Hymenolepis diminuta: Action of worm RNase against RNA

Hymenolepis diminuta possesses a tegumental ribonuclease (RNase) which hydrolyzes rat liver and degraded yeast RNA. Polyacrylamide gel electrophoresis and gel chromatography of rat liver RNA after incubation with intact worms demonstrated significant hydrolysis of the high molecular weight RNA fractions (28 S and 18 S), with the appearance of fractions of intermediate molecular weight (i.e., between 18 S and 4 S), as well as ethanol-soluble fractions. Hydrolysis of degraded yeast RNA (with a molecular weight of approximately 25,000) yielded a single ethanol-precipitable hydrolysis product, as well as ethanol-soluble hydrolysis products.     

Enzymatic acylation of hydroxypropyl cellulose in organic media and determination of ester formation by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy

Esters were prepared by acylation of hydroxypropyl cellulose with fatty acid catalyzed by immobilized lipase from Candida antarctica in tert-butanol. The nature of the substrates used, the initial water activity of the system, and the molecular weight of the hydroxypropyl cellulose were investigated. Moreover, Fourier transform-infrared (FT-IR) spectroscopy was used for determination of ester content on hydroxypropyl cellulose. Specifically, a linear relationship was established between the peak height assigned to the absorption of the esterified carboxyl groups of the cellulose and the ester content. At optimum reaction conditions, the ester content on the hydroxypropyl cellulose was about 11%.     

On using network RAM as a non‐volatile buffer

File systems and databases usually make several synchronous disk write accesses in order to make sure that the disk always has a consistent view of their data, so that it can be recovered in the case of a system crash. Since synchronous disk operations are slow, some systems choose to employ asynchronous disk write operations that improve performance at the cost of low reliability: in case of a system crash all data that have not yet been written to disk are lost. In this paper we describe a softwarebased NonVolatile RAM system that achieves the high performance of asynchronous write operations without sacrificing the reliability of synchronous write operations. Our system takes a set of volatile main memories residing in independent workstations and transforms it into a nonvolatile memory buffer – much like RAIDS do with magnetic disks. It then uses this nonvolatile buffer as an intermediate storage space in order to acknowledge synchronous write operations before actually writing the data to magnetic disk, but after writing the data to (intermediate) stable storage. We demonstrate the performance advantages of our system using both simulation and experimental evaluation.     

Dual effects of acupuncture on gastric motility in conscious rats

The effects of manual acupuncture on gastric motility were investigated in 35 conscious rats implanted with a strain gauge transducer. Twenty (57.1%) rats showed no cyclic groupings of strong contractions (type A), whereas 15 (42.9%) rats showed the phase III-like contractions of the migrating motor complex (type B) in the fasting gastric motility. Acupuncture at the stomach (ST)-36 (Zusanli), but not on the back [Weishu, bladder (BL)-21], increased the peak amplitude of contractions to 172.4 +/- 25.6% of basal in the type A rats (n = 20, P < 0.05). On the other hand, the motility index for 60 min after the acupuncture was not affected by the acupuncture in this group. On the contrary, acupuncture decreased the peak amplitude and motility index to 72.9 +/- 14.0% and 73.6 +/- 16.2% in the type B rats (n = 15, P < 0.05), respectively. The stimulatory and inhibitory effects of acupuncture observed in each type were reproducible on the separate days. In 70% of type A rats, acupuncture induced strong phase III-like contractions lasting for over 3 h that were abolished by atropine, hexamethonium, atropine methyl bromide, and vagotomy. Naloxone significantly shortened the duration of the stimulatory effects from 3.52 +/- 0.21 to 1.02 +/- 0.15 h (n = 3, P < 0.05). These results suggest that acupuncture at ST-36 induces dual effects, either stimulatory or inhibitory, on gastric motility. The stimulatory effects are mediated in part via vagal efferent and opioid pathways.     

Participation of bone marrow derived cells in cutaneous wound healing

Bone marrow has long been known to be a source of stem cells capable of regeneration of the hematopoeitic system. Recent reports, however, have indicated that bone marrow might also contain early stem cells that can differentiate into other organ tissues such as skin. While these studies have illustrated that bone marrow stem cells could find their way to the skin, they have not addressed the dynamics of how bone marrow stem cells might participate in the homeostatis and regeneration of skin. In this report we followed green fluorescent protein (GFP) labeled bone marrow transplanted into non-GFP mice in order to determine the participation of bone marrow stem cells in cutaneous wounds. Our results indicate that there are a significant number of bone marrow cells that traffic through both wounded and non-wounded skin. Wounding stimulated the engraftment of bone marrow cells to the skin and induced bone marrow derived cells to incorporate into and differentiate into non-hematopoietic skin structures. This report thus illustrates that bone marrow might be a valuable source of stem cells for the skin and possibly other organs. Wounding could be a stimulus for bone marrow derived stem cells to travel to organs and aid in the regeneration of damaged tissue.     

Hypoxic fetoplacental vasoconstriction in humans is mediated by potassium channel inhibition

Fetal to maternal blood flow matching in the placenta, necessary for optimal fetal blood oxygenation, may occur via hypoxic fetoplacental vasoconstriction (HFPV). We hypothesized that HFPV is mediated by K(+) channel inhibition in fetoplacental vascular smooth muscle, as occurs in several other O(2)-sensitive tissues. With the use of an isolated human placental cotyledon perfused at a constant flow rate, we found that hypoxia reversibly increased perfusion pressure by >20%. HFPV was unaffected by cyclooxygenase or nitric oxide synthase inhibition. HFPV and 4-aminopyridine, an inhibitor of voltage-dependent K(+) (K(v)) channels, increased pressure in a nonadditive manner, suggesting they act via a common mechanism. Iberiotoxin, a large conductance Ca(2+)-sensitive K(+) (BK(Ca)) channel inhibitor, had little effect on normoxic pressure. Immunoblotting and RT-PCR showed expression of several putative O(2)-sensitive K(+) channels in peripheral fetoplacental vessels. In patch-clamp experiments with smooth muscle cells isolated from peripheral fetoplacental arteries, hypoxia reversibly inhibited K(v) but not BK(Ca) or ATP-dependent currents. We conclude that human fetoplacental vessels constrict in response to hypoxia. This response is largely mediated by hypoxic inhibition of K(v) channels in the smooth muscle of small fetoplacental arteries.     

Analysis of metabolic networks using a pathway distance metric through linear programming

The solution of the shortest path problem in biochemical systems constitutes an important step for studies of their evolution. In this paper, a linear programming (LP) algorithm for calculating minimal pathway distances in metabolic networks is studied. Minimal pathway distances are identified as the smallest number of metabolic steps separating two enzymes in metabolic pathways. The algorithm deals effectively with circularity and reaction directionality. The applicability of the algorithm is illustrated by calculating the minimal pathway distances for Escherichia coli small molecule metabolism enzymes, and then considering their correlations with genome distance (distance separating two genes on a chromosome) and enzyme function (as characterised by enzyme commission number). The results illustrate the effectiveness of the LP model. In addition, the data confirm that propinquity of genes on the genome implies similarity in function (as determined by co-involvement in the same region of the metabolic network), but suggest that no correlation exists between pathway distance and enzyme function. These findings offer insight into the probable mechanism of pathway evolution.     

Plant transformation by coinoculation with a disarmed Agrobacterium tumefaciens strain and an Escherichia coli strain carrying mobilizable transgenes

Transformation of Nicotiana tabacum leaf explants was attempted with Escherichia coli as a DNA donor either alone or in combination with Agrobacterium tumefaciens. We constructed E. coli donor strains harboring either the promiscuous IncP-type or IncN-type conjugal transfer system and second plasmids containing the respective origins of transfer and plant-selectable markers. Neither of these conjugation systems was able to stably transform plant cells at detectable levels, even when VirE2 was expressed in the donor cells. However, when an E. coli strain expressing the IncN-type conjugation system was coinoculated with a disarmed A. tumefaciens strain, plant tumors arose at high frequencies. This was caused by a two-step process in which the IncN transfer system mobilized the entire shuttle plasmid from E. coli to the disarmed A. tumefaciens strain, which in turn processed the T-DNA and transferred it to recipient plant cells. The mobilizable plasmid does not require a broad-host-range replication origin for this process to occur, thus reducing its size and genetic complexity. Tumorigenesis efficiency was further enhanced by incubation of the bacterial strains on medium optimized for bacterial conjugation prior to inoculation of leaf explants. These techniques circumvent the need to construct A. tumefaciens strains containing binary vectors and could simplify the creation of transgenic plants.