Biosynthesis of phosphatidylinositol in Crithidia fasciculata.

Microsomal preparations from the protozoan (Crithidia fasciculata were shown to incorporate myo-[2-3H]inositol into phosphatidylinositol by both the CDPdiacylglycerol:myo-inositol phosphatidyltransferase reaction and by a myo-inositol exchange reaction. Non-ionic detergent and Mg2+ were necessary for the measurement of transferase activity. Untreated preparations could not be saturated with Mg2+, even at very high concentrations (50-75 mM). However, low concentrations of EGTA (75 micro M) both stimulated the activity 3-fold and reduced the Mg2+ required for saturation to 15-20 mM. EGTA also increased the apparent Km for CDPdiacylglycerol while increasing the sensitivity to substrate inhibition above 1 mM. The transferase activity was inhibited by relatively low concentrations of Ca2+ (50 micro M). This and the EGTA effect suggest a possible role for Ca2+ in the modulation of phosphatidylinositol synthesis. The myo-inositol exchange activity required Mn2+, was insensitive to Ca2+ inhibition and was only slightly stimulated by detergents and EGTA. This activity was preferentially inactivated by heating at 50 degrees C in the presence of Triton X-100. In a detergent solubilized preparation the exchange activity but not the transferase exhibited a non-specific requirement for phospholipid. The differences in properties of the two activities suggest the presence of a separate exchange enzyme.

Transfer RNA genes from the hyperthermophilic Archaeon, Methanopyrus kandleri.

Genes encoding the Leu (GAG), Ser (UGA), Gln (UUG) and Lys (UUU) tRNAs have been cloned and sequenced from the deep sea hyperthermophilic Archaeon, Methanopyrus kandleri. Sequences conforming to the TATA box element established for methanogen promoters are located upstream of the tRNA(Gln) and tRNA(Lys) genes. All four of the tRNA genes appear to encode the 3' terminal CCA residues of the mature tRNA. These methanogen tRNAs are predicted to contain most, but not all, invariant residues and are characterized by a high level of G + C base pairing, consistent with the 98 degrees C optimum growth temperature of M. kandleri.

Reopening after successful coil occlusion for patent ductus arteriosus.

OBJECTIVES: This study was performed to determine the frequency of patent ductus arteriosus (PDA) reopening and the factors that may predict reopening after successful coil occlusion. BACKGROUND: Transcatheter coil occlusion is a widely used and accepted method to close a PDA. After documented successful coil occlusion, we found PDAs that reopened. We hypothesized that specific factors are involved in those that reopened. METHODS: All patients who underwent percutaneous transarterial PDA coil occlusion were studied. Successful coil occlusion was documented. PDA reopening was determined when Doppler-echocardiography (DE) performed after the procedure was negative for PDA flow but at follow-up demonstrated PDA shunting. Patients with a reopened PDA were compared with all other patients in evaluating independent variables. RESULTS: Coil occlusion for PDA was attempted in 22 patients. Clinical success was achieved in 20 patients (91%), and DE was negative for PDA shunting in 19 patients (90%). At follow-up, five patients demonstrated reopening. The PDA minimal diameter was 1.4 +/- 0.5 mm (mean +/- SD) for the reopened group and 1.2 +/- 0.7 mm for the other patients. The PDA length was 2.9 +/- 1.9 mm for the reopened group and 7.1 +/- 3.2 mm for all other patients. All those with type B PDA were in the reopened group. When independent variables were compared between groups, only PDA length and type B PDA predicted reopening (p < 0.05). CONCLUSIONS: PDA reopening may occur after successful coil occlusion. Short PDA length and type B PDA are associated with reopening. The data suggest that in such anatomy, alternative strategies to the current coil occlusion technique should be considered.

The appearance of cartilage used in deep inferior epigastric perforator breast reconstruction surgery as a calcified mass on CT scan.

This paper describes an unusual radiological appearance of implanted cartilage on CT scan in a patient who had recently undergone deep inferior epigastric perforator (DIEP) breast reconstruction surgery following a mastectomy for ductal carcinoma in situ. The purpose of this paper is to alert medical practitioners involved with DIEP breast reconstruction surgery, as well as general radiologists, to the possibility of surgically implanted costal cartilage undergoing calcification and then appearing on imaging studies as a malignant process. Information on the patient was gathered from clinical records, imaging reports and pathological samples. A literature search was performed to identify similar cases and the results showed that this occurrence has never before been described and therefore represents an advancement of knowledge about the imaging characteristics of reconstructed breast tissue.

Genes encoding 5S rRNA and tRNAs in the extremely thermophilic archaebacterium Methanothermus fervidus.

Methanothermus fervidus was shown to have two 5S rRNA-encoding genes linked in rRNA operons to 16S and 23S rRNA-encoding genes. Sequencing of a cloned 5S rRNA gene confirmed that M. fervidus is a member of the Methanobacteriales, although its 5S rRNA is also similar in both primary sequence and predicted secondary structure to the 5S rRNA of the non-methanogenic, but also extremely thermophilic archaebacterium, Thermococcus celer. Two clusters of tRNA genes have also been cloned and sequenced form M. fervidus. The smaller cluster, cloned in pET5401, is composed of 5'-tRNA(UGUThr)-tRNA(UGGPro)-tRNA(GUCAsp)-tRNA(UUUL ys)-3' and the larger cluster, cloned in pET5475, is composed of 5'-tRNA(GUUAsn)-tRNA(CAUMet)-tRNA(UUCGlu)-tRNA(UAGL eu)-tRNA(GUGHis)-3'. The encoded tRNAs, with the exception of the tRNA(Leu), translate abundant codons in M. fervidus. The tRNA genes do not contain introns or encode 3'-terminal CCA residues. Homologous clusters of tRNA genes have been sequenced from Methanococcus vannielii and Methanococcus voltae, so that comparisons of transcription signals, gene organizations and primary sequences can be made and features possibly related to thermostability identified. During evolution, a 5S rRNA gene appears to have been incorporated into the cluster of tRNA genes in the methanococci but not in M. fervidus.

Genes encoding the 7S RNA and tRNA(Ser) are linked to one of the two rRNA operons in the genome of the extremely thermophilic archaebacterium Methanothermus fervidus.

Analysis of gene structure in the extremely thermophilic archaebacterium, Methanothermus fervidus, has revealed the presence of a cluster of stable RNA-encoding genes arranged 5'-7S RNA-tRNA(Ser)-16S rRNA-tRNA(Ala)-23S rRNA-5S rRNA. The genome of M. fervidus contains two rRNA operons but only one operon has the closely linked 7S RNA-encoding gene. The sequences upstream from the two rRNA operons are identical for 206 bp but diverge at the 3' base of the tRNA(Ser) gene. The secondary structures predicted for the M. fervidus 7S, 16S rRNA, tRNA(Ala) and tRNA(Ser) have been compared with those of functionally homologous molecules from moderately thermophilic and mesophilic archaebacteria. A consensus secondary structure for archaebacterial 7S RNAs has been developed which incorporates bases and structural features also conserved in eukaryotic signal-recognition-particle RNAs and eubacterial 4.5S RNAs.

Acute pulmonary toxicity in an infant from intravenous amiodarone.

Intravenous amiodarone is an effective treatment for supraventricular and ventricular tachyarrhythmias. We report a case of acute pulmonary toxicity in an infant from intravenous amiodarone and describe the clinical evaluation and laboratory studies leading to the diagnosis.

Valvular hemodynamics and arrhythmias with exercise following the Ross procedure.

Pulmonary autograft aortic valve replacement (Ross procedure) is increasing in popularity, particularly in children and young adults. We performed a controlled study of pediatric and adult Ross procedure patients to evaluate postoperative exercise valvular hemodynamics and cardiac rhythm. Thirty-one patients and 24 controls underwent stress echocardiography. Doppler and 2-dimensional echocardiography assessed valvular hemodynamics and right and left ventricular size at baseline and after exercise. Electrocardiography monitored cardiac rhythm. Patients and controls had neoaortic and neopulmonic valve insufficiency ranging from none to moderate that improved or did not change with exercise. Baseline and exercise mean peak transaortic gradients were not significantly different between patients (baseline 6.3 +/- 3.8 mm Hg, exercise 12.8 +/- 7.3 mm Hg) and controls (baseline 6.7 +/- 2.5 mm Hg, exercise 14.3 +/- 5.2 mm Hg). However, baseline and exercise mean peak transpulmonic gradients were significantly different between patients (baseline 20.7 +/- 9.6 mm Hg, exercise 45.2 +/- 23.5 mm Hg) and controls (baseline 3.7 +/- 1.3 mm Hg, exercise 10.6 +/- 3.7 mm Hg). Significant exercise-induced arrhythmias occurred in 8 patients (26%) and no controls. Occurrence of arrhythmias correlated with an older age at surgery and age at study. After the Ross procedure, patients have valve competence and transaortic gradients similar to controls at baseline and with exercise. However, patients have significantly increased baseline and exercise transpulmonic gradients compared with controls. Furthermore, exercise-induced arrhythmias occurred frequently in our patient group and were associated with an older age at surgery and age at study.

Pulmonary homograft repair of a mycotic aortic aneurysm in an infant.

Thoracic aortic aneurysms are rare in children and even more unusual in infants. The vast majority are mycotic. Frequently, those with mycotic thoracic aortic aneurysm do not survive and the diagnosis is made at autopsy. We present the case of an asymptomatic infant found to have a mycotic thoracic aortic aneurysm. The clinical course, diagnosis, and surgical repair of the aneurysm with pulmonary homograft are discussed.

Cardiac rupture with dobutamine stress echocardiography.

Dobutamine stress echocardiography is a safe method for the evaluation of coronary artery disease, myocardial function, and viability. The potential for cardiac rupture exists. Although clinical and electrocardiographic criteria may be helpful in identifying those patients at risk for cardiac rupture, the criteria are neither sensitive nor specific enough to exclude patients or make recommendations regarding which patients should undergo dobutamine stress echocardiography in the post-infarction period. Physicians must be aware of the possibility and be prepared to treat cardiac rupture when performing dobutamine stress echocardiography.

Pharmacologic stress echocardiography. Dobutamine and arbutamine stress testing.

Pharmacologic stress testing is an important noninvasive method for evaluating patients with known or suspected coronary artery disease who are unable to adequately exercise. Pharmacologic stress echocardiography using dobutamine has been developed over the last 10 to 15 years as an alternative to vasodilator stress testing using nuclear perfusion imaging. As experience has grown, digital subtraction echocardiogram has been shown to be a safe, convenient, and reliable method for stress testing in a variety of patient populations. Digital subtraction echocardiogram has comparable sensitivity, specificity, and accuracy when compared to other stress testing methods which employ cardiac imaging and is superior to the exercise echocardiogram. It has certain advantages over nuclear perfusion imaging in terms of cost and convenience. The recent addition of arbutamine echocardiography (which has been shown to be comparable to digital subtraction echocardiogram) provides another alternative method for pharmacologic stress testing. Continued improvement in echocardiographic image quality and the development of new technologies such as tissue harmonic imaging and contrast echocardiography will hopefully improve the echocardiographic evaluation of wall motion therefore increasing the diagnostic accuracy of echocardiographic stress testing.

Common cardiac diseases in adolescents.

Adolescent patients frequently present with symptoms potentially referable to the cardiovascular system; however, patients rarely have true cardiovascular disease. In many patients, the history is the key to determining whether additional testing or referral is necessary. Even though the history, physical examination, and preliminary laboratory data may indicate a benign cause, occasionally a referral to a cardiologist is necessary because of patient or parental anxiety. Patients with true cardiac pathology should be followed by a cardiologist in conjunction with the primary care physician.

Evaluation of syncope in adult congenital heart disease.

Approximately one million adults in the United States have congenital heart disease. The practitioner who sees one of these patients presenting with syncope must have a thorough understanding of: the underlying disease process; the associated congenital heart abnormalities; the type of surgery performed; the potential surgical residua; and the natural and unnatural history of this type of heart disease. Several types of congenital heart disease including: atrial septal defects; ventricular septal defects; left-sided obstructive lesions; Ebstein Anomaly; tetralogy of Fallot; and transposition of the great arteries are reviewed.

An expression vector for the archaebacterium Haloferax volcanii.

The recent development of an efficient transformation method and shuttle vectors for Haloferax volcanii has set the stage for rapid progress in archaebacterial molecular biology. We describe a shuttle-expression vector that can be selected for and maintained in either H. volcanii or Escherichia coli and permits the expression of cloned genes in H. volcanii. The vector, pWL204, was constructed by incorporating an H. volcanii tRNA(Lys) gene promoter into a derivative of the H. volcanii-E. coli shuttle vector pWL102. The vector has been used to express a modified, intron-containing, H. mediterranei tRNA(Trp) gene (tRNA(Trp)-O167). Transcription from the tRNA(Lys) gene promoter in vivo was detected by Northern (RNA) analysis with an oligonucleotide probe complementary to the unique intron sequence of tRNA(Trp)-O167. Dependence of transcription on the tRNA(Lys) promoter was demonstrated by the absence of transcription when the promoter sequence was deleted from the vector and by mapping the transcription initiation site by primer extension.

Recognition of exon-intron boundaries by the Halobacterium volcanii tRNA intron endonuclease.

The intron-containing tRNA(Trp) precursor from Halobacterium volcanii, like many intron-containing archaebacterial precursor tRNAs, can assume a structure in which the two intron endonuclease cleavage sites are localized in two three-nucleotide loops separated by four base pairs. To investigate the role of this structure in cleavage by the halophilic endonuclease, a series of mutant tRNA(Trp) RNAs were prepared and evaluated as substrates. We find that alterations in this structure result in the loss of cleavage at both 5' and 3' sites. Cleavage of a 35-nucleotide model RNA substrate, containing only these features, demonstrates that sequences and structures present at the exon-intron boundaries are sufficient for recognition and cleavage. We have also examined the mechanism used by the halophilic endonuclease to identify the cleavage sites. Addition of a single base, or a base pair in the anticodon stem above the cleavage sites, does not affect the cleavage site selection. The addition of nucleotides between the two cleavage sites significantly decreases cleavage efficiency and has an effect on the cleavage site selection. These results demonstrate that the halophilic endonuclease requires a defined structure at the exon-intron boundaries and does not identify its cleavage sites by a measurement mechanism like that employed by eukaryotic tRNA intron endonucleases.