PubMed Health⌕ Search

Biomedical subjects

R Schilling

Publications and source records attributed to R Schilling.

At least 19 recordsLinked to original sources
PubMed2001

Microscopic dynamics of molecular liquids and glasses: role of orientations and translation-rotation coupling.

We investigate the dynamics of a fluid of dipolar hard spheres in its liquid and glassy phases, with emphasis on the microscopic time or frequency regime. This system shows rather different glass transition scenarios related to its rich equilibrium behavior, which ranges from a simple hard sphere fluid to long range ferroelectric orientational order. In the liquid phase close to the ideal glass transition line and in the glassy regime a medium range orientational order occurs leading to a softening of an orientational mode. To investigate the role of this mode we use the molecular mode-coupling equations to calculate the spectra straight phi"lm(q,omega) and chi"lm(q,omega). In the center of mass spectra straight phi"00(q,omega) and chi"00(q,omega) we found, besides a high frequency peak at omega(hf), a peak at omega(op), about one decade below omega(hf) x omega(op) has almost no q dependence and exhibits an "isotope" effect omega(op) proportional to I(-1/2), with I the moment of inertia. We give evidence that the existence of this peak is related to the occurrence of medium range orientational order. It is shown that some of these features also exist for schematic mode coupling models.

Journal Article↗
PubMed2001

Non-cytolytic inhibition of hepatitis B virus replication in human hepatocytes.

BACKGROUND/AIMS: Interferon-gamma (IFN-gamma) has been shown to abolish hepatitis B virus (HBV) gene expression and replication in HBV transgenic mice without destroying infected hepatocytes. We investigated the characteristics of IFN-gamma induced non-cytolytic inhibition of viral replication in human HBV infection. METHODS: We used an in vitro model where lymphocytes from 15 HBsAg positive patients were co-cultured with transfected hepatocytes supporting HBV replication. The effector and target cells were separated by a membrane, which allowed transfer of soluble factors only, to determine whether IFN-gamma produced from antigen-specific CD4+ T cells or mitogen stimulated lymphocytes inhibits HBV replication. RESULTS: IFN-gamma produced following lymphocyte stimulation reduced cytoplasmic HBV DNA in the target cells. The degree of HBV DNA reduction correlated with the level of IFN-gamma in the supernatants. Further investigations using naturally infected human hepatocytes confirmed that recombinant IFN-gamma reduces HBV DNA and HBV RNA in these cells as well, in parallel with the induction of cellular interferon-responsive genes. This antiviral effect was without significant cytotoxicity and was more pronounced in hepatocytes from patients with low HBV replication. CONCLUSIONS: These results provide direct evidence that IFN-gamma can inhibit both HBV transcription and replication in human hepatocytes without cell lysis.

Adult↗
PubMed2000

Test of molecular mode coupling theory for general rigid molecules

We report recent progress on the test of mode coupling theory for molecular liquids (MMCT) for molecules of arbitrary shape. The MMCT equations in the long time limit are solved for supercooled water including all molecular degrees of freedom. In contrast to our earlier treatment of water as a linear molecule, we find that the glass-transition temperature T(c) is overestimated by the theory as was found in the case of simple liquids. The nonergodicity parameters are calculated from the "full" set of MMCT equations truncated at l(co)=2. These results are compared (i) with the nonergodicity parameters from MMCT with l(co)=2 in the "dipole" approximation n=n(')=0 and the diagonalization approximation n=n(')=0, l=l(') and (ii) with the corresponding results from a MD simulation. This work supports the possibility that a reduction to the most prominent correlators may constitute a valid approximation for solving the MMCT equations for rigid molecules.

Journal Article↗
PubMed2000

Molecular correlations in a supercooled liquid

We present static and dynamic properties of molecular correlation functions S(lmn,l(')m(')n('))(q-->,t) in a simulated supercooled liquid of water molecules, as a preliminary effort in the direction of solving the molecular mode-coupling theory (MMCT) equations for supercooled molecular liquids. The temperature and time dependence of various molecular correlation functions, calculated from 250 ns long molecular dynamics simulations, show the characteristic patterns predicted by MMCT and shed light on the driving mechanism responsible for the slowing down of the molecular dynamics. We also discuss the symmetry properties of the molecular correlation functions that can be predicted on the basis of the C(2v) symmetry of the molecule. Analysis of the molecular dynamics results for the static correlators S(lmn,l(')m(')n('))(q-->) reveals that additional relationships between correlators with different signs of n and n(') exist. We prove that for molecules with C(rv) symmetry this unexpected result becomes exact at least for high temperatures.

Journal Article↗
PubMed2000

Ideal glass transitions for hard ellipsoids

For hard ellipsoids of revolution we calculate the phase diagram for the idealized glass transition. Our equations cover the glass physics in the full phase space, for all packing fractions and all aspect ratios X0. With increasing aspect ratio we find the idealized glass transition to become primarily driven by orientational degrees of freedom. For needlelike or platelike systems the transition is strongly influenced by a precursor of a nematic instability. We obtain three types of glass transition line. The first one (straight phi((B))(c)) corresponds to the conventional glass transition for spherical particles which is driven by the cage effect. At the second one (straight phi((B'))(c)), which occurs for rather nonspherical particles, a glass phase is formed that consists of domains. Within each domain there is a nematic order where the center of mass motion is quasiergodic, whereas the interdomain orientations build an orientational glass. The third glass transition line (straight phi((A))(c)) occurs for nearly spherical ellipsoids where the orientational degrees of freedom with odd parity, e.g., 180 degrees flips, freeze independently from the positions.

Journal Article↗
PubMed2000

Molecular mode-coupling theory applied to a liquid of diatomic molecules

We study the molecular mode-coupling theory for a liquid of diatomic molecules. The equations for the critical tensorial nonergodicity parameters F(m)(ll('))(q) and the critical amplitudes of the beta relaxation H(m)(ll('))(q) are solved up to a cutoff l(co)=2 without any further approximations. Here l,m are indices of spherical harmonics. Contrary to previous studies, where additional approximations were applied, we find in agreement with simulations that all molecular degrees of freedom vitrify at a single temperature T(c). The theoretical results for the nonergodicity parameters and the critical amplitudes are compared with those from simulations. The qualitative agreement is good for all molecular degrees of freedom. To study the influence of the cutoff on the nonergodicity parameter, we also calculate the nonergodicity parameters for an upper cutoff l(co)=4. In addition, we also propose a method for the calculation of the critical nonergodicity parameter from the liquid side of transition.

Journal Article↗
PubMed2000

Inhibition of cholesteryl ester transfer protein by substituted dithiobisnicotinic acid dimethyl ester: involvement Of a critical cysteine.

SC-71952, a substituted analog of dithiobisnicotinic acid dimethyl ester, was identified as a potent inhibitor of cholesteryl ester transfer protein (CETP). When tested in an in vitro assay, the concentration of SC-71952 required for half-maximal inhibition was 1 microm. The potency of SC-71952 was enhanced 200-fold by preincubation of the inhibitor with CETP, and was decreased 50-fold by treatment with dithiothreitol. Analogs of SC-71952 that did not contain a disulfide linkage were less potent, did not display time dependency, and were not affected by dithiothreitol treatment. Kinetic and biochemical characterization of the inhibitory process of CETP by SC-71952 suggested that the inhibitor initially binds rapidly and reversibly to a hydrophobic site on CETP. With time, the bound inhibitor irreversibly inactivates CETP, presumably by reacting with one of the free cysteines of CETP. Liquid chromatography/mass spectroscopy (LC/MS) analyses of tryptic digests of untreated or SC-71952-inactivated CETP was used to identify which cysteine(s) were potentially involved in the time-dependent, irreversible component of inactivation by the inhibitor. One disulfide bond, Cys143-Cys184, was unaffected by treatment with the inhibitor. Inactivation of CETP by SC-71952 correlated with a progressive decrease in the abundance of free Cys-13 and Cys-333. Conversion of Cys-13 to alanine had no effect on the rapid reversible component of inactivation by SC-71952. However, it abolished the time-dependent enhancement in potency seen with the inhibitor when using wild-type CETP. These data indicate that Cys-13 is critical for the irreversible inactivation of CETP by SC-71952 and provides support for the structural model that places Cys-13 near the neutral lipid-binding site of CETP.

Amino Acid Substitution↗
PubMed1998

The high-risk sexual practices of crack-smoking sex workers recruited from the streets of three American cities. The Multicenter Crack Cocaine and HIV Infection Study Team.

BACKGROUND AND OBJECTIVES: Small ethnographic and clinic-based studies indicate that crack-smoking sex workers are at high risk for human immunodeficiency virus (HIV) and sexually transmitted diseases (STD). STUDY GOALS: To examine the prevalence of risky sexual behaviors and HIV and STD in a large sample of street-recruited crack-smoking sex workers. STUDY DESIGN: From 1991 to 1992, 419 crack-smoking sex workers were recruited from urban neighborhoods, interviewed, and serologically tested. RESULTS: Many female and male sex workers reported sex with injectors (30% to 41%) or HIV-infected persons (8% to 19%), past STD (73% to 93%), and inconsistent condom use (> 50% for all types of sex). Sex workers who worked in crack houses or vacant lots, were paid with crack, or injected drugs had the riskiest sex practices. Most sex workers initiated sex work before they first smoked crack. More than 25% were infected with HIV (27.9%), syphilis (37.5%), or herpes simplex virus type 2 (66.8%). CONCLUSIONS: Interventions to prevent HIV/STD transmission among crack-smoking sex workers are urgently needed.

Adult↗
PubMed1998

Cardiac syncope due to transient coronary artery occlusion: the role of percutaneous angioplasty.

A case of cardiac syncope is presented, associated with single vessel coronary disease. The mechanism of the syncope would appear to be a ventricular arrhythmia with transmural myocardial ischaemia due to transient occlusion of the diseased coronary artery. The symptoms and electrocardiographic abnormalities were reproduced and subsequently abolished by percutaneous coronary angioplasty.

Angina Pectoris, Variant↗
PubMed1998

Partner violence and sexual HIV-risk behaviors among women in an inner-city emergency department.

This study examines the relationship between partner violence and sexual risk behaviors in a sample of predominantly Latina and African American women who sought medical care from a New York City hospital emergency department. Eligibility criteria selected women between the ages of 18 and 55, who were sexually active in the past 90 days, and were triaged to nonemergency care. The interview addressed demographics, partner violence, childhood abuse, sexual behavior, and drug and alcohol use. Multiple logistic regression analysis was used to assess the association between partner violence and history of having a sexually transmitted disease (STD) and of having sex with a risky partner. Nearly one half of the 143 respondents (46.1%, n = 66) reported that they had experienced physical, sexual, or life-threatening abuse by a boyfriend or spouse in the past and 17.5% reported that abuse had occurred within the past year. In the univariate analyses, abused women were more likely than nonabused women to report having had an STD; engaging in sex with a risky partner; having more than one sexual partner; and being tested for HIV. After controlling for confounding variables, abused women were almost five times more likely than their counterparts to have reported an STD and four times more likely to engage in sex with a risky sexual partner. The relationship between partner violence and sexual risk behaviors among women seeking treatment in an emergency department suggests the need for the development of HIV-risk reduction strategies that address the needs of women in abusive relationships.

Adolescent↗
PubMed1998

Hmong/medicine interactions: improving cross-cultural health care.

BACKGROUND AND OBJECTIVES: There are now more than 100,000 Hmong (Southeast Asian) refugees in the United States. This study examined interactions between Hmong patients and their health care providers and identified specific factors that either enable or obstruct health care delivery. METHODS: We used semistructured interview techniques to investigate patients' and providers' experiences, looking for attitudes, ideas, or behaviors that could be modified to improve health care delivery. Interviews with 23 Hmong patients, 18 health care providers, and six translators were audiotaped, transcribed, and analyzed by a multidisciplinary team. Methods included text analysis, theme identification, rank ordering, participant observation, immersion-crystallization, and open-ended discussion. RESULTS: Hmong patients and their US-trained health care providers have different health belief systems. Both linguistic and cultural translation were seen as problematic. Additionally, an overwhelming number of patients identified kindness, caring, and a positive attitude as important provider characteristics. Providers noted difficulties in understanding Hmong conceptions of acute versus chronic diseases, illness prevention, and pain, both physical and psychological. Many respondents gave suggestions for improvement: 1) learn more about each other's cultures, 2) be patient, kind, and positive, 3) avoid negative statements or predictions, 4) improve translation quality, 5) explain medical terms using visual aids, 6) respect Hmong family-centered decision making, 7) increase the time allotted for translated clinical encounters, and 8) train Hmong health care providers. CONCLUSIONS: Many basic issues in relations between clinicians and Hmong patients must be addressed to improve health care communication.

Asia, Southeastern↗
PubMed1996

Type, prevalence, and significance of core promoter/enhancer II mutations in hepatitis B viruses from immunosuppressed patients with severe liver disease.

Little is known about the functional significance of hepatitis B virus (HBV) sequence heterogeneity. Here we analyzed the type, frequency, and function of mutations in the core promoter/enhancer II region of HBV in immunosuppressed patients. The major HBV population in immunosuppressed patients with severe liver disease had deletions, insertions, and/or base changes in this region. Such mutations were not found in immunosuppressed patients with mild disease. Except for two mutations, all created a hepatocyte nuclear factor 1 (HNF1) binding site or a potential HNF3 binding site. Occasionally, known binding sites for C/EBP and HNF4 were additionally duplicated. Eleven mutated core promoter prototype sequences were functionally tested in the context of a wild-type genome by transfection in Huh7 cells. Despite the diversity of mutations tested, all decreased steady-state levels of pre-C mRNA drastically and increased those of the C mRNA/ pregenomic RNA. This correlated with reduced levels of secreted hepatitis B e antigen and increased intracellular levels of core and Pol proteins and replicative HBV DNA intermediates. The levels of secreted HBV DNA-containing particles were also increased although most of the mutations reduced the levels of pre-S/S mRNA and pre-S1, and pre-S2 proteins as well as secretion of hepatitis B surface antigen. These data reveal a novel class of HBV variants with HNF1 binding sites in the core promoter which are characterized by a defect in hepatitis B e antigen expression, enhanced replication, and altered protein levels, all probably mediated by altered transcription factor binding. The phenotype of these variants and their prevalence only in immunosuppressed patients with severe liver disease may indicate that they play a role in pathogenesis.

Amino Acid Sequence↗
PubMed1996

Patients with personality disorders: functional status, health care utilization, and satisfaction with care.

BACKGROUND: Personality disorders are believed to occur in approximately 10% of the adult population, yet they are rarely diagnosed in primary care settings. This study compares the functional status, health care utilization, and satisfaction with care for patients who were at high risk for a personality disorder with those who were at low risk. METHODS: Patients at high risk for personality disorders were identified using a standardized psychometric instrument, the Structured Clinical Inventory for DSM-III Axis II (SCID-II). After assigning patients to risk categories, responses were compared on the Medical Outcomes Study Short Form-36, the Beck Depression Inventory, the CAGE alcohol use questionnaire, and an adapted version of the RAND Patient Satisfaction Questionnaire. RESULTS: Patients who were at high risk for any personality disorder had lower functional status, higher risk for depression or alcohol abuse, and lower levels of satisfaction with care. These differences could not be explained by demographic or socioeconomic differences between high- and low-risk patients. Being at high risk for specific personality disorders, such as borderline, schizoid, and dependent disorders, was associated with higher degrees of functional impairment and greater risk for depression and alcohol abuse. Patients at high risk for other disorders, such as obsessive-compulsive, narcissitic, and schizotypal, consistently showed no appreciable degree of impairment as compared with patients at low risk for any personality disorder. Medical care utilization was no higher when personality disorders were examined in aggregate, but a marked increase in utilization was noted among patients at high risk for histrionic and dependent disorders. CONCLUSIONS: Among primary care patients, having a personality disorder is associated with lower functional status, lower satisfaction with health care, and higher risk for depression and alcohol abuse.

Adult↗
PubMed1996

[Significance of isthmic spondylolisthesis in expert assessment of occupational disease of the lumbar spine].

In Germany, disc-related disease of the lumbar spine is eligible for workmen's compensation if caused by long-standing work requiring heavy lifting or carrying or extreme trunk-bending (BK 2108). The appraisal of causality is particularly difficult if conditions like isthmic spondylolisthesis preexist. 250 consecutive appraisals in nurses concerning the BK 2108 were analysed, 12 applicants (4.8%) had isthmic spondylolisthesis (4.6% of females and 5.9% of males). The literature about the natural history of isthmic spondylolisthesis is reviewed. A person who has isthmic spondylolisthesis is up to 25% more likely to have significant back trouble during his life than one who does not. Back pain in adults associated with spondylolisthesis is usually heralded by back pain in the late teens or early twenties. Progression of the slip is rarely seen after maturity. Due to the loss of protection by the posterior elements the disc is prone to premature degeneration which, however, does not become clinically apparent in most cases. Longstanding vocational heavy lifting or excessive stooping can negatively influence the natural history of isthmic spondylolisthesis. It can produce symptomatic disease in a person who would otherwise have remained asymptomatic, or it can cause a deterioration in those with preexisting symptoms. Criteria for the appraisal of causality are proposed. It is stressed that the course of the disease in relation to age and vocational strains has to be analysed in each individual case.

Adolescent↗
PubMed1995

Urban rape survivors: characteristics and prevalence of human immunodeficiency virus and other sexually transmitted infections. Multicenter Crack Cocaine and HIV Infection Study Team.

OBJECTIVE: To determine the prevalence of recent rape, the characteristics or recent rape survivors, and the seroprevalence of human immunodeficiency virus (HIV), syphilis, and genital herpes (HSV-2) among recent rape survivors. METHODS: We surveyed women 18-29 years old who were recruited from places unassociated with medical or drug treatment or the criminal justice system in three urban communities where illicit drug use is common. We compared characteristics and HIV, syphilis, and HSV-2 seroprevalence of women who reported recent rape with those of women who denied recent rape. RESULTS: One hundred fifty-one of 1104 (13.7%) women reported having been raped in the year before our interview. Rape survivors were more likely than women who denied recent rape to smoke crack cocaine (86.8 versus 56.7%; odds ratio [OR] 5.0, 95% confidence interval [CI] 3.2-7.8), to be homeless (17.2 versus 6.1%; OR 3.2, CI 2.0-5.2), to report a recent sexually transmitted disease (38.7 versus 18.7%; OR 2.7, CI 1.9-3.9), and to be infected with syphilis (42.4 versus 28.4%; OR 1.9, CI 1.3-2.6) and HSV-2 (71.9 versus 57.5%; OR 1.9, CI 1.3-2.8). Survivors were more likely to acknowledge any HIV risk behavior (including sex work) (85.4 versus 49.5%; OR 5.9, CI 3.9-9.0) and to be HIV-infected (23.3 versus 13.4%; OR 1.9, CI 1.3-2.9). Rape was not independently associated with HIV (OR 0.8, 95% CI 0.4-1.3), syphilis (OR 0.9, 95% CI 0.6-1.3), or HSV-2 (OR 1.3, 95% CI 0.9-2.0) infections after adjustment for confounding factors. CONCLUSION: One in seven women reported being raped recently. Rape was most common among sex workers, crack smokers, and the homeless. Most survivors reported HIV risk behaviors, and many were HIV-infected. Programs to prevent repeated rape, voluntary HIV counseling and testing, and other medical and social services may benefit survivors in these and similar communities.

Adolescent↗