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Biomedical subjects

C David

Publications and source records attributed to C David.

At least 37 records · Page 2Linked to original sources
PubMed1991

Fluconazole therapy for chronic disseminated candidiasis in patients with leukemia and prior amphotericin B therapy.

OBJECTIVE: To study the efficacy of fluconazole against chronic disseminated candidiasis (hepatosplenic candidiasis) in patients with leukemia in whom amphotericin B treatment had failed. DESIGN: Retrospective analysis of patients with chronic disseminated candidiasis treated with fluconazole on a compassionate investigational new drug protocol. SETTING: Multi-institutional. PATIENTS AND METHODS: Twenty consecutive patients received 100 to 400 mg of fluconazole per day for a median of 30 weeks. All had either failed to respond to treatment with more than 2 g of amphotericin B or had serious amphotericin B-related toxicities. RESULTS: Fourteen of 16 evaluable patients (88%) responded. Responses were observed in seven of nine patients in whom adequate doses of amphotericin B had failed and in all seven patients who had amphotericin B-related toxicities. In 12 patients, cytotoxic chemotherapy was continued without flare of the infection. Fluconazole was well tolerated with rare side effects. Aspergillus superinfection developed in three patients and contributed to the death of two of them. CONCLUSION: Fluconazole is a safe and effective agent with significant activity against chronic disseminated candidiasis.

Adult↗
PubMed1991

Integration site-dependent expression of a transgene reveals specialized features of cells associated with neuromuscular junctions.

After skeletal muscle is denervated, fibroblasts near neuromuscular junctions proliferate more than fibroblasts distant from synaptic sites, and they accumulate adhesive molecules such as tenascin (Gatchalian, C. L., M. Schachner, and J. R. Sanes. 1989. J. Cell Biol. 108:1873-1890). This response could reflect signals that arise perisynaptically after denervation, preexisting differences between perisynaptic and extrasynaptic fibroblasts, or both. Here, we describe a line of transgenic mice in which patterns of transgene expression provide direct evidence for differences between perisynaptic and extrasynaptic fibroblasts in normal muscle. Transgenic mice were generated using regulatory elements from a major histocompatibility complex (MHC) class I gene linked to the Escherichia coli beta-galactosidase (lacZ) gene. Expression of lacZ was detected histochemically. In each of eight lines, lacZ was detected in different subsets of cells, none of which included lymphocytes. In contrast, endogenous MHC is expressed in most tissues and at high levels in lymphocytes. Thus, the MHC gene sequences appeared inactive in the transgene, and lacZ expression was apparently controlled by genomic regulatory elements that were specific for the insertion site. In one line, cells close to the neuromuscular junction were lacZ positive in embryonic and young postnatal mice. Electron microscopy identified these cells as fibroblasts and Schwann cells associated with motor nerve terminals, as well as endoneurial fibroblasts, perineurial cells, and Schwann cells in the distal branches of motor nerves. No intramuscular cells greater than 200 microns from synaptic sites were lacZ positive. These results indicate that there are molecular differences between perisynaptic and extrasynaptic fibroblasts even in normal muscle and that diverse perisynaptic cell types share a specific pattern of gene expression.

Animals↗
PubMed1991

Antigenic mimicry and autoimmune diseases.

The finding of cross-reactive autoantibodies or sequence homology does not necessarily mean that this molecular mimicry is biologically meaningful or associated with disease pathogenesis. For example, relatives of persons with putative autoimmune insulin-dependent diabetes [123], and elderly humans [124] have a high incidence of autoantibodies which are generally not associated with autoimmune disease. In addition, natural antibodies to cell constituents [125] may be present in normal sera. These antibodies need to be directed against biologically important domains of host cell proteins in order to mediate autoimmune disease [27]. In spite of extensive homology between two sequences, a cross-reactive immune response may not be generated. The dissimilar amino acids should not be radical substitutions or affect the binding properties of the molecule. For instance, antibodies to synthetic peptides with only one substitution in a 19 amino acid sequence may not bind the whole protein [126]. Despite an identical six amino acid sequence shared by HLA-B27 and an EBV protein, no cross-reactive antibodies to EBV peptides were found in HLA-B27 positive patients with AS or RS. Unless the homology and subsequent crossreactive immune response can recognize a host protein intimately involved in disease pathogenesis, autoimmune disease is unlikely to occur.

Amino Acid Sequence↗
PubMed1991

[A new case of autochthonous visceral leishmaniasis in Bolivia].

A sixth autochthonous case of visceral leishmaniasis is reported in Bolivia. It is also the fourth case detected in the Yungas Valley (Department of La Paz) confirming the long-term existence of the disease in this area where cases of canine leishmaniasis and natural infestation of the phlebotomine sandfly, Lutzomyia longipalpis, were previously reported.

Antimony Sodium Gluconate↗
PubMed1991

Antipeptide antibodies localize N-(4-azido-3-[125I] iodophenethyl)spiperone binding to the carboxyl-terminal portion of the D2 dopamine receptor.

Antibodies against synthetic peptides of the D2 dopamine receptor were used, in combination with photoaffinity labeling, to localize the region of ligand binding in the receptor. Specific antibodies to peptide sequences 221-234 and 259-272 and to the carboxyl-terminal peptide 402-415, all corresponding to cytoplasmic regions in the D2 dopamine receptor, were elicited. After photoaffinity labeling with N-(4-azido-3-[125I]iodophenethyl)spiperone ([125I]NAPS), all three antibodies specifically immunoprecipitated the 90-kDa D2 dopamine receptor. Differential reactivity of the antipeptide antibodies with various proteolytic fragments indicates that [125I]NAPS binds covalently to a 13-kDa fragment of the D2 dopamine receptor. This fragment is immunoprecipitated with anti-peptide 402-415 and not with the other two antipeptide antibodies, indicating that the photoaffinity ligand binds to a fragment that begins beyond amino acid 272 and extends through the carboxyl-terminal end of the receptor.

Affinity Labels↗
PubMed1990

Isolation and partial characterization of ascites sialoglycoprotein-2 of the cell surface sialomucin complex of 13762 rat mammary adenocarcinoma cells.

Sialomucins are the dominant components of the cell surfaces of some carcinoma ascites cells and have been postulated to inhibit recognition of tumours by the immune system. The sialomucin ASGP-1 (ascites sialoglycoprotein-1) of the 13762 rat mammary adenocarcinoma is associated with the cell surface as a complex with a concanavalin-A-binding glycoprotein called ASGP-2. This sialomucin complex has been purified from ascites cell microvilli by extraction with Triton X-100 and CsCl density-gradient centrifugation. ASGP-1 (which has been purified previously) and ASGP-2 were dissociated in 6 M-guanidine hydrochloride and separated by gel filtration. The molecular mass of the undenatured detergent complex of ASGP-2, estimated by gel filtration and velocity sedimentation in Triton X-100, was 148 kDa. Since the apparent molecular mass by SDS/polyacrylamide-gel electrophoresis was about 120 kDa, ASGP-2 must be a monomer as extracted from the membrane. Studies of its chemical composition indicate that it contains about 45% carbohydrate by weight, including both mannose and galactosamine. Alkaline borohydride treatment of ASGP-2 converted approx. half of the N-acetylgalactosamine to N-acetylgalactosaminitol, demonstrating the presence of O-linked oligosaccharides. Analyses of mannose-labelled Pronase glycopeptides from ASGP-2 by lectin-affinity chromatography on concanavalin A and leucocyte-agglutinating phytohaemagglutinin suggested that 40% of the label was present in high-mannose/hybrid oligosaccharides, 20% in triantennary oligosaccharides substituted on the C-2 and C-4 mannose positions and 40% in tri- or tetra-antennary oligosaccharides substituted on C-2 and C-6. The presence of polylactosamine sequences on these oligosaccharides was suggested by lectin blots and by precipitation from detergent extracts with tomato lectin. From chemical analyses and lectin-affinity studies, we estimate that ASGP-2 contains four high-mannose and 13 complex N-glycosylated oligosaccharides, plus small amounts of polylactosamine and O-linked oligosaccharides. The presence of four different classes of oligosaccharides on this glycoprotein suggests that it will be an interesting model system for biosynthetic comparisons of the different glycosylation pathways.

Adenocarcinoma↗
PubMed1990

Comparison of four indirect methods for fluid superoxide dismutase activities.

Relatively small sample dilutions could render fluid extracellular (EC) superoxide dismutase (SOD) activity assays more subject to interfering compounds than tissue SOD assays. Highly variable relative SOD activities were obtained when comparing four indirect assays for several fluid samples (human plasma, human synovial fluid, and plasma from healthy or inflamed rats). Analysis of rat plasma fractionated with Sephadex G-150 showed that each assay (three xanthine oxidase based assays plus a modified pyrogallol assay) detected apparent SOD activity almost entirely at the same molecular weight as rat lung EC SOD. However, unfractionated fluid samples caused interferences with the xanthine oxidase based SOD assays, though not with the pyrogallol method. Example of interference were stimulation of xanthine oxidase activity, color formation without xanthine oxidase, color formation despite excess Cu-Zn SOD addition, and absorbance changes with cyanide inhibition of EC SOD that were above or below blank values. In summary, relative fluid SOD values depended on the assay used, and a modified pyrogallol assay was not subject to several interferences found for three xanthine oxidase based assays of fluid SOD activity.

Animals↗
PubMed1990

Expression and function of mutant Ia antigen in transgenic mice.

Cell surface expression of Ia antigens requires the assembly of alpha and beta heterodimers. We have produced a double transgenic mouse with a wild form Ak alpha gene and a mutant Ak beta (Ak beta MB) gene with d-allele substitution at positions 63 and 65-67. Initial studies indicated that the Ak alpha and Ak beta MB transgenes are not expressed on the surface of lymphoid cells of the transgenic mice. However, when spleen cells were stimulated with LPS prior to FACS analyses, Ak/Ak MB assembly and subsequent surface expression was induced. The tail skins from transgenic founder mice were rejected by the parental mice indicating a role for the mutant antigen on the allograft. In addition, the Ak transgenic mice on H-2q/q background can partially delete V beta 6+ T cells, suggesting the presence of the transgene product in the thymus.

Animals↗
PubMed1990

Endoscopic ultrasonography in staging rectal cancer.

Endoscopic ultrasonography (EUS) was used to stage rectal cancer by assessing depth of invasion through bowel wall layers and/or involvement of lymph nodes. EUS findings were correlated with histopathologic findings to discern the usefulness of this modality in predicting which patients could be candidates for sphinctersaving procedures and the avoidance of abdominoperineal resection. The Olympus EU-M3 endoscopic ultrasound system was used to assess depth of penetration through rectal wall layers and to identify lymph nodes. Comparison of EUS findings to histopathologic findings was possible in 13 patients. EUS agreed with histopathology in 9 of 13 cases (69.3%) ( p = 0.07, kappa statistic). EUS agreed with histopathology as the presence or absence of lymph nodes in 9 of 13 cases (69.3%) (p = 0.07). However, the presence of lymph nodes could not necessarily predict metastatic involvement of these nodes. In one patient, invasion of vaginal cuff was correctly predicted. In nine cases, computed tomographic analysis (CT) was available for comparison to EUS in detection of penetration beyond the bowel wall. CT agreed with histopathology in 3 of 9 (33%), whereas EUS agreed with histopathology in 7 of 9 (78%).

Adenocarcinoma↗
PubMed1990

Changes in membrane properties during in-vitro meiotic maturation of the limpet Patella vulgata.

Changes in the membrane properties of the oocyte of the mollusk, Patella vulgata, were analyzed following the induction of meiosis reinitiation by paleopedial ganglia extract or by the weak base ammonia. During maturation it was possible to distinguish between an early phase characterized by an initial hyperpolarization and a late phase consisting of a depolarization which triggers an action potential with a long-term overshoot (20 minutes) of the membrane potential. Major changes in individual ionic permeabilities were studied using both current and voltage clamp conditions. The depolarizing phase appears to depend on decreases in K+ membrane permeability. Finally we observed that the overshoot did not appear to be directly related to germinal vesicle breakdown (GVBD) since it was absent in Na-deprived artificial sea water and could be elicited in the presence of TEA bromide, which did not induce maturation. This last observation suggests that it may result from a change in specific K+ ion permeability due to the possible activation of stretch channels.

Action Potentials↗
PubMed1989

Osteosarcoma metastatic to the kidney.

Two clinically silent renal metastatic lesions from primary osteogenic sarcoma were first detected on radionuclide bone scan. A needle biopsy performed under the guidance of abdominal ultrasonography confirmed the diagnosis. Prior to nephrectomy, further definition of the metastatic lesion was attained using enhanced computed tomography. A review of the English literature revealed only six previous cases of metastatic osteosarcoma detected in the kidney prior to autopsy.

Adolescent↗
PubMed1989

Antibodies to synthetic peptide from the residue 33 to 42 domain of c-Ha-ras p21 block reconstitution of the protein with different effectors.

Residues 32 to 40, which are conserved among ras proteins from different species, are likely to participate in interactions with the p21 effector system. With the goal of understanding the structural basis of the regulatory functions of c-Ha-ras p21, we produced rabbit antisera against a synthetic peptide corresponding to amino acids 33 to 42 of the protein. The affinity-purified antibodies interacted specifically with p21 and with the antigenic peptide. The epitope recognized by the antibodies appeared to be centered on threonine 35. The antibodies inhibited both in vitro p21-induced production of cyclic AMP in detergent extracts of RAS-defective yeast membranes and GAP-stimulated GTPase activity. However, monoclonal anti-ras antibodies Y13-259 and Y13-238 were not capable of specifically inhibiting interactions of p21 with these two putative effector proteins. The apparent inhibitory effect of Y13-259 on stimulation of p21 by GAP was due to a greatly reduced rate of exchange of nucleotides in the binding pocket of the protein. These findings provide additional support for the essential role of the residue 32 to 40 domain as the true effector site and further evidence of the involvement of GAP as a cellular effector of ras proteins.

Amino Acid Sequence↗
PubMed1988

Purification of the D-2 dopamine receptor from bovine striatum.

The D-2 dopamine receptor has been purified 21500 fold from bovine striatal membranes. Solubilized receptor preparation was partially purified by affinity chromatography on a haloperidol adsorbent followed by gel filtration on a Sephacryl S-300 column. The fractions eluted from this column which contained the ligand binding activity were further chromatographed on wheat germ agglutinin conjugated to Sepharose. The resulting receptor preparation displays a major polypeptide band of an apparent molecular weight of 92 kDa, and exhibits a specific binding activity of 2490 pmol spiperone per mg protein. This purified receptor preparation can reabsorb specifically to the haloperidol affinity column indicating that the 92 kDa polypeptide represents the ligand binding unit of the D-2 dopamine receptor.

Animals↗
PubMed1988

Some properties of the membrane currents underlying the fertilization potential in sea urchin eggs.

1. The ionic currents that underly the fertilization potential of sea urchin eggs were studied in Lytechinus pictus using a single-electrode voltage clamp technique. 2. In unfertilized eggs, a transient inward current was activated at membrane potentials more positive than -45 mV. The maximum amplitude of the current was 0.56 +/- 0.35 nA (mean +/- S.D., n = 33) at a membrane potential of -35 to -25 mV. 3. The amplitude of this transient inward current was decreased by reducing the external concentration of calcium ions and by substituting barium or strontium ions for calcium in the external medium. Cobalt (10-20 mM) and gadolinium (200-500 microM) ions reduced the amplitude of this current in the presence of calcium ions. 4. A transient outward current was activated in unfertilized eggs at membrane potentials more positive than -10 mV. This current inactivates with a time constant of 16 ms at a membrane potential of -9 mV and re-activates over a period of several seconds at a membrane potential of -72 mV. 5. When unfertilized eggs were treated with the calcium ionophore A23187 under voltage clamp conditions, an inward current developed. It reached a maximum 30 s after its onset and declined thereafter. By 90 s it had become constant at 10% of its peak value. 6. The inward current induced by A23187 was voltage dependent. It was maximal at -25 mV in the steady state. 7. When eggs were fertilized under voltage clamp conditions, the fertilization current, If, was recorded. At a holding potential of -50 or -70 mV If had the following characteristics: (a) an initial inward shoulder with a duration ranging from 12 to 30 s; (b) an inward current peak that was attained between 40 and 100 s after the onset of the shoulder current and declined over the next 60 s; (c) an outward current that appeared after the inward current had declined. 8. Current-voltage relations obtained during If showed that the late component of the inward current was voltage dependent. It was maximal at -25 mV in the steady state and resembled the late component of the inward current recorded in A23187-activated eggs. 9. These results indicate that the form of the action potential in unfertilized eggs is due to the activation of a transient inward current and an inactivating outward current. The sustained depolarization after fertilization is due to the activation of a voltage-dependent inward current by the increase in intracellular free calcium concentration that occurs at fertilization.

Action Potentials↗
PubMed1988

[In vitro effect of combinations of netilmicin and amikacin with fosfomycin and pefloxacin on 31 strains of heterogeneous methicillin- resistant Staphylococcus aureus].

The Minimal Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) of 31 strains of Staphylococcus aureus resistant to methicillin and gentamicin were determined towards aminoglycosides: netilmicin (N) and amikacin (A). The results of the study showed a large discordance between the technic using dilution in Mueller-Hinton broth and the technic using agar diffusion with antibiotic discs. The level of sensitivity appears to decrease by dilution. The problem of using these aminoglycosides in combination with other antibiotics as fosfomycin (F) and pefloxacin (P) was faced. In vitro, antibacterial activity of combinations [N-F], [N-P] and [A-F], [A-P], was studied by microtiter checkerboard method. The antibacterial effects of these combinations were evaluated by determination of Fractional Bactericidal Indices (FBC-indices). The combination netilmicin or amikacin with pefloxacin has an additive bactericidal effect in most cases, without discrimination between the different aminoglycosides (FBC #0.82). Netilmicin or amikacin in combination with fosfomycin are found to be additive or moderately synergistic (FBC #0.53). No occurrence of antagonism was observed.

Amikacin↗