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Biomedical subjects

M P Westerman

Publications and source records attributed to M P Westerman.

At least 19 recordsLinked to original sources
PubMed1998

Phase changes in membrane lipids in sickle red cell shed-vesicles and sickle red cells.

Lipid phase transformations may occur in the membranes of sickle red cell shed-vesicles and sickle red cells. The presence of such phase changes could be important in sickle cell disease since membrane phase changes appear to contribute to the generation of antiphospholipid antibodies that are thrombophilic and occur in sickle cell disease. In the present study, we have evaluated sickle red cell shed-vesicles and sickle red cells for the presence of non-bilayer lipid phases using 31P-NMR spectroscopy. Results show that the spectra of both the shed-vesicles and the sickle red cells are compatible with the occurrence of non-bilayer phases in the membrane bilayers. The findings support the concept that these membranes could contribute to the generation of antiphospholipid antibodies in sickle cell disease.

Anemia, Sickle Cell↗
PubMed1997

Assessment of painful episode frequency in sickle-cell disease.

Frequency of painful episodes in sickle-cell disease is considered to be related to clinical severity and possibly to other aspects of the disease. Measurements of frequency often include only hospital-related or more severe, longer-lasting episodes. Since painful episodes, however, may regularly occur in nonhospital settings or be shorter-lasting with possible different pathologic effects, we measured all painful episodes in 10 adults with sickle-cell disease for 1.0-3.8 years, using a daily questionnaire. The results were related to other indices of disease severity and to possible precipitating factors, such as cold weather and menses. Sixty-one percent (on average) of the total number of episodes (243) were nonhospital-related, and 33% (on average) were shorter-lasting. Episode frequencies, whether determined as total, hospital-related, nonhospital-related, or shorter-lasting, were not related to each other or to other indicators of disease severity. The highest incidence of episode frequency occurred in the winter. The association of episodes with menses was moderately close in individual patients. The findings suggest that nonhospital-related painful episodes and shorter-lasting episodes may contribute significantly to episode frequency. Measurement of frequency of all painful episodes would require consideration when evaluating episode frequency and its relationship to disease severity, to possible precipitating factors of episodes, and to treatment of the disease, and for study of the natural course of the disease.

Adult↗
PubMed1995

Real-time X-ray diffraction study at different scan rates of phase transitions for dipalmitoylphosphatidylcholine in KSCN.

Multibilayer arrays of dipalmitoylphosphatidylcholine (DPPC) in 1 M KSCN were characterized using real-time X-ray diffraction and differential scanning calorimetry. A phase transition sequence was observed as a function of increasing temperature which involved changes from the interdigitated subgel (Lc(inter)) to interdigitated gel (L beta(inter)) to disordered (L alpha) bilayer states. The phase transition mechanisms were unambiguously determined by comparison of results from fast and slow scans. The Lc(inter)-->L beta(inter) phase transition was shown to involve a continuous change in acyl chain spacing between the rectangular subgel acyl chain unit cell into an hexagonal gel acyl chain unit cell. The mechanism is similar to that for subgel to gel state transitions involving non-interdigitated DPPC bilayers.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

Sterols stabilize the ripple phase structure in dihexadecylphosphatidylcholine.

The presence of various sterols in mixtures with dihexadecylphosphatidylcholine (DHPC) was studied using static X-ray diffraction of temperature equilibrated samples, and real-time X-ray diffraction of samples undergoing temperature scans. It was found that these sterols eliminate the interdigitation of the alkyl chains in the DHPC sub-gel and gel-state bilayers while stabilizing the ripple gel-state at the expense of the gel-state bilayer phase. The ripple-ripple phase transition previously observed for dipalmitoylphosphatidylcholine in the presence of low molar concentrations of sterols (Wolfe et al. (1992) Phys. Rev. Lett. 68, 1085-1088) was also observed for similar DHPC-sterol mixtures. In addition, we show the first evidence that the presence of 5 alpha-cholestane-3 beta,5,6 beta-triol will cause the lipid mixtures to continue to adopt a ripple mesophase structure even after the DHPC alkyl chain becomes disordered.

Cholestanols↗
PubMed1994

Effects of fibrinogens on phase transitions in lipid model membrane systems.

An abnormal fibrinogen that caused aggregation of red blood cells (RBC) in a patient with gangrene was examined by real-time X-ray diffraction to determine its effects on dipalmitoylphosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoylphosphatidylethanolamine (POPE) phase transitions. Similar studies were done with normal fibrinogen and results were compared. Both types of fibrinogen slightly increased the L alpha-->HII phase transition temperature and the HII phase parameters for POPE, while neither fibrinogen significantly affected the order-disordered acyl chain transitions in the lipid bilayer phase. However, fibrinogen differentially influenced the bilayer unit cell parameter of the gel and disordered bilayer and the gel state ripple phase. These results can be interpreted as indicating that fibrinogen has little effect on the balance of gel and disordered acyl chains in the lipid bilayer, but may influence membrane functions dependent on non-bilayer phases.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1994

Inhibition of cytolytic T lymphocyte activity by oxysterols.

The objective of this study was to investigate the effects of oxysterols (OS), namely 5 alpha-hydroxy-6-ketocholestanol, 6-ketocholestanol and 25-hydroxycholesterol, on specific cell-mediated cytotoxicity by C57BL/6 spleen cells against P815-X2 (a DBA/2 mastocytoma) target cells. Cytolytic T lymphocytes (CTL) were generated by intraperitoneally injecting C57BL/6 mice with P815-X2 tumor cells 10 d prior to the cytotoxicity experiments. Preincubation of CTL with 10(-5) M 5 alpha-hydroxy-6-ketocholestanol and 6-ketocholestanol for 45 min in lipoprotein-depleted medium resulted in an inhibition of cytolytic activity (73 and 43%, respectively) as measured by 4-h 51Cr release. At a concentration of 5 x 10(-6) M, 5 alpha-hydroxy-6-ketocholestanol inhibited CTL activity by 65%, whereas 6-ketocholestanol did not elicit any inhibition. By contrast, 25-hydroxycholesterol did not inhibit CTL at either concentration, although it is known to be a potent inhibitor of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, the rate-limiting enzyme in the cholesterol biosynthetic pathway. When CTL were preincubated with OS in lipoprotein-replete medium, there was no inhibition of CTL activity at the respective concentrations. The results suggest that the inhibition of CTL activity upon short-term incubation with OS is not due to the inhibition of cholesterol synthesis, but may be due to the insertion of OS into the plasma membrane to replace cholesterol and alteration of membrane physical properties.

Animals↗
PubMed1994

Intracellular Ca(2+)-containing vesicles in sickle cell disorders.

The frequency of red blood cells harboring Ca(2+)-containing vesicles was determined in patients with various sickle cell disorders; vesicles were identified by microscopy after the cells were stained with the fluorescent probe chlortetracycline. Specimens from 49 patients were studied. The highest frequencies of vesicle-containing cells were observed in samples from adults with homozygous sickle cell (SS) disease and in patients with S beta zero and SS(-alpha/alpha alpha) thalassemias. The frequency of cells with vesicles was less elevated in patients with SS(-alpha/-alpha) thalassemia and in patients with SS disease (Saudi Arabia high hemoglobin F), whereas a normal low frequency of positive cells was seen in patients with sickle cell-hereditary persistence of fetal hemoglobin and in patients with sickle trait. Deoxygenation induced an increase in the number of vesicle-containing cells that was proportional to the frequency of such cells in the oxygenated population. The frequency of Ca(2+)-containing vesicles in sickle red cells is associated with the clinical, hematologic, or clinical and hematologic severity of the sickle cell disorder.

Adult↗
PubMed1993

Antiphospholipid antibodies in sickle cell disease.

Antiphospholipid antibody formation can be induced in mice by phospholipid in a hexagonal II phase but not by phospholipid in a bilayer phase. Since sickle red cell membranes have increased hexagonal II phase content, we have measured serum antiphospholipid antibody levels in 25 patients with sickle cell disease to determine whether anti-phospholipid antibody may similarly be induced in these patients. Seventeen of the 25 patients (68%) had increased levels of antiphospholipid antibodies. Eleven patients (65%) had IgG and six each (35%) had IgM and IgA isotypes. Antiphosphatidylethanolamine, antiphosphatidylserine, antiphosphatidylinositol, and antiphosphatidic acid were the most frequently increased antibodies. The finding of increased antiphospholipid antibodies in these patients is compatible with the concept that antiphospholipid antibody formation is associated with structural changes in the red cell membrane and that such structural changes occur in the red cells of patients with sickle cell disease.

Antibodies, Antiphospholipid↗
PubMed1993

Intratumor heterogeneity of DNA ploidy and correlations with clinical stage and histologic grade in prostate cancer.

Paraffin blocks from 60 patients with prostate cancer were used to study the DNA ploidy patterns by flow cytometry. Nineteen patients had stage A disease, 11 had stage B, 9 had stage C, 20 had stage D, and 1 was of unknown stage. Histologically, 32 of the cancers were well differentiated, 21 were moderately differentiated, and 7 were poorly differentiated. Eighteen patients had an aneuploid or tetraploid (A/T) pattern and 42 had a diploid pattern. Seventy-one percent (5/7) of patients with poorly differentiated, 48% (10/21) with moderately differentiated, and 9% (3/32) with well-differentiated histology had A/T patterns (P < 0.01). Forty-five percent (9/20) of patients with stage D, 44% (4/9) with stage C, 27% (3/11) with stage B, and 5% (1/19) with stage A had A/T patterns (P < 0.05). Nine patients with an A/T pattern also had DNA ploidy studies done on the "benign" part of the specimen. These specimens showed diploid patterns although three of these patients had well-differentiated tumor in the "benign" designated part of the specimen. One patient with mixed histology had an aneuploid pattern on the poorly differentiated section and a diploid pattern on the well-differentiated section of the "malignant" designated part of the same specimen. We conclude that prostate cancer patients with non-diploid tumors have more advanced disease and less differentiated tumors than patients with diploid tumors and that considerable histological and ploidy heterogeneity may be present in different parts of the same paraffin-embedded specimen.

DNA, Neoplasm↗
PubMed1992

The effects of cholesterol oxidation products in sickle and normal red blood cell membranes.

The oxysterol content in normal and sickle red blood cell (RBC) membranes was assessed using thin-layer chromatography and capillary gas chromatography/mass spectrometry. Several more oxysterols were present in sickle RBCs compared to normal RBCs. Sickle RBC membranes had a higher concentration of 5 alpha,6 alpha-epoxycholesterol, 5 alpha-cholestane-3 beta,5,6 beta-triol, 7-ketocholesterol and 19-hydroxycholesterol than normal RBC membranes. The increased oxysterols in sickle RBC may be an effect of the increased oxidative stress which occurs in sickle RBC membranes. Physical characteristics of normal and sickle RBC membrane ghosts with and without inserted oxysterols were examined by Fourier transform infrared spectroscopy. The data are consistent with a greater sterol content in sickle cells compared to normal RBC membranes, and a possible oxysterol-cholesterol synergism.

Cholesterol↗
PubMed1992

Ca2+ accumulation and loss by aberrant endocytic vesicles in sickle erythrocytes.

Sickle cells contain internal vesicles which accumulate Ca2+. As shown here, the membrane enclosing the vesicles contains the plasma membrane Ca(2+)-ATPase, or Ca2+ pump, as judged by staining with an antibody directed against the protein. Moreover, the number of cells containing such vesicles increases upon deoxygenation. These findings argue strongly that the vesicles arise by endocytosis from the plasma membrane, and explain how they accumulate Ca2+. When sickle cells are depleted of ATP, Ca2+ is lost from the vesicles, as judged by the disappearance of staining with the Ca2+/membrane probe chlortetracycline (CTC), without a corresponding loss of antibody staining. This loss of Ca2+ can be inhibited by nitrendipine, a Ca2+ channel blocker. These results suggest that the vesicle membrane allows outward passage of Ca2+ by a nitrendipine-sensitive pathway, which can be overcome by the inward-directed activity of the Ca2+ pump of the vesicle membrane. If so, the Ca2+ which vesicles contain is in dynamic equilibrium with the cytoplasm of the sickle erythrocyte.

Anemia, Sickle Cell↗
PubMed1992

Inhibition of NK cell-mediated cytotoxicity by oxysterols.

Some of the oxidation products of cholesterol (oxysterols) have profound effects on plasma membrane structure and function. The present studies were undertaken to determine the effects of oxysterols on NK cell-mediated cytotoxicity. When mouse spleen cells were preincubated with certain oxysterols, NK cell cytotoxicity was inhibited without loss of effector cell viability. The strongest inhibition was observed with oxysterols that are oxidized at the C-5, C-6, or C-7 positions of the sterol nucleus. Among these, 7 beta-hydroxycholesterol caused more inhibition than 7 alpha-hydroxycholesterol suggesting that the spatial orientation of the hydroxyl group in the beta-position results in a greater perturbation in plasma membrane structure than that oriented in the alpha-position. In contrast, oxysterols that are oxidized at the C-20 and C-25 positions that are located on the C-17 acyl chain had little or no inhibitory effect, suggesting that oxidation in the cholesterol nucleus which is situated closer to the phospholipid headgroups at the lipid bilayer-aqueous interface results in a more profound effect on the plasma membrane physical structure. These results suggest that the lytic function of NK cell is sensitive to alterations in the physical state of its plasma membrane induced by oxysterols.

Animals↗
PubMed1992

Functional studies on long-term cryopreserved peripheral blood mononuclear cells from patients with lung cancer and from healthy subjects.

To determine the functional abilities of long-term cryopreserved peripheral blood mononuclear cells (PBMCs) from patients with lung cancer and from healthy subjects, we assayed the proliferative and plaque-forming cell (PFC) responses of cells from these individuals after the cells had been cryopreserved for up to 31 months. The stability of these cells for B and T cell quantitative assays was also determined by using their respective monoclonal antibodies. The patients' results were compared with those in healthy subjects to ascertain whether the conclusions derived from the assay of cryopreserved cells are consistent with our earlier studies on fresh cells from similar patients. The results show that proliferative and PFC responses of the frozen cells were not significantly affected by further storage, despite an initial, irreversible functional loss in some subsets of T lymphocytes and monocytes during the process of freezing. They also demonstrate that cryopreserved PBMCs from both patients and controls can be successfully utilized for B and T cell quantitative assays. The conclusions derived from the assay of cryopreserved cells are also consistent with our earlier observations on fresh cells from patients with lung cancer; those studies indicated a B cell functional abnormality caused in part by increased suppressor T cell and monocyte activity.

Aged↗
PubMed1991

Effect of inserted oxysterols on phospholipid packing in normal and sickle red blood cell membranes.

Fourier transform infrared (FTIR) spectroscopy was used to examine the effect of oxysterol insertion into normal and sickle RBC membranes and the total lipid extracts of the membranes. Examination of the FTIR C-H stretch and fingerprint regions reveal that the insertion of 7 alpha- and 7 beta-hydroxycholesterol has the greatest effect on the fluidity of RBC membranes and lipid extracts. The results confirm the observation that sterol molecules are oriented in the membrane so that the 7 position is located in the phospholipid head group region at the lipid/water interface. The substitution of a keto for a hydroxy group at the number seven position decreases the effect of the sterol on membrane packing.

Anemia, Sickle Cell↗
PubMed1991

Monozygotic twins with sickle cell anemia and discordant clinical courses: clinical and laboratory studies.

We describe a rare set of monozygotic twins with coexistent sickle cell anemia and alpha-/alpha alpha thalassemia who have asynchronous painful crises of different frequency and severity. Studies include measurements of cell deformability and other hemorheologic tests, cell density distribution, the percentage of irreversibly sickled cells, adherence of red cells to endothelial cells, membrane heme and membrane free iron, calcium containing internal vesicles and serum antioxidants. Results of these studies, including estimates of organ damage (bone, spleen, retina), were similar except for an increase in red cell membrane free iron in the patient with more frequent and severe painful crises. The study supports the concept that non-inherited factors are important contributors to the frequency and severity of painful crises in sickle cell anemia.

Adult↗
PubMed1990

Cryopreservation enhances interleukin-1 production in human mononuclear cells.

The effects of cryopreservation on bacterial lipopolysaccharide (LPS)-induced interleukin-1 (IL-1) production by unfractionated mononuclear cells (MNCs), adherent cells (ACs), and nonadherent cells (NACs) were studied. Culture supernatants from cryopreserved cells contained significantly larger concentrations of IL-1 [MNCs, 211 +/- 50; ACs, 640 +/- 41; NACs, 116 +/- 19 U/ml (mean +/- SEM)] as compared with supernatants from fresh cells (69 +/- 22, 427 +/- 69, and 72 +/- 33 U/ml, respectively). In addition, supernatants obtained from cocultures of autologous fresh and frozen cells contained much less than the expected quantities of IL-1 (78 +/- 8%), indicating that suppressor cells in the fresh population are responsible for the decreased IL-1 content. The studies suggest that functional inactivation of cryosensitive suppressor monocytes is associated with an increase in IL-1 production by the other subset. The results provide further evidence that lack of active suppressor monocytes and increased IL-1 production may be responsible for the previously reported enhanced plaque-forming cell responses of cryopreserved cells from normal controls and from patients with lung cancer.

Adult↗
PubMed1990

Radiation causes increased production and decreased utilization of IL-2 in human mononuclear cells.

The effects of radiation on the kinetics of Interleukin-2 (IL-2) production and utilization by mononuclear cells (MNCs) were studied. Mononuclear cells from normal, healthy individuals were subjected to various doses of radiation ranging from 0 to 2,000 rad and cultured in the presence of PHA. Supernatants from these cultures were harvested at various periods and their IL-2 contents determined by both the standard bioassay and ELISA. A radiation dose of 800 rad and higher had a marked effect on both IL-2 production and consumption. Although the supernatants from both the irradiated and non-irradiated MNCs contained maximal concentrations of IL-2 between 8 and 24 h of culture, the former had three times as much IL-2 as the latter. An increase in IL-2-mRNA levels was also noticed in irradiated, PHA-stimulated cells. Moreover, the supernatants from irradiated MNCs collected as late as 72 h after the initiation of culture contained more than 30% of the total IL-2 produced compared to less than 8% in supernatants from non-irradiated cells. Supernatants from non-irradiated cells incubated further with irradiated cells contained relatively higher quantities of IL-2 than those incubated continuously with non-irradiated cells. Supernatants from co-cultures of irradiated and non-irradiated MNCs contained less than expected amounts of IL-2 in two of the three subjects. Despite a difference in both the production and consumption of IL-2 between the irradiated and non-irradiated cells, there was no difference in their ability to generate IL-2 receptors. The results indicate that inactivation of radiosensitive suppressor T cells is associated with superinduction of IL-2 mRNA, increased production and decreased consumption of IL-2 by MNCs, thereby resulting in increased accumulation of IL-2.

Cell Survival↗