Search PubMed⌕ Search

Biomedical subjects

D Liao

Publications and source records attributed to D Liao.

101 records · Page 6Linked to original sources
PubMed1992

The organization and expression of essential transcription translation component genes in the extremely thermophilic eubacterium Thermotoga maritima.

A 5789-nucleotide-long EcoRI fragment from the genome of Thermotoga maritima, identified by cross-hybridization to L11, L1, L10, and L12 ribosomal protein gene sequences from Escherichia coli, was cloned and sequenced. The fragment encodes five tRNAs (tRNA(met1), anticodon complementary to AUG; tRNA(met2), AUG; tRNA(thr), ACA; tRNA(tyr), UAC; tRNA(trp), UGG), the transcription termination-antitermination factor nusG, the four 50 S subunit ribosomal proteins L11, L1, L10, and L12, and the amino-terminal portion of the RNA polymerase beta subunit protein. The five tRNA genes, the nusG gene, and the L11, L1, L10, and L12 ribosomal protein genes form a complex transcription unit. Transcripts appear to be initiated from an upstream promoter, P1, located in front of the tRNA(met1) gene and from three internal promoters: P2 is located immediately in front of the tRNA(met2) gene; PL10 is near the beginning of the L1-L10 intergenic space, and PL12 is at the end of the L10 gene sequence. The tRNA sequences are excised from the leader regions of the P1- and P2-initiated transcripts. Three putative but potentially important regulatory sequences were identified within this operon: an L1 translational control site, a transcription attenuator, and a strong rho-independent terminator. The strong terminator located distal to the L12 gene overlaps a fifth promoter, P beta, which is used to initiate transcripts of the downstream RNA polymerase beta subunit gene. The T. maritima NusG protein exhibits 43% amino acid sequence identity when aligned to the E. coli protein; the alignment is interrupted by a large 171-amino acid-long insertion into the T. maritima protein after codon 45.

Amino Acid Sequence↗
PubMed1992

Direct measurement of quantal changes underlying long-term potentiation in CA1 hippocampus.

The modification responsible for the long-term synaptic potentiation (LTP) that follows a brief conditioning period is not known. To elucidate this change, we have resolved quantal levels of transmission before and after induction of LTP. We find an increase both in the number of quanta released and in quantal amplitude, consistent with combined pre- and postsynaptic modifications. On average, about 60% of LTP can be accounted for by presynaptic enhancement. The increase in either quantal amplitude or quantal content varies significantly among different experiments, but is inversely correlated with its initial value. These results may help to reconcile the different views concerning the site of LTP expression.

Animals↗
PubMed1991

Preferential reductions in lymphocyte sub-populations induced by monthly pulses of chlorambucil: studies in patients with chronic progressive multiple sclerosis.

Thirty-three patients with chronic progressive multiple sclerosis (MS) were assigned to intervention groups receiving monthly pulses of chlorambucil (CB) for about one year. The monthly doses ranged from 0.4 to 1.5 mg/kg. Administration of CB resulted in preferential reduction in different lymphocyte subsets which was dose- and time-dependent. The number of B-cells (CD20) decreased more rapidly than NK-cells (CD16, CD56, CD16+CD56+) or T-cell (CD3) and T-cells subsets (CD4 and CD8). At 1.2 mg/kg, CB administration resulted in a preferential drop of T-suppressor/cytotoxic cells (CD8) compared with T-helper cells (CD4), and of the less mature "virgin" CD4 cells (CD4+CD45RA+) compared with "memory" CD4 cells (CD4+CD45RA-). The expression of activation markers (transferrin receptor, CALLa, HLA-Dr and CD38[OKT10]) within CD4, CD8 or CD20 lymphocytes was not altered by CB administration. Our data, which show that CB administration results in a preferential fall in B-cell numbers, contrast with the effects of long-term administration of the related immunosuppressive drugs, azathioprine and cyclophosphamide.

Antigens, CD↗
PubMed1991

[The influence of vagotomy on stomach endocrine cells in rat].

UNLABELLED: The effects of unilateral truncal vagotomy (UTV) and bilateral truncal vagotomy (BTV) on antrum EC cells, G cells and oxyntic gland area argyrophil cells were studied in rats by using immunohistochemistry processes, Grimelius argyrophil stain and microscopic image analysis technique. RESULTS: (1) In UTV animals, two weeks postoperation, the sectional areas of EC cells were significantly smaller in denervated side than In the other side (17%, P less than 0.05). In the innervated side of antrum, the sectional areas of EC cells were larger than those in controls (13.5%, P less than 0.05). But, five weeks after UTV, the size of EC cells was not significantly different in all animals. These suggest that vagal denervation can inhibit relatively the functional activity in a short period, but this inhibition could be compensated later. (2) There were no morphological changes in G cells of UTV rats. In BTV animals, the quantity of G cells in antrum increased by 36.2% (P less than 0.05) and their sectional areas were larger than those in sham by 26.2% (P less than 0.05). These indicate that the function of G cells is more active in BTV animals and the functional change of G cells is related to the pH value of gastric juice. (3) In UTV rats, the oxyntic gland area argyrophil cells (ECL cells are dominant) were significantly reduced in two weeks (26.8%, P less than 0.01) and in five weeks (20.1%, P less than 0.05) in denervated side after UTV. The cells became smaller also. These suggest that vagus can influence the function, proliferation and growth of ECL cells.

Animals↗
PubMed1987

Administration of monthly-pulse cyclophosphamide in multiple sclerosis patients. Effects of long-term treatment on immunologic parameters.

Eleven patients with chronic progressive multiple sclerosis received monthly pulses of cyclophosphamide (CY) for approximately one year. During the final 9 months the monthly dose ranged between 1000 mg/m2 and 2000 mg/m2. This resulted in a marked (47% or greater) reduction in CD4 (T helper/inducer) cells a less striking (22%) decrease in CD8 (T suppressor/cytotoxic) cells and a decline in the CD4/CD8 ratio. The magnitude of the decrease in CD4 cells correlated with the total dose received (r = 0.88, P less than 0.05). B cells were reduced 50% and FcR+ lymphocytes were reduced 48% without comparable reduction in natural killer cells or antibody-dependent cellular cytotoxicity. Proliferative responses to PHA were suppressed. Two patients improved, seven stabilized and two continued to worsen. Monthly pulses of CY can achieve substantial and differential reduction in immune parameters and appear to slow the disease progression in some MS patients.

Cyclophosphamide↗
PubMedDate not supplied

Successful intubation with the Combitube in acute asthmatic respiratory distress by a Parkmedic.

The Combitube is a relatively new device used for blind insertion emergency intubation. We report a case of successful Combitube treatment of an acute respiratory arrest secondary to an acute asthma exacerbation. An advanced EMT-II (National Park Service Parkmedic) utilized this device. Our review of the literature revealed no reported cases of an advanced EMT-II, nor any other cases, using the Combitube in asthma-related respiratory failure.

Adult↗
PubMedDate not supplied

Particulate matter and heart rate variability among elderly retirees: the Baltimore 1998 PM study.

This study investigates the relationship between ambient fine particle pollution and impaired cardiac autonomic control in the elderly. Heart rate variability (HRV) among 56 elderly (mean age 82) nonsmoking residents of a retirement center in Baltimore County, Maryland, was monitored for 4 weeks, from July 27 through August 22, 1998. The weather was seasonally mild (63-84 degrees F mean daily temperature) with low to moderate levels of fine particles (PM2.5 < 50 micrograms/m3). Two groups of approximately 30 subjects were examined on alternate days. A spline mixed-effects model revealed a negative relationship between outdoor 24-h average fine particulate matter (PM2.5) and high-frequency (HF) HRV that was consistent with our earlier Baltimore study for all but 2 days. These 2 days were the only days with significant precipitation in combination with elevated PM2.5. They were also unusual in that back-trajectory of their air masses was distinctly different from those on the other study days, emanating from the direction of rural Pennsylvania. Mixed-effects analysis for all 24 study days showed a small negative association of outdoor PM2.5 with HF HRV (-0.03 change in log[HF HRV] for a 10 micrograms/m3 increment in PM2.5) after adjustment for age, sex, cardiovascular status, trend, maximum temperature, average dew point temperature, random subject intercepts, and autocorrelated residuals. After excluding study days 4 and 5, this association was strengthened (-0.07 change in log[HF HRV] for 10 micrograms/m3 PM2.5, 95% CI -0.13 to -0.02) and was similar to that obtained in an earlier study (-0.12 change in log[HF HRV] for a 10 micrograms/m3 increment in outdoor PM2.5, 95% CI -0.24 to -0.00) [Liao D., Cai J., Rosamond W.D., Barnes R.W., Hutchinson R.G., Whitsel E.A., Rautaharju P., and Heiss G. Cardiac autonomic function and incident coronary heart disease: a population-based case-cohort study. The ARIC Study. Atherosclerosis Risk in Communities Study. Am J Epidemiol 1997: 145 (8): 696-706]. Acute (1 to 4 h) previous PM2.5 exposure did not have a stronger impact than the 24-h measure. A distributed lag model incorporating the six preceding 4-h means also did not indicate any effect greater than that observed in the 24-h measure. This study is consistent with earlier findings that exposures to PM2.5 are associated with decreased HRV in the elderly.

Aged↗
PubMedDate not supplied

Examination of the role of cGMP in long-term potentiation in the CA1 region of the hippocampus.

The mechanisms underlying the generation of NMDA receptor-dependent LTP in the CA1 region of the hippocampus continue to receive a great deal of attention because of the postulated importance of LTP as a synaptic mechanism for learning and memory. It is well accepted that the initial induction of LTP occurs in the postsynaptic cell, but the site of expression remains controversial. One prominent hypothesis is that LTP involves the release of one or more retrograde messengers that act on the presynaptic terminal to enhance transmitter release. Recently, evidence has been presented that retrograde messengers function to activate presynaptic guanylyl cyclase and that the resulting rise in presynaptic cGMP levels, when accompanied by presynaptic activity, is responsible for generating an early component of LTP. We have tested this hypothesis by examining whether synaptic strength is increased by coupling tetanic stimulation with application of a membrane-permeable analog of cGMP. The experiments were done in the presence of an NMDA receptor antagonist to block postsynaptic induction mechanisms. Under a variety of experimental conditions, this manipulation failed to generate LTP, suggesting that an increase in cGMP levels accompanied by presynaptic activity is not sufficient to generate LTP in the CA1 region of the hippocampus.

2-Amino-5-phosphonovalerate↗
PubMedDate not supplied

Deficiency in induction but not expression of LTP in hippocampal slices from young rats.

In this study we examine developmental changes between postnatal day (PND) 4 and 14 in synaptic transmission and plasticity in the CA1 region of hippocampal slices. We confirm previous results that tetanus-induced long-term potentiation (LTP) in field recordings is diminished in slices from younger animals. LTP in whole-cell current-clamp recordings is also diminished in younger animals. However, robust LTP can be induced in young animals if sufficient postsynaptic depolarization is provided during LTP induction. Furthermore, we find differences in synaptic transmission between PND 4 and 14, suggesting that the depolarization during tetanic stimulation in young tissue is ineffective to produce LTP. These results indicate that the smaller potentiation in field recordings in slices from younger animals is attributable to insufficient postsynaptic depolarization during LTP induction rather than a defect in expression mechanisms.

Aging↗
PubMedDate not supplied

Interpreting a living will after stroke.

Mr. Duffy is 83 years old and is admitted to rehabilitation 4 weeks after a right thalamic cerebral vascular accident (CVA). He has dysphagia, dysarthria, left hemiplegia, and is moderately-severely confused. He pulls out his nasogastric feeding tube and his physician decides not to reinsert it because of significant nasal tissue necrosis. The team recommends a gastrostomy tube for nutrition because of Mr. Duffy's lack of alertness and high risk for aspiration. Mr. Duffy has a Living Will that states he does not wish to have his life sustained with a feeding tube. He does not have a formal Durable Power of Attorney for Health Care. His wife has dementia and their daughters are making decisions for both parents. They are not sure about his wishes in this particular circumstance, but report that he said of a relative who died of cancer, "things went on too long because of that feeding tube." After 3 days, Mr. Duffy is more alert, and during a discussion about tube feedings he says, "I'll go for the works." His fluctuating alertness level prevents him from responding to this question again. His daughters feel he would not want the tube and suggest waiting to see if his swallowing improves in the next week before making a decision.

Aged↗