Organizational differences between cytoplasmic male sterile and male fertile Brassica mitochondrial genomes are confined to a single transposed locus

Comparison of the physical maps of male fertile (cam) and male sterile (pol) mitochondrial genomes of Brassica napus indicates that structural differences between the two mtDNAs are confined to a region immediately upstream of the atp6 gene. Relative to cam mtDNA, pol mtDNA possesses a 4.5 kb segment at this locus that includes a chimeric gene that is cotranscribed with atp6 and lacks an approximately 1kb region located upstream of the cam atp6 gene. The 4.5 kb pol segment is present and similarly organized in the mitochondrial genome of the common nap B.napus cytoplasm; however, the nap and pol DNA regions flanking this segment are different and the nap sequences are not expressed. The 4.5 kb CMS-associated pol segment has thus apparently undergone transposition during the evolution of the nap and pol cytoplasms and has been lost in the cam genome subsequent to the pol-cam divergence. This 4.5 kb segment comprises the single DNA region that is expressed differently in fertile, pol CMS and fertility restored pol cytoplasm plants. The finding that this locus is part of the single mtDNA region organized differently in the fertile and male sterile mitochondrial genomes provides strong support for the view that it specifies the pol CMS trait.

Structure of the maize mitochondrial replicon RNA b and its relationship with other autonomously replicating RNA species

The mitochondria of maize plants with S-type cytoplasm possess a family of single and double-stranded RNA molecules, termed RNA plasmids, that replicate in a DNA-independent manner typical of RNA viruses. We have determined the sequence of the smallest and most abundant member of this family, a single-stranded RNA termed RNA b. The 719 nucleotide sequence of RNA b lacks open reading frames of significant length. Probes complementary to the determined (+) strand sequence identified two larger RNA species of 2900 and > 4000 nucleotides in S-type maize mitochondria, the smaller of which corresponds to a previously identified member of the RNA plasmid family designated RNA a. These probes also unexpectedly identified a low abundance form of RNA b in N-type maize mitochondria. (+) strand probes identified corresponding (-) strand forms in S cytoplasm that likely represent components of replication intermediates. Primer extension experiments demonstrated that RNA b is an internally deleted form of the larger RNA plasmid, RNA a, and that it has a discrete and homogeneous 5' terminus. The solubility of RNA b in 2 M-LiCl as well as structural modelling studies indicated that it has a very high degree of secondary structure. Analysis of specific cleavage products generated by treatment of RNA b-oligonucleotide duplexes with RNase H indicated that the only identifiable forms of RNA b were linear molecules with relatively homogeneous 3' termini; no circular forms were detected. RNA b was found to share a 13 nucleotide sequence with the circular cadang-cadang viroid; 11 of these nucleotides fall within the central conserved region of viroid RNAs. In addition, RNA b shares certain structural similarities with phage Q beta and "variant" RNAs that serve as in vitro templates for the Q beta replicase. Collectively, our results indicate that RNA b is a "defective-interfering" member of an RNA family representing a new and apparently distinct class of RNA replicons.

Altered brain energy metabolism in demented patients with multiple subcortical ischemic lesions. Working hypotheses

We report the results of brain metabolic studies (using magnetic resonance spectroscopy) in three groups of individuals: (1) demented patients with multiple subcortical ischemic lesions (n = 18); (2) nondemented, age-matched controls (n = 21); and (3) demented patients with neurodegenerative disease, probably of the Alzheimer type (n = 19). Patients with dementia with subcortical vascular lesions, as demonstrated by appropriate imaging studies, had an increase of phosphate energy charge in areas of the cerebral cortex (especially prominent in the frontal regions) superficial to and excluded from the subcortical lesions. We hypothesize that this increased energy charge might be caused by reduced metabolic activity of disconnected brain tissue or by astrocytic hypertrophy and hyperplasia that accompanies subtle ischemic, cortical alterations.

Vascular dementia: neuropathologic alterations and metabolic brain changes

After reviewing the concepts of dementia, in general, and vascular dementia, in particular, this review discusses potential future approaches that may contribute to an improved definition of the clinical syndrome and the neuropathological features of vascular dementia. Specific brain alterations in high-energy phosphate compounds, as measured by nuclear magnetic resonance, may contribute to the separation between dementias with neurodegenerative diseases and those with ischemic (vascular or hemodynamic) disorders.

Restoration of broken cytology slides and creation of multiple slides from a single smear preparation

A technique was developed for restoring broken cytology slides so that they are close to their original condition and for making multiple slides from a single smear preparation. The method is applicable to both cytologic preparations and histologic sections. In this study the fragmented smear preparation was treated with Pro-Texx, which penetrated, impregnated and solidified the full thickness of the pieces of the smear, enabling them to be lifted from the pieces of the broken slide. The removed pieces of the smear preparation were reassembled onto a new slide, which was then restained and coverslipped. In preparing multiple teaching slides, the treated smear preparation was divided as planned, with each portion mounted onto a separate slide, which was then restained and coverslipped. Ten other fine needle aspiration cases with broken slides have been restored, and more teaching slides were prepared from a single smear preparation using the same technique. All were equally successful. This technique provides an excellent method of smear transfer in cases of broken slides and creation of multiple slides from a single smear preparation for cytology teaching. This is particularly useful for unusual cases.

Synthesis of Brassica oleracea/Brassica napus somatic hybrid plants with novel organeile DNA compositions

Broccoli (Brassica oleracea L. italica) hypocotyl protoplasts were fused with mesophyll protoplasts of two B. napus lines, one carrying the Ogura (ogu) cms cytoplasm, and the other carrying a hybrid cytoplasm consisting of ogu mitochondria combined with triazine-tolerance-conferring chloroplasts from ctr cytoplasm. Two male-sterile somatic hybrids were recovered from the fusion of broccoli protoplasts with those of ogu/ctr cybrid B. napus. The ogu mtDNAs and ctr cpDNAs were not altered in these hybrids. Four male-sterile plants were recovered from the somatic hybridization of broccoli with ogu cms B. napus. Three of these possessed mitochondrial genomes that appeared to have resulted from recombination between the ogu and normal B. oleracea (ole) mtDNAs, while the fourth possessed an unrearranged ogu mtDNA. All four of these plants had B. oleracea cpDNA, and none displayed the seedling chlorosis associated with ogu chloroplasts. Most of the plants recovered from these fusions had the chromosome number expected of B. oleracea + B. napus hybrids (2n = 56). The novel cytoplasms may prove to be useful for the molecular analysis of Brassica cms and for the production of hybrid Brassica.

Selective dissociations of sedation and amnesia following ingestion of diazepam

Forty-eight healthy volunteers received 0.2 mg/kg oral diazepam or a placebo in a double-blind manner. The effect of the drug on memory was assessed by the free recall of unrelated word lists, and arousal was assessed by subjective ratings of drowsiness, multiple trials of a digit cancellation task, and the rate at which subjects rehearsed aloud items from the word lists. As expected, diazepam, depressed both memory functioning and all three measures of arousal. However, within the diazepam group, rehearsal rate was the only arousal measure that correlated with performance on the recall task. When looking at change scores, or the degree to which performance deteriorated from baseline to the diazepam condition, digit cancellation reduction was the only arousal measure that correlated with recall deterioration. Analyses also revealed that the three arousal measures did not correlate with each other. Results support the view that the arousal/attentional system is composed of partially independent subsystems with varying relationships to memory functioning.

Suppression of cytoplasmic male sterility by nuclear genes alters expression of a novel mitochondrial gene region

To identify regions of the mitochondrial genome that potentially could specify the "Polima" (pol) cytoplasmic male sterility (CMS) of Brassica napus, transcripts of 14 mitochondrial genes from nap (male fertile), pol (male sterile), and nuclear fertility-restored pol cytoplasm plants were analyzed. Transcriptional differences among these plants were detected only with the ATPase subunit 6 (atp6) gene. Structural analysis of the atp6 gene regions of pol and nap mitochondrial DNAs showed that rearrangements in the pol mitochondrial genome occurring upstream of atp6 have generated a chimeric 224-codon open reading frame, designated orf224, that is cotranscribed with atp6. In CMS plants, most transcripts of this region are dicistronic, comprising both orf224 and atp6 sequences. Nuclear restorer genes at either of two distinct loci appear to specifically alter this transcript pattern such that monocistronic atp6 transcripts predominate. The differences in expression of this region appear to result, in part, from differential processing of a tRNA-like element comprising a tRNA pseudogene present immediately upstream of atp6 in both the sterile and fertile mitochondrial DNAs. Possible mechanisms by which expression of the orf224/atp6 locus and the Polima CMS trait may be specifically related are considered.

Cerebral blood flow and neuropsychological asymmetries in unilateral stroke

BACKGROUND AND PURPOSE

This study sought to determine the degree of agreement between asymmetries of neuropsychological functioning and nine methods of quantifying asymmetries of regional cerebral blood flow.

METHODS

The regional cerebral blood flow methods combined three markers of cerebral blood flow asymmetry (percent hemispheric difference, maximum percent probe-pair asymmetry, and number of probe-pair asymmetries) with three indexes of regional cerebral blood flow (fast compartment flow, initial slope index, and initial slope). Eleven patients with left hemispheric ischemic strokes and 13 with right hemispheric ischemic strokes were studied with the xenon-133 inhalation technique and neuropsychological tests.

RESULTS

Blind clinical judgments of neuropsychological asymmetry significantly correlated with all nine methods of cerebral blood flow asymmetry determination; correlations ranged from -0.42 to -0.77. Clinical judgment of asymmetry of neuropsychological functioning accurately predicted the hemisphere of lower flow in 71-92% of cases, depending on the method of cerebral blood flow asymmetry determination. Agreement between cerebral blood flow and neurobehavioral signs of asymmetry was greater for initial slope and initial slope index than for the fast flow index. The initial slope and initial slope index showed equally good agreement. The use of the number of asymmetrical probe pairs to detect cerebral blood flow asymmetries agreed less well with neurobehavioral asymmetry than did the other two markers studied.

CONCLUSIONS

Both the initial slope index and the initial slope measures of cerebral blood flow are useful in predicting neuropsychological asymmetries, especially when the magnitude of the asymmetry is taken into account.

Characterization of transcription initiation sites on the soybean mitochondrial genome allows identification of a transcription-associated sequence motif

Transcription initiation sites on the soybean mitochondrial genome have been characterized by sequence analysis of in vitro-capped soybean mtRNAs and corresponding mtDNA regions. The most abundant, discrete soybean mtRNA species labeled by guanylyltransferase and [alpha-32P]GTP are shown to correspond to the major transcript of the atp9 gene and to a group of small RNAs consisting of a discrete 80 nucleotide (nt) species plus heterogeneous species ranging in size from 133 to 148 nt. The 133-148 nt RNAs represent a set of transcripts with a common 5' terminus and ragged 3' ends, while the 80 nt RNA corresponds to positions 53-133 of the 133 nt species. The major, discrete in vitro-capped RNA species thus correspond to primary transcripts originating at three sites located in two regions of the soybean mitochondrial genome. The sequences extending from 13 nucleotides upstream to 8 nucleotides downstream of the initiation sites for the atp9 and 133-148 nt transcripts are identical at 18 of 21 positions. Sequences closely resembling this motif are located at some other 5' transcript termini of dicot plant mitochondria. Less closely related sequences are found at transcription initiation sites of wheat and maize mitochondria.

Efficient plant regeneration from hypocotyl protoplasts of broccoli (Brassica oleracea L. ssp. italica Plenck)

We have assessed the capacity of cultured protoplasts from two tissue sources of several commercially-grown broccoli cultivars to regenerate plants. A procedure that employs hypocotyl protoplasts and a culture medium with a high NAA:2,4-D auxin ratio was developed. The procedure permits highly efficient formation of colonies that regenerate shoots at frequencies of 8-17% with two of the four cultivars tested. The time required for the development of plants from protoplasts was 8-11 weeks. No mtDNA rearrangements were observed among any of 17 analysed regenerants. Double-stranded RNAs were detected in mitochondrial DNA (mtDNA) preparations of some, but not all, regenerants of one of the cultivars.

Transcriptional and Post-Transcriptional Regulation of RNA Levels in Maize Mitochondria

Relatively little is known about the mechanisms that govern the expression of plant mitochondrial genomes. We have addressed this problem by analyzing the transcriptional activity of different regions of the maize mitochondrial genome using both in vivo and isolated mitochondrial pulse-labeling systems. The regions examined included the protein genes atpA, atp6, and coxII, the 26S, 18S, and 5S rRNA genes, and sequences surrounding the rRNA genes. The rRNAs were found to be transcribed at rates fivefold to 10-fold higher than the protein genes. These rate differences are comparable with the differences in abundance of these species in the total or steady-state RNA population. Pulse-labeled RNA unexpectedly detected transcription of all regions examined, including approximately 21 kilobases of presumed noncoding sequences flanking the rRNA genes for which stable transcripts were not detected. The results obtained with RNA labeled for short pulses in vivo and in isolated mitochondria were similar, suggesting that isolated mitochondria provide a faithful run-on transcription assay. Our results indicate that the absence in total RNA of transcripts homologous to a given region of maize mitochondrial DNA does not necessarily exclude transcriptional activity of that region and that both transcriptional and post-transcriptional processes play important roles in maize mitochondrial genome expression.

In vivo 31P NMR profiles of Alzheimer's disease and multiple subcortical infarct dementia

We used in vivo phosphorus 31 nuclear magnetic resonance (31P NMR) spectroscopy to study regional high-energy phosphate and phospholipid metabolism in brains of patients with dementia associated with probable Alzheimer's disease (AD) and multiple subcortical cerebral infarctions (MSID). The MSID patients demonstrated elevations of the phosphocreatine (PCr)/inorganic orthophosphate (Pi) ratio in both the temporoparietal and frontal regions. Phosphomonoesters (PME) and the ratio of PME to phosphodiesters were elevated in the temporoparietal region of AD. Pi was also elevated in the frontal and temporoparietal regions of AD. Findings from 31P NMR were accurate in distinguishing MSID from AD. Values of PCr/Pi accurately classified 100% of the MSID patients and 92% of AD. Pi and PME, considered jointly, also accurately classified all MSID and all but 1 AD. Findings from in vivo 31P NMR spectroscopy appear to yield metabolic profiles useful in distinguishing AD from MSID.

Memory functioning following a left medial thalamic hematoma

A patient with a discrete, left medial thalamic hematoma developed a severe anterograde amnesia. The memory deficit was most consistent for verbal materials, but was also observed on several tests of figural memory. The patient appeared to have a normal short-term memory (STM) capacity, performed normally on a STM distractor task and was not abnormally sensitive to proactive inhibition. This case is evidence that unilateral damage to the medial thalamus alone can produce a severe memory deficit.

Bilateral posterior cerebral artery strokes in a young migraine sufferer

We report a young migraine sufferer who developed bilateral posterior cerebral artery territory infarcts during the course of his classic migraines, the second of which was associated with intraluminal clot in the posterior cerebral artery. To our knowledge, bilateral posterior cerebral artery stroke from spontaneous migraine has not been reported. Head computed tomographic, magnetic resonance imaging, and angiographic correlation is presented. The mechanism of migrainous infarction may be in part explained by caliber changes in arterioles and capillaries leading to flow reduction in the more proximal conduit arteries combined with the associated coagulopathy that has been previously documented during migraine attacks.

Length and restriction site heteroplasmy in the mitochondrial DNA of american shad (alosa sapidissima)

Restriction endonuclease analysis was used to assess mitochondrial DNA (mtDNA) variation in American shad (Alosa sapidissima) collected from 14 rivers ranging from Florida to Quebec. Two types of heteroplasmy were observed, one involving a major length polymorphism and the other a single restriction site. Shad mtDNA occurred in two principal size classes, 18.3 and 19.8 kb. Of 244 shad examined, 30 were heteroplasmic and carried both size classes of mtDNA in varying proportions; the remainder were homoplasmic for the smaller size class of mtDNA. The large mtDNA variant occurred most frequently at the southern end of the range, and except for two individuals from Nova Scotia, was not detected among shad from rivers north of the Delaware. In contrast, ten shad heteroplasmic for a SalI restriction site originated from rivers ranging from South Carolina to Nova Scotia. DNA mapping and hybridization experiments indicated that the length polymorphism is in the D-loop-containing region and consists of a tandemly repeated 1.5-kb DNA sequence occurring in two and three copies, respectively, in the two major size classes of shad mtDNA. Continuous length variation up to approximately 40 bp occurs among copies of the repeat both within and among individuals. Restriction site data support the conclusion that both forms of heteroplasmy in shad mtDNA have originated more than once.

Effects of lateralized cerebral dysfunction on the Continuous Paired-Associate Test

Some authorities have advocated matching tests on several critical psychometric properties before inferring the presence of a differential pattern of deficit. This study examined the effects of lateralized cerebral dysfunction on the matched Verbal and Design subtests of the Continuous Paired-Associate Test (CPAT). Patients with lateralized destructive lesions were studied in Experiment 1. Epileptic patients with lateralized electroencephalographic findings were studied in Experiment 2. Left but not right hemispheric abnormalities impaired performance on the Verbal CPAT, but only for destructive lesions. The Designs CPAT was a nonspecific indicator of cerebral dysfunction. For studies with the goal of predicting laterality of cerebral dysfunction, we advocate a two-step strategy of test development. The first step would make use of the principle of double dissociation in selecting items to compose subtests. The second step would involve an item analysis of subtests to determine the need for matching.

In organello transcription in maize mitochondria and its sensitivity to inhibitors of RNA synthesis

Purified mitochondrial preparations from etiolated maize shoots support the incorporation of radioactivity from labeled UTP into RNA. The incorporation is linear with time for up to 2 hours, shows Michaelis-Menton kinetics with respect to the concentration of the labeled substrate, UTP, and has salt and pH optima which are different than those previously reported for RNA synthesis by isolated chloroplasts. When a crude mitochondrial preparation is subjected to isopycnic sucrose gradient centrifugation, the bulk of the RNA synthetic activity co-sediments with mitochondrial marker enzymes and with the mitochondrial 26S and 18S rRNAs. Maize mitochondrial RNA synthesis is prevented by actinomycin D and ethidium bromide but unaffected by alpha-amanitin. It is strongly inhibited by rifampicin at concentrations which have no effect on nuclear and chloroplast RNA synthesis, but only moderately inhibited by rifampicin at concentrations which completely inhibit bacterial RNA synthesis. The optimization, cell fractionation, and inhibitor data all suggest that contaminating organelles and bacteria do not contribute appreciably to the RNA synthesis in purified mitochondrial preparations.

Neuropsychological deficits and real-world dysfunction in cerebral revascularization candidates

An assessment strategy using multiple levels of observation permitted description of problems in everyday living experienced by cerebral revascularization candidates. We contrasted the neuropsychological deficits and real-world dysfunction displayed by candidates for cerebral revascularization with that manifested by patients with severe spinal complaints. Correlations between selected neuropsychological scores and life quality measures were modest. Prediction of real-world performance in individuals likely will require multivariate combinations of measures. Relationships between life quality measures and neuropsychological scores may differ for patients with known or suspected neurological disease and patients with disorders which do not threaten cognitive functioning.

Phosphorus-31 nuclear magnetic resonance studies of spermatozoa from the boar, ram, goat and bull

1. Phosphorus-31 nuclear magnetic resonance spectroscopy (31P-NMR) was utilized to examine semen and spermatozoa isolated from boars, rams, goats and bulls. 2. Whole semen was found to contain high but variable levels of glycerylphosphocholine, most of which was located in the seminal plasma rather than in the spermatozoa. 3. Spermatozoa concentrated into a pellet were found to contain resonances for inorganic phosphate, phosphomonoesters including fructose-1,6-bisphosphate and glucose-6-phosphate, and free nucleotide triphosphate peaks. 4. A broad resonance was observed from 30 to -25 ppm which originated partly from nucleotide tri- and diphosphates. 5. No high energy molecules such as phosphoarginine or phosphocreatine which could act as energy shuttles were observed.

Structural conservation and variation in the D-loop-containing region of vertebrate mitochondrial DNA

The nucleotide sequences of the D-loop-containing regions of three rat mitochondrial DNAs (mtDNAs), two from the species Rattus norvegicus and one from R. rattus, were determined. Comparisons made among these sequences and with the mouse sequence showed that, on the basis of both base composition and frequency of nucleotide alterations, three domains could be defined within the D-loop-containing region: a central conserved segment, poor in L-strand adenine, flanked by two divergent, adenine-rich regions. Deletions and insertions were found to occur at an unexpectedly high frequency in these sequences and the conserved sequence block called CSB-1 was found not to be intact in the R. rattus sequence. Although in comparisons of more distantly related mtDNAs the D-loop region is the most divergent on the molecule, it does not diverge more than typical protein genes between R. norvegicus and R. rattus, and its central conserved domain appears to be one of the molecule's most conserved regions. The most variable domain borders the tRNAPhe gene and contains the L and H-strand promoters and the 5' terminus for H-strand DNA synthesis. Within this region we have found sequences in all the mtDNAs we have examined, including those of human, two artiodactyls and Xenopus, that are capable of folding into cloverleaf structures. In the other divergent domain of the same mtDNAs, we find sequences capable of assuming similar secondary structural configurations at or near the sites for the termination of D-loop DNA synthesis. The evolutionary preservation of the potential to form such structures despite the high primary-structural divergence of the regions they occur in, suggests the structures are of principal importance for some processes occurring in the D-loop-containing region.

Analysis of covariance as a remedy for demographic mismatch of research subject groups: some sobering simulations

Analysis of Covariance (ANCOVA) is often used in neuropsychological studies to effect ex-post-facto adjustment of performance variables amongst groups of subjects mismatched on some relevant demographic variable. This paper reviews some of the statistical assumptions underlying this usage. In an attempt to illustrate the complexities of this statistical technique, three sham studies using actual patient data are presented. These staged simulations have varying relationships between group test performance differences and levels of covariate discrepancy. The results were robust and consistent in their nature, and were held to support the wisdom of previous cautions by statisticians concerning the employment of ANCOVA to justify comparisons between incomparable groups. ANCOVA should not be used in neuropsychological research to equate groups unequal on variables such as age and education or to exert statistical control whose objective is to eliminate consideration of the covariate as an explanation for results. Finally, the report advocates by example the use of simulation to further our understanding of neuropsychological variables.

Construction of matched verbal and design continuous paired associate tests

We developed verbal and figural continuous paired associate tests (CPAT) that are matched on internal consistency and on the distributional properties of mean item difficulty, variance, and skewness. The Verbal CPAT is composed of high frequency nouns, verbs, and adjectives. Selection of the designs was guided by literature on the effects of right-hemisphere damage on memory for designs. One hundred subjects were given 80 items from the verbal CPAT and 80 items from the designs CPAT. Twenty subjects at these five ranges of Wechsler Memory Quotient were evaluated: less than or equal to 79, 80-89, 90-99, 100-109, greater than or equal to 109. The final 40-item version of the Verbal CPAT had a mean of 26.72, a SD of 7.03, and an alpha of .859. The Designs CPAT had a mean of 26.42, a SD of 7.75, and an alpha of .886. Neither test was significantly skewed. These matched tests should be useful in making inferences about differences between verbal and figural memory that are not confounded with the problem of differential test sensitivity.