Search PubMed⌕ Search

Biomedical subjects

Y Lin

Publications and source records attributed to Y Lin.

At least 613 records · Page 34Linked to original sources
PubMed1992

[Experience of focal debridement in the treatment of tuberculosis of lumbar spine].

Experiences of 882 cases with tuberculosis of lumbar spine treated by focal debridement during 1956-1986 all patients survived the operation and 661 patients were cured in our department were reported. The relationship between chemotherapy and focal debridement was discussed. The selection of the appropriate time for this operation and important points to which attention should be paid during operation were described in detail.

Adolescent↗
PubMed1992

[Acute and intermediate clinical and angiography results after coronary stent implantation].

The value of stenting in emergency situations in interventional angioplasty procedures is widely accepted. Stenting remains controversial as a therapeutic method for use beyond the acute phase, as the results reported in the acute phase are characterized by a wide range. This study reports the implantation results of Palmaz-Schatz stents in 64 cases mostly for failed PTCA. Stents were mounted on Monorail-PVC-balloon catheters. The acute success rate was 96.8%. In two cases with stent misplacement CABG was performed within 48 h. No lethal events occurred in the acute phase. Stent thrombosis has only been seen in four cases (6.5%) so far under subtle monitoring of the anticoagulant regime. Restenosis rate (definition: NHLBI-4) according to serial angiography 6 and 12 weeks after implantation was 4.25% at 6 weeks, with a cumulative rate of 19.4% up to 12 weeks. All recurrences eligible for PTCA have been successfully redilated. A high extracardiac complication rate--predominantly groin hematoma--is the main disadvantage of the procedure. Surgical repair was necessary in 11.4% up to 6 weeks after implantation. Surprisingly high was also the incidence of hematuria, also in 11.4%, in the phase of high anticoagulation. In conclusion, stenting is an effective therapeutic method to avoid emergency CABG and elective CABG in most cases of failed PTCA.

Adult↗
PubMed1992

Understanding HIV protease: can it be translated into effective therapy against AIDS?

The protease of human immunodeficiency virus (HIV) has been extensively studied. The structure and function relationships of this protease and its role in HIV life cycle is well known. We have use recombinant HIV protease and mutagenesis technology to study HIV protease and compare it to the eukaryotic aspartic proteases. When putative active-site hydrogen bonds are placed in the HIV protease, the pKa values of two active-site groups are only slightly downshifted. Corresponding removal of these H-bonds from the active sites of pepsin and rhizopuspepsin do not appreciably alter the active-site pKa values. The Kcat values are strongly decreased by these mutations. These observations suggest that the active-site H-bonds in HIV protease and other aspartic proteases control the rigidity of the catalytic apparatus but not the ionization of the active-site groups. A mechanism of catalysis by the HIV protease has been suggested based on kinetic and mutagenesis studies. The strategies involved in the development of HIV protease inhibitors are discussed. In spite of the pitfalls in each approach, it appears probable that a battery of inhibitors can be developed for the treatment of AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Inducible transformation of cells from transgenic mice expressing SV40 under lac operon control.

If it were possible to clone in vitro cells of any type, at any stage of differentiation, from an extensively characterized animal such as the mouse, many areas of cell biology would benefit. Indeed, it would be even more helpful if these cells could subsequently be restored to their normal in vivo phenotype whenever required. Here, we describe a step on the pathway to such an idealized "clonable" mouse. In principle, it seeks to link a "universal" transforming agent to a regulatory system that is relatively simple, yet quite foreign to the mouse. A plasmid containing the bacterial lac operator/promoter region linked to the SV40 large T antigen and a vector containing the lac repressor that can be expressed in mammalian cells were coinjected into fertilized mouse oocytes utilizing the standard techniques for generating transgenic mice. Two progeny were obtained that express large T antigen in the presence, but not the absence, of the nonmetabolizable lac inducer, isopropyl-beta-thio-D-galactoside. This report characterizes fibroblast cell lines established from these transgenics that are readily transformed in vitro with isopropyl-beta-thio-D-galactoside. A significant proportion of the cells are restored to their "normal" (nontransformed phenotype) when isopropyl-beta-thio-D-galactoside is removed.

Animals↗
PubMed1991

Limunectin. A phosphocholine-binding protein from Limulus amebocytes with adhesion-promoting properties.

A protein that binds to and precipitates with pneumococcal C-polysaccharide and a phosphocholine (PC) derivative of bovine serum albumin has been affinity purified from Limulus amebocytes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis reveals that the isolated protein consists of a single polypeptide chain of approximately 50 kDa. It is an intracellular protein localized in the secretory granules of amebocytes according to immunogold staining. Although it shares the PC-binding property with C-reactive protein isolated from Limulus and other animal species, it differs from C-reactive protein in that the latter binds to PC only in the presence of Ca2+, whereas the newly isolated protein binds to PC in a Ca(2+)-independent manner. In this respect, the newly isolated PC-binding protein resembles the antibodies to PC of mouse myelomas. The gene coding for this protein has been isolated. The gene sequence predicts a protein of 54 kDa with an unusual structural feature: it consists almost entirely of 10 contiguous segments, 45 amino acids in length, with extensive homology. Some limited sequence homologies were found between the 54-kDa protein and segments of vitronectin, gelatinase, and collagenase. It binds to bacterial cells, fixed amebocytes, and a number of extracellular matrix molecules. Due to its structural and some functional similarities to other adhesion molecules, the Limulus 54-kDa protein was named "Limunectin."

Amino Acid Sequence↗
PubMed1991

Muscarinic receptor agonist-mediated modulation of neuronal activity in rat cerebral cortex.

Multiple cortical neuronal responses were elicited by the iontophoretic application of muscarinic receptor agonists and antagonists in the rat cerebral sensorimotor cortex in vivo. (1) The muscarinic receptor agonist, oxotremorine-M induced a biphasic effect on spontaneous firing. This was evident as an early brief increase in the firing rate over the spontaneous discharge followed by secondary inhibition of spontaneous activity. The excitation could be blocked by the muscarinic receptor non-selective antagonist atropine and by both the M1 receptor antagonist pirenzepine and the M2 receptor antagonists gallamine or methoctramine. Oxotremorine-M inhibition of spontaneous activity was not affected by the M1 receptor antagonist pirenzepine, while evaluation of its sensitivity to gallamine and methoctramine was not possible since these two M2 receptor antagonists also depressed spontaneous activity, unlike pirenzepine. Of the other two muscarinic receptor agonists, oxotremorine had inconsistent and weak excitatory effects whilst McN-A-343 had only weak excitatory or inhibitory effects on spontaneous activity. (2) Oxotremorine-M, oxotremorine and McN-A-343 had a depressant action on neuronal discharges evoked by glutamate or acetylcholine. A depressant effect of oxotremorine-M was also demonstrated on the early excitation evoked by subsequent applications of oxotremorine-M itself. Of the three muscarinic receptor agonists tested, oxotremorine-M was the most potent in evoking a long-term depression of evoked discharges, lasting from several minutes (greater than 5 min) to as long as 40 min. Oxotremorine-M-induced depression of evoked responses was most sensitive to the M2 receptor antagonists, whereas oxotremorine-induced depression was more sensitive to the M1 receptor antagonist pirenzepine.(ABSTRACT TRUNCATED AT 250 WORDS)

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗
PubMed1991

Muscarinic agonist-mediated induction of long-term potentiation in rat cerebral cortex.

A long-lasting potentiation (usually following an initial short depression) of neuronal evoked responses was induced in neurons of rat sensorimotor cortex after a single application of the muscarinic agonists, oxotremorine, McN-A-343, or oxotremorine-M. The potentiation was characterized as being of slow onset (several minutes), progressive development, long-lasting (for as long as two hours), and was evident for both glutamate- and acetylcholine-evoked neuronal discharges. Potentiation was manifested as an increase in the frequency and duration of the evoked neuronal discharges, in a dose-dependent fashion. Blockade could be achieved if a muscarinic antagonist (atropine, pirenzepine or gallamine) was applied prior to, but not after, development of the long-lasting potentiation. These results suggest that certain muscarinic agonists may be useful in reducing the memory deficits of patients with Alzheimer's disease.

Acetylcholine↗
PubMed1991

Oxypurinol reduces focal ischemic brain injury in the rat.

When measured within 2 days of a unilateral occlusion of the middle cerebral artery (MCA) combined with tandem occlusion of the ipsilateral common carotid artery in rats, contralateral neurological deficits were detectable, with brain swelling and a consistent degree of neocortical infarction in the ipsilateral hemisphere. Oxypurinol (40 mg/kg i.p. administered 0.5 h prior to, and 24 h after, the onset of focal ischemia) significantly reduced the development of the ischemic infarct (P less than 0.001); attenuated tissue swelling (P less than 0.01) and ameliorated the neurological deficits (P less than 0.05). These findings suggest that this compound may be useful for the prevention or treatment of ischemic brain injuries, such as those occurring during stroke.

Animals↗
PubMed1991

In vitro selection of a cell line for resistance to lysis by tumor necrosis factor-alpha selects for reduced tumorigenicity.

Experimentally, TNF-alpha can mediate the hemorrhagic necrosis of certain tumors. Furthermore, evidence indicates that natural cytotoxic (NC) activity, a cell-mediated cytolytic activity that utilizes TNF-alpha in the lysis of target cells, is involved in preventing the outgrowth of certain NC/TNF-alpha-sensitive tumor cells. These observations raise the issue of whether soluble TNF-alpha normally serves as a tumor surveillance mechanism preventing the outgrowth of some tumors. To address this issue, we have used TNF-alpha to select TNF-alpha-resistant variants from the NC/TNF-alpha-sensitive mouse fibroblast cell line 10ME. Previously, we have demonstrated that 10ME is tumorigenic in immune-deficient mice but fails to form tumors in normal mice. Moreover, selection of NC-resistant variants from 10ME selects for both TNF-alpha resistance and tumorigenicity in normal mice. As cells that have been selected for NC resistance form tumors in normal mice, whereas the NC-sensitive parental cell line does not, it seems that escape from NC activity is sufficient to significantly increase the tumorigenic potential of the cell line. We show that the selection with TNF-alpha, although associated with NC resistance, does not increase the tumorigenic potential of 10ME cells but reduces it. Thus, NC activity appears to function as a mechanism to prevent tumor formation, and escape from NC activity allows for tumor formation; TNF-alpha does not have similar activity. Moreover, this suggests that NC activity is not equivalent to soluble TNF-alpha activity, but utilizes TNF-alpha more efficiently than soluble TNF-alpha, or NC activity involves both TNF-alpha and other effector mechanisms.

Animals↗
PubMed1991

Characterization of the depression of rat cerebral cortical neurons by selective adenosine agonists.

The identity of the receptors involved in mediating the depressant actions of adenosine and its analogs on the spontaneous firing of rat cerebral cortical neurons was elucidated by evaluating the effects of selective A1 and A2 receptor agonists and antagonists. The A1 agonist N6-cyclopentyladenosine (CPA) and the A2 agonist CGS 21680 both depressed cortical neuronal firing. At low doses (0.001-0.01 mg/kg) the A1 antagonist DPCPX blocked the effects of CPA, but not those of CGS 21680. At higher doses, it antagonized both agonists. The A2 antagonist CGS 15943 (0.01-0.1 mg/kg) selectively blocked the actions of CGS 21680. At 1 mg/kg it also antagonized the responses of some neurons to CPA. These results suggest that the depressant actions of adenosinergic agonists on the firing of rat cerebral cortical neurons involve both A1 and A2 receptors.

Adenosine↗
PubMed1991

Expression and characterization of the preS1 peptide of hepatitis B surface antigen in Escherichia coli.

The infectious particles of hepatitis B virus (HBV) contain 3 related surface antigens, i.e., small, medium, and large, all of which are encoded by one large open reading frame with multiple initiation codons. The large surface antigen (L-Ag) contains preS1, preS2, and S regions while both the middle and small surface antigens lack preS1. Several lines of evidence suggested that the preS1 region is involved in the binding of HBV to human hepatocytes as shown by its binding to HepG2 cells and isolated human hepatocyte membranes. To obtain large quantity of preS1 peptide, an expression vector was constructed containing a lac promoter, the 5' half of the beta-galactosidase gene, the Factor Xa tetrapeptide recognition sequence, and the coding region of preS1 plus preS2. This recombinant plasmid constitutively produced high concentration of a fusion protein in inclusion bodies in Escherichia coli. When the fusion protein was treated with Factor Xa, a peptide consisting of the N-terminal 91 amino acids of the preS1 region was released. This preS1 fragment purified by anion exchange chromatography was able to bind specifically to the isolated plasma membranes from human liver. Hence, this recombinant preS1 peptide can be used to identify and isolate hepatocyte receptors for HBV.

Base Sequence↗
PubMed1991

Muscarinic agonist oxotremorine-M-induced long-term depression in rat cerebral cortex.

A long-lasting depression (LTD) of neuronal-evoked responses was induced in a dose-dependent fashion in neurons of rat sensorimotor cortex by a brief application of the muscarinic agonist oxotremorine-M. The depression was characterized as being of rapid onset (within 30 seconds), long duration (up to 40 minutes), and was evident for both glutamate- and acetylcholine-evoked discharges. Antagonism could be achieved by application of the nonspecific muscarinic antagonist atropine, and with the M2 antagonists gallamine or methoctramine. The M1 antagonist pirenzepine displayed only a weak effect. LTD could also be induced by the muscarinic agonists, oxotremorine and McN-A-343, but their potencies were lower than that of oxotremorine-M. Oxotremorine-M may be a useful tool for studies of long-term changes in synaptic efficacy.

Acetylcholine↗
PubMed1991

Two New Glycosides from the Roots of Cynanchum versicolor.

Two new glycosides named cynanversicoside-A and -B, together with glaucogenin-C as the aglycone, were isolated from the Chinese crude drug "Pai-Wei", CYNANCHUM VERSICOLOR Bunge (Asclepiadaceae). Their structures were determined on the basis of spectral and chemical evidence as glaucogenin-C 3- O-beta- D-cymaropyranosyl-(1-->4)-alpha- L-diginopyranosyl-(1-->4)-beta- D-thevetopyranoside and glaucogenin-C 3- O-beta- D-glucopyranosyl-(1-->4)-beta- D-cymaropyranosyl-(1-->4)-alpha- L-diginopyranosyl-(1-->4)-beta- D-thevetopyranoside.

Journal Article↗
PubMed1991

Development of alveolar septa and cellular maturation within the perinatal lung.

To quantitate fetal lung cellularity and regional variation in alveolar maturation, guinea pig lungs were studied at 55, 60, and 65 d of gestation or within 2 h of birth (term = 68 d), and the data were analyzed for intralobar, interlobar, and age-group differences. Nine blocks from each left cranial and caudal lobe were all measured for volume, numerical, and surface densities in tissue (Vv(i,t), Nv(i,t), and Sv(i,t], and total volumes, numbers, and surface areas per lung (V, N, and S) of type I and type II epithelia, presumptive progenitor epithelium (cuboidal cells lacking lamellar bodies [LB]), interstitium, and endothelium. Total fixed lung volume, VL, increased 3-fold from day 55 through birth. At each age, there were no consistent intralobar or interlobar differences in Vv(i,t), Nv(i,t), or Sv(i,t) for any cell type. Within a septal tissue volume of 580 to 670 microliters at all ages, the N and V of type I cells did not vary with age, although their S increased from 1,240 cm2 at day 55 to 3,967 cm2 at birth. The N of morphologic type II cells per lung increased 7-fold from day 55 to day 60 and was constant thereafter, while the N of cuboidal cells decreased proportionally; type II cells contained only 4.8% (vol/vol) of LB at 55 d compared to 18.0% at birth. The N and V of interstitium did not vary by age. While endothelial V was constant over these ages, endothelial S increased from 897 cm2 to 3,398 cm2, and the V of capillary blood and the V of alveolar airspace each increased 4-fold.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Surfactant content and type II cell development in fetal guinea pig lungs during prenatal starvation.

Prenatal caloric restriction in guinea pigs causes intrauterine growth retardation and reduced neonatal viability and surfactant phospholipid (PL). We report here fetal surfactant levels in this model, and correlate total lung PL with ultrastructural maturation of surfactant type II cells and lamellar bodies (LB). Pregnant guinea pigs were fed ad libitum throughout their 68-d gestation (control), or fed 50% rations from d 45 until term (starved). Fetal lungs were examined at d 55, 60, and 65 for PL content and composition, including disaturated phosphatidylcholine (DPC), and compared with neonates for both groups. Lung lobes were analyzed ultrastructurally in d 65 fetuses for the numerical, volume, and surface densities of type II cells and the volume densities of LB. Prenatal starvation caused significant intrauterine growth retardation at all ages; body and dry lung weights were reduced on d 65 by 26 and 23%, respectively. By d 55 and thereafter, starvation decreased total lung PL by 43-45% but did not alter PL composition. On d 65, the total lung volumes and relative numbers, surface densities, and volumes of type II cells in tissue and the relative volumes of LB within type II cells did not differ by caloric regimen. Thus, starved and control fetuses had similar total volumes of LB per lung (13-15 microL), although starved animals had significantly less lung DPC. Although the total volume of LB per lung correlated well with total lung DPC from d 55 through birth in controls, starvation led to a significant departure from this relationship.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗