Characterization of Mitochondrial Small-Subunit Ribosomal RNAs from Holoparasitic Plants

Mitochondrial small-subunit (19S) rDNA sequences were obtained from 10 angiosperms to further characterize sequence divergence levels and structural variation in this molecule. These sequences were derived from seven holoparasitic (nonphotosynthetic) angiosperms as well as three photosynthetic plants. 19S rRNA is composed of a conservative core region (ca. 1450 nucleotides) as well as two variable regions (V1 and V7). In pairwise comparisons of photosynthetic angiosperms to Glycine, the core 19S rDNA sequences differed by less than 1.4%, thus supporting the observation that variation in mitochondrial rDNA is 3–4 times lower than seen in protein coding and rDNA genes of other subcellular organelles. Sequences representing four distinct lineages of nonasterid holoparasites showed significantly increased numbers of substitutions in their core 19S rDNA sequences (2.3–7.6%), thus paralleling previous findings that showed accelerated rates in nuclear (18S) and plastid (16S) rDNA from the same plants. Relative rate tests confirmed the accelerated nucleotide substitution rates in the holoparasites whereas rates in nonparasitic plants were not significantly increased. Among comparisons of both parasitic and nonparasitic plants, transversions outnumbered transitions, in many cases more than two to one. The core 19S rRNA is conserved in sequence and structure among all nonparasitic angiosperms whereas 19S rRNA from members of holoparasitic Balanophoraceae have unique extensions to the V5 and V6 variable domains. Substitution and insertion/deletion mutations characterized the V1 and V7 regions of the nonasterid holoparasites. The V7 sequence of one holoparasite (Scybalium) contained repeat motifs. The cause of substitution rate increases in the holoparasites does not appear to be a result of RNA editing, hence the underlying molecular mechanism remains to be fully documented. Received: 18 May 1997 / Accepted: 11 July 1997     

Decreased [3H]ouabain binding sites in skeletal muscle of rats with chronic heart failure

Pickar, Joel G., John P. Mattson, Steve Lloyd, and TimothyI. Musch. Decreased[³H]ouabainbinding sites in skeletal muscle of rats with chronic heart failure.J. Appl. Physiol. 83(1): 323-329, 1997.Abnormalities intrinsic to skeletal muscle are thought tocontribute to decrements in exercise capacity found in individualswith chronic heart failure (CHF).Na⁺-K⁺-adenosinetriphosphatase(the Na⁺ pump) is essential formaintaining muscle excitability and contractility. Therefore, weinvestigated the possibility that the number and affinity ofNa⁺ pumps in locomotor muscles ofrats with CHF are decreased. Myocardial infarction (MI) was induced in8 rats, and a sham operation was performed in 12 rats. The degree ofCHF was assessed ~180 days after surgery. Soleus and plantarismuscles were harvested, and Na⁺pumps were quantified by using a[³H]ouabain bindingassay. At the time of muscle harvest, MI and sham-operated rats weresimilar in age (458 ± 54 vs. 447 ± 34 days old, respectively).Compared with their sham-operated counterparts, MI rats had asignificant amount of heart failure, right ventricular-to-body weightratio was greater (48%), and the presence of pulmonary congestion wassuggested by an elevated lung-to-body weight ratio (29%). Leftventricular end-diastolic pressure was significantly increased in theMI rats (11 ± 1 mmHg) compared with the sham-operated controls (1 ± 1 mmHg). In addition, mean arterial blood pressure was lower inthe MI rats compared with their control counterparts. [³H]ouabain bindingsites were reduced 18% in soleus muscle (136 ± 12 vs. 175 ± 13 pmol/g wet wt, MI vs. sham, respectively) and 22% in plantaris muscle(119 ± 12 vs. 147 ± 8 pmol/g wet wt, MI vs. sham,respectively). The affinity of these[³H]ouabain bindingsites was similar for the two groups. The relationship between thereduction in Na⁺ pump number andthe reduced exercise capacity in individuals with CHF remains to bedetermined.

     

Population dynamics of a meiotic/mitotic expansion model for the fragile X syndrome.

A model to explain the mutational process and population dynamics of the fragile X syndrome is presented. The mutational mechanism was assumed to be a multipathway, multistep process. Expansion of CGG repeats was based on an underlying biological process and was assumed to occur at two time points: meiosis and early embryonic development (mitosis). Meiotic expansion was assumed to occur equally in oogenesis and spermatogenesis, while mitotic expansion was restricted to somatic, or constitutional, alleles of maternal origin. Testable hypotheses were predicted by this meiotic/mitotic model. First, parental origin of mutation is predicted to be associated with the risk of a woman to have a full mutation child. Second, "contractions" seen in premutation male transmissions are predicted not to be true contractions in repeat size, but a consequence of the lack of mitotic expansion in paternally derived alleles. Third, a portion of full-mutation males should have full-mutation alleles in their sperm, due to the lack of complete selection against the full-mutation female. Fourth, a specific premutation-allele frequency distribution is predicted and differs from that based on models assuming only meiotic expansion. Last, it is predicted that approximately 65 generations are required to achieve equilibrium, but this depends greatly on the expansion probabilities.     

The urgency of building global capacity for biodiversity science

The biodiversity sciences represent the disciplines of whole-organism biology, including systematics, ecology, population biology, behaviour and the fields of comparative biology. The biodiversity sciences are critically important to society because it is knowledge of whole-organisms that is essential for managing and conserving the world's species. Because of an acceleration in environmental degradation and global biodiversity loss in recent decades, the need for the biodiversity sciences has never been more urgent. Yet, biodiversity science is not well supported relative to other fields of science, and thus the need for knowledge about organisms and their environment is far outstripping biologists' ability to provide it. National and international capacity for biodiversity science must therefore be increased substantially. Each nation should establish a national biodiversity research programme coordinated across all government agencies. An international biodiversity research programme should also be established, perhaps with an organizational structure that parallels the International Geosphere-Biosphere Programme. Biodiversity scientists must assume a leadership role in educating the public and bringing about policy changes that will enhance our understanding of the world's species and their ecosystems.     

Stability in an evolutionary game

A behavior or strategy which is evolutionarily stable must be both optimal and stable. The strategy must be optimal in that it maximizes the expected fitness of all the individuals using it. In addition, the strategy must be resistant to invasion by a mutant. The difference between the Nash solution of game theory and the ESS used in ecology is that the Nash solution only satisfies an optimality criterion and not an evolutionary stability criterion. We extend the ESS definition of Maynard Smith and Price so that it can be applied directly to two-strategy evolutionary games. The concept of a balanced game is introduced, and necessary conditions are derived which are similar to the Nash necessary conditions. The balanced game necessary conditions may be used for direct calculation of ESS candidates. These results are used to examine the optimal flowering time of an annual plant experiencing competition from neighboring plants. The plant competition model is general, and the results may be applied to a wide range of interference competition problems.     

Perilymphatic Fistula—A Definitive and Curable Cause of Vertigo Following Head Trauma

Vertigo or disequilibrium occurring in patients after concussive and nonconcussive head trauma may be due to a pathologic perilymphatic fistula from the inner ear through the oval and round window areas of the middle ear. Of 33 patients who had successful grafting of the fistulous area at middle ear exploration, 32 had resolution of vertigo, and 12 of 23 who had an associated hearing loss had improved hearing. Perilymphatic fistulas associated with vertigo and hearing loss after head trauma can be diagnosed with great certainty and are surgically curable in the great majority of cases. Patients with post-concussive syndrome, whose symptoms include vertigo or disequilibrium, should have a thorough otologic evaluation for the possibility of a perilymphatic fistula.     

Nd-YAG Laser in Lung Cancer

We administered 45 Nd-YAG laser treatments in 29 patients (18 men) aged 39 to 82 years who had lung malignancy; 26 patients had primary non-oat cell lung cancer and three had metastatic airway malignancy. In all, 25 of the patients had been previously treated with combination(s) of surgical procedure, radiation therapy and chemotherapy. Indications for laser treatment included endobronchial airway obstruction with uncontrolled cough, hemoptysis, dyspnea or unresolved atelectasis-pneumonia. Of 15 patients with partially occluded tracheobronchial airway tumors, immediate palliative relief was achieved in 13 patients and lasted one to six months after a single treatment. In this group there was one postoperative death related to respiratory failure and two patients subsequently died of massive pulmonary hemorrhage. However, of 14 patients with totally obstructed airways, immediate palliative relief was achieved in only five patients and this lasted three weeks to three months after a single treatment. In this group there were two postoperative deaths related to progressive respiratory failure; in one case it was associated with endobronchial combustion of the fiberoptic bronchoscope. All three patients in both groups who died of respiratory failure were in acute respiratory distress and terminally ill before the procedure. These findings suggest that Nd-YAG laser therapy may be most beneficial in patients with partially rather than totally occluded airways due to lung malignancy.     

Electroencephalographic biofeedback of SMR and beta for treatment of attention deficit disorders in a clinical setting

Six children were provided with long-term biofeedback and academic treatment for attention deficit disorders. Their symptoms were primarily specific learning disabilities, and, in some cases, there were varying degrees of hyperkinesis. The training consisted of two sessions per week for 10 to 27 months, with a gradual phase-out. Feedback was provided for either increasing 12-to 15-Hz SMR or 16- to 20-Hz beta activity. Inhibit circuits were employed for blocking the SMR or beta when either gross movement, excessive EMG, or theta (4–8 Hz) activity was present. Treatment also consisted of combining the biofeedback with academic training, including reading, arithmetic, and spatial tasks to improve their attention. All children increased SMR or beta and decreased slow EEG and EMG activity. Changes could be seen in their power spectra after training in terms of increased beta and decreased slow activity. All six children demonstrated considerable improvement in their schoolwork in terms of grades or achievement test scores. None of the children are currently on any medications for hyperkinetic behavior. The results indicate that EEG biofeedback training, if applied comprehensively, can be highly effective in helping to remediate children who are experiencing attention deficit disorders.The authors would like to thank Mr. Kevin Bianchini for his assistance in this study.     

Comparison of chemical properties of purified plasma membranes and secretory vesicle membranes from the bovine adrenal medulla

Summary A highly enriched fraction of plasma membranes from the bovine adrenal medulla has been isolated by differential and sucrose gradient centrifugation. The membranes were found to occur as 0.1–0.5 diameter vesicles and to equilibrate at a density of 1.13–1.14 g/ml. This fraction was characterized by 4-fold elevated levels of adenylate cyclase and 20-fold elevated levels of 5-nucleotidase. Secretory vesicle membranes, isolated by repeated hypotonie and hypertonic shocks of whole vesicles, were found to equilibrate between d = 1.08 and d = 1.12 on a sucrose density step gradient. These membranes were highly enriched in cytochrome b₅₆₂ and dopamine--hydroxylase. Proteins in the two membranes were compared by SDS gel electrophoresis. All protein size classes found in the vesicle membrane fraction were also represented in the plasma membrane fraction, though in different proportions on the basis of staining intensity. The plasma membrane fraction contained prominent bands co-migrating with the - and -bands of tubulin, as well as a component co-migrating with actin. These bands were absent from the vesicle membranes. Fingerprint analysis of stained bands from the membrane fraction demonstrated that the components were indeed tubulin and actin. The plasma membranes contained twice as much sialic acid residues as did the chromaffin granule membranes, but had only half the cholesterol content on a weight basis. The cholesterolphospholipid ratio in the plasma membranes was 0.63, while in the secretory vesicle membranes it was 1.04. These results show that plasma membranes and secretory vesicle membranes are functionally and structurally different.Supported, in part, by a stipend to O.Z. from The Grant Foundation, New York