Showing papers by "University of London published in 1972"

Oral Health Surveys: Basic Methods

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A General Theory for Cluster and Ring Compounds of the Main Group and Transition Elements

Abstract: Simple rules are presented for rationalizing and predicting the geometries of complex polynuclear aggregates of atoms and molecular fragments

FUNCTIONAL and STRUCTURAL ASPECTS OF BIOLOGICAL MEMBRANES: A SUGGESTED STRUCTURAL ROLE FOR VITAMIN E IN THE CONTROL OF MEMBRANE PERMEABILITY and STABILITY

Abstract: Some biological membranes, such as the plasma membrane of the erythrocyte and the lysosomal membranes, may be regarded primarily as barriers that serve to compartmentalize living tissue. Physical studies have shown that phospholipids spontaneously form lipid bilayers, as a consequence of containing chemical groups some of which have a high and others a low affinity for water. The similarities of the permeability properties of these artificial lipid bilayers' to those of natural membranes provide a strong experimental justification for regarding the lipid bilayer as the physical basis of the ability of membranes to function as barriers. It is nevertheless equally apparent that the lysosomal membrane system depends for its successful functioning upon a controlled measure of membrane instability, which allows for the processes of endocytosis and exocytosis, the formation of secondary lysosomes, and the development of autophagic vacuoles, by various processes of membrane fusion. Such variations in membrane stability may depend on controlled equilibria between bilayer and micellar arrangements in the lipids of membranes.2 In the present paper it is proposed that uncontrolled changes in membrane permeability and stability may occur in the absence of vitamin E, and hence that a deficiency of this vitamin may lead to a failure of compartmentalization by biological membranes. Other membranes, such as the inner membranes of mitochondria and the membranes of the endoplasmic reticulum, although they also form compartments, are particularly important as sites for the localization and attachment of enzyme systems. If, as is proposed here, a deficiency of vitamin E results in a perturbation and a subsequent breakdown of structure in membranes of this type, failures of metabolic function will occur in a variety of subcellular organelles. The consequences to living cells of these changes will be at least as damaging as failures in the membranes that constitute cellular and subcellular boundaries.

Lysosomal localization of β-fructofuranosidase-containing liposomes injected into rats. Some implications in the treatment of genetic disorders

Abstract: Yeast β-fructofuranosidase (invertase) or 131I-labelled albumin were entrapped into liposomes composed of phosphatidylcholine, cholesterol and phosphatidic acid. Of the β-fructofuranosidase activity in the liposomal preparations 96–100% was latent. The following observations were made in experiments with rats injected with protein-containing liposomes. 1. After injection of β-fructofuranosidase-containing liposomes (220 units or 1.5mg of β-fructofuranosidase and 17.5mg of lipid), β-fructofuranosidase activity in blood retained its latency but the activity declined to 50% of the injected dose in 1h. Within 6h much of this activity was recovered in the liver and spleen (respectively 45% and 10% of that injected). For up to 21h after injection, the mitochondrial–lysosomal fraction was the principal location of the hepatic β-fructofuranosidase activity. 2. Lysosomal localization of liposomal protein was supported by the observed increase in the trichloroacetic acid-soluble radioactivity during incubation of the lysosome-rich fraction of the liver of rats injected with liposomes containing 131I-labelled albumin. 3. Association of liposomal protein with lysosomes was demonstrated on subfractionation of the mitochondrial–lysosomal fraction of the liver of rats injected with β-fructofuranosidase-containing liposomes in a Ficoll–mannitol gradient. β-Fructofuranosidase, lysosomal and mitochondrial enzyme marker activities were found to exhibit similar distribution patterns along the gradient. However, in similar experiments with rats previously injected with Triton WR-1339 or dextran (known to alter the specific gravity of lysosomes), only β-fructofuranosidase and lysosomal marker moved along the gradient, in strikingly similar patterns. 4. The lysosomal localization of injected liposome-entrapped material can probably be utilized in the treatment of certain disorders in man.

Ultrasound and mating behaviour in rodents with some observations on other behavioural situations

Abstract: Ultrasounds have been detected during mating behaviour in all 11 species of myomorph rodents in which this behaviour has been observed. The signals produced by each of the species studied are described. In all species except hamsters, these signals appear to be produced by the male. Ultrasounds have also been detected from rodents in other situations such as during and after disturbance and when placed in new surroundings. The possible significance of these ultrasonic signals in the lives of rodents is discussed.

Adenine derivatives as neurohumoral agents in the brain. The quantities liberated on excitation of superfused cerebral tissues.

Abstract: Adenine nucleotides of guinea-pig neocortical tissues were labelled by incubation with [(14)C]adenine and excess of adenine was then removed by superfusion with precursor-free medium. Adenine derivatives released from the tissue during continued superfusion, including a period of electrical stimulation of the tissue, were collected by adsorption and examined after elution and concentration. The stimulation greatly increased the (14)C output, and material collected during and just after stimulation had a u.v. spectrum which indicated adenosine to be a major component. The additional presence of inosine and hypoxanthine was shown by chromatography and adenosine was identified also by using adenosine deaminase. Total adenine derivatives released from the tissue during a 10min period of stimulation were obtained as hypoxanthine, after deamination and hydrolysis of adenosine and inosine, and amounted to 159nmol/g of tissue. This corresponded to the release of approx. 7pmol/g of tissue per applied stimulus. The hypoxanthine sample derived from superfusate hypoxanthine, inosine and adenosine was of similar specific radioactivity to the sample of inosine separated chromatographically, and each was of higher specific radioactivity than the adenine nucleotides obtained by cold-acid extraction of the tissue.

Metabolism of [14C]adenine and derivatives by cerebral tissues, superfused and electrically stimulated

Abstract: 1. Uptake of [ 14 C]adenine and [ 14 C]adenosine from surrounding fluids to guinea-pig cerebral tissues was measured during incubation in vitro . Output of 14 C-labelled compounds from the loaded tissues to superfusion fluids occurred on continued incubation, at about 0.2% of the tissue9s content/min, and this rate was increased about fourfold by electrical excitation of the tissue. 2. The compounds released from the tissue to superfusion fluids included adenine, adenosine, inosine and hypoxanthine with small amounts of nucleotides. Output of all these compounds, except adenine, increased on excitation. Media depleted of oxygen or glucose also increased the output of 14 C-labelled derivatives from [ 14 C]adenine-loaded tissues, and this augmented output was further increased by electrical stimulation. 3. [ 14 C]Adenosine was found as the main product from [ 14 C]ATP when this was added at low concentrations to fluids superfusing cerebral tissue. Metabolic and neurohumoural explanations of the liberation and action of adenosine derivatives in the tissue are discussed.

Autoradiographic localization of 3 H-GABA in rat retina.

Abstract: γ-AMINOBUTYRIC acid (GABA) is present in all layers of vertebrate retinae1–3: in the rabbit retina it seems to be most concentrated in the ganglion cell layers2 while in the frog it is concentrated primarily in cell layers which are rich in amacrine cells1. Recent autoradiographic studies of the distribution of 3H-GABA in rat brain slices after incubation in vitro suggest that the labelled amino-acid is selectively concentrated by certain neural elements4,5. In a study of the distribution of 3H-GABA in rabbit retina after injection of the labelled amino-acid into the eye, Ehinger6 found that radioactivity was accumulated principally in the inner plexiform, inner nuclear and ganglion cell and nerve fibre layers. Labelling was also concentrated in some cells occupying the same position as amacrine cells and in some nerve cells of the ganglion cell layer.

Active-site-directed irreversible inhibition of rat brain 4-aminobutyrate aminotransferase by ethanolamine O-sulphate in vitro and in vivo

Abstract: 1. Partially purified preparations of rat brain 4-aminobutyrate aminotransferase were inhibited in a time-dependent manner by ethanolamine O-sulphate. The inhibition was not reversed by dialysis. 2. The inhibitor formed an initial reversible complex with the enzyme (Ki=4.4×10−4m) and the rate of inactivation followed pseudo-first-order kinetics (k=7.15×10−4s−1). The inclusion of 4-aminobutyrate markedly slowed the rate of inactivation. 3. Ethanolamine O-sulphate did not inhibit glutamate decarboxylase, alanine aminotransferase or aspartate aminotransferase. 4. Intracisternal injection of ethanolamine O-sulphate into rats led to rapid inactivation of 4-aminobutyrate aminotransferase in vivo.

Personality in monkeys: factor analyses of rhesus social behaviour.

Abstract: Three factor analyses were performed on social interaction data from 168 juvenile macaques. Animals were tested in stable quadrad peer groups; in newly-formed dyads with infant, juvenile, and adult stimulus monkeys; and in similar triads with the stimulus animal plus a familiar cage-mate. Factors emerged, most strongly in the most stable condition, which were interpreted as affiliative, hostile and fearful. These factors were almost entirely independent and resembled the extraversion, psychoticism, and emotionality factors frequently found in humans. Stirling University Psychology Primate Unit, Stirling, FK9 4LA, Scotland. Institute of Psychiatry, University of London, London, S.E.5., England.

Release of Prostaglandins in Ocular Inflammation in the Rabbit

Abstract: VARIOUS studies have suggested that prostaglandins (PGs) may be involved in the ocular response to acute inflammation. PGs are present in ocular tissues1–4 and can reproduce many of the characteristic changes associated with ocular trauma in the rabbit5–7, cat8 and monkey9. We therefore examined the possibility that PGs are involved in the response of the rabbit eye to an acute immunological inflammatory reaction. Eighty-four adult albino rabbits of both sexes were used in 8 groups of 6 to 12, but 11 were discarded because uveitis did not develop and 1 because of infection. Uveitis was induced by a single intravitreal injection of a sterile solution of crystallized bovine serum albumin (British Drug Houses). The left eye was anaesthetized with topical 0·4% oxybuprocaine hydrochloride and bovine serum albumin (10 mg in 0·1 ml. normal saline) was then injected slowly into the anterior part of the vitreous. On subsequent days the eyes were examined with a slit-lamp. Immediately after the injection, small amounts of protein and cells appeared in the aqueous and a slight flare was seen. This was probably due to trauma and the eyes usually appeared normal by about the fifth day. On the 9th-15th day signs of uveitis appeared, characterized by a pronounced flare (due to liberation of large quantities of protein and cells into the anterior chamber) and by marked dilatation of iris and ciliary blood vessels. Occasionally, the pupillary margin was seen to adhere to the anterior surface of the lens (posterior synechiae). The contralateral control eye was usually unaffected, but in about 20% of cases fine filaments (probably strands of fibrin) were seen in the anterior chamber when uveitis occurred in the test eye. At the height of the inflammatory response, the animals were anaesthetized with pentobarbitone (25 mg/kg i.V.). The aqueous humour (approximately 0·2 ml./eye) was then withdrawn through a 25G needle and stored immediately at −20°C. In each group, the aqueous humour samples from the test (left) and control (right) eyes were pooled in separate containers. Biological activity was assayed on the rat fundus preparation10 in Krebs solution containing atropine, methy-sergide and mepyramine (all 2 × 10−7 g/ml.). Unextracted samples were assayed in some experiments, whereas in others the PG-like material was first extracted (chloroform method of Unger et al.11). Alkaline hydrolysis (0·2 M NaOH, 45 min, 37° C) was used to distinguish between PGE and PGF compounds and thin layer chromatography was used to separate the PGs (a II solvent system of Green and Samuelsson12; silica gel plates or impregnated paper13, treated with 3% w/v silver nitrate). Cuts of the chromatograms at and between the RF values of PGE1, PGE2 and PGF2α were eluted with Krebs solution containing excess (0.2 M) NaCl to remove the silver ions prior to extraction for PGs11,13. Samples of unextracted aqueous humour from the test eyes caused contractions (preceded by a relaxation in 1 of the 5 experiments) of the rat fundus preparation. Since atropine, methysergide and mepyramine were present the spasmogen was not acetylcholine, 5-hydroxytryptamine or histamine. The control aqueous had no effect. The material was PG-like since it extracted into chloroform11 when the aqueous humour was acidified and it caused contractions of the rat fundus which were reduced in parallel with PGE2 by the selective PG antagonist SC-1922014,15 (Fig. 1). The biological activity was completely destroyed by alkaline hydrolysis in 3 experiments, indicating E-type prostaglandin (Fig. 1) and approximately halved in another (samples from 2 batches of aqueous humour before chloroform extraction and 2 batches after extraction). PGE2 incubated at the same time was destroyed whereas PGF2α was unaffected.

Physiologic and clinical effects of chlorpromazine and their relationship to plasma level.

Abstract: Ten patients suffering from functional psychoses who had not received medication for one month were studied. After investigation before treatment, they received chlorpromazine in liquid form, 100 mg. every 8 hours for 5 to 6 weeks. Testing was carried out on Days 4, 8, 15, 22, 29, and 36 or 43 of treatment: (1) Blood samples were taken for chlorpromazine assessment at 0, 2, 4, and 6 hours after the morning dose; (2) blood pressure and pulse rate, pupil size, sweat gland activity, and electroencephalogram (EEG) were recorded at these times; (3) salivary secretion, EEG-evoked response, auditory reaction time, and handwriting tests were carried out at the 2 hour point; and (4) clinical ratings were made between 2 and 4 hours. Wide interpatient variation in plasma level was found; concentrations were maximal in the first 2 weeks, then consistently declined. Changes in the peripheral autonomic measures correlated with those in plasma level, but changes in the central measures were inconsistent. Plasma levels and clinical improvement were weakly related during the first 2 weeks of treatment only. Clinical improvement correlated with palmar skin conductance (sweating) and with some latencies of the electroencephalographic-evoked response. The determination of chlorpromazine plasma levels should be of use in investigating nonresponders and patients with severe autonomic effects.

Liquid Water: Dielectric Properties

Abstract: Dielectric investigations are directly relevant to questions of molecular structure. During the 1930’s many measurements of the dielectric constants of vapors and dilute solutions were made and the electric dipole moments of polar molecules deduced therefrom. Interpretations of the electric dipole moment in terms of bond length, bond angle, and electronegativity gave way to interpretations in terms of molecular wave functions. The electric moment is one of the most important molecular constants and its reproduction is a valuable test of the accuracy of a wave function. The molecular polarizability, or dipole induced by unit electric field, is another important quantity obtainable from dielectric measurements.

Participation of Central Noradrenergic Neurons in Arterial Baroreceptor Reflexes in the Rabbit: A STUDY WITH INTRACISTERNALLY ADMINISTERED 6-HYDROXYDOPAMINE

Abstract: Rabbits were given intracisternal injections of 6-hydroxydopamine (6-OH-DA) that caused selective ablation of central noradrenergic neurons without damaging peripheral sympathetic nerves. Administration of 6-OH-DA (600 µg/kg, intracisternally) to normal rabbits produced a permanent bradycardia of about 30%, which was initiated centrally and mediated mainly through the vagus, and caused a brief reduction in mean arterial blood pressure, which was due to transient withdrawal of alpha-sympathetic tone. Treatment with 6-OH-DA (600 µg/kg) completely prevented the increases in arterial blood pressure seen on the seventh and the fourteenth day after sinoaortic denervation in control rabbits, although there was a transient increase in blood pressure for 1 day after denervation in the group treated with 6-OH-DA. Central norepinephrine concentrations were reduced in all areas, especially in the spinal cord (to less than 10% of control), in the denervated rabbits treated with 6-OH-DA compared with the levels in denervated controls. When 6-OH-DA (600 µg/kg, intracisternally) was given to rabbits with neurogenic hypertension produced by buffer nerve section, it caused an immediate and persistent return of pressure to the level that existed before denervation. Probably, the integrity of central noradrenergic neurons is necessary for the development of sustained increases in arterial blood pressure following sinoaortic denervation. We suggest that central noradrenergic nerves form an essential link in the baroreceptor reflex arc, possibly at the bulbospinal level.

Chromosome Structure and Function

Abstract: The concept that chromosomes are essential constituents of cells is nearly a hundred years old. Genetical studies have demonstrated that chromosomes are the carriers of the genes, which determine the hereditary characteristics of the organism. Molecular genetics has given new insights into chromosomal structure and function, its mechanism of replication, the linear sequence of its repeating units which form the genetic code, and the process by which this code is transcribed into a specific protein structure. The chromosomes and their genes are acknowledged to be the biological basis of human variation in health and disease.

Residual effects of hypnotics.

Abstract: Ten normal subjects were tested on a large battery of physiological and psychological tests 12 h after a hypnotic dose of butobarbitone sodium (100 or 200 mg) or nitrazepam (5 or 10 mg) and compared with a placebo. The subjects received all five treatments in a balanced design. The tests used included self-ratings, the electroencephalogram, the auditory electroencephalographic evoked response, reaction time, tapping, card-sorting and the digit symbol substitution test. Both drugs were effective hypnotics according to the ratings but butobarbitone had more subjective “hangover” the following morning. The electroencephalogram showed significant changes after both drugs but the evoked response was affected most by 10 mg nitrazepam. The psychological tests showed some dose-related impairment after both drugs. Bioassay statistics suggested that with respect to these residual effects the relative potency of nitrazepam to butobarbitone was 27∶1.

Training and Education

Abstract: Click here to li schedule a free l consultation l i While we regularly offer free workshops to train users on what they can do with the Labnodes platform, we also offer group-based or individual training. Group-based: In person Introduction or request a specific topic/feature PowerPoint presentation and/or hands on learning (attendees bring their laptops) Individual: By phone and desktop-sharing (Lync preferred) In person

Bipolar Factors in Mood Adjective Checklists

Abstract: Previous attempts, using adjective checklists, to demonstrate the existence of mood factors have found only monopolar factors where commonsense would lead us to expect bipolar factors. This surprising effect is attributed to deficiencies in the rating scale used. An improved rating scale is compared with one commonly employed. The results show that monopolarity is associated with the old scale, whilst bipolarity emerges with a new improved scale. A complete reappraisal of the current status of mood adjective checklist factors is recommended.

Xanthoxin, a Recently Discovered Plant Growth Inhibitor

Abstract: The naturally occurring plant growth inhibitor xanthoxin which was discovered in these laboratories has been prepared in vitro by the oxidation of the pigment violaxanthin with neutral zinc permanganate solution. By the use of chemical and spectroscopic techniques, xanthoxin has been characterized as a mixture of the 2- cis , 4- trans - and 2- trans , 4- trans -isomers of 5-(19, 29, -epoxy-49-hydroxy-29, 69, 69-tri-methyl-19-cyclohexy)-3-methyl-pentadienal. These are also obtained by similar oxidations of neoxanthin, antheraxanthin and lutein epoxide. Cis, trans -xanthoxin probably arises from the corresponding cis -xanthophyll and its conversion to ( + )-ABA by simple chemical procedures is reported. The biological activity of cis, trans -xanthoxin has been shown to be considerably greater than that of the trans, trans -isomer. It is comparable with that of ( ± )-ABA in the wheat coleoptile section, the lettuce hypocotyl and bean petiole abscission tests, but greater than that of ( ± )-ABA in the cress seed germination test. Xanthoxin is shown to antagonize the growth-promoting effects of the plant hormones 3-indolylacetic acid, gibberellic acid and kinetin. Other xanthoxin derivatives have been prepared and their activities in several tests are also reported. The uptake of xanthoxin by tomato shoots leads to a subsequent large increase in the ABA content of the tissue. Evidence is presented for a possible biogenetic conversion of cis, trans -xanthoxin into ( + )-ABA by plants.

The Heterocysts of Blue-Green Algae. III. Differentiation and Nitrogenase Activity

Abstract: The course of heterocyst development in Anabaena cylindrica was studied in relation to the ability to fix nitrogen. When non-differentiated filaments, grown in the presence of ammonium-N, were transferred into a medium free from combined nitrogen and incubated under photosynthetic conditions, the cellular C:N ratio increased from 4.5:1 to 8:1 before the percentage heterocyst frequency and nitrogenase activity reached a steady value. The initial stages of differentiation were observed 24 h after transfer into nitrogen-free medium, but nitrogenase activity was only detected when the formation of the first heterocysts was completed. The transformation of a vegetative cell into a heterocyst is characterized by the dissolution of storage granules, the deposition of a multilayered envelope, the breakdown of photosynthetic thylakoids and the formation of new membraneous structures. The latter appear to develop by the coalescence of small newly formed vesicles arising in regions of pre-existing thylakoids. The course of heterocyst development was paralleled by that of nitrogenase activity both under aerobic and anaerobic conditions. Anaerobic incubation enhanced heterocyst production as well as nitrogenase activity. The results suggest that nitrogenase synthesis in Anabaena cylindrica is associated with heterocyst formation and that the primary factor which may regulate both processes is the cellular C:N balance of the alga.

Selective factors in memory. Part 2: affective disorder

Abstract: The relationship between the affective connotations of material and the ease of its recall two weeks later has been examined in a group of psychiatric inpatients suffering from affective disorder. The tendency to recall more pleasant than unpleasant material has been less marked in patients showing overt depression than in patients who were hypomanic or recovered from depression at the time of the experiment. This has been chiefly because of the higher negative tone of recalled material in the depressed patients. Other attributes of the material, relative to its impact on the subject, have also appeared to be less influential in recall in the presence of depression.