The infrared dichroism of transmembrane helical polypeptides

Polarized attenuated total internal reflectance techniques were applied to study the infrared dichroism of the amide I transition moment in two membrane-bound peptides that are known to form oriented transmembrane helices: gramicidin A in a supported phospholipid monolayer and Ac-Lys2-Leu24-Lys2-amide (L24) in oriented multibilayers. These studies were performed to test the ability of these techniques to determine the orientation of these peptides, to verify the value of optical parameters used to calculate electric field strengths, to examine the common assumptions regarding the amide I transition moment orientation, and to ascertain the effect of surface imperfections on molecular disorder. The two peptides exhibit marked differences in the shape and frequency of their amide I absorption bands. Yet both peptides are highly ordered and oriented with their helical axes perpendicular to the membrane surface. In the alpha-helix formed by L24, there is evidence for a mode with type E1 symmetry contributing to amide I, and the amide I transition moment must be more closely aligned with the peptide C=O (< 34 degrees) than earlier studies have suggested. These results indicate that long-standing assumptions about the orientation of amide I in a peptide require some revision, but that in general, infrared spectroscopy yields reliable information about the orientation of membrane-bound helical peptides.     

Crystal structure of the S-nitroso form of liganded human hemoglobin

Although numerous reports have documented that the S-nitrosylation of cysteine residues by NO alters the activities of a wide variety of proteins, the direct visualization and the structural consequences of this reversible modification have not yet been reported for any protein. Here we describe the crystal structure of S-nitroso-nitrosylhemoglobin determined at a resolution of 1.8 A. The specific reaction of NO with Cys93beta is confirmed in this structure, and a large S-nitrosylation-induced change in the tertiary structure of the COOH-terminal dipeptides of the beta subunits provides additional insight into the stereochemical mechanism by which blood flow is regulated by the interaction of NO with hemoglobin.     

Gallbladder volume and contractility in term and preterm neonates: normal values and clinical applications in ultrasonography

BACKGROUND: Normovolemic hemodilution is a well-accepted method for intraoperative blood salvage. However, some controversy exists concerning the possible risk of myocardial fiber injury as consequence of the reduced oxygen content. Laboratory diagnosis of perioperative myocardial fiber injury is difficult, since biochemical markers are elevated postoperatively due to the surgical trauma. Cardiac troponin I (cTnI) is a new, highly sensitive and specific marker for the detection of myocardial injury. The aim of our study was to investigate whether normovolemic hemodilution in patients with major orthopedic surgery (13 hemodiluted patients, 15 control) induces a release of cTnI. METHODS: cTnI as a highly specific and sensitive cardiac parameter, as well as total creatine kinase (CK), creatine kinase isoenzyme MB mass (CKMB mass) and myoglobin were measured after induction of anesthesia, after normovolemic hemodilution, prior to retransfusion of blood components, 3 h after surgery, and on the first and third postoperative days. RESULTS: Prior to retransfusion of blood components the hematocrit was decreased to 25.4 +/- 1.2% (mean +/- SEM; range: 18%-34%) in the control group and to 20.2 +/- 0.8% (mean +/- SEM; range: 17%-24%) in the hemodilution group. Total CK, CKMB mass as well as myoglobin concentration increased significantly in both groups, reaching their maxima within the first day of surgery. In contrast, cTnI was below the detection limit of assay (< 0.5 micrograms/L) at any time. CONCLUSIONS: We suggest that pre- and intraoperative hemodilution to a hematocrit of approximately 20% by maintaining normovolemia does not induce myocardial fiber injury in patients without preexisting cardiac diseases.     

Discontinuation of treatment with IFN-beta leads to exacerbation of experimental autoimmune encephalomyelitis in Lewis rats. Rapid reversal of the antiproliferative activity of IFN-beta and excessive expansion of autoreactive T cells as disease promoting mechanisms

BACKGROUND: It is important for HIV/AIDS control programmes to determine population knowledge on AIDS in order to develop appropriate Information, Education and Communication (IEC) messages. The objectives of our study were to determine the seroprevalence of HIV and syphilis among pregnant women, female prostitutes and long-distance truck drivers and to evaluate knowledge, attitudes, beliefs, and practice (KABP) with respect to the HIV/AIDS epidemic in these three groups in Burkina Faso. METHODS: We performed three cross-sectional serosurveys including face-to-face interviews on KABP between October 1994 and February 1995 in three population groups. RESULTS: Overall, 1,294 pregnant women, 236 long-distance truck drivers and 426 female prostitutes were recruited. HIV seroprevalence was 8% (95% Confidence Interval (CI): 6.6-9.6) among pregnant women, 18.6% (95% CI: 13.9-24.2) among long-distance truck drivers and 58.2% (95% CI: 53.4-62.9) in female prostitutes. The prevalence of syphilis was 2.5%, 9.3% and 15%, respectively. Most pregnant women (98%), long-distance truck drivers (96%) and female prostitutes (98%) had already heard of AIDS. However, the level of knowledge of HIV transmission routes, of risk factors for HIV transmission and of available preventive measures was very low. Consequently, 41% of pregnant women, 40% of long-distance truck drivers and an alarming 61% of female prostitutes reported that they did not feel themselves at risk for HIV. In each group, high levels of knowledge on AIDS were associated with increased awareness of AIDS risk and the adoption of preventive behaviours. Level of education was associated with knowledge of AIDS and condom use. However, in the 12 months preceding the surveys, condom use was very low among pregnant women (0.1%), long-distance truck drivers (18%) and among female prostitutes (42%). CONCLUSIONS: These results indicate that HIV is widespread in Burkina Faso and that there is an urgent need to develop and evaluate HIV prevention strategies in the general population and among core groups such as female prostitutes and long-distance truck drivers. Interventions must include information campaigns, condom promotion and distribution, and sexually transmitted diseases control.