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Biomedical subjects

M L Johnson

Publications and source records attributed to M L Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1999

Tumor necrosis factor alpha regulates collagenolytic activity in preovulatory ovine follicles: relationship to cytokine secretion by the oocyte-cumulus cell complex.

The pleiotropic cytokine tumor necrosis factor (TNF)-alpha has been implicated in the mechanism of ovulation. Experiments were designed to test the hypothesis that TNF-alpha secreted from the oocyte-cumulus cell complex stimulates follicular collagenase production and thereby contributes to ovarian wall degradation and ovulatory rupture. Proestrous ewes were treated with GnRH to synchronize the onset of the gonadotropin surge; ovulation occurs approximately 24 h later. There was an increase in TNF-alpha (immunoassay) in antral fluid of preovulatory follicles at 18 h after GnRH, which was related to tissue collagenolytic bioactivity (radiolabeled type I substrate digestion by enzymatic extract) and collagen (hydroxyproline) depletion. Intrafollicular injection of TNF-alpha antibodies at 12 h after GnRH negated the rise in follicular collagenolytic bioactivity (and is known to block ovulation in the sheep). Moreover, collagenase production was enhanced when follicular tissues (0 h GnRH) were incubated (6 h) with recombinant TNF-alpha; this effect was abolished by the transcriptional inhibitor actinomycin D. Secretion of TNF-alpha by oocyte-cumulus cell complexes isolated from preovulatory follicles simulated the in vivo circumstance. Immunostaining indicated that TNF-alpha was confined mainly to the oocyte before GnRH administration, accumulated in cumulus cells during the mid-to-late preovulatory period, and was expended with the imminent approach of ovulation. To our knowledge, this is the first report specifying that up-regulation of collagenase expression is a target mode of TNF-alpha action in preovulatory follicles. The oocyte-cumulus cell complex is an apparent source of soluble TNF-alpha.

Animals↗
PubMed1999

The association of quality of care and occurrence of in-hospital, treatment-related complications.

BACKGROUND: Little data exist supporting the association of quality of care and nonfatal adverse outcomes in hospitalized patients, yet those outcomes are routinely scrutinized in quality assessment efforts. OBJECTIVE: To determine whether measurable differences in quality of care are associated with the occurrence of non-fatal, in-hospital, and treatment-related complications. DESIGN: Retrospective cohort study. SUBJECTS: A total of 2,268 patients who were discharged alive from 9 Southwestern Veterans Affairs Medical Centers with congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD) or diabetes mellitus. MEASURES: Retrospective chart review was performed to collect information on patient severity of illness, in-hospital complication occurrence, and process quality of care. Process quality was assessed as the adherence scores for admission work-up and for treatment during the hospital stay. Process quality represents the proportion of applicable admission or treatment criteria that were met by that patient's care providers. Once severity of illness was taken into account Cox proportional hazards regression was used to assess the independent contribution of process quality of care to complication occurrence. RESULTS: Higher admission work-up adherence scores for COPD patients and higher treatment adherence scores for COPD and diabetes patients were associated with a lower risk of complication occurrence. The adjusted risk ratios of complications for higher versus lower adherence scores (with 95% CI) were 0.64 (0.43, 0.97) and 0.52 (0.33, 0.80) for admission and treatment, respectively, in COPD patients, and 0.51 (0.31, 0.83) for treatment in diabetics. No significant association was found in CHF patients. CONCLUSION: Better admission work-up and treatment quality in COPD patients, as well as treatment quality in diabetic patients, are associated with lower risk of nonfatal treatment-related complications in the study population.

APACHE↗
PubMed1999

An empirical assessment of the validity of explicit and implicit process-of-care criteria for quality assessment.

OBJECTIVE: To evaluate the validity of three criteria-based methods of quality assessment: unit weighted explicit process-of-care criteria; differentially weighted explicit process-of-care criteria; and structured implicit process-of-care criteria. METHODS: The three methods were applied to records of index hospitalizations in a study of unplanned readmission involving roughly 2,500 patients with one of three diagnoses treated at 12 Veterans Affairs hospitals. Convergent validity among the three methods was estimated using Spearman rank correlation. Predictive validity was evaluated by comparing process-of-care scores between patients who were or were not subsequently readmitted within 14 days. RESULTS: The three methods displayed high convergent validity and substantial predictive validity. Index-stay mean scores, using explicit criteria, were generally lower in patients subsequently readmitted, and differences between readmitted and nonreadmitted patients achieved statistical significance as follows: mean readiness-for-discharge scores were significantly lower in patients with heart failure or with diabetes who were readmitted; and mean admission work-up scores were significantly lower in patients with lung disease who were readmitted. Scores derived from the structured implicit review were lower in patients eventually readmitted but significantly so only in diabetics. CONCLUSIONS: These three criteria-based methods of assessing process of care appear to be measuring the same construct, presumably "quality of care." Both the explicit and implicit methods had substantial validity, but the explicit method is preferable. In this study, as in others, it had greater inter-rater reliability.

Case-Control Studies↗
PubMed1999

Expression of gap junctional proteins connexin 43, 32, and 26 throughout follicular development and atresia in cows.

Detection of connexin (Cx) proteins has been used as an indicator of the presence of structural and functional gap junctions in tissues. To examine the role of gap junctions during follicular growth and atresia, the presence of three major connexins, Cx43, Cx32, and Cx26, was evaluated in bovine ovaries by using immunohistochemistry and Western immunoblot analysis. Cx43 was not present in primordial follicles, but was present in granulosa cells of primary/secondary and antral follicles. Cx43 also was present on the borders between granulosa cells and the oocyte. Expression of Cx43 increased in healthy developing antral follicles, but decreased during follicular atresia. Cx32 was not present in healthy follicles but was present in granulosa cells of atretic antral, and especially small antral follicles. Cx26 was present in the oocyte of primordial and primary/secondary follicles, and in the granulosa and/or thecal cell layers of healthy antral follicles. The percentage of healthy antral follicles that expressed Cx26 also increased during follicular development, but decreased during atresia. Cx32 and Cx26 also were detected in ovarian blood vessels and in stromal tissues adjacent to the tunica albuginea in some ovaries. The pattern of expression of these Cx indicates that gap junctional proteins may be involved in the control of follicular growth and atresia in cows.

Animals↗
PubMed1999

Evaluation of the self-rating of the effects of alcohol form in Asian Americans with aldehyde dehydrogenase polymorphisms.

OBJECTIVE: In order to easily assess individual differences in response to alcohol, the Self-Rating of the Effects of Alcohol (SRE) form was recently developed and its psychometric properties tested in primarily white subjects. This study aimed to further evaluate the SRE in a population known to have genetically mediated variability in response to alcohol and risk for alcoholism, Asian Americans with ALDH2 polymorphisms. METHOD: Men and women of Chinese, Japanese or Korean heritage between the ages of 21 and 26 years (N = 156) completed the SRE and a blood sample was drawn for genotyping at the ALDH2 locus. RESULTS: SRE results were available from 137 (78 female) subjects. With the effects of gender, body weight, frequency of recent drinking and quantity of recent drinking controlled, ALDH2 genotype still accounted for a significant amount of variability in SRE score in this Asian-American sample. Evaluation of SRE scores 4.5 or higher indicated that a low response to alcohol was associated with ALDH2*1/2*1 genotype, male gender and Korean heritage, all factors associated with increased risk for alcoholism. CONCLUSIONS: These results provide additional support for the SRE as a valid instrument for assessing individual variability in response to alcohol and as a useful measure for identifying individuals at relatively increased or decreased risk for alcoholism based on level of reaction to alcohol.

Adult↗
PubMed1998

Time-resolved and steady-state fluorescence quenching of N-acetyl-L-tryptophanamide by acrylamide and iodide.

We examined the time-resolved and steady-state fluorescence quenching of N-acetyl-L-tryptophanamide (NATA) by acrylamide and iodide, over a range of viscosities in propylene glycol. The quenching of NATA by acrylamide and iodide results in heterogeneity of the intensity decay which increases with the quencher concentration. We attribute the complex decays of NATA to transient effects in diffusion and the nature of the fluorophore-quencher interaction. These data were compared using the phenomenological radiation boundary condition (RBC) and distance-dependent quenching (DDQ) models for collisional quenching. We used global analysis of the time-resolved frequency-domain and steady-state data to select between the models. Consideration of both the frequency-domain and steady state data demonstrate that the quenching rate depends exponentially on the fluorophore-quencher distance, indicating the validity of the DDQ model. The rate constants for acrylamide and iodide quenching, at the constant distance of 5 A, were found to be near 10(13) s-1 and 10(9) s-1, respectively. These rates reflect electron transfer and exchange interactions as the probable quenching mechanisms, respectively.

Acrylamide↗
PubMed1998

Clearance of HSV-2 from recurrent genital lesions correlates with infiltration of HSV-specific cytotoxic T lymphocytes.

The mechanisms involved in host clearance of symptomatic mucocutaneous herpes simplex virus (HSV) infection are unclear. We studied the functional properties of bulk cultures of skin-infiltrating lymphocytes from normal skin and serial biopsies of recurrent genital HSV-2 lesions, and compared HSV-specific and NK responses with viral clearance. HSV-specific CD4+ or CD8+ T cells were rarely detected in lymphocytes cultured from normal skin. The total lymphocyte count and HSV-specific and NK-like effector cell activities were markedly higher in cultures derived from lesional skin. HSV-specific CD4+ proliferative responses and NK-like cytotoxic responses were present at all stages of herpetic lesions, including biopsies early in the disease course. In contrast, cytotoxic T lymphocyte activity was generally low among cells derived from early culture-positive lesions, and increased during lesion evolution. Viral clearance from the lesion site was associated with a high level of local cytolytic activity towards HSV-infected cells. The phenotypes of cells with HSV-specific cytotoxic responses varied between patients, having CD4+ and CD8+ components. Immunotherapeutic approaches to HSV should be directed at improving in vivo cytolytic activity to HSV.

Adult↗
PubMed1998

Roles of nitric oxide in surgical infection and sepsis.

Recent advances in nitric oxide (NO) research have begun to elucidate the roles of NO in sepsis and infection. Although adequate levels of NO production are necessary to preserve perfusion and carry out cytoprotective functions in sepsis, overproduction appears to contribute to hemodynamic instability and tissue damage. These observations have led to the development of strategies to inhibit NO synthesis or scavenge excess NO in patients with septic shock. Local expression of the inducible NO synthase also has antimicrobial functions. The combination of NO with superoxide forms peroxynitrite which participates in bacterial killing in the peritoneal cavity. The capacity of red blood cells and hemoglobin to remove NO most likely accounts for the adjuvant effect of blood in peritonitis. This review will summarize the pathobiology of NO in surgical sepsis and infection.

Animals↗
PubMed1998

Graft-versus-host reactions in dermatology.

Graft-versus-host reactions frequently produce cutaneous and systemic complications in patients receiving bone marrow transplants. Characteristic skin involvement typically heralds graft-versus-host reactions and significantly contributes to the morbidity associated with marrow transplants. Familiarity with these reactions and their treatment is important to dermatologists involved in the care of marrow transplant recipients.

Acute Disease↗
PubMed1998

Expression of CD14 by hepatocytes: upregulation by cytokines during endotoxemia.

Studies were undertaken to examine hepatocyte CD14 expression during endotoxemia. Our results show that lipopolysaccharide (LPS) treatment in vivo caused a marked upregulation in CD14 mRNA and protein levels in rat hepatocytes. Detectable increases in mRNA were seen as early as 1.5 h after LPS treatment; these increases peaked at 20-fold by 3 h and returned to baseline levels by 24 h. In situ hybridization localized the CD14 mRNA expression to hepatocytes both in vitro and in vivo. Increases in hepatic CD14 protein levels were detectable by 3 h and peaked at 12 h. Hepatocytes from LPS-treated animals expressed greater amounts of cell-associated CD14 protein, and more of the soluble CD14 was released by hepatocytes from LPS-treated rats in vitro. The increases in hepatocyte CD14 expression during endotoxemia occurred in parallel to increases of CD14 levels in plasma. To provide molecular identification of the hepatocyte CD14, we cloned the rat liver CD14 cDNA. The longest clone consists of a 1,591-bp insert containing a 1,116-bp open reading frame. The deduced amino acid sequence is 372 amino acids long, has 81.8 and 62.8% homology to the amino acid sequences of mouse and human CD14, respectively, and is identical to the rat macrophage CD14. The expressed CD14 protein from this clone was functional, as indicated by NF-kappaB activation in response to LPS and fluorescein isothiocyanate-LPS binding in CHO cells stably transfected with rat CD14. A nuclear run-on assay showed that CD14 transcription rates were significantly increased in hepatocytes from LPS-treated animals, indicating that the upregulation in CD14 mRNA levels observed in rat hepatocytes after LPS treatment is dependent, in part, on increased transcription. In vitro and in vivo experiments indicated that interleukin-1beta and/or tumor necrosis factor alpha participate in the upregulation of CD14 mRNA levels in hepatocytes. Our data indicate that hepatocytes express CD14 and that hepatocyte CD14 mRNA and protein levels increase rapidly during endotoxemia. Our observations also support the idea that soluble CD14 is an acute-phase protein and that hepatocytes could be a source for soluble CD14 production.

Animals↗
PubMed1998

Recognition of herpes simplex virus type 2 tegument proteins by CD4 T cells infiltrating human genital herpes lesions.

The local cellular immune response to herpes simplex virus (HSV) is important in the control of recurrent HSV infection. The antiviral functions of infiltrating CD4-bearing T cells may include cytotoxicity, inhibition of viral growth, lymphokine secretion, and support of humoral and CD8 responses. The antigens recognized by many HSV-specific CD4 T cells localizing to genital HSV-2 lesions are unknown. T cells recognizing antigens encoded within map units 0. 67 to 0.73 of HSV DNA are frequently recovered from herpetic lesions. Expression cloning with this region of DNA now shows that tegument protein VP22 and the viral dUTPase, encoded by genes UL49 and UL50, respectively, are T-cell antigens. Separate epitopes in VP22 were defined for T-cell clones from each of three patients. Reactivity with the tegument protein encoded by UL21 was identified for an additional patient. Three new epitopes were identified in VP16, a tegument protein associated with VP22. Some tegument-specific CD4 T-cell clones exhibited cytotoxic activity against HSV-infected cells. These results suggest that herpes simplex tegument proteins are processed for antigen presentation in vivo and are possible candidate compounds for herpes simplex vaccines.

Amino Acid Sequence↗
PubMed1998

Effects of species raw material source, ash content, and processing temperature on amino acid digestibility of animal by-product meals by cecectomized roosters and ileally cannulated dogs.

We conducted experiments to determine amino acid (AA) digestibility of nine animal by-product meals using precision-fed cecectomized roosters and ileally cannulated dogs. The products initially evaluated in roosters were meat and bone meals (MBM) containing 24 or 34% ash, poultry by-product meals (PBP) containing 7 or 16% ash, lamb meals (LM) containing 15 or 24% ash, a LM analog containing a mixture of LM and turkey meal, and two MBM processed at either a low or high temperature. The MBM and PBP differing in ash, low-ash LM, and low-temperature MBM then were incorporated into extruded dry dog foods and evaluated in cecectomized roosters and ileally cannulated dogs. True digestibility of total AA in roosters averaged 76% for the nine meals fed alone, with the low-temperature MBM being highest at 84% and the low-ash LM being lowest at 66% (P < .05). No consistent differences in rooster AA digestibility were observed between pairs of meals differing in ash content. Digestibilities of AA were higher in the low-temperature MBM than in the high-temperature MBM. Differences in rooster AA digestibility values among the six extruded dog foods containing selected animal meals were similar to those observed when the animal meals were fed alone. The ileally cannulated dog assay yielded results for AA digestibilities that were highly correlated (r = .87 to .92) with those of the rooster assay, whereby the high-ash MBM and low-temperature MBM foods had the highest mean AA digestibility at 82% and the low-ash LM food had the lowest mean AA digestibility at 62% (P < .05). Again, no consistent differences in AA digestibilities for dogs were observed between pairs of dog foods containing MBM or PBP differing in ash content. Results of this study indicated that processing temperature influenced AA digestibility of MBM, but species raw material source and ash content had no consistent effect on AA digestibility. Results also indicated that the precision-fed cecectomized rooster assay could be used to predict differences in AA digestibility among animal by-product meals for dogs.

Amino Acids↗
PubMed1998

Statistically accurate estimation of hormone concentrations and associated uncertainties: methodology, validation, and applications.

We describe a data reduction procedure to assign statistically accurate estimates of unknown hormone concentrations, with associated uncertainties, based on experimental uncertainties in sample replicates and the fitted calibration curve. Three mathematical calibration curve functions are considered. The one providing optimal statistical characterization of reference calibrators is chosen for unknown evaluation. Experimental error is addressed by assigning and propagating uncertainty estimates for each measured response (including zero-dose responses) by an empirically determined discrete uncertainty profile and by propagating calibration curve uncertainty. Discrete uncertainty profiles account for both response precision (replicability) and accuracy (deviation from predicted calibration curves) without relying on assumed theoretical response variance-assay response relations. The validity of assigning variable response weighting by this procedure was assessed by Monte Carlo simulations based on chemiluminescence growth hormone calibration curves. Much-improved accuracy and estimated precision are achieved for unknown hormone concentrations, particularly extremely low concentrations, by using this variable response weighting procedure.

Data Interpretation, Statistical↗
PubMed1997

Paramyxovirus fusion (F) protein and hemagglutinin-neuraminidase (HN) protein interactions: intracellular retention of F and HN does not affect transport of the homotypic HN or F protein.

To investigate a possible intracellular coassociation of the paramyxovirus simian virus 5 (SV5) and human parainfluenza virus type 3 (HPIV-3) fusion (F) and hemagglutinin-neuraminidase (HN) glycoproteins in a living cell, without resorting to chemical crosslinking and antibody coimmunoprecipitation, we tagged the cytoplasmic N-terminus of SV5 HN with a RRRRR motif and HPIV-3 HN with a RRR motif for endoplasmic reticulum (ER) retention. In addition, we tagged the cytoplasmic C-terminus of SV5 and HPIV-3 F with a KK motif. The RRR- or RRRRR-tagged HN molecules were coexpressed in mammalian cells together with the homologous wt F proteins, and the KK-tagged F molecules were coexpressed with the homologous wt HN proteins, and in each case the transport of the wt F or HN molecules was investigated. The data suggest that an association of F and HN of sufficient affinity to alter the transport of the reporter molecule does not occur intracellularly in the ER or the Golgi apparatus.

Biological Transport↗
PubMed1997

Alcohol metabolism in Asian-American men with genetic polymorphisms of aldehyde dehydrogenase.

BACKGROUND: About half of certain Asians have a deficiency of the low-Km aldehyde dehydrogenase (ALDH2) isoenzyme. This deficiency results from inheritance of a mutant ALDH2*2 allele. OBJECTIVE: To determine whether Asian Americans with ALDH2*2 alleles differ from Asian Americans without this mutation in terms of blood levels of alcohol and acetaldehyde after ingestion of a moderate amount of alcohol. DESIGN: Double-blind, crossover study. SETTING: Private research institute. PARTICIPANTS: 35 healthy Asian-American men. Three men who became ill after alcohol ingestion and one who had outlying data were excluded. INTERVENTION: Alcoholic beverage, containing 0.56 g of alcohol per kg of body weight, or placebo beverage, containing 3 mL of alcohol, given orally on separate occasions. MEASUREMENTS: Blood levels of alcohol and acetaldehyde measured before and several times after ingestion of the alcoholic or placebo beverage. RESULTS: Participants with ALDH2*2 alleles had significantly higher blood acetaldehyde levels after ingesting alcoholic and placebo beverages than did participants with ALDH2*1 alleles, despite similar blood alcohol concentrations. CONCLUSIONS: Blood acetaldehyde levels rather than blood alcohol concentration may mediate enhanced alcohol sensitivity among Asians with ALDH2*2 alleles.

Acetaldehyde↗
PubMed1997

Preferential presentation of herpes simplex virus T-cell antigen by HLA DQA1*0501/DQB1*0201 in comparison to HLA DQA1*0201/DQB1*0201.

The HLA DQA1 locus is polymorphic. Haplotypes containing HLA DQA1*0501, but not HLA DQA1*0201, together with HLA DQB1*0201 are associated with Grave's disease and celiac sprue. In this report, we demonstrate a functional correlate of DQA1 polymorphism. T cells infiltrating a herpes simplex virus (HSV) lesion from a HLA DQ 2,7 individual yielded a virus-specific CD4+ clone restricted by DQ2. Presentation of viral peptide and protein segregated with DQA1 allele, because cell lines bearing DQA1*0501/DQB1*0201 heterodimers presented antigen in proliferation and cytotoxicity assays much more efficiently than cell lines bearing DQA1*0201/DQB1*0201. Binding of viral peptide to cell lines bearing DQA1*0201, in comparison to DQA1*0501, was only moderately reduced and may not explain this effect. Truncation and substitution analyses of peptide binding and T-cell activation were performed to determine which viral peptide residues contacting TCR might therefore be presented in an altered conformation by DQA1*0201/DQB1*0201. Residues 432, 435, 437, 438, and 440 (position P1, P4, P6, P7, and P9) contributed to DQ2 binding, whereas residues 431, 433, 434, and 436 (positions P 1, P2, P3, and P5) contributed to TCR contact. Differential presentation of peptide by HLA DQ2 heterodimers varying at the DQA1 locus may have relevance to host defense and the pathogenesis of HLA DQ2-associated autoimmune diseases.

Alleles↗