Changes of inducible nitric oxide synthase in aortic cells during the development of hypertension: effect of angiotensin II

Nitric oxide (NO) generation by inducible nitric oxide synthase (iNOS) in the vascular smooth muscle cells (VSMC), may play a role in blood vessel tone regulation. Lipopolysaccharide (LPS) induced iNOS activity and subsequent nitrite production by cultured aortic VSMC, from SHR with an established chronic blood pressure elevation (adult SHR) or during the period preceding the development of hypertension (young SHR) and from age-matched normotensive Wistar (W) rats were compared. Angiotensin II (Ang II) effect was also evaluated. Both basal LPS-induced iNOS activity and nitrite accumulation were significantly lower in young SHR VSMC compared to young W rat cells. In contrast, adult hypertensive and normotensive rat cells did not differ in NO generation. Besides, young SHR cells exhibited a significant smaller iNOS activity and nitrites than adult SHR cells. After 24 h-incubation with Ang II, both variables were markedly reduced in all groups. The proportional reduction of iNOS activity and nitrites by Ang II was not different between hypertensive and normotensive rat cells, at any age. However, this Ang II inhibitory effect was greater in both adult SHR and W cells than in VSMC from young rats. In conclusion, a reduced LPS-induced iNOS activity and NO generation was observed in VSMC form spontaneously hypertensive rats before the raise of blood pressure, but not in adult hypertensive rat cells. Additionally, an inhibitory effect of angiotensin II on these variables is described. We can speculate that the impairment in vascular smooth muscle NO production precedes the development of hypertension in SHR and may play a pathophysiologic role in the early blood pressure elevation in genetically hypertensive rats.

Binding thermodynamics of the transition state analogue coformycin and of the ground state analogue 1-deazaadenosine to bovine adenosine deaminase

Binding of the transition state analogue coformycin and the ground state analogue 1-deaazadenosine to bovine adenosine deaminase have been thermodynamically characterized. The heat capacity changes for coformycin and 1-deazaadenosine binding are -4.7 +/- 0.8 kJ/mole-K and -1.2 +/- 0.1 kJ/mole-K, respectively. Since the predominant source of heat capacity change in enzyme interactions are changes in the extent of exposure of nonpolar amino acid side chains to the aqueous environment and the hydrophobic effect is the predominant factor in native structure stabilization, we propose that the binding of either class of ligand is associated with a stabilizing enzyme conformational change with coformycin producing the far greater effect. Analysis of the T dependence of the second order rate constant for formation of the enzyme/coformycin complex further reveals that the conformational change is not rate limiting. We propose that the enzyme may facilitate catalysis via the formation of a stabilizing conformation at the reaction transition state.

Hepatitis C virus RNA-dependent RNA polymerase (NS5B) as a mediator of the antiviral activity of ribavirin

Ribavirin is administered in combination with interferon-alpha for treatment of hepatitis C virus (HCV) infection. Recently, we demonstrated that the antiviral activity of ribavirin can result from the ability of a viral RNA polymerase to utilize ribavirin triphosphate and to incorporate this nucleotide with reduced specificity, thereby mutagenizing the genome and decreasing the yield of infectious virus (Crotty, S., Maag, D., Arnold, J. J., Zhong, W., Lau, J. Y., Hong, Z., Andino, R., and Cameron, C. E. (2000) Nat. Med. 6, 1375-1379). In this study, we performed a quantitative analysis of a novel HCV RNA polymerase derivative that is capable of utilizing stably annealed primer-template substrates and exploited this derivative to evaluate whether lethal mutagenesis of the HCV genome is a possible mechanism for the anti-HCV activity of ribavirin. These studies demonstrate HCV RNA polymerase-catalyzed incorporation of ribavirin opposite cytidine and uridine. In addition, we demonstrate that templates containing ribavirin support CMP and UMP incorporation with equivalent efficiency. Surprisingly, templates containing ribavirin can also cause a significant block to RNA elongation. Together, these data suggest that ribavirin can exert a direct effect on HCV replication, which is mediated by the HCV RNA polymerase. We discuss the implications of this work on the development of nucleoside analogs for treatment of HCV infection.

The mechanism of action of ribavirin: lethal mutagenesis of RNA virus genomes mediated by the viral RNA-dependent RNA polymerase

Ribavirin (1-beta-D-ribofuranosyl-1,2,4-triazole) is a broad-spectrum antiviral nucleoside that is currently used in combination with interferon-alpha to treat hepatitis C virus infection and as a monotherapy to treat severe cases of respiratory syncytial virus infection and Lassa fever virus infection. The mechanism of action of ribavirin has been studied for decades. These studies have suggested that the antiviral activity of ribavirin may be related to its ability to cause a decrease in intracellular guanosine triphosphate pools, to inhibit capping of viral transcripts or to suppress humoral and cellular immune responses. Last year, another possibility was added to this list. The new proposition is that ribavirin, when converted to the triphosphate, is utilized by the viral RNA-dependent RNA polymerase and causes lethal mutagenesis of the viral genome. In this article, the data supporting this new hypothesis are reviewed. We discuss the implications of these data on alternative explanations for the apparent failure of ribavirin monotherapy in the treatment of hepatitis C virus infection, connections between developmental defects induced by ribavirin and posttranscriptional gene silencing/RNA interference, and the use of lethal mutagenesis and related concepts as strategies for antiviral therapy.

Aortic smooth muscle cell proliferation and endothelial nitric oxide synthase activity in fructose-fed rats

The aim of this study was to evaluate the proliferative behavior of vascular smooth muscle cells in primary culture (pC-SMC) and the endothelial nitric oxide synthase (eNOS) activity in the endothelial lining of the aorta of fructose-fed rats (FFR). This is an experimental model of syndrome X, a cluster of cardiovascular risk factors including hyperinsulinemia, insulin resistance, and hypertension that has been suggested to be of pathophysiologic importance for the development of atherosclerosis. Male Wistar rats were used: Control (n = 12) and FFR (n = 12). After receiving fructose in drinking water (10% w/v) during 8 weeks, biochemical parameters, systolic blood pressure (SBP) and relative heart weight (RHW) were determined. The proliferative effect of 10% fetal calf serum (FCS) was examined in aortic pC-SMC by [3H]thymidine incorporation and by cell counting. Ca2+/calmodulin-dependent NOS activity was estimated in aortic endothelial lining and in heart tissue homogenates by conversion of [3H]arginine into [3H]citrulline. Fructose-fed rats showed hyperinsulinemia (P = .0263), altered glucose tolerance test (P < .001), higher SBP (P < .0001), and RHW (P = .0145), compared to control rats. These animals also showed an increase of 10% FCS-induced [3H]thymidine incorporation (P < .0001) and cell number of aortic pC-SMC (P = .0049) and decreased eNOS activity in both aortic endothelium (P = .0147) and cardiac tissue (P < .0001). These data support the hypothesis that syndrome X is associated to changes in SMC proliferation and endothelial dysfunction, which could be involved in the onset or progression of the atherogenic process.

Evaluation of the impact of chemical control measures and entomological surveillance on Chagas' disease in the counties of Mambaí and Buritinópolis, Goiás State, Brazil

Epidemiological surveillance activities were implemented in 1980 in Mambaí and Buritinópolis counties, Goiás State. Twenty years later the authors evaluated the impact of these vector control measures on Chagas' disease transmission, based on entomological indicators. Entomological investigation was conducted using the man-hour technique and covering all domiciles. In order to study vector food sources the stomach contents of triatomines were analyzed using the modified precipitins technique. Triatomines were shown to be present in 48 (71.6%) of the 67 locations. Peridomiciliary infestation rates in Mambaí and Buritinópolis were 8.7% and 12.1%, respectively, while intradomiciliary rates were 0.7% and 1.2%. Triatoma sordida was the species identified in 97.3% of all captured specimens. It was also the only species found to be naturally infected with Trypanosoma cruzi. Birds were the most frequent food source (45%) for Triatoma sordida. The most significant result was the complete absence of Triatoma infestans in the two counties.

Asymptomatic lingual tonsillar hypertrophy and difficult airway management: a report of three cases

PURPOSE

To report on the airway management of three cases of asymptomatic lingual tonsillar hypertrophy (LTH).

MATERIAL

On three separate occasions, patients presenting for elective surgery were subsequently found to have asymptomatic LTH. In all cases preoperative airway examination was essentially unremarkable and no unusual difficulties were anticipated. In the first case, despite an inability to visualize the glottic opening, the patient was intubated successfully on the initial attempt and had no further problems in the perioperative period. In the second case, neither direct laryngoscopy, utilizing the MacIntosh and McCoy blades, nor fibreoptic visualization enabled successful intubation. Ventilation was maintained with a laryngeal mask airway (LMA) until the anesthetic was reversible. Upon awakening and removal of the LMA, the patient totally obstructed and could not be ventilated, necessitating emergency cricothyroidotomy. The third patient was an elderly gentleman in whom successful intubation was eventually achieved, with considerable difficulty, by the otorhinolaryngologist (ENT surgeon) utilizing a straight blade. On a second occasion, he was again intubated by the same ENT surgeon, this time utilizing the anterior commissure blade. All three patients were subsequently discharged without further sequelae.

CONCLUSION

Asymptomatic LTH can cause varying degrees of unexpected difficulty in securing the airway and, at present, no single method will necessarily improve the chances of successful intubation. Therefore, strategies to manage unanticipated difficult intubation secondary to supraglottic airway pathology need to be performed and practiced, including the establishment of a transtracheal airway.

[A 13-year clinical study on 190 chronic chagasic patients from Mambaí, Goiás, Brazil]

A prospective study was performed on the clinical, electrocardiographic (ECG) and radiologic aspects of the esophagus in 190 chagasic patients, for on average follow-up period of 13 years. We found 108 (56.8%) patients who remained in the same clinical state, 72 (37.9%) patients with progressive illness and 10 (5.3%) patients whose previous ECG abnormalities subsided. Thirty nine out of 72 patients with progressive disease developed cardiopathy or aggravation of previous illness, 32 developed into megaesophagus or an existing picture deteriorated and 12 developed or showed worsening of the colopathy. Of 72 patients, 11 presented with associated forms. The development of cardiopathy was greater in males 29.6% (21/71) than in females 15.1% (18/119), p =0.015. There were 19 new cases of cardiopathy, and 20 of aggravated previous disease. The incidence of megaesophagus was 14.9% (23/154), with nine patients whose previous disease worsened. The progression of colopathy was greater in females 9.2% (11/119) than in males 1.4% (1/71), p = 0.026.

A novel mechanism to ensure terminal initiation by hepatitis C virus NS5B polymerase

Hepatitis C virus (HCV) nonstructural protein 5B (NS5B) RNA-dependent RNA polymerase (RdRp) has acquired a unique beta-hairpin in the thumb subdomain which protrudes toward the active site. We report here that this beta-hairpin plays an important role in positioning the 3' terminus of the viral RNA genome for correct initiation of replication. The presence of this beta-hairpin interferes with polymerase binding to preannealed double-stranded RNA (dsRNA) molecules and allows only the single-stranded 3' terminus of an RNA template to bind productively to the active site. We propose that this beta-hairpin may serve as a "gate" which prevents the 3' terminus of the template RNA from slipping through the active site and ensures initiation of replication from the terminus of the genome. This hypothesis is supported by the ability of a beta-hairpin deletion mutant that utilizes dsRNA substrates and initiates RNA synthesis internally. The proposed terminal initiation mechanism may represent a novel replication strategy adopted by HCV and related viruses.

Personal and environmental factors associated with physical inactivity among different racial-ethnic groups of U.S. middle-aged and older-aged women

Personal, program-based, and environmental barriers to physical activity were explored among a U.S. population-derived sample of 2,912 women 40 years of age and older. Factors significantly associated with inactivity included American Indian ethnicity, older age, less education, lack of energy, lack of hills in one's neighborhood, absence of enjoyable scenery, and infrequent observation of others exercising in one's neighborhood. For all ethnic subgroups, caregiving duties and lacking energy to exercise ranked among the top 4 most frequently reported barriers. Approximately 62% of respondents rated exercise on one's own with instruction as more appealing than undertaking exercise in an instructor-led group, regardless of ethnicity or current physical activity levels. The results underscore the importance of a multifaceted approach to understanding physical activity determinants in this understudied, high-risk population segment.

Compartment syndrome following intravenous regional anesthesia

PURPOSE

To present two cases of upper extremity compartment syndrome following intravenous regional anesthesia.

CLINICAL FEATURES

Case 1: A 57-yr-old man presented for surgical release of a left-hand Dupuytren's contracture. The procedure was performed under iv regional anesthesia with 360 mg lidocaine and sedation with 150 microg fentanyl and 1.5 mg midazolam. Tourniquet time was 107 min at a pressure of 260 mmHg using three different tourniquet sites. Within minutes of tourniquet release, increased forearm muscle tension, hand anesthesia, pallor, and limited motor function developed. Serum CK and myoglobin levels rose. Myoglobinuria was present. Several fasciotomies and aggressive fluid therapy were performed. Patient made almost full recovery. Case 2: A 73-yr-old woman with controlled hypertension had Dupuytren fasciotomy of her right hand under iv regional anesthesia with 200 mg lidocaine and sedation using 75 microg fentanyl and 1.5 mg midazolam. Tourniquet time was 64 min at a pressure of 250 mmHg using three different tourniquet sites. The patient complained of pain at the iv site during injection of local anesthetic, third tourniquet inflation and after deflation of tourniquet. Thirty minutes after arrival in PACU, her fingers were bluish. She complained of pain and swelling of the forearm. Under general anesthesia, fasciectomy was performed. Myoglobin and CPK levels rose. CPK MB was high but troponin was negative. Three days later she developed pulmonary embolism. She was heparinized and subsequently discharged home. She recovered completely.

CONCLUSION

Compartment syndrome may have a rapid and severe onset. Etiology of our cases is still not established. We postulate that increased tissue pressure may be the cause. The anesthesiologists must be aware of compartment syndrome during regional anesthesia.

Absence of both circadian rhythm and Trypanosoma cruzi periodicity with xenodiagnosis in chronic chagasic individuals

Xenodiagnoses were performed every 3 hours using 10 Triatoma infestans 3rd instar for 24 to 72 hours, in 18 chronic chagasics with positive serology and/or xenodiagnosis. There was no statistically significant difference in the positivity of assays performed during the day (9:00 to 18:00 h) compared to those performed at night (21:00 to 6:00 h), (chi 2 = 0.1526 p = 0.696). Xenodiagnosis was performed in ten of the patients for 13 successive days but there was no periodicity detected in the positive assays.

Determinants of leisure time physical activity in rural compared with urban older and ethnically diverse women in the United States

STUDY OBJECTIVE

Determinants of leisure time physical activity (LTPA) in rural middle aged and older women of diverse racial and ethnic groups are not well understood. This study examined: (1) urban-rural differences in LTPA by sociodemographic factors, (2) urban-rural differences in LTPA determinants, and (3) the pattern of relations between LTPA determinants and LTPA.

DESIGN

A modified version of the sampling plan of the Behavioral Risk Factor Surveillance Survey (BRFSS) was used. Zip codes were selected with 20% or more of each of the following race/ethnic groups: African American, American Indian/Alaskan Native (AI/AN), and Hispanic. A comparison group of white women were also surveyed using standard BRFSS techniques.

PARTICIPANTS

Rural (n=1242) and urban (n=1096) women aged 40 years and older from the US Women's Determinants Study.

MAIN RESULTS

Rural women, especially Southern and less educated women, were more sedentary than urban women. Rural women reported more personal barriers to LTPA, cited caregiving duties as their top barrier (compared with lack of time for urban women), and had greater body mass indices. Rural women were less likely to report sidewalks, streetlights, high crime, access to facilities, and frequently seeing others exercise in their neighbourhood. Multivariate correlates of sedentary behaviour in rural women were AI/AN and African American race, older age, less education, lack of enjoyable scenery, not frequently seeing others exercise, greater barriers, and less social support (p<0.05); and in urban women, older age, greater barriers, less social support (p<0.05), and less education (p<0.09).

CONCLUSIONS

Rural and urban women seem to face different barriers and enablers to LTPA, and have a different pattern of determinants, thus providing useful information for designing more targeted interventions.

Eleven novel APC mutations identified in Portuguese FAP families

Germline mutations of the adenomatous polyposis coli (APC) gene are responsible for familial adenomatous polyposis (FAP), an autosomal dominant predisposition to colorectal cancer. In the present study we screened all of the exons of the APC gene in individuals belonging to 85 Portuguese FAP families. We here report eleven novel mutations which are predominantly frameshifts or single base substitutions, resulting in premature stop codons. Hum Mutat 16:178, 2000.

Characterization of the chitin biosynthesis process as a compensatory mechanism in the fks1 mutant of Saccharomyces cerevisiae

Deletion of the 1,3-beta-D-glucan synthase gene FKS1 in Saccharomyces cerevisiae induces a compensatory mechanism that is reflected in a significant increase in chitin synthase III (CSIII) activity, leading to high rates of chitin synthesis. Deregulation of CSIII activity is mainly due to the intracellular delocalization of Chs3p and Chs4p, the two main components of the CSIII active complex.

Personal and environmental factors associated with physical inactivity among different racial-ethnic groups of U.S. middle-aged and older-aged women

Personal, program-based, and environmental barriers to physical activity were explored among a U.S. population-derived sample of 2,912 women 40 years of age and older. Factors significantly associated with inactivity included American Indian ethnicity, older age, less education, lack of energy, lack of hills in one's neighborhood, absence of enjoyable scenery, and infrequent observation of others exercising in one's neighborhood. For all ethnic subgroups, caregiving duties and lacking energy to exercise ranked among the top 4 most frequently reported barriers. Approximately 62% of respondents rated exercise on one's own with instruction as more appealing than undertaking exercise in an instructor-led group, regardless of ethnicity or current physical activity levels. The results underscore the importance of a multifaceted approach to understanding physical activity determinants in this understudied, high-risk population segment.

Do changes in physical activity lead to dietary changes in middle and old age?

INTRODUCTION

Research examining the relationship between dietary factors and physical activity patterns has yielded conflicting findings. Few prospective studies have examined whether individuals who change their level of physical activity make corresponding changes in their diet.

METHODS

The current study examined, in two randomized clinical trials of physical activity, whether self-report of dietary factors changed over a 1-year period, whether these changes differed by gender or exercise-intervention group, and whether changes in physical activity led to changes in dietary factors. Participants included 268 men and women aged 50-65 years who participated in the Stanford-Sunnyvale Health Improvement Project I (SSHIP-I) and 103 men and women aged 65-82 years who participated in SSHIP-II. In both trials we recruited participants through random-digit telephone dialing and citywide promotion.

RESULTS

Overall, participants adopted healthier diets over the 1-year period. The SSHIP-I participants decreased their consumption of total calories, total fat, saturated fat, protein, and cholesterol. The SSHIP-II participants decreased their consumption of high-fat, high-cholesterol foods. The SSHIP-I women were more likely than men to decrease their intake of total fat and protein (p < 0.01), as well as total calories, saturated fat, and cholesterol (p < 0.05). However, we found that changes in physical activity were not associated with changes in self-report measures of dietary habits.

CONCLUSIONS

We found no evidence to support the idea that changes in physical activity are a gateway for changes in dietary factors in middle-aged and older adults.

[Analysis of the resonant frequency of the middle ear in otosclerosis]

Multifrequency tympanometry scans pressures and frequencies from 226 to 2000 Hz to analyze the resonant frequency of the middle ear, which determines the balance between stiffness and mass. We studied 143 patients (a total of 200 ears) diagnosed as otosclerosis at the E.N.T. Service of Santiago de Compostela University Hospital Complex, and 136 control subjects. The mean age of patients was 47.7 years; women were predominant (female/male ratio 2.25:1). The mean duration of the disease was 10.4 years. Using the Virtual model 310 tympanometer, we calculated the resonant frequency through the susceptance tympanogram, corresponding to the minimal frequency at which the central notch of the tympanograrn was equal to or less than the negative tail. The mean resonant frequency was 1230 Hz, the tympanometric amplitude was 88.32 daPa, and the admittance of the middle ear was 0.63 cc. We confirmed an increase in the resonant frequency in patients with otosclerosis compared with normal subjects (1132.33 Hz), and a decrease in the admittance of the middle ear. The relation between the two values was significant.

Molecular characterization and identification of biocontrol isolates of Trichoderma spp

The most common biological control agents (BCAs) of the genus Trichoderma have been reported to be strains of Trichoderma virens, T. harzianum, and T. viride. Since Trichoderma BCAs use different mechanisms of biocontrol, it is very important to explore the synergistic effects expressed by different genotypes for their practical use in agriculture. Characterization of 16 biocontrol strains, previously identified as "Trichoderma harzianum" Rifai and one biocontrol strain recognized as T. viride, was carried out using several molecular techniques. A certain degree of polymorphism was detected in hybridizations using a probe of mitochondrial DNA. Sequencing of internal transcribed spacers 1 and 2 (ITS1 and ITS2) revealed three different ITS lengths and four different sequence types. Phylogenetic analysis based on ITS1 sequences, including type strains of different species, clustered the 17 biocontrol strains into four groups: T. harzianum-T. inhamatum complex, T. longibrachiatum, T. asperellum, and T. atroviride-T. koningii complex. ITS2 sequences were also useful for locating the biocontrol strains in T. atroviride within the complex T. atroviride-T. koningii. None of the biocontrol strains studied corresponded to biotypes Th2 or Th4 of T. harzianum, which cause mushroom green mold. Correlation between different genotypes and potential biocontrol activity was studied under dual culturing of 17 BCAs in the presence of the phytopathogenic fungi Phoma betae, Rosellinia necatrix, Botrytis cinerea, and Fusarium oxysporum f. sp. dianthi in three different media.

Opsonic potential, protective capacity, and sequence conservation of the Treponema pallidum subspecies pallidum Tp92

By means of a differential screening technique, a 92-kDa antigen, designated Tp92, was identified from Treponema pallidum subspecies pallidum. This protein is similar in sequence to the protective surface antigens D15 from Haemophilus influenzae and Oma87 from Pasteurella multocida. Amino acid sequence analyses revealed a cleavable N-terminal signal sequence and predicted the outer membrane location for Tp92. In support of this, antiserum raised against recombinant Tp92 promotes opsonization and phagocytosis of T. pallidum by rabbit macrophages, and anti-Tp92 reactivity is absent from washed treponemal preparations presumed to be lacking outer membranes. The Tp92 amino acid sequence is 95.5%-100% conserved among 11 strains representing 4 pathogenic treponemes, and immunization with recombinant Tp92 partially protected rabbits from subsequent T. pallidum challenge. These results demonstrate that Tp92 is an invariant, immunoprotective antigen that may be present on the surface of T. pallidum and may represent a potential vaccine candidate for syphilis.

Multiple alleles of Treponema pallidum repeat gene D in Treponema pallidum isolates

Two new tprD alleles have been identified in Treponema pallidum: tprD2 is found in 7 of 12 T. pallidum subsp. pallidum isolates and 7 of 8 non-pallidum isolates, and tprD3 is found in one T. pallidum subsp. pertenue isolate. Antibodies against TprD2 are found in persons with syphilis, demonstrating that tprD2 is expressed during infection.

[Evaluation of an specific treatment for Trypanosoma cruzi in children, in the evolution of the indeterminate phase]

Twelve chagasic patients between the ages of seven and twelve, in the indeterminate phase with serology and xenodiagnosis positive, received the specific treatment. Eight of these were evaluated after an eight-year treatment period and four were followed-up during 20 years. Two patients took 7 mg/kg of nifurtimox during sixty and ninety days and ten of these used 5-7 mg/kg of benznidazole during 60 days. The clinical outcome was verified through clinical examination, electrocardiogram and contrasted X-ray of the esophagus. After the treatment, only one patient presented negativity in all the examinations. Seven (58.4%) remained in the indeterminate form and despite the precocious treatment four chagasic patients (33.3%) progressed clinically to second degree cardiopathy and/or megaesophagus.

Cutaneous primary paracoccidioidomycosis

Paracoccidioidomycosis is a common fungal infection in Latin America. Few cases have been described in non-endemic countries and their diagnosis without the correct suspicion, bearing in mind that the latency period might be up to 60 years, may not be easy. We report the case of a 59-year-old man who worked as a taxi driver for 25 years in Venezuela. Cutaneous paracoccidioidomycosis was diagnosed one year after he returned to Spain. No internal signs or symptoms of the disease were found and cell-mediated immunity showed no depression. Our case suggested us to consider direct cutaneous infection, although respiratory tract is believed to be the most frequent portal of entry for this infection.

[Inflammatory pseudotumor of the maxillary sinus: report of a new case and review of the literature]

A new case of inflammatory pseudotumor (IPT) of the maxillary sinus is presented. The clinical and histological features of this rare entity are discussed. Immunohistochemical studies support a possible myofibroblastic origin. Early diagnosis is important to prevent IPT, classified as a benign disease, from becoming a progressive destructive lesion.

The tprK gene is heterogeneous among Treponema pallidum strains and has multiple alleles

We have previously shown that the TprK antigen of T. pallidum, Nichols strain, is predominantly expressed in treponemes obtained 10 days after infection and that the hydrophilic domain of TprK is a target of opsonic antibodies and confers significant protection against homologous challenge. The T. pallidum genome sequence reported the presence of a single copy of the tprK gene in the Nichols strain. In the present study we demonstrate size heterogeneity in the central portions of the TprK hydrophilic domains of 14 treponemal isolates. Sequence analysis of the central domains and the complete open reading frames (ORFs) of the tprK genes confirms this heterogeneity. Further, multiple tprK sequences were found in the Nichols-defined tprK locus in three isolates (Sea 81-4, Bal 7, and Bal 73-1). In contrast, only a single tprK sequence could be identified in this locus in the Nichols strain. Alignment of the DNA and deduced amino acid sequences of the whole tprK ORFs shows the presence of seven discrete variable domains flanked by highly conserved regions. We hypothesize that these heterogeneous regions may be involved in antigenic heterogeneity and, in particular, evasion of the immune response. The presence of different tprK alleles in the tprK locus strongly suggests the existence of genetically different subpopulations within treponemal isolates.

Noninvasive evaluation of cardiac dysfunction by echocardiography in streptozotocin-induced diabetic rats

BACKGROUND

There has not been a noninvasive in vivo longitudinal evaluation of cardiac function in diabetic rats. The objective of this study is to examine the time course of development of cardiac dysfunction in streptozotocin (STZ)-induced diabetic rats.

METHODS AND RESULTS

Cardiac function was evaluated by M-mode and Doppler echocardiography in anesthetized Wistar rats at 2, 4, 5, 6, and 8 weeks after injection with 65 mg of STZ/kg and in age-matched control rats before and after the administration of isoproterenol. Body weight (BW) was significantly less and blood glucose level significantly greater in diabetic rats compared with controls at 2 weeks and remained at these levels at all time points. The calculated left ventricular (LV) mass appeared slightly decreased in diabetic rats. However, LV mass-BW ratios were similar in controls and diabetic rats at 2, 4, and 5 weeks, but were significantly greater in diabetic rats at 6 and 8 weeks. Basal heart rate (HR) was significantly lower in diabetic rats at all time points studied. Basal LV systolic and diastolic dimensions, fractional shortening (FS), velocity of circumferential shortening (Vcf), peak emptying rate (PER), peak filling rate (PFR), and aortic peak velocity (APV) were not significantly different between controls and diabetic rats at 2 and 4 weeks. PER and PFR were significantly less in 5-week diabetic rats. However, Vcf, PER, and PFR were significantly less and FS and APV were similar at 6 and 8 weeks. Administration of isoproterenol increased HR, Vcf, FS, PFR, and PER in controls at all time points, but the increases in diabetic rats at 5, 6, and 8 weeks were less compared with those in controls. The increase in APV was significantly less in diabetic rats at all time points studied.

CONCLUSION

STZ-induced diabetic rats showed bradycardia before contractile dysfunction. Overt and covert contractile dysfunction unmasked by isoproterenol begins at 5 weeks of diabetes. The overt LV systolic and diastolic dysfunction are fully manifested after 6 weeks of diabetes.

Intramolecular glycosylation to form 4-methoxy-2,6-dioxopyrimidine nucleosides via O6,5'-cyclonucleosides

Lewis-acid promoted intramolecular N1 glycosylation to form the novel O6,5'-cyclonucleoside 1a occurs in high yield from the corresponding acyclic thiophenyl-glycoside 12. The relative stability of the O6,5' tether compared with O2,5' and O2,3' tethers is reported. Cleavage of the anhydro bond was effected with aqueous base to yield the 4-methoxybarbituric acid nucleoside analogue 14.

Creation of a functional S-nitrosylation site in vitro by single point mutation

Here we show that in extrahepatic methionine adenosyltransferase replacement of a single amino acid (glycine 120) by cysteine is sufficient to create a functional nitric oxide binding site without affecting the kinetic properties of the enzyme. When wild-type and mutant methionine adenosyltransferase were incubated with S-nitrosoglutathione the activity of the wild-type remained unchanged whereas the activity of the mutant enzyme decreased markedly. The mutant enzyme was found to be S-nitrosylated upon incubation with the nitric oxide donor. Treatment of the S-nitrosylated mutant enzyme with glutathione removed most of the S-nitrosothiol groups and restored the activity to control values. In conclusion, our results suggest that functional S-nitrosylation sites can develop from existing structures without drastic or large-scale amino acid replacements.

Molecular dissection of transjunctional voltage dependence in the connexin-32 and connexin-43 junctions

Most gap junction channels are sensitive to the voltage difference between the two cellular interiors, termed the transjunctional voltage (V(j)). In several junctions, the conductance transitions induced by V(j) show more than one kinetic component. To elucidate the structural basis of the fast and slow components that characterize the V(j )dependence of connexin-32 (Cx32) and connexin-43 (Cx43) junctions, we created deletions of both connexins, where most of the carboxy-terminal (CT) domain was removed. The wild-type and "tailless" mutants were expressed in paired Xenopus oocytes, and the macroscopic gating properties were analyzed using the dual voltage clamp technique. Truncation of the CT domain of Cx32 and Cx43 abolished the fast mechanism of conductance transitions and induced novel gating properties largely attributable to the slow mechanism of gating. The formation of hybrid junctions comprising wild-type and truncated hemichannels allowed us to infer that the fast and slow components of gating reside in each hemichannel and that both gates close at a negative V(j) on the cytoplasmic side. Thus we conclude that the two kinetic components of V(j)-sensitive conductance are a result of the action of two different gating mechanisms. They constitute separate structures in the Cx32 and Cx43 molecules, the CT domain being an integral part of fast V(j) gating.

Methionine adenosyltransferase S-nitrosylation is regulated by the basic and acidic amino acids surrounding the target thiol

S-Adenosylmethionine serves as the methyl donor for many biological methylation reactions and provides the propylamine group for the synthesis of polyamines. S-Adenosylmethionine is synthesized from methionine and ATP by the enzyme methionine adenosyltransferase. The cellular factors regulating S-adenosylmethionine synthesis have not been well defined. Here we show that in rat hepatocytes S-nitrosoglutathione monoethyl ester, a cell-permeable nitric oxide donor, markedly reduces cellular S-adenosylmethionine content via inactivation of methionine adenosyltransferase by S-nitrosylation. Removal of the nitric oxide donor from the incubation medium leads to the denitrosylation and reactivation of methionine adenosyltransferase and to the rapid recovery of cellular S-adenosylmethionine levels. Nitric oxide inactivates methionine adenosyltransferase via S-nitrosylation of cysteine 121. Replacement of the acidic (aspartate 355) or basic (arginine 357 and arginine 363) amino acids located in the vicinity of cysteine 121 by serine leads to a marked reduction in the ability of nitric oxide to S-nitrosylate and inactivate hepatic methionine adenosyltransferase. These results indicate that protein S-nitrosylation is regulated by the basic and acidic amino acids surrounding the target cysteine.

Isokinetic assessment of spasticity in subjects with traumatic spinal cord injury (ASIA A)

OBJECTIVE

To assess resistance to passive isokinetic movements at specified speeds and range of motion, as a measure of muscular tonus.

METHODS

A group of 12 subjects with complete traumatic spinal cord injury and a group of 12 able-bodied subjects were analysed, distinguishing the level of spasticity in the SCI group. Maximum eccentric peak torque was observed in passive isokinetic flexion (F) and extension (E) knee movement in displacements of 30, 60 and 120 per second.

RESULTS

The Student t-test showed that the average torque in the injured group was significantly higher than in the control group (F= 120 degrees per second, P<0.001). Variance analysis showed that the lower level presented lower torque levels (E=60 and 120 degrees per second, P<0.032), while those in the higher level presented higher torque levels (F and E=60 and 120 per second, P<0.032) when compared to the control group. In the control group the Student t-test (P<0.0006) showed a significantly different muscle behavior (Flexion>Extension Torque).

CONCLUSION

By using isokinetic assessment it was possible to quantify hypertonic spasticity in a group of subjects with spinal cord injury, distinguishing groups with higher and lower levels of spasticity as compared to a control group.

Sequence conservation of glycerophosphodiester phosphodiesterase among Treponema pallidum strains

Previous investigations have demonstrated that immunization with Treponema pallidum subsp. pallidum glycerophosphodiester phosphodiesterase significantly protects rabbits from subsequent treponeme challenge. In this report, we show that the glycerophosphodiester phosphodiesterase amino acid sequence is conserved among 12 strains from a total of five pathogenic treponemes. The invariant nature of this immunoprotective antigen makes it an attractive candidate for inclusion in a universal subunit vaccine against T. pallidum infection. In addition, these studies show a silent nucleotide substitution at position 579 of the gpd open reading frame which is consistently observed in the non-T. pallidum subsp. pallidum strains. This sequence alteration introduces a PleI restriction site in the nonsyphilis strains and thus allows genetic differentiation from T. pallidum subsp. pallidum strains.

Altered formation of hemichannels and gap junction channels caused by C-terminal connexin-32 mutations

Hexamers of connexins (Cxs) form hemichannels that dock tightly in series via their extracellular domains to give rise to gap junction channels. Here we examined the ability of a variety of C-terminal Cx32 mutations, most of which have been identified in X-linked Charcot-Marie-Tooth disease, to form hemichannels and to complete gap junction channels using the Xenopus oocyte system. First, we show that undocked wild-type Cx32 hemichannels at the plasma membrane can be detected as opening channels activated by depolarization. We have been able to estimate the efficiency of assembly of complete channels by measuring the time-dependent incorporation of preformed hemichannels into gap junction channels after cell-to-cell contact. These data offer strong evidence that hemichannels are the direct precursors of gap junction channels. Of 11 Cx32 mutants tested, a group of 5 mutations prevented the formation of functional hemichannels at the cell surface, whereas 4 mutations were fully able to form precursors but reduced the ability of hemichannels to assemble into complete channels, and 2 mutants formed channels normally. The data revealed that a minimum length of human Cx32 including the residue Arg-215 is required for the expression of hemichannels at the cell surface and that the efficiency of hemichannel incorporation into complete channels decreased gradually with the progressive shortening of the cytoplasmic C-terminal domain.

Generation of null alleles for the functional analysis of six genes from the right arm of Saccharomyces cerevisiae chromosome II

Using PCR-ligated long flanking homology cassettes, null alleles of six open reading frames (ORFs) from chromosome II have been created in Saccharomyces cerevisiae. Deletants were constructed in three genetic backgrounds: FY1679, W303 and CEN.PK2. Tetrad analysis of heterozygous deletants revealed that none of the ORFs is essential for vegetative growth. Basic phenotypic analysis of haploid deletants showed that deletion of the YBR283c ORF causes a slight growth defect at 30 degrees C and 37 degrees C on glycerol-complete, glucose-complete, and glucose-minimal media only in the FY1679 and W303 backgrounds. Transformation of these deletants with the corresponding cognate gene in a centromeric plasmid complements the defects. Deletion of the YBR287w ORF leads to poor growth on glucose-minimal medium at 15 degrees C in the FY 1679 background. None of the six ORFs seems to be involved in mating or sporulation.

[The behavior of Trypanosoma cruzi parasitemia in chronic chagasics over 13 years]

The parasitemia of 202 chronic chagasics was studied for approximately 13 years by repeated conventional xenodiagnoses. Mean patient age was 41.1 years. They lived in an endemic area; 124 were females and 78 were males. It was seen that the level of parasitemia oscillated. It went up in 14 individuals, went down in 42 and stayed at the same level in 146. In general the parasitemia was reduced. The percentage of xenopositive chagasics, which was 37.6%, 48.5%, and 51% in the first, second and third xenodiagnosis, respectively, in 1976/78, changed to 30.2% in 1988/91 (p = 0.00003). The percentage of positive pools, which was 15.2%, 20.9%, 20.8% in the first, second and third xenodiagnosis, respectively, in 1976/78, changed to 10.4% in 1988/91, (p = 0.00000001). There were 62 patients whose xenodiagnoses were all negative and 23 whose exams were all positive. The percentage of chagasics with high, medium and low parasitemia, which in 1976/78 was 9.4%, 20.8% and 69.8%, respectively, changed to 4.4%, 12.9% and 82.7%, respectively, in 1988/91.

Treponema pallidum major sheath protein homologue Tpr K is a target of opsonic antibody and the protective immune response

We have identified a family of genes that code for targets for opsonic antibody and protective immunity in T. pallidum subspecies pallidum using two different approaches, subtraction hybridization and differential immunologic screening of a T. pallidum genomic library. Both approaches led to the identification of a polymorphic multicopy gene family with predicted amino acid homology to the major sheath protein of Treponema denticola. One of the members of this gene family, tpr K, codes for a protein that is predicted to have a cleavable signal peptide and be located in the outer membrane of the bacterium. Reverse transcription polymerase chain reaction analysis of T. pallidum reveals that Tpr K is preferentially transcribed in the Nichols strain of T. pallidum. Antibodies directed to purified recombinant variable domain of Tpr K can opsonize T. pallidum, Nichols strain, for phagocytosis, supporting the hypothesis that this portion of the protein is exposed at the surface of the treponeme. Immunization of rabbits with the purified recombinant variable domain of Tpr K provides significant protection against infection with the Nichols strain of T. pallidum. This gene family is hypothesized to be central to pathogenesis and immunity during syphilis infection.

Calcification of presumed ovarian carcinoma brain metastases following radiotherapy

Multiple brain metastases from ovarian carcinoma are rare. CT findings are reported in a case treated with whole brain radiation therapy and chemotherapy. Radiological complete-calcified brain metastases following treatment and long morphological changes occurred. Delayed neurological findings in relation to treatment are considered. Long survival with unmodified calcified lesions may suggest a stabilization of CNS disease.

Function and protective capacity of Treponema pallidum subsp. pallidum glycerophosphodiester phosphodiesterase

Infectious syphilis, caused by the spirochete bacterium Treponema pallidum subsp. pallidum, remains a public health concern worldwide. The immune-response evasion mechanisms employed by T. pallidum are poorly understood, and prior attempts to identify immunoprotective antigens for subsequent vaccine design have been unsuccessful. Previous investigations conducted in our laboratory identified the T. pallidum glycerophosphodiester phosphodiesterase as a potential immunoprotective antigen by using a differential immunologic expression library screen. In studies reported here, heterologous expression of the T. pallidum glycerophosphodiester phosphodiesterase in Escherichia coli yielded a full-length, enzymatically active protein. Characterization of the recombinant molecule showed it to be bifunctional, in that it exhibited specific binding to human immunoglobulin A (IgA), IgD, and IgG in addition to possessing enzymatic activity. IgG fractionation studies revealed specific binding of the recombinant enzyme to the Fc fragment of human IgG, a characteristic that may play a role in enabling the syphilis spirochete to evade the host immune response. In further investigations, immunization with the recombinant enzyme significantly protected rabbits from subsequent T. pallidum challenge, altering lesion development at the sites of challenge. In all cases, animals immunized with the recombinant molecule developed atypical pale, flat, slightly indurated, and nonulcerative reactions at the challenge sites that resolved before lesions appeared in the control animals. Although protection in the immunized rabbits was incomplete, as demonstrated by the presence of T. pallidum in the rabbit infectivity test, glycerophosphodiester phosphodiesterase nevertheless represents a significantly immunoprotective T. pallidum antigen and thus may be useful for inclusion in an antigen cocktail vaccine for syphilis.

[Comparison between classical and artificial xenodiagnosis in chronic Chagas disease]

Classical and artificial xenodiagnostic techniques made with Dipetalogaster maximus of first stage were performed simultaneously in 57 patients with chronic T. cruzi infection (22 male and 35 female patients, aged 7-80 years). With the exception of two patients with megaoesophagus, all had two previous positive serological reaction and a further test was done at the time of the examination. The patients came from the outpatient department of the university hospital or were resident in Mambaí, Goiás. Of the 57 patients, 24 (42%) had a positive xenodiagnoses. Of a total of 114 tests performed, 36(32%) were positive. Comparing the two xenodiagnostic techniques, no significant advantage was apparent statistically (p = 0.42), but the artificial technique has advantages because the blood is offered for triatomines through a device while in the classical technique, the triatomines suck through the patient's skin.

A countrywide programme of continuing professional development in Argentina. Argentine Society of Paediatrics, Subcommittee of Continuing Paediatric Education

The Argentinean Society of Paediatrics introduced in 1993 a continuing professional development (CPD) programme to raise standards of clinical practice. The aims of the project were to introduce a structured, distance learning programme accessible to all paediatricians in the country, but especially for those working far from centres of paediatric excellence. The programme is planned on an annual basis. It includes four activities: a written manual designed by a team of medical experts and educationalists comprising 12 topics; field work for participants; annual meetings in several locations in the country for discussion of the subjects; and an evaluation based on centrally designed multiple choice questions distributed by mail. In spite of a registration free of 90 Pounds a year, participation in the programme increased from 3357 in 1993 to 4126 in 1996, from a membership of 10 216 paediatricians in Argentina. The popularity of the programme may result from an appropriate interpretation of professional needs of paediatricians in Argentina, adequate organisational arrangements that reach all colleagues, including those working in remote areas, and a genuine motivation of paediatricians for participating in a learning process.

[The role of external radiotherapy in the treatment of medullary carcinoma of the thyroid]

Medullary carcinoma of the thyroid represents 3 to 10% of all thyroid cancers. Surgery is the main treatment. External beam radiotherapy has a fundamental role in the treatment of residual disease following surgery, in cases of cervical node involvement, and in unresectable tumors. Between 1975 and 1993, 12 patients with medullary carcinoma of the thyroid were treated at the Department of Radiotherapy of the Portuguese Institute of Oncology in Oporto. Nine of these patients (75%) were male and 3 (25%) female, ranging from 24 to 80 years of age (mean = 43). All of them had residual tumor after surgery and underwent treatment with external beam radiotherapy. The follow-up period ranged from 36 to 180 months, with a median of 78 months; 8 patients (66.7%) are alive, 5 of them show no evidence of disease. Average survival was 70 months, and 4 patients (33%) died with metastatic disease. The aim of this paper is to analyse the role of external beam radiotherapy in local control of these tumors, with a brief review of the literature.