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Biomedical subjects

M Lu

Publications and source records attributed to M Lu.

At least 361 records · Page 20Linked to original sources
PubMed1985

Localization of ornithine decarboxylase in rat testicular cells and epididymal spermatozoa.

We have employed a monospecific, polyclonal antibody to ornithine decarboxylase (ODC) for the immunocytochemical localization of ODC in freshly isolated testicular cells, epididymal spermatozoa, and cultured Sertoli cells. Antigenically detectable material was present in the cytoplasm of all cell types tested and was highly concentrated in the acrosomal vesicle of round spermatids and in the acrosome region of epididymal spermatozoa. The specific enzymatic activity of ODC, as measured biochemically, was much higher in the interstitial cells than in the other testicular cell types, and no ODC activity was detected in the epididymal spermatozoa or in the Sertoli cells after 5 days in culture. These studies showed that, while all testicular cell types studied contained ODC-like immunoreactive molecules, only testicular germ cells and interstitial cells exhibited detectable ODC activity.

Animals↗
PubMed1983

Effect of titration charge on the diffusion of bovine serum albumin.

Quasi-elastic light scattering studies were performed on purified bovine serum albumin sample under conditions of high and low ionic strength and pH. Two relaxation modes were observed in all cases. The apparent diffusion coefficient obtained in the asymptotic time window (T) limit T leads to 0-i.e., Dapp(T leads to 0)-was found to be approximately equal to 6.1 X 10(-7) cm2/sec under conditions that minimized electrical forces (100 mM KCl at pH 4.5). As the ionic strength was lowered to 0.1 mM KCl (pH 4.5) or the pH was raised to 10 (100 mM KCl), Dapp(T leads to 0) increased to 7.2-7.5 X 10(-7) cm2/sec. These observations for Dapp(T leads to 0) are interpretable in terms of small-ion-polyion coupled modes in accordance with the theory of Lin et al. regarding dynamic Donnan effects [Lin, S.-C., Lee, W. I. & Schurr, J. M. (1978) Biopolymers 17, 1041-1064] without having to invoke direct polyion-polyion interactions. These direct interactions may be important at extreme ionic strength and pH conditions (0.1 mM KCl at pH 10). Concomitant with an increase in Dapp(T leads to 0), under appropriate changes in solvent conditions, is an increase in the relative amplitude and relaxation time of the slow decay mode.

Animals↗
PubMed1975

Structure-activity relationships between meta-substituted N-ethylamphetamines and locomotor activity in mice.

The effects of N-ethylamphetamines substituted at the meta position of the phenyl ring with H, F, Cl, Br, I, CF3, CH3O, NO2 or OH were examined on locomotor activity in mice. With the exception of meta-CF3-N-ethylamphetamine (fenfluramine), all compounds stimulated locomotor activity to varying amounts as determined in dose-activity curves that included doses which were ineffective through doses which either decreased activity relative to lower doses or were lethal. Multiple linear regression analyses indicated that the extent to which these compounds increased locomotor activity was inversely related to meta-substituent steric effects (size, r equal to 0.90), whereas hydrophobic and electronic substituent effects did not contribute significantly to this relationship. In mice pretreated with pargyline (100 mg/kg, 4 hours), the stimulant effects of these compounds were potentiated and again were inversely related only to substituent size (r equal to 0.77). In reserpine-pretreated mice (5 mg/kg, 24 hours), no relationship was obtained with size, hydrophobic or electronic effects individually or together. Reserpine pretreatment eliminated the rate-increasing effects of the iodinated and hydroxylated derivatives but not those of the other compounds. Pretreatment with alpha-methyl-para-tyrosine (100 or 320 mg/kg, 1 hour) caused a dose-related abolition of N-ethylamphetamine-induced increases in acitivity. These data suggest that the amphetamine derivatives of the present study act indirectly, probably through release of catecholamines.

Amphetamine↗
PubMed1973

Characterization of a heat-stable protease of Pseudomonas fluorescens P26.

A heat-stable, extracellular proteolytic enzyme was isolated from Pseudomonas fluorescens P26. Brain heart infusion broth (Fisher Scientific Co.), pH 7.5, and incubation at 21 C provided the optimal conditions for bacterial growth for enzyme production. The organism had a D value of 2.6 min at 62.8 C (145 F). The enzyme, however, was quite heat-stable, requiring 15 hr at 62.8 C, 8 hr at 71.4 C, and 9 min at 121 C for complete inactivation. Milk, whey, and casein each had a protective effect on the enzyme against heat inactivation. Purification was accomplished by growth of organisms in broth, centrifugation, sterilization by filtration, ammonium sulfate precipitation (55% saturation), dialysis (against six changes of water), and protein separation by passage through a Sephadex G-100 column. Ultracentrifugation revealed a single band with a sedimentation coefficient of 1.51 which suggested a molecular weight of approximately 23,000. As little as 0.2 unit of the purified enzyme caused detectable flavor defects during 30 days of storage at 4 C, and the Hull test for liberation of tyrosine compared favorably in sensitivity with the sensory method in milk.

Amino Acids↗
PubMedDate not supplied

Reversible and irreversible immobilization of enzymes on Graphite Fibrils.

Graphite Fibrils are hollow tubes (0.01 x 1-10 microns) consisting of concentric layers of graphite. Fibrils can be chemically modified to introduce surface functionalities such as carboxyl groups. Carboxylated fibrils were further functionalized to amino alkyl derivatives which were covalently linked to an enzyme, horseradish peroxidase (HRP). HRP fibrils showed substantial catalytic activity. Additionally, carboxyl fibrils were derivatized with specific inhibitors of the enzymes beta-galactosidase (beta-Gal) and alkaline phosphatase (AP). Enzyme inhibitor-modified fibrils were used to specifically purify both beta-Gal (using beta-Gal inhibitor fibrils) and AP (using AP inhibitor fibrils) from mixtures of these two enzymes. These studies demonstrate the feasibility of using Graphite Fibrils as supports in biocatalysis and biospecific affinity chromatography.

Alkaline Phosphatase↗
PubMedDate not supplied

In vitro analysis of cell populations involved in Hodgkin's disease lesions and in the characteristic T cell immunodeficiency.

Hodgkin's disease (HD) is an aggressive human lymphoproliferative disease that displays a curious pleomorphic histopathologic appearance unlike that of any of the common non-Hodgkin's lymphomas (NHL). Although the bizarre giant cells of the HD lesion, the Reed-Sternberg cells (RSC) and mononuclear variant Hodgkin's cells (HC), have been considered to be malignant cells, little objective evidence supports this conclusion. We have studied the proliferative characteristics of T cell as well as RSC and HC-enriched populations from HD lesions, and found the majority of the proliferative activity in the T cell populations. RSC-enriched populations not only showed little spontaneous proliferation, but also did not respond to a variety of cytokine growth factors in vitro, suggesting that these cell populations are not actively growing cells. Further molecular studies to identify possible monoclonal T or B cell populations in HD lesions, using a TCR beta chain probe and IgH probes respectively on Southern blot analysis, revealed no evidence of monoclonal lymphoid cell populations. Additional studies on the characteristic T cell immunodeficiency in HD were also undertaken. Our previous studies had associated a decrement in IL-2 production with this defect. Our studies now show that an intrinsic T cell abnormality exists when HD patients' T cells are stimulated with agonistic MAb that can optimally activate and stimulate IL-2 production in normal control T cells.

Adolescent↗
PubMedDate not supplied

Worksite cancer screening and nutrition intervention for high-risk auto workers: design and baseline findings of the Next Step Trial.

BACKGROUND: This article describes the design and baseline findings of The Next Step Trial, a health promotion intervention targeting automobile industry employees at increased colorectal cancer risk. The intervention encouraged colorectal cancer screening participation and adoption of low-fat, high-fiber diets. METHODS: Twenty-eight worksites (n = 5,042) were randomized to control (a company-sponsored screening program) or intervention (an enhanced screening program including a personalized educational booklet and motivational telephone call and diet-change program including nutrition classes, self-help materials, and computer-generated personalized feedback). Outcomes included screening compliance and fat and fiber intake. RESULTS: Pretrial data indicated targeted employees were predominantly older, well educated, married, Caucasian men. Sixty-one percent (SE = 2) participated in the screening program in the preceding 2 years, and 24% (SE = 1) reported a history of colorectal polyps or cancer. Fifty-eight percent of the cohort responded to the baseline questionnaire; respondents were older and more educated; more were married, retired, and Caucasian than nonrespondents. Mean dietary intakes were 36.9% energy from fat (SE = 0.21), 8.8 g fiber/1000 kcal (SE = 0.07), and 3.4 servings of fruits and vegetables per day (SE = 0.04). CONCLUSIONS: Baseline data show moderate screening participation and dietary intakes that did not meet guidelines; hence intervention efforts were warranted. Data from this trial will support a rigorous test of whether this high-risk employee population is responsive to targeted health promotion, early cancer detection, and prevention interventions.

Automobiles↗
PubMedDate not supplied

Intention to screen for colorectal cancer among white male employees.

BACKGROUND: This study identifies factors associated with employee intention to participate in a company-sponsored program of continuous screening for colorectal cancer. Automobile industry pattern and model makers who had been offered screening for over a decade were included in the study. METHODS: Data were collected at the outset of a randomized trial of screening and nutrition interventions. A baseline survey was mailed to 4,490 white men without a history of colorectal cancer. This mailing generated complete responses from 2,693 (60%) individuals. Survey data obtained for these men, including measures of cognitive and psychological representations related to colorectal screening, social influence, and intention to screen, were supplemented by background information gathered from employment records of these men. Workplace screening services were documented via a survey of plant health care professionals. RESULTS: Fifty-eight percent of respondents reported a high level of intention to screen. Multivariate analyses showed that intention to screen was positively associated with employee past participation in screening, belief in the salience and coherence of screening, belief in screening efficacy, perceived self-efficacy, belief that polyp removal prevents colorectal cancer, perceived personal susceptibility to colorectal cancer or polyps, receptivity to family member support for screening, and workplace scheduling of screening examinations. CONCLUSIONS: Factors associated with intention to screen may contribute to participation in continuous screening programs. Research is needed to assess the impact of interventions that facilitate appointment scheduling, provide tailored education about screening, and encourage lay support.

Adult↗
PubMedDate not supplied

Production of human B and T cell growth factors is enhanced by thymic hormones.

The thymic preparations thymosin fraction 5 (TF5) and synthetic thymosin alpha 1 (T alpha 1) were examined for their ability to enhance growth factor production by human peripheral blood mononuclear cells (PBMC). The results showed that both TF5 and T alpha 1 were capable of enhancing the production of a B cell growth factor (BCGF-12kD) and T cell growth factor (TCGF; IL-2). Enhancement by T alpha 1 could be obtained at 100-200-fold lower concentrations than that seen with TF5. In contrast, no enhancement of growth factor production was obtained with control preparations of non-thymic tissue extracts at any concentrations used. It was observed that stimulation of BCGF-12kD and IL-2 was most significantly obtained when the PBMC were activated with lectin. Furthermore, no direct effect of thymic hormones on test B and T cells was observed. These observations provide the first direct evidence that production of B cell growth factors can be enhanced by thymic hormones. In addition, these studies suggest that thymic hormones may regulate B cell responses by acting on mature activated T lymphocytes.

B-Lymphocytes↗
PubMedDate not supplied

Isolation of praeruptorins A and B from Peucedanum praeruptorum Dunn. and their general pharmacological evaluation in comparison with extracts of the drug.

The root of Peucedanum praeruptorum Dunn. was extracted with solvents at different polarity obtaining three chemical fractions: aqueous (H2O), n-butanol (BuOH) and ethyl acetate (AcOEt). From AcOEt praeruptorins A and B were isolated by column chromatography on silica gel, using toluene/ethyl acetate as eluent, and identified by 1H and 13C NMR analysis. The extracts and the praeruptorins were tested for gross behavioural effects and acute toxicity in mice; the cytotoxicity on Artemia salina Leach and the antimicrobial activity were also evaluated. None of the tested substances evoked behavioural effects or acute toxicity after oral administration in mice; delayed mortality was observed with AcOEt and praeruptorin A only after intraperitoneal administration of high doses (1 g/kg). In Artemia salina test AcOEt, and praeruptorins A and B had LC50 values of 40.2, 121.2 and 34.5 microg/ml, respectively. AcOEt and praeruptorin A showed antimicrobial activity on Streptococcus agalactiae; their MIC values were 250 and 100 microg/ml, respectively.

Animals↗
PubMedDate not supplied

Aromatic hydrocarbon growth from indene.

Aromatic hydrocarbon growth from indene (C9H8), which contains the five-membered ring cyclopentadienyl moiety, was investigated experimentally in a 4 s flow reactor over a temperature range 650-850 degrees C. Major products observed were three C18H12 isomers (chrysene, benz[a]anthracene and benzo[c]phenanthrene), two C17H12 isomers (benzo[a]fluorene and benzo[b]fluorene), and two C10H8 isomers (naphthalene and benzofulvene). Reaction pathways to these products are proposed. Indenyl radical addition to indene produces a resonance-stabilized radical intermediate which further reacts by one of two routes. Rearrangement by intramolecular addition produces a bridged structure that leads to the formation of C17H12 and C10H8 products. Alternatively, beta scission produces biindenyl, which leads to the formation of C18H12 products by a ring condensation mechanism analogous to that proposed for cyclopentadiene-to-naphthalene conversion. Temperature dependencies of both the partitioning between these two routes and the product isomer distributions are consistent with thermochemical modeling using semi-empirical molecular orbital methods. The results further illustrate the role of resonance-stabilized radical rearrangement in aromatic growth and condensation of systems with cyclopentadienyl moieties.

Journal Article↗