Circadian locomotor rhythms in the desert iguana I. The role of the eyes and the pineal

Summary The pineal and the eyes are known to be important components in the circadian system of some species of lizards; their effects may be mediated by the hormone melatonin. We examined the role played by these structures in the desert iguana (Dipsosaurus dorsalis). Surgical removal of the pineal had no effect on circadian locomotor rhythms, even though this procedure abolished the circadian rhythm of melatonin in the blood. Furthermore, when the isolated pineal of Dipsosaurus was studied in organ culture, it showed no circadian rhythm of melatonin secretion, as do pineals of some other lizard species, although it did produce large quantities of this hormone. Bilateral ocular enucleation had only small effects on the freerunning period of locomotor rhythms, without affecting melatonin levels in the blood. Behavioral circadian rhythms persisted in desert iguanas subjected to both enucleation and pinealectomy. These data suggest that neither the pineal nor the eyes are central components of the circadian pacemaking system in Dipsosaurus, nor is melatonin critically involved in maintaining its organization.Abbreviations CT circadian time - ZT zeitgeber time - LL constant light - LD light-dark cycle - DD constant darkness - freerunning circadian period     

Actigraphy: A Means of Assessing Circadian Patterns in Human Activity

-Twenty-three diurnally active (0705-2333), healthy persons between 22 and 54 yrs of age and without history of sleep abnormality were monitored continuously for 120 consecutive hr (five days) by wrist actigraphy. Circadian rhythms of high amplitude were detected by cosinor analysis for each participant and for the groups of 10 males and 13 females with the average span of heightened activity timed between ∼1330 and 1605. The circadian peak-trough difference in wrist movement was marked, equalling aproximately 75% of the 24-hr mean level. In 19 of 23 participants, the 24-hr mean of wrist activity varied between 140-180 movements/min, with four persons exhibiting lesser means of 110-140 movements/min. With respect to the daytime span of activity, the mean wrist movement of individual participants ranged from 155-265 movements/min, with the majority (20/23) varying between 185-245 movements/min. During nocturnal sleep the mean wrist activity level was quite low, varying between individuals from 5 to 25 movements/min for 21 of 23 persons. Wrist actigraphy proved to be well-accepted and was a most reliable means of monitoring aspects of body movement during activity and sleep in ambulatory persons adhering to usual life habits and pursuits.     

Distribution of glutamate decarboxylase-like immunoreactivity in the sixth abdominal ganglion of the cockroach Periplaneta americana

Summary An antiserum against glutamate decarboxylase (GAD) of the rat brain was used to locate GAD activity in sections of the nervous system of the cockroach, Periplaneta americana. The sixth abdominal ganglion was chosen because electrophysiological evidence suggests the presence of GABAergic inhibitory synapses in the cereal-giant interneuron system. Groups of somata and numerous fibres and tracts were positively labelled by the GAD antiserum. A posterior group of labelled somata could be identified close to the entry of the cereal nerves. A line of somata clusters lay along a ventro-lateral furrow. Another discrete row of GAD-like cells was located dorso-laterally. Some small cells among the dorsal unpaired neurons were labelled. A small central group appeared under these cells. An abundance of GAD-like processes and transversal tracts were found within the neuropile. The different systems of GABAergic inhibitors in the ganglion are discussed; in particular we show that the fibres of cereal nerve X are not labelled. This demonstrates that the latter act on the giant fibres via interneurons. We suggest that the group that sends axons into the overlapping region between the cereal nerve and the giant fibre could be the inhibitory interneurons involved in this system.     

Complications of Gastroesophageal Reflux

An edited summary of an Interdepartmental Conference arranged by the Department of Medicine of the UCLA School of Medicine, Los Angeles. The Director of Conferences is William M. Pardridge, MD, Professor of Medicine.Several specialists have recently recognized that gastrointestinal reflux causes complications resulting in significant disease. It causes discomfort, indigestion, esophagitis, Barrett''s esophagus, and carcinoma of the esophagus. Pediatricians attribute many early pulmonary problems, and even some sudden deaths in infants, to the reflux of gastric contents. Otolaryngologists now recognize that many cases of nonbacterial, nonspecific pharyngitis and laryngitis are due to the reflux of gastrc acid secretions. Contact granuloma and cancer of the larynx may, in some instances, be secondary to nocturnal reflux. Thoracic surgeons and pulmonologists believe chronic tracheobronchitis and some cases of pulmonary disease are attributable to recurrent bathing of the respiratory epithelium by aspirated gastric contents. An awareness of the many complications of gastrointestinal reflux should lead to a multidisciplined attack on the factors responsible for these diseases.     

The synthetic precursor specific region of pre-pro-parathyroid hormone forms ion channels in lipid bilayers

We have used the chemically synthesized sequence of pre-pro-parathyroid hormone and several of its analogues to test the notion that the capacity of amphipathic peptides to aggregate in membranes and form ion-permeable channels correlates with their ability to function as signal sequences for secreted proteins. We found that pre-pro-parathyroid hormone (the signal sequence and pro-region of parathyroid hormone (M)), as well as some of its analogues, forms aggregates of monomers which are ion-permeable. The ion-permeable aggregates (2–3 monomers) formed by (M) are voltage-dependent and are more permeable for cations than for anions. The compounds which formed ion channels in bilayers also acted as potential signal sequences. We conclude that the ability of peptides to form ion-permeable pathways in bilayers may be correlated to their ability to function as signal peptides.     

Antibodies to Cholinergic Neurons in Alzheimer''s Disease

Alzheimer's disease (AD) is associated with degenerative changes in nuclei of the basal forebrain which provide most of the cholinergic input to the cortex and hippocampus and with a reduction in presynaptic cholinergic parameters in these areas. Although the etiology and pathogenesis of AD are not known, several reports indicate the involvement of immunological mechanisms. In the present work we examined the existence of antibodies in sera of AD patients that bind specifically to cholinergic neurons. As antigens we employed the purely cholinergic electromotor neurons of the electric fish Torpedo which are chemically homogeneous and cross-react antigenically with human and other mammalian cholinergic neurons. Our findings show that immunoglobulins from sera of AD patients bind to a specific antigen (molecular mass 200 kilodaltons) in the cell bodies and axons of Torpedo electromotor neurons and that the levels of such antibodies are significantly higher in AD patients than in controls. The possible role of these antibodies in the cholinergic dysfunction in AD and their diagnostic potential are discussed.     

Do holly leaf spines really deter herbivory?

Summary Although spinose teeth of holly leaves have been widely cited as an example of a physical defense against herbivores, this assumption is based largely on circumstantial evidence and on general misinterpretation of a single, earlier experiment. We studied the response of third and fifth instar larvae of the fall webworm, Hyphantria cunea Drury, a generalist, edge-feeding caterpillar, to intact American holly leaves and to leaves that had been modified by blunting the spines, by removing sections of leaf margin between the spines, or by removing the entire leaf margin. The results suggest that the thick glabrous cuticle and tough leaf margin of Ilex opaca are more important than the spinose teeth in deterring edge-feeding caterpillars. Microscopic examination of mature leaves revealed that the epidermis is thickened at the leaf margin, and that the leaf is cirucumscribed by a pair of fibrous veins. In simple choice tests neither domesticated rabbits nor captive whitetailed deer discriminated between spinescent holly foliage and foliage from which spines were removed. Nevertheless, we found little evidence of herbivory by mammals in the field, either on small experimental trees or in the forest understory. While it is possible that spinose teeth contribute to defense by reducing acceptibility of holly relative to other palatable plant species, we suggest that the high concentrations of saponins and poor nutritional quality of holly foliage may be more important than spines in deterring vertebrate herbivores. The degree of leaf spinescence and herbivory was compared at different heights with the tree canopy to test the prediction that lower leaves should be more spinescent as a deterrent to browsers. Leaves on lower branches of mature forest trees were slightly more spinescent than were upper leaves, and juvenile trees were slightly more spinescent than were mature trees. However, there was no relationship between degree of spinescence and feeding damage. The greater spinescence of holly leaves low in the canopy is probably an ontogenetic phenomenon rather than a facultative defense against browsers.The investigation reported in this paper (No. 87-7-8-77) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Dirctor     

Circumnutation in Phaseolus vulgaris. I. Growth, osmotic potential and cell ultrastructure in the free-moving part of the shoot

Circumnutation of Phaseolus vulgaris L. cv. Blanc de Juillet twining shoots was examined at the cellular level. Cell growth was monitored inside the free-moving part of the shoot as a function of time and position with respect to the terminal bud. Complete elongation of epidermal cells required >7 days. A 60% increase in length of the cells in the bending zone was observed. Scanning and transmission electron microscopy studies showed the elasticity of cell walls, the extent of plasmodesmata and endoplasmic reticulum of epidermal cells. The osmotic potential in epidermal cells of the bending zone displayed significant differences only between the concave and convex sides. The pattern of cell growth in twining shoots is discussed. Circumnutation could be seen as a consequence of periodic turgor changes inducing periodic growth.     

Growth Inhibition, Turgor Maintenance, and Changes in Yield Threshold after Cessation of Solute Import in Pea Epicotyls

The dependence of stem elongation on solute import was investigated in etiolated pea seedlings (Pisum sativum L. var Alaska) by excising the cotyledons. Stem elongation was inhibited by 60% within 5 hours of excision. Dry weight accumulation into the growing region stopped and osmotic pressure of the cell sap declined by 0.14 megapascal over 5 hours. Attempts to assay phloem transport via ethylenediaminetetraacetate-enhanced exudation from cut stems revealed no effect of cotyledon excision, indicating that the technique measured artifactual leakage from cells. Despite the drop in cell osmotic pressure, turgor pressure (measured directly via a pressure probe) did not decline. Turgor maintenance is postulated to occur via uptake of solutes from the free space, thereby maintaining the osmotic pressure difference across the cell membrane. Cell wall properties were measured by the pressure-block stress relaxation technique. Results indicate that growth inhibition after cotyledon excision was mediated primarily via an increase in the wall yield threshold.