A Quantitative Approach to Investigating the Hypothesis of Prokaryotic Intron Loss

Using a novel method, we show that ordered triplets of motifs usually associated with spliceosomal intron recognition are underrepresented in the protein coding sequence of complete Thermotogae, archaeal and bacterial genomes. The underrepresentation observed does not extend to the noncoding strand, suggesting that the cause of the asymmetry is related to mRNA rather than DNA. Our data do not suggest that the underrepresentation is due to gene transfer from eukaryotes. We speculate that one possible explanation for these observations is that the protein coding sequence of Thermotogae, Archaea and Bacteria was at some time in the past subjected to selection against certain motifs appearing in an order which might initiate splicing in environments harboring a functional spliceosome. This is consistent with, but certainly does not prove, a hypothetical scenario in which at least some prokaryote lineages once possessed a functional spliceosome. Thus, we present a new quantitative method, observations obtained using the method, and a speculative discussion of a possible explanation of the observations

A Primary Ecological Survey of Dardanelle Reservoir Prior to Nuclear Facility Effluent Discharge

A preliminary ecological survey of Dardanelle Reservoir during the construction phase of Arkansas Power and Light Company\u27s nuclear generating facility was conducted from January 1970 through June 1974. The reservoir is characterized by relatively shallow depths and a high flow-thru rate. A number of features were associated with these characteristics. The reservoir carried a great deal of suspended material and exhibited high turbidities throughout most of the year. Typical thermal stratification and oxygen depletion were only rarely observed. Many of the physico-chemical parameters exhibited relatively high values in comparison to other Arkansas lakes and reservoirs, but due to absence of prolonged periods of stratification and stagnation, they did not undergo the extreme fluctuations sometimes observed in other reservoirs. Plankton and benthic samples were collected at least nine times per year from ten stations. These stations were selected to include both shallow and deep locations and to include points both within and outside the projected area of thermal influence when the plant became operational. There were a great variety of forms in the phytoplankton with the diatoms making up a considerable portion. The level of turbidity appeared to dampen somewhat the extreme fluctuations sometimes found in bloom periods. In the zooplankton the rotifers Brachionus, Keratella, and Polyarthra predominated followed by the microcrustaceans Cyclops and Bosmina. Both the plankton and the benthic fauna showed great seasonal variation. The benthic fauna consisted primarily of Chironomidae, Oligochaeta, and Hexagenia with the Chironomidae predominating in the shallower depths and the Oligochaeta exhibiting increased abundance and importance in the deeper stations

Do rational numbers play a role in selection for stochasticity?

When a given tissue must, to be able to perform its various functions, consist of different cell types, each fairly evenly distributed and with specific probabilities, then there are at least two quite different developmental mechanisms which might achieve the desired result. Let us begin with the case of two cell types, and first imagine that the proportion of numbers of cells of these types should be 1:3. Clearly, a regular structure composed of repeating units of four cells, three of which are of the dominant type, will easily satisfy the requirements, and a deterministic mechanism may lend itself to the task. What if, however, the proportion should be 10:33? The same simple, deterministic approach would now require a structure of repeating units of 43 cells, and this certainly seems to require a far more complex and potentially prohibitive deterministic developmental program. Stochastic development, replacing regular units with random distributions of given densities, might not be evolutionarily competitive in comparison with the deterministic program when the proportions should be 1:3, but it has the property that, whatever developmental mechanism underlies it, its complexity does not need to depend very much upon target cell densities at all. We are immediately led to speculate that proportions which correspond to fractions with large denominators (such as the 33 of 10/33) may be more easily achieved by stochastic developmental programs than by deterministic ones, and this is the core of our thesis: that stochastic development may tend to occur more often in cases involving rational numbers with large denominators. To be imprecise: That simple rationality and determinism belong together, as do irrationality and randomness

Spinal Anaesthesia, with Special Reference to Neurological Complications

The studies reported in this thesis were undertaken because the author believed that the merits of spinal anaesthesia were being obscured by prejudice, and that a reassessment of the method was indicated. Consideration of the history of spinal anaesthesia, with the earlier reckless use of imperfect techniques, explains in part the persistence of distrust of the method. A survey of the literature revealed many clinical reports of serious neurological complications following spinal anaesthesia, but critical study of these reports showed that many were of doubtful value and could largely be discredited because either the details of administration were not divulged or the technique was at fault. The relevant Anatomy, physiology and Pharmacology is discussed. Experimental proof is quoted that the incidence of cauda equina lesions in cats is in direct proportion to the concentration of the anaesthetic solution. Stovaine was shown to be a damaging drug. The nature of neurological lesions after spinal anaesthesia, both experimental and clinical, is studied, of which a cauda equina lesion is the most common. The damage to the nervous tissues is directly due to a neurotoxic effect of the anaesthetic drug. Reports of histological examinations showed that the changes were mainly in the nerve roots and in the periphery of the cord. These changes consisted of swelling and fragmentation of the axis cylinders and degeneration of the myelin sheaths. There was also a meningeal reaction with leucocytic infiltration, which reaction may proceed to fibrosis. The development of spinal anaesthetic practice is traced, showing its evolution and the continuous improvements in technique. The use of covering anaesthesia, for example, has removed a previous objection to the method, without loss of any of its advantages. The rationale of total sympathetic block is set forth. It is not uncommon to find a vague, subconscious disquietude concerning spinal anaesthesia, and this is reflected in the opinions expressed to the writer by the Nursing Staff, and given in the text, although the general impression is favourable. The methods of sterilisation are reviewed and medicolegal aspects of meningitis following spinal anaesthesia discussed. The author's technique of spinal anaesthesia is described in detail, and the need for scrupulous asepsis is emphasised. The use of a 0.4% isotonic solution of amethocaine was recommended. There is presented a personal series of 1335 spinal anaesthetics. Of these patients, 536 were examined in detail before their departure from hospital, in order to disclose any evidence of neurological dysfunction, either overt or unsuspected, which may have been due to the spinal anaesthetic, and 76 patients were also re-examined six months to two years later, with the same purpose in view. The examination included a careful enquiry for headache, diplopia, retention of urine, incontinence of faeces, paraesthesiae and weakness of the lower limbs. Sensation was tested in the legs and sacral area, the reflexes examined, and anal sphincter tone estimated. The results confirmed the author's belief that no neurological sequelae of any import were arising in his cases. Spinal headache was divided into three grades of severity, and it was found that very slight headache occurred in 13.2%, and moderate headache in 6%, of these cases. Severe headache was not encountered and 80.8% of the patients did not suffer from headache at all. One case of fleeting diplopia was noted, and also one case of transient leg pains which may have been due to the spinal anaesthetic. No infective meningitis occurred. A short investigation into the effects of spinal anaesthesia on the cerebrospinal fluid was undertaken. The results did not substantiate the finding, quoted frequently in the literature, that spinal anaesthesia in nearly every case produces a definite rise in the cerebrospinal fluid cell-count, due to meningeal irritation. Specimens of cerebrospinal fluid from 46 patients were examined before the spinal anaesthetic was administered, and again about 24 hours later. In only one specimen was there a marked rise in the cell-count after spinal anaesthesia (390 per c.mm.) This patient was quite symptomless and afebrile, she made an uninterrupted recovery from operation and was well when re-examined nine months later. It was concluded that spinal anaesthesia is a satisfactory method of anaesthesia and there is no need to fear neurological complications following its use. Furthermore, the concentration of the anaesthetic solution was shown to be of the greatest consequence, and it was pointed out that there is a definite low and safe level of concentration, at which uncomplicated and effective anaesthesia can be achieved and which it is unnecessary and undesirable to exceed

The test-retest reliability of different ankle joint center location techniques

Accurate and reliable joint identification is imperative for the collection of meaningful kinetic and kinematic data. Of the lower kinetic chain both the hip and knee joints have received a considerable amount of attention in 3D modelling. However, the reliability of methods to define the ankle joint center have received very little attention. This study investigated the reliability of the two marker method (TMM) and the functional ankle method (FAM) on estimating the ankle joint center. Furthermore, the effects of the two-marker method reliability for defining the ankle joint center when the ankle was covered with a brace or protector was investigated. 3D kinematic data was collected from ten participants (8 female and 2 male) whilst walking. The ankle joint center was defined twice using each test condition; TMM (WITHOUT), FAM (FUNCTIONAL), TMM when the ankle was covered with a brace (BRACE), and TMM when the ankle was covered with a protector (PROTECTOR). Intraclass correlations (ICC) were utilised to compare test and retest waveforms and paired samples t-tests were used to compare angular parameters. Significant differences were found in the test-retest angular parameters in the transverse and sagittal planes for the WITHOUT, BRACE, and FUNCTIONAL conditions. The strongest test-retest ICC’s were observed in the WITHOUT and PROTECTOR conditions. The findings of the current investigation indicate that there are fewer errors using the TMM when the ankle is uncovered or when covered with soft foam that is easy to palpate through

Mycological studies in methods of improving the antibiotic yield of micro-organisms

This work was carried out in an attempt to increase the efficiency of mutation programmes designed to produce strains of micro -organisms giving greater antibiotic yield. The problem was approached from two angles. First, radioactive sulphur (S35),recently shown in America to be a very effective general muta- genic agent for Neurospora crassa, was used to treat two antibiotic -producing fungi, Penicillium chrysogenum (penicillin) and P. p atulum (griseofulvin), and with both these species it proved to be an efficient agent for inducing mutations capable of increased antibiotic production. Secondly, methods of screening putative mutants were developed that enable larger numbers of isolates to be screened per unit time than has hitherto been possible by the conventional methods.Treatment of P. chrysogenum var. brevisterigma with sulphur -35 consistently yielded isolates 60% of which had mutated in their potential penicillin pro- duction and slightly more than 1% of these gave higher yields than the parent strain. A primary screening technique, designed to pick out these higher yielding strains, was evolved. This was based on the principle of using the antibiotic production of the isolate grow- ing on the surface of an agar culture as a measure of its potential yield in submerged fermentation. It is similar to one developed recently in Japan, but avoids the inaccuracies that the Japanese author ascribes to his method by maintaining continuity of the fermentatioi medium throughout. By using sulphur -35 as the mutagenic agent, and this surface-culture screening technique, an improved penicillin -producing strain (Strain B) was found among the first 50v isolates tested; on accurate testing it showed a 25 -35% improvement on the parent, although it required a slightly richer medium to achieve this increase. A second similar mutation programme with Strain B as the parent produced, among 600 isolates tested, a second mutant (Strain C) capable of the same penicillin yield as Strain B, but not requiring an enriched medium for the purpose. Both these mutants were considered to be potentially useful for industrial production.With a culture of Penicillium patùlum, which produces the antibiotic griseofulvin, there were carrie out mutation programmes involving the use of sulphur -35 and ultra - violet irradiation as separate mutagenic agents. As the surface culture screening technique did not lend itself readily to the assay of griseo- fulvin, one based on a small -volume fermentation was developed. With this technique it was found that s sulphur -35 produced a high mutation rate (about 40 %) for antibiotic yield of the treated isolates, several of which showed considerably improved yields over the parent. Two of the first 400 sulphur - treated isolates gave, on accurate testing, almost 100% improvement in the yield of griseofulvin. 'l'he ultra- violet treatment, the although producing some improved mutants, did not give as many as the sulphur method, nor were those produced as satisfactory as the ones induced by the radioactive isotope.These results strongly indicate that sulphur -35 is an efficient mutagen for producing strains of fungi yielding increased quantities of antibiotics. This is considered at length in the general discussion. The two primary screening techniques developed have been shown to be at once sufficiently accurate and capable of dealing with greater numbers of isolates than the more conventional methods.In addition, some preliminary research is des- cribed, undertaken to find out the effects of griseo- fulvin on plant pathogenic fungi of the genus Bot Otis., Experiments in vitro and in vivo showed that the presence of the antibiotic upsets the mechanism of hyphal wall in the pathogen, leading in vivo ï to inability of the hyphae to penetrate the cell membranes of the host