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Biomedical subjects

S H Li

Publications and source records attributed to S H Li.

At least 109 records · Page 6Linked to original sources
PubMed1994

Purification and biochemical characterization of a recombinant mouse seminal vesicle trypsin inhibitor produced in Escherichia coli.

Escherichia coli cells were transformed with an expression vector constructed by inserting a DNA fragment encoding a Kazal-type trypsin inhibitor from mouse seminal vesicle into pGEX-2. The cloned cells were able to produce a high yield of a chimeric polypeptide made by fusing the trypsin inhibitor to glutathione S-transferase. The chimeric polypeptide could be purified through an affinity column of glutathione agarose beads. The purified protein could be digested with thrombin to release the recombinant trypsin inhibitor which could be further purified by HPLC of the thrombin digests on a reverse-phase C4 column. The recombinant trypsin inhibitor was homogeneous and showed trypsin inhibitor activity as strong as that of the naturally occurring trypsin inhibitor.

Amino Acid Sequence↗
PubMed1994

Triplet repeats in clinical subtypes of schizophrenia: variation at the DRPLA (B 37 CAG repeat) locus is not associated with periodic catatonia.

Clinical evidence for a dominant mode of inheritance and anticipation in periodic catatonia, a distinct subtype of schizophrenia, indicates that genes with triplet repeat expansions or other unstable repetitive elements affecting gene expression may be involved in the etiology of this disorder. Because patients affected with dentatorubral-pallidoluysian atrophy (DRPLA) may present with "schizophrenic" symptoms, we have investigated the DRPLA (B 37 CAG repeat) locus on chromosome 12 in 41 patients with periodic catatonia. The B 37 CAG repeat locus was highly polymorphic but all alleles in both the patient and control group had repeat sizes within the normal range. We conclude that variation at the DRPLA locus is unlikely to be associated with periodic catatonia. The evidence for dominant inheritance and anticipation as well as the high prevalence of human brain genes containing trinucleotide repeats justifies further screening for triplet repeat expansions in periodic catatonia.

Adult↗
PubMed1994

Three drugs inhibit phospholipase A2-induced high permeability of endothelial monolayers.

The permeability of aortic endothelial monolayers to fluid and albumin increased 13.5 and 16.1 times respectively after pretreatment with phospholipase A2 (PLA2, 100 U.ml-1) for 30 min. 1-(p-Chlorobenzoyl)-5-methylindole-3-acetic acid (1.16 mmol.L-1), SRI 63-441 (30 nmol.L-1), and 1,25-dihydroxycholecalciferol (0.1 mumol.L-1) decreased PLA2-induced high permeability. PLA2 did not damage the endothelial cells significantly. Our results indicate that the action of PLA2 to increase the permeability of endothelial monolayers is mainly due to PLA2-induced lipid mediators released from endothelial cells.

Animals↗
PubMed1994

Pentoxifylline attenuates platelet activating factor-induced permeable edema in isolated perfused guinea pig lungs.

The effect of pentoxifylline (Pen) on platelet activating factor (PAF)-induced pulmonary injury was studied in isolated guinea pig lungs perfused with cell-free Tris buffered Ringer solution. PAF (1.0 nmol.L-1) increased lung weight and pulmonary filtration coefficient (Kf), which indicated the formation of high permeable pulmonary edema. Pen (0.5 and 1.0 mmol.L-1) markedly attenuated the PAF-induced increment of lung weight and vascular permeability, but not the increment of pulmonary capillary pressure and venous resistance. There was no correlation between the severity of lung edema and the number of leukocytes in the perfusates. These results suggest that Pen has direct anti-permeability effect on pulmonary microvessels.

Animals↗
PubMed1993

Novel triplet repeat containing genes in human brain: cloning, expression, and length polymorphisms.

Human genes containing triplet repeats may markedly expand in length and cause neuropsychiatric disease, explaining the phenomenon of anticipation (increasing severity or earlier age of onset in successive generations in a pedigree). To identify novel genes with triplet repeats, we screened a human brain cDNA library with oligonucleotide probes containing CTG or CCG triplet repeats. Fourteen of 40 clones encoded novel human genes, and 8 of these inserts have been sequenced on both strands. All contain repeats, and 5 of the 8 have 9 or more consecutive perfect repeats. All are expressed in brain. Chromosomal assignments reveal a distribution of these genes on multiple autosomes and the X-chromosome. Further, the repeat length in two of the genes is highly polymorphic, making them valuable index linkage markers. We predict that many triplet repeat-containing genes exist; screening with the CTG probe suggests approximately 50-100 genes containing this type of repeat are expressed in the human brain. Since additional disorders, such as Huntington's disease, bipolar affective disorder, and possibly others, show features of anticipation, we suggest that these novel human genes with triplet repeats are candidates for causing neuropsychiatric diseases.

Base Sequence↗
PubMed1993

Influence of age on the secretory rates of the human minor salivary glands and whole saliva.

This investigation comprised two studies of healthy, unmedicated individuals. The first measured the effect of collection time on the volume of secretions of the minor salivary glands at four specified areas of the lower lip of 13 individuals before and after a mild gustatory stimulus. The second (n = 51) monitored the influence of age and gender on the secretory rates of unstimulated labial, buccal and palatal salivary glands. Also, unstimulated and stimulated flow rates of whole saliva were monitored to provide a point of reference. Volumes of minor gland secretions were measured with a Periotron unit. Results of the first study indicated a linear increase in volumes with collection time (15, 30, 45 and 60 s). Flow rates were similar among the four labial sites, approx. 1 microliter/cm2/min, and were not influenced by mild citric acid stimulation. Results of the second study indicated that flow rates differed significantly (p = 0.0001) among the anatomical sites, with similar rates on the right- and left-hand sides. Gender exerted no influence on flow from the minor salivary glands. Similarly, age exerted no influence on flow from the buccal or labial glands. However, the secretory rate for the palatal glands decreased significantly with age (r = -0.44; p < 0.005). As for unstimulated whole saliva, secretory rates were not influenced by age nor gender; rates for stimulated whole saliva increased with age (r = 0.31; p < 0.05). No association was detected between the flow rates of the whole saliva and that of the minor salivary glands.

Adult↗
PubMed1993

A method for measuring secretions from the palatal minor salivary glands.

This study investigated the secretory pattern of unstimulated minor salivary glands in 10 contiguous specified areas of the hard palate in 12 healthy unmedicated adult men and women. Each participant was assessed twice at each of two visits in the same specific palatal areas from the distal portion of the second molar to 30 mm anterior. The 10 areas were isolated, dried, and sampled with a paper strip for 60 seconds. The strips were read with a Periotron device. The rates of flow were significantly influenced by position; higher values were noted posteriorly and medially during testing and retesting at both visits. The rates of flow from the palatal glands were greatest in the area between the maxillary second molars. This method proved to be simple, accurate, and reliable for measuring the secretions of the palatal glands. This method may prove useful for investigating how the relationship between the pattern and the secretory rate of minor salivary glands influences retention of the complete maxillary denture.

Adult↗
PubMed1993

Genes with triplet repeats: candidate mediators of neuropsychiatric disorders.

Recently a new form of human mutation-expansion of trinucleotide repeats-has been found to cause the diseases of fragile X syndrome, spinal and bulbar muscular atrophy, myotonic dystrophy and, most recently, Huntington's disease. We review the emerging data on the genetics and neurobiology of these disorders. Three are characterized by unusual patterns of inheritance, in particular, genetic 'anticipation', in which the severity of the disorder increases and the age of onset decreases in successive generations of a pedigree. Several idiopathic neuropsychiatric disorders have features of inheritance consistent with anticipation. In bipolar affective disorder, there is evidence for both earlier age of onset and more severe illness in the second generation of a subset of unilineal pedigrees. There is also the suggestion of anticipation in some forms of schizophrenia, spinocerebellar atrophy and autism. Triplet repeats are present in additional known genes, both in coding regions and untranslated regions. Furthermore, many novel genes with triplet repeats are expressed in the human brain, and these are candidates to cause some forms of these neuropsychiatric disorders.

Humans↗
PubMed1993

Huntington's disease gene (IT15) is widely expressed in human and rat tissues.

Huntington's Disease (HD) is notable for selective neuronal vulnerability in the basal ganglia and cerebral cortex. We have investigated in human and rodent tissues the expression of the gene (IT15) whose mutation causes HD. IT15 is widely expressed, with highest levels of expression in brain, but also in lung, testis, ovary, and other tissues. Within the brain, expression is widespread with a neuronal pattern and is not enriched in the basal ganglia. Expression of IT15 is not reduced in the brain of HD patients when corrected for actin (though it is slightly decreased in the striatum when uncorrected, consistent with neuronal loss). Thus, the widespread distribution of IT15 expression does not correspond with the restricted distribution of neuropathologic changes in HD. We suggest that pathophysiology may relate to abnormal cell type-specific protein interactions of the HD protein.

Animals↗
PubMed1993

Modulation of leukocyte cyclic AMP phosphodiesterase activity by recombinant interferon-gamma: evidence for a differential effect on atopic monocytes.

Mechanisms of interferon-gamma (IFN-gamma) effects on monocytes are poorly defined. Evidence for altered IFN-gamma responses and increased monocyte cyclic AMP phosphodiesterase (PDE) activity in atopic dermatitis (AD) suggested a possible relationship. PDE activity in response to IFN-gamma was assessed in normal and atopic monocytes to evaluate the IFN-gamma regulatory role in cell function. Adherence-isolated peripheral blood monocytes were exposed to recombinant human IFN-gamma at 0.1-300 U/ml in Gey's balanced salt solution for varying time periods. Anti-IFN-gamma was used as control. PDE activity was measured by radioenzyme assay using 1 microM cyclic AMP as final substrate concentration. IFN-gamma caused a dose-dependent increase in PDE activity of normal monocytes and the effect was neutralized by anti-IFN-gamma. By contrast, in atopic monocytes, PDE activity was not affected by IFN-gamma at low dose, while at concentrations greater than 200 U/ml, it significantly reduced phosphodiesterase activity. IFN-gamma of PDE activity may alter normal monocyte functions by decreasing cyclic AMP levels. Paradoxical PDE unresponsiveness probably reflects maximal PDE activation in atopic monocytes. This elevated PDE activity is inhibited by high IFN-gamma levels. Reduction of atopic monocyte PDE activity may help to normalize immune function and could account for recent reports of therapeutic efficacy of IFN-gamma in AD.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1993

Increased interleukin 6 production by T cells derived from patients with atopic dermatitis.

Many immunologic aspects of atopic dermatitis have been studied, but basic pathobiologic mechanisms of this disease remain unknown. In this study, we measured the production of interleukin-6 (IL-6) by peripheral blood T cells and monocytes from patients with atopic dermatitis in comparison to normal control subjects and patients with chronic psoriasis. We found that peripheral blood T cells isolated from patients with atopic dermatitis produced significantly higher levels of IL-6 (36.1 +/- 5.1 units/ml, n = 22) than T cells derived from either normal subjects (12.6 +/- 1.9 units/ml, n = 22) or patients with chronic psoriasis (26.7 +/- 4.1 units/ml, n = 7). T-cell activation was also measured in the patients with atopic dermatitis by soluble serum IL-2 receptor levels and were found to be significantly higher (623.7 +/- 8.1 units/ml, n = 8) than normal subjects (357.2 +/- 26.0 units/ml, n = 8). In contrast to the increased production of IL-6 by T cells in atopic dermatitis, there was no significant difference in the IL-6 production by peripheral blood monocytes derived from patients with atopic dermatitis compared to normal subjects. Thus, peripheral blood T cells derived from patients with AD spontaneously produce increased amounts of IL-6 compared to T cells from normal subjects, which may reflect the increased activation state of T cells in atopic dermatitis. These data support the concept that activated T cells or subsets of T cells may be important effector cells in mediating inflammatory activity in atopic disease.

Biological Availability↗
PubMed1993

Increased interleukin-4 production by atopic mononuclear leukocytes correlates with increased cyclic adenosine monophosphate-phosphodiesterase activity and is reversible by phosphodiesterase inhibition.

Previous studies have shown that leukocytes from patients with atopic dermatitis have increased levels of cyclic adenosine monophosphate (cAMP)-phosphodiesterase activity. This increased activity accounts for subnormal cAMP responses and correlates with increased in vitro immunoglobulin E production. To better understand the mechanism of this effect, we studied the relationship between phosphodiesterase activity and interleukin-4, a T-cell-derived cytokine that is a major regulator of immunoglobulin E production. Cultures stimulated with anti-CD3 or with phorbol myristate acetate plus ionophore significantly increased interleukin-4 production, and levels were consistently highest in cells from atopic subjects. Interleukin-4 production was higher, on a per T-cell basis, in mononuclear leukocyte cultures than in cultures of pure T cells, suggesting the possibility of a monocyte factor acting to increase interleukin-4 production. We next examined the effect of the phosphodiesterase inhibitor Ro 20-1724 on interleukin-4 production and found a significant reduction in cultures of atopic mononuclear leukocytes. This phosphodiesterase inhibitor effect appeared to act primarily on monocytes and correlated with increased intracellular cAMP levels. These studies demonstrate increased interleukin-4 production by atopic T cells. This abnormality can be reversed by inhibition of cAMP-phosphodiesterase, suggesting a possible therapeutic target for control of atopic disease.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗
PubMed1993

Comparison of tooth surface-specific dental caries attack patterns in US schoolchildren from two national surveys.

The 1979-1980 and the 1986-1987 National Institute of Dental Research (NIDR) surveys of school-aged children revealed that virtually all tooth surfaces experienced a decrease in caries prevalence during the inter-survey period. Overall, there was a 28% decrease in the proportion of tooth surfaces attacked by caries for the primary dentition between the two surveys. The decrease for primary incisors was numerically small (5 surfaces per thousand surfaces at risk) and not statistically significant, whereas decreases in the canines and primary molars were considerably larger (23 surfaces per thousand) and statistically significant. For the permanent dentition, the overall decrease in the proportion of surfaces attacked was 35% during the 1979-87 period. Differences between the two surveys in the proportions of surfaces with caries were largest for pit and fissure surfaces (56 surfaces per thousand), followed by those for posterior approximal surfaces (14 surfaces per thousand) and all other smooth surfaces (5 surfaces per thousand). Almost all of these differences were statistically significant, except for some surfaces which experienced very few caries.

Adolescent↗
PubMed1993

Body and orofacial cathexis in edentulous complete-denture-wearing clients.

This description cross-sectional study examines cathexis, or satisfaction, with the body and the orofacial region in relationship to eight major demographic and health status variables in a nonprobability sample of 34 male and 47 female edentulous subjects aged 36 to 77 years. Kiyak's 27-item Body Cathexis Scale (BCS), including an innovative five-item Orofacial Cathexis Scale (OFCS), was shown to be reliable for use in elderly clients at least to age 77 (Cronbach's alpha = .95). More research is needed to validate the OFCS. Overall scores were in the neutral range, with teeth being the most negatively cathected body part. Longer periods of edentulism were associated with more dissatisfaction with the teeth. Body and orofacial cathexis were highly positively correlated. Chronic illness, education level, race, and religion were not significantly related to cathexis. Edentulism, especially recent edentulism in the elderly, female gender, and divorced marital status could be important indicators for body image disturbance.

Adult↗
PubMed1993

[Preliminary study on monoclonal antibodies against Cysticercus cellulosae].

In order to produce valuable monoclonal antibodies for immunodiagnosis of cysticercosis, hybridoma technique was adopted using the fusion of splenic lymphocytes from BALB/c mice immunized with Cysticercus cellulosae antigens and the myeloma cell line NS-1. Through screening and cloning, three monoclonal antibody cell lines have been established. Immunoglobulin subclasses of 3 lines were determined to be IgG1. These monoclonal antibodies were found to be highly specific and without cross reaction with Echinococcus granulosus hydatid cyst and Cysticercus fasciolasis. Antigen fractions specifically reacting to monoclonal antibodies were demonstrated with Western blot method. The results showed that specific reaction bands of SCW located in 25 kDa and 17 kDa regions.

Animals↗