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Biomedical subjects

S Alexander

Publications and source records attributed to S Alexander.

At least 91 records · Page 5Linked to original sources
PubMed1996

Capillary hemangioma--report of a case.

A ten-year-old girl was referred for the management of a recurrent lobulated mass present in the upper anterior region. Histopathological investigations were suggestive of capillary hemangioma. Surgical excision of the lesion was performed and postoperative recovery was uneventful.

Child↗
PubMed1995

Analysis of rejection outcomes and implications--a report of the North American Pediatric Renal Transplant Cooperative Study.

For this study, we analyzed the role of rejection in graft failure in children. Rejection results were examined after 3004 pediatric renal transplants (1367 living donor, 1637 cadaver source). A total of 3453 (1298 living donor, 2155 cadaver source) rejection episodes have occurred, for rejection ratios of .95 for living donor and 1.32 for cadaver source transplants, with a constant difference of 18% points after four months, in the percentage of patients ever experiencing a rejection. Rejection results were examined by patient age (0-1 vs. 2-5 vs. 6-12 vs. > or = 13). Rejection ratios, annualized rejection frequency, time to first rejection, and mean number of rejections for patients with rejection were not elevated in the younger patients. However, for the initial rejection episode, recipients less than six years of age had significantly (P < .001) poorer outcome from the rejection episode with an increased risk of graft failure in both donor source groups. This age effect on rejection outcome is only seen with the first rejection episode and is not observed with subsequent rejection episodes.

Adolescent↗
PubMed1995

pTIM3, a plasmid delivery vector for a transposon-based inducible marker gene system in gram-negative bacteria.

pTIM3 is a suicide plasmid vector for the delivery of a transposition defective derivative of Tn5, expressing inducible mercury resistance (HgR) and catechol 2,3-dioxygenase (C23O) activity, to a range of gram-negative microorganisms. pTIM3 was constructed by a four-stage process from pNMM1, a derivative of pSUP5011 containing a modified Tn5 where antibiotic-resistance determinants have been replaced by the mer operon of Tn501 and tdnC (encoding a C23O). In pTIM3, tdnC is fused to merD, to bring C23O expression under the control of the mer operon. pTIM3 was introduced into Acinetobacter calcoaceticus, Pseudomonas putida, Burkholderia cepacia, and Alcaligenes sp., and isolates were examined for loss of the vector, which is not stably maintained outside the Enterobacteriaceae, but retention of the Tn5 derivative. Transposition results from the action of a vector-encoded Tn5 transposase (Tnp) on the ends of IS50L and IS50R retained in the Tn5 construct. Between 10 and 20% of the isolates contained a single copy of the defective transposon in the chromosome. A single-copy isolate of each species was assayed for inducibility of C23O activity using HgCl2 as inducer. The increase in C230 activity was linear with increasing HgCl2 concentration and ranged between 10- and 20-fold at 20 micrograms/ml. HgR and C23O+ phenotypes were found to be stably maintained in each of the isolates following 40 generations of nonselective growth. A novel aspect of this marker gene system is that isolates can be recovered on nonselective medium and then sprayed with a catechol/HgCl2 mixture for rapid colorimetric detection. The system can be applied to the tracking of genetically modified microorganisms in the environment and has the advantage that their detection may be achieved cheaply and without the use of sophisticated equipment.

DNA Transposable Elements↗
PubMed1995

Maternal mortality in developed countries: not just a concern of the past.

OBJECTIVE: To review the activities in selected developed countries for strategies to identify maternal deaths, the impact of these strategies on underreporting, and the information needed to understand the events leading to death. DATA SOURCES: We reviewed the literature from the United States, Europe, and Australia for publications dealing with maternal death identification and investigation from 1980 to April 1995. We also obtained information directly from researchers involved in major maternal mortality studies. METHODS OF STUDY SELECTION: We included all 31 reports (from 14 countries) that discussed methods to improve the ascertainment of maternal deaths beyond the routine use of vital registration. Because of the nature of the subject matter, almost all reports relied on descriptive epidemiology. DATA EXTRACTION AND SYNTHESIS: We found that a variety of methods can be used to improve the ascertainment of maternal deaths, including linkage of birth and fetal death certificates, check-boxes on death certificates, periodic review of deaths of reproductive-age women, and ongoing birth registries and medical audits. Information from a variety of sources is also needed to understand the events leading to death. CONCLUSION: The numbers of deaths due to pregnancy and its complications are underestimated in most developed countries. Improved ascertainment of maternal death is needed to determine the magnitude of the problem and to assess trends and identify risk groups, allowing development of appropriate and effective strategies to prevent the morbidity and mortality associated with pregnancy.

Australia↗
PubMed1995

Steady improvement in renal allograft survival among North American children: a five year appraisal by the North American Pediatric Renal Transplant Cooperative Study.

From 1987 through 1994, the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) has enrolled 1641 cadaver donor transplants. For this study, we have analyzed one and two year graft survival by annual cohorts for the years 1987 through 1991. For the 1987 cohort one and two year graft survival was 72% and 65%, respectively, and for the 1991 cohort it was 83% and 78%, respectively. Using a proportional hazards model, and comparing the 1987 cohort to the 1991 cohort, the relative risk for graft failure was 1.40 (P = 0.02). Analysis of practice patterns revealed the following changes which may have been associated with this improved graft survival: (1) use of T cell induction antibody, 38% in 1987 and 67% in 1991 (P < or = 0.001); (2) the increased use of cyclosporine (CsA) post-transplant: in 1987, 87% were maintained on CsA at day 30 compared to 97% in 1991 (P < 0.001); (3) the mean higher daily maintenance CsA dose at 12 months post-transplant which in 1987 was 6.5 mg/kg compared to 7.5 mg/kg in 1991 (P = 0.03); (4) the decreased use of random transfusions, 54% receiving > 5 transfusions in 1987 compared to 37% in 1991 (P < 0.001); and (5) decreased use of younger cadaver donors between 1987 and 1991 (P < 0.001).

Antibodies, Monoclonal↗
PubMed1995

Multiple signal transduction pathways regulate discoidin I gene expression in Dictyostelium discoideum.

The expression of the discoidin I genes in Dictyostelium discoideum is regulated by the concerted action of the extracellular factors cyclic adenosine monophosphate (cAMP), folate, prestarvation factor (PSF) and conditioned media factor (CMF). However, the pathways by which these signals are transduced and the interactions between the pathways have been unexplored so far. We have analysed wild-type and mutant cells with defined lesions in signal transduction to elucidate these regulatory processes, and shown that different pathways are used for the down-regulation and induction of these genes. The cAMP receptor cARI is required for the cAMP-mediated down-regulation of discoidin I gene expression but not for the induction of discoidin I expression during development. Surprisingly, induction of the discoidin I genes requires G alpha 2, the G-protein subunit which is generally believed to couple to cARI, to control the expression of cAMP-inducible genes. Thus, our data suggest that G alpha 2 interacts with different receptors to regulate gene expression in early development. Furthermore, the analysis shows that discoidin induction in bacterially grown cells occurs in two sequential steps. The first is a low basal induction which occurs in late log-phase growth prior to starvation. PSF can induce the basal level, and the induction is independent of G alpha 2. The developmental induction following starvation is much stronger, dependent on G alpha 2 and probably signaled by CMF, which is secreted at that time.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Identification of human T cell lymphotropic virus type IIa infection in the Kayapo, an indigenous population of Brazil.

Human T cell lymphotropic virus type II (HTLV-II) infection is endemic in a number of indigenous populations in North, Central, and South America. In the present study we have employed serological and molecular methods to identify HTLV-II infection in Indian communities in the Amazon region of Brazil. Sera (1324) from 25 different Indian communities were analyzed by ELISA and Western blot. One hundred and four samples (7.8%) from a number of culturally distinct and geographically unrelated populations were found to have reactivities consistent with HTLV-II infection. Of these, 67 were from the Kayapo Indian communities, which had an overall seroprevalence rate of greater than 30%. In addition, high seroprevalence rates were observed in three other communities, the Munduruku, Arara do Laranjal and the Tyrio, suggesting that there are additional foci of endemic infection in the Amazon region. In the Kayapo, seroprevalence rates tended to increase with age, supporting the importance of sexual transmission of the virus, and family studies demonstrated that vertical transmission is also an important route of infection. Restriction fragment length polymorphism (RFLP) and nucleotide sequence analysis of a region of the env gene demonstrated that the Kayapo are infected with the HTLV-IIa subtype. Moreover, nucleotide sequence analysis of the LTR demonstrated that this belonged to a distinct HTLV-IIa phylogenetic group. The identification of HTLV-IIa in the Kayapo is, as far as we are aware, the first identified endemic focus of infection by this subtype of HTLV-II in the Americas.

Adolescent↗
PubMed1995

Prospective study of 210 consecutive cases of endocapsular phacoemulsification using the AMO SI-30NB 3-piece foldable lens.

PURPOSE: To assess the acceptability of clinical outcome achieved with use of the SI-30NB lens, as well as the incidence of any lens related complications. METHODS: This prospective study evaluated 210 consecutive eyes undergoing endocapsular phacoemulsification cataract surgery (EPECS), with implantation of the AMO SI-30NB foldable three-piece lens, commencing with the first patient in our practice receiving this implant. There was 99% follow-up for at least three months, with a mean of nine months, and a range of three to 14 months. Incisions were a maximum of 3.2 mm in size, and this allowed minimisation of astigmatism, and maximisation of early visual rehabilitation. RESULTS: The final visual acuity results were excellent, with 95% of cases achieving corrected vision of 6/12 or better. All cases without pre-existing ocular pathology achieved corrected vision of 6/6, apart from a single case which achieved 6/9, but the patient died before follow-up. The lens-related complication rate was less than 1% (two patients). No decentration of any other implant occurred, and no patient complained of edge glare. There were no cases of iris chafing or pigment dispersion. Only three patients (1.4%) required Yag posterior capsulotomy in the first 14 months of the study. Central bag-bag fixation was achieved in 206 of the 210 cases in the study (98%). CONCLUSION: The results achieved using the SI-30NB lens with a small incision phaco procedure were excellent. Lens-related complications occurred in only two cases and very few cases have had problems with posterior capsular opacification.

Aged↗
PubMed1995

The relationship between intraperitoneal volume and solute transport in pediatric patients. Pediatric Peritoneal Dialysis Study Consortium.

A multicenter study was conducted to determine the relationship between intraperitoneal volume and solute (e.g., urea, creatinine) transport as determined by the dialysate to plasma (D/P) ratio and mass transfer area coefficient (MTAC). Two 4-h peritoneal equilibration tests were conducted on each of 12 pediatric peritoneal dialysis patients (mean age, 10.8 yr; range, 0.2 to 19.2 yr). One test exchange volume was 900 mL/m2 body surface area (BSA), and the other was 1,100 mL/m2 BSA. Dialysate samples were collected at 0, 30, 60, 120, 180, and 240 min. Blood samples were drawn at 0 and 240 min. Solute equilibration was significantly more rapid with the 900 mL/m2 BSA exchange volume than with the 1,100 mL/m2 exchange volume when evaluated by the D/P ratio. In contrast, no differences in solute transport were noted with either exchange volume when assessed with the MTAC. In conclusion, solute D/P ratios vary with changes in the intraperitoneal volume, necessitating the use of a standardized exchange volume for the reliable interpretation of evaluations such as the peritoneal equilibration tests. In contrast, the use of the MTAC allows for an accurate assessment of solute transport over a wide range of exchange volumes.

Adolescent↗
PubMed1995

[Levels of low birth-weight in Europe: registration problems and effects of medical interventions].

The rate of low birthweight births, percentage of live births weighing less than 2500 grams is one of the perinatal health indicators recommended by the World Health Organisation. A review of the literature has revealed numerous problems related to this indicator. Some countries, including France and the Netherlands do not collect birthweight data. Elsewhere, there are more than 10% "unknown birthweight". The poorest registration is for birthweights below 1000 grams. Exclusion of babies who were registered as stillborn, when in fact they died shortly after birth can cause underregistration of low birthweights. Conversely, inclusion of true stillbirths will bring on an overestimation of low birthweight rate. Some countries have too few births to deliver accurate rates. Rates of medical interventions, such as infertility treatment and elective induction should be taken into account when analyzing differences between countries. Improvement in quality of registration and caution in the use of this indicator are warranted.

Bias↗
PubMed1994

Randomised controlled trial of routine cervical examinations in pregnancy. European Community Collaborative Study Group on Prenatal Screening.

Preterm delivery is strongly associated with neonatal mortality and morbidity. In some European countries, cervical examinations are used routinely during pregnancy to identify women at risk of preterm delivery. We sought to evaluate the efficacy and secondary effects of these routine cervical examinations. We did a randomised controlled trial in seven European countries, comparing two policies--namely, an attempt to do a cervical examination at every prenatal visit (2803 women) and avoidance of cervical examination if possible (2799). The median number of cervical examinations was 6 in the experimental group and 1 in the controls. There were 6.7% preterm (< 37 weeks) deliveries in the experimental group and 6.4% in the control group (risk ratio 1.05 [95% confidence interval 0.85-1.29]; non-significant). The low birthweight rate was 6.6% in the experimental group and 7.7% in the controls (non-significant). Premature rupture of membranes was not significantly more frequent in the experimental group (27.1% vs 26.5%). Our findings do not support the routine use of cervical examinations during pregnancy.

Adult↗
PubMed1994

Posttransplant deaths and factors that influence the mortality rate in North American children.

Of 2457 patients in the North American Pediatric Renal Transplant Cooperative Study registry who were followed for 5481 patient-years after the index transplantation, we observed 136 deaths, for an average annual rate of 24.8 deaths per 1000 patient-years. Death resulted primarily from infection (n = 55, 40%), cardiovascular causes (n = 28, 21%), hemorrhage (n = 16, 12%), and malignancies (n = 9, 7%). Cadaver-donor source was associated with greater mortality (6.7%) than a living-donor source (4.0%) (P < 0.005). Recipients aged 0-1, 2-5, 6-12, and 13-17 years old had mortality rates of 17.5, 8.0, 3.6, and 4.5%, respectively (P < .001). Mortality rates increased substantially when examined by recipient and cadaver donor ages (mortality rates of up to 45%), the greater the concordance between young donor and recipient ages. Interestingly, acute tubular necrosis and graft failure less than 30 days after transplantation (GH30) were each associated with markedly elevated mortality rates. (The risk ratio for ATN was 3.1 [P < 0.001] and for GF30 it was 6.4 [P < 0.001].) Mortality after transplantation was also affected by the underlying renal disease, with high mortality rates observed for oxalosis (n = 21, 33.3%), congenital nephrotic syndrome (n = 79, 15.2%), pyelo/interstitial nephritis (n = 54, 11.1%), and Drash syndrome (n = 14, 21.4%). When the joint effect of these risk factors was examined in a Cox proportional hazards model, young recipient age (0-1 years old) and GF30 were significant (P < .001) risk factors of mortality for recipients of living-donor organs. For recipients of cadaver kidneys, young recipient age--0-1 years old (P < .001) and 2-5 years old (P = .002)--ATN (P = .029), and GF30 (P < .001) were all significant risk factors. Recipient age is the major determinant of increased mortality after renal transplantation. Avoidance of acute tubular necrosis by reducing cold time and preventing early graft failure by better matching techniques in this vulnerable population may improve the mortality rate.

Adolescent↗
PubMed1994

Vibrational circular dichroism in ephedra molecules. Experimental measurement and ab initio calculation.

Vibrational circular dichroism (VCD) spectra in the OH- and NH-stretching regions have been measured for six pharmaceutical molecules in the ephedra class, (1S,2R)-norephedrine, (1), (1S,2S)-norpseudoephedrine (2), (1S,2R)-ephedrine (3), (1S,2S)-pseudoephedrine (4), (1S,2R)-N-methylephedrine (5) and (1S,2S)-N-methylpseudoephedrine (6), all in dilute C2Cl4 solution. Ab initio calculations of geometries and vibrational frequencies for a number of conformers of 1 to 6 have been carried out. The recently developed locally distributed origin gauge model for VCD was used to calculate VCD spectra of the conformers for each drug. This ground-state ab initio model, which does not require sum-over-states, magnetic field perturbation or localized molecular orbitals, has been found to give good agreement with experiment in this frequency region. Composite spectra obtained from weighted averages of the calculated conformer spectra agree within a factor of two with observed IR and VCD intensities for five of the ephedra drugs. For (1S,2S)-pseudoephedrine, the discrepancy between experiment and calculation has been interpreted in terms of a coupled-oscillator effect absent in the other molecules.

Circular Dichroism↗