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Biomedical subjects

H M Chen

Publications and source records attributed to H M Chen.

At least 91 records · Page 5Linked to original sources
PubMed1997

Depressive disorders among older residents in a Chinese rural community.

BACKGROUND: Two recent surveys of depression among Chinese elderly people sampled different populations, used different case ascertainment methods and resulted in a seven-fold difference in prevalence rates. The present study was conducted to compare prevalence rates obtained with two commonly used methods in the same population, and to examine the risk factors for depression. METHODS: The target population included all residents aged 65 years and over in a rural Chinese community. Participants were interviewed for demographic and medical information, examined by a neurologist and administered Chinese versions of the Geriatric Depression Scale-Short Form (GDS-S), the Cognitive Abilities Screening Instrument (CASI) and an Activities of Daily Living (ADL) form. Individuals who screened positive on the GDS-S were also interviewed by a psychiatrist for diagnosis according to the DSM-III-R criteria. RESULTS: Among the 1313 participants, 26% screened positive on the GDS-S and 13% were diagnosed as having a depressive disorder, including 6.1% with major depression. Individuals with depressive disorders were more likely to have poor ADL scores, lower CASI scores, and chronic physical illnesses. They were also more likely to be female, older, illiterate and without a spouse, but adding these variables did not increase the overall association with the GDS-S score. CONCLUSIONS: Depression was quite common in this Chinese rural geriatric population. The prevalence rate was twice as high when judged by depression symptomatology rather than clinical diagnosis. The critical risk factors were functional impairments, poor cognitive abilities and the presence of chronic physical illnesses.

Activities of Daily Living↗
PubMed1997

Propofol anesthesia increases dopamine and serotonin activities at the somatosensory cortex in rats: a microdialysis study.

We sought to estimate the activities of dopamine and serotonin in animals receiving propofol anesthesia. The in vivo microdialysis technique was used in Sprague-Dawley rats (n = 6) to measure the major metabolites of dopamine and serotonin, i.e. 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (4-hydroxy-3-methyphenylacetic acid; HVA) and 5-hydroxy indole acetic acid (5-HIAA) in the somatosensory cortex. We also measured the levels of propofol in the brain and blood by microdialysis sampling in another group of rats (n = 6). During the experiment, the rat was infused intravenously (IV) with propofol at a rate of 10 mg x kg(-1) x h(-1) for 60 min and 60 mg x kg(-1) x h(-1) for 40 min. We found that IV infusion of propofol at a rate of 60 mg x kg(-1) x h(-1) significantly increased DOPAC, HVA, and 5-HIAA. We also determined that these changes correlated well with propofol levels in the brain and blood. We concluded that anesthetic doses of propofol increased the functional activities of dopamine and serotonin in the cortex. These increases correlate well with propofol levels in the cortex and blood.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1997

The Kinmen Neurological Disorders Survey (KINDS): a study of a Chinese population.

We conducted an epidemiological study of several neurological disorders among the Chinese aged 50 years or older on the islet of Kinmen. All participants were interviewed and examined by neurologists. From the targeted population of 5,061 individuals, 3,915 (77.4%) of them completed the evaluations. Among the 4,087 individuals with whom face-to-face contact was made, the refusal rate was 4.2%. The disorders of interest were dementia, Parkinson's disease, essential tremor, stroke, transient ischemic attacks, and migraine. Among the 3,915 participants, 366 cases were found with 1 or more of the surveyed neurological disorders on the prevalence day, August 1, 1993, yielding a prevalence of 93.5/1,000. The purpose of this study, the general methodology, and some overall findings are presented in this communication in order to provide a common background for detailed findings on each disorder to be reported separately.

Age Factors↗
PubMed1997

Prevalence of headaches in a Chinese elderly population in Kinmen: age and gender effect and cross-cultural comparisons.

OBJECTIVE: To investigate the prevalence of headaches in a Chinese elderly population. BACKGROUND: There are few headache surveys in the elderly. Previous studies have shown a low headache prevalence in Chinese. METHODS TARGET POPULATION: eligible registered residents > or = 65 years old (N = 2,003) in two townships of Kinmen Island on August 1, 1993. All participants completed a headache questionnaire and underwent clinical evaluation and examination by a neurologist. Headache diagnoses were made according to the International Headache Society, 1988. RESULTS: 1,533 persons (77%) participated in the study, of whom 584 (38%) had at least one episode of headache in the previous year. One-year prevalence of migraine was 3.0%, and tension-type headache, 35%. The prevalence of migraine, but not tension-type headaches, continued to decline with age in the elderly. Life-time prevalence of "incapacitating headache" was 10%, and that of migraine, 5.2%. Forty-two percent of migraineurs stopped having migraine before this survey. In comparison with "10 years ago" 8% participants felt their current headaches were worse, 25% better, and 67%, no change, with a net improvement of 17%. CONCLUSIONS: We have reported the highest headache prevalence among different Chinese elderly populations, but these were still lower than those reported from Western series. More than half of the elderly life-time migraineurs still had attacks of migraine. Severe headaches, including migraine but not tension-type headaches, declined with age.

Aged↗
PubMed1997

[The synthesis and pharmacological activities of C-galactosides of furanosequiterpenes].

Four new C-galactosides were obtained by treatment of 1-O-trifluoroacetly-2, 3, 4, 6-tetra-O-benzly-alpha-D-galactopranose with 7-methoxy-6-(3-pentenyl)-3, 5-dimethylbenzofuran, 7-acetoxy-6-(3-pentenyl)-3, 5-dimethylbenzofuran and 1, 2-dihydrocacalohastin in the presence of Lewis acid. Their structures and compositions were elucidated by elemental analysis and spectroscopic methods. The results of the pharmacological test indicated that the sesquiterpenes are calcium antagonist but their C-galactosides are calcium agonist.

Calcium↗
PubMed1997

Preclinical evaluation of Fe-(5-C2H5-EHPG)- as a contrast agent in MR imaging of hepatobiliary system.

Iron(III)-N, N'-ethylenebis[2-(2-hydroxy-5-phenyl)glycine] [Fe-(5-C2H5-EHPG)-] is a paramagnetic complex designed for use as a hepatobiliary agent. Test procedures included synthesis, characterization, toxicity evaluation, biodistribution and experiments for animal MR images. The dose of LD50 in acute toxicity test of Fe-(5-C2H5-EHPG)- in mice was 3.49 mmol/kg. 111In-(5-C2H5-EHPG)- biodistribution studies revealed that the activities were (4.78 +/- 0.97, 5.34 +/- 0.91, 4.53 +/- 0.35)%ID and (0.88 +/- 0.18, 0.99 +/- 0.17, 0.84 +/- 0.06)%ID/gm in the liver at time intervals of 10, 30 and 60 minutes after injection; (5.76 +/- 0.15, 5.75 +/- 0.15, 4.00 +/- 0.04)%ID and (0.49 +/- 0.03, 0.49 +/- 0.05, 0.34 +/- 0.01)%ID/gm in the blood; (1.27 +/- 0.91, 1.46 +/- 1.00, 1.52 +/- 0.46) %ID and (0.89 +/- 0.17, 1.02 +/- 0.18, 1.06 +/- 0.08)%ID/gm in the kidneys, respectively. The results of image enhancement correlated well to the biodistribution. Analysis of the MR images showed degrees of maximal parenchymal % increase of signal to noise ratio (S/N) was 42.09 +/- 3.59% for normal liver at 30 minutes postinjection, which exceeded the value of pathologic liver with bile duct obstruction 16 hours 17.26 +/- 6.6 %, 1 week 19.80 +/- 6.46% and 4 weeks 32.20 +/- 9.01%, respectively, and acute hepatitis 16.50% +/- 4.02%. Persistent enhancement plateau was documented up to 60 minutes after injection and normalized to precontrast value within 22 hours. The common duct was opacified at 10-15 minutes after injection of contrast agent. These results indicated that the Fe-(5-C2H5-EHPG)- could be rapidly extracted from the blood stream by the hepatocytes and excreted into the bile duct. The initial evaluation of Fe-(5-C2H5-EHPG)- demonstrated that Fe-(5-C2H5-EHPG)- was well suited for enhancement of normal liver parenchyma and was compromised with deterioration of liver function. However, the increase of the liver intensities in the animal model of the total biliary obstruction group normalized to precontrast value within 22 hours, which indicated that renal clearance as an effective alternative pathway for biliary excretion. In conclusion, these results indicate that Fe-(5-C2H5-EHPG)- has the potential of becoming a safe and reliable magnetopharmaceutical for the hepatobiliary system.

Animals↗
PubMed1997

Gabexate mesilate improves pancreatic microcirculation and reduces lung edema in a rat model of acute pancreatitis.

We evaluated the effects of a protease inhibitor on the progression of acute pancreatitis in rats. The model was selected and modified to mimic an intermediate stage of the disease. The degree of microcirculatory derangement in the pancrease and of lung edema was determined to assess the effects of gabexate mesilate (ethyl-4-(6-guanidinohexanoyloxy) benzoate methane sulfonate), a synthetic antiprotease, in acute pancreatitis. Male Sprague-Dawley rats (225-275 g) were used. Experimental pancreatitis was established by four intramuscular injections of cerulein (50 micrograms/kg) at 1 hour intervals. Lipopolysaccharide (10 mg/kg) was injected intraperitoneally as an acute septic challenge. Gabexate mesilate was infused intravenously 6 hours after the initiation of induction of acute pancreatitis at doses of 0.01, 0.1, 1, or 10 mg/kg/h. Microcirculatory changes in the pancreas were studied using in vivo microscopy. All animals survived until the end of the experiments. Gabexate mesilate significantly improved pathologic criteria and decreased serum lipase levels at doses of 1 and 10 mg/kg/h. It significantly lessened the severity of lung edema and improved the microcirculatory environment in the pancreas by increasing flow velocity and reducing leukocyte sticking. These results indicate the beneficial effects of gabexate mesilate on pancreatic microcirculation and lung edema in the progression of acute pancreatitis with septic challenge in rats.

Acute Disease↗
PubMed1996

The Ets protein Spi-B is expressed exclusively in B cells and T cells during development.

Spi-B and PU.1 are hematopoietic-specific transcription factors that constitute a subfamily of the Ets family of DNA-binding proteins. Here we show that contrary to previous reports, PU.1 and Spi-B have very different expression patterns. PU.1 is expressed at high levels in B cells, mast cells, megakaryocytes, macrophages, neutrophils, and immature erythroid cells and at lower levels in mature erythrocytes. PU.1 is completely absent from peripheral T cells and most T cell lines based on sensitive RT-PCR assays. In contrast, Spi-B is expressed exclusively in lymphoid cells and can be detected in early fetal thymus and spleen. In situ hybridizations of adult murine tissues demonstrate Spi-B mRNA in the medulla of the thymus, the white pulp of the spleen, and the germinal centers of lymph nodes. Spi-B expression is very abundant in B cells and both Spi-B mRNA and protein are detected in some T cells. In situ hybridization and Northern blot analysis suggest that Spi-B gene expression increases during B cell maturation and decreases during T cell maturation. Gel-retardation experiments show that Spi-B can bind to all putative PU.1 binding sites, but do not reveal any preferred Spi-B binding site. Finally, both PU.1 and Spi-B function as transcriptional activators of the immunoglobulin light-chain enhancer E lambda 2.4 when coexpressed with Pip (PU.1-interaction partner) in NIH-3T3 cells. Taken together, these data suggest that differences in patterns of expression between Spi-B and PU.1 distinguish the function of each protein during development of the immune system.

B-Lymphocytes↗
PubMed1996

Least activation path for protein folding: investigation of staphylococcal nuclease folding by stopped-flow circular dichroism.

Is the pathway of protein folding determined by the relative stability of folding intermediates, or by the relative height of the activation barriers leading to these intermediates? This is a fundamental question for resolving the Levinthal paradox, which stated that protein folding by a random search mechanism would require a time too long to be plausible. To answer this question, we have studied the guanidinium chloride (GdmCl)-induced folding/unfolding of staphylococcal nuclease [(SNase, formerly EC 3.1.4.7; now called microbial nuclease or endonuclease, EC 3.1.31.1] by stopped-flow circular dichroism (CD) and differential scanning microcalorimetry (DSC). The data show that while the equilibrium transition is a quasi-two-state process, kinetics in the 2-ms to 500-s time range are triphasic. Data support the sequential mechanism for SNase folding: U3 <--> U2 <--> U1 <--> N0, where U1, U2, and U3 are substates of the unfolded protein and N0 is the native state. Analysis of the relative population of the U1, U2, and U3 species in 2.0 M GdmCl gives delta-G values for the U3 --> U2 reaction of +0.1 kcal/mol and for the U2 --> U1 reaction of -0.49 kcal/mol. The delta-G value for the U1 --> N0 reaction is calculated to be -4.5 kcal/mol from DSC data. The activation energy, enthalpy, and entropy for each kinetic step are also determined. These results allow us to make the following four conclusions. (i) Although the U1, U2, and U3 states are nearly isoenergetic, no random walk occurs among them during the folding. The pathway of folding is unique and sequential. In other words, the relative stability of the folding intermediates does not dictate the folding pathway. Instead, the folding is a descent toward the global free-energy minimum of the native state via the least activation path in the vast energy landscape. Barrier avoidance leads the way, and barrier height limits the rate. Thus, the Levinthal paradox is not applicable to the protein-folding problem. (ii) The main folding reaction (U1 --> N0), in which the peptide chain acquires most of its free energy (via van der Waals' contacts, hydrogen bonding, and electrostatic interactions), is a highly concerted process. These energy-acquiring events take place in a single kinetic phase. (iii) U1 appears to be a compact unfolded species; the rate of conversion of U2 to U1 depends on the viscosity of solution. (iv) All four relaxation times reported here depend on GdmCl concentrations: it is likely that none involve the cis/trans isomerization of prolines. Finally, a mechanism is presented in which formation of sheet-like chain conformations and a hydrophobic condensation event precede the main-chain folding reaction.

Circular Dichroism↗
PubMed1996

A door-to-door survey of Parkinson's disease in a Chinese population in Kinmen.

BACKGROUND: Most published studies have shown lower prevalence rates of Parkinson's disease (PD) in Asian and black African than in Western countries, leading to the hypothesis that Asians and blacks might be protected from PD. OBJECTIVE: To investigate the prevalence of PD in a Chinese population. DESIGN: Community-based survey. SETTING: Registered residents 50 years of age or older (N = 5061) on the islet of Kinmen located off the southeastern coast of China [corrected]. METHOD: Single-phase door-to-door survey by neurologists. All participants were administered a questionnaire and received motor examinations of the Unified Parkinson's Disease Rating Scale. RESULTS: The participation rate was 96% (N = 3915) among 4158 contacted individuals. Twenty-three cases of PD were identified, including three cases with dementia. The crude prevalence rate of PD was 587 (95% confidence interval (CI), 373 to 884) per 100,000 persons 50 years of age or older. Assuming no case of PD among individuals under 50 years of age, the prevalence rate was 119 (95% CI, 80 to 169) per 100,000 for the total population. CONCLUSIONS: The prevalence rates of PD in Kinmen were much higher than those reported from mainland China, but slightly lower than those reported from more developed countries. The present findings suggest that, instead of genetic factors, differences in case-ascertainment, life expectancy, and the length of survival with PD may be more important contributors to the variations in observed PD prevalence rates.

Aged↗
PubMed1996

The effect of gabexate mesilate on pancreatic and hepatic microcirculation in acute experimental pancreatitis in rats.

Microcirculatory derangements are important early features in many organs during the process of acute pancreatitis. However, dynamic evaluation of these factors has been difficult. Antiprotease has long been used for the treatment of acute pancreatitis, although its effects and mechanism have not been fully elucidated. The involvement of proteases and microcirculatory derangement early in the course of acute pancreatitis are the main concern of this study. A severe acute pancreatitis model in male Sprague-Dawley rats (225-275 g) was established by adding caerulein (15 microg/kg/ hr) in intravenous infusion fluid and intraductal injection of 0.1 ml glycodeoxycholic acid (5 mM). Gabexate mesilate [GM; ethyl-4-(6-guanidinohexanoyloxy)benzoate methanesulfonate], a synthetic antiprotease, was infused intravenously in doses of 0.01, 0.1, 1, and 10 mg as a therapeutic intervention in this model. Pathology hematocrit, serum amylase level, and glutamic-oxaloacetic transaminase (GOT) levels were used to confirm the severity of disease and effect of therapy. In vivo microscopic technique was used as a investigating tool in this study of microcirculatory derangement in pancreas and liver, 8 hr after induction of acute pancreatitis. GM can significantly improve pathologic criteria and changes of serum amylase levels in the range of 1-10 mg/kg/hr. The severity of changes of hematocrit and GOT was significantly lessened with GM in the range of 0.1-10 mg/kg/hr. This agent also could improve the microcirculatory environment in pancreas and liver after induction of acute pancreatitis according to the parameters, such as flow velocity and rolling leukocyte phenomenon, in the range of 1-10 mg/kg/hr. According to our observation, severity of hyperpermeability had not changed with the treatment of GM. These results indicated the beneficial effects of GM on pancreatic and hepatic microcirculation early in the course of acute pancreatitis. The beneficial effects were noted in serum parameters and hematocrit. The importance of protease activation and remote organ dysfunction is emphasized in the course of acute pancreatitis from this study.

Acute Disease↗
PubMed1996

Effects of 4-aminopyridine on saxitoxin intoxication.

Effects of 4-aminopyridine (4-AP) on neurotoxicity induced by saxitoxin (STX) are investigated in this study. In vitro, twitch tension evoked by nerve stimulation was depressed by STX (1.35 nM) in rat phrenic nerve-diaphragm preparations, and this inhibition was antagonized by 4-AP (0.1 mM). In addition, 4-AP (0.1 mM) restored the firing of membrane action potentials that were suppressed or even abolished by 0.334 nM STX in frog sartorius muscles. In vivo studies showed that 4-AP (0.3 mg/kg, iv) significantly reversed the respiratory rate, tidal volume, and blood pressure to normal values in anesthetized STX-toxicosis rats. Furthermore, 4-AP (0.75-6 mg/kg, ip) not only prolonged the survival time but also decreased the mortality of mice (71-43%) at a normally lethal dose (30 micrograms/kg, ip) of STX. The results suggest that 4-AP may be useful as an antidote for STX intoxication.

4-Aminopyridine↗
PubMed1996

Function of PU.1 (Spi-1), C/EBP, and AML1 in early myelopoiesis: regulation of multiple myeloid CSF receptor promoters.

Our studies of the promoters of the myeloid CSF receptors (M, GM, and G) in cell lines have led to the findings that the promoters are small, and are all activated by the PU.1 and C/EBP proteins. To date, we have only found evidence for involvement of C/EBP alpha, although further experiments will be needed to exclude the role of C/EBP beta and C/EBP delta in receptor gene expression. These studies suggest a model of hematopoiesis (Fig. 2) in which the lineage commitment decisions of multipotential cells are made by the alternative patterns of expression of certain transcription factors, which then activate growth factor receptors which allow those cells to respond to the appropriate growth factor to proliferate and survive. For example, expression of GATA-1 activates its own expression, as well as that of the erythropoietin receptor, inducing these cells to be capable of responding to erythropoietin. Similarly, expression of PU.1 activates its own promoter, and turns on the three myeloid CSF receptors (M, GM, and G), pushing these cells along the pathway of myeloid differentiation. C/EBP proteins, particularly C/EBP alpha, are also critical for myeloid receptor promoter function, and may also act via autoregulatory mechanisms. Murine C/EBP alpha has a C/EBP binding site in its own promoter. Human C/EBP alpha autoregulates its own expression in adipocytes by activating the USF transcription factor. Myeloid genes expressed later during differentiation, such as CD11b, are also activated by PU.1, which is expressed at highest levels in mature myeloid cells, but not by C/EBP alpha, which is downregulated in a differentiated murine myeloid cell line. Consistent with this model are the findings that overexpression of PU.1 in erythroid cells blocks erythroid differentiation, leading to erythroleukemia, and overexpression of GATA-1 in a myeloid line blocks myeloid differentiation. While these findings have provided some framework for understanding myeloid gene regulation, there are a number of critical questions to be addressed in the near future: What is the pattern of expression of the C/EBP proteins during the course of myeloid differentiation and activation of human CD34+ cells? What is the effect of targeted disruption and other mutations of the C/EBP and AML1 proteins on myeloid development and receptor expression? What are the interactions among these three different types of factors (ets, basic region-zipper, and Runt domain proteins) to activate the promoters? What is the effect of translocations, mutations, and alterations in expression of these factors, particularly in different forms of AML?

Animals↗
PubMed1996

Regulation and molecular structure of a circadian oscillating protein located in the cell membrane of the prokaryote Synechococcus RF-1.

When a light/light-adapted culture of Synechococcus RF-1 is exposed to a diurnal light/dark regimen, the synthesis of more than ten of its polypeptides is known to become entrained to a circadian oscillating pattern which persists for some time under free-running conditions. One of the circadian oscillating polypeptides, COP23, was found to be located in the cell membrane. The rate of COP23 synthesis is controlled at the transcription level. In addition to the protein synthesis rate, the content of COP23 also exhibited a circadian rhythm. Pulse labeling with [35S]methionine revealed that COP23 was relatively stable in an arrhythmic culture. However, the exposure of Synechococcus RF-1 to a light/dark regimen induced not only a circadian synthesis rhythm, but also a rapid degradation of COP23 protein at a defined period of time. The induction of rapid protein degradation was prevented by the presence of chloramphenicol. The gene encoding the COP23 polypeptide has been cloned and sequenced. The amino acid sequence derived from the open-reading frame revealed that a signal peptide (28 amino acids) does not appear to be part of the mature COP23. The mature COP23 does not have a membrane-associated segment, and it is suggested to be a peripheral molecule. With respect to their DNA base sequence and protein amino acid sequence, none of the proteins documented in the EMBL and PC/Gene data bases are significantly homologous with the COP23 molecule.

Amino Acid Sequence↗
PubMed1996

Identification of immunodominant, group-specific and subcomplex-specific, continuous epitopes in the core regions of Japanese encephalitis virus using synthetic peptides.

Two flaviviruses, Japanese encephalitis (JE) virus and Dengue (DEN) virus which have high pathogenicity for humans, continue to pose a serious public health problem in tropical and subtropical countries of the world. In order to identify the immunodominant B-cell epitopes for diagnostic application, we have prepared a series of 15-mer synthetic peptides from JE virus core protein based on computer analysis. Four linear, immunodominant epitopes corresponding to amino acids 91-105 (P78), 1-15 (P73), 8-22 (P74), and 34-48 (P75) of JE virus core proteins were identified by employing an enzyme-linked immunosorbent assay (ELISA), using high-titered immune sera from JE-vaccinated children. P78 was found to be the most immunodominant. The sero-specificity of these peptides was tested by binding to seroconverted samples from JE and DEN-1 patients. P78 and P74 belonged to group-specific epitopes which reacted with both JE and DEN-1 patient sera. P73 and P75 belonged to subcomplex-specific epitopes which reacted only with JE but not with DEN-1 patient sera. The study suggests that these peptides corresponding to the immunodominant epitopes of JE virus core protein might have the potential to be used as peptide-based diagnostic reagents for the detection and differentiation of JE and DEN antibody responses.

Adult↗
PubMed1996

Lessons learned from the non-obese diabetic mouse II: Amelioration of pancreatic autoimmune isograft rejection during pregnancy.

To determine whether pregnancy provides an improved milieu for fetal/neonatal pancreas/islet transplantation, we studied neonatal pancreatic implants into non-obese diabetic (NOD) female mice during early gestation. We monitored maternal glycemic status, birthweight of the offspring, and graft histology to assess the efficacy of transplantation. One hundred and thirteen twelve-week-old NOD female mice were randomized into four groups as follows: (1) non-pregnant NOD mice received a sham operation; (2) non-pregnant NOD mice received neonatal pancreatic transplants; (3) pregnant NOD mice received a sham operation; and (4) pregnant NOD mice received neonatal pancreatic transplants. Pancreas segments from 3 neonatal NOD mice were placed via an incision 1 to 2 mm distal to the ear-skull junction of each of the recipients. Maternal blood glucose and glycated hemoglobin were determined between days 18 and 20 after the surgery. Pups were weighed within 5 to 6 hours after delivery. Pregnant NOD that received transplants (n = 29) had lower glucose and glycated hemoglobin (GHb) than sham operated pregnant controls (n = 26) (4.9 +/- 0.05 versus 9.0 +/- 5.0 mmol/L, p < 0.001 for glucose and 2.0 > or = 0.2 versus 3.0 > or = 1.2%, p < 0.008 for GHb) at 18 to 20 days of gestation. Controlling for litter size showed a decrease in birthweight for offspring of transplant recipients versus offspring of pregnant controls (1.59 +/- 0.08 versus 1.65 +/- 0.08 g, p < 0.002). Histological scoring of transplanted tissue at day 21 indicated that the lymphocytic infiltration in the pregnant group was significantly less than the control group (2.9 +/- 1.2 versus 4.9 +/- 0.2, p < 0.0001). We conclude that the pregnant NOD mouse provides a useful transplant model, that pregnancy provides an opportunity to increase beta-cell mass with transplanted tissue, and that pancreatic transplantation decrease birthweight and macrosomia in the offspring of NOD mice.

Animals↗
PubMed1996

Effect of replacing helical glycine residues with alanines on reversible and irreversible stability and production of Aspergillus awamori glucoamylase.

To decrease irreversible thermoinactivation of Aspergillus awamori glucoamylase, five Gly residues causing helix flexibility were replaced with Ala residues. Mutation of Gly57 did not affect thermostability. Mutation of Gly137 doubled it at pHs 3.5 and 4.5 but barely changed it at pH 5.5. The Gly139-->Ala mutation did not change thermostability at pH 3.5, improved it at pH 4.5 and worsened it at pH 5.5. The Gly 137/Gly139-->Ala/Ala mutation gave 1.5-2-fold increased thermostabilities at pHs 3.5-5.5. Mutations of Gly251 and Gly383 decreased it at all pHs. Gly137-->Ala and Gly137/Gly139-->Ala/Ala glucoamylases are the most stable yet produced by mutation. Guanidine treatment at pH 4.5 decreased the reversible stabilities of Gly137-->Ala, Gly139-->Ala and Gly137/Gly139-->Ala/Ala glucoamylases at infinite dilution while not changing those of Gly251-->Ala and Gly383-->Ala glucoamylases, which is, in general, opposite to what occurred with thermoinactivation. Mutation of Gly57 greatly improved the extracellular glucoamylase production by yeast, that of Gly137 barely affected it and those of Gly139 and of both Gly137 and Gly139 strongly impeded it. These observations suggest that alpha-helix rigidity can affect reversible and irreversible glucoamylase stability differently, that the effects of multiple mutations within one alpha-helix to improve stability are not always additive and that even single mutations can strongly affect extracellular enzyme production.

Alanine↗