Measurement of pharyngeal cross-sectional area by finite element analysis.

A noninvasive measurement of pharyngeal cross-sectional area (CSA) during sleep would be advantageous for research studies. We hypothesized that CSA could be calculated from the measured pharyngeal pressure and flow by finite element analysis (FEA). The retropalatal airway was visualized by using a fiber-optic scope to obtain the measured CSA (mCSA). Flow was measured with a pneumotachometer, and pharyngeal pressure was measured with a pressure catheter at the palatal rim. FEA was performed as follows: by using a three-dimensional image of the upper airway, a mesh of finite elements was created. Specialized software was used to allow the simultaneous calculation of velocity and area for each element by using the measured pressure and flow. In the development phase, 677 simultaneous measurements of CSA, pressure, and flow from one subject during non-rapid eye movement (NREM) and rapid eye movement (REM) sleep were entered into the software to determine a series of equations, based on the continuity and momentum equations, that could calculate the CSA (cCSA). In the validation phase, the final equations were used to calculate the CSA from 1,767 simultaneous measurements of pressure and flow obtained during wakefulness, NREM, and REM sleep from 14 subjects. In both phases, mCSA and cCSA were compared by Bland-Altman analysis. For development breaths, the mean difference between mCSA and cCSA was 0.0 mm2 (95% CI, -0.1, 0.1 mm2). For NREM validation breaths, the mean difference between mCSA and cCSA was 1.1 mm2 (95% CI 1.3, 1.5 mm2). Pharyngeal CSA can be accurately calculated from measured pharyngeal pressure and flow by FEA.     

Peripheral chemoreflex responsiveness is increased at elevated levels of carbon dioxide after episodic hypoxia in awake humans.

We hypothesized that the acute ventilatory response to hypoxia is enhanced after exposure to episodic hypoxia in awake humans. Eleven subjects completed a series of rebreathing trials before and after exposure to eight 4-min episodes of hypoxia. During the rebreathing trials, subjects initially hyperventilated to reduce the partial pressure of carbon dioxide (Pet(CO(2))) below 25 Torr. Subjects then breathed from a bag containing normocapnic (42 Torr), low (50 Torr), or high oxygen (140 Torr) gas mixtures. During the trials, Pet(CO(2)) increased while a constant oxygen level was maintained. The point at which ventilation began to rise in a linear fashion as Pet(CO(2)) increased was considered to be the ventilatory recruitment threshold. The ventilatory response below and above the recruitment threshold was determined. Ventilation did not persist above baseline values immediately after exposure to episodic hypoxia; however, Pet(CO(2)) levels were reduced compared with baseline. In contrast, compared with baseline, the ventilatory response to progressive increases in carbon dioxide during rebreathing trials in the presence of low but not high oxygen levels was increased after exposure to episodic hypoxia. This increase occurred when carbon dioxide levels were above but not below the ventilatory recruitment threshold. We conclude that long-term facilitation of ventilation (i.e., increases in ventilation that persist when normoxia is restored after episodic hypoxia) is not expressed in awake humans in the presence of hypocapnia. Nevertheless, despite this lack of expression, the acute ventilatory response to hypoxia in the presence of hypercapnia is increased after exposure to episodic hypoxia.     

Production of fertile transgenic wheat plants by laser micropuncture.

A modified, non-damaging, protocol for the production of fertile transgenic wheat (Triticum aestivum L. cultivar Giza 164) plants by laser micropuncture was developed. The new homemade setup secures the transformation of as many as 60 immature embryo-derived calli (10000 cells each) in less than one hour using a UV excimer laser with two dimensional translation stages, a suitable computer program and a proper optical system. Five-day-old calli were irradiated by a focused laser microbeam to puncture momentarily made self-healing holes ( approximately 0.5 microm) in the cell wall and membrane to allow uptake of the exogenous DNA. The plant expression vector pAB6 containing bar gene as a selectable marker for the herbicide bialaphos resistance and GUS (uidA) gene as a reporter gene was used for transformation. No selection pressure was conducted during the four-week callus induction period. Induced calli were transferred to a modified MS medium with 1 mg l(-1) bialaphos for regeneration, followed by selection on 2 mg l(-1) bialaphos for rooting. Three regenerated putative transgenic events were evaluated for the integration and stable expression of both genes and results indicated that this modified procedure of laser-mediated transformation can be successfully used in transforming wheat.     

The action of lipoxin-A on glomerular microcirculatory dynamics in the rat

Intrarenal administration of 750 ng/kg/min of LX-A in euvolemic rats resulted in significant increases in single nephron GFR (38.4 +/- 1.7 to 45.5 +/- 3.0 nl/min) and plasma flow rate (95 +/- 6 to 127 +/- 9 nl/min). The latter was due to a dramatic fall in afferent arteriolar resistance. Mean transcapillary hydraulic pressure difference increased from 33 +/- 1 to 43 +/- 3 mmHg (p less than 0.05) and the glomerular capillary ultrafiltration coefficient fell from 0.060 +/- 0.013 to 0.033 +/- 0.005 nl/(s X mmHg) (p less than 0.05). These responses to LXA in the renal microcirculation are in sharp contrast to those previously observed for the leukotrienes, and thus may represent the first example of counterregulatory (constrictor/dilator) vascular interactions within the lipoxygenase pathways.     

EVIDENCE FOR CYTOPLASMIC DNA IN ROOT CELLS OF NICOTIANA

Sterile root cultures from Nicotiana tabacum were grown with H³-thymidine added to the medium for various intervals. Incorporation of the labeled nucleoside into nuclear DNA occurred in a fraction of the nuclei which increased with time. In addition, the cytoplasm of all cells incorporated enough tritium to be readily detected by autoradiography. The tritium was not removed by hydrolysis in 1 N HCl at 60°C for 10 minutes, but was removed by digestion in a DNase solution which also removed nuclear DNA. The amount of tritium in the cytoplasm increased during the first 2 hours, but did not appear to increase significantly during the following 5 hours. If the roots were transferred to unlabeled medium after 2 hours, the label was diluted faster than expected by growth without turnover of the labeled component. If FUdR was added to the unlabeled medium, the depletion occurred faster during the first 6 hours, but later appeared to level off so that at 10 hours these cultures did not differ from those incubated without FUdR. However, the addition of an excess of unlabeled carrier had no effect on the rate of depletion of the cytoplasmic label. Actinomycin D, which inhibited the incorporation of H³-cytidine into RNA in the root tips, had no effect on the incorporation of H³-thymidine into the cytoplasmic component. However, Mitomycin C or a high concentration of deoxyadenosine inhibited the incorporation of H³-thymidine into the cytoplasmic component as well as into the nuclear DNA. It is concluded that H³-thymidine is incorporated into a cytoplasmic fraction which has the characteristics of DNA, with a measurable rate of turnover. This fraction is synthesized regardless of whether or not the nucleus is synthesizing DNA. Although the function of cytoplasmic fraction is not yet known, it does not appear to be that of supplying precursors for the synthesis of the nuclear DNA.     

Synthesis of New Bis(pyrazolo[1,5-a]pyrimidines) Linked to Different Spacers as Potential MurB Inhibitors

An efficient protocol was adopted to efficiently prepare three new series of bis(pyrazolo[1,5-a]pyrimidines) linked to different spacers. The new bis(pyrazolo[1,5-a]pyrimidines) were prepared in 80–90 % yields by reacting the respective bis(enaminones) and 4-(4-substituted benzyl)-1H-pyrazole-3,5-diamines in pyridine at reflux temperature for 5–7 h. The new products showed a wide spectrum of antibacterial activity against six different bacterial strains. In general, propane- and butane-linked bis(pyrazolo[1,5-a]pyrimidines), which are attached to 3-(4-methyl- or 4-methoxybenzyl) units, had the best antibacterial activity with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values up to 2.5 and 5.1 μM, respectively. Additionally, the previous products demonstrated promising MurB inhibitory activity with IC₅₀ values up to 7.2 μM.     

Evaluation of the weed flora of Egypt from Predynastic to Graeco-Roman times

Macrofossils of weeds retrieved from archaeological sediments in Egypt are discussed in terms of their presence, preservation and representation significance. The study reveals 112 field weeds from 61 archaeological sites dating from Predynastic times (4500 B.C.) up to the Graeco-Roman period (A.D. 395). Most of the remains were preserved by desiccation. The 112 listed species include 24 taxa from Predynastic Hierakonpolis (3800–3500 B.C.) identified for the first time. This study is based on a selection of 97 species from the entire list. Interpretation of field weed finds from the archaeological contexts is discussed. The highest number of species, 63, is recorded from the Pharaonic period. The Predynastic era is represented by 46 species and the Graeco-Roman period by 34. The intensive archaeological excavation of Pharaonic settlements may explain the rich flora of that period compared with the two others. Floristic analysis shows that 57 species were introduced in association with crops from the Middle East and 40 may belong to the native vegetation of the Nile valley.