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Biomedical subjects

M Kim

Publications and source records attributed to M Kim.

At least 289 records · Page 16Linked to original sources
PubMed1996

A modified catalase assay suitable for a plate reader and for the analysis of brain cell cultures.

The enzyme catalase is present in relatively small amounts in neural tissue. A standard spectrophotometric assay for catalase has been modified to make it suitable both for automated assay with a plate reader and for the analysis of neural cell cultures. Catalase activity is determined by measuring residual hydrogen peroxide after incubation with the enzyme. Ferrous ions and thiocyanate are used for the spectrophotometric determination of hydrogen peroxide. The stable visible absorption of ferrithiocyanate can be measured either with a plate reader or a spectrophotometer. The method assays catalase activity from single wells of a tissue culture plate containing 2-3 mg of embryonic rat mesencephalon.

Animals↗
PubMed1995

Resonance Raman evidence that the thioester-linked 4-hydroxycinnamyl chromophore of photoactive yellow protein is deprotonated.

Resonance Raman spectra of the ground state of photoactive yellow protein (PYP), a photoactive pigment found in Ectothiorhodospira halophila, have been obtained with excitation at 413.1 nm using a microspinning sample cell. The resonance Raman spectra of the thioester-linked 4-hydroxycinnamyl chromophore in the protein are compared with the preresonance Raman spectra of the 4-hydroxycinnamyl phenyl thioester and 4-hydroxycinnamic acid model compounds at various pH values. Bands at 1568, 1542, 1500, 1434, and 1166 cm-1 in the Raman spectrum of the anionic form of the 4-hydroxycinnamyl phenyl thioester are shown to be characteristic for the deprotonation of the chromophore. The observation of bands in PYP exhibiting very similar frequency and intensity patterns provides strong evidence that the chromophore in PYP is stabilized as a phenolate anion at pH 7.4, in support of conclusions from crystallographic studies. Furthermore, the insensitivity of the PYP Raman spectrum to placement of the protein in D2O buffer is consistent with the absence of the exchangeable phenolic proton on the cinnamyl chromophore. These results establish the feasibility of elucidating the molecular mechanism of light-to-information transduction by this new photosensory pigment with resonance Raman spectroscopy.

Bacterial Proteins↗
PubMed1995

Characterization of uvi15+, a stress-inducible gene from Schizosaccharomyces pombe.

The uvi15+ gene of Schizosaccharomyces pombe is a member of a group of stress-inducible genes transcription levels of which increase in response to DNA-damaging agents or heat shock. It encodes a polypeptide of calculated molecular mass 11641 Da, with no significant sequence similarity to other known heat shock proteins. The steady-state level of the uvi15+ gene product of about 12 kDa was increased by heat shock and canavanine, an amino acid analog. This gene also showed a transient increase in expression as cells moved into diauxic shift phase. Although deletion of the uvi15+ gene did not affect the mitotic growth or thermotolerance of cells, the mutant cells rapidly lost viability in stationary phase and under starvation conditions. These cells also showed a defect in sporulation ability. These results suggest that the uvi15+ gene encodes a stress response protein involved in the maintenance of cell viability during entry into stationary phase or under starvation conditions.

Amino Acid Sequence↗
PubMed1995

Seroprevalence of herpes simplex virus infections in a family medicine clinic.

OBJECTIVES: To determine the prevalence of herpes simplex virus (HSV) antibody in a general medical practice setting and to assess the frequency of subclinical infection. DESIGN: Prevalence study. SETTING: A family practice clinic at the University of Washington Medical Center, Seattle. PARTICIPANTS: Five hundred randomly selected patients between the ages of 18 and 45 years. MAIN OUTCOME MEASURES: Serum samples were tested by Western blot assay to detect the presence of antibody to HSV type 1 (HSV-1) and HSV-2. Demographic information and clinical history of oral and genital herpes were obtained. RESULTS: One hundred fourteen patients (23%) were seropositive for HSV-2 antibody, 277 patients (56%) were seropositive for HSV-1 antibody, 59 patients (12%) were seropositive for both HSV-2 and HSV-1 antibodies, and 163 patients (33%) were seronegative for both. Women were almost twice as likely as men to be seropositive for HSV-2 antibody (28% vs 15%, P < .001). Blacks had the highest rates of HSV-2 antibody seropositivity (60%) compared with whites (20%) and Asians (6%) (P < .001). Other demographic correlates of seropositivity included being older, having fewer years of education, and having public insurance. The specificity of a clinical history of genital herpes or sores for HSV-2 infection was high (99%), but the sensitivity was low (27%). CONCLUSIONS: Herpes simplex virus infection is common among patients seeking primary care. Women, blacks, and patients of lower socioeconomic status are most likely to be seropositive for HSV-2 antibody. The high frequency of unrecognized HSV infection has implications for primary care physicians in counseling patients regarding HSV infection and transmission.

Adult↗
PubMed1995

Surface characteristics and properties of lumbrokinase-immobilized polyurethane.

Potent and novel fibrinolytic enzymes (lumbrokinase [LK]) were extracted from the earthworm, Lumbricus rubellus. These enzymes were very stable and showed greater antithrombotic activity than other currently used fibrinolytic proteins. An LK fraction showing the most potent fibrinolytic activity was immobilized onto a polyurethane (PU) surface to investigate its enzymatic activity and antithrombotic activity. A methanol-extracted PU surface was coated with 3% (wt/vol) maleic anhydride methylvinyl ether copolymer (MAMEC)/tetrahydrofuran (THF) solution, and the surface was incubated in an LK solution/phosphate-buffered saline (PBS, pH 7.4). The surface properties were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), electron spectroscopy for chemical analysis (ESCA), and dynamic contact angle. The stability of immobilized LK was determined by caseinolytic activity assay and the specificity of immobilized LK on fibrinogen/fibrin was observed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The antithrombotic activity of immobilized LK was evaluated using an ex vivo rabbit A-A shunt experiment. LK immobilization was confirmed by ATR-FTIR and ESCA. Immobilized LK demonstrated stable proteolytic activity during various incubation periods. Immobilized LK proteolyzed fibrinogen and fibrin almost specifically, while it hardly hydrolyzed other plasma proteins including plasminogen and albumin. In the ex vivo A-A shunt experiment, the LK-immobilized surface significantly prolonged occlusion time over control surfaces. This is primarily due to the high thrombolytic activity of immobilized LK. In this work, a highly efficient surface modification method on the PU surface was developed, and this LK immobilization technique will be very useful in improving the blood compatibility of blood-contacting devices.

Animals↗
PubMed1995

Augmentation of TNF cytotoxicity by protein kinase C inhibitors: role of arachidonic acid and manganese superoxide dismutase.

The protein kinase C (PKC) inhibitors bisindolylmaleimide, calphostin C, H-7 and staurosporine were examined for their effect on tumour necrosis factor (TNF) cytotoxic activity. PKC inhibitors potentiated the cytotoxic activity of TNF in TNF-sensitive cell lines (CL8-1 melanoma and WEHI-164 fibrosarcoma), but had no effect on TNF cytolytic activity in TNF-resistant cells (BL6-8 melanoma and MCA-102 fibrosarcoma). The mechanism(s) of PKC inhibitor-mediated potentiation of the cytotoxic activity of TNF was investigated by analysing the effect of PKC inhibitors on TNF-induced arachidonic acid release in TNF-sensitive and -resistant cells. TNF induced the release of arachidonic acid in TNF-sensitive cells but had no effect in TNF-resistant cells. The combination of PKC inhibitor and TNF potentiated the release of arachidonic acid from TNF-sensitive cells, but failed to induce arachidonic acid release in TNF-resistant cells. Kinetic analysis of TNF-induced arachidonic acid release in CL8-1 melanoma cells revealed that it was an early event which preceded TNF tumour lytic activity. TNF was further shown to induce manganese superoxide dismutase (MnSOD) production in TNF-sensitive cells but failed to induce MnSOD activity in TNF-resistant BL6-8 and MCA 102 cells. MnSOD acts as a scaveneger of toxic superoxide radicals and its induction by TNF paralleled arachidonic acid release. Although the PKC-selective inhibitor bisindolylmaleimide potentiated TNF-induced release of arachidonic acid, it blocked TNF-mediated induction of MnSOD in CL8-1 melanoma and WEHI-164 fibrosarcoma cells.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1995

A nested case-control study of mammographic patterns, breast volume, and breast cancer (New York City, NY, United States).

The relations of Wolfe mammographic patterns, quantitative mammographic densities, and mammographically estimated breast size to breast cancer risk were investigated prospectively in a case-control study nested in the New York University Women's Health Study, a cohort of 14,291 women in New York City, NY (United States). The archived mammograms of 197 breast cancer cases who were identified during the first 5.5 years of the study and of 521 individually matched controls from the same cohort were retrieved and classified according to Wolfe parenchymal patterns and mammographic densities by two expert radiologists. Breast size and volume were estimated on the mammogram's cranio-caudal projection. In both premenopausal and postmenopausal subjects, the risk of breast cancer increased progressively with increasing density and percent density area. A significantly increased risk was found also for Wolfe pattern DY in premenopausal women and P2 pattern in postmenopausal subjects. In premenopausal women, mammographically determined breast volume and breast height also were associated positively with breast cancer risk. Although the results of the present study confirmed that mammographic parenchymal patterns and densities were important predictors of breast cancer risk, their practical use in screening seems limited due to the high prevalence of high risk patterns.

Adult↗
PubMed1995

Increase of a urokinase receptor-related low-molecular-weight molecule in colorectal adenocarcinomas.

Proteolytic activity is important for tumor growth and metastasis. Plasminogen and urokinase-type plasminogen activator (u-PA) constitute one of the most extensively studied proteolytic systems believed to participate in these processes. u-PA cleaves plasminogen to plasmin, which in turn degrades surrounding extracellular matrix and allows tumor cells to migrate to other areas. The specific receptor for u-PA (u-PAR) has also been implicated as an essential modulator in this pathway. Eleven paired samples of colorectal cancers and normal mucosal tissues from the same patients were removed at surgery. The tissues were homogenized and the supernatants assayed for u-PAR immunoreactivity, u-PAR antigen concentration, u-PAR binding activity and u-PA activity. Immunoblot analysis showed that a major u-PAR species of approximately 55 kDa was present in all tissues. In addition, a protein band of approximately 41 kDa, which crossreacted with anti-u-PAR antibodies, was also found in the tumors. This protein band was either absent, or present in relatively small amounts in the normal colorectal tissues. Cross-linking experiments showed that the approximately 55 kDa band only, and not the approximately 41 kDa band, was able to bind either single chain urokinase-type plasminogen activator (scu-PA) or the amino terminal fragment of urokinase (ATF). The tumor samples also exhibited highly elevated u-PA activity and u-PAR antigen relative to the corresponding normal tissues. Elevated u-PA activity appeared to correlate with elevated u-PAR antigen in colorectal cancers, but not in the normal tissues. These increases were also associated with increase of the u-PAR-related, low-molecular-weight protein in the tumor samples. The measurement of u-PAR and the u-PAR-related protein, in addition to u-PA activity, could have diagnostic or prognostic value in this type of cancer.

Adenocarcinoma↗
PubMed1995

Myelin basic protein does not have a mitogenic effect on adult oligodendrocytes.

Increased numbers of oligodendrocytes and remyelination are frequently observed in multiple sclerosis plaques. It is presumed the increased numbers of oligodendrocytes are due to cell division, but this has not been proven. The mitogens within the lesion which might be responsible for this are unknown. Since oligodendrocyte proliferation occurs in areas in which there is myelin breakdown, we undertook the present study to determine if myelin basic protein (MBP) or its breakdown products could induce oligodendrocyte proliferation. MBP, or MBP digested by the neutral proteinase plasmin, was added in three concentrations to the media of adult bovine oligodendrocytes in culture. Oligodendrocytes were identified by staining for galactocerebroside. Bromodeoxyuridine incorporation was used as a measure of cell division. Oligodendrocytes were found to divide only rarely in regular culture media, in the presence of MBP, plasmin, or MBP digested by plasmin. The results indicate that MBP is not a significant mitogen for the mature oligodendrocyte.

Animals↗
PubMed1995

Non-nephrotic children with membranoproliferative glomerulonephritis: are steroids indicated?

Alternate-day steroids are currently recommended to treat children with membranoproliferative glomerulonephritis (MPGN). This recommendation is based largely on uncontrolled studies demonstrating improved renal survival with steroid therapy. We reviewed the outcome of 39 children who presented with MPGN between 1968 and 1990; 27 children were treated with steroids and 12 children received no drug therapy. Life-table analysis comparing renal survival of treated versus untreated children demonstrated no difference by log rank analysis. Treated and untreated groups were compared on the basis of nine features at presentation: age, sex, type of MPGN, presence and type of hematuria, hypocomplementemia renal insufficiency, hypertension, and nephrosis. Treated children were likely to be female (P < 0.01) and nephrotic (P < 0.02). Actuarial survival analyses were performed comparing the nine features with renal survival through 10 years of follow-up. Normotensive (P < 0.025) and non-nephrotic (P < 0.05) children had improved renal survival. The 11 non-nephrotic children demonstrated 100% long-term renal survival, including 7 who received no steroid therapy. At last follow-up, all non-nephrotic children had normal renal function, serum albumin levels > 3 g/dl, and were normotensive. These data suggest that non-nephrotic children with MPGN may forego steroid treatment without compromising long-term renal function. The current common practice of treating all children with MPGN with steroids should be re-examined.

Actuarial Analysis↗
PubMed1995

Issues in protection from galactic cosmic rays.

Radiation risks to astronauts depend on the microscopic fluctuations of energy absorption events in specific tissues. These fluctuations depend not only on the space environment but also on the modifications of that environment by the shielding provided by structures surrounding the astronauts and the attenuation characteristics of the astronaut's body. The effects of attenuation within the shield and body depends on the tissue biological response to these microscopic fluctuations. In the absence of an accepted method for estimating astronaut risk, we examined the attenuation characteristics using conventional linear energy transfer (LET)-dependent quality factors (as one means of representing relative biological effectiveness, RBE) and a track-structure repair model to fit cell transformation (and inactivation) data in the C3H10 T1/2 mouse cell system obtained for various ion beams. Although the usual aluminum spacecraft shield is effective in reducing dose equivalent with increasing shield thickness, cell transformation rates are increased for thin aluminum shields. Clearly, the exact nature of the biological response to LET and track width is critical to evaluation of biological protection factors provided by a shield design. A significant fraction of biological injury results from the LET region above 100 keV/mu m. Uncertainty in nuclear cross-sections results in a factor of 2-3 in the transmitted LET spectrum beyond depths of 15 g/cm2, but even greater uncertainty is due to the combined effects of uncertainty in biological response and nuclear parameters. Clearly, these uncertainties must be reduced before the shield design can be finalised.

Animals↗
PubMed1995

Hyperglycemia alters perception of rectal distention and blunts the rectoanal inhibitory reflex in healthy volunteers.

BACKGROUND/AIMS: Acute hyperglycemia has been shown to alter gastrointestinal motility. The effects of hyperglycemia on rectal afferent neural and anal sphincter function were studied. METHODS: Perception of rectal balloon distention, pressure-volume relationships, volumes necessary to induce reflex internal anal sphincter relaxation, resting anal sphincter pressure, and maximal anal sphincter squeeze pressure were measured under basal, hyperglycemic clamp, and euglycemic, hyperinsulinemic clamp conditions in 9 healthy volunteers. RESULTS: Hyperglycemic clamping (258 +/- 14 mg/dL) significantly blunted threshold perception and the urge to defecate in response to rectal distention without altering perception of maximally tolerated distention. In contrast, euglycemic, hyperinsulinemic clamping had no effect on perception of rectal distention. Rectal pressure-volume relationships after hyperglycemic clamping were unchanged compared with basal conditions. Hyperglycemic clamping caused a significant increase in the distention necessary to induce the rectoanal inhibitory reflex. This effect was not observed under euglycemic, hyperinsulinemic clamp conditions. Hyperglycemia did not significantly affect resting internal anal sphincter pressure or maximal external anal sphincter squeeze pressure. CONCLUSIONS: Acute hyperglycemia but not secondary hyperinsulinemia reduces sensation of rectal distention and blunts the onset of the rectoanal inhibitory reflex, suggesting effects both on visceral afferents projecting to the cortex and intrinsic afferents mediating local reflex activity.

Adult↗
PubMed1995

Behavioral and prophylactic pharmacological intervention studies of pediatric migraine: an exploratory meta-analysis.

In this review, the effectiveness of behavioral and pharmacological treatments for pediatric migraine was quantitatively summarized following the meta-analytic approach outlined by Hedges and Olkin (1985). A first meta-analysis based on treatment outcome within treatment conditions revealed that thermal biofeedback and interventions combining biofeedback and progressive muscle relaxation seem to be significantly more efficacious than other behavioral treatment modalities, psychological and drug placebo, and the more commonly used prophylactic drug regimens. Though there is some evidence suggesting good effectiveness of propranolol, the lack of systematic data precludes more definitive conclusions. A second meta-analysis that included only studies providing data on the comparison between control versus active treatment conditions replicated the initial findings only partially. In the light of the relative small number of studies that met basic inclusion requirements, the methodological flaws of many studies, and the under-representation of certain treatment types, conclusions regarding differential effectiveness of the treatment types have to be drawn with caution. Overall, our findings clearly demonstrate the need for direct comparisons between behavioral and pharmacological treatments and the need for more theory-driven research in order to determine the most promising treatment approaches for pediatric migraine.

Behavioral Medicine↗
PubMed1995

Enzymatic synthesis of a sialyl Lewis X dimer from egg yolk as an inhibitor of E-selectin.

A dimeric sialyl Lewis X (SLex) glycopeptide was synthesized enzymatically in three steps from an N-linked oligosaccharide prepared from egg yolk. Treatment of delipidated hen egg yolk with the protease Orientase and neuraminidase gave a dimeric N-acetyllactosamine-containing oligosaccharide linked to asparagine. Addition of sialic acid and fucose catalyzed by alpha-2,3-sialyltransferase and alpha-1,3-fucosyltransferase provided the dimeric SLex, which was shown to be as active as monomeric SLex as an inhibitor of E-selectin with IC50 0.75 mM. The synthetic dimeric SLex of the mucin type (i.e. SLex linked to the 3- and 6-OH groups of Gal) is, however, about five times as active as the monomer. It is suggested that dimeric SLex glycopeptides of the mucin type would be effective ligands for E-selectin.

Animals↗
PubMed1995

The clinical characteristics of 82 patients with Sertoli cell-only testis histology.

OBJECTIVE: To determine the clinical and laboratory features associated with Sertoli cell-only testis histology. DESIGN: Case-controlled retrospective analysis. SETTING: University-based male infertility clinic. PATIENTS: Eighty-two patients with germ cell aplasia histology on testis biopsy from 1984 to 1994. Hormonal findings from a control group of 34 fertile men with normal semen analyses were used for comparison. MAIN OUTCOME MEASURES: History, physical examination, semen analysis, and endocrine findings. RESULTS: Sertoli cell-only histology was observed in 82 of 652 (13%) biopsies performed in infertile men with azoospermia. A major medical illness or genital anomaly (hypospadias, cryptorchidism) was found in 31 men (38%). On physical examination, 75% of patients had small testis (< 18 mL volume) and 45% had abnormally soft testis. On hormone evaluation only serum FSH concentration was elevated significantly (33 mIU/mL [33 IU/L]) compared with fertile controls (7.1 mIU/L [7.1 IU/L]). Patients (6%) with confirmed elevations in serum PRL had lower FSH values than those men with normal PRL levels. Normal ejaculate volumes were observed in all patients. CONCLUSIONS: In approximately 38% of patients, germ cell aplasia is associated with underlying disease states; in the remainder it is largely idiopathic. The physical examination is often characteristic, along with an elevated serum FSH concentration. Normal FSH levels tend to be associated with hyperprolactinemia in these men.

Case-Control Studies↗
PubMed1995

Issues in space radiation protection: galactic cosmic rays.

When shielding from cosmic heavy ions, one is faced with limited knowledge about the physical properties and biological responses of these radiations. Herein, the current status of space shielding technology and its impact on radiation health is discussed in terms of conventional protection practice and a test biological response model. The impact of biological response on optimum materials selection for cosmic ray shielding is presented in terms of the transmission characteristics of the shield material. Although liquid hydrogen is an optimum shield material, evaluation of the effectiveness of polymeric structural materials must await improvement in our knowledge of both the biological response and the nuclear processes.

Astronauts↗
PubMed1995

Identification of a sequence-specific DNA binding factor required for transcription of the barley chloroplast blue light-responsive psbD-psbC promoter.

The plastid gene psbD encodes the photosystem II reaction center chlorophyll protein D2. psbD is located in a complex operon that includes psbC, psbK, psbl, orf62, and trnG. The operon is transcribed from at least three different promoters. One of the psbD promoters is differentially activated when plants are exposed to blue light. In this study, the psbD blue light-responsive promoter was accurately transcribed in vitro in high-salt extracts of barley plastids. Transcription required supercoiled templates and was inhibited by tagetitoxin, an inhibitor of plastid transcription. Escherichia coli RNA polymerase did not recognize the psbD light-responsive promoter with the same specificity as plastid RNA polymerase. Deletion analyses demonstrated that sequences between -39 and -68, upstream of the transcription initiation site, were required for transcription of the psbD blue light-responsive promoter. This DNA region is highly conserved among plant species and contains multiple AAG sequences. Gel shift assays and DNase I footprinting experiments demonstrated that the AAG-rich DNA sequence interacts with a sequence-specific DNA binding factor termed AGF. Point mutations in the AAG cis element decreased binding of AGF and inhibited transcription from the psbD light-responsive promoter. We concluded that AGF is an essential factor required for transcription of the psbD light-responsive promoter.

Base Sequence↗