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Biomedical subjects

D Lew

Publications and source records attributed to D Lew.

At least 37 records · Page 2Linked to original sources
PubMed1992

The role of estrogen response elements in expression of the Xenopus laevis vitellogenin B1 gene.

We have used site-directed mutagenesis and a homologous transient transfection system to investigate the role of the two imperfect estrogen response elements (EREs) located at -302/-334 in the 5'-flanking region of the estrogen-regulated Xenopus laevis vitellogenin B1 gene. Deletion of either ERE effectively abolishes estrogen-dependent transcription of the vitellogenin promoter. Neither replacement of the two imperfect EREs with a single consensus ERE at -334, nor insertion of one or two consensus EREs at -359, restores full estrogen responsiveness to the mutant promoter. In competition gel mobility shift assays using the DNA binding domain of the Xenopus estrogen receptor, the consensus ERE was a severalfold more effective competitor than the two imperfect B1 EREs. These data suggest that flanking DNA sequences may exert a significant effect on the activity of EREs as hormone-dependent transcription activators. When the imperfect EREs at -302/-334 were present, an additional consensus ERE at -359 exhibited synergistic activation of transcription. However, two consensus EREs located close to the TATA box showed additive, not synergistic, activation of transcription. In contrast, synergistic activation of transcription was observed in synthetic promoters containing two EREs and either the vitellogenin activator element or the NF1 or AP1 upstream activator elements.

Animals↗
PubMed1992

N-acetylcysteine enhances receptor-mediated phagocytosis by human neutrophils.

The effect of the sulphur compound N-acetylcysteine (NAC) on certain receptor-mediated cellular functions [chemiluminescence (CL), phagocytosis and degranulation] in human neutrophils was studied, to evaluate how a scavenger of certain toxic oxygen product can protect the phagocyte and the bystander tissue cells from oxidative damage. When using IgG-opsonized yeast particles as stimulating agent, preincubating the neutrophils with NAC (0.25 mg/ml = 1.5 mM) increased both the CL response and phagocytosis. Higher concentrations of NAC (0.50-1.00 mg/ml = 3-6 mM) decreased the CL response, whereas the phagocytic capacity was still enhanced. This effect was more pronounced with adherent neutrophils than with neutrophils in suspension. No increased CL or phagocytic activity was, however, induced by NAC when C3bi-opsonized particles were used as a prey. From the fact that NAC (i) inhibited extracellularly localized myeloperoxidase dependent activities, and (ii) had no effect on neutrophils from patients with chronic granulomatous disease (CGD), we conclude that the scavenger effect of NAC not only reduces the accumulation of oxidative metabolites per se, but also enhances receptor-mediated phagocytosis by protecting Fc(IgG)-receptors from oxidative damage mediated by myeloperoxidase (MPO) and hydrogen peroxide (H2O2). Since NAC can increase phagocytosis and reduce the extracellularly produced oxidative metabolites, we furthermore conclude that NAC possesses some ideal properties as an anti-inflammatory agent.

Acetylcysteine↗
PubMed1991

Purified estrogen receptor DNA binding domain expressed in Escherichia coli activates transcription of an estrogen-responsive promoter in cultured cells.

The region of the Xenopus laevis estrogen receptor responsible for interaction with DNA, the DNA binding domain (DBD), has been cloned and overexpressed in Escherichia coli using a T7 RNA polymerase expression system. Extracts from cells transformed with the DBD expression vector contain a single protein which reacts with polyclonal antibodies to estrogen receptor and exhibits sequence-specific binding to a DNA fragment containing a consensus estrogen response element. The DBD protein has been purified to near homogeneity. Determination of the rotational relaxation time of the dansylated DBD by fluorescence polarization and size fractionation by Superdex column chromatography indicate that the DBD is a monomer in solution. The DBD forms a single protein-estrogen response element complex in gel mobility shift assays at DBD concentrations of 18-3,600 nM, suggesting that the DBD is bound to both halves of the palindromic estrogen response element. To investigate the ability of the DBD expressed in bacteria to activate gene expression, we have developed a simple liposome-based system for delivery of protein into cultured cells. Transfected DBD protein elicited large, concentration-dependent increases in transcription of an estrogen receptor regulated reporter gene. These data demonstrate that the bacterially expressed DNA binding domain, which represents a small portion of the Xenopus laevis estrogen receptor, retains significant ability to activate transcription of an estrogen-responsive promoter in vertebrate cells.

Animals↗
PubMed1991

Osteomyelitis of the mandible as a result of sickle cell disease. Report and literature review.

Only five cases of osteomyelitis of the mandible as a result of sickle disease have been published. We report another case, which uniquely affected not only the osseous portion of the mandible, including the condyle, but also the adjacent musculature. Radical resection of the involved hard and soft tissue was necessary to cure the patient. Two possible etiologies are discussed. The first states that the sickle cell crisis caused a tissue anoxia in which this tissue became secondarily infected; the second states that the preexisting infection triggered or augmented the sickling phenomena.

Adult↗
PubMed1991

The effect of stepwise expansion on the mitotic activity and vascularity of subdermal tissue and induced capsule in the rat.

This study proposes that the mitotic activity and morphology of a subdermal induced capsule in response to a tissue expander can be regulated by the application of stepwise pressure increases in the expander. Tissue expanders were introduced into the fascial plane beneath the panniculus muscle of the rat and expanded in a stepwise fashion. Biopsies were taken at 48, 96, and 144 hours postexpansion at each increased pressure level. The developing capsule exhibited an increase in mitotic activity in its innermost layer, which reached a maximum 96 hours postexpansion. Application of constant pressure beyond 96 hours resulted in a progressive decrease in mitotic activity of the capsule. These observations suggest that cell proliferation and the resulting growth and differentiation of the extracellular matrix of the capsule may be controlled by appropriate pressure changes in the expander.

Animals↗
PubMed1991

Reconstruction of the severely atrophic edentulous mandible by means of autogenous bone grafts and simultaneous placement of osseointegrated implants.

A method of reconstructing the severely atrophic mandible that simultaneously provides additional strength and the ability to house osseointegrated implants is presented. The performance of the procedure from an external approach minimizes the possibility of oral contamination and, therefore, infection. The procedure has been performed on 10 patients, with a longest follow-up of 3 years. A 93% success rate has been achieved, and bone resorption at the implant sites has thus far been negligible. Prosthetic rehabilitation has been done in 9 of the 10 cases; 3 have been tissue-supported prostheses, and 6 have been completely implant-supported prostheses.

Adult↗
PubMed1991

The effect of electrical stimulation on bone formation around hydroxyapatite implants placed on the rabbit mandible.

Nonresorbable, nonporous, particulate hydroxyapatite (HA) was implanted on the mandible in rabbits and stimulated electrically, 4 hours per day, during the first postoperative week. Stimulated and control implant sites were recovered 8 weeks postoperatively and examined histologically. The HA migrated into the mandible in the electrically treated specimens, and was routinely found in intimate association with preexisting mandibular bone. In the controls, the HA remained superior to the mandibular surface. In further studies (without electrical stimulation) in which the implant site was recovered 26 weeks postoperatively, HA was observed in the mandible; some HA particles migrated completely through the mandible and were found in the adjacent soft tissue. It was concluded that, under the conditions studied, electrical stimulation does not promote bone growth into HA, but rather produces the opposite result--it promotes more rapid movement of HA particles into the mandibular bone. The HA particle migration into the mandible observed (longer postoperative times) in the absence of electrical stimulation suggests that migration is a general property of HA particles when placed over bone under muscle.

Animals↗
PubMed1991

Use of subperiosteal implants with distal filling ports in the correction of the atrophic alveolar ridge.

A subperiosteal tissue expander with a filling port attached to the distal end of the prosthesis has been successfully used on 10 patients during the past 2 years. The design has resulted in eliminating the dehiscence problem encountered when the midline incision was used to insert the original expander and its centrally placed filling port. The ability to use a bilateral incision or expander insertion has minimized the incidence of inferior alveolar nerve damage in the severely atrophic mandible.

Adult↗
PubMed1990

[Optic neuropathy and Lyme disease].

Lyme disease should be included in the differential diagnosis of acquired optic nerve disorders. Protean clinical manifestations of Lyme disease, diagnostic clues and treatment are reviewed.

Humans↗
PubMed1989

Serum levels of ciprofloxacin after single oral doses in patients with septicemia.

Ciprofloxacin serum levels were measured after administration of the drug to 36 patients with septicemia (at least one positive blood culture) who were able to take oral medication. Patients were randomly allocated to receive ciprofloxacin 500 mg p.o. (n = 21) or 200 mg i.v. over 30 min (n = 15). A first dose was administered 18-30 h after the last positive blood culture (day 1), and a second dose four days later (day 5) in some patients. In addition to ciprofloxacin, standard antibiotics were administered. Organisms isolated were Escherichia coli (15), other gram-negative bacteria (6), Streptococcus pneumoniae (7), Staphylococcus aureus (2), and other gram-positive bacteria (6). None of the patients vomited. Ciprofloxacin serum concentrations 1 h after oral administration were in the range 0.09-2.32 mg/l, and 2 h after administration in the range 0.5-7.27 mg/l. The average terminal half-life was 8.6 h. In individual patients serum concentrations and area-under-the-curve values were compared. Poor correlation was found between values measured on day 1 and day 5 after oral administration, whereas the correlation was excellent after i.v. administration. Serum levels 2 h after oral administration were 30-900 times the MICs for the gram-negative organisms, but were in the range of the MICs for the gram-positive organisms in some cases. In conclusion, ciprofloxacin serum levels are difficult to predict in septicemia patients after oral administration, but probably suffice to treat infections caused by gram-negative organisms.

Administration, Oral↗
PubMed1989

The use of tissue expanders in the reconstruction of orofacial defects secondary to congenital rubella: case report.

A patient with a severe orofacial defect secondary to congenital rubella is described. The absence of the lower portion of the orbicularis oris muscle, the death of tissue in the infralabial region, as well as the presence of only a vestigial lower lip has hitherto not been reported in the literature. Tissue expanders were used to provide tissue for restoration of the deficient soft tissue of the submental region, a bipedicled flap from the upper lip was used to create a normal anatomic lower lip, and osseointegrated implants were used to stabilize a full denture prosthesis.

Adult↗
PubMed1988

The use of tissue expanders in the correction of avulsive injuries of the mandible: report of two cases.

Two cases illustrating successful use of tissue expanders to correct both soft and bony defects of the facial region are presented. The tissue expanders allow the development of a flap that has the same color and texture as the lost tissue. It also precludes the need of a distantly developed flap with its associated morbidity. The highly vascular fibrous capsule developed around the expander provides the advantage of initially greater blood supply and increased bulk for coverage of a bone graft. Although this is temporary in nature, it provides a desirable receptor bed during the critical period of bony union. The ready availability of adjacent tissue, the esthetic considerations, and the comparative reduction in morbidity when compared with use of distant flaps makes the use of tissue expanders an attractive technique in maxillofacial reconstruction.

Bone Transplantation↗