Sequence arrangement of the 16S and 26S rRNA genes in the pathogenic haemoflagellate Leishmania donovani

Kinetic and chemical analysis show that the haploid genome of Leishmania donovani has between 4.6 and 6.5 X 10(7) Kb pairs of DNA. Cot analysis shows that the genome contains 12% rapidly reassociating DNA, U3% middle repetitive DNA with an average reiteration frequency of 77 and 62% single copy DNA. Saturation hybridization experiments show that 0.82% of the nuclear DNA is occupied by rRNA coding sequences. The average repetition frequency of these sequences is determined to be 166. Sedimentation velocity studies indicate the two major rRNA species have sedimentation values of 26S and 16S, respectively. The arrangement of the rRNA genes and their spacer sequences on long strands of purified rDNA has been determined by the examination of the structure of rRNA:DNA hybrids prepared for electron microscopy by the gene 32-ethidium bromide technique. Long DNA strands are observed to contain several gene sets (16S + 26S). One repeat unit contains the following sequences in the order given: (a) A 16S gene of length 2.12 Kb, (b) An internal transcribed spacer (Spl) of length 1.23 Kb, which contains a short sequence that may code for a 5.8S rRNA, (C) 26S gene with a length of 4.31 Kb which contains an internal gap region of length 0.581 Ib, (d) An external spacer of average length 5.85 Kb.

Application of the avidin-biotin method of gene enrichment to the isolation of long double-stranded DNA containing specific gene sequences

A method of enriching for long double-stranded segments of eukaryotic DNA carrying particular genes is described. A purified RNA coded for by the gene is covalently attached to biotin via the protein, cytochrome c. This modified RNA is hybridized to total nuclear, double-stranded DNA under conditions that allow the formation of R-loops. Avidin, which has a high affinity for biotin, is covalently attached to polymer spheres. The complexes of avidin-spheres with DNA:RNA-biotin R-loop hybrids band in CsCl at a much lower bouyant density than does free DNA. This density is a function of the length of DNA coupled per avidin-sphere. This method was used to prepare very long double-strands of DNA highly enriched in the coding sequences for the large rRNAs of D. melanogaster and L. donovani and the histone mRNAs of S. purpuratus.

The dashboard knee injury

An in-depth study of 74 motor vehicle accidents involving 222 people revealed that 57 of the 153 people injured sustained 69 knee injuries from contact with the instrument panel. There were 51 mild, 10 moderate, and 8 severe knee injuries. Low force contact caused bruising, and more serious injuries occurred when a greater magnitude of force was applied. Injury was most severe when this force was concentrated in a small area and caused lacerations, fractured patella, and open wounds of the joint. Legs trapped under the dashboard with simultaneous rotational, varus, valgus, or frontal forces by the inertial motion of the body produced serious injuries similar to those recieved in sports. Degenerative arthritis was more likely to occur in the seriously injured knees, but generally was not predictable. Long-term disability might be mitigated by early diagnosis and treatment of the specific injury.

A method for gene enrichment based on the avidin-biotin interaction. Application to the Drosophila ribosomal RNA genes

A method of enriching, from the total DNA of an organism, for long DNA strands carrying a particular gene is described. The purified RNA corresponding to the gene is covalently attached to biotin via a cytochrome c bridge. This modified RNA is hybridized to the total DNA. Those DNA strands which hybridize are separated from all the other DNA, using the avidin-biotin interaction, by one of two methods. Avidin is covalently attached to submicroscopic polymer spheres; the complexes of avidin spheres with the DNA: RNA-biotin hybrids band in CsCl at a much lower buoyant density than does free DNA. Alternatively, the DNA:RNA-biotin hybrids are isolated by affinity chromatography on an avidin-solid support column. These methods have been used to prepare long single strands of Drosophila ribosomal DNA (rDNA) in high yield and 42 to 80% pure.

Automated identification of cardiac conduction tissue in L-TGV and Ebstein's anomaly

The specialized cardiac conduction tissue was identified quickly and easily at operation in 2 patients with corrected transposition (L-TGV) and 1 with Ebstein's anomaly. In each of the former cases the tissue was located along the upper rim of the VSD, beneath the pulmonary outflow tract; in neither patient was there a disturbance in cardiac rhythm as a result of operation. In the patient with Ebstein's anomaly the bundle of His descended onto the ventricular septum more directly than was anticipated. There was only a transitory disturbance in atrioventricular conduction following tricuspid valve replacement. Accurate identification of the cardiac conduction tissue is a prerequisite to the safe repair of certain forms of complex congenital heart disease.

Sequence arrangement of the rDNA of Drosophila melanogaster

The sequence arrangement of genes coding for stable rRNA species and of the interspersed spacers on long single strands of rDNA purified from total chromosomal DNA of Drosophila melanogaster has been determined by a study of the structure of rRNA:DNA hybrids which were mounted for electron microscope observation by the gene 32-ethidium bromide technique. One repeat unit contains the following sequences in the order given. First, an 18 S gene of length 2.13 +/- 0.17 kb. Second, an internal transcribed spacer (Spl) of length 1.58 +/- 0.15 kb. A short sequence coding for the 5.8S and perhaps the 2S rRNA species is located within this spacer. Third, the 28S gene with a length of 4.36 +/- 0.23 kb. About 55% of the 28S genes are unbroken or continuous (C genes). However, about 45% of the 28S genes contain an insertion of an additional segment of DNA that is not complementary to rRNA (l genes). The insertion occurs at a reproducible point 2.99 +/- 0.26 kb from the junction with Spl. The insertions are heterogeneous in length and occur in three broad size classes: 1.42 +/- 0.47, 3.97 +/- 0.55, and 6.59 +/- 0.62 kb. Fourth, an external spacer between the 28S gene and the next 18S gene which is presumably mainly nontranscribed and which has a heterogeneous length distribution with a mean length and standard deviation of 5.67 +/- 1.92 kb. Short inverted repeat stems (100-400 nucleotide pairs) occur at the base of the insertion. It is known from other studies that I genes occur only on the X chromosome. The present study shows that the I and C genes on the X chromosomes are approximately randomly assorted. The sequence arrangement on the plasmid pDm103 containing one repeat of rDNA (Glover et al., 1975) has been determined by similar methods. The I gene on this plasmid contains an inverted repeat stem. The occurrence of inverted repeat sequences flanking the insertion supports the speculation that these sequences are translocatable elements similar to procaryotic translocons.

Urinary outputs of oxalate, calcium, and magnesium in children with intestinal disorders. Potential cause of renal calculi

24-hour urinary outputs of oxalate, calcium, and magnesium have been determined in a total of 62 children aged 3 months to 17 years who fell into the following groups: (i) 16 normal controls, (ii) 3 with primary hyperoxaluria, (iii) 9 with small and/or large intestinal resections, (iv) 9 with untreated coeliac disease, (v) 5 with pancreatic dysfunction, and (vi) a miscellaneous group of 20 children with a variety of intestinal disorders. Taken as a whole, 58% of patients with intestinal disorders had hyperoxaluria, and of these 7% had urinary outputs of oxalate which fell within the range seen in primary hyperoxaluria. The proportion of children with hyperoxaluria in the different diagnostic groups was as follows: intestinal resections (78%), coeliac disease (67%), pancreatic dysfunction (80%), and miscellaneous (45%). 35% of the patients with hyperoxaluria had hypercalciuria, whereas magnesium excretion was normal in all subjects studied. In 2 patients treatment of the underlying condition was accompanied by a return of oxalate excretion to normal. These results indicate that hyperoxaluria and hypercalciuria are common in children with a variety of intestinal disorders, and that such children may be at risk of developing renal calculi without early diagnosis and treatment.

The Waterston anastomosis with no deaths in the neonate

The Waterston anastomosis has been performed with no deaths in 11 consecutive neonates during the past 24 months. Seven neonates had pulmonary atresia with either single ventricle or hypoplastic right ventricle, 3 had tetralogy of Fallot, and one had severe pulmonary stenosis with a normal right ventricle. Six neonates were one day old and only one was older than 7 days. All have obtained symptomatic and documented (increase Po2) benefit. This level of success is attributed to (1) minimal delay between the recognition of cyanosis and operation (mean time between hospital admission and catheterization was 3 hours and between catheterization and operation, 4 hours); (2) correction of any base deficit prior to, during, and after operation; (3) accurate construction of the anastomosis to avoid excessive size, and (4) careful postoperative management of the pulmonary subsystem by experienced personnel. We have demonstrated that the high mortality rate previously reported for the Waterston anastomosis in the neonate can be markedly improved by an appropriate patient management program.

Complete correction of double-outlet right ventricle with situs inversus, 1-loop, and 1-malposition (I,L,L) with subaortic VSD and pulmonary stenosis

The repair a unique case of double-outlet right ventricle is reported. This case illustrates the increasingly difficult problem of developing an appropriate nomenclature in complex congenital heart disease. A classification of double-outlet right ventricle based upon Van Praagh's symbolic terminology is suggested.

The role of the kidney in essential hypertension

1. Many forms of human and experimental hypertension begin with compromised renal function. Essential hypertension may be another such case. 2. The kidneys of subjects with essential hypertension excrete normal amounts of salt and water at higher-than-normal renal perfusing pressures. Other overt signs of renal dysfunction are few; renal disease is excluded by definition. However, renal blood flow and glomerular filtration rate are usually less than normal in essential hypertension. 3. Renal afferent resistance can be calculated from arterial pressure, renal blood flow, and an estimate of glomerular capillary pressure. These calculations indicate that afferent resistance is increased to two or more times normal in essential hypertension. 4. It is not clear whether afferent constriction causes hypertension or results from it. The ability of high pressure to produce vascular damage points to the latter. But, most essential hypertensives show low-to-normal plasma renin levels and a marked afferent dilation after saline loading. These observations do not suggest nephrosclerosis: they are consistent with a causal role for afferent constriction. 5. We can speculate that, in essential hypertension, there is a defect in one of the mechanisms that sets afferent resistance. Afferent constriction could result from extrinsic influences (neural or humoral) or something totally within the kidney, such as abnormal handling of information from the macula densa. 6. The effect of afferent constriction on salt-and-water excretion would theoretically be offset by elevated arterial pressure so that the actual salt-and-water excretion would be normal, but only so long as the arterial pressure remained elevated.

Echocardiographic recognition of the congenital bicuspid aortic valve

Twenty-one patients (age four to 25 years) with bicuspid aortic valves proved by surgery and angiography (12) or angiography alone (9) were studied by echocardiography. Seventeen patients had aortic valve disease (11 stenosis, 6 incompetence) and four had coarctation of the aorta with normally functioning aortic valves. A comparison group of 16 patients (9 with aortic valve disease and 7 without aortic valve disease) who had proven tricuspid aortic valves was also studied. Echocardiograms in tricuspid aortic valve patients showed the closed position of the cusps near the middle of the aortic lumen. In contrast marked eccentricity of the aortic valve cusp echoes in diastole could be demonstrated in all with bicuspid aortic valves. The Eccentricity Index (½ aortic lumen diameter/minimum distance of the diastolic cusp echo from the nearest aortic margin) was low (range 1.0-1.25) with tricuspid aortic valves and high (range 1.5-5.6) with bicuspid aortic valves ( P < 0.001). This index was not significantly affected following successful valvotomy. Bicuspid aortic valve cusps showed normal systolic motion pattern resulting in marked asymmetry of leaflet images. About half of patients with bicuspid aortic valves also showed multilayered echoes in diastole in the absence of fluoroscopic evidence of valvular calcification. Echocardiography appears to be specific in the recognition of the bicuspid aortic valve.