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D L Lee

Publications and source records attributed to D L Lee.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effects of high-preference single-digit mathematics problem completion on multiple-digit mathematics problem performance.

The purpose of this study was to examine the effects of a sequence of three single-digit (1 digit x 1 digit) multiplication problems on the latency to initiate multiple-digit (3 digit x 3 digit) multiplication problems for 2 students in an alternative education school. Data showed that (a) during the preference assessment, both students selected the single-digit problems in a majority of the sessions, and (b) intervention resulted in a decrease in latency between problems for both students. Results are discussed in relation to using high-preference sequences to promote behavioral momentum in academic content areas.

Adolescent↗
PubMed1996

Why do some nematode parasites of the alimentary tract secrete acetylcholinesterase?

Many gastrointestinal nematodes secrete large amounts of acetylcholinesterases. Antibodies are produced against these secreted acetylcholinesterases and appear to give some protection against infection with some nematodes. The theory that acetylcholinesterase secreted by gastrointestinal nematodes may act as a biochemical holdfast by reducing contractions of the alimentary system has not been substantiated; a vasoactive intestinal polypeptide-like protein is secreted by some species and may be the biochemical holdfast. Secreted acetylcholinesterases may alter host cell permeability, have an anti-coagulant role, affect glycogenesis, and/or be important in certain aspects of acetate and choline metabolism. Probably the most important role for acetylcholinesterase secreted by nematodes is immune modulation and/or reduction of inflammation in the vicinity of the nematode. The reason why some species of gastrointestinal nematodes resistant to benzimidazoles contain elevated amounts of acetylcholinesterase is unclear.

Acetylcholinesterase↗
PubMed1996

A vasoactive intestinal polypeptide-like protein excreted/secreted by Nippostrongylus brasiliensis and its effect on contraction of uninfected rat intestine.

The 50-30 kDa fraction isolated from the excretory/secretory products (E/S) of the nematode Nippostrongylus brasiliensis significantly decreased the amplitude of contraction of segments of uninfected rat intestine when injected into the lumen of the segments maintained in an organ bath. Dot blot analysis of the fraction suggested that it was similar in immunoreactivity to porcine vasoactive intestinal polypeptide (VIP). When antiserum to porcine VIP was mixed with N. brasiliensis E/S and the mixtures were injected into the lumen of segments of rat intestine, the inhibitory effect of the E/S on amplitude of contraction decreased. When physiological concentrations of porcine VIP (12.9 pmol/ml) were injected into the lumen of segments of uninfected rat intestine the amplitude of contraction decreased significantly. Western blot analysis of the E/S, using antiserum to porcine VIP, recognized a 30 kDa protein in the E/S and also in whole worm homogenate suggesting that synthesis of the peptide occurs inside the nematode. Peptide histidine isoleucine (PHI)-like immunoreactivity was detected in a 68 kDa fraction of the E/S and the homogenate but this fraction did not affect the amplitude of contractions of the intestine.

Animals↗
PubMed1996

The effect of Trichinella spiralis infection on the mechanical properties of the mammalian diaphragm.

Trichinella spiralis larvae infect and develop within skeletal muscle cells causing major changes to their mechanical properties. The aim of this investigation was to determine the effects of T. spiralis on the power output and fatigue resistance of the mammalian diaphragm under conditions simulating in vivo operation and to relate these to respiratory performance. Infection with T. spiralis leads to major reductions in mechanical stress, work, power output and fatigue resistance. These changes are associated with the number of larvae present in the muscle and the duration of infection. However, the initial decline in mechanical performance occurs during the onset of infection when there are few larvae observed within the muscle cells, indicating that T. spiralis may affect the properties of muscle before encapsulation. This may correspond to the host's inflammatory response and the effects of larval excretory/secretory products. The decline in mechanical performance will have a profound effect on respiration both at rest and during exertion. This must influence the behaviour of the host and increase its chance of capture by predators, which is likely to benefit the parasite by facilitating its transmission.

Animals↗
PubMed1996

The serum immune response of young lambs to a primary infection with Nematodirus battus.

Young lambs (6-8 weeks of age) were infected with 50000 infective stage larvae of the trichostrongyle nematode Nematodirus battus. Initial mean adult worm burdens of 23884 +/- 1678 (S.E.M.) at day 14 post-infection (p.i.) were reduced significantly (P < 0.01) to a mean burden of 5383 +/- 1397 by day 21 p.i. Blood samples were taken and serum analysed using ELISA and Western blotting techniques for IgG antibodies specific for N. battus. Pre-infection serum from young naive animals showed IgG recognition of adult and larval N. battus whole worm homogenate. Recognition of adult antigens became reduced during the first 14 days after infection, followed by a subsequent increase beginning between days 14 and 18 p.i. and peaking at day 28 p.i. IgM recognition of N. battus antigens showed a single response peak, starting between days 14 and 18 p.i., without the pre-infection elevated titre as observed with IgG. These results show that young lambs can mount a significant serum response to a primary infection with N. battus during rejection of adult worms and that lambs receive from their dams IgG antibodies that are capable of recognizing adult and larval N. battus during the first few weeks of life.

Animals↗
PubMed1996

Vasoactive intestinal polypeptide-like and peptide histidine isoleucine-like proteins excreted/secreted by Nippostrongylus brasiliensis, Nematodirus battus and Ascaridia galli.

Vasoactive intestinal polypeptide (VIP)-like protein was detected by dot blot analysis in the excretions/secretions (E/S) of Nematodirus battus and Ascaridia galli and was confirmed in the E/S of Nippostrongylus brasiliensis. ELISA analysis showed that N. brasiliensis E/S contained the highest proportion of VIP-like protein (28.04 pmoles/mg of total E/S protein) and A. galli E/S contained the lowest (10.89 pmoles/mg of total E/S protein). Peptide histidine isoleucine (PHI)-like protein was detected by dot blot analysis in the E/S products of N. brasiliensis, N. battus and A. galli. ELISA analysis suggested that A. galli E/S contained the highest proportion of PHI (20.77 nmoles/mg of total E/S protein) and N. battus E/S contained the lowest (0.67 nmoles/mg of total E/S protein). The possible significance of VIP-like and PHI-like substances in the E/S of gastrointestinal nematodes is discussed.

Animals↗
PubMed1996

Improvement of projection-type associative memories by using a two-phase recalling procedure.

In this letter, we propose a Two-Phase Recalling Procedure (TPRP) to improve the recall capability of the projection-type associative memory. It is known that the conventional projection dynamic sometimes produces spurious states that do not belong to the space spanned by the prototype vectors (memory space). The proposed TPRP provides a trapped spurious state another chance to project onto the memory space such that the recall capability of the projection-type associative memories can be greatly improved. Finally a simulation result demonstrates the effectiveness of the TPRP.

Computer Simulation↗
PubMed1996

Equilibrium and attractivity analysis for a class of hetero-associative neural memories.

Based on the natural structure of Kosko's Bidirectional Associative Memories (BAM), a high-performance, high-capacity associative neural model is proposed which is capable of simultaneous hetero-associative recall. The proposed model, Modified Bidirectional Decoding Strategy (MBDS), improves the recall rate by adding some association fascicles to Kosko's BAM. The association fascicles are sparse coding neuron structures that provide activating strengths between two neuron fields (say, field X and field Y). The sufficient conditions for a state to become an equilibrium state of the MBDS network is derived. Based on these results, we discuss the basins of attraction of the training pairs in one iteration. The upper bound of the number of error bits which can be tolerated by MBDS is also derived. Because the attractivity of a stored training pair can be increased markedly with the aid of its corresponding association fascicles, we recommend a high capacity realization of MBDS, Bidirectional Holographic Memory (BHM), so that each training pair is stored uniquely and directly in the connection weights rather than encoded in a correlation matrix. Finally, computer simulations demonstrate the attractiveness of three different realizations of MBDS to verify our results.

Association↗
PubMed1995

A correlation significance learning scheme for auto-associative memories.

A new concept called correlation significance for expanding the attraction regions around all the stored vectors (attractors) of an asynchronous auto-associative memory is introduced. Since the well known outer product rule adopts equally-weighted correlation matrix for the neuron connections, the attraction region around each attractor is not maximized. In order to maximize these attraction regions, we devise a rule that all the correlations between two different components of two different stored patterns should be unequally weighted. By this formalism, the connection matrix T of the asynchronous neural network is designed by using the gradient descent approach. Additionally, an exponential type error function is constructed such that the number of successfully stored vectors can be directly examined during the entire learning process. Finally, computer simulations demonstrate the efficiency and capability of this scheme.

Computer Simulation↗
PubMed1995

[Outcome and cost of mechanical ventilation in patients with inoperable solid tumors and hematologic malignancies].

The application of mechanical ventilation can be life-saving in patients with acute respiratory failure, but is frequently ineffective in terminally ill patients. To analyze the outcome and cost of mechanical ventilation for patients with malignancies, we retrospectively reviewed 115 patients with inoperable solid tumors or hematologic malignancies who received mechanical ventilation. Eighty eight of these 115 patients (77%) died while on mechanical ventilation; 18 patients (16%) were weaned from mechanical ventilation but still died during their hospitalization. Six patients (5%) were discharged but survived less than 3 months and only three patients (3%) survived for more than 3 months after discharge. The total time of mechanical ventilation was 772 person-days, which represented 5.5% (772/13974) of the total mechanical ventilator use in our hospital in 1993. The total hospital cost from initiation of mechanical ventilation to discharge or death of these 115 patients was NT $11,238,022 (US $432,200) and daily hospital cost per person during mechanical ventilation was approximately NT $10,845 (US $420). The "daily cost of discharge survival" (defined as total hospitalization cost from the initiation of mechanical ventilation to discharge or death divided by total discharge person-days) for patients with inoperable solid tumors was NT $73,421 (US $2,820)/per person-day. We concluded that mechanical ventilation should not be routinely used in patients with inoperable solid tumors and hematologic malignancies. Physicians should explain the poor outcome to these patients and their families in advance and inquire about their willingness to forego mechanical ventilation.

Aged↗
PubMed1994

Changes in host muscles induced by excretory/secretory products of larval Trichinella spiralis and Trichinella pseudospiralis.

Excretory/secretory (ES) products obtained by in vitro culture of infective-stage larvae of Trichinella spiralis and T. pseudospiralis were injected intramuscularly at various intervals into mice. Mini-osmotic pumps containing T. spiralis ES products were also implanted subcutaneously and intraperitoneally into rats. The introduction of ES materials into muscles elicited extensive lesions which included dissolution of myofibres, mobilization of mononuclear and polymorphonuclear leucocytes, angiogenesis, hypertrophy of myonuclei, myotube formation, mitosis, muscle bundles becoming rounded and separated from each other, disappearance of Z, I and A bands of sarcomeres, increase in endoplasmic reticulum and Golgi complexes, decrease in glycogen and relocation of mitochondria. These are considered as degenerative/regenerative changes of muscles to injury. Immunodominant epitopes of specific 45-53 kDa glycoproteins in ES antigens of T. spiralis could not be detected in hypertrophic nuclei of injected muscles by using polyclonal and monoclonal antibodies and immunocytochemical methods. ES products of T. spiralis failed to stimulate unsensitized lymphocytes in the lymphocyte transformation test. Infective-stage larvae of T. spiralis released from muscles were found capable of forming nurse cells after injection subcutaneously into rats. It is postulated that the invasion of muscles by trichinellids elicits two independent events, i.e. a general degenerative/regenerative response of muscles and a specific change in genomic expression of myonuclei. The two events are probably mediated by different effector molecules.

Animals↗
PubMed1994

The effect of homogenates and excretory/secretory products of Nippostrongylus brasiliensis and of acetylcholinesterase on the amplitude and frequency of contraction of uninfected rat intestine in vitro.

Whole worm homogenates and excretory/secretory (E/S) products of adult Nippostrongylus brasiliensis significantly decreased the amplitude of contractions of segments of uninfected rat intestine maintained in an organ bath, with significantly larger volumes of E/S products being required to bring about a similar decrease to that caused by the whole worm homogenate. Boiled samples of homogenate and E/S products significantly decreased the amplitude of contractions of uninfected rat intestine, but larger volumes were needed than with unboiled samples. Frequency of contraction was unaltered by homogenates or E/S products. When electric eel AChE was injected into the lumen of segments of uninfected rat intestine maintained in an organ bath there was no significant decrease in the amplitude of contractions. These results suggest that substances present in the E/S products of N. brasiliensis significantly reduce the amplitude of contractions of uninfected rat intestine in vitro and that the biochemical holdfast responsible for this phenomenon may not be AChE.

Acetylcholinesterase↗
PubMed1994

The detection of AKH/HrTH-like peptides in Ascaridia galli and Ascaris suum using an insect hyperglycaemic bioassay.

Evidence for the presence of adipokinetic hormone/hypertrehalosaemic hormone (AKH/HrTH)-like peptides in the parasitic nematodes Ascaridia galli and Ascaris suum has been obtained using insect bioassays which measure hyperglycaemic responses to peptides belonging to the AKH/HrTH family of insect hormones. A peptide fraction extracted from heads and tails of Ascaridia galli evoked a dose-dependent hyperglycaemic response when injected into the cockroach, Periplaneta americana. Maximal bioactivity was obtained with material that was equivalent to 38 mg (wet weight) of nematode. Bioactivity appeared to be highest in extracts from heads and tails of both male and female worms and could be fractionated into at least three peaks of hyperglycaemic activity by reversed-phase high-performance liquid chromatography. An extract from heads and tails of A. suum also evoked a hyperglycaemic response when injected into the cockroach, Blaberus discoidalis. The bioactivity was inactivated on incubation with pure endopeptidase 24.11, confirming the peptidic nature of the bioactive material. These results provide evidence for the existence of peptides related to the insect AKH/HrTH family of peptides in parasitic nematodes.

Amino Acid Sequence↗
PubMed1994

The effect of Trichinella spiralis and Trichinella pseudospiralis on the mechanical properties of mammalian diaphragm muscle.

The isometric mechanical properties of diaphragm muscle were studied in mice infected with either Trichinella spiralis or Trichinella pseudospiralis. Measurements of muscle stress were taken at 15, 20, 30 and 40 days post-infection. Infected diaphragm muscle showed a significant (P < 0.001) reduction in muscle stress during both twitch and tetanic contractions when compared with muscle from control animals. T. spiralis caused a significant reduction in resistance to muscle fatigue. The consequences of these changes in muscle function to host pathology are discussed, and related to previous work on the effects of Trichinella on host biochemistry and the immune response.

Animals↗
PubMed1994

The effects of halothane on voltage-dependent calcium channels in isolated Langendorff-perfused rat heart.

BACKGROUND: Halothane has been previously shown in vitro to decrease both the inward calcium current in isolated cells and the density of calcium antagonist binding sites in cardiac sarcolemmal membranes prepared from several species, including humans, presumably contributing to the negative inotropic effects seen with volatile anesthetics. In this study we examined whether halothane produced similar changes in calcium channel antagonist binding characteristics ex vivo in an intact perfused heart by using isradipine, a dihydropyridine calcium channel blocker that binds specifically to the alpha 1 subunit of the L-type voltage-dependent calcium channel. METHODS: The rat hearts were perfused by the Langendorff method in the presence of halothane and unlabeled isradipine. After the hearts were homogenized and prepared into membranes, a radioligand binding assay was performed and binding curves obtained. Data were analyzed by nonlinear regression analysis of a one-site binding equation and were evaluated by a paired t test. RESULTS: Halothane protected or inhibited the binding of unlabeled isradipine to calcium channels in a dose-dependent manner such that as the halothane is removed during the membrane preparation process, previously obscured sites were then available for specific binding of the radioligand. The sites that were protected by halothane had a lower affinity for [3H]-isradipine than controls. CONCLUSIONS: In both isolated membranes and the intact heart, halothane changes the availability of calcium channel antagonist binding sites, indicating a change in conformation of the voltage-dependent calcium channel in the presence of anesthetic. This change may result from a direct effect on the protein or from an indirect effect mediated through the membrane lipid bilayer. It also is demonstrated that halothane "protected" channels are probably a modified class of channels compared to those in control tissues as exemplified by the much lower affinity that the protected channels have for [3H]-isradipine. We conclude that a major mechanism by which halothane depresses contractility is mediated through the voltage-dependent calcium channel, and this process results from a conformational change in the channel.

Animals↗
PubMed1993

A freeze-fracture study of the cuticle of adult Nippostrongylus brasiliensis (Nematoda).

The surface of the cuticle of adult Nippostrongylus brasiliensis has been studied by means of the freeze-fracture technique and by transmission electron microscopy. Some of the surface coat appears to have been shed from the surface of the cuticle of adults fixed in situ in the intestine of its host and from the surface of individuals removed from the intestine and freeze-fractured. Freeze-fracturing the cuticle of individuals removed from the host has shown that this surface coat varies in thickness from 30 to 90 nm. The epicuticle is about 20 nm thick and cleaves readily to expose E- and P-faces. The P-face of the epicuticle possesses a small number of particles, similar to intra-membranous particles, whilst the E-face possesses a few, widely scattered depressions. Despite the presence of these particles the epicuticle is not considered to be a true membrane. Freeze-fracturing the remainder of the cuticle has confirmed its structure as described by conventional transmission electron microscopy. Clusters of particles on the P-face of the outer epidermal (hypodermal) membrane and corresponding depressions on the E-face of the membrane are though to be associated with points of attachment of the cuticle to the epidermis (hypodermis). No differences in appearance of the cuticle and its surface layers were observed in individuals taken from 7-, 10-, 13- and 15-day infections.

Animals↗