Effects of nicotine exposure on T cell development in fetal thymus organ culture: arrest of T cell maturation

There is evidence for both physiological functions of the natural neurotransmitter, acetylcholine, and pharmacological actions of the plant alkaloid, nicotine, on the development and function of the immune system. The effects of continuous exposure to nicotine over a 12-day course of fetal thymus organ culture (FTOC) were studied, and thymocytes were analyzed by flow cytometry. In the presence of very low concentrations of nicotine many more immature T cells (defined by low or negative TCR expression) and fewer mature T cells (intermediate or high expression of TCR) were produced. In addition, the numbers of cells expressing CD69 and, to a lesser extent, CD95 (Fas) were increased. These effects took place when fetal thymus lobes from younger (13-14 days gestation) pups were used for FTOC. If FTOC were set up using tissue from older (15-16 days gestation pups), nicotine had little effect, suggesting that it may act only on immature T cell precursors. Consistent with an increase in immature cells, the expression of recombinase-activating genes was found to be elevated. Nicotine effects were partially blocked by the simultaneous addition of the nicotinic antagonist d-tubocurarine. Furthermore, d-tubocurarine alone blocked the development of both immature and mature murine thymocytes, suggesting the presence of an endogenous ligand that may engage nicotinic acetylcholine receptors on developing thymocytes and influence the course of normal thymic ontogeny.     

RELATIVE ELEMENTAL RATES OF ELONGATION AND THE PROTOXYLEM-METAXYLEM TRANSITION IN HYPOCOTYLS OF SOYBEAN SEEDLINGS

The transition from helical to reticulate wall patterns in the conducting elements of the xylem was located in etiolated soybean hypocotyls in conjunction with the distribution of elongation in the axis. The most acropetal reticulate elements are interpreted as the most acropetal metaxylem. Evidence is given that these elements experience strain as they mature. Predicted strain correlated significantly with maximum relative elemental rate of elongation (RELEL), which ranged from 0.08 to 0.12-hr^-1. RELEL varied from 0.03 to 0.06hr^-1 at the point of transition from helical to reticulate xylem element wall patterns. Estimates of strain to be experienced in the reticulate elements varied from 0.11 to 0.13 in untransplanted plants and from 0.04 to 0.11 in plants transplanted to the same, fully watered medium. Transplanting suppressed elongation in the region of maximum RELEL for ca. 12 hr and caused an upward migration of the region of depressed rates on the outside of the axis that accounts for hook-opening. Attention is called to the fact that this region of depressed growth corresponds with the onset of transverse enlargement of the hypocotyl axis.     

Polkepsilonema mombasae gen. et sp.n. andPternepsilonema servaesae gen. et sp.n. (Nematoda,Epsilonematidae) from East African coasts

Two new genera and species from Kenyan tidal areas,Polkepsilonema mombasae gen. et sp.n. andPternepsilonema servaesae gen. et sp.n., are described. Both are characterized by the presence of at least fourteen subcephalic setae and by thick thorns on the ventral body region of males. In the first genus, eight to ten subcephalic setae are situated anterior to the amphid, and the ambulatory setae are bisinuous. In the second, the subcephalic setae are situated at the posterior edge of the rostrum, and the ambulatory setae are straight.A key to the 13 genera of the Epsilonematidae is presented.Abbreviations a body length divided by maximum body diameter - abd body diameter at level of anus - amph % diameter of amphid as a percent of head diameter - Asl length of anteriormost ambulatory seta of external subventral row - b body length divided by pharyngeal length - c body length divided by tail length - cs length of cephalic setae - dcs distance from rostrum edge to cephalic setae - gub length of gubernaculum - L body length - lct length of copulatory thorns - lpt length of precloacal thorns - mbd maximum body diameter of posterior body region - (mdb) minimum body diameter - mbd/(mbd) maximum body diameter divided by minimum body diameter - mbd ph body diameter at level of pharyngeal bulb - N number of body rings - ph length of pharynx - spic length of spicule measured along the arc - SSph length of subdorsal somatic setae in pharyngeal region - t tail length - tmr length of nonannulated tail region - V position of vulva as a percentage of total body length from anterior     

Toward the production of artemisinin through tissue culture: Determining nutrient-hormone combinations suitable for cell suspension cultures

Summary Artemisia annua L. is the source of a potent antimalarial, artemisinin. As part of a program to produce artemisinin through tissue culture, a series of 14 multifactorial experiments were conducted to determine suitable conditions for initiating and maintaining friable callus fromA. annua. In the first six experiments, three different nutrient formulations [Gamborg B5 (B5), Murashige and Skoog (MS), and Whetmore and Rier (WR)], each with 32 combinations of auxins and cytokinins [2,4-dichlorophenoxyacetic acid (2,4-D) with benzyladenine (BA), or 1-naphthaleneacetic acid (NAA) with 6-furfurylaminopurine (kinetin)], were tested. Both B5 and WR nutrients supported friable callus formation from leaf explants with some combinations of auxin and cytokinin. Inasmuch as friable callus seemed to be produced over a wider range of auxin and cytokinin concentrations in combination with B5, the remaining experiments were conducted solely with this nutrient formulation. In the remaining eight experiments, it was determined that friable callus formed when combinations of NAA with kinetin or 2,4-D and BA were used with B5 medium. Lighter colored, more friable callus formed in response to 2,4-D and BA than with NAA and kinetin. No single combination of concentrations of auxin and cytokinin seemed to be “ideal” for producing friable callus. Ranges of 2,4-D from 0.5 to 2.0 with BA between 0.025 and 0.1, or NAA between 0.5 and 2.0 with kinetin between 0.5 and 1.0 mg/liter, produced acceptable results.     

Nucleic acid-binding ligands identify new mechanisms to inhibit telomerase

We screened a small library of known nucleic acid-binding ligands in order to identify novel inhibitors of recombinant human telomerase. Inhibitory compounds were classified into two groups: Group I inhibitors had a notably greater effect when added prior to telomerase assemblage and Group II inhibitors displayed comparable inhibition when added before or after telomerase assemblage. Hoechst 33258, a Group I inhibitor, was found to interact tightly (KD = 0.36 microM) with human telomerase RNA (hTR) leading us to propose that hTR is the molecular target for this and other Group I inhibitors. Our results suggest that hTR can be exploited as a small-molecule drug target and provide several new structural motifs for the further development of novel telomerase inhibitors.     

The biomechanics of Pachycereus pringlei root systems

We report on the root system of the large columnar cactus species Pachycereus pringlei to explore the hypothesis that increasing plant size decreases the ability to resist wind-throw but increases the capacity to absorb and store nutrients in roots (i.e., plant size limits the performance of these functions and may shift the performance of one function in favor of another as size increases). Based on 18 plants differing in size, the root system is characterized by a broad and deep bayonet-like root central to a shallow and extensive lateral system of root elements bearing sinker roots near the stem base. All root types have a living secondary cortex and contain wood with a large volume fraction of ray tissues that increases toward the stem base. Wood stiffness and tensile strength are correlated negatively with the ray tissue volume fraction and thus decrease toward the stem base in lateral and bayonet roots. Calculations show that the ability of the bayonet and proximal lateral root elements to resist wind-throw decreases with increasing plant size, whereas the nutrient absorption/storage capacity of the total root system increases with plant size (i.e., a size-dependent shift between these two root functions occurs).     

Women at altitude: carbohydrate utilization during exercise at 4,300 m.

To evaluate the hypothesis that exposure to high altitude would reduce blood glucose and total carbohydrate utilization relative to sea level (SL), 16 young women were studied over four 12-day periods: at 50% of peak O(2) consumption in different menstrual cycle phases (SL-50), at 65% of peak O(2) consumption at SL (SL-65), and at 4,300 m (HA). After 10 days in each condition, blood glucose rate of disappearance (R(d)) and respiratory exchange ratio were measured at rest and during 45 min of exercise. Glucose R(d) during exercise at HA (4.71 +/- 0.30 mg. kg(-1). min(-1)) was not different from SL exercise at the same absolute intensity (SL-50 = 5.03 mg. kg(-1). min(-1)) but was lower at the same relative intensity (SL-65 = 6.22 mg. kg(-1). min(-1), P < 0.01). There were no differences, however, when glucose R(d) was corrected for energy expended (kcal/min) during exercise. Respiratory exchange ratios followed the same pattern, except carbohydrate oxidation remained lower (-23.2%, P < 0.01) at HA than at SL when corrected for energy expended. In women, unlike in men, carbohydrate utilization decreased at HA. Relative abundance of estrogen and progesterone in women may partially explain the sex differences in fuel utilization at HA, but subtle differences between menstrual cycle phases at SL had no physiologically relevant effects.     

Forced IDO1 expression in dendritic cells restores immunoregulatory signalling in autoimmune diabetes

Indoleamine 2,3‐dioxygenase (IDO1), a tryptophan catabolizing enzyme, is recognized as an authentic regulator of immunity in several physiopathologic conditions. We have recently demonstrated that IDO1 does not merely degrade tryptophan and produce immunoregulatory kynurenines, but it also acts as a signal‐transducing molecule, independently of its enzymic function. IDO1 signalling activity is triggered in plasmacytoid dendritic cells (pDCs) by transforming growth factor‐β (TGF‐β), an event that requires the non‐canonical NF‐κB pathway and induces long‐lasting IDO1 expression and autocrine TGF‐β production in a positive feedback loop, thus sustaining a stably regulatory phenotype in pDCs. IDO1 expression and catalytic function are defective in pDCs from non‐obese diabetic (NOD) mice, a prototypic model of autoimmune diabetes. In the present study, we found that TGF‐β failed to activate IDO1 signalling function as well as up‐regulate IDO1 expression in NOD pDCs. Moreover, TGF‐β‐treated pDCs failed to exert immunosuppressive properties in vivo. Nevertheless, transfection of NOD pDCs with Ido1 prior to TGF‐β treatment resulted in activation of the Ido1 promoter and induction of non‐canonical NF‐κB and TGF‐β, as well as decreased production of the pro‐inflammatory cytokines, interleukin 6 (IL‐6) and tumour necrosis factor‐α (TNF‐α). Overexpression of IDO1 in TGF‐β‐treated NOD pDCs also resulted in pDC ability to suppress the in vivo presentation of a pancreatic β‐cell auto‐antigen. Thus, our data suggest that a correction of IDO1 expression may restore its dual function and thus represent a proper therapeutic manoeuvre in this autoimmune setting.