclosan or a matching placebo. Blood samples were taken for triclosan analysis at baseline and at 3 and 12 wks at 4 hrs after the morning dose.

RESULTS

In the single-dose study, Triclosan was absorbed into the systemic circulation with a T(1/2) of the terminal plasma concentration ranging between 6-63 hrs. The mean AUC(0-inf) after a single dose was found to be 2,809 ng x hr/ml. After 12 days of three times daily toothbrushing and ingestion of the dental slurry, the mean triclosan plasma concentration was 352 ng/ml in the steady state period, and the mean AUC in a 24-hr period (AUC24) was found to be 8,460 ng x hr/ml. This AUC24 was normalized for the number of brushings for comparison to the AUC(0-inf) after a single brushing. There was no significant (P = 0.93) difference between these AUC values suggesting a complete elimination of daily triclosan dose and no increase in the triclosan level during repeated brushing/ingestion. In the two other dentifrice studies, the triclosan blood concentration appeared to reach a steady state level by day 7 and was maintained at the steady state level (14 to 21 ng/ml) for up to 12 wks. These results support the conclusion that the elimination of a daily triclosan dose is complete and no accumulation of triclosan was observed even after three times daily toothbrushing with 1.25 g dentifrice containing 0.3% triclosan and full ingestion of the dentifrice.

Fourth branchial cyst presenting with neonatal respiratory distress

Fourth branchial cysts are quite rare. A neonate with a left lateral neck mass and respiratory distress was found to have a fourth branchial cyst, which was diagnosed with computed tomography and endoscopy. The characteristic computed tomography findings included an air-containing neck cyst, which was located at the anteromedial site of the common carotid artery with mediastinal extension. Endoscopic examination revealed an internal opening at the apex of the pyriform sinus, communicating with the cyst. Total excision of the cyst was performed, and the specimen, which showed ciliated columnar epithelium with a subepithelial lymphoid infiltrate, thyroid follicles, and thymic tissue, histologically confirmed the diagnosis.

Further studies on chromocentres and their implications in regeneration

Previous investigations using a number of invertebrates, as well as regenerative tissues/organs of various vertebrates, have promulgated the hypothesis that heterochromatin, in the form of nuclear chromocentres, is correlated with the ability to regenerate. In order to test the universality of this hypothesis, cells from a variety of additional animals were examined for the presence of nuclear chromocentres. In accordance with the hypothesis, cells from these organisms contained numerous chromocentres. Evidence indicates that chromocentres, double minute chromosomes, chromosome 'dots', and telomeres may be different forms of the same heterochromatin entity.

'Glowing' chromosomes in cells undergoing rapid division

Previous investigations in which metaphase plates of cells in rapid division were incubated in phosphate buffer at high temperature revealed numerous heterochromatic dots in chromosomes after Giemsa staining. In contrast, chromosomes from cells with a reduced capacity for reproduction were devoid of such dots, or the dots were sloughed-off into rings and patches of heterochromatin. In two types of cells which were rapidly dividing, namely HeLa cells (cervical cancer) and cells from regenerating planaria, phosphate incubation followed by Giemsa staining revealed an 'aura' or 'glowing' effect on the chromosomes, consisting of a densely staining core surrounded by a lightly stained periphery. This finding might be developed into a diagnostic test for certain malignancies, for cells undergoing dedifferentiation, or for tissues undergoing regeneration.

Effect of dexamethasone on the intestinal first-pass metabolism of indinavir in rats: evidence of cytochrome P-450 3A [correction of P-450 A] and p-glycoprotein induction

Indinavir, a potent and specific inhibitor of HIV protease, is a known substrate of cytochrome P-450 (CYP) 3A and p-glycoprotein. The purpose of this study is to investigate and compare the inducing effect of dexamethasone (DEX) on CYP3A and p-glycoprotein in the hepatic and intestinal first-pass metabolism of indinavir in rats. Pretreatment of rats with DEX had little effect on the pharmacokinetics (Cl and T(1/2)) after i.v. administration of indinavir, whereas DEX markedly altered the peak concentration (C(max)) and bioavailability of indinavir after oral dosing. The C(max) decreased from 2.8 microM in control rats to 0.28 microM in DEX-treated rats, and bioavailability decreased from 28 to 12.4%. The decreased bioavailability after DEX pretreatment was due mainly to an increase in first-pass metabolism. Intestinal first-pass metabolism (E(G)) increased from 6% in control rats to 34% in DEX-treated rats, and hepatic first-pass metabolism (E(H)) increased from 65 to 82%. Analysis of in vitro kinetic data revealed that the increased intestinal and hepatic metabolism by DEX was attributed to an increase in the V(max), as a result of CYP3A induction, without a significant change in the K(m) values. DEX pretreatment also induced p-glycoprotein in the intestine and liver of rats. p-Glycoprotein appeared to increase the intestinal metabolism of indinavir whereas it had little effect on the hepatic metabolism of indinavir. Although it has been suggested that the role of intestinal metabolism for some drugs is quantitatively greater than that of hepatic metabolism in the overall first-pass metabolism, the contribution of intestinal metabolism to the overall first-pass metabolism of indinavir in rats is not quantitatively as important as the hepatic metabolism, regardless of DEX induction.

Early dexamethasone therapy and blood cell count in preterm infants

OBJECTIVE

To assess the effects of early postnatal dexamethasone therapy on hematologic values in preterm infants.

MATERIALS AND METHODS

We reviewed the hematologic data of 179 preterm infants who participated in a double-blind clinical trial of early postnatal dexamethasone therapy (<12 hours after birth) for the prevention of chronic lung disease. One group (86 infants) received saline and the other group (93 infants) received dexamethasone. Dexamethasone was given intravenously every 12 hours in tapering doses: 0.25 mg/kg on days 1 to 7, 0.12 mg/kg on days 8 to 14, 0.05 mg/kg on days 15 to 21, and 0.02 mg/kg on days 21 to 28. Blood samples were obtained on days 0, 3, 7, 10, 14, 21, and 28. None of the infants received prenatal steroid therapy.

RESULTS

Multiple regression analysis revealed significant differences in the values versus time curves of the white blood cell, neutrophil, lymphocyte, basophil, and eosinophil counts between the two groups. The white blood cell count was significantly higher in the dexamethasone group on days 7 through 14, and this was associated with significantly higher numbers of segmented neutrophils and band forms and significantly lower numbers of lymphocytes and eosinophils. The hematocrit and platelet counts were similar in the two groups throughout most of the trial. Except for platelet count, steroid therapy did not alter the hematologic values for infants with bacteremia.

CONCLUSION

Dexamethasone affects white blood cell, segmented neutrophil, lymphocyte, basophil, and eosinophil counts in neonates. This should be taken into consideration when evaluating preterm infants who are receiving dexamethasone.early dexamethasone therapy; neonatal blood count; preterm infant; respiratory distress syndrome.

Prospective randomized comparison between pylorus-preserving and standard pancreaticoduodenectomy

BACKGROUND

Pancreaticoduodenectomy, with either gastrectomy (Whipple procedure) or pylorus-preserving pancreaticoduodenectomy (PPPD), is a complex procedure. Technical diversity, variation and sampling bias exist among surgeons. Previous reports comparing these two procedures are retrospective and not randomized. These factors should be considered seriously and eliminated in comparisons between the two procedures.

METHODS

From August 1994 to August 1997, a prospective randomized comparison was conducted between the Whipple procedure and PPPD performed by the same surgeon with the same approach and same anastomotic fashion for periampullary cancer. After exclusion of seven patients, 31 patients were eligible for the study, 16 receiving PPPD and 15 a Whipple procedure. No significant difference in the age, sex distribution, tumour localization or staging was noted between the two groups.

RESULTS

One operative death after PPPD and no operative death after the Whipple procedure resulted in a 3 per cent mortality rate in the 31 patients. Median duration of the Whipple operation was 235 (range 195-305) min, with a median blood loss of 500 (range 230-3100) ml and a median blood transfusion of 0 (range 0-10) units. In the patients who had PPPD, median operating time was 230 (range 170-275) min, median blood loss was 350 (range 100-1200) ml and median blood transfusion was 0 (range 0-4) units. There were two minor leaks from the pancreaticojejunostomy after the Whipple procedure and no leakage after PPPD, resulting in 6 per cent minor leakage in 31 patients. These outcomes were not significantly different. Delayed gastric emptying was observed more frequently after PPPD (six of 16 patients) than after the Whipple procedure (one of 15 patients), with marginal significance (P = 0.08, two-sided Fisher's exact test).

CONCLUSION

In this prospective randomized study, both PPPD and the Whipple procedure were associated with low mortality and operative morbidity rates. There was no significant difference between PPPD and Whipple resection in terms of operative mortality and morbidity, operating time, blood loss and blood transfusion. PPPD was associated with more frequent delayed gastric emptying, although study of more patients is needed to confirm this.

Effect of simulated sunlight on atrazine and metolachlor toxicity of surface waters

Atrazine and metolachlor are the two most widely used herbicides in the United States; through non-point-source runoff both herbicides may cause toxicity to aquatic organisms. Toxicity changes were measured for atrazine and metolachlor in surface waters after exposure to simulated sunlight (0, 20, and 40 kJ/m2) using a Xenon Weather-Ometer. A Microtox toxicity test, using the marine luminescent bacterium Vibrio fischeri, was conducted on deionized, river, and bay water samples mixed with atrazine or metolachlor herbicide (12 mg/liter) after exposure to simulated sunlight. Microtox test (EC50%) results demonstrated that the toxicity decreased with increasing light intensity for both herbicides in river and bay water. These results also indicate that the toxicity of the bay water, with high concentrations of organic and suspended matter, was reduced, for both herbicides, compared with the toxicity of the river water, possibly through photodegradation of pesticides.

An exploratory study of social support: a cross-cultural comparison of Chinese-, Japanese-, and Anglo-American breast cancer patients

This paper investigated the nature of social support for Asian- and Anglo-American women post breast cancer treatment. Forty-six Anglo- and Asian-American (13 Anglo-American, 18 Chinese-American and 15 Japanese-American women) women were assessed 6 months to 3 years post-treatment. Assessments consisted of a semi-structured interview plus standardized psychological tests. Three major hypotheses were developed and tested in the study. Results showed: (1) Anglo-American women indicated a greater need for social support than either of the two Asian-American groups in 66% of the categories; (2) no differences were found between the three ethnic groups in receipt of emotional or tangible social support; and (3) the network size and composition differed significantly in 83% of the categories between the Anglo group and at least one of the Asian groups. These differences were in size, mode, and perceived adequacy of social support. Implications for culturally-based clinical practice which emerge from these findings are discussed.

Serum hepatocyte growth factor levels in patients with inflammatory lung diseases

HGF is a pulmotrophic factor in the regeneration of an injured lung. However, the physiological role of HGF in vivo remains largely unknown. We studied HGF in patients with inflammatory lung diseases to investigate the clinical significance of HGF and compared with C-reactive protein (CRP) in inflammatory lung diseases. Forty-seven patients with inflammatory lung diseases (16 tuberculosis, 18 pneumonia, and 13 chronic obstructive pulmonary disease (COPD)) were studied. Fifty normal, healthy individuals were analyzed as normal control subjects. Serum HGF levels were measured by enzyme-linked immunosorbent assays (ELISA). Serum CRP levels were also performed. The mean +/- SE numbers of serum HGF levels in the patients with inflammatory lung diseases (4.33 +/- 0.41 ng/ml) were significantly elevated when compared with those in normal control subjects (0.36 +/- 0.02 ng/ml) (p < 0.0001). Serum HGF levels in patients with COPD was significantly lower than those were with tuberculosis or pneumonia (p < 0.05). There was a significant correlation between serum HGF levels and CRP in inflammatory pulmonary diseases (r = 0.48, p = 0.00087). The significantly decreased serum HGF levels in patients with improved inflammatory lung diseases were also observed subsequently. Our results suggest that secreted HGF may play an important role in bronchial epithelium reconstruction during respiratory inflammation.

The role of pulmonary inflammation in the development of pulmonary hypertension in newborn with meconium aspiration syndrome (MAS)

1. There was no clear correlation between the tracheal aspirate cytokines and the elevation of pulmonary arterial pressure in newborn piglets with MAS. The use of dexamethasone significantly suppressed tracheal aspirate cytokines but did not significantly alter pulmonary arterial pressure. Dexamethasone significantly increased the cardiac stroke volume and blood pressure. 2. Early dexamethasone therapy (< 12 hrs) for one week in infants with MAS significantly improved pulmonary ventilation and facilitated weaning from mechanical ventilation. 3. The mechanisms for the improvement in cardiopulmonary status following early dexamethasone therapy in MAS remain unclear. An overall improvement in cardiac hemodynamics, along with a significant decrease in lung inflammation may be responsible for the improvement.

Prevention of chronic lung disease in preterm infants by early postnatal dexamethasone therapy

Recent studies suggest that early dexamethasone therapy may lessen the pulmonary inflammation in preterm infants with respiratory distress syndrome (RDS). To investigate whether early (<12 hr) postnatal dexamethasone therapy would reduce the incidence of chronic lung disease (CLD), a randomized, double-blind, controlled trial was conducted in 40 infants (birth weights from 500 to 1,999 gm) who had severe RDS and required mechanical ventilation within 6 hr of birth. All infants received one dose of Survanta before they were randomly assigned to control (saline placebo) or dexamethasone-treated groups (0.5 mg/kg/d for 1 week, then tapered over 3 weeks). Sequential analysis was performed with the end point of assessment being the presence or absence of CLD on postnatal Day 28. Statistical significance favoring dexamethasone was reached when 12 consecutive pairs in which one infant had CLD and the other did not have CLD showed that ten pairs favored dexamethasone and two pairs favored control treatment. Among the survivors, 12/15 were extubated in the dexamethasone group and 9/16 in the control group at the end of study. Infants in the treated group had transient hyperglycemia and hypertension. There was no difference between the groups in mortality and in incidence of sepsis or intraventricular hemorrhage. We conclude that early postnatal dexamethasone therapy is potentially effective in the lessening of CLD in preterm infants. To substantiate our result, large randomized controlled trials are needed and warranted.

NH2-terminally truncated HER-2/neu protein: relationship with shedding of the extracellular domain and with prognostic factors in breast cancer

We identified an NH2-terminally truncated HER-2/neu product of M(r) 95,000 with in vitro kinase activity by Western blotting and immunoprecipitations using domain-specific antibodies. p95 levels correlated with the extracellular domain (ECD) shed from different cells under varied conditions. Both ECD and p95 were at approximately 20-fold lower levels in SKOV3 ovarian carcinoma cells, as compared to BT474 breast carcinoma cells. Both were stimulated by treatment of cells with the phorbol ester tumor promoter phorbol 12-myristate 13-acetate and the lysosomotrophic agent chloroquine. The hydroxamate inhibitor of metalloproteases, TAPI, suppressed both p95 and ECD in a dose-dependent fashion, with maximal inhibition at < or = 10 microM in BT474 cells. Cancer tissues were analyzed by Western blotting and scored for p95HER-2/neu and for p185HER-2/neu expression. Breast and ovarian cancer tissues were both found to express p95HER-2/neu in addition to p185HER-2/neu. Of 161 breast cancer tissues, 22.4% expressed p95, 21.7% overexpressed p185, and 14.3% were p95 positive and overexpressed p185. A higher proportion of node-positive patients (23 of 78) than node-negative patients (9 of 63) expressed p95 in all tumors combined (P = 0.032). In the group that overexpressed p185, those that contained p95 were associated with node-positive patients (15 of 21), whereas those that were p95 negative were associated with node-negative patients (8 of 11; P = 0.017). Neither p95- nor p185-rich patients significantly correlated with tumor size or with hormone receptor status in this study. Our findings show that breast cancers, which express the HER-2/neu oncogene, are heterogeneous with respect to HER-2/neu protein products. p95HER-2/neu appears to distinguish tumors that have metastasized to the lymph nodes from those in node-negative patients.

Efficacy of nasal intermittent positive pressure ventilation in treating apnea of prematurity

The efficacy of nasal intermittent positive pressure ventilation (NIPPV) in treating apnea of prematurity was evaluated. Apneic preterm infants were randomly assigned to receive either NIPPV or continuous positive airway pressure (NCPAP) for 4 hr when they failed to respond to conservative therapy. The amount of reduction in apneic spells and bradycardia in the two groups after treatment was compared. Thirty-four infants (18 with NIPPV, 16 with NCPAP) were enrolled. Their birth weights ranged from 590-1,880 g (mean, 1,021 g) and gestational ages from 25-32 weeks (mean, 27.6 weeks). The baseline characteristics were comparable in the two groups. Frequency of apnea and bradycardia was reduced during both forms of treatments. However, the infants receiving NIPPV had a greater reduction of apneic spells (P = 0.02) and a tendency to greater decrease in bradycardia (P = 0.09) than those receiving NCPAP. We conclude that NIPPV is more effective than NCPAP in reducing apnea in preterm infants. NIPPV may reduce bradycardia; however, this needs to be validated by a larger number of observations.

Extended life-span and stress resistance in the Drosophila mutant methuselah

Toward a genetic dissection of the processes involved in aging, a screen for gene mutations that extend life-span in Drosophila melanogaster was performed. The mutant line methuselah (mth) displayed approximately 35 percent increase in average life-span and enhanced resistance to various forms of stress, including starvation, high temperature, and dietary paraquat, a free-radical generator. The mth gene predicted a protein with homology to several guanosine triphosphate-binding protein-coupled seven-transmembrane domain receptors. Thus, the organism may use signal transduction pathways to modulate stress response and life-span.

Elastase in hyperpnea-induced guinea pig airway constriction

Aerosolized elastase has been shown to produce airway constriction in guinea pigs. In this study, we examined whether endogenous elastase plays a role in isocapnic hyperpnea-induced airway constriction using an elastase inhibitor, eglin-c. The study was divided into three experiments. In the first experiment, we used an elastase inhibitor, eglin-c, to suppress hyperpnea-induced bronchoconstriction. Twenty-two young male Hartley guinea pigs were divided into three groups: control (n=8), eglin-c(1) (a lower dose of eglin-c, n=7), and eglin-c(2) (a higher dose of eglin-c, n=7). In the second experiment, we tested whether eglin-c affects pulmonary function following 15 min of normal air ventilation in two groups of animals: control (n=8) and eglin-c (n=8). In the third experiment, animals were divided into two groups: control (n=7) and compound 48/80 (a mast cell degranulating agent, n=7). Airway function was examined in the anesthetized-paralyzed animal. In the first and third experiments, 15 min of isocapnic hyperpnea caused marked decreases in dynamic respiratory compliance, forced expiratory flow at 0.1 s and maximal expiratory flow at 50% total lung capacity, demonstrating hyperpnea-induced airway constriction. This bronchoconstriction was significantly attenuated by eglin-c and by pretreatment with compound 48/80. In the second experiment, eglin-c did not significantly affect bronchial function following normal air ventilation. These data suggest that elastase released from mast cells directly or indirectly induces hyperpnea-induced bronchoconstriction.

Effects of early postnatal dexamethasone therapy on calcium homeostasis and bone growth in preterm infants with respiratory distress syndrome

The effects of dexamethasone therapy on calcium homeostasis and bone growth were evaluated in 49 infants (24 placebo and 25 dexamethasone) who participated in a double-blind trial of early dexamethasone therapy for the prevention of chronic lung disease. Dexamethasone (0.25 mg kg(-1) b.i.d. on d 1-7; 0.12 mg kg(-1) b.i.d. on d 8-14; 0.05 mg kg(-1) b.i.d. on d 15-21; 0.02 mg kg(-1) b.i.d. on d 22-28) or saline placebo was given i.v. Serum calcium (Ca), phosphorus (P) and parathyroid hormone (PTH), and the corresponding urinary excretion of calcium (FECa) and phosphorus (FEP) were measured on d 2, 3, 7, 10, 14, 21 and 28 after starting the study. Radiographic evaluations of bone growth were also evaluated. Infants in the dexamethasone group had significantly higher PTH on d 2 (p < 0.01), 7 and 14 (p < 0.05) than infants in the placebo group. The dexamethasone-treated infants also had significantly higher FEP on d 2, 7 and 14 (p < 0.05) and lower FECa on d 7 and 14 (p < 0.05) than control infants. There was no significant difference between the groups in bone growth during the study. It was concluded that early dexamethasone therapy causes a transient elevation in PTH without apparent change in bone growth. The long-term effect remains to be evaluated further.

Airway closure during mixed apneas in preterm infants: is respiratory effort necessary?

Airway closure during mixed apneas in preterm infants may be due to lack of tone in the upper airway followed by collapse and obstruction or diaphragmatic action inducing obstruction. We examine whether respiratory efforts are necessary for airway closure using a new method of detecting airway obstruction, based on the disappearance of an amplified cardiac pulse observed on the respiratory flow tracing. We analyzed 198 episodes of mixed apnea of various lengths (> or = 3 seconds) observed in 33 preterm infants (birth weight, 1.4 +/- 0.1 kg [mean +/- SEM]; study weight, 1.7 +/- 0.1 kg; gestational age, 29 +/- 1 weeks; post-natal age, 33 +/- 4 days). The great majority of these episodes (88%) had a central, followed by an obstructive, component. Infants were studied by using a nosepiece and a flow-through system. Respiratory efforts (abdominal and chest movements) were recorded. Of the apneas, 20 were < 5 seconds; 78, 5 to < 10 seconds; 45, 10 to < 15 seconds; 27, 15 to < 20 seconds; and 28, > or = 20 seconds. Of the 198 mixed apneas, 151 (76%) occurred in the absence of any respiratory effort; 43 (22%) showed a simultaneous cessation of the cardiac oscillation and respiratory effort; and 4 (2%) showed diaphragmatic activity appearing after cessation of the cardiac oscillation (airway occlusion). Respiratory efforts never preceded the cessation of the cardiac oscillation. The findings suggest that diaphragmatic action is not needed to occlude the airway in mixed apneas. The simultaneous cessation of cardiac oscillations (airway occlusion) and onset of respiratory efforts may indicate that such effort contributes to closure or is induced by the same stimulus that closes the airway. We speculate that the mechanism for airway closure in mixed apneas is most likely a lack of upper airway tone, which normally occurs with the cessation of a central drive to breathe.

Cardiac output and mixed venous O2 content measurements by a tracer bolus method: animal validation study

A bolus method for noninvasive measurement of cardiac output (CO) and mixed venous oxygen content (O2) has been tested against absolute CO and O2 standards in dogs. No statistical differences in CO were found between bolus method and electromagnetic flowmeter measurement comparisons in an 18-dog study in which CO varied from 0. 5 to 3.0 l/min. The SD for all paired differences was 0.14 l/min; however, data averaging over 10-min intervals were found to reduce the CO measurement uncertainty to <0.08 l/min. The ability of the bolus method to follow rapid CO changes, experimentally produced by control of a pump (surgically placed between the superior and inferior vena cava and the right atrium), was documented and found to satisfy CO monitoring requirements of unstable subjects. O2 bolus values were found to be statistically equivalent to reference measurements.

U-37883A potently inhibits dopamine-modulated K+ channels on rat striatal neurons

An 85 pS K+ channel of rat caudate-putamen neurons, which is activated by dopamine D2 receptors and inhibited by sulfonylurea drugs, was studied using cell-attached patch-clamp electrophysiology. This channel was inhibited by externally-applied U-37883A (4-morpholinecarboximidine-N-1-adamantyl-N'-cyclohexyl hydrochloride), a blocker of vascular ATP-sensitive K+ channels, with a half-maximal effect at a concentration of approximately 0.1 microM. Channel inhibition occurred in a time-dependent fashion when U-37883A was applied to the membrane from a back-filled patch pipette. Inhibition was associated with a decrease in fractional open time, but was voltage-insensitive and did not alter channel conductance, suggesting an effect on channel gating at a site largely insensitive to the electrical field of the channel. U-37883A was about 50 times more potent at inhibiting this channel than was the sulfonylurea drug glibenclamide. This relative potency, opposite to that found in pancreatic tissue, indicates that U-37883A is a useful tool to distinguish amongst different subtypes of sulfonylurea-sensitive K+ channels.

Low and high frequency electroacupuncture at Hoku elicits a distinct mechanism to activate sympathetic nervous system in anesthetized rats

To address the effect of electroacupuncture (Ea) on autonomic nerve activity, the responses of rhythmic micturition contraction (RMC), urine excretion (UE), blood pressure (BP), renal sympathetic nerve activity (RNA) and pelvic parasympathetic nerve activity (PNA) to Ea were investigated in urethane-anesthetized rats. The acupoint Hoku (Li-4) was tested with two different stimulation frequencies (2 Hz and 20 Hz). Elongation of the RMC cycle and an increase in UE associated with the elevation of BP and RNA was elicited during Ea at Hoku. However, the pressor response induced by low frequency Ea (LFEa) was different from that by high frequency Ea (HFEa), i.e. a tonic effect was elicited by LFEa, while a phasic one was induced by HFEa. These results imply that: (1) Ea at Hoku may selectively activate the sympathetic, but not the parasympathetic nervous system, (2) Ea at Hoku with a different stimulation frequency may elicit a distinct mechanism to activate the sympathetic nervous system and (3) Ea at Hoku may ameliorate the hyperactive bladder in clinical therapy.

Early dexamethasone therapy in preterm infants: a follow-up study

OBJECTIVES

To study the outcome at 2-year corrected age of infants who participated in a double-blind controlled trial of early (<12 hours) dexamethasone therapy for the prevention of chronic lung disease (CLD).

METHODS AND MATERIALS

A total of 133 children (70 in the control group, 63 in the dexamethasone-treated group) who survived the initial study period and lived to 2 years of age were studied. All infants had birth weights of 500 to 1999 g and had severe respiratory distress syndrome requiring mechanical ventilation within 6 hours after birth. For infants in the treatment group, dexamethasone was started at a mean age of 8.1 hours and given 0.25 mg/kg every 12 hours for 1 week and then tapered off gradually over a 3-week period. The following variables were evaluated: interim medical history, socioeconomic background, physical growth, neurologic examinations, mental and psychomotor development index score (MDI and PDI), pulmonary function, electroencephalogram, and auditory and visual evoked potential.

RESULTS

Infants in the control group tended to have a higher incidence of upper respiratory infection and rehospitalization than did the dexamethasone-treated group because of respiratory problems. Although there was no difference between the groups in somatic growth in girls, the dexamethasone-treated boys had significantly lower body weight and shorter height than the control boys (10.7 +/- 3.0 vs 11.9 +/- 2.0 kg; 84.9 +/- 5.7 vs 87.5 +/- 4.8 cm). The dexamethasone-treated group had a significantly higher incidence of neuromotor dysfunction (25/63 vs 12/70) than did the control group. The dexamethasone-treated infants also had a lower PDI score (79 +/- 26) than did the control group (87 +/- 23), but the difference was not statistically significant. Both groups were comparable in MDI, incidence of vision impairment, and auditory and visual evoked potential. Significant handicap, defined as severe neurologic defect and/or intellectual defect (MDI and/or PDI </= 69), was seen in 22 children (31.4%) in the control group and 26 (41.2%) in the dexamethasone-treated group.

CONCLUSIONS

Although early postnatal dexamethasone therapy for 4 weeks significantly reduces the incidence of CLD, this therapeutic regimen cannot be recommended at present because of its adverse effects on neuromotor function and somatic growth in male infants, detected at 2 years of age. A longer follow-up is needed. If early dexamethasone therapy is to be used for the prevention of CLD, the therapeutic regimen should be modified. The proper route of administration, the critical time to initiate the therapy, and the dosage and duration of therapy remain to be defined further.

PKC activation is required by EGF-stimulated Na(+)-H+ exchanger in human pleural mesothelial cells

Epidermal growth factor (EGF) stimulates the Na(+)-H+ exchanger, leading to enhanced cell proliferation. In human pleural mesothelial cells (PMCs), the intracellular signaling mechanism mediating the EGF-induced stimulation of the Na(+)-H+ exchanger has not yet been identified. Using a pH-sensitive fluorescent probe, 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, to measure changes in intracellular pH (pHi), we found that 1) EGF and 12-O-tetradecanoylphorbol 13-acetate (TPA; a phorbol ester) both stimulate the ethylisopropyl amiloride-sensitive Na(+)-H+ exchanger; 2) TPA-induced alkalosis can be blocked by protein kinase C (PKC) inhibitors (chelerythrine and staurosporine) or by PKC down-regulation, indicating that PKC activation is involved in the stimulation of the Na(+)-H+ exchanger. However, TPA-induced alkalosis is not blocked by tyrosine kinase inhibitors; and 3) the stimulatory effect of EGF on the Na(+)-H+ exchanger acts via stimulation of tyrosine kinase-receptor activity because it is inhibited by tyrosine kinase inhibitors (genistein, lavendustin A, and herbimycin A). It also involves PKC activation because EGF-induced alkalosis was blocked by PKC inhibitors. These results suggest that PKC activation is one of the downstream signals for EGF-induced activation of the Na(+)-H+ exchanger in primary cultures of human pleural mesothelial cells.

Role of transesophageal echocardiography in the evaluation of patients with clinical pacemaker syndrome

OBJECTIVES

The goal of this study was to investigate the possible role of transesophageal echocardiography in the evaluation of patients with clinical pacemaker syndrome.

BACKGROUND

Several reports on transthoracic echocardiographic features of ventricular pacing were described; however, no previous study of transesophageal echocardiography has been undertaken in patients at the severe end of pacemaker syndrome who need reprogramming of dual-chamber pacing for symptom relief.

METHODS

Twelve patients with ventricular-inhibited pacemakers (VVI) with clinical symptomatic pacemaker syndrome (group I) and 10 patients with VVI without pacemaker syndrome (group II) were prospectively studied. The two groups were pacemaker dependent and had persistent ventriculoatrial conduction. Transesophageal echocardiographic parameters were assessed in group II and within 6 hours before reprogramming to the DDD mode in group I. Follow-up transesophageal echocardiographic study was performed 28+/-5 days after reprogramming in group I.

RESULTS

All patients in group I had subjective improvements of symptoms after DDD reprogramming. The atrial reverse flow velocities of pulmonary veins in group I before reprogramming were significantly higher in group II (39.3+/-11.4 versus 15.7+/-13.5 cm/sec, p < 0.0001). Spontaneous echo contrast in the descending aorta was detected in all patients from group I before reprogramming. The prevalence of significant mitral regurgitation (> or = moderate) was significantly higher in group I before reprogramming than in group II (67% versus 8%, p = 0.01). Significant mitral regurgitation and spontaneous echo contrast in the descending aorta in group I disappeared after reprogramming to the DDD mode.

CONCLUSIONS

Transesophageal echocardiography provides physiologic, pacemaker-related hemodynamic changes in paced patients. Significantly higher atrial reverse flow velocities of pulmonary veins, increased frequency of spontaneous echo contrast in the descending aorta, and significant mitral regurgitation are peculiar echocardiographic findings in patients with VVI with clinical pacemaker syndrome.

Long-term outcome of radiofrequency catheter ablation for typical atrial flutter: risk prediction of recurrent arrhythmias

INTRODUCTION

Little is known about the predictors of recurrent atrial flutter or fibrillation after successful radiofrequency ablation of typical atrial flutter. In addition, there is only limited evidence suggesting that elimination of atrial flutter would modify the natural history of atrial fibrillation in patients who experienced both of these arrhythmias. The aims of the present study were to investigate the long-term results of radiofrequency catheter ablation and to examine the predictors for late occurrence of atrial fibrillation in a large population with typical atrial flutter.

METHODS AND RESULTS

The study population consisted of 144 patients (mean age 56 +/- 18 years) with successful ablation of clinically documented typical atrial flutter. In the first 50 patients, successful ablation was defined as termination and noninducibility of atrial flutter; for the subsequent 94 patients, successful ablation was defined as achievement of bidirectional isthmus conduction block and no induction of atrial flutter. The clinical and echocardiographic variables were analyzed in relation to the late occurrence of atrial flutter or fibrillation. Over the follow-up period of 17 +/- 13 months, 14 (9.7%) patients had recurrence of typical atrial flutter. In the first 50 patients, 8 (16%) had recurrence of atrial flutter, compared with only 6 (6%) of the following 94 patients. Patients with incomplete isthmus block had a significantly higher incidence of recurrent atrial flutter than those with complete isthmus block (6/16 vs 0/78, P < 0.0001) in the following 94 patients. There was no predictor for recurrence of atrial flutter after successful ablation as determined by univariate and multivariate analysis. Although successful ablation of atrial flutter eliminated atrial fibrillation in 45% of patients with a prior history of atrial fibrillation, 31 (21.5%) of 144 patients undergoing this procedure developed atrial fibrillation during the follow-up period. Univariate analysis revealed that three clinical variables were related to the occurrence of atrial fibrillation: (1) the presence of structural heart disease; (2) a history of atrial fibrillation before ablation; and (3) inducible sustained atrial fibrillation after ablation. By multivariate analysis, only a history of atrial fibrillation and inducible sustained atrial fibrillation could predict the late development of atrial fibrillation after atrial flutter ablation.

CONCLUSION

Radiofrequency catheter ablation of typical atrial flutter is highly effective and associated with a low recurrence rate of atrial flutter, but atrial fibrillation continues to be a long-term risk for patients undergoing this procedure. The presence of structural heart disease and prior spontaneous or inducible sustained atrial fibrillation increases the risk of developing atrial fibrillation.

Endogenous regulation of angiogenesis in the rat aorta model. Role of vascular endothelial growth factor

The purpose of this study was to investigate the role of vascular endothelial growth factor (VEGF) in the rat aorta model of angiogenesis. Freshly cut aortic rings generated microvascular outgrowths in serum-free collagen gel culture. Angiogenesis was reduced to 10% when the explants were embedded in collagen 10 to 14 days after excision from the animal. Immunochemical studies of conditioned medium demonstrated secretion of VEGF by the aortic cultures. Levels of VEGF decreased during the second week of culture when the explants became quiescent and microvessels stopped growing. Treatment of quiescent aortic rings with exogenous VEGF stimulated angiogenesis and restored microvascular growth to values observed in cultures of freshly cut explants. Reverse transcriptase polymerase chain reaction of vasoformative collagen gel cultures of rat aorta demonstrated the expression of the alternatively spliced isoforms VEGF165, VEGF189, and the high affinity VEGF receptor flk-1. Reverse transcriptase-polymerase chain reaction of rat aorta-derived cell strains confirmed the presence of VEGF165 and VEGF189 in endothelial cells, smooth muscle cells, and fibroblasts. The flk-1 receptor was expressed by endothelial cells but not by fibroblasts or smooth muscle cells, which is consistent with the endothelial target specificity of VEGF. The spontaneous angiogenic response of freshly cut aortic rings was inhibited by 70% with a neutralizing antibody against VEGF, whereas nonimmune IgG had no effect (P < 0.001). These findings provide evidence for a VEGF-mediated autocrine/paracrine regulation of angiogenesis in the rat aorta model.

Relation of systemic arterial pulse pressure to coronary atherosclerosis in patients with mitral stenosis

The relation of a wide systemic arterial pulse pressure to coronary atherosclerosis has not been fully defined. One hundred fifty-nine patients > 40 years old with symptomatic mitral stenosis (MS) who received routine coronary angiography were classified into 2 groups according to the presence of > or = 50% diameter narrowing of > or = 1 coronary artery (n = 48) or no significant disease (n = 111). Pulse pressure was determined both by noninvasive sphygmomanometer and invasive catheterization methods. There were no significant differences in risk factors of coronary artery disease (CAD) or the severity of MS between the 2 groups. From multivariate logistic regression analysis, independent predictors of development of CAD in MS were age (standardized coefficient beta = 1.3437, p = 0.0025), gender (beta = 0.0107, p = 0.0105), mean blood pressure (beta = 1.1839, p = 0.0105), and pulse pressure (beta = 1.3157, p = 0.0008). A wide pulse pressure (> or = 60 mm Hg) correlated with the presence of angiographically significant CAD with a sensitivity and specificity of 88% and 77%. The negative predictive value was 93%. Pulse pressure assessed by sphygmomanometry provided important clinical information. A wide pulse pressure in patients with MS was associated with a high incidence of CAD.

Early postnatal dexamethasone therapy for the prevention of chronic lung disease in preterm infants with respiratory distress syndrome: a multicenter clinical trial

OBJECTIVES

To study whether early postnatal (<12 hours) dexamethasone therapy reduces the incidence of chronic lung disease in preterm infants with respiratory distress syndrome.

MATERIALS AND METHODS

A multicenter randomized, double-blind clinical trial was undertaken on 262 (saline placebo, 130; dexamethasone, 132) preterm infants (<2000 g) who had respiratory distress syndrome and required mechanical ventilation shortly after birth. The sample size was calculated based on the 50% reduction in the incidence of chronic lung disease when early dexamethasone is used, allowing a 5% chance of a type I error and a 10% chance of a type II error. For infants who received dexamethasone, the dosing schedules were: 0.25 mg/kg/dose every 12 hours intravenously on days 1 through 7; 0.12 mg/kg/dose every 12 hours intravenously on days 8 through 14; 0.05 mg/kg/dose every 12 hours intravenously on days 15 through 21; and 0. 02 mg/kg/dose every 12 hours intravenously on days 22 through 28. A standard protocol for respiratory care was followed by the participating hospitals. The protocol emphasized the criteria of initiation and weaning from mechanical ventilation. The diagnosis of chronic lung disease based on oxygen dependence and abnormal chest roentgenogram was made at 28 days of age. To assess the effect of dexamethasone on pulmonary inflammatory response, serial tracheal aspirates were assayed for cell counts, protein, leukotriene B4, and 6-keto prostaglandin F1alpha. All infants were observed for possible side effects, including hypertension, hyperglycemia, sepsis, intraventricular hemorrhage, retinopathy of prematurity, cardiomyopathy, and alterations in calcium homeostasis, protein metabolism, and somatic growth.

RESULTS

Infants in the dexamethasone group had a significantly lower incidence of chronic lung disease than infants in the placebo group either judged at 28 postnatal days (21/132 vs 40/130) or at 36 postconceptional weeks (20/132 vs 37/130). More infants in the dexamethasone group than in the placebo group were extubated during the study. There was no difference between the groups in mortality (39/130 vs 44/132); however, a higher proportion of infants in the dexamethasone group died in the late study period, probably attributable to infection or sepsis. There was no difference between the groups in duration of oxygen therapy and hospitalization. Early postnatal use of dexamethasone was associated with a significant decrease in tracheal aspirate cell counts, protein, leukotriene B4, and 6-keto prostaglandin F1alpha, suggesting a suppression of pulmonary inflammatory response. Significantly more infants in the dexamethasone group than in the placebo group had either bacteremia or clinical sepsis (43/132 vs 27/130). Other immediate, but transient, side effects observed in the dexamethasone group are: an increase in blood glucose and blood pressure, cardiac hypertrophy, hyperparathyroidism, and a transient delay in the rate of growth.

CONCLUSIONS

In preterm infants with severe respiratory distress syndrome requiring assisted ventilation shortly after birth, early postnatal dexamethasone therapy reduces the incidence of chronic lung disease, probably on the basis of decreasing the pulmonary inflammatory process during the early neonatal period. Infection or sepsis is the major side effect that may affect the immediate outcome. Other observable side effects are transient. In view of the significant side effects and the lack of overall improvement in outcome and mortality, and the lack of long term follow-up data, the routine use of early dexamethasone therapy is not yet recommended.

Manganese ion enhances T1-weighted MRI during brain activation: an approach to direct imaging of brain function

Present techniques for functional MRI rely on detecting changes in hemodynamics that result as a consequence of brain activation. It would be useful if MRI techniques could be developed that enable imaging of a parameter directly related to neuronal activity. Influx of calcium into neurons is necessary for release of neurotransmitters. Divalent manganese ions (Mn2+) can enter cells through voltage-gated calcium channels and Mn2+ is paramagnetic. Mn2+ accumulation in brain due to activation should alter relaxation times offering an approach to sensitize MRI to calcium influx in the brain. To test this idea, T1-weighted MRI was obtained from the rat brain in the presence of a continuous intravenous infusion of 3.6 mumol/min MnCl2. In the anesthetized rat brain, signal enhancement was detected in regions corresponding to ventricles. Activation of the brain with glutamate led to increase in MRI signal intensity in the brain to 238 +/- 23% of the original. This increase in signal was dependent on the presence of MnCl2 and was not due to changes in blood flow. It was necessary to break the blood brain barrier with mannitol to make Mn2+ accessible to the active sites for efficient detection. Enhancement of MRI signal in the brain was also detected with decreasing anesthesia and with somatosensory stimulation. Due to the slow clearance of Mn2+ from the stimulated region of the brain, MRI enhancement could also be detected after stimulation that occurred on awake, behaving rats outside the magnet. These data indicate that MnCl2 shows potential as a MRI contrast agent that is directly sensitive to brain activation.

Left atrial spontaneous echo contrast in patients with permanent pacemakers

OBJECTIVE

To determine the relations between left atrial appendage function, spontaneous echo contrast, and thromboembolism in patients with different modes of permanent pacemakers.

PATIENTS AND METHODS

88 patients with pacemaker implantation and 25 healthy controls in sinus rhythm had transoesophageal echocardiographic examination of the left atrial appendage. Left atrial size, appendage area, peak filling and emptying velocities of the atrial appendage, and the presence or absence of spontaneous echo contrast and thromboembolism were determined. The results in 63 patients with ventricular pacing (group 1, subdivided into subgroup 1A: 42 patients with sinus rhythm, and subgroup 1B: 21 patients with atrial fibrillation) were compared with those in 25 patients with synchronous pacing (group 2), and 25 normal control subjects (group 3).

RESULTS

Patients with ventricular pacing had two distinct appendage flow patterns: well defined biphasic filling and emptying waves in subgroup 1A, and irregular very low filling and emptying waves in subgroup 1B. The ejection fraction of the left atrial appendage in subgroup 1A was significantly better than that in subgroup 1B (mean (SD) 40.6 (12.0)% v 7.6 (5.0)%, P < 0.0001). The spontaneous echo contrast was observed in 90% of subgroup 1B patients but in only 19% in subgroup 1A (P < 0.05) and was not found in groups 2 and 3 (P < 0.0001). There was a trend for increased prevalence of spontaneous echo contrast in subgroup 1A v group 2 (P = 0.053). Thrombi were detected in two cases, and cardiogenic embolism occurred in one case in subgroup 1B. All patients with spontaneous echo contrast had ventricular pacing. Multivariate analysis showed that atrial fibrillation was associated with occurrence of spontaneous echo contrast in patients with ventricular pacing (P = 0.005).

CONCLUSIONS

The left atrial appendage ejection fraction was lower with ventricular pacing than with synchronous pacing. With ventricular pacing there was a trend towards increased prevalence of left atrial spontaneous echo contrast in patients in sinus rhythm, and a significantly increased prevalence in patients with atrial fibrillation.

Cardiac output and mixed venous oxygen content measurements by a tracer bolus method: theory

We present a bolus method of inert-gas delivery to the lungs that facilitates application of multiple inert gases and the multiple inert-gas-exchange technique (MIGET) model to noninvasive measurements of cardiac output (CO) and central mixed venous oxygen content Reduction in recirculation error is made possible by 1) replacement of sinusoidal input functions with impulse inputs and 2) replacement of steady-state analyses with transient analyses. Recirculation error reduction increases the inert-gas selection to include common gases without unusually high (and difficult to find) tissue-to-blood partition coefficients for maximizing the systemic filtering efficiency. This paper also presents a practical method for determining the recirculation contributions to inert expired profiles in animals and determining their specific contributions to errors in the calculations of CO and from simulations applied to published ventilation-perfusion ratio (V/Q) profiles. Recirculation errors from common gases were found to be reducible to the order of 5% or less for both CO and whereas simulation studies indicate that measurement bias contributions from recirculation, V/Q mismatch, and the V/Q extraction process can be limited to 15% for subjects with severe V/Q mismatch and high inspired oxygen fraction levels. These studies demonstrate a decreasing influence of V/Q mismatch on parameter extraction bias as the number of inert gases are increased. However, the influence of measurement uncertainty on parameter extraction error limits improvement to six gases.

Painless Prinzmetal's ST elevation related to propranolol: a case report

Previous studies have shown that propranolol, an effective mainstay for angina pectoris and unstable angina, can induce coronary arterial spasm in patients with variant angina. However, no report has yet associated it with painless Prinzmetal's ST elevation in patients without a history of variant angina. The present communication describes such an unusual and negligible case after propranolol overdose. Coronary arterial spasm can be induced by beta-blocker, not only in patients with variant angina but also in normal persons.

Identification of a promoter for the latent membrane protein 1 gene of Epstein-Barr virus that is specifically activated in human epithelial cells

Latent membrane protein 1 (LMP 1) is one of two Epstein-Barr virus (EBV)-encoded proteins that expressed in nasopharyngeal carcinoma (NPC) cells. Previous studies showed that a 3.5-kb transcript of the LMP 1 gene, in addition to the 2.8-kb transcript, was detected in a B95-8-EBV-containing, nude mice-passaged NPC tumor, C15. This indicated that a transcript was initiated from a region 5' to the putative promoter, ED-L1. We have isolated an EBV variant from a NPC tissue, and this virus strain contained a more pathogenic LMP 1 gene. DNA sequence analysis of the 5'-upstream region showed distinct variations as compared to that of B95-8 strain. To test if the LMP 1 gene of the NPC strain also contained an upstream promoter, we generated a series of deletion plasmids encompassing positions -1,030 to +20 of the LMP 1 promoter and tested for their abilities to drive the expression of the reporter gene in human epithelial cell lines, C-33A and NPC-TW076. We found that the region between -643 and -496 contained a promoter activity that was approximately five-fold higher than the putative promoter, ED-L1. This region between -643 and -496 was designated as ED-L1E. C-33A cells containing the genomic clone pT7(E) or the clone that had deleted a 94-bp ED-L1 sequence (delta94) was used to determine the transcription initiation sites by RNase protection assay. Results showed that a transcription initiation site was located at nucleotide 170,099 ("A") of EBV genome. The transcript was expressed in NPC biopsies and in human primary normal epithelial cells transfected with pT7(E) and delta94, respectively, as examined by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Furthermore, the ED-L1E was not regulated by the EBV-encoded nuclear antigen 1-mediated transcriptional enhancer family of repeats (FR) in C-33A cells. Our results suggested that the ED-L1E was specifically activated in epithelial cells. The biological significance of the selective usage of the ED-L1E promoter was discussed.

Congenital bilateral agenesis of diaphragm: report of a case

Bilateral agenesis of the diaphragm is a rare, life-threatening malformation. Infants with this defect rarely survive to have surgical intervention. We report a 32-week premature female infant who was born to a 36-year-old mother via vaginal delivery. The pregnancy course was complicated by hypertension and polyhydramnios. Cytogenetic study showed a normal 46 XX female karyotype. She had cyanosis, respiratory distress and scaphoid abdomen at birth. A roentgenograph confirmed the diagnosis of diaphragmatic hernia. Surgery was performed at 21 h of age. Bilateral agenesis of diaphragm, herniation of abdominal organs and oesophagus and pulmonary hypoplasia were noted. Furthermore, stomach and spleen were adherent to the mediastinum and vertebrae. The patient developed hypotension and persistent hypoxaemia and expired at age of 26 h. Autopsy revealed bilateral agenesis of diaphragm, hypoplasia of lungs, and pancreas fibrosis with mild hypoplasia of islets of Langerhans.

CONCLUSION

Bilateral agenesis of diaphragm associated with pancreas fibrosis is a rare entity, and its clinical significance needs further investigation.

Early postnatal dexamethasone therapy may lessen lung inflammation in premature infants with respiratory distress syndrome on mechanical ventilation

Early postnatal use of dexamethasone has recently been shown to be effective in improving the pulmonary status in premature infants with respiratory distress syndrome (RDS). To study the effect of dexamethasone on pulmonary inflammatory responses, we studied ten infants treated with dexamethasone and ten infants without this treatment. Serial tracheal aspirates were obtained for cell counts, neutrophil counts, total protein concentrations, and leukotriene B4 (LTB4) and 6-keto prostaglandin (PG)F(1 alpha) levels before and after starting the study. Infants in the dexamethasone-treated group required significantly lower mean airway pressures for ventilation and had lower PaCO2 values from day 3 to day 14 than infants in the control group, suggesting better pulmonary function. For infants in the dexamethasone group, the tracheal aspirates showed significantly lower cell and neutrophil counts, protein concentrations, and 6-keto-PGF(1 alpha) and LTB4 levels than in the control group. We conclude that early postnatal dexamethasone therapy may lessen lung inflammation and improve pulmonary function in infants with RDS.

The best operation for rectal prolapse

Rectal prolapse remains a disorder for which the cause is not clearly understood and the best method of management is debated. Because the natural history of prolapse frequently leads to complications of incontinence and constipation, we believe that all patients presenting with internal and external prolapse should be considered for repair. Although the type of operative repair recommended may vary, it is clear that all patients with external rectal prolapse should be offered some type of repair. What is not clear from the literature is the appropriate management of those patients with internal prolapse. As shown in the George Washington University experience, surgery is rarely performed for isolated internal prolapse. Most patients who present with internal prolapse also have an associated enterocele, rectocele, or cystocele. Repair of the internal prolapse and the associated disorder may benefit many of these patients. If internal prolapse is an isolated finding, it is not clear to what extent the prolapse is responsible for the patient's symptoms, and repair is generally not advised. These guidelines are easy to enumerate but may be difficult to practice in some patients. Therefore, ongoing evaluation of clinical results is critical to improve our understanding of these disorders. This discussion has outlined the current theories of the cause of rectal prolapse, the symptoms and findings patients present with, and the possible approaches to repair.

Intracellular pH regulation in cultured human pleural mesothelial cells

The human pleural space is lined by a single layer of mesothelial cells, the intracellular pH (pH(i)) of which has never been investigated. In the present study, the intrinsic buffering power of H+ ions (beta(i)) and the pH(i) regulatory systems were investigated in primary cultures of human pleural mesothelial cells (PMCs) with microspectrofluorimetry. We found: (1) that at the resting pH(i), the beta(i) was low and increased as the pH(i) decreased; (2) that the pH(i) recovery was largely inhibited either with Na+-free medium or nominally HCO3 free medium containing ethyl-isopropyl amiloride (EIPA); (3) a 4-4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS)-sensitive, Na+/HCO3-dependent, but Cl(-)-independent acid extrusion mechanism in CO2/HCO3 buffer; and (4) that in the same buffer, a DIDS- sensitive but Na+-independent alkalosis was induced by intracellular Cl- depletion. We therefore conclude that at least three membrane pH(i) regulators are involved in regulating the pH(i) in PMCs, these being the EIPA-sensitive Na+-H+ exchanger; a novel electroneutral, DIDS-sensitive Na+-HCO3 cotransporter; and the DIDS-sensitive Cl(-)-HCO3 exchanger. Furthermore, under physiologic conditions, the Na+-HCO3 cotransporter plays a more important role in extrusion of excess intracellular H+ ions than does the Na+-H+ exchanger.

Safety and immunogenicity of a conjugated Haemophilus influenzae type B polysaccharide-Neisseria meningitidis outer membrane protein vaccine

This study was performed to determine the immunogenicity and safety of a conjugate Haemophilus influenzae type b (Hib) vaccine (PedvaxHIB:Merck Sharp & Dohme Inc, West Point, PA, USA) in Taiwanese children. There were two groups in this study. Group A included 56 infants at 2 months of age, who received an initial dose of Hib conjugate vaccine at age 2 months and 4 months. Another booster dose was given between 12 and 15 months of age. Group B included 58 children, aged 11 to 14 months, who were vaccinated at the time of enrollment and 2 months after the first vaccination. The results showed that this Hib conjugate vaccine was highly immunogenic with 100% and 86% of vaccinees in group A developing anti-Hib polyribosylribitol phosphate (PRP) antibody titers above 0.15 microgram/mL and 1 microgram/mL, respectively, after two vaccinations. A slightly better response rate was observed in group B, with 100% and 97% of vaccinees developing antibody titers above 0.15 microgram/mL and 1 microgram/ml, respectively, after two vaccinations. A significant booster effect was seen in group A; the proportion of subjects with antibody titers above 1 microgram/mL increased from 38% to 95%, and the geometric mean titer increased from 0.68 microgram/mL to 11.92 micrograms/mL. Adverse reactions were uncommon. Mild reactions consisted of low-grade fever and local discomfort. We conclude that the Hib conjugate vaccine is highly immunogenic and safe when given to Taiwanese children as young as 2 months of age.

Heterochromatin (chromocentres) and regeneration of invertebrates and vertebrates: a correlation

Previous investigations using several species of invertebrates have indicated a correlation between nuclear chromocentre content and the ability to regenerate. Such findings have resulted in the formulation of the hypothesis that the ability to regenerate may be dependent on cellular heterochromatin content. In order to test this concept further, a number of additional invertebrates were stained for heterochromatin (nuclear chromocentres). In accordance with the hypothesis, each species tested was found to contain numerous chromocentres. Many chromocentres were also found in cells of several vertebrates capable of partial regeneration, thereby extending the hypothesis to vertebrate regeneration. These findings provide additional supporting evidence for a correlation between cellular heterochromatin and the ability to regenerate.

Phrenic nerve transfer in the repair of brachial plexus injuries: an animal model

Ten young mongrel dogs underwent unilateral denervation of the brachial plexus. In six dogs, a 2-cm segment of phrenic nerve autograft was sutured to either the resected musculocutaneous nerve or the radial nerve. A hemoclip was applied to either musculocutaneous or radial nerve in the control groups. Five months postoperatively, the grafted musculocutaneous nerve demonstrated less fibrous tissue and less muscle atrophy of the biceps when compared to the control group with clipped nerve. In the group with the grafted radial nerve, the electromyographic findings of multiphasic action potential and muscle contraction from electric stimulation suggested reinnervation of the radial nerve.

IN CONCLUSION

phrenic nerve transfer may be used to repair specific damages to nerve trunk with histological, electromyographic and clinical recovery.