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Biomedical subjects

D M King

Publications and source records attributed to D M King.

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

In-vitro resistance to zidovudine and alpha-interferon in HIV-1 isolates from patients: correlations with treatment duration and response.

OBJECTIVE: To measure in-vitro antiviral drug susceptibilities of human immunodeficiency virus type 1 (HIV-1) isolates recovered from patients treated with alpha-interferon or zidovudine and patients not treated with these drugs and to examine the relation of these susceptibility measurements to duration of therapy, disease stage, and response to alpha-interferon therapy. DESIGN: Cross-sectional study. SETTING: Outpatient HIV clinic. PATIENTS: Twenty-six ambulatory HIV-1-infected patients: Fifteen of these patients were receiving alpha-interferon therapy, and 11 had never received such therapy. Nine patients were participating in a clinical trial of combination therapy with zidovudine and alpha-interferon. MEASUREMENTS: The 50% inhibitory concentration (IC50) of zidovudine and alpha-interferon was determined for HIV-1 isolates recovered from each patient. Plasma concentrations of HIV-1 p24 antigen in the nine patients in the clinical trial were measured monthly after alpha-interferon was added to zidovudine monotherapy. RESULTS: Zidovudine IC50 (range, 0.01 to 4.87 microM) increased steadily with duration of zidovudine therapy (r = 0.57, P = 0.003). In contrast, alpha-interferon IC50 (range, 0.8 to 415 units/mL) was not related to duration of alpha-interferon treatment; in fact, high IC50s were found in isolates from patients who had never received exogenous alpha-interferon therapy. Resistance to alpha-interferon was greater in isolates from the 15 patients with the acquired immunodeficiency syndrome (AIDS) (median, 104 units/mL) than in those from the 10 patients without AIDS (median, 50 units/mL). Interferson activity was detected in plasma samples from 23 of 24 patients and was also at higher levels in patients with AIDS than in HIV-infected patients without AIDS. Reductions in plasma concentrations of HIV-1 p24 antigen in nine patients after beginning alpha-interferon therapy were greater in those with more susceptible isolates (r = -0.72, P = 0.03). CONCLUSIONS: Interferon resistance, possibly due to endogenous interferon, is not related to duration of interferon therapy but may limit the effectiveness of interferon therapy. Determinations of interferon susceptibility may identify patients most likely to benefit from this agent.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Resistance to ddI and sensitivity to AZT induced by a mutation in HIV-1 reverse transcriptase.

Serial human immunodeficiency virus type-1 (HIV-1) isolates were obtained from five individuals with acquired immunodeficiency syndrome (AIDS) who changed therapy to 2',3'-dideoxyinosine (ddI) after at least 12 months of treatment with 3'-azido-3'-deoxythymidine (zidovudine, AZT). The in vitro sensitivity to ddI decreased during the 12 months following ddI initiation, whereas AZT sensitivity increased. Analysis of the reverse transcriptase coding region revealed a mutation associated with reduced sensitivity to ddI. When this mutation was present in the same genome as a mutation known to confer AZT resistance, the isolates showed increased sensitivity to AZT. Analysis of HIV-1 variants confirmed that the ddI resistance mutation alone conferred ddI and 2',3'-dideoxycytidine resistance, and suppressed the effect of the AZT resistance mutation. The use of combination therapy for HIV-1 disease may prevent drug-resistant isolates from emerging.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Imaging properties of polydioxanone and titanium ligating clips following para-aortic lymphadenectomy for testicular cancer.

Stainless steel ligating clips produce serious artefacts on CT scans. Polydioxanone (PDS) and titanium ligating clips were used in 15 patients during para-aortic lymphadenectomy for residual metastatic testicular teratoma following chemotherapy, and follow-up CT images were compared with those following the use of stainless steel ligating clips. PDS ligating clips did not produce any artefacts and were progressively absorbed. Titanium ligating clips produced artefacts similar to but less intense than those of stainless steel. PDS ligating clips should be used when follow-up CT scanning is important.

Constriction↗
PubMed1991

Immunogenicity, antigenicity, and endothelial viability of aortic valves preserved at 4 degrees C in a nutrient medium.

In patients undergoing aortic valve replacement, allograft valves stored at 4 degrees C in a nutrient medium have been associated with excellent immediate and long-term results. The effects of this method of prolonged storage on the antigenic, immunological and cellular characteristics of these grafts are incompletely understood. This study was designed to study these phenomena in rat aortic valves subjected to antibiotic sterilization and stored for up to 3 weeks in RPMI containing 10% fetal calf serum. Selected valves from Brown Norway rats were implanted heterotopically into the abdominal aorta of Lewis rats. Other valves were studied prior to transplantation. Antigenicity was determined by immunocytochemical staining using monoclonal mouse antibodies directed at Class I and Class II rat antigens. Immunogenicity was determined by duration of second-set skin graft survival following heterotopic aortic valve implant. Endothelial cell viability was determined by flow cytometric analysis of endothelial cells harvested from aortic valve allografts by collagenase digestion. Only fresh valves and valves stored for 1 day were positive for Class I antigens; no valves were positive for Class II antigens. Duration of skin graft survival was prolonged with greater duration of storage, but grafts remained immunogenic after 21 days of storage. Endothelial cell viability declined from 95% in the fresh valves to 64% after 21 days of storage. With prolonged duration of allograft valve storage at 4 degrees C, there is an attenuation of antigenicity, immunogenicity, and endothelial cell viability. Loss of endothelial cells may contribute to the changes in immunological responses to the valve allografts. The expression of antigens on the endothelial surface is not a reliable predictor of immunological response.

Animals↗
PubMed1990

Preoperative cytology and mammography in patients with single-duct nipple discharge treated by surgery.

Microdochectomy has been the routine management for single-duct nipple discharge. Our review of 176 consecutive patients surgically treated between 1975 and 1988 revealed eight patients with in situ carcinomas and seven with infiltrative carcinomas. Seventeen patients had multiple papillomas, two had atypical hyperplasia and two had atypical epitheliosis. Case selection for surgery has recently been advocated. In our study, nipple discharge cytology was helpful in 67 per cent of cases with underlying malignant pathology. Mammography was found to be unreliable, alerting suspicion in only two of 15 cases.

Adolescent↗
PubMed1990

Binding of epidermal growth factor to its receptor is affected by membrane phospholipid environment.

Cells of epithelial origin generally require ethanolamine to grow in culture; when these cells are grown without ethanolamine, the phosphatidylethanolamine content of their membrane phospholipid becomes 1/2 to 1/3 of the normal amount, and growth stops. We have hypothesized that growth ceases because the phospholipid environment becomes unsuitable for membrane-associated function. Using ethanolamine-requiring rat mammary cells, we have investigated the possible effect of phosphatidylethanolamine deficiency on the binding characteristics of epidermal growth factor. Apparent dissociation constant for the high-affinity sites in cells having normal membrane phospholipid was 1.7 X 10(-10) M, whereas that of phosphatidylethanolamine-deficient cells was 2.7 X 10(-10) M: the difference was small, but significant. Pretreatment with phorbol ester caused the loss of high-affinity sites in cells having normal membrane, whereas binding characteristics of epidermal growth factor became refractory to the pretreatment in phosphatidylethanolamine-deficient cells. In addition, the rate of internalization of bound epidermal growth factor in phosphatidylethanolamine-deficient cells was about 1/4 of normal cells. Further, whether cells had normal or phosphatidylethanolamine-deficient membranes seemed to affect the phosphorylation patterns of membrane proteins in response to epidermal growth factor or phorbol ester. These results suggest that membrane phospholipid environment affects the activity of the epidermal growth factor receptor.

Animals↗
PubMed1990

Gentamicin iontophoresis in the treatment of bacterial otitis externa in the guinea pig model.

Pseudomonas otitis externa is one of the most common infections treated by otolaryngologists. Infections induced in 30 guinea pigs appeared similar to that seen in humans. The ears were then placed into four treatment groups: group A, which received a single cleaning; group B, which received a single cleaning followed by gentamicin drops 4 times daily; group C, which received a single cleaning followed by a single gentamicin iontophoresis treatment; and group D, the control group, which received no treatment. Infections were analyzed by grading edema, purulence, and erythema. An average of 10.2 days was required for control group to return to normal appearance. Groups A, B, and C had mean resolution times of 5.9, 4.7, and 4.3 days, respectively. Gentamicin iontophoresis appears to be promising, with results as good as drop therapy in otitis externa in the guinea pig model.

Animals↗
PubMed1988

Effects of phosphatidylethanolamine and phosphatidylcholine in membrane phospholipid on binding of phorbol ester in rat mammary carcinoma cells.

Mammalian cells in culture can be classified as either ethanolamine (Etn)-responsive or Etn-nonresponsive with regard to their growth. Epithelial cells and some of their transformed derivatives are the Etn-responsive type. When these cells are grown without Etn, the content of membrane phospholipid becomes significantly altered. Namely, the content of phosphatidylethanolamine is reduced and that of phosphatidylcholine is increased. In addition, the growth rate of these cells is reduced. Therefore, it is likely that the phosphatidylethanolamine deficiency or phosphatidylcholine excess is unsuitable for some membrane-associated functions resulting in the cessation of growth. In order to test the above hypothesis, we examined the binding of a tumor-promoting phorbol ester, [3H]phorbol 12,13-dibutyrate (PDB), to an Etn-responsive rat mammary carcinoma cell line 64-24 grown with (Etn-plus) or without Etn (Etn-minus). The time course of binding was very similar between Etn-plus and -minus cells, except that the level of saturation was higher in Etn-plus cells, whereas the time course of chase of the bound PDB was significantly different between the two types of cells. Both types of cells have one class of binding sites for PDB. The dissociation constant (Kd) for [3H]PDB in Etn-plus cells was 34.0 nM and the number of binding sites at saturation was 2.7 x 10(12)/mg protein or 3.6 x 10(5)/cell. The corresponding values in Etn-minus cells were 61.4 nM and 3.2 x 10(12)/mg protein or 5.4 x 10(5)/cell, respectively. Although the difference in Kd values of the two types of cells was only 2-fold, this difference was statistically significant. On the other hand, the number of binding sites/mg protein in these cells was very similar. Since the amount of protein/cell was 1.4-fold higher in Etn-minus cells as compared to that of Etn-plus cells, the number of binding sites/cell was larger in Etn-minus cells. PDB affected the rate of proliferation of 64-24 cells differently, depending on whether they were grown in the presence or absence of Etn. These results suggest that the phosphatidylethanolamine and/or phosphatidylcholine content of the membrane phospholipid affects cellular functions mediated by phorbol esters.

Animals↗
PubMed1988

Insufficiency of transformation by simian virus 40, polyomavirus, EJ-ras, or v-myc oncogenes for conversion of ethanolamine-responsive mammary cells to ethanolamine-nonresponsive cells.

Normal mammary epithelial cells (ethanolamine responsive) require ethanolamine to enable them to grow in defined culture medium because they cannot synthesize de novo a sufficient amount of phosphatidylethanolamine. Mammary tumor cells which retain properties of the normal tissue are also likely to be ethanolamine responsive, whereas dedifferentiated, highly tumorigenic mammary tumor cells are ethanolamine nonresponsive. The nonresponsive tumor cells are able to synthesize the necessary amount of phosphatidylethanolamine to sustain growth. Therefore, the progression of malignancy seems to convert ethanolamine-responsive mammary cells to ethanolamine-nonresponsive ones. In an attempt to prove the above assumption and to understand the mechanism responsible for the conversion during the progression of malignant transformation, mammary tumor cell line 64-24, which is typically ethanolamine responsive, was transfected with simian virus 40, polyomavirus, EJ-ras, or v-myc oncogenes, and the resulting transfectants were examined for their growth response to ethanolamine. Many of the transfectants exhibited typical transformed phenotypes; however, none of the transfectants converted to ethanolamine-nonresponsive cells. Some of the SV40 and polyomavirus transformants were able to grow in the absence of ethanolamine, although they grew better in the presence of ethanolamine, unlike typical ethanolamine-nonresponsive cells. These cells could grow in the absence of ethanolamine, even though their membrane phospholipid was phosphatidylethanolamine deficient. The present study indicates that the expression of any one of the four oncogenes tested, which allows the cells to exhibit transformed phenotypes in 64-24 cells, is not sufficient for the conversion of ethanolamine-responsive cells to -nonresponsive cells.

Animals↗
PubMed1987

Phosphatidylethanolamine biosynthesis in rat mammary carcinoma cells that require and do not require ethanolamine for proliferation.

Epithelial cells and some of their transformed derivatives require ethanolamine to grow normally in defined culture medium. When these cells are cultured without ethanolamine, the amount of cellular phosphatidylethanolamine is considerably reduced. Using a set of rat mammary carcinoma cell lines whose growth is responsive (64-24 cells) and not responsive (22-1 cells) to ethanolamine, the biochemical mechanism of ethanolamine responsiveness was investigated. The biosynthesis and metabolism of phospholipid, particularly of those involving phosphatidylethanolamine, were thus compared between the two types of cells. The incorporation of [3H]serine into phosphatidylserine and phosphatidylethanolamine in 64-24 cells was 60 and 37%, respectively, of those in 22-1 cells. However, the activity of phosphatidylserine decarboxylase was virtually the same in these cell lines. When these cells were cultured in the presence of [32P]phosphatidylcholine and [32P]phosphatidylethanolamine, the rate of accumulation of 32P-labeled phosphatidylserine from the radioactive phosphatidylethanolamine was considerably reduced in 64-24 cells compared to that in 22-1 cells, although the rate of synthesis of phosphatidylserine and phosphatidylethanolamine from the radioactive phosphatidylcholine was similar between the two cell lines. The rate of labeling phosphatidylcholine from the radioactive phosphatidylethanolamine was also reduced in 64-24 cells, although the difference was not as great as that of phosphatidylserine. Incorporation of 32P into phosphatidylethanolamine was correlated with the concentration of ethanolamine in the culture medium in 64-24 cells, whereas in 22-1 cells the incorporation was not influenced by ethanolamine. Enzyme activities of the CDP-ethanolamine pathway were not significantly different between the two cell lines. The rate of degradation of phosphatidylethanolamine was also similar in these cell lines. These results show that ethanolamine responsiveness of 64-24 cells, and probably other epithelial cells, is due to a limited ability to synthesize phosphatidylserine resulting from a limited base-exchange activity utilizing phosphatidylethanolamine.

Animals↗
PubMed1985

Differences in regulatory sequences of naturally occurring JC virus variants.

The regulatory region was sequenced for DNAs representative of seven independent isolates of JC virus, the probable agent of progressive multifocal leukoencephalopathy. The isolates included an oncogenic variant (MAD-4), an antigenic variant (MAD-11), and two different isolates derived from the urine (MAD-7) and from the brain (MAD-8) of the same patient. The representative DNAs were molecularly cloned directly from diseased brain tissue and from human fetal glial cells infected with the corresponding isolated viruses. The regulatory sequences of these DNAs were compared with those of the prototype isolate, MAD-1, sequenced previously (R. J. Frisque, J. Virol. 46:170-176, 1983). We found that the regulatory region of JC viral DNA is highly variable due to complex alterations of the previously described 98-base-pair repeat of MAD-1 DNA. On the basis of these alterations, there are two general types of JC virus. There were no consistent alterations in regulatory sequences which could distinguish brain tissue DNAs from tissue culture DNAs. Furthermore, for each isolate except MAD-1 (R. J. Frisque, J. Virol. 46:170-176, 1983), the regulatory regions of brain tissue and tissue culture DNAs were not identical. The arrangement, sequence, or both of potential regulatory elements (TATA sequence, GGGXGGPuPu, tandem repeats) of JC viral DNAs are sufficiently different from those in other viral and eucaryotic systems that they may effect the unique properties of this slow virus.

Animals↗
PubMed1984

The oxidation of some polysaccharides by the hydroxyl radical: an e.s.r. investigation.

E.s.r. Experiments employing a flow system in conjunction with the TiIII-H2O2 couple show that dextrans react with the hydroxyl radical (HO.) via indiscriminate attack (except that abstraction of hydrogen atoms from carbons which are both linked by glycosidic bonds and included in the pyranose ring may be inhibited, possibly for steric reasons). Acid- and base-catalysed transformations of first-formed radicals have been demonstrated; the suggestion that such reactions can lead to glycosidic cleavage is supported by viscosity studies which confirm the pH-dependence of radical-initiated degradation. For galacturonan and related compounds, e.s.r. results indicate that reaction with HO. proceeds preferentially via abstraction of the hydrogen on the carbon adjacent to the carboxyl group. The crucial step in the subsequent degradation pathway probably involves a pH-independent rearrangement.

Dextrans↗