Biomedical subjects

M Han

Publications and source records attributed to M Han.

At least 181 records · Page 10Linked to original sources

PubMed1993

Localization of the retinal protonated Schiff base counterion in rhodopsin.

Semiempirical molecular orbital calculations are combined with 13C NMR chemical shifts to localize the counterion in the retinal binding site of vertebrate rhodopsin. Charge densities along the polyene chain are calculated for an 11-cis-retinylidene protonated Schiff base (11-cis-RPSB) chromophore with 1) a chloride counterion at various distances from the Schiff base nitrogen, 2) one or two chloride counterions at different positions along the retinal chain from C10 to C15 and at the Schiff base nitrogen, and 3) a carboxylate counterion out of the retinal plane near C12. Increasing the distance of the negative counterion from the Schiff base results in an enhancement of alternating negative and positive partial charge on the even- and odd-numbered carbons, respectively, when compared to the 11-cis-RPSB chloride model compound. In contrast, the observed 13C NMR data of rhodopsin exhibit downfield chemical shifts from C8 to C13 relative to the 11-cis-RPSB.Cl corresponding to a net increase of partial positive or decrease of partial negative charge at these positions (Smith, S. O., I. Palings, M. E. Miley, J. Courtin, H. de Groot, J. Lugtenburg, R. A. Mathies, and R. G. Griffin. 1990. Biochemistry. 29:8158-8164). The anomalous changes in charge density reflected in the rhodopsin NMR chemical shifts can be qualitatively modeled by placing a single negative charge above C12. The calculated fit improves when a carboxylate counterion is used to model the retinal binding site. Inclusion of water in the model does not alter the fit to the NMR data, although it is consistent with observations based on other methods. These data constrain the location and the orientation of the Glu113 side chain, which is known to be the counterion in rhodopsin, and argue for a strong interaction centered at C12 of the retinylidene chain.

Amino Acid Sequence↗

PubMed1993

In vitro expansion of murine hematopoietic progenitor cells in liquid cultures for bone marrow transplantation: effects of stem cell factor.

In this study, we demonstrated that recombinant stem cell factor (SCF), when used in combination with interleukin-1 (IL-1), IL-3 and IL-1 plus IL-3, promoted the expansion of immature murine hematopoietic progenitor cells in liquid cultures. In cultures with IL-1 plus IL-3 plus SCF, high proliferative potential-colony forming cells (HPP-CFC) increased 7-8-fold compared with the increase in fresh bone marrow cells, while SCF alone had no effect on the expansion of HPP-CFC. SCF also increased the numbers of colony forming unit-spleen (CFU-S) cells in combination with IL-1 plus IL-3. Transplantation of bone marrow cells cultured with IL-1 plus IL-3 plus SCF resulted in reconstitution of hematopoiesis in lethally irradiated mice earlier than transplantation of fresh bone marrow cells. These results raised the possibility that in vitro expansion of hematopoietic progenitor cells, carried out with SCF in combination with IL-1 and IL-3 in liquid cultures, can be utilized in bone marrow transplantation.

Animals↗

PubMed1993

Endoscopic variceal ligation. Experience in 78 patients.

Endoscopic variceal ligation (EVL) is a new alternative to sclerotherapy in the treatment of esophageal variceal hemorrhage, which results in strangulation, necrosis and scar formation of varices without systemic or local adverse effect. From May 1, 1991 through July 1, 1992, EVL was performed in 78 consecutive patients, in 35 of them it was performed during active massive bleeding, and active bleeding was controlled by the initial session in 31 patients. With repeated EVL treatment, 32 patients had their varices obliterated. The varices had reduced in size in other patients. No ligation-related complications were observed. This procedure is a safe, effective and rather simple method to treat esophageal varices, especially in patients with poor liver function and recurrent bleeding after devascularization or shunt surgery.

Adolescent↗

PubMed1993

[Primary Waldenström's macroglobulinemia associated with pure red cell aplasia in which Ts/c lymphocytes inhibiting erythroid precursors were detected].

Waldenström's macroglobulinemia (WMG) is a malignancy of B lymphocytes manifesting heavy accumulation of monoclonal IgM in the plasma. In about 80% cases of WMG, Normocytic normochronic anemia (NNA) is complicated. A case of WMG complicated with pure red cell aplasia (PRCA) and the results of in vitro CFU-E colony assay of bone marrow mononuclear cells (BMMNC) cultured with the patient's serum and/or peripheral lymphocytes were described. A 59-year-old male was admitted with serum total protein Level of 9.7g/dl and 48.2% of gamma globulin. The diagnosis of WMG was made by monoclonal IgM in immunoelectrophoresis. Severe NNA was initially demonstrated on admission and gradually deteriorated further. Both reticulocytes in peripheral blood and erythroid precursors in bone marrow were markedly decreased. Erythropoietin showed high values in plasma. Complication by PRCA was considered to be present in vitro study of a CFU-E colony formation of BMMNC from a normal volunteer showed significant suppression on addition of the patient's peripheral lymphocytes and adverse enhancement by adding the patient's serum. This inhibition of CFU-E colony formation was most prominent by the addition of suppressor/cytotoxic T lymphocytes (Ts/c) and was dose dependent. This result showed the existence of inhibitory Ts/c against proliferation of allogeneic erythroid precursors.

Erythroid Precursor Cells↗

PubMed1992

The value of hysteroscopy in the diagnosis of infertility and habitual abortion.

Ninety cases of infertility and habitual abortion were analyzed by hysteroscopy between April 1983 and July 1990 in PUMC hospital. Abnormal changes of the uterine cavity were seen in 74.4%. The result of hysterosalpingography corresponded with that of hysteroscopy in 62.5%, and the result of B-ultrasound corresponded to that of hysteroscopy in 52.5%. The diagnosis of adhesion and polyps of the uterine cavity was made accurately by hysteroscopy, and both could be operated under hysteroscopy. After operative removal of the adhesion, an IUD should be put into the uterine cavity for 3 months. In 60 cases operations were performed during or after hysteroscopy. Of the 45 patients followed, 19 achieved pregnancy. Five patients achieved pregnancy after operative removal of the adhesion. It is concluded that hysteroscopy is more important than B-ultrasound and hysterosalpingography in the examination and treatment of infertility.

Abortion, Habitual↗

PubMed1992

[Hepatectomy under continuous normothermic interruption of hepatic blood flow in noncirrhotic patients].

Continuous normothermic interruption of hepatic blood flow for 20 minutes or longer was applied in 37 non-cirrhotic patients, including 7 having emergency operation and 30 elective operation. Hepatic blood inflow was interrupted for 40 to 47 minutes in 4 patients, 30 to 39 minutes in 7, 25 to 29 minutes in 14, and 20 to 24 minutes in 12. Postoperatively, 1 patient died of recurrent hemobilia, which was not related to intraoperative vascular interruption. Two patients had mild jaundice for 1 week after right trilobectomy, while the remaining 34 patients recovered uneventfully with no clinical hepatic insufficiency. This method is considered simple, safe, and acceptable for hepatic resection in non-cirrhotic patients.

Adolescent↗

PubMed1992

Synergistic effects of murine stem cell factor in combination with a variety of cytokines on the expansion of murine hematopoietic progenitor cells in short-term suspension cultures.

In the present study, it is represented that the ability of murine stem cell factor (SCF) to expand hematopoietic progenitor cells in short-term suspension culture when used alone or with IL-1 beta, IL-3, IL-6, M-CSF and IL1 beta Plus IL-3. SCF alone had a limited effect on the expansion of early primitive hematopoietic progenitor cells (CFU-HPP: high proliferative potential colony forming unit, and CFU-S: colony forming unit in spleen) even at a high concentration, but expanded mature hematopoietic progenitor cells (CFU-GM: colony forming unit-granulocyte/macrophage, and BFU-E: burst forming unit-erythroid) markedly at low concentrations. When SCF was used in combination with other cytokines, the expansion of primitive hematopoietic progenitor cells was significantly increased; namely, CFU-HPP were expanded approximately 2 to 5-fold compared with SCF alone. A marked expansion of hematopoietic progenitor cells was observed in a combination of SCF plus IL-1 beta plus IL-3. In this setting, CFU-S was increased 2.2-fold compared with the number of CFU-S in fresh bone marrow and CFU-HPP were increased 8.5-fold compared with the number of primary CFU-HPP. These results suggest that these factors may be utilized in experiments of murine bone marrow transplantation (BMT) and also in human BMT. Namely, the adequate number of hematopoiesic progenitor cells and stem cells required for the successful engraftment can be obtained from small volume of peripheral or bone marrow blood by this procedure, thus obtiating the donor's burden.

Animals↗

PubMed1992

Ras proteins in developmental pattern formation in Caenorhabditis elegans and Drosophila.

Recent studies of genetically isolated mutants in Caenorhabditis elegans and Drosophila have revealed ras functions in developmental pattern formation. The ras proteins act as genetic switches to determine cell fates between two alternative choices during C elegans vulval development (vulval versus hypodermal cells) and during Drosophila eye development (R7 versus cone cell). In both cases, ras proteins act downstream of a receptor tyrosine kinase in a signal transduction pathway that mediates cell-cell interactions. These genetic systems may allow the further elucidation of ras-mediated developmental regulatory pathways.

Animals↗

PubMed1991

Analysis of dominant-negative mutations of the Caenorhabditis elegans let-60 ras gene.

The let-60 gene of Caenorhabditis elegans controls the choice between vulval and hypodermal differentiation in response to an inductive signal from the gonad. let-60 encodes a ras protein that acts downstream of the let-23 receptor tyrosine kinase in a signal transduction pathway. Dominant-negative mutations of let-60 [let-60(dn)] cause a reduction of the gene activity in let-60(dn)/+ heterozygotes and a vulva-less mutant phenotype. We have found that nine let-60(dn) mutations cause replacements of conserved residues. Four are in two novel positions; others are in positions known previously to cause dominant-negative mutations in mammalian cells. The locations of these lesions suggest that they disrupt the ability of the ras protein to bind guanine nucleotides. Four let-60(dn) mutant genes were introduced into wild-type animals in the form of extrachromosomal arrays and were found to generate three dominant phenotypes--lethality, vulva-less, or multivulva--depending on gene dose and alleles. The dominant lethality caused by high-dose transgenic let-60(dn) genes suggests a toxic effect of these mutant genes in early development. The dominant-negative effects of these mutations in heterozygotes are likely to be caused by competition between let-60(dn) and let-60(+) protein for a positive regulator. All let-60(dn) mutations interfere with let-60(+) activity, but some alleles have partial constitutive activity, suggesting that the ability to interact with the activator is separable from the ability to exert a physiological effect (stimulation of vulval differentiation). These dn mutations might be useful for interfering with ras-mediated signal transduction pathways in other multicellular organisms.

Animals↗

PubMed1991

Short intussusception valves prevent reflux after jejunal interposition bilioduodenal anastomosis.

Short whole circumference and semi-circumference intussusception valves were created in interposition cholecysto-jejunal-duodenal conduits in pigs to determine which method best prevented gastrointestinal reflux into the biliary tract. Following intravenous injection of 99 mTc-HIDA the time interval for its excretion from the liver and appearance in the duodenum was not different in either whole or semi-circumference valve animals or in controls without valves. After intragastric administration of 99 mTc-DTPA the relative radioactivity of gallbladder contents (reflux) in the cohort without valves was significantly higher than in both cohorts with valves. Animals with semi-circumferential valves in turn had significantly higher levels of nuclide than those with whole circumference valves. Reflux was observed grossly in 100% of animals without valves, in 20% of those with semi-circumference valves, and in no animals with whole circumference valves. This study indicates that both whole and semi-circumference intussusception valves placed in jejunal biliary conduits allow unimpeded flow of bile into the gastrointestinal tract. Whole circumference valves are more effective for prevention of reflux than semi-circumferential valves.

Animals↗

PubMed1991

The influence of electrocortical biofeedback on performance in pre-elite archers.

The purpose of the present research was to determine whether EEG biofeedback training could improve archery performance as well as self-reported measures of concentration and self-confidence. Experienced pre-elite male (N = 16) and female (N = 8) archers were randomly assigned to one of three treatment conditions: (a) correct feedback (i.e., greater left hemisphere low frequency activity), (b) incorrect feedback (i.e., greater right hemisphere low frequency activity), and (c) no feedback control. The pretest and posttest consisted of 27 shots, with EEG data collected for the left and right temporal hemispheres (T3, T4). Feedback subjects were then given EEG biofeedback, while control subjects rested for 30 min. Analyses indicated that only the performance measure was significant. The correct feedback group significantly improved performance, while the incorrect feedback group showed a significant performance decrement from pre- to posttest (Ps less than 0.05). The control group showed no significant pre-post differences in performance. EEG analyses showed differences that were consistent with the training given to the incorrect, but not the correct, feedback group. Overall, the results provide some support for the use of known relationships between EEG and performance as an effective means of providing biofeedback to affect the performance of pre-elite archers.

Attention↗

PubMed1990

let-60, a gene that specifies cell fates during C. elegans vulval induction, encodes a ras protein.

Genetic analysis previously suggested that the let-60 gene controls the switch between vulval and hypodermal cell fates during C. elegans vulval induction. We have cloned the let-60 gene, and shown that it encodes a gene product identical in 84% of its first 164 amino acids to ras gene products from other vertebrate and invertebrate species. This conservation suggests that the let-60 product contains all the biochemical functions of ras proteins. Extrachromosomal arrays of let-60 ras DNA cause cell-type misspecification (extra vulval fates) phenotypically opposite to that caused by let-60 ras loss-of-function mutations (no vulval fates), and suppress the vulvaless phenotype of mutations in two other genes necessary for vulval induction. Thus, the level and pattern of let-60 ras expression may be under strict regulation; increase in let-60 ras activity bypasses or reduces the need for upstream genes in the vulval induction pathway.

Amino Acid Sequence↗

PubMed1990

Hemispheric asymmetry, cardiac response, and performance in elite archers.

Previous sport research on elite athletes has shown systematic changes in psychophysiological measures, such as heart rate (HR) deceleration and hemispheric asymmetries in EEG activity, in the few seconds prior to executing a motor response. These changes are believed to be due to a more focused attention on the external environment. Using archery (an attentive state), this investigation was designed to examine: (a) whether hemispheric asymmetry and HR deceleration would occur during the aiming period, and (b) if they did, whether this would affect performance. HR and left and right temporal EEG were recorded from 28 right-handed elite archers for 16 shots. The results indicated that (a) there was no HR deceleration; (b) during the aiming period, EEG alpha activity formed the dominant frequency and this was significantly greater in the left than in the right hemisphere; (c) there were no significant right hemisphere EEG changes in spectral power from 3 s before the shot to arrow release, but there were significant left hemisphere increases at 10, 12, and 24 Hz; and (d) at 1 s prior to the shot, there were no significant right hemisphere spectral power differences between best and worst shots, but there were significant left hemisphere differences at 6, 12, and 28 Hz. The relationships among hemispheric asymmetry, HR deceleration, attentional processes, and shooting performance are discussed.

Adolescent↗

PubMed1990

The let-60 locus controls the switch between vulval and nonvulval cell fates in Caenorhabditis elegans.

During induction of the Caenorhabditis elegans hermaphrodite vulva by the anchor cell of the gonad, six multipotent vulval precursor cells (VPCs) have two distinct fates: three VPCs generate the vulva and the other three VPCs generate nonspecialized hypodermis. Genes that control the fates of the VPCs in response to the anchor cell signal are defined by mutations that cause all six VPCs to generate vulval tissue (Multivulva or Muv) or that cause all six VPCs to generate hypodermis (Vulvaless or Vul). Seven dominant Vul mutations were isolated as dominant suppressors of a lin-15 Muv mutation. These mutations are dominant alleles of the gene let-60, previously identified only by recessive lethal mutations. Our genetic studies of these dominant Vul recessive lethal mutations, recessive lethal mutations, intragenic revertants of the dominant Vul mutations, and the closely mapping semi-dominant multivulva lin-34 mutations suggest that: (1) loss-of-function mutations of let-60 are recessive lethal at a larval stage, but they also cause a Vul phenotype if the lethality is rescued maternally by a lin-34 gain-of-function mutation. (2) The dominant Vul alleles of let-60 are dominant negative mutations whose gene products compete with wild-type activity. (3) lin-34 semidominant Muv alleles are either gain-of-function mutations of let-60 or gain-of-function mutations of an intimately related gene that elevates let-60 activity. We propose that let-60 activity controls VPC fates. In a wild-type animal, reception by a VPC of inductive signal activates let-60, and it generates into a vulval cell type; in absence of inductive signal, let-60 activity is low and the VPC generates hypodermal cells. Our genetic interaction studies suggest that let-60 acts downstream of let-23 and lin-15 and upstream of lin-1 and lin-12 in the genetic pathway specifying the switch between vulval and nonvulval cell types.

Alleles↗

PubMed1990

A proposed clinical classification of pelvic endometriosis.

Two hundred and forty-four cases of pelvic endometriosis were diagnosed by laparoscopy between Jan. 1979 and Dec. 1986. Consulting the principles designated by the American Fertility Society (AFS) and Revised American Fertility Society (RAFS) classification, diseases were staged as mild, moderate and severe. The results of clinical classification were compared with those of laparoscopic classification. The conformance rate between clinical and RAFS classification was 74.2%. The pregnancy rates after operation were 69.2%, 42.9% and 38.5% among 94 patients clinically classified as mild, moderate and severe, respectively, as compared with 65.2%, 41.4% and 35.7% in terms of RAFS classification. The authors point out that laparoscopy is an excellent procedure for diagnosing and staging endometriosis. In hospitals where laparoscopic equipment is not available, clinical classification can be used as a substitute for staging those highly suspected of having endometriosis.

Endometriosis↗

PubMed1988

Nucleosome loss activates yeast downstream promoters in vivo.

Nucleosome depletion can be made to occur in yeast by addition of glucose to strains containing the histone H4 gene under GAL promoter control. This leads to the activation of downstream promoter elements (TATA box and initiation, I, region) of three different regulated yeast promoters fused to the E. coli lacZ gene. Nucleosome loss activates the PHO5 downstream element in the presence or absence of the upstream activator sequences (UAS) through which PHO5 induction is normally mediated. The cytochrome C (CYC1) and galactokinase (GAL1) promoters are normally repressed by glucose through their UAS elements. However, when these UAS are deleted, the remaining downstream promoters are also activated by glucose-mediated nucleosome loss. These data suggest that nucleosome loss increases transcription initiation and subsequent elongation in vivo. They also indicate that the proteins which recognize the downstream promoter are activated and functional, at least in part, even in the absence of the UAS complex.

Cytochrome c Group↗

PubMed1988

Extremely conserved histone H4 N terminus is dispensable for growth but essential for repressing the silent mating loci in yeast.

Yeast histone H4 function was probed in vivo by deleting segments of this extremely conserved 102 amino acid protein. Deletions in the hydrophobic core of H4 are lethal and block chromosomal segregation. In contrast, deletions at the hydrophilic N terminus (residues 4-28) and C terminus (residues 100-102) are viable. However, N-terminal deletion alters normal chromatin structure and lengthens the cell cycle, especially G2. Surprisingly, removal of the H4 N terminus also derepresses the silent mating type loci, HML alpha and HMRa, disrupting mating. This activation is specific since other regulated genes (GAL10, PHO5, CUP1) are repressed and induced normally in these cells. Deletions of the hydrophilic N termini of H2A or H2B do not show this effect on mating. These experiments allow us to define a unique H4 function that is not shared by other histones (H2A and H2B).

Chromatin↗

PubMed1988

D-lysergic acid activation and cell-free synthesis of D-lysergyl peptides in enzyme fractions from the ergot fungus Claviceps purpurea.

The D-lysergic acid activating enzyme from the ergot fungus Claviceps purpurea was purified to near homogeneity. It has a native Mr of about 245,000 and in its denatured form is a single polypeptide chain of Mr 62,000. The enzyme catalyzes the ATP-pyrophosphate exchange reaction dependent on D-lysergic acid and, though much less, that dependent on dihydrolysergic acid. Western blot analysis of SDS electropherograms of crude protein extracts from C. purpurea using monospecific antibodies directed against the D-lysergic acid activating enzyme revealed the immunostaining of one particular band which was identical with that of the D-lysergic acid activating enzyme. No significant immunoreactive band with higher molecular weight was seen, which precludes the possibility that the enzyme had arisen from the proteolysis of a high molecular weight ergot peptide synthetase. An ammonium sulfate fractionated enzyme fraction was prepared from C. purpurea strain C1 that catalyzed the incorporation of D-lysergic acid into two peptides which besides D-lysergic acid contained alanine, phenylalanine, and proline. Dihydrolysergic acid was efficiently incorporated into the corresponding dihydrolysergic acid containing analogues of the two compounds. Radiochemical analysis and degradation studies suggest that the two D-lysergic acid containing peptides most probably are N-[N-(D-lysergyl)-L-alanlyl]-L-phenylalanyl-L-proline lactam and N-[N-(D-lysergyl)-L-analyl]-L-phenylalanyl-D-proline lactam, respectively. N-[N-(D-Lysergyl)-L-alanyl]-L-phenylalanyl-L-proline lactam is considered to be the immediate precursor of ergotamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell-Free System↗