IS THERE BIDIRECTIONAL TRANSPORT OF NORADRENALINE IN SYMPATHETIC NERVES?

The experiments were designed to detect somatopetal transport of [¹⁴C]noradrenaline in the postganglionic sympathetic nerves supplying the cat spleen and sheep eye. The animals were treated with nialamide to protect the radioactive noradrenaline, after uptake into the nerve terminals, from monoamine oxidase. In the spleen, the transmitter stores were labelled by infusion of [¹⁴C]noradrenaline into a branch of the splenic artery. The branches of the nerves to the infused and non-infused sides of the spleen were ligated in an attempt to arrest, distal to the constriction, any noradrenaline transported somatopetally in the axons from their terminals. After 24 hr, however, there was less radioactivity in the nerves distal compared to proximal to the constriction, despite heavier labelling of the terminal transmitter stores in the infused portion of the spleen. The proximal accumulation of radioactivity could be attributed to a somatofugal transport of [¹⁴C]noradrenaline. Experiments were also done on the intact sympathetic nerve supply of the sheep eye. The sympathetic nerve terminals in the smooth muscle of the left eye were heavily labelled 5 days after the injection of [¹⁴C]noradrenaline into the left vitreous humour. However, both superior cervical ganglia were only lightly labelled, and there was no significant difference in the radioactivity present in the two ganglia. The results provide no support for a bidirectional transport of noradrenaline in sympathetic nerves but are consistent with a somatofugal transport of the amine storage vesicles from their site of synthesis in the soma to the axon terminals.     

Egg Membrane Lytic Activity of Sperm Extract and its Significance in Relation to Sperm Entry in Hydroides hexagonus (Annelida)

Previous electron microscope studies indicated that the individual spermatozoön of Hydroides hexagonus forms a hole in the vitelline membrane by means of lysis. Other observations established that the hole is real, being visible in living material during sperm entry. During the present investigation sea water extracts from frozen-thawed sperm were tested for lytic effect on the membrane. In normal living eggs the membrane appears as a single thick envelope, but in electron micrographs of sections it is seen to consist of a narrow outer border layer, a wide principal or middle layer, and a narrow inner border layer. After immersion in sperm extract the outer border layer elevates but does not dissolve, the middle layer liquefies and disappears, and the inner border layer seems not to change. This is interpreted as lysis of the middle layer. The extract exerted the same effect on fertilized and unfertilized eggs. In electron micrographs the sections treated with extract greatly resemble that part of the membrane which has been penetrated by the individual spermatozoön. It is concluded that the individual spermatozoön, too, exerts a lytic effect. Together, the present and two earlier studies are considered clearly to demonstrate that in Hydroides the individual spermatozoön does indeed make an entry hole in the egg membrane by applying lytic material to that part of the membrane in its own vicinity.     

Mallory Weiss Syndrome

Head injury in infants and young children may produce lesions that are relatively unique for this age group. The uniqueness is generally due to the structural immaturity of the skull, meninges and brain.“Derby-hat” and diastatic fractures are common in this age group. Spurious meningoceles result from tearing of the dura which is closely adherent to the skull. The syndrome of “delayed” concussion is more commonly manifested in children. Extradural and subdural hemorrhage may develop from lacerations of the major venous sinuses. A classical extradural hematoma may occur in the absence of fracture across meningeal arterial channels.The management of patients with head injury has been improved by the more frequent use of tracheotomy, hypothermic techniques and drugs of the “lytic cocktail.” Solutions of urea in 10 per cent invert sugar are administered intravenously to control cerebral edema in selected patients.     

Homogeneity studies on human growth hormone

1. Human growth hormone preparations (Raben) have been found to contain 10-40% of denatured growth hormone as shown by radioimmunoassay, reaction of radioiodinated subfractions with antiserum to whole growth hormone, and amino acid analysis, and confirmed by bioassay using the tibia test. 2. The altered fraction was more electronegative than the intact hormone on starch-grain electrophoresis in barbitone buffer, pH8.6. Some heterogeneity of the active material was detectable in simple buffer extracts of a single acetone-stored pituitary gland. 3. The inert fraction was more completely separated from the active hormone as an unretarded fraction from Sephadex G-200 columns with a borate buffer. This separation was due to aggregation of the denatured growth hormone in borate buffer. The active fraction from the Sephadex column still contained some inert material and the amount of this remaining varied considerably between different batches of growth hormone. 4. The radioimmunoassay procedure detects only the immunologically and biologically intact fraction.     

Some Factors Affecting Undergraduate Academic Achievement

A related series of studies, most of which have been published previously, is described. These studies form a coherent whole and demonstrate the development of a theme, namely, the identification of factors in the student and the medical school which, in their interaction, influenced undergraduate academic performance at one medical school. In the population concerned no reliable positive or negative correlation could be demonstrated between cognitive ability and academic performance, when the former was measured by the Wechsler Adult Intelligence Scale and the Medical College Admission Test, and the latter by the current assessment methods of the medical school. Other factors, including socioeconomic and individual personality variables, are at present under investigation as to their effect on academic achievement. It is emphasized that the results of these studies cannot be regarded as valid for all medical schools, but the methods employed can be generalized.     

Role of Hydroxyl Radicals in Escherzchza Colz Killing Induced by Hydrogen Peroxide

Escherichia coli lethality by hydrogen peroxide is characterized by two modes of killing. In this paper we have found that hydroxyl radicals (OH -) generated by H₂O₂ and intracellular divalent iron are not involved in the induction of mode one lethality (i.e. cell killing produced by concentrations of H₂O₂ lower than 2.5 mM). In fact, the OH radical scavengers, thiourea, ethanol and dimethyl sulfoxide, and the iron chelator, desferrioxarnine, did not affect the survival of cells exposed to 2.5mM H₂O₂. In addition cell vulnerability to the same H₂O₂ concentration was independent on the intracellular iron content. In contrast, mode two lethality (i.e. cell killing generated by concentrations of H₂O₂ higher than 10mM) was markedly reduced by OH radical scavengers and desferrioxamine and was augmented by increasing the intracellular iron content.

It is concluded that OH. are required for mode two killing of E. coli by hydrogen peroxide.