bluuebunny/crossref_metadata_2025_split huggingface dataset:
BACTERIAL VIRUSES OR BACTERIOPHAGES
Authors: DELBROCK M. 
Published: January 2008

Summary(i) The following factors are held to be chiefly responsible for recent progress in the field of bacterial viruses: (a) the introduction of ‘one‐step growth experiments’, (b) the concentration of attention on a small group of bacterial viruses, (c) the proof that virus‐resistant mutants originate independently of the presence of virus, (d) the application of the electron microscope. (2) Types of virus morphology, as revealed by the electron microscope, are described. The virus particles of any one strain are of uniform size and shape. Many strains show a ‘head‐and‐tail’ structure. Sizes between 45 and 100 mμ have been found. (3) Classification of a group of seven viruses by serological cross reactions agrees perfectly with classification by morphology. (4) A method for determining the origin of mutations of bacteria from virus sensitivity to virus resistance is outlined. There is evidence that the classification of viruses by cross‐resistance tests is of little value in establishing natural relationships between viruses. (5) The phenomenon of ‘lysogenesis’ is discussed, and certain ambiguities in its definition are pointed out. (6) The physiological basis of resistance of a bacterial strain to the attack by a specific virus is discussed. Such resistance is generally coupled with failure on the part of the bacteria to fix the virus in question by adsorption. Evidence shedding a new light on the process of adsorption is reported. (7) Bacterial viruses can mutate in such a way that their host range is altered. These mutations occur during the multiplication of the virus in its host. (8) The technique and terminology of ‘one‐step growth experiments’ are briefly described. (9) When a bacterium is attacked simultaneously by several virus particles of the same strain or of different strains the bacterium reacts as if it had been attacked by only one particle (mutual exclusion effect). A detailed study of this phenomenon has led to the assumption that the membrane of the bacterium becomes impermeable to other virus particles after one particle has entered the cell (penetration hypothesis). The excluded virus particles may affect the yield of virus of the successful type (depressor effect). (10) The adaptation of the technique of the ‘one‐step growth experiment’ to biochemical studies of virus multiplication is described. (n) The controversies regarding the nature of bacterial viruses are briefly touched upon, particularly with reference to the evolutionary standing of these viruses. (12) It is pointed out that a thorough study of bacterial viruses may lead to a better understanding of all types of viruses.
THE STRUCTURE OF GLYCOGENS
Authors: BELL D. J. 
Published: January 2008

Summary1. The usual criteria for identification of glycogen are discussed. It is pointed out that these can be applied equally well to amylopectin and α‐amylodextrin. Numerous so‐called glycogens in plants and micro‐organisms may not be chemically identical with animal glycogens, which may quite well vary among themselves.2. Mention is made of the methods of isolation and purification. It is considered that precipitation by acetic acid gives the purest material in that nitrogen and phosphate can be eliminated, in many cases entirely.3. The limitations of the end‐group assay are discussed. This method reveals the sole fact that all glycogens are built up from ‘unit chains’, but gives no information as to the detailed structure of these chains. It is, therefore, not possible to say whether glycogens from different sources are chemically the same or not.4. A description is given of the difficulties in attempting to analyse glycogens from the aspect of determining the nature of the linkage uniting the unit chains. The suggestion is made that information to this end will have to be obtained by use of stepwise enzymic degradation of the polysaccharide.5. The latest work on molecular weights is summarized. There is considerable variation according to the type of source from which the glycogen has been isolated. This work is the first indication that there are at least physical differences between glycogens.
THE DEVELOPMENT AND FATE OF THE CORPUS LUTEUM IN THE VERTEBRATE SERIES
Authors: HARRISON R. J. 
Published: January 2008

Summary1. Published descriptions of the development of the corpus luteum show that the majority of the luteal cells are derived from the granulosa cells.2. In the vertebrates, other than mammals, the development of a corpus luteum does not appear to be associated solely with viviparity.3. The fate of the theca interna cells varies greatly, even in closely related species.4. The theca interna cells may remain in groups at the periphery of the gland, or they may invade the developing corpus luteum and either: (a) disappear entirely a few days after ovulation, (b) become indistinguishable from the granulosa cells, or (c) possibly revert to fibroblasts.5. The function of the theca interna or theca‐luteal cells in the mature corpus luteum is unknown. It is, however, possible that they secrete oestrogen.6. The blood vessels of the corpus luteum are derived from the theca interna plexus of capillaries; the corpus luteum is well vascularized by the time that implantation occurs.7. The connective tissue of the corpus luteum is believed by many authors to be derived from theca interna cells that have reverted to fibroblasts. In the Artiodactyla and in Macaca, and possibly in other animals, there is evidence that the endothelial cells give rise to the reticular framework.8. The corpus luteum is generally fully developed by the time of implantation of the blastocyst.9. The appearance of the vacuoles in the luteal cells of pregnant mammals is not necessarily indicative of impending cessation of function or of degeneration. Such vacuolation may mark a ‘resting period’ as in those animals in which implantation is delayed, or a ‘transition period’ during which the placenta is becoming established structurally and functionally.10. The time of appearance of retrogressive changes in the corpus luteum of pregnancy in any species is probably related to the degree of activity of the placenta in that species and to the prolactin level in the anterior pituitary.11. Accessory, aberrant and other atypical forms of corpora lutea have been reported in the macaque, the tree porcupine and the mare.
SEA‐URCHIN SPERMATOZOA
Authors: ROTHSCHILD LORD 
Published: January 2008

Summaryi. The head of the sea‐urchin spermatozoon is pear‐shaped and axially symmetrical. The sub‐microscopic morphology of the middle piece has not been investigated, but the tail, which terminates in an axial fibre, probably contains spiral or coiled structures, as in mammalian spermatozoa.2. Spermatozoa of Psammechinus miliaris swim in spirals (frequency, 30–40 per sec), at an average translatory speed of 200/x/sec. at 18o C. This figure applies to very dilute suspensions. The spermatozoa of Echinus esculentus do not always swim in spirals.3. The evidence in favour of sea‐urchin spermatozoa being attracted by egg secretions is not conclusive. Experiments to settle this controversial question could be done without great difficulty.4. Little is known about the metabolism of sea‐urchin spermatozoa. The most important features are:(a)No movement in absence of oxygen.(b)Negligible acid production in presence or absence of oxygen.(c)Over certain limits, oxygen consumption per spermatozoon an inverse function of sperm concentration.(d)Cytochromes a, b, c, e and a3, succinic dehydrogenase, cocarboxylase, and catalase (in significant quantities) present.(e)Endogenous substrate unknown, though possibly carbohydrate.(f) Respiration inhibited by cyanide, and photo‐reversibly by carbon monoxide.A large number of substances, of widely different types, are said to stimulate or maintain the oxygen consumption of semen or spermatozoa. Among these are succinate, malonate, iodoacetate, copper, zinc, calcium, albumin and seminal plasma. The mode of action of these substances is in general obscure.5. Sea‐urchin spermatozoa contain a proteolytic enzyme which decreases the viscosity of gelatine, and desoxyribonuclease.6. Sea‐urchin spermatozoa contain or secrete three substances with characteristic chemical and biological properties. These substances and their principal characteristics are:(a)Androgamone I. Not a protein. Inhibits sperm movement in certain circumstances.(b)Androgamone II. Protein. Dissolves or precipitates egg jelly. Also called Antifertilizin.(c)Androgamone III. Not a protein. Liquefies egg cortex. Sometimes called Sperm Lysin.7. The spontaneously reversible agglutination of sea‐urchin spermatozoa in the presence of egg secretions, and in particular of Gynogamone II, has a number of characteristics in common with serological reactions. In recent years this subject has been extensively studied and reviewed by Tyler (1948). Some of the more important conclusions are:(a)Spermatozoa and G. II are multivalent with respect to their complementary combining groups, a condition which is responsible for the agglutination of spermatozoa in G. II.(b)Multivalent G. II can be converted into a univalent form in which it reacts with homologous spermatozoa, but without causing agglutination.(c)The sperm‐G. II reaction exhibits the zone phenomenon (maximum agglutination when the two reactants are present in particular proportions).(d)The sperm‐G. II reaction causes a reduction in the fertilizing capacity of agglutinated spermatozoa.
EVALUATION OF THE SELECTIVITY OF α‐ADRENORECEPTOR BLOCKING DRUGS FOR POSTSYNAPTIC α1‐ AND α2‐ADRENORECEPTORS IN A SIMPLE ANIMAL MODEL
Authors: TIMMERMANS P. B. M. W. M. , VAN MEEL J. C. A. , VAN ZWIETEN P. A. 
Published: January 2008

The increase in diastolic pressure of pithed, normotensive rats was determined after i.v. administration of the α‐adrenoreceptor agonists L‐phenylephrine and B‐HT 933.
α‐Adrenoreceptor antagonists varied widely in their relative inhibitory effects towards either L‐phenylephrine‐ or B‐HT 933‐induced vasoconstrictor responses. Prazosin displayed the highest affinity for the postsynaptic α‐adrenoreceptor triggered by L‐phenylephrine. The rank order of potency was further: phentolamine > dihydroergotamine > clozapine > corynanthine > azapetine > yohimbine > piperoxan > tolazoline > mianserin > rauwolscine. On the other hand, the rank order of potency towards B‐HT 933 was: dihydroergotamine > rauwolscine > yohimbine > phentolamine > piperoxan > prazosin > tolazoline > mianserin > corynanthine > azapetine > clozapine. These data are in general agreement with the classification for α1‐(triggered by L‐phenylephrine) and α2‐(triggered by B‐HT 933) adrenoreceptors. Both populations are present postsynaptically in vascular smooth muscle of the pithed rat and are involved in vasoconstriction.
The ratio of KB post α2/KB post α1 was calculated as a measure of selectivity for either α‐adrenoreceptor site. The α‐adrenoreceptor antagonists used cover a 20,000‐fold range of activity ratios. The antagonists most selective for either type were prazosin (α1) and rauwolscine (α2). The selectivity of the α‐adrenoreceptor antagonists for postsynaptic α1‐ and α2‐adrenoreceptors in the intact circulatory system of the pithed rat is comparable with the reported selectivity of these blocking agents for α1 (postsynaptic)‐ and α2 (presynaptic)‐adrenoreceptors in the rabbit isolated pulmonary artery.
It is concluded that two distinct types of postsynaptic α‐adrenoreceptors participate in vasoconstriction in the pithed rat. Apart from the classical α1‐adrenoreceptor, vascular smooth muscle of the pithed rat contains postsynaptic α2‐adrenoreceptors resembling those previously found mainly presynaptically. The presence of separate classes of postsynaptic α1‐ and α2‐adrenoreceptors in the intact circulatory system of the pithed rat offers the possibility to use this relatively simple animal model as an in vivo test system for the pharmacological characterization of α‐adrenoreceptor agonists and antagonists.
ADRENORECEPTORS IN THE HUMAN PENIS
Authors: ADAIKAN P. G. , KARIM S. M. M. 
Published: January 2008

Adrenaline, noradrenaline and phenylephrine caused contraction of the corpus cavernosum muscle of the human penis. These sympathomimetic amines did not produce inhibitory effects even in the presence of the α‐adrenoreceptor blocker, phentolamine. The effect of dopamine was similar to that produced by these three sympathomimetic amines. Higher doses of isoprenaline and salbutamol also contracted this preparation.
Cocaine and guanethidine enhanced the motor response to adrenaline, noradrenaline and phenylephrine while the action of dopamine was blocked by these two drugs.
The motor response to adrenaline, noradrenaline and phenylephrine was antagonized by phentolamine and often potentiated by the β‐adrenoreceptor blocking drug, propranolol. The contractions produced by high doses of salbutamol and isoprenaline were also abolished by phentolamine. These findings indicate that the motor response to sympathomimetic amines is the result of activation of α‐adrenoreceptors in the corpus cavernosum muscle.
At low doses, isoprenaline and salbutamol relaxed the corpus cavernosum muscle strip. The inhibitory action was blocked by low concentrations of the β‐adrenoreceptor antagonist, propranolol but not by practolol (β1‐adrenoreceptor antagonist) and butoxamine (β2‐adrenoreceptor antagonist). β‐adrenorecepcors are present in the corpus cavernosum muscle but these are unlikely to be either of the β1 or β2 type. The possible existence of a third type of β‐adrenoreceptor is suggested.
METABOLISM AND PRESYNAPTIC INHIBITORY EFFECTS OF ADENOSINE IN RAT VAS DEFERENS
Authors: WILLEMOT JOAN , PATON DAVID M. 
Published: January 2008

In the rat vas deferens, adenosine caused rapid presynaptic inhibition of the twitch response stimulated at 0.2 Hz, this effect being maximal within 30 sec. The metabolism of [14C]adenosine was examined under these conditions. For 2–40juM adenosine and for incubations up to 120 sec, deamination of adenosine was quantitatively greater than incorporation into adenine ribonucleotides.
Exposure of tissues to 2juM deoxycoformycin reduced deamination of 10juM [14C]adenosine by about 90%, but did not alter the presynaptic inhibitory action of adenosine. Exposure of tissues to 1juM hydroxy‐nitrobenzylthioguanosine, an adenosine uptake inhibitor, reduced the incorporation of 2–40juM [14C]‐adenosine into adenine ribonucleotides by 25–39% and potentiated the presynaptic inhibitory action of adenosine by 46–105%.
Postganglionic sympathetic denervation of the tissue did not alter the metabolism of [14C]adenosine, indicating that the metabolism observed occurred almost exclusively in smooth muscle.
It is concluded that the concentration of adenosine in the immediate vicinity of the presynaptic adenosine receptor is not greatly affected by deamination but is influenced by adenosine uptake. It is also possible that hydroxynitrobenzylthioguanosine may modify the affinity or intrinsic activity of the presynaptic adenosine receptor.
RESPONSES OF THE ISOLATED ANOCOCCYGEUS MUSCLE OF THE MOUSE TO DRUGS AND TO FIELD STIMULATION
Authors: GIBSON A. , WEDMORE CAROLINE V. 
Published: January 2008

The responses of the isolated anococcygeus muscle of the mouse to drugs and to field stimulation were investigated.
Fluorescence micrographs of transverse sections of the muscle revealed fluorescent nerve fibres in control tissues, but not in tissues from mice pretreated with 6‐hydroxydopamine.
The isolated muscle displayed no spontaneous tone or rhythmic activity. Field stimulation produced frequency dependent contractions which were blocked by phentolamine and by low concentrations of guanethidine (500 nM). Higher concentrations of guanethidine (30 juM) raised muscle tone and, subsequently, field stimulation produced frequency dependent relaxations. In muscles from 6‐hydroxydopamine pretreated mice neither field stimulation nor guanethidine produced contractions, but when muscle tone was raised by carbachol inhibitory responses to field stimulation were still observed.
Contractions of the muscle were produced by noradrenaline (α‐adrenoreceptors), acetylcholine (muscarinic receptors), 5‐hydroxytryptamine, and prostaglandins E1, E2, and F2a.
Adenosine 5′‐triphosphate (ATP) normally produced muscle contraction, but following incubation of the tissue with indomethacin, ATP produced relaxations of carbachol‐induced tone.
Vasoactive intestinal polypeptide, but not bradykinin, produced relaxations of tissues in which tone had been raised by carbachol.
The isolated anococcygeus muscle of the mouse provides a useful preparation for the study of various aspects of autonomic neurotransmission in smooth muscle.
EFFECT OF THYROID STATUS ON β‐ADRENORECEPTORS AND MUSCARINIC RECEPTORS IN THE RAT LUNG
Authors: BAKER S. P. 
Published: January 2008

The effects of thyroid status on the specific binding of the muscarinic ligand (–)‐[3H] quinuclidinyl benzilate (QNB) and of the β‐adrenoreceptor ligand (–)‐[3H] dihydroalprenolol (DHA) in the adult rat lung were investigated.
The specific binding of (–)‐[3H] quinuclidinyl benzilate (QNB) to lung membranes was saturable and the equilibrium dissociation constant (KD) determined from Scatchard analysis was 54 pM. Kinetic analysis of the binding of [3H] QNB yielded a KD of 42 pM. [3H] QNB binding was inhibited by muscarinic agonists and antagonists, the order of their potency was l‐hyoscyamine>atropine>scopolamine>oxotremorine>carbachol. These data were consistent with [3H] QNB binding to the muscarinic receptor.
Adult male rats treated for 2 weeks with the antithyroid agent 3‐amino‐1,2,4‐triazole (ATZ) showed a 52% and 80% reduction in the serum concentration of triiodothyronine (T3) and thyroxine (T4) respectively. These hypothyroid rats also had a 39% decrease in the concentration of lung β‐adrenoreceptors and a 37% decrease in the concentration of lung muscarinic receptors as compared to euthyroid controls. Concurrent treatment of rats with ATZ and T4 for 2 weeks resulted in a reduction of 15% and 20% in the concentration of lung β‐adrenoreceptors and muscarinic receptors respectively. The KD values for [3H] DHA and [3H] QNB binding did not change with the ATZ or ATZ + T4 treated groups.
Administration of T4 (500 μg/kg/day) to male rats for 12 days did not result in any significant change in the concentration of either β‐adrenoreceptors or muscarinic receptors compared to euthyroid controls. No change in the KK values for [3H] DHA or [3H] QNB binding were detected.
The results show that hypothyroid rats have a reduced lung concentration of both β‐adrenoreceptors and muscarinic receptors whereas in hyperthyroid rats these receptors do not significantly change from euthyroid controls.
STRUCTURE‐ACTIVITY RELATIONS FOR PRESYNAPTIC INHIBITION OF NORADRENERGIC AND CHOLINERGIC TRANSMISSION BY ADENOSINE: EVIDENCE FOR ACTION ON A1 RECEPTORS
Authors: PATON D. M. 
Published: January 2008

This study was designed to determine the structure‐activity relations for presynaptic inhibition by adenosine of noradrenergic transmission in rat vas deferens and of cholinergic transmission in guinea‐pig ileum.
The mid‐portion of vasa deferentia and segments of ileum were continuously stimulated at 0.2 Hz and the IC50 values of adenosine analogues for inhibition of the twitch responses determined.
In both tissues, loss of the 2’and/or 3’hydroxyl groups resulted in a very marked loss of activity, whereas substitution at the 5’position was compatible with considerable activity.
In both tissues, an amino group at C6 on the purine moiety was essential for activity. Halide substitutions at the C2 position and bulky substitutions at the N6 position were compatible with increased activity.
The L‐diastereomer of N6‐phenylisopropyladenosine was approximately 100 times more potent than the D‐diastereomer in both tissues.
It was concluded that adenosine acts at presynaptic receptors with ‘R’ site characteristics to inhibit noradrenergic and cholinergic transmission and further that these receptors may belong to the A1 subtype.
THE EFFECTS OF INTRAVENOUS 6‐HYDROXYDOPAMINE ON PERIPHERAL α‐ADRENORECEPTORS
Authors: HAMILTON C. A. , REID J. L. 
Published: January 2008

Peripheral α‐adrenoreceptor‐mediated responses were studied in conscious intact rabbits and in animals pretreated with intravenous 6‐hydroxydopamine (50 mg/kg).
Treatment caused a large decrease in noradrenaline in plasma and peripheral tissue but only small falls in blood pressure.
There was a shift to the left in pressor dose‐response curves to the α‐adrenoreceptor agonist phenylephrine and the mixed α1/α2‐adrenoreceptor agonist noradrenaline in 6‐hydroxydopamine‐pretreated animals. The α1‐adrenoreceptor antagonist prazosin was less effective at blocking the phenylephrine pressor response in these animals.
There was no change in pressor responses to the α2‐adrenoreceptor selective agonists clonidine and guanabenz and α‐adrenoreceptor antagonists were equally effective at blocking this pressor response in 6‐hydroxydopamine‐pretreated and in intact rabbits.
In conscious animals 6‐hydroxydopamine pretreatment causes alteration in responses mediated by postsynaptic α1‐but not postsynaptic α2‐adrenoreceptors. These changes may help maintain blood pressure in the 6‐hydroxydopamine treated rabbits.
MODULATION OF ENDOGENOUS NORADRENALINE RELEASE BY PREJUNCTIONAL α‐ADRENORECEPTORS: COMPARISON OF A CEREBRAL AND PERIPHERAL ARTERY
Authors: DUCKLES SUE PIPER 
Published: January 2008

Stimulation‐evoked fractional release/pulse of noradrenaline (NA) is markedly different in the rabbit basilar artery as compared to the rabbit ear artery. Therefore, using both agonists and antagonists of prejunctional α‐adrenoreceptors, the hypothesis that there are differences in prejunctional mechanisms between these functionally different arteries was tested.
Clonidine (10−6M) had similar effects on NA release in both vessels, decreasing release at 2 Hz, but increasing release at 8 Hz. However, 10−5M clonidine had different effects in the two vessels.
α‐Adrenoreceptor antagonists, phentolamine (10−6M), yohimbine (10−5M), and phenoxybenzamine (10−5M), all increased NA release to a similar extent in both vessels. However, the effect of phenoxybenzamine was considerably greater than that of the other two antagonists, suggesting that it may have additional sites of action.
When the effects of modest drug concentrations were considered, no major qualitative or quantitative differences in the effects of agonists and antagonists on NA release from the two vessels were seen. Thus, the difference in fractional NA release between the basilar and ear arteries cannot be accounted for by differences in prejunctional α‐adrenoreceptor modulation.
THE INOTROPIC AND CHRONOTROPIC EFFECTS OF PHYSOSTIGMINE AND NEOSTIGMINE ON GUINEA‐PIG ISOLATED ATRIA
Authors: DE WILDT D. J. , OUD P. H. J. H. , PORSIUS A. J. 
Published: January 2008

Physostigmine (0.1‐1 mM) induced dose‐dependent negative and neostigmine (0.1–1 mM) positive inotropic effects on driven guinea‐pig isolated atria. Physostigmine decreased and neostigmine increased cardiac frequency of spontaneously beating atria.
The depression of amplitude of contraction by physostigmine cannot be attributed to its inhibitory effect on tissue cholinesterase. The negative inotropic action of physostigmine is not influenced by preincubation with atropine.
The positive inotropic effect of neostigmine is not caused by a nicotine‐like action of the drug. Neostigmine (1 mM) counteracts the negative inotropic effect of acetylcholine. The possible mechanisms of action are discussed.