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Biomedical subjects

W E Brown

Publications and source records attributed to W E Brown.

At least 19 recordsLinked to original sources
PubMed1992

Zinc rapidly induces a metal response element-binding factor.

Metal activation of metallothionein gene transcription is mediated by specific promoter sequences, termed metal regulatory elements (MREs). Nuclear extracts prepared from various human cell lines were assayed for their capacity to bind to a synthetic human MREa (hMREa) oligomer. Electrophoretic mobility-shift assays with extracts from control cells detected a single hMREa-containing complex. Addition to the growth medium of zinc, cadmium, or copper--metals known to induce MT biosynthesis in vivo--resulted in the rapid but reversible appearance of a second distinct hMREa-protein complex in all cell lines studied. This result was not seen when the metals were added directly to the extracts from control cells. DNA-binding protein blotting, UV crosslinking, and electroelution experiments were used to characterize the two hMREa-binding factors, termed BF1 and BF2. MRE-BF1 has an apparent molecular mass of approximately 86 kDa and binds to the hMREa in control cells, whereas MRE-BF2 consists of two molecules of approximately 28 kDa and binds to the hMREa in metal-treated cells. EDTA and o-phenanthroline inhibited binding of both factors to hMREa in a dose-dependent manner, indicating that a metal atom or atoms are essential for interaction of the factors with DNA.

Base Sequence↗
PubMed1992

Procedure for the study of acidic calcium phosphate precursor phases in enamel mineral formation.

Considerable evidence suggests that an acidic calcium phosphate, such as octacalcium phosphate (OCP) or brushite, is involved as a precursor in enamel and other hard tissue formation. Additionally, there is in vitro evidence suggesting that fluoride accelerates and magnesium inhibits the hydrolysis of OCP to hydroxyapatite (OHAp). As the amount of OCP or brushite in enamel cannot be measured directly in the presence of an excess of hydroxyapatite, a procedure was developed that allows for their indirect in vivo quantification as pyrophosphate. This permits study of the effects of fluoride and magnesium ions on enamel mineral synthesis. Rat incisor calcium phosphate was labeled by intraperitoneal injection of NaH2(32)PO4. The rats were then subjected to various fluoride and magnesium treatments with subcutaneous implanted osmotic pumps. They were then killed at predetermined intervals; the nascent sections of the incisors were collected, cleaned, and pyrolyzed at 500 degrees C for 48 hours to convert acidic calcium phosphates to calcium pyrophosphate; the pyrophosphate was separated from orthophosphate by anion-exchange chromatography; and the resulting fractions were counted by liquid scintillation spectrometry. The activities of the pyro- and orthophosphate fractions were used to calculate the amount of acidic calcium phosphate present in the nascent mineral. The results demonstrated that the percentage of radioactive pyrophosphate in nascent incisors decreased with time, with increasing serum F- concentration, and with decreasing serum magnesium content. The technique described here should prove to be a powerful new tool for studying the effects of various agents on biological mineral formation.

Administration, Cutaneous↗
PubMed1992

The effects of magnesium and fluoride on the hydrolysis of octacalcium phosphate.

The adsorption of Mg ions on octacalcium phosphate (OCP) and its effect on OCP hydrolysis, with and without F, were studied. The Mg adsorption isotherm was fitted by the Langmuir model with an affinity constant of 0.74 ml/mumol and maximum number of sites, 31.19 mumol/g. The hydrolysis rates were measured in a pH stat by titration of base and were strongly temperature dependent. The products were examined by X-ray diffraction and chemical analysis. OCP hydrolysis takes place in two stages: the fast initial process, which is attributed to the surface topotactical conversion, followed by the main, slower process, which involves the nucleation and crystal growth. Mg ions, as 1 mmol/l MgCl2, prevented the initial surface reaction and decreased the nucleation rate dramatically and the growth rate slightly; F increased the rates of surface reaction and both the nucleation and crystal growth processes. The Ca/P ratio (1.53) and the line broadening in the X-ray diffraction patterns of the apatitic products were not significantly affected by the F. Mg also did not affect the Ca/P ratio and the line broadening at (002) diffraction, but decreased the line broadening at (310) diffraction.

Adsorption↗
PubMed1991

Purification and partial characterization of a shed 66 kDa melanoma-associated antigen identified by autologous antibody.

We have previously reported the isolation of a 66 kDa melanoma-associated antigen, identified by autologous antibody, in serum and unfractionated spent tissue culture media by Western blot analysis. The antigen, detected by autologous serum S150, was found to be broadly represented on melanoma, glioma, renal cell carcinoma, neuroblastoma and head and neck carcinoma cell lines. S150 did not react with bladder or colon carcinoma, fetal fibroblasts, pooled platelets, lymphocytes and red blood cells, autologous cultured lymphocytes or fetal calf serum. To further characterize the antigen, spent tissue culture media, obtained from autologous melanoma cell line, Y-Mel 84:420, was separated by an isoelectric focusing column. Unabsorbed control serum S150 was noted to have a maximum titer of 1:2040 against autologous melanoma cells as measured by protein A hemadsorption. Following isoelectric focusing the greatest decrease in autologous antibody titer (30-fold) occurred with fractions having a pI between 2 and 3. Further resolution of the antigen was accomplished with high-pressure ion-exchange chromatography. One of these fractions showed a significantly higher concentration of antigen and was distinctly resolved from bulk serum albumin. Subsequent Western blot analysis, with autologous antibody, of the isolated antigen-containing fraction, confirmed the presence of a single 66 kDa band. Exposure of the antigen, purified by high-pressure ion-exchange chromatography, to neuraminidase ablated recognition by autologous antibody and suggests that sialic acid is present on the protein and may be part of the antigenic epitope. Binding of antigen, obtained following DEAE anion exchange chromatography, was noted to lectins derived from Triticum vulgaris, Dolichos biflorus and Lycopersicon esculentum. Preparative purification of the antigen was accomplished by anion exchange followed by lectin affinity chromatography with a Dolichos biflorus column. Antigen obtained following lectin affinity chromatography subjected to SDS-PAGE and silver stain revealed a single band at 66 kDa. We conclude that a melanoma-associated antigen detected by autologous antibody in spent tissue culture media is an unusually acidic glycoprotein (pI 2-3).

Antigens, Neoplasm↗
PubMed1991

The periapical tissue reactions to a calcium phosphate cement in the teeth of monkeys.

A calcium phosphate cement, Grossman sealer, and Sargenti N2 were compared under conditions where root canals of monkey incisors were deliberately overfilled and the apical tissue responses were evaluated histologically. The periapical tissues exposed to Sargenti N2 revealed severe irritation at all times through the 6-month experimental period. The reactions to Grossman sealer were milder but persisted throughout the observation period. The calcium-phosphate-cement treated animals showed mild tissue irritation after 1 month, but thereafter the adverse tissue reactions were minimal. New bone formation adjacent to the cement was also observed. These results point to the possibility that calcium phosphate cement might be used in simplified endodontic procedures. The compatibility of calcium phosphate cement with the periapical tissue suggests that the cement may have other applications in dentistry and medicine.

Animals↗
PubMed1991

The coronary collateral circulation in normal goats.

This study was undertaken to evaluate the coronary collateral circulation of the goat. Year old, castrated male goats were anesthetized with sodium pentobarbital. A branch of the left circumflex coronary artery was dissected and a snare placed around it. Regional myocardial blood flow was measured by injecting colored microspheres into the left atrium before and during 3 hr of occlusion of this coronary artery. The Area At Risk for infarction, as defined by a left atrial injection of Brilliant Green dye, was divided into a central Ischemic zone and a peripheral Ischemic Border zone. The degree of overlap in the blood flow distributions between the risk and the nonrisk areas was quantitatively assessed by injecting microspheres directly into the artery to the Area At Risk. Baseline blood flow to the normally perfused goat myocardium was 1.13 +/- 0.18 ml/min/g (mean +/- SE). Following occlusion, the flow to the Ischemic zone was 0.07 +/- 0.03 ml/min/g and to the Ischemic Border zone was 0.31 +/- 0.18 ml/min/g. Flow to either zone did not increase during the 3-hr observation period. Overlap at the perimeter of the risk and nonrisk areas was approximately 22%. We conclude that flow to the Ischemic zone is low because the goat has few native collateral blood vessels, and that flow to the Ischemic Border zone is significantly affected by overlap with normal myocardium.

Animals↗
PubMed1991

High-level viremia in adults and children infected with human immunodeficiency virus: relation to disease stage and CD4+ lymphocyte levels.

Sixty-eight adults and nine children infected with human immunodeficiency virus type 1 (HIV-1) were evaluated consecutively for the presence and amount of cell-free infectious virus in their plasma. Viremia was detected in 18 of 68 adults and in five of nine children; titers ranged from 10 to 100,000,000 TCID/ml plasma. Among the adults, none of 19 asymptomatic patients, 4 of 34 AIDS-related complex patients, and 14 of 15 AIDS patients had cell-free infectious virus in their plasma. None of 35 adult subjects with CD4+ lymphocyte counts greater than 400/mm3 were viremic, whereas 3 of 17 with 200-400 CD4+ lymphocytes/mm3 and 15 of 16 individuals with less than 200 CD4+ lymphocytes/mm3 were plasma viremic. In contrast to adults, each of five children infected with HIV-1 in utero or during the perinatal period were plasma viremic regardless of their CD4+ lymphocytes counts (range, 42-2227/mm3), duration of infection, or clinical stage; however, children infected by HIV-1 at older ages were less frequently plasma viremic. Therapy with zidovudine led to a 10- to 10(6)-fold decline in plasma HIV-1 TCID in all eight subjects studied before and after treatment.

Adult↗
PubMed1990

Clara cell 10 kDa protein (CC10): comparison of structure and function to uteroglobin.

The cellular localization, functional activities and structures of rat and human Clara cell 10 kDa proteins (CC10) are compared to rabbit uteroglobin. CC10 is present exclusively in the non-ciliated cells of the surface epithelium of the pulmonary airways, whereas uteroglobin is reported to be present in the lung and reproductive organs. There is about 55% identity between the amino acid sequences of rat CC10 and either rabbit uteroglobin or human CC10. The latter two have 61% identity. Using the known structure of uteroglobin as the model, correlations between the structure and function for this group of proteins are made. Substitution of the residues for the rat and human CC10 into the structure of uteroglobin suggests that these proteins may be members of a structurally homologous family. Some of the functional differences may be due to distortion of the hydrophobic pocket in the dimeric protein and a surface hypervariability located on one contiguous helix and beta turn. Rat CC10 and rabbit uteroglobin both, nearly equally, inhibit papain and bind progesterone. Human CC10 does not inhibit papain and has markedly lower progesterone binding (4.6% of rabbit uteroglobin). Antiinflammatory activity of synthetic peptides corresponding to a homologous sequence region of uteroglobin and the two Clara cell proteins was tested. The region chosen has sequence similarity to lipocortin I. The peptides not only failed to inhibit carrageenan-induced foot pad swelling but exacerbated it. All three proteins inhibit pancreatic phospholipase A2. The phospholipase A2 inhibitory effect of CC10 may be important in regulating the inflammatory responses in the lung.

Amino Acid Sequence↗
PubMed1990

Subcellular localization of newly incorporated myosin in rabbit fast skeletal muscle undergoing stimulation-induced type transformation.

Immunogold labelling was used to study the distribution of newly synthesized slow muscle myosin (SM) at the ultrastructural level as it replaced fast muscle myosin (FM) in rabbit muscles undergoing stimulation-induced type transformation. Control fast muscle was labelled strongly with antibody to FM and control slow muscle with antibody to SM; label was confined to the A-band. Well-defined differences in the distribution of label within the A-band suggested that the monoclonal antibodies used corresponded to epitopes on different parts of the myosin molecule; this was confirmed by Western blots of subfragments prepared from FM and SM. After 4 weeks of continuous stimulation at 10 Hz, fibres of the tibialis anterior muscle reacted with antibodies to both isoforms; after 6 weeks, labelling was obtained only with antibody to SM. After a 7-week period of stimulation and 3 further weeks of recovery, fibres again reacted with both antibodies. In all positively-labelled sections, the distribution of gold particles was characteristic of the antibody and independent of the origin or history of the fibres. This observation supports the conclusion that newly synthesized myosin is capable of being incorporated throughout the length and cross-section of the A-band.

Animals↗
PubMed1990

Setting reactions and compressive strengths of calcium phosphate cements.

Setting reactions and compressive strengths of a self-hardening calcium phosphate cement (CPC) were investigated. The CPC consists of tetracalcium phosphate (TTCP) and anhydrous dicalcium phosphate (DCPA). The cement specimens were prepared by mixing 0.7 g of the powder (TTCP 72.9 wt% + DCPA 27.1 wt%) with 0.175 mL of the liquid (25 mmol/L H3PO4 and 1.32 mmol/L sodium fluoride). The specimens were removed from the molds at pre-determined time intervals after being mixed, and their compressive strengths were measured. Immediately afterward, the fractured specimens were rapidly frozen in ethanol (-80 degrees C), lyophilized, and examined by powder x-ray diffraction and scanning electron microscopy (SEM). The results showed that (1) hydroxyapatite was the only reaction product; (2) the reaction was nearly completed within four h, during which both the reaction product and compressive strength increased linearly with time, resulting in a strong correlation between the two; and (3) fully set CPC consisted primarily of small rod-like crystals and some platy crystals.

Calcium Phosphates↗
PubMed1990

Cauda equina syndrome of long-standing ankylosing spondylitis. Case report and review of the literature.

Cauda equina syndrome as a neurological complication of long-standing ankylosing spondylitis was first reported in 1961. The syndrome is relatively uncommon and its pathophysiology is still poorly understood. Based on their experience with such a case, the authors review the clinical, electrographic, histological, and radiographic features of the syndrome, including the findings of magnetic resonance (MR) imaging. The addition of MR imaging to the evaluation of patients with ankylosing spondylitis and the cauda equina syndrome not only aids in the diagnosis of the syndrome but may also provide valuable insight into the pathophysiology of this condition.

Cauda Equina↗
PubMed1989

Uptake and distribution of 14C during and following inhalation exposure to radioactive toluene diisocyanate.

Inhalation of toluene diisocyanate (TDI) results in toxic responses ranging from pulmonary irritation to immunological sensitization. The use of radioactively labeled isocyanate has made it possible to follow the initial uptake of the compound into the bloodstream independent of the final fate of the isocyanate. This study shows that the rate of uptake into the blood is linear during exposure to concentrations ranging from 0.00005 to 0.146 ppm and that the uptake continues to increase slightly postexposure. It also demonstrates that the radioactivity clears from the bloodstream to a level corresponding to approximately a 100 nM concentration of tolyl group after 72 hr and persists at a nanomolar level even 2 weeks following the exposure. This is similar to the response previously reported by this group for radioactively labeled methyl isocyanate. The initial rate of 14C uptake is also a linear function of the concentration of TDI when expressed either as concentration (ppm) or as concentration multiplied by duration of exposure (ppm.hr). This is discussed in comparison with the toxic responses as a function of both ppm and ppm.hr. Finally, the inclusion of the data on methyl isocyanate indicates that the uptake into arterial blood is a function of exposure concentration, independent of isocyanate structure.

Administration, Inhalation↗
PubMed1989

Comparison of fluoride uptake produced by tray and flossing methods in vitro.

The purposes of this study were to compare: (i) the fluoride (F) uptake by enamel in approximal areas of teeth when the F agent was applied in vitro via a tray or a flossing technique; and (ii) the effectiveness of two treatments--acidulated phosphate fluoride (APF) alone and CaHPO4.2H2O (DCPD)-forming pre-treatment followed by APF. Groups of three teeth (one premolar and two molars) were mounted in impression compounds simulating their oral configuration. In the tray group, teeth received one four-minute treatment by means of custom-formed trays. In the flossing group, the approximal areas of teeth were flossed for 40 sec twice daily for three days with an absorbent floss wetted with the treatment solution. All teeth were incubated in a saliva-like solution except during treatment. At the end of the three-day period, teeth were unmounted and washed in 1 mol/L KOH for 24 hours. The F uptake was calculated from biopsy data obtained before and after the treatment. The results showed that (i) DCPD-APF produced significantly greater F uptake than APF alone in both the tray and flossing methods, and (ii) the flossing technique produced significantly greater F uptake in the approximal areas than the tray method for either treatment.

Dental Devices, Home Care↗
PubMed1989

Cerebral shift after lateral craniofacial resection and flap reconstruction.

The biomechanical effects on the cranial contents after craniectomy and immediate soft-tissue flap reconstruction are substantial and potentially life threatening. Once the rigid protective covering of the skull is removed, the cerebral component of the cranial contents is vulnerable to rising extrinsic pressure. Intracranial pressure falls, brain compliance rises, and contralateral cerebral shift may occur by virtue of the craniectomy alone. However, if flaps filling the defect should compress by weight or swelling, even greater midline or craniocaudal shift of the brain may occur. We present three cases in which midline cerebral shift was documented by CT scan after flap reconstruction of lateral craniofacial/craniotemporal resection. Three other patients undergoing anterior craniofacial resection during the same time period for skin cancer (one patient) and esthesioneuroblastoma (two patients) had no shift in intracerebral contents. Symptomatic or asymptomatic intracranial shift may occur soon after substantial craniectomy and soft-tissue flap reconstruction. Midline shift from lateral resection and reconstruction is more likely than anteroposterior shift from anterior craniofacial resection. Strategies for minimizing this compression or shift are described.

Adolescent↗
PubMed1989

Polytetrafluoroethylene interposition grafts in vertebral to carotid artery transposition. A long-term follow-up study.

Eight patients undergoing an end-to-side vertebral artery (VA) to common carotid artery transposition between August, 1979, and July, 1982, had a polytetrafluoroethylene (PTFE) interposition graft placed when a direct anastomosis was believed not to be satisfactory. Five of these patients are living; clinical and radiographic follow-up studies over periods ranging between 54 and 82 months show that their transpositions are patent. Two patients died perioperatively, one from an acute anterior myocardial infarction and the other from acute VA occlusion with a propagating thrombus. A third patient died of myocardial infarction 20 months after graft placement; the anastomosis had been found patent at 12 months. This report gives the clinical and radiographic follow-up results in a previously reported group of patients with PTFE interposition grafts. Some of these patients have been followed for over 6 years after surgery: the average radiographic follow-up period in the five survivors is 60 months, and all grafts are patent without evidence of progressive stenosis. Expanded PTFE appears to be an acceptable material for short interposition grafts in operations involving the VA; however, direct artery-to-artery anastomosis is preferred. The results of longer PTFE grafts in reconstructive cerebrovascular surgery have not been adequately studied.

Aged↗
PubMed1989

Skeletal muscle ventricles: improved performance at physiologic preloads.

We attempted to construct skeletal muscle ventricles (SMVs) so that they would develop optimal stroke work at physiologic preloads of 5 to 15 mm Hg. Thirty-one SMVs were constructed in mongrel dogs. The effects of electrical preconditioning with 2 Hz continuous and 25 Hz burst patterns were evaluated, as well as the application of passive stretch to the muscle fibers during preconditioning. We evaluated the stroke work developed by these SMVs at afterloads of 30 mm Hg and 80 mm Hg in vivo, using a mock circulation device. During mock circulation studies, the SMVs were stimulated via the thoracodorsal nerve with either a 25 Hz or 85 Hz burst pattern. SMVs with 2 Hz preconditioning developed significantly higher stroke work than SMVs with 25 Hz preconditioning under all conditions of afterload, preload, and stimulation frequency (p less than or equal to 0.001). Under these conditions, for the 2 Hz preconditioned SMVs, passive stretch during preconditioning resulted in a further significant increase in developed stroke work (p less than 0.05). For these SMVs, with an 85 Hz stimulation frequency, stroke work averaged 410% of canine RV stroke work, and 59% of canine LV stroke work at physiologic preloads and afterloads.

Animals↗