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B Davis

Publications and source records attributed to B Davis.

At least 109 records · Page 6Linked to original sources
PubMed1996

Determination of benzidine, N-acetylbenzidine, and N,N'-diacetylbenzidine in human urine by capillary gas chromatography/negative ion chemical ionization mass spectrometry.

We report an isotope dilution mass spectrometry method using capillary gas chromatography/negative ion chemical ionization to quantitate urine concentrations of benzidine (BZ) and of its acetylated metabolites N-acetylbenzidine (ABZ) and N,N'-diacetylbenzidine (DABZ). Urine samples were purified by solid-phase extraction columns, reduced with LiAlH4/THF, and derivatized with pentafluoropropionic anhydride. The derivatives were measured by selected ion monitoring relative to deuterium-labeled internal standards. A detection limit as low as 0.5, 0.8, and 1.5 ppt for BZ, ABZ, and DABZ, respectively, can easily be achieved. Urinary concentrations of ABZ substantially exceed those of either BZ or of DABZ in workers exposed to BZ or BZ-based dyes. This method has been successfully used to measure BZ, ABZ, and DABZ in 1.0-ml urine samples collected from workers involved in manufacturing BZ and BZ-based dyes. The method should be applicable to the measurement of other aromatic amines and their acetylated metabolites.

Benzidines↗
PubMed1996

Hematopoietic transcriptional regulation by the myeloid zinc finger gene, MZF-1.

Transcriptional regulators control much of hematopoiesis. One such transcriptional regulator is the myeloid zinc finger gene MZF-1. MZF-1 has been localized to the telomere of chromosome 19q, where a large number of related zinc finger genes reside. It has been found to be essential in granulopoiesis. It is a bi-functional transcriptional regulator, repressing transcription in non-hematopoietic cells, and activating transcription in cells of hematopoietic origins. Its consensus DNA binding site has been isolated, and sites in several promoters of myeloid-specific genes, such as CD34, lactoferrin, and myeloperoxidase, have been defined. In co-transfection experiments MZF-1 has been found to regulate transcription from the CD34 promoter.

Base Sequence↗
PubMed1996

The association among gastric mucosal pH, endotoxemia, and low systemic vascular resistance after cardiopulmonary bypass.

OBJECTIVE: Previously, it was found that a number of patients suffer a "low systemic vascular resistance syndrome" after cardiopulmonary bypass, and this was hypothesized to be secondary to endotoxemia, resulting from intestinal ischemia during bypass. DESIGN: Prospective cohort. SETTING: University teaching hospital. PARTICIPANTS: Thirty-two patients undergoing cardiac surgery. INTERVENTIONS: A number of variables relating to adequacy of tissue perfusion were measured at seven time periods perioperatively: cardiac output, systemic vascular resistance, oxygen delivery and consumption, oxygen extraction ratio, gastric mucosal pH, serum lactate, and endotoxin levels. MEASUREMENTS AND MAIN RESULTS: Investigators could not find any association between systemic vascular resistance and mucosal pH or endotoxin levels after bypass. There were significant changes in oxygen flux and extraction ratio (p < 0.001) as well as serum lactate (p < 0.001). There was no significant change in endotoxin levels or mucosal pH. The systemic vascular resistance at 6 hours postbypass could be predicted from the vascular resistance reading at 1 hour postbypass by a regression equation. A significant correlation between systemic vascular resistance and mixed venous oxygen was found at 4 and 6 hours postbypass (p < 0.01) as well as with oxygen extraction (p < 0.01). There was a negative correlation between mucosal pH and serum lactate, particularly at 6 hours postbypass (p < 0.01). There was no correlation between mucosal pH and endotoxin levels, oxygen flux, or cardiac output. CONCLUSIONS: The investigators therefore could not find any evidence that intestinal ischemia during bypass, as measured by gastric mucosal pH, predisposes to endotoxemia, or low systemic vascular resistance after cardiac surgery.

Adult↗
PubMed1996

Towards the complete structural characterization of a protein folding pathway: the structures of the denatured, transition and native states for the association/folding of two complementary fragments of cleaved chymotrypsin inhibitor 2. Direct evidence for a nucleation-condensation mechanism.

BACKGROUND: Single-module proteins, such as chymotrypsin inhibitor 2 (CI2), fold as a single cooperative unit. To solve its folding pathway, we must characterize, under conditions that favour folding, its denatured state, its transition state, and its final folded structure. To obtain a "denatured state' that can readily be thus characterized, we have used a trick of cleaving CI2 into two complementary fragments that associate and fold in a similar way to intact protein. RESULTS: Fragment CI2(1-40)-which contains the sequence of the single alpha-helix, spanning residues 12-24-and CI2(41-64), and mutants thereof, were analyzed by NMR spectroscopy, the transition state for association/folding was characterized by the protein engineering method, and the structure of the complex was solved by NMR and X-ray crystallography. Both isolated fragments are largely disordered. The transition state for association/folding is structured around a nucleus of a nearly fully formed alpha-helix, as is the transition state for the folding of intact CI2, from residues Ser12 to Leu21, Ala16, a residue from the helix whose sidechain is buried in the hydrophobic core, makes interactions with Leu49 and Ile57 in the other fragment. Ala16 makes its full interaction energy in the transition state for the association/folding reaction, just as found during the folding of the intact protein. CONCLUSIONS: The specific contacts in the transition state from a nucleus that extends from one fragment to the next, but the nucleus is only "flickeringly' present in the denatured state. This is direct evidence for the nucleation-condensation mechanism in which the nucleus is only weakly formed in the ground state and develops in the transition state. The low conformational preferences in the denatured state are not enough to induce significant local secondary structure, but are reinforced by tertiary interactions during the rapid condensation around the nucleus.

Amino Acid Sequence↗
PubMed1996

A novel hypothalamic peptide, pituitary adenylate cyclase-activating peptide, regulates the function of rat granulosa cells in vitro.

Pituitary adenylate cyclase-activating peptide (PACAP) is a novel peptide that was isolated from ovine hypothalamic tissue on the basis of its ability to stimulate cAMP accumulation in cultured rat pituitary cells. Recently we demonstrated that PACAP can stimulate cAMP accumulation and secretory function in cultured rat Sertoli cells. Since ovarian granulosa cells share many properties with Sertoli cells, we have examined the effect of PACAP (consisting of 38 or 27 amino acid residues) on cultured granulosa cell function. Granulosa cells were obtained from the ovaries of 25-day-old rats implanted with a silastic capsule containing diethylstilbestrol 5 days prior to culture. PACAP 38 (0.1 microM-0.01 pM), both alone and in the presence of the phosphodiesterase inhibitor, methylisobutylxanthine, stimulated cAMP accumulation 4-8-fold with an ED50 of approximately 100 pM. Maximal PACAP 38 or PACAP 27 stimulation of granulosa cell cAMP was significantly greater than that produced by a maximally effective concentration of FSH. Because PACAP 38 and 27 have 68% sequence homology with vasoactive intestinal peptide (VIP), and since VIP stimulates granulosa cell cAMP accumulation and estradiol and progesterone secretion, we examined the possibility that PACAP could be acting via the VIP receptor. VIP stimulated cAMP only at concentrations of 10 nM or greater, whereas the PACAP stimulation was evident at 10 pM. Moreover, only one of three potent VIP antagonists inhibited VIP stimulation of cAMP accumulation, and only at 1 microM or greater. This VIP antagonist did not inhibit PACAP 38 action at 2000-fold excess concentration. Interestingly PACAP 38 was more effective than PACAP 27 with regard to steroid secretion and the ability to induce LH responsiveness. PACAP and VIP stimulation of granulosa cell cAMP accumulation or estradiol or progesterone secretion was not additive. Thus, these data support the hypothesis that granulosa cells have specific PACAP 38 receptors and that VIP acts via these receptors. In addition, PACAPs 38 and 27 are more potent stimulators of cAMP accumulation in luteinized granulosa cells than LH. These results both pre- and postovulation, along with previous data indicating that the PACAPs are found in the ovaries, suggest a role for PACAP in the regulation of ovarian function.

1-Methyl-3-isobutylxanthine↗
PubMed1996

Illness experiences and health recovery behaviors of patients in southern Appalachia.

The purpose of this exploratory study was to gain a better understanding of the influences of Appalachian culture and rural living on illness experiences and health recovery behaviors. The study sample consisted of 257 randomly selected adult patients admitted to medical-surgical units in eight hospitals in West Virginia. Patients completed interviews in the hospital and by phone and in their homes 1 month after hospital discharge. In addition, 203 nurses and 79 physicians completed a values survey and decisional control questions. The triangulation of quantitative and qualitative data suggested that culture, age, gender, and rural residence affected responses to illness and recovery. Traditional values and roles persisted in this population and influenced health behaviors. The findings of this study support the need for culturally sensitive care and for innovative education programs to reduce health risks.

Adaptation, Psychological↗
PubMed1996

Restructuring dermatology education at Cleveland medical centers affiliated with Case Western Reserve University.

We describe our response to the changing needs for dermatologic education and training at Cleveland medical centers affiliated with Case Western Reserve University School of Medicine (CWRU) located in Cleveland, Ohio. Our departmental plan for change is a multifaceted approach that alters the number of dermatology residents we train and also the way we interact with and educate our generalist colleagues. Like many other dermatologists, we have both idealistic and practical reasons for increasing our involvement in interdisciplinary education. One of our primary objectives is maximizing quality of care for dermatologic patients in our community. Traditionally, the majority of skin care in the United States has been provided by nondermatologists, and with the growth of managed care, this proportion is increasing. This has motivated us to increase our medical student teaching activities and to support the American Academy of Dermatology in its current efforts to develop a dermatology core curriculum for students. We should also be involved in the education of generalist physicians, since prior studies have suggested that their knowledge of dermatology needs improvement. Our goals should be both to improve the direct patient care skills of primary care physicians and to teach clinically appropriate referral thresholds. The American Academy of Dermatology has recently issued guidelines for the referral of dermatology patients in managed care settings to help ensure that our specialty has input into this process. In addition, teaching gatekeeper physicians to use appropriate referral criteria is important to many dermatologists in capitated managed care systems who often prefer limited as opposed to unrestricted access to their services.

Curriculum↗
PubMed1996

Effects of azathioprine withdrawal in kidney recipients with stable function two years after transplant.

To assess the effects of azathioprine withdrawal, renal recipients with grafts > 2 yr function (103 study patients) were tapered off azathioprine over a 1-yr period and compared to 69 patients 2 yr after transplant who were not tapered (controls). Of the 103 study patients, 16 (15%) were living-donor transplants and 87 were cadaveric. Of the 69 control patients, 9 (13%) were living related transplants and 60 were cadaveric. The mean HLA match for those tapered was 3.3 Ag and 3.1 Ag for those remaining on azathioprine. Two study patients restarted azathioprine on their own. Age, sex, and cause of renal failure in both groups was similar. Of the 101 study patients remaining, 9 (8.8%) returned to dialysis due to biopsy proven chronic rejection. There were no acute rejection episodes. Six of the 69 control patients (8.7%) also returned to dialysis for the same reason. Of the 92 patients who have completed the taper, 85 have been off azathioprine for six or more months. There was not a significant difference between the mean 12- and 24-month creatinine levels of the study patients (1.6 mg%, 1.7 mg%) and those of the controls (1.5 mg%, 1.8 mg%). The mean 12- and 24-month hematocritis of patients tapered (41.3%, 40.8%) were comparable with patients not tapered (42.3%, 42.8%). Of interest, the mean hematocritis of both study and control patients rose from 28.9% and 33.5%, respectively, to 41.3% and 42.3% 1 yr following entry into the study. The mean 12- and 24-month white blood counts of those tapered (8.9, 8.7) did not differ significantly from those continued on azathioprine (8.8, 8.8). In stable renal transplant patients on triple drug immunosuppression for at least 2 yr, azathioprine can be discontinued, in a tapered protocol, without an increased risk of graft loss or compromise of renal function.

Azathioprine↗
PubMed1995

Perturbed pKA-values in the denatured states of proteins.

We show in this study that the ionisation equilibria of denatured proteins in pure water are inconsistent with the "fully-unfolded" conformation being an extended coil where the residues are isolated from one another by the intervening solvent. The effects of acid and salt on the stability of the barley chymotrypsin inhibitor 2 (CI2) were investigated and the pKA-values of all carboxylate residues in the native protein were determined by NMR. A comparison of the experimentally determined pH-dependence of the protein stability and that calculated using observed pKA-values in the native state, reveals that the pKA-values in the denatured state are, on average, 0.3 pH units lower than those of model compounds. An increase in ionic strength eliminates these pKA shifts in the denatured state. This shows that there are electrostatic interactions in the denatured state of CI2. Since previous studies on barnase and the Ovomucoid Third Domain also report anomalous titration behaviours of the denatured states, it appears that perturbed pKA-values in the denatured state is a general phenomenon, indicating that the unfolded conformation in pure water is a fairly compact species. In addition, we used a mutational approach to determine the pKA-values of a carboxylate group in both the native and denatured states. The pKA-value in the native state obtained by this method is in precise agreement with that obtained by NMR.

Hydrogen-Ion Concentration↗
PubMed1995

The myeloid zinc finger gene, MZF-1, regulates the CD34 promoter in vitro.

MZF-1 is a C2H2 zinc finger gene encoding a putative transcriptional regulator of myeloid differentiation. The MZF-1 protein contains 13 C2H2 zinc fingers arranged in bipartite DNA binding domains containing zinc fingers through 4 and, in the carboxy-terminus, 5 through 13. We previously identified the DNA consensus binding site recognized by the two DNA binding domains. To assess the transcription regulatory function of MZF-1, the full-length MZF-1 coding region was fused to the DNA binding domain of the yeast transactivator GAL4. The expression vector was cotransfected with the chloramphenicol acetyl transferase (CAT) reporter gene regulated by the thymidine kinase promoter containing GAL4 DNA binding sites into NIH 3T3, 293, K562, and Jurkat cell lines. MZF-1 represses CAT reporter gene expression via GAL4 binding sites in the nonhematopoietic cell lines NIH 3T3 and 293. In contrast, MZF-1 activates CAT reporter gene expression in the hematopoietic cell lines K562 and Jurkat. The MZF-1 binding sites are present in the promoters of several genes expressed during myeloid differentiation, including the CD34 promoter. MZF-1 transcriptional regulation of this physiologically relevant promoter was assessed in both hematopoietic and nonhematopoietic cell lines. Recombinant MZF-1 protein specifically binds to the consensus binding sites in the CD34 promoter in mobility shift assays. MZF-1 expression vectors were cotransfected with the luciferase reporter plasmids regulated by the CD34 promoter into both nonhematopoietic and hematopoietic cell lines. As with the heterologous DNA binding domain, MZF-1 represses reporter gene expression in nonhematopoietic cell lines and activates expression in hematopoietic cell lines. Activation of CD34 expression in hematopoietic cell lines is dependent on the presence of intact MZF-1 binding sites. The cell type-specific regulation of the CD34 promoter by MZF-1 suggests the presence of tissue-specific regulators/adapters or differential MZF-1 modifications that determine MZF-1 transcriptional regulatory function.

3T3 Cells↗
PubMed1995

Physical working capacity after acute myocardial infarction in patients with low ejection fraction and effect of captopril.

Previous studies after acute myocardial infarction (AMI) have reported conflicting results on the effects of angiotensin-converting enzyme inhibition on physical working capacity. In an effort to provide more insight into this subject, we examined the effects of captopril on working capacity of patients who had low ejection fractions but no congestive heart failure after AMI. One hundred sixty-six participants were recruited from 5 centers after randomization to either captopril or placebo for the Survival and Ventricular Enlargement study. Upright cycle ergometer tests were performed with continuous measurements of respiratory gases at 4, 12, and 24 months after AMI. Our study concurs with 2 of 3 previous post-AMI studies and supports the conclusion that working capacity is not affected by angiotensin-converting enzyme inhibition at 4 or 12 months after AMI in patients without congestive heart failure. In addition, no significant effect of captopril was noted at 24 months after AMI. Peak oxygen uptake tended to decrease between 12 and 24 months in the placebo group by an average (+/- SD) of -22 +/- 322 ml/min (n = 66), but to increase in the captopril group (+62 +/- 289, n = 57), a difference that was significant (Mann-Whitney chi-square, p = 0.02). This post-hoc observation suggests that a late beneficial effect may have been masked by inadequate study duration. Known benefits of captopril appear not to include an increase in working capacity within the first 24 months after AMI.

Aged↗
PubMed1995

Backbone dynamics of chymotrypsin inhibitor 2: effect of breaking the active site bond and its implications for the mechanism of inhibition of serine proteases.

The backbone dynamics of uniformly 15N-labeled chymotrypsin inhibitor 2 (CI2) and of the complex formed by the association of two fragments consisting of residues 20-59 and 60-83 have been studied. A data set consisting of 15N longitudinal (T1) and transverse (T1 rho) relaxation times and (1H)-15N NOE enhancements has been measured for all backbone NH groups in both proteins. Information on internal motions has been extracted from these data using the model-free approach to determine order parameters (S2) and effective internal correlation times (tau e). The data indicate that most of the backbone of CI2 is highly constrained (S2 approximately 0.9) with the exception of residues in the binding loop (residues 54-64), which have slightly lower order parameters. Most of the residues in the CI2(20-59).(60-83) complex are also highly constrained (S2 approximately 0.9). However, the loss of the covalent bond between Met59 and Glu60 leads to a large increase in the mobility of residues in the loop region. The residues in the first half of the loop region have significantly lower order parameters than those in the second half of the loop. This observation suggests that the NH2 group that is released on cleavage of the scissile bond remains anchored in its original position, inhibiting the attack of water on the acyl-enzyme that is formed between the protease and the cleaved inhibitor. More importantly, the NH2 group is optimally placed for reversing the formation of the acyl-enzyme so that the equilibrium between the cleaved and uncleaved inhibitor, bound to the protease, greatly favors the uncleaved complex.

Amino Acid Sequence↗
PubMed1995

Outbreak of HIV infection in a Scottish prison.

OBJECTIVE--To investigate the possible spread of HIV infection and its route of transmission among prison inmates. DESIGN--In response to an outbreak of acute clinical hepatitis B and two seroconversions to HIV infection, counselling and testing for HIV were offered to all inmates over a two week period in July 1993. Information was sought about drug injecting, sexual behaviour, and previous HIV testing. SETTING--HM Prison Glenochil in Scotland. SUBJECTS--Adult male prisoners. MAIN OUTCOME MEASURES--Uptake of HIV counselling and testing; occurrence and mode of HIV transmission within the prison. RESULTS--Of a total 378 inmates, 227 (60%) were counselled and 162 (43%) tested for HIV. Twelve (7%) of those tested were positive for antibody to HIV. One third (76) of those counselled had injected drugs at some time, of whom 33 (43%) had injected in Glenochil; all 12 seropositive men belonged to this latter group. Thirty two of these 33 had shared needles and syringes in the prison. A further two inmates who injected in the prison were diagnosed as positive for HIV two months previously. Evidence based on sequential results and time of entry into prison indicated that eight transmissions definitely occurred within prison in the first half of 1993. CONCLUSION--This is the first report of an outbreak of HIV infection occurring within a prison. Restricted access to injecting equipment resulted in random sharing and placed injectors at high risk of becoming infected with HIV. Measures to prevent further spread of infection among prison injectors are urgently required.

Adult↗
PubMed1995

Factors that influence the provision of sexual health care by Dutch cancer nurses.

A descriptive-correlational design was used with a sample of Dutch cancer nurses (n = 104) to describe provision of sexual health care (SHC) and to explore influential factors. This report is limited to the second goal. The Theory of Reasoned Action provided the conceptual framework for investigation of five previously identified factors and one unexplored factor. Knowledge, comfort, attitude (towards sexuality) and subjective norm were significantly related with provision of SHC. Multiple regression analysis demonstrated that knowledge and comfort were significant explanatory variables, accounting for 37% of the variance.

Adult↗