Biomedical subjects

T Smith

Publications and source records attributed to T Smith.

At least 127 records · Page 7Linked to original sources

PubMed2000

Cloning and characterization of rat dentin matrix protein 1 (DMP1) gene and its 5'-upstream region.

Rat dentin matrix protein 1 (DMP1) is a highly acidic 58-kDa phosphoprotein, and DMP1 was the first gene to be cloned from the mineralized dentin matrix. It exists as a highly phosphorylated protein with a pI of 3 in the dentin matrix and, in that state, might have an important role in the mineralization process. The spatio-temporal distribution during development indicates that the expression of this gene is tightly regulated in the odontoblasts. It is now known that DMP1 is not unique to dentin but is present in other mineralized tissues like long bone, calvaria, and ameloblasts. To study the transcriptional regulation and the function of DMP1 in these tissues, a genomic clone with a functional promoter, introns, and exons was isolated. Sequence analysis showed that the rat DMP1 gene is comprised of six exons and five introns and spans approximately 13 kilobases (kb). Exon 1 contains the 5'-untranslated sequences. Exon 2 encodes a total of 18 amino acids including the 16 amino acids of the signal sequence. Exons 3-5 encode 16, 11, and 15 amino acids, respectively. Exon 6 contains 1.3 kb of the coding sequence with the RGD domain, stop codon, and the 3'-untranslated region (1.1 kb). We have mapped two transcription start sites within the DMP1 promoter that are 280 and 321 base pairs, respectively, from the ATG start codon. The location of functional elements within the 5'-upstream DMP1 DNA fragment was determined by cloning it into a luciferase reporter gene. Transient transfection and luciferase assays revealed that the 3 kb fragment has the ability to drive the luciferase gene. However, this promoter activity was restricted to MC3T3-E1 cells (an osteoblast cell lineage). The promoter was silent in Chinese hamster ovary cells (an epithelial cell lineage), indicating the necessity of tissue-specific factors to drive the transcription.

5' Untranslated Regions↗

PubMed2000

Heritability of gastrointestinal nematode faecal egg counts in West African village N'Dama cattle and its relation to age.

Offspring-dam regression was used to estimate the heritability of strongyle faecal egg counts (FEC) of traditionally raised West African N'Dama cattle in the Central River Division in The Gambia. Faecal samples were taken monthly from June-October 1992, and again from July-October 1993, including 179-463 dams and their calves sampled on each occasion. The only proven genetic relationship was the dam-offspring relationship. Gastrointestinal strongyle FEC was expressed as epg (eggs per gram faeces). Regression of offspring FEC on dam FEC, showed a heritability (h(2)) of 0.18 (95% Confidence Limits 0.10, 0.25). Heritabilities were higher at the beginning and end of the rainy season than during the months of the peak rainy season. This is in line with earlier suggestions that genetic control of faecal egg counts is most effective during periods of low parasite transmission. There was a significant (p<0.001) increase in heritability of 0.086+/-0.018 with each year of age of the corresponding offspring. In view of the virtual absence of national cattle breeding systems in West Africa, which are a precondition for exploitation of heritable traits in cattle, integrated control using improved management and strategic prophylaxis remain the methods of choice to control gastrointestinal nematodes in the given conditions.

Africa, Western↗

PubMed2000

Structure-based design of potent, amidine-derived inhibitors of factor Xa: evaluation of selectivity, anticoagulant activity, and antithrombotic activity.

To enhance the potency of 1,2-dibenzamidobenzene-derived inhibitors of factor Xa (fXa), an amidine substituent was incorporated on one of the benzoyl side chains to interact with Asp189 in the S1 specificity pocket. Lead molecule 1 was docked into the active site of fXa to facilitate inhibitor design. Subsequently, iterative SAR studies and molecular modeling led to a 1000-fold increase in fXa affinity and a refined model of the new inhibitors in the fXa active site. Strong support for the computational model was achieved through the acquisition of an X-ray crystal structure using thrombin as a surrogate protein. The amidines in this series show high levels of selectivity for the inhibition of fXa relative to other trypsin-like serine proteases. Furthermore, the fXa affinity of compounds in this series (K(ass) = 50-500 x 10(6) L/mol) translates effectively into both anticoagulant activity in vitro and antithrombotic activity in vivo.

Amidines↗

PubMed2000

Purification and characterization of the human recombinant histidine-tagged prostaglandin endoperoxide H synthases-1 and -2.

We have used in vitro mutagenesis to introduce a six residue histidine sequence (His-tag) near the amino terminal end of the human PGHS-1 and -2 and have expressed these proteins using the baculovirus system. The His-tags are located one and two amino acids beyond the signal peptide cleavage sites of PGHS-1 and PGHS-2, respectively, positions that do not affect their activities or sensitivities to nonsteroidal anti-inflammatory drugs. When expressed in sf-21 cells, the His-tagged enzymes have K(m) values for arachidonate, and IC(50) values for inhibition by nonsteroidal anti-inflammatory drugs that are similar to values reported for the nontagged enzymes. The His-tags allowed for purification of the PGHSs by a simplified protocol involving nickel-affinity and anion exchange FPLC chromatography. The specific activities and recoveries for the purified enzymes were as good or better than those reported previously for purification of the non-tagged PGHS. These baculovirus constructs should provide a convenient source for pharmacologic and biophysical studies that require large scale preparation of human PGHSs.

Amino Acid Sequence↗

PubMed2000

Recording ionic events from cultured, DiI-labelled myenteric neurons in the guinea-pig proximal colon.

To date investigations of enteric neurons by patch clamping/calcium imaging have been limited by studying unidentified heterogeneous populations of neurons. In DiI-labelled colonic myenteric neurons, the feasibility of recording ionic events was determined by applying DiI either to the mucosa or the circular muscle, dispersing neurons after 48 h organotypic culture, and patch-clamping/calcium imaging labeled neurons after 3-7 days in culture. Myenteric neurons with diffuse DiI fluorescence were typically smooth and agranular. Neurons labeled after DiI was applied to circular muscle, fired in either a phasic or a tonic manner, and exhibited fast afterhyperpolarizations (100-300 ms duration) at the end of a depolarizing pulse. They expressed a fast inward current and at least three different outward currents. Action potentials elicited in DiI-labeled sensory neurons were followed by a prolonged afterhyperpolarization (AH, 4-6 s). The offset of a suprathreshold depolarizing step elicited a prolonged outward tail current that approximated the timecourse of the prolonged AH. In addition, in response to membrane depolarization in DiI-labeled neurons loaded with fura-2, robust Ca(2+) transients were recorded using the perforated patch technique. These results demonstrate that DiI labeling of cultured myenteric neurons is feasible, and patch clamp/Ca(2+) fluorescence recordings can be made from specific populations of cultured DiI-labeled colonic myenteric neurons.

Action Potentials↗

PubMed2000

Isolated musculocutaneous neuropathy caused by a proximal humeral exostosis.

We report an isolated musculocutaneous neuropathy caused by a proximal humeral osteochondroma that became symptomatic after the patient played recreational basketball. Lesion resection resulted in complete deficit resolution. Mass lesions involving the musculocutaneous nerve should be considered in patients with atraumatic, isolated musculocutaneous neuropathies that are recurrent or fail to recover, even in the setting of strenuous exercise.

Adult↗

PubMed2000

Cloning and characterization of a novel human dual flavin reductase.

Flavoprotein reductases play a key role in electron transfer in many physiological processes. We have isolated a cDNA with strong sequence similarities to cytochrome P-450 reductase and nitric-oxide synthase. The cDNA encodes a protein of 597 amino acid residues with a predicted molecular mass of 67 kDa. Northern blot analysis identified a predicted transcript of 3.0 kilobase pairs as well as a larger transcript at 6.0 kilobase pairs, and the gene was mapped to chromosome 9q34.3 by fluorescence in situ hybridization analysis. The amino acid sequence of the protein contained distinct FMN-, FAD-, and NADPH-binding domains, and in order to establish whether the protein contained these cofactors, the coding sequence was expressed in insect cells and purified. Recombinant protein bound FMN, FAD, and NADPH cofactors and exhibited a UV-visible spectrum with absorbance maxima at 380, 460, and 626 nm. The purified enzyme reduced cytochrome c, with apparent K(m) and k(cat) values of 21 microM and 1.3 s(-1), respectively, and metabolized the one-electron acceptors doxorubicin, menadione, and potassium ferricyanide. Immunoblot analysis of fractionated MCF7 cells with antibodies to recombinant NR1 showed that the enzyme is cytoplasmic and highly expressed in a panel of human cancer cell lines, thus indicating that this novel reductase may play a role in the metabolic activation of bioreductive anticancer drugs and other chemicals activated by one-electron reduction.

3T3 Cells↗

PubMed2000

The prostate expression database (PEDB): status and enhancements in 2000.

The Prostate Expression Database (PEDB) is an online resource designed to access and analyze gene expression information derived from the human prostate. PEDB archives >55 000 expressed sequence tags (ESTs) from 43 cDNA libraries in a curated relational database that provides detailed library information including tissue source, library construction methods, sequence diversity and sequence abundance. The differential expression of each EST species can be viewed across all libraries using a Virtual Expression Analysis Tool (VEAT), a graphical user interface written in Java for intra- and inter-library species comparisons. Recent enhancements to PEDB include: (i) the functional categorization of annotated EST assemblies using a classification scheme developed at The Institute for Genome Research; (ii) catalogs of expressed genes in specific prostate tissue sources designated as transcriptomes; and (iii) the addition of prostate proteome information derived from two-dimensional electrophoreses and mass spectrometry of prostate cancer cell lines. PEDB may be accessed via the WWW at http://www.mbt.washington.edu/PEDB/

Databases, Factual↗

PubMed2000

Young and elderly adults' perceptions of the Wechsler Adult Intelligence Scale-Revised.

Because little information exists on examinees' perceptions of the Wechsler Adult Intelligence Scale-Revised (WAIS-R), this study was designed to assess such perceptions in two groups: young adults (n = 50, age 18-25 years) and elderly adults (n = 46, age 65-96 years). Each participant completed the WAIS-R followed by an opinion questionnaire. Both groups gave positive ratings overall. However, elderly participants rated the WAIS-R more positively than young participants both globally and on six of the eleven subtests. These findings suggest that the WAIS-R is viewed favorably by most examinees, particularly elderly adults. Implications for practitioners are presented.

Adolescent↗

PubMed2000

Management of uterine Müllerian adenosarcoma with extrauterine metastatic deposits.

OBJECTIVE: The aim of this study was to provide the management and outcome of three patients who presented with uterine Müllerian adenosarcoma associated with extrauterine metastases. METHODS: A retrospective study of three patients who were referred to our hospital was performed. One patient was referred because of vaginal metastatic deposits that were noted during investigations for primary infertility. The other two were referred because of abnormal vaginal bleeding; one of these had a large polyp protruding through her cervix into the vagina. RESULTS: In two patients the preoperative diagnosis and extent of their disease were known while in the third patient the diagnosis was only made postoperatively. All patients had a type II radical abdominal hysterectomy, bilateral salpingo-oophorectomy, and omentectomy. Two patients were given three cycles of neoadjuvant chemotherapy and pelvic irradiation over 12 weeks. Both of these patients had their diagnosis made preoperatively and the chemotherapy consisted of 240 mg/m(2) carboplatin and 80 mg/m(2) farmorubicin per cycle. The pelvic irradiation consisted of daily fractions of 1.8-Gy irradiation to a total of 45 Gy over the first 6 weeks. The other patient was given the same regime postoperatively. All patients are still alive and free of disease between 34 and 56 months. CONCLUSION: Radical surgery, chemotherapy, and irradiation provide a management option with seemingly favorable outcome for patients with uterine Müllerian adenosarcoma associated with extrauterine metastases.

Adenosarcoma↗

PubMed2000

Human immunodeficiency virus infection and invasive cervical cancer in South Africa.

PURPOSE: The goal of this study was to determine whether South African HIV-seropositive women with invasive cervical cancer present with disease that is more advanced than that of HIV-seronegative women and whether degree of immunosuppression affects the extent of disease at initial presentation. METHODS: This study is a retrospective review of 60 HIV-seropositive and 776 HIV-seronegative new cases of invasive cervical carcinoma seen at the combined gynecologic oncology unit of the University of the Witwatersrand, Johannesburg, South Africa. RESULTS: The HIV seroprevalence was 7.2%. Squamous cell carcinoma was the histologic subtype in more than 90% of both cohorts of patients. Although the HIV-positive patients presented with invasive cervical cancer almost 10 years earlier than the HIV-negative patients, i.e., mean age 44 years +/- 9.8 versus 53 years +/- 12.7, respectively (P </= 0.001), there was no difference in the distribution of advanced lesions in the two groups, i.e., 65% in HIV-positive and 55.4% in HIV-negative patients (P = 0.177). At initial diagnosis 26 of the HIV-seropositive patients had a CD(4) cell count less than 200/mm(3), 20 (77%) of whom presented with stage III or IV cervical cancer; the remaining 34 had a CD(4) cell count above 200/mm(3), 19 (56%) of whom had advanced-stage disease. This was not significantly different (P = 0.109). However, HIV-seropositive patients with CD(4) cell counts less than 200/mm(3) had significantly more advanced-stage disease than HIV-seronegative patients, i.e., 77% versus 55.8% respectively (P = 0.041). CONCLUSION: HIV-seropositive patients presented with invasive cervical cancer almost 10 years earlier than HIV-seronegative patients. Even though HIV seropositivity on its own did not appear to adversely affect extent of disease at presentation, patients with CD(4) cell counts below 200/mm(3) are significantly more likely to have advanced-stage disease at initial diagnosis than HIV-negative patients.

Adult↗

PubMed2000

Detection and differentiation of Campylobacter jejuni and Campylobacter coli in broiler chicken samples using a PCR/DNA probe membrane based colorimetric detection assay.

Campylobacter enteritis in humans has been linked to consumption of poultry meat. Surveys show that 30-100% of poultry harbour Campylobacter as normal flora of the digestive tract which indicates a need to identify prevalent organism types in flocks and trace their epidemiology. In this study we describe a Campylobacter genus specific polymerase chain reaction (PCR) assay, amplifying the 16 S-23 S rRNA intergenic spacer region with an internal Campylobacter genus specific DNA probe and species specific probes for Campylobacter jejuni and Campylobacter coli designed for confirmation of the amplified PCR products by Southern blot and colorimetric reverse hybridization assays. The specificity of this assay was established by testing a range of food pathogens. Broiler chicken samples were tested following presumptive positive identification by the Malthus System V analyser (Malthus Instruments, UK). The combined PCR and colorimetric reverse hybridization assay is easy to perform and faster than conventional methods for confirmation and identification of Campylobacter species.

Animals↗

PubMed2000

Comparison of internal radiation doses estimated by MIRD and voxel techniques for a "family" of phantoms.

The aim of this study was to use a new system of realistic voxel phantoms, based on computed tomography scanning of humans, to assess its ability to specify the internal dosimetry of selected human examples in comparison with the well-established MIRD system of mathematical anthropomorphic phantoms. Differences in specific absorbed fractions between the two systems were inferred by using organ dose estimates as the end point for comparison. A "family" of voxel phantoms, comprising an 8-week-old baby, a 7-year-old child and a 38-year-old adult, was used and a close match to these was made by interpolating between organ doses estimated for pairs of the series of six MIRD phantoms. Using both systems, doses were calculated for up to 22 organs for four radiopharmaceuticals with widely differing biodistribution and emission characteristics (technetium-99m pertechnetate, administered without thyroid blocking; iodine-123 iodide; indium-111 antimyosin; oxygen-15 water). Organ dose estimates under the MIRD system were derived using the software MIRDOSE 3, which incorporates specific absorbed fraction (SAF) values for the MIRD phantom series. The voxel system uses software based on the same dose calculation formula in conjunction with SAF values determined by Monte Carlo analysis at the GSF of the three voxel phantoms. Effective doses were also compared. Substantial differences in organ weights were observed between the two systems, 18% differing by more than a factor of 2. Out of a total of 238 organ dose comparisons, 5% differed by more than a factor of 2 between the systems; these included some doses to walls of the GI tract, a significant result in relation to their high tissue weighting factors. Some of the largest differences in dose were associated with organs of lower significance in terms of radiosensitivity (e.g. thymus). In this small series, voxel organ doses tended to exceed MIRD values, on average, and a 10% difference was significant when all 238 organ doses were considered as a single group. In 12 comparisons of effective dose, the mean voxel to MIRD ratio was 1.07 (range 0.72-1.32). It was shown for the majority of cases that, whereas some large differences in SAF values exist, differences in source organ and effective dose values between the MIRD and voxel methods were largely accounted for by the respective organ mass differences. The reasons for various organ dose differences with the selected radiopharmaceuticals are discussed. Taking biological variation into account, there is reasonable agreement between the two methods but some significant differences exist that warrant further investigation. More extensive comparisons involving a wide variety of voxel phantoms are required to establish whether realistic voxel phantoms should eventually replace the MIRD system.

Adult↗

PubMed2000

Inhibition of Ca2+ release channel (ryanodine receptor) activity by sphingolipid bases: mechanism of action.

Sphingosine inhibits the activity of the skeletal muscle Ca2+ release channel (ryanodine receptor) and is a noncompetitive inhibitor of [3H]ryanodine binding (Needleman et al., Am. J. Physiol. 272, C1465-1474, 1997). To determine the contribution of other sphingolipids to the regulation of ryanodine receptor activity, several sphingolipid bases were assessed for their ability to alter [3H]ryanodine binding to sarcoplasmic reticulum (SR) membranes and to modulate the activity of the Ca2+ release channel. Three lipids, N,N-dimethylsphingosine, dihydrosphingosine, and phytosphingosine, inhibited [3H]ryanodine binding to both skeletal and cardiac SR membranes. However, the potency of these three lipids and sphingosine was lower in rabbit cardiac membranes when compared to rabbit skeletal muscle membranes and when compared to sphingosine. Like sphingosine, the lipids inhibited [3H]ryanodine binding by greatly increasing the rate of dissociation of bound [3H]ryanodine from SR membranes, indicating that these three sphingolipid bases were noncompetitive inhibitors of [3H]ryanodine binding. These bases also decreased the activity of the Ca2+ release channel incorporated into planar lipid bilayers by stabilizing a long closed state. Sphingosine-1-PO4 and C6 to C18 ceramides of sphingosine had no significant effect on [3H]ryanodine binding to cardiac or skeletal muscle SR membranes. Saturation of the double bond at positions 4-5 decreased the ability of the sphingolipid bases to inhibit [3H]ryanodine binding 2-3 fold compared to sphingosine. In summary, our data indicate that other endogenous sphingolipid bases are capable of modulating the activity of the Ca2+ release channel and as a class possess a common mechanism of inhibition.

Animals↗

PubMed2000

Effect of LDL+VLDL oxidizability and hyperglycemia on blood cholesterol, phospholipid and triglyceride levels in type-I diabetic patients.

Oxidative modification of low-density lipoproteins has been implicated in impaired lipid metabolism and its deposition in the arterial wall, and atherosclerosis. This study was carried out to determine the relationship between the in vitro oxidizability of low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL) and the cholesterol, phospholipid and triglyceride (TG) levels in the blood of Type-I diabetic patients. LDL+VLDL was isolated using a micro-affinity column from serum of diabetic patients (n = 34) and age-matched normal individuals (n = 22). The oxidative susceptibility of LDL+VLDL was determined by treatment with 25 microM CuCl(2) for 1.5 h. The levels of total-, LDL-, and HDL-cholesterol, phospholipids and triglycerides, as well as glycated hemoglobin (HbA(t)), were measured in the blood using standard methods. The diabetics had significantly higher levels of triglycerides and phospholipids, but cholesterol levels were similar between Type-I diabetics and age-matched normals. However, among diabetics, there was a significant correlation between the in vitro oxidation of LDL+VLDL at 1.5 h and total cholesterol (r = 0.49, P<0.002), and LDL cholesterol (r = 0.54, P<0.001) and TG (r = 0.34, P<0.05) levels. The level of in vitro oxidizability of LDL+VLDL did not have any correlation with HDL-cholesterol or phospholipid levels. The level of glycemic control (HbA(1)) did not have any correlation with levels of LDL- or HDL-cholesterol or triglycerides, but was significantly correlated with phospholipid levels (r = 0.48, P<0.005). This study suggests that the levels of LDL-cholesterol and triglycerides in the blood are directly related to the degree of in vitro oxidative susceptibility of low-density lipoproteins in Type-1 diabetic patients.

Adolescent↗

PubMed2000

Effect of Medicaid managed care on pregnancy complications.

OBJECTIVE: This study examined the impact of managed care on hospital obstetric outcomes in Medicaid-sponsored women. METHODS: The study sample consisted of a total of 525,517 maternal deliveries for singleton births from three payer groups, Medicaid managed care, Medicaid fee-for-service, and private managed care in 439 short-term-stay nonfederal hospitals in California and Florida. Quality of care comparisons were made using six indicators. Data were derived from linked computer files of birth certificates, hospital discharge abstracts, Medicaid eligibility records, Medicaid health care claims, and surveys of hospital characteristics. RESULTS: The overall multivariate likelihood of an adverse maternal outcome during hospitalization for a delivery was not significantly different between Medicaid managed care and Medicaid fee-for-service groups in California and Florida. However, mothers in the Medicaid managed care group compared with mothers in the private managed care group experienced a higher likelihood of eclampsia (California) (adjusted odds ratio = 1.26; 95% confidence interval 1.05, 1.57; P = .04). CONCLUSION: Overall, managed care has not adversely affected pregnancy outcomes in Medicaid-sponsored women. Yet, payer system changes may be insufficient to achieve complete parity of outcomes relative to private managed care patients.

California↗

PubMed2000

Spontaneous splenic rupture due to subcutaneous heparin therapy.

We report a case of spontaneous splenic rupture in a 59-year-old woman who was receiving 15,000 units of heparin subcutaneously (s.c. ) twice a day for deep venous thrombosis (DVT) prophylaxis. Her past medical history included multiple DVT, pulmonary emboli, and ovarian cancer stage III-C with known ascites. The diagnosis of splenic rupture was initially missed because of the ascites. This case illustrates both a previously undescribed complication of s.c. heparin therapy and a failure of ultrasound diagnosis. We emphasize the unique presentation, difficulty in diagnosis, and need for early surgical involvement to ensure the most favorable outcome.

Anticoagulants↗

PubMed2000

Comparison between anopheline mosquitoes (Diptera: Culicidae) caught using different methods in a malaria endemic area of Papua New Guinea.

The mosquito sampling efficiency of CDC (Centers for Disease Control) miniature light traps hung adjacent to mosquito nets, was compared with that of both indoor and outdoor human-bait collections in ten villages in the Wosera area of Papua New Guinea. The most frequently collected anopheline in the matched indoor and light trap samples was Anopheles koliensis Owen, followed by A. punctulatus Dönitz, A. karwari (James), A. farauti Laveran (sensu lato), A. longirostris Brug and A. bancroftii Giles. All species were much less frequent in the light traps than in landing catches. The hypothesis that the numbers of mosquitoes in light traps are proportional to human landing catches was examined using regression models that allowed for sampling error in both entomological measurements. Light traps under-sampled A. punctulatus and A. farauti s.l. at high densities. The models indicated that the ratio of light trap to landing catch females of A. koliensis and A. karwari increased with increasing mosquito density. Light trap catches of A. longirostris were proportional to indoor landing rates but when outdoor landing rates were high this species was under-sampled by light traps. Numbers of A. bancroftii in light traps were found to be proportional to those in outdoor landing catches, but were negatively related to those attempting to bite indoors. Circumsporozoite positivity rates for both Plasmodium falciparum Welch and P. vivax (Grassi & Feletti) in A. punctulatus and A. farauti s.l. were significantly higher in light trap collections than in either indoor or outdoor landing catches, suggesting that light traps may selectively sample older mosquitoes of these species.

Animals↗