Complete sequence of the mitochondrial DNA of the chlorophyte alga Prototheca wickerhamii. Gene content and genome organization

The complete nucleotide sequence of the circular mitochondrial (mt) DNA of the chlorophyte alga Prototheca wickerhamii has been determined (55,328 base-pairs, A+T content 74.2%). The genes identified encode three subunits of the cytochome oxidase, apocytochrome b, nine subunits of the NADH dehydrogenase complex (nad1 to 7, nad4L and nad9), three ATPase subunits (atp6, atp9, atp1 (also referred to as atpA)), three ribosomal RNAs (5 S (rrn5), small subunit (srn) and large subunit (lrn) RNA), 26 tRNAs, and 13 ribosomal proteins. A total of five group I introns reside in lrn and cox1, two of which include intronic open reading frames (ORFs). Five free-standing ORFs longer than 60 codons are present. Three of these ORFs are counterparts to genes encoding proteins of unknown function in plant mitochondria (orf25 and orfB of angiosperms and orf244 of liverwort), whereas two of them are unique. Mitochondrial genes are encoded on both DNA strands in a way that suggests the existence of two transcription units, each including approximately one half of the mitochondrial genome. The two intergenic regions in which transcription is believed to initiate and terminate are about ten times longer than the other intergenic regions (1118 and 1993 nt versus 100 to 150 nt). A total of 29 recurring sequence motifs (30 to 200 nt long) have been found in intergenic regions. Nine different types of motifs are present, most of them arranged as tandem repeats. These motifs may be implicated in transcription, e.g. as signals for initiation, termination and/or processing. Phylogenetic analysis on the basis of the cox1 gene strongly suggested that P. wickerhamii and plant mitochondrial genomes are monophyletic. The finding of plant-specific mitochondrial genes such as orf25, orf244, orfB and rrn5 in P. wickerhamii mitochondria corroborates this idea.

Changes in the retinal pigment epithelium close to retinal vessels in familial adenomatous polyposis

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) is known to occur in patients with familial adenomatous polyposis. Its relation to the course of the retinal blood vessels is emphasized in this publication. A 15-year-old girl with familial polyposis coli showed a longitudinal strip of whitish change following the course of a superior nasal artery of the left eye, falsely appearing to enclose the blood vessel like a sheath. A 34-year-old woman from another family with polyposis coli also showed a longitudinally orientated area of hypo- and hyperpigmentation close to temporal retinal veins. Two further patients revealed hyperpigmentation of the RPE under retinal vessels. It is hypothesized that these changes indicate an effect of the hypo- and hyperpigmentations of the RPE on the development of retinal vessels. In four patients, multiple dotlike hyperpigmentations were found in the extreme periphery of the retina; however, the bigger patchy hyperpigmentations were predominantly located in the midperiphery of the retina.

Two brothers with characteristic facial appearance, severe psychomotor retardation, hypospadias, contractures, and other symptoms: a new recessive syndrome?

We report on two severely mentally retarded male children of consanguineous parents who seem to be affected by an identical syndrome. The main physical anomalies are typical facial stigmata with a broad nasal bridge, a bulbous nose, upward slanting palpebral fissures, microretrognathia, low hair line, and large ears with an incompletely developed upper helix. In addition, both brothers had hypospadias type II, limb contractures, and delayed bone age. One child had a bilateral cleft lip with cleft palate and cryptorchidism, and developed scoliosis during adolescence. The other had bilateral inguinal hernias and strabismus. Chromosome analysis showed a normal karyotype in both. The striking similarity between the brothers, the dissimilarity to other known syndromes, and the parental consanguinity argue in favour of a new, hitherto undescribed, possibly autosomal recessive syndrome.

Continuous calculation of intratracheal pressure in tracheally intubated patients

BACKGROUND

Intratracheal pressure (Ptrach) should be the basis for analysis of lung mechanics. If measured at all, Ptrach is usually assessed by introducing a catheter into the trachea via the lumen of the endotracheal tube (ETT). The authors propose a computer-assisted method for calculating Ptrach on a point-by-point basis by subtracting the flow-dependent pressure drop delta PETT(V) across the ETT from the airway pressure (P(aw)), continuously measured at the proximal end of the ETT.

METHODS

The authors measured the pressure-flow relationship of adult endotracheal tubes with different diameters (ID, 7-9 mm) at different lengths and of tracheostomy tubes (ID, 8-10 mm) in the laboratory. The coefficients of an approximation equation were fitted to the measured pressure-flow curves separately for inspiration and expiration. In 15 tracheally intubated patients under volume-controlled ventilation and spontaneous breathing, the calculated Ptrach was compared with the measured Ptrach.

RESULTS

The authors present the coefficients of the "nonlinear approximation": delta PETT = K1.VK2, with delta PETT being the pressure drop across the ETT and K1 and K2 being the coefficients relating V to delta PETT. An important result was an inspiration/expiration asymmetry: the pressure drop caused by the inspiratory flow exceeds that of the expiratory flow. A complete description of the pressure-flow relationship of an ETT, therefore, requires a set of four coefficients: K1I, K2I, K1E, and K2E. The reason for this asymmetry is the abrupt sectional change between ETT and trachea and the asymmetric shape of the swivel connector. Comparison of calculated and measured Ptrach in patients gives a correspondence within +/- 1 cmH2O (mean limits of agreement). The mean root-mean-square (rms) deviation is 0.55 cmH2O.

CONCLUSIONS

Ptrach can be monitored by combining our ETT coefficients and the flow and airway pressure continuously measured at the proximal end of the ETT.

Genotoxicity assessment of waste products of aluminum plasma etching with the SOS chromotest

We evaluated 36 characteristic waste products from the plasma etching of aluminum for genotoxicity with the SOS chromotest. The majority of the samples showed genotoxic activity in tester strain Escherichia coli PQ37 without metabolic activation using S9 mix. In the presence of S9, a deactivation of the samples was regularly observed. Comparable studies with the Salmonella/microsome (Ames) test using tester strains Salmonella typhimurium TA98 and TA100 indicated actual mutagenicity of waste products. Gas chromatograms of the organic constituents of all waste products were performed in parallel with the genotoxicity assays. In contrast to the similarity of the peak patterns of all chromatograms, the biological effects of individual waste samples showed large differences. Information on chemical composition and the SOS chromotest results of a representative sample recovered over a period of 2 years is given. For this sample, the influences of sample preparation and cytotoxic matrix effects on the test parameters are also shown.

Stoichiometry and redox behaviour of metals in cytochrome-c oxidase

The early observation of extra copper in preparations of cytochrome-c oxidase has recently lead to a renewed interest in its stoichiometry and possible redox function. In various, pure preparations (heme A contents close to the theoretical value of 9.79 nmol/mg protein for the 13-subunit bovine enzyme) protein-related metal stoichiometries of 3 Cu, 2 Fe, 1 Zn, 1 Mg/monomer with M(r) 204266 were determined. Despite the presence of five potential redox metal ions, reductive and reoxidative titrations indicate the presence of only four one-electron-accepting/donating species in the ligand-free enzyme. Participation of two copper ions in a binuclear copper site acting as one-electron acceptor may explain both the observed copper stoichiometry and the redox behaviour. The homology of the C-terminal sequence of subunit II with one of the copper-binding sites in nitrous-oxide reductases provides possible ligands for complexing two copper ions in a binuclear center.

X-linked myoclonus epilepsy explained as a maternally inherited mitochondrial disorder

A family with myoclonus epilepsy has been described previously as suffering from an X-linked disorder, because at least four males were affected, and only mild and variable symptoms were seen in some female carriers. In this family, we have now identified a mitochondrial A-->G (8344) heteroplasmic point mutation. This point mutation has been described in families with maternally inherited myoclonus epilepsy and ragged red fibers. The degree of severity of the disorder in the different family members was reflected in the relative quantity of mutated mitochondrial DNA. It is concluded that the mode of inheritance in this family is not X-linked but maternal.

Mitochondrial genes in the colourless alga Prototheca wickerhamii resemble plant genes in their exons but fungal genes in their introns

The mitochondrial DNA from the colourless alga Prototheca wickerhamii contains two mosaic genes as was revealed from complete sequencing of the circular extranuclear genome. The genes for the large subunit of the ribosomal RNA (LSUrRNA) as well as for subunit I of the cytochrome oxidase (coxI) carry two and three intronic sequences respectively. On the basis of their canonical nucleotide sequences they can be classified as group I introns. Phylogenetic comparisons of the coxI protein sequences allow us to conclude that the P.wickerhamii mtDNA is much closer related to higher plant mtDNAs than to those of the chlorophyte alga C.reinhardtii. The comparison of the intron sequences revealed several unusual features: (1) The P.wickerhamii introns are structurally related to mitochondrial introns from various ascomycetous fungi. (2) Phylogenetic analyses indicate a close relationship between fungal and algal intronic sequences. (3) The P. wickerhamii introns are located at positions within the structural genes which can be considered as preferred intron insertion sites in homologous mitochondrial genes from fungi or liverwort. In all cases, the sequences adjacent to the insertion sites are very well conserved over large evolutionary distances. Our finding of highly similar introns in fungi and algae is consistent with the idea that introns have already been present in the bacterial ancestors of present day mitochondria and evolved concomitantly with the organelles.

On the genetics of mandibular prognathism: analysis of large European noble families

Mandibular prognathism is assumed to be a polygenic trait in the vast majority of cases. In a few families, this phenotype and perhaps a syndrome with a broader spectrum of facial anomalies seems to be determined by a single dominant gene of very low frequency (McKusick No *176700). The phenotype is known to have occurred independently in several European noble families. We constructed a pedigree comprising 13 of these families with 409 members in 23 generations in which mandibular prognathism has been segregating. Obviously, the presumed dominant gene is not fully penetrant in the heterozygous state. Pedigree analysis using the Elston-Stewart algorithm yields a maximum likelihood estimate (MLE) of p = 0.955 (SE 0.038) of the penetrance parameter.

Prenatal diagnosis of X-linked centronuclear myopathy by linkage analysis

The X-linked recessive centronuclear/myotubular myopathy (XLR-CNM/MTM1), a severe neonatal disorder characterized by generalized hypotonia, muscle weakness, and primary asphyxia, has recently been mapped to Xq28. This report presents the first four prenatal diagnoses of XLR-CNM using DNA markers of the Xq28 region. The analyses of one female and three male fetuses revealed maternal transmission of the XLR-CNM-associated alleles in all four cases. Two of the male fetuses have been aborted, and the pregnancies of the third male and the female fetuses have been continued. The diagnosis of XLR-CNM at the birth of the third boy, as well as the pathologic findings in the muscle of one of the aborted fetuses, confirmed the linkage results of the prenatal analyses. Our findings prove the DNA markers St14, cpX67, DX13, and pSt35-691 to be useful in prenatal diagnosis of XLR-CNM and present the possibility to confirm the diagnosis by histologic examination of the first-trimester abortus. This permits an indirect prenatal diagnosis of XLR-CNM in chorionic villus biopsies at 9 to 12 wk gestation, using DNA-based linkage analyses allowing early termination of an affected pregnancy.

Clinical reinvestigation and linkage analysis in the family with Episkopi blindness (Norrie disease)

We present the results of a clinical and genetic reinvestigation of the Cypriot family affected by an X chromosomally inherited eye disease originally published by Taylor et al, who coined the term Episkopi blindness. The pedigree was extended to 160 members, including 16 affected males out of 48 males at risk for the disease, most of whom were seen by one of us (PA). Affected males are blind with no associated symptoms and apparently are not mentally retarded. Thirty-nine family members agreed to blood sampling for genetic investigations. RFLP analysis was performed using probes from the region known to be deleted in some Norrie patients and polymorphic markers (DXS77, DXS7, MAOA, DXS255) from the proximal short arm of the X chromosome. There was no deletion for any of the probes in the affected males. Linkage analysis yielded positive lod scores for all informative markers (Z (DXS255, theta = 0) = 6.54, Z (MAOA, theta = 0) = 2.23, Z (DXS7, theta = 0) = 2.13). Thus, the conclusion that Episkopi blindness and Norrie disease (NDP, MIM *310600) are the same entity based on clinical evidence is now reinforced by gene mapping.

Delineation of a 50 kilobase DNA segment containing the recombination site in a sporadic case of Huntington's disease

No detectable rearrangements involving chromosome 4p16.3 have been observed in patients with Huntington's disease (HD). New mutations for HD could involve structural alterations which might aid the localization of the defective gene. We have reinvestigated a well documented sporadic case of HD. DNA haplotyping with markers between D4S10 and the telomeric locus D4S141 reveals a recombination event in one chromosome of the sporadic HD patient. The site of recombination maps within a 50 kilobase (kb) region, about 700 kb from the 4p telomere. Based on the extremely low HD mutation rate and significantly decreased recombination in the distal region of 4p, we hypothesize a direct link between the site of the recombination and HD in this patient.

[Basic principles of genetic counseling]

Genetic counseling and diagnosis are increasingly significant for individual and social life. In view of inherent practical and ethical problems in medical practice, the definition of rules in this field seems necessary. The paper provides a compilation and short argumentation of such rules. They should establish a certain qualitative standard and can serve as a foundation for future discussion.

Maneuver-free determination of compliance and resistance in ventilated ARDS patients

At present, most methods of lung mechanics analysis do not take nonlinearities of compliance and resistance into account. Nevertheless, nonlinearity of compliance is an inherent property of the respiratory system in ARDS and nonlinearity of resistance is an inherent property of the endotracheal tube. Herein we describe a computer-assisted multipoint method (LOOP) for breath-by-breath calculation of total respiratory system compliance (Ctrs) and total respiratory system resistance (Rtrs). Unlike our previously published method, LOOP excludes nonlinearities of compliance and resistance by confining the data used from the P/V/V loop to sequences with constant flow in inspiration and with steadily decreasing flow in expiration. LOOP was applied to five patients ventilated after open heart surgery (HEART group) and 12 patients ventilated for ARDS (ARDS group). The compliance results from LOOP were compared with the semistatic reference values corrected for intrinsic PEEP (CsST,IP). In the ARDS patients the compliance values from LOOP (46 ml/mbar) corresponded well with the semistatic compliance (CsST,IP = 42 ml/mbar). Despite the fact that there is no reference method for resistance known to date, we also determined the semistatic resistance (RsST) at end-inspiratory pause. The resistance values determined with LOOP were 8.5 mbar/L/s (RsST = 7.3 mbar/L/s) in the HEART group and 11.1 mbar/L/s (RsST = 8.6 mbar/L/s) in the ARDS group. LOOP gives a good correspondence between the linear RC model and the measured data in ARDS patients. In conclusion, LOOP requires neither an end-inspiratory pause (EIP) nor additional determination of intrinsic PEEP and gives Ctrs, automatically corrected for IPEEP, as well as Rtrs breath by breath at the bedside.

Clinical, cytogenetic and molecular investigations in three patients with Wolf-Hirschhorn syndrome

Clinical, cytogenetic and molecular studies were performed in three patients with Wolf-Hirschhorn syndrome (WHS). In all cases the altered chromosome 4 appeared to be the result of a de novo deletion. Cytogenetic investigations located the breakpoint at 4p15.3 and 4p13. With cytogenetic methods it was not possible to decide whether these deletions were terminal or interstitial. DNA methods also failed to define a distal breakpoint within the 4p16.3 region which might have indicated an interstitial deletion. According to the literature, the paternal chromosome 4 is preferentially deleted in most patients with WHS. DNA analysis with polymorphic markers out of the 4p16.3 region revealed that in two of the cases reported here the deleted segment was of paternal and in one case of maternal origin.

Intrinsic PEEP monitored in the ventilated ARDS patient with a mathematical method

Under mechanical volume-controlled ventilation, the intensive care patient can develop intrinsic positive end-expiratory pressure (iPEEP); that is, the passive expiration is terminated by the following inspiration before the alveolar pressure comes to its physical equilibrium value. We present a mathematical method to estimate this alveolar dynamic iPEEP breath by breath, without the need of a maneuver. We tested it in paralyzed patients ventilated for adult respiratory distress syndrome after multiple trauma and/or sepsis, and we compared the results obtained with the new mathematical method with those from the occlusion method introduced by Pepe and Marini. The results agreed well (median difference of 0.8 mbar in 201 investigations in 12 patients). However, the mathematically determined values, representing dynamic iPEEP, are systematically slightly smaller than those measured by the occlusion maneuver. A variation of expiratory time suggests that this difference might be due to mechanical time-constant inhomogeneity, viscoelastic processes, or other mechanisms showing time dependence.

Ethical and psychological aspects of living donorship and life with a donated organ

There is far-reaching consent in the literature that public and consensual agreements on the basics of the different aspects of medical ethics are inalienable before the instigation of any innovative transplant procedure. In the case of a certain method and/or of an individual patient, however, the ultimate ethical evaluation can most likely never be entirely complete before this application. Ethical evaluation depends on the actual criteria used, the present knowledge regarding the risk--benefit--balance as well as on the ethical evaluation of the patient's and his family's own feelings and expectations which are not entirely conscious. In relation to the so-called "fundamental and constant ethical guidelines" and under a psychological perspective potential, ethical conflict constellations are presented which have to be dealt with in the process of ethical and psychological evaluation before living organ transplantation.

Renal transplantation in 22 children with nephropathic cystinosis

In 1989, 22 children (11 boys, 11 girls aged 8-23 years) with nephropathic cystinosis, who had received a total of 28 renal allografts over the previous 14 years, were reviewed. Nineteen were alive, of whom 17 had functioning grafts 5 months to 13 years after transplantation. The mean serum creatinine level in these 17 was 135 mumol/l. Patient and graft survival did not differ from non-cystinotic children. Persistent hypothyroidism was found in 3 patients, transient diabetes mellitus in 1, severely disturbed vision in 1 and brain atrophy in 11. Arterial hypertension was present in 16 patients. Growth retardation was universal, although in 4 patients on cyclosporin A post-transplant catch-up growth occurred. Five patients over 15 years completed puberty. Readjustment in terms of school performance was good but was less good for psychosocial development. None of the patients had ever been treated with cystine-depleting agents; the data will therefore provide a historical control group with which to compare the results from a group treated with these agents.