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D Liao

Publications and source records attributed to D Liao.

At least 91 records · Page 5Linked to original sources
PubMed1995

Concerted evolution of the tandemly repeated genes encoding primate U2 small nuclear RNA (the RNU2 locus) does not prevent rapid diversification of the (CT)n.(GA)n microsatellite embedded within the U2 repeat unit.

The RNU2 locus encoding human U2 small nuclear RNA (snRNA) is organized as a nearly perfect tandem array containing 5 to 22 copies of a 5.8-kb repeat unit. Just downstream of the U2 snRNA gene in each 5.8-kb repeat unit lies a large (CT)n.(GA)n dinucleotide repeat (n approximately equal to 70). This form of genomic organization, in which one repeat is embedded within another, provides an unusual opportunity to study the balance of forces maintaining the homogeneity of both kinds of repeats. Using a combination of field inversion gel electrophoresis and polymerase chain reaction, we have been able to study the CT microsatellites within individual U2 tandem arrays. We find that the CT microsatellites within an RNU2 allele exhibit significant length polymorphism, despite the remarkable homogeneity of the surrounding U2 repeat units. Length polymorphism is due primarily to loss or gain of CT dinucleotide repeats, but other types of deletions, insertions, and substitutions are also frequent. Polymorphism is greatly reduced in regions where pure (CT)n tracts are interrupted by occasional G residues, suggesting that irregularities stabilize both the length and the sequence of the dinucleotide repeat. We further show that the RNU2 loci of other catarrhine primates (gorilla, chimpanzee, orangutan, and baboon) contain orthologous CT microsatellites; these also exhibit length polymorphism, but are highly divergent from each other. Thus, although the CT microsatellite is evolving far more rapidly than the rest of the U2 repeat unit, it has persisted through multiple speciation events spanning > 35 Myr. The persistence of the CT microsatellite, despite polymorphism and rapid evolution, suggests that it might play a functional role in concerted evolution of the RNU2 loci, perhaps as an initiation site for recombination and/or gene conversion.

Animals↗
PubMed1995

Age, race, and sex differences in autonomic cardiac function measured by spectral analysis of heart rate variability--the ARIC study. Atherosclerosis Risk in Communities.

To investigate the distribution of heart rate variability (HRV) spectral power in an unselected sample of the population, and to ascertain the population correlates of HRV, we examined 1,984 healthy persons, aged 45 to 64 years, randomly selected from the Atherosclerosis Risk in Communities (ARIC) study cohort. Resting, supine, 2-minute, beat-to-beat heart rate data were collected between 7 A.M. and 12 noon. The race- and sex-adjusted geometric means of low-frequency component (LF, 0.025 to 0.15 Hz) were 4.00 and 3.13 (beats/min)2; of high-frequency component (HF, 0.16 to 0.35 Hz), 1.65 and 1.21 (beats/min)2; and of the HF/LF ratio, 0.41 and 0.39, for 45-to-54 and 55-to-64 years age groups, respectively (test of mean difference by age, p < 0.01, p < 0.01, and p = 0.11 for LF, HF, and HF/LF ratio, respectively). Comparing black with white examinees, the age- and sex-adjusted geometric means of LF were 3.06 and 3.70 (beats/min)2; of HF, 1.66 and 1.36 (beats/min)2; of HF/LF, 0.54 and 0.37, respectively (test of mean difference by race, p < 0.01, p < 0.01, and p < 0.01). The age- and race-adjusted geometric means of LF for women and men were 3.12 and 4.10 (beats/min)2; of HF, 1.46 and 1.38 (beats/min)2; and of HF/LF, 0.47 and 0.34, respectively (test of mean difference, p < 0.01, p = 0.34, and p < 0.01). We conclude that HRV spectral indexes are associated with age, race, and sex. With increasing age, the parasympathetic and sympathetic spectral power components decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1995

Activation of postsynaptically silent synapses during pairing-induced LTP in CA1 region of hippocampal slice.

Long-term potentiation (LTP) is an enhancement of synaptic strength that can be produced by pairing of presynaptic activity with postsynaptic depolarization. LTP in the hippocampus has been extensively studied as a cellular model of learning and memory, but the nature of the underlying synaptic modification remains elusive, partly because our knowledge of central synapses is still limited. One proposal is that the modification is postsynaptic, and that synapses expressing only NMDA (N-methyl-D-aspartate) receptors before potentiation are induced by LTP to express functional AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate) receptors. Here we report that a high proportion of synapses in hippocampal area CA1 transmit with NMDA receptors but not AMPA receptors, making these synapses effectively non-functional at normal resting potentials. These silent synapses acquire AMPA-type responses following LTP induction. Our findings challenge the view that LTP in CA1 involves a presynaptic modification, and suggest instead a simple postsynaptic mechanism for both induction and expression of LTP.

Animals↗
PubMed1995

Association of vagal tone with serum insulin, glucose, and diabetes mellitus--The ARIC Study.

Reduced vagal activity assessed by heart rate variability (HRV) has been observed in studies of diabetics, but this association has not been reported at the population level. To investigate the association of HRV with diabetes mellitus, as well as fasting serum insulin, and glucose, we examined a stratified random sample of 1933 individuals (154 diabetics and 1779 non-diabetics), aged 45-65 years from the Atherosclerosis Risk in Communities (ARIC) study cohort. Two-minute, resting, supine beat-to-beat heart rate records were collected. Power spectral density estimation was used to derive HRV high frequency power (HF, 0.15-0.35 Hz) as the conventional marker of vagal function. Age, race, and gender-adjusted geometric means of HF were 0.78 and 1.27 (beat/min)(2) for diabetics and non-diabetics respectively (P for mean difference <0.01), reflecting a reduced vagal activity in diabetics. In individuals not diagnosed as diabetics, a graded, inverse association was observed between fasting serum insulin and HF (P for trend <0.01): the age, race, and gender-adjusted geometric mean values of HF in the lowest and highest quartiles of serum insulin were 1.34 and 1.14 (beat/minute)(2), respectively. A similar association was observed between glucose and HF in a univariate model, but not in the adjusted model. This first population-based study on this subject confirmed that diabetics have significantly lower vagal activity than non-diabetics. In individuals not diagnosed as diabetics, serum insulin, and, to a lesser degree, serum glucose were inversely associated with vagal function, suggesting a role in the pathogenesis of diabetic neuropathy.

Blood Glucose↗
PubMed1995

Vaccinia virus transfection of hippocampal slice neurons.

Here we describe a technique that uses a recombinant vaccinia virus to transfect neurons in rat hippocampal slices. This technique allows the use of molecular biological manipulations on neuronal tissue while maintaining intact synaptic function. This method should be useful in testing specific hypotheses regarding the role of synaptic proteins.

Animals↗
PubMed1995

Hormonal regulation of sex differentiated parameters in liver nodules from rats treated in the resistant hepatocyte model.

Sex differentiation of liver functions has been shown to be attenuated in preneoplastic rat liver nodules. The present study was performed to investigate whether nodules from male rats are to some extent withdrawn from the normal growth hormone (GH) regulation of these functions. Male and female Wistar rats were treated according to a modified resistant hepatocyte model (RH-model), with diethylnitrosamine initiation and promotion with intragastric administration of 2-acetylaminofluorene (2-AAF) combined with partial hepatectomy (PH). Eleven months post-initiation male rats were treated with either human (hGH) or bovine growth hormone (bGH) or ovine prolactin (oPRL) by continuous infusion for 1 week. The mRNA expression of a number of genes known to be sex differentiated in liver from adult control rats was compared in nodular and surrounding tissue from nodule-bearing male, female and hormone-treated male rats. The basal mRNA expression of the female-predominant cytochrome P4502C12 (CYP2C12) was increased and the male-predominant CYP2C11 was decreased in liver nodules from male rats compared with the surrounding liver. Expression of the prolactin receptor (PRL-r; female > male) and the steroid 5 alpha-reductase (female > male) genes was decreased in male nodules, whereas no difference was observed with respect to GH-receptor (GH-r; female > male) expression in nodules versus surrounding tissue. Early nodules obtained from males treated according to the original RH-model (dietary 2-AAF, 0.02%) and isolated 2 weeks after completion of the 2-AAF/PH treatment showed significantly lower GH-r mRNA levels than the total liver tissue. In hepatocellular carcinomas from hormonally unmanipulated males 11 months post-initiation the decrease in PRL-r expression was even more pronounced than in the nodules and a significant decrease in GH-r expression was seen. In female nodules the only significant difference with respect to the sex differentiated parameters was a lower 5 alpha-reductase expression than in the surrounding tissue. Continuous infusion of both hGH and bGH feminized the expression of all the sex differentiated genes in male tissues and eliminated the previously detected differences between nodules and surrounding tissue. oPRL also eliminated the differences between nodules and surrounding tissue in males and partly feminized the expression of both the 5 alpha-reductase and the PRL-r genes.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Somatic symptoms and HIV infection: relationship to depressive symptoms and indicators of HIV disease.

OBJECTIVE: This study examined the relationship of the somatic symptoms fatigue and insomnia with indicators of both psychiatric disturbance and HIV disease severity. METHOD: Study participants were 98 asymptomatic HIV-infected and 71 uninfected homosexual men; 82 HIV-infected and 64 uninfected men had 6-month follow-up examinations. Scales from the self-reported Profile of Mood States measured fatigue and dysphoric mood. Major depression diagnosis was determined by the Structured Clinical Interview for DSM-III-R. Selected items from the Hamilton depression and anxiety scales measured insomnia and other symptoms of depression. Performance on a battery of standardized tests determined neuropsychological function ratings. RESULTS: At study entry, complaints of fatigue and insomnia were associated with dysphoric mood, major depression, and other non-HIV-related symptoms of major depression but not with CD4 cell counts or neuropsychological functioning. Increases in levels of fatigue and insomnia over the 6-month follow-up period were associated with increases in non-HIV-related symptoms of depression and in severity of dysphoric mood. Increases in fatigue were also associated with decrements in motor functioning. Otherwise, fatigue or insomnia were not associated with HIV disease progression. CONCLUSIONS: These findings suggest that complaints of fatigue and insomnia in otherwise asymptomatic HIV-infected patients are likely to be related to psychological disturbances and possibly major depression, which can be treated. HIV-infected patients who complain of fatigue or insomnia should routinely be assessed for major depression.

Adult↗
PubMed1995

Stress-associated reductions of cytotoxic T lymphocytes and natural killer cells in asymptomatic HIV infection.

OBJECTIVE: Previous research has documented a possible relation of stress and depression to cell-mediated immunity. The authors examined how stressful events and depression may affect key parameters of cellular immunity in subjects with and without HIV infection. METHOD: Data were collected on 99 asymptomatic HIV-positive and 65 HIV-negative homosexual men as part of an ongoing, longitudinal study. Criticisms of previous studies of psychoimmunity were addressed by 1) using a comprehensive, semistructured interview to measure the objective context of stressful events, 2) double labeling of lymphocytes with monoclonal antibodies to measure subsets of cytotoxic/suppressor T lymphocytes and natural killer (NK) cells, and 3) controlling for circadian effects and methodological factors. RESULTS: In the HIV-positive men, severe stress was significantly associated with reductions in NK cell populations and a subset of T cells thought to represent cytotoxic T effector cells, particularly the CD8+ T cells expressing the CD57 antigen. In the HIV-negative men, no clear and consistent relation between stress and immune system measures was found. Depression was not correlated with any variables in either of the groups, perhaps due to the low levels of depressive symptoms. CONCLUSIONS: The findings suggest that stress is associated with reductions in killer lymphocytes (decreased NK cell and cytotoxic T lymphocyte phenotypes). The data provide evidence that stress may alter cell populations that provide cytotoxic defense against infection in HIV-positive men and indicate that the clinical significance of stress-related changes in cytotoxic T lymphocytes and NK cells in HIV infection warrants further study.

Adaptation, Psychological↗
PubMed1995

[Morphometric study on the cerebral cortex of partial status epilepticus rats induced by coriaria lactone].

Twenty adult male Wistar rats, divided into two groups were studied. Experimental rats were embedded with a particle containing Coriaria Lactone into the fore limb's representative area of cerebral motor cortex to induce epilepsy. Control rats were embedded with a particle containing distilled water. After 6 h motor cortex was cut and the structure was compared morphologically with control rats. Some pale neurons, dark shrunken neurons and severe sponginess of neuropil were observed in layers I-V of the epileptic rat under LM. Under EM, the mitochondria became swollen and other organelles migrated and close associated with the nucleus in pale neurons, and in dark neurons both cytoplasm and karyoplasm showed highly electron dense. The spongiform neuropil was mainly occupied by swollen glial processes. The number of neuron and neuroglia were counted from photos under LM. The number of synaptic terminal was counted directly and the areal fraction of the constituents in the neuropil was measured stereologically in the EM photos. The number of neuron and neueroglia decreased significantly. Both the number of synaptic terminal in neuropil and the areal fraction of synaptic terminal decreased significantly. These changes were most prominent in the focus area of epileptic rats and in the parafocus area, too. This may indicate that the decrease of areal fraction of synaptic terminal results from the decrease of the number of synaptic terminal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Molecular phylogenies based on ribosomal protein L11, L1, L10, and L12 sequences.

Available sequences that correspond to the E. coli ribosomal proteins L11, L1, L10, and L12 from eubacteria, archaebacteria, and eukaryotes have been aligned. The alignments were analyzed qualitatively for shared structural features and for conservation of deletions or insertions. The alignments were further subjected to quantitative phylogenetic analysis, and the amino acid identity between selected pairs of sequences was calculated. In general, eubacteria, archaebacteria, and eukaryotes each form coherent and well-resolved nonoverlapping phylogenetic domains. The degree of diversity of the four proteins between the three groups is not uniform. For L11, the eubacterial and archaebacterial proteins are very similar whereas the eukaryotic L11 is clearly less similar. In contrast, in the case of the L12 proteins and to a lesser extent the L10 proteins, the archaebacterial and eukaryotic proteins are similar whereas the eubacterial proteins are different. The eukaryotic L1 equivalent protein has yet to be identified. If the root of the universal tree is near or within the eubacterial domain, our ribosomal protein-based phylogenies indicate that archaebacteria are monophyletic. The eukaryotic lineage appears to originate either near or within the archaebacterial domain.

Amino Acid Sequence↗
PubMed1994

Ectopic pituitary grafts modify the response of male rats to sex differentiated promotion of diethylnitrosamine-initiated hepatic lesions with a choline-deficient diet.

The influence of implantation of ectopic pituitary grafts (PGs) under the kidney capsule in male rats on the sex differences in response to promotion with a choline-deficient (CD) diet was studied in the livers of diethylnitrosamine (DEN)-initiated Wistar rats. Growth of enzyme-altered foci, liver regeneration in response to partial hepatectomy (PH) and hepatic c-myc expression were studied. The area per enzyme-altered focus was significantly larger in initiated males fed a CD diet for 10 weeks when compared with the corresponding females. The sex difference was more pronounced 1 week after a PH performed following 10 weeks on the diet. In males carrying PGs the area per focus was reduced to the same size as in females. Liver weight gain after PH was reduced in males, but not in females, by the CD diet, and the level in PG-bearing males was intermediary, significantly different from that of males without grafts. A significantly lower labeling index in surrounding, but not in focal, hepatocytes was observed in initiated, CD-treated males than in the corresponding females 1 week after PH. In initiated as well as in uninitiated males on a CD diet the expression of the c-myc gene was 3- to 4-fold higher when compared with males fed a choline-supplemented diet at the time of PH. The mRNA level in females fed a CD diet was approximately 2.5-fold lower than in males, but still significantly above the level in females without the dietary treatment. A significant decrease in male c-myc expression was observed as a result of implantation of ectopic pituitaries. In conclusion, sex-differentiated promotion of DEN-initiated lesions with a CD diet is regulated by a pituitary influence on rat liver, in analogy with results previously obtained in the resistant hepatocyte model and with dietary deoxycholic acid promotion. This might suggest that pituitary factors are major determinants of sex-differentiated promotion in rat liver.

Animals↗
PubMed1994

[Morphometric study of motor cortex in acute focal epilepsy rat induced by coriaria lactone].

Twenty adult male Wistar rats were divided randomly into two groups (10 rats for LM, 10 rats for EM). The experimental rats were injected with convulsive dosage 3.8 microliters (19 micrograms) of coriaria lactone (CL) in the left cerebral motor cortex of the fore limb to induce acute focal epilepsy. The control rats were injected with normal saline of the same volume and at the same location. Motor cortex was cut coronally 2 hours after seizure and the layer V was studied morphometrically. Under x400 and x7000, take photos of focus, parafocus areas respectively for morphometric study. The number of neurons and neuroglias of layer V was counted in the LM photos. The number of presynaptic terminals of the neuropil was counted in the x7000 EM photos and the area fraction of each constitute in the neuropil was measured. The positive results demonstrated that the number of neurons and neuroglias in the focus and parafocus areas of the experimental animals was significantly lower than that in the control group, the side injected was lower than the other side and it was the lowest in the focus. The number and area fraction of the presynaptic terminals of the experimental rats at the focus neuropil decreased significantly, but the area fraction of neuroglial components increased significantly. The authors suggest that the convulsive dosage of CL may have toxic effect on some neurons and neuroglias and therefore to decrease the number of both types of cells and the number and area fraction of presynaptic terminals in the neuropil.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1994

[Quantitative study on cerebral motor cortex structure of kindling rat induced by coriaria lactone].

Ten male Wistar rats were divided into two groups. The experimental rats were injected with subconvulsive dosage of coriaria lactone (1 mg/kg) intramuscularly every 3.5 days to induce kindling seizures. The controls were injected with normal saline. Cerebral motor cortex of kindling rats was taken at the time between seizures and layer V was compared morphologically with that of the control. The number of neurons and neuroglias was counted from light micrographs. The numerical density and length fraction of boutons on the surface of pyramidal somata were measured from electron micrographs with MIAS 300 type image analyser. The number of synapses in neuropil was counted directly and the areal fraction of various constitute in neuropil was measured stereologically from EM photos. In the experimental rats, the number of neurons remained unchanged and the numerical density and length fraction of boutons on the surface of pyramidal somata showed no change, either. The number of synapses (or presynaptic terminals) decreased significantly in neuropil, but the areal fraction of synaptic terminals had no change and the areal fraction of dendrites and unmyelinated fibers decreased. The areal fraction of myelinated fibers increased significantly. The number of neuroglias and the areal fraction of neuroglial processes increased significantly in the experimental rats. The data suggest that the major morphological changes are manifested as a decline in the pyramidal dendritic components, especially dendritic spines, and the axons with its terminals from superficial neurons in motor cortex layer V of the kindling rats induced by coriaria lactone, besides the neurogliosis which is similar to that occurring in other long-term seizures.

Animals↗
PubMed1993

Modulated excitation of singly ligated carboxyhemoglobin.

We have extended the method of modulated excitation, a small perturbation kinetic method, to study ligand binding and conformational change of hemoglobin tetramers with a single ligand bound. To restrict the excitation to the first ligand, only 1% of the hemes have bound CO, and the remainder are kept unliganded. A detailed theory is presented which agrees well with the experimental observations. This method of observing ligand recombination also provides a novel and simple method for determination of hemoglobin concentration. Additional relaxation processes are also observed. By fitting independently determined spectra to the spectra associated with the relaxations, these processes are assigned as thermal excitation and thermally driven protonation/deprotonation reactions. These added relaxations arise from the deoxy-Hb portion of the samples, and demonstrate that modulated excitation can be used effectively for temperature perturbation in the absence of photodissociation. The spectra observed are not well described by the spectra of allosteric change, however, and we conclude that there is no significant mixing of quaternary states at the first ligation step. In an appendix we present a derivation of the particular features seen in thermally modulated protonation reactions.

Allosteric Site↗
PubMed1993

Sex differences at the initiation stage of rat liver carcinogenesis--influence of growth hormone.

Male and female rats were initiated with a single dose of 3'-methyl-4-dimethylaminoazobenzene (3'MeDAB), N-hydroxy-2-acetylaminofluorene (N-OH-AAF) or aflatoxin B1 (AFB1) and promoted with 2-acetylaminofluorene plus partial hepatectomy (2-AAF/PH). One group of male rats in each experiment received continuous infusion of pituitary growth hormone (GH) for one week prior to initiation to feminize the secretory pattern of GH and hepatic functions. A significantly larger number of foci in male than in female rats was observed after N-OH-AAF and AFB1 initiation. Continuous GH treatment of male rats decreased the number of N-OH-AAF-initiated foci to the level in females, while no effect of GH was observed on AFB1 initiation. Initiation with 3'MeDAB showed no sex differences in number of foci. In conclusion, the present study demonstrates that sex differences occur at the initiation stage and that the secretory pattern of GH is responsible for the dimorphism in initiation with N-OH-AAF, but not with AFB1.

2-Acetylaminofluorene↗
PubMed1993

Personality disorder in patients infected with HIV: a controlled study with implications for clinical care.

OBJECTIVE: Previous studies of psychiatric illness in populations infected with or at risk for HIV have not included systematic evaluation for personality disorders. The authors present the first controlled study of 1) personality disorders in HIV-positive and HIV-negative homosexual men and 2) the impact of personality disorder on coping, social support, and mood in asymptomatic HIV-positive homosexual men. METHOD: The authors studied 58 asymptomatic HIV-positive and 53 HIV-negative homosexual men living outside the high-prevalence epicenters of the AIDS epidemic. Personality disorder was assessed with a clinician-administered interview, the Structured Clinical Interview for DSM-III-R. RESULTS: There was a significantly higher prevalence of personality disorder in the HIV-positive (33%) than in the HIV-negative (15%) subjects. In the HIV-positive subjects, those with a personality disorder (compared to those without a personality disorder) showed 1) significantly greater mood disturbance, with higher scores on the Hamilton Rating Scale for Depression, Hamilton Rating Scale for Anxiety, Profile of Mood States Total Mood Dysfunction, and the Beck Hopelessness Scale, 2) greater use of denial and helplessness when coping with the threat of AIDS, and 3) greater social conflict. CONCLUSIONS: These findings suggest that personality disorder is common in the HIV-positive population. Compared with HIV-infected patients without a personality disorder, patients with a personality disorder may experience greater dysphoria and be more likely to cope with the threat of AIDS in a dysfunctional way. Recognition of the impact of personality disorder on coping with HIV infection is important for comprehensive, sensitive, and effective clinical care.

Acquired Immunodeficiency Syndrome↗