Circadian and Ultradian Rhythmicities in Very Premature Neonates Maintained in Incubators

Six very premature babies (born at 26–28 weeks gestational age) have been studied in hospital for 11–17 weeks, while in intensive care and in an incubator. Apart from suffering occasionally from the neonatal disorders of haemolytic jaundice and ‘respiratory distress of the newborn’, the babies were healthy and developed normally. Initially, the babies were continuously fed intravenously, and the lighting in the ward was on continuously. Routine care was given round the clock. When their medical condition permitted it, the babies were moved in their incubator to an adjacent ward, where they took frequent (2–4 hourly) small meals by mouth, the lighting was dimmed at night, and routine care tended to be given more in the daytime. Hourly recordings of insulated skin temperature were taken throughout the study, and it is the detection of rhythmicity in these measurements that has been the subject of the present study. The methods used were Phase-weighted Stacks, Phasor Walkout and Power Spectral Analysis. These methods have previously been used mainly in geophysical studies, and their value is that they can detect weak signals in noisy data and do not assume a particular waveform of any signal. Circadian rhythmicity was found in all babies for much of the time that were in the constant environment provided by the incubator. Ultradian rhythms were sometimes present also, but they were shorter-lived, and showed a wide range of changing periods, generally in excess of 8 h. When the babies were being treated for jaundice or respiratory distress, there was a tendency for the circadian rhythms to become weaker and for a broader spectrum of ultradian periods to appear. Placing babies in the 12 h : 12 h light : dark environment provided by the ward, and instituting feeding by mouth, had, in most cases, only modest effects upon either circadian or ultradian rhythms. Thus, circadian rhythms continued (but generally with a period not exactly equal to 24 h), and ultradian rhythms, when present, often did not show periods that could be related easily to feeding or care-giving. These results are discussed in terms of evidence for endogenous and exogenous origins of the observed rhythms, and of theories that have postulated the relationship between circadian and ultradian rhythms. It is concluded that the results from the present analyses are difficult to reconcile with the view that circadian rhythms develop from interactions between ultradian oscillators. We suggest that they indicate a matu-ration of the circadian system as a consequence of increasing associations between the circadian elements that are present in the suprachiasmatic nuclei and in other oscillators of the circadian system. The new analytical methods used here also indicate that the results obtained from time-frequency analysis depend to some extent upon the method used.     

Distribution of Adult Male and Female Baccharis concinna (Asteraceae) in the Rupestrian Fields of Serra Do Cipó, Brazil

Abstract: This study focuses on the sex ratio and spatial distribution of males and females in three populations of the endemic and restricted tropical dioecious shrub, Baccharis concinna (Asteraceae) in the mountainous region of Serra do Cipó, southeastern Brazil. The proportion of female plants in the population at lower elevation (1000 m a.s.l.) was significantly greater than of male plants. At this elevation of P/N and Ca/Al ratios in the soil were also greater indicating better nutritional status of the soils. The concentration of aluminium increased significantly with the elevation ( p < 0.001), perhaps rendering soils less conducive to female plants at higher elevations. Female plants are possibly adversely affected to a greater extent by soil quality than male plants. The spatial distribution of the populations within habitat was tested by the K(t) function, where the neighbourhood of a given individual was defined by a circle with a radius (t) up to 3 m. Despite the strong tendency for aggregation, the distribution of the sexes within habitats was random and the hypothesis was not supported. The independent distribution of the sexes within habitats may be explained by nutrient homogeneity of the soils, as well as by an absence of antagonism between the sexes. Nevertheless, we found a trend for males and females to be aggregated according to their gender.     

Elicitor-Induced l-Tyrosine Decarboxylase from Plant Cell Suspension Cultures : I. Induction and Purification

l-Tyrosine decarboxylase (EC 4.1.1.25) activity was induced in cell suspension cultures of Thalictrum rugosum Ait. and Eschscholtzia californica Cham. with a yeast polysaccharide preparation (elicitor). The highest l-tyrosine decarboxylase activity in extracts from 7-day-old cell cultures of E. californica was observed 5 hours after addition of 30 to 40 micrograms elicitor per gram cell fresh weight. The enzyme extracted from cells of E. californica was purified 1540-fold to a specific activity of 2.6 micromoles CO(2) produced per minute per milligram protein at pH 8.4 and 30 degrees C. Purified enzyme from T. rugosum showed a specific activity of 0.18 micromoles per minute per milligram protein. The purification procedure involved ammonium sulfate fractionation, anion-exchange fast protein liquid chromatography, ultrafiltration, and hydrophobic interaction chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the enzyme from the two plant cell cultures had subunits of identical molecular weight (56,300 +/- 300 daltons.     

Circadian rhythm of the endopeptidase 22.19 (EC 3.4.22.19) in the rat brain.

The endopeptidase 22.19 (EC 3.4.22.19) has been associated with the metabolism of neuropeptides by its ability to convert small enkephalin-containing peptides (8 to 13 amino acids) into enkephalins. In addition, this enzyme cleaves the Arg8-Arg9 bond of neurotensin and the Phe5-Ser6 bond of bradykinin. We analyzed the circadian variation of endopeptidase 22.19 in the whole and individual areas of the rat brain. Endopeptidase 22.19 activity was analyzed by high-performance liquid chromatography (HPLC) using bradykinin as an operative substrate. Enzymatic specific activities were analyzed by rhythmometric methods and indicate a circadian fluctuation of endopeptidase 22.19 specific activity (mU of enzyme/mg of protein) in the whole brain [p less than 0.001, mesor (M) = 7.62, amplitude (A) = 2.89, and acrophase (phi) = 23:08 h], striatum (p less than 0.001, M = 2.92, A = 0.62, phi = 23:03 h), hypothalamus (p less than 0.001, M = 3.15, A = 0.86, phi = 01:12 h), periaqueductal gray matter (p less than 0.005, M = 2.62, A = 0.34, phi = 22:35 h), and cerebellum (p less than 0.014, M = 4.27, A = 0.88, phi = 17:12 h). The circadian rhythmicity in endopeptidase 22.19 specific activity suggests that light may have an effect on the peptidase activity in whole brain and in areas of the central nervous system and may be essential for the mechanisms of circadian fluctuations of neuropeptides in the brain.     

Oestradiol is effective in stimulating 3H-thymidine incorporation but not on proliferation of breast cancer cultured cells

The growth of numerous human oestrogen target cell lines is said to have been stimulated by oestradiol. We studied the action of this hormone on the growth of two human cancer cell lines originating from endometrium (GUS), and from breast (FAM). Oestradiol was inactive on endometrial cell multiplication as well as on their tritiated thymidine uptake, but in FAM breast cancer cells, we noticed a discrepancy between tritiated thymidine uptake and actual cell proliferation: there was a 40% increase in DNA precursor uptake, but no change in either the number of cells or in their DNA content, both of which were verified by two different methods. Therefore, an actual increased nuclear (autoradiographic) uptake of thymidine did take place in oestrogenized cells, associated with an increase of incorporation into DNA (a rise of radioactivity in the acid-insoluble materials), but finally there was no greater total DNA increase in the whole treated population than in control cells. Then we examined the metabolism of tritiated thymidine in oestradiol-treated FAM cells. We extracted the radioactive thymine nucleotides and characterized them chromatographically: the oestradiol caused an increase in the labelling of deoxythymine monophosphate (TMP). How these results are consistent with both unmodified cell count and whole DNA content is discussed.     

Human chromosome 6- and 11-encoded factors support human immunodeficiency virus type 1 Rev function in A9 cells.

The precise mechanism of Rev-mediated expression of human immunodeficiency virus (HIV-1) late genes is not well characterized. We recently proposed a requirement for HIV-1 Rev responsive element (RRE) RNA binding host nuclear proteins in Rev function. In this report, using a transient transfection assay of Rev function, we further demonstrate the role of host cell factors in HIV-1 Rev function. Murine A9 cells, which are inefficient in forming RRE-host protein ribonucleoprotein complexes, are also inefficient in supporting Rev function. We also show that host cell factor(s) encoded by human chromosomes 6 and 11 can support HIV-1 Rev-mediated expression of unspliced viral mRNAs in murine A9 cells.     

Colonization factors of diarrheagenicE. coli and their intestinal receptors

WhileEscherichia coli is common as a commensal organism in the distal ileum and colon, the presence of colonization factors (CF) on pathogenic strains ofE. coli facilitates attachment of the organism to intestinal receptor molecules in a species- and tissue-specific fashion. After the initial adherence, colonization occurs, and the involvement of additional virulence determinants leads to illness. EnterotoxigenicE. coli (ETEC) is the most extensively studied of the five categories ofE. coli that cause diarrheal disease, and has the greatest impact on health worldwide. ETEC can be isolated from domestic animals and humans. The biochemistry, genetics, epidemiology, antigenic characteristics, and cell and receptor binding properties of ETEC have been extensively described. Another major category, enteropathogenicE. coli (EPEC), has virulence mechanisms, primarily effacement and cytoskeletal rearrangement of intestinal brush borders, that are distinct from ETEC. An EPEC CF receptor has been purified and characterized as a sialidated transmembrane glycoprotein complex directly attached to actin, thereby associating CF-binding with host-cell response. Three, additional categories ofE. coli diarrheal disease, their colonization factors and their host cell receptors are discussed. It appears that biofilms exist in the intestine in a manner similar to oral bacterial biofilms, and thatE. coli is part of these biofilms as both commensals and pathogens.Abbreviations CF colonization factor - CFA Colonization Factor Antigen - CS coli-surface-associated antigen - EAggEC enteroaggregativeE. coli - ECDD E. coli diarrheal disease - EHEC enterohemorrhagicE. coli - EIEC enteroinvasiveE. coli - EPEC enteropathogenicE. coli - ETEC enterotoxigenicE. coli - Gal galactose - GalNAc N-acetyl galactosamine - LT heat-labile toxin - NeuAc N-acetyl neuraminic acid - PCF Putative colonization factor - RBC red blood cells - SLT Shiga-like toxin - ST heat-stable toxin     

Subject: Migration

Research Notes on Avian Biology 1994: Selected Contributions from the 21st International Ornithological CongressGeneral Biology: Migration

Subject: Migration     

Sex determination and optimal development in the Moorish gecko,Tarentola mauritanica

Under temperature sex determination (TSD), sex is determined by temperature during embryonic development. Depending on ecological and physiological traits and plasticity, TSD species may face demographic collapse due to climate change. In this context, asymmetry in bilateral organisms can be used as a proxy for developmental instability and, therefore, deviations from optimal incubation conditions. Using Tarentola mauritanica gecko as a model, this study aimed first to confirm TSD, its pattern and pivotal temperature, and second to assess the local adaptation of TSD and variation of asymmetry patterns across four populations under different thermal regimes. Eggs were incubated at different temperatures, and hatchlings were sexed and measured. The number of lamellae was counted in adults and hatchlings. Results were compatible with a TSD pattern with males generated at low and females at high incubation temperatures. Estimated pivotal temperature coincided with the temperature producing lower embryonic mortality, evidencing selection towards balanced sex ratios. The temperature of oviposition was conservatively selected by gravid females. Asymmetry patterns found were likely related to nest temperature fluctuations. Overall, the rigidity of TSD may compromise reproductive success, and demographic stability in this species in case thermal nest choice becomes constrained by climate change.