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Biomedical subjects

P Alexander

Publications and source records attributed to P Alexander.

At least 19 recordsLinked to original sources
PubMed2003

Lupus headaches in childhood-onset systemic lupus erythematosus: relationship to disease activity as measured by the systemic lupus erythematosus disease activity index (SLEDAI) and disease damage.

The Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) is the most commonly used measure of disease activity for children with systemic lupus erythematosus (SLE). For headaches to be scored in the SLEDAI as a symptom of active disease, they have to be nonresponsive to narcotic analgesia. This may affect the overall estimation of disease activity, especially because headaches are common among children with SLE and narcotic analgesia is rarely used for headache therapy in paediatrics. Moreover, the importance of headaches for the development of damage and their relation to other clinical parameters and outcomes has not been well described for children with SLE. We reviewed the medical charts of an inception cohort of children (n = 63) who were newly diagnosed with SLE. Information on headaches and other disease parameters was obtained. Disease activity and damage were measured using the SLEDAI and the Systemic Lupus International Collaboration Clinics/American College of Rheumatology Damage Index (SDI), respectively. It has been shown that the accumulated burden of active disease as measured by serial SLEDAI scores over time is one of the best predictors of eventual damage to children with SLE. New-onset or significant increase of severe and/or persistent headaches (LHA) were reported in 43% of the patients during a mean follow-up of 3.6 years. LHA occurred preferentially among patients with elevated levels of antiphospholipid antibodies (aPL) (P < 0.02) and only 6% of all LHA episodes were treated with narcotics and thus considered for the measurement of disease activity in the SLEDAI. LHA were unrelated to proxy-measures of disease activity, such as the need to intensify therapies. When used in children, the insensitivity of the SLEDAI to capture LHA did not seem to decrease the responsiveness of the SLEDAI to detect clinically important worsening of disease, or negatively impact on its ability to predict damage.

Adolescent↗
PubMed2001

Stability and global fold of the mouse prohormone convertase 1 pro-domain.

We have purified the mouse prohormone convertase 1 (PC1) pro-domain expressed in Escherichia coli cells and demonstrated, using a number of biophysical methods, that this domain is an independent folding unit with a T(m) of 39 degrees C at a protein concentration of 20 microM and pH 7.0. This differs significantly from similar pro-domains in bacteria and human furin, which are unfolded at 25 degrees C and require the catalytic domain in order to be structured [Bryan et al. (1995) Biochemistry 34, 10310-10318; Bhattacharjya et al. (2000) J. Biomol. NMR 16, 275-276]. Using heteronuclear NMR spectroscopy, we have determined the backbone (1)H, (13)C, and (15)N assignments for the pro-domain of PC1. On the basis of (1)H/(13)C chemical shift indices, NOE analysis, and hydrogen exchange measurements, the pro-domain is shown to consist of a four-stranded beta-sheet and two alpha-helices. The results presented here show that both the bacterial pro-domain in complex with subtilisin and the uncomplexed mouse PC1 pro-domain have very similar overall folds despite a lack of sequence homology. The structural data help to explain the location of the secondary processing sites in the pro-domains of the PC family, and a consensus sequence for binding to the catalytic domain is proposed.

Amino Acid Sequence↗
PubMed2001

Lymph nodes in the human female breast: a review of their detection and significance.

Our experience led us to test the hypothesis that lymph nodes are not uncommon within the substance of the human female breast mound. The following specimen types and sources were used to survey the presence of intramammary lymph nodes in the human female breast mound: (1) cadaver breasts; (2) community hospital breast specimens; and (3) university and VA hospital specimens. We found true lymph nodes within and associated with breast specific tissue (ie, tissue that includes duct and gland structures), thereby validating the hypothesis posed. We discuss the significance of these findings in terms of our dominant patient care paradigm (the Triple Test-physical examination, imaging, and fine-needle aspiration [FNA]) and the choice of patient care management options. We conclude the following: lymph nodes occur in any quadrant of the breast mound; recognizing the possibility of intramammary lymph nodes is important when choosing between patient management options; intramammary lymph nodes can be sampled by FNA; intramammary lymph nodes can contain various disease processes; and in the Oregon Health Sciences University Multidisciplinary Breast Clinic, these intramammary lymph nodes are commonly identified by imaging methods and are more likely to be sampled by FNA than either by core or excisional biopsy.

Adult↗
PubMed2001

Bordetella pertussis autoregulates pertussis toxin production through the metabolism of cysteine.

Pertussis toxin (Ptx) expression and secretion in Bordetella pertussis are regulated by a two-component signal transduction system encoded by the bvg regulatory locus. However, it is not known whether the metabolic pathways and growth state of the bacterium influence synthesis and secretion of Ptx and other virulence factors. We have observed a reduction in the concentration of Ptx per optical density unit midway in fermentation. Studies were conducted to identify possible factors causing this reduction and to develop culture conditions that optimize Ptx expression. Medium reconstitution experiments demonstrated that spent medium and a fraction of this medium containing components with a molecular weight of <3,000 inhibited the production of Ptx. A complete flux analysis of the intermediate metabolism of B. pertussis revealed that the sulfur-containing amino acids methionine and cysteine and the organic acid pyruvate accumulated in the media. In fermentation, a large amount of internal sulfate (SO4(2-)) was observed in early stage growth, followed by a rapid decrease as the cells entered into logarithmic growth. This loss was later followed by the accumulation of large quantities of SO4(2-) into the media in late-stage fermentation. Release of SO4(2-) into the media by the cells signaled the decoupling of cell growth and Ptx production. Under conditions that limited cysteine, a fivefold increase in Ptx production was observed. Addition of barium chloride (BaCl2) to the culture further increased Ptx yield. Our results suggest that B. pertussis is capable of autoregulating the activity of the bvg regulon through its metabolism of cysteine. Reduction of the amount of cysteine in the media results in prolonged vir expression due to the absence of the negative inhibitor SO4(2-). Therefore, the combined presence and metabolism of cysteine may be an important mechanism in the pathogenesis of B. pertussis.

Adenylate Cyclase Toxin↗
PubMed2001

Quantification of the size of primary spontaneous pneumothorax: accuracy of the Light index.

BACKGROUND: The size of a pneumothorax (PTX) is usually estimated by the Light index. Treatment strategies of (primary, spontaneous) PTX partially depend upon the size of the PTX. To our knowledge, the Light index has not yet been correlated with the actual volume of the PTX. OBJECTIVES: To correlate the estimated size of a primary spontaneous PTX by means of the Light index, with the actual amount of air present in the pleural space. METHODS: Actual PTX volumes were measured by means of manual aspiration of air present in the pleural space in 18 patients with primary spontaneous PTX and correlated with the size estimation obtained by the Light index. RESULTS: Light index and volume measurements were strongly correlated (r = 0.84, p < 0.0001). CONCLUSIONS: The Light index is a good estimate of the actual size of a (primary spontaneous) PTX.

Adolescent↗
PubMed2001

Reduced length of stay by implementation of a clinical pathway for bariatric surgery in an academic health care center.

Bariatric surgery is being performed in increasing numbers in an era when reimbursements are being reduced. Academic health centers bear the responsibility for training surgeons to perform these operations yet must keep costs to a minimum and retain high quality. The UCLA Bariatric Surgery Program developed a clinical pathway for the pre- and postoperative management for gastric bypass patients to achieve these goals. Medical records for 182 consecutive gastric bypass patients were retrospectively reviewed before implementation of the pathway (Group I) during the fiscal year of 1998/1999. Data on average length of stay, average intensive care unit length of stay, average standard variable cost, percentage readmission rate, and percentage return to the operating room were collected. This information was compared with the data collected prospectively from 182 patients after implementation of the pathway in July of 1999 (Group II) during the fiscal year of 1999/2000. Hospital cost per admission was reduced by 40 per cent in Group II compared with Group I (P < 0.02). The average length of stay was reduced from 4.05 days in Group I to 3.17 days in Group II (P < 0.033). Overall readmission rate was decreased from 4.2 per cent in Group I to 3.2 per cent in Group II (P < 0.05). There were no differences in morbidities between both groups. The pathway reduced costs by reducing the hospital length of stay, intensive care unit utilization, and readmission rates. Quality was maintained as evidenced by a similar pattern of postoperative morbidities yet readmission rates were reduced. Our results indicate that implementation of a clinical pathway for bariatric surgery reduces cost and improves quality of care in an academic institution.

Academic Medical Centers↗
PubMed2000

Structure and dynamics of an acid-denatured protein G mutant.

NMR studies of protein denatured states provide insights into potential initiation sites for folding that may be too transient to be observed kinetically. We have characterized the structure and dynamics of the acid-denatured state of protein G by using a F30H mutant of G(B1) which is on the margin of stability. At 5 degrees C, F30H-G(B1) is greater than 95% folded at pH 7.0 and is greater than 95% unfolded at pH 4.0. This range of stability is useful because the denatured state can be examined under relatively mild conditions which are optimal for folding G(B1). We have assigned almost all backbone (15)N, H(N), and H(alpha) resonances in the acid-denatured state. Chemical shift, coupling constant, and NOE data indicate that the denatured state has considerably more residual structure when studied under these mild conditions than in the presence of chemical denaturants. The acid-denatured state populates nativelike conformations with both alpha-helical and beta-hairpin characteristics. To our knowledge, this is the first example of a denatured state with NOE and coupling constant evidence for beta-hairpin character. A number of non-native turn structures are also detected, particularly in the region corresponding to the beta1-beta2 hairpin of the folded state. Steady-state ¿(1)H-(15)N¿ NOE results demonstrate restricted backbone flexibility in more structured regions of the denatured protein. Overall, our studies suggest that regions of the helix, the beta3-beta4 hairpin, and the beta1-beta2 turn may serve as potential initiation sites for folding of G(B). Furthermore, residual structure in acid-denatured F30H-G(B1) is more extensive than in peptide fragments corresponding to the beta1-beta2, alpha-helix, and beta3-beta4 regions, suggesting additional medium-to-long-range interactions in the full-length polypeptide chain.

Amino Acid Sequence↗
PubMed2000

Regulation of amyloid precursor protein processing by presenilin 1 (PS1) and PS2 in PS1 knockout cells.

The presenilin 1 (PS1) and PS2 proteins are thought to play roles in processing of amyloid precursor protein (APP), but the nature of this role is not fully understood. Recent studies have shown that PS1 is necessary for cleavage of APP at the gamma-secretase site. We now show that PS1 and PS2 participate in other aspects of APP processing. Fibroblasts generated from PS1 knockout mice have increased levels of the APP cleavage products, secreted APP (APPs), and APP C-terminal fragments, but lower secretion of APPs and Abeta. We have also observed that loss of PS1 prevents protein kinase C or extracellular regulated kinase from increasing production of the APP cleavage products, APPs, and APP C-terminal fragments. Transfection of PS1 -/- cells with PS1 restores the responsiveness of APP processing to protein kinase C and extracellular regulated kinase. This suggests that the changes in APP processing in PS1 -/- cells result strictly from the absence of PS1. Transfection of PS1 -/- cells with PS2 is also able to correct the deficits in APP secretion, which suggests that the PS2 also has the ability to regulate APP processing. Finally, transfection of the truncated PS2 construct, Alg3, into cells lacking PS1 increases APP C-terminal fragments. This suggests that Alg3 can interfere with the processing of APP by PS2. These data point to roles for both PS1 and PS2 in regulating APP processing and suggest that the role of these proteins also includes coupling APP to signal transduction pathways.

Amyloid Precursor Protein Secretases↗
PubMed1999

Hydrogen bonding and equilibrium protium-deuterium fractionation factors in the immunoglobulin G binding domain of protein G.

Protium-deuterium fractionation factors (phi) were determined for more than 85% of the backbone amide protons in the IgG binding domains of protein G, GB1 and GB2, from NMR spectra recorded over a range of H2O/D2O solvent ratios. Previous studies suggest a correlation between phi and hydrogen bond strength; amide and hydroxyl groups in strong hydrogen bonds accumulate protium (phi < 1), while weak hydrogen bonds accumulate deuterium (phi > 1). Our results show that the alpha-helical residues have slightly lower phi values (1.03 +/- 0.05) than beta-sheet residues (1.12 +/- 0.07), on average. The lowest phi value obtained (0.65) does not involve a backbone amide but rather is for the interaction between two side chains, Y45 and D47. Fractionation factors for solvent-exposed residues are between the alpha-helix and beta-sheet values, on average, and are close to those for random coil peptides. Further, the difference in phiav between alpha-helix and solvent-exposed residues is small, suggesting that differences in hydrogen bond strength for intrachain hydrogen bonds and amide...water hydrogen bonds are also small. Overall, the enrichment for deuterium suggests that most backbone...backbone hydrogen bonds are weak.

Amino Acid Sequence↗
PubMed1999

Complete biliary avulsion from blunt compression injury.

The liver is the solid organ most commonly injured as a result of blunt abdominal trauma. Complete avulsion of the common hepatic duct is a rare and devastating type of hepatobiliary trauma. Here the authors report the case of a 7-year-old child who had complete biliary disruption as a result of an abdominal crush injury that was not diagnosed correctly preoperatively. The intraoperative diagnosis and treatment of this injury is discussed.

Abdominal Injuries↗
PubMed1999

Continuous flow methods for evaluating the response of a copper ion selective electrode to total and free copper in seawater.

This work describes the development of an instrument for measuring free and total copper in seawater by continuous flow analysis (CFA) with an Orion copper (II) ion selective electrode (CuISE). Sample analysis times are reduced considerably by using an extrapolation technique based on the fitting of an empirical mathematical expression to the electrode time-response curve enabling a prediction of the final equilibrium potential. CuISE measurements in seawater samples containing nanomolar levels of total copper can be very time consuming, and this predictive approach significantly reduces sample analysis time, and improves sample throughput. The time taken to measure pCu in seawater to a precision of +/- 0.1, using conventional potentiometry, varies considerably depending on the condition of the electrode membrane but can be reduced by a factor of 3-6 (typically from 60 to 10 min) by using the extrapolation technique in conjunction with CFA. Details are given of the protocols used for preconditioning the CuISE. The system can be used as a portable instrument for field measurements or for shipboard measurements of free copper in seawater. Extrapolated equilibrium potentials are within +/- 0.5 mV of true steady state values.

Chemistry Techniques, Analytical↗
PubMed1998

The initial impact of rabbit hemorrhagic disease on European rabbit populations in South Australia.

The calicivirus agent for rabbit hemorrhagic disease (RHD) escaped from an island quarantine station to the Australian mainland in October 1995. Within 2 wk it was detected at an established field study site where wild European rabbits (Oryctolagus cuniculus) were being monitored in the Flinders Ranges National Park (South Australia, Australia). During November 1995, RHD reduced the rabbit numbers on the site by 95%. Approximately 3% of the population survived challenge by RHD and developed antibodies. Most of the antibody-positive survivors were 3- to 7-wk-old when challenged. Many rabbits died underground, but counts of rabbit carcasses found on the surface indicated that approximately 1 million rabbits had died above ground in the National Park, and that > 30 million rabbits may have died in adjacent areas during the November epidemic.

Age Distribution↗
PubMed1998

Sex work and health: a question of safety in the workplace.

Sex work is an occupation or trade involving exchange of sexual services for economic compensation. Although health problems associated with prostitution, such as sexually transmitted diseases and violence, are commonly assumed to be "risks of the trade," the illegality and stigma of prostitution have prevented the medical establishment from viewing it through the lens of occupational safety and health. They have also resulted in a failure to look at such day-to-day conditions and illnesses as repetitive stress injuries and other musculoskeletal problems, bladder infections, and work-related stress that may be of more immediate concern to sex workers. This paper reviews what is known about the safety and health hazards associated with prostitution through some formal research, but primarily through informal discussions with sex workers over two decades. The overarching factor affecting the health of sex workers is the legal context, thus that is reviewed first; then I look at occupational hazards and conclude with some suggestions for immediate action and further research.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Diverting loop versus end ileostomy during ileoanal pullthrough procedure for ulcerative colitis.

A two-stage ileoanal pullthrough procedure (IAPP) is often used for patients with ulcerative colitis (UC) requiring proctocolectomy. We analyzed the recent University of California at Los Angeles experience with diverting end and loop ileostomies in patients undergoing a two-stage IAPP. A retrospective analysis of 21 patients with UC undergoing loop ileostomy between March 1992 and March 1995 was performed. Comparison was made with 21 age- and gender-matched patients undergoing end ileostomy between January 1991 and December 1995. There was no mortality or major septic complications. A second laparotomy was required in all patients with end ileostomies, whereas loop ileostomies were closed without abdominal exploration. During ileostomy closure, operative time and mean hospital stay were significantly reduced with the use of loop ileostomy. The time to oral feeding was not significantly different between end and loop ileostomy groups after ileostomy closure. The complication rate after IAPP was similar between groups. However, after ileostomy closure, the complication rate was significantly reduced with the use of loop ileostomy. We conclude that loop ileostomy is a desirable option for UC patients undergoing intestinal diversion during IAPP. Loop ileostomies can be created easily and without an increase in operative time. Subsequent ileostomy closure can be performed as a local procedure, which may shorten operative time and length of hospital stay.

Adolescent↗
PubMed1997

Preparation and characterization of recombinant tissue inhibitor of metalloproteinase 4 (TIMP-4).

TIMP-4, a novel human tissue inhibitor of metalloproteinase, was identified and cloned (Greene, J., Wang, M., Raymond, L. A., Liu, Y. E., Rosen, C., and Shi, Y. E. (1996) J. Biol. Chem. 271, 30375-30380). In this report, the production and characterization of recombinant TIMP-4 (rTIMP4p) are described. rTIMP4p, expressed in baculovirus-infected insect cells, was purified to homogeneity by a combination of cation exchange, hydrophobic, and size-exclusion chromatographies. The purified protein migrated as a single 23-kDa band in SDS-polyacrylamide gel electrophoresis and in Western blot using a specific anti-TIMP-4 antibody. Inhibition of matrix metalloproteinase (MMP) activities by rTIMP4p was demonstrated in five MMPs. Enzymatic kinetic studies revealed IC50 values (concentration at 50% inhibition) of 19, 3, 45, 8, and 83 nM for MMP-1, MMP-2, MMP-3, MMP-7, and MMP-9, respectively. Purified rTIMP4p demonstrated a strong inhibitory effect on the invasion of human breast cancer cells across reconstituted basement membranes. Thus, TIMP-4 is a new enzymatic inhibitor in MMP-mediated extracellular matrix degradation and may have therapeutic potential in treating cancer malignant progression.

Breast Neoplasms↗
PubMed1997

pKa measurements from nuclear magnetic resonance for the B1 and B2 immunoglobulin G-binding domains of protein G: comparison with calculated values for nuclear magnetic resonance and X-ray structures.

Two-dimensional homo- and heteronuclear nuclear magnetic resonance (NMR) spectroscopy was used to determine pKa values for all of the acidic residues in the B1 and B2 immunoglobulin G- (IgG-) binding domains of protein G. Due to the stability of protein G over a wide pH range, estimates of ionization constants were also obtained for some basic residues. These experimentally determined ionization constants were compared with values calculated from both X-ray and NMR-derived structures of B1 and B2 using the UHBD algorithm [Antosiewicz, J., et al. (1994) J. Mol. Biol. 238, 415-436]. This algorithm has been found to be predictive for pKa measurements in proteins and, in combination with experimental measurements, allowed some evaluation of the NMR and X-ray structures. Three regions where significant differences exist between the X-ray and NMR structures are (1) the position of the E56 side chain relative to the backbone amides of K10 and D40, (2) residues 33-37 in the helix, and (3) the Y45 side-chain conformation. For all three cases, the experimental pH titration curves are notably more consistent with the X-ray structures than the NMR structures. In contrast, a number of solvent-accessible side chains have experimental pKas more in agreement with mean pKas calculated from families of NMR structures. The conformations of these side chains may be susceptible to crystal packing effects. From titration experiments under basic conditions, it is noteworthy that the chemical shift of the Y45 C epsilonH resonance is invariant up to pDcorr 12. The Y45 side-chain hydroxyl group appears to maintain a nativelike hydrogen bond with D47 at pDcorr 12, even though the protein is approximately 90% unfolded. These results suggest that this short-range (i, i + 2) interaction, located in the beta3-beta4 hairpin, is present in the high-pH denatured state and may therefore form early in the folding of protein G.

Aspartic Acid↗
PubMed1996

Synthesis and antiviral activity of pyranosylphosphonic acid nucleotide analogues.

Pyranosyl nucleotide analogues have been designed so that the intramolecular base to phosphorus distance closely approximates that of natural nucleotides. This was achieved by attaching the phosphorus directly at the anomeric position and the base at the 4-position of the carbohydrate. A series of compounds incorporating natural bases and having this novel structure were made via a short synthesis starting from commercially available glycals. Addition of triisopropyl phosphite to the glycals furnished alpha- and beta-2-enopyranosylphosphonates which were then substituted with the heterocycle using Mitsunobu chemistry. Deprotection afforded the 2',3'-unsaturated isonucleotide analogue. In some cases the deprotection sequence induced double-bond migration leading to the 1',2'-unsaturated derivative. NMR spectroscopic structural analysis established an axial preference for the base and an equatorial preference for the beta-phosphorus which results in intramolecular base to phosphorus distances within 1 A of that of natural nucleotides. All of the deprotected compounds were screened for inhibition of HCMV, HSV-2, and HIV replication. Several compounds inhibited HCMV and HSV-2, the most potent of which was the unsaturated cytosine analogue 18 (HCMV IC50 = 10 microM, HSV-2 IC50 = 85 microM). None of the compounds were cytotoxic at the highest dose (1 mM) tested. None of the compounds were inhibitory to HIV.

Antiviral Agents↗